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4781-4800hit(20498hit)

  • In situ Observation of Direct Electron Transfer Reaction of Cytochrome c Immobilized on ITO Electrode Modified with 10-carboxydecylphosphonic Acid by Slab Optical Waveguide Spectroscopy and Cyclic Voltammetry

    Naoki MATSUDA  Hirotaka OKABE  

     
    BRIEF PAPER

      Vol:
    E98-C No:2
      Page(s):
    152-155

    To immobilize cytochrome $c$ (cyt.,$c$) on ITO electrode with keeping its direct electron transfer (DET) activity, 10-carboxydecylphosphonic acid (10-CDPA) self-assembled monolayer (SAM) film was formed on ITO electrode. After 100 times washing process with exchanging phosphate buffer saline solution in the cell to fresh one, extit{in situ} slab optical waveguide (SOWG) absorption spectral measurement proved that about 80% of cyt.,$c$ immobilized on 10-CDPA modified ITO electrode was adsorbed on ITO electrode. Additionally SOWG spectral change of cyt.,$c$ between oxidized and reduced forms was observed with setting the ITO electrode potential at 0.3 and $-$0.3,V vs. Ag/AgCl, respectively showing DET reaction between cyt.,$c$ and ITO electrode occurred. About 30% of a monolayer coverage was estimated from the coulomb amount in the surface area of oxidation and reduction peaks on cyclic voltammetry (CV) data. CV peak current maintained 84% for ITO electrode modified with 10-CDPA SAM film after 60,min continuous scan with 0.1,V/sec from 0.3 and $-$0.3,V vs. Ag/AgCl.

  • Resource Allocation for MDC Multicast in CRNs with Imperfect Spectrum Sensing and Channel Feedback

    Shengyu LI  Wenjun XU  Zhihui LIU  Kai NIU  Jiaru LIN  

     
    PAPER-Wireless Communication Technologies

      Vol:
    E98-B No:2
      Page(s):
    335-343

    In this paper, resource-efficient multiple description coding (MDC) multicast is investigated in cognitive radio networks with the consideration of imperfect spectrum sensing and imperfect channel feedback. Our objective is to maximize the system goodput, which is defined as the total successfully received data rate of all multicast users, while guaranteeing the maximum transmit power budget and the maximum average received interference constraint. Owing to the uncertainty of the spectrum state and the non-closed-form expression of the objective function, it is difficult to solve the problem directly. To circumvent this problem, a pretreatment is performed, in which we first estimate the real spectrum state of primary users and then propose a Gaussian approximation for the probability density functions of transmission channel gains to simplify the computation of the objective function. Thereafter, a two-stage resource allocation algorithm is presented to accomplish the subcarrier assignment, the optimal transmit channel gain to interference plus noise ratio (T-CINR) setting, and the transmit power allocation separately. Simulation results show that the proposed scheme is able to offset more than 80% of the performance loss caused by imperfect channel feedback when the feedback error is not high, while keeping the average interference on primary users below the prescribed threshold.

  • Fabrication of Step-Edge Vertical-Channel Organic Transistors by Selective Electro-Spray Deposition

    Hiroshi YAMAUCHI  Shigekazu KUNIYOSHI  Masatoshi SAKAI  Kazuhiro KUDO  

     
    PAPER

      Vol:
    E98-C No:2
      Page(s):
    80-85

    Step-edge vertical channel organic field-effect transistors (SVC-OFETs) with a very short channel have been fabricated by a novel selective electrospray deposition (SESD) method. We propose the SESD method for the fabrication of SVC-OFETs based on a 6,13-bis(triisopropyl-silylethynyl) pentacene (TIPS-pentacene) semiconductor layer formed by SESD. In the SESD method, an electric field is applied between the nozzle and selective patterned electrodes on a substrate. We demonstrated that the solution accumulates on the selected electrode pattern by controlling the voltage applied to the electrode.

  • Dispersibility Evaluation of Graphene Oxides with Alkyl Chain Groups by Using Optical Transparency

    Asami OHTAKE  Seiko UCHINO  Kunio AKEDO  Masanao ERA  Koichi SAKAGUCHI  

     
    BRIEF PAPER

      Vol:
    E98-C No:2
      Page(s):
    127-128

    The numerical dispersibility measurement system was fabricated based on optical transparency to objectively evaluate undetectable dispersibility by naked eyes. The small deference of dispersibility and the dispersibility behaviors were simultaneously elucidated by the system. The abundance of octadecyl groups was also discussed from the result of dispersibility behaviors. The objective numerical evaluation is needed for precise analysis of dispersibility with respect to graphene, graphene derivatives and graphene related materials.

  • Improved Iterative Receiver for Co-channel Interference Suppression in MIMO-OFDM Systems

    Zhiting YAN  Guanghui HE  Weifeng HE  Zhigang MAO  

     
    LETTER-Communication Theory and Signals

      Vol:
    E98-A No:2
      Page(s):
    776-782

    Co-channel interference (CCI) is becoming a challenging factor that causes performance degradation in modern communication systems. The receiver equipped with multiple antennas can suppress such interference by exploiting spatial correlation. However, it is difficult to estimate the spatial covariance matrix (SCM) of CCI accurately with limited number of known symbols. To address this problem, this paper first proposes an improved SCM estimation method by shrinking the variance of eigenvalues. In addition, based on breadth-first tree search schemes and improved channel updating, a low complexity iterative detector is presented with channel preprocessing, which not only considers the existence of CCI but also reduces the computational complexity in terms of visited nodes in a search tree. Furthermore, by scaling the extrinsic soft information which is fed back to the input of detector, the detection performance loss due to max-log approximation is compensated. Simulation results show that the proposed iterative receiver provides improved signal to interference ratio (SIR) gain with low complexity, which demonstrate the proposed scheme is attractive in practical implementation.

  • Usefulness of Transmission Ellipsometric Method for Evaluation of Electro-optic Materials

    Toshiki YAMADA  Akira OTOMO  

     
    BRIEF PAPER

      Vol:
    E98-C No:2
      Page(s):
    143-146

    A transmission ellipsometric method without an aperture was recently developed to characterize the electro-optic (EO) performance of EO polymers. The method permits much simpler optical setup compared to the reflection method, and allows easy performance of the incident angle dependence measurements using a conventional glass substrate and uncollimated beam. This paper shows the usefulness of this method for a simple and reliable evaluation of the EO coefficient both for organic and inorganic EO materials, as well as analysis for uniaxial anisotropic materials.

  • A Controlled Retransmission Scheme for Burst Segmentation in OBS Networks on the Consideration of Path Relevance

    Rui HOU  Tingting HE  Mingming ZHENG  Tengyue MAO  

     
    PAPER-Systems and Control

      Vol:
    E98-A No:2
      Page(s):
    676-683

    In this paper, we propose a controlled retransmission scheme in optical burst switching (OBS) networks. Different from previous works in the literature, we set a different value to retransmission probability at each contention and propose a retransmission analytical model for burst segmentation contention resolution scheme. In addition, we consider the effect of relevance in traffic come from multiple paths. We take into account the load at each link (include the given links and the other correlated links taking traffic) due to both the fresh and the retransmitted traffic and calculate the path blocking probability and the byte loss probability (ByLP) in cases of without and with full- wavelength conversion to evaluate the network performance. An extensive simulation is proposed to validate our analytical model, and results have shown that both path blocking probability and ByLP are affected by the load and the retransmission probability in each contention along a path and the correlated traffic carried links on the path.

  • Battery-Aware Loop Nests Mapping for CGRAs

    Yu PENG  Shouyi YIN  Leibo LIU  Shaojun WEI  

     
    PAPER-Architecture

      Vol:
    E98-D No:2
      Page(s):
    230-242

    Coarse-grained Reconfigurable Architecture (CGRA) is a promising mobile computing platform that provides both high performance and high energy efficiency. In an application, loop nests are usually mapped onto CGRA for further acceleration, so optimizing the mapping is an important goal for design of CGRAs. Moreover, obviously almost all of mobile devices are powered by batteries, how to reduce energy consumption also becomes one of primary concerns in using CGRAs. This paper makes three contributions: a) Proposing an energy consumption model for CGRA; b) Formulating loop nests mapping problem to minimize the battery charge loss; c) Extract an efficient heuristic algorithm called BPMap. Experiment results on most kernels of the benchmarks and real-life applications show that our methods can improve the performance of the kernels and lower the energy consumption.

  • A Multidimensional Configurable Processor Array — Vocalise

    Jiang LI  Yusuke ATSUMARI  Hiromasa KUBO  Yuichi OGISHIMA  Satoru YOKOTA  Hakaru TAMUKOH  Masatoshi SEKINE  

     
    PAPER-Computer System

      Pubricized:
    2014/10/27
      Vol:
    E98-D No:2
      Page(s):
    313-324

    A processing system with multiple field programmable gate array (FPGA) cards is described. Each FPGA card can interconnect using six I/O (up, down, left, right, front, and back) terminals. The communication network among FPGAs is scalable according to user design. When the system operates multi-dimensional applications, transmission efficiency among FPGA improved through user-adjusted dimensionality and network topologies for different applications. We provide a fast and flexible circuit configuration method for FPGAs of a multi-dimensional FPGA array. To demonstrate the effectiveness of the proposed method, we assess performance and power consumption of a circuit that calculated 3D Poisson equations using the finite difference method.

  • Recommender System Using Implicit Social Information

    Yusheng LI  Meina SONG  Haihong E  

     
    PAPER-Data Engineering, Web Information Systems

      Pubricized:
    2014/10/29
      Vol:
    E98-D No:2
      Page(s):
    346-354

    Social recommendation systems that make use of the user's social information have recently attracted considerable attention. These recommendation approaches partly solve cold-start and data sparsity problems and significantly improve the performance of recommendation systems. The essence of social recommendation methods is to utilize the user's explicit social connections to improve recommendation results. However, this information is not always available in real-world recommender systems. In this paper, a solution to this problem of explicit social information unavailability is proposed. The existing user-item rating matrix is used to compute implicit social information, and then an ISRec (implicit social recommendation algorithm) which integrates this implicit social information and the user-item rating matrix for social recommendation is introduced. Experimental results show that our method performs much better than state-of-the-art approaches; moreover, complexity analysis indicates that our approach can be applied to very large datasets because it scales linearly with respect to the number of observations in the matrices.

  • Iterative Channel Estimation and Decoding via Spatial Coupling

    Shuhei HORIO  Keigo TAKEUCHI  Tsutomu KAWABATA  

     
    PAPER

      Vol:
    E98-A No:2
      Page(s):
    549-557

    For low-density parity-check codes, spatial coupling was proved to boost the performance of iterative decoding up to the optimal performance. As an application of spatial coupling, in this paper, bit-interleaved coded modulation (BICM) with spatially coupled (SC) interleaving — called SC-BICM — is considered to improve the performance of iterative channel estimation and decoding for block-fading channels. In the iterative receiver, feedback from the soft-in soft-out decoder is utilized to refine the initial channel estimates in linear minimum mean-squared error (LMMSE) channel estimation. Density evolution in the infinite-code-length limit implies that the SC-BICM allows the receiver to attain accurate channel estimates even when the pilot overhead for training is negligibly small. Furthermore, numerical simulations show that the SC-BICM can provide a steeper reduction in bit error rate than conventional BICM, as well as a significant improvement in the so-called waterfall performance for high rate systems.

  • Reproduction of Four-Leg Animal Gaits Using a Coupled System of Simple Hardware CPG Models

    Hayate KOJIMA  Yoshinobu MAEDA  Taishin NOMURA  

     
    LETTER

      Vol:
    E98-A No:2
      Page(s):
    508-509

    We proposed a hard-wired CPG hardware network to reproduce the gaits of four-legged animals. It should reproduce walking and bounding, and they should be switchable with each other by changing the value of only one voltage.

  • Low-Power Loop Parallelization onto CGRA Utilizing Variable Dual VDD

    Bing XU  Shouyi YIN  Leibo LIU  Shaojun WEI  

     
    PAPER-Architecture

      Pubricized:
    2014/11/19
      Vol:
    E98-D No:2
      Page(s):
    243-251

    Coarse Grained Reconfigurable Architectures (CGRAs) are promising platform based on its high-performance and low cost. Researchers have developed efficient compilers for mapping compute-intensive applications on CGRA using modulo scheduling. In order to generate loop kernel, every stage of kernel are forced to have the same execution time which is determined by the critical PE. Hence non-critical PEs can decrease the supply voltage according to its slack time. The variable Dual-VDD CGRA incorporates this feature to reduce power consumption. Previous work mainly focuses on calculating a global optimal VDDL using overall optimization method that does not fully exploit the flexibility of architecture. In this brief, we adopt variable optimal VDDL in each stage of kernel concerning their pattern respectively instead of the fixed simulated global optimal VDDL. Experiment shows our proposed heuristic approach could reduce the power by 27.6% on average without decreasing performance. The compilation time is also acceptable.

  • Approach for Constructing Public Key Encryption with Multi-Dimensional Range Query

    Yu ZHANG  Songfeng LU  Hua ZHAO  

     
    LETTER-Cryptography and Information Security

      Vol:
    E98-A No:2
      Page(s):
    754-757

    Up until now, the best public key encryption with multi-dimensional range query (PKMDRQ) scheme has two problems which need to be resolved. One is that the scheme is selectively secure. The other is that the time of decryption is long. To address these problems, we present a method of converting a predicate encryption supporting inner product (IPE) scheme into a PKMDRQ scheme. By taking advantage of this approach, an instance is also proposed. The comparison between the previous work and ours shows that our scheme is more efficient over the time complexity. Moreover, our scheme is adaptively secure.

  • A Low Complexity Fixed Sphere Decoder with Statistical Threshold for MIMO Systems

    Jangyong PARK  Yunho JUNG  Jaeseok KIM  

     
    LETTER-Digital Signal Processing

      Vol:
    E98-A No:2
      Page(s):
    735-739

    In this letter, we propose a low complexity fixed sphere decoder (FSD) with statistical threshold for multiple-input and multiple-output (MIMO) systems. The proposed algorithm is developed by applying two threshold-based pruning algorithms using an initial detection and statistical noise constraint to the FSD. The proposed FSD algorithm is suitable for a fully pipelined hardware implementation and also has low complexity because the threshold of the proposed pruning algorithm is pre-calculated and independently applied to the path without sorting operation. Simulation results show that the proposed FSD has the performance of the original FSD as well as a low complexity compared to the original FSD and other low complexity FSD algorithms.

  • Design of Elevator-Group Control System to Save Energy Consumption by Dynamically Controlling the Number of Running Cars

    Yoshiyuki SAKAMAKI  Toshiaki TANAKA  Hisashi YAMADA  Toshio SUGIHARA  

     
    INVITED PAPER

      Vol:
    E98-A No:2
      Page(s):
    612-617

    In elevator-group control, the average number of running cars should be finely adjusted by the dynamically controlling the number of running cars (DCNRC). Traffic demand in an office building varies throughout the day. In this paper, we propose a new energy-saving method for elevator-group control that adjusts the number of running cars according to the traffic demand, simulate the proposed energy-saving method under nearly real traffic demand conditions of an office building, and reduce the daily energy consumption to the target level after several days.

  • Extension of Parallel Combinatory Multicode Transmission with Constant-Amplitude Signaling and Its Theoretical Analysis

    Tatsuya OHTA  Kouji OHUCHI  

     
    PAPER

      Vol:
    E98-A No:2
      Page(s):
    528-536

    A multicode transmission (MC) system can transmit multiple data streams at one time. However, the amplitude of the transmission signal has sharp fluctuations. To avoid this problem, constant amplitude (CA) signaling schemes were studied, and some MC systems were developed such as the MC system with CA signaling (MC-CA) and the parallel combinatory MC system with CA signaling (PCMC-CA). In this paper, extension systems of PCMC-CA system are developed. In particular, two demodulation methods are discussed for the extension systems. Then, the bit error rate (BER) and data transmission rate are theoretically analyzed. The results shows that the extension systems has a better performance than the MC-CA system in both of the BER and data transmission rate.

  • Circular Polarized Optical OFDM for Optical Wireless Communication

    Kazuo HAGIHARA  Kouji OHUCHI  

     
    PAPER

      Vol:
    E98-A No:2
      Page(s):
    520-527

    As one of optical wireless Orthogonal Frequency Division Multiplexing (OFDM) systems, there is Flip-OFDM, which separates an OFDM signal into positive and negative parts and transmits them. It has good power efficiency and low hardware complexity. However, the system halves transmission efficiency compared with Direct Current-biased Optical OFDM. In this paper, Circular Polarized Optical OFDM (CPO-OFDM) is presented. This system separates OFDM signals into positive and negative parts, and it converts these signals into left-handed and right-handed polarization, and it multiplexes these signals. CPO-OFDM is analyzed with an intensity modulation/direct detection channel model which considers the change of the state of polarization owing to free space propagation. As a result of the analysis, it is shown that CPO-OFDM is a flexible system like the conventional systems by using circular polarization and it has the equivalent bit error rate (BER) and the double transmission efficiency compared with Flip-OFDM. The IM/DD channel model which considers the degree of polarization (DOP) is also shown. As for the DOP, it improves by the increase of the propagation distance. Thus, we can achieve the equivalent BER obtained with a high DOP laser even if we use a low DOP laser.

  • An All-Digital Reconfigurable Time-Domain ADC for Low-Voltage Sensor Interface in 65nm CMOS Technology

    Yu HOU  Takamoto WATANABE  Masaya MIYAHARA  Akira MATSUZAWA  

     
    PAPER

      Vol:
    E98-A No:2
      Page(s):
    466-475

    An all-digital time-domain ADC, abbreviated as TAD, is presented in this paper. All-digital structure is intrinsically compatible with the scaling of CMOS technology, and can satisfy the great demand of miniaturized and low-voltage sensor interface. The proposed TAD uses an inverter-based Ring-Delay-Line (RDL) to transform the input signal from voltage domain to time domain. The voltage-modulated time information is then digitized by a composite architecture namely “4-Clock-Edge-Shift Construction” (4CKES). TAD features superior voltage sensitivity and 1st-order noise shaping, which can significantly simplify the power-hungry pre-conditioning circuits. Reconfigurable resolution can be easily achieved by applying different sampling rates. A TAD prototype is fabricated in 65nm CMOS, and consumes a small area of 0.016mm2. It achieves a voltage resolution of 82.7µV/LSB at 10MS/s and 1.96µV/LSB at 200kS/s in a narrow input range of 0.1Vpp, merely under 0.6V supply. The highest SNR of TAD prototype is 61.36dB in 20kHz bandwidth at 10MS/s. This paper also analyzes the nonideal effects of TAD and discusses the potential solutions. As the principal drawback, nonlinearity of TAD can be compensated by the differential-setup and digital calibration.

  • High Efficiency Bidirectional DC-DC Converter Topologies for Energy Storage Systems Using High Energy Density Batteries

    Akihiko KANOUDA  Takayuki OUCHI  Takae SHIMADA  

     
    INVITED PAPER

      Vol:
    E98-A No:2
      Page(s):
    460-465

    The bidirectional DC-DC converters that are used in backup power supplies, energy storage systems, and electric vehicles, are described in this paper, because they have recently attracted a lot of attention. First, this paper shows the main use of the bidirectional DC-DC converter, the optimum circuit topology in accordance with its use, and the characteristic properties of the circuits. In addition, the expected characteristics for the next generations of power semiconductor devices for each bidirectional converter circuit are shown.

4781-4800hit(20498hit)