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1.
Two types of transparent Y2O3 ceramics without including large scattering sources such as residual pores, one with very high optical homogeneity (type A) and another one with slightly insufficient optical homogeneity (type B), are purposely prepared, and their optical properties are investigated and compared qualitatively and quantitatively. Type A ceramic exhibits transmittance characteristics with very low internal loss in the visible to infrared wavelength region, while type B ceramic is inferior in various optical performances especially in the short (visible) wavelength region. In type B ceramic, birefringence occurs due to optical inhomogeneity in the visible region, resulting in a decrease in the extinction ratio. Non-uniform refractive index distribution is also observed in the Schlieren image of type B ceramic, hence the laser beam quality through that material is degraded. This study proved the importance of optical homogeneity of transparent ceramics and clarified the problems in actual applications.  相似文献   
2.
Perovskite-type La0.7Ca0.3CrO3 composite oxides were synthesized by a combustion method. The calcining condition of the synthesized powders and sintering temperature of ceramic specimens were studied. It was found that a pure perovskite structure was direct acquired in the combustion ash and the fine morphology (~100 nm) was observed in the sample calcined at 600 °C. In view of the relative density, microstructure and electrical conducting properties of the sintering ceramics at different temperatures, the preferred sintering temperature was ascertained to be 1300 °C, at which the sample attains a high relative density of 96.8%, showing an electrical conductivity of 53.6 S cm?1 at 800 °C and much lower activation energy of 0.122 ev. Compared with La0.7Ca0.3CrO3 synthesized by the conventional solid state reaction method, that synthesized by the combustion method exhibits fine morphology and superior sintering activity, effectively lowering the sintering temperature and enhancing electrical conducting properties of the material.  相似文献   
3.
This paper aims to relax the results in Xie and Tian (2009) from the following two aspects: completely removing the power order restriction and largely relaxing the growth conditions of nonlinear functions. By using the backstepping design method and homogeneous domination technique, this paper investigates the problem of adaptive state-feedback stabilization for a class of stochastic high-order nonlinear systems with nonlinear parameterization. The closed-loop system can be proved to be globally stable in probability and the states can be regulated to the origin almost surely. The efficiency of the adaptive state-feedback controller is demonstrated by a simulation example.  相似文献   
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5.
Tao Li  Y.H. Chen  J. Ma 《Mechatronics》2009,19(4):520-528
The series and parallel bimorph actuators were investigated to identify the limiting factors at high voltage operations. In the static condition, the series and parallel bimorph exhibit polarization-shaped and three-looped hysteresis curve, respectively. The parallel bimorph shows much larger magnitude of saturated and remnant polarization than the series bimorph. The series bimorph is mainly restricted by the breakdown voltage in contrast to the parallel bimorph, which is limited by the domain reorientation. In the dynamic condition, both types of actuators are mainly limited by the maximum stress and domain reorientation. The actuator tends to fracture at the location of maximum stress near the resonance when the voltage is increased to a certain degree. Further increasing the voltage, domain reorientation may happen at frequencies lower than the resonance. Comparatively, the series bimorph has higher resistance to the domain reorientation than the parallel bimorph.  相似文献   
6.
Inulin fructotransferase (IFTase; EC 4.2.2.18) has received great attention mainly due to its application in producing difructose anhydride III (DFA III), which is a novel functional sweetener. The object of this study was to investigate the induction of IFTase in Arthrobacter aurescens SK 8.001 with various carbon sources, especially inulin and DFA III. IFTase production could be significantly promoted by the supplement of inulin (5–50 g/L) and DFA III (5–20 g/L). Inulin at high initial concentrations gave no indication of catabolite repression, whereas 30 and 40 g/L DFA III intensely inhibited cell growth and IFTase activity. No fructose was detected in broth throughout the cultivation with inulin, and inulin was converted into DFA III and minor fructooligosaccharides. And when DFA III was the carbon source, DFA III was the only sugar detected in the broth. In conclusion, both DFA III and inulin are effective for IFTase induction, and inulin with higher IFTase activity proved to be a more potent inducer.  相似文献   
7.
Simulatable certificateless two-party authenticated key agreement protocol   总被引:1,自引:0,他引:1  
Key agreement (KA) allows two or more users to negotiate a secret session key among them over an open network. Authenticated key agreement (AKA) is a KA protocol enhanced to prevent active attacks. AKA can be achieved using a public-key infrastructure (PKI) or identity-based cryptography. However, the former suffers from a heavy certificate management burden while the latter is subject to the so-called key escrow problem. Recently, certificateless cryptography was introduced to mitigate these limitations. In this paper, we first propose a security model for AKA protocols using certificateless cryptography. Following this model, we then propose a simulatable certificateless two-party AKA protocol. Security is proven under the standard computational Diffie-Hellman (CDH) and bilinear Diffie-Hellman (BDH) assumptions. Our protocol is efficient and practical, because it requires only one pairing operation and five multiplications by each party.  相似文献   
8.
The intrinsic microstructure and crystalline phases of porous SiC ceramics with 5 vol% AlN–RE2O3 (RE = Sc, Y, Lu) additives were characterized by high-resolution transmission microscopy with energy-dispersive spectroscopy and X-ray diffraction. The homophase (SiC/SiC) and heterophase (SiC/junction) boundaries were found to be clean; that is, amorphous films were not observed in the specimens. In addition, ScN, YN, and LuN were formed as secondary phases. The flexural strength and thermal conductivity of the ceramics were successfully tuned using different additive compositions. The flexural strength of the ceramics improved by a factor of ~3, from 11.7 MPa for the specimen containing Y2O3 to 34.2 MPa for that containing Sc2O3, owing to the formation of a wide necking area between SiC grains. For the same reason, the thermal conductivity improved by ~56%, from 9.2 W·m?1·K?1 for the specimen containing Lu2O3 to 14.4 W·m?1·K?1 for that containing Sc2O3.  相似文献   
9.
Three new coordination polymers, namely, {[Cd(H2bptc)(IP)(H2O)]·2H2O} n (1), {[Mn2(IP)2(dstc)]·6H2O} n (2) and {[Zn2(IP)2(dstc)]·3H2O} n (3) (IP = 1H-imidazo[4,5-f][1,10]-phenanthroline, H4bptc = 3,3′,4,4′-benzophenonetetracarboxylic acid, and H4dstc = 3,3′,4,4′-diphenylsulfonetetracarboxylic acid) have rationally designed and characterized by single crystal X-ray diffraction. Polymer 1 shows a 1D ribbon-like structure. Although compounds 2 and 3 feature 2D grid networks, the coordinative modes of dstc ligand and the arrangements of IP ligand are very different. Furthermore, the luminescence properties for 1 and 3, as well as the magnetism of 2 are explored in detail.  相似文献   
10.
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