• Economic and Environmental Geology
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• v.40 no.6
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• pp.833-841
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• 2007

The groundwater heat pump system(GWHP) is one of the most efficient ground source heat pump system(GSHP) which uses low grade and shallow geothermal energy for cooling and heating purpose. The GWHP system shall be designed properly based on peak block load performance and optimum pumping rate of groundwater comparable to ground coupled heat pump system(GCHP). The optimum pumping rate depends on groundwater temperature at a specific site, size of plate heat exchanger, and total head loss occurred by whole system comprising pumps and pipings. The required optimum flow rates of the system per RT are ranged from 3.8 to 9.8lpm being less than the typical building loop flow of 9.5 to 11.4lpm.

• The Journal of Korean Academy of Prosthodontics
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• v.37 no.5
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• pp.597-606
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• 1999

This study was performed to evaluate the effect of aging and thermal cycling on the biaxial flexure strength of low commercially available veneering resin composites for crown(Dentacolor : DC, Artglass : AG, Esternia : ET and Targis : TG). Disc specimens were fabricated in a teflon mold giving 12mm in diameter and 1mm in thickness. All samples were divided into 4 groups. Group 1 was dried in a dessicator at $25^{\circ}C$ for 30 days. Group 2 was immersed in distilled water at $37^{\circ}C$ for 30 days. Group 3 was immersed in distilled water at $65^{\circ}C$ for 30 days. Group 4 was subjected to 10,000 thermal cycles between $5^{\circ}C\;and\;55^{\circ}C$, and the immersion time in each bath was 15 seconds per cycle. Biaxial flexure test was conducted using the ball-on-three-ball method at the cross head speed of 0.5mm/min and fracture surfaces were observed with scanning electoron microscope. The results obtained were summarized as follows; 1. Weibull modulus values, except for the AG group, decreased after thermal cycling treatment. 2. Biaxial flexure strength values of aging group at $37^{\circ}C$ were the lowest in all sample groups. Except for the DC group, strength values were significantly decreased for the drying group. 3. After thermal cycling test, the highest value of biaxial flexure strength of 188.8 MPa was observed in the ET group and the lowest value of 73.2 MPa was observed in the DC group. The strength values showed the significant differences in each group (p<0.05). 4. Observation of surfaces after thermal cycling test revealed the ditching in the part of surrounding large fillers.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.142-149
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• 2003

Blind hydraulic backfilling is a commonly used technique for subsidence control of the strata over unapproachable waterlogged underground excavations. In this investigation model studies on all the three variants of this technique, namely, hydro-pneumatic or air-assisted gravity backfilling, pumped-slurry backfilling and simple gravity backfilling, have been carried out in fully transparent models of the underground excavations. On examination of the filling process, it was revealed that in all the three cases, the basic process of filling occurs by sand transport along one or more meandering channels. The relative influence of sand, water and air flow rates on the area of filling from a single inlet point and the hydraulic pressure loss per unit length were studied in details. In hydro-pneumatic backfilling process, the air bubbles while moving upward through the meandering channels provide an additional buoyant force over and above the available hydraulic head. In this way the area of filling from a single borehole may be quite large even at small flow rates of water. During actual field implementation the injected air, if not released completely from the rise side holes, may cause troubles by way of creating potholes on the surface. The pumped-slurry technique has shown its capability of filling a relatively larger area at faster rate, especially when high-volume, low-pressure method was selected. But simple gravity filling was also found to be equally effective method as slurry pumping, especially when flow rates were high. In the second and third method discussed above, examination of variations of injection pressure was also done and its relation with physical phenomenon was also attempted. Some empirical relationships were also developed using multivariate regression with a view to help the practicing engineers.

• Journal of Korean Society on Water Environment
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• v.33 no.5
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• pp.572-579
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• 2017

Increased impervious surface caused by rapid urbanization serves to produce the discharge of non-point source pollutants such as total suspended solid (TSS). There exist various methods of removing TSS, including a filtration process using granular media (a well-known method to be practically used after the consideration of removal efficiency, clogging, and backwashing efficiency). To determine the TSS removal capability of the filter, we initially performed lab-scale experiments which assessed flow rates, influent concentrations, permeability co-efficients, the particular shapes of suspended solids and potential clogging, and also evaluated TSS removal efficiency when applied to filtration facility in a pilot-scale. In low filtration flux condition, the removal efficiency of suspended solids was more than 95 %, while decreased to 83% in high filtration flux. Regarding the clogging aspect of the experiment, total cumulative solids were loaded up to $19.15kg/m^2$, and TSS removal efficiency was noted to commence to decrease when the loaded solids exceeded $9.0kg/m^2$. It was also noted, however, that superior efficiency was maintained for six hours. In addition, for pilot-scale experiment, the removal efficiency was still high enough (83.4 %) for the solid concentration of 140 ~ 343 mg SS/L and after backwashing, head loss was recovered to 92 ~ 95 % during two hour filtration. With these results, It was confirmed that lifetime of the filter applied to the test was prolonged due to the high treatment efficiency and good backwashing efficiency for the cumulative solids load.

• Journal of the Korean earth science society
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• v.28 no.3
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• pp.357-366
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• 2007

In Gomso Bay, on the west coast of Korea, the surface sediments sampled in 1991 and 2006 were analysed to identify the long-term variations of tidal flat sediments. Silt and clay contents have decreased in the bay-mouth tidal flats whereas sand and clay contents have decreased on the inner-bay and bay-head tidal flats over the last 15 year period. In particular, the clay contents of the tidal flats in 2006 were relatively low when compared to those of both tidal flats adjacent to other semi-enclosed bays and those of the tidal flats in 1991. The variations of textural compositions in the tidal flat sediments have led to changes of the sedimentary facies. It indicates that the changes must have been made by the changes of hydrodynamic conditions impacted by human activities, such as the construction of sea-walls, land reclamation, structures of farms constructed compactly near the low water line, and the Saemangeum dyke constructed in the northern part of the area where this research was conducted.

• Korean Journal of Dental Materials
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• v.44 no.1
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• pp.69-77
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• 2017

The aim of this study was to investigate the effects of chitosan powder addition on the strengthening of conventional glass ionomer cement. Two types of chitosan powders with different molecular weight were mixed with conventional glass ionomer cement (GIC): low-molecular weight chitosan (CL; 50~190 kDa), high-molecular weight chitosan (CH; 310~375 kDa). The chitosan powders (CL and CH) were separately added into the GIC liquid (0.25-0.5 wt%) under magnetic stirring, or mixed with the GIC powder by ball-milling for 24 h using zirconia balls. The mixing ratio of prepared cement was 2:1 for powder to liquid. Net setting time of cements was measured by ISO 9917-1. The specimens for the compressive strength (CS; $4{\times}6mm$), diametral tensile strength (DTS; $6{\times}4mm$), three-point flexure (FS; $2{\times}2{\times}25mm$) with flexure modulus (FM) were obtained from cements at 1, 7, and 14 days after storing in distilled water at $(37{\pm}1)^{\circ}C$. All mechanical strength tests were conducted with a cross-head speed of 1 mm/min. Data were statistically analyzed by one-way ANOVA and Tukey HSD post-hoc test. The mechanical properties of conventional glass ionomer cement was significantly enhanced by addition of 0.5 wt% CL to cement liquid (CS, DTS), or by addition of 10 wt% CH (FS) to cement powder. The CL particles incorporated into the set cement were firmly bonded to the GIC matrix (SEM). Within the limitation of this study, the results indicated that chitosan powders can be successfully added to enhance the mechanical properties of conventional GIC.

• Journal of the Korean Geotechnical Society
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• v.37 no.7
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• pp.13-23
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• 2021

If roads, bridges, buildings, etc. are built on the ground with soft clay or organic soil, there may be a lot of problems in geotechnical engineering such as settlement and stability due to the large settlement and lack of bearing capacity. In extreme cases, it may appear due to shear failure or collapse of the constructed structure, so a ground improvement method is indispensable to increase the strength of the ground and to suppress settlement. In this study, the settlement according to each groundwater level condition was analyzed using the measurement results for the groundwater level conditions, one of the important factors in predicting the settlement in dredged and reclaimed ground, and the groundwater level conditions applied to the settlement analysis were proposed by comparing it with settlement generated 5 years after construction. As a result of the analysis, it is judged that it is reasonable to apply the measured groundwater level during construction and the low water ordinary neap tide (L.W.O.N.T) during load application for the groundwater level in the settlement analysis. In addition, in the case of the dredged and reclaimed ground, it is estimated that the water pressure acting on the clay layer is nonlinear, as the result of the observations of the head of water at the observation points above and below the in-situ clay layer were different.

• The Journal of Engineering Geology
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• v.28 no.2
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• pp.277-295
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• 2018

As it has become difficult to secure new water resources through dam construction due to the critical social public opinions on dam construction from 10 years ago, it is necessary to review the existing water resources through the review of existing dams. Accordingly, access methods, such as planning, construction and management, were carried out using technologies already accumulated in relation to the repair and reinforcement of the dam. As a result of the repair and reinforcement, permeation grouting has been performed in many dams, but the establishment of the technology is insufficient so far, and the published paper at home and abroad is extremely rare. In this thesis, low-pressure penetration and grouting reinforcement technologies for the YC dam are analyzed in detail. As a result, penetration grouting has shown that it can be effectively applied to the improvement in the constallability of the core fill-like a YC dam. In addition, the technical details of the experience-proven penetration grouting are given in relation to the injection criteria. It is deemed that the specific analysis data of the Fill Dam penetration grouting technology through this study can be used as useful data for strengthening the repair of Fill Dam and reservoir.

• Journal of Sasang Constitutional Medicine
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• v.16 no.3
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• pp.34-45
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• 2004

1. Objectives The purpose of this study is to investigate constitutional ordinary and pathological symptoms differences among each constitutional groups of stroke in-patients. 2. Methods 101 stroke in-patients(Soyangin(SY) $n^{a)}=52$, Taeumin(TE) n=39, Soeumin(SE) n=10) hospitalized at Kyung-Hee Oriental medical center from Nov. 2003 to Sept. 2004 were investigated through questionnaire which consists of 18 parts, 289 questions(156 questions concerned ordinary symptoms and 133 pathological symptoms). The answers were analyzed statistically in order to find the questions which represent the significant differences among each constitutional groups. ( a) number of patients) 3. Results As for the ordinary symptoms, majority of the Soyangin group replied that they experienced "frequent dreams during sleep" and "scarce constipation". Majority of the Taeumin group affirmed to "dark redness of face", "dry nose", "low intolerance of heat", "good appetite and digestion", and "frequent overeating experiences". Majority of the Soeumin group affirmed to "pale face", "insomnia", "frequent constipation", "poor appetite and digestion", "small amount of diet", "slow eating", "fond of warm or hot water", and "easily tired(especially after sweating)". As for the pathological symptoms, majority of the Taeumin group affirmed to "frequent optic fatigue", "frequent tinnitus", "frequent bitter mouth", "fond of cold water", "flatulent", "stuffiness in the navel area", "irregular stool habits", "frequent constipation", "large amount of sweat", and "frequent rigidity of neck". Majority of the Soeumin group affirmed to "bad appetite", "fond of warm or hot water", "drink small amount of water", "sensitive during sleep" and "frequent heavy head". 4. Conclusions Through this study, We found statistically significant questions distinguishing the characteristics of each constitutional group.

• The Korean Journal of Community Living Science
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• v.16 no.1
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• pp.149-163
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• 2005

Family has emerged as a key concept for health, and it has been identified as one of the most important conditions. The relationship between health habit and its management is different depending on family. The odd pair family, mostly rural lower income class, worry to have poor health because of no spouse and small family size. One thousand eight hundred and seventy(1870) subjects were collected in 9 provinces through the sampling of Probability Proportional to Size (PPS). Questionnaire method was conducted on health checking, bath states, alcohol consumption, cigarette smoking, and the prevalence of farmer's health related problems. The main results were as follows: 1) The characteristics of odd pair families are that the head of household is female(77% ), the size of family is small(1.76 persons), the education level is low(7.5 years for male, 3.1 years for female) and the age group is old (male: 89.78 year old, female: 73.69 year old). 2) For the odd pair family, the frequency of health checking is quite low with one or two times per year(l0.2%) and the rate of no-health checking is much higher(35.8%) .3) Bathing utility is not available 29.6% of the odd pair family and only cold water is supplied at home for the 11.5 % of them. However, for the paired family, 9.8 % of them has no bathing utility and the rate of the family supplied with only cold water is just 7.9%. 4) The bathing frequency score of odd pair family is l.74points for male and 1.25 points for female. 5) The rate of smoking habits for odd pair family is 68.5 % and specially it is 7.6% for female, which is higher comparing with that of pair family. 6) The smoking frequency score of odd pair family is 1.57 points. 7) Alcohol drinking frequency score of odd pair family is 1.79 points for male, and 3.24points for female. 8) Farmers' syndrome(FS) revealed 38.7% of odd pair family and it is lower than that of pair family(57.3%). Special pain of FS was huckle bone and muscle(28.4%) and articular pain(24.l %). The pain rate of huckle bone and muscle(43.l %) and articular pain(33.5%) were higher in a year in odd pair family were lower than those of pair family: farming machine caused accidents(6.5%) and pesticide poisoning(5.7%). l0) The odd pair family use more frequently medical clinic or public health center for the treatment of FS(74.7%) and pesticide poisoning(62.5%) than the pair family for FS(69.0%) and for pesticide poisoning(.53.6%). The score of FS treatment is 5.70 points for odd pair family and it is not significantly different from 5.62 points of the paired family. The result of pesticide poisoning treatment score is as same as that of FS.