Interfacial microstructure of cold gas spraying coated Al and Mg alloy substrates

The interface between cold gas sprayed zinc-based coatings and selected light weight alloy substrates (aluminium AA7022 and magnesium AZ91) has been investigated by scanning and transmission electron microscopy in combination with energy-dispersive X-ray spectroscopy. In both cases a non-uniform interfacial zone with a thickness of up to 10 microns is evident. It consists of coating and substrate phases as well as an approximately 1 micron thick, partially whirled layer. For the AA7022 substrate the interfacial layer contains nano and submicron sized crystallites of the binary MgZn₂ phase (η) which are embedded in an aluminium solid solution matrix. In the case of AZ91 substrate two ternary phases, Mg₅Zn₂Al₂ (φ) and Mg₁₁Zn₁₁Al₆ (τ) with particle size smaller than 50 nm are evident. The formation of these phases during spraying cannot be explained by diffusion process only, but a local melting is needed. Consequently, the assumption that the high kinetic energy of cold gas sprayed particles causes an intensive mechanical mixing of coating and substrate material accompanied by a high local temperature rise is proved.     

原子荧光法测定甘草中汞

利用还原气化的非色散型装置，以湿法消解的方式，对中药甘草中的痕量汞进行了原子荧光测定。研究了影响测定结果的条件，比较了两种玻璃仪器的洗涤方式，并以工作曲线法和加入作图法对照，试验回收率在86．9％－110．8％，误差＜13．1％，得出了满意的分析结果。     

Increasing the cold atom density in an integrating spherical cavity

A novel method of angled incidence for diffuse laser cooling of ⁸⁷Rb is presented to improve the distribution of cold atom density in an integrating sphere. The angled injection scheme could cool more atoms in the middle of the sphere compared to the previous normal injection scheme. The loading time of the cold atoms for the angled injection scheme is twice as that of the normal injection scheme. The SNR and the contrast of the detected signal would be improved in the angled injection scheme.     

Eigen-line in welded structures of thermoplastic polymers

Welding is widely used as a joining method for thermoplastics, and it is imperative to ensure the joining quality, particularly for critical applications. In a previous work by the authors, an Eigen-line was found in the electrofusion joint of polyethylene (PE) pipes based on ultrasonic tests and it could be used to detect and assess cold welding defects. However, the nature of the Eigen-line and reasons for the Eigen-line's existence in ultrasonic images have not yet been fully understood, which limited its applications. In this paper, Eigen-lines were observed in other thermoplastics including polypropylene (PP), polyamide 6 (PA 6), polyoxymethylene (POM) and polyethylene terephthalate (PET), suggesting that Eigen-lines have common existence. Microindentation tests were conducted on specimens cut from electrofusion joints and butt joints of PE pipes. It was found that a significant change of elastic modulus exists around the Eigen-line, which can partly explain the appearance of an Eigen-line in ultrasonic images. Scanning electron microscopy (SEM) and reflective optical microscopy were also employed to explore the nature of the Eigen-line. The results showed that an Eigen-line is a thin layer with polymer chain orientation between base material and welded zone.     

一种基于RDSS服务的加速导航定位接收机冷启动的方法

基于RDSS业务服务的导航定位接收机的首次定位时间是衡量接收机性能的一个重要指标。接收机冷启动过程中，由于要采用轮询的方式从所有可见卫星中锁定信号，积累星历数据，导致首次定位时间延长。本文提出了一种基于RDSS服务的加速接收机冷启动的方法，该方法能够有效的提高接收机冷启动首次定位的时间，具有一定的推广前景。     

Significant influence of particle surface oxidation on deposition efficiency, interface microstructure and adhesive strength of cold-sprayed copper coatings

The critical velocity for particle deposition in cold spraying is a key parameter, which depends not only on the material type, but also the particle temperature and oxidation condition. The dependency of deposition efficiency of cold spray Cu particles on the particle temperature and surface oxidation was examined. The effect of particle surface oxide scales on the interfacial microstructure and adhesive strength of the cold-sprayed Cu coatings was investigated. The results show that the deposition efficiency significantly increases with increasing the gas temperature but decreases with augmenting the oxygen content of the starting powder. The oxide inclusions at the interfaces between the deposited particles inhibit the effective bonding of fresh metals and remarkably lower the bond strength of the deposited Cu coatings on steel.     

Synthesis and application of a novel cold brand reactive dye to impart colouration,mosquito repellency,and UV protection to nylon

Mosquito-borne diseases are a great concern for human health, and an increment in urbanization causes a rise in the population of mosquitoes. The efficient methods and products for countering mosquito bites are the urgent need of the hour. To protect against mosquitoes, mosquito repellent textiles are an attractive substrate. An impartment of simultaneous dyeing and finishing effects on nylon is an urgent requirement as it can enhance its applicability in various technical applications. The present study reports the preparation of a mosquito repellent-cum-UV protective nylon using a novel reactive dye. The synthesis of dye involves the reaction of cyanuric chloride with H-acid (sodium 4-amino-5-hydroxy-2,7-naphthalene disulfonic acid) to generate cyanuric-H-acid, which was further reacted with diazotised 4-amino-N, N-diethyl-3-methylbenzamide (DEET-NH₂) to synthesise a novel cold brand reactive dye. Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (¹H NMR), elemental analysis (CHN analyser), UV–vis spectroscopy, and thermogravimetric analysis (TGA) were used to characterise the synthesised dye. The colouration of nylon was done in an infrared lab dyeing machine. The exhaustion and fixation of dye on nylon and the colouration properties (L*, a*, b*, C*, K/S) of dyed nylon were explored. Functional properties (mosquito repellency and UV protection) were evaluated even after laundering treatments. The dyed fabrics were also characterised using TGA and scanning electron microscope (SEM) analysis. An outstanding mosquito repellency (100 %) and good UV protection were achieved.     

电极结构对于大气压低温等离子体射流初始电场的影响——创新信息论坛优秀论文

为研究不同电极结构对于大气压低温等离子体射流电场的影响,建立了二维轴对称模型,利用COMSOL软件对三种不同的电极设置情况进行了仿真。仿真结果表明,只有针电极时,电场强度比较低,壁上加环电极时,最大电场强度显著增大,且环电极的宽度对它的大小也有影响,壁外加环电极时,最大电场强度也增大,但增加的幅度较环电极在壁上时小,且随着环电极距壁的距离越来越大,产生的影响也越来越小。     

Superradiant cascade emissions in an atomic ensemble via four-wave mixing

We investigate superradiant cascade emissions from an atomic ensemble driven by two-color classical fields. The correlated pair of photons (signal and idler) is generated by adiabatically driving the system with large-detuned light fields via four-wave mixing. The signal photon from the upper transition of the diamond-type atomic levels is followed by the idler one which can be superradiant due to light-induced dipole–dipole interactions. We then calculate the cooperative Lamb shift (CLS) of the idler photon, which is a cumulative effect of interaction energy. We study its dependence on a cylindrical geometry, a conventional setup in cold atom experiments, and estimate the maximum CLS which can be significant and observable. Manipulating the CLS of cascade emissions enables frequency qubits that provide alternative robust elements in quantum network.     

Temperature separation and friction losses in vortex tube

The process of energy separation and friction losses in a vortex tube is studied in detail. The hot and cold exit air temperatures were measured. Experiments have been conducted at inlet pressure of 3.5, 5, 7.5 and 9 bar, at inlet temperature of 292.15 and 298.15 K and at cold air mass ratio from 0 to1. The results demonstrate that the hot air temperature reaches its maximum value at a cold air mass ratio of nearly 0.82, while the minimum value of cold air temperature is found at a cold air mass ratio of 0.3. Based on energy and mass balances as well as on the definition of internal energy and on experimental results a new model for the determination of hot and cold exit gas temperature has been developed. The model includes the relevant primary parameters and predicts the experimental results as well as the data published in the literature sufficiently accurate for engineering purposes.A cross-section area m³ - D diameter of the pipe m - F model parameter - f friction factor - L length of the tube m - m mass flow rate kg/s - y cold air mass ratio - P static pressure Pa - T temperature K - t thickness of the orifice m - R gas constant J/kg K - v velocity of fluid m/s - density of the fluid kg/m³ - friction factor for pipe - friction factor for orifice and tee junction - 1 inlet of compressed gas - 2 exit of hot gas - 3 exit of cold gas - atm atmospheric pressure - c cold exit gas - f friction - h hot exit gas - o orifice plate - T tee junction