Mobile Localization Under Non-Line-of-Sight Conditions Using Scattering Information

A novel mobile localization algorithm under non-line-of-sight (NLoS) conditions involving at most two base stations (BS) is presented. By using such a small number of BSs, the proposed technique avoids problems related to weak mobile hearability and excessive network messaging overload. Based on a scattering model, the NLoS hybrid approximate maximum likelihood (NLoS HAML) approach presented herein estimates the distances between the mobile station (MS) and the scatterers through the measured hybrid time-of-arrival/angle-of-arrival (ToA/AoA) statistics. Then, it matches the calculated distances to a known scatterers’ distribution in a maximum likelihood (ML) sense. Numerical results prove that the proposed algorithm outperforms previous methods by providing an accuracy enhancement that reaches 60%. It is also shown that the performance enhancement provided by the proposed algorithm is maximized when the adequate scatterers distribution is adopted.     

Comparative study of dewatering characteristics of metal precipitates generated during treatment synthetic polymetallic and AMD solutions

The sludge dewatering characteristics expressed in terms of settling, filtration and centrifugation of metal precipitates generated during treatment of polymetallic solutions and synthetic acid mine drainage have been evaluated in this research. Results show that dewatering properties of metallic sludge vary depending on the type of matrix (Cl⁻; SO₄²⁻), precipitating agent, and metals present in effluent. Metal hydroxides (at pH 10.0) and metal phosphates precipitates (at pH 7.0) are amorphous in nature, thus difficult to dewater. In these treatment methods, the substitution of chloride matrix by sulphate one improves considerably dewatering properties (specific resistance to filtration = 6.60 × 10¹³ and 2.35 × 10¹³ m/kg for the chloride and sulphate matrix, respectively). In the case of sulphide and carbonate treatments (pH 8.0), precipitates obtained are semi crystalline, and crystalline form, respectively, and no influence of the matrix was detected on dewatering characteristics.     

Structural and Magnetocaloric Properties of ErFe 2 . 4 Al 0 . 6 Compound

The structural and magnetic properties of the single-phase pseudobinary ErFe _2.4Al _0.6 compound, obtained under arc-melting conditions, have been investigated. Single crystal X-ray diffraction analysis revealed that this compound is stabilized with a hexagonal CeNi ₃-type structure (space group P6 ₃ /mmc). The partial substitution of Fe by Al in this compound occurring at all the metallic sites is reflected in the decrease of the Curie temperature Tc. Magnetization curves (2–450 K; 0–5 T) indicate a ferrimagnetic ordering with four magnetic phases induced by competitional interactions between magnetic moments of both Er and Fe. The magnetocaloric effect has been estimated from the magnetic isotherms. The relative cooling power (RCP) value indicates relatively promising magnetic refrigerant material.     

Optimisation of springback in bending processes using FEM simulation and response surface method

The aim of this work includes the springback optimisation of bending processes using the concept of experimental design and response surface methodology (RSM). The optimisation method includes two phases. The first involves the objective function prediction using design of experiments and response surface method, while the second is an optimisation process using a FORTRAN gradient algorithm. Springback of sheet parts during bending processes is simulated using finite element model (FEM) including damage evolution effects within the sheet. The numerical simulation of the damage evolution has been modelled by means of continuum damage approach. The Lemaitre damage model, taking into account the influence of triaxiality, has been implemented into ABAQUS/Standard code in order to predict the external fibres rupture evolution during the process and the material characteristics changes after bending. The simulation included die corner radius and punch-die clearance as the main variables.     

The Capacity Performance of ASTC-MIMO-OFDM System in a Correlated Rayleigh Frequency-Selective Channel

Algebraic Space-Time Codes (ASTC) for Multiple Input Multiple Output (MIMO) systems are based on quaternion algebras. Thanks to their algebraic construction, the ASTC codes are full-rank, full-rate and have the non-vanishing determinant property. These codes have been proposed for MIMO flat fading channels in order to increase the spectral efficiency and to maximize the coding gain. The purpose of this work is to analyze the performance of the ASTC in a frequency selective Rayleigh channel. To deal with the frequency selectivity, we use the OFDM modulation. The capacity performances of an ASTC-MIMO-OFDM system, under correlated Rayleigh frequency-selective channel, have been evaluated.     

The fatty acid composition of Iraqi ewe's, goat's and cow's milk fat

The analysis of the fatty acid composition of 6 samples of the milk fat of each ewes and goats and of 3 samples of the milk fat of cows was accomplished using Hewlett-Packard gas-liquid chromatograph Model 5711 A, provided with an electronic integrator Model 3380. Separation of the methyl esters was performed on columns of 10% sailor on Chromosorb. Temperature programming between 100 degrees C and 180 degrees C was used. The milk fats were qualitatively similar but differed quantitatively. Both ewe's and goat's milk fat had a greater amount of short-chain fatty acids than cow's milk fat. Goat's milk fat contained a higher percentage of short-chain fatty acids compared to that of ewe's milk fat and of goat's milk fat reported in the literature.     

Requirements Analysis for Engineering Computation: A Systematic Approach for Improving Reliability

This paper argues that the reliability of engineering computation can be significantly improved by adopting software engineering methodologies for requirements analysis and specification. The argument centers around the fact that the only way to judge the reliability of a system is by comparison to a specification of the requirements. This paper also points to methods for documenting the requirements. In particular, a requirements template is proposed for specifying engineering computation software. To make the mathematical specification easily understandable by all stakeholders, the requirements documentation employs the technique of using tabular expressions. To clarify the presentation, this paper includes a case study of the documentation for a system for analyzing statically determinant beams.     

Cyclic Behavior and Damage Analysis of Brass under Cyclic Torsional Loading

Fatigue behavior of brass was studied at a constant deformation rate of 5.6 × 10⁻³ s⁻¹ to understand the cyclic behavior and fatigue life under cyclic torsional deformation. Strains were in the range of 0.35 to 4.2%. In the as-drawn condition, it was found that the cyclic hardening/softening behavior strongly depends on the strain amplitude. For low strain amplitude, cyclic saturation occurred after an initial cyclic hardening stage, but for high strain amplitude, saturation could not be reached. Cyclic stress-strain (CSS) curve showed the presence of three distinct regions with a short quasi-plateau region in the intermediate amplitude range. Quantitative fatigue damage was assessed by microscopic observations of surface cracks.     

Fracture criteria identification using an inverse technique method and blanking experiment

In order to optimize the blanking processes, it is important to identify the conditions within the deforming workpiece which may lead to fracture initiation and propagation. Within this framework, numerical simulations are widely used in industries to optimize sheet metal forming processes. However, in order to have a confidence in the results of such simulations, an accurate material model is required. The accuracy of a material model is affected by the constitutive equations and the values of the material parameters. In order to reduce the danger of fracture of metal parts during manufacturing processes, advanced optimal design requires knowledge of critical values of some fracture criteria of the material used. Experimental identification of fracture criteria are currently obtained by performing several complicated tests and long duration of experiments.This study presents a computation methodology allowing for the identification of critical values of fracture criteria in order to simulate crack initiation and propagation generated by shearing mechanisms, which are needed for metal blanking processes simulation. The approach is based on inverse technique using circular blanking experiments and finite element calibration model. The critical values of fracture criteria are obtained in such a way that the finite element force–penetration predicted curve fit the experimental plot deduced from blanking tests. The numerical results obtained by the simulation were compared with experimental ones to verify the validity of the proposed technique for fracture criteria identification.