• Journal of the Korean Ceramic Society
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• v.54 no.1
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• pp.1-8
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• 2017

Electrochemical water splitting to produce hydrogen energy is regarded as a promising energy conversion process for its environmentally friendly nature. To improve cell efficiency, the development of efficient water oxidation catalysts is essentially demanded. For several decades, 3d transition metal oxides have been intensively investigated for their high activity, good durability and low-cost. This review covers i) recent progress on 3d transition metal oxide electrocatalysts and ii) the reaction mechanism of oxygen evolving catalysis, specifically focused on the proposed pathways for the O-O bond formation step.

• The Journal of the Petrological Society of Korea
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• v.6 no.2
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• pp.88-95
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• 1997

High pressure X-ray diffraction study was carried out on a polycrystalline graphite to investigate the phase transition(s) at room temperature. Energy dispersive X-ray diffraction method was employed using a Mao-Bell type diamond anvil cell with an Wiggler synchrotron Radiation at the National Synchrotron Light Source. Sodium chloride power was used as the internal pressure sensor for the high pressure determinations as well as the pressure medium for quasihydrostatic pressure environment. Graphite transforms into a hexagonal didose not agree with the previously reported observations and this phase persists when pressure is released down to 0.1 MPa. This result dose not agree with the previously reported observations and this discrepancy would be due to the kinetics in phase transition as well as the uniaxially oriented pressure field in the diamond anvil cell.

• Journal of the Korean Ceramic Society
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• v.36 no.8
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• pp.859-862
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• 1999

• Proceedings of the KIEE Conference
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• summer
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• pp.120-122
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• 2004

This paper analyse impacts of Community Energy System (CES) on the grid during transition periods for integrating of the CES and the grid. In the near future, CES might be one of major energy supply structures. The basic concept of CES is that it supplies electrical and thermal energy to the local customer loads through the islanded power network separated from the grid. Therefore, the interconnection with the grid occurs only when the energy supply from the CES generators does not meet the demand of the local load. For avoiding impacting the grid during the transition operation modes of CES, it is necessary to thoroughly analyse the influences on the grid during those periods. In order to show them, in this paper, we model the CES with 2.34 WVA DG and simulate the impacts on the grid due to interconnection of CES The simulation results show that, in order to reduce bad influences of CES on the grid, CES need the efficient load management and generation control schemes during the transition periods.

• New & Renewable Energy
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• v.17 no.1
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• pp.7-18
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• 2021

This study analyzes the role of market actors in the energy transition process and the interaction between them and ordinary citizens, primarily focusing on the mini-PV project in Seoul. The study also proposes measures to harness market actors' activities and successfully implement the distribution of mini-PV systems in Seoul. In this study, practice theory is used as a theoretical resource to analyze the interaction between market actors and civil society actors and to help understand how market actors influence the decisions of regular citizens in installing mini-PV at their properties. After conducting surveys and hosting in-depth interviews with ordinary citizens and market actors, it was found that to further promote the role of market actors, the Seoul Metropolitan Government should actively support and monitor the public relations activities of market actors, while concurrently managing selected companies and establishing relevant administrative systems for continued effective use post-installation of mini-PV systems. In future studies of the energy transition process, market actors should also be recognized as key players, along with government and civil society actors, and their roles should be studied in a balanced way.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.10 no.4
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• pp.135-142
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• 2011

This paper proposes a performance evaluation method for power consumption of set-top box (STB) stand-by mode transition schemes. A stand-by mode transition scheme characterizes the timing of mode transition. The timing of mode transition affects the duration of stand-by mode operation, and the power consumptions of STB as well. Recently a fast stand-by mode transition scheme (FMT) has been proposed based on user input for selecting the device to be connected to TV. In this paper, we evaluate power consumption of FMT and a conventional mode transition scheme. For the computation of the duration of stand-by mode operation, the user input events are modeled as Poisson process. Simulation results based on the modeling reveals that the proposed scheme is more effective in power saving than the conventional scheme by up to 30%.

• Microbiology and Biotechnology Letters
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• v.28 no.1
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• pp.26-32
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• 2000

Electrostatic forces contribute to the high degree of enzyme transition state complementarity in enzyme catalyzed reaction and such forces are modified by the solvent through its dielectric constant and polar properties. The contributions of electrostatic interaction to the formation of ES complex and the stabilization of transition state of the trypsin catalyzed reaction were probed by kinetic studied with high pressure and solvent dielectric constant. A good correlation has been observed between the increase of catalytic efficiency of trypsin and the decrease of solvent dielectric constant. Activation volume linearly decreased as the dielectric constant of solvent decreased, which means the increase in the reaction rae. Moreover, the decrease of activation volume by lowering the solvent dielectric constant implies a solvent penetration of the active with and a reduction of electrostatic energy for the formation of dipole of the active site oxyanion hole. When the 야electric constant of the solvents was lowered to 4.7 unit, the loss of activation energy and that of free energy of activation were 2.262 KJ/mol and 3.169 KJ/mol, respectively. The results of this study indicate that the high pressure kinetics combined with solvent effects can provide unique information on enzyme reaction mechanisms, and the controlling the solvent dielectric constant can stabilize the transition state of the trypsin-catalyzed reaction.

• Korean Journal of Materials Research
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• v.30 no.9
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• pp.480-488
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• 2020

The electrocaloric effect can be observed in pyroelectric materials based on conversion between electrical and thermal energy, and can be utilized for the future environment-friendly refrigeration technology. Especially, a strong electrocaloric effect is expected in materials in which field-induced phase transition can be achieved. Emerging fluorite-structure ferroelectrics such as doped hafnia and zirconia, first discovered in 2011, are considered the most promising materials for next-generation semiconductor devices. Besides application of fluorite-structure ferroelectrics for semiconductor devices based on their scalability and CMOS-compatibility, field-induced phase transition has been suggested as another interesting phenomenon for various energy-related applications such as solid-state cooling with electrocaloric effect as well as energy conversion/storage and IR/piezoelectric sensors. Especially, their giant electrocaloric effect is considered promising for solid-state-cooling. However, the electrocaloric effect of fluorite-structure oxides based on field-induced phase transition has not been reviewed to date. In this review, therefore, the electrocaloric effect accompanied by field-induced phase transition in fluorite-structure ferroelectrics is comprehensively reviewed from fundamentals to potential applications.

• Asian-Australasian Journal of Animal Sciences
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• v.32 no.5
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• pp.648-656
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• 2019

Objective: An experiment was conducted to determine the effect of reduced energy density of close-up diets on metabolites, lipolysis and gluconeogenesis in cows during the transition period. Methods: Thirty-nine Holstein dry cows were blocked and assigned randomly to three groups, fed a high energy density diet (HD, 1.62 Mcal of net energy for lactation $[NE_L]/kg$ dry matter [DM]), a medium energy density diet (MD, $1.47Mcal\;NE_L/kg\;DM$), or a low energy density diet (LD, $1.30Mcal\;NE_L/kg\;DM$) prepartum; they were fed the same lactation diet to 28 days in milk (DIM). All the cows were housed in a free-stall barn and fed ad libitum. Results: The reduced energy density diets decreased the blood insulin concentration and increased nonesterified fatty acids (NEFA) concentration in the prepartum period (p<0.05). They also increased the concentrations of glucose, insulin and glucagon, and decreased the concentrations of NEFA and ${\beta}-hydroxybutyrate$ during the first 2 weeks of lactation (p<0.05). The plasma urea nitrogen concentration of both prepartum and postpartum was not affected by dietary energy density (p>0.05). The dietary energy density had no effect on mRNA abundance of insulin receptors, leptin and peroxisome proliferator-activated $receptor-{\gamma}$ in adipose tissue, and phosphoenolpyruvate carboxykinase, carnitine palmitoyltransferase-1 and peroxisome proliferator-activated $receptor-{\alpha}$ in liver during the transition period (p>0.05). The HD cows had higher mRNA abundance of hormone-sensitive lipase at 3 DIM compared with the MD cows and LD cows (p = 0.001). The mRNA abundance of hepatic pyruvate carboxy-kinase at 3 DIM tended to be increased by the reduced energy density of the close-up diets (p = 0.08). Conclusion: The reduced energy density diet prepartum was effective in controlling adipose tissue mobilization and improving the capacity of hepatic gluconeogenesis postpartum.

• Advances in concrete construction
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• v.8 no.3
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• pp.173-185
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• 2019

This article presents a comparative study of the effect of steel layouts on the seismic behavior of transition steel-concrete composite connections, both experimental and analytical investigations of concrete filled steel tube-reinforced concrete (CFST-RC) and steel reinforecd concrete-reinforced concrete (SRC-RC) structures were conducted. The steel-concrete composite connections were subjected to combined constant axial load and lateral cyclic displacements. Tests were carried out on four full-scale connections extracted from a real project engineering with different levels of axial force. The effect of steel layouts on the mechanical behavior of the transition connections was evaluated by failure modes, hysteretic behavior, backbone curves, displacement ductility, energy dissipation capacity and stiffness degradation. Test results showed that different steel layouts led to significantly different failure modes. For CFST-RC transition specimens, the circular cracks of the concrete at the RC column base was followed by steel yielding at the bottom of the CFST column. While uncoordinated deformation could be observed between SRC and RC columns in SRC-RC transition specimens, the crushing and peeling damage of unconfined concrete at the SRC column base was more serious. The existences of I-shape steel and steel tube avoided the pinching phenomenon on the hysteresis curve, which was different from the hysteresis curve of the general reinforced concrete column. The hysteresis loops were spindle-shaped, indicating excellent seismic performance for these transition composite connections. The average values of equivalent viscous damping coefficients of the four specimens are 0.123, 0.186 and 0.304 corresponding to the yielding point, peak point and ultimate point, respectively. Those values demonstrate that the transition steel-concrete composite connections have great energy dissipating capacity. Based on the experimental research, a high-fidelity ABAQUS model was established to further study the influence of concrete strength, steel grade and longitudinal reinforcement ratio on the mechanical behavior of transition composite connections.