Semi-Infinite Structure Analysis with Bimodular Materials with Infinite Element

The modulus of elasticity of some materials changes under tensile and compressive states is simulated by constructing a typical material nonlinearity in a numerical analysis in this paper. The meshless Finite Block Method (FBM) has been developed to deal with 3D semi-infinite structures in the bimodular materials in this paper. The Lagrange polynomial interpolation is utilized to construct the meshless shape function with the mapping technique to transform the irregular finite domain or semi-infinite physical solids into a normalized domain. A shear modulus strategy is developed to present the nonlinear characteristics of bimodular material. In order to verify the efficiency and accuracy of FBM, the numerical results are compared with both analytical and numerical solutions provided by Finite Element Method (FEM) in four examples.

Preparation of black-TiO2 and its application in photocatalytic removal of methyl orange dye

For a few decades, Titanium Dioxide (TiO2) has been the most studied photocatalyst due to its significant optical property. In the paper, TiO2 pigment powder (Anatase form) was selected as a precursor to prepare a variety of Black-TiO2 samples, and the typical material was then evaluated for its photocatalytic activity in organic pollutant treatment. Some properties of Black-TiO2 were determined via common methods such as sensory analysis, X-Ray diffraction, and bandgap measurement obtained from UV-Vis spectroscopy. As a result, the material was successfully converted to more than 40% organic pollutant as Methyl Orange (C14H14N3NaO3S) for an hour, as two times higher than that of the amount converted by pristine TiO2. In addition, Black-TiO2 performed much better photocatalytic activity in an acidic medium in comparison with a neutral one, and the material also remained its activity as more than 90% after three time-continuous recycling operations.

On the function of biosynthesized cellulose as barrier against bacterial colonization of VAD drivelines

Bacterial colonization of drivelines represents a major adverse event in the implantation of left ventricular assist devices (L-VADs) for the treatment of congestive heart failure. From the external driveline interface and through the skin breach, pathogens can ascend to the pump pocket, endangering the device function and the patient’s life. Surface Micro-Engineered Biosynthesized cellulose (BC) is an implantable biomaterial, which minimizes fibrotic tissue deposition and promotes healthy tissue regeneration. The topographic arrangement of cellulose fibers and the typical material porosity support its potential protective function against bacterial permeation; however, this application has not been tested in clinically relevant animal models. Here, a goat model was adopted to evaluate the barrier function of BC membranes. The external silicone mantle of commercial L-VAD drivelines was implanted percutaneously with an intervening layer of BC to separate them from the surrounding soft tissue. End-point evaluation at 6 and 12 weeks of two separate animal groups revealed the local bacterial colonization at the different interfaces in comparison with unprotected driveline mantle controls. The results demonstrate that the BC membranes established an effective barrier against the bacterial colonization of the outer driveline interface. The containment of pathogen infiltration, in combination with the known anti-fibrotic effect of BC, may promote a more efficient immune clearance upon driveline implantation and support the efficacy of local antibiotic treatments, therefore mitigating the risk connected to their percutaneous deployment.

Solar Cells Efficiency enhancement using multilevel Selective Energy Contacts (SECs)

High-energy coming photons can be absorbed and lead to generate hot carriers. In normal solar cells, these carriers are scattered, by electron-electron and electron-lattice mechanisms, and rapidly lose extra energy then approach the conduction band energy edge. This event in addition to other loss mechanisms causes the efficiency reduction in the solar cells to a limited value, theoretically 33%. Accordingly, the efficiency of solar cells can be enhanced considerably, if one makes the possibility for carriers that can be extracted rapidly before scattering and releasing extra energy to the lattice. This type of solar cell is called hot carrier solar cells (HCSCs). To this end, to improve the conversional efficiency, multilevel energy selective contacts (ESCs) as a new concept and new mechanism in solar cells can be utilized. In the other words, several appropriate energy levels as carrier extraction contacts in the conduction band are introduced. Here, we use multilevel ESCs, and based on our simulation it is shown that the maximum efficiency of 75% is achievable for low bandgap materials. For a typical material such as Si, the maximum efficiency is increased to 60% using ten ESCs.

Thick-Wall Cylinder Reference Stress Crack Solutions for API 579-1/ASME FFS-1 Annex 9C

A new set of reference stress solutions for cracks in thick-wall cylinders were computed for addition in the next edition of the API 579-1/ASME FFS-1 standard, and are described in this paper. The geometry cases used ratios for the cylinder radius, wall thickness, crack depth, and crack length. The crack locations included axial, circumferential, internal, and external cracks. 3-D crack meshes were generated for each case to compute J-integral versus pressure result trends, which were used to determine the reference stress. The Failure Assessment Diagram (FAD) method uses reference stress solutions to compute the Lr ratio on the FAD x–axis to evaluate cracks for plastic collapse; the FAD y-axis Kr ratio evaluates fracture failure. The elastic-plastic J-integral reference stress method will be briefly reviewed using results from this project. A stress-strain curve was selected to represent typical material used for high-pressure components. The computed reference stress was shown to depend on the yield strength to tensile strength ratio, and a ratio of 90% was selected for use in this project. Some shallow internal cracks in the thicker cylinder cases showed unexpected behavior in the J-integral versus pressure results, which prevented the reference stress from being computed. An alternative method was developed to use the maximum converged pressure as the nominal load to obtain reference stress solutions for those cases.

Quantifying Fugitive Dust Emissions From Limestone Quarries : Data Selection And Uncertainty Assessment

Accurate quantification of fugitive dust emissions from quarries helps maintain the integrity of the National Pollutant Release Inventory. Emissions from unpaved roads, material handling, and storage piles at three quarries were calculated using the AP-42 emissions factor method, and the error of using 30-year climate averages, the uncertainty introduced by typical material properties, and the limited availability of climate data were addressed. Using daily and hourly data predicted unpaved roads emissions between 38.95% and 43.50% higher, materials handling emissions 15.31% lower to 18.64% higher, and storage pile emissions 12.48% to 37.50% lower than calculations using 30-yer averages. Employing Monte Carlo simulation, the confidence intervals attributable to typical material properties ranged from 87.50% below to 650% above the mean. Krige-interpolated climate data showed potential for being more accurate that observations at the nearest station. Using site-specific, temporally-relevant data and assessing uncertainty promotes calculations that better match the goals of the inventory.

Quantifying Fugitive Dust Emissions From Limestone Quarries : Data Selection And Uncertainty Assessment

Accurate quantification of fugitive dust emissions from quarries helps maintain the integrity of the National Pollutant Release Inventory. Emissions from unpaved roads, material handling, and storage piles at three quarries were calculated using the AP-42 emissions factor method, and the error of using 30-year climate averages, the uncertainty introduced by typical material properties, and the limited availability of climate data were addressed. Using daily and hourly data predicted unpaved roads emissions between 38.95% and 43.50% higher, materials handling emissions 15.31% lower to 18.64% higher, and storage pile emissions 12.48% to 37.50% lower than calculations using 30-yer averages. Employing Monte Carlo simulation, the confidence intervals attributable to typical material properties ranged from 87.50% below to 650% above the mean. Krige-interpolated climate data showed potential for being more accurate that observations at the nearest station. Using site-specific, temporally-relevant data and assessing uncertainty promotes calculations that better match the goals of the inventory.

Study on the influencing factors of the deformation in the process of gear shaping

Ring gear is an important part of high-power transmission system. Because of its thin wall and low stiffness, it is easy to produce deformation in the process of gear shaping, which affects its accuracy. In order to ensure the machining quality of gear shaper, this research focuses on the typical material 42CrMo, which is used in the gear ring of automobile gearbox. Through the finite element simulation and actual test, the influence of gear shaper cutting parameters on the deformation of gear ring is studied. The results show that the influence of the main cutting parameters on the deformation of the ring gear is in the order of radial feed, circumferential feed, stroke speed and cutting depth. In the actual gear shaping process, the cutting parameters can be adjusted according to the deformation law of 42CrMo workpiece in the gear shaping process, so as to control the deformation of gear ring.

Microcomputed X-Ray Tomographic Imaging and Image Processing for Microstructural Characterization of Explosives

Microstructural characterization of composite high explosives (HEs) has become increasingly important over the last several decades in association with the development of high fidelity mesoscale modeling and an improved understanding of ignition and detonation processes. HE microstructure influences not only typical material properties (e.g., thermal, mechanical) but also reactive behavior (e.g., shock sensitivity, detonation wave shape). A detailed nondestructive 3D examination of the microstructure has generally been limited to custom-engineered samples or surrogates due to poor contrast between the composite constituents. Highly loaded (>90 wt%) HE composites such as plastic-bonded explosives (PBX) are especially difficult. Here, we present efforts to improve measurement quality by using single and dual-energy microcomputed X-ray tomography and state-of-the-art image processing techniques to study a broad set of HE materials. Some materials, such as PBX 9502, exhibit suitable contrast and resolution for an automatic segmentation of the HE from the polymer binder and the voids. Other composite HEs had varying levels of success in segmentation. Post-processing techniques that used commercially available algorithms to improve the segmentation quality of PBX 9501 as well as zero-density defects such as cracks and voids could be easily segmented for all samples. Aspects of the materials that lend themselves well to this type of measurement are discussed.

Linguistic recycling in language acquisition

The paper examines how children quote their parents’ utterances. In other words, it investigates linguistic recycling as an aspect of language learning and how the child-directed speech (CDS) of adults influences child speech (CS). This topic is examined especially in the light of research made in the crosslinguistic project on pre- and protomorphology in language acquisition. Premorphology is characterized by rote-learned forms, which the child has memorized and stored as chunks from CDS (e.g., Finn vettä, Est vett ‘water,’ partitive form). During protomorphology, the child imitates CDS and produces analogical forms (e.g. Finn CDS: söi vs. CS: syöi ‘ate’, Est CDS: ütles vs. CS: ükki ‘said’), which then gradually evolve into adult-like grammar. Usage-based approaches to language acquisition rely on the assumption that language structures are learned from language use. Typical material in present-day child language research is based on tape recordings and transcripts made from these recordings. This kind of data makes it possible to take into account the influence of CDS to CS in a more accurate way than the earlier data collecting methods, such as diary material, which usually contains mostly utterances produced by the child do. The article examines how CDS gives models to CS and how the acquisition proceeds from early rote-learned forms to adult-like grammar from the perspective of frequency distributions of inflectional patterns and elaboration on linguistic forms in CDS – CS interaction. On the basis of analyzed speech samples and previous results, it is obvious that the quoting in children’s and adults’ speech is present on different levels of language and is often bidirectional in nature.