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搅拌摩擦焊镁合金隔声性能的研究

刘成武,钱林方

《中国工程科学》 2014年第16卷第8期页码 93-98

摘要：

伴随搅拌摩擦焊在镁合金上的广泛应用，对其隔声特性研究尤为重要，基于自适应网格技术，对搅拌摩擦焊过程进行数值模拟，为后续声学计算提供约束模态，解决了材料属性难以确定的问题，一定程度上实现了焊接与声学的结合。自行设计和制造了混响箱，用以测量焊接镁合金板的隔声量，弥补了混响室测试小试件的不足。进而使用finite element-statistical energy analysis（FE-SEA）混合法计算焊接件的隔声量，与试验结果进行对比，吻合良好，表明此方法行之有效。通过对比焊接前后镁合金板件的隔声量，发现在吻合低谷区，焊接后板件的隔声有所降低。为了研究焊接参数对隔声的影响，分别改变焊接速度和搅拌头旋转速度，观察隔声量的变化，结果表明，这些参数都需要合理的设置，并非越大或者越小越好。

关键词：搅拌摩擦焊混响箱 FE-SEA混合法焊接速度搅拌头旋转速度

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Key problems and solutions in supercritical CO

Haizhu WANG, Gensheng LI, Bin ZHU, Kamy SEPEHRNOORI, Lujie SHI, Yong ZHENG, Xiaomei SHI

《能源前沿（英文）》 2019年第13卷第4期页码 667-672 doi: 10.1007/s11708-019-0626-y

摘要： Supercritical CO fracturing is considered to be a new method for efficient exploitation of unconventional reservoirs, such as shale gas, coal bed methane, and tight sand stone gas. Supercritical CO has many special properties including low viscosity, high diffusion coefficient, and lack of surface tension, which brings about great advantages for fracturing. However, these properties also cause several problems, such as difficulty in proppant transportation, high friction loss, and high pump displacement. In this paper, the above problems were analyzed by combining field test with laboratory study and specific solutions to these problems are given. The high frictionloss in the pipeline could be reduced by developing a new drag reducing agent and selecting large-size casing. Besides, for the problem of poor capacity in proppant carrying and sand plug, the methods of adding tackifier into supercritical CO , increasing pump displacement and selecting ultra-low density proppants are proposed. Moreover, for the problem of fast leak-off and high requirement for pump displacement, the displacement can be increased or the pad fluid can be injected into the reservoir. After solving the above three problems, the field test of supercritical CO fracturing can be conducted. The research results can promote the industrialization process of supercritical CO fracturing.

关键词： supercritical CO₂ fracturing friction loss proppant carrying flied test problem

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Analysis of nonlinear channel friction inverse problem

CHENG Weiping, LIU Guohua

《结构与土木工程前沿（英文）》 2007年第1卷第2期页码 205-210 doi: 10.1007/s11709-007-0024-0

摘要： Based on the Backus-Gilbert inverse theory, the singular value decomposition (SVD) for general inverse matrices and the optimization algorithm are used to solve the channel friction inverse problem. The resolution and covariance friction inverse model in matrix form is developed to examine the reliability of solutions. Theoretical analyses demonstrate that the convergence rate of the general Newton optimization algorithm is in the second-order. The Wiggins method is also incorporated into the algorithm. Using the method, noise can be suppressed effectively, and the results are close to accurate solutions with proper control parameters. Also, the numerical stability can be improved.

关键词： singular SVD second-order covariance Theoretical

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Effects of leakage and friction on the miniaturization of a Wankel compressor

Yilin ZHANG, Wen WANG

《能源前沿（英文）》 2011年第5卷第1期页码 83-92 doi: 10.1007/s11708-010-0125-7

摘要： This paper presents a numerical simulation of the performance of a meso-scale Wankel compressor and discusses the factors affecting its miniaturization. The discussion is related to the effect of leakage and friction on the design limit (cooling capacity and dimension) of the meso Wankel compressor. In the simulation, the main leakage comes from the gaps between the rotor and the endplates as well as between the seal apex and the cylinder. The largest friction originates from the clearance among the end face of the eccentric shaft, the end faces of the rotor, and the endplates. The decreasing cooling capacity of the meso Wankel compressor increases the proportion of leakage to displacement and causes the coefficient of performance COP and the mechanical efficiency to decrease. The rational design cooling capacity limit for the meso-scale Wankel compressor is approximately 4 W.

关键词： meso-scale Wankel compressor leakage friction

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A multi-probe micro-fabrication apparatus based on the friction-induced fabrication method

Zhijiang WU, Chenfei SONG, Jian GUO, Bingjun YU, Linmao QIAN

《机械工程前沿（英文）》 2013年第8卷第4期页码 333-339 doi: 10.1007/s11465-013-0276-4

摘要：

A novel multi-probe micro-fabrication apparatus was developed based on the friction-induced fabrication method. The main parts of the apparatus include actuating device, loading system, and control system. With a motorized linear stage, the maximum fabrication area of 50 mm × 50 mm can be achieved, and the maximum sliding speed of probes can be as high as 10 mm/s. Through locating steel micro balls into indents array, the preparation of multi-probe array can be realized by a simple and low-cost way. The cantilever was designed as a structure of deformable parallelogram with two beams, by which the fabrication force can be precisely controlled. Combining the friction-induced scanning with selective etching in KOH solution, various micro-patterns were fabricated on Si(100) surface without any masks or exposure. As a low-cost and high efficiency fabrication device, the multi-probe micro-fabrication apparatus may encourage the development of friction-induced fabrication method and shed new light on the texture engineering.

关键词： friction-induced fabrication silicon surface texture friction multi-probe

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Panoramic variation analysis of a family with neurodevelopmental disorders caused by biallelic loss-of-function

《医学前沿（英文）》 doi: 10.1007/s11684-023-1006-x

摘要： Highly clinical and genetic heterogeneity of neurodevelopmental disorders presents a major challenge in clinical genetics and medicine. Panoramic variation analysis is imperative to analyze the disease phenotypes resulting from multilocus genomic variation. Here, a Pakistani family with parental consanguinity was presented, characterized with severe intellectual disability (ID), spastic paraplegia, and deafness. Homozygosity mapping, integrated single nucleotide polymorphism (SNP) array, whole-exome sequencing, and whole-genome sequencing were performed, and homozygous variants in TMEM141 (c.270G>A, p.Trp90*), DDHD2 (c.411+767_c.1249-327del), and LHFPL5 (c.250delC, p.Leu84*) were identified. A Tmem141^{p.Trp90*/p.Trp90*} mouse model was generated. Behavioral studies showed impairments in learning ability and motor coordination. Brain slice electrophysiology and Golgi staining demonstrated deficient synaptic plasticity in hippocampal neurons and abnormal dendritic branching in cerebellar Purkinje cells. Transmission electron microscopy showed abnormal mitochondrial morphology. Furthermore, studies on a human in vitro neuronal model (SH-SY5Y cells) with stable shRNA-mediated knockdown of TMEM141 showed deleterious effect on bioenergetic function, possibly explaining the pathogenesis of replicated phenotypes in the cross-species mouse model. Conclusively, panoramic variation analysis revealed that multilocus genomic variations of TMEM141, DDHD2, and LHFPL5 together caused variable phenotypes in patient. Notably, the biallelic loss-of-function variants of TMEM141 were responsible for syndromic ID.

关键词： neurodevelopmental disorder autosomal recessive intellectual disability consanguinity spastic paraplegia hearing loss TMEM141

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微分和表观静摩擦系数的表式

王渭源

《中国工程科学》 2001年第3卷第8期页码 29-32

摘要：

当前，工程师和科学家都对微牛和纳牛量级载荷静摩擦系数（以下简称微牛纳牛静摩擦系数）很感兴趣。但文献中至今没有详细讨论过微牛纳牛静摩擦系数与载荷的关系，而且发表的实验结果都不相互讨论。从微分静摩擦系数的定义出发，导出几种典型模型下微分静摩擦系数和表观静摩擦系数的表式，并据此广泛讨论这些文献中的实验结果。

关键词：微分静摩擦系数微牛纳牛静摩擦系数表观静摩擦系数宏观静摩擦系数

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Air-side heat transfer and friction characteristics of biofouled evaporator under wet conditions

Hui PU, Guoliang DING, Xiaokui MA, Haitao HU, Yifeng GAO,

《能源前沿（英文）》 2010年第4卷第3期页码 306-312 doi: 10.1007/s11708-009-0067-0

摘要： The effects of biofouling on air-side heat transfer and friction characteristics under wet conditions of three biofouled finned tube heat exchangers and one clean finned tube heat exchanger were investigated experimentally. Experimental results indicate that the biofouled fin efficiency of the evaporator decreases by 15.5% compared with the clean evaporator under the condition of the biofouled area ratio of 60% at the inlet air velocity of 2.0m/s; The ranges of friction fouling factor and heat transfer fouling factor are 19.8%―43.1% and ―15.6%―13.1%, respectively; a small quantity of biofouled particles can enhance heat transfer at low Reynolds number, and the enhancement effect decreases with the increase of Reynolds number.

关键词： finned tube evaporator fouling heat transfer friction

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Modeling of the minimum cutting thickness in micro cutting with consideration of the friction around

Tianfeng ZHOU, Ying WANG, Benshuai RUAN, Zhiqiang LIANG, Xibin WANG

《机械工程前沿（英文）》 2020年第15卷第1期页码 81-88 doi: 10.1007/s11465-019-0561-y

摘要： Friction modeling between the tool and the workpiece plays an important role in predicting the minimum cutting thickness during TC4 micro machining and finite element method (FEM) cutting simulation. In this study, a new three-region friction modeling is proposed to illustrate the material flow mechanism around the friction zone in micro cutting; estimate the stress distributions on the rake, edge, and clearance faces of the tool; and predict the stagnation point location and the minimum cutting thickness. The friction modeling is established by determining the distribution of normal and shear stress. Then, it is applied to calculate the stagnation point location on the edge face and predict the minimum cutting thickness. The stagnation point and the minimum cutting thickness are also observed and illustrated in the FEM simulation. Micro cutting experiments are conducted to validate the accuracy of the friction and the minimum cutting thickness modeling. Comparison results show that the proposed friction model illustrates the relationship between the normal and sheer stress on the tool surface, thereby validating the modeling method of the minimum cutting thickness in micro cutting.

关键词： tool friction minimum cutting thickness finite element method tool edge radius micro cutting

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Study of base friction simulation tests based on a complicated engineered bridge slope

Liu HE, Guang WU, Hua WANG

《结构与土木工程前沿（英文）》 2012年第6卷第4期页码 393-397 doi: 10.1007/s11709-012-0174-6

摘要： In this paper, a physical base friction test model of a slope is established. The model is based on similarity principles and the geological conditions of a complicated bridge slope during construction, deformation and failure. The behavior of the slope in both its natural state and during excavation loading is qualitatively analyzed through base friction tests. The base friction test results are then subjected to comparison and analysis using finite element numerical simulation. The findings show that the whole engineered slope tends to stabilize in its natural state, whereas instabilities will arise at faulted rock masses located near bridge piers during excavation loading. Therefore, to ensure normal construction operation of bridge works, it is suggested that pre-reinforcement of faulted rock masses be performed.

关键词： base friction test slope stability evaluation bridge slope

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Parametric study on the Multangular-Pyramid Concave Friction System (MPCFS) for seismic isolation

Wei XIONG, Shan-Jun ZHANG, Li-Zhong JIANG, Yao-Zhuang LI

《结构与土木工程前沿（英文）》 2020年第14卷第5期页码 1152-1165 doi: 10.1007/s11709-020-0659-7

摘要： A series of comprehensive parametric studies are conducted on a steel-frame structure Finite-Element (FE) model with the Multangular-Pyramid Concave Friction System (MPCFS) installed as isolators. This new introduced MPCFS system has some distinctive features when compared with conventional isolation techniques, such as increased uplift stability, improved self-centering capacity, non-resonance when subjected to near-fault earthquakes, and so on. The FE model of the MPCFS is first established and evaluated by comparison between numerical and theoretical results. The MPCFS FE model is then incorporated in a steel-frame structural model, which is subjected to three chosen earthquakes, to verify its seismic isolation. Further, parametric study with varying controlling parameters, such as isolation foundation, inclination angle, friction coefficient, and earthquake input, is carried out to extract more detailed dynamic response of the MPCFS structure. Finally, limitations of this study are discussed, and conclusions are made. The simulations testify the significant seismic isolation of the MPCFS. This indicates the MPCFS, viewed as the beneficial complementary of the existing well-established and matured isolation techniques, may be a promising tool for seismic isolation of near-fault earthquake prone zones. This verified MPCFS FE model can be incorporated in future FE analysis. The results in this research can also guide future optimal parameter design of the MPCFS.

关键词： seismic isolation variable frequency near-fault earthquake numerical study Multangular-Pyramid Concave Friction System

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Power fluctuation and power loss of wind turbines due to wind shear and tower shadow

Binrong WEN, Sha WEI, Kexiang WEI, Wenxian YANG, Zhike PENG, Fulei CHU

《机械工程前沿（英文）》 2017年第12卷第3期页码 321-332 doi: 10.1007/s11465-017-0434-1

摘要：

The magnitude and stability of power output are two key indices of wind turbines. This study investigates the effects of wind shear and tower shadow on power output in terms of power fluctuation and power loss to estimate the capacity and quality of the power generated by a wind turbine. First, wind speed models, particularly the wind shear model and the tower shadow model, are described in detail. The widely accepted tower shadow model is modified in view of the cone-shaped towers of modern large-scale wind turbines. Power fluctuation and power loss due to wind shear and tower shadow are analyzed by performing theoretical calculations and case analysis within the framework of a modified version of blade element momentum theory. Results indicate that power fluctuation is mainly caused by tower shadow, whereas power loss is primarily induced by wind shear. Under steady wind conditions, power loss can be divided into wind farm loss and rotor loss. Wind farm loss is constant at 3α(3α−1)R²/(8H²). By contrast, rotor loss is strongly influenced by the wind turbine control strategies and wind speed. That is, when the wind speed is measured in a region where a variable-speed controller works, the rotor loss stabilizes around zero, but when the wind speed is measured in a region where the blade pitch controller works, the rotor loss increases as the wind speed intensifies. The results of this study can serve as a reference for accurate power estimation and strategy development to mitigate the fluctuations in aerodynamic loads and power output due to wind shear and tower shadow.

关键词： wind turbine wind shear tower shadow power fluctuation power loss

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Turnover and loss of nitrogenous compounds during composting of food wastes

YANG Yanmei, ZHANG Xiangfeng, YANG Zhifeng, XI Beidou, LIU Hongliang

《环境科学与工程前沿（英文）》 2008年第2卷第2期页码 251-256 doi: 10.1007/s11783-008-0042-8

摘要： Few people have so far explored into the research of the dynamics of various nitrogenous compounds (including water-soluble nitrogen) in composting of food wastes. This study aimed to investigate the solid-phase nitrogen, water-soluble nitrogen, nitrogen loss together with ammonia volatilization in the process of food wastes composting. A laboratory scale static aerobic reactor in the experiment was employed in the composting process of a synthetic food waste, in which sawdust was used as the litter amendment. In the experiment, oxygen was supplied by continuous forced ventilation for 15 days. The results have shown that the concentrations of total nitrogen and organic nitrogen decrease significantly in the composting process, whereas NH-N concentration increases together with little fluctuation in NO-N. After composting, the total content of the water-soluble nitrogen compounds in the compost greatly increased, the total nitrogen loss amounted to 50% of the initial nitrogen, mainly attributed to ammonia volatilization. 56.7% of the total ammonia volatilization occurred in the middle and late composting of the thermophilic stage. This suggested that the control at the middle and late composting of thermophilic stage is the key to nitrogen loss in the food waste compost.

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Winner determination problem with loss-averse buyers in reverse auctions

Xiaohu QIAN, Min HUANG, Yangyang YU, Xingwei WANG

《工程管理前沿（英文）》 2017年第4卷第2期页码 212-220 doi: 10.15302/J-FEM-2017019

摘要： Reverse auctions have been widely adopted for purchasing goods and services. This paper considers a novel winner determination problem in a multiple-object reverse auction in which the buyer involves loss-averse behavior due to uncertain attributes. A corresponding winner determination model based on cumulative prospect theory is proposed. Due to the NP-hard characteristic, a loaded route strategy is proposed to ensure the feasibility of the model. Then, an improved ant colony algorithm that consists of a dynamic transition strategy and a Max-Min pheromone strategy is designed. Numerical experiments are conducted to illustrate the effectiveness of the proposed model and algorithm. We find that under the loaded route strategy, the improved ant colony algorithm performs better than the basic ant colony algorithm. In addition, the proposed model can effectively characterize the buyer’s loss-averse behavior.

关键词： reverse auction loss aversion winner determination improved ant colony algorithm

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Laboratory and field evaluation of asphalt pavement surface friction resistance

Zhong WU, Chris ABADIE

《结构与土木工程前沿（英文）》 2018年第12卷第3期页码 372-381 doi: 10.1007/s11709-017-0463-1

摘要：

Pavement surface friction is a significant factor for driving safety and plays a critical role in reducing wet-pavement crashes. However, the current asphalt mixture design procedure does not directly consider friction as a requirement. The objective of this study was to develop a surface friction prediction model that can be used during a wearing course mixture design. To achieve the objective, an experimental study was conducted on the frictional characteristics of typical wearing course mixtures in Louisiana. Twelve wearing course mixtures including dense-graded and open-graded mixes with different combinations of aggregate sources were evaluated in laboratory using an accelerated polishing and testing procedure considering both micro- and macro texture properties. In addition, the surface frictional properties of asphalt mixtures were measured on twenty-two selected asphalt pavement sections using different in situ devices including Dynamic Friction Tester (DFT), Circular Texture Meter (CTM), and Lock-Wheel Skid Trailer (LWST). The results have led to develop a procedure for predicting pavement end-of-life skid resistance based on the aggregate blend polish stone value, gradation parameters, and traffic, which is suited in checking whether the selected aggregates in a wearing course mix design would meet field friction requirements under a certain design traffic polishing.

关键词： friction skid resistance polishing PSV LWST micro-texture macro-texture