In IEEE 802.11 wireless local area networks (WLANs); the binary exponential backoff (BEB) algorithm is used in the medium access control (MAC) protocol to resolve contortion problems. Unfortunately, BEB has been shown...
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In IEEE 802.11 wireless local area networks (WLANs); the binary exponential backoff (BEB) algorithm is used in the medium access control (MAC) protocol to resolve contortion problems. Unfortunately, BEB has been shown to be highly short-term unfair. In this paper, we propose a probabilistic contention window control mechanism to improve the fairness of the backoff procedure and we evaluate its performance on real-time applications such as voice over IP and video conferencing. Simulation results reveal improvements in fairness and throughput, without detriment to delay and jitter.
This paper proposes a new maximum power point tracking (MPPT) method in combination with one-cycle control for photovoltaic power generation. This control scheme is based on the automatic current-adjusting feature of ...
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This paper proposes a new maximum power point tracking (MPPT) method in combination with one-cycle control for photovoltaic power generation. This control scheme is based on the automatic current-adjusting feature of one-cycle control. The output current of the inverter can be adjusted according to the voltage of the photovoltaic (PV) array so as to extract the maximum power from it. In the mean time, one-cycle control guarantees that the output current is in the same shape of and in phase with the grid voltage. All these are accomplished in one power stage and a simple control circuit. No detection and calculation of power are needed. Compared with previously proposed approaches, this method is much more efficient and more cost-effective and yet exhibits excellent performance. The principle is explained qualitatively and extensive experiments have been carried out to verify and validate the proposed method.
In this paper, we present LiQuID, a tool for clustering lighting simulation data. Photographs are useful vehicles for both describing and making assessments of architectural lighting systems. A significant barrier to ...
In this paper, we present LiQuID, a tool for clustering lighting simulation data. Photographs are useful vehicles for both describing and making assessments of architectural lighting systems. A significant barrier to using photographs during the design process relates to the sheer volume of renderings that needs to be analyzed. Although there have been efforts to produce novel visualization systems to manage large sets of photographs, this research aims to reduce the complexity by classifying data into representative prototypes. A hypothetical case study is discussed.
In this paper, we model users of next generation services by means of utility differentiated classes. Noncooperative game theory is employed to explain user behavior with respect to the network price. Rate control alg...
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In this paper, we model users of next generation services by means of utility differentiated classes. Noncooperative game theory is employed to explain user behavior with respect to the network price. Rate control algorithms for attaining such a noncooperative Nash equilibrium are then presented. We extend our previous model of a single link fed by Poisson traffic to encompass a generic network and non-Poisson traffic. These results can be applied to a wide variety of future networks ranging from LSPs in MPLS networks to wavelength paths in WDM networks.
Frequency domain analysis of the R-R intervals was performed in subjects with and without sleep disordered breathing (SDB). Data from Physionet's Apnea-ECG database as well as data collected at our sleep disorders...
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Frequency domain analysis of the R-R intervals was performed in subjects with and without sleep disordered breathing (SDB). Data from Physionet's Apnea-ECG database as well as data collected at our sleep disorders clinic were used for this study. 15-minute ECG epochs were selected from polysomnography data. Power spectrum analysis of the resampled R-R interval series (1.2 Hz) was performed using Welch's averaged periodogram method. Normalized power in two bands, AB/sub 1/ (0.019 to 0.071 Hz) and AB/sub 2/ (0.019 to 0.036 Hz) were used to compare the impact of SDB events on the spectrum of R-R intervals. Normalized AB/sub 1/ power produced a sensitivity of 76% and a specificity of 100% in the data from the Apnea-ECG database. The same parameter produced a sensitivity of 76% and specificity of 52% in the data collected at our sleep laboratory. This difference in the results may be attributed to the severity and duration of SDB events present in the two datasets.
In 1960, Campbell derived a quantity that he defined as the coefficient rate of a random process that involves the process spectral entropy. However, no potential applications of the coefficient rate were identified. ...
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In 1960, Campbell derived a quantity that he defined as the coefficient rate of a random process that involves the process spectral entropy. However, no potential applications of the coefficient rate were identified. Two new derivations of Campbell's rate coefficient rate are presented. One derivation solidifies the interpretation of this quantity as a coefficient rate and allows definition of an effective bandwidth for the process. The second derivation implies a new approach for realization adaptive source compression. The coefficient rate can be used for realization adaptive coefficient selection in a sequence of source representations. Furthermore, the effective bandwidth is designated as Campbell bandwidth and contrasted with Fourier bandwidth and Shannon bandwidth. Several specific examples are presented that illustrate the differences among the three quantities.
This paper proposes the development of a fuzzy predictive control. Genetic algorithms (GA's) are used to automatically tune the controller. A recurrent neural network is used to identify the process, and then prov...
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This paper proposes the development of a fuzzy predictive control. Genetic algorithms (GA's) are used to automatically tune the controller. A recurrent neural network is used to identify the process, and then provides predictions about the process behavior, based on control actions applied to the system. These predictions are used by the fuzzy controller, in order to accomplish a better control of an alcoholic fermentation process from chemical industry. This problem has been chosen due to its non-linearity and large accommodation time, that make it hard to control by standard controllers. Comparison of performance is made with non-predictive approaches(PID and Fuzzy-PD), and also with another predictive approach, GPC(Generalized Predictive Control).
We propose a method for process monitoring of a semiconductor manufacturing process. Independent component analysis (ICA) is applied to characterize E-test parameter data. We calculate angular confidence intervals for...
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We propose a method for process monitoring of a semiconductor manufacturing process. Independent component analysis (ICA) is applied to characterize E-test parameter data. We calculate angular confidence intervals for the model, eliminate marginally significant components and implement control charts for significant components of interest. Alarms are generated off of deviations in the charted components. Alarms are easily used in process diagnosis based on the interpretation of the independent components.
A process was developed for patterning thin films of environmentally sensitive hydrogels onto silicon microcantilevers. Microcantilevers have been shown to be ultra-sensitive transducers for chemical, physical, and bi...
A process was developed for patterning thin films of environmentally sensitive hydrogels onto silicon microcantilevers. Microcantilevers have been shown to be ultra-sensitive transducers for chemical, physical, and biological microsensors. By patterning environmentally sensitive hydrogels onto silicon microcantilevers, novel microsensors were prepared for MEMS and BioMEMS applications. Specifically, a cross-linked poly(methacrylic acid) (PMAA) network containing significant amounts of poly(ethylene glycol) dimethacrylate (PEGDMA) was studied. This hydrogel exhibits a swelling dependence on pH. By increasing the environmental pH above the pKa of PMAA to cause ionization of the carboxylic acid groups, electrostatic repulsion is produced along the main polymer chain causing the polymer network to expand and swell. Therefore, a pH change induces swelling or shrinking of the polymer network and creates stress on the microcantilever surface causing it to bend. In this study, silicon microcantilevers were fabricated on p-type (100) SOI wafers. Covalent adhesion was gained between the polymer and the silicon surface through the modification of the silicon surface with ?-methacryloxypropyl trimethoxysilane. Hydrogels were patterned onto the silicon microcantilevers utilizing a mask aligner to allow for precise positioning. The micropatterned hydrogels were analyzed using optical microscopy and profilometry. The bending response of patterned cantilevers with a change in environmental pH was observed, providing proof-of-concept for a MEMS/BioMEMS sensor based on microcantilevers patterned with environmentally sensitive hydrogels.
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