检索结果-南通市图书馆

TM polarization characteristics on thermal radiation of a negative refractive index thin film

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2009年第10期54卷 1663-1668页

作者： CUl yi HUANG yong li Wen WAN Jun School of Aeronautical Science and Engineering Beijing University of Aeronautics and Astronautics Beijing 100191 China

Thermal radiation TM polarization characteristics of a negative refractive index thin film was studied based on the transmit matrix method and Kirchhoff radiation law. The influence of the thin film pa- rameters on the thermal radiation directional characteristics and spectral property were discussed. And the influence of the evanescent waves was also discussed. The results show that two factors play important roles in the thermal radiation of negative index thin film: one is the interference effect of the thin film structure to the electromagnetic waves; the other is the photon tunneling effect of the negative refractive index material, which was caused by the amplifying evanescent wave. These indicate that spectral and directional characteristics of the thermal emissivity can be modulated by modifying the structure and the physics parameters of the negative refraction index thin film.

关键词：薄膜参数负折射率偏振特性热辐射商标光子隧道效应光谱性质方向特性

A Method with Parameter for Solving the Spectral Radius of Nonnegative Tensor

在线全文

学校读者我要写书评

暂无评论

Journal of the Operations Research Society of China 2017年第1期5卷 3-25页

作者： yi-yong li Qing-Zhi Yang Xi He School of Mathematical Sciences and Lab of Pure Mathematics and Combinatic Nankai UniversityTianjin 300071China

In this paper,a method with parameter is proposed for finding the spectral radius of weakly irreducible nonnegative *** is more,we prove this method has an explicit linear convergence rate for indirectly positive ***,the algorithm is exactly the NQZ method(proposed by Ng,Qi and Zhou in Finding the largest eigenvalue of a non-negative tensor SIAM J Matrix Anal Appl 31:1090–1099,2009)by taking a specific ***,we give a modified NQZ method,which has an explicit linear convergence rate for nonnegative tensors and has an error bound for nonnegative tensors with a positive Perron ***,we promote an inexact power-type ***,some numerical results are reported.

关键词： Nonnegative tensor Indirectly positive tensors linear convergence Perturbation Complexity

Novel AC Servo Rotating and linear Composite Driving Device for Plastic Forming Equipment

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2017年第4期30卷 843-853页

作者： Jin-Tao liang Sheng-Dun Zhao yong-yi li Mu-Zhi Zhu School of Mechanical Engineering Xi'an Jiaotong UniversityXi'an 710049China School of Mechano-electronic Engineering Xidian UniversityXi'an 710071China Beijing Institute of Space Launch Technology Beijing 100076China

The existing plastic forming equipment are mostly driven by traditional AC motors with long trans- mission chains, low efficiency, large size, low precision and poor dynamic response are the common disadvantages. In order to realize high performance forming processes, the driving device should be improved, especially for com- plicated processing motions. Based on electric servo direct drive technology, a novel AC servo rotating and linear composite driving device is proposed, which features implementing both spindle rotation and feed motion with- out transmission, so that compact structure and precise control can be achieved. Flux switching topology is employed in the rotating drive component for strong robustness, and fractional slot is employed in the linear direct drive component for large force capability. Then the mechanical structure for compositing rotation and linear motion is designed. A device prototype is manufactured, machining of each component and the whole assembly are presented respectively. Commercial servo amplifiers are utilized to construct the control system of the proposed device. To validate the effectiveness of the proposed composite driving device, experimental study on thedynamic test benches are conducted. The results indicate that the output torque can attain to 420 N-m and the dynamic tracking errors are less than about 0.3 rad in the rotating drive, the dynamic tracking errors are less than about 1.6 mm in the linear feed. The proposed research provides a method to construct high efficiency and accu- racy direct driving device in plastic forming equipment.

关键词： Plastic forming Direct drive - Permanentmagnet motor linear feeding Servo control

Design and simulation about a self-Tuning fuzzy-PID controller

在线全文

学校读者我要写书评

暂无评论

重庆邮电大学学报（自然科学版） 2009年第2期21卷 192-195,227页

作者： ZHANG yi FU Wen-yong li Yan-hua DENG Hao-wen liU Hong-chang Research Center of Intelligent System and Robotics Chongqing University of Posts and Telecommunications Chongqing 400065 P. R. China

Fuzzy logic has attracted the attention of structural control engineers during the last few years,because fuzzy logic can handle nonlinearities,uncertainties,and heuristic knowledge effectively and *** this paper,a self-Tuning fuzzy-PID control method which used the technology of the fuzzy control and PID control unified is *** techniques can visualize the results and processes for structure *** techniques will also provide convenience for engineers and users,and have high practical *** MATLAB simulation result shows that the system precision and the efficiency are very high and the static error is small,and robustness was also validated.

关键词： PID控制器模糊逻辑仿真结果自调整模糊PID控制设计 Matlab 启发式知识

New-Level VR Marine Training System

在线全文

学校读者我要写书评

暂无评论

航海教育研究 2007年第z1期24卷 1-6页

作者： liU Xiu-wen JIV yi-cheng yiN yong li Zhi-hua Dalian Maritime Univ. Dalian 116026 China

Marine simulator is a valuable and effective medium for maritime education and training and is becoming widespread to foster the qualified and competent personnel for working in the maritime industry. However, many problems with most marine simulation systems today limit their pervasive use: the limited accessibility, immobility, the high expenditure, the long development cycle, and the difficult maintenance etc. A web-based maritime training environment is proposed in this paper as a new marine training level, which fully combining web technology, VR, high fidelity simulation, and e-learning tools to create a more costeffective and flexible training environment still with very realistic and high-interactive simulation characteristics, the system will provide a consistent and more flexible training medium for improving maritime education and training.

关键词： marine simulator virtual reality training

Comparative study of different machine learning models in landslide susceptibility assessment: A case study of Conghua District, Guangzhou, China

在线全文

学校读者我要写书评

暂无评论

China Geology 2024年第1期7卷 104-115页

作者： Ao Zhang Xin-wen Zhao Xing-yuezi Zhao Xiao-zhan Zheng Min Zeng Xuan Huang Pan Wu Tuo Jiang Shi-chang Wang Jun He yi-yong li Wuhan Center China Geological SurveyMinistry of Natural Resources(Geosciences Innovation Center of Central South China)Wuhan 430205China Guangzhou Institute of Geological Survey Guangzhou 510080China Hubei Transportation Planning Design Institute Co. LtdWuhan 430050China

Machine learning is currently one of the research hotspots in the field of landslide *** clarify and evaluate the differences in characteristics and prediction effects of different machine learning models,Conghua District,which is the most prone to landslide disasters in Guangzhou,was selected for landslide susceptibility *** evaluation factors were selected by using correlation analysis and variance expansion factor *** four machine learning methods namely Logistic Regression(LR),Random Forest(RF),Support Vector Machines(SVM),and Extreme Gradient Boosting(XGB),landslide models were *** analysis and evaluation of the model were conducted through statistical indices and receiver operating characteristic(ROC)*** results showed that LR,RF,SVM,and XGB models have good predictive performance for landslide susceptibility,with the area under curve(AUC)values of 0.752,0.965,0.996,and 0.998,*** model had the highest predictive ability,followed by RF model,SVM model,and LR *** frequency ratio(FR)accuracy of LR,RF,SVM,and XGB models was 0.775,0.842,0.759,and 0.822,*** and XGB models were superior to LR and SVM models,indicating that the integrated algorithm has better predictive ability than a single classification algorithm in regional landslide classification problems.

关键词： Landslides susceptibility assessment Machine learning Logistic Regression Random Forest Support Vector Machines XGBoost Assessment model Geological disaster investigation and prevention engineering

Melatonin abates liver ischemia/reperfusion injury by improving the balance between nitric oxide and endothelin

在线全文

学校读者我要写书评

暂无评论

Hepatobiliary & Pancreatic Diseases International 2006年第4期5卷 574-579页

作者： Wen-Hai Zhang, Jian-yi li and yong Zhou Department of 5th General Surgery, Second Affiliated Hospital , China Medical University, Shenyang 110004, China Department of 5th General Surgery Second Affiliated Hospital (Shengjing Hospital) China Medical University Shenyang 110004 China. surgeonzwh@***

BACKGROUND: Melatonin exerts complex physiological and pharmacological effects on multiple systems and organs. We hypothesized that melatonin might abate ischemia/ reperfusion (I/R) injury in the liver by inhibiting excessive oxidative stress and keeping nitric oxide (NO) from being scavenged by free radicals. The aim of the present study was to investigate whether melatonin protects the liver from I/R injury and, if so, by what underlying mechanism. METHODS: Under anesthesia, Wistar rats were intraperi- toneally injected with 20 mg/kg melatonin (dissolved in physiological saline containing 4% ethanol, Mel group), 4% alcohol (Alc group), or physiological saline (NS group). The artery, portal vein and bile duct of the left lobe of the liver were clamped for 60 minutes and then released. At different time points after I/R, the rats were sacrificed and blood samples were collected to measure the levels of serum alanine aminotransferase (ALT), lactic dehydrogenase (LDH), and NO. Hepatic tissue samples were collected for measuring endothelin expression by immunohistochemical staining and for routine morphological and histological examination. RESULTS: The levels of both ALT and LDH in the Mel group were significantly reduced for up to 24 hours after I/R compared with the Alc and NS groups (Plin-positive cells were significantly fewer in the Mel group than in the Alc and NS groups at 6 hours after I/R (Plity and decreased endothelin expre

关键词： melatonin liver ischemia/reperfusion nitric oxide endothelin

Clinical application of sternocleidomastoid myocutaneous composite resection of oral carcinoma modified flap after

在线全文

学校读者我要写书评

暂无评论

中国口腔颌面外科杂志 2008年第B5期6卷 91-92页

作者： Hui Ming Wang Jian Hua liu yi lin Zhi yong li Hui yong Zhu Dept. of Oral and Maxillofaxial Surgery Ist Affiliated HospitalMedical College of Zhejiang University Hangzhou 310003China

基于LQG/LTR的高超声速飞行器全通道姿态控制

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

飞行力学 2017年第5期35卷 66-69页

作者：杜立夫陈宜成闵勇李冬中国运载火箭技术研究院北京航天自动控制研究所北京100854

针对高超声速飞行器具有强烈的非线性、耦合及不确定性等特点,且存在系统噪声和量测噪声,使姿态控制变得困难的问题,提出了采用LQG/LTR控制方法进行全通道姿态控制的思路。首先,在平衡点通过小偏差线性化方法建立多变量耦合的控制模型;... 详细信息

针对高超声速飞行器具有强烈的非线性、耦合及不确定性等特点,且存在系统噪声和量测噪声,使姿态控制变得困难的问题,提出了采用LQG/LTR控制方法进行全通道姿态控制的思路。首先,在平衡点通过小偏差线性化方法建立多变量耦合的控制模型;然后,运用LQG/LTR控制方法设计姿态控制器。仿真结果表明,在有高斯噪声情况下,所设计的姿态控制系统实现了指令精确跟踪,具有较强的鲁棒性。

关键词：高超声速飞行器 LQG/LTR控制多变量控制