On the iterative refinement of the solution of ill-conditioned linear system of equations

Recently, Salkuyeh and Fahim [A new iterative refinement of the solution of ill-conditioned linear system of equations, Int. Comput. Math. 88(5) (2011), pp. 950–956] have proposed a two-step iterative refinement of the solution of an ill-conditioned linear system of equations. In this paper, we first present a generalized two-step iterative refinement procedure to solve ill-conditioned linear system of equations and study its convergence properties. Afterward, it is shown that the idea of an orthogonal projection technique together with a basic stationary iterative method can be utilized to construct a new efficient and neat hybrid algorithm for solving the mentioned problem. The convergence of the offered hybrid approach is also established. Numerical examples are examined to demonstrate the feasibility of proposed algorithms and their superiority to some of existing approaches for solving ill-conditioned linear system of equations.     

Satellite remote sensing of total ozone column (TOC) over Pakistan and neighbouring regions

Total ozone column (TOC) obtained from the Ozone Monitoring Instrument (OMI) on board the Aura satellite was utilized to examine the spatio-temporal distribution of atmospheric ozone over Pakistan and adjoining regions of Afghanistan, India, and Iran for October 2004 to March 2014. This region has not yet been evaluated in greater detail. A yearly spatial averaged value of 278 ± 2 DU was found over the region. A decadal increase of 1.3% in TOC value over study region was observed for the first time. Large spatial and temporal variability of TOC was found over the study region. Elevated ozone columns were observed over the regions with high NO₂ and CO concentrations. Analysis indicated that Srinagar city has the highest averaged value of 290 ± 3 DU whereas Jodhpur city showed the highest increasing trend of 1.9% per decade. A monthly averaged maximum value of 289 ± 8 DU and a minimum of 264 ± 5 DU were found during April and November, respectively, over the region. January showed a decreasing trend of ?0.8% and February exhibited the highest increasing trend of 5.1% per decade. Forward trajectory analysis showed the possibility of ozone transport from eastern parts of the study region towards the Indian Ocean (Bay of Bengal) through the subtropical jet stream creating low values at higher meridians in October. TOC data deduced from OMI and the Atmospheric Infrared Sounder were compared to check the level of correlation and the results showed significant correlation (r = 0.75) and an acceptable average relative difference of 4.2%.     

Geometry design of herringbone structures for cancer cell capture in a microfluidic device

Cancer cell detection with high capture efficiency is important for its extensive clinical applications. Herringbone structures in microfluidic devices have been widely adopted to increase the cell capture performance due to its chaotic effect. Given the fact of laminar flow in microfluidic devices, geometry-based optimization acting as a design strategy is effective and can help researchers reduce repetitive trial experiments. In this work, we presented a computational model to track the cell motion and used normalized capture efficiency to evaluate the tumor cell capture performance under various geometry settings. Cell adhesion probability was implemented in the model to consider the nature of ligand–receptor formation and breakage during cell–surface interactions. A facile approach was introduced to determine the two lumped coefficients of cell adhesion probability through two microfluidic experiments. A comprehensive geometric study was then performed by using this model, and results were explained from the fluid dynamics. Although most of the geometric guides agree with the general criterion concluded in the literature, we found herringbone structures with symmetric arms rather than a short arm–long arm ratio of 1/3 are optimal. This difference mainly comes from the fact that our model considers the particulate nature of cells while most studies in the literature optimize the geometry merely relying on mixing effects. Thus, our computational model implemented with cell adhesion probability can serve as a more accurate and reliable approach to optimize microfluidic devices for cancer cell capture.     

Abrasive waterjet cutting of cladded material: kerf taper and MRR analysis

Gas/plasma cutting of cladded materials provides inferior cut quality that demands subsequent finishing processes. Abrasive waterjet cutting could be a proficient alternate in terms of cut quality. However, the inherent problem of kerf taper and low material removal rate in comparison to the said thermal cutting processes limit its application. Therefore, potential of aforesaid machining process for cutting of stainless-clad steel is investigated with a prior focus on maximizing the material removal rate with minimum kerf taper. Abrasive mass flow, traverse speed, water pressure, and stand-off distance have been selected as input parameters. ANOVA analysis revealed that traverse rate as well as abrasive mass flow are the major contributing factors for both the responses. Optimal settings of parameters developed by S/N ratio analysis results in an improvement of 18.6% in material removal rate and 39% in the kerf taper. Moreover, regression models are developed and validated through various statistical tests.     

Electrical properties of some Y<Subscript>2</Subscript>O<Subscript>3</Subscript> and/or Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>-containing lithium silicate glasses and glass-ceramics

The ac electrical properties of some lithium silicate glasses and glass-ceramics containing varying proportions of Y₂O₃ and/or Fe₂O₃ were measured to investigate their electronic hopping mechanism. There is a clear variation of these properties with composition. The obtained results were related to the concentration and role of Y₂O₃ and/or Fe₂O₃ in the lithium silicate glass structure. In crystalline solids the electrical properties data obtained were correlated to the type and content of the mineral phases formed as indicated by X-ray diffraction analysis (XRD). The conductivity, dielectric constant and dielectric loss of the studied glasses were studied using the frequency response in the interval 30 Hz–100 KHz and the effect of compositional changes on the measured properties was investigated. The measurements revealed that the electrical responses of the samples were different and complex. The addition of Y₂O₃ generally, decreased the ac conductivity, dielectric constant and dielectric losses of the lithium silicate glasses. The addition of Fe₂O₃ in Y₂O₃-containing glasses increases the conductivity, while, the dielectric constant and dielectric losses were found to be decreased. However, the addition of Fe₂O₃ instead of Y₂O₃ led to decrease the ac conductivity and increased their dielectric constant and dielectric losses. The obtained data were argued to the internal structure of the lithium silicate glass and the nature or role-played by weakness or rigidity of the structure of the sample. Lithium disilicate-Li₂Si₂O₅, lithium metasilicate-Li₂SiO₃, two forms of yttrium silicate Y₂Si₂O₇ & Y₂SiO₅, iron yttrium oxide-YFeO₃, lithium iron silicate-LiFeSi₂O₆ and α-quartz phases were mostly developed in the crystallized glasses. The conductivity of the crystalline materials was found to be relatively lower than those of the glass. At low frequency, as the Y₂O₃ content increased the ac conductivity, dielectric constant and dielectric loss data of the glass-ceramics decreased. However, the addition of Fe₂O₃ to the Y₂O₃ containing glass-ceramic led to increase the conductivity. The addition of high content of Fe₂O₃ instead of Y₂O₃ in the glass ceramic led to increase the ac conductivity.     

Is the number of traffic fatalities in American hospitals decreasing?

Fatality Analysis Reporting System (FARS) data from 1977 to 2002 record a decreasing number of traffic fatalities taken to a hospital compared with traffic fatalities not taken to a hospital. In this study, we calculated the proportions of decedents reportedly taken to a hospital each year in each state, and the proportions surviving at least 1 h. We also used death certificate data from the National Center for Health Statistics (NCHS) for 1979-1999 to categorize the proportion of motor vehicle fatalities in each state by hospital patient status. The annual number of traffic fatalities decreased slightly over the period of observation. The proportion of decedents recorded in FARS as transported to a hospital fell from about 73 to 43%. However, this proportion decreased abruptly at certain times in some states, suggesting previous misclassification. The proportion surviving at least 1 h remained relatively constant. NCHS data showed a decline in the proportion declared dead in hospitals from 62 to 51%, including a decline in the proportion declared dead on arrival (DOA) from 20 to 8%. Along with occasional misclassification in some states, the decrease in cases transported only to be pronounced DOA could explain why FARS data show a decrease in deaths after hospital transport.     

Effectiveness of Polystyrene/Carbon Nanotube Composite in Electromagnetic Interference Shielding Materials: A Review

Polystyrene is an efficient thermoplastic having fine processability, chemical inertness, and mechanical performance. Technological advances have led to several industrial appliances of polystyrene-based materials ranging from insulation to electromagnetic interference shielding. In this state-of-the-art review, primarily structure and properties of carbon nanotube and polymer/carbon nanotube composite have been discussed. Carbon nanotube is considered as a brilliant filler for polymers. Therefore, a comprehensive discussion regarding high-performance polystyrene/carbon nanotube composite is presented. Main focus of review is the significance of electromagnetic interference shielding phenomenon in polystyrene/carbon nanotube composite. Owing to advantageous properties, these composite have potential to replace traditional shielding materials.     

The production of binderless granules and their mechanical characteristics

A granulation procedure is described for preparing model binderless granules from spherical polystyrene colloids. The deformation and breakage behaviour of the granules was also studied. Impact and slow diametrical compression experiments were used to simulate the mechanical response of the granules at high and low strain rates, respectively. They were found to deform elasto-plastically before fracturing in a semi-brittle manner. Densification or rearrangement of particle packing in the deformed region was concluded to be the main mechanism for energy dissipation under both impact and diametrical compression. In addition, the surface chemistry of the constituent particles within the granules was found to be one of the factors that govern the strength.     

An experimental study of the variability in the properties and quality of wet granules

For wet high-shear granulation, there can be a considerable variability in product quality in terms of the size, binder content, porosity, and appearance. Using the same equipment and feed material, it has been shown that such variability can be reduced by optimising the operating protocol. The associated narrowing of the range of mechanical properties for granules formed using an optimised procedure is exemplified by measurements of a number of parameters such as the coefficient of restitution.