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2021 ◽  
Vol 13 (22) ◽  
pp. 12796
Author(s):  
Tian Lan ◽  
Libo Hao ◽  
Jilong Lu ◽  
Yechang Yin ◽  
Xiaoqing Chen ◽  
...  

Rock weathering is the main source of element geochemical cycle, which has a very important impact on the environment. Three well-developed basalt weathering profiles in Changbai Mountain area are selected in this study, and the samples of parent rock, parent material layer, sedimentary layer, and leaching layer are systematically collected. The systematic study showed that the basalt in the study area experienced moderate chemical weathering under warm and humid climate conditions, with leaching of some major elements such as silicon and aluminum. The distribution of the rare earth elements (REE) in the weathering products recalls that of an alkali-basalt, with an evident fractionation between light- and heavy-REE. Such a feature is therefore referable to the parent volcanic rock, although with some degree of leaching.


Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6842
Author(s):  
Zygmunt Meyer ◽  
Magdalena Olszewska

Compressibility is one of the most important mechanical properties of soil. The parameter that characterizes compressibility is the constrained modulus of elasticity. Knowledge of this is important to calculate the settlement of a structure foundation on peat material. According to soil classification by EN ISO 14688-2, peat is an organic soil that contains min. 20% organic matter. It is a highly organic type of soil. Peat material has large compressibility. The value of the constrained elasticity modulus for peat is ca. 400 kPa, while it may be ca 1.0–1.6 MPa for consolidated peat. Due to the extensive range of the modulus, experimental research in this field is proposed. It is suggested to load the peat material layer with an embankment and to determine its total settlement. Based on this, a program was developed to determine the settlement–strain relationship. The authors propose an approach according to two models: the first is based on constant stress distribution in the soil with an oedometer test. The second considers the variability of stresses in the soil and the influence of the loaded area. Both methods were tested based on numerical simulations, and then an experimental field in Szczecin was used. The formulae for the constrained modulus of elasticity measurement were derived; in practical conditions, a uniaxial deformation state can be used with the combination of the total settlement.


2021 ◽  
Vol 11 (5) ◽  
pp. 149-156
Author(s):  
Drumil Newaskar ◽  
Shubham Gandhi ◽  
Preet Aligave

Additive manufacturing is a revolutionary technology because of its ability to creates objects by adding material layer by layer rather than removing material from a block or by moulding procedure. Additive manufacturing has been around for more than three decades but still, traditional manufacturing is the dominant method for manufacturing. COVID-19 pandemic has been a torment globally and has brought distress and instability to the global economy. Due to this, the manufacturing sectors are badly affected. In this time of crisis, additive manufacturing has played a major role. This paper discusses the upsurge of Additive manufacturing due global COVID-19 pandemic and its worldwide impact on supply chain management.


2021 ◽  
Vol 11 (20) ◽  
pp. 9693
Author(s):  
Andrej Thurzo ◽  
Filip Kočiš ◽  
Bohuslav Novák ◽  
Ladislav Czako ◽  
Ivan Varga

Three-dimensional (3D) printing with biocompatible resins offers new competition to its opposition—subtractive manufacturing, which currently dominates in dentistry. Removing dental material layer-by-layer with lathes, mills or grinders faces its limits when it comes to the fabrication of detailed complex structures. The aim of this original research was to design, materialize and clinically evaluate a functional and resilient shape of the orthodontic power-arm by means of biocompatible 3D printing. To improve power-arm resiliency, we have employed finite element modelling and analyzed stress distribution to improve the original design of the power-arm. After 3D printing, we have also evaluated both designs clinically. This multidisciplinary approach is described in this paper as a feasible workflow that might inspire application other individualized biomechanical appliances in orthodontics. The design is a biocompatible power-arm, a miniature device bonded to a tooth surface, translating significant bio-mechanical force vectors to move a tooth in the bone. Its design must be also resilient and fully individualized to patient oral anatomy. Clinical evaluation of the debonding rate in 50 randomized clinical applications for each power-arm-variant showed significantly less debonding incidents in the improved power-arm design (two failures = 4%) than in the original variant (nine failures = 18%).


Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5425
Author(s):  
Natalia V. Bulina ◽  
Sergey G. Baev ◽  
Svetlana V. Makarova ◽  
Alexander M. Vorobyev ◽  
Alexander I. Titkov ◽  
...  

Hydroxyapatite, being the major mineral component of tooth enamel and natural bones, is a good candidate for bone tissue engineering applications. One of the promising approaches for manufacturing of three-dimensional objects is selective laser sintering/melting which enables the creation of a dense structure directly during 3D printing by adding material layer-by-layer. The effect of laser irradiation with a wavelength of 10.6 μm on the behavior of mechanochemically synthesized hydroxyapatite under different treatment conditions was studied for the first time in this work. It was shown that, in contrast to laser treatment, the congruent melting is impossible under conditions of a relatively slow rate of heating in a furnace. Depending on the mode of laser treatment, hydroxyapatite can be sintered or melted, or partially decomposed into the more resorbable calcium phosphates. It was found that the congruent selective laser melting of hydroxyapatite can be achieved by treating the dense powder layer with a 0.2 mm laser spot at a power of 4 W and at a scanning speed of 700 mm/s. Melting was shown to be accompanied by the crystallization of a dense monolayer of oxyhydroxyapatite while preserving the initial apatite crystal lattice. The thickness of the melted layer, the presence of micron-sized pores, and the phase composition can be controlled by varying the scanning speed and laser power. This set of parameters permits the use of selective laser melting technology for the production of oxyhydroxyapatite biodegradable implants with acceptable properties by 3D printing.


2021 ◽  
Vol 63 (8) ◽  
pp. 40-43
Author(s):  
Quang Phuc Nguyen ◽  
◽  
Van Thang Vu ◽  

The method of designing flexible road structures under the guidance of AASHTO 1993 was used in many states in the US and Canada and is being applied by many other countries in Europe and Asia. The layer coefficient ai in the AASHTO design equation represents an empirical relationship between the structural index SN and thickness. The value of the layer coefficients (ai) is specified for each material layer depending on the quality shown mainly through resilient modulus. This paper presents the initial research results of influencing factors and value confirmation of resilient modulus (Eac) and layer coefficients (ai) of some types of hot dense asphalt concrete in Vietnam.


Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 974
Author(s):  
Shuai Wang ◽  
Yufeng Guo ◽  
Kuo Liu ◽  
Zhuang Yang ◽  
Yajing Liu ◽  
...  

The deposit-forming problem is one of the main bottlenecks restricting the yield and production benefit of iron ore pellets produced by coal-fired rotary kilns. In order to implement measures to ensure the efficient production of pellets by coal-fired rotary kilns, the mechanism and influencing factors on the deposit formation were reviewed. The pellet powder and coal ash come together to form the material base of the deposit. Meanwhile, the local reducing atmosphere caused by the continued combustion of residual carbon increases the FeO content, resulting in the formation of low-melting-point silicates. Moreover, alkali metal elements in coal ash can also promote liquid phase formation to cause serious deposit aggregation problems. During high-temperature roasting, the liquid phase corrodes the surface of the refractory brick to form the initial deposit, whereafter, it binds the pellet powder and coal ash from the material layer, which causes the deposit to accumulate continuously. The deposit formation of coal-fired rotary kilns is the result of interaction between many factors, which includes the quality of the green pellets, the composition of coal ash, the combustion efficiency of pulverized coal, roasting temperature, FeO content and alkali metal input. Finally, it is recommended that some measures to mitigate deposit formation can be adopted, such as increasing the compression strength of preheated pellets, choosing high-quality raw materials with low alkali metals, improving the combustion of pulverized coal.


2021 ◽  
Vol 5 (1) ◽  
pp. 15-30
Author(s):  
Dorota Laskowska ◽  
Katarzyna Mitura ◽  
Ewa Ziółkowska ◽  
Błażej Bałasz

The aim of the additive manufacturing (AM) is a production of physical objects by adding material layer-by-layer based on virtual geometry developed in the computer system. The main criteria for the division of additive manufacturing methods are the way to apply the layer and the type of construction material. In most projects, the choice of method is a compromise between costs and properties (e.g. physical, chemical or mechanical) of the manufactured object. Currently, AM methods have found application in many areas of life, including industrial design, automotive, aerospace, architecture, jewellery, medicine and veterinary medicine, bringing many innovative and revolutionary solutions. The purpose of this article is to review of the additive production methods and present the potential of medical application.


2021 ◽  
Author(s):  
Israel Alves Oliveira ◽  
I. L. Gomes Souza ◽  
V. F. Rodriguez-Esqu

Abstract Structures absorbing electromagnetic waves in the infrared spectral region are important optical components in key areas such as biosensors, infrared images and thermal emitters, and require special attention from reconfigurable devices. We propose a three-dimensional metal-dielectric plasmonic absorber with a layer of PCM's (Phase Change Materials). The phase shift effects of PCMs are analyzed, and it is possible to obtain a displacement control in the resonant absorption peaks between the amorphous and crystalline states using the Lorentz-Lorenz relation. Aided in this empirical relation, we analyzed the absorption shift in the intermediate phases between them. The geometric parameters of the structure with the pcm material layer in the semi-crystalline state were optimized to present strong absorption for normal incidence. The effects of the oblique incidence for the TM and TE polarization modes were also analyzed. Our results demonstrate that PCMs have great potential for reconfigurable nanophotonic devices.


2021 ◽  
pp. 108257
Author(s):  
Hang Wan ◽  
Gongsheng Huang ◽  
Sheng Liu ◽  
Shiguang Fan ◽  
Xinhua Xu ◽  
...  

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