• Economic and Environmental Geology
• /
• v.53 no.3
• /
• pp.271-285
• /
• 2020

In this study, a numerical experiment related to the stress-strain analysis was performed on 3-D discrete fracture network(DFN) systems based on the distinct element method to evaluate the effect of joint geometry on deformability of jointed rock masses. Using one or two joint sets with deterministic orientation, a total of 12 3-D DFN blocks having 10m cube domain were generated with different joint density and size distribution. Directional deformation modulus of the DFN cube blocks were estimated along the axis directions of 3-D cartesian coordinate. In addition, deviatoric stress directions were chosen at every 30° of trend and plunge in 3-D for some DFN blocks to examine the variability of directional deformation modulus with respect to joint geometry. The directional deformation modulus of the DFN block were found to reduce with the increase of joint size distribution. The increase in joint density was less likely to have a significant effect on directional deformation modulus of the DFN block in case of the effect of rock bridges was relatively large because of short joint size distribution. It, however, was evaluated that the longer the joint size, the increase in the joint density had a more significant effect on the anisotropic deformation modulus of the DFN block. The variation of the anisotropic deformation modulus according to the variations in joint density and size distribution was highly dependent on the number of joint sets and their orientation in the DFN block. Finally, this study addressed a numerical procedure for stress-strain analysis of jointed rock masses considering joint geometry and discussed a methodology for practical application at the field scale.

• Journal of Wetlands Research
• /
• v.23 no.4
• /
• pp.296-306
• /
• 2021

Elasticity is a statistical technique that interprets the changing pattern of another variable according to a change in one variable as a quantitative numerical value and provides more information than correlation analysis and is widely used in climate change research. In this study the elasticity was calculated and sensitivity analysis was performed using air temperature and water quality data of the major tributaries of the Nakdong River. In addition the confidence interval for the elasticity was calculated using the T-Test and the validity of the elasticity was examined. The strength of elasticity shows high strength in the order of summer>fall>spring>winter and the direction shows regional characteristics with both negative and positive elasticity. After performing hierarchical cluster analysis on monthly observation data they were classified into 5 clusters and the characteristics of each cluster were visually analyzed using a parallel coordinate graph. The direction and intensity of the air temperature elasticity show regional characteristics due to the relatively high population density and complex influencing factors such as sewage treatment plants, small-scale livestock houses and agricultural activities. In the case of TP it shows great regional variability according to the circulation of nutrients in the ecosystem caused by algae growth and death according to temperature changes. Since the air temperature elasticity of the major tributaries of the Nakdong River is over weak and is valid at the significance level of 5%, it was analyzed that there is a change in water quality according to the air temperature change.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.31 no.4
• /
• pp.362-371
• /
• 1995

This study describes with the sinking behaviour for the purse seine. The experiment was carried out using three model purse seines of knotless netting. The nettings were woven in same leg length(10.5mm) of polypropylene 170 denier, polyamide 210 denier and polyester 250 denier two thread ply twine, each of the seines were named PP seine, PA seine and PES seine. Dimension of Purse seine models were 420cm for corkline and 85cm for seine depth, each models rigged 65.8g, 50.6g and 35.8g(weight in water) of lead for a leadline, seine models will have the same weight in water. Experiments carried out in the observation channel in a flume tank under still water conditions. Sinking motion was recorded by the one set of TV-camera for VTR, and reading coordinate carried out by the video digitization system. The results obtained were as follows: 1) Netting bundle for PP seine was existence on the surface of the water, spread out a netting by sinking force of sinkers. 2) Netting bundle for PES seine was existence in the middle of corkline and leadline. 3) Average sinking speed of seine margin was fastest for 10.7cm/s of PP seine, followed by 9.7cm/s of PA and 9.2cm/s of PES seines. 4) In all seines, the force of horizontal movement for the seine setting was values of ranged in disregard.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2006.05a
• /
• pp.494-499
• /
• 2006

LSIV (Large Scale Image Velocimetry)는 영상 처리 기술을 이용하여 수표면의 유속을 측정하는 장비이다. 처리가 용이한 좋은 LSIV의 영상을 만들기 위해서는 높은 고도에서 내려다 보며 영상을 획득하는 것이 측정의 정밀도를 높이는 데 도움이 된다. 이를 위해 트럭에 장착된 기중기를 이용하는 이동용 LSIV를 개발하고 있다. 이 때 기중기의 흔들림에 따라 획득된 영상이 흔들리는 문제가 발생하며, 영상의 흔들림을 보정하여 유속을 측정할 수 있는 영상 처리 알고리듬이 필요하게 된다. 이 연구에서는 PTV(Particle Tracking Velocimetry)의 입자 추적 알고리듬과 LSIV의 좌표 변환 알고리듬, LSIV의 유속 산정 알고리듬을 조합하여 흔들리는 영상에서 표면 유속을 측정하는 알고리듬을 개발하였다. 입자 추적 알고리듬은 비디오 카메라로 촬영된 연속 영상의 참조점들의 움직임을 추적하여 카메라의 위치 변동을 파악한다. 영상 분석된 결과들을 이러한 참조점들을 기준으로 변환하였다. 개발된 알고리듬의 검증을 위해서 실험 수로에서 동일한 흐름에 대해 흔들리지 않은 영상과 흔들리는 영상의 두 가지 영상을 만들었다. 흔들림이 없는 영상의 처리결과를 기준으로 삼아, 흔들림이 있는 영상의 처리 결과를 검토하였다. 그 결과, 흔들림이 지나치게 커서 참조점들의 추적이 불가능한 경우를 제외하고는 두 자료의 처리 결과는 거의 동일하였으며, 유속 측정의 최대 오차는 약 5 % 내외로 나타났다. 이 오차는 흔들림 때문에 생기는 영상의 열화 때문으로 추정된다. 이 알고리듬은 이동용 LSIV 시스템에 효율적으로 활용될 수 있을 것으로 기대된다.비용적 측면이나 생태 보존적 측면에서 유리할 것으로 판단된다.one)을 설치하는 대책이 필요하다. 저수지 관리를 효과적으로 수행하기 위해서는 저수지 내부의 탁도 거동을 정확히 예측할 수 있어야 한다. 따라서 추후 동수역학 및 열역학에 기초한 3차원 수치모형 연구와 성층흐름에 정밀한 밀도류 실험연구 및 이에 대한 적용이 필요할 것으로 판단된다.함으로써 정보의 질적보장과 정보전환의 표준화방안을 제시하는 정보분석시스템이다.이용, 수자원의 지속적 확보기술의 특성에 따른 4개의 평가기준과 26개의 평가속성으로 이루어진 2단계 기술가치평가 모형을 구축하였으며 2개의 개별기술에 대한 시범적용을 실행하였다.하는 것으로 추정되었다.면으로의 월류량을 산정하고 유입된 지표유량에 대해서 배수시스템에서의 흐름해석을 수행하였다. 그리고, 침수해석을 위해서는 2차원 침수해석을 위한 DEM기반 침수해석모형을 개발하였고, 건물의 영향을 고려할 수 있도록 구성하였다. 본 연구결과 지표류 유출 해석의 물리적 특성을 잘 반영하며, 도시지역의 복잡한 배수시스템 해석모형과 지표범람 모형을 통합한 모형 개발로 인해 더욱 정교한 도시지역에서의 홍수 범람 해석을 실시할 수 있을 것으로 판단된다. 본 모형의 개발로 침수상황의 시간별 진행과정을 분석함으로써 도시홍수에 대한 침수위험 지점 파악 및 주민대피지도 구축 등에 활용될 수 있을 것으로 판단된다. 있을 것으로 판단되었다.4일간의 기상변화가 자발성 기흉 발생에 영향을 미친다고 추론할 수 있었다. 향후 본 연구에서 추론된 기상변화와 기흉 발생과의 인과관계를 확인하고 좀 더 구체화하기 위한 연구가 필요할 것이다.게 이루어질 수 있을 것으로 기대된다.는 초과수익

• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.31 no.4 s.54
• /
• pp.289-293
• /
• 2005

Nowadays there are many sun protection cosmetics including organic or inorganic UV filter as an active ingredient. Chemically stable inorganic sunsEreen agents, usually metal oxides, we widely employed in high SPF products. Titanium dioxide is one of the most frequently used inorganic UV filters. It has been used as pigments for a long period of cosmetic history. With the development of micronization techniques, it becomes possible to incorporate titanium dioxide in sunscreen formulations without whitening effect and it becomes an important research topic. However, there are very few works related to quantitations of titanium dioxide in sunscreen products. In this research, we analyzed amounts of titanium dioxide in sunscreen cosmetics by adapting redof titration, reduction of Ti(IV) to Ti(III) and reoxidation to Ti(IV). After calcification of other organic ingredients of cosmetics, titanium dioxide is dissolved by hot sulfuric acid. The dissolved Ti(IV) is reduced to the Ti(III) by adding aluminum metals. The reduced Ti(III) is titrated against a standard oxidizing agent, Fe(III) (ammonium iron(III) sulfate), with potassium thiocyanate as an indicator In order to test accuracy and applicability of the proposed method, we analyzed the amounts of titanium dioxide in four types of sunscreen cosmetics, such as cream, make-up base, foundation and powder, after adding known amounts of titanium dioxide $(1{\sim}25w/w%)$. The percent recoveries of the titanium dioxide in four types of formulations were in the range between 96 and 105%. We also analyzed 7 commercial cosmetic products labeled titanium dioxide as an ingredient and compared the results with those of obtained from ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry), one of the most powerful atomic analysis techniques. The results showed that the titrated amounts were well coincided with the analyzed amounts of titanium dioxide by ICP-AES. Although instrumental analytical methods, ICP-MS (Inductively Coupled Plasma-Mass Spectrometry) and ICP-AES, are the best for the analysis of titanium, it is hard to adopt because of their high prices for small cosmetic companies. It was found that the volumetric method presented here gat e quantitative and reliable results with routine lab-wares and chemicals.

• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.41 no.2
• /
• pp.23-34
• /
• 2004

Video camera can be a useful tool to capture images for use in colorimeter. However the RGB signals generated by different video camera are not equal for the same scene. The video camera for use in colorimeter is characterized based on the CIE standard colorimetric observer. One method of deriving a colorimetric characterization matrix between camera RGB output signals and CIE XYZ tristimulus values is least squares polynomial modeling. However it needs tedious experiments to obtain camera transfer matrix under various white balance point for the same camera. In this paper, a new method to obtain camera transfer matrix under different white balance by using 3${\times}$3 camera transfer matrix under a certain white balance point is proposed. According to the proposed method camera transfer matrix under any other white balance could be obtained by using colorimetric coordinates of phosphor derived from 3${\times}$3 linear transfer matrix under the certain white balance point. In experimental results, it is demonstrated that proposed method allow 3${\times}$3 linear transfer matrix under any other white balance having a reasonable degree of accuracy compared with the transfer matrix obtained by experiments.

• The Korean Journal of Ecology
• /
• v.26 no.5
• /
• pp.281-287
• /
• 2003

We present the first analysis of moor vegetation on the Moojechi of Ulsan including syntaxonomy and syndynamics. We classified plant communities according to the Braun-Blanquet approach. In order to better understand ecological alteration processes and changing species compositions along successional gradients we also examined synecological differences using Principal Coordinate Analysis(PCoA) in terms of moisture gradient, species richness, and community structure. Classification resulted in one association and five plant communities occupying distinct moor habitats: Hypericum laxum-Eleocharis acicularis for. longiseta community, Drosera rotundifolia-Eleocharis congesta community, Platanthero-Molinietum japonicae ass. nova hoc loco, Molinia japonica-Alnus japonica community, Miscanthus sinensis-Pinus densiflora community, and Convallaria keiskei-Quercus serrata community. Due to synecological correspondences and floristic similarities in supraregional perspective, Platanthero-Molinietum can be assigned to existing higher syntaxonomic units of Molinion and Molinietalia in Braun-Blanquet system, established in Japan. We propose to extend their range and designate the new class Molinietea japonicae representative to the intermediate moor (Zwischenmoor) vegetation in Northeast Asia. PCoA resulted in four types showing a sequencess of succession: Needle spike-rush type, moor-grass type (incl. alder forest type), eulalia type, and oak forest type. A combination of edaphic conditions (soil eutrphication and soil moisture) and hydrologic patterns of moor ecosystem related to topography, occurring as result of external geophysical forces, controls inter alia spatial patterns and floristic compositions of moor plant communities.

• Investigative Magnetic Resonance Imaging
• /
• v.15 no.1
• /
• pp.11-21
• /
• 2011

Purpose : Localization using MRI is difficult due to susceptibility induced artifacts caused by metal electrodes. Here we took an advantage of the B0 pattern induced by the metal electrodes by using an oblique-view imaging method. Materials and Methods : Metal electrode models with various diameters and susceptibilities were simulated to understand the aspect of field distortion. We set localization criteria for a turbo spin-echo (TSE) sequence usingconventional ($90^{\circ}$ view) and $45^{\circ}$ oblique-view imaging method through simulation of images with various resolutions and validated the criteria usingphantom images acquired by a 3.0T clinical MRI system. For a gradient-refocused echo (GRE) sequence, which is relatively more sensitive to field inhomogeneity, we used phase images to find the center of electrode. Results : There was least field inhomogeneity along the $45^{\circ}$ line that penetrated the center of the electrode. Therefore, our criteria for the TSE sequence with $45^{\circ}$ oblique-view was coincided regardless of susceptibility. And with $45^{\circ}$ oblique-view angle images, pixel shifts were bidirectional so we can detect the location of electrodes even in low resolution. For the GRE sequence, the $45^{\circ}$ oblique-view anglemethod madethe lines where field polarity changes become coincident to the Cartesian grid so the localization of the center coordinates was more facilitated. Conclusion : We suggested the method for accurate localization of electrode using $45^{\circ}$ oblique-view angle imaging. It is expected to be a novelmethodto monitoring an electrophysiological brain study and brain neurosurgery.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.3
• /
• pp.104-111
• /
• 2018

The sensorless control of high efficiency air compressors using a permanent magnet type synchronous motor as an oil-free air compressor is quite common. However, due to the nature of the air compressor, it is difficult to install a position sensor. In order to control the permanent magnet type synchronous motor at variable speed, the inclusion of a position sensor to grasp the position of the rotor is essential. Therefore, in order to achieve sensorless control, it is essential to use a permanent magnet type synchronous motor in the compressor. The position estimation method based on the back electromotive force, which is widely used as the sensorless control method, has a limitation in that position errors occur due either to the phase delay caused by the use of a stationary coordinate system or to the estimated back electromotive force in the transient state caused by the use of a synchronous coordinate system. Therefore, in this paper, we propose a method of estimating the position and velocity using a rotation angle tracking observer and reducing the speed ripple through a disturbance observer. An experimental apparatus was constructed using Freescale's MPU and the feasibility of the proposed algorithm was examined. It was confirmed that even if a position error occurs at a certain point in time, the position correction value converges to the actual vector position when the position error value is found.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.34 no.11
• /
• pp.991-998
• /
• 2010

The effect of increasing the elevation of an IHX (intermediate heat exchanger) on the transient performance of the KALIMER-600 reactor pool during the early phase of a loss of normal heat sink accident was investigated. Three reactors equipped with IHXs that were elevated to different heights were designed, and the thermal-hydraulic analyses were carried out for the steady and transient state by using the COMMIX-1AR/P code. In order to analyze the effects of the elevation of an IHX between reactors, various thermal-hydraulic properties such as mass flow rate, core peak temperature, RmfQ (ratio of mass flow over Q) and initiation time of decay heat removal via DHX (decay heat exchanger) were evaluated. It was found that with an increase in the IHX elevation, the circulation flow rate increases and a steep rise in the core peak temperature under the same coastdown flow condition is prevented without a delay in the initiation of the second stage of cooling. The available coastdown flow range in the reactor could be increased by increasing the elevation of the IHX.