Encounter

( Jiayi Liu ) 한국기초조형학회 2018 한국기초조형학회 작품집 Vol.2018 No.1

Dynamic Magnetic Field Measurement in the Air Gap of Magnetic Bearings Based on FBG-GMM Sensor

Liu Jiayi,Ding Guoping,Zhou Zude,Wang Huaqiang 한국광학회 2015 Current Optics and Photonics Vol.19 No.6

Magnetic field in magnetic bearings is the physical medium to realize magnetic levitation, the distributionof the magnetic field determines the operating performance of magnetic bearings. In this paper, a thin-sliceFiber Bragg Grating-Giant Magnetostrictive Material magnetic sensor used for the air gap of magneticbearings was proposed and tested in the condition of dynamic magnetic field. The static property of thesensor was calibrated and a polynomial curve was fitted to describe the performance of the sensor. Measurement of dynamic magnetic field with different frequencies in magnetic bearings was implemented. Comparing with the finite element simulations, the results showed the DC component of the magneticfield was detected by the sensor and error was less than 5.87%

PD-type ℓ2-ℓ∞ Intermittent Pinning Synchronization Control of Discrete Time-delay Nonlinear Dynamical Networks

Jiayi Zhang,Guoliang Wei,Shuai Liu,Derui Ding 제어·로봇·시스템학회 2020 International Journal of Control, Automation, and Vol.18 No.8

In this paper, the PD-type `2 − `∞ synchronization control problem is concerned for a class of discrete time-delayed nonlinear dynamical networks. A PD-type (proportional-derivative-type) pinning control protocol is proposed where only a small fraction of network nodes is controlled in order to achieve the global synchronization performance. Meanwhile, for the sake of decreasing the update frequency of the controller, the periodic intermittent control strategy is developed. The main purpose of the addressed problem is to design a PD-type intermittent pinning feedback controller such that the closed-loop system achieves both the exponential synchronization and the prescribed `2 −`∞ performance index. Subsequently, by means of the Lyapunov-Krasovskii functional method, a sufficient condition is established under which the addressed PD-type controller design problem is recast into a linear convex optimization one that can be easily solved via available software packages. Finally, a simulation example is given to show the applicability of the developed theoretical results.

Macrophage Migration Inhibitory Factor (MIF) Interacts with Bim and Inhibits Bim-mediated Apoptosis

Lingfeng Liu,Jinzhong Chen,Chaoneng Ji,Jiayi Zhang,Junlei Sun,Yao Li,Yi Xie,Shaohua Gu,Yumin Mao 한국분자세포생물학회 2008 Molecules and cells Vol.26 No.2

The pro-apoptotic Bcl-2 family member Bim acts as a sensor for apoptotic stimuli and initiates apoptosis through the mitochondrial pathway. To identify novel regulators of Bim, we employed the yeast two-hybrid system and isolated the human gene encoding macrophage migration inhibitory factor (MIF), a ubiquitously expressed proinflammatory mediator that has also been implicated in cell proliferation, the cell cycle and carcinogenesis. The interaction between MIF and Bim was confirmed by both in vitro and in vivo protein interaction assays. Intriguingly, protein complexes between MIF and the three major Bim isoforms (BimEL/BimL/BimS) could be detected in HEK293 and K562 cells, especially in cells undergoing apoptosis. Moreover, exogenous expression of MIF partially inhibited Bim-induced apoptosis in HEK293 cells. SiRNA-mediated knockdown of MIF increased apoptosis in K562 cells exposed to the chemical oxidant diamide. Endogenous MIF may regulate the pro-apoptotic activity of Bim and inhibit the release of cytochrome c from mitochondria.

5G Network Slices Embedding with Sharable Virtual Network Functions

Chengli Mei,Jiayi Liu,Jinyan Li,Lei Zhang,Menghan Shao 한국통신학회 2020 Journal of communications and networks Vol.22 No.5

Network slicing (NS) is recognized as a key technology for the 5G mobile network in enabling the network to support multiple diversified vertical markets over a shared physicalinfrastructure with efficiency and flexibility. A 5G NS instance iscomposed of a set of virtual network function (VNF) instances toform the end-to-end (E2E) virtual network for the slice to operateindependently. The deployment of a NS is a typical virtual network embedding (VNE) problem. We consider a scenario in whichVNF instances can be shared across multiple slices to further enhance the utilization ratio of the underlying physical resources. ForNSs with sharable VNF instances, the deployment of the slice instances is essentially the embedding of multiple virtual networkscoupled by the VNFs shared among slices. Hence, we formulatethis sharable-VNFs-based multiple coupled VNE problem (SVMVNE) through an integer linear program (ILP) formulation, anddesign a back-tracking coordinated virtual network mapping algorithm. Simulation results demonstrate that VNF-sharing can enhance the slice acceptance ratio with the same physical network,which represents higher physical resource utilization. Moreover,our approach achieves higher acceptance ratio by comparing to abaseline algorithm.

Design and Realization of Precise Indoor Localization Mechanism for Wi-Fi Devices

Su, Weideng,Liu, Erwu,Auge, Anna Calveras,Garcia-Villegas, Eduard,Wang, Rui,You, Jiayi Korean Society for Internet Information 2016 KSII Transactions on Internet and Information Syst Vol.10 No.12

Despite the abundant literature in the field, there is still the need to find a time-efficient, highly accurate, easy to deploy and robust localization algorithm for real use. The algorithm only involves minimal human intervention. We propose an enhanced Received Signal Strength Indicator (RSSI) based positioning algorithm for Wi-Fi capable devices, called the Dynamic Weighted Evolution for Location Tracking (DWELT). Due to the multiple phenomena affecting the propagation of radio signals, RSSI measurements show fluctuations that hinder the utilization of straightforward positioning mechanisms from widely known propagation loss models. Instead, DWELT uses data processing of raw RSSI values and applies a weighted posterior-probabilistic evolution for quick convergence of localization and tracking. In this paper, we present the first implementation of DWELT, intended for 1D location (applicable to tunnels or corridors), and the first step towards a more generic implementation. Simulations and experiments show an accuracy of 1m in more than 81% of the cases, and less than 2m in the 95%.

대학도서관의 다국어 맞춤형 서비스가 중국인 유학생의 이용자 만족도에 미치는 영향

유가의,이용정,Liu, Jiayi,Yi, Yong Jeong 한국정보관리학회 2021 정보관리학회지 Vol.38 No.2

대학도서관은 유학생들이 학습 자원을 얻는 가장 주요한 정보원에 속하므로 유학생들의 학업에 미치는 영향이 크다. 그러나 현재 대다수의 대학도서관은 영어를 제외한 다국어 지원 서비스를 적절히 제공하지 않기 때문에 영어가 모국어가 아닌 유학생들의 학업 수행을 어렵게 만들 수 있다. 따라서 본 연구는 대학도서관 서비스 중 다국어로 제공할 수 있는 서비스를 유학생 맞춤형 서비스로 정의하고, 이러한 맞춤형 서비스가 대학도서관 이용자 만족도에 미치는 영향을 살펴보고자 하였다. 더 나아가서, 본 연구는 유학생 맞춤형 서비스를 적절히 제공하고 있는 대학도서관의 유학생들과 그렇지 않은 대학도서관의 유학생들의 이용자 만족도를 비교하였다. 이를 위해 서로 다른 두 대학에 재학 중인 중국인 유학생을 대상으로 설문 조사하여 총 138부의 응답을 분석하였다. 본 연구는 유학생 맞춤형 서비스가 유학생의 대학도서관 이용 만족도에 영향을 미친다는 것을 발견하였다. 특히, 다국어 서비스의 지원은 안내 책자/표지판, 홈페이지를 통한 자료 접근 및 이용, 그리고 이용자 교육 등과 같은 서비스에 대한 만족도에 긍정적인 영향을 주었다. 본 연구의 결과는 대학도서관이 유학생들의 학업 활동을 효과적으로 지원하는 서비스에 대한 실질적 함의를 시사한다. An academic library is one of the largest information sources for international students to obtain learning resources, which have a great impact on their studies. However, most academic libraries currently have not provided adequate multilingual services except English, which makes it difficult for international students whose mother language is not English to perform academic work. Accordingly, the present study defines the customized services for international students as the ones that have been supported in ltiple languages among academic library services and aims to examine their effect on user satisfaction in academic libraries. Furthermore, the study has compared international students' satisfaction with academic libraries - one that provides appropriate customized services with the other that does not. The surveys have been conducted with Chinese international students in two different universities and a total of 138 responses were analyzed. The study found that the customized services for the international students influenced their satisfaction with library use. In particular, multilingual services had positive effects on satisfaction with services such as brochures/signs, access to and use of resources through the homepage, and user instruction. The findings of the study suggest practical insights on how academic libraries provide effective services for supporting international students' academic tasks.

Cross-Layer Rate Control and Resource Allocation in Spectrum-Sharing OFDMA Small-Cell Networks With Delay Constraints

Guo, Yashuang,Yang, Qinghai,Liu, Jiayi,Kwak, Kyung Sup IEEE 2017 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY Vol.66 No.5

<P>In this paper, we present a dynamic resource management scheme for delay-aware applications in two-tier small-cell networks (SCNs). We propose the scheme of joint rate control at the transport layer and resource allocation at the physical layer to manage the cross-tier interference. The joint rate control and resource allocation scheme is designed to maximize the time-averaged sum capacity of small cell users in the SCN subject to each small cell user's delay constraint and an interference constraint imposed by the macrocell. By using the Lyapunov optimization technique, we develop a delay-guaranteed capacity optimal algorithm (DCOA) to obtain the optimal rate control and resource allocation decisions. We show that without prior knowledge of the data arrivals and channel statistics, DCOA achieves a capacity of SCN that can arbitrarily approach the optimal capacity achieved by the algorithm with the complete knowledge of data arrivals and channel statistics. Simulations results confirm the theoretical analysis on the performance of DCOA and also show the adaptiveness of DCOA.</P>

Quality-Aware Streaming in Heterogeneous Wireless Networks

Guo, Yashuang,Yang, Qinghai,Liu, Jiayi,Kwak, Kyung Sup INSTITUTE OF ELECTRICAL AND ELECTRONICS ENGINEERS 2017 IEEE Transactions on Wireless Communications Vol. No.

<P>In this paper, dynamic resource management is investigated for serving on-demand video streaming users in heterogeneous wireless networks (HWNs) with time varying channel conditions. The HWN is equipped with multi-homing capability, simultaneously connecting to different wireless interfaces. In order to take advantage of the time varying nature of wireless channels, we utilize the joint quality selection associated with quality adjustment at application layer and resource allocation associated with power allocation, subcarrier assignment, and time fraction determination at physical layer to perform the dynamic resource management. By using Lyapunov optimization technique, we develop a quality-aware streaming (QAS) algorithm to maximize the network utility, which is the difference of time-averaged users’ perceived video quality and time-averaged HWN’s transmit power. Simulation results exhibit that the proposed QAS algorithm can significantly improve network utility compared with the state-of-art baselines, which are not specific for on-demand video streaming.</P>

Novel high‑power triple line‑voltage cascaded unity power factor rectifier

Cong Wang,Xia Liu,Zhuang Li,Hong Cheng,Ting Chen,Jiayi Kong 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.1

A novel high-power triple line-voltage cascaded three-phase unity power factor rectifier is proposed to address the complex topology and control of the three-phase rectifier stage in traditional high-power charging power supply modules. The topology is composed of three line-voltage cascaded traditional three-phase single-switch boost-type voltage rectifier modules. With the triple line-voltage cascaded structure, in the proposed topology, the number of the fully controlled power switches and the voltage stresses of each power switch are both effectively reduced. In addition, the proposed rectifier topology can operate at a unity power factor with a sinusoidal input current. In this paper, the circuit structure and the operation principle including the DC-link voltages output characteristics of the proposed topology are described, and a corresponding system control strategy based on one cycle control (OCC) is presented. Simulation and experimental results are given which verified the feasibility of the proposed topology and control strategy.