利用遥感SST反演上层海洋三维温度场

通过统计相关分析验证了一个简单的温度参数模型在太平洋海域的较好适用性。基于Argo观测资料及WOA09气候态温度数据,采用最大角度法求得此模型的相关参数,并利用高分辨率卫星遥感海表温度反演了太平洋上层海域空间分辨率为1°×1°的气候态月平均三维温度场。与实测资料的比较分析表明反演结果是较为真实可靠的,并可作为海洋数值模式积分的初猜场,为实现现场观测(如:Argo)与卫星观测的优势互补,构建太平洋海域完整的三维温度分析场提供一种新途径。

考虑器件工作温度影响的Si C功率MOSFET建模

提出一种基于MATLAB/Simulink的SiC功率MOSFET全工作区变温度参数建模方法。在Si基横向双扩散MOSFET模型的基础上,采用与温度相关的电流源和电压源补偿器件漏极电流和阈值电压的变化。通过补充实验拓展SiC功率MOSFET的饱和区工作特性曲线,并根据Si C功率MOSFET的工作特性,采用数学拟合的方法来提取模型参数。在保留各个参数物理意义的同时,摆脱建模过程对物理参数的依赖。在不同电压、电流及温度(25~200℃)的情况下对器件的输出特性、转移特性、阈值电压、导通电阻及开关损耗进行测试,将测试结果与MATLAB/Simulink模型仿真结果进行性比较。模型仿真结果与实际测试结果一致,开关损耗误差在7%之内,验证了模型的准确性及有效性,为实际应用Si C功率MOSFET时系统性能及损耗分析提供参考依据。

基于多源数据的黄河源区降雪比变化及其影响因素

黄河源区是黄河流域关键产流区域,对气候变化十分敏感。在气候变暖背景下,降水形态转变及其影响因素的研究依然不足。围绕这一重要科学问题,本研究基于地面气象站点观测和多源高分辨率气象数据集[China Meteorological Forcing Dataset(CMFD)、ECWMF ERA5-Land(ERA5-Land)、Multi-Source Weather(MSWX)],采用湿球温度参数化模型对1980—2015年黄河源区降水形态进行区分,并对降雪比长期变化趋势及其影响因素进行了综合研究。结果表明,1980—2015年黄河源区降水量整体呈增加趋势,降水形态向降雨转变,降雪量减少,平均降雪比呈显著下降趋势(P<0.05),四套数据源的降雪比平均下降速率为0.002 a^(-1)(P<0.05)。降雪比呈显著下降趋势(P<0.05)的格点占比分别为98.31%(ERA5-Land)、96.87%(MSWX)、67.62%(CMFD)。黄河源区中西部降雪比下降速率较快,下降速率最大的地区为玛多、达日等地。三套格点产品中CMFD能够较好地呈现降雪比变化趋势的空间差异,MSWX次之,而ERA5-Land降雪比变化趋势空间变异较小。源区降雪比与年平均气温、降水量相关性较高(P<0.05),相关系数r分别为-0.42和-0.48,亦受到西风的影响(r=-0.31,P=0.07)。研究结果有助于加深气候变暖对黄河源区水文气象过程影响的科学认识,为黄河流域区域水资源管理提供理论支撑。

Effect of wall temperature and random distribution of micro organic dust particles on their combustion parameters

The effect of wall temperature on the characteristics of random combustion of micro organic particles with recirculation was investigated. The effect of recirculating in micro-combustors is noticeable, hence it is necessary to present a model to describe the combustion process in these technologies. Recirculation phenomenon is evaluated by entering the exhausted heat from the post flam zone into the preheat zone. In this work, for modeling of random situation at the flame front, the source term in the equation of energy was modeled considering random situation for volatizing of particles in preheat zone. The comparison of obtained results from the proposed model by experimental data regards that the random model has a better agreement with experimental data than non-random model. Also, according to the results obtained by this model, wall temperature affects the amount of heat recirculation directly and higher values of wall temperature will lead to higher amounts of burning velocity and flame temperature.

Runaway Criterion in Fixed Bed Catalytic Reactors with Radial Temperature Profile

The discrepancy between pseudo-homogeneous one-dimensional model and pseudo-homogeneous two-dimensional model is studied. It is found that there are great differences between two models. This paper compares the maximum and minimum values of the radial temperature in the hot spot in case that a single exothermic reaction is carried out, a correlation is obtained with pseudo-homogeneous one-dimensional model to describe the entire reactor behavior. A new runaway criterion, based on the occurrence of inflection in the hot spot locus, is developed for the case of pseudo-homogeneous two-dimensional model. This criterion predicts the maximum allowable temperature for safe operation and the regions of runaway, respectively. The calculated results show that, compared with the results based on pseudo-homogeneous one-dimensional model, runaway will easily occur when the radial temperature gradient has to be considered.

Parameter estimation of cutting tool temperature nonlinear model using PSO algorithm

In cutting tool temperature experiment, a large number of related data could be available. In order to define the relationship among the experiment data, the nonlinear regressive curve of cutting tool temperature must be constructed based on the data. This paper proposes the Particle Swarm Optimization (PSO) algorithm for estimating the parameters such a curve. The PSO algorithm is an evolutional method based on a very simple concept. Comparison of PSO results with those of GA and LS methods showed that the PSO algorithm is more effective for estimating the parameters of the above curve.

核电用316H不锈钢的蠕变性能评估

通过对核电用316H不锈钢的蠕变数据分析,利用速率温度参数模型拟合得出材料蠕变本构方程。根据相关统计检验方法,确定了材料的蠕变可靠度函数。结合Z’参数的数据分布,分别得出316H不锈钢蠕变应力-RTP参数-可靠度曲线和温度-容许应力-可靠度曲线。结合ASME的评价规范,确定了316H不锈钢在550~700℃下的容许应力。结果表明,基于RMB’模型的蠕变本构方程在拟合精度方面优于其他传统模型。实测数据均位于蠕变可靠性模型预测结果的99.7%置信区间内。该模型可以较好地评估316H不锈钢的稳态蠕变性能及容许应力。