一种智能型全自动太阳跟踪装置的机械设计

该文介绍了一种智能型全自动太阳跟踪装置机械结构的设计、机械原理，并对定位系统的工作过程和遮光装置的设计进行了详细的描述。该仪器可用于太阳直接辐射、总辐射、散射辐射和长波辐射的测量，在现有结构的基础上，改进设计就可作为日照测量的标准仪器。     

An ultra-wideband antenna for the reinforced concrete detection

In this paper, an Ultra-Wideband （UWB） planar antenna is proposed for the reinforced concrete detection, which consists of a pair of planar waterdrop arms, a microstrip to coplanar par- allel-strips transition and a shallow rectangular cavity. In order to overcome the disadvantages of the shallow cavity, some absorbing material is loaded to weaken the narrow-band effect of the cavity and the crosstalk interference. The simulated and measured results show that the proposed antenna has a large bandwidth from 0.48 GHz to 3.6 GHz with Voltage Standing Wave Ratio （VSWR） below 2 and a fractional bandwidth about 200% under the center frequency of 1.6 GHz, directional radiation char- acteristics and small late-time ringing in the time domain, which can be suitable for nondestructive detection of the reinforced concrete.     

Predictive model of superplastic properties of aluminum bronze and of the superplastic extrusion test

The superplastic properties of aluminum bronze were studied by way of artificial neural network. The model was established using Levenberg–Marquardt algorithm. It was improved by studying superplastic tension test data of aluminum bronze such that the superplastic forming parameters were optimized. According to the parameters, the experiment of superplastic extrusion of a solid bearing was performed. It is shown that the model reflected well the relationship between superplastic properties of aluminum bronze and superplastic tension conditions. The relative error between the test values and the predicted values of the network is less than 8.5%, which meets perfectly the demands of superplastic deformation of aluminum bronze. Moreover, the superplastic forming of solid cage of aluminum bronze show that it is feasible to produce solid cage using superplastic extrusion process. This extrusion process has remarkable economic benefits as well.     

配电系统开关优化配置的混合整数线性规划模型

配电系统中的开关设备可以有效提高系统的运行可靠性,而开关的种类以及安装的位置对配电系统运行可靠性的影响有所不同。在此背景下,研究了计及可靠性的配电系统中开关优化配置策略。首先介绍了在不同预想故障条件下用户停电时间的计算方法。之后构建了以开关投资费用、运行维修费用和用户停电损失费用之和最小,以可靠性指标在给定阈值内为约束条件的开关优化配置模型。通过对用户停电损失函数线性化处理,将所提出的模型转换为混合整数线性模型,并通过高效商业求解器进行求解。最后,对IEEE RBTS-Bus 4系统和某实际中压配电系统进行测试分析,算例结果说明了所提出的模型与求解方法的基本特征。     

SiC/Si-W-Mo coating for protection of C/C composites at 1873 K

In order to prevent carbon/carbon composites from oxidation at 1873 K, an efficient oxidation protective SiC/Si-W-Mo coating was prepared by a two-step pack cementation technique. The microstructures and the phase composition of the as-received multi-coating were examined by scanning electron microscopy （SEM） and X-ray diffraction （XRD）. It is seen that the compact multi-coating is composed of α-SiC, Si, and （WxMO1-x）Si2. Oxidation test shows that, after oxidation at 1873 K in air for 102 h and thermal cycling between 1873 K and room temperature for 10 times, the weight loss of the SiC/Si-W-Mo coated C/C composites is only 0.26%. The invalidation of the multi-coating is attributed to the formation of penetrable cracks in the coating. 2008 University of Science and Technology Beijing. All rights reserved.     

Silicon assistant carbothermal reduction for SiC powders

The silicon assistant method to increase the reaction yield of carbothermal reduction of silica at a lower temperature is reported. The effect of silicon on the carbothermal reduction process has been investigated in detail. Compared with traditional reduction, the introduction of silicon can change the reaction path and further increase the conversion of silicon carbide at a lower temperature. It is considered that the assistant reduction consists of three steps: vaporizing and melting of silicon, formation of silicon monoxide, and synthesis of silicon carbide. The morphology of the synthesized SiC powders through the silicon assistant method can be affected apparently by the experimental temperature.     

A duplex coating composed of electrophoretic deposited graphene oxide inner-layer and electrodeposited graphene oxide/Mg substituted hydroxyapatite outer-layer on carbon/carbon composites for biomedical application

A duplex coating composed of electrophoretic deposited graphene oxide (GO) inner-layer and electrodeposited GO/Mg substituted hydroxyapatite (MH) outer-layer was prepared on carbon/carbon composites (CC). The morphology and microstructure of GO-GO/MH coating were researched by Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy. The bonding strength between GO-GO/MH coating and CC substrate was investigated by shear test. The in-vitro bioactivity of GO-GO/MH coating was analyzed by simulated body fluid (SBF) immersion test. The results demonstrated that electrophoretic deposited GO inner-layer was successfully introduced on CC and could serve as an interlayer between CC and following electrodeposited GO/MH outer-layer. GO/MH outer-layer presented a flake morphology with 150–250?nm in thickness and 1.5–2.5?µm in width, exhibiting porous three-dimensional networks structure uniformly. The shear test showed that the bonding strength between the duplex coating and CC reached 7.4?MPa, which was 80.49% higher than that of single-layered MH coating without GO. The duplex coating could induce the formation of flocculent and chapped apatite after SBF immersion, which demonstrated the in-vitro bioactivity of the duplex coating. These results suggested that GO-GO/MH coating might be a promising candidate in the field of biomaterials, especially for implant coatings.     

气相色谱/质谱联用分析液体推进剂偏二甲肼组分

采用气相色谱 /质谱法分析液体推进剂偏二甲肼所含组分 ,研究组分的色谱保留性质 ,质谱裂解规律 ,并分析了各组分对推进剂比推力的影响。结果表明 ,液体推进剂偏二甲肼中含有水、偏腙、二甲胺和乙醛二甲基腙等杂质 ,除二甲胺外 ,其余组分可降低推进剂的比推力。     

A dielectrophoretic barrier-based microsystem for separation of microparticles

This paper presents a microfluidic system for separation of microparticles based on the use of dielectrophoretic barriers, which are constructed by aligning two layers of microelectrode structure face-to-face on the top and bottom sides of the microchannel. The energized barriers tend to prevent the particles in the flow from passing through. However, particles may penetrate the barriers if a sufficiently high flow rate is used. The flow velocity at which the particles begin to penetrate the barrier is defined as threshold velocity. Different particles are of different threshold velocities so that they can be separated. In this paper, the electrodes are configured with open ends and aligned with a certain angle to the direction of the flow. Polystyrene microbeads of different sizes (i.e., 9.6 and 16 μm in diameter) are studied in the tests. Under the experimental conditions, two particle trajectories are observed: the 9.6 μm beads penetrate the barriers and move straightly toward the fluidic outlet, while the 16 μm beads snake their way along the electrode edges at a relatively low speed. The two subpopulations of particles are separated into spatial distance of ∼10 mm within tens of seconds. The system presents a rapid and dynamic separation process within a continuous flow.