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Construction of interfacial dynamic bonds for high performance lignin/polymer biocomposites

《化学科学与工程前沿（英文）》 2023年 第17卷 第10期   页码 1372-1388 doi: 10.1007/s11705-023-2302-3

摘要： Lignin is the largest natural aromatic biopolymer, but usually treated as industrial biomass waste. The development of lignin/polymer biocomposites can promote the high value utilization of lignin and the greening of polymers. However, the weak interfacial interaction between industrial lignin and polymer induces poor compatibility and serious agglomeration in polymer owing to the strong intermolecular force of lignin. As such, it is extremely difficult to prepare high performance lignin/polymer biocomposites. Recently, we proposed the strategy of in situ construction of interfacial dynamic bonds in lignin/polymer composites. By taking advantage of the abundant oxygen-containing polar groups of lignin, we inserted dynamic bonding connection such as hydrogen bonds and coordination bonds into the interphase between lignin and the polymer matrix to improve the interfacial interactions. Meanwhile, the natural amphiphilic structure characteristics of lignin were utilized to construct the hierarchical nanophase separation structure in lignin/polymer composites. The persistent problems of poor dispersity and interfacial compatibility of lignin in the polymer matrix were effectively solved. The lignin-modified polymer composites achieved simultaneously enhanced strength and toughness. This concise review systematically summarized the recent research progress of our group toward building high-performance lignin/polymer biocomposites through the design of interfacial dynamic bonds (hydrogen bonds, coordination bonds, and dynamic covalent bonds) between lignin and different polymer systems (polar plastics, rubber, polyurethane, hydrogels, and other polymers). Finally, the future development direction, main challenges, and potential solutions of lignin application in polymers were presented.

关键词： lignin     polymer     interfacial dynamic bonds    

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A total torque index for dynamic performance evaluation of a radial symmetric six-legged robot

Kejia LI, Xilun DING, Marco CECCARELL

《机械工程前沿（英文）》 2012年 第7卷 第2期   页码 219-230 doi: 10.1007/s11465-012-0320-9

摘要：

This article focuses on the dynamic index and performance of a radial symmetric six-legged robot. At first the structure of the robot is described in brief and its inverse kinematics is presented. Then the dynamic model is formulated as based on the Lagrange equations. A novel index of total torque is proposed by considering the posture of the supporting legs. The new index can be used to optimize the leg’s structure and operation for consuming minimum power and avoiding unstable postures of the robot. A characterization of the proposed six-legged robot is obtained by a parametric analysis of robot performance through simulation using the presented dynamic model. Main influences are outlined as well as the usefulness of the proposed performance index.

关键词： six-legged robots     dynamic modeling     performance index    

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Influence of the Mechanical Seals on the Dynamic Performance of Rotor–Bearing Systems

XU Hua, ZHU Jun

《机械工程前沿（英文）》 2006年 第1卷 第1期   页码 96-100 doi: 10.1007/s11465-005-0008-5

摘要：

In this paper, to consider the effects of mechanical seals, a lumped-mass model and the transfer matrix method are used to establish the equations for the dynamics performance of rotor bearing system. The general inverted iteration method is also used to solve the eigenvalue problem of these equations. To check the response of the rotor bearing system under unbalance motivation, the Gauss method is used to calculate the dynamic response of the constrained vibration. The results, based on the dynamic properties calculation of a typical mechanical spiral seal, such as stiffness coefficients and damping coefficients, exert the influence of the mechanical seal on the rotor bearing system of the high-speed machinery. Meanwhile, some structure parameters that may affect the dynamic performance and forced vibration under unbalance motivation of the rotor bearing system considering mechanical seals are analyzed in the paper. The analysis results show that the mechanical seal more or less has effects on the rotor bearing system. The mechanical seal has much more effects on the flexible rotor bearing system than on the rigid one. For instance, in a certain case, if the effects of the mechanical seal were taken into account, the system s critical speed may increase by 70 80%.

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Dynamic performance of submerged floating tunnel with different mooring styles subjected to anchor cable

《结构与土木工程前沿（英文）》 2023年 第17卷 第10期   页码 1443-1464 doi: 10.1007/s11709-023-0932-7

摘要： Submerged floating tunnels (SFTs) are novel structures for transportation across long- and deep-strait regions. Owing to severe wave and current excitation as well as the effects of underwater structures and corrosion, the risk of local anchor cable failure is high, which can result in the progressive failure of the entire structure. In this study, experimental and numerical investigations are conducted to analyze the dynamic behavior of an SFT with different mooring styles under local cable failure. A custom-designed cable failure device and the birth-and-death element method are used to simulate cable failure (i.e., progressive failure) via experiments and numerical simulation, respectively. A physical-scale segmental model of an SFT with different mooring styles under anchor cable failure is developed in this study. A segmental and entire-length mathematical model is developed using the ANSYS program to perform the numerical simulation. The results of the segmental numerical and experimental models indicate good agreement. The dynamic response of an SFT with different mooring styles under cable failure is comprehensively investigated by investigating the effects of key parameters (wave period, buoyant weight ratio, and cable failure mechanism). Moreover, the progressive failure of the SFT under cable failure is investigated via a segment model test and a numerical simulation of its entire length. The present study can serve as a reference for the safer designs of the SFT mooring style.

关键词： dynamic behaviors     submerged floating tunnel     cable failure     mooring style     progressive failure    

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Evaluation of the static and dynamic structural performance of segmental pre-stressed concrete box girder

Ali Fadhil NASER, Zonglin WANG

《结构与土木工程前沿（英文）》 2013年 第7卷 第2期   页码 164-177 doi: 10.1007/s11709-013-0196-8

摘要： The objectives of this study are to explain the repairing and strengthening methods which are used to improve the structural performance of the bridge structure, to analyze the static and dynamic responses after strengthening, and to evaluate the performance of the bridge structure after repairing and strengthening. The methods of repairing and strengthening include reconstruction the deck of the bridge by casting 10 cm layer of concrete, strengthening the web and bottom floor of box girders of middle spans and side spans by sticking the steel plates, strengthening the whole bridge structure by using external pre-stressing tendons, and treatment the cracks. The results of theoretical analysis show that the values of tensile stress and vertical deflection are decreased and the compressive stress is increased after strengthening. There are not tensile stresses are appeared in the sections of the bridge structure. The modal analysis results show that the value of natural frequency is equal to 2.09 Hz which is more than the values before strengthening which is equal to 1.64 Hz, indicating that the stiffness of the bridge structure is improved and the strengthening process is effective to improve the cracks resistance and bearing capacity of the bridge structure.

关键词： structural performance     steel plates     external pre-stressing     cracks     grouting method     static    

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Effects of a dynamic membrane formed with polyethylene glycol on the ultrafiltration of natural organic

Boksoon KWON, Noeon PARK, Jaeweon CHO,

《环境科学与工程前沿（英文）》 2010年 第4卷 第2期   页码 172-182 doi: 10.1007/s11783-010-0002-y

摘要： The formation of a dynamic membrane (DM) was investigated using polyethylene glycol (PEG) (molecular weight of 35000 g/mol, concentration of 1 g/L). Two natural organic matters (NOM), Dongbok Lake NOM (DLNOM) and Suwannee River NOM (SRNOM) were used in the ultrafiltration experiments along with PEG. To evaluate the effects of the DM with PEG on ultrafiltration, various transport experiments were conducted, and the analyses of the NOM in the membrane feed and permeate were performed using high performance size exclusion chromatography, and the pore size distribution ( PSD) and molecular weight cut off ( MWCO) were determined. The advantages of DM formed with PEG can be summarized as follows: (1) PEG interferes with NOM transmission through the ultrafiltration membrane pores by increasing the retention coefficient of NOM in UF membranes, and (2) low removal of NOM by the DM is affected by external factors, such as pressure increases during UF membrane filtration, which decreases the PSD and MWCO of UF membranes. However, a disadvantage of the DM with PEG was severe flux decline; thus, one must be mindful of both the positive and negative influences of the DM when optimizing the UF performance of the membrane.

关键词： dynamic membrane     natural organic matters     ultrafiltration membrane performance     effective PSD     effective molecular weight cutoff    

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Automatic detection and assessment of crack development in ultra-high performance concrete in the spatial

《结构与土木工程前沿（英文）》 2024年 第18卷 第3期   页码 350-364 doi: 10.1007/s11709-024-1042-x

摘要： Automatic detection and assessment of surface cracks are beneficial for understanding the mechanical performance of ultra-high performance concrete (UHPC). This study detects crack evolution using a novel dynamic mode decomposition (DMD) method. In this method, the sparse matrix ‘determined’ from images is used to reconstruct the foreground that contains cracks, and the global threshold method is adopted to extract the crack patterns. The application of the DMD method to the three-point bending test demonstrates the efficiency in inspecting cracks with high accuracy. Accordingly, the geometric features, including the area and its projection in two major directions, are evaluated over time. The relationship between the geometric properties of cracks and load-displacement curves of UHPC is discussed. Due to the irregular shape of cracks in the spatial domain, the cracks are then transformed into the Fourier domain to assess their development. Results indicate that crack patterns in the Fourier domain exhibit a distinct concentration around a central position. Moreover, the power spectral density of cracks exhibits an increasing trend over time. The investigation into crack evolution in both the spatial and Fourier domains contributes significantly to elucidating the mechanical behavior of UHPC.

关键词： dynamic mode decomposition     ultra-high performance concrete     crack detection     geometric features     Fourier domain    

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动力气垫地效翼船的流体空气动力性能研究

恽良,邬成杰,谢佑农

《中国工程科学》 2000年 第2卷 第4期   页码 48-52

摘要：

文章简要阐述了动力气垫地效翼船的空气-流体动力设计特点和难点，及“天鹅”号地效翼船的试验研究。由于采取一系列措施，使艇在静垫升性、两栖性、耐波性与气动力配平和运动稳定性等方面，在船模与实船上均取得令人满意的结果。

关键词： 动力气垫     地效翼船     性能    

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Seismic performance of moment resisting steel frame subjected to earthquake excitations

Fadzli M. NAZRI, Pang Yew KEN

《结构与土木工程前沿（英文）》 2014年 第8卷 第1期   页码 19-25 doi: 10.1007/s11709-014-0240-3

摘要： This study presents static and dynamic assessments on the steel structures. Pushover analysis (POA) and incremental dynamic analysis (IDA) were run on moment resisting steel frames. The IDA study involves successive scaling and application of each accelerogram followed by assessment of the maximum response. Steel frames are subjected to nonlinear inelastic time history analysis for 14 different scaled ground motions, 7 near field and 7 far field. The results obtained from POA on the 3, 6 and 9 storey steel frames show consistent results for both uniform and triangular lateral loading. Uniform loading shows that the steel frames exhibits higher base shear than the triangular loading. The IDA results show that the far field ground motions has caused all steel frame design within the research to collapse while near field ground motion only caused some steel frames to collapse. The POA can be used to estimate the performance-based-seismic-design (PBSD) limit states of the steel frames with consistency while the IDA seems to be quite inconsistent. It is concluded that the POA can be consistently used to estimate the limit states of steel frames while limit state estimations from IDA requires carefully selected ground motions with considerations of important parameters.

关键词： incremental dynamic analysis (IDA)     pushover analysis     performance-based seismic design    

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Performance comparison of cocurrent and countercurrent flow solid oxide fuel cells

Huisheng ZHANG, Shilie WENG, Ming SU

《能源前沿（英文）》 2011年 第5卷 第2期   页码 207-213 doi: 10.1007/s11708-011-0151-0

摘要： Solid oxide fuel cell (SOFC) is a complicated system with heat and mass transfer as well as electrochemical reactions. The flowing configuration of fuel and oxidants in the fuel cell will greatly affect the performance of the fuel cell stack. Based on the developed mathematical model of direct internal reforming SOFC, this paper established a distributed parameters simulation model for cocurrent and countercurrent types of SOFC based on the volume-resistance characteristic modeling method. The steady-state distribution characteristics and dynamic performances were compared and were analyzed for cocurrent and countercurrent types of SOFCs. The results indicate that the cocurrent configuration of SOFC is more suitable with regard to performance and safety.

关键词： solid oxide fuel cell (SOFC)     cocurrent     countercurrent     dynamic performance    

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Higher-order mode effects on the seismic performance of tall piers

Zhongguo GUAN, Jianzhong LI, Yan XU, Hao LU

《结构与土木工程前沿（英文）》 2011年 第5卷 第4期   页码 496-502 doi: 10.1007/s11709-011-0131-9

摘要： A comprehensive analysis was conducted to investigate the seismic performance of a typical tall bridge pier through incremental dynamical analysis (IDA). The effect of higher-order modes was studied specifically. The results showed that higher-order modes significantly contributed to the structural seismic response and should not be neglected. Including these modes resulted in an additional hinge midway up the pier. No plastic hinge would occur at this location for conventional bridge piers. Higher-order modes also led to an out-of-phase response between the hinge rotation at the pier bottom and the displacement at the top. This means that the displacement-based seismic design method cannot correctly predict the mechanical state of the critical hinge and therefore is not suitable for use in the seismic design of tall piers. Mistakenly using the displacement-based seismic design method for tall piers may result in a seriously unsafe condition.

关键词： tall bridges     higher-order mode effects     incremental dynamic analysis    

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Performance analysis of solar absorption-subcooled compression hybrid refrigeration system in subtropical

Xiangyang YE,Liming LIU,Zeyu LI

《能源前沿（英文）》 2019年 第13卷 第1期   页码 185-192 doi: 10.1007/s11708-017-0452-z

摘要： Solar absorption-subcooled compression hybrid refrigeration system is a new type of efficient and economical solar refrigeration device which always meets the demand of cooling load with the change of solar irradiance. The performance of the hybrid system is higher due to the improvement of evaporator temperature of absorption subsystem. But simultaneously, the variation of working process as well as performance is complicated since the absorption and compression subsystems are coupled strongly. Based on the measured meteorological data of Guangzhou, a subtropical city in south China, a corresponding parametric model has been developed for the hybrid refrigeration system, and a program written by Fortran has been used to analyze the performance of the hybrid system under different external conditions. As the condensation temperature ranges from 38°C to 50°C, the working time fraction of the absorption subsystem increases from 75% to 85%. Besides, the energy saving fraction also increases from 5.31% to 6.02%. The average COP of the absorption subsystem is improved from 0.366 to 0.407. However, when the temperature of the absorption increases from 36°C to 48°C, the average COP of hybrid system decreases from 2.703 to 2.312. Moreover, the working time fraction of the absorption subsystem decreases from 80% to 71.7%. The energy saving fraction falls from 5.67% to 5.08%. In addition, when the evaporate temperature increases from 4°C to 14°C, the average COP of the absorption subsystem decreases from 0.384 to 0.365. The work of the compressor decreases from 48.2 kW to 32.8 kW and the corresponding average COP of the absorption subsystem is improved from 2.591 to 3.082.

关键词： solar     absorption-subcooled     compression hybrid     dynamic simulation     performance analysis    

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Temperature segregation and its impact on the quality and performance of asphalt pavements

Minkyum KIM, Pranjal PHALTANE, Louay N. MOHAMMAD, Mostafa ELSEIFI

《结构与土木工程前沿（英文）》 2018年 第12卷 第4期   页码 536-547 doi: 10.1007/s11709-017-0451-5

摘要： Temperature segregation is non-uniform temperature distributionacross the uncompacted asphalt mat during paving operations and mayhave detrimental effects on the quality and performance of asphaltpavements. However, many research studies conducted across the UShave reported mixed observations regarding its effects on the initialquality and long-term performance of asphalt pavements.?The objectiveof this study was to determine the effects of the temperature segregationon the density and mechanical properties of Louisiana asphalt mixtures.Seven asphalt rehabilitation projects across Louisiana were selected.A multi-sensor infrared bar (Pave-IR) system and a hand-held portablethermal camera were used to measure the temperature of asphalt mats.Field core samples were collected from various areas with varyingseverity levels of temperature segregation and tested for the density,fracture resistance (J ) by semi-circular bending(SCB), rut depth by wheel tracking, and dynamic modulus (|E*|) byindirect tension (IDT) devices.?Two distinctive patterns of non-uniformtemperature distribution were observed: a cyclic and irregular temperaturesegregations. Laboratory test results showed that highly temperaturesegregated asphalt pavements (i.e., temperature differentials ≥41.7°C) can have significantly lower densities and the mechanicalproperties than the non-segregated area, especially when the temperaturedifferentials are measured at compaction.

关键词： temperature segregation     temperature differential     pavement density     semi-circular bending     wheel tracking     dynamic modulus    

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Variable stiffness and damping magnetorheological isolator

Yang ZHOU, Xingyu WANG, Xianzhou ZHANG, Weihua LI

《机械工程前沿（英文）》 2009年 第4卷 第3期   页码 310-315 doi: 10.1007/s11465-009-0039-4

摘要： This paper presents the development and characterization of a magnetorheological (MR) fluid-based variable stiffness and damping isolator. The prototype of the MR fluid isolator is fabricated, and its dynamic behavior is measured under various applied magnetic fields. The parameters of the model under various magnetic fields are identified, and the dynamic performance of the isolator is evaluated in simulation. Experimental results indicate that both the stiffness and damping capability of the developed MR isolator can be controlled by an external magnetic field.

关键词： magnetorheological (MR) fluid     stiffness     damping     mathematical model     dynamic performance     parameter identification    

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装甲用镁合金抗弹性能表征体系探讨

才鸿年,谭成文,王富耻,陈志勇

《中国工程科学》 2006年 第8卷 第2期   页码 30-33

摘要：

介绍了高应变率载荷条件下镁合金的吸能特性及变形特征；论述了对镁合金抗弹性能有重要影响的动态强度、高应变率能量吸收率、高应变率变形断裂特征和动态强度等科学问题；就镁合金在装甲领域的应用研究做了初步探讨。

关键词： 能量吸收率     绝热剪切变形局部化     动态强度     动态硬度    

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标题 作者 时间 类型 操作

Construction of interfacial dynamic bonds for high performance lignin/polymer biocomposites

期刊论文

A total torque index for dynamic performance evaluation of a radial symmetric six-legged robot

Kejia LI, Xilun DING, Marco CECCARELL

期刊论文

Influence of the Mechanical Seals on the Dynamic Performance of Rotor–Bearing Systems

XU Hua, ZHU Jun

期刊论文

Dynamic performance of submerged floating tunnel with different mooring styles subjected to anchor cable

期刊论文

Evaluation of the static and dynamic structural performance of segmental pre-stressed concrete box girder

Ali Fadhil NASER, Zonglin WANG

期刊论文

Effects of a dynamic membrane formed with polyethylene glycol on the ultrafiltration of natural organic

Boksoon KWON, Noeon PARK, Jaeweon CHO,

期刊论文

Automatic detection and assessment of crack development in ultra-high performance concrete in the spatial

期刊论文

动力气垫地效翼船的流体空气动力性能研究

恽良,邬成杰,谢佑农

期刊论文

Seismic performance of moment resisting steel frame subjected to earthquake excitations

Fadzli M. NAZRI, Pang Yew KEN

期刊论文

Performance comparison of cocurrent and countercurrent flow solid oxide fuel cells

Huisheng ZHANG, Shilie WENG, Ming SU

期刊论文

Higher-order mode effects on the seismic performance of tall piers

Zhongguo GUAN, Jianzhong LI, Yan XU, Hao LU

期刊论文

Performance analysis of solar absorption-subcooled compression hybrid refrigeration system in subtropical

Xiangyang YE,Liming LIU,Zeyu LI

期刊论文

Temperature segregation and its impact on the quality and performance of asphalt pavements

Minkyum KIM, Pranjal PHALTANE, Louay N. MOHAMMAD, Mostafa ELSEIFI

期刊论文

Variable stiffness and damping magnetorheological isolator

Yang ZHOU, Xingyu WANG, Xianzhou ZHANG, Weihua LI

期刊论文

装甲用镁合金抗弹性能表征体系探讨

才鸿年,谭成文,王富耻,陈志勇

期刊论文