Figure-of-merit

As mentioned, the phasing process usually leads to more than one trial solution and the most promising ones are detected by application of some FOMs. Several functions have been proposed, which are expected to be minima or 

When powder data are available and a molecular model has been obtained, the so-called figure of merit may be used. Its expression is  

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A brief review of the figures of merit (1) for thermal imaging (4) and gas detection is given to show the various trades-off required to image the thermal environment and detect atmospheric contamination. 

Parameter Definition Desired trend Best region of appHcation as a figure of merit... 

Composite Devices. Composites made of active-phase PZT and polymer-matrix phase are used for the hydrophone and medical imaging devices (see Composite materials, polymer-matrix Imaging technology). A usehil figure of merit for hydrophone materials is the product of hydrostatic strain coefficient dj and hydrostatic voltage coefficient gj where gj is related to the dj coefficient by (74)... 

Polymer Ferroelectrics. In 1969, it was found that strong piezoelectric effects could be induced in the polymer poly(vinyhdene fluoride) (known as PVD2 or PVDF) by apphcation of an electric field (103). Pyroelectricity, with pyroelectric figures of merit comparable to crystalline pyroelectric detectors (104,105) of PVF2 films polarized this way, was discovered two year later (106.)... 

From the write and read process sketched so far, some requirements for MO media can be derived (/) a high perpendicular, uniaxial magnetic anisotropy K in order to enable readout with the polar Kerr effect (2) a magnetoopticady active layer with a sufficient figure of merit R 0- where R is the reflectivity and the Kerr angle (T) a Curie temperature between 400 and 600 K, the lower limit to enable stable domains at room temperature and the upper limit because of the limited laser power for writing. 

Pigure 10 shows the typical commercial performance of LEDs used for optical data communication. Both free-space emission and fiber-coupled devices are shown, the latter exhibiting speeds of <10 ns. Typically there exists a tradeoff between speed and power in these devices, however performance has been plotted as a function of wavelength for purposes of clarity. In communication systems, photodetectors (qv) are employed as receivers rather than the human eye, making radiometric power emitted by the devices, or coupled into an optical fiber, an important figure of merit. 

Criticality Mnalysis. The criticaUty assessment provides a figure-of-merit for each failure mode. This figure of merit is based on the likelihood of occurrence of the failure mode (Occ), the criticaUty (severity) of the failure mode on system performance (Sev), and the detectabiUty of the failure mode by the user prior to occurrence (Det). 

At optical wavelength of 1.3. m. Values given are figures of merit. 

In an effort to identify materials appropriate for the appHcation of third-order optical nonlinearity, several figures of merit (EOM) have been defined (1—r5,r51—r53). Parallel all-optical (Kerr effect) switching and processing involve the focusing of many images onto a nonlinear slab where the transmissive... 

There are important figures of merit (5) that describe the performance of a photodetector. These are responsivity, noise, noise equivalent power, detectivity, and response time (2,6). However, there are several related parameters of measurement, eg, temperature of operation, bias power, spectral response, background photon flux, noise spectra, impedance, and linearity. Operational concerns include detector-element size, uniformity of response, array density, reflabiUty, cooling time, radiation tolerance, vibration and shock resistance, shelf life, availabiUty of arrays, and cost. 

Fig. 4. Dependence of thermoelectric parameters on carrier concentration, where (—) is the Seebek coefficient (5) the figure of merit Z) (-),...

Diamond and Refractory Ceramic Semiconductors. Ceramic thin films of diamond, sihcon carbide, and other refractory semiconductors (qv), eg, cubic BN and BP and GaN and GaAlN, are of interest because of the special combination of thermal, mechanical, and electronic properties (see Refractories). The majority of the research effort has focused on SiC and diamond, because these materials have much greater figures of merit for transistor power and frequency performance than Si, GaAs, and InP (13). Compared to typical semiconductors such as Si and GaAs, these materials also offer the possibiUty of device operation at considerably higher temperatures. For example, operation of a siUcon carbide MOSFET at temperatures above 900 K has been demonstrated. These devices have not yet been commercialized, however. 

Simplified Profitability Criteria. Approximate profitabihty criteria that do not require a detailed year-by-year financial analysis are sometimes employed as simple figure-of-merit measures. 

Another means of comparing the performance of a practical refrigerator is by the use of the figure of merit, FOM, defined as... 

In comparing alternative collectors for a given service, a figure of merit is desirable for ranking the different devices. Since power consumption is one of the most important characteristics of a collector, the ratio of Nt to power consumption is a useful criterion. Another is the ratio of Nt to capital investment. 

In the report analytieal figures of merit of ICP-MS and -AES teehniques in eombination with pre-eoneentration of traee elements for survey analysis of high purity metals and their oxides used as the preeursors for oxide monoerystals produetion will be presented and eompared to that of direet ICP-MS and -AES teehniques. 

If the rf source is applied to the analysis of conducting bulk samples its figures of merit are very similar to those of the dc source [4.208]. This is also shown by comparative depth-profile analyses of commercial coatings an steel [4.209, 4.210]. The capability of the rf source is, however, unsurpassed in the analysis of poorly or nonconducting materials, e.g. anodic alumina films [4.211], chemical vapor deposition (CVD)-coated tool steels [4.212], composite materials such as ceramic coated steel [4.213], coated glass surfaces [4.214], and polymer coatings [4.209, 4.215, 4.216]. These coatings are used for automotive body parts and consist of a number of distinct polymer layers on a metallic substrate. The total thickness of the paint layers is typically more than 100 pm. An example of a quantitative depth profile on prepainted metal-coated steel is shown as in Fig. 4.39. 

Fig.2. Thermal stress figure of merit for selected plasma facing materials...

As discussed in the introduction, disruptions cause the most severe thermomechanical loading experienced in a tokamak. In each of the 500 or so disruptions expected in ITER, approximately 10-20 MJ/m will be deposited onto the first wall in 0.01 to 3 seconds. Such a disruption will cause very high thermal stresses and significant material erosion (Section 4). As these events are transient in nature, the ability of the PFC to withstand the disruption depends on the material s ability to both conduct and to absorb the deposited heat, before reaching a temperature or stress limit. For comparative purposes, a disruption figure of merit takes this into account ... 

Another strategy reported by Sales links back to the superlattices discussed in Section 7.2.1.4. It was suggested by Mildred Dresselhaus s group at MIT (Hicks et al. 1993) that semiconductor quantum wells would have enhanced figures of merit compared with the same semiconductor in bulk form. PbTe quantum wells were confined by suitable intervening barrier layers. From the results, ZT values of 2 were estimated from single quantum wells. This piece of research shows the intimate links often found nowadays between apparently quite distinct functional features in materials. 

An algorithm for an assesment of chromatographic peak purity was proposed. In this study ethyl 8-methyl-4-oxo-4/7-pyrido[l, 2-u]pyrimidine-3-carboxylate was also used (97MI13). Ethyl 7-methyl-4-oxo-4//-pyrido[l,2-u]pyrimidine-3-carboxylate, among other compounds, was applied to show practical mathematical tools for the creation of several figures of merit of nth order instrumentation, namely selectivity, net analyte signal and sensitivity (96ANC1572). 

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