Non-compressive wideband spectrum sensing with sub-Nyquist sampling rates

In this paper, we propose a low complexity and reliable wideband spectrum sensing technique that operates at sub-Nyquist sampling rates. Unlike the majority of other sub-Nyquist spectrum sensing algorithms that rely on the Compressive Sensing (CS) methodology, the introduced method does not entail solving an optimisation problem. It is characterised by simplicity and low computational complexity without compromising the system performance and yet delivers substantial reductions on the operational sampling rates. The reliability guidelines of the devised non-compressive sensing approach are provided and simulations are presented to illustrate its superior performance. © 2013 IEEE.

Dynamics of microcystins-LR and -RR in the phytoplanktivorous silver carp in a sub-chronic toxicity experiment

A sub-chronic toxicity experiment was conducted to examine tissue distribution and depuration of two microcystins (microcystin-LR and microcystin -RR) in the phytoplanktivorous filter-feeding silver carp during a course of 80 days. Two large tanks (A, B) were used, and in Tank A, the fish were fed naturally with fresh Microcystis viridis cells (collected from a eutrophic pond) throughout the experiment, while in Tank B, the food of the fish were M. viridis cells for the first 40 days and then changed to artificial carp feed. High Performance Liquid Chromatography (HPLC) was used to measure MC-LR and MC-RR in the M. viridis cells, the seston, and the intestine, blood, liver and muscle tissue of silver carp at an interval of 20 days. MC-RR and MC-LR in the collected Microcystis cells varied between 268-580 and 110-292 mug g(-1) DW, respectively. In Tank A, MC-RR and MC-LR varied between 41.5-99.5 and 6.9-15.8 mug g(-1) DW in the seston, respectively. The maximum MC-RR in the blood, liver and muscle of the fish was 49.7, 17.8 and 1.77 mug g(-1) DW, respectively. No MC-LR was detectable in the muscle and blood samples of the silver carp in spite of the abundant presence of this toxin in the intestines (for the liver, there was only one case when a relatively minor quantity was detected). These findings contrast with previous experimental results on rainbow trout. Perhaps silver carp has a mechanism to degrade MC-LR actively and to inhibit MC-LR transportation across the intestines. The depuration of MC-RR concentrations occurred slowly than uptakes in blood, liver and muscle, and the depuration rate was in the order of blood > liver > muscle. The grazing ability of silver carp on toxic cyanobacteria suggests an applicability of using phytoplanktivorous fish to counteract cyanotoxin contamination in eutrophic waters. (C) 2003 Elsevier Ltd. All rights reserved.

Sub-nanosecond silicon-on-insulator optical micro-ring switch with low crosstalk

We demonstrate a sub-nanosecond electro-optical switch with low crosstalk in a silicon-on-insulator (SOI) dual-coupled micro-ring embedded with p-i-n diodes. A crosstalk of -23 dB is obtained in the 20-mu m-radius micro-ring with the well-designing asymmetric dual-coupling structure. By optimizations of the doping profiles and the fabrication processes, the sub-nanosecond switch-on/off time of < 400 ps is finally realized under an electrical pre-emphasized driving signal. This compact and fast-response micro-ring switch, which can be fabricated by complementary metal oxide semiconductor (CMOS) compatible technologies, have enormous potential in optical interconnects of multicore networks-on-chip.

Sub-nanosecond optical switch based on silicon racetrack resonator

We experimentally demonstrate a small-size and high-speed silicon optical switch based on the free carrier plasma dispersion in silicon. Using an embedded racetrack resonator with a quality factor of 7400, the optical switch shows an extinction ratio exceeding 13 dB with a footprint of only 2.2 x 10(-3) mm(2). Moreover, a novel pre-emphasis technique is introduced to improve the optical response performance and the rise and the fall times are reduced down to 0.24 ns and 0.42 ns respectively, which are 25% and 44% lower than those without the pre-emphasis.

Numerical study of sub-wavelength plasmonic waveguide

The authors present an analysis of a plasmonic waveguide, simulated using a two-dimensional finite-difference time-domain technique. With the surface structures located on the surface of the metal, the device is able to confine and guide light waves in a sub-wavelength scale. And two waveguides can be placed within 150 nm (similar to 6% of the incident wavelength) that will helpful for the optoelectronic integration. Within the 20 mu m simulation region, it is found that the intensity of the guided light at the interface is roughly two to four times the peak intensity of the incident light, and the propagation length can reach approximately 40 Pm at the wavelength of 2.44 mu m. (c) 2007 Elsevier B.V. All rights reserved.

Time-resolved photoluminescence of sub-monolayer InGaAs/GaAs quantum-dot-quantum-well heterostructures

Time-resolved photoluminescence (PL) of sub-monolayer (SML) InGaAs/GaAs quantum-dot-quantum-well heterostructures was measured at 5 K for the first time. The radiative lifetime of SML quantum dots (QDs) increases from 500 ps to 800 ps with the increase of the size of QDs, which is related to the small confinement energy of the excitons inside SML QDs and the exciton transfer from smaller QDs to larger ones through tunneling. The rise time of quantum-dot state PL signal strongly depends on the excitation power density. At low excitation power density, the rise time is about 35 ps, the mechanism of carrier capture is dominated by the emission of longitudinal-optical phonons. At high excitation power density, the rise time decreases as the excitation density increases, and Auger process plays an important role in the carrier capture. These results are very useful for understanding the working properties of sub-monolayer quantum-dot devices.

Detect the sub-wavelength data by applying a very-small-aperture laser

We present a theoretical and experimental research about applying a very-small-aperture laser (VSAL) to detect sub-wavelength data. Near-field distribution of a VSAL, which is essential for the application of such near-field devices, will be affected by the sample or fiber posited in the near-field region of the aperture. When the device is applied to detect the sub-wavelength data, the real resolution depends on the near-field spot size, the divergent angle of the beam and the distance from the aperture to the sample. Experimental results, including the near-field detection of the spot and detection of the sub-wavelength data by using the VSAL, are presented in this paper. We realize the two dimensional scanning about the sub-wavelength data (with the width 600 nm) by employing a VSAL with a 300 nm x 300 nm aperture.

Neuro-Stimulus Chip with Photodiodes Array for Sub-retinal Implants

A prototype neuro-stimulus chip for sub-retinal implants in blind patients affected by Age-related Macular Degeneration (AMD) or Retinitis Pigmentosa (RP) is presented in this paper. This retinal prosthetic chip was designed to replace the degenerated photoreceptor cells, and in order to stimulate directly the remaining healthy layers of retinal neurons. The current stimulus circuits are monolithic integrated with photodiodes (PD) array, which can convert the illumination on the eyes into bi-phasic electrical pulses. In addition, a novel charge cancellation circuit is used to discharge the electrodes for medical safty. The prototype chip is designed and fabricated in HJTC 0.18 mu m N-well CMOS 1P6M Mix-signal process, with a +/- 2.5 V dual voltage power supply.

An algorithm of analysis tools on points distribution in high dimension space: The distance of a point and an infinite sub-space

This paper discusses the algorithm on the distance from a point and an infinite sub-space in high dimensional space With the development of Information Geometry([1]), the analysis tools of points distribution in high dimension space, as a measure of calculability, draw more attention of experts of pattern recognition. By the assistance of these tools, Geometrical properties of sets of samples in high-dimensional structures are studied, under guidance of the established properties and theorems in high-dimensional geometry.

Sub-wavelength beam lasers with surface plasmon structures

The simulation of a plasmonic very-small-aperture laser is demonstrated in this paper. It is an integration of the surface plasmon structure and very-small-aperture laser (VSAL). The numerical results demonstrate that the transmission field can be confined to a spot with subwavelength width in the far field (3.5 mu m far from the emitting surface), and the output power density can be enhanced over 30 times of the normal VSAL. Such a device can be useful in the application of a high resolution far-field scanning optical microscope.

Gas-bearing fluid influx sub-system for gas hydrate geological system in Shenhu Area, Northern South China Sea

Based on the comprehensive interpretation and study of the Neogene fracture system and diapiric structure, it can be concluded that the diapiric structures, high-angle fractures and vertical fissure system are the main gas-bearing fluid influx sub-system for gas hydrate geological system in Shenhu Area, northern South China Sea. The Neogene fractures widely developed in the study area may be classed into two groups: NW (NNW)-trending and NE (NNE)-trending. The first group was active in the Late Miocene, while the second one was active since the Pliocene. The NE (NNE)-trending fractures were characterized by lower activity strength and larger scale, and cut through the sediment layers deposited since the Pliocene. Within the top sediment layers, the high-angle fracture and vertical fissure system was developed. The diapiric structures display various types such as a turtle-back-like arch, weak piercing, gas chimney, and fracture (or crack, fissure). On the seismic profile, some diapiric structures show the vertical chimney pathway whose top is narrow and the bottom is wide, where some ones extend horizontally into pocket or flower-shaped structures and formed the seismic reflection chaotic zones. Within the overlying sediment layers of the diapiric structure, the tree branch, flower-shaped high-angle fractures and vertical fissures were developed and became the pathway and migration system of the gas-bearing fluid influx. In the study area, the diapiric structures indicate a high temperature/over pressure system ever developed. Closely associated and abundant bright-spots show the methane-bearing fluid influx migrated vertically or horizontally through the diapiric structures, high-angle fractures and vertical fissures. In the place where the temperature and pressure conditions were favor for the formation of gas hydrate, the hydrate reservoir deposition sub-system was developed.

Pulse-front matched ultra-broadband optical parametric chirped pulse amplifier for sub-12 fs pulse generation

We propose a LBO-based ultra-broadband chirped pulse optical parametric amplifier employing pulse-front-matching to yield transform-limited sub-12-fs pulses. Measurement of the maximum possible gain bandwidth for the LBO-based OPCPA demonstrates more than 60nm gain bandwidth FWHM. For the generation of TL pulses by the use of this OPCPA, a suitable combination of OPCPA and PFM is first presented. The PFM pump geometry realizes tilt-free signal amplification, and permits this OPCPA to generate TL sub-12-fs pulses.