Solving singular control problems using uniform trigonometrization method

This study investigates the application of a recently developed construct, the uniform trigonometrization method (UTM), to the singular control problems in chemical engineering. The UTM involves minimal modifications to the original problem, thereby generating near-singular control solutions that can be used for conceptual design and serve as an alternate to direct techniques like nested and simultaneous approaches. Eight classical singular control problems with known analytical solutions and three complex singular control problems from chemical engineering domain are solved in this study. The results obtained using the UTM for these problems are found to match well with the literature and are of higher resolution as compared to the results obtained using a direct pseudospectral-based solver. The ability of the UTM to handle complex chemical engineering problems with both singular controls and state path constraints has also been demonstrated in this study.     

Formation of BaCrO4 NanoCrystallites within Thermally Evaporated Sodium Bis-2-Ethylhexyl-Sulfosuccinate and Stearic Acid Thin Films

This paper describes the growth of barium chromate (BaCrO₄) nanocrystallites within thermally evaporated thin films of stearic acid (StA) and sodium bis-2-ethylhexyl-sulfosuccinate by a process of Ba²⁺ ion entrapment followed by in situ reaction with CrO₄²⁻ ions. Dense spherical assemblies of BaCrO₄ nanocrystallites of very uniform size (∼50 nm) were obtained within the two different host matrices. The spherical assemblies were composed of smaller (ca. 5–10 nm size) BaCrO₄ crystals indicating that efficient size control over crystal size may be exercised by the matrix. Contact angle measurements of the BaCrO₄–StA and BaCrO₄–sodium bis-2-ethylhexyl-sulfosuccinate films indicated that they were hydrophobic, thus pointing to the possible role of hydrophobic interaction between the StA and sodium bis-2-ethylhexyl-sulfosuccinate monolayer-covered BaCrO₄ crystals in the assembly process.     

Thermal-gradient-induced interaction energy ramp and actuation of relative axial motion in short-sleeved double-walled carbon nanotubes

We investigate the phenomenon of actuation of relative linear motion in double-walled carbon nanotubes (DWNTs) resulting from a temperature gradient. Molecular dynamics simulations of DWNTs with short outer tube reveal that the outer tube is driven towards the cold end of the long inner tube. It is also found that the terminal velocity of the sleeve roughly depends linearly on the applied thermal gradient. We calculate the inter-tube interaction energy surface which is revealed to have a gradient depending upon the applied thermal gradient. Consequently, it is proposed that the origin of the thermophoretic motion of the outer tube may be attributed partially to the existence of such an energy gradient. A simple analytical model is presented accounting for the gradient in energy profile as well as the effect of biased thermal noise. It is shown that the proposed model predicts the dynamical behaviour of the long-time performance reasonably well.     

Prediction of the equilibrium,paraequilibrium and no-partition local equilibrium phase diagrams for multicomponent Fe-C base alloys

A method is described for the accurate prediction of Fe-C base multicomponent phasediagrams in the α-γ-cem range for both equilibrium and no-partitioning transformation states (paraequilibrium or no-partition local equilibrium) and applicable for total alloy contents (Mn + Si + Ni + Cr + Mo + Cu) less than 5 wt% and Si less than 1 wt%. The equilibrium predictions based on independent thermodynamic data collated by Uhrenius are in excellent agreement with Ae₃ temperatures given in the U.S.S. Atlas and published by Grange in Metal Progress. Calculations of the A₁ (eutectoid) temperatures indicate that Fe-C-Cr alloys transform in the equilibrium partition mode whereas Fe-C-Mn and Fe-C-Ni alloys tend to favour the paraequilibrium mode. This latter inference is in broad agreement with the pearlite partitioning experiments of Ridley and coworkers.     

Improved differential evolution based on multi-armed bandit for multimodal optimization problems

Applied Intelligence - The main aim of multimodal optimization problems (MMOPs) is to find and deal with multiple optimal solutions using an objective function. MMOPs perform the exploration and...     

E-Health Cloud Security Using Timing Enabled Proxy Re-Encryption

Mobile Networks and Applications - In the present era of Information Technology, almost all big and small scale companies are moving towards cloud to store and manage the data. Cloud computing is a...     

Investigation of the effects of commensurability on friction between concentric carbon nanotubes

That a commensurate contact usually leads to greater friction than an incommensurate one is a commonly held view in nanotribology. However, this perception seems paradoxical as commensurability is found to have negligible effect on the energy dissipation in double-walled carbon nanotube (DWNT) based oscillators. Using molecular dynamics simulations, we investigate such a paradox from the viewpoint of the atomic origin of friction. It is revealed that the commensurability cannot have a pronounced effect on friction unless the intertube interaction strength and the energy corrugation exceed their critical values. Both the commensurate and incommensurate oscillators constructed from natural DWNTs with an intertube distance of about 3.4 ?, may thus exhibit similar performance.     

Studies on thick films of photoconducting cadmium sulphide

Highly photosensitive films of CdS have been prepared using the thick film technique. The films obtained from the composition containing CdS-100, CdCl₂−10 and CuCl₂−0·05 parts by weight (reacted at 500° C) are found to give the best photosensitivity on firing at 600° C. The ratio of light to dark current ∼10⁸–10⁹ which is considerably higher than what is reported for thin films, single crystals and sintered layers. A strong chemisorption of oxygen is found to be responsible for high photosensitivity. The spectral response for doped CdS film is similar to that obtained for thin films, single crystals and sintered layers and also shows a red shift with increasing Cu concentration. However, the undoped CdS has a broad spectral response at room temperature ranging fromλ=550 to 690 nm; unlike the thin films and single crystals which give a sharp peak atλ=510 to 520 nm. A probable explanation has been suggested for this type of behaviour. NCL Communication No. 2502.     

Plasmon resonant enhancement of photocatalytic water splitting under visible illumination

We demonstrate plasmonic enhancement of photocatalytic water splitting under visible illumination by integrating strongly plasmonic Au nanoparticles with strongly catalytic TiO2. Under visible illumination, we observe enhancements of up to 66× in the photocatalytic splitting of water in TiO2 with the addition of Au nanoparticles. Above the plasmon resonance, under ultraviolet radiation we observe a 4-fold reduction in the photocatalytic activity. Electromagnetic simulations indicate that the improvement of photocatalytic activity in the visible range is caused by the local electric field enhancement near the TiO2 surface, rather than by the direct transfer of charge between the two materials. Here, the near-field optical enhancement increases the electron-hole pair generation rate at the surface of the TiO2, thus increasing the amount of photogenerated charge contributing to catalysis. This mechanism of enhancement is particularly effective because of the relatively short exciton diffusion length (or minority carrier diffusion length), which otherwise limits the photocatalytic performance. Our results suggest that enhancement factors many times larger than this are possible if this mechanism can be optimized.