This study focuses on speaker adaptation techniques for Computer-Assisted Language Learning (CALL). We first investigate the effects and problems of Maximum Likelihood Linear Regression (MLLR) speaker adaptation when used in pronunciation evaluation. Automatic scoring and error detection experiments are conducted on two publicly available databases of Japanese learners' English pronunciation. As we expected, over-adaptation causes misjudgment of pronunciation accuracy. Following the analysis, we propose a novel method, Regularized Maximum Likelihood Regression (Regularized-MLLR) adaptation, to solve the problem of the adverse effects of MLLR adaptation. This method uses a group of teachers' data to regularize learners' transformation matrices so that erroneous pronunciations will not be erroneously transformed as correct ones. We implement this idea in two ways: one is using the average of the teachers' transformation matrices as a constraint to MLLR, and the other is using linear combinations of the teachers' matrices to represent learners' transformations. Experimental results show that the proposed methods can better utilize MLLR adaptation and avoid over-adaptation.

Some new generalized cyclotomic sequences defined by C. Ding and T. Helleseth are proven to exhibit a number of good randomness properties. In this paper, we determine the defining pairs of these sequences of length pm (p prime, m ≥ 2) with order two, then from which we obtain their trace representation. Thus their linear complexity can be derived using Key's method.

A self-calibrating per-pin phase adjuster, which does not require any feedback from the slave chip and a multi-phase clock in the master and slave chips, is proposed for a high speed parallel chip-to-chip interface with a source synchronous double data rate (DDR) signaling. It achieves not only per-pin phase adjustment but also 90° phase shift of a strobe signal for a source synchronous DDR signaling. For this self-calibration, the phase adjuster measures and compensates the only relative mismatched delay among channels by utilizing on-chip time-domain reflectometry (TDR). Thus, variable delay lines, finite state machines, and a test signal generator are additionally required for the proposed phase adjuster. In addition, the power-gating receiver is used to reduce the discontinuity effect of the channel including parasitic components of chip package. To verify the proposed self-calibrating per-pin phase adjuster, the transceivers with 16 data, strobe, and clock signals for the interface with a source synchronous DDR signaling were implemented by using a 60 nm 1-poly 3-metal CMOS DRAM process with a 1.5 V supply. Each phase skew between Strobe and 16 Data was corrected within 0.028UI at 1.6-Gb/s data rate in a point-to-point channel.

In this letter, we generalize the binary sequence introduced by Li et al. in [S. Q. Li et al., On the randomness generalized cyclotomic sequences of order two and length pq, IEICE Trans. Fund, vol. E90-A, no.9, pp.2037-2041, 2007] to sequence over arbitrary prime fields. Furthermore, the auto-correlation distribution and linear complexity of the proposed sequence are presented.

We propose a multiuser MIMO precoding algorithm that combines the block Tomlinson-Harashima precoding and the vector perturbation (BTHP-VP). BTHP-VP supports multi-stream transmission without additional estimation of each user's effective channel and achieves full spatial diversity. Computer simulations show that BTHP-VP can achieve similar sum rate and improved BER performance compared to the BTHP with maximum likelihood receiver.

Recently, network coding (NC) has been popularly applied to wireless networks in order to improve scarce wireless capacity. In wireless LANs, NC can be applied to packet retransmission, and a base station can simultaneously retransmit multiple packets destined to different wireless stations by a single retransmission trial. On the other hand, NC creates additional packet delay at both base station and wireless stations, and hence, packet transfer delay may increase seriously. However, existing NC-based retransmission methods do not consider this additional delay explicitly. In addition, when the number of flows is small, NC exhibits less benefit because the chances of NC-based retransmission are highly reduced. Therefore, in this paper, we propose a novel NC-based retransmission method in order to improve packet transfer delay and jitter of received packets. Moreover, to achieve further improvement of delay, jitter and retransmission efficiency even when there exist a small number of traffic flows, we propose a retransmission method in which NC-based retransmission cooperates with the typical ARQ method. We overcome the disadvantage of NC-based retransmission by combining with ARQ cooperatively. Finally, we show the effectiveness of the proposed methods by extensive computer simulation.

This paper investigates the relationship between averaged SAR (Specific Absorption Rate) over 10 g mass and temperature elevation in Japanese numerical anatomical models when devices are mounted on the body. Simplifying the radiation source as a half-wavelength dipole, the generated electrical field and SAR are calculated using the FDTD (Finite-Difference Time-Domain) method. Then the bio-heat equation is solved to obtain the temperature elevation due to the SAR derived using the FDTD method as heat source. Frequencies used in the study are 900 MHz and 1950 MHz, which are used for mobile phones. In addition, 3500 MHz is considered because this frequency is reserved for IMT-Advanced (International Mobile Telecommunication-Advanced System). Computational results obtained herein show that the 10 g-average SAR and the temperature elevation are not proportional to frequency. In addition, it is clear that those at 3500 MHz are lower than that at 1950 MHz even though the frequency is higher. It is the point to be stressed here is that good correlation between the 10 g-average SAR and the temperature elevation is observed even for the body-worn device.

Clock gating is the insertion of control signal for registers to switch off unnecessary clock signals selectively without violating the functional correctness of the original design so as to reduce the dynamic power consumption. Commercial EDA tools usually have a mechanism to generate clock gating logic based on the structural method where the control signals specified by designers are used, and the effectiveness of the clock gating depends on the specified control signals. In the research, we focus on the automatic clock gating logic generation and propose a method based on the candidate extraction and control signal selection. We formalize the control signal selection using linear formulae and devise an optimization method based on BDD. The method is effective for circuits with a lot of shared candidates by different registers. The method is applied to counter circuits to check the co-relation with power simulation results and a set of benchmark circuits. 19.1-71.9% power reduction has been found on counter circuitsafter layout and 2.3-18.0% cost reduction on benchmark circuits.

Multi-pattern matching is a key technique for implementing network security applications such as Network Intrusion Detection/Protection Systems (NIDS/NIPSes) where every packet is inspected against tens of thousands of predefined attack signatures written in regular expressions (regexes). To this end, Deterministic Finite Automaton (DFA) is widely used for multi-regex matching, but existing DFA-based researches have claimed high throughput at an expense of extremely high memory cost, so fail to be employed in devices such as high-speed routers and embedded systems where the available memory is quite limited. In this paper, we propose a parallel architecture of DFA called Parallel DFA (PDFA) taking advantage of the large amount of concurrent flows to increase the throughput with nearly no extra memory cost. The basic idea is to selectively store the underlying DFA in memory modules that can be accessed in parallel. To explore its potential parallelism we intensively study DFA-split schemes from both state and transition points in this paper. The performance of our approach in both the average cases and the worst cases is analyzed, optimized and evaluated by numerical results. The evaluation shows that we obtain an average speedup of 100 times compared with traditional DFA-based matching approach.

The Firing Squad Synchronization Problem (FSSP), one of the most well-known problems related to cellular automata, was originally proposed by Myhill in 1957 and became famous through the work of Moore [1]. The first solution to this problem was given by Minsky and McCarthy [2] and a minimal time solution was given by Goto [3]. A significant amount of research has also dealt with variants of this problem. In this paper, from a theoretical interest, we will extend this problem to number patterns on a seven-segment display. Some of these problems can be generalized as the FSSP for some special trees called segment trees. The FSSP for segment trees can be reduced to a FSSP for a one-dimensional array divided evenly by joint cells that we call segment array. We will give algorithms to solve the FSSPs for this segment array and other number patterns, respectively. Moreover, we will clarify the minimal time to solve these problems and show that there exists no such solution.

In this paper, we calculate autocorrelation of new generalized cyclotomic sequences of period pn for any n > 0, where p is an odd prime number.

We succeeded to develop a reference light source in the range of very low luminance using a double integrating sphere system, and calibrated a commercial spectrophotometer below 110-5 cd/m2 levels, which is 1/100 lower than the specified limit for measurement. And we improved measurements in the ultra low luminance range of displays using the calibrated commercial spectrophotometer and a dark sphere to suppress the influence of the surround.

An algorithm is formulated for reconstructing a dielectric cylinder with the use of the T-matrix and the singular value decomposition (SVD) and is discussed through numerical examples under noisy conditions. The algorithm consists of two stages. At the first stage the measured data of scattered waves is transformed into the T-matrix. At the second stage we reconstruct the cylinder from the T-matrix. The singular value decomposition is applied in order to separate the radiating and the nonradiating currents, and the radiating current is directly obtained from the T-matrix. The nonradiating current and the object are reconstructed by decreasing a residual error of the current in the least square approximation, where linear equations are solved repeatedly. Some techniques are used in order to reduce the calculation time and to reduce the effects of noise. Numerical examples show us that the presented approach is simple and numerically feasible, and enables us to reconstruct a large object in a short time.

The rapid growth of IT technology has enabled ship navigation and automation systems to gain better functionality and safety. However, they generally have their own proprietary structures and networks, which makes interfacing with and remote access to them difficult. In this paper, we propose a total ship service framework that includes a ship area network to integrate separate system networks with heterogeneity and dynamicity, and a ship-shore communication infrastructure to support a remote monitoring and maintenance service using satellite communications. Finally, we present some ship service systems to demonstrate the applicability of the proposed framework.

Effects of atomic hydrogen annealing (AHA) on the film properties and the electrical characteristics of pentacene organic thin-film transistors (OTFTs) are investigated. The surface energy of SiO2 surface and grain size of pentacene film were decreased with increasing AHA treatment time. For the treatment time of 300 s, pentacene film showed the (00l) and (011') orientation and high carrier mobility in spite of small crystal grain.

This paper presents a novel method of enhancing esophageal speech using statistical voice conversion. Esophageal speech is one of the alternative speaking methods for laryngectomees. Although it doesn't require any external devices, generated voices usually sound unnatural compared with normal speech. To improve the intelligibility and naturalness of esophageal speech, we propose a voice conversion method from esophageal speech into normal speech. A spectral parameter and excitation parameters of target normal speech are separately estimated from a spectral parameter of the esophageal speech based on Gaussian mixture models. The experimental results demonstrate that the proposed method yields significant improvements in intelligibility and naturalness. We also apply one-to-many eigenvoice conversion to esophageal speech enhancement to make it possible to flexibly control the voice quality of enhanced speech.

The proposed automated scoring system for English writing tests provides an assessment result including a score and diagnostic feedback to test-takers without human's efforts. The system analyzes an input sentence and detects errors related to spelling, syntax and content similarity. The scoring model has adopted one of the statistical approaches, a regression tree. A scoring model in general calculates a score based on the count and the types of automatically detected errors. Accordingly, a system with higher accuracy in detecting errors raises the accuracy in scoring a test. The accuracy of the system, however, cannot be fully guaranteed for several reasons, such as parsing failure, incompleteness of knowledge bases, and ambiguous nature of natural language. In this paper, we introduce an error-weighting technique, which is similar to term-weighting widely used in information retrieval. The error-weighting technique is applied to judge reliability of the errors detected by the system. The score calculated with the technique is proven to be more accurate than the score without it.

A digital spiking neuron is a wired system of shift registers that can generate spike-trains having various spike patterns by adjusting the wiring pattern between the registers. Inspired by the ultra-wideband impulse radio, a novel theoretical synthesis method of the neuron for application to spike-pattern division multiplex communications in an artificial pulse-coupled neural network is presented. Also, a novel heuristic learning algorithm of the neuron for realization of better communication performances is presented. In addition, fundamental comparisons to existing impulse radio sequence design methods are given.

Energy efficiency is one of the most important attributes in sensor network protocols. In sensor nodes, communication related activities consume the major share of battery energy. Therefore, judicious choice of transmit power and frame size are very important to maximize the energy efficiency and hence the lifetime of nodes. While there have been a few recent studies on transmit power control implementation in sensor nodes, no report has thoroughly investigated transmit power control and the effect of its interplay with frame size on nodal energy saving. In this paper, we report our implementation of automatic transmit power control in wireless sensor nodes based on open loop parameters -- namely, link layer frame size, and close loop parameters -- namely, number of consecutive positive acknowledgments and receive signal strength. Our extensive indoor and outdoor experimental results show that, for low to moderate transmission distances, transmit power control has the energy saving benefit, and the larger the frame size the more the energy saving. At a higher transmission distance or at a more error-prone communication scenario, transmit power control as well as a large frame size are detrimental to energy saving performance. The results from this study could be useful in deciding power control strategies and optimum frame length.

This paper proposes and investigates a distributed adaptive contention window adjustment algorithm based on the transmission history for wireless LANs called the transmission-history-based distributed adaptive contention window adjustment (THAW) algorithm. The objective of this paper is to reduce the transmission delay and improve the channel throughput compared to conventional algorithms. The feature of THAW is that it adaptively adjusts the initial contention window (CWinit) size in the binary exponential backoff (BEB) algorithm used in the IEEE 802.11 standard according to the transmission history and the automatic rate fallback (ARF) algorithm, which is the most basic algorithm in automatic rate controls. This effect is to keep CWinit at a high value in a congested state. Simulation results show that the THAW algorithm outperforms the conventional algorithms in terms of the channel throughput and delay, even if the timer in the ARF is changed.