989 research outputs found

    Asymptotic Methods for Metal Oxide Semiconductor Field Effect Transistor Modeling

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    The behavior of metal oxide semiconductor field effect transistors (MOSFETs) with small aspect ratio and large doping levels is analyzed using formal perturbation techniques. Specifically, the influence of interface layers in the potential on the averaged channel conductivity is closely examined. The interface and internal layers that occur in the potential are resolved in the limit of large doping using the method of matched asymptotic expansions. This approach, together with other asymptotic techniques, provides both a pointwise description of the state variables as well as lumped current-voltage relations that vary uniformly across the various bias regimes. These current-voltage relations are derived for a variable doping model respresenting a particular class of devices

    Optical Properties of Amorphous Magnesium-Bismuth Alloys

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    The amorphous magnesium-bismuth alloys were prepared by the co-evaporation technique . The compositions of these alloys were determined from the rate of deposition of the two constituents using the quartz crystal oscillators. A new method to calculate the densities of the alloys from the rates of deposition is outlined. The electrical measurements of the d.c. resistivity shows that the Mg-Bi alloys close to the stoichiometric composition Mg3Bi2 has a very high resistivity. From the optical measurements, the stoichiometric Mg3Bi2 compound is found to have an optical band gap 0.264 + 0.006 ev. The dramatic changes in the optical band gap due to annealing make the proposed model densities of states of doubtful relevance

    Coupling of a high-energy excitation to superconducting quasiparticles in a cuprate from Coherent Charge Fluctuation Spectroscopy

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    Dynamical information on spin degrees of freedom of proteins or solids can be obtained by Nuclear Magnetic Resonance (NMR) and Electron Spin Resonance (ESR). A technique with similar versatility for charge degrees of freedom and their ultrafast correlations could move forward the understanding of systems like unconventional superconductors. By perturbing the superconducting state in a high-Tc cuprate using a femtosecond laser pulse, we generate coherent oscillations of the Cooper pair condensate which can be described by an NMR/ESR formalism. The oscillations are detected by transient broad-band reflectivity and found to resonate at the typical scale of Mott physics (2.6 eV), suggesting the existence of a non-retarded contribution to the pairing interaction, as in unconventional (non Migdal-Eliashberg) theories.Comment: Accepted for publication in the Proceedings of the National Academy of Sciences of the U.S.A. (PNAS

    Steganography in Arabic Text Using Full Diacritics Text

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    The need for secure communications has significantly increased with the explosive growth of the internet and mobile communications. The usage of text documents has doubled several times over the past years especially with mobile devices. In this paper we propose a new Steganogaphy algorithm for Arabic text. The algorithm employs some Arabic language characteristics, which represent as small vowel letters. Arabic Diacritics is an optional property for any text and usually is not popularly used. Many algorithms tried to employ this property to hide data in Arabic text. In our method, we use this property to hide data and reduce the probability of suspicions hiding. Our approach uses a performance metric involves the file size before and after adding Diacritics and ability to hide data with being suspicious

    Characterizations of Soil Collapsibility: Effect of Salts Dilution

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    Collapsibility of soils is the large change in volume of soil upon saturation or wetting.  This change may or may not be the result of the application of additional load.  Soil at a construction site may not always be suitable for supporting structures such as buildings, bridges, highways, and dams.  For example, if soil is placed in a certain none desire density, a large settlement will occur either due to loading or wetting of soil deposits.  Hence, a collapse will occur which will create a large subsidence or a sinkhole.In this study, soil samples of CL-ML soil were modified by adding different amounts of brine.  The main goal of which was to examine the effect of brine presence on the collapse potential of the soil.  Soil index properties, compaction characteristics, and a collapse potential were evaluated according to ASTM standards.  The test includes Atterberg's limit, Harvard miniature compaction, and double oedometer tests.It has been shown that brine additive has pronounced effect on the Atterberg’s limits; it is clearly shown that as the amount of brine increases both liquid limit and plastic limit decrease.  Compaction curve characteristics of soil were altered by the presence of brine, the maximum dry density, obtained using Harvard miniature device, increased as brine percentage increased, however, the optimum moisture content showed substantial decrease with increasing the amount of brine.

    Steganography in Text by Merge ZWC and Space Character

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    Secure communication is essential for data confidentiality and integrity especially with the massive growth of the internet and mobile communication. Steganography is an art for data hiding by embedding the data to different objects such as text, images, audio and video objects. In this paper we propose a new algorithm for data hiding using Text Steganography in Arabic language. Our algorithm uses the Zero Width Character from Unicode (U+200B) and space character to pass bits before and after space. Main advantage of our algorithm file format will not be change and this will decrease the ability of Stegoanalysis to observe hidden data. Moreover ZWC algorithm can be applied to any language (ASCII, Unicode)

    Characterizations of Soil Collapsibility: Effect of Salts Dilution

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    Collapsibility of soils is the large change in volume of soil upon saturation or wetting.  This change may or may not be the result of the application of additional load.  Soil at a construction site may not always be suitable for supporting structures such as buildings, bridges, highways, and dams.  For example, if soil is placed in a certain none desire density, a large settlement will occur either due to loading or wetting of soil deposits.  Hence, a collapse will occur which will create a large subsidence or a sinkhole.In this study, soil samples of CL-ML soil were modified by adding different amounts of brine.  The main goal of which was to examine the effect of brine presence on the collapse potential of the soil.  Soil index properties, compaction characteristics, and a collapse potential were evaluated according to ASTM standards.  The test includes Atterberg's limit, Harvard miniature compaction, and double oedometer tests.It has been shown that brine additive has pronounced effect on the Atterberg’s limits; it is clearly shown that as the amount of brine increases both liquid limit and plastic limit decrease.  Compaction curve characteristics of soil were altered by the presence of brine, the maximum dry density, obtained using Harvard miniature device, increased as brine percentage increased, however, the optimum moisture content showed substantial decrease with increasing the amount of brine.

    Characterizations of Soil Collapsibility: Effect of Salts Dilution

    Get PDF
    Collapsibility of soils is the large change in volume of soil upon saturation or wetting.  This change may or may not be the result of the application of additional load.  Soil at a construction site may not always be suitable for supporting structures such as buildings, bridges, highways, and dams.  For example, if soil is placed in a certain none desire density, a large settlement will occur either due to loading or wetting of soil deposits.  Hence, a collapse will occur which will create a large subsidence or a sinkhole.In this study, soil samples of CL-ML soil were modified by adding different amounts of brine.  The main goal of which was to examine the effect of brine presence on the collapse potential of the soil.  Soil index properties, compaction characteristics, and a collapse potential were evaluated according to ASTM standards.  The test includes Atterberg's limit, Harvard miniature compaction, and double oedometer tests.It has been shown that brine additive has pronounced effect on the Atterberg’s limits; it is clearly shown that as the amount of brine increases both liquid limit and plastic limit decrease.  Compaction curve characteristics of soil were altered by the presence of brine, the maximum dry density, obtained using Harvard miniature device, increased as brine percentage increased, however, the optimum moisture content showed substantial decrease with increasing the amount of brine.
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