• Structural Engineering and Mechanics
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• 제42권6호
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• pp.849-866
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• 2012

Single span historic bridges often contain non-prismatic members identified with a varying depth along their span lengths. Commonly, the symmetric parabolic height variations having the constant haunch length ratio of 0.5 have been selected to lower the stresses at the high bending moment points and to maintain the deflections within the acceptable limits. Due to their non-prismatic geometrical configuration, their assessment, particularly the computation of fixed-end horizontal forces (FEFs) and fixed-end moments (FEMs) becomes a complex problem. Therefore, this study aimed to investigate the behavior of non-prismatic beams with symmetrical parabolic haunches (NBSPH) having the constant haunch length ratio of 0.5 using finite element analyses (FEA). FEFs and FEMs due to vertical loadings as well as the stiffness coefficients and the carry-over factors were computed through a comprehensive parametric study using FEA. It was demonstrated that the conventional methods using frame elements can lead to significant errors, and the deviations can reach to unacceptable levels for these types of structures. Despite the robustness of FEA, the generation of FEFs and FEMs using the nodal outputs of the detailed finite element mesh still remains an intricate task. Therefore, this study advances to propose effective formulas and dimensionless estimation coefficients to predict the FEFs, FEMs, stiffness coefficients and carry-over factors with reasonable accuracy for the analysis and re-evaluation of the NBSPH. Using the proposed approach, the fixed-end reactions due to vertical loads, and also the stiffness coefficients and the carry-over factors of the NBSPH can be determined without necessitating the detailed FEA.

• International Journal of Computer Science & Network Security
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• 제22권2호
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• pp.167-174
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• 2022

Vehicular Ad hoc Networks are considered as special kind of Mobile Ad Hoc Networks. VANETs are a new emerging recently developed, advanced technology that allows a wide set of applications related to providing more safety on roads, more convenience for passengers, self-driven vehicles, and intelligent transportation systems (ITS). Delay Tolerant Networks (DTN) are networks that allow communication in the event of connection problems, such as delays, intermittent connections, high error rates, and so on. Moreover, these are used in areas that may not have end-to-end connectivity. The expansion from DTN to VANET resulted in Vehicle Delay Tolerant Networks (VDTN). In this approach, a vehicle stores and carries a message in its buffer, and when the opportunity arises, it forwards the message to another node. Carry-store-forward mechanisms, packets in VDTNs can be delivered to the destination without clear connection between the transmitter and the receiver. The primary goals of routing protocols in VDTNs is to maximize the probability of delivery ratio to the destination node, while minimizing the total end-to-end delay. DTNs are used in a variety of operating environments, including those that are subject to failures and interruptions, and those with high delay, such as vehicle ad hoc networks (VANETs). This paper discusses DTN routing protocols belonging to unicast delay tolerant position based. The comparison was implemented using the NS2 simulator. Simulation of the three DTN routing protocols GeOpps, GeoSpray, and MaxProp is recorded, and the results are presented.

• 한국통신학회논문지
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• 제34권3B호
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• pp.274-287
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• 2009

최선형 서비스를 제공하는 인터넷 환경에서 다양한 서비스 품질 요구사항을 가지는 서비스들을 제공하기 위해서는 홉 성능이 아닌 종단 간 성능을 보장해야 한다. 종단 간 성능은 트래픽 흐름의 경로를 따라 많은 요인들에 의하여 영향을 받는다. 대부분의 기존 모의실험은 단일 노드나 몇 개의 노드에 대한 성능을 구하는 것으로 한정되어 있다. 대규모 망의 모의실험을 위하여 모의실험 실행 시간을 고려한 상당히 다른 방법이 필요하다. 본 논문에서는 대규모 망의 모의실험을 위하여 시뮬레이터 구현을 위한 요구사항을 도출하고 모의실험 방법을 제시한다. OPNET을 이용하여 도출한 모의실험 방법에 대한 시뮬레이터를 설계하고 구현한다. 구현된 시뮬레이터를 이용하여 대규모 초고속 국가 망에 대한 성능 평가를 수행한다. 자기유사 트래픽 모델을 사용하여, 대규모 망에 대한 종단 간 성능에 대한 몇 가지 결과를 제시한다.

• Perspectives in Nursing Science
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• 제5권1호
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• pp.17-31
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• 2008

Purpose: The purpose of this study was to evaluate the usability of a prototype personal digital assistant (PDA)-based decision support system for the management of obesity through usability testing with end-users (Advanced Practice Nurses [APNs]) prior to its implementation in clinical settings. Methods: This descriptive study used observational and think aloud techniques to address the research question: what usability problems are perceived by end-users? Five APNs were provided with the scenarios and the list of tasks to evaluate the application. Their verbalizations were recorded through Morae usabil ity software. Data analysis was based on the data captured through Morae, transcriptions, notes, and the end-user survey. Results: End-users completed all the required tasks without encountering a severe usability problem, and agreed that the system was easy to use. clear, concise, and useful. Usability issues that were unrecognized by the developer or usability experts were identified by APNs. The usability problems were categorized according to positive characteristics, negative characteristics, and recommendations. The usability issues were discussed with the project team members, and solutions were suggested to improve the user interface of the PDA-based decision support system before the final implementation. Conclusions: This approach had an important impact on making the system easier to use and more useful from the perspective of design and content. The results of this evaluation provided iterative feedback regarding the design and implementation of the PDA-based decision support system for the management of obesity.

• 소성∙가공
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• 제16권1호
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• pp.15-19
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• 2007

This paper presents an integrated machining error compensation method based on captured images of tool deflection shapes in flat end-milling processes. This approach allows us to avoid modeling machining characteristics (cutting forces, tool deflections and machining errors etc.) and accumulating calculation errors induced by several simulations. For this, a high-speed camera captured images of real deformed tool shapes which were cutting under given machining conditions. Using image processes and a machining error model, it is possible to estimate tool deflection in cutting conditions modeled and to compensate for machining errors using an iterative algorithm correcting tool paths. This corrected tool path can effectively reduce machining errors in the flat end-milling process. Experiments are carried out to validate the approaches proposed in this paper. The proposed error compensation method can be effectively implemented in a real machining situation, producing much smaller errors.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.468-470
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• 2007

This paper is to present an approach for generating coarse resolution (MODIS data) fraction images of forested region in Korea peninsula using forest type area fraction derived from high resolution data (ASTER data) in regional forest area. A 15-m spatial resolution multi-spectral ASTER image was acquired under clear sky conditions on September 22, 2003 over the forested area near Seoul, Korea and was used to select each end-member that represent a pure reflectance of component of forest such as different forest, bare soil and water. The area fraction of selected each end-member and a 500-m spatial resolution MODIS reflectance product covering study area was applied to a linear mixture inversion model for calculating the fraction image of forest component across the South Korea. We found that the area fraction values of each end-member observed from high resolution image data could be used to separate forest cover in low resolution image data.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2011년도 한국컴퓨터종합학술대회논문집 Vol.38 No.1(D)
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• pp.131-134
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• 2011

Several Web Service security standards are widely utilized aiming at securing exchanges of SOAP messages among partners in a collaborative environment. Although such standards are suitable for ensuring end-to-end message level security, certain attacks such as XML rewriting may still occur and lead to significant security vulnerabilities. This paper explores the security vulnerabilities of SOAP messages and proposes an ontology-based approach that can successfully combat the security threats. We develop ontology-based schema to include SOAP structure information in outgoing SOAP message and validate this information in the receiving end. Thus, allow to detect XML rewriting attacks early in the validating process.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권9호
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• pp.3496-3514
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• 2015

One of the challenging tasks in Mobile Ad hoc Network is to discover precise optimal routing solution due to the infrastructure-less dynamic behavior of wireless mobile nodes. Ant Colony Optimization, a swarm Intelligence technique, inspired by the foraging behaviour of ants in colonies was used in the past research works to compute the optimal path. In this paper, we propose a Recurrent Ant Colony Optimization (RECACO) that executes the actual Ant Colony Optimization iteratively based on recurrent value in order to obtain an optimal path convergence. Each iteration involves three steps: Pheromone tracking, Pheromone renewal and Node selection based on the residual energy in the mobile nodes. The novelty of our approach is the inclusion of new pheromone updating strategy in both online step-by-step pheromone renewal mode and online delayed pheromone renewal mode with the use of newly proposed metric named ELD (Energy Load Delay) based on energy, Load balancing and end-to-end delay metrics to measure the performance. RECACO is implemented using network simulator NS2.34. The implementation results show that the proposed algorithm outperforms the existing algorithms like AODV, ACO, LBE-ARAMA in terms of Energy, Delay, Packet Delivery Ratio and Network life time.

• Journal of Chest Surgery
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• 제18권3호
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• pp.497-505
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• 1985

Bronchoplastic techniques represent the ideal surgical therapy for benign endobronchial tumors as well as tumors of low-grade malignant potential, such as bronchial adenomas, and for repair of traumatic airway injuries and benign strictures. This approach is also applicable to a select group of patients with carcinoma of the lung, with long-term survival being comparable to that achieved by standard pneumonectomy. Five bronchoplastic procedures were performed at Department of Thoracic and Cardiovascular Surgery, Seoul National University Hospital during 7 months periods from Dec. 1984 to Jun. 1985. Of the 5 patients, 3 patients were male and 2 patients were female and ages ranged from 8 years to 55 years old. The final diagnoses of 5 patients were as followed; traumatic bronchostenosis, endobronchial tuberculoma, carcinoid tumor, tuberculous bronchostenosis and traumatic bronchial fracture. Operative procedures of 5 patients were as followed; resection and end-to-end anastomosis of right main bronchus, left lower lobectomy and wedge resection of bronchus, left upper sleeve lobectomy, right middle and lower sleeve lobectomy and resection and end-to-end anastomosis of left main bronchus. And 2 lungs and 3 lobes could be preserved by these bronchoplastic procedures. There was no post-operative complication or mortality and all patients are being followed up without specific problem.

• Journal of Positioning, Navigation, and Timing
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• 제8권4호
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• pp.153-164
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• 2019

This paper presents the development of an end-to-end numerical simulator for signal design of the next generation global navigation satellite system (GNSS). The GNSS services are an essential element of modern human life, becoming a core part of national infra-structure. Several countries are developing or modernizing their own positioning and timing system as their demand, and South Korea is also planning to develop a Korean Positioning System (KPS) based on its own technology, with the aim of operation in 2034. The developed simulator consists of three main units such as a signal generator, a channel unit, and a receiver. The signal generator is constructed based on the actual navigation satellite payload model. For channels, a simple Gaussian channel and land mobile satellite (LMS) multipath channel environments are implemented. A software receiver approach based on a commercial GNSS receiver model is employed. Through the simulator proposed in this paper, it is possible to simulate the entire transceiver chain process from signal generation to receiver processing including channel effect. Finally, numerical simulation results for a simple example scenario is analyzed. The use of the numerical signal simulator in this paper will be ideally suited to design a new navigation signal for the upcoming KPS by reducing the research and development efforts, tremendously.