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Capacity limitation of nuclear units in grid based on analysis of frequency regulation

Yiping DAI, Pan JIANG, Lin GAO, Weimin KAN, Xiaoqing XIAO, Ge JIN

《能源前沿（英文）》 2012年第6卷第2期页码 148-154 doi: 10.1007/s11708-012-0174-1

摘要： The increasing capacity of nuclear units in power grid poses threat to system stability and security. Load disturbance may cause overspeed of the units and trigger the overspeed protection controller (OPC). Repeating actions of valves have a strong impact on the security of the equipment and may result in a collapse of the power system. Based on the analysis of frequency regulation, mathematic models for nuclear units in the grid are established in this paper to simulate the dynamic process when load disturbance occurs. The critical action of the OPC is proposed as the constraint of safe operation for the units. The relationship between different styles of frequency regulation and the allowable capacity of the nuclear units in the grid is discussed. This research can help to estimate the capacity limitation of nuclear units in the grid.

关键词： nuclear units capacity overspeed primary frequency control (PFC) second frequency control (SFC)

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Meta-analysis of the diagnostic efficiency of frequency-doubling technology for primary glaucoma

LIU Ting, HE Xiangge

《医学前沿（英文）》 2007年第1卷第1期页码 109-114 doi: 10.1007/s11684-007-0021-7

摘要： The overall diagnostic capabilities and utility of frequency-doubling technology (FDT) in patients with primary glaucoma, which was diagnosed by standard automated perimetry (SAP) and/or optic disc appearance as the gold standard, were assessed. A comprehensive electric retrieval in MEDLINE, EMBASE, Cochrane Library, BIOSIS, Previews, HMIC, IPA, OVID, CNKI, CBMdisc, VIP information, CMCC, CCPD, SSreader, 21dmedia and manual retrieval in related textbooks, journals, congress articles and their references at home and abroad were performed to identify relevant articles in English or Chinese. The corresponding references were retrieved by means of electric retrieval and manual retrieval from different databases or materials. Criteria for inclusion or exclusion were established according to validity criteria for diagnostic studies published by the Cochrane Methods Group on Screening and Diagnostic Tests. The quality of the included articles was then assessed and characteristics were extracted. Statistical analysis was performed with Meta Test version 0.6 software to test the heterogeneity of the included articles. The appropriate effects model was selected to calculate pooled weighted sensitivity and specificity. Summary receiver operating characteristic (SROC) curve was drawn and the area under the curve (AUC) was calculated. Finally, sensitivity analysis was performed. Twenty-one studies out of 206 retrieved articles were included, with a total of 3172 patients. The reported sensitivity of FDT ranged from 0.51 to 1.00, and specificity from 0.58 to 1.00. The pooled weighted sensitivity and specificity of FDT with 95% confidence intervals (95% CI) after correction for standard error were 0.86 (0.80 0.90) and 0.87 (0.81 0.91), respectively. The AUC of SROC was 93.01%. Sensitivity analysis demonstrated no disproportionate influences of individual studies. The included articles are of good quality and FDT can be a highly efficient diagnostic test for primary glaucoma based on Meta-analysis.

关键词： inclusion sensitivity analysis correction specificity appropriate

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Parameter identification of interconnected power system frequency after trip-out of high voltage transmission

Xuzhan ZHOU,Shanshan LIU,Mingkun WANG,Yiping DAI,Yaohua TANG

《能源前沿（英文）》 2014年第8卷第3期页码 386-393 doi: 10.1007/s11708-014-0323-9

摘要： Accurate modeling and parameters of high voltage (HV) grid are critical for stability research of system frequency. In this paper, simulation modeling of the system frequency was conducted of an interconnected power system with HV transmission lines in China. Based on recorded tripping data of the HV transmission lines, system parameters were identified by using genetic algorithm (GA). The favorable agreement between simulation results and recorded data verifies the validity of gird models and the accuracy of system parameters. The results of this paper can provide reference for the stability research of HV power grid.

关键词： high voltage (HV) grid frequency stability parameter identification primary frequency regulation (PFR)

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Frequency domain a9ctive vibration control of a flexible plate based on neural networks

Jinxin LIU, Xuefeng CHEN, Zhengjia HE

《机械工程前沿（英文）》 2013年第8卷第2期页码 109-117 doi: 10.1007/s11465-013-0252-z

摘要：

A neural-network (NN)-based active control system was proposed to reduce the low frequency noise radiation of the simply supported flexible plate. Feedback control system was built, in which neural network controller (NNC) and neural network identifier (NNI) were applied. Multi-frequency control in frequency domain was achieved by simulation through the NN-based control systems. A pre-testing experiment of the control system on a real simply supported plate was conducted. The NN-based control algorithm was shown to perform effectively. These works lay a solid foundation for the active vibration control of mechanical structures.

关键词： active vibration control (AVC) neural network (NN) low frequency noise frequency domain control multi-frequency control

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A comprehensive review of wind power based power system frequency regulation

《能源前沿（英文）》 2023年第17卷第5期页码 611-634 doi: 10.1007/s11708-023-0876-6

摘要： Wind power (WP) is considered as one of the main renewable energy sources (RESs) for future low-carbon and high-cost-efficient power system. However, its low inertia characteristic may threaten the system frequency stability of the power system with a high penetration of WP generation. Thus, the capability of WP participating in the system frequency regulation has become a research hotspot. In this paper, the impact of WP on power system frequency stability is initially presented. In addition, various existing control strategies of WP participating in frequency regulation are reviewed from the wind turbine (WT) level to the wind farm (WF) level, and their performances are compared in terms of operating principles and practical applications. The pros and cons of each control strategy are also discussed. Moreover, the WP combing with energy storage system (ESS) for system frequency regulation is explored. Furthermore, the prospects, future challenges, and solutions of WP participating in power system frequency regulation are summarized.

关键词： frequency regulation strategies wind turbine generators grid-forming control model predictive control energy storage system

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Load frequency control in deregulated power system with wind integrated system using fuzzy controller

Yajvender Pal VERMA, Ashwani KUMAR

《能源前沿（英文）》 2013年第7卷第2期页码 245-254 doi: 10.1007/s11708-012-0218-6

摘要： This paper presents the analysis of load frequency control (LFC) of a deregulated two-area hydro-thermal power system using fuzzy logic controller, with doubly fed induction generators (DFIGs) integrated into both the control areas. The deregulation of power sector has led to the formation of new companies for generation, transmission and distribution of power. The conventional two-area power system is modified to study the effects of the bilateral contracts of companies on the system dynamics. Deregulation creates highly competitive and distributed control environment, and the LFC becomes even more challenging when wind generators are also integrated into the system. The overall inertia of the system reduces, as the wind unit does not provide inertia and isolates from the grid during disturbances. The DFIGs integrated provide inertial support to the system through modified inertial control scheme, and arrests the initial fall in frequency after disturbance. The inertial control responds to frequency deviations, which takes out the kinetic energy of the wind turbine for improving the frequency response of the system. To enhance the participation of the doubly fed induction generator (DFIG) in the frequency control, optimal values of the speed control parameters of the DFIG-based wind turbine have been obtained using integral square error (ISE) technique. The dynamics of the system have been obtained for a small load perturbation, and for contract violation using fuzzy controller.

关键词： frequency regulation fuzzy controller de-regulated power system doubly fed induction generator (DFIG) bilateral contract

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Characterization on jointed rock masses based on PFC2D

Peitao WANG, Tianhong YANG, Qinglei YU, Honglei LIU, Penghai ZHANG

《结构与土木工程前沿（英文）》 2013年第7卷第1期页码 32-38 doi: 10.1007/s11709-013-0187-9

摘要： Geometrical parameters of discontinuities, such as spacing, length, dip and fault throw between joints have a great influence on the mechanical behavior of jointed rock masses. Accurate characterization for discontinuities is important for investigate the stability of rock masses. In this paper, the PFC2D is combined with joint network generation method to examine the mechanical behaviors of jointed mass. Taking Miaogou Open-pit Mine as an example, the information and statistical distributions of discontinuities of the slope rock masses are measured by ShapeMetriX3D measuring tool. Then, the automatic generation algorithm of random joints network based on the Monte-Carlo method is proposed using the programming language (FISH) embedded within PFC2D. This algorithm could represent the discontinuities compared with the geological surveys. In simulating the compression test of a jointed rock sample, the mechanical behavior and crack propagation were investigated. The results reveal that the failure mode and crack propagation of the jointed rock are dominated by the distribution of joints in addition to the intact rock properties. The simulation result shows the feasibility of the joints generating method in application to jointed rock mass.

关键词： jointed rock masses shape metrix3D monte-carlo stochastic simulation method PFC2D

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Dynamic contribution of variable-speed wind energy conversion system in system frequency regulation

Yajvender Pal VERMA, Ashwani KUMAR

《能源前沿（英文）》 2012年第6卷第2期页码 184-192 doi: 10.1007/s11708-012-0185-y

摘要： Frequency regulation in a generation mix having large wind power penetration is a critical issue, as wind units isolate from the grid during disturbances with advanced power electronics controllers and reduce equivalent system inertia. Thus, it is important that wind turbines also contribute to system frequency control. This paper examines the dynamic contribution of doubly fed induction generator (DFIG)-based wind turbine in system frequency regulation. The modified inertial support scheme is proposed which helps the DFIG to provide the short term transient active power support to the grid during transients and arrests the fall in frequency. The frequency deviation is considered by the controller to provide the inertial control. An additional reference power output is used which helps the DFIG to release kinetic energy stored in rotating masses of the turbine. The optimal speed control parameters have been used for the DFIG to increases its participation in frequency control. The simulations carried out in a two-area interconnected power system demonstrate the contribution of the DFIG in load frequency control.

关键词： doubly fed induction generator (DFIG) load frequency control inertial control wind energy conversion system (WECS)

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H_∞ control in the frequency domain for a semi-active floor isolation system

Yundong SHI, Tracy C BECKER, Masahiro KURATA, Masayoshi NAKASHIMA

《结构与土木工程前沿（英文）》 2013年第7卷第3期页码 264-275 doi: 10.1007/s11709-013-0214-x

摘要： A floor isolation system installed in a single floor or room in a fixed base structure is designed to protect equipment. With this configuration, the input motions to the floor isolation from the ground motions are filtered by the structure, leaving the majority of the frequency content of the input motion lower than the predominant frequency of the structure. The floor isolation system should minimize the acceleration to protect equipment; however, displacement must also be limited to save floor space, especially with long period motion. Semi-active control with an control was adopted for the floor isolation system and a new input shaping filter was developed to account for the input motion characteristics and enhance the effectiveness of the control. A series of shake table tests for a semi-active floor isolation system using rolling pendulum isolators and a magnetic-rheological damper were performed to validate the control. Passive control using an oil damper was also tested for comparison. The test results show that the control effectively reduced acceleration for short period motions with frequencies close to the predominant frequency of the structure, as well as effectively reduced displacement for long period motions with frequencies close to the natural frequency of the floor isolation system. The control algorithm proved to be more advantageous than passive control because of its capacity to adjust control strategies according to the different motion frequency characteristics.

关键词： semi-active floor isolation H_∞ control MR damper shaping filter shaking table test

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System construction of a four-side primary permanent-magnet linear motor drive mechanical press

Jintao LIANG, Zhengfeng MING, Peida LI

《机械工程前沿（英文）》 2020年第15卷第4期页码 600-609 doi: 10.1007/s11465-020-0597-z

摘要： A primary permanent-magnet linear motor (PPMLM) has a robust secondary structure and high force density and is appropriate for direct-drive mechanical press. The structure of a four-side PPMLM drive press is presented based on our previous research. The entire press control system is constructed to realize various flexible forming processes. The control system scheme is determined in accordance with the mathematical model of PPMLM, and active disturbance rejection control is implemented in the servo controller. Field-circuit coupling simulation is applied to estimate the system’s performance. Then, a press prototype with 6 kN nominal force is fabricated, and the hardware platform of the control system is constructed for experimental study. Punch strokes with 0.06 m displacement are implemented at trapezoidal speeds of 0.1 and 0.2 m/s; the dynamic position tracking errors are less than 0.45 and 0.82 mm, respectively. Afterward, continuous reciprocating strokes are performed, and the positioning errors at the bottom dead center are less than 0.015 mm. Complex pulse trajectories are also achieved. The proposed PPMLM drive press exhibits a fast dynamic response and favorable tracking precision and is suitable for various forming processes.

关键词： mechanical press direct drive primary permanent-magnet linear motor (PPMLM) servo system active disturbance rejection control (ADRC) prototype experiment

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基于语料库的小学英语认识率及教材选词策略研究 Article

Wen-yan XIAO,Ming-wen WANG,Zhen WENG,Li-lin ZHANG,Jia-li ZUO

《信息与电子工程前沿（英文）》 2017年第18卷第3期页码 362-372 doi: 10.1631/FITEE.1601118

摘要：词汇是语言学习中的基础任务之一，是语言学习者发展听、说、读、写语言技能的重要前提，在教材课文选择中要覆盖哪些词汇，是教材编写中的基本问题。针对这个问题，本文利用网络爬虫等技术构建英文网页语料库(EWC)，并进行词频分析；将EWC与英国国家语料库(BNC)进行词频对比分析，发现词频分布具有一定的时效性。通过我国目前小学英语教材词汇表与EWC, BNC, SUBTLEX-US，CBBC词频表的对比分析，给出了小学生在一般阅读时的英语词汇认识率，分析结果表明，小学生对一般语域和特定语域的词汇认识率都相对较低。通过这些定量分析，本文为我国小学英语教材编写提出了一些词汇选择方面的策略。

关键词：语料库；小学英语；认识率；词频；覆盖率

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基于频域的PID广义预测控制器的鲁棒性分析

王繁珍,陈增强,姚向峰,袁著祉

《中国工程科学》 2006年第8卷第10期页码 66-70

摘要：

推导了PID广义预测控制器(PID-GPC)的闭环反馈结构, 采用小增益定理获得了存在建模误差(MPM)情况下PID-GPC鲁棒稳定的一个充分条件。然后在频域内分析了PID-GPC控制器的参数选择对其鲁棒性的影响。

关键词：预测控制鲁棒性频域小增益定理 PID控制

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Evaluation of power regeneration in primary suspension for a railway vehicle

Ruichen WANG, Zhiwei WANG

《机械工程前沿（英文）》 2020年第15卷第2期页码 265-278 doi: 10.1007/s11465-019-0571-9

摘要： To improve the fuel economy of rail vehicles, this study presents the feasibility of using power regenerating dampers (PRDs) in the primary suspension systems of railway vehicles and evaluates the potential and recoverable power that can be obtained. PRDs are configured as hydraulic electromagnetic-based railway primary vertical dampers and evaluated in parallel and series modes (with and without a viscous damper). Hydraulic configuration converts the linear behavior of the track into a unidirectional rotation of the generator, and the electromagnetic configuration provides a controllable damping force to the primary suspension system. In several case studies, generic railway vehicle primary suspension systems that are configured to include a PRD in the two configuration modes are modeled using computer simulations. The simulations are performed on measured tracks with typical irregularities for a generic UK passenger route. The performance of the modified vehicle is evaluated with respect to key performance indicators, including regenerated power, ride comfort, and running safety. Results indicate that PRDs can simultaneously replace conventional primary vertical dampers, regenerate power, and exhibit desirable dynamic performance. A peak power efficiency of 79.87% is theoretically obtained in series mode on a top-quality German Intercity Express track (Track 270) at a vehicle speed of 160 mile/h (~257 km/h).

关键词： railway vehicle primary damper power regeneration ride comfort running safety

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Dynein axonemal heavy chain 10 deficiency causes primary ciliary dyskinesia in humans and mice

《医学前沿（英文）》页码 957-971 doi: 10.1007/s11684-023-0988-8

摘要： Primary ciliary dyskinesia (PCD) is a congenital, motile ciliopathy with pleiotropic symptoms. Although nearly 50 causative genes have been identified, they only account for approximately 70% of definitive PCD cases. Dynein axonemal heavy chain 10 (DNAH10) encodes a subunit of the inner arm dynein heavy chain in motile cilia and sperm flagella. Based on the common axoneme structure of motile cilia and sperm flagella, DNAH10 variants are likely to cause PCD. Using exome sequencing, we identified a novel DNAH10 homozygous variant (c.589C > T, p.R197W) in a patient with PCD from a consanguineous family. The patient manifested sinusitis, bronchiectasis, situs inversus, and asthenoteratozoospermia. Immunostaining analysis showed the absence of DNAH10 and DNALI1 in the respiratory cilia, and transmission electron microscopy revealed strikingly disordered axoneme 9+2 architecture and inner dynein arm defects in the respiratory cilia and sperm flagella. Subsequently, animal models of Dnah10-knockin mice harboring missense variants and Dnah10-knockout mice recapitulated the phenotypes of PCD, including chronic respiratory infection, male infertility, and hydrocephalus. To the best of our knowledge, this study is the first to report DNAH10 deficiency related to PCD in human and mouse models, which suggests that DNAH10 recessive mutation is causative of PCD.

关键词： DNAH10 mice motile cilia mutation primary ciliary dyskinesia

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Approach for natural gas to be a primary energy source in China

Weihe HUANG, Jindian CHEN, Chuan FU, Yan HUANG

《工程管理前沿（英文）》 2019年第6卷第4期页码 467-476 doi: 10.1007/s42524-019-0068-6

摘要： This work reveals the positioning of natural gas in the evolution of world energy and the general law of its development. In the long-term adjustment of energy structure, natural gas has gradually become the primary energy source because of five factors: policy, resources, technology, facilities, and market. To expedite the revolution of energy production and consumption, China must urgently expand the use of natural gas toward a more positive role in complementing coal and renewable energy and prioritize its usage in three areas, namely, urban gas, power generation, and industrial fuel. Natural gas is expected to account for approximately 15% of China’s total energy consumption in the future. For natural gas to be the primary energy, the exploitation of gas resources must be expanded, resource access must be improved, a flexible trade system must be set up, infrastructure investment must be increased, and the security system must be enhanced.

关键词： natural gas energy revolution primary energy utilization areas approaching means