• 제어로봇시스템학회논문지
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• 제7권11호
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• pp.891-895
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• 2001

An alternative inverse feedback structure for adaptive active control of periodic noise is introduced for systems with nonminimum phase cancellation path. To obtain the inverse model of the nonminimum phase cancellation path, the cancellation path model can be factorized into a minimum phase term and a maximum phase term. The maximum phase term containing unstable zeros makes the inverse model unstable. To avoid the instability, we alter the inverse model of the maximum phase system into an anti-causal FIR one. An LMS predictor estimates the future samples of the noise, which are necessary for causality of both anti-causal FIR approximation for the stable inverse of the maximum phase system and time-delay existing in the cancellation path. The proposed method has a faster convergence behavior and a better transient response than the conventional filtered-x LMS algorithms with the same internal model control structure since a filtered reference signal is not required. We compare the proposed methods with the conventional methods through simulation studies.

• International Journal of Naval Architecture and Ocean Engineering
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• 제8권1호
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• pp.38-52
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• 2016

This paper describes the nonlinear dynamic motion behavior of a ship equipped with a portable dynamic positioning (DP) control system, under external forces. The waves, current, wind, and drifting forces were considered in the calculations. A self-tuning controller based on a neuro-fuzzy algorithm was used to control the rotation speed of the outboard thrusters for the optimal adjustment of the ship position and heading and for path tracking. Time-domain simulations for ship motion with six degrees of freedom with the DP system were performed using the fourth-order RungeeKutta method. The results showed that the path and heading deviations were within acceptable ranges for the control method used. The portable DP system is a practical alternative for ships lacking professional DP facilities.

• 대한교통학회지
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• 제22권2호
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• pp.131-143
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• 2004

최적경로 알고리즘에서 링크표지를 활용하면 도시가로망 상에 나타나는 유턴이나 피턴과 같은 주행했던 교차로를 다시 주행하는 통행에 대한 설명이 가능하다. 본 연구에서는 링크표지기법을 표지갱신기반 다수경로탐색알고리즘으로 확대하는 것이 목적이다. 이를 위해 도시가로망에서 발생하는 운전자의 합리적 통행행태를 링크기반으로 개념화하고, 이들 행태가 반영되도록 링크표지갱신 다경로 알고리즘을 제안하였다. 소규모 네트워크 테스트를 통하여 알고리즘의 수행과정과 결과의 적정성을 확인하였다. 대규모 네트워크 컴퓨터 수행을 통해 해의 퇴화현상을 파악하고 소수의 대안경로 정보제공에 활용 가능한 (K-1)차원 알고리즘을 제안하였다. 결론적으로 제안된 다수경로 알고리즘으로 링크표지기법이 제공하는 합리적 통행행태의 고려가 다수의 경로에도 가능해졌을 뿐만 아니라, 효율적인 대안경로 제공의 활용단계를 위해 한단계 전진되었다.

• 대한세포병리학회지
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• 제18권2호
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• pp.143-152
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• 2007

Sono-guided fine needle aspiration (FNA) of the thyroid is widely used, but the aspirated samples are typically not well preserved and low cellularity makes diagnosis difficult in many cases. The object of the current study is to evaluate the adequacy and diagnostic accuracy of the use of $SurePath^{TM}$ liquid-based cytology (SP-LBC) in the sonoguided fine needle aspiration of the thyroid nodule and to compare its use with that of the use of a conventional smear (CS). A total of 172 sono-guided FNAs of thyroid nodules from April to June, 2006 were prepared by the use of the split method with either SP-LBC or CS; the samples were stained with the use of hematoxylin-eosin (H&E) and Papanicolaou (Pap) stains. A cyto-histological correlation was performed in 69 (30 SP and 39 CS) cases that had been histologically confirmed. The rate of producing unsatisfactory slides by the use of the SP-LBC method (9.3%) was less than that of the use of the CS method (20.9%). The diagnostic accuracy of the SP method (93.3%) was better than that of the CS method (85.3%). The sensitivity and specificity of the SP method (94.4% and 92.3%) was better than that of the CS method (83.3% and 70%), respectively (p < 0.05). The CS of sono-guided aspirated specimens had some unavoidable limitations related to inadequate sampling such as a bloody background, low cellularity and an indication that some clinicians smeared many useless slides (averaging four to ten slides), and that most slides showed only blood that included few follicular cells. The SP method resulted in more thinly smeared slides and showed cleaner background and greater cellularity than the use of the CS method. Each follicular cell shows superior nuclear detail, and more distinct cytoplasmic features than with the use of the CS method. SP-LBC appears to be an easy, highly accurate, and reliable cytological method for employ for a diagnostic approach of thyroid disease and thyroid nodules. The SP-LBC method is a suitable alternative to the CS method to overcome diagnostic difficulties.

• 디지털산업정보학회논문지
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• 제17권4호
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• pp.109-120
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• 2021

Despite the growing online exposure of retailes, offline retail channels still outperform online channels in the total retail volume of some countries. There is much interest in the physical layout plans of retail stores to expand sales. Product placement that have a large impact on customer purchasing behavior at offline retailers influences customer movement and sales volume. But in many cases, each retailer relies on unsystematic and autonomous product placement. When multiple products are sold with one purchase, the customer's movement for shopping may be evaluated in terms of customer efficiency and additional impulse purchase. In this paper, the social network is applied to sales data of a retail store and the result is used for evaluation of product placement and customer path. The frequent sales product composition was identified using k-core from sales data in the form of shopping baskets. The location was checked for the identified compositions of products, the spatial variance was measured and the customer's path was identified. With these results, the store arrangement of products was evaluated with appropriate improvement directions. The analysis method of this paper can be an alternative analysis approach for better layout of retail stores.

• 국제학술발표논문집
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• The 6th International Conference on Construction Engineering and Project Management
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• pp.114-116
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• 2015

This paper presents a Stochastic Time-Cost Tradeoff analysis system (STCT) that identifies optimal construction methods for activities, hence reducing the project completion time and cost simultaneously. It makes use of schedule information obtained from critical path method (CPM), applies alternative construction methods data obtained from estimators to respective activities, computes an optimal set of genetic algorithm (GA) parameters, executes simulation based GA experiments, and identifies near optimal solution(s). A test case verifies the usability of STCT.

• International Journal of Computer Science & Network Security
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• 제21권8호
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• pp.17-27
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• 2021

Non-abelian group based cryptosystems are a latest research inspiration, since they offer better security due to their non-abelian properties. In this paper, we propose a novel approach to non-abelian group based public-key cryptographic protocols using semidirect products of finite groups. An intractable problem of determining automorphisms and generating elements of a group is introduced as the underlying mathematical problem for the suggested protocols. Then, we show that the difficult problem of determining paths and cycles of Cayley graphs including Hamiltonian paths and cycles could be reduced to this intractable problem. The applicability of Hamiltonian paths, and in fact any random path in Cayley graphs in the above cryptographic schemes and an application of the same concept to two previous cryptographic protocols based on a Generalized Discrete Logarithm Problem is discussed. Moreover, an alternative method of improving the security is also presented.

• 소성∙가공
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• 제31권3호
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• pp.143-150
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• 2022

The purpose of this study was to investigate an innovative hydroforming process for the cost-effective manufacturing of double layered tube with circumferentially corrugated patterns. Conventional double pipe heat exchanger has relatively poor heat transfer efficiency because of the limited contact area resulting from the concentrically arranged simple cylindrical structure. As a promising alternative to enhance heat transfer efficiency, double layered tube with corrugated internal pattern was considered in this study. To fabricate corrugated inner tube, innovative tube hydroforming system was developed. The customized loading paths were established using the simulated forming pressure and contracting stroke at various bar diameters. Experimentally obtained cross-sectional profiles were analyzed to evaluate the reliability and applicability of the hydroformed tube with various patterns. The results demonstrate that the proposed hydroforming process can be a feasible alternative for manufacturing high-performance double-tube heat exchangers.

• Journal of Ecology and Environment
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• 제35권2호
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• pp.141-147
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• 2012

The rapid urbanization in developing countries is accelerating both the depletion and fragmentation of urban green space, despite the known positive effects of green spaces on the environmental conditions in cities and the quality of life of residents. Consequently, there is a need for practical tools that can support the development of networks of urban green spaces. This article presents a study that used a GIS-based least cost path (LCP) analysis to identify the best alternative for developing an urban green space network in the coastal city of Jakarta, Indonesia, which was based on the evaluation of topography and land use characteristics. Pair-wise analysis was used to reduce the sensitivity in the LCP model. The results showed that the coastal wetlands in the northern part of Jakarta and the agricultural fields in the suburban areas of Jakarta play an important role in connecting the green space network. On the other hand, some green spaces in the central part of Jakarta could not be connected by the LCP model. The method used in this study can serve as a tool to support the identification of networks of potential urban green spaces. It can also provide useful information for sustainable urban landscape planning and management in urban ecosystems. However, the inclusion of socio-economic criteria would further improve the model.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권2호
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• pp.679-687
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• 2019

This paper presents the autonomous swimming technology developed for an Autonomous Underwater Vehicle (AUV) operating in the underwater jacket structure environment. To prevent the position divergence of the inertial navigation system constructed for the primary navigation solution for the vehicle, we've developed kinds of marker-recognition based underwater localization methods using both of optical and acoustic cameras. However, these two methods all require the artificial markers to be located near to the cameras mounted on the vehicle. Therefore, in the case of the vehicle far away from the structure where the markers are usually mounted on, we may need alternative position-aiding solution to guarantee the navigation accuracy. For this purpose, we develop a sonar image processing based underwater localization method using a Forward Looking Sonar (FLS) mounted in front of the vehicle. The primary purpose of this FLS is to detect the obstacles in front of the vehicle. According to the detected obstacle(s), we apply an Occupancy Grid Map (OGM) based path planning algorithm to derive an obstacle collision-free reference path. Experimental studies are carried out in the water tank and also in the Pohang Yeongilman port sea environment to demonstrate the effectiveness of the proposed autonomous swimming technology.