• The korean journal of orthodontics
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• v.29 no.2 s.73
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• pp.147-156
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• 1999

Skeletal Cl III malocclusion is an orthopedic appliance mainly used for growing children with maxillary undergrowth, which largely entails skeletal Cl III malocclusion. It improves anterior crossbite and maxillary position and thus, enables patients to attain favorable Profile but often involves unfavorable profile with protrusive upper and lower lips. Therefore, if orthodontists have knowledge of which condition helps obtain favorable occlusion and profile, they are able to predict the prognosis and limitation of the treatment. This study was done in order to help obtain favorable Profile after treating growing skeletal Cl III children. In the study, we classified childern into two groups, the one with favorable profile(Group 1, n=12) and the other with unfavorable profile(Group 2, n=14) and, with retrospective study using pre- and post-treatment lateral cephalogram, drew the following conclusions. 1. As patients had more serious labioversion of upper incisors, they were more unlikely to have favorable profiles after the treatment. Protrusion of prosthion, which was related with maxillary incisors, also affected profiles. 2. As the NL-ML angle before the treatment was small, it was more likely to get favorable profile. 3. As the degree of lower lip protrusion was high, it was likely to have bialveolar protrusion after the treatment. 4. As the degree of downward and backward rotation of mandible was high, it was likely to get unfavorable profile.

• The korean journal of orthodontics
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• v.37 no.4
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• pp.293-304
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• 2007

The purpose of this study was to estimate the fracture resistance of commercially available ceramic brackets to torsional force exerted from arch wires and to evaluate the characteristics of bracket fracture. Methods: Lingual root torque was applied to maxillary central incisor brackets with 0.022-inch slots by means of a $022\;{\times}\;028-inch$ stainless steel arch wire. A custom designed apparatus that attached to an Instron was used to test seven types of ceramic brackets (n = 15). The torque value and torque angle at fracture were measured. In order to evaluate the characteristics of failure, fracture sites and the failure patterns of brackets were examined with a Scanning Electron Microscope. Results: Crystal structure and manufacturing process of ceramic brackets had a significant effect on fracture resistance. Monocrystalline alumina (Inspire) brackets showed significantly greater resistance to torsional force than polycrystalline alumina brackets except InVu. There was no significant difference in fracture resistance during arch wire torsional force between ceramic brackets with metal slots and those without metal slots (p > 0.05). All Clarity brackets partially fractured only at the incisal slot base and the others broke at various locations. Conclusion: The fracture resistance of all the ceramic brackets during arch wire torsion appears to be adequate for clinical use.

• Restorative Dentistry and Endodontics
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• v.31 no.2
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• pp.96-102
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• 2006

There are various factors affecting the fracture of NiTi rotary files. This study was performed to evaluate the effect of cross sectional area, pecking motion and pecking distance on the cyclic fatigue fracture of different NiTi files. Five different NiTi $files-Profile^{(R)}$ (Maillefer, Ballaigue, Switzerland), $ProTaper^{TM}$(Maillefer, Ballaigue, Switzerland), $K3^{(R)}$ (SybronEndo. Orange, CA) , Hero $642^{(R)}$ (Micro-mega, Besancon, France), Hero $Shaper^{(R)}$ (Micro-mega, Besancon, France)-were used. Each file was embedded in temporary resin, sectioned horizontally and observed with scanning electron microscope. The ratio of cross-sectional area to the circumscribed circle was calculated. Special device was fabricated to simulate the cyclic fatigue fracture of NiTi file in the curved canal,. On this device, NiTi files were rotated (300rpm) with different pecking distances (3 mm or 6 mm) and with different motions (static motion or dynamic pecking motion) . Time until fracture occurs was measured. The results demonstrated that cross-sectional area didn't have any effect on the time of file fracture. Among the files, $Profile^{(R)}$ took the longest time to be fractured. Between the pecking motions, dynamic motion took the longer time to be fractured than static motion. There was no significant difference between the pecking distances with dynamic motion, however with static motion, the longer time was taken at 3mm distance. In this study, we could suggest that dynamic pecking motion would lengthen the time for NiTi file to be fractured from cyclic fatigue.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.37 no.2
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• pp.1-14
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• 2000

The rosette-scan seeker, mounted on the infrared guided missile, is a device that tracks the target It can acquire the 2D image of the target by scanning a space about target in rosette pattern with a single detector Since the detected image is changed according to the position of the object in the field of view and the number of the object is not fixed, the unsupervised methods are employed in clustering it The conventional ISODATA method clusters the objects by using the distance between the seed points and pixels So, the clustering result varies in accordance with the shape of the object or the values of the merging and splitting parameters In this paper, we propose an Array Linkage Clustering Algorithm (ALCA) as a new clustering algorithm improving the conventional method The ALCA has no need for the initial seed points and the merging and splitting parameters since it clusters the object using the connectivity of the array number of the memory stored the pixel Therefore, the ALCA can cluster the object regardless of its shape With the clustering results using the conventional method and the proposed one, we confirm that our method is better than the conventional one in terms of the clustering performance We simulate the rosette scanning infrared seeker (RSIS) using the proposed ALCA as an infrared counter countermeasure The simulation results show that the RSIS using our method is better than the conventional one in terms of the tracking performance.

• Radiation Oncology Journal
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• v.3 no.2
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• pp.145-151
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• 1985

The peripheral dose distributions of wedge fields of Co-60 $\gamma-ray$ and 1 OMV x-ray were measured by the solid state detector controlled by means of semiautomatic water phentom system. The measurements were made on the principal plane parallel to the cross section of wedge filter (blade and ridge direction). For parallel motion of the detector to the beam axis the distance from the margin of radiation field at suface were 3, 5 and 10cm. For tranverse motion the depth of measurement were dm, 5, 10 and 15cm. The followings were drawn from the measurement. 1. The peripheral dose of the blade side of wedges was generally higher than that of the ridge side at symmetric point about beam axis. 2. In the superficial region phenomena of dose build-up appeared. 3. For Co-60 $\gamma-ray$ field, the peripheral dose did not monotonously decrease with the distance from the field margin but increase in some range, consequently showing a peak dose. 4. The peripheral dose did not only depend on radiation quality and field size, but also on wedge angle and wedge direction.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.5
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• pp.391-399
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• 2005

Laser-generated ultrasonic inspection system is a non-contact scanning inspection device with high spatial resolution and wide bandwidth. The amplitude of laser-generated ultrasound is varied according to the energy of pulse laser and the surface conditions of an object where the CW measuring laser beam is pointing. In this paper, we correct the generating errors by measuring the energy of pulse laser beam and correct the measuring errors by extracting the gain information of laser interferometer at each time. h dynamic stabilizer is developed to stably scan on the surface of an object for an laser-generated ultrasonic inspection system. The developed system generates ultrasound after adaptively finding the maximum gain time of an laser interferometer and processes the signal in real time after digitization with high speed. In this paper, we describe hardware configuration and control algorithm to build a stable laser-generated ultrasonic inspection system. Also, we confirmed through experiments that the proposed correction method for the generating errors and measuring errors is effective to improve the performance of a system.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.1
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• pp.98-102
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• 2000

Ectopic eruption is out of a normal position by local eruption disturbance in the developing permanent molar. The prevalence of ectopic eruption is reported to be the between 2 and 6%, most often associated maxillary first permanent molar whereas, the occurrence for the mandibular is quite rare. The etiologic factors of ectopic eruption are inadequate arch length, lack of growth in the posterior region of the jaw, mesially inclined eruption path of first permanent molars, abnormally large first permanent molars, hereditary factor and a stainless steel crown which has been improperly restored. Ectopic eruption can be treated by the use of brass wire, separating elastics, distal disking and Humphrey appliance and the use of removable appliance and cervical traction headgear after extraction of the second primary molar. This case was that lower right first permanent molar was mesially tilted state by locking on the stainless steel crown of a lower right second primary molar. The stainless steel crown was removed and Humphrey appliance was set. Like this case, ectopic eruption could be happened by the stainless steel crown which improperly restored. In restoration of the stainless steel crown, selection of proper size, trimming and contouring are very important.

• Journal of the korean academy of Pediatric Dentistry
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• v.37 no.2
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• pp.246-251
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• 2010

Impactions can occur because of malpositioning of the tooth bud or obstruction in the path of eruption. However, the exact mechanism is still unknown. The impaction of mandibular first molar is rare with prevalence rates of 0.01~0.25%, but it is important to deimpact the tooth as soon as possible to avoid complications such as dental caries, root resorption, and periodontal problems on the adjacent teeth. Several biomechanical strategies have been proposed for uprighting mesially tipped mandibular first molars. However, most of these have had problems with movement of the anchorage unit because of the reciprocal force. The recent development of skeletal anchorage system(SAS) allows direct application of precise force systems to the target tooth or segment, producing efficient tooth movement in a short time. In this case, an impacted mandibular left first molar with dilacerated roots was treated with a miniplate, which provided skeletal anchorage to upright the tooth. The miniplate was installed in the mandibular ramus, and 10 months after the application of orthodontic force, the impacted tooth was exposed in the oral cavity and uprighted. At this point, the mandibular left first molar was included in the orthodontic appliance with fixed mechanotherapy, the tooth could achieve a normal occlusion. Therefore, the use of SAS simplified the orthodontic procedures and reduced the orthodontic treatment period, and had few side effects.

• Composites Research
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• v.18 no.4
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• pp.27-34
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• 2005

Salt water spray and immersion tests were experimentally conducted for over 6 months to investigate the durability of glass fabric/phenolic composites under salt water environment. Mechanical properties such as tensile properties, flexural properties, and shear properties were evaluated and thermal analysis properties such as storage shear modulus, loss shear moduls, and tan 6 were obtained through a DMA. A change in chemical structures was analyzed through a FTIR. According to the results, mechanical properties and thermal analysis properties were sensitive to salt water environment and these properties began to degrade in increasing in exposure times. However, tensile and flexural moduli started to decrease and then slightly increase as increasing in exposure times due to plasticization and crosslinking in matrix as well as physical swelling in composites. Beyond a certain exposure times, these properties began to decrease as further increasing in exposure times. Also the shape and location of peaks in FTIR curves were insensitive to exposure times, but the intensity of peaks would be. finally we found that the durability of glass fabric/phenolic composites were affected on salt water immersion environment rather than salt water spray environment.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2003.09a
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• pp.36-36
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• 2003

목적 : 고감도 형광판과 필름을 이용하여 실시간으로 선량을 측정하여 IMRT 선량분포를 검증하는데 사용하는 가능성을 알아보고자 하였다. 대상 및 방법 : 본 연구에서 개발한 물팬텀은 지름 25cm 아크릴 원통과 원통의 중앙부분에 삽입되는 고감도 형광판으로 구성되어 있다. 이를 사용하여 dose linearity correction factor를 구하기 위해 dmax 지점에서 6MV x-ray를 고감도형광판에 조사하여 blurring correction factor를 구하였다. CCD를 이용하여 고감도 형광판에서 나오는 영상을 수집하였다. 고감도 형광판에서 수집한 영상의 x축 profile은 RTP에서 얻은 profile과 비교하였고, 이온전리함으로 scanning한 데이터를 이용하여 고감도 형광판과 물에서 빛에 의한 산란선 때문에 발생하는 blurring effect를 교정하였다. 여기서 계산된 blurring effect factor를 고감도 형광판에서 수집된 영상에 적용하였다. 결과 : CCD 카메라는 형광판의 전 영역을 감지할 수 있고, 조사시간은 형광판의 중첩된 영상의 선량에 비례하였다. 물팬텀에서 형광판의 blurring effect 는 가우시안 분포로 표현할 수 있었다. 또한 Deconvolution kernel은 원통 팬텀에서 지름 $\pm$5cm 이내의 범위에 위치하였고, 따라서 형광판 영상으로부터의 실제 선량분 포를 뽑아낼 수 있었다. RTP 에서 계산된 선량분포와 blurring correction factor로 교정한 후 중첩시켜 얻은 고감도 형광판 영상의 선량분포는 일치하였다. 결론 : 정기적인 IMRT 선량 검증에 대한 실시간 선량측정 방법이 개발되었다. 고감도 형광판 영상과 CCD 카메라를 사용한 물팬텀으로, IMRT 치료계획에 대한 선량분포를 검증할 수 있는 가능성을 보였다.비의 회전에 의한 오차 보정, 필름의 광학적 밀도에 관한 보정 등 여러 가지 계통적 오차들에 대한 보정들이 선량분포 확인과정의 이해와 그 기준마련에 도움이 되겠지만 우리가 다룬 원점 불일치에 비해서 상대적으로 무시할 수 있었다. 마지막으로 선량분포 확인의 최종목표인 3 차원 선량분포 확인의 실제 적용을 위한 연구가 최적화 알고리듬을 이용하여 실험 중에 있다.\times$5cm, 10$\times$10cm, 15$\times$l5cm, 20$\times$20cm인 경우, 측정하여 얻은 PSF가 0.8%, 0.2%, 0.4%, 0.2%로 약간 높지만, 두 값은 매우 유사한 것으로 나타났다. 그리고, 기존의 BSF를 이용해 구한 TAR과 BJR 25에서 권고하는 PSF를 이용해 구한 TAR을 비교한 결과 field size 에 따라 약 1%-1.5% 정도로 BSF를 이용하여 구한 TAR보다 PSF를 이용하여 구한 TAR이 1.3% 정도 높게 나타났지만, 이것은 두 값의 절대적인 차이일 뿐, 실제로는 PSF를 이용하여 구한 TAR이 측정해서 구한 TAR과는 매우 유사한 값을 보여주고 있다. 결론 : 기존의 BSF를 이용해 구한 TAR과 PSF를 이용해 구한 TAR을 비교하였을 때, 약 1.3% 정도 높게 내고 있지만, 기존의 TAR보다는 PSF를 이용해 구한 TAR이 BJR 25와 잘 일치하고 있으므로 Co-60 원격치료용 방사선 조사장치를 사용할 경우 BSF보다는 PSF를 사용하는 것이 타당한 것으로 사료된다.tokines의 변화는 비록 통계학적인 차이는 없지만 비타민 C를 사용한 환자의 cytokines이 모두 사용하지 않은 환자에 비해 감소하였음을 보였다. 비타민 C는 부작용이 거의 없는 안전한 약으로서 말기 암 환자에서 비타민 C사용은 임상 증상을 호전시키는 데 도움