Heat capacity of γ-Fe2SiO4 between 5 and 303 K and derived thermodynamic properties     

Wenjun Yong  E. Dachs  A. C. Withers  E. J. Essene 《Physics and Chemistry of Minerals》2007,34(2):121-127

A multi-anvil device was used to synthesize 24 mg of pure γ-Fe₂SiO₄ crystals at 8.5 GPa and 1,273 K. The low-temperature heat capacity (C _p) of γ-Fe₂SiO₄ was measured between 5 and 303 K using the heat capacity option of a physical properties measurement system. The measured heat capacity data show a broad λ-transition at 11.8 K. The difference in the C _p between fayalite and γ-Fe₂SiO₄ is reduced as the temperature increases in the range of 50–300 K. The gap in C _p data between 300 and 350 K of γ-Fe₂SiO₄ is an impediment to calculation of a precise C _p equation above 298 K that can be used for phase equilibrium calculations at high temperatures and high pressures. The C _p and entropy of γ-Fe₂SiO₄ at standard temperature and pressure (S°₂₉₈) are 131.1 ± 0.6 and 140.2 ± 0.4 J mol⁻¹ K⁻¹, respectively. The Gibbs free energy at standard pressure and temperature (ΔG° _f,298) is calculated to be −1,369.3 ± 2.7 J mol⁻¹ based on the new entropy data. The phase boundary for the fayalite–γ-Fe₂SiO₄ transition at 298 K based on current thermodynamic data is located at 2.4 ± 0.6 GPa with a slope of 25.4 bars/K, consistent with extrapolated results of previous experimental studies.  相似文献   

广州市冬夏季热岛的空间格局及其差异分析     

王芳  卓莉  冯艳芬 《热带地理》2007,27(3):198-202

利用2003年夏季和冬季两景Landsat ETM图像的热红外波段反演了广州市地表温度(LST)的空间变化,并对冬季和夏季热岛空间分布特征的差异及成因进行了分析。结果表明,广州市冬季和夏季热岛的空间分布具有明显的规律性,并且空间分布、强度差异很大;夏季热岛集中区主要是建筑物和道路等非渗透表面组成地域以及人口最密集区域,冬季热岛的分布主要与工业区和运输业的分布相伴。引起这种差异的原因主要是城市能耗布局、下垫面性质、冬夏季生物学和热学特征综合作用的结果。  相似文献   

中—β尺度强对流风暴和暴雨数值模拟中的一些问题   总被引：1，自引：0，他引：1       下载免费PDF全文

程锐  潘晓滨等 《气象科学》2002,22(1):28-39

本文利用数值模拟方法探讨各环境背景因子对强对流及暴雨系统发生发展所起的作用，分析了暴雨和强对流风暴的形成机制。结果表明：温度场和湿度场的垂直分布，决定着对流是否可以形成；其水平非均匀性只是改变风暴发展强度、生命期以及分裂特性。风场的动力影响对强风暴的移动、分裂及强度特征也十分重要。最后，对第三运动方程做了量纲分析，发现热浮力是对流风暴发展的决定性因素；而热浮力冲量能更细致地反映对流风暴的发展演变特征。  相似文献   

A Simple Single-Layer Urban Canopy Model For Atmospheric Models: Comparison With Multi-Layer And Slab Models   总被引：26，自引：7，他引：26  

Hiroyuki Kusaka  Hiroaki Kondo  Yokihiro Kikegawa  Fujio Kimura 《Boundary-Layer Meteorology》2001,101(3):329-358

We developed a simple, single-layer urban canopy model, and comparedit to both multi-layer and slab models. Our single-layer model has thefollowing features: (a) It is a column model of energy and momentumexchange between an urban surface and the atmosphere, (b) it includesthe influence of street canyons, which are parameterized to representthe urban geometry, (c) it includes shadowing from buildings andreflection of radiation, and (d) it estimates both the surfacetemperatures of, and heat fluxes from, three surface types: roof, wall,and road. In the simulation of the single-layer model, the roof washottest during the daytime, but coolest from midnight to early morning.This is consistent with output from the multi-layer model and fieldobservations at a residential area on a clear, summer day. The diurnalvariation of the energy budget from the single-layer model agrees wellwith that from the multi-layer model. Our single-layer model'sperformance is nearly that of a multi-layer model for studyingmesoscale heat islands. Nevertheless, it is simply parameterized,and thus easily included in larger-scale atmospheric models. The slabmodel has the largest nighttime cooling rate of the three models. Toovercome this, it needs more adjustments than for the canopy models.  相似文献   

西风爆发时赤道西太平洋的热量平衡：个例分析     

Liu Hailong  Zhang Xuehong  Li Wei 《大气科学进展》2001,18(5):882-896

The responses of sea surface temperature (SST) in the western equatorial Pacific warm pool to the west erly wind bursts (WWBs) play an important role in the relationship between WWB and ENSO. By using da ta collected from eight buoys of TOGA (Tropical Ocean-Global Atmosphere)-COARE (Coupled Ocean-Atmosphere Response Experiment), the heat balances of the upper ocean in the western equatorial Pacific around 0°. 156°E during two WWB events were calculated according to Stevenson and Niiler＇s (1983) method. In both events, SST increased before and after the WWBs, while decreased within the WWBs. The SST amplitudes approximated to l℃. Although sometimes the horizontal heat advections may become the biggest term in the heat balance, the variation of SST was dominated by the surface heat flux. On the other aspect, some different features of the two events are also revealed. The two cases have different variation of mixed layer depth. The depth of mixed layer is almost double in the first case (35 m to 70 m), which is caused by Ekman convergence, while only 10m increments due to entrainment in the second one. There are also differences in the currents structure. The different variations of thermal and currents struc ture in the mixing layers accounted for the different variation of the heat balance during the two events, es pecially the advection and residue terms. The seasonal variation of SST in this area is also investigated sim ply. The first WWB event happened just during the seasonal transition. So we considered that it is a normal season transition rather than a so-called anomaly. That also suggested that the seasonal distinction of the WWB is worthy of more attention in the researches of its relationship to ENSO.  相似文献   

南京地区中暑天气条件指数研究预报   总被引：4，自引：1，他引：4  

焦艾彩  茅志成等 《气象科学》2001,21(2):246-252

本文采用南京地区1988－1997年每年夏季逐日各项气象要素及全市各医院同期重症中暑人数进行统计筛选出热夏年：1988年、1994年、1995年，对这三年中暑期重症中暑病例资料与气象资料进行相关统计分析，找出相关性较好的气象因子，经过方程化筛选，得出气温、湿度、气压、对中暑影响较大。三日滑动平均值为主要预报因子。设计中暑指数数学模式。根据中暑病病理、程度将中暑天气条件分三个等级，给出三个不同的中暑天气条件指数临界值，经过1998年、1999年试报验证，准确率较高，社会效益较好。该指数预测模式基本可行。  相似文献   

青藏高原地表热通量变化及其对初夏东亚大气环流的影响   总被引：25，自引：4，他引：25       下载免费PDF全文

董敏  朱文妹等 《应用气象学报》2001,12(4):458-468

应用NCEP地面热通量资料, 研究了青藏高原地面感热、潜热的气候状况及其与初夏东亚大气环流之间的关系。发现高原地面热通量的异常将影响高原地区上空的垂直运动与辐散辐合运动, 从而引起东亚地区高度场及风场的异常。同时, 青藏高原地区地面热通量与后期东亚地区的环流变化也有密切关系, 这种关系可为预测东亚地区初夏环流异常提供有意义的指标。  相似文献   

天然气水合物的地热研究进展   总被引：8，自引：0，他引：8  

金春爽  汪集晻 《地球科学进展》2001,16(4):540-543

天然气水合物的地热研究在以下几个方面都取得了重要进展，热流与似海底反射层的关系，水合物稳定带的研究；水合物热物理参数的确定；水合物形成过程中的热状态；热导率的应用，指出了今后水合物的地热学研究方向。  相似文献   

Climate induced temperature effects on growth performance, fecundity and recruitment in marine fish: developing a hypothesis for cause and effect relationships in Atlantic cod (Gadus morhua) and common eelpout (Zoarces viviparus)     

H. O. Prtner  B. Berdal  R. Blust  O. Brix  A. Colosimo  B. De Wachter  A. Giuliani  T. Johansen  T. Fischer  R. Knust  G. Lannig  G. Naevdal  A. Nedenes  G. Nyhammer  F. J. Sartoris  I. Serendero  P. Sirabella  S. Thorkildsen  M. Zakhartsev 《Continental Shelf Research》2001,21(18-19)

Effects of global warming on animal distribution and performance become visible in many marine ecosystems. The present study was designed to develop a concept for a cause and effect understanding with respect to temperature changes and to explain ecological findings based on physiological processes. The concept is based on a wide comparison of invertebrate and fish species with a special focus on recent data obtained in two model species of fish. These fish species are both characterized by northern and southern distribution limits in the North Atlantic: eelpout (Zoarces viviparus), as a typical non-migrating inhabitant of the coastal zone and the cod (Gadus morhua), as a typical inhabitant of the continental shelf with a high importance for fisheries.Mathematical modelling demonstrates a clear significant correlation between climate induced temperature fluctuations and the recruitment of cod stocks. Growth performance in cod is optimal at temperatures close to 10°C, regardless of the population investigated in a latitudinal cline. However, temperature specific growth rates decrease at higher latitudes. Also, fecundity is less in White Sea than in North and Baltic Sea cod or eelpout populations. These findings suggest that a cold-induced shift in energy budget occurs which is unfavorable for growth performance and fecundity. Thermal tolerance limits shift depending on latitude and are characterized by oxygen limitation at both low or high temperatures. Oxygen supply to tissues is optimized at low temperature by a shift in hemoglobin isoforms and oxygen binding properties to lower affinities and higher unloading potential. Protective stimulation of heat shock protein synthesis was not observed.According to a recent model of thermal tolerance the downward shift of tolerance limits during cold adaptation is associated with rising mitochondrial densities and, thus, aerobic capacity and performance in the cold, especially in eurythermal species. At the same time the costs of mitochondrial maintenance reflected by mitochondrial proton leakage should rise leaving a lower energy fraction for growth and reproduction. The preliminary conclusion can be drawn that warming will cause a northern shift of distribution limits for both species with a rise in growth performance and fecundity larger than expected from the Q₁₀ effect in the north and lower growth or even extinction of the species in the south. Such a shift may heavily affect fishing activities in the North Sea.  相似文献   

The heat capacity of two natural chlorite group minerals derived from differential scanning calorimetry     

C. Bertoldi  A. Benisek  L. Cemic✓  E. Dachs 《Physics and Chemistry of Minerals》2001,28(5):332-336

The heat capacity of natural chamosite (X_Fe=0.889) and clinochlore (X_Fe=0.116) were measured by differential scanning calorimetry (DSC). The samples were characterised by X-ray diffraction, microprobe analysis and Mössbauer spectroscopy. DSC measurements between 143 and 623?K were made following the procedure of Bosenick et?al. (1996). The fitted data for natural chamosite (CA) in J?mol^?1?K^?1 give: C _p,CA = 1224.3–10.685?×?10³?×?T ^??0.5???6.4389?× 10⁶?×T ^??2?+?8.0279?×?10⁸?×?T ^??3 and for the natural clinochlore (CE): C _p,CE = 1200.5–10.908?×?10³?×T ^??0.5?? 5.6941?×?10⁶?×?T ^??2?+?7.1166?×?10⁸?×?T ^??3. The corrected C _p-polynomial for pure end-member chamosite (Fe₅Al)[Si₃AlO₁₀](OH)₈ is C _p,CAcor = 1248.3–11.116?× 10³?×?T ^??0.5???5.1623?×?10⁶?×?T ^??2?+?7.1867?×?10⁸×T ^??3 and the corrected C _p-polynomial for pure end-member clinochlore (Mg₅Al)[Si₃AlO₁₀](OH)₈ is C _p,CEcor = 1191.3–10.665?×?10³?×?T ^??0.5???6.5136?×?10⁶?×?T ^??2?+ 7.7206?×?10⁸?×?T ^??3. The corrected C _p-polynomial for clinochlore is in excellent agreement with that in the internally consistent data sets of Berman (1988) and Holland and Powell (1998). The derived C _p-polynomial for chamosite (C _p,CAcor) leads to a 4.4% higher heat capacity, at 300?K, compared to that estimated by Holland and Powell (1998) based on a summation method. The corrected C _p-polynomial (C _p,CAcor) is, however, in excellent agreement with the computed C _p-polynomial given by Saccocia and Seyfried (1993), thus supporting the reliability of Berman and Brown's (1985) estimation method of heat capacities.  相似文献