NACR: A New Adaptive Channel Reservation in Cellular Communication Systems

Future Personal Communication Networks (PCN) will employ microcells and picocells to support a higher capacity, thus increasing the frequency of handoff calls. Forced call terminations due to handoff call blocking are generally more objectionable than new call blocking. The proposed guard channel schemes for radio channel allocation in cellular networks reduce handoff call blocking probability at the expense of increases in new call blocking probability by giving resource access priority to handoff calls over new calls in call admission control. Under uniform traffic assumptions, it has been shown that a fixed number of guard channels leads to good performance results. In a more realistic system, non-uniform traffic conditions should be considered. In this case, the achieved call blocking probability may deviate significantly from the desired objective. In this paper, we propose a new adaptive guard channel scheme: New Adaptive Channel Reservation (NACR). In NACR, for a given period of time, a given number of channels are guarded in each cell for handoff traffic. An approximate analytical model of NACR is presented. Tabu search method has been implemented in order to optimize the grade of service. Discrete event simulations of NACR were run. The effectiveness of the proposed method is emphasized on a complex configuration.     

Dispersion of homogeneous and inhomogeneous waves in the Yeefinite-difference time-domain grid

The numerical dispersion relation governing the propagation of homogeneous plane waves in a finite-difference time-domain (FDTD) grid is well known. However, homogeneous plane waves, by themselves, do not form a complete basis set capable of representing all valid field distributions. A complete basis set is obtained by including inhomogeneous waves, where, in the physical world, constant phase planes must be orthogonal to constant amplitude planes for lossless media. In this paper, me present a dispersion analysis for both homogeneous and inhomogeneous plane waves in the Yee FDTD grid. We show that, in general, the constant amplitude and constant phase planes of inhomogeneous plane waves are not orthogonal, but they approach orthogonality for fine discretization. The dispersion analysis also shows that, for very coarsely resolved fields, homogeneous waves will experience exponential decay as they propagate and they may propagate faster than the speed of light. Bounds are established for the speed of propagation within the grid, as well as the highest frequency and the shortest wavelength that can be coupled into the grid. Analysis is restricted to the classic Yee algorithm, but a similar approach can be used to analyze other time-domain finite-difference methods     

Effect of autoclaving on dietary fibre content of beetroot (Beta vulgaris). Evaluation by different methods

Modifications of dietary fibre in beetroot during autoclaving have been evaluated by different methods: acid detergent (raw=1.45%; processed=1.17%) and neutral detergent (raw=2.30%; processed=2.00%), the enzymatic-gravimetric method of Asp (raw=3.35%; processed=3.34%), HPLC (raw=1.42%; processed=1.60%) and 3,5-dimethylphenol (raw=0.36; processed=0.28%). The correlation between different methodologies was studied. Autoclaving was carried out at 121°C under pressure for 15 min. Variance analysis indicated that quantitative variations originating in the thermic treatment were not statistically significant (P>0.05).     

Variational optical flow computation in real time.

This paper investigates the usefulness of bidirectional multigrid methods for variational optical flow computations. Although these numerical schemes are among the fastest methods for solving equation systems, they are rarely applied in the field of computer vision. We demonstrate how to employ those numerical methods for the treatment of variational optical flow formulations and show that the efficiency of this approach even allows for real-time performance on standard PCs. As a representative for variational optic flow methods, we consider the recently introduced combined local-global method. It can be considered as a noise-robust generalization of the Horn and Schunck technique. We present a decoupled, as well as a coupled, version of the classical Gauss-Seidel solver, and we develop several multgrid implementations based on a discretization coarse grid approximation. In contrast, with standard bidirectional multigrid algorithms, we take advantage of intergrid transfer operators that allow for nondyadic grid hierarchies. As a consequence, no restrictions concerning the image size or the number of traversed levels have to be imposed. In the experimental section, we juxtapose the developed multigrid schemes and demonstrate their superior performance when compared to unidirectional multgrid methods and nonhierachical solvers. For the well-known 316 x 252 Yosemite sequence, we succeeded in computing the complete set of dense flow fields in three quarters of a second on a 3.06-GHz Pentium4 PC. This corresponds to a frame rate of 18 flow fields per second which outperforms the widely-used Gauss-Seidel method by almost three orders of magnitude.     

An autocorrelation-based time domain analysis technique for monitoring perfusion and oxygenation in transplanted organs

In designing an implantable sensor for perfusion monitoring of transplant organs the ability of the sensor to gather perfusion information with limited power consumption and in near real time is paramount. The following work was performed to provide a processing method that is able to predict perfusion and oxygenation change within the blood flowing through a transplanted organ. For this application, an autocorrelation-based algorithm was used to reduce the acquisition time required for fast Fourier transform (FFT) analysis while retaining the accuracy inherent to FFT analysis. In order to provide data proving that the developed method is able to predict perfusion as accurately as FFT two experiments were developed isolating both periodic and quasi-periodic cardiac frequencies. It was shown that the autocorrelation-based method was able to perform comparably with FFT (limited to a sampling frequency of 300 Hz) and maintain accuracy down to acquisition times as low as 4 s in length.     

Lethal effect of electric fields on isolated ventricular myocytes

Defibrillator-type shocks may cause electric and contractile dysfunction. In this study, we determined the relationship between probability of lethal injury and electric field intensity ($E$ ) in isolated rat ventricular myocytes, with emphasis on field orientation and stimulus waveform. This relationship was sigmoidal with irreversible injury for $E ≫ hbox{50 V/cm}$ . During both threshold and lethal stimulation, cells were twofold more sensitive to the field when it was applied longitudinally (versus transversally) to the cell major axis. For a given $E$, the estimated maximum variation of transmembrane potential ( $Delta V_{max }$) was greater for longitudinal stimuli, which might account for the greater sensitivity to the field. Cell death, however, occurred at lower maximum $Delta V_{max }$ values for transversal shocks. This might be explained by a less steep spatial decay of transmembrane potential predicted for transversal stimulation, which would possibly result in occurrence of electroporation in a larger membrane area. For the same stimulus duration, cells were less sensitive to field-induced injury when shocks were biphasic (versus monophasic). Ours results indicate that, although significant myocyte death may occur in the $E$ range expected during clinical defibrillation, biphasic shocks are less likely to produce irreversible cell injury.      

Temperature-dependent characteristics and single-mode performanceof AlGaInP-based 670-690-nm vertical-cavity surface-emitting lasers

We report on temperature dependent characteristics and single mode performance of one-wave cavity, planar implanted, AlGaInP-based vertical-cavity surface emitting lasers. By optimizing the overlap between the gain peak and the cavity mode of the structure, we demonstrate record device performance, including 8.2 mW maximum output power and 11% power conversion efficiency for multimode operation and 1.9 mW and 9.6% power conversion efficiency for single mode operation at 687 nm. Improved performance at elevated temperatures is also achieved, with 1.5 mW output power demonstrated at 50°C from a 15-μm-diameter device     

Transformation champ proche — champ lointain bidimensionnelle et monodimensionnelle appliquée à des mesures de SER

In high frequency thercs measurement of large target must be done at important distances, so the distance of measurement (Fraunhofer’s distance) R is given by R ≥ 2d² /λ where d is the tranversal length of the target and λ the radiation wavelength. In this paper we present a method for target that are large relative to the curvature of the spherical wavefront and the curvature of the cylindrical wavefront. A two-dimensional analytical algorithm transforms the spherical wave (near-field) measurement into the desired plane wave (far-field) and a one-dimensionnal analytical algorithm transforms the cylindrical wave (near-field) measurement into the desired plane wave (far-field). We present some results on simulations and measurements. A comparison of one-dimensional and two-dimensional methods demonstrates the efficiency of the two dimensional methods.     

Effects of electrical and mechanical stunning methods on meat quality in ostriches

The effect of electrical and captive needle air pressure stunning methods on some meat quality parameters was examined in ostriches under practical conditions. One hundred and fifteen ostriches were used in three experiments. The ostriches were stunned either electrically (head only) or by using a captive needle with air pressure. In the first experiment the ostriches were stunned at 90 V (～effectively 52 V), 200 V and by captive needle using air pressure. In the second experiment voltages of 175 and 200 V were applied and a captive needle stunning method using air pressure. In the third experiment the birds were stunned at 175 V with a short stun/stick interval. Experiments 2 and 3 were performed in a different slaughterhouse from experiment 1. Meat quality was assessed by measuring the pH, temperature and colour at 45 min and 18 h post mortem and by determining water binding capacity and haemorrhage score at 18 h post mortem in the big drum, tender loin and triangular filet muscles. The measured stunning parameters in the first experiment were 204±96 mA (～52 V) during 11±1 s and 556±85 mA (～200 V) during 6±0 s. The stun/stick interval was 136±38 s. The rigor mortis value in the tender loin and both pH(1) and pH(2) in the big drum, tender loin and triangular filet muscles were (p<0.05) lower when stunned with air pressure compared with electrical stunning. Moreover internal light scattering remained higher. The measured currents in the second experiment were 561±226 mA (～173 V) during 6±2 s and 518±120 mA (～200 V) during 6 s. The stun/stick interval was 39±12 s. The pH at 45 min and 18 h differed (p<0.05) in the tender loin and triangular filet muscles as did the temperature at 45 min in the three muscles between the different stunning groups. The stunning in the third experiment was carried out with 548±180 mA during 6±2 s. The stun/stick interval was 5±2 s. After the short stun/stick interval the pH(2) was lower (p<0.05) for the tender loin and triangular filet muscles and the wetness of the filter paper of the big drum was (p<0.05) lower compared with the other groups. Our experiments showed that stunning methods affected several meat quality parameters. Using a high electrical stunning current, captive needle stunning or a short stun/stick interval may positively affect some parameters. More research is necessary to examine effects of pre slaughter handling on meat quality.     

Sur l’utilisation des équations intégrales en régime transitoire dans les problèmes d’électromagnétisme

It is possible in many cases by using space-time integral equations to compute the scattering and penetration of electromagnetic fields via explicit time-stepping diagrams. The case of conducting surfaces, thin scatterers, apertures and shieldings of finite conductivity are discussed with emphasis on the simplicity and the validity domain of the relevant equations. Examples concern the field of a far-located dipole incident on a cylinder with infinite conductivity, with an aperture or with resistive walls.