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Variational mode decomposition based modal parameter identification in civil engineering

Mingjie ZHANG, Fuyou XU

《结构与土木工程前沿（英文）》 2019年 第13卷 第5期   页码 1082-1094 doi: 10.1007/s11709-019-0537-3

摘要： An out-put only modal parameter identification method based on variational mode decomposition (VMD) is developed for civil structure identifications. The recently developed VMD technique is utilized to decompose the free decay response (FDR) of a structure into to modal responses. A novel procedure is developed to calculate the instantaneous modal frequencies and instantaneous modal damping ratios. The proposed identification method can straightforwardly extract the mode shape vectors using the modal responses extracted from the FDRs at all available sensors on the structure. A series of numerical and experimental case studies are conducted to demonstrate the efficiency and highlight the superiority of the proposed method in modal parameter identification using both free vibration and ambient vibration data. The results of the present method are compared with those of the empirical mode decomposition-based method, and the superiorities of the present method are verified. The proposed method is proved to be efficient and accurate in modal parameter identification for both linear and nonlinear civil structures, including structures with closely spaced modes, sudden modal parameter variation, and amplitude-dependent modal parameters, etc.

关键词： modal parameter identification     variational mode decomposition     civil structure     nonlinear system     closely spaced modes    

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Linear and nonlinear elastic analysis of closely spaced strip foundations using Pasternak model

Priyanka GHOSH, S. RAJESH, J. SAI CHAND

《结构与土木工程前沿（英文）》 2017年 第11卷 第2期   页码 228-243 doi: 10.1007/s11709-016-0370-x

摘要： In this study, an attempt is made to determine the interaction effect of two closely spaced strip footings using Pasternak model. The study considers small strain problem and has been performed using linear as well as nonlinear elastic analysis to determine the interaction effect of two nearby strip footings. The hyperbolic stress-strain relationship has been considered for the nonlinear elastic analysis. The linear elastic analysis has been carried out by deriving the equations for the interference effect of the footings in the framework of Pasternak model equation; whereas, the nonlinear elastic analysis has been performed using the finite difference method to solve the second order nonlinear differential equation evolved from Pasternak model with proper boundary conditions. Results obtained from the linear and the nonlinear elastic analysis are presented in terms of non-dimensional interaction factors by varying different parameters like width of the foundation, load on the foundation and the depth of the rigid base. Results are suitably compared with the existing values in the literature.

关键词： bearing capacity     linear and non-linear elasticity     foundation     interaction effect     numerical modeling     Pasternak model    

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Structural design and mechanical responses of closely spaced super-span double tunnels in strongly weathered

Jiaxin HE; Shaohui HE; Xiabing LIU; Jinlei ZHENG

《结构与土木工程前沿（英文）》 2022年 第16卷 第6期   页码 685-703 doi: 10.1007/s11709-022-0824-2

摘要： This paper presents a study of closely spaced double tunnels in Taizhou, China. One is Xiabei Mountain No. 2 four-line super-span high-speed railway tunnel (HRT), and the other is Xiabei Mountain double-line large-span subway tunnel (ST). The excavation spans of HRT and ST are 26.3 and 14 m, respectively. The two tunnels are located at different levels, and their separating distance is 17.2 m. Due to the short construction period, the HRT excavation was completed earlier than ST. The structural design of the HRT, taking account of the disturbance by the ST construction, was analyzed by a numerical simulation. It was found that the “yielding principle” design was more feasible than the “resistance principle” design when considering the safety and durability of the HRT secondary lining. The mechanical responses of the HRT during ST construction were comprehensively monitored and analyzed, including the vault settlement, horizontal convergence, surrounding rock pressure, and the internal stress in shotcrete and steel arch. Results show that the longitudinal influence range of the ST construction on the HRT was approximately 0.6–1.1 times the ST outer diameter; the disturbance was mainly generated in the ST upper bench excavation; and the final axial force of the HRT shotcrete was approximately 9–16 times that of the steel arch, which indicated that the shotcrete was the main bearing structure. The safety status of the HRT was assessed based on the monitoring data, and the minimum safety factors of the HRT shotcrete and steel arch were 1.61 and 1.89, respectively. Parametric studies were performed to show how the lining stress of HRT was affected by the relative angle, pillar width, ST excavation method and excavation footage. Finally, the design and construction optimization were proposed according to the monitoring data and parameter analysis results. This study might provide practical reference for similar projects.

关键词： double tunnels     super-span     structural design     mechanical response     numerical simulation     field monitoring    

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The impact of different voltage application modes on biodegradation of chloramphenicol and shift of microbial

《环境科学与工程前沿（英文）》 2022年 第16卷 第11期 doi: 10.1007/s11783-022-1576-x

摘要：

● Presented coupled system enhanced biodegradation of antibiotic chloramphenicol.

关键词： Electrical stimulation     Biodegradation     Microbial community     Chloramphenicol    

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Experimental analysis on strength and failure modes of wood beam-column connections

Zhenhua HUANG,Sheldon Q SHI,Liping CAI

《结构与土木工程前沿（英文）》 2014年 第8卷 第3期   页码 260-269 doi: 10.1007/s11709-014-0261-y

摘要： This research experimentally examined the strength, failure modes, and behaviors of dowel-bearing and fiber-bearing wood beam-column connections and explored the effects of cyclic loading on the strength, failure modes, and behaviors of those connections. Base on limited numbers of exploratory laboratory tests (6 preliminary tests in total), the authors observed that the typical bolted connection (dowel-bearing type wood beam-column connection with fiber-bearing surfaces) showed good behavior (large peak moment) under the monotonic loads, and the tenon joint connection (fiber-bearing wood beam-column connection) showed good behavior under cyclic loads. The cyclic property of loading reduced the strength of the dowel-bearing type wood beam-column connections, but increased the strength of fiber-bearing type wood beam-column connections. More importantly, the authors identified a possible location of safety concern in current national design specifications (NDS) standards for the typical bolted connection (dowel-bearing connection with fiber bearing surface) under cyclic loading because the tested value was smaller than the NDS calculated value. But, because of the small amount of tests conducted, no final conclusion can be drawn based on those preliminary observations yet. A large number of repetitive laboratory tests should be conducted.

关键词： wood     connection     dowel-bearing     fiber-bearing    

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Optimization for operating modes based on simulation of seasonal underground thermal energy storage

ZHAO Jun, CHEN Yan, LI Xinguo

《能源前沿（英文）》 2008年 第2卷 第3期   页码 298-301 doi: 10.1007/s11708-008-0053-y

摘要： A simulation was performed, which concerned the feasibility of seasonal underground thermal energy storage (UTES) in Tianjin, China. The investigated system consisted of 8 boreholes. In summer, residual solar thermal energy was emitted into the soil surrounding the borehole heat exchangers through which the stored energy was extracted in winter with a ground coupled heat pump (GCHP) to provide a proper heating temperature. A simulation study was performed to study the influence of system operation modes on thermal recovery based on the experimental data of a GCHP system, local meteorological conditions and soil properties in Tianjin. The results indicate a thermal recovery ratio of less than 67% and different temperature distributions under three modes. Finally, an operation mode was suggested based on both lower loss and better thermal recovery in the UTES.
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Multi-scale investigation of active failure for various modes of wall movement

《结构与土木工程前沿（英文）》 2021年 第15卷 第4期   页码 961-979 doi: 10.1007/s11709-021-0738-4

摘要： Retained backfill response to wall movement depends on factors that range from boundary conditions to the geometrical characteristic of individual particles. Hence, mechanical understanding of the problem warrants multi-scale analyses that investigate reciprocal relationships between macro and micro effects. Accordingly, this study attempts a multi-scale examination of failure evolution in cohesionless backfills. Therefore, the transition of retained backfills from at-rest condition to the active state is modeled using the discrete element method (DEM). DEM allows conducting virtual experiments, with which the variation of particle and boundary properties is straightforward. Hence, various modes of wall movement (translation and rotation) toward the active state are modeled using two different backfills with distinct particle shapes (spherical and nonspherical) under varying surcharge. For each model, cumulative rotations of single particles are tracked, and the results are used to analyze the evolution of shear bands and their geometric characteristics. Moreover, dependencies of lateral pressure coefficients and coordination numbers, as respective macro and micro behavior indicators, on particle shape, boundary conditions, and surcharge levels are investigated. Additionally, contact force networks are visually determined, and their influences on pressure distribution and deformation mechanisms are discussed with reference to the associated modes of wall movement and particle shapes.

关键词： discrete-element modelling     granular materials     retaining walls     particle shape     arching    

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Bi-modes alternation stepping ultrasonic motors

JIN Jiamei, ZHAO Chunsheng

《机械工程前沿（英文）》 2008年 第3卷 第1期   页码 101-105 doi: 10.1007/s11465-008-0018-1

摘要： Based on the principle of alternative operation of two bending vibration modes in an annular stator, this paper presents a standing-wave stepping ultrasonic motor characterized by no accumulative errors driven by an open-loop control circuitry. The driving forces are generated from the motions of projections on the stator in two modes. The positioning of the motor is achieved by the cooperation between the stator projections and rotor teeth, and the number of the rotors determines the stepping angle of the motor. Two-phase sinusoidal signals corresponding to the two modal frequencies drive the motor bi-direction stepping rotation via a switch unit. The prototype runs steadily without miss-step on trial. The single-step angle displacement of the motor is 2.5°.

关键词： miss-step     bi-direction     Two-phase sinusoidal     positioning     accumulative    

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Improvement to observability measures of LFO modes in power systems with DFIGs

Shenghu LI

《能源前沿（英文）》 2021年 第15卷 第2期   页码 539-549 doi: 10.1007/s11708-019-0617-z

摘要： Observation of the low-frequency oscillation (LFO) modes in power systems is important to design the damping scheme. The state equations of the power system with the doubly-fed induction generators (DFIGs) are derived to find the LFO modes related to the synchronous generator (SGs) and the DFIGs. The definition of the observability measure is improved to consider the initial output and the attenuation speed of the modes. The sensitivities of the observability measures to the control parameters are derived. The numerical results from the small and large-disturbance validate the LFO modes caused by the DFIGs, and different observability measures are compared. Adjustment of the control parameters is chosen based on the sensitivity model to improve the observability and damping ratio of the LFO mode, and the stability of the wind power system.

关键词： wind power system     low-frequency oscillation (LFO)     observability measure     sensitivity     doubly-fed induction generator (DFIG)    

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Macro-architectured cellular materials: Properties, characteristic modes, and prediction methods

Zheng-Dong MA

《机械工程前沿（英文）》 2018年 第13卷 第3期   页码 442-459 doi: 10.1007/s11465-018-0488-8

摘要：

Macro-architectured cellular (MAC) material is defined as a class of engineered materials having configurable cells of relatively large (i.e., visible) size that can be architecturally designed to achieve various desired material properties. Two types of novel MAC materials, negative Poisson’s ratio material and biomimetic tendon reinforced material, were introduced in this study. To estimate the effective material properties for structural analyses and to optimally design such materials, a set of suitable homogenization methods was developed that provided an effective means for the multiscale modeling of MAC materials. First, a strain-based homogenization method was developed using an approach that separated the strain field into a homogenized strain field and a strain variation field in the local cellular domain superposed on the homogenized strain field. The principle of virtual displacements for the relationship between the strain variation field and the homogenized strain field was then used to condense the strain variation field onto the homogenized strain field. The new method was then extended to a stress-based homogenization process based on the principle of virtual forces and further applied to address the discrete systems represented by the beam or frame structures of the aforementioned MAC materials. The characteristic modes and the stress recovery process used to predict the stress distribution inside the cellular domain and thus determine the material strengths and failures at the local level are also discussed.

关键词： architectured material     cellular materials     multi-scale modeling     homogenization method     effective material properties     computational method    

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Performance of completely autotrophic nitrogen removal over nitrite process under different aeration modes

GUO Jinsong, YANG Guohong, FANG Fang, QIN Yu

《环境科学与工程前沿（英文）》 2008年 第2卷 第4期   页码 439-445 doi: 10.1007/s11783-008-0046-4

摘要： In this study, three sequential batch biofilm reactors (SBBRs) were operated for 155 days to evaluate the performance of completely autotrophic nitrogen removal over nitrite (CANON) process under different aeration modes and dissolved oxygen (DO). Synthetic wastewater with 160-mg NH-N/L was fed into the reactors. In the continuously-aerated reactor, the efficiency of the ammonium nitrogen conversion and total nitrogen (TN) removal reached 80% and 70%, respectively, with DO between 0.8–1.0 mg/L. Whereas in the intermittently-aerated reactor, at the aeration/non-aeration ratio of 1.0, ammonium was always under the detection limit and 86% of TN was removed with DO between 2.0–2.5 mg/L during the aeration time. Results show that CANON could be achieved in both continuous and intermittent aeration pattern. However, to achieve the same nitrogen removal efficiency, the DO needed in the intermittently-aerated sequential batch biofilm reactor (SBBR) during the aeration period was higher than that in the continuously-aerated SBBR. In addition, the DO in the CANON system should be adjusted to the aeration mode, and low DO was not a prerequisite to CANON process.

关键词： Synthetic wastewater     process     Whereas     biofilm     detection    

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Performance monitoring of non-gaussian chemical processes with modes-switching using globality-locality

Xin Peng, Yang Tang, Wenli Du, Feng Qian

《化学科学与工程前沿（英文）》 2017年 第11卷 第3期   页码 429-439 doi: 10.1007/s11705-017-1675-6

摘要： In this paper, we propose a novel performance monitoring and fault detection method, which is based on modified structure analysis and globality and locality preserving (MSAGL) projection, for non-Gaussian processes with multiple operation conditions. By using locality preserving projection to analyze the embedding geometrical manifold and extracting the non-Gaussian features by independent component analysis, MSAGL preserves both the global and local structures of the data simultaneously. Furthermore, the tradeoff parameter of MSAGL is tuned adaptively in order to find the projection direction optimal for revealing the hidden structural information. The validity and effectiveness of this approach are illustrated by applying the proposed technique to the Tennessee Eastman process simulation under multiple operation conditions. The results demonstrate the advantages of the proposed method over conventional eigendecomposition-based monitoring methods.

关键词： non-Gaussian processes     subspace projection     independent component analysis     locality preserving projection     finite mixture model    

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生物燃料乙醇产业未来发展的新模式

王梦,田晓俊,陈必强,林海龙,岳国君

《中国工程科学》 2020年 第22卷 第2期   页码 47-54 doi: 10.15302/J-SSCAE-2020.02.007

摘要：

燃料乙醇产业是我国重点培育和发展的战略性新兴产业之一，在国家推进工业化与信息化深度融合的背景下，利用我国在工业互联网和第五代移动通信（5G）技术上的优势，以大数据、数字孪生和区块链等新技术为支撑，推进生物燃料乙醇产业的智能化、安全化发展新模式，对于我国燃料乙醇产业高质量发展具有重要意义。本文梳理并总结了国内外生物燃料乙醇产业的发展现状，凝练产业智能化、安全化发展面临的问题，提出了生物燃料乙醇产业智能生产新模式、安全生产新模式和产业管理新模式的总体思路。研究表明，我国生物燃料乙醇产业发展应在国家、地方和企业的保障与积极配合下，从国家战略层面引导产业发展，推进生物燃料乙醇产业基地特色化、联合化、智能化发展；加大“产学研”合作力度，创新生产模式和生产技术，提升国际市场竞争力；进一步开展关键技术攻关，实现以纤维素类生物质为原料的生物燃料乙醇技术突破，为国家粮食安全问题提供战略储备。

关键词： 燃料乙醇     智能生产     安全生产     新模式    

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Atomistic characterization of binding modes and affinity of peptide inhibitors to amyloid-

Fufeng LIU,Wenjie DU,Yan SUN,Jie ZHENG,Xiaoyan DONG

《化学科学与工程前沿（英文）》 2014年 第8卷 第4期   页码 433-444 doi: 10.1007/s11705-014-1454-6

摘要： The aggregation of amyloid -protein (A ) is tightly linked to the pathogenesis of Alzheimer’s disease. Previous studies have found that three peptide inhibitors (i.e., KLVFF, VVIA, and LPFFD) can inhibit A aggregation and alleviate A -induced neurotoxicity. However, atomic details of binding modes and binding affinities between these peptide inhibitors and A have not been revealed. Here, using molecular dynamics simulations and molecular mechanics Poisson Boltzmann surface area (MM/PBSA) analysis, we examined the effect of three peptide inhibitors (KLVFF, VVIA, and LPFFD) on their sequence-specific interactions with A and the molecular basis of their inhibition. All inhibitors exhibit varied binding affinity to A , in which KLVFF has the highest binding affinity, whereas LPFFD has the least. MM/PBSA analysis further revealed that different peptide inhibitors have different modes of interaction with A , consequently hotspot binding residues, and underlying driving forces. Specific residue-based interactions between inhibitors and A were determined and compared for illustrating different binding and inhibition mechanisms. This work provides structure-based binding information for further modification and optimization of these three peptide inhibitors to enhance their binding and inhibitory abilities against A aggregation.

关键词： Alzheimer’s disease     amyloid β-protein     peptide inhibitors     protein-protein interaction     molecular dynamics simulation    

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Characteristics and energy distribution of modulated multi-pulse injection modes based diesel HCCI combustion

LIU Bin, SU Wanhua, WANG Hui, HUANG Haozhong

《能源前沿（英文）》 2007年 第1卷 第4期   页码 420-427 doi: 10.1007/s11708-007-0061-7

摘要： Cycle fuel energy distribution and combustion characteristics of early in-cylinder diesel homogenous charge compression ignition (HCCI) combustion organized by modulated multi-pulse injection modes are studied by the engine test.

关键词： combustion     compression     homogenous     in-cylinder     modulated multi-pulse    

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标题 作者 时间 类型 操作

Variational mode decomposition based modal parameter identification in civil engineering

Mingjie ZHANG, Fuyou XU

期刊论文

Linear and nonlinear elastic analysis of closely spaced strip foundations using Pasternak model

Priyanka GHOSH, S. RAJESH, J. SAI CHAND

期刊论文

Structural design and mechanical responses of closely spaced super-span double tunnels in strongly weathered

Jiaxin HE; Shaohui HE; Xiabing LIU; Jinlei ZHENG

期刊论文

The impact of different voltage application modes on biodegradation of chloramphenicol and shift of microbial

期刊论文

Experimental analysis on strength and failure modes of wood beam-column connections

Zhenhua HUANG,Sheldon Q SHI,Liping CAI

期刊论文

Optimization for operating modes based on simulation of seasonal underground thermal energy storage

ZHAO Jun, CHEN Yan, LI Xinguo

期刊论文

Multi-scale investigation of active failure for various modes of wall movement

期刊论文

Bi-modes alternation stepping ultrasonic motors

JIN Jiamei, ZHAO Chunsheng

期刊论文

Improvement to observability measures of LFO modes in power systems with DFIGs

Shenghu LI

期刊论文

Macro-architectured cellular materials: Properties, characteristic modes, and prediction methods

Zheng-Dong MA

期刊论文

Performance of completely autotrophic nitrogen removal over nitrite process under different aeration modes

GUO Jinsong, YANG Guohong, FANG Fang, QIN Yu

期刊论文

Performance monitoring of non-gaussian chemical processes with modes-switching using globality-locality

Xin Peng, Yang Tang, Wenli Du, Feng Qian

期刊论文

生物燃料乙醇产业未来发展的新模式

王梦,田晓俊,陈必强,林海龙,岳国君

期刊论文

Atomistic characterization of binding modes and affinity of peptide inhibitors to amyloid-

Fufeng LIU,Wenjie DU,Yan SUN,Jie ZHENG,Xiaoyan DONG

期刊论文

Characteristics and energy distribution of modulated multi-pulse injection modes based diesel HCCI combustion

LIU Bin, SU Wanhua, WANG Hui, HUANG Haozhong

期刊论文