• Title/Summary/Keyword: 파동 방향성

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An Experimental Study of Sand Beach Profile Evolution under Regular Waves Corresponding to Storm and Normal Conditions (규칙파 조건에서의 사질해안 폭풍파와 평상파 단면변화 실험연구)

  • Choi, Junwoo;Roh, Min
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.37 no.2
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    • pp.333-342
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    • 2017
  • In order to understand the mechanism of the cross-shore evolution of storm (barred) and normal (nonbarred) profiles of a sandy beach, the vertically two-dimensional laboratory experiment was performed with a movable bed. The beach profiles and free surface motion were measured under monochromatic wave conditions evolving the storm and normal beach profiles. The observation was conducted in the surf zone during the alternation of the two wave conditions to reach its quasi-equilibrium state. The sandbar-crest and trough and the steep berm were evolved due to the plunging breakers in the storm case, and the bar-trough was decayed due to the spilling breakers in the normal case. From the measurements, it was found that the storm wave case was in an erosion state and the normal wave case was in an accretion state. The strong undertow, which is a dominant factor of the offshore migration mechanism, was developed in the storm wave case, and the weak undertow was developed in the normal wave case. The skewness and the asymmetry of the nonlinear wave motion, which is a dominant factor of the onshore migration mechanism, was measured similarly in both cases.

Variation Characteristics of Wave Field around Three-Dimensional Low-Crested Structure (3차원저천단구조물(LCS) 주변에서 파동장의 변동특성)

  • Lee, Jun Hyeong;Bae, Ju Hyun;An, Sung Wook;Lee, Kwang Ho;Kim, Do Sam
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.31 no.3
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    • pp.180-198
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    • 2019
  • In recent years, countries like Europe and Japan have been involved in many researches on the Low-Crested Structure (LCS) which is the method to protect beach erosion and it is regarded as an alternative to the submerged breakwaters, and compiled its results and released the design manual. In the past, studies on LCS have focused on two-dimensional wave transmission and calculating required weight of armor units, and these were mainly examined and discussed based on experiments. In this study, three-dimensional numerical analysis is performed on permeable LCS. The open-source CFD code olaFlow based on the Navier-Stokes momentum equations is applied to the numerical analysis, which is a strongly nonlinear analysis method that enables breaking and turbulence analysis. As a result, the distribution characteristics of the LCS such as water level, water flow, and turbulent kinetic energy were examined and discussed, then they were carefully compared and examined in the case of submerged breakwaters. The study results indicate that there is a difference between the flow patterns of longshore current near the shoreline, the spatial distribution of longshore and on-offshore directions of mean turbulent kinetic energy in case of submerged breakwaters and LCS. It is predicted that the difference in these results leads to the difference in sand movement.

Fish length dependance of acoustic target strength for large yellow croaker (부세에 대한 음향반사강도의 체장 의존성)

  • 강희영;이대재
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.39 no.3
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    • pp.239-248
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    • 2003
  • This paper was conducted as an attempt in order to construct the data bank of target strength for acoustic estimation of fish length in the coastal waters of Korea. The fish length dependence of acoustic target strength for 13 large yellow croakers (Pseudosciaena crocea) at 75 kHz was investigated and the prediction of the target strength by using the Kirchhoff-Ray Mode model (KRM model) was compared with target strength measurements. The results obtained are summarized as follows; 1. In the averaged target strength pattern for 13 large yellow croakers the maximum target strength was -35.13 dB at $-13.35^{\circ}$ on a tilted angle. 2. The relationship between fork length(L, cm) and averaged target strength(TS, dB) was expressed as follows; TS=23. 76log (L) -73.45 (r=0.47) TS=20log(L) -67.35 From this result, the conversion coefficient was -73.45 dB and 6.1 dB lower than the coefficient -67.35 dB where the value of the slope of the regression equation is forced to be 20. 3. Averaged target strength and a length conversion coefficient derived from a target strength histogram for 13 large yellow croakers of mean length 25.59 cm were -41.23 dB, -69.72 dB, respectively. 4. In the range of $$2;{\ll} L (fish length /{\lambda}(wave length);{\ll}40$$, the prediction of the averaged target strength by the KRM model increased gradually with the increasing of $L/{\lambda}$ and was lower than the measured target strength.

Disputes over IPR between Korea & US and Korea's policy response (한.미 지적재산권 분쟁과 대응방향)

  • Song, Ha-Seong
    • International Commerce and Information Review
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    • v.2 no.1
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    • pp.129-148
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    • 2000
  • 지적재산권은 기술개발의욕 자극을 위해 새로이 물건이나 사상 등의 창작자에게 일종의 배타적 독점권을 부여한 것으로서 1980년대 이후 국제적 관심이 고조되기 시작하였는데, 두 차례의 석유파동 이후 기술이 국제 경쟁력의 주요 결정요인으로 등장하던 시기에 한국을 비롯한 개도국들이 선진국의 기술을 모방하여 첨단기술제품 분야에서 경쟁적 우위를 확보하자 자신들의 경쟁력 확보를 위해 선진국들이 자신들의 통상교섭력을 바탕으로 GATT/UR 등 국제적 협상을 통해 지적재산권 보호문제를 통상문제로 확대시킨 것이다. 이러한 지적재산권에 대한 통상문제와 관련하여 가장 문제가 되는 국가는 역시 미국인데, 미국은 통상법 301조 중 지적재산권 보호에 적용되는 Special 301조를 이용하여 지적재산권 보호에 대한 실효성을 확보하였으며, 당초 제품수입상의 불공정거래행위에 적용하던 관세법 337조를 지적재산권을 침해하는 수입 판매행위에도 적용할 수 있도록 개정함으로써 그 보호수단을 더욱 강화하였는데, 이에 따라 우리도 적절한 대응방안의 모색이 요구되고 있다. 우선 정부의 입장에서는 대내적으로 원천기술 및 개량기술 개발을 통한 기술의 해외의존도 축소, 인센티브 도입 등 직무발명제도 활성화, 해외특허권 취득확대를 위한 중소기업의 해외출원비용 지원, 심사관의 전문화롤 통한 심사의 처리속도 및 질 향상, 특허기술정보 이용체제 개선을 위한 특허청의 정보전산화 및 산업기술정보원 톡허정보센타와의 유기적인 협조체제 구축, 기업의 특허분쟁대응능력 향상을 위한 전담부서 마련 및 국제특허분쟁 전문변리사 양성 등의 대안을 마련할 필요가 있으며, 대외적으로는 PLT협약 등 차후에 있을 국제협약에의 적극적인 참여를 통한 우리나라의 이익도모, 남북 가교역할의 강화 및 한 미 양국간의 법제적 차이에 대한 오해불식, 해당 산업에 영향을 줄 수 있는 로비 활동의 활성화 등의 대안이 필요하다. 또한 기업의 입장에서는 사전적으로 과감한 연구개발투자를 통한 산업재산권 확보, 기술 법률 언어능력을 고루 갖춘 특허전문가의 확보, 국제특허분쟁에 대한 대응체계 구축, 특허권 분쟁발생 방지를 위한 책임소재의 명확화 등의 근본적인 대책과 국제특허분쟁 차단을 위한 철저한 선행기술 조사, 해외기술의 개량 및 이용 촉진을 위한 크로스-라이센스의 활성화, 부실특허권에 대한 적극적인 무효심판청구, 제소정보에 대한 조기 입수, 설계변경이나 특허무효자료조사 등 침해회피 방법의 준비, 위험특허에 대한 철저한 예비조사 등의 부수적인 대책을 마련할 필요가 있으며, 일단 특허분쟁이 발생한 경우에는 당해 분쟁의 자사 생산 제품과의 관련여부 검토, 사건에 필요한 광범위한 정보 수집을 위한 전담팀 구성, 제소인의 특허권에 대한 면밀한 법률적 검토, 제소자에 대한 정확한 정보파악 및 최종 대응방안에 대한 신속한 결정, 자사의 특허를 이용한 제소자에 대한 역제소 등의 대응방안을 강구할 필요가 있는 것이다.

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Development of 3D Reverse Time Migration Software for Ultra-high-resolution Seismic Survey (초고해상 탄성파 탐사를 위한 3차원 역시간 구조보정 프로그램 개발)

  • Kim, Dae-sik;Shin, Jungkyun;Ha, Jiho;Kang, Nyeon Keon;Oh, Ju-Won
    • Geophysics and Geophysical Exploration
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    • v.25 no.3
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    • pp.109-119
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    • 2022
  • The computational efficiency of reverse time migration (RTM) based on numerical modeling is not secured due to the high-frequency band of several hundred Hz or higher for data acquired through a three-dimensional (3D) ultra-high-resolution (UHR) seismic survey. Therefore, this study develops an RTM program to derive high-quality 3D geological structures using UHR seismic data. In the traditional 3D RTM program, an excitation amplitude technique that stores only the maximum amplitude of the source wavefield and a domain-limiting technique that minimizes the modeling area where the source and receivers are located were used to significantly reduce memory usage and calculation time. The program developed through this study successfully derived a 3D migration image with a horizontal grid size of 1 m for the 3D UHR seismic survey data obtained from the Korea Institute of Geoscience and Mineral Resources in 2019, and geological analysis was conducted.

Influence of Detailed Structure and Curvature of Woven Fabric on the Luminescence Effect of Wearable Optical Fiber Fabric (직물의 세부 구조 및 굴곡이 웨어러블 광섬유의 발광 효과에 미치는 영향)

  • Yang, Jin-Hee;Cho, Hyun-Seung;Kwak, Hwy-Kuen;Oh, Yun-Jung;Lee, Joo-Hyeon
    • Science of Emotion and Sensibility
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    • v.21 no.4
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    • pp.55-62
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    • 2018
  • The two main requirements of wearable optical fiber fabrics are that they must presuppose a high degree of flexibility and they must maintain the luminance effect in both flat and bent conformations. Therefore, woven optical fiber fabrics that satisfy the above conditions were developed by both weaving and by using computer embroidery. First, we measured the brightness of the wearable optical fiber fabric in the flat state at a total of 10 measurement points at intervals of 1 cm. Second, the wearable optical fiber fabric was placed horizontally on the forearm, where three-dimensional bending occurs, and the luminance values were recorded at the same 10 measurement points. For the woven fabric in the flat state, the maximum, minimum, average, and standard deviation luminance values were $5.23cd/m^2$, $2.74cd/m^2$, $3.56cd/m^2$, and $1.11cd/m^2$, respectively. The corresponding luminance values from the bent forearm were $7.92cd/m^2$ (maximum), $2.37cd/m^2$ (minimum), $4.42cd/m^2$ (average), and $2.16cd/m^2$ (standard deviation). In the case of the computer-embroidered fabric, the maximum, minimum, average, and standard deviation luminance values in the flat state were $7.56cd/m^2$, $3.84cd/m^2$, $5.13cd/m^2$, and $1.04cd/m^2$, respectively, and in the bent forearm state were $9.6cd/m^2$, $3.63cd/m^2$, $6.13cd/m^2$, and $2.26cd/m^2$, respectively. Therefore, the computer-embroidered fabric exhibited a higher luminous effect than the woven fabric because the detailed structure reduced light-loss due to the backside fabric. In both types of wearable optical fiber fabric the luminance at the forearm was 124% and 119%, respectively, and the light emitting effect of the optical fiber fabric was maintained even when bent by the human body. This is consistent with the principle of Huygens, which defines the wave theory of light, and also the Huygens-Fresnel-Kirchhoff principle, which states that the intensity of light increases according to the magnitude of the angle of propagation of the light wavefront (${\theta}$).

Seismic wave propagation through surface basalts - implications for coal seismic surveys (지표 현무암을 통해 전파하는 탄성파의 거동 - 석탄 탄성파탐사에 적용)

  • Sun, Weijia;Zhou, Binzhong;Hatherly, Peter;Fu, Li-Yun
    • Geophysics and Geophysical Exploration
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    • v.13 no.1
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    • pp.1-8
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    • 2010
  • Seismic reflection surveying is one of the most widely used and effective techniques for coal seam structure delineation and risk mitigation for underground longwall mining. However, the ability of the method can be compromised by the presence of volcanic cover. This problem arises within parts of the Bowen and Sydney Basins of Australia and seismic surveying can be unsuccessful. As a consequence, such areas are less attractive for coal mining. Techniques to improve the success of seismic surveying over basalt flows are needed. In this paper, we use elastic wave-equation-based forward modelling techniques to investigate the effects and characteristics of seismic wave propagation under different settings involving changes in basalt properties, its thickness, lateral extent, relative position to the shot position and various forms of inhomogeneity. The modelling results suggests that: 1) basalts with high impedance contrasts and multiple flows generate strong multiples and weak reflectors; 2) thin basalts have less effect than thick basalts; 3) partial basalt cover has less effect than full basalt cover; 4) low frequency seismic waves (especially at large offsets) have better penetration through the basalt than high frequency waves; and 5) the deeper the coal seams are below basalts of limited extent, the less influence the basalts will have on the wave propagation. In addition to providing insights into the issues that arise when seismic surveying under basalts, these observations suggest that careful management of seismic noise and the acquisition of long-offset seismic data with low-frequency geophones have the potential to improve the seismic results.