环己酮肟液相重排反应机理及动力学研究

研究了环己酮肟重排反应生成己内酰胺的机理及反应动力学方程。在建立用分光光度法测定环己酮肟浓度方法的基础上,实验研究了反应温度为20~45℃范围内的液相重排反应动力学。提出了此反应的化学反应动力学速率方程式: -r肟= k0exp (-E/RT)Ca肟Cb硫酸,其中环己酮肟反应级数a为2,硫酸反应级数b为1,活化能为-E/R = -19.86 kJmol-1, 频率因子k0为1.35×1027。通过实验研究证实了作为催化剂的硫酸参与重排反应的机理,认为重排反应过程中游离SO3不参与反应,仅作为水的吸收剂,此结论对环己酮肟液相重排反应的生产技术改造提供了有力依据,并在生产中得到了应用。     

数据转换系统中放大器的选择

随着广播电视技术的不断发展 ,模拟信号传输向数字信号传输的转换已成为必然。介绍模数转换系统中放大器的性能、关键技术 ,并就放大器的选择作详细探讨。     

变频调速技术在济钢焦化厂高压氨水泵上的应用

济钢焦化厂高压氨水泵变频调速系统采用变频器和PLC相结合的方式 ,具有调速精度高、节能等多种功能 ,保证氨水泵正常工作。全年可增加经济效益 77.3万元。     

动态规划模型在生产存贮中的应用

利用动态规划模型研究了生产管理中生产存贮问题的数学模型，给出了动态规划的最优性原理和动态规划基本方程，并给出了该数学模型求解的一个实例。     

Image analysis of comet assay measurements

In the last decade the 'comet assay' or 'single cell gel electrophoresis assay' has been established as a sensitive method for the detection of DNA damage and the measurement of its recovery. The results published in the literature have often been obtained with different methods for comet structure measurement. In most cases these data are not comparable with each other. Even when using similar systems for the analysis, it is difficult to obtain matching data. This presentation will describe some technical aspects of our measurement equipment and evaluation software. It focuses on necessary experimental conditions to minimize errors in obtaining such data. The software developed here allows the rapid analysis of the microscopic samples (< 2 s per image). The image analysis was designed with respect to the morphological shapes of comet cells, which were investigated with a confocal laser microscope. The system is built with standard components which are commercially available. As a measure of the amount of DNA damage the ratio of fluorescence intensity was used inside the comet tail and the fluorescence intensity of the comet head. Other parameters such as DNA content, comet area, head radius, tail length and tail moment are also determined. The reproducibility of the system has been evaluated in several experiments over a period of 5 years.     

近期全国建材市场走势展望

结合当前我国建材市场的形势 ,就建材市场“涨价风潮”的起因 ,从经济增长的结果、市场运行的规律等方面进行了论述 ,提出了涨价风潮对近期全国建材市场的影响     

Microstructure of Pd_(77.5)Au_6Si_(16.5) Alloy Droplet Solidified in a Drop Tube Process

The microstructure development of Pd77.5Au6Si16.5 alloy droplet solidified in a drop tube process was studied. It was found that two distinct microstructures, i.e. (Pd,Au)3Si primary phase and Pd+(Pd,Au)3Si eutectic can be obtained when the droplet diameter is within the range between 2.3~0.4 mm. The morpologies of the (Pd,Au)3Si developed from dendrite trunk-like with single branching only into dendrite cluster-like with ternary branching with the decrease of the droplet diameter. When the droplet diameter is about 0.25 mm, the primary phase (Pd,Au)3Si almost disappears and the microstructure mainly shows Pd+(Pd,Au)3Si eutectic. The morphology of the eutectic transforms from fiber-like to plate-like with the decrease of the droplet diameter in the range between 2.3-0.25 mm. When the droplet diameter is about 0.19 mm, the microstructure is only the single phase of Pd solid solution     

TiO_2压敏陶瓷晶粒半导化

本文主要研究 TiO_2陶瓷晶粒半导化的途径及晶粒电阻率的测试方法。实验结果表明,通过掺入Nb_2O_5施主杂质可以有效地降低晶粒电阻率,并使 TiO_2系陶瓷具有良好的压敏特性。     

VITAMIN C AND β-CAROTENE IN FRESH AND FROZEN GREEN BEANS AND BROCCOLI IN A SIMULATED SYSTEM

The reduced ascorbic acid and β-carotene contents of “retail market-fresh” (RMF) and “fresh-frozen” (FF) green beans and broccoli in a simulated handling system were determined. Changes in ascorbic acid content in the two vegetables during a retail market period and frozen storage followed different patterns. In green beans, ascorbic acid content decreased during refrigerated storage for up to 7 days, but in broccoli there was a significant increase. Blanching resulted in a loss of approximately 40% of the ascorbic acid in broccoli. Ascorbic acid content of FF green beans stored at-20C for 16 weeks was approximately twice that in RMF green beans, but in FF broccoli stored under the same conditions it was only about half that of RMF broccoli. β-carotene content of green beans and broccoli did not change during either the retail market simulation of frozen storage and did not differ from that of fresh.     

Gate and drain currents in off-state buried-type p-channel LDDMOSFETs

The buried-type p-channel LDD MOSFETs biased at high positive gate voltage exhibit novel characteristics: (1) the ratio of the drain to gate currents is about 1×10^-3 to 5×10^-3; and (2) the gate and drain currents both are functions of only the gate voltage minus the n-well bias. Such characteristics are addressed based on the formation of the surface n ⁺ inversion layer due to the punchthrough of the buried channel to the underlying shallow p-n junction. The measured gate current is due to the Fowler-Nordheim tunneling of electrons from this inversion layer surface and the holes generated within the high-field oxide constitute the drain current. The n⁺ inversion layer surface potential is found to be equal to the n-well bias plus 0.55 V. As a result, both the oxide field and the gate and drain currents are independent of drain voltage