On global Hessenberg based methods for solving Sylvester matrix equations

In the first part of this paper, we investigate the use of Hessenberg-based methods for solving the Sylvester matrix equation $AX+XB=C$. To achieve this goal, the Sylvester form of the global generalized Hessenberg process is presented. Using this process, different methods based on a Petrov–Galerkin or on a minimal norm condition are derived. In the second part, we focus on the SGl-CMRH method which is based on the Sylvester form of the Hessenberg process with pivoting strategy combined with a minimal norm condition. In order to accelerate the SGl-CMRH method, a preconditioned framework of this method is also considered. It includes both fixed and flexible variants of the SGl-CMRH method. Moreover, the connection between the flexible preconditioned SGl-CMRH method and the fixed one is studied and some upper bounds for the residual norm are obtained. In particular, application of the obtained theoretical results is investigated for the special case of solving linear systems of equations with several right-hand sides. Finally, some numerical experiments are given in order to evaluate the effectiveness of the proposed methods.     

Ranking alternatives in a preferential voting system using fuzzy concepts and data envelopment analysis

In this paper, a new method for aggregating the opinions of experts in a preferential voting system is proposed. The method, which uses fuzzy concept in handling crisp data, is computationally efficient and is able to completely rank the alternatives. Through this method, the number of votes for certain rank position that each alternative receives are first grouped together to form fuzzy numbers. The nearest point to a fuzzy number concept is then used to introduce an artificial ideal alternative. Data envelopment analysis is next used to find the efficiency scores of the alternatives in a pair-wise comparison with the artificial ideal alternative. Alternatives are rank based on these efficiency scores. If the alternatives are not completely ranked, a weight restriction method also based on fuzzy concept is used on the un-discriminated alternatives until they are completely ranked. Two examples are given for illustration of the method.     

Utilization of the yarn pullout test in estimation of the reserved energy of rib knitted fabrics

The yarn pullout test is a prevailing and particular method to evaluate the effects of yarn properties and the structural characteristics of the fabric on the fabric mechanical performance. In this research, a theoretical model of yarn pull out is presented to determine the reserved energy of weft-knitted fabrics with rib 1 × 1 structure. This model is based on the fabric dimensional properties, i.e. stitch length, wale density, yarn diameter and contact angle of yarns. In order to appraise the proposed model, five different double jersey weft-knitted fabrics with rib 1 × 1 structure were produced and exposed to pullout test. Comparison between deviations of theoretical results from experimental results demonstrates that the presented theoretical model exhibits a rational estimation of the reserved energy in these fabrics.     

Viscosity of Imidazolium-Based Ionic Liquids at Elevated Pressures: Cation and Anion Effects

The viscosity of imidazolium-based ionic liquids with four different cations and three different anions was measured to pressures of 126 MPa and at three temperatures (298.15 K, 323.15 K, and 343.15 K). The high-pressure viscosity of 1-ethyl-3-methylimidazolium ([EMIm]), 1-n-hexyl-3-methylimidazolium ([HMIm]), and 1-n-decyl-3-methylimidazolium ([DMIm]) cations with a common anion, bis(trifluoromethylsulfonyl)imide ([Tf₂N]), was measured to determine the alkyl-chain length effect of the cation. An increase in the alkyl-chain length increased the viscosity at elevated pressures. [DMIm] exhibited a larger nonlinear increase with pressure over the shorter alkyl substituents. Anion effects were investigated with [HMIm] as a common cation and anions of [Tf₂N], hexafluorophosphate ([PF₆]), and tetrafluoroborate ([BF₄]). [HMIm][PF₆], with the highest viscosity, demonstrated a very nonlinear pressure dependence even at relatively moderate pressures (to 30 MPa), similar to the results for [BMIm][PF₆]. A combined Litovitz and Tait equation was utilized to describe the viscosity of the ionic liquids with pressure and temperature and demonstrated good correlation with the experimental data.     

An investigation into the effect of fabric structure on the compressional properties of woven fabrics

Lateral compression is one of the most important mechanical aspects of fabrics, which reflects their handle. Fabric compressional features depend on the compressional characteristics of constituent yarns and the fabric structure. In order to consider the effect of fabric structural parameters on its compressional properties, woven fabrics with five different weave patterns (plain, hopsack 2/2, twill 2/2, twill 3/1, warp rib 2/2) were produced with three different nominal weft densities (12, 15, 18 cm^?1). The compressional properties of produced fabrics were evaluated at different pressure values using a conventional fabric thickness tester. It was observed that increasing the weft density leads to decrease in the dissipated compression energy as well as the compressibility of the fabric, while the thickness recovery of the fabric increases. Moreover, the plain woven fabric exhibited the lowest dissipated compression energy and compressibility, while the highest thickness recovery. Besides, at the low pressure level, the fabrics with the lower weft densities demonstrate the higher thickness. By increase in the pressure level, the fabric thickness decreases by decreasing the weft density.     

Theoretical investigation of corrosion inhibition effect of imidazole and its derivatives on mild steel using cluster model

Interaction energies of imidazole and its seven derivatives on the surface of mild steel were calculated via a cluster model by using quantum chemical calculations at density functional theory level. The mild steel surface and its adsorption sites were considered as some clusters taken from two-layered (0 0 1) planes and the quantum chemical calculations which were carried out consist of adsorption of the inhibitor molecules on the surface of these clusters. It is shown that 90% of inhibition variations of the imidazole derivatives are described by considering perpendicular interaction of the inhibitors by iron atom in the mild steel unit cell.     

Hemodialysis cost in Tehran,Iran

The purpose of this study was to assess the health service cost of hemodialysis (HD) delivered at hospitals in Iran as a developing country with a well‐defined program of renal replacement therapy. A cost analysis was performed from the viewpoint of the 2 hospitals, with 3 shifts and full chairs, on current practice for dialysis maintenance. Cost and patient data were collected in 2006 and from April 1 to May 31, 2007, respectively. A total of 22,464 HD sessions were performed and 247 patients were studied during the study period. The reference year for the value of USD for different mentioned costs was 2006. Health care sector costs associated with each HD session were estimated at US$78.87. Most of the total maintenance expenditure was made up of medical supplies (36.19%), with dialyzers as the major cost driver. Staff salaries represented 17% of the cost and fixed direct capital costs accounted for 21.4%. Of the family members, 32.4% accompanied their patients. The mean cost for transportation of patients and accompanied person was US$3.15 ± 2.83 and US$1.5 ± 0.29, respectively. These findings are important in the light of limited available resources coupled with the increasing prevalence of kidney failure. A major attempt should also be made to increase peritoneal dialysis coverage as in some centers we cannot keep all chairs full, especially in some vast areas. It is highly recommended to place initial focus on strategies and treatments that slow disease progression, to postpone renal replacement therapy to save resources.     

Prototyping and analyzing physical properties of Weft knitted spacer fabrics as a substitute for wound dressings

In this research, the required physical properties of weft knitted spacer fabrics, as an alternative for wound dressings have been investigated. For this purpose, weft knitted spacer fabrics with five different fabric structures have been produced on the electronic flat knitting machine. Moreover, in order to compare the properties of the produced fabrics with available wound dressings in the market, two kinds of wound dressing have been prepared from the market. Then, the physical properties of the spacer fabrics and the wound dressings such as air permeability, water vapor permeability, thermal conductivity, compressibility and absorbency have been measured and compared. The results show that in weft knitted spacer fabrics with the same fabric structure of the outer layer and different inclination angle (the angle formed between the outer layer and the spacer yarn), by decreasing the inclination angle, the fabric air permeability, water vapor permeability and absorbency decrease and the thermal conductivity and compressibility increase. Moreover, the use of tuck stitches in the outer layer of the spacer fabric leads to an increase of air permeability, water vapor permeability, absorbency and thermal conductivity and decrease of compressibility. The wound dressings also exhibit less air permeability and compressibility than weft knitted spacer fabrics. On the other hand, they possess higher water vapor permeability and absorbency. According to the results, among the examined weft knitted spacer fabrics in this research, the fabric with the tuck stitches in the outer layer is specified as the most appropriate alternative for wound dressing, in case of wounds with low exudates.     

Selenocysteine's mechanism of incorporation and evolution revealed in cDNAs of three glutathione peroxidases

The nonsense codon, UGA, has for the first time recently beenshown to encode selenocysteine in two proteins, mouse glutathioneperoxidase (GSH-Px) (EC 1.11.1.9 [EC] ) and bacterial formate dehydrogenase.A co-translational rather than post-translational selenium-incorporationmechanism has been implicated. Furthermore, high expressionlevels of GSH-Px have suggested that suppression of terminationis efficient and specific. We have isolated and characterizedpituitary, kidney and placenta cDNAs for bovine, human and mouseGSH-Px respectively. It is demonstrated that this novel suppressionevent occurs in diverse tissues, in at least three mammalianspecies and at the translational step. Surprisingly, GSH-Pxis shown to be extramitochondrially encoded, indicating a cytosolicsuppression event rather than one utilizing the mitochondria'swell-documented extended codon-reading ability. Sequence analysisreveals that a simple proximal contextual pattern responsiblefor readthrough does not exist. Analysis of predicted secondarystrucutres of mRNAs, however, has revealed a conformation whichmay be unique to selenocysteine proteins and may prove usefulas a tool for artificial incorporation of selenocysteines. Ahuman intron for GSH-Px from an unspliced mRNA has been isolatedwhose position indicates an ancient, divergent evolutionaryrelationship with thioredoxin-S₂, rather than an independentconvergent one.