Image reconstruction from localized phase

The authors present a novel approach to image representation using partial information defined by the localized phase. The scheme is implemented using the short-time (short-distance) Fourier transform. This is a generalization of the Gabor scheme which is well-established with regard to biological representation of visual information at the level of the visual cortex. Similar to processing in vision, the DC component is first extracted from the signal and treated separately. Computational results and theoretical analysis indicate that image reconstruction from the localized phase representation requires fewer computer operations and yields an improved rate of convergence compared to reconstruction from the global phase representation. It is also implementable with fast algorithms using highly parallel architecture     

Frictional properties of thermally bonded 3D nonwoven fabrics prepared from polypropylene/polyester bi‐component staple fiber

The frictional properties of the three‐dimensional nonwoven samples produced using the recently developed air laying and through‐air thermal bonding system are evaluated. The samples were made from commercially available polypropylene (PP)/polyester (PET) (sheath/core) bi‐component staple fiber. In particular, the effects of the process parameters on the frictional properties were investigated by employing a statistical approach involving the uniform design of experiments and regression analysis. Stick‐slip frictional traces were obtained as a result of the presence of fiber loops, overlapping of fibers at bonding points, and deformation of fibers due to melting. The effect of normal load on both the static and dynamic friction forces can be described using the power‐law relationship. Both the static and dynamic friction factors increase with increase of the thermal bonding temperature and the dwell time. POLYM. ENG. SCI., 46:853–863, 2006. © 2006 Society of Plastics Engineers     

Signal representation in the combined phase-spatial space:reconstruction and criteria for uniqueness

Motivated by the major roles of the spectral phase in signal structure and by previous results on the importance of localized representation in images, we develop conditions for unique representation of a signal by a combination of its spectral (Fourier) phase and spatial samples. Methods for signal reconstruction from various combinations of spatial and phase information are introduced. It is concluded that most of the previous results in the area of phase-only representation and reconstruction are special cases of the general approach presented here     

Measurement of Fibre Tuft Weight in an Air Duct using Optical Methods

The feasibility of using a Charge-Coupled Device (CCD) linescan camera to evaluate the weight of fibre tufts moving in an air duct is reported. A theoretical study of the measurement of the light transmission of fibre tufts is presented and the theoretical models are verified by experimental results. The accuracy of the results is improved by a modification of the air duct shape. The fibre tuft speed and the optical uniformity are also discussed.     

Constant-bulk False-twist Texturing. Part I: Principle and Method

Current false-twist texturing processes are all carried out under constant-temperature conditions. White the product is good and commercially acceptable, changes in bulk and hence in dyeability do occur, due, for example, to alterations in yarn properties caused by changes in package build from inside to outside. New work described in this paper shows that, by texturing at constant bulk, substantially improved yarn and fabrics can be obtained. The new process developed at UMIST uses very small heaters (4–8 inches in length) under feedback control. The bulk and dyeability of the textured yarn are monitored on-line. A closed-loop system is used, and texturing conditions are automatically changed to keep the bulk and dyeability of the textured yarn constant. In this new process, the texturing temperature is changed in such a way as to keep the bulk constant. The process is therefore non-isothermal, in contrast to the isothermal, constant-temperature approach of all current false-twist texturing equipment. The principles of on-line bulk measurement are briefly discussed and it is shown theoretically that, if a tension barrier is deliberately introduced into the second zone of the false-twist threadline, then measurement of yarn velocity correlates with bulk.     

The achievable accuracy in estimating the instantaneous phase andfrequency of a constant amplitude signal

The approach is based on modeling the signal phase by a polynomial function of time on a finite interval. The phase polynomial is expressed as a linear combination of the Legendre basis polynomials. First, the Cramer-Rao bound (CRB) of the instantaneous phase and frequency of constant-amplitude polynomial-phase signals is derived. Then some properties of the CRBs are used to estimate the order of magnitude of the bounds. The analysis is extended to signals whose phase and frequency are continuous but not polynomial. The CRB can be achieved asymptotically if the estimation of the phase coefficients is done by maximum likelihood. The maximum-likelihood estimates are used to show that the achievable accuracy in phase and frequency estimation is determined by the CRB of the polynomial coefficients and the deviation of true phase and frequency from the polynomial approximations     

Comments on "On estimating the orders of an autoregressive process"

This correspondence makes some critical remarks on the method suggested in the above paper for estimating the order of an autoregressive process. An alternative method is then suggested.