Optical Spectra of the Colloidal Fe-doped Manganate CaMn1−xFexO3 (x = 0, 0.01, 0.03, 0.05)

Duc Huyen Yen Pham,Duc Tho Nguyen,Duc Thang Pham,Nam Nhat Hoang,The Tan Pham 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.12

We report the optical behaviors of the Fe-doped CaMnO3 family of compounds at low dopingconcentrations x 5%. The study aims at assisting the evaluation of the competition between ferroandantiferromagnetic orderings, which is believed to be a cause of many interesting properties of thisclass of compounds, including the magnetization reversal effect recently discovered. The structuralcharacterization showed a predominant orthorhombic phase with slightly increased cell constantsdue to doping. The Raman spectra revealed changes associated with the Mn sites, and the IRabsorption spectrum showed a characteristic Fe band at 1.2 eV, which should be accompanied bya change of spin. The analysis of the magnetization data allowed us to predict that while thedoping reduced the ferromagnetic coupling strength, and therefore the TC, the maximal dopingconcentration for the effective exchange to be zero was around 14%.

Large Magnetocaloric Effect above 300 K and Magnetoresistance in (La0.5Pr0.5)1-xPbxMnO3 Perovskites

Nguyen Chau,Duong Thi Hanh,Bui Cong Tinh,Nguyen Hoang Luong,Nguyen Duc Tho,Nguyen Hoang Hai 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5

Perovskite compounds (La0.5Pr0.5)₁- xPbxMnO₃ (x = 0.1 - 0.5) with orthorhombic structure were prepared by using a solid-state reaction technique. In the studied samples, the spin-glass-like state occurs at low temperatures and the Curie temperature, Tc, increases from 170 K (x = 0.1) to 336 K (x = 0.5) because of a strong double exchange. The magnetic entropy change, │△Sm│, reached its largest value of 2.06 J/kg·K at △H = 13.5 kOe for the sample with x = 0.4 (Tc = 323 K). Due to the large │△Sm│ and high Tc, these materials are suggested for use as active magnetic refrigerants for magnetic refrigeration technology at temperatures above room temperature. While the conductivity of the samples with x = 0.1 and 0.2 exhibits only a semiconducting behavior over the whole measured temperature range, there is insulator-metallic phase transition on the R(T) curves of the samples with x = 0.3 - 0.5. The magnetoresistance of the samples was measured and large values for MR were found. Perovskite compounds (La0.5Pr0.5)₁- xPbxMnO₃ (x = 0.1 - 0.5) with orthorhombic structure were prepared by using a solid-state reaction technique. In the studied samples, the spin-glass-like state occurs at low temperatures and the Curie temperature, Tc, increases from 170 K (x = 0.1) to 336 K (x = 0.5) because of a strong double exchange. The magnetic entropy change, │△Sm│, reached its largest value of 2.06 J/kg·K at △H = 13.5 kOe for the sample with x = 0.4 (Tc = 323 K). Due to the large │△Sm│ and high Tc, these materials are suggested for use as active magnetic refrigerants for magnetic refrigeration technology at temperatures above room temperature. While the conductivity of the samples with x = 0.1 and 0.2 exhibits only a semiconducting behavior over the whole measured temperature range, there is insulator-metallic phase transition on the R(T) curves of the samples with x = 0.3 - 0.5. The magnetoresistance of the samples was measured and large values for MR were found.

Optic foramen location on computed tomography

Vuong Duc Nguyen,Minh Tran Quang Le,Chuong Dinh Nguyen,Tho Thi Kieu Nguyen Korean Cleft Palate-Craniofacial Association 2023 Archives of Craniofacial Surgery Vol.24 No.4

Background: This study aimed to identify the location of the optic foramen in relation to the anterior sphenoid sinus wall, which is essential information for surgeons in planning and performing endoscopic transnasal surgery. Methods: Computed tomography scans of 200 orbits from 100 adult patients with no abnormalities were examined. The results included the location of the optic foramen in relation to the anterior sphenoid sinus wall and the distance between them, as well as the distance from the optic foramen and the anterior sphenoid sinus wall to the carotid prominence in the posterior sphenoid sinus. Results: The optic foramen was anterior to the anterior sphenoid sinus wall in 48.5% of orbits, and posterior in the remaining 51.5%. The mean distance from the optic foramen to the anterior sphenoid sinus wall was 3.82±1.25 mm. The mean distances from the optic foramen and the anterior sphenoid sinus wall to the carotid prominence were 7.67±1.73 and 7.95±2.53 mm, respectively. Conclusion: The optic foramen was anterior to the anterior wall of the sphenoid sinus in approximately half of the orbits examined in this study, and posterior in the remaining half. The mean distance from the optic foramen to the anterior sphenoid sinus wall of the sphenoid sinus was 3.82±1.25 mm.

20세기 초 한국과 베트남의 유교 진흥 경향의 동이점 - 박은식(朴殷植)과 진중금(陳仲金)을 중심으로 -

응웬토득 ( Nguyen Tho Duc ) 퇴계학연구원 2019 退溪學報 Vol.145 No.-

베트남과 한국은 유교의 수용과 운용 및 발전의 역사에서 유사점이 매우 많다. 하지만 양국은 역사적 발전단계가 동일하지 않을 뿐만 아니라 서로 다른 역사적 배경을 가지고 있기 때문에 구체적 현실 문제를 해결하기 위한 유교 사상의 운용과 학설 및 사상의 전개와 발전은 다를 수밖에 없다. 이러한 점에서 베트남과 한국의 유교를 일반적인 관점에서 비교 연구하는 것을 넘어 구체적인 관점을 적용하여 20세기 초에 전개된 한국과 베트남의 유교 진흥 경향을 비교 연구하는 것은 의미가 있다. 왜냐하면 이러한 연구는 자국의 구체적 문제들을 해결하기 위해 전개된 두 나라의 유교사상에서 드러나는 유사점과 차이점을 보여 줄 수 있으며, 일반적인 관점에서 이루어진 중국 유교와 한국 및 일본, 그리고 베트남 유교에 대한 기존의 비교 연구와 차별점을 드러낼 수 있기 때문이다. 한국에서 현대 신유학이 전개되고, 베트남에서 유교 진흥 경향이 형성 발전되던 20세기 초에 양국은 서구 세력의 군사적 문화적 침략에 대응하여 뚜렷한 대책을 마련하지 못한 채 무기력함을 보여주었다. 유교는 전면적으로 위기에 봉착하였고, 유교에 기초한 과거제도 등은 해체되었다. 베트남과 한국은 각각 프랑스와 일본으로부터 침략을 받은 후 식민 지배하에 놓이게 되었다. 이러한 역사적 배경을 고려할 때, 20세기 초 베트남 유교 진흥의 경향과 한국 현대 신유학에 대한 비교 연구를 통해 학계에 한국 현대 신유학의 흐름을 고찰하고 소개하는 일은 대규모의 연구 과정들을 거쳐야 하는 주제라 할 수 있다. 한국 현대 신유학에 대한 논자의 이해가 부족하지만, 본고에서는 20세기 초에 활동한 朴殷植과 陳仲金이 각각 제시한 유교 사상의 현대화 내용을 비교하여 베트남의 유교 진흥 경향과 한국의 현대 신유학 사이의 유사점과 차이점을 제시하고자 하였다. Vietnamese Confucianism and Korean Confucianism have similarities in the history of integration and development. However, due to the different historical background, the development of Confucian thought and its application to solve practical problems of each country in periods are not quite the same. Studies of Korean Confucianism and Vietnamese Confucianism from comparative perspectives in general, and Korean Modern Neo-Confucianism and Vietnamese Confucianism Revitalization movement in the early 20th century in particular could indicate the similarities and differences between the two countries integrating Confucianism from China to solve the specific problems of each country. This trend is different from the common comparative studies of Confucianism in Korea, Japan or Vietnam and Confucianism in its origin - China. Both Korean Modern Neo-Confucianism and Vietnamese Confucianism Revitalization movement were established and developed in the early twentieth century, when Confucian monarchies of the two countries laid bare their weaknesses and were defeated by Western military force and culture. As the result, Korea and Vietnam were invaded and ruled by the Japanese and French colonial empire while Confucianism fell into a full-fledged crisis and the Imperial Examinations ended. Introducing Korean Modern Neo-Confucianism to Vietnamese scholars and conducting comparative studies between Korean Modern Neo-Confucianism and Vietnamese Confucianism Revitalization movement in the early twentieth century are definitely substantial topics requiring large-scale researches. Based on a limited understanding of Korean Neo-Confucianism, this article will compare the thought of Confucian modernization presented by Park Un-Sik and Tran Trong Kim to denote some similarities and differences between Korean Neo-Confucianism and Vietnamese Confucianism Revitalization movement.

Effect of Annealing Temperature on the Permeability and Magneto-Impedance Behaviors of Fe<SUB>68.5</SUB>Mn<SUB>5</SUB>Si<SUB>13.5</SUB>B<SUB>9</SUB>Nb₃Cu₁ Amorphous Alloy

Anh-Tuan Le,Nguyen Duy Ha,Chong-Oh Kim,Jang-Roh Rhee,Nguyen Chau,Nguyen Quang Hoa,Nguyen Duc Tho,Heebok Lee 한국자기학회 2006 Journal of Magnetics Vol.11 No.1

The effect of annealing temperature on the permeability and giant magneto-impedance (GMI) behaviors of Fe68.5Mn5Si13.5B9Nb₃Cu₁ amorphous alloy has been systematically investigated. The nan℃rystalline Fe68.5Mn5- Si13.5B9Nb3Cu1 alloys consisting of ultra-fine (Fe,Mn)₃Si grains embedded in an amorphous matrix were obtained by annealing their precursor alloy at the temperature range from 500℃ to 600℃ for 1 hour in vacuum. The permeability and GMI profiles were measured as a function of external magnetic field. It was found that the increase of both the permeability and the GMI effect with increasing annealing temperature up to 535℃ was observed and ascribed to the ultrasoft magnetic properties in the sample, whereas an opposite tendency was found when annealed at 600℃ which is due to the microstructural changes caused by high-temperature annealing. The study of temperature dependence on the permeability and GMI effect showed some insights into the nature of the magnetic exchange coupling between nan℃rystallized grains through the amorphous boundaries in nan℃rystalline magnetic materials.

Using Online Respondent Driven Sampling for Vietnamese Youths’ Alcohol Use and Associated Risk Factors

Melvyn WB Zhang,Bach Xuan Tran,Huong Lan Thi Nguyen,Huong Thi Le,Nguyen Hoang Long,Huong Thi Le,Nguyen Duc Hinh,Tran Dinh Tho,Bao Nguyen Le,Vu Thi Minh Thuc,Chau Ngo,Nguyen Huu Tu,Carl A. Latkin,Roger 대한의료정보학회 2017 Healthcare Informatics Research Vol.23 No.2

Objectives: The average alcohol consumption per capita among Vietnamese adults has consistently increased. Although alcoholrelated disorders have been extensively studied, there is a paucity of research shedding light on this issue among Internet users. The study aimed to examine the severity of alcohol-related disorders and other associated factors that might predispose individuals towards alcohol usage in a sample of youths recruited online. Methods: An online cross-sectional study was conducted with 1,080 Vietnamese youths. A standardized questionnaire was used. Respondent-driven sampling was applied to recruit participants. Multivariate logistic and Tobit regressions were utilized to identify the associated factors. Results: About 59.5% of the males and 12.7% of the total youths declared that they were actively using alcohol. From the total sample, a cumulative total of 32.3% of the participants were drinking alcohol, with 21.8% and 25.0% of the participants being classified as drinking hazardously and binge drinkers, respectively. The majority of the participants (60.7%) were in the pre-contemplative stage. Conclusions: A high prevalence of hazardous drinking was recognized among online Vietnamese youths. In addition, we found relationships between alcohol use disorder and other addictive disorders, such as tobacco smoking and water-pipe usage. Our results highlighted that the majority of the individuals are not receptive to the idea of changing their alcohol habits, and this would imply that there ought to be more government effort towards the implementation of effective alcohol control policies.

사출성형을 통한 CNT 및 Carbon fiber를 이용한 차량용 경량 복합재료 제작 연구

Nguyen Tran Huu Duc,Chi-Vinh Ngo,Hoang Van Tho,염영진(Young-Jin Yum),천두만(Doo-Man Chun) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.4-3

Pressure effects on EXAFS Debye-Waller factor and melting curve of solid krypton

Khac Hieu Ho,Viet Tuyen Nguyen,Nguyen Van Nghia,Nguyen Ba Duc,Vu Quang Tho,Tran Thi Hai,Doan Quoc Khoa 한국물리학회 2019 Current Applied Physics Vol.19 No.1

The pressure effects on atomic mean-square displacement, extended X-ray absorption fine structure (EXAFS) Debye-Waller factor and melting temperature of solid krypton have been investigated in within the statistical moment method scheme in quantum statistical mechanics. By assuming the interaction between atoms can be described by Buckingham potential, we performed the numerical calculations for krypton up to pressure 120 GPa. Our calculations show that the atomic mean-square displacement and EXAFS Debye-Waller factor of krypton crystal depend strongly on pressure. They make the robust reduction of the EXAFS peak height. Our results are in good and reasonable agreements with available experimental data. This approach gives us a relatively simple method for qualitatively calculating high-pressure thermo-physical properties of materials. Moreover, it can be used to verify future high-pressure experimental and theoretical works.

Microstructure and Magnetic Characteristics of Mn-doped Finemet Nanocomposites

Anh-Tuan Le,Chong-Oh Kim,Nguyen Chau,Nguyen Duc Tho,Nguyen Quang Hoa,Heebok Lee 한국자기학회 2006 Journal of Magnetics Vol.11 No.1

A thorough study about the influences of Mn substitution for Fe on the microstructure and magnetic characteristics of Fe73.5-xMnxSi13.5B9Nb₃Cu₁ (x = 1, 3, 5) alloys prepared by the melt-spinning technique has been performed. Nanocomposites composed of nanoscale (Fe,Mn)₃Si magnetic phase embedded in an amorphous matrix were obtained by annealing their amorphous alloys at 535℃ for 1 hour. The addition of Mn causes a slight increase in the mean grain size. The Curie temperatures of the initial amorphous phase and of the nanocrystals phase decreased, while the Curie temperature of the remaining amorphous phase remained nearly constant with increasing Mn content. Soft magnetic properties of the crystallized samples have been significantly improved by a proper thermal treatment. Accordingly, the giant magnetoimpedance effect is observed and ascribed to the increase of the magnetic permeability, and the decrease of the coercivity of the samples. The increased magnetic permeability is resulted from a decrease in the magnetocrystalline anisotropy and saturation magnetostriction.

Microstructure and Magnetic Properties of Au-doped Finemet-type Alloy

Anh-Tuan Le,Chong-Oh Kim,Nguyen Duy Ha,Nguyen Chau,Nguyen Duc Tho,Heebok Lee 한국자기학회 2006 Journal of Magnetics Vol.11 No.1

In this report, we demonstrate a comprehensive analysis of the effects of Au addition on the microstructure and magnetic properties of Fe73.5Si13.5B9Nb₃Au₁ Finemet-type alloy. It was found that the as-quenched alloys were the amorphous state and turned into nanocrystalline state under heat treatments. The DSC analysis indicates that the sharply exothermal peak corresponding to the crystallization of the α-Fe(Si) was observed at 547- 579℃ depending on the heating rates, which is little higher than that of original Finemet (542-570℃, respectively). Besides, the thermomagnetic result confirmed that the full substitution of Cu by Au with the single phase structure in the M(T) curve along cooling cycle. Ultrasoft magnetic properties of the nanocrystallized samples were significantly enhanced by the proper annealing such as the increase of permeability and the decrease of the coercivity. The optimum annealing condition was found at the annealing temperature of 540℃ and the increase of the annealing time up to 90 min.