Predicting freshwater habitat conditions by the distribution of macroinvertebrates using artificial neural network

Artificial Neural Networks were used to model the relationship between habitat conditions and macroinvertebrate assemblages in the Queensland river and stream system. The clean water approach was used to determine the relationship between presence and absence of macroinvertebrate taxa and physical predictor variables, studying data from reference sites in near pristine conditions. Trained models were applied to assess habitat conditions of impacted and test sites. The dirty water approach studied interrelationships between physical, chemical and biological processes. Sensitivity analyses were carried out by manipulating the values of input parameters and assessing the resulting changes in outputs. Artificial Neural Networks proved an effective computational approach to support bioassessment.Thesis (M.App.Sc.) -- University of Adelaide, Dept. of Soil and Water, 200

THE IMPACT OF DATA SECURITY ON THE INTENTION OF VIETNAMESE CONSUMERS TO USE E-WALLETS

E-wallets are used as a form of payment that brings many benefits to users. This article studies the impact of data security on consumer intentions to use e-wallets in the rapidly growing economy of Vietnam. The data consist of 236 observations from a survey of consumers in Vietnam. Covariance-based structural equation modeling (CB-SEM) was employed to test the proposed hypotheses. Research results show that security trust has the greatest impact on the intention to use e-wallets, followed by perceived privacy risk, social influence, and information sensitivity. The study also reveals the role of privacy policies and security concerns in consumer intentions to use e-wallets. Based on the research results, the study provides recommendations for consumers, e-wallet providers, and governmental agencies to increase awareness of and responsibility for information security among the consumers who use e-wallets

Bivariate modelling of precipitation and temperature using a non-homogeneous hidden Markov model

Aiming to generate realistic synthetic times series of the bivariate process of daily mean temperature and precipitations, we introduce a non-homogeneous hidden Markov model. The non-homogeneity lies in periodic transition probabilities between the hidden states, and time-dependent emission distributions. This enables the model to account for the non-stationary behaviour of weather variables. By carefully choosing the emission distributions, it is also possible to model the dependance structure between the two variables. The model is applied to several weather stations in Europe with various climates, and we show that it is able to simulate realistic bivariate time series

Petrology, geochemistry, and Sr, Nd isotopes of mantle xenolith in Nghia Dan alkaline basalt (West Nghe An): implications for lithospheric mantle characteristics beneath the region

Study of petrological and geochemical characteristics of mantle peridotite xenoliths in Pliocene alkaline basalt in Nghia Dan (West Nghe An) was carried out. Rock-forming clinopyroxenes, the major trace element containers, were separated from the xenoliths to analyze for major, trace element and Sr-Nd isotopic compositions. The data were interpreted for source geochemical characteristics and geodynamic processes of the lithospheric mantle beneath the region. The peridotite xenoliths being mostly spinel-lherzolites in composition, are residual entities having been produced following partial melting events of ultramafic rocks in the asthenosphere. They are depleted in trace element abundance and Sr-Nd isotopic composition. Some are even more depleted as compared to mid-ocean ridge mantle xenoliths. Modelled calculation based on trace element abundances and their corresponding solid/liquid distribution coefficients showed that the Nghia Dan mantle xenoliths may be produced of melting degrees from 8 to 12%. Applying various methods for two-pyroxene temperature- pressure estimates, the Nghia Dan mantle xenoliths show ranges of crystallization temperature and pressure, respectively, of 1010-1044°C and 13-14.2 kbar, roughly about 43km. A geotherm constructed for the mantle xenoliths showed a higher geothermal gradient as compared to that of in the western Highlands (Vietnam) and a conductive model, implying a thermal perturbation under the region. The calculated Sm-Nd model ages for the clinopyroxenes yielded 127 and 122 Ma. 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Stakeholder Involvement and the Attainment of SDGs at Local Tourism Destinations: A Case Study in Vietnam

This paper explores how the United Nations Sustainable Development Goals (SDGs) can be achieved at local tourism destinations through the collective efforts of stakeholders. A multiple-case study is conducted at Da Nang and Hue in Vietnam. These destinations experience a controversial concern between tourism development and natural/cultural preservation. A thematic analysis of qualitative data reveals the cooperation of various stakeholders to prevent the encroachment of tourism development in the natural environment in Da Nang or balance heritage preservation and tourism development in Hue. These collective efforts facilitate the achievement of the seventeen Sustainable Development Goal to attain various SDGs in each case. This research contributes to sustainability research by revealing the contribution and effects of collective actions in achieving the common goals related to the sustainable development of local destinations

Interrogating electrocatalytic mechanisms and developing nano-porous catalysts for energy conversion reactions: I. Oxygen evolution reaction, and II. Carbon dioxide reduction reaction

The objectives of my thesis were to interrogate electrocatalytic mechanisms and develop new nano-porous catalysts for energy conversion reactions including the oxygen evolution reaction (OER) and carbon dioxide reduction reaction (CRR). First, I examined the oxygen evolution reaction in basic electrolytes using in situ electrochemical surface stress measurements. Second, I developed a new electrolyte additive-controlled electrodeposition method for the preparation of porous films of Ni and NiFe catalysts with high OER activity. Third, I exploited the additive-controlled electrodeposition method to synthesize Cu and CuAg films with high surface area and tunable morphology for high activity and selectivity of CRR to ethylene. In Chapter 1, I provide background information to the electrochemical energy conversion reaction and lay out the challenges and potential approaches at present in the field. In Chapter 2, I describe our effort to determine the relationship between changes in the OER catalyst surface and activity. In situ electrochemical surface stress measurements were utilized to interrogate oxide formation before and during OER on several common catalysts, including Ir, Ni, Co, Au, and Pt. The stress measurements report directly on changes in oxidation state and phase of the electrode material as the potential is varied. Hysteresis observed in the potential-dependent stress with Ir, Au and Pt electrodes is associated with irreversible composition and roughness changes in the electrode. The stress data also quantitatively reports on the in-plane change in strain developing in bonding during oxide oxidation. The magnitude of the surface stress is nearly identical to that the predicted from bond strains obtained from reported XAS data. Interestingly, there is a rough linear relationship between the change in stress and the amount of oxide formed. More importantly, the stress data shows that metals with higher activity exhibit larger stress and more oxide formation. The origin of this relationship could be explained by differences in conductivity and porosity of different oxides. In Chapter 3, I focus on developing a stable and effective OER catalyst using an additive-controlled electrodeposition. We find that 3,5-diamino-1,2,4-triazole (DAT) acts as a deposition inhibitor that dramatically changes Ni morphology resulting in black Ni films, a phenomenon indicative of small particle formation. Ni films electrodeposited with DAT (NiDAT) exhibit much higher active surface areas with fractal-like behavior. Correspondingly, NiDAT films show a much larger oxidation wave and higher OER rates compared to the Ni film deposited without the DAT additive. Co-electrodeposition of Ni and Fe in the presence of DAT (NiFeDAT) is also explored as Fe is known to increase the OER activity from Ni films. NiFeDAT films are very active toward OER exhibiting 100 mA/cm2 with high stability > 72 hours at 1.50V vs RHE in 1 M NaOH. These metrics make NiFeDAT among the most active OER electrocatalyst reported to date. Equally important, the high activity can be tuned to nearly any arbitrary value by altering the amount of NiFe electrodeposited without film degradation. In Chapter 4, I present electrochemical measurements that examine the effect of deuteration on the OER with Ni and Co catalysts, and an effort to identify the rate-determining step (RDS) of these intricate electrocatalytic reactions involving multiple proton-coupled electron transfer (PCET) processes. The OER Tafel slope and kinetic isotope effect (KIE) calculated from electrochemical data shows that both Ni and Co exhibits inverse secondary KIE, which is never observed before in an electrochemical experiment. These results contribute to a more complete understanding of the OER mechanism and allow for the future development of improved nonprecious-metal catalysts. In Chapter 5, I discuss exploiting the additive-controlled electrodeposition method to synthesize Cu films with high surface area and tunable morphology for high activity and selectivity of CRR to ethylene. Electrodeposition of Cu films from plating baths containing DAT (CuDAT) as an inhibitor exhibit high surface area and high CO2 reduction activities. By changing pH and deposition current density, the morphologies of the Cu films are varied to exhibit wires, dots, or amorphous structures. Among these Cu films, the CuDAT-wire samples exhibit the best CO2 reduction activity with a Faradaic efficiency (FE) of the C2H4 product formation reaching 41% at -0.47 V vs. RHE, a FE for C2H5OH formation reaching 22% at -0.55 V vs. RHE, and a mass activity for CO2 reduction at -0.65V vs. RHE of ~ 720 A/g. In Chapter 6, I present our strategy to enhance C2 production from CO2 electroreduction by doping low Ag contents (<10%) into Cu-wire film. The CuAg-wire catalyst with nanoporous structure and homogenous mixed of Cu and Ag atoms was fabricated by additive-controlled electrodeposition method using DAT. The CuAg-wire catalyst exhibits large active surface and high selectivity of CO2 reduction to C2H4 (~60% Faradaic efficiency - FE) and C2H5OH (~25% FE) at relatively low overpotential (~ -0.7V vs RHE)

Development of PSO for tracking Maximum Power Point of Photovoltaic Systems

For a photovoltaic system, the relationship of the output voltage and power is usually non-linear, so it is essential to equip a MPPT controller in PV systems. Furthermore, the hotspot problem is a common phenomenon, resulting from the PV system operating under PSC. Partial shading not only damages the PV cells, but also makes it difficult to find the global MPP in the characteristic curves of P-V. The paper proposes a novel version of PSO, namely PPSO in order to detect the global peak among the multiple peaks, known as the true maximum energy from PV panel. For this, the PPSO algorithm makes the velocity of each particle be perturbed once the particles are struck into a local minima state in order to find the best optimum solution in the MPPT problem. The perturbation in the velocity vector of each particle not only helps them tracking the MPP accurately under the changing environmental conditions, such as large fluctuations of insolation and temperature like PSC; but also removes the steady-state oscillation. The proposed approach has been tested on a MPPT system, which controls a dc-dc boost converter connected in series with a resistive load. Moreover, the obtained results are compared to those obtained without any MPPT controller to prove the efficiency of the suggested method. In addition, this novel version gives the highest accuracy of tracking the optimum power in the least iteration number as compared to the conventional PSO

Factors affecting the flipped classroom in the educational context of Vietnam

In the context of the implementation of the 2018 General Education Program, teachers are required to implement a teaching model oriented to the development of students’ quality and competence. Teachers are encouraged to adapt the flipped classroom model of teaching in schools as its advantages are suitable for novel teaching strategies. This study focuses on analyzing factors affecting the application of this model in the teaching and learning process by collecting feedback from 351 teachers from various cities in Vietnam. The questionnaire included Likert-type questions analyzed by IBM SPSS Statistics version 20 for quantitative analysis and an open question for qualitative analysis with context and personal information. The research-oriented factors focus on the group of potential internal factors (perception, proficiency, desire and readiness of teachers) and the group of external factors (infrastructure, facilities and support resources, training programs). The results showed that those factors include the school’s infrastructure and information communication technology (ICT) condition, the teacher’s ICT competence as well as competence-related teaching and assessment methodologies and the students’ internet access conditions. Finally, the study offers suggestions on how to apply this model in teaching practice to meet the requirements of educational innovation in Vietnam