Performance comparison of available interstitial antennas formicrowave hyperthermia

The authors have developed a numerical model which calculates the current distribution and radiation characteristics of multisection antennas have varying diameters of the center conductor and/or the types and thicknesses of the insulation. They briefly describe the model and compare the numerical results with the experimental data published by T.P. Ryan and J.W. Strohbehn (1987). Excellent correlation between the experimental and calculated patterns was obtained. The numerical model was then used to examine some interesting changes in the commercial designs, such as the effect of the tip termination of the antenna and the diameters of the conducting sections (collars) on the heating patterns of the BSD Medical antenna. Important observations regarding the role of each section, in multisection antenna designs, in guiding along the antenna vs. coupling to the ambient were also investigated and verified     

Performance of multicode DS/CDMA with noncoherent M-ary orthogonal Modulation in multipath fading channels

This paper presents the performance analysis and simulation of a multicode direct-sequence code-division multiple-access system with noncoherent M-ary modulation, in a multipath fading environment. This type of transceiver is specified for the reverse link of the IS-95B and cdma2000 (radio configurations 1 and 2) systems and is intended to serve high-rate applications such as data transfer and video communications. While previous studies considered the analytical error performance of coherent multicode systems, little attention has been devoted in the literature to the noncoherent case. We provide concise and useful expressions for the interference terms as a function of the commonly used aperiodic cross correlation functions. After a statistical characterization of these terms, we make use of the Gaussian approximation (GA) in order to obtain the bit-error rate (BER). However, unlike some other analyses (for coherent detection) relying on the GA, in our derivation, we take into account the fact that all the codes transmitted by a mobile user fade in unison. As demonstrated via computer simulations, this fact is crucial to obtain a reliable estimate of the BER, especially when equal-gain combining (EGC) is used at the receiver. The analysis is also extended to include a simple closed-loop power control algorithm and hard handoff between multiple cells. In particular, we verify-for the multicode case-previous observations that the use of EGC allows improvement only for a certain range of values of the total interference seen at the receiver: When either the number of interfering users is too large, or too many codes are assigned to the high-rate user, the noncoherent combining loss becomes such that the use of many diversity branches can decrease the performance as compared to a system with little or no diversity.     

PROBA-V mission for global vegetation monitoring: standard products and image quality

PROBA-V is a new global vegetation monitoring mission, to be launched in the second quarter of 2013. PROBA-V has been developed to show a consistent performance with SPOT-VEGETATION (SPOT-VGT) data, with similar spectral bands but with an improved spatial resolution of 1/3 km. The innovative mission concept has led to several key research topics related to image quality, which are discussed in this article. To support the existing VEGETATION user community, the data products for PROBA-V continue to provide daily top of canopy synthesis (S1-TOC) and 10 day synthesis products (S10-TOC). In addition, the new top of atmosphere daily synthesis (S1-TOA) products and a radiometrically/geometrically corrected (level 1C) product in raw resolution will also be provided for scientific users.     

Comparison of Accelerated Compressive Creep Behavior of Virgin HDPE Using Thermal and Energy Approaches

This article compares two available approaches for accelerating the creep response of viscoelastic materials, such as High Density Polyethylene (HDPE), which is increasingly gaining attention for use in construction. Thermal acceleration methods to predict the tensile creep of polymers are already available. The Time-Temperature Superposition (TTS) phenomenon is the basis of several available methods, and an ASTM standard for tensile creep of geosynthetics is based on one of its derivatives, the Stepped Isothermal Method (SIM). In this article, both TTS and SIM have been adapted to study the compressive creep of virgin HDPE. An alternate approach, based on the equivalence of strain energy density (SED) between conventional constant-stress creep tests and strain-controlled stress-strain tests, is also adapted for accelerated compressive creep of HDPE. There is remarkably a good agreement among the creep behaviors obtained from conventional tests, TTS, SIM, and SED predictions for virgin HDPE.     

Biophysical studies on bone cement composites based on polyester fumarate

In this study poly(vinlyl chloride) (PVC) was modified by using ethylenediamine, diethylenetriamine, and ethanolamine as a crosslinker in dimethylformamide. Reaction variables were optimized for getting desired crosslinked PVC, which was further reacted with maleic anhydride to form graft polymer. The anhydride group on further hydrolysis gives carboxylic group, which can exchange proton with other cations.The polymers were characterized by FTIR spectroscopy and thermal analysis (TGA/DTA). Swelling behavior was examined in various electrolytic solutions. Modified PVC have shown good thermal stabilities and absorption capacities in neutral and acidic media, due to which these polymers might find applications in cation exchanger resin and chromatography. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Finite time thermodynamic evaluation of endoreversible Stirling heat engine at maximum power conditions

Maximum power and efficiency at the maximum power point of an endoreversible Stirling heat engine with finite heat capacitance rate of external fluids in the heat source/sink reservoirs with regenerative losses are treated. It was found that the thermal efficiency depends on the regenerator effectiveness and the internal irreversibility resulting from the working fluid for a given value of reservoir temperature. It was also concluded that it is desirable to have larger heat capacity of the heat sink in comparison to the heat source reservoir for higher maximum power output and lower heat input.     

Reliability-Based Pipe Size Computation of On-Demand Irrigation Systems

The variability of flow regimes in on demand pressurized irrigation systems leads to uncertainty in head at the nodes affecting the system performance, and thus it should be considered when designing and/or rehabilitating water distribution systems. Based on these considerations a new approach for the optimization of on demand pressurized irrigation systems is presented combining the minimization of cost with the maximization of reliability taking into account the stochastic variability of the flows into each section of the network. The new model, Clément and the cumulated random generated discharges model (FAO model) were applied to three pressurized irrigation networks of different dimensions (large, medium and small) operating on demand in Southern Italy. The optimization algorithm used in all the cases is the Labye iterative discontinuous method, a formulation of the dynamic programming. The results of the different models were compared showing that the cost of the optimal network calculated using the new model was reduced by more than 20%, without any significant decrease of the system reliability or reduction of the network capacity.     

Outage probability of dual-branch coherent equal-gain combining in correlated Nakagami-m fading

The exact outage probability of mobile radio receivers using dual-branch coherent equal-gain combining is analytically derived for correlated Nakagami-m fading. Expressions in the form of infinite series are obtained for the two cases of identical parameters on both diversity branches, and identical m-parameters (multiples of a half-integer) but not-necessarily identical fading powers on each branch.