Abstract: A new kind of polymer dispersed liquid crystal (PDLC) films based on nematic liquid crystal E7 and pre-polymeric composition epoxy resin E51 were prepared by polymerization induced phase separation via heating curing in this paper. The electro-optical properties of PDLC films were affected by many processing factors, for example, the weight ratio of the pre-polymer and liquid crystal, the curing temperature, curing time and film thickness. The electro-optical properties of PDLCs fabricated under different conditions were tested. The performance parameters such as contrast ratio, threshold voltage and the saturation voltage were calculated. In our case, the optimal preparation condition was 65% liquid crystal content with a curing time of 6 hours at 65oC. The PDLC film prepared in this paper showed a threshold voltage of 14.11V and a saturation voltage of 49.47V. The effect of film thickness on the electro-optical properties of PDLCs had been analyzed as well. The threshold voltage and saturation voltage of PDLC increase as the film thickness increases as so as the contrast ratio.
Abstract: The higher order crack tip fields for an anti-plane crack in functionally graded piezoelectric materials (FGPMs) under mechanical and electrical loadings are studied. Different from previous analyses, all material properties of FGPMs are assumed to be linear functions of x parallel to the crack. The boundary conditions on crack surfaces are assumed to be the stress free and electrically impermeable. By using the eigen-expansion method, the problem is reduced to solving the system of ordinary differential equations. The higher order stress and electric displacement crack tip fields for FGPMs are obtained by solving the ordinary differential equations.
Abstract: The higher order crack-tip fields for an anti-plane crack situated in the interface between functionally graded piezoelectric materials (FGPMs) and homogeneous piezoelectric materials (HPMs) are presented. The mechanical and electrical properties of the FGPMs are assumed to be linear functions of y perpendicular to the crack. The crack surfaces are supposed to be insulated electrically. By using the method of eigen-expansion, the higher order stress and electric displacement crack tip fields for FGPMs and HPMs are obtained. The analytic expressions of the stress intensity factors and the electric displacement intensity factors are derived.
Abstract: Cadmium zinc telluride (CZT) material is one of the preferred materials for the fabrication of X-ray and gamma-ray detector. In this paper, it is presented an experimental detector system based on pixellated CZT semiconductor detector. The aim of this study is to get the photon energy suitable for different thickness detector, different photon energy acts on pixel CdZnTe detector of different thickness. We can obtain the energy spectrum estimation, energy resolution and peak efficiency by the experiment and simulation with the radiation source of 241Am and 137Cs acting on pixel CdZnTe detector. From experiment results, it can be found that at the high energy of 662keV the thicker CdZnTe detector is high. The characteristic of detector is better at the low energy when the detector thickness is thinner.
Abstract: Roadbed filling undergo at least one freeze-thaw cycle every year in seasonal frozen soil areas, which will lead subgrade to boiling, settlement, strength weakening etc. and has a strong impact on traffic safety and smooth, need to be solved urgently . In recent years, cement improved soil is applied to dissolve frost damage because it can be obtained locally, and has high performance and low price. However, how to evaluate strength of cement soil under repeated freeze-thaw cycles is the key to its further application in those regions. In the paper, the cement improved silty clay is selected as the object which is most common in Heilongjiang roadbed, many groups of freeze-thaw tests and direct shear tests are conducted at different conditions. From these tests, some conclusions about shear strength index and are obtained: 1. the first freeze-thaw cycle has important effect on cohesion of cement soil, during freeze-thaw cycle, the lower temperature is, the faster is decreasing. 2. decreases with freeze-thaw cycles increase, and there is a peak value existing after the seventh cycle, then reduce rapidly. 3. the internal friction angle appears decreasing – increasing–reducing– increasing trend during cycles but the range of change is little. 4. reduces smaller and increases more when temperature is lower.
Abstract: The collapsibility of loess ground can directly affect the stability of the subgrade. Therefore, How to adopt practical technical measures to reduce or eliminate its collapse deformation is an important content in foundation design in collapsible loess zone. Taking collapsible loess of the Liaoning Fuxin to Chaoyang highway as an example, the dispensing formula tests of cement were done. Mix cement in varying proportions with loess of different water content, then unconfined compression strengths of samples at four different ages were tested, and the relationship between improved soil strength and content of quick lime as well as ages was analyzed. The results indicate: 1) When the ages are certain, the strength of loess increases along with the mixture ratio increases, when the cement mixture ratio between 4%-14%, the scope of increases is quite obvious; 2) When the mixture ratio of specimens is certain, the intensity of test specimens increases along with the stadium increases, the intensity grows obviously in 28 days, and the growth rate is small in 28 to 90 days, the intensity will tend to be steady in the stadium of 90 days.
Abstract: The effect of constant-strain aged and unaged on microstructure, martensite transformation, Curie temperature and magnetic field induction strain of Ni53Mn23.5Ga23.5 ferromagnetic shape memory alloy was investigated in detail. The results show that reverse martensitic transformation temperatures of constant-strain aged sample slowly decrease, which martensitic transformation temperatures almost unchanged. In addition, Curie temperature of constant-strain aged sample is almost maintains consistent with solution-treated sample, but slowly increases saturation magnetization of constant-strain aged sample than solution-treated sample. Finally, the sample of constant-strain aged sample showed a larger magnetic field induction strain of 402 ppm.
Abstract: The NiCr-Cr3C2 coatings were deposited on 38CrMoAl substrate by a laser hybrid plasma spraying (LHPS) technology in this study. The coatings’ microstructures and anti-wear performances with different laser power were characterized using an optical microscope, a scanning electron microscope, and the SRV test. The test results indicated that the laser power has great effect on the microstructure and performances of the LHPS coatings. And when the laser power is at the appropriate value, it can make the coating have more compact and homogeneous microstructure, exhibit less pores or micro-cracks, and the higher bonding strength and more excellent anti-wear performance of the coating are achieved.
Abstract: In the concrete salt-soaking durability test, the dynamic elastic modulus of concrete is more sensitive to the concrete damage than the mass, and can reflect the concrete durability better. In this paper,the relative dynamic elastic modulus of concrete is used as the evaluation index of concrete durability. Its attenuation law is made the multiple linear regression by using MATLAB software. The evaluation model and its applicable conditions of the relative dynamic elastic modulus of air-entraining concrete under the action of the long-term salt immersion are obtained, which can be used to evaluate and precast the durable degree of air-entraining concrete in the salt environment.
Abstract: In order to understand the characteristics and flow characteristics of the low permeability carbonate reservoir of Middle East, in this paper, we take a Middle Eastern oil field as an example, using constant-rate mercury penetration technique, analyzing the micro pore structure characteristics of carbonate cores. The results show that, the pore radius distribution characteristics of different permeability is similar, mostly between 90-200μm, the peak occur at about 120μm. After that, we get the main factor affecting the reservoir physical quality of carbonate reservoir is throat rather than pore. And compared with the same permeability of sandstone cores, found that even if a poor sorting and strong heterogeneity of carbonate cores, but due to its throat contribution to permeability is very balanced, show the low permeability carbonate difficulty of development smaller than sandstone, only reducing the pore throat ratio, improve the ability of reservoir seepage, can have a good development effect.