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971.
Baolin Tan 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2007,39(12):1826-1830
The distributing profile of electric current in solar plasma loop is a key factor for the MHD instabilities of the loops. However, it is very difficult to measure such profile in single loop. In this paper, we assume that, in spite of the complexity of the structure in most of the sunspots, the distribution of the electric current in some small simple sunspots may reflect the main feature of the distribution in solar plasma loops. We utilize the high-cadence, high-resolution vector magnetograms observed by Big Bear Solar Observatory (BBSO) to derive the longitudinal electric current and analyze the distribution of the longitudinal electric current in the region of sunspots, and simulate the distributing features of the solar plasma loops. From these analysis, we find that the electric current in some small simple sunspots, or to say in plasma loops, are concentrated to their center. Such distribution feature is consistent with the theory of pinch effect in current-carrying plasma loops. 相似文献
972.
李峻 《西安航空技术高等专科学校学报》2007,25(4):31-32
随着服务业的迅猛发展,服务企业间的竞争日趋激烈,提供优质服务已成为企业管理者越来越重视的问题。通过从服务特点中的不可分离性入手,确立了“真实瞬间”的概念,并由此提出了服务性企业提高服务质量的对策。 相似文献
973.
介绍了多惯性仪表冗余惯性测量系统数据融合前的测量异常值去除、系统误差修正和一致性检验的基本方法。针对测量数据一致性检验,讨论了置信距离测度和信任度函数两种处理方法。仿真结果表明后者能更好地确定一致性的惯性仪表测量数据。 相似文献
974.
Electrochemical machining (ECM) is an effective and economical manufacturing method for machining hard-to-cut metal materials that are often used in the aerospace field. Cathode design is very complicated in ECM and is a core problem influencing machining accuracy, especially for complex profiles such as compressor blades in aero engines. A new cathode design method based on iterative correction of predicted profile errors in blade ECM is proposed in this paper. A math-ematical model is first built according to the ECM shaping law, and a simulation is then carried out using ANSYS software. A dynamic forming process is obtained and machining gap distributions at different stages are analyzed. Additionally, the simulation deviation between the prediction profile and model is improved by the new method through correcting the initial cathode profile. Further-more, validation experiments are conducted using cathodes designed before and after the simulation correction. Machining accuracy for the optimal cathode is improved markedly compared with that for the initial cathode. The experimental results illustrate the suitability of the new method and that it can also be applied to other complex engine components such as diffusers. 相似文献
975.
976.
R.N. Boroyev M.S. Vasiliev 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(1):348-354
In this work, the relation of high-latitude indices of geomagnetic activity (AE, Kp) with the rate of storm development and a solar wind electric field during the main phase of magnetic storm induced by the CIR and ICME events is investigated. 72 magnetic storms induced by CIR and ICME events have been selected. It is shown that for the CIR and ICME events the increase of average value of the Kp index (Kpaver) is observed with the growth of rate of storm development. The value of Kpaver index correlates with the magnitude of minimum value of Dst index (|Dstmin|) only for the ICME events. The analysis of average values of AE and Kp indices during the main phase of magnetic storm depending on the SW electric field has shown that for the CIR events, unlike the ICME events, the value of AEaver increases with the growth of average value of the electric field (Eswaver). The value of Kpaver correlates with the Eswaver only for the ICME events. The relation between geomagnetic indices and the maximum value of SW electric field (Eswmax) is weak. However, for the ICME events Kpaver correlates with Eswmax. 相似文献
977.
李峻 《西安航空技术高等专科学校学报》2007,25(4):31-32
随着服务业的迅猛发展,服务企业间的竞争日趋激烈,提供优质服务已成为企业管理者越来越重视的问题。通过从服务特点中的不可分离性入手,确立了“真实瞬间”的概念,并由此提出了服务性企业提高服务质量的对策。 相似文献
978.
This paper describes the end-to-end validation process for the Attitude Control Subsystem (ACS) of the satellite INTA-NanoSat-1B (NS-1B). This satellite was launched on July 2009 and it has been fully operative since then. The development of its ACS modules required an exhaustive integration and a system-level validation program. Some of the tests were centred on the validation of the drivers of sensors and actuators and were carried out over the flying model of the satellite. Others, more complex, constituted end-to-end tests where the concurrency of modules, the real-time control requirements and even the well-formedness of the telemetry data were verified. This work presents an incremental and highly automatised way for performing the ACS validation program based on two development suites and an end-to-end validation environment. The validation environment combines a Flat Satellite (FlatSat) configuration and a real-time emulator working in closed-loop. The FlatSat is built using the NS-1B Qualification Model (QM) hardware and it can run a complete version of the on-board software with the ACS modules fully integrated. The real-time emulator, running on an industrial PC, samples the actuation signals and emulates the sensors signals to close the control loop with the FlatSat. This validation environment constitutes a low-cost alternative to the classical three axes tilt table, with the advantage of being easily configured for working under specific orbit conditions, in accordance with any of the selected tests. The approach has been successfully applied to the NS-1B in order to verify different ACS modes under multiple orbit scenarios, providing an exhaustive coverage and reducing the risk of eventual errors during the satellite's lifetime. The strategy was applied also during the validation of the maintenance and reconfiguration procedures required once the satellite was launched. This paper describes in detail the complete ACS validation process that was performed and it shows the most relevant errors detected and fixed during testing. Finally it summarises some of the most significant conclusions. 相似文献
979.
丁叙生 《南昌航空工业学院学报》2000,14(3):26-29
本文介绍以主轴系统刚度与总功耗之比值最大比值最大为目标函数、主轴系统刚度的校验准则为主要约束条件的液体静压轴承优化设计方法,与普通设计方法相比,两种不同结构液体静压承经优化设计后,其单位总功耗的主轴系统刚度都成倍增加。 相似文献
980.
Solar Nebula Magnetohydrodynamics 总被引:1,自引:0,他引:1
The dynamical state of the solar nebula depends critically upon whether or not the gas is magnetically coupled. The presence
of a subthermal field will cause laminar flow to break down into turbulence. Magnetic coupling, in turn, depends upon the
ionization fraction of the gas. The inner most region of the nebula (≲0.1 AU) is magnetically well-coupled, as is the outermost
region (≳10 AU). The magnetic status of intermediate scales (∼1 AU) is less certain. It is plausible that there is a zone
adjacent to the inner disk in which turbulent heating self-consistently maintains the requisite ionization levels. But the
region adjacent to the active outer disk is likely to be magnetically ``dead.' Hall currents play a significant role in nebular
magnetohydrodynamics.
Though still occasionally argued in the literature, there is simply no evidence to support the once standard claim that differential
rotation in a Keplerian disk is prone to break down into shear turbulence by nonlinear instabilities. There is abundant evidence—numerical,
experimental, and analytic—in support of the stabilizing role of Coriolis forces. Hydrodynamical turbulence is almost certainly
not a source of enhanced turbulence in the solar nebula, or in any other astrophysical accretion disk.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献