• Title/Summary/Keyword: thermal effects

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Application of Multivariate Statistical Analysis Technique in Landfill Investigation (매립물 특성 조사를 위한 다변량 통계분석 기법의 응용)

  • Kwon, Byung-Doo;Kim, Cha-Soup
    • Journal of the Korean earth science society
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    • v.18 no.6
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    • pp.515-521
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    • 1997
  • To investigate the nature of the waste materials in the Nanjido Landfill, we have conducted multivariate statistical analysis of geophysical data set comprised of magnetic, gravity, LandSat TM thermal band and surface depression measurement data. Because these data sets show different responses to the depth, we have transformed the observed total field magnetic data and gravity data to the residual reduced-to-pole(RTP) magnetic anomalies and the three dimensional density anomalies, respectively, and utilized the informations about the upper shallow part of the landfills only in the following process. For the statistical analysis at the points of depression measurement, the magnetic, density and LandSat data values at these points are determined by interpolation process. Since the multivarite statistical analysis technique utilizes a clustering algorithm for classification of data set and we have measured the dissimilarity between objects by using Euclidean distance, standardization was applied prior to distance calculation in order to eliminate any scaling effects due to different measurement unit of each data set. The hierarchial grouping technique was used to construct the dendrogram. The optimum number of statistical groups(clusters), which are classified on the basis of geophysical and geotechnical characteristics, appeared to be six on the resulting dendrogram. The result of this study suggests that the dimension and nature of the multicomponent waste landfills can be identified by application of the multivarite statistical analysis technique to integrated geophysical data sets.

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Effects of Oxygen Vacancies on the Electrical Properties of High-Dielectric (Ba,Sr)TiO$_3$Thin Films (산소 결핍이 고유전 BST 박막에 미치는 영향)

  • 김일중;이희철
    • Journal of the Korean Institute of Telematics and Electronics D
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    • v.36D no.4
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    • pp.63-69
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    • 1999
  • The electrical properties of rf-magnetron sputtered $Ba_{0.5}Sr_{0.3}TiO_3$ (BST) capacitors were investigated by varying annealing temperature and atmosphere of the rapid thermal annealing (RTA). The electrical properties of Pt/BST/Pt capacitors were found to strongly depend on the RTA condition. It seems that the dependence of the electrical properties of the Pt/BST/Pt capacitors on the RTA condition is related to the oxygen vacancies in BST thin films. In order to clarify the relation between the oxygen vacancies and the electrical properties of Pt/BST/Pt capacitors, we have examined the two different annealing methods. One annealing method was performed in $O_2$ gas and the other was done in $O_2$-plasma at the same condition of 450$^{\circ}C$, 20 mtorr. It was found that the leakage current densities of $O_2$-plasma annealed capacitor were much lower than those of $O_2$ annealed capacitor. The dielectric constants of $O_2$ annealed capacitor decreased about 14% comparing with those of as-deposited. In contrast, there was no decrease in the dielectric constant of $O_2$-plasma annealed. These results indicate that $O_2$-plasma annealing is very effective in compensation the oxygen vacancies in BST thin films. It can be also concluded that the oxygen vacancies greatly affect the electrical properties of Pt/BST/Pt capacitors.

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The Effects of Dokhwalgisaeng-tang(Duhuoqisheng-tang ) and Jungsongouhyul Pharmacopuncture on Pain Control and Nerve Regeneration in the Crush-induced Sciatic Nerve Injury of the Rat Model (독활기생탕(獨活寄生湯) 및 중성어혈약침(中性瘀血藥鍼)이 좌골신경 압좌손상 백서의 통증과 신경 재생에 미치는 영향)

  • Lee, Sang-Gyu;Won, Jae-Kyun;Yeom, Seung-Ryong;Lee, Su-Kyung;Song, Yung-Sun;Kwon, Young-Dal
    • Journal of Korean Medicine Rehabilitation
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    • v.19 no.3
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    • pp.15-32
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    • 2009
  • Objectives : The purpose of this Study was to identify the effect of Dokhwalgisaeng-tang(Duhuoqisheng-tang) and Jungsongouhyul pharmacopuncture on pain control and nerve regeneration after crush injury in rat sciatic nerve. Methods : Neuropathic pain was induced by crush-induced model of right sciatic nerve. Animal groups were divided as follows; Group I: no treatment control group, Group II : experimental group treated with Dokhwalgisaeng-tang(Duhuoqisheng-tang), Group III : experimental group treated with Jungsongouhyul pharmacopuncture, and Group IV : experimental group treated with Dokhwalgisaeng-tang(Duhuoqisheng-tang) and Jungsongouhyul pharmacopuncture. To evaluate pain intensity, each group was observed paw withdrawal threshold and immunoreactivity on the c-fos before and after respective treatments in five hours, first, third, and fifth day. To evaluate nerve regeneration, those were observed SFI(Sciatic Functional Index) and GAP-43(Growth Associated Protein 43) after each treatment in seventh and thirteenth day. Results : 1. Paw withdrawal threshold to the mechanical stimuli made the significant difference between group IV and the control group after five days of the experiment. 2. Paw withdrawal threshold to the thermal stimuli made the significant difference between group I and III, I and IV, II and IV. 3. In immunohistochemical response of c-fos, as time passes, the immunoreactivity of all groups was decreased gradually. Especially, group IV was observed the lowest after three days. 4. The differences of sciatic function indexes in each group were significantly between group I and III, I and IV, II and IV after 14 days, and between group I and III, I and IV, II and IV, III and IV after 21 days. 5. In immunohistochemical response of GAP-43, all groups had higher GAP-43 immunoreactivity at the 14 days from post-injury and group IV showed highest immunoreactivity. Conclusions : Based on above the results, it is proposed that Dokhwalgisaeng-tang(Duhuoqisheng-tang) and Jungsongouhyul pharmacopuncture may be helpful as a treatment in neuropathic pain and nerve regeneration in rat model.

Development of an Aerodynamic Simulation for Studying Microclimate of Plant Canopy in Greenhouse - (1) Study on Aerodynamic Resistance of Tomato Canopy through Wind Tunnel Experiment - (공기유동해석을 통한 온실내 식물군 미기상 분석기술 개발 - (1) 풍동실험을 통한 토마토 식물군의 공기저항 연구 -)

  • Lee In-Bok;Yun Nam-Kyu;Boulard Thierry;Roy Jean Claude;Lee Sung-Hyoun;Kim Gyoeng-Won;Lee Seung-Kee;Kwon Soon-Hong
    • Journal of Bio-Environment Control
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    • v.15 no.4
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    • pp.289-295
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    • 2006
  • A computational fluid dynamics (CFD) numerical model has been developed to effectively study the ventilation efficiency of multi-span greenhouses with internal crops. As the first step of the study, the internal plants of the CFD model had to be designed as a porous media because of the complexity of its physical shapes. In this paper, the results of the wind tunnel tests were introduced to find the aerodynamic resistance of the plant canopy. The Seogun tomato was used for this study which made significant effects on thermal and mass exchanges with the adjacent air as well as internal airflow resistance. With the main factors of wind speed, static pressure, and density of plant canopy, the aerodynamic resistance factor was statically found. It was finally found to be 0.26 which will be used later as an input data of the CFD model. Moreover, the experimental procedure of how to find the aerodynamic resistance of various plants using, wind tunnel was established through this study.

Analysis of Apparent Fracture Toughness of a Thick-Walled Cylinder with an FGM Coating at the Inner Surface Containing a Radial Edge Crack (반경방향의 모서리 균열을 갖고 내면이 경사기능재료(FGM)로 코팅된 두꺼운 실린더의 겉보기 파괴인성해석)

  • Afsar, A.M.;Rasel, S.M.;Song, J.I.
    • Composites Research
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    • v.23 no.2
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    • pp.1-9
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    • 2010
  • This study analyzes the apparent fracture toughness of a thick-walled cylinder with a functionally graded material (FGM) coating at the inner surface of the cylinder. The cylinder is assumed to have a single radial edge crack emanating from its inner surface. The crack surfaces and the inner surface of the cylinder are subjected to an internal pressure. The incompatible eigenstrain developed in the cylinder due to nonuniform coefficient of thermal expansion as a result of cooling from sintering temperature is taken into account. Based on a method of evaluating stress intensity factor introduced in our previous study, an approach is developed to calculate apparent fracture toughness. The approach is demonstrated for a cylinder with a TiC/$Al_{2}O_{3}$ FGM coating and some numerical results of apparent fracture toughness are presented graphically. The effects of material distribution profile, cylinder wall thickness, application temperature, and coating thickness on the apparent fracture toughness are investigated in details. It is found that all of these factors play an important role in controlling the apparent fracture toughness of the cylinder.

Effects on the Oxidation Rate with Silicon Orientation and Its Surface Morphology (실리콘배향에 따른 산화 속도 영향과 표면 Morphology)

  • Jeon, Bup-Ju;Oh, In-Hwan;Um, Tae-Hoon;Jung, Il-Hyun
    • Applied Chemistry for Engineering
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    • v.8 no.3
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    • pp.395-402
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    • 1997
  • The $SiO_2$ films were prepared by ECR(electron cyclotron resonance) plasma diffusion method, Deal-Grove model and Wolters-Zegers-van Duynhoven model were used to estimate the oxidation rate which was correlated with surface morphology for different orientation of Si(100) and Si(111). It was seen the $SiO_2$ thickness increased linearly with initial oxidation time. But oxidation rate slightly decrease with oxidation time. It was also shown that the oxidation process was controlled by the diffusion of the reactive species through the oxide layer rather than by the reaction rate at the oxide interface. The similar time dependency has been observed for thermal and plasma oxidation of silicon. From D-G model and W-Z model, the oxidation rate of Si(111) was 1.13 times greater than Si(100) because Si(111) had higher diffusion and reaction rate, these models more closely fits the experimental data. The $SiO_2$ surface roughness was found to be uniform at experimental conditions without etching although oxidation rate was increased, and to be nonuniform due to etching at experimental condition with higher microwave power and closer substrate distance.

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Effects of Ventilation Condition on the Fire Characteristics in Compartment Fires (Part II: Multi-dimensional Fire Dynamics) (구획화재에서 환기조건의 변화가 화재특성에 미치는 영향 (Part II: 다차원 화재거동))

  • Kim, Jong-Hyun;Ko, Gwon-Hyun;Park, Chung-Hwa;Hwang, Cheol-Hong
    • Fire Science and Engineering
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    • v.24 no.5
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    • pp.32-38
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    • 2010
  • Multi-dimensional fire dynamics were studied numerically with the change in ventilation conditions in a full-scale ISO 9705 room. Fire Dynamic Simulator (FDS) was used for the identical conditions conducted in previous experiments. Flow rate and doorway width were changed to create over-ventilated fire (OVF) and under-ventilated fire (UVF). From the numerical simulation, it was found that the internal flow pattern rotated in the opposite direction for the UVF relative to the OVF so that a portion of products recirculated to the inside of compartment. Significant change in flow pattern with ventilation conditions may affect changes in the complex process of CO and soot formation inside the compartment due to increase in the residence time of high-temperature products. The fire behavior in the UVF created complex 3D characteristics of species distribution as well as thermal and flow structures. In particular, additional burning near the side wall inside the compartment significantly affected the flow pattern and CO production. The distribution of CO inside the compartment was explained with 3D $O_2$ distribution and flow patterns. It was observed that gas sampling at local positions in the upper layer were insufficient to completely characterize the internal structure of the compartment fire.

A Study on Infrared Emissivity Measurement of Material Surface by Reflection Method (반사법에 의한 재료표면의 적외선 방사율 측정에 관한 연구)

  • Kang, Byung-Chul;Kim, Sang-Myoung;Choi, Joung-Yoon;Kim, Gun-Ok
    • Journal of the Korean Society for Nondestructive Testing
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    • v.30 no.5
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    • pp.484-488
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    • 2010
  • Infrared emissivity is one of the most important factors for the temperature measurement by infrared thermography. Although the infrared emissivity of an object can be measured from the ratio of blackbody and the object, at room temperature it is practically difficult to measure the value due to the background effects. Hence, quantitative reflectance of bare steel plate and the surface of coating was measured by FT-IR spectroscopy and emissivity was calculated from this. The emissivity of polished bare steel surface was from 0.06 to 0.10 and the value for the unpolished bare steel can not be achieved because optical characteristics changes of surface roughness induces erroneous results. Emissivity of transparent paint coated steel was from 0.50 to 0.84. Depends on the IR absorption regions, which is a characteristic value of the coating, emissivity changes. This study suggests surface condition of material, thickness, roughness et cetra are important factor for IR optical characteristics. Emissivity measurement by reflection method is useful technique to be applied for metal and it with coating applied on the surface. The range of experimental errors of temperature can be narrowed by the application of infrared thermography from the measured thermal emissivity.

Comparison of Thermal Properties and Surface Structures of Unmodified, Spray-Dried, and Extrusion-Dried Agar (일반한천, 분무건조한천, 압출성형한천의 열 특성 및 표면구조의 비교)

  • 김희구;손홍주
    • The Korean Journal of Food And Nutrition
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    • v.10 no.2
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    • pp.234-240
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    • 1997
  • Agar has widely been used as medical aids and food ingredients due to its pecular physicochemical and rheological properties. In this paper, the effects of spray drying and extrusion drying on functional properties of agar were investigated to clarify the sol-gel transition mechanism at low temperature and microstructure of agar gel by measuring phase transition by differential scanning calorimetery, structural differences by light microscope and scanning electron microscope observation. The lowest endothermic onset(To), peak(Tp), conclusion(Tc) temperature and enthalpy($\Delta$H) using differential scanning calorimetery were showed in extrusion-dried agar wic were checked in 41.30, 61.72, 80.50 and 0.73cal/g. In cases of unmodified and spray-dried, the values were 81.20, 95.51, 112.14 and 3.22cal/g, and 60.11, 76.45, 89.54 and 1.53cal/g, respectively. When all samples were reheated using differential scanning calorimetery after gelling fully, no significant differences of endothermic To, Tp, Tc and $\Delta$H appeared. The surface structure of unmodified agar powder observed by light microscope and scanning electron microscope appeared a continuous surface without any indication of small pores, gaps or point of discontinuity. In cases of spray-dried agar, the unstable structures with pores was resulted. The microstructures of extrusion-dried agar, however, was solid with large gaps and areas of discontinuity in the surface. From the results above, it was suggested that significant differences in phase transition and surface microstructures were clearly related to the physicochemical changes and rheological properties, solubility and gelling ability of the types of agar gel.

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A Numerical Model to Evaluate Fire-Resistant Capacity of the Reinforced Concrete Members (화재에 손상된 철근콘크리트 부재의 수치모델 및 내화성능해석)

  • Hwang, Jin-Wook;Ha, Sang-Hee;Lee, Yong-Hoon;Kim, Wha-Jung;Kwak, Hyo-Gyoung
    • Journal of the Korea Concrete Institute
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    • v.25 no.5
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    • pp.497-508
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    • 2013
  • This paper introduces a numerical model which can evaluate the fire-resistant capacity of reinforced concrete members. On the basis of the transient heat transfer considering the heat conduction, convection and radiation, time-dependent temperature distribution across a section is determined. A layered fiber section method is adopted to consider non-linear material properties depending on the temperature and varying with the position of a fiber. Furthermore, effects of non-mechanical strains of each fiber like thermal expansion, transient strain and creep strain are reflected on the non-linear structural analysis to take into account the extreme temperature variation induced by the fire. Analysis results by the numerical model are compared with experimental data from the standard fire tests to validate an exactness of the introduced numerical model. Also, time-dependent changes in the resisting capacities of reinforced concrete members exposed to fire are investigated through the analyses and, the resisting capacities evaluated are compared with those determined by the design code.