Self-supporting cylindrical multiwire proportional chambers with two dimensional read-out

Cylindrical MWPCs have been constructed with anode diameters of 240–430 mm and a length of 750 mm. Cathode strips run helically with 38°–61° to the anode wires, and the induced charges were read out by ADC. Both the anode and the cathode efficiency were well above 99%. The resolution (σ) for the longitudinal position of the avalanche was 0.6 mm by the centre of gravity method, if the cathode was read out per 12 mm width by summing two adjacent cathode strips.     

An instrument for mechanical testing on the nanometre scale

A microprobe for hardness testing of advanced engineering materials is described.     

基于健康风险的水源地水质安全评价

将健康风险评价引入水源地水质安全评价中,以致癌风险和危害指数分别反映源水中污染物对人体致癌危害与非致癌慢性毒害的程度.选取我国华东一重要城市的最大水源地进行分析,结果表明,该水源中12种致癌物质总致癌风险为4.76×10-5,其中砷是最主要的致癌污染物,致癌风险为4.00×10-5;24种污染物总危害指数为0.906,其中位列第一、第二位的是氟化物和砷,其危害指数分别为0.393和0.207;不同类型污染物健康风险的分析对比表明,无机污染物是最主要的风险贡献源,应予以重点监控;汛期与非汛期健康风险的对比表明,汛期应为水质重点监控时段,同时应重视面源污染的治理.     

水利工程模型试验计算机测量与控制系统

采用计算机测量与控制系统应用于水利工程模型试验,设计应用先进的水流循环系统、电磁流量计、电子式电动调节阀、控制接口和软件组成计算机流量闭环自动控制系统;计算机测量与控制系统通过实际使用运行,证明达到了设计指标的要求,大大提高了模型试验测量与控制的精度和工作效率,缩短了模型试验周期,有利于水利工程研究成果质量和科研水平的提高.     

A high-resolution method for the depth-integrated solute transport equation based on an unstructured mesh

This paper presents a high-resolution numerical method for solving mass transport problems involving advection and anisotropic diffusion in shallow water based on unstructured mesh. An alternating operator-splitting technique is adopted to advance the numerical solution with advection and diffusion terms solved separately in two steps. By introducing a new r-factor into the Total Variation Diminishing (TVD) limiter, an improved finite-volume method is developed to solve the advection term with significant reduction of numerical diffusion and oscillation errors. In addition, a coordinate transformation is introduced to simplify the diffusion term with the Green-Gauss theorem used to deal with the anisotropic effect based on unstructured mesh. The new scheme is validated against three benchmark cases with separated and combined advection and diffusion transport processes involved. Results show that the scheme performs better than existing methods in predicting the advective transport, particularly when a sharp concentration front is in presence. The model also provides a sound solution for the anisotropic diffusion phenomenon. Anisotropic diffusion has been largely neglected by existing flow models based on unstructured mesh, which usually treat the diffusion process as being isotropic for simplicity. Based on the flow field provided by the ELCIRC model, the developed transport model was successfully applied to simulate the transport of a hypothetical conservative tracer in a bay under the influence of tides.     

Coupling climate and hydrological models: Interoperability through Web Services

Understanding regional-scale water resource systems requires understanding coupled hydrologic and climate interactions. The traditional approach in the hydrologic sciences and engineering fields has been to either treat the atmosphere as a forcing condition on the hydrologic model, or to adopt a specific hydrologic model design in order to be interoperable with a climate model. We propose here a different approach that follows a service-oriented architecture and uses standard interfaces and tools: the Earth System Modeling Framework (ESMF) from the weather and climate community and the Open Modeling Interface (OpenMI) from the hydrologic community. A novel technical challenge of this work is that the climate model runs on a high performance computer and the hydrologic model runs on a personal computer. In order to complete a two-way coupling, issues with security and job scheduling had to be overcome. The resulting application demonstrates interoperability across disciplinary boundaries and has the potential to address emerging questions about climate impacts on local water resource systems. The approach also has the potential to be adapted for other climate impacts applications that involve different communities, multiple frameworks, and models running on different computing platforms. We present along with the results of our coupled modeling system a scaling analysis that indicates how the system will behave as geographic extents and model resolutions are changed to address regional-scale water resources management problems.     

Making a mesh router/gateway from a smartphone: Is that a practical solution?

This paper aims at answering the question whether it is practical to build a mesh-phone or not. A mesh-phone is a smartphone acting as a mesh router, i.e. either actively participating in the process of packet forwarding towards a mesh gateway, or acting itself as a gateway toward the Internet. Technical aspects of the mesh-phone implementation, such as design constraints and implementation details, are addressed. The technical feasibility is validated by describing the implementation of a prototype of the mesh-enabled phone over the Openmoko^TM open platform. Besides technical feasibility also convenience of the addressed solution is analyzed in terms of the consumed power, and some “energy-saving” related enhancements are suggested to be applied to future user’s devices.     

The effect of Zr on the microstructure and tensile properties of hot-extruded Al–Mg2Si composite

This work was carried out to investigate the effect of different amounts of Zr on the microstructure and tensile properties of homogenized and hot extruded Al-15% Mg₂Si composite using optical microscopy and scanning electron microscopy (SEM). The results showed that Zr addition has no significant effect on the morphology of both primary and eutectic Mg₂Si phase in as-cast condition. But, applying homogenizing and extrusion processes changed the morphology of Mg₂Si phases from irregular to a more spherical shape. Further results demonstrated that the average size of primary Mg₂Si decreases with the addition of Zr up to 0.1% from 56 μm to 24 μm in hot-extruded condition. As the mount of Zr increased up to 0.1 wt.%, ultimate tensile strength (UTS) and elongation values were also increased from 160 MPa and 3.2% to 292 MPa and 9.5%, respectively. Fracture surface examinations revealed a transition from brittle fracture mode in as-cast composite to ductile fracture in hot-extruded Zr-modified specimens. This can be attributed to the changes in size and morphology of Mg₂Si intermetallic and porosity content.     

A two-stage shape retrieval (TSR) method with global and local features

A robust two-stage shape retrieval (TSR) method is proposed to address the 2D shape retrieval problem. Most state-of-the-art shape retrieval methods are based on local features matching and ranking. Their retrieval performance is not robust since they may retrieve globally dissimilar shapes in high ranks. To overcome this challenge, we decompose the decision process into two stages. In the first irrelevant cluster filtering (ICF) stage, we consider both global and local features and use them to predict the relevance of gallery shapes with respect to the query. Irrelevant shapes are removed from the candidate shape set. After that, a local-features-based matching and ranking (LMR) method follows in the second stage. We apply the proposed TSR system to MPEG-7, Kimia99 and Tari1000 three datasets and show that it outperforms all other existing methods. The robust retrieval performance of the TSR system is demonstrated.     

黎河河道演变的数学模型——天然河道用作输水通道后的演变

天然条件下的山前性河流黎河被用作引滦入津的输水河道，来水条件的巨变和大量工程引起的河床调整，为研究这一调整我们建立了具有如下特点的数学模型：1、考虑了自上而下床沙粒径的巨大变化；2、反映了卵石夹沙河床宽级配的输沙特点以及清水冲刷时的粗化过程；3、模拟了粘性土河床的冲刷特性；4、考虑了跌水坎的不规则断面宽顶堰的过流特点以及有工程措施和人为干扰下的河床演变特点。本文介绍了上述数学模型的主要内容，这对于其它跨流域引水工程和河道治理工程有参考价值。