• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.6
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• pp.1143-1148
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• 2002

This paper analyses the transient response of a spherical elastic shell located near fee surface and impinged by spherical step-exponential acoustic shock waves. The problem is solved through extension of a method (Huang, 1969) previously formulated for the excitation in an infinite domain, which employs the classical separation of variables, series solutions, and Laplace transform technique The effect of the free surface reflection is taken into account using the image source method. The reflection of the incident wave has been treated by the same image formulation. If the reflection of the pressure field scattered and radiated by the shell is considered, the problem becomes that of multiple scattering by two spheres. However, this is in general negligible considering errors inherent from other sources and that the scattered and radiated pressure waves emanating from the shell are small. Thus, the problem is reduced to that of a structure immersed in an infinite fluid and impinged upon the origin and the image incident.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.2
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• pp.109-114
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• 2016

Nowadays, lower gear vibration and noise are necessary for drivers in automotive gearbox, which means that transmission gearbox should be optimized to avoid noise annoyance and fatigue before quantity production. Transmission error (T.E.) is the excitation factor that affects the noise level known as gear whine, and is also the dominant source of noise in the gear transmission system. In this paper, the research background, the definition of T.E. and gear micro-modification were firstly presented, and then different transmission errors of loaded torques for the spur gear pair were studied and compared by a commercial software. It was determined that the optimum gear micro-modification could be applied to optimize the transmission error of the loaded gear pair. In the future, a transmission test rig which is introduced in this paper is about to be used to study the T.E. after gear micro-geometry modification. And finally, the optimized modification can be verified by B&K testing equipment in the semi-anechoic room later.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.506-509
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• 2006

Shaped Sound Focusing is defined as the generation of acoustically bright shape in space using multiple sources. The acoustically bright shape is a spatially focused region with relatively high acoustic potential energy level. In view of the energy transfer, acoustical focusing is essential because acoustic energy is very small to use other type of energy. Practically, focused sound shape control not a point is meaningful because there are so many needs to enlarge the focal region especially in clinical uses and others. If focused sound shape can be controlled, it offers various kinds of solutions for clinical uses and others because a regional focusing is essentially needed to reduce a treatment time and enhance the performance of transducers. For making the shaped-sound field, control variables, such as a number of sources, excitation frequency, source positioning, etc., should be taken according to geometrical sound shape. To verify these relations between them, wavenumber domain matching method is suggested because wavenumber spectrum can provide the information of control variables of sources. In this paper, the procedures of shaped sound focusing using wavenumber domain matching and relations between control variables and geometrical sound shape are covered in case of an acoustical ring.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.4
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• pp.70-75
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• 2011

Nowadays, modern gearboxes are characterized by high torque load demands, low running noise and compact design. Also durability of gearbox is specially a major issue for the industry. For the gearbox which used in wind turbine, gear transmission error(T.E.) is the excitation that leads the tonal noise known as gear whine, and radiated gear whine is also the dominant source of noise in the whole gearbox. In this paper, tooth modification for the high speed stage is used to compensate for the deformation of the teeth due to load and to ensure a proper meshing to achieve an optimized tooth contact pattern. The gearbox is firstly modeled in Romax software, and then the various combination analysis of the tooth modification is presented by using Windows LDP software, and the prediction of transmission error under the loaded torque for the helical gear pair is investigated, the transmission error, contact stress, root stress and load distribution are also calculated and compared before and after tooth modification under one torque condition. The simulation result shows that the transmission error and stress under the loads can be minimized by the appropriate tooth modification.

• Journal of Food Hygiene and Safety
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• v.23 no.1
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• pp.26-30
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• 2008

Polycyclic Aromatic Hydrocarbons(PAHs) contamination arises from several source including processing of food(smoking, direct drying, cooking) and environmental contamination of air, water or soil. A red ginseng is produced by steaming the root followed by drying. The methodology involved extraction with n-hexane and washing with water, clean-up on Sep-Pak Florisil Cartridges and determination by HPLC/FLD. The mobile phase was a mixture of acetonitrile and water in 8:2 by the isocratic elution and the excitation wavelength of fluorescence detector was 294 nm and its emission wavelength was 404 nm. The average recovery was about 105% and the relative standard deviation was 0.5. The levels of benzopyrene in the selected red ginseng beverage samples were not detected.

• The Journal of the Korea Contents Association
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• v.5 no.3
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• pp.167-173
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• 2005

In a speech coding system using excitation source of voiced and unvoiced, it would be involved a distortion of speech quality in case coexist with a voiced and unvoiced consonants in a frame. So, I propose TSIUVC(Transition Segment Including Unvoiced Consonant) extraction method by using pitch pulses and Zero Crossing Rate in order to unexistent with a voiced and unvoiced consonants in a frame. And this paper present a TSIUVC approximate-synthesis method by using frequency band division. As a result, this method obtains a high quality approximation-synthesis waveform within TSIUVC by using frequency information of 0.547kHz below and 2.813kHz above. And the TSIUVC extraction rate was $91\%$ for female voice and $96.2\%$ for male voice respectively This method has the capability of being applied to a new speech coding of Voiced/Silence/TSIUVC, speech analysis, and speech synthesis.

• Journal of Korea Multimedia Society
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• v.6 no.3
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• pp.462-468
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• 2003

In a speech coding system using excitation source of voiced and unvoiced, it would be involved a distortion of speech quality in case coexist with a voiced and an unvoiced consonants in a frame. So, I propose TSIUVC(Transition Segment Including Unvoiced Consonant) searching and extraction method in order to uncoexistent with a voiced and unvoiced consonants in a frame. This paper present a new method of TSIUVC approximate-synthesis by using Least Mean Square and frequency band division. As a result, this method obtain a high quality approximation-synthesis waveforms within TSIUVC by using frequency information of 0.547KHz below and 2.813KHz above. The important thing is that the maximum error signal can be made with low distortion approximation-synthesis waveform within TSIUVC. This method has the capability of being applied to a new speech coding of Voiced/Silence/TSIUVC, speech analysis and speech synthesis.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2007.05a
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• pp.166-169
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• 2007

최근에 정부의 "15/30 LED조명 보급정책"에 힘입어 개발된 8W급 조명용 LED광원의 CIE 색도좌표 (chromaticity coordinate)와 주파장(dominant wavelength)등을 측정 고찰 하였다. 적색(R), 녹색(G), 청색(B), 백색(W)순으로 주파장은 각각 620[nm], 531[nm], 465[nm], 579[nm]이고, 자극순도(excitation purity)는 0.98, 0.82, 0.97, 0.15이며, 휘도순도(colorimetric putity)는 45[%], 16[%], 279[%], 6[%]로 나타났다. Power LED의 최적배치 설계로서, 특히 백색 LED광원의 경우 백열전구(15 lm/W)에 비해 3배 이상의 높은 효율(47.71m/W)을 보였고, 배광측정에서는 78.7%의 효율로 나타났다. 현재 LED광원은 MR16이나 베이스 타입 등의 형태로 제작하여 스탠드, 복도등, 비상유도등, 침실용 등의 용도에 사용되고, 일부는 LED의 원형이나 면(flat)타입으로 가로등이나 투광등으로도 활용되고 있다. 따라서 이들에 대한 각각의 특성들을 제시해 둘 필요성인 인지되어 국내 최초로 개발된 R/G/B/W 8W급 LED광원에 대한 기본적인 광특성 결과를 얻었으며, 이중에서 HB 백색 LED램프의 색도좌표 값을 얻어 CIE표준광과의 색도좌표(x, y) 위치를 비교 검토할 수 가 있었다.

• KIEE International Transactions on Electrophysics and Applications
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• v.2C no.5
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• pp.246-252
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• 2002

Two-dimensional steady state simulations of planar type radio frequency inductively coupled plasma (RFICP) have been performed. The characteristics of RFICP were investigated in terms of power transfer efficiency, equivalent circuit analysis, spatial distribution of plasma density and electron temperature. Plasma density and electron temperature were determined from the equations of ambipolar diffusion and energy conservation. Joule heating, ionization, excitation and elastic collision loss were included as the source terms of the electron energy equation. The electromagnetic field was calculated from the vector potential formulation of ampere's law. The peak electron temperature decreases from about 4eV to 2eV as pressure increases from 5 mTorr to 100 mTorr. The peak density increases with increasing pressure. Electron temperatures at the center of the chamber are almost independent of input power and electron densities linearly increase with power level. The results agree well with theoretical analysis and experimental results. A single turn, edge feeding antenna configuration shows better density uniformity than a four-turn antenna system at relatively low pressure conditions. The thickness of the dielectric window should be minimized to reduce power loss. The equivalent resistance of the system increases with both power and pressure, which reflects the improvement of power transfer efficiency.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.3
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• pp.116-121
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• 2012

In recent years, world is faced with a transportation energy dilemma, and the transportation is dependent on a single fuel - petroleum. However, Hybrid Electric Vehicle(HEV) technology holds more advantages to reduce the demand for petroleum in the transportation by efficiency improvements of petroleum consumption. Therefore, there is a trend that lower gear noise levels are demanded in HEV for drivers to avoid annoyance and fatigue during operation. And meshing transmission error(T.E.) is the excitation that leads to the tonal noise known as gear whine, and radiated gear whine is also the dominant source of noise in the whole gearbox. This paper presents a method for the analysis of gear tooth profile and lead modification, and the predictions of transmission error and load distribution are shown under one loaded torque for the 1st gear pair of HEV gearbox. The test is also obtained before tooth micro-modification under the torque. At last, the appropriate tooth modification is used to minimize the transmission error and load distribution under the loaded torque. It is a good approach which the simulated result is used to improve the design in order to minimize the radiation gear whine noise.