• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.33 no.6
• /
• pp.255-260
• /
• 2023

As demanding the detection of explosive molecules, it is required to develop rapidly and precisely responsive sensors with ultra-high sensitivity. Since two-dimensional semiconductors have an atomically thin body nature where mobile carriers accumulate, the abrupt modulation carrier in the thin body channel can be expected. To investigate the effectiveness of WSe₂ semiconductor materials as a detection material for TNT (Trinitrotoluene) explosives, WSe₂ was synthesized using thermal chemical vapor deposition, and afterward, WSe₂ FETs (Field Effect Transistors) were fabricated using standard photo-lithograph processes. Raman Spectrum and FT-IR (Fourier-transform infrared) spectroscopy reveal that the adsorption of TNT molecules induces the structural transition of WSe₂ crystalline. The electrical properties before and after adsorption of TNT molecules on the WSe₂ surface were compared; as -50 V was applied as the back gate bias, 0.02 μA was recorded in the bare state, and the drain current increased to 0.41 μA with a dropping 0.6% (w/v) TNT while maintaining the p-type behavior. Afterward, the electrical characteristics were additionally evaluated by comparing the carrier mobility, hysteresis, and on/off ratio. Consequently, the present report provides the milestone for developing ultra-sensitive sensors with rapid response and high precision.

• Journal of Korea Water Resources Association
• /
• v.56 no.12
• /
• pp.871-881
• /
• 2023

This study investigates the geomorphic changes and Bed Relief Index of the river downstream of the Yeongju Dam by Nays2DH, a two-dimensional numerical model, in order to grasp the dynamics of the downstream river while applying various flow patterns such as pulse discharge. It shows that the geomorphic and the bed elevations changes are the largest under the condition of the normalized pulse discharge. The total change in the riverbed is 29.88 m for uniform flow, 27.46 m for normalized hydrograph, 29.63 m for pulse flow and 31.87 m for pulse flow with normalized hydrograph which result in the largest variation in scour and deposition. The Bed Relief Index (BRI) increases with time under conditions of uniform flow, pulse flow and pulse flow with normalized hydrograph. However, BRI increased rapidly until 30 hrs after the peak flow (14 hrs), but decreased from 56 hrs under the condition of normalized hydrograph. Therefore, the condition of normalized hydrograph gives greater dynamics than the condition of a single flood or constant flow, and the dynamics increase downstream than upstream, resulting in an effect on improving the environment of the river downstream of the dam.

• Resources Recycling
• /
• v.33 no.1
• /
• pp.22-30
• /
• 2024

To synthesize the Ti₃AlC₂ MAX phase, a crucial precursor for generating the two-dimensional material MXene, the use of Ti scrap as an initial material is an economically feasible approach. This study aims to optimize the synthesis conditions for the phase fraction of the Ti₃AlC₂ MAX phase utilizing Ti scrap as the Ti source. The deoxidation of Ti powders, prepared through the hydrogenation-dehydrogenation process from Ti scrap, was effectively accomplished using the deoxidation in solid-state (DOSS) process. The optimal synthesis conditions were established by blending DOSS-Ti, Al, and graphite powders with particle sizes ranging from 25 ~ 32 ㎛ in a molar ratio of 3:1.1:2. The resulting phase fractions were as follows: Ti₃AlC₂ at 97.25 wt.%, TiC at 0.93 wt.%, and Al₃Ti at 1.82 wt.%. Furthermore, the oxygen content of the Ti₃AlC₂ MAX powder, spanning from 25 ~ 45 ㎛, was measured at 4,210 ppm.

• Journal of Adhesion and Interface
• /
• v.25 no.1
• /
• pp.169-274
• /
• 2024

Recent attention has been drawn to materials that undergo reversible expansion and contraction in response to external stimuli, leading to morphological changes. These materials hold potential applications in various fields including soft robotics, sensors, and artificial muscles. In this study, a novel material capable of responding to high temperatures for protection or encapsulation is proposed. To achieve this, liquid crystal elastomer (LCE) with nematic-isotropic transition properties and polyimide (PI) with high mechanical strength and thermal stability were utilized. To utilize a solution process, a dope solution was synthesized and introduced into micro-printing techniques to develop a two-dimensional pattern of LCE/PI bilayer structures with sub-millimeter widths. The honeycomb-patterned LCE/PI bilayer mesh combined the mechanical strength of PI with the high-temperature contraction behavior of LCE, and selective printing of LCE facilitated deformation in desired directions at high temperatures. Consequently, the functionality of selectively and reversibly encapsulating specific high-temperature materials was achieved. This study suggests potential applications in various actuator fields where functionalities can be implemented across different temperature ranges without the need for electrical energy input, contingent upon molecular changes in LCE.

• Korean Journal of Radiology
• /
• v.22 no.5
• /
• pp.829-839
• /
• 2021

Objective: To compare the diagnostic performance of contrast-enhanced radial T1-weighted gradient-echo 3-tesla (3T) magnetic resonance imaging (MRI) and computed tomography (CT) for the detection of visceral pleural surface invasion (VPSI). Visceral pleural invasion by non-small-cell lung cancer (NSCLC) can be classified into two types: PL1 (without VPSI), invasion of the elastic layer of the visceral pleura without reaching the visceral pleural surface, and PL2 (with VPSI), full invasion of the visceral pleura. Materials and Methods: Thirty-three patients with pathologically confirmed VPSI by NSCLC were retrospectively reviewed. Multidetector CT and contrast-enhanced 3T MRI with a free-breathing radial three-dimensional fat-suppressed volumetric interpolated breath-hold examination (VIBE) pulse sequence were compared in terms of the length of contact, angle of mass margin, and arch distance-to-maximum tumor diameter ratio. Supplemental evaluation of the tumor-pleura interface (smooth versus irregular) could only be performed with MRI (not discernible on CT). Results: At the tumor-pleura interface, radial VIBE MRI revealed a smooth margin in 20 of 21 patients without VPSI and an irregular margin in 10 of 12 patients with VPSI, yielding an accuracy, sensitivity, specificity, positive predictive value, negative predictive value, and F-score for VPSI detection of 91%, 83%, 95%, 91%, 91%, and 87%, respectively. The McNemar test and receiver operating characteristics curve analysis revealed no significant differences between the diagnostic accuracies of CT and MRI for evaluating the contact length, angle of mass margin, or arch distance-to-maximum tumor diameter ratio as predictors of VPSI. Conclusion: The diagnostic performance of contrast-enhanced radial T1-weighted gradient-echo 3T MRI and CT were equal in terms of the contact length, angle of mass margin, and arch distance-to-maximum tumor diameter ratio. The advantage of MRI is its clear depiction of the tumor-pleura interface margin, facilitating VPSI detection.

• Journal of The Korean Association For Science Education
• /
• v.27 no.7
• /
• pp.645-662
• /
• 2007

The purpose of this study was to explore the manners in which models are used in secondary science classrooms. A total of thirteen video-recordings of science lessons dealing with the domains of atmospheric and oceanic earth sciences and their verbatim transcripts were analysed both quantitatively and qualitatively. Interviews with three inservice science teachers were also conducted. Six interrelated assertions were generated as the result of the study: 1) The most frequently used models in secondary earth science classrooms include two-dimensional pictorial, symbolic, iconic, and diagrammatic ones; 2) Science teachers employ models as a mode of representation to make the subject matter available to students; 3) In earth science classrooms, teachers use typical forms of models in intensive manners; 4) Students themselves deal with models on a few occasions, but they just follow similar procedures with the same models; 5) Teachers talk rarely about the nature of scientific models and provide few opportunities for students to think about it; and, 6) Teachers in practice think that the value of using models should be appraised in consideration of the pedagogical intentions of the teacher. Implications for science education and science education research were discussed.

• Food Science of Animal Resources
• /
• v.44 no.1
• /
• pp.165-177
• /
• 2024

Volatile compounds (VOCs) are an important factor affecting meat quality. However, the characteristic VOCs in different parts of donkey meat remain unknown. Accordingly, this study represents a preliminary investigation of VOCs to differentiate between different cuts of donkey meat by using headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) combined with chemometrics analysis. The results showed that the 31 VOCs identified in donkey meat, ketones, alcohols, aldehydes, and esters were the predominant categories. A total of 10 VOCs with relative odor activity values ≥1 were found to be characteristic of donkey meat, including pentanone, hexanal, nonanal, octanal, and 3-methylbutanal. The VOC profiles in different parts of donkey meat were well differentiated using three- and two-dimensional fingerprint maps. Nine differential VOCs that represent potential markers to discriminate different parts of donkey meat were identified by chemometrics analysis. These include 2-butanone, 2-pentanone, and 2-heptanone. Thus, the VOC profiles in donkey meat and specific VOCs in different parts of donkey meat were revealed by HS-GC-IMS combined with chemometrics, whcih provided a basis and method of investigating the characteristic VOCs and quality control of donkey meat.

• Journal of Adhesion and Interface
• /
• v.24 no.3
• /
• pp.100-104
• /
• 2023

Van der Waals heterostructures have garnered significant attention in recent research due to their excellent electronic characteristics arising from the absence of dangling bonds and the exclusive reliance on Van der Waals forces for interlayer coupling. However, most studies have been confined to fundamental research employing the Scotch tape (mechanical exfoliation) method. We fabricated Van der Waals vertical heterojunction transistors to advance this field using materials exclusively grown via chemical vapor deposition (CVD). CVDgrown graphene was patterned through photolithography to serve as electrodes, while CVD-grown MoSe₂ was employed as the pickup/transfer material, resulting in the realization of Van der Waals heterojunction transistors with interlayer charge transfer effects. The electrical characteristics of the fabricated devices were thoroughly examined. Additionally, we observed variations in the transistor's performance based on the presence of defects in MoSe₂ layer.

• Pediatric Gastroenterology, Hepatology & Nutrition
• /
• v.27 no.1
• /
• pp.15-25
• /
• 2024

Purpose: This study aimed to investigate the presence of autoantigens in the gastric juices of children. Methods: Gastric juice and serum samples were obtained from 53 children <15 years of age who underwent gastric endoscopy. Among these, 8, 22, and 23 participants were in the age groups 0-5, 6-10, and 11-15 years, respectively. These samples were analyzed using two-dimensional electrophoresis (2-DE), immunoblot analysis, and matrix-assisted laser desorption ionization-time of-flight mass spectrometry. Furthermore, we reviewed the histopathological findings and urease test results and compared them with the results of 2-DE and immunoblot analysis. Results: There were no statistically significant differences in urease test positivity, grades of chronic gastritis, active gastritis, or Helicobacter pylori infiltration of the antrum and body among the three age groups. Three distinct patterns of gastric juice were observed on 2-DE. Pattern I was the most common, and pattern III was not observed below the age of 5 years. Histopathological findings were significantly different among active gastritis (p=0.037) and H. pylori infiltration (p=0.060) in the gastric body. The immunoblots showed large spots at an approximate pH of 3-4 and molecular weights of 31-45 kDa. These distinct, large positive spots were identified as gastric lipase and pepsin A and C. Conclusion: Three enzymes, which are normally secreted under acidic conditions were identified as autoantigens. Further investigation of the pathophysiology and function of autoantigens in the stomach is required.

• Industry Promotion Research
• /
• v.9 no.1
• /
• pp.167-177
• /
• 2024

The purpose of this paper is to restore the academic status of Gungwi perception a little. The symbolism of Gungwi, or Year Month Day Hour, likened to Geun Myo Hwa Sil, is not just a technique of interpretation. Recognizing that it corresponds to Saju's most fundamental Mingli principle, the study was conducted to the effect that more academic research should be conducted in the future. The intrinsic idea that constitutes Saju is the yin-yang and the five elements, the letters recorded are twelve-dimensional, and the elements in charge of the space and time are Cheongan, Jeeji, and Gungwi, which are woven into four pillars. Through this consideration of Gungwi's perception, we presented the "spectrum of time" phenomenon that past time and information pass through the point of time, spread like a spectrum, and lead future time and action at the time when humans are born, that is, the energy of the universe is formatted throughout the brain and body. We discussed the change point of Eight Trigrams used by Lim Cheol Cho as a basis for explaining 'Won Hyong I Jeong' and the assumption that the time change or distortion of the two cones penetrating the present, which is assumed in parallel theory, one of the modern cosmologies, leaves an afterimage in the future universe as Gungwi's deductive basis.