Corrosion Failure of Bottom Plates of an Aboveground Storage Tank

This paper describes the investigation of a corrosion failure of bottom plates on an aboveground tank used for the storage of potable water. The tank was internally inspected for the first time after six years of service. Paint blisters and rust spots were observed on the bottom plates and first to third course shell plates. Sand blasting and repainting of the bottom plates and first course shell plates was to be used as a remedial measure. However, during the sand blasting, holes and deep pitting were observed on the bottom plates. On-site visual inspection, magnetic flux leakage (MFL) inspection, ultrasonic testing (UT), and evaluation of the external cathodic protection (CP) system were used in the failure analysis. The corrosion products were analyzed using energy-dispersive X-ray analysis (EDAX). The failure is attributed to the ingress of water and its impoundment under the tank bottom along the periphery inside the ring wall and failure of water side epoxy coating. Various measures to prevent such failures in the future are recommended.     

Correlation-based double-directional stochastic channel model for multiple-antenna ultra-wideband systems

A correlation-based double-directional stochastic channel model for indoor multiple-input multiple-output (MIMO) ultra-wideband (UWB) propagation channels is proposed. The proposed model extends the IEEE 802.15.3a standard model to spatially correlated MIMO channels. Both angular and temporal statistics are taken into account in the modelling procedure. Spatial correlation is introduced into the multipath amplitude and time-of-arrival (ToA) matrices of the channel model. Each amplitude matrix consists of entries of correlated lognormal random variables, whereas each ToA matrix is obtained as the sum of a reference matrix and a difference matrix. The frequency-dependent spatial correlation function is derived to give an insight of model properties. Model parameters are determined based on well-known measurement campaigns. In addition, simulation-based analysis indicates that this model has desirable spatial correlation properties in both the time and frequency domains. The ToA correlation matrix was also found to have dominant effects on the correlation characteristics. This suggests that future research into spatial correlation properties of MIMO-UWB channels should focus on ToA correlation characteristics, rather than amplitude correlation characteristics, which are the current focus of narrowband and wideband MIMO channel research.     

The Dependence of the Melting Temperature of Cobalt–Carbon Eutectic on the Morphology of its Microstructure

Fixed points provide a reliable way to realize and verify temperature scales. High-temperature fixed points are being developed based upon alloys, since single-phase materials are impractical to use above the copper freezing point. In particular, eutectic alloys have been shown to be sufficiently reproducible to warrant consideration as a way to significantly improve high-temperature metrology. However, eutectic alloys have certain characteristics requiring that they are used differently from the current ITS-90 fixed points. As their freezing temperature depends on the freezing rate, the melting temperature is preferred, though it has been shown that for some alloys, notably iron–carbon and cobalt–carbon, the apparent melting temperature can depend on the rate of the preceding freeze. This behavior will need to be explained and quantified if such fixed points are to be acceptable. The effect of varying the freezing rate on subsequent melting has been investigated for cobalt–carbon eutectic fixed points. The apparent melting temperature varies by up to 50 mK. Measurements were made of two different fixed-point blackbodies with very similar results. Optical microscopy of samples produced at different freeze rates shows a change in scale of the microstructure. Electron back-scatter diffraction (EBSD) shows evidence of high levels of residual strain in rapidly frozen samples. The effect of annealing on the melting behavior and microstructure has also been investigated. It is suggested that disordered phase boundaries and residual strain lead to changes in the melting behavior as nonequilibrium conditions may lead to a significant level of pre-melting. Whether this actually changes the liquidus temperature, or whether the melting temperature variation is due to the way the melting point is defined, is also discussed. The variation requires consideration if the highest accuracy is to be achieved, and will be a contributory factor to any uncertainty budget.     

A survey on resource allocation in high performance distributed computing systems

An efficient resource allocation is a fundamental requirement in high performance computing (HPC) systems. Many projects are dedicated to large-scale distributed computing systems that have designed and developed resource allocation mechanisms with a variety of architectures and services. In our study, through analysis, a comprehensive survey for describing resource allocation in various HPCs is reported. The aim of the work is to aggregate under a joint framework, the existing solutions for HPC to provide a thorough analysis and characteristics of the resource management and allocation strategies. Resource allocation mechanisms and strategies play a vital role towards the performance improvement of all the HPCs classifications. Therefore, a comprehensive discussion of widely used resource allocation strategies deployed in HPC environment is required, which is one of the motivations of this survey. Moreover, we have classified the HPC systems into three broad categories, namely: (a) cluster, (b) grid, and (c) cloud systems and define the characteristics of each class by extracting sets of common attributes. All of the aforementioned systems are cataloged into pure software and hybrid/hardware solutions. The system classification is used to identify approaches followed by the implementation of existing resource allocation strategies that are widely presented in the literature.     

Adaptive rank weighted switching filter for impulsive noise removal in color images

Journal of Real-Time Image Processing - In this paper, a novel approach to the problem of impulsive noise removal in color digital images is presented. The described switching filter is based on...     

Price sensitive demand with random sales price – a newsboy problem

Up to now, many newsboy problems have been considered in the stochastic inventory literature. Some assume that stochastic demand is independent of selling price (p) and others consider the demand as a function of stochastic shock factor and deterministic sales price. This article introduces a price-dependent demand with stochastic selling price into the classical Newsboy problem. The proposed model analyses the expected average profit for a general distribution function of p and obtains an optimal order size. Finally, the model is discussed for various appropriate distribution functions of p and illustrated with numerical examples.     

Instrumentation and computer capabilities for improving sodar data acquisition

A computer program has been developed to exploit the multimedia capabilities of a personal computer for a new design of sodar (sonic detection and ranging) data acquisition and control system with minimized hardware elements. Advantages include trouble-free, cost-effective and user-friendly sodar data acquisition using any standard computer. The new design overcomes limitations due to using an add-on data acquisition card with conventional computer-controlled sodar. The data can be processed to produce online display of the dynamics of prevailing atmospheric boundary layer thermal structures and inversion/mixing depth for environmental applications.     

Temperature–enthalpy curve for energy targeting of distillation columns

The temperature–enthalpy (T–H) diagram of a distillation column at practical near-minimum thermodynamic condition (PNMTC) or the column grand composite curve (CGCC) is a useful representation for energy targeting studies and may be generated from a converged simulation of a base-case column design. The calculation procedure for the CGCC involves determination of the net enthalpy deficit at each stage by generating envelopes from either the condenser end (top-down approach) or the reboiler end (bottom-up approach). However, the values calculated by the two approaches differ for stages with feeds because existing procedures for CGCC generation do not consider the enthalpy balances at the feed stages. In fact, the net enthalpy deficits at feed stages calculated by both approaches are erroneous even for the simplest case of binary distillation. A feed stage correction (FSC) that rigorously considers the mass and enthalpy balance equations at feed stages is proposed in this work to resolve the discrepancy. Instead of assuming that the compositions obtained from the converged simulation for a feed stage will remain unchanged at PNMTC, the pinched compositions for the feed are determined by the intersection of the equilibrium curve and the feed q-line. Rather than perform an additional flash calculation to establish the pinched feed compositions, a quadratic approximation is developed here for column targeting purposes by assuming the relative volatility obtained from the simulation to remain constant in the neighborhood of the feed stage. The proposed FSC ensures that the CGCC is identical whether the calculations are performed by the top-down approach or the bottom-up approach. The effect of the FSC on the targets for energy conservation by reflux modification, feed conditioning, and introduction of side reboilers/condensers is discussed. As the energy target for reflux modification is determined by the CGCC pinch which typically occurs at or close to the feed location, the significance of the FSC on the reflux modification target is highlighted through several case studies including a complex column featuring multiple feeds and consequently multiple pinch points. The CGCCs for these case studies are generated by a computer program based on the FSC and a single analytical equation for the calculation of the net enthalpy deficits that allows every stage to have a feed, liquid product, vapor product, and side exchanger. The studies show that the reflux modification targets may be erroneous in many cases, if the FSC is ignored.     

Study of inductively coupled Cl2/BCl3 plasma process for high etch rate selective etching of via-holes in GaAs

We have investigated the selective etching of 50 μm diameter via-holes for etch depth >200 μm using 30 μm thick photo resist mask in Inductively Coupled Plasma system with Cl₂/BCl₃ chemistry. Resultant etch rate/etch profiles are studied as a function of ICP process parameters and photo resist mask sidewall profile. Etch yield and aspect ratio variation with process pressure and substrate bias is also investigated at constant ICP power. The etch yield of ICP process increased with pressure due to reactant limited etch mechanism and reached a maximum of ∼19 for 200 μm depth at 50 mTorr pressure, 950 W coil power, 80 W substrate bias with an etch rate ∼4.9 μm/min. Final aspect ratio of etched holes is increased with pressure from 1.02 at 20 mTorr to 1.38 at 40 mTorr respectively for fixed etch time and then decreased to 1.24 at 50 mTorr pressure. The resultant final etch profile and undercut is found to have a strong dependence on the initial slope of photo resist mask sidewall angle and its selectivity in the pressure range of 20-50mTorr.     

A novel algorithm for estimation of depth map using image focus for 3D shape recovery in the presence of noise

Three-dimensional shape recovery from one or multiple observations is a challenging problem of computer vision. In this paper, we present a new Focus Measure for the estimation of a depth map using image focus. This depth map can subsequently be used in techniques and algorithms leading to the recovery of a three-dimensional structure of the object, a requirement of a number of high level vision applications. The proposed Focus Measure has shown robustness in the presence of noise as compared to the earlier Focus Measures. This new Focus Measure is based on an optical transfer function implemented in the Fourier domain. The results of the proposed Focus Measure have shown drastic improvements in estimation of a depth map, with respect to the earlier Focus Measures, in the presence of various types of noise including Gaussian, Shot, and Speckle noises. The results of a range of Focus Measures are compared using root mean square error and correlation metric measures.