• The korean journal of orthodontics
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• v.31 no.1 s.84
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• pp.25-38
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• 2001

The purpose of this study was to compare the force, the displacement and the stress distribution on the maxillary first molars altered by the application of various asymmetric head-gear. For this study, the finite element models of unilateral Cl II maxillary dental arch was made. Also, the finite element models of asymmetric face-bow was made. Three types of asymmetric face-bow were made : each of the right side 15mm, 25mm and 35mm shorter than the left side. We compared the forces, the displacement and the distribution of stress that were generated by application of various asymmetric head-gear, The results were as follows. 1. The total forces that both maxillary first molars received were similar in all groups. But the forces that mesially positioned tooth received were increased as the length of the outer-bow shortened, and the forces that normally positioned tooth received were decreased as the length of the outer-bow shortened. 2. In lateral force comparison, the buccal forces that normally positioned tooth received were increased as the length of the outer-bow shortened, and the buccal fortes that mesially positioned tooth received were decreased as the length of the outer-bow shortened. Though the net lateral force moved to the buccal side of normally positioned tooth as the length of the outer-bow shortened, both maxillary first molars received the buccal force. That showed 'Avchiai Expansion Effect' 3. The distal forces, the extrusion forces and the magnitudes of the crown distal tipping that mesially positioned tooth received were increased as the length of the outer-bow shortened, and the forces that normally positioned tooth received were decreased as the length of the outer-bow was shortened. 4. The magnitude of the distal-in rotation that normally positioned tooth received were increased as the length of the outer-bow was shortened. But, mesially positioned tooth show two different results. For the outer-bow 15mm shortened, mesially positioned tooth showed the distal-in rotation, hut for the outer-bow 25mm and 35mn shortened, mesially positioned tooth showed the distal-out rotation. Thus, the turning point exists between 15mm and 25mm. 5. This study of the initial stress distribution of the periodontal ligament at slightly inferior of the furcation area revealed that the compressive stress in the distobuccal root of the normally positioned tooth moved from the palatal side to the distal side and the buccal side successively as the length of the outer-bow shortened. 6. This study of the initial stress distribution of the periodontal ligament at slightly inferior of the furcation area revealed that the magnitudes of stress were altered but the total stress distributions were not altered in the mesiobuccal root and the palatal root of normally positioned tooth, and also three roots of mesially positioned tooth as the length of the outer-bow shortened.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.1
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• pp.31-48
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• 2019

The artificial ground freezing (AGF) method is a groundwater cutoff and/or ground reinforcement method suitable for constructing underground structures in soft ground and urban areas. The AGF method conducts a freezing process by employing a refrigerant circulating through a set of embedded freezing pipes to form frozen walls serving as excavation supports and/or cutoff walls. However, thermal expansion of the pore water during freezing may cause excessive deformation of the ground. On the other hand, as the frozen soil is thawed after completion of the construction, mechanical characteristics of the thawed soil are changed due to the plastic deformation of the ground and the rearrangement of soil fabric. This paper performed a field experiment to evaluate the freezing rate of marine clay in the application of the AGF method. The field experiment was carried out by circulating liquid nitrogen, which is a cryogenic refrigerant, through one freezing pipe installed at a depth of 3.2 m in the ground. Also, a piezo-cone penetration test (CPTu) and a lateral load test (LLT) were performed on the marine clay before and after application of the AGF method to evaluate a change in strength and stiffness of it, which was induced by freezing-thawing. The experimental results indicate that about 11.9 tons of liquid nitrogen were consumed for 3.5 days to form a cylindrical frozen body with a volume of about $2.12m^3$. In addition, the strength and stiffness of the ground were reduced by 48.5% and 22.7%, respectively, after a freezing-thawing cycle.

• Magazine of the Korea Concrete Institute
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• v.7 no.3
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• pp.199-210
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• 1995

We could say that the concrete filled steel tube structure is superior in the vlew of various structure properties as to promote improvement of structural capacity to dtmonstrate heterogeneous material properties interdependently. The compressive strength is increased by putting to tri axial stress because lateral expansion of concrete 1s confined by the steel tube, when concrete conflned by steel tube fall under centric axial load. Also, it have an advantage that decreasr of load carrying capacity 1s small, not occuring section deficiency due to protect falling piienornonon by co~nprrssion fallurc of concrete. So this study investigated for structural behaviors yroprrtiex of concwir. confined by steel tube throughout a series of experlmerit with kcy parxncter, such as diameter-to-thickness(D / t) ratio, strength of concrete as a study on properties of structural behaviors of confined concrete confined by circular steel tube( tri axial stress). Frorn the expcrment results, the obtained results, are surnrnarised as foliow. (1) The restraint effect of concrete by steel tube was presented significantly as the D /t ratio of steel tube and the strength of filled concrete decrease, and the confined concrete by circular steel tube was increased respectively twice as much as 4-7 in deformation capacity at the ultimate strength ,compared with those of non-confined concrete, so expected to increase flexible effect of concrete. (2) The emprical formula to predict the ultimate capacity of confined concrete by steel tube and concrete filled steel tube column using restraint coefficient of concrete were proposed.

• Journal of the Korean Geosynthetics Society
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• v.17 no.3
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• pp.19-32
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• 2018

Gravel Compaction Pile (GCP) method is currently being designed and constructed by empirical method because quantitative design method has not been developed, leading to various types of and frequent destruction such as expansion failure and shear failure and difficulties in establishing clear cause and developing measure to prevent destruction. In addition, despite the difference with domestic construction equipment and material characteristics, the methods applied to the overseas ground is applied to the domestic as it is, leading to remarkable difference between applied values and measured values in variables such as bearing capacity and the settlement amount. The purpose of this study was, therefore, to propose a reasonable and safe design method of GCP method by analyzing the settlement and stress behavior characteristics according to ground strength change under GCP method applied to domestic clay ground. For the purpose, settlement amount of composite ground, stress concentration ratio, and maximum horizontal displacement and expected location of GCP were analyzed using ABAQUS. The results of analysis showed that the settlement and Settlement reduction rate of composite ground decreased by more than 60% under replacement ratio of 30% or more, that the maximum horizontal displacement of GCP occurred at the depth 2.6 times pile diameter, and that the difference in horizontal displacement is slight under replacement ratio of 30%.

• Journal of Chest Surgery
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• v.29 no.4
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• pp.403-407
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• 1996

One hundred and twenty three patients underwent 137 thoracostomies for spontaneous pneumothorax in the department of Thoracic and Cardiovascular Surgery, Gyeongsang National University from January 1987 to December 1994. There were 118 men and 6 women and average age was )2.4 years. The two most common surgical Indications were recurrent pneumothorax and continuous air leakage. Other indications were visible bullae on simple X-ray, previous contralateral pneumothorax, incomplete expansion of the lung, and bilateral pneumothoraces. Methods of thoracotomy were subaxillary thoracotomy in 82 cases, lateral minithoracotomy in 12 cases and posterolateral thoracotomy in 43 cases. Operation time was 63.0 $\pm$ 30.8, 98.3 $\pm$ 37.9, 186.9 $\pm$ 87.9 minutes respectively, and postoperative chest tube keeping time was 5.2 $\pm$ 4.1 days in subaxillary thoracotomy, 6.2 $\pm$ 5.0 days in minithoracotomy and 10.0 $\pm$ 5.8 days in posterolateral thoracotomy Bullae were present mostly at the apex in spontaneous and tuberculous pneumothorax comparred to the cases of chronic obstructive or emphysematous lung disease, where there were no redilection of presence of bullae (p< 0.01). Operative procedures were wedge resection, bullae obliteration and lobectomy. Postoperative complications were continuous air leakage, bleeding, brachial plexus injury, empyema, and wound infection, but all the complications were cured by the time of discharge. There was no mortality.

• The Korean Journal of Malacology
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• v.27 no.3
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• pp.181-190
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• 2011

This study was investigated to find out the change of reproductive and histological biomarkers of Ruditapes philippinarum exposed to nonylphenol (NP). Experimental period was 16 weeks. Experimental groups were composed of one control condition and three NP exposure conditions (0.05, 0.1, $0.2 mg\;NP\;L^{-1}$). Gonad index was higher in exposure group than control in female and higher in control than exposure group in male. Intersexuality in the NP exposure group was 14.56% with male exhibiting higher ratio than female. Histological analysis of organ system illustrated expansion of hemolymph sinus, loss of striated border of inner epidermis and degeneration of mucous cell in the mantle. In the gill partially disappearance of frontal and lateral cilia, degeneration of mucous cell were observed. Also, hyperplasia of epithelium and disappearance of striated border were observed in the foot. As the concentration of NP increased, the accumulation of lipofuscin increased in the digestive gland. The results of this study suggest that NP induces reduction of survival rate, histopathology and intersex of R. philippinarum. Furthermore, it is indentified that NP functions as an estrogenic effector on the reproduction of R. philippinarum.

• Geomechanics and Engineering
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• v.19 no.5
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• pp.421-434
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• 2019

It is of great significance to study the mechanical properties and failure mechanism of the defected rock for geological engineering. The defected sandstone modeling with power-law distribution of pre-cracks was built in this paper by Particle Flow Code software. Then the mechanical properties of sandstone and the corresponding failure process were meticulously analyzed by changing the power-law index (PLI) and the number of pre-cracks (NPC). The results show that (1) With the increase of the PLI, the proportion of prefabricated long cracks gradually decreases. (2) When the NPC is the same, the uniaxial compressive strength (UCS) of sandstone increases with the PLI; while when the PLI is the same, the UCS decreases with the NPC. (3) The damage model of rock strength is established based on the Mori-Tanaka method, which can be used to better describe the strength evolution of damaged rock. (4) The failure mode of the specimen is closely related to the total length of the pre-crack. As the total length of the pre-crack increases, the failure intensity of the specimen gradually becomes weaker. In addition, for the specimens with the total pre-crack length between 0.2-0.55 m, significant lateral expansion occurred during their failure process. (5) For the specimens with smaller PLI in the pre-peak loading process, the concentration of the force field inside is more serious than that of the specimens with larger PLI.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.37 no.1
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• pp.81-85
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• 2011

The uvulopalatal flap (UPF) technique is a modification of uvulopalatopharyngoplasty (UPPP) for the surgical treatment of obstructive sleep apnea. In the UPF technique, an uvulopalatal flap is fabricated and sutured to the residual mucosa of the soft palate to expand the antero-posterior dimensions of the oropharyngeal inlet. In the extended uvulopalatal flap (EUPF) technique, an incision at the tonsillar fossa is added to the classical UPF technique followed by the removal of mucosa and submucosal adipose tissue for additional expansion of the lateral dimension. The EUPF technique is more conservative and reversible than UPPP. Therefore, complications, such as velopharyngeal insufficiency, dysphagia, dryness, nasopharyngeal stenosis and postoperative pain, are reduced. In the following case report, the patient was diagnosed with obstructive sleep apnea and treated with the EUPF technique. The patient's total respiratory disturbance events per hour (RDI) was decreased to 15.4, the $O_2$ saturation during the sleep was increased, and the excessive daytime sleepiness had disappeared after the surgery without complications. The authors report this case with a review of the relevant literature.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.6
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• pp.21-30
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• 2013

As increasing number of large-size earthquake, the social interest of seismic retrofitting of RC structure is growing. Especially, the RC columns that are not reflected seismic design can not resist lateral loads by the earthquake. The brittle fracture of Non-seismic designed columns lead to full collapse of the building. Thus, the emergency columns reinforcement method is needed. That have a fast construction time, do not cause damage to the column. In the past, cross-sectional expansion method, a steel plate reinforcing method is applied mainly, but in recent years, carbon fiber sheet taking advantage of FRP (Fiber Reinforced Polymer) is widely used. In this study, retrofitting effect of seismic performance of FRP seismic reinforcement, which is possible to emergency construction, was examined. Reinforced concrete specimens were constructed to experimental study. The seismic performence of specimes retrifitted with FRP seismic reinforcement were evaluated. As a result, the seismic performance of specimen reinforced with FRP seismic reinforcement has been improved.

• Journal of Periodontal and Implant Science
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• v.31 no.4
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• pp.669-687
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• 2001

On the basis of the evidence that electrical stimulation could promote healing and regeneration of bone, this study was performed to investigate the effects of electrical stimulation on rat extraction socket, and to evaluate the potential of clinical application of electrical stimulation. Forty rats were used and divided into control groups(l0)and the experimental groups(30) in this study. The maxillary 1st molar were extracted in both groups. In experimental group, electrical stimulation was given at the current intensity of lmA(Test-1), l0mA(Test-2), 25mA(Test-3) each day. At 1,3,5,7 days after the tooth extraction, rats in both groups were serially sacrificed. And the specimens were prepared with Hematoxylin-Eosin stain for the light microscopic evaluation. The results of this study were as follows; 1. At 1 day after the extraction, the periodontal ligament was found in the extraction socket wall. The formation of blood clot with dense infiltration of inflammatory cells in control group and there were less inflammatory cells in test group. 2. At 3 day after the extraction, the cells and collagen of the periodontal ligament were so actively proliferated and synthesized that invaded into the connective tissue of the extraction sockets in the control group. There were the formation of new bone in the basal & lateral portion of socket wall in test -2 and -3. 3. At 5 days after the extraction, there were no formation of new bone in control group. But the more electrical stimulation was applied, the more formation of new bone in test group. 4. At 7 days after the extraction, the extraction sockets were almost filled with trabecular bone in each group. Bone maturarity was remarkable in test-3. 5. The electrical stimulation at l0mA and 25mA was more effective in the bone formation at 5 and 7 days after the extraction. From the above results, electrical stimulation could promote the extraction socket wound healing, and be utilized in the clinical application of the residual ridge expansion.