• The Journal of Engineering Geology
• /
• v.22 no.3
• /
• pp.331-341
• /
• 2012

Granitoid rocks are generally high-quality rock from a geotechnical perspective, because they rarely contain systematic joints or fragmented fault zones. Although the rock type at the Sanhak site is granite, a collapsed slope has a deep soil layer and shows no residual structures such as discontinuities or faults; surface avalanches from this slope can be observed in several places. To study the stability of this slope, we investigated rainfall duration, variation in pore-water pressure, and the factor of safety considering three cases (current cross-section, initial planning cross-section, revised planning cross-section). With increasing duration of rainfall, the groundwater level rises, up to 20 m in height from ground surface. In the initial planning cross-section, safety was secure for rainfall of 2 days duration, but inadequate for rainfall of 4 days duration. In the revised planning cross-section, however, safety factors were secure for rainfall of 4 days duration. Therefore, to ensure permanent stability at the Sanhak site, a slope degree of 1:1.8 should be maintained during cutting.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.40 no.4
• /
• pp.260-267
• /
• 2013

The aim of this study was to analyze the three dimensional characteristics of the size, shape and location of mesiodens and their effect on permanent teeth arrangement using Cone-beam computed tomography(CBCT). 191 patients under 15 years old who had visited the hospital between June 2006 and December 2012 and taken CBCT were investigated. Among them, 43 patients with diastema were analyzed to investigate the correlation between the amount of diastema and the mesiodens. The results showed that mesiodens were found in males 3.9 times more than females and found most in 7 years old. The mean length of mesiodens was 13 mm and the width was 6.8 mm. The conical shape comprised of 52.9%. Many mesiodens were located in the palatal side rather than the labial side and located vertically near the crown. 63.0% of mesiodens were reversed and the common complications were delayed eruption followed by diastema, and teeth rotation. And the amount of diastema had correlation with size and mesiodistal position of the mesiodens. The current study used 3D analysis to show the size and position of mesiodens and occurrence distribution of complication. Among these, the amount of diastema had shown the correlation with the size and mesiodistal position of mesiodens.

• The Korean Journal of Air & Space Law and Policy
• /
• v.19 no.1
• /
• pp.79-107
• /
• 2004

Shielding theory is to allow the construction of a structure that would be shielded by existing permanent structures even thought such structure extends above the height limits prescribed for such zones. This theory is mentioned as recommended practices in ICAO Annex, and is adopted, with modification, in the current Military Airbase Law, amended in August 26th 2002. However, the Military Airbase Law adopts shielding standard allowing 45 meters uniformly, which is a unique standard compared to other countries shielding guideline. The basic principle in applying the shielding theory is, after considering the circumstances of location of shielded structure, whether such structure has physical effect on aeronautical operations. Based upon the basic principle of shielding theory, the uniform application of shielding standard in the Military Airbase Law would undermine the safety of aeronautical operations. This article is to review subsection 2 of section 8 of the Military Airbase Law, which adopts modified shielding theory, and is to suggest better guideline. From a comparative analysis perspective, shielding guidelines of ICAO and other countries will be discussed. Based upon this discussion, the general problems of shielding theory and the specific problems in the Military Airbase Law will be examined. Finally, this article suggests the case-by-case application of shielding theory, considering circumstances of location, for the purpose of ensuring aviation safety.

• Journal of Korean Society of Forest Science
• /
• v.104 no.3
• /
• pp.427-433
• /
• 2015

This study was conducted to provide a method of establishing two-storied forests by the adjustment of stand structures in natural deciduous forests of Pyeongchang area. Three permanent sampling plots of 0.09 ha were established in study site and some tree variables were measured in each sampling plot before the treatment of two-storied system. Stand attributes and stand structures before treatment were estimated based on the data measured in sampling plots. The results indicate that the current stand status is different from typical stand structures of two-storied forests. A simulation technique was applied to predict stand attributes and stand structures after the treatment of two-storied system. Results suggest that significant time is required to accomplish target stand structures even after applying the treatment of two-storied system. Number of trees in the upper canopy class after treatment was predicted to be 170 trees/ha, which adequately meets the target of two-storied forests. It was predicted, however, that the lower canopy class trees has much less trees compared with the typical stand structures of two-storied forests. This problem could be solved with ingrowth of infant trees over time or by under-planting of tolerant species. It is confirmed that the target growing stock volumes of the upper canopy class should be approximately $150m^3/ha$ considering stand status after treatment. It is predicted that twenty years of conversion period is required to accomplish this goal. The changes in stand structures over time should be assessed based on stand inventory carried out every five years, and additional treatments for inducing two-storied forests should be applied if necessary.

• Journal of Gastric Cancer
• /
• v.3 no.4
• /
• pp.182-185
• /
• 2003

Purpose: Preoperative staging of gastric cancer is crucial because the treatment modality and the prognosis depend upon the stage of gastric cancer. Current treatment modalities for early gastric cancer have focused on the quality of life. Endoscopic ultrasonography (EUS) and abdominal computed tomography (CT) are commonly used diagnostic tools to evaluate the invasiveness (T stage) of the primary tumor. The purpose of this paper is to evaluate the sensitivity and the specificity of preoperative EUS and CT in comparison with postoperative pathology. Materials and Methods: From October 2001 to October 2002, EUS and abdominal CT were performed simultaneously on 75 patients who underwent radical gastric surgery for the treatment of gastric cancer. Through analyzing the clinical T stage and the pathologic T stage, We evaluated the diagnostic sensitivities and specificities of endoscopic ultrasonography and abdominal computed tomography. Results: The male-to-female sex ratio was 1 : 0.6 (males: 47, females: 28). The mean age was 55.4 years in males (range: $28\~81$) and 54.4 years in females (range: $23\∼77$). The clinical T stage based on EUS included 22 T1mm, 7 T1sm, 22 T2, and 24 T3. The clinical T stage based on CT included 20 Tx, 23 T2, and 32 T3. The permanent pathologic report confirmed 23 T1mm, 10 T1sm, 17 T2, 24 T3, and 1 T4. The sensitivity and specificity of EUS were $84.2\%\;and\;94.7\%$, respectively. However, the sensitivity and specificity of abdominal CT were $53.3\%\;and\;77.0\%$, respectively. Conclusion: Our data suggest that EUS is a very useful diagnostic tool for evaluating the T stage of gastric cancer because EUS has higher specificity than abdominal CT. Therefore, EUS may have a significant role as a preoperative diagnostic modality in patients undergoing minimally invasive surgery.

• Earthquakes and Structures
• /
• v.11 no.6
• /
• pp.1101-1121
• /
• 2016

Base isolation, one of the popular seismic protection approaches proven to be effective in practical applications, has been widely applied worldwide during the past few decades. As the techniques mature, it has been recognised that, the biggest issue faced in base isolation technique is the challenge of great base displacement demand, which leads to the potential of overturning of the structure, instability and permanent damage of the isolators. Meanwhile, drain, ventilation and regular maintenance at the base isolation level are quite difficult and rather time- and fund- consuming, especially in the highly populated areas. To address these challenges, a number of efforts have been dedicated to propose new isolation systems, including segmental building, additional storey isolation (ASI) and mid-storey isolation system, etc. However, such techniques have their own flaws, among which whipping effect is the most obvious one. Moreover, due to their inherent passive nature, all these techniques, including traditional base isolation system, show incapability to cope with the unpredictable and diverse nature of earthquakes. The solution for the aforementioned challenge is to develop an innovative vibration isolation system to realise variable structural stiffness to maximise the adaptability and controllability of the system. Recently, advances on the development of an adaptive magneto-rheological elastomer (MRE) vibration isolator has enlightened the development of adaptive base isolation systems due to its ability to alter stiffness by changing applied electrical current. In this study, an innovative semi-active storey isolation system inserting such novel MRE isolators between each floor is proposed. The stiffness of each level in the proposed isolation system can thus be changed according to characteristics of the MRE isolators. Non-dominated sorting genetic algorithm type II (NSGA-II) with dynamic crowding distance (DCD) is utilised for the optimisation of the parameters at isolation level in the system. Extensive comparative simulation studies have been conducted using 5-storey benchmark model to evaluate the performance of the proposed isolation system under different earthquake excitations. Simulation results compare the seismic responses of bare building, building with passive controlled MRE base isolation system, building with passive-controlled MRE storey isolation system and building with optimised storey isolation system.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.3
• /
• pp.875-888
• /
• 2013

The researches have recently progressed toward the use of the superelastic shape memory alloys (SMAs) to develop new smart control systems that reduce permanent deformation occurring due to severe earthquake events and that automatically recover original configuration. The superelastic SMA materials are unique metallic alloys that can return to undeformed shape without additional heat treatments only after the removal of applied loads. Once the superelastic SMA materials are thus installed at the place where large deformations are likely to intensively occur, the structural system can make the best use of recentering capabilities. Therefore, this study is intended to propose new buckling-restrained braced frames (BRBFs) with superelastic SMA bracing systems. In order to verify the performance of such bracing systems, 6-story braced frame buildings were designed in accordance with the current design specifications and then nonlinear dynamic analyses were performed at 2D frame model by using seismic hazard ground motions. Based on the analysis results, BRBFs with innovative SMA bracing systems are compared to those with conventional steel bracing systems in terms of peak and residual inter-story drifts. Finally, the analysis results show that new SMA bracing systems are very effective to reduce the residual inter-story drifts.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.37 no.5
• /
• pp.343-348
• /
• 2011

Introduction: Third molar extraction is one of the most common procedures in oral and maxillofacial surgery. The impacted third molar causes many pathological conditions, such as pericoronitis, caries, periodontitis, resorption of adjacent teeth, and cyst or tumors associated with impacted teeth. Extraction is often considered the treatment of choice for impacted lower third molars. On the other hand, imprudent extraction of deeply impacted third molars can cause permanent complications, such as inferior alveolar nerve damage. Therefore, guidelines for the extraction of lower third molars should be set to prevent embarrassing complications. This study examined the indication and current trends of the extracted lower third molars in the dental hospital of a dental college. Materials and Methods: 557 extracted third molars were evaluated at the department of oral and maxillofacial surgery of Yonsei University. The chief complaint, diagnosis, age and degree of impaction were analyzed to determine the tendency for the extraction of asymptomatic lower third molars. Results: The percentage of asymptomatic third molars was 40.8%. In cases of full impacted tooth or full erupted tooth, the percentage of asymptomatic teeth was more than 50% (52.4% and 54.3, respectively). Among those partially impacted teeth, 73.1% of them showed symptoms, such as pain, tenderness and swelling. In terms of age, pericoronitis was evident at a younger age, and dental caries/periodontitis was the main cause of removal in those aged over 50. Twenty nine cases (1.6%) had teeth associated with pathological changes Conclusion: The incidence of pathological changes to the lower third molar was relatively low. Surgical extraction is recommended in cases of partially impacted teeth. In Korea, the incidence of asymptomatic third molar extraction was relatively higher than in European countries. More careful attention would be desirable to consider the risks and benefits of lower third molar extraction.

• Journal of Biomedical Engineering Research
• /
• v.26 no.6
• /
• pp.393-398
• /
• 2005

An electromechanical type is the most useful mechanism in the various pumping mechanisms. It, however, requires a movement converting system including a ball screw, a helical cam, or a solenoid-beam spring, which makes the device complex and may lessen reliability. Thus, the authors have hypothesized that an electromagnetic actuator mechanism can eliminate the movement converting system and that thereby enhance the mechanical reliability and operative simplicity of an electro­pneumatic pump. The purpose of this study was to show a novel application of electromagnetic actuator mechanism in pulsatile pump and to provide preliminary data for further evaluations. The electromagnetic actuator consists of stators with a single winding excitation coil and movers with a high energy density neodymium-iron-boron permanent magnet. A 0.5mm diameter wire was used for the excitation coil, and 1000 turns were wound onto the stators core with parallel. A prototype of extracorporeal electro-pneumatic pump was constructed, and the pump performance tests were performed using a mock system to evaluate the efficiency of the electromagnetic actuator mechanism. When forward and backward electric currents were supplied to the excitation coil, the mover effectively moved back and forth. The nominal stroke length of the actuator was 10mm. The actuator dimension was 120mm in diameter and 65mm in height with a mass of 1.4kg. The prototype pump unit was 150mm in diameter, 150mm in thickness and 4.5kg in weight. The maximum force output was 70N at input current of 4.5A and the maximum pump rate was 150 beats per minute. The maximum output was 2.0 L/minute at a rate of 80bpm when the afterload was 100mmHg. The electromagnetic actuator mechanism was successfully applied to construct the prototype of extracorporeal electro­pneumatic pump. The authors provide the above results as a preliminary data for further studies.

• The Korean Journal of Archival Studies
• /
• no.64
• /
• pp.119-155
• /
• 2020

The records management system in Korea has a short history of about 20 years. However, the system is relatively stable. This compressed development has been mainly in public records. This is because the laws and regulations related to private records management were insufficient. Fortunately, Two local permanent records management institutions have recently been established. Therefore, interest in the management of local records has been growing. The Management of private records is an important part of the management of local records. The collection of private records is based on ordinances established by local governments. This study aims to analyze the ordinances of local governments, which are the legal basis for the collection and management of private records. The subject of analysis is the ordinance related to the management of private records that are currently established in Korea. The progress of the study analyzed the current state of the ordinance, the background of the ordinance, and the contents of the ordinance regarding the management of private records. The results of this study can be used as basic research for reference in the enactment of the ordinances related to the management of private records in the future since the ordinances for collecting and managing private records in Korea targets.