Providing application-level QoS in 3G/4G wireless systems: a comprehensive framework based on multirate CDMA

The emerging applications for 3G and 4G wireless systems typically require highly heterogeneous and time-varying quality of service from the underlying protocol layers. The wireless links, however, provide only an unreliable communication channel that suffers from temporal outages. As a consequence, protocol mechanisms are needed that, based on the unreliable wireless links, provide the different service qualities required by the emerging applications. We identify the emerging IP-based applications for 3G and 4G wireless systems and categorize their QoS requirements. We discuss the wireless access mechanisms that show promise as the basis for supporting these applications. We then propose a set of protocol mechanisms that, based on the discussed wireless access mechanisms, provide the required QoS for the different application categories.     

Microwave beam imaging by recombination continuum from the positive column of gas discharge in a cesium vapor-xenon mixture

A new sensitive method for imaging of the spatial distribution of microwave intensity is proposed. The method is based on the imaging of the 6P-recombination continuum of cesium, emitted from a nonequilibrium plasma of the positive column of gas discharge in a cesium vapor-xenon mixture. It is demonstrated that the spatial distribution of intensity of 35-GHz microwave radiation measured by this method in a focal plane of a lens well coincides with the pattern obtained with the aid of a movable microwave detector. The time resolution of the proposed microwave imaging system reaches 1 ms.     

A study on hydrogen storage by use of cryoadsorbents

This paper reports investigations on the techniques and economics of hydrogen storage by means of cryoadsorption. Also a comparison with alternative storage methods is included. The hydrogen storage capacity of several adsorbents in the temperature range 65–150 K has been investigated experimentally. Based on these data, economics and operating conditions for minimum total costs of the system are calculated. Utilization-factor and capacity-factor parameters are shown to be decisive for outlining the favourable ranges of application for competitive hydrogen storage methods.     

Dynamic light scattering by gels under hydrostatic pressure

Measurements of variation with pressure of the collective diffusion constant D_c in polyacrylamide gels using both a good solvent (water) and a theta solvent (methanol 30% - water 70% by volume) are reported. From these observations the variation of ξ_h, the hydrodynamic screening length in the gel, is obtained, and compared with ξ_st, the static screening length. The latter is obtained from measurements of the density of the polymer solutions. In the concentration range studied (3%–10%) and for pressures up to 3 kbar, both ξ_h and ξ_st diminish with increasing pressure (i.e. the solvent quality improves), but the variation of ξ_h is more than an order of magnitude smaller than ξ_st for both the poor and good solvent cases.     

Novel bipolar differential input/output current-controlled current source

A new bipolar differential input/output current-controlled current source (CCCS) is described. The basic cell consists of a translinear array of six transistors with two bipolar inputs, and is suited for the input stage of a differential current-mode operational amplifier.     

Dicyanate semi IPNs—A new class of high performance,high temperature plastics

Dicyanate Semi-Interpenetrating Polymer Networks (semi IPNs) are made by dissolving a thermoplastic in crosslinking dicyanates and then curing the resulting mixture. The semi IPNs produced are strong, with tensile strengths of 10,000 to 12,000 psi, and flexible, with elongations to break of 10 to 17 percent. Dicyanate semi IPNs also have good thermal stability and the softening temperatures of the IPNs are significantly, higher than those of the corresponding thermoplastics.     

The concept of an endurance limit for adhesive joints

The effect of cyclic stressing on the strength of single lap adhesive joints has been studied and a considerable reduction in strength observed when the maximum stress exceeds about 40% of the ultimate tensile strength, but whether or not a true endurance limit exists is not proven. Fallacies are shown in some of the techniques which have been proposed for studying the fatigue behaviour of adhesive joints.     

Randomized unbiased design of regression experiments on functionals in a Hilbert space

Translated from Kibernetika, No. 2, pp. 58–66, March–April, 1991.     

Neural network payload estimation for adaptive robot control

A concept is proposed for utilizing artificial neural networks to enhance the high-speed tracking accuracy of robotic manipulators. Tracking accuracy is a function of the controller's ability to compensate for disturbances produced by dynamical interactions between the links. A model-based control algorithm uses a nominal model of those dynamical interactions to reduce the disturbances. The problem is how to provide accurate dynamics information to the controller in the presence of payload uncertainty and modeling error. Neural network payload estimation uses a series of artificial neural networks to recognize the payload variation associated with a degradation in tracking performance. The network outputs are combined with a knowledge of nominal dynamics to produce a computationally efficient direct form of adaptive control. The concept is validated through experimentation and analysis on the first three links of a PUMA-560 manipulator. A multilayer perceptron architecture with two hidden layers is used. Integration of the principles of neural network pattern recognition and model-based control produces a tracking algorithm with enhanced robustness to incomplete dynamic information. Tracking efficacy and applicability to robust control algorithms are discussed.