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An identification method for enclosed voids restriction in manufacturability design for additive manufacturing structures

Shutian LIU,Quhao LI,Wenjiong CHEN,Liyong TONG,Gengdong CHENG

《机械工程前沿（英文）》 2015年 第10卷 第2期   页码 126-137 doi: 10.1007/s11465-015-0340-3

摘要：

Additive manufacturing (AM) technologies, such as selective laser sintering (SLS) and fused deposition modeling (FDM), have become the powerful tools for direct manufacturing of complex parts. This breakthrough in manufacturing technology makes the fabrication of new geometrical features and multiple materials possible. Past researches on designs and design methods often focused on how to obtain desired functional performance of the structures or parts, specific manufacturing capabilities as well as manufacturing constraints of AM were neglected. However, the inherent constraints in AM processes should be taken into account in design process. In this paper, the enclosed voids, one type of manufacturing constraints of AM, are investigated. In mathematics, enclosed voids restriction expressed as the solid structure is simply-connected. We propose an equivalent description of simply-connected constraint for avoiding enclosed voids in structures, named as virtual temperature method (VTM). In this method, suppose that the voids in structure are filled with a virtual heating material with high heat conductivity and solid areas are filled with another virtual material with low heat conductivity. Once the enclosed voids exist in structure, the maximum temperature value of structure will be very high. Based upon this method, the simply-connected constraint is equivalent to maximum temperature constraint. And this method can be easily used to formulate the simply-connected constraint in topology optimization. The effectiveness of this description method is illustrated by several examples. Based upon topology optimization, an example of 3D cantilever beam is used to illustrate the trade-off between manufacturability and functionality. Moreover, the three optimized structures are fabricated by FDM technology to indicate further the necessity of considering the simply-connected constraint in design phase for AM.

关键词： additive manufacturing     topology optimization     manufacturability constraints     design for additive manufacturing     simply-connected constraint    

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Vibration analysis of a simply supported beam under moving mass based on moving finite element method

Zhuchao YE, Huaihai CHEN,

《机械工程前沿（英文）》 2009年 第4卷 第4期   页码 397-400 doi: 10.1007/s11465-009-0044-7

摘要： In this paper, a moving finite element (MFE) method is proposed to perform the dynamic analysis of a simply supported beam for a moving mass (MM). The MFE method treats the moving mass as a moving part of the entire system, so that the transverse inertial effects caused by the moving mass may easily be taken into account. The solution to the beam’s dynamic behaviors including its displacement is obtained via a Newmark-β method; the effects of the velocity and weight of the MM on the beam’s dynamic behaviors are further discussed. The numerical examples show that the inertial effects of the MM significantly affect the transverse responses of the simply supported beam.

关键词： simply supported beam     moving mass (MM)     transverse vibration     moving finite element (MFE)    

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Ambient vibration testing and updating of the finite element model of a simply supported beam bridge

Ivan Gomez ARAUJO, Esperanza MALDONADO, Gustavo Chio CHO

《结构与土木工程前沿（英文）》 2011年 第5卷 第3期   页码 344-354 doi: 10.1007/s11709-011-0124-8

摘要： An ambient vibration test on a concrete bridge constructed in 1971 and calibration of its finite element model are presented. The bridge is characterized by a system of post-tensioned and simply supported beams. The dynamic characteristics of the bridge, i.e. natural frequencies, mode shapes and damping ratios were computed from the ambient vibration tests by using the Eigensystem Realization Algorithm (ERA). Then, these characteristics were used to update the finite element model of the bridge by formulating an optimization problem and then using Genetic Algorithms (GA) to solve it. From the results of the ambient vibration test of this type of bridge, it is concluded that two-dimensional mode shapes exist: in the longitudinal and transverse; and these experimentally obtained dynamic characteristics were also achieved in the analytical model through updating. The application of GAs as optimization techniques showed great versatility to optimize any number and type of variables in the model.

关键词： modal analysis     parameter identification     ambient vibration test     Eigensystem Realization Algorithm (ERA) method     finite element method    

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Modeling and control of photovoltaic energy conversion connected to the grid

Rebei NAJET, Ben Ghanem BELGACEM, Hasnaoui OTHMAN

《能源前沿（英文）》 2012年 第6卷 第1期   页码 35-46 doi: 10.1007/s11708-012-0169-y

摘要： This paper presents modeling and control of a photovoltaic generator (PVG) connected to the grid. The parameters of the PVG have been identified in previous work (series and parallel resistance, reverse saturation current and thermal voltage) using Newton-Raphston and the gradient algorithm. The electrical energy from a PVG is transferred to the grid via two static converters (DC/DC and DC/AC). The objective of the proposed control strategy is to maximize energy captured from the PVG. The adapted control law for extracting maximum power from the PVG is based on the incremental conductance algorithm. The developed algorithm has the capability of searching the maximum photovoltaic power under variable irradiation and temperature. To control the DC/AC inverter, an intelligent system based on two structures is constructed: a current source control structure and a voltage source control structure. The system has been validated by numerical simulation using data obtained from the PVG installed in the laboratory research (INSAT, Tunisia).

关键词： photovoltaic generator (PVG)     maximum power point tracker     grid-connected     static converters    

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Technology and system of constraint programming for industry production scheduling

Yarong CHEN, Zailin GUAN, Yunfang PENG, Xinyu SHAO, Muhammad HASSEB

《机械工程前沿（英文）》 2010年 第5卷 第4期   页码 455-464 doi: 10.1007/s11465-010-0106-x

摘要： The use of techniques and system of constraint programming enables the implementation of precise, flexible, efficient, and extensible scheduling systems. It has been identified as a strategic direction and dominant form for the application into planning and scheduling of industrial production. This paper systematically introduces the constraint modeling and solving technology for production scheduling problems, including various real-world industrial applications based on the Chip system of Cosytec Company. We trend of some concrete technology, such as modeling, search, constraint propagation, consistency, and optimization of constraint programming for scheduling problems. As a result of the application analysis, a generic application framework for real-life scheduling based on commercial constraint propagation (CP) systems is proposed.

关键词： constraint programming     production scheduling     constraint propagation     search     consistency     optimization    

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Fine-grained P2P traffic classification by simply counting flows

Jie HE,Yue-xiang YANG,Yong QIAO,Wen-ping DENG

《信息与电子工程前沿（英文）》 2015年 第16卷 第5期   页码 391-403 doi: 10.1631/FITEE.1400267

摘要： The continuous emerging of peer-to-peer (P2P) applications enriches resource sharing by networks, but it also brings about many challenges to network management. Therefore, P2P applications monitoring, in particular, P2P traffic classification, is becoming increasingly important. In this paper, we propose a novel approach for accurate P2P traffic classification at a fine-grained level. Our approach relies only on counting some special flows that are appearing frequently and steadily in the traffic generated by specific P2P applications. In contrast to existing methods, the main contribution of our approach can be summarized as the following two aspects. Firstly, it can achieve a high classification accuracy by exploiting only several generic properties of flows rather than complicated features and sophisticated techniques. Secondly, it can work well even if the classification target is running with other high bandwidth-consuming applications, outperforming most existing host-based approaches, which are incapable of dealing with this situation. We evaluated the performance of our approach on a real-world trace. Experimental results show that P2P applications can be classified with a true positive rate higher than 97.22% and a false positive rate lower than 2.78%.

关键词： Traffic classification     Peer-to-peer (P2P)     Fine-grained     Host-based    

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Recent development in low-constraint fracture toughness testing for structural integrity assessment of

Jidong KANG, James A. GIANETTO, William R. TYSON

《机械工程前沿（英文）》 2018年 第13卷 第4期   页码 546-553 doi: 10.1007/s11465-018-0501-2

摘要：

Fracture toughness measurement is an integral part of structural integrity assessment of pipelines. Traditionally, a single-edge-notched bend (SE(B)) specimen with a deep crack is recommended in many existing pipeline structural integrity assessment procedures. Such a test provides high constraint and therefore conservative fracture toughness results. However, for girth welds in service, defects are usually subjected to primarily tensile loading where the constraint is usually much lower than in the three-point bend case. Moreover, there is increasing use of strain-based design of pipelines that allows applied strains above yield. Low-constraint toughness tests represent more realistic loading conditions for girth weld defects, and the corresponding increased toughness can minimize unnecessary conservatism in assessments. In this review, we present recent developments in low-constraint fracture toughness testing, specifically using single-edge-notched tension specimens, SENT or SE(T). We focus our review on the test procedure development and automation, round-robin test results and some common concerns such as the effect of crack tip, crack size monitoring techniques, and testing at low temperatures. Examples are also given of the integration of fracture toughness data from SE(T) tests into structural integrity assessment.

关键词： fracture toughness     constraint effect     single-edge-notched tension test     pipeline     structural integrity assessment    

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Development of rocking constraint device with vertical damping capacity for three-dimensional base-isolated

《结构与土木工程前沿（英文）》 2023年 第17卷 第3期   页码 350-367 doi: 10.1007/s11709-022-0923-0

摘要： A new rocking constraint device (RCD) is developed for three-dimensional (3D) base-isolated frame structures by connecting a custom-designed cylinder pair to provide vertical damping with replaceable damping components installed outside the cylinders when the superstructure undergoes translational motion, and rocking constraint capacity when the superstructure is susceptible to rocking. Theoretical formulas for calculating the damping and rocking constraint stiffness of the RCD are proposed. Two series of sinusoidal loading tests are conducted at different loading frequencies and amplitudes to verify the damping and rocking constraint performance of the RCD. The test results show that the cylinder without orifices on its piston can provide the desired damping with a replaceable damping component, and that the RCD can effectively suppress rocking. Although the vertical stiffness of an individual cylinder is affected by the location of the replaceable damping component and loading frequency, the average vertical stiffness of the two cylinders, which determines the rocking constraint stiffness of the RCD, is independent of the two factors. Comparisons of the test and theoretical results indicate that the errors of the proposed formulas for calculating the damping and rocking constraint stiffness of the RCD do not exceed 12.9% and 11.0%, respectively.

关键词： three-dimensional isolation     rocking behavior     rocking constraint device     replaceable damping component     sinusoidal test    

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Research on constraint-based virtual assembly technologies

YANG Rundang, WU Dianliang, FAN Xiumin, YAN Juanqi

《机械工程前沿（英文）》 2007年 第2卷 第2期   页码 243-249 doi: 10.1007/s11465-007-0043-5

摘要： To realize a constraint-based virtual assembly operation, the unified representations of the assembly constraint, the equivalent relation between the constraint and the degree of freedom (DOF), and the movement DOF reduction in a virtual environment are proposed. Several algorithms about the constraint treatment are submitted. First, the automatic recognition algorithm based on the assembly relation is used to determine the position and orientation relation between two geometry elements of constraint whether they meet the given errors. Second, to satisfy the new constraint, according to the positing solving algorithm, the position and orientation of an active part are modified with minimal adjustment after the part has satisfied the affirmed constraints. Finally, the algorithm of movement navigation based on the generalized coordinate system is put forward, and the part movement is guided. These algorithms have been applied to the integrated virtual assembly environment (IVAE) system. Experiments have indicated that these algorithms have well supported constraint treatments in the IVAE and realized the closer combination of the virtual and the real assembly processes.

关键词： movement DOF     recognition algorithm     assembly     orientation     combination    

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Topology optimization of transient problem with maximum dynamic response constraint using SOAR scheme

《机械工程前沿（英文）》 2021年 第16卷 第3期   页码 593-606 doi: 10.1007/s11465-021-0636-4

摘要： This paper proposes a novel method for the continuum topology optimization of transient vibration problem with maximum dynamic response constraint. An aggregated index in the form of an integral function is presented to cope with the maximum response constraint in the time domain. The density filter solid isotropic material with penalization method combined with threshold projection is developed. The sensitivities of the proposed index with respect to design variables are conducted. To reduce computational cost, the second-order Arnoldi reduction (SOAR) scheme is employed in transient analysis. Influences of aggregate parameter, duration of loading period, interval time, and number of basis vectors in the SOAR scheme on the final designs are discussed through typical examples while unambiguous configuration can be achieved. Through comparison with the corresponding static response from the final designs, the optimized results clearly demonstrate that the transient effects cannot be ignored in structural topology optimization.

关键词： topology optimization     solid isotropic material with penalization     transient response     aggregation function     second-order Arnoldi reduction    

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Generating capacity adequacy evaluation of large-scale, grid-connected photovoltaic systems

Amir AHADI,Seyed Mohsen MIRYOUSEFI AVAL,Hosein HAYATI

《能源前沿（英文）》 2016年 第10卷 第3期   页码 308-318 doi: 10.1007/s11708-016-0415-9

摘要： Large-scale, grid-connected photovoltaic systems have become an essential part of modern electric power distribution systems. In this paper, a novel approach based on the Markov method has been proposed to investigate the effects of large-scale, grid-connected photovoltaic systems on the reliability of bulk power systems. The proposed method serves as an applicable tool to estimate performance (e.g., energy yield and capacity) as well as reliability indices. The Markov method framework has been incorporated with the multi-state models to develop energy states of the photovoltaic systems in order to quantify the effects of the photovoltaic systems on the power system adequacy. Such analysis assists planners to make adequate decisions based on the economical expectations as well as to ensure the recovery of the investment costs over time. The failure states of the components of photovoltaic systems have been considered to evaluate the sensitivity analysis and the adequacy indices including loss of load expectation, and expected energy not supplied. Moreover, the impacts of transitions between failures on the reliability calculations as well as on the long- term operation of the photovoltaic systems have been illustrated. Simulation results on the Roy Billinton test system has been shown to illustrate the procedure of the proposed frame work and evaluate the reliability benefits of using large-scale, grid-connected photovoltaic system on the bulk electric power systems. The proposed method can be easily extended to estimate the operating and maintenance costs for the financial planning of the photovoltaic system projects.

关键词： adequacy assessment     Markov method     large-scale grid-connected photovoltaic(PV) systems     long-term operation    

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Fast removal of ocular artifacts from electroencephalogram signals using spatial constraint independent

Bang-hua YANG,Liang-fei HE,Lin LIN,Qian WANG

《信息与电子工程前沿（英文）》 2015年 第16卷 第6期   页码 486-496 doi: 10.1631/FITEE.1400299

摘要： Ocular artifacts cause the main interfering signals within electroencephalogram (EEG) signal measurements. An adaptive filter based on reference signals from an electrooculogram (EOG) can reduce ocular interference, but collecting EOG signals during a long-term EEG recording is inconvenient and uncomfortable for the subject. To remove ocular artifacts from EEG in brain-computer interfaces (BCIs), a method named spatial constraint independent component analysis based recursive least squares (SCICA-RLS) is proposed. The method consists of two stages. In the first stage, independent component analysis (ICA) is used to decompose multiple EEG channels into an equal number of independent components (ICs). Ocular ICs are identified by an automatic artifact detection method based on kurtosis. Then empirical mode decomposition (EMD) is employed to remove any cerebral activity from the identified ocular ICs to obtain exact artifact ICs. In the second stage, first, SCICA applies exact artifact ICs obtained in the first stage as a constraint to extract artifact ICs from the given EEG signal. These extracted ICs are called spatial constraint ICs (SC-ICs). Then the RLS based adaptive filter uses SC-ICs as reference signals to reduce interference, which avoids the need for parallel EOG recordings. In addition, the proposed method has the ability of fast computation as it is not necessary for SCICA to identify all ICs like ICA. Based on the EEG data recorded from seven subjects, the new approach can lead to average classification accuracies of 3.3% and 12.6% higher than those of the standard ICA and raw EEG, respectively. In addition, the proposed method has 83.5% and 83.8% reduction in time-consumption compared with the standard ICA and ICA-RLS, respectively, which demonstrates a better and faster OA reduction.

关键词： Ocular artifacts     Electroencephalogram (EEG)     Electrooculogram (EOG)     Brain-computer interface (BCI)     Spatial constraint independent component analysis based recursive least squares (SCICA-RLS)    

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工程监理委托代理关系中激励约束与参与约束的研究

秦旋

《中国工程科学》 2007年 第9卷 第4期   页码 45-49

摘要：

基于委托－代理理论对工程监理委托－代理关系中的激励约束与参与约束进行若干拓展研究，与参 与约束（IR）相比，激励相容约束（IC）更为重要，一个机制不满足激励约束，那将是一个无效机制。业主想要 提高工程监理制度的运作效率，就必须通过相应的激励措施诱使工程师努力工作，使“道德风险”得以抑制， 为我国工程监理制度的健康发展提供了有益的启示。

关键词： 工程监理     业主     工程师     委托代理     激励相容约束     参与约束    

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THD reduction with reactive power compensation for fuzzy logic DVR based solar PV grid connected system

Akhil GUPTA,Saurabh CHANANA,Tilak THAKUR

《能源前沿（英文）》 2014年 第8卷 第4期   页码 464-479 doi: 10.1007/s11708-014-0307-9

摘要： Dynamic voltage restorer (DVR) is used to protect sensitive loads from voltage disturbances of the distribution generation (DG) system. In this paper, a new control approach for the 200 kW solar photovoltaic grid connected system with perturb and observe maximum power point tracking (MPPT) technique is implemented. Power quality improvement with comparison is conducted during fault with proportional integral (PI) and artificial intelligence-based fuzzy logic controlled DVR. MPPT tracks the actual variable DC link voltage while deriving the maximum power from a photovoltaic array and maintains DC link voltage constant by changing modulation index of the converter. Simulation results during fault show that the fuzzy logic based DVR scheme demonstrates simultaneous exchange of active and reactive power with less total harmonic distortion (THD) present in voltage source converter (VSC) current and grid current with fast tracking of optimum operating point at unity power factor. Standards (IEEE-519/1547), stipulates that the current with THD greater than 5% cannot be injected into the grid by any distributed generation source. Simulation results and validations of MPPT technique and operation of fuzzy logic controlled DVR demonstrate the effectiveness of the proposed control schemes.

关键词： fuzzy logic     maximum power point tracking (MPPT)     proportional integral (PI)     control     voltage restorer    

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Research on the influence of contact surface constraint on mechanical properties of rock-concrete composite

Baoyun ZHAO, Yang LIU, Dongyan LIU, Wei HUANG, Xiaoping WANG, Guibao YU, Shu LIU

《结构与土木工程前沿（英文）》 2020年 第14卷 第2期   页码 322-330 doi: 10.1007/s11709-019-0594-7

摘要： The contact form of rock-concrete has a crucial influence on the failure characteristics of the stability of rock-concrete engineering. To study the influence of contact surface on the mechanical properties of rock-concrete composite specimens under compressive loads, the two different contact forms of rock-concrete composite specimens are designed, the mechanical properties of these two different specimens are analyzed under triaxial compressive condition, and analysis comparison on the stress-strain curves and failure forms of the two specimens is carried out. The influence of contact surface constraint on the mechanical properties of rock-concrete composite specimens is obtained. Results show that the stress and strain of rock-concrete composite specimens with contact surface constraint are obviously higher than those without. Averagely, compared with composite specimens without the contact surface, the existence of contact surface constraint can increase the axial peak stress of composite specimens by 24% and the axial peak strain by 16%. According to the characteristics of the fracture surface, the theory of microcrack development is used to explain the contact surface constraint of rock-concrete composite specimens, which explains the difference of mechanical properties between the two rock-concrete composite specimens in the experiment. Research results cannot only enrich the research content of the mechanics of rock contact, but also can serve as a valuable reference for the understanding of the corresponding mechanics mechanism of other similar composite specimens.

关键词： rock-concrete     composite specimen     contact surface     mechanical properties     failure mechanism    

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标题 作者 时间 类型 操作

An identification method for enclosed voids restriction in manufacturability design for additive manufacturing structures

Shutian LIU,Quhao LI,Wenjiong CHEN,Liyong TONG,Gengdong CHENG

期刊论文

Vibration analysis of a simply supported beam under moving mass based on moving finite element method

Zhuchao YE, Huaihai CHEN,

期刊论文

Ambient vibration testing and updating of the finite element model of a simply supported beam bridge

Ivan Gomez ARAUJO, Esperanza MALDONADO, Gustavo Chio CHO

期刊论文

Modeling and control of photovoltaic energy conversion connected to the grid

Rebei NAJET, Ben Ghanem BELGACEM, Hasnaoui OTHMAN

期刊论文

Technology and system of constraint programming for industry production scheduling

Yarong CHEN, Zailin GUAN, Yunfang PENG, Xinyu SHAO, Muhammad HASSEB

期刊论文

Fine-grained P2P traffic classification by simply counting flows

Jie HE,Yue-xiang YANG,Yong QIAO,Wen-ping DENG

期刊论文

Recent development in low-constraint fracture toughness testing for structural integrity assessment of

Jidong KANG, James A. GIANETTO, William R. TYSON

期刊论文

Development of rocking constraint device with vertical damping capacity for three-dimensional base-isolated

期刊论文

Research on constraint-based virtual assembly technologies

YANG Rundang, WU Dianliang, FAN Xiumin, YAN Juanqi

期刊论文

Topology optimization of transient problem with maximum dynamic response constraint using SOAR scheme

期刊论文

Generating capacity adequacy evaluation of large-scale, grid-connected photovoltaic systems

Amir AHADI,Seyed Mohsen MIRYOUSEFI AVAL,Hosein HAYATI

期刊论文

Fast removal of ocular artifacts from electroencephalogram signals using spatial constraint independent

Bang-hua YANG,Liang-fei HE,Lin LIN,Qian WANG

期刊论文

工程监理委托代理关系中激励约束与参与约束的研究

秦旋

期刊论文

THD reduction with reactive power compensation for fuzzy logic DVR based solar PV grid connected system

Akhil GUPTA,Saurabh CHANANA,Tilak THAKUR

期刊论文

Research on the influence of contact surface constraint on mechanical properties of rock-concrete composite

Baoyun ZHAO, Yang LIU, Dongyan LIU, Wei HUANG, Xiaoping WANG, Guibao YU, Shu LIU

期刊论文