Statistical Model‐Based Voice Activity Detection Based on Second‐Order Conditional MAP with Soft Decision

In this paper, we propose a novel approach to statistical model‐based voice activity detection (VAD) that incorporates a second‐order conditional maximum a posteriori (CMAP) criterion. As a technical improvement for the first‐order CMAP criterion in [1], we consider both the current observation and the voice activity decision in the previous two frames to take full consideration of the interframe correlation of voice activity. This is clearly different from the previous approach [1] in that we employ the voice activity decisions in the second‐order (previous two frames) CMAP, which has quadruple thresholds with an additional degree of freedom, rather than the first‐order (previous single frame). Also, a soft‐decision scheme is incorporated, resulting in time‐varying thresholds for further performance improvement. Experimental results show that the proposed algorithm outperforms the conventional CMAP‐based VAD technique under various experimental conditions.     

Power Analysis Attacks and Countermeasures on ηT Pairing over Binary Fields

Since many efficient algorithms for implementing pairings have been proposed such as η_T pairing and the Ate pairing, pairings could be used in constraint devices such as smart cards. However, the secure implementation of pairings has not been thoroughly investigated. In this paper, we investigate the security of η_T pairing over binary fields in the context of side‐channel attacks. We propose efficient and secure η_T pairing algorithms using randomized projective coordinate systems for computing the pairing. This work was supported partly by the MIC (Ministry of Information and Communication), Rep. of Korea, under the ITRC (Information Technology Research Center) support program supervised by the IITA (Institute of Information Technology Assessment) (IITA‐2008‐(C1090‐0801‐0025)) and by the IT R&D program of MIC/IITA, Rep. of Korea [2005‐S088‐04, Development of Security technology for Secure RFID/USN Service].     

Differential Power Analysis on Countermeasures Using Binary Signed Digit Representations

Side channel attacks are a very serious menace to embedded devices with cryptographic applications. To counteract such attacks many randomization techniques have been proposed. One efficient technique in elliptic curve cryptosystems randomizes addition chains with binary signed digit (BSD) representations of the secret key. However, when such countermeasures have been used alone, most of them have been broken by various simple power analysis attacks. In this paper, we consider combinations which can enhance the security of countermeasures using BSD representations by adding additional countermeasures. First, we propose several ways the improved countermeasures based on BSD representations can be attacked. In an actual statistical power analysis attack, the number of samples plays an important role. Therefore, we estimate the number of samples needed in the proposed attack.     

New Type of Collision Attack on First‐Order Masked AESs

This paper introduces a new type of collision attack on first‐order masked Advanced Encryption Standards. This attack is a known‐plaintext attack, while the existing collision attacks are chosen‐plaintext attacks. In addition, our method requires significantly fewer power measurements than any second‐order differential power analysis or existing collision attacks.     

Bienenstock,Cooper, and Munro Learning Rules Realized in Second‐Order Memristors with Tunable Forgetting Rate

Memristors with synaptic functions are very promising for developing artificial neural networks. Compared with the extensively reported spike‐timing‐dependent plasticity (STDP), Bienenstock, Cooper, and Munro (BCM) learning rules, the most accurate model of the synaptic plasticity to date, are more compatible with the neural computing system; however, the progress in the realization of the BCM rules has been quite limited. The realized BCM rules so far mostly performs just the spike‐rate‐dependent plasticity (SRDP), however, without a tunable sliding frequency threshold, because the memristors used to realize the BCM rules do not have tunable forgetting rates. In this work, the BCM rules with a tunable sliding frequency threshold are biorealistically implemented in SrTiO₃‐based second‐order memristors; the forgetting rate of the memristors is tuned by engineering the electrode/oxide interface through controlling the electrode composition. The approach of this work is precise and efficient, and the biorealistic implementation of the BCM rules in memristors improves the efficiency of the neural network for the artificial intelligent system.     

Analysis on the Calculation of Plasma Medium with Parallel SO‐FDTD Method

This paper introduces a novel parallel shift operator finite‐difference time‐domain (SO‐FDTD) method for plasma in the dispersive media. We calculate the interaction between the electromagnetic wave of various frequencies and non‐magnetized plasma by using the parallel SO‐FDTD method. Then, we compare the results, which are calculated with serial and parallel SO‐FDTD executions to obtain the speedup ratio and validate the parallel execution. We conclude that the parallel SO method has almost the same precision as the serial SO method, while the parallel approach expands the scope of memory and reduces the CPU time.     

Adaptive Standby Mode Scheduling Method Based on Analysis of Activation Pattern for Improving User Experience of Low‐Power Set‐Top Boxes

The lowest power mode (passive‐standby mode) was proposed for reducing the power consumption of set‐top boxes in a standby state when not receiving content. However, low‐power set‐top boxes equipped with the lowest power mode have been rarely commercialized because of their low‐quality user experience. In the lowest power mode, they deactivates almost all of operational modules and processes, and thus require dozens of seconds for activation latency (that is, the latency for activating all modules of the set‐top boxes in a standby state). They are not even updated in a standby state because they deactivate their network interfaces in a standby state. This paper proposes an adaptive standby mode scheduling method for improving the user experience of such boxes. Set‐top boxes using the proposed method can analyze the activation pattern and find the frequently used time period (that is, when the set‐top boxes are frequently activated). They prepare for their activation during this frequently used time period, thereby reducing the activation latency and enabling their update in a standby state.     

An Improved Optical Method for Determining the Order Parameter in Thin Oriented Molecular Films and Demonstration of a Highly Axial Dipole Moment for the Lowest Energy π–π* Optical Transition in Poly(9,9‐ dioctylfluorene‐co‐bithiophene)

Understanding the complex interplay between the 3D structural hierarchy within thin films of conjugated polymers and the properties of devices based thereon is starting to be recognized as an important challenge in the continued development of these materials for a range of applications. As a result, for example, accurate measurements of molecular orientation and elucidation of its influence on optical characteristics are of significant interest. Here we report an improved optical method to determine both the order parameter and the angle between the polymer backbone director and the optical transition dipole moment for the lowest energy π–π* absorption peak in uniaxially aligned thin films of conjugated polymers. The method uses a combination of polarized Raman spectroscopy and UV‐vis spectroscopy and is based on a general theoretical treatment to describe the expected Raman and optical absorption anisotropies of such films. It is applied to study the orientation within thermotropically aligned films of the electroluminescent fluorene‐based copolymer poly(9,9‐dioctylfluorene‐co‐bithiophene) (F8T2). A more highly axial transition dipole moment is found for the dominant long wavelength absorption peak of F8T2 compared to that of other fluorene‐based (co)polymers. The angle between the polymer backbone director and the transition dipole is estimated to be β ≤ 3°, a deduction that helps to explain the relatively large optical dichroism for aligned films of F8T2 and that offers the prospect of highly polarized electroluminescence from F8T2‐based light‐emitting diodes.