bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical characterization of dispersion coefficients by meshless‐based inverse analysis
Authors: Sheu Guang Y. 
Published: March 2010

AbstractThis study presents the preliminary development of a meshless‐based indirect inverse analysis. Two goals are desired to be attained: (a) identifying fewer quantities in an indirect inverse analysis and (b) getting the interpolation results of spatial variation of a quantity insensitive to the replacement of one or few interpolation points with other points. This idea is illustrated by modifying a meshless local Petrov‐Galerkin (MLPG) formulation of a two‐dimensional (2D) contaminant transport problem under the concept of boundary control. Thus, dispersion coefficients to be identified are solved from measured or prescribed pollutant concentrations.A field problem is introduced to test the performance of resulting meshless‐based indirect inverse analysis procedure. This test finds a major motive and a minor one for performing a meshless‐based indirect inverse analysis. The major motive is attaining the aforementioned Goal (b), while the above‐mentioned Goal (a) is the minor motive. In conclusion, the development of a meshless‐based indirect inverse analysis procedure can be a valuable application of the MLPG method. Copyright © 2010 John Wiley & Sons, Ltd.
Fully coupled poromechanical back analysis of the pulse test by inverse method
Authors: Giot Richard , Giraud Albert , Auvray Christophe , Homand Françoise , Guillon Théophile 
Published: March 2010

AbstractIn this paper, we investigate the pulse test, which is usually considered as efficient for measuring the permeability of weakly permeable porous media. The pulse is first analyzed and we show that it is a fully poromechanical coupled problem. Owing to those couplings, the problem is 2D‐axisymmetrical, rather than 1D as is usually considered to be the case. As a consequence, the 1D solutions, for example under constant mean stress hypothesis, although giving good approximates of permeability and storage coefficient, are not rigorous and an enhanced back analysis of the test requires 2D solutions. Therefore, no analytical solution exists, and the problem has to be solved using 2D‐axisymmetrical numerical modelings of the pulse test. The finite element method is considered in this paper. We then proceed to formulate the pulse test back analysis as a parameter identification problem, and we focus on intrinsic permeability, Biot coefficient, drained Young's modulus and reservoir compressibility levels. This parameter identification problem is solved by an inverse method consisting of the minimization of a cost‐functional, through a gradient‐based algorithm. This new method of interpretation of the pulse test is finally applied to laboratory tests on Meuse/Haute–Marne argillite and is shown to give encouraging results. Copyright © 2010 John Wiley & Sons, Ltd.
A partial characterization of the optimal ordering/rationing policy for a periodic review system with two demand classes and backordering
Authors: Chen Shaoxiang , Xu Jianjun , Feng Youyi 
Published: March 2010

AbstractWe consider a finite horizon periodic review, single product inventory system with a fixed setup cost and two stochastic demand classes that differ in their backordering costs. In each period, one must decide whether and how much to order, and how much demand of the lower class should be satisfied. We show that the optimal ordering policy can be characterized as a state dependent (s,S) policy, and the rationing structure is partially obtained based on the subconvexity of the cost function. We then propose a simple heuristic rationing policy, which is easy to implement and close to optimal for intensive numerical examples. We further study the case when the first demand class is deterministic and must be satisfied immediately. We show the optimality of the state dependent (s,S) ordering policy, and obtain additional rationing structural properties. Based on these properties, the optimal ordering and rationing policy for any state can be generated by finding the optimal policy of only a finite set of states, and for each state in this set, the optimal policy is obtained simply by choosing a policy from at most two alternatives. An efficient algorithm is then proposed. © 2010 Wiley Periodicals, Inc. Naval Research Logistics, 2010
Effects of motion and b‐matrix correction for high resolution DTI with short‐axis PROPELLER‐EPI
Authors: Aksoy Murat , Skare Stefan , Holdsworth Samantha , Bammer Roland 
Published: March 2010

AbstractShort‐axis PROPELLER‐EPI (SAP‐EPI) has been proven to be very effective in providing high‐resolution diffusion‐weighted and diffusion tensor data. The self‐navigation capabilities of SAP‐EPI allow one to correct for motion, phase errors, and geometric distortion. However, in the presence of patient motion, the change in the effective diffusion‐ encoding direction (i.e. the b‐matrix) between successive PROPELLER ‘blades’ can decrease the accuracy of the estimated diffusion tensors, which might result in erroneous reconstruction of white matter tracts in the brain. In this study, we investigate the effects of alterations in the b‐matrix as a result of patient motion on the example of SAP‐EPI DTI and eliminate these effects by incorporating our novel single‐step non‐linear diffusion tensor estimation scheme into the SAP‐EPI post‐processing procedure. Our simulations and in‐vivo studies showed that, in the presence of patient motion, correcting the b‐matrix is necessary in order to get more accurate diffusion tensor and white matter pathway reconstructions. Copyright © 2010 John Wiley & Sons, Ltd.
Wafer reuse for repeated growth of III–V solar cells
Authors: Bauhuis G. J. , Mulder P. , Haverkamp E. J. , Schermer J. J. , Bongers E. , Oomen G. , Köstler W. , Strobl G. 
Published: March 2010

AbstractThe epitaxial lift‐off (ELO) technique can be used to separate a III–V solar cell structure from its underlying GaAs or Ge substrate. ELO from 4‐inch Ge wafers is shown and 2‐inch GaAs wafer reuse after lift‐off is demonstrated without degradation in performance of the subsequent thin‐film GaAs solar cells that were retrieved from it. Since a basic wet chemical smoothing etch procedure appeared insufficient to remove all the surface contamination, wafer re‐preparation is done by a chemo‐mechanical polishing procedure. Copyright © 2010 John Wiley & Sons, Ltd.
Optimal design of periodic surface texture for thin‐film a‐Si:H solar cells
Authors: Čampa Andrej , Isabella Olindo , van Erven Rob , Peeters Patrick , Borg Herman , Krč Janez , Topič Marko , Zeman Miro 
Published: March 2010

AbstractOptical analysis of hydrogenated amorphous silicon (a‐Si:H) solar cells with a periodic texture applied to the interfaces was carried out by two‐dimensional optical simulator. The optical simulator solves the electromagnetic wave equations by means of finite element method using triangular elements for the discretization of space. The periodic texture with rectangular‐like shape acts as a diffraction grating which scatters light into selective angles and thus gives a potential for significant prolongation of optical paths in thin absorber layers of the cells. Optimization of the geometrical parameters (period, height and duty‐cycle) of the periodic texture was carried out in order to obtain the highest photocurrent from a‐Si:H solar cells. The a‐Si:H solar cell with the optimal periodic texture parameters (period of 300 nm, height of 300 nm and duty cycle of 50%) and the absorber layer thickness of 300 nm generates up to 35% more photocurrent in comparison to the cell with flat interfaces. The optical analysis demonstrates that the optimal periodic texture in the a‐Si:H solar cell results in the best trade‐off between the antireflection effect at front interfaces, light scattering efficiency and the absorption losses at realistic metal back contact. Copyright © 2010 John Wiley & Sons, Ltd.
Wire bonding as a cell interconnection technique for polycrystalline silicon thin‐film solar cells on glass
Authors: Gress Peter J. , Widenborg Per I. , Varlamov Sergey , Aberle Armin G. 
Published: March 2010

AbstractThe interconnection of solar cells is a critical part of photovoltaic module fabrication. In this paper, a high‐yield, low‐cost method for interconnecting polycrystalline silicon thin‐film solar cells on glass is presented. The method consists of forming adjacent, electrically isolated groves across the cells using laser scribing, and then forming wire bonds over each laser scribe, resulting in series interconnection of the individual solar cells. Wire bonds are also used to connect the first and last solar cell in the string to external (tabbing) leads, forming a mini‐module. A layer of white paint is then applied, which acts as both an encapsulation layer and an additional back surface reflector. Using this method, an 8·3% efficient mini‐module has been fabricated. By exploiting recent developments in wire bonding technology, it appears that this process can be automated and will be capable of forming solar cell interconnections on large‐area modules within relatively short processing times (∼10 min for a 1 m2 module). Copyright © 2010 John Wiley & Sons, Ltd.
Analysis of one‐axis tracking strategies for PV systems in Europe
Authors: Huld Thomas , Cebecauer Tomáš , Šúri Marcel , Dunlop Ewan D. 
Published: March 2010

AbstractWe present a method for estimating the energy output from one‐axis tracking non‐concentrating PV systems and compare the yields from different configurations. The method is based on the use of solar radiation and temperature databases and models for the performance of PV modules under given geographic conditions. In the resulting maps of energy yield for Europe it is found that there are two different one‐axis configurations that perform almost as well as a full two‐axis sun‐tracking system: one with a vertical axis and inclined modules, and the other with an inclined axis directed north–south and modules in the plane of the axis. When the inclination angles of the modules are optimized, these two configurations have an energy yield compared to an optimal fixed mounting that is approximately 30% higher in southern Europe, about 20–25% higher in central Europe, and up to 50% higher in northern Scandinavia. Compared to the two‐axis tracking, the yields are only 1–4% lower, making such one‐axis tracking systems very attractive in terms of performance relative to technical complexity and price. Copyright © 2010 John Wiley & Sons, Ltd.
Optimization of moth‐eye antireflection schemes for silicon solar cells
Authors: Boden Stuart A. , Bagnall Darren M. 
Published: March 2010

AbstractNanostructured moth‐eye antireflection schemes for silicon solar cells are simulated using rigorous coupled wave analysis and compared to traditional thin film coatings. The design of the moth‐eye arrays is optimized for application to a laboratory cell (air–silicon interface) and an encapsulated cell (EVA‐silicon interface), and the optimization accounts for the solar spectrum incident on the silicon interface in both cells, and the spectral response of both types of cell. The optimized moth‐eye designs are predicted to outperform an optimized double layer thin film coating by approximately 2% for the laboratory cell and approximately 3% for the encapsulated cell. The predicted performance of the silicon moth‐eye under encapsulation is particularly remarkable as it exhibits losses of only 0·6% compared to an ideal AR surface. Copyright © 2010 John Wiley & Sons, Ltd.
Modeling solar cells with the dopant‐diffused layers treated as conductive boundaries
Authors: Brendel Rolf 
Published: March 2010

ABSTRACTModeling of transport and recombination of charge carriers in solar cells is useful for understanding and improving the device performance. We implement the fully coupled transport equations for electrons and holes into the finite‐element partial differential equation solverCOMSOL. The dopant‐diffused surface regions such as junctions, floating junctions, or back surface field layers are treated as conductive boundaries of the volume in which the semiconductor equations are solved. This so‐called conductive boundary (CoBo) model characterizes diffused layers by their sheet resistances and diode saturation current densities. Both are directly experimentally accessible. The CoBo model exhibits excellent numerical stability and enables two‐dimensional simulations on a laptop. We find agreement when testing the two‐dimensionalCOMSOLimplementation of the CoBo model for one‐dimensional devices against simulations using the code PC1D. We apply the CoBo model to elucidate how the sheet resistance of diffused vias impacts the power conversion efficiency of emitter wrap through solar cells. Copyright © 2010 John Wiley & Sons, Ltd.
High‐rate deposition of microcrystalline silicon in a large‐area PECVD reactor and integration in tandem solar cells
Authors: Parascandolo Gaetano , Bugnon Grégory , Feltrin Andrea , Ballif Christophe 
Published: March 2010

AbstractWe study the high‐rate deposition of microcrystalline silicon in a large‐area plasma‐enhanced chemical‐vapor‐deposition (PECVD) reactor operated at 40.68 MHz, in the little‐explored process conditions of high‐pressure and high‐silane concentration and depletion. Due to the long gas residence time in this process, the silane gas is efficiently depleted using moderate feed‐in power density, thus facilitating up‐scaling of the process to large surfaces. As observed in more traditional deposition processes, the deposition rate and performance of device‐quality material are limited by the inter‐electrode gap of the reactor. We significantly increase the cell performances by reducing this gap. X‐ray diffractometry (XRD) and secondary ion mass spectroscopy (SIMS) are used to characterize the microcrystalline material deposited in the modified reactor at a rate of 1 nm/s. Comparison with a microcrystalline process at a low deposition rate demonstrates that the crystallographic orientation of the absorbing layer of the cell and the concentrations of contaminants are strongly correlated and dependent on the process. We use microcrystalline cells with absorber layer grown at a rate of 1 nm/s integrated as bottom cells in amorphous‐microcrystalline (micromorph) tandem solar cells using the superstrate configuration. We report an initial efficiency of 10.8% (9.6% stabilized) for a tandem cell with 1.2 cm2surface. Copyright © 2010 John Wiley & Sons, Ltd.
A self‐calibrating led‐based solar test platform
Authors: Krebs Frederik C. , Sylvester‐Hvid Kristian O. , Jørgensen Mikkel 
Published: March 2010

AbstractA compact platform for testing solar cells is presented. The light source comprises a multi‐wavelength high‐power LED (light emitting diode) array allowing the homogenous illumination of small laboratory solar cell devices (substrate size 50 × 25 mm) within the 390–940 nm wavelength range. The spectrum can be synthesized by independent tuning of the 18 different wavelengths to mimic AM1.5G as well as various indoor lamp spectra. The intensity can be controlled with a 214‐bit accuracy and intensities up to 3 suns are possible with an approximate AM1.5G spectral distribution. For several wavelengths intensities up to 10 suns is possible, and for a few wavelengths up to 30 suns can be reached. The setup is equipped with reference diodes and an optical fibre coupling enabling calibration, monitoring and control of the light impinging on the sample. Through a computer controlled interface, it is possible to perform all the commonly employed measurements on the solar cell at very high speed without moving the sample. In particular, the LED‐based illumination system provides an alternative to light‐biased incident photon‐to‐current efficiency measurement to be performed which we demonstrate. Both top and bottom contact is possible and the atmosphere can be controlled around the sample during measurements. The setup was developed for the field of polymer and organic solar cells with particular emphasis on enabling different laboratories to perform measurements in the same manner and obtain a common basis for comparing data. The use of the platform is demonstrated using a standard P3HT:PCBM polymer solar cell but is generally applicable to any solar cell technology with a spectral response in the 390–950 nm region. Copyright © 2010 John Wiley & Sons, Ltd.
Multijunction solar cell model for translating I–V characteristics as a function of irradiance, spectrum, and cell temperature
Authors: Domínguez César , Antón Ignacio , Sala Gabriel 
Published: March 2010

AbstractWe describe here a lumped diode model for concentrator multijunction solar cells, in which the temperature, irradiance and spectrum dependences are explicitly included. Moreover an experimental method based on it for the prediction of the I‐V curve under any irradiance‐spectrum‐temperature conditions from a single input measurement is proposed and applied to a set of commercial triple‐junction solar cells in order to demonstrate its validity. Component ‘isotype’ cells are used as reference cells for intensity and spectrum, sparing the measurement of light spectrum and cell spectral response. Finally, a mean RMS prediction error of 0.85% over a range of 100X‐25°C to 700X‐75°C is reported for the whole set when the model parameters inherent in the cell are assumed to be the same for every sample. If optimum parameters are extracted for every cell, the RMS error is reduced to 0.53%. Copyright © 2010 John Wiley & Sons, Ltd.
An observation study of reading instruction provided to elementary students with learning disabilities in the resource room
Authors: Swanson Elizabeth A. , Vaughn Sharon 
Published: March 2010

AbstractThis study documents the amount and quality of reading instruction provided to second‐ through fifth‐grade students with learning disabilities provided resource‐room services. Reading instruction provided by 10 special education resource‐room teachers was observed. Findings reveal that teachers and students were on task during instructional time that included phonological awareness, word study, comprehension, reading fluency, and vocabulary instruction of average to high average quality. Although class size was small overall, whole‐group instructional delivery was most common. Students made statistically significant gains in oral reading fluency but did not increase their standard scores on measures of comprehension or word reading. © 2010 Wiley Periodicals, Inc.
Identification of bioactive compounds from flowers of black elder (Sambucus nigra L.) that activate the human peroxisome proliferator‐activated receptor (PPAR) γ
Authors: Christensen Kathrine B. , Petersen Rasmus K. , Kristiansen Karsten , Christensen Lars P. 
Published: March 2010

AbstractObesity is one of the predisposing factors for the development of overt Type 2 diabetes (T2D). T2D is caused by a combination of insulin resistance and β‐cell failure and can be treated with insulin sensitizing drugs that target the nuclear receptor peroxisome proliferator‐activated receptor (PPAR) γ. Extracts of elderflowers (Sambucus nigra) have been found to activate PPARγ and to stimulate insulin‐dependent glucose uptake suggesting that they have a potential use in the prevention and/or treatment of insulin resistance. Bioassay‐guided chromatographic fractionation of a methanol extract of elderflowers resulted in the identification of two well‐known PPARγ agonists; α‐linolenic acid and linoleic acid as well as the flavanone naringenin. Naringenin was found to activate PPARγ without stimulating adipocyte differentiation. However, the bioactivities of these three metabolites were not able to fully account for the observed PPARγ activation of the crude elderflower extracts and further studies are needed to determine whether this is due synergistic effects and/or other ligand‐independent mechanisms. Elderflower metabolites such as quercetin‐3‐O‐rutinoside, quercetin‐3‐O‐glucoside, kaempferol‐3‐O‐rutinoside, isorhamnetin‐3‐O‐rutinoside, isorhamnetin‐3‐O‐glucoside, and 5‐O‐caffeoylquinic acid were unable to activate PPARγ. These findings suggest that flavonoid glycosides cannot activate PPARγ, whereas some of their aglycones are potential agonists of PPARγ. Copyright © 2010 John Wiley & Sons, Ltd.
The cover time of random geometric graphs
Authors: Cooper Colin , Frieze Alan 
Published: March 2010

AbstractWe study the cover time of random geometric graphs. Let
$I(d)=[0,1]^{d}$
denote the unit torus in d dimensions. Let $D(x,r)$
denote the ball (disc) of radius r. Let $\Upsilon_d$
be the volume of the unit ball $D(0,1)$
in d dimensions. A random geometric graph $G=G(d,r,n)$
in d dimensions is defined as follows: Sample n points V independently and uniformly at random from $I(d)$. For each point x draw a ball $D(x,r)$
of radius r about x. The vertex set $V(G)=V$
and the edge set $E(G)=\{\{v,w\}: w\ne v,\,w\in D(v,r)\}$. Let $G(d,r,n),\,d\geq 3$
be a random geometric graph. Let $C_G$
denote the cover time of a simple random walk on G. Let $c>1$
be constant, and let $r=(c\log n/(\Upsilon_dn))^{1/d}$. Then whp the cover time satisfies

© 2010 Wiley Periodicals, Inc. Random Struct. Alg., 38, 324–349, 2011
Piercing random boxes
Authors: Tran Linh V. 
Published: March 2010

AbstractConsider a set of n random axis parallel boxes in the unit hypercube in
${\bf R}^{d}$, where d is fixed and n tends to infinity. We show that the minimum number of points one needs to pierce all these boxes is, with high probability, at least $\Omega_d(\sqrt{n}(\log n)^{d/2-1})$
and at most $O_d(\sqrt{n}(\log n)^{d/2-1}\log \log n)$. © 2011 Wiley Periodicals, Inc. Random Struct. Alg., 38, 365–380, 2011
Mining and tracking evolving web user trends from large web server logs
Authors: Hawwash Basheer , Nasraoui Olfa 
Published: March 2010

AbstractRecently, online organizations became interested in tracking users' behavior on their websites to better understand and satisfy their needs. In response to this need, web usage mining tools were developed to help them use web logs to discover usage patterns or profiles. However, since website usage logs are being continuously generated, in some cases, amounting to a dynamic data stream, most existing tools are still not able to handle their changing nature or growing size. This paper proposes a scalable framework that is capable of tracking the changing nature of user behavior on a website, and represent it in a set of evolving usage profiles. These profiles can offer the best usage representation of user activity at any given time, and they can be used as an input to higher‐level applications such as a web recommendation system. Our specific aim is to make the hierarchical unsupervised niche clustering (HUNC) algorithm more scalable, and to add integrated profile tracking and cluster‐based validation to it. Our experiments on real web log data confirm the validity of our approach for large data sets that previously could not be handled in one shot. Copyright © 2010 Wiley Periodicals, Inc. Statistical Analysis and Data Mining 3: 106‐125, 2010