• Journal of the Korean institute of surface engineering
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• v.47 no.1
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• pp.13-19
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• 2014

The various surface treated conditions of Fe-3.0%Ni-0.7%Cr-1.4%Mn-X steel such as as-received, ion nitriding, DLC coated, DLC coated after nitriding for 3 hrs and 6 hrs were investigated to evaluate the beneficial effect for plastic mold steel. Micro Vickers hardness tester was used to estimate nitriding depth from the hardness profile and to measure hardness on the surface. Elastic modulus and residual stress were measured by a nanoindentator. Scratch test and SP (small ball punch test) were utilized to assess the adhesive strength of DLC coating. The depth of nitriding layer was measured as $50{\mu}m$ for the condition of 3 hrs nitriding and $90{\mu}m$ for that of 6 hrs nitriding. Hardness, elastic modulus, residual stress of DLC coating were 20.37 GPa, 162.78 GPa and -1456 MPa respectively. Residual stress on the surface of DLC coating after nitriding could increase to -3914 MPa by introducing nitriding before DLC coating. During the 'Ball-On-Disc' test ${\gamma}^{\prime}$ particles pulled out from the surface of nitrized layer tend to enhance abrasive wear mode since the fraction of ${\gamma}^{\prime}$ (Fe4N) in ion-nitrized layer is known to increases with nitriding time. Thus the specific wear rate of the nitriding layer increased. Comparing with nitriding the specific wear rate in work piece disc as well as ball decreased prominently in DLC coating due to the remarkable reduction in friction coefficient.

• Journal of the Korea Organic Resources Recycling Association
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• v.17 no.1
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• pp.58-72
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• 2009

In this study, the organic matter and biomass was characterized by using respirometry based on ASM No.2d (Activated Sludge Model No.2d). The activated sludge models are based on the ASM No.2d model, published by the IAWQ(International Association on Water Quality) task group on mathematical modeling for design and operation of biological wastewater treatment processes. For this study, OUR(Oxygen Uptake Rate) measurements were made on filtered as well as non-filtered wastewater. Also, GC-FID and LC analysis were applied for the estimation of VFAs(Volatile Fatty Acids) COD(S_A) in slowly bio-degradable soluble substrates of the ASM No.2d. Therefore, this study was intended to clearly identify slowly bio-degradable dissolved materials(S_S) and particulate materials(X_I). In addition, a method capable of determining the accurate time to measure non-biodegradable COD(S_I), by the change of transition graphs in the process of measuring microbial OUR, was presented in this study. Influent fractionation is a critical step in the model calibrations. From the results of respirometry on filtered wastewater, the fraction of fermentable and readily biodegradable organic matter(S_F), fermentation products(S_A), inert soluble matter(S_I), slowly biodegradable matter(X_S) and inert particular matter(X_I) was 33.2%, 14.1%, 6.9%, 34.7%, 5.8%, respectively. The active heterotrophic biomass fraction(X_H) was about 5.3%.

• The Korean Journal of Pain
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• v.9 no.1
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• pp.63-68
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• 1996

Background; Epidural analgesia for controlling labor pain has recently gained world-wide popularity. However, many patients scheduled for continuous epidural analgesia voice concern over harmful effects to their fetus and other possible complications such as hemodynamic changes, back pain and neurologic sequelae etc. The aim of this study was to evaluate the hemodynamic changes with and without epidural block as a measure to determine the safety of epidural analgesia during labor and delivery. Methods: Twenty healthy subjects were divided equally into two groups(Group 1 without epidural block, and Group 2 with epidural block) and serial hemodynamic measurements were taken in all subjects with transcutaneous impedence cardiography. The epidural catheter was inserted at the level of $L_{3,4}$ in Group 2 and analgesia was maintained using 0.25% bupivacaine mixed with fentanyl. Results: Cardiac output increased slightly with cervical dilatation in both groups, but no significant differences were found between the two groups. Similarly, no significant differences were found in blood pressures between the two groups. Stroke volume and end-diastolic volume indices were slightly decreased in group 1 and slightly increased in group 2. However, there were no significant differences between the two groups. The ejection fraction was nearly constant and ranging 56~59%. Conclusion: We concluded epidural analgesia for labor and delivery is a safe technique for the parturients since results indicated no significant differences in hemodynamic changes, as compared to the control group.

• Journal of Radiation Industry
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• v.6 no.1
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• pp.89-94
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• 2012

Three-dimensional network hydrogels were prepared by ${\gamma}$-irradiation of aqueous solutions of poly(vinyl alcohol) (PVA) and glycerol (Gly). Oven-drying was used to measure the gel fraction (G), hydration (H) or swelling behavior (S) of the prepared hydrogels. This study made a hypothesis that hydrogen bonds due to addition of glycerol and change of dry states such as freeze-drying (FD), room-drying (RD) and oven-drying (OD) acts on the G, H, and S. Interesting results on the hydrogen bonding effect in the prepared hydrogels are monitored at different drying conditions. The FD samples have a higher G values with increase in glycerol content as compared with the OD and RD samples. The formation of strong hydrogen bonding network among Gly molecules and hydrogel matrix was considered as the main driving force, resulting in the changes in the G, H, and S of the hydrogels under different drying conditions.

• Journal of Plant Biotechnology
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• v.42 no.1
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• pp.55-59
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• 2015

The extracts of Aruncus dioicus were investigated for anti-oxidant and biological activities in order to verify its potential as functional ingredients of cosmetic products. The ethyl acetate (EtOAc) extract of A. dioicus showed excellent scavenging activity using DPPH and ABTS anti-oxidant analysis at the $1,000{\mu}g/mL$ concentration. While tyrosinase inhibitory effect was measure for whitening assay and showed 59.2%, the suppression levels of elastase and collagenase were 56% and 90% respectively for anti-wrinkle activity. Therefore, it is plausible to conclude that A. dioicus extract, especially EtOAc fraction which has outstanding whitening, anti-oxidant, and anti-wrinkle activities, could be used as a new functional materials for cosmetics.

• The KIPS Transactions:PartC
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• v.10C no.1
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• pp.61-70
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• 2003

I-Business providers and customers have chosen the service availability as the most important technical parameter which should be included in their SLA to succeed in their business. This means that web Service availability management is crucial to the web-based service providers. Application availability is originally defined as a measure of the fraction of time during a defined period when the service provided is deemed to be better than user expectation of service performance. But, because most web service availability measurement tools simply monitor disconnected state, they do not satisfy user's expectation of extended availability concept. In this paper, We propose the web service availability measurement method which supports extended availability concept. It takes account of performance degradation of web service based on response time, and determines what is the cause of unavailability of the service. We developed a measurement tool, WebSerAvail.

• School Mathematics
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• v.7 no.2
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• pp.103-121
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• 2005

This article compares and analyzes mathematics textbooks of North Korea, South Korea, China and Japan and draws meaningful ways for introducing the division algorithm of fractions. The analysis is based on the five contexts: 'measurement division', 'determination of a unit rate', 'reduction of the quantities in the same measure', 'division as the inverse of multiplication or Cartesian product', 'analogy with multiplication algorithm of fractions'. The main focus of the analysis is what context is used to introduce the algorithm and how much it can appeal to students. This analysis supports that there is a few differences of introducing methods the division algorithm of fractions among those countries and more meaningful way can be considered than ours. It finally suggests that we teach the algorithm in a way which can have students easily see the reason of multiplying the reciprocal of a divisor when they divide with fractions. For this, we need to teach the meaning of a reciprocal of fraction and consider to use the context of determination of a unit rate.

• Journal of Korean Medicine for Obesity Research
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• v.21 no.2
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• pp.69-79
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• 2021

Objectives: This study aimed to compare the anti-obesity effects of raw and pickled garlic in vitro in 3T3-L1 preadipocytes. Methods: The pickled garlic samples comprised the following: garlic aged in vinegar (VG), garlic aged in soy sauce, and vinegar (1:1, v/v) (PG) and raw garlic (RG) as control. Hexane, butanol, and distilled water were used to prepare the fractions. The pancreatic lipase inhibitory activity was used as a measure of anti-obesity effects of the extracts. The lipid droplet accumulation and triglyceride content in the 3T3-L1 cells were measured using Oil red O staining and triglyceride assay kits, respectively. The adipogenesis related protein expression levels were analyzed using the kits and the western blot method. Results: The pancreatic lipase inhibitory activity of the garlic extracts (VG, PG, RG) was the highest in the butanol fraction, and the inhibitory effect was the highest in RG, followed by PG and VG. All garlic butanol extracts suppressed triglyceride accumulation in differentiated adipocytes (P<0.05) through the activation of cyclic adenosine monophosphate (AMP), AMP-activated protein kinase, carnitine palmitoyl transferase-1, and the inhibition of fatty acid synthase. Raw garlic extracts significantly inhibited the expression of proteins involved in adipogenesis as compared to pickled garlic. Conclusions: Raw garlic has the potential to be an effective natural material for reducing obesity compared to pickled garlic with vinegar or soy sauce.

• Composites Research
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• v.12 no.2
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• pp.70-81
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• 1999

Resin transfer molding(RTM) as a composite manufacturing process is currently of great interest in the aerospace industry requiring high performance composite parts. In this study, an analysis of mold filling in the RTM process was carried out by numerical simulation using finite element/control volume technique. Experimental work for the visualization of resin flow through fibrous preform was also conducted in order to quantitatively measure the permeabilities of the fiber mats and to evaluate the validity of the developed numerical code. The different types of fiber mats and silicon oils were selected as reinforcements and resin materials, respectively. The effects of fibrous preform structure, mold geometry, and preplaced insert on the flow front patterns during mold filling were examined by integrating the model predictions and experimental results. The flow fronts predicted by numerical simulation were in good agreement with those observed experimentally. However, according to the regions of the mold, some deviations between predicted and observed flow fronts could be found because of non-uniform fiber volume fraction. Weldline locations for the resin flow through round insert preplaced in the mold could be qualitatively deduced based on predicted flow fronts.

• Journal of the Korean Society for Nondestructive Testing
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• v.17 no.2
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• pp.89-99
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• 1997

Although discontinuously reinforced metal matrix composite(MMC) is one of the most promising materials for applications of aerospace, automotive industries, the thermal residual stresses developed in the MMC due to the mismatch in coefficients of thermal expansion between the matrix and the fiber under a temperature change has been pointed out as one of the serious problem in practical applications. There are very limited nondestructive techniques to measure the residual stress of composite materials. However, many difficulties have been reported in their applications. Therefore it is important to establish analytical model to evaluate the thermal residual stress of MMC for practical engineering application. In this study, an elastic model is developed to predict the average thermal residual stresses in the matrix and fiber of a misoriented short fiber composite. The thermal residual stresses are induced by the mismatch in the coefficient of the thermal expansion of the matrix and fiber when the composite is subjected to a uniform temperature change. The model considers two-dimensional in-plane fiber misorientation. The analytical formulation of the model is based on Eshelby's equivalent inclusion method and is unique in that it is able to account for interactions among fibers. This model is more general than past models to investigate the effect of parameters which might influence thermal residual stress in composites. The present model is to investigate the effects of fiber volume fraction, distribution type, distribution cut-off angle, and aspect ratio on thermal residual stress for in-plane fiber misorientation. Fiber volume fraction, aspect ratio, and distribution cut-off angle are shown to have more significant effects on the magnitude of the thermal residual stresses than fiber distribution type for in-plane misorientation.