Loss of precious metal from Pt-Rh alloy under refractory oxide environments

Loss of precious metals from a Pt-10 wt% Rh alloy was studied at 1300° C in refractory oxides and fused quartz environments. After 60 and 150 h annealings, samples exposed to gaseous environments showed significant weight loss. The surface was attacked and characterized by micron-sized pits, as well as river-like striations. The pits were found to be enriched with silicon and/or aluminium depending upon the heating environment. Laser Raman microprobe identified that the major compound formed in the pits is -cristobalite.Direct solid state contact of Pt-Rh with Al₂O₃ and SiO₂ showed interactions between materials. The interaction was more extensive between Pt-Rh with SiO₂ than with Al₂O₃. On the other hand, no evidence of interaction except pitting and striation was observed on Pt-Rh when exposed to a vapour environment.The presence of pits and striation patterns indicated that refractory oxides attacked Pt-Rh under atmospheric conditions, and gave rise to the weight loss. Calculation of weight loss by an oxidation mechanism shows one to two orders of magnitude lower value than the actual weight loss. A new loss mechanism is proposed and discussed in this article.     

Presentation attack detection based on score level fusion and challenge-response technique

Biometrics is the state of the art in dealing with identity identification and verification based on the physical and behavioral characteristics and widely used in the fields of Fintech, such as mobile payment and online banking due to its security and convenience. However, there are various attacks against the biometrics system. The presentation attack is one of the most common attacks that an imposter presents fake biometrics to the sensor trying to fool the system. This paper proposes a multimodal presentation attack detection (PAD) method against photo-attack and video-attack in face recognition system by using score level fusion and challenge-response scenario. The proposed challenge-response scenario is that requesting the user to speak out the randomly prompted words. Then, the recognized speech text and the user’s mouth motion are detected simultaneously to verify if the user is liveness. Two weighted score level fusion rules, namely weighted sum and weight product, are used to combine the speech and mouth motion traits as a matching score. The final score is fed into supervised machine learning algorithms and trained for classifying spoofing. The experiments are conducted in the self-built database. Experimental results show that the proposed method can achieve the best half total error rate at 3.64% and can effectively improve facial recognition system security.

     

Distributed and incremental travelling salesman algorithm on time-evolving graphs

The Journal of Supercomputing - Travelling salesman problem (TSP) is a graph problem that has been widely used in many applications, especially for transportation and logistics. Because TSP is a NP...     

SOME ASPECTS OF THE THERMODYNAMICS OF MELTS

为了从二元系中两组元活度的测定值之比求得该两组元的活度值,导出了一个变通的 Gibbs-Duhem 方程式,并在 PbCl_2-SnCl_2,PbCl_2-CdCl_2,AgCl-CuCl,Cu_2S-FeS,PbO-BiO_(1.5),PbO-SbO_(1.5),CaO-CaF_2及 CaO-SiO_2-CaF_2等冶金熔体中得到应用.多年前所发展的从 Ag 和 Pb 二元相图求得两组元活度的方法已扩大到含有单个 AB 化合物的二元系.用这一方法已求得 In-Sb 和 Sn-Te 系中各组元的活度.在研究某些黑色冶金渣与金属间的平衡时,用一适当选择的非铁金属代替 Fe作为熔剂金属有助于克服某些实验上的困难.采用 Sn 或 Cu 与熔渣平衡研究了 CaO-SiO_2,CaO-Al_2O_3和 CaO-SiO_2-Al_2O_3体系.对 CaO-SiO_2二元系获得的数据可以认为具有足够的准确度来验证 Masson 模型的合理性.     

Preparation of fluoroacrylate nanocopolymer by miniemulsion polymerization used in textile finishing

Latex based on fluoroacrylate (TAN) and other comonomers was prepared via miniemulsion polymerization in the presence of stearyl trimethyl ammonium chloride (STAC) and 2, 2′‐azobis (2‐amidinopropane) dihydrochloride (ABAP) as a water soluble initiator. Light transmittance studies demonstrated that the light transmittance of prepared emulsions increases with the amount of TAN, STAC, cosolvent DPM, and hydrophobe DM. Given suitable reaction temperature and quantities of TAN, STAC, DPM, and DM, a copolymer emulsion of fluoroacylate with a particle size of 50 nm was produced. The water repellency tested on polyester fabrics displayed greater effectiveness than that of commercial products with higher fluorine content. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1466–1472, 2004     

负载奈米银之二氧化钛光触媒及其光催化活性之研究

利用自制之奈米银粒子,或用化学还原法将银微粒直接沉淀在市售二氧化钛粉末上,并比较二者对亚甲基蓝光催化效果,由于银微粒可降低电子与电洞对再结合之效果,而使二氧化钛粒子光催化活性提高,其中并以直接沉淀法为佳.此外亦藉由高温氢气对二氧化钛粉末进行还原,形成部分的Ti3+,藉此亦达到提升光催化之效果.最后将奈米银负载于经还原过后之二氧化钛粒子,于紫外光与可见光下对酚作光催化分解,发现其亦得到一定程度的分解效果.     

Elastic Response and Effect of Transverse Cracking in Woven Fabric Brittle Matrix Composites

This paper examines the linear elastic tensile and fracture behavior of biaxial plain weave SiC/SiC ceramic woven fabric composites. Iso-phase mode and random-phase mode have been adopted to simulate multilayer stacking and to predict the initial linear elastic constants. It has been found that both modes predict very close results. Porosities in the composite affect the stiffness significantly, while fiber undulation shows only minimal effect. The nonlinear stress-strain relation of the composite is due to transverse cracks, which initiate mainly from interyarn pores. In the second part of this paper, two methods, classical fracture mechanics and energy balance approach, have been used to examine the crack initiation and growth. A finite element method and a modified shear-lag method have been developed to evaluate the stress distribution in the yarn with transverse cracks. The composite stiffness reduction due to transverse cracking has been obtained by both the finite element and shear-lag methods. Strain energy release rates of the growth of transverse cracks have been studied by the crack-closure procedure, using finite element methods. Effects of the yarn size and crack position on the strain energy release rate have been quantified. It is concluded that thinner yarns lead to higher critical strains for transverse cracking.     

Paired electrooxidation IV. Decarboxylation of sodium gluconate to D-arabinose

A paired electrooxidative method has been developed to synthesize D-arabinose in a divided cell. D-arabinose is a material which has an important role in the production of vitamin B2 and DNA. Sodium gluconate was directly oxidized at the anode and indirectly oxidized in the catholyte by bubbling oxygen which was reduced to H₂O₂ and OH free radicals. In the catholyte, indirect oxidation of sodium gluconate was mediated by Fe³⁺ and OH free radicals. The optimal current efficiencies for D-arabinose production in the anolyte and catholyte were found to be 88.37% and 39.12%, respectively, and the total current efficiency of the paired electrooxidation was 127.49%. The paired electrosynthesis of D-arabinose is more economical in terms of power consumption than electrosynthesis that employ a single anode or cathode as the working electrode. The influence of cathodic/anodic CV and I/E curves, redox mediators and the amount of charge passed were also examined.     

Evaluation of two cooling systems under a firefighter coverall

Firemen often suffer from heat strain. This study investigated two chest cooling systems for use under a firefighting suit. In nine male subjects, a vest with water soaked cooling pads and a vest with water perfused tubes were compared to a control condition. Subjects performed 30 min walking and 10 min recovery in hot conditions, while physiological and perceptual parameters were measured. No differences were observed in heart rate and rectal temperature, but scapular skin temperature and fluid loss were lower using the perfused vest. Thermal sensation was cooler for the perfused vest than for the other conditions, while the cool pad vest felt initially cooler than control. However, comfort and RPE scores were similar. We conclude that the cooling effect of both tested systems, mainly providing a (temporally) cooler thermal sensation, was limited and did not meet the expectations.     

羟基磷灰石/β-磷酸三钙/海藻酸钠复合多孔支架的制备与研究

本文讨论了羟基磷灰石/β-磷酸三钙/海藻酸钠(HAP/β-TCP/AG)多孔支架的制备,并通过电子显微镜观察了其微观结构、研究其干细胞亲和性和生物相容性。研究表明:该多孔支架具有三维连通网状结构,干细胞在支架上黏附、生长良好,具有良好的干细胞亲和性和生物相容性。