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This paper describes a novel inversion algorithm for determining the 3-D position coordinates and environmental complex permittivity of wireless nodes embedded in a dispersive propagation media. In this paper, wireless sensors are...
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This paper describes a novel inversion algorithm for determining the 3-D position coordinates and environmental complex permittivity of wireless nodes embedded in a dispersive propagation media. In this paper, wireless sensors are considered to form part of a network for monitoring salient parameters, such as temperature and humidity, in large wheat-filled storage vessels, where the highly reflective nature of the propagation environment engenders extreme multipath effects. Under such conditions, the inherent difficulties in deriving reliable pulse propagation delay and amplitude estimates greatly diminishes the effectiveness of conventional free-space positioning methods. These limitations have lead to the development of alternative inversion techniques capable of retrieving both geometric positioning and electromagnetic propagation data. The inversion algorithm developed within is formulated as a nonlinear least squares problem in which the misfit between time domain positioning measurements and modeled data is minimized via application of a novel minimum single-level linkage optimization algorithm. In developing a more refined propagation forward solution incorporating position coordinates, host media electromagnetic properties and antenna radiation patterns, accurate positioning resolutions and macroscopic permittivity estimates are obtained under challenging propagation conditions.
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Recognition of objects in still images has traditionally been regarded as a difficult computational problem. Although modern automated methods for visual object recognition have achieved steadily increasing recognition accuracy, e...
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Recognition of objects in still images has traditionally been regarded as a difficult computational problem. Although modern automated methods for visual object recognition have achieved steadily increasing recognition accuracy, even the most advanced computational vision approaches are unable to obtain performance equal to that of humans. This has led to the creation of many biologically inspired models of visual object recognition, among them the hierarchical model and X (HMAX) model. HMAX is traditionally known to achieve high accuracy in visual object recognition tasks at the expense of significant computational complexity. Increasing complexity, in turn, increases computation time, reducing the number of images that can be processed per unit time. In this paper we describe how the computationally intensive and biologically inspired HMAX model for visual object recognition can be modified for implementation on a commercial field-programmable aate Array, specifically the Xilinx Virtex 6 ML605 evaluation board with XC6VLX240T FPGA. We show that with minor modifications to the traditional HMAX model we can perform recognition on images of size 128$,times,$128 pixels at a rate of 190 images per second with a less than 1% loss in recognition accuracy in both binary and multiclass visual object recognition tasks.
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The continuing trend toward greater electrification and control of functions in consumer, commercial, industrial, transportation, and even medical applications promises a dynamic and increasingly important role for power electroni...
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The continuing trend toward greater electrification and control of functions in consumer, commercial, industrial, transportation, and even medical applications promises a dynamic and increasingly important role for power electronics. The growing penetration of power electronics in energy systems is driven by new materials such as SiC and GaN, as well as new packaging technologies which allow the physical integration of electronics with powered and controlled devices such as motors. Advances in very high-frequency conversion led by the application of SiC and GaN devices promises to make converter-on-a-chip technology possible, but concurrent advances in passive component technology are necessary. The principal challenge to application penetration remains cost reduction.
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Virtual flux (VF)-oriented control (VFOC) and VF-based direct power control (DPC) (VF-DPC) have been developed to improve voltage-oriented control and DPC of three-phase active rectifiers. The VF space vector is utilized in transf...
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Virtual flux (VF)-oriented control (VFOC) and VF-based direct power control (DPC) (VF-DPC) have been developed to improve voltage-oriented control and DPC of three-phase active rectifiers. The VF space vector is utilized in transformations between stationary and rotating coordinates in VFOC and in obtaining instantaneous power in VF-DPC. The VF space vector is calculated by integrating the grid voltage space vector. This integration is usually performed using a first-order low-pass (LP) (FOLP) filter, which counteracts the saturation and dc-drift problems associated with pure integrators. However, the dynamics of FOLP filters can be enhanced to a great extent. This paper presents a new, simple, and fast integration algorithm for VF-based control methods. Simulations and experimental tests on a VF-DPC-based system showed that the proposed algorithm leads to rapid recoveries after grid voltage sags occur. Moreover, the performance of VF-DPC under nonideal grids is discussed.
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This paper investigates the propagation characteristics of circular waveguides whose interior surface is coated with a thin metamaterial liner possessing dispersive, negative, and near-zero permittivity. A field analysis of this s...
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This paper investigates the propagation characteristics of circular waveguides whose interior surface is coated with a thin metamaterial liner possessing dispersive, negative, and near-zero permittivity. A field analysis of this system produces the dispersion of complex modes, and reveals in detail intriguing phenomena such as backward-wave propagation below the unlined waveguide's fundamental-mode cutoff, resonant tunneling of power, field collimation, and miniaturization. It is shown how the waveguide geometry and metamaterial parameters may be selected to engineer the lined waveguide's spectral response. Theoretical dispersion and transmission results are closely validated by full-wave simulations.
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This paper considers the technical and economical feasibility of the introduction of automated demand response from domestic smart appliances in a European setting as a means to create a significant amount of regulating power. Sim...
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This paper considers the technical and economical feasibility of the introduction of automated demand response from domestic smart appliances in a European setting as a means to create a significant amount of regulating power. Simplified power-time flexibility models for appliances are introduced on which generic economic simulations can be based. These simulations permit a good indication of the economic value that can be attained as a function of model parameters. This shows that classical load shifting of washing appliances creates sufficient value in the day-ahead market to justify investments in smart energy control services. Cooling appliances create significant value on the balance market and while full scale deployment would lead to significant price erosion in today's market, it could accommodate additional unbalance caused future sustainable generation. The scale of domestic demand response resources can be quantified in two simple parameters: regulation power and storage capacity. For the Dutch situation these are 700 MW, equivalent to 5% of average national power consumption and 5 GWh storage: around 20 minutes of average national power consumption. Smart appliances can deliver a 100% efficient and ${rm CO}_{2}$ friendly complement to the unpredictability of e.g., large scale wind power as planned in large parts of Europe in 10 to 15 years.
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Magnetic resonance force microscopy (MRFM), which combines magnetic resonance imaging with scanning probe microscopy together, is capable of performing ultra-sensitive detection of spin magnetization. In an attempt to observe dyna...
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Magnetic resonance force microscopy (MRFM), which combines magnetic resonance imaging with scanning probe microscopy together, is capable of performing ultra-sensitive detection of spin magnetization. In an attempt to observe dynamic nuclear polarization (DNP) in an MRFM experiment, which could possibly further improve its sensitivity towards a single proton spin, a film of perdeuterated polystyrene doped with a nitroxide electron-spin probe was prepared. A high-compliance cantilever with a 4-$mu{hbox {m}}$-diameter magnetic tip was brought near the film at a temperature of 7.3 K and in a background magnetic field of $sim$0.6 T. The film was irradiated with 16.7-GHz microwaves while the resulting transient change in cantilever frequency was recorded in real time. In addition to observing the expected prompt change in cantilever frequency due to saturation of the nitroxide's electron-spin magnetization, we observed a persistent cantilever frequency change. Based on its magnitude, lifetime, and field dependence, we tentatively attribute the persistent signal to polarized deuteron magnetization created via transfer of magnetization from electron spins. Further measurements of the persistent signal's dependence on the cantilever amplitude and tip-sample separation are presented and explained by the cross-effect DNP mechanism in high magnetic field gradients.
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There is a reduced group of Ce very heavy Fermions (VHF) which do not order magnetically down to at least $T approx 500$ mK because they are very close to a $T_{rm ord} = 0$ critical point. These compounds are at the top of the $l...
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There is a reduced group of Ce very heavy Fermions (VHF) which do not order magnetically down to at least $T approx 500$ mK because they are very close to a $T_{rm ord} = 0$ critical point. These compounds are at the top of the $lim_{Tto 0} C_{m}/T$ specific heat values because they collect very high density of low energy excitations. From the analysis of $C_{m}(T)/T$ and entropy $S_{m}(T)$ dependencies performed on selected CePd$_3$M$_x$ ternaries (where ${rm M} = {rm B}$ and Be) a quantitative evaluation of an upper limit for the density of excitations can be proposed. These observations exclude any evidence of $C_{m}(T)/T$ divergency as $Tto 0$ in agreement with thermodynamic laws. A comparison with selected Yb-base VHF supports these features.
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Insulating oils ordinarily used in transformers have high stability toward oxidation, and much effort has been directed toward reducing the oxygen absorption qualities of such oils. Contrary to usual practice, however, the tests r...
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Insulating oils ordinarily used in transformers have high stability toward oxidation, and much effort has been directed toward reducing the oxygen absorption qualities of such oils. Contrary to usual practice, however, the tests reported in this paper were made with a readily oxidizable or “overrefined” oil on the basis that the oxidizing qualities of this oil will maintain automatically an inert gas above the oil and thus reduce explosion hazards. On the basis of these tests, it is said that transformers equipped for restricted breathing can be operated with overrefined oil over long periods without servicing as far as the oil is concerned. Among the chief disadvantages of such oil is its high cost — approximately twice that of present commonly used oils.
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In our previous work, soft magnetic composite (SMC) material was employed to design cores for two kinds of permanent magnet (PM) motors, namely transverse flux machine (TFM) and claw pole motor. Compared with motors designed by tr...
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In our previous work, soft magnetic composite (SMC) material was employed to design cores for two kinds of permanent magnet (PM) motors, namely transverse flux machine (TFM) and claw pole motor. Compared with motors designed by traditional silicon steel sheets, these motors require 3D flux design with new material and new manufacturing method. Meanwhile, the performances of these motors highly depend on the material and manufacturing parameters besides structure parameters. Therefore, we present a robust design optimization method for high quality manufacturing of these PM-SMC motors to improve their industrial applications. Thereafter, from the design analysis of a PM-SMC TFM, it can be found that the proposed method can significantly improve the manufacturing quality and reliability of the motor, and reduce the manufacturing cost.
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