微波消解-石墨炉原子吸收光谱法测定芦笋中的铜、铅、镉和铬

建立微波消解-石墨炉原子吸收光谱法测定芦笋中Cu,Pb,Cd和Cr的方法。研究了微波消解体系和消解条件对消解效果的影响,选择HNO3-H2O2-H2O体系和梯度增压方式,得到较好的消解效果;研究了磷酸二氢铵溶液的质量浓度、灰化温度、原子化温度对吸光度的影响。通过单因素试验,分别确定了测定Cu,Pb,Cd和Cr时各自的最佳条件。在此条件下,测定芦笋中Cu,Pb,Cd和Cr含量分别为15.2,5.64,0.314和1.72μg/g,精密度分别为3.81%,2.80%,2.35%和2.92%,检出限分别为3.37,2.91,0.21和0.76ng/mL,加标回收率分别为92.5%,106.0%,102.5%和97.0%。微波消解-石墨炉原子吸收光谱法测定芦笋中Cu,Pb,Cd和Cr,方法快速、准确、污染少,具有较高的实用价值。     

Robust partial pole assignment problem for high order control systems

In this paper, we consider the partial pole assignment problem (PPAP) for high order control systems. It is shown that solving the PPAP is essentially solving a pole assignment for a linear system of a much lower order, and the robust PPAP is then concerning the robust pole assignment problem for this linear system. Based on this theory, a rather simple algorithm for solving the robust PPAP is proposed, and numerical examples show that this algorithm does lead to comparable results with earlier algorithms, but at much lower computational cost.     

Optimal design of butterfly-shaped linear ultrasonic motor using finite element method and response surface methodology

A new method for optimizing a butterfly-shaped linear ultrasonic motor was proposed to maximize its mechanical output. The finite element analysis technology and response surface methodology were combined together to realize the optimal design of the butterfly-shaped linear ultrasonic motor. First, the operation principle of the motor was introduced. Second, the finite element parameterized model of the stator of the motor was built using ANSYS parametric design language and some structure parameters of the stator were selected as design variables. Third, the sample points were selected in design variable space using latin hypercube Design. Through modal analysis and harmonic response analysis of the stator based on these sample points, the target responses were obtained. These sample points and response values were combined together to build a response surface model. Finally, the simplex method was used to find the optimal solution. The experimental results showed that many aspects of the design requirements of the butterfly-shaped linear ultrasonic motor have been fulfilled. The prototype motor fabricated based on the optimal design result exhibited considerably high dynamic performance, such as no-load speed of 873 mm/s, maximal thrust of 27.5 N, maximal efficiency of 43%, and thrust-weight ratio of 45.8.     

Oxidation behaviors of Ni-Cr-Al superalloy foams at 1 000 ℃ in air

The oxidation behaviors of Ni-16Cr-xAl （x=4.5%, 9.0%, mass fraction） superalloy foams in air at 1000℃ were investigated. The effects of AI content on the resistance to high temperature oxidation were examined. The oxidation mechanisms of the foams were discussed. The results show that the resistance to the oxidation of the Ni-16Cr-xA1 based alloy at 1 000 ℃ increases with the content of A1 increasing from 4.5% to 9.0%. Complex oxide products are formed on the surface of the superalloy foams after the oxidation. Cr203 and A1203 are the predominant oxides for the scales of the foams with 4.5% A1 and 9% A1, respectively. Excellent high temperature oxidation resistance and superior pore conformation stability for the Ni-16Cr-xA1 based superalloy foam with 9% A1 can be mainly attributed to the formation of relatively continuous and protective A1203 oxides on the surface of the foam.     

数字化电气信息采集对继电保护可靠性的影响

数字化电气信息采集为数字化变电站乃至智能电网信息化提供直接支撑.针对电子式互感器和合并单元的特点,给出数字化电气信息采集系统的功能模块.从互感器结构、数字传输、数据验证、采样频率和系统配置方面,分析数字化电气信息采集对继电保护可靠性的影响,着重说明了数据同步对差动保护的影响.指出由于存在电子式互感器的稳定性以及网络通讯可依赖性问题,目前数字化变电站继电保护系统在很大程度上仍沿用传统保护的设计思路,有待进行深入研究和突破.     

乙烯基-β-紫罗兰醇的合成

以氯乙烯和金属镁为原料,反应制得格氏试剂乙烯基氯化镁;再与β-紫罗兰酮发生加成反应得到合成维生素A的重要中间体乙烯基-β-紫罗兰醇。通过对反应条件和工艺的研究和优化,确定了最佳工艺条件为：金属镁与β-紫罗兰酮的摩尔比为1.3∶1.0,滴加β-紫罗兰酮的温度为0~5℃,在反应温度20~25℃时继续反应3~4h,得到乙烯基-β-紫罗兰醇的收率为98.0%,气相色谱（GC）分析含量为92.5%。该工艺条件得到了实验室放大的验证。     

The influence of oleic acid on the hydration and mechanical properties of portland cement

To investigate the effects of OA on the portland cement using oleic acid （OA） as grinding aid and the effects of OA on the portland cement, we characterized the different perfermances of the cement, discussed the characteristics of properties. The results reveal that the OA can reduce the water requirement of normal consistency. With the content of OA added, setting time was extended. The OA can significantly improve the rheological properties of cement-based materials, while the compressive strength decreases.     

宣城市小型农田水利工程建设与管理存在的问题

文章分析了当前宣城市小型农田水利建设与管理方面存在的主要问题,针对存在的问题提出了解决措施。     

警察身体素质训练课的改革研究

良好的身体素质是组成公安战斗力诸因素的重要物质基础。为了促使警察把身体素质训练作为终身锻炼的行为,在警察培训教学中教授学员切合公安实践需要简单实用的教学内容和训练方法,培养自我学习和锻炼的能力,是警察培训身体素质训练课应解决的问题。     

基于P89LPC935便携式智能电疗仪的设计

在医疗器械领域里,电疗器械有了较大的发展,但目前电疗治疗仪的一些不足之处使其很难得到推广使用。本论文介绍了目前电疗治疗仪现状与不足,据此研制了一种新型便携式智能电疗仪。该电疗仪采用电疗的机理,选用Philips公司的低功耗的P89LPC935单片机为控制核心,具有键盘扫描、数据显示和频率强度不断变化脉冲波形输出等功能。通过便携式智能电疗治疗仪的设计,探索出一条研制便携式智能医疗器械的思路,为开发其它理疗器械提供设计参考。