Positron emission particle tracking-Application and labelling techniques

The positron emission particle tracking (PEPT) technique has been widely used in science and engineering to obtain detailed information on the motion and flow fields of fluids or granular materials in multiphase systems, for example, fluids in rock cracks, chemical reactors and food processors; dynamic behaviour of granular materials in chemical reactors, granulators, mixers, dryers, rotating kilns and ball mills. The information obtained by the PEPT technique can be used to optimise the design, operational conditions for a wide range of industrial process systems, and to evaluate modelling work. The technique is based on tracking radioactively labelled particles (up to three particles) by detecting the pairs of back-to-back 511 ke V -γ-rays arising from annihilation of emitted positrons. It therefore involves a positron camera, location algorithms for calculating the tracer location and speed, and tracer labelling techniques. This paper will review the particle tracking technique from tracking algorithm, tracer labelling to their application.     

Measurement of the magnetic field-dependent refractive index of magnetic fluids in bulk

An optical alignment-free and highly accurate method is employed to measure the magnetic field-dependent refractive index of magnetic fluid(MF) in bulk.The measured refractive index decreases significantly with the increasing magnetic strength and then tends to saturate in the high intensity range.By applying a tunable magnetic field ranging between 0 and 1661 Oe,the maximum shift of the refractive index of MF in bulk iS found to be 0.0231.     

拉桥朗日—欧拉方法模拟高分子复杂流体平面收缩流动

为验证拉格朗日－欧拉方法的准确性,对高分子溶液的４：１平面刷缩流动问题进行了数值模拟,采用单松驰时间的Ｐｈａｎ Ｔｈｉｅｎ－Ｔａｎｎｅｒ本构方程,得到ＰＩＢ／Ｃ１４溶液在Ｄｅ＝３．０的收缩流动的计算结果,同Ｑｕｉｎｚａｎｉ等所做的收缩流动实验中的稳态流场物理量结果进行了比较,在定量上取得较好的一致性。证明拉格朗日－欧拉方法能够在定性上乃至在定量上准确地预报高分子复杂流体的流动行为,在描述真实的物理     

High promoting of selective oxidation of ethylbenzene by Mn-ZSM-5 synthesized without organic template and calcination

Research on Chemical Intermediates - Acetophenone is a valuable and widely applied intermediate in chemical industry, but limited by the synthesis with low-cost and efficient heterogeneous...     

Producing virtual face images for single sample face recognition

For single sample face recognition, there are limited training samples, so the traditional face recognition methods are not applicable to this problem. In this paper we propose to combine two methods to produce virtual face images for single sample face recognition. We firstly use a symmetry transform to produce symmetrical face images. We secondly use the linear combination of two samples to generate virtual samples. As a result, we convert the special single sample problem into a non-single sample problem. We then use the 2DPCA method to extract features from the samples and use the nearest neighbor classifier to perform classification. Experimental results show that the proposed method can effectively improve the recognition rate of single sample face recognition.     

Analysis of performance of RFS-based optical comb influenced by linewidth of laser source

The laser source is an important element whose properties have influence on the output performance of single sideband(SSB) optical comb based on recirculating frequency shifter(RFS).The theoretical and experimental results show that the tone-to-noise ratio(TNR),flatness,and stability of optical comb improve using laser source with narrower linewidth.In order to obtain the optical comb with TNR larger than 42 dB and degree of stability(DOS) smaller than-6.7 dB,external cavity laser(ECL) with linewidth from 100 kHz to 1 MHz is a trade-off choice.     

A Facile Synthesis of N′-Benzoyl Thiophosphoryluras

Twelve title compounds 3a-l were synthesized by nuclophilic addition of thiophosphoramide 1 to benzoylisocyanate 2. The yield of compounds 3a-f and 3g-l is 72–83% and 18–33%.     

破片撞击下YAG透明陶瓷复合靶的破坏特性

YAG透明陶瓷兼具有优秀的透光性能和抗冲击破坏性能,是武器装备透明部分的优秀防护材料,在军事装备、航天等国防领域具有良好的应用前景。冲击载荷下材料的加载响应特性对掌握材料破坏机制至关重要,能为透明复合靶设计提供依据。为获得YAG透明陶瓷多层复合靶的冲击破坏特性,利用内径9 mm的气体驱动发射平台进行了碳化钨球形破片在20～310 m/s速度下撞击YAG透明陶瓷复合靶的实验,通过高速摄影捕捉的陶瓷表面损伤演化过程,计算了典型径向、环向裂纹扩展速度。通过观测回收的靶体和YAG碎片的宏细观破坏特征,分析了撞击速度与靶体破坏特征之间的联系。结果表明,YAG陶瓷层径向裂纹和环向裂纹扩展速度均随着时间的延长线性降低,且裂纹扩展速度几乎不受撞击速度影响。陶瓷层中心粉碎区面积随撞击速度的提高而增大,且中间玻璃层破坏区域面积与陶瓷锥底面积相关联,陶瓷锥角与撞击速度关联性不强。同时,观察到陶瓷层在冲击破坏过程中出现了裂纹簇,获得了裂纹簇数量与破片撞击速度之间的关系,分析了裂纹簇的特征及其成因。裂纹变向、应力波作用会显著影响细观断面破坏特征。径向、环向和锥裂纹中沿晶断裂的比例均随着裂纹扩展距离的增大而增加,且穿晶比例随着撞击速度的提高而增加。