• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.2
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• pp.49-58
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• 2003

The linear motor has not only no backlash and less friction, resulting in very high accuracy, but also mechanical simplicity, higher reliability, and longer lifetime. In this study, a large-capacity hybrid mass damper using linear motor principle has been developed to suppress vibration of large structures. It is designated linear motor damper in this paper. The LMD has been designed to be able to move the auxiliary damper mass of 155kg up to $\pm$250mm stroke. A series of performance tests for LMD control system with $H_{winfty}$ robust controller have been carried out on the full-scale steel frame structure. Through the performance tests, it is confirmed that vibration response levels are reduced down 10dB for the first and second modes of the test structure.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.4
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• pp.495-502
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• 2014

Fast recovery diodes (FRDs) were developed using the $p^{{+}{+}}/n^-/n^{{+}{+}}$ epitaxial layers grown by low temperature epitaxy technology. We investigated the effect of electrostatic discharge (ESD) stresses on their electrical and switching properties using current-voltage (I-V) and reverse recovery time analyses. The FRDs presented a high breakdown voltage, >450 V, and a low reverse leakage current, < $10^{-9}$ A. From the temperature dependence of thermal activation energy, the reverse leakage current was dominated by thermal generation-recombination and diffusion, respectively, at low and high temperature regions. By virtue of the abrupt junction and the Pt drive-in for the controlling of carrier lifetime, the soft reverse recovery behavior could be obtained along with a well-controlled reverse recovery time of 21.12 ns. The FRDs exhibited excellent ESD robustness with negligible degradations in the I-V and the reverse recovery characteristics up to ${\pm}5.5$ kV of HBM and ${\pm}3.5$ kV of IEC61000-4-2 shocks. Likewise, transmission line pulse (TLP) analysis reveals that the FRDs can handle the maximum peak pulse current, $I_{pp,max}$, up to 30 A in the forward mode and down to - 24 A in the reverse mode. The robust ESD property can improve the long term reliability of various power applications such as automobile and switching mode power supply.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.9
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• pp.1562-1570
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• 2003

The prediction of the inelastic behavior of the structure is an essential part of reliability assessment procedure, because most of the failures are induced by the inelastic deformation, such as creep and plastic deformation. During decades, there has been much progress in understanding of the inelastic behavior of the materials and a lot of inelastic constitutive equations have been developed. The complexity of these constitutive equations generally requires a stable and accurate numerical method. The radial return mapping is one of the most robust integration scheme currently used. Nonlinear kinematic hardening model of Armstrong-Fredrick type has recovery term and the direction of kinematic hardening increment is not parallel to that of plastic strain increment. In this case, The conventional radial return mapping method cannot be applied directly. In this investigation, we expanded the radial return mapping method to consider the nonlinear kinematic hardening model and implemented this integration scheme into ABAQUS by means of UMAT subroutine. The solution of the non-linear system of algebraic equations arising from time discretization with the generalized midpoint rule is determined using Newton method and bisection method. Using dynamic yield condition derived from linearization of flow rule, the integration scheme for elastoplastic and viscoplastic constitutive model was unified. Several numerical examples are considered to demonstrate the efficiency and applicability of the present method.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.12
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• pp.74-82
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• 2008

In this paper, we propose a P2P based IPTV system using a multiple chain architecture. Proposed system is robust to the peer churn. As opposed to the internet the IPTV network managed by a single ISP has fewer bandwidth constraints and end-to-end connectivity. So, we emphasize preferentially robustness of a P2P network in IPTV environment. A single chain structure which was proposed previously emphasizes simplicity, however there exists considerable delay time at the end part of peers as the number of peers increasing. As a solution to the problem, we propose the scheme which seperates the chain into several levels and again divides each level into spans to diminish a delay time. Though the chain is separated into level and span, basic structure of proposed scheme is still a chain structure. So the scheme simplifies the recovery procedure caused by join or departure of peers. We will show the improved performance of proposed scheme rather than single chain structure with respect to the delay time and reliability.

• Journal of Internet Computing and Services
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• v.15 no.2
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• pp.9-18
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• 2014

The sensors attached on/in a person are moved since human body frequency changes their activity, therefore in wireless body area networks, nodal mobility and non-line-of-sight condition will impact on performance of networks such as energy efficiency and reliable communication. We then proposed schemes which study on forwarding decisions against frequent change of topology and channel conditions to increase reliable connections and improve energy efficiency. In this work, we control the size of packets, forwarding rate based on ratio of input links and output links at each node. We also robust the network topology by extending the peer to peer IEEE 802.15.4-based. The adaptive topology from chain-based to grid-based can optimal our schemes. The simulation shows that these approaches are not only extending network lifetime to 48.2 percent but also increase around 6.08 percent the packet delivery ratio. The "hot spots" problem is also resolved with this approach.

• Nuclear Engineering and Technology
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• v.43 no.2
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• pp.187-194
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• 2011

Korea Nuclear Fuel is developing the X-GEN fuel which shows high performance and robust reliability for the worldwide supply. However, the simplified code systems such as CESEC-III which were developed in 1970s are still used in the current Non-LOCA safety analysis of OPR1000 and APR1400 plants. Therefore, it is essential to secure an advanced safety analysis methodology to make the best use of the merits of X-GEN fuel. To accomplish this purpose, the $\b{i}$ntegrated $\b{s}$afety $\b{a}$nalysis $\b{m}$ethodology (iSAM), is developed by selecting the best-estimate thermal-hydraulic code RETRAN. iSAM possesses remarkable advantages, such as generality, integrity, and designer-friendly features. That is, iSAM can be applied to both OPR1000 and APR1400 plants and uses only one computer code, RETRAN, in the whole scope of the non-LOCA safety analyses. Also the iSAM adopts the unique and automatic initialization and run tool, $\b{a}$utomatic $\b{s}$teady-$\b{s}$tate $\b{i}$nitialization and $\b{s}$afety analysis too l (ASSIST), to enable unhandy designers to use the new design code RETRAN without difficulty. In this paper, a brief overview of the iSAM is given, and the results of applying the iSAM to typical non-LOCA transients being checked during the reload design are reported. The typical non-LOCA transients selected are the single control element assembly withdrawal (SCEAW) accident, the asymmetric steam generator transients (ASGT), the locked rotor (LR) accident, and bank CEA withdrawal (BCEAW) event. Comparison to current licensing results shows a close resemblance; thus, it reveals that the iSAM can be applied to the non-LOCA safety analysis of OPR1000 and APR1400 plants.

• The Research Journal of the Costume Culture
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• v.29 no.2
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• pp.240-251
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• 2021

The purpose of this study is to establish the relationship between wedding companies and wedding planners and understand the influence of relationship factors on the relationship performance and relationship continuation intention of wedding companies. We conducted an online survey from June to July 2017, and collected 201 responses which were used during analysis. Statistical analysis, including technical statistical analysis, factor analysis, reliability analysis, and regression analysis, was undertaken using SPSS 23. This study shows that among the relationship factors affecting the wedding planner and the wedding company, the computational tie-up has a significant impact on both the financial and non-financial performance of the wedding company, while emotional tie-ups have a significant impact on the non-financial performance of the wedding company, but not on financial performance. As for the effects of relationship commitment to wedding planners on wedding shops' relationship continuation intention, each factor for relationship commitment significantly affected wedding shops' relationship continuation intention. Regarding the effects of wedding shops' relational performance on relationship continuation intention, each factor of performance significantly affected relationship continuation intention. Therefore, wedding companies should make continuous efforts to maintain this relationship and recognize the need for robust relationships with wedding planners as a sure and important competitive tool for attracting customer and generating revenue.

• Safety and Health at Work
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• v.13 no.3
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• pp.326-335
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• 2022

Background: One of the important actions for enhancing human reliability in any industry is assessing human error probability (HEP). The HEART technique is a robust tool for calculating HEP in various industries. The traditional HEART has some weaknesses due to expert judgment. For these reasons, a hybrid model is presented in this study to integrate HEART with Best-Worst Method. Materials Method: In this study, the blasting process in an iron ore mine was investigated as a case study. The proposed HEART-BWM was used to increase the sensitivity of APOA calculation. Then the HEP was calculated using conventional HEART formula. A consistency ratio was calculated using BWM. Finally, for verification of the HEART-BWM, HEP calculation was done by traditional HEART and HEART-BWM. Results: In the view of determined HEPs, the results showed that the mean of HEP in the blasting of the iron ore process was 2.57E-01. Checking the full blast of all the holes after the blasting sub-task was the most dangerous task due to the highest HEP value, and it was found 9.646E-01. On the other side, obtaining a permit to receive and transport materials was the most reliable task, and the HEP was 8.54E-04. Conclusion: The results showed a good consistency for the proposed technique. Comparing the two techniques confirmed that the BWM makes the traditional HEART faster and more reliable by performing the basic comparisons.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.21 no.5
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• pp.218-232
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• 2022

Researches are underway to use a radar sensor, a sensor used for object recognition in vehicles, for position estimation. In particular, a method of classifying dynamic and static objects using the Doppler velocity, the output from the radar sensor, and calculating ego-motion using only static objects has been researched recently. Also, for the existing dynamic object classification, several methods using RANSAC or robust filtering has been proposed. Still, a classification method with higher performance is needed due to the nature of the position estimation, in which even a single failure causes large effects. Hence, in this paper, we propose a method to improve the classification performance compared to existing methods through tracking and filtering of dynamic objects. Additionally, the method used a GMPHD filter to maximize tracking performance. In effect, the method showed higher performance in terms of classification accuracy compared to existing methods, and especially shows that the failure of the RANSAC could be prevented.

• Proceedings of the ESK Conference
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• 1997.04a
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• pp.56-60
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• 1997

The study of human erroneous actions has traditionally taken place along two different lines of approach. One has been concerned with finding and explaining the causes of erroneous actions, such as studies in the psychology of "error". The other has been concerned with the qualitative and quantitative prediction of possible erroneous actions, exemplified by the field of human reliability analysis (HRA). Another distinction is also that the former approach has been dominated by an academic point of view, hence emphasising theories, models, and experiments, while the latter has been of a more pragmatic nature, hence putting greater emphasis on data and methods. We have been developing a method to make predictions about error modes. The input to the method is a detailed task description of a set of scenarios for an experiment. This description is then analysed to characterise thd nature of the individual task steps, as well as the conditions under which they must be carried out. The task steps are expressed in terms of a predefined set of cognitive activity types. Following that each task step is examined in terms of a systematic classification of possible error modes and the likely error modes are identified. This effectively constitutes a qualitative analysis of the possibilities for erroneous action in a given task. In order to evaluate the accuracy of the predictions, the data from a large scale experiment were analysed. The experiment used the full-scale nuclear power plant simulator in the Halden Man-Machine Systems Laboratory (HAMMLAB) and used six crews of systematic performance observations by experts using a pre-defined task description, as well as audio and video recordings. The purpose of the analysis was to determine how well the predictions matiched the actually observed performance failures. The results indicated a very acceptable rate of accuracy. The emphasis in this experiment has been to develop a practical method for qualitative performance prediction, i.e., a method that did not require too many resources or specialised human factors knowledge. If such methods are to become practical tools, it is important that they are valid, reliable, and robust.