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Damage assessment and diagnosis of hydraulic concrete structures using optimization-based machine learning technology

《结构与土木工程前沿（英文）》页码 1281-1294 doi: 10.1007/s11709-023-0975-9

摘要： Concrete is widely used in various large construction projects owing to its high durability, compressive strength, and plasticity. However, the tensile strength of concrete is low, and concrete cracks easily. Changes in the concrete structure will result in changes in parameters such as the frequency mode and curvature mode, which allows one to effectively locate and evaluate structural damages. In this study, the characteristics of the curvature modes in concrete structures are analyzed and a method to obtain the curvature modes based on the strain and displacement modes is proposed. Subsequently, various indices for the damage diagnosis of concrete structures based on the curvature mode are introduced. A damage assessment method for concrete structures is established using an artificial bee colony backpropagation neural network algorithm. The proposed damage assessment method for dam concrete structures comprises various modal parameters, such as curvature and frequency. The feasibility and accuracy of the model are evaluated based on a case study of a concrete gravity dam. The results show that the damage assessment model can accurately evaluate the damage degree of concrete structures with a maximum error of less than 2%, which is within the required accuracy range of damage identification and assessment for most concrete structures.

关键词： hydraulic structure curvature mode damage detection artifical neural network artificial bee colony

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Moment-curvature relationship of FRP-concrete-steel double-skin tubular members

Mingxue LIU, Jiaru QIAN

《结构与土木工程前沿（英文）》 2009年第3卷第1期页码 25-31 doi: 10.1007/s11709-009-0012-7

摘要： Tests were conducted on 3 specimens to study the flexural behavior of fiber reinforced polymer (FRP)-concrete-steel double-skin tubular members (DSTMs). The strip method was used to calculate the section moment-curvature curves of the 3 specimens and 12 models. A theoretical formula is presented for the flexural strength of DSTMs. The test results show that the tension zone of the specimen FRP tubes was in hoop compression while the compression zone was in hoop tension. The load-carrying capacity did not decrease even when the mid-span deflection reached about 1/24 of the span length. The tests, simulation and theoretical analysis resulted in a simplified formula for the flexural strength of DSTMs and a tri-linear moment-curvature model was expressed as a function of the section bending stiffness for DSTMs.

关键词： fiber reinforced polymer (FRP) concrete steel double-skin tubular members (DSTMs) moment-curvature curve flexural strength

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Soft curvature sensors for measuring the rotational angles of mechanical fingers

Haixiao LIU, Li LI, Zhikang OUYANG, Wei SUN

《机械工程前沿（英文）》 2020年第15卷第4期页码 610-621 doi: 10.1007/s11465-020-0596-0

摘要： The design, fabrication, and testing of soft sensors that measure elastomer curvature and mechanical finger bending are described in this study. The base of the soft sensors is polydimethylsiloxane (PDMS), which is a translucent elastomer. The main body of the soft sensors consists of three layers of silicone rubber plate, and the sensing element is a microchannel filled with gallium-indium-tin (Ga-In-Sn) alloy, which is embedded in the elastomer. First, the working principle of soft sensors is investigated, and their structure is designed. Second, the relationship between curvature and resistance is determined. Third, several sensors with different specifications are built in accordance with the structural design. Experiments show that the sensors exhibit high accuracy when the curvature changes within a certain range. Lastly, the soft sensors are applied to the measurement of mechanical finger bending. Experiments show that soft curvature sensors can effectively reflect mechanical finger bending and can be used to measure the bending of mechanical fingers with high sensitivity within a certain working range.

关键词： soft sensor Ga-In-Sn alloy strain sensing curvature sensing mechanical finger bending

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弧齿锥齿轮主曲率计算的幺正活动标架法

王裕清,梁剑

《中国工程科学》 2001年第3卷第12期页码 68-70

摘要：

曲面上点的主曲率计算是确定轮齿啮合压痕平面投影形状的关键。文章摈弃通常运用啮合原理和坐标变换计算的思路，从曲面本身的性质出发，把幺正活动标架和外微分引入主曲率计算，得到简明、有效的主曲率计算的新算法，并结合压痕公式给出了一个应用实例。该算法可以推广到任意曲面的主曲率计算。

关键词：弧齿锥齿轮主曲率幺正活动标架

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地震曲率技术在地震资料解释中的应用

柏冠军,赵汝敏,杨松岭,李培培

《中国工程科学》 2011年第13卷第5期页码 23-27

摘要：

通过地震曲率属性的分析，寻找适合研究区的地震曲率，研究其解释技术。系统总结了地震曲率技术的解释应用及应注意的问题。针对小断层在常规地震剖面上表现为同相轴的微小变化、扭曲、振幅突然变弱等特征，利用这些微小的变化在地震层曲率属性上表现为线性构造，进行小断层识别，异常的长度和方向分别代表着断层的延展长度和断层的走向。二维曲率属性有比较明确的物理意义，相对一阶导数属性（如微分、倾角、方位角等），它在构造特征识别上有明显的长处。它们对刻画地质体轮廓、分层结构、断裂系统等非常有效。实例表明，地震曲率属性对断层的轨迹、沉积体边界的刻画清晰、连续，利于解释，减少解释多解性。

关键词：地震曲率断层解释沉积体刻画 3D层位

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Effects of fiber curvature on the microstructure of the interfacial transition zone in fresh concrete

CHEN Huisu, SUN Wei, ZHAO Qingxin, L. J. Sluys, P. Stroeven

《结构与土木工程前沿（英文）》 2007年第1卷第1期页码 99-106 doi: 10.1007/s11709-007-0010-6

摘要： The study on the interfacial transition zone (ITZ) of concrete has received lots of attention in the last decade. However, no information is available on the influence of the curvature of a rigid surface on the microstructure of ITZ. This paper employed computer simulation technology to study the influence of fiber curvature on the initial microstructure of ITZ in concrete. For the sake of simplification, the investigation was first focused on the mono-size spherical particle packing system around a cylindrical fiber with different diameters. An algorithm of serial cylindrical sectioning was developed. The curve of the solid volume fraction versus the distance to the surface of the fiber was used as a parameter to characterize the microstructure of the ITZ. Then, the influence of the ratio of fiber diameter to particle diameter on the initial ITZ s microstructure was studied. These curves were compared with the ones from flat aggregate surface on which mono-size spherical particles were packed. Furthermore, the multi-size spherical particles system was further investigated. The simulation results demonstrate that no matter whether the spherical particles system is mono-size or multi-size, the fresh ITZ s microstructure is irrelevant to the curvature of the fiber. The shape of the curve of solid volume fraction versus the distance from the surface of the fiber is similar to that around a flat aggregate surface. In all cases, the horizontal coordinates of the first peak of the curves are located at around half the mean weight diameter of the particles. The thickness of ITZ reduces slightly with the decrease in water/cement ratio. Therefore, one may use the ITZ s microstructure around a flat aggregate surface to represent the ITZ s microstructure around a cylindrical fiber in the fresh state, and vice versa.

关键词： diameter initial microstructure influence surface spherical particle

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使用曲率尺度空间描述符从单眼深度图像中提取手关节

Shao-fan WANG,Chun LI,De-hui KONG,Bao-cai YIN

《信息与电子工程前沿（英文）》 2016年第17卷第1期页码 41-54 doi: 10.1631/FITEE.1500126

摘要：

我们提出了使用曲率标度空间（CSS）描述符从单眼深度图像中进行手关节检测的框架。我们从输入的深度图像中提取手部轮廓，并使用轮廓的修改CSS映射的局部极值获得轮廓的指尖和手指谷。然后我们根据轮廓内部点深度的局部变化恢复未检测到的指尖。与使用角度检测器或凸包检测器的传统基于外观的方法相比，修改后的CSS描述符可以更精确地提取指尖和手指谷，因为它对嘈杂或损坏的数据更可靠；此外，深度的局部极值可以恢复指尖不能很好地弯曲手指，而传统的基于外观的方法在不匹配手模型的情况下几乎无法工作。实验结果表明，与三种基于外观的最先进方法相比，我们的方法能够更精确地捕获手部关节。

关键词：曲率尺度空间；手部关节；凸包；手形轮廓

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Robust SVM-direct torque control of induction motor based on sliding mode controller and sliding mode

Abdelkarim AMMAR,Amor BOUREK,Abdelhamid BENAKCHA

《能源前沿（英文）》 2020年第14卷第4期页码 836-849 doi: 10.1007/s11708-017-0444-z

摘要： This paper proposes a design of control and estimation strategy for induction motor based on the variable structure approach. It describes a coupling of sliding mode direct torque control (DTC) with sliding mode flux and speed observer. This algorithm uses direct torque control basics and the sliding mode approach. A robust electromagnetic torque and flux controllers are designed to overcome the conventional SVM-DTC drawbacks and to ensure fast response and full reference tracking with desired dynamic behavior and low ripple level. The sliding mode controller is used to generate reference voltages in stationary frame and give them to the controlled motor after modulation by a space vector modulation (SVM) inverter. The second aim of this paper is to design a sliding mode speed/flux observer which can improve the control performances by using a sensorless algorithm to get an accurate estimation, and consequently, increase the reliability of the system and decrease the cost of using sensors. The effectiveness of the whole composed control algorithm is investigated in different robustness tests with simulation using Matlab/Simulink and verified by real time experimental implementation based on dS pace 1104 board.

关键词： induction motor direct torque control (DTC) space vector modulation (SVM) sliding mode control (SMC) sliding mode observer (SMO) dS1104

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基于双重分组和密钥计数的并行认证模式

黄玉划,胡爱群,宋宇波

《中国工程科学》 2004年第6卷第7期页码 70-74

摘要：

由于CBC－MAC模式不可并行处理，提出了一种基于双重分组的并行认证模式(PKCB)。PKCB模式同并行认证模式PMAC相比，安全性和速率都有显著提高，PKCB认证模式与CTR（计数器）加密模式结合可构成分组密码算法的一种全工作模式。在此基础上提出了一种基于密钥计数的并行认证模式（KCTR－MAC）。KCTR－MAC模式安全性比PMAC模式高得多，而速率未降低，KCTR－MAC认证模式和CTR加密模式结合也可构成分组密码算法的一种全工作模式（2CTR），2CTR模式的综合性能不亚于标准模式CCM（CTR with CBC－MAC），是一种安全快速的实用模式。

关键词：认证模式 CBC－MAC模式 PMAC模式 CTR模式 CCM模式

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Probabilistic stability of uncertain composite plates and stochastic irregularity in their buckling mode

《结构与土木工程前沿（英文）》页码 179-190 doi: 10.1007/s11709-022-0888-z

摘要： In this study, the mechanical properties of the composite plate were considered Gaussian random fields and their effects on the buckling load and corresponding mode shapes were studied by developing a semi-analytical non-intrusive approach. The random fields were decomposed by the Karhunen−Loève method. The strains were defined based on the assumptions of the first-order and higher-order shear-deformation theories. Stochastic equations of motion were extracted using Euler–Lagrange equations. The probabilistic response space was obtained by employing the non-intrusive polynomial chaos method. Finally, the effect of spatially varying stochastic properties on the critical load of the plate and the irregularity of buckling mode shapes and their sequences were studied for the first time. Our findings showed that different shear deformation plate theories could significantly influence the reliability of thicker plates under compressive loading. It is suggested that a linear relationship exists between the mechanical properties’ variation coefficient and critical loads’ variation coefficient. Also, in modeling the plate properties as random fields, a significant stochastic irregularity is obtained in buckling mode shapes, which is crucial in practical applications.

关键词： uncertain composite plate stochastic assume mode method Karhunen−Loève theorem polynomial chaos approach plate buckling irregularity in buckling mode shapes

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Experimental investigation of evolutive mode-I and mode-II fracture behavior of fiber-reinforced cemented

《结构与土木工程前沿（英文）》 2023年第17卷第2期页码 256-270 doi: 10.1007/s11709-022-0924-z

摘要： The curing temperature-dependent cement hydration causes the nonlinear evolution of fracture behavior and properties of fiber-reinforced cemented paste backfill (CPB) and thus influences the stability of mine backfill materials in deep mines. Therefore, the coupled effect of curing temperature (20, 35, and 45 °C) and cement hydration at different curing times (3, 7, and 28 d) on the mode-I and mode-II fracture behavior and properties of fiber-reinforced CPB is investigated. A comprehensive experimental testing program consisting of semicircular bend tests, direct shear tests, measurement of volumetric water content and matric suction, TG/DTG tests, and SEM observation is carried out. The results show that the coupled thermochemical effect results in strongly nonlinear development of pre- and post-peak behavior of fiber-reinforced CPB. Moreover, the results discover a positive linear correlation between fracture toughness and shear strength parameters and also reveal the vital role played by matric suction in the formation of fracture toughness. Furthermore, predictive functions are developed to estimate the coupled thermochemical effect on the development of K_Ic and K_IIc. Therefore, the findings and the developed mathematical tools have the potential to promote the successful application of fiber-reinforced CPB technology in deep underground mines.

关键词： fiber reinforcement cemented paste backfill fracture behavior underground mine cement hydration

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几率波与量子效应的扭率问题

欧阳首承,李智兰,袁东升

《中国工程科学》 2005年第7卷第6期页码 1-6

摘要：

按曲率空间的扭率，对含有三阶非线性变量导数的Schrödinger变形等价程进行了数值分析，发现几率波的几率性原来是扭率的疏密流在特定条件下的准规则流，并为势场强度和粒子体元密度的相互作用与量子扭率效应项综合作用的结果；纯量子效应作用为非规则流。

关键词：扭率几率量子效应非线性不稳定曲率空间

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Elastic modulus and thermal stress in coating during heat cycling with different substrate shapes

Daniel GAONA,Alfredo VALAREZO

《机械工程前沿（英文）》 2015年第10卷第3期页码 294-300 doi: 10.1007/s11465-015-0351-0

摘要：

The elastic modulus of a deposit (E_d) can be obtained by monitoring the temperature (?T) and curvature (?k) of a one-side coated long plate, namely, a one-dimensional (1D) deformation model. The aim of this research is to design an experimental setup that proves whether a 1D deformation model can be scaled for complex geometries. The setup includes a laser displacement sensor mounted on a robotic arm capable of scanning a specimen surface and measuring its deformation. The reproducibility of the results is verified by comparing the present results with Stony Brook University Laboratory’s results. The ?k-?T slope error is less than 8%, and the E_d estimation error is close to 2%. These values reveal the repeatability of the experiments. Several samples fabricated with aluminum as the substrate and 100MXC nanowire (Fe and Cr alloy) as the deposit are analyzed and compared with those in finite element (FE) simulations. The linear elastic behavior of 1D (flat long plate) and 2D (squared plate) specimens during heating/cooling cycles is demonstrated by the high linearity of all ?k-?T curves (over 97%). The E_d values are approximately equal for 1D and 2D analyses, with a median of 96 GPa and standard deviation of 2 GPa. The correspondence between the experimental and simulated results for the 1D and 2D specimens reveals that deformation and thermal stress in coated specimens can be predicted regardless of specimen geometry through FE modeling and by using the experimental value of E_d. An example of a turbine-blade-shaped substrate is presented to validate the approach.

关键词： in-plane Young’s modulus curvature temperature thermal stress coating

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An adaptive sliding mode control technology for weld seam tracking

Jie LIU,Youmin HU,Bo WU,Kaibo ZHOU,Mingfeng GE

《机械工程前沿（英文）》 2015年第10卷第1期页码 95-101 doi: 10.1007/s11465-015-0332-3

摘要：

A novel adaptive sliding mode control algorithm is derived to deal with seam tracking control problem of welding robotic manipulator, during the process of large-scale structure component welding. The proposed algorithm does not require the precise dynamic model, and is more practical. Its robustness is verified by the Lyapunov stability theory. The analytical results show that the proposed algorithm enables better high-precision tracking performance with chattering-free than traditional sliding mode control algorithm under various disturbances.

关键词： weld seam tracking welding robotic manipulator adaptive control sliding mode control

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Relative vibration identification of cutter and workpiece based on improved bidimensional empirical mode

Jiasheng LI, Xingzhan LI, Wei WEI, Pinkuan LIU

《机械工程前沿（英文）》 2020年第15卷第2期页码 227-239 doi: 10.1007/s11465-020-0587-1

摘要： In the process of cutting, the relative vibration between the cutter and the workpiece has an important effect on the surface topography. In this study, the bidimensional empirical mode decomposition (BEMD) method is used to identify such effect. According to Riesz transform theory, a type of isotropic monogenic signal is proposed. The boundary data is extended on the basis of a similarity principle that deals with serious boundary effect problem. The decomposition examples show that the improved BEMD can effectively solve the problem of boundary effect and decompose the original machined surface topography at multiple scales. The characteristic surface topography representing the relative vibration between the cutter and the workpiece through feature identification is selected. In addition, the spatial spectrum analysis of the extracted profile is carried out. The decimal part of the frequency ratio that has an important effect on the shape of the contour can be accurately identified through contour extraction and spatial spectrum analysis. The decomposition results of simulation and experimental surface morphology demonstrate the validity of the improved BEMD algorithm in realizing the relative vibration identification between the cutter and the workpiece.

关键词： bidimensional empirical mode decomposition spatial spectrum analysis boundary effect vibration identification surface topography