Electronic structure calculations for point defects, interfaces, and nanostructures of TiO2

Transparent conducting oxides (TCOs) play an important role not only in optoelectronic and photovoltaic devices but also in future transparent electronics. A transparent conductor arises upon degenerately doping a semiconductor (insulator) so that the conduction becomes metallic (resistivity ~ temperature). The extra electrons occupy the conduction band (CB) states of the host and the conductivity is determined by the electron optical effective mass. Recently, anatase TiO2 films doped with Nb, i.e., Ti1-xNbxO2 (TNO), have attracted a great deal of interest as a promising candidate for TCO applications because of their low resistivity (~ 10^-4 Omega.cm) and high optical transmittance (90 % in the visible light region). A few experimental studies have been reported for the optical effective mass of electrons as a function of the carrier concentration in Nb-doped anatase, on the directions which are either orthogonal or parallel to the tetragonal axis of the crystal. In this thesis, I have determined the optical effective mass of electrons in Nb-doped anatase based on band structure calculations. The anisotropy of the crystal and the nonparabolicity of the bands have both been taken into account. I have found that in the range concentration which is relevant to transparent conductive oxide applications, the optical effective mass is determined by several branches of the conduction band, leading to a complicated dependence on the carrier concentration. The function for the optical effective mass obtained by our calculations agrees well with that obtained experimentally. In particular, the strong anisotropy of the optical effective mass has already been confirmed. Although Ta-doping of anatase TiO2 appears to be effective as well, this possibility has been not well explored. I have compared the two dopants, i.e., Nb and Ta, for doping anatase TiO2. The Ta dopant has a considerably higher solubility and a lower optical effective mass, thus acquiring more advantages than Nb. Moreover, my calculations have also explained why a reducing atmosphere is necessary for the efficient dopant incorporation, without invoking oxygen vacancies as proposed in the literature. There is no study on the effects from the quantum confinement of dopants in anatase nanowires (ANWs). Therefore, I report here the first demonstration on the role of Nb- and Ta-dopants in ANWs. The pure ANWs cut by keeping the screw axis of the original bulk structures are consistently lower in energy than the similarly oriented nanowires in which the screw symmetry is destroyed. Both Nb and Ta dopants prefer the sub-corner sites of the most stable ANWs. At the highest symmetry, the band structure of the doped ANW is similar to that of the perfect one. The increase of the photocatalytic activity upon mixing rutile and anatase powders is usually explained by assuming change separation between the two phases. There are many contradicting theories regarding the particular charge transfer between these phases. Therefore, another goal of this thesis is to study the electronic properties of the interface between anatase and rutile phases of TiO2. By calculating the band line-up of a rutile-anatase interface, I have found that both the conduction band minimum (CBM) and the valence band maximum (VBM) of the rutile phase are higher than those of the anatase phase. As a result, electrons are expected to transfer from the rutile phase to the anatase phase while holes move in the opposite direction. In my work, the optical electron effective mass is determined from the band structure of the material, which is in turn calculated by the version of density functional theory (DFT) in the generalized gradient approximation (GGA) implemented in the Vienna Ab Initio Simulation Package (VASP) package. For bulk materials, both the Perdew-Berke-Enzerhof (PBE) and the screened hybrid functional (HSE06) are used for the exchange energy. Although the HSE06 functional gives better results compared with the existing experimental measurements for Nb- and Ta-doped anatase TiO2 bulk materials, similar calculations with HSE06 for nanowires are far more expensive. Therefore, my calculations for nanowires are carried out only with the pure GGA-PBE functional. To determine the rutile-anatase interface, I have used the density functional based tight binding (DFTB) method for the molecular dynamic simulations, and then relaxed by ab initio calculations with PBE functional at 0K

ENGLISH-MAJORED STUDENTS' MOST COMMON CAREER OPTIONS AND THE LEVELS OF READINESS FOR THE CAREERS

EFL students nowadays have a variety of career options. Most of them, however, still do not have a well-understanding or a strong readiness for their job targets. This study was conducted to find out the EFL students’ most career options, some language standards when selecting careers and to what extent students feel that they are ready for their future careers. To answer these questions, we use exploratory questionnaires to survey the participants. The findings demonstrate that teaching English is the most attractive career that EFL students want to attend after graduating, followed by the freelancer. However, a group of students still cannot locate their future careers. Additionally, juniors and seniors are considered to have better preparation for their career prospects than freshmen and sophomores.  Article visualizations

Trends in socioeconomic inequalities in full vaccination coverage among vietnamese children aged 12–23 months, 2000–2014: Evidence for mitigating disparities in vaccination

There has been no report on the situation of socioeconomic inequalities in the full vaccination coverage among Vietnamese children. This study aims to assess the trends and changes in the socioeconomic inequalities in the full vaccination coverage among Vietnamese children aged 12–23 months from 2000 to 2014. Data were drawn from Multiple Indicator Cluster Surveys (2000, 2006, 2011, and 2014). Concentration index (CCI) and concentration curve (CC) were applied to quantify the degree of the socioeconomic inequalities in full immunization coverage. The prevalence of children fully receiving recommended vaccines was significantly improved during 2000–2014, yet, was still not being covered. The total CCI of full vaccination coverage gradually decreased from 2000 to 2014 (CCI: from 0.241 to 0.009). The CC increasingly became close to the equality line through the survey period, indicating the increasingly narrow gap in child full immunization amongst the poor and the rich. Vietnam witnessed a sharp decrease in socioeconomic inequality in the full vaccination coverage for over a decade. The next policies towards children from vulnerable populations (ethnic minority groups, living in rural areas, and having a mother with low education) belonging to lower socioeconomic groups may mitigate socioeconomic inequalities in full vaccination coverage. © 2019 by the authors. Licensee MDPI, Basel, Switzerland. **Please note that there are multiple authors for this article therefore only the name of the first 5 including Federation University Australia affiliate “Huy Nguyen” is provided in this record*

Human Ecosystem Approach to The Dynamics of Sustainable Development in Komodo National Park, Indonesia

This article aims to present the dynamics of sustainable development in Komodo National Park (KNP) using a human ecosystem model. The Human Ecosystem model is a coherent system of biophysical and social factors capable of adaptation and sustainability over time. A rural village in Komodo island, Labuan Bajo, East Nusa Tenggara, Indonesia can be considered a human ecosystem because it has identifiable boundaries, essential ecosystem functions, resource flows, social structures, social processes (including adaptive responses to changed conditions), and dynamic continuity over a period. In 2020, the “Jurassic Park” tourism project in Komodo National Park has become a hot topic on social media after a photo of a Komodo dragon blocking a truck popped up. The project’s rejection became the most popular topic on Twitter with the hashtag #savekomodo. Various groups believe that the project will destroy the Komodo dragon’s natural habitat, evict the local population, and be carried out solely for financial gain. As a result, it is critical to understand the current situation there. The HEM helps us identify the critical resources and the social systems, as well as the key flows that contribute to the dynamic of the human ecosystem in KNP. This article yields three important findings that should be considered in the future management of KNP. First and foremost, the Komodo dragon population is still stable, but it has the potential to decline in the long term due to changes in spatial planning, an increase in tourists, a decrease in food, and poaching. Second, expanding large-capital corporations that can replace local businesses such as boat rentals, car rentals, homestay businesses, restaurants, souvenirs, and tour guides/rangers will reduce local people’s income from tourism. Third, kinship relationships between Komodo dragons and the clan of Ota Moda are eroding because of fewer encounters between Komodo dragons and the island’s indigenous tribal communities. Artikel ini bertujuan untuk menyajikan dinamika pembangunan berkelanjutan di Taman Nasional Komodo (TNK) dengan menggunakan model human ekosistem. Model human ekosistem adalah system koheren dari faktor biofisik dan sosial yang mampu beradaptasi dan berkelanjutan dari waktu ke waktu. Sebuah desa di pulau Komodo, Labuan Bajo, Nusa Tenggara Timur, Indonesia dapat dianggap sebagai human ekosistem karena memiliki batas-batas yang dapat diidentifikasi, fungsi ekosistem esensial, aliran sumber daya, struktur sosial, proses sosial (termasuk respons adaptif terhadap kondisi yang berubah), dan kontinuitas dinamis selama suatu periode. Pada tahun 2020, proyek wisata “Jurassic Park” di Taman Nasional Komodo menjadi topik hangat di media sosial setelah muncul foto Komodo yang menghalangi truk. Penolakan proyek tersebut menjadi topik paling populer di Twitter dengan tagar #savekomodo. Berbagai kalangan percaya bahwa proyek tersebut akan menghancurkan habitat alami komodo, menggusur penduduk setempat, dan dilakukan semata-mata untuk keuntungan finansial. Akibatnya, sangat penting untuk memahami situasi saat ini di sana. HEM membantu untuk mengidentifikasi sumber daya penting dan sistem sosial, serta arus utama yang berkontribusi pada dinamika human ekosistem di TNK. Artikel ini menghasilkan tiga temuan penting yang harus dipertimbangkan dalam pengelolaan TNK di masa mendatang. Pertama dan terpenting, populasi komodo masih stabil, tetapi berpotensi menurun dalam jangka panjang karena perubahan tata ruang, peningkatan wisatawan, penurunan makanan, dan perburuan liar. Kedua, ekspansi perusahaan modal besar yang dapat menggantikan usaha lokal seperti persewaan kapal, persewaan mobil, usaha homestay, restoran, cinderamata, dan pemandu wisata/ranger akan mengurangi pendapatan masyarakat lokal dari pariwisata. Ketiga, hubungan kekerabatan antara komodo dan klan Ota Moda terkikis karena lebih sedikit pertemuan antara komodo dan komunitas suku asli pulau itu

Extended state observer based load frequency controller for three area interconnected power system

In this paper, we develop a new extended state variable observer based LFC scheme for three-area interconnected power systems. The extended state observerbased load frequency controllers are developed which utilize disturbance estimation techniques. The propose control approach assures that the fluctuating things of the load frequencies reaches to a safer range and the load frequencies can also be made at a very minimal not to have an effect on power quality and power flow in multi-area interconnected power system. The results of the simulations using MATLAB/SIMULINK done did not only address that the proposed newly control method works effectively but also change powerfully the parameter variations of the interconnected areas of the power system. Especially, it works very well to limit disturbances impact on interconnected areas in the system. Therefore, the performance of interconnected power system under different multi-conditions is simulated with the new control method to demonstrate the feasibility of the system

Load Shedding in Microgrid System with Combination of AHP Algorithm and Hybrid ANN-ACO Algorithm

This paper proposes a new load shedding method based on the application of intelligent algorithms, the process of calculating and load shedding is carried out in two stages. Stage-1 uses a backpropagation neural network to classify faults in the system, thereby determining whether or not to shed the load in that particular case. Stage-2 uses an artificial neural network combined with an ant colony algorithm (ANN-ACO) to determine a load shedding strategy. The AHP algorithm is applied to propose load shedding strategies based on ranking the importance of loads in the system. The proposed method in the article helps to solve the integrated problem of load shedding, classifying the fault to determine whether or not to shedding the load and proposing a correct strategy for shedding the load. The IEEE 25-bus 8-generator power system is used to simulate and test the effectiveness of the proposed method, the results show that the frequency of recovery is good in the allowable range

Chemical profile and antibacterial activity of acetone extract of Homalomena cochinchinensis Engl. (Araceae)

Homalomena cochinchinensis Engl. is a rare species which is found in Southern China, Cambodia, Laos and Vietnam and its chemical constituents and bioactivity have not been determined yet. In this study, we identified 32 and 38 compounds in acetone extracts of H. cochinchinensis aerial part and rhizome, respectively via gas chromatography mass spectrometry (GC/MS). The main constituents of acetone extract of the aerial part were 3-((4Z,7Z)-Heptadeca-4,7-dien-1-yl)phenol (18.73%); cis-9,cis-12-Octadecadienoic acid (12.04%); linolenic acid (11.08%); n-Hexadecanoic acid (10.13%); (Z)-3-(Heptadec-10-en-1-yl)phenol (7.09%); ?-Sitosterol (5.58%) and linalool (5.56%). On the other hand, acetone extract of rhizome contained linalool (28.42%); 1,2,3-Propanetriol, 1-acetate (10.13%); 3-((4Z,7Z)-Heptadeca-4,7-dien-1-yl)phenol (5.28%); 3-Buten-2-one, 3-methyl-4-(1,3,3-trimethyl-7-oxabicyclo[4.1.0]heptan-1-yl)- (5.28%) and 4-(2,6,6-Trimethyl-cyclohex-1-enyl)-butyric acid (4.54%). Furthermore, this study has also proved the antibacterial activity of acetone extracts from the aerial part and the rhizome of this species for the first time using disk diffusion method. The results showed that the extract of the aerial part could inhibit the growth of 5 out of a total 6 bacterial strains, including Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa, Salmonella enteritidis and Staphylococcus aureus; while the susceptible strains to the rhizome extract were 5 strains, such as B. cereus, E. coli, P. aeruginosa, Salmonella typhimurium and S. aureus. The findings suggest the further application of this species in pharmacology and medicine

A Conceptual Design and Numerical Analysis for a Small-Scale and Low-Cost Plastic Recycling Machine

A new conceptual design for a small-scale and low-cost plastic recycling machine is generated by combining melting part and compression process. Starting with one of the outstanding requirements is in terms of an affordable-priced machine that can perform two processes with high accuracy and capacity, some issues related to balancing among quality, capacity and cost of machine occurred during a discussion. After implementing various designing methods such as Quality Function Deployment, Reverse Engineering, Morphological Matrix and Pugh Method, an idea of final concept about using an electric oven and hydraulic system to melt down and compress plastic tile which has a dimension of 300x300x9 mm was created. The design of concept is divided into two parts which are mechanical and electrical systems. In a mechanical section, the technical drawing and simulation are made to see how machine performs under operation. Besides, we examined the forces that applied in the moulds to evaluate the strength of the system. In heating and electricity section, we chose electrical components, designed oven parameters and conducted the heating simulation on the mould. In addition, the heating and cooling time was calculated based on the principles of thermodynamics and heat transfer. Furthermore, the manufacturing plan is created to estimate the essential resources producing a certain number of heat-forming machines. In general, the machine needs to be prototyped for controlling its main function and finding practical issues. After that, some improvements could be made to enhance efficiency and increase capacity by designing an optimal mould to more heat absorb and reduce post process, calculate and design more efficient oven, create faster lock mechanism and other improvements for an automatizing machine

Disinfection performance of an ultraviolet lamp: a CFD investigation

Ultraviolet (UV)-based devices have shown their effectiveness on various germicidal purposes. To serve their design optimisation, the disinfection effectiveness of a vertically cylindrical UV lamp, whose wattage ranges from P = 30 − 100 W, is numerically investigated in this work. The UV radiation is solved by the Finite Volume Method together with the Discrete Ordinates model. Various results for the UV intensity and its bactericidal effects against several popular virus types, i.e., Corona-SARS, Herpes (type 2), and HIV, are reported and analysed in detail. Results show that the UV irradiance is greatly dependent on the lamp power. Additionally, it is indicated that the higher the lamp wattage employed, the larger the bactericidal rate is observed, resulting in the greater effectiveness of the UV disinfection process. Nevertheless, the wattage of P ≤ 100W is determined to be insufficient for an effective disinfection performance in a whole room; higher values of power must hence be considered in case intensive sterilization is required. Furthermore, the germicidal effect gets reduced with the viruses less sensitive to UV rays, e.g, the bactericidal rate against the HIV virus is only ∼8.98% at the surrounding walls