摘要:

Magnetic resonance imaging is used to determine the vocal tract area functions of a speaker producing five steady vowel sounds. The data is used in an acoustic tube model, formed by concatenating short uniform sections, and the acoustic spectra of the computed output from the model are compared with those of natural speech. For all but one of the vowels good agreement (typically within 120 Hz) is obtained for the first three formant frequencies. To compensate for measurement errors, optimisation procedures are applied, aimed at adjusting the areas to minimise a chosen cost function. A cost function which combines a windowed cepstral error with a Euclidean distance penalty for the areas is effective in finding area functions that gave much closer spectral matches, but which still lie largely within the estimated errors of measurement. These adjusted functions provide suitable root shapes for use in articulatory speech synthesis.

DOI:10.1049/ip-i-2.1992.0074

出版商:IEE    

年代:1992

数据来源: IET

摘要:

A new discrimination method based on fuzzy subset theory is proposed. This approach uses Zernike moment invariants of the silhouette of the unknown object to form a set of fuzzy-weighted quantities called fuzzy quaternions. These are matched against those of known objects at predetermined viewpoints. To speed up the recognition process, a modified simplex version of the Nelder-Mead algorithm is utilised. Results obtained demonstrate the potential of the fuzzy quaternion as a viable basis for discrimination.

DOI:10.1049/ip-i-2.1992.0075

出版商:IEE    

年代:1992

数据来源: IET

摘要:

An extensive literature survey presented in Reference 1 has revealed that the majority of previous work in infrared image processing has ignored the processes leading to the formation of infrared images. In this paper, we address the problem of infrared image formation and derive an irradiation equation for simple infrared scenes. We consider the complications caused by mutual illumination of one or more bodies and indicate how the infrared irradiation equation can also be specified for more complex scenes. The infrared irradiation equation we derive is solved in closed form for some simple geometries for both Lambertian and non-Lambertian surfaces. Experimental results from a variety of scene geometries compare favourably with the theoretically derived equations, indicating the validity of the theoretical analysis. We describe how a knowledge of the formation of infrared images can be used to predict the image irradiation pattern of a particular object. We also show how, with a knowledge of the radiance properties and surface geometry of the object, it is possible to detect instances of that object in a scene. Examples are given of successful object detection based on an understanding of the image irradiation.

DOI:10.1049/ip-i-2.1992.0076

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The technique described has been developed from the still-picture version of the recursive binary nesting algorithm to code moving image sequences efficiently at low bit rates. The technique, based on quad-tree decomposition and spatial interpolation, had to be modified from its previous form so that it could make use of the additional time-axis redundancy available in a moving sequence, and also to remove a number of disturbing artifacts that were initially present. Once these topics were successfully dealt with, aspects of coding efficiency were considered by concentrating on controlling the degree of image decomposition. Details of these techniques are described in the paper, which concludes with comparisons with other coding techniques.

DOI:10.1049/ip-i-2.1992.0077

出版商:IEE    

年代:1992

数据来源: IET

摘要:

A new algorithm, word-based dynamic Lempel-Ziv (WDLZW) for universal (lossless) data compression, is introduced. The novel feature is that the algorithm is optimised for the compression of natural language data, in which all the spaces between words are deleted whenever copy codes or literal codes are sent out. Therefore better compression rates can be achieved. The algorithm can still compress alternative forms of data. The structure, operation and implementation of the WDLZW is described. A comparison with other algorithms when compressing a wide range of data forms is reported. For text-based information WDLZW offers attractive performance. For other forms of data, WDLZW provides compression rates similar to those of dynamic Lempel-Ziv systems.

DOI:10.1049/ip-i-2.1992.0078

出版商:IEE    

年代:1992

数据来源: IET

摘要:

Generalised Hermite polynomials are employed for the reconstruction of an unknown signal from a knowledge of its zero-crossings, under certain conditions on its spatial/spectral width, but dispensing with the assumption of bandlimitedness. A computational implementation of the proposed method is given for one-variable (or one-dimensional) signals, featuring an application of simulated annealing for optimal reconstruction.

DOI:10.1049/ip-i-2.1992.0079

出版商:IEE    

年代:1992

数据来源: IET

摘要:

In the paper, new maximum-likelihood synchronisation algorithms for quadraturequadrature phase shift keying (Q2PSK) signals are presented and evaluated. A brief description of the Q2PSK modulation scheme is given. The digital implementation of the algorithms used in the simulation of a constant-envelope Q2PSK modem system and their computational loads are presented. Bit error rate performance of the modem system has been evaluated. Bit-by-bit and symbolby-symbol detection receivers are simulated and evaluated. Phase and timing variances obtained with the new synchronisation procedures have been calculated and are given.

DOI:10.1049/ip-i-2.1992.0080

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The authors propose an ‘integrated packet reservation multiple access’ (IPRMA) protocol for transmitting both speech and data information. While speech users are allowed contend for reservation slots on a frame-by-frame basis, data users may reserve multiple slots across a frame to increase throughput. The protocol includes a priority mechanism which ensures that speech users have greater access to idle slots since speech packets have a more demanding delay constraint. The proposed scheme is shown to provide equitable access to channel resources for both types of users yielding improvements in overall system performance while significantly increasing data throughput compared to a system without data packet reservation.

DOI:10.1049/ip-i-2.1992.0081

出版商:IEE    

年代:1992

数据来源: IET

摘要:

To relieve the contention in packet initiations in CDMA packet radio networks, a novel protocol, the busy code broadcasting and sensing protocol, is proposed, and its steady-state throughput-delay performance upper bounds are numerically analysed. The results reveal that a high throughput of about 0.47 (when the normalised channel trafficr= 1) and a stable performance of the network can be achieved by busy code broadcasting and sensing to avoid possible packet conflicts in the CDMA packet radio channel. The hidden terminal problem which exists in carrier sense multiple access is avoided in the proposed protocol. The study also shows that the new protocol can use CDMA spreading codes more efficiently than can other conventional spreading code protocols.

DOI:10.1049/ip-i-2.1992.0082

出版商:IEE    

年代:1992

数据来源: IET

摘要:

A Monte Carlo simulation was conducted to assess the performance, in terms of bit error probability, of a direct sequence spread spectrum multiple access (DS/SSMA) radio system in indoor Rician fading channels using differential phase shift keying (DPSK). Simulation results are presented for a DS/SSMA indoor radio system using selection diversity. Importance sampling techniques were used to accelerate the simulation. The results are compared with the analytical results obtained earlier

DOI:10.1049/ip-i-2.1992.0083

出版商:IEE    

年代:1992

数据来源: IET