Yeungnam University

About: Yeungnam University is a education organization based out in Daegu, South Korea. It is known for research contribution in the topics: Thin film & Catalysis. The organization has 9885 authors who have published 22075 publications receiving 372798 citations.

Analysis of temporal behavior of beams diffracted by volume gratings formed in photopolymers

Abstract: The temporal behavior of beams diffracted by volume gratings in photopolymer thin films are measured and analyzed by solution of the diffusion equation for the monomer concentration inside the thin films. Two contributors to the refractive-index change that forms the volume gratings are assumed: One is the phase grating formed by modulation of the monomer concentration, and the other is the phase grating formed by modulation of the density of the polymeric materials. The phase grating that is due to monomer modulation is responsible for the initial fast rise and decay of the diffracted signal, and the phase grating that is due to modulation of density of the polymeric materials is responsible for the slowly rising and then steady signal. The temporal behavior of the diffracted beams is determined by the ratio of magnitudes of the incident beam intensity and the diffusion coefficient.

Down-Regulation of a Forkhead Transcription Factor, FOXO3a, Accelerates Cellular Senescence in Human Dermal Fibroblasts

Abstract: The signaling pathway of insulin/insulin-like growth factor/phosphatidylinositol-3 kinase/Akt/forkhead transcription factors is known to control life span and senescence in organisms ranging from yeast to mice. The FOXO family of forkhead transcription factors, FOXO1, FOXO3a, and FOXO4, play a critical role in this signal transduction pathway. However, the impact of FOXO3a activation on life span of primary cultured human dermal fibroblasts (HDFs) is unknown. To investigate the role of FOXO3a in the regulation of cellular senescence, we prepared FOXO3a-siRNA stable HDFs. We found that the down-regulation of FOXO3a RNA and protein in HDFs induced many senescent phenotypes, including changes in cell morphology, increases in population doubling times, senescence-associated beta-galactosidase staining and the cellular reactive oxygen species, and up-regulation of p53/p21 protein expression. Our data provide evidence of the key role of FOXO3a transcription factor as a mediator of cellular senescence in HDFs, and suggest that the mechanism of senescence is conserved in HDFs.

Enhanced dissolution of ibuprofen using solid dispersion with poloxamer 407

Abstract: To improve its dissolution, ibuprofen solid dispersions (SDs) were prepared, characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR), and evaluated for solubility, and in-vitro ibuprofen release. Loss of individual surface properties during melting and re-solidification as revealed by SEM micrographs indicated the formation of effective SDs. Absence or shifting towards the lower melting temperature of the drug peak in SDs and physical mixtures in DSC study indicated the possibilities of drug-polymer interactions. FTIR spectra showed the presence of drug crystalline in SDs. The effect of improved dissolution on the oral absorption of ibuprofen in rats was also studied. Quicker release of ibuprofen from SDs in rat intestine resulted in a significant increase in AUC and Cmax, and a significant decrease in Tmax over pure ibuprofen. Comparison of the enhanced solubility, dissolution, AUC, and Cmax of ibuprofen from different poloxamers suggested that the preparation of ibuprofen SDs using P 407 as a meltable hydrophilic polymer carrier could be a promising approach to improve its solubility, dissolution and absorption rate.

High-Efficiency SiC-Based Isolated Three-Port DC/DC Converters for Hybrid Charging Stations

Abstract: This article proposes a novel isolated three-port dc/dc converter based on a series resonant converter and a dual active bridge (DAB) converter for electric-vehicle charging stations with fast and slow charging functions. With this three-port structure, the proposed converter has fewer components, which results in lower system cost and volume compared with separate charger systems. A simple control method using phase-shift and frequency modulations was developed to control the output power of the fast and slow charging ports simultaneously. An optimal phase-shift angle was also derived to minimize the transformer current for when only the DAB converter is operated for slow charging. To verify the converter operation, a 5-kW SiC-based prototype with a power density of 2.74 kW/dm3 was built and tested with an input voltage of 600 V. A high-efficiency performance over a wide output voltage range has been achieved, and the peak efficiency is 98.2% at the rated conditions.

Heartbeat Sound Signal Classification Using Deep Learning.

Abstract: Presently, most deaths are caused by heart disease. To overcome this situation, heartbeat sound analysis is a convenient way to diagnose heart disease. Heartbeat sound classification is still a challenging problem in heart sound segmentation and feature extraction. Dataset-B applied in this study that contains three categories Normal, Murmur and Extra-systole heartbeat sound. In the purposed framework, we remove the noise from the heartbeat sound signal by applying the band filter, After that we fixed the size of the sampling rate of each sound signal. Then we applied down-sampling techniques to get more discriminant features and reduce the dimension of the frame rate. However, it does not affect the results and also decreases the computational power and time. Then we applied a purposed model Recurrent Neural Network (RNN) that is based on Long Short-Term Memory (LSTM), Dropout, Dense and Softmax layer. As a result, the purposed method is more competitive compared to other methods.