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A method is proposed to improve the GPS broadcast ionospheric time-delay correction accuracy, using GPS observation data from the globally distributed international GNSS service (IGS) observation stations and the Crust Movement Ob...
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A method is proposed to improve the GPS broadcast ionospheric time-delay correction accuracy, using GPS observation data from the globally distributed international GNSS service (IGS) observation stations and the Crust Movement Observation Network of China (CMONOC). A new set of Klobuchar-Self coefficients can be estimated using the method. Primary results demonstrate that the refined Klobuchar-Self coefficients developed may provide better ionospheric delay corrections for single-frequency GPS receivers and improve standard single point positioning accuracies.
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Intrusion detection systems (IDSs) attempt to identify unauthorized use, misuse, and abuse of computer systems. In response to the growth in the use and development of IDSs, the authors have developed a methodology for testing IDS...
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Intrusion detection systems (IDSs) attempt to identify unauthorized use, misuse, and abuse of computer systems. In response to the growth in the use and development of IDSs, the authors have developed a methodology for testing IDSs. The methodology consists of techniques from the field of software testing which they have adapted for the specific purpose of testing IDSs. They identify a set of general IDS performance objectives which is the basis for the methodology. They present the details of the methodology, including strategies for test-case selection and specific testing procedures. They include quantitative results from testing experiments on the Network Security Monitor (NSM), an IDS developed at UC Davis. They present an overview of the software platform that has been used to create user-simulation scripts for testing experiments. The platform consists of the UNIX tool expect and enhancements that they have developed, including mechanisms for concurrent scripts and a record-and-replay feature. They also provide background information on intrusions and IDSs to motivate their work.
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Quantifying the measure of similarity between two trees is a problem of intrinsic importance in the study of algorithms and data structures and has applications in computational molecular biology, structural/syntactic pattern reco...
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Quantifying the measure of similarity between two trees is a problem of intrinsic importance in the study of algorithms and data structures and has applications in computational molecular biology, structural/syntactic pattern recognition and in data management. In this paper we define and formulate an abstract measure of comparison, /spl Omega/(T/sub 1/, T/sub 2/), between two trees T/sub 1/ and T/sub 2/ presented in terms of a set of elementary intersymbol measures /spl omega/(.,.) and two abstract operators /spl oplus/ and /spl otimes/. By appropriately choosing the concrete values for these two operators and for /spl omega/(.,.), this measure can be used to define various quantities including: (1) the edit distance between two trees, (2) the size of their largest common subtree, (3) Prob(T/sub 2/|T/sub 1/), the probability of receiving T/sub 2/ given that T/sub 1/ was transmitted across a channel causing independent substitution and deletion errors, and (4) the a posteriori probability of T/sub 1/ being the transmitted tree given that T/sub 2/ is the received tree containing independent substitution, insertion and deletion errors. The recursive properties of /spl Omega/(T/sub 1/, T/sub 2/) have been derived and a single generic iterative dynamic programming scheme to compute all the above quantities has been developed. The time and space complexities of the algorithm have been analyzed and the implications of our results in both theoretical and applied fields has been discussed.
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This paper introduces a high-performance voltage-scalable SRAM design in a 32 nm strain-enhanced high-k + metal-gate logic CMOS technology. The 291 Mb SRAM design features a 0.171 ¿m2 six-transistor bitcell that supports a broa...
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This paper introduces a high-performance voltage-scalable SRAM design in a 32 nm strain-enhanced high-k + metal-gate logic CMOS technology. The 291 Mb SRAM design features a 0.171 ¿m2 six-transistor bitcell that supports a broad range of operating voltages for low-power and high-frequency embedded applications. The tileable 128 kb SRAM subarray achieves 72% array efficiency with 4.2 Mb/mm2 bit density, and consumes 5 mW of leakage power at the supply voltage of 1 V. The design provides 4 GHz and 2 GHz of operating frequencies at the supply voltages of 1.0 V and 0.8 V, respectively. The integrated power management scheme features close-loop memory array leakage control, floating bitline, and wordline driver sleep transistor, resulting in a 58% reduction in subarray leakage power consumption.
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The nature of the surface region formed between Ti-6Al-4V and the mild steel tooling used to define the shape of net shape hot isostatically pressed (hipped) Ti-6Al-4V components has been evaluated. The surface topography has been...
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The nature of the surface region formed between Ti-6Al-4V and the mild steel tooling used to define the shape of net shape hot isostatically pressed (hipped) Ti-6Al-4V components has been evaluated. The surface topography has been assessed and analytical scanning electron microscopy (SEM) has been used to define the local changes in composition obtained under several hipping conditions. The tensile and fatigue properties of net shape hipped samples of Ti-6Al-4V have been compared with those obtained from samples produced by machining samples from larger hipped cylinders so that the surface layer is removed. The as hipped surface is irregular on the scale of the original powder particles and a 150 μm thick diffusion layer is produced under the standard hipping conditions. It has been found that the tensile properties of samples with the as hipped or machined surfaces are very similar. The fatigue limits of samples which were tested with the as hipped surface were significantly below those of samples which were machined to remove the as hipped surface. Electropolishing the as hipped samples to a depth of ∼150 μm leads to fatigue properties which are slightly higher than the properties of machined samples. These results are discussed in terms of the failure mechanisms during fatigue and issues in the production of net shape hipped products.
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We report a systematic study of the switching and recording characteristics of perpendicular magnetic recording media in which the exchange coupling between granular oxide and continuous cap layers was varied. The interfacial exc...
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We report a systematic study of the switching and recording characteristics of perpendicular magnetic recording media in which the exchange coupling between granular oxide and continuous cap layers was varied. The interfacial exchange coupling strength was controlled by adjusting the magnetization $({rm M}_{rm s})$ and the thickness (t) of the exchange control layer (ECL) between granular oxide and cap layers. The media switching mechanism highly depends on the oxide-to-cap exchange coupling strength as well as the relative moment ratio of cap and oxide layers. Reversal process is coherent for medium with only granular oxide layer and becomes incoherent with incorporation of ECL and continuous cap layers. Optimizing granular oxide-to-cap exchange coupling improves the media writeability as well as the media signal-to-noise ratio $({rm SNR}_{rm m})$. At optimum exchange coupling condition, the switching field is significantly reduced even with higher thermal stability factor (${rm K}_{rm u} {rm V/k}_{rm B}$ T). However, when the interlayer coupling strength is too weak, independent switching of oxide and cap layers occurs, resulting in poor writeability and high media noise. An optimum design of oxide-to-cap exchange coupling is critical in attaining recording properties for high density recording through selection of appropriate ECL and cap materials.
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The fracture toughness and interfacial adhesion properties of a coating on its substrate are considered to be crucial intrinsic parameters determining performance and reliability of coating-substrate system. In this work, the frac...
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The fracture toughness and interfacial adhesion properties of a coating on its substrate are considered to be crucial intrinsic parameters determining performance and reliability of coating-substrate system. In this work, the fracture toughness and interfacial shear strength of a hard and brittle Cr coating on a normal medium carbon steel substrate were investigated by means of a tensile test. The normal medium carbon steel substrate electroplated with a hard and brittle Cr coating was quasi-statically stretched to induce an array of parallel cracks in the coating. An optical microscope was used to observe the cracking of the coating and the interfacial decohesion between the coating and the substrate during the loading. It was found that the cracking of the coating initiated at critical strain, and then the number of the cracks of the coating per unit axial distance increased with the increase in the tensile strain. At another critical strain, the number of the cracks of the coating became saturated, i.e. the number of cracks per unit axial distance became a constant after this critical strain. Based on the experiment result, the fracture toughness of the brittle coating can be determined using a mechanical model. Interestingly, even when the whole specimen fractured completely under an extreme strain of the substrate, the interfacial decohesion or buckling of the coating on its substrate was completely absent. The test result is different from that appeared in the literature though the identical test method and the brittle coating/ductile metal substrate system are taken. It was found that this difference can be attributed to an important mechanism that the Cr coating on the steel substrate has a good adhesion, and the ultimate interfacial shear strength between the Cr coating and the steel substrate has exceeded the maximum shear flow strength level of the steel substrate. This result also indicates that the maximum shear flow strength level of the ductile steel substrate can be only taken as a lower bound estimate on the ultimate shear strength of the interface. This estimation of the ultimate interfacial shear strength is consistent with the theoretical analysis and prediction presented in the literature.
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New monotonicity properties of optimal scalar quantizers are discussed. These monotonicities reveal a globally optimal scalar quantizer structure depending on the probability mass functions and on the number of quantizer levels. B...
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New monotonicity properties of optimal scalar quantizers are discussed. These monotonicities reveal a globally optimal scalar quantizer structure depending on the probability mass functions and on the number of quantizer levels. By incorporating the monotone quantizer structure into a dynamic programming process, the time complexities of previous algorithms for designing globally optimal scalar quantizers can be significantly reduced for very general classes of distortion measures.
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The papers in this special issue are divided into the following areas: High-Performance Digital; Low-Power Digital; Memory; and Technology Directions. The IEEE International Solid-State Circuits Conference (ISSCC) was held in San ...
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The papers in this special issue are divided into the following areas: High-Performance Digital; Low-Power Digital; Memory; and Technology Directions. The IEEE International Solid-State Circuits Conference (ISSCC) was held in San Francisco, CA, February 8-12, 2009.
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Based on the constitutive tensor of the perfect regular polygonal cloak, the effects of different kinds of losses on the performance of regular polygonal cloak are investigated. The cloak is modeled and simulated using full wave ...
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Based on the constitutive tensor of the perfect regular polygonal cloak, the effects of different kinds of losses on the performance of regular polygonal cloak are investigated. The cloak is modeled and simulated using full wave package COMSOL MULTIPHYSICS. It is found that if the loss tangents are imposed on one or more components of constitutive tensors, especially on the off-diagonal components, the performance of the cloak in the backward region is significantly different from the results of the traditional case, in which losses are the same in all components of magnetic and electric loss tangents. We believe that the results are helpful for the practical situations.
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