• Title, Summary, Keyword: Inhomogeneous

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Synthesis of P-type Zeolite Using Melting Slag from Municipal Incineration Ash (도시 소각재 용융슬래그로부터 P형 제올라이트 합성)

  • Lee Sung-Ki;Jang Young-Nam;Chae Soo-Chun;Ryu Kyoung-Won;Bae In-Kook
    • Journal of the Mineralogical Society of Korea
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    • v.19 no.1
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    • pp.7-14
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    • 2006
  • Melting slag generated from the lots of municipal incineration ash, which causes the one of big urban problems in modern industrial society, was used as starting material for the hydrothermal synthesis of zeolite. P-type zeolite has been successfully synthesized by the combined process of both 'hydrogelation' and 'clay conversion' method. Commercial sodium silicate was used as Si source, and $NaAlO_2$ was prepared by the reaction in a $Na_{2}O/Al_{2}O_{3}$ molar ratio of 1.2. The optimum conditions for zeolite synthesis was found to be the $SiO_{2}/Al_{2}O_{3}$ ratio in the 3.2 and 4.2 range, the $H_{2}O/Na_{2}O$ ratio in the 70.7 and 80.0 range, and more than 15-hour reaction time at $80^{\circ}C$, In the synthesized zeolite, inhomogeneous melting slag particles were disappeared and homogeneous P-type zeolite crystal was grown. The cation exchange capacity of the synthesized zeolite was determined to be approx. 240 cmol/kg.

Seismic Traveltime Tomography in Inhomogeneous Tilted Transversely Isotropic Media (불균질 횡등방성 매질에서의 탄성파 주시토모그래피)

  • Jeong, Chang-Ho;Suh, Jung-Hee
    • Geophysics and Geophysical Exploration
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    • v.10 no.4
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    • pp.229-240
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    • 2007
  • In this study, seismic anisotropic tomography algorithm was developed for imaging the seismic velocity anisotropy of the subsurface. This algorithm includes several inversion schemes in order to make the inversion process stable and robust. First of all, the set of the inversion parameters is limited to one slowness, two ratios of slowness and one direction of the anisotropy symmetric axis. The ranges of the inversion parameters are localized by the pseudobeta transform to obtain the reasonable inversion results and the inversion constraints are controlled efficiently by ACB(Active Constraint Balancing) method. Especially, the inversion using the Fresnel volume is applied to the anisotropic tomography and it can make the anisotropic tomography more stable than ray tomography as it widens the propagation angle coverage. The algorithm of anisotropic tomography is verified through the numerical experiments. And, it is applied to the real field data measured at limestone region and the results are discussed with the drill log and geological survey data. The anisotropic tomography algorithm will be able to provide the useful tool to evaluate and understand the geological structure of the subsurface more reasonably with the anisotropic characteristics.

Imaging Features of Mucinous Breast Carcinoma (점액암의 영상소견)

  • Han, Hye-Jung;Kim, Sung-Hun;Cha, Eun-Suk;Kim, Hyun-Sook;Kang, Bong-Joo;Choi, Jae-Jung;Lee, Jee-Hye;Lee, Ah-Won
    • Investigative Magnetic Resonance Imaging
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    • v.14 no.1
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    • pp.21-30
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    • 2010
  • Purpose : To examine the imaging findings of mucinous breast carcinoma and to evaluate the difference in these findings based on the histopathologic grade. Materials and Methods : We retrospectively analyzed the imaging features according to BI-RADS in 29 patients with surgically proven mucinous carcinoma. The histopathologic grade was classified as well-differentiated, moderately-differentiated and poorly-differentiated. Based on these criteria, the differences in imaging findings were statistically analyzed. Results : Mammography was available in 20 cases, which contained 17 mass lesions (85%) and 3 cases of normal findings. On ultrasonography (27 cases), mucinous carcinoma was observed as a mass with an oval shape (59.3%), a microlobulated margin (55.6%) or an inhomogeneous isoechogenicity (74.1%). On MRI (21 cases), mucinous carcinoma was commonly observed to have a lobular shape (76%), smooth margin (86%) or heterogeneous contrast-enhancement (61.9%). On the kinetic curve, there was a delayed wash-out pattern (52.3%). There were no significant differences in the imaging findings for each histopathologic grade except that a welldifferentiated tumor had an abrupt interface. Conclusion : A well-differentiated mucinous carcinoma tended to have an abrupt interface on ultrasonography, as compared with the moderately-differentiated one. Mucinous carcinoma showed a heterogeneous enhancement and a delayed washout kinetic curve pattern on dynamic MRI.

Growth of Metal Nano-Particles on Polarity Patterned Ferroelectrics by Photochemical Reaction (광화학적 반응을 이용한 편극 패턴된 강유전체 표면에 금속 나노입자의 증착에 관한 연구)

  • Park, Young-Sik;Kim, Jung-Hoon;Yang, Woo-Chul
    • Journal of the Korean Vacuum Society
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    • v.20 no.4
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    • pp.300-306
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    • 2011
  • We report the surface distribution of metal (Ag, Au) nanoparticles grown on polarity-patterned ferroelectric substrates by photochemical reaction. Single crystal periodically polarity-patterned $LiNbO_3$(PPLN) was used as a ferroelectric substrate. The nanoparticles were grown by ultra-violet (UV) light exposure of the PPLN in the aqueous solutions including metas. The surface distribution of the grown nanoparticles were measured by atomic force microscopy and identification of the orientation of the polarity of the ferroelectric surface was performed by piezoelectric force microscopy. The Ag- and Au-nanoparticles grown on +z polarity regions are larger and denser than that on -z polarity regions. In particlur, the largest and denser Ag-nanoparticles were grwon on the polarity boundary regions of the PPLN while Au-nanoparticles were not specifically grown on the boundary regions. Thus, we found that the size and position of metal nanoparticles grown on ferroelectric surfaces can be controlled by UV-exposure time and polarity pattern structures. Also, we discuss the difference of the surface distribution of the metal nano-particles depending on the polarity of the ferroelectric surfaces in terms of surface band structures, reduced work fucntion, and inhomogeneous electric field distribution.

Seismic First Arrival Time Computation in 3D Inhomogeneous Tilted Transversely Isotropic Media (3차원 불균질 횡등방성 매질에 대한 탄성파 초동 주시 모델링)

  • Jeong, Chang-Ho;Suh, Jung-Hee
    • Geophysics and Geophysical Exploration
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    • v.9 no.3
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    • pp.241-249
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    • 2006
  • Due to the long tectonic history and the very complex geologic formations in Korea, the anisotropic characteristics of subsurface material may often change very greatly and locally. The algorithms commonly used, however, may not give sufficiently precise computational results of traveltime data particularly for the complex and strong anisotropic model, since they are based on the two-dimensional (2D) earth and/or weak anisotropy assumptions. This study is intended to develope a three-dimensional (3D) modeling algorithm to precisely calculate the first arrival time in the complex anisotropic media. Considering the complex geology of Korea, we assume 3D TTI (tilted transversely isotropy) medium having the arbitrary symmetry axis. The algorithm includes the 2D non-linear interpolation scheme to calculate the traveltimes inside the grid and the 3D traveltime mapping to fill the 3D model with first arrival times. The weak anisotropy assumption, moreover, can be overcome through devising a numerical approach of the steepest descent method in the calculation of minimum traveltime, instead of using approximate solution. The performance of the algorithm developed in this study is demonstrated by the comparison of the analytic and numerical solutions for the homogeneous anisotropic earth as well as through the numerical experiment for the two layer model whose anisotropic properties are greatly different each other. We expect that the developed modeling algorithm can be used in the development of processing and inversion schemes of seismic data acquired in strongly anisotropic environment, such as migration, velocity analysis, cross-well tomography and so on.

Dielectric Characteristics of Gaseous $SF_6$ for Impulse Voltages in Presence of a Metallic Particle in GIS (가스절연개폐장치에 있어서 금속입자 존재시 임펄스전압에 대한 $SF_6$가스의 절연특성)

  • 이복희;이경옥;이창준
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.14 no.1
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    • pp.22-29
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    • 2000
  • This paper deals with the dielectric characteristics of $SF_6$ gas gap stressed by $\pm$1.2/44[$mutextrm{s}$] non-oscillating impulse and $\pm$0.4[$mutextrm{s}$]/1.14[MHz] oscillating impulse voltages in the presence of a needle-shape metallic particle in gas-insulated switchgear(GIS). Breakdown voltage-time (V-t) and breakdown voltage-gas pressure (V-p) characteristics were investigated and discussed. The experiments were carried out under highly inhomogeneous field geometry with a needle protrusion whose length and radius are 10[mm] and 0.5[mm], respectively. The gas pressure ranges from 0.1 to 0.5[㎫]. As a result, it was found that the electrical breakdown for both the positive and negative polarity develops with steplike pulses in leader mechanism, When subjected to the positive oscillating impulse voltage, the minimum breakdown voltages appeared in all the gas pressure ranges and the V-t curves have a pronounced upturning at short times to breakdown and give a little dependence of the gas pressure. On the other hand, in the case of the negative polarity the dependence of the V-t and V-p characteristics on the wave shape of the applied voltages is known to be appreciable.

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Characteristics of Al2O3/ZrO2 Ceramics by the Dispersion Process of ZrO2 Particles (ZrO2 입자의 분산방법에 따른 Al2O3/ZrO2 요업체의 특성)

  • Youn, Sang-Hum;Kim, Jae-Jun;Hwang, Kyu-Hong;Lee, Jong-Kook;Kim, Hwan
    • Journal of the Korean Ceramic Society
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    • v.42 no.8
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    • pp.561-566
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    • 2005
  • For the homogeneous dispersion of $ZrO_2$ particles in $Al_2O_3/ZrO_2$ceramics, Zr-precusors were mixed with oxide $Al_2O_3$powders by chemical routes such as partial precipitation or partial polymerization of Zr-nitrate solutions. In case of the mechanical mixing of ultrafine $Al_2O_3$ and $ZrO_2$ oxide powders, relatively homogeneous dispersion was difficult to achieve so that the particle size and distributions of $ZrO_2$ were relatively inhomogeneous after sintering at high temperature. But when the Zr-Y-hydroxide were co-precipitated to ultrafine $Al_2O_3$ oxide powders followed by calcinations, homogeneous dispersion of nano-sized $ZrO_2$ particles in $Al_2O_3/ZrO_2$ composite ceramics were obtained. But because of the coalescence of dispersed $ZrO_2$ particles, dispersed $ZrO_2$ was grown up to more than 0.2${mu}m$ (200 nm) when sintered at the temperature of higher than $1500^{\circ}C$ But when the sintering temperature was kept to lower than $1400^{\circ}C$ by using nano-sized $\alpha-alumina$, the particle size of dispersed $ZrO_2$ could be sustained below 0.1 ${\mu}m$. But the coalescence of dispersed $ZrO_2$ between $Al_2O_3$ particles could not be avoided so that the mechanical properties were not enhanced contrary to the expectations. So Zr-polyester precursors were precipitated and coated to the surface of ultrafine $\alpha-alumina$ powders by the polymerization of Ethylene Glycol with Citric Acid and Zirconium Nitrate. By this dispersion much more uniform dispersion of $ZrO_2$ was achieved at $1450\~1600^{\circ}C$ of sintering temperature ranges. And due to especially discrete dispersion of $ZrO_2$ between $Al_2O_3$ particles, their mechanical strength was more enhanced than mechanical mixing or hydroxide precipitation methods.

A review of the effects of rock properties on waterjet rock cutting performance (암석물성이 워터젯 암석절삭 성능에 미치는 영향고찰)

  • Oh, Tae-Min;Park, Eui-Seob;Cheon, Dae-Sung;Cho, Gye-Chun;Joo, Gun-Wook
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.17 no.5
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    • pp.533-551
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    • 2015
  • The rock fracturing during waterjet cutting is very complicated because rock is inhomogeneous and anisotropic, compared with artificial materials (e.g., metal or glass). Thus, it is very important to verify the effects of rock properties on waterjet rock cutting performance. Properties affecting the rock cutting efficiency have been variously described in the literature, depending on the experimental conditions (e.g., water pressure, abrasive feed rate, or standoff distance) and rock-types studied. In this study, a rock-property-related literature review was performed to determine the key properties important for waterjet rock cutting. Porosity, uniaxial compressive strength, and hardness of the rock were determined to be the key properties affecting waterjet rock cutting. The results of this analysis can provide the basic knowledge to determine the cutting efficiency of waterjet rock cutting technology for rock excavation-related construction.

Magnetic Resonance Imaging of Lumen Wall using Quadrature-typed Inside-out Receiver Coil (회전자계 역수신 코일을 이용한 관벽의 자기공명 영상)

  • 문치웅;조종운
    • Journal of Biomedical Engineering Research
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    • v.22 no.5
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    • pp.385-392
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    • 2001
  • This study Proposes a quadrature-typed inside-out receiver coil to obtain magnetic resonance(MR) images of lumen wall. This means that the coil should receive the signals from out-side of receiver coil. This coil has wide and uniform sensitive region to compare with previous coils such as anti-solenoid coil, octal-pole coil and so on. These coils have the disadvantages that sensitive region is narrow and inhomogenous. The proposed coil is consist of two saddle coils of which directions are orthogonal to one another. The sensitivity maps of octal-Pole coil single-saddle coil and quadrature-typed inside-out coil were obtained by computer simulation. And phantom images for each coil were obtained to evaluate the performances of the coil using both 1.5T superconducting and 0.3 Permanent magnet MRI system. The uniformity of quadrature coil's sensitivity map was superior to that of octal-polel coil. Experimentally measured SNR of quadrature coil is also 36% higher than that of single-saddle coil This study shows the possibility of quadrature-typed inside-out receiver coil for the MR lumen wall images.

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Intercomparison of Change Point Analysis Methods for Identification of Inhomogeneity in Rainfall Series and Applications (강우자료의 비동질성 규명을 위한 변동점 분석기법의 상호비교 및 적용)

  • Lee, Sangho;Kim, Sang Ug;Lee, Yeong Seob;Sung, Jang Hyun
    • Journal of Korea Water Resources Association
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    • v.47 no.8
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    • pp.671-684
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    • 2014
  • Change point analysis is a efficient tool to understand the fundamental information in hydro-meteorological data such as rainfall, discharge, temperature etc. Especially, this fundamental information to change points to future rainfall data identified by reasonable detection skills can affect the prediction of flood and drought occurrence because well detected change points provide a key to resolve the non-stationary or inhomogeneous problem by climate change. Therefore, in this study, the comparative study to assess the performance of the 3 change point detection skills, cumulative sum (CUSUM) method, Bayesian change point (BCP) method, and segmentation by dynamic programming (DP) was performed. After assessment of the performance of the proposed detection skills using the 3 types of the synthetic series, the 2 reasonable detection skills were applied to the observed and future rainfall data at the 5 rainfall gauges in South Korea. Finally, it was suggested that BCP (with 0.9 posterior probability) could be best detection skill and DP could be reasonably recommended through the comparative study. Also it was suggested that BCP (with 0.9 posterior probability) and DP detection skills to find some change points could be reasonable at the North-eastern part in South Korea. In future, the results in this study can be efficiently used to resolve the non-stationary problems in hydrological modeling considering inhomogeneity or nonstationarity.