Influence of Cu off-stoichiometry on wide band gap CIGSe solar cells

The electric properties of solar cells based on co-evaporated Cu(In,Ga)Se₂ (CIGSe) thin film show a good tolerance regarding the absorber Cu content (y = [Cu]/([In] + [Ga])) for standard Ga concentration, i.e. x = [Ga] / ([In] + [Ga]) ~ 0.3. In the present contribution, we show that this tolerance is lost when the gallium content is increased. Wide bandgap CIGSe samples (x ~ 0.55) with a variation in y from 0.97 to 0.84 have been grown. The efficiency of the cells decreases from 12.6% to 6.5% for y = 0.97 and 0.84 respectively. For the lowest y, the efficiency is harmed because of a low short-circuit current density (J_sc), an increased voltage dependency in the current collection, which affects the fill factor (FF), and a decrease of the open-circuit voltage (V_oc). For y = 0.97 and 0.84 respectively, the decrease of the activation energy (E_a) from 1.36 to 1.24 eV indicates a shift of the area of the dominant recombination from the space charge region towards the interface. There seems to be evidence that reducing the Cu-content in the CIGSe thin film will cause a decrease in the width of the space charge region. Solar cells based on Cu-rich CIGSe (1.03 < y < 1.09) have also been fabricated and characterized. A strong deterioration of their electrical properties is observed despite the KCN etch of the segregated Cu_2 − xSe binary phases at the surface, suggesting the presence of residual Cu_2 − xSe precipitates within the layer.     

Microstructure and texture of copper/niobium composites processed by ECAE

The structure refinement is a challenge for conductors used for the winding of resistive coils producing non-destructive pulsed magnetic fields over 80T. These nanocomposite conductors composed of a conducting multiscale Cu matrix embedding Nb reinforcing nanofilaments are usually manufactured by using a Severe Plastic Deformation (SPD) process based on hot extrusion, accumulative cold drawing and bundling (ADB) steps [Thilly et al. Philos Mag A 82:925, 2002]. Equal-channel angular extrusion (ECAE) is investigated here as an alternative route since it may provide faster refinement to obtain the ultrafine structure needed for optimized electrical and mechanical properties of the conductors. Therefore, copper-niobium specimens obtained by hot extrusion were processed by ECAE at room temperature. The specific die of the ECAE tool used here is constituted by a round channel with three angles corresponding to a total equivalent strain of about 2.5. Deformed samples were examined by optical microscopy and characterized by hardness profiles and x-ray diffraction (texture pole figures). After one ECAE-pass, the shape of the samples is modified but no trace of damage appeared at the Cu-Nb interfaces. An increase of the hardness values localized in the copper matrix is revealed whereas the hardness of the niobium remains unchanged. Prior to ECAE, the hot extrusion process induced a fibre texture for both copper and niobium. Two fibre texture components were observed for copper: <111> and <200>. A single <110> fibre texture component is evidenced for the niobium. After ECAE a significant variation of the texture is observed in relation with the strong shear induced by this process.     

Characterisation of VOCs emitted by open cells receiving municipal solid waste

This study gives relevant information on the variation of concentrations of certain volatile organic compounds (BTEX, alkanes, organochlorides and terpenes) emitted by open cells receiving municipal solid waste. These compounds represent a large fraction of the total trace components present in landfill gas. The VOC measurements were carried out in the atmosphere of an open landfill cell as a function of time and meteorological parameters, but also as a function of the activity of trucks unloading waste and compaction vehicles, in order to identify the factors that influence VOC emissions. Comparisons were performed systematically between the surface of the open cell and the corresponding mechanical activity. The measurements carried out during the course of the day highlighted the influence of air temperature and waste composition on VOC emissions while measurements of activity showed that the activity of fresh waste compaction vehicles is responsible for the highest VOC emissions. Such information is essential since most of the data in the literature relate to analyses of VOC traces in the biogas network and not in the air of the open cells as a function of different parameters (i.e. meteorological parameters, activity on the site). The highest VOC concentrations (in microg/m3) in the area of an open cell were obtained for: tetrachloroethylene (9810), toluene (8230), limonene (4550), m-xylene (3980) and trichloroethylene (3680). The results showed that the TWA values (the time-weighted average concentrations for up to an 8-h workday) established by INRS/France for the personnel in the station were complied with on the site studied.     

CFA local binary patterns for fast illuminant-invariant color texture classification

Journal of Real-Time Image Processing - This paper focuses on the classification of color textures acquired by single-sensor color cameras under various illuminants. Local binary patterns (LBPs)...     

Job mobility, its determinants, and its effects: Longitudinal data from the Maastricht cohort study.

This prospective study of 12,140 employees examined the effects of work characteristics and situational, psychological, and health aspects on job mobility. Before job change, the mobility group reported significantly more conflicts with the supervisor, higher physical and emotional strain, higher degree of job insecurity, lower job satisfaction, and lower degree of commitment compared with employees who did not change jobs. After job change, the mobility group reported improved autonomy, task diversity, decreased occurrence of conflicts with the supervisor, decreased physical and emotional strain, and improved training possibilities and job security than before the change. Changing jobs had a positive effect on employees with respect to job perception and job satisfaction and led to reduced fatigue and need for recovery. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Alfred Binet and higher education.

At the beginning of the 20th century, Alfred Binet sought teaching positions at the Colfte de France and the Sorbonne. Binet wanted to develop experimental psychology in France, but the strong psychopathological orientation of French psychology blocked his ambition. The 1st part of this article relates the history of the introduction of psychology, via Théodule Ribot, to the Sorbonne and the Coll6ge de France. Ribot's premature retirement from the Collège de France in 1901 triggered a battle that led to Binet's repeated failure to gain access to these institutions of higher education and the success in 1902 of Ribot's students: Pierre Janet at the Colfte de France and Georges Dumas at the Sorbonne. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cross‐comparison of convergence algorithms to solve trip‐based dynamic traffic assignment problems

Solving a dynamic traffic assignment problem in a transportation network is a computational challenge. This study first reviews the different algorithms in the literature used to numerically calculate the user equilibrium (UE) related to dynamic network loading. Most of them are based on iterative methods to solve a fixed‐point problem. Two elements must be computed: the path set and the optimal path flow distribution between all origin–destination pairs. In a generic framework, these two steps are referred to as the outer and the inner loops, respectively. The goal of this study is to assess the computational performance of the inner loop methods that calculate the path flow distribution for different network settings (mainly network size and demand levels). Several improvements are also proposed to speed up convergence: four new swapping algorithms and two new methods for the step size initialization used in each descent iteration. All these extensions significantly reduce the number of iterations to obtain a good convergence rate and drastically speed up the overall simulations. The results show that the performance of different components of the solution algorithm is sensitive to the network size and saturation. Finally, the best algorithms and settings are identified for all network sizes with particular attention being given to the largest scale.     

Oxidation Mechanisms and Kinetics of 1D-SiC/C/SiC Composite Materials: II, Modeling

A model, based on a simple axisymmettical fiber/interphase/ matrix assembly, is derived to depict the oxidation behavior of ID-SiC/C/SiC composites within the temperature range 900–1300°C and for 10 < P _O2 < 100 kPa. It takes into account (i) the changes versus time of the geometry of the annular pore resulting from the consumption by oxidation of the carbon interphase, (ii) the may transfers by diffusion along the pore of the reactant and products, and (iii) the chemical reactions with oxygen of both the pore walls (yielding silica) and the pore bottom (consisting of carbon). The model gives the gaseous species concentration and silica thickness profiles along the pore, the length of carbon consumed by oxidation, and the relative weight change. The model depicts in a satisfactory manner the features of the TGA curves recorded on actual composites and it is in excellent agreement with the measurements of the carbon interphase lengths consumed by oxidation. It shows that the oxidation resistance of ID-SiC/C/SiC composites is better at high temperatures ( T 1100°C) and for thin carbon interphases ( e 0.1 μm). Under such conditions, the materials exhibit a self-healing behavior.     

Calculation of Contraction Coefficient under Sluice Gates and Application to Discharge Measurement

The contraction coefficient under sluice gates on flat beds is studied for both free flow and submerged conditions based on the principle of momentum conservation, relying on an analytical determination of the pressure force exerted on the upstream face of the gate together with the energy equation. The contraction coefficient varies with the relative gate opening and the relative submergence, especially at large gate openings. The contraction coefficient may be similar in submerged flow and free flow at small openings but not at large openings, as shown by some experimental results. An application to discharge measurement is also presented.