Ayush Jain

Effect of dynamic crosslinking on impact strength and other mechanical properties of polypropylene/ethylene-propylene-diene rubber blends

The deformation and fracture behavior of several dynamic vulcanizate blends of isotactic polypropylene with ethylene-propylene-diene rubber (EPDM) was examined and compared with those of uncrosslinked blends of PP/EPDM. These blends were prepared by melt mixing in an internal mixer at 190°C in a composition range of 10–40 wt % EPDM rubber. The variation in yield stress, the strength of fibrils of the craze, and the number density of the EPDM rubber domains (morphology fixation) that are dominant factors for enhancing interfacial adhesion and toughness in dynamic vulcanizate blends were evaluated. The ductility and toughness of these materials were explained in light of the composition between crack formation and the degree of plastic deformation through crazing and shear yielding. The physicomechanical properties including the hardness, yield stress, Youngs modulus, percentage elongation, impact strength, flexural strength, and flexural modulus of dynamic vulcanized blends were found to be consistent and displayed higher values compared with uncrosslinked blends. The nucleation effect of the crosslinked particles and the decrease of crystallinity of the EPDM rubber were also considered to contribute to the improvement in the impact strength.

Robust acoustic echo cancellation using Kalman filter in double talk scenario

Kalman filtering framework.Joint acoustic echo and noise cancellation.Double talk detector.Linear prediction coding analysis.Expectation maximisation algorithm. In this work, a novel Kalman filtering framework is developed for joint acoustic echo and noise cancellation in a double talk scenario. The efficiency of echo cancellation algorithms is reduced when signals other than the echoed far end signal are present, since the echo path cannot be modelled accurately in such cases. A double talk detector is also used in conjunction with an acoustic echo canceller to handle such a double talk scenario. The method presented in this work is able to model both the near-end speech signal and background noise, which makes lt robust in double talk scenarios. Apart from jointly cancelling echo and noise, another advantage of this framework is that it does not require a double talk detector. Additionally an expectation maximisation based algorithm is also proposed in this work to estimate linear prediction coefficients of the near end signal. Extensive performance evaluation over the NOIZEUS corpus demonstrates that the proposed framework performs reasonably better than other speech enhancement methods in terms of misalignment of the estimated echo path and perceptual quality of the reconstructed near-end speech signal.

On redundancy rate of FDLZ algorithm and its variants

We use the machinery developed by Wyner [1], for the sources satisfying Markov condition, to obtain an upper bound on the contribution of pointer bits to the compression ratio for fixed database Lempel-Ziv (FDLZ) algorithm to be H + O(1/ log2n) which is an improvement from the previous bound of H + H(1 + o(1))log2 log2n/ log2n . We use the definition of compression ratio as in Yang and Kieffer [2]. Here H is the entropy rate of the source and n is the size of the database. Then using the same definition of compression ratio we obtain an upper bound on the contribution of phrase length bits for the variant of FDLZ suggested in [3] to be O(1/ log2n), which gives an upper bound of O(1/ log2n) on the redundancy rate itself for this version of FDLZ.

Point-wise analysis of redundancy in SWLZ algorithm for φ-mixing sources

In this paper, we bound the number of phrases of the sliding window Lempel-Ziv (SWLZ) algorithm using an upper bound on the expected number of phrases in the fixed database Lempel-Ziv (FDLZ) algorithm for a class of φ-mixing sources which includes Markov sources, unifilar sources and finite state sources as special cases, as developed by Yang and Kieffer [1]. We use this bound to obtain a point-wise upper bound on the redundancy rate of SWLZ algorithm to be 2H(log₂log₂n_w/log₂n_w) + O(log₂log₂log₂n_w/log₂n_w). Here H is the entropy rate of the source and n_w is the window size.

Toxicity and mutagenicity of exhaust from compressed natural gas: Could this be a clean solution for megacities with mixed-traffic conditions?

Despite intensive research carried out on particulates, correlation between engine-out particulate emissions and adverse health effects is not well understood yet. Particulate emissions hold enormous significance for mega-cities like Delhi that have immense traffic diversity. Entire public transportation system involving taxis, three-wheelers, and buses has been switched from conventional liquid fuels to compressed natural gas (CNG) in the Mega-city of Delhi. In this study, the particulate characterization was carried out on variety of engines including three diesel engines complying with Euro-II, Euro-III and Euro-IV emission norms, one Euro-II gasoline engine and one Euro-IV CNG engine. Physical, chemical and biological characterizations of particulates were performed to assess the particulate toxicity. The mutagenic potential of particulate samples was investigated at different concentrations using two different Salmonella strains, TA98 and TA100 in presence and absence of liver S9 metabolic enzyme fraction. Particulates emitted from diesel and gasoline engines showed higher mutagenicity, while those from CNG engine showed negligible mutagenicity compared to other test fuels and engine configurations. Polycyclic aromatic hydrocarbons (PAHs) adsorbed onto CNG engine particulates were also relatively fewer compared to those from equivalent diesel and gasoline engines. Taken together, our findings indicate that CNG is comparatively safer fuel compared to diesel and gasoline and can offer a cleaner transport energy solution for mega-cities with mixed-traffic conditions, especially in developing countries.

On point-wise redundancy rate of Bender-Wolf's variant of SWLZ algorithm

In this paper we analyse the redundancy rate of a variant of sliding window Lempel-Ziv (SWLZ) proposed by Bender and Wolf, which encodes phrase lengths differently from the original algorithm. We examine upper bound on the contribution of phrase length bits for this variant to get an overall upper bound of O(1/log nw) on the redundancy rate for Markov sources which is better than the lower bound of O(log log nw/log nw), established by the Lastras-Montano for SWLZ algorithm. Here nw denotes the window size.

Acoustic echo and noise cancellation using Kalman filter in a modified GSC framework

In this paper a novel method for acoustic echo and noise cancellation in a generalized sidelobe canceler framework is described. The primary contribution of this work is the development of multichannel adaptive Kalman filter (MCAKF) in a modified generalized sidelobe canceler (MGSC) framework. Additionally, in this work both the near end speech signal and noise is assumed to be unknown. In the proposed method speech acquired by a microphone array is subject to adaptive beamforming using MVDR method. On the other hand a blocking matrix filter is used to attenuate the near end speech signal while passing both the noise and residual echo. A MCAKF is developed in this context to also estimate the noise and residual echo. Hence, a difference of MCAKF output and the adaptive beamformer (ABF) output gives an estimate of the near end speech signal. The performance of proposed method is evaluated using subjective and objective measures on the ARCTIC database. Distant speech recognition experiments are also conducted on the ARCTIC database. The proposed method gives reasonable improvements both in terms of perceptual evaluation and distant speech recognition.

On optimality and redundancy of side information version of SWLZ

In this work, we establish the pointwise optimality of side information version of SWLZ algorithm for stationary ergodic sources. We also obtain a pointwise upper bound on the redundancy rate of this side information version of SWLZ algorithm for a subclass of φ-mixing sources, which includes Markov sources as a special case. This upper bound obtained differs only by a constant factor from the best bound that has been obtained on redundancy rate for the original SWLZ algorithm itself.

Exponential rates of convergence for waiting times and generalized AEP

In this work, we first relate rate of convergence of waiting times Wn(D), until a D-close version of the first n symbols of a realization of a process appears in the realization of another independent process, with rate of convergence in generalized AEP. We then identify the conditions under which exponential rates of convergence holds in generalized AEP and for waiting times.