• 전기학회논문지
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• 제56권1호
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• pp.174-182
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• 2007

In this paper, we study the influence of infection ratio on gradual reduction of drug dose for the five state HIV infection model that explicitly includes the population of the virus. We first compute all equilibrium points of the model and investigate the stabilities of them. As a result, a bifurcation diagram is obtained which shows a change in the equilibrium points, or in their stability properties, as the drug effect $\eta$ is varied from 0 to 1(alternatively, drug dose is changed from 1 to 0). Based on the bifurcation diagram, we show that the gradual reduction of drug dose can be applied for the treatment of AIDS patients. Moreover, we analyze the influence of the variation of infection ratio on the gradual reduction treatment. Computer simulation results are also presented to validate the proposed results.

• 대한방사선기술학회지:방사선기술과학
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• 제23권1호
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• pp.97-101
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• 2000

In this study, the highly sensitive $CaSO_4:Tm$-PTFE TLDs has been fabricated for the purpose of measurement of high energy electron. $CaSO_4:Tm$ phosphor powder was mixed with polytetrafluoroethylene(PTFE) powder and moulded in a disk type(diameter 8.5 mm. thickness $90\;mg/cm^2$) by cold pressing. The absorbed dose distribution and ranges for high energy electron were measured by using the $CaSO_4:Tm$-PTFE TLDs. The ranges determined were $R_{100}=14.5mm$, $R_{50}=24.1mm$ and $R_P=31.8mm$, respectively and the beam flatness, the variation of relative dose in 80% of the field size, was 4.5%. The fabricated $CaSO_4:Tm$-PTFE TLDs nay be utilized in radiation dosimetry for personal, absorbed dose and environmental monitoring.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.565-568
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• 2002

The value of charge current, discharge current, $\varepsilon_r$' $\varepsilon_r"$, residual voltage was measured inorder to investigate electric properties in Ethylene Prophylene Rubber for is irradiated $CO^{60}\gamma$ ray 0-38.1 Mrad. The value of charge current and the discharging current of the EPR is influenced by $CO^{60}-{\gamma}$-irradiation dose The charging current and the discharging current of EPR increase, depending on the ratio of degradation. As the irradiation dose is increased, the peak of residual voltage moves to the slorter time. The properties specific electric constant due to time variation was appeared dispersion by plentiful $CO^{60}-{\gamma}$-irradiation dose. The increase of peak in $\varepsilon_r"$ is attrib uted to the irratiation dose almost proportionally.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2002년도 추계학술대회
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• pp.253-259
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• 2002

The value of charge currnet, discharge current, ${\varepsilon}r^'$,${\varepsilon}r^{'}$ residual voltage was measured inorder to investigate electric properties in Ethylene Prophylene Rubber for is irradiated C0$^{60}$$\gamma$ ray 0~38.1 Mrad. The value of charge current and the discharging current of the EPR is influenced by C0$^{60}$-$\gamma$- irradiation dose. The charging current and the discharging current of EPR increas, depending on the ratio of degradation. As the irradiatin dose is increased, the peak of residual voltage moves to the slorter time. The properties specific electric constant due to time variation was appeared dispersion by plentiful C0$^{60}$$\gamma$- irradiation dose. The increase of peak in ${\varepsilon}r^{'}$ is attrib uted to the irratiation dose almost proportionally.

• 한국산업보건학회지
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• 제31권4호
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• pp.342-352
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• 2021

Objectives: This study analyzed the local exposure levels of radiation emitted from the equipment with soft X-ray ionizers to investigate the radiation exposure levels in Liquid Crystal Display(LCD) manufacturing processes. Methods: This study measured the local radiation levels for the equipment installed in two LCD manufacturing companies. The equipment were installed at diverse processes and equipped with various number of ionizers. The local radiation levels were measured on the surface of the equipment by using direct reading equipment, and the measurements were converted into annual effective dose by considering the radiation exposure time of workers. Statistical analyses were performed to investigate the radiation exposure characteristics. Results: Annual effective doses for 97.6% of the equipment being measured were less than 1 mSv. However, the range of annual effective doses was 0.004 mSv ~ 2.167 mSv, which indicated a large variation among the equipment. Statistical analyses of the study found that this large variation was raised due to improper shielding of the equipment rather than process and/or equipment characteristics. To pinpoint the cause of this large variation in annual effective dose, this study improved the shielding of the equipment being radiated over 1 mSv and found that their average effective dose was reduced from 1.604 mSv to 0.126 mSv after shielding improvement. Conclusions: Relatively high exposure levels of radiation were observed in some equipment where their shielding were insufficiently thick and/or sealed. This finding implies that the shielding of the equipment is an important engineering countermeasure to control the radiation exposure levels in industries.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.269-271
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• 2002

It is reported that exposure for the patient and the medical staff from IVR is large. Direct measurement of patient exposure is difficult, since the measurement disturbs reading of images. The fluorescence glass-dosimeter system consisting of small-size glass chips is developed in recent years. Owing to its small size and physical characteristics, direct monitoring of surface dose may be feasible. The dose measurement for patient and medical staff during head interventional radiology (IVR) examinations was tried by using the fluorescence glass-dosimeter system. A dose response of the glass dosimeter is almost linear in large dose range but its energy dependency is high. About 20% variation of sensitivity was observed in the effective energy of 45-60keV which was used in IVR. In spite of this shortcoming, the fluorescence glass-dosimeter system is a convenient means for a dose monitoring during IVR performance.

• Radiation Oncology Journal
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• 제11권2호
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• pp.455-461
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• 1993

Experimental measurements of dose characteristics with pentagonal applicator at nominal energy of 4, 6, 9, 12 and 15 MeV electron beam were performed for intraoperative radiotherapy (IORT) in ML-15MDX linear accelerator. This paper presents the percent depth dose, surface dose, beam flatness and output factors of using the IORT applicator in different electron beam energy. The output factor showed as a 24 percent higher in IORT applicator than that of reference $10{\times}10cm^2$ applicator. The surface dose of using the IORT applicator showed 7.7 and 2.7 percent higher than that of reference field in 4 and 15 MeV electron beam, respectively. In our experiments, the variation of percent depth dose was very small but the output factor and flatnees at 0.5 cm depth have showed a large value in IORT applicator.

• 대한방사선기술학회지:방사선기술과학
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• 제41권6호
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• pp.603-610
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• 2018

This study examined the following: accuracy of the exposure conditions in the inverter device and three-phase device; output waveform over the exposure conditions; and average and standard deviation of the output waveform. After assessing whether the dose corresponding to the theoretical dose was presented, the following conclusions were obtained: 1. The accuracy of the tube voltage(kVp) and tube current(mA) exposure time(sec) was within the tolerable level prescribed in Korea's Safety Management Standards. In the error, Inverter device was large the tube voltage and exposure time, the three-phase device was large the tube current. 2. In terms of the output waveform of the exposure conditions and the average and standard deviation of the output waveform, the higher tube voltage and larger tube current resulted in greater standard deviation in pulsation. Moreover, the standard deviation of pulsation was shown to be greater in the inverter device than the three-phase device; there was also greater standard deviation in the inverter device considering the exposure time. 3. Regarding the exposure conditions over the output dose, all linearity showed the coefficient of variation which had an allowable limit of error within 0.05. Although the output dose ratio for the inverter device was 1.00~1.10 times no difference that of the three-phase device, there was almost no difference in dose ratio between the tube currents.

• Imaging Science in Dentistry
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• 제42권2호
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• pp.65-70
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• 2012

Purpose : The aim of this study was to compare the effective dose for imaging of mandible between multi-detector computed tomography (MDCT) and cone-beam computed tomography (CBCT). An MDCT with low dose technique was also compared with them. Materials and Methods : Thermoluminescent dosimeter (TLD) chips were placed at 25 organ sites of an anthropomorphic phantom. The mandible of the phantom was exposed using 2 different types of MDCT units (Somatom Sensation 10 for standard-dose MDCT, Somatom Emotion 6 for low-dose MDCT) and 3 different CBCT units (AZ3000CT, Implagraphy, and Kavo 3D eXaM). The radiation absorbed dose was measured and the effective dose was calculated according to the ICRP 2007 report. Results : The effective dose was the highest for Somatom Sensation 10 (425.84 ${\mu}Sv$), followed by AZ3000CT (332.4 ${\mu}Sv$), Somatom Emotion 6 (199.38 ${\mu}Sv$), and 3D eXaM (111.6 ${\mu}Sv$); it was the lowest for Implagraphy (83.09 ${\mu}Sv$). The CBCT showed significant variation in dose level with different device. Conclusion : The effective doses of MDCTs were not significantly different from those of CBCTs for imaging of mandible. The effective dose of MDCT could be markedly decreased by using the low-dose technique.

• 대한방사선기술학회지:방사선기술과학
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• 제41권6호
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• pp.561-566
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• 2018

Field-in-Field Technique is applied to the radiation therapy of breast cancer patients, and it is possible to compensate the difference in breast thickness and deliver uniform dose in the breast. However, there are several fields in the treatment field that result in a more complex dose delivery than a single field dose delivery. If the patient's respiration is irregular during the delivery of the dose by several fields and the change of respiration occurs, the dose distribution in the breast changes. Therefore, based on the computed tomography images of breast cancer patients, a human model was created by using a 3D printer (Builder Extreme 1000) to describe the volume in the same manner. A computerized tomography (CT) of the human body model was performed and a treatment plan of 260 cGy / fx was established using a 6-MV field-in-field technique using a computerized treatment planning system (Eclipse 13.6, Varian, USA). The distribution of the dose in the breast according to the change of the respiration was measured using a moving phantom at 0.1 cm, 0.3 cm, 0.5 cm amplitude, using a MOSOXIDE Silicon Field Effect Transistor (MOSFET, Best Medical, Canada) Were measured and compared. The distribution of dose in the breast according to the change of respiration showed similar value within ${\pm}2%$ in the movement up to 0.3 cm compared to the treatment plan. In this experiment, we found that the dose distribution in the breast due to the change of respiration when the change of respiration was increased was not much different from the treatment plan.