微带天线设计及在局部放电检测中的应用

电气设备的局部放电既是绝缘劣化的主要因素,又是有效表征绝缘缺陷的重要参量。对局部放电进行准确检测,可以及时发现危及设备安全的潜在故障。特高频检测具有实时性好、抗干扰强的优势,在放电检测中应用广泛,但现有微带天线传感器受结构尺寸限制,工作带宽难以提高。本文采用部分接地板技术结合斜切式曲流技术改善结构,综合考虑天线尺寸与工作带宽的非线性关系优化尺寸,在保持天线面积不变的前提下扩展工作带宽,并以聚酰亚胺为基底研制了新型微带天线传感器。针对尺寸优化过程中存在的单尺寸参数调整导致天线性能不稳定的问题,提出利用径向基(RBF)神经网络建立多尺寸与工作带宽之间的关系模型,运用改进白鲸优化(IBWO)算法优化天线尺寸。仿真结果表明新型柔性微带天线尺寸缩小了59.59%;工作带宽由0.598~0.6 GHz增加到0.3~3 GHz,完全满足局部放电检测的应用需求。通过模拟局部放电检测试验,并与阿基米德螺旋天线、立体螺旋天线进行比较测试,结果显示新型柔性微带天线具有更高效的检测性能。

天然气场站流量调节阀技术改造分析及应用

在天然气场站日常生产输气过程中利用流量调节阀对管道天然气进行流量控制,可以有效地完成下游用户企业的气量调配,保护相关的分输设备,并在一定程度上缓解峰谷差给天然气场站带来的压力。但在流量调节阀的选型上,轴流式与曲流式流量调节阀在日常生产实际中却表现出一定的差异。现根据湖北省天然气发展有限公司仙人渡接收站已完成的将场站部分曲流式流量调节阀更换为四川长仪的流量调节阀技术改造,列举了轴流型调节阀与曲流式调节阀的区别与联系,分别分析了轴流式调节阀与曲流式流量调节阀特点。

Reactor Network Synthesis Based on Instantaneous Objective Function Characteristic Curves

It is believed that whether the instantaneous objective function curves of plug-flow-reactor (PFR) and continuous-stirred-tank-reactor (CSTR) overlap or not, they have a consistent changing trend for complex reactions (steady state, isothermal and constant volume). As a result of the relation of the objective functions (selectivity or yield) to the instantaneous objective functions (instantaneous selectivity or instantaneous reaction rate), the optimal reactor network configuration can be determined according to the changing trend of the instantaneous objective function curves. Further, a recent partition strategy for the reactor network synthesis based on the instantaneous objective function characteristic curves is proposed by extending the attainable region partition strategy from the concentration space to the instantaneous objective function-unreacted fraction of key reactant space. In this paper, the instantaneous objective function is closed to be the instantaneous selectivity and several samples are examined to illustrate the proposed method. The comparison with the previous work indicates it is a very convenient and practical systematic tool of the reactor network synthesis and seems also promising for overcoming the dimension limit of the attainable region partition strategy in the concentration space.

Study on Inhibitionof Growth of ACHN Cells via shRNA Expression Vector-Mediated Cycline1 Gene Silencing

OBJECTIVE To explore the inhibition of ACHN cells via shRNAexpression vector mediated cyclinE1 gene silencing.METHODS The shRNA targeting at cyclinE1 gene was designedand synthesized. By ligation, the fragment was inserted intopGenesil-1-U6 to construct the recombinant plasmid pGenesil-1-U6-cyclinE1. The identified recombinant plasmid was introducedinto ACHN cells with lipofectamine 2000. The inhibition ofcyclinE1 mRNA and protein expression were analyzed by RT-PCRand western-blotting. MTT method was used for observing cellproliferation and drawing growth curve. The cell cycle and ratiosof apoptotic cell were assessed by flow cytometric detection. Theability of invasion and speed of cell migration were detected bytranswell chamber invasive models and cell scratch method.RESULTS The inhibition of expression of cyclinE1 in ACHN cellsmediated by recombinant vector (0.0933 ± 0.05) was significantlylower than that in the group of transfected with empty vector(0.8827 ± 0.04) and the control group (0.9021 ± 0.03) (P < 0.05).Flow cytometry showed that recombinant cells were blocked inthe G_1 phase and the apoptotic ratio was increased significantly(11.15 ± 4.00)% (P < 0.05). The curves of cell growth indicated thatthe proliferation of cell transfected with recombinant plasmid wasinhibited significantly compared with that in control group (P <0.05). The results of transwell and cell scratch suggested that theabilities of invasion and migration of the cells transfected withrecombinant plasmid were decreased conspicuously (P < 0.05).CONCLUSION The expression of cyclinE1 could be inhibitedsuccessfully by RNA interference induced by shRNA expressionvector. This consequently inhibits the cell growth and inducesapoptosis. Our study provided a preliminary result in searching ofRNA interference (RNAi) therapy for renal cell carcinoma.

Turbine efficiency test on a large hydraulic turbine unit

The flow rate measurements are the most difficult part of efficiency tests on prototype hydraulic turbines.Among the numerous flow rate measurement methods,the Winter Kennedy method is preferred for measuring turbine flow rates,since it is convenient,practical and economical.This paper describes efficiency tests on a large 300 MW Francis turbine,with the flow rate measured using the Winter Kennedy method and the Winter Kennedy flow rate coefficient calibrated using the Gibson method.The measured turbine efficiency curve is then compared with the curve provided by the manufacturer.The CFD calculations including the spiral case are then used to analyze the influence with the coefficient K and index n in the Winter Kennedy flow rate formula on the flow rate measurement.The uncertainty values of n and K are a key reason for the differences between the curves obtained from the efficiency test and the curves provided by the manufacturer.

HARMONIC FUNCTIONS ON A COMPLETE NONCOMPACT MANIFOLD WITH ASYMPTOTICALLY NONNEGATIVE CURVATURE

The authors prove the space of harmonic functions with polynomial growth of a fixed rate on a complete noncompact Riemannian manifold with asymptotically nonnegative curvature is finite dimensional.

Experimental study of heat-transfer coefficient of Al-Zn-Mg-Cu ultra-thick hot plate during multi-stage quenching

Experiments were conducted to investigate the cooling manner of an ultra-thick hot aluminum alloy plate during multistage quenching. Cooling curves and heat flux curves of different rapid quenching flux varied from 23 to 40 L min-1 and were analyzed in detail. In this investigation, cooling process was divided into the following four steps： （Ⅰ） starting step, （Ⅱ） rapid cooling step, （Ⅲ） slow cooling step, and （Ⅳ） stopping step. Based on the curves, the calculation method for surface transfer coefficient was provided, and the effects of coefficient on surface temperature and quenching flux were discussed. Results showed that the transfer coefficient disagreed with heat flux and that it is a nonlinear function of surface temperature. The highest coefficient was observed not in the rapid cooling step with the largest heat flux but in the slow cooling step with lower heat flux. The coefficient increased with surface temperature ranging from 480 to 150℃, and a coefficient peak appeared in the temperature range of 150- 100℃. The coefficient also increased with quenching flux. Finally, a simulation was performed using the finite element method to verify the reliability of the coefficient results, which showed good agreement with the measurement values.

On the Conditions of Extending Mean Curvature Flow

The authors consider a family of smooth immersions F（., t） ：M^n→R^n＋1 of closed hypersurfaces in R^n＋1 moving by the mean curvature flow F（p,t）/ t=-H（p,t）.v（p,t） for t E [0, T）. They show that if the norm of the second fundamental form is bounded above by some power of mean curvature and the certain subcritical quantities concerning the mean curvature integral are bounded, then the flow can extend past time T. The result is similar to that in [6-9].

Study on S-shaped characteristic of Francis reversible unit by on-site test and CFD simulation

The operation parameters （vibration, shaft displacement and pressure fluctuation） of No. 1 Francis reversible unit of Baoquan pumped-storage power station were measured on site in the no-load mode at net heads of 518.04, 522.01 and 530.38 m, re- spectively. The rotational speed fluctuations in the no-load mode at three net heads were beyond synchronization requirement with obvious S-shaped characteristic, and misaligned guide vanes （MGV） had to be put into use for synchronization. Further analysis demonstrated that the rotating frequency signal was generally dominant in vibration and shaft displacement mixing signal in the no-load mode, while the frequency domain was wide without an obvious main frequency in pressure fluctuation mixing signal. Besides, the SSTκ-ω turbulence model was adopted to simulate the four quadrant characteristic curves of Baoquan model pump-turbine at three gate openings, and the relative error between simulation results and model test data was within ±6%, indicating that the simulation method in this paper is feasible and S-shaped characteristic of the pump-turbine can be simulated with CFD method.

Curvature identities on almost Hermitian manifolds and applications

We systematically derive the Bianchi identities for the canonical connection on an almost Hermitian manifold.Moreover,we also compute the curvature tensor of the Levi-Civita connection on almost Hermitian manifolds in terms of curvature and torsion of the canonical connection.As applications of the curvature identities,we obtain some results about the integrability of quasi K¨ahler manifolds and nearly K¨ahler manifolds.

Variational formulas of higher order mean curvatures

In this paper, we establish the first variational formula and its Euler-Lagrange equation for the total 2p-th mean curvature functional .M2p of a submanifold Mn in a general Riemannian manifold gn^n＋m for p = 0, 1,..., [n/2]. As an example, we prove that closed complex submanifolds in complex projective spaces are critical points of the functional M2p, called relatively 2p-minimal submanifolds, for all p. At last, we discuss the relations between relatively 2p-minimal submanifoIds and austere submanifolds in real space forms, as well as a special variational problem.

Pressure Wave and Fluid Velocity in a Bend-Mode Inkjet Nozzle with Double PZT Actuators

A new concept of bend-mode inkjet nozzle with double PZT (lead zirconate titanate) actuators has been designed and fabricated in the present study. Then the pressure wave and fluid velocity at the nozzle exit have been investigated. The complex pressure behavior inside the channel was solved numerically based on the narrow channel acoustic theory. The two PZTs attached to a rectangular channel were actuated sequentially by setting the waveforms of each PZT to be center-aligned with various pulse widths. As a result, the double PZT actuation is superior to the single PZT actuation in view of strong momentum force and fast dissipation of residual pressure. The maximum fluid velocity at the nozzle exit is observed when the respective pulse widths equal to their optimum pulse widths. The numerical results are supported by the experimental results with the fabricated inkjet device by measuring the speed of meniscus just out of the nozzle.

Equivalent and Nonequivalent Barotropic Modes for Rotating Stratified Flows

All the possible equivalent barotropic (EB) laminar solutions are firstly explored,and all the possible non-EB elliptic circulations and hyperbolic laminar modes of rotating stratified fluids are discovered in this paper.The EB circulations (including the vortex streets and hurricane like vortices) possess rich structures,because either the arbitrary solutions of arbitrary nonlinear Poisson equations can be used or an arbitrary two-dimensional stream function is revealed which may be broadly applied in atmospheric and oceanic dynamics,plasma physics,astrophysics and so on.The discovery of the non-EB modes disproves a known conjecture.