• Steel and Composite Structures
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• 제32권3호
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• pp.305-312
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• 2019

In this study, we investigated the effect of fatigue crack propagation of the beams which have a vital importance in engineering applications, on the natural frequency of the system. Beams which have a wide range of applications, are used as fundamental structural elements in engineering structures. Therefore, early detection of any damages in these structures is of vital importance for the prevention of possible destructive damages. One of the widely used methods of early detection of damages is the vibration analysis of the structure. Hence, it is of vital importance to detect and monitor any changes in the natural frequencies of the structure. From this standpoint, in this study we experimentally investigated the effect of fatigue crack propagation on beams produced from 4140 steel, of the natural frequency of the beam. A crack was opened on the $8{\times}16{\times}500mm$ beam using a 3 mm long and 0.25 mm wide wire erosion. The beam, then, underwent 3 point bending tests at 10 Hz with a dynamic fatigue device and its natural frequencies were measured in scheduled intervals and any changes taking place on the natural frequencies of the beam were measured. This data allowed us to identify and measure the crack occurring on the beam subjected to dynamic loading, during the propagation phase. This method produced experimental data. The experimental data showed that the natural frequency of the beam decreased with the propagation of the fatigue crack on the beam.

• 한국지진공학회논문집
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• 제23권1호
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• pp.19-29
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• 2019

Recent earthquakes in Korea caused some damages to stone pagodas and thereby awakened the importance of earthquake preparedness. Korean stone pagodas which have been built with very creative style of material use and construction method are worthy of world heritage. Each stone pagoda consists of three parts: top; body; and base. However each tower is uniquely defined by its own features, which makes it more difficult to generalize the seismic assessment method for stone pagodas. This study has focused on qualitative preliminary evaluation of stone pagodas that enables us to compare the relative seismic performance across major aspects among many various Korean pagodas. Specifically an analytical model for multi-block stone pagodas is to be proposed upon the investigation of structural characteristics of stone pagoda and their dynamic behavior. A strategy for seismic evaluation of heritage stone pagodas is to be established and major evaluation factors appropriate for the qualitative evaluation are identified. The evaluation factors for overall seismic resisting behavior of stone pagodas are selected based on the dynamic motions of a rigid block and its limit state. Numerical simulation analysis using discrete element method is performed to analyze the sensitivity of each factor to earthquake and discuss some effects on seismic performance.

• Earthquakes and Structures
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• 제21권6호
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• pp.601-612
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• 2021

The paper concerns the selection of a design accelerograms used for the slope stability assessment under earthquake excitation. The aim is to experimentally verify the Arias Intensity as an indicator of the excitation threat to the slope stability. A simple dynamic system consisting of a rigid block on a rigid inclined plane subjected to horizontal excitation is adopted as a slope model. Strong ground motions recorded during earthquakes are reproduced on a shaking table. The permanent displacement of the block serves as a slope stability indicator. Original research stand allows us to analyse not only the relative displacement but also the acceleration time history of the block. The experiments demonstrate that the Arias Intensity of the accelerogram is a good indicator of excitation threat to the stability of the slope. The numerical analyses conducted using the experimentally verified extended Newmark's method indicate that both the Arias Intensity and the peak velocity of the excitation are good indicators of the impact of dynamic excitation on the dam's stability. The selection can be refined using complementary information, which is the dominant frequency and duration of the strong motion phase of the excitation, respectively.

• International Journal of Computer Science & Network Security
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• 제23권9호
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• pp.65-70
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• 2023

The "information roadway" will give us an impact of new PC based assignments and administrations, yet the unusualness of this new condition will ask for another style of human-PC association, where the PC transforms into a sharp, dynamic and customized partner. Interface administrators are PC programs that use Artificial Intelligence frameworks to give dynamic help to a customer with PC based errands. Operators drastically change the present client encounter, through the similitude that a specialist can go about as an individual collaborator. The operator procures its capability by gaining from the client and from specialists helping different clients. A couple of model administrators have been gathered using this methodology, including authorities that give customized help with meeting planning, electronic mail taking care of, Smart Personal Assistant and choice of diversion. Operators help clients in a scope of various ways: they perform assignments for the client's sake; they can prepare or educate the client, they enable diverse clients to work together and they screen occasions and methods.

• 한국건설관리학회논문집
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• 제20권1호
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• pp.73-85
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• 2019

2000년대 이후 많은 한국의 건설 및 엔지니어링 기업들은 급속하게 변화하는 동적환경에서 경쟁 심화, 높은 리스크, 경기 침체, 실적 부진, 이윤 감소 등의 어려움에 직면해 있다. 이러한 도전을 극복하기 위해서는 패러다임 변화에 적극적으로 대응할 수 있는 특별한 역량의 확보가 요구된다. 그 중 하나가 프로젝트 포트폴리오 기반에서 기업 내 조직자원을 적극적이고 통합적으로 관리할 수 있는 프로젝트관리 역량이라고 할 수 있다. 본 연구의 목적은 기업 내 프로젝트 조직자원의 동적역량이 기업의 경쟁우위와 성과에 어떤 영향을 미치는 지를 조사하는 데 있다. 국내 건설 및 엔지니어링 기업의 프로젝트 조직에서 근무하는 직원을 대상으로 설문 자료를 분석하고 구조방정식 모형과 경로분석 등의 통계분석을 통해서 이를 실증하였다. VRIN 조직자원과 조직 동적역량간의 영향을 분석한 결과, VRIN 특성의 프로젝트 조직자원을 보유하고 있다면 프로젝트 조직의 동적역량에 유의한 영향을 미치는 것으로 나타났고, 프로젝트 조직의 동적역량도 기업의 경영성과를 개선하고 경쟁우위를 창출하는데 긍정적인 영향을 미치는 것으로 나타났다. 또한 조직자원은 기업의 경쟁우위와 성과에 직접적인 영향을 끼치며 조직 동적역량이 VRIN 속성의 조직자원과 경쟁우위 사이에서 매개효과의 영향이 있는 것으로 확인되었다. 본 연구가 학문적으로는 자원기반관점과 동적역량관점을 통합하는 입장에서 프로젝트 조직자원이 기업의 경쟁우위에 미치는 영향을 실증하고 프로젝트관리의 학문적 영역을 확장하는데 기여하였다. 실무적으로는, 건설 및 엔지니어링 산업에서 경쟁우위를 확보하기 위하여 기업들이 전략적으로 어떻게 프로젝트 조직자원을 활용해야 하는지에 대한 구체적인 방안을 제시하였다.

• 한국콘텐츠학회논문지
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• 제6권8호
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• pp.184-191
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• 2006

본 연구의 목적은 최근 새롭게 텔레비전 뉴스 프로그램 제작에 등장한 VJ의 영상표현상의 특성을 카메라 기자의 영상표현상의 특성과 비교 분석하고 그 차이에 대한 함의를 알아보기 위한 것이다. 본 연구에서 분석대상으로 선정한 텍스트는 2005년 7월부터 동년 12월까지 6개월간 KBS2TV를 통해 방송된 '뉴스타임' 120회분으로, 뉴스의 내용별, 취재원별 분류과정을 거쳐 샘플로 추출된 영상을 대상으로 화면의 크기, 카메라워크, 샷의 지속시간, 카메라 앵글 등이 어떻게 표현되고 있는지를 분석하였다. 연구결과 텔레비전 뉴스 프로그램에서 VJ는 사회분야, 경제분야, 문화분야를 중심으로 한 연성뉴스를 주로 취재하고, 정치분야, 건강과학분야 등 사회적으로 민감하고 국민생활 전반에 큰 영향을 미칠 수 있는 경성뉴스의 취재에는 철저히 소외되고 있으며, 영상표현상의 특성으로는 VJ가 카메라기자에 비해 현장 밀착형 취재방식을 선호하여 그룹샷보다 원샷을 자주 사용하고, 기동성과 역동성 있는 카메라워크를 선호하여 팔로우잉과 줌을 지나치게 자주 사용하며, 몰래카메라 형식의 로우앵글을 선호하는 특성을 가지고 있는 것으로 나타났다.

• 한국정보과학회논문지:시스템및이론
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• 제26권12호
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• pp.1468-1475
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• 1999

컴퓨터망 보안을 위해서는 취약점의 빠른 발견과 그에 따르는 신속한 조치가 요구된다. 이를 위해 컴퓨터망 여러 곳에서 사용자가 원하는 보안 정보를 수집, 분석하고 수집된 보안 정보들을 효과적으로 보여주는 통합적인 보안 관리를 제공하는 모니터링 방식이 필요하다. 본 논문에서는 보안 관리를 위한 동적 모니터링 형식 모델을 제시한다. 동적 모니터링은 상태 전이에 의한 시스템 상태, 사용자와의 상호작용, 시각 및 모니터링 객체의 동적 활성화를 이용하여 컴퓨터망 통합 보안 관리를 제공한다. 계속적으로 변하는 보안 정보, 컴퓨터망 관리자의 관심점과 모니터링 레벨의 변화를 즉각적으로 반영함으로써 관리자에게 컴퓨터망 관리의 정확성, 효율성 그리고 편의성을 제공한다. 모니터링 시스템을 형식적으로 모델링하여 여러 모니터링 응용프로그램의 개발이 가능한 모니터링 플랫폼으로 발전시킬 수 있다. Abstract It is highly required to quickly detect the vulnerability of a computer network system and an appropriate action toward it should be followed as soon as possible for its security. It leads us to the need of a monitoring schema that can provide an integrated security management with carefully selected and analysed data through the computer network for its users. This paper presents a formal model of dynamic monitoring for security management. It provides the comprehensive security management using continuously changing security information, user interactions and dynamic activation of visual and monitoring objects. It enables system security officers to manage computer systems accurately, efficiently and conveniently by reflecting the state transition and the transformation of concerns and a monitoring level of system security officers immediately. This model can be used as the basis of a monitoring platform.

• 제어로봇시스템학회논문지
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• 제10권10호
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• pp.855-868
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• 2004

There are several types of singularities in controlling robotic manipulators: kinematic singularity, algorithmic singularity, semi-kinematic singularity, semi-algorithmic singularity, and representation singularity. The kinematic and algorithmic singularities have been investigated intensively because they are not predictable or difficult to avoid. The problem with these singularities is an unnecessary performance reduction in non-singular region and the difficulty in performance tuning. Tn this paper, we propose a method of avoiding kinematic and algorithmic singularities by applying a task reconstruction approach while maximizing the task performance by calculating singularity measures. The proposed method is implemented by removing the component approaching the singularity calculated by using singularity measure in real time. The outstanding feature of the proposed task reconstruction method (TR-method) is that it is based on a local task reconstruction as opposed to the local joint reconstruction of many other approaches. And, this method has dynamic task priority assignment feature which ensures the system stability under singular regions owing to the change of task priority. The TR-method enables us to increase the task controller gain to improve the task performance whereas this increase can destabilize the system for the conventional algorithms in real experiments. In addition, the physical meaning of tuning parameters is very straightforward. Hence, we can maximize task performance even near the singular region while simultaneously obtaining the singularity-free motion. The advantage of the proposed method is experimentally tested by using the 7-dof spatial manipulator, and the result shows that the new method improves the performance several times over the existing algorithms.

• 한국자동차공학회논문집
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• 제19권6호
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• pp.30-36
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• 2011

The current test methods are insufficient to evaluate and ensure the safety and reliability of vehicle system for all possible dynamic situation including the worst case such as rollover, spin-out and so on. Although the known NHTSA Sine with dwell steering maneuvers are applied for the vehicle performance assessment, they aren't enough to estimate other possible worst case scenarios. Therefore, it is crucial for us to verify the various worst cases including the existing severe steering maneuvers. This paper includes useful worst case based upon the existing worst case scenarios mentioned above and worst case evaluation for vehicle dynamic controller in simulation basis and UCC HILS. The only human steering angle is selected as a design parameter here and optimized to maximize the index function to be expressed in terms of both yaw rate and side slip angle. The obtained scenarios were enough to generate the worst case to meet NHTSA worst case definition. It has been concluded that the new procedure in this paper is adequate to create other feasible worst case scenarios for a vehicle dynamic control system.

• Journal of Microbiology and Biotechnology
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• 제15권3호
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• pp.551-559
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• 2005

The recent rapid increase in genomic data related to many microorganisms and the development of computational tools to accurately analyze large amounts of data have enabled us to design several kinds of simulation approaches for the complex behaviors of cells. Among these approaches, dFBA (dynamic flux balance analysis), which utilizes FBA, differential equations, and regulatory events, has correctly predicted cellular behaviors under given environmental conditions. However, until now, dFBA has centered on substrate concentration, cell growth, and gene on/off, but a detailed hierarchical structure of a regulatory network has not been taken into account. The use of Boolean rules for regulatory events in dFBA has limited the representation of interactions between specific regulatory proteins and genes and the whole transcriptional regulation mechanism with environmental change. In this paper, we adopted the operon as the basic structure, constructed a hierarchical structure for a regulatory network with defined fundamental symbols, and introduced a weight between symbols in order to solve the above problems. Finally, the total control mechanism of regulatory elements (operons, genes, effectors, etc.) with time was simulated through the linkage of dFBA with regulatory network modeling. The lac operon, trp operon, and tna operon in the central metabolic network of E. coli were chosen as the basic models for control patterns. The suggested modeling method in this study can be adopted as a basic framework to describe other transcriptional regulations, and provide biologists and engineers with useful information on transcriptional regulation mechanisms under extracellular environmental change.