Hyperspectral image compression based on lapped transform and Tucker decomposition

In this paper, we present a hyperspectral image compression system based on the lapped transform and Tucker decomposition (LT-TD). In the proposed method, each band of a hyperspectral image is first decorrelated by a lapped transform. The transformed coefficients of different frequencies are rearranged into three-dimensional (3D) wavelet sub-band structures. The 3D sub-bands are viewed as third-order tensors. Then they are decomposed by Tucker decomposition into a core tensor and three factor matrices. The core tensor preserves most of the energy of the original tensor, and it is encoded using a bit-plane coding algorithm into bit-streams. Comparison experiments have been performed and provided, as well as an analysis regarding the contributing factors for the compression performance, such as the rank of the core tensor and quantization of the factor matrices.     

Particle Swarm Optimization inspired by starling flock behavior

Swarm intelligence is a meta-heuristic algorithm which is widely used nowadays for efficient solution of optimization problems. Particle Swarm Optimization (PSO) is one of the most popular types of swarm intelligence algorithm. This paper proposes a new Particle Swarm Optimization algorithm called Starling PSO based on the collective response of starlings. Although PSO performs well in many problems, algorithms in this category lack mechanisms which add diversity to exploration in the search process. Our proposed algorithm introduces a new mechanism into PSO to add diversity, a mechanism which is inspired by the collective response behavior of starlings. This mechanism consists of three major steps: initialization, which prepares alternative populations for the next steps; identifying seven nearest neighbors; and orientation change which adjusts velocity and position of particles based on those neighbors and selects the best alternative. Because of this collective response mechanism, the Starling PSO explores a wider area of the search space and thus avoids suboptimal solutions. We tested the algorithm with commonly used numerical benchmarking functions as well as applying it to a real world application involving data clustering. In these evaluations, we compared Starling PSO with a variety of state of the art algorithms. The results show that Starling PSO improves the performance of the original PSO and yields the optimal solution in many numerical benchmarking experiments. It also gives the best results in almost all clustering experiments.     

Generation of a 50-tone optical frequency comb with a tone-to-noise ratio larger than 37 dB

By inserting an asymmetric Mach–Zehnder interferometer (AMZI) into the re-circulating frequency shift loop, we experimentally obtained a 50-tone optical frequency comb with a tone-to-noise ratio larger than 37 dB. The simulation and experimental results show that the amplified spontaneous emission (ASE) noise of the optical frequency comb can be suppressed by 3 dB after the first loop, and the tone-to-noise ratio of the 50-tone optical frequency comb is enhanced by 23.5 dB compared to that without the AMZI.     

A cross-layer elastic CAC and holistic opportunistic scheduling for QoS support in WiMAX

QoS provisioning is an important issue in the deployment of broadband wireless access networks with real-time and non-real-time traffic integration. An opportunistic MAC (OMAC) combines cross-layer design features with opportunistic scheduling scheme to achieve high system utilization while providing QoS support to various applications. A single scheduling algorithm cannot guarantee all the QoS requirements of traffics without the support of a suitable CAC and vice versa. In this paper, we propose a cross-layer MAC scheduling framework and a corresponding opportunistic scheduling algorithm in tandem with the CAC algorithm to support QoS in WiMAX point-to-multipoint (PMP) networks. Extensive experimental simulations have been carried out to evaluate the performance of our proposal. The simulation results show that our proposed solution can improve the performance of WiMAX networks in terms of packet delay, packet loss rate and throughput. The proposed CAC scheme can guarantee the admitted connections to meet their QoS requirements.     

Dynamics range enhancement in digital fringe projection technique

In this paper a new approach to enhance the dynamic range of a fringe projection system for measuring 3D profile of objects with wide variation in their optical reflections is proposed. The high dynamic range fringe images are acquired by recursively controlling the intensity of the projection pattern at pixel level based on the feedback from the reflected images captured by the camera. A four step phase shifting algorithm combined with a quality guided algorithm is used to obtain the unwrapped phase map of the object from the acquired high dynamic range fringe images. Simulation and experimental results show that the proposed technique can accurately measure the 3D profile of objects with wide variation in their optical reflectivity.     

Reduction of radial magnetic fields in HTS solenoids with different constraint conditions

The critical current of HTS solenoid is heavily dependent on the value of radial magnetic fields in the coil winding section: the higher radial magnetic field in the winding section, the lower critical current of HTS solenoid is. So, we need to reduce the radial magnetic field components of the solenoid as much as possible to get high performance HTS magnet. In this paper we investigate various HTS coil shapes, obtained from the optimum algorithm, in which the radial magnetic field components are minimized. Three different constraints were used during optimization calculation: (1) fixed magnet volume condition, (2) fixed center magnetic field condition, and (3) maximum magnetic energy storage condition. The calculated results using those three different constraints showed almost similar shapes to one another and turned out to be effective to reduce the radial magnetic fields in the winding section. Finally, it is pointed out that two or three sectioned multi-magnet shape, which can be deduced from the calculated shape, could be more optimal to reduce the radial magnetic field in the coil, and more practical to fabricate.     

Density-matrix-formalism based scheme for polarization mode dispersion monitoring and compensation in optical fiber communication systems

We propose a density-matrix-formalism based scheme to study polarization mode dispersion (PMD) monitoring and compensation in optical fiber communication systems. Compared to traditional monitoring and compensation schemes based on the PMD vector in the Stokes space, the scheme we proposed requires no auxiliary matrices and can be handily extended to any higher-dimensional modal space, which is advantageous in mode-division multiplexing (MDM) systems. A 28 GBaud polarization division multiplexing quadrature phase-shift keying (PDM-QPSK) coherent simulation system is built to demonstrate that our scheme can implement the monitoring and compensation of 170 ps large differential-group-delay (DGD) that far exceeds the typical DGDs in practical optical communication systems. The results verify the effectiveness of the density-matrix-formalism based scheme in PMD monitoring and compensation, thus pave the way for further applications of the scheme in more general MDM optical communication systems.     

Improvement of viewing angle dependence of the white organic light emitting diodes with tandem structure by introduction of nanoporous polymer films

We fabricated nanoporous polymer films (NPFs) with different pore size distribution [e.g., P1 (3000–5000 nm), P2 (1000–1200 nm), and P3 (300–500 nm)] by using simple spin coating process and utilized those NPFs as a viewing angle compensation layer for white organic light emitting diodes (WOLEDs) with tandem structure. In this research, all NPFs could alleviate serious peak wavelength shift according to the variation of viewing angle (e.g., up to angles of 60°). Especially, NPF with 300–500 nm air voids (P3) showed the best optical characteristic among three types of NPFs when we utilized them for WOLEDs with tandem structure. Indeed, P3 could efficiently reduce the color shift [Δ (u′, v′) of 0.0264] compared to that of WOLED without NPFs [Δ (u′, v′) of 0.0558] in Commision Internationale de l’Éclairage 1976 standards (CIE 1976), which implies such NPFs have great potential as a viewing angle compensation layer for the future.     

Overlay multi-hop FEC scheme for video streaming

Overlay networks offer promising capabilities for video streaming, due to their support for application-layer processing at the overlay forwarding nodes. In this paper, we focus on the problem of providing lightweight support at selected intermediate overlay forwarding nodes to achieve increased error resilience on a single overlay path for video streaming. We propose a novel overlay multi-hop forward error correction (OM-FEC) scheme that provides FEC encoding/decoding capabilities at intermediate nodes in the overlay path. Based on the network conditions, the end-to-end overlay path is partitioned into segments, and appropriate FEC codes are applied over those segments. Architecturally, this flexible design lies between the end-to-end and hop-by-hop paradigms, and we argue that it is well suited to peer-based overlay networks. We evaluate our work by both simulations and controlled Planet-Lab network experiments. These evaluations show that OM-FEC can outperform a pure end-to-end strategy up to 10–15 dB in terms of video peak signal-to-noise ratio (PSNR), and can be much more efficient than a heavyweight hop-by-hop strategy.     

Morphology modulation of organic photovoltaics with block copolymer additive based on rational design strategies

Organic photovoltaics are a promising alternative to silicon-based solar cells with benefits of low-cost production and large scalability. However, its performance is restricted by a non-equilibrium phase-separated morphology. Additive compositions of block copolymer P3HT-b-PFTBT are most likely to mix up and form donor and acceptor morphologies. The parallel bulk-heterojunction model was proposed to show the characteristic photovoltaic parameters and the effect of the parallel cascading heterojunction formation made up of isolated PCBM acceptor domains. We demonstrate block copolymer-based stretchable solar cells on plastic foil substrates, with good power conversion efficiency. To compare the efficiency and stretchability, organic photovoltaic devices were constructed using P3HT/PC₆₁BM, PTB7/PC₇₁BM and P3HT/P3HT-b-PFTBT/PCBM active layer combinations. We find that through rational design of the component ratio, the block-copolymer-based solar cell can withstand tensile strain up to 37%.