text:
Rhetoric and Composition/Writing Applications

Overview
The first part of this book is about the stages of the writing process. Now it's time to shift gears and start thinking about the kinds of assignments you're likely to encounter in college. Each "writing mode" requires a different mode of thinking, and that's why teachers and professors often ask for different kinds of writing (they want you to think about a subject in a variety of ways). But generally, assignments will require you to apply several modes, simultaneously, to accomplish a well-rounded body of writing. Few professors beyond the first-year level of coursework require an assignment that merely focuses on description or narration; other modes are required to generate a well-rounded piece of writing that entertains, informs, and persuades (i.e., narrative, explication, argument).

Most of the time, you'll find yourself switching among all of these modes as you write. You would have a hard time, for instance, reviewing a car without spending any time describing it, and the strength of an argument depends on how well you've evaluated its evidence. What's important is that you recognize the difference between them. Many students lose points each year when they offer their teacher a description instead of the evaluation or argument called for by the assignment. Below, we first give you some hints about analyzing assignments to find out what different types of writing task you need to do. Then, we break down some common writing modes, telling you their characteristics and what makes them unique, then offer examples of informal and formal writing that show them in action.

How to analyze an assignment
Writing successfully for your college classes depends a lot on finding out as much as possible about what you need to do to fulfill the assignment each time you write. While many instructors try hard to clarify their expectations, the final responsibility for making sure you know what it takes to fulfill an assignment is yours. Be your own advocate!

This chapter will give you strategies for interpreting assignments successfully and break down eighteen words commonly used in assignments to help you understand what critical and writing tasks you need to do.

Description
One key difference between a good writer and a bad one is the ability to write vivid, detailed descriptions. What does something look like? Sound like? Feel like? Good descriptions make all the difference when you're trying to hook readers and keep them interested. We don't want to read, "The house was scary." We want to read a great description of the house that actually makes us feel that fear for ourselves. This can only be accomplished by observant writers who are willing to "show" as well as "tell" their readers about their subject.

This chapter will introduce you to description and offers some good advice about writing highly descriptive essays.

Narration
"Narrative" is really just a fancy way of saying "story." When you are narrating, you are describing an event, step-by-step, usually in the order that it happened. In other words, a "narration" is a "description" of something taking place in time. As you can probably guess, narration and description are highly related. You can't narrate very well if you lack the ability to describe accurately and vividly what is taking place.

This chapter will introduce you to narration and some strategies for telling good stories.

Exposition
Expository writing is writing that explains or informs. You may encounter expository writing in an assignment that has you describing a process or developing a set of clear instructions. You aren't just describing a "what" ("What is fishing?") but explaining a "how" ("How do you fish?"). Writers with excellent exposition skills are generally good learners, since describing processes well requires a thorough understanding of the process.

This chapter offers tips and suggestions for expository writing and some helpful examples.

Evaluation
Magazines like Consumer Reports and movie reviewers like Roger Ebert are famous for the quality of their evaluative writings. They give people the information they need to determine if a car is worth buying or a movie is worth seeing. You'll also find lots of evaluations in business, in which they are used to determine an employee's eligibility for promotion or a manager's effectiveness at overseeing an important project.

This chapter will tell you all about evaluative writing and the strategies you'll need to do it right.

Argumentation
Some people think of arguments as a lot of shouting and cursing (but that's not what college professors mean when they use the term "argumentation"). What they have in mind is a clear-headed, logical, and convincing style of speaking or writing that makes a valid point and supports it with good evidence. An argument isn't just summarizing or restating what others may have said about an issue. You'll need to research the issue, evaluate the evidence, reach a conclusion, figure out the best way to support it, and arrange your thoughts effectively. Writing a good argumentative paper is probably the most difficult of all types of writing assignments, but we'll give you advice and discuss some strategies that will get you on the right track.

This chapter describes what college professors mean by the term "argumentation," and discuss some methods that will earn good grades on these common but challenging assignments.


text:
Toyota Prius/FAQ

This page is a repository of frequently asked questions about the Toyota Prius with major contribution from members of PriusChat.

Official Toyota Links

 * USA
 * Canada
 * United Kingdom

2006 Model Year

 * 2006 Prius eBrochure
 * Complete 2006 Prius Information and Pricing
 * The picture is of the Japanese Prius with the new badge above the side-blinkers. Shipping was also increased $40 for 2006, making the total increase $490.

 * HybridCars.about.com 2006 Toyota Prius - Profile of the 2006 Toyota Prius

 * Toyota Fleet - Model Year 2006 Color Chart
 * Although not shown on the chart Magnetic Gray will be available for the Prius in May 2006.

Extended Warranty

 * Toyota.com - Benefit Comparison
 * Toyota.com - Component Comparison
 * Toyota.com - MSRP Pricing

Fuel Economy
From FuelEconomy.gov - 2006 Model Year Alternative Fuel Vehicle Fuel Economy:

All miles-per-gallon figures are based on standards set in 1972-1976 and accurate standards will be available in cars of 2008 and beyond. *Based on 15000 annual miles and a fuel price of $ 3.00 per gallon.
 * EPA Fuel Economy
 * Fuel Type - Regular Gasoline
 * MPG (city) - 60
 * MPG (highway) - 51
 * MPG (combined) - 55
 * EPA Fuel Economics
 * Cost to Drive 25 Miles $1.35
 * Fuel to Drive 25 Miles 0.45 gal
 * Cost of a Fill-up $35.70
 * Miles on a Tank 589 miles
 * Tank Size 11.9 gal
 * Annual Fuel Cost* $909

Fill-up cost and the distance you can travel on a tank are calculated based on the combined MPG and the assumption that you will re-fuel when your tank is 10% full.

Emissions
Hybrid Electric Vehicle Testing Data and Results-Toyota Prius

Specifications
From FuelEconomy.gov - 2006 Model Year Alternative Fuel Vehicle Fuel Economy:
 * Engine (Atkinson cycle type) - 1.5 liters - 76 hp - Torque 82 ft/lb
 * Electric motor - 67 hp - Torque 295 ft/lb
 * Cylinders - 4
 * Transmission - Automatic (fully variable gear ratios)
 * Drive - Front-wheel drive
 * Turbocharger - no
 * Supercharger - no
 * Passenger Volume - 96 ft3 (HB)
 * Luggage Volume - 16 ft3 (HB)
 * Engine Characteristics - HEV

Safety
NHTSA.DOT.gov - NHTSA Crash Test Ratings

Comparisons With Other Hybrids
FuelEconomy.gov - Compare Hybrids Side by Side

Inside

 * Amber snowflake icon: Page 116 of the 2005 Owner's Manual. On the forward dash, this light flashes 3-times and will stay on when the outside ambient temperature is below +3°C (+37°F). It serves as a reminder that the road may be icy. There is no known way to disable it, although black electrical tape works well to hide it.  Starting with the 2006 model year, the dash icon has been removed.  Instead, a brief message appears on the MFD when the temperature reaches +3°C (+37°F).
 * Vent in USA-passenger-side rear seatback: Page 16 of the 2005 Owner's Manual. This is the fan-assisted air inlet for the vehicle hybrid battery cooling system. Do not block this vent.
 * Glove box light: This light is on whenever the headlights are on; it does not turn off with the glove box closed. This is normal. Power use is negligible because it is an LED.

Audio

 * Basic facts
 * Chris Dragon's dash dissembly guide
 * Sparky's speaker replacement guide
 * iPod connectivity
 * The VAIStech SoundLinQ SLI provides a complete AUX input solution through the Apple iPod's dock-connector that's compatible with the non-JBL and JBL audio system. By selecting MiniDisc mode, the SLI will not conflict with an internal or external cd-changer that's already connected.

 * JBL
 * Prius JBL Audio system response, specs, and photos
 * schematics
 * installation thread & PDF

 * XM radio
 * Eddie Bell's installation guide

Bluetooth

 * Prius models with navigation have a Bluetooth handsfree kit for cell phones, allowing you to use the speakers and microphone already in the car as a speakerphone with compatible phones.
 * Bluetooth Addressbook Transfer using Laptop
 * Bluetooth Addressbook Transfer using PDA
 * ProClip phone / accessory mount for Prius

Heating and Cooling

 * Since the 2004 model year, the Prius has electric air conditioning that does not need the engine to remain running. However, the air conditioning does present a drain on the battery, so the engine will run more often with it on or set colder than if it were off or set warmer.

 * The majority of the heat comes from the engine, like any traditional car. In cold weather, the engine will run longer and more often. Turning the temperature down helps some. There is also an electric heater which helps warm the car. The electric heater can be brought into play by adjusting the desired cabin temperature to "Hi" (that's one notch above 85 degrees). Like most vehicles, the Prius will heat up faster when driven and there is no need to allow the car to idle to warm up before driving.

Navigation System
Starting in the 2006 model and in any upgrade from older GPS software to version 6.1, it is no longer possible to override the "greying out" of the function buttons while the car is in motion. This means that while the car is moving, your passenger cannot input a destination address. Previous to this, there was an override function available.
 * Override stopped working after 2005

The link below has information on pre-2005/V6.1 units, but is missing any information for later units.
 * Override Navigation Disabling While in Motion

The voice command can be disabled, as shown in the following link, but there is still a delay equal in length to the original voice command, so disabling it does not completely solve the problem. Also, some voice preambles reportedly remain even after disabling the main preamble.

 * Disable Voice Command Preamble Before the Beep

Seats

 * Many people have reported that the seats in the Prius are hard and uncomfortable.
 * If comfort is a priority for you, make sure you take a test drive or two before deciding to buy.
 * US version of the Prius does not have height-adjustable driver seats;
 * European and Asian versions do.

Fuel System

 * Fuel Type: The Prius is designed to run on unleaded 87 octane fuel (85 in high altitudes) (R+M)/2 method ; there is no advantage to using higher-grade fuel.

 * The FTC says:
 * "In most cases, using a higher octane gasoline than your owner's manual recommends offers absolutely no benefit. It won't make your car perform better, go faster, get better mileage or run cleaner."

 * Octane is the measure of a fuel's resistance to autoignition (detonation or pre-ignition) that can occur as the fuel/air mixture is compressed. Engines with higher compression ratios generally require higher antiknock index fuel, while lower-compression engines safely burn regular-grade gasoline. Modern engines frequently incorporate piezoelectric sensors that detect pre-ignition (knocking) and quell it by retarding the spark timing, which can prevent engine damage but usually reduces performance and efficiency.

 * Fuel Tank/Gauge: The North American Prius uses a rubber bladder system besides a charcoal filter for gas vapor emissions control. However, the rubber is temperature sensitive and will shrink/stiffen in cooler weather lowering the tank capacity from the default 11.9 gallons, and contributing to a wildly inconsistent fuel gauge.  This is similar to the "memory" in NiCad batteries.  Slow filling of the tank with careful "burping" of the fuel inlet past the first "click-off", without spilling, will stretch the bladder back out and restore the original tank capacity.

 * Page 206; The tank is 45L (11.9 gal., 9.9 Imp.gal) and decreases by 5L (1.3 gal., 1.1 Imp.gal) @ -10°C/14°F.

 * MPG display on the Multi-Function Display (MFD): The numbers shown on the Consumption screen are the instantaneous values measured from the fuel-flow through the fuel-injectors. On the 2005 model, the average MPG will reset if the tank is refilled with more than 3? gallons of gas so allowing only tank MPG.  On the 2006 model it will not reset until the reset button has been pressed thus allowing lifetime MPG.

Tires
Goodyear Integrity x 4 Tires without "Low Rolling Resistance" (LRR) will negatively affect gas mileage by as much as 6mpg.
 * 2004-2006 HSD Prius
 * 185/65 R15 (855 revs per mile)
 * 15" OEM wheels (rims) are 6.45kg (14.2lbs)
 * 16" OEM wheels (rims) are 6.90kg (15.2lbs)
 * Plus Sizing:
 * plus 0 (R15): 195/60 (+1.0% fast)
 * plus 1 (R16): 195/55 (+0.1% fast), 215/50 (0% exact match)
 * plus 2 (R17): 195/50 (-0.9% slow), 205/45 (+0.8% fast), 215/45 (-0.6% slow) not recommended due to MPG loss by increased unsprung weight and rolling resistance
 * http://onlinepubs.trb.org/onlinepubs/sr/SR286Rolling_Resistance_Data.pdf
 * http://onlinepubs.trb.org/onlinepubs/sr/sr286.pdf

Driving Techniques

 * Tricks to reduce fuel consumption
 * Hypermiler Driving

Electronic

 * Beeps
 * The beeps you hear from making selections on the touchscreen can not be disabled in models prior to 2005(?).
 * How to eliminate the reverse beep & seatbelt beep
 * Or http://www.vfaq.net/FAQ-misc.html   also to eliminate reverse beep & seatbelt beep (for 2005).

 * EV Button Installation
 * The EV button, present on Prius models outside of North America, allows the vehicle to travel a short distance on battery power alone (given conditions such as sufficient charge and battery temperature).
 * efusco-style
 * htmlspinnr-style

 * Plug-in Conversions
 * The Prius is a preferential candidate for plug-in in conversions due to availability of model, the ease of the EV Button mod as well as a range of conversions available.
 * Engineer Conversion - most popular conversion

Physical

 * Sunroof/Moonroof
 * The Prius has an aerodynamically curved roofline different from other vehicles. This generally prevents a cookie-cutter installation of one.
 * However, PriusChat thread about custom installers who will do it

Shopping

 * BT Tech
 * BT Tech Chassis Stiffening Plate

 *
 * BT Tech Prius Tower Strut Brace

 *
 * BT Tech Prius Skid Plate

 * Sigma Automotive
 * Almost every Japanese Domestic Model (JDM) OE part available here for ordering

 * Toyota Prius For Sale and Auction
 * Toyota Prius cars and parts for sale and auction, new listings HOURLY!

Government

 * Toyota.com - Prius - Tax Info
 * ASE.org - Alliance to Save Energy - New Energy-Efficiency Home and Vehicle Tax Credits
 * EERE.Energy.gov - U.S. Dept. of Energy - State and Federal Laws and Incentives
 * go.UCSUSA.org - Union of Concerned Scientists - List of all Federal and State incentives for prospective hybrid owners.

2006 Federal Tax Credit
The 2006 federal income tax credit for the Toyota Prius was$1575 for purchases until March 31, 2007.
 * Purchases from January 1, 2006 through September 30, 2006 qualified for the full $3150 credit.

 * American Council for an Energy-Efficient Economy ACEEE.org
 * News Release - New Light-Duty Hybrid and Diesel Tax Credits for Consumers Estimated by ACEEE
 * Estimates of tax credits for 31 hybrid and diesel cars and light trucks

 * This credit is intended to offset the cost of a car being outfitted with hybrid technology.
 * Individuals can claim the credit for each vehicle that they purchase.

 * Since this is a tax credit your tax bill is reduced dollar for dollar, it will not reduce your tax bill below your alternative minimum tax.

 * Earned income credit and additional child tax credit are the only refundable credits (you can get back more than your tax liability if you qualify for these credits).
 * If your tax liability is less than the hybrid tax credit, it will reduce your tax liability to $0 but you will receive none of the remainder of the credit nor can it be carried over to the next tax year.
 * Planning Ahead for the Hybrid Car Tax Credit

 * Alternative Minimum Tax
 * Itemized deductions that are allowed for AMT are:
 * mortgage interest for purchase or remodeling of your home
 * medical/dental expenses above 10% of AGI
 * charitable gifts
 * casualty and theft losses
 * some miscellaneous deductions

 * Some itemized deductions that are not allowed for AMT are:
 * state and local income taxes
 * real and personal property taxes
 * loan interest not related to buying or improving your home

 * AMT allows fewer itemized deductions than the regular tax calculation. However, the AMT exemption is larger than the personal exemption.

 * Regular taxable income is taxed at 10%, 15%, 25%, 28%, 31%, and 35% in a progressive manner. Income subject to AMT is taxed at 26% and 28%, also progressive.

 * AMT used to be for the richest people, but it's affecting an increasing number of the middle class. A lot of people seem to think that they will get the full $3150 tax credit by buying a Prius in early 2006. It's better to crunch the numbers now and find out for sure than to get a nasty surprise in April 2007.

 * CNN Money - Alternative Minimum Tax 101

 * AMT Calculation
 * IRS.gov - AMT Assistant
 * HRBlock.com - H&R Block 2005 AMT Estimator
 * IRS Form 6251 - Alternative Minimum Tax—Individuals: instructions

 * Phase-out of the hybrid tax credit
 * ASE.org - Alliance to Save Energy - Phase-out of the hybrid tax credit
 * In short, the period for the full hybrid vehicle tax credit lasts at least through the second quarter of 2006.
 * The date you take possession of the vehicle (not the order date) is the applicable date for purposes of the tax credit.
 * The 60,000 hybrid vehicle threshhold includes all models the manufacture sells after December 31, 2005.

 * The 60k hybrid vehicles limit was reached by Toytoa in the second quarter of 2006, so the tax credit will follow the following schedule:
 * (2006Q1) - 100% $3150
 * (2006Q2) - 100% $3150
 * (2006Q3) - 100% $3150
 * (2006Q4) - 50%  $1575
 * (2007Q1) - 50%  $1575
 * (2007Q2) - 25%  $787.50
 * (2007Q3) - 25%  $787.50

 * Energy Policy Act of 2005
 * ne.DOE.gov - Energy Policy Act of 2005

 * Transcribed from Energy Policy Act of 2005
 * “(f) Limitation on Number of New Qualified Hybrid and Advanced Lean-Burn Technology Vehicles Eligible for Credit.--
 * “(1) In general.—In the case of a qualified vehicle sold during the phaseout period, only the applicable percentage of the credit otherwise allowable under subsection (c) or (d) shall be allowed.
 * “(2) Phaseout period.—For purposes of this subsection, the phaseout period is the period beginning with the second calendar quarter following the calendar quarter which includes the first date on which the number of qualified vehicles manufactured by the manufacturer of the vehicle referred to in paragraph (1) sold for use in the United States after December 31, 2005, is at least 60,000.
 * “(3) Applicable percentage.—For purposes of paragraph (1), the applicable percentage is—
 * “(A) 50 percent for the first 2 calendar quarters of the phaseout period,
 * “(B) 25 percent for the 3d and 4th calendar quarters of the phaseout period, and
 * “(C) 0 percent for each calendar quarter thereafter.

 * 2006 Tax Credit Strategy, How to get your $ faster

2005 Federal Tax Deduction
Under the current law, those in the top tax bracket would realize a maximum tax savings of $700 if they purchase a hybrid vehicle before January 01, 2006.
 * A deduction of $2000 was in effect until the end of 2005

 * How to Claim a Federal Tax Deduction
 * The Internal Revenue Service (IRS) requires that purchasers retain normal proof of purchase documentation as well as the Toyota Certification letter and Internal Revenue Service Acknowledgement letter as substantiation for the deduction.

 * Federal Tax Deduction Guidelines
 * The purchase of a new Prius (model years 2001 - 2005) must be completed on or before December 31, 2005, for the $2000 deduction.

Before using this important federal tax deduction on your tax return, please check with your tax advisor for possible additional state tax benefits and for any changes in the federal tax laws that might have occurred.

The federal tax deduction is not available for Prius lessees or purchasers of used Prius vehicles. To the extent applicable, this deduction is available to Prius purchasers regardless of whether you itemize deductions on your federal income tax return. Your overall federal tax benefit will depend on your individual tax situation, particularly if you claim depreciation deductions on your Prius. See your tax advisor for more details.

HOV Lane Access
Bay Area: from MercuryNews.com - Hybrid perks and more
 * California
 * HOV-lane access. As of early October, the DMV had issued about 27,000 carpool-access stickers to drivers of the Prius, Civic and Insight. The program will end once 75,000 permits are issued. Bay Area residents must apply for a FasTrak transponder. The state legislation requires a minimum of 45 mpg, so the Prius, Civic and older models of the Insight are eligible.
 * Santa Clara County - No Expressway Access (includes link to the Mercury News Mr Roadshow article): Loophole in the law, the carpool stickers do not apply to all diamond lanes. This refers to some carpool lanes Santa Clara County, not sure if it's the same in other counties.
 * New York
 * Pending - assembly.state.ny.us - A04278 Provides that operators of hybrid vehicles shall be permitted to travel in high occupancy vehicle lanes regardless of the number of passengers in such vehicle.

Local
New York’s Clean Pass Program - New York’s DMV Clean Pass Info. -
 * Clean Pass is an innovative program that will allow eligible low-emission, energy-efficient vehicles to use the 40-mile Long Island Expressway High Occupancy Vehicle (LIE/HOV) lanes beginning March 1st, regardless of the number of occupants in the vehicle. The program will result in an estimated reduction of 6,000 tons of greenhouse gas emissions and savings in excess of 500,000 gallons of gasoline You can apply by phone calling the State Department of Motor Vehicles at 1 (518) 486-9786, menu option 7, between 8 a.m. and 4 p.m., Monday through Friday.

 * Based on certain federal emission and fuel economy standards, eligible vehicles include the Toyota Prius Hybrid, model year 2001-2006; the Honda Civic Hybrid, model year 2003-2006; and the Honda Insight Hybrid, model year 2000-2004.

New York State Thruway Authority: E-ZPass Green Pass Discount Plan -
 * Offers a special 10% discount to Hybrid vehicles getting at least 45 miles to the gallon and meeting the California Super Ultra Low Emission Vehicle (SULEV)or pre-model year 2005 hybrid vehicles which are certified to the California Ultra Low Emission Vehicle (ULEV) standard.
 * The following is a list of currently eligible vehicles*:
 * Honda Insight - model years 2000-2004**
 * Toyota Prius - model years 2001-2006
 * Image: Honda Civic Hybrid - model years 2003-2006: * (No other alternate fuel or hybrid vehicles are eligible for the program at this time)
 * ** Note - Honda Insights - model years 2005-2006 do not meet the eligibility criteria because they do not meet California Air Resources Board SULEV emission requirements.

Complete List - see http://www.whybuyhybrid.com/hybrid-buying-incentives.htm#States

Private Sector

 * HybridCars.com - Corporate Incentives
 * - Helping Employees Into Hybrids
 * Mercury News - Hybrid perks and more

Buyers Guides

 * MercuryNews.com - 2006 hybrid buyers guide

Taking Delivery of Your Prius

 * Prius Pick-up Checklist

Glossary

 * Acronyms and Abbreviations Glossary

More Information

 * Hybrid Car Articles, Photos, Videos Articles, Photos, Videos
 * John's Information, tips, and photos
 * hobbit's huge and very complete link-farm
 * Yahoo's Prius-2G group FAQ
 * Prius Visual FAQ Home This is a listing of FAQs/VFAQs from the 2004 Prius community for various Modifications or Repairs.
 * FAQfarm
 * Toyota's FAQ
 * Toyota's paper on how the 2004 Prius is different from earlier models (in PDF, 2 MB)
 * Yale Faculty of Engineering Wiki

How Hybrids Work

 * FuelEconomy.gov
 * HowStuffWorks.com
 * How Hybrids Work

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Toyota Prius/FAQ


text:
Georgia Water/History

Chapter 5. Planning

 * 5.3. History of Water Resources Planning in Georgia
 * Contributors

 * 1963 - Southeastern River Basin Plans  by river basin
 * 1974 - CWA Section 303e River Basin Water Quality Reports by river basin
 * 1981 - State Planning Grant from U.S. Water Resources Council
 * 1984 - EPD Water Use and Availability Reports  by river basin
 * 1989 - Georgia Growth Strategies Commission
 * 1990 - Georgia Regional Reservoir Plan (appendix in West Georgia Reservoir report)
 * 1992 - Georgia River Basin Management Planning Act, plans for each river basin
 * 1998 - ACF Comprehensive Study
 * 2002 - Georgia Joint Study Committee Report
 * 2003 - Metropolitan North Georgia Water Resources Planning District
 * 2003 - Georgia Drought Management Plan
 * 2004 - Georgia Comprehensive Statewide Water Resources Planning Act
 * 2005 - Georgia Coastal Sound Science Initiative

title: Georgia Water/History


text:
Wikijunior:Ancient Civilizations/Arabian

When did Arabian civilization exist?
The earliest known mention of Arabian people was in 853 BC where they were listed as one of the peoples defeated by the Assyrians.

Where did they live?

Arabians lived in Arabia, a peninsula in the southwest of Asia.

Arabia has several different regions. The biggest part, which is the interior part of the peninsula, is desert. It was populated by nomadic tribes who frequently invaded richer lands and their caravans.

The northern and southern regions were inhabited by more civilized people. Arabians in the northern regions were in contact with the Romans and Persians.

The southern part (Arabia Felix) was relatively greener than the other regions. Its people were engaged in trading, particularly trading spices from India as well as expensive aromatic substances, called frankincense and myrrh, which were obtained from certain trees of their land and were used in perfumery and medicines.

What did they eat?
Arabians ate dates, camel milk, bread (made of barley and wheat), lizards, locusts, meat, grapes, and olives.

What did they wear?
Arabians wore simple, loose, long garments and headwear.

What did their writing look like?
Their writing was similar to other Semitic writing. They wrote from right to left. They did not have any dedicated letters for vowels.

What do they believe?
Most Arabians were polytheistic pagan people; that means they believed in many gods. Of all the gods they believed in, the sun god and the moon god were most important. There were also some Jewish tribes in Arabia before the rise of Islam.

What did their buildings look like?
Many Arabians preferred to live in tents, particularly the nomadic Arabs. Others lived in houses made of mud. Some Arabians of northern Arabia built structures by excavating solid rock out of mountains.

Legend says the first building of Arabia was the Holy Kaaba, the house of God, built by Prophet Ibrahim and his son, Ismail.

Are some of them famous even today?
The Queen of Sheba, who according to the Bible had a visit to King Solomon, is believed by some to have been from the south Arabian Kingdom of Saba.

Muhammad, who lived in Arabia, was the last prophet of Islam.

Wikijunior Alte Zivilisationen/ Araber


text:
High School Physics

This book will educate high school students in the concepts of physics and how they apply to everyday life. The eventual goal of this book is to help student to understand difficult concepts by breaking them down into smaller parts and using analogy. The goal is a Physics book that makes sense to anyone who desires to understand it. It should strive to use helpful diagrams and be entertaining. It should utilize the online format to take advantage of videos, animations, simulations and other tools not available in print media to aid understanding.

How to use this book

 * 1) /Newtons Apple/: Using the bounty of the internet to expand upon concepts.

Introduction

 * 1) /Introduction to physics/: Why physics is relevant and useful
 * 2) Si units and conversions: Things are only relative.
 * 3) /A brief look/: What are we going to study under each chapter.

Translational Motion

 * 1) /Vector Kinematics/
 * 2) /Force/: Why sumo wrestlers tend to break tables and eat lots of food.
 * 3) /Acceleration/: The speed of competitive eaters.
 * 4) /Velocity/: Speed at its best.
 * 5) /Projectile motion/: Why Newton could not possibly catch the apple on his head.
 * 6) Momentum and Impulse: Energy and airbags.
 * 7) /Gravitation/: Why satellites are so predictable and gravity brings all object down at a constant acceleration (without air resistance)
 * 8) /Simple Oscillation/: The bouncing of springs.

Rotational Motion

 * 1) /Rotational Motion/: How round can you spin?
 * 2) /Energy/: Why sumo wrestlers have so much endurance.
 * 3) /Waves/: Why things tend to wiggle and wobble.
 * 4) /Optics/: Light
 * 5) /Acoustics/: Sound

Thermodynamics

 * 1) /Temperature Scales/: Lord Kelvin's battle with heat.
 * 2) /Heat/: The true nature of exploding things
 * 3) /Concept Summary/: All the concepts and equations in an easy to digest page.

Fluids

 * 1) Fluids: Pressure: Can you handle the pressure?

Electric Circuits

 * 1) Ohms law: Gloves and Toasters
 * 2) Voltage, Current: 24,000 volt schocker!
 * 3) Parallel, Series: To share or not to share.

Appendices

 * 1) /Index of physics equations/: All the good stuff in one place.
 * 2) /How to solve physics problems/: our good friend the triangle and the doodle.
 * 3) /Physical intuition/: How to use real world observations and make reasonable predictions.
 * 4) /Physics experiments/: Readings based experiments.

Supplemental Materials for learning

 * /Mid semester cheat sheet / equation reference/: A printable page which will include physics equations. in very small print!
 * /Applied Physics Experiments/: Experiments which are made with common household materials. Expands on concepts.
 * /Physics: The Cookbook Approach/: At this level of understanding, all you need is your essential "equation" ingredients and the right know how of how to do it.
 * /The Beauty of Physics/: How nature is expressed by such simple equations.
 * /Physics and Philosophy/: How natural movement of such forces leads to the universal understanding of the cosmos.

Contributors

 * 146.244.137.105 — Toni Nguyen, San Diego State University

Fysiikan oppikirja Fisica per le superiori Fisika SMA 高等学校物理 Fizyka dla liceum Fysik A

title: High School Physics


text:
User:Sykil~enwikibooks

I'm normal.

title: User:Sykil~enwikibooks


text:
Talk:Bookbinding/Bone folder

I'm not sure that this should be an article in wikibooks. It looks more like a stub in wikipedia. More likely, it should be merged with the rest of the "equipment" part of the article.

title: Talk:Bookbinding/Bone folder


text:
Talk:Bookbinding/Saddle stitch

Should we have a glossary for bookbinding terms within this wikibook, or should we instead link to wikipedia and make articles there?

Gutter seems too obscure to warrant a wikipedia article, but signature, pamphlet and many of the tools seem important enough to warrant an encyclopedic article on their history for instance.

Wikipedia's bookbinding article has a wonderful terms section, is it possible to hotlink the individual sections of an article? I have a feeling it is, I just have to figure out how.

Also, I don't think stapling is really a kind of saddle stitch. It serves the same purpose, but a how-to on saddle stitch would be more useful. At the Minnesota Center for the Creation of Book Art, most people call stapling "stapling" and call sewing a single codex "pamphlet stitch" and use the term saddle stitch for sewing a whole book with multiple codices.

Lotusduck 01:34, 9 November 2005 (UTC)lotusduck

title: Talk:Bookbinding/Saddle stitch


text:
User:Lotusduck~enwikibooks

I am the lotusduck.

I am feverently overjoyed by the how-to section here, and the language section. Learning is for everyone.

I am adding to botany some transitions and contrasts evolution-wise between the articles. I will likely be actively editing and adding to that and the wikipedia articles related to it until Christmas, when my botany class ends and I have far less need to study botany.

I have started Tagalog/Lesson 1 with my mom. Lessons are basically copied from french (with the french replaced with tagalog) for want of ideas of what to teach. She is a native from Manila, and we will be recording her saying the things on the module shortly. We don't know anyone who speaks another Philippine language. Sorry! Do you? Seriously, somebody help, or try to learn tagalog or something. I need input. And help.

For the time being my contributions will be more academic than book arts, because I'm just a little wound up in all this ecology business. But consider this to be an official to-do: it is absolutely neccessary that there is a developed wiki page for people to learn and share bookbindings. I will do diagrams of slightly more complicated japanese stab bindings, and find my stiff leaf book I made so I can remember how that goes.

Finally, I find the Arts Dance section to be a potential to free people that just want to learn something and get some exercise from being conned by some of those expensive dance videos. As such, I am recruiting an extremely good dancer I know to make videoclips and articles on various dance forms. Expect some small changes and additions to dance pages in the meantime, and videoclips and expanded descriptions over witer break.

title: User:Lotusduck~enwikibooks


text:
Talk:Botany/Plant morphology

Experts! Many people have talked to me about a "plant boundry layer" which has been described as the air around a leaf. A plant expands it's boundry layer by having rattly leaves and makes it's boundry layer small and humid by having hairs on it's leaves, or by having compound leaves (I think!). However- I cannot find any resources for this concept. Usually I've had luck finding public domain science information through government sites, but there is an unrelated (again, I think) physics concept that plagues these searches. So, yeah. Any help? - Lotusduck 01:44, 4 November 2005 (UTC)lotusduck
 * Well I think you are right in that the concept you are pursuing makes sense and there must exist sources of information out there that can provide details. I suspect your problem is this: you are putting too much faith in the internet. As great a source of information as the internet is, it is unreal to expect that all knowledge is now available on-line if only you could figure out where to look.  If I learned nothing else as a graduate student, it was how to move out from the more general knowledge contained in books (i.e., textbooks) to what we called the foreskin of science.  To track a specific question or esoteric point or subject to its very end point: where the published knowledge presently exists. It is a process that must be done in a good University library, using various sources that track journal publications. That effort will usually get you to within a few years of current knowledge.  Crossing that final gap requires knowing who is doing what research in the field or on the specific question and then contacting them. Until you get into the journals on published literature on the subject of "boundary layer" concepts, you will not see much about it. - marsh 04:29, 4 November 2005 (UTC)

title: Talk:Botany/Plant morphology


text:
User:FourOhFour

I am not the Wikipedia user Fourohfour. I am, however, the Wikipedia user FourOhFour, although I don't edit there much. Sorry for any confusion this may have caused.

title: User:FourOhFour


text:
User:JVz

Go see my Wikipedia user page instead.

Current Works

 * The Science of Su Doku

title: User:JVz


text:
User:FlyingPenguins

Please refer to my Wikipedia user page for more information about me. Place Wikibooks-related discussions in my user discussion page.

title: User:FlyingPenguins


text:
Engineering Acoustics/Acoustics in Violins

= Acoustics of the Violin =

For detail anatomy of violin, please refer to Atelierla Bussiere.

General Concept
When a violinist bows a string, which can produce vibrations with abundant harmonics. The vibrations of the strings are structurally transmitted to the bridge and the body of the instrument through the bridge. The bridge transmits the vibrational energy produced by the strings to the body through its feet, further triggering the vibration of body. The vibration of the body determines sound radiation and sound quality, along with the resonance of the cavity.

String
The vibration pattern of the strings can be easily be observed. To the naked eye, the string appears to move back and forth in a parabolic shape (see figure), which resembles the first mode of free vibration of a stretched string. The vibration of strings was first investigated by Hermann Von Helmholtz, the famous mathematician and physicist in 19th century. A surprising scenario was discovered that the string actually moves in an inverse “V” shape rather than parabolas (see figure). What we see is just an envelope of the motion of the string. To honor his findings, the motion of bowed strings had been called “Helmholtz motion.”

Bridge
The primary role of the bridge is to transform the motion of vibrating strings into periodic driving forces by its feet to the top plate of the violin body. The configuration of the bridge can be referred to the figure. The bridge stands on the belly between f holes, which have two primary functions: One is to connect the air inside the body with outside air, and the other one is to make the belly between f holes move more easily than other parts of the body. The fundamental frequency of a violin bridge was found to be around 3000 Hz when it is on a rigid support, and it is an effective energy-transmitting medium to transmit the energy from the string to body at frequencies from 1 kHz to 4 kHz, which is in the range of keen sensitivity of human hearing. If a violinist desires a darker sound from the violin, he or she may attach a mute to the top of the bridge. The mute is actually an additional mass which reduces the fundamental frequency of the bridge. As a result, the sound at higher frequencies is diminished since the force transferred to the body has been decreased. On the other hand, the fundamental frequency of the bridge can be raised by attaching an additional stiffness in the form of tiny wedges, and the sound at higher frequencies will be amplified accordingly.

The sound post connects the flexible belly to the much stiffer back plate. The sound post can prevent the collapse of the belly due to high tension force in the string, and, at the same time, couples the vibration of the plate. The bass bar under the belly extends beyond the f holes and transmits the force of the bridge to a larger area of the belly. As can be seen in the figure, the motion of the treble foot is restricted by the sound post, while, conversely, the foot over bass bar can move up and down more easily. As a result, the bridge tends to move up and down, pivoting about the treble foot. The forces appearing at the two feet remain equal and opposite up to 1 kHz. At higher frequencies, the forces become uneven. The force on the soundpost foot predominates at some frequencies, while it is the bass bar foot at some.

Body
The body includes top plate, back plate, the sides, and the air inside, all of which serve to transmit the vibration of the bridge into the vibration of air surrounding the violin. For this reason, the violin needs a relatively large surface area to push enough amount of air back and forth. Thus, the top and back plates play important roles in the mechanism. Violin makers have traditionally pay much attention on the vibration of the top and back plates of the violin by listening to the tap tones, or, recently, by observing the vibration mode shapes of the body plates. The vibration modes of an assembled violin are, however, much more complicated.

The vibration modes of top and back plates can be easily observed in a similar technique first performed by Ernest Florens Friedrich Chaldni (1756–1827), who is often respectfully referred “the father of acoustics.” First, the fine sand is uniformly sprinkled on the plate. Then, the plate can be resonated, either by a powerful sound wave tuned to the desired frequencies, by being bowed by a violin bow, or by being excited mechanically or electromechanically at desired frequencies. Consequently, the sand disperses randomly due to the vibration of plate. Some of the sand falls outside the region of plate, while some of the sand is collected by the nodal regions, which have relatively small movement, of the plate. Hence, the mode shapes of the plate can be visualized in this manner, which can be referred to the figures in the reference site, Violin Acoustics. The first seven modes of the top and back plates of violin are presented, with nodal lines depicted by using black sands.

The air inside the body is also important, especially in the range of lower frequencies. It is like the air inside a bottle when you blow into the neck, or, as known as Helmholtz resonance, which has its own modes of vibration. The air inside the body can communicate with air outside through the f holes, and the outside air serves as medium carrying waves from the violin.

see www.violinbridges.co.uk for more articles on bridges and acoustics.

Sound Radiation
A complete description of sound radiation of a violin should include the information about radiation intensity as functions both of frequency and location. The sound radiation can be measured by a microphone connected to a pressure level meter which is rotatably supported on a stand arm around the violin, while the violin is fastened at the neck by a clip. The force is introduced into the violin by using a miniature impact hammer at the upper edge of the bridge in the direction of bowing. The detail can be referred to Martin Schleske, master studio for violinmaking. The radiation intensity of different frequencies at different locations can be represented by directional characteristics, or acoustic maps. The directional characteristics of a violin can be shown in the figure in the website of Martin Schleske, where the radial distance from the center point represents the absolute value of the sound level (re 1Pa/N) in dB, and the angular coordinate of the full circle indicates the measurement point around the instrument. According to the directional characteristics of violins, the principal radiation directions for the violin in the horizontal plane can be established. For more detail about the principal radiation direction for violins at different frequencies, please refer to reference (Meyer 1972).

References And Other Links
Back to the main page
 * Violin Acoustics
 * Paul Galluzzo's Homepage
 * Martin Schleske, master studio for violinmaking
 * Atelierla Bussiere
 * Fletcher, N. H., and Rossing, T. D., The physics of musical instrument, Springer-Verlag, 1991
 * Meyer, J., "Directivity of bowed stringed instruments and its effect on orchestral sound in concert halls", J. Acoustic. Soc. Am., 51, 1972, pp. 1994–2009


text:
Wikijunior:New Book Collaboration

Wikijunior New Book Collaboration is a way to give new books exposure on the front page of Wikijunior.

Current Wikijunior New Book Collaboration
edit template

Previous Voting Results

 * 2nd Quarter 2006 - Wikijunior: Languages (8 votes)
 * 3rd Quarter 2006 - Wikijunior: How Things Work (9 votes)
 * 4th Quarter 2006 - Wikijunior: The Elements (7 votes)
 * 1st Quarter 2007 - Wikijunior: Bugs (11 votes)
 * 2nd Quarter 2007 - Wikijunior: Human Body (7 votes)
 * 3rd Quarter 2007 - Wikijunior: World War II (4 votes)
 * July 2007 - inconclusive

title: Wikijunior:New Book Collaboration


text:
Talk:Dutch/Alfabet

/Archive/

IPA
The usage of the International Phonetic Alphabet is inconsequent. Sometimes SAMPA and IPA are mixed with eachother. There are soms errors, for example "keur" pronounced as /kœːr/. That is wrong, and it should be [kʏːr]. The next week I will look into it. Hans Kamp (discuss • contribs) 13:37, 21 April 2016 (UTC)

title: Talk:Dutch/Alfabet


text:
Template:Wikijunior:New Book Voting Rules

Voting Rules
Nomination

 * Wikijunior projects will be at first proposed on New Title Suggestions to organize the proposal.
 * Anyone can make a proposal and add a nomination.
 * Once the project has been described to the satisfaction of the nominators, it can be added as an option to the voting page.

Voting
 * Only registered Wikibooks users, who are logged in and have a minimum of 20 edits, are eligible to vote. (checked by contribution history)
 * A voter can vote in support of as many nominated titles as he or she likes by editing the appropriate sections and inserting on a new line  # ~ . This adds a new numbered list item with your username and the time your vote was casted.
 * Lengthy comments and discussions should take place on the New Title Suggestions page. A short comment giving a simple reason for voting is acceptable.

Evaluation
 * Votes will be evaluated on the first day of each subsequent month.
 * The winning project is the nomination with the most valid support votes and a minimum of 5 votes. Opposing votes are discarded. (see Approval voting).
 * In case of a tie, the older projects will be selected (by project proposal history).
 * Each project that receives any valid support votes will be automatically nominated for the following month.
 * Winning projects will be added to the list of "approved" Wikijunior projects and the new project will be formally started.


text:
Wikijunior:New Book of the Quarter/2006-1st Quarter Vote

Voting for the Wikijunior New Book of the Quarter is open from now until January 1st, 2006 00:01 UTC. The winning New Book of the Quarter will become the next Wikijunior project and will influence the future direction of Wikijunior.

How Things Work
Votes:
 * 1) Rob Horning 08:10, 4 November 2005 (UTC)
 * 2) Klingoncowboy4 07:45, 28 November 2005 (UTC)
 * 3) JMRyan 22:07, 29 November 2005 (UTC)
 * 4) Mattwj2002 14:06, 1 December 2005 (UTC)
 * 5) Snargle 19:24, 7 December 2005 (UTC)
 * 6) Lincher 16:07, 16 December 2005 (UTC)
 * 7) Bvcxz 15:23, 17 December 2005 (UTC)

Dinosaurs
Votes:
 * 1) --Enyo 10:52, 4 November 2005 (UTC)
 * 2) --Lord Voldemort  (Dark Mark)  17:29, 4 November 2005 (UTC)
 * 3) -- user:zanimum
 * 4) ∞ 19:06, 26 November 2005 (UTC)
 * 5) Klingoncowboy4 07:45, 28 November 2005 (UTC)
 * 6) JMRyan 22:07, 29 November 2005 (UTC)
 * 7) N1person 22:15, 19 December 2005 (UTC)
 * 8) kokostephi 20:04, 27 December 2005 (UTC)

The Elements
Votes:
 * 1) --Lord Voldemort  (Dark Mark)  17:42, 4 November 2005 (UTC)
 * 2) ∞ 19:07, 26 November 2005 (UTC)
 * 3) Klingoncowboy4 07:45, 28 November 2005 (UTC)
 * 4) Magicmonster 01:42, 7 December 2005 (UTC)
 * 5) Shanel 22:26, 11 December 2005 (UTC)
 * 6) N1person 14:54, 21 December 2005 (UTC)

Learning Series
Votes:

Moving and Growing
Votes:
 * 1) --Lord Voldemort  (Dark Mark)  17:29, 4 November 2005 (UTC)
 * 2) Bvcxz 16:19, 19 December 2005 (UTC)
 * 3) Klingoncowboy4 20:22, 20 December 2005 (UTC)
 * 4) N1person 14:54, 21 December 2005 (UTC)


text:
User:Xanous

Introduction
Hello, I'm Xanous. Very new to Wiki, don't hurt me.

Current Project
Medieval_Total_War_Guide

title: User:Xanous


text:
Corset/History/Victorian

Victorian Corsets, c1880 - 1901
Most people have an idea of a "Victorian corset"; however, the British Victorian era comprised a long period of changes in culture and fashion from 1837 to 1901. During that time many styles of corsets were in use. The most ubiquitous feature was the "horizontal waist" which was common from about 1850 to 1899.

title: Corset/History/Victorian


text:
Talk:Bicycles/Penetrating oil

kroil is the best.can not be beat

title: Talk:Bicycles/Penetrating oil


text:
CAT-Tools/DéjàVu X/use the Build Lexicon option

For more information on Déjà Vu's Lexicon feature, please read the DVX Help.  A nice review of this feature (applying to both DV3 and DVX) written by Ruud Harmsen is found here: http://rudhar.com/sfreview/dv/lexicon.htm

How to use the Build Lexicon option in DVX (As outlined by Dave Turner in a message to dejavu-l@yahoogroups.com - Thanks Dave!)

Scope: Current file or All files. occurrences Source text (ascending) occur most frequently empty targets
 * Lexicon > Build lexicon > Limit maximum number of words per entry to: 4.
 * Lexicon > Remove entries > Rows with: 4 or less words in source, 2 or less
 * Select the Lexicon in the File Navigator and click on Toggle sorting.
 * Sort by 1. Number of words (ascending), 2. Frequency (descending), 3.
 * Start by translating the immediately obvious 2-word and 3-word terms that
 * Delete all rows with empty targets: Lexicon > Remove entries > All rows with


text:
Talk:Ancient History/Greece/Sparta

Oh, wow, David, I absolutely *love* the edits you made. :-) --Enyo 10:34, 4 November 2005 (UTC)

 * Well, um, thank you! I now have the page on my watchlist, so will happily read / edit / comment on in future. Good luck!  David Kernow 18:01, 4 November 2005 (UTC)

Why dont you put something political about the spartans on here? And next time, dont put edit on any of these. Jeez. Honestly. Some people actually come on here to learn things. I mean you learn a whole lot of things from this site, dont get me wrong, but put something political about them. I'm sure people would want to know about their political environment. I would put something political about the Spartans on here, but I dont know anything political about them. Make people actually want to come to this site. —The preceding unsigned comment was added by 71.211.149.102 (talk • contribs) 05:11, 24 Jan 2007 (UTC)

title: Talk:Ancient History/Greece/Sparta


text: Template:IndicText

title: Template:IndicText


text:
Engineering Acoustics/Attenuation of Sound Waves

Back to main page

Introduction
When sound travels through a medium, its intensity diminishes with distance. This weakening in the energy of the wave results from two basic causes, scattering and absorption. The combined effect of scattering and absorption is called attenuation. For small distances or short times the effects of attenuation in sound waves can usually be ignored. Yet, for practical reasons it should be considered. So far in our discussions, sound has only been dissipated by the spreading of the wave, such as when we consider spherical and cylindrical waves. However this dissipation of sound in these cases is due to geometric effects associated with energy being spread over an increasing area and not actually to any loss of total energy.

Types of Attenuation
As mentioned above, attenuation is caused by both absorption and scattering. Absorption is generally caused by the media. This can be due to energy loss by both viscosity and heat conduction. Attenuation due to absorption is important when the volume of the material is large. Scattering, the second cause of attenuation, is important when the volume is small or in cases of thin ducts and porous materials.

Viscosity and Heat conduction
Whenever there is a relative motion between particles in a media, such as in wave propagation, energy conversion occurs. This is due to stress from viscous forces between particles of the medium. The energy lost is converted to heat. Because of this, the intensity of a sound wave decreases more rapidly than the inverse square of distance. Viscosity in gases is dependent upon temperature for the most part. Thus as you increase the temperature you increase the viscous forces.

Boundary Layer Losses
A special type of absorption occurs when a sound wave travels over a boundary, such as a fluid flowing over a solid surface. In such a situation, the fluid in immediate contact with the surface must be at rest. Subsequent layers of fluid will have a velocity that increases as the distance from the solid surface increases such as in the figure below.

The velocity gradient causes an internal stress associated with viscosity, that leads to a loss of momentum. This loss of momentum leads to a decrease in the amplitude of a wave close to the surface. The region over which the velocity of the fluid decreases from its nominal velocity to that of zero is called the acoustic boundary layer. The thickness of the acoustic boundary layer due to viscosity can be expressed as

$$\delta_{visc}=\sqrt{\left(\frac{ 2*\mu}{\omega*\rho_o}\right)}$$

Where $$ \mu \,$$ is the shear viscosity number. Ideal fluids would not have a boundary layer thickness since $$ \mu=0 \,$$.

Relaxation
Attenuation can also occur by a process called relaxation. One of the basic assumptions prior to this discussion on attenuation was that when a pressure or density of a fluid or media depended only on the instantaneous values of density and temperature and not on the rate of change in these variables. However, whenever a change occurs, equilibrium is upset and the media adjusts until a new local equilibrium is achieved. This does not occur instantaneously, and pressure and density will vary in the media. The time it takes to achieve this new equilibrium is called the relaxation time, $$ \theta \,$$. As a consequence the speed of sound will increase from an initial value to that of a maximum as frequency increases. Again the losses associated with relaxation are due to mechanical energy being transformed into heat.

Modeling of losses
The following is done for a plane wave. Losses can be introduced by the addition of a complex expression for the wave number

$$k=\ \beta-j\alpha$$

which when substituted into the time-solution yields

$$\ p = A e^{-\alpha x}e^{jwt-j\beta x}$$

with a new term of $$\ e^{-\alpha x}$$ which resulted from the use of a complex wave number. Note the negative sign preceding $$\alpha$$ to denote an exponential decay in amplitude with increase values of $$x$$.

$$\ \alpha$$ is known as the absorption coefficient with units of nepers per unit distance and $$\ \beta$$ is related to the phase speed. The absorption coefficient is frequency dependent and is generally proportional to the square of sound frequency. However, its relationship does vary when considering the different absorption mechanisms as shown below.

The velocity of the particles can be expressed as

$$\ u=\frac{k}{w*\rho_o}p= \frac{1}{\rho_o c}\left(1-j\frac{\alpha}{k}\right)p$$

The impedance for this traveling wave would be given by

$$\ z= \rho_o c\frac{1}{1-j\frac{\alpha}{k}}$$

From this we can see that the rate of decrease in intensity of an attenuated wave is $$\ a=8.7\alpha$$


text:
Embedded Systems/RTOS Implementation

The chapters in this section will discuss some of the general concepts involved in writing your own Real-Time Operating System. Readers may be able to read and understand the material in these pages without prior knowledge in operating system design and implementation, but a background knowledge in those subjects would certainly be helpful.

Memory Management
An important point to remember is that some embedded systems are locked away and expected to run for years on end without being rebooted. If we use conventional memory-management schemes to control memory allocation, we can end up with fragmented memory which can take valuable time to defragment and really is a major problem for tasks that are time-sensitive. This page then will talk about how to implement a memory management scheme in an RTOS, and will talk through to a basic implementation of malloc and free.

There are a variety of ways to deal with memory:
 * Some systems never do a malloc or free -- all memory is allocated at compile time.
 * Some systems use malloc and free with manual garbage collection.
 * With manual garbage collection, it's possible to fragment memory so badly that one day the system locks up because there is no one piece of memory large enough for a reasonably-large malloc request, although the total size of the many free pieces of memory add up to far more than that the requested malloc, which would be bad.
 * A small, almost unnoticeable bug could slowly leak memory until the system ran out of memory and locked up, which would be bad.
 * Some early automatic garbage collection schemes did a "stop the world" for several seconds during garbage collection and/or memory defragmentation. Such a system could miss real-time deadlines, which would be bad.
 * Some later automatic garbage collection schemes do "incremental" garbage collection and memory defragmentation.
 * Many real-time systems allocate memory one block at a time from a pool of fixed-size memory blocks. This entirely eliminates external fragmentation.

What is a Task
Embedded systems have a microprocessor connected to some piece of hardware (LEDs, buttons, limit switches, motors, serial port(s), battery chargers, etc.).

Each piece of hardware is generally associated with a little bit of software, called a "task". For example, "Check the keyboard and figure out which (if any) key has been pressed since the last check". Or "Check the current position of the spindle, and update the PID".

Often a task has a real-time limits, such as
 * the motors must be shut off within 1/10 second after hitting the limit switch to avoid permanent damage
 * the PID loop must be updated at least every 1/100 second to avoid oscillation
 * the MP3 player must decode a new sample at 44.1 kHz—no faster, or it sounds chipmunk-like—no slower, or it sounds like it's underwater.

Some embedded systems have only one task.

Other embedded systems have a single microcontroller connected to many different pieces of hardware—they need to "multi-task".

task communication and synchronization
Most RTOSes have some way to allow tasks to communicate and synchronize with each other, usually one or more of:
 * message passing (often highest-priority-message first, rather than first-in first-out)
 * event flags
 * mutual exclusion mechanisms: serializing tokens, mutex, semaphore, monitor, etc.

What is the Scheduler
The "task scheduler" (or often "scheduler") is the part of the software that schedules (chooses) which task to run next.

The scheduler is arguably the most difficult component of an RTOS to implement. Schedulers maintain a table of the current state of each task on the system, as well as the current priority of each task. The scheduler needs to manage the timer too.

In general, there are 3 states that a task can be in:

 * 1) Active. There can be only 1 active thread on a given processor at a time.
 * 2) Ready. This task is ready to execute, but is not currently executing.
 * 3) Blocked. This task is currently waiting on a lock or a critical section to become free.

Some systems even allow for other states:

 * 1) Sleeping. The task has voluntarily given up control for a certain period of time.
 * 2) Low-Priority. This task only runs when all other tasks are blocked or sleeping.

There are 2 ways the scheduler is called:
 * the current task voluntarily yields to the scheduler, calling the scheduler directly, or
 * the current task has run "long enough", the timer hardware interrupts it, and the timer interrupt routine calls the scheduler.

The scheduler must save the current status of the current task (save the contents of all registers to memory associated with that task), it must look through the list of tasks to find the highest priority task in the Ready state, and then must switch control back to that task (by restoring all register values from memory associated with the new task).

The scheduler should first check to ensure that it is enabled. If the scheduler is disabled, it shouldn't preempt the current thread. This can be accomplished by checking a current global flag value. Some functions will want to disable the scheduler, so this flag should be accessible by some accessor method. An alternate method to maintaining a global flag is simply to say that any function that wants to disable the scheduler can simply disable the timer. This way the scheduler never gets called, and never has to check any flags.

A few RTOSes disable the process scheduler during the entire duration of system calls—to avoid missing deadlines, this requires that system calls finish very quickly. Other RTOSes have preempt-able system calls; they only disable the process scheduler and other interrupts for extremely short "critical sections".

We will talk more about those functions that need to (briefly) disable the scheduler, inside their critical sections, in the next chapter, ../Locks and Critical Sections/.

Another book Operating System Design/Scheduling Processes/Preemption goes into more detail on various scheduler algorithms.

Interrupts
One main difference between an RTOS and other operating systems is that a RTOS attempts to minimize interrupt latency—the response time to external hardware. This requires minimizing the amount of time that interrupts (including the timer interrupt) are disabled. Some RTOS vendors publish worst-case interrupt disable times.

title: Embedded Systems/RTOS Implementation


text:
Embedded Systems/Locks and Critical Sections

An important part of an RTOS is the lock mechanisms, and the Critical Section (CS) implementation. This section will talk about some of the problems involved in creating these mechanisms.

Basic Critical Sections
Most embedded systems have at least one data structure that is written by one task and read by another task. With a preemptive scheduler, it is all too easy to write software that *seems* to work fine most of the time, but occasionally the writer will be interrupted right in the middle of updating the data structure, the RTOS switches to the reader task, and then the reader chokes on the inconsistent data.

We need some way of arranging things so that a writer's modification appears "atomic"—a reader always sees only the (consistent) old version, or the (consistent) new version, never some partially-modified inconsistent state.

There are a variety of ways to avoid this problem, including:
 * Design the data structure so that the writer can update it in such a way that it is always in a consistent state. This requires hardware that supports atomic primitives powerful enough to update the data structure from one consistent state to the next consistent state in one atomic operation. lock-free and wait-free algorithms. For example, the read twice and compare algorithm we discuss elsewhere.
 * Have the writer turn off the task scheduler while it is updating the data structure. Then the only time the reader could possibly see the data structure, the data structure is in a consistent state.
 * Have the writer turn off all interrupts (including the timer interrupt that kicks off the task scheduler) while it is updating the data structure. Then the only time the reader could possibly see the data structure, the data structure is in a consistent state. But this makes interrupt latency much worse.
 * Use a "lock" associated with each data structure. When the reader sees that the writer is updating the data structure, have the reader tell the task scheduler to run some other process until the writer is finished. (There are many kinds of locks).
 * Use a "monitor" associated with every routine that uses a data structure.

Whenever a lock or CS mechanism is called, it is important that the RTOS disable the scheduler, to prevent the atomic operations from being preempted and executed incorrectly. Remember that embedded systems need to be stable and robust, so we cannot risk having the operating system itself being preempted while it is trying to create a lock or critical section. If we have a function called DisableScheduler, we can call that function to disable the scheduler before any atomic operation is attempted, and we can then have a function called EnableScheduler to restore the scheduler, and continue with normal operation.

Let us now create a general function for entering a critical section: and one for exiting a critical section: By disabling the scheduler during the critical section, we have guaranteed that no preemptive task-switching will occur during the critical section.

This method has a disadvantage that it slows down the system, and prevents other time-sensitive tasks from running. Next, we will show a method by which critical sections can be implemented to allow for preemption.

Critical Section Objects
Critical Sections, like any other term in computing can have a different definition than simply an operation that prevents preemption. For instance, many systems define a CS as being an object that prevents multiple tasks from entering a given section of code. Let us say that we are implementing a version of malloc on our system. We want to ensure that once a memory allocation attempt has started, that no other memory allocation attempts can begin. Only 1 memory allocation attempt can be happening at one time. However, we want to allow for the malloc function to be preempted just like every other function. To implement this, we need a new data object called a CRITICAL_SECTION, or CRIT_X, or something of that nature. Our malloc function will now look like this: If two tasks call malloc at nearly the same time, the first one will enter the critical section, while the second one will wait, or be "blocked" at the EnterCS routine. When the first malloc is finished, the second malloc's EnterCS function will return, and the function will continue.

To allow other processes looking at other data structures to continue even though this data structure has been locked, EnterCS is typically redefined something like: The value to creating a Critical Section object, and using that to prevent preemption of sensitive areas is that this scheme does not slow down the system, the way the first scheme does (by disabling the scheduler, and preventing other tasks from executing).

Some OSes, such as Dragonfly BSD, implement EnterCS and ExitCS using "serializing tokens", in such a way that when a process attempts to get a lock on another data structure, the OS briefly releases all locks that process holds, before giving that process a lock on all requested locks.


text:
Engineering Acoustics/Noise from cooling fans

Proposal
As electric/electronic devices get smaller and functional, the noise of cooling device becomes important. This page will explain the origins of noise generation from small axial cooling fans used in electronic goods like desktop/laptop computers. The source of fan noises includes aerodynamic noise as well as operating sound of the fan itself. This page will be focused on the aerodynamic noise generation mechanisms.

Introduction
Inside a desktop computer, there may be three (or more) fans. Usually there is a fan on the heat sink of the CPU, in the rear of the power supply unit, on the case ventilation hole, and maybe on the graphics card, plus one on the motherboard chipset if it is a very recent one. The noise from a computer that annoys people is mostly due to cooling fans if the hard drive(s) is fairly quiet. When Intel Pentium processors were first introduced, there was no need to have a fan on the CPU at all, but most modern CPUs cannot function even for several seconds without a cooling fan, and some CPU's (such as Intel's Prescott core) have extreme cooling requirements, which often causes more and more noise. The type of fan used in a desktop computer is almost always an axial fan, while centrifugal fans are commonly used in laptop computers. Several fan types are shown here (pdf format). Different fan types have different characteristics of noise generation and performance. The axial flow fan is the main type considered in this page.

Noise Generation Mechanisms
The figure below shows a typical noise spectrum of a 120 mm diameter electronic device cooling fan. One microphone is used at the point 1 m far from the upstream side of the fan. The fan has 7 blades, 4 struts for motor mounting and operates at 13V. Certain amount of load is applied. The blue plot is background noise of anechoic chamber, and the green one is sound loudness spectrum when the fan is running. (*BPF = Blade Passing Frequency) Each noise elements shown in this figure is caused by one or more of following generation mechanisms.

Blade Thickness Noise - Monopole (But very weak)
Blade thickness noise is generated by volume displacement of fluid. Fan blades has its thickness and volume. As the rotor rotates, the volume of each blade displaces fluid volume, then they consequently fluctuate pressure of near field, and noise is generated. This noise is tonal at the running frequency and generally very weak for cooling fans, because their RPM is relatively low. Therefore, thickness of fan blades hardly affects to electronic cooling fan noise.

(This kind of noise can become severe for high speed turbomachines like helicopter rotor)

Uniform Inlet Flow (Negligible)
The sound generation due to uniform and steady aerodynamic force has very similar characteristic as the blade thickness noise. It is very weak for low speed fans, and depends on fan RPM. Since at least of ideal steady blade forces are necessary for a fan to do its duty, even in an ideal condition, this kind of noise is impossible to be avoided. It is known that this noise can be reduced by increasing the number of blades.

Non-uniform Inlet Flow
Non-uniform (still steady) inlet flow causes non-uniform aerodynamic forces on blades as their angular positions change. This generates noise at blade passing frequency and its harmonics. It is one of the major noise sources of electronic cooling fans.

Rotor-Casing interaction
If the fan blades are very close to a structure which is not symmetric, unsteady interaction forces to blades are generated. Then the fan experiences a similar running condition as lying in non-uniform flow field.

Impulsive Noise (Negligible)
This noise is caused by the interaction between a blade and blade-tip-vortex of the preceding blade, and not severe for cooling fans.

Rotating Stall
Click here to read the definition and an aerodynamic description of stall.

The noise due to stall is a complex phenomenon that occurs at low flow rates. For some reason, if flow is locally disturbed, it can cause stall on one of the blades. As a result, the upstream passage on this blade is partially blocked. Therefore, the mean flow is diverted away from this passage. This causes increasing of the angle of attack on the closest blade at the upstream side of the originally stalled blade, the flow is again stalled there. On the other hand, the other side of the first blade is un-stalled because of reduction of flow angle. repeatedly, the stall cell turns around the blades at about 30~50% of the running frequency, and the direction is opposite to the blades. This seriese of phenomenon causes unstedy blade forces, and consequently generates noise and vibrations.

Non-uniform Rotor Geometry
Asymmetry of rotor causes noise at the rotating frequency and its harmonics (not blade passing frequency obviously), even when the inlet flow is uniform and steady.

Unsteady Flow Field
Unsteady flow causes random forces on the blades. It spreads the discrete spectrum noises and makes them continuous. In case of low-frequency variation, the spread continuous spectral noise is around rotating frequency, and narrowband noise is generated. The stochastic velocity fluctuations of inlet flow generates broadband noise spectrum. The generation of random noise components is covered by the following sections.

Turbulent Boundary Layer
Even in the steady and uniform inlet flow, there exist random force fluctuations on the blades. That is from turbulent blade boundary layer. Some noise is generated for this reason, but dominant noise is produced by the boundary layer passing the blade trailing edge. The blade trailing edges scatter the non-propagating near-field pressure into a propagatable sound field.

Incident Turbulent
Velocity fluctuations of the intake flow with a stochastic time history generate random forces on blades, and a broadband spectrum noise.

Vortex Shedding
For some reason, a vortex can separate from a blade. Then the circulating flow around the blade starts to be changed. This causes non-uniform forces on blades, and noises. A classical example for this phenomenon is 'Karman vortex street'. (some images and animations.) Vortex shedding mechanism can occur in a laminar boundary layer of low speed fan and also in a turbulent boundary layer of high frequency fan.

Flow Separation
Flow separation causes stall explained above. This phenomenon can cause random noise, which spreads all the discrete spectrum noises, and turns the noise into broadband.

Tip Vortex
Since cooling fans are ducted axial flow machines, the annular gap between the blade tips and the casing is important parameter for noise generation. While rotating, there is another flow through the annular gap due to pressure difference between upstream and downstream of fan. Because of this flow, tip vortex is generated through the gap, and broadband noise increases as the annular gap gets bigger.

Installation Effects
Once a fan is installed, even though the fan is well designed acoustically, unexpected noise problem can come up. It is called as installation effects, and two types are applicable to cooling fans.

Effect of Inlet Flow Conditions
A structure that affects the inlet flow of a fan causes installation effects. For example Hoppe & Neise [3] showed that with and without a bellmouth nozzle at the inlet flange of 500mm fan can change the noise power by 50dB (This application is for much larger and noisier fan though).

Acoustic Loading Effect
This effect is shown on duct system applications. Some high performance graphic cards apply duct system for direct exhaustion.

The sound power generated by a fan is not only a function of its impeller speed and operating condition, but also depends on the acoustic impedances of the duct systems connected to its inlet and outlet. Therefore, fan and duct system should be matched not only for aerodynamic noise reasons but also because of acoustic considerations.

Closing Comment
Noise reduction of cooling fans has some restrictions:

 * 1) Active noise control is not economically effective. 80mm cooling fans are only 5~10 US dollars. It is only applicable for high-end electronic products.
 * 2) Restricting certain aerodynamic phenomenon for noise reduction can cause serious performance reduction of the fan. Increasing RPM of the fan is of course much more dominant factor for noise.

Different stories of fan noise are introduced at some of the linked sites below like active RPM control or noise camparison of various bearings used in fans.

Links to Interesting Sites about Fan Noise
Some practical issue of PC noise are presented at the following sites:

 * Cooling Fan Noise Comparison - Sleeve Bearing vs. Ball Bearing (pdf format)
 * Brief explanation of fan noise origins and noise reduction suggestions
 * Effect of sweep angle comparison
 * Comparisons of noise from various 80mm fans
 * Noise reduction of a specific desktop case
 * Noise reduction of another specific desktop case
 * Informal study for noise from CPU cooling fan
 * Informal study for noise from PC case fans
 * Active fan speed optimizators for minimum noise from desktop computers
 * Some general fan noise reduction technics
 * Various applications and training in - Brüel & Kjær


text:
User:Jonathan Webley

 * me at Wikipedia
 * me at Wikiversity
 * me at Wikitionary

 * User:Jonathan Webley/sandbox

Books

 * Esperanto
 * LaTeX
 * TeX

title: User:Jonathan Webley


text:
Engineering Acoustics/Human Vocal Fold

Physiology of Vocal Fold
Human vocal fold is a set of lip-like tissues located inside the larynx, and is the source of sound for a human and many animals.

The Larynx is located at the top of trachea. It is mainly composed of cartilages and muscles, and the largest cartilage, thyroid, is well known as the "Adam's Apple."

The organ has two main functions; to act as the last protector of the airway, and to act as a sound source for voice. This page focuses on the latter function.

Links on Physiology: Discover The Larynx

Voice Production
Although the science behind sound production for a vocal fold is complex, it can be thought of as similar to a brass player's lips, or a whistle made out of grass. Basically, vocal folds (or lips or a pair of grass) make a constriction to the airflow, and as the air is forced through the narrow opening, the vocal folds oscillate. This causes a periodical change in the air pressure, which is perceived as sound.

Vocal Folds Video

When the airflow is introduced to the vocal folds, it forces open the two vocal folds which are nearly closed initially. Due to the stiffness of the folds, they will then try to close the opening again. And now the airflow will try to force the folds open etc... This creates an oscillation of the vocal folds, which in turn, as I stated above, creates sound. However, this is a damped oscillation, meaning it will eventually achieve an equilibrium position and stop oscillating. So how are we able to "sustain" sound?

As it will be shown later, the answer seems to be in the changing shape of vocal folds. In the opening and the closing stages of the oscillation, the vocal folds have different shapes. This affects the pressure in the opening, and creates the extra pressure needed to push the vocal folds open and sustain oscillation. This part is explained in more detail in the "Model" section.

This flow-induced oscillation, as with many fluid mechanics problems, is not an easy problem to model. Numerous attempts to model the oscillation of vocal folds have been made, ranging from a single mass-spring-damper system to finite element models. In this page I would like to use my single-mass model to explain the basic physics behind the oscillation of a vocal fold.

Information on vocal fold models: National Center for Voice and Speech

Model

Figure 1: Schematics

The most simple way of simulating the motion of vocal folds is to use a single mass-spring-damper system as shown above. The mass represents one vocal fold, and the second vocal fold is assumed to be symmetry about the axis of symmetry. Position 3 respresents a location immediately past the exit (end of the mass), and position 2 represents the glottis (the region between the two vocal folds).

The Pressure Force
The major driving force behind the oscillation of vocal folds is the pressure in the glottis. The Bernoulli's equation from fluid mechanics states that:

Neglecting potential difference and applying $$ to positions 2 and 3 of Figure 1,

Note that the pressure and the velocity at position 3 cannot change. This makes the right hand side of $$ constant. Observation of $$ reveals that in order to have oscillating pressure at 2, we must have oscillation velocity at 2. The flow velocity inside the glottis can be studied through the theories of the orifice flow.

The constriction of airflow at the vocal folds is much like an orifice flow with one major difference: with vocal folds, the orifice profile is continuously changing. The orifice profile for the vocal folds can open or close, as well as change the shape of the opening. In Figure 1, the profile is converging, but in another stage of oscillation it takes a diverging shape.

The orifice flow is described by Blevins as:

Where the constant C is the orifice coefficient, governed by the shape and the opening size of the orifice. This number is determined experimentally, and it changes throughout the different stages of oscillation.

Solving $$ and $$, the pressure force throughout the glottal region can be determined.

The Collision Force
As the video of the vocal folds shows, vocal folds can completely close during oscillation. When this happens, the Bernoulli equation fails. Instead, the collision force becomes the dominating force. For this analysis, Hertz collision model was applied.

where

$$ k_H = \frac{4}{3} \frac{E}{1 - \mu_H^2} \sqrt{r}$$

Here delta is the penetration distance of the vocal fold past the line of symmetry.

Simulation of the Model
The pressure and the collision forces were inserted into the equation of motion, and the result was simulated.

Figure 2: Area Opening and Volumetric Flow Rate

Figure 2 shows that an oscillating volumetric flow rate was achieved by passing a constant airflow through the vocal folds. When simulating the oscillation, it was found that the collision force limits the amplitude of oscillation rather than drive the oscillation. Which tells us that the pressure force is what allows the sustained oscillation to occur.

The Acoustic Output
This model showed that the changing profile of glottal opening causes an oscillating volumetric flow rate through the vocal folds. This will in turn cause an oscillating pressure past the vocal folds. This method of producing sound is unusual, because in most other means of sound production, air is compressed periodically by a solid such as a speaker cone.

Past the vocal folds, the produced sound enters the vocal tract. Basically this is the cavity in the mouth as well as the nasal cavity. These cavities act as acoustic filters, modifying the character of the sound. The acoustics of vocal tract have traditionally been described on the basis of a source-filter theory. Whereas the glotis produces a sound of many frequencies, the vocal tract selects a subset of these frequencies for radiation from the mouth. These are the characters that define the unique voice each person produces.

Related Links
FEA Model

Two Mass Model

title: Engineering Acoustics/Human Vocal Fold


text:
Engineering Acoustics/Microphone Design and Operation

Introduction
Microphones are devices which convert pressure fluctuations into electrical signals. Two main methods of achieving this are used in the mainstream entertainment industry today - dynamic microphones and condenser microphones. Piezoelectric transducers can also be used as microphones but they are not commonly used in the entertainment industry.

Dynamic microphones
Dynamic microphones utilise 'Faraday’s Law'. The principle states that when an electrical conductor is moved through a magnetic field, an electrical current is induced within the conductor. In these microphones the magnetic field comes from permanent magnets. There are two common arrangements for the conductor.

Figure 1: Sectional View of Moving-Coil Dynamic Microphone

The first conductor arrangement has a moving coil of wire. The wire is typically copper and is attached to a circular membrane or piston usually made from lightweight plastic or occasionally aluminum. The impinging pressure fluctuation on the piston causes it to move in the magnetic field and thus creates the desired electrical current.

Figure 2: Dynamic Ribbon Microphone

The second conductor arrangement is a ribbon of metallic foil suspended between magnets. The metallic ribbon moves in response to a pressure fluctuation and an electrical current is produced. In both configurations, dynamic microphones follow the same principals as acoustical transducers.

Condenser Microphones
Condenser microphones convert pressure fluctuations into electrical potentials by changes in electrical capacitance, hence they are also known as capacitor microphones. An electrical capacitor consists of two charged electrical conductors placed at some relatively small distance to each other. The basic relation that describes capacitors is:

 * $$Q=C\times V$$

where Q is the electrical charge of the capacitor’s conductors, C is the capacitance, and V is the electric potential between the capacitor’s conductors. If the electrical charge of the conductors is held at a constant value, then the voltage between the conductors will be inversely proportional to (a) the capacitance and (b) the distance between the conductors.

Figure 3: Sectional View of Condenser Microphone

The capacitor in a condenser microphone consists of two parts: the diaphragm and the backplate. The diaphragm moves due to impinging pressure fluctuations and the backplate is held in a stationary position. When the diaphragm moves closer to the backplate, the capacitance increases and a change in electric potential is produced. The diaphragm is typically made of metallic coated Mylar. The assembly that houses both the backplate and the diaphragm is commonly referred to as a capsule.

To keep the diaphragm and backplate at a constant charge, an electric potential must be presented to the capsule. There are various ways this can be achieved. The first uses a battery to supply the needed DC potential to the capsule (figure 4). The resistor across the leads of the capsule is very high, in the range of 10 mega ohms, to keep the charge on the capsule close to constant.

Figure 4: Internal Battery Powered Condenser Microphone

An alternative technique for providing a constant charge on the capacitor is to supply a DC electric potential through the microphone cable that carries the microphones output signal. Standard microphone cable is known as XLR cable and is terminated by three pin connectors. Pin one connects to the shield around the cable. The microphone signal is transmitted between pins two and three.

Figure 5: Dynamic Microphone Connected to a Mixing Console via XLR Cable

48V Phantom Powering
The most popular method of providing a DC potential through a microphone cable is to supply +48 V to both of the microphone output leads, pins 2 and 3, and use the shield of the cable, pin 1, as the ground to the circuit. Because pins 2 and 3 see the same potential, any fluctuation of the microphone powering potential will not affect the microphone signal seen by the attached audio equipment. The +48 V will be stepped down at the microphone using a transformer and provide the potential to the backplate and diaphragm in a similar fashion as the battery solution.

Figure 6: Condenser Microphone Powering Techniques

12V T-Powering
A less popular method of running the potential through the cable is to supply 12 V between pins 2 and 3. This method is referred to as T-powering. The main problem with T-powering is that potential fluctuation in the powering of the capsule will be transmitted into an audio signal because the audio equipment analyzing the microphone signal will not see a difference between a potential change across pins 2 and 3 due to a pressure fluctuation and one due to the power source electric potential fluctuation.

Electret Condenser Microphones
Finally, the diaphragm and backplate can be manufactured from a material that maintains a fixed charge, known as 'electret' (from electric+magnet, because these materials can be seen as the electric equivalents of permanent magnets). As a result, these microphones are termed electret condenser microphones (ECM). In early electret designs, the charge on the material tended to become unstable over time. Advances in science and manufacturing have effectively eliminated this problem in present designs.

Conclusion
Two types of microphones are used in the entertainment industry.
 * Dynamic microphones, which are found in the moving-coil and ribbon configurations. The movement of the conductor in dynamic microphones induces an electric current which is then transformed into the reproduction of sound.
 * Condenser microphones which utilize the properties of capacitors. The charge on the capsule of condenser microphones can be accomplished by battery, by phantom powering, by T-powering, and by using 'electrets' - materials with a fixed charge.

Microphone Manufactures Links
AEA

AKG

Audio Technica

Audix

Bruel & Kjaer

Neumann

Rode

Shure

sE Electronics

Back to Engineering Acoustics


text:
Engineering Acoustics/Room Acoustics and Concert Halls

=Room Acoustics and Concert Halls=

Introduction
From performing on many different rooms and stages all over the United States, I thought it would be nice to have a better understanding and source about the room acoustics. This Wikibook page is intended to help the user with basic technical questions/answers about room acoustics. Main topics that will be covered are: what really makes a room sound good or bad, alive or dead. This will lead into absorption and transmission coefficients, decay of sound in the room, and reverberation. Different use of materials in rooms will be mentioned also. There is no intention of taking work from another. This page is a switchboard source to help the user find information about room acoustics.

Sound Fields
Two types of sound fields are involved in room acoustics: Direct Sound and Reverberant Sound.

Direct Sound
The component of the sound field in a room that involves only a direct path between the source and the receiver, before any reflections off walls and other surfaces.

Reverberant Sound
The component of the sound field in a room that involves the direct path and the path after it reflects off of walls or any other surfaces. How the waves deflect off of the mediums all depends on the absorption and transmission coefficients.

Good example pictures are shown at Crutchfield Advisor, a Physics Site from MTSU, and Voiceteacher.com

Room Coefficients
In a perfect world, if there is a sound shot right at a wall, the sound should come right back. But because sounds hit different materials types of walls, the sound does not have perfect reflection. From 1, these are explained as follows:

Absorption & Transmission Coefficients
The best way to explain how sound reacts to different mediums is through acoustical energy. When sound impacts on a wall, acoustical energy will be reflected, absorbed, or transmitted through the wall.

Absorption Coefficient: NB: this chemical structure is unrelated to the acoustics being discussed.

Transmission Coefficient:

If all of the acoustic energy hits the wall and none is reflected, the alpha would equal 1. The energy had zero reflection and was absorbed or transmitted. This would be an example of a dead or soft wall because it takes in everything and doesn't reflect anything back. Rooms that are like this are called Anechoic Rooms which looks like this from Axiomaudio.

If all of the acoustic energy hits the wall and all reflects back, the alpha would equal 0. This would be an example of a live or hard wall because the sound bounces right back and does not go through the wall. Rooms that are like this are called Reverberant Rooms like this McIntosh room. Look how the walls have nothing attached to them. More room for the sound waves to bounce off the walls.

Room Averaged Sound Absorption Coefficient
Not all rooms have the same walls on all sides. The room averaged sound absorption coefficient can be used to have different types of materials and areas of walls averaged together.

RASAC:

Absorption Coefficients for Specific Materials
Basic sound absorption Coefficients are shown here at Acoustical Surfaces.

Brick, unglazed, painted alpha ~ .01 - .03 -> Sound reflects back

An open door alpha equals 1 -> Sound goes through

Units are in Sabins.

Sound Decay and Reverberation Time
In a large reverberant room, a sound can still propagate after the sound source has been turned off. This time when the sound intensity level has decay 60 dB is called the reverberation time of the room.

Great Reverberation Source

Great Halls in the World
Foellinger Great Hall

Japan

Budapest

Carnegie Hall in New York

Carnegie Hall

Pick Staiger at Northwestern U

Concert Hall Acoustics


text:
User talk:Zondor~enwikibooks

Wikijunior Alaska
Was there some discussion on adding Alaska? I know I have put this comment elsewhere, but I think it is important to figure out. Thanks. --Lord Voldemort (Dark Mark)  17:50, 4 November 2005 (UTC)

 * Thank you for trying to help clean up Wikibooks. Wikijunior, however, is trying to experiment with a "slow growth" policy right now that started with the creation of that sub-project.  I know it is kind of un-wiki like in the fact that new modules must achieve some sort of community concensus.  I started the Wikijunior:New Title Suggestions as a forum to decide what to start next, modeled after Proposals for new projects but with the intention of actually trying to allow some of these project ideas a chance to develop.  I'm going to put the Wikijunior Alaska into the new project area for now.  This module was developed because some people wanted to add to Wikijunior, but there was no social mechanism to add new book projects.  I've started that process now, so hopefully there will be some valuable new additions to Wikijunior in the future.  --Rob Horning

Your account will be renamed
Hello,

The developer team at Wikimedia is making some changes to how accounts work, as part of our on-going efforts to provide new and better tools for our users like cross-wiki notifications. These changes will mean you have the same account name everywhere. This will let us give you new features that will help you edit and discuss better, and allow more flexible user permissions for tools. One of the side-effects of this is that user accounts will now have to be unique across all 900 Wikimedia wikis. See the announcement for more information.

Unfortunately, your account clashes with another account also called Zondor. To make sure that both of you can use all Wikimedia projects in future, we have reserved the name Zondor~enwikibooks that only you will have. If you like it, you don't have to do anything. If you do not like it, you can pick out a different name.

Your account will still work as before, and you will be credited for all your edits made so far, but you will have to use the new account name when you log in.

Sorry for the inconvenience.

Yours, Keegan Peterzell Community Liaison, Wikimedia Foundation 23:55, 17 March 2015 (UTC)

Renamed
 This account has been renamed as part of single-user login finalisation. If you own this account you can |log in using your previous username and password for more information. If you do not like this account's new name, you can choose your own using this form after logging in: . -- Keegan (WMF) (talk) 05:40, 19 April 2015 (UTC)

title: User talk:Zondor~enwikibooks


text:
Lush

Lush is a lisp-like object-oriented programming language designed for researchers, experimenters, and engineers interested in numerical applications, including computer vision and machine learning. Lush is designed to be used in situations where one would want to combine the flexibility of a high-level, weakly-typed interpreted language, with the efficiency of a strongly-typed, natively-compiled language, and with the easy integration of code written in C, C++, or other languages.

Contents
Basic Lush: Packages: Advanced Lush:
 * /Features/
 * /Installation/
 * Beginning Lush
 * /Classes and Objects/
 * /Compiling/
 * /Debugging/
 * /The Vector, Matrix, Tensor library/
 * /Input and Output/
 * /libplot/
 * /libnum/
 * /GBLearn/
 * /OGRE/
 * /libsdl/
 * /Macros/
 * /Lisp tricks/
 * /Hooks/
 * /Standalone lush programs/

title: Lush


text:
Talk:The Once and Future King

I am particularly fond of spark-notes for their abridgements, they generally have the answers that teachers find acceptable, and using them works better than reading and drawing your own conclusions, as far as the grade goes.

Lotusduck 18:16, 4 November 2005 (UTC)lotusduck

title: Talk:The Once and Future King