Search results for: third-order shell theory

Authors: Lele Zhang, Hui Leng Choo, Alexander Konyukhov, Shuguang Li

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Finite Element (FE) model of simplified e-bike structure was generated by main frame with two tiers, which consisted of pipe, mass, beam, and shell elements (pipe 289, beam188, shell 181, shell 281, combin14, link11, mass21). These elements would be introduced and demonstrated using mathematical formulas. Based on coupling theory, constrain equations was proposed. Exporting all the parameters obtained from theory part, the connection stiffness matrix of the whole e-bike structure between each of these elements was detected.

Keywords: coupling theory, stiffness matrix, e-bike, finite element model

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Authors: Djamal Hamadi, Ashraf Ayoub, Ounis Abdelhafid, Chebili Rachid

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In this paper, a new computationally-efficient rectangular flat shell finite element named 'ACM_RSBEC' is presented. The formulated element is obtained by superposition of a new rectangular membrane element 'RSBEC' based on the strain approach and the well known plate bending element 'ACM'. This element can be used for the analysis of thin shell structures, no matter how the geometrical shape might be. Tests on standard problems have been examined. The convergence of the new formulated element is also compared to other types of quadrilateral shell elements. The presented shell element ‘ACM_RSBEC’ has been demonstrated to be effective and useful in analysing thin shell structures.

Keywords: finite element, flat shell element, strain based approach, static condensation

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Authors: Odunayo Olawuyi Fadodun

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Dielectric elastomers (DEs) are a type of intelligent materials with salient features like electromechanical coupling, lightweight, fast actuation speed, low cost and high energy density that make them good candidates for numerous engineering applications. This paper adopts a new nonlinear electroelastic constitutive theory to examine radial deformation of a pressurized thick-walled spherical shell of soft dielectric material with compliant electrodes on its inner and outer surfaces. A general formular for the internal pressure, which depends on the deformation and a potential difference between boundary electrodes or uniform surface charge distributions, is obtained in terms of special function. To illustrate the effects of an applied electric field on the mechanical behaviour of the shell, three different energy functions with distinct mechanical properties are employed for numerical purposes. The observed behaviour of the shells is preserved in the presence of an applied electric field, and the influence of the field due to a potential difference declines more slowly with the increasing deformation to that produced by a surface charge. Counterpart results are then presented for the thin-walled shell approximation as a limiting case of a thick-walled shell without restriction on the energy density. In the absence of internal pressure, it is obtained that inflation is caused by the application of an electric field. The resulting numerical solutions of the theory presented in this work are in agreement with those predicted by the generally adopted Dorfmann and Ogden model.

Keywords: constitutive theory, elastic dielectric, electroelasticity, finite deformation, nonlinear response, spherical shell

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Authors: Ying Weiyong

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The micro/mesoporous core-shell composites compromising SSZ-13 cores and mesoporous silica shells were synthesized successfully with the soft template of cetytrimethylammonium. The shell thickness could be tuned from 25 nm to 100 nm by varying the TEOS/SSZ-13 ratio. The BET and SEM results show the core-shell composites possessing the tunable surface area (544.7-811.0 m2/g) with plenty of mesopores (2.7 nm). The acidity intensity of the strong acid sites on SSZ-13 was remarkably impaired with the decoration of the mesoporous silica shell, which leads to the suppression of the hydrogen transfer reaction in MTO reaction. The micro/mesoporous core-shell composites exhibit better methanol to olefins reaction performance with a prolonged lifetime and the improvement of light olefins selectivity.

Keywords: core-shell, mesoporous silica, methanol to olefins, SSZ-13

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Authors: J. Ranjbarn, A. Alibeigloo

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In this paper, we present an analytical method for analysis of nano-scale spherical shell subjected to thermo-mechanical shocks based on nonlocal elasticity theory. Thermo-mechanical properties of nano shpere is assumed to be temperature dependent. Governing partial differential equation of motion is solved analytically by using Laplace transform for time domain and power series for spacial domain. The results in Laplace domain is transferred to time domain by employing the fast inverse Laplace transform (FLIT) method. Accuracy of present approach is assessed by comparing the the numerical results with the results of published work in literature. Furtheremore, the effects of non-local parameter and wall thickness on the dynamic characteristics of the nano-sphere are studied.

Keywords: nano-scale spherical shell, nonlocal elasticity theory, thermomechanical shock, dynamic response

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Authors: A. Pourahmad, Sh. Gharipour

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The present work describes the preparation and characterization of nanosized SiO₂@PbS core-shell particles by using a simple wet chemical route. This method utilizes silica spheres formation followed by successive ionic layer adsorption and reaction method assisted lead sulphide shell layer formation. The final product was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis spectroscopic, infrared spectroscopy (IR) and transmission electron microscopy (TEM) experiments. The morphological studies revealed the uniformity in size distribution with core size of 250 nm and shell thickness of 18 nm. The electron microscopic images also indicate the irregular morphology of lead sulphide shell layer. The structural studies indicate the face-centered cubic system of PbS shell with no other trace for impurities in the crystal structure.

Keywords: core-shell, nanostructure, semiconductor, optical property, XRD

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Authors: Nosakhare Enoma, Alphose Zingoni

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The requirements for various toroidal shell forms are increasing due to new applications, available storage space and the consideration of appearance. Because of the complexity of some of these structural forms, the finite element method is nowadays mainly used for their analysis, even for simple static studies. This paper presents an easy-to-use analytical algorithm for pressurized multi-segmented toroidal shells of revolution. The membrane solution, which acts as a particular solution of the bending-theory equations, is developed based on membrane theory of shells, and a general approach is formulated for quantifying discontinuity effects at the shell junctions using the well-known Geckeler’s approximation. On superimposing these effects, and applying the ensuing solution to the problem of the pressurized toroid with four segments, closed-form stress results are obtained for the entire toroid. A numerical example is carried out using the developed method. The analytical results obtained show excellent agreement with those from the finite element method, indicating that the proposed method can be also used for complementing and verifying FEM results, and providing insights on other related problems.

Keywords: bending theory of shells, membrane hypothesis, pressurized toroid, segmented toroidal vessel, shell analysis

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Authors: B. Navidshad

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The main objective of this study was to examine the effects of enzymatic treatment and shell content of palm kernel expeller (PKE) on the ileal Lactobacilli and Escherichia coli populations in broiler chickens. At the finisher phase, one hundred male broiler chickens (Cobb-500) were fed a control diet or the diets containing 200 g/kg of normal PKE (70 g/kg shell), low shell PKE (30 g/kg shell), enzymatic treated PKE or low shell-enzymatic treated PKE. The quantitative real-time PCR were used to determine the ileal bacteria populations. The lowest ileal Lactobacilli population was found in the chickens fed the low shell PKE diet. Dietary normal PKE or low shell-enzymatic treated PKE decreased the Escherichia coli population compared to the control diet. The results suggested that PKE could be included up to 200 g/kg in the finisher diet, however, any screening practice to reduce the shell content of PKE without enzymatic degradation of β-mannan, decrease ileal Lactobacilli population.

Keywords: palm kernel expeller, exogenous enzyme, shell content, ileum bacteria, broiler chickens

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Authors: Xu Chen, Zhao Caiqi

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In addition to the advantages of light weight, resistant corrosion and ease of processing, aluminum is also applied to the long-span spatial structures. However, the elastic modulus of aluminum is lower than that of the steel. This paper combines the high performance aluminum honeycomb panel with the aluminum latticed shell, forming a new panel-and-rod composite shell structure. Through comparative analysis between the static and dynamic performance, the conclusion that the structure of composite shell is noticeably superior to the structure combined before.

Keywords: combination of aluminum honeycomb panel, rod latticed shell, dynamic performence, response spectrum analysis, seismic properties

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Authors: Yusuf Emirov, Abdullatif Hakami, Prasanta K Biswas, Elias K Stefanakos, Sesha S Srinivasan

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This study is aimed to develop microencapsulated thermochromic materials and the analysis of core-shell formation using high resolution electron microscopy. The candidate metal oxides (e.g., titanium oxide and silicon oxide) used for the microencapsulation of thermochromic materials are based on the microemulsion route that involves the micelle formation using different surfactants. The effectiveness of the core-shell microstructure formationrevealed the influence of surfactants and the metal oxide precursor concentrations. Additionally, a detailed thermal and color chromic behavior of these core-shell microcapsules are evaluated with the pristine thermochromic dye particles.

Keywords: core-shell thermochromic materials, core-shell microstructure formation, thermal and color chromic behavior of core-shell microcapsules, development micro-capsulated thermochromic materials

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Authors: Hene L. Hapinat, Mae D. Dumapig

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This study aimed to determine the lime potential of 3 mollusks, namely: Crassostrea iredalei (Oyster shell), Turritella terebra (Turret shell), and Anodontia edentula (Mangrove clam shell) as alternative for commercially produced agricultural lime. The hydrogen ion concentration (pH) and the lime concentration using Calcium Carbonate Equivalent (CCE) of each shellfish species were measured and tested for the enhancement of an acidic soil. The experiment was laid out in a Completely Randomized Design (CRD) with 4 treatments replicated 3 times. The treatments were as follows: Treatment A- 100 g agricultural lime; B- 100 g oyster shell lime; C- 100 g turret shell lime; and D- 100 g mangrove clam shell lime. Each treatment was combined to the acidic soil sample. The results were statistically analyzed using One-way Analysis of Variance (ANOVA) and Least Square Difference (LSD) at 0.01 and 0.05 levels of significance. Results revealed that lime produced from the 3 selected mollusks can be a potential source of alternative and/or supplement materials for agricultural lime in dealing with soil acidity, entailing lower cost of farm production.

Keywords: shell lime, pH, calcium carbonate concentrations, mollusks, agricultural lime, lime potential concentration, acidic soil

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Authors: Wannee Sutthachaidee

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The study of the production process of coconut-shell product in Amphawa, Samutsongkram Province is objected to study the pattern of the process of coconut-shell product by focusing in the 3 main processes which are inbound logistics process, production process and outbound process. The result of the research: There were 4 main results from the study. Firstly, most of the manufacturer of coconut-shell product is usually owned by a single owner and the quantity of the finished product is quite low and the main labor group is local people. Secondly, the production process can be divided into 4 stages which are pre-production process, production process, packaging process and distribution process. Thirdly, each 3 of the logistics process of coconut shell will find process which may cause the problem to the business but the process which finds the most problem is the production process because the production process needs the skilled labor and the quantity of the labor does not match with the demand from the customers. Lastly, the factors which affect the production process of the coconut shell can be founded in almost every process of the process such as production design, packaging design, sourcing supply and distribution management.

Keywords: production process, coconut-shell product, Amphawa District, inbound logistics process

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Authors: S. S. Pati, L. Herojit Singh, A. C. Oliveira, V. K. Garg

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Chitosan functionalized Fe3O4-Au core shell nanoparticles have been prepared using a two step wet chemical approach using NaBH4 as reducing agent for formation of Au inethylene glycol. X-ray diffraction studies shows individual phases of Fe3O4 and Au in the as prepared samples with crystallite size of 5.9 and 11.4 nm respectively. The functionalization of the core-shell nanostructure with Chitosan has been confirmed using Fourier transform infrared spectroscopy along with signatures of octahedral and tetrahedral sites of Fe3O4 below 600cm-1. Mössbauer spectroscopy shows decrease in particle-particle interaction in presence of Au shell (72% sextet) than pure oleic coated Fe3O4 nanoparticles (88% sextet) at room temperature. At 80K, oleic acid coated Fe3O4 shows only sextets whereas the Chitosan functionalized Fe3O4 and Chitosan functionalized Fe3O4@Au core shell show presence of 5 and 11% doublet, respectively.

Keywords: core shell, drug delivery, gold nanoparticles, magnetic nanoparticles

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Authors: Nasreen Thebo, W. Shaikh, A. J. Laghari, P. Nangni

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Prunus dulcis (Almond) shell extract is demonstrated for its biomedical applications. Shell extract prepared by soxhlet method and further characterized by UV-Visible spectrophotometer, atomic absorption spectrophotometer (AAS), FTIR, GC-MS techniques. In this study, the antifungal activity of almond shell extract was observed against clinically isolated pathogenic fungi by strip method. The antioxidant potential of crude shell extract of was evaluated by using DPPH (2-2-diphenyl-1-picryhydrazyl) and radical scavenging system. The possibility of short term therapy was only 20 days. The total antioxidant activity varied from 94.38 to 95.49% and total phenolic content was found as 4.455 mg/gm in almond shell extract. Finally the results provide a great therapeutic potential against Tinea capitis infection of scalp. Included in this study of shell extract that show scientific evidence for clinical efficacy, as well as found to be more useful in the treatment of dermatologic disorders and without any doubt it can be recommended to be Patent.

Keywords: Tinea capitis, DPPH, FTIR, GC-MS therapeutic treatment

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Authors: Oleg Ye Sysoyev, Artem Yu Dobryshkin, Nyein Sitt Naing

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Cylindrical shells are widely used in the construction of buildings and structures, as well as in the air structure. Thin-walled casings made of aluminum alloys are an effective substitute for reinforced concrete and steel structures in construction. The correspondence of theoretical calculations and the actual behavior of aluminum alloy structures is to ensure their trouble-free operation. In the laboratory of our university, "Building Constructions" conducted an experimental study to determine the effect of the system of attached masses on the natural oscillations of shallow cylindrical shells of aluminum alloys, the results of which were compared with theoretical calculations. The purpose of the experiment is to measure the free oscillations of an open, sloping cylindrical shell for various variations of the attached masses. Oscillations of an open, slender, thin-walled cylindrical shell, rectangular in plan, were measured using induction accelerometers. The theoretical calculation of the shell was carried out on the basis of the equations of motion of the theory of shallow shells, using the Bubnov-Galerkin method. A significant splitting of the flexural frequency spectrum is found, influenced not only by the systems of attached маsses but also by the values of the wave formation parameters, which depend on the relative geometric dimensions of the shell. The correspondence of analytical and experimental data is found, using the example of an open shell of alloy D19, which allows us to speak about the high quality of the study. A qualitative new analytical solution of the problem of determining the value of the oscillation frequency of the shell, carrying a system of attached masses is shown.

Keywords: open hollow shell, nonlinear oscillations, associated mass, frequency

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Authors: Kristine D. de Leon, Junifer A. Abatayo, Jose Cristina M. Pariña

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The current study is a comparative analysis of the use of shell nouns as a cohesive device (CD) in an English for Second Language (ESL) setting in order to identify their use and relationship in the quality of second language (L2) writing. As these nouns were established to anticipate the meaning within, across or outside the text, their use has fascinated writing researchers. The corpus of the study included published articles from reputable journals and graduate students’ papers in order to analyze the frequency of shell nouns using “highly prevalent” nouns in the academic community, to identify the different lexicogrammatical patterns where these nouns occur and to the functions connected with these patterns. The result of the study implies that published authors used more shell nouns in their paper than graduate students. However, the functions of the different lexicogrammatical patterns for the frequently occurring shell nouns are somewhat similar. These results could help students in enhancing the cohesion of their text and in comprehending it.

Keywords: anaphoric, cataphoric, lexico-grammatical, shell nouns

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Authors: Serafino Di Rosario

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ReS is a sustainable hand-built temporary acoustic shell, developed since 2011 and built during the architectural workshop at Villa Pennisi in Musica in Acireale, Sicily, each year since 2012. The design concept aims to provide a portable structure by reducing the on-site construction problems and the skills required by the builders together with maximizing the acoustic performance for the audience and the musicians. The shell is built using only wood, recycled for the most part, and can be built and dismantled by non-specialized workers in just three days. This paper describes the research process, which spans over four years and presents the final results in form of acoustic simulations performed by acoustic modeling software and real world measurements. ReS is developed by the ReS team who has been presented with the Peter Lord Award in 2015 by the Institute of Acoustics in the UK.

Keywords: acoustic shell, outdoor natural amplification, computational design, room acoustics

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Authors: Mohan Singh Mehata, R. K. Ratnesh

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CdSe, CdSe/ZnS, and CdSe/CdS core-shell quantum dots (QDs) of 3-4 nm were developed by using chemical route and following successive ion layer adsorption and reaction (SILAR) methods. The prepared QDs have been examined by using X-ray diffraction, high-resolution electron microscopy and optical spectroscopy. The photoluminescence (PL) quantum yield (QY) of core-shell QDs increases with respect to the core, indicating that the radiative rate increases by the formation of shell around core, as evident by the measurement of PL lifetime. Further, the PL of bovine serum albumin is quenched strongly by the presence of core-shall QDs and follow the Stern-Volmer (S-V) relation, whereas the lifetime does not follow the S-V relation, demonstrating that the observed quenching is predominantly static in nature. Among all the QDs, the CdSe/ZnS QDs shows the least cytotoxicity hence most biocompatibility.

Keywords: biocompatibility, core-shell quantum dots, photoluminescence and lifetime, sensing ability

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Authors: Ionel D. Craiu, Mihai Nedelcu

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Thin-walled cylinders are often used by the offshore industry as columns of floating installations. Based on observed strains, the inverse Finite Element Method (iFEM) may rebuild the deformation of structures. Structural Health Monitoring uses this approach extensively. However, the number of in-situ strain gauges is what determines how accurate it is, and for shell structures with complicated deformation, this number can easily become too high for practical use. Any thin-walled beam member's complicated deformation can be modeled by the Generalized Beam Theory (GBT) as a linear combination of pre-specified cross-section deformation modes. GBT uses bar finite elements as opposed to shell finite elements. This paper proposes an iFEM/GBT formulation for the shape sensing of thin-walled cylinders based on these benefits. This method significantly reduces the number of strain gauges compared to using the traditional inverse-shell finite elements. Using numerical simulations, dent damage detection is achieved by comparing the strain distributions of the undamaged and damaged members. The effect of noise on strain measurements is also investigated.

Keywords: damage detection, generalized beam theory, inverse finite element method, shape sensing

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Authors: M. Altekin, R. F. Yükseler

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Geometrically nonlinear axisymmetric bending of a shallow spherical shell with a point support at the apex under linearly varying axisymmetric load was investigated numerically. The edge of the shell was assumed to be simply supported or clamped. The solution was obtained by the finite difference and the Newton-Raphson methods. The thickness of the shell was considered to be uniform and the material was assumed to be homogeneous and isotropic. Sensitivity analysis was made for two geometrical parameters. The accuracy of the algorithm was checked by comparing the deflection with the solution of point supported circular plates and good agreement was obtained.

Keywords: Bending, Nonlinear, Plate, Point support, Shell.

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Authors: Mahidin, Yanna Syamsuddin, Samsul Rizal

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In order to fulfill world energy demand, several efforts have been done to look for new and renewable energy candidates to substitute oil and gas. Biomass is one of new and renewable energy sources, which is abundant in Indonesia. Palm kernel shell is a kind of biomass discharge from palm oil industries as a waste. On the other hand, Jatropha curcas that is easy to grow in Indonesia is also a typical energy source either for bio-diesel or biomass. In this study, biomass was used as co-fuel in briquetting of low-rank coal to suppress the release of emission (such as CO, NO_x and SO_x) during coal combustion. Desulfurizer, CaO-base, was also added to ensure the SO_x capture is effectively occurred. Ratio of coal to palm kernel shell (w/w) in the bio-briquette were 50:50, 60:40, 70:30, 80:20 and 90:10, while ratio of calcium to sulfur (Ca/S) in mole/mole were 1:1; 1.25:1; 1.5:1; 1.75:1 and 2:1. The bio-briquette then subjected to physical characterization and combustion test. The results show that the maximum weight loss in the durability measurement was ±6%. In addition, the highest stove efficiency for each desulfurizer was observed at the coal/PKS ratio of 90:10 and Ca/S ratio of 1:1 (except for the scallop shell desulfurizer that appeared at two Ca/S ratios; 1.25:1 and 1.5:1, respectively), i.e. 13.8% for the lime; 15.86% for the oyster shell; 14.54% for the scallop shell and 15.84% for the green mussel shell desulfurizers.

Keywords: biomass, low-rank coal, bio-briquette, new and renewable energy, palm kernel shell

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Authors: Balwinder Singh

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In the current competitive environment, casting industry has several challenges such as production of intricate castings, near net shape castings, decrease lead-time from product design to production, improved casting quality and to control costs. The raw materials used to make ceramic shell play an important role in determining the overall final ceramic shell characteristics. In this work, primary slurries were formulated using various combinations of zircon flour, fused silica and aluminosilicate powders as filler, colloidal silica as binder along with wetting and antifoaming agents (Catalyst). Taguchi’s parameter design strategy has been applied to investigate the effect of primary slurry parameters on the viscosity of the slurry and primary coating of shell. The result reveals that primary coating with low viscosity slurry has produced a rough surface of the shell due to stucco penetration.

Keywords: ceramic shell, primary slurry, filler, slurry viscosity, surface roughness

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Authors: Qasim Idrees, Gao Liangtian, Liu Bo, Miao Yiran

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In order to improve the efficiency and accuracy of the pressure hull structure, optimization of underwater vehicle based on response surface methodology, a method for optimizing the design of pressure hull structure was studied. To determine the pressure shell of five dimensions as a design variable, the application of thin shell theory and the Chinese Classification Society (CCS) specification was carried on the preliminary design. In order to optimize variables of the feasible region, different methods were studied and implemented such as Opt LHD method (to determine the design test sample points in the feasible domain space), parametric ABAQUS solution for each sample point response, and the two-order polynomial response for the surface model of the limit load of structures. Based on the ultimate load of the structure and the quality of the shell, the two-generation genetic algorithm was used to solve the response surface, and the Pareto optimal solution set was obtained. The final optimization result was 41.68% higher than that of the initial design, and the shell quality was reduced by about 27.26%. The parametric method can ensure the accuracy of the test and improve the efficiency of optimization.

Keywords: parameterization, response surface, structure optimization, pressure hull

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Authors: Suheyla Kocaman, Gulnare Ahmetli, Alaaddin Cerit, Alize Yucel, Merve Gozukucuk

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Shell wastes represent a considerable quantity of byproducts in the shellfish aquaculture. From the viewpoint of ecofriendly and economical disposal, it is highly desirable to convert these residues into high value-added products for industrial applications. So far, the utilization of shell wastes was confined at relatively lower levels, e.g. wastewater decontaminant, soil conditioner, fertilizer constituent, feed additive and liming agent. Shell wastes consist of calcium carbonate and organic matrices, with the former accounting for 95-99% by weight. Being the richest source of biogenic CaCO₃, shell wastes are suitable to prepare high purity CaCO₃ powders, which have been extensively applied in various industrial products, such as paper, rubber, paints and pharmaceuticals. Furthermore, the shell waste could be further processed to be the filler of polymer composites. This paper presents a study on the potential use of mussel shell waste as biofiller to produce the composite materials with different epoxy matrices, such as bisphenol-A type, CTBN modified and polyurethane modified epoxy resins. Morphology and mechanical properties of shell particles reinforced epoxy composites were evaluated to assess the possibility of using it as a new material. The effects of shell particle content on the mechanical properties of the composites were investigated. It was shown that in all composites, the tensile strength and Young’s modulus values increase with the increase of mussel shell particles content from 10 wt% to 50 wt%, while the elongation at break decreased, compared to pure epoxy resin. The highest Young’s modulus values were determined for bisphenol-A type epoxy composites.

Keywords: biocomposite, epoxy resin, mussel shell, mechanical properties

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Authors: Hassan Youssef Mohamed

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In this paper, we show new wave equations, and by using the equations, we concluded that the strong force and the weak force are not fundamental, but they are quantum effects for electromagnetism. This result is different from the current scientific understanding about strong and weak interactions at all. So, we introduce three evidences for our theory. First, we prove the asymptotic freedom phenomenon in the strong force by using our model. Second, we derive the nuclear shell model as an approximation of our model. Third, we prove that the leptons do not participate in the strong interactions, and we prove the short ranges of weak and strong interactions. So, our model is consistent with the current understanding of physics. Finally, we introduce the electron-positron model as the basic ingredients for protons, neutrons, and all matters, so we can study all particles interactions and nuclear interaction as many-body problems of electrons and positrons. Also, we prove the violation of parity conservation in weak interaction as evidence of our theory in the weak interaction. Also, we calculate the average of the binding energy per nucleon.

Keywords: new wave equations, the strong force, the grand unification theory, hydrogen atom, weak force, the nuclear shell model, the asymptotic freedom, electron-positron model, the violation of parity conservation, the binding energy

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Authors: Haider M. Alsaeq

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The present research is an attempt to figure out the best configuration of composite cylindrical shells of the sandwich type, i.e. the lightest design of such shells required to sustain a certain load over a certain area. The optimization is based on elastic-plastic geometrically nonlinear incremental-iterative finite element analysis. The nine-node degenerated curved shell element is used in which five degrees of freedom are specified at each nodal point, with a layered model. The formulation of the geometrical nonlinearity problem is carried out using the well-known total Lagrangian principle. For the structural optimization problem, which is dealt with as a constrained nonlinear optimization, the so-called Modified Hooke and Jeeves method is employed by considering the weight of the shell as the objective function with stress and geometrical constraints. It was concluded that the optimum design of composite sandwich cylindrical shell that have a rigid polyurethane foam core and steel facing occurs when the area covered by the shell becomes almost square with a ratio of core thickness to facing thickness lies between 45 and 49, while the optimum height to length ration varies from 0.03 to 0.08 depending on the aspect ratio of the shell and its boundary conditions.

Keywords: composite structure, cylindrical shell, optimization, non-linear analysis, finite element

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Authors: Yunzhe Tong, Jun Fan, Bin Wang

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The vibroacoustic behavior of an immersed infinite cylindrical shell with periodic lengthwise ribs has been studied in this paper. The motions of the shell are described by the Donnell equations. Each lengthwise rib is modeled as an elastic beam. The motions of the bulkheads are decomposed into the longitudinal motions and flexural motions. The analytical expressions of the shell motions can be obtained through circumferential mode expansion, Fourier Transform and periodic boundary condition in the circumferential direction. Furthermore, the far-field radiated pressure has been obtained using the stationary phase. The analysis of wavenumber domain shows that periodic lengthwise stiffeners in the circumferential direction can produce flexural Bloch waves. The dominant feature in far-field pressure amplitude is the resonance of the supersonic components of the flexural Bloch waves in the circumferential direction.

Keywords: flexural Bloch wave, stiffened shell, vibroacoustics, wavenumber analysis

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Authors: András Szekrényes

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Delamination is one of the major failure modes in laminated composite structures. Delamination tips are mostly captured by spatial numerical models in order to predict crack growth. This paper presents some mechanical models of delaminated composite shells based on shallow shell theories. The mechanical fields are based on a third-order displacement field in terms of the through-thickness coordinate of the laminated shell. The undelaminated and delaminated parts are captured by separate models and the continuity and boundary conditions are also formulated in a general way providing a large size boundary value problem. The system of differential equations is solved by the state space method for an elliptic delaminated shell having simply supported edges. The comparison of the proposed and a numerical model indicates that the primary indicator of the model is the deflection, the secondary is the widthwise distribution of the energy release rate. The model is promising and suitable to determine accurately the J-integral distribution along the delamination front. Based on the proposed model it is also possible to develop finite elements which are able to replace the computationally expensive spatial models of delaminated structures.

Keywords: J-integral, levy method, third-order shell theory, state space solution

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Authors: Usman D. Hamza, Noor S. Nasri, Mohammed Jibril, Husna M. Zain

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Activated carbons (M4P0, M4P2, and M5P2) used in this research were produced from palm shell and polyetherether ketone (PEEK) via carbonization, impregnation, and microwave activation. The adsorption/desorption process was carried out using static volumetric adsorption. Regeneration is important in the overall economy of the process and waste minimization. This work focuses on the thermal regeneration of the CO2 exhausted microwave activated carbons. The regeneration strategy adopted was thermal with nitrogen purge desorption with N2 feed flow rate of 20 ml/min for 1 h at atmospheric pressure followed by drying at 1500C. Seven successive adsorption/regeneration processes were carried out on the material. It was found that after seven adsorption regeneration cycles; the regeneration efficiency (RE) for CO2 activated carbon from palm shell only (M4P0) was more than 90% while that of hybrid palm shell-PEEK (M4P2, M5P2) was above 95%. The cyclic adsorption and regeneration shows the stability of the adsorbent materials.

Keywords: activated carbon, palm shell-PEEK, regeneration, thermal

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Authors: A. Bello-Olusoji, M. O. Sodamola, Y. A. Adejola, D. D Akinbola

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An eight (8) weeks study was carried out on Four hundred and five (405) African catfish (Clarias gariepinus) juveniles to examine the effect of graded levels of egg shell on their growth performance and survival rates. They were acclimatized for two (2) weeks after which they were weighed and allotted into five dietary treatments of three (3) replicates each and 27 fishes per replicate making a total number of eighty-one (81) fishes per treatment. The dietary treatments contained 0, 25, 50, 75 and 100(%) egg shell inclusion from treatment one to treatment five respectively. Parameter on daily feed intake, weekly weight gain, and daily mortalities were recorded. The result of the experiment indicated that treatment four (4) with 75% inclusion of egg shell was the best in terms of weight gain and survival rates and was significantly different (P<0.05) when compared with the other treatments. For Catfish farming to remain viable in the nearest future, lower feed cost and increased profit are required; it is therefore recommended that diets of African catfish (Clarias gariepinus) be supplemented with well processed egg shell at 75% level of inclusion to achieve this.

Keywords: African catfish, egg shell, performance, performance, survival rate, weight gain

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