Natural convection is one of the most important modes of fluid flow and heat transfer. This paper presents a review of the research on turbulent natural convection in rectangular cavities using ...numerical and experimental techniques. In this review we have attempted to summarize the published papers on this topic with some interesting and important results. Numerous configurations of the enclosures with different initial and boundary conditions, heat source locations and radiative properties of medium and walls have been considered under the effects of various parameters such as the Rayleigh and Prandtl numbers, surface emissivity, cavity inclination angle, thermal properties, etc. Finally, some suggestions have been provided for future studies in the considered area.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
A number of fracture criteria are available for predicting the cracking behavior under combined contribution of opening-tearing damage mechanism (i.e. mixed-mode I/III). But most of them have some ...limitations or discrepancies with the experimental results. In this research, a new form of maximum tangential strain criterion called 3D-MTSN is developed for predicting mixed-mode I/III fracture phenomenon. This criterion was used originally for analyzing the mixed-mode I/II fracture but we extended its ability for mixed mode I/III as well. Also, the influence of T-stress in addition to modes I and III stress intensity factors was also considered in driving the fracture toughness and fracture angle formulations of the 3D-MTSN criterion. According to this strain-based criterion it is shown that both sign and magnitude of T-stress can affect the fracture behavior of mixed mode I/III. In general, positive T-stress increases the mixed mode I/III fracture envelope and conversely negative sign of T-stress can decrease it. Meanwhile, the Poisson’s ratio (v) has noticeable influence on the mixed mode I/III fracture envelopes and by increasing v, the mixed mode fracture curve predicted by the generalized MTSN criterion shifts down except for those specimens having positive T-stress values and subjected to dominantly pure mode I loading conditions. The practical ability and validity of 3D-MTSN criterion is examined by predicting different sets of mixed mode I/III experimental results reported in the literature for different brittle and quasi-brittle materials tested with different test samples including edge-notch disc bend (ENDB), inclined single edge notch beam (ISENB) and semi-circular bend (SCB) specimens. A comprehensive comparison with the well-known 3D-MTS (stress-based) criterion was also performed. Compared to the other available energy-based fracture models, the presented 3D-MTSN criterion provided better estimations for the experimental results of different materials and specimens under dominantly mode III conditions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This paper proposes an innovative tuning approach for fuzzy control systems (CSs) with a reduced parametric sensitivity using the Grey Wolf Optimizer (GWO) algorithm. The CSs consist of servo system ...processes controlled by Takagi-Sugeno-Kang proportional-integral fuzzy controllers (TSK PI-FCs). The process models have second-order dynamics with an integral component, variable parameters, a saturation, and dead-zone static nonlinearity. The sensitivity analysis employs output sensitivity functions of the sensitivity models defined with respect to the parametric variations of the processes. The GWO algorithm is used in solving the optimization problems, where the objective functions include the output sensitivity functions. GWO's motivation is based on its low-computational cost. The tuning approach is validated in an experimental case study of a position control for a laboratory nonlinear servo system, and TSK PI-FCs with a reduced process small time constant sensitivity are offered.
•The tensile response of Textile Reinforced Concrete can be softer compared to fabric.•The failure load of the composite may be lower with respect to the bare fabric.•Experimental observations can be ...justified by differential activation of filaments.•Bond lag can be implemented in a coaxial ring model for the composite.•Such approach allows calculating the cracked stiffness and failure load of the composite.
Textile Reinforced Concrete (TRC) is a cementitious composite material where a carbon or glass fabric is embedded as reinforcement. The use of TRC allows building thin and light structures, with reduced concrete covers and an enhanced durability due to the absence of corrosion problems. In this article, the response of TRC elements subjected to tension is reviewed by means of an experimental and theoretical investigation. A test programme comprising 28 specimens reinforced with uncoated and coated carbon textile fabrics is presented. Detailed measurements were performed by using Digital Image Correlation allowing to investigate on the crack development and failure in tension of the specimens. On this basis, a comprehensive approach to address the tensile response of TRC is presented based on a coaxial ring model incorporating different constitutive laws for the core and sleeve filaments and their interfaces. The model is observed to consistently predict the various responses measured experimentally, both in terms of the stabilised cracking phase and failure load, avoiding the need to consider empirical efficiency factors. The results are finally compared to available tests in the scientific literature showing consistent and fine agreement.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The main aim of this research is to investigate the performance of ammonia-powered microtubular solid oxide fuel cells in order to use ammonia as a possible candidate for eco-friendly and sustainable ...power generation systems. The performance of a direct ammonia-powered cell has been elucidated and validated with the experimental results of pure hydrogen gas at Niğde Ömer Halisdemir University Prof. T. Nejat Veziroğlu Clean Energy Research Center. For both studies, the cathode electrode is supplied with atmospheric air. The performance of anode, electrolyte, and cathode-supported microtubular solid oxide fuel cells has been compared numerically. The findings confirmed that the peak possible power densities obtained numerically using direct ammonia, hydrogen and experimentally using pure hydrogen gas are is 628.92 mW/cm2, 622.29 mW/cm2, and, 589.28 mW/cm2 respectively at the same geometrical dimensions, component materials, and operating parameters. Thus, the results of this study demonstrate that simultaneous experimental and numerical studies make a great contribution to minimizing biases due to literature data during model validation. The numerical simulation also indicates that the performance of cathode supported is superior to that of anode supported cells run with hydrogen and ammonia fuel. Likewise, parametric sweep analysis asserts that the working temperature has a greater effect than operating pressure on tubular cell performance. Therefore, the results of this study advise that ammonia will become a carbon-free alternative fuel for solid oxide fuel cells in the coming years.
•Numerical and experimental investigation of MT-SOFC has been conducted simultaneously.•The performance of AS-MT-SOFC is superior next to CS-MT-SOFC.•The effect of working cell temperature is more influential than the operating pressure.•The predicted maximum possible power density for direct ammonia fed is very close to hydrogen.•The numerical result suggested that ammonia will be the primary fuel for SOFCs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
6.
Optomechanical Dark Mode Dong, Chunhua; Fiore, Victor; Kuzyk, Mark C. ...
Science (American Association for the Advancement of Science),
12/2012, Volume:
338, Issue:
6114
Journal Article
Peer reviewed
Open access
Thermal mechanical motion hinders the use of a mechanical system in applications such as quantum information processing. Whereas the thermal motion can be overcome by cooling a mechanical oscillator ...to its motional ground state, an alternative approach is to exploit the use of a mechanically dark mode that can protect the system from mechanical dissipation. We have realized such a dark mode by coupling two optical modes in a silica resonator to one of its mechanical breathing modes in the regime of weak optomechanical coupling. The dark mode, which is a superposition of the two optical modes and is decoupled from the mechanical oscillator, can still mediate an effective optomechanical coupling between the two optical modes. We show that the formation of the dark mode enables the transfer of optical fields between the two optical modes. Optomechanical dark mode opens the possibility of using mechanically mediated coupling in quantum applications without cooling the mechanical oscillator to its motional ground state.
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A new optimization/statistical approach of “Robust Weighted Least Squares Support Vector Regression” algorithm (RWLS-SVR) is provided for the first time. The experimental achieved amounts of the ...thermal conductivity for a new hybrid nanofluid of water/Graphene Oxide–Silicon Carbide, are examined at different values of temperature and nanoparticles volume fraction. A Support Vector Regression is a supervised learning regression algorithm based on the Support Vector Machine methodology. However in the Least Squares Support Vector Machine method, the inequality constraints are converted to equality constraints and the sum squared error function is employed. Moreover a LS-SVR is applied to the problem in order to calculate the error variables. Afterwards, the weights computed based on the error variables are applied to the optimization problem in order to reduce the effects of outliers on the final results. As a result, the WLS-SVR method does not significantly increase the computational burden, but it provides sparseness and robustness.
•Providing new optimization/statistical approach of RWLS-SVR algorithm.•Estimate thermal conductivity of water/Graphene Oxide-Silicon Carbide nanofluid.•A LS-SVR is applied to the problem in order to calculate the error variables.•WLS-SVR method provides sparseness and robustness.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We report on the first measurement of the charmed baryon Λc± production at midrapidity (|y|<1) in Au+Au collisions at sNN=200 GeV collected by the STAR experiment at the Relativistic Heavy Ion ...Collider. The Λc/D0 denoting (Λc++Λc−)/(D0+D¯0) yield ratio is measured to be 1.08±0.16 (stat)±0.26 (sys) in the 0%–20% most central Au+Au collisions for the transverse momentum (pT) range 3<pT<6 GeV/c. This is significantly larger than the pythia model calculations for p+p collisions. The measured Λc/D0 ratio, as a function of pT and collision centrality, is comparable to the baryon-to-meson ratios for light and strange hadrons in Au+Au collisions. Model calculations including coalescence hadronization for charmed baryon and meson formation reproduce the features of our measured Λc/D0 ratio.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
Due to the influence of the complex underwater environment, safety, smoothness, real-time requirements and poor integrity, the path of autonomous underwater vehicles is mainly determined by ...perception, decision-making and control systems. These not only achieve object detection and environmental investigation but also ensure the safety and reliability of autonomous navigation systems. This paper proposes a whale optimization algorithm based on forward-looking sonar to tackle the three-dimensional path planning of autonomous underwater vehicles. The purpose of path planning is to effectively avoid threatened regions and obtain the shortest and safest paths with minimal fuel and time. The whale optimization algorithm based upon bubble-net hunting behavior imitates the contraction surrounding mechanism, logarithmic spiral position updating mechanism and stochastic searching mechanism to effectively solve the complex problem in the solution space. The whale optimization algorithm not only avoids premature convergence and avoids falling into the local optimum to achieve the global optimal solution but also utilizes exploration and exploitation to enhance the convergence speed and calculation accuracy. To verify the superiority and overall optimization performance of the whale optimization algorithm, the optimization results of the algorithm are compared with other algorithms by minimizing the fitness value. The experimental results reveal that the whale optimization algorithm has better planning efficiency, shorter execution time, faster convergence speed and higher solution precision, which is effective and efficient for path planning.
1.Three-dimensional optimal path planning for autonomous underwater vehicles based on a whale optimization algorithm is studied.2.The whale optimization algorithm not only avoids premature convergence and avoids falling into the local optimum to achieve the global optimal solution but also utilizes exploration and exploitation to enhance the convergence speed and calculation accuracy.3.The proposed algorithm can effectively avoid threatened regions and achieve the shortest and safest paths with minimal fuel and time.4.The experimental results reveal that the whale optimization algorithm has better planning efficiency, shorter execution time, faster convergence speed and higher solution precision, which is effective and efficient for path planning.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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