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Tribology

Tribology is the science and engineering of understanding friction, lubrication and wear phenomena for interacting surfaces in relative motion. It is highly interdisciplinary, drawing on many academic fields, including physics, chemistry, materials science, mathematics, biology and engineering. The fundamental objects of study in tribology are tribosystems, which are physical systems of contacting surfaces. Subfields of tribology include biotribology, nanotribology and space tribology. It is also related to other areas such as the coupling of corrosion and tribology in tribocorrosion and the contact mechanics of how surfaces in contact deform. Approximately 20% of the total energy expenditure of the world is due to the impact of friction and wear in the transportation, manufacturing, power generation, and residential sectors.

This section will provide an overview of tribology, with links to many of the more specialized areas.

Etymology
The word tribology derives from the Greek root τριβ- of the verb τρίβω, tribo, "I rub" in classic Greek, and the suffix -logy from -λογία, -logia "study of", "knowledge of". Peter Jost coined the word in 1966, in the eponymous report which highlighted the cost of friction, wear and corrosion to the UK economy.

Early history
Despite the relatively recent naming of the field of tribology, quantitative studies of friction can be traced as far back as 1493, when Leonardo da Vinci first noted the two fundamental 'laws' of friction. According to Leonardo, frictional resistance was the same for two different objects of the same weight but making contact over different widths and lengths. He also observed that the force needed to overcome friction doubles as weight doubles. However, Leonardo's findings remained unpublished in his notebooks.

The two fundamental 'laws' of friction were first published (in 1699) by Guillaume Amontons, with whose name they are now usually associated. They state that: Although not universally applicable, these simple statements hold for a surprisingly wide range of systems. These laws were further developed by Charles-Augustin de Coulomb (in 1785), who noticed that static friction force may depend on the contact time and sliding (kinetic) friction may depend on sliding velocity, normal force and contact area.
 * the force of friction acting between two sliding surfaces is proportional to the load pressing the surfaces together
 * the force of friction is independent of the apparent area of contact between the two surfaces.

In 1798, Charles Hatchett and Henry Cavendish carried out the first reliable test on frictional wear. In a study commissioned by the Privy Council of the UK, they used a simple reciprocating machine to evaluate the wear rate of gold coins. They found that coins with grit between them wore at a faster rate compared to self-mated coins. In 1860, Theodor Reye proposed Reye's hypothesis. In 1953, John Frederick Archard developed the Archard equation which describes sliding wear and is based on the theory of asperity contact.

Other pioneers of tribology research are Australian physicist Frank Philip Bowden and British physicist David Tabor, both of the Cavendish Laboratory at Cambridge University. Together they wrote the seminal textbook The Friction and Lubrication of Solids (Part I originally published in 1950 and Part II in 1964). Michael J. Neale was another leader in the field during the mid-to-late 1900s. He specialized in solving problems in machine design by applying his knowledge of tribology. Neale was respected as an educator with a gift for integrating theoretical work with his own practical experience to produce easy-to-understand design guides. The Tribology Handbook, which he first edited in 1973 and updated in 1995, is still used around the world and forms the basis of numerous training courses for engineering designers.

Duncan Dowson surveyed the history of tribology in his 1997 book History of Tribology (2nd edition). This covers developments from prehistory, through early civilizations (Mesopotamia, ancient Egypt) and highlights the key developments up to the end of the twentieth century.

The Jost report
The term tribology became widely used following The Jost Report published in 1966. The report highlighted the huge cost of friction, wear and corrosion to the UK economy (1.1–1.4% of GDP). As a result, the UK government established several national centres to address tribological problems. Since then the term has diffused into the international community, with many specialists now identifying as "tribologists".

Significance
Despite considerable research since the Jost Report, the global impact of friction and wear on energy consumption, economic expenditure, and carbon dioxide emissions are still considerable. In 2017, Kenneth Holmberg and Ali Erdemir attempted to quantify their impact worldwide. They considered the four main energy consuming sectors: transport, manufacturing, power generation, and residential. The following were concluded:
 * In total, ~23% of the world's energy consumption originates from tribological contacts. Of that, 20% is to overcome friction and 3% to remanufacture worn parts and spare equipment due to wear and wear-related.
 * By taking advantage of the new technologies for friction reduction and wear protection, energy losses due to friction and wear in vehicles, machinery and other equipment worldwide could be reduced by 40% in the long term (15 years) and 18% in the short term (8 years). On a global scale, these savings would amount to 1.4% of GDP annually and 8.7% of total energy consumption in the long term.
 * The largest short term energy savings are envisioned in transport (25%) and in power generation (20%) while the potential savings in the manufacturing and residential sectors are estimated to be ~10%. In the longer term, savings would be 55%, 40%, 25%, and 20%, respectively.
 * Implementing advanced tribological technologies can also reduce global carbon dioxide emissions by as much as 1,460 million tons of carbon dioxide equivalent (MtCO2) and result in 450,000 million Euros cost savings in the short term. In the long term, the reduction could be as large as 3,140 MtCO2 and the cost savings 970,000 million Euros.

Classical tribology covering such applications as ball bearings, gear drives, clutches, brakes, etc. was developed in the context of mechanical engineering. But in the last decades tribology expanded to qualitatively new fields of applications, in particular micro- and nanotechnology as well as biology and medicine.

Tribosystem
The concept of tribosystems is used to provide a detailed assessment of relevant inputs, outputs and losses to tribological systems. Knowledge of these parameters allows tribologists to devise test procedures for tribological systems.

Tribofilm
Tribofilms are thin films that form on tribologically stressed surfaces. They play an important role in reducing friction and wear in tribological systems.

Stribeck curve
The Stribeck curve shows how friction in fluid-lubricated contacts is a non-linear function of lubricant viscosity, entrainment velocity and contact load.

Friction
The word friction comes from the Latin "frictionem", which means rubbing. This term is used to describe all those dissipative phenomena, capable of producing heat and of opposing the relative motion between two surfaces. There are two main types of friction:
 * Static friction: Which occurs between surfaces in a fixed state, or relatively stationary.
 * Dynamic friction: Which occurs between surfaces in relative motion.

The study of friction phenomena is a predominantly empirical study and does not allow to reach precise results, but only to useful approximate conclusions. This inability to obtain a definite result is due to the extreme complexity of the phenomenon. If it is studied more closely it presents new elements, which, in turn, make the global description even more complex.

Laws of friction
All the theories and studies on friction can be simplified into three main laws, which are valid in most cases: Coulomb later found deviations from Amontons’ laws in some cases. In systems with significant nonuniform stress fields, Amontons’ laws are not satisfied macroscopically because local slip occurs before the entire system slides.
 * First Law of Amontons: The frictional force is directly proportional to the normal load.
 * Second Law of Amontons: Friction is independent of the apparent area of contact.
 * Third Law of Coulomb: Dynamic friction is independent of the relative sliding speed.

Static friction
Consider a block of a certain mass m, placed in a quiet position on a horizontal plane. If you want to move the block, an external force $$\vec F_{out}$$ must be applied, in this way we observe a certain resistance to the motion given by a force equal to and opposite to the applied force, which is precisely the static frictional force $$\vec F_{s.f.}$$.

By continuously increasing the applied force, we obtain a value such that the block starts instantly to move. At this point, also taking into account the first two friction laws stated above, it is possible to define the static friction force as a force equal in modulus to the minimum force required to cause the motion of the block, and the coefficient of static friction $$\mu$$ as the ratio of the static friction force $$\vec F_{s.f.}$$. and the normal force at block $$\vec N$$, obtaining$${\left|\vec F_{s.f.}\right|}\leq \mu {\left|\vec N\right|}$$

Dynamic friction
Once the block has been put into motion, the block experiences a friction force with a lesser intensity than the static friction force $$\vec F_{s.f.}$$. The friction force during relative motion is known as the dynamic friction force $$\vec F_{d.f.}$$. In this case it is necessary to take into account not only the first two laws of Amontons, but also of the law of Coulomb, so as to be able to affirm that the relationship between dynamic friction force $$\vec F_{d.f.}$$, coefficient of dynamic friction k and normal force N is the following:$$\left|\vec F_{d.f.}\right|= k {\left|\vec N\right|}$$

Static and dynamic friction coefficient
At this point it is possible to summarize the main properties of the static friction coefficients $$\mu$$ and the dynamic one $$k$$.

These coefficients are dimensionless quantities, given by the ratio between the intensity of the friction force $$\vec F_{f}$$and the intensity of the applied load $$\vec W$$, depending on the type of surfaces that are involved in a mutual contact, and in any case, the condition is always valid such that: $$\mu > k $$.

Usually, the value of both coefficients does not exceed the unit and can be considered constant only within certain ranges of forces and velocities, outside of which there are extreme conditions that modify these coefficients and variables.

In systems with significant nonuniform stress fields, the macroscopic static friction coefficient depends on the external pressure, system size, or shape because local slip occurs before the system slides.

The following table shows the values of the static and dynamic friction coefficients for common materials:

Rolling friction
In the case of bodies capable of rolling, there is a particular type of friction, in which the sliding phenomenon, typical of dynamic friction, does not occur, but there is also a force that opposes the motion, which also excludes the case of static friction. This type of friction is called rolling friction. Now we want to observe in detail what happens to a wheel that rolls on a horizontal plane. Initially the wheel is immobile and the forces acting on it are the weight force $$ m \vec g $$ and the normal force $$ \vec N $$given by the response to the weight of the floor.

At this point the wheel is set in motion, causing a displacement at the point of application of the normal force which is now applied in front of the center of the wheel, at a distance b, which is equal to the value of the rolling friction coefficient. The opposition to the motion is caused by the separation of the normal force and the weight force at the exact moment in which the rolling starts, so the value of the torque given by the rolling friction force is$${\vec M_ {r.f.}} = \vec b \times m \vec g$$What happens in detail at the microscopic level between the wheel and the supporting surface is described in Figure, where it is possible to observe what is the behavior of the reaction forces of the deformed plane acting on an immobile wheel.

Rolling the wheel continuously causes imperceptible deformations of the plane and, once passed to a subsequent point, the plane returns to its initial state. In the compression phase the plane opposes the motion of the wheel, while in the decompression phase it provides a positive contribution to the motion.

The force of rolling friction depends, therefore, on the small deformations suffered by the supporting surface and by the wheel itself, and can be expressed as $$|\vec F_ {r}| = b |\vec N|$$, where it is possible to express b in relation to the sliding friction coefficient $$\mu$$ as $b = {\mu v \over r}$, with r being the wheel radius.

The surfaces
Going even deeper, it is possible to study not only the most external surface of the metal, but also the immediately more internal states, linked to the history of the metal, its composition and the manufacturing processes undergone by the latter.

it is possible to divide the metal into four different layers:
 * 1) Crystalline structure – basic structure of the metal, bulk interior form;
 * 2) Machined layer – layer which may also have inclusions of foreign material and which derives from the processing processes to which the metal has been subjected;
 * 3) Hardened layer – has a crystalline structure of greater hardness than the inner layers, thanks to the rapid cooling to which they are subjected in the working processes;
 * 4) Outer layer or oxide layer – layer that is created due to chemical interaction with the metal's environment and from the deposition of impurities.

The layer of oxides and impurities (third body) has a fundamental tribological importance, in fact it usually contributes to reducing friction. Another fact of fundamental importance regarding oxides is that if you could clean and smooth the surface in order to obtain a pure "metal surface", what we would observe is the union of the two surfaces in contact. In fact, in the absence of thin layers of contaminants, the atoms of the metal in question, are not able to distinguish one body from another, thus going to form a single body if put in contact.

The origin of friction
Contact between surfaces is made up of a large number of microscopic regions, in the literature called asperities or junctions of contact, where atom-to-atom contact takes place. The phenomenon of friction, and therefore of the dissipation of energy, is due precisely to the deformations that such regions undergo due to the load and relative movement. Plastic, elastic, or rupture deformations can be observed:

 * Plastic deformations – permanent deformations of the shape of the bumps;
 * Elastic deformations – deformations in which the energy expended in the compression phase is almost entirely recovered in the decompression phase (elastic hysteresis);
 * Break deformations – deformations that lead to the breaking of bumps and the creation of new contact areas.

The energy that is dissipated during the phenomenon is transformed into heat, thus increasing the temperature of the surfaces in contact. The increase in temperature also depends on the relative speed and the roughness of the material, it can be so high as to even lead to the fusion of the materials involved.

In friction phenomena, temperature is fundamental in many areas of application. For example, a rise in temperature may result in a sharp reduction of the friction coefficient, and consequently, the effectiveness of the brakes.

The cohesion theory
The adhesion theory states that in the case of spherical asperities in contact with each other, subjected to a $$\vec W$$ load, a deformation is observed, which, as the load increases, passes from an elastic to a plastic deformation. This phenomenon involves an enlargement of the real contact area $$A_{r}$$, which for this reason can be expressed as:$$A_ {r} = {\vec W \over D}$$where D is the hardness of the material definable as the applied load divided by the area of the contact surface.

If at this point the two surfaces are sliding between them, a resistance to shear stress t is observed, given by the presence of adhesive bonds, which were created precisely because of the plastic deformations, and therefore the frictional force will be given by$$\vec F_ {a} = A_ {r} \vec t$$At this point, since the coefficient of friction is the ratio between the intensity of the frictional force and that of the applied load, it is possible to state that$$\mu = {t \over D}$$thus relating to the two material properties: shear strength t and hardness. To obtain low value friction coefficients $$\mu$$ it is possible to resort to materials which require less shear stress, but which are also very hard. In the case of lubricants, in fact, we use a substrate of material with low cutting stress t, placed on a very hard material.

The force acting between two solids in contact will not only have normal components, as implied so far, but will also have tangential components. This further complicates the description of the interactions between roughness, because due to this tangential component plastic deformation comes with a lower load than when ignoring this component. A more realistic description then of the area of each single junction that is created is given by$${A_ {i}} ^ 2 = \left(\frac {\vec W_i}{D} \right) ^ 2 + \alpha \left(\frac{\vec F_i}{D}\right) ^ 2$$with $$\alpha$$ constant and a "tangent" force $$\vec F_{i}$$ applied to the joint.

To obtain even more realistic considerations, the phenomenon of the third body should also be considered, i.e., the presence of foreign materials, such as moisture, oxides or lubricants, between the two solids in contact. A coefficient c is then introduced which is able to correlate the shear strength t of the pure "material" and that of the third body $$t_ {t.b.}$$$$t = c \cdot t_ {t.b.}$$with 0 < c < 1.

By studying the behavior at the limits it will be that for c = 0, t = 0 and for c = 1 it returns to the condition in which the surfaces are directly in contact and there is no presence of a third body. Keeping in mind what has just been said, it is possible to correct the friction coefficient formula as follows:$$\mu = \frac{c}{[\alpha (1-c ^ 2)] ^ {1/2}}$$In conclusion, the case of elastic bodies in interaction with each other is considered.

Similarly to what we have just seen, it is possible to define an equation of the type$$A = K \vec W$$where, in this case, K depends on the elastic properties of the materials. Also for the elastic bodies the tangential force depends on the coefficient c seen above, and it will be$$\vec F_ {T} = cAs$$and therefore a fairly exhaustive description of the friction coefficient can be obtained$$\mu = cKs$$

Friction measurements
The simplest and most immediate method for evaluating the friction coefficient of two surfaces is the use of an inclined plane on which a block of material is made to slide. As can be seen in the figure, the normal force of the plane is given by $$mg \cos \theta $$, while the frictional force is equal to $$mg \sin \theta $$. This allows us to state that the coefficient of friction can be calculated very easily, by means of the tangent of the angle in which the block begins to slip. In fact we have$$\mu = {F_ {a} \over N} = {mg \sin \theta \over mg \cos \theta} = {\sin \theta \over \cos \theta} = \tan \theta$$Then from the inclined plane we moved on to more sophisticated systems, which allow us to consider all the possible environmental conditions in which the measurement is made, such as the cross-roller machine or the pin and disk machine. Today there are digital machines such as the "Friction Tester" which allows, by means of a software support, to insert all the desired variables. Another widely used process is the ring compression test. A flat ring of the material to be studied is plastically deformed by means of a press, if the deformation is an expansion in both the inner and the outer circle, then there will be low or zero friction coefficients. Otherwise for a deformation that expands only in the inner circle there will be increasing friction coefficients.

Lubrication
To reduce friction between surfaces and keep wear under control, materials called lubricants are used. Unlike what you might think, these are not just oils or fats, but any fluid material that is characterized by viscosity, such as air and water. Of course, some lubricants are more suitable than others, depending on the type of use they are intended for: air and water, for example, are readily available, but the former can only be used under limited load and speed conditions, while the second can contribute to the wear of materials.

What we try to achieve by means of these materials is a perfect fluid lubrication, or a lubrication such that it is possible to avoid direct contact between the surfaces in question, inserting a lubricant film between them. To do this there are two possibilities, depending on the type of application, the costs to address and the level of "perfection" of the lubrication desired to be achieved, there is a choice between:
 * Fluidostatic lubrication (or hydrostatic in the case of mineral oils) – which consists in the insertion of lubricating material under pressure between the surfaces in contact;
 * Fluid fluid lubrication (or hydrodynamics) – which consists in exploiting the relative motion between the surfaces to make the lubricating material penetrate.

Viscosity
The viscosity is the equivalent of friction in fluids, it describes, in fact, the ability of fluids to resist the forces that cause a change in shape.

Thanks to Newton's studies, a deeper understanding of the phenomenon has been achieved. He, in fact, introduced the concept of laminar flow: "a flow in which the velocity changes from layer to layer". It is possible to ideally divide a fluid between two surfaces ($$S_{1}$$, $$S_{2}$$) of area A, in various layers.

The layer in contact with the surface $$S_{2}$$, which moves with a velocity v due to an applied force F, will have the same velocity as v of the slab, while each immediately following layer will vary this velocity of a quantity dv, up to the layer in contact with the immobile surface $$S_{1}$$, which will have zero speed.

From what has been said, it is possible to state that the force F, necessary to cause a rolling motion in a fluid contained between two plates, is proportional to the area of the two surfaces and to the speed gradient:$$F \propto A {dv \over dy}$$At this point we can introduce a proportional constant $$\mu$$, which corresponds to the dynamic viscosity coefficient of the fluid, to obtain the following equation, known as Newton's law$$F = \mu A {dv \over dy}$$The speed varies by the same amount dv of layer in layer and then the condition occurs so that dv / dy = v / L, where L is the distance between the surfaces $$S_{1}$$ and $$S_{2}$$, and then we can simplify the equation by writing$$F = \mu A {v \over L}$$The viscosity $$\mu$$ is high in fluids that strongly oppose the motion, while it is contained for fluids that flow easily.

To determine what kind of flow is in the study, we observe its Reynolds number$$Re = { {\rho L v} \over \mu}$$This is a constant that depends on the fluid mass $$\rho$$ of the fluid, on its viscosity $$\mu$$ and on the diameter L of the tube in which the fluid flows. If the Reynolds number is relatively low then there is a laminar flow, whereas for $$Re \simeq 2000$$ the flow becomes turbulent.

To conclude we want to underline that it is possible to divide the fluids into two types according to their viscosity:

 * 1) Newtonian fluids, or fluids in which viscosity is a function of temperature and fluid pressure only and not of velocity gradient;
 * 2) Non-Newtonian fluids, or fluids in which viscosity also depends on the velocity gradient.

Viscosity as a function of temperature and pressure
Temperature and pressure are two fundamental factors to evaluate when choosing a lubricant instead of another. Consider the effects of temperature initially.

There are three main causes of temperature variation that can affect the behavior of the lubricant:

 * Weather conditions;
 * Local thermal factors (like for car engines or refrigeration pumps);
 * Energy dissipation due to rubbing between surfaces.

In order to classify the various lubricants according to their viscosity behavior as a function of temperature, in 1929 the viscosity index (V.I.) was introduced by Dean and Davis. These assigned the best lubricant then available, namely the oil of Pennsylvania, the viscosity index 100, and at the worst, the American oil of the Gulf Coast, the value 0. To determine the value of the intermediate oil index, the following procedure is used: two reference oils are chosen so that the oil in question has the same viscosity at 100 °C, and the following equation is used to determine the viscosity index$$V.I. = {{L-O_ \text{Test}} \over {L-H}} \times 100$$This process has some disadvantages:

 * For mixtures of oils the results are not exact;
 * There is no information if you are outside the fixed temperature range;
 * With the advancement of the technologies, oils with V.I. more than 100, which can not be described by the method above.

In the case of oils with V.I. above 100 you can use a different relationship that allows you to get exact results$$V.I. = {{10 ^ {N-1} }\over {0.00715 }}+ 100$$$$N = {{\operatorname{Log} (H) - \operatorname{Log} (O_ \text{Test})} \over {\operatorname{Log} (v)}}$$where, in this case, H is the viscosity at 100 °F of the oil with V.I. = 100 and v is the kinematic viscosity of the study oil at 210 °F.

We can therefore say, in conclusion, that an increase in temperature leads to a decrease in the viscosity of the oil. It is also useful to keep in mind that, in the same way, an increase in pressure implies an increase in viscosity. To evaluate the effects of pressure on viscosity, the following equation is used$$\mu = \mu_ {0} \exp {(\alpha p)}$$where $$ \mu $$ is the pressure viscosity coefficient p, $$\mu_ {0} $$ is the viscosity coefficient at atmospheric pressure and $$ \alpha $$ is a constant that describes the relationship between viscosity and pressure.

Viscosity measures
To determine the viscosity of a fluid, viscosimeters are used which can be divided into 3 main categories:
 * Capillary viscometers, in which the viscosity of the fluid is measured by sliding it into a capillary tube;
 * Solid drop viscometers, in which viscosity is measured by calculating the velocity of a solid that moves in the fluid;
 * Rotational viscometers, in which viscosity is obtained by evaluating the flow of fluid placed between two surfaces in relative motion.

The first two types of viscometers are mainly used for Newtonian fluids, while the third is very versatile.

Wear
The wear is the progressive involuntary removal of material from a surface in relative motion with another or with a fluid. We can distinguish two different types of wear: moderate wear and severe wear. The first case concerns low loads and smooth surfaces, while the second concerns significantly higher loads and compatible and rough surfaces, in which the wear processes are much more violent. Wear plays a fundamental role in tribological studies, since it causes changes in the shape of the components used in the construction of machinery (for example). These worn parts must be replaced and this entails both a problem of an economic nature, due to the cost of replacement, and a functional problem, since if these components are not replaced in time, more serious damage could occur to the machine in its complex. This phenomenon, however, has not only negative sides, indeed, it is often used to reduce the roughness of some materials, eliminating the asperities. Erroneously we tend to imagine wear in a direct correlation with friction, in reality these two phenomena can not be easily connected. There may be conditions such that low friction can result in significant wear and vice versa. In order for this phenomenon to occur, certain implementation times are required, which may change depending on some variables, such as load, speed, lubrication and environmental conditions, and there are different wear mechanisms, which may occur simultaneously or even combined with each other:
 * 1) Adhesive wear;
 * 2) Abrasive wear;
 * 3) Fatigue wear;
 * 4) Corrosive wear;
 * 5) Rubbing wear or fretting;
 * 6) Erosion wear;
 * 7) Other minor wear phenomena (wear by impact, cavitation, wear-fusion, wear-spreading).

Adhesive wear
As known, the contact between two surfaces occurs through the interaction between asperities. If a shearing force is applied in the contact area, it may be possible to detach a small part of the weaker material, due to its adhesion to the harder surface. What is described is precisely the mechanism of the adhesive wear represented in the figure. This type of wear is very problematic, since it involves high wear speeds, but at the same time it is possible to reduce adhesion by increasing surface roughness and hardness of the surfaces involved, or by inserting layers of contaminants such as oxygen, oxides, water, or oils. In conclusion, the behavior of the adhesive wear volume can be described by means of three main laws

 * Law 1 – Distance: The mass involved in wear is proportional to the distance traveled in the rubbing between the surfaces.
 * Law 2 – Load: The mass involved in wear is proportional to the applied load.
 * Law 3 – Hardness: The mass involved in wear is inversely proportional to the hardness of the less hard material.

An important aspect of wear is emission of wear particles into the environment which increasingly threatens human health and ecology. The first researcher who investigated this topic was Ernest Rabinowicz.

Abrasive wear
The abrasive wear consists of the cutting effort of hard surfaces that act on softer surfaces and can be caused either by the roughness that as tips cut off the material against which they rub (two-body abrasive wear), or from particles of hard material that interpose between two surfaces in relative motion (three-body abrasive wear). At application levels, the two-body wear is easily eliminated by means of an adequate surface finish, while the three-body wear can bring serious problems and must therefore be removed as much as possible by means of suitable filters, even before of a weighted machine design.

Fatigue wear
The fatigue wear is a type of wear that is caused by alternative loads, which cause local contact forces repeated over time, which in turn lead to deterioration of the materials involved. The most immediate example of this type of wear is that of a comb. If you slide a finger over the teeth of the comb over and over again, it is observed that at some point one or more teeth of the comb come off. This phenomenon can lead to the breaking of the surfaces due to mechanical or thermal causes. The first case is that described above in which a repeated load causes high contact stresses. The second case, however, is caused by the thermal expansion of the materials involved in the process. To reduce this type of wear, therefore, it is good to try to decrease both the contact forces and the thermal cycling, that is the frequency with which different temperatures intervene. For optimal results it is also good to eliminate, as much as possible, impurities between surfaces, local defects and inclusions of foreign materials in the bodies involved.

Corrosive wear
The corrosive wear occurs in the presence of metals that oxidize or corrode. When the pure metal surfaces come into contact with the surrounding environment, oxide films are created on their surfaces because of the contaminants present in the environment itself, such as water, oxygen or acids. These films are continually removed from the abrasive and adhesive wear mechanisms, continually recreated by pure-contaminating metal interactions. Clearly this type of wear can be reduced by trying to create an 'ad hoc' environment, free of pollutants and sensible to minimal thermal changes. Corrosive wear can also be positive in some applications. In fact, the oxides that are created, contribute to decrease the coefficient of friction between the surfaces, or, being in many cases harder than the metal to which they belong, can be used as excellent abrasives.

Rubbing wear or fretting
The rubbing wear occurs in systems subject to more or less intense vibrations, which cause relative movements between the surfaces in contact within the order of nanometers. These microscopic relative movements cause both adhesive wear, caused by the displacement itself, and abrasive wear, caused by the particles produced in the adhesive phase, which remain trapped between the surfaces. This type of wear can be accelerated by the presence of corrosive substances and the increase in temperature.

Erosion wear
The erosion wear occurs when free particles, which can be either solid or liquid, hit a surface, causing abrasion. The mechanisms involved are of various kinds and depend on certain parameters, such as the impact angle, the particle size, the impact velocity and the material of which the particles are made up.

Factors affecting wear
Among the main factors influencing wear we find
 * Hardness
 * Mutual Solubility
 * Crystalline structure

It has been verified that the harder a material is, the more it decreases. In the same way, the less two materials are mutually soluble, the more the wear tends to decrease. Finally, as regards the crystalline structure, it is possible to state that some structures are more suitable to resist the wear of others, such as a hexagonal structure with a compact distribution, which can only deform by slipping along the base planes.

Wear rate
To provide an assessment of the damage caused by wear, we use a dimensionless coefficient called wear rate, given by the ratio between the height change of the body $$ \Delta h $$ and the length of the relative sliding $$ \Delta l $$.$$T_ \text{wear} = {\delta h \over \Delta l}$$This coefficient makes it possible to subdivide, depending on its size, the damage suffered by various materials in different situations, passing from a modest degree of wear, through a medium, to a degree of severe wear. Instead, to express the volume of wear V it is possible to use the Holm equation

 * $$V = k {W \over H} l$$ (for adhesive wear)
 * $$V = k_ {a} {W \over H} l $$ (for abrasive wear)

where W / H represents the real contact area, l the length of the distance traveled and k and $$k_ {a}$$ are experimental dimensional factors.

Wear measurement
In experimental measurements of material wear, it is often necessary to recreate fairly small wear rates and to accelerate times. The phenomena, which in reality develop after years, in the laboratory must occur after a few days. A first evaluation of the wear processes is a visual inspection of the superficial profile of the body in the study, including a comparison before and after the occurrence of the wear phenomenon. In this first analysis the possible variations of the hardness and of the superficial geometry of the material are observed. Another method of investigation is that of the radioactive tracer, used to evaluate wear at macroscopic levels. One of the two materials in contact, involved in a wear process, is marked with a radioactive tracer. In this way, the particles of this material, which will be removed, will be easily visible and accessible. Finally, to accelerate wear times, one of the best-known techniques used is that of the high pressure contact tests. In this case, to obtain the desired results it is sufficient to apply the load on a very reduced contact area.

Transport and manufacturing
Historically, tribology research concentrated on the design and effective lubrication of machine components, particularly for bearings. However, the study of tribology extends into most aspects of modern technology and any system where one material slides over another can be affected by complex tribological interactions.

Traditionally, tribology research in the transport industry focused on reliability, ensuring the safe, continuous operation of machine components. Nowadays, due to an increased focus on energy consumption, efficiency has become increasingly important and thus lubricants have become progressively more complex and sophisticated in order to achieve this. Tribology also plays an important role in manufacturing. For example, in metal-forming operations, friction increases tool wear and the power required to work a piece. This results in increased costs due to more frequent tool replacement, loss of tolerance as tool dimensions shift, and greater forces required to shape a piece.

The use of lubricants which minimize direct surface contact reduces tool wear and power requirements. It is also necessary to know the effects of manufacturing, all manufacturing methods leave a unique system fingerprint (i.e. surface topography) which will influence the tribocontact (e.g. lubricant film formation).

Fields
Tribology research ranges from macro to nano scales, in areas as diverse as the movement of continental plates and glaciers to the locomotion of animals and insects. Tribology research is traditionally concentrated on transport and manufacturing sectors, but this has considerably diversified. Tribology research can be loosely divided into the following fields (with some overlap):
 * Classical tribology is concerned with friction and wear in machine elements (such as rolling-element bearings, gears, plain bearings, brakes, clutches, wheels and fluid bearings) as well as manufacturing processes (such as metal forming).
 * Biotribology studies friction, wear and lubrication in biological systems. The field is gaining importance as human lifetime expectancy increases. Human hip and knee joints are typical biotribology systems.
 * Green tribology aims to minimize the environmental impact of tribological systems along their entire lifecycle. In particular, green tribology aims to reduce tribological losses (e.g., friction and wear) using technologies with minimal environmental impact. This is in contrast to traditional tribology, where the means of reducing tribological losses are not holistically evaluated.
 * Geotribology studies friction, wear, and lubrication of geological systems, such as glaciers and faults.
 * Nanotribology studies tribological phenomena at nanoscopic scales. The field is becoming increasingly important as devices become smaller (e.g. micro/nanoelectromechanical systems, MEMS/NEMS), and research has been aided by the invention of Atomic Force Microscopy.
 * Computational tribology aims to model the behavior of tribological systems through multiphysics simulations, combining disciplines such as contact mechanics, fracture mechanics and computational fluid dynamics.
 * Space tribology studies tribological systems that can operate under the extreme environmental conditions of outer space. In particular, this requires lubricants with low vapor pressure that can withstand extreme temperature fluctuations.
 * Open system tribology studies tribological systems that are exposed to and affected by the natural environment.
 * Triboinformatics is an application of Artificial Intelligence, Machine Learning and Big Data methods to tribological systems.
 * Triboinformatics is an application of Artificial Intelligence, Machine Learning and Big Data methods to tribological systems.

Recently, intensive studies of superlubricity (phenomenon of vanishing friction) have sparked due to increasing demand for energy savings. Furthermore, the development of new materials, such as graphene and ionic liquids, allows for fundamentally new approaches to solve tribological problems.

Societies
There are now numerous national and international societies, including: the Society of Tribologists and Lubrication Engineers (STLE) in the US, the Institution of Mechanical Engineers and Institute of Physics (IMechE Tribology Group, IOP Tribology Group) in the UK, the German Society for Tribology (Gesellschaft für Tribologie), the Korean Tribology Society (KTS), the Malaysian Tribology Society (MYTRIBOS), the Japanese Society of Tribologists (JAST), the Tribology Society of India (TSI), the Chinese Mechanical Engineering Society (Chinese Tribology Institute) and the International Tribology Council.

Research approach
Tribology research is mostly empirical, which can be explained by the vast number of parameters that influence friction and wear in tribological contacts. Thus, most research fields rely heavily on the use of standardized tribometers and test procedures as well component-level test rigs.

title: Tribology


text: User talk:152.163.253.68

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

title: User talk:152.163.253.68


text:
Pattani, Thailand

Pattani is a town (thesaban mueang) in the far south of Thailand, near the border with Malaysia. It is the capital of Pattani Province. The city has a population of 44,353 (2018). It covers the whole tambon Sabarang, Anoru and Chabang Tiko of Mueang Pattani district.

Pattani lies 1,056 km south of Bangkok, and is located at the mouth of the Pattani River. The historic centre of Patani was originally located a few miles away near the Krue Se Mosque, but developed at the present location after the older Patani was captured and sacked in 1785.

The local dialect of Malay is called Pattani Malay or Yawi in Thai (derived from Jawi).

Etymology
Some believe that the name Pattani originated from Malay name Patani (Jawi: ڤطاني), which can mean "this beach" in Pattani Malay language. (In standard Malay, this would be pantai ini.) According to a legend, the founder of Pattani was a raja from Kota Malikha named Phaya Tunakpa. Phaya Tunakpa went hunting one day and saw a beautiful albino mouse-deer the size of a goat, which then disappeared. He asked his men where the animal had gone, and they replied: "Pata ning lah!" ("This beach!" in the Pattani Malay language). They searched for the mouse-deer but found instead an old couple, where the old man identified himself as Che' Tani ("Mister Tani"). The old man said that he was sent by the raja's grandfather to build a new town further beyond but had fallen ill on the journey; as he could not go any further, he stayed at that place. The raja then ordered a town be built at the site where the mouse-deer had disappeared. The town became Patani, which is believed to be named either after "this beach" where the mouse-deer had disappeared. Alternatively, it has also been said to be named after the old man as Pak Tani meaning "Father Tani".

Some also say the word Pattani is derived from "Petani" in Malay which means "farmer". Another suggestion is that it derives from a Sanskrit word pathini, meaning "virgin nymph"; Pathini is also said to be the title of a daughter of Merong Mahawangsa, founder of the preceding kingdom of Langkasuka.

History
Pattani is located at the mouth of the Pattani River. The river may have changed course and empty into the sea at the current location in the 16th century. A small port existed in the current location at Kuala Bekah at the mouth of Sungai Patani by the early 17th century. However, the older historical centre of the Pattani Kingdom that ruled over the region of Patani was located a 6–7 km to the east of the present city; near Ban Kru Se or Kampong Kersik, which is where the Krue Se Mosque is located. The older Pattani was captured and sacked by the Siamese, and a new town centre later developed in the current location and the Sultan moved to Cabang Tiga at the southern side of present-day Pattani in the 19th century. The Patani City municipality was established in 1935 by royal decree.

Climate
Pattani has a tropical monsoon climate according to the Köppen climate classification, with a lengthy wet season and a brief dry season. The temperatures and humidity are high year round, with slightly higher temperatures in April, just as the monsoon arrives. The wet season is long, lasting May-December, and the dry season short, covering only January-April. The months of October, November, and December are particularly wet.

title: Pattani, Thailand


text:
Baron Avebury

Baron Avebury, of Avebury in the County of Wiltshire, is a title in the Peerage of the United Kingdom. It was created 22 January 1900 for the banker, politician and archaeologist Sir John Lubbock, 4th Baronet. He was succeeded by his eldest son, the second Baron. On his death the titles passed to his nephew, the third Baron. He was the son of Harold Fox Pitt Lubbock, fourth son of the first Baron, who died in 1971. The title then passed to the third Baron's first cousin, the fourth Baron, the son of Maurice Fox Pitt Lubbock, sixth son of the first Baron. The fourth baron was a Liberal Democrat politician and one of the ninety excepted hereditary peers who remained in the House of Lords after the passing of the House of Lords Act 1999. He was succeeded by his son, the fifth Baron, in 2016.

The Lubbock baronetcy, of Lamas, was created in the Baronetage of the United Kingdom on 9 April 1806 for John Lubbock, with remainder to his nephew John William, the son of William Lubbock. Lubbock was a successful merchant and banker in London. He was succeeded according to the special remainder by his nephew William, who became the second Baronet. He was also a banker. His grandson, the aforementioned fourth Baronet, was elevated to the peerage as Baron Avebury in 1900.

Lubbock baronets, of Lamas (1806)

 * Sir John Lubbock, 1st Baronet (1744–1816)
 * Sir John William Lubbock, 2nd Baronet (1773–1840)
 * Sir John William Lubbock, 3rd Baronet (1803–1865)
 * Sir John Lubbock, 4th Baronet (1834–1913) (created Baron Avebury in 1900)

Baron Avebury (1900)

 * John Lubbock, 1st Baron Avebury (1834–1913)
 * John Birkbeck Lubbock, 2nd Baron Avebury (1858–1929)
 * John Lubbock, 3rd Baron Avebury (1915–1971)
 * Eric Reginald Lubbock, 4th Baron Avebury (1928–2016)
 * Lyulph Ambrose Jonathan Lubbock, 5th Baron Avebury (born 1954)

The heir apparent is his only son, the Hon. Alexander Lyulph Robert Lubbock (born 1985).

title: Baron Avebury


text:
Baron Ashton of Hyde

Baron Ashton of Hyde, of Hyde in the County of Chester, is a title in the Peerage of the United Kingdom. It was created on 28 June 1911 for the industrialist and Liberal politician Thomas Ashton. He had earlier represented Hyde and Luton in the House of Commons.

Since 2008, the title has been held by his great-grandson, the fourth Baron, who won a by-election to the House of Lords in July 2011 taking the Earl of Onslow's room. Ashton was appointed Chief Whip and Captain of the Honourable Corps of Gentlemen-at-Arms in July 2019.

Barons Ashton of Hyde (1911)

 * Thomas Gair Ashton, 1st Baron Ashton of Hyde (1855–1933)
 * Thomas Henry Raymond Ashton, 2nd Baron Ashton of Hyde (1901–1983)
 * Thomas John Ashton, 3rd Baron Ashton of Hyde (1926–2008)
 * Thomas Henry Ashton, 4th Baron Ashton of Hyde (b. 1958)

The heir presumptive is the present holder's brother John Edward Ashton (b. 1966). At this time, there are no further heirs to the Barony.

title: Baron Ashton of Hyde


text:
Baron Alvingham

Baron Alvingham, of Woodfold in the County Palatine of Lancaster, is a title in the Peerage of the United Kingdom. It was created on 10 July 1929 for Robert Yerburgh. He had previously represented Dorset South in the House of Commons as a Conservative. His father, Robert Yerburgh, had earlier represented Chester in Parliament. In 1916, Royal approval was given to a peerage to whom he had been signified, but he died before the patent was issued. The first Baron's son, the second Baron, who succeeded his father in 1955, served in the Coldstream Guards and retired in 1981 as a Major-General and Director of Army Quartering. the title is held by his son, the third Baron, who succeeded his father in that year.

The family seat is Bix Hall, near Henley-on-Thames, Oxfordshire.

Barons Alvingham (1929)

 * Robert Daniel Thwaites Yerburgh, 1st Baron Alvingham (1889–1955)
 * Robert Guy Eardley Yerburgh, 2nd Baron Alvingham (1926–2020)
 * Robert Richard Guy Yerburgh, 3rd Baron Alvingham (b. 1956)

The heir apparent is the present holder's son Robert William Guy Yerburgh (b. 1983). The heir apparent's heir apparent is his son Robert Rafe Guy Yerburgh (b. 2015).

title: Baron Alvingham


text:
Baron Altrincham

Baron Altrincham, of Tormarton in the County of Gloucester, is a title in the Peerage of the United Kingdom. It was created on 1 August 1945 for the politician Edward Grigg. His son, the second Baron, was a politician, journalist, historian and writer. Soon after the passage of the Peerage Act 1963 on 31 July 1963, he disclaimed the title for life. the title is held by his nephew, who succeeded as 4th Baron on his father's death in that year.

Barons Altrincham (1945)
The heir apparent is the present holder's son Edward Laurence Dundas de Miramont Grigg (b. 1995).
 * Edward William Macleay Grigg, 1st Baron Altrincham (1879–1955)
 * John Edward Poynder Grigg, 2nd Baron Altrincham (1924–2001) (disclaimed 1963)
 * Anthony Ulick David Dundas Grigg, 3rd Baron Altrincham (1934–2020)
 * (Edward) Sebastian Grigg, 4th Baron Altrincham (b. 1965).

Line of succession

 * Coronet of a British Baron.svg Edward William MacLeay Grigg, 1st Baron Altrincham (1879—1955)
 * [[Image:Coronet of a British Baron.svg|15px]] John Edward Poynder Grigg, 2nd Baron Altrincham (1924–2001) (disclaimed 1963)
 * Coronet of a British Baron.svg Anthony Ulrick David Dundas Grigg, 3rd Baron Altrincham (1934–2020)
 * Coronet of a British Baron.svg Edward Sebastian Grigg, 4th Baron Altrincham (b. 1965)
 * (1) The Hon. Edward Laurence Dundas De Miramont Grigg (b. 1995)
 * (2) The Hon. Anthony George Seymour Sebastian Grigg (b. 1997)
 * (3) The Hon. Arthur John R. R. (b. 2003)
 * (4) The Hon. Steven Thomas Grigg (b. 1969)

title: Baron Altrincham


text:
Grammy Award for Best Album Notes

The Grammy Award – Best Album Notes has been presented since 1964. From 1973 to 1976 (the 15th through 18th Awards), a second award was presented for Best Album Notes – Classical. Those awards are listed under those years below. The award recognizes albums with excellent album notes, sometimes referred to as liner notes. It is presented to the album notes author or authors, not to the artists or performers on the winning work, except if the artist is also the album notes author.

Years reflect the year in which the Grammy Awards were presented, for works released in the previous year.

title: Grammy Award for Best Album Notes


text:
Baron Amwell

Baron Amwell, of Islington in the County of London, is a title in the Peerage of the United Kingdom. It was created on 16 July 1947 for the Labour politician Frederick Montague. He had previously represented Islington West in the House of Commons and served as Under-Secretary of State for Air from 1929 to 1931. the title is held by his grandson, the third Baron, who succeeded his father in 1990.

Barons Amwell (1947)

 * Frederick Montague, 1st Baron Amwell (1876–1966)
 * Frederick Norman Montague, 2nd Baron Amwell (1912–1990)
 * Keith Norman Montague, 3rd Baron Amwell (b. 1943)

The heir apparent is the present holder's son the Hon. Ian Keith Montague (b. 1973) The heir apparent's heir, and next in line, is his son Oliver Montague (b. 2007)

title: Baron Amwell


text:
Superdelegate

In American politics, a superdelegate is a delegate to a presidential nominating convention who is seated automatically.

In Democratic National Conventions, superdelegates—described in formal party rules as the party leaders and elected official (PLEO) category—make up slightly under 15% of all convention delegates. Before 2018, Democratic superdelegates were free to support any candidate for the presidential nomination in all rounds of balloting. (This contrasts with pledged delegates, who were selected based on the party presidential primaries and caucuses in each U.S. state, in which voters choose among candidates for the party's presidential nomination.) In 2018, the Democratic National Committee reduced the influence of superdelegates by barring them from voting on the first ballot at the Democratic National Convention, allowing them to vote only in a contested convention.

In Republican National Conventions, three Republican Party leaders of each state, territory, and Washington D.C. are automatically seated as delegates, but they are pledged to vote according to the results of their party branch's presidential primaries at least on the first ballot.

Description of superdelegates
Of all the delegates to the Democratic National Convention, slightly under 15% are superdelegates. According to the Pew Research Center, superdelegates are "the embodiment of the institutional Democratic Party – everyone from former presidents, congressional leaders and big-money fundraisers to mayors, labor leaders and longtime local party functionaries." Democratic superdelegates are formally described (in Rule 9.A) as automatic (or unpledged) party leader and elected official (PLEO) delegates; each falls into one or more of the following categories based on other positions they hold:

 * 1) Elected members of the Democratic National Committee. Elected DNC members include "the chairs and vice chairs of each state and territorial Democratic Party; 212 national committeemen and committeewomen elected to represent their states; top officials of the DNC itself and several of its auxiliary groups (such as the Democratic Attorneys General Association, the National Federation of Democratic Women and the Young Democrats of America); and 75 at-large members who are nominated by the party chairman and chosen by the full DNC." Most at-large DNC members "are local party leaders, officeholders and donors or representatives of important Democratic constituencies, such as organized labor." At the 2016 Democratic National Convention, there were 437 DNC members (with 433 votes) who were superdelegates.
 * 2) Democratic governors (including territorial governors and the mayor of the District of Columbia).  There were 21 Democratic governors who were superdelegates at the 2016 Democratic National Convention.
 * 3) Democratic members of Congress. There were 191 U.S. representatives (including non-voting delegates from Washington, D.C., and territories) and 47 U.S. senators (including Washington, D.C., shadow senators) who were superdelegates at the 2016 Democratic National Convention.
 * 4) Any sitting Democratic president or vice president, if applicable.
 * 5) Distinguished party leaders: consisting of all former Democratic presidents, vice presidents, congressional leaders (Democratic speakers of the U.S. House of Representatives, Democratic minority leaders of the House, and Democratic leaders of the Senate, and DNC chairs).  There were 20 of these who were superdelegates at the 2016 Democratic National Convention.

Because the number of superdelegates depends on the number of Democratic members of Congress and Democratic governors, the exact number of superdelegates may change during the primary season (ahead of the convention) due to officials' deaths, resignations, or special elections.

Not all superdelegates attend the convention. For example, during his time in Congress, Democratic U.S. Representative Jim Matheson skipped every convention. Former Vice President Al Gore skipped the 2016 Convention. Most Democratic members of Congress skipped the 2020 Convention, choosing not to physically attend in light of the COVID-19 pandemic.

State residency
Under party rules, automatic delegates shall "legally reside in their respective state and ... shall be recognized as part of their state's delegation" (Rule 9.E). For example, in the 2008 convention, former Maine Governor Kenneth M. Curtis was a superdelegate (by virtue of his position as a past DNC chair), but because he had moved to Florida in 2006, he was counted as part of the Florida delegation, not the Maine delegation.

Loss of superdelegate status
Additionally, under party rules, automatic delegates are automatically disqualified if they have "publicly expressed support for the election of, or has endorsed, a presidential candidate of another political party" (Rule 9.E) and no delegate "shall participate or vote in the nominating process for a Democratic presidential candidate who also participates in the nominating processes of any other party for the corresponding elections" (Rule 2.E). Thus, a person who would otherwise qualify as a superdelegate loses his or her superdelegate status by endorsing another party's presidential candidate. In 2008, Senator Joe Lieberman of Connecticut endorsed Republican John McCain, which, according to the chairwoman of the Connecticut Democratic Party, resulted in his disqualification as a superdelegate. Lieberman's status had, however, previously been questioned because, although he was a registered Democratic voter and caucused with the Democrats, he won re-election as the candidate of the Connecticut for Lieberman Party and was listed as an "Independent Democrat" on the ballot. Lieberman did not attend the Democratic Convention; he was instead a speaker at the Republican Convention.

Comparison with pledged delegates
The remaining 85% of delegates are pledged to a candidate and chosen in primaries and caucuses. Unlike the Republican primary process (in which many states have a "winner-take-all" process, awarding all or most votes to the candidate who wins a plurality of the vote), Democrats follow a proportionality rule. All candidates who received at least 15% of the vote are awarded delegates in proportion to their share of the vote. Most pledged delegates are allotted based on candidates' proportions of the vote at the district level (these generally correspond to congressional districts, but in some states correspond to state senate districts or specially designated "delegate districts"). Additional delegates (the "at-large" delegates) are awarded to candidates based on statewide results. Finally, there are pledged "party leader and elected official" (PLEO) delegates. These are large city mayors, state legislative leaders, and county party officials who are pledged to a certain candidate; like the statewide at-large delegates, pledged PLEO delegates are allocated proportionally to presidential candidates based on the statewide primary or caucus vote. The district, at-large, and PLEO delegates collectively constitute a state or territory's pledged delegation.

Unlike superdelegates, who may support a candidate of their choice, pledged delegates generally must support the candidate to whom they are pledged. Since 1982, the party rules have stated that: "Delegates elected to the national convention pledged to a presidential candidate shall in all good conscience reflect the sentiments of those who elected them."

If a candidate who has earned pledged delegates drops out before the national convention, then that candidate's delegates who were elected at the district level are released from their obligation to the dropped-out candidate. Pledged delegates who are allocated at the district level to a candidate who subsequently drops out of the race become "free agents": they often support the candidate whom the dropped-out candidate endorses, but are not obligated to do so. By contrast, statewide pledged delegates are usually proportionally reallocated to candidates still in the race at the time when the states formally elect their delegates: this typically takes place at a statewide convention held after the primary or caucus, but before the national convention in mid-summer.

By contrast, many superdelegates choose to announce endorsements, but they are not bound to those preferences, and may support any candidate they wish, including a candidate who has dropped out of the presidential race.

Origins
In the aftermath of the chaotic 1968 Democratic National Convention, the Democratic Party sought to shift the balance of power in the selection of the party's presidential candidate to primary elections and caucuses, mandating that all delegates be chosen via mechanisms open to all party members; these rules were implemented following the recommendations of the McGovern-Fraser Commission. This increased grassroots control of Democratic conventions. However, after Democratic George McGovern lost in a landslide to Richard Nixon in 1972, and after a decisive fight over the rules at the 1980 convention between supporters of Jimmy Carter and supporters of Edward M. Kennedy, followed by Carter's defeat by Ronald Reagan in 1980, the party changed its nominating rules again.

A commission headed by North Carolina Governor Jim Hunt issued a report in 1982, on a 47–6 vote, to set aside 550 unpledged delegate seats held by party officials, to vote alongside the 3,300 Democratic pledged votes. This partial reversal of the trend toward grassroots control was supported by mainstream party leaders in Congress, as well as organized labor. It increases the power of the institutional party "regulars" against insurgent "outsider" maverick candidates. Their initial proposal to have superdelegates represent 30% of all delegates to the national convention was defeated in favor of a compromise proposal by Geraldine A. Ferraro, in which superdelegates made up about 14% of delegates. The proportion of superdelegates eventually expanded over time, reaching about 20% at the 2008 convention.

1984 and 1988
In 1984, only state party chairs and vice chairs were guaranteed superdelegate status. The remaining spots were divided two ways. Democratic members of Congress were allowed to select up to 60% of their members to fill some of these spots. The remaining positions were left to the state parties to fill with priority given to governors and big-city mayors, led by Democrats and based on population. In the 1984 election, the major contenders for the presidential nomination were Gary Hart, Jesse Jackson, and Walter Mondale. Entering the final handful of primaries on June 5, Mondale was leading Hart in the delegate count, with Jackson far behind. The battle for delegates became more dramatic that night when Hart won three primaries, including the big prize of California in a cliffhanger. The Mondale campaign said, and some news reports agreed, that Mondale secured the needed 1,967 delegates to clinch the nomination that night in spite of losing California. But the Associated Press concluded he was "barely short of the magic majority." Mondale wanted to make it indisputable that he had enough delegate votes, and his campaign set a deadline of one minute before noon; he made 50 calls in three hours to nail down an additional 40 superdelegates and declared at a press conference that he had 2,008 delegate votes. At the convention in July, Mondale won on the first ballot.

In 1988, this process was simplified. Democrats in Congress were now allowed to select up to 80% of their members. All Democratic National Committee members and all Democratic governors were given superdelegate status. This year also saw the addition of the distinguished party leader category (although former DNC chairs were not added to this category until 1996, and former House and Senate minority leaders were not added until 2000). In 1992 was the addition of a category of unpledged "add-ons", a fixed number of spots allocated to the states, intended for other party leaders and elected officials not already covered by the previous categories. Finally, beginning in 1996, all Democratic members of Congress were given superdelegate status. The superdelegates have not always prevailed, however. Howard Dean took an early lead in delegate counts before the first primaries in the 2004 Democratic presidential primaries, but was later defeated by John Kerry, who won a succession of primaries and caucuses and, ultimately, the nomination. In 1988, a study found that delegates selected through the primary and caucus process were not substantively different from superdelegates in terms of issue viewpoints. However, superdelegates are more likely to prefer candidates with Washington experience than outsider candidates.

2008 election
At the 2008 Democratic National Convention, the superdelegates made up approximately one-fifth of the total number of delegates. The closeness of the race between the leading contenders, Hillary Clinton and Barack Obama, led to speculation that the superdelegates would play a decisive role in selecting the nominee, a prospect that caused unease among some Democratic Party leaders. Obama led in pledged delegates at the end of voting in the state contests while not winning enough to secure the nomination without the superdelegates. In May 2008, however, Obama took the lead in superdelegate endorsements for the first time; Clinton dropped out four days after Obama clinched the nomination.

Pledged delegates from state caucuses and primaries eventually numbered 3,573, casting 3,566 votes, resulting in a total number of delegate votes of 4,419. A candidate needed a majority of that total, or 2,209, to win the nomination. Superdelegates accounted for 19.6% of convention delegates, while delegates chosen in the Democratic caucuses and primaries accounted for approximately four-fifths (80.4%) of the Democratic convention delegates. At the convention, Obama won 3,188.5 delegate votes and Clinton won 1,010.5 with 1 abstention and 218 delegates not voting.

2016 election
In 2016, a campaign for superdelegates was a feature of the campaign between former Secretary of State Hillary Rodham Clinton and U.S. Senator Bernie Sanders for the Democratic nomination; Sanders' campaigns and his supporters initially criticized the role of superdelegates, the majority of whom favored Clinton. Several mainstream media outlets included superdelegates in the candidate delegate totals during the primary elections although superdelegates do not vote until the convention and may change their minds on whom they are planning to vote for anytime before the convention. The DNC asked media outlets to not include superdelegate pledges in delegate totals, but many outlets, including the Associated Press, NBC, CBS, and Politico, continued to report total pledged delegates, lumping together superdelegates and pledged delegates. Sanders supporters objected to this practice, argued that it inflated Clinton's lead and discouraged Sanders supporters. Sanders initially said that the candidate with the majority of pledged delegates should be the nominee; in May 2016, after falling behind in the elected delegate count, he shifted, pushed for a contested convention and arguing that, "The responsibility that superdelegates have is to decide what is best for this country and what is best for the Democratic Party." Ultimately, Clinton won the nomination without relying on the votes of superdelegates; she led Sanders by a substantial number of elected delegates (from primary and caucus votes), as well by a substantial margin in the popular vote. She became the presumptive nominee in early June 2016, after the California primary; at the time, Clinton had 1812 pledged delegates and 572 superdelegates, and Sanders had 1520 pledged and 46 superdelegates. Sanders continued to campaign after the last Democratic primary, unsuccessfully seeking to persuade superdelegates to switch their allegiance to him; ultimately, he conceded the race and endorsed Clinton on July 12, 2016.

DNC Unity Reform Commission (2016–17)
On July 23, 2016, ahead of the 2016 Democratic National Convention, the 2016 DNC Rules Committee voted overwhelmingly (158–6) to adopt a superdelegate reform package. The new rules were the result of a compromise between the Hillary Clinton and the Bernie Sanders presidential campaigns; in the past, Sanders had pressed for the complete elimination of superdelegates.

Under the reform package, a 21-member unity commission, chaired by Clinton supporter Jennifer O'Malley Dillon and vice-chaired by Sanders supporter Larry Cohen, was appointed after the 2016 general election. The commission's recommendations would be voted on at the next Democratic National Committee meeting, well before the beginning of the 2020 Democratic primaries. The commission was to consider "a mix of Clinton and Sanders ideas": expanding the ability of eligible voters to participate in caucuses (an idea supported by Clinton) and expanding the ability of unaffiliated or new voters to join the Democratic Party and vote in Democratic primaries via same-day registration and re-registration (an idea supported by Sanders). The commission drew comparisons to the McGovern–Fraser Commission, which established party primary reforms before the 1972 Democratic National Convention.

By April 2017, the complete commission had been appointed. In accordance with the compromise agreement, the 21 members include, in addition to O'Malley Dillon and Cohen; nine members selected by Clinton, seven selected by Sanders, and three selected by the DNC chair (Tom Perez). By May 2017, the DNC Unity Reform Commission had begun to meet to begin drafting reforms, including superdelegate reform as well as primary calendar and caucus reform.

The commission met in the summer and fall of 2017. Different proposals on superdelegates were considered by the party. One proposal was to bind all or some superdelegates to the results of state primaries and caucuses. Whether to abolish superdelegates altogether remained controversial within the party. In December 2017, the Unity Commission's recommendations were delivered to the DNC Rules and Bylaws Committee. Perez and Deputy DNC Chair Keith Ellison co-authored an op-ed for CNN, announcing that the party would make a "significant" cut in the number of superdelegates who vote to decide on the presidential nominee.

Adoption of superdelegate reform (2018)
Ultimately, the DNC decided to prevent superdelegates from voting on the first ballot, instead of reducing their numbers. On August 25, 2018, the DNC approved a plan to reduce the influence of superdelegates by barring them from voting on the first ballot at the Democratic National Convention, allowing them to vote only in a contested convention (i.e., if a Democratic National Convention did not choose the nominee on the first ballot, because no candidate received an absolute majority [more than 50%] of the pledged delegates elected from the outcome of primaries and caucuses). This does not preclude superdelegates from publicly endorsing a candidate of their choosing before the convention.

The plan, which was endorsed by DNC chair Tom Perez, former DNC chair Howard Dean, and other party leaders, passed by an overwhelming margin; the New York Times noted that the compromise was a "rare mind meld between the Democratic establishment and progressive activists who have often chided the party's elite." The only dissenter on the DNC Rules Committee was former DNC chairman Donald L. Fowler, who argued that the existing system worked.

2020 election
The first Democratic presidential primaries cycle under the new 2016–2018 superdelegate reform measures took place in 2020.

Criticism and defenses
The votes of superdelegates have never actually determined the Democratic nominee, although in 1984 they may have helped Walter Mondale win on the first ballot at the convention.

Critics
Critics have assailed superdelegates' role in Democratic National Conventions both before and after the 2017 reforms. Susan Estrich argued in 2008 that superdelegates have more power than other delegates because of their greater freedom to vote as they wish beginning with the first ballot. (Superdelegates' ability to vote on the first ballot was eliminated after the 2017 reform.) U.S. Senator Tim Kaine, Hillary Clinton's former running mate, said in 2017 that he agreed with Bernie Sanders that superdelegates should be eliminated from the process: "I have long believed there should be no superdelegates. These positions are given undue influence in the popular nominating contest and make the process less democratic." Prominent Democratic strategists Bob Shrum and Bill Carrick have also opposed superdelegates, and called for them to be dropped from the nominating process.

The role of superdelegates in the nominating process has also been criticized as unrepresentative. In 2007, Politico found that about half of the superdelegates were white men, compared to 28% of the Democratic primary electorate. Of the superdelegates at the 2016 Convention, 58% were male and 62% were non-Hispanic white (20% were black and 11% were Hispanic). The average age was about 60. There is no bar on lobbyists serving as DNC members (and thus superdelegates); ABC News found that about 9% of superdelegates at the 2016 Democratic National Convention (67 people in all) were former or current lobbyists registered on the federal and state level.

Defenders
Author Jonathan Rauch and political scientist Ray La Raja argued in 2019 that the U.S. has given too much power to primary voters, and that this inflicts harms to democracy. They argue that "the role of superdelegates in the Democratic nomination process could be strengthened instead of weakened" and that this form of early vetting was positive, suggesting that this formal form of the "invisible primary" can be a positive force to counter-balance populism "by restoring the Madisonian pillars of pluralism, checks on power, and deliberative institutions."

In February 2016, U.S. Representative Debbie Wasserman Schultz, chair of the Democratic National Committee, defended the role of superdelegates in an interview with Jake Tapper, arguing that unpledged delegates ensure "that party leaders and elected officials don't have to be in a position where they are running against grass-roots activists" and minimizes competition between the two groups.

In Republican National Conventions
In the Republican Party, as in the Democratic Party, members of the party's national committee automatically become delegates. There are three Republican National Committee delegates (the national committeeman, national committeewoman, and party chair) for each state, territory, and Washington, D.C..

At the 2012 Republican National Convention, convention rules were amended to obligate unpledged RNC members (the "superdelegates") to vote according to the result of the primaries held in their states. Pledged delegates selected by Republican primaries are assigned either on a proportional or a "winner-take-all" basis.

However, if a candidate does not win the party's nomination on the first ballot (i.e., by securing a majority—more than 50%), then some delegates become "unbound" free agents, depending on rules specific to state parties. For most states, delegates are "unbound" as soon as a first ballot concludes without a nominee being selected; for other states (including Texas) delegates are not unbound until a second ballot also fails to produce a majority for a candidate; and delegates from some other states (including Kansas and Alabama) remain bound to their candidate until the candidate releases them. These rules apply to both pledged delegates and superdelegates, meaning that superdelegates would play a role in selecting the nominee at a contested convention.

Superdelegates make up about 7% of all delegates to Republican national conventions. In the 2008 Republican National Convention, 123 RNC delegates among the 2,380 total delegates were not pledged to any candidate. In the 2016 Republican National Convention, 168 delegates among the 2,472 total delegates were "super" (unbound).

title: Superdelegate


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Wikipedia:Main Page alternatives/(Classic 2004)

Welcome to Wikipedia, a multilingual, free-content encyclopedia. We started in January 2001 and are now working on articles in the English version. Visit the help page and experiment in the sandbox to learn how you can edit any article right now!

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Talk:Edwin Herbert Land

This article should be merged with the existing one Edwin H. Land, but I don't know under which name. Lady Tenar 01:18, 26 Feb 2004 (UTC)

title: Talk:Edwin Herbert Land


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Baron Astor of Hever

Baron Astor of Hever, of Hever Castle in the County of Kent, is a title in the Peerage of the United Kingdom. It was created in 1956 for John Jacob Astor, a prominent newspaper proprietor and Conservative politician. He was the fourth child of William Waldorf Astor, 1st Viscount Astor. Lord Astor of Hever was succeeded in 1971 by his eldest son, the second Baron, who served as Lord Lieutenant of Kent between 1972 and 1982.

, the title is held by the latter's eldest son, the third Baron, who succeeded in 1984. He is one of the ninety elected hereditary peers who remain in the House of Lords after the passing of the House of Lords Act of 1999, and he sits on the Conservative benches. As a male-line descendant of the first Viscount Astor, Lord Astor of Hever is also in remainder to this peerage and its subsidiary title Baron Astor, of Hever Castle in the County of Kent.

John Astor, third son of the first Baron, served as a Conservative Member of Parliament from 1964 to 1974.

Barons Astor of Hever (1956)

 * John Jacob Astor, 1st Baron Astor of Hever (1886–1971)
 * Gavin Astor, 2nd Baron Astor of Hever (1918–1984)
 * John Jacob Astor, 3rd Baron Astor of Hever (b. 1946)

The heir apparent is the present holder's son, Hon. Charles Gavin John Astor (b. 1990).

title: Baron Astor of Hever


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Laser broom

A laser broom is a proposed ground-based laser beam-powered propulsion system that sweeps space debris out of the path of artificial satellites (such as the International Space Station) to prevent collateral damage to space equipment. It heats up one side of the debris to shift its orbit trajectory, altering the path to hit the atmosphere sooner. Space researchers have proposed that a laser broom may help mitigate Kessler syndrome, a runaway cascade of collision events between orbiting objects. Additionally, laser broom systems mounted on satellites or space station have also been proposed.

Mechanism
Lasers brooms are proposed to target space debris between 1 and(-) in diameter. Collisions with these high-velocity debris not only cause considerable damage to the satellites but secondary fragmented debris from the collided satellite parts. A laser broom is intended to be used at a high power to penetrate through the atmosphere and ablate material from the targeted debris. The ablating material imparts a small thrust that lowers its orbital perigee towards the upper atmosphere, thereby increasing drag so that its remaining orbital life is cut short. The laser would operate in a pulsed fashion to avoid the target from self-shielding via its ablated plasma. The power levels of lasers in this concept are well below the power levels in concepts for more rapidly effective anti-satellite weapons.

Research into this field reveal the precise physical constraints required, noting the significant relevance to the space debris's orientation and resultant trajectory of the ablated object. Using a laser guide star and adaptive optics, a sufficiently large ground-based laser (1 megajoule pulsed HF laser) can offset the orbits of dozens of debris daily at a reasonable cost.

History
The Space Shuttle routinely showed evidence of "tiny" impacts upon post-flight inspection.

Orion was a proposed ground-based laser broom project in the 1990s, estimated to cost $500 million.

A space-based laser also called "Project Orion" was planned to be installed on the International Space Station in 2003. In 2015, Japanese researchers proposed adding laser broom capabilities to the Extreme Universe Space Observatory telescope, to be launched to the ISS in 2017.

In 2014, the European CLEANSPACE project published a report studying a global architecture of debris tracking and removal laser stations.

title: Laser broom


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Baron Aldington

Baron Aldington, of Bispham in the County Borough of Blackpool, is a title in the Peerage of the United Kingdom. It was created on 29 January 1962 for the Conservative politician and businessman, Sir Toby Low. On 16 November 1999 he was made a life peer as Baron Low, of Bispham in the County of Lancashire, as were all hereditary peers of the first creation following the House of Lords Act 1999. On his death in 2000 the life peerage became extinct while he was succeeded in the hereditary barony by his son Charles, the second and present holder of the title.

Lord Aldington was controversially accused of sending 70,000 cossacks and their families who had surrendered to the British forces in Austria after the Second World War over the border to the Soviets. This highly secret act contravened the Geneva Convention as they were not citizens of the USSR, and it was obvious that they would be massacred or sent to GULAGs. Aldington's superior was Harold Macmillan, the future prime minister, who has been accused of being an agent for Stalin. The historian Nikolai Tolstoy said as much in print and was sued by Aldington in 1989 for defamation. In a highly controversial court case, Aldington won and Tolstoy was asked to pay £1.5m in damages and £0.5m for Aldington's legal fees.

Barons Aldington (1962)

 * Toby Austin Richard William Low, 1st Baron Aldington, Baron Low (1914–2000)
 * Charles Harold Stuart Low, 2nd Baron Aldington (b. 1948)

The heir apparent and sole heir to the peerage is the present holder's son, Philip Toby Augustus Low (b. 1990)

title: Baron Aldington