A support vector regression approach to detection in large-MIMO systems

We propose a support vector regression approach for symbol detection in large-MIMO systems employing spatial multiplexing. We explore the applicability of machine learning algorithms, in particular support vector machines, to address one of the recent research problem in communications.The machine learning capability is exploited to achieve fast detection in large dimension systems. The performance of the proposed method is compared with lattice reduction aided detection which is currently the popular choice and the improvement in terms of bit error rate is demonstrated. The sparse formulation of the problem matrix reduces the computational complexity and enables faster detection. The proposed detection algorithm is tailored to address both uncorrelated and correlated channel conditions as well.     

A post-growth processing methodology to achieve barium strontium titanate thin films with low dielectric loss and high tunability for reconfigurable tunable devices

Ba_0.60Sr_0.40TiO₃ (BST) thin films, grown via RF-sputtering and the metalorganic solution deposition (MOSD) techniques, were post-growth annealed via conventional thermal annealing (CTA) and UV-photon irradiation annealing. With respect to the conventional thermal annealed films the UV-photon irradiation annealed films possessed improved structural properties and dielectric response. The optimization of the UV-photon irradiation annealing process parameters (using RF-sputtered BST films) was achieved via a detailed set of iso-thermal/chronal annealing experiments. The optimized UV-process parameters, applied to MOSD synthesized BST films revealed further enhanced dielectric response, i.e., 23% reduction in tan δ with sustained tunability of 42%. The improvements in the material properties of the UV-photon irradiation annealed BST thin films are attributed to stoichiometry and structural changes enabled through the UV-photon irradiation annealing process.     

Stress analysis & life prediction of a cryogenic rocket engine thrust chamber considering low cycle fatigue, creep and thermal ratchetting

The paper deals with stress analysis, cyclic and creep life prediction of a cryogenic rocket engine thrust chamber, being used in one of the satellite launch vehicles of ISRO. The thrust chamber is of double walled construction wherein high conductivity copper alloy is used for the inner wall and stainless steel for the outer. Regenerative cooling of the chamber is achieved by passing the fuel through rectangular coolant passages milled on outer surface of the inner wall. The inner and outer walls are bonded together by brazing at high temperature. Failure of a double walled chamber occurs due to thinning of the inner wall and bulging into the chamber due to three mechanisms viz. (i) low cycle fatigue (ii) thermal ratchetting and (iii) creep. To capture the structural behaviour of the chamber in a complete sequence of operation of the engine, axisymmetric modeling and cyclic stress analysis is carried out using the ANSYS finite element analysis software package. High temperature mechanical properties, low cycle fatigue and creep properties of copper are characterised. Results of creep tests conducted at various temperatures are utilized for evaluating creep constants of Norton secondary creep model available in ANSYS. Analysis is performed in a seven load step sequence simulating one complete hot test of the engine. Life prediction is done using the cumulative damage accumulation methodology, considering the above three damage mechanisms. Allowable number of hot runs permissible is then arrived at after assigning suitable factors of safety for each damage mode.     

Effect of Hydrogen and Magnetic Field on the Mechanical Behavior of High Strength AISI 4340 Steel

Presence of hydrogen in materials is known to affect their mechanical properties due to hydrogen embrittlement problem. Steels used in various applications are prone to be exposed to aqueous electrochemical environments, which may introduce hydrogen into the alloy. These alloys are also prone to be simultaneously exposed to magnetic field, which may affect the hydrogen embrittlement susceptibility of these alloys. Therefore, it is important to examine the effect of hydrogen and magnetic field on the mechanical behavior of iron-based alloys. In this work, the effect of hydrogen and magnetic field on the fracture behavior of high strength AISI 4340 steel was examined. Three-point bend test was used to study the fracture behavior. In all the cases, the samples tested with hydrogen charging show a drastic reduction in ductility and fracture stress values. The effect of magnetic field was seen to be negligible. The hydrogen embrittlement was characterized by a change in the fracture surface from a ductile-type fracture to a brittle cleavage-type fracture. Acoustic emission signals collected during the test corresponds to the fracture behavior.     

Two-Phase (Air and Water) Flow through Rock Joints: Analytical and Experimental Study

This research study deals with the characterization of two-phase flow in a fractured rock mass. A comprehensive mathematical model with which to predict the quantity of each flow component in a single joint is developed. A joint with two parallel walls filled with layers of water and air (stratified) is analyzed. The effects of mechanical deformation of the joint, the compressibility of fluids, the solubility of air in water, and the phase change between fluids have been taken into account to develop analytical expressions which describe the behavior at the air–water interface. The model was calibrated using a newly designed two-phase (high-pressure) triaxial cell. Tests were conducted on fractured hard rock samples for different confining pressures with inlet water and inlet air pressures. As in single-phase flow, it was found both experimentally and theoretically, that the flow quantities of each phase decreases considerably with an increase in confining stress. The results also confirm that the effect of joint deformation and compressibility of fluids governs the flow volume of two-phase flow. Good agreement was obtained between the experimental data and numerical predictions.     

QoS assurances through class selection and proportional differentiation in wireless networks

Quality-of-service (QoS) in wireless ad hoc networks is adversely affected by node mobility, changing network topologies, and uncontrolled medium contention. The paper addresses the challenges in concurrently providing a wide range of end-to-end throughput and delay assurances in such networks. The proposed solution is based on the neighborhood proportional delay differentiation (NPDD) service model. With NPDD, applications achieve their desired end-to-end QoS using dynamic class selection (DCS) algorithms. With simulations in various distinct mobile network scenarios, we demonstrate the significantly better QoS assurances achieved with the proposed mechanism as compared with best effort and strict priority approaches. With game theoretic concepts, we model DCS applications in an NPDD network as selfish players in a noncooperative game. For such games, we prove for single-hop and multihop NPDD networks the existence of an equilibrium, the feasibility of an equilibrium, and the guaranteed convergence to a feasible equilibrium when one exists.     

Solvothermal‐assisted green synthesis of hybrid Chi‐Fe3 O4 nanocomposites: a potential antibacterial and antibiofilm material

In this present study, a hybrid Chi‐Fe₃ O₄ was prepared, characterised and evaluated for its antibacterial and antibiofilm potential against Staphylococcus aureus and Staphylococcus marcescens bacterial pathogens. Intense peak around 260 nm in the ultraviolet–visible spectrum specify the formation of magnetite nanoparticles. Spherical‐shaped particles with less agglomeration and particle size distribution of 3.78–46.40 nm were observed using transmission electron microscopy analysis and strong interaction of chitosan with the surface of magnetite nanoparticles was studied using field emission scanning microscopy (FESEM). X‐ray diffraction analysis exhibited the polycrystalline and spinel structure configuration of the nanocomposite. Presence of Fe and O, C and Cl elements were confirmed using energy dispersive X‐ray microanalysis. Fourier transform infrared spectroscopic analysis showed the reduction and formation of Chi‐Fe₃ O₄ nanocomposite. The antibacterial activity by deformation of the bacterial cell walls on treatment with Chi‐Fe₃ O₄ nanocomposite and its interaction was visualised using FESEM and the antibiofilm activity was determined using antibiofilm assay. In conclusion, this present study shows the green synthesis of Chi‐Fe₃ O₄ nanocomposite and evaluation of its antibacterial and antibiofilm potential, proving its significance in medical and biological applicationsInspec keywords: visible spectra, particle size, magnetic particles, nanocomposites, nanoparticles, X‐ray diffraction, nanofabrication, transmission electron microscopy, X‐ray chemical analysis, nanomagnetics, microorganisms, antibacterial activity, iron compounds, ultraviolet spectra, biomedical materials, field emission scanning electron microscopy, Fourier transform infrared spectra, filled polymers, crystal growth from solution, polymer structureOther keywords: potential antibacterial material, antibiofilm potential, magnetite nanoparticles, solvothermal‐assisted green synthesis, hybrid Chi‐Fe₃ O₄ nanocomposites, staphylococcus aureus, staphylococcus marcescens, bacterial pathogens, ultraviolet–visible spectrum, spherical‐shaped particles, particle size, transmission electron microscopy, FESEM, field emission scanning electron microscopy, X‐ray diffraction, spinel structure, polycrystalline structure, energy dispersive X‐ray microanalysis, Fourier transform infrared spectroscopic analysis, deformation, bacterial cell walls, Fe₃ O₄      

Detecting vascular access dysfunction

Access flow (QACC) is a major determinant of patency. Access recirculation (AR > 2%), normalized venous intra-access pressure (vPIA/MAP), and QACC are used to detect access dysfunction. We compared these three measures of access function (ultrasound dilution to measure AR and QACC). A total of 779 measurements were performed on 58 arteriovenous fistulas (AVFs) and 114 polytetrafluoroethylene (PTFE) grafts (1-8/access) over 13 months, and the access parameters at the beginning of each period were related to access events within that period. Pump blood flow averaged > 420 ml/min. AR occurred uncommonly (3.8%), and in half the cases, resulted from technical error by staff. In accesses that thrombosed or underwent intervention for stenosis, AR was present in only 3 of 11 AVFs and 8 of 57 PTFE accesses. When AR was present in grafts, QACC averaged 270 +/- 23, and access thrombosis followed unless intervention occurred. In grafts, vPIA/MAP averaged 0.34 +/- 0.01 in those remaining patent, 0.52 +/- 0.08 in those that had undergone intervention, and 0.54 +/- 0.04 in those that had thrombosed. QACC averaged 1,121 +/- 26, 605 +/- 45, and 550 +/- 65 ml/min, respectively, in the three groups. By contrast, QACC differed significantly in patent AVFs (1,053 +/- 35) compared with failing AVFs (363 +/- 48), but vPIA/MAP did not. AR is thus a late manifestation of access failure. QACC is the best diagnostic test of access dysfunction in AVFs. Interpretation of vPIA/MAP in grafts is enhanced by periodic QACC measurements.     

Selection of timed token protocol parameters to guarantee messagedeadlines

Networks that use the timed token protocol (such as the 100 Mbit/s FDDI network) are well suited for real-time applications because they guarantee, to each node, an average bandwidth and a bounded access time to the communication network. This guarantee is necessary but not sufficient for the timely delivery of deadline-constrained messages; protocol parameters must be carefully selected to ensure that these messages meet their deadlines. This paper addresses the issue of selecting the protocol parameters TTRT (target token rotation time) and the synchronous capacities assigned to each node. The objective is to guarantee that each synchronous message is transmitted before its deadline. An upper bound is derived on the worst case achievable utilization (WCAU) of any parameter selection scheme. The WCAU of a scheme is defined as the maximum utilization U such that the scheme guarantees all synchronous messages as long as their utilization is less than U. An algorithm for selecting the above parameters is proposed, The algorithm is shown to have a WCAU that is very close to the upper bound     

Fault-tolerant clock synchronization in distributed systems

Existing fault-tolerant clock synchronization algorithms are compared and contrasted. These include the following: software synchronization algorithms, such as convergence-averaging, convergence-nonaveraging, and consistency algorithms, as well as probabilistic synchronization; hardware synchronization algorithms; and hybrid synchronization. The worst-case clock skews guaranteed by representative algorithms are compared, along with other important aspects such as time, message, and cost overhead imposed by the algorithms. More recent developments such as hardware-assisted software synchronization and algorithms for synchronizing large, partially connected distributed systems are especially emphasized