Effect of tungsten and tantalum on the low cycle fatigue behavior of reduced activation ferritic/martensitic steels

Reduced activation ferritic/martensitic (RAFM) steels are candidate materials for the test blanket modules of International Thermonuclear Experimental Reactor (ITER). Several degradation mechanisms such as thermal fatigue, low cycle fatigue, creep fatigue interaction, creep, irradiation hardening, swelling and phase instability associated irradiation embrittlement must be understood in order to estimate the component lifetime and issues concerning the structural integrity of components. The current work focuses on the effect of tungsten and tantalum on the low cycle fatigue (LCF) behavior of RAFM steels. Both alloying elements tungsten and tantalum improved the fatigue life. Influence of Ta on increasing fatigue life was an order of magnitude higher than the influence of W on improving the fatigue life. Based on the present study, the W content was optimized at 1.4 wt.%. Softening behavior of RAFM steels showed a strong dependence on W and Ta content in RAFM steels.     

Effect of different stages of tensile deformation on micromagnetic parameters in high-strength, low-alloy steel

The influence of tensile deformation on the magnetic Barkhausen emissions (MBE) and hysteresis loop has been studied in a high-strength, low-alloy steel (HSLA) and its weldment. The magnetic measurements were made both in loaded and unloaded conditions for different stress levels. The rootmean-square (RMS) voltage of the MBE has been used for analysis. This study shows that the preyield and postyield deformation can be identified from the change in the the MBE profile. The initial elastic deformation showed a linear increase in the MBE level in the loaded condition, and the MBE level remained constant in the unloaded condition. The microplastic yielding, well below the macroyield stress, significantly reduces the MBE, indicating the operation of grain-boundary dislocation sources below the macroyield stress. This is indicated by the slow increase in the MBE level in the loaded condition and the decrease in the MBE level in the unloaded condition. The macroyielding resulted in a significant increase in the MBE level in the loaded condition and, more clearly, in the unloaded condition. The increase in the MBE level during macroyielding has been attributed to the grain rotation phenomenon, in order to maintain the boundary integrity between adjacent grains, which would preferentially align the magnetic domains along the stress direction. With progressive plastic deformation, the MBE level remains more or less constant in the loaded condition and decreases linearly with strain in the unloaded condition. This constant MBE behavior in the loaded condition is attributed to the opposing effect of applied tensile stress (which tends to align the domains along the stress direction) and the dislocation density (which reduces the domain-wall displacement). The decreasing MBE in the unloaded condition is attributed to the combined effect of compressive residual stress at the surface layers (which tends to align the domain wall perpendicular to the stress direction) and the dislocation density. This study shows that MBE during tensile deformation can be classified into four stages: (1) perfectly elastic, (2) microplastic yielding, (3) macroyielding, and (4) progressive plastic deformation. A multimagnetic parameter approach, combining the hysteresis loop and MBE, has been suggested to evaluate the residual stresses.     

MOF‐Derived Hollow Cage NixCo3−xO4 and Their Synergy with Graphene for Outstanding Supercapacitors

Highly optimized nickel cobalt mixed oxide has been derived from zeolite imidazole frameworks. While the pure cobalt oxide gives only 178.7 F g^?1 as the specific capacitance at a current density of 1 A g^?1, the optimized Ni:Co 1:1 has given an extremely high and unprecedented specific capacitance of 1931 F g^?1 at a current density of 1 A g^?1, with a capacitance retention of 69.5% after 5000 cycles in a three electrode test. This optimized Ni:Co 1:1 mixed oxide is further used to make a composite of nickel cobalt mixed oxide/graphene 3D hydrogel for enhancing the electrochemical performance by virtue of a continuous and porous graphene conductive network. The electrode made from GNi:Co 1:1 successfully achieves an even higher specific capacitance of 2870.8 F g^?1 at 1 A g^?1 and also shows a significant improvement in the cyclic stability with 81% capacitance retention after 5000 cycles. An asymmetric supercapacitor is also assembled using a pure graphene 3D hydrogel as the negative electrode and the GNi:Co 1:1 as the positive electrode. With a potential window of 1.5 V and binder free electrodes, the capacitor gives a high specific energy density of 50.2 Wh kg^?1 at a high power density of 750 W kg^?1.     

Trust based authentication technique for cluster based vehicular ad hoc networks (VANET)

Since Vehicular ad hoc networks (VANETs) are vulnerable to various kinds of attacks, there is a need to fulfill the security requirements like message privacy, integrity, and authentication. The authentication technique is said to be efficient if it detects compromised nodes accurately with less complexity, reduced authentication delay, and keying overhead. In this paper, a trust-based authentication scheme for cluster-based VANETs is proposed. The vehicles are clustered, and the trust degree of each node is estimated. The trust degree is a combination of direct trust degree and indirect trust degree. Based on this estimated trust degree, cluster heads are selected. Then, each vehicle is monitored by a set of verifiers, and the messages are digitally signed by the sender and encrypted using a public/ private key as distributed by a trusted authority and decrypted by the destination. This verifies the identity of sender as well as receiver thus providing authentication to the scheme. By simulation results, we prove that the proposed technique provides high security with less overhead and delay.     

Protein Corona Influences Cell–Biomaterial Interactions in Nanostructured Tissue Engineering Scaffolds

Biomaterials are extensively used to restore damaged tissues, in the forms of implants (e.g., tissue engineered scaffolds) or biomedical devices (e.g., pacemakers). Once in contact with the physiological environment, nanostructured biomaterials undergo modifications as a result of endogenous proteins binding to their surface. The formation of this macromolecular coating complex, known as “protein corona,” onto the surface of nanoparticles and its effect on cell–particle interactions are currently under intense investigation. In striking contrast, protein corona constructs within nanostructured porous tissue engineering scaffolds remain poorly characterized. As organismal systems are highly dynamic, it is conceivable that the formation of distinct protein corona on implanted scaffolds might itself modulate cell–extracellular matrix interactions. Here, it is reported that corona complexes formed onto the fibrils of engineered collagen scaffolds display specific, distinct, and reproducible compositions that are a signature of the tissue microenvironment as well as being indicative of the subject's health condition. Protein corona formed on collagen matrices modulated cellular secretome in a context‐specific manner ex vivo, demonstrating their role in regulating scaffold–cellular interactions. Together, these findings underscore the importance of custom‐designing personalized nanostructured biomaterials, according to the biological milieu and disease state. The use of protein corona as in situ biosensor of temporal and local biomarkers is proposed.     

Toward wafer scale fabrication of graphene based spin valve devices

We demonstrate injection, transport, and detection of spins in spin valve arrays patterned in both copper based chemical vapor deposition (Cu-CVD) synthesized wafer scale single layer and bilayer graphene. We observe spin relaxation times comparable to those reported for exfoliated graphene samples demonstrating that chemical vapor deposition specific structural differences such as nanoripples do not limit spin transport in the present samples. Our observations make Cu-CVD graphene a promising material of choice for large scale spintronic applications.     

Diatomaceous Earth as a Source of Silicon and its Impact on Soil Physical and Chemical Properties,Yield and Quality,Pests and Disease Incidence of Arabica Coffee cv. Chandragiri

Silicon - To assess the impact of Diatomaceous Earth (DE) as a source of silicon on soil physical-chemical properties, yield attributes and clean coffee yield of Arabica coffee cv. Chandragiri,...     

Mechanical properties of fly ash composites—A review

Composites are widely used as a lightweight material in automotive, aerospace, transportation, wind turbines, and leisure industry. Different reinforcement materials are used in composites of which fly ash attracts the researchers as an important reinforcement due to its enhanced mechanical properties such as low density, improved ultimate tensile strength, toughness, compressive strength, impact strength, hardness, and decrease in ductility. Fly ash composites are manufactured by stir casting, in situ deposition technique, hand lay-up technique, and compo casting technique.     

Inclusive Elliptical Curve Cryptography (IECC) for Wireless Sensor Network Efficient Operations

Wireless sensor networks are the most vulnerable to all the wireless devices due to the massive damage caused by disrupting these networks. A good number of attacks have been launched in the wireless networks which are prevalent in the antagonist world. However, the most difficult of all the attacks is the identification and prevention of the replication of nodes. The time it takes to identify and isolate a cloned/replicated node is usually greater than any other attack detection techniques due to the similar id and features replicated by the attacker. Elliptical curve cryptography is well known for providing security in wireless networks. This paper explores a property of the ECC that is designed into a full pledged IECC protocol for keeping away replicated nodes from attacking the WSNs and MWSNs. In terms of application, the focus is to secure an industrial area using the IECC mechanism for efficient remote monitoring. Simulation analysis shows that the IECC performs well in static WSN and MWSNs over the existing baseline protocols.     

Finite element analysis of spherical indentation to study pile-up/sink-in phenomena in steels and experimental validation

The ball indentation technique based on deforming a material with a spherical indenter is an useful non-destructive tool for evaluating mechanical properties from a very small volume of material. In this work, the indentation test carried out using a 1.0 mm diameter tungsten carbide ball to penetration depths of around 100–200 μm is modeled using finite element (FE) method and analyzed for three steels having different yield stress and strain hardening exponent. The FE generated load–depth curve is compared and verified with the experimental load–depth data for the three materials. The role of the contact friction at the indenter–specimen interface on both the load—depth plot and indentation profile are examined. The development of pile-up/sink-in during indentation and its dependence on strain hardening characteristics of the material, contact friction and indentation depth are analyzed using the FE model. The indentation profiles obtained from simulation are compared with experimental profiles and the implication of pile-up phenomenon on accurate evaluation of stress–strain values from the experimental indentation load–depth data is discussed.