• Journal of Mechanical Science and Technology
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• v.15 no.5
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• pp.569-579
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• 2001

This study investigates the effects of operating conditions on the chattering of an automotive disk brake by experimental and computational methods. Design factors, which cause chattering in automobiles, have attracted great attentions for long time; but they are not well understood yet. For this study, we construct a brake dynamometer for measuring the disk surface temperature during chattering, and propose an efficient hybrid algorithm (combining FFT-FEA and traditional FEA program) for analyzing the thermo-elastic behavior of three-dimensional brake system. We successfully measure the judder in a brake system via the dynamometer and efficiently simulate the contact pressure variation by the hybrid algorithm. The three-dimensional simulation of thermo-mechanical interactions on the automotive brake, showing the transient thermo-elastic instability phenomenon, is presented for the first time in this academic community. We also find from the experimental study that the disk bulk temperature strongly influences the brake chattering in the automotive disk brakes.

• Vacuum Magazine
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• v.4 no.3
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• pp.12-15
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• 2017

Surface enhanced Raman scattering (SERS) is considered as one of promising medical and diagnostic technologies. The SERS effect is caused by the localized surface plasmon resonance (LSPR) from metal nanoparticles with narrow hot spots. The mechanism of LSPR, development of nanostructure fabrication, and corresponding researches are discussed. The flexible, label-free, low-cost, and highly-sensitive Au/ZnONRs/G is introduced. The Au/ZnONRs/G detects and distinguishes cataract, age-related macular degeneration, and diabetic macular edema from aqueous humor. Comprehension of SERS provides further improvement in bio sensing technology including early diagnosis and prolonged life expectancy.realize highly stretchable electrodes.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1322-1323
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• 2011

This study is to analysis on electrical characteristics according to the pollution of the outdoor exposed modules. Output of module is generated locally because there are various factors of pollution on the front glass of the modules. The experiments is carried out by measuring out output of the module with MP-160 and hot spots with a IR camera. This study is to analysis on electrical characteristics according to the pollution of the outdoor exposed modules.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.12
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• pp.214-220
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• 2010

This paper presents the results of a study on an electrodeless high intensity discharge (HID) lamp system that is powered by circularly polarized microwaves (CPMs). The technique to generate CPMs enables an electrodeless high intensity discharge lamp to be turned on without the retation of the bulb but conventional electrodeless high intensity discharge lamps use rotating bulbs in order to prevent a puncture in a hot spots that are formed by the linearly polarized microwaves in the circular cavity. The technique to generate CPMs is described and the salient features of the lamp characteristics are presented.

• Journal of Communications and Networks
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• v.18 no.5
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• pp.773-783
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• 2016

Both coordinated multi-point transmission and frequency reuse are effective approaches to mitigate inter-cell interference and improve network coverage. The motivation of this work is to explore the manner to effectively utilize the spectrum resource by reasonably combining cooperation and frequency reuse. The $Mat{\acute{e}}rn$ cluster process, which is appropriate to model networks with hot spots, is used to model the spatial distribution of base stations. Two cooperative mechanisms, coherent and non-coherent joint transmission (JT), are analyzed and compared. We also evaluate the effect of multiple antennas and imperfect channel state information. The simulation reveals that the proposed approach to combine cooperation and frequency reuse is effective to improve the network coverage for users located at both the center and the boundary of the cooperative region.

• Journal of the Korean Society of Combustion
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• v.6 no.2
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• pp.29-35
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• 2001

Unsteady numerical study has been conducted on combustion dynamics of a lean-premixed swirl-stabilized gas turbine swirl injector. A three-dimensional computation method utilizing the message passing interface (MPI) parallel architecture, large eddy simulation(LES), and proper orthogonal decomposition (POD) technique was applied. The unsteady turbulent flame dynamics are simulated so that the turbulent flame structure can be characterized in detail. It was observed that some fuel lumps escape from the primary combustion zone, and move downstream and consequently produce hot spots. Those flame dynamics coincides with experimental data. In addition, basis modes of the unsteady turbulent flame are characterized using proper orthogonal decomposition (POD) analysis. The flame structure based on odd basis modes is apparently larger than that of even ones. The flame structure can be extracted from the summation of the basis modes and eigenvectors at any moment.

• Journal of the Korean Society of Combustion
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• v.23 no.1
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• pp.28-35
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• 2018

Entropy waves(or hot spots) in a gas turbine combustor are generated by irregular heat release from flames, then can be coupled with acoustic waves when they are accelerated at the exit of the combustor. This coupling mechanism between the entropy and the acoustic waves is generally known to be one of the triggers for combustion instability, which is commonly called "indirect" combustion noise. This paper reviews the fundamental theories on generation, propagation, and coupling with acoustic field of entropy waves and recent research results on the indirect combustion noise for gas turbine combustors.

• Proceedings of the Korea Contents Association Conference
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• 2011.05a
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• pp.173-174
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• 2011

현대의 경찰활동은 지역사회 경찰활동(Community Policing)으로 귀결된다. 지역사회 경찰활동에 대한 많은 논의가 있어왔지만 지역사회 경찰활동이라는 패러다임에 관한 통합적인 모색은 등한시 되어 온 것이 사실이다. 지역사회 경찰활동에서 파생된 프로그램 및 전략들은 실질적인 경찰활동과 관련이 있다. 이러한 프로그램들은 경찰조직의 이슈 혹은 특정한 문제를 해결하기 위하여 지역사회 경찰활동보다 의도적으로 좁은 범위로 한정하고 있다. 그러한 초점을 가진 대표적인 프로그램은 문제지향적 경찰활동(Problem-oriented policing), 깨진 창(Broken Windows), 컴스탯(Comstat), 제3자 경찰활동(Third party policing), 우범지대(Hot spots)로 볼 수 있다. 그러나 이러한 프로그램 및 전략들은 매우 한정된 범위 내에서 존재하고 운영되는 것들이기 때문에 오늘날의 경찰활동의 근거나 기초를 지역사회 경찰활동만큼 제공해주지 못하고 있다. 지역사회 경찰활동과 관련된 경찰개혁 프로그램이나 전략들을 통합하여 다시 한 번 의미를 재정립하는 것은 현장의 경찰관들이 보다 쉽게 경찰행정의 의미를 이해하고 실제로 실현해 나갈 수 있는 방법을 안내하기 위함이다.

• Smart Structures and Systems
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• v.21 no.1
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• pp.99-111
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• 2018

Wind induced large bending oscillation amplitudes in tall and slender telecommunication steel towers may lead to precocious fatigue cracks and consequent risk of collapse of these structures, many of them installed in rural areas alongside highways and in highly populated urban areas. Varying stress amplitudes at hot spots may be attenuated by means of passive control mechanical devices installed in the tower. This paper gives an account of both mathematical-numerical model and the technique applied to design and evaluate the performance of a double controller installed in existing towers which is composed by a nonlinear pendulum and a novel type of passive controller described herein as a planar motion disk mounted on shear springs. Results of experimental measurements carried out on two slender tubular steel towers under wind action demonstrate the efficiency of the double controllers in attenuating the towers bending oscillation amplitudes and consequent stress amplitudes extending the towers fatigue life.

• Progress in Superconductivity and Cryogenics
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• v.1 no.2
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• pp.49-53
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• 1999

We fabricated a resistive superconducting fault current limiter (SFCL) with a shunt resistor in order to bypass the transient current at faults. The SFCL consists of a YBCO films coated with an Au layer (10$\Omega$ at room temperature). which is to disperse the heat generated at hot spots in the YBCO films, and a 5$\Omega$ shunt resistor. The minimum quench current of the SFCL was found to be 12.2Apeak. This SFCL successfully controlled the fault current to below 23 Apeak. Which is otherwise to increase up to 103 Apeak. With the shunt resistor, the temperature of the SFCL rose the temperature of the SFCL rose three times slower than without the shunt, whereby the SFCL is protected at high currents.