Conventional Figures Of Merit Research Articles

Figure of merit for front electrodes of solar cells

Conventional figures of merit often characterize the optical and electrical properties of transparent conductive thin films and are widely applied in research and industry. However, an appropriative figure is necessary to evaluate the front electrodes of solar cells. So an appropriate figure of merit is therefore proposed in this paper, specifically designed for the evaluation of the front electrodes of solar cells. The proposed figure is adapted from ΦTC, the most commonly used conventional figure of merit, with two changes. First, external quantum efficiency functions for different types of solar cells are explicitly considered. Second, data from the air mass 1.5 spectrum are used as weight factors to calculate the mean optical transmittance. With these two changes, the proposed figure of merit is shown to be well adapted to the photovoltaic field. To validate it, silicon heterojunction solar cells with different front electrodes were simulated as examples. By comparing the simulation results and the respective values of the proposed figure, it is evident that this figure of merit provides values that are proportional to the conversion efficiencies of solar cells. The proposed figure can therefore be used in the selection and manufacturing of front electrodes of solar cells. In addition, two variations on this figure of merit are proposed, specifically adapted to the characteristics of multiple electron-hole pairs cells and thermophotovoltaic cells.

Comparison of microconcentric and membrane-desolvation sample introduction systems for determination of low rare earth element concentrations in surface and subsurface waters using sector field inductively coupled plasma mass spectrometry

Analytical performances of a microconcentric nebulizer (MCN) and a membrane-desolvation sample introduction system (Aridus) were compared for determination of low concentrations of rare earth elements (REEs) in surface and subsurface waters using a double focusing sector field inductively coupled plasma mass spectrometer. Conventional figures of merit were employed, such as sensitivities, limits of detection (LOD), REE–O + formation, matrix induced interferences, long term signal variations, and recovery from spiked sea water samples and a pristine water CRM. Sensitivity as a function of mass for the MCN was quite flat with the exception of light REE (LREE +) which was dependent on REE–O + generation. Signal responses using the Aridus were enhanced by factors of 4–10. Large sensitivity enhancements were observed for 139La +, 140Ce + and 141Pr +, due to the attenuation of their REE–O + (where the Aridus 140Ce 16O +/ 140Ce + was three orders of magnitude lower than that determined using the MCN) as a result of water analysis reduction in the plasma. Despite higher sensitivities, Aridus LODs were not significantly different from those obtained using the MCN, and values varied from 0.05 to 0.2 ng L − 1 and 0.1 to 0.2 ng L − 1 for the MCN and Aridus systems, respectively. When using the MCN, LREE + signals were closely associated with REE–O bond strengths, implying that LREE–O + production and breakdown are related to the strength of REE–O bonds in REE–O + ions suggesting that medium REE (MREE)–O + and heavy REE (HREE)–O + if formed, were thermally unstable in the plasma. In the presence of conservative Na concentrations, MCN LREE + signal suppressions varied from about 15 to 25% and about 5 to 10% for MREE + and HREE +. In contrast, regular 15% signal suppressions for all REE + were observed for the Aridus. In the case of the MCN, more than one internal standard is required for compensation for these different effects, whereas a single internal standard ( 159Tb +) compensated for REE + signal variations with the Aridus. Long term uncompensated REE + signal % RSDs using the MCN varied from about 2 to 5%, and % recoveries were about 95–110%. With internal standardization, % RSD varied irregularly from about 1 to 3% and % recoveries were not significantly improved. In contrast, with the Aridus, high % RSDs of about 8% and recoveries of about 80% were compensated with 159Tb + as the internal standard (< 0.5% and recoveries of about 100%, respectively). Accuracy was determined by analyzing spiked sea water CRM (NAAS-5) (1:100 v/v) spiked with 1 µg L − 1 REEs and CRM SLRS-4 using an external calibration procedure. With the Aridus system, REE recoveries were about 100% with 159Tb + as the internal standard. REE determinations of SLRS-4 were in good agreement with the reported values indicating that very low REE concentrations can be determined directly without matrix separation and analyte preconcentration.

Critical factors limiting the interpretation of regression vectors in multivariate calibration

It is common to see published manuscripts and presentations making interpretive comments about correct or incorrect features of the regression vector obtained from multivariate-calibration methods. While model validation is crucial, a considerable body of literature casts doubt on the value of qualitative interpretation of the regression vector. Following a review of this literature, we discuss two simple examples, which illustrate the exceptionally complex behavior of the inverse calibration methods that dominate current chemometrics practice. We show that the behavior of regression vectors in inverse calibration is too complex to be interpreted transparently unless an unusual amount of system information is available. If explicit information about sensitivity and selectivity is desired, it should be quantified using conventional figures of merit.

Count rate studies of a box-shaped PET breast imaging system comprised of position sensitive avalanche photodiodes utilizing monte carlo simulation

We are investigating a high-sensitivity, high-resolution positron emission tomography (PET) system for clinical use in the detection, diagnosis and staging of breast cancer. Using conventional figures of merit, design parameters were evaluated for count rate performance, module dead time, and construction complexity. The detector system modeled comprises extremely thin position-sensitive avalanche photodiodes coupled to lutetium oxy-orthosilicate scintillation crystals. Previous investigations of detector geometries with Monte Carlo indicated that one of the largest impacts on sensitivity is local scintillation crystal density when considering systems having the same average scintillation crystal densities (same crystal packing fraction and system solid-angle coverage). Our results show the system has very good scatter and randoms rejection at clinical activity ranges (≈200 μCi).

Application of known X-ray phases in the crystallographic study of a small protein.

Phase information, assumed known from three-beam diffraction experiments, has been used successfully as input to direct methods to re-determine the crystal structure of rubredoxin. With data at 1.54 A resolution, starting sets containing 26 single phases, or alternatively 45 triplet phases, in both cases known with a mean error of +/-22.5 degrees, were sufficient to initiate solution of the structure. Conventional figures of merit were employed in the early stages to reject the majority of the incorrect phase models. The presence of a FeS(4) cluster in the structure was used in the interpretation of the initial maps. Phase sets including 2500 E's with a mean single phase error <Deltaphi> approximately 70 degrees or a mean triplet phase error <DeltaPhi(3)> approximately 80 degrees, both relative to the model from the crystallographic refinement, could be refined and expanded by Fourier recycling using the SAYTAN formalism. Several parameters have been varied to study their influence on phase expansion and refinement.

A tangent formula derived from Patterson-function arguments. III. Structure determination of zeolitic and layered materials from low-resolution powder diffraction data

The viability of solving the structure type of zeolitic and layered materials applying multisolution direct methods to low-resolution (~2.2 A) powder diffraction data is shown. The phases are refined with the tangent formula derived from Patterson-function arguments [Rius (1993). Acta Cryst. A49, 406–409] and the correct phase sets are discriminated with the conventional figures of merit. The two test examples presented are (a) the already known tetragonal zeolite ZSM-11 (space group 1{\bar 4}m2) at 2.3 A resolution and (b) the hitherto unknown layer silicate RUB-15 (Ibam) at 2.2 A resolution. In both cases, the tetrahedral Si units appear as resolved peaks in the Fourier maps computed with the phases of the highest-ranked direct-methods solutions.

On the application of phase relationships to complex structures. XXXII. A small protein at low resolution.

The direct-methods program SAYTAN is applied to data at various restricted resolutions for a small protein. It is shown that useful sets of phases can be obtained even down to 3 A resolution. Conventional figures of merit are not very discriminating for the phase sets developed, but modified figures of merit seem capable of selecting the better phase sets, at least for those generated from 2 A or higher resolution data.

Correlation between conventional control figures of merit and the Q matrix of the quadratic cost function : Third-order plant†

In conventional control theory the techniques for achieving some or all of the desired figures of merit have been highly developed (D'Azzo and Houpis 1966). Modern control theory optimizes a system performance based upon a desired performance index, PI. The work of Rynaski and Whitbeek (1966) is extended to form the basis for the correlation between the conventional control figures of merit (Mp, tp, ts and wd, and steady-state error) and the diagonal elements of the Q matrix of the quadratic PI (the off-diagonal terms being zero). This correlation is established for a third-order single-input, single-output system, enabling a system designer to optimize a system and at the same time satisfying some or all of the conventional figures of merit.