• Journal of Ocean Engineering and Technology
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• v.17 no.5 s.54
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• pp.25-31
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• 2003

Numerical experiments have been conducted using the nonlinear combined refraction-diffraction model, in order to analyze the generation characteristics of stem wave, which is formed by the interaction between vertical structure and the oblique incident waves. The results of stem wave are discussed through the stem wave height distribution along/normal vertical structure, under the wide range of incident wave conditions-wave heights, periods, depths, and angles. Under the same wave height and period, the larger the incident wave angle, the higher the stem wave heights. According to the results of wave height distribution, in front of vertical structure, the maximum of stern wave heights occurs in the location bordering the vertical wall. Furthermore, the most significant result is that stem waves occur under the incident angles between $0^{\circ}\;and\;30^{\circ}$, and the stem wave height ratio has the maximum value, which is approximately 1.85 times the incident wave height when the incident wave angle becomes $23^{\circ}$.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.10a
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• pp.138-143
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• 2001

Based on mild slope equation and parabolic approximation the forward diffraction of monochromatic waves by a straight breakwater are studied numerically. The characteristics and effects of stem wave along breakwater and the relations between the stem wave and incident wave angle are discussed.

• Journal of Navigation and Port Research
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• v.41 no.5
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• pp.345-352
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• 2017

Recently, a new port reserves deep water depth for safe navigation and mooring, following the trend of larger ship building. Larger port facilities include long and huge breakwaters, and mainly adopt vertical type considering low construction cost. A vertical breakwater creates stem waves combining inclined incident waves and reflected waves, and this causes maneuvering difficulty to the passing vessels, and erosion of shoreline with additional damages to berthing facilities. Thus, in this study, the researchers have investigated the response of stem waves at the vertical breakwater near the entrance channel and applied numerical models, which are commonly used for the analysis of wave response at the harbor design. The basic equation composing models here adopted both the linear parabolic approximation adding the nonlinear dispersion relationship and nonlinear parabolic approximation adding a linear dispersion relationship. To analyze the applicability of both models, the research compared the numerical results with the existing hydraulic model results. The gap of serial breakwaters and aligned angles caused more complicated stem wave generation and secondary stem wave was found through the breakwater gap. Those analyzed results should be applied to ship handling simulation studies at the approaching channels, along with the mooring test.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.6
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• pp.429-436
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• 2010

Hydraulic experiments were conducted to analyze the characteristics of stem waves due to multidirectional random wave incidence with the different incident angles of main wave direction. Both multi-directional and uni-directional random waves were used to generate the stem waves and their results were compared with each other. The experiment shows multi-directional random waves developed along the vertical wall tend to increase as the incident angle increases similar to the uni-directional waves. Moreover, the stem wave widths were almost same as those in uni-directional random wave cases. However, the experiment demonstrate the stem wave heights were significantly smaller in multi-directional random wave cases than in uni-directional random wave cases.

• 한국가시화정보학회:학술대회논문집
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• 2002.11a
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• pp.113-116
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• 2002

The shock wave discharged from an annular duct leads to very complicated flow features, such as Mach stem, spherical waves, and vortex rings. In the current study, the merging phenomenon and propagation characteristics of the shock wave are numerically investigated using a CFD method. The Harten-Yee's total variation diminishing (TVD) scheme is used to the unsteady, axisymmetric, two-dimensional, compressible Euler equations. The Mach number of incident shock wave $M_s$ is varied in the range below 2.0. The computational results are visualized to observe the major features of the annular shock waves discharged from the tube. On the symmetric axis, the peak pressure produced by the shock wave and its location depend upon strongly the radius of the annular tubes. A Mach stem is generated along the symmetric axis of the annular tubes.

• Journal of Korea Water Resources Association
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• v.45 no.12
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• pp.1275-1292
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• 2012

This study investigates the characteristics of stem waves along a vertical structure under overtopping conditions through laboratory experiments in a wave basin. The uni-directional random waves with Bretschneider-Mitsuyasu frequency spectrum as incident waves were used. This study is focused on the reduction of wave height due to the variation of relative freeboard height (R) and the results for wave overtopping conditions are compared with those for non-overtopping conditions. Though the relative wave height along a vertical structure decreases with the decrease of relative freeboard, the variation of stem width is not significant. For the relative freeboard is greater than 1, the reduction effect of stem wave height by overtopping can be ignored in this experiments. The reduction effect of wave height along the structure for R =0.5 is about 10% comparing with R =1.5.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4B
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• pp.405-412
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• 2006

This study investigates the characteristics of stem waves along a vertical wall generated by obliquely incident monochromatic waves through laboratory experiments conducted in a wave basin and numerical simulations using parabolic approximation equations. The investigation is focused on the nonlinear effect of incident waves on the propagation characteristics of stem waves. Numerical results are compared with laboratory measurements and good agreements are obtained. The main results of this study show that the normalized stem wave height along the wall decreases and the stem width increases as the angle of incident waves decreases or the nonlinearity of the incident waves increases.

• Journal of Biomedical Engineering Research
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• v.3 no.2
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• pp.105-112
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• 1982

Using electronic cochlear implant system, we studied in cats the difference in the response of the brain stem evoked response (BER) during the stimulation with the acoustic signals and the electric signals. These brain stem electric responses were analyzed using the integral pulse frequency modulation method of the auditory nervous system. Animal experimental results and the analysis show that the carrier wave hasimprored the frequency specificity. of the electronic auditory prosthesis.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.2 no.1
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• pp.51-57
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• 1990

Based on second-order Stokes wave and parabolic approximation, a refraction-diffraction model for linear and nonlinear waves is developed. With the assumption that the water depth is slowly varying, the model equation describes the forward scattered wavefield. The parabolic approximation equations account for the combined effects of refraction and diffraction, while the influences of bottom friction, current and wind have been neglected. The model is tested against laboratory experiments for the case of submerged circular shoal, when both refraction and diffraction are equally significant. Based on Boussinesq equations, the parabolic approximation eq. is applied to the propagation of shallow water waves. In the case without currents, the forward diffraction of Cnoidal waves by a straight breakwater is studied numerically. The formation of stem waves along the breakwater and the relation between the stem waves and the incident wave characteristics are discussed. Numerical experiments are carried out using different bottom slopes and different angles of incidence.

• Journal of Acupuncture Research
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• v.18 no.4
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• pp.116-124
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• 2001

Background and Objetive : The aim of this study was to investigate the effect of various electroacupuncture stimulation on NADPH-diaphorase in cerebral cortex, brain stem, cerebellum of spontaneously hypertensive rats. Materials and Methods : We evaluated the changes of NADPH-d-positive neurons using a histochemical method. The staining intensity of NADPH-d-positive neurons was assessed in a quantitative fashion using a microdensitometrical method based on optical density by means of an image analyzer. Results and Conculsion : The average optical density of NADPH-d-positive neurons of 100 Hz (bipolar square wave 0.2 ms duration and 100 Hz frequency) electroacupuncture treatment group significantly increased in most cortical areas comparison between the manual acupuncture and 2 Hz (bipolar square wave 0.2 ms duration and 2 Hz frequency) electroacupuncture groups. In the brain stem, the optical density of NADPH-d-positive neuron at only superficial gray layer of the superior colliculus area was same as cerebral cortex. We conclude that the morphological evidence for NADPH-d-positive neurons may be have regional change in cerebral cortex brain stem and cerebellum according to various electroacupuncture stimulations.