未胶结钙质砂中表面基础承载力研究

本文针对南海未胶结钙质砂开展室内表面基础模型试验、大变形有限元模拟和三轴排水试验,获得钙质砂承载特性与力学性质。通过进行室内模型试验,获得松砂和中密砂中反力-位移曲线,且发现基础周围颗粒破碎不明显。然后采用商业软件Abaqus中的大变形有限元模块耦合欧拉-拉格朗日(CEL)开展表面基础有限元计算,本构模型采用摩尔-库伦模型,本构参数通过三轴排水试验确定。有限元模型经室内模型试验结果验证可靠后,开展变参计算,探究基础尺寸和土体相对密实度对表面基础承载力的影响。结果表明,表面基础承载力随基础直径增加而增大,满足幂函数变化规律,进而给出了容许承载力和极限承载力随基础直径变化的预测公式。

《材料表面工程基础》课程教学改革探索

《材料表面工程基础》作为金属材料专业学生的必修课程,本课程的开设目的是让金属材料专业的学生学习理解材料表面工程的基础知识,《材料表面工程基础》是金属材料工程专业的一门重要的专业教育必修理论课程,在培养金属材料工程专业领域内材料的开发和应用能力有重要作用。本课程的主要任务是使学生学习涂料的各个重要组分的作用和特征,以及涂料中重要原料的合成原理、特点及制备方法,能够根据金属材料表面性能的需要,合理选择所需涂料,并能够熟练应用涂料生产的基本理论、科学地设计涂料生产工艺、合理选型涂料生产的重要设备等解决涂料从开发到生产全流程过程中的实际复杂工程问题。针对此课程知识面涉及广泛,内容抽象,实践性强,教学难度较大的特点,作者从教学内容、教学手段、考核方式等几个方面进行相关探索,充分调动学生学习该课程的积极性,活跃课堂气氛,提高教学质量。

表面矩形基础阻抗函数的集中参数模型

本文在系统地研究了Ｗｏｌｆ二阶集中参数模型的基础上．完整地给出了表面刚性矩形基础阻抗函数的集中参数模型。同以往的工作相比，本文给出的集中参数模型能在更宽的频段上反映精确解的变化。

建筑物表面泛白原因及对策分析

通过对已完成建筑物检查发现,个别基础表面及墙体表面呈现泛白现象,影响外观质量及墙体粉刷质量,个别工程甚至混凝土强度不能满足设计要求,对于这种现象需引起足够重视,并对出现的问题应区别对待。从多方面对泛白现象进行原因分析,阐述了泛白现象所引起的后果,并就如何做好预防措施,尽可能避免出现泛白现象。

A new algorithm for designing developable Bézier surfaces

A new algorithm is presented that generates developable Bézier surfaces through a Bézier curve called a directrix. The algorithm is based on differential geometry theory on necessary and sufficient conditions for a surface which is developable, and on degree evaluation formula for parameter curves and linear independence for Bernstein basis. No nonlinear characteristic equations have to be solved. Moreover the vertex for a cone and the edge of regression for a tangent surface can be obtained easily. Aumann’s algorithm for developable surfaces is a special case of this paper.

Wave Trapping by Dual Porous Barriers Near a Wall in the Presence of Bottom Undulation

Trapping of oblique surface gravity waves by dual porous barriers near a wall is studied in the presence of step type varying bottom bed that is connected on both sides by water of uniform depths. The porous barriers are assumed to be fixed at a certain distance in front of a vertical rigid wall. Using linear water wave theory and Darcy's law for flow past porous structure, the physical problem is converted into a boundary value problem. Using eigenfunction expansion in the uniform bottom bed region and modified mild-slope equation in the varying bottom bed region, the mathematical problem is handled for solution. Moreover, certain jump conditions are used to account for mass conservation at slope discontinuities in the bottom bed profile. To understand the effect of dual porous barriers in creating tranquility zone and minimum load on the sea wall, reflection coefficient, wave forces acting on the barrier and the wall, and surface wave elevation are computed and analyzed for different values of depth ratio, porous-effect parameter, incident wave angle, gap between the barriers and wall and slope length of undulated bottom. The study reveals that with moderate porosity and suitable gap between barriers and sea wall, using dual barriers an effective wave trapping system can be developed which will exert less wave force on the barriers and the rigid wall. The proposed wave trapping system is likely to be of immense help for protecting various facilities/infrastructures in coastal environment.

Study on manufacturing freeform surface parts in micro EDM based on skin effect theory

Micro fabrication of freeform surface parts made of hard and brittle materials is always a tough job in micro machining field. This paper tries to fabricate freeform surface feature by using smooth surface of tool electrode after tool wear in micro EDM. According to the skin effect theory, the tool end shape in the stage of uniform wear can be changed by adjusting the frequency of discharge pulse. The electrical energy distributing rule of tool electrode section in RC circuit has been investigated under the influence of skin effect, and the law of spark location change has been summarized. The experimental studies demonstrate that different shapes of tool ends can be achieved by varying the pulse frequencies of discharge power supply. Additionally, a micro part of freeform surface feature with high precision and good surface quality has been successfully obtained by micro EDM through adopting the smooth surface after tool wear.

Study on Lubrication Properties of Modified Nano ZnO in Base Oil

ZnO nanoparticles with an average size of 125 nm were prepared via homogeneous precipitation method and were characterized by SEM.The products were surface-modified by the surfactant SDS.Surface-modified nano particles were added at a mass ratio of 1.0%,2.0%,3.0%,and 4.0%,respectively,in base oil and their friction and wear behaviors were evaluated on a MRS-10D type four-ball wear tester.After four-ball wear tests,the morphology of the rubbing surfaces was evaluated with metallographic microscope.It was revealed that the modified nano ZnO had excellent behavior for improving anti-wear property and friction coefficient,which could greatly reduce the friction of machine parts.

Simulation of thermomechanical behavior during continuous casting process based on MiLE method

A new method called mixed Lagrangian and Eulerian method （MILE method） was used to simulate the thermomechanical behavior during continuous casting process of steel YF45MnV. The simulation results are basically in agreement with the measured data. The delaying period at the beginning of solidification is about 0.1. in square root of solidification time which is agreement with the data in literatures, and shell thickness increases in linear relation to square root of solidification time. The bloom surface temperature decreases gradually as the casting proceeds. The effective stress in the comer is much larger than that in the mid-face. The comer area is the dangerous zone of cracking. The effects of mold flux break temperature on the air gap and hot tearing indicator were also modeled. The model predicts that the bloom surface temperature increases with the increase of the mold flux break temperature, but the heat flux decreases with the increase of the mold flux break temperature. ,The hot tearing indicator is much smaller when the mold flux break temperature is higher.

Hydrogen Storage Capacity of C120 Nanocapsules： Density Functional Theory Based Treatments

The adsorption of hydrogen molecule on the external surface of pure 0120 nanocapsule and endohedrallyH2 @C120 complex has been examined using the density functional theory calculations. Several different bonding configu- rations are considered for the hydrogen molecule approaching the outer surface of the considered nanocages. It has been found that the adsorbed H2 molecule bound weakly to the outer surface of the pure C1~0 nanocapsules in agreement with the recent experimental and theoretical results while, it prefers to be adsorbed rather strongly on the side wall of the endohedrally /-/2@C120 complex. The adsorption of a single layer and bi-layer of two tt2 molecules on the most stable states of the considered H2@C120 complex appears to be feasible, although the molecules of the second layer are weakly bound. Furthermore, it is found that the formation of 100% coverage is favorable thermodynamically, which corresponds to about 20% by weight storage of 1-12 molecules. Thus, surprisingly, we arrive at the prediction that the C120 nanocapsules can be implemented as a novel material for energy storage.

有限厚度金属薄膜等离激元振荡

表面等离子体(surface plasmons,SPS)是一种电磁表面波,它在表面处场强最大,在垂直于界面方向是指数衰减场,它能够被电子也能被光波激发。表面等离子体是目前凝聚态的一个重要的研究方向,它受到了包括物理学家、化学家材料学家、生物学家等多个领域人士的极大的关注。

A finite volume algorithm based on overlapping meshes for simulation of hydrodynamic problems

A finite volume algorithm was established in order to investigate two-dimensional hydrodynamic problems. These include viscous free surface flow interaction with free rigid bodies in the case of large and/or relative motions. Two-phase flow with complex deformations at the interface was simulated using a fractional step-volume of fluid algorithm. In addition, body motions were captured by an overlapping mesh system. Here, flow variables are transferred using a simple fully implicit non-conservative interpolation scheme which maintains the second-order accuracy of implemented spatial discretisation. Code was developed and an appropriate set of problems investigated. Results show good potential for development of a virtual hydrodynamics laboratory.

Development of Online Machining and Measurement System in Die and Mold Manufacturing： Concept and Fundamental Experiments

The corrective machining to compensate the resulting errors is usually tried at plural times based on the trial-and-error process when the machining is realized in die and mold manufacturing. This corrective machining has an influence on accuracy and efficiency and is an important factor. The measurement system for measuring the forms of die and mold at all times is essential in order to machine the die and mold with high accuracy and efficiency. However, the problems of management and operation errors are found in compensating process of die and mold machining. In this paper, an online machining and measurement system in die and mold manufacturing is developed in order to overcome these problems. In this online system, 2-axis control system is added to a surface roughness measuring instrument, and both NC machining program and measured data are linked and controlled using a same computer. Therefore, the machining and measurement can be recognized for consistent process, and can be realized on the machine. This system has the advantages such as the high accuracy, low-price, and online convenience and so on. The possibility of practical use of this online system was investigated by fundamental experiments.

Bio-inspired special wetting surfaces via self-assembly

Self-assembly is the fundamental principle, which can occur spontaneously in nature. Through billions of years of evolution, nature has learned what is optimal. The optimized biological solution provides some inspiration for scientists and engineers. In the past decade, tinder the multi-disciplinary collaboration, bio-inspired special wetting surfaces have attracted much attention for both fundamental research and practical applications. In this review, we focus on recent research progress in bio-inspired special wetting surfaces via self-assembly, such as low adhesive superhydrophobic surfaces, high adhesive superhydrophobic surfaces, superamphiphobic surfaces, and stimuli-responsive surfaces. The challenges and perspectives of this research field in the future are also briefly addressed.

Analysis of the complex morphology of sediment particle surface based on electron microscope images

The morphology of sediment particles plays an important role in interfacial interactions.The difficulties in complex morphological description significantly limit the research on interfacial interactions.In this study,images of a single sediment particle extracted from electron microscope photos were used to analyze the gray values and present the probability of shape of the sediment particles.Moreover,the morphological features of the sediment particles were qualitatively described using the fractal method(surface area-volume method).The fractal dimension D of a single sediment particle was calculated to analyze the features and quantitative complexity of the sediment particle morphology.Results indicate that the probability of shape can provide intuitive morphological structure and fully describe the complex morphological characteristics of sediment particle surfaces.The fractal dimension abstractly described the complexity of the morphology of a sediment particle surface and matched well with the experimental results.The methods discussed in this study are suitable for describing the complex morphology of the sediment particle surface and lay the scientific foundation for further research on the interfacial interaction between the sediment particle and the pollutant.

China land soil moisture EnKF data assimilation based on satellite remote sensing data

Soil moisture plays an important role in land-atmosphere interactions. It is an important geophysical parameter in research on climate, hydrology, agriculture, and forestry. Soil moisture has important climatic effects by influencing ground evapotranspi ration, runoff, surface reflectivity, surface emissivity, surface sensible heat and latent heat flux. At the global scale, the extent of its influence on the atmosphere is second only to that of sea surface temperature. At the terrestrial scale, its influence is even greater than that of sea surface temperatures. This paper presents a China Land Soil Moisture Data Assimilation System (CLSMDAS) based on EnKF and land process models, and results of the application of this system in the China Land Soil Moisture Data Assimilation tests. CLSMDAS is comprised of the following components: 1) A land process mo del—Community Land Model Version 3.0 (CLM3.0)—developed by the US National Center for Atmospheric Research (NCAR); 2) Precipitation of atmospheric forcing data and surface-incident solar radiation data come from hourly outputs of the FY2 geostationary meteorological satellite; 3) EnKF (Ensemble Kalman Filter) land data assimilation method; and 4) Observa tion data including satellite-inverted soil moisture outputs of the AMSR-E satellite and soil moisture observation data. Results of soil moisture assimilation tests from June to September 2006 were analyzed with CLSMDAS. Both simulation and assimila tion results of the land model reflected reasonably the temporal-spatial distribution of soil moisture. The assimilated soil mois ture distribution matches very well with severe summer droughts in Chongqing and Sichuan Province in August 2006, the worst since the foundation of the People’s Republic of China in 1949. It also matches drought regions that occurred in eastern Hubei and southern Guangxi in September.

An automatic compensation method on compression effect and surface elasticity measurement based on the deflection signal of AFM

Atomic force microscope （AFM）, as an important instrument in micro/nano operation, has been widely used to measure sampie＇s height information. However, the so called compression effect, due to force aroused from the contact of AFM tip with a sample surface, would result in imprecision of the surface＇s height measurement, i.e., the measured height is lower than expected. Up to now, there is not any effective and rapid method to attenuate this kind of measurement error. Thus, in this paper, an algorithm to obtain high accurate height measurement is proposed. Firstly, the concept of force curve is used to analyze the basic principle of the compression effect. Secondly, an automatic compensation method by fusing the height signal and the deflection signal is proposed. The proposed algorithm can also be used to obtain a surface elasticity image. Finally, in order to validate the proposed method, two experiments are conducted with respect to mufti-wall nano-carbon tubes on a silicon substrate and graphemes on a mica substrate.

Remote sensing based monitoring of interannual variations in vegetation activity in China from 1982 to 2009

Terrestrial vegetation is one of the most important components of the Earth's land surface. Variations in terrestrial vegetation directly impact the Earth system's balance of material and energy. This paper describes detected variations in vegetation activity at a national scale for China based on nearly 30 years of remote sensing data derived from NOAA/AVHRR(1982–2006) and MODIS(2001–2009). Vegetation activity is analyzed for four regions covering agriculture, forests, grasslands, and China's Northwest region with sparse vegetation cover(including regions without vegetation). Relationships between variations in vegetation activity and climate change as well as agricultural production are also explored. The results show that vegetation activity has generally increased across large areas, especially during the most recent decade. The variations in vegetation activity have been driven primarily by human factors, especially in the southern forest region and the Northwest region with sparse vegetation cover. The results further show that the variations in vegetation activity have influenced agricultural production, but with a certain time lag.

Visible characteristics of space-based targets based on bidirectional reflection distribution function

A precise modeling method of visible characteristics of the space-based target was presented based on bidirectional reflection distribution function (BRDF). The background characteristics of the space-based target were represented to build models of direct solar radiation and reflected radiation of the Earth based on blackbody radiation theory. The geometry characteristics of the target were analyzed to establish a surface equation of each surface based on its body coordinate system. The material characteristics of the target surface were described by introducing a BRDF model which considers the character of surface Gauss statistics and self-shadow and is obtained by measurement and modeling in advance. The relative positions of the space-based target, the background radiation sources and the observation platform were determined based on coordinate con- version to judge contributing surface of the target to observation system. Then a mathematical model on visible characteristics of the space target for the given optical system was built by summing reflection components of all the surfaces. Simulation of visible characteristics of the space-based target in orbit was achieved according to its given geometrical dimensions, physical parameters and orbital parameters. The results show that the method is effective for analysis on visible characteristics of the space-based target when single reflection is considered and its surface is regularly described in a surface equation, which provides a way to real-time calculation of visible characteristics of the space-based target.