• Applied Chemistry for Engineering
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• v.9 no.5
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• pp.680-688
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• 1998

The macroreticular (MR) type glycidylmethacrylate (GMA)-divinylbenzene (DVB) copolymer (polyglycidylmethacrylate) beads (RG) were prepared by a suspension polymerization using 0~100 vol % of 2,2,4-trimethylpentane (TMP) as a diluent. Macroreticular type cation exchange resins containing phosphoric acid groups (RGP) were prepared by the reaction of GMA-DVB copolymer and poly (glycidyl methacrylate) bead (RG) with phosphoric acid in the presence of benzene. In this study, the effect of degree of crosslinking and the amount of the diluent on physical properties and adsorbability of uranium of RGP resins were investigated respectively. The chemical and physical properties of RGP resins were affected by both of the amount of the diluent and the degree of crosslinking. The effect of degree of crosslinking on the adsorbed amount of uranium for RGP resins were decreased in the order of $$RGP-10(50){\sim_=}RGP-1(50)>RGP-2(50)>RGP-5(50)>RGP-0$$. The effect of the diluent amount were as follows RGP-2(100)>RGP-2(75)>RGP-2(50)>RGP-2(30)>RGP-2(0). The crosslinking degree effect on uranium adsorbability depended on pore structure, cation exchange capability and swelling ratio. On the other hand, the effect of the diluent amount were relied on surface area and pore structure raher than cation exchange capability.

• Restorative Dentistry and Endodontics
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• v.23 no.1
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• pp.68-93
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• 1998

The physical properties of polymer are greatly influenced by the extent to which a resin cures. The presence of un reacted monomer can, have a plasticizing effect on the polymer, thereby altering the physical and mechanical properties of dentin bonding agent (DBA). If the DBA does not polymerize sufficiently, it will leave a weak bonding layer and lead to lower bond strength. The purpose of this study was to evaluate the shear bond strengths(SBS) and the degree of conversion (DC) of 4 commercialy avilable dentin bonding systems which are composed of 2 multi-bottle systems [Scotchbond Multi-Purpose (SMP), AeliteBond(AB)] and 2 onebottle systems [SingleBond(SB), One-Step(OS)]. For shear bond strength measurement, labial surfaces of freshly extracted bovine incisors were ground with # 600 grit SiC paper to expose dentin. Four different groups of samples were formed, with 10 samples. being made for each of the 4 commercial DBA in each group according to the curing sequences of DBA and overlayer thickness of composites: Group I (standard cure and 1mm thick composites) : The DBA was light cured and the composites of 1mm thickness was applied ; Group II (standard cure and 2mm thick composites) : The DBA was light cured and the composites of 2mm thickness was applied; Group III (simultaneous cure and 1mm thick composites) : The DBA was not light-cured and simultaneously cured with composites of 1mm thickness; Group N (simultaneous cure and 2mm thick composites) : The DBA was. not light-cured and simultaneously cured with composites of 2mm thickness. The SBS was measured immediately after the composites was bonded to the bovine dentin using an Instron machine. The DC of the DBA was examined in a thin film under simulated conditions of the experimental groups according to the curing sequences and overlayer thickness of composites in the SBS test. using a Fourier transform Infrared(FTIR) spectrometer. The following results were obtained from SBS tests and DC measurements 1. In SBS tests, the multi-bottle DBA(SMP, AB) had a generally higher bond strength values than the one bottle DBA(SB, OS). In DC measurements, the one bottle DBA(SB, OS) had a significantly higher DC than the multi-bottle DBA(SMP, AB). 2. In all DBAs except OS, there was no significant difference between the bond strength of group I (standard cure and 1mm thick composites) and that of group III (simultaneous cure and 1mm thick composites). SMP, SB in Group I had a significantly higher DC than those in group III, but AB, OS in group I had a significantly lower DC than those in group III 3. All DBAs in Goup II (standard cure and 2mm thick composites) had significantly higher bond strength and DC than those in Group N (simultaneous cure and 2mm thick composites). 4. In all DBAs, there was no significantly different SBS and DC between Group I and Group II, but all DBAs in Group III had significantly higher SBS and DC than those in Group IV.

• Journal of Adhesion and Interface
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• v.15 no.1
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• pp.22-30
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• 2014

Self-photoinitiating acrylate (SPIA) which can undergo self-initiation under UV irradiation was synthesized by a Michael addition in the presence of a base catalyst. The SPIA polymerizations were investigated by photo-differential scanning calorimeter (photo-DSC) and surface physical properties such as pendulum hardness and pencil hardness. The results showed that the SPIA can cure upon UV irradiation by itself without a photoinitiator. But we found out that both the curing rate and the conversion were too low for the self-curing reaction of SPIA. In order to improve the SPIA curing properties, we introduced the SPIA/cationic hybrid system and observed the effects of the addition of commercial free radical type monomer and photoinitiator on the curing behaviors. SPIA/cationic hybrid system was the best suitable to improve the SPIA curing properties. The kinetic analysis indicated that the cationic monomer and photoinitiator apparently accelerated the cure reaction and rate of the hybrid SPIA system, mostly due to the synergistic effect of cationic monomer and photoinitiator increasing the mobility of active species and the generation of reactive species (free radical, cation) during the photopolymerization process. The physical properties showed that, unlike typical free radical system, the hybrid systems did not show oxygen inhibition effect because of cationic reaction on the coating surface.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.6
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• pp.297-305
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• 2019

This study was conducted to compare the factors affecting quality of life according to the perception of subjective body image in adult women as a secondary study of the 7th 1st year Korean National Health and Nutrition Examination Survey data. The subjects were 3,392 adult women and their general characteristics, physical factors and psychological factors were analyzed. Data were analyzed using the IBM SPSS 25.0 program after generating weighted composite sample plans and the significance level was set at 0.05. Factors influencing the quality of life of subjects who perceived their subjective body image as thin were education level, birth experience, depression, and subjective health and their explanatory power was 43.1%. Factors influencing the quality of life for those who perceived their bodies as moderate were education level, depression, and subjective health, and their explanatory power was 26.5%. Factors that affected quality of life for those who perceive their bodies as obese were age, weight change for one year, weight control for one year, presence of high blood pressure, BMI, and subjective health, and their explanatory power was 40.9%. The results of this study indicate it is necessary consider the factors influencing each subjective perception to improve individual quality of life.

• Korean Journal of Clinical Laboratory Science
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• v.51 no.2
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• pp.134-144
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• 2019

Metabolic syndrome and allergic rhinitis are two important chronic diseases that affect people all over the world. Metabolic syndrome very often induces other diseases and the prevalence of allergic rhinitis is currently increasing. Aging is known to affect the pathogenesis of various diseases such as metabolic syndrome and allergy. This study examined the effects of metabolic syndrome and the prevalence of allergic rhinitis depending on different age groups and several general characteristics. This study was conducted by using the data from the Korea National Health and Nutrition Examination Survey from the 4th, 5th, 6th, and 7th-1 (2007~2016). The data used for this study was obtained from 51,854 people. In all age groups, our studies have shown that people without metabolic syndrome have a higher prevalence of allergic rhinitis than those people with metabolic syndrome, and the younger age group had the higher prevalence of allergic rhinitis (P<0.05). Overall, the results of this study found a significant effect on the prevalence of allergic rhinitis in each category of age, general characteristics (physical activity, smoking and drinking) and the presence or absence of metabolic syndrome (P<0.05). The evidence found in this study will help to understand the correlation between metabolic syndrome and allergy, and specifically allergic rhinitis.

• Journal of Korea Entertainment Industry Association
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• v.13 no.6
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• pp.175-186
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• 2019

Purposes: This study aimed to investigate the differences in the prevalence of obesity according to sex and age and self-rated health in adults with metabolic syndrome according to sex, age, and the presence or absence of metabolic syndrome. Methods: The study subjects were 5,674 adults, who completed all three components of the KNHANES VI-2. The subjects were categorized, using life transition periods, into young adults, middle-aged adults, and older adults. Research methods were selected based on the research objectives of the KNHANES VI-2. IBM SPSS 23.0 was used for complex samples cross-tabulation and a complex samples general linear model analysis. Results: Obesity was prevalent in 77.2% of young male adults, 66.2% of middle-aged male, and 52.3% of older male adults with metabolic syndrome, whereas it was prevalent in 72.4% of young female adults, 73.9% of middle-aged female adults, and 64.6% of older female adults with metabolic syndrome. Men had higher self-rated health than women. As age increased, self-rated health status decreased. Those with metabolic syndrome had lower self-rated health status than those without metabolic syndrome. Conclusion: The prevalence of obesity was found to be high in those with metabolic syndrome. This study found that based on sex, men had the highest self-rated health status, and based on age, young adults had the highest self-rated health status, whereas those with metabolic syndrome had low self-rated health status.

• Geophysics and Geophysical Exploration
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• v.27 no.3
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• pp.181-195
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• 2024

This tutorial explains that the static effect in the magnetotelluric (MT) survey is a physical phenomenon caused by charges accumulated on the boundaries of subsurface inhomogeneities. To facilitate understanding of the physical phenomenon, differences between static induction and charge accumulation on the boundary are explained and analyzed with help of schematic illustrations. Subsequently, from the electromagnetic (EM) integral equation formulation, it is clearly shown that the secondary electric field due to charges accumulated on the interface in the presence of the primary field appears as the static effect. Therefore, except in the cases of the layered earth or a two-dimensional earth with transverse magnetic (TM) mode excitation, the static effect always exists in MT responses and further, it is not 'static' but rather frequency dependent. Despite the fact that the static effect is a secondary electric field due to inhomogeneity, inevitable under-sampling in the frequency and spatial domains prevent the effect from being handled properly in numerical inversion. Therefore, considering the practical aspects of the MT survey, which cannot be a continuous measurement covering the entire survey area over a wide frequency band, a three-dimensional (3-D) inversion incorporating the static shift as a constraint with the Gaussian distribution is introduced. To enhance understanding of the integral equation EM modeling, the formulation of the 3-D integral equation and mathematical analyses of the Green tensor and scattering current are described in detail in the Appendix.

• Corrosion Science and Technology
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• v.6 no.4
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• pp.206-210
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• 2007

Aerospace aluminum alloys such as Al alloy 2024-T3 and 7075-T6 are subject to localized corrosion due the existence of intermetallics containing Cu, Mg or Zn. Chromate is currently widely used in the aerospace industry as the corrosion inhibitor for these alloys. However, chromate needs to be replaced due to its strong carcinogenicity. In this study, an extensive pigment screening has been performed to find replacements for chromates. Different categories of inhibitors were evaluated by immersion tests, DC polarization tests and other methods. Phosphates, zinc salts, cerium salts, vanadates and benzotriazole were found to be effective inhibitors for AA7075. Among those inhibitors, zinc phosphate was found to be the most effective in our novel, silane-based, one-step aqueous primer system. The performance of this primer is comparable to that of currently used chromate primers in accelerated corrosion tests, while it is completely chromate-free and its VOC is about 80% less than that of current primers. Studies by SEM/EDS showed that the unique structure of the superprimer accounts for the strong anti-corrosion performance of the zinc phosphate pigment. The self-assembled stratified double-layer structure of the superprimer is characterized by a less-penetrable hydrophobic layer at the top and a hydrophilic layer accommodating the inhibitors underneath. The top layer functions as the physical barrier against water ingress, while the lower layer functions as a reservoirfor the inhibitor, which is leached out only if the coating is damaged by a scratch or scribe. The presence of a silane in the primer further improves the adhesion and anti-corrosion performance of the primer.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.17 no.2
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• pp.149-162
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• 2006

Objectives : This study examined psychopathology, abuse history and the relation of them in sheltered runaway adolescents. The purpose is to investigate characteristics of adolescents who are in shelters according to abuse type and then to offer basic data which are needed in establishing comprehensive protection policy for runaway adolescents. Methods : One hundred twenty eighty adolescents who stay in the runaway shelters were asked to complete self-report questionnaires including basic sociodemographic data, Korean Youth Self Report (K-YSR), Minnestota Multiphasic Personality Inventory (MMPI), and Symptom Checklist-90-Revised (SCL-90-R) and then examined the correlation of psychopathology and abuse in runaway adolescents. Results : In abused runaway adolescents, social performance scale of K-YSR was higher than school performance sealer and among scales of behavioral problem syndrome delinquent scale was highest. Scales of behavioral problem syndrome showed relatively significant correlation with abuse history. In MMPI scale of psychopathic deviate scale was highest, social introversion showed significant correlation with emotional abuse, and psychopathic deviate and hypomania showed significant correlation with physical abuse, neglect and sexual abuse. In SCL-90-R somatization scale was highest. Scales of somatization, hostility, and paranoid ideation scale were significantly high in adolescents with emotional abuse and neglect history, and scores of anxiety and depression scale were significantly high in sexually abused adolescents. Conclusion : Runaway adolescents who had abuse experience showed significantly higher level of psychopathology than general adolescents and there were various interrelations between them according to the presence and the type of abuse. More precise psychiatric evaluation and detailed treatment intervention for runaway adolescents are needed.

• Journal of the Korea Society of Computer and Information
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• v.18 no.4
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• pp.113-121
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• 2013

In this paper, simulations were carried out to determine the efficiency of the rotation efficiency according to the draft of waterwheel in open rectangular channel. In the small hydroelectric generators to get the highest efficiency of waterwheel is very important. But the presence of various elements(free water surface flow, non-uniform velocity distribution because of the waterways wall friction etc) makes it difficult to create a mathematical formula. In this paper, we made a scale model and perform a physical simulation where the draft, gradient and flux is variable. Scale modelling with 10-step draft, 3-step gradients and 2-step flux, as well were constructed then computerized automatic experimental system were configured to acquire the rotational efficiency vs. draft of itself. Rotational efficiency is analyzed as for the draft of waterwheel using the acquired data by varying the gradient and flux of canal. Reviewing the analyzed data, it is confirmed that phenomena of efficiency shown at previous and present experiment is similar and revealed that computerized system shows more sophisticated numerical figures.