• 한국시뮬레이션학회논문지
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• 제19권4호
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• pp.161-167
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• 2010

유-헬스케어(U-Healthcare)에서 이동 환자 상태에 대한 모니터링 기술은 필수적이다. 모니터링 기술에서는 이동 환자의 생체 정보가 동적 위치 정보와 함께 정해진 목적지 서버로 전송되어야 하는데 모니터링할 환자의 수가 증가하며 각 환자의 이동성이 불규칙함에 따라 적절한 부하균형 단계가 중간에 필요해진다. 토르소(Torus) 구조를 기반으로 한 이동 환자 상시 모니터링 시스템에서는 이를 반영하여 먼저 환자 생체 정보를 중간노드로 전송한 후 부하균형 기반의 우선순위 정책에 따라 목적지 서버로 연이어 전송된다. 본 논문에서는 계층적이며 객체지향적인 정형화 명세를 기반으로 하는 시스템 명세 기법을 사용하여 이러한 이동 환자 상시 모니터링 시스템의 전체 구조와 구성 노드들의 결합 관계를 정의한 후 각 요소의 기능을 유사코드로 설계함으로써 본 시스템이 효과적인 환자 정보 수집과 전송, 분배 및 판단에 효율적임을 시스템 명세 기법을 통하여 검증한다.

• 자동차안전학회지
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• 제15권2호
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• pp.42-48
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• 2023

In recent years, automated vehicles have garnered attention in the multidisciplinary research field, promising increased safety on the road and new opportunities for passengers. High-Definition (HD) maps have been in development for many years as they offer roadmaps with inch-perfect accuracy and high environmental fidelity, containing precise information about pedestrian crossings, traffic lights/signs, barriers, and more. Demonstrating autonomous driving requires verification of driving on actual roads, but this can be challenging, time-consuming, and costly. To overcome these obstacles, creating HD maps of real roads in a simulation and conducting virtual driving has become an alternative solution. However, existing HD maps using high-precision data are expensive and time-consuming to build, which limits their verification in various environments and on different roads. Thus, it is challenging to demonstrate autonomous driving on anything other than extremely limited roads and environments. In this paper, we propose a new and simple method for implementing HD maps that are more accessible for autonomous driving demonstrations. Our HD map combines the CARLA simulator and OpenStreetMap (OSM) data, which are both open-source, allowing for the creation of HD maps containing high-accuracy road information globally with minimal dependence. Our results show that our easily accessible HD map has an accuracy of 98.28% for longitudinal length on straight roads and 98.42% on curved roads. Moreover, the accuracy for the lateral direction for the road width represented 100% compared to the manual method reflected with the exact road data. The proposed method can contribute to the advancement of autonomous driving and enable its demonstration in diverse environments and on various roads.

• 한국지반공학회논문집
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• 제31권7호
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• pp.13-28
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• 2015

본 연구에서는 잔류간극수압의 추정에 관한 기존의 해석해에서 지적된 오류를 수정한 Lee et al.(2015a)의 연구결과를 진행파와 흐름의 공존장으로 확장한다. 이 때, 흐름이 없는 경우를 대상으로 한 Lee et al.(2015a)의 이론결과에 흐름에 의한 입사파의 주기와 파장의 변화를 고려하여야 한다. 검증에서는 Laplace 변환법으로부터 무한 두께의 경우에 대해서만 해를 제시한 Jeng and Seymour(2007)의 해석해와 Fourier 급수전개법에 의한 본 해석해의 두 결과를 비교하여 각각 상이한 형태를 갖는 두 해석해의 결과가 완전히 동일하다는 것을 확인할 수 있었다. 따라서, 유한, 무한 및 얕은 두께의 해저지반에 대한 각 해석해에 흐름속도의 크기와 방향, 지반두께 및 입사파 주기 등을 변화시켜 잔류간극수두의 변화특성을 면밀히 분석 검토하였다. 제시되는 각 해석해에서 지반두께의 변화에 의해 유한 두께의 토층에서 얕은 두께로의 점근적인 접근은 가능하지만, 무한 두께로의 접근은 불가능하며, 유한 두께와 무한 두께의 사이에는 동일한 토층 두께에 대해서도 서로의 결과가 일치하지 않는 경우가 있다는 것을 확인할 수 있었다.

• 한국컴퓨터정보학회논문지
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• 제28권5호
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• pp.67-74
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• 2023

본 논문에서는 2022년에 Hussain et al.이 제안한 DRM을 위한 인증 프로토콜에 대해 분석하고, 개선된 해결방법을 제시한다. Hussain et al.은 자신들의 인증 프로토콜이 중간자 공격과 재생 공격, 그리고 상호 인증을 보장한다고 주장하였다. 그러나 본 논문에서 Hussain et al.의 인증 프로토콜을 분석한 결과, Hussain et al.의 인증 프로토콜은 그들이 지적하였던 Yu et al.의 인증 프로토콜의 문제점인 내부자 공격 문제가 여전히 존재한다. 이로 인하여 내부 공격자가 모바일 기기의 정보를 획득할 경우 사용자 가장 공격 등도 가능하였다. 또한 사용자의 ID 형식 확인 부재의 문제와 서버와 사용자간의 디지털 컨텐츠의 비밀키 불일치의 문제점이 존재하였다. 그러므로 본 논문에서는 이러한 문제를 해결하기 위하여 개선된 해결방법을 제안한다. 개선된 해결방법을 본 논문에서 분석한 결과, 스마트카드 공격, 내부자 공격, 패스워드 추측 공격 등 여러 공격에 안전하여 DRM의 사용자를 안전하게 인증할 수 있다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2003년도 봄 학술발표회 논문집
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• pp.291-298
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• 2003

The resonant column testing is a laboratory testing method to determine the shear modulus and the material damping factor of soils. The method has been widely used for many applications and its importance has been increased. Since the establishment of the testing method in 1963, the low-technology electronic devices for testing and data acquisition have limited the measurement to the amplitude of the linear spectrum. The limitations of the testing method were also attributed to the assumption of the linear-elastic material in the theory of the resonant column testing and to the use of the wave equation for the dynamic response of the specimen. For the better theoretical formulation of the resonant column testing, this study derived the equation of motion and provided its solution. This study also proposed the improved data reduction and analysis method for the resonant column testing, based on the advanced data acquisition system and the proposed theoretical solution for the resonant column testing system. For the verification of the proposed data reduction and analysis method, the numerical simulation of the resonant column testing was performed by the finite element analysis. Also, a series of resonant column testing were peformed for Joomunjin sand, which verified the feasibility, of the proposed method and showed the limitations of the conventional data reduction and analysis method.

• 해양환경안전학회지
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• 제24권3호
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• pp.367-372
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• 2018

The objective of this paper is to optimize the cross-section of aluminum decking units used in the bass boats under operating conditions, and to verify the optimized model from the results via by ANSYS software. Aluminum decking unit is needed to endure specific loading while leisure activity and sailing. For a stiffer and more cost-neutral aluminum decking unit, optimization is often considered in the naval and marine industries. This optimization of the aluminum decking unit is performed using the ANSYS program, which is based on the topology optimization method. The generation of finite element models and stress evaluations are conducted using the ANSYS Multiphysics module, which is based on the Finite Element Method (FEM). Through such a series of studies, it was possible to determine the most suitable case for satisfying the structural strength found among the phase-optimized aluminum deck units in bass boats. From these optimization results, CASE 1 shows the best solution in comparison with the other cases for this optimization. By linking the topology optimization with the structural strength analysis, the optimal solution can be found in a relatively short amount of time, and these procedures are expected to be applicable to many fields of engineering.

• Smart Structures and Systems
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• 제21권6호
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• pp.741-749
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• 2018

Structural health monitoring (SHM) systems are necessary to achieve smart predictive maintenance and repair planning as well as they lead to a safe operation of mechanical structures. In the context of vibration-based SHM the measured structural responses are employed to draw conclusions about the structural integrity. This usually leads to a mathematically illposed inverse problem which needs regularization. The restriction of the solution set of this inverse problem by using prior information about the damage properties is advisable to obtain meaningful solutions. Compared to the undamaged state typically only a few local stiffness changes occur while the other areas remain unchanged. This change can be described by a sparse damage parameter vector. Such a sparse vector can be identified by employing $L_1$-regularization techniques. This paper presents a novel framework for damage parameter identification by combining sparse solution techniques with an Extended Kalman Filter. In order to ensure sparsity of the damage parameter vector the measurement equation is expanded by an additional nonlinear $L_1$-minimizing observation. This fictive measurement equation accomplishes stability of the Extended Kalman Filter and leads to a sparse estimation. For verification, a proof-of-concept example on a quadratic aluminum plate is presented.

• 대한기계학회논문집A
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• 제26권11호
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• pp.2409-2414
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• 2002

The surfaces of prototypes become rough due to the stair-stepping which is the inevitable phenomenon in the Rapid Prototypes are not used only for the verification of feature. The grinding, coating, or the composition of them is a main operation in post-processing in which lots of costs and long build time are needed. The solution is proposed to increase the efficiency of rapid prototyping by minimizing or removing the composition of them is a main operation in post-processing in which lots of costs and long build time are needed. the solution is proposed to increase the efficiency of rapid prototyping by minimizing or removing the regions for post-processing. the factors to cause the surface roughness and their effects are analyzed through the experiments. Software modules are developed to predict the surface roughness of each face in the prototyping with the result. An experimental compensation method is developed to apply the modules to various RP equipments, materials and build styles. The build direction is searched with use of genetic algorithm to maximize the total areas of the surface of which roughness is better than the user-defined value.

• 한국해양공학회지
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• 제18권5호
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• pp.29-35
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• 2004

A new approach, referred to as a successive zooming genetic algorithm (SZGA), is proposed for identifying a global solution, using continuous zooming factors for optimization problems. In order to improve the local fine-tuning of the GA, we introduced a new method whereby the search space is zoomed around the design variable with the best fitness per 100 generation, resulting in an improvement of the convergence. Furthermore, the reliability of the optimized solution is determined based on the theory of probability, and the parameter used for the successive zooming method is optimized. With parameter optimization, we can eliminate the time allocated for deciding parameters used in SZGA. To demonstrate the superiority of the proposed theory, we tested for the minimization of a multiple function, as well as simple functions. After testing, we applied the parameter optimization to a truss problem and wicket gate servomotor optimization. Then, the proposed algorithm identifies a more exact optimum value than the standard genetic algorithm.

• Structural Engineering and Mechanics
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• 제76권1호
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• pp.115-127
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• 2020

This study presents an analytical approach to investigate the thermodynamic behavior of functionally graded beam resting on elastic foundations. The formulation is based on a refined deformation theory taking into consideration the stretching effect and the type of elastic foundation. The displacement field used in the present refined theory contains undetermined integral forms and involves only three unknowns to derive. The mechanical characteristics of the beam are assumed to be varied across the thickness according to a simple exponential law distribution. The beam is supposed simply supported and therefore the Navier solution is used to derive analytical solution. Verification examples demonstrate that the developed theory is very accurate in describing the response of FG beams subjected to thermodynamic loading. Numerical results are carried out to show the effects of the thermodynamic loading on the response of FG beams resting on elastic foundation.