PWM可调直流稳压控制电源电路的设计研究

设计了一种基于KA3525的单片机辅助PWM控制电源电路.给出了输出电路、调控电路以及调控电路所包含的控制电路、稳压电路的原理与实现方法.保护电路以及抗干扰电路的设计能够保证电路正常和安全运行.通过试验,得到了不同输出电压的VDS电压波形图.结果证明该方案有效,实用于大功率可调控制电源.     

淹水胁迫对湖北海棠生长及叶绿素荧光动力学的影响

【目的】评价湖北海棠耐涝性,并从色素含量和叶绿素荧光动力学角度分析其耐涝机制。【方法】通过人工模拟淹水胁迫,对淹水胁迫过程中湖北海棠生长形态、叶片外观及叶绿素快相荧光动力学特征进行分析。【结果】(1)淹水处理显著抑制湖北海棠的生长,但淹水30~200 d苗木成活率仍为100%。(2)淹水后叶色转红,叶绿素与类胡萝卜素(Car)和花青素(Anth)的相对含量比值(m_(Chl)/m_(Car+Anth))显著下降。(3)进行叶绿素荧光动力学观测发现,处理叶片在O相的初始荧光F_o显著高于对照,在P相的最大荧光F_m显著低于对照,且淹水后在J相处的可变荧光V_j升幅(3.4%~9.0%)大于K相处的可变荧光V_k升幅(3.8%~11.6%)。随着淹水时间的延长,叶片单位面积的反应中心数目(RC/CSm)和PSⅡ电子受体库容量(S_m)显著降低,电子由Q_A向Q_B的传递过程受抑制,导致PSⅡ向PSⅠ的电子传递能力降低(Ψ_o和φ_(Ro)),最终表现为综合性能参数(PI_(total))受到显著抑制,而叶片的热耗散(DI_o/CS_m)显著递增。【结论】淹水胁迫显著抑制湖北海棠生长,但并不致死,因此可认为其具备一定的耐水淹能力。虽然淹水对湖北海棠叶片PSⅡ电子受体侧的影响大于供体侧,但叶片可通过增加热耗散比及Car和Anth相对含量比例来降低激发能的产生,以及过剩激发能的伤害,从而提高其耐水淹能力。     

Preparation of high-strength Al-Mg-Si-Cu-Fe alloy via heat treatment and rolling

An Al-Mg-Si-Cu-Fe alloy was solid-solution treated at 560°C for 3 h and then cooled by water quenching or furnace cooling. The alloy samples which underwent cooling by these two methods were rolled at different temperatures. The microstructure and mechanical properties of the rolled alloys were investigated by optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis, and tensile testing. For the water-quenched alloys, the peak tensile strength and elongation occurred at a rolling temperature of 180°C. For the furnace-cooled alloys, the tensile strength decreased initially, until the rolling temperature of 420°C, and then increased; the elongation increased consistently with increasing rolling temperature. The effects of grain boundary hardening and dislocation hardening on the mechanical properties of these rolled alloys decreased with increases in rolling temperature. The mechanical properties of the 180°C rolling water-quenched alloy were also improved by the presence of β″ phase. Above 420°C, the effect of solid-solution hardening on the mechanical properties of the rolled alloys increased with increases in rolling temperature.     

A loss-of-function RNA interference screen for molecular targets in cancer

The pursuit of novel therapeutic agents in cancer relies on the identification and validation of molecular targets. Hallmarks of cancer include self-sufficiency in growth signals and evasion from apoptosis; genes that regulate these processes may be optimal for therapeutic attack. Here we describe a loss-of-function screen for genes required for the proliferation and survival of cancer cells using an RNA interference library. We used a doxycycline-inducible retroviral vector for the expression of small hairpin RNAs (shRNAs) to construct a library targeting 2,500 human genes. We used retroviral pools from this library to infect cell lines representing two distinct molecular subgroups of diffuse large B-cell lymphoma (DLBCL), termed activated B-cell-like DLBCL and germinal centre B-cell-like DLBCL. Each vector was engineered to contain a unique 60-base-pair 'bar code', allowing the abundance of an individual shRNA vector within a population of transduced cells to be measured using microarrays of the bar-code sequences. We observed that a subset of shRNA vectors was depleted from the transduced cells after three weeks in culture only if shRNA expression was induced. In activated B-cell-like DLBCL cells, but not germinal centre B-cell-like DLBCL cells, shRNAs targeting the NF-kappaB pathway were depleted, in keeping with the essential role of this pathway in the survival of activated B-cell-like DLBCL. This screen uncovered CARD11 as a key upstream signalling component responsible for the constitutive IkappaB kinase activity in activated B-cell-like DLBCL. The methodology that we describe can be used to establish a functional taxonomy of cancer and help reveal new classes of therapeutic targets distinct from known oncogenes.     

A PPARγ-FGF1 axis is required for adaptive adipose remodelling and metabolic homeostasis

Although feast and famine cycles illustrate that remodelling of adipose tissue in response to fluctuations in nutrient availability is essential for maintaining metabolic homeostasis, the underlying mechanisms remain poorly understood. Here we identify fibroblast growth factor 1 (FGF1) as a critical transducer in this process in mice, and link its regulation to the nuclear receptor PPARγ (peroxisome proliferator activated receptor γ), which is the adipocyte master regulator and the target of the thiazolidinedione class of insulin sensitizing drugs. FGF1 is the prototype of the 22-member FGF family of proteins and has been implicated in a range of physiological processes, including development, wound healing and cardiovascular changes. Surprisingly, FGF1 knockout mice display no significant phenotype under standard laboratory conditions. We show that FGF1 is highly induced in adipose tissue in response to a high-fat diet and that mice lacking FGF1 develop an aggressive diabetic phenotype coupled to aberrant adipose expansion when challenged with a high-fat diet. Further analysis of adipose depots in FGF1-deficient mice revealed multiple histopathologies in the vasculature network, an accentuated inflammatory response, aberrant adipocyte size distribution and ectopic expression of pancreatic lipases. On withdrawal of the high-fat diet, this inflamed adipose tissue fails to properly resolve, resulting in extensive fat necrosis. In terms of mechanisms, we show that adipose induction of FGF1 in the fed state is regulated by PPARγ acting through an evolutionarily conserved promoter proximal PPAR response element within the FGF1 gene. The discovery of a phenotype for the FGF1 knockout mouse establishes the PPARγ–FGF1 axis as critical for maintaining metabolic homeostasis and insulin sensitization.     

Towards a Cost-Efcient MapReduce: Mitigating Power Peaks for HadoopClusters简

Distributed data processing system is becoming one of the most important components for data-intensive computational tasks in the enterprise software infrastructure. Deploying and operating such systems require large amount of costs, including hardware costs to build clusters and energy costs to run clusters. To make these systems sustainable and scalable, power management has been an important research problem. In this paper, we take Hadoop as an example to illustrate the power peak problem which causes power inefficiency and provides in-depth analysis to explain issues with existing system designs. We propose a novel power capping module in the Hadoop scheduler to mitigate power peaks. Extensive simulation studies show that our proposed solution can effectively smooth the power consumption curve and mitigate temporary power peaks for Hadoop clusters.     

正弦波,三角波的自动识别

介绍了一种用单片机系统提取正弦波特性的方法,采用汇编语言编程,用模板法自动识别正弦波、三角波     

PQ magic5.0的应用

要改变硬盘分区,通常只能先将硬盘中有价值的资料全部备份出来,然后再对硬盘重新分区、重新格式化。PQ magic 5.0是实现硬盘动态分区和无损分区的上佳选择。Partition—Magic 支持超过20GB 的大容量硬盘,能在 FAT 和 FAT32分区间方便地实现相互转换,并在不丢失资料     

稻田生态系统中杂草地捕食性节肢动物群落研究

采用吸虫器法采样，对稻田生态系统中杂草地捕食性节肢动物天敌群落物种多样性、结构动态等进行了系统的研究。在杂草地生境中采集到73种捕食性节肢动物，其中55种为捕食性蜘蛛，18种为捕食性昆虫。在冬春闲期，杂草地生境的捕食性节肢动物物种多样性和单位面积内的个体数量较高。水稻移栽后，杂草地中的捕食性节肢动物种群迁进稻田，为稻田提供天敌移居者，杂草地生境中的捕食性天敌物种数减少，单位面积内的个体数量降低；水稻成熟后、夏闲期始及冬闲期始，杂草地接纳从稻田中迁出的天敌种群，捕食性天敌物种数和单位面积内的个体数量呈上升趋势。杂草地为保护稻田捕食性天敌，提供了一个良好的庇难所。     

基于WebGIS 的汉江水环境管理信息系统

依据互联网地理信息系统（WebGIS）的实现技术及特点,分析了ArcIMS的体系结构及其运行机制,通过基于ArcIMS9平台并结合JS,JSP等技术,提出一种新的具有多层结构的WebGIS解决方案,并结合具体实例阐述了其在水环境管理信息系统的实现．结合水环境管理信息系统的需求,给出了基于WebGIS的水环境管理信息系统的功能体系结构．采用Apache＋Tomcat作为网络服务器、ArcIMS作为地图服务器完成了系统功能设计,实现了网上数字地图的处理、传送,以及基于地图的水环境信息查询、评估、统计、分析,和排放污染总量与污染源的控制决策．