• Journal of Periodontal and Implant Science
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• v.47 no.6
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• pp.352-362
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• 2017

Purpose: Furcation involvement in the molars is difficult to treat, and has been recognized as a risk factor for tooth loss. Although periodontal regenerative therapies, including guided tissue regeneration and various types of bone grafts, have been applied to furcation defects, the effects of these treatments are limited, especially in large class III furcation defects. The purpose of this pilot study was to investigate the effect of reciprocal autologous root transplantation on periodontal wound healing and regeneration in class III furcation defects in dogs. Methods: Furcation defects (7 mm wide and 6 mm high) were surgically created after root separation of the unilateral third and fourth premolars in 4 dogs. Eight furcation defects were randomized to receive either reciprocal autologous root transplantation (test) or no further treatment (control). In the test group, the mesial and distal roots were transplanted into the distal and mesial extraction sockets, respectively. The animals were sacrificed 10 weeks after surgery for histologic evaluation. Results: The healing pattern in the control group was characterized by extensive collapse of the flap and limited periodontal regeneration. New bone formation in the test group ($3.56{\pm}0.57mm$) was significantly greater than in the control group ($0.62{\pm}0.21mm$). Dense collagen fibers inserting into the residual cementum on the transplanted root surfaces were observed in the test group. Slight ankylosis was observed in 2 of the 4 specimens in the test group on the mesiodistal sides where the root-planed surfaces faced the existing bone. Root resorption (RR) was detected in both the control and test groups. Conclusions: Within the limits of this study, it can be concluded that reciprocal autologous root transplantation was effective for bone regeneration in class III furcation defects in dogs. However, further studies are required to standardize the approach in order to prevent unwanted RR prior to clinical application.

• Journal of Korean Foot and Ankle Society
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• v.15 no.4
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• pp.201-206
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• 2011

Purpose: Subtalar distraction arthrodesis is useful treatment option for restore hindfoot alignment. but, using structural autograft have high risk of donor site morbidity. Recently, by replacing the structural allograft has been reported satisfactory clinical results. Therefore, the authors reviewed the results of subtalar distraction arthrodesis using a structural allograft, retrospectively. Materials and Methods: From January 2008 to May 2010, 12 patients (12 feets; 9 male, 3 female) underwent subtalar distraction arthrodesis using frozen structural allograft. 9 cases were calcaneal malunion, 2 were nonunion or malunion after subtalar arthrodesis, 1 was other cause. Mean age was 38.9 (12~66) years old and follow up period was 16.5 (12~36) months. Surgical was performed with posterolateral approach and tricortical allobone block of frozen femoral neck was used. Analysis was done with retorspective manner to evaluate preoperative, postoperative, and final follow up radiologic measurement and AOFAS ankle-hindfoot scale. Results: There was statistically significant increase (p<0.05) of ankle-hindfoot scale from preoperative 27.5 points to postoperative 72.5 points, talocalcaneal height by 6.62 mm, calcaneal pitch angle by 5.73 degrees, lateral talocalcaneal angle by 6.38 degrees and significant decrease (p<0.05) of tali-1st metatarsal angle by 5.23 degrees. 11 feet (91.7%) acquired bony union and it takes average 5.1 months. Final post-operative result revealed talocalcaneal height changed by 2.57 mm, calcaneal pitch anble, lateral talocalcaneal angle, talar-1st metatarsal angle were changed by 2.63 degrees, 1.62 degrees, 1.18 degrees, respectively (p<0.05). 3 cases of partial osteonecrosis of posterior facet of calcaneus were observed in operation field, 4 cases of complication were developed (1 case of nonunion, 1 collapse of allobone graft, 1 screw loosening, 1 superficial skin necrosis). Conclusion: Subtalar distraction arthrodesis using frozen structural allobone graft is useful alternative treatment method of arthrodesis with structural autobone graft.

• Korean Journal of Clinical Laboratory Science
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• v.39 no.2
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• pp.141-146
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• 2007

Obstructive Sleep Apnea-Hypopnea Syndrome (OSAHS) is a disorder characterized by the repetitive collapse of the pharyngeal airway during sleep, which leads to oxygen desaturation, sleep fragmentation, daytime sleepiness, and increased risk for hypertension and stroke. We investigated the clinical factors related to the severity of OSAHS. Polysomnography was performed in three hundred and ninety five consecutive adult patients with clinical symptoms of obstructive sleep apnea syndrome. All patients completed the sleep questionnaire and the Epworth Sleepiness Scale before polysomnography. Patients were classified into four groups based on the severity of their polysomnographic data: Non-OSA group, characterized by Apnea-Hypopnea Index (AHI) < 5; mild OSA group, by AHI 5-15; moderate OSA group, by AHI 16-30; and severe OSA group, by AHI > 30. Neck circumference was also measured at the cricothyroid level. A total of 395 patients (336 men and 59 women) were studied. In the non-OSA group, there were 55 patients; their mean neck circumference was $39.63{\pm}4.24cm$ and mean BMI was $24.48{\pm}3.53$. In the mild group, there were 101 patients; their mean neck circumference was $41.93{\pm}3.75cm$ and mean BMI was $25.33{\pm}2.94$. In the moderated group, there were 93 patients; their mean neck circumference was $43.27{\pm}3.50cm$ and BMI was $25.90{\pm}2.88$. In the severe group, there were 146 patients; their mean neck circumference was $44.94{\pm}3.93cm$ and mean BMI was $26.81{\pm}3.76$. Men had significantly larger neck circumference than women ($Mean{\pm}SD$, $43.72{\pm}3.83$ vs $39.17{\pm}4.30$, p < 0.001), and higher AHI than women ($29.12{\pm}22.65$ vs $14.63{\pm}14.11$, p < 0.001). Multiple regression analysis revealed that neck circumference was the most significant predictor of AHI. Neck circumference and BMI were positively correlated with the severity of OSAHS. The severity of OSAHS was greater in men than in women.

• Journal of Energy Engineering
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• v.24 no.4
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• pp.192-199
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• 2015

Under the economic banner of "self-reliance," North Korea has focused on hydro and thermal power as its main energy supply sources. However, in the face of extreme energy penury caused by machinery and material supply instability in the wake of the collapse of the former communist block as well as equipment aging and deterioration due to floods and other disasters, North Korea and international aid organizations are increasingly turning their attention toward energy source diversification. In particular, renewable energy is recognized as the best strategic energy source for North Korea and it is a decentralized energy option that is suitable in light of North Korea's power distribution networks and its pursuit of self-reliance. Biogas can contribute to improving the human rights situation of North Koreans in conjunction with an increase in food production. For this reason, renewable energy is the most promising option for an energy source that is likely to secure humanitarian aid from international organizations such as the Food and Agricultural Organization (FAO) and the World Food Programme (WFP). However, the implementation of such humanitarian aid has been hampered by rising concerns about the diversion of provided energy materials for military purposes and the disguised introduction of dual use items strategic materials as well as UN Security Council resolutions and sanctions of the international community against North Korea's military provocation, including nuclear tests and missile launches. This paper explores the possibility of solving this dilemma and proceeding with the humanitarian aid to North Korea by evaluating the potential for sanction and the risk of diversion of the possible products for biogas-related aid on the basis of the list of UN-sanctioned items.

• International Journal of High-Rise Buildings
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• v.10 no.4
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• pp.345-364
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• 2021

Developments in the understanding of fire behaviour for large open-plan spaces typical of tall buildings have been greatly outpaced by the rate at which these buildings are being constructed and their characteristics changed. Numerous high-profile fire-induced failures have highlighted the inadequacy of existing tools and standards for fire engineering when applied to highly-optimised modern tall buildings. With the continued increase in height and complexity of tall buildings, the risk to the occupants from fire-induced structural collapse increases, thus understanding the performance of complex structural systems under fire exposure is imperative. Therefore, an accurate representation of the design fire for open-plan compartments is required for the purposes of design. This will allow for knowledge-driven, quantifiable factors of safety to be used in the design of highly optimised modern tall buildings. In this paper, we review the state-of-the-art experimental research on large open-plan compartment fires from the past three decades. We have assimilated results collected from 37 large-scale compartment fire experiments of the open-plan type conducted from 1993 to 2019, covering a range of compartment and fuel characteristics. Spatial and temporal distributions of the heat fluxes imposed on compartment ceilings are estimated from the data. The complexity of the compartment fire dynamics is highlighted by the large differences in the data collected, which currently complicates the development of engineering tools based on physical models. Despite the large variability, this analysis shows that the orders of magnitude of the thermal exposure are defined by the ratio of flame spread and burnout front velocities (V_S / V_BO), which enables the grouping of open-plan compartment fires into three distinct modes of fire spread. Each mode is found to exhibit a characteristic order of magnitude and temporal distribution of thermal exposure. The results show that the magnitude of the thermal exposure for each mode are not consistent with existing performance-based design models, nevertheless, our analysis offers a new pathway for defining thermal exposure from realistic fire scenarios in large open-plan compartments.

• Journal of the Korean Institute of Gas
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• v.22 no.6
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• pp.44-51
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• 2018

As the LNG storage tank is aged, if there is a crack in the outer wall concrete or corrosion of the reinforcing steel, there is a risk of a major accident such as collapse of the structure depending on the type and degree of damage. Since 2014, LNG storage tanks have undergone precise safety diagnosis and safety inspection has been carried out. The condition evaluation criteria for each component have been revised and applied in January 2016. The condition evaluation standard is to evaluate the status of storage tanks based on the appearance survey and material test results of LNG storage tanks and it is important for maintenance. In addition, the representative condition evaluation standard that shows the comprehensive state of each LNG storage tank is important in maintenance, but the related standard for LNG storage tank outer concrete is not available in Korea and abroad, and development of the condition evaluation standard is necessary. In this paper, we examined the structural characteristics of LNG storage tanks, analyzed the status of the condition evaluation criteria for each member, and developed a comprehensive status rating system by weighting the members. We used the AHP(Analytic Hierarchy Process) technique and developed a representative conditon evaluation criteria through surveys of professional organizations.

• Journal of Korean Society of Forest Science
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• v.107 no.4
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• pp.385-392
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• 2018

The slope stabilization analysis was performed by conducting survey and selecting the representative section in order to improve slope composition and management technology of masonry embankments in the quarry area, The mean slope of the masonry retain wall (A, B, C, D, E, F) was $38.5^{\circ}$, although the steep slope of the lowest slope (A) as $59^{\circ}$. The horizontal distance of the masonry embankments is 66.2 m and the slope height is 48.3 m. However, the inclination of the masonry embankments is relatively steep and visually unstable. The slope stability analysis for the slope stability analysis was taken into account during the drying and saturation. The slope stability analysis during saturation was performed by modeling the fully saturated slope. The strength constants of the ground were divided into two groups. The safety factor for dry period was 1.850 and the safety factor for rainy season was 1.333. The safety rate of dry period and rainy season was above 1.5 and 1.2. However, the weathered granite on the upper part of the masonry embankments at the time of heavy rainfall is considered to have a high risk of slope erosion and collapse. Therefore, it is considered necessary to take measures for stabilization through appropriate maintenance such as drainage installation.

• Journal of Korean Society of Archives and Records Management
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• v.19 no.3
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• pp.29-48
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• 2019

This study reviews the basics of earthquake preparedness from several archives and international cases of earthquake damage and restoration to establish an earthquake preparedness plan in Korean archives. The results of the study are as follows: first, to establish the direction of an earthquake preparedness plan, the study summarizes the basic characteristics of an earthquake and its damages, as well as applies the key elements of disaster preparedness planning after reviewing its basic principles. Second, the study analyzes four international cases that may have significant implications for the earthquake preparedness plan in Korea. Given this, four international cases present lessons and limitations such as the book dropping of a library in Japan, the collapse of archives in Germany, damaged archives because of a massive earthquake in New Zealand, and earthquake preparedness and recovery plans in cultural heritage sectors. Third, to apply the information from overseas cases to domestic, the study examines the lessons, the key elements of earthquake preparedness planning, and the public record standard for Korean archives through the mutual linking process, as well as issues that should be considered. The issues reviewed in this study could help Korean archives establish a realizable earthquake preparedness plan in the future.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.1
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• pp.33-40
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• 2021

In recent years, many construction projects become large and complicated, and construction accidents also steadily increase, which grows interest in the safety and maintenance during construction. Many of the construction accidents are related to temporary construction and structures, but the safety evaluation and management during construction are unclear and indefinite due to the short operating period and continuous change in the formation of the temporary structure. The system support, which is one of the temporary structures to support the pouring load of concrete, was proposed to easily install and dismantle members with connection parts pre-manufactured. The use of the system support is increasing to improve the safety of the temporary structure during construction. However, the system support, which consists of multiple members, still has uncertainties in connectivity between members and supports of vertical members. Therefore, this study analyzed the structure, load, and accident cases of the system support to define the damage scenarios for member connection, support condition, and lateral displacement. The decrease rate of the critical load was analyzed according to the damage scenarios based on the defined unit structure of the system support. In addition, this study provided vulnerable members for each damage scenario, which could induce instability of the temporary structures during design, construction, and operation of the structure.

• Journal of the Korean Institute of Gas
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• v.25 no.6
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• pp.35-44
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• 2021

The PR (Photo Resist) process in the semiconductor process is a process that uses a mixture of flammable substances. Due to the process equipment is installed in a clean room and when flammable substances leak, there is a high risk of suffocation, fire, and explosion. It is necessary to analyze the impact of accidents that may occur during operation and to evaluate whether the safety of workers can be guaranteed. In this study, the value of radiant heat and temperature change at the monitor point set up virtual inside the clean room was confirmed through CFD simulation of 10 leak and fire scenarios using the FLACS CFD - Fire Module. A fire that occurs inside a clean room transfers high radiant heat to the inter-story structure, but its scope is quite limited, and it is unlikely that it will collapse in a single fire accident. There was no scenario in which two stairs leading to the exit were exposed to high radiant heat at the same time due to a fire accident, therefore workers were able to escape in case of a fire. In addition, it was confirmed that the level of radiant heat and temperature rise rapidly decreased as they moved downstairs. According to the API 520 standard, workers exposed to 6.31 kW/m² of radiant heat that workers can withstand for 30 seconds were confirmed that it was possible to sufficiently escape from the inside.