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In this study, the heat input from friction stir welding of AA2024 and AA7075 dissimilar alloys was calculated, and the relationship between the heat input and mechanical properties was studied in detail. Additionally, the effect of heat on welding was analyzed. When the welding parameters were 800 rpm-400 mm/min, the Ultimate tensile strength of the joint was at its highest (346 MPa), and the elongation was 3%. A significantly higher or lower temperature led to lower tensile strength and elongation. Too low heat input failed to deform the material completely, and the fluidity of the material formed from the two base metals was poor. Excessive heat input led to the dissolution of precipitates, grain coarsening, reduced grain bonding, and other microstructural changes. When the heat input is higher, the cooling rate is faster, which can easily cause holes at the bonding interface. In the stir zone, owing to the difference in the thermal gradient of the upper and lower parts, the bottom of the material is not softened completely owing to the lack of heat, and stress concentration occurs.

A novel scheme of optical readout based on thermo-optic cavity coupled plasmonic scattering for infrared imaging sensor is proposed to lessen the complex and bulky of existed systems using reflective or diffractive optical readout schemes. This new scheme readouts thermally-modulated back-scattering visible light signals of metallic nanostructures under large angle dark field illumination. Numerical simulation is employed to reveal the mechanisms of large temperature sensitivity and low angular sensitivity of scattering,which is attributed to the thermal-optic effects of Fabry-Perot (F-P) microcavity coupled with local surface plasmon resonance (LSPR) generated from metallic nanostructures. The feasibility of the proposed scheme is demonstrated by preliminary experiments and optical measurements. Thermal-optic modulated scattering spectra have been obtained for 3.39 μm infrared illumination and a temperature sensitivity of 0.24 nm/°C for 605~640 nm band has been reached.

Biconvex tube is prone to problems such as severe wall thickness reduction or wrinkling in hydroforming due to the big diameter-thickness ratio and large expansion ratio. In this paper, the segmented dies were employed to manufacture the biconvex tube, and the forming performance of the part under different loading paths was simulated by ABAQUS/Explicit software, then the corresponding results were obtained. The influence of loading path–related factors on the formability of the biconvex tube was analyzed by the response surface method. Based on the optimization evaluation criteria, the predicted loading path was determined to be linear loading, and the maximum axial feeding was 13 mm and the maximum internal pressure was 89 MPa.

We study the optimal harvesting policy for fishery in the marine protected and unreserved areas. In the literature, it is generally assumed that the fish population follows a concrete growth law. In contrast, we consider an abstract model with migration from the reserved area to the unreserved one. Then we examine and analyze the existence and stability of a nontrivial equilibrium point of the model. We also discuss the bionomic equilibrium. After that, we use the Pontryagin maximum principle to obtain the optimal harvest policy, where, instead of the well-known Hamiltonian function, we use the current Hamiltonian function to ease the calculation. Finally, we give some numerical examples to further illustrate our statements, where we also find that in practice the impreciseness of the parameters can influence the existence of the system positive equilibrium.

In recent years, deploying and running data-intensive workflows in cloud platform has become more and more popular in many areas. Unlike computation-intensive applications, a data-intensive workflow typically requires to deal with bulk data transferring between different resource sites, which means some traditional energy-efficiency optimization technologies are difficult to be enforced when running data-intensive workflows. In this paper, we first formulate the power model of a data-intensive workflow, which takes into account power consumption caused by data transferring. Based on this power model, we introduce a novel metric called Shortest Path in terms of Energy Consumption and design an energy-efficient heuristic scheduling algorithm, which is aiming at reducing the extra energy consumption caused by delays of bulk data transferring. Extensive experiments and performance evaluations show that the proposed scheduling algorithm can significantly reduce the overall energy consumption of running data-intensive workflows comparing with several existing algorithms. In addition, the proposed algorithm also exhibits better adaptiveness and robustness when a cloud system is facing intensive and unpredicted workloads.

Combining two or several functionalities into a single metadevice is of significant importance and attracts growing interest in recent years. We here introduce the concept of modularization design in dual-wavelength multifunctional metadevice, which is composed of a lower metasurface and an upper metasurface with an indium-tin-oxide (ITO) layer. Benefiting from the fact that ITO holds high infrared (IR) reflection while transparence at visible wavelengths, the metadevice can work in reflection and transmission modes at two very distinct wavelengths, one is 2365 nm in the IR band and the other 650 nm in the visible range. More interestingly and importantly, the two metasurface layers with different functionalities are easy to flexibly integrate into a series of dual-wavelength multifunctional metadevices, with negligible interaction between them and no need of re-designing or re-optimizing their structure parameters. Based on modularization design and functional integration, four kinds of dual-wavelength multifunctional metadevices are demonstrated, which can perform reflective deflection/focusing at 2365 nm and transmissive deflection/focusing at 650 nm. We believe our work may open a straight-forward and flexible way in designing multi-wavelength multifunctional metadevices and photonic integrated devices.

We systematically investigate the classification of incidence ways (represented by different field polarization and propagation directions of the impinging electromagnetic (EM) wave) and their influences on the EM resonant characteristics of split-ring resonators (SRRs). It is found that the resonance absorption varies noticeably with incidence ways and the variation could reach as large as 60 %, while transmittance almost keeps unchanged. When resonant electric response and resonant magnetic response are both excited in SRRs, EM resonance characteristics are found to be mainly dependent upon electric response rather than on magnetic response. The results also indicate that magnetic resonant wavelength (λH) induced by coupled magnetic field H component of the EM wave is longer than electric resonant wavelength (λE) induced by coupled electric field E, and the mechanism is discussed.

A multiplex real-time PCR method for discriminating deer and common domestic species, including cattle, goat, horse, donkey, pig, and chicken was developed. Species-specific primer pairs were designed and used to produce different size DNA fragments with diverse melting temperature (T m ) values. The specificity and sensitivity of these primer pairs were separately confirmed using simplex real-time PCR analysis. Multiplex real-time PCR analysis was performed using combined primers, yielding distinct melting curve profiles for each species. The sensitivity limit of the multiplex PCR method was evaluated. Trace DNA of other species in deer DNA could be identified. Common deer products, including blood, meat, and antler were tested using this multiplex PCR method and different species of deer and domestic animals were identified. The rapid multiplex real-time PCR assay described herein is a specific, sensitive, and reliable method for high-throughput authentication of deer and domestic animal products.

AlN buffer layer is proposed to improve the growth of AlN films on the sapphire substrate by pulsed laser deposition. The buffer layers were pre-deposited under vacuum for different time, which was aimed to suppress the negative nitridation effect in the initial growth stage, and their effects on the surface morphology, crystal structure and bandgap of AlN films were characterized. It is found that AlN-buffered films exhibit a single (0002) preferred orientation and the crystallinity improves as the pre-deposition time increases from 5 to 20 min. Al-polarity AlN films are obtained at the pre-deposition time of 5 and 10 min, while the polarity inversion from the Al- to N-polarity is observed at 20 min. Based on the analysis of optical transmittance spectra, the bandgap of AlN films decreases with increasing pre-deposition time, which may be resulted from the decrease of axial ratio c/a.

The influence of V/III ratio on the formation of quantum dots (QDs) grown by metal-organic chemical vapor deposition (MOCVD) is investigated by atomic force microscopy (AFM) and photoluminescence (PL) measurements. As V/III ratio increases, the density of QDs decreases accompanied by the transition of QD size distribution from bimodal (at V/III = 9) to single-modal (at V/III = 15), and then to bimodal (at V/III = 25) again, which is attributed to the change of the indium-species migration length at different V/III ratios. There are PL spectrum redshifts and the PL peak intensity decreases as V/III ratio increases.

Self-assembled InAs quantum dots with graded composition strain-reducing layer (SRL) grown on exact substrates were studied. It is shown that a graded In x Ga1 − x As SRL leads to growth quality improvement, emission efficiency enhancement, and wavelength blueshift. Samples grown on 2° misoriented substrates with different In contents in graded In x Ga1 − x As SRL were also investigated, and emission efficiency enhancement and wavelength blueshift were found when graded SRL was introduced and when the change rate of In content in graded In x Ga1 − x As SRL was enlarged.

A circuit model of a quantum dot semiconductor optical amplifier is proposed by employing standard rate equations. Using this model, the saturation property and dynamic performance of the quantum dot semiconductor optical amplifier are analyzed by PSPICE simulation. We also investigate wavelength conversion based on cross-gain modulation for the quantum dot semiconductor optical amplifier. The corresponding results are in agreement with the previous published works.

Blue and green dual wavelength InGaN/GaN multi-quantum well (MQW) light-emitting diode (LED) has wide applications in full color display, monolithic white LED and solid state lighting, etc. Blue and green dual wavelength LEDs, which consist of InGaN strain-reduction layer, green InGaN/GaN MQWand blue InGaN/GaN MQW, were grown by metal-organic chemical vapor deposition (MOCVD), and the luminescence properties of dual wavelength LEDs with different well arrangements were studied by photoluminescence and electroluminescence. The experimental results indicated that well position played an important role on the luminescence evolvement from photoluminescence to electroluminescence.

In recent years, the stability of hybrid stochastic delay systems, one of the important issues in the study of stochastic systems, has received considerable attention. However, the existing results do not deal with the structure of the diffusion but estimate its upper bound, which induces conservatism. This paper studies delay-dependent robust stability of hybrid stochastic delay systems. A delay-dependent criterion for robust exponential stability of hybrid stochastic delay systems is presented in terms of linear matrix inequalities (LMIs), which exploits the structure of the diffusion. Numerical examples are given to verify the effectiveness and less conservativeness of the proposed method.

The dynamics of soil animals was studied in seven representative forest communities in the north of the Da Hinggan Mountains, Northeast China. The results indicate that it was distinctive in the changes of the numbers of soil animals and groups and diversity in relationship with seasons for macrofauna and meso-micro fauna in the study area. The numbers of the observed soil animals in different months were: October>August>June. Group number was larger in August and October, but smaller in June. The change of diversity index in different months was: August>June>October. The biomass for macrofauna in different months was: October>June>August. The composition and number of each functional group was relatively stable. In the community of the predominant soil environment, the percentage of saprophagous animals was higher than carnivorous animals and herbivorous animals. The dynamics changes of saprophagous and carnivorous animals were distinctive, increasing from June to October, while the change of herbivorous animals was unremarkable.