Numerical Analysis of Saturated Sand Under Dynamic Loads

In this study, the behavior of reclaimed soils including the effects of excess pore water pressure and the loss of strength under dynamic loads or earthquakes are investigated and simulated. The constitutive model based on the disturbed state concept (DSC) is introduced and DSC-DYN2D program is utilized in a numerical analysis. In the laboratory test, quasi-static and cyclic triaxial tests were carried out to determine parameters for the numerical analysis. Field tests were executed in Inchon International Airport with a 10 tons hydraulic hammer. In the field test, the data of dynamic loads and excess pore water pressure were measured using a 3-D geophone and a pressure transducer respectively, The data of field tests showed the accumulation of excess pore water pressure when rapid dynamic loads were applied. Especially, a back-prediction program based on DSC model is developed and verified its accuracy using various parameters from the cyclic triaxial test. As the results of numerical simulation, the predicted trends for excess pore water pressure compare well with the observed data. Based on the result of this research, it is found that the numerical analysis based on the DSC model is compatible to predict the softening behavior of saturated reclaimed soils under dynamic loads

Kinetic study for the optimization of ginsenoside Rg3 production by heat treatment of ginsenoside Rb1

AbstractBackgroundGinsenoside Rg3 is a promising anticancer agent. It is usually produced by heat treatment of ginseng, in which ginsenoside Rb1 is the major ginsenoside. A kinetic study was conducted to optimize ginsenoside Rg3 production by the heat treatment of ginsenoside Rb1.MethodsGinsenoside Rb1 was heated using an isothermal machine at 80°C and 100°C and analyzed using HPLC. The kinetic parameters were calculated from the experimental results. The activation energy was estimated and used to simulate the process. The optimized parameters of ginsenoside Rg3 production are suggested based on the simulation.ResultsThe rate constants were 0.013 h−1 and 0.073 h−1 for the degradation of ginsenosides Rb1 and Rg3 at 80°C, respectively. The corresponding rate constants at 100°C were 0.045 h−1 and 0.155 h−1. The estimated activation energies of degradation of ginsenosides Rb1 and Rg3 were 69.2 kJ/mol and 40.9 kJ/mol, respectively. The rate constants at different temperatures were evaluated using the estimated activation energies, and the kinetic profiles of ginsenosides Rb1 and Rg3 at each temperature were simulated based on the proposed kinetic model of consecutive reaction. The optimum strategies for producing ginsenoside Rg3 from ginsenoside Rb1 are suggested based on the simulation. With increased temperature, a high concentration of ginsenoside Rg3 is formed rapidly. However, the concentration decreases quickly after the reaching the maximal concentration value.ConclusionThe optimum temperature for producing ginsenoside Rg3 should be the highest temperature technically feasible below 180°C, in consideration of the cooling time. The optimum reaction time for heat treatment is 30 min

Tunable resistivity of correlated VO2(A) and VO2(B) via tungsten doping

Applications of correlated vanadium dioxides VO2(A) and VO2(B) in electrical devices are limited due to the lack of effective methods for tuning their fundamental properties. We find that the resistivity of VO2(A) and VO2(B) is widely tunable by doping them with tungsten ions. When x < 0.1 in V1−xWxO2(A), the resistivity decreases drastically by four orders of magnitude with increasing x, while that of V1−xWxO2(B) shows the opposite behaviour. Using spectroscopic ellipsometry and X-ray photoemission spectroscopy, we propose that correlation effects are modulated by either chemical-strain-induced redistribution of V−V distances or electron-doping-induced band filling in V1−xWxO2(A), while electron scattering induced by disorder plays a more dominant role in V1−xWxO2(B). The tunable resistivity makes correlated VO2(A) and VO2(B) appealing for next-generation electronic devices. © 2020, The Author(s).1

Optical spectroscopic investigation on the coupling of electronic and magnetic structure in multiferroic hexagonal RMnO3 (R = Gd, Tb, Dy, and Ho) thin films

We investigated the effects of temperature and magnetic field on the electronic structure of hexagonal RMnO3 (R = Gd, Tb, Dy, and Ho) thin films using optical spectroscopy. As the magnetic ordering of the system was disturbed, a systematic change in the electronic structure was commonly identified in this series. The optical absorption peak near 1.7 eV showed an unexpectedly large shift of more than 150 meV from 300 K to 15 K, accompanied by an anomaly of the shift at the Neel temperature. The magnetic field dependent measurement clearly revealed a sizable shift of the corresponding peak when a high magnetic field was applied. Our findings indicated strong coupling between the magnetic ordering and the electronic structure in the multiferroic hexagonal RMnO3 compounds.Comment: 16 pages including 4 figure

Serum Levels of Interleukin-8 and Tumor Necrosis Factor-alpha in Coal Workers' Pneumoconiosis: One-year Follow-up Study

Objectives: Various cytokines induced by inhalation of coal dust may mediate inflammation and lead to tissue damage or fibrosis, such as coal workers' pneumoconiosis (CWP).Methods: To investigate the relevance of serum cytokines in CWP, the levels of serum interleukin-8 (IL-8) and tumor necrosis factor-alpha (TNF-α) as CWP biomarkers in 110 retired coal miners (22 controls and 88 CWP subjects) were related to cross sectional findings and 1-year progressive changes of the pneumoconiosis. Progressive changes of CWP were evaluated by paired comparison of chest radiographs. Analysis by a receiver operating characteristic (ROC) curve assessed the biomarker potential of each cytokine.Results: The mean serum IL-8 level was significantly higher in CWP compared to controls and IL-8 levels correlated with the degree of CWP. The median serum TNF-α level was significantly higher in subjects with progressive CWP compared to subjects without CWP progression. The area under the ROC curve for IL-8 (0.70) and TNF-α (0.72) for CWP identification and progression, respectively, indicated the biomarker potential of the two cytokines. Serum cutoff values of IL-8 and TNF-α were 11.63 pg/ml (sensitivity 69%; specificity 64%) and 4.52 pg/ml (sensitivity 67%; specificity 79%), respectively.Conclusion: The results suggest that high levels of serum IL-8 are associated with the presence of CWP and those of serum TNF-α are associated with the progression of CWP

Characteristics of InP/InGaAs HPT-based Optically Injection-Locked Self-oscillating Optoelectronic Mixers and Their Influence on RoF System Performance

Abstract A 30GHz optically injection-locked self-oscillating optoelectronic mixer (OIL-SOM) is implemented with a high-performance InP/InGaAs heterojunction phototransistor. The sub-harmonic conversion efficiency and phase noise characteristics of OIL-SOM are investigated and used for analyzing OIL-SOM-based 60GHz radio-on-fiber downlink data transmission performance. The OIL-SOM characteristics provide lower and upper boundaries for the input optical LO power range within which the link performance does not significantly depend on input optical LO power. Index Terms: heterojunction phototransistor (HPT), optically injection-locked selfoscillating optoelectronic mixer (OIL-SOM), phase noise, conversion efficiency, 60GHz, radio-on-fiber system, optical LO power