bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Development of Frost‐weathering Microstructures on Sand‐sized Quartz Grains: Examples from Poland and Mongolia
Authors: Woronko Barbara , Hoch Małgorzata 
Published: July 2011

ABSTRACTQuartz grains, 0.25−1.0 mm in diameter, taken from Pleistocene sands and a palaeo‐active layer in Poland (Łódź Teofilów) and from silty‐clayey sediments of the contemporary active layer near Ulaanbaatar (Mongolia) were analysed using a scanning electron microscope (SEM). Other analyses included granulometric composition, and frosting and rounding of quartz grains. The effects of frost weathering comprise several microstructures, such as breakage blocks (>10 µm and <10 µm), surface coating and scaling, among which breakage blocks <10 µm are apparently the most common. Two types of frost weathering were distinguished. Weathering of the P type is mainly initiated on convex fragments of grains as the result of ice segregation. Weathering of the F type is linked to the volumetric expansion of ice and usually observed within concave linear microstructures. A frost action index (FAI) was developed based on the frequency of occurrence of microstructures from frost weathering. The FAI value varies between 0 and 3, and the higher the value, the more intensive the frost weathering. The value of the FAI in sediments from the Polish study site is relatively low with a maximum barely exceeding 1. The FAI values from the Ulaanbaatar site are higher in all of the sediment samples with a maximum of 2. Copyright © 2011 John Wiley & Sons, Ltd.
Statistical Analyses of Active Patterned Ground Occurrence in the Taillon Massif (Pyrénées, France/Spain)
Authors: Feuillet Thierry 
Published: July 2011

ABSTRACTStatistical approaches were used to describe and explain the presence or absence of active patterned ground features in a mid‐latitude alpine area. The relative rarity of these landforms can be problematic for such analyses but this issue was resolved by a novel spatial sampling strategy that considers only terrain within circles drawn around each observed patterned ground feature, which is then subdivided into a grid. This strategy focuses only on fields with potential patterned ground occurrence and can be used for all statistical studies concerning the occurrence of scattered features over extensive areas. These data were examined using factor analyses (multiple correspondence analysis and hierarchical ascendant classification) blended with a complementary bivariate method to associate patterned ground occurrence with eight environmental variables (elevation, exposure, height‐distance ratio, drift, glacier influence, vegetation cover, slopewash and lithology). The absence of active patterned ground is associated with low elevation, glacier absence, no slopewash, a low height‐distance ratio and talus fans. Zones where active patterned ground features are present are divided into three homogeneous subzones and are mostly associated with glacier influence, a large height‐distance ratio and an absence of vegetation. Their location is controlled by the presence of till from different glacial sequences so that the former and current presence of glaciers favours the development of patterned ground features at the landscape scale. Copyright © 2011 John Wiley & Sons, Ltd.
Crystal structure of New Delhi metallo‐β‐lactamase reveals molecular basis for antibiotic resistance
Authors: King Dustin , Strynadka Natalie 
Published: July 2011

Abstractβ‐Lactams are the most commonly prescribed class of antibiotics and have had an enormous impact on human health. Thus, it is disquieting that an enzyme called New Delhi metallo‐β‐lactamase‐1 (NDM‐1) can confer Enterobacteriaceae with nearly complete resistance to all β‐lactam antibiotics including the carbapenams. We have determined the crystal structure of Klebsiella pneumoniae apo‐NDM‐1 to 2.1‐Å resolution. From the structure, we see that NDM‐1 has an expansive active site with a unique electrostatic profile, which we propose leads to a broader substrate specificity. In addition, NDM‐1 undergoes important conformational changes upon substrate binding. These changes have not been previously observed in metallo‐β‐lactamase enzymes and may have a direct influence on substrate recognition and catalysis.
Surface chemistry of the preferred (111) and (220) crystal oriented microcrystalline Si films by radio‐frequency plasma‐enhanced chemical vapor deposition
Authors: Ohba Daisuke , Koshino Hideto , Tang Zeguo , Shirai Hajime 
Published: July 2011

AbstractThe surface chemistry of the preferentially (111) and (220) crystal orientated chlorinated hydrogenated microcrystalline silicon (µc‐Si:H:Cl) films was studied using a rf PE‐CVD of a dichlorosilane (SiH2Cl2) and H2 mixture. The growing surface for the preferentially (220) crystal oriented µc‐Si:H:Cl films included much voids and dangling bonds, whereas the growing surface with the preferential (111) crystal orientation was chemically stable relatively. These findings suggest that the sticking process of deposition precursors and/or the reconstruction of Si clusters within the sub‐surface determine the preferential crystal orientation. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Light management of a‐Si:H solar cells using textured zinc oxide with adjustable haze values
Authors: Zhang Liping , Yunaz Ihsanul Afdi , Kasashima Shunsuke , Wada Hidetoshi , Hongsingthong Aswin , Krajangsang Taweewat , Kurokawa Yasuyoshi , Konagai Makoto 
Published: July 2011

AbstractBoron doped zinc oxide (ZnO) films to be applied as transparent conductive oxide (TCO) in single junction pin hydrogenated amorphous silicon (a‐Si:H) solar cells were fabricated using metal organic chemical vapour deposition (MOCVD) technique. ZnO films with various haze values and surface root mean square (RMS) roughnesses were obtained by adjusting the thickness of films. B‐doped concentration presented a little effect on the RMS roughness of ZnO films but produced an adjustable sheet resistance. A series of ZnO films with a similar sheet resistance of ∼10 Ω/□ but different RMS roughnesses were applied in a‐Si:H solar cells as TCOs. The intrinsic a‐Si:H thin films with different thicknesses were used as the active layer of solar cells. It was found that the optimum RMS roughness strongly depended on the thickness of active layer. It was also confirmed that higher short‐circuit current density (Jsc) could be achieved by employing TCO with higher RMS roughness due to effective light trapping. A stabilized conversion efficiency of 9.3% and a Jsc of 16.9 mA/cm2 were obtained by utilizing ZnO TCO with a surface RMS roughness of 95 nm for a single junction pin a‐Si:H solar cell without any antireflective coating. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Large area PECVD of a‐Si:H/a‐Si:H tandem solar cells
Authors: Gabriel Onno , Kirner Simon , Leendertz Caspar , Gerhardt Mario , Heidelberg Andreas , Bloeß Harald , Schlatmann Rutger , Rech Bernd 
Published: July 2011

AbstractWe report on recent developments of a‐Si:H/a‐Si:H based thin film solar cells on Gen8.5 module area. The initial efficiency of 5.7 m² modules and 1.4 m² sub‐modules has been increased from 5% to 8% using standard floatline, low‐cost glass substrates coated with SnO2:F front TCO. The improvements based on optimizations of the n1/p2 tunnel recombination junction and of the p/i interfaces. The device simulation software AFORS‐HET has been extended with an improved model for the n/p junction to describe measured module properties. Model input parameters are taken from measured properties of single thin films. The presented progress indicates the high potential of thin‐film silicon based solar cells produced on large area. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thinner silicon‐based tandem solar cell with high efficiency made by hot wire CVD
Authors: Xin Jin , van der Werf K. H. M. , Schropp R. E. I. 
Published: July 2011

AbstractWe developed thin film silicon tandem cells with hot‐wire deposited amorphous (protocrystalline) and nanocrystalline i‐layers, with a total thickness of only 1.43 µm. This is considerably thinner than the thickness of 2.5–3.0 µm normally needed, which is important to significantly reduce production costs for this type of cells. An initial efficiency of 8.84% was obtained. The top cell is ∼220 nm and the bottom cell only ∼1210 nm thick. No intermediate reflector layer is introduced. Compared to standard PECVD tandem cells, the Voc is remarkably high, consistent with the beneficial effect of thin i‐layers on Voc and with the high Voc of 0.57 V obtained for single junction HWCVD nc‐Si:H cells. After over 2000 hours of light soaking, a stabilized efficiency of 7.63% was obtained (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hybrid sensitized solar cells using Si nanoparticles and ruthenium dye
Authors: Uchida Giichiro , Kawashima Yuki , Yamamoto Kosuke , Sato Muneharu , Nakahara Kenta , Matsunaga Takeaki , Yamashita Daisuke , Matsuzaki Hidefumi , Kamataki Kunihiro , Itagaki Naho , Koga Kazunori , Kondo Michio , Shiratani Masaharu 
Published: July 2011

AbstractWe fabricated hybrid sensitized solar cells using ruthenium (Ru) dye and silicon (Si) nanoparticles synthsized by multi‐hollow discharge plasma CVD using SiH4/H2 gas mixture. The power conversion efficiency (η) was measured as a parameter of the Si nanoparticles/TiO2 weight ratio to reveal effects of Si nanoparticles on the device performance. The short circuit current increases with the weight ratio. The η of the hybrid sensitized solar cells is improved up to 3.0% compared to 2.4% of the cell without Si nanoparticles under AM 1.5, 100 mW/cm2 light irradiation. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Comparative Life Cycle Assessment of Disposable and Reusable Packaging for the Distribution of Italian Fruit and Vegetables
Authors: Levi Marinella , Cortesi Sara , Vezzoli Carlo , Salvia Giuseppe 
Published: July 2011

Each year in Italy, millions of tons of fruits and vegetables are harvested, packed and transported to national and foreign retail outlets. Packaging is an essential component of this system, but what is its environmental impact?This study takes into consideration the delivery from the field to the retail outlet of 12 types of fruits and vegetables grown and harvested in Italy and sold in Italy and Europe. The study compares two different packaging and distribution systems: one‐way with corrugated boxes and reusable with plastic containers.A number of different scenarios were generated by combining the most diffused packaging sizes with the most important production and selling locations for each type of fruit and vegetable and by considering the specific route required to perform the transportation with each distribution system.The environmental impact of each system in each scenario has then been analysed using the life cycle assessment methodology.Two algorithms and a number of coefficients were derived to simplify data collection and impact analysis for all scenarios. This provides an easy tool to evaluate the potential environmental burden of the two alternative distribution systems in a specific scenario by taking into consideration only a few variables (such as size of packaging and transportation distance).These algorithms and coefficients are presented in the work, along with the process that led to their generation and with considerations about the main critical environmental aspects for both distribution systems. The work aims to suggest possible design solutions that can make each system more sustainable. Copyright © 2011 John Wiley & Sons, Ltd.
On the Statistical Distribution of Road Vehicle Vibrations
Authors: Garcia‐Romeu‐Martinez Manuel‐Alfredo , Rouillard V. 
Published: July 2011

SUMMARYThis paper presents an alternative method for characterizing the random vibrations produced by transport vehicles. The paper discusses the significance and limitations of the average power spectral density and explains why it is not always adequate as the sole descriptor of road vehicle vibrations as the process generally tends to be non‐stationary and non‐Gaussian. The paper adopts an alternative analysis method, based on the statistical distribution of the moving root‐mean‐square (rms) vibrations, as a supplementary indicator of overall ride quality. A variety of sample vibration records, collected from various vehicle types and routes in Spain and Australia, were used to investigate the suitability of various mathematical models, based on the Weibull distribution. It shows that the model can also effectively describe the statistical parameters of the process, namely the mean, median, standard deviation, skewness and kurtosis. The paper proposes a single mathematical model that can accurately describe the statistical character of the non‐stationary random vibrations generated by road vehicles in general. The proposed generic distribution model, based on the Weibull distribution, was developed to afford additional control over various aspects of the shape of the distribution function. The model was found to be general enough to be able to produce a range of well‐known distributions. Curve‐fitting results using the sum‐of‐squared error (least squares) optimization were found to produce non‐convergent results, which required inclusion of the mean, median, standard deviation, skewness and kurtosis in the optimization algorithm. The paper also shows how the model is capable of accurately describing the statistical parameters of the process, namely the mean, median, standard deviation, skewness and kurtosis. This result is relevant not only for the characterization of ride quality but also for the accurate synthesis of road vehicle vibrations in the laboratory. The results can be used to assist in developing a novel method for simulating non‐stationary (modulated) vibration in the laboratory. The rms distribution function can be used to create an rms level schedule that will enable the synthesis of random vibrations with varying rms levels to better represent the road transport vibration process. Copyright © 2011 John Wiley & Sons, Ltd.
The mesoscale structure of a polar low: airborne lidar measurements and simulations
Authors: Wagner J. S. , Gohm A. , Dörnbrack A. , Schäfler A. 
Published: July 2011

AbstractThe mesoscale structure of a mature polar low was studied on the basis of high‐resolution airborne measurements and numerical modelling. A polar low was measured by light detection and ranging (lidar) and dropsonde observations over the Norwegian Sea on 3 and 4 March 2008. Lidar observations provided cross‐sections of water‐vapour mixing ratio, backscatter ratio and horizontal wind speed around the polar low and through its centre. Mesoscale structures, such as shallow convection in a cold‐air outbreak, a dry intrusion in the eye‐like centre of the cyclone and deep convection surrounding it could be identified. Numerical simulations were performed with the European Centre for Medium‐Range Weather Forecasts (ECMWF) Integrated Forecast System (IFS) and a high‐resolution, polar version of the Weather Research and Forecasting (WRF) model. WRF simulations reproduced these structures and showed that the polar low had a warm, upper‐level core with descending motions. The eye‐like centre had a diameter of about 100–150 km and was characterized by rather stable stratification, horizontally constant potential temperatures and calm winds. Beyond the centre, wind speeds increased rapidly. The observed radial wind and temperature profiles support previous idealized simulations. Several WRF sensitivity tests showed the influence of the initialization time and sensible and latent heat fluxes from the surface on the simulated polar‐low development. The polar‐low simulations were more accurate in runs starting at the mature stage. Heat fluxes from the surface were important for the polar‐low energetics, especially at the final stages. Copyright © 2011 Royal Meteorological Society
Predicting outliers in ensemble forecasts
Authors: Siegert Stefan , Bröcker Jochen , Kantz Holger 
Published: July 2011

AbstractAn ensemble forecast is a collection of runs of a numerical dynamical model, initialized with perturbed initial conditions. In modern weather prediction for example, ensembles are used to retrieve probabilistic information about future weather conditions. In this contribution, we are concerned with ensemble forecasts of a scalar quantity (say, the temperature at a specific location). We consider the event that the verification is smaller than the smallest, or larger than the largest ensemble member. We call these events outliers. If a K‐member ensemble accurately reflected the variability of the verification, outliers should occur with a base rate of 2/(K + 1). In operational forecast ensembles though, this frequency is often found to be higher. We study the predictability of outliers and find that, exploiting information available from the ensemble, forecast probabilities for outlier events can be calculated which are more skilful than the unconditional base rate. We prove this analytically for statistically consistent forecast ensembles. Further, the analytical results are compared to the predictability of outliers in an operational forecast ensemble by means of model output statistics. We find the analytical and empirical results to agree both qualitatively and quantitatively. Copyright © 2011 Royal Meteorological Society
Adaptive dynamic surface control for pure‐feedback systems
Authors: Zhao Qichao , Lin Yan 
Published: July 2011

SUMMARYThis paper proposes a novel dynamic surface control algorithm for a class of uncertain nonlinear systems in completely non‐affine pure‐feedback form. Instead of using the mean value theorem, we construct an affine variable at each design step, and then neural network is employed to deduce a virtual control signal or an actual control signal. As a result, the unknown control directions and singularity problem raised by the mean value theorem is circumvented. The proposed scheme is able to overcome the explosion of complexity inherent in backstepping control and guarantee the tracking performance by introducing an initialization technique based on a surface error modification. Simulation results are presented to demonstrate the efficiency of the proposed scheme. Copyright © 2011 John Wiley & Sons, Ltd.
On the robust stability of time‐varying uncertain genetic regulatory networks
Authors: Chesi Graziano , Chen Luonan , Aihara Kazuyuki 
Published: July 2011

SUMMARYThis paper investigates robust stability of time‐varying uncertain genetic regulatory networks (GRNs). In particular, the considered model includes, as special cases, SUM and PROD regulatory functions typically considered in the literature. It is supposed that the coefficients of the GRN are affine linear functions of an uncertain vector constrained in a polytope, and that the activation functions are uncertain into sector‐type regions. As the first problem, we consider to establish whether the GRN is robustly globally stable for all admissible uncertainties. It is shown that this problem can be addressed by solving a linear matrix inequality (LMI) feasibility test built by exploiting homogeneous polynomial Lyapunov functions. As the second problem, we consider to determine the slowest speed with which the concentrations of mRNAs and proteins reach their equilibrium values. It is shown that a guaranteed underestimate of such a speed can be provided by solving a generalized eigenvalue problem built from the proposed stability condition. Some numerical examples illustrate the proposed approaches. It is worth remarking that this paper proposes for the first time in the literature the use of nonquadratic Lyapunov functions for studying robust stability of uncertain GRNs, whereas existing works have addressed the problem only via quadratic Lyapunov functions (either common or parameter‐dependent), which are known to be conservative for time‐varying uncertainty. Copyright © 2011 John Wiley & Sons, Ltd.
Pósa's conjecture for graphs of order at least 2 × 108
Authors: Châu Phong , DeBiasio Louis , Kierstead H.A. 
Published: July 2011

AbstractIn 1962 Pósa conjectured that every graph G on n vertices with minimum degree
\documentclass{article} \usepackage{mathrsfs} \usepackage{amsmath,amssymb,amsfonts} \pagestyle{empty} \begin{document} \begin{align*}\delta(G)\ge \frac{2}{3}n\end{align*} \end{document}
contains the square of a hamiltonian cycle. In 1996 Fan and Kierstead proved the path version of Pósa's Conjecture. They also proved that it would suffice to show that G contains the square of a cycle of length greater than
\documentclass{article} \usepackage{mathrsfs} \usepackage{amsmath,amssymb,amsfonts} \pagestyle{empty} \begin{document} \begin{align*}\frac{2}{3}n\end{align*} \end{document}. Still in 1996, Komlós, Sárközy, and Szemerédi proved Pósa's Conjecture, using the Regularity and Blow‐up Lemmas, for graphs of order n ≥ n0, where n0 is a very large constant. Here we show without using these lemmas that n0:= 2 × 108 is sufficient. We are motivated by the recent work of Levitt, Sárközy and Szemerédi, but our methods are based on techniques that were available in the 90's. © 2011 Wiley Periodicals, Inc. Random Struct. Alg., 2011
X‐ray microanalysis of porous materials using Monte Carlo simulations
Authors: Poirier Dominique , Gauvin Raynald 
Published: July 2011

AbstractQuantitative X‐ray microanalysis models, such as ZAF or φ(ρz) methods, are normally based on solid, flat‐polished specimens. This limits their use in various domains where porous materials are studied, such as powder metallurgy, catalysts, foams, etc. Previous experimental studies have shown that an increase in porosity leads to a deficit in X‐ray emission for various materials, such as graphite, Cr2O3, CuO, ZnS (Ichinokawa et al., '69), Al2O3, and Ag (Lakis et al., '92). However, the mechanisms responsible for this decrease are unclear. The porosity by itself does not explain the loss in intensity, other mechanisms have therefore been proposed, such as extra energy loss by the diffusion of electrons by surface plasmons generated at the pores–solid interfaces, surface roughness, extra charging at the pores–solid interface, or carbon diffusion in the pores. However, the exact mechanism is still unclear. In order to better understand the effects of porosity on quantitative microanalysis, a new approach using Monte Carlo simulations was developed by Gauvin (2005) using a constant pore size. In this new study, the X‐ray emissions model was modified to include a random log normal distribution of pores size in the simulated materials. This article presents, after a literature review of the previous works performed about X‐ray microanalysis of porous materials, some of the results obtained with Gauvin's modified model. They are then compared with experimental results. SCANNING 33: 126–134, 2011. © 2011 Wiley Periodicals, Inc.
Mediated Effects of Physical Risk Factors, Leader–Member Exchange and Empowerment in Predicting Perceived Injury Risk
Authors: Muldoon Jeffery , Matthews Russell A. , Foley Caroline 
Published: July 2011

AbstractIn the context of conservation of resources theory, we examine the indirect (mediated) effects of physical risk factors, leader–member exchange (LMX) and empowerment on perceived injury risk in a heterogeneous sample (N = 226) of individuals employed in occupations related to production, construction and installation/maintenance. Positioning work role stressors and upward safety communications as two important mediating variables, as predicted, LMX and empowerment demonstrated significant indirect effects on perceived injury risk. Results from our model also provide preliminary evidence that an asymmetrical dualistic process exists in terms of the effect physical risk factors have on perceived injury risk via depletion of both psychological (i.e. role stressors) and physical resources (i.e. physical symptoms). Theoretical and practical implications based on the results of our model are also discussed. Copyright © 2011 John Wiley & Sons, Ltd.