Finite-Memory Systems

Let K be a field, k and n positive integers and let matrices with coefficients in K. For any function

Variance and Covariance Computations for 2-D ARMA Processes

An algorithm is presented to compute the variance of the output of a two-dimensional (2-D) stable auto-regressive moving-average (ARMA) process driven by a white noise bi-sequence with unity variance. Actually, the algorithm is dedicated to the evaluation of a complex integral of the form , where and G(z₁,z₂) = B(z₁, z₂) / A(z₁, z₂) is stable (z₁,z₂)-transferfunction. Like other existing methods, the proposed algorithmis based on the partial-fraction decomposition G(z₁,z₂)G(z ₁ ^-1 , z ₂ ^-1 ) = X(z₁, z₁) / A(z₁,z₂)+ X(z ₁ ^-1 , z ₂ ^-1 ) / A(z ₁ ^-1 , z ₂ ^-1 ). However,the general and systematic partial-fraction decomposition schemeof Gorecki and Popek [1] is extended to determine X(z₁,z₂).The key to the extension is that of bilinearly transforming thediscrete (z₁, z₂)-transfer function G(z₁,z₂)into a mixed continuous-discrete (s₁, z₂)-transferfunction . As a result, the partial-fraction decomposition involves only efficient DFT computations for the inversion of a matrix polynomial, and the value of I is finally determined by the residue method with finding the roots of a 1-D polynomial. The algorithm is very easy to implement and it can be extended to the covariance computation for two 2-D ARMA processes.     

APPROXIMATION ANALYSES FOR FUZZY VALUED FUNCTIONS IN L_1(μ)-NORM BY REGULAR FUZZY NEURAL NETWORKS

 By defining fuzzy valued simple functions and giving L1(μ) approximations of fuzzy valued integrably bounded functions by such simple functions, the paper analyses by L1(μ)-norm the approximation capability of four-layer feedforward regular fuzzy neural networks to the fuzzy valued integrably bounded function F : Rn → FcO(R). That is, if the transfer functionσ: R→R is non-polynomial and integrable function on each finite interval, F may be innorm approximated by fuzzy valued functions defined as to anydegree of accuracy. Finally some real examples demonstrate the conclusions.     

BIBO Stability of D-Dimensional Filters

Consider the class of d-dimensional causal filters characterized by a d-variate rational function analytic on the polydisk . The BIBO stability of such filters has been the subject of much research over the past two decades. In this paper we analyze the BIBO stability of such functions and prove necessary and sufficient conditions for BIBO stability of a d-dimensional filter. In particular, we prove if a d-variate filter H(z) analytic on has a Fourier expansion that converges uniformly on the closure of , then H(z) is BIBO stable. This result proves a long standing conjecture set forth by Bose in [3].     

An Implantable CMOS Amplifier for Nerve Signals

In this paper, a low noise high gain CMOS amplifier for minute nerve signals is presented. The amplifier is constructed in a fully differential topology to maximize noise rejection. By using a mixture of weak- and strong inversion transistors, optimal noise suppression in the amplifier is achieved. A continuous-time current-steering offset-compensation technique is utilized in order to minimize the noise contribution and to minimize dynamic impact on the amplifier input nodes. The method for signal recovery from noisy nerve signals is presented. A prototype amplifier is realized in a standard digital 0.5 m CMOS single poly, n-well process. The prototype amplifier features a gain of 80 dB over a 10 kHz bandwidth, a CMRR of more than 87 dB and a PSRR greater than 84 dB. The equivalent input referred noise in the bandwidth of interest is 4.8 nV/ . The amplifier power consumption is 275 W, drawn from a power supply; V _DD = –V _SS = 1.5 V.     

Linear systems in a saturated mode and convergence as gain becomes large of asymptotically stable equilibrium points of neural nets

We study solutions of the linear system in a saturated mode

Estimation of Energy Aliasing Error for Nonbandlimited Signals

In this paper, we investigate the problem of approximating a given (not necessarily bandlimited) signal, x(t), by a (bandlimited) interpolation or sampling series of the form:

Influence of a strong longitudinal static electric field on free carrier faraday effect in an n-type InSb at room temperature at submillimeter wave frequencies

The expression for free carrier Faraday rotation θ and for ellipticity Δ, as the function of the applied parallel static electric field \(\mathop {E_0 }\limits_ \to \) and static magnetic field \(\mathop {B_0 }\limits_ \to \) for a given value of wave angular frequency and electron concentration N₀, are obtained and theoretically analyzed with the aid of one-dimensional linearized wave theory and Kane's non-parabolic isotropic dispersion law. It is shown that the maximum Faraday rotation occurs near the cyclotron resonance condition, which can be expressed as \(\chi \omega = \omega _{ce} \) , where \(\chi = 1{1 \mathord{\left/ {\vphantom {1 {\sqrt {1 - ({{v_0 } \mathord{\left/ {\vphantom {{v_0 } {v_c }}} \right. \kern-0em} {v_c }})^2 } }}} \right. \kern-0em} {\sqrt {1 - ({{v_0 } \mathord{\left/ {\vphantom {{v_0 } {v_c }}} \right. \kern-0em} {v_c }})^2 } }}\) , \(v_c = \sqrt {{{\varepsilon _g } \mathord{\left/ {\vphantom {{\varepsilon _g } {2m}}} \right. \kern-0em} {2m}}} *\) , and \(\omega _{ce} = ({{eB_0 } \mathord{\left/ {\vphantom {{eB_0 } {m*}}} \right. \kern-0em} {m*}})\) . Here m^* and e denote the effective mass and charge of electron, respectively. ?_g is the forbidden bandgap of semiconductor. v₀ is the carrier drift velocity, which is a non-linear function of E₀ in high field condition. A possibility of a simple way of determining the non-linear “v₀ vs E₀” characteristics of semiconductors by the measurement of Faraday rotation is also discussed.     

Four-Dimensional Gallant–Lambert–Vanstone Scalar Multiplication

The GLV method of Gallant, Lambert, and Vanstone (CRYPTO 2001) computes any multiple kP of a point P of prime order n lying on an elliptic curve with a low-degree endomorphism Φ (called GLV curve) over $\mathbb{F}_{p}$ as $$kP = k_1P + k_2\varPhi(P) \quad\text{with } \max \bigl\{ |k_1|,|k_2| \bigr\} \leq C_1\sqrt{n} $$ for some explicit constant C ₁>0. Recently, Galbraith, Lin, and Scott (EUROCRYPT 2009) extended this method to all curves over $\mathbb{F}_{p^{2}}$ which are twists of curves defined over $\mathbb{F}_{p}$ . We show in this work how to merge the two approaches in order to get, for twists of any GLV curve over $\mathbb{F}_{p^{2}}$ , a four-dimensional decomposition together with fast endomorphisms Φ,Ψ over $\mathbb{F}_{p^{2}}$ acting on the group generated by a point P of prime order n, resulting in a proven decomposition for any scalar k∈[1,n] given by $$kP=k_1P+ k_2\varPhi(P)+ k_3\varPsi(P) + k_4\varPsi\varPhi(P) \quad \text{with } \max_i \bigl(|k_i| \bigr)< C_2\, n^{1/4} $$ for some explicit C ₂>0. Remarkably, taking the best C ₁,C ₂, we obtain C ₂/C ₁<412, independently of the curve, ensuring in theory an almost constant relative speedup. In practice, our experiments reveal that the use of the merged GLV–GLS approach supports a scalar multiplication that runs up to 1.5 times faster than the original GLV method. We then improve this performance even further by exploiting the Twisted Edwards model and show that curves originally slower may become extremely efficient on this model. In addition, we analyze the performance of the method on a multicore setting and describe how to efficiently protect GLV-based scalar multiplication against several side-channel attacks. Our implementations improve the state-of-the-art performance of scalar multiplication on elliptic curves over large prime characteristic fields for a variety of scenarios including side-channel protected and unprotected cases with sequential and multicore execution.     

Creep behavior of eutectic Sn-Cu lead-free solder alloy

Tensile creep behavior of precipitation-strengthened, tin-based eutectic Sn-0.7Cu alloy was investigated at three temperatures ranging from 303–393 K. The steady-state creep rates cover six orders of magnitude (10⁻³−10⁻⁸ s⁻¹) under the stress range of σ/E=10⁻⁴−10⁻³. The initial microstructure reveals that the intermetallic compound Cu₆Sn₅ is finely dispersed in the matrix of β-Sn. By incorporating a threshold stress, σ _th, into the analysis, the creep data of eutectic Sn-Cu at all temperatures can be fitted by a single straight line with a slope of 7 after normalizing the steady-state creep rate and the effective stress, indicating that the creep rates are controlled by the dislocation-pipe diffusion in the tin matrix. So the steady-state creep rate, , can be expressed as exp , where Q_c is the activation energy for creep, G is the temperature-dependent shear modulus, b is the Burgers vector, R is the universal gas constant, T is the temperature, σ is the applied stress, A is a material-dependent constant, and , in which σ _OB is the Orowan bowing stress, and k_R is the relaxation factor. An erratum to this article is available at .     

Low Voltage High-Speed CMOS Square-Law Composite Transistor Cell

A new low voltage high-speed CMOS composite transistor is presented. It lowers supply voltage down to |V _t |+2 V _ds,sat and considerably extends input voltage operating range and achieves high speed operation. As an application example, it is used in the design of a high-speed four quadrant analog multiplier. Simulations results using MOSIS 2 m N-well process with a 3 V supply are given.     

Extruded Bismuth-Telluride-Based <Emphasis Type="Italic">n</Emphasis>-Type Alloys for Waste Heat Thermoelectric Recovery Applications

Thermoelectric (TE) generator modules for a number of waste heat recovery applications are required to operate between room temperature and 500 K, a temperature range for which the composition of bismuth-telluride-based alloys needs to be adjusted to optimize performance. In particular n-type alloys do not perform as well as p-type and require a more systematic study. We have produced, by mechanical alloying followed by hot extrusion, alloys, within the range with fixed carrier concentration () to optimize their TE performance in the temperature range 300 K to 420 K. The optimum composition has been identified to be and which is very close to the composition that also maximizes the ratio of the electron mobility to the lattice component of the thermal conductivity. The optimized alloy performance can be further increased by adjusting the carrier concentration.     

Some applications of counting process models with partially observed covariates

A broad array of data series have embedded discrete event‐occurrences, cumulative counts of which can be viewed as superpositions of independent identically distributed (iid) counting processes with intensities of the form , where ϑ is unknown, n may be unknown, Z _i are unobservable iid vectors, and V(t) is an observable “environmental” vector process, but the function h is known or hypothesized. It is shown how such data‐structures and models arise naturally within the application areas of environmental epidemiology and software reliability, and lead to statistical analyses using novel forms of Poisson regression models with random effects. Such models are potentially very useful in analysis and characterization of teletraffic patterns. This revised version was published online in June 2006 with corrections to the Cover Date.     

Direct Digital Frequency Synthesis Based on a Two-Level Table-Lookup Scheme

In this work, a new direct digital frequency synthesizer (DDFS) is proposed, which is based on a new two-level table-lookup (TLTL) scheme combined with Taylor’s expansion. This method only needs a lookup-table size of total bits, one multiplier, one n × 3n/4-bit multiplier and two additional smaller multipliers, to generate both sine and cosine values (where n is the output precision). Compared with several notable DDFS’s, the new design has a smaller lookup-table size and higher SFDR (Spurious Free Dynamic Range) for high-precision output cases, at comparable multiplier and adder complexities. The DDFS is verified by FPGA and EDA tools using Synopsys Design Analyzer and UMC 0.25 μm cell library, assuming 16-bit output precision. The designed 16-bit DDFS has a small gate count of 2,797, and a high SFDR of 110 dBc.

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Robust Low Power CMOS Single-Ended to Fully-Balanced Converter Circuits

In this paper two novel single-ended-input fully-balanced-output circuits (SFC), namely unbuffered and buffered SFCs, are proposed for input interface to fully balanced signal processing systems. The unbuffered SFC overcomes the drawback of uncontrollable process variations of resistors and generate well-controlled process invariant common mode output voltage, V _o,com . The adopted active current common mode feedback compensation makes this possible. Simulations using MOSIS 2 m N-well process and a 3 V supply, show that with ±100% variation, V _o,com only varies by less than ±2%. In addition, it is shown that V _o,com is accurately controlled by a preset DC voltage. On the other hand, the buffered SFC adopts a novel body effect-free class AB buffer so as to have low standby power consumption but high current driving capability. It is implemented without resistors and common-mode feedback circuitry. Measurement results from a 1.2 m N-well CMOS chip indicate a bandwidth of 5.5 MHz while driving a 40 pF load with a supply voltage of ±1.5 V. The circuit is capable of supplying more than 3 mA of output current while consuming 1.1 mW of standby power. The THD is less than –55 dB at 1 KHz and the phase error is less than 2° for frequencies up to 1 MHz.     

Structural Analysis of CdTe Hetero-epitaxy on (211) Si

X-ray diffraction full-width at half-maximum (XRD FWHM), reflection high-energy electron diffraction (RHEED), and atomic force microscopy (AFM) indicate a mosaic structure for molecular-beam epitaxy (MBE) (211)B CdTe/Si. AFM measurements indicate long, thin, small-angle-disoriented grains for CdTe/Si epilayers. These disoriented grains are ~1 μm in the [] direction and are ~40 nm in the [] direction. The RHEED pattern in the [] direction depicts nearly ideal single-crystal periodicity. The RHEED pattern in the [] direction is indicative of small-angle-disoriented crystalline grains. Scanning electron microscopy (SEM), AFM, and XRD measurements all indicate an approximate factor of 10 increase in the Everson etch pit density (EPD) over standard Nomarski microscopy Everson EPD determination.     

Pump-free crossed-field free-electron laser

Starting from basic concepts, we propose a new kind of free-electron laser (FEL): the pump-free crossed-field FEL in which the condition E_o+V_o×B_o=0 is not satisfied, and the electron orbit without radition fields and undulator or wiggler fields is not straight line (in planar configuration) or cycloid (in magnetron-like configuration). This paper presents a fluid dynamical analysis of the pump-free crossed-field FEL, in which the space charge effect is not taken into consideration. FEL instability is found near resonance \(\omega _{ \pm 1} - k\dot z_a = 0\) . While no FEL instability is found near resonance \(\omega _q - k\dot z_a \pm \sqrt {1 - \beta \mathop z\limits^2 a^\omega o} = 0\)      

How r-Plane Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Surface Modifications Impact the Growth of Epitaxial (001) CeO<Subscript>2</Subscript> Thin Films

We present evidence that it is the presence or absence of atomic terraces with a specific crystallographic orientation on the (102) Al₂O₃ surface that promotes growth of single-crystal (001) CeO₂ films over polycrystalline (111) CeO₂ films. The CeO₂ film nucleates so that the [010] and [100] directions of the film align parallel and perpendicular to the terrace edges. In the absence of terraces, multidomain (111) CeO₂ films result in which the in-plane orientation of the two domains are rotated by 85.71°, so that a [110] CeO₂ direction aligns parallel to either the or Al₂O₃ direction.