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Analysis of the dynamic hysteresis characteristic of finger seal

LEI Yanni, CHEN Guoding

《机械工程前沿（英文）》 2007年 第2卷 第1期   页码 32-36 doi: 10.1007/s11465-007-0005-y

摘要： The research about hysteresis characteristic of finger seal (FS), which was carried out based on the model with static loads, could not reflect the dynamics behavior of FS system when the rotor runs at high speed. To solve this problem, the relations between the dynamics parameters, structure parameters as well as working parameters in the system were given out through the analysis of finite element analysis result. A mass spring damper dynamics model of FS system was proposed and the hysteresis characteristic of the FS system was analyzed. This work shows that the dynamics characteristic analysis of the FS is necessary and the dynamics model proposed in this paper is valid. This dynamics model is the basis for the optimization design of FS system.

关键词： FS     necessary     hysteresis characteristic     optimization     spring    

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Purification of ice structuring protein complexes from winter wheat using Triton X-114 phase partitioning

Huaneng XU, Haiying CHEN, Weining HUANG,

《化学科学与工程前沿（英文）》 2009年 第3卷 第4期   页码 383-385 doi: 10.1007/s11705-009-0249-7

摘要： Ice structuring proteins (ISPs) isolated from the cold-acclimated plants have a great potential in improving the quality of frozen foods. The purification of ISP complexes from winter wheat was achieved using an aqueous two-phase system of Triton X-114. The highly reactive phenols were removed, and the ISP complexes remained in the aqueous phase after phase separation. The ISP complexes treated by this procedure retained higher thermal hysteresis activity than those treated by ammonium sulfate method. The phase separation technique provides a simple and mild way for removing phenols from ISP complexes.

关键词： separation technique     thermal hysteresis     cold-acclimated     purification     X-114    

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Research on applications of piezoelectric materials in smart structures

Jinhao QIU, Hongli JI

《机械工程前沿（英文）》 2011年 第6卷 第1期   页码 99-117 doi: 10.1007/s11465-011-0212-4

摘要：

Piezoelectric materials have become the most attractive functional materials for sensors and actuators in smart structures because they can directly convert mechanical energy to electrical energy and vise versa. They have excellent electromechanical coupling characteristics and excellent frequency response. In this article, some research activities on the applications of piezoelectric materials in smart structures, including semi-active vibration control based on synchronized switch damping using negative capacitance, energy harvesting using new electronic interfaces, structural health monitoring based on a new type of piezoelectric fibers with metal core, and active hysteresis control based on new modified Prandtl-Ishlinskii model at the Aeronautical Science Key Laboratory for Smart Materials and Structures, Nanjing University of Aeronautics and Astronautics are introduced.

关键词： piezoelectric materials     vibration control     energy harvesting     structural health monitoring     piezoelectric hysteresis    

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Dynamic characteristics of a magnetorheological pin joint for civil structures

Yancheng LI,Jianchun LI

《机械工程前沿（英文）》 2014年 第9卷 第1期   页码 15-33 doi: 10.1007/s11465-014-0283-0

摘要：

Magnetorheological (MR) pin joint is a novel device in which its joint moment resistance can be controlled in real-time by altering the applied magnetic field. The smart pin joint is intended to be used as a controllable connector between the columns and beams of a civil structure to instantaneously shift the structural natural frequencies in order to avoid resonance and therefore to reduce unwanted vibrations and hence prevent structural damage. As an intrinsically nonlinear device, modelling of this MR fluid based device is a challenging task and makes the design of a suitable control algorithm a cumbersome situation. Aimed at its application in civil structure, the main purpose of this paper is to test and characterise the hysteretic behaviour of MR pin joint. A test scheme is designed to obtain the dynamic performance of MR pin joint in the dominant earthquake frequency range. Some unique phenomena different from those of MR damper are observed through the experimental testing. A computationally-efficient model is proposed by introducing a hyperbolic element to accurately reproduce its dynamic behaviour and to further facilitate the design of a suitable control algorithm. Comprehensive investigations on the model accuracy and dependences of the proposed model on loading condition (frequency and amplitude) and input current level are reported in the last section of this paper.

关键词： Magnetorheological pin joint     hyperbolic hysteresis model experimental testing frequency dependence    

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Influence evaluation of loading conditions during pressurized thermal shock transients based on thermal-hydraulics

Jinya KATSUYAMA, Shumpei UNO, Tadashi WATANABE, Yinsheng LI

《机械工程前沿（英文）》 2018年 第13卷 第4期   页码 563-570 doi: 10.1007/s11465-018-0487-9

摘要：

The thermal hydraulic (TH) behavior of coo-lant water is a key factor in the structural integrity assessments on reactor pressure vessels (RPVs) of pressurized water reactors (PWRs) under pressurized thermal shock (PTS) events, because the TH behavior may affect the loading conditions in the assessment. From the viewpoint of TH behavior, configuration of plant equipment and their dimensions, and operator action time considerably influence various parameters, such as the temperature and flow rate of coolant water and inner pressure. In this study, to investigate the influence of the operator action time on TH behavior during a PTS event, we developed an analysis model for a typical Japanese PWR plant, including the RPV and the main components of both primary and secondary systems, and performed TH analyses by using a system analysis code called RELAP5. We applied two different operator action times based on the Japanese and the United States (US) rules: Operators may act after 10 min (Japanese rules) and 30 min (the US rules) after the occurrence of PTS events. Based on the results of TH analysis with different operator action times, we also performed structural analyses for evaluating thermal-stress distributions in the RPV during PTS events as loading conditions in the structural integrity assessment. From the analysis results, it was clarified that differences in operator action times significantly affect TH behavior and loading conditions, as the Japanese rule may lead to lower stresses than that under the US rule because an earlier operator action caused lower pressure in the RPV.

关键词： structural integrity     reactor pressure vessel     pressurized thermal shock     thermal hydraulic analysis     pressurized water reactor     weld residual stress    

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Assessment indices for uniform and non-uniform thermal environments

ZHANG Yufeng, SUN Shufeng, ZHAO Rongyi

《能源前沿（英文）》 2008年 第2卷 第2期   页码 129-133 doi: 10.1007/s11708-008-0029-y

摘要： Different assessment indices for thermal environments were compared and selected for proper assessment of indoor thermal environments. 30 subjects reported their overall thermal sensation, thermal comfort, and thermal acceptability in uniform and non-uniform conditions. The results show that these three assessment indices provide equivalent evaluations in uniform environments. However, overall thermal sensation differs from the other two indices and cannot be used as a proper index for the evaluation of non-uniform environments. The relationship between the percentage and the mean vote for each index is established.

关键词： thermal sensation     proper assessment     relationship     equivalent     thermal acceptability    

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Liquid metal thermal hydraulics R&D at European scale: achievements and prospects

《能源前沿（英文）》 2021年 第15卷 第4期   页码 842-853 doi: 10.1007/s11708-021-0743-2

摘要： A significant role for a future nuclear carbon-free energy production is attributed to fast reactors, mostly employing a liquid metal as a coolant. This paper summarizes the efforts that have been undertaken in collaborative projects sponsored by the European Commission in the past 20 years in the fields of liquid-metal heat transfer modeling, fuel assembly and core thermal hydraulics, pool and system thermal hydraulics, and establishment of best practice guidelines and verification, validation, and uncertainty quantification (UQ). The achievements in these fields will be presented along with the prospects on topics which will be studied collaboratively in Europe in the years to come. These prospects include further development of heat transfer models for applied computational fluid dynamics (CFD), further analysis of the consequences of fuel assembly blockages on coolant flow and temperature, analysis of the thermal hydraulic effects in deformed fuel assemblies, extended validation of three-dimensional pool thermal hydraulic CFD models, and further development and validation of multi-scale system thermal hydraulic methods.

关键词： liquid metal     thermal hydraulics     Europe    

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Coupling evaluation for material removal and thermal control on precision milling machine tools

《机械工程前沿（英文）》 2022年 第17卷 第1期   页码 12-12 doi: 10.1007/s11465-021-0668-9

摘要： Machine tools are one of the most representative machining systems in manufacturing. The energy consumption of machine tools has been a research hotspot and frontier for green low-carbon manufacturing. However, previous research merely regarded the material removal (MR) energy as useful energy consumption and ignored the useful energy consumed by thermal control (TC) for maintaining internal thermal stability and machining accuracy. In pursuit of energy-efficient, high-precision machining, more attention should be paid to the energy consumption of TC and the coupling relationship between MR and TC. Hence, the cutting energy efficiency model considering the coupling relationship is established based on the law of conservation of energy. An index of energy consumption ratio of TC is proposed to characterize its effect on total energy usage. Furthermore, the heat characteristics are analyzed, which can be adopted to represent machining accuracy. Experimental study indicates that TC is the main energy-consuming process of the precision milling machine tool, which overwhelms the energy consumption of MR. The forced cooling mode of TC results in a 7% reduction in cutting energy efficiency. Regression analysis shows that heat dissipation positively contributes 54.1% to machining accuracy, whereas heat generation negatively contributes 45.9%. This paper reveals the coupling effect of MR and TC on energy efficiency and machining accuracy. It can provide a foundation for energy-efficient, high-precision machining of machine tools.

关键词： machine tools     cutting energy efficiency     thermal stability     machining accuracy     coupling evaluation    

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An autonomous system for thermal convection of viscoelastic fluids in a porous layer using a thermal

Qi WEI, Xiaohui ZHANG

《能源前沿（英文）》 2010年 第4卷 第4期   页码 507-516 doi: 10.1007/s11708-010-0017-x

摘要： Thermal convection of viscoelastic fluids saturating a horizontal porous layer heated from below is analyzed using a thermal nonequilibrium model to take account of the interphase heat transfer between the fluid and the solid. The viscoelastic character of the flow is considered by a modified Darcy’s law. An autonomous system with five differential equations is deduced by applying the truncated Galerkin expansion to the momentum and heat transfer equations. The effects of interphase heat transfer on the thermal convection of viscoelastic fluids in a porous medium are analyzed and discussed. The results show that the weak interphase heat transfer tends to stabilize the steady convection.

关键词： thermal convection     porous media     viscoelastic fluid     thermal nonequilibrium model    

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ANN-exhaustive-listing method for optimization of multiple building shapes and envelope properties with maximum thermal

Yaolin LIN, Wei YANG

《能源前沿（英文）》 2021年 第15卷 第2期   页码 550-563 doi: 10.1007/s11708-019-0607-1

摘要： With increasing awareness of sustainability, demands on optimized design of building shapes with a view to maximize its thermal performance have become stronger. Current research focuses more on building envelopes than shapes, and thermal comfort of building occupants has not been considered in maximizing thermal performance in building shape optimization. This paper attempts to develop an innovative ANN (artificial neural network)-exhaustive-listing method to optimize the building shapes and envelope physical properties in achieving maximum thermal performance as measured by both thermal load and comfort hour. After verified, the developed method is applied to four different building shapes in five different climate zones in China. It is found that the building shape needs to be treated separately to achieve sufficient accuracy of prediction of thermal performance and that the ANN is an accurate technique to develop models of discomfort hour with errors of less than 1.5%. It is also found that the optimal solutions favor the smallest window-to-external surface area with triple-layer low-E windows and insulation thickness of greater than 90 mm. The merit of the developed method is that it can rapidly reach the optimal solutions for most types of building shapes with more than two objective functions and large number of design variables.

关键词： ANN (artificial neural network)     exhaustive-listing     building shape     optimization     thermal load     thermal comfort    

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Flow and thermal modeling of liquid metal in expanded microchannel heat sink

《能源前沿（英文）》   页码 796-810 doi: 10.1007/s11708-023-0877-5

摘要： Liquid metal-based microchannel heat sinks (MCHSs) suffer from the low heat capacity of coolant, resulting in an excessive temperature rise of coolant and heat sink when dealing with high-power heat dissipation. In this paper, it was found that expanded space at the top of fins could distribute the heat inside microchannels, reducing the temperature rise of coolant and heat sink. The orthogonal experiments revealed that expanding the top space of channels yielded similar temperature reductions to changing the channel width. The flow and thermal modeling of expanded microchannel heat sink (E-MCHS) were analyzed by both using the 3-dimensional (3D) numerical simulation and the 1-dimensional (1D) thermal resistance model. The fin efficiency of E-MCHS was derived to improve the accuracy of the 1D thermal resistance model. The heat conduction of liquid metal in Z direction and the heat convection between the top surface of fins and the liquid metal could reduce the total thermal resistance (Rt). The above process was effective for microchannels with low channel aspect ratio, low mean velocity (Um) or long heat sink length. The maximum thermal resistance reduction in the example of this paper reached 36.0%. The expanded space endowed the heat sink with lower pressure, which might further reduce the pumping power (P). This rule was feasible both when fins were truncated (h2 < 0, h2 is the height of expanded channel for E-MCHS) and when over plate was raised (h2 > 0).

关键词： liquid metal cooling     heat sink     expanded microchannel     flow and thermal modeling    

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Electromagnetic modeling and control of switched reluctance motor using finite elements

Ali ARIF,Abderrazak GUETTAF,Ahmed Chaouki MEGHERBI,Said BENRAMACHE,Fateh BENC HABANE

《能源前沿（英文）》 2014年 第8卷 第3期   页码 355-363 doi: 10.1007/s11708-014-0319-5

摘要： This paper considered the implementation of a current control method for switched reluctance motors (SRMs) and presented a novel approach to the accurate online modeling of a three phase 6/4 SRM drive. A three phase 6/4 SRM is given theoretical calculation of inductance of the SRM model. The SRM was then tested in a Matlab/Simulink environment and numerically analyzed by using nonlinear 2D look-up tables created from its calculated flux linkage and static torque data. The simulation studied the hysteresis and voltage control strategies. The ideal waveform of stator current under the voltage-current condition and improved shape of rotor were proposed.

关键词： switched reluctance motor (SRM)     hysteresis     control     finite element analysis    

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Encapsulation of polyethylene glycol in cellulose-based porous capsules for latent heat storage and light-to-thermal

《化学科学与工程前沿（英文）》 2023年 第17卷 第8期   页码 1038-1050 doi: 10.1007/s11705-022-2279-3

摘要： Phase change materials are potential candidates for the application of latent heat storage. Herein, we fabricated porous capsules as shape-stable materials from cellulose-based polyelectrolyte complex, which were first prepared using cellulose 6-(N-pyridinium)hexanoyl ester as the cationic polyelectrolyte and carboxymethyl cellulose as the anionic polyelectrolyte to encapsulate polyethylene glycol by the vacuum impregnation method. Furthermore, the multi-walled carbon nanotube or graphene oxide, which were separately composited into the polyelectrolytes complex capsules to enhance thermal conductivity and light-to-thermal conversion efficiency. These capsules owned a typical core–shell structure, with an extremely high polyethylene glycol loading up to 34.33 g∙g‒1. After loading of polyethylene glycol, the resulted cellulose-based composite phase change materials exhibited high thermal energy storage ability with the latent heat up to 142.2 J∙g‒1, which was 98.5% of pure polyethylene glycol. Further results showed that the composite phase change materials demonstrated good form-stable property and thermal stability. Moreover, studies involving light-to-thermal conversion determined that composite phase change materials exhibited outstanding light-to-thermal conversion performance. Considering their exceptional comprehensive features, innovative composite phase change materials generated from cellulose presented a highly interesting choice for thermal management and renewable thermal energy storage.

关键词： cellulose     polyelectrolytes     phase change materials     thermal energy storage     light-to-thermal conversion    

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Non-thermal plasma enhances performances of biochar in wastewater treatment and energy storage applications

《化学科学与工程前沿（英文）》 2022年 第16卷 第4期   页码 475-483 doi: 10.1007/s11705-021-2070-x

摘要： Surface functionalization or modification to introduce more oxygen-containing functional groups to biochar is an effective strategy for tuning the physicochemical properties and promoting follow-up applications. In this study, non-thermal plasma was applied for biochar surface carving before being used in contaminant removal and energy storage applications. The results showed that even a low dose of plasma exposure could introduce a high number density of oxygen-functional groups and enhance the hydrophilicity and metal affinity of the pristine biochar. The plasma-treated biochar enabled a faster metal-adsorption rate and a 40% higher maximum adsorption capacity of heavy metal ion Pb2+. Moreover, to add more functionality to biochar surface, biochar with and without plasma pre-treatment was activated by KOH at a temperature of 800 °C. Using the same amount of KOH, the plasma treatment resulted in an activated carbon product with the larger BET surface area and pore volume. The performance of the treated activated carbon as a supercapacitor electrode was also substantially improved by>30%. This study may provide guidelines for enhancing the surface functionality and application performances of biochar using non-thermal-based techniques.

关键词： non-thermal plasma     surface functionalization     biochar modification     wastewater treatment     supercapacitor    

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Synthesis, characterization and assessment thermal properties of clay based nanopigments

Mohammad Banimahd KIEVANI, Milad EDRAKI

《化学科学与工程前沿（英文）》 2015年 第9卷 第1期   页码 40-45 doi: 10.1007/s11705-015-1505-7

摘要： Nano-clay based pigments (NCP) are new type of pigments composed of organic dyes and layered silicate-clay nano-particles, and have already been used in polymeric coatings to improve mechanical thermal and stability properties. In this paper, the basic blue 41(BB41) was intercalated into Na - montmorillonite in an aqueous medium. The dye-intercalated montmorillonite was centrifuged, dried, and milled to prepare the nanopigment particles. X-ray diffraction showed an increase in the basal spacing, thus confirming intercalation of the BB41 molecules within the nanostructures of the interlayer spaces. Fourier transform infrared spectroscopy was used for identifying the functional groups and chemical bounding of Na -montmorillonite, BB41 and montmorillonite-BB41. The morphology of NCP was also studied by transmission electron microscopy. Finally, thermo-gravimetric analysis and differential thermograms suggested the thermal stability of the intercalated dye was improved.

关键词： nanopigment     layered silicate     cationic dye     thermal properties    

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标题 作者 时间 类型 操作

Analysis of the dynamic hysteresis characteristic of finger seal

LEI Yanni, CHEN Guoding

期刊论文

Purification of ice structuring protein complexes from winter wheat using Triton X-114 phase partitioning

Huaneng XU, Haiying CHEN, Weining HUANG,

期刊论文

Research on applications of piezoelectric materials in smart structures

Jinhao QIU, Hongli JI

期刊论文

Dynamic characteristics of a magnetorheological pin joint for civil structures

Yancheng LI,Jianchun LI

期刊论文

Influence evaluation of loading conditions during pressurized thermal shock transients based on thermal-hydraulics

Jinya KATSUYAMA, Shumpei UNO, Tadashi WATANABE, Yinsheng LI

期刊论文

Assessment indices for uniform and non-uniform thermal environments

ZHANG Yufeng, SUN Shufeng, ZHAO Rongyi

期刊论文

Liquid metal thermal hydraulics R&D at European scale: achievements and prospects

期刊论文

Coupling evaluation for material removal and thermal control on precision milling machine tools

期刊论文

An autonomous system for thermal convection of viscoelastic fluids in a porous layer using a thermal

Qi WEI, Xiaohui ZHANG

期刊论文

ANN-exhaustive-listing method for optimization of multiple building shapes and envelope properties with maximum thermal

Yaolin LIN, Wei YANG

期刊论文

Flow and thermal modeling of liquid metal in expanded microchannel heat sink

期刊论文

Electromagnetic modeling and control of switched reluctance motor using finite elements

Ali ARIF,Abderrazak GUETTAF,Ahmed Chaouki MEGHERBI,Said BENRAMACHE,Fateh BENC HABANE

期刊论文

Encapsulation of polyethylene glycol in cellulose-based porous capsules for latent heat storage and light-to-thermal

期刊论文

Non-thermal plasma enhances performances of biochar in wastewater treatment and energy storage applications

期刊论文

Synthesis, characterization and assessment thermal properties of clay based nanopigments

Mohammad Banimahd KIEVANI, Milad EDRAKI

期刊论文