• Progress in Medical Physics
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• v.32 no.4
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• pp.145-152
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• 2021

Purpose: During the treatments of cancer patients with a linear accelerator (LINAC) using photon beams with energies ≥8 MV, the components inside the LINAC head get activated through the interaction of photonuclear reaction (γ, n) and neutron capture (n, γ). We used spectroscopy and measured the dose rate for the LINAC in operation after the treatment ended. Methods: We performed spectroscopy and dose rate measurements for three units of LINACs with a portable high-purity Germanium (HPGe) detector and a survey meter. The spectra were obtained after the beams were turned off. Spectroscopy was conducted for 3,600 seconds, and the dose rate was measured three times. We identified the radionuclides for each LINAC. Results: According to gamma spectroscopy results, most of the nuclides were short-lived radionuclides with half-lives of 100 days, except for ⁶⁰Co, ⁶⁵Zn, and ¹⁸¹W nuclides. The dose rate for three LINACs obtained immediately in front of the crosshair was in the range of 0.113 to 0.129 µSv/h. The maximum and minimum dose rates measured on weekends were 0.097 µSv/h and 0.092 µSv/h, respectively. Compared with the differences in weekday data, there was no significant difference between the data measured on Saturday and Sunday. Conclusions: Most of the detected radionuclides had half-lives <100 days, and the dose rate decreased rapidly. For equipment that primarily used energies ≤10 MV, when the equipment was transferred after at least 10 minutes after shutting it down, it is expected that there will be little effect on the workers' exposure.

• Journal of Microbiology and Biotechnology
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• v.10 no.1
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• pp.1-7
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• 2000

Bioconversion of fumarate to succinate was anaerobically conduced in a synthetic medium containing glycerol as a hydrogen donor and fumarate as a hydrogen acceptor. We investigated the effects of pH, carbon and nitrogen sources, conversion substrate, and other culture conditions on the production of succinate using a nwely isoloated Enterococcus facalis PKY1. Addition of a variety of carbonates to the medium significantly increasd the rates of production of succinate. The production of succinate and cell growth were relatively satisfactory in the pH range of 7.0-7.6. By using glycerol as a hydrogen donor, high purity succinate was produced with few byproducts. Yeast extract as a sole nitrogen source was the most effective for producing succinalte. As a result, the optimum condition of biconversion was obtained at a medium containing 20g/I glycerol, 50 g/l fumarate, 15 g/l yeast extract, 10 g/l $K_2HPO_4$, 1 g/I NaCl, 50ppm $MgCl_2{\cdot}6H_2O$, 10ppm $FeSo_4{\cdot}7H_2O$, and 5 g/I $Na_2CO_3$ at pH 7.0-7.6. Under the optimum condition, a succinate concentration of 153 g/I was produced in 36 h. The total volumetric production rate and the molar yield of succinate were 4.3 g/l/h and 85%, respectively.

• Journal of the Korean Society of Radiology
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• v.14 no.4
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• pp.487-494
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• 2020

The distance between the source and the detector, the diameter of the detector, and the volume effect of the radiation source result in a change in solid angle at the detector entrance, which affects the determination of detection efficiency by causing a difference in path length within the detector. A typical analysis method for calculating solid angles was useful only for a source (⁶⁰Co) with a simple geometric structure, so in this experiment, the distance between the detector and the source was measured by switching on for up to 25 cm with the reference point of window cap 0.5 cm. In addition, 450 and 1000 ㎖ Marinelli beaker of standard volumetric sources were closely adhered to the detector. For circular point sources co-axial with the detector, the change in the solid angle to the distance from the detector window is equal to half the square radius of the source versus the square radius of the detector, if the resulting relationship of the calculation analysis results in the detector being less than the radius of the source. Since the solid angular difference is 0.5 the result of Monte Carlo is acceptable. The relationship between detector and source distance is shown. Solid angles have been verified to decrease rapidly with distance. Measurement and simulation results for a volumetric source show a difference of ±1.01% from a distance of 0 cm and less than 4 % when the distance is reduced to 5 and 10 cm. It can be seen that the longer distance, the smaller efficiency angle, and the exponential increase in attenuation as the energy decreases, is reflected in the calculation of efficiency. Thus, the detection efficiency has proved sufficient for the use of solid angle and Monte Carlo codes.

• Food Engineering Progress
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• v.13 no.4
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• pp.275-281
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• 2009

Sesame oils are partially mixed with other vegetable oils due to high price in a Korean market. To find out authentic sesame oil, a mass spectrometer-based electronic nose (MS-based E-nose) was used. Sesame oil (Se) was blended with soybean oil (So) or corn oil (Co) at the ratio (Se:So, Se:Co) of 97:3, 94:6, 91:9, 88:12 and 85:15, respectively. Intensities of each fragment from sesame oil by MS-based E-nose were completely different from those of soybean oil or corn oil. The obtained results were used for discriminant function analysis (DFA). Volatile organic components (VOC) of soybean oil or corn oil were similar to those of fresh air and DFA plot indicated a significant separation of pure sesame oil and pure other oil. The group of the mixed oil was seperated with that of sesame oil in DFA plot and the added amount of soybean oil to sesame oil was correlated with discriminant function first score (DF1). MS based E-nose system could be used as an efficient method to investigate the purity of sesame oil.

• Journal of Mushroom
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• v.3 no.1
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• pp.35-39
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• 2005

Highly Activated Calcium(below HAC) is the oxidized calcium made by dissolving shell materials with high voltage about 15,000V and high temperature ($1,500{\sim}5,000^{\circ}C$). This HAC is a material with a very high degree of purity without toxicant. This HAC decreases chemical reaction so the degree of being active and dissolving living material is outstanding. The effects of HAC on the propagation of mushrooms are following. In the case of the Pleurotus ostreatus, when controlling media moisture by mixing with the HAC, mycelium cultivating days were shortened by 2days. The day required for primordial formation after inoculation(DPI) were one day faster. The number of stem was 15 and individual weight was 248g/850cc, a 6.5% increase. In the case of Pleurotus eryngii, when controlling media moisture by mixing with the highly activated calcium, mycelium cultivating days were shortened by 3days. DPI were l day faster. The day required for colonization after inoculation was shortened by 6days and individual weight was 108.8g/850cc, a 9.7% increase. In the case of Flammulina velutipes, the highly activated calcium was the best for scraping up mycelium. Mycelium incubating days were shortened by 2days. DPI were shortened by 3days. The day required for colonization after inoculation was 1day faster and the period of cultivation was shortened by 3days. Individual weight was 165g/850cc, a 6.7% increase. In the case of Lentinula edodes, when mixing media with the highly cultivated calcium, cultivating days were shortened by 3 days. The days for becoming brown in color were 2 days faster and the days of the first harvest were shortened by 4 days. The weight of mushrooms was 169g/2kg, a 9.7% increase.

• Membrane Journal
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• v.32 no.4
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• pp.218-226
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• 2022

Hydrogen, a carrier of large-capacity chemical and clean energy, is an important industrial gas widely used in the petrochemical industry and fuel cells. In particular, hydrogen is mainly produced from fossil fuels through steam reforming and gasification, and carbon dioxide is generated as a by-product. Therefore, in order to obtain high-purity hydrogen, carbon dioxide should be removed. This review focused on free-standing polymeric membranes and mixed-matrix membranes (MMMs) that separate hydrogen from carbon dioxide reported in units of Barrer [1 Barrer = 10^-10 cm³ (STP) × cm / (cm² × s × cmHg)]. By analyzing various recently reported papers, the structure, morphology, interaction, and preparation method of the membranes are discussed, and the structure-property relationship is understood to help find better membrane materials in the future. Robeson's upper bound limits for hydrogen/carbon dioxide separation were presented through reviewing the performance and characteristics of various separation membranes, and various MMMs that improve separation properties using technologies such as crosslinking, blending and heat treatment were discussed.