一种基于相对自相关序列的语音端点检测法

在研究单边自相关序列(One-sided autocorrelation,OSA)和相对自相关序列(Relative autocorrelation sequences,RAS)的基础上,提出了一种基于相对自相关序列的语音信号的端点检测算法。该方法利用相对自相关算法能够消除噪声的原理,以语音信号相对自相关序列短时平均幅度代替双门限比较法中的语音信号短时平均幅度,以语音信号短时平均幅度代替语音信号的短时平均过门限率,实验表明,在低信噪比下检测精度要高于传统的双门限比较法。     

Low-consumption phase change material with good data retention selected from SbxTe

Various compositions of SbxTe phase-change films have been investigated by means of in situ temperature-dependent resistance measurement. Although crystallization temperature of Sb3Te is about 536 K, a little lower than those of Sb2Te and Sb4Te, it has a better data retention performance than the other two compositions. X-ray diffraction patterns imply that poly-crystalline structures of Sb-Te alloys are all hexagonal, and phase separation appears in SbTe3, Sb2Te, Sb3Te and Sb4Te alloys. Sb2Te and Sb3Te have been selected for phase-change random access memory devices. RESET voltage for Sb3Te is 1.2 V when the voltage pulse width is 50 ns, 0.3 V lower than that for Sb2Te. By using the voltage pulse width of 200 ns, Sb3Te needs 1.8 V and 4 V to complete SET-RESET performance, 0.4 V and 0.5 V lower than Sb2Te respectively. It indicates that Sb3Te is more suitable for the application of phase-change random access memory.     

Binary arrays with perfect odd-periodic autocorrelation

Arrays with good autocorrelation functions are required for coded aperture imaging. A generalized folding procedure is derived that permits the construction of arrays with good correlation properties from well correlating sequences for many array sizes. This synthesis method is applied to the construction of approximately square binary arrays with a single zero element and perfect odd-periodic autocorrelation functions. In addition, new binary arrays with constant sidelobes of their periodic autocorrelation functions (uniformly redundant arrays) can be generated with the generalized folding method.     

Temporal phase unwrapping of digital hologram sequences

A method for recording and evaluating digital image-plane holograms is presented. Hundreds of holograms of an object that has been subjected to dynamic deformation (e.g., vibrations) are recorded. The phase of the wave front is calculated from the recorded holograms by use of a two-dimensional digital Fourier-transform method. By temporal phase unwrapping it is possible to determine the absolute deformation (included the direction of motion) of the object. Experimental results are presented, and the advantages of temporal phase unwrapping compared with spatial phase unwrapping are discussed.     

Displacement vector measurement using instantaneous ultrasound signal phase - multidimensional autocorrelation and doppler methods

Two new methods of measuring a multidimensional displacement vector using an instantaneous ultrasound signal phase are described, i.e., the multidimensional autocorrelation method (MAM) and multidimensional Doppler method (MDM). A high measurement accuracy is achieved by combining either method with the lateral Gaussian envelope cosine modulation method (LGECMM) or multidirectional synthetic aperture method (MDSAM). Measurement accuracy is evaluated using simulated noisy echo data. Both methods yield accurate measurements comparable to that of our previously developed cross-spectrum phase gradient method (MCSPGM); however, they require less computational time (the order, MDM < MAM approximate, equals MCSPGM) and would provide realtime measurements. Moreover, comparisons of LGECMM and MDSAM performed by geometrical evaluations clarifies that LGECMM has potentials to yield more accurate measurements with less computational time. Both MAM and MDM can be applied to the measurement of tissue strain, blood flow, sonar data, and other target motions.     

自相关域信号相位匹配原理的正弦信号参数估计

对单路接收信号的自相关函数使用等间隔或变间隔时延截取得到M段信号,进而采用相位匹配原理进行正弦信号参数估计,能够进一步改善估计性能,尤其是变间隔时延可抑制大部分奇异峰。仿真结果表明,自相关域信号相位匹配原理的正弦信号参数估计精度优于频域信号相位匹配原理的参数估计精度。     

Mechanical and wear properties of GO-enhanced irradiated UHMWPE with good oxidation resistance

In this study, the effects of incorporating graphene oxide (GO) and γ irradiation on the mechanical and wear properties of ultra-high-molecular-weight polyethylene (UHMWPE) were investigated. Moreover, the crystallinity and oxidation index of irradiated GO/UHMWPE composites were studied. The results indicated that the crystallinity, compression performance, and hardness of UHMWPE were improved owing to the incorporation of GO and γ irradiation treatment. Furthermore, the incorporation of GO and γ irradiation treatment could effectively reduce the wear rate of UHMWPE. In addition, the incorporation of GO could improve the oxidative resistance of irradiated and aged UHMWPE.     

The synthesis of magnetic recording trellis codes with good hamming distance properties

In this paper we present, by means of an example, a systematic procedure to synthesize combined modulation/error correcting trellis codes, suitable for Viterbi decoding. This synthesis is based on firstly selecting a suitable linear convolutional code, secondly by analysing the state system of this code to determine the important Hamming distance building properties, and finally by mapping a code with the desired restrictions on its sequences onto this state system. As an example we develop a R = 3/6 dc free (b,l,c) = (0,3,2) code withd_{min} = 4. This code improves on the best codes in [1]. Codes havingb geq 1, and which will thus be more suitable for magnetic recording, can also be synthesized following the proposed procedure.     

Image-based cardiac phase retrieval in intravascular ultrasound sequences

Longitudinal motion during in vivo pullbacks acquisition of intravascular ultrasound (IVUS) sequences is a major artifact for 3-D exploring of coronary arteries. Most current techniques are based on the electrocardiogram (ECG) signal to obtain a gated pullback without longitudinal motion by using specific hardware or the ECG signal itself. We present an image-based approach for cardiac phase retrieval from coronary IVUS sequences without an ECG signal. A signal reflecting cardiac motion is computed by exploring the image intensity local mean evolution. The signal is filtered by a band-pass filter centered at the main cardiac frequency. Phase is retrieved by computing signal extrema. The average frame processing time using our setup is 36 ms. Comparison to manually sampled sequences encourages a deeper study comparing them to ECG signals.     

Transparent anti-stain coatings with good thermal and mechanical properties based on polyimide-silica nanohybrids

In this work, we synthesized polyimide/silica hybrid materials via sol-gel method using a fluorinated poly(amic acid) silane precursor and a variety of perfluorosilane contents. We studied the influence of a hybrid coating film with the following characteristics; hydrophobicity, oleophobicity, optical transparency, and surface hardness of the coating films. The hybrid coatings with the fluorosilane contents up to 10 wt% are optically transparent and present good thermal stability with a degradation temperature of > 500 degrees C as well as a glass transition of > 300 degrees C. Both water contact angle and oil contact angle increase rapidly with introducing small amount of the fluorosilane in the hybrids and reaches the maximum of 115 degrees and 61 degrees, respectively. The hardness of the hybrid coatings increases up to 5H with an increase of the FTES content in the hybrids. These colorless, transparent, and thermally stable hybrid materials could be suitable for applications as anti-stain coatings.     

Estimation of the coupling delay time from time series of self-oscillatory systems with allowance for the autocorrelation function of phase noise

We propose to determine the delay time of coupling between self-oscillatory systems using a modification of the well-known method based on a model of the oscillation phase dynamics, which ensures its applicability in the case of nonwhite noises influencing this dynamics. For this purpose, the method of calculating a confidence interval is refined by allowance for the correlation time of the phase noise. The applicability of the proposed estimator is illustrated by the results of numerical experiments with systems of standard coupled oscillators.     

Plastics products: successful firms,innovation and good design

A research project has examined some sectors of the UK manufacturing industry whose products are covered by Design Council Awards and Design Centre Selection Schemes. This paper reports on findings in the plastic products industry, looking at goals and strategies, marketing, design, price and commercial success. It concludes that good design and commercial success are possible, despite a previous bad image.     

Non-covalently modified reduced graphene oxide/polyurethane nanocomposites with good mechanical and thermal properties

Non-covalently modified graphene nanosheets were prepared by reduction graphene oxide with hydrazine hydrate and simultaneous non-covalent functionalization via 1-allyl-methylimidazolium chloride (AmimCl) ionic liquid. Atomic force microscopy revealed that AmimCl ionic liquid modified graphene (IL-G) was well-dispersed in a single exfoliation with a thickness of around 0.96 nm in DMF. Subsequently, the prepared IL-G nanosheets were incorporated into polyurethane (PU) to fabricate IL-G/PU nanocomposites by solution blending. X-ray diffraction disclosed an exfoliated morphology of IL-G nanosheets dispersed in the PU matrix, while the fractured morphology of the IL-G/PU nanocomposites showed that IL-G nanosheets presented a wrinkled morphology when dispersed in the matrix. Both techniques revealed homogeneous dispersion and good compatibility of IL-G nanosheets with PU matrix, indicating the existence of interfacial interactions. At 0.608 wt% loadings of IL-G nanosheets, the tensile strength and storage modulus of the composites were increased by 68.5 and 81.1 %, respectively. High thermal properties were also achieved at a low loading of IL-G nanosheets. An approximately 40 °C improvement in temperature of 5 % weight loss and 34 % increase in thermal conductivity were obtained at just 0.608 wt% loading of IL-G nanosheets.     

Estimating mean scatterer spacing with the frequency-smoothedspectral autocorrelation function

The quasiperiodicity of regularly spaced scatterers results in characteristic patterns in the spectra of backscattered ultrasonic signals from which the mean scatterer spacing can be estimated. The mean spacing has been considered for classifying certain biological tissue. This paper addresses the problem of estimating the mean scatterer spacing from backscattered ultrasound signals using the frequency-smoothed spectral autocorrelation (SAC) function. The SAC function exploits characteristic differences between the phase spectrum of the resolvable quasiperiodic scatterers and the unresolvable uniformly distributed (diffuse) scatterers to improve estimator performance over other estimators that operate directly on the magnitude spectrum. Mean scatterer spacing estimates are compared for the frequency-smoothed SAC function and a cepstral technique using an AR model. Simulation results indicate that SAC-based estimates converge more reliably over smaller amounts of data than cepstrum-based estimates. An example of computing an estimate from liver tissue scans is also presented for the SAC function and the AR cepstrum     

Autocorrelation techniques in color flow imaging: signal model andstatistical properties of the autocorrelation estimates

A review of the scattering theory for moving blood, and a model for the signal in a multigated pulsed wave Doppler system is presented. The model describes the relation between a general time-variable velocity field and the signal correlation in space and time, including the effect of movement of the ultrasonic beam for color flow imaging systems with mechanical scanning. In the case of a constant and rectilinear velocity field, a parametric model for the autocorrelation function is deduced. General formulas for a full second order characterization of the set of autocorrelation estimates, with arbitrary lags in the spatial and temporal directions, are developed. The formulas are applied to the parametric model, and numerical results for the estimator variance are presented. A qualitative evaluation of the theoretical results has been performed by offline-processing of 2-D Doppler signals from a color flow imaging scanner. The benefit of spatial and temporal averaging is demonstrated by using different averaging filters to the same set of recorded data     

Development in high-grade dual phase steels with low C and Si design

Cold rolled dual phase steels with low C and Si addition were investigated in terms of combination of composition and processing in order to improve mechanical properties and workability including welding and galvanizing. Mo and Cr could be used as alloying elements to partially replace C and Si to assure enough hardening ability of the steels and also give solute-hardening. Mo addition is more effective than Cr addition in terms of obtaining the required volume fraction of martensite and mechanical strength. The ferrite grain was effectively refined by addition of Nb microalloying, which gives optimized mechanical properties. The experimental results show that it is possible to obtain the required mechanical properties of high grade 800 MPa dual phase steel, i.e., tensile strength>780 MPa, elongation>15%, and yield/tensile strength ratio<0.6 in the condition of low carbon (C<0.11 wt.%) and low silicon design (Si<0.05 wt.%) through adequate combination of composition and processing.