Performance characteristic

Primary performance characteristic benchmarks of UV/Vis detectors are sensitivity, linear dynamic range, and band dispersion. These are primarily controlled by the design of the optics and the flow cell. 

A critical part of the electron spectrometer is the detector which registers the energy-analysed electrons. Channeltrons or channelplates are very convenient detectors, and they will now be discussed with respect to their performance characteristics, the use of channelplates as position-sensitive detectors and their detection efficiencies. 

The names of both detectors reflect that these devices are channels which act as continuous dynode electron multipliers. If there is one channel, it is called a channeltron (channeltron electron multiplier, CEM), if many microchannels are used to form a plate it is called a microchannel electron multiplier plate (in short a microchannelplate, MCP, or channelplate), see Fig. 4.17. A comprehensive description of these devices is given in [Wiz79]. 

A channeltron consists of one channel (about 1 mm in diameter, and 50 mm in length) with a special shape (a curved channel with often a cone at the entrance) 

From the function of a channeltron/channelplate detector it is obvious that high gains are desirable. However, ion feedback and space charge effects limit the gain with increasing charge of the electron avalanche, electron impact ionization with molecules of the residual gas or molecules desorbed under electron bombardment from the channel surface occurs more frequently. The ions produced are then accelerated towards the channel input. If such an ion hits the surface at the channel entrance, it may release an electron which again can start an avalanche of practically the same size, i.e., it causes after-pulses. 

For straight channel multipliers, the onset of ion feedback sets an upper limit to the operation gain of approximately 104. At such a gain, the pulse height 

1 The word channeltron is a registered trademark of the Galileo Electro-Optics Corporation. 

In a quadrupole field, resolution is proportional to the square of the number (n) of rf cycles to which an ion is subjected (i.e., a n ) and is given by the expression 

Because of the lower energy per unit volume, vehicles using neat biodiesel should experience a loss in fuel economy of about 7% on average. 

Biodiesel has higher viscosity and higher pour points compared to typical diesel fuel, which could affect operation in very cold temperatures. Like diesel fuels, pour point additives are effective at decreasing pour point. 

14 Clean diesel is a term that applies to diesel fuel that has low sulfur and aromatic content, along with other characteristics that facilitate low emissions from diesel engines. 

Engine oil dilution is a potential problem with biodiesel since it is more prone to oxidation and polymerization than diesel fuel. The presence of biodiesel in engine oil could cause thick sludge to occur with the consequence that the oil becomes too thick to pump. Special formulations of engine oil are being developed to minimize the effects of dilution with biodiesel. 

The dry and very tough radius threads of orb web-building spiders such as Nephila spp. or Araneus diadematus show good extendibility (up to and 

As shown earlier, orb weavers like the garden spider Araneus or the golden silk spider Nephila coat the capture threads with an aqueous solution that forms sticky droplets. Coat and droplets are crucial for the function of these capture threads as their elasticity derives largely from the high water content of the coat. However, water is important not only for these threads, but for many other types of thread as well, and the role of water as well as other solvents for understanding and manipulating the mechanical properties of spider silk caimot be understated (Fig. 8.9). This can be of special interest if we aim to produce bio-engineered silks with specific properties. 

Major ampullate dragline silk immNephila spiders has high initial modulus 

8 (A) The mechanical properties of different spider dragline silks. Stress-strain characteristics of silk reeled from spiders belonging to widely diverging taxa (1) Euprosthenops sp. (Pisauridae), 

9 (A) Experimental set-up for in situ X-ray diffraction during forced siiking. The spider is fixed by soft tape and mylar bandages to a metai support. The path of the thread from the spinnerets to the motorised reei is schematically indicated. Distance indications (to the spinneret exit) correspond to points where X-ray diffraction data were recorded. (B) Optical image of draw-down of N. edulis spider silk at a drawing speed of 20 mm s T (C) Diffraction pattern obtained at 23.5 +. 5°C. Miller s indices are indicated for selected reflections (for details see ref. 87). 

The buyer s risk increases if one or more suppliers acquire the technological knowledge of the buyer, as those suppliers now becomes potential competitors. Thomson Consumer Electronics, a supplier of JVC, eventually moved into the JVC s market space as a competitor after acquiring the technologies from JVC (Bleeke and Ernst 1995). In additirai, if the technologies that suppliers bring to the supply base are critical for the buyer, the suppliers may threaten to hold it back it becomes a structural risk for the buyer. 

Thus both the differentiatiOTi and relationship dimensions can increase the difficulty in coordinating with the supply base, increasing the probability of undesirable events occurring. Indeed, close relationships among suppliers in the supply 

In addition, information sharing among suppliers may increase supply risk. When suppliers become too close the buyer loses control over the flow of information between the suppliers that it could otherwise have leveraged for its own benefit, and the cooperative relationship may lead to collusive activities (Choi and Hong 2002). Therefore, information exchanges among suppliers in a supply base increases the potential for collusion among them. 

Supplier responsiveness can increase in the size the supply base because a larger supply base increases the competitive pressure on suppliers, causing them to be more responsive. At the other extreme, a close relationship between the buyer and its suppliers also motivates supplier responsiveness (Liker and Choi 2004). Therefore, optimal supplier responsiveness can be achieved with a supply base that is neither too large nor too small. It follows that by working with a limited number of preferred suppliers the buyer can be more effective in communicating its needs and can better induce the suppliers to be responsive. 

The linkages in a supply base help in absorbing, sifting, and classifying new technology developments. Therefore, low levels of linkages would be expected to lead to less innovative improvements in suppliers operations. 

---

Valcarcel, M. Tuque de Castro, M. D. A Hierarchical Approach to Analytical Chemistry, Trends Anal. Chem., 1995,14, 242-250. Further details on evaluating analytical methods may be found in Wilson, A. L. The Performance-Characteristics of Analytical Methods, Part l-Talanta, 1970, 17, 21-29 Part ll-Talanta, 1970, 17, 31M4 Part lll-Talanta, 1973, 20, 725-732 Part IV-Talanta, 1974,21, 1109-1121. 

D. H. Pontius, L. G. Felix, and W. B. Smith, "Performance Characteristics of a Pilot Scale Particle Charging Device," Preprint 76-42.6, 69th APPCA Annual Meeting Portland, Oregon, June 27—July 1, 1976. 

Table 4. Thermochemical, Thermodynamic, and Performance Characteristics of Nitrocellulose Gun Propellants ...

Black Powder. Black powder is mainly used as an igniter for nitrocellulose gun propellant, and to some extent in safety blasting fuse, delay fuses, and in firecrackers. Potassium nitrate black powder (74 wt %, 15.6 wt % carbon, 10.4 wt % sulfur) is used for military appHcations. The slower-burning, less cosdy, and more hygroscopic sodium nitrate black powder (71.0 wt %, 16.5 wt % carbon, 12.5 wt % sulfur) is used industrially. The reaction products of black powder are complex (Table 12) and change with the conditions of initia tion, confinement, and density. The reported thermochemical and performance characteristics vary greatly and depend on the source of material, its physical form, and the method of determination. Typical values are Hsted in Table 13. 

Fig. 10. Performance characteristics for axial flow fans ( ndashrule ), ptopeUet fan (—), tube-axial fan and ( ), siagle-stage and (.), two-stage...

The ratio of stress to strain in the initial linear portion of the stress—strain curve indicates the abiUty of a material to resist deformation and return to its original form. This modulus of elasticity, or Young s modulus, is related to many of the mechanical performance characteristics of textile products. The modulus of elasticity can be affected by drawing, ie, elongating the fiber environment, ie, wet or dry, temperature or other procedures. Values for commercial acetate and triacetate fibers are generally in the 2.2—4.0 N/tex (25—45 gf/den) range. 

Variable-Area Flow Meters. In variable-head flow meters, the pressure differential varies with flow rate across a constant restriction. In variable-area meters, the differential is maintained constant and the restriction area allowed to change in proportion to the flow rate. A variable-area meter is thus essentially a form of variable orifice. In its most common form, a variable-area meter consists of a tapered tube mounted vertically and containing a float that is free to move in the tube. When flow is introduced into the small diameter bottom end, the float rises to a point of dynamic equiHbrium at which the pressure differential across the float balances the weight of the float less its buoyancy. The shape and weight of the float, the relative diameters of tube and float, and the variation of the tube diameter with elevation all determine the performance characteristics of the meter for a specific set of fluid conditions. A ball float in a conical constant-taper glass tube is the most common design it is widely used in the measurement of low flow rates at essentially constant viscosity. The flow rate is normally deterrnined visually by float position relative to an etched scale on the side of the tube. Such a meter is simple and inexpensive but, with care in manufacture and caHbration, can provide rea dings accurate to within several percent of full-scale flow for either Hquid or gas. 

Cost bilizers. The variety of known costabiHzers for the mixed metal stabilizers is a very long listing. There are, however, a relatively small number of commercially used costabiHzers. Some of these additives can also be added by the PVC compounder or processor ia addition to the stabilizer package to further enhance the desired performance characteristics. The epoxy compounds and phenoHc antioxidants are among the most commonly used costabiHzers with the mixed metal stabilizers. 

High Water-Base Fluids. These water-base fluids have very high fire resistance because as Httle as 5% of the fluid is combustible. Water alone, however, lacks several important quaUties as a hydrauHc fluid. The viscosity is so low that it has Httle value as a sealing fluid water has Httle or no abiHty to prevent wear or reduce friction under boundary-lubrication conditions and water cannot prevent mst. These shortcomings can be alleviated in part by use of suitable additives. Several types of high water-based fluids commercially available are soluble oils, ie, od-in-water emulsions microemulsions tme water solutions, called synthetics and thickened microemulsions. These last have viscosity and performance characteristics similar to other types of hydrauHc fluids. 

Most hydrocarbon resins are composed of a mixture of monomers and are rather difficult to hiUy characterize on a molecular level. The characteristics of resins are typically defined by physical properties such as softening point, color, molecular weight, melt viscosity, and solubiHty parameter. These properties predict performance characteristics and are essential in designing resins for specific appHcations. Actual characterization techniques used to define the broad molecular properties of hydrocarbon resins are Fourier transform infrared spectroscopy (ftir), nuclear magnetic resonance spectroscopy (nmr), and differential scanning calorimetry (dsc). 

Addition Polymers. The most commonly referenced reaction of isocyanates iavolves their addition to polyhydroxyl, polyamine, or polycarboxyhc acid compounds to yield addition polymers. Due to the wide diversity of raw material characteristics and the broad range of functionahty, polyurethane polymers having a wide range of processiag and performance characteristics are available. 

Product standards may stipulate performance characteristics, dimensions, quaUty factors, methods of measurement, and tolerances and safety, health, and environmental protection specifications. These are introduced principally to provide for interchangeabiUty and reduction of variety. The latter procedure is referred to as rationalization of the product offering, ie, designation of sizes, ratings, etc, for the attribute range covered and the steps within the range. The designated steps may foUow a modular format or a preferred number sequence. 

CH2—CI2—) —(—CF2— CFH—) (39). Ceramic crystals have a higher piezoelectric efficiency. Their high acoustic impedance compared to body tissues necessitates impedance matching layers between the piezoelectric and the tissue. These layers are similar in function to the antireflective coatings on a lens. Polymer piezoelectric materials possess a more favorable impedance relative to body tissues but have poorer performance characteristics. Newer transducer materials are piezoelectric composites containing ceramic crystals embedded in a polymer matrix (see Composite materials, polymer-MATRIX Piezoelectrics). 

Nondestmctive tests differ from methods of laboratory analysis and testing where specimens are generally sectioned, broken, damaged, or destroyed. Nondestmctive tests can be performed on materials, components, and stmctures or systems that actually are to be used. Thus, effective use of NDE requires engineering knowledge of the stmcture, the performance characteristics, and service environment, as well as the test method. More complete information on all of the topics discussed herein are available (1 6). 

AH-acryHc (100%) latex emulsions are commonly recognized as the most durable paints for exterior use. Exterior grades are usuaHy copolymers of methyl methacrylate with butyl acrylate or 2-ethyIhexyl acrylate (see Acrylic ester polymers). Interior grades are based on methyl methacrylate copolymerized with butyl acrylate or ethyl acrylate. AcryHc latex emulsions are not commonly used in interior flat paints because these paints typicaHy do not require the kind of performance characteristics that acryHcs offer. However, for interior semigloss or gloss paints, aH-acryHc polymers and acryHc copolymers are used almost exclusively due to their exceUent gloss potential, adhesion characteristics, as weU as block and print resistance. 

AEROPHINE 3418A promoter is widely used ia North and South America, AustraHa, Europe, and Asia for the recovery of copper, lead, and ziac sulfide minerals (see Elotatton). Advantages ia comparison to other collectors (15) are said to be improved selectivity and recoveries ia the treatment of complex ores, higher recoveries of associated precious metals, and a stable grade—recovery relationship which is particularly important to the efficient operation of automated circuits. Additionally, AEROPHINE 3418A is stable and, unlike xanthates (qv), does not form hazardous decomposition products such as carbon disulfide. It is also available blended with other collectors to enhance performance characteristics. 

Polymers based on trimellitic anhydride are widely used in premium electromagnetic wire enamels requiring high temperature performance. Several types of trimellitic anhydride-derived polymers are used as wire enamels poly(amide—imide)s (133), poly(ester—imide)s (134), and poly(amide—imide— ester)s (135). Excellent performance characteristics are imparted by trimellitic anhydride-based polymers for wire enamel requirements of flexibiUty, snap, burnout, scrap resistance, heat shock, and dielectric strength. 

Performance Characteristics Polyester resins undergo a rapid transformation from a viscous Hquid to a soHd plastic state that comprises a three-dimensional cross-linked polymer stmcture. The level of polyester polymer unsaturation determines essential performance characteristics (Table 7), although polymer components can influence subtle features that affect thermal, electrical, and mechanical performance as defined by ASTM procedures. 

Polypropylene. PP is a versatile polymer, use of which continues to grow rapidly because of its excellent performance characteristics and improvements in its production economics, eg, through new high efficiency catalysts for gas-phase processes. New PP-blend formulations exhibit improved toughness, particularly at low temperatures. PP has been blended mechanically with various elastomers from a time early in its commercialisation to reduce low temperature brittleness. 

Proprietary blend formulations based on polysulfone, polyethersulfone, and polyphenylsulfone are sold commercially by Amoco Corporation to meet various end use requirements. The blends based on polysulfone are sold under the MINDEL trademark. A glass fiber-reinforced blend based on PES is offered under the trade name RADEL AG-360. This offers most of the performance characteristics of 30% glass fiber-reinforced polyethersulfone but at a lower cost. Two blend product lines are offered based on PPSF. These are designated as the RADEL R-4000 and R-7000 series of products. The former is a lower cost alternative to RADEL R PPSF homopolymer offering most of the performance attributes unique to PPSF. The R-7000 series of resins have been formulated for use in aircraft interiors for civil air transport. They exhibit a very high degree of resistance to flammabihty and smoke release. 

Table 6. Performance Characteristics of Thermally Curable Polymer Backbone Systems...

Validation and Application. VaUdated CFD examples are emerging (30) as are examples of limitations and misappHcations (31). ReaUsm depends on the adequacy of the physical and chemical representations, the scale of resolution for the appHcation, numerical accuracy of the solution algorithms, and skills appHed in execution. Data are available on performance characteristics of industrial furnaces and gas turbines systems operating with turbulent diffusion flames have been studied for simple two-dimensional geometries and selected conditions (32). Turbulent diffusion flames are produced when fuel and air are injected separately into the reactor. Second-order and infinitely fast reactions coupled with mixing have been analyzed with the k—Z model to describe the macromixing process. 

Recreational surfaces must provide certain performance characteristics with acceptable costs, lifetimes, and appearance. Arbitrary but useful distinctions may be made for classification purposes, depending on the principal function a covering intended primarily to provide an attractive surface for private leisure activities, eg, patio surfaces a surface designed for service in a specific sport, eg, track surfaces or a grass-like surface designed for a broad range of heavy-duty recreational activities, including professional athletics, eg, artificial turf for outdoor sports. 

---