• Journal of Korean Tunnelling and Underground Space Association
• /
• v.25 no.6
• /
• pp.541-554
• /
• 2023

The utilization of underground spaces in relation to tunnels and energy/waste storage is on the rise. To ensure the stability of underground spaces, it is crucial to reinforce rock fractures and discontinuities. Discontinuities, such as joints, can weaken the strength of the rock and lead to groundwater inflow into underground spaces. In order to enhance the strength and stability of the area around these discontinuities, rock grouting techniques are employed. However, during rock grouting, it is impossible to visually confirm whether the grouting material is being smoothly injected as intended. Without proper injection, the expected increases in strength, durability, and degree of consolidation may not be achieved. Therefore, it is necessary to predict in advance whether the grouting material is being injected as designed. In this study, we aimed to assess the injection performance based on injection variables such as the water/cement mixture ratio, injection pressure, and injection flow using UDEC (Universal Distinct Element Code) numerical program. Additionally, numerical results were validated by the lab experiment. The results of this study are expected to help optimize variables such as injection material properties, injection time, and pump pressure in the grouting design in the field.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.39 no.6
• /
• pp.779-788
• /
• 2019

The compaction grouting method is one of the conventional ground improvement methods, which consolidates and compacts the surrounding ground through the injection of grout materials with low mobility. Injecting the grout into the ground can improve the soil properties, as well as form a composite of soil-grout columns. However, the conventional grout pumping is not applicable to handle multiple injection holes at the same time, which may diminish its constructability when the construction time is not enough. This paper proposes a simultaneous multiple compaction-grouting method using a new pump system developed to cover up simultaneously three injection holes at a time. Field injection tests with a single injection hole and with triangular arrangement of injection holes were conducted to evaluate the applicability of the proposed method to soft clay ground. In addition, a series of standard penetration tests (SPTs) were performed to assess the efficiency of each arrangement in improving the soft ground. It is noted from the in-situ test results that the interval distances between injection holes and the elapse time for ground stabilization are the crucial factors governing the applicability of the simultaneous multiple compaction-grouting method to improve the soft clay ground.

• Environmental and Resource Economics Review
• /
• v.24 no.2
• /
• pp.311-342
• /
• 2015

We evaluate two main rationales of massive policy intervention of Lee Administration in the Korean transportation fuel market: high market share of domestic refineries, perceived by the Administration as the result of high market concentration, and asymmetry in price adjustment, perceived as the result of collusion. Domestic refineries, huge in capacity and located at seaports, maintain international competitiveness in price. Considering market openness offering preferential treatment to importers, they set domestic prices competitively on the basis of MOPS prices. Yet, the price competitiveness of domestic refineries is so high that they are able to sustain high market share. We confirm that the Korean before-tax consumer prices of gasoline and diesel are lower than Japan's and the weighted averages of 27 EU countries by as much as 159KRW and 21KRW per liter in the case of gasoline and 170KRW and 63KRW in the case of diesel. Price asymmetry is caused by diverse economic and managerial reasons and, as FTC (2005) states, price asymmetry does not immediately imply exercise of market power or collusion. We analyzed price asymmetry in Korea, Japan and 14 EU countries, and found asymmetry in Korea and 11 EU countries in the case of gasoline and in Korea and 8 EU countries in the case of diesel.

• Applied Chemistry for Engineering
• /
• v.9 no.1
• /
• pp.82-88
• /
• 1998

In an effort to obtain high efficiency in air cooled absorption heat pump, a new working fluid has developed with the addition of $LiNO_3$ and LiCl to the conventional solution of $LiBr-H_2O$. The solubility and vapor pressure of the multicomponent salts solution developed in this work were measured and compared with the results of $LiBr-H_2O$ solution. It was observed that there exists an optimal molar ratio of the inorganic salts in terms of solubility. The molar ratio of LiBr, $LiNO_3$ and LiCl was found to be about 5:1 in the $LiBr-LiNO_3$ mixture, and in the case of $LiBr-LiNO_3-LiCl$ mixture, the molar ratio of LiBr, $LiNO_3$ and LiCl was found to be around 5:1:2. The vapor pressure of the multicomponent salts solution of the optimal molar ratio was increased with adding $LiNO_3$, while decreased with adding LiCl.

• Journal of the Korean Society of School Health
• /
• v.14 no.1
• /
• pp.115-130
• /
• 2001

Dieting behaviors prevail among most women and are highly increasing among female adolescents who don't have to lose weight. The dieting behaviors of normal or low weight groups are highly related to the negative impact of health risk behaviors. We need a strategy for intervening in the dieting behaviors of relevant groups. With this background, a study was conducted to examine the current situation of dieting behaviors and related factors in middle school girls, and to provide guidelines for the relevant dieting group. This survey was carried out by self-questionnaires passed out to 901 middle school girls from 3 middle schools in Seoul. Data were collected from April 10th, 2000 to April 17th, 2000 and 794 respondents' data were finally selected for analysis. The instruments of this study were Shin's scale for effects of mass-media, Birleson's depression self-rating scale translated by shim, Rosenberg's self-esteem scale, Smilkstein's Family APGAR score translated by Yoon, Kim's school-related adjustment scale. The credibility of instruments was 0.41~0.83 in the pilot study and 0.70~0.86 in the main study. The summary of results was as follows: 1. The general characteristics of respondents were analyzed. In comparison of grade and dieting behaviors, the subjects of the group perceived that their body image was obeser than their real body image and their ideal body image was slenderer than their current body image. A dieter's body image was seriously distorted. 2. The dieting behaviors were analyzed. The Subjects' BMI was within the normal to low range -- they didn't have to lose weight. But actually 47.3% of the respondents were dieters. Their main dieting methods were exercise(71.8%), computer games(64.9%) such as DDR and pump, and intake reduction(64.1%). Most dieters were using desirable methods such as exercise and intake control. But unhealthy methods such as saunax, smoking and harmful drug-use were also used by a few dieters. The main reason for dieting was attractiveness. The chief resources of dieting methods were mass-media(67.8%), friends(64.3%), and parents & relatives(35.1%). Only a few subjects obtained the information from health professionals. While they were trying to lose weight, 42.1% of the subjects experienced side effects such as dizziness(45.0%), apathy(20.5%), appetite loss(18.5%), amenorrhea and the irregularity of the menstrual cycle(16.6%). 3. The relationship between dieting behaviors and factors was analyzed. Dieting behaviors were significantly related to the experience of menarche, the experience of dating with heterosexuals, perceived body image, self-esteem, depression, family's relationship, school instruction-related adjustment, school life-related adjustment, and the effect of mass-media. After that, the multiple logistic regression was used. The analysis revealed that dating, perceived body image, the experience of menarche and the effect of mass media were significant factors. In conclusion, strategies for preventing irrelevant dieting behaviors are urgently required to enhance female adolescents' ability to choose the right information from countless others and to recognize their optimum body image.

• Journal of Chest Surgery
• /
• v.9 no.2
• /
• pp.220-238
• /
• 1976

Six cases of congenital heart disease were operated on by means of cardiopulmonary bypass between December, 1975 and April, 1976. Two cases of ventricular septal defects (VSD), two cases of VSD, associated with ruptured aneurysm of sinus Valsalva, two cases of atrial septal defects (ASD) and one case of pulmonic stenosis with patent ductus arteriosus were operated. Sarns roller pumps and Bentley Temptrol oxygenators were used for extracorporeal circulation. Pump oxygenator was primed with Ringer's lactate solution, 5% dextrose in water, mannitol, and ACD blood. Flow rate ranged from 2.0 to $2.4L/M^2/min$. Bicarbonate was added to the oxygenator with estimated amount as 15 mEq/L/hr. Venous catheters were introduced into superior and inferior vena cava, and oxygenated blood was returned to the body through aortic cannula inserted into ascending aorta. Moderate hypothermia ($30^{\circ}C$) was induced by core cooling. Aorta was cross clamped for 15 minutes and released for 3 minutes, and repeated clamping when necessary. Atrial and ventricular septal efects were closed by direct sutures. Aneurysms of sinus Valsalva ruptured into the right ventricle were repaired through right ventriculotomy by d:rect closure with Dacron patch reinforcement. Cardiopulmonary bypass time varied from 66 to 209 minutes, and aorta cross clamping time ranged from 13 to 56 minutes. Postoperative bleeding was minimal except one case who needed for evacuation of substernal hematoma. Intra- and postoperative urinary output was satisfactory. Acid-base balance, partial pressure of $O_2$, electrolytes, and hematological changes during intra- and post-perfusion period remained at the acceptable ranges. No mortality was experienced.

• Child Health Nursing Research
• /
• v.3 no.1
• /
• pp.99-107
• /
• 1997

The subjects of the study were the 120 mothers who had children hospitalized in 6 hospitals in P city during the period from Feb. 1. to May 30. 1996. The purpose of the study are(1) the problems encountered when they carried out Home Care after discharge and (2) the degrees of demand that they had against Home Care Services. In order to investigate the purposes above-mentioned the researchers used the 55 items of Home Care services belonging to 10 areas selected by Korea Home-Care Association in 1994. The items were modified and supplemented to 4-point scale. The selected data were analyzed by SPSS : PC+ and the following results were derived. 1. The subjects payed great attention to 5 items such as 'pain control, OPD visits, diet-control problems' among the 15 sources of anxiety that they had against Home Care services after discharge. Especially, 'OPD visits and knowledge deficit' would to be overcome by the nursing activities of the Home Care Nurses. 2. The acknowledge level of the subjects to the Home Care Project that governmental plans to carry out was surveyed and found as under 50. 0% responded they heard about Home Care Nursing System. 60.8% said that they thought the system was 'very necessary' and 'somewhat necessary'. 65.0% said they would like to use the system. However, the acknowledge level of 50.0% is still low and is thought to need further national promotion and propagation. 3. The demand of the subjects against 55 Home Care Services was investigated and found as