Novel Online Diagnostic Analysis for In-Flight Particle Properties in Cold Spraying

In cold spraying, powder particles are accelerated by preheated supersonic gas stream to high velocities and sprayed on a substrate. The particle velocities depend on the equipment design and process parameters, e.g., on the type of the process gas and its pressure and temperature. These, in turn, affect the coating structure and the properties. The particle velocities in cold spraying are high, and the particle temperatures are low, which can, therefore, be a challenge for the diagnostic methods. A novel optical online diagnostic system, HiWatch HR, will open new possibilities for measuring particle in-flight properties in cold spray processes. The system employs an imaging measurement technique called S-PTV (sizing-particle tracking velocimetry), first introduced in this research. This technique enables an accurate particle size measurement also for small diameter particles with a large powder volume. The aim of this study was to evaluate the velocities of metallic particles sprayed with HPCS and LPCS systems and with varying process parameters. The measured in-flight particle properties were further linked to the resulting coating properties. Furthermore, the camera was able to provide information about variations during the spraying, e.g., fluctuating powder feeding, which is important from the process control and quality control point of view.     

γ-聚谷氨酸高产菌株的筛选及改良酸化植烟土壤效果研究

为挖掘具有缓解植烟土壤酸化能力的微生物菌株,采用盆栽试验和大田试验相结合的方法,应用生物形态学和分子生物学筛选鉴定了γ-聚谷氨酸（γ-PGA）高产菌株并研究其对酸化植烟土壤的改良效果。结果表明：（1）从黄土高原干旱土壤中筛选得到一株谷氨酸非依赖型γ-PGA高产菌株副地衣芽孢杆菌285-3（Bacillus paralicheniformis）;（2）菌株285-3可有效缓解根系分泌物和复合肥料导致的土壤酸化,土壤pH平均提高0.3个单位以上;（3）菌株285-3配施有机肥,可显著降低酸化植烟土壤可交换酸度,对烟草青枯病的防效达到47.05%,同时提高烟叶产质量。综上所述,副地衣芽孢杆菌285-3对酸化植烟土壤有较好的改良效果,与有机肥合用具有控病和提高烟叶产质量的作用。     

Tunable microwave devices using low-sintering-temperature screen-printed barium strontium titanate (BST) thick films

A tunable microwave phase shifter composed of a low-sintering-temperature, screen-printable barium strontium titanate (BST) film and silver metallization was fabricated on an alumina substrate and co-fired at 900 °C for 3 h. The dielectric properties of the films were characterized in a frequency range of 0.8–8 GHz using scattering parameter measurements and a quasi-static coplanar waveguide transmission line model. The temperature dependency of the films was measured through capacitance measurements in a frequency range of 0.5–2.5 GHz. The figure of merit (phase shift/dB of insertion loss) of the phase shifter was found to be 14.6 at 3 GHz with an applied bias field strength of 2.5 V/μm. The performance of the phase shifter is briefly discussed and compared with other phase shifters fabricated by direct screen-printing of BST films.     

Thermoplastic 0–3 Ceramic–Polymer Composites With Adjustable Magnetic and Dielectric Characteristics for Radio Frequency Applications

Magnetic and electrical properties of thermoplastic ceramic-polymer 0–3 composites with Z-type hexaferrite, and MnZn ferrite inclusions were investigated. The complex permeability and permittivity were measured up to 1 GHz where maximum values of ɛ′_r=30.47 and μ′_r=4.32 and ɛ′_r=10.95 and μ′_r=1.80 were obtained for MnZn-ER182 and Co₂Z-ER182 composites with ∼44.7 vol% and 43.0 vol% filler loadings, respectively. MnZn and Co₂Z composites exhibit miniaturization factors as low as 0.09 and 0.23, together with reduced magnetic losses and frequency dispersion. The results indicate that the composites offer novel possibilities for wider feasible frequency bandwidth and adjustable impedance matching and magnetic and dielectric properties.     

The microstructure and its properties of Ni3Al based composite

 Composites of B-doped ductile Ni₃Al alloy matrix with no-oxide WC ceramic powders were produced by mechanical alloying, half-sintering and build-up welding. WC powders form non-continuous hardening phases, which are distributed in Ni₃Al matrix, wetting well with the matrix. The hardness and the structure stability are retained to temperatures of at least 850°C. After build-up welding, most of the NiAl phase left after sintering was changed into other phases and some graphite was precipitated in the matrix. The sand-laden water wear test showed expected results. Received: 12 October 1998/Accepted: 2 November 1998     

遥感模糊图像分割与像元分析

卫星遥感对地观测获取的图像信息其像元的数据往往是多种地表成分的复合，因此地表反射、辐射反映在像元上就带有一定的模糊性。基于模糊数学的理论和方法，同时利用了TM（1，2，3；4，5，7）对六个波段的数据信息，对一幅图像进行非监督分割，并用模糊算法对单个像无所隶属的各聚类中心的成分进行了数值分析。结果显示出尽管分割后一些像元属同一类别，但其复合成分则不尽相同。该方法对于TM像无分析精度的可靠性有待地面工作的进一步验证。     

低温等离子体对低密度聚乙烯材料的表面改性

用低温等离子体对 LDPE 进行表面改性,工作气体和处理时间对改性效果有重要影响。经等离子体处理后,LDPE 表面的接触角减小,表面能增加,尤其是其中的极性分量显著增加,粘接强度提高22—29倍。XPS 分析表明表面引进了极性基团。     

高分散系高传质好氧生化系统的研究与实践

本文探讨了均匀受限曝气的机理 ,并通过在一汽污水厂进行的运行对比研究 ,充分表明了该法处理有机废水效率高、能耗低、出水好、切实可行     

Graphene Microbolometers with Superconducting Contacts for Terahertz Photon Detection

We report on noise and thermal conductance measurements taken in order to determine an upper bound on the performance of graphene as a terahertz photon detector. The main mechanism for sensitive terahertz detection in graphene is bolometric heating of the electron system. To study the properties of a device using this mechanism to detect terahertz photons, we perform Johnson noise thermometry measurements on graphene samples. These measurements probe the electron–phonon behavior of graphene on silicon dioxide at low temperatures. Because the electron–phonon coupling is weak in graphene, superconducting contacts with large gap are used to confine the hot electrons and prevent their out-diffusion. We use niobium nitride leads with a \(T_\mathrm {c}\approx 10\)  K to contact the graphene. We find these leads make good ohmic contact with very low contact resistance. Our measurements find an electron–phonon thermal conductance that depends quadratically on temperature above 4 K and is compatible with single terahertz photon detection.