유무선 통합형 차량 내 네트워크 응용 서비스 연구

SUN XIA(Sun, Xia),박상현(Park, Sanghyun),권영구(Kwon, Younggoo) 한국IT서비스학회 2009 한국IT서비스학회 학술대회 논문집 Vol.2009 No.1

최근 차량용 IT 기술이 발달함에 따라 네비게이션, 위치추적, 인터넷 접수, 원격 차량진단, 사고감지, 긴급구난, 교통정보 등을 제공하는 서비스들이 등장하고 있다. 또한 차량의 편의성과 안정성을 추구함과 동시에 친환경 등에 대한 요구도 증가하고 있다. 그리고 최근차량 상호간 정보의 교환이 더욱 필요해짐에 따라 차량간의 무선 통신 기능이 중요해지고 있으며 차량 내의 네트워크 기술에 대한 연구도 필요하다. 현재 차량 내 네트워크로는 CAN, LIN, MOST등의 유선으로 된 버스 시스템을 중심으로 한 차량 제어 시스템과 멀티미디어 시스템으로 크게 구분할 수 있다. 그러나 자동차 내에 장치 배선이 복잡해짐에 따라 차량의 무게 증가, 고장율의 증가, 연비 저하 등으로 이어지고 있다. 이러한 문제를 보완하기 위해 차량 내에 무선 센서 네트워크 시스템과의 통합 개발이 요구되고 있다. 본 논문에서는 빠르게 발전하고 있는 차량 내 네트워크에 대한 기술개발 동향을 분석하고, 유무선 통합형 차량 내 네트워크 응용 서비스들을 제시하고자 한다.

Atomic adsorption induced recovery of half metallicity at Fe₃O₄(100) surface

Xia SUN,Andrew PRATT,Mitsunori KURAHASHI,Yasushi YAMAUCHI,Zejun DING 한국진공학회 2016 한국진공학회 학술발표회초록집 Vol.2016 No.8

조건부 변동성과 상관관계 전이모델을 이용한 산업별 주가동조화 현상연구

( Xia Sun Ling ),김명현 ( Myeong Hyeon Kim ) 한국금융학회 2015 금융연구 Vol.29 No.2

본 논문은 글로벌 중요지수와 12개의 국내 산업별 포트폴리오의 상관관계 전이효과를 Dynamic Conditional Correlation(DCC) 모델과 비대칭성을 고려한 Asymmetric Dynamic Conditional Correlation (ADCC) 모델을 사용하여 분석한다. 2008년 금융위기와 2010년 유럽위기에 방점을 두고 국내 주식시장에 중요한 영향을 미치는 미국, 일본, 유럽과 중국 시장의 대표지수를 활용해 글로벌 대표지수들로부터 산업별 포트폴리오에 전이되는 메커니즘을 분석하였다. 종합지수(Index)를 활용한 선행연구의 결과와 부합하게, 산업레벨의 지수에서도 위기시 상관관계의 증가를 확인할 수가 있었다. 또한, 시간가변 상관계수의 산업간 변이의 결정요인을 탐구하고자 기업변수들을 활용한 패널회귀 식을 통해, 국내 산업포트폴리오의 각국 마켓지수와의 조건부 상관계수를 설명하는 요인이 다르며, 국내 산업의 각국의 상관계수 변이에 대한 반응이 다르게 나타남을 밝혀냈다. This paper examines how the outside markets` shocks are propagated to the Korean sectors by employing the Dynamic Conditional Correlation (DCC) and the Asymmetric Dynamic Conditional Correlation (ADCC) methodologies. Our special interests are paid on the recent two crisis periods, namely, the 2008 Global Financial Crisis and the 2010 European Sovereign Debt Crisis. For this purpose, we focus on the 4 market indices outside of Korea, i.e., S&P500, STOXX Europe 600, TOPIX,and Shanghai Stock Exchange A-share Index, which are widely used to present for the overall stock markets of America, Europe, Japan, and China. To construct the Korean sector indices, we follow the Fama and French`s classification of the 12 industries that are based on the 4-digit SIC codes. The 12 industries are consumer nondurables, consumer durables, manufacturing, oil, gas, and coal extraction and products, chemicals and allied products, business equipment, telephone and television transmission, utilities, whole sale, retail, and some services (shops), healthcare, medical equipment, and drugs, finance and Other. Our main findings based on the DCC and ADCC methodologies are summarized as follows. The first finding is that we have verified the stylized fact that conditional correlations between the market indices tend to increase during the crisis periods. This finding has been confirmed by the sectoral conditional correlations and also by the panel regression results. Our second finding is that conditional correlation dynamics exhibit significant differences among country-level indices, among sector-level indices, as well as between the two crises. Specifically, the Korean sectors` conditional correlations with the American S&P 500 index capture the well-known financial crisis stories such as the Lehman Brothers collapse however, the Korean sectors` conditional correlations with the STOXX Europe 600 index and the Japanese TOPIX show some puzzling patterns. To be specific, the Korean sectors` conditional correlations with the STOXX Europe 600 and the TOPIX keep decreasing after the Lehman Brothers shock. This pattern to some extent may contradict to the argument that the financial crisis has been a global common factor. In addition, variations among sectoral conditional correlations differ significantly. Variations among sectoral conditional correlations with the American and Chinese indices are larger than those with the European and Japanese during both crisis periods. Also, the absolute magnitude of the conditional correlations with the TOPIX is the largest during both crises. We further investigate the determinants of the sector-level correlations by conducting a panel regression analysis. Specifically, we associate the sector-level correlations with the crisis dummies and several sectorlevel corporate finance variables. Our finding is that crisis dummies and industry-specific variables, such as Tobin`s Q, PPE, Debt ratio, and ROAare significantly associated with the magnitude of conditional correlations. To our best knowledge, this is the first study to examine the determinants that drive a positive co-movement among conditional correlations during the crisis periods by analyzing the Korean sector-level data. Our findings thus contribute to the existing literature by figuring out what microdeterminants drive co-movement among the sector-level correlations and by associating the conditional correlations dynamics with the corporate investment and financing activities.

Dynamic analysis of coupled train - ladder track - elevated bridge system

Xia, He,Deng, Yushu,Xia, Chaoyi,De Roeck, G.,Qi, Lin,Sun, Lu Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.47 No.5

As a new type of vibration reduction, the ladder track system has been successfully used in engineering. In this paper, a numerical model of the train-track-viaduct system is established to study the dynamic responses of an elevated bridge with ladder track. The system is composed of a vehicle submodel, a track submodel and a bridge submodel, with the measured track irregularities as the system self-excitation. The whole time histories of a train running through an elevated bridge with $3{\times}27m$ continuous PC box girders are simulated. The dynamic responses of the bridge such as deflections, lateral and vertical accelerations, and the vehicle responses such as derailment factors, offload factors and car-body accelerations are calculated. The calculated results are partly validated through the comparison with the experimental data. Compared to the common slab track, adapting the ladder sleeper can effectively reduce the accelerations of the bridge girder, and also reduce the car-body accelerations and offload factors of the train vehicle.

Vibration control of high-speed trains self-excitation under-chassis equipment by HSLDS vibration isolators

Yu Sun,Jinsong Zhou,Dao Gong,Wenjing Sun,Zhanghui Xia 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.1

To minimize the self-excitation effects of the equipment on the carbody, a high static and low dynamic stiffness (HSLDS) vibration isolator is proposed by connecting a negative stiffness unit and a positive linear stiffness spring in parallel. The nonlinear stiffness of the HSLDS isolator can be designed according to the needs of any target stiffness curve. A vibration test is applied to obtain the vibration acceleration of the under-chassis equipment. A rigid-flexible coupling multi-body dynamic model of a high-speed train is established which considers the elastic vibration of the carbody and the self-excitation of the under-chassis equipment based on the tested result. Different connection methods of the under-chassis equipment including rigid hanging, vibration isolation theory (VIT) hanging, dynamic vibration absorber (DVA) hanging and HSLDS hanging are applied and their effects on the carbody vibration and ride quality are investigated. The simulation results reveal that the proposed HSLDS vibration isolator can effectively isolate the self-excitation of the under-chassis equipment from the carbody and enhance the ride quality of the high-speed train.

An Optimal ODAM-Based Broadcast Algorithm for Vehicular Ad-Hoc Networks

( Weifeng Sun ),( Feng Xia ),( Jianhua Ma ),( Tong Fu ),( Yu Sun ) 한국인터넷정보학회 2012 KSII Transactions on Internet and Information Syst Vol.6 No.12

Broadcast routing has become an important research field for vehicular ad-hoc networks (VANETs) recently. However, the packet delivery rate is generally low in existing VANET broadcast routing protocols. Therefore, the design of an appropriate broadcast protocol based on the features of VANET has become a crucial part of the development of VANET. This paper analyzes the disadvantage of existing broadcast routing protocols in VANETs, and proposes an improved algorithm (namely ODAM-C) based on the ODAM (Optimized Dissemination of Alarm Messages) protocol. The ODAM-C algorithm improves the packet delivery rate by two mechanisms based on the forwarding features of ODAM. The first distance-based mechanism reduces the possibility of packet loss by considering the angles between source nodes, forwarding nodes and receiving nodes. The second mechanism increases the redundancy of forwarding nodes to guarantee the packet success delivery ratio. We show by analysis and simulations that the proposed algorithm can improve packet delivery rate for vehicular networks compared against two widely-used existing protocols.

An Improved Privacy Preserving Construction for Data Integrity Verification in Cloud Storage

( Yingjie Xia ),( Fubiao Xia ),( Xuejiao Liu ),( Xin Sun ),( Yuncai Liu ),( Yi Ge ) 한국인터넷정보학회 2014 KSII Transactions on Internet and Information Syst Vol.8 No.10

The increasing demand in promoting cloud computing in either business or other areas requires more security of a cloud storage system. Traditional cloud storage systems fail to protect data integrity information (DII), when the interactive messages between the client and the data storage server are sniffed. To protect DII and support public verifiability, we propose a data integrity verification scheme by deploying a designated confirmer signature DCS as a building block. The DCS scheme strikes the balance between public verifiable signatures and zero-knowledge proofs which can address disputes between the cloud storage server and any user, whoever acting as a malicious player during the two-round verification. In addition, our verification scheme remains blockless and stateless, which is important in conducting a secure and efficient cryptosystem. We perform security analysis and performance evaluation on our scheme, and compared with the existing schemes, the results show that our scheme is more secure and efficient.

Bacthing Auditing of Data in Multicloud Storage

Zhihua Xia,Xinhui Wang,Xingming Sun,Yafeng Zhu,Peng Ji,Jin Wang 보안공학연구지원센터 2014 International Journal of Database Theory and Appli Vol.7 No.6

Cloud storage enables users to outsource their data to cloud servers and enjoy the on-demand services. However, this new paradigm also introduces integrity threats toward user’ outsourced data. This paper develops an efficient auditing mechanism, which support batch auditing for multiple data files in multi-cloud environment. By constructing a sequence-enforced Merkle Hash Tree, the proposed protocol can resist the replace attack. By using the bilinear map, the proposed protocol achieves stateless and transparent verification. By putting the computation of intermediate values of the verification on cloud servers, our method can greatly reduce the computing burden of the auditor. The performance analysis proves the good efficiency of the proposed protocol.

Dynamic analysis of coupled train - ladder track - elevated bridge system

He Xia,Yushu Deng,Chaoyi Xia,G. De Roeck,Lin Qi,Lu Sun 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.47 No.5

As a new type of vibration reduction, the ladder track system has been successfully used in engineering. In this paper, a numerical model of the train-track-viaduct system is established to study the dynamic responses of an elevated bridge with ladder track. The system is composed of a vehicle submodel, a track submodel and a bridge submodel, with the measured track irregularities as the system self-excitation. The whole time histories of a train running through an elevated bridge with 3×27m continuous PC box girders are simulated. The dynamic responses of the bridge such as deflections, lateral and vertical accelerations, and the vehicle responses such as derailment factors, offload factors and car-body accelerations are calculated. The calculated results are partly validated through the comparison with the experimental data. Compared to the common slab track, adapting the ladder sleeper can effectively reduce the accelerations of the bridge girder, and also reduce the car-body accelerations and offload factors of the train vehicle.

Fingerprint Liveness Detection Using Difference Co-occurrence Matrix Based Texture Features

Zhihua Xia,Chengsheng Yuan,Xingming Sun,Rui Lv,Decai Sun,Guangyong Gao 보안공학연구지원센터 2016 International Journal of Multimedia and Ubiquitous Vol.11 No.11

Fingerprint authentication systems have been widely deployed in both civilian and government applications, however, whether fingerprint authentication systems is security or not has been an important issue under fraudulent attempts through artificial spoof fingerprints. In this paper, inspired by popular feature descriptors such as gray level co-occurrence matrix (GLCM) and Gradient (difference matrix (DM)), we propose a novel software-based fingerprint liveness detection algorithm called difference co-occurrence matrix (DCM). In doing so, quantization operation is firstly conducted on the images. DMs are constructed by calculating difference matrices of horizontal and vertical pixel values of images; difference co-occurrence arrays are constructed from the difference matrices between adjacent pixels. To reduce the influence of abnormal pixel values, truncation is used for DMs. Then, we compute four parameters (Angular Second Moment, Entropy, Inverse Differential Moment and Correlation) used as feature vectors of fingerprint images. For the first time in the fingerprint liveness detection, we construct eight difference co-occurrence matrices and extract texture features from processed DCMs. Finally, SVM classifier is used to predict classification accuracy. The experimental results reveal that our proposed method can achieve more accurate classification compared with the best algorithms of 2013 Fingerprint Liveness Detection Competition, while being able to recognize spoofed fingerprints with a better degree of accuracy.