• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.6
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• pp.3273-3308
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• 2017

Building appropriate trust evaluation models is an important research issue for security guarantee in social networks. Most of the existing works usually consider the trust values at the current time slot, and model trust as the stochastic variable. However, in fact, trust evolves over time, and trust is a stochastic process. In this paper, we propose a novel time-variant stochastic trust evaluation (TSTE) model, which models trust over time and captures trust evolution by a stochastic process. Based on the proposed model, we derive the time-variant bound of untrustworthy probability, which provides stochastic trust guarantee. On one hand, the time-variant trust level of each node can be measured by our model. Meanwhile, by tolerating nodes with relatively poor performance, our model can effectively improve the node resource utilization rate. Numerical simulations are conducted to verify the accuracy and consistency of the analytical bounds on distinguishing misbehaved nodes from normal ones. Moreover, simulation results on social network dataset show the tradeoff between trust level and resource utilization rate, and verify that the successful transmission rate can be improved by our model.

• International Journal of Contents
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• v.9 no.4
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• pp.22-29
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• 2013

In this paper, we propose a integrated real-time monitoring system for recycling agriculture resourcing based on USN. We design and implement the monitoring system so that we can integrate the quality control of farmyard and liquid manures, barn environment monitoring, and positioning information control into a total management system performing recycling of excrement and manure. Selection of sensors and sensor-node construction and requirements, structure of wire/wireless communication networks, and design of monitoring program are also presented. As a result of operating our system, we can get over various drawbacks of conventional separated system and promote the proper circulation of excrement up to the farmyard. We confirm that these advanced effects arise from the effective management of the total system integrating quality control of farmyard/liquid manure, barn/farmhouse information, and vehicle moving monitoring information etc. Moreover, this monitoring system is able to exchange real-time information throughout communication networks so that we can construct a convenient information environment for agricultural community by converging IT technology with farm and stockbreeding industries. Finally we present some results of processing using our monitoring system. Sensing data and their graphs are processed in real-time, positioning information on the v-world map offers various moving paths of vehicles, and statistical analysis shows all the procedure from excrement occurrence to recycling and resourcing.

• The Transactions of the Korea Information Processing Society
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• v.5 no.5
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• pp.1083-1097
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• 1998

The conventional geographic information systems(GIS) is a software which handles spatial and aspatial information of objects in the real world. The system can not support users time-varying information because it manipulates their snapshot data in the spatial database. Also even though it supports time-varying information, it is very limited and hs many difficulties in presenting and processing queries. This paper therefore describes an integrated spatiotemporal data model using loosely-coupled approach which is extended a time dimension for the previous spatial database and which handles time-varying historical information of spatial objects. Conclusionally this paper not only designed a data structure for spatiotemporal database, but also implemented spatial comparison operations varying over time.

• Journal of the Korean Society for Library and Information Science
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• v.31 no.3
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• pp.209-237
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• 1997

The main purpose of this study is to find the difference of information searching behaviours consist of information pursuit cognition and searching character by time pressure of researchers. The majar findings and result by time pressure of researchers are summarized as follows : In terms of information retrieval systems, according to the time pressure, there is a significant difference in recall, precision and diversity. In terms of main used material, there is a significant difference in a book, a research report, and a Journal. In terms of resource types, there is a significant difference in both record and human resource. Also, in terms of searching behaviours, there is a difference to spend time for information collection and information searching strategy, and to decide information searching method and degree of searching.

• Information and Communications Magazine
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• v.18 no.6
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• pp.119-125
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• 2001

1990년 초반부터 송신 다이버시티에 대한 연구가 있어 왔다. 1990년 후반부터는 송수신 다이버시티에 대한 실용적인 결과가 부호 이론과 접목이 되면서 나오기 시작한다. 그 중에서 매우 유용한 결과인 Space-Time 부호에 대하여 다룬다. 본 논문에서는 직교 Space-Time block code. Layered Space-Time processing, 그리고 Space-Time trellis Coding의 세 가지로 분류하여 내용을 정리한다.

• Spatial Information Research
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• v.20 no.3
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• pp.83-93
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• 2012

Recent environmental concerns have made interest in environment-friendly transportation means such as walking, biking, and public transportation. However, since it is difficult to move long distance by walking or biking, their scope of application is rather limited. On the other hand, public transportation can solve traffic congestion, a recent social issue, though its usability may depend on its time schedule. Currently available information services on public transportation in the Web do not reflect well such traits of the public transportation; thus, in some cases, they may provide wrong information to end users. To solve such problems and provide information based on timetable of public transportations, this paper proposes a STP(Space Time Point) data model. Unlike existing space-time data models, this model recognizes the bottommost element of an object as a point and structures these points in hierarchical way to define an object. In particular, It can make it possible to implement a variety of dynamic spatial objects changing object information according to time. An objective of this study is to design a STP model for bus and subway based on timetables of public transportation in Daejeon area and builds a system to provide path navigation. With the designed navigation function, a path from the Daejeon National Cemetery to Hannam University was searched by time slot. The result showed that the system provided different paths by time, as the system guided different paths when bus operation was limited in midnight. As existing data model could not provide such results, it is confirmed that the system can provide path navigation based on real-time traffic information. It is expected that based on such functionality, it is possible to provide additional functionalities by applying diverse data models such as real-time transport information or traffic history information.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.3
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• pp.21-28
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• 2016

File Time information has a significant meaning in digital forensic investigation. File time information in Linux Ext4 (Extended File System 4) environment is the Access Time, Modification Time, Inode Change Time, Deletion Time and Creation Time. File time is variously changed by user manipulations such as creation, copy and edit. And, the study of file time change is necessary for evidence analysis. This study analyzes the change in time information of files or folders resulting from user manipulations in Linux operating system and analyzes ways to determine real time of malware infection and whether the file was modulation.

• The KIPS Transactions:PartD
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• v.12D no.2 s.98
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• pp.319-326
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• 2005

Recently, the information appliance devices integrating information technology, appliance technology, and communication technology are appeared in home. And this environment requires that the monitoring technology should include the interaction and the real-time controlling among these devices using home network. In this paper, we implemented the active objects for information appliances by applying the Time-triggered Message-triggered Object(TMO) scheme supporting real-time service. Based on distributed real-time services supporting platform using the TMO Support Middleware(TMOSM), we also constructed the real-time information appliance controlling simulator supporting the remote controlling and monitoring service among active objects. The information appliance devices implemented by the TMO scheme can exchange the housing information by autonomous triggering. And we can conveniently reconfigure the executing environment for information appliances when new devices were inserted. For constructing the simulator on the distributed real-time service supporting platform, we described the functions of the active TMOs for information appliances that execute the temperature management, the illuminance management, and the time management controlling services, and designed the remote interaction among them. Finally, by implementing the simulating environment of information appliance devices on distributed platform, we showed whether the procedures of the real-time controlling and the monitoring service for the active objects of information appliances corresponding to physical devices are processed in given executing conditions correctly.

• Journal of the Korea Society of Computer and Information
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• v.20 no.2
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• pp.89-97
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• 2015

In this paper, we propose a handoff method supporting LBS (Location Based Services) Information in mobile clouding environment. In mobile clouding computing, handoff delay and re-authentication is occurred. A mobile node needs re-authentication procedure from cloud server whenever it arrives new AP. But Using of location information of node enables to reduce delay time due to re-authentication. To reduce re-authentication delay time, proposed method stores location information of APs on WiFi based location server to complement. GPS-based technology which can't receive satellite signal in indoor and then node collects location information of AP at handoff time. And also enables to process LBS without increasing handoff delay by splitting the process of handoff from process of requesting location information. For analysis of proposed method, We analyze handoff delay and location information process time and have compared previous handoff method in cloud environment. We confirmed that proposed method shows lower delay time without increasing LBS process time than previous method because node receives location information from location information server when handoff is occurred.

• International Journal of Control, Automation, and Systems
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• v.5 no.1
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• pp.70-78
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• 2007

We prove that TCP Vegas globally converges to its equilibrium point in finite time assuming no feedback information delay. We analyze a continuous-time TCP Vegas model with discontinuity and high nonlinearity. Using the upper right-hand derivative and applying the comparison lemma, we cope with the discontinuous signum function in the TCP Vegas model; using a change of state variables, we deal with the high nonlinearity. Although we ignore feedback information delay in analyzing the model of TCP Vegas, the simulation results illustrate that TCP Vegas in the presence of feedback information delay shows very similar dynamic trends to TCP Vegas without feedback information delay. Consequently, dynamic properties of TCP Vegas without feedback information delay can be used to estimate those of TCP Vegas in the presence of feedback information delay.