Investigation of CuAlO2 composite dielectric properties and selective metallization by laser direct structure technology

In this work, we investigated CuAlO₂ ceramic composite dielectric properties and potential application to laser direct structuring (LDS) technology. To sinter at low temperature various amounts of glass was added to CuAlO₂ and their microstructure, dielectric properties were systematically investigated. The Glass +30 wt% CuAlO₂ composite sintered at 800 °C for 1 h was measured to have a high relative density of 84.5 %, low dielectric constant and loss of 4.6 and 0.08 at 9.1 GHz. Using this composite after laser irradiation well-defined copper metal patterns were fabricated on ceramic composite surface. Two important factors which enabled metallization was observed to be morphology of the ceramic composite surface and reduction of Cu⁺, Cu²⁺ in the CuAlO₂ composite to Cu⁰ after laser irradiation.     

Electrochemical behavior of lead alloys in sulfuric and phosphoric acid electrolyte

The electrochemical behavior of lead, lead–calcium–tin–aluminum and lead–calcium–tin–aluminium–bismuth alloy electrode has been studied in the electrolyte of sulfuric, phosphoric and mixed acid electrolyte. The electrochemical measurements were performed using a cyclic voltammetry technique (CV) with three-electrode system. The results demonstrated that bismuth(III) doped in the lead electrode can increase electrical capacity. The oxidation peak potential of lead alloy electrode in phosphoric acid shifted to the positive compared to that in sulfuric acid. The formation of PbHPO₄ in phosphoric acid and its passivation are responsible for the positive shift of the oxidation.     

Diameter effect on supercritical heat transfer

The objective of this review is to assess and analyze the literature on the effect of tube diameter on heat transfer at super-critical (SC) pressures. The review is based on SC heat transfer data obtained in tubes with a diameter range of 3.18 to 38.1 mm, cooled by carbon dioxide, water, R-22, and R-12. The majority of experimental studies show that, for the same flow conditions, the heat transfer coefficient (HTC) in the ‘normal’ heat transfer mode increases with a decrease in tube diameter. Furthermore, it was found that at SC pressures, heat transfer is more prone to deteriorate in large tube diameters. In the “deteriorated” heat transfer mode, the HTC also appears to decrease with an increase in tube diameter.     

A new adaptive cascaded stochastic resonance method for impact features extraction in gear fault diagnosis

Gearboxes are widely used in engineering machinery, but tough operation environments often make them subject to failure. And the emergence of periodic impact components is generally associated with gear failure in vibration analysis. However, effective extraction of weak impact features submerged in strong noise has remained a major challenge. Therefore, the paper presents a new adaptive cascaded stochastic resonance (SR) method for impact features extraction in gear fault diagnosis. Through the multi-filtered procession of cascaded SR, the weak impact features can be further enhanced to be more evident in the time domain. By analyzing the characteristics of non-dimensional index for impact signal detection, new measurement indexes are constructed, and can further promote the extraction capability of SR for impact features by combining the data segmentation algorithm via sliding window. Simulation and application have confirmed the effectiveness and superiority of the proposed method in gear fault diagnosis.     

Warm with high color rendering index white light from hybridization of Ca2BO3Cl:Eu2+ yellow phosphor and CdSe/ZnS nanocrystals

Yellow emitting Ca₂BO₃Cl:Eu²⁺ phosphor was prepared by solid state reaction at 900 °C. The particle was monoclinic crystal structure, and showed broad band emission at around 540–590 nm due to the 5d–4f transition. Single Ca₂BO₃Cl:Eu²⁺ phosphor converted white LED exhibited the CIE coordinates of (0.3441, 0.2675) with low CRI of 67.4. Hybridization of Ca₂BO₃Cl:Eu²⁺ with 535 and 610 nm emitting CdSe/ZnS nanocrystals contributed to increasing white spectrum and generated the warm color temperature (4055 K) with high CRI (83.9) of white light. The acceptable color stability was also observed from (0.3687, 0.3051) at 20 mA to (0.3645, 0.3101) at 80 mA.     

铝合金薄壁构件应力继承机制与分布特征研究

为获得厚板-薄壁构件成形过程中应力演变对变形的影响规律,运用铣削加工有限元应力仿真和实验应力测试技术,研究了厚板到薄壁构件阶段应力演变的规律,阐述了应力分布特征.结果表明:薄壁件应力特征分为两部分,一部分以构件变形机制驱动的继承了原有应力分布特征的底部应力场,另一部分则是可进行变形控制的对原有应力分布兼有继承和释放效果的薄壁应力场;加工应力固然影响构件变形,但初始应力和构件形状分布对其影响更显著,并在此基础上提出了薄壁构件变形的控制策略.     

High speed detection of potato and clod using an acoustic based intelligent system

Discriminating between potato tubers and clods is the first step in developing an automatic separation system on potato harvesters. In this study, an acoustic-based intelligent system was developed for high speed discriminating between potato tubers and soil clods. About 500 kg mixture of potato tubers and clods were loaded on a belt conveyer and were impacted against a steel plate at four different velocities. The resulting acoustic signals were recorded, processed and potential features were extracted from the analysis of sound signals in both time and frequency domains. A multilayer perceptron neural network with a back propagation algorithm was used for pattern recognition. Altogether, 17 potential discriminating features were selected and fed as input vectors to the artificial neural network models. Optimal network was selected based on mean square error, correct detection rate and correlation coefficient. At the belt velocity of 1 m s^?1, detection accuracy of the presented system was about 97.3% and 97.6% for potatoes and clods, respectively. Increasing the belt velocity resulted in the reduction of detection accuracy and increase in the number of miss classified samples. By using this system, it is expected that a potato harvester may operate at a capacity of 20 ton hr^?1 with the accuracy of about 97%.     

基于模糊遗传算法的楼宇火灾报警系统

针对目前火灾报警系统中存在的敏感度低,可靠性差的现状,结合城市楼宇环境,提出并设计了一种基于模糊遗传算法的智能火灾报警系统,采用模糊算法提高报警系统灵敏度的同时,利用遗传算法的自适应能力对模糊隶属度进行优选,提高了整个系统的智能化程度和适应性,减少了火灾报警系统漏报率和误报率。     

光伏/光热-地源热泵联合供热系统运行性能研究

为解决太阳电池的发电效率随温度升高而下降以及地源热泵系统供热引起的土壤热失衡问题,以典型居住建筑的光伏/光热-地源热泵（PV/T-GSHP）联合供热系统为研究对象,基于TRNSYS软件,采用土壤温度、地源热泵机组季节能效比、光伏发电效率和太阳能保证率为评价指标,对该联合供热系统进行运行性能分析。研究结果表明：夏热冬冷地区（以长沙为例）太阳能保证率相对较高,PV/T组件面积为满屋顶最大化安装（900 m²）时,第20年末土壤温度相比初始地温仅升高0.8 ℃,热泵机组季节能效比约为5.1,太阳能保证率为97.0%~98.7%;不同气候地区的太阳能保证率与PV/T组件面积和建筑全年累计供热量有关,通过定义单位建筑全年累计供热量PV/T组件面积指标,得到中国不同气候地区的太阳能保证率与该指标的耦合关系,回归方程的决定系数R²为0.983,得出在已知建筑全年累计供热量和太阳保证率设计目标值的条件下所需PV/T组件面积的计算方法。PV/T-GSHP联合供热系统的全年运行能耗显著小于平板太阳能集热器-地源热泵联合系统（最小降幅为沈阳,49.7%）,远小于空气源热泵（最小降幅为石家庄,79.8%）和燃气壁挂炉（最小降幅为沈阳,65.1%）。     

Spark plasma assisted carbothermal reduction-nitridation synthesis of (Ti,W, Mo)(C,N)-(Ni,Co) powders

Ultrafine (Ti, W, Mo)(C, N)-(Ni, Co) cermet powders were rapidly synthesized from various metal oxides, mainly anatase-TiO₂, by spark plasma assisted carbothermal reduction-nitridation (SPCRN) at low temperature. The phase evolution of the SPCRN reaction was investigated using X-ray diffraction (XRD) and the microstructure of the product powders was observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). NiO, Co₃O₄ and MoO₃ were converted to Ni, Co and Mo₂C by CR reaction at temperatures below 900 °C. WO₃ was successively transformed from W₂C to WC by CR reaction up to 1100 °C. Finally, at up to 1350 °C, (Ti, W, Mo)(C, N) formed into the sequence of TiO₂, Ti₄O₇, Ti₃O₅, Ti(O, N), Ti(C, N), (Ti, W)(C, N) and (Ti, W, Mo)(C, N). The crystal structure of (Ti, W, Mo)(C, N)-(Ni, Co) cermet powders was analyzed by the Rietveld method and transmission electron microscopy (TEM). The findings demonstrated that the pure (Ti, W, Mo)(C, N)-(Ni, Co) cermet powders with grain size of below 0.5 µm were synthesized from metal oxides by SPCRN reaction at 1400 °C for 10 min.