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排序方式: 共有977条查询结果,搜索用时 9 毫秒
1.
主要对各国3G许可证与使用技术标准的抽绑政策.各国对2G/3G网络漫游的管制规定。以及3G网络之间共享的种类及实施方式等方面做了详尽的讲解,并进行比较和分析。 相似文献
2.
近两年.IP电话又叫网络电话的发展受到全球的关注。随着宽带接入的发展,基于宽带接入提供的网络电话具有了更大的生命力。从宽带电话的经营模式出发,探究这类业务的出现时现有话音业务市场的影响,进而分析这类业务的发展前景。 相似文献
3.
A. K. Shuaibov A. I. Dashchenko I. V. Shevera A. A. General 《Technical Physics Letters》2003,29(12):1009-1010
We report on the optimized characteristics of a small-size bactericidal lamp pumped by transverse RF (f=1.76 MHz) discharge, operating on a system of the molecular emission bands of chlorine in a wavelength range of 195–310 nm.
The spectral characteristics of the plasma emission were measured and the intensity of chlorine emission bands were studied
as functions of the total pressure and partial composition of a helium-chlorine mixture. Oscillograms of the pumping current
and output radiation intensity were measured and the total output radiation power was determined. It is established that the
lamp radiates predominantly in a bactericidal wavelength interval on an electron-vibrational transition at 200 nm in Cl2** molecules. The optimum partial pressures of helium and chlorine are 100–300 and 90–120 Pa, respectively. The maximum output
power of UV emission from the side cylindrical surface of the lamp reached 10 W. The lamp can be used in photochemistry, ecology,
genetics, and medicine. 相似文献
4.
5.
Sascha Stanic Thomas Koch Klaus Schmid Simone Knaus Vasiliki-Maria Archodoulaki 《应用聚合物科学杂志》2021,138(28):50659
The influence of two peroxides (peroxydicarbonate/dilauroyl peroxide) with various concentrations (10–200 mmol/kg PP) and their effective opportunity to introduce long chain branched (LCB) were investigated. The dependence of a single and double extrusion step and the changes of the properties were studied. Experiments were carried out in a single screw extruder at 180°C for the first extrusion step (modification) and at 240°C for the second extrusion step (processing simulation). Melt flow rate and dynamic rheological properties were studied at a measuring temperature of 230°C. For the definitive determination of long chain branched polypropylene (LCB-PP) served the extensional rheology measurements. The mechanical properties were examined via tensile test and impact tensile test. Summarized, LCB (melt strength) could be observed via extensional rheology for all modified specimens and the mechanical properties were maintained or even improved for the modified samples. Particularly, samples containing dilauroyl peroxide display excellent mechanical properties in this study. 相似文献
6.
Guo Xianjian Beijing General Research lnstitute for Nonferrous Metals Beijing China 《中国有色金属学会会刊》1993,(1)
The process parameters for bath autogenous smelting of copper were selected based on dynamic analysis of the experimental data and calculation of the mathematical model. Selecting the slag composition of SiO_2/Fe=0.80 and CaO%=16. desulphur ratio less than 80 wt.-% in system. and the copper content of matte less than 60 wt.-%, it is able to limit Fe_3O_4 formation and obtain a high desulphurization. The critical oxygen content of the blast increased with decrease of the sulphur content of the concentrate and increase of copper contents of the matte. If the copper contents of the concentrate are respectively of 30 and 35 wt.-%, the critical oxygen contents of the blast will be 48 and 69 wt.-% respectively. The smelling rate increases linearly with the blast intensity. When the sulphur content of the concentrate is 30 wt.-%, the oxygen content of the blast 70 vol.-% and the copper content of the matte 60 wt.-%, a blast intensityy of 700 Nm~3/m~2·h results in a smeling rate of 48.81 t/m~2·d. 相似文献
7.
Basing on TGA (thermal gravimetric analysis) of thermal nitridation at l200, l250, l300℃, respectively,analysis of high temperature kinetics for nitridation of silicon monocrystal has been carried out. According tothe theory for kinetics of reaction of vapour with solid phase a nitridation kinetic model, from which it can beshown thal the rate of nitridation reaction of silicon crystal should be controlled by three stage limiting factors,was proposed. These limiting factors are chemical reaction, chemical reaction mixed with diffusion and diffu-sion. Using this model to treat our experimental data, satisfactory correlation coefficient and apparentactivation energy of nitridation of p-type (lll) silicon crystal have been obtained. The nitride film was identi'fied to be a-Si_3N_4 (Hexagonal, a=0.7758nm,c_o=0.5623nm) by X-ray diffraction analysis. Morphology ofthe nitride films formed in different nitridation duration was observed in both planar andcross-sectional viewsby SEM (scanning electron microscope). 相似文献
8.
Li Yichun General Research Institute For Non-ferrous Metals Beijing China Shao Wenzhu An Xiyun Harbin Institute of Technology Harbin China 《中国有色金属学会会刊》1993,(3)
The process of aging precipitation in SiC_p/6061 and Al_2O_3/6061 composites were investigated. Hardness testing, differential scanning calorimetry(DSC) and transmission electron microscopy were employed. Results showed that the precipitation phase form directly along dislocation lines in the composites because the particles produce high densities of dislocations which makes vacancy densities in the composites decrease, and the main precipitation phase at peak hardness was β′ phase. 相似文献
9.
本文以含高Al(Al76%,Si18.9%,Fe5.1%)的Al-Si-Fe合金为还原剂,在不同温度下进行热法还原Mg实验,测定了Mg的蒸气压为lgp_(Mg)=-8853/T+10.58.与用Si-Fe还原剂相比,在相同的p_(Mg)下,还原温度可下降约200℃。 用Bonnier法和本实验所测定的数据计算了Al-Si-Fe合金在不同温度下各组元的活度。结果表明,三元系中各组元活度均有负偏差,尤其Fe的偏差很大。另外,由以上所得的活度数据还计算了还原反应的平衡常数和热焓,分别为: lgK_[Al]=-18.40×10~4/T+117.2,ΔH=3529.5KJ 相似文献
10.
本文运用作者提出的从三个对应的二元系的热力学性质预示三元溶液的热力学性质的新对称几何模型,推导得到三元溶液中三个组元的偏摩尔热力学性质的数学表达式。进而将这一结果应用于NaCl-BaCl_2-SrCl_2三元熔盐相图的计算中,得到此三元系的液相析出面及若干等温截面。计算所得结果与实测结果偏差小于5℃,说明此模型在一些熔盐体系中有较好的适用性。 相似文献