Single edge-cracked orthotropic strip under three-point load

The problem of an orthotropic strip having a crack of unit length normal to one edge and subjected to a bending moment resulting from three-point loading is solved using integral transform method. The mixed boundary conditions lead to dual integral equations which are ultimately reduced to a Fredholm integral equation of second kind. The integral equation thus obtained is solved by the method developed by Fox and Goodwin. Numerical solutions for a fibre-reinforced composite material have been carried out to determine the stress intensity factor of an orthotropic medium. The same has been compared with the isotropic case.     

Delamination of Mg-Al Layered Double Hydroxide on Starch: Change in Structural and Thermal Properties

Mg-Al layered double hydroxide decorated starch bionanocomposites (starch/layered double hydroxide) are prepared by solution intercalation method. The bionanocomposites are systematically characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and high-resolution transmission electron microscopy techniques. The thermal stability of starch is enhanced due to dispersion of layered double hydroxide within the starch matrix. The chemical resistance property of starch is improved substantially with slight sacrifice in biodegradation behavior by the delamination of layered double hydroxide in starch matrix. Herein, layered double hydroxide acts as potential laminated filler for change in structural, thermal, and chemical resistance properties of starch with little sacrifice in biodegradable behavior.     

Influence of Al Substitution on Structural,Dielectric and Magnetic Properties of M-type Barium Hexaferrite

Polycrystalline Al-substituted BaFe₁₂O₁₉ samples were synthesized and investigated in order to study their structural, dielectric, and magnetic properties. Analysis of powder X-ray diffractions by Rietveld refinement shows the single-phase nature of samples with hexagonal structure. The magnetic properties of the samples were investigated by measuring temperature and field variations of magnetization using vibrating sample magnetometer. The temperature variation of magnetization measurement shows that all samples exhibit ferrimagnetic transition, and the transition temperature is found to decrease from 720 K for x = 0 to 709 K for x = 0.08. The saturation magnetization value at room temperature is found to decrease with increase in Al concentration, and on the other hand, the coercivity is found to increase. The dielectric spectrum of pure and Al-doped samples shows the typical exponential fall in dielectric constant with increase in frequency. The magnitude of dielectric constant at 100 Hz falls from 2000 for x = 0 to 400 for x = 0.10. The permeability spectrum of Al-doped samples is found to be almost independent of frequency for f>100 MHz.     

Surface functionalization of BiFeO<Subscript>3</Subscript>: A pathway for the enhancement of dielectric and electrical properties of poly(methyl methacrylate)–BiFeO<Subscript>3</Subscript> composite films

A novel two-phase composite film is prepared by the solvent casting method employing poly(methyl methacrylate) (PMMA) as polymer matrix and bismuth ferrite (BFO) as ceramic filler. The surfaces of BFO are functionalized by proper hydroxylating agents to activate their chemical nature. The structural analysis of the composite films confirms that the composites made up of functionalized BFO (BFO-OH) have a distorted rhombohedral structure. The morphological analysis shows that BFO-OH particles are equally distributed over the polymer matrix. The -OH functionality of BFO-OH is confirmed by FTIR. The dielectric and electrical studies at a frequency range from 100 Hz to 1 MHz reveal that PMMA-(BFO-OH) composites have enhanced dielectric constant as well as electrical conductivities, much higher than that of unmodified composites. According to the ferroelectric measurement result, the hydroxylated composite film shows a superior ferroelectric behavior than that of the unmodified one, with a remanent polarization (2P_r) of 2.764 μC/cm².     

Microwave antennas—An intrinsic part of RF energy harvesting systems: A contingent study about its design methodologies and state‐of‐art technologies in current scenario

With the significant rise of low power embedded devices in various applications of both consumer and commercial usage, the surge for continuous power requirements has initiated promising research toward alternative sources of energy. It includes the domain of wireless power transmission, internet‐of‐things, wireless sensor nodes, machine‐to‐machine, and radio frequency identification. Thus, the overall scope of this review article is to witness microwave antennas and its implementation in RF energy harvesting system through ambient RF signals. For this reason, unified understanding of classical electromagnetism is needed; beginning with the fundamentals of RF transmission and the exploration of concepts such as Fraunhofer's Distance and Friis Transmission Equation. It is followed up by the analogy of dependency of parameters like circuit build‐up, conversion efficiencies and amount of power harvested, which is quite crucial from the rectifier point‐of‐view. For better improvisement in RF energy harvesting systems, five different cases of monopole antennas are explored with reflector surfaces such as PEC (perfect electrical conductor) and AMC (artificial magnetic conductor) integrated with the rectifier circuit. Implementation with wide diversity has proposed a generalized solution for achieving tradeoffs: polarization and pattern diversity with consistent system efficiency; leads to clean and sustainable energy for low power‐embedded devices.     

Development of rubber pressure molding technique using butyl rubber to fabricate fiber reinforced plastic components based on glass fiber and epoxy resin

A rubber pressure molding (RPM) technique is developed to prepare fiber reinforced plastic components (FRP) using glass fiber and epoxy resin. The technique is based on the matching die set, where the die is made of hard metal like steel and the punch from flexible rubber like materials. The use of flexible rubber punch helps to intensify and uniformly redistribute pressure (both operating pressure and developed hydrostatic pressure due to the flexible rubber punch) on the surface of the product. A split steel die and rubber punch were designed and fabricated to prepare the FRP components. The same split die was also used to cast the rubber punch. Butyl rubber was used to prepare a rubber punch in this investigation. Burn test, coin test, scanning electron microscopy and mechanical tests like interlaminar fracture toughness, interlaminar shear test, tension test, etc were carried out to know the fiber content, void content, presence of delamination, bonding between fiber and resin, microstructure, and mechanical properties of the composite materials. These properties were also compared with FRP components made by the conventional technique to evaluate its performance in the structural applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1095–1102, 2006     

Prioritizing test scenarios from UML communication and activity diagrams

Due to the large size and complexity of software, exhaustive testing becomes impossible. Hence, testing must be done in an optimized way keeping in mind factors, such as requirements of the customer, cost and time. For this, there is a need to generate test cases and exercise them to gain maximum throughput by uncovering defects. Test case/scenario prioritization is a well known and efficient technique to ensure the software quality. Prioritization of test scenarios helps in early detection of bugs. In this paper, we present an integrated approach and a prioritization technique to generate cluster-level test scenarios from UML communication and activity diagrams. In our approach, we first construct a tree representation of communication diagrams, and then a tree representation of activity diagrams. We convert them into an intermediate tree named as COMMACT tree. We, then carry out a post-order traversal of the constructed tree for selecting conditional predicates from the intermediate tree. Then, we propose an algorithm to generate test scenarios from the constructed tree. Next, the necessary information, such as method-activity sequence, associated objects, and constraint conditions is extracted from test scenario. The test sequences are a set of theoretical paths starting from initialization to end, while taking conditions (pre- and post-condition) into consideration. Each generated test sequence corresponds to a particular scenario of the considered use case. The third phase is to generate test scenarios from the tree satisfying the message–activity path test adequacy criteria. Preliminary results obtained on a case-study indicate that the technique is effective in extracting the critical scenarios from the communication and activity diagrams. Our approach generates redundant test scenarios and still achieves adequate test coverage.     

Fuzzy finite element analysis of imprecisely defined structures with fuzzy nodal force

This paper presents the fuzzy finite element analysis for static displacements of fixed free stepped rectangular beam, truss and simplified bridge structure with fuzzy nodal force. The material and geometric properties of the structures are taken as crisp. Fuzzy finite element analysis of static problem for the above structures converts the problem into fuzzy system of linear equations. As such the coefficient matrix and the right-hand side vector become crisp and fuzzy respectively. A new approach is used here to solve the fuzzy system of linear equations. Numerical results for the three stepped rectangular beam, three-bar truss and simplified bridge with fifteen elements are presented to illustrate the computational aspects of the developed method. The results obtained are depicted in term of plots.