• Journal of the Korean Society of Radiology
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• v.16 no.1
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• pp.61-66
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• 2022

The purpose of this study is to derive photon energy fluence and mass energy absorption coefficient for 1 Gy of absorbed dose of water in brachytherapy using an Ir¹⁹² source. From the radiotherapy physics written by Khan, the half-value of lead for the gamma ray beam of the Ir¹⁹² source was obtained. The linear attenuation coefficient and the mass attenuation coefficient were calculated from the obtained half-value layer of lead. By matching the calculated lead mass attenuation coefficient with the NIST mass attenuation coefficient data, the photon energy of the matching mass attenuation coefficient was determined as the effective energy. By matching the determined effective energy with the photon energy of the NIST data on the mass energy absorption coefficient of water, the mass energy absorption coefficient of water was obtained as 0.03273 cm²/g(32.73 cm²/kg). The photon energy fluence was calculated as 0.03055 J/cm² by dividing the obtained mass energy absorption coefficient (32.73 cm²/kg) by the absorbed dose of water 1 Gy.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1994.05a
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• pp.103-108
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• 1994

리튬브로마이드 수용액이 수직관내면을 따라 액막의 형태로 흘러 내릴때 수증기와의 흡수과정에 대하여 열 및 물질전달 특성을 실험하였다. 실험에서 열 및 물질전달계수는 막레이놀즈수를 30에서 200까지 변화시키면서 실시하였다. 일정한 냉방능력에서 시스템 압력을 변화시켰을 때의 열 및 물질전달계수를 측정하였다. 액막의 열전달계수는 레이놀즈수가 증가함에 따라 감소하였다. 최대 질량유량에서 최적의 막레이놀즈수가 존재하였다.

• Applied Chemistry for Engineering
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• v.21 no.1
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• pp.71-75
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• 2010

The efficient performance of absorber is of great importance for the absorption heat pump cycle. The experimental study of absorber with spiral tube of tangential feeding of liquid phase has been investigated using methanol-glycerine as a working fluid. The effect of change in absorber operating conditions was analyzed to improve the performance. The increase in solution flow rate and cooling flow rate positively affects the absorber performance while an increse in the solution concentration negatively affects the absorber performance. The results showed that mass absorption flux was in the range of $0.2{\sim}0.6kgm^{-2}sec^{-1}$, the solution heat transfer coefficient between 1.6 and $4.2kwm^{-2}K^{-1}$, the absorber thermal load from 0.9 to 1.5kw and the mass transfer coefficient from 0.9 to 1.7 m/sec.

• Radiation Oncology Journal
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• v.15 no.2
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• pp.153-158
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• 1997

Purpose : The Dual-Energy Quantitative Computed Tomography(DEQCT) was compared with bone equivalent $K_2HPO_4$ standard solution and ash weight of animal cadaveric trabecular bone in the measurement of bone mineral contents(BMC). Method and Materials : The attenuation coefficient of tissues highly depends on the radiation energy density and effective atomic number of composition, The bone mineral content of DEQCT in this experiments was determined from empirical constants and mass attenuation coefficients of bone,fat and soft tissue equivalent solution in two photon spectra. In this experiments, the BMC of DEQCT with 80 and $120kV_p$ X rays was compared to ash weight of animal trabecular bone. Results : We obtained the mass attenuation coefficient of 0.2409 0.5608 and 0.2206 in $80kV_p$, and 0.2046, 0.3273 and $0.1971cm^2/g$ in $120kV_p$ X-ray spectra for water bone and fat equivalent materials, respectively. The BMC with DEQCT was acomplished with empirical constants $K_1=0.3232,\;K_2$=0.2450 and mass attenuation coefficients has very closed to ash weight of animal trabecular bone The BMC of empirical DEQCT and that of manufacturing DEQCT were correlated with ash weight as a correlation r= 0.998 and r= 0.996, respectively. Conclusion : The BMC of empirical DEQCT using the experimental mass attenuation coefficients and that of manufacture have showed very close to ash weight of animal trabecular bone.

• Progress in Medical Physics
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• v.11 no.2
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• pp.131-139
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• 2000

We designed high dose rate Ir-192 source which was prepared for substitute the Co-60 source in Ralstron unit (Simatsu, Japan) which is supplied for cervical cancer treatment. The source dimension is 1.5 mm in a diameter and 1.5mm thickness of cylinder and encapsulated with 3 mm diameter of stainless steel(SUS316L) to substituted for the Co-60 source size. The Ir-192 source was prepared the dose model for tissue dose computation through the experimental determination of apparent activity and applied the empirical tissue correction factors extended to 20cm distance. The tissue dose model was applied the 4.69 R/cm-mCi-hr gamma constant and the ratio of energy absorption coefficient of water to that of air showed 1.112 include filteration of the self-absorptions. In this experiments, we prepared the dose computation software to clinical usefulness.

• Journal of Biosystems Engineering
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• v.2 no.2
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• pp.1-14
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• 1977

현재 선진국에서 널리 이용되고있는 곡물의 화력건조는 곡물의 품질을 손상시킬 뿐만 아니라 손실을 증가시키고 있다. 화력에 의한 건조는 또한 연료의 절약면에서 볼 때 역시 문제점을 내포하고있다.l 이러한 문제점들을 해결하기 위하여 근래에는 실리카 젤과 같은 흡습성의 건조제를 사용한 곡물의 건조 실험이 진행 중에 있으며 좋은 결과를 보여주고 있다. 실리카겔은 그 자체무게의 40% 까지 동적 및 정적하에서 수분을 흡수하는 성질을 가지고 있으며 일단 포화상태가 되면 수천번 재생이 가능하다. 본 연구에서는 이와같은 실리카텍의 재생실험을 일차적으로 실내에서 공기의 온도를 일정하게 한 상태에서 실시하였으며 일반적으로 실리카 젤은 $300^{\circ}F$에서 완전재생이 가능하나 본 실험에서 사용된 재생온도는 평면식 태양열 집열기로부터 얻을 수 있는 $150^{\circ}F$ 내외에서 시도하였다. 본실험과 병행하여 건조중 공기와 실리카 젤의 에너지 및 질량변화에 따른 이론식을 만들어 주어진 여러 가지 조건에 대하여 4개의 미분방정식을 컴퓨터에 의하여 해결하였으며 건조(재생) 시간에 따른 공기의 온도와 흡습 및 실리카 젤의 함수량을 구하였다. 위의 이론적인 분석결과는 후에 태양열집열기를 이용한 재생실험을 분석하는데 적용될 것이다. 본 연구결과를 요약하면 다음과 같다. 1. 본 연구에서 유도한 이론식은 실리카 젤의 재생온도를 만족스럽게 표시하였으며 재생시간에 따른 공기의 온도와 흡습 및 실리카 젤의 함수량변화의 이론치는 실험치와 근사하였다. 2. 이론치와 실험치를 일치시키기위하여 흡착온도에서 산출된 열 및 질량 전달계수를 1/5로 조정 사용하였다. 3. 실리카 젤은 $120^{\circ}F$에서 9 %, $180^{\circ}F$에서 1% 내외로 재생이 가능하였다. 4. 본 연구에서 유도된 이론적 분석방법은 다른 여러 가지 형태의 물질 및 건조 또는 냉각 과정을 분석하는데 사용될 수 있다.

• Journal of the Korean Society of Radiology
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• v.10 no.5
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• pp.327-335
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• 2016

The study is enforce to study image quality evaluation of condition provide the IEC and combination of clinical conditions each quality of radiation that image quality to assess the conditions provided to IEC in the clinical environment to conduct image quality assessment of the digital radiography system in the detector have environmental limits. First, image quality evaluation was evaluated by measuring the MTF, NPS using four quality of radiation and Using MCNPX simulation lastly DQE make a image quality evaluation after calculating the particle fluence to analyze spectrum quality of radiation. Second, Using MCNPX simulation of four quality of radiation was evaluated absorbed dose rate about electronic 1 per unit air, water, muscle, bone by using Radiation flux density and energy, mass-energy absorption coefficient of matter. Results of evaluation of image quality, MTF of four quality of radiation was satisfied diagnosis frequency domain 1.0 ~ 3.0 lp/mm of general X-ray that indicated 1.13 ~ 2.91 lp/mm spatial frequency. The NPS has added filter, spatial frequency 0.5 lp/mm at standard NPS showed a tendency to decrease after increase. Unused added filter, spatial frequency 0.5 lp/mm at standard NPS showed a certain NPS result value after decrease. DQE in 70 kVp / unuesd added filter(21 mm Al) / SID 150 cm that patial frequency 1.5 lp/mm at standard showed a tendency to decrease after certain value showed. Patial frequency in the rest quality of radiation was showed a tendency to decrease after increase. Results of evaluation of absorbed dose, air < water < muscle < bone in the order showed a tendency to increase. Based on the results of this study provide to basic data that present for the image quality evaluation method of a digital radiation imaging system in various the clinical condition.

• Journal of radiological science and technology
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• v.38 no.4
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• pp.355-363
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• 2015

Advancement in the medical field provides an opportunity for the development of medical equipment and also enable accurate diagnosis for the inspection and the treatment of diseases. The aging of equipment due to the frequent operation produce uncertainty in the patient exposure dose, so a quality control was implemented by establishing a safety management system on a regular basis. The x-ray tube voltage (kVp), which is directly involved in the patient exposure dose and the life of the equipment, needs periodic performance for the quality control, but it has a limitation due to the time and the cost. In this study, we proposed a new method for measuring the kVp with ease by using the Y and Cu to solve the problem of the time and cost. We also evaluated the usefulness and the effectiveness of the new method and its accuracy through the kVp measurement. After securing the condition, the amount of the tube current and evaluating the usefulness and effectiveness of kVp measured using Y and Cu. The density range used was at 0.5-1.0, kVp was in the range of ${\pm}10%$, then, we recorded the change in concentration as % of Y and Cu. This experiment showed that when Cu and Y was at 75 kVp, concentration was the same, and when the kVp was changed to 65 ~ 85 %, a gradual increase in concentration to 85 ~ 110 % was noted.

• Progress in Medical Physics
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• v.9 no.1
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• pp.55-64
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• 1998

In recent, the demand of development of the high dose rate brachytherapy source increased for substitute for Co-60 source by iridium source, since the supplying Co-60 source is very depressed and the high dose rate brachytherapy sources are entirely imported from the abroad. This study investigated the exposure rates and isotropic dose distributions for the Ir-192 source produced from $\^$191/Ir(n,r)$\^$192/Ir by nuclear reactor in Korea Atomic Energy Research Institute. The activity of source was obtained an 1.012 Ci (the initial activity without encapsulation was 2,87Ci) by measurement with encapsuled stainless steel. The exposure rate of provided Ir-192 source was determined on 6.36 ${\pm}$ 0.147 Rm$^2$/h-GBq (2.350 ${\pm}$ 0.054 Rcm$^2$/mCi-hr) within ${\pm}$ 2.2% discrepancy with IC-10 ion chamber (0.14 cc) which was mounted on the acrylic jig to 5, 10 and 20 cm from the center of source. The calculated doses with 22 most significant spectrum lines were corrected with intrinsic efficiency of the germanium detector were compared to measured exposure dose rates within ${\pm}$3.8 % discrepancy. The authors confirmed the high dose rate Ir-192 source could be replaced the long decayed Co-60 source via investigation of the isotropic dose distributions in lateral, source axis and diagonal direction of source center are very closed to within 3% uncertainties. Especially, this exposure rate constant and isotropic dose distribution will be fundamental to build the high dose rate source and develop the computed therapy planning system.