Preparation and photoluminescence properties of Sr4Al14O25:Eu2+ phosphors synthesized via the microemulsion route

Strontium aluminate phosphors doped with europium ions (Sr₄Al₁₄O₂₅:Eu²⁺) were successfully synthesized via the microemulsion route. In comparison with the traditional solid-state reaction process, the calcination temperature of Sr₄Al₁₄O₂₅:Eu²⁺ phase in this study was lowered to 1,100 °C when the flux was added. In addition, the particle size of Sr₄Al₁₄O₂₅:Eu²⁺ phosphors prepared via the microemulsion route was greatly reduced to 50 nm. The lowered synthesis temperature and reduced particle size are attributed to nano-scaled micelles formed in the microemulsion system. The emission and excitation intensity of Sr₄Al₁₄O₂₅:Eu²⁺ phosphors were increased with an increase in the synthesis temperature. In addition, the rise in the calcination temperature lowered the afterglow characteristics of Sr₄Al₁₄O₂₅:Eu²⁺ phosphors. The microemulsion route was demonstrated to be an more effective process than the solid-state reaction process for preparing Sr₄Al₁₄O₂₅:Eu²⁺ phosphors.     

A Water-Wave Broadcast Scheme for Emergency Messages in VANET

Vehicular Ad Hoc Network (VANET) is an emerging new technology and a promising platform for the intelligent transportation system. The most important application of VANET is disseminating emergency messages to drivers in case of dangerous events. The effectiveness depends on the design of a broadcast scheme. A simple broadcast scheme encounters many problems such as broadcast storm, connection hole, building shadow, and intersection problems. In this paper, we propose an efficient broadcast scheme that simulates water wave propagation to spread emergency messages. This scheme provides warning services with both space and time constraints. Most existing broadcast schemes provide inadequate strategies for limiting the time period of a warning. We verified the performance of our proposed scheme in a simulated street environment with vehicle movements to show the superiority of this scheme in high broadcast coverage areas.     

A compatible and crosslinked poly(2-allyl-6-methylphenol-co-2,6-dimethylphenol)/polystyrene blend for insulating adhesive film at high frequency

A polymer blend consisting of poly(2-allyl-6-methylphenol-co-2,6-dimethylphenol) (APPE) and polystyrene (PS) with additives such as 1,2-bis(4-vinylphenyl)ethane, cyanate ester, and nitrile butadiene rubber was formulated as an insulating high-frequency adhesive film. The polymer blend of APPE and PS showed very high compatibility to these additives, and the resulting thermally cured polymer blend exhibited an excellent mechanical strength, as shown by an ultimate tensile strength of 51 MPa and Young's modulus of 1.4 GPa. Moreover, the blend exhibited very good dielectric properties, with a dielectric constant of 2.3 and a dissipation factor of 0.0030 at 10 GHz. The glass-transition temperature of the cured polymer blend was 141 °C, as determined by differential scanning calorimetry, and the 5% weight loss temperature was 372 °C, indicating relatively high thermal resistance characteristics. Furthermore, its peel strength to a copper foil reached 0.80 N/mm. The present study suggested that the thermally cured APPE/PS polymer blend with additives will have potential applications for the next-generation high-frequency adhesives in microelectronic circuits. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47828.     

Fully sintered alumina with a higher Vickers hardness prepared using a gel-casting process

The dispersant (commercial ammonium polyacrylate), sintering additive (Mg²⁺), and chelating agent (EDTA) effects on the Zeta potential and rheological behavior of alumina slurry with high solid content were investigated. The alumina ceramic green microstructures and sintered microstructures prepared using slurries with different additives using the gel-casting process were also studied. It was observed that the dispersion deteriorated after adding Mg²⁺. Slurry simultaneously added with dispersant and EDTA-chelated Mg²⁺ produced higher absolute Zeta potential value and low viscosity due to EDTA chelating with Mg²⁺. The sample added with dispersant and EDTA-chelated Mg²⁺ exhibited a uniform green microstructure, high relative sintered density (99.5% theoretical density), and a nearly pore-free microstructure with an average grain size of about 1.5 μm. For the first time to our knowledge, the maximum Vickers hardness (22 GPa) was obtained for alumina simultaneously added with Mg²⁺ and EDTA, pressureless sintered at 1500°C in air.     

Using MEMS-based inertial sensor with ankle foot orthosis for telerehabilitation and its clinical evaluation in brain injuries and total knee replacement patients

Microsystem Technologies - Telerehabilitation is an emerging field of rehabilitation. Combining medicine and engineering, telerehabilitation provides an alternative method of rehabilitation therapy...     

Precise CMOS current sample/hold circuits using differential clockfeedthrough attenuation techniques

New CMOS current sample/hold (CSH) circuits capable of overcoming the accuracy limitations in conventional circuits without significantly reducing operating speed are proposed and analyzed. A novel differential clock feedthrough attenuation (DCFA) technique is developed to attenuate the signal-dependent clock feedthrough errors. Unlike conventional techniques, the DCFA circuit allows the use of dynamic mirror techniques, and results in no additional finite output resistance errors or device mismatch errors. The test chip of the proposed fully differential CSH circuit with multiple outputs has been fabricated in 1.2-μm CMOS technology. Using a single 5-V power supply, experimental results show that the signal-dependent clock feedthrough error current is less than ±0.4 μA for the input currents from -550 μA to 550 μA. The acquisition time for a 900-μA step transition to 0.1% settling accuracy is 150 ns. For a 410-μA_p-p input at 250 MHz with the fabricated fully-differential CSH circuit clocked at 4 MHz, a total harmonic distortion of -60 dB, and a signal-to-noise ratio of 79 dB have been obtained. The active chip area and power consumption of the fabricated CSH circuit are 0.64 mm² and 20 mW, respectively. Both simulation and experimental results have successfully verified the functions and performance of the proposed CSH circuits     

Characterization of random glass fiber-reinforced polypropylene for processing

DSC thermal analysis and multi-channel recording have been used to investigate the processing conditions for fiber-reinforced thermoplastic composites. The process combined the film stacking and intermingled fiber techniques using needle-punching to improve the fiber-matrix distribution. The preheating temperature and mold temperature for fiber-reinforced polypropylene composites were in the ranges of 180 200 °C and 60 100 °C, respectively. DSC analysis and X-ray methods showed the presence of an a crystalline form for PP and PP/GF with the cooling rate at 10 °C/min. Increasing the cooling rate to 20 °C/min, they revealed the presence of a mixture of the monoclinic a crystalline form and the hexagonal crystalline form. A multi channel recorder was used to determine the completion of impregnation on multi-layer glass fiber reinforced polypropylene, which could significantly reduce the manufacturing cycle time. The main steps in the processing cycle on the surface of composite or inside the composite were determined. The concept of a processing window with respect to solidification rate and molding pressure is introduced and briefly discussed. The mechanical properties of fiber-reinforced polypropylene composite inside the processing window were better than those outside the processing window and were comparable to GE AZDEL®.     

基于位置补偿技术的模具监视系统

针对模具制品射出成型过程中因制品滞留在模腔中造成的夹模问题,提出集数字图像采集与处理以及模式识别等技术的解决方案,实现在注塑行业成型模具的监视系统。运用自适应阈值分割算法进行图像处理,运用图像差影检测算法进行模式匹配比较分析,并利用基于搜索空间与相似度测量技术的位置补偿算法,通过自动位置补偿将采集到的图像进行矫正。结果表明,生产制品的品质合格品率由90%提高到99%,注塑成型机的使用率由75%提高到96%。     

Positioning strategic competitiveness of green business innovation capabilities using hybrid method

There are intensive studies on the issues of environment practice and business innovation capability, have been dealt with extensively from practitioners and academicians, however, studies on the evaluation of green business innovation capabilities (GBICs) are few. This study tackles the evaluation assessment using fuzzy set theory, analytical network process and importance–performance analysis. Specifically, this study is using the theoretical framework of GBICs and proposed hybrid approach, which are new in the theoretical and empirical literatures. An expert group was empirical assessment to the perception on PWB sector and a manufacturing firm is evaluated. The analytical results indicated that this proposed hybrid method is a suitable and effective method for identifying and analyzing the strategic competitiveness of GBICs at case firm, especially when evaluation criteria are dependent in uncertainty.     

Electrical characterization of SiOx and SiNxprepared by PECVD technique on In0.53Ga0.47As

We have analyzed the electrical properties of both SiO_x on InGaAs and SiN_x on InGaAs, by utilizing a metal-insulator-semiconductor (MIS) structure. For improving film or interface quality, both oxide and nitride samples underwent furnace annealing (FA) in hydrogen at various temperatures. From the leakage current and capacitance characterization, we found that the electrical properties of the nitride samples such as leakage current, injected charges, and interface trap density are improved by FA, while on the contrary, the properties of the oxide samples are slightly deteriorated. The optimum annealing temperature for nitride samples is in the temperature range of ~400 to 450°C. Also, by secondary ion mass spectroscopy (SIMS) analysis, we provide evidence of inter-diffusion occurring in the oxide samples after annealing