• Journal of Advanced Marine Engineering and Technology
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• v.41 no.1
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• pp.62-69
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• 2017

This paper presents a methodology for evaluating the performance of wall-climbing robots. In the literature on wall-climbing robots, there is little information on indices and evaluation methods for consistent and exact performance. Because various types of wall-climbing robots can be developed with regard to adherence and locomotion, a general method of measuring their performance regardless of type is needed. Therefore, we propose two major performance indices-the vertical adhering weight and vertical climbing speed-and their stepwise evaluation procedures. To verify the effectiveness of the proposed method, we applied it to a hull-climbing robot that we previously developed. The target robot was evaluated to have a vertical adhering weight of 18.5 kg through a slip measurement procedure and a vertical climbing speed of 41 cm/s with a position control system.

• Journal of the Korean Vacuum Society
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• v.16 no.5
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• pp.311-321
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• 2007

We have researched the chemical defects of NiO ultrathin films grown on Ag(001) by x-ray photoelectron spectroscopy. In particular, O 1s and Ni 2p spectra were analyzed consistently with control film thickness, $O_2\;and\;H_2O$ partial pressure and substrate temperature. As a result, we could identify each chemical defect. In addition, we suggest the optimum growth condition to minimize the defect density.

• Proceedings of the KAIS Fall Conference
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• 2006.05a
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• pp.517-521
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• 2006

네트워크 가상현실 시스템은 먼 거리에 떨어진 사용자들 사이에 일관성 있는 가상 세계를 제공하며, 군사, 오락, 건축 등 여러 부분에 응용되고 있다. 본 논문에서는 그 동안 고성능 그래픽 워크스테이션 환경에서 중심적으로 연구되어 왔던 네트워크 가상현실 시스템을 가장 보편적인 플랫폼인 네트워크 환경에서 구현할 때 생기는 3차원 그래픽 처리 성능의 문제 등과 같은 이에 대한 해결책들을 제시하고 미로 환경과 지형 환경에 근거한 가상 세계를 응용 실험 대상으로 삼아 성능을 분석하였다. 실시간으로 상호 작용하는 어플리케이션은 성능을 유지하면서 모든 참가자들에게 동일한 뷰를 보여주는 것이 중요하다. 동일한 뷰를 제공하기 위해 참가자들이 전송하는 이벤트마다 재생 지연 시간을 설정하고, 수신한 이벤트에 대해서는 예정 재생 시각까지 버퍼에 저장하여 모든 참가자들이 동시에 이벤트를 실행하도록 하는 기법이 제안되어 왔다. 그러나 네트워크 트래픽이 동적으로 변하므로 네트워크 상에서 발생하는 전송 지연 시간도 동적으로 변화한다. 그러므로 고정된 재생 지연 시간을 사용할 경우, 네트워크 트래픽 감소에 따라 상호 작용 성능을 향상시킬 수 있는 기회를 상실하게 되고, 네트워크 트래픽 증가에 따라 이벤트 손실률이 크게 증가하게 되어 참가자들 간에 일치하지 않는 뷰를 초래하게 된다. 네트워크 트래픽이 적어서 전송 지연 시간이 짧을 경우 짧은 재생 지연 시간을 적용하여 상호작용 성능을 높여주고, 트래픽이 많은 경우에는 재생 지연 시간을 늘림으로써 상호 작용 성능을 해치지 않는 범위에서 이벤트 손실률을 줄인다. 실험을 통하여 제안하는 기법의 성능을 평가하였으며 그 결과 본 동기화 기법이 고부하(heavily loaded) 네트워크 상태가 지속되는 동안 기존 기법에 비해 참가자들에게 일치된 뷰를 제공할 수 있고, 저부하(lightly loaded) 네트워크 상태에서는 상호 작용 성능을 향상시킬 수 있다는 것을 확인하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.11
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• pp.2418-2423
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• 2012

A smart phone which is one of the new IT technologies can be viable on various enterprise applications since it provides easily information and services. Especially, a smart phone can request queries to a server which finds massive data for decision making and receive the results of the queries from the server. However, a smart phone has a drawback that its battery is consumed easily due to the 4G communication. In this paper, we propose mobile views in order to reduce the easy consumption of a battery on mobile client-server environment. The proposed mobile view scheme reduces the number of communication which is leading to power consumption using materialized views for processing queries. We also classify the methods to control the consistency of the mobile view as the sources of the view are changed and present the cost of each method based on the cost model of battery consumption.

• The KIPS Transactions:PartD
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• v.8D no.3
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• pp.265-272
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• 2001

In case of implementing a complicated application like WAP (Wireless Application Protocol) in a mobile terminal with the characteristics of bare machine and versatile kernel aspects of which are control, interrupt and IPC(Inter Process Communication), a special methodology should be needed. If not, it will cause more cost and human resources, even delayed product into launching for the time-to-market. This paper suggests AKL, (Abstract Kernel Layer) for the design and implementation of WAP on basis of multi-platform. AKL is running on the various kernel including REX, MS-DOS, MS-Window, UNIX and LINUX. For the purpose of it, AKL makes machine-dependant features be minimized and supports a consistent interface on API (Application Program Interface) point of view. Therefore, it makes poring times of a device be shorten and makes easy of maintenance. We validated our suggestion as a consequent of porting WAP into PlamV PDA and mobile phone with AKL.

• The Transactions of the Korea Information Processing Society
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• v.7 no.10
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• pp.3171-3181
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• 2000

With a remarkable growth and expansionof Internet, the security issues emerged from intrusions and attacks such as computer viruses, dental of servives and backings to destroy intormation have been considered as serious threats for Internet and the provate networks. To protect networks from those attacks, many nendors have developed various security systems such as firewalls, intrusion detection systems, and access control systems. However managing those systems individually requres too much work and high cost. Thus, integrated security managemanet and eatabliashment of consistent security policy for various security products has become more important. In this paper, we propose integrated security manabement system called WISMSF(Web based Integrated Security Management System for Fireswalls) to monitor and contro various kinds of firewalls WISMSF consists of three components-clients, integrated engine, and agents. It supports the transparent management functions of security products, easy ways of defining security policies, and simple expansion of managed ranges.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.12
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• pp.16-22
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• 2020

The characteristics of the LCL filter for grid-connected inverters have been discussed in academia and industry. An online simulation tool was applied to compare and analyze the difference between the LCL filter and L filter. LCL filters were modeled and simulated using a range of professional simulation simulators, and the LCL filters were found to have good filtering effects for high-frequency harmonics. First, this paper summarizes the transfer functions of the LCL filter and provides the Bode plot diagram. The accuracy and validity of the filter attenuation characteristics were confirmed by a fast Fourier transform based on off-line simulation tools, such as PSIM and MATLAB, depending on the given parameters of the LCL filter. Finally, the Typhoon HIL402 real-time simulation was performed for hardware in the loop simulation to verify the actual filtering characteristics of the LCL filter.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.1
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• pp.157-164
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• 2023

In modern society, smart home has become a part of people's daily life. But traditional smart home systems often have problems such as security, data centralization and easy tampering, so a blockchain is an emerging technology that solves the problems. This paper proposes a blockchain-based smart home system which consists in a home and a blockchain network part. The blockchain network with 8 nodes is implemented by HyperLeger Fabric platform on Docker. ECC(Elliptic Curve Cryptography) technology is used for data transmission security and RBAC(role-based access control) manages the certificates of network members. Raft consensus algorithm maintains data consistency across all nodes in a distributed system and reduces block generation time. The query and data submission are controlled by the smart contract which allows nodes to safely and efficiently access smart home data. The experimental results show that the proposed system maintains a stable average query and submit time of 84.5 [ms] and 93.67 [ms] under high concurrent accesses, respectively and the transmission data is secured through simulated packet capture attacks.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.34 no.2
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• pp.229-244
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• 2024

Recently, supply chain attacks against nuclear facilities such as "Evil PLC" are increasing due to the application of digital technology in nuclear power plants such as the APR1400 reactor. Nuclear supply chain security requires a asset management system that can systematically manage a large number of providers due to the nature of the industry. However, due to the nature of the control system, there is a problem of inconsistent management of attribute information due to the long lifecycle of software assets. In addition, due to the availability of the operational technology, the introduction of automated configuration management is insufficient, and limitations such as input errors exist. This study proposes a systematic asset management system using SBOM(Software Bill Of Materials) and an improvement for input errors using natural language processing techniques.

• Journal of KIISE:Databases
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• v.30 no.1
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• pp.64-79
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• 2003

In client-server computing environments, update transactions of spatial data have the following characteristics. First, a transaction to update maps needs interactive work, and therefore it nay take a long time to finish. Second, a long transaction should be allowed to read the dirty data to enhance parallelism of executing concurrent transactions. when %he transaction is rolled back, it should guarantee the cascading rollback of all of the dependent transactions. Finally, two spatial objects may have a weak dependency constraint, called the spatial relationship, based on geometric topology. The existing recovery approaches cannot be directly applied to this environment, due to the high rollback cost and the overhead of cascading rollbacks. Furthermore, the previous approaches cannot guarantee the data integrity because the spatial relationship, which is a new consistency constraint of spatial data, is not considered. This paper presents new recovery schemes for update transactions of spatial data. To guarantee the data integrity, this paper defines recovery dependency as a rendition of cascading rollbacks. The partial-rollback is alto suggested to solve the problem of high rollback cost. The recovery schemes proposed in this paper can remove the unnecessary cascading rollbacks by using undo-delta, partial -redo and partial-undo. Finally, the schemes are performed to ensure the correctness.