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91.
92.
研究单位球面S^n 1中具有常平均曲率H的超曲面M^n,得到supRic≥2。并具体给出了当n≥3时。supRic=n-2可能出现的情况。 相似文献
93.
聚合所得初生聚乙烯的晶型伍青,张启兴,卢泽俭,王海华,欧阳巍,林尚安,张光华(中山大学高分子研究所,广州,510275)(中国科学院广州化学研究所)关键词聚乙烯,结晶,单斜晶,颗粒形态热力学稳定的聚乙烯晶型为正交晶系[1].当聚乙烯受一定应力作用时如... 相似文献
94.
A new type of macrocyclic polyethers has been synthesized. It consists of an azacrown ether as mother ring, e.g. 1,7-dioxa-4,10-diaza-cyclododecane (1a) or 1,7,10,16-tetraoxa-4,13-diazacycloocatadecane (1b), and two side chains attached on the two nitrogen atoms of 1a or 1b. A number of these new crown ethers are obtained by alkylation of the two secondary amino groups of 1a or 1b with corresponding halides, BrCH2(CH2OCH2)nCH2OR, in the presence of potassium carbonate. The crown-alkali metal complex thus obtained is hydrolyzed by acid. In order to obtain pure crown ether the reaction mixture is treated with tetramethylammonium hydroxide and followed by solvent extraction. The ability of complexing alkali cations of macrocyclic polyethers in terms of the equilibrium constant have been studied by the method of solubilities of salts in chloroform. It is shown that the size of the mother ring, the number of oxygen atoms either in the ring or in the side-chains, and the ionic radius of the alkali metal are the factors governing the stability of the metal complexes. Most of these new crown ethers possess high ability for alkali metal complexation some of them, such as N,N′- di-β-methoxyethyl-1,7-dioxa-4,10-diaza-cyclododecanc (13a), possesses higher selectivity for Na+ and K+ ions than 18-crown-6- and 4,4′(5′)-dimethylbenz-30-crown-10. 相似文献
95.
For toroidal topology we solve the shape equation for axisymmetric vesicles numerically. The phase diagram is found to be similar to that from another shape equation. This similarity is the result of the insensitive dependence of beading energy upon detailed shape of vesicles and the constant volume and area ensemble we are considering. We argue that the very small distance between two opposite cusps of the sickle-shaped vesicle makes it unstable and fuse into two encompassed spheres which might be observed in experiment. The spontaneous curvatures of the observed Clifford tori are also estimated. 相似文献
96.
The phenomenon of striation has been investigated experimentally in a macroscopic ac-plasma display panel (PDP). The relationship between the characteristics of striation and the operation conditions including voltage, frequency, rib, and electrode configuration, etc is obtained experimentally. The origin of the striations is considered to be the ionization waves in the transient positive column near the dielectric surface in the anode area during the discharge, and the perturbation is caused by resonance kinetic effects in inert gas. 相似文献
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99.
Study on the pre-chopper in CSNS LEBT 总被引:2,自引:0,他引:2
Physical designing of the pre-chopper in CSNS LEBT is carried out, which includes the deflecting voltage, the length and the width of the deflecting plates, and the gap between the deflecting plates. The most outstanding feature of the design is that both the gap and the width vary with the beam envelope size. So both the requried deflecting voltage and the loaded capacitance are lowered. In order to avoid destruction of the space charge neutralization by the pre-chopper in the whole LEBT, an electron-trapping electrode is arranged to confine the electrostatic field of the pre-chopper to the local area. To examine the reliability of the pre-chopping design in CSNS LEBT, a similar pre-chopping design in ADS RFQ LEBT is set up and an experiment on the pre-chopper is prepared. 3-dimensional simulations are carried out to determine the loaded capacitance and the applied voltage of the electron-trapping electrode. 相似文献
100.
Bulk工艺气体微网探测器的研究 总被引:1,自引:0,他引:1
In this paper, we present a study of a micromegas detector prototype built with bulk technology. Following a short discussion of the micromegas detector's structure and working mechanism, the bulk fabrication process is described, and some testing results of the prototype are presented. 相似文献