• Korean Journal of Optics and Photonics
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• v.34 no.2
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• pp.76-83
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• 2023

In this paper, the results of analyzing the frequency lock-in breaking characteristics of a ring laser gyroscope with random dithering through numerical experiments are presented. By observing the variant features in the frequency lock-in characteristics according to the dithering amplitude noise, it was possible to analyze the minimum noise condition that causes the frequency lock-in to be broken. It was confirmed that the result is closely related to the relative difference between the dynamic frequency lock-in corresponding to the average dithering amplitude and the frequency determined by the Sagnac effect corresponding to an input rotational angular velocity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.6
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• pp.793-801
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• 1993

We show theoretically that the performance characteristics of an external cavity semiconductor laser, such as frequency locking and frequency noise reduction, can be greatly improved by just inserting a high finesse Fabry-Perrot(F-P) etalon inside the external reflector. For example, when the F-P etalon of finesse 30 and optical thickness 1.5cm is inserted inside the external cavity of length 3.0cm, the frequency locking accuracy and the linewidth reduction ration are increased up to 7.6 times and 86 times respectively compared with the conventional external-cavity laser under the same operation condition.

• Transactions of the Korean Society of Automotive Engineers
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• v.25 no.1
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• pp.19-27
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• 2017

In this paper, a simulator hardware and control design for an electronic parking brake (EPB) are proposed for emergency vehicle braking when the hydraulic break and anti-lock brake systems (ABS) fail to function. EPB systems are designed specifically for park braking and are usually installed on the rear wheels. However, in an emergency situation when all vehicle brake systems fail, the EPB can be utilized to stop the vehicle and track the target slip ratio as the ABS. This paper analyzed the non-linear EBP of the type of motor on caliper (MoC) based on experiments. A simulator hardware is also designed to validate the performance of the designed EPB controller in terms of braking distance and performance in tracking the target slip ratio. Through the experimental analysis, it is confirmed that a sliding mode controller can be applied on a non-linear EPB to track the target slip ratio.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.05a
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• pp.158-162
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• 2003

정보통신산업은 대규모 설비투자, 자연독점성, 망의 부성이 지배적으로 나타나고, 공급 및 수요의 잠김효과와 쏠림현상이 크며 기술의 혁신정도가 매우 크다는 규제의 대상이 되어 오고 있다. 그러나 최근 정보통신업은 다각적인 측면에서 급변하고 있다. 이러한 급격한 재반 변화는 규제자체에 대한 재고의 여지가 있고, 경쟁상황평가에 대한 근본적 인식의 전환이 요구되는 것이다. 본 고는 규제의 시발점이라고 할 수 있는 시장의 정의, 관련시장의 경쟁상황 평가와 시장지배적사업자 선정에 이어 규제옵션 및 규제수준을 설정하는 합리적 방향에 대해서 서술하고 있다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.3
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• pp.540-547
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• 1994

Contact and frictional locking conditions and the effect of shielding due to contact at the facet, which could be represented by the difference in energy release rate, as a function of phase angle of loading are analyzed in this study for the case of interfacial cracks by assuming single crack-kink model. The analysis of contact effects on interfacial fracture resistance shows that relative shielding increases as the shear component was increased, which indicates a qualitative agreement with the previous experimental results.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.6
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• pp.719-730
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• 2007

This study presents a thin-walled space frame element based on the classical Timoshenko beam theory. The element is derived according to the assumed strain field in order to resolve the shear-locking phenomenon. The shape function is developed in accordance with the strain field which is assumed to be constant at a 2-noded straight frame element. In this study, the geometrically nonlinear analysis applies the Corotational procedure in order to evaluate unbalanced loads. The bowing effect is also considered faithfully. Two numerical examples are given; monosymmetric curved and nonsymmetric straight cantilever. When these example structures behave lateral-torsional bucking, the critical loads are obtained by this study and ABAQUS shell elements. Also, the post-buckling behavior is examined. The results give good agreement between this study and ABAQUS shell.

• Journal of the Korean Orthopaedic Association
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• v.55 no.6
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• pp.495-502
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• 2020

Purpose: The aim of this study was to assess the effectiveness of domestically developed volar locking plate which has the concept of double-tiered subchondral support (DSS) in maintaining the reduction after distal radial fracture surgery. Materials and Methods: From July 2017 to December 2018, 54 patients were assessed. Plain radiographs were obtained immediately after surgery and at the last follow-up, and the radiographic parameters were measured in those images: radial length, radial inclination, volar tilt, ulnar variance, and distal dorsal cortical distance. The patients were subdivided into their age, type of fracture, and the position of the plate to evaluate the influence of each factors on the reduction maintenance. Results: Distal dorsal cortical distance in radiographs after the surgery was 5.91 mm (standard deviation, ±1.95 mm) on average. Significant differences in the radial length (p=0.038) and ulnar variance (p=0.001) were observed between immediately after surgery and at the last follow-up. When the parameters were evaluated by dividing the patients into subgroups according to the three specific factors, the ulnar variance showed a significant increase at the last follow-up when the patients were included 65-years-old or older. AO/OTA type C3 fracture, and Soong classification grade 0 plate position (p=0.007, p=0.012, p=0.046, respectively). Conclusion: Using the domestically developed DSS-type volar locking plate, significant reduction after distal radial fracture surgery could be maintained successfully. On the other hand, further study will be needed to determine about the reduction loss of the lunate facet identified in special cases that deal with fractures in elderly patients, unstable AO/OTA type C3 distal radial fractures, and Soong classification grade 0 plate position.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.454-454
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• 2016

하천의 치수안정성 확보 및 수심유지, 생태복원 등과 같은 다양한 요구를 충족하기 위한 보의 성능 개선에 대한 연구가 필요하며, 계단형 보는 재료에 의한 폭기효과 및 서식처 효과 등의 환경적요소를 내포하고 있다. 기존 연구는 표면류 흐름특성을 검증하고 유량변화에 따른 하류단 도수발생위치 변화를 분석하는 등 계단형 보에 대해 수리특성을 정량화한 연구가 대부분이며 흐름변화에 따른 유속장에 관한 연구는 미흡한 실정이다. 따라서 본 연구는 기능성 친환경 횡단 구조물 유형 중 하나인 계단형 보의 안정성 검토를 위한 수리적 특성을 분석하고자 함으로써 구조물 안정성에 영향을 줄 수 있는 자체 및 하류 보호공 주변의 유속 분석을 통한 흐름 특성을 검토하고 설계시 외력 고려를 위한 자료를 제공하기 위한 목적이 있다. 이를 위해 계단형 보모형에 대해 수리모형실험을 수행하였다. 폭 0.24 m, 총 길이 3.70 m, 높이 0.30 m인 순환실험수로를 이용하였으며, 계단형 보 모형은 5단으로 단 높이 2 cm와 단 길이 5 cm이며, 보 높이는 10 cm, 보 길이는 25 cm 모형으로 실험하였다. 하류에 전도식 게이트를 설치하여 하류 수위를 증가시키면서 보 하류부에서 발생하는 완전도수부터 하류수심이 보 높이를 초과하는 잠김흐름 조건에 대해 실험하였다. 측정기법은 입자영상측정계(Particle Image Velocimetry; PIV)를 이용하였으며, 상류영역부터 하류영역에 대해 보 주변 흐름의 순간적 유속분포를 확인하였다. 또한 측정된 전반적 흐름 양상에 대해 통계적 수리분석을 수행하였다. 흐름특성에 대한 연구는 향후 계단형 보의 물받이 길이 및 보의 적정 규모 설계시 중요한 자료가 될 것으로 기대한다.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.8
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• pp.1220-1225
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• 2009

In this paper, a tunable fiber feedback laser based on the use of Sagnac loop filter and fiber Bragg grating (FBG) is proposed. The Sagnac loop filter using a high birefringence fiber provides precise 0.33-nm channel spacing as a multi-wavelength grid filter. Ni-Cr wire wound on the FBG is useful to induce the thermo-optic effect of the fiber. Two types of FBG structures, which have a different length of wire, are demonstrated to show the wavelength shift and separation. To tune FBG by resistant heat, some current is supplied into the wire. When the wavelength matched with one of the cavity modes of Sagnac loop filter, the mode-locked lasing is occurred. The electrical power sensitivity of the resonant wavelength is measured to 1.75pm/mW. This laser configuration can be applied the electrical power system for monitoring the power fluctuation.

• Journal of the Economic Geographical Society of Korea
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• v.20 no.1
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• pp.70-83
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• 2017

Traditionally, economic growth has been uneven over the space. It has also been true for the recovery from social and economic crisis in old industrial areas of the advanced economies. Even if many of such old industrial areas were seriously affected by de-industrialization, some areas have been showing progress, while others have not been so. While interpreting this phenomenon used to be a key issue in economics, main stream liberal economic theorists' explanation was uneven distribution of economic resources, such as raw materials, labour and money. However, some revolutionary economic theorists have brought in the concept of "history" in explaining the phenomenon. Path dependence theorists, for example, interpretate the emergence of different growth paths with the concept of historical accidents. This contrasts to the recent argument of the group of scholars suggesting the concept of "regional resilience," who argue that uneven growth and different growth paths are originated from different regional resilience. This paper introduces the backgrounds, characteristics and utilities of the two theories: path dependence theory and the concept of regional resilience.