Technion – Israel Institute of Technology

About: Technion – Israel Institute of Technology is a education organization based out in Haifa, Israel. It is known for research contribution in the topics: Population & Nonlinear system. The organization has 31714 authors who have published 79377 publications receiving 2603976 citations. The organization is also known as: Technion Israel Institute of Technology & Ṭekhniyon, Makhon ṭekhnologi le-Yiśraʼel.

Noise spectrum estimation in adverse environments: improved minima controlled recursive averaging

Abstract: Noise spectrum estimation is a fundamental component of speech enhancement and speech recognition systems. We present an improved minima controlled recursive averaging (IMCRA) approach, for noise estimation in adverse environments involving nonstationary noise, weak speech components, and low input signal-to-noise ratio (SNR). The noise estimate is obtained by averaging past spectral power values, using a time-varying frequency-dependent smoothing parameter that is adjusted by the signal presence probability. The speech presence probability is controlled by the minima values of a smoothed periodogram. The proposed procedure comprises two iterations of smoothing and minimum tracking. The first iteration provides a rough voice activity detection in each frequency band. Then, smoothing in the second iteration excludes relatively strong speech components, which makes the minimum tracking during speech activity robust. We show that in nonstationary noise environments and under low SNR conditions, the IMCRA approach is very effective. In particular, compared to a competitive method, it obtains a lower estimation error, and when integrated into a speech enhancement system achieves improved speech quality and lower residual noise.

Discrimination in a Segmented Society: An Experimental Approach

Abstract: This paper proposes an experimental approach to studying different aspects of discrimination. We let participants play various games with opponents of distinct ethnic affiliation. Strategies based upon such ethnic affiliation provide direct evidence of ethnic discrimination. This approach was utilized to study ethnic discrimination in Israeli Jewish society. Using the “trust game,” we detected a systematic mistrust toward men of Eastern origin. A “dictator game” experiment indicated that this discrimination was due to (mistaken) ethnic stereotypes and not to a “taste for discrimination.” The “ultimatum game” enabled us to trace another ethnic stereotype that reversed the discrimination’s direction. One of the surprising results is that this ethnic discrimination is an entirely male phenomenon.

Majority is not Enough: Bitcoin Mining is Vulnerable

Abstract: The Bitcoin cryptocurrency records its transactions in a public log called the blockchain. Its security rests critically on the distributed protocol that maintains the blockchain, run by participants called miners. Conventional wisdom asserts that the protocol is incentive-compatible and secure against colluding minority groups, i.e., it incentivizes miners to follow the protocol as prescribed. We show that the Bitcoin protocol is not incentive-compatible. We present an attack with which colluding miners obtain a revenue larger than their fair share. This attack can have significant consequences for Bitcoin: Rational miners will prefer to join the selfish miners, and the colluding group will increase in size until it becomes a majority. At this point, the Bitcoin system ceases to be a decentralized currency. Selfish mining is feasible for any group size of colluding miners. We propose a practical modification to the Bitcoin protocol that protects against selfish mining pools that command less than 1/4 of the resources. This threshold is lower than the wrongly assumed 1/2 bound, but better than the current reality where a group of any size can compromise the system.

Hidden Markov processes

Abstract: An overview of statistical and information-theoretic aspects of hidden Markov processes (HMPs) is presented. An HMP is a discrete-time finite-state homogeneous Markov chain observed through a discrete-time memoryless invariant channel. In recent years, the work of Baum and Petrie (1966) on finite-state finite-alphabet HMPs was expanded to HMPs with finite as well as continuous state spaces and a general alphabet. In particular, statistical properties and ergodic theorems for relative entropy densities of HMPs were developed. Consistency and asymptotic normality of the maximum-likelihood (ML) parameter estimator were proved under some mild conditions. Similar results were established for switching autoregressive processes. These processes generalize HMPs. New algorithms were developed for estimating the state, parameter, and order of an HMP, for universal coding and classification of HMPs, and for universal decoding of hidden Markov channels. These and other related topics are reviewed.

Electromechanical integration of cardiomyocytes derived from human embryonic stem cells.

Abstract: Cell therapy is emerging as a promising strategy for myocardial repair. This approach is hampered, however, by the lack of sources for human cardiac tissue and by the absence of direct evidence for functional integration of donor cells into host tissues. Here we investigate whether cells derived from human embryonic stem (hES) cells can restore myocardial electromechanical properties. Cardiomyocyte cell grafts were generated from hES cells in vitro using the embryoid body differentiating system. This tissue formed structural and electromechanical connections with cultured rat cardiomyocytes. In vivo integration was shown in a large-animal model of slow heart rate. The transplanted hES cell-derived cardiomyocytes paced the hearts of swine with complete atrioventricular block, as assessed by detailed three-dimensional electrophysiological mapping and histopathological examination. These results demonstrate the potential of hES-cell cardiomyocytes to act as a rate-responsive biological pacemaker and for future myocardial regeneration strategies.