有限区域海面风场数值模式的建立

目前,国内外大尺度天气预报数值模式已经取得很大成就,如在预报地面气旋系统的移动和发展等方面。然而,这些模式的铅直分辨率一般不高,通常不包括边界层的动力过程,因而,在预报海面风场上,数值天气预报模式还没有令人满意的效果。目前所用的边界层预报模式尽管具有较高的水平分辨率和垂直分辨率,但要求大量的计算和资料,很难用于日常业务预报;另一种边界层诊断模式,用到的风场数据是气象工作者从天气形势(大尺度)分析中,通过差值等方法获得的,缺乏针对性,而且精度较低(WMO,1988;WMO,1990)。 作者认为,适于海洋要素预报的风场模式应是定位于有限区域,或称中尺度模式,并根据台站的具体资料来源和工作状况力争建立一套适于海洋要素预报的中尺度风场数值模式。鉴于以上,作者建立了一个适于海洋要素预报的有限区域海面风场数值模式。模式采用符合动力及热力学条件的简化方程组对大尺度风场进行加密,通过数值模拟得到适于海洋要素预报的有限区域海面风场。并将该模式运用于渤海这一有限区域,获得了良好的效果,说明该模式对海洋要素预报具有很好的应用前景。     

基于极限分析上限方法的海底斜坡稳定性评价

极限平衡法仍是当前海底斜坡稳定性的主要工程评价方法,但该法只能给出稳定性分析的近似解答。基于极限分析运动学定理,假定海底斜坡发生对数螺线型滑移破坏模式,将滑体有效自重和简化波浪力等以外荷载形式叠加引入到虚功率方程中,与潜在滑动面上由黏聚力产生的内能耗散率相平衡,建立考虑一阶简化波浪效应的海底斜坡上限解法;利用多变量无导数求极值的逐级迭代方法与最优化技术,结合抗剪强度折减思想,求解波浪加载下不同时刻的海底斜坡稳定性与相应的临界破坏机构,并针对典型算例开展有限元数值解的验证。进而联合采用数值法与上限解,探讨波高、波长、水深等波浪参数对海底斜坡稳定性与滑动机制的影响。结果表明,本文提出的上限解与数值解吻合较好,获得的安全系数与破坏模式等符合一般规律,为波浪作用下海底斜坡的稳定性评价提供了新的途径。     

欧洲数值预报产品在深圳2次强降温预报中的释用

详细分析了欧洲数值预报产品在2006年深圳2次强降温过程中的应用,提出如何利用欧洲数值预报产品进行深圳市降温预报的思路.结果发现,欧洲数值预报对地面冷空气的强度和西风槽有较强的预报能力;欧洲中心数值预报850 hPa温度场是进行气温预报的一个重要依据,当欧洲中心数值预报反映深圳850 hPa温度场有明显降温时,要考虑深圳可能出现强降温过程.     

模糊层次分析法在山区大农业发展决策中的应用

采用模糊层次分析方法,综合考虑自然资源条件和市场需求,分析并提出陇南山区白龙江流域各垂直气候层中农业各部门的优先发展顺序,为山区大农业发展提供决策依据。     

The lithologic diversity of the Moon recorded in lunar meteorites Northwest Africa 7611 and 10480

Northwest Africa (NWA) 7611/10480 are lunar regolith breccia meteorites, composed of mineral fragments and various clasts including mare basalts, volcanic glasses, gabbroic lithologies, and a diverse variety of highland materials (ferroan anorthosite, Mg-suite, magnesian anorthosite, and alkali suite rocks) as well as different subvarieties of impact melt breccia. The Apollo two-component mixing model calculation reveals that the NWA 7611 source region contains 58 wt% mare materials and 42 wt% highland components, but the estimated mare components in NWA 10480 have a higher abundance (66 wt%). The predominantly very low-Ti (VLT) composition in both fine-grained basaltic and coarse-grained gabbroic lithologies indicates a provenance associated with a thick lava flow or a single magmatic system. The co-occurrence of zoning patterns and fine-scale exsolution lamellae in pyroxene debris supports a cryptomare deposit as the best candidate source. Phosphate Pb–Pb ages in matrix fragments, impact melt breccia, and basaltic clast indicate that the breccia NWA 7611 records geological events spanning approximately 4305–3769 Ma, which is consistent with the ages of ancient lunar VLT volcanism and the products of basin-forming impacts on the lunar nearside. The youngest reset age at ~3.2 Ga is potentially related to the strong shock lithification process of breccia NWA 7611. Moreover, the similar petrology, texture, geochemistry, cosmic-ray exposure data, and crystallization ages support that basaltic component in Yamato (Y)-793274, and Queen Alexandra Range (QUE) 94281, NWA 4884, and NWA 7611 clan came from the same basalt flow.     

城市景观湖泊不同时间尺度CH4通量特征及影响因素分析——以南京市莫愁湖为例

城市景观湖泊对温室气体的收支发挥着重要作用。本文以南京市莫愁湖为研究对象,采用静态箱—温室气体分析仪法实时监测湖泊水—气界面CH₄通量,分析湖泊主要温室气体CH₄在日尺度和季节尺度上因冒泡和扩散排放方式不同对其通量的影响,探究影响湖泊CH₄通量的因素。结果表明:(1)在日尺度上,四季24 h内CH₄均呈排放状态,受白天冒泡影响,四季CH₄总通量均存在白天高于夜间的日变化特征。(2)在季节尺度上,莫愁湖CH₄排放通量呈现显著的时空异质性,受冒泡通量的影响夏季CH₄通量明显高于春、秋、冬三季;B区的CH₄总通量(6.04 nmol/(m²·s))显著高于A区(3.82 nmol/(m²·s)),水体的营养化程度和离岸距离是空间变化的主要影响因素。A、B两区CH₄排放夏季以冒泡排放为主,春、秋、冬以扩散排放为主。(3)在日尺度上,CH₄     

00~h00~m 00°00′天区的类星体物端棱镜光谱巡天(Ⅴ)巡天结果的讨论(英文)

本文总结巡天的结果并对结果进行讨论,同时发表69个Q=3的紫外超天体的坐标,B_J~*及证认图。     

周期和振幅相结合检测地震方法研究

分析了单纯用地震波振幅作为报警阈值的缺点,通过数字地震仪与模拟地震仪报警机制的对比,提出用检测周期和振幅相结合的方法来实现地震报警.     

Non‐uniqueness of critical state line in compression and extension conditions

Experimental evidence has indicated that the critical state line determined from undrained compression tests is not identical to that determined from undrained extension tests. The purpose of this paper is to investigate a modelling method that accounts for the non‐uniqueness of critical state lines in the compression and the extension testing conditions. Conventional elastic–plastic cap models can predict only a unique critical state line for the compression and the extension tests. A new micromechanical stress–strain model is developed considering explicitly the location of critical state line. The model is then used to simulate undrained triaxial compression and extension tests performed on isotropically consolidated samples with different over‐consolidated ratios. The predictions are compared with experimental results as well as that predicted by models with kinematic hardening of yield surface. All simulations demonstrate that the proposed micromechanical approach is capable of modelling the undrained compression and the undrained extension tests. Copyright © 2009 John Wiley & Sons, Ltd.