• Journal of the Korea Concrete Institute
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• v.24 no.4
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• pp.399-406
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• 2012

Beam-column joints are generally recognized as the critical regions in the moment resisting reinforced concrete (RC) frames subjected to both lateral and vertical loads. As a result of severe lateral load such as seismic loading, the joint region is subjected to horizontal and vertical shear forces whose magnitudes are many times higher than in column and adjacent beam. Consequently, much larger bond and shear stresses are required to sustain these magnified forces. The critical deterioration of potential shear strength in the joint area should not occur until ductile capacity of adjacent beams reach the design demand. In this study, a method was provided to predict the deformability of reinforced concrete beam-column joints failing in shear after the plastic hinges developed at both ends of the adjacent beams. In order to verify the deformability estimated by the proposed method, an experimental study consisting of three joint specimens with varying tensile reinforcement ratios was carried out. The result between the observed and predicted behavior of the joints showed reasonably good agreement.

• Restorative Dentistry and Endodontics
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• v.21 no.1
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• pp.187-201
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• 1996

The purpose of this study was to evaluate the sealing ability of a calcium hydroxide plug treated with a bonding agent. Ninety extracted human anterior teeth and premolars with single canal were used in this study. Crowns were removed. the canal's were instrumented. and the roots were randomly divided into three groups of 30 each. In control group. a single apical seat was prepared with #60 K file 1mm short of the apex and the root canal was obturated with Gutta-percha and Sealapex by the lateral condensation method. In experimental group 1 and group 2. to prepare an apical isthmus of 1mm in length. the first apical seat was prepared with a #45 K file 1mm short of the anatomical apex and with a #60 K file 2mm short for the second apical seat. Dry calcium hydroxide powders were packed in the apical isthmus with a hand plugger and #60 K file and then. the root canal was obturated with Gutta-percha and Seal apex by the lateral condensation method. In experimental group 2. following an application of the bonding agent to the plug. the root canal was obturated in the same way. The teeth of each group were immersed in a 2% methylene blue dye solution. for 1, 2, and 4 weeks. The distance from the tip of the cone to the deepest penetration was measured using the Tool maker's microscope. The results were as follows : 1. The teeth having the calcium hydroxide plug treated with the dentin bonding agent (experimental group 2) showed the lowest leakage with 1.4705mm and the control group without apical plug(no apical isthmus) showed the highest leakage with 3.1735mm. 2. The control group without apical plug showed higher leakage than experimental group 1 having the calcium hydroxide plug treated without the dentin bonding agent(p>0.05). 3. The control group without apical plug and experimental group 1, having the calcium hydroxide plug treated without the dentin bonding agent. showed higher leakage than experimental group 2. having the calcium hydroxide plug treated with the dentin bonding agent(p<0.001). 4. The immersion time had no significant effect on the degree of leakage. In conclusion, the results showed that the calcium hydroxide plug treated with the dentin bonding agent could decrease the microleakage from the root apex effectively.

• Journal of Trauma and Injury
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• v.26 no.3
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• pp.163-169
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• 2013

Purpose: This study was conducted to confirm the anatomic conformity of the new periarticular locking plates designed by Zimmer on Korean adult bones and to identify the structures at risk during the application of these implants. Methods: The study was performed on the humerus, radius, and tibia of 10 adult cadavers(6 males and 4 females) procured from the cadaveric lab of our hospital. Anteroposterior (AP) and lateral X-rays were taken to confirm that the cadavers were free of any unusual lesions or anatomic variations. We used the 3.5-mm proximal humerus plate, 2.7-mm distal radius plate, 3.5- and 5.0-mm proximal tibia plates, and 3.5-mm distal tibia plate developed by Zimmer, Inc. (Zimmer periarticular locking plate). The longest plate from each group was used to confirm anatomical conformity. Standard approaches were used for each area, and soft tissue was retracted in order to pass the plate beneath the muscle. The position of the plate was confirmed using standard AP and lateral view X-rays. After this procedure had been completed, the region was dissected along the length of the implant to determine the conformity of the implant to bone and the penetrations of screws into the articular surface or violations of any vital structures, such as nerves, blood vessels, or tendons. Results: Excellent anatomical conformity was observed with Zimmer periarticular locking plates for Korean adults. The tibial nerve and the posterior tibial artery were found to be structures at risk when applying a distal tibial plate. Conclusion: Additional posterolateral fixation is recommended when dealing with cases of tibial plateau fracture when the fracture line extends to the posterolateral cortex. We recommend taking proper views using 10~15 degrees of internal rotation to ensure correct screw length and, thus, avoid penetration of vital structures and tendons.

• Restorative Dentistry and Endodontics
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• v.20 no.2
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• pp.463-486
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• 1995

The effect of moistening and air-drying of acid-conditioned dentin before priming on the formation of resin-dentin hybrid zone was investigated, Freshly extracted human molars were used and divided at random into 5 groups, Groups 1 - 3 consisted of specimens conditioned with 10 % phosphoric acid for 20 seconds; Group 1 served as a control in which the conditioned dentin was simply blot-dried with a damp facial tissue; Group 2 was air dried for 30 seconds ; Group 3 was air dried for 30 seconds and immediately remoistened for 10 seconds with air-water syringe. and then the specimen was blot-dried with a damp facial tissue. Groups 4-5 were not acid conditioned ; In group 4, the smear layer on the dentin was blot dried before primer placement; Group 5 was air dried only for 30 seconds, The acetone-based primer and bonding agent of All Bond 2 (Bisco. Inc., USA) and composite resin (Z-100, 3M Dental products, USA) were applied for acid conditioned dentin and non-conditioned dentin. The morphologic ultrastructure of resin-dentin hybrid zone was examined by the use of SEM and TEM. and the existence of inorganic material and analysis of Ca/P weight-percent ratio in the resin-dentin hybrid zone were revealed by the EDAX, The results were as follows : 1. In the moistened specimens from acid-conditioned groups, the resin penetrated about 3-$4{\mu}m$ into dentin and the denatured collagen smear layer was not present at the surface. The resin tag was formed to a thickeness of 3-$4{\mu}m$ at the upper part of dentinal tubule and compactively connected to each other by means of many lateral branching. 2. In the air-dried specimens from acid-conditioned groups, the resin penetrated about 2.0-$2.5\;{\mu}m$ into dentin and an upper thin black layer to a thickness of 30-35nm was identified between adhesive resin and demineralized collagen layer. The resin tag to have a diameter of $2.5{\mu}m$ was formed at the upper part of dentinal tubule. However the funnel shape of the tag was not notable compared to the moistened specimens. 3. In the remoistened specimens from acid conditioned groups, the resin penetrated about 2.0-$2.5{\mu}m$ into dentin and an upper black layer was not present. The resin tag at the upper part of dentinal tubule was formed less than $2{\mu}m$ and was weakly connected to each other by means of few lateral branching. 4. In the non-conditioned groups, the smear layer was formed to a thickness of $0.5{\mu}m$ at dentin surface. However, the resin-dentin hybrid zone was not identified by TEM. The evidence of resin penetration into intertubular and intratubular dentin did not show. 5. All the acid-conditioned groups showed that the detected calcium and phosphorus weight percent ratios at the $2{\mu}m$ upper portion from the resin-dentin interface into the resin were much higher than that at the $2{\mu}m$ lower portion from the resin-dentin interface to dentin. (P<0.01).

• Fire Science and Engineering
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• v.29 no.4
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• pp.67-72
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• 2015

A series of fire tests was conducted to examine the fire characteristics of flaming and smoldering combustion of engineered wood products, which have been widely used for furniture and finishing materials in buildings. The engineered wood products of MDF, plywood, and chipboard were ignited by a radiant cone heater with incident heat flux of $50kW/m^2$. During the fire test, key parameters representing the fire characteristics such as the heat release rate, yield rate of combustion product, and effective heat of combustion were quantified in terms of thickness. The tests show two peak points of HRRPUA due to lateral fire propagation in the initial stage, followed by later fire penetration through the specimen thickness. The mass loss rate of flaming combustion was 5 times higher than that of smoldering combustion, while the CO yield rate of smoldering combustion was 10 times higher than that of flaming combustion. This study can contribute to the understanding of fire behavior of wood combustibles and provide useful data for fire analysis.

• Journal of the Korean Geotechnical Society
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• v.18 no.1
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• pp.41-48
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• 2002

Anisotropy of stiffness, from extremely small strains to post-failure strains, of isotropically consolidated air-pluviated sands in plane strain compression was studied by using the newly developed instrumentation fur small strain measurements, Seven types of sand of world-wide origins were tested, which have been extensively used for research purposes. Stress-strain relationships for a wide range of strain from about 0.0001% to the peak were obtained by measuring axial and lateral strains locally free from the effects of bedding and membrane penetration errors at the specimen boundaries. The result showed that the relationship between the principal stress ratio and the principal strain increment ratio was constant, being rarely affected by the over-consolidation ratio and the confining pressure. Although in the small strain the anisotropy hardly affected the relationship between the principal stress ratio and the principal strain increment ratio, the K value around the peak varied according to the $\delta$ value. In general, Rowe\`s stress-dilatancy equation works fairly well from the small strain to the peak.

• Journal of the Korean Geotechnical Society
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• v.16 no.4
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• pp.95-105
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• 2000

Anisotropy of stiffiness, from extremely small strains to post-failure strains, of isotropically consolidated air-pulviated sands in plane strain compression was studied by using the newly developed instrumentation for small strain measurements. Seven types of sand of the world-wide origins were tested, which have been extensively used for research purposes. Stress-strain relationships for a wide range of strain from about 0.0001% to 10% were obtained with measuring axial and lateral strains locally free from the effects of bedding and membrane penetration errors at the specimen boundaries. It was found that the maximum shear modulus Gmax was irrespective of the angle $\delta$of the $\sigma$1 direction relative to the bedding plane. However, the normalized Gmax was varied with the types of sand. Furthermore, the dependency of the strain and stress level on the stiffness increased as decreased.

• Journal of the Korean Geotechnical Society
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• v.30 no.4
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• pp.101-106
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• 2014

The penetration testing provides 1 dimensional profiles of properties applicable to limited investigation areas, although N-value has been linked to a wide range of geotechnical design parameters based on empirical correlations. The nondestructive test using elastic waves is able to produce 2 or 3 dimensional property maps by inversion process with high efficiency in time and cost. As both N-value and elastic wave velocities share common dominant factors that include void ratio, degree of saturation, and in-situ effective stress, the correlation between the two properties has been empirically proposed by previous studies to assess engineering properties. This study presents the experimentally measured elastic wave velocities of Jumunjin sands under at-rest lateral displacement condition with varying the initial void ratio and degree of saturation. Results show that the stress condition predominantly influences the wave velocities whereas void ratio and saturation determine the stress-velocity tendency. The correlation among the dominant factors is proposed by multiple regression analysis with the discussion of relative impacts on parameters.

• Clinics in Shoulder and Elbow
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• v.8 no.2
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• pp.63-67
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• 2005

Osteochondritis dissecans is a common cause of lateral elbow pain in throwing athletes and gymnasts between the age of 10 and 15 years. The pain frequently is insidious and progressive in nature and is relieved with rest in most cases. Compressive forces at the radiocapitellar joint along with a tenuous blood supply to the region may play a role in the etiology of this condition. Treatment is directed according to presenting symptoms, radiographic findings and status of the involved segment. Surgical management involves either an excision of a loose lesion and removal of loose bodies or reattachment of an osteochondral fragment. The role of subchondral penetration of debridement of the defect after fragment excision is unclear. Whether to excise and debride or to fix an unstale fragment is a highly controversial topic. The clinician should recognize osteochondritis dissecans of the elbow as a potentially disabling condition where the prognosis for return to sport is guarded

• Restorative Dentistry and Endodontics
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• v.22 no.2
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• pp.596-608
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• 1997

The purpose of this study was to compare the apical leakage and adaptation to the dentinal wall of a glass ionomer root canal cement(Ketac-Endo) with those of AH-26 and Tubli-Seal. 102 single-rooted teeth were insrumented with step-back technique and randomly divided into four groups according to kinds of root canal cements: Ketac-Endo, AH-26, Tubli-Seal, and no root canal cement. Four experimental groups were as follows; Group 1 : Filling with gutta-percha and Ketac-Endo Group 2 : Filling with gutta-percha and AH-26 Group 3 : Filling with gutta-percha and Tubli-Seal Group 4 : Filling with gutta-percha without root canal cement All the specimens were obturated with lateral condensation technique, and stored in 100% humidity for 4 days. 20 teeth in each group were placed in centrifuge tube filled with India ink, and then centrifuged for 20 minutes at 3,000 rpm. And they were evaluated for linear dye leakage using a stereoscope and analyzed by one-way ANOVA. 22 teeth were split longitudinally and evaluated the adaptation to the dentinal wall using scanning electron microscope(4 teeth in each group) and stereoscope(2 teeth in 1, 2, 3 group). The obtained results were as follows ; 1. In case of not used root canal cement(Group 4), there was showed much degree of dye penetration comparerd with used root canal cements (Group 1, 2, 3)(P<0.01). 2. In the case of used root canal cements(Group 1, 2, 3), there was no significant difference in linear leakage in groups(P>0.01). 3. In the case of used root canal cements(Group 1, 2, 3), there was showed intimate adaptation to the dentinal wall independent on kinds of root canal cements. 4. Fractured surfaces indicated failure of cohesion in Ketac-Endo, and failure of adhesion to dentine in AH-26 and Tubli-Seal. 5. According to similar apical leakage and adaptability to the dentinal wall to another root canal cements, it is possible to be used glass-ionomer cement as root canal cement.