• Structural Engineering and Mechanics
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• 제39권5호
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• pp.733-750
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• 2011

Recently, identification of modal parameters using the response only data has attracted considerable attention particularly where the classic modal testing methods is difficult to conduct. One drawback of the response only data, also known as Operational Modal Analysis (OMA), is that only the unscaled mode shapes can be obtained which restricts the applications of OMA. The Mass change method is a usual way to scale the operational mode shapes. In this article a new method is proposed to optimize the additive mass for scaling of the unscaled mode shapes from OMA for which a priori knowledge of the Finite Element model of structure is required. It is shown that the total error of the scaled mode shapes is minimized using the proposed method. The method is validated using a numerical case study of a beam. Moreover, the experimental results of a clamped-clamped beam demonstrate the applicability of the method.

• 산업경영시스템학회지
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• 제22권52호
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• pp.203-210
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• 1999

We report on some of the preliminary results of the physiological responses resulting from vehicular speed changes. Healthy human subjects (n=5) were studied for the experiments. We measured the physiological responses of the subjects such as Heart Rate Variability (HRV), Galvanic Skin Response (GSR), and skin temperature for day and night vehicular speed change experiments, respectively. Before and after the tasks, we carried out a self-report for acquiring correlation with experiment results. Mean heart rate variability (HRV) and amplitude of GSR and skin temperature were calculated for 3 minutes duration in each state. The analysis of the physiological measures of ANS activity revealed that vehicle speed change-based affective state evoked arousal response pattern featured by HR acceleration, decrease of skin temperature, and increase of GSR amplitude. The obtained results show that despite some differences observed between each state, overall physiological responses show that the activity of the sympathetic nervous system increases as a result of the increase of speed.

• 융합경영연구
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• 제3권3호
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• pp.1-6
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• 2015

Quality auditor and auditors of larger firms have a positive effect on profit is unusual. The auditors smaller negative effect on profit companies profit is unusual. Change to larger audit shows the quality of earnings and to respond more investors positive changes in income and increased costs and reduced profitability is less negative price changes. Similarly, switching to a smaller auditor confirms the low quality of earnings, resulting in a negative response to the market. In this article market reaction (response investors) the quality of the audit and the auditor were studied in the Tehran Stock Exchange. in general, information about companies in capital market accounting to investors and the capital market is considered to be valuable.

• Journal of Information Processing Systems
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• 제19권6호
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• pp.817-829
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• 2023

Variable wireless channel is a big challenge for real-time video applications, and the rate adaptation of realtime video streaming becomes a hot topic. Intra-video coding is important for high-quality video communication and industrial video applications. In this paper, we proposed a novel adaptive scheme for real-time video transmission with intra-only coding over a wireless network. The key idea of this scheme is to estimate the instantaneous remaining capacity of the network to adjust the quality of the next several video frames, which not only can keep low queuing delay and ensure video quality, but also can respond to bandwidth changes quickly. We compare our scheme with three different schemes in the video transmission system. The experimental results show that our scheme has higher bandwidth utilization and faster bandwidth change response, while maintaining low queuing delay.

• 한국재난정보학회 논문집
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• 제15권2호
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• pp.223-238
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• 2019

연구목적: 본 논문은 재난의 복잡다단한 맥락을 구성하는 정치 경제 사회의 다양한 이해관계자들이 생성해내는 담론과 사회적 실천의 함의를 파악하여 국내의 효율적 재난대응 방안 모색을 위한 기초자료를 제공하고자 한다. 연구방법: 페어클로(Fairclough)의 비판적 담론분석(Critical Discourse Analysis) 모델을 적용하여 국내 대표적인 세 일간지에 실린 2017년 11월 포항지진 관련 신문기사를 분석하였다. 연구결과: 담론분석 결과, 첫째, 세 언론사에서는 지진 발생 이후 대응의 측면에서 재난대응 매뉴얼과 대피훈련의 낮은 실효성을 지적하였다. 둘째, 지진피해 복구 측면에서 대피소 서비스 강화와 이재민 지원 확대의 필요성을 강조하였다. 셋째, 내진설계 강화 및 문자알림 서비스 질 향상 등 향후 피해를 미연에 방지하기 위한 실천 노력을 제시하였다. 결론: 본 연구에서는 효과적인 국내 재난대응을 위하여 재난 예방 대책의 현실성 실효성 제고, 유기적이고 통합적인 재난대응체계 마련, 시민의 역할과 참여 강조, 전문가 집단의 책임감 및 이에 대한 견제, 재난대응 관련 건전한 담론형성을 위한 미디어의 역할을 제안하였다.

• Journal of Electrical Engineering and Technology
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• 제10권3호
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• pp.983-989
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• 2015

Power transformer is one of the major and key apparatus in electric power system. Monitoring and diagnosis of transformer fault is necessary for improving the life period of transformer. The failures caused by short circuits are one of the causes of transformer outages. The short circuit currents induce excessive forces in the transformer windings which result in winding deformation affecting the mechanical and electrical characteristics of the winding. In the present work, a transformer producing only the radial flux under short circuit is considered. The corresponding axial displacement profile of the windings is computed using Finite Element Method based transient structural analysis and thus obtained displacements are compared with the experimental result. The change in inter disc capacitance and mutual inductance of the deformed windings due to different short circuit currents are computed using Finite Element Method based field analyses and the corresponding Sweep Frequency Responses are computed using the modified electrical equivalent circuit. From the change in the first resonant frequency, the winding movement can be quantified which will be useful for estimating the mechanical withstand capability of the winding for different short circuit currents in the design stage itself.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.486-486
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• 2013

Silicon nanowire devices fabricated by bottom-up methods are attracted due to their electrical, mechanical, and optical properties. Especially, to functionalize the surface of silicon nanowires by molecules has received interests. The changes in the characteristics of the molecules is delivered directly to the surface of the silicon nanowires so that the silicon nanowire can be utilized as an efficient read-out device by using the electronic state change of molecules. The surface treatment of the silicon nanowire with light-sensitive molecules can change its optical characteristics greatly. In this paper, we present the optical response of a SiNW field-effect-transistor (FET) conjugated with porphyrin molecules. We fabricated a SiNW FET and performed porphyrin conjugation on its surface. The characteristic and the optical response of the device shows a large difference after conjugation while there is not much change of the surface in the SEM observation. It attributed to the existence of few layer porphyrin molecules on the SiNW surface and efficient variation of the surface potential of the SiNW due to light irradiation.

• 수산경영론집
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• 제46권1호
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• pp.93-107
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• 2015

This study aims to analyze causalities among Hairtail prices by distribution channel using a vector autoregressive model. This study applies unit-root test for stability of data, uses Granger causality test to know interaction among Hairtail Prices by distribution channel, and employes the vector autoregressive model to estimate statistical impacts among t-2 period variables used in model. Analyzing results of this study are as follows. First, ADF, PP, and KPSS tests show that the change rate of Hairtail price by distribution channel differentiated by logarithm is stable. Second, a Granger causality test presents that the producer price of Hairtail leads the wholesale price and then the wholesale price leads the consumer price. Third, the vector autoregressive model suggests that the change rate of Hairtail producer price of t-2 period variables statistically, significantly impacts change rates of own, wholesale, and consumer prices at current period. Fourth, the impulse response analysis indicates that impulse responses of the structural shocks with a respectively distribution channel of the Hairtail prices are relatively more powerful in own distribution channel than in other distribution channels. Fifth, a forecast error variance decomposition of the Hairtail prices points out that the own price has relatively more powerful influence than other prices.

• Structural Engineering and Mechanics
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• 제26권3호
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• pp.315-341
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• 2007

A sudden change of stiffness in a structure, associated with the events such as weld fracture and brace breakage, will cause a discontinuity in acceleration response time histories recorded in the vicinity of damage location at damage time instant. A new damage index is proposed and implemented in this paper to detect the damage time instant, location, and severity of a structure due to a sudden change of structural stiffness. The proposed damage index is suitable for online structural health monitoring applications. It can also be used in conjunction with the empirical mode decomposition (EMD) for damage detection without using the intermittency check. Numerical simulation using a five-story shear building under different types of excitation is executed to assess the effectiveness and reliability of the proposed damage index and damage detection approach for the building at different damage levels. The sensitivity of the damage index to the intensity and frequency range of measurement noise is also examined. The results from this study demonstrate that the damage index and damage detection approach proposed can accurately identify the damage time instant and location in the building due to a sudden loss of stiffness if measurement noise is below a certain level. The relation between the damage severity and the proposed damage index is linear. The wavelet-transform (WT) and the EMD with intermittency check are also applied to the same building for the comparison of detection efficiency between the proposed approach, the WT and the EMD.

• 대한기계학회논문집A
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• 제26권10호
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• pp.2130-2141
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• 2002

A unique technique to estimate the magnitude or contribution ratio of each stage backlash in a system with a two-stage gear reducer is proposed. The concept to estimate the magnitude or contribution ratio of each stage backlash is based on the change of frequency response characteristic, in particular, the change of anti-resonant frequency and resonant frequency, due to the change of each stage backlash magnitude, even though the total backlash magnitude of a system with a two-stage gear reducer is constant. The validity of the technique is verified in a seeker gimbal and satisfactory results are obtained. It is thought that the diagnosis and maintenance of the manufacturing machines and systems with two-stage gear reducers will become more efficient and economical by virtue of the proposed technique.