• Journal of Korean Society of Steel Construction
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• v.25 no.2
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• pp.115-130
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• 2013

In this study, lateral-torsional buckling (LTB) strength of high-strength H-beams built up from 800MPa tensile-strength steel was experimentally and analytically evaluated according to current lateral stability provisions (KBC 2009, AISC-LRFD 2010). The motivation was to evaluate whether or not current LTB provisions, which were originally developed for ordinary steel with different stress-strain characteristics, are still applicable to high-strength steel. Two sets of compact-section specimens with relatively low (Set A) or high (Set B) warping stiffness were prepared and tested under uniform moment loading. Laterally unbraced lengths of the test specimens were controlled such that inelastic LTB could be induced. All specimens exhibited LTB strength exceeding the minimum limit required by current provisions by a sufficient margin. Moreover, some specimen in Set A reached a rotation capacity required for plastic design, although its laterally unbraced length belonged to the inelastic LTB range. All the test results indicated that extrapolation of current provisions to high-strength steel is conservative. In order to further analyze the test results, the relationship between inelastic moment and laterally unbraced length was also derived in explicit form for both ordinary- and high-strength steel based on the effective tangent modulus of inelastic section. The analytical relationship derived again showed that extrapolation of current laterally unbraced length limit leads to a conservative design in the case of high-strength steel and that the laterally unbraced length to control the inelastic LTB behavior of high-strength steel beam should be specified by including its unique post-yield strain-hardening characteristics.

• Korean Journal of Applied Biomechanics
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• v.14 no.3
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• pp.67-82
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• 2004

The purpose of this study was to evaluate the function and the safety of an additional weight shoe developed for the improvement of aerobic capacity, and to improve some problems found by subject's test for an additional weight shoe. The subjects employed for this study were 10 college students. 4 video cameras, AMTI force platform and Pedar insole pressure distribution measurement device were used to analyze foot motions. The results of the study were as follows: 1 The initial achilles tendon angle and initial rearfoot pronation angle of an additional weight shoe during walking were 183.7 deg and 2.33 deg, respectively, and smaller than a barefoot condition. Maximum achilles tendon angle and the angular displacement of achilles tendon angle were 185.35 deg and 4.21 deg respectively, and smaller than barefoot condition. Thus rearfoot stability variables were within the permission value for safety. 2. Maximal anterior posterior ground reaction force of additional weight shoe was appeared to be 1.01-1.2 B.W., and was bigger than a barefoot condition. The time to MAPGRF of an additional weight shoe was longer than a barefoot condition. Maximal vertical ground reaction force of additional weight shoe was appeared to be 2.3-2.7 B.W., and was bigger than a barefoot condition in propulsive force region. But A barefoot condition was bigger in braking force region. The time to MVGRF of an additional weight shoe was longer than a barefoot condition. 3. Regional peak pressure was bigger in medial region than in lateral region in contrast to conventional running shoes. The instant of regional peak pressure was M1-M2-M7-M4-M6-M5 -M3, and differed form conventional running shoes. Regional Impulse was shown to be abnormal patterns. There were no evidences that an additional weight shoe would have function and safety problems through the analysis of rearfoot control and ground reaction force during walking. However, There appeared to have small problem in pressure distribution. It was considered that it would be possible to redesign the inner geometry. This study could not find out safety on human body and exercise effects because of short term research period. Therefore long term study on subject's test would be necessary in the future study.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.1
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• pp.61-71
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• 2009

Anchorage control is important in orthodontic treatment. Recently miniscrew is widly used as maximum anchorage in orthodontic treatment, and then it is important to install miniscrew safely without damaging adjacent anatomic structure. In a view of Miniscrew's stability, maxilla is unfavorable than mandible, and moreover maxillary soft buccal bone has disadvantage on stability. so palatal area comes into notice for installation area. We measured distance between palatal roots and bone thickness at midpalatal area using 3D computed tomography, and have found following results. 1. On the comparison of distance between palatal roots, the distance between 2nd premolar and 1st molar was significantly longest and the distance between premolars was significantly shortest. 2. Going toward lateral area from midpalatal suture and posterior area from zero point, bone thickness significantly became shorter and shorter. And 5.0mm palatal sagittal plane has more significance decrease of bone thickness than 2.5mm palatal sagittal plane. According to these results, we can conclude that the palatal installation of miniscrew between 2nd premolar and 1st molar is safest. And it is more safe that comes closer to midpalatal suture and to anterior area in regard to incisive canal.

• Journal of Bio-Environment Control
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• v.15 no.2
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• pp.138-148
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• 2006

This study was carried out to evaluate the structural safety fur both the attached wind-protecting wall in greenhouse and the detached one installed outside. Regarding the attached wind-protecting wall in greenhouse, the analysis was conducted by doing a fluid-structure coupled field analysis using both CFX-5.7 and ANSYS 8.1 and also under the design condition of an instantaneous maximum wind velocity of $30.9m{\cdot}s^{-1}$. Three kinds of the width ranged from 30 to 90cm were considered in this study. With regard to the detached wind-protecting wall, the structural saffty was analyzed under the pressure difference of 1,117 Pa which corresponded to a wind velocity of $50m{\cdot}s^{-1}$ and the analytical results were also compared with theoretical ones. The result showed that there was little difference in the distribution of velocity overall and total pressure on the lateral side according to the width of the attached wind-protecting wall, but greenhouse with wind-protecting widths of 30 to 60cm has been reinforced to the extent of about 11% when compared with the case of being without the wall. The result also showed that the detached wind-protecting wall with a main-column interval of 3m was not stable so that it was necessary for the detached wind-protecting wall to be adequately reinforced to secure structural stability. Finally, there was great difference between analytical results and theoretical studies. The difference meant that there was some possibility of including errors when a theoretical study was done in three dimensional structure.

• The korean journal of orthodontics
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• v.33 no.2 s.97
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• pp.91-102
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• 2003

This study was performed to investigate the effect of immediate orthodontic force on soft md hard tissues surrounding C-Palatal $Plate^{TM}$ in beagle Dog. Immediately after this appliance was implanted on the midpalate of 4 adult beagle Dogs, 400gm continuous orthodontic force was applied. Experimental animals were euthanized at 8weeks, 18weeks, and 22weeks (including post-removal healing time of 4weeks), and a control animal was euthanized at 8weeks after implantation without orthodontic force application. The appliance and the surrounding tissue were studied radiographically, macroscopically, and histologically. The results were as follows: 1. The lateral radiographs taken after euthanasia showed very slight displacement of the vortical plate in the experimental animals, compared with the control animal. Mobility test of all animals confirmed primary stability without any increase of mobility during experimental period. 2. No pathologic changes were found in the healing condition of covering soft tissue and bone-screw interface in experimental animals as well as a control animal. 3. Osseointegration was achieved in the bone-screw interface in 8weeks after implantation and the amount of osseointegration increased in 18weeks. There was little difference of osseointegration between the compression side and the tension side. 4. In the marginal bone area, slight bone apposition and resorption were found regardless of compression and tension side, while there was no change in the control animal. 5. Both 8week-animal and 18week-animal showed the new bone apposition along the surface of screws which were perforated into the nasal cavity, while the control animal showed no change. 6. After 4weeks of plate removal, the covering epithelium was repaired intactly, while the connective tissue showed loose and irregular rearrangement and the connective tissue capsule remained. The C-Palatal $Plate^{TM}$ manifested sufficient anchorage capacity in the context of histological study as well as clinical outcomes, when immediate orthodontic force was applied after implantation.

• Journal of the Korean Arthroscopy Society
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• v.7 no.2
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• pp.160-168
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• 2003

Purpose : To analyze the anterior stability and functional results after the arthroscopic ACL reconstruction and meniscectomy based on meniscus status at the time of surgery. Materials and Methods : From October 1997 to October 2002, 78 patients (male 64 female 14) were treated by arthroscopic ACL reconstruction and meniscectomy and followed more than 12 months (range, $12\~72$ months, average: 32 months). Average age was 32 years old (range, $18\~57$ years old). We divided the patients into 4 groups; Both menisci was intact (BMI, control group), lateral meniscus removed (LMR), medial meniscus removed (MMR) and both menisci removed (BMR). Anterior passive displacement (objective stability) was estimated using KT-2000 arthrometer under the loading of 15lb,20lb and 30lb and evaluated anterior drawer test, Lachman test, range of motion, thigh circumference. Functional evaluation system of IKDC, OAK and Lysholm knee score was used. Results : Average anterior displacement under the loading of 30lb were 2.47 mm, 2.96 mm, 2.96 mm and 3.57 mm in each group(BMI, LMR, MMR, BMR) and it was statistically significant difference (p<0.05). There is no statistically significant difference in average anterior displacement under the loading of 15lb and 20lb in each group but it has showed decreasing tendency in meniscal removed groups. The mean anterior displacement was within 3 mm in 21 cases, 15 cases, 24 cases and 12 cases (total 72 cases, $94\%$) under the loading of 15lb and 20 cases, 15 cases, 24 cases and 11 cases (total 70 cases, $91\%$) under the loading 20lb of in each group and postoperative knee joint stability has showed increasing tendency (p>0.05). The mean score was 94.5, 93.2, 92.2 and 90.4 points in each group and 71 cases $(91\%)$ were more than excellent or good with a OAK score and fair results were noted 4 cases in both meniscal removed group. There were 65 cases $(83\%)$ with a Lysholm knee score more than excellent or good, and IKDC grading were more than normal or nearly normal in 74 cases $(95\%)$ except 4 cases (2 cases in MMR group and 2 cases in BMR group). Conclusion : Long-term anterior stability and functional results of a successful ACL reconstruction affected by tile status of the menisci at the time of surgery and KT-2000 arthrometer was good for estimation of objective follow up.

• Journal of Radiation Protection and Research
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• v.27 no.1
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• pp.37-49
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• 2002

The accuracy of radiation dose delivery to target volume is one of the most important factors for good local control and less treatment complication. In vivo dosimetry is an essential QA procedure to confirm the radiation dose delivered to the patients. Transmission dose measurement is a useful method of in vivo dosimetry and it's advantages are non-invasiveness, simplicity and no additional efforts needed for dosimetry. In our department, in vivo dosimetry system using measurement of transmission dose was manufactured and algorithms for estimation of transmission dose were developed and tested with phantom in various conditions successfully. This system was applied in clinic to test stability, reproducibility and applicability to daily treatment and the accuracy of the algorithm. Transmission dose measurement was performed over three weeks. To test the reproducibility of this system, X-tay output was measured before daily treatment and then every hour during treatment time in reference condition(field size; $10 cm{\times} 10 cm$, 100 MU). Data of 11 patients whose pelvis were treated more than three times were analyzed. The reproducibility of the dosimetry system was acceptable with variations of measurement during each day and over 3 week period within ${\pm}2.0%$. On anterior- posterior and posterior fields, mean errors were between -5.20% and +2.20% without bone correction and between -0.62% and +3.32% with bone correction. On right and left lateral fields, mean errors were between -10.80% and +3.46% without bone correction and between -0.55% and +3.50% with bone correction. As the results, we could confirm the reproducibility and stability of our dosimetry system and its applicability in daily radiation treatment. We could also find that inhomogeneity correction for bone is essential and the estimated transmission doses are relatively accurate.