http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Quantitative analysis of NaI(Tl) gamma-ray spectrometry using an artificial neural network
Kim, Jinhwan,Lim, Kyung Taek,Kim, Junhyeok,Kim, Chang-jong,Jeon, Byoungil,Park, Kyeongjin,Kim, Giyoon,Kim, Hojik,Cho, Gyuseong Elsevier BV * North-Holland 2019 Nuclear Instruments & Methods in Physics Research. Vol. No.
<P><B>Abstract</B></P> <P>In this manuscript, we propose an algorithm based on an artificial neural network (ANN) for the analysis of the NaI(Tl) gamma-ray spectra with radioisotope (RI) mixtures to identify RIs and determine the relative activity levels of the identified RIs. The ANN was trained based on the spectra that were generated by synthesizing previously identified spectra from single RIs, considering the characteristics of the measurement environments, such as gain shift effects and statistical fluctuations in the spectrum. The proposed ANN was evaluated through several measured spectra that contained up to six certified reference materials for a quantitative analysis. We also evaluated the shift in the spectra due to temperature variations in the range of 0–50 °C and the low-count spectra with a one-second acquisition period. These results were compared with those from an ANN trained through simulated spectra to emphasize the importance of acquiring a high-quality training dataset. In addition, we show that complex low-resolution spectra can be accurately analyzed with the proposed ANN under various scenarios, in which the maximum root mean square error was found to be 2.8%.</P>
Antiferromagnetic coupling of van der Waals ferromagnetic Fe<sub>3</sub>GeTe<sub>2</sub>
Kim, Dongseuk,Park, Sijin,Lee, Jinhwan,Yoon, Jungbum,Joo, Sungjung,Kim, Taeyueb,Min, Kil-joon,Park, Seung-Young,Kim, Changsoo,Moon, Kyoung-Woong,Lee, Changgu,Hong, Jisang,Hwang, Chanyong IOP Pub 2019 Nanotechnology Vol.30 No.24
<P>Among two-dimensional (2D) layered van der Waals materials, ferromagnetic 2D materials can be useful for compact low-power spintronic applications. One promising candidate material is Fe<SUB>3</SUB>GeTe<SUB>2</SUB> (FGT), which has a strong perpendicular magnetic anisotropy and relatively high Curie temperature. In this study, we confirmed that an oxide layer (O-FGT) naturally forms on top of exfoliated FGT and that an antiferromagnetic coupling (AFC) exists between FGT and O-FGT layers. From a first-principles calculation, oxide formation at the interface of each layer induces an AFC between the layers. An AFC causes a tailed hysteresis loop, where two-magnetization reversal curves are included, and a negative remanence magnetization at a certain temperature range.</P>
Kim, Jinhwan,Park, Kyeongjin,Cho, Gyuseong Elsevier 2019 Applied radiation and isotopes Vol.147 No.-
<P><B>Abstract</B></P> <P>Radioisotope identification using a plastic scintillation detector has been a challenging issue because of the poor spectral resolution and low cross-sections of these types of detectors when used for photoelectric absorption. In this paper, we propose an algorithm that identifies a single radioisotope and multiple radioisotopes from the gamma spectrum of a plastic scintillator using an artificial neural network. The spectra were simulated using Monte Carlo N-Particle Transport Code 6 to formulate the training set, and the spectra were measured by a two-inch EJ-200 to create the test set (1440 spectra in total). The ANN-based algorithm presented here ensures an identification accuracy of 98.9% for a single radioisotope and 99.1% for multiple radioisotopes. Even if the spectra were intentionally shifted by 36 keV for low and high energies, the trained ANN predicts radioisotopes with high accuracy. In addition, we have determined the minimal required number of detected counts to identify the radioisotope with 5% false negative and false positive.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Multi-radioisotopes were identified using an artificial neural network (ANN). </LI> <LI> The ANN was trained with simulated spectra by MCNP6. </LI> <LI> The algorithm was evaluated using measured plastic gamma spectra. </LI> <LI> Shifted spectra were also evaluated by the trained ANN. </LI> </UL> </P>
Microfluidic Fabrication of Multistimuli-Responsive Tubular Hydrogels for Cellular Scaffolds
Kim, Dongwan,Jo, Ara,Imani, Kusuma Betha Cahaya,Kim, Dowan,Chung, Jin-Woong,Yoon, Jinhwan American Chemical Society 2018 Langmuir Vol.34 No.14
<P>Stimuli-responsive hydrogel microfibers and microtubes are in great demand for biomedical applications due to their similarity to the native extracellular matrix. In this study, we prepared pH- and temperature-responsive hydrogel microfibers and microtubes using a microfluidic device through alginate-templated photopolymerization. Hydrogel monomer solutions containing <I>N</I>-isopropylacrylamide (NIPAm) and sodium acrylate (SA) or allyl amine (AA) were irradiated with UV light to invoke in situ photopolymerization. A repulsive force between the ionized SA or AA groups caused by protonation/deprotonation of the acrylate or amine groups, respectively, led to changes in the diameters and wall thicknesses of the fibers and/or tubes depending on the pH of the medium. Poly(NIPAm) is a well-known thermally responsive polymer wherein the NIPAm-based copolymer microfibers exhibited a thermal behavior close to the lower critical solution temperature. We have demonstrated that these multistimuli-responsive volume changes are fully reversible and repeatable. Furthermore, the positively charged microfibers were shown to exhibit cell adhesion, and the number of cells attached to the microfibers could be further increased by supplying nutrients, presenting the possibility of their application in tissue engineering and other biomedical fields.</P> [FIG OMISSION]</BR>
Kim, Jinhwan,Ji, Jae-Hoon,Shin, Dong-Jin,Koh, Jung-Hyuk Elsevier 2018 CERAMICS INTERNATIONAL Vol.44 No.18
<P><B>Abstract</B></P> <P>Piezoelectric energy harvesting is the most widely investigated technology for renewable energy applications. In this work, (1-<I>x</I>)(Na<SUB>0.5</SUB>K<SUB>0.5</SUB>)NbO<SUB>3</SUB>-<I>x</I>LiSbO<SUB>3</SUB> piezoelectric ceramics were prepared through conventional mixed oxide fabrication methods with different sintering temperatures. Although the (Na<SUB>0.5</SUB>K<SUB>0.5</SUB>)NbO<SUB>3</SUB> piezoelectric material is representative among the lead-free ceramics, it is difficult to densify by typical sintering techniques owing to its easy evaporation properties of potassium (K<SUP>+</SUP>) and sodium ion (Na<SUP>+</SUP>). Hence, lithium (Li<SUP>+</SUP>) and antimony ion (Sb<SUP>5+</SUP>) were used for the partial substitution of (Na<SUB>0.5</SUB>K<SUB>0.5</SUB>)NbO<SUB>3</SUB>. With the optimized sintering temperature, Li<SUP>+</SUP> and Sb<SUP>5+</SUP> are expected to be crucial in increasing the density and enhance the piezoelectric and ferroelectric properties. In this study, the phase, microstructure, and dielectric and electrical properties of (1-<I>x</I>)(Na<SUB>0.5</SUB>K<SUB>0.5</SUB>)NbO<SUB>3</SUB>-<I>x</I>LiSbO<SUB>3</SUB> ceramics depending on the sintering temperature is examined by employing X-ray diffraction, field emission scanning electron microscopy, impedance analyzer, and mechanical force system for energy harvesting.</P>