• Journal of the Mineralogical Society of Korea
• /
• v.13 no.1
• /
• pp.22-36
• /
• 2000

중원지역 지열수의 CO2 가스의 용축과 수반된 탄산염 침전물의 광물학적 특성을 밝히기 위하여 탄산염 침전물에 대해 광물학적 및 지구화학적 분석방법을 적용하여 보았다. 이들은 매년 수 mm의 두께로 저수조내에 침전되며 미세한 층상으로 결정화되어 있고, 검은 갈색의 얇은 층들이 반복적으로 존재하고 있다. 침전물은 비교적 순수한 방해석으로 되어 있으며 1M HCl로 처리하여 잔류물을 XRD 분석한 결과는 카올린 광물 및 일라이트질 광물이 확인되었다. 전자현미분석에 의하면 검은 갈색층은 주로 방해석과 Fe나 Mn 산화광물의 집합체이며 소량의 점토광물도 함께 섞여 있는 것으로 추정된다. Fe의 경우에는 주로 방해석내 Ca자리를 치환하여 존재하며 일부 산화광물로 함께 침전된 것으로 보인다. 반면에 Mn의 경우는 일부는 Fe처럼 방해석결정구조 내에서 Ca를 치환하면서 존재하기도 하지만 주로 산화물의 형태로 존재하는 것으로 보인다. 후방산란전자상(BSEI) 관찰에 의하면 Fe와 Mn 모두 매우 미세한 입자의 산화광물들로 밀집해 있는 부분이 관찰되기도 한다. 중원지역 탄산수로부터 방해석이 침전되는 과정은 CO2 가스가 방출되면서 pH가 증가하면서 방해석 및 Fe, Mn 산화물이 과포화상태가 되어 침전되는 것으로서 해석할 수 있다. 또한 지하 심부를 순환하면서 활발한 물-암석반응의 결과로 Si나 Al 및 기타 이온들의 함량이 상대적으로 높았던 탄산수가 pH가 높아지면서 카올린 광물이나 일라이트질 광물, 석영등의 규산염 광물들이 함께 침전하였을 것이다. 그러나 방해석의 침전과정이 이루어지는 과정 동안에, 온천공으로부터 채수되는 탄산수의 양이 수요에 따라 매우 불규칙해서 탄산수의 수요가 많은 경우 탄산수가 지속적으로 과잉 채수되면 주변 천층지하수가 탄산수에 혼합되어 Fe, Mn 등의 농도를 상대적으로 낮추게 되어 산화물형태로 침전되기가 어려워져서 거의 순수한 방해석만이 침전하게 된다. 결과적으로 거의 순수한 방해석 층에 검붉은 층이 불규칙하게 반복되고 있는 중원지역 탄산염침전물은 침전작용이 일어나는 대부분의 기간 동안 지속적으로 주변 전층지하수의 유입이 일어났음을 지시하고 있다. 또한 Fe, Mn 등의 함량이 높은 탄산수로부터의 침전은 매우 짧은 기간동안 단속적으로 일어났음을 지시한다.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.40 no.1
• /
• pp.23-31
• /
• 2016

In this study, we modified the conventional tensile split Hopkinson bar(TSHB) apparatus typically used for the high strength steel to evaluate the tensile deformation behavior of soft metallic sheet materials under high strain rates. Stress-strain curves of high purity single and multi-crystalline materials were obtained using this experimental procedure. Grain morphology and initial crystallographic orientation were characterized by EBSD(Electron Backscattered Diffraction) method measured in a FE-SEM(Field emission-scanning electron microscopy). The fractured surfaces were observed by using optical microscopy. The relationship between plastic deformation of aluminum crystalline materials under high-strain rates and the initial microstructure and the crystallographic orientations has been addressed.

• Journal of Adhesion and Interface
• /
• v.11 no.4
• /
• pp.174-180
• /
• 2010

The effect of carbon nanotube surface treatment on the interface and thermal conductivity of carbon nanotube-based poly(methylmethacrylate) (PMMA) composites was investigated. Coagulation and atomic-transfer radical polymerization (ATRP) was applied to modify the surface of multi-wall carbon nano-tube. The composite of ATRP method used carbon nanotube showed the higher transparency and thermal conductivities than that of the coagulation method used. In comparison to the thermal conductivity of pure PMMA, 0.21 W/mK, the ATRP carbon nanotube used PMMA/MWNT composite showed a thermal conductivity of 0.38 W/mK. The interface between carbon nanotube and PMMA was observed by scanning electron microscope and uniform dispersion of carbon nanotube was observed without any void in the PMMA matrix. It may be beneficial to transport the phonon without any scattering and it may result in a higher thermal conductivity.

• Journal of the Mineralogical Society of Korea
• /
• v.15 no.1
• /
• pp.11-21
• /
• 2002

A mineralogical study was made in order to identify the relationship between uranium content in groundwater and rock chemistry using core rocks recovered from the drilling holes for wells in the Daebo Granite areas. Uraniferous minerals are of primary origin and occur as inclusions in accessory minerals such as zircon, monazite, and xenotime. Since the uraniferous minerals are very small to be 1 ~ 2 $\mu$m in size, it is difficult to distinguish their mineralogical species precisely. The frequent presence of dissolution cavities or dissolved textures in the accessory minerals suggests that uraniferous minerals dissolved partially and contributed to the groundwater chemistry. Because there is no clear relationship between host rocks and groundwater for uranium concentration, mineralogical characteristics of uraniferous minerals, together with aqueous geochemical conditions favorable for uranium dissolution, could play important roles in groundwaster chemistry.

• Economic and Environmental Geology
• /
• v.53 no.2
• /
• pp.183-196
• /
• 2020

This study aimed to recover native gold from the concentrate using microwave-nitric acid leaching and magnetic/hydro separation experiments. The insoluble-residue was filtered from leaching solution through microwave-nitric acid leaching experiment. As a result of the atomic absorption spectrometer(AAS) analysis of the filtered leaching solution, it was discovered that Au content was not eluted at all and it was observed from the back scattered electron(BSE) image that native gold was liberated in the insoluble-residue. When magnetic/hydro separation experiments were applied for the insoluble-residue, magnetic and non magnetic minerals were separtated from insoluble-residue. Magnetite was recovered from the magnetic minerals and as a result of applying the hydro separation experiment again for the non-magnetic mineral, native gold was recovered. The native gold was identified through the X-ray diffraction(XRD) analysis and BSE image.

• The Journal of the Petrological Society of Korea
• /
• v.23 no.2
• /
• pp.139-144
• /
• 2014

A series of the planar cathodoluminescence (CL) and backscattered-electron (BSE) images of magmatic zircon from the Paleozoic Yeongdeok pluton in the southeastern Korean Peninsula were taken using a scanning electron microscope for a 3D reconstruction of internal zonation of zircon. Seven zircon crystals mounted in epoxy were serially polished with average $3{\mu}m$ thickness to their disappearance. Their 3D reconstruction of zonation was performed using the Volume Viewer function in the ImageJ software. The 3D oscillatory zoning pattern of zircon was apparently shown in all the analyzed crystals. This method can further be applied to zircon crystals of multiple growth histories as well as other geological materials.

• Journal of the Korean Magnetics Society
• /
• v.7 no.6
• /
• pp.308-313
• /
• 1997

The magnetoresistance (MR) and the saturation field behavior of the CoFe-Ag nano granular films as a function of the ferromagnetic underlayer and overlayer materials were investigated. The maximum MR ratio of 25.7 % and the saturation field of 2.1 kOe in the as-deposited 3000 $\AA$ $(Co_{92}Fe_8)_{31}Ag_{69}$ single alloy films at room temperature were obtained. The MR ratio and the saturation field of the 100 $\AA$ alloy film were 1.2 % and 5.2 kOe, respectively. Those of the sandwiched alloy films of 200 $\AA$ thick with the Fe under and overlayer of 100 $\AA$ were 11 % and 1.8 kOe respectively. The reduction of saturation field in the sandwiched alloy films is due to the exchange coupling between the ferromagnetic layers and the alloy layer. Among the Fe and FeNi, the more effective materials to reduce the saturation field of the sandwiched alloy films was Fe.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.25 no.9
• /
• pp.930-937
• /
• 2014

Inverse synthetic aperture radar (ISAR) images can be generated by radar which radiates the electromagnetic wave to a target and receives signal reflected from the target. ISAR images can be widely used to target detection and recognition. This paper proposed a method of generation of high resolution ISAR images by synthesizing frequency spectrums of each stepped chirp waveform in one burst and sub-sampling in frequency domain. This process is performed over entire bursts during coherent processing interval. Conventional ISAR image generation method using stepped frequency waveform has a severe problem of short unambiguous range, loading to ghost phenomenon. However, this problem can be resolved by the proposed method. In simulations, we generate high resolution ISAR image of the moving target which is Boeing-737 aircraft model composed of several ideal point scatterers.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.300.2-300.2
• /
• 2014

테라헤르쯔(terahertz : THz)파는 0.1~10 THz 의 범위로 적외선과 방송파 사이에 광대역 주파수 스펙트럼을 차지하고 있으며 직진성, 투과성, 그리고 낮은 에너지(meV)를 가지고 있어 비 파괴적이고 무해한 장점을 지니고 있다. Ti:sapphire laser와 같은 femto-pulse source 등이 많은 발전이 되어 현재 많은 연구와 발전이 이루어지고 있다. femto-pulse source를 이용한 THz 응용에서는 높은 저항, 큰 전자이동도, 그리고 아주 짧은 전하수명의 기판을 요구하는데 저온에서 성장한(low-temperature grown : LT) InGaAs는 격자 내에 Gallium 자리에 Arsenic이 치환 하면서 AsGa antisite가 발생하여 전하수명을 짧아지는 것을 응용하여 가장 많이 이용되고 있다. 본 연구에서는 보다 높은 저항을 얻기 위하여 molecular beam epitaxy를 이용하여 semi-insulating InP:Fe 기판위에 격자 정합된 LT-InGaAs:Be/InAlAs multi quantum well (MQW)를 well과 barrier를 가각 $10{\mu}m$ 씩 100주기 성장을 하였고 Ti와 Au를 각각 30, $200{\mu}m$로 dipole antenna를 제작 하였다. 이 때 Ti:sapphire femto-pulse laser (30 fs/90 MHz)를 excitation source로 사용하였을 때 9000 pA로 LT-InGaAs epilayer (180 pA)보다 50배 이상 큰 전류 신호를 얻을 수 있었다. THz 발생과 검출을 초소형, 초경량, 고효율로 하기 위해서는 fiber-optic를 이용해야 하는데 이때 분산과 산란 손실이 가장 적은 1550 nm 대역에서 많은 연구가 이루어 졌다. 780, 1560 nm의 mode-locking laser (90 fs/100 MHz)를 사용하여 현재 많이 이용되고 있는 Ti:sapphire femto-pulse laser와 비교하여 THz 특성 변화를 확인하는 연구를 진행 하고 있다.

• Economic and Environmental Geology
• /
• v.27 no.5
• /
• pp.491-498
• /
• 1994

The integral equation method is used for magnetotelluric (MT) modeling of a finite inhomogeneity in a two-layered earth. An integral equation relates the incident plane-wave field and the scattering currents in the three-dimensional (3-D) inhomogeneity through the electric tensor Green's function appropriate to a layered earth. This paper describes an effect of overburden and basement on MT responses of 3-D body. The effect of overburden is to reduce the detectability of target, and the reduction of detectability is more apparent for conductive overburden than for resistive one. The effect of basement, on the other hand, may enhance the anomaly due to 3-D body in the upper layer. In case of the resistive basement current perturbations about the body tend to be confined to the more conductive upper layer.