• Journal of Magnetics
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• v.17 no.3
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• pp.168-171
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• 2012

Irreversible magnetization between the zero-field-cooled (ZFC) and field-cooled (FC) states in $Y_{1-x}Sr_xMnO_3$ (x=0 and 0.2) was investigated. $YMnO_3$ and $Y_{0.8}Sr_{0.2}MnO_3$ have a hexagonal structure and the lattice parameter a decreases from 7.4408 ${\AA}$ to 7.4327 ${\AA}$ while c increases from 12.2244 ${\AA}$ to 12.2287 ${\AA}$ for $YMnO_3$ and $Y_{0.8}Sr_{0.2}MnO_3$, respectively. An anomaly is observed at around 74 K in ZFC and FC magnetization measurements for $YMnO_3$, whereas in $Y_{0.8}Sr_{0.2}MnO_3$ the ${\sigma}_{ZFC}$ and ${\sigma}_{FC}$ are split at low temperature, indicating glass-like behavior.

• Journal of the Korean Institute of Landscape Architecture
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• v.45 no.3
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• pp.129-140
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• 2017

This study aims to interpret the current landscape design of the place and landscape of memory, such as post-industrial parks and memorials that have an old, aging appearance from an aesthetic perspective. The objects of the study are large parks and open spaces that have collective memories for visitors. Visitors' aesthetic experience from these places and landscapes of memory could be explained by aesthetic concepts such as the sublime, nostalgia, and melancholy. Because these aesthetic concepts are associated with past traumas, visitors may be affected morbidly. However, due to the capability of the media to form an aesthetic experience when visitors visit a given place and landscape, visitors can autonomously adjust the distance to the place of memory and gain an aesthetic experience. The aesthetic experiences through the sublime, nostalgia, and melancholy are based on temporality and irreversibility. Temporality here refers to a characteristic of memory, and time in the place and landscape of memory and is based on the irreversibility of time, as time cannot go back. Both the place memory and the memory that is recalled from the combination with visitor's past memories and knowledge are two major factors involved in the construction of the aesthetic experience in the place and landscape of memory. The results of the present study are meaningful in that this study presents a framework for a better understanding and use of both the place memory and appreciators' memory in the design process of a place and landscape of memory and also criticizes a materialistic approach that fails to take into account the visitors' memories.

• Journal of Korean Society for Quality Management
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• v.14 no.2
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• pp.33-39
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• 1986

This paper is to present basic concepts of availability, irreversibility, dead states, its relationship to other thermodynamic functions, and the history of availability. The balance of availability and effectiveness has also been formulated in order to build basis on which further study and actual application of availability in estimation of available energy are to be thought.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.4
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• pp.317-324
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• 2015

In this study, a solar thermal system is designed to provide hot water and electricity for improvement of solar thermal energy availability in an apartment complex. The electricity is generated with Organic Rankine Cycle (ORC) by the solar thermal energy. R134a, R141b and R245fa are selected for operating fluid of the solar thermal ORC system. ORC with R245fa shows the best performance based on the variation of pressure. The irreversibility of component showed that the technology advance of the evaporator ensures a performance improvement. The sensitivity study results indicate that the turbine performance is most effective way to improve the performance of ORC system. An economic analysis showed that approximately 50% more income could be achieved by a solar thermal ORC system with a hot water supply.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.1
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• pp.225-229
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• 1990

As a basic study of optimal design conditions of refrigeration systems, the reversed carnot cycle, including heat transfer processes through the finite temperature differences between heat sources and the working fluids, is analyzed with the capacity of heat exchanger as a design parameter. When the temperatures of heat sources and the input work are fixed as constants, the optimal design condition is obtained as an optimum ratio of capacities of heat exchangers, which is exactly unity when the exergy output and effectiveness are maximum. In addition, the optimum ratio is slightly increased from unity as the irreversibility of the cycle increases.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.8
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• pp.2177-2183
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• 1994

The rapid expansion or condensible gas such as moist air of steam gives rise to nonequilibrium condensation. As a result of irreversibility of condensation process in the supersonic cascade flow of low pressure steam turbine, the entropy of the flow is increased, and the efficiency of the turbine is decreased. In the present study, to investigate the flow of moist air in 2-dimensional cascade made as the configuration of the tip section of the last actual steam turbine moving blade, the static pressure at both sides of pressure and suction of blade are measured by static pressure taps and the distribution of Mach number on both surfaces of the blade are obtained by using the measured static pressure. Also, the flow field is visualized by a schlieren system. From the experimental results, the effects of the stagnation temperature and specific humidity on the flow properties in a 2-dimensional stationary cascade of a practical steam turbine blade are clearly identified.

• Journal of Preventive Medicine and Public Health
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• v.26 no.4 s.44
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• pp.480-507
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• 1993

Environmental pollution is common problem of the present world that is intimately related to the future survival of human beings. The problems of environmental pollution originate from the pursuit of benefit by enterprises, insufficient countermeasure of government and ignorant life style of the people. Health hazards due to environmental pollution have characteristics of irreversibility, difficulty in measurement and ineffectiveness of personal prevention. Objects of this article are to review the various aspects of environmental pollution, to outline the present status of environmental pollution and strategy to control environmental pollution in Korea. In the first part of this article, causes of environmental pollution are presented. International relationships, world-wide status of environmental pollution and health hazards due to environmental pollution are briefly reviewed. In the second part, present status of air, water, soil and ocean pollution in Korea is presented. Pollution by radioactive materials, noise, vibrations, odor, wastes and chemicals is reviewed. Climate changes related to environmental poisoning, problems of workplace environment, pesticide and defoliants are also reviewed. Finally, control measures for environmental pollution including the role of government are reviewed.

• Journal of the Korean Magnetic Resonance Society
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• v.9 no.1
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• pp.21-28
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• 2005

$^{11}B$ nuclear magnetic resonance (NMR) measurements have been performed to investigate electronic structures and vortex states of $M_gB_2$ superconductor. The central transition shows a narrow peak down to 25 K at 3.15 T. Below 25 K, an extra line starts to show up and dominates. The extra line is broad and asymmetric with a long tail in the high frequency side, which confirms that this originates from vortex pinning below the irreversibility temperature. From temperature evolution of the fraction and linewidth of the broad portion, temperature dependence of coherence length and penetration depth are extracted.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.6
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• pp.564-568
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• 1984

An analysis has been performed for the internally reversible heat engine with the finite heat transfer rate. In the heat engine operating between two fluid streams, there exist the optimum temperatures at which the engine has maximum power. The optimum values can be expressed in terms of the temperatures of the heat source and sink. The condition for the maximum power can be explained as the minimum entropy generation by the finite heat transfer rate.

• Computers and Concrete
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• v.1 no.2
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• pp.131-150
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• 2004

We present in this work a coupled phenomenological chemo-mechanical model that represents the degradation of concrete-like materials. The chemical behaviour is described by the nowadays well known simplified calcium leaching approach. And the mechanical damage behaviour is described by a continuum damage model which involves the gradient of the damage quantity. The coupled nonlinear problem at hand is addressed within the context of the finite element method. For the equation governing the calcium dissolution-diffusion part of the problem, special care is taken to treat the highly nonlinear calcium conductivity and solid calcium functions. The algorithmic design is based on a Newton-type iterative scheme where use is made of a recently proposed relaxed linearization procedure. And for the equation governing the damage part of the problem, an augmented Lagrangian formulation is used to take into account the damage irreversibility constraint. Finally, numerical simulations are compared with experimental results on cement paste.