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Issue 2 • Date Mar 1989

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Displaying Results 1 - 25 of 3882757
  • Characteristics of high-transmission-probability tunnel junctions for use as particle detectors

    Page(s): 1343 - 1346
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    Interest in the problem of the galactic dark matter has stimulated development of particle detectors sensitive to very low energies. The authors describe superconducting tunnel junctions with thin barriers which may be suitable for this purpose. They present I-V (current-voltage) characteristics and data on the temperature dependence of the subgap tunneling current. They examine the barrier transmission probability and the resistance of the null junction. They also present some scanning-electron-microscope observations of the thin films of the tunnel junctions, which show that faster deposition produces smaller grains and increasing film thickness results in larger grains from an apparent fusing of smaller grains View full abstract»

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  • Fast optical spectrum estimation using a digital coherent receiver

    Page(s): 1 - 3
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (219 KB)  

    We investigate the use of a fast switching DSDBR tunable laser in a coherent receiver to enable microsecond sweeping time over the C-band. Thomson's Multitaper method is used to estimate spectral slices which are then digitally stitched to form the complete scanned spectrum. View full abstract»

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  • Research on Online Detecting Method for Cam Based on Quality Control

    Page(s): 132 - 135
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (364 KB) |  | HTML iconHTML  

    Online product quality detection is an effective process of product quality control. It can be fused into the machine tool by rebuilding and updating the machine tool. It can also be realized by changing the process of the product line, feeding back the testing results to the machine tool or the operating persons and applying it to the current machining system or to grade the products. The implement of parameter comparison of the processed cam and the standard cam based on wavelet filtering, cubic spline interpolation, long signal correlation is proposed. The theory and methodology of realizing high precision measurement with cheap but good in anti-shock and anti-pollution sensors is stressed, especially how to get rid of the risk caused by poor surface quality and local deformation, reach higher precision and achieve the purpose of quality control. View full abstract»

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  • Genetic k-means-algorithm-based classification of direct load-control curves

    Page(s): 489 - 495
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (199 KB)  

    To improve the load factors of a power system, direct load control (DLC) of air conditioners is one effective approach adopted by utilities. However, the performance of a DLC programme should be evaluated periodically to validate the preferential tariff provided to the customers involved. Prior to evaluating the performance, the DLC curves recorded should be categorised properly. The only further factor evaluated is the category of the DLC curves that comply with the required control pattern. Therefore, developing efficient approaches for classifying DLC curves is needed. In the paper, with the aim of reducing the number of variables for classification and enhancing the classification effectiveness, autoregression moving-averaging (ARMA) modelling techniques are employed to extract the features of the DLC curves. To ensure the adequacy of the ARMA models used for the DLC curves, the Akaike information criterion is assessed. Based on the features extracted, the genetic k-means algorithm is then adopted for classification owing to its ability to partition given global data optimally into a specified number of clusters. Through the proposed approaches, categories are derived of the DLC curves complying and noncomplying with the control pattern. The results obtained from the comparisons with the artificial-neural-network approach show that the clusters divided using the proposed approach exhibit very high classification rates for the practical data on Taiwan Power Company DLC programmes. View full abstract»

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  • Phonon-mediated detection of X-rays in silicon crystals using superconducting transition edge phonon sensors

    Page(s): 1347 - 1350
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    The authors present data on the operation of thin-film superconducting strips of titanium as phonon sensors on the surface of silicon crystals. The superconducting films are biased at the foot of the resistive transition in temperature and below the critical latching current (the current above which a normal region in the film grows from self-heating). The interaction of an incident X-ray in the Si crystal generates a phonon source which propagates to the surface at the speed of sound. Such an event produces a several-microsecond-long self-terminating voltage pulse which is proportional to the amount of the sensor area driven normal. It is shown that these Ti superconducting transition edge sensors operated at 0.3 K have sufficient resolution for detecting particles with energy deposition above several keV, which makes them good candidates for use in neutrino (and other) experiments View full abstract»

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  • All-optical phase-preserving amplitude regeneration of a 640 Gbit/s RZ-DPSK signal

    Page(s): 1 - 3
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (314 KB)  

    Phase-preserving amplitude regeneration based on optical parametric amplification has been experimentally demonstrated for a 640 Gbit/s RZ-DPSK signal. Improvement of 2.2 dB in receiver sensitivity at a BER of 10-9 together with 13.3 dB net gain have been successfully achieved. View full abstract»

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  • Torsional Free Vibration Characteristics of Hybrid Clinched Joints

    Page(s): 1027 - 1030
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (317 KB) |  | HTML iconHTML  

    The aim of this study is to predict the torsional free vibration characteristics of single lap-jointed cantilevered hybrid clinched joints. The focus of the analysis is to reveal the influence on the natural frequencies, natural frequency ratios and mode shapes of single lap-jointed cantilevered hybrid clinched joints caused by variations in the material properties of the structural adhesives. It is shown that the torsional natural frequencies of single lap jointed cantilevered hybrid clinched joints increase significantly as the Young's modulus of the adhesive increase, but only slight changes are encountered for variations of Poisson's ratio. The mode shapes show that there are different deformations in the jointed section of the odd and even modes. View full abstract»

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  • Student paper contest finalists

    Page(s): xxviii
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    Freely Available from IEEE
  • Characterization of talker radiation pattern using a microphone array

    Page(s): II/257 - II/260 vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (360 KB)  

    A microphone array has the capability of capturing the properties of a significant portion of a talker's radiation pattern. In this paper, potential implications of measuring the radiation pattern of a talker for the recognition and enhancement of speech are discussed. Current applications of microphone arrays entail their installation in small enclosures such as a conference room or an automobile, typically placing a talker in the array's near field. Fitting a nominal acoustic model to a sparse sampling of the radiation pattern yields parameter estimates which should prove useful as features for speech recognition. Parameter-estimation results using fixed-radius sources (loudspeakers) are presented. Other considerations unique to placement of a talker in close proximity to an array are discussed View full abstract»

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  • Characterization of thermal and curing behaviors of epoxy molding compounds

    Page(s): 369 - 372
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (512 KB) |  | HTML iconHTML  

    In this paper, both isothermal and dynamic differential scanning calorimetry (DSC) are employed to characterize the thermal properties of two commercial epoxy molding compounds designated as EMC-A and EMC-B respectively. In dynamic curing, the heat flow of uncured powder samples weighting 10±0.5 mg are measured at the heating rates of 5, 10 and 15 °C /min from room temperature to 220 °C. The isothermal curing tests are performed under the constant temperatures of 130, 140 and 150 °C for 30 min. The experimental results show that compared with EMC-B, EMC-A has smaller average curing reaction enthalpy and activation energy showing a better moldability. The parameters of autocatalytic Kamal equation for these two EMCs are obtained by the isothermal curing tests and the curing kinetic model exhibits good agreement with the experimental data generally. View full abstract»

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  • On the Hilbert Transform of Wavelets

    Page(s): 1890 - 1894
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (333 KB) |  | HTML iconHTML  

    A wavelet is a localized function having a prescribed number of vanishing moments. In this correspondence, we provide precise arguments as to why the Hilbert transform of a wavelet is again a wavelet. In particular, we provide sharp estimates of the localization, vanishing moments, and smoothness of the transformed wavelet. We work in the general setting of non-compactly supported wavelets. Our main result is that, in the presence of some minimal smoothness and decay, the Hilbert transform of a wavelet is again as smooth and oscillating as the original wavelet, whereas its localization is controlled by the number of vanishing moments of the original wavelet. We motivate our results using concrete examples. View full abstract»

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  • The Implementation of E-Learning in the Lebanese University - Lebanon and in the Al-Quds Open University - Palestine

    Page(s): 674 - 678
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1920 KB) |  | HTML iconHTML  

    The aim of the paper is to present an experience about the implementation of e-learning at Al-Quds Open University (QOU) - Palestine and at the Lebanese University (LU) and to describe particularly their experience within the framework of the Avicenna project. This paper also focuses on two points, which seem important to us, as this is the first experience of e-learning in our universities: copyrights/author rights contracts: specific clauses and pedagogical model developed for Avicenna project: describing different components of this model View full abstract»

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  • Characteristics of Nb-based Josephson junctions at a temperature below 1 K

    Page(s): 1354 - 1357
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    A lithographic technique for Josephson LSI (large scale integrated) circuits was applied to the production of a superconducting tunnel junction for radiation detection. Nb-Al/aluminum oxide/Nb tunnel junctions with different junction sizes and barrier oxidation times have been fabricated. The current-voltage curves were measured in the temperature range from 4.2 to 0.45 K. The junctions showed some amounts of leakage current, which remained below 2 K. The behavior of the leakage current was successfully understood from its experimental dependence on the junction size View full abstract»

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  • Receiver sensitivity enhancement by using subcarrier reliability aware soft LDPC in CO-OFDM systems

    Page(s): 1 - 3
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (205 KB)  

    We propose a concatenated LDPC and Reed-Solomon coding scheme for CO-OFDM systems taking consideration of varying reliability among different subcarriers. BER performance measurement shows that such reliability-aware soft LDPC is effective in combating near-DC noise for CO-OFDM systems. View full abstract»

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  • Experimental Study on Damage Detection of a Continuous Girder Bridge Based on Wavelet Packet Energy Accumulated Variation Index

    Page(s): 186 - 190
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (558 KB) |  | HTML iconHTML  

    Based on the ability of catching the change of energy distribution in frequency band for changing in the structure condition by the wavelet packet analysis method, the wavelet packet energy accumulated variation index was proposed to distinguish structural damage in the paper. And the damage index was applied into the damage recognitions of a two-span continuous girder bridge model. The results of measured acceleration time history from three different kinds of excitation ways, including vehicle excitation, environment excitation and hammer excitation, indicated that, the wavelet packet energy accumulated variation index could be applied in the structure damage recognition feasibly and effectively. Uniting more than one damage identification index results is possible to distinguish the different structural damage condition accurately. This damage index in the paper is suitable to all three kinds of acceleration response from different excitation sources, which shows that this index has the universal serviceability. View full abstract»

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  • High SNR performance analysis of F-ESPRIT

    Page(s): 1003 - 1007 Vol.1
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (693 KB) |  | HTML iconHTML  

    A performance analysis of a recently derived method for harmonic retrieval is conducted. The algorithm, which is referred to as F-ESPRIT, has a frequency selective feature which enables the user to select data from frequency subbands in which the signal harmonics are known to reside. This way an efficient suppression of out-of-band disturbances is obtained without the need of explicit data prefiltering. A first order perturbation analysis is conducted, which results in a closed form expression of the mean square error of the parameter estimates. Monte Carlo simulations and the Cramer-Rao lower bound validate the derived expression empirically. View full abstract»

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  • Full-wave Quasi-TEM characteristic impedance of an imperfectly-conducting strip transmission line

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (350 KB) |  | HTML iconHTML  

    The quasi-TEM characteristic impedance of an imperfectly-conducting strip transmission line based on a full-wave analysis is investigated. The effect of the imperfect outer conductors of the stripline are accommodated via a dyadic Green's function satisfying surface impedance boundary conditions. The imperfect center conductor is accommodated through the use of a resistive sheet boundary condition and leads to an EFIE formulation for the quasi-TEM strip current. This center strip current subsequently allows computation of the quasi-TEM characteristic impedance. The effect that finite conductivity has on the quasi-TEM characteristic impedance is investigated. The importance of these results for use in future applications is discussed. View full abstract»

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  • A mixed signal CMOS readout chain for imaging spectroscopic pixel X-ray detectors

    Page(s): 405 - 408 vol.1
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    A CMOS readout chain for pixel X-ray detectors has been designed and prototyped in 0.8 μm technology. The system is capable of simultaneous imaging and spectroscopic functions. Each pixel circuitry incorporates both analog and digital features to perform the dual tasks. It exhibits excellent linearity in the range of 0-1 fC with a gain of 514 mV/fC. With a silicon area of 0.05 mm2 and a power consumption of 1.8 mW per pixel at a 3.3 V it is a promising solution for biomedical applications. The paper describes the system architecture and reports simulation results obtained after back-annotation from the physical design View full abstract»

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  • A successive-approximation ADC for CMOS image sensors

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (704 KB) |  | HTML iconHTML  

    The CMOS image sensors are achieving a growing presence in today's mobile applications as the industry acknowledges the advances of the CMOS-based technology and its scaling possibilities. The roadmap recently unveiled for CMOS Image Sensor is announcing ever smaller pixels, after 1.4μm pixel pitch, demos with a pitch of 1.1μm were presented, and it also announces the future generation of pixels with 0.9μm pixel size. This steady decrease in pixel size has had a profound impact on sensors analog readout electronics, and, in particular, on their ADC architecture. For mobile applications, the ADCs are mostly placed in each column of image arrays, as the width of each converter need to fit in the image array pitch. The design becomes a true challenge as the available area for layout is very critical. To overcome this limitation, a compromise between column level and chip level ADCs can be used. A solution using a converter per 32 columns of the pixel array is proposed. The converter is a Successive Approximation (SA) ADC of apparent resolution 12 bits and is obtained from a 9 bits converter. This work presents a conversion architecture, particularly well adapted to image sensors where the noise level varies along with the amplitude of the useful signal. The proposed design presents the benefit of increasing the number of bits of the ADC without excessively increasing its complexity or its processing time. The converter is designed in CMOS 65nm technology, and will be implemented in a 5Megapixel sensor, at a sampling rate of 8.33MS/s. The simulations show good linearity and verify the concept of the new architecture. View full abstract»

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  • An Iterative Approach to Eigenvalue Assignment for Nonlinear Systems.

    Page(s): 977 - 982
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (196 KB) |  | HTML iconHTML  

    In this paper, the authors present a method of eigenvalue assignment for nonlinear systems. A time-varying approach to nonlinear exponential stability via eigenvalue placement is studied based on an iteration technique that approaches a nonlinear system by a sequence of LTV equations. The convergent behavior of this method is shown and applied to a practical example to illustrate these ideas View full abstract»

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  • Fuzzy logic: issues, contentions and perspectives

    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (84 KB)  

    There has been a rapid growth in the number and variety of applications of fuzzy logic. The successes of fuzzy logic have also generated a skeptical reaction. Most of the criticisms directed at fuzzy logic are rooted in a misunderstanding of what it is and/or a lack of familiarity with it. In many cases, what is not recognized is that the term fuzzy logic (FL) is actually used in two different senses. In a narrow sense, fuzzy logic (FLn) is a logical system which is an extension of multivalued logic and is intended to serve as a logic of approximate reasoning. But in a wider sense, fuzzy logic (FLw) is more or less synonymous with the theory of fuzzy sets (FST). Today the term fuzzy logic is used predominantly in its wider sense. It is in this sense that any field X can be fuzzified-and hence generalized by replacing the concept of a crisp set in X by a fuzzy set. What is gained through fuzzification is greater generality, higher expressive power, an enhanced ability to model real-world phenomena and a methodology for exploiting the tolerance for imprecision. Most of the applications of fuzzy logic relate to control in the context of industrial systems and consumer products. What is discernible, however, is (a) the trend toward the use of fuzzy logic in task-oriented-rather than set-point-oriented-control; and (b) the incorporation of fuzzy logic and neural network techniques in the conception and design of complex systems in which control and expert system techniques are used in combination View full abstract»

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  • Finite element analysis of graphene resonator tuned by pressure difference

    Page(s): 516 - 519
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (574 KB) |  | HTML iconHTML  

    The vibrational mechanical properties of a graphene resonator were investigated by finite element analysis (FEA) modeling and simulation. By applying a pressure difference across the membrane, the natural frequency of the graphene sheets is changed. The resonance frequency increases with increasing pressure difference. The maximum deflection occurs at the center of graphene. As the initial tension in the graphene increases, the tunable range decreases. Smaller the dimension of the graphene sheets is, higher the resonance frequency will be, and so as the tunable range. The thickness of the graphene sheets has the similar phenomenon as the dimension has, both the frequency and tunable range will increase if the thickness turns smaller. The geometric nonlinearity is considered, too. We compare the simulation results with previous theoretical and experimental results, and find them in good agreement. The pressure difference can be tuned by changing the pressure in and outside the microchamber. These conclusions will be helpful for graphene in the application of high-quality resonators. View full abstract»

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  • Coprimality of Certain Families of Integer Matrices

    Page(s): 1481 - 1490
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (406 KB) |  | HTML iconHTML  

    Commuting coprime pairs of integer matrices have been of interest in multidimensional multirate systems, and more recently in array processing. In multirate systems they arise, for example, in the design of interchangeable cascades of decimator and expander matrices. In array processing they arise in the construction of dense coarrays from sparse sensors located on a pair of lattices. For the important case of two dimensional signals, these matrices have size 2 × 2. In this paper the condition for coprimality is derived for several classes of 2 × 2 integer matrices, namely circulant, skew-circulant, and triangular families. The first two are also commuting families. For each class, the special case of adjugate pairs, which automatically commute, is also elaborated. It is also shown that the problem of testing coprimality of two 2 × 2 matrices is equvialent to testing coprimality of a pair of triangular matrices, which can be done almost by inspection. Also considered is the case of 3 × 3 triangular matrices and their adjugates, which have potential applications in three dimensional signal processing. View full abstract»

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  • E-learning at Islamic University of Gaza

    Page(s): 679 - 684
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4252 KB) |  | HTML iconHTML  

    E-learning is a new form of education and is a tool to reach students everywhere. In Gaza Strip it was used to solve the difficulty in movement problem. It was used as an enhancement tool in the educational process. IUG started experimenting with e-learning since 1999. IUG started a systematic approach in developing it e-learning teams. Joint partnership with Middlesex University help set up a system. Couple of courses were available to all university students and limited success was enjoyed View full abstract»

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  • Polarization Patterns Hide and Display Using Photoinduced Anisotropy of a Novel Photochromic Diarylethene

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (319 KB) |  | HTML iconHTML  

    A new unsymmetrical photochromic diarylethene, 1(2-methyl-5-(3-methylphenyl)-3-thienyl)-2-[2-methyl-5-(3fluorophenyl)-3-thienyl]-perfluorocyclo-pentene (1a), was synthesized and its photochromic and fluorescent properties were investigated. Diarylethene la changed the color from colorless to blue upon irradiation with 313 nm UV light, in which absorption maxima were observed at 579 nm in hexane and at 593 nm in PMMA amorphous film, respectively. The cyclization and cycloreversion quantum yields of la in hexane were determined to be 0.44 and 0.017. This new photochromic system also exhibited remarkable fluorescence intensity both in solution and in PMMA film. Using diarylethene 1c/PMMA film as recording medium and a linearly polarized 633 nm laser diode for recording and readout, polarization multiplexed image recording can be carried out in this film. The results demonstrated that the compound was very sensitive responding to 633 nm recording laser, and the recorded holographic images have good contrast, which illustrated that the diarylethene can be potentially used as holographic optical recording medium. View full abstract»

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