Synthesis of (S)-gizzerosine, a potent inducer of gizzard erosion in chicks

(S)-Gizzerosine, a potent inducer of gizzard erosion in chicks, was synthesized using successive zinc-mediated and palladium-catalyzed coupling reactions as the key steps.     

Ultrasonic cavitation in thin liquid layers

The generation of ultrasonic cavitation in a thin liquid layer trapped between a large radiating surface and a hard reflector and bounded laterally by a gas–liquid interface is investigated. The theoretical analysis predicts that a large amplification of the acoustical pressure is obtained with this configuration. Experiments are conducted by driving the layer with horn-type transducers having a large emitting surface. Ultrasonic cavitation is obtained in a broad frequency range at low input intensity due to the amplification effect. Erosion tests on metallic foils demonstrate the existence of a region of intense cavitation activity which can be localised by controlling the input intensity.     

Modelling the trade‐offs between farm income and the reduction of erosion and nitrate pollution

Water is a very limited resource in Tunisia, both in quantity and in quality. Problems of quality are related to urban, industrial and agricultural activity. Erosion is causing dams to silt up and is leading to phosphorus accumulation in water. The use of agrochemicals, primarily nitrogen and phosphorus, is causing problems of eutrophication. This paper presents the results of a study of sediment and nitrate pollution. The methodology used is based on the EPIC simulation model and a multiobjective programming model (MOPM). The data generated by EPIC are input for the MOPM together with the economic variables. These tools are applied to a 486 ha farm located in northern Tunisia which includes an irrigated area of 300 ha. The study considers three objectives: maximization of gross margin, minimization of erosion, and minimization of nitrate losses. The noninferior set estimation method is implemented to generate the tradeoff curves between the objectives. Results show that nitrate losses are important for both rainfed and irrigated land. The same conclusion is valid for erosion. It is shown that the farmer can reduce the environmental burden without decreasing gross margin, since he is operating below the efficiency curve.     

Analytical solutions to mathematical models of the surface and bulk erosion of solid polymers

The process by which polymeric materials hydrolyze and disappear into their environments is often called erosion. Two types of erosion have been defined according to how the hydrolysis takes place. If hydrolysis occurs throughout the entire specimen at the same time, it is called bulk erosion. If the hydrolysis is mainly confined to a region near the surface of the specimen and the surface continuously degrades by moving inward, it is termed surface erosion. In this article, a kinetic relationship for bulk erosion is developed. This relationship provides a method for estimating the hydrolysis kinetic constants for bulk‐eroding polymers. This same relationship is also applicable to surface erosion at a microscopic level. Through its combination with a diffusion–reaction equation and the provision of moving boundary conditions, an analytical solution to the steady‐state surface‐erosion problem is obtained. The erosion rate, erosion front width, and induction time can all be expressed as simple functions of the rate of polymer bond hydrolysis, water diffusivity, and solubility, plus other parameters that can be experimentally determined. The erosion front width is the product of the induction time and the erosion rate. The ratio of the erosion front width to the polymer specimen thickness is a parameter that determines whether the specimen undergoes surface or bulk erosion. Theoretical results are compared with experimental observations from the literature, and agreement is found. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 383–397, 2005     

A physical,mechanistic and fully coupled hillslope hydrology model

We present the mathematical development and numerical solution of a new model of flow processes on an infiltrating hillslope. We also present validation and sample applications. The model is a distributed, mechanistic, physically based hillslope hydrologic model. The model describes the small‐scale processes associated with overland flow, erosion, and sediment transport on an infiltrating surface and is capable of capturing small‐scale variations in flow depth, flow velocities, interactive infiltration, erosion rates, and sediment transport. The model couples the fully two‐dimensional hydrodynamic equations for overland flow, the one‐dimensional Richards equation for infiltration, and a sediment detachment and transport model. Two simulations are presented highlighting the model's ability to capture and describe the interaction between precipitation, overland flow, erosion and infiltration at very small scales. Results of the two‐dimensional simulations indicate the system of equations produces hillslopes possessing characteristics of self‐organization as observed in real world systems. Copyright © 2005 John Wiley & Sons, Ltd.     

Bases for predicting gas-particle flows with particular reference to turbomachinery

Advances in the understanding of particle dynamics and their trajectories and the resultant erosion of solid surfaces are reviewed. Particular attention is given to the calculation procedures used in the analysis of gas-particle flows, always with the intention of application to turbo-machines. One, two and three-dimensional analyses are considered and the limitations of each are discussed. As in the analysis of a real fluid flows, resort is made to empirical correlations of many phenomena and, even then, the predictions of particle trajectories are restricted. The correlation and restrictions are discussed where appropriate.     

高岭土填充改性超高分子量聚乙烯的浆体冲蚀磨损特性

分别采用机械混合和釜内聚合方法在UHMWPE基体上填充高岭土,制得两类UHMWPE／Kaolin复合材料,考察了两类UHMWPE／Kaolin复合材料的浆体冲蚀磨损特性及其与冲击速度和高岭土含量之间的关系,通过对磨损表面形貌的观察分析,探讨了UHMWPE／Kaolin复合材料的磨损机理。结果表明,采用聚合方法制备的含高岭土约6．6％（质量分数）UHMWPE／Kaolin复合材料的浆体冲蚀磨损性能优于UHMWPE,是一种有应用前景的复合材料。     

电弧能量对浸金属碳滑板材料载流摩擦磨损性能的影响

在销盘式高速载流摩擦磨损试验机上,通过正交试验考查了电弧能量对浸金属碳滑板材料载流摩擦磨损性能的影响;利用统计学相关系数理论和非线性回归分析,对电弧能量与摩擦系数、比磨损率进行定量比较分析,发现电弧能量与摩擦系数间存在一定的相关性,并与比磨损率间存在幂函数的关系;借助扫描电子显微镜、能谱分析仪和X射线衍射仪结合摩擦表面宏观温度的测量,分别对销试样电弧侵蚀后的表面膜微观结构、相组成及磨屑进行分析.结果表明:电弧能量严重影响摩擦副的载流摩擦磨损性能;电弧热效应使得局部接触表面温度超过熔点,浸渗金属熔融渗出摩擦表面,并使基体碳气化沉积于摩擦盘上,使得电弧侵蚀机理表现为材料转移和熔融喷溅.     

红石河堰塞湖漫顶溃坝风险评估

四川省青川县红石河堰塞湖是2008年5月12日汶川大地震形成的34座大型堰塞湖之一,是由东河口滑坡堵塞红石河形成的。该堰塞体高度约50 m、宽度约250 m、顺河向长度约500 m、形成的最大库容约400万m3。本文作者对红石河堰塞体做了较详尽的现场试验,包括土的冲蚀试验、土的基本物性试验等。基于现场试验数据,对土的冲蚀性和漫顶溃坝风险做了详细的分析。结果显示,从土的抗冲蚀性角度考虑,只要有水溢出就会有土体被冲蚀,这说明红石河堰塞体的漫顶溃决可能性较高。本文还提出经验公式来预测红石河堰塞体漫顶的溃决时间,大约为4.5d,如果考虑到大石块对抗冲蚀稳定性的有利影响,这一数值会增大。此外,还研究了溃决深度随时间的变化规律。     

气固两相边界层中拟序结构对壁面磨损的影响

本文由计算和实验首次说明在边界层入口处施加扰动能减轻固粒对壁面的磨损,而且加入扰动的强度越大,磨损量越小。该方法比壁面加肋条具有更好的抗磨效果,且负面作用较小,结论对工程应用有指导意义。