1,721,650 research outputs found
The Documentation of Ho Chi Minh City Sign Language and The Wellbeing of Deaf People in Viet Nam
Get PDFWhile education for deaf people in Viet Nam began in 1886, there was only one school for deaf people in Viet Nam until 1975. While there was some usage of sign language in the southern part Viet Nam in the early history of deaf education in Viet Nam, by the latter part of the 1900’s almost all education was oral only; the highest grade taught to Vietnamese deaf people was 5th grade; and the difficulties of using a tonal language only to teach deaf people normally meant that it required at least 8 years for deaf students to complete 5 grades. By 2000, it was clear that deaf people in Viet Nam had maintained three distinct, but historically related sign languages underground: Ho Chi Minh City SL, Ha Noi SL, and Hai Phong SL. However, only Dong Nai Province in the southern part of Viet Nam, expressed a willingness to allow sign language research and the use of sign language in an experimental educational program. By June 2000, a program was underway in Dong Nai Province, to train fluent adult Deaf users of any sign language in Viet Nam in language documentation and language teaching. Since Dong Nai Province is in the southern part of Viet Nam, the primarily focus was on Ho Chi Minh City Sign Language. Deaf trainees then taught certified hearing teachers how to sign, and then the hearing teachers taught the Deaf adult trainees junior high school, senior high school, and university education, resulting in the first Vietnamese Deaf graduates of junior high school, senior high school, and university. This presentation will include information on the content and length of the training in language documentation and language teaching provided to Deaf people; the teaching handbooks and companion dictionaries developed as part of the project; the results of Deaf people teaching their sign language to their prospective hearing teachers; the content, length of training, and results of Deaf signers compared with their hearing peers in high school and university education; and comments from users of HCMCSL and other sign languages in Viet Nam on their sense of wellbeing as a result of their participation
Modelling of food waste digestion using ADM1 integrated with Aspen Plus
No full textThe aim of this research was to produce an integrated modelling platform in which an anaerobic digester could be linked to the other unit operations which serve it, both in maintaining the physical-chemical conditions in the digester and in transforming the digestion products to useful fuel and nutrient sources. Within these system boundaries an accurate mass and energy balance could be determined and further optimised, particularly where the desired energy products are a mix of heat, power, and biomethane. The anaerobic digestion of food waste was choosen as the subject of the research because of its growing popularity and the availability of validation data. Like many other organic substrates, food waste is potentially a good source of renewable energy in the form of biogas through anaerobic digestion. A number of experimental studies have, however, reported difficulties in the digestion of this material which may limit the applicability of the process. These arise from the complexity of the biochemical processes and the interaction between the microbial groups that make up the anaerobic community. When using food waste there is a tendency to accumulate intermediate volatile fatty acid products, and in particular propionic acid, which eventually causes the pH to drop and the digester to fail. Two factors are important in understanding and explaining the changes in the biochemical process that leads to this condition. The first is due to the differential in sensitivity to free ammonia of the two biochemical pathways that lead to methane formation. The acetoclastic methanogenic route is inhibited at a lower concentration than the hydrogenotrophic route, and methane formation therefore occurs almost exclusively via acetate oxidation to CO2 and H2 at high free ammonia concentrations. The accumulation of propionic acid is thought to be because formate, a product of its degradation, cannot be converted to CO2 and H2 as the necessary trace elements to build a formate dehydrogenase enzyme complex are missing. The Anaerobic Digestion Model No. 1 (ADM1) was modified to reflect ammonia inhibition of acertoclastic methanogenesis and an acetate oxidation pathway was added. A further modification was included which allowed a 'metabolic switch' to operate in the model based on the availability of key trace elements. This operated through the H2 feedback inhibition route rather than creating a new set of equations to consider formate oxidation in its own right: the end result is, however, identical in modelling terms. With these two modifications ADM1 could simulate experimental observations from food waste digesters where the total ammoniacal nitrogen(TAN) concentration exceeded 4 gN l-1. Under these conditions acetate accumulation is first seen, followed by proprionate accumulation, but with the subsequent decrease in acetate until a critical pH is reached. The ADM1 model was implemented in MATLAB with these modifications incorporated. The second part of the research developed an energy model which linked ADM1 to the mechanical processes for biogas upgrading, Combined Heat and Power (CHP)production, and the digester mixing system. The energy model components were developed in the framework of the Aspen Plus modelling platform, with sub-units for processes not available in the standard Aspen Package being developed in Fortran, MS Excel or using the Aspen Simulation Workbook (ASW). This integration of the process components allows accurate sizing of the CHP and direct heating units required for an anaerobic digestion plant designed for fuel grade methane production. Based on the established model and its sub-modules, a number of case studies were developed. To this end the modified ADM1 was applied to mesophilic digestion of Sugar Beet Pulp to observe how the modified ADM1 responded to different substrate types. Secondly, to assess the capability of adding further mechanical processes the model was used to integrate and optimise single stage biogas upgrading. Finally, the digestion of food waste in the municipal solid waste stream of urban areas in Vietnam was considered
비첨가, 희토류, 알칼리토금속이 첨가된 BaFeO3-δ의 자성 연구
No full text학위논문 (석사)-- 서울대학교 대학원 : 물리·천문학부, 2016. 2. Nguyen Hoa Hong.Abstract
Magnetic Studies of Pristine,
Rare-Earth, and Alkaline-Earth- Doped BaFeO3-δ
Jang Gun Kim
Dept. of Physics and Astronomy
The Graduate School
Seoul National University
BaFeO3-δ (BFOδ) is a potential candidate for bubble domain devices that may have fast and high-capacity data storage. The stoichiometric BaFeO3 is ferromagnetic, however, its Tc is low (111K). Thus, it is meaningful to improve the magnetic properties of oxygen deficient BFOδ with higher transition temperature. In this work, we studied magnetic properties of the polycrystalline powders and thin films of undoped, half-doped BFOδ fabricated by coprecipitation method and pulsed laser deposition, respectively. BFOδ itself shows room temperature ferromagnetism possibly induced by the decrease in its grain size. In general, Rare-Earth (Ho3+, Sm3+) doping does not improve the magnetic properties of BFOδ due to the introduction of Fe3+ by trivalent Rare Earth ions, leading to antiferromagnetic superexchange interaction. The magnetizations of SmFeO3 and Ba0.5Ho0.5FeO3-δ films, however, show strong responses to perpendicular field. Powders doped with Alkaline-Earth (Ca2+, Sr2+) ions still maintain their room temperature ferromagnetism and have a larger magnetization when comparing to Rare-Earth doped ones. Moreover, Sr doping can turn BFOδ into a hard magnet.Chapter 1 Introduction 1
1.1 Orthoferrites: Materials with Fascinating Magnetic Properties 1
1.2 BaFeO3-δ with Unique Properties due to its High Iron Valency 2
1.3 The Goal of Our Research 4
Chapter 2 Experimental Methods 6
2.1 Sample Preparation 6
2.1.1 Powders 6
2.1.2 Films 7
2.2 Measurements 9
2.2.1 X-ray Diffraction 9
2.2.2 Superconducting Quantum Interference Device 10
Chapter 3 Results and Discussions 11
3.1 Structural Properties 11
3.2 Magnetic Properties 15
3.2.1 Undoped BFOδ 15
3.2.2 RE-containing Samples 20
3.2.3 AE-containing Samples 26
Chapter 4 Conclusions 33
Appendix 34
References 36
국문초록 (Abstract in Korean) 38Maste
상온의 낮은 자기장에서 높은 자기 모멘트를 보이는 희토류가 첨가된 비스무스 철산화물의 강자성
Get PDF학위논문 (석사)-- 서울대학교 대학원 : 물리·천문학부(물리학전공), 2013. 2. Nguyen Hoa Hong.BiFeO3 is a promising multiferroic material due to its high ferroelectric (1103 K) and antiferromagnetic (643 K) ordering temperatures. Previous reports have suggested that by reducing the dimensionality, the spiral magnetic ordering could be suppressedtherefore, the magnetic properties could be modified. In BiFeO3, if Bi is partially substituted by a small amount of divalent or trivalent metal ions, or Fe is substituted by transition metal ion, a significant enhancement in magnetization can be achieved. Thin films of Rare Earth (Re) - doped BiFeO3 (where RE = Sm, Ho, Pr and Nd) were grown on LaAlO3 substrates by using pulsed laser deposition technique. All the films show a single phase of rhombohderal structure with space group R3c. The saturated magnetization in the Ho- and Sm- doped films is much larger than those reported in literature, and was observed at a quite low field as of 0.2 T. In the case of Ho and Sm doping, the magnetization increases when the film becomes thinner, suggesting that the observed magnetism is mostly due to surface effect. In the case of Nd doping, even though the thin film has large magnetic moment, the mechanism seems to be different.Contents
ABSTRACT………………………………………………………………Ⅰ
List of Figures………………………………………………………………V
List of Tables………………………………………………………………VII
Chapter 1: Introduction……………………………………………………1
1.1. Multiferroic materialsBismuth Ferrite Oxides (BFO).……1
1.2. Ferromagnetic enhancement in BiFeO3 thin films:
Dimension and Doping ………………………………………3
Chapter 2: Experimental Methods……………………………………4
2.1. Sample Preparation…………………………………………4
2.1.1. Sol-gel auto ignition Method……………………………..5
2.1.2. Pulsed Laser Deposition (PLD)…………………………5
2.2. Measurements………………………………………………7
2.2.1. X-Ray Diffraction (XRD)………………………………………7
2.2.2. Superconducting Quantum Interference Device
(SQUID) ……………………………………………………………8
2.2.3. X-Ray Photoelectron Spectroscopy (XPS) .........…………9
Chapter 3: Results and Discussions………………………………………10
3.1. Structural Properties………………………………………10
3.2. Magnetic Properties…………………………………………13
3.2.1. Sm- and Ho- doped BFO thin films…………………………………13
3.2.2. RE- doped BFO thin films ………………………………………17
3.3. BFO Films Chemical States………………………………20
Chapter 4: Conclusions……………………………………………………………22
Appendix…………………………………………………………………23
References…………………………………………………………………25
국문초록 (Abstract in Korean)…………………………………………26
감사의 글 (Acknowledgements)………………………………………27Maste
Water resource protection and management
No full textThe book is in Vietnamese and includes 7 chapters providing principles of water resources, water quality modelling, technical methods on water conservasion etc
Energy potential from the anaerobic digestion of food waste in municipal solid waste stream of urban areas in Vietnam
Get PDFAnaerobic digestion (AD) was introduced in Vietnam more than 10 years ago, but at a small scale to deal with agricultural wastes, manure, etc. Despite its many advantages, AD does not yet make a significant contribution to resolving Vietnams urban waste issues due to a lack of information, data and experience. This paper, using an energy model of food waste digestion, provides a usable source of information regarding energy potential of food waste generated from urban areas in Vietnam in forms of electricity, heat, and upgraded biogas under two different scenarios. Results show that if food waste is separated from the municipal solid waste (MSW) stream and sent to AD plants, total available energy equivalent each day is about 19, 20 and 45 GWh in 2015, 2020, and 2025, respectively. This could contribute between 2.4 and 4.1 % of the electricity demand of Vietnam, as well as double this amount of energy in the form of heat. Alternatively, upgraded biogas could contribute approximately 2.2–4.7 % of fuel consumption for transportation. This suggests AD is a promising method to treat MSW in cities, especially when considering the problematic aspects of other current waste disposal methods such as: landfilling, composting and, incineration
Ferromagnetism in C-doped SnO2 thin films
No full text학위논문 (석사)-- 서울대학교 대학원 : 물리·천문학부(물리학전공), 2012. 2. Nguyen Hoa Hong.In 2010, a theoretical group investigated the case of carbon doping, to see if defects can induce FM in SnO2.[1] It was predicted that C can create surface-magnetism in SnO2, and the magnetic moment was calculated to be 2μB/C. Since C is known as an element that can create obvious defects, it is interesting to elucidate this specific case. In this dissertation, I will report about study on structural and magnetic properties of C-doped SnO2 thin films, thus give a direct experimental feedback to such an important theoretical statement.
First, in order to make C-doped SnO2 ceramics used to pulsed laser deposition (PLD) process, we used the solid state reaction method. The Sn1-xCxO2 films were grown on the LaAlO3 (LAO) substrates from the targets the solid state reaction method by using the PLD technique (where x = 0%, 1%, 5% and 10%). Morphological and structural studies were carried on by Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and X-Ray Diffraction (XRD) methods.
To study the magnetic properties, we used Superconducting Quantum Interference Device (SQUID) system. Room temperature ferromagnetism (FM) was indeed observed in laser ablated C-doped SnO2 thin films. The greatest value of the saturated magnetization is found in SnO2 films doped with 1% of C (about 16 emu/cm3) and reduces lightly as the C concentration increases.
By subtracting the base of pure SnO2 that is also magnetic, one can find that C-doping actually enhances ferromagnetism in the host SnO2. It suggests that carbon really causes defect-induced magnetism of about 3.91 μB/C into SnO2.
Measurements on C-doped SnO2 bulks show that the observed properties are unique for films (low dimensions, having surface/interface effect).
The investigation on thickness dependence shows a change in magnetization when going from thin to thick films, implying that somehow if magnetism is due to defects then those must be located more on or near the surface than in deeper layers.
Anisotropy is also observed, enforcing the assumption for the origin of magnetism due to defects in C-doped SnO2.2010년 한 연구그룹에서 탄소 첨가에 의한 결함들이 이산화 주석에서의 강자성을 유도할 수 있는지를 연구했다. 탄소는 이산화 주석의 표면자성을 생성시킬 수 있고 그에 따른 자성 모멘트는 2 μB/C로 계산되었다. 탄소는 명백한 결함을 만들 수 있는 요소로 알려졌기 때문에 이런 특별한 경우를 설명하는 것은 흥미로운 일이다. 이 논문을 통해 탄소가 첨가된 이산화 주석 박막들에서의 구조적 자기적 특성들에 대한 연구결과에 대해 보고할 것이고 이는 이론적 진술에 대한 직접적인 실험상의 증명이 될 것이다.
우선 펄스 레이저 증착 공정에서 쓰여질 탄소가 첨가된 이산화 주석 타깃을 만들기 위해 고상반응법을 사용했다. Sn1-xCxO2 (x = 0%, 1%, 5%, 10%) 박막들은 PLD 기법을 사용해서 고상반응법으로 제작된 타깃으로부터 LAO 기판 위에 증착 되었다. 형태학적 구조적 연구는 AFM, SEM, EDS 그리고 XRD를 사용하여 진행되었다.
자기적 특성을 연구하기 위해 초전도 양자 간섭장치를 사용했다. 레이저를 이용하여 LAO 기판 위에 증착 시킨 탄소가 첨가 된 SnO2 박막들에서 상온 강자성이 관찰되었다. 1T에서 측정된 포화자기화는 탄소를 1% 도핑 시킨 SnO2 박막에서 16emu/cm3으로 측정되었고 탄소의 첨가 농도가 증가됨에 따라 그 값이 조금씩 감소되었다.
탄소를 첨가한 박막들로부터 역시 강자성을 띄는 순수한 SnO2 박막의 기반을 제거함으로 SnO2기반의 박막에서 탄소의 첨가가 강자성을 강화시킴을 확인했고 이때 탄소가 SnO2로 하여금 약 3.91 μB/C의 결함 유도 자성을 야기함을 제안한다.
탄소가 첨가 된 덩어리 SnO2에서의 자성 측정은 강자성의 특성들이 낮은 차원, 표면과 경계면 효과를 갖는 박막에서 유일함을 보여준다.
두께 의존도 검사에서 자기화는 얇고 두꺼움의 정도에 따라 변화하였고 만약 자성이 결함들에 의한 것이라면 그것들은 깊숙한 격자보다는 표면근처에 더 많이 위치하고 있어야 한다.
또한 탄소가 첨가된 SnO2박막에서 이런 자성의 근원이 결함이라는 가정을 뒷받침하는 이방성이 관찰되었다.Maste
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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