Reading Channel Research Articles

Power efficient MoS2 synaptic devices based on Maxwell–Wagner interfacial charging in binary oxides

Synaptic devices with tunable weight hold great promise in enabling non-von Neumann architecture for energy efficient computing. However, conventional metal-insulator-metal based two-terminal memristors share the same physical channel for both programming and reading, therefore the programming power consumption is dependent on the synaptic resistance states and can be particularly high when the memristor is in the low resistance states. Three terminal synaptic transistors, on the other hand, allow synchronous programming and reading and have been shown to possess excellent reliability. Here we present a binary oxide based three-terminal MoS2 synaptic device, in which the channel conductance can be modulated by interfacial charges generated at the oxide interface driven by Maxwell-Wagner instability. The binary oxide stack serves both as an interfacial charge host and gate dielectrics. Both excitatory and inhibitory behaviors are experimentally realized, and the presynaptic potential polarity can be effectively controlled by engineering the oxide stacking sequence, which is a unique feature compared with existing charge-trap based synaptic devices and provides a new tuning knob for controlling synaptic device characteristics. By adopting a three-terminal transistor structure, the programming channel and reading channel are physically separated and the programming power consumption can be kept constantly low (∼50 pW) across a wide dynamic range of 105. This work demonstrates a complementary metal oxide semiconductor compatible approach to build power efficient synaptic devices for artificial intelligence applications.

Theoretical study of a memory-based optical converter with degenerate Zeeman states

Coherent optical memory based on electromagnetically induced transparency (EIT) offers a convenient way to convert the frequency or polarization of an optical probe pulse by storing in one $\mathrm{\ensuremath{\Lambda}}$ system and retrieving in another $\mathrm{\ensuremath{\Lambda}}$ system. We present a theoretical study on the efficiency variation of such an EIT-memory-based optical converter in an atomic system with degenerate Zeeman states. Based on the Maxwell-Bloch equation, we obtain an approximate analytic solution for the converted light pulses which clarifies that two major factors affect the efficiency of the converted pulses. The first one is the finite bandwidth effect of the pulses and the difference in the delay-bandwidth product of the writing and reading channel due to the difference in the transition dipole moment. The second one is the mismatch between the stored ground-state coherence and the ratio of the Clebsch-Gordan coefficients for the probe and control transition in the reading channel, which results in a nonadiabatic energy loss. To correspond to real experimental conditions, we also perform a numerical calculation of the variation in conversion efficiency versus the Zeeman population distribution under the Zeeman-state optical pumping in storing a ${\ensuremath{\sigma}}^{+}$-polarized pulse and retrieving with ${\ensuremath{\sigma}}^{\ensuremath{-}}$ polarization in cesium atoms. Our work provides essential physical insights and quantitative knowledge for the development of a coherent optical converter based on EIT-memory.

Group-based Latent Dirichlet Allocation (Group-LDA): Effective audience detection for books in online social media

Most current book recommendation and marketing strategies in online social media are implemented by creating topics or posting advertisements for the brand. They do not precisely target the audiences who are interested in these books, so the recommendation or marketing quality is not guaranteed. In order to solve this problem, we propose an effective audience detection method based on Group-based Latent Dirichlet Allocation (Group-LDA) in order to precisely detect book audiences. Group-LDA is a new probabilistic topic model derived from Latent Dirichlet Allocation (LDA), which introduces a new latent concept of group to describe the topic relevance among documents by incorporating book module and book chapter information into the model. Group-LDA is evaluated on Weibo.com with fifty popular books randomly sampled from the reading channel on Douban.com. According to the evaluation results, Group-LDA can effectively detect different types of readers for most categories of books. It outperforms LSA, LDA, author-topic model (ATM) and some other collaborative filtering methods in terms of precision, recall, F1-score and MAP for book audience detection.

Assessing the Performance of a Novel Tag-based Reader-to-Reader Communication Paradigm under Noisy Channel Conditions

The widespread deployment of radio frequency identification (RFID) tags and readers paved the way for research activities focused on applications that go well beyond the mere identification of people and goods. In this context, the paper investigates an innovative paradigm, according to which the residual data storage capacity of passive RFID tags is used as a kind of “virtual” communication channel to exchange data in RFID ecosystems of the Internet of Things (IoT). The performance of the paradigm is assessed through the evaluation of a number of important communication parameters, such as goodput and delay. The analytical study, validated through simulations, evaluates the impact that the following key parameters have on the system performance: 1) radio channel errors; 2) collisions; 3) number of involved readers; 4) memory block reading size under noisy channel conditions; and 5) heterogeneous storage capacity of available tags. This allows obtaining design directives for a well-performing implementation of the proposed communication paradigm. In particular, accounting for the negative effects of channel errors on the system goodput, in this paper, we highlight the relationship between optimal memory reading block size and channel errors to maximize the communication performance.

Information cascades in online reading: an empirical investigation of panel data

Purpose – The purpose of this paper is to examine information cascades in the context of users’ e-book reading behavior and differentiate it from alternative factors that lead to herd behavior, such as network externalities and word-of-mouth effects. Design/methodology/approach – This paper constructed panel data using information concerning 226 e-books in 30 consecutive days from Sina.com’s reading channel (Book.Sina.com.cn) from October 2, 2013, to October 31, 2013 of the same year in China. A multinomial logit market-share model was employed. Findings – E-books’ ranking has a significant impact on their market share, as predicted by informational cascades theory. Higher ranking e-books’ clicks will see a greater increase as a result of an increase in clicks ranking. Due to the information cascades effect, review volume had no impact on the market share of popular e-books. Total votes had a powerful impact on the market share of e-books, showing that once information cascade occurred, it could be enhanced by the increase in total votes. The total clicks of e-books had a significant impact on their market share, suggesting that online reading behavior would be influenced by network externalities. Practical implications – As important information, the ranking or popularity of e-books should be carefully considered by online reading web sites, publishers, and authors. It is not enough for the authors and publishers of e-books to simply pay attention to the content. They should design their marketing strategies to allow network externalities and informational cascades to work for them, not against them. Online reading web sites should also focus on eliminating certain behavior, such as “brush clicks” and “brush votes,” in order to prevent an undesirable information cascade due to false information. Originality/value – To the best of the knowledge, this is the first study to examine information cascades in the context of users’ e-book reading behavior. Moreover, this study can help other researchers by utilizing a large sample of daily data from one of the earliest online reading platforms in China.

Spatial transport of atomic coherence in electromagnetically induced absorption with a paraffin-coated Rb vapor cell.

We report the spatial transport of spontaneously transferred atomic coherence (STAC) in electromagnetically induced absorption (EIA), which resulted from moving atoms with the STAC of the 5S(1/2) (F = 2)-5P(3/2) (F' = 3) transition of (87)Rb in a paraffin-coated vapor cell. In our experiment, two channels were spatially separate; the writing channel (WC) generated STAC in the EIA configuration, and the reading channel (RC) retrieved the optical field from the spatially transported STAC. Transported between the spatially separated positions, the fast light pulse of EIA in the WC and the delayed light pulse in the RC were observed. When the laser direction of the RC was counter-propagated in the direction of the WC, we observed direction reversal of the transported light pulse in the EIA medium. Furthermore, the delay time, the magnitude, and the width of the spatially transported light pulse were investigated with respect to the distance between the two channels.

An Equalized Partial Response Multidimensional Detector for Perpendicular Magnetic Recording Channels

Recently, a multidimensional detector for magnetic recording channels has been proposed in order to better exploit the high media noise due to jitter and pulse broadening. The ideal scheme implementation is based on a bank of receiver filters matched to a Taylor approximation of the reading channel model. In this paper, the performance of a sub-optimal Baud-spaced multidimensional detector is evaluated for perpendicular channel systems, where the matched filters are replaced by partial response equalizers. Simulation results look promising, showing that the proposed detector may outperform the standard monodimensional linear predictor detector despite its suboptimal realization.

Approach of Improving Disk Performance to High-Quality Gap Control in Near-Field Optical Disk Drive System

Near-field technology has been expected as one of the promising techniques for increasing the recording density in an optical storage disk system since it was introduced. In a near-field optical disk drive system (NFDD), the gap between a disk and a solid immersion lens (SIL) is required to be less than one-tenth laser wavelength with a high accuracy in order to generate an evanescent wave for reading or writing a signal. This is because the gap performance has detrimental effects on the RF amplitude vibration in a reading channel and on the signal laser peak power vibration in a writing channel. In this study, we first clarify whether specific disk resonances cause the deterioration of the gap performance in the NFDD. We then demonstrate an approach of improving the disk mechanical performance in order to achieve a highly precise gap performance. Finally, we investigate a high-performance gap servo system by utilizing the disk substrate suitable for the NFDD.

Dosimetry of ultrasoft x-rays (1.5 keV AlKα) using radiochromatic films and colour scanners

This work explores the possibility of measuring the absorbed dose of ultrasoft x-rays (USX, 1.5 keV AlKα) with GAFCHROMIC® HD-810 radiochromatic dosimetry films (HD-810 films) and colour scanners. HD-810 films were exposed to USX, soft x-rays (14.8 keV) and γ-rays (60Co) for various times. The response of HD-810 films to absorbed doses of γ-rays in water was calibrated with Fricke dosimetry and used for the calibration of USX. The optical density of the HD-810 films was quantified with an HP ScanJet 6100C scanner and Corel Picture Paint 7. The choice of the reading channel and colour adjustment settings were optimized to either improve sensitivity or expand the measurable dose range. The response of the HD-810 films to the absorbed dose in water decreased by 50% when the effective photon energy decreased from 1.25 MeV to 14.8 keV. The ratio of the mass energy absorption coefficient of the active layer of HD-810 films to that of water was found to play a major role in this decrease. The mean absorbed doses of the active layer of the HD-810 films exposed to USX were derived. The calculation of the initial photon fluence rate and the mean absorbed doses of USX to biological samples such as plasmid DNA is discussed. This study suggests that radiochromatic dosimetry films are promising secondary dosimeters for measuring the absorbed dose of USX.

Large area thin film semiconductor detectors using multichannel counting Castor readout chip

The performance of charged particle counters associating thin diamond or amorphous silicon (a-Si) detectors to Castor VLSI analog-digital circuits for the fabrication of large area detectors are reported. The 20 /spl mu/m thick semiconductor detectors were synthesised using the chemical vapour deposition (CVD) technique. Detectors of 2.5/spl times/2.5 cm/sup 2/ area were segmented in 32 sub-areas of 13 mm/sup 2/ in order to limit the electronic noise per reading channel. The 32 channel circuit was used to record the counting rate and the total number of counts on each segment. Such detection systems were tested under alpha particles (/sup 241/Am) as well as under low energy beta particles (/sup 14/C). The results show that large area detection systems can readily be fabricated at low cost by the association of an application specific readout chip (ASIC) with chemically vapour deposited semiconductor detectors.

Le “déjà vu": élaboration d’un modèle d’approche hypothétique

Although psychiatric literature abounds in allusions to the phenomenon of ‘dÉjÀ vu’, few communications were devoted to an analysis of this interesting psychological state. After a short review of the ‘dÉjÀ vu’ conditions, the author proposes a model consisting of two channels. Under normal conditions, the first deals with the reading of information already stored, and the second, the engrammic channel, will store future information. The ‘dÉjÀ vu’ condition is produced when the reading channel and the engrammic channel meet in the same area. This mechanism can explain the various etiological possibilities of ‘dÉjÀ vu’, ranging from more or less ordinary cases such as fatigue or anguish to the most important etiology which is a psychotic process.