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Mechanical, electrical and wear properties of Cu-TiB2 nanocomposites fabricated by MA-SHS and SPS
Ji-Soon Kim,Dae-Hwan Kwon,Thuy Dang Nguyen,Khoa Xuan Huynh,Pyuck-Pa Choi,Myung-Gyu Chang,Young-Jin Yum,Young-Soon Kwon 한양대학교 세라믹연구소 2006 Journal of Ceramic Processing Research Vol.7 No.3
Cu-TiB2 nanocomposite powders were obtained by means of a combination of mechanical treatment and combustion reaction. Spark plasma sintering (SPS) was used to inhibit grain growth and thereby obtain fully dense Cu-TiB2 sintered bodies with a nanocomposite structure. The phases of the synthesized product were identified using X-ray diffraction and results showed only Cu and TiB2, with no other phases existing in the product. The particle size of self-propagating high-temperature synthesized powder was smaller than 250 nm. Mechanical and electrical properties were investigated after SPS at 650 oC for 30 minutes, the electrical conductivity decreased from 75 to 54% International Annealed Copper Standard (IACS) with the TiB2 content increased from 2.5 to 10 wt.%. while the hardness increased from 56 to 97 HRB. In addition, the tensile strength and wear resistance of the composites increased as the TiB2 content increased. Cu-TiB2 nanocomposite powders were obtained by means of a combination of mechanical treatment and combustion reaction. Spark plasma sintering (SPS) was used to inhibit grain growth and thereby obtain fully dense Cu-TiB2 sintered bodies with a nanocomposite structure. The phases of the synthesized product were identified using X-ray diffraction and results showed only Cu and TiB2, with no other phases existing in the product. The particle size of self-propagating high-temperature synthesized powder was smaller than 250 nm. Mechanical and electrical properties were investigated after SPS at 650 oC for 30 minutes, the electrical conductivity decreased from 75 to 54% International Annealed Copper Standard (IACS) with the TiB2 content increased from 2.5 to 10 wt.%. while the hardness increased from 56 to 97 HRB. In addition, the tensile strength and wear resistance of the composites increased as the TiB2 content increased.
Le Thi Thuy Lien,Nguyen Khoi Viet,Hoang Van Hoa,Phung Bao Ngoc,Nguyen Ngoc Trang,Vu Thi Kim Thoa,Nguyen Cong Tien,Phan Anh Phuong,Pham Minh Thong,Vu Dang Luu 아시아심장혈관영상의학회 2022 Cardiovascular Imaging Asia Vol.6 No.2
Objective: To compare left ventricular (LV) function, ejection fraction (EF), end-diastolic volume (EDV), end-systolic volume (ESV), and regional wall motion analyzed in 256-slice dualsource coronary CT angiography (DSCT) with 2D transthoracic echocardiography (TTE). Materials and Methods: One hundred twelve patients suspected of coronary artery disease underwent DSCT and 2D-TTE within one week for LVEF, EDV, and ESV. The correlation between DSCT and 2D-TTE measurements was analyzed through linear regression and Bland- Altman analysis. Regional wall motion was visually scored with a 3-point scale (1, normal; 2, hypokinesia; 3, dysphagia, akinesia). Results: Average LVEF at 66.45%±1.27% (range 23%–85%) as determined on DSCT compared with 66.09%±1.01% (range 25%–84%) on 2D-TTE. LVEF exhibited a good correlation between DSCT and 2D-TTE (r=0.715; p<0.001). Good correlations between DSCT and 2D-TTE were demonstrated for LVEDV (r=0.732; p<0.001) and LVESV (r=0.841; p<0.001). Mean differences (±SD) of 1.78±24.10 mL (p<0.05) and 0.77±13.70 mL (p<0.05) were observed between DSCT and 2D-TTE for LVEDV and LVESV, respectively. LVEF was slightly overestimated with DSCT (0.52%±9.59%; p<0.05). Although the LVEF values calculated by DSCT and 2D-TTE were similar, EDV and ESV from DSCT were statistically higher than those from 2D-TTE (p<0.05). Agreement between DSCT and 2D-TTE in regional wall motion was 96.4%, κ=0.840. Conclusion: DSCT can provide comparable results to those using 2D-TTE for LV function (EF, EDV, and ESV) and regional wall motion assessment in a heterogeneous population.
Kwon Dae-Hwan,Nguyen Thuy Dang,Dudina Dina,Kum Jong-Won,Choi Pyuck-Pa,Kim Ji-Soon,Kwon Young-Soon 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
Cu- nanocomposite powders were synthesized by combining high-energy ball-milling of Cu-Ti-B mixtures and subsequent self-propagating high temperature synthesis (SHS). Cu-40wt.% powders were produced by SHS reaction and ball-milled. The milled SHS powder was mixed with Cu powders by ball milling to produce Cu-2.5wt.% composites. particles less than 250nm were formed in the copper matrix after SHS-reaction. The releative density, electrical conductivity and hardness of specimens sintered at were nearly 98%, 83%IACS and 71HRB, respectively. After heat treatment at 850 to for 2 hours under Ar atmosphere, hardness was descedned by 15%. Our Cu- composite showed good thermal stability at eleveated temperature.
A Nonlinear Sliding Mode Controller for IPMSM Drives with an Adaptive Gain Tuning Rule
Jung, Jin-Woo,Dang, Dong Quang,Vu, Nga Thi-Thuy,Justo, Jackson John,Do, Ton Duc,Choi, Han Ho,Kim, Tae Heoung The Korean Institute of Power Electronics 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.3
This paper presents a nonlinear sliding mode control (SMC) scheme with a variable damping ratio for interior permanent magnet synchronous motors (IPMSMs). First, a nonlinear sliding surface whose parameters change continuously with time is designed. Actually, the proposed SMC has the ability to reduce the settling time without an overshoot by giving a low damping ratio at the initial time and a high damping ratio as the output reaches the desired setpoint. At the same time, it enables a fast convergence in finite time and eliminates the singularity problem with the upper bound of an uncertain term, which cannot be measured in practice, by using a simple adaptation law. To improve the efficiency of a system in the constant torque region, the control system incorporates the maximum torque per ampere (MTPA) algorithm. The stability of the nonlinear sliding surface is guaranteed by Lyapunov stability theory. Moreover, a simple sliding mode observer is used to estimate the load torque and system uncertainties. The effectiveness of the proposed nonlinear SMC scheme is verified using comparative experimental results of the linear SMC scheme when the speed reference and load torque change under system uncertainties. From these experimental results, the proposed nonlinear SMC method reveals a faster transient response, smaller steady-state speed error, and less sensitivity to system uncertainties than the linear SMC method.
( Lieu My Dong ),( Nguyen Thi Thuy Linh ),( Nguyen Thi Hoa ),( Dang Thi Kim Thuy ),( Do Dang Giap ) 한국미생물 · 생명공학회 2021 한국미생물·생명공학회지 Vol.49 No.3
Ngoc Linh ginseng is one of the most valuable endemic medicinal herbs in Vietnam. In this study, Ngoc Linh ginseng callus was fermented by Lactobacillus plantarum ATCC 8014 (at 6, 7, and 8 log CFU/ml) to evaluate the extraction efficiency of bioactive compounds. The post-fermentation solution was spray-dried using maltodextrin with or without Stevia rebaudiana (3% and 6% v/v) as the wall material. Bioactive compounds such as polyphenols, polysaccharides, and total saponins, and L. plantarum viability during fermentation and after spray-drying, as well as under simulated gastric digestion, were evaluated in this study. The results showed that probiotic density had a significant effect on bioactive compounds, and L. plantarum at 8 log CFU/ml showed the best results with a short fermentation time compared to other tests. The total content of polyphenols, polysaccharides, and saponins reached 5.16 ± 0.18 mg GAE/g sample, 277.2 ± 6.12 mg Glu/g sample, and 4.17 ± 0.15 mg/g sample, respectively after 20 h of fermentation at the initial density of L. plantarum (8 log CFU/ml). Although there was no difference in the particle structure of the preparation, the microencapsulation efficiency of the bioactive compound in the samples containing S. rebaudiana was higher than that with only maltodextrin. The study also indicated that adding S. rebaudiana improved the viability of L. plantarum in gastric digestion. These results showed that S. rebaudiana, a component stimulating probiotic growth, combined with maltodextrin as a co-prebiotic, improved the survival rate of L. plantarum in simulated gastric digestion.
Lieu My Dong,Nguyen Thien Luan,Dang Thi Kim Thuy 한국미생물·생명공학회 2020 한국미생물·생명공학회지 Vol.48 No.2
The objective of the study was to assess the survival of microencapsulated Lactobacillus plantarum ATCC8014 produced using the emulsion technique in alginate gel combined with pectin and maltodextrin components. The microcapsules were then added to cupcake dough that was further baked at 200℃ for 12 min. The viability of L. plantarum was assessed during baking and the 10 days of storage at 4℃ as well as in simulated gastrointestinal conditions. In addition, yeast-mold and water activity were investigated. After baking, the samples with microencapsulated L. plantarum contained more than 5 log CFU/g, which was higher compared to the bacterial concentration of the control samples. The concentration of L. plantarum was more than 6 logs CFU/g after the end of the storage; therefore, the probiotic functioned as a biopreservative in the cake. The prebiotic component strengthened the microcapsules network and helped protect the viability of L. plantarum in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) media. The results show that the addition of L. plantarum microencapsules did not affect the sensory scores of the cupcake while ensuring the viability of the probiotic during baking and storing.
Production of Dispersion-strengthened Cu-TiB2 Alloys by Ball-milling and Spark-plasma Sintering
Kwon Dae-Hwan,Kum Jong-Won,Nguyen Thuy Dang,Dudinad Dina,Choi Pyuck-Pa,Kim Ji-Soon,Kwon Young-Soon 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
Dispersion-strengthened copper with was produced by ball-milling and spark plasma sintering (SPS).Ball-milling was performed at a rotation speed of 300rpm for 30 and 60min in Ar atmosphere by using a planetary ball mill (AGO-2). Spark-plasma sintering was carried out at for 5min under vacuum after mechanical alloying. The hardness of the specimens sintered using powder ball milled for 60min at 300rpm increased from 16.0 to 61.8 HRB than that of specimen using powder mixed with a turbular mixer, while the electrical conductivity varied from 93.40% to 83.34%IACS. In the case of milled powder, hardness increased as milling time increased, while the electrical conductivity decreased. On the other hand, hardness decreased with increasing sintering temperature, but the electrical conductiviey increased slightly
Dong, Lieu My,Luan, Nguyen Thien,Thuy, Dang Thi Kim The Korean Society for Microbiology and Biotechnol 2020 한국미생물·생명공학회지 Vol.48 No.2
The objective of the study was to assess the survival of microencapsulated Lactobacillus plantarum ATCC8014 produced using the emulsion technique in alginate gel combined with pectin and maltodextrin components. The microcapsules were then added to cupcake dough that was further baked at 200℃ for 12 min. The viability of L. plantarum was assessed during baking and the 10 days of storage at 4℃ as well as in simulated gastrointestinal conditions. In addition, yeast-mold and water activity were investigated. After baking, the samples with microencapsulated L. plantarum contained more than 5 log CFU/g, which was higher compared to the bacterial concentration of the control samples. The concentration of L. plantarum was more than 6 logs CFU/g after the end of the storage; therefore, the probiotic functioned as a biopreservative in the cake. The prebiotic component strengthened the microcapsules network and helped protect the viability of L. plantarum in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) media. The results show that the addition of L. plantarum microencapsules did not affect the sensory scores of the cupcake while ensuring the viability of the probiotic during baking and storing.