• Earthquakes and Structures
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• v.15 no.5
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• pp.487-498
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• 2018

Buckling-restrained braces are passive control devices with high level of energy dissipation ability. However, they suffer from low post-yield stiffness which makes them vulnerable to severe ground motions, especially near-field earthquakes. Among the several methods proposed to improve resistance of BRB frames, mega-brace configuration can be a solution to increase frame lateral strength and stiffness and improve distribution of forces to prevent large displacement in braces. Due to the limited number of research regarding the performance of such systems, the current paper aims to assess seismic performance of BRB frames with mega-bracing arrangement under near-field earthquakes via a detailed probabilistic framework. For this purpose, a group of multi-story mega-BRB frames were modelled by OpenSEES software platform. In the first part of the paper, simplified procedures including nonlinear pushover and Incremental Dynamic Analysis were conducted for performance evaluation. Two groups of near-fault seismic ground motions (Non-pulse and Pulse-like records) were considered for analyses to take into account the effects of record-to-record uncertainties, as well as forward directivity on the results. In the second part, seismic reliability analyses are conducted in the context of performance based earthquake engineering. Two widely-known EDP-based and IM-based probabilistic frameworks are employed to estimate collapse potential of the structures. Results show that all the structures can successfully tolerate near-field earthquakes with a high level of confidence level. Therefore, mega-bracing configuration can be an effective alternative to conventional BRB bracing to withstand near-field earthquakes.

• Journal of Korean Society of Steel Construction
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• v.13 no.2
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• pp.115-122
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• 2001

Even in today's computer-oriented world with all its sophisticated analysis tools, engineering judgement is required to assess the adequacy of computer output. Approximate analysis method can be a feasible tool to check solutions from computer softwares roughly. It can be a simple tool for structural engineer to check force distribution in frame. Also, it can serve as a basis in selecting preliminary member sizes. The objective of this study is length factor and inflection points. The validity of this method is examined by comparing the results of this method with those of existing methods, showing improvement in the prediction of structural behavior.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.1
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• pp.58-66
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• 2010

Topology design optimization is a method to determine the optimal distribution of material that yields the minimal compliance of structures, satisfying the constraint of allowable material volume. The method is easy to implement and widely used so that it becomes a powerful design tool in various disciplines. In this paper, a large-scale topology design optimization method is developed using the efficient adjoint sensitivity and optimality criteria methods. Parallel computing technique is required for the efficient topology optimization as well as the precise analysis of large-scale problems. Parallelized finite element analysis consists of the domain decomposition and the boundary communication. The preconditioned conjugate gradient method is employed for the analysis of decomposed sub-domains. The developed parallel computing method in topology optimization is utilized to determine the optimal structural layout of human powered vessel.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.4A
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• pp.356-363
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• 2002

Video scene segmentation is fundamental role for content based video analysis and many kinds of scene segmentation schemes have been proposed in previous researches. However, there is a problem, which is to find optimal threshold value according to various kinds of movies and its content because only fixed single threshold value usually used for cut detection. In this paper, we proposed the variable dynamic threshold method, which change the threshold value by a probability distribution of cut detection interval and information of frame feature differences and cut detection interval in previous cut detection is used to determine the next cut detection. For this, we present a cut detection algorithm and a parameter generation method to change the threshold value in runtime. We also show the proposed method, which can minimize fault alarm rate than the existing methods efficiently by experimental results.

• Smart Structures and Systems
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• v.15 no.3
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• pp.699-715
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• 2015

A modal parameter based damage sensitive feature (DSF) is defined to mimic the relative change in any diagonal element of the stiffness matrix of a model of a structure. The damage assessment is performed in a statistical pattern recognition framework using empirical complementary cumulative distribution functions (ECCDFs) of the DSFs extracted from measured operational vibration response data. Methods are discussed to perform probabilistic structural health assessment with respect to the following questions: (a) "Is there a change in the current state of the structure compared to the baseline state?", (b) "Does the change indicate a localized stiffness reduction or increase?", with the latter representing a situation of retrofitting operations, and (c) "What is the severity of the change in a probabilistic sense?". To identify a range of normal structural variations due to environmental and operational conditions, lower and upper bound ECCDFs are used to define the baseline structural state. Such an approach attempts to decouple "non-damage" related variations from damage induced changes, and account for the unknown environmental/operational conditions of the current state. The damage assessment procedure is discussed using numerical simulations of ambient vibration testing of a bridge deck system, as well as shake table experimental data from a 4-story steel frame.

• Journal of Research and Publication Ethics
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• v.2 no.2
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• pp.11-16
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• 2021

Purpose: The purpose of this study is to analyze the research trends of domestic research ethics and to draw implications for the limitations of existing research and future development directions through this. Research design, data and methodology: To this end, this study first examined the concept of research ethics and research area to derive an analysis frame. In addition, 72 academic papers published in domestic journals from 2000 to November 2020 were analyzed according to the research period, research area, research subject, research field, research method, and the nature of the journal. Results: As a result of the analysis, it is judged that social interest in research ethics led to academic interest after the 2005 Hwang Woo-seok incident. These characteristics show that the interest of academia is changing and increasing significantly when issues related to research ethics are raised socially. Of the 72 papers to be analyzed, 29 (40.3%) conceptual and theoretical studies on research ethics and 43 (59.7%) studies on practical measures were surveyed. Conclusions: In the case of published journals on research ethics, the proportion of publications in humanities and social sciences and pedagogical journals was high, and in research methods, literature and theoretical studies were the highest.

• Journal of Korean Academy of Nursing
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• v.49 no.5
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• pp.562-574
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• 2019

Purpose: The purpose of this study was to identify the response patterns of nursing unit managers regarding workplace bullying. Methods: Q methodology was used to identify the response patterns. Thirty-six Q samples were selected from the Q population of 210 that included literature reviews and in-depth interviews with clinical nurses and nursing managers. Participants were 30 nursing unit managers who had experience managing workplace bullying and they classified the Q samples into a normal distribution frame measured on a nine-point scale. The data were analyzed using the PC-QUANL program. Results: Five types of response patterns were identified: (1) sympathetic-understanding acceleration, (2) harmonious-team approach, (3) preventive-organizational management, (4) passive observation, and (5) leading-active intervention. The preventive-organizational management type was most frequently used by the nursing unit managers. Conclusion: The results of this study indicated that nursing unit managers attempted to prevent and solve workplace bullying in various ways. Therefore, it is necessary to develop and conduct leadership training and intervention programs that appropriately address the response patterns of nursing unit managers, such as those identified in this study.

• Journal of Distribution Science
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• v.17 no.4
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• pp.77-85
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• 2019

Purpose - Statistics of Traditional Market is the only source of information on traditional markets, shopping street, and underground shopping street. The government conducts a survey of traditional market conditions every year to look at the current status of traditional markets and provide effective support. Therefore, this study examines the necessity and validity of updating about the Survey Population of Traditional Market Research design, data, and methodology - This study investigated the necessity of updating about the Survey Population of Traditional Market through literature review. Therefore this study examined the necessity of the current population based on the review of the population related to the sample design, methods, and the sampling frame. Next, we examined the change patterns of the population and the sample by dividing the population and sample of the current survey of the traditional market survey into the market unit, the store unit within the market, and finally the individual store unit. Results - As a result, the population of traditional market changes about 4~6%. Next, the analysis of the store unit in the market shows that the number of stores is very variable even though the market is continuously included in the survey target. Finally, as a result of examining the characteristics of individual stores, the stores with less than one year were more than 6% of the total surveyed stores based on the traditional market. These results are generally inconsistent with the idea that stores in traditional markets will operate for a long time in one place. Next, we proposed the establishment of a management system, applying Citizen Generated Data, and circulation survey. Additionally, this study proposes to change the stratification variables at the regional level rather than the market unit. Conclusions - Therefore, in this study, it is suggested that a current population of traditional market is needed updating, and that a population survey should be updated at least four years. In addition, a system for investigating traditional markets and districts was established and a circulation survey was proposed for efficient use of budgets. Based on these research results and policy suggestions, the future research directions are suggested.

• Earthquakes and Structures
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• v.14 no.1
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• pp.1-10
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• 2018

Seismic retrofitting of existing buildings and design of earth-quake resistant buildings are important issues associated with earthquake-prone zones. Use of metallic-yielding dampers as an energy dissipation system is an acceptable method for controlling damages in structures and improving their seismic performance. In this study, the optimal distribution of dampers for reducing the seismic response of steel frames with multi-degrees freedom is presented utilizing the uniform distribution of deformations. This has been done in a way that, the final configuration of dampers in the frames lead to minimum weight while satisfying the performance criteria. It is shown that such a structure has an optimum seismic performance, in which the maximum structure capacity is used. Then the genetic algorithm which is an evolutionary optimization method is used for optimal arrangement of the steel dampers in the structure. In continuation for specifying the optimal accurate response, the local search algorithm based on the gradient concept has been selected. In this research the introduced optimization methods are used for optimal retrofitting in the moment-resisting frame with inelastic behavior and initial weakness in design. Ultimately the optimal configuration of dampers over the height of building specified and by comparing the results of the uniform deformation method with those of the genetic algorithm, the validity of the uniform deformation method in terms of accuracy, Time Speed Optimization and the simplicity of the theory have been proven.

• Journal of Korean Neurosurgical Society
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• v.43 no.1
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• pp.26-30
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• 2008

Objective : The authors developed a stereotactic device for irradiation of small animals with Leksell Gamma Knife Model C. Development and verification procedures were described in this article. Methods : The device was designed to satisfy three requirements. The mechanical accuracy in positioning was to be managed within 0.5 mm. The strength of the device and structure were to be compromised to provide enough strength to hold a small animal during irradiation and to interfere the gamma ray beam as little as possible. The device was to be used in combination with the Leksell G-$frame^{(R)}$ and $KOPF^{(R)}$ rat adaptor. The irradiation point was determined by separate imaging sequences such as plain X-ray images. Results : The absolute dose rate with the device in a Leksell Gamma Knife was 3.7% less than the value calculated from Leksell Gamma $Plan^{(R)}$. The dose distributions measured with $GAFCHROMIC^{(R)}$ MD-55 film corresponded to those of Leksell Gamma $Plan^{(R)}$ within acceptable range. The device was used in a series of rat experiments with a 4 mm helmet of Leksell Gamma Knife. Conclusion : A stereotactic device for irradiation of small animals with Leksell Gamma Knife Model C has been developed so that it fulfilled above requirements. Absorbed dose and dose distribution at the center of a Gamma Knife helmet are in acceptable ranges. The device provides enough accuracy for stereotactic irradiation with acceptable practicality.