Ergodic and adaptive control of nearest-neighbor motions

The self-tuning approach to adaptive control is applied to a class of Markov chains called nearest-neighbor motions. These have a countable state space and move from any state to at most finitely many neighboring states. For compact parameter and control spaces, the almost-sure optimality of the self-tuner for an ergodic cost criterion is established under two sets of assumptions.     

Instruction level power analysis and optimization of software

The increasing popularity of power constrained mobile computers and embedded computing applications drives the need for analyzing and optimizing power in all the components of a system. Software constitutes a major component of today's systems, and its role is projected to grow even further. Thus, an ever increasing portion of the functionality of today's systems is in the form of instructions, as opposed to gates. This motivates the need for analyzing power consumption from the point of view of instructions—something that traditional circuit and gate level power analysis tools are inadequate for. This paper describes an alternative, measurement based instruction level power analysis approach that provides an accurate and practical way of quantifying the power cost of soft-ware. This technique has been applied to three commercial, architecturally different processors. The salient results of these analyses are summarized. Instruction level analysis of a processor helps in the development of models for power consumption of software executing on that processor. The power models for the subject processors are described and interesting observations resulting from the comparison of these models are highlighted. The ability to evaluate software in terms of power consumption makes it feasible to seach fow low power implementations of given programs. In addition, it can guide the development of general tools and techniques for low power software. Several ideas in this regard as motivated by the power analysis of the subject processors are also described.     

Study of optical properties and light induced effects on Inq3 thin film used in organic light emitting devices

In this report, the optical properties of tris-(8-hydroxyquinoline) metal complex Inq₃; used as light-emitting layer in electroluminescent (EL) devices are shown. The material has been synthesized and the thin films have been deposited by thermal evaporation on quartz and silicon substrates. The optical constants (n and k) of Inq₃ thin films have been determined using spectroscopic ellipsometry. Light induced effects on optical properties of films have been studied using ellipsometry, photoluminescence and UV–visible transmission measurements. Enhanced photoluminescence intensity with shift in peak position as well as modification in optical constants on light exposure in vacuum indicates phase transformation in Inq₃ films.     

Decomposition of monazite concentrate in sulphuric acid

A sulphuric acid bake-leach process was investigated for the extraction of rare earth elements (REEs), uranium, and thorium from a monazite concentrate. X-ray diffraction analysis showed the formation of water-soluble sulphates that readily dissolved during the water leach step. Nearly complete extraction of REEs, uranium, and thorium was achieved when the concentrate was baked at 250°C for 4?h with a sulphuric acid to concentrate (S/C) weight ratio of 4:1. At the 1:1 sulphuric acid to concentrate ratio ～65% of REEs were leached while only ～2–5% of uranium and thorium were extracted. Temperature (180–250°C) had little effect on the extraction of REEs, but greatly affected the extraction of thorium and uranium. In general, the extraction of thorium and uranium decreased with an increase in temperature. The effect of particle size (48–137?µm) was also tested and found to have little effect on the extraction of REEs. Acid consumption was calculated and found to increase with longer baking times (0.3–0.8?g acid/g concentrate). The major mineralogical phases formed because of the sulphation reaction included potassium cerium sulphate hydrate (2K₂SO₄·Ce(SO₄)₂·2H₂O), lanthanum sulphate hydrate (La₂(SO₄)₃·2H₂O), sodium praseodymium sulphite hydrate (NaPr(SO₃)₂·2H₂O), and neodymium sulphate hydrate (Nd₂(SO₄)₃·5H₂O), all of which were water-soluble.     

Secure Cloud Data Storage System Using Hybrid Paillier–Blowfish Algorithm

Cloud computing utilizes enormous clusters of serviceable and manageable resources that can be virtually and dynamically reconfigured in order to deliver optimum resource utilization by exploiting the pay-per-use model. However, concerns around security have been an impediment in the extensive adoption of the cloud computing model. In this regard, advancements in cryptography, accelerated by the wide usage of the internet worldwide, has emerged as a key area in addressing some of these security concerns. In this document, a hybrid cryptographic protocol deploying Blowfish and Paillier encryption algorithms has been presented and its strength compared with the existing hybrid Advanced Encryption Standard (AES) and Rivest Shamir Adleman (RSA) techniques. Algorithms for secure data storage protocol in two phases have been presented. The proposed hybrid protocol endeavors to improve the power of cloud storage through a decrease in computation time and cipher-text size. Simulations have been carried out with Oracle Virtual Box and Fog server used on an Ubuntu 16.04 platform. This grouping of asymmetric and homomorphic procedures has demonstrated enhanced security. Compression usage has helped in decreasing the storage space and computation time. Performance analysis in terms of computation overhead and quality of service parameters like loads of parameters with and without attacks, throughput, and stream length for different modes of block cipher mode has been carried out. Security analysis has been carried out by utilizing the Hardening Index as an audit parameter using Lynis 2.7.1. Similarly, for halting the aforementioned approaches and for regulating traffic, firewall protection has been generated in the chosen hybrid algorithms. Finally, enhancements in the performance of the Paillier and Blowfish hybrid scheme with and without compression compared to the existing schemes using RSA and AES procedures have been demonstrated.     

Surface analysis of stationary shoulder friction stir processed AZ31B magnesium alloy

We propose a stationary shoulder friction stir process (SSFSP) to produce a smooth surface finish. The use of a stationary shoulder tool contributes to reducing the heat input during friction stir processing (FSP). Hence, a stationary shoulder tool is advantageous for FSP in heat sensitive alloys like magnesium. The present short communication investigates the surface finish of AZ31B magnesium alloy processed by SSFSP without using additional cooling. Surface analysis of the processed region was carried out by 2D and 3D surface mapping using digital microscopy. The surface mapping indicated that there was very little flash generation on the processed zone, while 3D mapping quantified the surface roughness in the longitudinal as well as transverse directions of the processing zone.     

Particle‐resolved simulations of methane steam reforming in multilayered packed beds

Particle‐resolved CFD simulations of multilayered packed beds containing 30 particles of different particle shapes (trilobe, daisy, hollow cylinder, cylcut, and 7‐hole cylinder) with a tube to particle diameter ratio of 5, were performed to understand the effect of particle shape on pressure drop (ΔP), dispersion, CH₄ conversion and effectiveness factors for methane steam reforming reactions. The effect of different boundary conditions and particle modeling approaches were analyzed in detail. The empirical correlations (Ergun and Zhavoronkov et al.) over‐predicted the ΔP and a modified correlation was developed to predict ΔP for the particles with different shapes. Overall, the externally shaped particles (trilobe and daisy) offered lower ΔP and higher dispersion because of the lower surface area and higher back flow regions, whereas the internally shaped particles (cylcut, hollow, and 7‐hole cylinder) offered higher CH₄ conversion and effectiveness factors because of the better access for the reactants. The cylcut‐shape offered the highest CH₄ conversion/ΔP. © 2018 American Institute of Chemical Engineers AIChE J, 64: 4162–4176, 2018     

X-ray study of weak interactions in two flavonoids

X-ray diffraction studies were carried out on single crystals of two flavonoids, viz. 5-hydroxy-6,7,4′-trimethoxyflavone, C₁₈H₁₆O₆, (I) and 5-hydroxy-3,7,4′-trimethoxyflavone, C₁₈H₁₆O₆, (II). Crystal structures of both the flavonoids were solved by direct methods and refined by full-matrix least-squares procedures. In both the molecules, the benzopyran moiety is planar. The dihedral angle between the phenyl ring and the benzopyran portion is 5.50(4)° in (I) and 29.11(5)° in (II). In (I), the crystal packing is influenced by O-H…O hydrogen bonds, and weak C-H…O and π…π interactions whereas in (II) the crystal structure is stabilized by the presence of four intermolecular short contacts of the type C-H…O. There is also one C-H…π hydrogen bond with H… centroid distance of <2.7 Å. The molecules are further stabilized by π-π interactions.