• The korean journal of orthodontics
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• v.30 no.3 s.80
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• pp.317-333
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• 2000

The purpose of this study was to determine the proliferative activity of the osteoblasts and fibroblasts in the midpalatal area and to investigate the adjacent periodontal tissues of individual tooth following rapid expansion of the palate. Ten young adult dogs, aged approximately ten months, were used in the experiment. The experimental design was consisted of 1 week expansion group(Group E1, 3 dogs), 2 week expansion group(Group E2, 3 dogs), 2 week expansion and 2 week retention group(Group E3, 3 dogs), and control group(Group C, 1 dog). For each group, expansion screw was activated one time per day(1/4 turn;$90^{\circ}$) following Hyrax-screw application. The experimental animals in each group were sacrificed at 1, 2 and 4 weeks following palatal expansion. Maxillary tissue blocks were obtained and prepared ior the histomorphologic and immunohistochemical studies. Light mcroscope, polarizing microscope, and soft X-ray apparatus were used in this study, and following results were obtained. 1. In polarizing microscopic study, the expansion groups(E1 & E2) showed blue color representing bone resorption and new bone formation in midpalatal suture area. E3 groups skewed less blue color compared to the E1 and E2 group. But yellow color increased by calcification in the E3 groups. 2. Immunohistochemical study revealed that positive responses of the osteoblasts to PCNA and undifferentiated fibroblasts to EGF in E1 group were somewhat increased. Positive response to PCNA and EGF were increased in fibroblasts and the osteoblasts forming new bone in E2 group. In E3 group, the positive response cell concentrated the periphery of edge of palatal process in both PCNA and EGF. 3. Throughout the expansion period(E1 & E2), light microscopic study showed the edges of the extensive resorption and new palatal processes, indicating bone remodeling within the suture. E3 group exhibited less remodeling of midpalatal suture area. E2 group and E3 group showed cementum formation and resorption at the apex of 3rd premolar and 1st molar E3 group exhibited extensive hyalinized zone on the cervical portion of buccal side of 1st molar. 4. Soft X-ray analysis of E1 group showed hypomineralized defect and microfractures in various parts of the suture areas when compared with control animals. There was no significant difference in the degree of mineralization in the midpalatal suture region between the C and E3 groups. Tooth axis showed tipping of 3rd premolar and 1st molar in the E2 group and E3 group. Based upon these experimental results, it is concluded that the undifferentiated mesenchymal cells always presented in midpalatal suture area following RPE. Differentiated osteoblasts and fibroblasts possess proliferating cellular activity until the 2 week retention period. The posterior teeth are tend to tip buccally as RPE force applied. Retention group exhibited irreversible response with severe hyalinized zone on the buccal surface of the first molar.

• Journal of the Korean Wood Science and Technology
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• v.34 no.1
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• pp.15-22
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• 2006

ln order to manage efficiently many ancient wooden buildings, which have been preserved as cultural properties in Korea, the internal state of wood members should be evaluated exactly and periodically by a NDE (non-destructive evaluation) method. A research project was planned to develop an X-ray CT (computed tomography) system as a NDE method for wood, which could be easily applied in field. This paper includes the first part of this project. First of all, to establish a measuring procedure of wood density using X-ray radiography, the correlation between X-ray intensity and the film brightness was evaluated. Also, initial X-ray intensity was quantified with various radiate conditions controlled by the tube voltage and tube current. And then, the effects of density, annual ring angle, and thickness on the mass attenuation coefficient of wood were examined. Finally, Beer's law was modified with the above results and adopted to calculate the density of wood. As a result of this study, the measuring procedure of wood density was established using a portable soft X-ray device and this procedure was verified with some small wood specimens. This results will he used valuably for the following researches to develop a portable X-ray CT system.

• The Journal of the Korean dental association
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• v.50 no.7
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• pp.420-430
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• 2012

Purpose: The purpose of this study was to measure the absorbed dose and to calculate the effective dose for full-mouth periapical radiography using the portable dental x-ray machine and panoramic radiography Material and Method: Thermoluminescent chips were placed at 25sites throughout the layers of the head and neck of a tissue-equivalent human skull phantom. The man phantom was exposed with the portable dental x-ray machine and panoramic unit. During full-mouth periapical radiography the exposure setting was 60 kVp, 2 mA and 0.15 ~ 0.25 seconds, while during panoramic radiography the selected exposure setting was 72 kVp, 8 mA and 18 seconds. Absorbed dose measurements were obtained and equivalent doses to individual organs were summed using ICRP 103 to calculate of effective dose. Result: In the full-mouth periapical radiography, the highest absorbed dose was recorded at the mandible body follow with submandibular glands and cheek. Using panoramic unit, the highest absorbed dose was parotid glands and the following was back of neck and submandibular glands. The effective dose in full-mouth periapical radiography using portable dental x-ray machine was 46 ${\mu}Sv$. In panoramic radiography, the effective dose was 38 ${\mu}pSv$. Conclusion: It was recommended to panoramic radiography for general check in the head and neck area because that the effect dose in the panoramic radiography was lower than the dose in the full-mouth periapical radiography using portable dental x-ray machine.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.3
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• pp.32-41
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• 2008

In this paper, we describe the synthesis of robust and non-fragile $H^{\infty}$ state feedback controllers for linear systems with affine parameter uncertain tracking servo system of blu-ray disc drive, as well as static state feedback controller with polytopic uncertainty Similarity any other control system, the objective of the track-following system design for optical disc drives is to construct the system with better performance and robustness against modeling uncertainties and various disturbances. Also, the obtained condition can be rewritten as parameterized linear matrix inequalities(PLMIs), that is, LMIs whose coefficients are functions of a parameter confined to a compact set. We show that the resulting controller guarantees the asymptotic stability and disturbance attenuation of the closed loop system in spite of controller gain variations within a resulted polytopic region.

• Journal of the Korean Wood Science and Technology
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• v.16 no.1
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• pp.9-20
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• 1988

Lespedeza species have been widely used not only as plant resources for bark, leaves and honey, but also as erosion control materials. This study was carried out to investigate the structural and wood tiber characteristics in order to obtain basic information for the utilization of the wood. The wood structure was investigated for 10 selected species and the wood fiber, for the 5 selected species among Lespedeza species distributed all over the country. The following results were obtained. In the cross section, campylotropis showed ray diffuse porous wood, L. bicolor, L. cyrtobotrya, L. thunbergii var. intermedia, diffuse porous wood, and L. tomentella, L. angustifolioides. L. maritima, L. robusta, L. patentibicolor, ring porous wood. The maximum diameter of a single vessel ranged 66-123 ${\mu}$ in all species. Campylotropis showed the most number of vessels, L. angustifolioides, the least. The number of ray per mm ranged 7-22, Campylotropis showed the most number of rays, L. angustifolioides, the least. In the radial section the average length of vessel ranged 121-250 ${\mu}$ in all species. L. thunbergii var. intermedia showed the longest vessel, L. tomentella, the shortest. In tangential section the average width of the uniseriate ray ranged 9.2-14.7${\mu}$, that of the multiseriate ray, 19.2-42.1 ${\mu}$. The average height of the uniseriate ray ranged 143.0-1162.0 ${\mu}$. The width of fiber ranged 10.12-13.61 ${\mu}$, L. maximowiezii showed the narrowest tiber, L. thunbergii var. intermedia. the widest, the thickness of fiber wall ranged 2.93-3.71 ${\mu}$ in the five species. L. maximowiezii showed the most thin fiber wall, L. thunbergii var. intermedia, the thickest, L. cyrtobotrya showed the difference in the size of fiber between the shade and the sunny sites but L. maximowiezii showed no difference. There was significant difference in fiber length, fiber width and wall thickness between L. eyrtobotrya and L. maximowiezii.

• Journal of Ginseng Research
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• v.18 no.2
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• pp.128-133
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• 1994

Color characteristics were investigated for white ginseng powder immediately and during storage following treatments of gamma ray or ethylene oxide (EO) for microbial decontamination. The variation in fatand water-soluble pigments of the sample was negligible immediately after both treatments, however an apparent increase was observed in the samples stored for four months at $25^{\circ}C$ and RH 90%, in the order of nontreated control, EO-fumigated, and 5 key-irradiated samples. Hunter's color a and b values of white ginseng powder increased slightly in proportion to irradiation doses, whereas EO fumigation caused a decrease in L value and an increase in a and b values of the sample, showing overall color difference (${\delta}^E$) of 1.8. Considering the higher ${\delta}^E$ in the higher RH conditions, airtight packaging and sterilization using like gamma ray were considered an effective means for maintaining high quality of color characteristics in stored white ginseng powder.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.10 no.1
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• pp.57-61
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• 1980

In dental roentgenograph it is of mutual benefit to the patient and the dentist to use the minimum amount of radiation capable of producing roentgenograms with maximum interprtive informations. Recent increases in the number of diagnostic x-ray examinations made in this country have caused attention to be paid to the quantity of radiation delivered to the population and operator. The purposes of this study was to assess the quality of dental x-ray units, the amount of films, the average processing procedures and the radiation protection methods in korea. The results were as following: 1. Most of radiation generating system were used in low voltage such as 60Kvp, 10㎃. 2. High sensitivity films such as 'D' group of Kodak or Rinn were mainly used and average 14.7 films used per weeks. 3. Some dentists practiced visual processing technic in simple dark room, and others used instant films. 4. 68.26% of patient held the film themselves, but 27.30% were assisted by dentists film holding. 5. In radiation protection method, 7.85% of dentists had protection equipments such as protective barrier, 2.73% wore protective apron, 27.9% made it a rules to avoid beam, and 7.51% used to maintain a distance from the radiation source.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.791-794
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• 2013

Electronic systems may be cause of various serious failures due to an ionizing radiation effect when exposed to a prompt gamma-ray pulse. This transient electrical malfunction can, in some cases, results in a failure of the electronic system of which the circuits are a part. Transient radiation measurement and evaluation system is required to development for enhanced radiation-resistance against the initial nuclear radiation produced by the detonation of a nuclear weapon of semiconductor devices. In these studies, we performed the following work. In the first part of the work, we carried out a SPICE simulation applied to nuclear radiation condition for PN diode and we also investigated the photocurrent by a pulsed gamma-ray on a PN diode using a TCAD simulation.

• Korean Journal of Microbiology
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• v.10 no.1
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• pp.29-34
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• 1972

The present study is of ultra-fine structure of Cryptococcus neoformans by means of electron microscopy and reveals the following : 1) In constrast to the bacteria, the normal Cryptococcus neofrmans contains nuclear enveloped with nuclear menbrane, mitochondria, endoplasmic reticulum, distinct cell wall and cell membrane, vacuoles and storage granules as observed in the eucaryotic cells. 2) In apparent cell walls and cell membrane with the appearance of electron transparent area (ETA) and changes of cell morphology were observed in the ultra-violet ray irradiated cell. 2) In apparent cell walls and cell membrance with the appreance of electron transparent area (ETA) and changes of cell morphology were observed in the ultra-violet ray irradiated cell. 3) Morphology changes and cytoplasmic element abnormality was increased with irradiated time. 4) Increase of electron transparent area was thought to be associated with degradation of cell.

• Journal of Radiation Protection and Research
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• v.46 no.3
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• pp.120-126
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• 2021

Background: This paper aims to evaluate the clinical utility and radiation dosimetry, for the mobile X-ray imaging of patients with known or suspected infectious diseases, through the window of an isolation room. The suitability of this technique for imaging coronavirus disease 2019 (COVID-19) patients is of particular focus here, although it is expected to have equal relevance to many infectious respiratory disease outbreaks. Materials and Methods: Two exposure levels were examined, a "typical" mobile exposure of 100 kVp/1.6 mAs and a "high" exposure of 120 kVp/5 mAs. Exposures of an anthropomorphic phantom were made, with and without a glass window present in the beam. The resultant phantom images were provided to experienced radiographers for image quality evaluation, using a Likert scale to rate the anatomical structure visibility. Results and Discussion: The incident air kerma doubled using the high exposure technique, from 29.47 µGy to 67.82 µGy and scattered radiation inside and outside the room increased. Despite an increase in beam energy, high exposure technique images received higher image quality scores than images acquired using lower exposure settings. Conclusion: Increased scattered radiation was very low and can be further mitigated by ensuring surrounding staff are appropriately distanced from both the patient and X-ray tube. Although an increase in incident air kerma was observed, practical advantages in infection control and personal protective equipment conservation were identified. Sites are encouraged to consider the use of this technique where appropriate, following the completion of standard justification practices.