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The dual-deck architecture with aligned upper and lower decks is considered a promising technology to meet the demand of increasing word-line (WL) layers of 3D NAND flash. However, the relevant reliability studies are still lacking for the dual-deck 3D NAND array. In this work, it is reported an abnormal program disturbance phenomena of the bottom WLs in the upper-deck, and the physical mechanisms were studied. According to experimental analysis and TCAD simulations, the un-programmed dummy WLs at the joint region can introduce excessive joint residual electrons in the channel before the program, resulting in insufficient channel self-boosting potential, which is responsible for the degraded program disturbance. Thus, a novel program scheme is proposed to alleviate the program disturbance, which has been validated by experiments. [ABSTRACT FROM AUTHOR]

The detection of temporal correlations among event-driven data streams is widely demanded in data-intensive applications such as edge computing. In this work, temporal correlation detection is enabled by the combination of 3D NAND flash and in-memory computing. Different from mathematical scheme by covariance matrix calculation, here the detection is implemented by exploiting the physical process of charge tunneling and accumulation. Thus the intrinsic charge-trapping dynamics in 3D NAND flash can be leveraged to perform in-memory computing. The computing results are stored and imprinted in the threshold voltages of the 3D NAND device array, enabling co-existence of computation and storage in the same devices. On this basis, the validation of temporal correlation detection further paves the way for 3D NAND application in high-level non-von Neumann computing. [ABSTRACT FROM AUTHOR]

A novel axial strain sensor based on an optical microfiber coupler (OMC) operating at the dispersion turning point (DTP) was designed to realize high-sensitivity measurements of axial strain. First, we explain the measurement principle of axial strain sensors based on microfiber couplers. Then, we calculate the measurements, with the theoretical calculations showing that the sensor has high sensitivity when the effective refractive index (ERI) difference between the odd and even modes in the coupling region of the OMC is equal to zero. Finally, we carried out axial tensile experiments on the OMC. The results show that the OMC has the highest axial strain sensitivity when it operates at the DTP. The maximum sensitivity is 166.9 pm/ $\mu \varepsilon $ , with a linear range of 0- $400 ~\mu \varepsilon $. The sensor is highly sensitive to axial strains and has a simple structure. It has broad application prospects in the measurement of mechanical quantities such as strain, acceleration and vibration. [ABSTRACT FROM AUTHOR]

Temporary read errors (TRE) refers to the high temporary fail bit count (FBC) in the first read, when 3D NAND recovers froman idle state. This can seriously deteriorate the Quality of Service (QoS) of 3D NAND Flash-based storage devices. The characteristics and mechanism of the TRE issue of 3D NAND Flash are investigated in this work. Based on the experimental analysis, a physicalmodel is proposed to interpret the physical mechanism of TRE. When 3D NAND array recovers from an idle state, the grain boundary traps (GBTs) discharging during the idle time lead to the low GBTs occupancy, which is responsible for the high temporary FBC in the first read. Based on the physical model, a novel approach to alleviate TRE is proposed and has been validated by experiments. [ABSTRACT FROM AUTHOR]

In this article, we demonstrate an on-demand two-step fabrication strategy for optical microfiber couplers (OMCs) with precisely controlled dispersion turning points (DTPs). Firstly, an OMC with a relatively thick width is obtained through the fusion elongation method. Secondly, the as-fabricated OMC is placed in a low-concentration hydrofluoric acid solution whose refractive index (RI) is adjusted to match that of the target working environment to fine etch the width of the OMC. During the etching process, the real-time output spectrum of the OMC is monitored in-line to track the position of the OMC. The etching process is terminated once the desired DTP appears. Our study shows that by accurately controlling the reaction time, the DTP can be tuned from 1600 to 900 nm with high precision better than 1 nm in both water and a liquid medium with a high RI of 1.365. Finally, we experimentally demonstrate that the OMC fabricated by the proposed method can work as an ultrasensitive RI sensor with a sensitivity of −1.61×105±0.15×105 nm/RIU at 1.333 and a biosensor for carcinoembryonic antigen (CEA) with a limit of detection of 2 pg/mL. [ABSTRACT FROM AUTHOR]

Latent Dirichlet Allocation (LDA) is a popular tool for analyzing discrete count data such as text and images, which are required to model datasets and a large number of topics, e.g., tens of thousands of topics for industry scale applications. Although distributed CPU systems have been used to address this problem, they are slow and resource inefficient. GPU-based systems have emerged as a promising alternative because of their high computational power and memory bandwidth. However, existing GPU-based LDA systems can only learn thousands of topics, because they use dense data structures, and have linear time complexity to the number of topics. In this article, we propose SaberLDA, a GPU-based LDA system that implements a sparsity-aware algorithm to achieve sublinear time complexity to learn a large number of topics. To address the challenges introduced by sparsity, we propose a novel data layout, a warp-based sampling kernel, an efficient sparse matrix counting method, and a fine-grained load balancing strategy. SaberLDA achieves linear speedup on 4 GPUs and is 6–10 times faster than existing GPU systems in thousands of topics. It can learn 40,000 topics from a dataset of billions of tokens in two hours, which was previously only achievable using clusters of tens of CPU servers. [ABSTRACT FROM AUTHOR]

Real-time and high-sensitivity monitoring of heavy metal ions in solution is of great significance in environmental monitoring. The traditional electrochemical methods suffer from electrochemical noise and environmental interferences for heavy metal trace detection. To address these issues, we propose a novel electrochemical surface plasmon resonance (EC-SPR) optical fiber sensor. The sensor comprises a tilted fiber Bragg grating imprinted in a commercial single-mode fiber and coated with a nanoscale gold film for high-efficiency SPR excitation. The gold-coated optical fiber serves as a working electrode, performing the dual functions of anodic stripping voltammetry and SPR optical sensing. We demonstrate detection of Pb2+ as an example of a typical heavy metal ion. We show a stable and reproducible correlation between the real-time ion deposition–stripping cycles and the optical transmission of the optical fiber, with a limit of detection of 10−10 M and a dynamic range of nearly five orders of magnitude. Moreover, by taking derivative of the SPR amplitude change, we can clearly identify the peak stripping potential of the detected ions, and therefore, realize specific ion identification. The method proposed is inherently immune to temperature cross-talk because the core mode is temperature dependent but insensitive to the surrounding media. The proposed EC-SPR fiber-optic sensor has the advantages of compact size, flexible shape, and remote operation capability, thereby, opening the way for other opportunities for electrochemical monitoring in various hard-to-reach locations and remote environments. [ABSTRACT FROM AUTHOR]

We propose and demonstrate an ultra-sensitive plasmonic fiber-optic hot-wire anemometer. This instrument comprises a highly tilted fiber Bragg grating-assisted surface plasmon resonance (SPR) sensor, which is coated with carbon nanotubes as the photothermal conversion element. The carbon nanotubes on the sensor surface efficiently convert light from the heating laser, of which wavelength matched to the SPR window, into heat, thereby setting the sensor in an elevated temperature state. Air flow draws away surface heat, thus inducing both a strong SPR wavelength shift and power modulation. Using this anemometer, we experimentally achieve a dynamic range of 0.05 to 0.65 m/s for wind speed measurement. Furthermore, we demonstrate real-time monitoring of wind speed by measuring the intensity of the heating laser. This sensor is simple and robust in structure. It has a wide range of potential applications in both scientific research and industrial production. [ABSTRACT FROM AUTHOR]

We present a systematic study on the spectral characteristics and ultrahigh sensitivity near the dispersion turning point (DTP) of optical microfiber couplers. Numerical simulations reveal that a DTP exists when the group effective refractive index (RI) difference between the even mode and the odd mode equals zero, where both ultrahigh positive RI sensitivities and negative RI sensitivities can be achieved. The position of the DTP is dependent on the coupler width, and it always exists over the surrounding RI (SRI) range of 1.333–1.41, which enables the ultrasensitive RI sensing in this wide RI range. Then, we studied the interference spectra characteristics around the DTP both theoretically and experimentally. We further experimentally demonstrate ultrahigh sensitivities of 59624 nm/refractive index unit (RIU) and −58470 nm/RIU around the SRI of 1.333 and 26999 nm/RIU and −29267 nm/RIU around the SRI of 1.35, respectively. High figure of merits of 4192 and 5280 are also achieved around the SRI of 1.333 and 1.35, respectively. Finally, utilizing the exceptional RI sensitivity, we demonstrate an ultrasensitive temperature sensor with a negative sensitivity of −15.23 nm/°C and a positive sensitivity of +16.78 nm/°C. [ABSTRACT FROM AUTHOR]