• Journal of radiological science and technology
• /
• v.33 no.3
• /
• pp.245-252
• /
• 2010

This study analyzed speed of sound, impedance, attenuation coefficient in accordance with acoustic characteristic standard of body soft tissue corresponding with Annex DD of IEC standard 60601-2-37(2007) which is about tissue mimicking materials (TMM) synthesized by polyurethane as a main material and new type of n-type scatter materials. This study reached the following conclusion after analyzing and evaluating image characteristic with SONOACE 9900 c PRIME (MEDESON Co.) and brightness, maximum penetration with convex probe (2.5~5.0 MHz). When n-type scatter materials are increasingly synthesised 0~8% with prepolymer as a main material and polyol mixture as a catalyst, 1. The more scatter materials are increased, the more sound speed of TMM becomes closely similar to soft tissue. 2. The more scatter materials are decreased, the more acoustic impedance becomes closely similar to soft tissue. 3. The more scatter materials are increased, the more attenuation coefficient is increased. 4. The more scatter materials are increased, the more average brightness of images is increased, but there is threshold. 5. The maximum penetration becomes closely similar to soft tissue at the 6% TMM as a scatter material.

• Journal of the Korean Institute of Gas
• /
• v.27 no.2
• /
• pp.39-48
• /
• 2023

This study presents the experimental results to measure the adsorption amount of methane gas by coal according to the conditions of a coalbed methane (CBM) reservoir. Adsorbed gas to coal seam particles was measured under reservoir conditions (normal pressure ~ 1,200 psi pressure range, temperature range15 ~ 45℃) using coal samples obtained from random mines in Kalimantan Island, North Indonesia. The obtained amount of absolute adsorbed gas was applied to triangular with linear interpolation to calculate the maximum amount of adsorbed gas according to temperature and pressure change, at which no experiment was performed. As a result, it was revealed that the amount of adsorbed gas to coal particles increased as the pressure increased and temperature decreased, but the increase of the amount of adsorbed gas decreased at more than an appropriate depth(1,000 ft). In the cleat permeability and cleat porosity for each depth of the coal bed considering the effective stress, the cleat permeability was 28.86 ~ 46.81 md, and the cleat porosity was 0.83 ~ 0.98%. This means that the gas productivity varies significantly with the depth because the reduction of the permeability according to the depth in the coal seam is significant. Therefore, a coalbed depth should be considered essential when designing the spacing of production wells in a coalbed methane reservoir in further study.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.37 no.2
• /
• pp.117-123
• /
• 2001

Anchovy scoop nets, a kind of lift net have been used in the coastal area of Cheju and South sea of Korea. An incandescent lamp(AC 100V, 1kW) is being used as a fishing lamp for gathering anchovy. Fishing lamp was installed at 1m ahead of the prow and 1.5m higher than the water surface. The fishing lamp let fish school rise to the water surface and attract to bag net. Accordingly, a successful anchovy catching depends on controling of fishing lamp. On the study, the distribution of spectral irradiance illumination of incandescent lamp(1kw) and the irradiance efficiency of reflection plate were analyzed and discussed to investigate the ability of fishing lamp which can attract anchovy school effectively. The results obtained are summarized as follows : 1. Around 180% of irradiance efficiency of incandescent lamp was increased by using the reflection plate. The light of lamp was radiated into water with circular shape. 2. The irradiance illumination of incandescent lamp in air was a maximum in wave length of 994nm but it was 690nm at 0.5m and 1.0m of water depth. 3. The relationship between water depth(x) and water illumination(y) of vertical light is represented as follows : y=146.03e supper(-0.37x) 4. The light of incandescent lamp(1kW) pass through much better into vertical direction than horizontal but it was estimated that the light was not able to reach depth of 20m.

• Journal of the Korean Institute of Gas
• /
• v.27 no.3
• /
• pp.98-107
• /
• 2023

This study presents a well spacing design for coalbed methane(CBM) reservoirs using the experimental results of methane gas adsorption measurement of coal samples obtained from North Kalimantan Island, Indonesia. The gas productivity analysis shows that the cumulative gas production increases as the Langmuir volume increases. This indicates that the maximum gas adsorption directly affects the gas production. In addition, the maximum gas production increases with the increase of reservoir permeability, and the dewatering period is shortened. In particular, the cumulative gas production increases as the production influence area increases. However, when comparing productivity per unit well, the maximum cumulative gas production is found between 2,000 ft of depth and 80-160 acres of the influence area. When reservoir depth and production influence area are considered simultaneously, the results of the appropriate well depth and spacing calculations show that gas productivity is highest between 600-2,000 ft. In this case, it is appropriate to design well spacing in the range of 80-160 acres. Therefore, well spacing design considering coalbed depth in undeveloped CBM reservoirs can be accomplished using gas sorption test results from coal samples.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2005.05b
• /
• pp.996-1000
• /
• 2005

본 연구에서는 마포대교 확장 공사의 인해 일부 교각의 우물통 기초 주변 하상변화와 세굴 현상을 파악하기 위한 심도추정 방법으로 현재 다양하게 토목분야에서 적용되고 있는 치하투과레이더 탐사기법을 사용하였다. 교각 우물통 주변의 안정적인 GPR 탐사를 수행하기 위한 보조장비를 고안하여 마포대교 P6의 우물통 주변을 2004년 6월(1차)과 2004년 10월(2차)에 걸쳐 탐사를 실시하였으며, 탐사 기간 중 약 12,000 cms의 유출량이 발생하여 국부세굴과 하상 변화 가능성을 충분히 검토 할 수 있을 것으로 판단되었다. 수집된 자료를 통해 양질의 자료 획득을 위해서 자료의 보정 과정을 마친 후 각각의 구간에 대해서 1, 2차 탐사된 두 개의 자료를 비교 분석하였다. 전구간의 반사파를 이용하여 기존의 연구결과에서 얻어진 반사파의 양상(Beres and Haeni, 1991)과 비교한 결과 하상 표면은 미사 혹은 실트로 구성되어 있고 주요한 하상 하부 매질은 전석(boulder), 호박돌 등으로 이루어져 있었다. 그리고 1차 및 2차 탐사 자료와 DATAPCS의 세굴센서가 설치된 측점을 기준으로 심도 및 위치 보정을 한 결과 큰 오차는 발생하지 않았으며, 400 MHz 안테나를 활용하여 최대수심 약 10 m 이상 하상을 탐사할 수 있었다. 수심이 깊은 구간은 하상과 가까운 위치에서 탐사를 실시하여 양질의 하상 변화 양상을 파악할 수 있어 하상 재료의 정성적인 평가를 높일 수 있도록 하였다. 마포대교의 탐사 대상 교각 우물통 주변은 계획홍수량의 1/3 수준으로 비교적 적은 홍수량이 발생한 2004년의 호우사상으로 인해 일부구간이 약 $10\~20\;cm$ 정도의 퇴적과 세굴 영향이 나타난 것을 제외하고는 유의할 만한 세굴과 하상 변화가 발생하지 않고 매우 안정적인 상태를 보이고 있으며 되메움이나 두드러진 퇴적층의 양상 또한 확인할 수 없었다. 대상구간에 설치한 유속계 최대유속이 2.0 m/s 이상 발생하였지만 우물통 주변의 자갈 및 호박돌 등과 같은 평균입경이 큰 유사의 이동에 절대적인 한계유속을 초과하지 못한 것으로 판단된다. GPR 탐사의 적용 한계성을 극복한 본 연구는 홍수 전$\cdot$후의 하상변화 및 최대세굴심, 되메움 깊이 및 범위 등의 세굴현상을 현장탐사를 바탕으로 현재 다양하게 적용하고 있는 세굴 실험식과 비교 분석함으로써 우물통 주변의 효율적인 세굴 보호 대책을 강구하는 목적으로 그 활용성을 증대할 수 있을 것이다.

• Journal of the Korean Geophysical Society
• /
• v.1 no.1
• /
• pp.59-68
• /
• 1998

Ground penetrating radar (GPR) experiments were performed in a sand tank to study the ability of detection of buried pipes and to characterize the signal of the reflection wave. The ratios of diameter of buried pipes to the depth were set 4 up to 24 % and materials were metal, synthetic resin, and wood. In case of groundwater table below buried materials, strong reflection signals were observed irrespective of diameter and depth except for wood. While it is very difficult to detect the reflection signals in case that the groundwater table is set to higher than buried materials. The reflection signals from the bottom of the sand tank, however, were clearly observed even in case of higher groundwater table. This implies that the weak reflection signals from the buried materials are not all due to the wave attenuation. The vertical reflection profiling method is recommended in case that the object of the survey is to find horizontal position of buried material because this method has the advantage in cost and time of survey. However, the full or partial CMP gather method is recommended in case that the objects of the survey are to get the detailed subsurface information, i.e. the depth to buried material, interval velocity of geological layer, and mapping the groundwater table.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.38 no.4
• /
• pp.293-299
• /
• 2002

The anchovy scoop net fishery is one of the important in the South sea and coastal of Jeju of Korea. They are using incandescent lamp as a fishing lamp at night to gather anchovy shoals in the water surface. Fishing lamp (AC 100 V 500 W$\times$2~3 or AC 100 V 1 ㎾$\times$1) was installed at 1 m ahead of the prow and 1.5 m height from the water surface. The fishing lamp let anchovy shoals rise to the water surface and are attracted to bag net. On this study, the distribution of submarine illumination of 1㎾ and 2 ㎾ incandescent lamp were analyzed and discussed to investigate the ability of fishing lamp which can gather anchovy shoals effectively. The submarine illumination of incandescent lamp showed peak in wave length 690 nm. The relationship between submarine illumination (L) and water depth (Z) of 1 ㎾ and 2 ㎾ incandescent lamp in vertical light is 1 ㎾ : L = 3851. 9 $e^{-1.4587Z}$ $R^2$=0.9952 2 ㎾ : L= 8211.9 $e^{-1.2852Z}$ $R^2$=0.9977 The submarine illumination of 2 ㎾ incandescent lamp of 0～4 m layers appeared to be 3 to 4 times higher than 1 ㎾ incandescent lamp, and in more deep layers than 6 m appeared to be equal value of each lamp. The light of incandescent lamp (1 ㎾) pass through much better into vertical direction than horizontal, and submarine illumination of 20 m layers was 1.0 l$\chi$. Therefore, fishing lamp power is thought that 1 ㎾ incandescent lamp is more efficient than 2 ㎾ to gather anchovy shoals in depth of 15~20 m to water surface.