资源类型

期刊论文 71

年份

2023 4

2022 8

2021 3

2020 5

2019 6

2018 5

2017 5

2016 2

2015 3

2014 3

2013 5

2012 5

2011 1

2010 4

2009 5

2007 1

2006 1

2004 2

2003 2

展开 ︾

关键词

力常数 2

大规格 2

无应力长度 2

键能 2

键长 2

1860 MPa等级 1

3D打印 1

4250 m 1

ANSYS二次开发 1

PCB缺陷检测 1

S-N曲线 1

TORCH 1

cDNA克隆 1

一致性 1

不对称双连拱隧道 1

主缆索股 1

优化 1

促黄体激素（LH） 1

修补 1

展开 ︾

检索范围：

排序： 展示方式：

The defect-length effect in corrosion detection with magnetic method for bridge cables

Qiwei ZHANG, Rongya XIN

《结构与土木工程前沿（英文）》 2018年 第12卷 第4期   页码 662-671 doi: 10.1007/s11709-018-0512-4

摘要：

Quantitative evaluation of the steel corrosion in cables is significant for the safe operation of cable-supported bridges. The magnetic flux (MF) examination shows great potential to detect the corrosion defect, or loss of metallic cross-sectional area (LMA). An LMA defect in steel cables can be measured accurately when it is longer than a certain length. However, for defects in early stage, where the length of corrosion area is short, the MF examination may produce unacceptable error. In this study, the effect of defect length on the MF examination for corrosion detection of bridge cables is investigated through theoretical analysis and model experiments. An original analytical model to quantify the influence of defect length is proposed based on the equivalent magnetic circuit method. Then, MF examination experiments are performed on a series of cable models with different defect lengths and locations to verify the analytical model. Further, parameter study is conducted based on the proposed analytical model to clarify the mechanism of the defect-length effect. The results show that the area loss caused by short corrosion damage will be underestimated if the defect-length effect is neglected, and this effect can be quantified efficiently with the proposed analytical model.

关键词： bridge cable     corrosion detection     defect length     MF examination     quantitative evaluation    

HTML PDF 收藏

Acoustic fault signal extraction via the line-defect phononic crystals

《机械工程前沿（英文）》 2022年 第17卷 第1期   页码 10-10 doi: 10.1007/s11465-021-0666-y

摘要： Rotating machine fault signal extraction becomes increasingly important in practical engineering applications. However, fault signals with low signal-to-noise ratios (SNRs) are difficult to extract, especially at the early stage of fault diagnosis. In this paper, 2D line-defect phononic crystals (PCs) consisting of periodic acrylic tubes with slit are proposed for weak signal detection. The defect band, namely, the formed resonance band of line-defect PCs enables the incident acoustic wave at the resonance frequency to be trapped and enhanced at the resonance cavity. The noise can be filtered by the band gap. As a result, fault signals with high SNRs can be obtained for fault feature extraction. The effectiveness of weak harmonic and periodic impulse signal detection via line-defect PCs are investigated in numerical and experimental studies. All the numerical and experimental results indicate that line-defect PCs can be well used for extracting weak harmonic and periodic impulse signals. This work will provide potential for extracting weak signals in many practical engineering applications.

关键词： phononic crystals     line-defect     fault signal extraction     acoustic enhancement    

HTML PDF 收藏

Research progress of defect-engineered UiO-66(Zr) MOFs for photocatalytic hydrogen production

《能源前沿（英文）》 2021年 第15卷 第3期   页码 656-666 doi: 10.1007/s11708-021-0765-9

摘要： In recent years, defect-engineered Zr-based UiO-66 metal-organic frameworks (UiO-66(Zr) metal-organic frameworks (MOFs)) have shown huge advantages in catalytic, functional materials, adsorption, and other fields due to their large surface areas, well-ordered porous structures, and flexible tailorability. It is extremely challenging to introduce defect sites in the synthesis of MOFs to regulate the physicochemical properties of materials such as (energy band structure, pore structure, etc.) to obtain an excellent performance. This paper reviews the recent research results of synthesis methods, characterization technologies, and application fields of defect-engineered UiO-66(Zr) MOFs materials in order to provide new insights to synthesize high-performance UiO-66(Zr) MOFs materials and promote the development of UiO-66(Zr) in various fields.

关键词： defect engineering     metal-organic frameworks     UiO-66     photocatalysis    

HTML PDF 收藏

Single-electromagnet levitation for density measurement and defect detection

Yuhan JIA, Peng ZHAO, Jun XIE, Xuechun ZHANG, Hongwei ZHOU, Jianzhong FU

《机械工程前沿（英文）》 2021年 第16卷 第1期   页码 186-195 doi: 10.1007/s11465-020-0608-0

摘要： This paper presents a single-electromagnet levitation device to measure the densities and detect the internal defects of antimagnetic materials. The experimental device has an electromagnet in its lower part and a pure iron core in the upper part. When the electromagnet is activated, samples can be levitated stably in a paramagnetic solution. Compared with traditional magnetic levitation devices, the single-electromagnet levitation device is adjustable. Different currents, electromagnet shapes, and distances between the electromagnet and iron core are used in the experiment depending on the type of samples. The magnetic field formed by the electromagnet is strong. When the concentration of the MnCl aqueous solution is 3 mol/L, the measuring range of the single-electromagnet levitation device ranges from 1.301 to 2.308 g/cm . However, with the same concentration of MnCl aqueous solution (3 mol/L), the measuring range of a magnetic levitation device built with permanent magnets is only from 1.15 to 1.50 g/cm . The single-electromagnet levitation device has a large measuring range and can realize accurate density measurement and defect detection of high-density materials, such as glass and aluminum alloy.

关键词： single-electromagnet     electromagnetic levitation     density measurement     defect detection    

HTML PDF 收藏

Effects of slip length and hydraulic diameter on hydraulic entrance length of microchannels with superhydrophobic

Wenchi GONG, Jun SHEN, Wei DAI, Zeng DENG, Xueqiang DONG, Maoqiong GONG

《能源前沿（英文）》 2020年 第14卷 第1期   页码 127-138 doi: 10.1007/s11708-020-0661-8

摘要： This paper investigated effects of slip length and hydraulic diameter on the hydraulic entrance length of laminar flow in superhydrophobic microchannels. Numerical investigations were performed for square microchannels with Re ranging between 0.1 and 1000. It is found that superhydrophobic microchannels have a longer hydraulic entrance length than that of conventional ones by nearly 26.62% at a low Re. The dimensionless hydraulic entrance length slightly increases with the increasing slip length at approximately Re<10, and does not vary with the hydraulic diameter. A new correlation to predict the entrance length in square microchannels with different slip lengths was developed, which has a satisfying predictive performance with a mean absolute relative deviation of 5.69%. The results not only ascertain the flow characteristics of superhydrophobic microchannels, but also suggest that super hydrophobic microchannels have more significant advantages for heat transfer enhancement at a low Re.

关键词： laminar flow     hydraulic entrance length     super hydrophobic surface     slip length     hydraulic diameter    

HTML PDF 收藏

Structural behavior of intermediate length cold-formed steel rack columns with C-stitches

M. ANBARASU, Mahmud ASHRAF

《结构与土木工程前沿（英文）》 2019年 第13卷 第4期   页码 937-949 doi: 10.1007/s11709-019-0528-4

摘要： This article presents an experimental and numerical investigation on the strength and performance of intermediate length rack column sections with C-stitches under axial compression. The test program consisted of 10 axial concentric compression tests on columns with and without C-stitches under pin end conditions for two different geometric lengths. Finite element (FE) models were developed using commercial FE package ABAQUS considering material and geometric nonlinearities as well as initial geometric imperfections. The elastic buckling properties of the section were calculated using readily available linear elastic buckling analysis tools based on Generalized Beam Theory (GBT) and Finite Strip Method (FSM). Obtained FE results were compared with those obtained experimentally, and once verified the developed FE modeling technique was used to carry out a parametric study to examine changes in structural response due to variations in length, depth and spacing of C-stitches. Observed influences of C-stitches on the behavior and resistance of the considered columns were carefully analyzed, and key design aspects are presented herein.

关键词： cold-formed steel columns     C-stitches     intermediate length columns     distortional buckling    

HTML PDF 收藏

Association between telomere length and survival in cancer patients: a meta-analysis and review of literature

null

《医学前沿（英文）》 2016年 第10卷 第2期   页码 191-203 doi: 10.1007/s11684-016-0450-2

摘要：

The relationship between telomere length and cancer survival has been widely studied. To gain a deeper insight, we reviewed the published studies. A total of 29 studies evaluated telomere length in the peripheral blood; 22 studies evaluated telomere length in the tumor tissue. First, in the peripheral blood studies, for solid tumor patients with shortened telomere length, the combined hazard ratios (HRs) for mortality and tumor progression were 1.21 (95%CI, 1.10–1.32) and 1.71 (95%CI, 1.37–2.13), respectively. Meanwhile, in hematology malignancy, the combined HRs for mortality and tumor progression were 2.83 (95%CI, 2.14–3.74) and 2.65 (95%CI, 2.18–3.22), respectively. Second, in the studies that use tumor tissue, for patients with shortened telomeres, the combined HRs for mortality and tumor progression were 1.26 (95%CI, 0.95–1.66) and 1.65 (95%CI, 1.26–2.15), respectively. In the studies that calculate the telomere length ratios of tumor tissue to adjacent normal mucosa, for patients with lower telomere length ratios, the combined HRs were 0.66 (95%CI, 0.53–0.83) and 0.74 (95%CI, 0.41–1.32) for mortality and tumor progression, respectively. In conclusion, shortened telomere in peripheral blood and tumor tissue might indicate poor survival for cancer patients. However, by calculating the telomere length ratios of tumor tissue to adjacent normal mucosa, the lower ratio might indicate better survival.

关键词： telomere     survival     cancer     meta-analysis    

HTML PDF 收藏

Statistical analysis of recombination properties of the boron-oxygen defect in p-type Czochralski silicon

Nitin NAMPALLI,Tsun Hang FUNG,Stuart WENHAM,Brett HALLAM,Malcolm ABBOTT

《能源前沿（英文）》 2017年 第11卷 第1期   页码 4-22 doi: 10.1007/s11708-016-0442-6

摘要： This paper presents the application of lifetime spectroscopy to the study of carrier-induced degradation ascribed to the boron-oxygen (BO) defect. Specifically, a large data set of p-type silicon samples is used to investigate two important aspects of carrier lifetime analysis: ① the methods used to extract the recombination lifetime associated with the defect and ② the underlying assumption that carrier injection does not affect lifetime components unrelated to the defect. The results demonstrate that the capture cross section ratio associated with the donor level of the BO defect ( ) vary widely depending on the specific method used to extract the defect-specific recombination lifetime. For the data set studied here, it was also found that illumination used to form the defect caused minor, but statistically significant changes in the surface passivation used. This violation of the fundamental assumption could be accounted for by applying appropriate curve fitting methods, resulting in an improved estimate of (11.90±0.45) for the fully formed BO defect when modeled using the donor level alone. Illumination also appeared to cause a minor, apparently injection-independent change in lifetime that could not be attributed to the donor level of the BO defect alone and is likely related to the acceptor level of the BO defect. While specific to the BO defect, this study has implications for the use of lifetime spectroscopy to study other carrier induced defects. Finally, we demonstrate the use of a unit-less regression goodness-of-fit metric for lifetime data that is easy to interpret and accounts for repeatability error.

关键词： Czochralski silicon     boron-oxygen defect     injection dependent lifetime spectroscopy     goodness-of-fit     repeatability error    

HTML PDF 收藏

Modelling of dynamic contact length in rail grinding process

null

《机械工程前沿（英文）》 2014年 第9卷 第3期   页码 242-248 doi: 10.1007/s11465-014-0305-y

摘要：

Rails endure frequent dynamic loads from the passing trains for supporting trains and guiding wheels. The accumulated stress concentrations will cause the plastic deformation of rail towards generating corrugations, contact fatigue cracks and also other defects, resulting in more dangerous status even the derailment risks. So the rail grinding technology has been invented with rotating grinding stones pressed on the rail with defects removal. Such rail grinding works are directed by experiences rather than scientifically guidance, lacking of flexible and scientific operating methods. With grinding control unit holding the grinding stones, the rail grinding process has the characteristics not only the surface grinding but also the running railway vehicles. First of all, it’s important to analyze the contact length between the grinding stone and the rail, because the contact length is a critical parameter to measure the grinding capabilities of stones. Moreover, it’s needed to build up models of railway vehicle unit bonded with the grinding stone to represent the rail grinding car. Therefore the theoretical model for contact length is developed based on the geometrical analysis. And the calculating models are improved considering the grinding car’s dynamic behaviors during the grinding process. Eventually, results are obtained based on the models by taking both the operation parameters and the structure parameters into the calculation, which are suitable for revealing the process of rail grinding by combining the grinding mechanism and the railway vehicle systems.

关键词： rail grinding     contact length     dynamic model     Hamiltonian system     grinding stone     rail grinding car    

HTML PDF 收藏

桥面铺装病害检测技术研究

郭成超,许朋飞,崔璨

《中国工程科学》 2017年 第19卷 第6期   页码 38-43 doi: 10.15302/J-SSCAE-2017.06.006

摘要：

在桥梁的全生命周期中，桥面板是最容易出现病害的部分。桥面铺装层常常由于施工方法选择不当、混凝土老化、钢筋锈蚀等原因产生各种病害，这对桥梁结构、使用性能都会造成不利影响，因此有必要对相关病害进行检测，并对桥面质量做出相关评价。本文介绍了国内外四种主要无损检测方法（半电池电位法、探地雷达法、冲击回波法、红外热成像法）的工作原理以及相应的检测设备，利用其中一种或几种方法能准确评估桥面板的恶化情况，对桥面板状况进行快速、无损检测，为实现桥面铺装的准确检测提供技术支持，从而减少结构病害，延长桥梁的使用寿命。

关键词： 桥面铺装     病害     无损检测    

HTML PDF 收藏

Optimization of aero-engine pipeline for avoiding vibration based on length adjustment of straight-line

《机械工程前沿（英文）》 2022年 第17卷 第1期   页码 11-11 doi: 10.1007/s11465-021-0667-x

摘要： In the design and troubleshooting of aero-engine pipeline, the vibration reduction of the pipeline system is often achieved by adjusting the hoop layout, provided that the shape of pipeline remains unchanged. However, in reality, the pipeline system with the best antivibration performance may be obtained only by adjusting the pipeline shape. In this paper, a typical spatial pipeline is taken as the research object, the length of straight-line segment is taken as the design variable, and an innovative optimization method of avoiding vibration of aero-engine pipeline is proposed. The relationship between straight-line segment length and parameters that determine the geometric characteristics of the pipeline, such as the position of key reference points, bending angle, and hoop position, are derived in detail. Based on this, the parametric finite element model of the pipeline system is established. Taking the maximum first-order natural frequency of pipeline as the optimization objective and introducing process constraints and vibration avoidance constraints, the optimization model of the pipeline system is established. The genetic algorithm and the golden section algorithm are selected to solve the optimization model, and the relevant solution procedure is described in detail. Finally, two kinds of pipelines with different total lengths are selected to carry out a case study. Based on the analysis of the influence of straight-line segment length on the vibration characteristics of the pipeline system, the optimization methods developed in this paper are demonstrated. Results show that the developed optimization method can obtain the optimal single value or interval of the straight-line segment length while avoiding the excitation frequency. In addition, the optimization efficiency of the golden section algorithm is remarkably higher than that of the genetic algorithm for length optimization of a single straight-line segment.

关键词： length adjustment     spatial pipeline     aero-engine     vibration avoidance optimization     genetic algorithm     golden section algorithm    

HTML PDF 收藏

Effect of cavity defect on the triaxial mechanical properties of high-performance concrete

Yanbin ZHANG; Zhe WANG; Mingyu FENG

《结构与土木工程前沿（英文）》 2022年 第16卷 第5期   页码 600-614 doi: 10.1007/s11709-022-0821-5

摘要： The stress concentration of pipe structure or cavity defect has a great effect on the mechanical properties of the high-performance concrete (HPC) members in deep underground locations. However, the behaviour of HPC with cavities under triaxial compression is not understood, especially when pressurized liquid flows into the fractures from the cavity. This study aims to investigate the effect of the cavity and the confining pressure on the failure mechanisms, strengths, and deformation properties of HPC with a new experimental scheme. In this experiment, the pressurized liquid can only contact the surface of the sample in the cavity, while the other surfaces are isolated from the pressurized liquid. To further explore the effect of the cavity, the same experiments are also conducted on sealed and unsealed intact samples without a cavity. The failure modes and stress-strain curves of all types of the samples are presented. Under various confining pressures, all the samples with a cavity suffer shear failure, and there are always secondary tensile fractures initiating from the cavity sidewall. Additionally, it can be determined from the failure modes and the stress-strain curves that the shear fractures result from the sidewall failure. Based on the different effects of the cavity on the lateral deformations in different directions, the initiation of the sidewall fracture is well predicted. The experimental results show that both the increase of the confining pressure and the decrease of the cavity size are conducive to the initiation of sidewall fracture. Moreover, the cavity weakens the strength of the sample, and this study gives a modified Power-law criterion in which the cavity size is added as an impact factor to predict the strength of the sample.

关键词： high-performance concrete     cavity     conventional triaxial compression     pressurized liquid     modified power-law criterion    

HTML PDF 收藏

Construction of defect-containing UiO-66/MoSe heterojunctions with superior photocatalytic performance

《化学科学与工程前沿（英文）》 2023年 第17卷 第4期   页码 449-459 doi: 10.1007/s11705-022-2226-3

摘要： Metal–organic frameworks are recognized as promising multifunctional materials, especially metal–organic framework-based photocatalysts, which are considered to be ideal photocatalytic materials. Herein, a new type of UiO-66/MoSe2 composite was prepared using the solvothermal method. The optimum composite was selected by adjusting the mass ratio of UiO-66 and MoSe2. X-ray diffraction analysis showed that the mass ratio influenced the crystal plane exposure rate of the composite, which may have affected its photocatalytic performance. The composite is composed of ultra-thin flower-like MoSe2 that wrapped around cubic UiO-66, a structure that increases the abundance of active sites for reactions and is more conducive to the separation of carriers. The photocatalytic properties of the composite were evaluated by measuring the degradation rate of Rhodamine B and the catalyst’s ability to reduce Cr(VI)-containing wastewater under visible light irradiation. Rhodamine B was decolorized completely in 120 min, and most of the Cr(VI) was reduced within 150 min. The photochemical mechanism of the complex was studied in detail. The existence of Mo6+ and oxygen vacancies, in addition to the Z-type heterojunction promote the separation of electrons and holes, which enhances the photocatalytic effect.

关键词： UiO-66/MoSe2     photocatalysis     dye-containing wastewater     heavy metal wastewater     oxygen vacancies    

HTML PDF 收藏

New form of geodetic coordinate system taking two length quantity as coordinate parameters

Yimin SHI, Ziyang ZHU, Yeming FAN

《结构与土木工程前沿（英文）》 2009年 第3卷 第1期   页码 105-110 doi: 10.1007/s11709-009-0014-5

摘要： A new form of geodetic coordinate system based on geodesic coordinates instead of geodetic longitude and latitude was proposed. The vertical and horizontal geodesic coordinates measured with length were defined as coordinate parameters, but the two families of coordinate curves were still meridians and parallel circles. The first fundamental form on the ellipsoidal surface and its three coefficients were deduced by the geodesic coordinate. The formula for the latitudinal scale factor of length for geodetic parallel lines was derived, by which the obtained result conformed to that standard value calculated from geodetic latitude, and it is applicable in the range of 400 km from north to south. Therefore, it lays the foundation for establishing the differential equation and differential relationship based on this type of coordinate parameters; and consequently, it is convenient and accurate enough to operate on the ellipsoidal surface in this new form of geodetic coordinate system.

关键词： geodetic coordinate system     meridian and parallel circle     coordinate parameter     the first fundamental form on the ellipsoidal surface     latitudinal scale factor of length    

HTML PDF 收藏

Secondary transfer length and residual prestress of fractured strand in post-tensioned concrete beams

Lizhao DAI; Wengang XU; Lei WANG; Shanchang YI; Wen CHEN

《结构与土木工程前沿（英文）》 2022年 第16卷 第3期   页码 388-400 doi: 10.1007/s11709-022-0809-1

摘要： An experimental study is performed on five post-tensioned concrete beams to explore the effects of different fracture positions on secondary transfer length and residual prestress of fractured strand. A numerical model is developed and used to predict the secondary transfer length and residual prestress of fractured strand in post-tensioned concrete beams. The model change interaction, which can deactivate and reactivate the elements for simulating the removal and reproduction of parts of the model, is used to reproduce the secondary anchorage of fractured strand. The numerical model is verified by experimental results. Results shows that the fractured strand can be re-anchored in concrete through the secondary anchorage, and the secondary transfer length of fractured strand with the diameter of 15.2 mm is 1133 mm. The residual prestress of fractured strand increases gradually in the secondary transfer length, and tends to be a constant beyond it. When the fractured strand is fully anchored in concrete, a minor prestress loss will appear, and the average prestress loss is 2.28% in the present study.

关键词： post-tensioned concrete beams     strand fracture     secondary transfer length     residual prestress    

HTML PDF 收藏

标题 作者 时间 类型 操作

The defect-length effect in corrosion detection with magnetic method for bridge cables

Qiwei ZHANG, Rongya XIN

期刊论文

Acoustic fault signal extraction via the line-defect phononic crystals

期刊论文

Research progress of defect-engineered UiO-66(Zr) MOFs for photocatalytic hydrogen production

期刊论文

Single-electromagnet levitation for density measurement and defect detection

Yuhan JIA, Peng ZHAO, Jun XIE, Xuechun ZHANG, Hongwei ZHOU, Jianzhong FU

期刊论文

Effects of slip length and hydraulic diameter on hydraulic entrance length of microchannels with superhydrophobic

Wenchi GONG, Jun SHEN, Wei DAI, Zeng DENG, Xueqiang DONG, Maoqiong GONG

期刊论文

Structural behavior of intermediate length cold-formed steel rack columns with C-stitches

M. ANBARASU, Mahmud ASHRAF

期刊论文

Association between telomere length and survival in cancer patients: a meta-analysis and review of literature

null

期刊论文

Statistical analysis of recombination properties of the boron-oxygen defect in p-type Czochralski silicon

Nitin NAMPALLI,Tsun Hang FUNG,Stuart WENHAM,Brett HALLAM,Malcolm ABBOTT

期刊论文

Modelling of dynamic contact length in rail grinding process

null

期刊论文

桥面铺装病害检测技术研究

郭成超,许朋飞,崔璨

期刊论文

Optimization of aero-engine pipeline for avoiding vibration based on length adjustment of straight-line

期刊论文

Effect of cavity defect on the triaxial mechanical properties of high-performance concrete

Yanbin ZHANG; Zhe WANG; Mingyu FENG

期刊论文

Construction of defect-containing UiO-66/MoSe heterojunctions with superior photocatalytic performance

期刊论文

New form of geodetic coordinate system taking two length quantity as coordinate parameters

Yimin SHI, Ziyang ZHU, Yeming FAN

期刊论文

Secondary transfer length and residual prestress of fractured strand in post-tensioned concrete beams

Lizhao DAI; Wengang XU; Lei WANG; Shanchang YI; Wen CHEN

期刊论文