• 제목/요약/키워드: Homogeneous solution

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Primary Solution Evaluations for Interpreting Electromagnetic Data (전자탐사 자료 해석을 위한 1차장 계산)

  • Kim, Hee-Joon;Choi, Ji-Hyang;Han, Nu-Ree;Song, Yoon-Ho;Lee, Ki-Ha
    • Geophysics and Geophysical Exploration
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    • v.12 no.4
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    • pp.361-366
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    • 2009
  • Layered-earth Green's functions in electormagnetic (EM) surveys play a key role in modeling the response of exploration targets. They are computed through the Hankel transforms of analytic kernels. Computational precision depends upon the choice of algebraically equivalent forms by which these kemels are expressed. Since three-dimensional (3D) modeling can require a huge number of Green's function evaluations, total computational time can be influenced by computational time for the Hankel transform evaluations. Linear digital filters have proven to be a fast and accurate method of computing these Hankel transforms. In EM modeling for 3D inversion, electric fields are generally evaluated by the secondary field formulation to avoid the singularity problem. In this study, three components of electric fields for five different sources on the surface of homogeneous half-space were derived as primary field solutions. Moreover, reflection coefficients in TE and TM modes were produced to calculate EM responses accurately for a two-layered model having a sea layer. Accurate primary fields should substantially improve accuracy and decrease computation times for Green's function-based problems like MT problems and marine EM surveys.

In-situ Cross-linked Gel Polymer Electrolyte Using Perfluorinated Acrylate as Cross-linker (과불소화된 아크릴레이트 가교제로 제조된 직접 가교형 겔 고분자 전해질의 전기화학적 특성)

  • Oh, Si-Jin;Shim, Hyo-Jin;Kim, Dong-Wook;Lee, Myong-Hoon;Lee, Chang-Jin;Kang, Yong-Ku
    • Journal of the Korean Electrochemical Society
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    • v.13 no.2
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    • pp.145-152
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    • 2010
  • The gel polymer electrolyte(GPE) were prepared by in-situ thermal cross-linking reaction of homogeneous precursor solution of perfluorinated phosphate-based cross-linker and liquid electrolyte. Ionic conductivities and electrochemical properties of the prepared gel polymer electrolyte with the various contents of liquid electrolytes and perfluorinated organophosphate-based cross-linker were examined. The stable gel polymer electrolyte was obtained up to 97 wt% of the liquid electrolyte. Ionic conductivity and electrochemical properties of the gel polymer electrolytes with the various chain length of perfluorinated ethylene oxide and different content of liquid electrolytes were examined. The maximum ionic conductivity of liquid electrolyte was measured to be $1.02\;{\times}\;10^{-2}\;S/cm$ at $30^{\circ}C$ using the cross-linker($PFT_nGA$). The electrochemical stability of the gel polymer electrolyte was extended to 4.5 V. The electrochemical performances of test cells composed of the resulting gel polymer electrolyte were also studied to evaluate the applicability on the lithium polymer batteries. The test cell carried a discharge capacity of 136.11mAh/g at 0.1C. The discharge capacity was measured to be 91% at 2C rate. The discharge capacity decreased with increase of discharge rate which was due to the polarization. After 500th charge/discharge cycles, the capacity of battery decreased to be 70% of the initial capacity.

Preparation of Coil-Embolic Material Using Syndiotactic Poly(vinyl alcohol) Gel Spun Fibers (교대배열 PVA 젤 섬유를 이용한 고분자 색전 코일 제조)

  • Seo, Young Ho;Oh, Tae Hwan;Han, Sung Soo;Joo, Sang Woo;Khil, Myeong Seob
    • Polymer(Korea)
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    • v.37 no.4
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    • pp.486-493
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    • 2013
  • The structure, morphology, and physical properties of syndiotatic poly(vinyl alcohol) (s-PVA) gel spun fibers were investigated to prepare polymeric embolization coils. S-PVA was prepared by saponification of the poly(vinyl acetate)/poly(vinyl pivalate)(PVAc/PVPi) copolymer. The viscosity of s-PVA solutions showed shear thinning behavior and the solution formed a homogeneous phase. Based on shear viscosity change with concentration, the optimum dope concentration was selected as 13 wt%, after which s-PVA fibers were spun and the solvent was removed. The fibers were then drawn with a maximum draw ratio of 15. A polymeric embolization coil was made of the s-PVA gel-spun fibers. The fibers were wound densely onto rigid rod and then annealed at different annealing temperatures. The polymeric embolization coil annealed at $200^{\circ}C$ was similar to metallic coils and its shape was maintained well after extension. Overall, gel-spun PVA fibers performed well for the preparation of primary and secondary coils to replace metallic coils.

An Application of Artificial Intelligence System for Accuracy Improvement in Classification of Remotely Sensed Images (원격탐사 영상의 분류정확도 향상을 위한 인공지능형 시스템의 적용)

  • 양인태;한성만;박재국
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.20 no.1
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    • pp.21-31
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    • 2002
  • This study applied each Neural Networks theory and Fuzzy Set theory to improve accuracy in remotely sensed images. Remotely sensed data have been used to map land cover. The accuracy is dependent on a range of factors related to the data set and methods used. Thus, the accuracy of maps derived from conventional supervised image classification techniques is a function of factors related to the training, allocation, and testing stages of the classification. Conventional image classification techniques assume that all the pixels within the image are pure. That is, that they represent an area of homogeneous cover of a single land-cover class. But, this assumption is often untenable with pixels of mixed land-cover composition abundant in an image. Mixed pixels are a major problem in land-cover mapping applications. For each pixel, the strengths of class membership derived in the classification may be related to its land-cover composition. Fuzzy classification techniques are the concept of a pixel having a degree of membership to all classes is fundamental to fuzzy-sets-based techniques. A major problem with the fuzzy-sets and probabilistic methods is that they are slow and computational demanding. For analyzing large data sets and rapid processing, alterative techniques are required. One particularly attractive approach is the use of artificial neural networks. These are non-parametric techniques which have been shown to generally be capable of classifying data as or more accurately than conventional classifiers. An artificial neural networks, once trained, may classify data extremely rapidly as the classification process may be reduced to the solution of a large number of extremely simple calculations which may be performed in parallel.

Preparation of Nanocrystalline ZrO2 Film by Using a Zirconium Naphthenate and Evaluation of Calcium Phosphate Forming Ability (지르코늄 나프테네이트를 이용한 나노결정질 ZrO2 박막의 제조와 칼슘 포스페이트 형성 능력의 평가)

  • Oh, Jeong-Sun;Ahn, Jun-Hyung;Yun, Yeon-Hum;Kang, Bo-An;Kim, Sang-Bok;Hwang, Kyu-Seog;Shim, Yeon-A
    • Journal of the Korean Ceramic Society
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    • v.39 no.9
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    • pp.884-889
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    • 2002
  • In order to investigate the calcium phosphate forming ability of nanocrystalline $ZrO_2$ film, we prepared $ZrO_2/Si$ structure by using a chemical solution deposition with a zirconium naphthenate as a starting material. Precursor sol was spin-coated onto the (100)Si substrate and prefired at 500$^{\circ}C$ for 10 min in air, followed by final annealing at 800$^{\circ}C$ for 30 min in air. Crystallinity of the annealed film was examined by X-ray diffraction analysis. Surface morphology and surface roughness of the film were characterized by field emission-scanning electron microscope and atomic force microscope. After annealing, nanocrystalline $ZrO_2$ grains were obtained on the surface of the film with a homogeneous interface between the film and substrate. After immersion for 1 or 5 days in a simulated body fluid, formation of calcium phosphate was observed on $ZrO_2$ film annealed at 800$^{\circ}C$ by energy dispersive X-ray spectrometer. The fourier transform infrared spectroscopy revealed that carbonate was substituted into the calcium phosphate.

Structural and Electrical Properties of [(Co1-xCux)0.2(Ni0.3Mn0.7)0.8]3O4 Spinel Thin Films for Infrared Sensor Application (적외선 센서용 [(Co1-xCux)0.2(Ni0.3Mn0.7)0.8]3O4 스피넬 박막의 구조 및 전기적 특성)

  • Lee, Kui Woong;Jeon, Chang Jun;Jeong, Young Hun;Yun, Ji Sun;Cho, Jeong Ho;Paik, Jong Hoo;Yoon, Jong-Won
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.27 no.12
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    • pp.825-830
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    • 2014
  • $[(Co_{1-x}Cu_x)_{0.2}(Ni_{0.3}Mn_{0.7})_{0.8}]_3O_4$ ($0{\leq}x{\leq}1$) thin films prepared by metal organic decomposition process were fabricated on SiN/Si substrate for infrared sensor application. Their structural and electrical properties were investigated with variation of Cu dopant. The $[(Co_{1-x}Cu_x)_{0.2}(Ni_{0.3}Mn_{0.7})_{0.8}]_3O_4$ (CCNMO) film annealed at $500^{\circ}C$ exhibited a dense microstructure and a homogeneous crystal structure with a cubic spinel phase. Their crystallinity was further enhanced with increasing doped Cu amount. The 120 nm-thick CCNMO (x=0.6) thin film had a low resistivity of $53{\Omega}{\cdot}cm$ at room temperature while the Co-free film (x=1) showed a significantly decreased resistivity of $5.9{\Omega}{\cdot}cm$. Furthermore, the negative temperature coefficient of resistance (NTCR) characteristics were lower than $-2%/^{\circ}C$ for all the specimens with $x{\geq}0.6$. These results imply that the CCNMO ($x{\geq}0.6$) thin films are a good candidate material for infrared sensor application.

Forward probing utilizing electrical resistivity and induced polarization for predicting soil and core-stoned ground ahead of TBM tunnel face (전기비저항과 유도분극을 활용한 TBM 터널 굴착면 전방 토사지반 및 핵석지반 예측 기법)

  • Kang, Daehun;Lee, In-Mo;Jung, Jee-Hee;Kim, Dohyung
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.21 no.3
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    • pp.323-345
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    • 2019
  • It is essential to predict ground conditions ahead of a tunnel face in order to successfully excavate tunnels using a shield TBM. This study proposes a forward prediction method for a mixed soil ground and/or a ground containing core stones by using electrical resistivity and induced polarization exploration. Soil conditioning in EPB shield TBM is dependent upon the composition of mixed soils; a special care need to be taken when excavating the core-stoned soil ground using TBM. The resistivity and chargeability are assumed to be measured with four electrodes at the tunnel face, whenever the excavation is stopped to assemble one ring of a segment lining. Firstly, the mixed ground consisting of weathered granite soil, sand, and clay was modeled in laboratory-scale experiments. Experimental results show that the measured electrical resistivity considerably coincides with the analytical solution. On the other hand, the induced polarization has either same or opposite trend with the measured resistivity depending on the mixed ground conditions. Based on these experimental results, a method to predict the mixed soil ground that can be used during TBM tunnel driving is suggested. Secondly, tunnel excavation from a homogeneous ground to a ground containing core stones was modeled in laboratory scale; the irregularity of the core stones contained in the soil layer was modeled through random number generation scheme. Experimental results show that as the TBM approaches the ground that contains core stones, the electrical resistivity increases and the induced polarization fluctuates.

Influence of Bacterial Attachment on Arsenic Bioleaching from Mine Tailings: Dependency on the Ratio of Bacteria-Solid Substrate (광물찌꺼기 내 비소의 미생물 침출 시 박테리아 흡착 영향: 박테리아와 고체 기질 비율에 관한 연구)

  • Park, Jeonghyun;Silva, Rene A.;Choi, Sowon;Ilyas, Sadia;Kim, Hyunjung
    • Resources Recycling
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    • v.30 no.3
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    • pp.30-40
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    • 2021
  • The present study investigates the bioleaching efficiencies of arsenic via contact and non-contact mechanisms. The attachment of Acidithiobacillus ferrooxidans was restricted by a partition system comprising a semi-permeable membrane with a molecular weight cutoff of 12-14 kDa. The results were compared for two arsenic concentrations in the system (1.0% and 0.5% w/v) to maintain a homogeneous system. The overall bacterial performance was monitored by comparing total arsenic and iron concentrations, Fe ion speciation, pH, and solution redox potentials in flask bioleaching experiments over a period of 10 d. Our results indicated that bacterial attachment could increase arsenic extraction efficiency from 20.0% to 44.9% at 1.0 % solid concentrations. These findings suggest that the bacterial contact mechanism greatly influences arsenic bioleaching from mine tailings. Therefore, systems involving two-step or non-contact bioleaching are less effective than those involving one-step or contact bioleaching for the efficient extraction of arsenic from mine tailings.

Inference of the Probability Distribution of Phase Difference and the Path Duration of Ground Motion from Markov Envelope (Markov Envelope를 이용한 지진동의 위상차 확률분포와 전파지연시간의 추정)

  • Choi, Hang;Yoon, Byung-Ick
    • Journal of the Earthquake Engineering Society of Korea
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    • v.26 no.5
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    • pp.191-202
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    • 2022
  • Markov envelope as a theoretical solution of the parabolic wave equation with Markov approximation for the von Kármán type random medium is studied and approximated with the convolution of two probability density functions (pdf) of normal and gamma distributions considering the previous studies on the applications of Radiative Transfer Theory (RTT) and the analysis results of earthquake records. Through the approximation with gamma pdf, the constant shape parameter of 2 was determined regardless of the source distance ro. This finding means that the scattering process has the property of an inhomogeneous single-scattering Poisson process, unlike the previous studies, which resulted in a homogeneous multiple-scattering Poisson process. Approximated Markov envelope can be treated as the normalized mean square (MS) envelope for ground acceleration because of the flat source Fourier spectrum. Based on such characteristics, the path duration is estimated from the approximated MS envelope and compared to the empirical formula derived by Boore and Thompson. The results clearly show that the path duration increases proportionately to ro1/2-ro2, and the peak value of the RMS envelope is attenuated by exp (-0.0033ro), excluding the geometrical attenuation. The attenuation slope for ro≤100 km is quite similar to that of effective attenuation for shallow crustal earthquakes, and it may be difficult to distinguish the contribution of intrinsic attenuation from effective attenuation. Slowly varying dispersive delay, also called the medium effect, represented by regular pdf, governs the path duration for the source distance shorter than 100 km. Moreover, the diffraction term, also called the distance effect because of scattering, fully controls the path duration beyond the source distance of 300 km and has a steep gradient compared to the medium effect. Source distance 100-300 km is a transition range of the path duration governing effect from random medium to distance. This means that the scattering may not be the prime cause of peak attenuation and envelope broadening for the source distance of less than 200 km. Furthermore, it is also shown that normal distribution is appropriate for the probability distribution of phase difference, as asserted in the previous studies.

Synthesis of LiDAR-reflective Hollow-structured Black Materials and Recycling of Their Etched Waste for Semiconductor Epoxy Molding Compound (라이다 반사형 중공구조 검은색 물질의 개발 및 코어 에칭 폐액 재활용을 통한 반도체용 에폭시 몰딩 컴파운드 응용)

  • Ha-Yeong Kim;Min Jeong Kim;Jiwon Kim;Suk Jekal;Seon-Young Park;Jong Moon Jung;Chang-Min Yoon
    • Journal of the Korea Organic Resources Recycling Association
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    • v.31 no.1
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    • pp.5-14
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    • 2023
  • In this study, LiDAR-reflective black hollow-structured silica/titania(B-HST) materials are successfully synthesized by employing the NaBH4 reduction and etching method on silica/titania core/shell(STCS) materials, which also effectively enhance near-infrared(NIR) reflectance. Moreover, core-etched supernatant solutions are collected and recycled for the synthesis of extracted silica(e-SiO2) process, which successfully applies as filler materials for semiconductor epoxy molding compound(EMC). In detail, B-HST materials, fabricated by the sequential experimental steps of sol-gel, reduction, and sonication-mediated etching method, manifest blackness(L*) of 13.2 similar to black paint and excellent NIR reflectance(31.1%). Consequently, B-HST materials are successfully prepared as LiDAR-reflective black materials. Additionally, core-etched supernatant solution with silanol precursors are employed for synthesis of homogeneous silica filler materials via sol-gel method. As-synthesized silica fillers are incorporated with epoxy resin and carbon black for the preparation of semiconductor EMC. Experimentally synthesized EMC exhibits comparable mechanical-chemical properties to commercial EMC. Conclusively, this study successfully proposes designing procedure and practical experimental method for simultaneously synthesizing the NIR-reflective black materials for self-driving vehicles and EMC materials for semiconductors, which are materials suitable for the industrial 4.0 era, and presented their applicability in future industries.