Analytical modeling and experimental investigation of laser induction hybrid rapid cladding for Ni-based WC composite coatings

Laser induction hybrid rapid cladding (LIHRC) cannot only increase the cladding efficiency, but can also eliminate porosity and cracking of ceramic–metal composite coatings. In order to obtain a deep understanding of LIHRC with rapid cladding speed and high powder deposition rate, an analytical model of LIHRC for Ni-based WC composite coatings is proposed in the paper. The predictions of cladding height and powder efficiency obtained with this model are in good agreement with experimental results. Injection angles at which the attenuation rate of laser power is relatively low are identified and crack-free composite coatings with smooth surface, good profile and metallurgical bonding to substrate can be obtained. The calculated results for the temperature of the powder particles are compared to experimental data of the microhardness profiles and show a similar trend.     

Photonic instantaneous microwave frequency measurement based on two different phase modulation to intensity modulation conversions

A novel photonic technique for instantaneous frequency measurement of microwave signal based on phase modulation to intensity modulation conversion is proposed and demonstrated. In the proposed system, an optical carrier is modulated by a microwave signal with its frequency to be measured through a phase modulator. The phase-modulated optical signal is then converted to intensity-modulated signals in two independent paths using a dispersive media and a frequency discriminator respectively. Since the dependence of the received microwave power on the input microwave frequency in the two paths differs, the microwave power ratio between the two paths can be used to uniquely determine the microwave frequency. The major advantages of the approach lie in that only one laser source and the bias-free phase modulator is employed in the system, which improves the stability of the system. Experimental demonstrations of the frequency measurement based on the proposed approach are presented.     

Percolative effects and giant dielectric tunability of BaTiO3–LuFe2O4 composites

We report on exotic dielectric properties of composite materials consisting of traditional ferroelectric BaTiO₃ and electronic ferroelectric LuFe₂O₄. The composites were synthesized by a simple ceramic processing method with properties that can be tailored by adjusting LuFe₂O₄ concentration. A percolative effect was observed at the volume fraction of ～0.26, which led to an abrupt increase in the dielectric permittivity. For composites with high LuFe₂O₄ fractions, a giant dielectric tunability was observed over a broad temperature interval, which is in strong contrast to traditional ferroelectrics.     

Knockout reaction mechanism studied by 6He projectile

Knockout reaction experiment was carried out by using the ⁶He beams at 61.2 MeV/u impinging on a CH₂ target. The α core fragments at forward angles were detected in coincidence with the recoiled protons at larger angles. From this exclusive measurement the valence nucleon knockout mechanism and the core knockout mechanism can be distinguished by the relation between the polar angles of the core fragments and the recoiled protons, respectively. It is demonstrated that the core knockout mechanism may result in some strong contamination to the real invariant mass spectrum.

     

16O+natS全熔合激发函数

在入射能量为55—75MeV的范围内,借助于位置灵敏的△E-E望远镜系统测量了¹⁶O+^natS反应的全熔合激发函数并做了讨论分析,提取了模型参数.激发函数存在着粗结构,其峰位分别为EcM=38、43、48MeV.     

High power nano-LiMn2Oa cathode materials with high-rate pulse discharge capability for lithium-ion batteries＊

Nano-LiMn2O4 cathode materials with nano-sized particles are synthesized via a citric acid assisted sol-gel route. The structure, the morphology and the electrochemical properties of the nano-LiMn204 are investigated. Compared with the micro-sized LiMn2O4, the nano-LiMn2O4 possesses a high initial capacity （120 mAh/g） at a discharge rate of 0.2 C （29.6 mA/g）. The nano-LiMn2O4 also has a good high-rate discharge capability, retaining 91% of its capacity at a discharge rate of 10 C and 73~ at a discharge rate of 40 C. In particular, the nano-LiMn2O4 shows an excellent high-rate pulse discharge capability. The cut-off voltage at the end of 50-ms pulse discharge with a discharge rate of 80 C is above 3.40 V, and the voltage returns to over 4.10 V after the pulse discharge. These results show that the prepared nano-LiMn2O4 could be a potential cathode material for the power sources with the capability to deliver very high-rate pulse currents.     

Holographic imaging of full-color real-existing three-dimensional objects with computer-generated sequential kinoforms

We propose a computational method for generating sequential kinoforms of real-existing full-color threedimensional (3D) objects and realizing high-quality 3D imaging.The depth map and color information are obtained using non-contact full-color 3D measurement system based on binocular vision.The obtained full-color 3D data are decomposed into multiple slices with RGB channels.Sequential kinoforms of each channel are calculated and reconstructed using a Fresnel-diffraction-based algorithm called the dynamicpseudorandom-phase tomographic computer holography (DPP-TCH).Color dispersion introduced by different wavelengths is well compensated by zero-padding operation in the red and green channels of object slices.Numerical reconstruction results show that the speckle noise and color-dispersion are well suppressed and that high-quality full-color holographic 3D imaging is feasible.The method is useful for improving the 3D image quality in holographic displays with pixelated phase-type spatial light modulators (SLMs).     

HL－1装置中LHCD和等离子体参数的关系

本文研究了在ＨＬ－１托卡马克的不同放电阶段的低混杂波驱动特性。给出了驱动电流及驱动效率和等离子体参数，如电子平均密度ｎｅ、等离子体电流Ｉｐ及纵向磁场的关系。也给出和分析了波驱动和入射波功率的关系。在放电平段，对正反向驱动效率进行了研究和比较。     

Characterization of Cr‐doped Sb2Te3 films and their application to phase‐change memory

Phase‐change memory (PCM) is regarded as one of the most promising candidates for the next‐generation nonvolatile memory. Its storage medium, phase‐change material, has attracted continuous exploration. Along the traditional GeTe–Sb₂Te₃ tie line, the binary compound Sb₂Te₃ is a high‐speed phase‐change material matrix. However, the low crystallization temperature prevents its practical application in PCM. Here, Cr is doped into Sb₂Te₃, called Cr–Sb₂Te₃ (CST), to improve the thermal stability. We find that, with increase of the Cr concentration, grains are obviously refined. However, all the CST films exhibit a single hexagonal phase as Sb₂Te₃ without phase separation. Also, the Cr helps to inhibit oxidation of Sb atoms. For the selected film CST_10.5, the resistance ratio between amorphous and crystalline states is more than two orders of magnitude; the temperature for 10‐year data retention is 120.8 °C, which indicates better thermal stability than GST and pure Sb₂Te₃. PCM cells based on CST_10.5 present small threshold current/voltage (4 μA/0.67 V). In addition, the cell can be operated by a low SET/RESET voltage pulse (1.1 V/2.4 V) with 50 ns width. Thus, Cr–Sb₂Te₃ with suitable composition is a promising novel phase‐change material used for PCM with high speed and good thermal stability performances. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)