Review on solar water heater collector and thermal energy performance of circulating pipe

The effect of thermal conductivity of the absorber plate of a solar collector on the performance of a thermo-siphon solar water heater is found by using the alternative simulation system. The system is assumed to be supplied of hot water at 50 °C and 80 °C whereas both are used in domestic and industrial purposes, respectively. According to the Rand distribution profile 50, 125 and 250 l of hot water are consumed daily. The condition shows that the annual solar fraction of the planning functions and the collector's configuration factors are strongly dependent on the thermal conductivity for its lower values. The less dependence is observed beyond a thermal conductivity of 50 W/m °C for the solar improper fraction and above 100 W/m °C for the configuration factors. In addition, the number of air ducts and total mass flow rate are taken to show that higher collector efficiency is obtained under the suitable designing and operating parameters. Different heat transfer mechanisms, adding natural convection, vapor boiling, cell nucleus boiling and film wise condensation is observed in the thermo-siphon solar water heater with various solar radiations. From this study, it is found that the solar water heater with a siphon system achieves system characteristic efficiency of 18% higher than that of the conventional system by reducing heat loss for the thermo-siphon solar water heater.     

Development of Al 6063–TiB2 in situ composites

In situ TiB₂ reinforced Al 6063 composites have been successfully synthesized through the chemical reaction between Al–10%Ti and Al–3%B master alloys in the Al 6063 alloy using liquid metallurgy route. The amount of TiB₂ formed in the composite is estimated using gravimetric analysis. Mechanical properties in terms of microhardness, ultimate tensile strength and modulus of elasticity have been improved by 21%, 47% and 65% respectively in comparison with matrix alloy. Further, ductility in terms of percentage elongation of the composites was found to increase by about 368% when compared with the matrix alloy. The improvement in ductility may be associated with the grain refinement of the composite with an increase in the content of Al–3%B master alloy.     

Separation of metal ions by the influence of a cation‐exchange terpolymer involving 2‐amino‐6‐nitrobenzothiazole–ethylenediamine–formaldehyde

A novel terpolymer involving 2‐amino‐6‐nitrobenzothiazole and ethylenediamine with formaldehyde was synthesized by a polycondensation technique using glacial acetic acid as a reaction medium. The resulting chelating terpolymer resin was characterized using elemental analysis, physicochemical parameters, and UV‐visible, Fourier transform infrared, ¹H NMR and ¹³C NMR spectral studies. Average molecular weights of the terpolymer were determined using gel permeation chromatography. The surface morphology and the nature of the terpolymer were investigated using scanning electron microscopy and X‐ray diffraction. The chelation ion‐exchange property of the terpolymer was determined against some common metal ions such as Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺ and Pb²⁺ using the batch equilibrium method. Effects of parameters such as the pH, contact time and various electrolyte concentrations were studied. The reusability of the terpolymer was checked in terms of its effective repeated usage. The results of the Langmuir and Freundlich adsorption isotherm models were best fitted with each other and the reaction kinetics followed pseudo second‐order kinetics. The terpolymer showed good results against Fe³⁺, Cu²⁺ and Ni²⁺ ions compared to those against the other metal ions. © 2014 Society of Chemical Industry     

Intramuscular injection as a provoking factor for paralysis in acute poliomyelitis. A case control study

In order to identify the role of intramuscular injection (IM) as a provoking factor for poliomyelitis, a case control study as done at the Institute of Child Health, Madras from May 1988 to May 1989. The case was defined as acute poliomyelitis if he had acute asymmetric flaccid paralysis of lower motor neurone type without objective sensory disturbance following a short episode of fever. Controls were taken from children attending outpatient department for fever. Two controls matched for aged and sex were recruited for each case. Recruitment, data collection and clinical examination were done by a single pediatrician. IM injection received within 30 days prior to onset of paralysis or illness was considered to be the risk factor. The total number of cases and controls recruited were 257 and 515, respectively. Among cases, 172 (66.9%) out of 257 and among controls 252 (48.9%) out of 515, received IM injection within one month earlier to onset of paralysis or illness. The overall risk of paralysis, estimated for IM injection, was increased [odds ratio (OR) 2.1 (95% CI, 1.5-3.0)]. The maximum risk for paralysis was observed to be 2 weeks preceding the illness; the ORs for < 7 days was 2.2 (95% CI, 1.6-3.2) and for 7-13 days 3.2 (95% CI, 1.8 to 5.8). The risk of paralysis associated with IM injection was similar for unimmunized and immunized cases (OR 2.4 and 2.2). Multiple injections were not associated with a higher risk of developing paralysis.(ABSTRACT TRUNCATED AT 250 WORDS)     

Optimal repair stage for K-out-of-N systems

Optimization studies on reliability systems is currently a fascinating area of research. In recent investigations, optimization techniques have been extended to cover even more complex reliability systems with larger applicational scope. In this paper, we study a complex system in terms of a K-out-of-N system (for example, occuring in mass transmission and computer networks) with provision for a repair facility. We develop an optimization procedure to help identify the Optimal Repair Stage for the system under certain conditions. The applicational use of the theoretical results is illustrated through numerical work, specifically the negative exponential law governing stochastic repair times.     

Projection operator-based robust adaptive control of an aerial robot with a manipulator

This paper describes a quadcopter manipulator system, an aerial robot with an extended workspace, its controller design, and experimental validation. The aerial robot is based on a quadcopter with a three degree of freedom robotic arm connected to the base of the vehicle. The work aims to create a stable airborne robot with a robotic arm that can work above and below the airframe, regardless of where the arm is attached. Integrating a robotic arm into an underactuated, unstable system like a quadcopter can enhance the vehicle's functionality while increasing instability. To execute a mission with accuracy and reliability during a real-time task, the system must overcome the inter-coupling effects and external disturbances. This work presents a novel design for a robust adaptive feedback linearization controller with a model reference adaptive controller and hardware implementation of the quadcopter manipulator system with plant uncertainties. The closed-loop stability of the aerial robot and the tracking error convergence with the robust controller is analyzed using Lyapunov stability analysis. The quadcopter manipulator system is custom developed in the lab with an off-the-shelf quadcopter and a 3D-printed robotic arm. The robotic system architecture is implemented using a Jetson Nano companion computer for autonomous onboard flight. Experiments were conducted on quadcopter manipulator system to evaluate the autonomous aerial robot's stability and trajectory tracking with the proposed controller.     

Auto-tuned Krylov methods on cluster of graphics processing unit

Exascale computers are expected to have highly hierarchical architectures with nodes composed by multiple core processors (CPU; central processing unit) and accelerators (GPU; graphics processing unit). The different programming levels generate new difficult algorithm issues. In particular when solving extremely large linear systems, new programming paradigms of Krylov methods should be defined and evaluated with respect to modern state of the art of scientific methods. Iterative Krylov methods involve linear algebra operations such as dot product, norm, addition of vectors and sparse matrix–vector multiplication. These operations are computationally expensive for large size matrices. In this paper, we aim to focus on the best way to perform effectively these operations, in double precision, on GPU in order to make iterative Krylov methods more robust and therefore reduce the computing time. The performance of our algorithms is evaluated on several matrices arising from engineering problems. Numerical experiments illustrate the robustness and accuracy of our implementation compared to the existing libraries. We deal with different preconditioned Krylov methods: Conjugate Gradient for symmetric positive-definite matrices, and Generalized Conjugate Residual, Bi-Conjugate Gradient Conjugate Residual, transpose-free Quasi Minimal Residual, Stabilized BiConjugate Gradient and Stabilized BiConjugate Gradient (L) for the solution of sparse linear systems with non symmetric matrices. We consider and compare several sparse compressed formats, and propose a way to implement effectively Krylov methods on GPU and on multicore CPU. Finally, we give strategies to faster algorithms by auto-tuning the threading design, upon the problem characteristics and the hardware changes. As a conclusion, we propose and analyse hybrid sub-structuring methods that should pave the way to exascale hybrid methods.     

A Si MMIC compatible ferroelectric varactor shunt switch for microwave applications

This letter describes a ferroelectric thin-film based varactor shunt switch, for microwave and millimeterwave switching applications. Our implementation is based on a coplanar waveguide transmission line shunted by a ferroelectric varactor. The concept of switching ON and OFF is based on the dielectric tunability of the ferroelectric barium strontium titanium oxide (BST) thin-films. From experimental verification, the isolation of a switch with a varactor area of 75/spl mu/m/sup 2/ was approximately 20dB at 35GHz and the insertion loss was below 4.5dB up to 35GHz. This letter addresses the design and experimental verification of the first ferroelectric varactor shunt switch with an Si monolithic microwave integrated circuit compatible process.