In this article, we show that a code division multiple access (CDMA) system employing long codes can be interpreted as a multiple input multiple output system where the transmit filters are time-varying. We derive con...
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In this article, we show that a code division multiple access (CDMA) system employing long codes can be interpreted as a multiple input multiple output system where the transmit filters are time-varying. We derive conditions for existence of zero-forcing equalizers and verify through simulations that these conditions are useful guidelines for the design of appropriate solution in the presence of noise. Compared to similar works in the literature, the derived conditions allow a reduction in the length of the equalizer filters, while imposing no constraints on the channel order.
This paper introduces a multi-paradigm dynamic system simulator based on discrete time and discrete event formalism for simulating a supply chain as a complex adaptive system. Little is known about why such a diversit...
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This paper introduces a multi-paradigm dynamic system simulator based on discrete time and discrete event formalism for simulating a supply chain as a complex adaptive system. Little is known about why such a diversity of supply chain structures exist. Simulating dynamic supply chain networks over extended periods using the multi-paradigm dynamic system simulator allows us to observe the emergence of different structures. The simulator is implemented using a software agent technology, where individual agents represent firms in a supply chain network. In this paper, we present an example scenario run on the simulator and the preliminary results that have been observed. This multi-paradigm tool provides a valuable investigation instrument for real life supply chain problems.
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 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.
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.
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.
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.
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