可改进太阳能电池的新型电特性

由铋、铁和氧组成的晶体能够实现可逆的二极管 美国Rutgers大学的一组物理学家发现了一种材料所具有的特殊电特性,能够提升太阳能电池效率并改善计算机芯片设计.这种由铋、铁和氧组成的晶体能够实现可逆的二极管,这种二极管在光照条件下就能产生电流.传统的半导体二极管是不可逆的,其电流方向在制造时就已经确定下来了.     

Insecticidal effect of Steinernema feltiae (Filipjev) (Nematoda: Steinernematidae) against Tribolium confusum du Val (Coleoptera: Tenebrionidae) and Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae) in stored wheat

The confused flour beetle, Tribolium confusum, and the Mediterranean flour moth, Ephestia kuehniella, are important pests of stored grain products. The insecticidal effect of three strains (UK 76 [=Nemasys], USA/SC, and Hawaii) of the entomopathogenic nematode Steinernema feltiae was determined in the laboratory, in wheat, against these pests. The nematodes were applied at three dose rates: 100, 300 and 900 nematodes/insect individual. The Hawaii strain was most virulent against T. confusum adults and larvae, with a significant dose effect in the case of the larvae. Larval mortality of this species reached 79% and 100% after 7 and 14 d of exposure to the nematodes, respectively, at the highest dose applied. On the other hand, adult mortality of T. confusum did not exceed 66%. In the case of E. kuehniella larvae, USA/SC performed best causing 52% and 69% mortality after 7 and 14 d exposure, respectively, at the highest dose tested. Since very few data are available on the effect of entomopathogenic nematodes against these pests, it is concluded that the Hawaii and USA/SC strains of S. feltiae should be further investigated as promising biological control agents for T. confusum and E. kuehniella.     

Removal of antimony from copper by injection of soda ash

The removal of Sb from molten copper is of importance in the development of processes which can smelt copper concentrates directly into copper in a single furnace. A promising method is injection of oxygen and sodium carbonate in a modified anode furnace. This study encompassed a thermodynamic analysis of the impurity removal reactions and an experimental investigation of antimony removal from molten copper in a 15 kW induction furnace. The results showed that the reaction was controlled by diffusion of Sb in the metal phase. The reaction between metal and injected flux can be divided into two subprocesses-. (1) “transitory contact” reaction to the injected flux particles as they rise through the melt and (2) “permanent contact” reaction across the interface between the metal bath and the supernatant slag layer. On the basis of the experimental work, the overall volumetric mass transfer coefficient (cm³/s) at 1473 K was expressed in terms of the two subprocesses as follows:(k _d A) _ov = (k _d A) _pc +(k _d A) _tc = 1.25Q _g ^0.29 + 0.28(H Q _f ) whereQ _g is the injection gas flow rate in normal liters per minute,H is the depth of injection in centimeters, andQ _f the rate of flux injection in grams per second.     

Anisotropic Elastoplastic Bounding Surface Model for Cohesive Soils

The initial stresses existing in the natural ground are anisotropic in the sense that the vertical stress is typically larger than the lateral stresses. The construction activities, such as embankments and excavation, induce anisotropy in the stress system. The stress-deformation behavior and excess pore water pressure response of soils are affected by the inherent and induced stress anisotropy. This paper presents an improved soil model based on the anisotropic critical state theory and bounding surface plasticity. The anisotropic critical state theory of Dafalias was extended into three-dimensional stress space. In addition to the isotropic hardening rule, rotational and distortional hardening rules were incorporated into the bounding surface formulation with an associated flow rule. The projection center that is used to map the actual stress point to the imaginary stress point was specified along the K0 line instead of the hydrostatic line or at the origin of the stress space. A simplified form of plastic modulus was used and the proposed model requires a total of 12 material parameters, the same number as that of the single-ellipse time-independent version of the Kaliakin–Dafalias model. The model was validated against the undrained isotropic and anisotropic triaxial test results under compression and extension shearing modes for Kaolin Clay, San Francisco Bay Mud, and Boston Blue Clay. The effects of stress anisotropy and overconsolidation were well captured by the model. The time effect was not included in the formulations presented in this paper.     

创新的ADC结构在速度和功耗上取得进展

Xignal Technologies（混合信号IC开发商）（Munich，德国）在连续时间△∑式A／D转换技术上取得突破，可为在高采样速率条件下需要高动态范围的空间有限的应用，比如下一代便携式超声波仪器，提供高速、低功耗的A／D转换。     

A Japanese Center of Excellence: The Institute for Advanced Materials Processing (Sozaiken) of Tohoku University

It has been stated that the Japanese society is effectively closed to foreigners. During our four-month stay in Sendai and our trips throughout Japan by train and car, we found that such was certainly not the case, neither in social nor professional terms. We think fondly of our time there and of the many friends that we made and hope to see again. U.S. faculty who have, or can create, an opportunity to visit the universities of Japan should do so. They will not be disappointed, and the effort may help build bridges that dispel mistrust and foster collaboration among nations. This is true for graduate students who want to broaden their horizons and are not intimidated by so-called language barriers. Finally, it is interesting to note that Japan, which in comparison to the United States has few mineral resources, continues to nurture academic research on the recovery and processing of metals. In contrast, government support to U.S. universities in this area was practically extinguished in the eighties, and one of the last remaining flickers, the Mineral and Mining Resources Research Institutes program of the U.S. Department of the Interior, is in danger.     

Screening of excitons in single, suspended carbon nanotubes

Resonant Raman spectroscopy of single carbon nanotubes suspended across trenches displays red-shifts of up to 30 meV of the electronic transition energies as a function of the surrounding dielectric environment. We develop a simple scaling relationship between the exciton binding energy and the external dielectric function and thus quantify the effect of screening. Our results imply that the underlying particle interaction energies change by hundreds of meV.     

Extracting a polyhedron from a single-view sketch: Topological construction of a wireframe sketch with minimal hidden elements

An essential prerequisite to construct a manifold trihedral polyhedron from a given natural (or partial-view) sketch is solution of the “wireframe sketch from a single natural sketch (WSS)” problem, which is the subject of this paper. Published solutions view WSS as an “image-processing”/“computer vision” problem where emphasis is placed on analyzing the given input (natural sketch) using various heuristics. This paper proposes a new WSS method based on robust tools from graph theory, solid modeling and Euclidean geometry. Focus is placed on producing a minimal wireframe sketch that corresponds to a topologically correct polyhedron.