Influences of land use/cover on water quality in the upper and middle reaches of River Njoro, Kenya

Data from 10 sampling sites along the River Njoro are used to examine the contribution of nutrients from upstream land uses draining each of the sampling sites. The data also are used to assess whether both the proportion of land uses and the size of the subwatersheds account for the variability in water quality in the River Njoro watershed. Geographical Information System analysis was used to determine the spatial distribution of land‐cover types and subwatersheds contributing run‐off to the sampling sites in the River Njoro. Standard Digital Elevation Model‐based routines were used to establish the watershed area contributing run‐off to each sampling site. Water and sediment samples were collected for chemical analysis, and the nutrient levels were related to the upstream land‐use types and the size of the subwatersheds. The mid‐stream portion of the River Njoro (near Egerton University) accounts for the highest nutrient contributions. The percentage contribution is magnified by additions from industrial, human settlements and agricultural land uses around the University. There is a significant decrease in nutrient levels downstream, however, indicating natural purification as the river flows through an area of large‐scale farming with intense, well‐preserved riparian and in‐stream vegetation. Steep slopes of the land upstream of Egerton University enhance erosion and nutrient losses from those subwatersheds. Mixed small‐scale agricultural and bare lands contribute over 55% of the phosphorus load to the upper and mid‐reaches of the River Njoro. The size of the subwatershed accounts for about 53% of the variability in the soluble phosphorus in the river. The land‐use subwatershed proportions are important for characterizing and modelling water quality in the River Njoro watershed. Upland land uses are as important as near‐stream land uses. We suggest that conservation of intact riparian corridor along the river and its tributaries contributes significantly to natural purification processes and recovery of the ecological integrity of the River Njoro ecosystem.     

柴达木盆地天然气中稀有气体同位素特征

为了确定柴达木盆地勘探新层系，测试并分析了该盆地5个油气田的8个天然气样品的氦、氩同位素比值，探讨了其在大地构造背景、大地热流和气源方面的示踪意义。研究结果如下：①柴达木盆地8个天然气样品³He/⁴He值分布在2.0×10^-8～5.48×10^-8的范围，总体平均为3.7×10^-8，均在10^-8量级，体现了典型的壳源成因氦同位素的特征。②据³He/⁴He计算的大地热流值较低，分布于41.2~48.2 mW/m²之间，平均44.9 mW/m²，低于东部地区大地热流平均值73 mW/m²，表明该盆地具有较稳定的构造背景。③根据天然气⁴⁰Ar/³⁶Ar的年代积累效应，结合烃源岩分布特征推测，柴达木盆地东部凹陷区伊克雅乌汝构造伊深1井天然气应源于上第三系；西部坳陷区尕斯油田尕斯8-6井和尕斯475井天然气应源于下第三系；碱山构造碱1井天然气应源于侏罗系，碱山构造碱2井的天然气应源于上第三系；北缘块断带南八仙油气田仙试1井的天然气应源于侏罗系；南八仙油气田仙试8井和马北构造马北1井的天然气可能主要源于侏罗系。     

Influence of the Preheat Treatment on the Microstructure and Properties of X37CrMoV5-1 Steel

The technological properties of the hot-work tool steels depend on their microstructural quality induced by the production process and the heat treatment. One of the frequently applied methods to improve microstructure is preheat treatment. The treatment of carbonitriding X37CrMoV5-1 steel has been investigated in fluidized bed furnaces. Thickness and phase composition have been conducted using optical microscopy Neophot 32 and scanning microscopy, JEOL 5400, after etching in nital.     

巴彦浩特探区钻井液技术初探

巴彦浩特探区钻井液工艺技术的重点是，解决疏松砂砾岩地层水涌漏同层、侏罗系地层水的HCO3^-污染及可能出现的火成岩地层井塌复杂。结合内蒙古巴彦浩特探区地层和井身结构特点，采用了两性聚合物／氯化钾钻井液和氯化钾／石膏-聚磺钻井液体系。该体系抑制能力强，性能稳定．容易实现低固相、低密度近平衡钻井，保护储层效果好。对复杂情况采取了有针对性的处理办法：平稳操作和合理的钻井工程措施是预防水层涌漏同层和火成岩井塌复杂的重要手段；用井场易得的固井水泥或石膏配合烧碱处理HCO3^-污染简便易行；处理火成岩井塌复杂，控制合适的钻井液性能是必要的。     

Micromechanical modelling of ductile crack growth in the binder phase of WC–Co

This study focuses on numerical simulation of ductile failure in the Co binder phase of WC–Co hardmetal. The growth of edge cracks under mode I loading is considered. A computational micromechanics approach is taken where the Co binder ligaments are explicitly represented in finite element models. An embedding technique is employed. Crystal plasticity theory is used to represent plastic deformation in the Co ligaments. Crack propagation in the binder is simulated using an element removal technique based on a modified Rice and Tracey model for ductile void growth, and fracture resistance curves are generated. Parameter studies are performed for variations in microstructrual parameters such as numbers of Co ligaments ahead of the crack tip and local Co volume fraction. The importance of thermal residual stresses and finite element mesh density are also investigated.     

A Bluetooth Routing Protocol Using Evolving Fuzzy Neural Networks

In this paper, a routing protocol which utilizes the characteristics of Bluetooth technology is proposed for Bluetooth-based mobile ad hoc networks. The routing tables are maintained in the master devices and the routing zone radius for each table is adjusted dynamically by using evolving fuzzy neural networks. Observing there exists some useless routing packets which are helpless to build the routing path and increase the network loads in the existing ad hoc routing protocols, we selectively use multiple unicasts or one broadcast when the destination device is out of the routing zone radius coverage of the routing table. The simulation results show that the dynamic adjustment of the routing table size in each master device results in much less reply time of routing request, fewer request packets and useless packets compared with two representative protocols, Zone Routing Protocol and Dynamic Source Routing.     

A new minimum zone method for evaluating flatness errors

A new minimum zone method for flatnes error analyis is proposed in this article. Based on the criteria for the minimum zone solution and strict rules for data exchange, a simple and rapid algorithm, called the control plane rotation scheme, is developed for the flatness analysis of a flat surface. Experimental work was performed, and some examples are given in terms of the minimum zone and least-squares solutions.     

永丰县上保水库溢洪道采用异型进口的效益

本溢洪道设计采用了异型进口水力设计的科研成果，与常规设计相比，这种溢洪道具有进口布置灵活，增加堰长，减小单宽溢流量，降低堰上溢流水头等特点，上保水库溢洪道由于采用了异型进口，在不断加工程投资和最高库水位不变的条件下，使堰顶高程提高1．39m，增加有效库容、灌溉面积分别为27．8％和27．7％，经济效益显著，由此可见，溢洪道异型进口确实是一项值得推广的工程实用技术。     

关于松辽盆地内部地体碰撞的探讨

通过对地震资料中特殊现象的解释提出了松辽盆地内部东西地体碰撞的看法,合理地解释了松辽盆地滨北地区地质现象的形成机制,并且认为地体碰撞带可能是无机生油的有利场所。     

Effects of crack size and weld metal mismatch on the has cleavage toughness of wide plates

The heat affect zone (HAZ) is in many cases considered to be the most critical part of a weldment. In this paper, the effect of crack size and weld metal mismatch on the HAZ cleavage toughness of wide plate specimens with X-groove has been investigated by the J-Q-M theories and a simple micromechanism for cleavage fracture. Two crack sizes have been studied (a/w = 0.1 and 0.3). In the analyses, the HAZ yield strength is assumed to be higher than the base metal. For each crack size, weld metal local overmatch and local evenmatch with respect to the HAZ are considered. For a given global strain, the results indicate that weld metal overmatch and evenmatch yield the same crack tip loading in terms of J-integral for a/w = 0.3. For a/w = 0.1, overmatch gives lower crack tip loading than evenmatch. For a given crack tip loading, weld metal local evenmatch in general results in less effective crack tip loading than the overmatch. Overmatch is detrimental to HAZ toughness, but this detrimental effect becomes less significant when the crack size decreases.