Dual effect synergistically triggered Ce:(Y,Tb)3(Al,Mn)5O12 transparent ceramics enabling a high color-rendering index and excellent thermal stability for white LEDs

Ce:Y₃Al₅O₁₂ transparent ceramics (TCs) with appropriate emission light proportion and high thermal stability are significant to construct white light emitting diode devices with excellent chromaticity parameters. In this work, strategies of controlling crystal-field splitting around Ce³⁺ ion and doping orange-red emitting ion, were adopted to fabricate Ce:(Y,Tb)₃(Al,Mn)₅O₁₂ TCs via vacuum sintering technique. Notably, 85.4 % of the room-temperature luminescence intensity of the TC was retained at 150 °C, and the color rendering index was as high as 79.8. Furthermore, a 12 nm red shift and a 16.2 % increase of full width at half maximum were achieved owing to the synergistic effects of Tb³⁺ and Mn²⁺ ions. By combining TCs with a 460 nm blue chip, a warm white light with a low correlated color temperature of 4155 K was acquired. Meanwhile, the action mechanism of Tb³⁺ ion and the energy transfer between Ce³⁺ and Mn²⁺ ions were verified in prepared TCs.     

Fabrication of nano-porous silicon oxide layers by plasma polymerisation methods

We report on the synthesis of nano-porous silicon oxide (SiO₂) layers by gas phase polymerisation reactions of hexamethy disiloxane and oxygen. The SiO₂ layers are deposited onto one or more layers of poly(methylmethacrylate) (PMMA) particles spin coated onto the substrate surface. Subsequent annealing of the films to high temperature (500 °C) leads to the pyrolysis of the polymeric particles resulting in a 3D nanoporosity in the film. X-ray Photoelectron (XPS) and Fourier Transform Infra Red Spectroscopy (FTIR) show an SiO₂-like surface chemistry and virtually complete removal of the organic components. These materials offer a very high surface area-to-volume ratio suitable for sensing applications.     

A generalized self consistent model for effective elastic moduli of human dentine

Closed-form expressions are presented for effective material properties of human dentine in this paper. The derivation is based a Generalized Self Consistent Method and the strain energy principle. The Generalized Self Consistent Model for cell model of fiber-reinforced composites is extended to the case of hollow cylinder model and the corresponding cell model is chosen to consist of a circular hollow cylinder filled with liquid or gas phase, which surrounded by a circular cylindrical shell of matrix phase. Each layer of cylindrical shell is here considered as a kind of composite consisting of collagen fibrils, with mineralized hydroxyapatite, loosely connected to their neighbours, and water (or gas in the case of dry dentine composite). Using the cell model, the effect of Poisson’s ratio and volume fraction of intertubular dentine on effective mechanical constants is analyzed. Results obtained from the proposed model are compared with those from other models such as nano-indentation method.     

Influence of channel-height on heat transfer in rectangular channels with skewed ribs at different bleed conditions

An infrared imaging system is used to measure detailed distributions of local heat transfer coefficient from rectangular channels with two opposite wide walls roughened by 45° staggered ribs of twenty test cases. Nusselt number (Nu) contours over the ribbed surfaces are presented for five sets of channels with an identical rib-floor configuration, but different channel-heights where the complex Nu distributions without bleed and then with bleeds from the scanned rib-floor or from the ribbed wall opposite to the scanned rib-floor or from the smooth sidewall are analyzed to examine the synergetic effects of variable channel-heights and different bleed conditions on heat transfer. Spatially averaged heat transfer results for the entire set of test channels are generated with the thermal performance factors compared to establish the heat transfer correlations with applications to the design of coolant channels in a gas turbine blade.     

The ability of eye-tracking metrics to classify and predict the perceived driving workload

Traffic safety is directly related to the mental and physical condition of the driver. Performing regular secondary tasks while driving is an additional activity that dissipates attention and adds to the drivers' workload. Identifying driver fatigue and workload based on gaze behavior is one way to ensure a safe driving experience. The purpose of this paper is to classify and predict driving perceived workload using a set of eye-tracking metrics (gaze fixation, duration, pointing, and pupil diameter). The ability of eye-tracking metrics to predict driving workload has been investigated. As a result, frustration, performance, and temporal load showed a correlation with gaze metrics. Gaze point, duration, fixation, and pupil diameter significantly influence driving workload.Relevance to industry: Results will supply the specialists in eye-tracking/sensor technologies and traffic safety with new knowledge to improve the design of the driving performance and safety monitoring systems and efficiency of the driving process.     

直线电动机在数控机床中应用的特殊性问题研究

直线电动机不需经过任何中间转换机构就可直接进行直线驱动,是现代数控机床高速、高精度伺服系统进给驱动的理想部件.详细讨论了直线电动机在数控机床上应用过程中的特殊性问题,包括直线电动机的选型、与机床本体的结构对接、电动机的发热与冷却、导轨的选择和工作台的轻化等,还分析了直线电动机的端部效应、防磁措施、法向磁吸力和伺服控制策略以及其它一些相关的特殊性问题,并提出了相应的解决方法.     

拼焊板盒形件充液拉深的数值模拟

随着汽车行业对能源消耗和汽车尾气排放的要求,应用拼焊板成形技术显得越来越重要.以差厚拼焊板拉深方盒件为研究对象,采用板料成形分析软件DYNAFORM对充液拉深和传统拉深工艺进行分析和对比.研究发现,盒形件不同部位其焊缝有不同的移动趋势,传统拉深最大焊缝移动量发生在盒形件底部中心处,充液拉深件焊缝移动最大量发生在侧壁顶部,增大充液拉深凹模油腔的压力,可以有效地减少焊缝移动量和坯料的减簿量.     

Interface structure and mechanical properties of the brazed joint of TiC cermet and steel

A commercially available Ag–Cu braze alloy foil with Zn was used to join TiC cermet and steel. According to the experimental observations, the interface structure is (Cu, Ni)/Ag (s.s.) + Cu (s.s.)/(Cu, Ni)/(Cu, Ni) + (Fe, Ni) from TiC cermet to steel side. With increased brazing temperature or time, the amounts of (Cu, Ni) near the base metals/Ag–31Cu–23Zn interface and (Cu, Ni) + (Fe, Ni) near the Ag–31Cu–23Zn/steel interface increase, while the amount of Ag (s.s.) + Cu (s.s.) in the middle of the braze alloy decreases. The whole joining process consists of diffusion and solution among atoms of the braze alloy foil and base metals. The maximum shear strength is 120.7 MPa for the joint brazed at 850 °C for 10 min.     

1D helical ZnII metal–organic polymers: Syntheses,structures and fluorescent properties

Hydrothermal reactions of 1,1′-(1,5-pentanediyl)bis-1H-benzimidazole (pbbm) with ZnCl₂ afford two 1D helical metal–organic polymers {[ZnCl₂(pbbm)] · (H₂O)_1/8}_n (1) and {[Zn(pbbm)₂] · Cl₂ · (H₂O)_1/2}_n (2). Polymer 1 features a 1D single helical architecture, whereas 2 possesses a 1D cationic double helical chain framework. Photoluminescence investigations reveal that both of them display strong emissions in the solid state at room temperature, which could originate from a ligand-to-ligand charge-transfer (LLCT) transition, as confirmed by the molecular orbital (MO) calculations.     

激光冲击LY2铝合金的薄膜性能

脉冲激光冲击LY2铝合金,在试样表面形成约1.7mm的薄膜,研究了薄膜与基体接合处横截面的微观形貌以及激光冲击搭接率和激光冲击次数对薄膜层残余应力的影响。研究结果表明:激光冲击的光斑搭接率对试样横截面的残余应力影响显著;在薄膜层最大残余应力存在于试样的表层或者近表层,深度方向的残余应力值和残余压应力值变化率均与表层深度成反比;多次冲击能够获得较大的残余应力值,但对于激光冲击LY2铝合金薄膜深度影响较小。