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Development of simple and accurate methods for the detection of As

Coherent supercontinuum (SC) generation in optical fibers has spurred extensive research interest and found many applications. Here, we report a hybrid optical crystal fiber with an yttrium aluminum garnet (YAG) core. The optimized fiber features broad and flat near-zero normal dispersion and three wavelengths where the dispersion slope is zero. Through numerical modeling, we in detail investigate the influence of the pump wavelengths near the three wavelengths on the spectral broadening. The spectral broadening shows asymmetric towards the high-frequency region. The longer the pump wavelength, the more is the short wavelength components of the generated SC. Thus, the high-frequency components of the SC spectra can be engineered in the fiber. Interestingly, the occurrence of optical wave breaking (OWB) in the low-frequency region is prior to that in the high-frequency region when the pump wavelength is at 1660 nm. The broadest spectrum could be obtained when the pump wavelength is near the middle wavelength where the dispersion slope is zero. The result provides a new strategy for fiber design and broadband SC generation, which is different from the viewpoint that the broadest spectrum can be obtained when the pump wavelength near the local maximum dispersion. Combined with high nonlinearity and flat dispersion, the hybrid fiber allows octave-spanning SC generation with the pump power low to 1 kW at 1100 nm. This provides the potentials for high-power, broadband, and coherent SC generation at 1064 nm where the dispersion slope is near zero.

Development of simple and accurate methods for the detection of As3+is highly desirable and technically important. In this work, a highly sensitive and selective long-period fiber gratings sensor based on surface plasmon resonance (LPFG-SPR) was developed for As3+detection by designing glutathione-functionalized Au nanoparticles as a signal amplification tag. Based on the chemical interaction between As3+and glutathione, the self-assembling glutathione on the surface of the gold film combines selectively with As3+, and then anchors the glutathione-functionalized Au nanoparticles, which changes the refractive index of the surrounding environment, resulting in a shift of the transmission spectrum. Results show that the sensor could detect As3+with concentrations ranging from 0.02 ppb to 2 ppb. The sensor exhibited excellent specificity for As3+against other metal ions, such as Na+, K+, Fe3+, Mg2+, Cu2+, Pb2+, Ni2+, Ba2+, Ca2+, and Co3+. The fiber sensor was successfully employed to detect As3+in pond water samples, demonstrating that it has the potential for As3+detection with the advantages of low cost, high sensitivity, and a simple structure.

In Cognitive Wireless Sensor Networks(CWSN), spectrum sensing which attracts a lot of interest is a significant task, and the OFDM technology provides a good platform for CWSN because of its agile choice mechanism of frequency. This paper introduces a novel spectrum detection scheme for CWSN, which based on energy detection exploits the cyclic prefix (CP) unaffected by the effects of pollution of an orthogonal frequency division multiplexing(OFDM)symbol as well as idle period containing no information symbols. The simulation results show that the proposed algorithm has a good performance whether it is used in AWGN channels or frequency selective fading channels.

Parabolic flumes were designed in the 1994 [7] as an efficient way to provide accurate flow measurement in U-shaped channels. Three-dimensional flow fields in parabolic flumes, long-throated flumes, and Parshall flumes are simulated using the volume-of-fluid model. The hydraulic model was validated by using data of physical model testing. The velocity and turbulent kinetic energy dissipation rate in typical sections of the three measuring flumes are analyzed and the total head curves of the three flumes are obtained. The results indicate that the Parshall flume installed in a U-shaped channel leads to a high water head loss, whereas the water head loss for the parabolic flume is only 35% of that of the long-throated flume or 30% of the Parshall flume, which makes parabolic flumes more suitable for U-shaped channels. A formula for calculating discharge that is applicable to channels of various slopes is theoretically derived. Parabolic flumes are demonstrated to be accurate enough to satisfy the demands of water discharge measurement.

The intrusion detection system and technology of classified layered-wireless sensor network was able to meet the high safety requirements of wireless sensor network, it is urgent for us to improve the identification and generalization of detection system about characters of intrusion. In this paper, we design an intelligent intrusion detection system which realize intelligence, the effective and direct way was to add the methods, and it was used for identification and generalization of intrusion characters to the Agent function of intrusion detection. It could obtain credible judgment by updating and examining the database for the actions which the general misuse detection or anomaly detection were not sure if the intrusion was formed. DOI: http://dx.doi.org/10.11591/telkomnika.v11i8.2347

The model of UWB WSN(wireless sensor networks) was proposed firstly, by UWB and non-coherent detection technology, a non-coherent detection receiver for UWB WSN was designed and the transmission capacity was studied. We found it will benefit to improve the transmission capacity of the UWB wireless sensor network if employing the non-coherent detection technology.

This This paper addresses the lower and upper bound of transmission capacity of hierarchical wireless networks from the views of information theory, and draws the conclusion that the lower bound capacity is the information rate defined in the paper, and the upper bound capacity, if the wireless channel is symmetric fading in the broad sense, will not exceed the term T(n5/ 2).

The importance of multiuser detection for CDMA-based ad hoc network is addressed in this paper. Conventionally, the terminal in CDMA-based ad hoc network uses matched filter to receive packets, so the performance (e.g., throughput) of the network suffers from multi-access interference (MAI). Different from above scheme, in this paper, each terminal of the ad hoc network is equipped with an adaptive blind linear multiuser detector, so the ability of MAI-resistance is gained. Based on fully-connected network model and Log-distance path loss radio propagation model, the throughput of ad hoc network with multiuser detection is studied. Simulation results show that multiuser detection can remarkably enlarge the throughput of ad hoc network.