• Journal of Advanced Marine Engineering and Technology
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• 제22권2호
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• pp.225-231
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• 1998

Flame propagation speed characteristics of methante-air mixtures were experimentally investigated in combustion chamber modelled engine. Flame propagation process was known as a funtion of equivalence ratio initial pressure and initial temperature. Ion probe and schlieren photograph were applied to measure the local flame speed and flame radius in quiescent mixtures. Pressure was also measured to make sure of the reproducibility and to apply combustion analysis. Burning velocity was calculated from the flame propagation speed and combustion analysis. Flames were developed faster with higher initial pressure and initial temperature but showed maximum propagation speed at equivalence ratio 1.1 regardless of initial pressure and temperature. Local flame speed was maximum values at near midpoint between center and wall.

• 산업기술연구
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• 제20권B호
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• pp.131-138
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• 2000

In this paper, we would like to develop the bending collapse specific equation of aluminum members which are usually used in light-weight vehicle or electromobiles. The result of the developed equation are compared with that of test and finite element methods as the moment-rotational angle curves. Three types of aluminum members are tested with the pure bending collapse test rig. PAM-CRASH and ABAQUS program are used for finite element analysis. As the result the developed bending collapse governing equation is accurate in estimating the yield moment and the maximum moment. Especially, in the case of the local buckling and the delayed buckling, the developed equation is better effective than F.E.M.

• 전기학회논문지
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• 제63권10호
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• pp.1441-1447
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• 2014

A robust new algorithm for R wave detection named for Multiscale-based Peak Detection(MSPD) is assessed in this paper using MIT/BIH Arrhythmia Database. MSPD algorithm is based on a matrix composed of local maximum and find R peaks using result of standard deviation in the matrix. Furthermore, By reducing needless procedure of proposed algorithm, improve algorithm ability to detect R peak efficiently. And algorithm performance is assessed according to detection rates about various arrhythmia database.

• 대기
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• 제23권4호
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• pp.413-424
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• 2013

Urban Heat Island (UHI) intensity is one of vital parameters in studying urban boundary layer meteorology as well as urban planning. Because the UHI intensity is defined as air temperature difference between urban and rural sites, an objective sites selection criterion is necessary for proper quantification of the spatial variations of the UHI intensity. This study quantified the UHI intensity and its spatial pattern, and then analyzed their connections with urban structure and metabolism in Seoul metropolitan area where many kinds of land use and land cover types coexist. In this study, screen-level temperature data in non-precipitation day conditions observed from 29 automatic weather stations (AWS) in Seoul were analyzed to delineate the characteristics of UHI. For quality control of the data, gap test, limit test, and step test based on guideline of World Meteorological Organization were conducted. After classifying all stations by their own local climatological properties, UHI intensity and diurnal temperature range (DTR) are calculated, and then their seasonal patterns are discussed. Maximum UHI intensity was $4.3^{\circ}C$ in autumn and minimum was $3.6^{\circ}C$ in spring. Maximum DTR appeared in autumn as $3.8^{\circ}C$, but minimum was $2.3^{\circ}C$ in summer. UHI intensity and DTR showed large variations with different local climate zones. Despite limited information on accuracy and exposure errors of the automatic weather stations, the observed data from AWS network represented theoretical UHI intensities with difference local climate zone in Seoul.

• 대한조선학회논문집
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• 제59권3호
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• pp.134-140
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• 2022

Ship local structure sometimes experiences severe vibration due to the resonance with an excitation force generated by the propulsion system. In that case, the installation of dynamic vibration absorber such as Tuned Mass Damper (TMD) on the structure can be considered as an effective alternative countermeasure to reduce the troublesome vibration if structural modification or change of excitation frequencies is difficult. Meanwhile, the conventional optimal design method of TMD premises the target structure exposed on an excitation force without the constraint of its magnitude and frequency range. However, the frequencies of major ship excitation forces due to propulsion system are normally bounded and its magnitude is varied according to its operation speed. Hence, the optimal design of TMD to reduce the resonant vibration of ship local structure should be differently approached compared with the conventional ones. For the purpose, this paper proposes an optimal design method of TMD considering maximum frequency and magnitude variation of a target harmonic excitation component. It is done by both lowering the resonant response at the 1st natural frequency and locating the 2nd natural frequency over maximum excitation frequency for the idealized 2 degree of freedom system consisted of the structure and the TMD. For the validation of the proposed method, a numerical design case of TMD for a ship local structure exposed on resonant vibration due to a propeller excitation force is introduced and its performance is compared with the conventionally designed one.

• 한국지능시스템학회논문지
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• 제23권1호
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• pp.72-79
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• 2013

본 논문에서는 태양광 발전시스템의 최대전력점을 추종하기 위해, 개방회로전압과 가까운 첫 번째 지역극대전력점(local peak power point)의 전압 및 전류값이 특정한 범위 내에 있을 경우, 첫 번째 지역극대점이 전역극대전력점(global peak power point)인지 판단할 수 있도록 패턴을 분석하였다. 직-병렬 어레이로 연결된 태양전지 모듈에 부분그늘문제(partial shading problem)가 발생할 경우 다수의 지역극대전력점이 관찰될 수 있어, 전역극대전력점을 찾는데 어려움이 있다. 부분선형 태양전지 모델을 이용한 태블로 해석(Tableau analysis)으로 태양전지 어레이 회로의 V-I 특성을 시뮬레이션하여 지역극대전력점과 전역극대전력점을 확인하고, 그에 해당하는 전압 및 전류 값과 V-I 특성곡선의 패턴을 분석하였다. 분석된 패턴을 통해 특정한 영역을 설정하여 첫 번째 지역극대전력점이 전역극대전력점 인지 판단하여 발전하는 경우, 첫 번째 지역극대전력점으로만 발전했을 때에 비해 효율이 향상되었다.

• Journal of Information Display
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• 제11권4호
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• pp.173-181
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• 2010

In this paper, light-emitting-diode (LED) backlight driving circuits and dimming method for medium-sized and large liquid crystal displays (LCDs) are proposed. The double loop control method, the intelligent-phase-shifted PWM dimming method, the fast-switching current regulator, and the current matching techniques are proposed to improve not only the current regulation characteristics and the power efficiency but also the current matching characteristics and the transient response of the LED current. The brightness of the backlight using the proposed local dimming method was determined from the histogram of the local block to reduce the power consumption of the backlight without image distortion. The measured maximum power efficiency of the LED backlight driving circuit for medium-sized LCDs was 90%, and the simulation results showed an 88% maximum power efficiency of the LED backlight driving circuit for large LCDs. The maximum backlight power-saving ratio of the proposed dimming method was 41.7% in the simulation with a high-contrast image. The experiment and simulation results showed that the performance of LEDs as LCD backlight units (BLUs) improved with the proposed circuits and method.

• 한국연초학회지
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• 제5권2호
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• pp.17-24
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• 1983

Varietal difference of crop stand, growth of each organs and the factors of dry matter Production at different growth stage of three local tobacco varieties (Hyangcho, Youngwolyub and Yonginyub) were investigated in 1979 and 1980. Varietal variation of total standing crops was clear from 45th day after transplanting to end maximum value of photosyntheticinon-photosynthetic organs was Hyangcho: 1.9, Youngwolyub; 1.6, Yonginyub; 2.3. Maximum value of L/S and T/R ratio was clear from 35th day after transplanting to 45th day. RGR, NAR and CGR were in decreasing order of Yonginyub) Youngwolyub)Hyangcho through out growth stage, LAR and SLA were in decreasing from early growth stage to last growth stage, LAI was obtained to maximum value in the large growth state and LAI was increasing order of during the total growth period that it was Hyangcho is 7.6. Youngwolyub is 9.1 and Yonginyub is 8.7, SLA was Hyangcho;$2.088\textrm{cm}^2$/g/leaf, Youngwclyub;$2.173\textrm{cm}^2$/g/leaf and Yonginyub;$2.020\textrm{cm}^2$/g/leaf, respectively.

• 대한기계학회논문집B
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• 제21권5호
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• pp.691-699
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• 1997

The effects of concave hemispherical surface curvature on the local heat transfer from a turbulent round impinging jet were experimentally investigated. The liquid crystal transient method was used for these measurements. This method, which is a variation on the transient method, suddenly exposes a preheated wall to an impinging jet while video recording the response of liquid crystals for the measurement of the surface temperature. The Reynolds number ranges from Re=11,000 to 50,000, the nozzle-to- surface distance from L/d=2 to 10, and the surface curvature from D/d=6 to 12.The present results are also compared to those for the flat plate case. In the experiment, the local Nusselt numbers tend to increase in all regions with an increasing surface curvature. The maximum Nusselt number for all Reynolds numbers occurred at L/d .ident. 6 and a second maximum in the Nusselt number occurred at R/d .ident. 2 for both Re=23,000 and Re=50,000 in the case of L/d=2 and for Re=50,000 only in the case of L/d=4. Meanwhile, as the surface curvature increases, the value of the secondary maximum Nusselt number decreases. All the other cases exhibit monotonically decreasing values of the Nusselt number along the curved surface. The stagnation point Nusselt numbers are well correlated with Re, L/d, and D/d.

• International Journal of Computer Science & Network Security
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• 제23권6호
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• pp.193-201
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• 2023

In this paper, we consider the maximum scatter traveling salesman problem (MSTSP), a travelling salesman problem (TSP) variant. The problem aims to maximize the minimum length edge in a salesman's tour that travels each city only once in a network. It is a very complicated NP-hard problem, and hence, exact solutions can be found for small sized problems only. For large-sized problems, heuristic algorithms must be applied, and genetic algorithms (GAs) are found to be very successfully to deal with such problems. So, this paper develops a hybrid GA (HGA) for solving the problem. Our proposed HGA uses sequential sampling algorithm along with 2-opt search for initial population generation, sequential constructive crossover, adaptive mutation, randomly selected one of three local search approaches, and the partially mapped crossover along with swap mutation for perturbation procedure to find better quality solution to the MSTSP. Finally, the suggested HGA is compared with a state-of-art algorithm by solving some TSPLIB symmetric instances of many sizes. Our computational experience reveals that the suggested HGA is better. Further, we provide solutions to some asymmetric TSPLIB instances of many sizes.