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同眼相向双胬肉的切除与结膜瓣上下转向埋植术1例
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作者 禹鑫 周华丽 曹丽辉 《黑龙江医药科学》 2013年第3期76-77,共2页
1例同眼相向双翼状胬肉经切除与结膜瓣上下转向埋植术进行手术治疗,随访2年未见复发。分析现报道如下。
关键词 显微外科手 同眼相向双胬肉 转向埋植
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再谈各种营销术
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作者 周虎良 周庆章 《商业研究》 CSSCI 1995年第10期22-25,共4页
再谈各种营销术周虎良,周庆章时代术。随着社会的进步,时代的变化,其经济结构、消费结构、市场结构、商品结构、家庭结构等等,随之也在起变化。作为经营者要随时认识和适应这种变化,按这种变化的要求而经营。例如:现在家庭成员结... 再谈各种营销术周虎良,周庆章时代术。随着社会的进步,时代的变化,其经济结构、消费结构、市场结构、商品结构、家庭结构等等,随之也在起变化。作为经营者要随时认识和适应这种变化,按这种变化的要求而经营。例如:现在家庭成员结构,大多数是二代同堂,甚至是一代同... 展开更多
关键词 市场营销 营销 时代 便客 通告 转向术
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Automatic Guidance of an Agricultural Tractor along with the Side Shift Control of the Attached Row Crop Cultivator 被引量:8
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作者 Javad Robati Hossein Navid +1 位作者 Mahdi Rezaei Amir Rikhtehgar Ghiasi 《Journal of Agricultural Science and Technology(B)》 2012年第1期151-158,共8页
This paper presents the automatic guidance system of an agricultural tractor and the side shift control of the attached row crop cultivator using electro-hydraulic actuators. In order to simulate the dynamic behaviour... This paper presents the automatic guidance system of an agricultural tractor and the side shift control of the attached row crop cultivator using electro-hydraulic actuators. In order to simulate the dynamic behaviour of the tractor along with the attached cultivator, the modified bicycle model was adopted. Steering angle sensor, fibre optic gyroscope (FOG) and RTK-DGPS technologies are assumed for measurements of the steering angle, yaw rate and the lateral position of the tractor, respectively. The kinematics model was used for the implement. In this study four cascade controllers were designed and simulated for tractor guidance which consists ofPD, PD, P and PID controllers. Other PI and PID controllers also had been designed for implement side shifting purpose. Then, these two systems were combined and the performance of the whole system was evaluated through the simulation results. According to the results tractor reaches the desired path after less than 10 seconds. Simulations showed that the maximum deviation of the tractor from the desired path was about 5 cm within this period. And the cultivator blades would follow the predetermined path with steady state error of about 5 cm too. 展开更多
关键词 Row crop cultivator yaw rate servo valve servo cylinder cascade controller.
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V-BLAST-based demodulate-and-forward two-way relaying:protocol design and the detection
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作者 贠超 Xiong Haitao +2 位作者 Wang Ping Li Mingqi Bu Zhiyong 《High Technology Letters》 EI CAS 2009年第4期388-393,共6页
We propose a novel vertical Bell Laboratories layered space-time (V-BLAST) based two-way relaying protocol that comprises two user terminals and one multi-antenna demodulate-and-forward (DMF) relay station. We con... We propose a novel vertical Bell Laboratories layered space-time (V-BLAST) based two-way relaying protocol that comprises two user terminals and one multi-antenna demodulate-and-forward (DMF) relay station. We consider the situation when these two user temainals employ different modulation types and investigate its detection techniques. The key feature of the detection techniques is that we quantify decision reliability at the relay station by introducing a so-called normalized correlation coefficient (CORR), rather than having full confidence in demodulation at the relay station. With the assistance of the normalized correlation coefficient, we develop detection methods at both the relay station and user terminals. In particular, we propose a CORR-based ordering algorithm at the relay station which can be applied to detection for general V-BLAST architectures. Simulation results demonstrate the superiority of the CORR- based ordering algorithm over the conventional signal-to-noise based ordering algorithm. Finally, we demonstrate overall error-performance of the V-BLAST-based DMF two-way relaying protocol via simulations. 展开更多
关键词 RELAYING demodulate-and-forward (DMF) vertical Bell Laboratories layered space-
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Unsteady Tip Clearance Flow in an Isolated Axial Compressor Rotor 被引量:11
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作者 Hongwu ZHANG Xiangyang DENG +1 位作者 Jingyi CHEN Weiguang HUANG 《Journal of Thermal Science》 SCIE EI CAS CSCD 2005年第3期211-219,共9页
The paper investigates effects of operating conditions, tip clearance sizes and external unsteady excitations on the unsteady tip clearance flow in an isolated axial compressor rotor by unsteady 3D Navier-Stokes simul... The paper investigates effects of operating conditions, tip clearance sizes and external unsteady excitations on the unsteady tip clearance flow in an isolated axial compressor rotor by unsteady 3D Navier-Stokes simulations. The results show that the unsteady tip clearance vortex takes a periodic flow behavior in the rotor tip region. With the decrease of the flow coefficient, the unsteady tip clearance vortex is enhanced and its frequency becomes lower. A larger tip clearance size can cause bigger unsteady fluctuation amplitude and a lower fluctuation frequency of the tip clearance vortex at the near stall operating condition. The unsteady excitation with the natural frequency of the tip clearance vortex can enhance the unsteadiness of the tip clearance vortex and improve the overall rotor performance. The frequency of the unsteady tip clearance vortex is independent of external unsteady excitations with different frequencies. 展开更多
关键词 tip clearance flow COMPRESSOR UNSTEADY
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