Abnormal alignment of misfit dislocations in In0.52Al0.48As/InxGa1-xAs/In0.52Al0.48As/InP heterostructure

It was observed with transmission electron microscopy in the In0.52Al0.48As/InxGa1-xAs/In0.52Al0.48As/InP heterostructure that misfit dislocation lines deviate from the [110] directions at a certain angle depending on the indium content x. Such an abnormal alignment of misfit dislocations is explained in terms of an alloy effect on the formation of single jogs on the misfit dislocations in the interface between the III-V ternary compounds.

Abnormal temperature dependent photoluminescence of self-assembled InAs/GaAs surface quantum dots with high areal density

We have investigated temperature dependent photoluminescence of both buried and surface self-assembled InAs/GaAs quantum dots with an areal density up to similar to 10(11)/cm(2). Different from the buried quantum dots, the peak energy of surface quantum dots shows a blueshift relative to the bulk material variation from 15 to 130K. Besides the line width and the integrated intensity both first decrease and then increase in this temperature interval. The observed phenomena can be explained by carrier trapping effects by some shallow localized centers near the surface quantum dots.

Formal specification and refinement of a safe train control function

Motivated by the design and development challenges of the BART case study, an approach for developing and analyzing a formal model for reactive systems is presented. The approach makes use of a domain specific language for specifying control algorithms able to satisfy competing properties such as safety and optimality. The domain language, called SPC, offers several key abstractions such as the state, the profile, and the constraint to facilitate problem specification. Using a high-level program transformation system such as HATS being developed at the University of Nebraska at Omaha, specifications in this modelling language can be transformed to ML code. The resulting executable specification can be further refined by applying generic transformations to the abstractions provided by the domain language. Problem dependent transformations utilizing the domain specific knowledge and properties may also be applied. The result is a significantly more efficient implementation which can be used for simulation and gaining deeper insight into design decisions and various control policies. The correctness of transformations can be established using a rewrite-rule based induction theorem prover Rewrite Rule Laboratory developed at the University of New Mexico.

低分子有机酸对辣椒生长发育及叶片活性氧代谢的影响

采用盆栽试验与室内分析相结合的方法,研究了6种低分子有机酸和一种有机酸盐对辣椒生长发育和叶片活性氧代谢的影响。结果表明:柠檬酸、乙酰丙酸和有机酸钾处理不仅可显著提高辣椒根系干质量,增加辣椒vC含量,而且提高了辣椒的产量。甲酸、柠檬酸、乙酰丙酸和有机酸钾处理使根系活力比对照分别提高83%、93.8%、96.75%和99.5%。柠檬酸、乙酰丙酸和有机酸钾处理提高了辣椒叶片的SOD和POD活性,降低了膜脂过氧化产物MDA含量,延缓了叶片衰老。但是低分子有机酸处理对CAT活性的影响较小。

Abnormal photoabsorption in high resistance GaN epilayer

Unintentionally doped GaN epilayers are grown by the metalorganic chemical vapor deposition (MOCVD). Photovoltaic (PV) spectroscopy shows that there appears an abnormal photoabsorption in some undoped GaN films with high resistance. The peak energy of the absorption spectrum is smaller than the intrinsic energy band gap of GaN. This phenomenon may be related to exciton absorption. Then metal-semiconductor-metal (MSM) Schottky photodetectors are fabricated on these high resistance epilayers. The photo spectrum responses are different when the light individually irradiates each of the two electrodes with the photodetector which are differently biased. When the excitation light irradiates around the reverse biased Schottky junction, the responsivity is almost one order of magnitude larger than that around the forward biased junction. Furthermore, when the excitation light irradiates the reverse biased Schottky junction, the peak energy of the spectrum has a prominent red-shift compared with the peak energy of the spectrum measured with the excitation light irradiating the forward biased Schottky junction. The shift value is about 28 meV, and it is found to be insensitive to temperature. According to the analyses of the distribution of the electric field within the MSM device and the different dependences of the response on the electric field intensity between the free carriers and excitons, a reliable explanation for the different response among various areas is proposed.

A NEW RESULT IN TRANSIENT CURRENT EXPERIMENT ON A-SI-H P/I/N AND N/I/N DEVICES

The transient current response of a-Si:H in both p/i/n and n/i/n structures has been measured as a function of pulse intermittence and pulse amplitude. The results are consistent with the picture that in p/i/n samples the peculiar current response is caused by the competing contributions of electrons and holes which show themselves in different time scales.

Temperature-stimulated abnormal annealing of neutron-induced damage in high-resistivity silicon detectors

Neutron-irradiated high-resistivity silicon detectors have been subjected to elevated temperature annealing (ETA). It has been found that both detector full depletion voltage and leakage current exhibit abnormal annealing (or ''reverse annealing'') behaviour for highly irradiated detectors: increase with ETA. Laser induced current measurements indicate a net increase of acceptor type space charges associated with the full depletion voltage increase after ETA. Current deep level transient spectroscopy (I-DLTS) and thermally stimulated current (TSC) data show that the dominant effect is the increase of a level at 0.39 eV below the conduction band (E(c) - 0.39 eV) or a level above the valence band (E(v) + 0.39 eV). Candidates tentatively identified for this level are the singly charged double vacancy (V-V-) level at E(c) - 0.39 eV, the carbon interstitial-oxygen interstitial (C-i-O-i) level at E(v) + 0.36 eV, and/or the tri-vacancy-oxygen center (V3O) at E(v) + 0.40 eV.

CO2浓度升高对三种树木叶片化学和舞毒蛾幼虫取食及生长的影响

探讨全球气候变化的生物学和生态学效应是当今生态学中的热点，研究大气CO2浓度升高对植物-昆虫相互作用关系的影响具有重要的理论和实践意义。本文使用开顶式气室（Open-top chamber，OTC）在野外条件下研究了CO2浓度升高对三种树木（小青杨、白桦和蒙古栎）叶片化学成分含量的影响，以及树木叶片品质变化对一种广食性森林昆虫（舞毒蛾）幼虫取食、生长发育和取食偏嗜性的影响。得出如下结果：（1）CO2浓度升高对3个受试树种叶片中的营养成分及次生代谢物含量均有显著影响，总体表现为氮含量降低，而碳氮比、非结构性碳水化合物、总酚和缩合丹宁含量增加。叶片中的化学成分含量可随时间发生显著变化，不同树种、甚至同一树种不同冠层高度的叶片对CO2浓度升高的响应强度也是不同的。叶片的干物质含量和比叶重对CO2浓度升高的响应不显著。（2）室内非选择性取食实验、室内选择性取食实验以及上树取食饲养方式下的多龄期取食实验，均发现高浓度CO2处理组内舞毒蛾幼虫的生长发育受到显著抑制。但对四龄舞毒蛾幼虫所进行的短期生物测定并未发现不同CO2浓度处理下幼虫的生长发育速率、对食物的取食率和转化率等昆虫营养指标存在显著差异。（3）叶片品质的降低是导致舞毒蛾幼虫生长发育受抑制的主要原因。但是总体上，CO2浓度升高导致的叶片品质变化并未显著影响幼虫的取食率和取食量。（4）舞毒蛾幼虫对不同叶片种类表现出清晰的取食选择性，这种选择性在其幼龄期就可表现出来。幼虫对小青杨上层叶片有最显著的偏嗜性，对蒙古栎下层叶片有最明显的拒食性。但是CO2浓度升高导致的叶片品质变化对舞毒蛾幼虫的取食选择性和寄主偏嗜行为并未产生显著影响。（5）检测出高浓度CO2处理组内舞毒蛾幼虫虫粪中含有浓度更高的植物次生代谢物质（总酚和缩合单宁），这很可能是昆虫整体生长发育受抑制的重要原因之一。

Influence of processing temperature on microstructure and microhardness of copper subjected to high-pressure torsion

Cu samples were subjected to high-pressure torsion (HPT) with up to 6 turns at room temperature (RT) and liquid nitrogen temperature (LNT), respectively. The effects of temperature on grain refinement and microhardness variation were investigated. For the samples after HPT processing at RT, the grain size reduced from 43 mu m to 265 nm, and the Vickers microhardness increased from HV52 to HV140. However, for the samples after HPT processing at LNT, the value of microhardness reached its maximum of HV150 near the center of the sample and it decreased to HV80 at the periphery region. Microstructure observations revealed that HPT straining at LNT induced lamellar structures with thickness less than 100 nm appearing near the central region of the sample, but further deformation induced an inhomogeneous distribution of grain sizes, with submicrometer-sized grains embedded inside micrometer-sized grains. The submicrometer-sized grains with high dislocation density indicated their nonequilibrium nature. On the contrary, the micrometer-sized grains were nearly free of dislocation, without obvious deformation trace remaining in them. These images demonstrated that the appearance of micrometer-sized grains is the result of abnormal grain growth of the deformed fine grains.

Extinction of lean near-limit methane/air flames at elevated pressures under normal- and reduced-gravity

perimentally at evaluated pressures and under normal- and micro-gravity conditions utilizing the 3.5 s drop tower of the National Microgravity Laboratory of China. The results showed that under micro-gravity conditions the natural convection is minimized and the flames become more planar and symmetric compared to normal gravity. In both normal- and micro-gravity experiments and for a given strain rate and fuel concentration, the flame luminosity was found to enhance as the pressure increases. On the other hand, at a given pressure, the flame luminosity was determined to weaken as the strain rate decreases. At a given strain rate, the fuel concentration at extinction was found to vary non-monotonically with pressure, namely it first increases and subsequently decreases with pressure. The limit fuel concentration peaks around 3 and 4 atm under normal- and micro-gravity, respectively. The extinction limits measured at micro-gravity were in good agreement with predictions obtained through detailed numerical simulations but they are notably lower compared to the data obtained under normal gravity. The simulations confirmed the non-monotonic variation of flammability limits with pressure, in agreement with previous studies. Sensitivity analysis showed that for pressures between one and 5 atm, the near-limit flame response is dominated by the competition between the main branching, H + O2 ? OH + O, and the pressure sensitive termination, H+O2+M? HO2 + M, reaction. However, for pressures greater than 5 atm it was determined that the HO2 kinetics result in further chain branching in a way that is analogous to the third explosion limit of H2/O2 mixtures. 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

A laboratory study of rheological properties of mudflows in Hangzhou Bay, China

A laboratory study of the rheology of mudflows in Hangzhou Bay, China, is reported in this paper. Both the steady and oscillatory (dynamic) rheological properties are studied using RMS-605 rheometer. A Dual-Bingham model is proposed for analyzing flow curves and compared with Worrall-Tuliani model. It is found that Dual-Bingham plastic rheological model is easier to implement than Worrall-Tuliani model and can provide satisfactory representations of the steady mudflows in Hangzhou Bay and other published data. The dependence of the yield stress and viscosity on sediment concentration is discussed based on the data from Hangzhou Bay mud and other published data. For the dynamic rheological properties of Hangzhou Bay mud, empirical expressions for elastic modulus and dynamic viscosity are provided in the form of exponential functions of sediment volume concentration, and comparisons with other published data also discussed.