• Journal of Electrochemical Science and Technology
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• v.7 no.4
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• pp.316-326
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• 2016

Development and discovery of efficient, cost-effective, and robust electrocatalysts are imperative for practical and widespread implementation of water electrolysis and fuel cell techniques in the anticipated hydrogen economy. The electrochemical reactions involved in water electrolysis, i.e., hydrogen and oxygen evolution reactions, are complex inner-sphere reactions with slow multi-electron transfer kinetics. To develop active electrocatalysts for water electrolysis, the physicochemical properties of the electrode surfaces in electrolyte solutions should be investigated and understood in detail. When electrocatalysis is conducted using nanoparticles with large surface areas and active surface states, analytical techniques with sub-nanometer resolution are required, along with material development. Scanning electrochemical microscopy (SECM) is an electrochemical technique for studying the surface reactions and properties of various types of electrodes using a very small tip electrode. Recently, the morphological and chemical characteristics of single nanoparticles and bio-enzymes for catalytic reactions were studied with nanometer resolution by combining SECM with atomic force microscopy (AFM). Herein, SECM techniques are briefly reviewed, including the AFM-SECM technique, to facilitate further development and discovery of highly active, cost-effective, and robust electrode materials for efficient electrolysis and photolysis.

• Composites Research
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• v.30 no.3
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• pp.169-174
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• 2017

Demand of glass fiber reinforced composites (GFRC) increased with developing aircraft and defense industries using resin transfer molding (RTM) process to produce complex product. In this research, wetting, interfacial, and mechanical properties were evaluated with different Cross-linking Density by Molecular Weight of Hardener. Epoxy resin as matrices was used bisphenol-A type and amine-type hardeners with different molecular weight. Specimens were manufactured via RTM and wetting property of resin and glass fiber (GF) mat was evaluated to viscosity of epoxy and injection time of epoxy matrix. Mechanical property of GFRC was determined via flexural strength whereas interfacial properties were determined by interlaminar shear strength (ILSS) and interfacial shear strength (IFSS). The difference in mechanical property depends upon the fiber weight fraction (wt %) of GFRC by RTM as well as the different Molecular Weight of Hardener.

• Journal of Life Science
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• v.14 no.5
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• pp.752-760
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• 2004

The function of the [4Fe-4S] cluster containing iron (Fe-) protein in nitrogenase catalysis is to serve as the nucleotide-dependent electron donor to the MoFe protein which contains the sites for substrate binding and reduction. The ability of the Fe protein to function in this manner is dependent on its ability to adopt the appropriate conformation for productive interaction with the MoFe protein and on its ability to change redox potentials to provide the driving force required for electron transfer. The MgADP-bound (or off) conformational state of the nitrogenase Fe protein structure described reveals mechanisms for long-range communication from the nucleotide-binding sites to control affinity of association with the MoFe protein component. Two pathways, termed switches I and II, appear to be integral to this nucleotide signal transduction mechanism. In addition, the structure of the MgADP bound Fe protein provides the basis for the changes in the biophysical properties of the [4Fe-4S] observed when Fe protein binds nucleotides. The structures of the nitrogenase Fe protein with defined amino acid substitutions in the nucleotide dependent signal transduction pathways of the Switch I and Switch II have been determined by X-ray diffraction methods. These two pathways have been also implicated by site directed mutagenesis studies, structural analysis and analogies to other proteins that utilize similar nucleotide dependent signal transduction pathways. We have examined the validity of the assignment of these pathways in linking the signals generated by MgATP binding and hydrolysis to macromolecular complex formation and intermolecular electron transfer. The results provide a structural basis for the observed biophysical and biochemical properties of the Fe protein variants and interactions within the nitrogenase Fe protein-MoFe protein complex.

• Journal of Embryo Transfer
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• v.32 no.3
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• pp.65-71
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• 2017

The elevated temperature and high humidity has been known as main reason for heat stress on animals and cause detrimental effects on productivity of organisms and physiological conditions of normal bioactivities. The aims of this study were to evaluate the relationship between time of heat shock simulation during in vitro maturation and developmental competence of subsequent embryo after in vitro fertilization. Heat shocked cumulus-oocyte complexes (COCs) of Korean native cattle were subjected to normal conditions for 22, 21, 18 and 12 h respectively and transferred to heat stress inducing condition at $40.5^{\circ}C$ in other incubator for 0 (control), 1 and 4 h. After maturation for 22 h, the oocytes were fertilized and cultured in mSOF media for 8 d and examined the developmental capacity of embryos. There were no differences in maturation and cleavage rates between 0, 1 and 4 h heat socked oocytes, but blastocysts formation were lower in the 4 h heat stressed oocytes. The apoptotic cells of developed blastocysts were also increased in at day 8 with 4 h heat shocked oocytes. These results indicate that heat shock on oocytes during maturation could cause negative effects on the developmental competence of embryos.

• Archives of Plastic Surgery
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• v.46 no.4
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• pp.365-370
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• 2019

The syndrome of the trephined is a neurologic phenomenon that manifests as sudden decline in cognition, behavior, and sensorimotor function due to loss of intracranial domain. This scenario typically occurs in the setting of large craniectomy defects, resulting from trauma, infection, and/or oncologic extirpation. Cranioplasty has been shown to reverse these symptoms by normalizing cerebral hemodynamics and metabolism. However, successful reconstruction may be difficult in patients with complex and/or hostile calvarial defects. We present the case of a 48-year-old male with a large cranial bone defect, who failed autologous cranioplasty secondary to infection, and developed rapid neurologic deterioration leading to a near-vegetative state. Following debridement and antibiotic therapy, delayed cranioplasty was accomplished using a polyetheretherketone (PEEK) implant with free chimeric latissimus dorsi/serratus anterior myocutaneous flap transfer for vascularized resurfacing. Significant improvements in cognition and motor skill were noted in the early postoperative period. At 6-month follow-up, the patient had regained the ability to speak, ambulate and self-feed-correlating with evidence of cerebral/ventricular re-expansion on computed tomography. Based on our findings, we advocate delayed alloplastic implantation with total vascularized soft tissue coverage as a viable alternative for reconstructing extensive, hostile calvarial defects in patients with the syndrome of the trephined.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10b
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• pp.1639-1645
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• 1991

Because of the important role LD converters play in the production of high quality steel, various dynamic models have been attempted in the past by many researchers not only to understand the complex chemical reactions that take place in the converter process but also to assist the converter operation itself using computers. And yet no single dynamic model was found to be completely satisfactory because of the complexity involved with the process. The process indeed involves dynamic energy and mass balances at high temperatures accompanied by complex chemical reactions and transport phenomena in the molten state. In the present study, a mathematical model describing the dynamic behavior of LD converter process has been developed. The dynamic model describes the time behavior of the temperature and the concentrations of chemical species in the hot metal bath and slag. The analysis was greatly facilitated by dividing the entire process into three zones according to the physical boundaries and reaction mechanisms. These three zones were hot metal (zone 1), slag (zone 2) and emulsion (zone 3) zones. The removal rate of Si, C, Mn and P and the rate of Fe oxidation in the hot metal bath, and the change of composition in the slag were obtained as functions of time, operating conditions and kinetic parameters. The temperature behavior in the metal bath and the slag was also obtained by considering the heat transfer between the mixing and the slag zones and the heat generated from chemical reactions involving oxygen blowing. To identify the unknown parameters in the equations and simulate the dynamic model, Hooke and Jeeves parttern search and Runge-Kutta integration algorithm were used. By testing and fitting the model with the data obtained from the operation of POSCO #2 steelmaking plant, the dynamic model was able to predict the characteristics of the main components in the LD converter. It was possible to predict the optimum CO gas recovery by computer simulation

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.8
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• pp.1051-1057
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• 2010

This paper proposes a method that involves a combination of FDM and FEM for analyzing casting process. At present, many numerical analysis methods such as FDM, FEM, and BEM are used for solving engineering problems. For a given problem, a specific method that is suited to the problem is adopted; in general, FDM or FVM is favored for problems related to fluid flow or heat transfer, and FEM is adopted in stress analysis. However, there is an increasing need for using a combined method for complex and coupled phenomena analysis. Hence, we proposed a method in which FDM and FEM are coupled in three-dimensional space, and we applied this method to analyze casting process. In the proposed method, solidification and heat transfer was analyzed by using FDM. The field data such as temperature distribution were converted into a format suitable for FEM analysis that was used for calculating thermal stress distribution. Using the proposed method, we efficiently analyzed the analysis process from the viewpoints of work and time.

• Bulletin of the Korean Chemical Society
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• v.30 no.7
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• pp.1553-1558
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• 2009

A series of Eu(III) complexes with various neutral ligands (2,2’:6’,2"-terpyridine (T), diglyme (D), 1N-(2-dimethylamino) ethyl)-1N, 2N, 2N-trimethylethane-1,2-diamine (PT), di-(2-picolyl)-amine derivative (HT), and multidentate terpyridine derivative (DT)) were synthesized to investigate the effect of coordination environment on the sensitized luminescence of Eu(III) complexes. The nine coordination sites of the $Eu^{3+}$ ion are occupied by three bidentate carboxylate moieties and one neutral ligand. The highest emission intensity is obtained for $Eu^{3+}$- $[NA]_3$ (PT), due to the difference in energy transfer efficiency and symmetry of the first coordination sphere of $Eu^{3+}$ ion. But, the lowest emission intensity is obtained for $Eu^{3+}$-$[NA]_3$(T). Terpyridine may not play an important role antenna for photosensitizing $Eu^{3+}$ ion. It could be attributed to the weak spectral overlap integral J value between its phosphorescence band and $Eu^{3+}$ion absorption band. Therefore, different coordination environment of $Ln^{3+}$ ion play an important role in providing sensitization of lanthanide ion emission.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1697-1703
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• 2010

Hydraulic hoses are used as pipelines for transferring power from hydraulic systems in various machineries such as construction equipments, automobiles, and aircraft. Hydraulic hoses protect the system from vibration or impacts, and they are being used to transfer energy in all segments of the industry. In order to protect the system from various external environmental conditions, hydraulic hose assemblies must be able to withstand a wide range of temperatures and pressures, as well as variations in other factors. In previous studies, an acceleration model for the hydraulic hose assembly was developed by taking into account only one of the acceleration factors (temperature or pressure). Therefore, the objective of this study is to develop a comprehensive acceleration model that takes both temperature and pressure into consideration.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.6
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• pp.527-536
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• 2013

In order to predict structural vibration and radiated noise of high-voltage transformer in operation, it is necessary to precisely find the excitation force generated by the coils and core. However, finding the excitation force through experiments of high voltage transformer in operation is not possible. Therefore, this paper deals with identifying the excitation force by using the acceleration data measured through experiments and the transfer function estimated through finite element model. A method to predict structural vibration and radiated noise was also proposed. Three-phase windings and the core are the source of high-voltage transformer. The excitation forces were identified using the acceleration data and the transfer function of the surface of the tank. Structural vibration and radiated noise from the surface of the tank was predicted by using the identified excitation force. As a result of the interpretation of the experimental and computational analysis of structural vibration from the surface of the tank and radiated noise from the field point, the interpretation of the computational analysis showed relatively good accordance with the experiment.