polycrystalline silicon是什么意思

英语翻译
The majority of PV solar cells are made from crystalline silicon,either single crystal or multi-crystalline silicon.This account for around 90% of the current production.The remainder comprises various forms of thin film solar cells where the absorber material is deposited onto a suitable substrate such as glass.The absorber materials for thin film cells are either amorphous/polycrystalline silicon or compound semiconductors such as cadmium telluride,gallium arsenide,copper indium diselenide etc.Organic solar cells in the form of either dye sensitized solar cells or polymer absorbers are a newer low cost PV option that until recently has been confined to the laboratory but a recent investment by G24i in Wales is set to produce large volumes of flexible,dye sensitized,solar cells for niche applications.
The common characteristic to all the inorganic absorber materials is that they are semiconductors where absorption of light results in excitation band as illustrated in Fig.1.
Unfortunately,not all the light can be absorbed in this way as the low energy photons,corresponding to the longer wavelengths of solar radiation will be insufficient to excite an electron hole pair.Selecting a very narrow band gap semiconductor absorber will result in more photons being absorbed but less voltage being produced.To achieve maximum power there is a compromise between the current (photons absorbed) and the voltage of the cell.This will result in a predicted optimum band gap for the absorber of around 1.3 eV and a maximum theoretical efficiency under normal terrestrial solar light of around 30%[1-3].Unfortunately this is only part of the process as the electrons excited into the conduction band in p-type semiconductors are unstable and will tend to recombine,releasing heat.A junction is needed to draw the photo-generated electrons into n-type material where they are stable and extract an electric current via an external circuit.The n-type side of the junction can be made of the same material or a different semiconductor material to the absorber.
The dominance of the PV solar market by silicon is partly historical but is also a result of the development of silicon for the electronics industry.PV solar energy has been able to ride on the back of the developments in electronics until recently when more high purity silicon was being produced for PV solar than for electronics.However,the absorption coefficient of silicon is poor ,because it is not a direct band gap semiconductor,which is why direct band gap compound semiconductors have been developed gap compound semiconductors have been developed for the thin film applications.In reality this means that crystalline silicon cells require approximately 200 m,whereas direct..Band gap semiconductors require only 1-2 m thickness of absorber.Thia factor will be discussed later in the context of cost of PV solar modules.

英语翻译
polycrystalline diamond element comprising ultra-dispersed diamond grain structures and applications utilizing same
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翻译 采纳答案后追加50分
3.3. Crystalline structure
The glassy systems investigated presented a crystalline phase after the thermal treatment, exception made for frit D. Figs. 9 and 10 show the XRD patterns, after sintering, for frits B and D, respectively. We can see there the amorphous structure of the raw frit D (0 8C). In the case of the raw frit B, as well as for raw frits C and E (patterns not shown here), a crystalline structure already existed in the raw frit. The peaks at 38,5 and 44,88 2u refer to the aluminium in the sample support.
In the case of frit A, the results have shown that it remains amorphous until 800 8C and only after that it starts to form anorthite and diopside. At 920 8C, the sample exhibits a high amount of crystalline phase but, at 1050 8C, it is possible to notice a small decrease of the anorthite peak intensity, benefiting the growth of diopside. The final product also contains residual gehlenite.
The final product X-ray patterns for frit B are given in Fig. 11. It has been shown previously, in Fig. 9, that the raw sample contains spinel. Between 850 and 940 8C (first exothermic peak), the frit devitrificates leading to the formation of spodumene and a magnesium aluminosilicate (MgAl2- Si3O10). For this temperature, cordierite also crystallizes though in a very small amount. During the second crystallization peak, XRD continues to detect spodumene indicating, however, the additional production of cordierite and indialite which are, now, the main crystalline phases. Therefore, MgAl2Si3O10, formed during the first peak, was converted to form cordierite and indialite.
TheXRDresults for frit C showthat the rawmaterial contains vestigial celsian and baric orthoclase (K,Ba)(Si,Al)4O8. Celsian continues to form during the exothermic event (810–860 8C) becoming the principal crystalline structure. Banalsite formation is also detected during the exothermic peak.

英语翻译
For example,does iron in solution or as crystalline phases during the formation of kaolinite affect crystal growth or is iron accidentally incorporated into the kaolinite so that the extent of incorporation is affected by crystal morphology and not the reverse.

英语翻译
Metals are crystalline when in the solid state and,with few exceptions (e,g,.mercury),are solid at ambient temperatures.They are good conductors of heart and electricity and are opaque to light.They usually have a comparatively high density.Many metals are ductile — that is,their shape can be changed permanently by the application of a force without breaking.The forces required to cause this deformation and those required finally to break or fracture a metal are comparatively high,the fracture forces is not nearly as high as would be expected from simple considerations of the forces required to tear apart atoms of the metal.
The word automatic implies that there is a certain amount of sophistication in the control system.By automatic,it generally means that the system is usually capable of adapting to a variety of operating conditions and is able to respond to a class of inputs satisfactorily.However,not any type of control system has the automatic feature.Usually,the automatic feature is achieved by feeding the output variable back and comparing it with the command signal.When a system does not have the feedback structure,it is called an open-loop system,which is the simplest and most economical type of control system.Unfortunately,open-loop control system lack accuracy and versatility and can be used in none but the siplest types pf applications.
Comparisons were made in three categories:basic research,advanced development,and product implementation.Except for machine vision and software,Japanese basic research was comparable to the United States,with the Japanese closing in fast in machine vision system technology.Japanese artificial intelligence research is falling behind,primarily because the Japanese do not consider it an essential ingredient of their future systems.They appear capable of closing even that gap,if required.In the advanced development and product implementation areas,japan is equal to or better than the United States,and is continuing to pull ahead at this time.