黄土高原地表能量不闭合度与垂直感热平流的关系

地表能量不平衡问题一直是陆面过程研究的一个重要科学难题.本文利用在陇中黄土高原观测的陆面过程资料,分析了气候地表能量不闭合度和短期地表能量不闭合度的分布特征,研究了地表能量不闭合度与垂直速度之间的关系,发现地表能量不闭合与垂直速度具有很好的相关性.并且,估算了近地层垂直感热平流通量,分析了考虑垂直感热平流后的地表能量平衡的特征,发现引入垂直感热平流输送对地表能量不闭合度有明显的改进.关键词：黄土高原非均匀性垂直感热平流能量不闭合度     

黄土高原区域气候暖干化对地表能量交换特征的影响

本文将观测试验资料与陆面过程模式模拟资料相结合, 对目前4个流行的陆面过程模式的模拟资料进行了验证分析, 发现通用陆面模式(CLM)模式的模拟资料在黄土高原地区比较可靠. 在此基础上,利用近几十年CLM模式模拟资料和气象站观测资料, 分析了黄土高原地区的区域气候和地表能量交换特征的变化规律, 研究了该地区地表能量交换对降水和温度变化的响应特征, 讨论了该地区气候变化对地表能量交换特征的影响机理. 研究发现,近几十年来黄土高原区域气候表现为明显的暖干化趋势, 从而引起太阳总辐射、地表反射辐射和地表长波向上辐射的增加 及地表长波向下辐射的减小,并由此造成地表净辐射通量减少. 与之相对应,不仅地表潜热通量呈减小趋势,而且地表感热通量和土壤热通量也呈减小趋势, 但地表热量分量的分配比例基本不变.并且发现,地表感热通量的年变化主要由太阳辐射控制, 而潜热通量的年变化则受太阳辐射和降水共同影响;地表热量分量的年际变化均对降水变化响应很敏感, 而对温度变化响应不太敏感,气候干旱化对地表能量平衡的影响比气温变暖的影响更突出.关键词：黄土高原区域气候暖干化陆面过程模拟陆面能量交换     

空气热储存、光合作用和土壤垂直水分运动对黄土高原地表能量平衡的影响

地表能量不平衡问题一直是陆面过程研究的一个重要科学难题. 本文利用黄土高原陆面过程试验(LOPEX)资料, 在将垂直感热平流项引入地表能量平衡方程的基础上, 估算了空气热储存和光合作用储存的大小, 并分别用水分守恒关系和两层土壤温度方法计算了浅层土壤水分垂直通量, 考察了空气热储存、光合作用储存和水分垂直运动热量输送对地表能量平衡的影响.结果表明: 黄土高原区自然植被下垫面的空气热储存、光合作用储存和土壤水分垂直运动热量输送平均日变化峰值分别达到1.5, 2.0和7.9 W·m^-2; 在能量平衡方程中引入这三项后, 地表能量闭合度由88.1%提高到89.6%. 空气热储存、光合作用储存和水分垂直运动热量输送对于改善黄土高原地表能量不平衡状况有一定作用, 研究区域的半干旱气候背景和植被状况是导致各热储存量与其他试验区存在差异的根本原因.     

黄土高原地表能量平衡分量年际变化及其对气候波动的响应

本文利用兰州大学半干旱气候与环境观测站(SACOL站)2006—2012年陆面过程观测资料和榆中站气象资料,分析了7年间榆中气温降水的气候变化背景,讨论了陆面地表能量平衡分量的年际变化,研究了波文比、能量闭合度的年际波动,探讨了地表能量平衡分量以及各陆面过程参数对黄土高原气温、降水年际波动的反馈.结果显示,地表各能量分量都对气候背景的波动做出响应,但敏感性各有不同,净辐射与气温相关性最强,感热潜热与降水相关性较好.分为冬夏半年讨论后得出,冬半年地表平衡分量与气候波动的相关性更好.冬半年中,各分量又与气温有着较高的相关,可见该地区地表能量各分量对冬半年气温波动的响应更为敏感.波文比的上升趋势与该地区降水量减少的背景响应,说明干旱程度的加深.能量闭合度的波动变化显示了在气候变化的背景下该地区陆面能量不闭合程度的加深.     

黄土高原半干旱区露水形成的大气物理特征研究

运用2009年在黄土高原典型半干旱区定西的观测资料,分析了半干旱区露水变化特征及其大气影响因子.研究结果表明:在黄土高原半干旱区秋季,日最大凝结量可以达到0.33 mm,最小日凝结量0.09 mm,日平均凝结量为0.23 mm,这对半干旱区而言是可观的水分输入;露水凝结持续时间可以长达14 h.露水的出现频率与风速、大气相对湿度、气温、地-气温差等大气影响因子有显著关系.露水的形成机理十分复杂,是湿度因子、热力因子和动力因子综合作用的结果.在露水形成过程中,大气湿度是内因,为露水形成提供所需水汽;温度则是露水形成的关键,为露水形成提供\"源动力\",而风速则是重要的外部影响因素,既可以促进露水形成,也可以阻碍露水形成,是露水形成过程中不确定因子.从露水发生频率的分布特征来看,在风速0.5—2 m/s、相对湿度>80%及温度-露点差-3—6℃时、地-气温差<±2℃条件下更易形成露水.关键词：黄土高原半干旱区露水形成大气影响因子发生频率     

同步加速器中束流能量的修正

叙述了同步加速器中束流能量测量和修正的原理,推导出关于闭合轨道畸变和校正二极子强度的束流能量的修正公式,介绍了这些公式在北京正负电子对撞机（BEPC）上的应用,并对其结果进行了讨论．     

同步加速器中束流能量的修正

叙述了同步加速器中束流能量测量和修正的原理,推导出关于闭合轨道畸变和校正二极子强度的束流能量的修正公式,介绍了这些公式在北京正负电子对撞机(BEPC)上的应用,并对其结果进行了讨论.     

能量修正的Glauber模型对中能反应总截面的影响

叙述了对Glauber模型中的透射系数进行半经验的能量修正,并利用该修正模型计算了^12—14C,⁶Li,⁷Be,⁸B+¹²C和⁶Li,⁷Be,⁸B+⁹Be以及²⁰Ne+¹²C,¹²C+²⁷Al等系统的激发函数(能区范围10—1000MeV/u),经与实验值比较,能量修正的Glauber理论计算值能够很好地描述中能条件下的反应总截面实验测量值.     

段能量平衡方程组主变量修正法及与其他几种算法的比较

详细介绍主变量修正法的原理及求解过程,采用典型算例,从初值要求、迭代次数等方面比较其优越性,进一步证明主变量修正法在求解段能量平衡方程组方面的实用性和优越性.     

波段外10.6 μm激光辐照下光导型HgCdTe探测器的电学响应

利用描述半导体内热载流子效应的１维能量平衡模型,对波段外10.6 μm激光辐照下光导型HgCdTe探测器的电学响应进行了数值模拟。结果表明：在激光开始辐照和停止辐照瞬间,探测器电阻的快速变化是由载流子温度的迅速变化引起的;在激光辐照过程中以及激光停照后,探测器电阻的缓慢变化是由晶格温度的缓慢变化进而导致载流子温度发生缓慢变化所致。模拟结果与对实验曲线的定性分析得出的结论一致。     

压缩等离子体流脉冲能量密度修正方法

介绍了压缩等离子体流能量密度诊断存在的问题,基于能量的耗散走向分析及热传导计算模型,针对汽化过程对诊断带来的误差,给出了一种基于测量的质量损失,通过表面退行的有限元计算反推损失相同质量所需输入能量的能量密度修正方法,并对能量密度修正进行了评估,通过此方法得到的修正能量密度与实验结果相吻合,但要获得更准确的能量密度,还需针对屏蔽等离子体、反冲应力波等因素进行能量密度修正,或开发出更准确的能量密度诊断方法。     

Aging Effects on the Structure Underlying Balance Abilities Tests

Balance impairment is one of the biggest risk factors for falls reducing inactivity, resulting in nursing care. Therefore, balance ability is crucial to maintain the activities of independent daily living of older adults. Many tests to assess balance ability have been developed. However, few reports reveal the structure underlying results of balance performance tests comparing young and older adults. Covariance structure analysis is a tool that is used to test statistically whether factorial structure fits data. This study examined aging effects on the factorial structure underlying balance performance tests. Participants comprised 60 healthy young women aged 22 ± 3 years (young group) and 60 community-dwelling older women aged 69 ± 5 years (older group). Six balance tests: postural sway, one-leg standing, functional reach, timed up and go (TUG), gait, and the EquiTest were employed. Exploratory factor analysis revealed that three clearly interpretable factors were extracted in the young group. The first factor had high loadings on the EquiTest, and was interpreted as ‘Reactive’. The second factor had high loadings on the postural sway test, and was interpreted as ‘Static’. The third factor had high loadings on TUG and gait test, and was interpreted as ‘Dynamic’. Similarly, three interpretable factors were extracted in the older group. The first factor had high loadings on the postural sway test and the EquiTest and therefore was interpreted as ‘Static and Reactive’. The second factor, which had high loadings on the EquiTest, was interpreted as ‘Reactive’. The third factor, which had high loadings on TUG and the gait test, was interpreted as ‘Dynamic’. A covariance structure model was applied to the test data: the second-order factor was balance ability, and the first-order factors were static, dynamic and reactive factors which were assumed to be measured based on the six balance tests. Goodness-of-fit index (GFI) of the models were acceptable (young group, GFI=0.931; older group, GFI=0.923). Static, dynamic and reactive factors relating to balance ability had loadings 0.21, 0.24, and 0.76 in the young group and 0.71, 0.28, and 0.43 in the older group, respectively. It is suggested that the common factorial structure of balance abilities were static, dynamic and reactive, and that for young people reactive balance ability was characterized and explained by balance ability, whereas for older people it was static balance ability.     

黄土高原水蚀风蚀交错区不同类型生物土壤结皮光谱特征

黄土高原水蚀风蚀交错区生物土壤结皮光谱特征的研究,为基于遥感的区域尺度生物土壤结皮的识别提供了重要的科学价值,为进一步估算生物土壤结皮在区域水土流失防治中所起的作用提供了重要的技术支持。采用地物光谱测定技术,在黄土高原水蚀风蚀交错区六道沟小流域对不同覆盖度藻类和不同类型藓类生物土壤结皮以及不同高等植被进行了光谱测定,并进行定量分析。研究表明,黄土高原水蚀风蚀交错区藻类生物土壤结皮与土壤具有相似的光谱特征,光谱曲线没有明显的“峰-谷”。藻类生物土壤结皮光谱特征主要表现为光谱反射率随生物土壤结皮覆盖度增加而降低的变化规律;其中可见光区,覆盖度10%~20%,30%~40%及50%~60%藻类生物土壤结皮相比于裸地,反射率归一化均值分别下降了8.64%,15.80%和23.09%。随藻类结皮覆盖度增加,680 nm处吸收特征(叶绿素)越来越明显,2 200 nm处吸收谷(次生矿物)越来越小。藓类生物土壤结皮光谱曲线表现出与高等植物相似的特征,形成绿波段的反射峰和红光波段的吸收谷以及近红外波段的高反射。但在760~930 nm区间,藓类生物土壤结皮的斜率明显大于高等植物, 藓类生物土壤结皮的光谱斜率Slope_(930/760)是高等植物的2.5～4.5倍。黄土高原生物土壤结皮光谱特征的研究可为生物土壤结皮的遥感识别提供一定的理论依据和技术支持。     

Finite size nucleonic effects in the nuclear medium

The finite size effects of nucleons inside a nucleus is investigated. This new approach is entirely different from Hagedorn’s volume correction method and is more rigorous. The size of the nucleon is varied and the magnitude of the hard-core potential is extracted by minimising the energy with respect to the nuclear radius.     

An energy-consistency-preserving large eddy simulation-scalar filtered mass density function (LES-SFMDF) method for high-speed flows

An energy-consistency-preserving large eddy simulation-scalar filtered mass density function (LES-SFMDF) method is developed to improve the existing LES-SFMDF method in high-speed flows, especially supersonic flows. The high-speed source term in the SFMDF transport equation is analysed theoretically from a new point of view, and then several primary principles are proposed for the LES-SFMDF to achieve a good consistency even along discontinuities. Based on these principles and further theoretical analysis, the high-speed source term of the enthalpy in the SFMDF is modelled and computed from both MC and LES variables rather than the usually used solely LES variables. This new LES-SFMDF method is used for simulating the flows in a shock tube and in a subsonic temporally developing mixing layer. This method shows a better particle energy consistency than the existing method when applied across discontinuities in supersonic laminar flows. Unlike the existing method, with this energy-consistency-preserving LES-SFMDF method, particle energy consistency is consistent with particle mass consistency so that particle energy consistency can benefit from particle velocity correction. This method also demonstrates robustness for various numbers of particles.     

电磁场的复矢量表示

在麦克斯韦方程组及洛伦兹力密度公式基础上引入电磁场复矢量,讨论了电磁场普遍规律的新公式,包括对复矢量电磁场的建立,电荷守恒定律,能量守恒定律,电磁场矢势与标势,电磁场动量、能量、张量、相对论协变性等的研究,并和电动力学相比较,得出一些结论.     

入射粒子与靶相互作用中电子能损的高阶修正

研究了在较高能入射离子（He离子、 12_C离子）与靶相互作用中电子能量损失的物理机制, 分别探讨了电子能量损失中的相对论修正、 壳修正、 密度修正以及Barkas效应和Bloch效应等修正的贡献, 发现壳修正、 Barkas效应修正和Bloch效应修正在能量小于100 MeV时是重要的, 而相对论修正和密度修正是在能量大于100 MeV时起作用。 加入各种修正项之后, 电子阻止本领的计算结果和实验值（ICRU49）符合更好。 The mechanisms of electronic energy loss in the process of incident particles interaction with Si and Al₂O₃ at proper energies are investigated. The contribution to the electronic energy loss from high order corrections, such as the relativistic correction, the shell correction, the density correction, the Barkas effect correction and the Bloch effect correction are discussed respectively. It is found that the shell correction, the Barkas effect correction and the Bloch effect correction are important at low energies, the relativistic correction and the density correction are important at high energies. The calculated results with these higher order corrections are in good agreement with the experiment data (ICRU49).