• The Journal of Korean Academy of Prosthodontics
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• v.48 no.4
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• pp.266-272
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• 2010

Purpose: The purpose of this study was to investigate the effects of the surface morphology of the implant neck on marginal bone stress measured by using finite element analysis in six implant models. Materials and methods: The submerged type rescue implant system (Dentis co., Daegu, Korea) was selected as an experimental model. The implants were divided into six groups whose implant necks were differently designed in terms of height (h, 0.4 and 1.0 mm) and width (platform width, w = 3.34 + 2b [b, 0.2, 0.3 and 0.4 mm]). Finite element models of implant/bone complex were created using an axisymmetric scheme. A load of 100 N was applied to the central node on the top of crown in parallel with the implant axis. The maximum compression stress was calculated and compared. Results: Stress concentration commonly observed around dental implants did not occur in the marginal bone around all six test implant models. Marginal bone stress varied according to the implant neck bevel which had different width and height. The stress was affected more markedly by the difference in height than in width. Conclusion: This result indicates that the implant neck bevel may play an important role in improving stress distribution in the marginal bone area.

• Progress in Medical Physics
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• v.11 no.1
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• pp.1-18
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• 2000

For wedged photon beams, the variation of the wedge factor with field size was reported by several authors. However, until now such variation with field size had not been explained quantitatively. Therefore, the variation of the wedge factor was investigated by measuring outputs with field sizes increasing from 4 cm $\times$ 4 cm to 25 cm $\times$ 25 cm for open and wedged 6 and 10MV X-ray beams. The relative outputs for wedged fields to 10 cm $\times$ 10 cm have been obtained. The results show the Increase of the wedge factor caused by the change in fluence of high energy Photon beam with field size, up to 8.0% for KD77-6MV X-ray beam. This increase could be explained as a linear function of the irradiated wedge volume except small field size up to about 10 cm. In the cases of the narrow rectangular beam parallel to the wedge direction, the wedge factor decreases slightly with increasing field size up to about 10-15 cm due to a relatively reduced photon fluence from the change of the wedge thickness. We could explain the causes of a wedge factor variation with field size as the fluences of primary photon passed throughout the wedge, contributing to the dose at the central beam axis and that the fluences were affected by the gradient of the wedge with the change of field size. For clinical use, the formula developed to describe the wedge factor variation with field size has been corrected.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.23-30
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• 2017

Most superconducting magnets which generate more than 20 T consist of nested magnets. A combination of LTS and HTS magnets is conventionally used, but high field magnets which use only HTS magnets have been developed recently. As HTS wires have very strong magnetic anisotropy, appropriate techniques should be used to consider this effect properly. The load line method has been conventionally used to design nested magnets for high field generation. Because this method considers only parallel and perpendicular magnetic fields, the effect of their orientation is not taken into account. In this paper, the actual orientation of the magnetic fields from 0 to 90 degrees is considered. The critical currents of the two kinds of high field nested magnets designed using the proposed method are calculated. The finite element method is used to calculate the distribution of the magnetic fields and the evolution strategy is used to find the critical current which maximizes the central magnetic field.

• Journal of radiological science and technology
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• v.21 no.2
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• pp.36-42
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• 1998

Treatment of a large diseased area with electron often requires the use of two or more adjoining fields. In such cases, not only electron beam divergence and lateral scattering but also fields overlapping and separation may lead to significant dose inhomogeneities(${\pm}20%$) at the region of junction of fields. In this study, we made Acrylic Electron Wedges to improve dose inhomogeneities(${\pm}5%$) in these junction areas and to apply it to clinical practices. All measurements were made using 6, 9, 12, 16, 20 MeV Electron beams from a linear accelerator for a $10{\times}10\;cm$ field at 100cm of SSD. Adding a 1 mm sheet of acryl gradually from 1 mm to 15 mm acquires central axis depth dose beam profile and isodose curves in water phantom. As a result, for all energies, the practical range was reduced by approximately the same distance according to the acryl insert, e.g. a 1 mm thick acryl insert reduces the practical range by approximately 1 mm. For every mm thickness of acryl inserted, the beam energy was reduced to approximately 0.2 MeV. These effects were almost Independent of beam energy and field size. The use of Acrylic Electron Wedges produced a small increase(less than 3%) in the surface dose and a small increase(less than 1%) in X-ray contamination. For acryl inserts, thickness of 3 mm or greater, the penumbra width increased nearly linear for all energies and isodose curves near the beam edge were nearly parallel with the incident beam direction at the point of penumbra width($35\;mm{\sim}40\;mm$). We decide heel thickness and angle of the wedge at this point. These data provide the information necessary to design Acrylic Electron Wedge which can be used to improve dose uniformity at electron field junctions and it will be effectively applied to clinical practices.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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• v.24 no.1
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• pp.142-170
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• 2011

Objective : The purpose of this study is to investigate dizziness of Plain Questions $\ll$素問$\gg$ and Miraculous Pivot $\ll$靈樞$\gg$. Methods : We conducted a study on the original text paragraphs of Internal Classic $\ll$內經$\gg$ containing the dizziness and analysis of Yang, Ma, Zhang, Wang etc. We drew a parallel between dizziness from Internal Classic $\ll$內經$\gg$and matching diagnoses from western medicine. Results : The results were as follows. 1. Dizziness in Ok Ki Jin Jiang Ron <玉機眞藏論> and Pyo Bon Byeong Jeon Ron <標本病傳論> had relation to liver and was similar to dizziness caused by tension, hypertension, anemia and cerebrovascular accident etc. in western medicine. 2. Dizziness in Ja Yeol<刺熱>, O Sa<五邪> and Hai Ron<海論> had relation to kidney and was similar to dizziness caused by aging and peripheral vertigo concurrent with tinnitus and difficulty in hearing in western medicine. 3. Dizziness in O Sa<五邪> had relation to heart(pericardium) and was similar to dizziness caused by cardiac output loss and psychogenic dizziness in western medicine. 4. In Internal Classic $\ll$內經$\gg$ the main etiology of dizziness was infirmity(虛), which were Qi(氣) of the upper portion of the body being insufficient(上氣不足), blood depletion(血枯), deficiency of marrow-reservoir(髓海不足) etc. 5. In Dae Hok Ron<大惑論> etiology and pathogenesis of dizziness were mentioned and dizziness was similar to dizziness caused by eye disorder, psychogenic dizziness and central dizziness in western medicine. 6. In Internal Classic $\ll$內經$\gg$ the meridian of acupuncture points which was used much for dizziness was Bladder Meridian. Aqupunture points used in treatment of dizziness were Ch'onju(天柱), Kollyun(崑崙), Taejo, Chok-t'ongkok(足通谷) etc. Conclusion : We found out etiology, pathogenesis, treatments of dizziness in Internal Classic $\ll$內經$\gg$. Further we compared with western medicine to develop better understanding of dizziness.

• Journal of Dental Rehabilitation and Applied Science
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• v.27 no.4
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• pp.371-392
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• 2011

The purpose of this study was to comparatively analyze the stress distribution according to the inclinations of abutments and angulations of the implant fixtures under occlusal loading force. Three study models with straight and $15^{\circ}$ and $25^{\circ}$-angled abutments were prepared following the insertion of Implants parallel to the long axis of the tooth. Additional two experimental models were fabricated with $15^{\circ}$ and $25^{\circ}$ fixture inclinations. Using ANSYS 11, a finite element analysis program, the magnitudes of stress distribution were analyzed. The magnitude of stress under loading was lowest when the load was applied vertically onto the axis of implant. And the magnitude of stress under compound(vertical+oblique) loading was increased as the inclination of implant abutment and fixture was increase. But, the distribution of stress was different as the loading conditions, because of the horizontal offset. As the offset between the axis of loading and the central axis of the implant increased, the stress was increased.

• Journal of the Korean Chemical Society
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• v.32 no.5
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• pp.476-482
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• 1988

Kinetic studies and theoretical investigations were made to illustrate the mechanism of the aquation of cis-[Co(en)$_2$YCl]$^{r+}$ (Y = NH$_3$, NO$_2^-$, NCS$^-$, $H_2O$) in $Hg^{2+}$ aqueous solution UV/vis-spectrophotometrically. The aquation of cis-[Co(en)$_2$YCl]$^{r+}$ have been found to be the second order for overall reaction as first order for each of substrate and Hg$^{2+}$+ catalyst. The reaction rate was increased in the order of Y=NH$_3$ < NCS$^-$- < $H_2O$ < $NO_2^-$, which are neighboring group of Cl. The step of bond formation was found to be the rate determining one, because the net charge of central metal ion run parallel with the observed rate constant. On the basis of rate determining step, kinetic data and the observed activation parameters, we have proposed the Id mechanism for the reaction system. The rate equation derived from the proposed mechanism has been in agreement with the observed rate equation.

• Development and Reproduction
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• v.2 no.1
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• pp.89-99
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• 1998

This study was carried out to investigate the morphological changes of gonadotropes in pituitary gland and spermatogenic cells in testis, obtained from 150 of 3-year-old immature and mature male rainbow trout (Oncorhynchus mykiss) during the reproductive cycles from March to February in the following year. In the maturation cycle of the pituitary gonadotropes of cultured rainbow trout, three periods can be distinguished i.e. a period of resting(March-August), a period of full spermatogenesis (September-November), and a period of breeding (December-February). The ultrastructures of the gonadotropes largely parallel the cyclical changes in the tests. The seminiferous tubules contain all spermatogenetic stages and sperm cells in a period of early maturation. At first, the size of the nucleus and cytoplasm decrease gradually at every stages from spermatogonia to spermatids. In the secondary spermatocytes, the small mitochondria are located over the outer cytoplam. In spermatids, the cytoplasmic masses move toward the posterior part of the nucleus. In spermatids, the two large mitochondria are located over the cytoplasm. In spermatids, the cytoplasmic masses move towark the posterior part of the nucleus. In spermatids, the two large mitochondria are located over the cytoplasm and begin to elongate. In spermatozoa, the surface of the nucleus devreases in volume. Examination by TEM shows that the nuclear envelope and plasma membrane are slightlywrinkled and closely adhered to the nucleus of spermatozoa. Two oval mitochondria are quite separated and the flagellum is inserted into the base of the spermatozoa head.The axoneme in this fish has the typical pattern such as nine peripheral doublets and a central doublet(9+2). there are remarkable individual differences in the size and morphology of spermatozoa head as observed by transmission and scanning electron microscopy.

• Journal of the Korean Society for Library and Information Science
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• v.23
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• pp.263-301
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• 1992

In recent years, Korean public libraries, placed under changing circumstances, require that some new and positive financial policies be formulated for the improvement of their services. T he purpose of this study is to propose a scheme to ensure the revenues of Korean public libraries. The main contents of this study are as follows : (1) Public finance theory is applied to the question of why the public library is publicly supported. The public library does not contribute to stabilization, but it does playa role in each of the other public sector functions : allocation of resources and redistribution of income. In public finance terms there is justification for at least partial subsidy of public library services, which have the attributes of public goods, merit goods and externalities. (2) Public libraries in Korea find themselves suffering from limited budgets. They are neglected in national and local budgets. The lack of adequate funding for library collections prevents libraries from rendering efficient services. (3) In order to put the finances of the Korean public library system on a firm basis, the following proposals are made: 1) It is proposed that the parallel administration under which public libraries are organized be unified to be directly under the local governments. 2) It is proposed that the legislative and administrative system for public library finance be strengthened. (1) Library expenses should be itemized independently in the calculation of general grants-in-aid to local governments. (2) A fixed portion of the total municipal revenue should be appropriated for public library services. It can be executed by making provisions expressly in the annual guidelines for budgeting, municipal ordinances, or in the Library Promotion Law. The rate of allocation should be specified as a part of the national public library development plan. (3) Library tax as a local tax can be imposed. An indirect tax is preferable in order to avoid public misunderstanding and antagonism. 3) The augmentation of the specific grants-in-aid for the public library is proposed. The Library Promotion Law and the Law on Budget and Administration of Grants should be amended to oblige the central government to give financial assistance to local public libraries. 4) It is proposed that strategies to encourage private endowments be worked out. Revision of the Law on Tax Reduction and Exemption and the activation of an advisory library committee at each public library are recommended. 5) Funding and utilization of the envisioned Library Promotion Foundation is proposed. Government contributions, contributions from the Culture and Arts Foundation, and donations from individuals, corporations, and enterprises can be considered as the financial resources of the Foundation. 6) It is proposed that the structure of the Korean Library Association be consolidated to exercise greater influence over the formation of national policy on the public library system. 7) It is proposed as an ultimate guarantee of the health of the public libraries that the citizenry be educated to strongly support library services in responce to the active services provided by the public libraries.

• Radiation Oncology Journal
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• v.7 no.1
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• pp.93-100
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• 1989

Several combinations of measuring devices and phantoms were studied to measure electron beams. Silicon Pmt junction diode was used to find the dependence of depth dose profile on field size on axis of electron beam Depths of 50, 80 and $90\%$ doses increased with the field size for small fields. For some larger fields, they were nearly constant. The smallest of field sizes over which the parameters were constant was enlarged with increase of the energy of electron beams. Depth dose distributions on axis of electron beam of $10\times10cm^2$ field were studied with several combinations of measuring devices and phantoms. Cylindrical ion chamber could not be used for measurement of surface dose, and was not convenient for measurement of near surface region of 6MeV electron. With some exceptions, parameters agreed well with those studied by different devices and phantoms. Surface dose in some energies showed $4\%$ difference between maximum and minimum. For 18MeV, depths of 80 and $90\%$ doses were considerably shallower by film than by others. Parallel-plate ion chamber with polystyrene phamtom and silicon PN junction would be recommended for measurement of central axis depth dose of electron beams with considerably large field size. It is desirable not to use cylindrical ion chamber for the purpose of measurement of surface dose or near surface region for lower energy electron beam. It is questionable that film would be recommended for measurement of dose distribution of electron with high energy like as 18MeV.