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박근창(Geunchang PARK),서정명(Jeongmyeong SEO),오우석(Wooseok OH),이경훈(Kyounghoon LEE) 전남대학교 어업기술연구소 2018 어업기술연구소보고지 Vol.11 No.1
This study was aimed at measuring the acoustic impedance of Japanese black porgy to estimate its sustainable production and resources. The acoustic impedance need to know density contrast and sound speed contrast of target fish. The density contrast is obtained by the Pipette method and sound speed contrast is obtained by the Time-of-flight method. To get basic information on the Japanese black porgy in the experiment, 10 different sizes used. As a result, the body length increases as the weight of the Japanese black porgy was increased. The correlation between the body length and density contrast of the Japanese black porgy was very low. Also, the acoustic speed contrast was shown at very low correlation. However, due to lack of 20~25cm of Japanese black porgy, the standard deviation value is not constant. The impedance results of Japanese black porgy will should be used as basic date of acoustic scattering characteristic and identification of fish.
Park Hajung,Kim Nahun,Yu Jaeyoung,Rhie Jiyeah,Choi Geunchang,Bahk Young-Mi 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.81 No.12
Drugs or foods in various forms, such as hydrate and anhydrous forms, can afect the diferent therapeutic efect, which is crucial to identify pseudo-polymorphic state. Cafeine, taken in various routes such as cofee, energy drinks, and drugs, has diferent characteristics in the form of cafeine hydrate or anhydrous cafeine. Here, we investigate a dehydration process of cafeine hydrate by monitoring temporal evolution of terahertz absorption spectra under various exposure times in ambient. It was observed that the main absorption peak of cafeine hydrate at 2.3 THz moves to 1.3 THz indicating anhydrous cafeine during the dehydration process. Moreover, we represent the dehydration process with a simple parameter by extracting the ratio between the absorption values at 2.3 THz and 1.3 THz corresponding to the main absorption resonances of cafeine hydrate and anhydrous cafeine, respectively. Our results demonstrate the feasibility of terahertz spectroscopy technique to monitor dehydration in real time during the manufacturing process in pharmaceutical or biological industries.
Terahertz conductivity of high-quality indium films deposited using a substrate cooling method
Choi Geunchang,Choi Dong-Hwan,Ryeom Junho,Park Dae Young,Kim Wu-Sin,Kim Ju-Jin,Bahk Young-Mi,Jeong Mun Seok 한국물리학회 2023 Current Applied Physics Vol.52 No.-
High-quality indium thin films were fabricated by substrate cooling method during the metal deposition. The cooling effect reduced the threshold thickness for insulator-to-metal transition, which originates from the interconnections between the indium nano-islands. The complex conductivities of the films were measured by terahertz time-domain spectroscopy. We showed that the conductivity of the indium films prepared by substrate cooling were ~10 times higher than that deposited at room temperature, even though thickness of the former was lower than that of the latter film. Our results suggest that substrate cooling is promising for the applications of metal thin films and contacts.
Evaluation of moisturizing cream using terahertz time-domain spectroscopy
Choi Geunchang,Lee Do-Hee,Park Ikpyeong,Kang Daecheol,Lee Hyun Kyung,Rhie Jiyeah,Bahk Young-Mi 한국물리학회 2022 Current Applied Physics Vol.39 No.-
Terahertz time-domain spectroscopy is a useful tool for material characterization because it provides both temporal and frequency domain information. In this work, we perform terahertz time-domain spectroscopy for evaluation of commercial moisturizing cream cosmetics. By measurement of terahertz transmission, the change of complex refractive index by exposure of the cosmetic samples in ambient condition is obtained. The tendency of terahertz transmission change is different from that of mass change, which implies that terahertz response becomes a new characterization tool for moisturizing cosmetics. Our results show that terahertz time-domain spectroscopy has potential application on cosmetic testing.