• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.33 no.2
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• pp.103-114
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• 2023

Objectives: This study was conducted to evaluate hand-arm vibration (HAV) exposure levels due to the use of power hand tools and to evaluate the determinants in the automobile assembly process. Methods: The exposure level to HAV was evaluated for 30 work lines in five assembly processes (body, engine, chassis, door, and design) that use air-powered tools and battery-powered tools and operate in circulation for two hours. The 2-hr equivalent energy vibration acceleration, A (2), of the task was measured. The 8-hr equivalent energy vibration acceleration, A (8), was estimated in consideration of the number of tasks that can be performed per day by each process. In addition, a survey on the working environment was conducted with workers exposed to vibration. Results: The geometric mean of the HAV exposure level, A (2), for a total of 30 tasks was 2.51 m/s², and one case was 10.30 m/s², exceeding TLV (2hr). The HAV exposure level of A (8) was evaluated from 1.03 m/s² to 5.36 m/s². A (2) showed a statistically significant difference (P<0.01) for each process, and the chassis process (GM=3.90 m/s²) was the highest. The larger the tool size and the longer the tool length, the higher was the vibration acceleration when using a battery-powered tool than an air-powered tool (P<0.01). Battery-powered tool users showed higher dissatisfaction on all items than did air-powered tool users. Conclusions: As a result of this study, it is necessary to implement a program to reduce the HAV exposure levels.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.308-308
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• 2021

다목적댐의 홍수조절운영에 있어서 댐유입량은 직접 관측의 어려움과 오차로 인해 정확한 유량을 산정하는데 한계가 있다. 남강댐 유역의 경우 유역면적대비 과소한 저수용량으로 말미암아 급격한 홍수유입이 발생할 경우 유출률이 비정상적 수치를 보이는 경우가 종종 발생하고 있다. 본 연구에서는 물리기반의 격자형 유출모형을 댐 직상류 잔유역에 적용하여 유출률을 산정 후 남강댐 계측유입량의 타당성을 간접적으로 검증할 수 있는 방법론을 제시하고자 한다. 댐유역에서 잔유역은 직상류 수위표지점 하류의 유역을 일컬으며, 이들 수위표지점에서 홍수시의 배수영향은 최소화될 만큼 이격되어 있고, 댐체 혹은 취수탑에 부착된 수위표와는 달리 기계적 진동의 영향이 최소화되어 있다고 가정한다면, 수위계측지점의 유량을 경계조건으로 활용하여 작은 면적에 대한 정밀한 수문학적 유출모델링을 통하여 비교적 신뢰성있는 유출값을 추정할 수 있다는 장점이 있다. 남강댐 잔유역은 유역 내 산청, 신안, 창촌 수위관측소를 기준으로 상류의 유역을 제외한 부분으로 설정하였다. 본 연구에서는 210m 격자에 대하여 모든 입력자료를 가공하였으며, 입력자료 중 지형자료는 WAMIS에서 제공한 DEM, 토지피복도, 토양도를 활용하였다. 강우자료는 유역 내 위치한 25개 강우관측소의 시단위 강우자료를 활용하였고, 강우사상은 진주 기상관측소의 일우량 100mm 이상을 기준으로 총 8개의 강우사상을 선정하였다. 남강댐 유역의 유출률을 산정하기 위해 산청, 창촌, 신안 등 3개의 수위관측소의 관측유량을 경계조건으로 사용하였고, 모의된 수문곡선의 총유량과 첨두유량을 관측값과 비교하였다. 유출률을 산정하기 위한 기준시간은 강우시작부터 강우종료 후 48시간으로 설정하였다. 유출률은 강우사상별로 편차가 심한 특성을 보이고 있었으며, 전체적으로는 계측유량기준 106~39.1%의 유출률이 보정된 유량을 통해서는 85~33%의 유출률로서 계측유량이 전반적으로 과대추정 되는 경향이 있었음을 확인할 수 있었다. 이들 중 2010년 7월 강우사상은 관측 유입량 기준 95.6%의 유출률을 보여, 추정유량 58.5%대비 상당한 과대추정 경향을 보인 사례로 판단할 수 있었다. 수문학적 유입량 추정방법은 현장계측을 대체할 수 있는 기법으로는 무리가 있으나 현장계측의 신뢰도를 평가하기 위한 목적으로는 유용한 대안이 될 수 있을 것으로 기대된다.

• Journal of the Korean Geotechnical Society
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• v.39 no.10
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• pp.5-18
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• 2023

The construction timeline for earthworks can be significantly reduced by substituting the conventional layer-by-layer compaction using a vibratory roller with single-layer compaction through the rapid impact compaction (RIC) method. Dynamic load compaction is well-suited for coarse-grained soils like sand. However, as the supply of sand, the primary reclamation material, becomes scarcer, the utilization of soil with fines is on the rise. To implement the dynamic load compaction, such as RIC, with reclaimed materials containing fines, it's imperative to determine the effective improvement depth. In this study, we assess the impact of the RIC method on the effective improvement depth for clean sand and public fill with fines, comparing field test results before and after RIC application. Our focus is on the cone resistance (q_c) as it pertains to compaction quality control criteria. In conclusion, it becomes evident that standardizing the cone resistance is vital for the quality control of various reclaimed soils with fines. We have evaluated the compaction quality control criteria corresponding to a relative density (Dr) of 70% for clean sand as Q_tn,cs = 110. As a result of this analysis, we propose new quality control criteria for q_c, taking into account the fines content of reclaimed soils, which can be applied to RIC quality control.

• Journal of Korea Water Resources Association
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• v.56 no.12
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• pp.883-893
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• 2023

While South Korea's dependence on imported grains is very high, droughts impacts from exporting countries have been overlooked. Using the Evaporative Stress Index (ESI), this study globally analyzed frequency, extent, and long-term trends of agricultural droughts and their relation to natural oscillations and global crop prices. Results showed that global-scale correlations were found between ESI and soil moisture anomalies, and they were particularly strong in crop cultivation areas. The high correlations in crop cultivation areas imply a strong land-atmosphere coupling, which can lead to relatively large yield losses with a minor soil moisture deficits. ESI showed a clear decreasing trend in crop cultivation areas from 1991 to 2022, and this trend may continue due to global warming. The sharp increases in the grain prices in 2012 and 2022 were likely related to increased drought areas in major grain-exporting countries, and they seemed to elevate South Korea's producer price index. This study suggests the need for drought risk management for grain-exporting countries to reduce socioeconomic impacts in South Korea.

• Journal of the Korean Geotechnical Society
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• v.40 no.1
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• pp.5-14
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• 2024

PHC piles demonstrate superior resistance to compression and bending moments, and their factory-based production enhances quality assurance and management processes. Despite these advantages that have resulted in widespread use in civil engineering and construction projects, the design process frequently relies on empirical formulas or N-values to estimate the soil-pile friction, which is crucial for bearing capacity, and this reliance underscores a significant lack of experimental validation. In addition, environmental factors, e.g., the pH levels in groundwater and the effects of seawater, are commonly not considered. Thus, this study investigates the influence of vibrating machine foundations on PHC pile models in consideration of the effects of varying pH conditions. Concrete model piles were subjected to a one-month conditioning period in different pH environments (acidic, neutral, and alkaline) and under the influence of seawater. Subsequent repeated direct shear tests were performed on the pile-soil interface, and the disturbed state concept was employed to derive parameters that effectively quantify the dynamic behavior of this interface. The results revealed a descending order of shear stress in neutral, acidic, and alkaline conditions, with the pH-influenced samples exhibiting a more pronounced reduction in shear stress than those affected by seawater.

• Clinical and Experimental Pediatrics
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• v.48 no.10
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• pp.1132-1138
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• 2005

Purpose : The mucopolysaccharidoses (MPSs) are a heterogeneous group of lysosomal storage disorders. They are caused by a deficiency of the enzymes involved in the degradation of glycosaminoglycans. Early recognition is important because recombinant enzyme replacement therapy is now available for MPS. We studied the clinical characteristics of 80 MPS children with the object of determining the epidemiological, clinical and radiological features in Korean MPS children. Methods : Diagnosis of MPS was confirmed by skin fibroblast enzyme analysis in 80 patients between February 1995 and December 2004. Charts were retrospectively reviewed for clinical and radiological findings, as well as for intelligence and speech evaluations. Results : Hunter syndrome (MPS type II) was the most prevalent type, appearing in 51/80 cases (64 %), followed by Sanfilippo syndrome (MPS III-18%), Hurler syndrome (MPS I-15%), and Morquio syndrome (MPS IV-4%). The average age at diagnosis was 5.5 years (range 1 to 20), and the male-to-female ratio was 4.7 : 1. Typical radiographic changes were observed in 45/54 cases (83%). Mitral regurgitation was the most common cardiac defect. Moderate to profound mental retardation and hearing loss were present in 14/35 cases (56%) and 33/38 cases (82%), respectively. Four MPS II patients had bone marrow transplantation, with mixed outcomes. Five MPS I patients are currently on enzyme replacement therapy. Conclusion : Our study showed a high proportion of MPS II cases (64%), which may represent population variability. By studying the clinical features of these patients, we hope to alert pediatricians of the warning signs of MPS.

• The Journal of Korean Academy of Prosthodontics
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• v.51 no.3
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• pp.167-174
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• 2013

Purpose: This study was conducted to evaluate the roughness and surface alternations of three differently blasted titanium discs treated by $Nd:YVO_4$ Laser irradiation in different conditions. Materials and methods: Thirty commercially pure titanium discs were prepared and divided into three groups. Each group was consisted of 10 samples and blasted by $ZrO_2$ (zirconium dioxide), $Al_2O_3$ (aluminum oxide), and RBM (resorbable blasted media). All the samples were degreased by ultrasonic cleaner afterward. Nine different conditions were established by changing scanning speed (100, 300, 500 mm/s) and repetition rate (5, 15, 35 kHz) of $Nd:YVO_4$ Laser (Laser Pro D-20, Laserval $Korea^{(R)}$, Seoul, South Korea). After laser irradiation, a scanning electron microscope, X-ray diffraction analysis, energy dispersive X-ray spectroscopic analysis, and surface roughness analysis were used to assess the roughness and surface alternations of the samples. Results: According to a scanning electron microscope (SEM), titanium discs treated with laser irradiation showed characteristic patterns in contrast to the control which showed irregular patterns. According to the X-ray diffraction analysis, only $Al_2O_3$ group showed its own peak. The oxidation tendency and surface roughness of titanium were similar to the control in the energy dispersive X-ray spectroscopic analysis. The surface roughness was inversely proportional to the scanning speed, whereas proportional to the repetition rate of $Nd:YVO_4$. Conclusion: The surface microstructures and roughness of the test discs were modified by the radiation of $Nd:YVO_4$ laser. Therefore, laser irradiation could be considered one of the methods to modify implant surfaces for the enhancement of osseointegration.

• Journal of the Korean Society of Food Science and Nutrition
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• v.35 no.6
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• pp.683-689
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• 2006

This study was established to investigate the effect of germanium-fortified yeasts on the serum lipid composition and immune system of human body. All 50 subjects with the age range of $50{\sim}75$ were entered in this clinical trial for 6 months. The effects were determined by the proliferative responses of immune-mediated cells, T-cell, B-cell and NK-cell during daily supplementation with/without germanium-fortified yeast. The results of hematology and blood chemistry didn't show any significant differences during administration periods. Serum lipid compositions also didn't show any significant differences during administration periods except triglyceride (TG) and VLDL-cholesterol. TG and VLDL-cholesterol levels were increased significantly by the consumption of germanium-fortified yeast (p<0.05). Immune mediated T-celt and NK-cell didn't increased in both control and test group supplemented with germanium fortified yeast, while B-cell increased in the germanium fortified yeast group after 8 week (p<0.05). Also $TNF-{\alpha}$ increased in the group of germanium fortified yeast after 8 week (p<0.05) but not in the control group. From the above results, germanium fortified yeast is expected to be useful on the improvement of the cellular immune response and protection of organs from various chronic diseases.

• Childhood Kidney Diseases
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• v.8 no.1
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• pp.33-42
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• 2004

Purpose : Children with nephrotic syndrome(NS) are under high risk for metabolic bone disease(MBD) as a complication of long-term glucocorticoid therapy. We prospectively evaluated the effect of oral bisphosphonate(alendronate) therapy in children with NS, which has proven efficacy in adult patients with glucocorticoid induced MBD. Methods : Among 58 children with NS, aged 5 to 8 years and haying a disease duration of more than 2 years, 30(51.7%) were enrolled to meet the selection criteria, less than -1.0 Z-scores of lumbar spine bone mineral density(BMD) by dual energy X-ray absorptiometry (DEXA). These 30 children were divided into three groups and each were assigned to receive alendronate, calcitriol, and no-medication, respectively for one year. Lumbar spine BMD was followed up every 6 months and the biochemical indexes were measured before and 1 year after the treatment. There were no significant difference among groups with respect to the average age, the initial BMD, and the cumulative steroid doses. Analysis of the treatment efficacy was done by the % change of BMD and by the changes in Z-scores of lumbar spine BMD. Results : Mean age and disease duration of patients at the initial lumbar spine BMD evaluation was $7.4{\pm}1.7$ years and $2.2{\pm}1.2$ years, respectively. Twenty-three of 30 children(76%) had osteopenia, and seven(23%) had osteoporosis. There was no difference in the biochemical values among the groups, before and 1 year after the treatment(P<0.05). Twenty two children(73.3%) with frequent relapsing or steroid dependant NS had more frequent MBD, compared to the 8 children(26.6%) with infrequent relapsing NS. The one year % changes of BMD were 8.56 in alendronate group, 5.79 in calcitriol group, and 1.9 in no-medication group. The changes in Z-score of lumbar spine BMD increased in the alendronate group and the calcitriol group, but not in the no-medication group. One year % changes of BMD were different among groups(P=0.0002). Significant differences were found between the alendronate and the no-medication group, and between the calcitriol and the no-medication group(P<0.05). There was no difference between the alendronate and the calcitriol group. No serious adverse effect was observed in the alendronate group. Conclusion : Children with NS receiving high dose steroids are under the high risk of BMD and should undergo regular BMD evaluation. Z-score of lumbar spine BMD was a useful parameter in diagnosing low bone mass in children. Alendronate weekly oral therapy was effective and relatively safe in increasing the lumbar spine BMD in children with NS having steroid induced MBD.

• Journal of dental hygiene science
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• v.9 no.4
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• pp.453-459
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• 2009

The purposes of this research were to evaluate the relationships of between characteristics of noise and annoyance of dental hygienist by noise in dental clinic. To investigate the dental clinic workers' reactions to noise when occurred in dental clinic, the noise level test in dental clinic and questionnaire were taken. As a result of noise evaluation, It shows that the range of noise level was 67.7~78.3dB(A) and frequency was very high (more than 4KHz). It's seem to be begins occurrence of stamina-loss, contraction of peripheral blood vessel, decrease of adrenocortical hormones. Most of respondents were affected by noise: 67% of respondents were nervous about noise and the rest of respondents were bearable. Analysis by NR-curve showed that it was exceed the noise permit level in working space. As a result of correlation - test, the more exposed dental hygienist to noise, the more felt the unpleasantness and fatigue. It's hard to sufficient explanation to patients about the dental treatment. So it's thoughts that insufficient explanation will negative impact on the patients' satisfaction and increase competitiveness in dental clinics. To remedy a unpleasantness and fatigue of noise in dental hygienist, it's considered that making an offer the ear protection and choosing the low noise-vib. equipment and using the masking effect. Therefore, It can be provide a pleasant working environment with dental hygienist and It will have a great advantage to dental clinics to improve their competitiveness.