In this paper, we study four-dimensional topological black hole solutions of Einsteinian cubic gravity in the presence of nonlinear Born–Infeld electrodynamics and a bare cosmological constant. ...First, we obtain the field equations which govern our solutions. Employing Abbott–Deser–Tekin and Gauss formulas, we present the expressions of conserved quantities, namely total mass and total charge of our topological black solutions. We disclose the conditions under which the model is unitary and perturbatively free of ghosts with asymptotically (A)dS and flat solutions. We find that, for vanishing bare cosmological constant, the model is unitary just for asymptotically flat solutions, which only allow horizons with spherical topology. We compute the temperature for these solutions and show that it always has a maximum value, which decreases as the values of charge, nonlinear coupling or cubic coupling grows. Next, we calculate the entropy and electric potential. We show that the first law of thermodynamics is satisfied for spherical asymptotically flat solutions. Finally, we peruse the effects of model parameters on thermal stability of these solutions in both canonical and grand canonical ensembles.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Enhancement of the heat transfer rate inside the double pipe heat exchangers is significant for industrial applications. In present work, the usage of non-uniform magnetic field on the heat transfer ...rate of the nanofluid flow streamed inside double pipe heat exchangers are comprehensively studied. Computational technique of CFD is used for the visualization of the nanofluid hydrodynamic in existence of the magnetic source. Influences of the magnetic intensity and nanofluid velocity on the heat transfer are also presented. Simple algorithm is used for the modeling of the incompressible nanofluid flow with addition of magnetic source. Presented results show that magnetic source intensifies the formation of the circulation in the gap of the inner tube and consequently, heat transfer is enhanced in our domain. Comparison of different geometries of tube reveals that the triangle tube is more efficient for improvement of the heat transfer of nanofluid flow. Our results indicate that heat transfer in the tube with triangular shape is more than other configurations and its performance is 15% more than smooth tube.
•Pretwins changed the dominant mechanism during deformation of AZ31 alloy.•Detwinning and twin growth were observed to be ceased at 250 C.•The pretwins increased the grain size and fraction of DRX at ...250 C.•Pretwins could modify the grain boundary characteristics.•Pretwins influenced DRX texture obtained after compression along normal direction.
In this work, the effects of pretwins on the flow behavior, microstructure, and texture evolution of a rolled AZ31 magnesium alloy during hot deformation along three different orthogonal directions were studied via compression tests conducted at 25–350 °C. The flow behavior along different directions was discussed based on the operation of different deformation mechanisms in twinned and untwinned regions. Detwinning was the dominant deformation mechanism during compression in the normal direction at low temperatures, but ceased as the temperature increased to 250 °C. In the latter condition, the effect of pretwins on the texture reorientation led to a decrease in the yield strength. Pretwins stimulate the microstructure condition preceding dynamic recrystallization (DRX) during the compression of samples along the rolling and transverse directions, leading to lower peak strains. The results showed that the pretwins increased the grain size and fraction of DRX at 250 °C. The greatest increase in the DRX fraction was obtained for deformation parallel to the normal direction. The effect of pretwins on the grain boundary characteristics of the samples deformed along the normal direction was investigated. The pretwinned samples showed more significant texture rotation for dynamically recrystallized grains compared with parent grains during deformation parallel to the normal direction.
Hydrological observatories bear a lot of resemblance to the more traditional research catchment concept, but tend to differ in providing more long-term facilities that transcend the lifetime of ...individual projects, are more strongly geared towards performing interdisciplinary research, and are often designed as networks to assist in performing collaborative science. This paper illustrates how the experimental and monitoring set-up of an observatory, the 66 ha Hydrological Open Air Laboratory (HOAL) in Petzenkirchen, Lower Austria, has been established in a way that allows meaningful hypothesis testing. The overarching science questions guided site selection, identification of dissertation topics and the base monitoring. The specific hypotheses guided the dedicated monitoring and sampling, individual experiments, and repeated experiments with controlled boundary conditions. The purpose of the HOAL is to advance the understanding of water-related flow and transport processes involving sediments, nutrients and microbes in small catchments. The HOAL catchment is ideally suited for this purpose, because it features a range of different runoff generation processes (surface runoff, springs, tile drains, wetlands), the nutrient inputs are known, and it is convenient from a logistic point of view as all instruments can be connected to the power grid and a high-speed glassfibre local area network (LAN). The multitude of runoff generation mechanisms in the catchment provides a genuine laboratory where hypotheses of flow and transport can be tested, either by controlled experiments or by contrasting sub-regions of different characteristics. This diversity also ensures that the HOAL is representative of a range of catchments around the world, and the specific process findings from the HOAL are applicable to a variety of agricultural catchment settings. The HOAL is operated jointly by the Vienna University of Technology and the Federal Agency for Water Management and takes advantage of the Vienna Doctoral Programme on Water Resource Systems funded by the Austrian Science Funds. The paper presents the science strategy of the set-up of the observatory, discusses the implementation of the HOAL, gives examples of the hypothesis testing and summarises the lessons learned. The paper concludes with an outlook on future developments.
In this work, cristobalite crystallization and its effects on mechanical and chemical behaviour of injection moulded silica-based ceramic cores were investigated. In order to simulate casting process ...condition, the sintered samples at 1220°C were also heated up to 1430°C. Flexural strength test was carried out on both sintered and heat treated samples. Chemical resistance of the cores was evaluated by leaching the samples inside 43wt% KOH solution at its boiling point. Phase evolution and microstructure were investigated by thermal analyses (DTA and DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and optical microscopy (OM). Results showed that cristobalite was crystallized on the surface of fused silica grains at about 1380°C. Flexural strength of the sintered cores was decreased after simulated casting heat treatment due to cristobalite phase transformation. The formed cristobalite on the surface of fused silica grains dramatically decreased the leachability of ceramic cores.
Multi-layered Al/Cu composites were produced by accumulative roll bonding (ARB) process using Al 1100 and Cu strips. It was observed that as passes of ARB proceeded, copper layers were necked and ...fractured. After five ARB passes, a multi-layer Al/Cu composite including homogeneously distributed fragmented copper layers in an aluminum matrix was achieved. Structure and mechanical properties of these composites were studied within different stages of ARB process. With increasing strain during ARB passes strength, microhardness, and elongation of these composites increased. Enhancement of the strength is higher than the tensile strength of Al/Al multi-layered strips produced by ARB process. Fracture surfaces after tensile tests were examined by scanning electron microscopy (SEM). Observation revealed that rupture mode after ARB process is shear ductile fracture.
Summary
We assessed the impact of weight loss strategies including calorie restriction and exercise training on BMD in adults using a systematic review of randomized controlled trials. Weight ...reduction results in reduced BMD at the hip, but has less effect on the spine. Both calorie restriction and a combination of calorie restriction and exercise result in a decrease in hip bone density, whereas weight loss response to exercise training without dietary restriction leads to increased hip BMD.
Introduction
Findings are not consistent on the effect of weight loss on bone mineral density (BMD). We conducted a systematic review on the randomized controlled trials to assess the effect of weight loss strategies, including calorie restriction and exercise programs on BMD in adults.
Methods
A structured and comprehensive search of MEDLINE and EMBASE databases was undertaken up to March 2016. Study-specific mean differences (MD) were pooled using a random-effects model. Subgroup analysis and meta-regression were used to find possible sources of between-study heterogeneity.
Results
Thirty-two randomized controlled trials met predetermined inclusion criteria. The meta-analysis revealed no significant difference on total BMD (MD 0.007, 95 % CI −0.020–0.034,
p
= 0.608). In contrast, the pooled data of studies showed a significant effect of weight loss on hip BMD (MD −0.008, 95 % CI −0.09 to −0.006 g/cm
2
,
p
< 0.001) and also lumbar spine BMD (MD −0.018 g/cm
2
, 95 % CI −0.019 to −0.017,
p
< 0.001). BMD in the hip site decreased after more than 4 months, especially in those who were obese. Moreover, calorie restriction interventions longer than 13 months showed a significant decreased in lumbar spine BMD.
Conclusion
Weight loss led to significant decreases at the hip and lumbar spine BMD but not at the total. Weight loss response following calorie restriction resulted in a decrease in hip and lumbar spine bone density especially more than 1 year; whereas an exercise-induced weight loss did not.
In this paper, a bio-inspired computational intelligence technique is presented for solving nonlinear doubly singular system using artificial neural networks (ANNs), genetic algorithms (GAs), ...sequential quadratic programming (SQP) and their hybrid GA–SQP. The power of ANN models is utilized to develop a fitness function for a doubly singular nonlinear system based on approximation theory in the mean square sense. Global search for the parameters of networks is performed with the competency of GAs and later on fine-tuning is conducted through efficient local search by SQP algorithm. The design methodology is evaluated on number of variants for two point doubly singular systems. Comparative studies with standard results validate the correctness of proposed schemes. The consistent correctness of the proposed technique is proven through statistics using different performance indices.
This paper provides new formulations to derive the impulse response matrix, which is then used in the problem of load identification with application to wind induced vibration. The applied loads are ...inversely identified based on the measured structural responses by solving the associated discrete ill-posed problem. To this end — based on an existing parametric structural model — the impulse response functions of acceleration, velocity and displacement have been computed. Time discretization of convolution integral has been implemented according to an existing and a newly proposed procedure, which differ in the numerical integration methods. The former was evaluated based on a constant rectangular approximation of the sampled data and impulse response function in a number of steps corresponding to the sampling rate, while the latter interpolates the sampled data in an arbitrary number of sub-steps and then integrates over the sub-steps and steps. The identification procedure was implemented for a simulation example as well as an experimental laboratory case. The ill-conditioning of the impulse response matrix made it necessary to use Tikhonov regularization to recover the applied force from noise polluted measured response. The optimal regularization parameter has been obtained by L-curve and GCV method. The results of simulation represent good agreement between identified and measured force. In the experiments the identification results based on the measured displacement as well as acceleration are provided. Further it is shown that the accuracy of experimentally identified load depends on the sensitivity of measurement instruments over the different frequency ranges.
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