• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.11a
• /
• pp.132-135
• /
• 2003

핸드폰에 장착된 반투과형 LCD (Liquid Crystal Display) 패널에서 반사판을 제거하면 투과형 LCD 마스크로 이용할 수 있다. LCD 패널의 광 흡수 실험에서 얻은 스펙트럼을 참고하여 다양한 파장대의 광원으로 리소그래피 하였다. 컴퓨터 이미지 프로그램으로 편집한 그림을 핸드폰 전용 통신 케이블을 통하여 LCD 패널로 전송하여, 다양한 모양의 패턴을 기판위에 전사하는데 성공하였다. 픽셀간의 경계가 현상되어 끊어지는 패턴이 형성되는 LCD 마스크의 단점을 극복하여 연속적인 패턴결과를 얻는데도 성공하였다. 이로부터 프로젝션 리소그래피의 응용에 쉽게 접근할 수 있는 발판이 마련된 것으로 생각된다.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.32 no.5
• /
• pp.564-572
• /
• 2012

Harmonic imaging is introduced in the present article and its principle and physical characteristics is described in contrast to conventional ultrasonic imaging. The principle of the conventional image which uses ultrasonic echoes reflected at the interfaces between tissues is presented, and the nonlinear ultrasonic propagation which results in harmonic components is conceptually described. The pulse inversion technique which effectively extracts the harmonic components from the ultrasonic echo signals is introduced, and the advantages of the constructed harmonic images are summarized comparing with those of conventional ultrasonic images. The harmonic images are classified according to the mechanism of harmonic production, and the typical harmonic images obtained from patients are presented in contrast to the corresponding sonograms. Clinical significance and prospects of harmonic imaging and the future research areas are discussed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2008.11a
• /
• pp.349-352
• /
• 2008

Thrust vectoring control by injection of secondary jet inside a convergent-divergent supersonic nozzle was studied by both experimentally and computationally. For various stagnation pressure of the secondary jet injected at a specific location(12 mm-downstream of throat) in the divergent section of nozzle, the characteristics of thrust vectoring were observed. Present numerical results were compared with previous investigators' results and Schlieren flow visualizations for the identical boundary conditions, and it showed a qualitatively good agreement. It was also noticed that the characteristics of thrust vectoring is strongly related to the reflection structure of oblique shock inside nozzle, ie., the pressure ratio of the secondary jet, SPR.

• Korean Journal of Optics and Photonics
• /
• v.9 no.1
• /
• pp.5-8
• /
• 1998

In calculating the light propagation in inhomogeneous uniaxial materials by using a conventional $4{\times}4$ matrix method, Fabry-Perot effect is caused by inherent multiple internal reflections at interfaces for monochromatic light source. In this paper we propose an apodization method by which we can eliminate in negligible time the interference fringe in the $4{\times}4$ matrix optics. For a cell with k abrupt interfaces, the new apodization method can be implemented simply by, at maximum, (k+1) addtional $4{\times}4$ matrix multiplications in calculating the complete transfer matrix of the cell.

• Geophysics and Geophysical Exploration
• /
• v.13 no.1
• /
• pp.24-30
• /
• 2010

This study utilises repeated numerical tests to understand the effects of variable near-surface conditions on time-lapse seismic surveys. The numerical tests were aimed at reproducing the significant scattering observed in field experiments conducted at the Naylor site in the Otway Basin for the purpose of $CO_2$ sequestration. In particular, the variation of elastic properties of both the top soil and the deeper rugose clay/limestone interface as a function of varying water saturation were investigated. Such tests simulate the measurements conducted in dry and wet seasons and to evaluate the contribution of these seasonal variations to seismic measurements in terms of non-repeatability. Full elastic pre-stack modelling experiments were carried out to quantify these effects and evaluate their individual contributions. The results show that the relatively simple scattering effects of the corrugated near-surface clay/limestone interface can have a profound effect on time-lapse surveys. The experiments also show that the changes in top soil saturation could potentially affect seismic signature even more than the corrugated deeper surface. Overall agreement between numerically predicted and in situ measured normalised root-mean-square (NRMS) differences between repeated (time-lapse) 2D seismic surveys warrant further investigation. Future field studies will include in situ measurements of the elastic properties of the weathered zone through the use of 'micro Vertical Seismic Profiling (VSP)' arrays and very dense refraction surveys. The results of this work may impact on other areas not associated with $CO_2$ sequestration, such as imaging oil production over areas where producing fields suffer from a karstic topography, such as in the Middle East and Australia.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.12 no.3
• /
• pp.139-148
• /
• 2000

In this paper, the interaction of oblique incident waves with a bottom-mounted and fluid-filled flexible membrane structure is investigated in the frame of linear hydro-elastic theory. The static shape of a membrane structure containing the fluid of a specific density is initially unknown and must be calculated before the hydrodynamic analysis. To solve hydrodynamic problem, the fluid domain is divided into the inner and outer region. The inner solution based on discrete membrane dynamic model and simple-source distribution over the entire fluid boundaries is matched to the outer solution ba~ed on an eigenfunction expansion method. The numerical results were compared to a series of Ohyama's experimental results. The measured reflection and tran¬smission coefficients reasonably follow the trend of predicted values. Using the computer program developed, the performance of a bottom-mounted and fluid-filled flexible membrane strocture is tested with various system parameters (membrane shape, internal pressure, density ratio) and wave characteristics (wave frequencies, incident wave angle). It is found that a bottom-mounted and fluid-filled flexible membrane structure can be an effel;tive wave barrier if properly designed.

• The Korean Journal of Petroleum Geology
• /
• v.14 no.1
• /
• pp.63-73
• /
• 2008

The seismic interpretation was carried out to understand the evolution of the Sora and North Sora Sub-basins, South Sea of Korea. Both sub-basins belong to the Domi Basin, which is located in the northeastern margin of East China Sea Basin with Fukue Basin of Japan. Age assignment of each strata in this study was based on the data of boreholes and seismic interpretation in NW Japan. Four regional horizons were identified, and five geological units; Y(basement), Q(Eocene$\sim$Middle Oligocene), M(Middle Oligocene$\sim$Early Miocene), L(Early Miocene$\sim$Late Miocene) and D(Late Miocene$\sim$Present) groups in ascending order. Structural trends of the main boundary faults and the basin-fill sediment are different between the Sora and North Sora Sub-basins; i.e., trend of the main boundary-faults, dip of horizons, distribution of basin and development of growth fault. These results imply that the Sora Sub-basin would have opened earlier than the North Sora Sub-basin.

• KIPS Transactions on Computer and Communication Systems
• /
• v.11 no.10
• /
• pp.345-352
• /
• 2022

Recent LiDAR(Light Detection And Ranging) sensor is used for scanning object around in real-time. This sensor can detect movement of the object and how it has changed. As the production cost of the sensors has been decreased, LiDAR begins to be used for various industries such as facility guard, smart city and self-driving car. However, LiDAR has a large input data size due to its real-time scanning process. So another way for processing a large amount of data are needed in LiDAR system because it can cause a bottleneck. This paper proposes edge computing to compress massive point cloud for processing quickly. Since laser's reflection range of LiDAR sensor is limited, multiple LiDAR should be used to scan a large area. In this reason multiple LiDAR sensor's data should be processed at once to detect or recognize object in real-time. Edge computer compress point cloud efficiently to accelerate data processing and decompress every data in the main cloud in real-time. In this way user can control LiDAR sensor in the main system without any bottleneck. The system we suggest solves the bottleneck which was problem on the cloud based method by applying edge computing service.

• The Journal of Engineering Geology
• /
• v.23 no.3
• /
• pp.201-216
• /
• 2013

Ground penetrating radar (GPR) surveys were conducted in a sand tank model in a laboratory and at an alluvial field site to detect the groundwater table and to investigate the influence of saturation on GPR response in the unsaturated zone. In the sand tank model, the groundwater table and saturation in the sand layer were altered by injecting water, which was then drained by a valve inserted into the bottom of the tank. GPR vertical reflection profile (VRP) data were obtained in the sand tank model for rising and lowering of the groundwater table to estimate the groundwater table and saturation. Results of the lab-scale model provide information on the sensitivity of GPR signals to changes in the water content and in the groundwater table. GPR wave velocities in the vadose zone are controlled mainly by variations in water content (increased travel time is interpreted as an increase in saturation). At the field site, VRP data were collected to a depth of 220 m to estimate the groundwater table at an alluvial site near the Nakdong river at Iryong-ri, Haman-gun, South Korea. Results of the field survey indicate that under saturated conditions, the first reflector of the GPR is indicative of the capillary fringe and not the actual groundwater table. To measure the groundwater table more accurately, we performed a GPR survey using the common mid-point (CMP) method in the vicinity of well-3, and sunk a well to check the groundwater table. The resultant CMP data revealed reflective events from the capillary fringe and groundwater table showing hyperbolic patterns. The normal moveout correction was applied to evaluate the velocity of the GPR, which improved the accuracy of saturation and groundwater table information at depth. The GPR results show that the saturation information, including the groundwater table, is useful in assessing the hydrogeologic properties of the vadose zone in the field.

• Journal of the Korean Geophysical Society
• /
• v.2 no.1
• /
• pp.39-44
• /
• 1999

High-resolution images are drawn from existing seismic data which were originally obtained by Korea Ocean Research & Development Institute (KORDI) during 1994-1997 for deep seismic studies on the East Sea of Korea. These images are analyzed for mapping Quaternary faults and near-bottom gas pockets. First 12 channels are selected from shot gathers for reprocessing. The processing sequence adopted for high-resolution seismic images comprises data copy, trace editing, true amplitude recovery, common-midpoint sorting, initial muting, prestack deconvolution, bandpass filtering, stacking, highpass filtering, poststack deconvolution, f-x migration, and automatic gain control (AGC). Among these processing steps, predictive deconvolution, highpass filtering, and short window AGC are the most significant in enhancement of resolution. More than 200 Quaternanry faults are interpreted on the migrated sections in the shallow depths beneath the seafloor. Although numerous faults are found mostly at the western continental slope and boundaries of the Ulleung Basin, significant amount of the faults are also indicated within the basin. Many of these faults are believed to be formed with reactivation of basement, from geotectonic activities including volcanism, and often originated in Tertiary, indicating that the tectonic regime of the East Sea might be unstable. Existence of shallow gas pockets casts real hazardous warnings to deep-sea drillings and/or to underwater constructions such as inter-island cables and gas pipelines. On the other hand, discovery of these gas pockets heightens the interests in developing natural resources in the East Sea. Reprocessed seismic sections, however, show no typical seismic characteristics for gas hydrates such as bottom-simulating reflectors in the western continental slope and ocean floor.