• Journal of the Korean Physical Society
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• v.73 no.9
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• pp.1334-1339
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• 2018

Spherical nickel ferrite nanoparticles were synthesized using the thermal decomposition method and coated with cetyl trimethyl ammonium bromide (CTAB) after the synthesis. Transmission electron microscopy images showed that the average diameter of the particles was 9.40 nm. The status of the CTAB-coating on the surface of the particles was checked using Fourier-transform infrared spectroscopy. Their hysteresis curve showed that the particles exhibited a superparamagnetic behavior. The $T_1$ and the $T_2$ relaxations of the nuclear spins were observed in aqueous solutions of the particles with different particles concentrations by using a magnetic resonance imaging (MRI) scanner, which showed that the $T_1$ and the $T_2$ relaxivities of the particles in water were $0.57mM^{-1}{\cdot}s^{-1}$ and $10.42mM^{-1}{\cdot}s^{-1}$, respectively. In addition, using an induction heating system, we evaluated their potentials for magnetic hyperthermia applications. The aqueous solution of the particles with a moderate concentration (smaller than 6.5 mg/mL) showed a saturation temperature larger than the hyperthermia target temperature of $42^{\circ}C$. These findings show that the CTAB-coated nickel ferrite particles are suitable for applications as $T_2$ contrast agents in MRI and heat generators in magnetic hyperthermia.

• Corrosion Science and Technology
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• v.23 no.2
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• pp.145-153
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• 2024

In the automotive industry, the hole expanding test is widely used to assess the formability of punched holes in sheets. This test provides a good representation of formability within the framework defined by the ISO 16630 standard. During hole expanding tests on galvanized high strength steels, a negative effect was observed when there was a delay between hole punching and expansion, as compared to performing both operations directly. This effect is believed to be caused by hydrogen aging, which occurs when hydrogen diffuses towards highly-work hardened edges. Therefore, the aim of this study is to demonstrate the migration of hydrogen towards work-hardened edges in high strength Zn-coated steel sheets using a novel Thermal Desorption Analyzer (TDA) designed for small samples. This newly-developed TDA setup allows for the quantification of local diffusible hydrogen near cut edges. With its induction heating and ability to analyze Zn-coated samples while reducing artifacts, this setup offers flexible heat cycles. Through this method, a hydrogen gradient is observed over short distances in shear-cut galvanized steel sheets after a certain period of time following punching.

• Journal of the Korean Society of Food Science and Nutrition
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• v.18 no.3
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• pp.247-254
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• 1989

In deep-fat frying, the fats and oils are used over and over again, and moisture and air are mixed in to the hot oil. Many reports related to these fats and oils have been established that thermal and oxidative decomposition products and polymers formed under the conditions of deep fat frying are harmful to health. This work was carried out with 3 domestic frying oils and 6 used oils commercially, and that there were difficulties in finding a good definition between fresh oil and used oil with adding unheated oil. As starting materials, commercially used soybean oil and rapeseed oil already passed over induction period in the lipids oxidation standard. From the qualitative point of view, they were inferior to domestic frying oils. Free fatty acid and peroxide value of heated oils were increased gradually by the time pass whereas iodine value were decreased. After adding unheated oil to the heated oil, these values were restored to that of initial levels. On the other hand, content of polar components in the heated oil were directly related to the heating time. This result showed that polar compounds may be a clear indicator of used oils. Fatty acid composition in the used oils, unsaturated fatty acids such as linoleic and linolenic acid decreased while saturated fatty acid content increased with heating.

• The Journal of the Korea Contents Association
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• v.9 no.11
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• pp.247-253
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• 2009

We investigated the cell growth rate according to the change of temperature of the Thermo-rod used for the local hyperthermia therapy. For this study, we fabricated the Thermo-rods (TR) using Duplex Stainless Steels having magnetic properties as well as non magnetic properties. To evaluate cell growth rates up to 15 days, we conducted cell proliferation test using cell counting methods. For the tests, the CAPEs and Osteoblats were seeded on the 6-we11 plates with the induction heated thermo-rods 30 mins a day for 15 days with 2 days interval and without induction heated thermo-rods as control group respectively. We calculated cell growth rates, 6 hours after heating. From the results, in case of CAPEs and Osteobalsts seeded groups, the cell growth rates in all groups increased drastically for 6 days after seeding, but decreased irregularly after 6 days. In conclusion, the cell growth rates showed no significant difference among all groups and it indicated that there were no effects of temperate ($41^{\circ}C$) on cell growth rates.

• The Korean Journal of Malacology
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• v.25 no.2
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• pp.113-119
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• 2009

Artificial induction of maturation by heating of the hard clam, Meretrix petechiails (Lamarck) broodstock was investigated from 25 May to 30 June in 2008. We experimented maturation by keeping the breeding water temperature at 20, 25 and $30^{\circ}C$ and as the natural water temperature and found the following results. In case of the female, maturation was the quickest in the experiment group of $30^{\circ}C$ and the maturation tended to be slower as the water temperature was lower. The similar trend was displayed among the male. At experiment completion, maturation induction rate was found to be the highest at 46.0% in the experiment group of $30^{\circ}C$ followed by 35.0% in the experiment group of $15^{\circ}C$, 18.0% in the experiment group of natural water temperature and 12.0% in the experiment group of $20^{\circ}C$. During the period of the experiment, the survival rate was of 90% or more in all groups.

• Biomedical Science Letters
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• v.11 no.3
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• pp.343-347
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• 2005

Bambusae caulis in Liquamen is one of the important herbal medicine produced by heating bamboo indirectly and is used for treatment of stroke, hypertension, and diabetes etc. Recently the mechanism of clinical effects on Bambusae caulis in Liquamen has been studied. This experiment was conducted to confirm the clinical effects of Bambusae caulis in Liquamen on type 1 diabetes and its related mechanism. We divided C57BL/6 mice into 3 groups and induced them to be type 1 diabetes by injection of streptozocin into peritoneum. The dosage of each group was 150 mg/kg once only, 140 mg/kg once only and 40 mg/kg for 5 days respectively. The two groups injected streptozocin for once took orally Bambusae caulis in Liquamen after the induction of diabetes, and the other one group was given Bambusae caulis in Liquamen during the diabetes inducing period. As the result, the two diabetes-induced groups showed blood glucose decreasing effect by Bambusae caulis in Liquamen on an average, but they didn't show the signiftcant differences statistically. But Bambusae caulis in Liquamen showed the anti-diabetic effect suppressing blood sugar rising trend during the diabetes inducing peried (P<0.05). The anti-oxidative effect of Bambusae caulis in Liquamen was measured with the hypoxanthine/xanthine oxidase (HX/XOD) system. The quantity of ROS was measured using DCFDA reagent indirectly. As the result, $10\%$ solution of Bambusae caulis in Liquamen showed anti-oxidative effect by scavenging $93.4\%$ superoxide as compared with control group. It is suspected that the anti-oxidative effect of Bambusae caulis in Liquamen suppressed the increase of blood glucose in the diabetes-inducing group. These results could be useful data to understand the effect of Bambusae caulis in Liquamen on type 1 diabetes and type 1 diabetes developing because ROS were closely connected with the induction and complications of diabetes.

• The Korean Journal of Malacology
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• v.20 no.1
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• pp.75-84
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• 2004

Reproductive cycle, the condition index, sex ratio of the Pacific oysters, Crassostrea gigas were investigated by histological and morphometric data. The specimens were collected in the two oyster farms of Geoje and Namhae, Gyeongsangnam-do, Korea, from November 1995 to October 1996. Growth of shell length in two regions was similar, but growth of total weight of the oyster in Namhae was faster than that in Geoje oyster farm. The spawning periods in female and male clams were from July to October in Geoje and from June to October in Namhae oyster farm. Ripe oocytes were approximately 50 m in diameter. The reproductive cycle of in females and males in Geoje and Namhae oyster farms can be divided into five successive stages: early developing, late developing, ripe, partially spawned and spent/inactive. Monthly changes in gonad developmental phases showed somewhat different patterns between female and male clams except for the spawning period. On the whole, however, monthly changes in the gonad developmental phases showed a similar pattern in the same sex. The sex ratios of females to males in Geoje and Namhae oyster farms were not significantly different from a 1:1 sex ratio ($x^2$ = 0.55 (p > 0.05) in Geoje and $x^2$ = 0.27 ( p > 0.05) in Namhae). Artificial induction of maturation by heating of adult oysters (two-year-old) was investigated from 17 January to 18 March in 1996. Maturity at the fixed water temperature group of $20^{\circ}C$ was 80%, it showed the highest maturity of experimental groups cultured for five weeks. The survival (%) of Crassostrea gigas in the raised water temperature experimental groups (15, 20, $25^{\circ}C$) were over 98.5%, as similar to the control group (100%). But, the survival of C. gigas in the fixed water temperature experimental groups (15, 20, 25, $30^{\circ}C$) were decreased with the increase of the water temperatures. In the fixed water temperature experimental group of $30^{\circ}C$, the survival was 51.1%. Base on these results, the fixed water temperature of $20^{\circ}C$ was the best condition for artificial induction of sexual maturation.

• The Korean Journal of Malacology
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• v.22 no.2
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• pp.175-182
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• 2006

Artificial induction of maturation by heating of the ark shell, Scapharca broughtonii (Schrenck) broodstock was investigated from 10th March to 21th May in 2004. Maturity at the fixed water temperature group of $23^{\circ}C$ was 60.5％, and it was the highest in maturity among experimental groups cultured for seven weeks. The proportions of organism surviving to start of S. broughtonii in the raised water temperature experimental groups (20 and $23^{\circ}C$) were over 90.5％, as similar to the control group (natural water temperature, 84.8％). But, the proportions of organism surviving to start of S. broughtonii in the fixed water temperature experimental groups (20, 23, and $26^{\circ}C$) were decreased with the increasing of the water temperature. In the fixed water temperature experimental groups of $26^{\circ}C$, the survival was 18.1％. Base on these results, the fixed water temperature of $20^{\circ}C$ (accumulated water temperature; $1,295^{\circ}C$) was the best condition for artificial induction of sexual maturation.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.32 no.4
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• pp.381-392
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• 2022

Objectives: Objective of this study is to review briefly exposure characteristics, monitoring instruments and threshold limit values for extremely low frequency-magnetic field (ELF-MF) methods. This study was undertaken through brief literature review. We performed a literature search in PubMed to identify ELF-MF studies conducted in workplaces. Initial search keywords such as 'extremely low frequency-magnetic field (ELF-MF)' and 'electromagnetic fields (EMF)' combined or singly. We limited our review to occupational rather than general nonworkplace environmental exposures. Methods: The contents we reviewed: key industry and occupations generating ELF-MF, several direct-reading instruments monitoring ELF-MF and threshold limit values (TLV) preventing health effects may be caused by the exposure to ELF-MF. Results: The industries related to the generation and supply of electricity, electrolytic installations, welding, and induction heating and more were regarded as high ELF-MF exposure industries. All jobs handling or employed performed in power cable lines, electrical wiring, and electrical equipment are found to be exposed to ELF-MF. Threshold or ceiling limit, 1,000 µT, is established to prevent acute effects of exposure to low-frequency EMFs on the nervous system: the direct stimulation of nerve and muscle tissues and the induction of retinal phosphenes. The International Agency for Research on Cancer (IARC) has classified ELF-MF as possibly carcinogenic to humans chiefly based on epidemiological studies on childhood leukemia. However, a causal relationship between magnetic fields and several types of cancer including childhood leukemia has not been established nor has any other long-term effects. Risk management using precautionary measures, has been initiated by the US and EU to prevent chronic health effects related to ELF-MF exposure in workplaces. Conclusion: This study recommends the implementation of various measures such as theestablishment of occupational exposure limit values for ELF-MF and precautionary principle to prevent potential chronic occupational health effects may be caused by ELF-MF in Korea.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.1
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• pp.109-117
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• 2000

A full bridge type double resonant high frequency resonant inverter to give VVVF function in the inverter used as power source of induction heating at high frequency is presented in this paper. This proposed inverter can reduce distribution of the switching current because of using the current of serial resonant circuit to the input current of the parallel one and this paper also realize the output control of independence irrespective of the switching frequency using Phase-shift. The analysis of the proposed circuit is generally described by using the normalized parameters. Also, the principle of basic operating and the its characteristics are estimated by the parameters, such as switching frequency, the variation of phase angle ($\phi$) of Phase-shift.