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Acoustic characteristics of bi-directional turbines for thermoacoustic generators

Dongdong LIU, Yanyan CHEN, Wei DAI, Ercang LUO

《能源前沿（英文）》 2022年 第16卷 第6期   页码 1027-1036 doi: 10.1007/s11708-020-0702-3

摘要： Bi-directional turbines combined with rotary motors may be a feasible option for developing high power thermoacoustic generators with low cost. A general expression for the acoustic characteristics of the bi-directional turbine was proposed based on theoretical derivation, which was validated by computational fluid dynamics modeling of an impulse turbine with fixed guide vanes. The structure of the turbine was optimized primarily using steady flow with an efficiency of near 70% (the shaft power divided by the total energy consumed by the turbine). The turbine in the oscillating flow was treated in a lumped-parameter model to extract the acoustic impedance characteristics from the simulation results. The key acoustic impedance characteristic of the turbine was the resistance and inertance due to complex flow condition in the turbine, whereas the capacitance was treated as an adiabatic case because of the large-scale flow channel relative to the heat penetration depth. Correlations for the impedance were obtained from both theoretical predictions and numerical fittings. The good fit of the correlations shows that these characteristics are valid for describing the bi-directional turbine, providing the basis for optimization of the coupling between the thermoacoustic engine and the turbine using quasi-one-dimensional theory in the frequency domain.

关键词： thermoacoustic power generator     acoustic characteristics     bi-directional impulse turbine     energy conversion    

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A Bayesian modeling approach to bi-directional pedestrian flows in carnival events

S. Q. XIE, S. C. WONG, William H. K. LAM

《工程管理前沿（英文）》 2017年 第4卷 第4期   页码 483-489 doi: 10.15302/J-FEM-2017023

摘要： Bi-directional pedestrian flows are common at crosswalks, footpaths, and shopping areas. However, the properties of pedestrian movement may vary in urban areas according to the type of walking facility. In recent years, crowd movements at carnival events have attracted the attention of researchers. In contrast to pedestrian behavior in other walking facilities, pedestrians whose attention is attracted by carnival displays or activities may slow down and even stop walking. The Lunar New Year Market is a traditional carnival event in Hong Kong held annually one week before the Lunar New Year. During the said event, crowd movements can be easily identified, particularly in Victoria Park, where the largest Lunar New Year Market in Hong Kong is hosted. In this study, we conducted a video-based observational survey to collect pedestrian flow and speed data at the Victoria Park Lunar New Year Market on the eve of the Lunar New Year. Using the collected data, an extant mathematical model was calibrated to capture the relationships between the relevant macroscopic quantities, thereby providing insight into pedestrian behavior at the carnival event. Bayesian inference was employed to calibrate the model by using prior data obtained from a previous controlled experiment. Results obtained enhance our understanding of crowd behavior under different conditions at carnival events, thus facilitating the improvement of the safety and efficiency of similar events in the future.

关键词： pedestrian flow model     bi-directional interactions     empirical studies     Bayesian inference    

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Technological development and engineering applications of novel steel-concrete composite structures

Jianguo NIE, Jiaji WANG, Shuangke GOU, Yaoyu ZHU, Jiansheng FAN

《结构与土木工程前沿（英文）》 2019年 第13卷 第1期   页码 1-14 doi: 10.1007/s11709-019-0514-x

摘要：

In view of China’s development trend of green building and building industrialization, based on the emerging requirements of the structural engineering community, the development and proposition of novel resource-saving high-performance steel-concrete composite structural systems with adequate safety and durability has become a kernel development trend in structural engineering. This paper provides a state of the art review of China’s cutting-edge research and technologies in steel-concrete composite structures in recent years, including the building engineering, the bridge engineering and the special engineering. This paper summarizes the technical principles and applications of the long-span bi-directional composite structures, the long-span composite transfer structures, the comprehensive crack control technique based on uplift-restricted and slip-permitted (URSP) connectors, the steel plate concrete composite (SPCC) strengthen technique, and the innovative composite joints. By improving and revising traditional structure types, the comprehensive superiority of steel-concrete composite structures is well elicited. The research results also indicate that the high-performance steel-concrete composite structures have a promising popularizing prospect in the future.

关键词： high-performance composite structure     bi-directional composite     composite transfer     uplift-restricted and slip-permitted connectors     steel plate concrete composite strengthen    

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Observation of a higher JAK2 V617F homozygous mutated clone in polycythemia vera compared to essential thrombocythemia

LIU Hongxing, TONG Chunrong, CAI Peng, GU Jiangying, LIN Yuehui, TENG Wen, WANG He, ZHANG Ying, ZHU Ping

《医学前沿（英文）》 2008年 第2卷 第3期   页码 309-313 doi: 10.1007/s11684-008-0059-1

摘要： Single-tube bi-directional allele specific amplification (SB-ASA) and real-time quantitative polymerase chain reaction (RQ-PCR) assays were developed and performed for JAK2V617F detection on 40 polycythemia vera (PV) samples, 31 essential thrombocythemia (ET) samples, 40 acute leukemia samples, and 40 healthy control samples. Differences between detect limitations of the two assays and their influence on the mutation detection rate were analyzed. The results showed that in some samples, the JAK2V617F burden was as low as nearly 1%, and thus more JAK2V617F-positive samples were detected by RQ-PCR than by SB-ASA assay due to the former higher detect limitation. Mutation allele ratios in PV and ET samples and their relevance to biological characteristics were also analyzed. The results showed that the mutation allele ratio was 0.436 ± 0.261 in PV, higher than the 0.216 ± 0.207 in ET; percentage of certainly homozygous mutation carriers in PV was 40.54%, higher than the 10% in ET. However, statistical analysis showed no relevance between mutation allele burden and sex or age. Our result shows that the pathogenesis of PV and ET may be related to the mutation allele burden of JAK2V617F.

关键词： specific amplification     essential thrombocythemia     Single-tube bi-directional     JAK2V617F-positive     JAK2V617F detection    

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基于Spark面向分布式EEMDN-SABiGRU模型的乘客热点预测

夏大文,耿建,黄瑞曦,申冰琪,胡杨,李艳涛,李华青

《信息与电子工程前沿（英文）》 2023年 第24卷 第9期   页码 1316-1331 doi: 10.1631/FITEE.2200621

摘要： 针对出租车与乘客之间的供需不平衡问题，本文提出一种基于Spark的分布式归一化集合经验模态分解和面向空间注意力机制的双向门控循环单元（EEMDN-SABiGRU）模型，实现乘客热点的精准预测，旨在于降低盲目巡航开支、提高载客效率和实现收益最大化。首先，提出一种归一化的集合经验模态分解方法（EEMDN），处理网格中乘客热点数据，解决非平稳序列问题和数值差异过大造成的预测精度下降问题，避免EMD本征模态函数（IMF）存在的模态混叠现象。其次，构建一种基于乘客上下车热点的权重和乘客的空间规律性的空间注意力机制，捕捉每个网格中的乘客热点特征。再次，融合一种双向门控循环单元（GRU）算法，解决GRU仅能获取前向信息而忽略后向信息问题，提高特征提取的准确性。最后，在Spark并行计算框架下，采用真实的出租车GPS轨迹数据，基于EEMDN-SABiGRU模型实现了乘客热点的准确预测。实验结果表明，在00网格4个数据集上，与LSTM、EMDL-STM、EEMD-LSTM、GRU、EMD-GRU、EEMD-GRU、EMDN-GRU、CNN和BP相比，EEMDN-SABiGRU的平均绝对百分比误差、平均绝对误差、均方根误差和最大误差值分别降低了43.18%、44.91%、55.04%和39.33%。

关键词： 乘客热点预测     集合经验模态分解（EEMD）     空间注意力机制     双向门控循环单元（BiGRU）     GPS轨迹     Spark    

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Layout optimization of steel reinforcement in concrete structure using a truss-continuum model

《结构与土木工程前沿（英文）》 2023年 第17卷 第5期   页码 669-685 doi: 10.1007/s11709-023-0963-0

摘要： Owing to advancement in advanced manufacturing technology, the reinforcement design of concrete structures has become an important topic in structural engineering. Based on bi-directional evolutionary structural optimization (BESO), a new approach is developed in this study to optimize the reinforcement layout in steel-reinforced concrete (SRC) structures. This approach combines a minimum compliance objective function with a hybrid truss-continuum model. Furthermore, a modified bi-directional evolutionary structural optimization (M-BESO) method is proposed to control the level of tensile stress in concrete. To fully utilize the tensile strength of steel and the compressive strength of concrete, the optimization sensitivity of steel in a concrete–steel composite is integrated with the average normal stress of a neighboring concrete. To demonstrate the effectiveness of the proposed procedures, reinforcement layout optimizations of a simply supported beam, a corbel, and a wall with a window are conducted. Clear steel trajectories of SRC structures can be obtained using both methods. The area of ​​critical tensile stress in concrete yielded by the M-BESO is more than 40% lower than that yielded by the uniform design and BESO. Hence, the M-BESO facilitates a fully digital workflow that can be extremely effective for improving the design of steel reinforcements in concrete structures.

关键词： bi-directional evolutionary structural optimization     steel-reinforced concrete     concrete stress     reinforcement method     hybrid model    

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Improved directional-distance filter

JIN Lianghai, LI Dehua

《机械工程前沿（英文）》 2008年 第3卷 第2期   页码 205-211 doi: 10.1007/s11465-008-0025-2

摘要： This paper proposes a new spatial-distance weighting function. By combining the weighting function and the traditional directional-distance filter (DDF) in a novel way, a new vector filter - the adaptive distance-weighted directional-distance filter (ADWDDF) - is presented. The experimental results show that the proposed solution provides better filtering performance and preserves better image chromaticity and edge or detail information compared with the traditional DDF and some other typical vector filters.

关键词： information     distance-weighted directional-distance     ADWDDF     traditional DDF     spatial-distance weighting    

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Influence of the intensity and loading time of direct current electric field on the directional migration

null

《医学前沿（英文）》 2016年 第10卷 第3期   页码 286-296 doi: 10.1007/s11684-016-0456-9

摘要：

Exogenic electric fields can effectively accelerate bone healing and remodeling through the enhanced migration of bone marrow mesenchymal stem cells (BMSCs) toward the injured area. This study aimed to determine the following: (1) the direction of rat BMSC (rBMSC) migration upon exposure to a direct current electric field (DCEF), (2) the optimal DCEF intensity and duration, and (3) the possible regulatory role of SDF-1/CXCR4 axis in rBMSC migration as induced by DCEF. Results showed that rBMSCs migrated to the positive electrode of the DCEF, and that the DCEF of 200 mV/mm for 4 h was found to be optimal in enhancing rBMSC migration. This DCEF strength and duration also upregulated the expression of osteoblastic genes, including ALP and OCN, and upregulated the expression of ALP and Runx2 proteins. Moreover, when CXCR4 was inhibited, rBMSC migration due to DCEF was partially blocked. These findings indicated that DCEF can effectively induce rBMSC migration. A DCEF of 200 mV/mm for 4 h was recommended because of its ability to promote rBMSC migration, proliferation, and osteogenic differentiation. The SDF-1/CXCR4 signaling pathway may play an important role in regulating the DCEF-induced migration of rBMSCs.

关键词： DCEF     migration     osteogenesis differentiation     rBMSCs     SDF-1/CXCR-4    

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聚能效应在岩石定向断裂控制爆破中的研究

罗勇,沈兆武

《中国工程科学》 2006年 第8卷 第6期   页码 78-82

摘要：

针对目前石材开采面临的问题，对采用聚能药包岩石定向断裂控制爆破技术时的裂缝（纹）起裂和扩展的机理进行了探讨，同时对该法的爆破参数进行了设计；实验室和现场试验验证结果表明，由聚能射流形成的切缝有明显的定向作用，使爆生气体的能量沿预定方向集中，裂纹的定向断裂控制效果良好，表明该法是一种比较理想的断裂控制爆破技术；研究成果对相关理论研究和现场应用均有一定的指导意义，该法将会成为岩石定向断裂控制爆破发展的一个方向。

关键词： 聚能效应     定向断裂爆破     模型试验     药型罩     致裂    

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Topology optimization of piezoelectric bi-material actuators with velocity feedback control

Mariana MORETTI, Emílio C. N. SILVA

《机械工程前沿（英文）》 2019年 第14卷 第2期   页码 190-200 doi: 10.1007/s11465-019-0537-y

摘要： In recent years, the new technologies and discoveries on manufacturing materials have encouraged researchers to investigate the appearance of material properties that are not naturally available. Materials featuring a specific stiffness, or structures that combine non-structural and structural functions are applied in the aerospace, electronics and medical industry fields. Particularly, structures designed for dynamic actuation with reduced vibration response are the focus of this work. The bi-material and multifunctional concepts are considered for the design of a controlled piezoelectric actuator with vibration suppression by means of the topology optimization method (TOM). The bi-material piezoelectric actuator (BPEA) has its metallic host layer designed by the TOM, which defines the structural function, and the electric function is given by two piezo-ceramic layers that act as a sensor and an actuator coupled with a constant gain active velocity feedback control (AVFC). The AVFC, provided by the piezoelectric layers, affects the structural damping of the system through the velocity state variables readings in time domain. The dynamic equation analyzed throughout the optimization procedure is fully elaborated and implemented. The dynamic response for the rectangular four-noded FE analysis is obtained by the Newmark’s time-integration method, which is applied to the physical and the adjoint systems, given that the adjoint formulation is needed for the sensitivity analysis. A gradient-based optimization method is applied to minimize the displacement energy output measured at a predefined degree-of-freedom of the BPEA when a transient mechanical load is applied. Results are obtained for different control gain values to evaluate their influence on the final topology.

关键词： topology optimization method     bi-material piezoactuator     active velocity feedback control     time-domain transient analysis     host structure design     vibration suppression    

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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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Cu-doped Bi/Bi2WO6 catalysts for efficient N2 fixation by photocatalysis

《化学科学与工程前沿（英文）》 2023年 第17卷 第10期   页码 1412-1422 doi: 10.1007/s11705-023-2312-1

摘要： In this paper, Cu-doped Bi2WO6 was synthesized via a solvothermal method and applied it in photocatalytic N2 immobilization. Characterization results showed the presence of a small amount of metallic Bi in the photocatalyst, indicating that the synthesized photocatalyst is actually Bi/Cu-Bi2WO6 composite. The doped Cu had a valence state of +2 and most likely substituted the position of Bi3+. The introduced Cu did not affect the metallic Bi content, but mainly influenced the energy band structure of Bi2WO6. The band gap was slightly narrowed, the conduction band was elevated, and the work function was reduced. The reduced work function improved the transfer and separation of charge carriers, which mainly caused the increased photoactivity. The optimized NH3 generation rates of Bi/Cu-Bi2WO6 reached 624 and 243 μmol·L–1·g–1·h–1 under simulated solar and visible light, and these values were approximately 2.8 and 5.9 times higher those of Bi/Bi2WO6, respectively. This research provides a method for improving the photocatalytic N2 fixation and may provide more information on the design and preparation of heteroatom-doped semiconductor photocatalysts for N2-to-NH3 conversion.

关键词： Bi2WO6     Cu doping     work function     photocatalytic N2 fixation     charge separation    

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Modeling the impact of uncertainty in emissions trading markets with bankable permits

Yongliang ZHANG, Bing ZHANG, Jun BI, Pan HE

《环境科学与工程前沿（英文）》 2013年 第7卷 第2期   页码 231-241 doi: 10.1007/s11783-012-0431-x

摘要： The various forms of uncertainty that firms may face in bankable emission permit trading markets will affect firms’ decision making as well as their market performance. This research explores the effect of increased uncertainty over future input costs and output prices on the temporal distribution of emission. In a dynamic programming setting, the permit price is a convex function of stochastic prices of coal and electricity. Increased uncertainty about future market conditions increases the expected permit price and causes a risk neutral firm to reduce ex ante emissions in order to smooth out marginal abatement costs over time. Finally, safety valves, both low-side and high-side, are suggested to reduce the impact of uncertainty in bankable emission trading markets.

关键词： uncertainty     bankable     emission trading     market performance    

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Proportional directional valve based automatic steering system for tractors Project supported

Jin-yi LIU,Jing-quan TAN,En-rong MAO,Zheng-he SONG,Zhong-xiang ZHU

《信息与电子工程前沿（英文）》 2016年 第17卷 第5期   页码 458-464 doi: 10.1631/FITEE.1500172

摘要： Most automatic steering systems for large tractors are designed with hydraulic systems that run on either constant flow or constant pressure. Such designs are limited in adaptability and applicability. Moreover, their control valves can unload in the neutral position and eventually lead to serious hydraulic leakage over long operation periods. In response to the problems noted above, a multifunctional automatic hydraulic steering circuit is presented. The system design is composed of a 5-way-3- position proportional directional valve, two pilot-controlled check valves, a pressure-compensated directional valve, a pressurecompensated flow regulator valve, a load shuttle valve, and a check valve, among other components. It is adaptable to most open-center systems with constant flow supply and closed-center systems with load feedback. The design maintains the lowest pressure under load feedback and stays at the neutral position during unloading, thus meeting the requirements for steering. The steering controller is based on proportional-integral-derivative (PID) running on a 51-microcontroller-unit master control chip. An experimental platform is developed to establish the basic characteristics of the system subject to stepwise inputs and sinusoidal tracking. Test results show that the system design demonstrates excellent control accuracy, fast response, and negligible leak during long operation periods.

关键词： Automatic steering system     Hydraulic circuit     Proportional directional valve     Proportional-integral-derivative (PID) control    

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Optimal placement of wind turbines within a wind farm considering multi-directional wind speed using

A.S.O. OGUNJUYIGBE, T.R. AYODELE, O.D. BAMGBOJE

《能源前沿（英文）》 2021年 第15卷 第1期   页码 240-255 doi: 10.1007/s11708-018-0514-x

摘要： Most wind turbines within wind farms are set up to face a pre-determined wind direction. However, wind directions are intermittent in nature, leading to less electricity production capacity. This paper proposes an algorithm to solve the wind farm layout optimization problem considering multi-angular (MA) wind direction with the aim of maximizing the total power generated on wind farms and minimizing the cost of installation. A two-stage genetic algorithm (GA) equipped with complementary sampling and uniform crossover is used to evolve a MA layout that will yield optimal output regardless of the wind direction. In the first stage, the optimal wind turbine layouts for 8 different major wind directions were determined while the second stage allows each of the previously determined layouts to compete and inter-breed so as to evolve an optimal MA wind farm layout. The proposed MA wind farm layout is thereafter compared to other layouts whose turbines have focused site specific wind turbine orientation. The results reveal that the proposed wind farm layout improves wind power production capacity with minimum cost of installation compared to the layouts with site specific wind turbine layouts. This paper will find application at the planning stage of wind farm.

关键词： optimal placement     wind turbines     wind direction     genetic algorithm     wake effect    

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标题 作者 时间 类型 操作

Acoustic characteristics of bi-directional turbines for thermoacoustic generators

Dongdong LIU, Yanyan CHEN, Wei DAI, Ercang LUO

期刊论文

A Bayesian modeling approach to bi-directional pedestrian flows in carnival events

S. Q. XIE, S. C. WONG, William H. K. LAM

期刊论文

Technological development and engineering applications of novel steel-concrete composite structures

Jianguo NIE, Jiaji WANG, Shuangke GOU, Yaoyu ZHU, Jiansheng FAN

期刊论文

Observation of a higher JAK2 V617F homozygous mutated clone in polycythemia vera compared to essential thrombocythemia

LIU Hongxing, TONG Chunrong, CAI Peng, GU Jiangying, LIN Yuehui, TENG Wen, WANG He, ZHANG Ying, ZHU Ping

期刊论文

基于Spark面向分布式EEMDN-SABiGRU模型的乘客热点预测

夏大文,耿建,黄瑞曦,申冰琪,胡杨,李艳涛,李华青

期刊论文

Layout optimization of steel reinforcement in concrete structure using a truss-continuum model

期刊论文

Improved directional-distance filter

JIN Lianghai, LI Dehua

期刊论文

Influence of the intensity and loading time of direct current electric field on the directional migration

null

期刊论文

聚能效应在岩石定向断裂控制爆破中的研究

罗勇,沈兆武

期刊论文

Topology optimization of piezoelectric bi-material actuators with velocity feedback control

Mariana MORETTI, Emílio C. N. SILVA

期刊论文

Bi-modes alternation stepping ultrasonic motors

JIN Jiamei, ZHAO Chunsheng

期刊论文

Cu-doped Bi/Bi2WO6 catalysts for efficient N2 fixation by photocatalysis

期刊论文

Modeling the impact of uncertainty in emissions trading markets with bankable permits

Yongliang ZHANG, Bing ZHANG, Jun BI, Pan HE

期刊论文

Proportional directional valve based automatic steering system for tractors Project supported

Jin-yi LIU,Jing-quan TAN,En-rong MAO,Zheng-he SONG,Zhong-xiang ZHU

期刊论文

Optimal placement of wind turbines within a wind farm considering multi-directional wind speed using

A.S.O. OGUNJUYIGBE, T.R. AYODELE, O.D. BAMGBOJE

期刊论文