Academic Journals

Nucleation behavior of ω o phase in TiAl alloys at different elevated temperatures

The Behavior Analyst - Sun, 04/01/2018 - 00:00
Abstract

In this study, the location, morphology and composition of the ωo phase, which transformed from B2 phase in Ti–45Al–8.5Nb-(W, B, Y) (at.%) alloy, were investigated by short-time heat treatments in an intermediate temperature range. The results showed that the characteristics of B2 → ωo phase transformation differ with the reduction in temperature. Below the ωo solves, the B2 → ωo phase transformation will take place within B2 area. There are existing two stages in the phase transformations during cooling from 850 to 700 °C. When the temperature is high (850 °C), granular ωo populated along the dislocations existing in B2 phase and B2 grain boundaries, due to higher energy and the enrichment of Nb element at the B2/γ boundaries. It is worth noting that only two ωo variants nucleate at 850 °C. With the decrease in temperature, the nucleation sites of ωo phase would be migrated from the B2 boundaries to the inner area. At the temperature of 700 °C, four ωo variants with different orientations nucleate homogenously within B2 grain. The ordered ωo formation process of Ti–45Al–8.5Nb-(W, B, Y) alloy during cooling was postulated in this study.

Categories: Academic Journals

Enhancing the reactivity of aluminosilicate materials toward geopolymer synthesis

The Behavior Analyst - Sun, 04/01/2018 - 00:00
Abstract

Geopolymers are alternative materials to portland cement, obtained by alkaline activation of aluminosilicates. They exhibit excellent properties and a wide range of potential applications in the field of civil engineering. Several natural aluminosilicates and industrial by-products can be used for geopolymer synthesis, but a lot of starting materials have the disadvantage of poor reactivity and low strength development. This paper presents a comprehensive review of the main methods used to alter the reactivity of aluminosilicate materials for geopolymer synthesis, as reported recently in the literature. The methods consist of mechanical, thermal, physical separation and chemical activation, of which mechanical activation is the most commonly employed technique. The reactivity of the activated aluminosilicate materials is mainly related to the activation method and the treatment parameters. Chemical activation by alkaline fusion is a promising method allowing preparation of one-part geopolymer materials, an alternative class of geopolymeric binders. However, the resulting alkaline-fused geopolymer products are vulnerable to attack by excessive alkalis.

Categories: Academic Journals

A three-dimensional porous hydroxyapatite nanocomposite scaffold with shape memory effect for bone tissue engineering

The Behavior Analyst - Sun, 04/01/2018 - 00:00
Abstract

It is known that scaffold is a key factor in bone tissue engineering. The aim of this study was to improve the design of scaffold in order to achieve an effect of precisely matching the irregular boundaries of bone defects as well as facilitate clinical application. In this study, controllable three-dimensional porous shape memory polyurethane/nano-hydroxyapatite composite scaffolds were successfully fabricated. Detailed studies were performed to evaluate its structure, porosities, and mechanical properties, emphasizing the effect of different apertures of scaffolds on shape recovery behaviors and biological performance in vitro. Results showed its compression recovery ratios and shape recovery ratios of all scaffolds could reach more than 99 and 90%, respectively, which could let it more accurately match the irregular boundaries of bone defects. And also its cell proliferation ability was improved with the increase in the apertures. Thus, these scaffolds have potential applications for the bone tissue engineering.

Categories: Academic Journals

Improved electrochemical performance of bagasse and starch-modified LiNi 0.5 Mn 0.3 Co 0.2 O 2 materials for lithium-ion batteries

The Behavior Analyst - Sun, 04/01/2018 - 00:00
Abstract

Organic carbon-coated LiNi0.5Mn0.3Co0.2O2 materials are prepared by mixing 2 or 5% starch or bagasse evenly with the synthesized LiNi0.5Mn0.3Co0.2O2 material and calcining for 10 h at 750 °C. The microstructures and electrochemical performance are investigated by X-ray diffraction, scanning electron microscopy, carbon/sulfur analysis, transmission electron microscopy and electrochemical testing. The results indicate that the organic carbon coated on the surface of LiNi0.5Mn0.3Co0.2O2 material does not change the surface morphology and crystal structure, but greatly improves the conductivity, rate and cycle performance of the LiNi0.5Mn0.3Co0.2O2 cathode in a Li-ion battery. The initial discharge capacity of the synthesized LiNi0.5Mn0.3Co0.2O2 material is 147.8 mAh g−1, which increases to 152.4 and 153.3 mAh g−1 for 2% starch and bagasse, respectively. After 100 cycles, the capacity retention rates are 70.7% (uncoated), 83.3% (coated with 2% starch), 90.1% (coated with 2% bagasse), 83.1% (coated with 5% starch) and 91.1% (coated with 5% bagasse). The influence of the percentage of coated carbon and its dispersion uniformity on the performance of the battery is analyzed. A small coating capacity and uniform carbon film can achieve better performance. Rational organic carbon coating technology is an effective way to improve the electrochemical performance of LiNi1−xy Mn x Co y O2-based material.

Categories: Academic Journals

Topological Fulde-Ferrell and Larkin-Ovchinnikov states in spin-orbit-coupled lattice system

The Psychological Record - Sun, 04/01/2018 - 00:00
Abstract

The spin-orbit coupled lattice system under Zeeman fields provides an ideal platform to realize exotic pairing states. Notable examples range from the topological superfluid/superconducting (tSC) state, which is gapped in the bulk but metallic at the edge, to the Fulde-Ferrell (FF) state (having a phase-modulated order parameter with a uniform amplitude) and the Larkin-Ovchinnikov (LO) state (having a spatially varying order parameter amplitude). Here, we show that the topological FF state with Chern number (C = -1) (tFF1) and topological LO state with C= 2 (tLO2) can be stabilized in Rashba spin-orbit coupled lattice systems in the presence of both in-plane and out-of-plane Zeeman fields. Besides the inhomogeneous tSC states, in the presence of a weak in-plane Zeeman field, two topological BCS phases may emerge with C = -1 (tBCS1) far from half filling and C = 2 (tBCS2) near half filling. We show intriguing effects such as different spatial profiles of order parameters for FF and LO states, the topological evolution among inhomogeneous tSC states, and different non-trivial Chern numbers for the tFF1 and tLO1,2 states, which are peculiar to the lattice system. Global phase diagrams for various topological phases are presented for both half-filling and doped cases. The edge states as well as local density of states spectra are calculated for tSC states in a 2D strip.

Categories: Academic Journals

Topological Fulde-Ferrell and Larkin-Ovchinnikov states in spin-orbit-coupled lattice system

The Behavior Analyst - Sun, 04/01/2018 - 00:00
Abstract

The spin-orbit coupled lattice system under Zeeman fields provides an ideal platform to realize exotic pairing states. Notable examples range from the topological superfluid/superconducting (tSC) state, which is gapped in the bulk but metallic at the edge, to the Fulde-Ferrell (FF) state (having a phase-modulated order parameter with a uniform amplitude) and the Larkin-Ovchinnikov (LO) state (having a spatially varying order parameter amplitude). Here, we show that the topological FF state with Chern number (C = -1) (tFF1) and topological LO state with C= 2 (tLO2) can be stabilized in Rashba spin-orbit coupled lattice systems in the presence of both in-plane and out-of-plane Zeeman fields. Besides the inhomogeneous tSC states, in the presence of a weak in-plane Zeeman field, two topological BCS phases may emerge with C = -1 (tBCS1) far from half filling and C = 2 (tBCS2) near half filling. We show intriguing effects such as different spatial profiles of order parameters for FF and LO states, the topological evolution among inhomogeneous tSC states, and different non-trivial Chern numbers for the tFF1 and tLO1,2 states, which are peculiar to the lattice system. Global phase diagrams for various topological phases are presented for both half-filling and doped cases. The edge states as well as local density of states spectra are calculated for tSC states in a 2D strip.

Categories: Academic Journals

Prevalence of Military Sexual Trauma and Sexual Orientation Discrimination Among Lesbian, Gay, Bisexual, and Transgender Military Personnel: a Descriptive Study

The Psychological Record - Thu, 03/01/2018 - 00:00
Abstract

Despite the repeal of Don’t Ask, Don’t Tell, Don’t Pursue (DADT) and the update to the Transgender Policy, there remain concerns about the persistence of military sexual trauma (MST) and sexual orientation discrimination against lesbian, gay, bisexual, and transgender (LGBT) service members. A sample of 253 participants (89 women, 164 men) completed an Internet-based survey that assessed the prevalence of sexual orientation discrimination (e.g., offensive speech, physical or discriminatory behaviors) and MST (e.g., sexual harassment and sexual assault). The survey was conducted between April 2012 and October 2013. Women and men reported similar levels of sexual orientation discrimination in the military. Participants reported experiencing more threats and intimation, vandalism, and physical assault outside of the military than inside the military (p < 0.05). Although the prevalence of MST (both sexual harassment and sexual assault) in the military was high among both genders, women were more likely to report experiences of sexual harassment compared to men (p < 0.05). Our findings demonstrate the prevalence of MST and sexual orientation discrimination among LGBT service members in the military and point to the need for strong accountability and oversight to protect sexual minority persons while they are serving their country.

Categories: Academic Journals

Prevalence of Military Sexual Trauma and Sexual Orientation Discrimination Among Lesbian, Gay, Bisexual, and Transgender Military Personnel: a Descriptive Study

The Behavior Analyst - Thu, 03/01/2018 - 00:00
Abstract

Despite the repeal of Don’t Ask, Don’t Tell, Don’t Pursue (DADT) and the update to the Transgender Policy, there remain concerns about the persistence of military sexual trauma (MST) and sexual orientation discrimination against lesbian, gay, bisexual, and transgender (LGBT) service members. A sample of 253 participants (89 women, 164 men) completed an Internet-based survey that assessed the prevalence of sexual orientation discrimination (e.g., offensive speech, physical or discriminatory behaviors) and MST (e.g., sexual harassment and sexual assault). The survey was conducted between April 2012 and October 2013. Women and men reported similar levels of sexual orientation discrimination in the military. Participants reported experiencing more threats and intimation, vandalism, and physical assault outside of the military than inside the military (p < 0.05). Although the prevalence of MST (both sexual harassment and sexual assault) in the military was high among both genders, women were more likely to report experiences of sexual harassment compared to men (p < 0.05). Our findings demonstrate the prevalence of MST and sexual orientation discrimination among LGBT service members in the military and point to the need for strong accountability and oversight to protect sexual minority persons while they are serving their country.

Categories: Academic Journals

The Riemann Problem for the Multidimensional Isentropic System of Gas Dynamics is Ill-Posed if It Contains a Shock

The Psychological Record - Thu, 03/01/2018 - 00:00
Abstract

In this paper we consider the isentropic compressible Euler equations in two space dimensions together with particular initial data. This data consists of two constant states, where one state lies in the lower and the other state in the upper half plane. The aim is to investigate whether there exists a unique entropy solution or if the convex integration method produces infinitely many entropy solutions. For some initial states this question has been answered by Feireisl and Kreml (J Hyperbolic Differ Equ 12(3):489–499, 2015), and also Chen and Chen (J Hyperbolic Differ Equ 4(1):105–122, 2007), where there exists a unique entropy solution. For other initial states Chiodaroli and Kreml (Arch Ration Mech Anal 214(3):1019–1049, 2014) and Chiodaroli et al. (Commun Pure Appl Math 68(7):1157–1190, 2015), showed that there are infinitely many entropy solutions. For still other initial states the question on uniqueness remained open and this will be the content of this paper. This paper can be seen as a completion of the aforementioned papers by showing that the solution is non-unique in all cases (except if the solution is smooth).

Categories: Academic Journals

Homogeneous Solutions of Stationary Navier–Stokes Equations with Isolated Singularities on the Unit Sphere. I. One Singularity

The Psychological Record - Thu, 03/01/2018 - 00:00
Abstract

We classify all (−1)-homogeneous axisymmetric no-swirl solutions of incompressible stationary Navier–Stokes equations in three dimension which are smooth on the unit sphere minus the south pole, parameterize them as a two dimensional surface with boundary, and analyze their pressure profiles near the north pole. Then we prove that there is a curve of (−1)-homogeneous axisymmetric solutions with nonzero swirl, having the same smoothness property, emanating from every point of the interior and one part of the boundary of the solution surface. Moreover we prove that there is no such curve of solutions for any point on the other part of the boundary. We also establish asymptotic expansions for every (−1)-homogeneous axisymmetric solutions in a neighborhood of the singular point on the unit sphere.

Categories: Academic Journals

The Riemann Problem for the Multidimensional Isentropic System of Gas Dynamics is Ill-Posed if It Contains a Shock

The Behavior Analyst - Thu, 03/01/2018 - 00:00
Abstract

In this paper we consider the isentropic compressible Euler equations in two space dimensions together with particular initial data. This data consists of two constant states, where one state lies in the lower and the other state in the upper half plane. The aim is to investigate whether there exists a unique entropy solution or if the convex integration method produces infinitely many entropy solutions. For some initial states this question has been answered by Feireisl and Kreml (J Hyperbolic Differ Equ 12(3):489–499, 2015), and also Chen and Chen (J Hyperbolic Differ Equ 4(1):105–122, 2007), where there exists a unique entropy solution. For other initial states Chiodaroli and Kreml (Arch Ration Mech Anal 214(3):1019–1049, 2014) and Chiodaroli et al. (Commun Pure Appl Math 68(7):1157–1190, 2015), showed that there are infinitely many entropy solutions. For still other initial states the question on uniqueness remained open and this will be the content of this paper. This paper can be seen as a completion of the aforementioned papers by showing that the solution is non-unique in all cases (except if the solution is smooth).

Categories: Academic Journals

Homogeneous Solutions of Stationary Navier–Stokes Equations with Isolated Singularities on the Unit Sphere. I. One Singularity

The Behavior Analyst - Thu, 03/01/2018 - 00:00
Abstract

We classify all (−1)-homogeneous axisymmetric no-swirl solutions of incompressible stationary Navier–Stokes equations in three dimension which are smooth on the unit sphere minus the south pole, parameterize them as a two dimensional surface with boundary, and analyze their pressure profiles near the north pole. Then we prove that there is a curve of (−1)-homogeneous axisymmetric solutions with nonzero swirl, having the same smoothness property, emanating from every point of the interior and one part of the boundary of the solution surface. Moreover we prove that there is no such curve of solutions for any point on the other part of the boundary. We also establish asymptotic expansions for every (−1)-homogeneous axisymmetric solutions in a neighborhood of the singular point on the unit sphere.

Categories: Academic Journals

A Duality Approach for a Class of Semivectorial Bilevel Programming Problems

The Psychological Record - Thu, 03/01/2018 - 00:00
Abstract

In this paper, we present a duality approach using conjugacy for a semivectorial bilevel programming problem (S) where the upper and lower levels are vectorial and scalar respectively. This approach uses the Fenchel–Lagrange duality and is given via a regularization of problem (S) and the operation of scalarization. Then, using this approach, we provide necessary optimality conditions for a class of properly efficient solutions of (S). Finally, sufficient optimality conditions are given for (S) regardless of the duality approach. Examples are given for illustration.

Categories: Academic Journals

A Duality Approach for a Class of Semivectorial Bilevel Programming Problems

The Behavior Analyst - Thu, 03/01/2018 - 00:00
Abstract

In this paper, we present a duality approach using conjugacy for a semivectorial bilevel programming problem (S) where the upper and lower levels are vectorial and scalar respectively. This approach uses the Fenchel–Lagrange duality and is given via a regularization of problem (S) and the operation of scalarization. Then, using this approach, we provide necessary optimality conditions for a class of properly efficient solutions of (S). Finally, sufficient optimality conditions are given for (S) regardless of the duality approach. Examples are given for illustration.

Categories: Academic Journals

Automatic performance prediction of multithreaded programs: a simulation approach

The Psychological Record - Thu, 03/01/2018 - 00:00
Abstract

The performance of multithreaded programs is often difficult to understand and predict. Multiple threads engage in synchronization operations and use hardware simultaneously. This results in a complex non-linear dependency between the configuration of a program and its performance. To better understand this dependency a performance prediction model is used. Such a model predicts the performance of a system for different configurations. Configurations reflect variations in the workload, different program options such as the number of threads, and characteristics of the hardware. Performance models are complex and require a solid understanding of the program’s behavior. As a result, building models of large applications manually is extremely time-consuming and error-prone. In this paper we present an approach for building performance models of multithreaded programs automatically. We employ hierarchical discrete-event models. Different tiers of the model simulate different factors that affect performance of the program, while interaction between the model tiers simulates mutual influence of these factors on performance. Our framework uses a combination of static and dynamic analyses of a single representative run of a system to collect information required for building the performance model. This includes information about the structure of the program, the semantics of interaction between the program’s threads, and resource demands of individual program’s components. In our experiments we demonstrate that models accurately predict the performance of various multithreaded programs, including complex industrial applications.

Categories: Academic Journals

Automatic performance prediction of multithreaded programs: a simulation approach

The Behavior Analyst - Thu, 03/01/2018 - 00:00
Abstract

The performance of multithreaded programs is often difficult to understand and predict. Multiple threads engage in synchronization operations and use hardware simultaneously. This results in a complex non-linear dependency between the configuration of a program and its performance. To better understand this dependency a performance prediction model is used. Such a model predicts the performance of a system for different configurations. Configurations reflect variations in the workload, different program options such as the number of threads, and characteristics of the hardware. Performance models are complex and require a solid understanding of the program’s behavior. As a result, building models of large applications manually is extremely time-consuming and error-prone. In this paper we present an approach for building performance models of multithreaded programs automatically. We employ hierarchical discrete-event models. Different tiers of the model simulate different factors that affect performance of the program, while interaction between the model tiers simulates mutual influence of these factors on performance. Our framework uses a combination of static and dynamic analyses of a single representative run of a system to collect information required for building the performance model. This includes information about the structure of the program, the semantics of interaction between the program’s threads, and resource demands of individual program’s components. In our experiments we demonstrate that models accurately predict the performance of various multithreaded programs, including complex industrial applications.

Categories: Academic Journals

NSE characterization of the Chevalley group $$\varvec{G}_{\varvec{2}} {\varvec{(4)}}$$...

The Psychological Record - Thu, 03/01/2018 - 00:00
Abstract

Let G be a group and \(\omega (G)=\{o(g)|g\in G\}\) be the set of element orders of G. Let \(k\in \omega (G)\) and \(s_k=|\{g\in G |o(g)=k\}|\) . Let \(nse(G)=\{s_k|k\in \omega (G) \}\) . In this paper, we prove that if G is a group and \(G_2 (4)\) is the Chevalley group such that \(nse(G)=nse(G_2 (4))\) , then \(G\cong G_2 (4)\) .

Categories: Academic Journals

General solution for MHD-free convection flow over a vertical plate with ramped wall temperature and chemical reaction

The Psychological Record - Thu, 03/01/2018 - 00:00
Abstract

The aim of the article is to study the unsteady magnetohydrodynamic-free convection flow of an electrically conducting incompressible viscous fluid over an infinite vertical plate with ramped temperature and constant concentration. The motion of the plate is a rectilinear translation with an arbitrary time-dependent velocity. Closed-form solutions for the temperature, concentration and velocity fields of the fluid are obtained. The influence of transverse magnetic field that is fixed relative either to fluid or plate is studied. Furthermore, the effects of system parameters on the fluid velocity are analyzed through numerical simulations and graphical illustrations.

Categories: Academic Journals

NSE characterization of the Chevalley group $$\varvec{G}_{\varvec{2}} {\varvec{(4)}}$$...

The Behavior Analyst - Thu, 03/01/2018 - 00:00
Abstract

Let G be a group and \(\omega (G)=\{o(g)|g\in G\}\) be the set of element orders of G. Let \(k\in \omega (G)\) and \(s_k=|\{g\in G |o(g)=k\}|\) . Let \(nse(G)=\{s_k|k\in \omega (G) \}\) . In this paper, we prove that if G is a group and \(G_2 (4)\) is the Chevalley group such that \(nse(G)=nse(G_2 (4))\) , then \(G\cong G_2 (4)\) .

Categories: Academic Journals

General solution for MHD-free convection flow over a vertical plate with ramped wall temperature and chemical reaction

The Behavior Analyst - Thu, 03/01/2018 - 00:00
Abstract

The aim of the article is to study the unsteady magnetohydrodynamic-free convection flow of an electrically conducting incompressible viscous fluid over an infinite vertical plate with ramped temperature and constant concentration. The motion of the plate is a rectilinear translation with an arbitrary time-dependent velocity. Closed-form solutions for the temperature, concentration and velocity fields of the fluid are obtained. The influence of transverse magnetic field that is fixed relative either to fluid or plate is studied. Furthermore, the effects of system parameters on the fluid velocity are analyzed through numerical simulations and graphical illustrations.

Categories: Academic Journals

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