• 대한기계학회논문집A
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• 제23권7호
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• pp.1065-1074
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• 1999

This study proposes the analysis and evaluation method of time series ultrasonic signal using the chaotic feature extraction for ultrasonic pattern recognition. Features extracted from time series data using the chaotic time series signal analysis quantitatively welding defects. For this purpose analysis objective in this study is fractal dimension and Lyapunov exponent. Trajectory changes in the strange attractor indicated that even same type of defects carried substantial difference in chaoticity resulting from distance shills such as 0.5 and 1.0 skip distance. Such differences in chaoticity enables the evaluation of unique features of defects in the weld zone. In experiment fractal(correlation) dimension and Lyapunov exponent extracted from 6dB ultrasonic defect signals of weld zone showed chaoticity. In quantitative chaotic feature extraction, feature values(mean values) of 4.2690 and 0.0907 in the case of porosity and 4.2432 and 0.0888 in the case of incomplete penetration were proposed on the basis of fractal dimension and Lyapunov exponent. Proposed chaotic feature extraction in this study enhances ultrasonic pattern recognition results from defect signals of weld zone such as vertical hole.

• 한국분무공학회지
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• 제22권3호
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• pp.109-115
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• 2017

The aim of this study is to investigate the effect of physical properties of fuels on spray characteristics in the gasoline direct injection system. Injection rate, spray visualization, and spray pattern experiments were performed to analyze the spray characteristics of ethanol, gasoline, and ethanol/gasoline blends. We measured injection rate of each fuel via the Bosch method. The spray visualization experiment was also carried out at atmospheric pressure using a high-speed camera. Finally, the average of drop surface area per unit volume was measured using the optical patternator. The experimental results from Bosch method showed that peak injection rate increased when the volume fraction of ethanol increased. In addition, higher viscosity of ethanol than that of gasoline leads to longer injection delay. At the initial injection region before reaching 0.8 ms, the spray tip penetration becomes longer as increasing the volume fraction of ethanol, but reversely shorter after 0.8 ms. It was found that ethanol makes spray angle become larger. The surface area per unit volume of the drop was decreased as the distance from the injection tip or the concentration of the gasoline increased.

• 한국소음진동공학회논문집
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• 제13권1호
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• pp.70-78
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• 2003

This paper dealt with an experimental study on the hydroelastic vibration of clamped perforated rectangular plates submerged in water. The penetration of holes in the plates had a triangular pattern with P/D (pitch to diameter) 1.750, 2.125, 2.500, 3.000 and 3.750. The natural frequencies of the perforated plates in air were obtained by the analytical method based on the relation between the reference kinetic and maximum potential energy and compared with the experimental results. Good agreement between the results was found for the natural frequencies of the perforated plates in air. It was empirically found that the natural frequencies of the perforated plate in air increase with an increase of P/D, on the other hand, the natural frequencies of the perforated plate in contact with water decrease with an increase of P/D. Additionally. the effect of the submerged depth on the natural frequency was investigated.

• Reproductive and Developmental Biology
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• 제36권3호
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• pp.147-154
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• 2012

본 연구에서는 제주흑우의 유전자원 보존과 증식에 있어 성공적인 인공수정을 위한 안정적인 동결정액 제조법을 수립하고 동결 융해 후 정자의 품질을 개선하기 위하여 제주흑우의 동결 정액 제조시 LDL, taurine, hypotaurine 그리고 trehalose를 첨가하여 이들이 동결 융해 후 정자의 성상에 미치는 영향에 대하여 알아보고자 수행하였다. 제주흑우의 정액 동결 시 LDL, LDL-taurine, LDL-hypotaurine 그리고 LDL-trehalose의 첨가는 ($63.40%{\pm}7.39$, $69.70%{\pm}6.12$, $67.25%{\pm}3.21$, $64.55%{\pm}2.43$) 대조구에($56.25%{\pm}6.42$) 비하여 모두 유의적인 생존율의 증가를 나타냈다 (p<0.05). 정자막 온전성 검사를 통한 꼬리막 팽창 정자의 비율은 LDL-taurine을 첨가 실험구에서 $70.55%{\pm}5.16$, LDL-hypotaurine 첨가 실험구에서 $64.45%{\pm}5.85$, LDL-trehalose 실험구에서 $64.50%{\pm}2.78$, LDL 단독 첨가 실험구에서 $61.65%{\pm}5.18$로 대조구 $51.90%{\pm}9.99$보다 모두 유의적으로 높은 결과를 나타냈다 (p<0.05). 동결 융해 후 정자의 첨체막 변화 양상에 있어서는 B pattern의 비율은 대조구와 실험구 모두 유의적 차이가 없었으며, F pattern은 LDL-taurine의 조합만이 대조구와 유의적인 차이를 나타내며 증가하였다 (p<0.05). 그러나 AR pattern의 비율은 LDL-taurine, LDL-trehalose, LDL-hypotaurine 그리고 LDL 처리의 순으로 대조구에 비하여 모두 유의적으로 낮은 수준의 AR pattern의 비율을 나타냈다(p<0.05). 정자의 수정능력 평가에 있어 LDL-taurine, LDL-hypotaurine 그리고 LDL-trehalose 모두 대조구에 대하여 유의적으로 높은 웅성전핵 형성율과 SFI를 나타냈으며 (p<0.05), 특히 LDL-taurine의 첨가는 LDL의 단독 처리에 비하여도 유의적으로 높은 수준의 웅성전핵 형성율과 SFI를 나타냈다 (p<0.05). 또한, decondenced sperm 비율에 있어 LDL, LDL-taurine, LDL-hypotaurine 그리고 LDL-trehalose 실험구 모두 대조구에 비하여 유의적으로 높은 결과를 나타냈다 (p<0.05). 본 연구의 결과는 제주흑우 정액의 동결정액 제조에 있어 안정적인 제조법을 공급할 수 있으며, 동결 융해 후 정자의 기능 개선 방법에 보다 많은 정보를 제공할 수 있을 것으로 사료된다.

• 동력기계공학회지
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• 제9권2호
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• pp.14-18
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• 2005

In this study, the spray characteristics of blended fuels with biodiesel were investigated. The experiments were performed for the effect of mixing ratio and injection pressures on the spray behavior. Conventional diesel fuel and biodiesel fuel and blended fuels were used as test fuels. Through the spray visualization system, composed of a Halogen lamp and High speed camera. The process of spray injection was visualized. Fuel containing biodiesel has different spray pattern on account of the high viscosity and large surface tension. Through this experimental result, we found that, after solenoid driving pulse generates, the increase of injection pressure enables delay time to get shorter, but the increase of mixing ratio makes delay time lengthen.

• 대한기계학회논문집B
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• 제33권9호
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• pp.722-727
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• 2009

The effect of the intake flow on the spray structure of a high pressure 11-hole fuel injector were examined in a single cylinder optical direct injection spark ignition (DISI) engine. The effects of injection timing and in-cylinder charge motion were investigated using the 2-dimensional Mie scattering technique. It was confirmed that in the homogeneous charge mode, the in-cylinder swirl charge motion played a major role in the fuel spray distribution during the induction stroke rather than the tumble flow. But, in the stratified charge mode, the effect of the in-cylinder charge was not so large that the injected spray pattern was nearly maintained and the increase of in-cylinder pressure by the upward moving piston reduced the fuel spray penetration.

• 한국생산제조학회지
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• 제26권4호
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• pp.430-435
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• 2017

The effect of the surface profile on CFRP and aluminum metal bonding was studied. A small number of steps were made on the aluminum surface, and the shear stress and elongation were measured using a shear test after bonding with an autoclave method. As the number of surface steps increased, the shear stress and elongation increased. The surface bonding strength increased because of the effect of the mechanical and chemical bonding. When the number of effective stages was exceeded, the shear strength decreased again due to the aspect ratio of the step and the reduction of the penetration effect of the resin into the groove.

• 오토저널
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• 제14권3호
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• pp.102-108
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• 1992

To clarify the structure of a diesel spray, a transient non-evaporating diesel spray injected under different ambient pressure and different injection pressure was studied. Spray tip penet- ration and spray angle were measured by taking the high speed shadowgraph of spray and Sauter mean Diameter(SMD) was also measured by light scattering technique at different positions along the spray axis and at different time from the start of injection. The effects of the operating parameters on the spray shape and SMD were investigated. By increasing the injection pressure, the spray tip penetration and the spray angle increased and the change of the ambient pressure also resulted in the considerable change in the shape of the spray. The analysis of SMD measurement showed that the atomization is a process that continues in sp- ace and time. As the injection pressure increases SMD decreases rapidly and with the increa- se of the ambient pressure the atomization process ends faster than the lower ambient press- ure and at lower pressure the atomization process continues to much farther downstream and far afterward.

• 한국연소학회지
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• 제7권1호
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• pp.44-51
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• 2002

This paper presents an atomization model for sprays under flash boiling conditions. The atomization is represented by the secondary breakup of a bubble/droplet system, and the breakup is considered as the results of two competing mechanisms, aerodynamic force and bubble growth. The model was applied to predict the atomization of a hollow-cone spray from pintle injector under flash boiling conditions. In the regimes this study considered, sprays are atomized by bubble growth, which produces smaller SMD#s than aerodynamic forces alone. With decreasing ambient pressures, the spray thickness, fuel vaporization rate and vapor radial penetration increases, and the drop size decreases. With increasing the fuel and ambient temperatures to some extent, the effect of flash boiling and air entrainment completely change the spray pattern.

• 한국레이저가공학회지
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• 제2권3호
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• pp.19-31
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• 1999

This paper introduces the monitoring scheme of laser welding quality using neural network. The developed monitoring scheme detects light signal emitting from plasma formed above the weld pool with optic sensor and DSP-based signal processor, and analyzes to give a guidance about the weld quality. It can automatically detect defects of laser weld and further give an information about what kind of defects it is, specially partial penetration and porosity among the interior defects. Those could be detected only by naked eyes or X-ray after welding, which needs more processes and costs in mass production. The monitoring scheme extracts four feature vectors from signal processing results of optical measuring data. In order to classify pattern for extracted feature vectors and to decide defects, it uses single-layer neural network with perceptron learning. The monitoring result using only the first feature vector shows confidence rate in recognition of 90%($\pm$5) and decides whether normal status or defects status in real time.