Doping profiles in CdTe/CdS thin film solar cells

CdS/CdTe thin film solar cells showing comparable properties as commercial cells have been prepared by close space sublimation (CSS) in our own laboratory. We characterised the cells by capacitance-voltage profiling (C-V), thermal admittance spectroscopy (TAS), and thermally stimulated capacitance measurements (TSCAP). The doping profiles of the CdTe layer obtained by C-V measurements confirm the well known rise in dopant concentration with increasing depth if the usual evaluation procedure is employed. However, the TAS and TSCAP measurements reveal deep acceptors in the CdTe layer with a large concentration exceeding that of the shallow dopants. Under these conditions, C-V measurements are shown to yield an apparently rising dopant concentration even for homogeneous doping. A combined simulation of doping profiles measured at different temperatures using a fixed and uniform shallow and deep doping fits well to measured doping concentration. These results indicate how to get reliable information on the shallow dopant concentration.     

Elasticity Mapping of Pore‐Suspending Native Cell Membranes

The mechanics of cellular membranes are governed by a non‐equilibrium composite framework consisting of the semiflexible filamentous cytoskeleton and extracellular matrix proteins linked to the lipid bilayer. While elasticity information of plasma membranes has mainly been obtained from whole cell analysis, techniques that allow addressing local mechanical properties of cell membranes are desirable to learn how their lipid and protein composition is reflected in the elastic behavior on local length scales. Introduced here is an approach based on basolateral membranes of polar epithelial Madin–Darby canine kidney (MDCK) II cells, prepared on a highly ordered porous substrate that allows elastic mapping on a submicrometer‐length scale. A strong correlation between the density of actin filaments and the measured membrane elasticity is found. Spatially resolved indentation experiments carried out with atomic force and fluorescence microscope permit relation of the supramolecular structure to the elasticity of cellular membranes. It is shown that the elastic response of the pore spanning cell membranes is governed by local bending modules rather than lateral tension.     

Comparative efficiencies of bread crumb softeners at varied bread storage temperatures

A series of commercial surfactants was evaluated in white pan bread for their crumb antifirming effects during storage at 10, 20, 30, 40 and 50 C. These agents produced softer breads at all temperatures as compared to bread without surfactants. Although breads kept at 40 and 50 C remained softer than at room temperature (25 C), storage at elevated temperatures is not advised due to possible organoleptic and microbial deteriorations. At temperatures below 25 C, faster firming generally occurred, but was much less in the presence of surfactants. This observation suggests that a surfactant system might be found to retard firming at those conditions.     

Macroscopic theory of chemisorption and partial charge transfer processes on semiconductor electrodes

Partial charge transfer models have recently been extended in order to understand chemisorption processes on semiconductor electrodes. The present paper first gives a short summary of macroscopic charge balance expressions from which measurable quantities such as impedance and photoresponse are derived. Specifically, the following points are treated: (a) Explicit inclusion of partial charge transfer chemisorption kinetics into semiconductor electrode impedance (Sections 4–6); (b) Connection of majority and minority carrier transport with partial charge transfer kinetics (Sections 7, 8); (c) Interfacial and chemisorption contributions to surface photovoltage (Becquerel effect), firstly for zero current limit (Section 9).     

Über den Kationenaustausch bei anionischen Polyurethan-Dispersionen mit Natriumsulfonat-gruppen

In aqueous dispersions of anionic polyurethanes with SO groups and Na⁺ as counter-ion, Na⁺ was ion exchanged for other cations (H⁺, Ag⁺, Ca⁺⁺, Ba⁺⁺, Ni⁺⁺, Cu⁺⁺, Zn⁺⁺, Pb⁺⁺ and AI⁺⁺⁺). With the exception of AI⁺⁺⁺ the ion exchange took place nearly quantitatively, indicating that site binding of counter-ions did not occur at the particle surface. In addition, the influence of the counter-ion was studied with respect to stability of the dispersion and the mechanical properties of the films.     

Synthesis and behavior of poly(vinyl chloride)-based latex interpenetrating polymer networks

Poly(vinyl chloride)/poly(butadiene–co–acrylonitrile) interpenetrating polymer networks (IPN's) were synthesized in latex form. Dynamic mechanical spectroscopy as a function of temperature revealed that the glass transitions of the individual networks were broadened and in some cases spanned the entire temperature range between the two individual polymer transitions. This was interpreted to indicate extensive but incomplete mixing between the two networks. Depending on overall composition, the cast or molded films were either plastic or tough elastomers at room temperature. Some aspects of phase continuity and structure, including a graded core-shell model, are discussed.     

High-quality torque control at zero and very high speed operation

This article focuses on the design and analysis of a direct field orientation (DFO) approach based upon a closed-loop loop rotor flux observer. The approach is ideally suited for applications requiring both zero and very high (i.e., several times base) speed operation. Such applications are common in manufacturing automation where both zero speed position control and high traverse rates with controlled position trajectories are required. Examples include robot motion control systems as used for assembly and the more traditional machining center axis control. The quality of the proposed approach is largely based on the unique structure of its flux observer. The observer effectively combines the best accuracy attributes of rotor flux indirect (feedforward) field orientation (IFO) and stator flux DFO. The parameter sensitivity is similar to IFO at low and zero speeds and to stator flux DFO at high speeds. The closed-loop structure of the observer provides a smooth transition between two open-loop rotor flux observers referred to as the current and voltage models in a deterministic manner set by the closed-loop bandwidth (eigenvalues). The proposed DFO approach is analytically evaluated in comparison with both IFO and stator flux DFO. Experimental results verify the viability of this approach     

Building analysis system — BAS

In our laboratory we use several different programs dealing with the same fundamental problem: the calculation of thermal loads and annual consumptions. The programs must by used at different stages of the design process. The main disadvantage of using separate programs can disappear if the programs are gathered in a single structure with one entry point.