• The Journal of Engineering Geology
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• v.15 no.3
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• pp.257-268
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• 2005

In situ rock mass is generally heterogeneous and discontinuous, with varying degrees of strength along the planes of weakness. The planes of weakness such as joints, faults, cracks and bedding planes, control the strength and deformation characteristics of the rock mass. Subsequently, the stability of underground opening depends upon the spatial distribution of discontinuities and their mechanical properties in relation with geometrical shape of openins as well as the mechanical properties of intact rock materials. Understanding the behaviour of a discontinuous rock mass remains a key issue for improving excavation design in hiかy stressed environments. Although recent advances in rock mechanics have provided guidelines for the design of underground opening in isotropic rock mass, prediction and control of deformation in discontinuous rock masses are still unclear. In this study, parametric study was performed to investigate the plastic zone size, stress distribution and deformation behavior around underground opening in a discontinuous rock mass using a continuum joint model. The solutions were obtained by an elasto-plastic finite difference analysis, employing the Mohr-Coulomb failure criteria. Non-associated flow rule and perfectly plastic material behavior are also assumed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.2
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• pp.102-105
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• 2009

The accelerated life time test of the MLCCs with different $BaTiO_3$ particle sizes were conducted at $150^{\circ}C$, 75 V condition and the effect of $BaTiO_3$ particle size on the breakdown voltage and degradation characteristics of MLCCs was investigated. The MLCCs were prepared by using the $BaTiO_3$ particles having the size of $0.525{\mu}m$, $0.555{\mu}m$, $0.580{\mu}m$ and Ni-electrode, respectively. The MLCCs which have the particle size of $0.525{\mu}m$, $0.555{\mu}m$, and $0.580{\mu}m$, respectively were confirmed to meet the standard requirements of X5R(change capacitance within ${\pm}15%$ at $-55{\sim}85^{\circ}C$) by TCC(Temperature Coefficient of Capacitance). The effect of the $BaTiO_3$ particle size on the insulation resistance behavior of MLCCs was confirmed by BDV(Breakdown Voltage) measurements and the cause and degree of degradation of MLCCs were characterized by XPS analysis after the accelerated life test. The MLCCs with $0.525{\mu}m-BaTiO_3$ showed better insulation resistance and BDV characteristics compare to other MLCCs and XPS analysis revealed that the MLCCs degradation is caused by the NiO peak and $BaTiO_3$ peak decrease.

• Journal of the Korea Concrete Institute
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• v.23 no.2
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• pp.135-144
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• 2011

Recently, researches about fiber reinforced polymer (FRP) which has excellent durability, corrosion resistance, and tensile strength as a substitution material to steel tendon have been actively pursued. This study is performed to examine FRP tendon used prestressed beam's safety under service load. The specimen was a prestressed concrete beam with internal bonded FRP tendon. In order to compare the member fatigue capacity, a control specimen of a prestressed concrete beam with ordinary steel tendon was tested. A fatigue load was applied at a load range of 60%, 70%, and 80% of the 40% ultimate load, which was obtained though a static test. The fatigue load was applied as a 1~3 Hz sine wave with 4 point loading setup. Fatigue load with maximum 1 million cycles was applied. The specimen applied with a load ranging between 40~60% did not show a fatigue failure until 1 million cycles. However, it was found that horizontal cracks in the direction of tendons were found and bond force between the tendon and concrete was degraded as the load cycles increased. This fatigue study showed that the prestressed concrete beam using FRP tendon was safe under a fatigue load within a service load range. Fatigue strength of the specimen with FRP and steel tendon after 1 million cycles was 69.2% and 59.8% of the prestressed concrete beam's static strength, respectively.

• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.339-347
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• 2002

An in-situ experiment was performed to evaluate the pullout resistance capacity of chains which is used as a reinforcement of reinforced earth wall. It was also considered that chain was combined with a bar or L-type steel angle by the transverse reinforcement member in the experiment. About 80 pullout tests were peformed with varying the lengths of chain(2.0m, 2.5m, and 3.0m), the combination of each transverse members(chain only, chain＋bar, or chain＋angle), and the vertical placement of reinforcements. In the case that uses a chain only and a chain combined with bar, the maximum displacement was about 150mm and load continuously increased to the ultimate tensile strength of chain, and then tension failure of chains occurred. But in the case of a chain combined with angle, the displacement decreased to about 100mm and so it was expected that this combination can constrain the displacement of chain. On the other hand, comparing the yielding pullout load measured in the field to that calculated by theoretical equation, it is shown that measured values are 1.2~3.0 times greater than those of calculated values according to the length of chain, normal vertical stress, and the combination of chain with transverse members. However, the difference in the increment of yielding pullout load between bar and angle is not clear but it appears almost the same increment. It is expected that chain can be safely used as reinforcements of reinforced earth wall, although a theoretical estimation of the pullout resistance capability of chain is too conservative.

• The Korean Journal of Food And Nutrition
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• v.17 no.2
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• pp.163-170
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• 2004

Effect of several factors for Preparation of whole egg gel (WEG) on texture and color of WEG were investigated in this study. The factors studied were amount of water addition, heating temperature and time, pH and NaCl. The whole egg gel was prepared by mixing of whole egg and steaming at 100$^{\circ}C$ for 7 min followed by cooling at 22$^{\circ}C$ for 90 min. The results showed that the increase in water addition decreased significantly with viscosity values of whole egg solution (WES) and the addition of more than 50％ water resulted in a significant decrease in the stress at failure (SF) and the hardness of WEG. The color a and b values of WES decreased and the value of WEG also decreased significantly in negative range. The increase in heating temperature decreased the coagulation time and increased in SF while SF decreased. Addition of NaCl up to 1.3％ resulted a significant increase in SF and hardness and a little changes in color of WEG. As the pH of WES changed from 4.0 to 10.0, the viscosity of WES was minimal and SF and hardness were maximal at pH 6.0. The L and b values of WEG were significantly reduced at higher pH values of 8.0.

• Journal of Korean Society of Steel Construction
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• v.21 no.5
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• pp.505-514
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• 2009

This paper describes the structural behavior and the ultimate strengths of circular hollow steel (CHS) sections based on a series of compression tests. The ultimate strengths of CHS section columns are mainly dependent on both diameter-thickness ratio and column slenderness ratio. For the CHS sections with a high diameter-thickness ratio, an elastic or an inelastic local buckling may occur prior to the overall buckling, and it may decrease the column strength. Test sections were fabricated from SM400 steel plate of 2.8 mm and 3.2 mm in thickness and were tested to failure. The diameter-thickness ratios of the test sections ranged from 45 to 170 to investigate the effect of local buckling on the column strength. The compression tests indicated that the CHS sections of lower diameter-thickness ratio than the yield limit in the current design specifications showed an inelastic local buckling and a significant post-buckling strength in the local mode. Their ultimate stresses were larger than the nominal yield stress. It was known that the allowable stresses of the sections predicted by the Korean Highway Bridge Design Specifications (2005) were too conservative in comparison with test results. The Direct Strength Method which was newly developed was calibrated for application to the CHS sections by the experimental and numerical results. The Direct Strength Method proposed can predict properly the ultimate strength of CHS section columns whether a local buckling and an overall buckling occur nearly simultaneously or not.

• Journal of Chest Surgery
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• v.20 no.1
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• pp.112-127
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• 1987

Myasthenia gravis is a neuromuscular transmission function disorder characterized by fatigue and weakness of voluntary muscles. This muscular weakness is intensified by activity and stress, and improved by the use of anticholinesterase compounds. It was initially described by Erb in 1879 and later named myasthenia gravis by Jolly in 1895. Although the pathogenesis is Known to be an autoimmune related reduction in the number of available acetylcholine receptors at neuromuscular junctions, the role of thymus in myasthenia gravis is still unclear and under investigation. Thymectomy in the management of myasthenia gravis has become increasingly important since Dr. Blalock observed in 1939 that some patients with thymic tumors and myasthenia gravis improved following thymectomy. A clinical study of 102 cases of myasthenia gravis was performed at Yonsei University College of Medicine. Seoul, Korea from Jan. 1976 to Jun. 1986. In order to determine which factors are of prognostic significance, attention is focused upon pre-operative patient evaluation, problems in operative and post-operative care, and long-term follow-up observations. The results were as follows: 1. The sex distribution was 67 females and 35 males, the mean age of onset was 28.95*1.69 years, and the maximal incidence occurred between 21 and 40 years of age [56 cases: 54.9%]. 2. Clinical manifestations of ocular symptoms were seen to 70 patients [68.6%] extremities weakness in 33 [32.3%], bulbar weakness in 29 [28.4%], and dyspnea in 13 [12.7%]. 3. Study cases more than two thirds were classified as mild types [MG 1 and MG 11A] and 6 cases as grave [MG 1V] based on the modified Osserman`s classification system, 4. Thymectomy was performed in 19 cases which presented in severe myasthenia symptoms and showed no improvement with cholinergic drugs. Histologic examination of the excised thymus glands revealed no abnormalities in 4 cases, thymic hyperplasia in 5, benign thymoma in 5, and malignant thymoma in 5. 5. Immediate post-operative complications included 2 cases of pneumothorax which were treated by tube thoracostomies, there was no operative mortality. 6. The response to cholinergic drugs in 36 cases younger than 20 years old and in 27 cases older than 40 years was relatively poor, while that in 35 cases between the ages of 21 and 40 years old was good. 7. Thirty of 39 cases in groups IIB, III & IV improved markedly with medical or surgical management while only 16 of 59 cases in the mild groups [I and IIA] improved, almost all surgical cases improved in all categories. 8. There were 5 deaths. occurring between 7 months and 3 years 3 months of treatment of myasthenia gravis. The causes of death were myasthenic crisis in 2 cases, respiratory failure due to candidiasis & radiation pneumonitis in one case, cerebral hemorrhage due to high blood pressure in two case.

• Korean Journal of Health Education and Promotion
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• v.16 no.1
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• pp.149-166
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• 1999

Self-care and the performance of their own role might be important for the prevention of complications and improvement of quality of life in hemodialysis patients with chronic renal failure(CRF). To improve well-being and quality of life for the patients, the author estimated the level of self-care and associating factors through a questionnaire. The information was composed of the knowledge for hemodialysis and renal disease, the level of self-care, health belief, supports from the family, disease-related stresses, personal characteristics, medical history, relationships with medical personnel, etc. The data was gathered from 126 hemodialysis patients who were undergoing hemodialysis in one university hospital and five hospitals in Kyungsangnam-Do area from December 1997 to January 1998, and was analyzed by PC SAS program(version 6.12) with the level of significance($\alpha$=0.05). The mean age of subjects was 47.0$\pm$13.5years with no significant difference in gender distribution. The mean duration of hemodialysis was 39.0 months, and their frequencies of hemodialysis were more than three times per week(77.0%). Only 21.4% had the specific education on hemodialysis and CRF. In the level which was expressed as the score out of 100, the mean of knowledge was 90.7$\pm$9.1 and the mean of self-care was 73.9$\pm$12.7, that means, they only partially carried their knowledge into practice. They showed a significant correlation between knowledge and health belief($\gamma$=0.282); self-care and health belief($\gamma$=0.357), family supports and knowledge($\gamma$=0.221), self-care($\gamma$=0.402), health belief($\gamma$=0.431); and health belief and stress($\gamma$=-0.361). Age, religion, marrital status, education, and relationships with medical personnel showed positive correlations, and smoking showed negative correlation with self-care. In the multiple regression with the level of self-care as dependent variable, and each of the characeristics as independent variables, supports from the family($\beta$=6.615=0.158), the experience of disease specific education($\beta$=4.959), relationships with medical personnel($\beta$=6.615), current smoking($\beta$=-6.986), and current drinking ($\beta$=-7.095) were detected as significant factors. The value of R-square was 34%. In summary, to promote the level self-care and to improve the well beings and Quality of life for the hemodialysis patients, it would be emphasized that they terminate smoking and drinking, and it would be recommended that the education programs and supports from the family be strengthened. And, because there was a considerable difference between the level of knowledge and self-care, it would also be emphasized to propose the education programs which focused on execution. In addition to that, there is a need to improve relationships between the patients and medical personnel through positive changes in the attitudes of the medical personnel.

• Journal of the Korea Concrete Institute
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• v.19 no.5
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• pp.623-630
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• 2007

Grouting materials are used for the unification of superstructural and substructural body like bridge seat (shoe) or machinery pedestal and e.t.c by filling their intercalary voids. Accordingly, grouting materials have been developed and used mainly with products of high strength because those materials are constructed specially in a part receiving large or impact load. In this situation, the structural body constructed by grouting materials with high stiffness-centered (caused by high strength) products is apt to cause brittle failure when receiving over a limit stress and to cause cracks according to cumulative fatigue by continuous and cyclic load. In addition, grouting materials are apt to cause cracks by using too much rapid hardening agents that give rise to high heat of hydration to maintain high strength at early age. In this study, to overcome these problems, cement type grouting materials including powder of waste tire and resin as elastic materials which aim to be more stable construction and to be improvement of mother-body's unification are developed and endowed with properties of high toughness and high durability add to existing properties of high flowability, non-shrinkage and high strength. Besides, this study contribute to of for green construction materials for being possible recycling industrial waste like waste tire and flyash. On the whole, seven type mixing conditions are tested and investigated to choose the best mixing condition.

• Journal of the Korea Concrete Institute
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• v.26 no.4
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• pp.421-428
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• 2014

This paper describes the experimental results of insulated concrete sandwich wall panels (CSWP) with corrugated glass fiber-reinforced polymer (GFRP) shear connectors under in-plane shear loading. Corrugated GFRP shear connectors were used to improve the thermal property of insulated CSWP and to achieve composite action between the interior and exterior concrete wall panels. Test specimens were consist of three concrete panels with two insulation layers between concrete panels and middle concrete panels was loaded in the direction of gravity. To evaluate the effects of insulation types (extruded polystyrene, XPSS and expanded polystyrene, EPS), shear connector pitch (300 and 400 mm) and width (10 and 15 mm) on in-plane shear behavior of insulted CSWP, failure mode and shear flow-average relative slip relationship of specimens were investigated. Test results indicate that the bond stress between concrete panel and insulation is considerable initially. Especially in case of insulated CSWP without shear connector, initial stiffness of CSWP with XPSS is superior to that of CSWP with EPS. The shear connector's contribution to in-plane shear performance of insulated CSWP depends on the type of insulation.