bluuebunny/crossref_metadata_2025 huggingface dataset:
Noise Characteristics Analysis of the Horizontal Axis Hydrokinetic Turbine Designed for Unmanned Underwater Mooring Platforms
Authors: Dang Zhigao , Mao Zhaoyong , Song Baowei , Tian Wenlong
Published: December 2019

Operating horizontal axis hydrokinetic turbine (HAHT) generates noise affecting the ocean environment adversely. Therefore, it is essential to determine the noise characteristics of such types of HAHT, as large-scale turbine sets would release more noise pollution to the ocean. Like other rotating machinery, the hydrodynamic noise generated by the rotating turbine has been known to be the most important noise source. In the present work, the transient turbulent flow field of the HAHT is obtained by incompressible large eddy simulation, thereafter, the Ffowcs Williams and Hawkings acoustic analogy formulation is carried out to predict the noise generated from the pressure fluctuations of the blade surface. The coefficient of power is compared with the experimental results, with a good agreement being achieved. It is seen from the pressure contours that the 80% span of the blade has the most severe pressure fluctuations, which concentrate on the region of leading the edge of the airfoil and the suction surface of the airfoil. Then, the noise characteristics around a single turbine are systematically studied, in accordance with the results of the flow field. The noise characteristics around the whole turbine are also investigated to determine the directionality of the noise emission of HAHT.
Development of a Blended Time-Domain Program for Predicting the Motions of a Wave Energy Structure
Authors: Wang Hao , Somayajula Abhilash , Falzarano Jeffrey , Xie Zhitian
Published: December 2019

Traditional linear time-domain analysis is used widely for predicting the motions of floating structures. When it comes to a wave energy structure, which usually is subjected to larger relative (to their geometric dimensions) wave and motion amplitudes, the nonlinear effects become significant. This paper presents the development of an in-house blended time-domain program (SIMDYN). SIMDYN’s “blend” option improves the linear option by accounting for the nonlinearity of important external forces (e.g., Froude-Krylov). In addition, nonlinearity due to large body rotations (i.e., inertia forces) is addressed in motion predictions of wave energy structures. Forced motion analysis reveals the significance of these nonlinear effects. Finally, the model test correlations examine the simulation results from SIMDYN under the blended option, which has seldom been done for a wave energy structure. It turns out that the blended time-domain method has significant potential to improve the accuracy of motion predictions for a wave energy structure.
Managing Shariah Non-Compliance Risk via Islamic Dispute Resolution
Authors: Bhatti Maria
Published: December 2019

This article discusses Shariah non-compliance risk as a form of operational risk intending to ensure that operations in the Islamic and banking finance industry comply with Shariah procedures. In the field of Islamic finance, Shariah non-compliance risk refers to the possibility that Islamic finance transactions may be challenged based on Shariah non-compliance. This article uses a comparative and normative approach as well as a legal analysis of the case of Beximco. The article proposes the management of Shariah non-compliance risk by augmenting the effectiveness of Shariah governance systems with Islamic banking and finance arbitration; arbitration should be an enforced part of Islamic finance institutional arrangements—as it always has been classically—to provide flexibility for dispute resolution. To this end, the article examines contemporary implementations of Shariah arbitration rules to assess how Shariah non-compliance risk can be better managed via Islamic dispute resolution procedures.
Performance Comparison of Closed-Form Least Squares Algorithms for Hyperbolic 3-D Positioning
Authors: Khalaf-Allah Mohamed
Published: December 2019

An accurate 3-D wireless local positioning system (LPS) is a highly demanded tool for increasing safety in, e.g., emergency response and security operations. An LPS is an attractive approach that can meet stringent requirements and can achieve acceptable accuracies for a long time during extended operations in global navigation satellite system (GNSS)-denied environments. In this work, three closed-form (CF) least squares (LS) algorithms were considered, where two of them were adapted to exploit the knowledge about nuisance parameters for accurate 3-D positioning based on time difference of arrival (TDoA) measurements. The algorithms utilize the single set (SS) of the TDoA measurements, an extended SS (ExSS) of the TDoA measurements, or the full set (FS) of the TDoA measurements, and were denoted, respectively, as the CFSSLS, CFExSSLS, and CFFSLS solutions. The performance of the algorithms was investigated with simulations and real-world measurements, where the wireless system transmitters were placed in a quasi-coplanar arrangement. At moderate to high signal-to-noise ratio (SNR) levels, the CFSSLS solution has the best performance, followed by the CFExSSLS solution and then by the CFFSLS solution. At low SNR levels, the CFFSLS algorithm outperformed the other two algorithms. Both the CFSSLS and CFFSLS solutions estimate nuisance parameters that are utilized in refining the vertical position estimate of the receiver. The CFFSLS solution delivers more accurate refined vertical position estimates since it utilizes more nuisance parameters, i.e., more information. The experimental results confirmed the simulation study in which the CFFSLS algorithm outperformed the other two algorithms, where the experimental environment was dominated by total non-line-of-sight (NLoS) conditions and low SNR levels at the receiver to be located. Therefore, it is recommended to use the FS TDoA measurements for 3-D positioning in bad signal conditions, such as high noise levels and NLoS propagation.
A Numerical Procedure Based on Orowan’s Theory for Predicting the Behavior of the Cold Rolling Mill Process in Full Film Lubrication
Authors: Valigi Maria Cristina , Malvezzi Monica , Logozzo Silvia
Published: December 2019

In this paper, a numerical model for predicting the working parameters of the cold rolling mill process in full film lubrication is presented. The model is useful from an industrial point of view, because it can forecast the thickness reduction of the metal sheet and the pressure trend, so that the rolling mill process parameters can be regulated to obtain a specific output thickness. Experimental tests were performed, and results are compared to the theoretical ones resulting from the model. The novelty of the proposed model is that it combines Orowan’s theory for the plastic deformation analysis with the Reynolds equation in full film lubrication and the continuity conditions. The lubricant flow and viscosity are studied, taking in account their dependence on pressure and temperature. The proposed model describing the full film regime is also compared to another one, previously proposed by the authors, based on the well-known slab analysis and sharing with it the representation of the lubrication regime, the mathematical procedure, and the boundary conditions. The results show that the proposed model provides a better prediction of the working parameters with respect to the model based on the slab analysis.
N-(2-Hydroxy-1,1-dimethylethyl)-3-methylbenzamide
Authors: Al Mamari Hamad H. , Al Lawati Yousuf
Published: December 2019

The title compound, N-(2-hydroxy-1,1-dimethylethyl)-3-methylbenzamide was synthesized by reacting 3-methylbenzoyl chloride or 3-methylbenzoic acid with 2-amino-2-methyl-1-propanol. In the present report, the synthesized target compound was fully characterized by various spectroscopic methods (1H NMR, 13C NMR, IR, GC-MS), its composition confirmed by elemental analysis, and its structure determined and confirmed by X-ray analysis. The importance of this compound lies in its possession of an N,O-bidentate directing group. Such a structural motif is potentially suitable for metal-catalyzed C–H bond functionalization reactions.
Concrete Protective Layer Cracking Caused by Non-Uniform Corrosion of Reinforcements
Authors: Zhang Lu , Niu Ditao , Wen Bo , Luo Daming
Published: December 2019

The volume expansion of reinforcement corrosion products resulting from the corrosion of steel reinforcement embedded into concrete causes the concrete’s protective layer to crack or spall, reducing the durability of the concrete structure. Thus, it is necessary to analyze concrete cracking caused by reinforcement corrosion. This study focused on the occurrence of non-uniform reinforcement corrosion in a natural environment. The characteristics of the rust layer were used to deduce the unequal radial displacement distribution function of concrete around both angular and non-angular bars. Additionally, the relationship between the corrosion ratio and the radial displacement of the concrete around the bar was established quantitatively. Concrete cracking due to the non-uniform corrosion of reinforcements was simulated using steel bars embedded in concrete that were of uneven displacement because of rust expansion. The distribution of the principal tensile stress around the bar was examined. A formula for calculating the critical radial displacement at the point when cracking began was obtained and used to predict the corrosion ratio of the concrete cover. The determined analytical corrosion ratio agreed well with the test result. The effect factor analysis based on the finite element method indicated that increasing the concrete strength and concrete cover thickness delays concrete cracking and that the adjacent rebar causes the stress superposition phenomenon.
Dynamic Tensile Stress-Compressive Stress Behavior of Thermoplastic Matrix Composite Materials Reinforced with Continuous Fiber for Automotive Damping and Anti-Vibration Structural Elements
Authors: Tobalina-Baldeon D. , Sanz-Adan F. , Martinez-Calvo M.A. , Santamaría-Pena J.
Published: December 2019

Continuous Fibers-Reinforced Thermoplastic Composites (CFRTP) are presented as light materials, capable of offering a short production time with the possibility of being recycled. These properties make them ideal for automotive applications, aiming to reduce the consumption and emission of polluting gases. This article analyzed the dynamic tensile stress-compressive stress behavior of CFRTP in structural elements of the car with anti-vibration and damping functions. The data available in the literature on the reliable and usual compliance of the properties required for CFRTP, to be applied in the automotive structural elements, is scarce and insufficient. In order to analyze whether CFRTP feeds the demanding requirements of car manufacturers and if they provide advantages over the metal materials currently used, this article developed a method of reliable verification of their dynamic tensile and compression behavior. The methodology developed could be used as a guide to characterizing any combination of vulcanized rubber adhesive joints with CFRTP, regardless of the materials and additives used. The results obtained showed that there exists CFRTP that fits the requirements of the car manufacturers for this type of component and also offers dynamic advantages over the materials currently used as anti-vibration elements.
Fracture Analysis and Shear Strength of Aluminum/CFRP and GFRP Adhesive Joint in Fiber Metal Laminates
Authors: Ostapiuk Monika , Bieniaś Jarosław
Published: December 2019

Fiber metal laminates (FMLs) were initially developed under the motivation of the aerospace industry. Generally, they consist of aluminum and high strength glass fiber in polymeric layers, but the new challenge is to apply them with a carbon fiber. Pretreatment of aluminum is the main factor responsible for the adhesion between metallic and polymeric layers. The shear strength test a very popular method in the experimental joint of two components. In this article, the main aim was to compare the surface pretreatment and configuration of fibers in FMLs based on aluminum with glass and carbon fibers. The decisive factor of strength in adhesive or cohesive failure is first the type of fibers, and second, the surface preparation.
Comparative Study on the Effects of Various Modified Admixtures on the Mechanical Properties of Styrene-Acrylic Emulsion-Based Cement Composite Materials
Authors: Wang Tengjiao , Xu Jinyu , Zhu Congjin , Ren Weibo
Published: December 2019

This study carried out tensile tests at definite elongation, tensile and shear tests on 4 admixture-modified styrene-acrylic emulsion-based cement composites (SECCs), and measured the strength, deformation, and energy consumption indexes of test specimens, so as to investigate the influences of coalescing agent, plasticizer, silane coupling agent, and nanometer aluminium oxide on the bond, tensile, and shear mechanical properties of the test specimens. Additionally, the Field Emission Scanning Electron Microscope (FE-SEM) test and Mercury Intrusion Porosimetry (MIP) test were conducted on the composite material specimens, to analyze the microscopic mechanism of different admixtures in modifying the mechanical properties of the SECC. The results suggested that the addition of coalescing agent, plasticizer, silane coupling agent, and nanometer aluminium oxide improved the bond, tensile and shear properties of the SECC specimens to various degrees. Of them, the coalescing agent promoted the mutual cross-linking of organic polymers with inorganic products, and optimized the transition interface to enhance the comprehensive mechanical properties of the test specimens; by contrast, nanometer aluminium oxide developed secondary hydration reaction with the inorganic products, and refined the pore structure to modify the mechanical properties of test specimens. Therefore, both of them achieved significant modification effects. Typically, the optimal bond properties of FFAMC, PLMC, SCAMC, and NAMC test specimens were achieved at the coalescing agent, plasticizer, silane coupling agent, and nanometer aluminium oxide addition amounts of 4%, 1.5%, 3%, and 1%, respectively. Besides, the improving effects of different admixtures on the tensile property of SECC specimens followed the order of coalescing agent > nanometer aluminium oxide > plasticizer > silane coupling agent, with the optimal addition amounts of 4%, 1.5%, 1%, and 2%, respectively. In addition, the improving effects of different admixtures on the shear performance of SECC specimens followed the order of coalescing agent > nanometer aluminium oxide > silane coupling agent > plasticizer, with the optimal addition amounts of 4%, 1.5%, 1%, and 1%, respectively.
Research and Optimization of Surface Roughness in Milling of SLM Semi-Finished Parts Manufactured by Using the Different Laser Scanning Speed
Authors: Matras Andrzej
Published: December 2019

The paper studies the potential to improve the surface roughness in parts manufactured in the Selective Laser Melting (SLM) process by using additional milling. The studied process was machining of samples made of the AlSi10Mg alloy powder. The simultaneous impacts of the laser scanning speed of the SLM process and the machining parameters of the milling process (such as the feed rate and milling width) on the surface roughness were analyzed. A mathematical model was created as a basis for optimizing the parameters of the studied processes and for selecting the sets of optimum solutions. As a result of the research, surface with low roughness (Ra = 0.14 μm, Rz = 1.1 μm) was obtained after the face milling. The performed milling allowed to reduce more than 20-fold the roughness of the SLM sample surfaces. The feed rate and the cutting width increase resulted in the surface roughness deterioration. Some milled surfaces were damaged by the chip adjoining to the rake face of the cutting tool back tooth.
Elastic Asymmetry of PLA Material in FDM-Printed Parts: Considerations Concerning Experimental Characterisation for Use in Numerical Simulations
Authors: Pastor-Artigues Ma-Magdalena , Roure-Fernández Francesc , Ayneto-Gubert Xavier , Bonada-Bo Jordi , Pérez-Guindal Elsa , Buj-Corral Irene
Published: December 2019

The objective of this research is to characterise the material poly lactic acid (PLA), printed by fused deposition modelling (FDM) technology, under three loading conditions—tension, compression and bending—in order to get data that will allow to simulate structural components. In the absence of specific standards for materials manufactured in FDM technology, characterisation is carried out based on ASTM International standards D638, D695 and D790, respectively. Samples manufactured with the same printing parameters have been built and tested; and the tensile, compressive and flexural properties have been determined. The influences of the cross-sectional shape and the specimen length on the strength and elastic modulus of compression are addressed. By analysing the mechanical properties obtained in this way, the conclusion is that they are different, are not coherent with each other, and do not reflect the bimodular nature (different behaviour of material in tension and compression) of this material. A finite element (FE) model is used to verify these differences, including geometric non-linearity, to realistically reproduce conditions during physical tests. The main conclusion is that the test methods currently used do not guarantee a coherent set of mechanical properties useful for numerical simulation, which highlights the need to define new characterisation methods better adapted to the behaviour of FDM-printed PLA.
Explicit Simulation of Circular CFST Stub Columns with External Steel Confinement under Axial Compression
Authors: Alatshan Faesal , Osman Siti Aminah , Mashiri Fidelis , Hamid Roszilah
Published: December 2019

Concrete-filled steel tube (CFST) structural members have been widely used in engineering projects for their superior strength and ductility. However, the different lateral dilation characteristics between concrete infill and steel tube have caused imperfect composite interaction during the early loading stage. To overcome this issue, external steel confinements in the form of rings and spiral were previously suggested to minimise the lateral expansion of the steel tube and enhance the concrete confinement effects. This study presented the analytical behaviour of circular CFST short columns with an external ring or spiral confinements which are subjected to axial loading. An explicit finite element (FE) model was developed and verified based on previous experimental findings. Besides that, this study analysed the failure modes, axial load–strain relationship, stress distributions, and bond strength of the composite column components. Parametric analysis was also undertaken to evaluate the impact of material strengths, total steel ratio, and diameter-to-thickness ratio. The results suggest that the use of external steel confinement can enhance the compressive behaviour of CFSTs better than increasing the thickness of the steel tube when using the same steel ratio. Finally, simplified design formulations were developed to accurately calculate the ultimate capacity of CFST columns with and without external steel confinement.
A Compressive Peak Strength Model for CFRP-Confined Thermal Insulation Materials under Elevated Temperature
Authors: Li Yeou-Fong , Sio Wai-Keong , Tsai Ying-Kuan
Published: December 2019

In this paper, a compressive peak strength model for CFRP-confined thermal insulation materials under elevated temperature was proposed. The thermal insulation material was made by Portland cement with different portions of perlite. The compressive strengths of four different perlite ratios in weight, such as 0%, 10%, 20%, and 30% of thermal insulation materials, confined by one-layer, two-layer, and three-layer carbon fiber-reinforced polymer (CFRP) composite materials, were obtained. The test results indicated that the specimen’s compressive strength decreased with an increase in the amount of perlite replacement and increased with an increase in the number of CFRP wrapping layers. Based on the test results, a theoretical compressive peak strength model with some parameters was proposed. In the meantime, the compressive strengths of the above four different perlite ratios of thermal insulation materials under elevated temperature, such as ambient temperature, 100 °C, 150 °C, 200 °C, 250 °C, and 300 °C, were obtained. For compression tests of specimens with a fixed amount of perlite, the test results indicated that the specimen’s compressive strength decreased with an increase in temperature, highlighting a thermal softening phenomenon. Based on the test results, a compressive peak strength model with a thermal softening parameter was proposed to predict the peak strength under elevated temperature. Finally, a compressive peak strength model for thermal insulation material with CFRP confinement under different elevated temperature was derived, and it achieved acceptable results in comparison to the experimental results.
Room-Temperature-Processed Amorphous Sn-In-O Electron Transport Layer for Perovskite Solar Cells
Authors: Baek Seungtae , Han Jeong Woo , Vidyasagar Devthade , Cho Hanbyeol , HA Hwi-Heon , Kim Dong Hoe , Heo Young-Woo , Lee Sangwook
Published: December 2019

We report amorphous tin-indium-oxide (TIO, Sn fraction: >50 atomic percentage (at%)) thin films as a new electron transport layer (ETL) of perovskite solar cells (PSCs). TIO thin films with Sn fraction of 52, 77, 83, 92, and 100 at% were grown on crystalline indium-tin-oxide (ITO, Sn fraction: ~10 at%) thin films, a common transparent conducting oxide, by co-sputtering In2O3 and SnO2 at room temperature. The energy band structures of the amorphous TIO thin films were determined from the optical absorbance and the ultraviolet photoelectron spectra. All the examined compositions are characterized by a conduction band edge lying between that of ITO and that of perovskite (here, methylammonium lead triiodide), indicating that TIO is a potentially viable ETL of PSCs. The photovoltaic characteristics of the TIO-based PSCs were evaluated. Owing mainly to the highest fill factor and open circuit voltage, the optimal power conversion efficiency was obtained for the 77 at%-Sn TIO ETL with TiCl4 treatment. The fill factor and the open circuit voltage changes with varying the Sn fraction, despite similar conduction band edges. We attribute these differences to the considerable changes in the electrical resistivity of the TIO ETL. This would have a significant effect on the shunt and/or the series resistances. The TIO ETL can be continuously grown on an ITO TCO in a chamber, as ITO and TIO are composed of identical elements, which would help to reduce production time and costs.
Characterization of Ultrasonic Bubble Clouds in A Liquid Metal by Synchrotron X-ray High Speed Imaging and Statistical Analysis
Authors: Wang Chuangnan , Connolley Thomas , Tzanakis Iakovos , Eskin Dmitry , Mi Jiawei
Published: December 2019

Quantitative understanding of the interactions of ultrasonic waves with liquid and solidifying metals is essential for developing optimal processing strategies for ultrasound processing of metal alloys in the solidification processes. In this research, we used the synchrotron X-ray high-speed imaging facility at Beamline I12 of the Diamond Light Source, UK to study the dynamics of ultrasonic bubbles in a liquid Sn-30wt%Cu alloy. A new method based on the X-ray attenuation for a white X-ray beam was developed to extract quantitative information about the bubble clouds in the chaotic and quasi-static cavitation regions. Statistical analyses were made on the bubble size distribution, and velocity distribution. Such rich statistical data provide more quantitative information about the characteristics of ultrasonic bubble clouds and cavitation in opaque, high-temperature liquid metals.
Processability of Atypical WC-Co Composite Feedstock by Laser Powder-Bed Fusion
Authors: Al-Thamir Mohaimen , McCartney D. Graham , Simonelli Marco , Hague Richard , Clare Adam
Published: December 2019

Processing of tool materials for cutting applications presents challenges in additive manufacturing (AM). Processes must be carefully managed in order to promote the formation of favourable high-integrity ‘builds’. In this study, for the first time, a satelliting process is used to prepare a WCM-Co (12 wt.% Co) composite. Melting trials were undertaken to evaluate the consolidation behaviour of single tracks within a single layer. Tracks with continuous and relatively uniform surface morphology were obtained. These features are essential for high-quality AM builds in order to encourage good bonding between subsequent tracks within a layer which may reduce porosity within a 3D deposition. This study elucidates the formation of track irregularities, melting modes, crack sensitivity, and balling as a function of laser scanning speed and provides guidelines for future production of WCM-Co by laser powder-bed fusion.
Metal–Halogen Bonding Seen through the Eyes of Vibrational Spectroscopy
Authors: Oliveira Vytor P. , Marcial Bruna L. , Machado Francisco B. C. , Kraka Elfi
Published: December 2019

Incorporation of a metal center into halogen-bonded materials can efficiently fine-tune the strength of the halogen bonds and introduce new electronic functionalities. The metal atom can adopt two possible roles: serving as halogen acceptor or polarizing the halogen donor and acceptor groups. We investigated both scenarios for 23 metal–halogen dimers trans-M(Y2)(NC5H4X-3)2 with M = Pd(II), Pt(II); Y = F, Cl, Br; X = Cl, Br, I; and NC5H4X-3 = 3-halopyridine. As a new tool for the quantitative assessment of metal–halogen bonding, we introduced our local vibrational mode analysis, complemented by energy and electron density analyses and electrostatic potential studies at the density functional theory (DFT) and coupled-cluster single, double, and perturbative triple excitations (CCSD(T)) levels of theory. We could for the first time quantify the various attractive contacts and their contribution to the dimer stability and clarify the special role of halogen bonding in these systems. The largest contribution to the stability of the dimers is either due to halogen bonding or nonspecific interactions. Hydrogen bonding plays only a secondary role. The metal can only act as halogen acceptor when the monomer adopts a (quasi-)planar geometry. The best strategy to accomplish this is to substitute the halo-pyridine ring with a halo-diazole ring, which considerably strengthens halogen bonding. Our findings based on the local mode analysis provide a solid platform for fine-tuning of existing and for design of new metal–halogen-bonded materials.
Type II Topp Leone Power Lomax Distribution with Applications
Authors: Al-Marzouki Sanaa , Jamal Farrukh , Chesneau Christophe , Elgarhy Mohammed
Published: December 2019

In many areas of applied sciences, the last step of a study often consists in analyzing in depth the collected data. Among all the kinds of data, the lifetime data are well-known to convey a great deal of information whose capture is necessary to identify one or more key phenomena. In this regards, numerous mathematical models have been proposed, including those based on lifetime distributions. In this paper, we introduce a new four-parameter lifetime distribution based on the type II Topp-Leone-G family and the power Lomax distribution. In comparison to the existing distributions, the new one is characterized by very flexible probability functions: increasing, decreasing, J, and reverse J shapes are observed for the probability density and hazard rate functions, giving first signs on the potential of adaptability of the related model. With this idea in mind, the new distribution is studied in detail, from both the theoretical and applied sides. After showing its main mathematical properties, the related model is investigated with estimation of the parameters by the maximum likelihood method. We applied it to two practical datasets, including the well-know aircraft windshield data. We show that the new model performs better than several modern adversary models, motivating its use in an applied setting.
A New Hybrid Evolutionary Algorithm for the Treatment of Equality Constrained MOPs
Authors: Cuate Oliver , Ponsich Antonin , Uribe Lourdes , Zapotecas-Martínez Saúl , Lara Adriana , Schütze Oliver
Published: December 2019

Multi-objective evolutionary algorithms are widely used by researchers and practitioners to solve multi-objective optimization problems (MOPs), since they require minimal assumptions and are capable of computing a finite size approximation of the entire solution set in one run of the algorithm. So far, however, the adequate treatment of equality constraints has played a minor role. Equality constraints are particular since they typically reduce the dimension of the search space, which causes problems for stochastic search algorithms such as evolutionary strategies. In this paper, we show that multi-objective evolutionary algorithms hybridized with continuation-like techniques lead to fast and reliable numerical solvers. For this, we first propose three new problems with different characteristics that are indeed hard to solve by evolutionary algorithms. Next, we develop a variant of NSGA-II with a continuation method. We present numerical results on several equality-constrained MOPs to show that the resulting method is highly competitive to state-of-the-art evolutionary algorithms.
A Reallocation Approach for Software Trustworthiness Based on Trustworthy Attributes
Authors: Tao Hongwei , Chen Yixiang , Wu Hengyang
Published: December 2019

Software trustworthiness is an important research field in software engineering. In order to appropriately evaluate it, some different measurement approaches have been proposed, which have important guiding significance for improving software trustworthiness. Recently, we have investigated attributes-based approaches. That is, how to maximize trustworthy degree of some software satisfying a given threshold by adjusting every attribute value such that the cost is minimal, i.e., the sum of all attribute values is as small as possible. The work is helpful to improve the software quality under the same cost. This paper continues this work and considers a reallocation approach to dealing with the problem that the threshold and the minimal constraints of every attribute values dynamically increase. In this process, the costs of trustworthiness improvement should be ensured to be minimal. For this purpose, we firstly define a reallocation model by mathematical programming. Then we introduce the notion of growth function. Based on this, a polynomial reallocation algorithm is designed to solve the above reallocation model. Finally, we verify our work on spacecraft softwares and the results show that this work is valid.
A Characterization of Quasi-Metric Completeness in Terms of α–ψ-Contractive Mappings Having Fixed Points
Authors: Romaguera Salvador , Tirado Pedro
Published: December 2019

We obtain a characterization of Hausdorff left K-complete quasi-metric spaces by means of α – ψ -contractive mappings, from which we deduce the somewhat surprising fact that one the main fixed point theorems of Samet, Vetro, and Vetro (see “Fixed point theorems for α – ψ -contractive type mappings”, Nonlinear Anal. 2012, 75, 2154–2165), characterizes the metric completeness.
Links between Contractibility and Fixed Point Property for Khalimsky Topological Spaces
Authors: Han Sang-Eon
Published: December 2019

Given a Khalimsky (for short, K-) topological space X, the present paper examines if there are some relationships between the contractibility of X and the existence of the fixed point property of X. Based on a K-homotopy for K-topological spaces, we firstly prove that a K-homeomorphism preserves a K-homotopy between two K-continuous maps. Thus, we obtain that a K-homeomorphism preserves K-contractibility. Besides, the present paper proves that every simple closed K-curve in the n-dimensional K-topological space, S C K n , l , n ≥ 2 , l ≥ 4 , is not K-contractible. This feature plays an important role in fixed point theory for K-topological spaces. In addition, given a K-topological space X, after developing the notion of K-contractibility relative to each singleton { x } ( ⊂ X ) , we firstly compare it with the concept of K-contractibility of X. Finally, we prove that the K-contractibility does not imply the K-contractibility relative to each singleton { x 0 } ( ⊂ X ) . Furthermore, we deal with certain conjectures involving the (almost) fixed point property in the categories KTC and KAC, where KTC (see Section 3) (resp. KAC (see Section 5)) denotes the category of K-topological (resp. KA-) spaces, KA-) spaces are subgraphs of the connectedness graphs of the K-topology on Z n .
On Cocyclic Hadamard Matrices over Goethals-Seidel Loops
Authors: Álvarez Víctor , Armario José Andrés , Falcón Raúl M. , Frau María Dolores , Gudiel Félix , Güemes María Belén , Osuna Amparo
Published: December 2019

About twenty-five years ago, Horadam and de Launey introduced the cocyclic development of designs, from which the notion of cocyclic Hadamard matrices developed over a group was readily derived. Much more recently, it has been proved that this notion may naturally be extended to define cocyclic Hadamard matrices developed over a loop. This paper delves into this last topic by introducing the concepts of coboundary, pseudocoboundary and pseudococycle over a quasigroup, and also the notion of the pseudococyclic Hadamard matrix. Furthermore, Goethals-Seidel loops are introduced as a family of Moufang loops so that every Hadamard matrix of Goethals-Seidel type (which is known not to be cocyclically developed over any group) is actually pseudococyclically developed over them. Finally, we also prove that, no matter if they are pseudococyclic matrices, the usual cocyclic Hadamard test is unexpectedly applicable.
Diffusion Dynamics and Impact of Noise on a Discrete-Time Ratio-Dependent Model: An Analytical and Numerical Approach
Authors: Das Kalyan , Srinivas M. N. , Huda Gazi Nurul
Published: December 2019

The paper deals with the dynamical behavior of a discrete-time ratio-dependent predator–prey system. The predator dependence is one of the main concerns of the system. The stability analysis of this 2-dimensional map was carried out analytically. Numerical simulation was carried out to verify the analytical results. We analyzed some specific features that could arise in discrete system. Basin of attraction was found for the endemic equilibrium state. We extended the numerical simulation for the maximal Lyapunov exponent. The presence of positive Lyapunov exponent indicated chaotic behavior of the map. The sensitive dependence on initial condition is one of the criteria for a discrete system. We showed that the system is sensitive on the initial conditions. We also carried out the analysis of diffusion and impact of noise.
Bioactive Secondary Metabolites from the Culture of the Mangrove-Derived Fungus Daldinia eschscholtzii HJ004
Authors: Liao Hai-Xia , Shao Tai-Ming , Mei Rong-Qing , Huang Guo-Lei , Zhou Xue-Ming , Zheng Cai-Juan , Wang Chang-Yun
Published: December 2019

Two new polyketides, 8-O-methylnodulisporin F (1) and nodulisporin H (2), two new naphthoquinones, 5-hydroxy-2-methoxy-6,7-dimethyl-1,4-naphthoquinone (3) and 5-hydroxy-2-methoxynaphtho[9–c]furan-1,4-dione (4), and a new naphthofuran 1,3,8-trimethoxynaphtho[9–c]furan (5), along with five known compounds 4-O-methyl eleutherol (6), 2-acetyl-7-methoxybenzofuran (7), (-)-orthosporin (8), diaporthin (9), and 6-hydroxymellein (10), were obtained from the EtOAc extract of the mangrove-derived fungus Daldinia eschscholtzii HJ004. The structures of the isolated compounds were elucidated by extensive NMR and MS analyses, while the absolute configurations of the stereogenic carbons were established based on experimental and calculated electronic circular dichroism spectra. Compounds 4 and 7 displayed a potent inhibitory activity against α-glucosidase with the IC50 values of 5.7 and 1.1 μg/mL, respectively. Compounds 1 and 2 showed a moderate antibacterial activity against Staphylococcus aureus, methicillin-resistant S. aureus (MRSA) and Bacillus cereus, with minimum inhibitory concentration (MIC) values ranging from 6.25 to 12.5 μg/mL. Compound 3 exhibited antibacterial activity against B. cereus with the MIC value of 12.5 μg/mL.
A Strain Rate Dependent Fracture Model of 7050 Aluminum Alloy
Authors: Cao Jun , Li Fuguo , Ma Weifeng , Wang Ke , Ren Junjie , Nie Hailiang , Dang Wei
Published: December 2019

The purpose of this research is to predict fracture loci and fracture forming limit diagrams (FFLDs) considering strain rate for aluminum alloy 7050-T7451. A fracture model coupled Johnson-Cook plasticity model was proposed to investigate its strain rate effect. Furthermore, a hybrid experimental-numerical method was carried out to verify the strain rate-dependent fracture model by using fracture points of uniaxial tension, notched tension, flat-grooved tension, and pure shear specimens. The results show that the fracture points are in accordance with the fracture loci and FFLDs under different strain rates. The increasing strain rate decreases the FFLDs of aluminum alloy 7050-T7451. The difference of force-displacement responses under different strain rates is larger for notched tension and pure shear conditions.
The Deformation Characteristics, Fracture Behavior and Strengthening-Toughening Mechanisms of Laminated Metal Composites: A Review
Authors: Gao Kuan , Zhang Xin , Liu Baoxi , He Jining , Feng Jianhang , Ji Puguang , Fang Wei , Yin Fuxing
Published: December 2019

Multilayer metal composites have great application prospects in automobiles, ships, aircraft and other manufacturing industries, which reveal their superior strength, toughness, ductility, fatigue lifetime, superplasticity and formability. This paper presents the various mechanical properties, deformation characteristics and strengthening–toughening mechanisms of laminated metal matrix composites during the loading and deformation process, and that super-high mechanical properties can be obtained by adjusting the fabrication process and structure parameters. In the macroscale, the interface bonding status and layer thickness can effectively affect the fracture, impact toughness and tensile fracture elongation of laminated metal matrix composites, and the ductility and toughness cannot be fitting to the rule of mixture (ROM). However, the elastic properties, yield strength and ultimate strength basically follow the rule of mixture. In the microscale, the mechanical properties, deformation characteristics, fracture behavior and toughening mechanisms of laminated composites reveal the obvious size effect.
Comment on the Paper Entitled “A New Cumulative Fatigue Damage Rule Based on Dynamic Residual S-N Curve and Material Memory Concept” by Peng Z., Huang H., Zhou J. and Li Y. Published in Metals (2018; 8 (6): 456)
Authors: Hectors Kris , De Waele Wim
Published: December 2019

Dear Editors, [...]
Effects of Alloying Elements Addition on Delayed Fracture Properties of Ultra High-Strength TRIP-Aided Martensitic Steels
Authors: Hojo Tomohiko , Kobayashi Junya , Sugimoto Koh-ichi , Nagasaka Akihiko , Akiyama Eiji
Published: December 2019

To develop ultra high-strength cold stamping steels for automobile frame parts, the effects of alloying elements on hydrogen embrittlement properties of ultra high-strength low alloy transformation induced plasticity (TRIP)-aided steels with a martensite matrix (TM steels) were investigated using the four-point bending test and conventional strain rate tensile test (CSRT). Hydrogen embrittlement properties of the TM steels were improved by the alloying addition. Particularly, 1.0 mass% chromium added TM steel indicated excellent hydrogen embrittlement resistance. This effect was attributed to (1) the decrease in the diffusible hydrogen concentration at the uniform and fine prior austenite grain and packet, block, and lath boundaries; (2) the suppression of hydrogen trapping at martensite matrix/cementite interfaces owing to the suppression of precipitation of cementite at the coarse martensite lath matrix; and (3) the suppression of the hydrogen diffusion to the crack initiation sites owing to the high stability of retained austenite because of the existence of retained austenite in a large amount of the martensite–austenite constituent (M–A) phase in the TM steels containing 1.0 mass% chromium.
Optimization of Flow Field in Slab Continuous Casting Mold with Medium Width Using High Temperature Measurement and Numerical Simulation for Automobile Exposed Panel Production
Authors: Jiang Peng , Yang Jian , Zhang Tao , Xu Gangjun , Liu Hongjun , Zhou Junjun , Qin Wei
Published: December 2019

In the present work, mathematical modeling combined with measurement of the velocities near mold surface with rod deflecting method at the high temperature was carried out to optimize the flow field of slab continuous casting mold with medium width of 1230 mm for the production of an automobile exposed panel. The results show that the measured results of the velocities near the mold surface are in good agreement with the calculated results. The velocities near the mold surface increase with increasing the casting speed and decreasing the argon gas flow rate. When the casting speed is increased from 1.0, to 1.3, 1.5, and 2.0 m/min, the flow pattern in the mold is changed from single-roll flow (SRF), to unstable flow (UF), and then to double-roll flow (DRF), the top surface level fluctuations has the smallest value at 1.5 m/min. When the argon gas flow rate is 1 and 4 L/min, the velocity near the mold surface has a moderate value, and the flow pattern in the mold is DRF and the top surface level fluctuation is small and symmetrical. When the submerged entry nozzle (SEN) submergence depth is increased to 200 mm, the velocities near the mold surface decrease, and the top surface level fluctuation becomes small. The optimized flow field in the mold can be judged to be favorable to the surface quality of the automobile exposed panel; if the velocities near the mold surface are relatively small, the flow pattern in the mold is DRF and the top surface level fluctuation is small and symmetrical.
Transient Softening at the Fusion Boundary of Resistance Spot Welds: A Phase Field Simulation and Experimental Investigations for Al–Si-coated 22MnB5
Authors: Sherepenko Oleksii , Kazemi Omid , Rosemann Paul , Wilke Markus , Halle Thorsten , Jüttner Sven
Published: December 2019

This work gives an insight into the transient softening at the fusion boundary of resistance spot welds on hot stamped steel. Metallographic investigations and hardness mapping were combined with finite phase–field modeling of phase evolution at the fusion boundary. Saturation of weld nugget growth in the welding process was observed. For industrially relevant, long welding times, the fusion boundary of a spot weld is therefore isothermally soaked between the peritectic and solidus temperatures. This leads to a carbon segregation to the liquid phase due to higher carbon solubility and possibly to δ-Fe formation at the fusion boundary. Both results in a local carbon depletion at the fusion boundary. This finding is in good agreement with carbon content measurements at the fusion boundary and the results of hardness measurements.
Structural and Electrochemical Properties of Nesting and Core/Shell Pt/TiO2 Spherical Particles Synthesized by Ultrasonic Spray Pyrolysis
Authors: Košević Milica G. , Zarić Milana M. , Stopić Srećko R. , Stevanović Jasmina S. , Weirich Thomas E. , Friedrich Bernd G. , Panić Vladimir V.
Published: December 2019

Pt/TiO2 composites were synthesized by single-step ultrasonic spray pyrolysis (USP) at different temperatures. In an in-situ method, Pt and TiO2 particles were generated from tetra-n-butyl orthotitanate and chloroplatinic acid, and hydrothermally-prepared TiO2 colloidal dispersion served as Pt support in an ex-situ USP approach. USP-synthesized Pt/TiO2 composites were generated in the form of a solid mixture, morphologically organized in nesting huge hollow and small solid spheres, or TiO2 core/Pt shell regular spheroids by in-situ or ex-situ method, respectively. This paper exclusively reports on characteristic mechanisms of the formation of novel two-component solid composites, which are intrinsic from the USP approach and controlled precursor composition. The generation of the two morphological components within the in-situ approach, the hollow spheres and all-solid spheres, was indicated to be caused by characteristic sol-gel/solid phase transition of TiO2. Both the walls of the hollow spheres and the cores of all-solid ones consist of TiO2 matrix populated by 10 nm-sized Pt. On the other hand, spherical, uniformly-sized, Pt particles of a few nanometers in size created a shell uniformly deposited onto TiO2 spheres of ca. 150 nm size. Activities of the prepared samples in an oxygen reduction reaction and combined oxygen reduction and hydrogen evolution reactions were electrochemically tested. The ex-situ synthesized Pt/TiO2 was more active for oxygen reduction and combined oxygen reduction and hydrogen reactions in comparison to the in-situ Pt/TiO2 samples, due to better availability of Pt within a core/shell structure for the reactions.
Characterization and Corrosion Resistance Behavior of Shape Memory Stainless Steel Developed by Alternate Routes
Authors: Dias David , Nakamatsu Sandra , Della Rovere Carlos Alberto , Otubo Jorge , Mariano Neide Aparecida
Published: December 2019

The microstructural characterization and corrosion resistance behavior of Fe-Mn-Si-Cr-Ni alloy with shape memory effect was studied under different mechanical processing conditions and heat treatments, which were produced using conventional casting and routing methods to reduce costs and make production viable. Microstructural characterization was performed with electron microscopy and x-ray diffraction techniques, electrochemical tests with polarization, and thermogravimetry techniques. The cast condition presented a dendritic structure and the presence of the secondary phases: ferrite-δ and Chi-X phase. The heat treatment eliminated phases, reincorporated elements in the matrix, and increased the austenitic grain. After the hot rolling process, the alloy exhibited a refined microstructure with recrystallized austenitic grains. The heat-treated condition presented better oxidation resistance than the other conditions, while the hot-rolled condition showed repassivation of the pits, raising them to higher levels. All conditions presented low corrosion resistance in environments containing chloride ions.
High-Speed Deformation of Pinless FSWed Thin Sheets in AA6082 Alloy
Authors: Forcellese Archimede , Simoncini Michela
Published: December 2019

The high-speed deformation behavior of friction stir-welded thin sheets in AA6082-T6 aluminum alloy, under biaxial balanced stretching, was investigated by means of a hemispherical punch test carried out using direct tension-compression Split Hopkinson Bar. The friction stir welding process was performed on thin sheet blanks using a pinless tool; the rotational and welding speeds were kept constant during process. The dynamic tests were carried out, with a punch speed of 4500 mm/s, at different punch stroke values until failure of the friction stir welded sample. It was seen that failure occurs along the welding line at a dome height about 11% higher than that at the onset of necking. Fractographic analysis shows that deformation is localized in the fracture zone. The results were compared with those obtained on friction stir welded blanks deformed under quasi-static condition in order to evaluate the influence of the loading rate on the weld deformation and fracture mechanisms. It was shown that joints deformed under dynamic loading condition are characterized by a dome height at the onset of necking significantly higher than the one measured under quasi-static condition.