基于dsPIC33和MCP3909的三相监控终端研究与设计

为使三相监控终端测得的电压电流能实时同步采样并保证监控终端结构简单、运行可靠,设计了新型三相监控终端,在硬件上CPU采用高性能的dsPIC33FG256GP710和电表专用的电能质量计量芯片MCP3909,软件采用了具有工程实用性的准同步采样法。主站通过GPRS网络与各个监控终端通信,对监控终端进行管理维护,便于数据管理。实验结果表明,该设计在电能质量测量方面准确可靠。     

微通道板输出电极的最佳深度

本文给出了微通道板(MCP)输出电极的最佳深度表达式。在此最佳条件下,MCP输出电子能量分布(EDOE)曲线只有锐的低能主峰,它的半宽度达到极限值,能在极限空间分辨率下工作。解释了以前所报道的MCP的EDOE特性,那实际上是偏离最佳条件下的MCP的特性。     

天然放射性同位素产生的MCP噪声

本文计算了天然放射性同位素产生的MCP噪声(以A/cm2表示)。计算结果给出:Rb87产生的噪声最大,K40次之;最小为La138和V50。这表明:某些应用领域要求低噪声或超低噪声的MCP时,则该MCP的皮料中不能含有天然放射性同位素Rb87或K40。     

CAN总线在石油仪器组合导航系统中的应用

基于DSP + FPGA结构的石油仪器组合导航系统中CAN总线系统设计,为了使数据能够在整个CAN总线网络协调、有效、快速、稳定的传输,提出了一种使用FPGA作为CAN总线节点结构中的核心处理器的设计方法;CAN控制器采用具有SPI接口的MCP2515,利用FPGA实现MCP2515的初始化、数据的发送和接收,实现了DSP处理器的CAN总线扩展应用;该方法由于把CAN节点控制的大量的工作交给FPGA实现,DSP只需要对FPGA中CAN数据接收FIFO和CAN数据发送FIFO进行读写操作,即可完成CAN总线的数据读写操作,大大减轻了DSP的数据处理压力;试验测试及产品应用表明,该设计有效、稳定可靠、可扩展性好,易于修改和移植,具有较强的工程实用价值。     

现代电子封装技术

根据国际电子封装的发展，论述了电子封装的地位和作用，回顾了电子封装的发展简史，提出现代电子封装的概念，并就发展我国电子封装发表几点建议。     

RTD Pt100的一种单电源信号调理电路

介绍一种由单电源CMOS四运算放大器MCP604实现电阻式温度传感器Pt100的激励和信号放大电路。其中,Pt100由MCP604中两个放大器形成的浮动电流源激励;采用3线制接入由运放组成的引线补偿电路中进行引线补偿;补偿后的电压信号由MCP604中另外两个放大器构成的放大电路进行采样放大。     

基于并行约束规划的最大团识别研究

为提高大数据平台下大规模图例的最大团问题求解效率,提出一种基于并行约束规划的最大团识别算法.通过BMT图划分策略将一个复杂图例分割为若干个可独立计算的子图,并将其分配给Spark集群中的计算节点,每个计算节点采用约束规划方法对分割产生的子问题分别进行建模和求解,实现最大团问题的并行化处理.引入时间预测模型,设计基于任务运行时间预测模型的并行图划分方法,从而有效解决计算节点的负载均衡问题.实验结果表明,与基于BMC图划分策略的最大团并行识别算法相比,该算法具有更高的求解效率,可取得近似线性的加速比.     

A water-assisted nucleophilic mechanism utilized by BphD,the meta-cleavage product hydrolase in biphenyl degradation

As members of the α/β-hydrolase superfamily, Meta-cleavage product (MCP) hydrolases generally utilize a Ser-His-Asp catalytic triad to hydrolyze the cleavage of CC bond during the aerobic catabolism of aromatic compounds by bacteria. BphD is one kind of MCP hydrolase that catalyzes the hydrolysis of 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoic acid (HOPDA) to 2-hydroxypenta-2,4-dienoic acid (HPD) and benzoate. In this article, a combined quantum mechanics and molecule mechanics (QM/MM) approach has been employed to explore the reaction mechanism of BphD from Burkholderia xenovorans LB400. On the basis of the recently resolved crystal structures, three computational models have been constructed. Our calculation results reveal that BphD utilizes a water-assisted nucleophilic mechanism, which contains acylation and deacylation stages. In acylation reaction, an active site water molecule assists the proton transfer from Ser112 to the carbanion intermediate (substrate) by forming hydrogen bonds with Ser112 and His265, and this proton transfer is in concert with the nucleophilic attack of deprotonated Ser112 on the C6-carbonyl of substrate to form the acylated intermediate. In deacylation, the Asp237-His265 dyad acts as a general base to activate the hydrolytic water, whose nucleophilic attack leads to the collapses of acyl-enzyme intermediate. The acylation and deacylation process correspond to the highest energy barriers of 21.0 and 23.9 kcal/mol, respectively. During the catalytic reaction, the active site water and Asp237-His265 dyad play an important role for each elementary steps.     

Partially acidulated phosphate rocks-reactions with water

This work investigated suggested interactions between the phosphate rock component and the acidic solution formed by hydrolysis of monocalcium phosphate (MCP) as partially acidulated phosphates absorb water.Two approaches are reported. First, various materials were incubated in humid atmospheres for up to seven weeks and solubilities determined. Secondly, rock particles were mixed with a synthetic solution based on the hydrolysis products of MCP.Neither approach gave any enhanced solubility in neutral ammonium citrate solution which showed that the residual phosphate rock had not reacted.     

Photodegradation of phenoxyacetic acid and carbamate pesticides on TiO2

An equation representing photocatalytic degradation rate of three phenoxyacetic acid and two carbamate pesticides was proposed, which includes substrate adsorbability to TiO₂ and Hammett’s constant of substituent groups. The data fitting to this equation indicated that the adsorption was a predominant factor in determining the degradation rate. A study was also conducted on the degradation process of 4-chloro-2-methylphenoxyacetic acid (MCP) by identifying aromatic (4-chloro-o-cresol, 4-chlorocatechol and methylhydroquinone) and aliphatic acid (acetic, formic, glyoxylic and glycolic acids) intermediates. Particularly acetic acid formation was related to methyl substituent on aromatic ring.