Data Mining In Oil Price Time Series Analysis

This paper sums up the applications of statistic models such as ARCH-family models, cointegration theory and Granger causality etc in oil price time series analysis and introduces the method of data mining combined with statistic knowledge to analysis oil price time series. In addition, the paper also explains advantages, functions, relevant technologies of this method and its potential applications in hedging the oil shock risk

Research in nonlinearity of surface acoustic wave devices

Surface acoustic wave (SAW) devices are one of the indispensable components in the radio frequency (RF) front-end of mobile phones. With the development of mobile communication technology, the requirements for linear specification of devices are more and more strict. Nonlinear distortions of SAW devices have a serious influence on the application of mobile RF modules. To satisfy the strict requirement of linearity of communication system, it is necessary to understand the generation mechanism of nonlinearity and study the accurate modeling, appropriate measurement methods, and nonlinear response elimination technology. In this paper, we summarize the research progress on the nonlinearity of SAW devices in recent years from four aspects: the generation mechanism, simulation methods, measurement system, and suppression technology. The nonlinear harmonics with the nonlinear Mason equivalent circuit model are simulated. Furthermore, harmonics and intermodulation signals of SAW filters are tested by the authors. Thanks to these research studies, it is of great significance to the development of future RF front-end modules with high linear SAW devices

Inter-diffusion of Plasmonic Metals and Phase Change Materials

This work investigates the problematic diffusion of metal atoms into phase change chalcogenides, which can destroy resonances in photonic devices. Interfaces between Ge2Sb2Te5 and metal layers were studied using X-ray reflectivity (XRR) and reflectometry of metal-Ge2Sb2Te5 layered stacks. The diffusion of metal atoms influences the crystallisation temperature and optical properties of phase change materials. When Au, Ag, Al, W structures are directly deposited on Ge2Sb2Te5 inter-diffusion occurs. Indeed, Au forms AuTe2 layers at the interface. Diffusion barrier layers, such as Si3N4 or stable diffusionless plasmonic materials, such as TiN, can prevent the interfacial damage. This work shows that the interfacial diffusion must be considered when designing phase change material tuned photonic devices, and that TiN is the most suitable plasmonic material to interface directly with Ge2Sb2Te5.Comment: 23 pages, 8 figures, articl

Geometric Distribution-Based Readers Scheduling Optimization Algorithm Using Artificial Immune System

In the multiple-reader environment (MRE) of radio frequency identification (RFID) system, multiple readers are often scheduled to interrogate the randomized tags via operating at different time slots or frequency channels to decrease the signal interferences. Based on this, a Geometric Distribution-based Multiple-reader Scheduling Optimization Algorithm using Artificial Immune System (GD-MRSOA-AIS) is proposed to fairly and optimally schedule the readers operating from the viewpoint of resource allocations. GD-MRSOA-AIS is composed of two parts, where a geometric distribution function combined with the fairness consideration is first introduced to generate the feasible scheduling schemes for reader operation. After that, artificial immune system (including immune clone, immune mutation and immune suppression) quickly optimize these feasible ones as the optimal scheduling scheme to ensure that readers are fairly operating with larger effective interrogation range and lower interferences. Compared with the state-of-the-art algorithm, the simulation results indicate that GD-MRSOA-AIS could efficiently schedules the multiple readers operating with a fairer resource allocation scheme, performing in larger effective interrogation range

Improved tribological behavior of DLC films under water lubrication by surface texturing

Textured diamond-like carbon (DLC) films with the pattern of parallel grooves were developed by depositing DLC on textured stainless substrates in a PVD system. The texturing effects on tribological performance of DLC in water-lubricated condition were investigated. Results show that introducing specific patterns into DLC film not only retains the low friction coefficients, but also dramatically extends coating lifetime through affecting the coating delamination behavior and graphitization process during friction. Besides the adherence difference induced by surface texturing which could influence the delamination, another possible mechanism, ‘‘buffer stripes’’, which is characteristic of the lateral soft/hard periodical structure,was proposed by us based on the Micro Raman spectroscopy and nanoindentation analysis. Additionally, a much lower graphitization for textured DLC during friction may also be responsible for the improved wear resistance

Refractory high-entropy alloys fabricated using laser technologies: a concrete review

Refractory high-entropy alloys (RHEAs) have attracted widespread attention in recent years as multi-component alloys applied to high-temperature fields. High melting point elements endow special microstructures and properties to RHEAs, which differ from those of conventional alloys and pose a challenge to conventional fabricating technologies. Laser fabrication technologies are attractive in fabricating RHEAs since a high-power density laser beam can be used as a controllable heat source to quickly melt refractory elements and then followed by rapid cooling and solidification to optimize the dependent properties. This paper reviews recent research progress in the fabricating process and the influence of processing on microstructural evolution and phase formation of laser-fabricated RHEAs, aiming to address the use of laser technologies for improving room temperature and high-temperature properties of RHEAs, thereby providing a reference for research community. The current methods of laser fabricating RHEAs, namely selective laser melting, laser metal deposition and laser cladding, are first introduced, and then the relationships between chemical composition, microstructure and properties of RHEAs are analyzed from experimental and simulation perspectives. In addition, the microhardness, oxidation resistance, wear resistance, corrosion resistance, irradiation resistance, and biocompatibility of laser fabricated RHEAs are discussed. Finally, the critical challenges and opportunities for laser fabricating RHEAs in the research field are highlighted, based on the research perspective of this topic

The complete chloroplast genome sequence of Pennisetum centrasiaticum, a widespread grass in Tibet, China

The complete chloroplast genome of Pennisetum centrasiaticum was sequenced and reported here. The total genome size was 138,294 bp in length, containing a large single-copy region of 81,229 bp, a small single-copy region of 12,419 bp, and a pair of inverted repeat regions of 22,288 bp. The GC content of P. centrasiaticum chloroplast genome was 38.6%. It encodes a total of 119 unique genes, including 81 protein-coding genes, 34 tRNA genes, and four rRNA genes. Phylogenetic analysis showed a strong sister relationship with Cenchrus ciliaris and Cenchrus purpureus. Our findings provide fundamental information for further evolutionary and phylogenetic researches of P. centrasiaticum