An exploratory study of factors affecting single trial P300 detection

A threshold detector for single-trial P300 detection has been evaluated. The detector operates on the 0-4 Hz band, isolated from the raw electroencephalogram using low-pass filtering, wavelet transforms, or the piecewise prony method (PPM). A detection rate around 70% was found, irregardless of stimulus type, interstimulus interval (ISI), probability of occurrence (Pr) of the target stimuli, intrasession and intersession effects, or filtering method. This suggests that P300-based brain-machine interfaces can use an ISI as short as 1 s and a Pr of 45%, to increase throughput.     

Cooley-Tukey-type algorithm for the Haar transform

It is shown that the Haar transform can be computed using a Cooley-Tukey-type algorithm that is implemented in 2(N?1) additions/subtractions. This algorithm is derived by relating the Haar transform to the modified Walsh-Hadamard transform using a simple bit-reversal scheme.     

一种快速高效的二维一级小波变换的硬件实现

提出了一种针对9/7小波滤波器的二维一级小波变换的硬件平台,整体结构采用流水方式实现,数据分组输入,列变换采用多个小波变换单元,行变换模块为可重构硬件结构,行列变换之间不需要片上存储器。与已有结构相比,该结构可以通过更少的硬件资源消耗获得更高的处理速度。     

Single-mode fibre Fourier transform spectrometer

A single-mode all-fibre Fourier transform spectrometer is described. A resolution of ?1 cm?1 (?0.7 ?) is demonstrated at 820 nm. The device can be configured as a remote gas sensor.     

Reduction in Sampling-Point Numbers for 2-D Discrete Fourier Transform Used in Harmonic Balance Method

This paper discusses how to reduce the numbers of sampling points to obtain the 2-D discrete Fourier transform used in harmonic balance method. A method of embedding a 2-D Fourier transform into a 1-D one has already been proposed. This paper proposes a method of reducing the numbers of sampling points in a 1-D Fourier transform, by using bandpass sampling. A 2-D Fourier transform for harmonic balance method can be embedded into a 1-D one with a reduced number of sampling points by combining the previously proposed and the present methods. The extension of these methods to higher dimensional cases is also briefly discussed.      

Physical-layer secrecy in AWGN via a class of chaotic DS/SS systems: analysis and design

We study a class of pseudo-chaotic spread spectrum systems for secure communication over additive white Gaussian noise (AWGN) channels, whereby a symbol stream is linearly modulated on a spreading sequence generated by iterating an initial condition through a suitably chosen chaotic map. We compare the uncoded probability of error (Pr(/spl epsiv/)) attainable by intended receivers that know the initial condition to the associated Pr(/spl epsiv/) of unintended receivers that know the modulation scheme but not the initial condition. The sensitive dependence of chaotic sequences on initial conditions, together with the presence of channel noise, can be exploited to provide substantially lower Pr(/spl epsiv/) to intended than to unintended receivers. We develop computationally efficient methods for obtaining tight bounds on the best P r(/spl epsiv/) performance of intended and unintended receivers. In the process, we identify chaotic map attributes that affect the relative Pr(/spl epsiv/) advantages provided to intended receivers and develop methods for designing maps that achieve a target gap between the intended and unintended receiver Pr(/spl epsiv/).     

Pr3+掺杂SrTiO3薄膜的聚合物前驱体法制备及发光性能

采用聚合物前驱体法,在LaNiO<,3>/si(100)衬底上低温制备了Pr<,3+>掺杂SrTiO<,3>薄膜.用XRD,AFM、PL手段分析了薄膜的晶体结构、表面形貌与发光性能.结果显示,退火温度决定SrTiO<,3>薄膜的晶粒大小和表面形貌,在600℃退火2 h获得的薄膜表面均匀、无裂痕,晶粒大小约为60 nm,...     

Fast number-theoretic transforms for digital filtering

A special number-theoretic transform that can be computed, using a high-radix fast Fourier transform, is defined on primes of the form (2n ? 1) 2n +1. Methods for finding these primes and the primitive dth roots of unity in a field modulo such primes are also included.     

Yb,Ho,Pr:GYTO晶体生长、结构及光谱性能（特邀）

首次采用提拉法成功生长出了新型中红外激光晶体Yb,Ho,Pr:GYTO,采用X射线Rietveld精修方法得到了晶体的结构参数。测量了Yb,Ho,Pr:GYTO晶体（100)、(010)和(001)衍射面的X射线摇摆曲线,衍射峰的半峰宽分别为0.036°、0.013°和0.077°,表明生长出的晶体是单晶并且具有较高的结晶质量。采用激光剥蚀电感耦合等离子体质谱法测定了Yb,Ho,Pr:GYTO晶体中Yb3+、Ho3+、Pr3+和Y3+的浓度,Yb,Ho,Pr:GYTO晶体中Yb3+、Ho3+、Pr3+和Y3+的有效分凝系数分别为0.624、1.220、1.350和0.977。测量了Yb,Ho,Pr:GYTO晶体室温下的极化吸收谱,并指认了相应的能级吸收跃迁。940 nm半导体激光器激发的2.9 μm荧光光谱表明,最大发射波长为2908 nm。此外,还论证了GYTO中Yb-Ho-Pr的能量传递机制。与Ho:GYTO晶体相比,Yb,Ho,Pr:GYTO晶体的5I₇能级寿命降低了87.13%,与上能级5I₆的寿命相近,说明Yb,Ho,Pr:GYTO晶体更容易实现粒子数反转和激光输出。     

Active Cheby?shev filters

The synthesis technique described below permits active RC realisation of transfer functions of the type K/(anxn+an?1xn?1+an?2xn?2+ ? + a0), where x is the complex transform frequency variable s, or its reciprocal 1/s. This procedure has the advantage that the active devices are nonideal low-gain amplifiers which may be realised quite simply using transistors.     

Scaling-free McClellan transform for 2-D digital filters

The original McClellan transformation used in the design of 2-dimensional digital filters having quadrantally symmetrical magnitude response, involves the substitution cos ? = F(cos ?1, cos ?2). For real frequencies, a scaling procedure was proposed by Mersereau et al. (1976) to guarantee that |F|?1 using the two values Fmax and Fmin. In the letter, we first present extremely simple formulas for the scaling factors, then suggest a modified transform which not only is scaling-free but also contains one less coefficient than the original transform.     

Spectral attenuation measurement for fluoride glass single-mode fibres by Fourier transform techniques

A new spectral attenuation measurement system using a Fourier transform spectrometer is developed. The Fourier transform spectral attenuation measurement (FT-SAM) system makes the signal acquisition time for a wide wave-length range of 1.0?4.2? much shorter than measurement with a conventional dispersive spectral attenuation measurement system. The spectral attenuation for a fluoride glass single-mode fibre, with a minimum loss of 3±1 dB/km at 2.5?m, is measured with this system.     

Beratungs- und IT-Preis der Wirtschaftskammer

Aktuell?sterr. Normungsinstitut

Barfu? folgt Korinek als Pr?sident     

Fast biased polynomial transforms for 2D prime length discrete Fourier transforms

The fast biased polynomial transform (FBPT) is defined directly over a ZN ? 1 ring instead of the conventional cyclotomic polynomial rings. For N prime, these FBPTs can be used for the efficient evaluation of the 2D prime length DFT.     

Parallel and pipeline computation of fast unitary transforms

The letter discusses the parallel and pipeline organisation of fast-unitary-transform algorithms such as the fast Fourier transform, and points out the efficiency of a combined parallel-pipeline processor of a transform such as the Haar transform, in which 2n?1 hardware `butterflies? generate a transform of order 2n every computation cycle.     

Total Coloring of G×Pn and G×Cn

It is proved that if G is a (△+1)-colorable graph, so are the graphs G×Pn and C×Cn, where Pn and Cn are respectively the path and cycle with n vertices, and △ the maximum edge degree of the graph. The exact chromatic numbers of the product graphs Pr1×Pr1×...×Prn× and C3k×C2m1×C2m2×...×C2mn are also presented. Thus the total coloring conjecture is proved to be true for many other graphs.     

五磷酸镨晶体的生长

本文采用高温溶液法从磷酸溶液中生长PrP_5O_(14)和Pr_(0.9)La_(0.1)P_5O_(14)晶体。已获得大于1厘米~3、光学质量好的大晶体,并测定了晶体的光谱和结构。     

Ga1?xAlxAs material for high-sensitivity pressure sensors

The resistivity of n-type Ga1?xAlxAs alloys has been found to be very sensitive to both the purely hydrostatic and small nonhydrostatic pressures. For some alloy compositions, the resistivity variation with pressure is almost linear. For typical alloy composition x = 0.23, the coefficients are ~ 1.7 kbar?1 and ~ ?0.15 kbar?1 for low (P ? 18 kbars) and high pressures (P > 18 kbars), respectively. For the same composition, the temperature coefficients of resistivity are ~ 4.3 × 10?3 K?1 and ~ 0.22 K?1 for temperature intervals 300 > T > 125 K and T < 125 K, respectively.     

On The Estimation of Pr {Y ? X} for Exponential Families

The minimum variance s-unbiased estimator of Pr{Y ? X} is derived for the case in which X and Y are s-independent r.v.'s each with a Cdf belonging to the exponential family but otherwise not necessarily of the same type.     

稀土元素Pr替位改性的高温CaBi_2Nb_2O_9压电陶瓷

采用普通陶瓷工艺制备了由稀土元素Pr替位改性的高温Ca1-xPrxBi2Nb2O9(x=0～0.100)无铅压电陶瓷,研究了Pr含量对CaBi2Nb2O9(CBNO)压电陶瓷介电及压电性能的影响。结果表明:Pr对Ca的替换明显提高了CBNO压电陶瓷的压电性能。其中,Pr含量x为0.050的Ca0.95Pr0.05Bi2Nb2O9压电陶瓷表现出最好的压电性能,其压电常数d33高达14pC/N,且在800℃以下表现出良好的温度稳定性。