Dynamic rate adaptation based on multidimensional multicode DS-CDMA in cellular wireless networks

Dynamic rate adaptation for uplink data transmission in a cellular multidimensional multicode (MDMC) direct-sequence code-division multiple-access packet data network is modeled and analyzed. An analytical framework is developed to evaluate the performances of radio link level dynamic rate adaptation schemes under multipath fading and log-normal shadowing. The radio link level throughput under optimal dynamic rate adaptation (having exponential computational complexity) and different heuristic-based suboptimal rate adaptation schemes can be assessed under the presented analytical framework. The performance of MDMC signaling is compared with that of the single-code variable spreading factor (VSF) signaling. To this end, based on an equilibrium point analysis of the system in steady-state, a base station-assisted and mobile-controlled dynamic rate adaptation scheme is presented.     

A robust timing and frequency synchronization for OFDM systems

A robust symbol-timing and carrier-frequency synchronization scheme applicable to orthogonal frequency-division-multiplexing systems is presented. The proposed method is based on a training symbol specifically designed to have a steep rolloff timing metric. The proposed timing metric also provides a robust sync detection capability. Both time domain training and frequency domain (FD) training are investigated. For FD training, maintaining a low peak-to-average power ratio of the training symbol was taken into consideration. The channel estimation scheme based on the designed training symbol was also incorporated in the system in order to give both fine-timing and frequency-offset estimates. For fine frequency estimation, two approaches are presented. The first one is based on the suppression of the interference introduced in the frequency estimation process by the training symbol pattern in the context of multipath dispersive channels. The second one is based on the maximum likelihood principle and does not suffer from any interference. A new performance measure is introduced for timing estimation, which is based on the plot of signal to timing-error-induced average interference power ratio against the timing estimate shift. A simple approach for finding the optimal setting of the timing estimator is presented. Finally, the sync detection, timing estimation, frequency estimation, and bit-error-rate performance of the proposed method are presented in a multipath Rayleigh fading channel.     

Up-regulation of brain N-methyl-D-aspartate receptors following multiple intracerebroventricular injections of [D-Pen2, D-Pen5] enkephalin and [D-Ala2, Glu4]deltorphin II in mice

The effects of chronic administration of [D-Pen2, D-Pen5]enkephalin and [D-Ala2, Glu4]deltorphin II, the selective agonists of the delta 1- and delta 2-opioid receptors, on the binding of [3H]MK-801, a noncompetitive antagonist of the N-methyl-D-aspartate receptor, were determined in several brain regions of the mouse. Male Swiss-Webster mice were injected intracerebroventricularly (i.c.v.) with [D-Pen2, D-Pen5]enkephalin or [D-Ala2, Glu4]deltorphin II (20 micrograms/mouse) twice a day for 4 days. Vehicle injected mice served as controls. Previously we have shown that the above treatment results in the development of tolerance to their analgesic activity. The binding of [3H]MK-801 was determined in brain regions (cortex, midbrain, pons and medulla, hippocampus, striatum, hypothalamus and amygdala). At 5 nM-concentration, the binding of [3H]MK-801 was increased in cerebral cortex, hippocampus, and pons and medulla of [D-Pen2, D-Pen5]enkephalin treated mice. In [D-Ala2, Glu4]deltorphin II treated mice, the binding of [3H]MK-801 was increased in cerebral cortex and hippocampus. The changes in the binding were due to increases in the Bmax value of [3H]MK-801. It is concluded that tolerance to delta 1- and delta 2-opioid receptor agonists is associated with up-regulation of brain N-methyl-D-aspartate receptors, however, some brain areas affected differ with the two treatments. The results are consistent with the recent observation from this laboratory that N-methyl-D-aspartate receptors antagonists block tolerance to the analgesic action of delta 1- and delta 2-opioid receptor agonists.     

Maximum-likelihood diversity combining in partial-band noise

Maximum-likelihood diversity combining is investigated for an FFH/MFSK spread spectrum system in partial-band noise (PBN). The structure of maximum-likelihood diversity reception in PBN plus white Gaussian noise is derived. It is shown that signal-to-noise ratio and the noise variance at each hop have to be known to implement this optimum diversity combiner. Several suboptimum diversity combining schemes are also considered. The performance of the optimum combining scheme is evaluated. It is shown that adaptive gain control diversity combining actually achieves the optimum performance when interference is not very weak     

A solar air heater with variable flow passage width

Different designs of solar air heaters with variable width of the flow channels are investigated.

Four possible geometries for the flow passage are considered with the aim to improve the efficienc of the system by maintaining a constant temperature of the absorber plate.

Efficiencies and plate temperatures are calculated for various designs, among them the most efficient is the one with decreasing duct width.     

GFEM analysis of MHD nanofluid flow toward a power‐law stretching sheet in the presence of thermodiffusive effect along with regression investigation

In the current study, we use Galerkin finite‐element simulation to analyze the concept of triple diffusive flow with magnetic field effect toward a power law stretching sheet. The fluid comprises dissolved solutal particles and nanoparticles in the base fluid. The three important mechanisms that are responsible for rise in phenomenon of convective transportation are diffusophoresis, thermophoresis along with Brownian motion have been considered. Recently, the proposed nanoparticles' mass flux and heat flux boundary conditions have been imposed. Nanoparticle mass transportation, solutal mass transportation with heat transportation for prominent physical parameters, such as stretching parameter, magnetic influence parameter, thermophoresis parameter, and Brownian motion parameter are calculated. To further verify and understand the strength of the relationship between heat transportation rate and controlling parameters, the multiple regression process is used. The finite difference approach was adopted to numerically solve the nonlinear governing equations and the linked boundary conditions. In the present study, we used MATLAB software for finding the final outcomes and relating the concluding results for $?{{\theta }_{\delta }}^{\prime }\left(0\right)$ with extant outcomes in the literature as a limiting case in the absence of the magnetic intensity parameter and an excellent agreement was noted. It was observed that the magnetic field has a positive effect on heat and mass transfer. This study also helps in understanding and thus controlling the velocity of the flow along with solutal depositions, which has a significant engineering application in the process of extrusion. The findings of the present study help to control the rate of heat and mass transfer, aiding manufacturing companies in obtaining the desired quality of product.     

Creating gold nanoprisms directly on quartz crystal microbalance electrodes for mercury vapor sensing

A novel electrochemical route is used to form highly {111}-oriented and size-controlled Au nanoprisms directly onto the electrodes of quartz crystal microbalances (QCMs) which are subsequently used as mercury vapor sensors. The Au nanoprism loaded QCM sensors exhibited excellent response-concentration linearity with a response enhancement of up to ～ 800% over a non-modified sensor at an operating temperature of 28?°C. The increased surface area and atomic-scale features (step/defect sites) introduced during the growth of nanoprisms are thought to play a significant role in enhancing the sensing properties of the Au nanoprisms toward Hg vapor. The sensors are shown to have excellent Hg sensing capabilities in the concentration range of 0.123-1.27 ppm(v) (1.02-10.55 mg m(-3)), with a detection limit of 2.4 ppb(v) (0.02 mg m(-3)) toward Hg vapor when operating at 28?°C, and 17 ppb(v) (0.15 mg m(-3)) at 89?°C, making them potentially useful for air monitoring applications or for monitoring the efficiency of Hg emission control systems in industries such as mining and waste incineration. The developed sensors exhibited excellent reversible behavior (sensor recovery) within 1 h periods, and crucially were also observed to have high selectivity toward Hg vapor in the presence of ethanol, ammonia and humidity, and excellent long-term stability over a 33 day operating period.     

Theory of infrared microspectroscopy for intact fibers

Infrared microspectroscopy is widely used for the chemical analysis of small samples. In particular, spectral properties of small cylindrical samples are important in forensic analysis, understanding relationships between microstructure and mechanical properties in fibers or fiber composites, and development of cosmetics and drugs for hair. The diameters of the constituent cylinders are typically of the order of the central wavelength of light used to probe the sample. Hence, structure and material spectral response are coupled and recorded spectra are usually distorted to the extent of becoming useless for molecular identification. In this paper, we apply rigorous optical theory to predict the spectral distortions observed in IR microspectroscopic data of fibers. The theory is used, first, to compute the changes that are observed for cylinders of various dimensions under different instrument configurations when compared to the bulk spectrum from the same material. We provide a method to recover intrinsic material spectral response from fibers by correcting for distortion introduced by the cylindrical structure. The theory reported here should enable the routine use of IR microspectroscopy and imaging for the molecular analysis of cylindrical domains in complex materials.