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.     

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.     

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.     

Low‐Carbon Magnesia‐Carbon Refractory: Use of N220 Nanocarbon Black

Addition of nanocarbon black up to 3 wt% was done in MgO‐C refractories, containing fixed 3 and 5 wt% of graphite, to study the effect on various refractory properties. Uniform distribution of carbon particles even at 1 wt% of nanocarbon black with 3 and 5 wt% of graphite was found to improve the refractory properties. The coked strength, hot strength, corrosion resistance, and oxidation resistance were found to be improved for nanocarbon‐containing MgO‐C refractory compared with the conventional refractory due to in situ formation of Al₄C₃. Higher amount of nanocarbon black was found to deteriorate the refractory properties.     

Plant Secondary Metabolites as Defense Tools against Herbivores for Sustainable Crop Protection

Plants have evolved several adaptive strategies through physiological changes in response to herbivore attacks. Plant secondary metabolites (PSMs) are synthesized to provide defensive functions and regulate defense signaling pathways to safeguard plants against herbivores. Herbivore injury initiates complex reactions which ultimately lead to synthesis and accumulation of PSMs. The biosynthesis of these metabolites is regulated by the interplay of signaling molecules comprising phytohormones. Plant volatile metabolites are released upon herbivore attack and are capable of directly inducing or priming hormonal defense signaling pathways. Secondary metabolites enable plants to quickly detect herbivore attacks and respond in a timely way in a rapidly changing scenario of pest and environment. Several studies have suggested that the potential for adaptation and/or resistance by insect herbivores to secondary metabolites is limited. These metabolites cause direct toxicity to insect pests, stimulate antixenosis mechanisms in plants to insect herbivores, and, by recruiting herbivore natural enemies, indirectly protect the plants. Herbivores adapt to secondary metabolites by the up/down regulation of sensory genes, and sequestration or detoxification of toxic metabolites. PSMs modulate multi-trophic interactions involving host plants, herbivores, natural enemies and pollinators. Although the role of secondary metabolites in plant-pollinator interplay has been little explored, several reports suggest that both plants and pollinators are mutually benefited. Molecular insights into the regulatory proteins and genes involved in the biosynthesis of secondary metabolites will pave the way for the metabolic engineering of biosynthetic pathway intermediates for improving plant tolerance to herbivores. This review throws light on the role of PSMs in modulating multi-trophic interactions, contributing to the knowledge of plant-herbivore interactions to enable their management in an eco-friendly and sustainable manner.     

Modulating the physical properties of sunflower oil and sorbitan monopalmitate‐based organogels

The present study deals with the modulation of the sunflower oil (SO) and sorbitan monopalmitate (SM) organogels using water. The gels were prepared by heating either SO–SM mixture or SO–SM–water mixture at 60°C and subsequently cooling the mixture to room temperature. The gels were characterized by microscopy (light and electron), Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), differential thermal analysis, rheometry, pH, dc impedance, hemocompatibility, and antimicrobial studies. The gels without water (G) were found to be pale yellow in color while gels containing water (GW) were white in color. Both types of gels were thermoreversible in nature. The microscopic analysis revealed that clusters of rod‐shaped tubules were responsible in the formation of network. GW also showed the presence of water droplets encapsulated within the networked structure. FTIR studies indicated the presence of intermolecular hydrogen bonding, responsible for gel formation. Gel‐to‐sol transition temperatures (T_gs) of the GW gels were higher than G gels, which might be accounted to the higher crystallinity of the GW gels. XRD studies confirmed the higher crystallinity of the GW gels. The gels showed pseudoplastic flow behavior and were hemocompatible in nature. Ciprofloxacin‐loaded gels showed good anti‐microbial properties against Bacillus subtilis. Based on the preliminary results, the developed gels may be used as delivery vehicles for various bioactive agents. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Experimental and theoretical studies of a two-stage pulse tube cryocooler operating down to 3 K

The development of a two-stage Pulse Tube Cryocooler (PTC) which produces a no-load temperature of ～3 K and delivers a refrigeration power of ～250 mW at 5 K is reported in this work. The system uses stainless steel meshes along with lead (Pb) granules and combinations of Pb, Er₃Ni and HoCu₂ in layered structures as the first and second stage regenerator materials respectively. With Helium as a working fluid, the pressure oscillations are generated using a 6 kW water-cooled Helium compressor along with an indigenous rotary valve. Different configurations of pulse tube systems have been experimentally studied, by both varying the dimensions of pulse tubes and regenerators as well as the second stage regenerator material composition. The pulse tube Cryocooler has been numerically analyzed by using both the isothermal model and the model based on solving the energy equations. The predicted refrigeration powers as well as the temperature profiles have been compared with the experimental results for specific pulse tube configurations.