Delay Estimator and Improved Proportionate Multi-Delay Adaptive Filtering Algorithm

This paper pertains to speech and acoustic signal processing, and particularly to a determination of echo path delay and operation of echo cancellers. To cancel long echoes, the number of weights in a conventional adaptive filter must be large. The length of the adaptive filter will directly affect both the degree of accuracy and the convergence speed of the adaptation process. We present a new adaptive structure which is capable to deal with multiple dispersive echo paths. An adaptive filter according to the present invention includes means for storing an impulse response in a memory, the impulse response being indicative of the characteristics of a transmission line. It also includes a delay estimator for detecting ranges of samples within the impulse response having relatively large distribution of echo energy. These ranges of samples are being indicative of echoes on the transmission line. An adaptive filter has a plurality of weighted taps, each of the weighted taps having an associated tap weight value. A tap allocation/control circuit establishes the tap weight values in response to said detecting means so that only taps within the regions of relatively large distributions of echo energy are turned on. Thus, the convergence speed and the degree of estimation in the adaptation process can be improved

Voice Activity Detection for Speech Enhancement Applications

This paper describes a study of noise-robust voice activity detection (VAD) utilizing the periodicity of the signal, full band signal energy and high band to low band signal energy ratio. Conventional VADs are sensitive to a variably noisy environment especially with low SNR, and also result in cutting off unvoiced regions of speech as well as random oscillating of output VAD decisions. To overcome these problems, the proposed algorithm first identifies voiced regions of speech and then differentiates unvoiced regions from silence or background noise using the energy ratio and total signal energy. The performance of the proposed VAD algorithm is tested on real speech signals. Comparisons confirm that the proposed VAD algorithm outperforms the conventional VAD algorithms, especially in the presence of background noise

Distributed rate allocation in switch-based multiparty videoconference

Multiparty videoconferences, or more generally multiparty video calls, are gaining a lot of popularity as they offer a rich communication experience. These applications have however, large requirements in terms of both network and computational resources and have to deal with sets of heterogenous clients. The multiparty videoconferencing systems can be grouped in two classes. They are based either on expensive central nodes, called multipoint control units (MCU), with transcoding capabilities, or, on a peer-to-peer strategy where users help each other to distribute the different video streams. Whereas the first one requires an expensive central hardware, the second one depends completely on the redistribution capacity of the users, which sometimes might neither provide sufficient bandwidth nor be reliable enough. In this work we propose an alternative solution where we use a central node to distribute the video streams but at the same time we maintain the hardware complexity and the computational requirements of this node as low as possible. The proposed solution uses a distributed algorithm to allocate the users' rates in a Quality of Service (QoS) aware manner. The allocation algorithm is also extremely fast and is able to quickly reallocate the rates in case the conditions change. We have further implemented our solution in a network simulator where we show that our rate allocation algorithm is able to properly optimize users' QoS and adapt to dynamic changes in the system. We also illustrate the benefits of our solution in terms network usage and average utility when compared to a baseline heuristic method operating on the same system architecture

Prognostic and preventive role of various factors in corneal rejection after keratoplasty

The literature review is devoted to the analysis of modern publications on the immunological and pathogenetic mechanisms of transplanted corneal rejection, risk factors, predictors and methods of the prevention of this complication. The prevention of corneal rejection is challenging.Currently, there is no single algorithm for the predicting methods of the corneal graft rejection, so further research in this area is needed.Purpose. To assemble the current data on immunological and non-immunological predictors of postoperative complications after keratoplasty. The analysis of modern publications on the immunological and pathogenetic mechanisms of corneal transplant rejection, risk factors, predictors and methods of prevention of this complication is presented. The databases used were CyberLeninka, PubMed, and Medline. The focus was on the publications of the last 10 year s.Conclusion. The data presented in the review make it possible to identify signs of corneal transplant rejection and to determine treatment in a timely manner, as well as to implement methods for preventing these complications

A device for intravitreal and endolymphatic drug administration and reflexogenic zone blockade in ophthalmology

Currently, most surgeons use 27G needles to perform intravitreal and endolymphatic administration and reflexogenic zone blockade. However, their use is associated with certain disadvantages and complications.Aim. To develop a device for intravitreal and endolymphatic drug administration and sinocarotid zone blockade.Methods. A device for intravitreal and endolymphatic drug administration and sinocarotid zone blockade was developed. It consists of an original adapter, 30G carpule needle, and a syringe. Pre-clinical trials included comparative evaluation of this device and a rather well-known instrument for intravitreal and endolymphatic drug administration and sinocarotid zone blockade (a syringe with 27G needle). Clinical trials involved 150 patients aged 36 years and older.Results. The device consists of a syringe, 30G carpule needle, and an original three-stage hollow adapter that attaches the needle to the syringe. The needle has a cannula to be attached to the adapter. The cannula and the second stage of the adapter have the thread with an aligning arrangement The third stage of the adapter is made in a form of a truncated cone that tightly goes into the cannula thus providing reliable fixation of the needle. The device: (1) minimizes the leakage of a drug in the course of the procedure thus providing more accurate drug administration and preventing its overuse; (2) reduces complication risk and improves the safety of intravitreal and endolymphatic drug administration and sinocarotid zone blockade; (3) improves the tolerability of intravitreal and endolymphatic drug administration and sinocarotid zone blockade; (4) improves personal readiness to undergo maintenance retreatment. The utility model application was filed, and the filing receipt No. 2014109466 was acquired on March 12, 2014.Conclusion. The device provides optimal intravitreal and endolymphatic drug administration and sinocarotid zone blockade