• Progress in Medical Physics
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• v.8 no.2
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• pp.87-102
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• 1997

The absolute absorbed dose can be determined according to the measurement conditions; measurement material, detector, energy and calibration protocols. The purpose of this study is to compare the absolute absorbed dose due to the differences of measurement condition and calibration protocols for photon beams. Dosimetric measurements were performed with a farmer type PTW and NEL ionization chambers in water, solid water, and polystyrene phantoms using 6MV photon beams from Siemens linear accelerator. Measurements were made along the central axis of 10cm $\times$ 10cm field size for constant target to surface distance of 100cm for water, solid water and polystyrene phantom. Theoretical absorbed dose intercomparisons between TG21 and IAEA protocol were performed for various measurement combinations of phantom, ion chamber, and electrometer. There were no significant differences of absorbed dose value between TG21 and IAEA protocol. The differences between two protocols are within 1％ while the average value of IAEA protocol was 0.5％ smaller than TG21 protocol. For the purpose of comparison, all the relative absorbed dose were nomalized to NEL ion chamber with Keithley electrometer and water phantom, The average differences are within 1％, but individual discrepancies are in the range of - 2.5％ to 1.2％ depending upon the choice of measurement combination. The largest discrepancy of - 2.5％ was observed when NEL ion chamber with Keithley electrometer is used in solid water phantom. The main cause for this discrepancy is due to the use of same parameters of stopping power, absorption coeficient, etc. as used in water phantom. It should be mentioned that the solid water phantom is not recommended for absolute dose calibration as the alternative of water, since absorbed dose show some dependency on phantom material other than water. In conclusion, the trend of variation was not much dependent on calibration protocol. However, it shows that absorbed dose could be affected by phantom material other than water.

• Journal of the Korean Institute of Landscape Architecture
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• v.37 no.3
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• pp.21-32
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• 2009

As an alternative for restoring a sense of community which has been broken up due to urban residence redevelopment, this study focuses on structural characteristics according to physical location of central squares in apartment complexes. Central squares do not simply function as inner-aiming and self-completed spaces for the residents, but their role can be expanded to a core location which encourages neighbors to communicate and interact with each other. The suppositions for this study are as follows. Structural characteristics according to the physical locations of the central squares in apartment complexes affect apartment residents' openness toward their neighbors and non-residents' accessibility to the square. At the same time, it influences the sense of community. In addition, psychological distance which is represented as psychological openness and accessibility forms a reciprocal relationship with the sense of community. For the study, we first categorized central squares as either open-structure or closed-structure based on how accessible it is from outside the apartment complex. According to these types of central squares, Sillim Prugio, Banghak Deasang Town Hyundai, Gwanak Prugio and Banghak Samsung Raemian 1 which have similar conditions and different structures were selected as sites of the study. Then each apartment complex was classified by apartment residents and non-residents so that eight groups were prepared for the survey. The results of the questionnaire survey especially regarding measuring the sense of community, psychological openness and accessibility indicated that the suppositions were right. Hence, the sense of community, psychological openness and accessibility are high in a central square with an open-structure while high standards of psychological openness and accessibility guarantee a positive sense of community. This study is meaningful in that it verifies that the physical location of central squares is reciprocally related to psychological openness, accessibility and a sense of community. At the same time, this study may serve as theoretical grounds for the planning and construction of practical central squares.

• Development and Reproduction
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• v.11 no.3
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• pp.235-243
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• 2007

Human umbilical cord blood(HUCB) contains a rich source of hematopoietic stem cells, mesenchymal stem cells and endothelial cell precursors. Mesenchymal stem cells(MSCs) in HUCB are multipotent stem cells, differ from hematopoietic stem cells and can be differentiated into neural cells. We studied on transdifferentiation-promoting conditions in neural cells and cholinergic neuron induction of HUCB-derived MSCs. Neural differentiation was induced by addingdimethyl sulphoxide(DMSO) and butylated hydroxyanisole(BHA) in Dulbeco's Modified Essential Medium(DMEM) and fetal bovine serum(FBS). Differentiation of MSCs to cholinergic neurons was induced by combined treatment with basic fibroblast growth factor(bFGF), retinoic acid(RA) and sonic hedgehog(Shh). MSCs treated with DMSO and BHA rapidly assumed the morphology of multipolar neurons. Both immunocytochemistry and RT-PCR analysis indicated that the expression of a number of neural markers including $\beta$-tubulin III, GFAP and MBP, was markedly elevated during this acute differentiation. The differentiation rate was about $32.3{\pm}2.9%$ for $\beta$-tubulin III-positive cells, $11.0{\pm}0.9%$ for GFAP, and $9.4{\pm}1.0%$ for Gal-C. HUCB-MSCs treated combinatorially with bFGF, RA and Shh were differentiated into cholinergic neurons. After cholinergic neuronal differentiation, the $\beta$-tubulin III-positive cell population of total cells was $31.3{\pm}3.2%$ and of differentiated neuronal population, $70.0{\pm}7.8%$ was ChAT-positive showing 3 folds higher in cholinergic population than neural induction. Conclusively, HUCB-derived MSCs can be differentiated into neural and cholinergic neurons and these findings suggest that HUCB are alternative cell source of treatment for neurodegenerative diseases such as Alzheimer's disease.

• Journal of Life Science
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• v.27 no.10
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• pp.1137-1144
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• 2017

The microalgae Chlorella vulgaris has been considered an important alternative resource for biodiesel production. However, its industrial-scale production has been constrained by the low productivity of the biomass and lipid. To overcome this problem, we isolated and characterized a potentially economical oleaginous strain of C. vulgaris via the random mutagenesis technique using UV irradiation. Two types of mass production systems were compared for their yield of biomass and lipid content. Among the several putatively oleaginous strains that were isolated, the particular mutant strain designated as UBM1-10 in the laboratory showed an approximately 1.5-fold higher cell yield and lipid content than those from the wild type. Based on these results, UBM1-10 was selected and cultivated under outdoor conditions using two different types of reactors, a tubular-type photobioreactor (TBPR) and an open pond-type reactor (OPR). The results indicated that the mutant strain cultivated in the TBPR showed more than 5 times higher cell concentrations ($2.6g\;l^{-1}$) as compared to that from the strain cultured in the OPR ($0.5g\;l^{-1}$). After the mass cultivation, the cells of UBM1-10 and the parental strain were further investigated for crude lipid content and composition. The results indicate a 3-fold higher crude lipid content from UBM1-10 (0.3%, w/w) as compared to that from the parent strain (0.1% w/w). Therefore, this study demonstrated that the economic potential of C. vulgaris as a biodiesel production resource can be increased with the use of a photoreactor type as well as the strategic mutant isolation technique.

• Korean Journal of Social Welfare
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• v.58 no.2
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• pp.273-302
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• 2006

The introduction of cash payments for care is a distinct trend that characterizes changes in care policies since the 1990s. Recently, many developed countries have newly introduced or extended cash payments for care that allow care users to be able to plan themselves for their cares instead of receiving direct care services from the state. Cash payments for care can be said to be one of the alternative policies by which user choices are extended, and it becomes possible to establish demand-cantered care delivery systems more economically and effectively, hence addressing the issue of the financial limitations and rigid systems that are common in modern welfare states, which make it difficult to response to various needs. However, the design and administration of cash for care vary across different countries. Such variations of cash for care policies influence on the combination of consumerism (based on liberal market values intrinsic in the care market) and citizenship based on social solidarity. Those variations eventually produce impacts on the balance of responsibilities and the roles of families, the state and market regarding care in other words, balancing of welfare pluralism. This paper has attempted to find general meanings and particularity of cash for care polices in modem welfare states by means of looking at the characteristics of cash for care policies of four different countries (Netherlands, France, Germany and Italy) and their impacts on their care market. If the four countries are ranked by the degree that they emphasize citizenship in light with social rights, the Netherlands, France, Germany and Italy could be placed in due order. From an economic point of view and in terms of cost containment, those countries will be placed in an inverse order, It is apparent that in the course of planting cash for care policies in the existing social systems involving different socio-cultural conditions and labour markets, sometimes more emphasis is placed on the citizenship of care users, family carers and care providers than on cost containment issue, and sometimes vice versa. Behind this lies the process of different social valuation on what care is about; who can better deliver care; who should be responsible for care; how responsibilities should be shared and so on.

• Clean Technology
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• v.24 no.2
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• pp.127-134
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• 2018

To reduce the environmental pollution by $NO_x$ from ship engine, International maritime organization (IMO) announced Tier III regulation, which is the emmision regulation of ship's exhaust gas in Emission control area (ECA). Selective catalytic reduction (SCR) process is the most commercial $De-NO_x$ system in order to meet the requirement of Tier III regulation. In generally, commercial ceramic honeycomb SCR catalyst has been installed in SCR reactor inside marine vessel engine. However, the ceramic honeycomb SCR catalyst has some serious issues such as low strength and easy destroution at high velocity of exhaust gas from the marine engine. For these reasons, we design to metallic structured catalyst in order to compensate the defects of the ceramic honeycomb catalyst for applying marine SCR system. Especially, metallic structured catalyst has many advantages such as robustness, compactness, lightness, and high thermal conductivity etc. In this study, in order to support catalyst on metal substrate, coating slurry is prepared by changing binder. we successfully fabricate the metallic structured catalyst with strong adhesion by coating, drying, and calcination process. And we carry out the SCR performance and durability such as sonication and dropping test for the prepared samples. The MFC01 shows above 95% of $NO_x$ conversion and much more robust and more stable compared to the commercial honeycomb catalyst. Based on the evaluation of characterization and performance test, we confirm that the proposed metallic structured catalyst in this study has high efficient and durability. Therefore, we suggest that the metallic structured catalyst may be a good alternative as a new type of SCR catalyst for marine SCR system.

• Journal of Korea Water Resources Association
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• v.47 no.6
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• pp.537-546
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• 2014

Surface image velocimetry was introduced as an efficient and sage alternative to conventional river flow measurement methods during floods. The conventional surface image velocimetry uses a pair of images to estimate velocity fields using cross-correlation analysis. This method is appropriate to analyzing images taken with a short time interval. It, however, has some drawbacks; it takes a while to analyze images for the verage velocity of long time intervals and is prone to include errors or uncertainties due to flow characteristics and/or image taking conditions. Methods using spatio-temporal images, called STIV, were developed to overcome the drawbacks of conventional surface image velocimetry. The grayscale-gradient tensor method, one of various STIVs, has shown to be effectively reducing the analysis time and is fairly insusceptible to any measurement noise. It, unfortunately, can only be applied to the main flow direction. This means that it can not measure any two-dimensional flow field, e.g. flow in the vicinity of river structures and flow around river bends. The present study aimed to develop a new method of analyzing spatio-temporal images in two-dimension using cross-correlation analysis. Unlike the conventional STIV, the developed method can be used to measure two-dimensional flow substantially. The method also has very high spatial resolution and reduces the analysis time. A verification test using artificial images with lid-driven cavity flow showed that the maximum error of the method is less than 10 % and the average error is less than 5 %. This means that the developed scheme seems to be fairly accurate, even for two-dimensional flow.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.12
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• pp.715-732
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• 2009

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2008. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) Research trends in thermal and fluid engineering have been surveyed in the categories of general fluid flow, fluid machinery and piping, new and renewable energy, and fire. Well-developed CFD technologies were widely applied in developing facilities and their systems. New research topics include fire, fuel cell, and solar energy. Research was mainly focused on flow distribution and optimization in the fields of fluid machinery and piping. Topics related to the development of fans and compressors had been popular, but were no longer investigated widely. Research papers on micro heat exchangers using nanofluids and micro pumps were also not presented during this period. There were some studies on thermal reliability and performance in the fields of new and renewable energy. Numerical simulations of smoke ventilation and the spread of fire were the main topics in the field of fire. (2) Research works on heat transfer presented in 2008 have been reviewed in the categories of heat transfer characteristics, industrial heat exchangers, and ground heat exchangers. Research on heat transfer characteristics included thermal transport in cryogenic vessels, dish solar collectors, radiative thermal reflectors, variable conductance heat pipes, and flow condensation and evaporation of refrigerants. In the area of industrial heat exchangers, examined are research on micro-channel plate heat exchangers, liquid cooled cold plates, fin-tube heat exchangers, and frost behavior of heat exchanger fins. Measurements on ground thermal conductivity and on the thermal diffusion characteristics of ground heat exchangers were reported. (3) In the field of refrigeration, many studies were presented on simultaneous heating and cooling heat pump systems. Switching between various operation modes and optimizing the refrigerant charge were considered in this research. Studies of heat pump systems using unutilized energy sources such as sewage water and river water were reported. Evaporative cooling was studied both theoretically and experimentally as a potential alternative to the conventional methods. (4) Research papers on building facilities have been reviewed and divided into studies on heat and cold sources, air conditioning and air cleaning, ventilation, automatic control of heat sources with piping systems, and sound reduction in hydraulic turbine dynamo rooms. In particular, considered were efficient and effective uses of energy resulting in reduced environmental pollution and operating costs. (5) In the field of building environments, many studies focused on health and comfort. Ventilation. system performance was considered to be important in improving indoor air conditions. Due to high oil prices, various tests were planned to examine building energy consumption and to cut life cycle costs.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.12
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• pp.1098-1125
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• 2000

A review on the papers published in the Korean Journal of Air-Conditioning and Refrigerating Engineering in 1998 and 1999 has been done. Focus has been put on current status of research in the aspect of heating, cooling, ventilation, sanitation and building environment. The conclusions are as follows. 1) A review of the recent studies on fluid flow, turbomachinery and pipe-network shows that many experimental investigations are conducted in applications of impingement jets. Researches on turbulent flows, pipe flows, pipe-networks are focused on analyses of practical systems and prediction of system performance. The results of noise reduction in the turbomachinery are also reported. 2) A review of the recent studies on heat transfer analysis and heat exchanger shows that there were many papers on the channel flow with the application to the design of heat exchanger in the heat transfer analysis. Various experimental and numerical papers on heat exchanger were also published, however, there were few papers available for the analysis of whole system including heat exchanger. 3) A review of the recent studies on heat pump system have focused on the multi-type system and the heat pump cycle to utilize treated sewage as the heat source. The defrosting and the frosting behaviors in the fin-tube heat exchanger is experimentally examined by several authors. Several papers on the ice storage cooling system are presented to show the dynamic simulation program and optimal operation conditions. The study on the micro heat pipes for the cooling of high power electronic components is carried out to examine the characteristics of heat and mass transfer processed. In addition to these, new type of separate thermosyphon is studied experimentally. 4) The recent studies on refrigeration/air conditioning system have focused on the system performance and efficiency for new alternative refrigerants. New systems operating with natural refrigerants are drawing lots of attention. In addition to these, evaporation and condensation heat transfer characteristics of traditional and new refrigerants are investigated for plain tubes and also for microfin tubes. Capillary tubes and orifice are main topics of research as expansion devices and studies on thermophysical properties of new refrigerants and refrigerant/oil mixtures are widely carried out. 5) A review of the recent studies on absorption cooling system shows that numerous experimental and analytical studies on the improvement of absorber performance have been presented. Dynamic analysis of compressor have been performed to understand its vibration characteristics. However research works on tow-phase flow and heat transfer, which could be encountered in the refrigeration system and various phase-change heat exchanger, were seemed to be insufficient. 6) A review of recent studies on duct system shows that the methods for circuit analysis, and flow balancing have been presented. Researches on ventilation are focused on the measurement of ventilation efficiency, and variation of ventilation efficiency with ventilation methods by numerous experimental and numerical studies. Furthermore, many studies have been conducted in real building in order to estimate indoor thermal environments. Many research works to get some information for cooling tower design have been performed but are insufficient. 7) A review on the recent studies on architectural thermal environment and building mechanical systems design shows that thermal comfort analysis is sitting environment, thermal performance analysis of Korean traditional building structures., and evaluation of building environmental load have been performed. However research works to improve the performance of mechanical system design and construction technology were seemed to be insufficient.

• Korean Journal of Environment and Ecology
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• v.30 no.5
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• pp.837-847
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• 2016

In this study, the bird fauna of Sihwa Lake in Gyeonggi Province were investigated from 2009 to 2014 to identify the effect of the restored intertidal zone on bird community. Based upon the analysis of the habitat status and distribution change of water birds in the intertidal zone, the following conclusions were obtained. The number of water bird individuals increased by approx. 40 thousand after the restoration. Most of water bird species increased, but diving ducks decreased. Analysis of the number of individuals of water birds before and after the intertidal zone restoration showed that there was a significant increase in the number of shorebird individuals. There is a habitat use pattern change in the southern tideland intertidal zone that includes the largest area of widened intertidal zone and the inland waters of the intertidal zone. This is related to the change of benthic ecosystem which is the food source of birds. The benthic ecosystem in restoring Sihwa Lake has been stabilized with a decrease in opportunistic species and consistent increase in equilibrium species that are sensitive to pollution. As a result, the environmental conditions for shorebirds have been improved. The restoration of intertidal zone affected the habitat use and distribution patterns of water birds in a short period of time. Compared to before restoration, all the water birds now use the wide area of the intertidal zone with no partiality and it is confirmed that the restoration greatly affected the distribution of shorebirds and swan & geese. This study was conduced to identify the effects of an artificial restoration of intertidal zone due to tidal power generation of bird species. In terms of maintaining and improving biodiversity, the intertidal zone restoration was recognized to be important and still shows positive results. This study is expected to provide a direction when an alternative is required to maintain and improve biodiversity in a similar situation in the future.