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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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Novel casting processes for single-crystal turbine blades of superalloys

Dexin MA

《机械工程前沿（英文）》 2018年 第13卷 第1期   页码 3-16 doi: 10.1007/s11465-018-0475-0

摘要：

This paper presents a brief review of the current casting techniques for single-crystal (SC) blades, as well as an analysis of the solidification process in complex turbine blades. A series of novel casting methods based on the Bridgman process were presented to illustrate the development in the production of SC blades from superalloys. The grain continuator and the heat conductor techniques were developed to remove geometry-related grain defects. In these techniques, the heat barrier that hinders lateral SC growth from the blade airfoil into the extremities of the platform is minimized. The parallel heating and cooling system was developed to achieve symmetric thermal conditions for SC solidification in blade clusters, thus considerably decreasing the negative shadow effect and its related defects in the current Bridgman process. The dipping and heaving technique, in which thin-shell molds are utilized, was developed to enable the establishment of a high temperature gradient for SC growth and the freckle-free solidification of superalloy castings. Moreover, by applying the targeted cooling and heating technique, a novel concept for the three-dimensional and precise control of SC growth, a proper thermal arrangement may be dynamically established for the microscopic control of SC growth in the critical areas of large industrial gas turbine blades.

关键词： superalloy     investment casting     Bridgman process     directional solidification     single crystal     turbine blade    

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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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Reliability-based design optimization of offshore wind turbine support structures using RBF surrogate

《结构与土木工程前沿（英文）》   页码 1086-1099 doi: 10.1007/s11709-023-0976-8

摘要： Reliability-based design optimization of offshore wind turbine support structures using RBF surrogate model

关键词： RBF     surrogate model     turbine support structures    

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Condition monitoring of a wind turbine generator using a standalone wind turbine emulator

Himani,Ratna DAHIYA

《能源前沿（英文）》 2016年 第10卷 第3期   页码 286-297 doi: 10.1007/s11708-016-0419-5

摘要： The intend of this paper is to give a description of the realization of a low-cost wind turbine emulator(WTE) with open source technology from graze required for the condition monitoring to diagnose rotor and stator faults in a wind turbine generator (WTG). The WTE comprises of a 2.5 kW DC motor coupled with a 1 kW squirrel-cage induction machine. This paper provides a detailed overview of the hardware and software used along with the WTE control strategies such as MPPT and pitch control. The emulator reproduces dynamic characteristics both under step variations and arbitrary variation in the wind speed of a typical wind turbine (WT) of a wind energy conversion system (WECS). The usefulness of the setup has been benchmarked with previously verified WT test rigs made at the University of Manchester and Durham University in UK. Considering the fact that the rotor blades and electric subassemblies direct drive WTs are most susceptible to damage in practice, generator winding faults and rotor unbalance have been introduced and investigated using the terminal voltage and generated current. This wind turbine emulator (WTE) can be reconfigured or analyzed for condition monitoring without the need for real WTs.

关键词： condition monitoring (CM)     wind turbine emulator (WTE)     wind turbine generator (WTG)     maximum power point tracking (MPPT)     tip speed ratio (TSR)     rotor faults     stator faults    

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认知无线电网络中利用信道冲击响应的主用户仿真攻击检测技术 Article

Qiao-mu JIANG, Hui-fang CHEN, Lei XIE, Kuang WANG

《信息与电子工程前沿（英文）》 2017年 第18卷 第10期   页码 1665-1676 doi: 10.1631/FITEE.1700203

摘要： 认知无线电通过将空闲频谱动态地分配给未授权用户,可以有效地解决频谱资源稀缺的问题。然而，在认知无线电网络中，存在着一种严重的拒绝服务攻击，称为“主用户仿真攻击”，该攻击会导致认知无线电网络系统性能的下降。在本文中，我们提出了一种在认知无线电网络中利用无线信道信息进行主用户仿真攻击检测的方法。在该方法中，我们利用信号源与从用户之间信道冲激响应的独特性，判断从用户接收到的信号来源是主用户还是仿真主用户。我们进一步推导了所提出检测方法的虚警概率和检测概率的闭合表达式。另外，为使所提出的检测方法在从用户没有主用户信号结构和内容先验信息的场景下也能顺利工作，我们提出了一种改进的基于子空间的盲信道估计方法。仿真结果表明，即使主用户与仿真主用户到从用户之间信道冲激响应的差别较小，所提出的主用户仿真攻击检测方法也能取得较好的检测性能。

关键词： 认知无线电网络；主用户仿真攻击；基于子空间的盲信道估计；信道冲击响应    

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Review of aeroelasticity for wind turbine: Current status, research focus and future perspectives

Pinting ZHANG, Shuhong HUANG

《能源前沿（英文）》 2011年 第5卷 第4期   页码 419-434 doi: 10.1007/s11708-011-0166-6

摘要： Aeroelasticity has become a critical issue for Multi-Megawatt wind turbine due to the longer and more flexible blade. In this paper, the development of aeroelasticity and aeroelastic codes for wind turbine is reviewed and the aeroelastic models for wind turbine blade are described, based on which, the current research focuses for large scale wind turbine are discussed, including instability problems for onshore and offshore wind turbines, effects of complex inflow, nonlinear effects of large blade deflection, smart structure technologies, and aerohydroelasticity. Finally, the future development of aeroelastic code for large scale wind turbine: aeroservoelasticity and smart rotor control; nonlinear aeroelasticity due to large blade deflection; full-scale 3D computational fluid dynamics (CFD) solution for dynamics; and aerohydroelasticity are presented.

关键词： wind turbine     aeroelasticity     aeroelastic code    

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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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Anefficient quadrature demodulator for medical ultrasound imaging

Hao ZHOU,Yin-fei ZHENG

《信息与电子工程前沿（英文）》 2015年 第16卷 第4期   页码 301-310 doi: 10.1631/FITEE.1400205

摘要： Quadrature demodulation is used in medical ultrasound imaging to derive the envelope and instantaneous phase of the received radio-frequency (RF) signal. In quadrature demodulation, RF signal is multiplied with the sine and cosine wave reference signal and then low-pass filtered to produce the base-band complex signal, which has high computational complexity. In this paper, we propose an efficient quadrature demodulation method for B-mode and color flow imaging, in which the RF signal is demodulated by a pair of finite impulse response filters without mixing with the reference signal, to reduce the computational complexity. The proposed method was evaluated with simulation and in vivo experiments. From the simulation results, the proposed quadrature demodulation method produced similar normalized residual sum of squares (NRSS) and velocity profile compared with the conventional quadrature demodulation method. In the in vivo color flow imaging experiments, the time of the demodulation process was 5.66 ms and 3.36 ms, for the conventional method and the proposed method, respectively. These results indicated that the proposed method can maintain the performance of quadrature demodulation while reducing computational complexity.

关键词： B-mode ultrasound imaging     Color flow imaging     Quadrature demodulation     Finite impulse response filter    

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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

Novel casting processes for single-crystal turbine blades of superalloys

Dexin MA

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

Reliability-based design optimization of offshore wind turbine support structures using RBF surrogate

期刊论文

Condition monitoring of a wind turbine generator using a standalone wind turbine emulator

Himani,Ratna DAHIYA

期刊论文

认知无线电网络中利用信道冲击响应的主用户仿真攻击检测技术

Qiao-mu JIANG, Hui-fang CHEN, Lei XIE, Kuang WANG

期刊论文

Review of aeroelasticity for wind turbine: Current status, research focus and future perspectives

Pinting ZHANG, Shuhong HUANG

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

Anefficient quadrature demodulator for medical ultrasound imaging

Hao ZHOU,Yin-fei ZHENG

期刊论文