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Frequency Regulation of VSC-MTDC System with Offshore Wind Farms

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Journal of Modern Power Systems and Clean Energy 2024年第1期12卷 275-286页

作者： Haoyu liu Chongru liu North China Electric Power University Beijing 102206China

Frequency regulation of voltage source converter-based multi-terminal high-voltage direct current(VSC-MTDC)system with offshore wind farms enhances the frequency stability by compensating the power for a disturbed AC ***,it is difficult to reasonably allocate frequency-regulation resources due to a lack of coordination mechanisms between wind farms and the MTDC ***,it is difficult for the frequency control of the wind farms to manage changes in wind speed;and the risk of wind-turbine stalls is ***,based on the kinetic energy of wind turbines and the power margin of the converters,the frequency-regulation capability of wind turbines is evaluated,and a dynamic frequency-support scheme considering the real-time frequency-support capability of the wind turbines and system frequency evolution is proposed to improve the frequency-support performance.A power adaptation technique at variable wind speeds is developed;the active power in the frequency-support stage and restoration stage is switched according to the wind speed.A hierarchical zoning frequency-regulation scheme is designed to use the frequency-regulation resources of different links in the MTDC system with wind *** simulation results show that the novel frequency-regulation strategy maintains frequency stability with wind-speed changes and avoids multiple frequency dips.

关键词： Wind generation voltage source converter-based multi-terminal high-voltage direct current(VSC-MTDC) frequency regulation cooperative control adaptive control variable wind speed

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基于金属有机骨架的水中微量乙醇光纤传感器

光学学报 2021年第23期41卷 219-227页

作者：刘恒畅张翔程迪陆云清许吉王瑾梁忠诚南京邮电大学电子与光学工程学院、微电子学院江苏南京210023 南京邮电大学通信与信息工程学院江苏南京210023

设计并制备了一种基于金属有机骨架(MOF)的光纤传感器,该传感器包括通过在无芯光纤两端熔接单模光纤所构建的单模-无芯-单模结构,以及采用原位结晶技术在无芯光纤表面生长的ZIF-8纳米薄膜。光信号从单模光纤耦合进无芯光纤时会激发出多... 详细信息

设计并制备了一种基于金属有机骨架(MOF)的光纤传感器,该传感器包括通过在无芯光纤两端熔接单模光纤所构建的单模-无芯-单模结构,以及采用原位结晶技术在无芯光纤表面生长的ZIF-8纳米薄膜。光信号从单模光纤耦合进无芯光纤时会激发出多种高阶模式并形成多模干涉,干涉结果对无芯光纤周围折射率的变化异常敏感。利用ZIF-8材料的多孔性和对乙醇分子特异性吸附能力,吸附乙醇分子后的ZIF-8纳米薄膜因孔隙被填充,其折射率将发生变化,改变了无芯光纤中多模干涉条件,导致其透射谱线发生偏移,从而实现水溶液中微量乙醇的检测,实验结果表明传感器最低检测乙醇体积分数可达1%,灵敏度为1.3 nm·%^(-1)。该传感器结构简单,易于制备,在水中微量有机分子检测方面具有一定的应用前景。

关键词：传感器金属有机骨架光纤传感无芯光纤多模干涉效应

基于双向堆叠简单循环单元的滚动轴承寿命预测

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基于多惩罚因子优化VMD的滚动轴承故障特征提取方法

机械强度 2021年第4期43卷 786-792页

作者：李博阳姚德臣刘恒畅杨建伟北京建筑大学机电与车辆工程学院北京100044 北京建筑大学城市轨道交通车辆服役性能保障北京市重点实验室北京100044

为解决传统滚动轴承寿命预测方法精度差,效率低的问题.提出一种基于双向堆叠简单循环单元(Bidirectional Stack Simple Recurrent Unit,Bi-SRU)的预测方法.从原始信号中提取多种时、频域特征构建多维数据集,增强信息表征,避免了单一特... 详细信息

为解决传统滚动轴承寿命预测方法精度差,效率低的问题.提出一种基于双向堆叠简单循环单元(Bidirectional Stack Simple Recurrent Unit,Bi-SRU)的预测方法.从原始信号中提取多种时、频域特征构建多维数据集,增强信息表征,避免了单一特征对轴承退化能力反映不足的缺点.依靠循环神经网络(Recurrent Neural Network,RNN)处理时序数据的能力,构建SRU模型,重构传统RNN串行运算结构,提升训练效率.并在单层SRU的基础上反向堆叠,使模型能够获取学习时间维度上的双向信息,提升预测准确性.实验结果表明,所提方法在预测精度和训练效率上均有提升.

关键词：滚动轴承简单循环单元反向堆叠双向信息寿命预测

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系统工程与电子技术 2023年第11期45卷 3690-3698页

作者：李波胡哿郗石剑钧刘恒畅洪涛电子科技大学航空航天学院四川成都611731 飞行器集群智能感知与协同控制四川省重点实验室四川成都611731

针对变分模态分解(variational mode decomposition,VMD)在提取滚动轴承故障特征时预先设置多惩罚因子具有不确定性的问题,结合灰狼优化(grey wolf optimization,GWO)算法提出一种基于多惩罚因子优化VMD的滚动轴承故障特征提取方法。首... 详细信息

针对变分模态分解(variational mode decomposition,VMD)在提取滚动轴承故障特征时预先设置多惩罚因子具有不确定性的问题,结合灰狼优化(grey wolf optimization,GWO)算法提出一种基于多惩罚因子优化VMD的滚动轴承故障特征提取方法。首先利用GWO算法实现VMD的多惩罚因子自适应优化,再利用优化得到的参数将滚动轴承的振动信号分解为多个本征模态函数(intrinsic mode function,IMF),最后对各个IMF分量作包络解调提取滚动轴承的故障频率特征。研究结果表明,在优化VMD参数时,该方法相对其他方法优化效率有了明显提高,并且提取滚动轴承故障特征效果显著,得到特征频率幅值为其他方法的2~4倍,证明了该方法的有效性和优越性。

关键词：特征提取变分模态分解本征模态函数滚动轴承

A Novel Design of a Pre-separation Panel Structure to Protect Against the Impact of an Explosion in an Aircraft Plenum Chamber

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Acta Mechanica Solida Sinica 2024年第1期37卷 166-180页

作者： Zongxing liu Xiang Yang Jun liu School of Aeronautics Northwestern Polytechnical UniversityXi'an 710072China COMAC Shanghai Aircraft Design and Research Institute Shanghai 201210China

To reduce the damage of the pressurizing panel structure of a fuselage caused by an explosion at the“least risk bomb location”in an aircraft structure,a new pre-separation panel structure was designed to resist blast ***,the dynamic strain response and morphology of impact damage of the new pre-separation panel were measured in an impact damage ***,the commercial software LS-DYNA was used to calculate the propagation of the blast shock wave,and the results were compared with empirical equations to verify the rationality of the numerical calculation ***,the fluid–structure coupling method was used to calculate the damage process of the pre-separation panel structure under the impact of an explosion wave and an impact *** calculated results were in good agreement with the test results,which showed the rationality of the calculation method and the *** residual strength of the damaged pre-separation panel was significantly higher than that of the original damaged *** results show that the new pre-separation panel structure is reasonable and has certain significance for guiding the design of plenum chambers with strong resistance to implosion for aircraft fuselages.

关键词： Pre-separation panel structure Explosive response Residual strength Aircraft plenum chamber Least risk bomb location

Effectiveness and safety of acupuncture in treatment of pregnancyrelated symptoms:a systematic review and Meta-analysis

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Journal of Traditional Chinese Medicine 2024年第1期44卷 16-26页

作者： liu Tingting liu Tongou liu Mingfu School of Traditional Chinese Medicine Clinical Medicine Hubei University of Traditional Chinese MedicineWuhan 430000China First Clinical College of Hubei University of Traditional Chinese Medicine Wuhan 430000China Department of Acupuncture and Tuina Affiliated Hospital of Hubei University of Traditional Chinese MedicineHubei Provincial Hospital of Traditional Chinese MedicineWuhan 430000China

OBJECTIVE:To systematically evaluate the efficacy and safety of acupuncture(AM)in the treatment of pregnancyrelated symptoms such as acute vomiting during ***:We comprehensively searched the available literature up to November 2021,including Pub Med,Embase,Cochrane Library,Chinese Biomedical Literature Database,and China National Knowledge Infrastructure Database,for randomized controlled trials(RCTs)on AM for the treatment of severe vomiting,insomnia,pharyngeal and pelvic pain,mood abnormalities,and dyspepsia during ***:Sixteen RCTs with a cumulative sample size of 1178 cases were *** these,964 patients were included in the *** Meta-analysis results showed that AM was more efficient than Western medicine in treating discomfort during pregnancy[odds ratio(OR)=1.19,95%confidence interval(CI)(1.11,1.28),P<0.01].AM was better than the control group in improving the visual analog scale scores[standard mean difference(SMD)=0.62,95%CI(0.53,0.71),P<0.01].AM was superior to the control group in improving Numerical Rating Scale(NRS)symptom scores[OR=7.31,95%CI(3.36,15.94),P<0.01].There was no significant difference in adverse effects between the AM and sham-AM groups and the analgesic drug group[OR=0.70,95%CI(0.39,1.28),P=0.25],but the treatment and control groups had mild adverse effects with a low ***:AM is more effective than other treatments or pharmacotherapy alone in the treatment of pregnancy-related symptoms,and is relatively ***,the quality of the included trials was rather poor,and high-quality studies are required to confirm our findings.

关键词： acupuncture pregnancy nausea vomiting sleep initiation and maintenance disorders low back pain pelvic pain mood abnormalities Meta-analysis systematic review

Stochastic Unit Commitment with High-Penetration Offshore Wind Power Generation in Typhoon Scenarios

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Journal of Modern Power Systems and Clean Energy 2024年第2期12卷 535-546页

作者： Yanqi liu Dundun liu Hongcai Zhang State Key Laboratory of Internet of Things for Smart City and Department of Electrical and Computer Engineering University of MacaoMacao 999078China University of Macao Zhuhai UM Science and Technology Research Institute ZhuhaiChina

To tackle the energy crisis and climate change,wind farms are being heavily invested in across the *** China's coastal areas,there are abundant wind resources and numerous offshore wind farms are being *** secure operation of these wind farms may suffer from typhoons,and researchers have studied power system operation and resilience enhancement in typhoon ***,the intricate movement of a typhoon makes it challenging to evaluate its spatial-temporal *** published papers only consider predefined typhoon trajectories neglecting *** address this challenge,this study proposes a stochastic unit commitment model that incorporates high-penetration offshore wind power generation in typhoon *** adopts a data-driven method to describe the uncertainties of typhoon trajectories and considers the realistic anti-typhoon mode in offshore wind farms.A two-stage stochastic unit commitment model is designed to enhance power system resilience in typhoon *** formulate the model into a mixed-integer linear programming problem and then solve it based on the computationally-efficient progressive hedging algorithm(PHA).Finally,numerical experiments validate the effectiveness of the proposed method.

关键词： Unit commitment two-stage stochastic programming offshore wind farm typhoon

Devolatilization of high viscous fluids with high gravity technology

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Chinese Journal of Chemical Engineering 2024年第7期71卷 249-257页

作者： Jibing Qi Youzhi liu Yandong liu Taiyuan University Taiyuan 030032China Shanxi Province Key Laboratory of Higee-Oriented Chemical Engineering North University of ChinaTaiyuan 030051China

Volatile organic compounds(VOCs)are generally toxic and harmful substances that can cause health and environmental *** removal of VOCs from polymers has become a key *** effective devolatilization to remove VOCs from high viscous fluids such as polymer is necessary and is of great *** this study,the devolatilization effect of a rotating packed bed(RPB)was studied by using polydimethylsiloxane as the viscous fluid and acetone as the *** devolatilization rate and liquid phase volume(KLa)have been *** results indicated that the optimum conditions were the high-gravity factor of 60,liquid flow rate of 10 L·h^(-1),and vacuum degree of 0.077 *** dimensionless correlation of KLa was established,and the deviations between predicted and experimental values were less than±28%.The high-gravity technology will result in lower mass transfer resistance in the devolatilization process,enhance the mass transfer process of acetone,and improve the removal effect of *** work provides a promising path for the removal of volatiles from polymers in combination with high-gravity *** can provide the basis for the application of RPB in viscous fluids.

关键词： High-gravity technology Devolatilization rate High viscous fluid Volatile organic compounds(VOCs)

环孢素A与吗替麦考酚酯对微小病变型肾病患儿血浆可溶性尿激酶型纤溶酶原激活物受体水平的影响

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中华实验外科杂志 2015年第9期32卷 2279-2282页

作者：王凯臣张赟刘恒昌晋学飞吉林大学中日联谊医院泌尿外科长春130021 吉林大学第一医院胃结直肠外科

目的观察环孢素A（CsA）与吗替麦考酚酯（MMF）对微小病变型肾病（MCD）患儿血浆中可溶性尿激酶型纤溶酶原激活物受体（suPAR）水平变化的影响,及探讨suPAR在微小病变型肾病中的作用.方法将29例MCD患儿随机分为CsA组（A组）和MMF组（... 详细信息

目的观察环孢素A（CsA）与吗替麦考酚酯（MMF）对微小病变型肾病（MCD）患儿血浆中可溶性尿激酶型纤溶酶原激活物受体（suPAR）水平变化的影响,及探讨suPAR在微小病变型肾病中的作用.方法将29例MCD患儿随机分为CsA组（A组）和MMF组（B组）,分别给予CsA和MMF联合强的松治疗12个月,采用酶联免疫吸附试验法（ELISA）检测治疗前后血浆中suPAR水平,并对患儿进行至少12个月的门诊随访,观察治疗效果.结果治疗12个月后,B组血浆suPAR水平为（2 208.3±395.4） ng/L,较治疗前下降,A组为（2984.6±804.7）ng/L较治疗前上升,且显著高于B组（P＜0.05）;两组患儿治疗后尿蛋白和24h尿蛋白均较治疗前显著降低（P＜0.05）,但组间差异无统计学意义（P＞0.05）;A组治疗后肾小球滤过率（GFR）较治疗前显著下降,B组显著升高,且显著高于A组（P＜0.05）;A组不良反应发生率为57.14％（8/14）,总缓解率为85.71％（12/14）,复发率为14.29％（2/14）,B组不良反应发生率为35.71％（5/14）,总缓解率为78.57％（11/14）,复发率为35.71％（5/14）,两组差异无统计学意义（P＞0.05）.结论 CsA和MMF对MCD患儿的治疗效果较好,两者对血浆中suPAR水平和GFR起相反作用,但对于尿蛋白和24h尿蛋白无明显影响.

关键词：微小病变性肾病可溶性尿激酶型纤溶酶原激活物受体环孢素A 吗替麦考酚酯