黄土高原多沙粗沙区高含沙水流发生频率的时间变化

高含沙水流的频繁发生是黄土高原多沙粗沙区产生高强度侵蚀的重要原因。本文基于1967—1989年的系列泥沙资料和面雨量资料,分析了黄土高原多沙粗沙区8个流域高含沙水流发生频率随时间的变化过程。根据其不同的变化趋势,将研究区所有流域分成了两类。第一种类型高含沙水流发生频率随时间逐渐减小;第二种类型高含沙水流随时间呈先减小后增大的变化趋势。从汛期降雨量（6—9月）及人类活动（包括人为的减沙活动和人为增沙活动）两个方面对高含沙水流随时间变化趋势的产生原因进行了分析。结果表明,第一种类型主要受到同期汛期降雨量的减少以及各种水利水保措施减沙量从上世纪60一80年代逐渐增大的影响;第二种类型的流域在上世纪60年代末到80年代初高含沙水流发生频率的减小主要是因为上世纪60、70年代大量修建的淤地坝在70年代发挥了显著的拦减泥沙的作用;但到了80年代以后,新建淤地坝很少。原有淤地坝已大部失效,另外人为的增沙活动,如修路、开矿、建窑等活动在80年代以后显著增加,上述因素促使高含沙水流发生频率在80年代初期以后呈随时间增加的趋势。     

Digital Yellow River Model

Soil erosion is one of the key concerns in land use management for the Loess Plateau of the Yellow River, where serious soil loss is the root cause of environmental and ecological degradation of the basin. In this paper, a physically-based, distributed-parameter, and continuous erosion prediction model at the river basin scale was developed with the aim of assisting in developing better land use management strategies. The framework, the major supporting techniques, and the typical erosion processes are described. The physical processes of sediment yield and transport in the Loess Plateau are divided into three sub-processes, including the runoff and sediment yield on hillslopes, gravitational erosion in gullies, and hyperconcentrated flow routing in channels. For each sub-process, a physically-based simulation model was developed and embedded into the whole model system. The model system was applied to simulate the runoff and sediment yield in several typical years in the coarse sediment source area of the Loess Plateau, and the simulated results were in reasonably good agreement with the measured values.     

建设“模型黄河”工程

“物理模型黄河”（简称“模型黄河”）可对“原型黄河”所反映的自然现象进行反演，模拟和试验，从而提示其内在的自然规律。一方面直接为“原型黄河”提供治理开发方案，中一方面为“数字黄河”工程建设提供物理参数，同时，“模型黄河”还应成为“数字黄河”运行结果中试环节。“模型黄河”工程体系包括黄土高原模型，水库模型，河道模型及河口模型，要保证“模型黄河”工程的建设及正常运行，必须做好工程的总体设计，建立稳定的投资渠道，树立科学的决策意识，培养和造就一流的科研人才队伍。     

Charge exchange and the “Plateau” effect in YBa2Cu3O7?y

The superconducting properties of YBa₂Cu₃O_7- y, (YBCO) depend strongly on the oxygen content, whereas the transition temperatureT _cremains relatively constant for oxygen content between 6.8 and 7.0 (the Plateau effect) this effect has attracted considerable attention [see, e.g., D. de Fontaineet al., Nature (London) 343, 544 (1990); H. Paulsenet al., Nature (London) 349, 594 (1991); J. Jorgensen,Phys. Today 44, No. 6, 34 (1991)]. In this letter we introduce a microscopic theory of this phenomenon.     

Apparent solubility of drugs in partially crystalline systems

Using several griseofulvin samples, representing different solid-state structures, the solubility behavior of drugs in both one-state (totally ordered, semiordered or disordered) and two-state systems was studied. Special attention was directed towards the surface structure of the particles. The partially crystalline samples were obtained by milling the raw material (crystalline standard) or storing the quenched sample (amorphous standard). The solid-state structure of the materials was studied using x-ray diffraction (XRD), differential scanning calorimetry (DSC), isothermal microcalorimetry (IMC), and scanning electron microscopy (SEM). The saturation concentration of the materials was studied in suspensions containing different dispersion concentrations of drug after centrifugation and filtration, using spectrophotometry. In all cases these dispersion concentrations exceeded the solubility of the drug. The solubilities were plotted vs. dispersion concentrations for each sample. Several solubility plateaus were found. The lowest and highest solubility plateaus corresponded to the solubilities of crystalline and amorphous standards. These plateaus were reached at 8 and 44 µg/mL for crystalline and amorphous griseofulvin standards, respectively. An intermediate plateau served as an indication of the existence of a totally semiordered structure. This was reached at 19 µg/mL for griseofulvin. Any deviation from these plateaus was suggested to be indicative of the existence of heterogeneity on the surface structure, which in most cases could be described as a two state system. In such cases, the apparent solubility was a function of dispersion concentration, until at very high dispersion concentrations (4000-20,000 µg/mL) the saturation concentration of the totally disordered (44 µg/mL) or semiordered (19 µg/mL) one-state phase was reached. No reduction in these values was observed during storage for 50 days. It is thus concluded that, in partially crystalline systems, the saturation concentration is an interfacial phenomenon, which depends on the amount, reactivity, and solid-state structure of the exposed solid surfaces in equilibrium with the solution. A simplified solubility model is proposed to qualitatively describe the relationship between established apparent solubilities (saturation concentrations) and different combinations of solid-state structures.     

对我国“南水北调”方案几点建议 第十三届全国结构工程学术会议特邀报告

本文主要对“南水北调”的两种方案进行了阐述与比较.旨在探索出一条.从生态建设入手,因地 制宜的,全力开发和利用地下空间,能从青藏高原深处及大兴安岭北端.实现中国“南水北调”2000 亿米3,“北水南调”200亿米3可持续发展治水之路.     

一个基于XML数据仓库系统的设计与实现

黄土高原数据仓库系统以分布式数据仓库为核心,包含多个异质数据源。系统采用中间件技术不仅提供多层次资源查询服务,并且还使用数据挖掘技术和信息检索技术对资源数据进行深加工,能够主动地为用户提供黄土高原生态环境咨询、评测、预测与决策支持服务。论文重点介绍了一种基于XML的统一模式查询语言———XUSQL,用以解决多数据源中多模式数据融合问题。XUSQL使得在数据仓库中的查询与数据源模式无关,把数据源和数据仓库隔离开,从而有利于构造分布式数据仓库,便于异质数据源之间数据融合以及数据源本身的结构调整。     

基于MapObjects的区域地质文献管理系统的建立

在进行区域地质研究的过程中,会涉及到大量的参考文献。当研究区域范围比较大、研究方法比较多的情况下,查找文献就会变成一项负担。本文以青藏高原的研究为例,利用VB开发了基于MapObjects的区域地质文献库管理系统。在对文献库进行综合管理的基础上,实现了由文献查找区域、在区域上查找文献等功能,很好地完成了地图与数据库的交互。     

青藏高原油气勘探前景

青藏高原为我国中新生代海相沉积最发育的地区,存在着众多的中、新生代沉积盆地,油气勘探前景很大,尤其是羌塘和措勤盆地,但由于特殊地理条件的限制,区内地质研究程度很低,在海相中生界石油勘探方面,几乎为空白区。羌塘盆地为青藏高原面积最大、构造上较稳定的地区,基底埋深大,存在着隆、坳相间的构造格局,生油岩厚度大,生储盖组合条件较好。措勤盆地基底埋深较大,也存在较厚的生油岩。