The Experts below are selected from a list of 624717 Experts worldwide ranked by ideXlab platform
S Gajdos - One of the best experts on this subject based on the ideXlab platform.
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spin Rate Distribution of small asteroids
Icarus, 2008Co-Authors: P Pravec, A W Harris, David Vokrouhlický, Brian D Warner, P Kusnirak, K Hornoch, Donald P Pray, David Higgins, A Galad, S GajdosAbstract:Abstract The spin Rate Distribution of main belt/Mars crossing (MB/MC) asteroids with diameters 3–15 km is uniform in the range from f = 1 to 9.5 d−1, and there is an excess of slow rotators with f 1 d−1. The observed Distribution appears to be controlled by the Yarkovsky–O'Keefe–Radzievskii–Paddack (YORP) effect. The magnitude of the excess of slow rotators is related to the residence time of slowed down asteroids in the excess and the Rate of spin Rate change outside the excess. We estimated a median YORP spin Rate change of ≈ 0.022 d −1 / Myr for asteroids in our sample (i.e., a median time in which the spin Rate changes by 1 d−1 is ≈ 45 Myr ), thus the residence time of slowed down asteroids in the excess is ≈ 110 Myr . The spin Rate Distribution of near-Earth asteroids (NEAs) with sizes in the range 0.2–3 km (∼5 times smaller in median diameter than the MB/MC asteroids sample) shows a similar excess of slow rotators, but there is also a concentration of NEAs at fast spin Rates with f = 9 – 10 d −1 . The concentration at fast spin Rates is correlated with a narrower Distribution of spin Rates of primaries of binary systems among NEAs; the difference may be due to the apparently more evolved population of binaries among MB/MC asteroids.
Jeffrey G. Andrews - One of the best experts on this subject based on the ideXlab platform.
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uplink Rate Distribution in heterogeneous cellular networks with power control and load balancing
International Conference on Communications, 2015Co-Authors: Sarabjot Singh, Xinchen Zhang, Jeffrey G. AndrewsAbstract:Load balancing through proactive offloading users onto small cells is critical for tapping the potential of dense heterogeneous cellular networks (HCNs). However, the impact of such offloading on the uplink performance is not well understood, primarily due to the lack of tractable models. Uplink power control and spatial interference correlation further complicate the mathematical analysis as compared to the downlink. In this paper, we propose a tractable and general model to characterize the uplink SIR and Rate Distribution in a K-tier HCN as a function of the association and power control parameters. Using the developed analysis, it is shown that the optimal degree of channel inversion (for uplink power control) increases with load imbalance in the network. Minimum path loss association is shown to maximize uplink Rate coverage. Moreover, with minimum path loss association and full channel inversion, uplink coverage is shown to be invariant of infrastructure density.
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downlink Rate Distribution in heterogeneous cellular networks under generalized cell selection
arXiv: Information Theory, 2013Co-Authors: Harpreet S. Dhillon, Jeffrey G. AndrewsAbstract:Considering both small-scale fading and long-term shadowing, we characterize the downlink Rate Distribution at a typical user equipment (UE) in a heterogeneous cellular network (HetNet), where shadowing, following any general Distribution, impacts cell selection while fading does not. Prior work either ignores the impact of channel randomness on cell selection or lumps all the sources of randomness into a single variable, with cell selection based on the instantaneous signal strength, which is unrealistic. As an application of the results, we study the impact of shadowing on load balancing in terms of the optimal per-tier selection bias needed for Rate maximization.
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Rate Distribution in heterogeneous cellular networks with resource partitioning and offloading
Global Communications Conference, 2013Co-Authors: Sarabjot Singh, Jeffrey G. AndrewsAbstract:Mobile users proactively offloaded from macro cells to small cells in heterogeneous cellular networks (HCNs) encounter less congestion but higher interference. Resource partitioning protects the offloaded users from macro tier interference by muting the macro tier on certain fraction of resources and scheduling the offloaded users on those resources. However, the extent to which joint offloading and resource partitioning is needed remains unanswered. This is partly due to the lack of tractable frameworks to analyze downlink Rate in the presence of such techniques. In this paper, we develop a tractable framework to analyze joint resource partitioning and offloading in a two-tier cellular network and derive the downlink Rate Distribution over the entire network. Each tier of base stations is modeled as a Poisson point process (PPP) where each tier differs in transmit power and deployment density. Using the developed analysis, we show that the optimal combination of load balancing and resource partitioning improves the Rate of cell edge users in co-channel heterogeneous networks.
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GLOBECOM - Rate Distribution in heterogeneous cellular networks with resource partitioning and offloading
2013 IEEE Global Communications Conference (GLOBECOM), 2013Co-Authors: Sarabjot Singh, Jeffrey G. AndrewsAbstract:Mobile users proactively offloaded from macro cells to small cells in heterogeneous cellular networks (HCNs) encounter less congestion but higher interference. Resource partitioning protects the offloaded users from macro tier interference by muting the macro tier on certain fraction of resources and scheduling the offloaded users on those resources. However, the extent to which joint offloading and resource partitioning is needed remains unanswered. This is partly due to the lack of tractable frameworks to analyze downlink Rate in the presence of such techniques. In this paper, we develop a tractable framework to analyze joint resource partitioning and offloading in a two-tier cellular network and derive the downlink Rate Distribution over the entire network. Each tier of base stations is modeled as a Poisson point process (PPP) where each tier differs in transmit power and deployment density. Using the developed analysis, we show that the optimal combination of load balancing and resource partitioning improves the Rate of cell edge users in co-channel heterogeneous networks.
Richard C. Hendriks - One of the best experts on this subject based on the ideXlab platform.
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EUSIPCO - Sensor Selection and Rate Distribution Based Beamforming in Wireless Acoustic Sensor Networks
2019 27th European Signal Processing Conference (EUSIPCO), 2019Co-Authors: Jie Zhang, Richard Heusdens, Richard C. HendriksAbstract:Power usage is an important aspect of wireless acoustic sensor networks (WASNs) and reducing the amount of information that is to be transmitted is one effective way to save it. In previous contributions, we presented sensor selection as well as Rate Distribution methods to reduce the power usage of beamforming algorithms in WASNs. Taking only transmission power into account, it was shown that Rate Distribution is a generalization of sensor selection and that Rate Distribution is more efficient than sensor selection with respect to the power usage versus performance trade-off. However, this excludes the energy consumption that it takes to keep the WASN nodes activated. In this paper, we present a more detailed comparison between sensor selection and Rate-allocation by taking also into account the power to keep sensors activated for centralized WASNs. The framework is formulated by minimizing the total power usage, while lower bounding the noise reduction performance. Numerical results show that whether Rate Distribution is more efficient than sensor selection depends on the actual power that is used to keep sensors activated.
Jozef L. Kokini - One of the best experts on this subject based on the ideXlab platform.
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Estimation and prediction of shear Rate Distribution as a model mixer
Journal of Food Engineering, 2000Co-Authors: Subbalakshmi Prakash, Jozef L. KokiniAbstract:Abstract The shear Rate Distribution in the model mixer, the Brabender Farinograph, is non-homogenous and varies with the relative positions of the sigma blades, which rotate at differential speeds. The non-invasive technique of Laser-Doppler Anemometry (LDA) was used to determine velocity and shear Rate Distributions in the mixer. A two-dimensional argon-ion Laser-Doppler Anemometer was used to obtain three-dimensional velocity measurements in the model mixer with optically clear model fluids (Corn syrup, CMC, and Carbopol-940 seeded with polystyrene DVB microspheres). Local velocity gradient data obtained using infinitesimal movements of the traverse were used to calculate the shear Rate Distribution in the model mixer. The shear Rate was found to be a function of blade geometry, blade position, and location. Shear Rate values ranged from 0 to 400 s −1 . Based on these data, a predictive equation for shear Rate in the model mixer was developed.
Noah Brosch - One of the best experts on this subject based on the ideXlab platform.
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Photometry and spin Rate Distribution of small-sized main belt asteroids
Icarus, 2009Co-Authors: David Polishook, Noah BroschAbstract:Abstract Photometry results of 32 asteroids are reported from only seven observing nights on only seven fields, consisting of 34.11 cumulative hours of observations. The data were obtained with a wide-field CCD ( 40.5 ′ × 27.3 ′ ) mounted on a small, 46-cm telescope at the Wise Observatory. The fields are located within ±1.5° from the ecliptic plane and include a region within the main asteroid belt. The observed fields show a projected density of ∼23.7 asteroids per square degree to the limit of our observations. 13 of the lightcurves were successfully analyzed to derive the asteroids' spin periods. These range from 2.37 up to 20.2 h with a median value of 3.7 h. 11 of these objects have diameters in order of two kilometers and less, a size range that until recently has not been photometrically studied. The results obtained during this short observing run emphasize the efficiency of wide-field CCD photometry of asteroids, which is necessary to improve spin statistics and understand spin evolution processes. We added our derived spin periods to data from the literature and compared the spin Rate Distributions of small main belt asteroids ( 5 > D > 0.15 km ) with that of bigger asteroids and of similar-sized NEAs. We found that the small MBAs do not show the clear Maxwellian-shaped Distribution as large asteroids do; rather they have a spin Rate Distribution similar to that of NEAs. This implies that non-Maxwellian spin Rate Distribution is controlled by the asteroids' sizes rather than their locations.
