A comparative study on laminated and randomly oriented Luffa-Kevlar Reinforced hybrid composites

In this article, an investigation has been carried out to hybridize Luffa (L) and Kevlar (K) for the first instant. Three laminated and three randomly oriented samples were fabricated with LL, LK, and KK combination. The fabricated samples were characterized using void fraction, water absorption, density, tensile, and flexural test. The surface morphology of fragmented specimens is examined using scanning electron microscope. The tensile strength of LK laminate was lower than the KK laminate, but with a decrease in both strength and associated cost, hybridization can be accepted. This study provides valuable information to designers for hybridizing Luffa and Kevlar together and subsequently reduced the production cost.     

Performance comparison of up-flow microbial fuel cells fabricated using proton exchange membrane and earthen cylinder

Continuous bioelectricity generation was studied in a novel up-flow bio-cathode microbial fuel cell (MFC). The performance of MFC-1, employing commercially available proton exchange membrane (PEM), was evaluated under different organic loading rates (OLRs). Maximum volumetric power density of 10.04 W m⁻³ was obtained in MFC-1 at the OLR of 0.923 kg COD m⁻³ d⁻¹. Overall chemical oxygen demand (COD) removal efficiency more than 90% was achieved under all the OLRs. The performance of MFC-1 was compared with MFC-2, in which the inner anode chamber was made up of earthen cylinder, without employing polymer membrane. MFC-2 generated maximum volumetric power density of 14.59 W m⁻³ at OLR of 0.923 kg COD m⁻³ d⁻¹, which was 46% higher than that produced in MFC-1. The internal resistance of MFC-1 (96 Ω) was higher than MFC-2 (69 Ω). The earthen cylinder MFC demonstrated better COD removal and power generation than the MFC employing PEM.     

Dielectric and impedance properties of Nd3/2Bi3/2Fe5O12 ceramics

The polycrystalline sample of Nd_3/2Bi_3/2Fe₅O₁₂ was prepared by a high- temperature solid-state reaction technique. Preliminary X-ray structural analysis exhibits the formation of a single-phase tetragonal structure at room temperature. Microstructural analysis by scanning electron microscopy shows that the sintered sample has well defined grains. These grains are distributed uniformly throughout the surface of the sample. Detailed studies of dielectric response at various frequencies and temperatures exhibit a dielectric anomaly at 400 °C. The electrical properties (impedance, modulus and conductivity) of the material were studied using a complex impedance spectroscopy technique. These studies reveal a significant contribution of grain and grain boundary effects in the material. The frequency dependent plots of modulus and the impedance loss show that the conductivity relaxation is of non-Debye type. Studies of electrical conductivity with temperature demonstrate that the compound exhibits Arrhenius-type of electrical conductivity. Study of ac conductivity with frequency suggests that the material obeys Jonscher’s universal power law.     

Development of flame retardant high loft polyester nonwovens

The improvement in flame retardancy of high loft polyester nonwovens was studied based on two different strategies (1) role of synergistic study of carbon micro/nano particles and flame retardant (FR) finishing agent and (2) role inherent flame retardant fibers in blend. The samples coated with FR chemical finish alone showed maximum resistance for flame propagation, however with more smoke formation. When the samples were coated with carbon micro/nano particles alone, the appearance of distinct flame was found with less amount of smoke formation. The synergistically coated samples revealed intermediate behavior with respect to those samples coated with carbon micro/nano particles alone and FR chemical finish alone. When inherent flame retardant polyester fibers (i.e. Toray Esfron, Trevira CS, Huvis FR) were blended with regular high loft polyester, the formation of flame was found negligible without smoke. However, the samples exhibited higher tendency of melt dripping without formation of char.     

Modelling the geometry of the unit cell of woven fabrics with integrated stiffener sections

Composite-stiffened panels of naval and aerospace applications are under the risk of delamination due to the lack of reinforcement at the joints of panel and stiffener section. One of the sustainable remedy to overcome such problems is to use 3D woven performs as a reinforcement. The benefit of 3D weaving is its intricate weave architecture and its ability to create near net shaped preforms for structural reinforcements. The technique provides endless permutations and combinations for weave design, however, repeat unit cell is the common factor that represents the complete weave architecture of the fabric. The behavior of the unit cell represents the behavior of the composite as a whole. The work presented in this paper details on the geometrical representation of an unit cell of woven stiffener fabrics and formulation of a modeling approach to determine its total weight and Fiber Volume Fraction. In this work, woven fabrics with integrated stiffener sections of four different configurations were produced using modified face-to-face (terry) weaving principle and their geometrical parameters were formulated through the modeling approach. The computed results from the models show close approximation with experimental values thus justifying the prediction of performance through them.     

Irrigation water requirement models of some major crops

A case study of the Mahanadi-Kathjori-Devi delta of Orissa, India was undertaken for the formulation of irrigation water requirement models of some major crops. Principal crops such as paddy (both during the Kharif and Rabi Seasons), sugarcane, jute, chilly, mustard, groundnuts, etc., which are mostly grown in the delta, were taken into account for the present study. Effective rainfall and irrigation water requirements are the two basic parameters of the developed models. The models help in predicting irrigation water requirements for different crops once the values of effective rainfalls are ascertained. This irrigation water requirement, estimated by models so developed, includes water requirements for consumptive use only and when any other water used for special requirements such as leaching, seed bed preparation, etc., is added to it, the total irrigation water requirement is determined. The models so developed can be used for the same crops grown in other areas having the same hydrometeorological characteristics.     

Potential field method to navigate several mobile robots

Navigation of mobile robots remains one of the most challenging functions to carry out. Potential Field Method (PFM) is rapidly gaining popularity in navigation and obstacle avoidance applications for mobile robots because of its elegance. Here a modified potential field method for robots navigation has been described. The developed potential field function takes care of both obstacles and targets. The final aim of the robots is to reach some pre-defined targets. The new potential function can configure a free space, which is free from any local minima irrespective of number of repulsive nodes (obstacles) in the configured space. There is a unique global minimum for an attractive node (target) whose region of attraction extends over the whole free space. Simulation results show that the proposed potential field method is suitable for navigation of several mobile robots in complex and unknown environments. Saroj Kumar Pradhan is faculty of Mechanical Engineering Department with N.I.T., Hamirpur, HP, India. He has received his B.E. degree in Mechanical Engineering from Utkal University and M.E. in Machine Design and Analysis from NIT Rourkela. He has published more than 17 technical papers in international journals and conference proceedings. His areas of research include mobile robots navigation and vibration of multilayred beams. Dayal R. Parhi is working as Assistant Professor at NIT Rourkela, India. He has obtained his first Ph.D. degree in “Mobile Robotics” from United Kingdom and Second Ph.D. in “Mechanical Vibration” from India. He has visited CMU, USA as a “Visiting Scientist” in the field of “Mobile Robotics”. His main areas of current research are “Robotics” and “Mechanical Vibration”. He is supervising five Ph.D. students in the fields of Robotics and Vibration. Email: dayalparhi@yahoo.com. Anup Kumar Panda Received his M.Tech degree from IIT, Kharagpur in 1993 and Ph.D. degree from Utkal University in 2001. He is currently an assistant professor in the Department of Electrical Engineering at National Institute of Technology, Rourkela, India. His areas of research include robotics, Machine Drives, harmonics and power quality. He has published more than 30 technical papers in journals and conference proceedings. He is now involved in two R&D projects funded by Government of India. R. K. Behera is a Senior Lecturer of Mechanical Engineering at National Institute of Technology, Rourkela, India. He has been working as lecturer for more than 10 years. He obtained his BE degree from IGIT, Sarang, of Utkal University. He obtained his ME and Ph.D degrees, both in the field of mechanical engineering from NIT Rourkela.     

Sintering and microstructural study of mullite prepared from kaolinite and reactive alumina: Effect of MgO and TiO2

Mullite ceramic was prepared using kaolinite and synthesized alumina (combustion route) by solid-state interaction process. The influence of TiO₂ and MgO additives in phase formation, microstructural evolution, densification, and mechanical strengthening was evaluated in this work. TiO₂ and MgO were used as sintering additives. According to the stoichiometric composition of mullite (3Al₂O₃·2SiO₂), the raw materials, ie kaolinite, synthesized alumina, and different wt% of additives were wet mixed, dried, and uniaxially pressed followed by sintering at different temperature. 1600°C sintered samples from each batch exhibit enhanced properties. The 1 wt% TiO₂ addition shows bulk density up to 2.96 g/cm³ with a maximum strength of 156.3 MPa. The addition of MgO up to 1 wt% favored the growth of mullite by obtaining a density and strength matching with the batch containing 1 wt% TiO₂. These additives have shown a positive effect on mullite phase formation by reducing the temperature for complete mullitization by 100°C. Both additives promote sintering by liquid phase formation. However, the grain growth, compact microstructure, and larger elongated mullite crystals in MgO containing batch enhance its hardness properties.     

Doping Nanoscale Graphene Domains Improves Magnetism in Hexagonal Boron Nitride

Carbon doping can induce unique and interesting physical properties in hexagonal boron nitride (h‐BN). Typically, isolated carbon atoms are doped into h‐BN. Herein, however, the insertion of nanometer‐scale graphene quantum dots (GQDs) is demonstrated as whole units into h‐BN sheets to form h‐CBN. The h‐CBN is prepared by using GQDs as seed nucleations for the epitaxial growth of h‐BN along the edges of GQDs without the assistance of metal catalysts. The resulting h‐CBN sheets possess a uniform distrubution of GQDs in plane and a high porosity macroscopically. The h‐CBN tends to form in small triangular sheets which suggests an enhanced crystallinity compared to the h‐BN synthesized under the same conditions without GQDs. An enhanced ferromagnetism in the h‐CBN emerges due to the spin polarization and charge asymmetry resulting from the high density of C? N and C? B bonds at the boundary between the GQDs and the h‐BN domains. The saturation magnetic moment of h‐CBN reaches 0.033 emu g^?1 at 300 K, which is three times that of as‐prepared single carbon‐doped h‐BN.