Numerical investigation of thermal and hydraulic performance in novel oblique geometry using nanofluid

To capitalize the advantage of oblique fin heat sink (OFHS) with Al₂O₃–water nanofluids of different volumetric concentration (1, 2, and 4%), a comprehensive computational analysis has been performed for OFHS with nanofluid through the single-phase modeling. The present investigation focuses on the full domain simulation because the conventional periodic computational model approach is unable to investigate the flow migration effect and predicts higher value of Nusselt number. Apart from the disruption of boundary layer, vortices are observed in the secondary oblique channel due to flow separation that promotes an additional heat transfer enhancement. Higher Severity of the flow migration and hence more non-uniformity of nanofluid flow rate through the primary and secondary channels was observed at higher Reynolds numbers. The increment observed in the average Nusselt number (Nu_avg) at Re = 750 for OFHS is about 90% and 115% for water and 4% volumetric concentration of nanofluid respectively compared to conventional SCHS. Also, Al₂O₃–water nanofluid exhibits about 30% higher enhancement at 4% volumetric concentration at Re = 750 in the OFHS with compared to water. The increase in heat transfer exceeded the pressure drop penalty at all the Reynolds numbers.     

An analytical parasitic resistance dependent Id–Vd model for planar doped InAlAs/InGaAs/InP HEMT using non-linear charge control analysis

An analytical parasitic resistance dependent model for the current voltage characteristics for InAlAs/InGaAs/InP HEMT is proposed. The model uses a new polynomial dependence of sheet carrier concentration on gate voltage to calculate I_d–V_d characteristics and has been extended to obtain transconductance, output conductance and cut-off frequency of the device. A maximum cut-off frequency of 83 and 175 GHz was obtained for channel length of 0.25 and 0.1 μm, respectively. Close agreement with published results confirms the validity of our approach.     

Studies of sedimentation behaviour of high pigmented alkyd primer: A rheological approach

These rheological studies are carried out to understand the sedimentation tendency of pigments in solvent borne alkyd primer (SP). Three high pigment volume concentration (PVC) primers with varying wetting agents are studied comparatively with benchmark low PVC primer with good antisettling performance. Rheological tests namely control shear rate (CSR), creep recovery, oscillatory amplitude sweep and frequency sweep were performed on these samples and correlation with natural and accelerated stability tests was established. Here the correlation of rheological parameters like yield stress, crossover point, zero shear viscosity, deformation, loss factor, etc. with the respective pigment sedimentation tendencies in primer samples gave good understanding of their importance in primer formulation. This not only helps making better primer but also reduces development time for a product and thus improved productivity.     

Investigating the commonality attributes for scaling product families using comprehensive product platform planning (CP3)

A product family with a platform paradigm is expected to increase the flexibility of the manufacturing process to market changes, and to take away market share from competitors that develop one product at a time. The recently developed Comprehensive Product Platform Planning (CP³) method (i) presents a generalized model, (ii) allows the formation of product sub-families, and (iii) provides simultaneous identification and quantification of platform/scaling design variables. The CP³ model is founded on a generalized commonality matrix that represents the platform planning process as a mixed-binary nonlinear programming (MBNLP) problem. This MBNLP problem is high-dimensional and multimodal, owing to the commonality constraint. In this paper, the complex MBNLP model is reduced to a tractable MINLP problem without resorting to limiting approximations; along the reduction process, redundancies in the original commonality matrix are also favorably addressed. To promote a better understanding of the importance of a reduced MINLP, this paper also provides a uniquely comprehensive formulation of the number of possible platform combinations (or commonality combinations). In addition, a new commonality index (CI) is developed to simultaneously account for the inter-product commonalities (based on design variable sharing) and the overlap between groups of products sharing different platform variables. To maximize the performance of the product family and the commonality index yielded by the new CP³ model, we apply an advanced mixed-discrete Particle Swarm Optimization algorithm. The potential of the new CP³ framework is illustrated through its application to design scalable families of electric motors. Maximizing the new CI produced families with more commonality among similar sets of motor variants (compared to maximizing the conventional CI), which can be a beneficial platform attribute for a wide range of product families.     

Enhancing the Route Optimization Using Hybrid MAF Optimization Algorithm for the Internet of Vehicle

Wireless Personal Communications - Wireless Sensor Networks (WSNs) in modern times enables security techniques to secure the information transmitted via the interconnected network. The poor...     

Photonic Bandgap Hepta-Band Stacked Microstrip Antenna for L,S and C Band Applications

Wireless Personal Communications - This paper proposed a novel design of hepta-band microstrip patch antenna which is realized by a rectangular patch. The proposed patch antenna resonates between 1...     

Implementation of Vertex-Fed Multiband Antenna for Wireless Applications with Frequency Band Reconfigurability Characteristics

In this paper authors present the design and analysis of split ring resonator based multiband antenna for wireless applications with frequency-band reconfigurable features. The proposed design has octagonal shape SRR structure fed at vertex as radiating section and rectangular shape switchable slotted ground part. The antenna has dimensions of 44?×?39?×?1.6 mm³ and fabricated on FR4 substrate. The proposed structure exhibit hexa operating resonance characteristics at 3.3, 5.0, 5.8, 6.6, 9.9 and 15.9 GHz to cover the wireless standards at lower WiMAX, upper WLAN, super extended C-band, middle X band and lower K_U band respectively. Antenna achieve the frequency band reconfigurability characteristics by inserting PIN diode in slotted ground (reclined L-shaped) as triple/hexa resonant bands during OFF/ON switching state of PIN diode. An acceptable gain, stable and consistent radiation patterns with low cross polarization and good impedance matching are obtained at targeted frequency bands of proposed design.

     

Utilization of Flyash as Filler Material in Hybrid Polyester Composites for Improved Thermo-Mechanical and Erosion Wear Behavior

The present work was carried out for the utilization of major quantities of flyash as filler material in the short fiber reinforced polyester resin composites in various engineering and structural applications. The incorporation of flyash modifies the hardness, tensile, flexural, impact and damping behavior of the composites. It is observed that hardness, flexural modulus and impact strength of flyash filled composites increases with increase in the flyash filler contents. Whereas, with the addition of flyash contents it is observed that there is decrease in tensile strength and flexural strength. But beyond the 10 wt.-% flyash filler addition in the composite the flexural strength increases. At the end, the erosion wear behavior of all the composites has been studied by Taguchi experimental design. It is found that unfilled glass polyester composite suffers greater erosion loss as compare to particulate filled glass polyester composites. The eroded surface morphology is examined by SEM and the related erosion wear mechanism is discussed in detail.     

Porous polyimides from polycyclic aromatic linkers: Selective CO2 capture and hydrogen storage

Porous polyimides are important class of macromolecules owing to their excellent redox behaviour, efficient capture of CO₂ and H₂ gases, interesting photocatalytic properties and superior thermal and chemical stabilities. Here we describe in detail, the synthesis and gas storage properties of a series of porous polyimides (Tr-NPI, Tr-PPI, Tr-CPI, Td-PPI and Td-CPI) with various network topologies derived from polycyclic aromatic hydrocarbon linkers. These polyimides are synthesized in a single step by the condensation of corresponding polycyclic aromatic dianhydrides (NDA, PDA and CDA) with structure directing amine (TAPA and TAPM) monomers, having trigonal and tetrahedral geometry. The structure of all the polymers was fully characterized by various techniques. The present work also introduces for the first time porous polyimides containing rigid polycyclic aromatic compounds such as coronene. All the polyimides presented here exhibit high thermal stability and show selectivity towards CO₂ uptake at room temperature (293 K), due to the presence of aromatic clouds and CO₂ phillic oxygen and nitrogen functionalities on their pore surface. Moreover these polymers also showed significant uptake of H₂ gas (77 K). The present work has significant implications on the design of robust porous organic solids from small molecules for efficient capture of CO₂ and H₂ gases.     

Synthesis and structural characterization of single-crystalline branched nanowire heterostructures

We report the synthesis of three-dimensional single-crystalline branched nanowire heterostructures, where the backbones and branches are assembled with ZnS and CdS, respectively. Growth of branch and backbones with control over the compositions was enabled via sequential seeding of gold nanocluster catalysts. Elemental mapping data confirmed that branched nanowire heterostructures were synthesized with the intended chemical modulation, CdS branches on ZnS backbones. Transmission electron microscopy studies showed that the growth of heterostructure branches occurs epitaxially from the backbone while maintaining single-crystalline structure. This unique class of heterostructures holds great potential in assembling electronics and photonics in three dimensions.