Theoretical performance limits of a syngas-diesel fueled compression ignition engine from second law analysis

The present study is an attempt to investigate a syngas-diesel dual fueled diesel engine operation under varying load conditions from the second law point of view. The fuel type in dual fuel operation is achieved by varying the volumetric fractions of hydrogen (H₂) and carbon monoxide (CO) content in syngas. It is revealed that increasing the hydrogen quantity of syngas increases the cumulative work availability and reduces the destroyed availability. This enhancement is due to a better combustion process and increased work output when a high amount of H₂ quantity is employed. At lower loads, the in-cylinder combustion temperatures are reduced in case of the dual fuel combustion. Hence, the destruction availability is increased due to poor combustion and reduced heat transfer availability losses. When the engine is operated beyond 40% load, the destroyed availability reduced due to higher combustion temperature and pressure. The increase in the both exhaust gas and cooling water availabilities are reflected in an increase in second law efficiency with increasing load. The dual fuel cumulative work availability is increased at higher loads and thus, the exergy efficiency is increased.     

A Novel Multi-agent Formation Control Law With Collision Avoidance

In this paper a stable formation control law that simultaneously ensures collision avoidance has been proposed. It is assumed that the communication graph is undirected and connected. The proposed formation control law is a combination of the consensus term and the collision avoidance term (CAT). The first order consensus term is derived for the proposed model, while ensuring the Lyapunov stability. The consensus term creates and maintains the desired formation shape, while the CAT avoids the collision. During the collision avoidance, the potential function based CAT makes the agents repel from each other. This unrestricted repelling magnitude cannot ensure the graph connectivity at the time of collision avoidance. Hence we have proposed a formation control law, which ensures this connectivity even during the collision avoidance. This is achieved by the proposed novel adaptive potential function. The potential function adapts itself, with the online tuning of the critical variable associated with it. The tuning has been done based on the lower bound of the critical variable, which is derived from the proposed connectivity property. The efficacy of the proposed scheme has been validated using simulations done based on formations of six and thirty-two agents respectively.      

Wave interaction with a floating and submerged elastic plate system

Surface gravity wave interaction with a floating and submerged elastic plate system is analyzed under the assumption of small-amplitude surface water wave theory and structural response. The plane progressive wave solution associated with the plate system is analyzed to understand the characteristics of the flexural gravity waves in different modes. Further, linearized long-wave equations associated with the wave interaction with the elastic plate system are derived. The dispersion relations are derived based on small-amplitude wave theory and shallow-water approximation and are compared to ensure the correctness of the mathematical formulation. To deal with various types of problems associated with gravity wave interaction with a floating and submerged flexible plate system, Fourier-type expansion formulae are derived in the cases of water of both finite and infinite depths in two dimensions. Certain characteristics of the eigensystems of the developed expansion formulae are derived. Source potentials for surface wave interaction with a floating flexible structure in the presence of a submerged flexible structure are derived and used in Green’s identity to obtain the expansion formulae for flexural gravity wavemaker problems in the presence of submerged flexible plates. The utility of the expansion formulae and associated orthogonal mode-coupling relations is demonstrated by investigating the diffraction of surface waves by floating and submerged flexible structures of two different configurations. The accuracy of the computational results is checked using appropriate energy relations. The present study is likely to provide fruitful solutions to problems associated with floating and submerged flexible plate systems of various configurations and geometries arising in ocean engineering and other branches of mathematical physics and engineering including acoustic structure interaction problems.     

Effect of Layered MoS2 Nanoparticles on the Frictional Behavior and Microstructure of Lubricating Greases

Lithium stearate soap and layered MoS₂ nanoparticles encapsulated in lithium stearate soap are prepared in the laboratory, and their lubricating properties are compared with respect to the particle and particle concentration. The tribotracks after friction test was investigated with Raman Spectroscopy, scanning electron microscopy (SEM) and 3D optical profilometry to understand the action mechanism. The status of the soap particles on a tribotrack changes with time, contact pressure and sliding speed. At low pressure and speed, individual solid undeformed soap particle stand proud of the surface and the topography shows marginal difference with sliding time. In these conditions, no frictional difference between the performance of grease with and without the nanoparticles is observed. Increasing the contact pressure and temperature (low speed and high speed) has a dramatic effect as the soap particles melt and the liquid soap flows over the track releasing the hitherto encapsulated nanoparticles. Consequently, the soap smears the track like a liquid, and the nanoparticles now come directly into the interface and are sheared to generate a low-friction tribofilm. At high particle concentration, the sliding time required for melting of the soap and release of MoS₂ is reduced, and the tribofilm is more substantial and uniform consisting of smeared MoS₂ and carboxylate soap as observed by SEM and 3D optical profilometry. A change in the Raman Spectra is observed with particle concentration, and this is related to morphology and microstructure of the tribofilm generated.     

Enhanced dielectric,thermal stability,and energy storage properties in compositionally engineered lead-free ceramics at morphotropic phase boundary

Structural inhomogeneity at morphotropic phase boundary (MPB) offers a novel paradigm to explore and modulate the physical properties of dielectric materials to design next-generation multifunctional devices. In this work, two lead free materials at MPB; Ba_0.85Ca_0.15Zr_0.1Ti_0.9O₃ (BCZT) and (Bi_0.5Na_0.5)TiO₃-0.06BaTiO₃ (BNTBT), are combined together to synthesize polycrystalline composite samples of (1-x) BCZT-xBNTBT with x = 0.0, 0.25, 0.50, 0.75, and 1.0. Structural investigations using XRD show the coexistence of double phases for pristine BCZT (tetragonal (P4mm) + rhombohedral (R3m)), and for pristine BNTBT (tetragonal (P4bm) + rhombohedral (R3c)). However, all the doped samples with x = 0.25, 0.5, and 0.75 display a coexistence of triple phases with P4mm, P4bm, and R3c symmetries. Detailed dielectric study reveals a normal ferroelectric to macroscopic ergodic relaxor crossover for samples with x = 0.25 and 0.75. Intriguingly, sample x = 0.25 displays a coexistence of high dielectric constant (4050), ultralow dielectric loss (≤0.02), high temperature thermal stability of permittivity (variation ≤ ±15%) in a temperature range 135 °C–450 °C, large recoverable energy density (W_rec = 423 mJ/cm³) with ultrahigh energy storage efficiency (η = 95.4%) at low applied electric field - 23 kV/cm. Nevertheless, at similar applied field strength, the obtained values of W_rec and η exceed most of the selected lead-free energy storage materials. This work may pave a new path to design superior high-temperature dielectrics, through intermixing of MPBs, for energy storage applications.     

3‐Substituted Indazoles as Configurationally Locked 4EGI‐1 Mimetics and Inhibitors of the eIF4E/eIF4G Interaction

4EGI‐1, the prototypic inhibitor of eIF4E/eIF4G interaction, was identified in a high‐throughput screening of small‐molecule libraries with the aid of a fluorescence polarization assay that measures inhibition of binding of an eIF4G‐derived peptide to recombinant eIF4E. As such, the molecular probe 4EGI‐1 has potential for the study of molecular mechanisms involved in human disorders characterized by loss of physiological restraints on translation initiation. A hit‐to‐lead optimization campaign was carried out to overcome the configurational instability in 4EGI‐1, which stems from the E‐to‐Z isomerization of the hydrazone function. We identified compound 1 a , in which the labile hydrazone was incorporated into a rigid indazole scaffold, as a promising rigidified 4EGI‐1 mimetic lead. In a structure–activity relationship study directed towards probing the structural latitude of this new chemotype as an inhibitor of eIF4E/eIF4G interaction and translation initiation we identified 1 d , an indazole‐based 4EGI‐1 mimetic, as a new and improved lead inhibitor of eIF4E/eIF4G interaction and a promising molecular probe candidate for elucidation of the role of cap‐dependent translation initiation in a host of pathophysiological states.     

Seismic performance of buckling-restrained braced frames with varying beam-column connections

The effect of beam-column connections and brace configurations on the overall seismic response of a medium-rise bucklingrestrained braced frame (BRBF) is analytically evaluated in the present study. Two types of brace configurations (chevron and Double-X) and a combination of the moment-resisting and the non-moment-resisting beam-column connections are considered. A total of five design cases are studied for a seven-story BRBF in which a constant value of response reduction (R) factor equal to 8 is considered in the design. Nonlinear dynamic analyses are carried out for all study frames for an ensemble of forty ground motions representing the DBE and MCE hazard levels. Fragility curves are developed for all study frames considering the interstory drift ratio and residual drift ratio as the damage parameters. Results showed that a higher value of response reduction factor should be adopted in the design of BRBFs for both pinned and rigid beam-column connections. Further, in order to achieve the desired seismic performance of BRBFs, Double-X brace configurations and rigid beam-column connections at the alternate story levels should be used.     

Modelling and simulation of a bio-fuelled conventional engine

In the present work, a simulation model based on two different zones of combustion in compression ignition (CI) engines has been modified to predict the performance of a four-stroke CI engine. The modified model for the calculation of closed cycle of a four-stroke diesel engine is presented and applied for its operation with vegetable oil (Jatropha), which is considered as promising bio-fuels now a days. For the local temperature and cylinder pressure calculations, the mass and state equations are applied in each zone. The effect of fuel injection pressure and advance angle of fuel injection point on the brake thermal efficiency, brake-specific fuel consumption and nitric oxide emission has been analysed. The results from a computer program are compared and verified with the corresponding measurements from an experimental investigation conducted on the test bed. A good synchronisation is observed between the model's prediction and the available theoretical and experimental results. Engineering equation solver has been used as the programming input to the model.     

Synthesis, characterization and densification of WCu nanocomposite powders

In the present investigation, W20-40wt.% Cu nanocomposite powders with average sizes ranging between 25 and 30 nm were synthesized by a soft chemical approach using tungsten hexacarbonyl [W(CO)₆] and copper acetonyl acetonate [Cu(acac)₂] as metal precursors. Particle size, morphology and distribution were measured using transmission electron microscope (TEM) and small angle X-ray scattering (SAXS). Surfactant coating on WCu composite powders was removed on heat treatment of powders at 450 °C in hydrogen atmosphere for 1 h. Elemental analyses of as-synthesized and annealed (at 450 °C) WCu nanocomposite powders were carried out using inductively coupled plasma-optical emission spectrometer (ICP-OES) and Leco gas analyzers. X-ray diffraction studies showed that the tungsten phase is amorphous while the crystal structure of copper phase is fcc in as-synthesized WCu nanocomposite powders. After annealing at 700 °C peaks corresponding to bcc tungsten are observed and peaks corresponding to fcc copper become sharper. Relative densities of 98.2%, 98.8% and 99.2% were achieved for W20wt.% Cu, W30wt.% Cu, and W40wt.% Cu composite powders respectively when sintered at 1000 °C.     

Improvement of grinding characteristics of Indian coal by microwave pre-treatment

The influence of microwave pretreatment on the grindability of high-ash Indian coal was investigated. Scanning electron microscope analysis characterized the micro fractures in microwave treated coal samples, which may be due to the thermal stress cracking resulting from the microwave pretreatment. X-ray diffraction analysis showed that the microwave treated coal had a higher peak compared to the untreated coal indicates that the crystallinity increased with the microwave exposure time. The calculation of the Hardgrove grindability index indicated an increase in the ease of grinding or an increase in the grindability index of the microwave treated coal. Bond grindability tests showed that the work index decreased 15.4% after a microwave exposure time of 120 s. Grindability tests showed that the microwave treated coal ground much more rapidly initially than the untreated coal, with the specific rate of breakage (S₁) increasing by an average of 15%. The results showed that the rates of breakage of both microwave untreated and treated coal samples were dependent on particle size.