• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.4
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• pp.297-305
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• 2012

In recent large-scale semiconductor manufacturing clean rooms, the energy consumption of outdoor air conditioning systems to heat, humidify, cool and dehumidify incoming outdoor air represents about 45% of the total air conditioning load required to maintain a clean room environment. Therefore, the energy performance evaluation and analysis of outdoor air conditioning systems is useful for reducing the outdoor air conditioning load for a clean room. In the present study, an experiment was conducted to compare the energy consumption of outdoor air conditioning systems with a simple air washer, an exhaust air heat recovery type air washer and a DCC return water heat recovery type air washer. It was shown from the present lab-scale experiment with an outdoor air flow of 1,000 $m^3/h$ that the exhaust air heat recovery type and DCC return water heat recovery type air washer outdoor air conditioning systems were more energy-efficient for the summer and winter operations than the simple air washer outdoor air conditioning system and furthermore, the DCC return water heat recovery type one was the most energy-efficient in the winter operation.

• Journal of the Korea Institute of Building Construction
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• v.2 no.4
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• pp.145-152
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• 2002

High fluid concrete unlike OPC concrete is made with various material, and the phase of fresh concrete is considerably different. In order to understand fluidity phase and mix properties of high fluid concrete, concrete is required to access as suspension structure which consists of aggregate and paste. The focus of this paper is to analyze the test results and quantify the effect of mix proportions of mortar and fineness modulus of sand on the properties of fresh mortar. The effect of water-binder ratio. sand-binder ration. contents of ggbs (by mass of total cementitious materials). and various contents of water reducing agent on the yield stress and plastic viscosity of the mix is studied. Based on the experimental results, the fellowing conclusions can be drawn: (1) The mixing time needed for high fluid mortar was approximately two times more than that of ordinary portland mortar. (2) The fluidity phase of mortar could be explained by yield stress of mix and the fluidity of mortar. (3) As the content of ggbs increased, yield stress of mortar was decreased and plastic viscosity of it was increased. (4) For the high fluid mortar, it was appeared that sand-binder ratio should be below 1.5.

• Journal of Conservation Science
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• v.25 no.1
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• pp.77-86
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• 2009

The physical properties of the epoxy resins were studied with an addition of filler content and the application of artificial weathering test. When talc as a filler was added to the epoxy resin (L-30), the water resistance seemed to be increased because of the results of the reducing of water absorption rate and the increasing of contact angle. Although the adhesive strength of epoxy resins was not affected by the increasing amount of talc, its compressive strength was reduced. The physical properties of the epoxy resins had different trends according to the site environments. The artificial weathering test with the change of temperature and humidity showed that the changes of water absorption rate and colour differences of the epoxy resins containing talc were lower than the pure epoxy resin itself. However, the contact angle was higher. The artificial weathering test with ultraviolet irradiations showed the opposite result; the damage of epoxy resins was increased with the increasing of talc content. These mean the site environment of the stone monuments should be considered to determine the content of talc added to increase the durability of epoxy resin.

• Microbiology and Biotechnology Letters
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• v.48 no.2
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• pp.129-137
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• 2020

This study aims to evaluate the efficacy of the Ultrasonication-Assisted (UA) extraction on the functionality of the herbaceous biennial plant maca (Lepidium meyenii). The specific objectives include comparison of the antioxidant activities among various maca extracts, determination of the macamide B content of the extracts, and in vitro evaluation of maca on cell viability and creatine kinase (CK) activity. The antioxidant activities of the water, ethanol, and UA extracts were compared by determining the total phenolic and flavonoid contents, the 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activities, and the ferric reducing antioxidant power (FRAP) of the extracts. The macamide B content of maca extracts were analyzed by HPLC. The effects of the extracts on muscle cell viability and creatine kinase activity were also determined using C2C12 myoblasts. UA extraction significantly increased the total phenolic content (2.90 GAE ㎍/mg, p < 0.05), without affecting the flavonoid content. DPPH radical scavenging activity did not exhibit any statistical difference among the extracts. The ethanol and UA extracts exhibited significantly higher FRAP than the water extract (p < 0.05). The macamide B content of ethanol and UA extracts were 0.087 and 0.083 ㎍/mg, respectively. The water and UA extracts exhibited higher C2C12 muscle cell viability than the ethanol extract, and both extracts resulted in a significantly lower CK level than the H₂O₂-treated control group. This research suggests that the maca extract can protect muscle cells and serve as an antifatigue agent under oxidative stress conditions.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.6
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• pp.4216-4227
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• 2015

In this study, a model is developed based on Life Cycle Energy Analysis (LCEA) method with Genetic Algorithm (GA) to determine optimal diameter of Water Distribution System (WDS). For hydraulic analysis the EPANET2.0 program is linked with developed model, pipe-aging equation and pipe-breakage equation are built in to developed model to simulate pipe change through life cycle. The model is then applied to two sample WDSs for optimal energy design. After determining optimal diameter for each WDS, the total cost is calculated based on determined diameter and compared with well-known optimal diameter set of each WDS. Results show that optimal energy design of WDSs through the developed model can be an alternative option for optimal design of WDSs for reducing energy with lower in cost.

• Journal of radiological science and technology
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• v.11 no.2
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• pp.65-71
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• 1988

Radiation dose outside the radiotherapy treatment field can be significant and therefore is of clinical interest estimating organ dose. We have made measurements of dose at distances up to 70 cm from the central axis of $5{\times}5$, $10{\times}10$, $15{\times}15$, and $25{\times}25$ cm radiation fields of Co-60 ${\gamma}-ray$, at 5 cm depth in water. Contributions to the total secondary radiation dose from water scatter, machine (collimator) scatter and leakage radiation have been seperated. We have found that the component of dose from water scatter can be described by simple exponential function of distance from the central axis of the radiation field for all field sizes. Machine scatter contributes 20 to 60% of the total secondary dose depending on field size and distance from the field. Leakage radiation contributes very little dose, but becomes the dominant componant at distance beyond 40 cm from the central axis. Then, wedges can cause a factor 2 to 3 increase in dose at any point outside the field compared with the dose when no wedge is used. Adding blocks to a treatment field can cause an increase in dose at points outside the field, but the effect is much smaller than the effect of a wedge. From the results of these measurements, doses to selected organs outside the field for specified treatment geometries were estimated, and the potential for reducing these organ doses by additional shielding was assessed.

• Membrane Journal
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• v.15 no.1
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• pp.22-33
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• 2005

Asymmetric PVDF membranes were prepared by the phase inversion from casting solutions containing PVDF, NMP as solvent and 1,4-dioxane, DGDE, acetone, or GBL as additives by immersing them in water. The effects of various additives on the casting solution properties, permeation properties, and membrane structures were investigated. Low miscibility of 1,4-dioxane, DGDE and acetone with the coagulant (water) compared with NMP resulted in reducing the membrane pore size. When DGDE is used as an additive, the pore size was reduced because of its incipient sharp interface formation in the water. GBL increased membrane pore size because of its polarity compared to that of NMP. The PVDF membranes with various pore sizes could be obtained by controlling the amount of additive. The effect of mixed solvent (aqueous and non-aqueous solution) on permeation through membrane was investigated. Not only solution viscosity but surface tension affected solvent permeation.

• Korean Journal of Food Science and Technology
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• v.28 no.1
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• pp.109-116
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• 1996

The relationship between antioxidant activities and physicochemical properties of several fractions obtained from freeze-dried (FD) coffee were investigated. The nine kinds of fraction were consecutively extracted from FD coffee with solvents in increasing order of polarity, and the higher polarity of the solvent the higher extraction yield of the fraction. The antioxidant activities of the fractions were determined by Rancimat and oven test on edible oils. The antioxidant activities of the fractions increased in the order of acetone>ethanol>methanol>50% methanol/water>water fraction, and the antioxidant activities of them were higher on lard than on soybean oil. The antioxidant activity of each fraction was strongly related to the contents of total phenol, total nitrogen content and acidity, whereas color intensity, reducing power, carboxylic acid content showed little contribution to the activity. All fractions had three peaks maxima at 208, 275 and 324 nm on UV-visible spectra, but the only one at 324 nm was linealy proportional to the antioxidant activities of the fractions.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.236-236
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• 2015

Flood is one of the major natural disasters affecting millions of people. Thailand also, frequently faces with this type of disaster. Especially, 2011 mega flood in Central Thailand, inundated highway severely attributed to the failure of national economic and risk to life. Lesson learned from such an extreme event caused flood monitoring and warning becomes one of the sound mitigations. The highway flood hazard mapping accomplished in this research is one of the strategies. This is due to highway flood is the potential risk to life and limb, and potential damage to property. Monitoring and warning therefore help reducing live and property losses. In this study, degree of highway flood hazard was assessed by weighting factors for each cause of the highway flood using Multi Criteria Analysis (MCA) based Analytic Hierarchy Process (AHP). These weighting factors are the essential information to classify the degree of highway flood hazard to enable pinpoint on flood monitoring and flood warning in hazard areas. The highway flood causes were then investigated. It was found that three major factors influence to the highway flood are namely the highway characteristics, the hydrological characteristics and the land topography characteristics. The weight of importance for each cause of the highway flood in the whole country was assessed by weighting 3 major factors influence to the highway flood. According to the result of MCA analysis, the highway, the hydrological and the land topography characteristics were respectively weighted as 35, 35 and 30 percent influence to the cause of highway flood. These weighting factors were further utilized to classify the degree of highway flood hazard. The Weight Linear Combination (WLC) method was used to compute the total score of all highways according to each factor. This score was later used to categorize highway flood as high, moderate and low degree of hazard levels. Highway flood hazard map accomplished in this research study is applicable to serve as the handy tool for highway flood warning. However, to complete the whole warning process, flood water level monitoring system for example the camera gauge should be installed in the hazard highway. This is expected to serve as a simple flood monitor as part of the warning system during such extreme or critical event.

• Polymer(Korea)
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• v.33 no.2
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• pp.153-157
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• 2009

The resin matrix in the dental composite is generally composed of 2,2-bis[4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propane (Bis-GMA) as a base resin and triethylene glycol dimethacrylate (TEGDMA) as a diluent for the reduction of viscosity. The applications of dental composite were often limited in dentistry due to the relatively large amounts of volumetric shrinkage during polymerization and water uptake caused by the addition of TEGDMA to the resin matrix. In this study, in order to solve problems stemmed from the TEGDMA by reducing amount of diluent added to resin matrix, diethylene glycol dimethacrylate (DEGDMA) and ethylene glycol dimethacrylate (EGDMA) were explored as new diluents. A decrease in the volumetric shrinkage and an increase in the mechanical strength were observed by replacing TEGDMA in the dental composite to DEGDMA (or EGDMA). Reduction in the mechanical strength of the dental composite containing DEGDMA (or EGDMA), was not serious in comparison with that of the dental composite containing TEGDMA after water uptake.