• Journal of the Korean Society of Radiology
• /
• v.9 no.7
• /
• pp.433-438
• /
• 2015

To evaluate the radiation exposure level based on radiation workers' locations in dental radiography, the radiation dose rate in the radiographic room, lead glass, and operation system was measured. To that end, various devices were used, such as a Standard(Max-GLS, Shinhung), a panorama (PCH-2500, Vatech), a cephalometric radiography (PCH-2500), and a cone beam CT (PHT-30LFO, Vatech), as well as a PM1405 equipment as a radiation meter. Radiography conditions were set the same as the factors used in the clinical setting. As the result, the cone beam CT turned out the highest with 98 uSv and the standard showed the lowest level with 0.4 uSv/h. The panorama was measured to be higher than the Cephalo due to its different focus mode. On the lead glass surface and in the operation stand, the oral radiography device, panoramic, and Cephalo all were measured below the recording level. However, the cone beam CT was measured to have the leakage dose. Thus, radiation involved workers should be equipped with appropriate protection tools and reduce radiography time as much as possible. In addition, the structure of the radiation chamber should be also designed efficiently. Dental radiography has continued to grow in recent years, so it is necessary take appropriate protection measures for patients and radiation workers.

• Progress in Medical Physics
• /
• v.29 no.2
• /
• pp.47-52
• /
• 2018

To investigate the effect of low magnetic field on dose distribution in SABR plans for liver cancer, we calculated and evaluated the dose distribution to each organ with and without magnetic fields. Ten patients received a 50 Gy dose in five fractions using the $ViewRay^{(R)}$ treatment planning system. For planning target volume (PTV), the results were analyzed in the point minimum ($D_{min}$), maximum ($D_{max}$), mean dose ($D_{mean}$) and volume receiving at least 90% ($V_{90%}$), 95% ($V_{95%}$), and 100% ($V_{100%}$) of the prescription dose, respectively. For organs at risk (OARs), the duodenum and stomach were analyzed with $D_{0.5cc}$ and $D_{2cc}$, and the remained liver except for PTV was analyzed with $D_{mean}$, $D_{max}$, and $D_{min}$. Both inner and outer shells were analyzed with the point $D_{min}$, $D_{max}$, and $D_{mean}$, respectively. For PTV, the maximum change in volume due to the presence or absence of the low magnetic field showed a percentage difference of up to $0.67{\pm}0.60%$. In OAR analysis, there is no significant difference for the magnetic field. In both shell structure analyses, although there are no major changes in dose distribution, the largest value of deviation for $D_{max}$ in the outer shell is $2.12{\pm}2.67Gy$. The effect of low magnetic field on dose distribution by a Co-60 beam was not significantly observed within the body, but the dose deposition was only appreciable outside the body.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.14 no.5
• /
• pp.529-545
• /
• 2012

Three-dimensional (3D) finite element analyses have been performed to study the behaviour of a single pile to open face tunnelling in stiff clay. Several key factors such as tunnelling-induced ground and pile settlement, and shear transfer mechanism have been studied in detail. Tunnelling resulted in the development of pile settlement larger than the Greenfield soil surface settlement. In addition, due to changes in the shear transfer between the pile and the soil next to the pile with tunnel advancement, axial force distributions along the pile change drastically. The apparent allowable pile capacity was reduced up to about 30% due to the development of tunnelling-induced pile head settlement. The skin friction on the pile was increased with tunnel advancement associated with the changes of soil stresses and ground deformation and hence axial pile force distribution was reduced. Maximum tunnelling-induced tensile force on the pile was about 21% of the designed pile capacity. The zone of influence on the pile behaviour in the longitudinal direction may be identified as ${\pm}1$-2D (D: tunnel diameter) from the pile centre (behind and ahead of the pile axis in the longitudinal direction) based on the analysis conditions assumed in the current study. Negative excess pore pressure was mobilised near the pile tip, while positive excess pore pressure was computed at the upper part of the pile. It has been found that the serviceability of a pile experiencing adjacent tunnelling is more affected by pile settlement than axial pile force changes.

• Journal of the Korean Vacuum Society
• /
• v.17 no.1
• /
• pp.28-33
• /
• 2008

Lanthanum modified lead zirconate titanate ($Pb_{1.1}La_{0.08}Zr_{0.65}Ti_{0.35}O_3$) thin films were fabricated on indium doped tin oxide (ITO)-coated glass substrate by R.F magnetron sputtering method. The thin films were deposited at $500^{\circ}C$ and post-annealed with various temperature ($550-750^{\circ}C$) by rapid thermal annealing technique. The structure and morphology of the films were characterized with X-ray diffraction (XRD) and atomic force microscopy (AFM) respectively. The hysteresis loops and fatigue properties of thin films were measured by precision material analyzer. As the annealing temperature was increased, the remnant polarization value was increased from $10.6{\mu}C/cm^2$ to $31.4{\mu}C/cm^2$, and coercive field was reduced from 79.9 kV/cm to 60.9 kV/cm. As a result of polarization endurance analysis, the remnant polarization of PLZT thin films annealed at $700^{\circ}C$ was decreased 15% after $10^9$ switching cycles using 1MHz square wave form at ${\pm}5V$.

• Polymer(Korea)
• /
• v.24 no.6
• /
• pp.737-743
• /
• 2000

Polyquinonediimines (PQDI) which have stable structure on heat and contains mono-azobenzene in the side chain were synthesized by means of condensation polymerization under TiCl$_4$. The synthesized monomers and polymers were identified by FT-IR, $^1$H-NMR, and elementary analysis. Especially, PQDI was comfirmed by the double-bonding peak of >C=N appeared near 1625 $cm^{-1}$ / by means of FT-IR spectrum. PQDI containing mono-azobenzene group in both side chains wat not soluble in non-polar solvents at all but partially soluble in the polar solvents having small dielectric constant, and dissolved in the strong acid such as sulfuric acid and $CH_3$SO$_3$H. Molecular weight distribution of PQDI measured by GPC showed 1.74. It was confirmed through X-ray diffraction analysis that the polymer was partially crystalline at the low angle region, but amorphous after heat treatment at 1$25^{\circ}C$. The glass transition temperature (T$_{g}$ ) of synthesized polymer was measured as 1$25^{\circ}C$ by differential scanning calorimetry. The SHG value for $\chi$$^{(2)}$ after poling at 1$25^{\circ}C$ was 8.6 pm/V (λ=1.542 ${\mu}{\textrm}{m}$). The SHG value slowly decreased with time from the start but appeared temporal stability after 100 hours.

• Korean Journal of Environmental Agriculture
• /
• v.10 no.2
• /
• pp.149-157
• /
• 1991

In order to elucidate the possible change in the non-extractable bound residue of TCAB(3,3' 4,4' - tetrachloroazobenzene) in soil as a function of aging period, uniformly ring-labelled $^{14}C-TCAB$ was treated to soil(organic matter : 1.8%), and aged for 3, 6, 9, 12 and 15 months at $21{\pm}1^{\circ}C$, respectively. $^{14}CO_2$ evolution and volatilization loss during the aging were negligible. The amounts of non-extractable bound residue of TCAB increased gradually from 7.55% in 3-month aging to 19.32% in 15-month aging. Partition data suggested no formation of polar groups in the chemical structure of TCAB. Most of $^{14}C-radioactivity$ of bound residues was present in humin in the range of 50.52 to 58.93%. The fact that the number of microorganisms in soil decreased relative to the control suggested no chance of their involvement in the formation of non-extractable bound residues. Accordingly, the increase in the non-extractable bound residue of TCAB in soil with aging period is believed to be due to the transformation of the trans isomer to the cis one which is more polar and more adsorptive than the former.

• The Journal of Korean Society of Virology
• /
• v.29 no.2
• /
• pp.119-127
• /
• 1999

Phylogenetic analysis was conducted to monitor transmission of HIV and to investigate the genetic structure of primary isolates from 12 HIV-1 subtype A infected Koreans. The individuals infected with subtype A viruses had been diagnosed as HIV-1 seropositives during the period 1987 to 1995 and blood samples have been collected from 1991 to 1997. DNA of each individual was isolated from uncultured or cultured peripheral blood mononuclear cells. V3-V5 (0.7 kb) fragment of HIV-1 env gene was amplified by nested polymerase chain reaction and the PCR products were sequenced. The mean value of the divergence of nucleotide of HIV-1 env V3-V5 fragment was $17.0{\pm}4.06%$ ($8.6{\sim}25.8%$) within HIV-1 subtype A isolates from Koreans. This diversity was higher than those of African isolates ($13.7{\pm}2.66%$). In the phylogenetic tree, Korean subtype A isolates were not grouped together, but intermingled into African isolates. The results of this study suggested that HIV-1 subtype A variants be introduced from multiple sites of Africa into Korea and the big genetic diversity of Korea HIV-1 subtype A isolates may be further influenced by the range of geographic locations in which the infection occurred rather than the elapsed time between infection and collection of samples and the disease progression.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.38 no.4
• /
• pp.371-377
• /
• 2014

In tissue engineering, a scaffold is a three-dimensional(3D) structure that serves as a template for regeneration the functions of damaged tissues or organs. Among materials for scaffolds, polycaprolactone(PCL) and ${\beta}$-tricalcium phosphate(${\beta}$-TCP) are biodegradable and biocompatible. In this study, we fabricated 3D PCL, blended PCL (60 wt %)/${\beta}$-TCP (40 wt %), and pure ${\beta}$-TCP scaffolds by a multi-head scaffold fabrication system. Scaffolds with a pore size of $600{\pm}20{\mu}m$ was observed by scanning electron microscopy. The effects of 3D PCL, blended PCL (60 wt %)/${\beta}$-TCP (40 wt %) and pure ${\beta}$-TCP scaffolds were analyzed by evaluating their mechanical characteristics. In addition, in an in-vitro study using osteoblast-like saos-2 cells, we confirmed the effects of 3D scaffolds on cellular behaviors such as cell adhesion and proliferation. In summary, the 3D blended PCL (60 wt %)/${\beta}$-TCP (40 wt %) scaffold was found to be suitable for human cancellous bone in terms of its the compressive strength, biocompatibility, and osteoconductivity. Thus, blending PCL and ${\beta}$-TCP could be a promising approach for fabricating 3D scaffolds for effective bone regeneration.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.9 no.1
• /
• pp.37-48
• /
• 2007

Forest vegetation types and growth characteristics of Seongin-bong at Ulleung Island in Korea were studied by using importance values, distributions of diameter classes, and annual growth analysis. Vegetation types were classified into 7 groups. The number of existing woody plant and herbaceous plant species varied from 17 to 21 species per $100m^2$. In case of life-forms importance values, woody and herbs showed average values of 47% and 53% across 5 groups. But in Tsuga sieboldii-Pinus parviflora and Fague engleriana- Taxus cuspidata var. latifolia groups, woody importance values were 68% and 54%, respectively. Diameter classes in most stand types were regularly distributed and showed continuous growth in annual diameter growth. from these results, this site is expected to maintain a stable vegetation structure continuously. F. engleriana, which forms major species in this site, showed 0.46-0.62 cm in annual average diameter growth. The annual average diameter growth of broad-leaved tree species was 0.2-0.6 cm, while the growth rate of T. sieboldii and P. parviflora was 0.38 cm and that of T. cuspidata var, latifolia was below 0.1 cm.

• Journal of the Korean Vacuum Society
• /
• v.7 no.1
• /
• pp.66-71
• /
• 1998

Two kinds of $Ga_2S_3:Er$ (type A and type B) single crystals were grown by the chemical transport reaction method using iodine as a transport agent. The single crystals were crystallized into a monoclinic structure. The optical energy band gaps were found to 3.375 eV for the $Ga_2S_3:Er$ (type A) single crystal and 3.365 eV fir the $Ga_2S_3:Er$ (type B) single crystal at 13K. When the $Ga_2S_3:Er$ (type A and type B) single crystals were excited by the 325 nm-line of a Cd-He laser, Photoluminescence spectra of the $Ga_2S_3:Er$ (type A) single crystal exhibited blue emission band peaked at 444 nm and green and red emission bands peaked at 518 nm and 690 nm. Pgitikynubescebce soectra if the $Ga_2S_3:Er$ (typeB) single crystal showed green and red emission bands peaked at 513 nm and 695 nm. Sharp emission peaks in the two kinds if $Ga_2S_3:Er$ single crystal were observed near 525 nm, 553 nm, 664 nm, 812 nm, 986 nm, and 1540 nm and analysed as originating from the electron transitions between the energy levels of $Er^{3+}$ ion.