Improving the photovoltaic performance of co‐evaporated Cu2ZnSnS4 thin‐film solar cells by incorporation of sodium from NaF layers

We have investigated the influence of sodium (Na) on the properties of co‐evaporated Cu₂ZnSnS₄ (CZTS) layer microstructures and solar cells. The photovoltaic performance and diode properties were improved by incorporating Na from NaF layers into the CZTS layers, while Na had a negligible effect on the microstructural properties of the layer. The best cell fabricated by using an optimal CZTS layer (Cu/(Zn + Sn) = 0.70, Zn/Sn = 1.8) yielded an active area efficiency of 5.23%. The analysis of device properties suggests that charge‐carrier recombination at CZTS/CdS interface is suppressed by intentional Na incorporation from NaF layers. Copyright © 2016 John Wiley & Sons, Ltd.     

A large discrepancy between CPM and ESR defect densities in light-soaked a-Si:H

A large discrepancy between defect densities evaluated by constant photocurrent method (CPM) and electron spin resonance (ESR) is investigated for hydrogenated amorphous silicon (a-Si:H) with various thicknesses in the process of light soaking (LS). It is shown by a computer simulation that the inhomogeneous defect distribution across the film thickness caused by a rather small penetration depth of the white light in the thick film is one of the possible origins of the discrepancy. But various other causes should also bring about the discrepancy, and the problem is still a puzzling one.     

Thermo-acoustical waves in thermo-plastic materials

Summary The propagation velocities and the variation of the amplitudes of thermo-acoustical waves in thermo-plastic materials are theoretically investigated. The constitutive equations of anisotropic thermo-plastic materials are derived from the concept of imaginary decomposition of the deformation rate tensor into the elastic and plastic contributions and from that of the plastic potential. From generalized Vernotte's heat conduction law the propagation condition of the jumps of the velocity gradients and of the temperature rate is obtained. In isotropic materials and in the case of a normal stress vector on the wave front we have two purely mechanical transverse waves and two thermo-longitudinal coupled waves. Formulae for the velocities and amplitudes are quite similar with those for thermo-elastic materials. The variation of the amplitude is discussed. There are, in general, three effects on the variation, that is, the non-planar, heat conduction and plastic flow effects. The transverse waves are subjected only to the non-planar effect, while the thermo-longitudinal waves may grow or decay according to the above three effects.     

HVEM study of crack-tip dislocations in Si crystals prepared by FIB and twin-blade cutting method

Crack-tip dislocations in silicon crystals have been examined by using high-voltage electron microscopy. Cracks were introduced by the Vickers indentation method at room temperature and the indented specimens were annealed at high temperatures to induce dislocations around crack tips under the presence of residual stress due to the indentation. A selected area around a crack tip was thinned by a focused ion beam (FIB) technique. Specimens were thinned in advance by a twin-blade cutting (TBC) method, which is a simple cutting process for saving FIB machine time. A combination of FIB and TBC can be a useful thinning procedure for the efficient preparation of transmission electron microscopy specimens. Characteristic dislocation structures were observed around the tip of a crack, aiding the elucidation of dislocation processes, which is essential to increase the fracture toughness of materials.     

Cardiac Arrival Time Analyzer

The sequence of excitation of cardiac muscles is greatly affected by any abnormality in the conduction system of the heart. Epicardial mapping for the measurement of activation time at different points is helpful for the diagnosis of such abnormalities. For the measurement of activation time at different points of the epicardial surface, a number of sophisticated instruments, including microcomputer-based ones, have been reported. However, the need for a reliable, low-cost, and easy to operate instrument cannot be denied. In this note, such a cardiac arrival time analyzer is described.     

A fuzzy model to control the temperature in the cooling of metal molds with a spray robot

In a die-casting operation, the die spray is the key to quality and productivity, but the die-spray operation depends on parameter settings such as the spray volume and the operator's experience, even when a robot sprayer is used. The purpose of this study was to establish an intelligent system to control the surface temperature of a die with a water-based mist spray. A fuzzy model was applied to determine the optimum mist spray volume. The results generated show a good match with the actual measurements of the rate of the temperature drop versus the spray-mist volume. After the fuzzy analysis, the spray parameters calculated were used to control an actual die temperature experiment conducted on a heated plate model. The fuzzy model constructed by using fundamental experiments allowed the die spray operation to maintain a predetermined spray volume. This work was presented in part at the Fourth International Symposium on Artificial Life and Robotics, Oita, Japan, January 19–22, 1999     

Sumi-Nagashi: adding corporeality and tactile sensation to digital painting

The application lets people experience the feeling - literally and physically - that they are digitally painting in a manner derived from the Japanese traditional streaming art of Sumi-Nagashi. The Proactive Desk desk-style force feedback device makes this experience possible. Dynamic visual and haptic changes in colors and shapes arouse a new inspiration in painters.