• 공업화학
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• 제21권4호
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• pp.385-390
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• 2010

초음파를 에너지원으로 하는 에스테르 교환 반응에 의해 콩기름과 포도씨 기름, 옥수수 기름, 카놀라 오일 등 식물성 유지로부터 바이오디젤을 제조하였다. 초음파를 이용한 식물성 유지의 에스테르 교환 반응 특성과 생성된 바이오디젤의 생성물 분포 및 물리화학적 특성을 조사하였다. 또한, 초음파와 열에너지에 의한 에스테르 교환 반응의 반응속도도 비교하였다. 초음파를 이용한 에스테르 교환 반응에 의한 바이오디젤 수율은 산촉매보다 균일계 알칼리 촉매에서 높았다. 초음파를 이용한 식물성 유지의 에스테르 교환 반응에서 수산화칼륨 촉매를 식물성 유지에 대해 무게비로 1% 사용하고, 식물성 유지에 대한 메탄올의 몰 비가 6 : 1일 때 지방산 메틸에스테르의 수율이 가장 높았다. 초음파를 에스테르 교환 반응의 에너지원으로 사용하면 열에너지를 사용한 반응 결과 보다 반응속도가 빨랐다. 초음파를 이용한 식물성 유지의 에스테르 교환 반응에 의해 생성된 바이오디젤은 원료유지보다 산가가 30% 이상 낮아졌다.

• 한국자동차공학회논문집
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• 제16권4호
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• pp.38-46
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• 2008

An object of this study is to understand the correlation between the characteristics of an engine performance and combustion characteristics, applying BD20 fuel reformed by ultrasonic energy irradiation to diesel engines. Before conducting the main experiment, an experiment was performed to determine the optimum injection timimg of reformed BD20 by ultrasonic energy irradiation. To control the duration of the ultrasonic energy irradiation, the capacity of an ultrasonic energy fuel supply system was tested with 550cc and 1100cc chambers. As the result of the analysis of the regular BD20 and reformed BD20 by ultrasonic energy irradiation, the BSFC and the Power of the reformed BD20 was improved 3% and 6%, respectively compared to those of non-irradiated BD20. When the fuel injection timing was delayed by $5^{\circ}$, the engine power was improved by 3%, and the BSFC was improved by 2%. The maximum cylinder pressure of reformed BD20 was improved by a maximum of 6% in comparison to that of regular BD20, and demonstrated a synergistic effect of 3% by delaying the injection timing $5^{\circ}$.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.395-400
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• 2004

For the purpose of monitoring by ultrasonic test of the ball bearing conditions in rotating machinery, a system for their diagnosis was developed. ultrasonic technique is used to detect abnormal conditions in the bearing system. And various data such as frequency spectrum, energy and amplitude of ultrasonic signals, and ultrasonic parameters were acquired during experiments with the simulated ball bearing system. Based on the above results and practical application for power plant, algorithms and judgement criteria for diagnosis system was established. Bearing diagnosis system is composed of four parts as follows : sensing part for ultrasonic sensor and preamplifier, signal processing part for measuring frequency spectrum, energy and amplitude, interface part for connecting ultrasonic signal to PC using A/D converter, graphic display and software part for display of bearing condition and for managing of diagnosis program.

• Journal of Forest and Environmental Science
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• 제23권2호
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• pp.73-78
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• 2007

Ultrasonic deinkings of white ledger were carried out to confirm whether the ink removal efficiency and pulp qualities can be improved by the ultrasonic deinking. The effects of conventional pulping and ultrasonic treatment of white ledger on the ink particle size distribution and ink removal coefficient were compared. The physical properties of paper, energy consumption and effluent qualities were measured. The ultrasonic treatment of white ledger resulted in the ink particle size distribution suitable for flotation. The ink removal efficiency, brightness, breaking length and effluent quality were improved by the ultrasonic deinking. It is expected that the competitiveness of ultrasonic deinking system can be improved by the optimization of treatment condition.

• Journal of Mechanical Science and Technology
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• 제16권7호
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• pp.927-934
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• 2002

The HANARO ( High-flux Advanced Neutron Application Reactor) has been operated since 1995. The Cold Neutron (CN) hole was implanted in the reflector tank from the design stage. Before a vacuum chamber and a moderator cell for the cold neutron source are installed into the CN hole, it is necessary to measure exactly the size of the inside diameter and thickness of the CN hole to prevent the interference problem. Due to inaccessibility and high radiation field in the CN hole, a mechanical measurement method is not permitted. The immersed ultrasonic technique is considered as the best way to measure the thickness and the diameter of the CN hole. The 4-Axis manipulator was designed and fabricated for locating the ultrasonic sensors. The transducer of an ultrasonic sensor having 10 MHz frequency leads to high resolution as much as 0.03mm. The inside diameter and thickness of 550 points of the CN hole were measured using 2 channel ultrasonic sensors. The results show that the thickness and inside diameter of the CN hole is in the range of 3.3∼6.7mm and 156∼ 165mm, respectively. This data will be a good reference for the design of the cold neutron source facility.

• 한국분무공학회지
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• 제2권3호
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• pp.17-24
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• 1997

A simplified experiment was performed to figure out the atomization characteristics of rice-bran oil which it is highly viscous liquid by applying ultrasonic energy. A spray system, an ultrasonic system, and three kinds of hole-type nozzles(hole diameter: 0.31, 0.34, 0.37mm) were manufactured. To investigate the effects of ultrasonic energy on the atomization of a highly viscous liquid, a phase doppler particle analyzer was used for measurement and calculation of spray droplets data. Nozzle opening pressures were chosen of 3 levels, i.e, 16, 20, and 24MPa. As a result, it could be concluded that the ultrasonic energy was effective to improve the spray atomization when it applied to the fuel by means of 3 different nozzles because of the effects of the liquid fuel cavitation and relaxation between molecules caused by ultrasonic energy. The improvement rate of the spray atomization by the ultrasonic method compared with the conventional spray increased about 15% in the case of hole type nozzles. By increasing of the nozzle opening pressure and decreasing of the hole diameter, the atomization of spray droplets was improved.

• 에너지공학
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• 제20권2호
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• pp.84-89
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• 2011

본 연구는 하수슬러지에 알칼리처리와 초음파처리를 적용하여 최적의 가용화 조건을 도출하고자 각각의 단일처리, 병합처리로 가용화율을 확인하였다. 단일처리 중 알칼리처리는 4종의 알칼리시약을 각각 적용하여 전처리한 결과, NaOH를 이용한 방법이 27.6%로 가장 높은 가용화율을 확인할 수 있었으며, 주입농도가 높아지더라도 가용화에 미치는 영향에는 한계가 있음을 확인하였다. 초음파처리는 140 W/L의 조사밀도에서 가용화율이 가장 높았으며(33~39%), 조사주기의 증대는 가용화율에 큰 영향을 미치지 않는 것으로 확인되었다. 알칼리 처리와 초음파처리를 혼재한 병합처리 시 알칼리처리 후 초음파처리를 적용한 방법이 $70.4{\pm}9.4%$의 가용화율로 초음파처리 후 알칼리처리 방법에 비해 약 22% 높은 결과를 나타내었다. 각 조건에서의 SCOD 증가속도는 병합처리(알칼리처리 후 초음파처리)에서 0.076 $min^{-1}$으로 가장 높은 결과를 나타내었다.

• Nuclear Engineering and Technology
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• 제49권7호
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• pp.1463-1471
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• 2017

In order to monitor the pipe thinning caused by flow-accelerated corrosion (FAC) that occurs in coolant piping systems, a shear horizontal ultrasonic pitch-catch waveguide technique was developed for accurate pipe wall thickness monitoring. A clamping device for dry coupling contact between the end of the waveguide and pipe surface was designed and fabricated. A computer program for multi-channel on-line monitoring of the pipe thickness at high temperature was also developed. Both a four-channel buffer rod pulse-echo type and a shear horizontal ultrasonic waveguide type for high-temperature thickness monitoring system were successfully installed to the test section of the FAC proof test facility. The overall measurement error can be estimated as ${\pm}10{\mu}m$ during a cycle from room temperature to $200^{\circ}C$.

• 에너지공학
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• 제11권3호
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• pp.262-268
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• 2002

The present paper investigated the effect of ultrasonic vibrations on the melting process of phase-change materials (PCM). Furthermore, the present study considered constant heat-flux boundary condition, whereas many of the previous researches had adopted constant wall-temperature condition. The results of the present study revealed that ultrasonic vibrations accompanied the effects like acoustic streaming, cavitation, and thermally-oscillating flow. Such effects are a prime mechanism in the overall melting process when ultrasonic vibrations are applied. They speed up the melting process as much as 2.5 times, compared with the result of natural melting. Also, energy can be saved by applying ultrasonic vibrations to the natural melting. In addition, temperature and Nusselt numbers over time provided a conclusive evidence of the important role of ultrasonic vibrations on the melting phenomena.

• International Journal of Automotive Technology
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• 제5권4호
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• pp.303-309
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• 2004

In this paper, an interfacial crack length has been detected by using the ultrasonic attenuation coefficient on the adhesively bonded double-cantilever beam (DCB) joints. The correlations between energy release rates which were investigated by experimental measurement, the boundary element method (BEM) and Ripling's equation are compared with each other. The experimental results show that the interfacial crack length for the ultrasonic attenuation coefficient and energy release rate increases proportionally. From the experimental results, we propose a method to detect the interfacial crack length by using the ultrasonic attenuation coefficient and discuss it.