A Sensitivity-Enhanced Refractive Index Sensor Using a Single-Mode Thin-Core Fiber Incorporating an Abrupt Taper

A sensitivity-enhanced fiber-optic refractive index (RI) sensor based on a tapered single-mode thin-core diameter fiber is proposed and experimentally demonstrated. The sensor head is formed by splicing a section of tapered thin-core diameter fiber (TCF) between two sections of single-mode fibers (SMFs). The cladding modes are excited at the first SMF-TCF interface, and then interfere with the core mode at the second interface, thus forming an inter-modal interferometer (IMI). An abrupt taper (tens of micrometers long) made by the electric-arc-heating method is utilized, and plays an important role in improving sensing sensitivity. The whole manufacture process only involves fiber splicing and tapering, and all the fabrication process can be achieved by a commercial fiber fusion splicer. Using glycerol and water mixture solution as an example, the experimental results show that the refractive index sensitivity is measured to be 0.591 nm for 1% change of surrounding RI. The proposed sensor structure features simple structure, low cost, easy fabrication, and high sensitivity

Gas-Purged Headspace Liquid Phase Microextraction System for Determination of Volatile and Semivolatile Analytes

In order to achieve rapid, automatic, and efficient extraction for trace chemicals from samples, a system of gas-purged headspace liquid phase microextraction (GP-HS-LPME) has been researched and developed based on the original HS-LPME technique. In this system, semiconductor condenser and heater, whose refrigerating and heating temperatures were controlled by microcontroller, were designed to cool the extraction solvent and to heat the sample, respectively. Besides, inert gas, whose gas flow rate was adjusted by mass flow controller, was continuously introduced into and discharged from the system. Under optimized parameters, extraction experiments were performed, respectively, using GP-HS-LPME system and original HS-LPME technique for enriching volatile and semivolatile target compounds from the same kind of sample of 15 PAHs standard mixture. GC-MS analysis results for the two experiments indicated that a higher enrichment factor was obtained from GP-HS-LPME. The enrichment results demonstrate that GP-HS-LPME system is potential in determination of volatile and semivolatile analytes from various kinds of samples

Mark ratio modulation over pulse position modulation

Orthogonal modulation superimposes non-amplitude-modulated signals on Manchester coded or pulse position modulated amplitude shift keying (ASK) signals, allowing two traffic flows with different bit rates to be modulated on the same wavelength channel, and hence improving spectrum efficiency. Inspired by the orthogonal modulation, this paper proposes a novel modulation format, i.e., mark ratio modulation over pulse position modulation (PPM), which utilizes the mark ratio difference between the PPM symbols and the inverse PPM symbols to deliver an overlaid signal. Better than traditional orthogonal modulation, in the mark ratio modulation over PPM, both low-speed and high-speed traffic flows are modulated by ASK with no need to sacrifice the extinction ratio, while keeping the reception simple and easy. According to theoretical analysis and test, we found 4PPM is a good option, which can balance the trade-off between the PPM signal\u27s effective bit rate and the mark ratio modulated signal\u27s quality

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Bandwidth Prediction Based Resource Allocation Scheme for Low-Latency and Energy-Efficient PONs With Heterogeneous ONU Propagation Delays

To achieve low-latency and energy-efficient in a 10 Gbps Ethernet Passive Optical Network (10G-EPON) having heterogeneous Optical Network Unit (ONU) propagation delays, this article proposes a resource allocation scheme based on bandwidth requirements prediction and ONU polling sequence scheduling. By a) predicting the upstream (US) and downstream (DS) bandwidth requirements of each ONU using Long Short-Term Memory (LSTM) networks and b) arranging the ONU polling sequence and the US and DS transmission start times of each ONU based on the predicted bandwidth requirements and the ONU propagation delays, the proposed scheme minimizes bandwidth waste of the network as well as the overall operating time of each ONU. Therefore, low-latency performance is achieved, and the energy consumption of ONUs is reduced as ONU sleeping time is extended. Simulation results indicate that the proposed scheme reduces network latency and improves energy efficiency effectively. Compared to the conventional Interleaved Polling with Adaptive Cycle Time scheme that adopts the shortest propagation delay first rule and ONU doze mode, the proposed scheme can reduce the average one-way packet delay by at least 28.9%, and can reduce the per bit energy consumption by 73.7% when concerning data transmitted under the 1 ms latency constraint

Highly dispersive Ba(0.6)Sr(0.4)TiO(3) nanoparticles modified P(VDF-HFP)/PMMA composite films with improved energy storage density and efficiency

Polymer composite films with high energy density as well as high efficiency are promising dielectric materials in pulsed power systems. In improving the energy discharged efficiency, poly vinylidene fluoride-hexafluoropropylene [P(VDF-HFP)] film blended with 20 vol.% poly(methylmethacrylate) (PMMA), which has a much slimmer ferroelectric hysteresis loop, is employed as the polymer matrix. Highly dispersive Ba(0.6)Sr(0.4)TiO(3) (BST) nanoparticles with an average particle size of 12.1 nm are utilised to improve the polarisation of the blend film without sacrificing the dielectric strength. Uniform nanocomposite films with high flexibility and excellent energy-storage performance are obtained. Especially, due to the optimisation of both polymer matrix and fillers, the BST modified P(VDF-HFP)/PMMA blend films show improved breakdown strength and depressed energy loss, which leads to an enhanced energy density of 10.3 J/cm^3 at 378 kV/mm

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GPS technology provides a new powerful approach for measuring atmospheric water vapor. In this paper the experiment of observing integrated atmospheric water vapor or the precipitable water (PW) using ground-based GPS receivers performed in southwestern region of China is presented. Zenith total delay (ZPD) data are collected in a GPS network consisting of 10 stations. Time series of water vapor in one hour bins for 10 months is retrieved. The results of 3 stations in southwestern region affected by many monsoons show that the water vapor has large variability in spatial and temporal scales. The water vapor derived from GPS is compared with retrievals from the radiosondes. The GPS PW agrees well with data from radiosondes, which indicates GPS PW are correct at this locations. The difference of PW from them is larger when the humidity is higher and more variable in summer. The results of comparison with the NCEP reanalysis PW data show that they are consistent with each other. In the mountain areas where observations are few, PW from GPS can be used to validate the PW from numerical model analyses. Finally, long-term monitoring water vapor using ground-based GPS is discussing.Environmental SciencesMeteorology & Atmospheric SciencesOceanographyOpticsEICPCI-S(ISTP)

A novel artificial intelligence based wireless local area network channel access control scheme for low latency e‐health applications

Abstract To effectively support low‐latency e‐health applications, a novel artificial intelligence‐based wireless local area network (WLAN) channel access control scheme named intelligent hybrid channel access (IHCA) is proposed and studied. In the IHCA scheme, each beacon interval comprises multiple cycles, with each cycle containing a contention‐free period (CFP) and a contention period (CP). By adopting an artificial neural network (ANN) and utilizing its calculation outputs to (1) decide whether to poll a hub during the CFP and (2) determine the initial backoff count (IBC) of each hub, polling of empty hubs during CFP can be reduced, and collisions during CP can be relieved. The authors’ simulation results show that the IHCA scheme can effectively reduce latency compared to the Hybrid coordination function Controlled Channel Access (HCCA) and the Request based Polling Access (RPA) reference designs

Strongest Angle-of-Arrival Estimation for Hybrid Millimeter Wave Architecture with 1-Bit A/D Equipped at Transceivers

This paper proposes an effective strongest angles of arrival (AoAs) estimation algorithm for a hybrid millimeter wave (mmWave) communication system with 1-bit analog-to-digital/digital-to-analog converters (A/Ds) equipped at transceivers. The proposed algorithm aims to reduce the required number of estimation overheads, while maintaining the root mean square error (RMSE) of strongest AoA estimates at the base station. We obtain the quantization thresholds of A/Ds for different signal-to-noise ratios (SNRs) and numbers of antennas via numerical simulations, based on which, the strongest AoAs can be estimated with a small amount of overheads. The proposed algorithm is compared with conventional schemes including 1-bit FFT and 1-bit exhaustive search, as well as 1-bit Cramér-Rao lower bound. Simulation results verify the effectiveness of our proposed algorithm in terms of reducing estimation overheads while maintaining reasonable estimation performance in low SNRs