Investigation on high-strength low alloy 0.35Cr-1.9Ni-0.55Mo steel deposited on 20Cr substrate by wire and arc-based directed energy deposition

This article aims to observe the microstructure, mechanical properties, and interface bonding of a 0.35Cr-1.9Ni-0.55Mo alloy deposited on 20Cr steel by wire and arc-based directed energy deposition (WA-DED). For this purpose, different characterization techniques such as optical microscope, scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and high-resolution X-ray diffractometer were used to analyze microstructure, chemical composition, and phases of the deposited material. Microhardness and tensile tests were also carried out. The results show that the microstructure of the deposited material is relatively homogeneous with a slight increase in grain size from the bottom to the top of the deposited part, thus resulting in a gradually decreasing trend in microhardness, from 288±16.78 HV0.1 (in the bottom) to 256±17.04 HV0.1 (in the top). The heat-affected zone (HAZ) is the hardest (301±2.70 HV0.1), while the substrate has the lowest microhardness (203±17.64 HV0.1). The tensile strengths of deposited materials are relatively isotropic in both the horizontal direction (HD) and vertical (VD) direction: UTSVD = 1013±9.29 MPa, USTHD = 985±24.58 MPa, YS(0.2%)VD = 570±4.51 MPa, and YS(0.2%)HD = 614±19.66 MPa. The tensile strengths of interface specimens are also comparable to those of the substrate materials (e.g., 951 vs. 972 MPa in UTS), indicating an excellent metallurgical bonding between the deposited and substrate materials. The results of this work confirm the efficiency of WA-DED technique to produce high-quality components in industr

Metallurgical Characterization of SS 316L Repurposed by Wire plus Arc Additive Manufacturing

This research aims to analyze the microstructures and mechanical characteristics of stainless steel (SS) 316L repurposed by wire plus arc additive manufacturing (WAAM). The SS 316L wire is deposited on a SS 316 substrate, which can be repurposed. This deposited material underwent optical microscopy, X-ray diffraction, and tensile test, and the results indicate that it features cellular and columnar dendrites at the bottom and equiaxial grains at the top. The tensile strength of the interface region between the deposited material (DM) and the base material (BM) is the highest (559 ± 4.16 MPa vs. 510 ± 4.93 MPa in DM and 540 ± 2.65 in BM), indicating that the BM and the deposited layers are strongly bonded. All the results from the defect observation, microstructures, and mechanical characteristics confirm the potential of the WAAM process for repurposing

APPLING HIGH WATER PRESSURES EJECTOR SYSTEM TO CONTROL DUST IN QUANG NINH UNDERGROUND COAL MINE

In recent years, in Quang Ninh coal underground mine, longwall mining has been increasingly applied to meet the energy demand. This has resulted in the potential for increased mining dust. Coal dust is not only harmful to workers but also creates a risk for coal dust explosions in the mine. Therefore, in order to control the mine dust problem, it is necessary to develop a set of dust removal equipment suitable for underground coal mining. High-pressure water ejector system is selected to control dust in Quang Ninh mine. In addition, parameters and criteria for the design of the high-pressure water jet ejector systems have been presented

Simulation of suspended sediment and black carbon transport in surface water layer of Ha Long bay

Delft3D model employed to simulate the distribution and transport of suspended sediment and black carbon in Ha Long bay shows outcomes meeting with results from previous experiment studies. In the rainy season, suspended matter in surface layer is mainly in waters of western and southwestern Cat Ba island regions, and from Cua Luc toward the south nearshore areas with concentration of 50–130 g/m3. The concentration of suspended setdiment in the waters from Cua Luc to the north nearshore area is from 20 g/m3 to 50 g/m3 and that of offshore areas is 2–20 g/m3. In the dry season, the average concentrations of suspended matter are lower, approximately 110–150 g/m3 compared to the rainy season. In the rainy season, the total particulate carbon in surface layer is 0.0016–0.0028 kg/m3 and in the dry season, it ranges from 0.0001–0.005 kg/m3

Optimization of Superplastic Forming Process of AA7075 Alloy for the Best Wall Thickness Distribution

This work aims to optimize the process parameters for improving the wall thickness distribution of the sheet superplastic forming process of AA7075 alloy. The considered factors include forming pressure p (MPa), deformation temperature T (°C), and forming time t (minutes), while the responses are the thinning degree of the wall thickness ε (%) and the relative height of the product h*. First, a series of experiments are conducted in conjunction with response surface method (RSM) to render the relationship between inputs and outputs. Subsequently, an analysis of variance (ANOVA) is conducted to verify the response significance and parameter effects. Finally, a numerical optimization algorithm is used to determine the best forming conditions. The results indicate that the thinning degree of 13.121% is achieved at the forming pressure of 0.7 MPa, the deformation temperature of 500°C, and the forming time of 31 minutes

Effects of different nutrient solutions on growth and flower quality of gerbera (Gerbera jamesonii) grown in hydroponic close system

The nutrient solution is the decisive factor for the growth and development of hydroponic plants. This study was conducted to determine the effect of five nutrient solutions, namely, Hoagland, Knop, Hydro Umat F, BKFAST, and Bio-Life, on the growth and development of gerbera (Gerbera jamesonii) in the hydroponic system. The results show that Hydro Umat F is the most suitable solution for planting gerbera in terms of plant height, number of leaves, leaf size, and root volume. In addition, the flower yield of the gerbera plants nourished on Hydro Umat F is also the highest, with 8.7 flowers per plant after five months in the hydroponic system. The flowers have a diameter of 9.8 cm and natural durability of 19.67 days. Meanwhile, gerbera plants stop growing after 15 days in the Bio-Life solution and 30 days in the Knop solution

Molecular phylogeny of Annonaceae species from Binh Chau-Phuoc Buu Nature Reserve based on two chloroplast gene regions

In this study, based on molecular biology techniques, the matK and trnL-F regions of ten Annonaceae species grown in Binh Chau-Phuoc Buu Nature Reserve, Vietnam were successfully amplified and sequenced for the first time. Along with other highly homologous DNA sequences from the GenBank database, the molecular phylogeny of ten studied species was also established. By using the alignment tool of NCBI database, the percentage of identity among sequences of studied species was also presented. The study aims to partially contribute to the further understanding of the evolutionary relationships among Annonaceae species

Using additive and subtractive manufacturing technologies in a new remanufacturing strategy to produce new parts from End-of-Life parts

La technique de fabrication additive est aujourd'hui considérée comme une technique de la troisième révolution industrielle. Cette technique permet de créer une pièce « vraie matière » par ajout de matière couche par couche à partir d'un modèle CAO. La prise en compte des performances de ces techniques dans une nouvelle stratégie de remanufacturing devrait permettre de transformer une pièce en fin de vie en une nouvelle pièce sans retourner au niveau du matériau premier. L'objectif de cet article est de découvrir la faisabilité technologique de ces techniques pour le remanufacturing, et de poser les pistes pour mettre en place une nouvelle stratégie permettant de donner une nouvelle vie aux pièces en fin de vie. Ces pièces étant destinées à un autre produit.Nowadays, additive manufacturing technique is considered as a technique of the third industrial revolution. The technique makes it possible to build a ?real-material? part by adding materials, layer by layer, based on a CAD model. Taking into account the performances of these techniques, a new remanufacturing strategy seems possible to transform an End-of-Life (EoL) part into a new part without returning to the level of raw material. The purposes of this paper is to explore the technological feasibility of such additive manufacturing techniques for remanufacturing, and then propose the ways in order to establish a new strategy for giving a new life to EoL parts. The new parts produced are intended to be different - and have different functionalities - from the original

Aplicação do método da jurisprudência comentando em formação especializada em direito

The method of case law commenting is a method of teaching and training in the field of law that is widely applied in many advanced countries around the world. Different from the traditional lecture method, in the teaching method of case commenting, theoretical teaching will be carried out in parallel with precedents that are searched and selected to explain and illustrate the lesson. The article analyzes case law and the role of applying the method of case law commenting in law specialized training. On that basis, the article proposes the structure and method of implementing the case law commenting method in law specialized training.El método de comentario sobre jurisprudencia es un método de enseñanza y capacitación en el campo del derecho que se aplica ampliamente en muchos países avanzados de todo el mundo. Distintamente del método de exhibición tradicional, en el método de enseñanza del comentario de casos, la enseñanza teórica se llevará a cabo en paralelo con los precedentes que se investigan y seleccionan para explicar e ilustrar la lección. El artículo examina la jurisprudencia y el papel de la aplicación del método de la observación jurisprudencial en la formación especializada en Derecho. A partir de esto, el artículo propone la estructura y el método de implementación del método de comentario de la jurisprudencia en la formación especializada en derecho.O método de comentário de jurisprudência é um método de ensino e treinamento no campo do direito que é amplamente aplicado em muitos países avançados ao redor do mundo. Diferentemente do método expositivo tradicional, no método de ensino de comentário de casos, o ensino teórico será realizado em paralelo com precedentes que são pesquisados e selecionados para explicar e ilustrar a aula. O artigo analisa a jurisprudência e o papel da aplicação do método de comentário jurisprudencial na formação especializada em direito. Com base nisso, o artigo propõe a estrutura e o método de implementação do método de comentário de jurisprudência na formação especializada em direito