Transducers in medical ultrasound. Part 4: Transducer safety

Transducer safety encompasses a wide spectrum of topics. It may range from mechanical construction reliability to biological effects created by ultrasound radiation. In this Paper the electrical and acoustical safety aspects are summarized and initial experience with sterilization of echocardiographic transducers for peroperative cardiac scanning is mentioned.     

冲击波温度和压力对二氧化钛相变的影响

 介绍了一种简便易行的降低疏松固体物质冲击波温度的方法，其要点是用液体石蜡充填样品的空隙。以用粉末锐钛矿压装成型的样品为例，对比了不充填和充填液态石蜡时冲击波作用的结果。在同样的冲击加载条件下（均为钢飞片，撞击速度为3.16 km/s），估算两种样品中达到的压力分别为36.3 GPa和46.8 GPa，平均温度分别约为4.7×10³ ℃和2.0×10³ ℃，即：充填液态石蜡的样品中压力增加了约10 GPa，但平均温度降低了近3×10³ ℃。对冲击后回收样品的分析结果表明，不充填石蜡样品的主要产物为金红石，即冲击波产生的高温起了主要作用。而充填液态石蜡时，主要生成β-TiO₂高压相，即高压起了主要作用。     

The preparation of nanophase tungsten carbide powder with zeolite-X catalysts

The reduction–carburization of tungsten trioxide (WO₃) under carbon monoxide flow was studied in the temperature range of 300–750 °C. The reduction–carburization of WO₃ was improved by mechanically mixing with zeolite-HX, -NaX and -KX. The interaction between cation in zeolite-X and oxygen in WO₃ affected the improvement of the reduction–carburization of WO₃ to WC. Moreover, the improved reduction–carburization of WO₃ could lead to the decrease of reaction temperature. Because the particle size of WC is in contact with a reaction temperature, the nanophase WC can be prepared at low temperature. In particular, the particle size of WC was controlled by reaction temperature. The particle sizes of produced WC at 550, 650 and 700 °C were 25, 50 and 100 nm respectively.     

Comment on “Quantum Signature Scheme with Weak Arbitrator”

This comment explains that the quantum signature scheme proposed by Ming-Xing Luo et al. (in Int. J. Theor. Phys. 51:2134, 2012) cannot satisfy the signature requirements. The comment presents methods of possible attacks by forgers, while also demonstrating that it is difficult to proceed by the normal protocol because of some errors in the formula of the scheme.     

Misalignment tolerance analysis and fabrication for highly efficient parallel optical-electrical convertor module

A compact, highly efficient, and passively assembled parallel optical-electrical convertor module (POECM) for active optical cable application is proposed. This paper presents our POECM structure, optical design simulation results, fabrication process, and data transmission test results, in sequence. The POECM has a compact size of \(18.5\hbox {mm} \times 10\hbox {mm} \times 2.8\hbox {mm}\) . We confirm a data rate of total throughput at 21.6 Gbps ( \(5.4\hbox {Gbps} \times 4\) channels) with a bit error rate of less than \(10^{-12}\) .     

K_2(9~1∑~+_g)高位电子态与H_2碰撞中H_2的能量分布

光学-光学双共振激发K2到91∑+g高位态,研究了K2(91∑+g)与H2的电子-振转碰撞能量转移。利用相干反斯托克斯(CARS)光谱技术探测H2的振转态分布,扫描CARS谱表明H2在(1,1)、(2,1)、(2,2)、(3,1)、(3,2)、(3,3)和(3,5)能级上有布居。由时间分辨CARS轮廓得到H2各振转能级上粒子数之比,得到H2的平均振动能和平均转动能分别为9063cm-1和388cm-1。从91∑+g→11∑+u、11∑+u→11∑+g、33∏g→13∑+u跃迁的时间分辨激光感应荧光(LIF)强度得到它们的自发辐射率和碰撞转移率。在H2压强为3×103Pa时,K2(91∑+g)与H2的碰撞转移能为16930cm-1。H2的平均振转能占平均转移能的56%。     

Preparation of BA/ST/AM nano particles by ultrasonic emulsifier-free emulsion polymerization

A kind of nano particle of butyl acrylate (BA)/styrene (ST)/acrylamide (AM) was prepared through a new method that was ultrasonic emulsifier-free emulsion polymerization, which was a kind of environmental protection and economical method. And no any volatile organic solvent (VOC), emulsifier and initiator were used in this method. Only water was used as solvent. The effects of sonic intensity, sonic time, inorganic salt content, N2 flow velocity, etc. on monomer conversion were studied. TEM photographs showed that its particles size was about 80 nm, which was less than particles size (about 140 nm) through conventional emulsifier-free emulsion polymerization method. The FTIR spectrum showed that after extracted by water for 48 h, CHCl3 for 48 h and THF for 48 hr, respectively, the sample obtained by this way was a ternary copolymer of BA, ST and AM, but not a blend of poly(butyl acrylate), polystyrene and polyacrylamide.