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61.
Gert Schubring 《NTM》2003,11(2):90-99
Enno Heeren Dirksen (1788–1850) was one of several mathematicians originating from Eastern Frisia at the end of the eighteenth
century to acquire prominence in neohumanist reformed Prussia. While striving—like so many of his contemporaries—for more
rigour in the foundations of calculus, his work is significant due to his unusual emphasis on the semiotic aspects of the
basic concepts. As a clear-sighted propagator of Cauchy's conceptual innovations in Germany, his achievements in improving
sign expressions of such concepts enabled him to clarify hitherto not differentiated multiple limit processes—although less
successfully in constructive concept formation itself.
The contribution is based on the analysis of Dirksen's published texts and on the numerous texts which remained drafts for
his projected voluminousOrganon der gesamten Analysis.
Menso Folkerts zum 60. Geburtstag gewidmet 相似文献
Menso Folkerts zum 60. Geburtstag gewidmet 相似文献
62.
Yang Aiying Wang Ziyu Zhang Zhaoyi Chen Zhangyuan Wu Deming 《电子科学学刊(英文版)》2003,20(6):461-466
A 10Gbit/s recirculating system is configured with Chirped Fiber Bragg Grating (CFBG) for the dispersion compensation. For the first time, the transmission distance in the loop reaches 1000km with bit error rate of 10-9. The effect of the group delay ripple of the fiber grating is also investigated in the recirculating systems, and it is shown that the transmission distance is limited to 4 cycles (4×167.1km ) in the loop with the power penalty fluctuation below 1.0dB. Thus the group delay ripple should be reduced to allow for the wavelength drift of±5GHz. At the end of this letter, the principles are given for designing long haul recirculating systems with dispersion compensation CFBG. 相似文献
63.
Ferrite particles coated with biocompatible phases can be used for hyperthermia treatment of cancer. We have synthesized substituted
calcium hexaferrite, which is not stable on its own but is stabilized with small substitution of La. Hexaferrite of chemical
composition (CaO)0.75(La203)0.20(Fe2O3)6 was prepared using citrate gel method. Hydroxyapatite was prepared by precipitating it from aqueous solution of Ca(NO3)2 and (NH4)2HPO4 maintaining pH above 11. Four different methods were used for coating of hydroxyapatite on ferrite particles. SEM with EDX
and X-ray diffraction analysis shows clear evidence of coating of hydroxyapatite on ferrite particles. These coated ferrite
particles exhibited coercive field up to 2 kOe, which could be made useful for hysteresis heating in hyperthermia. Studies
by culturing BHK-21 cells and WBC over the samples show evidence of biocompatibility. SEM micrographs and cell counts give
clear indication of cell growth on the surface of the sample. Finally coated ferrite particle was implanted in Kasaulli mouse
to test its biocompatibility. The magnetic properties and biocompatibility studies show that these hydroxyapatite coated ferrites
could be useful for hyperthermia. 相似文献
64.
Chloride doped polyaniline conducting polymer films have been prepared in a protic acid medium (HCl) by potentiodynamic method
in an electrochemical cell and studied by cyclic voltammetry and FTIR techniques. The FTIR spectra confirmed Cl- ion doping in the polymers. The polymerization rate was found to increase with increasing concentration of aniline monomer.
But the films obtained at high monomer concentration were rough having a nonuniform flaky polyaniline distribution. Results
showed that the polymerization rate did not increase beyond a critical HCl concentration. Cyclic voltammetry suggested that,
the oxidation-reduction current increased with an increase in scan rate and that the undoped polyaniline films were not hygroscopic
whereas chloride doped polyaniline films were found to be highly hygroscopic. 相似文献
65.
集输系统热回水管线腐蚀分析 总被引:2,自引:0,他引:2
中国石油天然气股份有限公司华北分公司第三采油厂油气集输系统热回水管线普遍存在着腐蚀问题,影响原油生产和集输的正常运行。介绍了腐蚀较严重的13个站点的水质普查、水质结垢倾向和腐蚀性情况,并在水质分析的基础上进行了热水管线腐蚀因素的试验研究,确定腐蚀主要因素为水中的溶解氧含量高,从而造成腐蚀。 相似文献
66.
67.
为了提高现代网络信息传输的安全性,利用无理数小数点后数字的无穷性、无规律性、分布均匀性,提出一种全新的加密算法,并用它所产生的密钥流进行数字签名,实现身份验证不可抵赖、信息传输无篡改,确保信息传输的完整性、真实性,达到提高加密效率、相互认证的效果。 相似文献
68.
69.
钻井井喷失控井喷流出口速度预测方法研究 总被引:6,自引:0,他引:6
失控井喷流出口速度、喷口内压力、喷层产量都是井喷失控处理方案设计、作业施工中重要的基础数据。由于井喷失控井井口环境条件复杂,井喷失控后无法在井口安装测量仪表及在高速喷流中放入参照物,不能直接获取以上数据。文章利用地质、钻井过程获得的地层物性参数和气体动力学方程,探讨井喷失控井天然气喷流在不同井筒流动尺寸及组合的喷流速度预测模型,可应用薄剪切模型或RNG修正的k-ε模型定量描述速度场、温度场、浓度场颁。为井喷失控井处理方案设计、施工作业提供基础数据。 相似文献
70.
介绍如何利用AutoCAD开发适合电气专业使用的CAD系统,通过编制电气CAD的功能菜单,构造电气元件库,增强CAD的专业性能。编制电气CAD可以有效地统一本单位电气制图标准,方便电气工程师使用CAD进行专业设计。 相似文献