一种用于遥感图像云雾处理的小波系数加权算法

依据小波变换理论分析,得出图像经多层小波变换后,低层细节系数频率高于高层细节系数,近似系数的频率最低.遥感图像景物的频率较高,云雾频率较低.提出通过选择合理的分界层数,将景物信息尽量分配到低层细节系数,云雾噪声尽量分配到高层细节系数,对低层、高层细节系数、近似系数分别给予权重,增大低层细节系数,突出景物信息,减小高层细节系数,削弱云雾噪声,依据近似系数包含云雾状态,保持或减小近似系数.同时还提出以信息熵作为分界层数和权重选择的依据.实验证明,该算法优于同态滤波和Retinex算法.     

Reliability of 1.3 ?m V-grooved inner-stripe laser diodes under high-power operation

Aging tests of 1.3 ?m laser diodes were performed under extremely high power levels up to 85% of the maximum CW output powers. We have verified high reliability under high power levels as high as 75% of the maximum CW output powers at room temperature. The median lifetime is estimated to be 7×104 h at 75% of the maximum CW output power.     

Open circuit voltage decay in p-n junction diodes at high levels of injection

The open circuit voltage decay (OCVD) in p-n junction diodes at high levels of injection is discussed in this paper. Theoretical results are given for thick base diodes and for BSF solar cells including the effect of recombination in the emitter. It is found that the recombination in the emitter becomes important at high levels of injection and makes the voltage decay faster. The experimental results in BSF solar cells at high levels of injection are also reported and found to be in good agreement with the theoretical results derived in this paper.     

一种用于模式识别的新型开关电流Hamming神经网络

本文首次提出了一种用于模式识别的新型开关电流Ｈａｍｍｉｎｇ神经网络，它采用电流镜计算待识模式与标准模式的匹配度，然后，通过开关电流型排序电路进行匹配度的比较并输出识别结果，该Ｈａｍｍｉｎｇ神经网络可以按匹配度大小的顺序依次输出匹配度以及相应的标准模式，这将十分有利于改善系统的性能同时，该Ｈａｍｍｉｎｇ网络还可以进行绝对拒识和相对拒识的判断，这大大地提高了系统的可靠性，通过ＰＳＰＩＣＥ模拟，结果表明     

Influence of high substrate doping levels on the threshold voltageand the mobility of deep-submicrometer MOSFETs

The high levels of substrate doping needed in deep-submicrometer MOS devices affect device properties strongly. The authors present a detailed experimental study of high-doping effects on the threshold voltage, which is shown to be affected by the quantum-mechanical splitting of the energy levels in the conduction band. A simple expression to account for these effects is proposed and the consequences for device scaling and design are discussed. Furthermore, the increasing levels of substrate doping and high normal electric fields affect the channel mobility through Coulomb and surface-roughness scattering. Several empirical models for the surface mobility are compared with the characteristics of experimental devices     

Exploration of factors limiting biomass estimation by polarimetric radar in tropical forests

Direct inversion of radar return signals for forest biomass estimation is limited by signal saturation at medium biomass levels (roughly 150 ton/ha for P-band). Disturbing factors such as forest structural differences - and, notably, at low biomass levels, terrain roughness, and soil moisture variation - cause further complications. A new and indirect inversion approach is proposed that may circumvent such problems. Using multifrequency polarimetric radar the forest structure can be assessed accurately. Ecological relationships link these structures with biomass levels, even for high biomass levels. The LIFEFORM model is introduced as a new approach to transform field observations of the complex tropical forest into input files for the theoretical UTARTCAN polarimetric backscatter model. The validity of UTARTCAN for a wide range of forest structures is shown. Backscatter simulations for a wide range of forest structures, terrain roughness, and soil moisture clearly show the limitations of the direct approach and the validity of the proposed indirect approach up to very high levels of biomass.     

Low-voltage micromechanical test structures for measurement of residual charge in dielectrics

Analysis of residual dielectric charge levels using micromechanical test structures is often difficult because the application of high bias voltages across thin dielectrics alters charge levels in the dielectric, thereby skewing measurement results. The use of low-voltage test structures to overcome this problem is demonstrated, and the technique is illustrated by evaluating residual charge levels in silicon oxide.     

Simulation of solar cells with quantum wells and comparison with conventional solar cells

The efficiency of photoconversion in solar cells based on GaAs with InGaAs quantum wells under the AM 1.5 conditions for various levels of base doping has been simulated using the software package Sim-Windows. The results obtained are compared with the efficiency of photoconversion in conventional solar cells. It is shown that solar cells with quantum wells can exhibit a fairly high efficiency of photoconversion in comparison with the photoconversion efficiency of conventional solar cells under the following conditions: (i) the lifetimes of for charge carriers in the quantum wells are longer than those in the barrier material and (ii) the level of doping of the base is not very high. It is established that the maximum efficiency of photoconversion in conventional solar cells is higher than the photoconversion efficiency in solar cells with quantum wells. This efficiency is attained at high doping levels in the base (～3 × 10¹⁸ cm^?3 at the parameters used in calculations). This is related to a more intense radiative recombination and also to specific features of screening and charge transport in solar cells with quantum wells at high doping levels. It is shown that, at fairly large values for the degree of concentration of incident radiation, the values for the photoconversion efficiency in solar cells with quantum wells for the low and high levels of doping of the base come closer to each other.

     

Contribution of Auger recombination to saturation of the light-current characteristics in high-power laser diodes (λ = 1.0–1.9 m m)

Spectral and light-current characteristics of lasers based on the asymmetric separate-confinement heterostructures InGaAs/InGaAsAl/InP and InGaAs/GaAs/AlGaAs/GaAs were studied in the pulsed mode of lasing. It is shown that, at high levels of current pumping, the charge-carrier concentration in the active region of semiconductor lasers for the near-infrared optical region increases beyond the oscillation threshold; drastic saturation of the light-current characteristics is observed. Processes occurring in lasers as the charge-carrier concentration increases beyond the lasing threshold are studied theoretically. It is established that, at high pump levels, the rate of stimulated recombination decreases, the lifetime of charge carriers increases, and both the concentration of emitted photons and the quantum yield of stimulated radiation decrease. It is shown that variations in stimulated recombination, the decrease in the quantum efficiency, and saturation of the light-current characteristic in semiconductor lasers at high levels of current pumping are caused by the contribution of the nonradiative Auger recombination.     

The impact of process noise on VLSI process improvement

Process improvement is critical to commercial success in VLSI fabrication, especially during ramp-up. This paper investigates one of the factors-process noise-that drives the success of process improvement. Split-lot controlled experiments are vulnerable to confounding by experimental noise, caused by process variability. Fabs with low noise levels have a higher potential for learning (and hence improving their production processes) than high noise fabs. Detailed probe yield data from five semiconductor fabs were examined to estimate process noise levels. A bootstrap simulation was used to estimate the error rates of identical controlled experiments conducted in each fab. Absolute noise levels were high for all but the best fabs, leading to lost learning. The magnitude of lost learning is estimated numerically; it ranges from ten percent to above one hundred percent of the theoretically possible learning in an experiment. In some cases, experiments are little better than coin flipping. Standard statistical methods are either expensive or ineffective for dealing with these high noise levels. Some alternative nonstatistical countermeasures are recommended     

Theory of four-wave mixing wavelength conversion in quantum dot semiconductor optical amplifiers

Detailed theoretical analysis of four-wave mixing (FWM) wavelength conversion in quantum dot semiconductor optical amplifier (QD-SOA) is presented. The model takes into account the effect of the multidiscrete QD energy levels and the wetting layer. Good agreement between calculated and experimental data is obtained. Because of the discreteness of the energy levels, QD-SOAs demonstrate high FWM conversion efficiencies at high detuning frequency. Our calculations show that carrier escape from the ground state significantly affects the performance of the amplifier.     

Dual-polarised wideband microstrip antenna

A dual-polarised aperture-coupled microstrip antenna with a wide bandwidth, a high isolation, low cross-polarisation levels and low backward radiation levels is presented. The square patch is fed at two corners via H-shaped apertures. The measured return loss exhibits a bandwidth of over 24.4% and the isolation is better than 30 dB over the bandwidth. The cross-polarisation levels and the front-to-back ratio are better than -23 and 22 dB, respectively     

Static V-I relationships in transistors at high injection levels

At high injection levels the static V-I characteristics of p-n junction devices must be modified to account for nonlinear transport mechanisms and for relationships between the injected carrier concentrations and the applied voltages which differ from the familiar low-injection relationships. These carrier-concentration-voltage relationships differ in part because of ohmic voltage drops and in part because of conductivity-modulation effects. It is difficult to explore experimentally the high-level extensions of p-n junction theory in diodes because ohmic drops usually dominate the VI characteristics at high levels. However, these effects can be studied experimentally in a transistor which operates in the avalanche mode, with zero base current, because the ohmic drops can be suppressed. Experimental results are presented which support an analysis of the high-level V-I characteristics of the emitter junction of a transistor. This analysis does not predict ane^{qV/2kT}dependence of the junction current at high levels, but yields instead ane^{qV/(1 pm m)kT}dependence, where m is a parameter having a value of about 0.3 in germanium, and V is the applied voltage less the ohmic drops. The plus sign applies for a p⁺-n junction while the minus sign holds for an n⁺-p junction. In accordance with this theory, complementary n-p-n and p-n-p transistors exhibit markedly different behavior at high injection levels.     

Novel concept for high level overdrive tolerance of GaAs based FETs

A novel FET concept, using low temperature grown GaAs as surface passivation and buffer layer material, has been developed to tolerate high levels of input overdrive and to improve electrostatic discharge (ESD) resistance. It is shown that high input levels 17 dB beyond the 1 dB compression point, do not lead to the burnout of the device and that, at the same time, the ESD failure voltage can be increased compared to conventional GaAs based MESFETs.     

桑白皮总黄酮抗糖尿病作用的初步研究

目的：通过建立Ⅱ型糖尿病大鼠模型,观察桑白皮总黄酮对糖尿病大鼠作用影响。方法：采用高糖高脂饲养并腹腔注射STZ建立糖尿病大鼠模型,成模大鼠随机分成5组,桑白皮总黄酮高、中、低剂量组,罗格列酮对照组和模型组,每组5只。灌胃给药14天后,测量大鼠空腹血糖和甘油三酯水平,肝糖原含量。结果：桑白皮总黄酮高剂量组和中剂最组可显著降低糖尿病大鼠血糖水平（P〈0．01和P〈0．05）。桑白皮总黄酮高剂量组可降低柑尿病大鼠甘油三酯水平（P〈0．05）和升高肝糖原含量（P〈0．05）,中、低剂量组作用不明显。结论：桑白皮总黄酮可降低Ⅱ型糖尿病大鼠血糖和血甘油三酯水平,升高肝糖原含量,具有抗糖尿病作用。     

Nonuniformity of electrical properties for the PbTe single crystals in the growth direction

It is established that nonuniformity of electrical parameters conditioned by a nonuniform distribution of excess Te exists along the single-crystal PbTe ingot. In addition to the shallow acceptor and donor levels, deep acceptor levels with activation energy of ～0.1 eV exist in the band gap of the PbTe single crystals. These levels are not associated with excess Te and manifest themselves in the samples with a low concentration in the shallow levels at relatively high temperatures.     

Scaring the Already Scared: Some Problems With HIV/AIDS Fear Appeals in Namibia

Fear appeals are often used in public health campaigns in Africa to prevent further spread of HIV/AIDS. Based on the extended parallel processing model framework (K. Witte, 1991), this research assessed the impact of such messages in a high-fear situation. A 2 (high threat, low threat) × 2 (high efficacy, no efficacy) experiment with a no-message offset control and efficacy-only conditions tested several predictions. Participants demonstrated high preexisting fear about HIV/AIDS. As a likely consequence, statistical equivalence tests indicated that messages' threat levels had little impact on perceptions of fear or on outcome measures such as attitudes, intentions, or behaviors. It is concluded that the use of fear appeals to persuade audience with high levels of preexisting fear is ill-advised and ineffective.     

Wideband dual-polarised microstrip patch antenna

A dual-polarised microstrip antenna capable of achieving a wide bandwidth, a high isolation, low cross-polarisation levels and low backward radiation levels is presented. The H-shaped coupling aperture is used. For wide bandwidth and easy integration with active circuits, it uses the aperture-coupled stacked microstrip square patches. Measured return loss exhibits a bandwidth of over 20.9%, and isolation is better than 36 dB over the bandwidth. Cross-polarisation levels and the front-to-back ratio are better than 22 and 21 dB, respectively     

Anomalous relaxation of photoconductivity in silicon at high excitation levels

Anomalous relaxation of excess carries at high injection levels is observed in silicon samples upon their excitation with a pulse of light from a laser diode (1060 nm/500 mW). Microwave conductivity measurements and conventional photoconductivity-relaxation measurements were employed in these experiments. Unusual behavior takes place at the initial stage of the photoconductivity’s relaxation after the end of a pulse of light. To explain the anomalous-relaxation effect, we suggest a simplified model that involves excitons at high excitation levels.     

Output Saturation and Linearity of Waveguide Unitraveling-Carrier Photodiodes

Waveguide unitraveling-carrier photodiodes (UTC-PDs) with different absorber and collector layer doping levels have been fabricated and characterized. These photodiode (PD) structures are fabricated on a platform that allows for the monolithic integration of multiquantum-well optical phase modulators and couplers for realizing novel coherent receivers. Compared to PD A, PD B has a lower and more graded p-doping profile in the absorber layer and also a higher n-doping level in the collector layer. For PD B a larger field is induced in the absorber layer at high photocurrent levels. Also the higher n-doping in the collector layer is adequate for providing charge compensation. For PD B, there is an enhancement in the RF response as the photocurrent level is increased. At a frequency of 1 GHz, the saturation current for PD A is around 65 mA and that for PD B is around 63 mA. For PD B, the third-order output intercept point at photocurrent levels of 30 and 40 mA is 37.2 and 34.9 dBm, respectively. That for PD A is 35.8 and 30.4 dBm. PD B is, therefore, favorable for linear operation at high current levels.