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等流速法在板式换热器传热试验中的应用 被引量:29
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作者 欧阳新萍 吴国妹 刘宝兴 《动力工程》 CSCD 北大核心 2001年第3期1260-1262,共3页
在换热器的传热性能试验中 ,对流换热系数的测定是一个重要的组成部分。对于板式换热器而言 ,用等雷诺数法来获得其对流换热系数是比较合适的一种方法 ,但对试验过程的控制要求比较高。文中阐述了一种修正的等雷诺数方法——等流速法 ,... 在换热器的传热性能试验中 ,对流换热系数的测定是一个重要的组成部分。对于板式换热器而言 ,用等雷诺数法来获得其对流换热系数是比较合适的一种方法 ,但对试验过程的控制要求比较高。文中阐述了一种修正的等雷诺数方法——等流速法 ,它使试验过程的控制十分方便。通过实例 ,介绍了该方法的具体应用。表 2参 展开更多
关键词 等流速 板式换热器 传热试验
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基于PLC的等流速在线烟尘采样控制装置设计 被引量:3
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作者 程志彪 何小刚 《仪表技术与传感器》 CSCD 北大核心 2016年第12期53-56,共4页
针对目前广泛使用的烟尘测量方法普遍存在无法在线连续测量、价格昂贵、效率低下等问题,设计一种基于PLC的等流速在线烟尘采样控制装置,该装置使用PLC和WINCC上位机对采样数据进行实时处理,并对系统各部分进行实时监控,实现烟尘采样的... 针对目前广泛使用的烟尘测量方法普遍存在无法在线连续测量、价格昂贵、效率低下等问题,设计一种基于PLC的等流速在线烟尘采样控制装置,该装置使用PLC和WINCC上位机对采样数据进行实时处理,并对系统各部分进行实时监控,实现烟尘采样的等速采样要求。装置目前安装于太原第二热电厂,现场应用表明:该装置实现了等速采样控制以及在线监测与无人值守,对于监测各电厂烟尘排放含量具有重要意义。 展开更多
关键词 等流速控制 烟尘采样装置 在线监测 可编程逻辑控制器 WINCC
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等流速下新型脉冲磁场对纯铝凝固组织的影响
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作者 李刚 孙亚威 +3 位作者 赵振 姚博怀 翟启杰 龚永勇 《铸造》 CAS 北大核心 2022年第11期1389-1396,共8页
以工业纯铝为研究对象,采用凝固试验、数值模拟和理论分析相结合的方法,研究了等流速条件下新型脉冲磁场作用下电流强度与周期组合对纯铝凝固组织的影响。结果表明:新型脉冲磁场能明显细化纯铝凝固组织,并且流速相同情况下纯铝凝固组织... 以工业纯铝为研究对象,采用凝固试验、数值模拟和理论分析相结合的方法,研究了等流速条件下新型脉冲磁场作用下电流强度与周期组合对纯铝凝固组织的影响。结果表明:新型脉冲磁场能明显细化纯铝凝固组织,并且流速相同情况下纯铝凝固组织细化效果并不相同。在无隔离网条件下,通过数值模拟分析发现电磁力密度方向主要指向熔体内部,并且熔体主要受电磁力峰值作用使液面发生振荡从而产生大量晶核。在有隔离网条件下,通过动力学分析认为晶核受时均电磁力作用下晶核穿过边界层进入熔体促使晶粒增殖是晶粒细化的主要原因。 展开更多
关键词 新型脉冲磁场 工业纯铝 等流速 晶粒细化
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近端等流速面面积法测算二尖瓣狭窄之瓣口面积
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作者 张辉 刘汉英 +2 位作者 孟宪强 程克正 宋松 《中华心血管病杂志》 CAS CSCD 北大核心 1996年第5期377-379,共3页
近端等流速面面积(PISA)法是根据近端血流汇聚(PFC)原理,用彩色多普勒血流显像(CDFM)技术测定狭小孔径流量的一种新方法。本研究用PISA法测算二尖瓣狭窄瓣口的面积(cM-VA)与手术标本实测值(aMVA)相... 近端等流速面面积(PISA)法是根据近端血流汇聚(PFC)原理,用彩色多普勒血流显像(CDFM)技术测定狭小孔径流量的一种新方法。本研究用PISA法测算二尖瓣狭窄瓣口的面积(cM-VA)与手术标本实测值(aMVA)相比较。结果表明,所有病人均可清晰显示二尖瓣口左房侧的PFC区,cMVA与aMVA具有良好的相关性。本研究证实了PISA法估测二尖瓣口面积是可行,且精确的。 展开更多
关键词 超声心动图 二尖瓣狭窄 瓣口面积 等流速
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板式换热器性能的数值模拟 被引量:43
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作者 徐志明 王月明 张仲彬 《动力工程学报》 CAS CSCD 北大核心 2011年第3期198-202,共5页
建立了人字形板式换热器冷热双流道的流体流动与传热计算模型,利用计算流体力学软件对5组不同速度工况下换热器内流体的流动和传热进行了数值模拟,分析了换热器流道内的速度场、温度场和压力场.结果表明:数值模拟得到的板式换热器进、... 建立了人字形板式换热器冷热双流道的流体流动与传热计算模型,利用计算流体力学软件对5组不同速度工况下换热器内流体的流动和传热进行了数值模拟,分析了换热器流道内的速度场、温度场和压力场.结果表明:数值模拟得到的板式换热器进、出口温差和压降与试验测量值的误差均小于6%;换热器内流体的流动和传热存在明显的不均匀性,导致其进、出口的另一侧出现明显的传热"死区";换热器的总传热系数和流道阻力均随着流体流速的增大而增大. 展开更多
关键词 板式换热器 流动 传热 等流速 数值模拟
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板壳式换热器传热准则关系式的分析与实验研究 被引量:9
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作者 刘家瑞 赵巍 +2 位作者 黄晓东 张华 余晓明 《动力工程学报》 CAS CSCD 北大核心 2015年第6期469-475,共7页
假设板壳式换热器为特殊板式换热器,介绍了板壳式换热器传热准则关系式的研究方法.分析比较了壁面温度测定法、等雷诺数法、威尔逊法和等流速法等的适用性,确定了利用等流速法来进行实验研究,并分别进行了测定实验和验证实验,测定实验... 假设板壳式换热器为特殊板式换热器,介绍了板壳式换热器传热准则关系式的研究方法.分析比较了壁面温度测定法、等雷诺数法、威尔逊法和等流速法等的适用性,确定了利用等流速法来进行实验研究,并分别进行了测定实验和验证实验,测定实验控制进出口流速相同,验证实验控制热侧流速不变,改变冷侧流速,采用实验获得的数据拟合传热准则关系式,计算出传热系数的相对误差.结果表明:传热系数的相对误差小于5%,所得传热准则关系式是合理的,表明板式换热器的研究方法适用于板壳式换热器. 展开更多
关键词 板壳式换热器 等流速 传热准则关系式 传热系数
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一种板壳式换热器传热准则关系式的实验分析 被引量:5
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作者 刘家瑞 赵巍 +2 位作者 黄晓东 张华 余晓明 《动力工程学报》 CAS CSCD 北大核心 2015年第11期893-900,共8页
基于板式换热器的研究成果,对板壳式换热器进行实验研究,利用等流速法求解传热准则关系式.通过控制冷流体、热流体流速相同,对1/1流程组合的板壳式换热器进行实验,并对比和分析实验数据.结果表明:利用板式换热器的经验值拟合得到的传热... 基于板式换热器的研究成果,对板壳式换热器进行实验研究,利用等流速法求解传热准则关系式.通过控制冷流体、热流体流速相同,对1/1流程组合的板壳式换热器进行实验,并对比和分析实验数据.结果表明:利用板式换热器的经验值拟合得到的传热准则关系式在不同定性温度下并不相同;1/1流程组合板壳式换热器冷流体、热流体的传热准则关系式的参数均为定值,即系数为0.182 5,雷诺数指数为0.75,普朗特数指数为0.34;板壳式换热器的传热准则关系式与板程流程数无关,且与壳程1流程和2流程也无关,但与3流程和4流程则呈现出系数相关的结论,3流程和4流程的系数分别为1流程的0.82倍和0.68倍. 展开更多
关键词 板壳式换热器 传热准则关系式 等流速 流程数 定性温度
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去学水电站泄洪洞底坡选择的水力特性研究 被引量:1
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作者 王利 赵轶 吴浩 《水力发电》 北大核心 2011年第3期45-46,71,共3页
去学水电站采用表孔溢洪洞和中孔泄洪洞联合泄洪,溢洪洞及泄洪洞明流洞纵坡均选择为8%,水力计算和模型试验研究表明,其底坡是合适的。两洞内流速分别呈现加速和"等速流"特性,流速控制在30 m/s以内,避免了超高速水流问题。提出... 去学水电站采用表孔溢洪洞和中孔泄洪洞联合泄洪,溢洪洞及泄洪洞明流洞纵坡均选择为8%,水力计算和模型试验研究表明,其底坡是合适的。两洞内流速分别呈现加速和"等速流"特性,流速控制在30 m/s以内,避免了超高速水流问题。提出的"等流速"明流泄洪洞底坡的计算及底坡选择可供同类工程参考使用。 展开更多
关键词 等流速 底坡 计算 溢洪洞 泄洪洞 去学水电站
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EXPERIMENTAL INVESTIGATION ON INDUCED FLOW VELOCITY OF PLASMA AERODYNAMIC ACTUATION
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作者 李益文 李应红 +3 位作者 周章文 贾敏 宋慧敏 吴云 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2009年第1期23-28,共6页
Plasma flow control is an active flow control technology that based on the plasma aerodynamic actuation. It can be used to enhance the aerodynamic characteristics of aircraft and propulsion systems. To study the pheno... Plasma flow control is an active flow control technology that based on the plasma aerodynamic actuation. It can be used to enhance the aerodynamic characteristics of aircraft and propulsion systems. To study the phenomena occurring in plasma aerodynamic actuation and the mechanism of plasma flow control, the induced flow velocity of the plasma aerodynamic actuator is experimentally investigated under a variety of parameter conditions. The results indicate that plasma aerodynamic actuation accelerates the near surface air at velocities of a few meters per second, and there is an angle about 5° between the mainstream and the actuator wall and a spiral vortex is formed when the induced flow is moving along the wall. Besides, with the fixed frequency, the induced flow velocity increases linearly with the applied voltage, but it is insensitive to the frequency when the applied voltage is fixed. And the configuration is an effective factor for the performance of the plasma aerodynamic actuator. 展开更多
关键词 plasma flow control flow velocity aerodynamic ACTUATOR
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Isothermal extrusion speed curve design for porthole die of hollow aluminium profile based on PID algorithm and finite element simulations 被引量:3
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作者 Jie YI Zhi-wen LIU Wen-qi ZENG 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2021年第7期1939-1950,共12页
The isothermal extrusion process of hollow aluminium profile was investigated using incremental proportional-integral-derivative(PID)control algorithm and finite element simulations.The range of extrusion speed was de... The isothermal extrusion process of hollow aluminium profile was investigated using incremental proportional-integral-derivative(PID)control algorithm and finite element simulations.The range of extrusion speed was determined by considering the maximum extrusion load and production efficiency.By taking the optimal solution temperature of the secondary phase as the target temperature,the extrusion speed–stroke curve for realizing the isothermal extrusion of the aluminium profile was obtained.Results show that in the traditional constant extrusion speed process,the average temperature of the cross-section of the aluminium profile at the die exit rapidly increases and then slowly rises with the increase in ram displacement.As the extrusion speed increases,the temperature difference at the die exit of the profile along the extrusion direction increases.The exit temperature difference between the front and back ends of the extrudate along the extrusion direction obtained by adopting isothermal extrusion is about 6.9℃.Furthermore,the heat generated by plastic deformation and friction during extrusion is balanced with the heat transfer from the workpiece to the container,porthole die and external environment. 展开更多
关键词 isothermal control extrusion speed curve porthole die extrusion PID control heat balance
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Combustion characteristics of supersonic strut-cavity combustor under plasma jet-assisted combustion 被引量:1
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作者 ZHANG Zhe JIN Xing XI Wen-xiong 《Journal of Central South University》 SCIE EI CAS CSCD 2021年第1期311-324,共14页
Plasma jet has been widely used in supersonic combustor as an effective ignition and combustion assisted method,but currently it is mostly combined with the traditional wall fuel injection method,while the application... Plasma jet has been widely used in supersonic combustor as an effective ignition and combustion assisted method,but currently it is mostly combined with the traditional wall fuel injection method,while the application combined with the central fuel injection method is less.In order to expand the combustion range,the plasma jet was introduced into a strut-cavity combustor with an alternating-wedge.The effects of total pressure of strut fuel injection,total pressure of cavity fuel injection,total pressure of plasma jet injection and plasma jet media on the combustion characteristics were analyzed in supersonic flow by numerical calculations in a three-dimensional domain.The combustion field structure,wall pressure distribution,combustion efficiency and distribution of H2O at the exit of the combustor with different injection conditions were analyzed.The results show that the combustion efficiency decreases with the increase of the strut fuel injection total pressure.However,the combustion area downstream increases when the total pressure of the strut fuel injection increases within the proper range.The combustion range is expanded and the combustion efficiency is improved when the cavity fuel injection total pressure is increased within the range of 0.5−2.0 MPa,but a sharp drop in combustion efficiency can be found due to limited fuel mixing when the total injection pressure of the cavity fuel is excessively increased.With the increased total injection pressure of the plasma jet,the height of the cavity shear layer is raised and the equivalence ratio of the gas mixture in the cavity is improved.When the total pressure of the plasma jet is 1.25 MPa,the combustion efficiency reaches a maximum of 82.1%.The combustion-assisted effect of different plasma jet media is significantly different.When the medium of the plasma jet is O2,the combustion-assisted effect on the combustor is most significant. 展开更多
关键词 plasma jet STRUT CAVITY supersonic combustion numerical simulation combustion efficiency
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Hot deformation behavior and constitutive relationship of Q420qE steel 被引量:2
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作者 禹宝军 关小军 +3 位作者 王丽君 赵健 刘千千 曹宇 《Journal of Central South University》 SCIE EI CAS 2011年第1期36-41,共6页
Isothermal compression tests at temperatures from 1 273 to l 423 K and strain rates from 0.1 to 10 s-q were carried out to investigate the flow behaviors of Q420qE steel. Stress-strain data collected from the tests we... Isothermal compression tests at temperatures from 1 273 to l 423 K and strain rates from 0.1 to 10 s-q were carried out to investigate the flow behaviors of Q420qE steel. Stress-strain data collected from the tests were employed to establish the constitutive equation, in which the influence of strain was incorporated by considering the effect of strain on material constants Q, n, a, and lnA. The results show that the flow stress curves are dependent on the strain, strain rate and deformation temperature. They display typical dynamic recrystallization behavior and consist of three stages, i.e., hardening stage, softening stage and steady stage. The flow stress decreases with increasing the deformation temperature and decreasing the strain rate. In addition, the flow stress data predicted by the proposed constitutive model agree well with the corresponding experimental results, and the correlation coefficient and the average absolute relative error between them are 0.990 3 and 3.686%, respectively. 展开更多
关键词 Q420qE bridge steel hot compression flow stress strain dependent constitutive equation
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Inverse Piston Problem for the System of One-Dimensional Isentropic Flow 被引量:5
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作者 Tatsien LI 《Chinese Annals of Mathematics,Series B》 SCIE CSCD 2007年第3期265-282,共18页
In this paper, the authors consider the inverse piston problem for the system of one-dimensional isentropic flow and obtain that, under suitable conditions, the piston velocity can be uniquely determined by the initia... In this paper, the authors consider the inverse piston problem for the system of one-dimensional isentropic flow and obtain that, under suitable conditions, the piston velocity can be uniquely determined by the initial state of the gas on the right side of the piston and the position of the forward shock. 展开更多
关键词 Inverse piston problem System of one-dimensional isentropic flow Shock
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Multipoint observations of Pi2 pulsations and correlation with dynamic processes in the near-Earth magnetotail on March 18,2009 被引量:5
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作者 LUO Hao CHEN GengXiong DU AiMin 《Science China Earth Sciences》 SCIE EI CAS 2014年第2期359-371,共13页
Simultaneous measurements from THEMIS spacecraft, GOES11 and ground stations (Canadian Array for Realtime Investiga tions of Magnetic Activity or CARISMA, and 210 magnetic meridian or MM) on March 18, 2009 allow the... Simultaneous measurements from THEMIS spacecraft, GOES11 and ground stations (Canadian Array for Realtime Investiga tions of Magnetic Activity or CARISMA, and 210 magnetic meridian or MM) on March 18, 2009 allow the study of dynamic processes in the nearEarth magnetotail and corresponding Pi2 pulsations on the ground in great detail. Fast earthward flows along with traveling Alfv6n waves and fast mode waves in the Pi2 band were observed by three Time History of Events and Macroscale Interactions during Substorms (THEM/S) probes (P3, P4 and P5) in the nearEarth plasmasbeet. At the mid to highlatitude nightside, the CARISMA stations located near the foot points of the three probes recorded Pi2s with two periods, about 80 s after the earthward fast flows observed by the P4 probe. The longperiod Pi2 (140-150 s) belongs to the transient response Pi2 (TR Pi2), since the travel time of the Alfv6n waves between the plasma sheet and CARISMA stations is very close to half the period of the longperiod Pi2. The shortperiod Pi2 (60-80 s) has the same period band as the perpendicular velocity of the fast flows, which indicates that it may relate to the inertial current caused by periodic braking of the earthward fast flows. The 210 MM stations located at the lowlatitude duskside also observed Pi2s with the same start time, waveform and frequency, about 120 s after the earthward fast flows. Strong poloidal oscillations are shown by GOES11 (23 MLT) and the compressional component (Bb) is highly correlated with H components of the 210 MM stations, whereas the other two components (Br and Be) are not. These results confirm that the lowlatitude Pi2s are generated by cavity mode resonance, which is driven by an impulsive broadband source in the nearEarth magnetotail. 展开更多
关键词 Pi2 pulsations earthward fast flows Alfvn waves cavity mode resonance
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Low Speed Axial Compressor Stall Margin Improvement by Unsteady Plasma Actuation 被引量:4
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作者 LI Gang XU Yanji +3 位作者 YANG Lingyuan DU Wei ZHU Junqiang NIE Chaoqun 《Journal of Thermal Science》 SCIE EI CAS CSCD 2014年第2期114-119,共6页
This research investigates the use of single dielectric barrier discharge(SDBD) actuators for energizing the tip leakage flow to suppress rotating stall inception and extend the stable operating range of a low speed a... This research investigates the use of single dielectric barrier discharge(SDBD) actuators for energizing the tip leakage flow to suppress rotating stall inception and extend the stable operating range of a low speed axial compressor with a single rotor.The jet induced by the plasma actuator adds momentum to the flow in the tip region and has a significant impact on the tip-gap flow.Experiments are carried out on a low speed axial compressor with a single rotor.The static pressure is measured at both the rotor inlet and outlet.The flow coefficient and pressure rise coefficient are calculated.Then the characteristic line is acquired to show the overall performance of the compressor.With unsteady plasma actuation of 18kV and 60W the compressor stability range improvement is realized at rotor speed of 1500 r/min – 2400 r/min. 展开更多
关键词 axial compressor plasma actuation stall margin improvement
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Nonexistence of a Globally Stable Supersonic Conic Shock Wave for the Steady Supersonic Isothermal Euler Flow
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作者 Yuchen LI Gang XU 《Chinese Annals of Mathematics,Series B》 SCIE CSCD 2013年第4期557-574,共18页
In this paper, for the full Euler system of the isothermal gas, we show that a globally stable supersonic conic shock wave solution does not exist when a uniform supersonic incoming flow hits an infinitely long and cu... In this paper, for the full Euler system of the isothermal gas, we show that a globally stable supersonic conic shock wave solution does not exist when a uniform supersonic incoming flow hits an infinitely long and curved sharp conic body. 展开更多
关键词 Supersonic flow Conic shock Full Euler system Isothermal gas NONEXISTENCE
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Characteristics of low altitude ionospheric electric field over Hainan Island,China 被引量:1
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作者 LI RenKang CHEN Tao +9 位作者 MAN Feng JIANG XiuJie LUO Jing HE ZhaoHai ZHANG HuiMing WANG LinFeng LIU Cheng Francisco Carlos de MENESES WANG GuoJun XU JiYao 《Science China Earth Sciences》 SCIE EI CAS CSCD 2017年第4期770-775,共6页
A sounding rocket experiment undertaken by the Chinese Meridian Project from a low latitude station on Hainan Island(19.5°N,109.1°E),China,measured the DC electric field during 05:45-05:52 LT on April 5,2013... A sounding rocket experiment undertaken by the Chinese Meridian Project from a low latitude station on Hainan Island(19.5°N,109.1°E),China,measured the DC electric field during 05:45-05:52 LT on April 5,2013.The data observed using a set of electric field double probes,as part of the rocket's scientific payload,revealed the special profile of how the vectors of the DC electric field vary with altitude between 130 and 190 km.During the experiment,the vertical electric field was downward,and the maximum vertical electric field was nearly 5.1 mV/m near the altitude of 176 km.The zonal electric field was eastward and slightly less than 0.6 mV/m.The plasma drift velocity was estimated from the E×B motion,and the zonal drift velocity was eastward and of the order of 100 m/s.The zonal wind velocity was also estimated using the drift velocity near the maximum density height in the F1-region,and it was found to be nearly 120 m/s.This work constituted the first in situ measurement of the DC electric field conducted within the Fl-region(between 130 and 190 km) in the East Asian Sector. 展开更多
关键词 Kuroshio intrusion Luzon Strait South China Sea Nonlinear dynamics
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