Single Sourcing Methods

Single sourcing is a possibility when a relatively small number of parts are procured. In this section, we will discuss two most commonly used methods in single sourcing. 

Linear weighted point (LWP) method The linear weighted point (LWP) method is the most widely used approach for single sourcing. The approach uses a simple scoring method that heavily depends on human judgment. Some of the references that discuss this approach include Wind and Robinson (1968) and Zenz (1981). The multiple 

Criteria Weights Supplier A Supplier B Ideal Value 

To illustrate the LWP method, consider a simple supplier selection problem with two suppliers and five criteria (Quality, service, capacity, price, and risk) as shown in Table 6.3. Each criterion is measured over a scale of 1-10, with higher numbers preferred over lower ones. Note that Supplier A has higher quality, service, and capacity but costs more and has higher risk of supply disruptions. The ideal values in Table 6.3 represent the best values for each criterion. However, the ideal values are not achievable simultaneously for all the criteria, because the criteria conflict with one another. 

The LWP method has several drawbacks. It is generally difficult to come up with exact criteria weights. The method also requires all the criteria values to be scaled properly if the measurement units are very different. For example, quality may be measured in percent defectives, service may be measured by lead-time in days, capacity in hundreds of units, and price in dollars. The use of linear additive value fimction violates the normal economic principle of Diminishing Marginal Utility. In Section 6.3, we will discuss several methods for ranking suppliers that overcome these drawbacks. 

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Copper selenide is also used in solar cells [200]. TOPO-capped CuSe nanoparticles were synthesized from Cu(Se2CNEt2)2 using a single-source method [201]. Copper selenide nanoparticles have also been prepared and XPS spectra, valence bands and Auger transitions reported for the molecular clusters Cui46Se73(PPh(3))(202) and Cu2Se [203]. Photoemission features were reported for both species. 

Many approaches have been taken to prepare colloidal doped semiconductor nanocrystals. For example, hot-injection methods have been used to synthesize colloidal Mn2+-doped CdSe (47, 48), ZnSe (49), and PbSe (50) colloidal nanocrystals. Colloidal ZnO DMS-QDs doped with Co2+, Ni2+, and Mn2+ have been prepared by low-temperature hydrolysis and condensation (51-54). Sol-gel methods have been used to prepare colloidal doped TiC>2 (55-57) and Sn02 (58-62) nanocrystals. Inverted micelle methods have been used for preparation of a range of doped II-VI sulfide DMS-QDs at low temperatures (63-68). A high-temperature lyothermal single-source method was used to synthesize Co2+- and Eu3+-doped CdSe nanocrystals (69, 70). Autoclaving has occasionally been used to induce crystallization at lower temperatures than reached under atmospheric pressures while retaining colloidal properties, for... 

Wastestreams containing the chemical may have a single source or may be aggregates of many sources. For example, process water from several pieces of equipment at your facility may be combined prior to treatment. Report treatment methods that apply to the aggregate wastestream, as well as treatment methods that apply to individual wastestreams. If your facility treats various wastewater streams containing the chemical in different ways, the different treatment methods must each be listed separately. 

This book brings together a wide range of tools and techniques used by human factors and human reliability specialists, which have proved to be useful in the context of human performance problems in the CPI. Although many human factors practitioners will be familiar with these methods, this book is intended to provide ready access to both simple and advanced techniques in a single source. Where possible, uses of the techniques in a CPI context are illustrated by means of case studies. 

Active Metals is a single source of hands-on information about the large repertoire of preparation methods and syntheses possible with active metals. This book will help chemists and materials scientists to fully benefit from the recent advances in the field. 

The continued development of new single-source molecular precursors should lead to increasingly complex mixed-element oxides with novel properties. Continued work with grafting methods will provide access to novel surface structures that may prove useful for catalytic apphcations. Use of molecular precursors for the generation of metal nanoparticles supported on various oxide supports is another area that shows promise. We expect that the thermolytic molecular precursor methods outlined here will contribute significantly to the development of new generations of advanced materials with tailored properties, and that it will continue to provide access to catalytic materials with improved performance. 

More recently, the same author [41] has described polymer analysis (polymer microstructure, copolymer composition, molecular weight distribution, functional groups, fractionation) together with polymer/additive analysis (separation of polymer and additives, identification of additives, volatiles and catalyst residues) the monograph provides a single source of information on polymer/additive analysis techniques up to 1980. Crompton described practical analytical methods for the determination of classes of additives (by functionality antioxidants, stabilisers, antiozonants, plasticisers, pigments, flame retardants, accelerators, etc.). Mitchell... 

As evident from Scheme 7.13, most modern ionisation techniques have been used for TLC-MS, and no single ionisation method is used exclusively with TLC-MS. Various ionisation methods may be applied that avoid the need to evaporate the sample into an El or Cl source these are based in particular on sputtering (FAB, SIMS) or laser desorption. Several sputtering methods of ionisation do not require the use of a liquid matrix, e.g. TLC-SIMS [797], Recent developments include the use of matrix-assisted laser desorption ionisation (MALDI) and surface-assisted laser desorption ionisation (SALDI). It is obvious that TLC-MS is complemented with TLC-MS11 [800] and TLC-HRMS techniques. Table 7.82 lists the general characteristics of TLC-MS. 

Initially, the main disadvantage of using single-source precursors was their lack of volatility. However, the advent of ultralow-pressure and vacuum CVD techniques, along with the use of alternative delivery methods which do not rely primarily on precursor volatility, means that many compounds that are essentially nonvolatile can now be considered as potential CVD precursors. A major problem that remains, however, is that of stoichiometry control a molecular precursor containing two (or more) elements in a specific ratio, as desired within the thin film to be grown, will not necessarily deposit those elements in the same proportions. 

The used variables may originate from the same source (for instance data from a single spectroscopic method), but may also have very different origins and... 

This handbook is an encyclopedic treatment of chemical elements and their most important compounds intended for professionals and students in many areas of chemistry throughout the manufacturing, academic, and consulting communities. Chemicals are presented in alphabetical order in a descriptive format highlighting pertinent information on physical, chemical, and thermodynamic properties of chemicals, methods of preparation, industrial applications, chemical analyses, and toxic and hazardous properties. Synonyms, CAS Registry Numbers, brief history of discovery and natural occurrence are provided for many entries. The objective is to provide readers a single source for instant information about important aspects each substance. In this sense it should serve as a combination handbook and encyclopedia. 

Another method of preventing acid mine drainage is to construct barriers around the mine itself. The most important single source of AMD are abandoned coal mines. In some cases, the entrances to those mines can be sealed or barriers can be constructed to prevent the outflow of acidic water from the mines into lakes and streams. Finally, abandoned mines can sometimes simply be filled with sand, gravel, fly ash, or other materials, effectively immobilizing any potential acid-producing substances remaining within them. 

The third contribution is particularly devoted to the concept of so-called single source precursors (SSPs). SSPs contain all the atoms of the different elements necessary for the deposition of the desired material in one single molecule. One motivation for using this concept is to simplify the accompanying gas-phase reactions and thus reduce the process parameters to be controlled and optimised. However, SSPs may offer a unique chance of depositing metastable materials that cannot be derived by other methods. M. Veith and S. Mathur provide such an example in their paper entitled Single-Source-Precursor CVD Alkoxy and Siloxy Aluminum Hydrides . 

Additional details on some of these methods are described in other sections of this review. Attempts have also been made to determine excited-state populations in single-source mass-spectrometric experiments from an analysis of ionization efficiency curves.38ad There are several difficulties in applying such methods. For instance, it is now known from photoionization studies that ionization processes may be dominated by autoionization. Therefore, the onset of a new excited state is not necessarily characterized by an increased slope in the electron-impact ionization-efficiency curve, which is proportional to the probability of producing that state, as had been assumed earlier. Another problem arises because of the different radiative lifetimes that are characteristic of various excited ionic states (see Section I.A.4). 

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