• Bulletin of the Society of Naval Architects of Korea
• /
• v.24 no.1
• /
• pp.35-41
• /
• 1987

An approximate method for calculating added resistance due to regular wave reflection has been established. In order to confirm the applicability of this method, an experimental work was carried out using a Series 60 model with oscillations in the 6-degrees of freedom restricted. Particular attention was paid to the case of the shorter wave length range where the effect of wave reflection is dominant compared to the effects of the ship's motions($\lambda/H=10.6-101.0,\;\lambda/L=0.23-1.18,\;F_n=0.10-0.25$). When comparing the measured and the computed resistance due to wave reflection in a head sea, good agreement is shown. This paper is based on research done by the Author as a member of the Ship Performance Group in the Department of Naval Architecture and Shipbuilding of the University of Newcastle-upon-Tyne in England, under the supervision of Dr. R.L. Townsin.

• Journal of Digital Contents Society
• /
• v.14 no.4
• /
• pp.545-555
• /
• 2013

Recently student portfolio is widely used as an evaluation method for self-directed performance in engineering education of the university. Especially, as many of the Innovation Centers for Engineering Education and ABEEK held student portfolio competitions, a lot of students in engineering college participate in student portfolio includes the contents and careers of the entire process of university. However, except for courses related to capstone design, there are few regular courses applied to Learning Portfolio in engineering education. Through using Learning Portfolio in courses, students take opportunities of organized collection of learning contents and critical reflection. Under these background study, the regular course in engineering education is may be appropriate for using Learing Portfolio in lecture. In this paper, we present the case study for the Data Structure course opened in the first semester of 2013 which is organized as a Learning Portfolio. According to the results of applying Learning Portfolio to the regular course, it turns out that learners can develope self-directed learning ability in exploring the learning process, and manage a learning process systematically through self-reflection in learning process.

• Journal of Korea Water Resources Association
• /
• v.37 no.9
• /
• pp.729-736
• /
• 2004

Analysis of reflection of random waves propagating over rectangular submerged non-porous breakwaters was performed by using the eigenfunction expansion method. In this study, random waves were generated by superposition of several monochromatioc waves. Reflection coefficients were calculated by summing each numerical results of regular waves. Predicted results from the eigenfunction expansion method were in a good agreement with the results of laboratory measurements. Reflection coefficients of random waves were also resonated at the Bragg reflection condition.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.5 no.3
• /
• pp.198-203
• /
• 1993

Hydraulic experiments were carried out to investigate the reflection characteristics of perforated breakwaters in regular wave conditions varying the width of wave chamber and the shape of perforated wall. It was found that the reflection coefficient of the perforated breakwater was very sensitive to the change of wave chamber width. giving its minimal value when the width of the wave chamber is approximately 0.2 times the wave length in the wave chamber. This phenomenon may be resulted from the wave resonance inside the wave chamber. The reflection coefficients slightly varied for all shapes of perforated wall. i.e., vortical slit, horizontal slit or circular hole. However, the reflection trend of the structure was not significantly affected by the shape of the perforated wall.

• Journal of the Korean Society of Safety
• /
• v.22 no.6
• /
• pp.13-19
• /
• 2007

Diesel car's smoke measurement equipment and method were investigated based on the exhaust gas regulations. Reflection photo method and light extinction method for measuring smoke were compared under conditions of both no load mode and Lug-down 3 mode. Free acceleration mode at no load condition was used for regular inspection of diesel car, and Lug-down 3 mode was used for fine inspection of the diesel car. A correlation between no load mode and Lug-down 3 mode was investigated in this research. The smoke measured with reflection photo method was 1.5${\sim}$2 times higher than that of light extinction method The correlation coefficient between reflection photo method and light extinction method for measuring smoke was 0.83, which shows comparatively high correlation between the two methods for measuring smoke in diesel engines.

• Proceedings of the KSME Conference
• /
• 2002.08a
• /
• pp.165-168
• /
• 2002

This paper describes the dynamics of the weak shock wave propagating inside some kinds of branched pipe bends. Computations are carried out by solving the two-dimensional, compressible, unsteady Euler Equations. The second-order TVD(Total Variation Diminishing) scheme is employed to discretize the governing equations. For computations, two types of branched pipe($90^{\circ}$ branch,$45^{\circ}$ branch) with a diameter of D are used. The incident normal shock wave is assumed at D upstream of the pipe bend entrance, and its Mach number is changed between 1.1 and 2.4. The flow fields are numerically visualized by using the pressure contours and computed schlieren images. The comparison with the experimental data performed for the purpose of validation of computational work. Reflection and diffraction of the propagating shock wave are clarified. The present computations predicted the experimented flow field with a good accuracy.

• Proceedings of the KSME Conference
• /
• 2001.11b
• /
• pp.456-461
• /
• 2001

This paper depicts the weak shock wave propagating inside some kinds of pipe bends. Computational work is to solve the two-dimensional, compressible, unsteady Euler Equations. The second-order TVD scheme is employed to discretize the governing equations. For the computations, the incident normal shock wave is assumed at the entrance of the pipe bend, and its Mach number is changed between 1.1 and 1.7. The turning angle and radius of the curvature of the pipe bend are changed to investigate the effects on the shock wave structure. The present computational results clearly show the shock wave reflection and diffraction occurring in the pipe bend. In particular, the vortex generation, which occurs at the edge of the bend, and its shedding mechanism are discussed in details.

• 한국전산유체공학회:학술대회논문집
• /
• 2003.10a
• /
• pp.135-136
• /
• 2003

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
• /
• 2002.08a
• /
• pp.263-265
• /
• 2002

외해에서 전파되어 온 파랑은 상대적으로 수심이 얕은 천해로 이동하면서 바닥지형의 영향으로 회절, 굴절, 반사, 천수 및 쇄파 등과 같은 다양한 현상을 경험한다. 본 연구에서는 바닥지형의 변화에 따른 파랑의 반사에 대해 검토하였다. (중략)

• Proceedings of the Korean Geotechical Society Conference
• /
• 2001.03a
• /
• pp.167-174
• /
• 2001

Reflection method using ultrasonic source has been attempted to obtain the information about tunnel lining structures composed of lining, shotcrete, water barrier and voids at the back of lining. In this work, two different types of sources, i.e. single-pulse source and sweep source, can be used. Single-pulse source with short time duration has the frequency content whose amplitudes tend to be concentrated around the dominant frequency, whereas sweep source with long time duration denotes a flat distribution of relatively larger amplitude over a broad frequency band, although the peak to peak amplitude of single-pulse source wavelet is equivalent to that of sweep source one. In traditional seismic application, a single-pulse source(weight drop, dynamite) is typically used. However, to investigate the fine structure, as it is the case in the tunnel lining structure, the sweep wavelet can be also a desirable source waveform primarily due to the higher energy over a broad frequency band. For the investigation purposes of sweep source, a physical modeling is a useful tool, especially to study problems of wave propagation in the fine layered media. The main purpose of this work was using a physical modeling technique to explore the applicability of sweep source to the delineation of inner layer boundaries. To this end, a two-dimensional physical model analogous to the lining structure was built and a special ultrasonic sweep source was devised. The measurements were carried out in the sweep frequency range 10 ∼ 60 KHz, as peformed in the regular reflection survey(e.g. roll-along technique). The measured data were further rearranged with a proper software (cross-correlation). The resulting seismograms(raw data) showed quitely similar features to those from a single-pulse source, in which high frequency content of reflection events could be considerably emphasized, as expected. The data were further processed by using a regular data processing system "FOCUS" and the results(stack section) were well associated with the known model structure. In this context, it is worthy to note that in view of measuring condition the sweep source would be applied to benefit the penetration of high frequency energy into the media and to enhance the resolution of reflection events.