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The purpose of this study was to assess the validity of School-Level Environment Questionnaire (SLEQ) in the Vietnam context. The study tested the nomological validity of the main measurement model and a competing model. The participants included 29 interviewees and 408 Vietnamese high-school teachers in Ho Chi Minh City. Interview data were used to seek preliminary support for the measurement model and indicators. Survey data were analyzed employing Exploratory Factor Analysis, Confirmatory Factor Analysis and Structural Equation Modelling. A 9-dimension SLEQ with 38 indicators was validated. The dimensions of school climate have various effects on teachers' job satisfaction.

This study examines a cooperative non-orthogonal multiple access (NOMA) network utilizing an energy-constrained unmanned aerial vehicle (UAV) relay (UAVR) to expand coverage and improve network throughput. In order to provide energy to the UAVR, we consider the hybrid simultaneous wireless information and power transmission (SWIPT) method, which allows the UAVR to harvest energy from the source (i.e., sink node) signal. Herein, a hybrid time switching (TS)-based and power splitting (PS)-based relaying scheme is applied to improve the UAVR’s energy harvesting (EH) efficiency and the system performance. Given this context, we derive the closed-form expression of the outage probability (OP) for the sensors to evaluate the network performance. Based on the achieved analytical results, we apply the bat algorithm optimization (BAO) method to determine the optimal working point (as a fraction of received power and power allocation coefficients, and the 3-D positions of the UAVR) for the system such that the OP is minimized. The numerical analysis indicates that BAO is effective in both exploring and exploiting solutions, making it a suitable choice for similar non-convex optimization problems in continuous search spaces for cooperative NOMA IoT networks.

Gastronomy tourism plays a very important role in a country's economy. Gastronomy tourism has been proven to have a positive impact on competitive dynamics and the long-term viability of a destination, as well as the local economy and regional development. Therefore, this study aims to examine the influence of gastronomic tourism on tourist satisfaction. Apart from that, this study also tested the influence of tourist satisfaction on revisit intention and recommendation intention. This study involved 462 domestic tourists in Surabaya. Data were analyzed using Structural Equation Modeling (SEM) analysis with SmartPLS. This study reveals that the quality of gastronomy tourism influences tourist satisfaction and will ultimately encourage potential revisit intention and recommendation intention for tourists to visit gastronomy tourism. Other findings show that tourist satisfaction mediates the effect of gastronomy tourism quality on tourists' revisit intention and recommendation intention to visit gastronomy tourism. The results of this study provide important implications for gastronomy tourism businesses to build tourist satisfaction by improving the quality of gastronomy tourism. By paying attention to and improving the quality of gastronomy tourism, a country can build a positive image, increase competitiveness and support economic growth through a sustainable tourism industry.

AbstractPrevious research suggests the existence of variables that can moderate the influence of country of origin (COO) on consumer preferences for food products. However, there is a scarcity of studies investigating the moderating effect of consumer animosity on the connection between COO attributes and consumer preferences. This study represented an initial attempt to examine consumer preferences for imported fruit from countries involved in disputes with a target country, compared to countries with fewer or no disputes. A choice-based experiment was conducted with 180 respondents in Vietnam’s Mekong River Delta region, using Random Utility Theory (RUT) and the Generalized Multinomial Logit model. The results show significant heterogeneity in consumer preferences for attributes such as COO, traceability label, organic label, and price. However, there is homogeneity in preference for fruit size. Consumer animosity towards a specific country plays a crucial role in shaping choice behavior, as higher animosity leads consumers to prefer the same product from other countries. This study effectively addresses domestic bias by isolating the effects of consumer ethnocentrism, making it a valuable contribution to the field. It also provides practical implications for fruit importers, domestic producers, and retailers in Vietnam by highlighting the importance of different attributes of foreign fruit.

AbstractStudies suggest that quality management professionals need a range of skills to simultaneously exploit current operational models and explore digital transformation. However, there is limited research on the impact of digitalisation on improvement work, associated practices and the skills and competencies of quality management professionals. To contribute to this gap, this study draws on a framework based on a conceptual combination of the principles of quality management and the field of occupational competence. The study aims to understand how digitalisation influences the role of quality management professionals, by assessing its influence on the professionals’ improvement practices. The study employs a multiple cross-case research design with data from interviews with nine interviewees, and two focus groups. The results show a so far nascent and limited influence of digitalisation on improvement practices, a need for explorative and team-based practices. Moreover, nine needed skills areas to enhance the professionals’ potential to benefit from digitalisation in improvement work are suggested. These are Integrator, Pragmatic approach based on a good understanding of possibilities, Change management, Process management, General project management, Improvement analysis, Predictive and proactive approach in QM, General IT and Big data proficiency.

Tuning range extension strategies for varactor-based frequency-reconfigurable planar patch antennas are presented. The three tuning range optimization methods described in the paper include co-optimization of antenna dimensions and varactor properties, exploitation of multiple radiation modes, and reduction of parasitic capacitance. The first two strategies are emphasized by briefly reviewing two previously reported wide tuning range frequency-agile planar antennas. Importantly, the influence of parasitic capacitance on reducing the tuning range of the varactor-based frequency-reconfigurable antennas is then demonstrated by examining two antennas. The three tuning range extension methods are then combined to further expand the frequency tuning range of a reported frequency-reconfigurable antenna. The antenna has been re-designed, fabricated and experimentally characterized to demonstrate enhanced performance, which validates the proposed techniques, and their simultaneous application to reconfigurable antenna designs.

Recently, the combination of cognitive radio networks with the nonorthogonal multiple access (NOMA) approach has emerged as a viable option for not only improving spectrum usage but also supporting large numbers of wireless communication connections. However, cognitive NOMA networks are unstable and vulnerable because multiple devices operate on the same frequency band. To overcome this drawback, many techniques have been proposed, such as optimal power allocation and interference cancellation. In this paper, we consider an approach by which the secondary transmitter (STx) is able to find the best licensed channel to send its confidential message to the secondary receivers (SRxs) by using the NOMA technique. To combat eavesdroppers and achieve reasonable performance, a power allocation policy that satisfies both the outage probability (OP) constraint of primary users and the security constraint of secondary users is optimized. The closed-form formulas for the OP at the primary base station and the leakage probability for the eavesdropper are obtained with imperfect channel state information. Furthermore, the throughput of the secondary network is analyzed to evaluate the system performance. Based on that, two algorithms (i.e., the continuous genetic algorithm (CGA) for CR NOMA (CGA-CRN) and particle swarm optimization (PSO) for CR NOMA (PSO-CRN)), are applied to optimize the throughput of the secondary network. These optimization algorithms guarantee not only the performance of the primary users but also the security constraints of the secondary users. Finally, simulations are presented to validate our research results and provide insights into how various factors affect system performance.

This article deals with the analysis of the fractal dimension of streamers propagating in mineral oil, under lightning impulse voltage, using the box counting method; the method and technique of calculation are described therein. In the considered experimental conditions, the average velocities of recorded streamers are of 2.4 km/s and 1.8 km/s for positive and negative streamers, respectively; these velocities correspond to the 2nd mode of streamers propagation. It is shown that the streamers present the fractal dimension D ; and the higher D is the bushier are the streamers (i.e. with high branch density). The positive streamers can have higher D than the negative ones, if they are bushier.

The most popular additive manufacturing (AM) technologies to produce titanium alloy parts are electron beam melting (EBM), selective laser melting (SLM) and directed energy deposition (DED). This investigation explores mainly these three techniques and compares these three methods comprehensively in terms of microstructure, tensile properties, porosity, surface roughness and residual stress based on the information available in the literature. It was found that the microstructure is affected by the highest temperature generated and the cooling rate which can be tailored by the input variables of the AM processes. The parts produced from EBM have strength comparable to that of conventionally fabricated counterparts. SLM and DED yield superior strength, which can be up to 25% higher than traditionally manufactured products. Due to the presence of larger tensile residual stress, surface roughness and porosity, AM fabricated parts have lower fatigue life compared to those of from traditional methods. EBM parts have slightly lower fracture toughness (i.e., lower fatigue life) than conventionally produced parts while SLM and DED have significantly lower fracture toughness. Annealing, hot isostatic pressing, stress relief and additional machining processes improve the characteristics of parts produced from AM. Ti–6Al–4V alloy parts fabricated via AM may have limited applications despite the high demands in aerospace or biomedical engineering. Since rapid product development using 3D printers leads to significant cost reductions more recently, it is expected that more opportunities may soon be available for the AM of titanium alloys with newer AM processes such as cold spray additive manufacturing (CSAM) and additive friction stir deposition (AFSD).

In this article, deep learning probabilistic models are applied to a case study on evaluating the influence of specialized mini projects (SMPs) on the performance of engineering students on their final year project (FYP) and cumulative grade point average (CGPA). This approach also creates a basis to predict the final performance of undergraduate students based on their SMP scores, which is a vital characteristic of engineering training. The study is conducted in two steps: (i) establishing a database by collecting 2890 SMP and FYP scores and the associated CGPA of a group of engineering students that graduated in 2022 in Hanoi; and (ii) engineering two deep learning probabilistic models based on Bayesian neural networks (BNNs) with the corresponding architectures of 8/16/16/1 and 9/16/16/1 for FYP and CGPA, respectively. The significance of this study is that the proposed probabilistic models are capable of (i) providing reasonable analysis results such as the feature importance score of individual SMPs as well as an estimated FYP and CGPA; and (ii) predicting relatively close estimations with mean relative errors from 6.8% to 12.1%. Based on the obtained results, academic activities to support student progress can be proposed for engineering universities.

This paper examines the impact of earnings quality (EQ) on the Vietnam companies’ cost of debt (COD). We use data from companies listed on the Vietnam stock market from 2010 to 2019. In this paper, we develop a model to investigate the influence of audit quality and foreign ownership on COD. We find that EQ had a negative relationship with COD. However, when firm is in financial distressed, EQ has a positive relationship with COD. As an intermediate variable, EQ also has a negative relationship with COD.

This paper studies the relationship between accounting information reflected in financial statements and stock return in Vietnam Stock Market. The authors propose a research model to define the relationship. Besides, machine learning algorithms are used in researching and forecasting, with data obtained from observed firms during the period from 2009 to 2020. Research results show that gradient boosting algorithm has the best self-reporting performance and finan-cial ratios also have great impact on stock returns, including operating income growth, stock earnings volatility, dividend yield, earnings before tax-to-equity ratio, cash holding ratio, and accrual quality. Based on the research results, the authors make some recommendations for investors, firms, and policy makers.

This paper presents a novel study on the transient response of simply supported rectangular functionally graded nanoplates with porosities. Nonlocal elasticity theory is employed in the analysis, incorporating the effect of surface energy. The motion equations of the nanoplates are derived from Hamilton’s principle within the framework of Reddy's higher-order shear deformation theory. The closed-form solutions are obtained for transient analysis under diverse impulsive loading scenarios using Navier’s technique. A very good agreement between the results of the present model and those available in the literature is found. This study reveals that the transient response of the nanoplate is significantly influenced by various factors, including nonlocal parameters, surface elastic constants, porosity distribution patterns, and elastic foundation stiffness. Notably, the surface energy effect has a greater impact on vibration amplitude compared to the nonlocal effect. The approach presented in this paper could serve as a valuable benchmark for the design, production, and operation of such nanoplates. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effects of different surface preparation techniques on the surface microstructure, the shear bond strength (SBS) between zirconia and an MDP-containing light-cured veneer adhesive system, and the adhesive failure mode. Sixty-four zirconia specimens were divided into four groups based on surface preparation methods (n = 16), including zirconia sandblasting (ZSB), zirconia vitrification or glaze-on (ZVG), zirconia surface architecture technique (ZSAT), and ZSAT-ZVG combined technique (ZSATVG) groups. Sixteen lithium disilicate specimens prepared by etching with hydrofluoric acid (HF) were used as a positive control group (LDE). Surface roughness measurement and scanning electron microscopy (SEM) evaluation were performed before and after surface preparation. All specimens were then bonded with an MDP-containing light-cured adhesive system, followed by SBS testing and adhesive failure mode analysis. The ZVG and ZSATVG groups showed the greatest differential roughness value and microscopic irregularities, while the ZSAT and LDE groups had the least surface change but the most micromechanical retentive structures for resin infiltration. SBS values were significantly different among groups (p < 0.001) with the highest SBS observed in the ZSAT group, followed by the ZSB group, LDE group, ZSATVG group, and lastly, the ZVG group. There was a statistically significant difference in failure types among the surface preparation groups (p < 0.001). The ZSAT group had the highest frequency of mixed failure, followed by the ZSB group, LDE group, and the ZSATVG and ZVG groups. Establishing direct micromechanical retention within zirconia itself yields a higher bond strength than indirect micromechanical retention within a glass ceramic layer. [ABSTRACT FROM AUTHOR]

A lab-scale flat sheet membrane bioreactor (MBR) system was used for the treatment of piggery wastewater to produce an effluent with the appropriate ratio of nitrite:ammonia (1:1 to 1:1.3) as a pre-treatment for the anammox process. The feed wastewater, which was the effluent of a biogas digester, contained 253±49 (n=60) mg.l-1 as COD, 231±18 mg.l-1 as N-ammonia, 223±19 mg.l-1 as total Kjeldalh nitrogen (TKN), alkalinity of 1433±153 mg.l-1 as CaCO3, and pH=7.5±0.3. This study aimed to determine the suitable hydraulic retention time (HRT) and alkalinity to yield the appropriate influent for the annamox process. The results showed that the suitable effluent of the partial nitrification with ratio of nitrite:ammonia 1.0:1.1 at HRT of 7h30, equivalent to total nitrogen loading of 0.77 kgNm-3d-1. The nitrite accumulation rate (NAR) was 82% at HRT of 7h30, whereas NAR were 11 and 63% at HRT of 12h30 and 8h45, respectively, due to the high growth of nitrite oxidation bacteria (NOB) at long HRTs. As increasing alkalinity of up to 1600 mg.l-1 and pH of 8.0 at HRT of 8h45, NAR was increased from 63 to 73%, ratio of ammonia:nitrite reduced from 1.0:1.8 to 1.0:1.6 and free ammonia concentration reached to 20.2 mg.l-1 nitrogen. This shows that the increase of alkalinity inhibited strongly NOB.

Abstract Herbivores control algae and promote coral dominance along coral reefs. However, the majority of previous studies have focused on herbivorous fish. Here we investigated grazing effects of the sea urchin Diadema savignyi on algal abundance and coral recruitment processes. We conducted an in situ cage experiment with three density conditions of D. savignyi (0, 8, 16 indiv. m−2) for three months during the main coral recruitment season in Taiwan. Results demonstrated a strong algal control by D. savignyi. At the end of the experiment, average algal cover was 95% for 0 indiv. m−2, compared to 47% for 8 indiv. m−2 and 16% for 16 indiv. m−2. Average algal biomass at 8 indiv. m−2 declined by one third compared to 0 indiv. m−2 and almost zero at 16 indiv. m−2. On the other hand, a negative grazing effect of D. savignyi was observed on coral recruitment processes. Notably, at 16 indiv. m−2, the density of coral recruits declined and mortality of small coral fragments (proxy of coral juveniles) increased. Our results confirm findings of previous studies and indicate the need to balance both positive (strong algal control) and negative (physical damage) influences of Diadema grazing to facilitate the coral recruitment process.

Cash management plays an important role in the business operations. However, holding too much cash results in unnecessary expenses such as opportunity costs, management costs, and representation costs due to negative cash holdings. This study examines the sensitivity of cash flows to cash holdings. The paper uses regression methods for table data, including FEM, REM, GLS, and GMM regression, with a research dataset including non-financial companies listed on Vietnam’s stock market in the period 2008–2018. Empirical results show that cash flows are positively associated with cash holdings levels. At the same time, research has shown an asymmetry in cash flows sensitivity to cash holdings. The study also classified the companies with limited and no financial restrictions. In the Vietnamese context, compared to unrestricted companies, financially restricted companies have a lower cash flows sensitivity. The research results are the basis for enterprises to manage cash better and increase business efficiency in the future.