• Ocean Systems Engineering
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• 제9권4호
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• pp.391-407
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• 2019

Tracking the location (position) of a surface or underwater marine vehicle is important as part of guidance and navigation. While the Global Positioning System (GPS) works well in an open sea environment but its use is limited whenever testing scaled-down models of such vehicles in the laboratory environment. This paper presents the design, development and implementation of a low energy ultrasonic augmented single beacon-based localization technique suitable for such requirements. The strategy consists of applying Extended Kalman Filter (EKF) to achieve location tracking from basic dynamic distance measurements of the moving model from a fixed beacon, while on-board motion sensor measures heading angle and velocity. Iterative application of the Extended Kalman Filter yields x and y co-ordinate positions of the moving model. Tests performed on a free-running ship model in a wave basin facility of dimension 30 m by 30 m by 3 m water depth validate the proposed model. The test results show quick convergence with an error of few centimeters in the estimated position of the ship model. The proposed technique has application in the real field scenario by replacing the ultrasonic sensor with industrial grade long range acoustic modem. As compared with the existing systems such as LBL, SBL, USBL and others localization techniques, the proposed technique can save deployment cost and also cut the cost on number of acoustic modems involved.

• 한국컴퓨터정보학회논문지
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• 제9권3호
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• pp.45-53
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• 2004

2-계층 C/S 시스템을 구성하는 경우 사용자의 응답시간이 길어지는 약점이 있다는 것이 기존의 C/S 시스템 개발자들에게는 잘 알려져 있으나 PDA등을 이용하여 모바일 환경을 제공하는 새로운 개발자들은 곧 잘 이러한 사실을 모르고 종래의 2-계층 방식으로 시스템을 구성하여 실패하는 경우가 있다. 2-계층 C/S 시스템은 개발이 용이하다는 장점을 제외하고는 응답시간, 응용프로그램의 설치. 보안, 확정성, 응용 프로그램의 재사용, 이기종 DBMS지원, 가용성 등에 많은 문제가 있다. 본 논문에서는 간단한 트랜잭션이 2-계층과 3-계층 C/S 시스템에서 작동할 때의 응답시간을 시뮬레이션 하여 분석한다. 비록 문제공간을 2-계층과 3-계층에 국한해서 시뮬레이션 했지만 도출된 결과는 다계층 시스템에서도 적용할 수 있을 것이다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권7호
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• pp.2548-2567
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• 2015

Recently, there has been a clear trend towards the application of ad hoc networking technology in civil aviation communication systems, giving birth to a new research field, namely, aeronautical ad hoc networks (AANETs). An AANET is a special type of ad hoc wireless network with a significantly larger scale and distinct characteristics of its mobile nodes. Thus, there is an urgent need to develop a simulator to facilitate the research in these networks. In this paper, we present a network simulator, Aero-Sim, for AANETs. Aero-Sim, which is based on the freely distributed NS-2 simulator, enables detailed packet-level simulations of protocols at the MAC, link, network, transport, and application layers by composing simulations with existing modules and protocols in NS-2. Moreover, Aero-Sim supports three-dimensional network deployment. Through several case studies using realistic China domestic air traffic, we show that the proposed simulator can be used to simulate AANETs and can reproduce the real world with high fidelity.

• Journal of Information Processing Systems
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• 제7권2호
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• pp.299-320
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• 2011

The overhead of processing fine-grain tasks on a grid induces the need for batch processing or task group deployment in order to minimise overall application turnaround time. When deciding the granularity of a batch, the processing requirements of each task should be considered as well as the utilisation constraints of the interconnecting network and the designated resources. However, the dynamic nature of a grid requires the batch size to be adaptable to the latest grid status. In this paper, we describe the policies and the specific techniques involved in the batch resizing process. We explain the nuts and bolts of these techniques in order to maximise the resulting benefits of batch processing. We conduct experiments to determine the nature of the policies and techniques in response to a real grid environment. The techniques are further investigated to highlight the important parameters for obtaining the appropriate task granularity for a grid resource.

• 신재생에너지
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• 제8권1호
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• pp.35-43
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• 2012

Patent analysis is the extracting knowledge which is needed for the company's research and development strategy through accumulated worldwide patent database. In order to set the future direction corresponding technology which is scheduled to be developed, the technology trends and deployment processes are identified by analyzing results of present patent applications. The patent analysis provides the required results for analyzing present patent applications. In this paper, technology classification for related patent analysis methods and system, and patent analysis for desalination technology using solar energy development was carried out as well. The patents in Korea, USA, Japan, China, and Europe were searched. The technology trend desalination technology using solar energy was analyzed based on patent application year, countries, main applications, and each technologies. The application status of desalination patents showed a tendency to increase slightly. It was found that the number of patent for applied desalination was USA patent 21.0%, Japan patent 27.0%, China 24.8%, EU 2.7% and Korea patent 24.5%, respectively.

• Journal of Korean Neurosurgical Society
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• 제51권4호
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• pp.222-226
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• 2012

The waffle-cone technique is a modified stent application technique, which involves protrusion of the distal portion of a stent into an aneurysm fundus to provide neck support for subsequent coiling. The authors report two cases of wide necked basilar bifurcation aneurysms, which were not amenable to stent assisted coiling, that were treated using the waffle-cone technique with a Solitaire AB stent. A 58-year-old woman presented with severe headache. Brain CT showed subarachnoid hemorrhage and angiography demonstrated a ruptured giant basilar bifurcation aneurysm with broad neck, which was treated with a Solitaire AB stent and coils using the waffle-cone technique. The second case involved an 81-year-old man, who presented with dizziness caused by brain stem infarction. Angiography also demonstrated a large basilar bifurcation unruptured aneurysm with broad neck. Solitaire AB stent deployment using the waffle-cone technique, followed by coiling resulted in near complete obliteration of aneurysm. The waffle-cone technique with a Solitaire AB stent can be a useful alternative to conventional stent application when it is difficult to catheterize bilateral posterior cerebral arteries in patients with a wide-necked basilar bifurcation aneurysm.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제16권6호
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• pp.722-726
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• 2010

최근 RIA(Rich Internet Application)의 등장으로 인해 자바스크립트 코드의 복잡도가 증가함에 따라 이를 위한 고성능 자바스크립트 엔진들이 경쟁적으로 발표되고 있다. 또한 이들 엔진의 성능 측정을 위한 도구로서 SunSpider 벤치마크가 널리 사용되고 있다. 본 논문에서는 대표적인 고성능 자바스크립트 엔진인 Mozilla의 Trace-Monkey, Google의 V8, 그리고 Apple의 SquirrelFish Extreme에 대해 자바스크립트 코드 수행 방식을 비교하고 SunSpider 벤치마크를 이용해 각 엔진의 성능을 측정한다. 또한 각 엔진들의 수행 방식과 SunSpider 각각의 코드 특성을 토대로 하여 성능 결과를 분석하여 각 엔진의 장단점을 평가한다.

• Journal of Korean Neurosurgical Society
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• 제48권6호
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• pp.485-489
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• 2010

Objective : To introduce the frequency and segment analysis of in-stent stenosis for intracranial stent assisted endovascular treatment on complex aneurysms. Methods : A retrospective study was performed in 158 patients who had intracranial complex aneurysms and were treated by endovascular stent application with or without coil embolization. Of these, 102 patients were evaluated with catheter based angiography after 6, 12, and 18 months. Aneurysm location, using stent, time to stenosis, stenosis rate and narrowing segment were analyzed. Results : Among follow-up cerebral angiography done in 102 patients, 8 patients (7.8%) were shown an in-stent stenosis. Two patients have unruptured aneurysm and six patients have ruptured one. Number of Neuroform stents were 7 cases (7.5%) and Enterprise stent in 1 case (11.1%). Six patients demonstrated in-stent stenosis at 6 months after stent application and remaining two patients were shown at 12 months, 18 months, respectively. Conclusion : In-stent stenosis can be confronted after intracranial stent deployment. In our study, no patient showed symptomatic stenosis and there were no patients who required to further treatment except continuing antiplatets medication. In-stent stenosis has been known to be very few when they are placed into the non-pathologic parent artery during the complex aneurysm treatment, but the authors found that it was apt to happen on follow up angiography. Although the related symptom was not seen in our cases, the luminal narrowing at the stented area may result the untoward hemodynamic event in the specific condition.

• 정보처리학회논문지D
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• 제8D권6호
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• pp.637-644
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• 2001

컴포넌트 기반 애플리케이션의 개발 및 배치를 위한 명세를 제공하는 EJB(Enterprise JavaBeans)는 엔터프라이즈 환경에서 가장 복잡한 트랜잭션 관리, 퍼시스턴스, 동시성 제어 등을 자동적으로 관리해주는 J2EE 환경의 핵심으로서 분산개발을 가능하게 한다. 본 논문에서는 EJB 기반 레거시 시스템에서 DAO의 트랜잭션 로직 복잡성과 시스템의 성능저하 문제를 해결하고자 한다. 따라서, 본 논문에서는 Iterator 패턴을 적용한 IDAO를 설계 및 구현하였다. IDAO는 컨테이너 관리 트랜잭션을 통해 데이터베이스 커넥션에 따른 트랜잭션 로직의 복잡성과 시스템의 과부하 감소 및 시스템의 성능저하를 감소시키는 효과를 얻었다.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2014년도 추계학술발표대회
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• pp.516-519
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• 2014

Cloud computing is an up-and-coming paradigm shift transforming computing models from a technology to a utility. However, security concerns related to privacy, confidentiality and trust are among the issues that threaten the wide deployment of cloud computing. With the advancement of ubiquitous mobile-based clients, the ubiquity of the model suggests a higher integration in our day to day life and this leads to a rise in security issues. To strengthen the access control of cloud resources, most organizations are acquiring Identity Management Systems (IDM). This paper presents one of the most popular IDM systems, specifically OAuth, working in the scope of Mobile Cloud Computing which has many weaknesses in its protocol flow. OAuth is a Delegated Authorization protocol, and not an Authentication protocol and this is where the problem lies. This could lead to very poor security decisions around authentication when the basic OAuth flow is adhered to. OAuth provides an access token to a client, so that it can access a protected resource, based on the permission of the resource owner. Many researchers have opted to implement OpenlD alongside OAuth so as to solve this problem. But OpenlD similarly has several security flows. This paper presents scenarios of how insecure implementations of OAuth can be abused maliciously. We incorporate an authentication protocol to verify the identities before authorization is carried out.