Quality intrinsic

Conversion efficiencies as high as 20% might be achieved by the end of the decade if good-quality intrinsic alloys can be developed for stacked junction cells (see Section 8). Wu and Williams (1983) have estimated a theoretical limit of 38% for a structure employing two stacked junctions, but their calculations did not include the effect of tail states. Kuwano et al. (1983) have estimated that the maximum practical efficiency is -24% for a structure with three stacked junctions. 

What do we mean when we speak of an inherently safer chemical process Inherent has been defined as existing in something as a permanent and inseparable element, quality, or attribute (American College Dictionary, 1967). A chemical manufacturing process is inherently safer if it reduces or eliminates the hazards associated with materials and operations used in the process, and this reduction or elimination is permanent and inseparable. To appreciate this definition fully, it is essential to understand the precise meaning of the word hazard. A hazard is defined as a physical or chemical characteristic that has the potential for causing harm to people, the environment, or property (adapted from CCPS, 1992). The key to this definition is that the hazard is intrinsic to the material, or to its conditions of storage or use. Some specific examples of hazards include ... 

Rossiter (1986) demonstrated the procedure for the production process of crystalline common salt from brine. It was found that the optimal median size is determined by the entrainment limit in the crystallizer. The crystallizer had to be operated at maximum allowable temperature and the slurry density measured for quality constraints. It was also suggested that cost discontinuities should be imposed based on temperatures of the available heat sources, possible materials of construction and other intrinsic properties of the system. 

Well designed products have the value added approach that results in customer satisfaction and profit gains. Value is an amount regarded as a fair equivalent for something, that which is desirable or worthy of esteem, or product of quality having intrinsic worth. 

The Production Department was not amused, because lower values had been expected. Quality Control was blamed for using an insensitive, unse-lective, and imprecise test, and thereby unnecessarily frightening top management. This outcome had been anticipated, and a better method, namely polarography, was already being set up. The same samples were run, this time in duplicate, with much the same results. A relative confidence interval of 25% was assumed. Because of increased specificity, there were now less doubts as to the amounts of this particular heavy metal that were actually present. To rule out artifacts, the four samples were sent to outside laboratories to do repeat tests with different methods X-ray fluorescence (XRFi °) and inductively coupled plasma spectrometry (ICP). The confidence limits were determined to be 10% resp. 3%. Figure 4.23 summarizes the results. Because each method has its own specificity pattern, and is subject to intrinsic artifacts, a direct statistical comparison cannot be performed without first correcting the apparent concentrations in order to obtain presumably true... 

The nature of the performance metric, y, is determined by the characteristics of the specific process under analysis. Since we are particularly interested in analyzing situations where y is related to product or process quality, it is quite common to find systems where a categorical variable y is chosen to classify and evaluate their performance. This may happen due to the intrinsic nature of y (e.g., it can only be measured and assume qualitative values, such as good, high, and low ), or because y is derived from a quantization of the values of a surrogate continuous measure of performance (e.g., y = good if some characteristic z of the product has value within the range of its specifications, and y= bad, otherwise). 

Note that we have defined "interface angle" as the angle between the growing crystal and the residual melt. Rate of pulling also ciffects the quality of the crystal as well as the actual number of intrinsic defects which may appear in the final crystal. In the upper left of 6.4.7., aflat-... 

With regard to choice and consumption of food, all human sensory perceptions are involved. Among them, vision is the most important one for selecting food and appreciating its quality. Color is an intrinsic property of food. A color change of food often is caused by a quality change. Consumers are attracted by the color of a food product. This imphes three main consequences for food producers ... 

Food quality management aims to realize food quality that complies with or even exceeds customer or consumer requirements. Food quality is not only affected by intrinsic properties and applied technological conditions, but is also influenced by the people who design, control, improve, and assure food quality. While the emphasis of previous chapters is on providing insights into the physics, chemistry, biochemistry, and perception of food colorants, this chapter illustrates the importance of this fundamental knowledge and information for food quality management. 

Solution viscosity measurements have sometimes been utilized as qioality control tests for this polymer. Chromatographs of three samples that showed Identical intrinsic viscosities (0.8 g/dl) in toluene are shown in Figure 9. These chromatographs indicate that the identical viscosities are the result of different combinations of high and low MW components. These three polymer samples probably have significantly different physical properties and if viscosity measurments alone are utilized for quality control purposes, they may be quite misleading. 

The peak profile analysis techniques allow separating the intrinsic and extrinsic causes producing peak broadening and shift. Accurate peak profile analysis requires the instrumental broadening well characterized and, in general, significantly smaller than the one due to sample defects (size and strain). New high quality X-ray sources and... 

Over the past decades the term device quality has come to refer to intrinsic PECVD hydrogenated amorphous silicon that has optimum properties for application in a certain device. Of course, depending on the type of device, different optimum values are required nevertheless the properties as listed in Table I are generally accepted, e.g. [6, 11]. Many of these properties are interrelated, which has to borne in mind when attempting to optimize only one of them. 

In the plasma reactor dedicated for intrinsic material deposition (2 in Fig. 5), only hydrogen and silane are used, along with argon. A mixture of trimethylboron (5% TMB in H2), SiHa, and methane (CH4) is used in the / -plasma reactor (3 in Fig. 5). Diborane can also be used. A mixture of phosphine [PH3 (1% in H2)] and SIH4 is used in an n-plasma reactor (4 in Fig. 5). All gases are of 6.0 quality (99.9999% pure) if available from manufacturers, and otherwise as pure as possible. 

The low background pressure (10 mbar) together with the purity of the gases used ensures a low concentration of contaminants. Amorphous silicon films made in the intrinsic reactor have been analyzed by using ERD, which is available in our laboratory [114]. The determined oxygen content in these films typically is lower than 3 x lO cm - which is somewhat lower than the values required for obtaining device quality films reported by Morimoto et al. [167]. 

The intrinsic material fabricated at the frequencies reported above was incorporated in p -i-n solar cells [493]. The p- and n-layer were prepared by the conventional 13.56-MHz discharge. The device quality films indeed yield good solar cells, of 10% efficiency, as is shown in Figure 60. This cell is manufactured with a 500-nm-thick t -layer made at 65 MHz with a power density of 42 mW/cm , resulting in excellent properties. The deposition rate still is 2-3 times higher than... 

Madan et al. [515] have presented the effect of modulation on the properties of the material (dark conductivity and photoconductivity) and of solar cells. They also observe an increase in deposition rate as a function of modulation frequency (up to 100 kHz) at an excitation frequency of 13.56 MHz, in their PECVD system [159]. The optimum modulation frequency was 68 kHz, which they attribute to constraints in the matching networks. Increasing the deposition rate in cw operation of the plasma by increasing the RF power leads to worse material. Modulation with a frequency larger than 60 kHz results in improved material quality, for material deposited with equal deposition rates. This is also seen in the solar cell properties. The intrinsic a-Si H produced by RF modulation was included in standard p-i-n solar cells, without buffer or graded interface layers. For comparison, solar cells employing layers that were deposited under cw conditions were also made. At a low deposition rate of about 0.2 nm/s, the cw solar cell parameters... 

The many modifications to the conventional RF PECVD method show that one still is trying to find methods that will in the end lead to improved material properties. This is especially the case for the intrinsic metastability of a-Si H. In this respect, the stable material that is obtained at discharge conditions at the edge of crystallinity is very promising. Also, the quest for higher deposition rates while at least maintaining device quality material properties shows the industrial drive behind the research. Faster deposition allows for more solar cells to be produced in the same time. 

As part of maintenance, some equipment may need to be calibrated. SOPs must include calibration methods, and a report format needs to be available at the time of calibration. Calibration SOPs must include pass/fail specifications as well as corrective actions to be taken in the event of calibration failure. For quality calibration standards use National Institute of Standards and Technology (NIST) traceable standards or other intrinsic standards of known purity, quality, and stability. These standards should have certificates attesting to their performance properties. After calibration, the metrologist or other responsible person should review the calibration reports to identify any issues with the equipment that may need further attention. 

The overall performance of a separation method is intrinsically linked to that of the detector used as part of the system. A detector is a device that monitors, in the dimensions of space or time, the presence of the components of a mixture that has been subjected to a chromatographic process. The detection methods provide evidence concerning the quality of the separation and serve especially to increase sensitivity and selectivity. The quantitative aspects of chromatographic analyses are dependent upon the detector capabilities. 

Two sensibly priced commercial databases for solubility exist [366,507], An article in the journal Analytical Profiles of Drug Substances carries solubility data [496]. Abraham and Le [508] published a list of intrinsic aqueous solubilities of 665 compounds, with many ionizable molecules. It is difficult to tell from published lists what the quality of the data for ionizable molecules is. Sometimes, it is not clear what the listed number stands for. For example, Sw, water solubility, can mean several different things either intrinsic value, or value determined at a particular pH (using buffers), or value measured by saturating distilled water with excess compound. In the most critical applications using ionizable molecules, it may be necessary to scour the original publications in order to be confident of the quality of reported values. 

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