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We represent risk factors as sums of orthogonal components capturing fluctuations with cycles of different length. The representation leads to novel spectral factor models in which systematic risk is allowed—without being forced—to vary across frequencies. Frequency-specific systematic risk is captured by a notion of spectral beta. We show that traditional factor models restrict the spectral betas to be constant across frequencies. The restriction can hide horizon-specific pricing effects that spectral factor models are designed to reveal. We illustrate how the methods may lead to economically meaningful dimensionality reduction in the factor space.

Herein we present a robust methodology to simulate the solar cells electrical response using optical-electrical finite-difference mathematical models and experimental data of solar spectrum. In this methodology, we suggest the use of mathematical PV models for three purposes: 1) to find the unknown solar cell electrical parameters from experimental J-V curves; 2) to simulate the response of solar cells under narrow-band incident radiation; and lastly 3) to simulate the short-circuit current response to experimental solar spectra. We used APE (Average Photon Energy) and SF (Spectral Factor) to assess the solar cells spectral response. We applied the method for data collected from the city of Belo Horizonte, Brazil. Both APE and SF analyses have shown that OPV presents relatively better spectral response than p-Si cells, because Belo Horizonte solar radiation is predominantly shifted to a blue-rich spectrum, compared to the AM1.5G. OPV cells show an annual average SF of 1.10, compared to the approximately 1.00 of p-Si cells. The methodology is presented in a workflow format, and we hope it will be useful for other researchers that are looking for procedures to simulate solar cells electrical response.

In this paper, a low-redundant cosine-modulated nonuniform filter bank (LR-CMNFB) and its design method are proposed. The proposed LR-CMNFB consists of two parallel subsystems which have the same frequency division scheme. The nonuniform analysis and synthesis filters of the first subsystem are formed by directly merging the consecutive cosine-modulated versions of a lowpass prototype filter, and the filters of the second subsystem are derived to meet the aliasing cancelation condition. Since the aliasing of the two subsystems is structurally canceled without guardband constraint on the filter location, the shift-invariance and flexible nonuniform frequency division, two important properties in many signal and image processing applications, can be achieved simultaneously at the cost of low redundancy (that is less than 2). From a particular analysis on the filter characteristic and the reconstruction error of the whole system, it is found that the good characteristics of filters and the good reconstruction performance of LR-CMNFB can be jointly obtained by constraining the prototype filter to be the linear-phase spectral factor of a 2 Mth band filter. Several design examples are given to illustrate the performance of the proposed LR-CMNFB and its potential in practical applications.

PURPOSE: SPECT imaging with two radiotracers at the same time is feasible if two different radioisotopes are employed, given their distinct energy emission spectra. In the case of (123)I and (125)I, dual SPECT imaging is not straightforward: (123)I emits photons at a principal energy emission spectrum of 143.1-179.9keV. However, it also emits at a secondary energy spectrum (15-45keV) that overlaps with the one of (125)I and the resulting cross-talk of emissions impedes the accurate quantification of (125)I. In this paper, we describe three different methods for the correction of this cross-talk and the simultaneous in vivo [(123)I]IBZM and [(125)I]R91150 imaging of D2/3 and 5-HT2A receptors in the rat brain. METHODS: Three methods were evaluated for the correction of the effect of cross-talk in a series of simultaneous, [(123)I]IBZM and [(125)I]R91150 in vivo and phantom SPECT scans. Method 1 employs a dual-energy window (DEW) approach, in which the cross-talk on (125)I is considered a stable fraction of the energy emitted from (123)I at the principal emission spectrum. The coefficient describing the relationship between the emission of (123)I at the principal and the secondary spectrum was estimated from a series of single-radiotracer [(123)I]IBZM SPECT studies. In Method 2, spectral factor analysis (FA) is applied to separate the radioactivity from (123)I and (125)I on the basis of their distinct emission patterns across the energy spectrum. Method 3 uses a modified simplified reference tissue model (SRTMC) to describe the kinetics of [(125)I]R91150. It includes the coefficient describing the cross-talk on (125)I from (123)I in the model parameters. The results of the correction of cross-talk on [(125)I]R91150 binding potential (BPND) with each of the three methods, using cerebellum as the reference region, were validated against the results of a series of single-radiotracer [(123)I]R91150 SPECT studies. In addition, the DEW approach (Method 1), considered to be the most straightforward to apply of the three, was further applied in a dual-radiotracer SPECT study of the relationship between D2/3 and 5-HT2A receptor binding in the striatum, both at the voxel and at the regional level. RESULTS: Average regional BPND values of [(125)I]R91150, estimated on the cross-talk corrected dual-radiotracer SPECT studies provided satisfactory correlations with the BPND values for [(123)I]R91150 from single-radiotracer studies: r=0.92, p

The absorbing aerosol influence on the brightness spectral coefficient (Rrs (λ)) of the Black sea by insitu AERONET-OC and MODIS satellite data has been studied. It is shown that the registration of dust transfer at wavelengths of 412, 488, 531 and 547 shows the most significant (more than 3 times) difference between the values of Rrs (λ) insitu AERONETOC and Rrs (λ) MODIS.

The spectral factorization is an important operation in many different applications. This paper studies whether the spectral factor of a given computable spectral density can always be computed on an abstract machine (a Turing machine). It is shown that there are computable spectral densities with very comfortable analytic properties (smoothness and finite energy) such that the corresponding spectral factor can not be determined on a Turing machine. As an application, the paper discusses the possibility of calculating the optimal Wiener filter from computable spectral densities.

A Typical Meteorological Year (TMY) is frequently used in solar power for long-term energy yield analysis. Different approaches have been reported focusing on concentrating solar power or photovoltaic power plants that have established different relative contributions of the involved variables (mainly solar irradiance components and temperature) according to the application. For PV applications the estimation of the spectral gains and losses requires of on-site spectral measurements. Long-term analysis of the spectral influence on PV technologies has been performed for over seven years of measured spectral global tilted irradiance in Madrid. The experimental spectra were measured with an EKO spectroradiometer in the wavelength range of 300–1100 nm. The TMY methodology has been used to create a typical spectral year of global tilted irradiance that can be used for computing the spectral factor. This paper shows the different steps in applying the TMY methodology to spectral irradiance and the resulting spectral factors computed for seven different PV technologies. Thus, this approach can effectively be used to characterize the long-term spectral influence of PV technologies in a selected site.

In Part I of this work, a comprehensive outdoor characterisation of a concentrating photovoltaic monomodule was presented where the importance of atmospheric parameters on the performance of such systems was highlighted. In this work, Part II, the power ratings of a concentrating photovoltaic monomodule are determined using different methods and filtering criteria that account for the spectrum. Spectral variations are considered to be a major parameter that contributes to the uncertainty of concentrating photovoltaic power ratings due to the dynamic behaviour of outdoor conditions. In order to address the sensitivity of such variations, Concentrator Standard Operating Conditions (CSOC) and Concentrator Standard Test Conditions (CSTC) power rating estimations are performed using different scenarios and compared with measurements obtained using a Helios 3198 solar simulator. The application of different methods and filtering criteria, in terms of the spectral matching ratio (SMR) of the middle to bottom subcell, exhibits differences of up to 3.64% and 1.37% for the CSOC and CSTC estimations respectively. The comparison with the CSTC power rating obtained indoors shows a difference of up to 8.45%; this is attributed to the tracking errors and also the temperature dependence of the refractive optics. The application of the spectral factor (SF) as filtering criterion reduces the CSTC power rating difference to 6.74% compared to the corresponding value obtained indoors. In addition, the CSOC power rating estimation using the SF filtering exhibits similar results to the standardised procedure using the SMR indices (within 1.21%).

We represent risk factors as sums of orthogonal components capturing fluctuations with cycles of different length. The representation leads to novel spectral factor models in which systematic risk is allowed (without being forced) to vary across frequencies. Frequency-specific systematic risk is captured by a notion of spectral beta. We show that traditional factor models restrict the spectral betas to be constant over frequencies. The restriction can hide horizon-specific pricing effects which spectral factor models are designed to reveal. We illustrate how the methods may lead to economically-meaningful dimensionality reduction in the factor space.

The spectral dependence of concentrator photovoltaic devices shows a larger and more complex behaviour than conventional photovoltaic devices due to the use of multi-junction solar cells and optical elements. The spectral factor is a widely used index for evaluating the spectral influence on the performance of conventional photovoltaics in outdoors. However, the experimental analysis of this index as a tool to evaluate the spectral influence on the performance of concentrator devices has not been undertaken and still remains unknown. The aim of this paper is to analyse the spectral factor as an index for estimating the spectral influence on the power and energy output of concentrator photovoltaic systems. The final goal is to contribute to the development of new procedures for predicting the performance of this technology under real operating conditions. To achieve this goal, two concentrator modules have been monitored over the course of two years in Southern Spain. Results show that the spectral factor has a larger and different spectral sensitivity than the power output. However, this index can be used as a good first approximation for quantifying the spectral influence on the maximum power and energy yield of a concentrator photovoltaic system under real operating conditions.

Nowadays, investors, customers, and even suppliers focus on the bankability of photovoltaic (PV) technologies. However, few studies have investigated the annual net effect of solar spectrum. In this study, we estimate the net effect of the solar spectrum on the annual energy yield of c-Si and a-Si modules by two parameters. One parameter is a direct calculation from spectral factor (SF). The other parameter uses average photon energy (APE) and a regression line or curve. The estimations by the two parameters are quite consistent, whereas there is 1.2% difference between the estimations at most. Therefore, APE would be a useful index to quantify the effect of the solar spectrum.

Uno de los aspectos necesarios para el adecuado desarrollo de la tecnología de alta concentración fotovoltaica (HCPV) es el estudio de su comportamiento en condiciones reales de funcionamiento. En concreto, el estudio de la respuesta de los dispositivos HCPV ante las variaciones espectrales de la radiación solar incidente es crucial, ya que esta tecnología se ve más afectada por estos cambios que la fotovoltaica convencional (PV). Con el desarrollo de la presente tesis se pretende arrojar luz sobre esta cuestión clave, realizando un estudio profundo del impacto que producen las variaciones espectrales en los sistemas HCPV. Los resultados indicaron, entre otras conclusiones, que la sensibilidad espectral de los módulos HCPV no es una limitación crucial para la expansión del mercado de esta tecnología y más aun teniendo en cuenta que sus eficiencias de conversión son mucho más altas que las de la tecnología fotovoltaica convencional One of the main challenges associated with the development of high concentration photovoltaic (HCPV) technology is the study of its behaviour under real operating conditions. In particular, the study of HCPV devices’ response to the spectral variations of incident solar radiation is crucial, because this technology is more sensitive to these changes than conventional photovoltaic (PV). The aim of this doctoral thesis is to shed light on this key issue by studying the influence of spectral variations on the performance of HCPV systems. The results showed, among others conclusions, that spectral changes are not a crucial limitation for the market expansion of HCPV systems, especially considering that their conversion efficiencies are is significantly higher than those of PV technology Tesis Univ. Jaén. Departamento Ingeniería Electrónica y Automática. Leída el 14 de junio de 2017

Multi-junction (MJ) solar cells show an important dependence on the incident spectrum due to the internal series connection of several cells with different band gap energies. The influence of spectral variations on the performance of HCPV modules or systems is different from that in MJ solar cells since they use optical devices to concentrate the light on the solar cell surface. The spectral distribution of irradiance is affected by atmospheric parameters and changes during the course of day, month or year. Because of this, several authors have done different studies to analyse and quantify the spectral effects on the performance of HCPV modules. However, there are still important issues that have not been addressed. In this paper, a deep analysis of the spectral effects on the performance of different HCPV modules with different multi-junction solar cells and Fresnel lenses on an annual time scale and their study and comparison at locations with different climate conditions is conducted. In order to address this issue, ground-based climatologies at the locations studied, spectra simulations with the SMARTS model and the spectral factor of a HCPV module have been used. Results show that the annual spectral losses vary from 6% to 51% depending on the climate conditions of the location and the HCPV module.

The performance of six photovoltaic (PV) modules composed of polycrystalline silicon (pc-Si), amorphous silicon (a-Si), and hydrogenated amorphous silicon/crystalline silicon (a-Si:H/c-Si) modules was investigated at eight locations in Japan from August 2007 to December 2008. In addition, solar irradiance, solar spectrum, and module temperature were simultaneously measured in these round-robin measurements. In this study, we evaluate quantitatively the effects of module temperature and solar spectrum on the performance of the PV modules as thermal factor (TF) and spectral factor (SF), respectively. Furthermore, we investigate the variation in module performance, which is converted into module performance under standard test conditions (STC) using the TF and SF. In the case of the pc-Si modules, the variations in performance ratio under STC (PRSTC) for these modules range from 0.056 to 0.074 through the round-robin measurements. The TF indicates that the contribution of module temperature to the variation in performance is large, between about 15 and 20%. However, the SF suggests that the contribution of solar spectrum is quite small, less than 3%. In the case of the a-Si modules, the contribution of module temperature is about 8%. The performance is largely influenced by solar spectrum, more than 12% at its maximum. Consequently, the variations in the corrected PRSTC of the a-Si modules are between 0.117 and 0.141. These large variations may result from the effects of thermal annealing and light soaking. The variation in PRSTC of the a-Si:H/c-Si module is similar to that of the pc-Si modules. Copyright © 2010 John Wiley & Sons, Ltd.

By analyzing two significant facors,skin physical characteristics and system characteristics,which affect the multispectral face recognition,a novel Band-Adjusting HOSVD (BA-HOSVD) multispectral face recognition algorithm is proposed.The spectral factor is treated separately with the weighted fusion method,which retains more information of the spectrum.Simulation results show that BA-HOSVD can be applied in multispectral face recognition,and it has a better recognition result than the other methods which do not consider the band characteristics.

This chapter is devoted to continuous-time versions of the basic results in Chaps. 6, 8 and 9 In this context, the linear stochastic model (6.1) corresponds to a system $$\displaystyle{ \left \{\begin{array}{@{}l@{\quad }l@{}} dx = Axdt + Bdw\quad \\ dy = Cxdt + Ddw\quad \end{array} \right. }$$ of stochastic differential equations driven by the increments of a vector Wiener process w. The state process x will still be a stationary process, but the output process y has stationary increments. In the case when D = 0, we may instead consider a model $$\displaystyle{ \left \{\begin{array}{@{}l@{\quad }l@{}} dx = Axdt + Bdw\quad \\ \phantom{d}y = Cx\quad \end{array} \right. }$$ for which the output is a stationary process.

Following the model of DeVos and Pauwels (1981), we calculated the spectral factor of efficiencies (η1) for n +-p or n +-i-p heterojunctions that can be formed by different thin absorber materials (p-type or intrinsic(i)) with n +-type CdS thin films produced by conversion of chemically deposited CdS thin films by doping with Cl or In as reported before. The materials with η1 comparable to that of CuInSe 2 (Eg, 1.01 eV: 57%) are AgBiS 2 (Eg, 0.9 eV: 56%), Cu 2 SnS 3 (Eg, 0.91 eV: 57%), PbSnS 3 (Eg, 1.05 eV: 57%), PbSbS 4 (Eg, 1.13 eV: 56%).

We use state-space methods to show that any proper, rational indefinite spectral density invertible at infinity has a proper, rational, stable, and minimum phase spectral factor of some degree, and we write down a formula for such factors.

Given a rational spectral density and a minimal spectral factor, a parameterization of all minimal spectral factors is derived. A minimal realization of each minimal spectral factor is also provided. This parameterization is shown to hold under the condition of nonintersection between the spectra of two matrices. This condition, first introduced in previous work by Ferrante et al. (1993), is proved here to be also necessary. Finally these results are applied to the stochastic realization problem. >