A New Parameter Estimation Method for a Zipf-like Distribution for Geospatial Data Access

Rui Li,Weifeng WU,Hao Wang,Huayi Wu 한국전자통신연구원 2014 ETRI Journal Vol.36 No.1

Many reports have shown that the access pattern forgeospatial tiles follows Zipf’s law and that its parameter αrepresents the access characteristics. However, visits togeospatial tiles have temporal and spatial popularities, andthe α-value changes as they change. We construct amathematical model to simulate the user’s access behaviorby studying the attributes of frequently visited tile objectsto determine parameter estimation algorithms. Becausethe least squares (LS) method in common use cannotobtain an exact α-value and does not provide a suitable fitto data for frequently visited tiles, we present a newapproach, which uses a moment method of estimation toobtain the value of α when α is close to 1. When α isfurther away from 1, the method uses the associated cachehit ratio for tile access and uses an LS method based on acritical cache size to estimate the value of α. The decreasein the estimation error is presented and discussed in thesection on experiment results. This new method, whichprovides a more accurate estimate of α than earliermethods, promises more effective prediction of requestsfor frequently accessed tiles for better caching and loadbalancing.

Robust Observer-based Sensor Fault Reconstruction for Discrete-time Systems via a Descriptor System Approach

Qingxian Jia,Huayi Li,Yingchun Zhang,Xueqin Chen 제어·로봇·시스템학회 2015 International Journal of Control, Automation, and Vol.13 No.2

This paper addresses the problem of observer-based sensor fault reconstruction for discrete-time systems subject to external disturbances via a descriptor system approach. First, an augmented descriptor system is formulated by letting the sensor fault term be an auxiliary state vector; then a discrete-time descriptor state observer is constructed to achieve concurrent reconstructions of original system states and sensor faults. Sufficient and necessary conditions for the asymptotic stability of the proposed observer are explicitly provided. To broaden its application scope, less restrictive existence conditions are further discussed. Further, sufficient conditions for the robust stability of the proposed observer are formulated in terms of linear matrix inequalities (LMIs) that can be conveniently solved using LMI optimization techniques. After that, an extension of the proposed linear approach to discrete-time nonlinear systems with Lipschitz constraint is investigated. At last, two illustrative examples are given to verify the effectiveness of the proposed techniques.

Coordinated Attitude Control for Synthetic Aperture Radar Satellites with Quantization and Communication Delay

Jingbo Fu,Ming Liu,Huayi Li,Xibin Cao 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.7

This paper studies the coordinated attitude control problem of synthetic aperture radar satellites andproposes two types of terminal sliding mode control schemes. The first control law is investigated based on theconventional non-singular terminal sliding mode approach and modified Rodrigues parameters with the consideration of signal quantization and communication delay. Based on the first control scheme, we develop the secondcontrol method with an integral-based event triggering condition to reduce the updating frequency of the controlcommand from controllers to actuators. Finally, numerical simulation examples based on a cluster of three satellitesare presented to show the effectiveness of the proposed two designed control methods.

Robust Actuator Fault Reconstruction for Takagi-Sugeno Fuzzy Systems with Time-varying Delays via a Synthesized Learning and Luenberger Observer

Qingxian Jia,Lina Wu,Huayi Li 제어·로봇·시스템학회 2021 International Journal of Control, Automation, and Vol.19 No.2

This paper addresses the problem of robust actuator fault reconstruction for Takagi-Sugeno (T-S) fuzzy systems subjects to actuator faults, unknown inputs and time-varying delays via a Fuzzy Synthesized Learning and Luenberger Observer (FSL2O). Through a coordinate transformation, the original T-S fuzzy system is decomposed into two subsystems: subsystem-1 effected by actuator faults and subsystem-2 effected by unknown inputs. In the presented FSL2O methodology, a Reduced-Order Fuzzy Learning Observer (ROFLO) is explored for the subsystem1 to reconstruct actuator faults accurately while a Reduced-Order Fuzzy State (Luenberger) Observer (ROFSO) is designed for the subsystem-2 based on the H∞ control technique such that it has strong robustness against the unknown inputs. The synthesized design of the ROFLO and the ROFSO is formulated in a unified manner in terms of Linear Matrix Inequalities (LMIs) that can be conveniently solved using LMI optimization technique. In addition, as a comparison, a full-order FLO is suggested for robust actuator fault reconstruction. Finally, a numerical exampleand simulation are provided to demonstrate the effectiveness of the proposed approaches.

Effects of Three Types of Resistant Starch on Intestine and Their Gastric Ulcer Preventive Activities in vivo

Yu Qian,Xin Zhao,Gui-Jie Li,Kai Zhu,Huayi Suo,Peng Sun 한국응용생명화학회 2013 Applied Biological Chemistry (Appl Biol Chem) Vol.56 No.6

To examine the effects of three types of resistant starch (RS) on intestinal metabolites, structure and their gastric injury preventive activities, Sprague-Dawley mice were fed diet containing 15% RS for 4 weeks. Response relationships among three types of RS (RS2, RS3, and RS4) food intake, body weight gain, food efficiency, wet weight of cecum (with or not with contents), pH, ammonia production, and short-chain fatty acids (SCFAs) concentration of cecal contents as well as intestinal structure were investigated. All three types of RS had effects on food intake, weight control, lowering of pH, ammonia production in cecal contents, increasing the wet weight of cecum (with or without contents), changes in SCFAs concentration of cecal contents, and physiological structure of small intestine and cecum compared to the control group (common starch-fed rats). RS3group showed minimum weight gain and food efficiency,compared to both the control group and the other two types of RS diet. RS3 group showed more significant lowering of pH,ammonia production, and SCFAs of cecal contents. In addition, all three types of RS shortened villous height, and muscle and mucosal thickening in small intestine, resulting in significantly decreased villous height and mucosal thickness, whereas significantly increased muscle thickness in the cecum. However,they did not cause detectable pathological changes in the small intestine and cecum. Animal model was also used to check its gastric ulcer preventive effects. The gastric ulcer level was significantly down-regulated by RS3, demonstrating its antiinflammatory properties. RS3 reduced the levels of serum proinflammatory cytokines of IL-6, IL-12, TNF-α, and IFN-γcompared to RS2 and RS4. RS3 increased the somatostatin (SS)and vasoactive intestinal peptide (VIP), decreased the motillin (MOT) and substance P (SP) serum levels. These results suggest that RS3 shows the best gastric ulcer preventive effect.

The Compact Pulsed Hadron Source: A Design Perspective

Jie Wei,Huaibi Chen,Cheng Cheng,Qiang Du,Zhe Feng,Xialin Guan,Xiaoxue Han,Tuchen Huang,Renkai Li,Chun K. Loong,Beibei Shao,Chuanxiang Tang,Qingzi Xing,Yigang Yang,Hao Zha,Huayi Zhang,Shuxin Zheng,Bin 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.61

During the past decades, large-scale national neutron sources have been developed in Asia, Europe,and North America. Complementing such efforts, compact hadron beam complexes and neutron sources intended to serve primarily universities and industrial institutes have been proposed,and some have recently been established. Responding to the demand in China for pulsed neutron/proton-beam platforms that are dedicated to fundamental and applied research for users in multiple disciplines from materials characterization to hadron therapy and radiography to accelerator-driven sub-critical reactor systems (ADS) for nuclear waste transmutation, we have initiated the construction of a compact, yet expandable, accelerator complex-the Compact Pulsed Hadron Source (CPHS). It consists of an accelerator front-end (a high-intensity ion source, a 3-MeV radio-frequency quadrupole linac (RFQ), and a 13-MeV drift-tube linac (DTL)), a neutron target station (a beryllium target with solid methane and room-temperature water moderators/reflector),and experimental stations for neutron imaging/radiography, small-angle scattering, and proton irradiation. In the future, the CPHS may also serve as an injector to a ring for proton therapy and radiography or as the front end to an ADS test facility. In this paper, we describe the design of the CPHS technical systems and its intended operation.