Tailoring the ionic transfer characteristics of polyvinyl chloride-based heterogeneous ion exchange membranes by embedding carboxy methyl cellulose in membrane channels

Polyvinyl chloride-based heterogeneous cation exchange membranes were modified by embedding carboxy methyl cellulose in ionic transfer channels of membrane. The effect of CMC to PVC blend ratios on properties of membranes was studied. SOM images showed uniform distribution and surfaces for prepared membranes relatively. The SEM images showed uniform and dense structure for the membranes. The XRD pattern also demonstrated amorphous structure for the membranes. Membrane water content was improved from 25 to 39 % by increase of CMC concentration up to 32 %wt. Similar trend was found for membrane surface hydrophilicity. The membrane ion exchange capacity, fixed ion concentration, membrane potential, charge density, transport number, permselectivity, and ionic flux were enhanced initially by increase of CMC ratio up to 16 %wt and then began to decrease by increase in CMC concentration from 16 to 32 %wt. The membrane oxidative stability and areal electrical resistance showed decreasing trends by utilizing of carboxy methyl cellulose in the membrane matrix. Membrane transport number and selectivity were also increased by increase of electrolyte concentration. Similar trend was found for the membrane electrical conductivity by increase of electrolyte concentration. Also prepared membranes showed higher transport number, selectivity, and areal electrical resistance at pH 7 compared to other pH values.     

Evaluation of rutting resistance of asphalt binders and asphalt mixtures modified with polyphosphoric acid

In this research, a polyphosphoric acid (PPA) additive was used to modify a performance graded binder (PG 58-22). Experimental program included use of three PPA contents (0.5%, 1%, and 1.5%) by weight of bitumen and use of antistripping limestone aggregates. High-temperature rheological properties of asphalt binders were evaluated through the frequency sweep test. Complex modulus test was also used to evaluate rutting characteristics of asphalt mixtures. Results showed that PPA significantly improved rutting resistance of both unmodified asphalt binder and unmodified asphalt mixture, especially for the asphalt binder.     

Equivalent viscous damping in direct displacement‐based design of steel braced reinforced concrete frames

Performance‐based design method, particularly direct displacement‐based design (DDBD) method, has been widely used for seismic design of structures. Estimation of equivalent viscous damping factor used to characterize the substitute structure for different structural systems is a dominant parameter in this design methodology. In this paper, results of experimental and numerical investigations performed for estimating the equivalent viscous damping in DDBD procedure of two lateral resistance systems, moment frames and braced moment frames, are presented. For these investigations, cyclic loading tests are conducted on scaled moment resisting frames with and without bracing. The experimental results are also used to calibrate full‐scale numerical models. A numerical investigation is then conducted on a set of analytical moment resisting frames with and without bracing. The equivalent viscous damping and ductility of each analytical model are calculated from hysteretic responses. On the basis of analytical results, new equations are proposed for equivalent viscous damping as a function of ductility for reinforced concrete and steel braced reinforced concrete frames. As a result, the new equation is used in direct displacement‐based design of a steel braced reinforced concrete frame. Copyright © 2012 John Wiley & Sons, Ltd.     

A new low-power 10T SRAM cell with improved read SNM

This paper describes the characteristics of a new 10T structure for SRAM cell that works quite well in the sub-threshold region. This new architecture has good characteristics in write and read delay and energy compared with other new structures. This new 10T topology improves read static noise margin (SNM) and write operation speed with respect to other topologies in the same or even lower power consumption. The new topology has at least 13% lower power consumption compared with the best of recent architectures. Its write characteristics also are similar to those of 6T-SRAM, which has improved write delay and energy. The new 10T SRAM cell also consumes lower power compared with other cells. The stacking is used to suppress the standby leakage through the read path. The simulations were performed using HSPICE 2011 in a 16 nm bulk CMOS Berkeley predictive technology model (BPTM).     

Optimal design of EMAT transmitters

A three-part finite element model is developed that characterizes the ultrasonic pulse produced by an electromagnetic acoustic transducer (EMAT). The model represents several significant improvements over previously published works, as follows: (a) spatial inhomogeneities in the magnetic flux density are calculated and then incorporated in the determination of body forces, (b) an improved model of the electromagnetic induction phenomenon is formulated, allowing a more accurate evaluation of the ultrasonic pulse launched by an EMAT transmitter and (c) results from the model are compared directly with experimental measurements, yielding discrepancies of the order of 15% in the amplitude of the ultrasonic pulse. The new model is used to optimize the design of the EMAT system. In particular, a parametric study was conducted on the effects of varying an EMAT's magnet-to-coil width ratio. For the EMAT configuration considered, significant improvements can be achieved in the ultrasonic beam amplitude and profile by increasing the ratio to about 1.2; further increases in magnet dimensions yield only marginal improvements in the ultrasonic beam, at the cost of excessive EMAT size.     

A simple and accurate Ritz formulation for free vibration of thick rectangular and skew plates with general boundary conditions

The Ritz method is one of the most elegant and useful approximate methods for obtaining solutions for the natural frequencies and vibration modes of elastic plates. It is simple to use and also straightforward to implement. In conventional Ritz method, the geometric boundary conditions are only satisfied and hence the Ritz method is known as a method that can produce upper bound solution results for the natural frequencies of elastic plates. On the other hand, the accuracy of the Ritz method for the solution of differential equations with mixed natural boundary conditions at the boundary lines is not very satisfactory. To overcome this difficulty, this paper presents a simple and accurate Ritz formulation in which the natural boundary conditions are exactly implemented. The versatility, accuracy, and efficiency of the proposed method for free vibration analysis of thick rectangular and skew plates are tested against other solution procedures. It is revealed that the proposed method to handle the mixed natural boundary conditions is simple to use and can produce highly accurate solutions for the natural frequencies of thick rectangular and skew plates involving free edges.     

Determination of unstable singularities in parallel robots with N arms

Parallel mechanisms frequently possess an unstable type of singularity that has no counterpart in serial mechanisms. When the mechanism is at or near this type of singularity, it loses the ability to counteract external forces in certain directions. The determination of unstable singular configurations in parallel robots is challenging, and in the past, has been tackled by exhaustive numerical searches of the mechanism workspace using an accurate analytical model of the mechanism kinematics. This paper considers the singularity-determination problem from a geometric perspective for n-legged spatial parallel mechanisms. By using the constraints on the passive joint velocities, a necessary condition for an unstable singularity is derived.     

Co-polarised and cross-polarised antenna arrays for breast, cancer detection

The detection capabilities of two novel co-polarised and cross-polarised antenna arrays consisting of two slot antennas have been studied and compared for the purpose of ultra-wideband breast cancer detection. For both arrays, the measured antenna return loss is below -10 dB from 3.1 to 10 GHz. The measured coupling between the two elements is below - 20 dB for the co-polarised and - 25 dB for the cross-polarised formation. It is shown through simulations and measurements that the cross-polarised array improves the signal-to-clutter ratio for tumours close to a planar chest wall.     

Growing up and growing old: Continuity and change in wishes and desires over the course of life.

This report summarizes the panel held at the annual meeting of the American Psychological Association, Division 39 (Psychoanalysis). The panel explored the meaning of desire in childhood, adolescence, and adulthood. The discussants focused on the subjective experience of desire, its preconditions, and its significance in different developmental stages. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Thermophysical Properties of Nitrogen from a New Potential Energy Surface Using the Mason–Monchick Approximation

A recent N₂–N₂ potential has been used to calculate the second virial, viscosity, and diffusion coefficients. Calculations have been done up to the first quantum correction for virial coefficients and the second-order kinetic theory approximation for transport coefficients. The Mason–Monchick approximation (MMA) has been used for the calculation of collision integrals and, via a numerical analysis, a common intersection point has been found for reduced cross sections and collision integrals of different orientations. This regularity has been interpreted with the aim of the orientation dependence of the potential energy and different types of collisions between molecules. The overall agreement of the calculated second virial coefficient with experiment is reasonable but suggests that a slight re-scaling of the potential would be beneficial. In the case of transport properties, calculated and experimental results show an average deviation of about 1.6% and 0.7% for viscosity and relative diffusion coefficients, respectively.