In this paper we provide a review of important ambulance allocation models developed in the last 40 years. These models include both strategic and operational level decisions. The review aims to provide researchers with an easy to-understand, comprehensive and up-to-date summary of deterministic, probabilistic, and dynamic ambulance location models.
Intersections are an integral part of a traffic system, thus, studying their safety and considering countermeasures to increase their safety should improve the overall safety of the traffic system. In this study, we looked into the intersections with the highest reported accidents in the Kingdom of Bahrain through the years 2013-2016, for which the data was provided by Bahrain General Directorate of Traffic. The intersections with most recurring crashes are singled out and studied in more details, following the procedure of intersection screening detailed in the AASHTO Highway Safety Manual (HSM).
In the present study 1D Stefan evaporation and 2D film boiling problems will be studied numerically using the volume of fluid (VOF) method under OpenFOAM 2.4.0 CFD package. The mass transfer across the interface vapour/liquid is determined using the model of Lee. The results show excellent agreement for 1D Stefan evaporation problem compared to the exact solution. For 2D film boiling case, the obtained averaged Nusselt number presents a deviation about 19%, compared to the available correlations from the literature (Kleminko, 1981), which is consistent with previous research results. Through this validation, mathematic models and solver developed in this paper can be quickly applied to study phase change processes of interest.
In this paper, a meshfree numerical wave tank (NWT) was proposed with: absorbing boundary, partial reflection, and full reflection boundary condition. The numerical analysis and the problem studied are treated by the method of fundamental solutions (MFS). Our basic interest in this work is to extend a new partial reflection from the absorbing boundary condition, based on actual present-day meshfree numerical method.
Laser Surface Alloying employs high laser power density to melt alloying material and a portion of the underlying substrate to form an alloyed layer over substrate. As melting temperature of Ti alloys is very high, it poses difficulty in alloying using conventional methods. Titanium alloys are vulnerable to induced thermal stresses at high temperature. In this study thermal analysis of laser surface alloyed Ti6Al4V with TiC at different laser power and laser spot diameter is modelled. Melt pool depth and developed thermal stresses at different process parameters are predicted. Subsequently, model is verified with published experimental results. It is observed that developed model is adequate in predicting pool depth with 6.43% error. The von-Mises stress is observed to be lower than the yield strength of the material, indicating less possibility of thermally induced cracks.
In this paper, we present a watering system based on Economic Model Predictive Control (EMPC) that anticipates the water demand of the crop, and maintains an optimal soil moisture while reducing water consumption. The algorithm relies on a model of the soil moisture incorporating variables such soil evapotranspiration and deep percolation. This model, that was developed based on climatological data of the Kingdom of Bahrain, is formulated as a linear stochastic state space model. Simulation studies demonstrate the potential of the proposed model and algorithm. Compared to traditional operation of on-off automated irrigation systems based on sensors, the optimized EMPC operating strategy leads to significant saving in water consumption approximately around 10-15%, while maintaining an optimal soil moisture level.
The project work concentrates on the development of a geothermal residential heating system during cold winter. Available geothermal energy in Saudi Arabia was first studied. Thereafter, a suitable heat exchanger was developed to deliver the required heating requirements. In the development of the heat exchanger, graphs describing the performance of a cross flow heat exchanger operating in parallel flow configuration were generated in terms of critical dimensionless factors. Performance charts will readily help the heat exchanger designers in designing the most cost effective heat exchanger.
This work proposes a simpler automatic fault classifier that uses multi-layer perceptron (MLP) to identify faults in rotating machines. For classification, only statistical features and rotation frequency was taken in to consideration. Synthetic Minority Over-sampling Technique (SMOTE) was incorporated to handle imbalance classes in the machinery fault database. The proposed approach was evaluated on Machinery Fault Database (MAFAULDA) database. The proposed system has achieved an accuracy of 96.2%, which is comparable with the reported results in the literature. Results indicate that handling imbalance classes greatly increases the generalizability power of the MLP classifier on the machinery fault database.
The present paper focuses on analyzing the performance of three different advanced classifiers on hyperspectral data for improved land use/land cover classification. Considering the limitations of spatial and spectral resolution of high resolution multispectral and hyperspectral datasets, image fusion techniques were used for obtaining a spectrally and spatially rich space borne hyperspectral data. The Gram Schmidt sharpening, Principal Component sharpening and Color Normalized spectral sharpening were used for fusing the 30m, 242 band EO-1 Hyperion image with the 1.8m eight band World View 2 data. Correlation, SNR and entropy measures were adopted for analyzing the performance of the fused outputs. Color Normalized spectral sharpening was observed to exhibit highest correlation of 0.78 between spectra of Hyperion and fused images. Classification of the fused and unfused images was performed using three different classifiers - Spectral Angle Mapper, Artificial Neural Networks and Support Vector Machine by taking end members from the image and the ground spectra. Confusion matrix was generated using a ground truth points obtained during field visit. Support Vector Machine classifier with RBF kernel and lOO penalty value was observed to give an improved classified output than the remaining classifiers with an accuracy of 89.56% and a kappa coefficient of 0.88%.
Graphical methods (GM), based on analysing data derived from tracer passages, are robust tool used to estimate the descriptive parameters related to a microvasculature. These parameters known as: fractional plasma volume (vp), transfer constant (Ktrans), total distribution volume (vD). This study examines the time frame at which these methods can produce more accurate results. To do so sets of uptake tissue curves (Ct) were simulated by using approximation to the tissue homogeneity model (AATH) and the arterial input function (Cp) is constructed by adding three Gamma-variant. The tissue uptake curve is divided into five time frames, as follows: initial time to AIF's peak [t0,tp], AIF's peak to AIF's first pass [tp,tfp], first time passage [to, tfp], at equilibrium teq, initial time to equilibrium [t0, teq], and initial time to washout time [t0, tf] The study revealed that care should be taken in using GM during the bolus passages; more accurate Ktrans estimates can be determined more accurately from the initial data obtained from the first passage of the bolus within the time frames [t0, tp] and [tp, tfp]. Contrary to expectation, the unidirectional model decline to measure vp. On the other hand, the bidirectional is success to estimate vD more accurately within the time frame [tfp, tf].
Permutation, a discrete structure, is a sequence over the corresponding alphabet Σ where every element of Σ occurs exactly once. The set of permutations over Σ forms a symmetric group denoted by S n . In evolutionary biology, permutation models a genome. If π = (π 1 , π 2 , π 3 ,..., π n ) is a permutation over Σ = {0, 1, ... ,n - 1} then π i , and π i +1 form an adjacency if π i +1 = π i , + 1, 0 ≤ i ≤ n-1. Various operations that model genomic mutations are defined over permutations. An operation is defined by a set of generators. Execution of a specific generator is a move. The distance between a pair of permutations α and ß under a given operation ⊕ is the minimum number of moves that are required to transform a into ß. It denotes genomic dissimilarity between a and ß. Computation of distance is intractable for various operations including transposition. We call prefix transposition, suffix transposition and transposition as block-moves. Based on properties of S n related to adjacencies we develop a model that estimates the expected block-move distance between any pair of permutations.
This paper considers an offline scheduling problem of identical parallel machines where every machine is subject to at most one unavailability period. We assume that the jobs can be interrupted and resumed at any available machine. In other words, if a job is interrupted because of the unavailability of a machine it can be whether resumed at the same machine when it becomes available, or at any other available machine. The objective is to minimize the completion time of the last job C max. The problem can be represented as P m |r-a, pmtn|C max. To solve this problem, we proposed a new method based on list scheduling techniques. In addition, we developed new theoretical lower and upper bounds. Then, we developed absolute performance bounds for the method. An absolute performance bound is a bound between the method's makespan and the optimal makespan for all possible instances of the problem. In addition, we formulated the studied problem as a mixed integer quadratic model that is sued to generate optimal solutions. Finally, we conducted an experimental study in which many instances of different sizes and parameters were generated and solved. The results proved that the new methods are performing very well for most of the tested instances.
Diabetes mellitus is a metabolic disorder characterized by chronic hyperglycemia with disturbances of carbohydrate, fat and protein metabolism resulting from defect in insulin secretion, insulin action, or both. The three main types of diabetes are: type 1 diabetes, type 2 diabetes and gestational diabetes. As it is associated to a deficient insulin production, type 1 diabetes requires daily administration of insulin accompanied with a strict continuous control of carbohydrate intake in order to ensure a diabetes-free glycemic level. In this paper, a mathematical model governed by ordinary differential equations is presented to describe interaction between insulin, glucose, free fatty acids and growth hormone in the case of type 1 diabetes. Stability analysis is carried out and the dynamics of glucose is illustrated by a simulation using different parameter values.
In this paper, the three-phase cascaded VSI topology is proposed for PV grid-connection. The proposed control scheme is based on the classical control scheme, which is then extended to control the presented multilevel topology. Simulation is achieved by using SIMULINK environment. The obtained results proved that the proposed topology works well to improve the grid's voltages and currents quality. The control scheme succeed in keeping the grid currents in phase with the grid voltages, and the grid current's THD are within the acceptable range. To validate the effectiveness of the configuration and the accurate control, the proposed topology was built in a lab. Data acquisition and generation of gating signals to fire the switches were implemented on a MicroLabBox real-time controller. Experimental results are also provided to verify the viability of the proposed topology.
A finite element modelling starts with the heat equation, heat flux input and thermal modelling and the material definition. In this study a laser welding model with heat transfer is defined and analyzed for a 3mm thick SS316LN material, the temperature dependent thermal and structural properties are taken for analysis. The laser has not formed the keyhole, yet lateral conduction forms the weld bead will progress and convection and radiation from the top surface. Modelling of these thermal inputs with symmetric BC's of heat at the fusion zone centre was used in modelling ANSYS solid70 element to obtain the Thermal temperature distribution. Sequentially, this thermal load is given as input to the solid45 to obtain the structural distortion. An orthogonal Array of 9 experiments with three levels of Laser Power, Weld speed and Shield gas flow rate were conducted and analyzed. The optimum levels obtained were 2750Watts, 2500 mm/min and 10LPM. The shield gas flow rate was related to the convective heat transfer coefficient, h in the model. Experimental validation of distortion by experiments had within 8% agreement.
In this paper, we solve evolutionary partial differential equations for simulating symmetric diffusion. By means of domain decomposition method, we numerically solve and computationally analyze the adveclion diffusion problem. We combine the domain decomposition method for the lime-space integration and a Barycentric interpolation method for approximating interface solutions. The solution is carried out as piecewise function on all subdomains and the interface ones. Finally, different types of symmetric diffusions are simulated.
Terahertz images are of great interest in allowing the image of a biological object to be achieved. The inverse scattering problem of three-dimensional terahertz medical imaging is investigated. Dielectric object of known permittivity is located in situated medium around the object and illuminated by a group of unrelated incident Terahertz waves. The scattered field is received in a plain situated behind the object. The theoretical analysis is based on the principle that the scattered electromagnetic field is function of the volume distribution of equivalent currents inside the biological object. Numerical results are given to demonstrate the capability of the inverse scattered problem algorithm. In order to test this method the image of dielectric sphere is obtain from the calculated scattered electromagnetic field. The results of scattered electromagnetic field measurements carried out on different material objects are given. Good reconstruction is obtain from measured data even the results of scattered electromagnetic field measurements carried out on different material objects are given.
The cloud workload refers to charge made by a huge diversity of independent services and applications located on cloud infrastructures. Workload characteristics can be defined by tasks or Virtual Machines (VMs). Then again, tasks/VMs scheduling, allocation, workload predictions are important topics, which are gaining steadily increasing attention particularly in the past few years. In all these fields, clustering methods are often used to recognize groups of workload components characterized by comparable behaviors. In order to attain an effective clustering, the appropriate clustering technique needs to be selected. This choice is vital especially when there are vast choices that provide different results. To address such issue, this paper presents a comprehensive review of clustering categories application in cloud workload clustering. This paper also proposes a novel systematic framework to select the suitable tasks/VMs clustering method in large-scale data centers based on clustering purpose, validation indices and comparison of results.
Due to the promising technical feasibility of PV powered RO unit, many studies worldwide are carried out to further enhance their performance. In this simulation studies, we investigate the performance and efficiency of a battery free portable PV-RO unit powered directly and continuously from the PV array and compare it to the performance of a solar battery driven RO unit. The solar battery is charged during daytime using the PV array and runs the RO setup during nighttime. However, the energy provided by the PV array is intermittent and depends on daily available irradiations. Fortunately, in the case of the battery less unit the energy consumption of the RO unit can be adjusted by manipulating the brine flow rate or/and system pressure. In this work, we discuss two techniques for automatic adjustment of RO parameter (e.g. valve position at the brine) so that RO power consumption matches the maximum power provided by PV arrays. Matlab/Simulink implementations performed in these studies are presented and simulation results of battery less PV-RO system driven by UM and solar battery driven RO system are presented and compared.
The present article investigates the non-isothermal nanofluids flow in a squared porous cavity. The model consists of the conservation laws of energy, momentum, and mass. The cavity boundaries are modeled by mixed Dirichlet-Neumann boundary conditions. The discretization of time derivatives is developed by a time-splitting multiscale technique. The momentum and continuity equations are solved implicitly to find the pressure, then the velocity of the field is explicitly calculated. Therefore, both energy equation is solved implicitly. The Courant-Friedrichs-Lewy condition has been used to achieve the time step-size adaptation. Two numerical cases are considered for different boundary conditions. The effects of the nanofluid volume fraction of the on pressure, velocity, temperature and Nusselt number have been investigated. It was found that the temperature decreases as the volume fraction increases. We also found that the pressure and velocity increase while the local Nusselt number decreases as the volume fraction increases.
