A solvent extraction technique for the isotopic measurement of dissolved copper in seawater

Stable copper (Cu) isotope geochemistry provides a new perspective for investigating and understanding Cu speciation and biogeochemical Cu cycling in seawater. In this work, sample preparation for isotopic analysis employed solvent-extraction with amino pyrollidine dithiocarbamate/diethyl dithiocarbamate (APDC/DDC), coupled with a nitric acid back-extraction, to concentrate Cu from seawater. This was followed by Cu-purification using anion-exchange. This straightforward technique is high yielding and fractionation free for Cu and allows precise measurement of the seawater Cu isotopic composition using multi-collector inductively coupled plasma mass-spectrometry. A deep-sea profile measured in the oligotrophic north Tasman Sea shows fractionation in the Cu isotopic signature in the photic zone but is relatively homogenised at depth. A minima in the Cu isotopic profile correlates with the chlorophyll a maximum at the site. These results indicate that a range of processes are likely to fractionate stable Cu isotopes in seawater.     

Correlative studies in optical reflectance measurements of cerebral blood oxygenation

A numerical study is made of correlation development for measuring cerebral blood oxygen saturation (StO) noninvasively using optical reflectance ratio of dual wavelengths. The Monte Carlo (MC) method was used for simulating reflectance measurements in a model neck tissue, where the cerebral blood oxygenation was monitored through the blood flows in the common carotid artery (CCA) and jugular vein. Reflectance ratios between two wavelengths at 633 and 800 nm were obtained under different blood vessel conditions. The results revealed a quantifiable correlation between the reflectance ratio and the cerebral StO level. Correlations for each of the blood vessel parameters such as the location, size, and hemoglobin concentration of the CCA or jugular vein (JV) were developed.     

基于80c196MC的一种直流母线电压补偿设计

针对单相大功率宽频带低失真逆变器这一特殊要求，提出了一种基于80c196MC的直流母线电压补偿方法，并给出具体的设计方案．该设计方案在一台容量为4kVA的单相SPWM电压型并联四重化逆变器进行实验，实验结果表明，该方法补偿效果较好，而且实现起来简单容易，具有一定的工程价值．     

The Rings Characterized by Minimal Left Ideals

We study these rings with every minimal left ideal being a projective, direct summand and a p-injective module, respectively. Some characterizations of these rings are given, and the relations among them are obtained. With these rings, we characterize seinisiinple rings. Finally, we introduce MC2 rings, and give some characterizations of MC2 rings.     

Molecular MC SCF calculations by direct minimization

Calculations on the H₂CO ground state and excited states at the equilibrium planar geometry, using the single excitation MC SCF method, are described for two basis sets. The results obtained by a full calculation including all the electrons are compared with those obtained by a pseudopotential version of the method including only the valence electrons. The results agree quite well both with each other and with the observed values.     

中频逆变电源软件设计

介绍了单相全桥式逆变的400HZ中频电源软件主程序设计、中断及其采样程序设计.简单介绍80C196MC芯片的特点以及由此可实现的电源稳压模式或者限流模式.为了实现逆变电源的智能化特点,特设计串行通讯模块与上位机通讯.     

工程机械车载终端中GPRS通信的分析及实现

针对工程机械车载终端的GPRS通信进行了分析和实现.在对工程机械车载终端进行硬件设计的基础上,进行了GPRS通信时和服务器连接建立和实现的分析,包括不同服务器网络终端连接方式的分析,以及PPP和TCP/IP协议栈的设计实现等.最终,以合理的流程实现了车载终端和中心站服务器的GPRS通信.     

抽油机直接驱动无刷直流电动机控制器设计

为改善传统抽油机高速驱动、多级传动带来的效率低、功率因数低、维护费用高、噪声大等缺点,设计了基于MC33035的无刷直流电动机控制器,采用低速运行的大轮盘永磁电机直接驱动抽油机实现油杆的往复运动.     

MC55在LED点阵控制系统中的应用

针对目前LED点阵控制显示屏应用的日益广泛和GPRS技术发展成熟,提出了基于GPRS技术的无线LED点阵控制系统方案。详细介绍了系统结构和软硬件设计过程,该系统以ARM模块LPC2103为控制器、MC55为无线数据传输模块,以公用GPRS和以太网为承载网络,实现LED点阵控制终端的无线控制。与传统方式相比,具有高速、可靠、维护费用低、实时性强、覆盖面广等优点,应用前景广阔。     

300V无刷直流电机控制系统的设计

本文提出了一种基于MC33035和MC33039构成的300V直流无刷电机驱动器的设计.该设计主要电源电路、核心控制电路、功率驱动电路和电机保护电路(过流、过热、欠压保护)构成.该驱动器现已成功应用于驱动300V/1.5kw的直流无刷电机,电机运行最高转速达到12000r/min,取得了比较好的经济效益.