MCP2515在ARM7的CAN口扩展中的应用

ARM7嵌入式平台采用ATMEL公司的AT91SAM7X256芯片,它内部只集成了一个CAN总线控制器。本文介绍了一种新型的CAN通信控制器MCP2515,给出其在ARM7平台的CAN总线扩展中的应用实例。硬件设计给出了电路原理图,软件设计给出了测试程序主要代码。具有两路CAN的ARM7平台可用于卫星故障复现嵌入式硬件系统中。     

Time dependent model of gain saturation in microchannel plates and channel electron multipliers

We present and discuss a time dependent solution of the transmission line model of a channel electron multiplier, introduced in a previous paper and already solved in steady-state conditions. The model is applicable to all the situations in which the multiplier input current is sufficiently large so that the statistical variations of the gain for each electron can be ignored and it does not apply to photon counting detectors. By introducing the appropriate boundary conditions the time dependent non-linear equations of the model are reduced to an integral equation in implicit form, whose solution can be calculated numerically by a perturbative approach. In this way the multiplying current signal i(z,t) and the voltage V(z,t) are found as functions of the position z along the channel, and of the time t during the pulse itself, for any arbitrary shape of the input current waveform. The important case of the amplification of input current pulses with a short duration compared to the multiplier recovery time is investigated in detail, showing that the non-linear behavior can be entirely described by a general function of a conveniently defined saturation parameter and that this function is characteristic of any uniform channel multiplier. The model is then used to investigate the recovery of the multiplier after a saturating pulse, and it is found that the gain recovery from weak or moderate saturation levels is exponential to a very good approximation, but with a time constant different from the characteristic time constant RC of the multiplier. Finally the case of pulses of arbitrary shape and duration is considered and examples are given of the amplification of step pulses and of a regular sequence of identical pulses. A remarkable feature of the model is that the solution can be calculated from the time shape of the output pulse, rather than from the input. This makes possible to implement methods for pulse restoration, i.e. for recovering the original input pulse shape from a measured saturated output.     

电子元器件封装技术发展趋势

晶圆级封装、多芯片封装、系统封装和三维叠层封装是近几年来迅速发展的新型封装方式,在推动更高性能、更低功耗、更低成本和更小形状因子的产品上,先进封装技术发挥着至关重要的作用。晶圆级芯片尺寸封装(WCSP)应用范围在不断扩展,无源器件、分立器件、RF和存储器的比例不断提高。随着芯片尺寸和引脚数目的增加,板级可靠性成为一大挑战。系统封装(SIP)已经开始集成MEMS器件、逻辑电路和特定应用电路。使用TSV的三维封装技术可以为MEMS器件与其他芯片的叠层提供解决方案。     

电感耦合等离子体发射光谱法测定饲钙中的砷、铅、镉、铬含量

介绍ICP-OES发射光谱法的工作原理和用ICP-OES发射光谱法测定饲料级磷酸氢钙、磷酸二氢钙和磷酸一二钙中砷(As)、铬(Cr)、镉(Cd)、铅(Pb)含量的方法。从仪器参数选择、样品处理、标准曲线配制、试验步骤及结果讨论等方面研究,并得到了较为满意的结果。     

苦瓜多糖对小鼠淋巴细胞免疫调节作用的影响（网络首发、推荐阅读）

以苦瓜多糖(MCP)为研究对象,在细胞和分子水平上探讨其对小鼠脾淋巴细胞的免疫调节作用机制。以空白组和左旋咪唑组为对照,小鼠脾淋巴细胞经不同质量浓度(40,80,160,320μg/mL)的MCP体外刺激,检测MCP对小鼠脾淋巴细胞增殖的影响,腹腔巨噬细胞的吞噬活性,淋巴细胞上清液中IL-4、IFN-γ、IL-6和IL-12分泌与mRNA表达水平。分析发现,与空白组相比,随浓度的升高细胞增殖指数倍数增长(P<0.05),MCP能不同程度的促进细胞增殖、不同程度的增强巨噬细胞的吞噬能力(P<0.05);与空白组相较,细胞因子IL-4、IFN-γ、IL-6和IL-12的分泌量最大增幅分别为:42.73%、18%、27.81%、29.42%;IL-4、IFN-γ、IL-6和IL-12的mRNA表达显著上升,最高表达水平分别为空白组的9.18、7.53、9.37、8.95倍,存在显著性差异(P<0.05)。结果表明,MCP能有效提高细胞因子IL-4、IFN-γ、IL-6和IL-12的分泌和mRNA表达水平,促进细胞增殖,增强巨噬细胞的吞噬活性,从而提高机体免疫功能。     

A simple pretreatment with low O2 to alleviate superficial scald in Granny Smith apples

Sealing Granny Smith apples in a low‐O₂ atmosphere for 7 days at 20 °C (LO₂‐20C) prior to cold storage reduced superficial scald development after 6 and 8 months at 0 °C plus 10 days at 20 °C. This LO₂‐20C treatment reduced the O₂ levels that induce endogenous production of significant amounts of CO₂, acetaldehyde and ethanol, and thereby reduced ethylene production in cold storage, which in turn reduced scald development. Treatment with ethanol vapour (20 mL L^?1) for 1 day at 20 °C plus 6 days at 1 °C or with low O₂ for 1 day at 20 °C plus 6 days at 1 °C (LO₂‐1C) did not reduce scald effectively. 1‐Methylcyclopropene (1‐MCP) treatment at 0.5 µL L^?1 was the most efficient at reducing scald development. In all treatments, superficial scald development proceeded from the distal blossom end towards the proximal stem end of fruits. After 6 months of cold storage at 0 °C, peel browning and membrane leakage, measured as electrical conductivity in situ, were greater at the blossom end than at the stem end of control, ethanol‐ and LO₂‐1C‐pretreated fruits. In LO₂‐20C‐ and 1‐MCP‐pretreated fruits, colour indices (hue angle, lightness and chroma) and electrolyte leakage were similar at both the stem and blossom ends and were associated with less scald development after 6 months at 0 °C. The reduction in scald development was also associated with lower peroxidase and polyphenol oxidase activities in the peel of LO₂‐20C‐ and 1‐MCP‐pretreated fruits. A simple treatment at 20 °C (LO₂‐20C) prior to regular cold storage could also be suitable for organically grown apples that cannot be treated with diphenylamine or 1‐MCP. Copyright © 2007 Society of Chemical Industry     

MCP像增强器开门/关门时间特性研究

门控型MCP像增强器具有光选通和图像增强两个作用,与CCD器件耦合组成高灵敏度高速图像记录系统,广泛应用于惯性约束核聚变研究中的时空分辨图像诊断。开门时刻和关门时刻叠加在MCP像增强器的光电阴极上的选通电压具有较强的"孔栏"效应,"孔栏"效应时间在ns级时间范围内,在ns级时间分辨图像诊断中对图像轮廓强度分布影响较大。本文首先从理论上分析了引起"孔栏"效应的物理过程,并进行了模拟计算[1],然后进行相关的实验研究。在实验中使用波长为532 nm、脉冲宽度约为300 ps的脉冲激光作为光源,实验测量MCP像增强器的开门/关门时间,实验结果表明:双紧贴MCP像增强器的开门时间和关门时间约为1.8 ns,对于半宽度约为20ns电脉冲信号,MCP曝光开门时间约为30 ns,电脉冲宽度与实际曝光时间具有一定的差异。进一步的理论分析表明,为了获得亚ns级以下的时间分辨图像,需要采用单紧贴MCP像增强器或增加导电基体的厚度以牺牲荧光透过率等技术途径。     

毛叶枣贮藏保鲜技术研究

分别对毛叶枣的贮藏适性、涂膜保鲜技术及1-MCP对毛叶枣的贮藏性的影响进行了较深入地研究。试验结果表明:贮藏温度2～5℃,RH90%～100%范围为毛叶枣适宜的贮藏条件;经过1-MCP处理的毛叶枣果实贮藏性明显高于未经处理的果实。涂膜保鲜试验表明:以瓜尔豆胶1.1g、卡拉胶2.75g、分子蒸馏单甘酯0.5g、乙醇50mL、水500mL、杀菌剂和防腐剂若干配制的涂膜剂处理毛叶枣果实,在室温条件下其货架可达到12d,在2～5℃贮藏条件下其贮藏期可达50d,商品率100%。     

Decentralized beamforming design and power allocation for limited coordinated multi-cell network

Multi-cell processing （MCP） is capable of providing significant performance gain, but this improvement is accompanied by dramatic signaling overhead between cooperative base stations. Therefore, balancing the performance gain and overhead growth is crucial for a practical multi-base cooperation scheme. In this paper, we propose a decentralized algorithm to jointly optimize the power allocation and beamforming vector with the goal of maximizing the system performance under the constraint of limited overhead signal and backhaul link capacity. In particular, combined with calculating the transmission beamforming vector according to the local channel state information, an adaptive power allocation is presented based on the result of sum capacity estimation. Furthermore, by utilizing the concept of cell clustering, the proposed framework can be implemented in a practical cellular system without major modification of network architecture. Simulation results demonstrate that the proposed scheme improves the system performance in terms of the sum capacity and cell-edge capacity.     

西门子840D系统MCP和HHU在双通道中的自由切换

利用西门子系统提供的MMC通道状态信号及MCP、HHU控制的PLC标准子程序实现了两通道中的自由切换.