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Correlation between tension softening relation and crack extension resistance in concrete

Xiufang ZHANG , Shilang XU ,

《结构与土木工程前沿（英文）》 2009年 第3卷 第3期   页码 323-329 doi: 10.1007/s11709-009-0041-2

摘要： Changes of the material fracture energy consumption with crack propagation can be described by a crack extension resistance curve, one of the fundamental fracture criteria in crack mechanics. Recently, experimental observation of the fracture behavior in concrete was used to develop a new fracture criterion, the crack extension resistance curve, to analyze crack propagation during the entire concrete fracture process. The variation of the crack extension resistance is mainly associated with the energy consumption in the fracture process zone ahead of the stress-free crack tip. The crack extension resistance is then a function of the softening curve, which is a basic mechanical property in the fracture process zone. The relationship between the softening curve and the crack extension resistance curve is then analyzed based on results of three-point bending beams tests. The results indicate that the characteristic points of the crack extension resistance curve is closely related to the characteristic point on used tension softening curve.

关键词： concrete     fracture process zone     crack extension GR resistance     tension softening curve    

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Behavior of dam concrete under biaxial compression-tension and triaxial compression-compression-tension

WANG Huailiang, SONG Yupu

《结构与土木工程前沿（英文）》 2008年 第2卷 第4期   页码 323-328 doi: 10.1007/s11709-008-0043-5

摘要： In order to meet the requirement for nonlinear analysis and design of mass concrete structures, the deformation behavior and strength of three-graded concrete specimens 250 mm × 250 mm × 400 mm with a maximum aggregate size of 80 mm and the corresponding wet-screened concrete specimens 150 mm × 150 mm × 300 mm with a maximum aggregate size of 40 mm were studied experimentally. Specimens subjected to biaxial compression-tension (C-T) and triaxial compression-compression-tension (C-C-T) stress states. Test data indicate that both the deformation and strength of the mass concrete specimens are lower than those of the corresponding wet-screened concrete small specimens, but the initial tangent modulus of the stress-strain curve of the former is greater than that of the latter. Test results show that the wet-screened effect and size effect of the specimens under complex stress states are obvious such that these should be considered in the design of mass concrete structures. In addition, respective failure criteria for mass concrete in principal stress space and octahedron stress space are proposed.

关键词： requirement     wet-screened concrete     compression-tension     maximum aggregate     principal    

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Is there an inverted U-shaped curve?Empirical analysis of the Environmental Kuznets Curve in agrochemicals

Fei LI,Suocheng DONG,Fujia LI,Libiao YANG

《环境科学与工程前沿（英文）》 2016年 第10卷 第2期   页码 276-287 doi: 10.1007/s11783-014-0700-y

摘要： As the largest contributor to water impairment, agriculture-related pollution has attracted the attention of scientists as well as policy makers, and quantitative information is being sought to focus and advance the policy debate. This study applies the panel unit root, heterogeneous panel cointegration, and panel-based dynamic ordinary least squares to investigate the Environmental Kuznets Curve on environmental issues resulting from use of agricultural synthetic fertilizer, pesticide, and film for 31 provincial economies in mainland China from 1989 to 2009. The empirical results indicate a positive long-run co-integrated relationship between the environmental index and real GDP per capita. This relationship takes on the inverted U-shaped Environmental Kuznets Curve, and the value of the turning point is approximately 10,000–13,000, 85,000–89,000 and over 160,000 CNY, for synthetic fertilizer nitrogen indicator, fertilizer phosphorus indicator and pesticide indicator, respectively. At present, China is subject to tremendous environmental pressure and should assign more importance to special agriculture-related environmental issues.

关键词： Environmental Kuznets Curve     agrochemical     China    

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Seismic stability of earth slopes with tension crack

Yundong ZHOU, Fei ZHANG, Jingquan Wang, Yufeng GAO, Guangyu DAI

《结构与土木工程前沿（英文）》 2019年 第13卷 第4期   页码 950-964 doi: 10.1007/s11709-019-0529-3

摘要： Cracks at the crest of slopes frequently occur during earthquakes. Such cracks result from limited tension strength of the soil. A tension cut-off in Mohr-Coulomb shear strength can represent this limited strength. Presented is an extension of variational analysis of slope stability with a tension crack considering seismicity. Both translational and rotational failure mechanisms are included in a pseudo-static analysis of slope stability. Developed is a closed-form to assess the seismic stability of slopes with zero tensile strength. The results indicate that the presence of the tension crack has significant effects on the seismic stability of slopes, i.e. leading to small value of the yield acceleration. Considering soil tension strength in seismic slope analysis may lead to overestimation on the stability, as much as 50% for vertical slopes. Imposing tension crack results in transit of the critical failure mode to a straight line from a log-spiral, except for flat slopes with small soil cohesion. Under seismic conditions, large cohesion may increase the depth of crack, moving it closer to the slope.

关键词： slope stability     tension     crack     limit equilibrium     seismic effect    

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Surface tension of liquid metal: role, mechanism and application

Xi ZHAO, Shuo XU, Jing LIU

《能源前沿（英文）》 2017年 第11卷 第4期   页码 535-567 doi: 10.1007/s11708-017-0463-9

摘要： Surface tension plays a core role in dominating various surface and interface phenomena. For liquid metals with high melting temperature, a profound understanding of the behaviors of surface tension is crucial in industrial processes such as casting, welding, and solidification, etc. Recently, the room temperature liquid metal (RTLM) mainly composed of gallium-based alloys has caused widespread concerns due to its increasingly realized unique virtues. The surface properties of such materials are rather vital in nearly all applications involved from chip cooling, thermal energy harvesting, hydrogen generation, shape changeable soft machines, printed electronics to 3D fabrication, etc. owing to its pretty large surface tension of approximately 700 mN/m. In order to promote the research of surface tension of RTLM, this paper is dedicated to present an overview on the roles and mechanisms of surface tension of liquid metal and summarize the latest progresses on the understanding of the basic knowledge, theories, influencing factors and experimental measurement methods clarified so far. As a practical technique to regulate the surface tension of RTLM, the fundamental principles and applications of electrowetting are also interpreted. Moreover, the unique phenomena of RTLM surface tension issues such as surface tension driven self-actuation, modified wettability on various substrates and the functions of oxides are discussed to give an insight into the acting mechanism of surface tension. Furthermore, future directions worthy of pursuing are pointed out.

关键词： surface tension     liquid metal     soft machine     printed electronics     electrowetting     self-actuation    

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Calculation method of load distribution on pipe threaded connections under tension load

Shoujun CHEN, Lianxin GAO, Qi AN

《机械工程前沿（英文）》 2011年 第6卷 第2期   页码 241-248 doi: 10.1007/s11465-011-0219-x

摘要：

This paper presents a new calculation method that can calculate the load distribution on pipe threaded connections under tension load. On the basis of elastic mechanics, the new method was developed by analyzing each thread tooth, and a new deformation and covariant equation by making a mechanics analysis on each thread tooth was obtained. Compared with the traditional method proposed by the previous references, the new deformation and covariant equation could be used to describe the relation between the previous and the next thread tooth. By applying the new method on the sample of P-110S pipe threaded connection, the obtained results show that the load on thread tooth mainly concentrates on the four or five threads engaged and the middle teeth were not utilized well to bear the loads. The model offers a new way to calculate the loads carried on the thread teeth under tension load.

关键词： load distribution     calculation method     pipe threaded connections     tension load    

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Comparing the effects of Bassini versus tension-free hernioplasty: 3 years’ follow-up

Yulong SHI, Zhongxue SU, Leping LI, Hongjun LIU, Changqing JING,

《医学前沿（英文）》 2010年 第4卷 第4期   页码 463-468 doi: 10.1007/s11684-010-0050-5

摘要： In order to compare the effects of Bassini and tension-free mesh hernioplasty, a total of 552 patients with inguinal hernia who were subjected to surgical treatment in our hospital were randomly divided into the following two groups: the Bassini group (=269) and the tension-free mesh group (=283). The recurrence rates, pain, discomfort, and other complications were recorded, and the causes of the complications were explored. The recurrence rate in the Bassini group was 8.9% (24/269), significantly higher than that in the tension-free repair group (2.8%, 8/283). In addition, the recurrence rates in the Bassini and tension-free groups before 2004 were 12.6% and 5.6%, respectively, which were markedly higher than the rates after 2004 (5.3% and 0.7%, respectively). The rate of post-operative discomfort and pain within the first three months was higher in the Bassini group compared to the tension-free group (25.7% 18.5%, respectively). However, there was no difference after three months in the rate of post-operative discomfort and pain, incidence of infection, or scrotal edema between the two groups. The average hospital stay in the Bassini group was longer than that in the tension-free repair group (7.6€±€1.2 4.5€±€2.2 days, respectively), but the cost was lower (4518.0€±€510 6221.3€±€578 yuan, respectively). Thus, tension-free mesh hernioplasty is indicated for most inguinal hernia patients due to the low recurrence rate, rapid recovery time, and treatment success, but the traditional Bassini procedure has lower cost and other beneficial effects and is still suitable for some patients.

关键词： hernioplasty     Bassini repair     tension-free repair     complication    

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Learning curve of totally thoracoscopic pulmonary segmentectomy

Weibing Wu, Jing Xu, Wei Wen, Yue Yu, Xinfeng Xu, Quan Zhu, Liang Chen

《医学前沿（英文）》 2018年 第12卷 第5期   页码 586-592 doi: 10.1007/s11684-017-0566-z

摘要：

Totally thoracoscopic pulmonary segmentectomy (TTPS) is a feasible and safe technique that requires advanced thoracoscopic skills and knowledge of pulmonary anatomy. However, data describing the learning curve of TTPS have yet to be obtained. In this study, 128 patients who underwent TTPS between September 2010 and December 2013 were retrospectively analyzed to evaluate the learning curve and were divided chronologically into three phases, namely, ascending phase (A), plateau phase (B), and descending phase (C), through cumulative summation (CUSUM) for operative time (OT). Phases A, B, and C comprised 39, 33, and 56 cases, respectively. OT and blood loss decreased significantly from phases A to C (P <0.01), and the frequency of intraoperative bronchoscopy for target bronchus identification decreased gradually (A, 8/39; B, 4/33; C, 3/56; P = 0.06). No significant differences were observed in demographic factors, conversion, complications, hospital stay, and retrieved lymph nodes among the three phases. Surgical outcomes and techniques improved with experience and volume. CUSUMOT indicated that the learning curve of TTPS should be more than 72 cases.

关键词： thoracoscopic     segmentectomy     learning curve     CUSUM    

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High-precision gyro-stabilized control of a gear-driven platform with a floating gear tension device

《机械工程前沿（英文）》 2021年 第16卷 第3期   页码 487-503 doi: 10.1007/s11465-021-0635-5

摘要： This study presents an improved compound control algorithm that substantially enhances the anti-disturbance performance of a gear-drive gyro-stabilized platform with a floating gear tension device. The tension device can provide a self-adjustable preload to eliminate the gap in the meshing process. However, the weaker gear support stiffness and more complex meshing friction are also induced by the tension device, which deteriorates the control accuracy and the ability to keep the aim point of the optical sensors isolated from the platform motion. The modeling and compensation of the induced complex nonlinearities are technically challenging, especially when base motion exists. The aim of this research is to cope with the unmeasured disturbances as well as the uncertainties caused by the base lateral motion. First, the structural properties of the gear transmission and the friction-generating mechanism are analyzed, which classify the disturbances into two categories: Time-invariant and time-varying parts. Then, a proportional-integral controller is designed to eliminate the steady-state error caused by the time-invariant disturbance. A proportional multiple-integral-based state augmented Kalman filter is proposed to estimate and compensate for the time-varying disturbance that can be approximated as a polynomial function. The effectiveness of the proposed compound algorithm is demonstrated by comparative experiments on a gear-drive pointing system with a floating gear tension device, which shows a maximum 76% improvement in stabilization precision.

关键词： inertially stabilized platform     floating gear tension device     nonlinear friction     disturbance compensation     proportional multiple-integral observer    

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Soil-water interaction in unsaturated expansive soil slopes

ZHAN Liangtong

《结构与土木工程前沿（英文）》 2007年 第1卷 第2期   页码 198-204 doi: 10.1007/s11709-007-0023-1

摘要： The intensive soil-water interaction in unsaturated expansive soil is one of the major reasons for slope failures. In this paper, the soil-water interaction is investigated with the full-scale field inspection of rainwater infiltration and comprehensive experiments, including wetting-induced softening tests, swelling, and shrinkage tests. It is demonstrated that the soil-water interaction induced by seasonal wetting-drying cycles is very complex, and it involves coupled effects among the changes in water content, suction, stress, deformation and shear strength. In addition, the abundant cracks in the expansive soil play an important role in the soil-water interaction. The cracks disintegrate the soil mass, and more importantly, provide easy pathways for rainfall infiltration. Infiltration of rainwater not only results in wetting-induced softening of the shallow unsaturated soil layers, but also leads to the increase of horizontal stress. The increase of horizontal stress may lead to a local passive failure. The seasonal wetting-drying cycles tend to result in a down-slope creeping of the shallow soil layer, which leads to progressive slope failure.

关键词： strength     intensive soil-water     comprehensive     Infiltration     wetting-induced softening    

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Forward osmosis coupled with lime-soda ash softening for volume minimization of reverse osmosis

Jiandong Lu, Shijie You, Xiuheng Wang

《环境科学与工程前沿（英文）》 2021年 第15卷 第1期 doi: 10.1007/s11783-020-1301-6

摘要： Abstract • Forward osmosis (FO) coupled with chemical softening for CCI ROC minimization • Effective removal of scale precursor ions by lime-soda ash softening • Enhanced water recovery from 54% to 86% by mitigation of FO membrane scaling • High-purity CaCO3 was recovered from the softening sludge • Membrane cleaning efficiency of 88.5% was obtained by EDTA for softened ROC Reverse osmosis (RO) is frequently used for water reclamation from treated wastewater or desalination plants. The RO concentrate (ROC) produced from the coal chemical industry (CCI) generally contains refractory organic pollutants and extremely high-concentration inorganic salts with a dissolved solids content of more than 20 g/L contributed by inorganic ions, such as Na+, Ca2+, Mg2+, Cl−, and SO42−. To address this issue, in this study, we focused on coupling forward osmosis (FO) with chemical softening (FO-CS) for the volume minimization of CCI ROC and the recovery of valuable resources in the form of CaCO3. In the case of the real raw CCI ROC, softening treatment by lime-soda ash was shown to effectively remove Ca2+/Ba2+ (>98.5%) and Mg2+/Sr2+/Si (>80%), as well as significantly mitigate membrane scaling during FO. The softened ROC and raw ROC corresponded to a maximum water recovery of 86% and 54%, respectively. During cyclic FO tests (4 × 10 h), a 27% decline in the water flux was observed for raw ROC, whereas only 4% was observed for softened ROC. The cleaning efficiency using EDTA was also found to be considerably higher for softened ROC (88.5%) than that for raw ROC (49.0%). In addition, CaCO3 (92.2% purity) was recovered from the softening sludge with an average yield of 5.6 kg/m3 treated ROC. This study provides a proof-of-concept demonstration of the FO-CS coupling process for ROC volume minimization and valuable resources recovery, which makes the treatment of CCI ROC more efficient and more economical.

关键词： Coal chemical industry     Forward osmosis     Chemical softening     Reverse osmosis concentrate    

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悬索桥短吊索索力测试的探讨

齐东春,郭健,沈锐利

《中国工程科学》 2010年 第12卷 第7期   页码 78-83

摘要：

因难以准确确定吊索的计算长度和抗弯刚度，按照公式法计算短吊索的索力误差一般较大。以新沟河大桥悬索桥吊索索力测试为研究背景，分析了吊索的边界条件、抗弯刚度、计算索长及线密度等因素对索力测试精度的影响，表明公式法的简化假设对短吊索不适用。介绍了有限元法分析吊索索力的方法，按吊索的实际尺寸建立有限元模型，首先识别出吊索的抗弯刚度，然后建立各吊索的索力—频率对应表格，查表即可得到实测频率对应的索力。该方法应用到新沟河大桥的施工监控，证明是一种行之有效的方法。

关键词： 短吊索     索力测试     频率法     抗弯刚度     有限元法    

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Numerical investigation of circle defining curve for two-dimensional problem with general boundaries

Chung Nguyen VAN

《结构与土木工程前沿（英文）》 2019年 第13卷 第1期   页码 92-102 doi: 10.1007/s11709-018-0472-8

摘要： The scaled boundary finite element method (SBFEM) is applied to the static analysis of two dimensional elasticity problem, boundary value problems domain with the domain completely described by a circular defining curve. The scaled boundary finite element equations is formulated within a general framework integrating the influence of the distributed body force, general boundary conditions, and bounded and unbounded domain. This paper investigates the possibility of using exact geometry to form the exact description of the circular defining curve and the standard finite element shape function to approximate the defining curve. Three linear elasticity problems are presented to verify the proposed method with the analytical solution. Numerical examples show the accuracy and efficiency of the proposed method, and the performance is found to be better than using standard linear element for the approximation defining curve on the scaled boundary method.

关键词： exact geometry     circular defining curve     general boundaries     SBFEM    

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薄板坯连铸连轧铁素体+珠光体类型钢的强化与软化

傅杰,吴华杰,刘阳春

《中国工程科学》 2008年 第10卷 第4期   页码 65-72

摘要：

根据钢的综合强化理论，控制A1附近温度下钢中碳的析出，研究了HSLC钢的强化与软化问题。结果表明：薄板坯连铸连轧HSLC钢，强度还可进一步提高；通过回火缓冷，薄板坯连铸连轧HSLC钢ZJ330的σs从344 MPa降至225 MPa，能满足冷轧基板要求。讨论了有关铁素体轧制、超细晶粒钢以及一种可能的新型建筑材料等问题。

关键词： HSLC钢     强化     软化     冷轧基板     超级钢    

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表面张力辅助去核法对小鼠卵母细胞的去核研究

孟庆刚,朱士恩,曾申明,张忠诚

《中国工程科学》 2001年 第3卷 第11期   页码 65-69

摘要：

论述了一种新的小鼠卵母细胞去核方法一一表面张力辅助去核法（STA),并同时与其他3种去核方 法（简称A法、B法、C法）进行比较。STA法是将卵母细胞核在固定管的辅助下，借助液体表面张力通过透 明带上的破口被挤出。经STA法去核的卵母细胞质体用于电融合介导的小鼠耳成纤维细胞核移植实验，结果有 76.1 %细胞与细胞质体融合形成重组胚，85.4 %的重组胚形成原核，49.4%卵裂形成2-细胞。

关键词： 表面张力辅助     去核     卵母细胞     小鼠    

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标题 作者 时间 类型 操作

Correlation between tension softening relation and crack extension resistance in concrete

Xiufang ZHANG , Shilang XU ,

期刊论文

Behavior of dam concrete under biaxial compression-tension and triaxial compression-compression-tension

WANG Huailiang, SONG Yupu

期刊论文

Is there an inverted U-shaped curve?Empirical analysis of the Environmental Kuznets Curve in agrochemicals

Fei LI,Suocheng DONG,Fujia LI,Libiao YANG

期刊论文

Seismic stability of earth slopes with tension crack

Yundong ZHOU, Fei ZHANG, Jingquan Wang, Yufeng GAO, Guangyu DAI

期刊论文

Surface tension of liquid metal: role, mechanism and application

Xi ZHAO, Shuo XU, Jing LIU

期刊论文

Calculation method of load distribution on pipe threaded connections under tension load

Shoujun CHEN, Lianxin GAO, Qi AN

期刊论文

Comparing the effects of Bassini versus tension-free hernioplasty: 3 years’ follow-up

Yulong SHI, Zhongxue SU, Leping LI, Hongjun LIU, Changqing JING,

期刊论文

Learning curve of totally thoracoscopic pulmonary segmentectomy

Weibing Wu, Jing Xu, Wei Wen, Yue Yu, Xinfeng Xu, Quan Zhu, Liang Chen

期刊论文

High-precision gyro-stabilized control of a gear-driven platform with a floating gear tension device

期刊论文

Soil-water interaction in unsaturated expansive soil slopes

ZHAN Liangtong

期刊论文

Forward osmosis coupled with lime-soda ash softening for volume minimization of reverse osmosis

Jiandong Lu, Shijie You, Xiuheng Wang

期刊论文

悬索桥短吊索索力测试的探讨

齐东春,郭健,沈锐利

期刊论文

Numerical investigation of circle defining curve for two-dimensional problem with general boundaries

Chung Nguyen VAN

期刊论文

薄板坯连铸连轧铁素体+珠光体类型钢的强化与软化

傅杰,吴华杰,刘阳春

期刊论文

表面张力辅助去核法对小鼠卵母细胞的去核研究

孟庆刚,朱士恩,曾申明,张忠诚

期刊论文