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We propose and experimentally demonstrate a vertical fiber interfacing interleaved angled multimode interference (MMI) coupler for wavelength-division multiplexing (WDM) applications. This four-channel WDM device comprises two 1 × 2 angled MMI couplers and a bidirectional grating-based Mach–Zehnder interferometer (MZI) structure. In the MZI optical interleaver, the uniform bidirectional grating functions as both the perfectly vertical grating coupler and the 3 dB power splitter. Benefitting from the flat-top coupling spectrum of the grating coupler, a high-uniformity wavelength-division (de)multiplexing can be achieved with a simulated insertion loss of 3.15–3.36 dB (the nonuniformity of 0.22 dB). The angled MMIs (AMMIs) are designed and optimized using the eigenmode expansion method. For wavelength matching between the MZI and AMMIs, the circuit simulation model of the interleaved AMMI is built by importing the S-parameter matrices of all the optical components extracted from the physical level simulations. The device was fabricated using standard CMOS technology and all the features were patterned with the 193-nm deep-UV lithography. Experimental results obtained without thermal tuning are in good agreement with the simulation results. The device exhibits an insertion loss of 4.5–4.65 dB (nonuniformity of 0.15 dB), channel spacing of 10 nm, and cross talk of − ( 21.62 − 26 ) d B .

Y2.85Al5-ySiyO12-(3x-y)/2Nx: Ce3+0.15 phosphors were prepared using aluminum nitride (AlN) and silica (SiO2) as the sources of N and Si by the high temperature solid state reaction method. XRD patterns of the phosphors present a pure phase but have a slight translation compared to the standard card of Y3Al5O12(YAG). The Al3+-N3- bonds and Y3+-N3- bonds were detected by the analysis of X-ray photoelectron spectroscopy (XPS). The tendency to bond with N3− ions for the cations changes from Y3+>Ce3+ to Ce3+>Y3+ for the samples introduced SiO2. Photoluminescence spectra (PL & PLE) show that the crystal field splitting (CFS) and the nephelauxetic effect (NE) play a conflicting role in spectral shifting. When x = y, NE plays a major role and the emission red shift reaches the maximum. The thermoluminescence tests (TL) confirm that temperature quenching of the phosphors is caused by the thermally-activated crossover process.

The dredger fill of Shanghai Hengsha Island Dongtan is solidified by curing agents with different fly ash content, and the shear strength index of solidified dredger fill is measured by the direct shear test. The microscopic images of solidified dredger fill are obtained by using SEM. The microscopic images are processed and analyzed by using IPP, and the fractal dimension including particle size fractal dimension Dps, aperture fractal dimension Dbs and particle surface fractal dimension Dpr is calculated by fractal theory. The quantitative analysis of the relationship between shear strength index and fractal dimension of solidified dredger fill is done. The research results show that the internal friction angle and the cohesion are closely related to the fly ash content λ and the curing period T, and the addition of fly ash can improve the effect of curing agent; There is no obvious linear relationship between the internal friction angle and the three fractal dimensions; The smaller particle surface fractal dimension Dpr and particle size fractal dimension Dps, the larger aperture fractal dimension Dbs, the greater the cohesion, and the cohesion has a good linear relationship with three fractal dimensions, and the correlation coefficient R2 is above 0.91.

Breakdown characteristics of ferroelectric glass-ceramic capacitors in the PbO-SrO-Na2O-Nb2O5-SiO2 system were studied, including under dc charging and pulse charging. Results revealed that capacitance before and after charging was with no significant alternation. Relationship between dielectric constant and electric field was also explored. Meanwhile, a peculiar phenomenon was found that the breakdown strength of glass-ceramic dielectric under pulse charging was much lower than that under dc charging, which is of considerable discrepancy to common theory. Possible explanations were summarized afterward.

In this paper, we proposed a micro-heater based on Al/Ti-film resistors for MEMS application. The film heater, designed with unique Zig-Zag configuration, has a high heating efficiency as generated Joule heat could be confined in Zig-Zag area. Consequently, much higher maximum temperature could be achieved under the lower applied voltage, compared with conventional strategy. Based on MEMS technique, thin film based micro-heater was fabricated, and experimental characterization was carried out in room temperature. Since the micro-heaters are all in the form of thin film-resistors, the structure design is simple and fabrication process compatibility is good, which is particularly suitable in the fields of MEMS integration and actuation application.

Intravascular ultrasound (IVUS) has been used for diagnosis of coronary diseases. According to the outstanding transducer performance, Ba 0.5 Na 0.5 TiO 3 (BNT)-based piezoelectric materials are good candidates for the IVUS applications. In this paper, lead-free BNT piezoelectric thick film has been used to fabricate a linear array transducer. The BNT based transducer array has a 2×16-element pattern. In the fabrication process of transducers, micro-machining technologies have been adopted. Wet etching was used to pattern the silicon substrate. The thin layers of Si 3 N 4 and SiO 2 , are used as etching masks, and patterned by reactive etching and buffered oxide etch (BOE), respectively. After that, the part of Si not covered by the patterned masks is etched by 30% KOH solution. BNT slurry prepared by mixing BNT solution and BNT powder has been deposited on the substrate by spin coating and then thermally treated to obtain the thick film. The PiezoCAD software has been employed to analyze the performance of the array, and the simulation results show that the BNT film array has a center frequency of 82.84 MHz and a −6 dB bandwidth of 46.77%.

The mechanical properties of concrete pavement were studied under the various frost-salt conditions using Capillary Suction of De-icing Chemicals and Freeze-thaw Test Method (CDF method). The test results show that: with the increasing of freeze-thaw cycles, concrete surface damage has a tendency to accelerate. The concrete which is in a 5% concentration chloride snow-thawing agent solution has the greatest impact damage after 150 frost-salt cycles compared with soaking in other different densities (3%, 20%). Mixing appropriate amount of silica fume and high-performance air-entraining agent in concrete can effectively improve the resistance of frost-salt scaling. With the frost-salt cycles increase, the concrete strength and the relative dynamic elastic modulus continues to decrease.

Discharged energy properties of PbO–SrO–Na2O–Nb2O5–SiO2 glass-ceramics with crystallization time from 1 to 1000 min were investigated by measuring their hysteresis loops (described as quasi-static measuring method) and pulse-discharge current-time curves (described as dynamic measuring method). The results show the same trend for both measuring methods: With the increment of crystallization time, the discharged energy density increases gradually, while the energy efficiency decreases. The highest energy efficiencies were obtained in the sample with crystallization time of 1 min, which are 96.3% and 82.4%, corresponding quasi-static and dynamic measurement, respectively. The reduction of energy efficiency with crystallization time is attributed to combined effect of ferroelectric polarization and interfacial polarization, and part of the corresponding energy could not release in the pulse-discharge process.

In this paper, a non-axisymmetric structure multistage depressed collector (MDC) for sheet beam vacuum electronics devices is proposed. After the beam-wave interaction, the sheet beam is incident into the new MDC, and the electron motion is rotated under the magnetic field. The electronic residual energy leads to a different radius. So, high efficiency MDC can be achieved with carefully design. At the same time, high-energy electrons bombardment of the MDC will produce secondary electrons with low energy, which can not run to the injection hole under the electric field and the magnetic field of the MDC. In addition, this collector is simple and easy-fabricated. The simulation shows that this collector efficiency of the new MDC can be up to 99.1% and the back-streaming rate is zero by optimizing these structure parameters. The research of this paper provides a design reference for further improving the overall efficiency of the sheet beam devices.

The industrial x-ray diode with high impedance configuration is usually adopted to generate repetitive x-ray, but its performance would be worsened due to lower electric field on the cathode of diode when a voltage of several hundreds of kV is applied. To improve its performance, a novel metal-ceramic cathode is proposed in this paper. Key factors (width, relative permittivity of ceramic, and so on) affecting electric field distribution on triple points are analyzed by electrostatic field calculation program, so as to optimize the design of this novel cathode. Experiments are done to study the characteristics including emission current of cathode, diode voltage duration, diode mean dynamic impedance, and diode impedance drop velocity within diode power duration. The results show that metal-ceramic cathode could improve diode performance by enhancing emission current and stabling impedance; the impedance drop velocity of diode with spoke-shaped metal-ceramic cathode was reduced to -5 Ω ns(-1) within diode power duration, comparing to -15 Ω ns(-1) with metal foil cathode.

Microarray technology has been proved to be greatly helpful for biomedical and biological diagnosis. And the evaluation of its biological applications lies in the detection sensitivity, which requires high intensity and stability of the signal. Recently, several nanomaterials, especially semiconductor nanomaterials, due to their excellent fluorescence properties, have been widely used to construct microarrays for biosensors. Here, we presented an approach for constructing CdSe/ZnS quantum dot (QD) microarray in microfluidic channels on a glass slide by photolithography. The conditions for immobilizing stable and uniform QD microarray on the glass slide were optimized. Several types of QD microarrays with different emission wavelengths and modified groups were constructed using silanization and lithography technology. Based on the fluorescence quenching effect of Cu2+ on QDs, the microfluidic chip with QD microarray was applied for the determination of Cu2+. 1 nmol/L Cu2+ could be detected by this method.

The paper presents a 500 kV all-solid-state Marx generator adopting Z type circuit. In this Marx generator, twenty-eight isolated gate bipolar transistors(IGBTs) serial modules were utilized as controllable switches. The maximum working voltage of each IGBTs module was designed as high as 22 kV, and the repetition rate at full load condition was designed as high as 200 Hz. The ladder type pulse-forming-networks (PFNs) consisting of metallized film capacitors and wound inductors were designed as energy storage and pulse-forming components. Experimental results indicate that the Marx generator can run with 500 kV output pulses and 50 Hz repetition rate in burst-mode successfully. The peak output pulse voltage of this generator is approximately the same as that of the highest power solid-state Marx generator ever reported, while the peak current is almost twice, reaching 1 000 A. The maximum pulsed power of the generator is as high as 500 MW. As the capacitors were utilized as energy storage components, the pulse width can be adjusted from 3 s to 10 s continuously.

We present a simple yet effective one-step approach with a specially designed substrate holder to synthesize single crystalline ternary CdSxSe1–x nanobelts with uniform chemical stoichiometry and accurately controllable compositions (0 ≤ x ≤ 1). The micromorphologies and detailed structures of these nanobelts were studied by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, micro-Raman spectra, and energy-dispersive X-ray spectroscopy. The elements distribution was explored using elemental mapping. All the characteristic results indicate that the nanobelts exhibit high quality single crystalline wurtzite structure. Photoluminescence spectra obtained from these nanobelts show that the near-band-edge energy can be systematically modulated in the range of 1.73 to 2.44 eV. Functional electrical application of these nanobelts was achieved by a fabricated CdSxSe1–x nanonet-field effect transistor (FET). A lower threshold voltage and a much higher ON–OFF ratio tha...

Two kinds of Photoconductive semiconductor switch(PCSSs) with bulk structure are studied experimentally, which are fabricated from semi-insulating GaAs. The first switch has a size of 10 mm×10 mm×0.6 mm, whose electrodes are 6 mm in diameter on the opposite side of the chip. The second one has a size of 15 mm×15 mm×3 mm, whose electrodes are 8 mm in diameter on the opposite side of the chip. The withstand voltage of the first switch is tested under pulse voltages with different full-width-at-half-maximum. A maximum withstand voltage of 7.6 kV is achieved, which means the breakdown electric field is 127 kV/cm. The volt-ampere performance at DC bias voltage and dark condition of the second switch is tested as well as its triggered performance. The maximum current of the switch is more th

In this paper semi-insulating GaAs photoconductive semiconductor switch(PCSS) and SiC PCSS were fabricated. Triggered by laser pulse at a wavelength of 1 064 nm, photoconductivity tests of the PCSSs were performed at different bias voltages. Dark current-voltage characteristics of GaAs PCSS and the absorption depth of GaAs with different wavelength were obtained experimentally. GaAs PCSSs both in linear mode and nonlinear mode were studied, and peculiar photoconductivity of high-power GaAs PCSS in nonlinear mode was discussed. High-power SiC PCSSs employing extrinsic photoconductivity are under development, and initial experimental results are presented in this paper.

In this study, Al–10.8Zn–2.8Mg–1.9Cu alloy was synthesized by the spray atomization and deposition technique. Microstructure and mechanical properties of the spray-deposited alloy processed through hot rolling and heat treatment were investigated by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction and tensile test. The results indicate that the microstructure of the spray-deposited alloy is mainly composed of the Al matrix and the Mg(ZnCu) 2 compounds. The fragmentation of the Mg(ZnCu) 2 phases in the alloy has been regarded as one of the main feature during hot rolling. After solution treating, the microstructure is found to be composed of the Al matrix and a spot of Al 7 Cu 2 Fe, Al 9 FeNi compounds. The spray-deposited Al–Zn–Mg–Cu alloy in the T6 temper displays superior strength due to the presence of two types of coherent GP zones (spherical GPI zones and thin platelet GPII zones).

The deformation mechanism of the spray formed 70Si30A1 alloy was studied by hot compression on a Gleeble-1500 test machine. It is shown that hot deformation of the spray formed 70Si30Al alloy is achieved by liquid flow due to isostatic pressure and movement of solid particles due to shear force. Deformation condition depends on the nucleation rate and closure rate of the cavities. The flow stress slightly varies when the difference between the nucleation rate and closure rate of the cavities is small; however, it decreases when the nucleation rate of the cavities is greater than the closure rate of the cavities.

We report the size effects on the metal-insulator phase transition of vanadium dioxide (VO2) nanowires prepared by chemical vapor deposition. The phase transition temperature can be tuned from 67 °C in the bulk VO2 to as low as 29°C by reducing the diameter of VO2 nanowires to nanoscale. Temperature-dependent Raman spectra display a clear dynamic picture on the metal-insulator phase transition process of the VO2 nanowires. Whilst, Raman study shows no remarkable strain effect on the phase transition behaviors of our samples. The increasing surface defect density with reducing nanowire size facilitates the decreasing phase transition temperature. In addition, the polarized-photocurrent effect was observed, resulting from the anisotropy of the photoresponse and also caused by the reduced dimensionality.Our results indicate that size of VO2 nanostructures can dominate their thermoelectric and photoelectrical properties.

This paper presents the microstructures and mechanical and absorbing properties of double and triple layer, cement-based, composite panels. The results obtained show that the frequency range in 2-18GHz had less than −10dB effective bandwidth, which correlates with 3.7and 10.8GHz in double and triple layer cement-based composite panels. Furthermore, the double layer panel's compressive strength at 7 and 28 days was 40.2 and 61.2MPa, respectively. For the triple layer panel, the strength values were 35.6MPa and 49.2MPa. The triple layer panel's electromagnetic wave (EMW) absorbing properties were superior compared to the properties of the double layer panel. However, the triple layer panel's mechanical performance was inferior to that of the double layer panel. This study proposes that carbon nanotubes can effectively improve the compressive strength and interface structure of cement-based composite panels.

A compact, low-jitter, and high repetitive rate all-solid-state flash x-ray generator making use of photo conductive semiconductor switches was developed recently for the diagnostic purpose of some hydrokinetical experiments. The generator consisted of twelve stages of Blumlein pulse forming networks, and an industrial cold cathode diode was used to generate intense x-ray radiations with photon energy up to 220 keV. Test experiments showed that the generator could produce >1 kA electron beam currents and x-ray pulses with ∼40 ns duration under 100 Hz repetitive rates at least (limited by the triggering laser on hand), also found was that the delay time of the cathode explosive emission is crucial to the energy transfer efficiency of the whole system. In addition, factors affecting the diode impedance, how the switching synchronization and diode impedance determining the allowable operation voltage were discussed.

Molecular dynamics simulation has been performed for investigating the glass transition of Pd-Ni alloy nanoparticles in the solidification process. The results showed that the Pd-Ni nanoparticles with composition far from pure metal should form amorphous structure more easily, which is in accordance with the results of the thermodynamic calculation. There are some regular and distorted fivefold symmetry in the amorphous Pd-Ni alloy nanoparticles. The nanoclusters with bigger difference value between formation enthalpies of solutions and glasses will transform to glass more easily than the other Pd-Ni alloy nanoclusters.

The process parameters were optimized by bead weld in high nitrogen austenitic stainless steel with 12mm thickness. High nitrogen austenitic stainless steel plates with 20mm and 40mm thickness were welded with the optimum process parameters. The mechanical properties of weld joints were inspected. The experimental results indicate that the best process parameters of bead weld are that welding current is 260 A, welding speed is 600 mm.min, the flow rate of gas is 20 L.min, and torch height is 15 mm, the angle of welding torch is 6 degree. The internal qualities of weld bead were beyond the grade and heat II -affected zone were small. The mechanical properties of welded joints were excellent. For instance, the tensile strength can achieved move 80% than that of the base metal and the impact absorbing energies also approach 50% than that of the substrate metal. The optimum process parameters can effectively solve the problem of welding process of high nitrogen steels with mid-thickness by MIG welding. Introduction High nitrogen austenitic stainless steels obtain the austenite by replacing the bulk of nickel in the traditional stainless steels with nitrogen elements. Low production costs, excellent corrosion resistance and high strength-toughness can be achieved by nitrogen alloying [1]-[6]. High nitrogen austenitic stainless steel is a developing new engineering material [7]. Its application depends not only on the excellent comprehensive properties but the welding characteristics [8][9]. In the some fields of particular application, tandem MIG welding is a widely used and high-efficiency bonding technology. Therefore, the research on tandem MIG welding process of high nitrogen austenitic stainless steels for the application and research has a very important significance. High nitrogen austenitic stainless steel with 12mm thickness was tested by bead welding, and the welding parameters of bead welding were optimized. High nitrogen austenitic stainless steel plates with 20mm and 40mm thickness were welded with the optimum process parameters. The internal qualities, mechanical properties and micro-hardness of weld joints were tested. Experimental Materials and Procedure High nitrogen austenitic stainless steel (HNS) was used in the experiment and its chemical compositions (mass fraction in percent) as showed in Tab.1. Welding wire ER309L with the diameter of 1.2mm was used to bead welding. The shielding gas consisted of 5% N2 and 95% Ar. The flow rate of gas is 20L.min. The microstructure of the HNS is austenite with a small quantity of δ-ferrite. TAB.1. Chemical compositions of the HNS Elements C Cr Mn Si N Ni Fe Mass % 0.11 21.4 14.94 0.32 0.64 1.8 Balance A Robot and the tandem MIG welding machine were used in the bead welding experiment for 12mm-thickness HNS. The middle of the HNS weld was cut by water cutting jet. The internal cracks and penetration were observed and measured by etching the weld junction with FeCl3 International Conference on Education Technology and Information System (ICETIS 2013) © 2013. The authors Published by Atlantis Press 908 hydrochloric acid solution. And then the results of weld quality were recorded in detail. Besides, high nitrogen austenitic stainless steel plates with 20mm and 40mm thickness were welded with the optimum process parameters. The butt weld groove of the samples was double-V, and the angle was 60 degree, and the width of gap was 2mm. There were four-pass weld in the sample of 20mm-thickness HNS and seven in 40mm thickness for needing more enough filler metal. An X-ray detection machine XXQ 1650 was used to check the internal quality of weld for non-destructive testing after tandem MIG welding. The standard samples of tensile and impact were prepared by water cutting jet. The micro-structure of the heat-affected zone was observed by the optical and scanning electron microscopy, and the mechanical properties and micro-hardness of weld joints were tested. Results and Discussions Experiment of Bead Welding In the welding process of HNS, the stable welding arc, small welding spatter, excellent external appearance and non-gas cavity in surface. Figure 1 shows the cross sectional morphology of bead welding. There is no obvious welding crack and the weld fusion zones are all V-shaped. Fig.1. Cross sectional morphology of bead welding The weld width, weld reinforcement and weld penetration were measured in order to further explore the effects on different welding process of weld quality. The results were shown in figure 2. From Fig.2a and Fig.2c, it can be observed that the weld width B, weld reinforcement h and weld penetration H have no change with the different torch height and the flow rate of gas. The torch height and the flow rate of gas have no effect on the weld quality. Therefore, the flow rate of gas is 20L.min and torch height is 15mm can be set as the best welding process of bead welding for reducing the waste of shielding gas and torch head burned. 160 180 200 220 240 260 280 0 2 4 6 8 10 12 14 16 18 20 weld width B weld renforcement h weld penetration H H+h(torch height 15mm) torch height10mm

Y2O3:Eu3+ phosphors co-doped with different metal cations (Li+, Na+, K+, Mg2+, Ca2+) are prepared by the gel-combustion method with Y2O3, Eu2O3, and R(NO3) x (R = Li, Na, K, Mg, Ca) serving as raw materials and glycine as fuel, calcined at 1000 °C for 2 h. The synthesized Y2O3:Eu3+ phosphors doped with different metal cations and doping ratios are characterized by x-ray diffractometry (XRD), fluorescence and phosphorescent spectrophotometer. The co-doping metal cations are advantageous to the development of Y2O3:Eu3+ lattice. All the samples can emit red light peaked at 611 nm under 254-nm excited. The luminescence intensities of co-doping samples are increased because the cations increase the electron transition probability of Eu3+ from 5D0 level to 7F level. The fluorescence lifetime of Eu3+ (5D0 → 7F2) is increased by doping metal cations.

Summary form only given. Vertical geometry PCSSs (Photoconductive Semiconductor Switches) with opposing electrical contacts were fabricated using 0.4mm thick, vanadium compensated, semi-insulating, 6H-SiC (Silicon Carbide) “c”-plane wafer. Ultrafast photocurrent waveforms were obtained when the switches were illuminated laterally by