实现多射频的软硬件方案

今天,忙碌穿梭的消费者也许觉得随身携带的不过是一台手机,而实际上,他们正带着七个以上射频,用于处理多频段蜂窝工作、Wi—Fi网络、蓝牙连接、辅助GPS（全球定位系统）等等功能。今后,他们还会拥有实现Adhoc式设备间通信的射频,     

Amplified spontaneous emission in pulse-pumped Raman amplifiers

We discuss amplified spontaneous emission (ASE) generated in Raman amplifiers that are counter-pumped with trains of pulses. Our experimental and theoretical results show that if the peak power of the pump pulses is too high, the ASE output from the amplifier can be significantly higher than that from a continuous-wave pumped amplifier providing the same gain. This effect places a lower limit on the duty cycle of pump pulses one can use for a given level of Raman gain. Furthermore, we report an additional ASE enhancement if there is insufficient walkoff between the pump pulses and copropagating ASE to average the effects of higher frequency pump intensity noise. As a result, less pump intensity noise can be tolerated when pulse-pumping a fiber having a zero-dispersion wavelength located midway between the pump and signal wavelengths.     

防浪涌芯片不只是控制电流

许多电子系统必须保证不间断的、连续的工作.因此技术员们必须在不关闭电源的情况下向这些"高可用性的"系统中添加新的板卡,或者更换其中报废的及受损的板卡.不过,将板卡从通电的底板抽出,或者插入底板,都会带来问题.底板从本质上来说,往往等效于在板卡边缘连接器和电源的大容量电容间的大电感.如果通电的板卡与周围断开时,底板中会出现环振和高压尖峰.例如,在一个-48V的分布式系统中,拔走一块带电板卡会产生足以损伤连接器接触点的电弧.更糟糕的是,当插入新板卡、电压线刚一接触时,对板卡的大容量电容进行充电的、极大的底板电流会在周围电路上产生有害的瞬态浪涌.     

Proximate Composition and Seed Lipid Components of Sorghum Cultivars from Argentina

Seeds of 11 sorghum cultivars ( Sorghum bicolor ) from Argentina were analysed for proximate composition, fatty acids and sterols. Oil, protein, carbohydrate and ash contents varied between 41 and 66 g kg⁻¹, 111 and 156 g kg⁻¹, 670 and 730 g kg⁻¹ and 13·8 and 20·6 g kg⁻¹ of dry matter, respectively. Fatty acid profiles revealed that the major acids were palmitic (15·1–24·8%), oleic (29·9–41·8%) and linoleic (35·9–51·3%). Unsaponifiable matter was examined for sterols. Sitosterol was the prominent component in all cultivars (43·8–57·9%), followed by campesterol (18·7–29·1%) and stigmasterol (12·4–20·5%).     

Arm Poses Modeling for Pedestrians with Motion Prior

Arm pose of human, plays an import role for understanding human behaviours. It can directly carry information of people identity, action style, interaction manner, personal habit etc. However the high dynamics of arm parts, especially the movement of forearms and hands, makes that modeling arm parts with high accuracy is challenging. In order to overcome this problem in a specific application, such as modeling arm pose of pedestrians, this paper adopts multiple priors to decrease the uncertainty of arm parts. Firstly, the human structure information, i.e. the prior of human arm parts size, is adopted to remove the impossible arm configuration. Secondly, the prior of arm parts configuration of a specific action is used to constrain the co-occurrence relations of all arm components. Therefore, a Bayesian approach is presented for modeling arm pose to incorporate the multiple priors and the likelihoods from visual observation. This paper proposes an arm model in which its priors can be represented easily. It also describes the priors estimation from the CMU motion dataset by a kernel density estimation, and maximum a posteriori for modeling the parameters of arm parts. Since there are priors for walking style, this method can be directly used for arm pose modeling of pedestrians without pre-training. It is found perform effectively on a HKU campus testing dataset, and also been evaluated on different human sizes and lighting conditions.     

Scene categorization based on local–global feature fusion and multi-scale multi-spatial resolution encoding

With the bag-of-contextual-visual-word (BOCVW) models, we propose a scene categorization method based on local–global feature fusion and multi-scale multi-spatial resolution encoding. First, the performances of the BOCVW models belonging to different features are mutually reinforced by fusing other types of features within local regions. Then, the spatial configuration information is explored using a multi-scale multi-spatial resolution encoding approach. Furthermore, these encoded BOCVW models are globally fused using an improved maximum-margin optimization strategy, which considers the margin between input vectors of different categories and the diameter of the smallest ball containing feature vectors simultaneously. The proposed method has been evaluated on three scene categorization datasets consisting of scene categories 8, 15, and 67, respectively. And its effectiveness has been verified by these experimental results.     

Dielectric spectroscopy of fresh fruit and vegetable tissues from 10 to 1800 MHz.

Dielectric spectroscopy data from measurements on tissue samples of nine fresh fruits and vegetables were used to study their dielectric behavior over the frequency range from 10 MHz to 1.8 GHz at 5 to 65 degrees C. Dielectric constant and loss-factor data are presented graphically for apple, avocado, banana, cantaloupe, carrot, cucumber, grape, orange, and potato, showing dielectric constants ranging from values of several hundred at 10 MHz to less than 100 at 1.8 GHz and loss factors on the order of one thousand at 10 MHz to less than 20 at 1.8 GHz. The dielectric loss factor increased consistently with increasing temperature at frequencies below 1 GHz. The dielectric constant increased with temperature at lower frequencies, but it decreased with temperature at the higher frequencies. This reversal of the sign of the temperature coefficient occurred at some point in the frequency range between 20 and 120 MHz where the temperature dependence of the dielectric constant was zero. At frequencies below this point, ionic conduction dominates the dielectric behavior, but above that point dipolar relaxation appears to control the behavior. Multiple linear regression provided equations for calculation of the loss factor in the frequency range from 10 to 300 MHz at temperatures from 5 to 65 degrees C. The data provide new information useful in understanding dielectric heating behavior and evaluating dielectric properties of such agricultural products for quality sensing applications.     

手工式模拟设计获得自动化辅助

模拟仿真器与设计捕捉工具在EDA市场已有长久的历史,这个市场一直在为数字仿真器增加某些Spice。不过,当仿真结果要转换为正弦波和硅片时,模拟EDA工具就会远远落后于数字EDA工具的水平。这种情况正在开始改变,传统数字EDA供应商正在出现以纳米尺度数字工艺支持模拟功能晶圆制作的工具。另外,代工厂专用工具包也正在简化用模拟工艺实现模拟、RF大电压功能的过程。     

Non‐Geminate Recombination as the Primary Determinant of Open‐Circuit Voltage in Polythiophene:Fullerene Blend Solar Cells: an Analysis of the Influence of Device Processing Conditions

The physical origin of the open‐circuit voltage in bulk heterojunction solar cells is still not well understood. While significant evidence exists to indicate that the open‐circuit voltage is limited by the molecular orbital energies of the heterojunction components, it is clear that this picture is not sufficient to explain the significant variations which often occur between cells fabricated from the same heterojunction components. We present here an analysis of the variation in open‐circuit voltage between 0.4–0.65 V observed for a range of P3HT/PCBM solar cells where device deposition conditions, electrode structure, active‐layer thickness and device polarity are varied. The analysis quantifies non‐geminate recombination losses of dissociated carriers in these cells, measured under device operating conditions. It is found that at open‐circuit, losses due to non‐geminate recombination are sufficiently large that other loss pathways may effectively be neglected. Variations in open‐circuit voltage between different devices are shown to arise from differences in the rate coefficient for non‐geminate recombination, and from differences in the charge densities in the photoactive layer of the device. The origin of these differences is discussed, particularly with regard to variations in film microstructure. By separately quantifying these differences in rate coefficient and charge density, and by application of a simple physical model based upon the assumption that open‐circuit is reached when the flux of charge photogeneration is matched by the flux of non‐geminate recombination, we are able to calculate correctly the open‐circuit voltage for all the cells studied to within an accuracy of ±5 mV.     

Effects of Photo‐oxidation on the Performance of Poly[2‐methoxy‐5‐(3′,7′‐dimethyloctyloxy)‐1,4‐phenylene vinylene]:[6,6]‐Phenyl C61‐Butyric Acid Methyl Ester Solar Cells

A study of the photo‐oxidation of films of poly[2‐methoxy‐5‐(3′,7′‐dimethyloctyloxy)‐1,4‐phenylene vinylene] (MDMO‐PPV) blended with [6,6]‐phenyl C₆₁‐butyric acid methyl ester (PCBM), and solar cells based thereon, is presented. Solar‐cell performance is degraded primarily through loss in short‐circuit current density, J_SC. The effect of the same photodegradation treatment on the optical‐absorption, charge‐recombination, and charge‐transport properties of the active layer is studied. It is concluded that the loss in J_SC is primarily due to a reduction in charge‐carrier mobility, owing to the creation of more deep traps in the polymer during photo‐oxidation. Recombination is slowed down by the degradation and cannot therefore explain the loss in photocurrent. Optical absorption is reduced by photo‐bleaching, but the size of this effect alone is insufficient to explain the loss in device photocurrent.