Evolution of particle morphology during char conversion processes applied for the CFD modeling of an entrained-flow gasifier

The change in morphology of a char particle affects both its trajectory and carbon consumption rate, hence the performance and efficiency of an entrained-flow gasifier. Among key processes taking place in the gasifier, the char conversion process is a limiting step for the overall carbon conversion. For that reason, the Ph.D. thesis presents the evolution of morphology of char particles during the carbon conversion process using particle-resolved transient CFD calculations. Analyses of numerical data obtained from the transient CFD calculations were carried out. As a result, new sub models related to the drag coefficient and the fundamental parameters of char conversion model were emerged. The new sub models were applied for modeling a pressured entrained-flow gasifier at laboratory scale. The numerical results of the gasifier show a good agreement with experimental data and an improvement of the sub models applied

Catalytic Dye Oxidation over CeO2 Nanoparticles Supported on Regenerated Cellulose Membrane

A novel regenerated cellulose (RC) membrane containing cerium oxide (CeO2) nanoparticles is described in detail. In this work, CeO2 nanoparticles with high surface area and mesoporosity were prepared by a modified template-assisted precipitation method. Successful synthesis was achieved using cerium nitrate as a precursor, adjusting the final pH solution to around 11 by ammonium hydroxide and ethylene diamine, and annealing at 550 °C for 3 hours under a protective gas flow. This resulted in a surface area of 55.55 m².g–1 for the nanoparticles. The regenerated cellulose membrane containing CeO2 particles was synthesized by the novel and environmentally friendly method. The catalyst CeO2 and cellulose/CeO2 membrane were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Electron paramagnetic resonance (EPR), and Brunauer-Emmett-Teller (BET) measurements. The g-value of 2.276 has confirmed the presence of the surface superoxide species of CeO2 nanoparticles in EPR. The photocatalytic activity of the catalyst and the membrane containing the catalyst was evaluated through the degradation of methylene blue under visible light irradiation by UV-VIS measurements. The cellulose/CeO2 membrane degraded 80% of the methylene blue solution in 120 minutes, showing a better photocatalytic activity than the CeO2 catalyst, which degraded approximately 62% in the same period. It has been proven that the RC membrane is not only a good transparent supporting material but also a good adsorption for high-performance of CeO2 catalyst. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Evolution of particle morphology during char conversion processes applied for the CFD modeling of an entrained-flow gasifier

The change in morphology of a char particle affects both its trajectory and carbon consumption rate, hence the performance and efficiency of an entrained-flow gasifier. Among key processes taking place in the gasifier, the char conversion process is a limiting step for the overall carbon conversion. For that reason, the Ph.D. thesis presents the evolution of morphology of char particles during the carbon conversion process using particle-resolved transient CFD calculations. Analyses of numerical data obtained from the transient CFD calculations were carried out. As a result, new sub models related to the drag coefficient and the fundamental parameters of char conversion model were emerged. The new sub models were applied for modeling a pressured entrained-flow gasifier at laboratory scale. The numerical results of the gasifier show a good agreement with experimental data and an improvement of the sub models applied

Corporate social responsibility and behavioral intentions in an emerging market: The mediating roles of green brand image and green trust

This study is driven by the absence of thorough investigations into the behavioral intentions of organizational consumers in the B2B market for paint and coatings, particularly within the industrial and marine coatings sector in Vietnam. Employing the stimulus–organism–response model, we tested the relationship between corporate social responsibility (CSR), green brand image (GBI), green trust (GT), and behavioral intentions (word-of-mouth intention, willingness to pay, and purchase intention) in the Vietnamese industrial and marine coatings industry. We also examined how GBI and GT mediate the relationship between CSR and behavioral intentions. Structural equation modeling was used to test the structural and measurement models and hypothetical relationships. The sample comprised 332 responses from stakeholders in the Vietnamese coating industry. Evidently, GT and CSR positively influenced word-of-mouth, willingness-to-pay, and green purchase intentions, with trust and commitment to sustainability being important drivers. While GBI positively influences purchase intention and willingness-to-pay, it has a weak effect on word-of-mouth intention, indicating that additional strategies are needed to stimulate word of mouth. Further, GT mediates the relationship between green purchase intentions and GBI, as well as between CSR and green purchase intentions. The outcomes highlight the value of incorporating CSR, GT, and GBI into the business strategies of Vietnamese industrial and marine coating companies. We discuss several theoretical and managerial implications, and the importance of studying the influence of GT, CSR, and GBI on consumers’ behavioral intentions across various cultural contexts

Numerical Study on Measures for Protecting the Go-Cong Coastlines (Vietnam) from Erosion

Every year, in the Vietnam Mekong Delta Coastal Zone (VMDCZ), erosions cause approximately 300 ha of agricultural land loss. Therefore, measures for shoreline protection are urgently needed. This paper discusses the impacts of protection measures in the Go-Cong Coastal Zone to prevent erosion/accretion processes, predicted by two numerical models, MIKE21-FM and TELEMAC-2D. Hard and soft measures have been proposed using breakwaters and sandbars, respectively. The simulations show that the erosion/accretion trends provided by both models are similar. For breakwaters, MIKE21-FM provides less accretion than TELEMAC-2D in areas extending over 300 m and 500 m from shorelines. However, for sandbars, MIKE21-FM shows higher accretion within areas extending over 500 m but less than 300 m. Sandbars cause higher accretion in a larger area, extending over 1000 m offshore. The simulation results allow us to propose two alternative measures: (1) a row of several breakwater units will be implanted at 300 m offshore. The length of each unit is 600 m, with a gap between two neighbouring units of 70 m and a crest elevation of 2.2 m above mean sea level (MSL). (2) A row of sandbar units will be posed at 500 m offshore, with a unit length of 1000 m and a gap between the two neighbouring units of 200 m. The crest elevation is fixed at MSL

Numerical Study on Measures for Protecting the Go-Cong Coastlines (Vietnam) from Erosion

Every year, in the Vietnam Mekong Delta Coastal Zone (VMDCZ), erosions cause approximately 300 ha of agricultural land loss. Therefore, measures for shoreline protection are urgently needed. This paper discusses the impacts of protection measures in the Go-Cong Coastal Zone to prevent erosion/accretion processes, predicted by two numerical models, MIKE21-FM and TELEMAC-2D. Hard and soft measures have been proposed using breakwaters and sandbars, respectively. The simulations show that the erosion/accretion trends provided by both models are similar. For breakwaters, MIKE21-FM provides less accretion than TELEMAC-2D in areas extending over 300 m and 500 m from shorelines. However, for sandbars, MIKE21-FM shows higher accretion within areas extending over 500 m but less than 300 m. Sandbars cause higher accretion in a larger area, extending over 1000 m offshore. The simulation results allow us to propose two alternative measures: (1) a row of several breakwater units will be implanted at 300 m offshore. The length of each unit is 600 m, with a gap between two neighbouring units of 70 m and a crest elevation of 2.2 m above mean sea level (MSL). (2) A row of sandbar units will be posed at 500 m offshore, with a unit length of 1000 m and a gap between the two neighbouring units of 200 m. The crest elevation is fixed at MSL

Social norms and political constructions of drug use: A narrative story of Vietnam

Situated close to the Golden Triangle region, and lying across important South-East Asian region traffic routes, Vietnam has a long history of drug use. The negative attitudes among Vietnamese people towards drug use have emerged from the past actions of colonial governments and recently been influenced by social media and political factors. Yet the reality of drug use is more complex, and it is essential to move beyond the overly simple axiom that drug use causes addiction and crime. Combining historical narratives and grey literature, this paper argues that drug use has been politically and socially constructed in Vietnam rather than based on evidence or rationale. Moving forward on harm reduction in drug policy, Vietnam should need more specific actions with its clear plans to at least support drug users during and post detoxication in voluntary community’s models as well as methadone maintenance treatment rather than in compulsory treatment centres

ẢNH HƯỞNG CỦA DẠNG PHÂN KALI VÀ LƯU HUỲNH ĐẾN CÂY CÀ PHÊ CHÈ GIAI ĐOẠN KINH DOANH TRÊN ĐẤT BAZAN TẠI LÂM ĐỒNG

The experiments consisted of four treatments with three types of potassium and sulfur fertilizers, arranged in a randomized complete block design with three replications. These experiments were conducted in 2018 and 2019 on basalt soil for growing coffee in Da Lat City, Lam Dong province, to identify the types of potassium and sulfur fertilizer suitable for Arabica coffee in the business stage. The results show that the yield and quality of coffee depend on the types of potassium and sulfur fertilizer application. The highest yields at 15.6 tons of fresh bean/ha (2018) and 17.4 tons of fresh bean/ha (2019) were obtained with K2SO4 at a rate of 300 kg K2O/ha + 60 kg S/ha. The quality of beans is also the highest with this type of fertilizer. Therefore, it is recommended to apply this fertilizer rate and a mixture of 300 kg K2O + 60 kg S + 10 tons of decomposed chicken manure + 280 kg N + 120 kg P2O5 + 500 kg lime for 1 ha of Catimor coffee at the business stage to achieve the highest yield and quality.Thí nghiệm gồm có bốn công thức bón phân với ba dạng phân kali và lưu huỳnh, bố trí theo kiểu khối đầy đủ ngẫu nhiên, ba lần nhắc lại, được tiến hành trong năm 2018 và 2019 trên đất bazan chuyên trồng cà phê chè tại thành phố Đà Lạt, tỉnh Lâm Đồng, nhằm mục đích xác định được dạng phân kali và lưu huỳnh phù hợp cho cây cà phê chè giai đoạn kinh doanh. Kết quả cho thấy năng suất và chất lượng cà phê chè phụ thuộc vào dạng phân kali và lưu huỳnh. Năng suất thực thu cao nhất năm 2018 là 15,6 và năm 2019 là 17,4 tấn quả chín tươi/ha khi dạng phân kali và lưu huỳnh là K2SO4; chất lượng hạt cà phê cũng cao nhất. Do đó, nghiên cứu đã xác định được dạng phân kali và lưu huỳnh bón phù hợp cho cây cà phê chè giai đoạn kinh doanh trồng trên đất bazan tại tỉnh Lâm Đồng là K2SO4 với lượng bón 300 kg K2O + 60 kg S + 280 kg N + 120 kg P2O5 + 500 kg vôi + 10 tấn phân gà hoai mục trên 1 ha để đạt được năng suất và chất lượng hạt cao nhất

Related party transactions and firm value in an emerging market: Does corporate social responsibility matter?

AbstractThis study investigates the effect of related party transactions (RPTs) on firm value (FV) with moderating role of corporate social responsibility (CSR) in the context of an emerging market. For a sample of 625 listed firms on the Vietnamese Stock Exchange from 2015 to 2019, we do quantitative analysis utilizing the appropriate method for panel data with modification to strengthen the study’s robustness. We design a regression model to test the result. According to the findings of the study, RPTs have an effect on corporate value. This is in keeping with the belief that CSR reporting, which represents a company’s ethical concerns, might act as a deterrent to opportunism by management. Our study makes recommendations to improve transaction transparency with corporate stakeholders, contributing to the growth of the Vietnamese stock exchange

SpinDoctor: A MATLAB toolbox for diffusion MRI simulation

International audienceThe complex transverse water proton magnetization subject to diffusion-encoding magnetic field gradient pulses in a heterogeneous medium can be modeled by the multiple compartment Bloch-Torrey partial differential equation. Under the assumption of negligible water exchange between compartments, the time-dependent apparent diffusion coefficient can be directly computed from the solution of a diffusion equation subject to a time-dependent Neumann boundary condition.This paper describes a publicly available MATLAB toolbox called SpinDoctor that can be used 1) to solve the Bloch-Torrey partial differential equation in order to simulate the diffusion magnetic resonance imaging signal; 2) to solve a diffusion partial differential equation to obtain directly the apparent diffusion coefficient; 3) to compare the simulated apparent diffusion coefficient with a short-time approximation formula.The partial differential equations are solved by P1 finite elements combined with built-in MATLAB routines for solving ordinary differential equations. The finite element mesh generation is performed using an external package called Tetgen. SpinDoctor provides built-in options of including 1) spherical cells with a nucleus; 2) cylindricalcells with a myelin layer; 3) an extra-cellular space enclosed either a) in a box or b) in a tight wrapping around the cells; 4) deformation of canonical cells by bending and twisting; 5) permeable membranes; Built-in diffusion-encoding pulse sequences include the Pulsed Gradient Spin Echo and the Oscillating Gradient Spin Echo.We describe in detail how to use the SpinDoctor toolbox. We validate SpinDoctor simulations using reference signals computed by the Matrix Formalism method. We compare the accuracy and computational time of SpinDoctor simulations with Monte-Carlo simulations and show significant speed-up of SpinDoctor over Monte-Carlo simulations in complex geometries. We also illustrate several extensions of SpinDoctor functionalities, including the incorporation of $T2$ relaxation, the simulation of non-standard diffusion-encoding sequences, as well as the use of externally generated