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Search Results: 1 - 10 of 126960 matches for " DongKai Li "
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GNSS-R data acquisition system design and experiment
DongKai Yang,Yan Wang,Yong Lu,WeiQiang Li,ZiWei Li
Chinese Science Bulletin , 2010, DOI: 10.1007/s11434-010-4141-0
Abstract: In this paper, the design of a GNSS-R data acquisition system is described, including the antenna, RF (radio frequency) front-end and FPGA (field programmable gate array) based logic circuit for data storage interface. Two RF front-ends are connected with the RHCP (right-hand circular polarization) and LHCP (left-hand circular polarization) antenna to collect the direct and reflected signal separately. Both the specifications and the circuit connections are given in detail. Experiments are performed for statics at the seashore and dynamic scenario in the sea using airplanes. The results of the data analysis show that the proposed data acquisition system is suitable for GNSS-R primitive data collection.
The role and clinical implications of microRNAs in hepatocellular carcinoma
Xue Zhao,Zhen Yang,GuangBing Li,DongKai Li,Yi Zhao,Yan Wu,Simon C. Robson,Lian He,YiYao Xu,RuoYu Miao,HaiTao Zhao
Science China Life Sciences , 2012, DOI: 10.1007/s11427-012-4384-x
Abstract: Hepatocellular carcinoma (HCC) is common and one of the most aggressive of all human cancers. Recent studies have indicated that miRNAs, a class of small noncoding RNAs that regulate gene expression post-transcriptionally, directly contribute to HCC by targeting many critical regulatory genes. Several miRNAs are involved in hepatitis B or hepatitis C virus replication and virus-induced changes, whereas others participate in multiple intracellular signaling pathways that modulate apoptosis, cell cycle checkpoints, and growth-factor-stimulated responses. When disturbed, these pathways appear to result in malignant transformation and ultimately HCC development. Recently, miRNAs circulating in the blood have acted as possible early diagnostic markers for HCC. These miRNA also could serve as indicators with respect to drug efficacy and be prognostic in HCC patients. Such biomarkers would assist stratification of HCC patients and help direct personalized therapy. Here, we summarize recent advances regarding the role of miRNAs in HCC development and progression. Our expectation is that these and ongoing studies will contribute to the understanding of the multiple roles of these small noncoding RNAs in liver tumorigenesis.
A Novel Position Estimation Method Based on Displacement Correction in AIS
Yi Jiang,Shufang Zhang,Dongkai Yang
Sensors , 2014, DOI: 10.3390/s140917376
Abstract: A new position estimation method by using the signals from two automatic identification system (AIS) stations is proposed in this paper. The time of arrival (TOA) method is enhanced with the displacement correction, so that the vessel’s position can be determined even for the situation where it can receive the signals from only two AIS base stations. Its implementation scheme based on the mathematical model is presented. Furthermore, performance analysis is carried out to illustrate the relation between the positioning errors and the displacement vector provided by auxiliary sensors. Finally, the positioning method is verified and its performance is evaluated by simulation. The results show that the positioning accuracy is acceptable.
Adaptive State-Feedback Stabilization for Stochastic Nonholonomic Mobile Robots with Unknown Parameters
Wenli Feng,Qingli Sun,Zhijun Cao,Dongkai Zhang,Hua Chen
Discrete Dynamics in Nature and Society , 2013, DOI: 10.1155/2013/808249
Abstract: The stabilizing problem of stochastic nonholonomic mobile robots with uncertain parameters is addressed in this paper. The nonholonomic mobile robots with kinematic unknown parameters are extended to the stochastic case. Based on backstepping technique, adaptive state-feedback stabilizing controllers are designed for nonholonomic mobile robots with kinematic unknown parameters whose linear velocity and angular velocity are subject to some stochastic disturbances simultaneously. A switching control strategy for the original system is presented. The proposed controllers that guarantee the states of closed-loop system are asymptotically stabilized at the zero equilibrium point in probability. 1. Introduction In the past decades, the control of nonholonomic systems has been widely pursued. By the results of Brockett [1], the nonholonomic system cannot be stabilized at a single equilibrium point by any static smooth pure state-feedback controller. To solve this problem, lots of novel approaches have been considered: discontinuous feedback control [2–4], smooth time-varying feedback controller [5], and the method of LMI [6]. The control of nonholonomic mobile robots plays an important role in that of nonholonomic systems because they are a benchmark for these systems. There is much attention devoted to the control of nonholonomic mobile robots. The nonholonomic mobile robots were classified into four types, which were characterized by generic structures of the model equations [7]. Based on the backstepping technique, the control for nonholonomic mobile robots was discussed: tracking problems [8] and stabilizing problems [9, 10]. Hespanha et al. introduced the mobile robot with parametric uncertainties [11], which were further discussed [12, 13]. But all the above articles discussed the nonholonomic systems in the deterministic case, which was not considered a stochastic disturbance. In recent years, stochastic nonlinear systems have received much attention [14, 15], especially for stochastic control when backstepping designs were firstly introduced [16, 17]. For stochastic nonholonomic systems, there were a few papers. The almost global adaptive asymptotical controllers of stochastic nonholonomic chained form systems were discussed by using discontinuous control [18]. The adaptive stabilization problem of stochastic nonholonomic systems with nonlinear drifts was considered [19–21]. By using state-scaling method, backstepping controllers were proposed to deal with exponential stabilization for nonholonomic mobile robots with stochastic disturbance [22, 23].
Finite-Time Stabilization of Dynamic Nonholonomic Wheeled Mobile Robots with Parameter Uncertainties
Hua Chen,Wen Chen,Chaoli Wang,Dongkai Zhang,Binwu Zhang
Journal of Function Spaces , 2013, DOI: 10.1155/2013/595849
Abstract: The finite-time stabilization problem of dynamic nonholonomic wheeled mobile robots with parameter uncertainties is considered for the first time. By the equivalent coordinate transformation of states, an uncertain 5-order chained form system can be obtained, based on which a discontinuous switching controller is proposed such that all the states of the robots can be stabilized to the origin equilibrium point within any given settling time. The systematic strategy combines the theory of finite-time stability with a new switching control design method. Finally, the simulation result illustrates the effectiveness of the proposed controller. 1. Introduction Stabilization problem of nonholonomic systems is theoretically challenging and practically interesting. As pointed out in [1], although every nonholonomic system is controllable, it cannot be stabilized to a point with pure smooth (or even continuous) state feedback law. In order to overcome the difficulty of Brocket's condition [1], a variety of sophisticated feedback stabilization methods have been proposed which mainly include continuous time-varying feedback control laws [2–4], discontinuous feedback control laws [5–8], and hybrid feedback control laws [9]. A common characteristic of these designs of controllers above is based on kinematic model, where only a kinematic model is considered and the velocities are taken as control inputs. But in fact, for some mechanical systems with nonholonomic constraints, it is more realistic to formulate the control problems at dynamic levels, where the torque and force are chosen as new inputs. Some results can be found in recent papers, for example, the dynamic tracking control of wheeled mobile robots in the presence of both actuator saturations and external disturbances is considered in [10], where a computationally tractable moving horizon tracking scheme is presented. In [11, 12], the saturated stabilization and tracking control are discussed for simple dynamic nonholonomic mobile robot. For uncertain dynamic nonholonomic systems, Ma and Tso [13] have given a robust control law for the exponential regulation of an uncertain dynamic nonholonomic wheeled mobile robot, in which the authors improved the convergence speed of regulating the state to a desired set point for the first time. In order to drive a system to the equilibrium point with a fast convergence rate, finite-time stability theory has become a studying focus recently, for example, finite-time stabilization problems have been studied mostly in the contexts of optimality, controllability, and
Acute Toxicity of Perfluorooctane Sulfonate (PFOS) and Its Substitutes to Amphibian Tadpoles

Su Hongqiao,Ren Dongkai,Cao Shan,Qin Zhanfen,

生态毒理学报 , 2012,
Abstract: In this paper, the acute toxicity of perfluorooctane sulfonate (PFOS) and four substitutes on Xenopus laevis tadpoles and Rana nigromaculata tadpoles were compared. 96 h-LC50 for tri-fabric finishing agent synthetized using telomerization method (tri-fabric finishing agent) on Xenopus laevis tadpoles and Rana nigromaculata tadpoles were 8 and 21 mg·L-1, respectively, while that for PFOS on the two tadpoles were 92 and 81mg·L-1. It is indicated that acute toxicity of tri-fabric finishing agent is significantly higher than PFOS. The other three alternatives C4 and C6 tri-proof finishing agents (C4 and C6 emulsion) synthetized by electrolysis fluorination method, and 50% perfluorobutyl organic ammonium salt cationic surfactant (50% cationic surfactants) are not toxic to tadpoles at the concentration of 100 mg·L-1. Therefore, to acute toxicity, C4, C6 emulsion and 50% cationic surfactants can be used as substitutes for PFOS, however, tri-fabric finishing agent should not be a alternative of PFOS. The toxicity of PFOS and tri-fabric finishing agent on Rana nigromaculata tadpoles is different from that on Xenopus laevis tadpoles. To protect local amphibians in China, it is of practical significance that toxicity assessment will be carried out using Rana nigromaculata rather than Xenopus laevis.
GPS satellite simulatior signal estimation based on ANN

Kou Yanhong,Yang Dongkai,Chang Qing,Zhang Qishan,

电子与信息学报 , 2003,
Abstract: Multi-channel GPS satellite signal simulator provides realistic test signals for GPS receivers and navigation systems. In this paper, signals arriving the antenna of GPS receiver are analyzed from the point of view of simulator design. Focus is put on the estimation methods of several signal parameters that are difficult to determine directly according to existing experiential models due to various error factors. Based on the theory of Artificial Neural Network (ANN), an approach to simulate signal propagation delay, carrier phase, power, and other parameters using ANN is proposed. The architecture of the hardware-in-the-loop test system is given. The ANN training and validation process is described. Experimental results demonstrate that the ANN designed can simulate sample data statistically in high fidelity. Therefore the computation of signal state based on this ANN can meet the design requirement, and can be directly applied to the development of multi-channel GPS satellite signal simulator.
A Meta-Analysis of Randomized Controlled Trials of Low-Volume Polyethylene Glycol plus Ascorbic Acid versus Standard-Volume Polyethylene Glycol Solution as Bowel Preparations for Colonoscopy
Qingsong Xie, Linghui Chen, Fengqing Zhao, Xiaohu Zhou, Pengfei Huang, Lufei Zhang, Dongkai Zhou, Jianfeng Wei, Weilin Wang, Shusen Zheng
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0099092
Abstract: Background Standard-volume polyethylene glycol (PEG) gut lavage solutions are safe and effective, but they require the consumption of large volumes of fluid. A new lower-volume solution of PEG plus ascorbic acid has been used recently as a preparation for colonoscopy. Aim A meta-analysis was performed to compare the performance of low-volume PEG plus ascorbic acid with standard-volume PEG as bowel preparation for colonoscopy. Study Electronic and manual searches were performed to identify randomized controlled trials (RCTs) that compared the performance of low-volume PEG plus ascorbic acid with standard-volume PEG as bowel preparation for colonoscopy. After a methodological quality assessment and data extraction, the pooled estimates of bowel preparation efficacy during bowel cleansing, compliance with preparation, willingness to repeat the same preparation, and the side effects were calculated. We calculated pooled estimates of odds ratios (OR) by fixed- and/or random-effects models. We also assessed heterogeneity among studies and the publication bias. Results Eleven RCTs were identified for analysis. The pooled OR for preparation efficacy during bowel cleansing and for compliance with preparation for low-volume PEG plus ascorbic acid were 1.08 (95% CI = 0.98–1.28, P = 0.34) and 2.23 (95% CI = 1.67–2.98, P<0.00001), respectively, compared with those for standard-volume PEG. The side effects of vomiting and nausea for low-volume PEG plus ascorbic acid were reduced relative to standard-volume PEG. There was no significant publication bias, according to a funnel plot. Conclusions Low-volume PEG plus ascorbic acid gut lavage achieved non-inferior efficacy for bowel cleansing, is more acceptable to patients, and has fewer side effects than standard-volume PEG as a bowel preparation method for colonoscopy.
Constructing LEO-R Ocean Remote Sensing Constellation Using BeiDou System

高超群, 杨东凯, 裘雪敬, 朱云龙
GAO Chaoqun
, YANG Dongkai, QIU Xuejing, ZHU Yunlong

- , 2018, DOI: 10.13203/j.whugis20160440
Abstract: 北斗是中国独立研发的导航系统,其反射事件的数量和分布规律有特殊的优势,也是设计低轨道反射信号(low earth orbit-reflection,LEO-R)星座的重要指标。利用具有均匀性和稳定性优势的Walker架构,设计了LEO-R星座,实现基于北斗反射信号的全球海洋遥感探测。分析星座与北斗的几何关系,推导了北斗反射事件被覆盖的判断条件。提出了标记-遍历的镜点计算方法,定量分析星座参数对北斗反射事件数量和分布规律的影响,并模拟36 h的尼伯特台风场景作为探测对象。结果表明,星座的覆盖时间百分比为97.619 73%,最大重访时间为404.511 s,验证了该星座全球遥感探测的有效性
Developmental Toxicity of Perfluorooctane Sulfonate (PFOS) and Its Substitutes to Amphibian Embryos

Ren Dongkai,Su Hongqiao,Liu Pengyan,Wei Rongguo,Qin Zhanfen,

生态毒理学报 , 2012,
Abstract: In this study, the developmental toxicity of perfluorooctane sulfonate (PFOS) and its four substitutes on Xenopus laevis embryos and Rana nigromaculata embryos studied comparatively. It was found that tri-fabric finishing agent synthetized using telomerization method (tri-fabric finishing agent) and 50% perfluorobutyl organic ammonium salt cationic surfactant (50% cationic surfactants) as well as PFOS had obvious toxicity to X. laevis embryos. Moreover, the toxicity of tri-fabric finishing agent and 50% cationic surfactant was significantly higher than that of PFOS. C4 and C6 tri-proof finishing agent (C4 and C6) synthetized by electrolysis fluorination method were not toxic to X. laevis embryos. To R. nigromaculata embryos, PFOS and four substitutes had no obvious toxicity. In term of biological safety, these results show that C4 and C6 might be used as the substitutes for PFOS, while tri-fabric finishing agent and 50% cationic surfactant should be considered carefully.
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