• Geomechanics and Engineering
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• v.13 no.2
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• pp.217-235
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• 2017

The stability prediction of shallow buried tunnels is one of the most difficult tasks in civil engineering. The aim of this work is to predict the state of collapse in shallow tunnel in layered soils by employing non-associated flow rule and nonlinear failure criterion within the framework of upper bound theorem. Particular emphasis is first given to consider the effects of dilation on the collapse mechanism of shallow tunnel. Furthermore, the seepage forces and surface settlement are considered to analyze the influence of different dilation coefficients on the collapse shape. Two different curve functions which describe two different soil layers are obtained by virtual work equations under the variational principle. The distinct characteristics of falling blocks up and down the water level are discussed in the present work. According to the numerical results, the potential collapse range decreases with the increase of the dilation coefficient. In layered soils, both of the single layer's dilation coefficient and two layers' dilation coefficients increase, the range of the potential collapse block reduces.

• Broadcasting and Media Magazine
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• v.2 no.3
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• pp.32-39
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• 1997

Virtual Reality의 많은 응용 분야 중 중요한 한가지는 collaboration 분야이다. collaboration이란 거리적으로 떨어져 있는 사람들이 네트워크를 통해 상호 작용하고 공동의 작업을 할수 있게 해 주는 것으로, 시스템은 사용자의 의지를 있는 그대로 표출할 수 있도록 다양한 멀티미디어 서비스를 제공해 주어야 한다. 본 논문에서는 다양한 멀티미디어 서비스를 제공하여 네트워크상의 사용자들이 collaboration work을 수행할 수 있게 해주는 시스템인 Webber에 대해서 설명한다. Webber는 서버/클라이언트 구조를 기반으로 구현되었고, 네트워크로 연결된 사용자들이 가상의 환경에서 키보드, 마우스, 펜 입력 장치 또는 마이크를 사용하여 의사소통을 할 수 있는 환경을 제공한다. Webber는 시스템에서 제공되는 서비스를 담당하는 Service-PUP(Processing Unit Plug-in)이라는 서비스 블럭(Service Block과 이들PUP들을 관리하고 이들간의 통신을 담당하는 Framework로 구성되어 있다. 각 ,Service-Pup들은 하나의 기계에 다중 프로세스로 구축되거나 네트워크로 연결된 서로 다른 기계에 분산될 수 있고, 이들 PUP의 독립성으로 인해 서비스의 유지 보수, 새로운 서비스의 추가 삭제가 간편하다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1C
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• pp.1-8
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• 2009

Cooperative diversity is a novel technique to improve diversity gains, capacity gains, and energy saving. This technique involves multiple terminals sharing resources in order to build a virtual antenna array in a distributed fashion. In this paper, we propose a multi-user cooperative diversity protocol called Relay-assisted Multiple Access Channel(R-MAC) that allows multiple source terminals to transmit their signals simultaneously and the relay terminal forwards the aggregated signal received from the source terminals to the destination terminal. The proposed protocol converts the distributed antenna channels into an effective MIMO channel by exploiting a relay, increasing both diversity gain and system throughput. We investigate the performance of the proposed protocol in terms of outage probability and diversity-multiplexing tradeoff where we assume block fading channel environment. Our simulation results show that the proposed protocol outperforms direct transmission in the high spectral efficiency regime where the conventional cooperative diversity protocols cannot outperform direct transmission.

• Journal of information and communication convergence engineering
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• v.11 no.2
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• pp.112-117
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• 2013

In order to reuse a register transfer level (RTL)-based IP block, it takes another architectural exploration in which the RTL will be put, and it also takes virtual platforms to develop the driver and applications software. Due to the increasing demands of new technology, the hardware and software complexity of organizing embedded systems is growing rapidly. Accordingly, the traditional design methodology cannot stand up forever to designing complex devices. In this paper, I introduce an electronic system level (ESL)-based approach to designing complex hardware with a derivative of SystemVerilog. I adopted the concept of reuse with higher levels of abstraction of the ESL language than traditional HDLs to design multiplication server farms. Using the concept of ESL, I successfully implemented server farms as well as a test bench in one simulation environment. It would have cost a number of Verilog/C simulations if I had followed the traditional way, which would have required much more time and effort.

• Educational Technology International
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• v.20 no.2
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• pp.137-168
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• 2019

This study examined the effects of information volume and distribution on learners' cognitive load and recall in a mobile augmented reality (AR) environment. Information volume refers to the degree of information users are provided in a learning task, while information distribution indicates the way in which information is distributed, either in a virtual or real format. Sixteen undergraduate students participated in the study, which employed a 2 × 3 randomized block factorial design with repeated measures. Information volume and distribution were independent variables, and factors in learners' cognitive load (mental effort, perceived ease of use, and perceived task difficulty) and recall test scores were the dependent variables. Information volume had significant main effects on perceived ease of use and task difficulty, and recall test scores, while information distribution had significant main effects on perceived task difficulty and test scores. A detailed discussion and implications are provided.

• Annual Conference of KIPS
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• 2007.05a
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• pp.1167-1170
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• 2007

This paper introduces a data storage transport protocol internet Advanced Technology Attachment (iATA) for ATA storage devices that can be accessed over (TCP/IP) networks. As the access speed of Advanced Technology Attachment (ATA) type storage is increasing, the importance of sharing the ATA type storages over internet is also increasing. We are proposing a protocol in which we have implemented the basic ATA command set to access the ATA type remote storage devices over the TCP/IP networks.In this paper, we give basic details of the protocol and discuss the existing storage protocols which are mainly used for accessing block storage like internet Small Computer System Interface (iSCSI) Hyper Small Computer System Interface (HyperSCSI) and ATA over Ethernet (AoE).

• Journal of KIISE:Computing Practices and Letters
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• v.9 no.6
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• pp.635-645
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• 2003

One of very important features that are necessarily supported by clustered parallel computer systems is a single I/O system image in which users can access both the local and remote I/O resources transparently. In this paper, we propose an efficient disk sharing technique supporting a single disk I/O system image architecture. The design separates the I/O subsystem of a cluster into the file system and a set of virtual hard disk drivers. The virtual hard disk driver deals with a hard disk in the remote node as a local hard disk. All services provided by it are performed in the device driver level without any modification of file systems. Users can, therefore, access all the disks in the cluster regardless of their locations. Our virtual hard disk driver is implemented under the linux, and also tested in a linux cluster system. We find by experiments that it can successfully support a single disk I/O space, and at the same time it shows better performance than NFS. We are sure that this paper can be a guideline for single I/O space of other devices to be easily constructed.

• Spatial Information Research
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• v.21 no.4
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• pp.63-70
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• 2013

With the increasing use of high-performance mobile devices such as smartphones, users have been able to connect to the Internet anywhere, anytime, so that Location Based Services(LBSes) have been popular among the users in order to obtain personalized information associated with their locations. The services have advanced to provide the information realistically and intuitively by adopting Augmented Reality(AR) technology, where the technology utilizes various sensors embedded in the mobile devices. However, the services have inherent problems due to the small screen size of the mobile devices and the complexity of the real world environment. Overlapping contents on a small screen and user's possible movement should be taken into consideration in displaying the icons on objects that block user's environment such as trees and buildings. The problems mainly happen when the services use only user's location and sensor data to calculate the position of the displayed information. In order to solve the problems, this paper proposes a method that applies street data extracted from a digital map. The method uses the street data as well as the location and direction data to determine contents that are placed on both sides of a virtual street which augments the real street. With scrolling the virtual street, which means a virtual movement, some information far away from the location of the user can be identified without user's actual movement. Also the proposed method is implemented for region "Aenigol", and the efficiency and usefulness of the method is verified.

• The Journal of the Korea Contents Association
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• v.16 no.8
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• pp.706-716
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• 2016

Because of efficient space utilization and fast key search times, B-trees have been widely accepted for the use of indexes in HDD-based DBMSs. However, when the B-ree is stored in flash memory, its costly operations of node updates may impair the performance of a DBMS. This is because the random updates in B-tree's leaf nodes could tremendously enlarge I/O costs for the garbage collecting actions of flash storage. To solve the problem, we make all the parents of leaf nodes the virtual nodes, which are not stored physically. Rather than, those nodes are dynamically generated and buffered by referring to their child nodes, at their access times during key searching. By performing node updates and tree reconstruction within a single flash block, our proposed B-tree can reduce the I/O costs for garbage collection and update operations in flash. Moreover, our scheme provides the better performance of key searches, compared with earlier flash-based B-trees. Through a mathematical performance model, we verify the performance advantages of the proposed flash B-tree.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.6
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• pp.1355-1360
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• 2014

In this paper, we apply the learning of the mobile robot insect augmented reality Digilog Book. In the era of electronic, book written in paper space just have moved to virtual reality space. The virtual reality, constraints spatial and physical, in the real world, it is a technique that enables to experience indirectly situation not experienced directly as user immersive experience type interface. Applied to the learning robot Digilog Book that allows the fusion of paper analog and digital content, using the augmented reality technology, to experience various interactions. Apply critical elements moving, three-dimensional images and animation to enrich the learning, for easier block assembly, designed to grasp more easily rank order between the blocks. Anywhere at any time, is capable of learning of the robot in Digilog Book to be executed by the mobile phone in particular.