We proposes a new adaptive spectral masking method of algebraic vector quantization (AVQ) for non-sparse signals in the modified discreet cosine transform (MDCT) domain. This paper also proposes switching the adaptive spectral masking on and off depending on whether or not the target signal is non-sparse. The switching decision is based on the results of MDCT-domain sparseness analysis. When the target signal is categorized as non-sparse, the masking level of the target MDCT coefficients is adaptively controlled using spectral envelope information. The performance of the proposed method, as a part of ITU-T G.711.1 Annex D, is evaluated in comparison with conventional AVQ. Subjective listening test results showed that the proposed method improves sound quality by more than 0.1 points on a five-point scale on average for speech, music, and mixed content, which indicates significant improvement.

A photovoltaic (PV)-assisted CMOS rectifier was developed for efficient energy harvesting from ambient radio waves as one example of the synergistic energy harvesting concept. The rectifier operates truly synergistically. A pn junction diode acting as a PV cell converts light energy to DC bias voltage, which compensates the threshold voltage (Vth) of the MOSFETs and enhances the radio frequency (RF) to DC power conversion efficiency (PCE) of the rectifier even under extremely low input power conditions. The indoor illuminance level was sufficient to generate gate bias voltages to compensate Vths. Although the same PV cell structure for biasing nMOS and pMOS transistors was used, photo-generated bias voltages were found to become unbalanced due to the two-layered pn junction structures and parasitic bipolar transistor action. Under typical indoor lighting conditions, a fabricated PV-assisted rectifier achieved a PCE greater than 20% at an RF input power of -20dBm, a frequency of 920MHz, and an output load of 47kΩ. This PCE value is twice the value obtained by a conventional rectifier without PV assistance. In addition, it was experimentally revealed that if symmetric biasing voltages for nMOS and pMOS transistors were available, the PCE would increase even further.

This paper studies the complexity of computing discrete logarithms over algebraic tori. We show that the order certified version of the discrete logarithm problem over general finite fields (OCDL, in symbols) reduces to the discrete logarithm problem over algebraic tori (TDL, in symbols) with respect to the polynomial-time Turing reducibility. This reduction means that if the prime factorization can be computed in polynomial time, then TDL is equivalent to the discrete logarithm problem over general finite fields with respect to the Turing reducibility.

Two classes of 3rd order correlation immune symmetric Boolean functions have been constructed respectively in [1] and [2], in which some interesting phenomena of the algebraic degree have been observed as well. However, a good explanation has not been given. In this paper, we obtain the formulas for the degree of these functions, which can well explain the behavior of their degree.

We have optimized and evaluated organic thin-film solar cell devices with a structure of graded junction. The graded junction consisting of donor and accepter materials was fabricated by varying the deposition rates of both materials with a continuous grading, using two evaporation sources of cupper phthalocyanine and fullerene as p- and n-type materials, respectively. By evaluating device characteristics, optimized device structure ITO/CuPc (10 nm)/graded layer (35 nm)/C60 (15 nm)/BCP (10 nm)/Ag (100 nm) with an efficiency of 1.36% was obtained. In the structure, short-circuit current density was the largest and existence of larger voltage dependence in current density was observed. In addition, we have measured temperature dependences of current density versus voltage characteristics in the graded organic solar cell under illumination. The carrier extraction was enhanced by changing voltage possibly due to the internal electric field of the graded junction.

A non-photorealistic rendering technique is presented for generating images such as stippling images and paper mosaic images with various shapes of paper pieces. Paper pieces are spatially arranged by using an anisotropic Lp poisson disk sampling. The shape of paper pieces is adaptively varied by changing the value of p. We demonstrate with experiments that edges and details in an input image are preserved by the pieces according to the anisotropy of their shape.

This paper introduces the basics of energy harvesters and demonstrates two specific vibratory-type energy harvesters developed at the University of Hyogo. The fabrication and evaluation results of the vibratory-type energy harvesters, which employ electrostatic and electromagnetic mechanisms, are described. The aim of developing these devices is to realize a power source for an autonomous human monitoring system. The results of harvesting from actual human activities obtained using a data logger are also described. Moreover, challenges in the power management of electronic circuitry used for energy harvesting are briefly discussed.

We demonstrated the reduced surface roughness of poly (3-hexylthiophene) (P3HT):(6,6)-phenyl-C61-butyric acid methyl ester (PCBM) thin films with different ratios fabricated by the electrospray deposition (ESD) method. Aggregated structures were observed at the lower voltage, and the uniformity became bad at the higher voltage. Anyway, the minimum root mean square (RMS) roughness was 1.46 nm by optimizing the applied voltage.

In this paper, we give some results towards the conjecture that σ2t+1l-1,2t are the only nonlinear balanced elementary symmetric Boolean functions where t and l are positive integers. At first, a unified and simple proof of some earlier results is shown. Then a property of balanced elementary symmetric Boolean functions is presented. With this property, we prove that the conjecture is true for n=2m+2t-1 where m,t (m>t) are two non-negative integers, which verified the conjecture for a large infinite class of integer n.

Compressive sensing enables quite lower sampling rate compared with Nyquist sampling. As long as the signal is sparsity in some basis, the random sampling with CS can be employed. In order to make CS applied in the practice, the Analog to Information Converter (AIC) should be involved. Based on the Limited Random Sequence (LRS) modulation, the AIC with LRS can be designed with high performance according to the fixed sparsity. However, if the sparsity of the signal varies with time, the original AIC with LRS is not efficient. In this paper, the adaptive AIC which adapts its scheme of LRS according to the variation of the sparsity is proposed and the prototype system is designed. Due to the adaption of the AIC with the scheme of LRS, the sampling rate can be further reduced. The simulation results confirm the performance of the proposed adaptive AIC scheme. The prototype system can successfully fulfil the random sampling and adapt to the variation of sparsity, which verify and consolidate the validity and feasibility for the future implementation of adaptive AIC on chip.

In this paper, we put forward a new method to construct n-variable Boolean functions with optimal algebraic immunity based on the factorization of n. Computer investigations for small values of n indicate that a class of Boolean functions constructed by the new method has a very good nonlinearity and also a good behavior against fast algebraic attacks.

Because of the algebraic attacks, a high algebraic immunity is now an important criteria for Boolean functions used in stream ciphers. In 2011, X.Y. Zeng et al. proposed three constructions of balanced Boolean functions with maximum algebraic immunity, the constructions are based on univariate polynomial representation of Boolean functions. In this paper, we will improve X.Y. Zeng et al.' constructions to obtain more even-variable Boolean functions with maximum algebraic immunity. It is checked that, our new functions can have as high nonlinearity as X.Y. Zeng et al.' functions.

Ultra-Wide-Band (UWB) devices need detect and avoid techniques in order to avoid or reduce interference to primary systems whose spectra overlap bands of the UWB systems. Some avoidance techniques require a knowledge of signal level received from the primary systems to control the transmitted power. Thus, detection schemes have to accurately estimate the primary signal level using the observed signal includes an additive noise and to provide it for the avoidance schemes. In this paper, we propose a new method to estimate the Primary Signal to Noise Ratio (PSNR) for the detection scheme. Our proposed method uses the fast Fourier transform output of a Multi-Band Orthogonal Frequency Division Multiplexing system. We generate models based on whether the primary signals are present, estimate the PSNR using a maximum likelihood criterion in each model and obtain the PSNR estimate by selecting the most preferable model using an Akaike information criterion. The propose method does not need any a priori information of the primary signal and the additive noise. By computer simulations, we evaluate an accuracy of the PSNR estimation of the proposed method.

Permutation polynomial based interleavers over integer rings, in particular quadratic permutation polynomials have been widely studied. In this letter, higher degree permutation polynomials for interleavers are considered for interleavers and permutation polynomials superior to quadratic permutation polynomials are found for some lengths.

Limited Random Sequence (LRS) is quite important for Analog-to-Information Converter (AIC) because it determines the random sampling scheme and the resultant performance. LRS is established with the elements of “0” and “1”. The “1” appears randomly in the segment of the sequence, so that the production of the original signal and LRS can be considered as the approximation of the random sampling of the original signal. The random sampling result can perfectly recover the signal with Compressive Sensing (CS) algorithm. In this paper, a high order LRS is proposed for the AIC design in Distributed Compressive Sensing (DCS), which has the following three typical features: 1) The high order LRS has the elements of integer which can indicate the index number of the sensor in DCS. 2) High order LRS can adapt to the sparsity variation of the original signal detected by each sensor. 3) Employing the AIC with high order LRS, the DCS algorithm can recover the signal with very low sampling rate, usually above 2 orders less than the traditional distributed sensors. In the paper, the scheme and the construction algorithm of high order LRS are proposed. The performance is evaluated with the application studies of the distributed sensor network and the camera picture correspondingly.

In this paper, a block-constrained trellis coded vector quantization (BC-TCVQ) algorithm is combined with an algebraic codebook to produce an algebraic trellis vector code (ATVC) to be used in ACELP coding. ATVC expands the set of allowed algebraic codebook pulse position, and the trellis branches are labeled with these subsets. The Viterbi algorithm is used to select the excitation codevector. A fast codebook search method using an efficient non-exhaustive search technique is also proposed to reduce the complexity of the ATVC search procedure while maintaining the quality of the reconstructed speech. The ATVC block code is used as the fixed codebook of AMR-NB (12.2 kbps), which reduces the computational complexity compared to the conventional algebraic codebook.

In this comment, an inequality of algebraic immunity of the sum of two Boolean functions is pointed out to be generally incorrect. Then we present some results on how to impose conditions such that the inequality is true. Finally, complete proofs of two existing results are given.

It is well known that Boolean functions used in stream and block ciphers should have high algebraic immunity to resist algebraic attacks. Up to now, there have been many constructions of Boolean functions achieving the maximum algebraic immunity. In this paper, we present several constructions of rotation symmetric Boolean functions with maximum algebraic immunity on an odd number of variables which are not symmetric, via a study of invertible cyclic matrices over the binary field. In particular, we generalize the existing results and introduce a new method to construct all the rotation symmetric Boolean functions that differ from the majority function on two orbits. Moreover, we prove that their nonlinearities are upper bounded by .

Permutation polynomial based interleavers over integer rings have recently received attention for their excellent channel coding performance, elegant algebraic properties and simplicity of implementation. In this letter, it is shown that permutation polynomial based interleavers of practical interest is decomposed into linear permutation polynomials. Based on this observation, it is shown that permutation polynomial based interleavers as well as their inverses can be efficiently implemented.

T-function is a kind of cryptographic function which is shown to be useful in various applications. It is known that any function f on F2n or Z2n automatically deduces a unique polynomial fF ∈ F2n[x] with degree ≤ 2n-1. In this letter, we study an algebraic property of fF while f is a T-function. We prove that for a single cycle T-function f on F2n or Z2n, deg fF=2n-2 which is optimal for a permutation. We also consider a kind of widely used T-function in many cryptographic algorithms, namely the modular addition function Ab(x)=x+b ∈ Z2n[x]. We demonstrate how to calculate deg Ab F from the constant value b. These results can facilitate us to evaluate the immunity of the T-function based cryptosystem against some known attacks such as interpolation attack and integral attack.