• Title/Summary/Keyword: Contact potential

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Adsorption Equilibrium, Kinetics and Thermodynamics Studies of Malachite Green Using Zeolite (제올라이트를 이용한 말라카이트 그린의 흡착평형, 동력학 및 열역학 연구)

  • Lee, Jong-Jib
    • Clean Technology
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    • v.18 no.1
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    • pp.76-82
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    • 2012
  • The paper includes utlization of zeolite as potential adsorbent to remove a hazardous malachite green from waste water. The adsorption studies were carried out at 298, 308 and 318 K and effects of temperature, contact time, initial concentration on the adsorption were measured. On the basis of adsorption data Langmuir and Freundlich adsorption isotherm model were also confirmed. The equilibrium process was described well by Freundlich isotherm model, showing a selective adsorption by irregular energy of zeolite surface. From determined isotherm constants, zeolite could be employed as effective treatment for removal of malachite green. From kinetic experiments, the adsorption process followed the pseudo second order model, and the adsorption rate constant ($k_2$) decreased with increasing initial concentration of malachite green. Thermodynamic parameters like activation energy, change of free energy, enthalpy, and entropy were also calculated to predict the nature adsorption. The activation energy calculated from Arrhenius equation indicated that the adsorption of malachite green on the zeolite was physical process. The negative free energy change (${\Delta}G^{\circ}$ =-6.47~-9.07 kJ/mol) and the positive enthalpy change (${\Delta}H^{\circ}$ = +32.414 kJ/mol) indicated the spontaneous and endothermic nature of the adsorption in the temperature range 298~318 K.

The Fabrication of Poly-Si Solar Cells for Low Cost Power Utillity (저가 지상전력을 위한 다결정 실리콘 태양전지 제작)

  • Kim, S.S.;Lim, D.G.;Shim, K.S.;Lee, J.H.;Kim, H.W.;Yi, J.
    • Solar Energy
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    • v.17 no.4
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    • pp.3-11
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    • 1997
  • Because grain boundaries in polycrystalline silicon act as potential barriers and recombination centers for the photo-generated charge carriers, these defects degrade conversion effiency of solar cell. To reduce these effects of grain boundaries, we investigated various influencing factors such as thermal treatment, various grid pattern, selective wet etching for grain boundaries, buried contact metallization along grain boundaries, grid on metallic thin film. Pretreatment above $900^{\circ}C$ in $N_2$ atmosphere, gettering by $POCl_3$ and Al treatment for back surface field contributed to obtain a high quality poly-Si. To prevent carrier losses at the grain boundaries, we carried out surface treatment using Schimmel etchant. This etchant delineated grain boundaries of $10{\mu}m$ depth as well as surface texturing effect. A metal AI diffusion into grain boundaries on rear side reduced back surface recombination effects at grain boundaries. A combination of fine grid with finger spacing of 0.4mm and buried electrode along grain boundaries improved short circuit current density of solar cell. A ultra-thin Chromium layer of 20nm with transmittance of 80% reduced series resistance. This paper focused on the grain boundary effect for terrestrial applications of solar cells with low cost, large area, and high efficiency.

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Development of an Active Dry EEG Electrode Using an Impedance-Converting Circuit (임피던스 변환 회로를 이용한 건식능동뇌파전극 개발)

  • Ko, Deok-Won;Lee, Gwan-Taek;Kim, Sung-Min;Lee, Chany;Jung, Young-Jin;Im, Chang-Hwan;Jung, Ki-Young
    • Annals of Clinical Neurophysiology
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    • v.13 no.2
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    • pp.80-86
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    • 2011
  • Background: A dry-type electrode is an alternative to the conventional wet-type electrode, because it can be applied without any skin preparation, such as a conductive electrolyte. However, because a dry-type electrode without electrolyte has high electrode-to-skin impedance, an impedance-converting amplifier is typically used to minimize the distortion of the bioelectric signal. In this study, we developed an active dry electroencephalography (EEG) electrode using an impedance converter, and compared its performance with a conventional Ag/AgCl EEG electrode. Methods: We developed an active dry electrode with an impedance converter using a chopper-stabilized operational amplifier. Two electrodes, a conventional Ag/AgCl electrode and our active electrode, were used to acquire EEG signals simultaneously, and the performance was tested in terms of (1) the electrode impedance, (2) raw data quality, and (3) the robustness of any artifacts. Results: The contact impedance of the developed electrode was lower than that of the Ag/AgCl electrode ($0.3{\pm}0.1$ vs. $2.7{\pm}0.7\;k{\Omega}$, respectively). The EEG signal and power spectrum were similar for both electrodes. Additionally, our electrode had a lower 60-Hz component than the Ag/AgCl electrode (16.64 vs. 24.33 dB, respectively). The change in potential of the developed electrode with a physical stimulus was lower than for the Ag/AgCl electrode ($58.7{\pm}30.6$ vs. $81.0{\pm}19.1\;{\mu}V$, respectively), and the difference was close to statistical significance (P=0.07). Conclusions: Our electrode can be used to replace Ag/AgCl electrodes, when EEG recording is emergently required, such as in emergency rooms or in intensive care units.

Characteristics and Biocompatibility of Electrospun Nanofibers with Poly(L-lactide-co-ε-caprolactone)/Marine Collagen (전기 방사법을 통해 제조된 Poly(L-lactide-co-ε-caprolactone)/Marine Collagen 나노파이버의 특성 및 세포친화력 평가)

  • Kim, Woo-Jin;Shin, Young-Min;Park, Jong-Seok;Gwon, Hui-Jeong;Kim, Yong-Soo;Shin, Heung-Soo;Nho, Young-Chang;Lim, Youn-Mook;Chong, Moo-Sang
    • Polymer(Korea)
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    • v.36 no.2
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    • pp.124-130
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    • 2012
  • The uniform nanofibers of poly(L-lactide-$co$-${\varepsilon}$-caprolactone) (PLCL) with different contents of marine collagen (MC) were successfully prepared by electrospinning method. The effects of the major parameters in electrospinning process such as tip to target distance (TTD), voltage, nozzle size and flow rate on the average diameter of the electrospun nanofiber were investigated in generating composite nanofiber. The diameter and morphology of the nanofibers were confirmed by a scanning electron microscopy (SEM). Also, we measured a water contact angle to determine the surface wettability of the nanofibers. The average diameter of the nanofibers decreased as the value of TTD, MC contents, and voltages increased in comparison with that of pristine PLCL nanofiber. In contrast, the diameter of the nanofibers increased as the flow rate and inner diameter of nozzle increased in comparison with that of pristine PLCL. In addition, the hydrophilicity of the nanofiber and attachment of MG-63 cells on the sheets increased as incorporated collagen contents increased. Therefore, the marine collagen would be a potential material to enhance cellular interactivity of synthetic materials by mimicking the natural tissue.

Effect of Sodium Hydroxide Treatment on Scaffold by Solid Freeform Fabrication (조형가공기술을 이용한 인공지지체의 수산화나트륨 개질 효과)

  • Park, SuA;Lee, JungBok;Kim, YangEun;Kim, JiEun;Kwon, IlKeun;Lee, JunHee;Kim, WanDoo;Kim, HyungKeun;Kim, MiEun;Lee, JunSik
    • Polymer(Korea)
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    • v.38 no.6
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    • pp.815-819
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    • 2014
  • Scaffolds of tissue engineering should be biocompatible and biodegradable for cell attachment, proliferation and differentiation. In the various scaffold fabrication, 3D printing technique can make the three dimensional scaffold with interconnected pores for cell ingrowth. Polycaprolactone (PCL) is biodegradable polyester with a low melting temperature and has been approved by the Food and Drug Administration (FDA). In this study, PCL scaffold was fabricated by 3D bioprinting system and surface modification of PCL scaffold was controlled by NaOH treatment. Morphological change and wetability of NaOH-treated scaffold were observed by SEM and contact angle measurement system. The remnant of PCL treated with NaOH was measured by ATR-FTIR. In vitro study of scaffolds was evaluated with WST-1 and ALP activity assay. NaOH treatment of PCL scaffolds increased surface roughness, hydrophilicity, cell proliferation and osteogenic differentiation. These results indicate that NaOH-treated PCL scaffold made by 3D bioprinting has tissue engineered potential for the development of biocompatible material.

Study on Telemedicine system in Medical Law (의료법상의 원격의료 제도에 관한 고찰)

  • Joung, Soon-Hyoung;Park, Jong-Ryeol
    • Journal of the Korea Society of Computer and Information
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    • v.17 no.12
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    • pp.241-249
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    • 2012
  • The rapid development of the current information and communication brings big changes and progress in the health service delivery system. And it is becoming the worldwide trend increasingly. As the name of medical information, by more rapid, detail and more quickly to the patients and diagnosis of the disease it provides not only a high level of health care services but also hospitals and related institutions are making increase the efficiency of the work. Among them, the Telemedicine, that system has many advantage which can expect the shorten the waiting time and the uniform high level of medical, etc. without visiting medical institutions. Especially, the most advantage is it can increase the accessibility of information about extensive medical, without regard to the time and place. But this is the reality, which compared speed the development of modern science and technology with lack of operational regulations and mindset. Current in our Medical Law, it regulates the Telemedicine, but it has Institutional, facility, and environmental constraints. Because, there is no detailed legal relationship. And it takes that in terms of a special form called by a non-face-to-face contact with medical practice rather than the scene. Therefore, in this paper will find a way out to activate the Telemedicine by presupposes the development potential is infinite and find the legal issues and improvements.

Development of Program to Facilitate High School Students' Search for Potential College Majors and Future Career as Career Education: Focusing on Connection between High School Home Economics and College of Human Ecology Majors (진로교육 차원에서 고등학생의 전공적합성 탐색을 위한 프로그램 개발: 고등학교 가정교과-생활과학대학 전공 연계를 중심으로)

  • Jeon, Sohyeon;Kim, Seohyun;Go, Youngshin;Jung, Soohee
    • Journal of Korean Home Economics Education Association
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    • v.27 no.2
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    • pp.53-75
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    • 2015
  • In the modern society, the adolescence needs the career development competency which makes them probe changing social phenomenon critically and use the given environment and resources progressively. Thus, adolescence should be offered with the career development competency education, but the education in the school fields remains as school entrance coaching focusing on the academic clique and career coaching as a mere job education. As a result, the study connection between high school and university was destroyed and it caused students' study-unfitness and dropouts after the university entrance. Hence, career education to culture major suitability of high school students in the new paradigm should be developed through high school-university connection. So, this study developed a career education program through the collaboration among the professor of college of human ecology, a home economics specialist, undergraduates majoring in human ecology, and a high school student, using the ADDIE model. The result of this study is as followed. First, this study searched for the direction of the program for the career development competency reinforcement of high school students. Second, the program arranged the newest issues of each department of human ecology to make high school students come in contact with and study them easily, aiming at cultivation of major suitability of high school students. Third, the study established the teaching-learning materials that is managed by the high school-college of human ecology committee. Fourth, this program will be the good opportunity for students who are interested in departments of human ecology to check their major suitability.

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Evaluation on the Basic Properties of Phosphate Modified Portland Cement Paste for Potential Application of Geologic CO2 Sequestration (이산화탄소 지중 격리용 인산염 혼입 시멘트 페이스트에 관한 기초물성 평가)

  • Yoon, Ju-Han;Kim, Seong-Geun;Kim, Ji-Hyun;Lee, Jae-Yong;Chung, Chul-Woo
    • Journal of the Korea Institute of Building Construction
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    • v.17 no.3
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    • pp.253-260
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    • 2017
  • As global warming became a worldwide issue, a significant effort has been made on the development of technology related to $CO_2$ capture and storage. Geologic sequestration of $CO_2$ is one of those technologies for safe disposal of $CO_2$. Geologic sequestration stores $CO_2$ in the form of supercritical fluid into the underground site surrounded by solid rock, and concrete is used for prevention of $CO_2$ leakage into the atmosphere. In such case, concrete may experience severe damage by attack of supercritical $CO_2$, and especially in contact with underground water, very aggressive form of carbonation can occur. In this work, to prevent such deterioration in concrete, calcium phosphates were added to the portland cement to produce hydroxyapatite, one of the most stable mineral in the world. Temperature rise, viscosity, set and stiffening, and strength development of cement paste incorporating three different types of calcium phosphates were investigated. According to the results, it was found that the addition of calcium phosphate increased apparent viscosity, but decreased maximum temperature rise and 28 day compressive strength. It was found that monocalcium phosphate was found to be inappropriate for portland cement based material. Applicability of dicalcium and tricalcium phosphates for portland cement needs to be evaluated with further investigation, including the long term compressive strength development.

A Study on the Safety Grounding for Prevention of Electric Shock Hazard in Construction of Industrial Plant in Maritime Landfill Area (해상 매립 지역 산업 플랜트 건설 시 감전 재해 예방을 위한 안전 접지에 관한 연구)

  • Kim, Hong-Yong;Jang, Ung-Burm
    • Journal of the Society of Disaster Information
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    • v.13 no.3
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    • pp.305-312
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    • 2017
  • In our society, the advanced, advanced, and information industries have continued to grow and now live in the era of the fourth industrial revolution. As the industry develops, the load of the users has also increased so much that it is deepened by the energy shortage phenomenon and the construction of additional energy facilities is required. Therefore, energy plant construction work is being actively carried out in the coastal area. In particular, it is common to build a plant in the ground by filling the coast with soil in other regions, reflecting the fact that Korea is lacking in the country when constructing power plants, gas and petrochemical plants. Current domestic grounding designs are designed or constructed to suit only the use of grounding resistors based on the electrical equipment design technical standards. However, in the case of a plant facility constructed in the untested buried soil, when the lightning current and the abnormal current are inputted, the facility operator or the user due to the elevation of the ground potential is seriously exposed to the risk of electric shock disaster. In this paper, we analyze the ground resistivity of the landfilled soil and use a computer program (CDEGS) based on KS C IEC 61936-1, We analyze the contact voltage and stratification voltage and propose a grounding design optimized for plant installation.

Recent Research Trends of Mixed Matrix Membranes for CO2 Separation (이산화탄소 분리용 혼합 매질 분리막 최신 연구 동향)

  • Chi, Won Seok;Lee, Jae Hun;Park, Min Su;Kim, Jong Hak
    • Membrane Journal
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    • v.25 no.5
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    • pp.373-384
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    • 2015
  • In the past few decades, polymeric membrane has played an important role in gas separation applications. For the separation of $CO_2$, one of greenhouse gases, high permselectivity, long-term stability and scale-up are needed. However, conventional polymeric membranes have shown a trade-off relation between permeability and selectivity while inorganic materials are highly permeable but expensive. Mixed matrix membranes (MMMs) combining the advantages of both polymeric and inorganic materials have become a possible breakthrough for the next-generation gas separation membranes. The MMMs could be either symmetric or asymmetric but the latter is more preferred to improve the permeance. Important factors influencing the MMM fabrication include homogeneous distribution of inorganic particles and good interfacial contact between inorganic filler and organic matrix. Recently, metal organic frameworks (MOFs) have received much attention as a new class of porous crystalline materials and a potential candidate for $CO_2$ separation. Zeolitic imidazolate frameworks (ZIFs), a sub-branch of MOFs, are the most widely used in MMMs due to small particle size and appropriate pore size for $CO_2$ separation. One of the major issues associated with the incorporation of porous particles in a polymeric membrane is to control the microstructure of the porous particle materials such as particle size, orientation, and boundary conditions etc. In this review, major challenges surrounding MMMs and the strategies to tackle these challenges are given in detail.