text:
Materials Science and Engineering/Derivations/Models of Micro and Nanoscale Processing/Thermodynamics

Gibbs Free Energy
$$G = U - TS + PV\;$$ $$G = H - TS\;$$ $$G = F + PV\;$$ $$G = \sum_i n_i \mu_i\;$$

Chemical Potential of Component i
$$\mu_i = \left ( \frac{\partial G}{\partial n_i} \right )_{n_{j \ne i}, T, P}$$

$$g \left ( \frac{ \mbox{energy} }{ \mbox{mole} } \right ) = \sum_i x_i \mu_i$$

Criterion of Equilibrium
$$\mu_{i,\alpha} = \mu_{i, \beta}$$

Solution Theory
$$\Delta g_s = g_{AB} - g_A - g_B$$ $$\Delta g_s = \Delta h_s - T \Delta s_s$$ $$\Delta g_s = \sum_i x_i ( \mu_i - \mu_i^o )$$

Ideal Solution
In chemistry, an ideal solution or ideal mixture is a solution in which the enthalpy of solution is zero; the closer to zero the enthalpy of solution, the more "ideal" the behavior of the solution becomes. Equivalently, an ideal mixture is one in which the activity coefficients (which measure deviation from ideality) are equal to one.

More formally, for a mix of molecules of A and B, the interactions between unlike neighbors (UAB) and like neighbors UAA and UBB must be of the same average strength i.e. 2UAB=UAA+ UBB and the longer-range interactions must be nil (or at least indistinguishable). If the molecular forces are the same between AA, AB and BB, i.e. UAB=UAA=UBB, then the solution is automatically ideal.

$$\Delta h_s = 0\;$$ $$\Delta \mu_i = RT \ln (x_i)\;$$ $$\Delta g_s = \sum_i x_i RT \ln (x_i)\;$$

Non-Ideal Solution
Deviations from ideality can be described by the use of Margules functions or activity coefficients. A single Margules parameter may be sufficient to describe the properties of the solution if the deviations from ideality are modest; such solutions are termed regular.

In contrast to ideal solutions, where volumes are strictly additive and mixing is always complete, the volume of a non-ideal solution is not, in general, the simple sum of the volumes of the component pure liquids and solubility is not guaranteed over the whole composition range.

$$\Delta h_s \ne 0\;$$ $$\Delta \mu_i = RT \ln (a_i)\;$$

An activity coefficient is a factor used in thermodynamics to account for deviations from ideal behaviour in a mixture of chemical substances. In an ideal mixture the interactions between each pair of chemical species are the same (or more formally, the enthalpy of mixing is zero) and, as a result, properties of the mixtures can be be expressed directly in terms of simple concentrations or partial pressures of the substances present e.g. Raoult's law. Deviations from ideality are accommodated by modifying the concentration by an activity coefficient. Analogously, expressions involved gases can be adjusted for non-ideality by scaling partial pressures by a fugacity coefficient.

$$a_i = \gamma_i x_i\;$$

Raoultion Solutions
As $$x_i$$ approaches 1, the activity coefficient, $$\gamma_i = 1$$ approaches 1

Henrien Solutions
As $$x_i$$ approaches 0, the activity coefficient, $$\gamma_i$$, approaches a constant

Regular Solution
A regular solution is a solution that diverges from the behavior of an ideal solution only moderately.

More precisely it can be described by Raoult's law modified with a Margules function with only one parameter α:

A regular solution is both Raoltion and Henrien

Quasichemical Model of Regular Solutions
$$\Delta \phi = \phi_{12} - \frac{\phi_{11} + \phi_{22}}{2}$$

Calculating Thermodynamic Quantities
$$c_P = \frac{dH}{dT}$$

$$dS = \frac{dH}{dT}$$

$$G = H - TS\;$$

Free energy of transition of a pure material

$$\Delta G^{l \rightarrow s} \approx \Delta S_f (T_m - T)$$

Chemical Equilibria
$$aA + bB \leftarrow \rightarrow cC + dD$$

$$K = \frac{x_C^c x_D^d}{x_A^a x_B^b}$$

$$K = \exp \left ( \frac{ - \Delta g_R}{RT} \right )$$

Elingham Diagram
In metallurgy, the Ellingham diagram is used to predict the equilibrium temperature between a metal, its oxide and oxygen.

Ellingham diagrams follow from the Second Law of Thermodynamics [ΔG = ΔH - TΔS] and are a particular graphical form of it. ΔG is the Gibbs Free Energy Change,ΔH is the Enthalpy Change and ΔS is the Entropy Change

The Ellingham diagram plots the Gibbs free energy change (ΔG) for the oxidation reaction versus the temperature. In the temperature ranges commonly used, the metal and the oxide are in a condensed state (liquid or solid) with the oxygen gaseous, the reactions may be exothermic or endothermic, but the ΔG of the oxidation always becomes more negative with higher temperature, and thus the reaction becomes more probable statistically. At a sufficiently high temperature, the sign of ΔG may invert (becoming negative) and the oxide can spontaneously reduce to the metal.

As with any chemical reaction prediction based on purely energetic grounds the reaction may or may not take place spontaneously on kinetic grounds if one or more stages in the reaction pathway have very high Activation Energies EA.

If two metals are present, two equilibriums have to be considered, so that the metal with the more negative ΔG reduces, the other oxidizes.

In industrial processes, the reduction of metal oxides is obtained using carbon, which is available cheaply in reduced form (as coal).

Moreover, when carbon reacts with oxygen it forms gaseous composts carbon monoxide and carbon dioxide, therefore the dynamics of its oxidation is different from that for metals: its oxidation has a more negative ΔG with higher temperatures. Using this property, reduction of metals may be performed as a double redox reaction at relatively low temperature.

Equilibrium Between a Binary Solid and Liquid
B-rich solid and liquid solutions

$$\mu_B^s = \mu_B^l$$

$$\mu_B^{s,0} + RT \ln ( \gamma_B^s x_B^s ) = \mu_B^{l,0} + RT \ln ( \gamma_B^l x_B^l )$$

$$\Delta \mu_B^{l \rightarrow s, 0} = \mu_B^{s,0} - \mu_B^{l,0}$$

$$\Delta \mu_B^{l \rightarrow s, 0} = RT \ln \left ( \frac{ \gamma_B^s x_B^s }{ \gamma_B^l x_B^l} \right )$$

$$\Delta g_B^{l \rightarrow s, 0} = \Delta \mu_B^{l \rightarrow s, 0}$$

$$\Delta g_B^{l \rightarrow s, 0} = \Delta s_{f,B}^{l \rightarrow s, 0} (T_{m,B} - T)$$

$$\Delta g_B^{l \rightarrow s, 0} = \Delta s_{f,B}^{l \rightarrow s, 0} \Delta T_B$$

$$\Delta s_{f, B}^{l \rightarrow s, 0} \Delta T_{m, B} \approx RT \ln \left ( \frac{ \gamma_B^s x_B^s }{ \gamma_B^l x_B^l} \right )$$

Ideal liquid solution and pure solid

$$\Delta s_{f, B} \Delta T = RT \ln (x_B^l)$$

$$\Delta s_{f, B} \Delta T \approx RT \left ( \frac{ \gamma_B^l x_B^l }{ \gamma_B^s x_B^s } \right )$$

$$\Delta s_{f, B} = RT \left ( \ln \left ( \frac{ \gamma_B^l}{\gamma_B^s} \right ) + \ln \left ( \frac{ \gamma_B^l}{\gamma_B^s} \right ) \right )$$

With $$\Delta s_{f, B}$$ and the phase diagram, the ratio $$\gamma_B^l / \gamma_B^s $$


text:
Talk:Radio Discussion/Living on Earth/2008.1.18/Segment 4

Just a few thoughts... Cloning in farm animals was presented very optimistically in video report by Fox. It is said that it is possible to duplicate (multiplicate) the best producing animals. What they didn't said, that this approach leads to enormous loss of genetic variability (i.e. biodiversity) in farm animals. The situation is bad even now, when we use "just" the artificial insemination. Breeds of farm animals disappear every day. I'm not against the cloning as method, but I am afraid what it's large scale application could cause. This issue is well written in The New York Times article. I was extremely surprised, when I heard of the speech of mr. Sundolf about labeling the products from clones, saying that "It's not a matter of whether or not we think we should or not. It's a matter of—do we have the authority to require that companies label their product. And clearly in this case we don't believe that we do." I am not from US, but to say the truth, I was very pissed off. Do not have the authority?? Here in EU it is required to have all the information about the animal/meat (including the places where it was born, raised, slaughtered). To label GMO and clone products is no question. Don't have the authority? Than who has? The purpose of the FDA is protect interests of farmers, meat industry or consumers? --Gbaor 06:38, 4 February 2008 (UTC)

 * Actually it might be the USDA that has the authority. What I would worry even more about is if they made a law saying that meat could not be labeled as coming from non-cloned animals. There are efforts underway now to ban labeling "growth hormone-free" milk in many states, including here in Pennsylvania. --SB_Johnny | talk 13:40, 4 February 2008 (UTC)

 * Well, actually don't mind who has the authority, the point is, that it should be at least labeled to give customers the chance to choose.
 * Growth hormones? You are kidding... Growth hormones in milk you give to children? Even when it is known to cause health problems? And you even don't know which milk is safe? Now I'm just wondering... The use of growth hormones is long prohibited in the EU and also in other states. Please accept my overwhelming support in this case, to label the milk at all costs (Probably it won't help in the official decision, but you can say that you have supporters around the Globe. :) ) Ext. links: Open letter to governor of Pennsylvania (2007) - Growth hormones in milk - Growth hormones in meat --Gbaor 06:11, 5 February 2008 (UTC)
 * Well, you can still buy organic milk (which can't have hormones), but it's very expensive. You can also buy directly from the farmer, they just can't label it. --SB_Johnny | talk 11:03, 5 February 2008 (UTC)
 * And what if you live in a big city and you don't have money to buy the organic milk? There might be some differences in customer acceptance between US and EU (certainly are), but here even the existence of milk from hormone threated cows is irritating. My opinion is, that it should be prohibited, while the hormones get through to the milk and meat. It is the same, if the customers were hormone-threated themselfs. --Gbaor 11:24, 5 February 2008 (UTC)

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


text:
User talk:Drsim

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Hello Drsim, and welcome to Wikiversity! If you need help, feel free to visit my talk page, or contact us and ask questions. After you leave a comment on a talk page, remember to sign and date; it helps everyone follow the threads of the discussion. The signature icon in the edit window makes it simple. To get started, you may
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User talk:Maths4

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Hello Maths4, and welcome to Wikiversity! If you need help, feel free to visit my talk page, or contact us and ask questions. After you leave a comment on a talk page, remember to sign and date; it helps everyone follow the threads of the discussion. The signature icon in the edit window makes it simple. To get started, you may
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User talk:P858snake

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Hello Peachey88, and welcome to Wikiversity! If you need help, feel free to visit my talk page, or contact us and ask questions. After you leave a comment on a talk page, remember to sign and date; it helps everyone follow the threads of the discussion. The signature icon in the edit window makes it simple. To get started, you may
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User talk:Dangwhatno

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Hello Dangwhatno, and welcome to Wikiversity! If you need help, feel free to visit my talk page, or contact us and ask questions. After you leave a comment on a talk page, remember to sign and date; it helps everyone follow the threads of the discussion. The signature icon in the edit window makes it simple. To get started, you may
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User talk:Abc-maths

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Hello Abc-maths, and welcome to Wikiversity! If you need help, feel free to visit my talk page, or contact us and ask questions. After you leave a comment on a talk page, remember to sign and date; it helps everyone follow the threads of the discussion. The signature icon in the edit window makes it simple. To get started, you may
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User talk:Youyou99~enwikiversity

Welcome
Hello Youyou99, and welcome to Wikiversity! If you need help, feel free to visit my talk page, or contact us and ask questions. After you leave a comment on a talk page, remember to sign and date; it helps everyone follow the threads of the discussion. The signature icon in the edit window makes it simple. To get started, you may
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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 Youyou99. To make sure that both of you can use all Wikimedia projects in future, we have reserved the name Youyou99~enwikiversity 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 23:48, 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) 06:25, 19 April 2015 (UTC)

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User talk:Jre~enwikiversity

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Hello Jre, and welcome to Wikiversity! If you need help, feel free to visit my talk page, or contact us and ask questions. After you leave a comment on a talk page, remember to sign and date; it helps everyone follow the threads of the discussion. The signature icon in the edit window makes it simple. To get started, you may
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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 Jre. To make sure that both of you can use all Wikimedia projects in future, we have reserved the name Jre~enwikiversity 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 23:40, 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) 06:12, 19 April 2015 (UTC)

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User talk:Asikhi

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Hi Asikhi, I replied at Requests_for_Deletion. Cormaggio talk 14:04, 8 February 2008 (UTC)

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User talk:Chimpunkchim

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User talk:Librarylady77

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User talk:Maths5

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User talk:BigDunc

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text:
Computer Architecture Lab/Winter2007/SHWH/TanteEmmaAnalysis

Tante Emma Analysis
In this section we want to analyse our Tante Emma Processor in a more abstract way. We want to show features acourding to the Computer Architecture VO.

Instruction Set Architecture
Our Tante Emma is a Register Register / load store architecture. One Instruction has 16 bit width and has different types of opcode width. Tante Emma has 28 opcodes with 8 bit and 8 opcodes with 4 bit. We have 16 registers whereas reg0 is always zero and reg15 is the return-address memory for procedure calls. The 14 registes left are general purpose registers. For more details see our ISA description.

ISA Design Hint for the LU
When ISA design is done for the practical unit, we recommend to write the assembler demo programms at the beginning of the ISA design phase. So you can decide better which instructions are needed for the ISA and which are useless. So you can reduce the number of instructions of your ISA, to have for example a fixed opcode width, which is easier to implement.

Pipelining
Our Processor has 4 pipelinestages.
 * Instruction Fetch
 * Instruction Decode
 * Instruction Execution and Memory(LD/ST)
 * Write Back (Registers)

Structual Hazards
We are using a Harvard architecture to avoid a bootle neck with 2 separate memorys for instruction and data.

Data Hazards
To avoid RAW hazards, we do forwaring.
 * Read After Write (RAW)

We do in order execution. We also do LD or ST only in stage 3.
 * Write After Read (WAR)

We do in order execution. We also do LD or ST only in stage 3.
 * Write After Write (WAW)

Cache
We have a write back cache with only one block. We have a simple instruciton and Data cache but we learned from other groups that the Rams are fast enough to reach a f_max of the processor of about 50 MHz, in our design with cache we also reach a f_max of about 50 Mhz. We want to annotate that the information about the MHz of the processor was from Quartus II Timeanalysis. For a real timeanalyisis, this has to be done with a hardware measurement.


text:
Wikimedian Demographics/Reminders

Participants who ask for reminders should be notified on their main talk pages of update announcements (about once per month).

Wikiversity

 * User talk:Bellayet
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 * User talk:Dereckson
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Wikipedia

 * w:User_talk:Aleta
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 * w:User_talk:GuillaumeTell
 * w:User_talk:Horologium
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Wikibooks

 * b:User talk:Jomegat
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Commons

 * commons:User talk:Bastique

Meta
meta:User talk:Cbrown1023

Reminders

 * /February, 2008/

title: Wikimedian Demographics/Reminders


text:
Computer Architecture Lab/WS2007/Project -1 Lab4/AssemblerSyntax

Assembler syntax
Arithmetic functions ADD("1","0","1E"); /* Add Random Number (contained in reserved Register $1E) with 0 (contained always in reserved Register $0) and store the result in $1 */ ADDU("1","3","2"); /* Adds unsigned values contained in $3 with unsigned value in $2 and stores the result in $1 */ SUB("3","1","2"); /* Substract $1 by $2 and store the result in $3 */ SUBU("1","3","2"); /* Substracts unsigned values contained in $3 with unsigned value in $2 and stores the result in $1 */

Logical functions: AND("1","3","2"); /* $1 = $3 and $2 */ OR("1","3","2"); /* $1 = $3 or $2 */ XOR("1","3","2"); /* $1 = $3 xor $2 */

Shift functions: SLL("2","5","1"); /* Shift the value contained in $5 left by 1 and store the result in $2 */ SLLV("2","5","1"); /* Shift the value contained in $5 left by value of $1 and store the result in $2 */ SRA("1","4","3"); /* Shift the value contained in $4 arithmetical right by 3 and store the result in $1 */ SRL("A","3","1"); /* Shift the value contained in $3 right by value of $1 and store the result in $A */ SRLV("A","5","1"); /* Shift the value contained in $5 left by 1 and store the result in $A */

(Un)Conditional functions: BZS(LABEL); /* Branch if ZeroFlag is set, jump to LABEL */ BZC(LABEL); /* Branch if ZeroFlag is clear, jump to LABEL */ BNS(LABEL); /* Branch if NegativeFlag is set, jump to LABEL */ BNC(LABEL); /* Branch if NegativeFlag is clear, jump to LABEL */ BOS(LABEL); /* Branch if OverflowFlag is set, jump to LABEL */ BOC(LABEL); /* Branch if OverflowFlag is clear, jump to LABEL */ BOR(LABEL); /* Branch if RandomFlag is set, jump to LABEL */ BR(LABEL); /* jump to LABEL */ JR("3"); /* Jump to address contained in Register $3 */

Load and Store functions: LLI("2","1"); /* Load value 1 to Register $2 */ LW("3","2"); /* Load value contained in Register $2 to Register $3 */ SW("3","2"); /* Store value contained in Register $2 to Register $3 */

NOOP: NOOP; /* do nothing */

RAMENTER: Writes a String into the RAM

RAMENTER ("4","7","11","Hello World. ",&pc); /* "$1 ... Addressregister, $2 ... Length register, $3 ... Increment Register Arguments: $1 ... Destination Address Register Number $2 ... Buffer Length Register: Gets the number of stored characters $3 ... Address Step Register: defines the address distance between two stored characters in RAM $4 ... String &pc .. (decoration) */

CALL Function CALL (Label) /* Jump to Function "Label" */

RETURN from CALL RETURN

Simple UART output UART_SEND_STRING("Hello World",&pc); /* writes "Hello World" to the Terminal */

Debug output DEBUG_SEND("1",&pc); /* Writes "Content of reg 0x01 is: " and the hex-value of the value contained in $1 */

Load a 32-bit Value: LOAD_BIG_NUMBER("1","11","12345678",&pc); /* Load the whole 32-Bit hex-value into $1 with the temporary help of $11 */

Code Samples
Substraction example: LLI("1",6);      /* Load to Value 6 to Register $1 */ LLI("2",5);      /* Load to Value 5 to Register $2 */ SUB("3","1","2"); /* Substract $1 by $2 and store the result in $3 */

Add 2 numbers and check if there is an overflow: LABEL(START)       /* Define Label START */ ADD("1","3","4");  /* ADD $3 with $4 and store the result in $1 */ BOS(OVERFLOWLABEL); /* if OverflowFlag is set jump to OVERFLOWLABEL */ BR(START);         /* jump to START */ LABEL(OVERFLOWLABEL)/* define Label OVERFLOWLABEL */ UART_SEND_STRING("Warning: Overflow after ADD Operation!",&pc); /* Send warning to UART */

for further program samples go to Code Samples


text:
User talk:Mpompoli

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Supporting the Sustainability Agenda through the effective use of ICT

What this page is all about hi This wiki page is the first attempt by the Institution of Civil Engineers' Information Systems panel to make use of Wikis to enacourage wider participation in the development of ideas and hence papers or /ICE briefing sheets/ to be published by the /ICE/. Although open to the public to edit, specific ICE contacts have been invited to contribute to the development of the paper, which once it reaches maturity will be published on the ICE website. For those not familiar with wikis the "how to edit a wiki page" is particularly useful.

This paper argues that Information and Communications Technologies (ICT) play an increasingly important role in the delivery of projects in the built environment, and therefore also play a key role in supporting the delivery of the architecture, engineering and construction (AEC) industry's sustainability agenda.

Executive Summary
ICT has poor 'green' credentials and the AEC industry can play its part by mitigating the negative impacts of ICT use. In particular, AEC professionals can:
 * adopt ICT tools and working practices which reduce energy use
 * promote efficient use of hardware
 * reduce consumption of consumables such as paper, ink and toner
 * use their buying power as major customers of some key software suppliers, to demand applications that are more fully interoperable with other tools

There is growing recognition of the key role ICT can play in delivering a more efficient AEC industry, particularly since the publication of Accelerating Change in 2002, and the AEC industry had already begun to adopt a wide range of ICT tools to streamline project design and delivery processes, to reduce its carbon footprint, and to improve the quality and sustainability of its finished outputs. This document identifies some key strategies (and outlines some of the benefits identified to date), including:

 * Designing for sustainability - the potential of new design tools and approaches, notably building information modelling (BIM), to improve how projects are designed with full recognition of their carbon footprint before, during and after construction
 * More efficient information and process management - use of electronic communication technologies (eg: email, 'extranets', etc) to:
 * reduce paper consumption
 * reduce resources involved in paper production, management and storage
 * reduce transportation, processing and distribution
 * Process improvements – including greater re-use of information
 * Better knowledge management
 * Improved mobility, productivity and 'respect for people'
 * Rationalising and centralising some ICT hardware and software, and related consumption of power

However, it is clear that the potential of ICT to support the delivery of the AEC industry's sustainability agenda also requires the industry to address some fundamental people and process issues. Improvements to existing technologies and investment in new technologies needs to proceed in parallel with the development of new structures and processes, and education and training initiatives, to equip the future workforce with the skills necessary to make full use of these tools.

Introduction
Information and communications technologies (ICT) play an increasingly important role in the delivery of projects in the built environment, and thus play a key role in supporting the delivery of the architecture, engineering and construction (AEC) industry's sustainability agenda. However, there was only one mention of ICT in the BERR Draft Strategy for Sustainable Construction (2007), a conspicuous omission, particularly considering the potential for ICT as an enabler to support the AEC industry in its efforts to develop, implement, manage, measure and report on sustainability initiatives.

ICT and sustainability - key issues
The AEC industry – sometimes erroneously portrayed as ‘technophobic’ – has been an enthusiastic proponent of ICT tools to streamline industry processes and improve productivity. Like other sectors, AEC professionals today routinely use standard office tools, and have adopted a wide range of specialist applications to automate activities that were previously undertaken manually, from drawing production, through structural calculations to visualization, for example, saving manpower and time.

However, the positive benefits of ICT adoption come with an environmental cost. ICT has poor ‘green’ credentials, and, like the rest of UK industry and commerce, the UK AEC industry can play its part in striving for a more sustainable built environment by being aware of the negative impacts of ICT and, where possible, adjusting its ICT procurement, use and disposal processes:

Production of ICT hardware
Production of ICT hardware places high demands on energy and natural resources (a UN study found that manufacturing a PC consumes 10 times the machine's weight in fossil fuels and chemicals). "When you look at the whole product lifetime of a computer 75% of the environmental damage is done before the computer is switched on for the first time. ... It is the production, the mining, the factories producing the kit and the use of toxic materials - that is where the environmental damage is done."

Operation of ICT hardware
Operation of ICT hardware consumes high levels of energy – at remote data-centres, in-house data centres, in offices and at home. Many computer users have, of course, made some savings by replacing heat-generating cathode ray tube (CRT) monitors with LCD flat screen technologies, personal computers’ power-saving features have improved of late, and measures such as server virtualisation in data centres can cut their electricity consumption, but data-processing remains energy-hungry and the resulting heat often adds to the energy consumption problem:

"The year 2008 represents a watershed for corporate IT. While the costs of running the data centres that power most businesses has historically been dominated by the price of the IT equipment they house, from 2008, the cost of the energy required to power that kit will – for the first time – surpass the cost of the computer kit itself. [the most] significant factor is the rapid rise in the amount of power being drawn by today’s servers, networking equipment and storage systems, and the equally large quantity of electricity being used to keep that from overheating." "Modern data centres have become insatiable consumers of power. Server racks traditionally operating at two kilowatts of power per hour have been forced to accommodate more tightly-packed, power-hungry servers, eating up to 25 kilowatts every hour. These servers are also generating tremendous amounts of heat, which needs to be moved away from the equipment if it is to operate smoothly. The cooling adds further costs and draws more energy. According to computer maker Hewlett-Packard, for every kilowatt of energy consumed in processing, a further kilowatt is used for cooling. …

"IT departments spent 17 cents per dollar to power and cool servers in 1996. Ten years later, by September 2006, IT departments were spending 48 cents per dollar to power and cool servers, according to IDC research. IDC predicts that this cost will grow to 78 cents per dollar by 2010. The focus on green is as much about cost reduction as it is about the environment." "… A fully-equipped 30,000 square foot data centre … will consume enough electricity in a single year to result in 44,000 tonnes of carbon dioxide being pumped into the atmosphere."

"In the UK … there are approximately 10 million work PCs currently in active service. Research conducted by the National Energy Foundation … estimates that of these, around 1.7 million are routinely left running when not in use. For the UK business community, this equates to around 1.5 billion kilowatt of electricity wasted every year, carrying a price tag of £115 million. Nearly one sixth of all PCs are not turned off at night, or on weekends. … The majority of large organisations are forced to expend even more energy on air-conditioning – itself a notorious energy-hungry utility – in order to counteract the wasted heat generated by droves of unproductive PCs."

ICT power and heat management
ICT's power and heat management requirements often mean substantial building services provision. Office building designers, for example, have already worked with ICT professionals to model the impacts of low-emission ICT and wireless technologies on cabling and air-conditioning needs – designing buildings with lower storey heights, fewer service risers, smaller floorplates and greater spatial flexibility.

ICT human resources
ICT support requires substantial human resources - adding further to the consumption of buildings, power, heating, lighting, travel, etc.

ICT hardware disposal
Disposal of ICT hardware can be highly polluting (UK companies dispose of around 1.5 million PCs, equal to 125,000 tonnes of IT equipment, in landfill sites every year).

ICT consumables
ICT consumables such as toner and ink are often supplied in wasteful cartridges and packaging. A billion ink and toner cartridges are thrown out worldwide every year; many printer manufacturers’ techniques make it uneconomic to refill, rather than replace proprietary toner cartridges – though some businesses (eg: Xerox, Danwood) are adopting 'remanufacturing' approaches to reuse cartridges.

ICT over-specification
Much hardware and software is over-specified and under-utilised, with manufacturers often encouraging premature obsolescence.

Paper production
Despite its potential to reduce paper consumption, processing, transport and storage (widespread adoption of email, for example, has reduced the volume of letters and packages sent by conventional postal and courier services), ICT has often encouraged rather than reduced paper outputs.

Although an estimated 9 trillion pages a year are confined to computer screens, the number of printed pages stands at between 2.5 and 2.8 trillion worldwide and is predicted to grow over the next 10 years. Office workers throw away 45 per cent of everything they print within a day. British offices print up to 120 billion pieces of paper every year, the equivalent of a paper mountain more than 8,000 miles high.

'Information overload'
ICT can also create 'information overload', reducing individual productivity and efficiency.

Government information policies
Some government policies prevent efficient and cost-effective re-use of information. For example, data created by UK government agencies such as Ordnance Survey, UK Hydrographic Office and the Highways Agency is only available at a cost, with sometimes onerous restrictions on the data’s re-use.

Poor software interoperability
Poor interoperability inhibits re-use of data, generating considerable re-keying and re-checking of duplicate information, duplication of software, expense of data translators, etc. In the AEC sector, poor interoperability adds an estimated 3.1% to project costs, and costs the global industry an estimated $60 billion (£120 billion) a year.

However, information duplication is only partly due to poor interoperability. Many individuals and organizations adopt attitudes, behaviours, policies and regulations that prevent sharing of information and/or promote local retention of copies (hard, soft and sometimes both) of all data (leading to the development of numerous, near-duplicate 'islands of information'). This is not surprising. In many respects, electronic collaboration systems and other ICT tools have simply replaced existing manual AEC processes with electronic ones; while some industry customers and their project teams have adopted 'partnering' or 'collaborative working' approaches that encourage transparency, sharing and re-use of information, these still constitute a minority of projects.

ICT and sustainability in the AEC sector - strategies
While a growing amount of attention is quite rightly being paid to the role of the AEC sector in achieving a more sustainable industry, the potential impacts and benefits of ICT in this endeavour have largely been ignored. This is at least consistent with official assessments of the role of ICT in the AEC industry: ICT has only begun to feature in AEC industry change initiatives in this decade.

For example, there was no specific mention of the role of ICT in the 1994 Latham report or 1998 Egan report. However, four years later Accelerating Change was one of the first AEC industry reports to explicitly describe how ICT could support integrated teams and collaborative working. In its vision (p.10), it talked about "Integrated teams, created at the optimal time in the process and using an integrated IT approach", and later in the report 'IT and e-business' was identified as a cross-cutting issue:

7.8 IT and E-business, as enablers, have already radically transformed many operations in the construction sector and there is still a vast potential for more. IT can deliver significant benefits for designers, constructors and building operators. Deriving the maximum benefit from introducing IT solutions will not, however, be easy. There is the potential to drastically reduce infrastructure cost behind the tendering side of the industry by adopting the wider use of the Internet and e-procurement specifically. 7.9 The widespread adoption of e-business and virtual prototyping requires the construction industry to transform its traditional methods of working and its business relationships. Key barriers to this transformation include organisational and cultural inertia, scale, awareness of the potential and knowledge of the benefits, skills, perceptions of cost and risk, legal issues and standards. Weighed against this, the potential benefits are:
 * Efficiencies and skills development from knowledge management
 * Economy and speed of construction;
 * Improved business relationships;
 * Product and process improvement; and
 * Technology and entrepreneurship.

Having put ICT at the heart of a modern, forward-looking AEC industry, it was gratifying that four years later when the 2012 Construction Commitments were published, the signatories said: "IT-based collaborative tools and communication technologies will be exploited."

However, despite the clear role that Accelerating Change identified for ICT, there was only one mention of ICT in the BERR Draft Strategy for Sustainable Construction (2007). Although it is recognised that ICT is not a means to an end in itself, rather it is an enabler, its absence is conspicuous.

In this first decade of the 21st century, the AEC industry has already begun to adopt a wide range of ICT tools to streamline industry processes and improve finished outputs. Industry professionals are routinely employing standard office tools (word processing, spreadsheets, email, personal calendar, etc), and an increasingly sophisticated range of specialist applications, eg:
 * CAD applications and, increasingly, building information modelling (BIM) software (taking design from 2D through 3D to 4D and beyond: nD), including cost, energy and thermal modelling that can be used to support assessment tools (eg: BREEAM) and performance indicators (eg: Environmental Performance Indicators, EPIs)
 * document and drawing management tools, also known as 'construction collaboration technologies' or 'extranets'
 * project management tools
 * tendering, estimating and e-procurement applications

In addition to these existing tools, new applications and technologies are emerging that have the potential to revolutionise the AEC industry still further over the next decade and beyond:
 * search-related applications (including RSS and Google alerts to allow users to access existing data rather than 'reinventing the wheel')
 * online meeting tools (eg: Microsoft LiveMeeting, WebEx)
 * Web2.0 social applications (‘virtual’ worlds such as Second Life are already being explored by some architects as a way to show client 'avatars' around design concepts)
 * Mashups – online services typically created by combining data from two or more data sources (eg: linking real-time traffic data with Google Maps).
 * Using RFID (radio-frequency identification) tags to help gather in-service data from assets providing a whole-life cost per m2 or similar metrics

But, in the meantime, as Accelerating Change (s7.9) anticipated, traditional methods of working and business relationships often still create barriers to efficient use of ICT. While many construction organisations are increasingly sophisticated at managing internal information (frequently creating considerable internal ICT departments in the process), they are often less good at sharing information with other project team members, and/or with the ultimate owner/operator/occupier/user of the facility they create. 'Whole life' information issues are rarely considered.

Fortunately, there is a small but growing section of the UK AEC industry that, even if it has not yet embraced the key messages relating to integrated teams and collaborative working, has recognised that real efficiency savings can be achieved by adopting a range of conventional and Software-as-a-Service (Saas) ICT tools. In many instances these tools can also contribute towards improvements in sustainability. While the full potential of new design tools has yet to be realised, some parts of the AEC industry have already begun to deploy information and process management applications, including those delivered on a SaaS basis, to good effect.

Designing for sustainability
Architects, engineers and other designers have an increasingly sophisticated array of tools at their disposal to help them design new built assets more efficiently. These tools can often also be deployed to:
 * support more sustainable planning, design and construction (this can extend to the very earliest consultation stages where stakeholders might discuss the suitability of early 3D concepts to their immediate and future local needs, and extend through the design process to allow users to ‘walk-through’ or ‘fly-through’ the proposed asset)
 * provide ‘carbon calculators’, albeit too often focused on the asset – its materials and its energy performance - rather than the processes employed by the designers, contractors and suppliers involved in its construction
 * after handover, to reduce the carbon footprint associated with operation and maintenance throughout its working life
 * recycling of materials following demolition/dismantling of the asset.

For example, building information management (BIM) applications are being used during design to provide architects, engineers and designers with feedback about the impact of their design decisions on the BREEAM or EcoHomes ratings of a project. Such tools allow design teams to continually assess the sustainability performance of their proposed designs, including:
 * embodied energy in construction materials, including transport to site
 * off-site fabrication, just-in-time delivery to site, and construction sequencing
 * energy use (particularly in lighting, refrigeration and heating, ventilation and air-conditioning), including use of renewables (eg: solar power, wind turbines, etc) and solar gain
 * water use (including ‘grey water’ reuse)
 * storm water run-off
 * recycled material content
 * carbon footprint
 * daylighting

However, the UK AEC industry is still some way from adopting BIM approaches across a significant number – let alone the majority - of projects. People and process issues (including professional education, legal, insurance and contractual issues) remain a considerable hurdle to be overcome if the full benefits of BIM are to be realised.

More efficient information and process management
Traditional project planning, design and construction management processes have historically been heavily reliant upon paper. Fragmented project teams based in geographically dispersed locations with no or poor telecommunications, and working in a highly-contractual, risk-averse commercial environment, have generally focused on the exchange of information in a tangible, paper-based form.

From the 1980s onwards, substantial amounts of this information were generated electronically, but only latterly have project teams begun to use distribute, discuss, document decisions and then archive this information electronically. The emergence of de facto standards (eg: Microsoft Office) for office software has been a factor, as has the adoption of internet-based tools (including email, websites and – during the past 10 years – locally-hosted and SaaS-delivered web applications) and the development of various data standards and viewer technologies.

While there is still much to do, some parts of the UK AEC industry (like their counterparts in north America and some European countries) have begun to address paper-related issues. The following three sections briefly describe, through examples, how the industry has:
 * reduced paper consumption
 * reduced resources devoted to paper production, management and storage
 * reduced transportation and distribution

Reduced paper consumption
For example, adoption of construction collaboration technologies ('extranets') has reduced the amount of paper produced and disseminated within project teams.

BIW Technologies is one of the UK’s leading providers of collaboration technologies and, according to its own internal research, a typical construction drawing or document is copied and distributed to eight recipients. From January 2000 to October 2007, BIW users published 3 million original construction drawings, which were potentially distributed via 24 million copies. Similarly, 1.7 million original documents, plus 13.6 million copies, were also published. Electronic publication and dissemination does not eliminate paper altogether; some items will still be printed out – but around 60% will not. So far as the BIW user community alone is concerned, this equates to a paper saving of around 16 million drawings and 9 million other documents – equivalent to a pile of paper 4.3km high, weighing 1700 tonnes. "Note: this is just the paper saving arising from the paper items themselves. It does not include associated transmittal notes, printing cover sheets, packaging, etc." (BIW is urging fellow members of the NCCTP to collate figures for their users to improve understanding of the potential paper savings arising from employing such technologies).

Reduced paper production, management and storage
Reduced production of paper-based drawings and documents has also led to reductions in the requirement for hardware, consumables, personnel and other associated overheads:
 * fewer plotters, printers, photocopiers, scanners, faxes, etc – for example, teams may require fewer (and/or lower-specification) printers
 * lower overheads - being less heavily-used they break-down less frequently and require less maintenance
 * reduced energy consumption - using fewer, smaller devices will also reduce an organisation’s energy use for power and heat-reduction
 * reduced consumption of consumables, ie: ink, toner
 * fewer filing cabinets, suspending files, archive boxes, etc
 * lower ‘warehousing’ requirements - for example, on one traditionally-managed project, an airport operator collated enough paper to fill an entire Portakabin full of filing cabinets
 * reduced personnel – producing less paper and producing what little is required more efficiently can both result in lower manpower requirements, with a corresponding environmental benefit in terms of building-related costs (floorspace, furniture, heating, lighting, etc)

Reduced transportation and distribution of paper
Looking at the expenses associated with processing and distribution of project paperwork, substantial quantifiable transport and manpower savings can also be achieved. For example, US research found

 * on a single three-year project in the US, e-collaboration saved $160,992 [c. £80,000] in FedEx courier costs
 * processing 807 RFIs saved $13, 457 [£6,700] in manpower costs and a further $694 [£350] in printing, fax and mailing costs
 * RFI turnaround cut from average 14 days (paper-based system) to 5.44 days for e-RFIs
 * E-tendering of 20 work packages instead of traditional paper-based tendering saved $23,520 [£11,750] manpower costs and $29,000 [£14,500] printing and mailing costs

Based on an analysis of some five million paper items distributed during 251 projects since 2000, UK collaboration vendor Cadweb has calculated that it has saved distribution of 140 tonnes of paper, saving 87,000 litres of fuel and 407 tonnes of CO2 emissions.

Automating official processes involving central or local government and/or statutory agencies can also reduce travel requirements. Allowing online completion and submission of forms has been shown to reduce carbon dioxide emissions; web self-service has also been found to be more cost-efficient than conducting administrative tasks in person.

Process improvement
Reliance on some paper-based documentation has already begun to decline as project teams expand their reliance on electronic tools to manage certain processes such as compilation of the project Health & Safety File (see following example). Such tools also encourage re-use of data within projects and for post-construction purposes: Under the CDM Regulations, project teams are obliged to produce a substantial Health and Safety File for each completed project. Once comprising paper-based as-built information, this would typically be contained in a large number of ring-binders. It was normally produced retrospectively at the end of a project, was time-consuming to produce, repeated information in different sections, and was usually out-of-date by the time it was delivered. Using an electronic collaboration platform, however, the Health and Safety File could be compiled progressively during the project, and comprised a single indexed instance of all relevant data. Managed online or saved to a hard disk drive, the electronic health and safety file is quickly searchable and provides a powerful online ‘whole life’ information resource from which data can be extracted for repair, maintenance, extension, refurbishment, due diligence during asset sale, etc, and then updated.

Of course, some information may need to be reused across a range of projects, perhaps by several different project teams all working for the same customer. For example, corporate standards (ie: standard designs, branding, contracts, specifications, etc) may need to applied to a succession of projects for a particular client. Again, online collaboration tools are already being deployed to manage such cross-project reference.

There are also, of course, opportunities to use online collaboration platforms to manage AEC project processes which are specifically focused on sustainability. For example:
 * site waste management plans became compulsory from 6 April 2008 for all projects in England over £300,000, and - like CDM requirements – involve creation and periodic updating by different team members of a shared repository of information
 * supply chain delivery logistics could also be managed online via browser-based programs

Better knowledge management
Similar efficiency savings can be achieved by using intranets and/or extranets for knowledge management processes where information needs to be created and stored for later reference, re-use and update.

Many AEC firms have invested in intranets to manage communications and both general and specialist knowledge within their organisations: Arup, for example, has created numerous ‘communities of practice’ within the firm, where a combination of face-to-face and ‘virtual’ meetings – facilitated by the company’s intranet - are used to develop the firm’s intellectual capital in a wide variety of specialisms. Similarly, Bovis Lend Lease has ‘ikonnect’, a web-enabled information-sharing service that provides staff with quick and direct access to the best available knowledge anywhere in the company.

Wiki technologies also have potential. For example, architects Fielden Clegg Bradley and Edward Cullinan Associates have both deployed intranet-based wikis to manage knowledge within their practice, allowing authorized users to add, edit and update information at any time via a standard web-browser.

As already mentioned, the explosion of electronic communication and the proliferation of web-based information sources can create 'information overload', reducing individual productivity and efficiency. Yet, tools exist to help AEC users find key information more quickly, whether it is on their own PC, within a community of practice or project team group, or available on the worldwide web. For example: Tools also exist that allow users to be automatically notified when new information relevant to their interests appears on the web; for example:
 * Desktop search applications help users find information stored on their own personal computers more quickly
 * Most intranets and extranets incorporate powerful content search engines
 * ‘feed readers’ deliver content from RSS ("Really Simple Syndication") ‘feeds’ of updated content such as blog entries, news headlines or podcasts
 * Users can create and configure their own ‘home pages’ featuring feeds from regularly used information sources (newspaper headlines, blog entries, weather information) and simple desktop applications (eg: currency converters, clocks, maps, puzzles, etc) – iGoogle pages, for instance, can be populated from a choice of literally hundreds of linked feeds and gadgets.
 * Google alerts are automated searches conducted at defined intervals which generate emails to the user highlighting information on specified keywords or phrases
 * Many online discussion forums and special interest websites feature alert functions that notify users when new information on a particular topic has been published or when a particular webpage has been updated.

However, this is perhaps a need to educate many AEC computer users about such tools.

Improved mobility, productivity and 'Respect for People'
Using electronic tools can lead to dramatic increases in personal productivity, partly arising from the automation of some previously laborious or routine clerical processes – creation and management of RFIs, transmittals and other forms via extranets, for example, or faster searches for information via extranets, intranets, the web, etc. Some organisations have found that a single document controller using extranet technology can manage two or more parallel projects without having to be based on-site (as previously mentioned such reduced manpower requirements can lead to lower building-related costs).

Moreover, the automation of repetitive clerical tasks has resulted in an improved quality of work for some staff. Instead of being focused on inputting and recording paper processes, document control staff become local experts in using the collaboration platforms, performing first-wave helpdesk, training and trouble-shooting functions (one major contractor has devised a career structure that retains competent document controllers within the company instead of releasing them at the end of a project-related contract, reducing staff ‘churn’ and recruitment costs in the process).

Mobile ICT solutions can also facilitate reductions in construction time and capital costs. Using hand-held devices to capture data on-site, for example, eliminates re-keying of information and, combined with GPS (Global Positioning System) capability, can provide certainty about the physical location where the data was retrieved. Network Rail have successfully deployed such technologies for earthworks inspections, BIW Technologies has developed a mobile, PDA-based defects management solution which is integrated with its web-based collaboration platform, and there is clear potential to develop mobile solutions incorporating bar-code readers and/or RFID tags to manage the logistics of components and materials deliveries and to manage efficient use of these items - ie: the elimination, or at least reduction, of on-site waste.

The capacity for mobile ICT to support flexible working should also not be under-estimated. While some face-to-face meetings will always be necessary, it is not always vital for individuals to be based in a particular office in order to work. The new generation of web-based collaboration tools make project-related data accessible anywhere, anytime, on any PC, meaning team members can sometimes work from home or other locations – useful if individuals need flexibility to manage their home/work balance.

Similarly, some meetings can also be ‘attended’ virtually, using online meeting applications (eg: Microsoft LiveMeeting and WebEx) – perhaps in parallel with telephone calls, and/or in combination with webcams or video-conferencing – to eradicate travel time and cut costs and carbon footprint. Even if individuals cannot attend the meeting in real-time, they may still be able to review a recording of the event via a streamed video or downloadable podcast.

Rationalising and centralising ICT hardware
Software-as-a-Service (Saas) is the term used to cover software applications (and associated data) that do not reside on the user’s own computer or network, but are hosted remotely by the software vendor and are accessed via a standard web-browser. In the AEC industry, construction collaboration technologies tend to be delivered on a SaaS basis; there is no shrink-wrapped software to transport: no disks to load, no packaging, no bulky manuals. Externally-hosted, web-based solutions also mean no, low or lower in-house IT hosting, support and storage requirements – widespread use of SaaS applications could dramatically reduce the scale of in-house ICT resources, with a corresponding reduction in hardware, data storage, personnel, energy use and other overheads. Of course, some may argue that out-sourcing application and data-hosting to a SaaS provider simply moves overheads elsewhere. However, in-house technology is often only replaced and updated infrequently and is reliant upon existing, often energy-inefficient hardware and systems. By contrast, SaaS providers centralise the operations of multiple customers in single data centres, managing customers’ software and data on a multi-tenant basis (ie: sharing a common but scalable infrastructure, usually in a dedicated, secure, purpose-built facility, with multiple back-up systems). Rather than project team members running several separate hosting environments, all consuming power even when the systems are not fully utilised, the SaaS approach concentrates all the hardware and software in industrial-scale facilities that makes optimum use of energy to power the hardware, provide cooling, etc - “economies of scale”. Thus, while such server-farm facilities are demanding in their use of power, they will consume less energy than the multiple end-users trying to maintain their own separate ICT infrastructures. Market forces will also help ensure such data centres remain efficient; faced with rising energy costs, data centre owners must invest in energy-efficient equipment and techniques (including consolidation, workload balancing, server virtualization and use of ‘blade’ servers) to remain agile and competitive.

It is also worth considering the potential impact of web-delivered applications and data on what type of devices are used by end-users. With software and associated data sitting ‘in the cloud’ (ie: hosted on a remote server and accessed via the internet), there is less requirement for users to have large numbers of applications and related files sitting on their hard-drives. Assuming the availability and capacity of broadband connections – especially wireless (3G, GPRS, WiMax) - continues to grow, then users may start to employ simpler, smaller, lighter and more portable devices requiring less power and maintenance and which become obsolete less quickly. Such ‘thin-client’ alternatives are already less material-intensive and more energy-efficient (even allowing for the power to run the remote central servers) than conventional PCs. A case study on adoption of thin-client technology (plus consolidation and virtualization) by recruitment firm Reed Managed Services showed that this strategy reduced power consumption by about 5.4M Kilowatt hours (and reduced annual IT spend by 20%).

Many SaaS solutions are also simpler to implement, requiring less face-to-face consultancy and training, and so reducing travel requirements. SaaS providers also frequently provide a centralised helpdesk service that can be contacted 24/7, and which aggregates experience and knowledge across multiple customer and end-user organizations to deliver a faster, higher quality support service; such a service obviates the need to establish and maintain an in-house resource.

Concluding remarks
Sustainability is the major challenge facing the AEC industry, and ICT has a key role to play. Electronic construction collaboration systems and other ICT tools have already begun to deliver quantifiable benefits to the AEC industry. Emerging and future ICT developments have the potential to extend these benefits still further. Yet, many of the benefits remain relatively modest due to an industry tendency to replicate existing manual AEC processes with electronic versions of the same processes. The AEC industry needs to address some very fundamental people and process issues to unleash the full benefits.

For example, ICT is a potentially powerful tool to support industry customers and project teams who want to adopt more transparent, collaborative ways of working, with early and full involvement of their supply chains. A vision of how this might work was created in the final report of the ICT and Automation working party for the National Platform for the Built Environment (2007): the vision was dubbed Built Environment 2020:

Clients work with a multi-disciplinary team to use existing knowledge about their activities, anticipated future requirements, and industry knowledge about similar client needs to agree a brief - describing the organisational need for future facilities, and working on the principles of best whole-life value. As the brief is developed, additional team members are brought into the team as early as possible, and begin to use a virtual environment to prototype or model solutions which meet all the various dimensions of the brief – functionality, aesthetics, logistics, ease and safety of construction, operation and maintenance, whole life cost, sustainability, etc. Regardless of their location, all authorised project participants can interact with this virtual environment using various different computer hardware/software combinations, with the latest model version being readily available online, and over time being progressively populated to increasing levels of detail. Once a consensus is reached about the finished form of parts of the facility, manufacturers and suppliers (already involved in the design process) reuse model information for offsite fabrication (perhaps extensively automated) of the required components in the optimum sequence for just-in-time delivery to the correct zone at the facility’s location. Each component has an embedded device that carries all relevant information about its manufacture, material, service requirements, etc, and its arrival on site is, of course, automatically recorded. Once delivered, each component is swiftly and safely installed in its precise position by skilled site operatives - supported, where appropriate, by robot devices. All site operatives, project managers and other personnel wear small devices that monitor their exact position, giving warnings, where necessary, regarding the individual’s safety and security. These wearable devices can also provide data about individuals’ immediate surroundings (drawing on the embedded data in installed components and data stored in the virtual model), helping, for example, operatives to undertake site activities, with context-sensitive viewing tools (e.g. VR glasses) providing audio-video installation guidance. Those with managerial responsibilities can interrogate the online environment to get real-time updates on schedules, projects costs and other performance parameters – the same data also being available simultaneously to, for example, a client representative sitting in a remote geographic location – perhaps in another time-zone. As on-site processes are completed, the virtual environment is populated with as-built data that can be seamlessly reused for operation and maintenance purposes. The building model thus becomes a powerful asset management tool, linking the facility owner/operator with relevant suppliers or maintenance contractors, with all repairs or replacements automatically recorded. The actual in-service performance of building components is logged and can be interrogated by the owner/operator, manufacturers/suppliers, and by authorised professionals tasked with designing and delivering similar facilities for the same or (subject to confidentiality limits) similar clients. Similarly, any extensions, alterations or changes of use of the facility are also recorded for feedback purposes, and to inform future developments.

Sustainability is just one dimension considered in this vision, but the scenario described above shows how radically the industry could change, supported by ICT and automation. The AEC industry must embrace opportunities to:
 * 1) overcome existing regulatory and technological hurdles – such as constraints on reuse of public data, and interoperability
 * 2) research, develop and implement new ICT tools and technologies
 * 3) develop new structures and processes that allow it to take full advantage of new ICT, and
 * 4) perhaps most importantly, educate and train users in these new processes and the associated technologies.

Clearly, the successful development, introduction and deployment of new technologies and new ways of working will require very different skills of the future workforce. With the future of the planet’s resources at stake, the AEC industry cannot afford to prevail with existing project delivery processes. It needs to be prepared to develop and implement new ways of working alongside the new generation of ICT capabilities.


text:
User talk:SarahB

Welcome
Hello SarahB, and welcome to Wikiversity! If you need help, feel free to visit my talk page, or contact us and ask questions. After you leave a comment on a talk page, remember to sign and date; it helps everyone follow the threads of the discussion. The signature icon in the edit window makes it simple. To get started, you may
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And don't forget to explore Wikiversity with the links to your left. Be bold, and see you around Wikiversity! --JWSchmidt 17:44, 4 February 2008 (UTC)

title: User talk:SarahB


text:
Supporting the Sustainability Agenda through the effective use of ICT/ICE briefing sheets

What is a Briefing Sheet
A briefing sheet is a very concise summary of a subject or document, intended to provide easily accessible information for professionals and interested laypeople.

Their intention is to fill a gap between lightweight journalistic reporting, and long publications that can take many hours to read and absorb. They help the reader understand the general scope and content of a subject, or document, and to act as an aide memoire. They are not intended as working documents. Individuals are advised to consult source documents for definitive information.

Types of Briefing Sheet
There are two main types of briefing sheet

 * best practice reviews
 * precis of publications

The Best Practice type of briefing sheet provide the reader with a concise, easy to read overview of a subject. The Precis type briefing sheets provide the reader with an overview of a document, such as a key government policy document or guidance.

Content
Not a word wasted

Make your summary add to the document - make it simpler - try to enhance the document’s logical structure - even when it doesn’t have one.

Add Diagrams and Graphics- Produce a diagram to express the logical structure if you think it appropriate. Add graphics, or flow diagrams if that would help the reader understand.

Use the headings in your briefing sheet to summarise the document - the aim should be for the reader to be able to get an immediate grasp of the document just by reading the headings of the briefing sheet. Ensure the headings mean something.

Lists - Always arrange lists with a separate line or bullet for each item - rather than compressed into a paragraph - surveys show they are easier to take in when laid out in the former way.

Sentence Structure - Consider arranging the sentence structure on lists so that you have the subject, or main recommendation at the start of the sentence, you can then put it in bold print - which the reader can then scan - eg:

place the sentence subject first - this makes it easier for the reader to scan the briefing sheet. (but don’t go over the top with bold text).

Respect Copyright
Where the copyright of a document you are summarising belongs to someone else - you can

 * ask them for their permission to make the summary - which can be no bad thing, as it potentially generates good will, or alternatively

If ICE or Thomas Telford holds the copyright, then you may lift text liberally.
 * completely re-write the document to ensure that there is nothing that is directly lifted from the source document.

Suggested Structure for the Briefing Sheet
Start with an introduction which states what the briefing sheet is about and other reference details.

This briefing sheet is a summary of a report by the published 1998 and available from - price.

Add a highly compressed summary of the key points in the document Super Summary

Add the main summary of the document. Use your judgement as to what you summarise as opposed to stating what the document includes.

Add appendices

In many instances it will be enough to list them – perhaps giving a flavour of what it contains.


text:
Computer Architecture Lab/WS2007/Project -1 Lab4/Samples

Sample Files
To write a program for the Lucky Processor following steps are necessary:

 * 1) Use the assembler instructions to write an assembler program and save it as MyProgram.asm
 * 2) Drag the MyProgram.asm File on the "ToInstrMemUpdate ROM-File ASM.bat" Icon; Press Enter when it's finished
 * 3) Compile the Lucky.qpf Project in Quartus
 * 4) In the Command Prompt type in: "USBRunner MIPTop.rbf"

RandomBitTest.asm
Counts the number of 0s and 1s and writes, this and the content of the Random Register, to the Terminal.

UART_SEND_STRING("Let's Go!",&pc); LLI ("4", "0"); //Initial Value of Register 4 that contains 0s = 0 LLI ("5", "0"); //Initial Value of Register 5 that contains 1s = 0 LLI ("6", "1"); //Adder value LABEL(OUTPUT) //Here the actual values of $1E and counted 0s and 1s are written to the terminal ADD("1","0","1E"); /* get current random value */ UART_SEND_STRING("\r\nInhalt Random Register: ",&pc); DEBUG_SEND("1",&pc); /* send random value */ UART_SEND_STRING("\r\nANZAHL 0en: ",&pc); DEBUG_SEND("4", &pc); /* send counted 0s */ UART_SEND_STRING("\r\nANZAHL 1en: ",&pc); DEBUG_SEND("5", &pc); /* send counted 1s */ BOR(TAKEN); ADD("4", "4", "6"); //if Random Bit is not set Add 1 to 0s-Register BR(OUTPUT); //Jump to OUTPUT LABEL(TAKEN) ADD("5", "5", "6"); //if Random Bit is set Add 1 to 1s-Register BR(OUTPUT); //Jump to OUTPUT

HelloWorld.asm
Writes "Hello World! " to the Terminal

UART_SEND_STRING("Hello World! ",&pc); LABEL(infinity) NOOP; BR(infinity);

BlinkingLEDs.asm
Toggles 2 LEDs

LLI("0", "0");			// $0:= 0 LLI ("1",io_WD); LLI ("2", io_LED0); LLI ("3", io_LED1); LLI("4", "1");			// $4:= 1; SW("1","4");			// MEM(io_WD) = 1 SW("2","4");			// MEM(io_LED0) = 1 SW("3","4");			// MEM(io_LED1) = 1 LLI("8", "1");			// $8:= 1; LABEL(prewait) LLI("6","0000"); 		// $6:= 0 SLL("6","6","8");		// $6:= 0 LLI("7","04");			// $7:= 4 ADD("6","6","7");		// $6:= 4 LABEL(wait) SUB("6","6","4");		// $6:= 3 .. 2 .. 1 .. 0 		BZS(selectswap); BR(wait); LABEL(selectswap) ADD("8","8","0");		// ...... $8:= 1 		BZS(swap); BR(swap2); LABEL(swap) SW("1","0"); SW("2","4"); SW("3","4"); LLI("8", "1"); BR(prewait); LABEL(swap2) SW("1","4");			// ...... SWITCH Leds .... SW("2","0"); SW("3","4"); LLI("8", "0"); BR(prewait);

casino.asm
A Slotmachine: Press any key to start the game, use Button0 to increase coins

/* **** Casino 0.1 **** Coins: 1 Result: x x x ********************** **** Casino 0.1 **** Coins: 1 Result: x x x YOU HAVE WON y COIN(s)!!! NEW GAME      PRESS SWITCH 1 INSERT COIN    PRESS SWITCH 2 ********************** Gewinn wird in Coins ausgezahlt x = {A, B, C} Wenn Alle gleich => +3 Coins Fang immer mit A B C an Schleife 32 x Timer ... Je nach ZV wechsle x1 .. x3 	Beim Wechseln piepe, toggle Leds ZV: xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx 1111 1111 0101 0010 0100 1000 1000 1000 	A 1111 0101 0010 0100 1000 1000 1000 0100 	A*	= 0xF5248884 1010 1010 0100 1000 1000 1000 0100 0010 	B*	= 0xAA488842 0010 0100 1000 1000 1000 0100 0010 0001 	C*	= 0x24888421 0100 1000 1000 1000 0100 0010 0000 1000      B 1000 1000 1000 0100 0010 0000 1000 0010       B* 1000 1000 0100 0010 0000 1000 0010 0000       A* 1000 0100 0010 0000 1000 0010 0000 0100	A 0100 0010 0000 1000 0010 0000 0100 0000	C* 0010 0000 1000 0010 0000 0100 0000 1000	C */ //***************************************************** D E  F  I  N  E  S ***************************************************** // ******************************************** PROG PARAMETERS // ******************************************** ASCII // ******************************************** MEMORY // ******************************************** REGISTER-INDEX // Special Regs // PUSHED TO STACK // must watch consistency for yourself START //******************************************** I N  I  T  I  A  L  I  Z  A  T  I  O  N ************************************* // Standard-Register inits LLI (LED0_REG, io_LED0); LLI (LED1_REG, io_LED1); SW(LED0_REG, ZERO_REG); SW(LED1_REG, ZERO_REG); LLI (INC_REG, "1"); LLI (RN_MEM_REG, RN_MEM); // store init values for random numbers into RAM ADD (TR1, RN_MEM_REG, ZERO_REG); LOAD_BIG_NUMBER (TR2, TR3, "F5248884", &pc);		// speichere schnelles A 	SW (TR1, TR2); ADD (TR1, TR1, INC_REG); LOAD_BIG_NUMBER (TR2, TR3, "AA488842",&pc);		// speichere schnelles B 	SW (TR1, TR2); ADD (TR1, TR1, INC_REG); LOAD_BIG_NUMBER (TR2, TR3, "24888421",&pc);		// speichere schnelles C 	SW (TR1, TR2); // ###FIX: C wird viermal reingespeichert, da vom random generator ein index im Bereich [0,3] geliefert wird ADD (TR1, TR1, INC_REG); SW (TR1, TR2); // Init Coin Number and Results LLI (TMEMR1, COINS); LLI (TR1, "3"); SW (TMEMR1, TR1); LLI (TMEMR1, RN2); LLI (TR1, "1"); SW (TMEMR1, TR1); LLI (TMEMR1, RN3); LLI (TR1, "2"); SW (TMEMR1, TR1); //### default is zero //***************************************************** M  A   I   N    ***************************************************** LABEL(MAIN) //******************* G E T    R A N D O M    N U M B E R S //******************* S T A R T    G A M E 	LOAD_BIG_NUMBER (GLOBAL_INDEX_REG, TR3, "80000000",&pc); // decrement coins LLI (TMEMR1, COINS); LW (TR1, TMEMR1); SUB (TR1, TR1, INC_REG); SW (TMEMR1, TR1); CALL (SHOW_BOARD); CALL (GET_RANDOM_NR); LABEL(SWAP_CONTINUE) CALL(WAIT); CALL (SWAP); CALL (SHOW_BOARD_REFRESH_RNs); SRL (GLOBAL_INDEX_REG, GLOBAL_INDEX_REG, "1"); BZS (SWAP_END); BR(SWAP_CONTINUE); LABEL(SWAP_END) CALL (CALCULATE_COINS); CALL (WAIT_FOR_NEXT_GAME); BR (MAIN); //***************** G E T  R A N D O M   N U M B E R S ************************************************* LABEL(GET_RANDOM_NR) LLI (TR2, "3"); //###FIX: RNMEM+3 moeglich, daher wurde oben der Wert fuer C zweimal eingefuegt LLI (TMEMR1, RN1_SWAP); LLI (TMEMR2, RN3_SWAP); ADD (TMEMR2, TMEMR2, INC_REG); LABEL(INIT_RNs_LOOP) AND (TR1, RANDOM_REG, TR2);	//###FIX: TR4 uebernimmt vorlaufig Part des Random Registers ADD (TR3, TR1, RN_MEM_REG);	// TR3 := Random_Number (untere 2 Bits) + Addresse vom schnellen A bzw B, C 	LW (TR1, TR3); SW (TMEMR1, TR1); 		// MEM (RN1_SWAP) := MEM (TR3); ADD (TMEMR1, TMEMR1, INC_REG); // inkrementiere Pointer solange bis RN1_SWAP bis RN3_SWAP geschrieben wurde SUB (TR1, TMEMR2, TMEMR1); BZS (INIT_RNs_END); BR(INIT_RNs_LOOP); LABEL(INIT_RNs_END) RETURN; //***************** C A L C U L A T E   C O I N    N U M B E R     ************************************************* LABEL(CALCULATE_COINS) LLI(WIN_REG, WIN); LLI (LMEMR1, RN1); LLI (LMEMR2, RN2); LW(TR1, LMEMR1); LW(TR2, LMEMR2); SUB(TR3, TR1, TR2); BZC(NO_WIN); LLI (LMEMR1, RN3); LW(TR2, LMEMR1); SUB(TR3, TR1, TR2); BZC(NO_WIN); // WIN SW(WIN_REG, INC_REG); LLI (TMEMR1, COINS); LLI (TR2, "3"); LW (TR1, TMEMR1); ADD (TR1, TR1, TR2); SW (TMEMR1, TR1); UART_SEND_STRING ("\a\n\r Y O U   W I N    3    C O I N S !!!!! \n\r",&pc); BR(CALCULATE_COINS_END); LABEL(NO_WIN) SW(WIN_REG,"0"); UART_SEND_STRING ("\a\a\n\r Y O U   L O O S E    1    C O I N!!!!! \n\r",&pc); LABEL(CALCULATE_COINS_END) RETURN; //*********************************************************** S W A P    ************************************************* LABEL(SWAP) LLI (LR1, "0"); LLI (TR3, "3"); LLI (LMEMR2, RN1); LLI (LMEMR1, RN1_SWAP); LLI (TMEMR1, RN3_SWAP); LABEL(SWAP_LOOP) LW (TR1, LMEMR1); AND (TR2, GLOBAL_INDEX_REG, TR1); BZS (NO_SWAP); LABEL(DO_SWAP) LLI (LR1, "1"); LW (TR1, LMEMR2); ADD (TR1, TR1, INC_REG); SUB(TR2, TR1, TR3); BZC(SWAP_RN); LLI (TR1, "0"); LABEL(SWAP_RN) SW (LMEMR2, TR1); LABEL(NO_SWAP) ADD (LMEMR1, LMEMR1, INC_REG); ADD (LMEMR2, LMEMR2, INC_REG); SUB (TR1, TMEMR1, LMEMR1); BNS (END_SWAP); BR(SWAP_LOOP); LABEL(END_SWAP) SUB(LR1, LR1, INC_REG); BZC(END_SWAP2); UART_SEND_STRING ("\a",&pc); LABEL(END_SWAP2) RETURN; //*********************************************************** W A  I  T     ************************************************* LABEL(WAIT) LOAD_BIG_NUMBER (TR1, TR3, WAIT_VALUE,&pc); 	// Index bit ist MSB LABEL(WAIT_LOOP) SUB (TR1, TR1, INC_REG); BZS (WAIT_END); NOOP; BR(WAIT_LOOP); LABEL(WAIT_END) RETURN; //********************************************* D I  S  P  L  A  Y   B  O  A  R  D     ************************************ LABEL(SHOW_BOARD) UART_SEND_STRING ("\f\r\n**** Casino 0.1 **** \n\r\nCoins: ",&pc); LLI (TMEMR1, COINS); LW (TR1, TMEMR1); ADD (TR1, INC_REG, TR1);	// Notwendig damit die Schleife richtig terminiert LABEL(SHOW_BOARD_COINS) SUB (TR1, TR1, INC_REG); BZS (SHOW_BOARD_RNS_INIT); UART_SEND_STRING ("c",&pc); BR(SHOW_BOARD_COINS); LABEL(SHOW_BOARD_RNS_INIT) UART_SEND_STRING("\n\rResults: ",&pc); LABEL(SHOW_BOARD_RNS) LLI (LMEMR1, RN1); SUB (LMEMR1, LMEMR1, INC_REG); // Notwendig damit die Schleife richtig terminiert LLI (LMEMR2, RN3); ADD (LMEMR2, LMEMR2, INC_REG); // Notwendig damit die Schleife richtig terminiert LABEL(SHOW_BOARD_RNS_LOOP) ADD (LMEMR1, LMEMR1, INC_REG); SUB(TR1, LMEMR2, LMEMR1); BZS (SHOW_BOARD_END); LW (TR1, LMEMR1);		// TR1 ist aktueller Wert der betrachteten Zufallsvariablen SUB (TR2, TR1, INC_REG);	// Wenn TR1 == 1 dann PRINT B 	BZS (PRINT_B); SUB (TR2, TR2, INC_REG);	// Wenn TR2 == 2 dann PRINT C 	BZS (PRINT_C); //PRINT_A: UART_SEND_STRING ("A ",&pc);	// Ansonsten PRINT A 	BR(SHOW_BOARD_RNS_LOOP); LABEL(PRINT_B) UART_SEND_STRING ("B ",&pc); BR(SHOW_BOARD_RNS_LOOP); LABEL(PRINT_C) UART_SEND_STRING ("C ",&pc); BR(SHOW_BOARD_RNS_LOOP); LABEL(SHOW_BOARD_END) RETURN; LABEL(SHOW_BOARD_REFRESH_RNs) UART_SEND_STRING ("\b\b\b\b\b\b",&pc); BR(SHOW_BOARD_RNS); LABEL(WAIT_FOR_NEXT_GAME) UART_SEND_STRING (" \n\r",&pc); UART_SEND_STRING (" \n\r",&pc); UART_SEND_STRING ("**********************\n\r",&pc); LABEL(check_UARTInput_INIT) LLI (TR1, io_UART_RXD_HAS_NEW_VALUE); LLI (TR2, io_BUTTON0); LABEL(checkUARTInput)		// wait on any uart input LW (TR3, TR1);		// check io_UART_RXD_HAS_NEW_VALUE BZC(START_NEW_GAME); 	// wait on new received byte LW (TR3, TR2); BZC(INSERT_COIN); BR(checkUARTInput); LABEL(NO_COINS_AVAILABLE) UART_SEND_STRING ("** S O R R Y, Y O U  H A V E   N O   M O R E   C R E D I T S! ** \n\r",&pc); BR(check_UARTInput_INIT); LABEL(INSERT_COIN) UART_SEND_STRING ("+ + Coin inserted + +\n\r", &pc); LLI (TMEMR1, COINS); LW (TR3, TMEMR1); ADD (TR3, TR3, INC_REG); SW (TMEMR1, TR3); CALL(WAIT); BR(check_UARTInput_INIT); LABEL(START_NEW_GAME) LLI (TMEMR1, COINS); LW (LR1, TMEMR1); ADD (LR1, LR1, "0"); BZS (NO_COINS_AVAILABLE); LABEL(SHOW_BOARD_FINISH_END) RETURN;
 * 1) define WAIT_VALUE		"00025B9A"
 * 1) define BACKSPACE		"8"
 * 2) define LF			"A"
 * 3) define CR			"D"
 * 1) define RN_MEM			"10"
 * 2) define COINS			"60"
 * 3) define RN1			"61"
 * 4) define RN2			"62"
 * 5) define RN3			"63"
 * 6) define RN1_SWAP		"64"
 * 7) define RN2_SWAP		"65"
 * 8) define RN3_SWAP		"66"
 * 9) define WIN			"67"
 * 1) define ZERO_REG		"0"
 * 2) define RANDOM_REG		"1E"
 * 1) define INC_REG			"1"
 * 2) define RN_MEM_REG		"2"
 * 3) define LMEMR1			"3"
 * 4) define LMEMR2			"4"
 * 5) define LED0_REG		"5"
 * 6) define LED1_REG		"6"
 * 7) define WIN_REG			"7"
 * 8) define LR1			"8"
 * 1) define FUNC_RET_REG		"9"
 * 2) define TR1			"A"
 * 3) define TR2			"B"
 * 4) define TR3			"C"
 * 5) define TMEMR1			"D"
 * 6) define TMEMR2			"E"
 * 7) define GLOBAL_INDEX_REG 	"F"
 * 8) define TR4			"10"


text:
User:Patrickwilliams

Patrick Williams

BS Sociology MS Computer Systems Management

title: User:Patrickwilliams


text:
Materials Science and Engineering/Derivations/Models of Micro and Nanoscale Processing/Surfaces and Interfaces

Pseudomorphic Growth
Occurs with similar lattice constant and structure

Growth types depend on processing conditions

Lattice typically needs to be less than 0.5%

Grow diamond tin and zincblende possible because interface energy is low enough to stabilize phase

Metastable growth - thickness beyond which the phase transforms to stable phase

Interface energy effect becomes smaller

Misfit Accomodation
Coherently strained - becomes energetically favorable to form misfits

Glide and leave a misfit dislocation

Dislocations can multiply

Nucleate a dislocation at surface

Glide and remove strain at film

Critical Thickness
Thermodynamic quantity

Kinetics determine whether dislocations form

Depend on temperature - grow metastable film to higher thickness

Kinetic Phenomena
Treatment of kinetics

Mathews
Dislocation motion

Assume Boltzman like jump

Strain energy relief rate is proportional to v

Tendency to overestimate extent to which it is possible to grow strained film

Dodson and Tsao
Improved understanding

Dislocation motion also dependent on stress

Revisit with atomistic models

Nucleation of a Dislocation Loop
Treat nucleation similar to nucleation of phase transition

Energy per unit length of dislocation and step at the surface

Closed 1D defect loop

Shear over area distance equal to the Burger's vector

Calculate the critical energy to create a stable loop

Nucleation loops very unlikely

Comparison with growth on mesas

Most patches remain dislocation free

Estimate concentration by looking at how density depends on size of patches

Types of Defects

 * Stacking faults
 * Interfacial misfit dislocations
 * Threading screw dislocations
 * Growth spiral
 * Stacking fault in film
 * Stacking fault in substrate
 * Hillock
 * Precipitate or void

Stacking Fault
Two-dimensional feature

Use substrates with ledges on surface

Ensure that the surface is free of patches of oxide

Propagate existing ledges - choice of stacking determined

Modes of Heteroepitaxy
Transition depends on temperature

Rough film evolves into islands

Frank-Van der Merwe Growth
Pseudomorphic growth

Add Ge and achieve pseudomorphic growth

Volmer-Weber Growth
Island, "3D"

Stranski-Krastanov Growth
Starts 2D, becomes 3D

Highly strained surface
Reduce strain by developing roughness

Hydrogen induced embrittlement

Rediscover analysis

Strain relief process results in islanding

Pertubation in strained surface

Square wave with amplitude c

Strain energy times volume per unit area

Increase surface area by creating wave

Critical stress

With a critical stress, there is a wavelength above which the pertubation is stable

Longer wavelength corresponds to smaller rate of growth

Surface energy cost too high with high k number

Instability possible through evaporation

Islanding is a method of strain relief

Kinetic mechanism is surface diffusivity

Relieve stress through islanding or misfit dislocation

Activation energy of glide : 0.1 ev

Activation energy of surface diffusion : 0.5 eV

Islanding at high temperature

SiGe greater than critical thickness

Want islanding: high temperature

Volmer-Weber Growth
Occurs with wide range of materials

Single crystal film

Crystallographic orientation templated by substrate

Film can be single crystal and still contain many defects

Growth by any mechanism other than Frank-Van der Merwe is not epitaxy

Nucleation of islands

Island growth

Growth of GaAs on Si

Always grow with islands

Islands start pseudomorphic

Growth errors lead to dislocations

Slight island rotations

PbTe on CaF2 - Volmer-Weber Growth

Ag on NaCl - with stacking faults

Epitaxial alignment

Interface energy that is strongly dependent on orientation of substrate to island

Growth of islands with particular energies

Interface energy minimization leads to epitaxial alignment

Iron on gallium arsenide

Match every other atom

Matching forms a deep cusp

CdTe on GaAs

Many metal-metal combinations

Same relationship to FCC

Grow epitaxial films by Volmer-Weber

Avoid defects if possible

To avoid SK and VW growth:

 * Work with lattice matched systems
 * Live with strain
 * Manage strain relief

Pseudobinary solution
Lattice matched substrate

GaAs and GaSb form pseudobinary solution

Plot relationship by plotting lattice constant as function of mole fraction

Strained Layer Superlattices
Grow a layer with small critical thickness

Grow another layer with low critical thickness with misfit in opposite direction

Cancel effects of distortion

Grow strained layer superlattice

Graded Layer
Learn how to engineer dislocations

Threading dislocation

Not enough strain to produce islanding

Enough strain to cause dislocation to glide

Threading dislocation concentration low in substrate

Begin with graded layer and create GaAs layer

Compound semiconductor with direct band gap on silicon