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- 저자 : Le Hong Phuc (검색결과 14 건)
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Switching and Electrical Memory Effect in the Colossal Permittivity Material La2NiO4+δ
Le Van Hong,Tran Dang Thanh,Dao Nguyen Hoai Nam,,Nguyen Xuan Phuc 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5
La2NiO4+δ ceramic samples were manufactured by using a solid state reaction method. The crystalline structural, magnetic and dielectric properties of the material were recorded and analyzed. A dielectric resonance, which is thought to be associated with the multiferroic behavior of the material, was observed at frequencies below 1 MHz. The I/V characteristics were easured on a capacitor-like structure, which exhibited resistance and capacitance switching when opposite voltage pulses of about 2.5 volts with a duration time of 500 ms were applied. The maximum ratios of the changes in the resistance and the capacitance were estimated to be of about 50 % and 35 % at room temperature, respectively. The electrical switching was reversible, with resistive states remaining for a rather long time. The observed capacitance switching and memory effects provide evidence for the presence of charge transfer and accumulation in the material.
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Interacting Superparamagnetism in La0.7Sr0.3MnO3 Nanoparticles
Le Van Hong,D. H. Manh,Ha M. Nguyen,N. X. Phuc,Y. D. Yao 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5
ThemagneticorderofLa0:7Sr0:3MnO3nanoparticles(NPs)fabricatedinaSPEXD800milwas systematicalystudied. TheLa0:7Sr0:3MnO3 nanocrystalsgrowfromthemiledconstituentoxides during the miling proceses. The magnetization data obtained by using a SQUID magnetometer show the NPs as a superparamagnet in terms of anhysteretic curves near rom temperature. Un- overlaping of the scaled M(Hext;T)=Ms vs. Hext=T plots and the dc susceptibility obeying the Curie-Weis behavior rather than the Curie law at high temperatures provide evidence that the NPs are interacting superparamagnetic ensembles. A mean-eld corection to the Langevin func- tion L([Hext+M]=kBT) worked wel for the magnetic ordering of the NPs. By means of the Langevinting,thediameteroftheNPwasestimatedtobelowerthan15nm,dependingonthe miling time. The saturation magnetization of NPs varied from 48.5 em/g to 19 emu/g, with the highervaluecorespondingtoalargerparticlesize. Acore-shelstructureoftheNPwasadopted, with the NP having the core-shel magneticaly-eective mas density.
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LE Thi Lan Huong,HOANG Vu Hiep,HOANG Mai Duc Minh,NGUYEN Hong Phuc,BUI Xuan Bach 한국유통과학회 2022 유통과학연구 Vol.20 No.6
Purpose: This research aims to provide empirical evidence on the impact of digital literacy on behavioural intention regarding using technology for distribution of higher education. Design, Methodology, and Approach: Quantitative analysis was carried out using Covariance-Based Structural Equation Model with data collected from 901 students who fully experienced 2-year study online at different universities in Vietnam. The structural model was built with digital literacy as the primary indicator and other variables were included based on modified version of Unified Theory of Acceptance and Use of Technology (UTAUT2) by adopting performance expectancy, effort expectancy, social influence, habit, and hedonic motivation variables specifically for education sector. Self-efficacy was added to eliminate possible bias in technology acceptance. Results: From the results of model estimation, digital literacy presented positive impact on the online distribution of higher education in Vietnam. The mediating effects of various indicators such as performance expectancy, effort expectancy, social influence, habit, hedonic motivation, and self-efficacy are significantly determined by research model. Conclusion: The higher level of digital literacy of the students, the more likely that they will use technology in higher education study, especially online learning. Additionally, the mediating effects of indicators from the UTAUT2 theoretical model were also evident to be positively significant.
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Port logistics service quality and customer satisfaction: Empirical evidence from Vietnam
Le Duc Nha,Nguyen Hong Thi,Hoang Truong Phuc 한국해운물류학회 2020 The Asian journal of shipping and Logistics Vol.36 No.2
This paper aims to validate five determinants of service quality and to examine the service qualitycustomer satisfaction link in the port logistics service industry of a developing and transitional economy. First,the research reviews literature pertinentto service quality and customer satisfaction. Second, it uses both qualitative and quantitative methods through focus group discussion and directinterviews with 212 respondents who are the employees of firms that have been using port logistics service provided by Cat Lai Port, Ho Chi Minh City, Vietnam. Finally, the multivariate analysis is subsequently employed to analyze data obtained from surveys by structural equation modeling (SEM) technique. Findings indicate that port logistics service quality is positively determined by five factors including responsiveness, assurance, reliability, tangibles and empathy. In addition, port logistics service quality exerts positive influence on customer satisfaction. Most noticeably, as embedded in the tangibles component, technological advancements appear to enhance service quality which ultimately satisfies customers in the port logistics service industry.
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Tuning of the Curie Temperature in La1-xSrxMn1-yTiyO₃
N. X. Phuc,N. T. Hieu,N. T. H. Le,D. H. Manh,N. A. Tuan,L. V. Hong,L. T. C. Tuong 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5
Magnetic nanoparticles of La₁-xSrxMn₁-yTiyO₃ were prepared by using a sol-gel method, followed by annealing at various elevated temperatures. We found that the Curie temperature of the manganite nanoparticles could easily be tuned (from TC ~ 90 ℃ down to ~20 ℃) by substitution of nonmagnetic Ti⁴+ ions (from y = 0 to 7 %) for Mn. A comparison showed that the titanium substitution approach had advantages such as the phase transition being sharper and the magnetization remaining higher than in the case of the earlier known way of TC reduction by decreasing the Sr content from the optimal value of x = 0.3. The new features seem to make La1..xSrxMn₁..yTiyO₃ nanoparticles promising for hyperthermia application. Magnetic nanoparticles of La₁-xSrxMn₁-yTiyO₃ were prepared by using a sol-gel method, followed by annealing at various elevated temperatures. We found that the Curie temperature of the manganite nanoparticles could easily be tuned (from TC ~ 90 ℃ down to ~20 ℃) by substitution of nonmagnetic Ti⁴+ ions (from y = 0 to 7 %) for Mn. A comparison showed that the titanium substitution approach had advantages such as the phase transition being sharper and the magnetization remaining higher than in the case of the earlier known way of TC reduction by decreasing the Sr content from the optimal value of x = 0.3. The new features seem to make La1..xSrxMn₁..yTiyO₃ nanoparticles promising for hyperthermia application.
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Grain-Size Effect on the Dielectric Properties of La1.5Sr0.5NiO₄ Nano-Particle Materials
Tran Dang Thanh,Le Van Hong,Nguyen Xuan Phuc 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.6
We have manufactured ceramic samples of La1.5Sr0.5NiO₄and studied their dielectric proper-ties. The samples were prepared by using a reactive mechanical milling technique on D8000-Spex combined with an annealing at a temperature in the range of 700 ℃ - 1000 ℃. The crystalline structure and the sample's purity were checked by means of X-ray diffraction (XRD) on a SIEMENS D5000 spectrograph. The obtained XRD patterns conrmed that all the samples belonged to the F4K2Ni perovskite layer tetragonal structure with a space group of I4/mmm (139). The grain size of a ceramic sample was estimated based on the Field-emission scanning electron microscopy (FE- SEM) images and was calculated by using the Warren-Averbach method based on the Full Width at Half Maximum (FWHM) of the XRD lines. The results obtained by using the two methods were quite the same. The mean grain size (< D >) of the samples varied from 16.2 nm to 95 nm with the annealing temperature. Dielectric constant (ε) of all the samples was estimated from the capacitance measurement at different temperatures in the frequency range of 1 kHz - 13 MHz. The estimated ε of all the samples was about 105 over the whole frequency range up to 1 MHz. The temperature and the frequency dependences of ε(f T), the dielectric constant, were observed and are discussed for all the samples. We have manufactured ceramic samples of La1.5Sr0.5NiO₄and studied their dielectric proper-ties. The samples were prepared by using a reactive mechanical milling technique on D8000-Spex combined with an annealing at a temperature in the range of 700 ℃ - 1000 ℃. The crystalline structure and the sample's purity were checked by means of X-ray diffraction (XRD) on a SIEMENS D5000 spectrograph. The obtained XRD patterns conrmed that all the samples belonged to the F4K2Ni perovskite layer tetragonal structure with a space group of I4/mmm (139). The grain size of a ceramic sample was estimated based on the Field-emission scanning electron microscopy (FE- SEM) images and was calculated by using the Warren-Averbach method based on the Full Width at Half Maximum (FWHM) of the XRD lines. The results obtained by using the two methods were quite the same. The mean grain size (< D >) of the samples varied from 16.2 nm to 95 nm with the annealing temperature. Dielectric constant (ε) of all the samples was estimated from the capacitance measurement at different temperatures in the frequency range of 1 kHz - 13 MHz. The estimated ε of all the samples was about 105 over the whole frequency range up to 1 MHz. The temperature and the frequency dependences of ε(f T), the dielectric constant, were observed and are discussed for all the samples.
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Tran Hoang Hai,Le Hong Phuc,Doan Thi Kim Dung,Nguyen Thi Le Huyen,Bui Duc Long,Le Khanh Vinh,Nguyen Thi Thanh Kieu,Massanori Abe 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.2
Magnetic resonance imaging (MRI) has become a major and promising topic in medical researching because of its numerous potential applications. Due to the specic uptake by macrophage and not entirely captured by liver and spleen at first-pass, Superparamagnetic nanoparticles (SPIONs) are widely investigated as diagnostic tracer for magnetic resonance imaging (MRI). Surfactantcoated Fe3O4 particles (6 nm diameter) have been synthesized by using a wet chemical method (co-precipitation). Our study concentrated on synthesizing magnetic nanoparticles Fe3O4 coating oleic acid and Dextran and Starch polysaccharides.
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