温度场内尺度估算方法的研究

用三维超声风速计测量了合肥地区风速脉动和温度脉动数据,从Kolmogorov的4/5定律估算湍流动能耗散率ε,从Yaglom的4/3定律估算温度方差耗散率ε_θ,指出现有文献提供的公式不适合计算温度场的内尺度.提出了一种温度场内尺度计算公式,式中含有温度方差耗散率ε_θ,得到的内尺度大小正确反映了与_n^2强弱的对应关系.

散热结构拓扑优化目标函数的讨论

将几何平均温度作为最高温度的近似引入到散热结构拓扑优化中,建立了新的散热结构拓扑优化模型,采用伴随法推导了与该函数对应的灵敏度分析列式,并通过比较最高温度、最大温度梯度以及温度方差(衡量温度场均匀程度的指标)等特征指标来研究基于几何平均温度的优化模型与两个传统优化模型在散热结构拓扑优化设计中的差异以及各自适用的设计范围。

花岗岩单轴疲劳过程中热红外特征研究

利用热红外技术监测花岗岩试样单轴疲劳过程中的热红外热像演化、热红外温度变化以及温度方差随应力的响应特征。研究结果表明:(1)花岗岩试件破裂前会有明显的前兆信息,临空面有明显热像异常现象,热像异常出现位置与未来破裂处相吻合,热红外温度-时间曲线会出现异常转折性变化,热红外前兆出现先后顺序为:平均热红外温度>热红外热像;(2)低周多级循环荷载作用下,应力循环造成热红外温度方差的波动变化,应力等级越高,波动响应特征越显著。

Identification of structural entities in NdF_3-LiF melts with cryoscopic method

Nd-F species in NdF3-LiF melts were studied using cryoscopic method.Liquidus temperatures of melts of various compositions were determined by differential thermal analysis(DTA).Based on the different model calculations,NdF4- was identified as the most likely Nd-F entity in the melts in which the mole fraction of NdF3 was lower than 20%,considering only one single Nd species in the melt,and which was formed in accordance with Temkin model or Flood model.Then,activities of different components in the melts were researched.The results show that activity of LiF decreases,and that of NdF3 increases with increasing the mole fraction of NdF3.The value of activity coefficient of NdF3 is higher than 1,and that of LiF is lower than 1.

Evaluation and Preprocess of Chinese Fengyun-3A Sea Surface Temperature Experimental Product for Data Assimilation

Validated satellite-derived sea surface temperatures (SSTs) are widely used for climate monitoring and ocean data assimilation systems. In this study, the Fengyun-3A (FY-3A) SST experimental product is evaluated using Advanced Very High Resolution Radiometer (AVHRR)-merged and in situ SSTs. A comparison of AVHRR-merged SSTs reveals a negative bias of more than 2K in FY-3A SSTs in most of the tropical Pacific and low-latitude Indian and Atlantic Oceans. The error variance of FY-3A SSTs is estimated using three-way error analysis. FY-3A SSTs show regional error variance in global oceans with a maximum error variance of 2.2 K in the Pacific Ocean. In addition, a significant seasonal variation of error variance is present in FY-3A SSTs, which indicates that the quality of FY-3A SST could be improved by adjusting the parameters in the SST retrieval algorithm and by applying regional and seasonal algorithms, particularly in key areas such as the tropical Pacific Ocean. An objective analysis method is used to merge FY-3A SSTs with the drifter buoy data. The errors of FY-3A SSTs are decreased to-0.45K comparing with SST observations from GTSPP.

Numerical Simulation and Experimental Verification of Temperature Distribution of Piezoelectric Stack with Heating and Thermal Insulation Device

This paper discusses the temperature field distribution of piezoelectric stack with heating and thermal insulation device in cryogenic temperature environment. Firstly,the model of the piezoelectric damper is simplified and established by using partial-differential heat conduction equation. Secondly,the two-dimensional Du Fort-Frankel finite difference scheme is used to discretize the thermal conduction equation,and the numerical solution of the transient temperature field of piezoelectric stack driven by heating film at different positions is obtained by programming iteration. Then,the cryogenic temperature cabinet is used to simulate the low temperature environment to verify the numerical analysis results of the temperature field. Finally,the finite difference results are compared with the finite results and the experimental data in steady state and transient state,respectively. Comparison shows that the results of the finite difference method are basically consistent with the finite element and the experimental results,but the calculation time is shorter. The temperature field distribution results obtained by the finite difference method can verify the thermal insulation performance of the heating system and provide data basis for the temperature control of piezoelectric stack.

The REMO Ocean Data Assimilation System into HYCOM(RODAS_H):General Description and Preliminary Results

The first version of the Brazilian Oceano- graphic Modeling and Observation Network （REMO） ocean data assimilation system into the Hybrid Coordi- nate Ocean Model （HYCOM） （RODAS H） has recently been constructed for research and operational purposes. The system is based on a multivariate Ensemble Optimal Interpolation （EnOI） scheme and considers the high fre- quency variability of the model error co-variance matrix. The EnOl can assimilate sea surface temperature （SST）, satellite along-track and gridded sea level anomalies （SLA）, and vertical profiles of temperature （T） and salinity （S） from Argo. The first observing system experiment was carried out over the Atlantic Ocean （78°S-50°N, 100°W-20°E） with HYCOM forced with atmospheric reanalysis from 1 January to 30 June 2010. Five integra- tions were performed, including the control run without assimilation. In the other four, different observations were assimilated： SST only （A SST）; Argo T-S profiles only （AArgo）; along-track SLA only （A_SLA）; and all data employed in the previous runs （A_All）. The A_SST, A_Argo, and A_SLA runs were very effective in improv- ing the representation of the assimilated variables, but they had relatively little impact on the variables that were not assimilated. In particular, only the assimilation of S was able to reduce the deviation of S with respect to ob- servations. Overall, the A_All run produced a good analy- sis by reducing the deviation of SST, T, and S with respect to the control run by 39%, 18%, and 30%, respectively, and by increasing the correlation of SLA by 81%.

Thermophysical Properties of Channel Catfish at Freezing Temperatures

Freezing is the most common method used to preserve and minimize loss in quality of catfish during storage. Since freezing is a heat transfer process, the design and selection of freezing equipment require knowledge of thermophysical properties such as freezing temperature, enthalpy of freezing, unfreezable water and specific heat. Channel catfish thermophysical properties at freezing temperature were determined using differential scanning calorimetry. Using the combination of Raoult＇s law and Classius-Clapeyron equations, the amount of unfreezable （bound water） was estimated to be 0.129 g H20 g^-1 During freezing （or melting）, the specific heat increased from about 1.5 J g^-1 ℃^-1 to about 30.6 J g^-1 ℃^-1 It was found that freezing of catfish occur over a wide temperature range with the peak and incident freezing temperatures occurring at temperatures of-1.88 ℃ and -6.10 ℃, respectively. About 250 J g^-1 of heat have to be removed from catfish when it is to be frozen to -40 ℃. The implication is that any system that will be designed to freeze catfish must be able to remove 250 J g^-1 of heat.

海洋湍流对单光子捕获概率的影响

为了研究海洋湍流对单光子捕获概率的影响,基于模厄米高斯光束和Nikishov海洋湍流模型,根据Rytov近似和Kolmogorov谱,推导出了海洋湍流环境下的单光子捕获概率模型,并对不同海洋湍流参数对单光子捕获概率的影响进行了分析。结果表明:在传播百米后,海洋湍流环境下的单光子捕获概率下降明显;随着温度方差耗散率的增大,单光子捕获概率降低;当盐度因素主导海洋湍流时,单光子捕获概率也随盐度的增大而降低,盐度变化对海洋湍流环境下的单光子捕获概率的影响显著。增大接收机孔径值与缩短脉冲间隔可以有效提升单光子捕获概率,但温度方差耗散率的增加和传输距离的减少会降低脉冲间隔对单光子捕获概率的影响。

Does the variance of incubation temperatures always constitute a significant selective force for origin of reptilian viviparity？

To test the hypothesis that the variance of incubation temperature may have constituted a significant selective force for reptilian viviparity, we incubated eggs of the slender forest skink Scincella modesta in five thermally different natural nests and at two constant temperatures （18℃ and 21 ℃）. Our manipulation of incubation temperature had significant effects on incubation length and several hatchling traits （snout-vent length, tail length, fore-limb length, and sprint speed）, but not on hatching success and other hatchling traits examined （body mass, head size, and hind-limb length）. Incubation length was nonlinearly sensitive to temperature, but it was not correlated with the thermal variance when holding the thermal mean constant. The 18 ℃ treatment not only produced smaller sized hatchlings but also resulted in decreased sprint speed. Eggs in the nest with the greatest proportion of temperatures higher than 28 ℃ also produced smaller sized hatchlings. None of the hatchling traits examined was affected by the thermal variance. Thermal fluctuations did result in longer incubation times, but females would benefit little from maintaining stable body temperatures or selecting thermally stable nests in terms of the reduced incubation length. Our data show that the mean rather than the variance of temperatures has a key role in influencing incubation length and hatchling phenotypes, and thus do not support the hypothesis tested .

Influence of Temperature Difference Calculation Method on the Evaluation of Rankine Cycle Performance

In the new century, energy and environmental problems are becoming more critical, and the development of natural energy is desired. Low-grade Thermal Energy Conversion(LTEC) is refocused as one of the renewable energy methods. The usefulness of LTEC is expected using hot springs and waste heat. In the case of the Rankine cycle using ammonia as the working fluid, the thermal properties of the working fluid changes in the evaporator. The traditional evaluation method of heat exchanger performance is the LMTD(Logarithmic Mean Temperature Difference) method. On the other hand, the GMTD(Generalized Mean Temperature Difference) method allows the variation of thermal properties in the heat exchanger. The aim of this study is to compare the two methods for the calculation of temperature differences and the corresponding influence on the total performance of the Rankine cycle that is operated using ammonia as a working fluid. As a result, the thermal efficiency of the Rankine cycle is greater than that of the LMTD method. Moreover, the computable range of the GMTD calculation method is less than that of the LMTD calculation method.

Assessment of air temperatures from different meteorological reanalyses for the East Antarctic region between Zhongshan and Dome A

The accuracy of daily mean 2 meter air temperatures from five reanalyses are assessed against in-situ observations from Automatic Weather Stations in East Antarctica for 2005 to 2008. The five reanalyses all explain more than 70% of the average variance, and have annual root mean square errors （RMSE） between 3.4 and 6.9℃. The NOAA reanalyses, NCEP-1, NCEP-2 and 20CRv2, have cool biases of 2.5, 1.4 and 1.5℃, respectively. The ERA Interim and JCDAS reanalyses have warm biases of 1.7 and 2.0℃. All reanalyses generally perform better in the austral spring and worse in winter and autumn. They also show the best performance at an inland plateau site at 2800 m elevation, but are worst at Dome A, the summit of the East Antarctic ice sheet. In general, ERA Interim is superior to the other reanalyses, probably because of its 4D assimilation scheme. The three NOAA reanalyses perform worst; Their assimilation scheme is more constrained by limited observations and 20CRy2 has less input data, assimilating only surface pressure observations. Despite deficiencies and limitations, the reanalyses are still powerful tools for climate studies in the Antarctic region. However, more in-situ observations are required, especially from the vast interior of Antarctica.