A general method for calculating three-dimensional laminar and turbulent boundary layers on ship hulls

A general method for representing the flow properties in the three-dimensional boundary layers around ship hulls of arbitrary shape is described. It makes use of an efficient two-point finite-diffirence schem to solve the boundary-layer equations and includes an algebraic eddy-viscosity representaion of the Reynolds-stress ternsor. The numericzal method contains novel and desirable features and allows the calculation of flows in which the circumferential velocity component contains regions of flow reversal across the boundary layer. The inviscid pressure distribution is determined with the Douglas-Neumann method which, if necessary, can conveniently allow for the boundary-layer displacement surface. To allow its application to ships, and particularly to those with double-elliptic and flat-bottomed hulls, a non-orthogonal coordinate system has been developed and is shown to be economical, precise and comparatively easy to use. Present calculations relate to zero Froude number but they can be extended to include the effects of a water wave and local regions of flow separation which may stem from bulbous-bow geometries.     

格尔木河流域河水钾硼锂元素分布特征及富集规律

在柴达木格尔木河流域,随着内陆流域水系的产生与地表径流的消亡,从山区至盐湖区钾(K)硼(B)锂(Li)等有益元素的分布可以划分为淋溶-径流区、径流-蒸发区与溶滤-蒸发浓缩富集区3个具有显著特点的水文化学分带。河水中,K、B、Li含量随矿化度升高而升高,且呈正相关关系。在盐湖区,K、B、Li等资源性元素明显富集。研究发现,格尔木河东部主流(秀水河)是格尔木河水中B和Li的主要贡献者。     

典型农区农用地承包经营权流转价格及对策研究(英文)

河南既是农业大省又是中国重要的粮食主产区,农用地流转顺畅及适度规模经营对区域经济发展和国家粮食安全产生重要影响。借助于土地使用权评估的基本方法,并使用土地承包经营权的权属特性进行修正,构建了土地承包经营权流转价格模型,并对典型区域沁阳市西万村进行了实证分析。结果表明,土地承包经营权流转价格应该包括经济价格、社会价格和修正价格。价格模型的应用,应甄别理论价格和实际流转费用的区分,农用地流转后经营项目没有转变,流转价格为经济价格和社会保障价格是总和。农用地流转后经营项目发生转变,比如耕地改种经济作物,流转价格则是经济价格、社会价格与修正价格三者的总和。收益分配格局存在复杂性,流转收益应在流出方、流入方、管理者和所有者之间合理、公平分配。政府应建立合理有序的农用地承包经营权流转市场,并以农用地流转市场为载体,构建农用地流转价格体系。     

Total N,total P and organic matters content in floodplain soils of Xianghai Nature Reserve

Soil sediment samples of 10 layers with a spacing of 10 cm each were collected in different floodplain zones adjacent to Huolin River in the Xianghai Nature Reserve, and contents of total N, total P and organic matters were analyzed. The results showed that contents of total N, total P and organic matters were generally decreasing with the increase of distance from sample locations to the river channel, and contents of the three items were generally higher in the upper soil layer than that in the lower soil layer. The content variations displayed how flooding functions influenced nutrient matter content variations in floodplain soils since the flood inundation frequencies of the sample locations varied. The correlation analysis displayed that there were remarkable relativities between total N, total P and organic matters within definite spatial distance from the Huolin River channel.     

文化旅游吸引物表征符号理论体系的探讨

通过文献总结法,理论探讨文化旅游吸引物表征符号系统。根据文化结构的三层次说,建立文化旅游吸引物表征符号结构与表征符号内容:历史文化表征符号、现代文化表征符号、民俗文化表征符号、伦理道德文化表征符号。认为制度文化表征系统与精神文化表征系统可视为"舞台"的"帷幕",引导游客由"前台"向"后台"探索,从而避免对目的地文化认识的肤浅化和片面化。对符号意义和价值的编码存在着一种社会选择机制,需根据主流价值观进行社会建构,以符合社会心理取向和游客兴趣。     

Molecular abundances and nucleation in protostellar envelopes

This work is basically concerned with grain nucleation occurring in protostellar envelopes. On the basis of the dissociation equilibrium theory, molecular and atomic abundances are obtained for massive protostar envelopes. Application of time-independent homogeneous nucleation theory results in the possibility of atomic Fe condensation.     

近20年气候变暖对黑龙江省水稻增产的贡献

研究过去的气候变暖对作物产量的影响是认识变暖对农业影响的有效途径,但如何定量区分出气候变化和技术发展对粮食作物的影响程度是目前研究的难点。本文提出的算法在一定程度上可以克服传统算法缺陷,用此方法估算过去20年气候变暖对黑龙江省水稻单产增加的贡献率,结果表明：20世纪80年代相对于70年代水稻单产增加了30.6%,其中由气候变暖带来的增产量占实际增产量的12.8%~16.1%,相当于使70年代的单产增加3.9%~4.9%。20世纪90年代水稻单产较80年代增产42.7%,其中,气候变暖对单产增加的贡献率约为23.2%~28.8%,相当于在20世纪80年代的单产水平上增产9.9%~12.3%。     

Application of analytical hierarchy process (AHP) for flood risk assessment: a case study in Malda district of West Bengal,India

A field experiment was conducted from 2 May 2010 to 1 May 2012 in the Gurbantunggut Desert, the second largest desert in China, to investigate saltation activity and its threshold velocity, and their relations with atmospheric and soil conditions. The results showed that saltation activity occurred more frequently during 08:00–20:00 Local Standard Time in spring and summer, with air temperatures between 20.0 and 29.0 °C, water vapor pressures between 0.6 and 0.9 kPa, soil temperatures between 25.0 and 30.0 °C, and a soil moisture lower than 0.04 m³/m³. At 2 m height, the saltation threshold velocity varied between 11.1 and 13.9 m/s, with a mean of 12.5 m/s. Threshold velocity showed clear seasonal variations in the following sequence: spring (11.7 m/s) < autumn (12.7 m/s) < summer (13.6 m/s). Affected by soil conditions, aeolian sand transport was weak, with an average annual aeolian sand that transported across a section (1.0 m × 2.0 m) of less than 6.0 kg.