Question answering (QA) is the task of retrieving an answer in response to a question by analyzing documents. Although most of the efforts in developing QA systems are devoted to dealing with electronic text, we consider it is also necessary to develop systems for document images. In this paper, we propose a method of document image retrieval for such QA systems. Since the task is not to retrieve all relevant documents but to find the answer somewhere in documents, retrieval should be precision oriented. The main contribution of this paper is to propose a method of improving precision of document image retrieval by taking into account the co-occurrence of successive terms in a question. The indexing scheme is based on two-dimensional distributions of terms and the weight of co-occurrence is measured by calculating the density distributions of terms. The proposed method was tested by using 1253 pages of documents about the major league baseball with 20 questions and found that it is superior to the baseline method proposed by the authors.

A statistically uniform E-field is created in a reverberation chamber by moving mechanical stirrers to vary boundary conditions. The uniformity of the spatial electric-field distribution in an ideal reverberation chamber can be theoretically estimated by calculating the probability density function of its distribution. However, uniformity in an actual chamber is affected by the dimensions of the chamber and the structure of the stirrers. We experimentally and theoretically evaluated the effect of stirrers on the spatial uniformity of the average, median, and maximum electric-field distributions. When the dimensions of a chamber equipped with effective stirrers are large compared to the wavelength at the operating frequency, that is, when resonant modes above approximately 105 exist below the operating frequency, the spatial uniformity experimentally evaluated agrees well with theoretical values estimated by calculating the probability density function of their distributions.

In this paper we focus on the decoding error of the Log-Likelihood Ratio Belief Propagation (LLR-BP) decoding algorithm caused by oscillation. The decoding error caused by the oscillation is dominant in high Eb/N0 region. Oscillation of the LLR of the extrinsic value in the bit node process (ex-LLR) is propagated to the other bits and affects the whole decoding. The Ordered Statistic Decoding (OSD) algorithm is known to improve the error rate performance of the LLR-BP decoding algorithm. The OSD algorithm is performed by deciding the reliability of each bit based on a posteriori probability. In this paper we propose two decoding algorithms based on two types of oscillations of LLR for LDPC codes. One is the oscillation-based OSD algorithm with deciding the reliability of each bit based on oscillation. The other is the oscillation-based LLR-BP decoding algorithm that modifies ex-LLR based on oscillation. In the oscillation-based LLR-BP decoding algorithm, when ex-LLR oscillates, then we reduce the magnitude of this ex-LLR to reduce the effects on the other bits. Both algorithms improve the decoding errors caused by oscillation. From the computer simulations, we show that paying attention to the oscillation, we can improve the error rate performance of the LLR-BP decoding algorithm.

A method for constructing low-density convolutional (LDC) codes with the degree distribution optimized for block low-density parity-check (LDPC) codes is presented. If the degree distribution is irregular, the constructed LDC codes are also irregular. In this letter we give the encoding and decoding method for LDC codes, and study how to avoid the short cycles of LDC codes. Some simulation results are also presented.

We are developing a simple three-dimensional (3-D) display method that uses only two transparent images using luminance division displays without any extra equipment. This method can be applied to not only electronic displays but also the printed sheets. The method utilizes a 3-D visual illusion in which two ordinary images with many edges can be perceived as an apparent 3-D image with continuous depth between the two image planes, when two identical images are overlapped from the midpoint of the observer's eyes and their optical-density ratio is changed according to the desired image depths. We can use transparent printed sheets or transparent liquid crystal displays to display two overlapping transparent images using this 3-D display method. Subjective test results show that the perceived depths changed continuously as the optical-density ratio changed. Deviations of the perceived depths from the average for each observer were sufficiently small. The depths perceived by all six observers coincided well.

This paper describes two circuit techniques useful for the design of high density and high speed low cost double data rate memories. One is a highly flexible row and column redundancy circuit which allows the division of flexible row redundancy unit into multiple column redundancy unit for higher flexibility, with a new test mode circuit which enables the use of the finer pitch laser fuse. Another is a compact read data path which allows the smooth data flow without wait time in the high frequency operation with less area penalty. These circuit techniques achieved the compact chip size with the cell efficiency of 60.6% and the high bandwidth of 400 MHz operation with CL=2.5.

Next generation advanced power devices show remarkable progress in wide band-gap power devices such as silicon carbide and gallium nitride devices, as well as novel silicon devices called as super junction FETs and so on. The future direction of power electronics applications is surveyed in terms of output power density as an index of future power electronics development, instead of the power conversion efficiency, taking the device progress in sight. Over the last 30 years, the output power density of power electronics apparatuses has increased by a factor of two figures. New markets, such as a power supply for future generation CPU, a compact unit inverter and a electric vehicle-driving inverter unit, are expected to grow rapidly from 2010 to 2015 with the advance in the out power density of power converter. The possibility of power electronics innovation with progress in the output power density will be discussed in conjunction with development of next generation advanced power devices and related technologies.

The volume of mass unsolicited electronic mail, often known as spam, has recently increased enormously and has become a serious threat not only to the Internet but also to society. This paper proposes a new spam detection method which uses document space density information. Although the proposed method requires extensive e-mail traffic to acquire the necessary information, it can achieve perfect detection (i.e., both recall and precision is 100%) under practical conditions. A direct-mapped cache method contributes to the handling of over 13,000 e-mail messages per second. Experimental results, which were conducted using over 50 million actual e-mail messages, are also reported in this paper.

Density evolution has recently been used to analyze the iterative decoding of Low Density Parity Check (LDPC) codes, Turbo codes, and Serially Concatenated Convolutional Codes (SCCC). The density evolution technique makes it possible to explain many characteristics of iterative decoding including convergence of performance and preferred structures for the constituent codes. While the analytic density evolution methods were applied to LDPC codes, the simulation based density evolution methods were used for Turbo codes and SCCC due to analytic difficulties. In this paper, several density evolution ideas in the literature are used to analyze common code structures and it is shown that those ideas yield consistent results. In order to do that, we derive expressions for density evolution of SCCC with a simple 2-state constituent code. The analytic expressions are based on the sum-product and min-sum algorithms, and the thresholds are evaluated for both message passing algorithms. Particularly, for the min-sum algorithm, the density evolution with Gaussian approximation is derived and used to analyze the effect of scaling soft information. The scaling of extrinsic information slows down the convergence of soft information or avoids an overestimation effect of it and results in better performance, and its gain is maximized in particular constituent codes. Similar approaches are made for LDPC code. We show that the scaling gain is noticeable in the LDPC code as well. This scaling gain is analyzed with both density evolution and simulation performance. The expected scaling gain by density evolution matches well with the achievable scaling gain from simulation results. These results can be extended to the irregular LDPC codes based on the degree distribution for the min-sum algorithm. All density evolution algorithms used in this paper are based on the Gaussian approximation for the exchanged messages.

This paper reviews process, device and circuit technologies of high-density flash memories, whose market has grown explosively as bridge media. In this memory, programming throughput as well as low bit costs is critical issue. To meet the requirements, we have developed multi-level AG (Assist Gate)-AND type flash memory with small effective cell size and 10 MB/s programming throughput. We clarify three challenges to the multilevel flash memory in terms of operation method, high reliability for data retention, and high-speed multilevel programming. Future trends of high-density flash memories are also discussed.

In this paper, we propose a method for constructing quasi-cyclic low-density parity-check codes randomly using cyclic shift submatrices on the basis of the girth of the Tanner graphs of these codes. We consider (3, K)-regular codes and first derive the necessary and sufficient conditions for weight-4 and weight-6 codewords to exist. On the basis of these conditions, it is possible to estimate the probability that a random method will generate a (3, K)-regular code with a minimum distance less than or equal to 6, and the proposed method is shown to offer a lower probability than does conventional random construction. Simulation results also show that it is capable of generating good codes both regular and irregular.

We analyze the Lagarias-Odlyzko low-density attack precisely, and show that this low-density attack can be applied to the Chor-Rivest and the Okamoto-Tanaka-Uchiyama cryptosystemes, which are considered to be secure against the low-density attack. According to our analysis, these schemes turn out to be no longer secure against the low-density attack.

The present paper proposes differential transmission line structures on Si ULSI. Interconnect structures are examined using numerical results from a two-dimensional electromagnetic simulation (Ansoft, 2D Extractor). The co-planar and diagonal-pair lines are found to have superior characteristics for gigahertz signal propagation through long interconnects. The proposed diagonal-pair line can reduce the crosstalk noise and interconnect resource concurrently.

Recently, low-density parity-check (LDPC) codes have attracted much attention. LDPC codes can achieve the near Shannon limit performance like turbo codes. For the LDPC codes, the reduced complexity decoding algorithms referred to as uniformly most powerful (UMP) BP- and normalized BP-based algorithms were proposed for BPSK on an additive white Gaussian noise (AWGN) channel. The conventional BP and BP-based algorithms can be applied to BPSK modulation. For high bit-rate transmission, multilevel modulation is preferred. Thus, the BP algorithm for multilevel modulations is proposed in . In this paper, we propose the BP algorithm with reduced complexity for multilevel modulations, where the first likelihood of the proposed BP algorithm is modified to adjust multilevel modulations. We compare the error rate performance of the proposed algorithm with that of the conventional algorithm on AWGN and flat Rayleigh fading channels. We also propose the UMP BP- and normalized BP-based algorithms for multilevel modulations on AWGN and flat Rayleigh fading channels. We show that the error rate performance of the proposed BP algorithm is almost identical to that of the algorithm in, where the decoding complexity of the proposed BP algorithm is less than that of the algorithm in. We also show that the proposed BP-based algorithms can achieve the good trade-off between the complexity and the error rate performance.

In order to improve the critical current density (Jc) of c-axis-oriented EuBa2Cu3O7 (c-EBCO) thin films deposited on R-plane sapphires (R-Al2O3) with a CeO2 buffer layer, insertion of an Sm2O3 buffer layer and optimization of its deposition condition were attempted. The effects of substrate temperature and film thickness of an Sm2O3 buffer layer on the orientation, crystallinity, surface morphology and superconducting properties of EBCO thin films were examined. As a result, EBCO thin films with Jc = 5.7 MA/cm2 at 77.3 K were obtained on a sapphire with a CeO2(80 )Sm2O3(200 ) buffer layer. Epitaxial relations of sputter-deposited films were clarified.

In this letter, we propose the Low-Density Parity-Check (LDPC) coded Orthogonal Frequency Division Multiplexing (OFDM) systems to improve the error rate performance of OFDM. We also evaluate the iterative decoding performance on both an AWGN and a frequency-selective fading channels. We show that when the energy per information bit to the noise power spectral density ratio Eb/N0 is not small, the LDPC coded OFDM (LDPC-COFDM) systems have the good error rate performance with a small number of iterations. We also show that when the Eb/N0 is small, the BER of the LDPC-COFDM systems is worse than that of the Turbo coded OFDM (TCOFDM) systems, while when the Eb/N0 is not small, the BER of the LDPC-COFDM systems is better with a small number of iterations.

Space-time transmit diversity (STTD) and space-time block coding (STBC) are attractive techniques for high bit-rate and high capacity transmission. The concatenation scheme of turbo codes and STBC (Turbo-STBC) was proposed and it has been shown that the Turbo-STBC can achieve the good error rate performance. Recently, low-density parity-check (LDPC) codes have attracted much attention as the good error correcting codes achieving the near Shannon limit performance like turbo codes. The decoding algorithm of LDPC codes has less complexity than that of turbo codes. Furthermore, when the block length is large, the error rate performance of the LDPC codes is better than that of the turbo codes with almost identical code rate and block length. In this letter, we propose a concatenation scheme of LDPC codes and STBC. We refer to it as the LDPC-STBC. We evaluate the error rate performance of the LDPC-STBC by the computer simulation and show that the error rate performance of the LDPC-STBC is almost identical to or better than that of the Turbo-STBC in a flat Rayleigh fading channel.

Richardson and Urbanke developed a powerful method density evolution which determines, for various channels, the capacity of irregular low-density parity-check code ensembles. We develop generalized density evolution for minutely represented ensembles and show it includes conventional representation as a special case. Furthermore, we present an example of code ensembles used over binary erasure channel and binary input additive white Gaussian noise channel which have better thresholds than highly optimized ensembles with conventional representation.

To develop ultra high density magnetic recording systems, a quasi-static system with a reciprocating medium motion against a stand still head was developed for a read/write tester. Double-layered perpendicular recording media and merged GMR heads assembled on a conventional head-gimbal assembly (HGA) were applied to evaluate the read/write performances. A smooth sliding contact motion was achieved, however, the head-to-medium spacing was varied depending on the head motion direction. The spacing in the reverse running direction of the conventional head slider seems to be smaller than that of the flying height in a high-speed spin stand. A merged ring head was suitable for perpendicular magnetic recording in the case of the reverse direction sliding.

Document retrieval is a fundamental but important task for intelligent access to a huge amount of information stored in documents. Although the history of its research is long, it is still a hard task especially in the case that lengthy documents are retrieved with very short queries (a few keywords). For the retrieval of long documents, methods called passage-based document retrieval have proven to be effective. In this paper, we experimentally show that a passage-based method based on window passages is also effective for dealing with short queries on condition that documents are not too short. We employ a method called "density distributions" as a method based on window passages, and compare it with three conventional methods: the simple vector space model, pseudo relevance feedback and latent semantic indexing. We also compare it with a passage-based method based on discourse passages.