Symmetry restrictions on the constitutive equations for magnetic materials

A group-theoretical procedure is given for the decomposition of magnetic material tensors with intrinsic symmetry into basic symmetry types. This decomposition is used in finding the total number of independent components of magnetic material tensors in linear constitutive equations, and it simplies the determination of polynomial integrity bases in non-linear constitutive equations. Next, a method is devised to obtain the independent components of magnetic material tensors explicitly. Using the isomorphism between a classical point group and the corresponding magnetic point groups together with the property of basic quantities, determination of polynomial integrity bases is made immediate.     

Surface polymerization of iron particles for magnetorheological elastomers

Magnetorheological Elastomers (MREs) are synthesized from silicone RTV (room temperature vulcanizing) elastomer with magnetically soft iron particles. The iron particle concentration of the MREs is 70 wt %. To reduce the effect of oxidation on the MREs, the ATRP technique is used for surface polymerization of iron particles with fluorinated styrene as monomer. The mechanical properties of MREs are characterized using a mechanical testing instrument, and the surface coated polymer is characterized using Fourier transform infrared spectroscopy (FTIR), X‐ray energy dispersive spectrometry (XEDS), differential scanning calorimetry (DSC), and the alignment of iron particles within MRE was characterized using scanning electron microscopy (SEM). The MRE samples are characterized using the mechanical testing instrument at 0 Tesla (off–state) and applied magnetic field from 0.46 Tesla to 0.62 Tesla (on–state). The required force at 0.62 Tesla increased approx. 3% to achieve 20% strain after 72 h of oxidation for surface coated MRE. On the other hand, the required force for non‐surface coated MREs at 0.62 Tesla increased up to 17% to achieve 20% strain after 72 h of oxidation. MREs with surface coated iron particles have higher oxidation stability based on the force–displacement test results, and MREs have excellent potential to be used as intelligent materials with high durability for a vibration isolator. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Estimating the energy production of the wind turbine using artificial neural network

Due to fluctuating weather conditions, estimating wind energy potential is still a significant problem. Artificial neural networks (ANNs) have been commonly used in short-term and just-in-time modeling of wind power generation systems based on main weather parameters such as wind speed, temperature, and humidity. Two different datasets called hourly main weather data (MWD) and daily sub-data (DSD) are used to estimate a wind turbine power generation in this study. MWD are based on historically observed wind speed, wind direction, air temperature, and pressure parameters. Besides, DSD created with statistical terms of MWD consist of maximum, minimum, mean, standard deviation, skewness, and kurtosis values. The main purpose of this study in particular was to develop a multilinear model representing the relationship between the DSD with the calculated minimum (P _min) and maximum (P _max) power generation values as well as the total power generation (P _sum) produced in a day by a wind turbine based on the MWD. While simulation values of the turbine, P _min, P _max, and P _sum, were used as the separately dependent parameters, DSD were determined as independent parameters in the estimation models. Stepwise regression was used to determine efficient independent parameters on the dependent parameters and to remove the inefficient parameters in the exploratory phase of study. These efficient parameters and simulated power generation values were used for training and testing the developed ANN models. Accuracy test results show that interoperability framework models based on stepwise regression and the neural network models are more accurate and more reliable than a linear approach.     

A comparative study for the location and scale parameters of the Weibull distribution with given shape parameter

Nine parametric estimators of the location and scale parameters of a two-parameter Weibull distribution are compared in terms of their bias and efficiency in a simulation study. The estimators considered are the maximum likelihood estimators (MLE), moment estimators (ME), generalized spacing estimators (GSE), modified maximum likelihood estimators I (MMLE-I), modified maximum likelihood estimators II (MMLE-II), Tiku's modified maximum likelihood estimators (TMMLE), least-squares estimators (LSE), weighted least-squares estimators (WLSE) and percentile estimators (PCE). The aim of the comparisons is to identify the most efficient estimators among these nine estimators for different shape parameters and sample sizes.     

Evaluation of dimensional stability,weathering and decay resistance of modified pine wood by in-situ polymerization of styrene

Abstract

In this study, polystyrene modified Scots pine (Pinus sylvestris L.) wood was investigated upon artificial weathering, decay resistance, dimensional stability and water uptake properties. Polystyrene modification was carried out on pretreated wood by immersion of wood into styrene monomer and further polymerization. The resistance of modified wood against cycles of UV and water exposures was examined by artificial weathering test for 672?hours, and decay resistance was evaluated by attacks of Coniophora puteana and Trametes versicolor on the samples. During the artificial weathering, color and surface roughness of the samples, and macroscopic changes were determined periodically. Changes in the surface chemistry and morphology of the weathered samples were investigated by ATR-FTIR and SEM, respectively. It was proven that polystyrene effectively protected pine samples from both fungi even after leaching procedure, but it was more effective in preventing C. puteana attacks than T. versicolor attacks. As a result of artificial weathering, the surface of all samples was darkened. However, changes in color and roughness as well as crack formations of the modified sample surfaces were found less than those of the untreated samples. Polystyrene also provided considerable improvement on dimensional stability, as well as water repellence of wood.     

Designing ionic liquid solvents for carbon capture using property-based visual approach

Recently, ionic liquids (ILs) have been introduced as potential carbon dioxide (CO₂)-capturing solvents, as a substitute to conventional amine-based solvents. Conventional amine-based solvents that are used for CO₂ capture show some drawbacks, such as high solvent loss, high regeneration energy requirement, and solvent degradation. These shortcomings can be potentially overcome if IL-based solvents are considered. ILs have negligible vapour pressure, high thermal stability, and wide range of thermophysical properties. Nonetheless, using experimentation to identify suitable ILs as CO₂-capturing solvents is a tedious and costly task, as there are more than a million possible combinations of cations and anions that make up the ILs. Computer-aided tools have been previously developed for targeted IL design, which often involve non-linear programming. However, non-linear programming sometimes fails to converge, due to enlarged search space for optimal solution and its complex formulations. In this paper, the authors present a simple yet systematic visual approach to design IL solvents for carbon capture. Property integration framework is employed in this approach to systematically design IL, where the design problem can be mapped from the property domain into a cluster domain through clustering technique. The advantage of the visual approach is the ability to enumerate novel IL candidates. Group contribution (GC) method is included in the framework to estimate the properties of designed ILs. By combining property integration framework and GC method, the proposed approach is able to provide a property-based platform to visualise the performance of designed ILs on a ternary diagram. A case study is presented to illustrate the validity of the proposed approach.     

Geography and the costs of local telephone networks

This paper expands past research on the cost structure of local telephone networks by considering the cost effects of geographical factors, such as service territory size, land uses, street patterns, population density, soil types, slopes, and the spatial partitioning of a company into local exchanges. A translog cost function is estimated using data on 41 telephone companies operating within the New York State, together with GIS-derived geographical data. The results confirm the importance of geography as a determinant of local telephone costs, and suggest that earlier estimates of size thresholds between economies and diseconomies of scale may be too low. The trade-offs between geographical factors in shaping the frontier between economies and diseconomies of scale are assessed. The implication for public policy on competition at the local level is that natural monopoly may be more prevalent than previously assumed. An earlier version of this paper was presented at the 50th Annual North American Meeting of the Regional Science Association International, 20–22 November 2003, Philadelphia, PA.     

Off-axis mirror based optical system design for circularization, collimation, and expansion of elliptical laser beams

In this paper, we present two optical system design methods for beam circularization, collimation, and expansion of semiconductor laser output beam for possible application in LIDAR systems. Two different optical mirror systems are investigated: an off-axis hyperbolic/parabolic mirror system and an off-axis parabolic mirror system. Equations specific to these mirror systems are derived and computer package programs such as ZEMAX and MATLAB are used to simulate the optical designs. The beam reshaping results are presented.     

Exergetic sustainability indicators for a high pressure hydrogen production and storage system

This study examines the exergetic sustainability effect of PEM electrolyzer (PEME) integrated high pressure hydrogen gas storage system whose capacity is 3 kg/h. For this purpose, the indicators, previously used in the literature, are taken into account and their variations are parametrically studied as a function of the PEME operating pressure and storage pressure by considering i) PEME operating temperature at 70 °C, ii) PEME operating pressures at 10, 30, 50 and 100 bar, iii) hydrogen gas flow rate at 3 kg/h and iv) storage pressure between 200 and 900 bar. Consequently, the results from the parametric investigation indicate that, with the ascent of storage pressure from 200 to 900 bar at a constant PEME operating pressure (=50 bar), exergetic efficiency changes decreasingly between 0.612 and 0.607 while exergetic sustainability between 1.575 and 1.545. However, it is estimated that waste exergy ratio changes increasingly between 0.388 and 0.393 while environmental effect factor between 0.635 and 0.647. Additionally, it is said that the higher PEME outlet pressure causes the higher exergetic sustainability index, the lower environmental effect factor, the lower waste exergy output, the higher exergetic efficiency. However, the higher storage pressure causes the lower exergetic efficiency, the higher waste exergy output, the higher environmental effect factor and the lower exergetic sustainability index. Thus, it is recommended that this type of the system should be operated at higher PEME outlet pressure, and at an optimum hydrogen storage pressure.     

Purification of alginate and feasible production of monoclonal antibodies by the alginate-immobilized hybridoma cells

Alginate has an extensive usage in the immobilization of many cell types. Although they have high biocompatibility, commercial alginates contain various degrees of contaminants such as polyphenols, endotoxins and proteins. Thus, these alginates show cytotoxicity against sensitive cell types such as hybridoma cells. In the studies so far, owing to this fact, commercially purchased high-priced ultrapure alginates have been used in the immobilization of hybridoma cells for monoclonal antibody production. However in this study, as a novelty, low-priced commercial alginate was purified, and then the cultivation of alginate-immobilized hybridoma cells was performed for feasible monoclonal antibody production. Low-priced commercial alginate was purified with a profitability ratio of 40%. Then, an optimized immobilization procedure was conducted effectively by using the purified alginate. During more than 25 days of cultivation, serum concentration was kept low, and approximately 2 times greater monoclonal antibody production was achieved, in comparison with its free suspended counterpart. The results showed that the efficiency of monoclonal antibody production via alginate-immobilized hybridoma cultivation can be increased by performing a proved in-house purification method. By shedding light on the efficiency of the in-house purification method, the results also indicated a feasible way of monoclonal antibody production.