• Journal of the Society of Naval Architects of Korea
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• v.53 no.2
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• pp.85-91
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• 2016

The most important factor in the structural design of ships and offshore structures operating in arctic region is ice load, which results from ice-structure interaction during the ice collision process. The mechanical properties of ice related to strength and failure, however, show very complicated aspect varying with temperature, volume fraction of brine, grain size, strain rate and etc. So it is nearly impossible to establish a perfect material model of ice satisfying all the mechanical characteristics completely. Therefore, in general, ice collision analysis was carried out by relatively simple material models considering only specific aspects of mechanical characteristics of ice and it would be the most significant cause of inevitable errors in the analysis. Especially, it is well-known that the most distinctive mechanical property of ice is high dependency on strain rate. Ice shows brittle attribute in higher strain rate while it becomes ductile in lower strain rate range. In this study, the simulation method of ice collision to ship hull using the nonlinear dynamic FE analysis was dealt with. To consider the strain rate effects of ice during ice-structural interaction, strain rate dependent constitutive model in which yield stress and hardening behaviors vary with strain rate was adopted. To reduce the huge amount of computing time, the modeling range of ice and ship structure were restricted to the confined region of interest. Under the various scenario of ice-ship hull collision, the structural behavior of hull panels and failure modes of ice were examined by nonlinear FE analysis technique.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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• v.27 no.4
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• pp.58-66
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• 2014

Objectives : The purpose of this study was to investigate the clinical manifestations and influences of occupation, concomitant allergic diseases, various aggravating factors and seasonal changes for patients with dyshidrotic eczema. Methods : A total of 219 patients who showed clinical manifestations of dyshidrotic eczema were included in this study. We retrospectively reviewed the clinical characteristics of all the patients. Results : 1. Among 219 patients, there were 76 male patients (34.7%), 143 female patients (65.3%), male to female ratio was 1: 1.88. The average age of the patients at admission was $31.9{\pm}9.8$ years, had a lot of 20s and 30s the distribution. 2. The average of duration of the admission to the clinic after the onset was $4.01{\pm}4.42$ years. 3. Common accompaning diseases dyshidrotic eczema patients have were allergic rhinitis(87 cases), and atopic dermatitis(55 cases), sweating(45 cases), and asthma(10 cases) in order. 4. The most commonly occurring sites for dyshidrotic eczema patients are fingers(60.3%), palm(53.4%), dorsum of hand(19.2%) and nails(5.5%) in order. 5. The most commonly contacted materials for dyshidrotic eczema patients are water(130 cases), cosmetics(40 cases) and rubber gloves(34 cases) in order. The aggravating factors of dyshidrotic eczema patients are emotional stress(110 cases), fatty food(22 cases) and alcohol(22 cases) in order. 6. The number of patients showing seasonal changes in symptoms was 111. The season with the most severe symptom was summer with 76 cases, which was statistically significant. Conclusions : This study demonstrated the various clinical characteristics of Korean patients with dyshidrotic eczema.

• Computers and Concrete
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• v.21 no.6
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• pp.623-635
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• 2018

In order to research the influence of different recycled aggregate contents on the mechanical properties of pervious concrete, the experimental study and numerical simulation analysis of the mechanical properties of pervious concrete with five kinds of recycled aggregates contents (0%, 25%, 50%, 75% and 100%) are carried out in this paper. The experimental test were first performed on concrete specimens of different sizes in order to determine the influence of recycled aggregate on the compressive strength and splitting tensile strength, direct tension strength and bending strength. Then, the development of the internal cracks of pervious concrete under different working conditions is studied more intuitively by $PFC^{3D}$. The experimental results show that the concrete compressive strength, tensile strength and bending strength decrease with the increase of the recycled aggregate contents. This trend of reduction is not only related to the brittleness of recycled aggregate concrete, but also to the weak viscosity of recycled aggregate and cement paste. It is found that the fracture surface of pervious concrete with recycled aggregate is smoother than that of natural aggregate pervious concrete by $PFC^{3D}$, which means that the bridging effect is weakened in the stress transfer between the left and right sides of the crack. Through the analysis of the development of the internal cracks, the recycled aggregate concrete generated more cracks than the natural aggregate concrete, which means that the recycled aggregate concrete is easier to form a coalescence fracture surface and eventually break.

• Journal of Korean Dental Hygiene Science
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• v.3 no.1
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• pp.25-36
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• 2020

Introduction: The legal duties of Korean dental hygienists are different from the actual tasks. These factors cause dental hygienists to experience work stress. Therefore, it is necessary to investigate what tasks the dental hygienist expects to perform. Methods: This study examined the perception of dental hygienists' work on 158 prospective graduates of the 3rd-year and 4th-year course of dental hygiene. The questionnaire about the dental hygienist's duties was prepared based on the job description of dental hygienists by the Korea Health Personnel Licensing Examination Institute. Results: More than 84% said that all of the work in the second job description was possible as dental hygienists. subjects responded that the following items were not dental hygienists' duties: treatment plan based on medical history and dental history, treatment plan based on an intraoral and extraoral examination, treatment plan based on the results of teeth and periodontal examination, analysis of oral health data in community, planning of oral health promotion in community, planing of water fluoridation, reading of radiography, root planing, physical treatment on head and neck, using an ultrasonic device on head and neck, dealing with laser devices, making a temporary crown, suture and stitch-out, and intramuscular injection. Conclusions: Most graduates of dental hygiene departments have recognized that the tasks described in the second job description are dental hygienists' work; therefore, it is necessary to improve the gap between expected work and legal work.

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.5
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• pp.315-323
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• 2021

The air-cooled proton exchange membrane fuel cells (PEMFC) stacks, which is widely used in small-sized PEMFC, have a problem in that durability is weaker than that of the water-cooled type. Because the cathode is open to the atmosphere and the structural problem of the air-cooled stack, which is difficult to maintain airtightness, is highly likely to form a hydrogen/air boundary during start-up/shut-down (SU/SD). Through the accelerated durability evaluation of the 20 W air-cooled PEMFC stack, the purpose of this study was to find out the cause of the degradation of the stack and to contribute to the improvement of the durability of the air-cooled PEMFC stack. In this study, it was possible to evaluate durability in a relatively short time by reducing 20-30% of initial performance by repeating SU/SD 1,000 to 1,200 times on an air-cooled PEMFC stack. After disassembling the stack, each cell was divided into two and the performance analysis showed that the electrode degradation was more severe in the anode outlet membrane electrode assembly (MEA), which facilitates air inflow as a whole, than in the inlet MEA. It was shown that the cathode Pt was dissolved/precipitated to deteriorate the polymer ionomer inside the membrane.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.3
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• pp.389-396
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• 2021

In this paper, it was evaluated that the effect of self-healing microcapsules on the quality and healing properties of cement composites. In the mixing of microcapsules, the plastic viscosity and yield stress of the cement composites decreased due to the particle properties of the microcapsules, and decreased in proportion to the mixing ratio. The table flow showed a tendency to decrease as the core material acted as a stimulant due to the loss of microcapsules, and the compressive strength could be supplemented through unit quantity correction. As a result of evaluating the effect of microcapsule mixing on the healing properties of cement composites, it was found that the unit water flow rate decreased by the healing reaction immediately after crack initiation. When more than 3% of microcapsules were mixed, it was found that there was a healing rate of more than 95% at 7 days of healing age.

• Journal of the Korean Dietetic Association
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• v.27 no.3
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• pp.162-178
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• 2021

The study examined the perceived health status, dietary habits, and health-related lifestyle habits of middle-aged men and women in Seoul and Gyeonggi-do areas. The survey was conducted on 670 individuals (320 men and, 350 women), aged 40~64 years, in Seoul and Gyeonggi-do areas. The online and written data were analyzed using the SPSS WIN 25.0 program. Although there was a significant difference in the perceived health status (P < 0.01), there were no significant differences in the subjective stress and the current disease status according to sex. For dietary habits, the scores for fruit intake (P < 0.05), meat and fish intake (P < 0.05), milk and dairy products intake (P < 0.01), and seaweed intake (P < 0.05) were higher in women than men. The scores for three-meal eating (P < 0.05) and water intake (P < 0.01) were higher in men than women. For the health-related habits, alcohol-drinking frequency, daily alcohol consumption, smoking experience, and daily smoking were higher in men than women (P < 0.001). In contrast, caffeinated beverage intake, exercise frequency, and daily smart-phone, computer, and TV using time were similar in both sexes. The meal-eating time was faster in men than women (P < 0.01). For dietary behavior changes, only appetite showed a significant gender difference (P < 0.05). This study provides essential information on the perceived health status, dietary habits, and health-related lifestyle habits in middle-aged men and women. Nevertheless, further research and a practical nutrition program will be needed to solve undesirable dietary habits and improve the health and lifestyle of middle-aged adults according to sex.

• Journal of Physiology & Pathology in Korean Medicine
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• v.33 no.1
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• pp.10-16
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• 2019

In order to investigate the effects of Eucomiae Cortex extracts on the depression caused by aging, histochemistry and immunohistochemistry were performed on the hippocampus of aged rats and the following results were obtained. Experimental animals were divided into three groups as follows: 8 week old ICR male mice, Aging-elicited group (AE group) and Eucomiae Cortex treatment group (EC group) 50 week old male ICR mice were used. The control group and AE group did not take any treatment and did not restrict diets and negatives. In the EC group, 0.51g/kg of Eucomiae Cortex extract was dissolved in distilled water once a day for 6 months. The Eucomiae Cortex extract reduced pyramidal neuronal damage in C3 hippocampus and dentate gyrus, increased DJ-1, SHH positive responses in aged mouse hippocampus, and 8-OHdG positivity was reduced, ${\beta}$-endorphin positivity was reduced in aged mouse substantia nigra. Therefore, based on the above results, Eucomiae Cortex extract reduces damage of pyramidal neurons in the hippocampus caused by aging, inhibits neuronal cell death, induces proliferation and differentiation of stem cells in the hippocampus, reduces DNA damage-induced oxidative stress, so improves the reduction of hippocampus volume. It is also thought to improves depression due to aging through ${\beta}$-endorphin which enhances mood through the inhibition of pain.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.4
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• pp.16-25
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• 2019

Recently, due to labor shortages in rural areas within South Korea, the demand for upland-field machinery is growing. In addition, there is a lack of development of systematic performance testing of upland-field machinery. Thus, this study examined structural safety and drawbar pull based on soil properties, as a first step for systematic performance testing on the test bed. First, the properties of soil samples from 10 spots within the experimental site were examined. Second, the strain was measured and converted into stress on 8 points of an onion harvester that are likely to fail. More specifically, the chosen parts are linked to the power, along with the drawbar pull, using a 6-component load cell equipped between the tractor and the onion harvester. The water content of the soil ranged between 5.7%-7.5%, and the strength between 250-1171 kPa. The test soil was subsequently classified into loam soil based on the size distribution ratio of the sieved soil. The onion harvester can be considered as structurally safe based on the derived safety factor and the drawbar pull of 115-1194 kgf, according to the working speed based on agricultural fieldwork.

• Biomolecules & Therapeutics
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• v.27 no.1
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• pp.71-77
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• 2019

Previous studies have shown that spinosin was implicated in the modulation of sedation and hypnosis, while its effects on learning and memory deficits were rarely reported. The aim of this study is to investigate the effects of spinosin on the improvement of cognitive impairment in model mice with Alzheimer's disease (AD) induced by $A{\beta}_{1-42}$ and determine the underlying mechanism. Spontaneous locomotion assessment and Morris water maze test were performed to investigate the impact of spinosin on behavioral activities, and the pathological changes were assayed by biochemical analyses and histological assay. After 7 days of intracerebroventricular (ICV) administration of spinosin ($100{\mu}g/kg/day$), the cognitive impairment of mice induced by $A{\beta}_{1-42}$ was significantly attenuated. Moreover, spinosin treatment effectively decreased the level of malondialdehyde (MDA) and $A{\beta}_{1-42}$ accumulation in hippocampus. $A{\beta}_{1-42}$ induced alterations in the expression of brain derived neurotrophic factor (BDNF) and B-cell lymphoma-2 (Bcl-2), as well as inflammatory response in brain were also reversed by spinosin treatment. These results indicated that the ameliorating effect of spinosin on cognitive impairment might be mediated through the regulation of oxidative stress, inflammatory process, apoptotic program and neurotrophic factor expression,suggesting that spinosin might be beneficial to treat learning and memory deficits in patients with AD via multi-targets.