弹性椭圆夹杂的线性温变问题

研究了线性温变作用下椭圆夹杂的热弹性问题。通过构造辅助函数 ,将复变函数的分区全纯函数理论 ,Riemann边值问题和Cauchy型积分相结合 ,求得各分区之间的解析关系 ,从而获得了无穷远均匀加载和线性温变共同作用下椭圆夹杂平面热弹性场的封闭形式解。从本文解答的特殊情况可直接得到已有的若干结果 ,并可得到一些具有实际意义的新结果。本文发展的分析方法 ,为求解复杂多连通域的平面热弹性问题提供了一条有效途径。

线性温变和点热源作用下椭圆夹杂问题中的温度函数

探讨了如何求解线性温变和点热源作用下椭圆夹杂问题的温度函数.通过将复变函数的分区全纯函数理论、Cauchy型积分和Riemann边值问题相结合,求得各分区之间的解析关系,获得了问题的温度场.

复合材料的三相圆形夹杂的线性温变场

探讨了如何求解线性温变下复合材料的三相圆形夹杂的温度场.通过将复变函数的分区全纯函数理论、Cauchy型积分和Riemann边值问题相结合,求得各分区之间的解析关系,获得了问题的温度场.

复合材料的椭圆夹杂模型线性温变问题的界面热应力分析

利用处理平面多连通域热弹性问题的一种有效方法 ,获得了椭圆夹杂模型线性温变问题的热弹性场解答 ,并讨论了夹杂和基体材料的热膨胀系数、热传导系数以及剪切模量对界面热应力的影响规律 ,所获得的结论为增强复合材料的设计与应用提供了有价值的参考依据。

Single-Stage Wide-Range CMOS VGA with Temperature Compensation and Linear-in-dB Gain Control

A novel wide-range CMOS variable gain amplifier （VGA） topology is presented. The proposed VGA is composed of a variable transconductor and a novel variable output resistor and can offer a high gain variation range of 80dB while using a single variable-gain stage. Temperature-compensation and decibel-linear gain characteristic are achieved by using a control circuit that provides a gain error lower than ±1.5dB over the full temperature and gain ranges. Realized in 0.25μm CMOS technology, a prototype of the proposed VGA provides a total gain range of 64.5dB with 55.6dB-linear range,a P-1dB varying from - 17.5 to 11.5dBm,and a 3dB-bandwith varying from 65 to 860MHz while dissipating 16.5mW from a 2.5V supply voltage.

Molecular dynamics study on temperature and strain rate dependences of mechanical tensile properties of ultrathin nickel nanowires

Based on the EAM potential, a molecular dynamics study on the tensile properties of ultrathin nickel nanowires in the （100〉 orientation with diameters of 3.94, 4.95 and 5.99 nm was presented at different temperatures and strain rates. The temperature and strain rate dependences of tensile properties were investigated. The simulation results show that the elastic modulus and the yield strength are gradually decreasing with the increase of temperature, while with the increase of the strain rate, the stress--strain curves fluctuate more intensely and the ultrathin nickel nanowires rupture at one smaller and smaller strain. At an ideal temperature of 0.01 K, the yield strength of the nanowires drops rapidly with the increase of strain rate, and at other temperatures the strain rate has a little influence on the elastic modulus and the yield strength. Finally, the effects of size on the tensile properties of ultrathin nickel nanowires were briefly discussed.

The Evolutionary Characteristics of the Temperature in Typical Counties in Southwest China——Taking Meitan County in Guizhou Province as an Example

Based on the method of linear trending,analysis was made upon the daily temperature statistics of Meitan County from 1951 to 2009,and the results showed that the temperature in general was on the rise.With 1980 as the turning point,it was on the decline before while later the temperature increased quickly.Among these figures,the variation rates of annual average temperature,annual maximum temperature,and annual minimum temperature are 0.11 ℃/10 a,0.08 ℃/10 a,and 0.36 ℃/10 a.The variation rates of average temperature in spring,summer,fall and winter are respectively 0.12 ℃/10 a,0.07 ℃/10 a,0.12 ℃/10 a,and 0.13 ℃/10 a.Morlet wavelet was adopted to analyze the periodicity of temperature change which has periods of different scales.But since 2000,during different time scales most of the areas have been in the period of temperature rises.Besides,certain rule exists in the periodicity of maximum temperature and minimum temperature.Before 1970s,they had opposite changing rules,and the alteration of the peak value occurred.However,in the late 1980s,they had similar changing rules,and their peak values appeared at the same time.It means that against the background of global warming,the reaction of temperature evolution in Meitan County is quite remarkable.

Statistically Downscaled Temperature Scenarios over China

Monthly mean temperatures at 562 stations in China are estimated using a statistical downscaling technique. The technique used is multiple linear regressions （MLRs） of principal components （PCs）. A stepwise screening procedure is used for selecting the skilful PCs as predictors used in the regression equation. The predictors include temperature at 850 hPa （7）, the combination of sea-level pressure and temperature at 850 hPa （P＋T） and the combination of geo-potential height and temperature at 850 hPa （H＋T）. The downscaling procedure is tested with the three predictors over three predictor domains. The optimum statistical model is obtained for each station and month by finding the predictor and predictor domain corresponding to the highest correlation. Finally, the optimum statistical downscaling models are applied to the Hadley Centre Coupled Model, version 3 （HadCM3） outputs under the Special Report on Emission Scenarios （SRES） A2 and B2 scenarios to construct local future temperature change scenarios for each station and month, The results show that （1） statistical downscaling produces less warming than the HadCM3 output itself; （2） the downscaled annual cycles of temperature differ from the HadCM3 output, but are similar to the observation; （3） the downscaled temperature scenarios show more warming in the north than in the south; （4） the downscaled temperature scenarios vary with emission scenarios, and the A2 scenario produces more warming than the B2, especially in the north of China.

Effect of Fluctuating Temperatures on Forest SoilNitrogen Mineralization

Nitrogen mineralization in forest soil was studied in laboratory by incubating undisturbed soil cores enclosed within PVC columns at different temperatures to compare the effect of fluctuating temperature with that of constant temperature, and to find out whether soil nitrification shows linearity over time. The results showed that there was no significant difference between soil nitrification at fluctuating temperature and that at constant temperature, and suggested that it must be careful to make the conclusion that soil nitrification has linearity over time.

Linear trends in mean and extreme temperature in Xiongan New Area, China

On 1 April 2017 China established Xiongan New Area in Hebei Province, which was described as ‘a strategy crucial for a millennium to come＇. A point of interest for the public is to be aware of the historical climate change in this new area; however, results from previous global-scale or largerregional-scale averages provide relatively limited information because of the distinct regional differences in climate change. This study analyzes the changes in mean and extreme temperature in this area, based on homogenized daily temperature data for the period 1960–2016. The results show a significant warming in the indices of annual, summer, and winter mean temperature（Tmean）, maximum temperature（Tmax）, and minimum temperature（Tmin）. The linear rate of annual Tmean is 0.34 °C/decade. Temperatures on the hottest day, the warmest night, the coldest day, and the coldest night, every year, all show increasing trends, with the trends in the two nighttime-related indices being significant. An increasing occurrence of warm days, warm nights, hot days, and tropical nights, but a decreasing occurrence of cold days, cold nights, icing days, and frost days, are found, all of which are significant, except for the occurrences of hot days and icing days. A significant extension of the length of the thermal growing season is also found. The magnitudes of change in most of the temperature indices in Xiongan New Area are larger than those of the adjacent Jing-Jin-Ji and North China regional mean. These results could provide valuable information for policymakers, city planners, engineers, and migrants to this new area.

Free Vibration of Geometrically Nonlinear Functionally Graded Micro-switches under Electrostatic Force and Temperature Change

The free vibration characteristics of functionally graded micro-switches under combined electrostatic, axial residual stress and temperature change is investigated, with an emphasis on the effect of geometric nonlinear deformation due to mid-plane stretching, the influence of volume fraction profile parameter and temperature change. The micro-switch considered in this study is made of either homogeneous material or non-homogeneous functionally graded material with two material phases. Taking the temperature-dependency of the effective material properties into consideration, the Voigt model is used to simulate the material properties of the FGMs （functionally graded materials）. The principle of virtual work is used to derive the nonlinear governing differential equation. The eigenvalue problem which describes free vibration of the micro-beam at its statically deflected state is then solved using DQM （differential quadrature method）. The natural frequencies of clamped-clamped micro-switches are obtained. The solutions are validated through direct comparisons with experimental results reported in previous studies. A parametric study is conducted to show the effects of geometric nonlinearity, material composition, temperature change and geometrical parameters for the natural frequencies.

Optimal nonlinear excitation of decadal variability of the North Atlantic thermohaline circulation

Nonlinear development of salinity perturbations in the Atlantic thermohaline circulation(THC) is investigated with a three-dimensional ocean circulation model,using the conditional nonlinear optimal perturbation method.The results show two types of optimal initial perturbations of sea surface salinity,one associated with freshwater and the other with salinity.Both types of perturbations excite decadal variability of the THC.Under the same amplitude of initial perturbation,the decadal variation induced by the freshwater perturbation is much stronger than that by the salinity perturbation,suggesting that the THC is more sensitive to freshwater than salinity perturbation.As the amplitude of initial perturbation increases,the decadal variations become stronger for both perturbations.For salinity perturbations,recovery time of the THC to return to steady state gradually saturates with increasing amplitude,whereas this recovery time increases remarkably for freshwater perturbations.A nonlinear(advective) feedback between density and velocity anomalies is proposed to explain these characteristics of decadal variability excitation.The results are consistent with previous ones from simple box models,and highlight the importance of nonlinear feedback in decadal THC variability.

Time-Dependent Nonlinear Forcing Singular Vector-Type Tendency Error of the Zebiak-Cane Model

Based on the Zebiak-Cane model, the timedependent nonlinear forcing singular vector （NFSV）-type tendency errors with components of 4 and 12 （denoted by NFSV-4 and NFSV-12） are calculated for predetermined El Nifio events and compared with the constant NFSV （denoted by NFSV-1） from their patterns and resultant prediction errors. Specifically, NFSV-1 has a zonal dipolar sea surface temperature anomaly （SSTA） pattern with negative anomalies in the equatorial eastern Pacific and positive anomalies in the equatorial central-western Pa- cific. Although the first few components in NFSV-4 and NFSV-12 present patterns similar to NFSV-1, they tend to extend their dipoles farther westward; meanwhile, the positive anomalies gradually cover much smaller regions with the lag times. In addition, the authors calculate the predic- tion errors caused by the three kinds of NFSVs, and the results indicate that the prediction error induced by NFSV-12 is the largest, followed by the NFSV-4. However, when compared with the prediction errors caused by random tendency errors, the NFSVs generate significantly larger prediction errors. It is therefore shown that the spatial structure of tendency errors is important for producing large prediction errors. Furthermore, in exploring the tendency errors that cause the largest prediction error for E1 Nifio events, the timedependent NFSV should be evaluated.

Model study of relationship between local temperature and artificial heat release

In recent decades,it presents a more obvious temperature rise in urban area along with the global warming.City is generally the center of human society,so the study on urban temperature variation will be helpful to our city development planning that is to reduce urban warming.The study is also helpful to a more comprehensive understanding of the causes of climate warming,which could provide a theoretical support to the government to make more reasonable international energy policies.Local temperature rise has different mechanisms with the global warming:large quantities of artificial heat release from the energy consumption will stay in urban areas for a period of time,which will inevitably influence the short-term trend of the local temperature change.Based on that view,a structural thermodynamic model was established in this paper to investigate the effect of the artificial heat release on the urban local temperatures.In the model,the city environment was divided into Human,Local,Outer three blocks,and then the heat and temperatures of the blocks were analyzed based on the laws of thermodynamics.After that,the effect of artificial heat release in Human block on the local temperatures was clarified.The model shows that the artificial heat release has an approximately linearly promoting effect on the local temperature rise,and the more the heat release is,the stronger the effect is.In addition,a validation of that model was carried out based on some national statistical data.The data of temperatures and artificial heat release of some provincial capitals of China were analyzed with linear regression extrapolation method and Pearson correlation statistical method.The results show that in most capital cities,the temperature variations basically depend on the artificial heat release in a linear relationship,which usually becomes more apparent with the increase of the artificial heat release in both spatial and temporal dimensions.The conclusions of the statistics have good conformity with the model and the rationality of the model is verified.