Finite Number Of Positions Research Articles

Frequency Estimation of the Plenoptic Function Using the Autocorrelation Theorem

The frequency estimation of the plenoptic function (POF) is an important research topic in spectral analysis for determining the minimum sampling rate of image-based rendering. In this paper, we mathematically derive a frequency estimation function of the POF using the autocorrelation theory. The autocorrelation function (ACF) of the POF is studied along both the spatial and image plane frequency axes. The influence of the scene's complexity and depth on the ACF of the POF is analyzed. Furthermore, we study the frequency estimation error to analyze the performance of the method. Existing techniques typically use Fourier transformation to determine the frequency of the POF. The technique presented herein simply starts from measurements of the light field in a finite number of positions, and the information from the light field is analyzed in the spatial domain. Finally, experimental results are presented to demonstrate that the proposed method can effectively estimate the frequency of the POF. The results are shown to be in good agreement with traditional methods.

Spherical harmonic analysis applied to the reconstruction of the sound field radiated by a loudspeaker

The three dimensional acoustic radiation patterns generated by different models of loudspeaker have been measured in an anechoic environment using an array of 40 omnidirectional microphones, arranged on a hemispherical surface. The acquired data have been numerically processed in order to obtain the complete three dimensional reconstruction of the analysed sound field. The theory of the applied method is based on the spherical harmonic decomposition of the sound field defined over the surface of a sphere containing the sound source and sampled at a finite number of positions. The reconstruction of the sound field in the region of the space inside and outside the measurement surface has been obtained by multiplying each coefficient of the spherical harmonic series by the corresponding spherical propagator, defined as the ratio of two spherical Hankel functions. The conditioning of the inverse problem related to the reconstruction of the sound field in the interior of the measurement surface has been analysed and put in relation to the behaviour of the spherical propagators of different orders.

The Plenacoustic Function and Its Sampling

The spatialization of the sound field in a room is studied, in particular the evolution of room impulse responses as a function of their spatial positions. It was observed that the multidimensional spectrum of the solution of the wave equation has an almost bandlimited character. Therefore, sampling and interpolation can easily be applied using signals on an array. The decay of the spectrum is studied on both temporal and spatial frequency axes. The influence of the decay on the performance of the interpolation is analyzed. Based on the support of the spectrum, the number and the spacing between the microphones is determined for the reconstruction of the sound pressure field up to a certain temporal frequency and with a certain reconstruction quality. The optimal sampling pattern for the microphone positions is given for the linear, planar and three-dimensional case. Existing techniques usually make use of room models to recreate the sound field present at some point in the space. The presented technique simply starts from the measurements of the sound pressure field in a finite number of positions and with this information the sound pressure field can be recreated at any spatial position. Finally, simulations and experimental results are presented and compared with the theory

System for recognizing sentence patterns and a system for recognizing sentence patterns and grammatical cases

A slot table contains (1) all possible sentence patterns (VPs), arranged in rows, which a predicate in an input sentence can take, and (2) arguments of the VPs expressed as slot conditions in slots positioned in a finite number of positions. A grammatical case pattern table contains columns corresponding to respective grammatical cases of the basic patterns arranged in the order in which the cases appear in a basic pattern before shifting; all the grammatical case patterns are expressed as binary values representing existing/non-existing ones of the respective grammatical cases in respective rows corresponding to the grammatical case patterns. The binary values are added up to numbers of the position information in the basic pattern, and the grammatical cases, which correspond to columns that correspond to the last number among numbers of the binary values, are treated as grammatical cases for arguments of the VP. One position on the slot table is selected with respect to candidates for arguments of VPs in the input sentence, and a candidate's features are compared with the slot conditions of all possible VPs in slots in the same position. Plural VPs are processed in parallel by recognizing as being appropriate only those VPs with slots whose slot conditions match the candidate's features, and only the grammatical cases that have been described in the slots of such recognized VPs are recognized as appropriate. Because a finite number of positions is set on the slot table, comparison of slot conditions, in positions other than the specific position, with candidate's features is unnecessary.

Active Control Of Acoustic Fields And The Reproduction Of Sound

In recent studies of the active control of acoustic fields analytical methods and multi-channel signal processing techniques have been used that can be usefully applied to problems in sound reproduction. In this paper several aspects of the reproduction of sound are considered. First, the possibility is considered of the perfect reproduction of an acoustic field in both space and time. Results from classical acoustics suggest a means by which this could be achieved, but it is soon concluded that this is an unrealistic objective in practice. The reproduction of a sound field over a restricted spatial region is also considered. Some new results are presented which demonstrate that a field can be reproduced that closely approximates the original by first recording the acoustic signals at a finite number of positions in the original sound field. The signals are processed via a matrix of linear filters in order to produce the inputs to a number of sources used for reproduction. An analysis in the frequency domain shows that such a strategy could be useful, but its practicability at high frequencies appears to be limited by the need to provide adequate spatial samping of the original field. Another approach that is considered is to concentrate on ensuring that the direction of propagation of the waves in the original field are well approximated in the reproduced field. This approach appears to be a more practicable alternative, and offers the promise of successful operation over a wide frequency bandwidth. Some discussion is presented of the realizability of the optimal filter matrix and a practical, adaptive, filter design technique is presented which has already provded successful in some limited experiments. Finally, some further possibilities are suggested in which the same principles are used to improve the quality of existing stereophonic sound reproduction systems.

A Priority-Based Admission Scheme for a Multiclass Queueing System

We consider a queueing problem involving multiple priority classes where the station is divided into waiting and service areas. The service area has a finite number of positions where a customer of a particular class has access to only a subset of these positions. The admission into the service area is controlled by a mechanism that allows customers within a priority class to enter the service area on a first-come first-served basis. The customers of different classes are assumed to be indistinguishable once they have entered the service area. We consider service under three different disciplines: last-come first-served preemptive resume, multiple server, and processor sharing. We show that the waiting time of a customer is related to that of a customer in an equivalent M/G/1 queue. We characterize the Laplace-Stieltjes transform of the time spent in the service area. We also discuss three potential applications in the area of computer and communication systems.