• Progress in Medical Physics
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• v.26 no.4
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• pp.223-228
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• 2015

Double-focused micro-Multileaf Collimator (${\mu}MLC$) is able to create radiation fields having sharper dose gradients at the field edges than common MLC. Therefore, ${\mu}MLC$ has been used for the stereotactic radiosurgery (SRS) and Stereotactic Radiotherapy (SRT). We evaluated the dosimetric characteristics of a doublefocused Dynamic-${\mu}MLC$ (DMLC) attached to the Elekta Synergy linear accelerator. For this study, the dosimetric parameters including, Percent Depth Dose (PDD), Leaf leakage and penumbra, have been measured by using of the radiochromic films (GafChromic EBT2), EDGE diode detector and three-dimensional water phantom. All datas were measured on 6 MV x-ray. As a result, The DMLC shows transmission below to 1% and because of double-focused construction of the DMLC, the penumbras of fields with DMLC are independent from the field sizes. In this paper, the resulting dosimetric evaluations proved the applicability of the DMLC attached to the Elekta Synergy linear accelerator.

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

• Journal of Chest Surgery
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• v.21 no.6
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• pp.979-983
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• 1988

Calcium channel blockers may prevent myocardial injury during cardioplegia and reperfusion. This study was done to evaluate the effects of diltiazem cardioplegia on myocardial protection during ischemic arrest and recovery of myocardial function after reperfusion. Four formulations of crystalloid cardioplegic solutions, GIK solution[group I, n=12], diltiazem[lug/ml GIK] in GIK solution[group II, n=7], ],diltiazem[2ug/ml GIK] in GIK solution[group III, n=6] and diltiazem[4ug/ml GIK] in GIK solution[group IV, n=6] were compared in isolated working rat heart subjected to a long period [2 hours] of hypothermic arrest with multi-dose infusion. Diltiazem cardioplegia[group II, III and IV]was found to be superior in nearly all aspects. Diltiazem cardioplegia showed faster recovery of regular rhythm and lower incidence of ventricular fibrillation than group I did. In comparing mechanical function in all experimental hearts, the mean postischemic recoveries of aortic flow, cardiac output, peak aortic pressure, stroke volume and stroke work[expressed as a percentage of its preischemic control] were significantly greater in group II, III and IV[diltiazem cardioplegia] than in group I. The infused amount of cardioplegic solution was more increased by the addition of diltiazem to GI K solution. [p < 0.01] Creatine kinase leakage tended to be lower in hearts receiving diltiazem cardioplegia, especially in group III and IV[p<0.05] than in those receiving GIK solution only[group I]. Diltiazem cardioplegia results in the increased flow of cardioplegic solution and the decreased ischemic injury of myocardium during ischemic arrest and the improved recovery of myocardial function after reperfusion, and a dose-response relation must be established before clinical use.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.6
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• pp.38-48
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• 1993

A recessed n-p Juction diode with the self-aligned sturcture is proposed and fabricated by using the polysilicon as an n$^{+}$ diffusion source. The diode structure can be applicable to the emitter-base formation of high performance bipolar divice and the n$^{+}$ polysilicone mitter has an important effect on the device characteristics. The considered parameters for the polysilicon formation are the deposition condition. As$^{+}$ dose for the doping of the polysilicon and the annealing condition using RTP system. The vertical depth profiles of the fabricated diode are obtained by SIMS and the electrical characteristics are analyzed in terms of the ideality factor of diode (n), contact resistance and reverse leakage current. In addition, n$^{+}$-p junction diodes are formed by using the amorphous silicon (of combination of amorphous and polysiliocn) instead of polysilicon and their characteristics are compared with those of the standard sample. The As$^{+}$ dose for the formation of good junction is about 1~2${\times}10^{16}cm^{2}$ at given RTA conditions (1100.deg. C, 10sec).

• Korean Journal of Pharmacognosy
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• v.36 no.3 s.142
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• pp.224-228
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• 2005

Protective effects of various natural flavonoids on carbon tetrachloride $(CCl_4)-induced$ hepatotoxicity were investigated in primary cultured rat hepatocytes. Some of these flavonoids decreased the ALT and LDH releases induced by $CCl_4$ in A dose-dependent manner. Neohesperidin, hesperetin, baicalin, baicalein and quercetin inhibited $CCl_4-induced$ alanine aminotransferase (ALT) release. In addition, quercetin, quercitrin, neohesperidin, baicalin, baicalein and naringin reduced $CCl_4$ induced lactate dehydrogenase (LDH) leakage. Among these flavonoids, quercitrin, quercetin, baicalin and baicalein possessed potent protective effects and were selected for the further investigation on lipid peroxidation. These four flavonoids inhibited dose dependently $CCl_4-induced$ lipid peroxidation. Especially, the protective effects of quercetin and baicalein were similar to silybin as a well-known hepatoprotective agent. These results suggest that these four flavonoids have significant cytoprotective effects and possibility of therapeutic effect on chemical-induced liver diseases.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.21 no.4
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• pp.531-541
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• 2023

The Wolsong Nuclear Power Plant (NPP) operates an on-site spent fuel dry storage facility using concrete silo and vertical module systems. This facility must be safely maintained until the spent nuclear fuel (SNF) is transferred to an external interim or final disposal facility, aligning with national policies on spent nuclear fuel management. The concrete silo system, operational since 1992, requires an aging management review for its long-term operation and potential license renewal. This involves comparing aging management programs of different dry storage systems against the U.S. NRC's guidelines for license renewal of spent nuclear fuel dry storage facilities and the U.S. DOE's program for long-term storage. Based on this comparison, a specific aging management program for the silo system was developed. Furthermore, the facility's current practices-periodic checks of surface dose rate, contamination, weld integrity, leakage, surface and groundwater, cumulative dose, and concrete structure-were evaluated for their suitability in managing the silo system's aging. Based on this review, several improvements were proposed.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.1
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• pp.27-35
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• 2015

Objectives: To investigate safety and health management, conditions in factories or facilities handling radiation-generating devices and radioactive isotopes were reviewed in terms of regulations of radiation safety control in Korea. Radiation exposure levels generated at those facilities were directly measured and evaluated for establishing an effective safety and health management plan. Methods: Government organizations with laws and systems of radiation safety and health were investigated and compared. There are three laws governing radiation-related employment such as occupational safety and health acts, nuclear safety acts, and medical service acts. We inspected 12 workplaces as research objects:four workplaces that manufacture and assemble semiconductor devices, three non-destructive inspection workplaces that perform inspections on radiation penetration, and five workplaces in textile and tire manufacturing. Monitoring of radiation exposure was performed through two methods. Spatial and surface monitoring using real-time radiation instruments was performed on each site handling radiation generating devices and radioactive isotopes in order to identify radiation leakage. Results: According to the occupational safety and health act, there is no legal obligation to measure ionizing radiation and set dose limits. This can cause confusion in the application of the laws, because the scopes and contents are different from each other. Surface dose rates in radiation generating devices such as implanters, thickness gages and accelerators, which were registered according to nuclear safety acts, using surveymeters, and seven of 36 facilities(19.4%) exceeded the international standards for surface radiation dose of $10{\mu}Sv/hr$. Conclusions: The results showed that occupational health and safety acts require a separate provision for measuring and assessing the radiation exposure of workers performing radiation work. Like noise, ionizing radiation will also periodically be controlled by including it in the object factors of work-environment measurement.

• Journal of Ginseng Research
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• v.36 no.3
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• pp.248-255
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• 2012

Potential antioxidant effect of processed ginseng (sun ginseng, SG) on oxidative stress generated by tert-butyl hydroperoxide (t-BHP) was investigated in HepG2 cells. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and lactate dehydrogenase (LDH) leakage test demonstrated that SG dose-dependently prevents a loss of cell viability against t-BHP-induced oxidative stress. Also, SG treatment dose-dependently relieved the increment of activities of hepatic enzymes, such as aspartate aminotrasferase and alanine aminotransferase, and lipid peroxidation mediated by t-BHP treatment in HepG2 cells. SG increased the gene expression of antioxidant enzymes such as superoxide dismutase, catalase, and glutathione peroxidase. However, high dose of SG treatment caused decrease in mRNA level of glutathione peroxidase as compared to low dosage of SG-treated cells. The gene expression of glutathione reductase was found to be slightly increased by SG treatment. In addition, SG extract attributed its hepaprotective effect by inducing the mRNA level of bcl-2 and bcl-xL but reducing that of bax. But, the gene expression of bad showed no significant change in SG-treated HepG2 cells. These findings suggest that SG has hepatoprotective effect by showing reduction of LDH release, activities of hepatic enzymes and lipid peroxidation and regulating the gene expression of antioxidant enzymes and apoptosis-related molecules against oxdative stress caused by t-BHP in HepG2 cells.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.39 no.6
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• pp.42-48
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• 2002

The design, construction and performance test of a convenient multi-purpose irradiator is described. A multi-purpose irradiator using Cesium-137 has been developed for studies of low dose radiation effects in biology and for calibration of Thermo Luminescent dosimeter(TLD). During the operation, three rods of radioactive material which are 10cm in length revolve 180 degrees and irradiate biological samples, or TLD, and return to their shielded position, after the programmed time. A programmable Logic Controller(PLC) controls the sequence of operation, interlock, motor rotation and safety system. The rotation speed of biological samples can vary up to 20 RPM. A real time monitoring system was also incorporated to check and control the operation status of the irradiator. The capacity of the irradiation chamber was 4.5 liters. The isodose distribution at arbitrary vertical planes was measured by using film dosimetry. The dose-rate was 0.13 cGy/min in air and 0.11 cGy/min in water equivalent material in the case of Cesium-137. Range of activity was 2 Ci. The homogeneity of dose distribution in the chamber was ${\pm}$7%. The actual radiation level on the surface was within permissible levels. The irradiator had a maximum 0.35 mR/min radiation leakage on its surface.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.11
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• pp.490-492
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• 2005

A study on radiation hardening of infrared(IR) detector, the chief component of IR camera was performed. The radiation test on IR sensor passivated with the ZnS by Co$^{60}$ gamma-ray over 1 Mrads showed the reduction in Ro by 1/100 which was related to the noise level. This effect that was caused by carrier trapping in the ZnS passivation layer increased the leakage current and resulted in degradation in the device performance. For the radiation hardening of IR devices we suggested the ones with CdTe passivation layer which had a tendency to reluctant to carrier trapping in its layer and developed test patterns. Radiation test to the patterns showed that the our CdTe passivated device could survived over 1 Mrad gamma-ray dose.