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51.
An investigation is carried out on the effect of dissipative heat energy on the flow of an electrically conducting viscous fluid past a shrinking sheet. Both viscous and Joule dissipation effects are considered along with heat generation/absorption for the enhancement of heat transfer properties. The governing nonlinear coupled partial differential equations are transformed into nonlinear ordinary differential equations by a suitable choice of similarity transformations. However, the complex transformed equations are solved by an approximate analytical method known as the Adomian decomposition method with a suitable initial guess solution assumed from the known initial conditions. Moreover, the behavior of several parameters characterizing the flow phenomena are studied via graphs and the numerical computations for the engineering coefficients are obtained and presented through tables. However, the major outcomes of the results are that a higher suction is required to resist the fluid temperature and sinks as well as the dissipative heat energy favors enhancing the fluid temperature at all points in the flow domain. 相似文献
52.
Marble dust generated during processing of the marble producing rocks is a major solid waste with a detrimental impact on environment. Analysis shows that this waste has constituents having compounds like SiO2, Al2O3, Fe2O3, CaO, MgO, etc., in different proportions. This paper explores on the possible use of waste marble dust as secondary filler in glass-polyester composites and reports on its dry sliding wear characteristics. Such hybrid composites with unsaturated polyester as the matrix are fabricated by keeping the woven glass fibre loading fixed and by varying the weight fraction of the particulate filler, that is, marble dust through a simple hand layup route. Dry sliding wear trials are conducted under different test conditions as per ASTM G 99-05 following the L30 model of response surface method (RSM). A parametric appraisal of the wear process is made using RSM and the significant control factors and their interactions influencing the specific wear rates are identified. Scanning electron microscopy of the worn composite surfaces is done to ascertain the wear mechanism. It is found that the presence of marble dust improves the wear resistance of unfilled glass-polyester composites substantially. Further, prediction of wear rate of the composites for a wide range of filler content and sliding velocities is conducted using RSM and another prediction model based on fuzzy logic and the outcomes are compared. 相似文献
53.
Liangtao Yang Liang-Yin Kuo Juan Miguel López del Amo Prasant Kumar Nayak Katherine A. Mazzio Sebastian Maletti Daria Mikhailova Lars Giebeler Payam Kaghazchi Teófilo Rojo Philipp Adelhelm 《Advanced functional materials》2021,31(38):2102939
A known strategy for improving the properties of layered oxide electrodes in sodium-ion batteries is the partial substitution of transition metals by Li. Herein, the role of Li as a defect and its impact on sodium storage in P2-Na0.67Mn0.6Ni0.2Li0.2O2 is discussed. In tandem with electrochemical studies, the electronic and atomic structure are studied using solid-state NMR, operando XRD, and density functional theory (DFT). For the as-synthesized material, Li is located in comparable amounts within the sodium and the transition metal oxide (TMO) layers. Desodiation leads to a redistribution of Li ions within the crystal lattice. During charging, Li ions from the Na layer first migrate to the TMO layer before reversing their course at low Na contents. There is little change in the lattice parameters during charging/discharging, indicating stabilization of the P2 structure. This leads to a solid-solution type storage mechanism (sloping voltage profile) and hence excellent cycle life with a capacity of 110 mAh g-1 after 100 cycles. In contrast, the Li-free compositions Na0.67Mn0.6Ni0.4O2 and Na0.67Mn0.8Ni0.2O2 show phase transitions and a stair-case voltage profile. The capacity is found to originate from mainly Ni3+/Ni4+ and O2-/O2-δ redox processes by DFT, although a small contribution from Mn4+/Mn5+ to the capacity cannot be excluded. 相似文献
54.
Channapatna Gopalkrishna Raghavendra Raghu Srivatsa Marasandra Prakash Vignesh Nayak Panemangalore 《ETRI Journal》2021,43(4):650-659
Multi-carrier waveforms have several advantages over single-carrier waveforms for radar communication. Employing multi-carrier complementary phase-coded (MCPC) waveforms in radar applications has recently attracted significant attention. MCPC radar signals take advantage of orthogonal frequency division multiplexing properties, and several authors have explored the use of MCPC signals and the difficulties associated with their implementation. The sidelobe level and peak-to-mean-envelope-power ratio (PMEPR) are the key issues that must be addressed to improve the performance of radar signals. We propose a scheme that applies pattern-based scaling and geometric progression methods to enhance sidelobe and PMEPR levels in MCPC radar signals. Numerical results demonstrate the improvement of sidelobe and PMEPR levels in the proposed scheme. Additionally, autocorrelations are obtained and analyzed by applying the proposed scheme in extensive simulation experiments. 相似文献
55.
In water-cooled nuclear reactors, the maximum power which can be extracted from the core is limited by critical heat flux (CHF). CHF in the high-quality region is known as dryout. In advanced nuclear reactors, the coolant flow occurs solely by virtue of natural circulation; however, instabilities may occur during off-normal operations. This may lead to premature dryout due to lower coolant flow rates seen by the heater during such oscillations. This paper describes the experimental investigation on the effect of flow oscillations on the CHF with the time period of 120 s, which is observed typically in the large-scale natural circulation system. Based on observations made with respect to temperature transient, the continuous dryout is preceded by the transient dryout for higher flow oscillations. But as flow fluctuation decreases, the transient dryout phenomenon is found to disappear. The applicability of the look-up table to predict CHF under oscillatory flow conditions using suitable correction factors (CFs) for premature dryout has been evaluated. CFs for the CHF under oscillations suggested by previous authors have been compared. The maximum possible degradation in CHF value suggested by previous authors has been found to agree with the present experimental data. Percentage fluctuation in heat transfer coefficient (HTC) at fully developed annular flow conditions has been evaluated, and it is found that fluctuation in HTC is in phase with the fluctuation in flow. 相似文献
56.
It is apparent that non-Newtonian nanofluids (especially, Casson and Carreau) find their ubiquitous utilization in diverse industrial processes. The magnetohydrodynamics concept is significantly implemented in the engineering design process. Darcy–Forchheimer's effect characterized by inertia and boundary effects ameliorates the rate of heat transportation outstandingly in association with the flow of nanofluids. Entropy optimization analysis is accentuated as its minimization is the best measure to enhance the efficiency of thermal systems. In view of this, the present article is intended to investigate electromagnetic flow and thermal characteristics of Casson and Carreau nanofluids over the exponential stretched surface. Microrotation facets are entailed. Arrhenius pre-exponential factor law and Robin's condition are implemented. The nondimensional governing equations are solved by the spectral quasi-linearization method. The major outcomes of this study are that axial and transverse flow velocities and heat transfer rate get controlled due to strengthening Casson and microinertia density parameters. More thermal stratification augments the rate of heat transportation efficaciously. Amplification of the Weissenberg parameter intensifies the axial and transverse flow velocities and the associated boundary layer widths. Axial and transverse surface viscous drag enervate due to the rise in porosity, inertia, and magnetic parameters. The entropy generation rate is regulated by the varied Reynolds number. 相似文献
57.
The present research work concentrates on viscous dissipation, Dufour, and heat source on an unsteady magnetohydrodynamics natural convective flow of a viscous, incompressible, and electrically conducting fluid past an exponentially accelerated infinite vertical plate in the existence of a strong magnetic field. The presence of the Hall current induces a secondary flow in the problem. The distinguishing features of viscous dissipation and heat flux produced due to gradient of concentration included in the model along with heat source as they are known to arise in thermal-magnetic polymeric processing. The flow equations are discretized implicitly using the finite difference method and solved using MATLAB fsolve routine. Numerical values of the primary and secondary velocities, temperature, concentration, skin friction, Nusselt number, and Sherwood number are illustrated and presented via graphs and tables for various pertinent parametric values. The Dufour effect was observed to strengthen the velocity and temperature profile in the flow domain. In contrast, due to the impact of viscous dissipation, the local Nusselt number reduces. The study also reveals that the inclusion of the chemical reaction term augments the mass transfer rate and diminishes the heat transfer rate at the plate. 相似文献
58.
K. P. Bhuvana R. Joseph Bensingh M. Abdul Kader S. K. Nayak 《Polymer-Plastics Technology and Engineering》2018,57(17):1784-1800
Polymer Light Emitting Diodes (PLEDs), the most promising name in the field of display technology has received tremendous attention from various research groups. The research on light emitting polymers are an interdisciplinary zone which has challenging investigates on materials science and engineering, physics of device architecture and technology. This review addresses the wide range of tailored polymers, evolution of LED device structure for high performance, single and multicolor polymer based LEDs. Though, polymers are possessing better efficiency and easy fabrication processes, it has very low stability and short life. This study also reviews, device degradation during device fabrication and operation. 相似文献
59.
Shanti Kiran Nayak Angelica D. Benavidez Fernando H. Garzon 《Journal of the American Ceramic Society》2019,102(6):3738-3744
Molybdenum carbide has immense potential as an active catalyst for reaction systems such as synthesis of important chemicals like ammonia. However, the carbide is not used as a commercial catalyst or support as the current synthesis processes produce low surface area material or have contaminants such as excess carbon and surface and chemisorbed oxygen. Moreover, attempts to refine the synthesis pathways are usually not supported by any thermochemical modeling. In this study, a facile and reproducible method to synthesize high surface area molybdenum carbide was developed with the help of thermochemical modeling to better understand molybdenum-carbon phase behavior. We have synthesized 2-5 nm particles of MoxC with surface areas of up to 360 m2/g as characterized using a variety of techniques including X-ray diffraction and electron microscopy. 相似文献
60.