• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.6
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• pp.1059-1075
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• 2017

The objective of this study was to evaluate the freezing and thawing resistance of the existing drainage system for leakage treatment of underground concrete structures operating in cold regions. The freezing and thawing test was conducted on 4 types of drainage system specimens to evaluate the freezing and thawing resistance of the drainage system. The freezing and thawing resistance was evaluated on 4 types of Hotty-gel, as a waterproofing material, connection methods and on two methods to fix the drainage board with Hotty-gel on the surface of cement concrete specimen. One cycle of the freeze-thaw testing was 48 hours (24 hours of freezing and 24 hours of thawing), and the temperatures of freezing and thawing were at $-18^{\circ}C$ and $10^{\circ}C$, respectively. Among the 4 types of Hotty-gel connection methods, leakage occurred after 28 cycles (8 weeks) of freeze-thawing only in the Hotty-gel connection method with the 'V' groove applied to the corner of the drainage board. No leakage occurred in the 3 types of Hotty-gel connection methods. In two fixing methods, leakage occurred in the method of fixing the drainage board on the cement concrete specimen using the washer, screw and plastic wall plug. Leakage occurred at one point after 10 cycles (3 weeks) of freezing and thawing. After 28 cycles (8 weeks) of freezing and thawing, leakage point increased to 5 points. As time passed, the leak point was not increased, but the amount of leakage was increased at each leak point. The Hotty-gel connection method with cross-sectional diagonal shape was evaluated to be the highest in the production efficiency considering the production time and manufacturing method of the Hotty-gel connection shape. In the construction efficiency considering the construction time and construction method, the fixing method of air nailer, fixed nail and washer was superior to that of the washer, screw and plastic wall plug.

• Korean Journal of Agricultural Science
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• v.10 no.1
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• pp.129-134
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• 1983

Importance has been increased on farming mechanization in harvesting, handling and processing of forage in Korea. Small grasslands are most spread and popular in Korea in comparison with those of Europe and America. Therefore shearing characteristics of some major forage crops should be studied to be contributed to the basic data to develop a moderate size forage harvester being suitable to the small grassland. They were studied on six kinds of forage crops - reed canarygrass, alfalfa, red clover, orchardgrass, meadow fescue and birdsfoot trefoil-in regarding with moisture content levels and shearing angles. The results were as follows; 1. The increase rate of the linear density in relation to the diameter was greater in red clover than other kinds, and order of increase rate in greatness was reed canarygrass, alfalfa and meadow fescue. 2. The increase rates of the maximum shear forces were high in relation to their cross - sectional area in alfalfa and birdsfoot trefoil with hard stems, and the shear energy were comparatively large in orchardgrass and meadow fescue with soft stems, also reed canarygrass and red clover had high values in both the maximum shear force and the shear energy. 3. The shear energy per unit area or shear strength in relation to moisture content showed concave curves with the minimum values at about 70%w. b. which was in the beginning stage of drying in meadow fescue and orchardgrass, nevertheless reed canarygrass and red clover had convex curves with the maximum values at about 40%w.b. 4. The shear force in relation to the shear angle decreased generally with decrease of shear angle from $90^{\circ}$ to $70^{\circ}$ or $50^{\circ}$.

• Sleep Medicine and Psychophysiology
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• v.5 no.1
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• pp.88-102
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• 1998

Objectives : We attempted to study obstructive sleep apnea symptoms prevalence and sleep apnea-associated factors in Korean rural adult population. Methods : In 1,441 adult subjects of three rural communities selected by cluster sampling, we administered an epidemiologic survey using questionnaire methods from July 14, 1996 to July 28, 1996. Results : 1) In 14.1% of the subjects, snoring was reported to occur almost daily and 2.9% of the subjects reported sleep apnea symptoms occurring almost daily. 2) Snoring and sleep apnea symptoms were found more frequently in males or in mid-aged group(45 - 64 years old) than in females or in younger- and older-aged groups, respectively. Compared with the subjects who have no snoring, the subjects who have snoring or sleep apnea symptoms had greater body mass index(BMI), waist-hip ratio, hemoglobin level, RBC count, and higher diastolic blood pressure. 3) Cigarette smoking and alcohol drinking more than once a week were significantly associated with suffering from sleep apnea symptoms. 4) In multiple logistic regression analysis, being male, mid-aged, and greater BMI were independently associated with the presence of snoring and sleep apnea symptoms. Conclusion : We conclude that, in the Korean rural adult population, males or mid-aged group suffers more from snoring and sleep apnea symptoms than females or younger- and older-aged groups. In addition, being male, mid-aged, and greater BMI were significantly associated independently with the presence of snoring and sleep apnea symptoms.

• Tuberculosis and Respiratory Diseases
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• v.42 no.6
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• pp.913-922
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• 1995

Background: When we define the pressure of pulmonary vasculature in which a recruitment of blood flow occurs as $P_I$ and the proportion of change in pulmonary artery to that in cardiac output as IR and then we compare PI and IR with pulmonary vascular resistance, we would find some problems in pulmonary vascular resistance. In other words, it is the theory that, IR should be increased mainly in pulmonary embolism in which decreases the cross sectional area of pulmonary vasculature. But there are many contradictory reports resulted from various researches and the fact is known widely that any difference exists between PVR and PI, IR. For this reason, the purpose of this study is to observe how PI and IR change at the time of the outbreak and during treatment of the pulmonary embolism, and to find out the meaning of these new indicators and the difference from the pulmonary vascular resistance used generally when we subdivide the pulmonary vascular resistance into PI and IR. Method: After making AV fistula in experimental dog, we controlled cardiac output at the intervals of 15 minute in case of three kinds(all AV fistula are obstructed, only one of fistula is open and all of fistula is open), and after evoking massive pulmonary embolism with radioactive autologous blood clots, we measured the mean pulmonary artery pressure, and calculated PI and IR. We observed the pattern of change in PI and IR, without giving the control group any specific treatment and with injecting intravenously rtPA in the Group 1 and Group 2 at the dose of 1mg per kg, for 15 minutes fot the former and 3 hours for the latter. Result: 1) Pulmonary vascular resistance showed a change similar to that of pulmonary artery pressure and in all three group, PVR increased significantly, but group 1 and group 2 showed tendency that PVR keeps on decreasing after treatment, and the rate of decrease in group 1 is more rapid than group 2 significantly. 2) Both intersection(PI) and degree(IR) are proved statistically significant, in view of the straight line relationship between cardiac output and pulmonary artery pressure, calculated by minimal regression method. 3) PI changed similarly to pulmonary vascular resistance, while in the IR which is theoretically more similar to PVR, there was no significant difference or change after rtPA infusion. Conclusion: In the pulmonary embolism, Both change in IR which means real resistance of pulmonary vasculature and PI which was developed due to secondary vasoconstriction by pulmonary embolism are reflected same time.

• Restorative Dentistry and Endodontics
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• v.32 no.1
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• pp.37-46
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• 2007

The C-shaped canal system is an anatomical variation mostly seen in mandibular second molars, although it can also occur in maxillary and other mandibular molars. The main anatomical feature of C-shaped canals is the presence of fins or web connecting the individual root canals. The complexity of C-shaped canals prevents these canals from being cleaned, shaped, and obturated effectively during root canal therapy, and sometimes it leads to an iatrogenic perforation from the extravagant preparation. The purpose of this study was to provide further knowledge of the anatomical configuration and the minimal thickness of dentinal wall according to the level of the root. Thirty extracted mandibular second molars with fused roots and longitudinal grooves on lingual or buccal surface of the root were collected from a native Korean population. The photo images and radiographs from buccal, lingual, apical direction were taken. After access cavity was prepared, teeth were placed in 5.25% sodium hypochlorite solution for 2 hours to dissolve the organic tissue of the root surface and from the root canal system. After bench dried and all the teeth were embedded in a self-curing resin. Each block was sectioned using a microtome (Accutom-50, Struers, Denmark) at interval of 1 mm. The sectioned surface photograph was taken using a digital camera (Coolpix 995, Nikon, Japan) connected to the microscope. 197 images were evaluated for canal configurations and the minimal thickness of dentinal wall between canal and external wall using 'Root Thickness Gauge Program' designed with Visual Basic. The results were as follows : 1. At the orifice level of all teeth, the most frequent observed configuration was Melton's Type C I (73%), however the patterns were changed to type C II and C III when the sections were observed at the apical third. On the other hand, the type C III was observed at the orifice level of only 2 teeth but this type could be seen at apical region of the rest of the teeth. 2. The C-shaped canal showed continuous and semi-colon shape at the orifice level, but at the apical portion of the canal there was high possibility of having 2 or 3 canals 3. Lingual wall was thinner than buccal wall at coronal, middle, apical thirds of root but there was no statistical differences.

• Journal of Nutrition and Health
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• v.47 no.2
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• pp.113-123
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• 2014

Purpose: Vitamin D has been known to play an important role in the central nervous system and brain functions in the human body, and cumulative evidence has shown that vitamin D deficiency might be linked with various mental health conditions. Epidemiologic studies have shown that vitamin D deficiency may be associated with higher risk of depression in the US and European populations. However, limited information is available regarding the association between vitamin D status and depression in the Korean population. The objective of this study was to examine the associations between vitamin D levels and prevalence of depression. Methods: We conducted a cross-sectional analysis using nationally representative data from the 2008-2010 Korean National Health and Nutrition Examination Survey from which serum 25-hydroxyvitamin D concentrations were available. A total of 18,735 adults who had available demographic, dietary, and lifestyle information were included in our analysis. We defined "depression" with a diagnosis by a physician. "Depressed condition" was defined as having feelings of sadness or depression without diagnosis by a physician. Results: The prevalence of depression was 1.63% and 5.43% in Korean men and women, respectively; 12.5% of men and 26.1% of women were defined as the group having depressed conditions. In multivariate logistic regression models, no significant associations were observed between vitamin D status and prevalence of depression or depressed conditions in Korean men and women. Conclusion: We found no association between vitamin D insufficiency and depression/depressed conditions in Korean adults. Future large prospective studies and randomized controlled trials are needed to confirm this relationship.

• The Korean Journal of Malacology
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• v.29 no.3
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• pp.189-195
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• 2013

Experiments for net cage culture at sea were conducted in each $2.4{\times}2.4$ m in area and took the samples from four different densities: 150, 300, 450 and 600 per cross-sectional area ($m^2$) of shelter. The same stocking densities applied to indoor tank culture to investigate the growth and survival rate. The size of juvenile abalone sample was $36.14{\pm}2.28$ mm for net cage culture and $38.62{\pm}3.22$ mm or indoor tank. Feed such as raw brown sea mustard, raw kelp and dried kelp was sufficiently provided to the abalone. In net cage culture experiment, the growth of the spat of juvenile abalone was the fastest $60.53{\pm}5.75$ mm in the 150 abalone cage per square meter ($m^2$), followed by the 300 abalone cage at $54.01{\pm}5.17$ mm, 450 abalone cage at $51.48{\pm}5.37$ mm and 600 abalone cage at $51.09{\pm}4.96$ mm in order. In the meantime, in the indoor tank experiment, the 150 abalone indoor tank was the fastest $47.50{\pm}6.31$ mm per square meter, followed by the 300 abalone tank at $45.92{\pm}5.23$ mm, the 450 abalone tank at $44.24{\pm}5.59$ mm and the 600 abalone tank at $43.62{\pm}4.44$ mm in order. The survival rate was more than 97.9% in all the experiments, not showing a significant difference.

• Korean journal of health promotion
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• v.17 no.2
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• pp.109-118
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• 2017

Background: Abdominal obesity as measured by waist-to-height ratio (WHtR) may have stronger and inverse associations with cardiovascular (CV) health than overall obesity as measured by body mass index (BMI). However, there was some challenges for controversies. We aimed to examine the associations of WHtR and BMI with CV health among Korean children using data of the 2010-2012 Korea National Health and Nutrition Examination Survey. Methods: A cross-sectional study was conducted with the sample of 2,363 children by analyzing by gender and two-age groups (10-12 and 13-18 years). Overall obesity was categorized into 3 groups by BMI percentile: non-overweight (<85), overweight (${\geq}85$), and obesity groups (${\geq}95$). Abdominal obesity was categorized into 2 groups by WHtR: normal (<0.5) and abdominal obesity groups (${\geq}0.5$). The CV health score was defined as a z-score by calculating the sum of 7 CV factors. Results: The overweight/obesity groups had significantly lower CV health scores than the normal group (P<0.05) in boys and girls aged either 10-12 years or 13-18 years after adjusting for covariates. The abdominal obesity group also showed significantly lower CV health scores than the normal group (P<0.05) in all the groups; this significant association remained significant in boys aged 13-18 years even after further adjusting for BMI category (P<0.01). Conclusions: Among boys aged 13-18 years, abdominal obesity as measured by WHtR was significantly and inversely associated with CV health, independent of BMI category. Therefore, it should be considered to assess the level of abdominal obesity as a measure of CV health in late adolescent boys.

• The Journal of the Korean Institute of Forest Recreation
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• v.22 no.4
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• pp.59-69
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• 2018

This is a cross-sectional study that suggests ways to activate forest welfare services (FWS) by investigating the infrastructure, service status, and perception on FWS in Korea. In August 2016, a structured email survey was conducted in nation widely. The respondents were mostly directors and general secretary (75.0%). The considerable number (16.3%) of nursing homes (NH) use some floors of the complex buildings that would be difficult to have FWS infrastructure and about 30% of those without forests near the facilities. The directors of NH recognize that FWS has positive effects on the elderly. However, FWS is not an requisite of the longterm care insurance benefit, and so costly and effort-intensive that FWS has not been activated so far. In order to activate FWS in NHs, it is necessary to develop and disseminate the guidelines on FWS that anyone can easily followed. In addition, when the National Health Insurance Corporation evaluates NHs, they should evaluate not only whether there is a wandering or walking space, but also whether it has forest healing factors such as forests. It is also necessary to create a barrier-free environment both inside and outside of NHs, increasing accessibility to the toilet in gardens, paving a passage for wheelchairs and lifts in forests near NHs. Through these efforts, it is expected that FWS will be activated to provide physical, mental rest and comfort, appropriate cognitive stimulation to the NH residents at the end of life.

• Journal of the korean academy of Pediatric Dentistry
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• v.48 no.4
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• pp.437-448
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• 2021

The purpose of this study is to analyze morphological characteristics of maxillary primary molar's root and root canal. 268 children aged 3 - 7 years (175 boys, 93 girls) who had CBCT (152 children) and 3D CT (116 children) taken in Seoul National University Dental Hospital from January 2006 to April 2020 were included. The number of roots and root canals were analyzed in 1002 teeth without any root resorption or periapical pathologies. Curvature, angulation, length of root and root canal, as well as cross-sectional shapes of the root canal were analyzed in 218 teeth. By using Mimics and 3-Matics software, volume, surface area, and volume ratio of root canal was analyzed in 48 teeth. More than half of maxillary primary molars have 3 roots and 3 root canals. The degree of symmetry of root canal type was about 0.63 (Cohen's kappa coefficient). The most frequent shape of roots and canals was linear in 1^st primary molars and curved in 2^nd primary molars. Angulation, length of root and root canals was the largest on palatal roots. Most teeth showed ovoid or round shapes at apex. The largest root canal volume, surface area, volume ratio was found in the palatal roots.