Effect of {332}< 113 > Twins Combined with Isothermal omega-Phase on Mechanical Properties in Ti-15Mo Alloy with Different Oxygen ContentsEI北大核心CSCD

beta-type alloys have a wide application prospect in aerospace, biomedical and marine engineering and other fields, owing to their high specific strength, good corrosion resistance and low elastic modulus. Their yield strength and uniform elongation are affected by the second phase precipitation, plastic deformation mode and interstitial element, especially the oxygen element. In this work, the effect of tensile pre-deformation induced {332}< 113 > twins combined with isothermal w-phase after subsequent ageing on the mechanical properties of beta-type Ti-15Mo alloy with different oxygen contents from 0.1% to 0.5% (mass fraction) was examined by OM, XRD, TEM and DSC, Vickers hardness tester and tensile testing machine. The results indicated that with increasing the oxygen content, the formation of mechanical twins and isothermal omega-phase in the alloy was suppressed, and the effect of pre-deformation induced twins on the precipitation of isothermal omega-phase was negligible. After pre-deformation combined with subsequent ageing, the alloy with low oxygen content had the relatively high yield strength and large uniform elongation, but it with high oxygen content exhibited the brittle fracture. A good combination of strength with ductility in the alloy with low oxygen content was contributed to the twinning and dislocation slip coupled deformation. The high yield strength was mainly dominated by the dislocation slip, and the large uniform elongation was due to the static and dynamic grain refinement effects, which were caused by the pre-deformation induced twins and subsequent twinning deformation, respectively. Through utilizing the alloying element of oxygen effectively, and changing the plastic deformation mode and phase precipitation behavior based on the reasonable process of pre-deformation and heat treatment, the combination of strength and ductility can be controlled in a large range for the beta-type titanium alloys.     

Convergence analysis of dynamic stochastic approximation

Stochastic approximation method concerns the sequential estimation of the root or the extreme of a function observed with noise. The idea is then extended to the moving root case by Dupa , and it is called as the dynamic stochastic approximation method. Its convergence properties are derived here by using a randomly varying truncation technique under weaker conditions in comparison with the previous work: the growth rate restriction on the function has been removed and the condition on the observation noises has been weakened to the possibly weakest ones.     

Novel optical FSK heterodyne single filter detection system using a directly modulated DFB-laser diode

A novel optical FSK heterodyne single filter detection system, which can use direct modulation and can tolerate the relatively large spectral width of a laser diode, is proposed. The receiver sensitivity improvement, as much as 8 dB over direct detection using a Ge APD, has been achieved after 105 km transmission at 100 Mbit/s.     

Local Structure Around Cs+ Ion in Na2CsC60 Superconductor

Cs K-edge EXAFS studies are carried out for the first time on the superconducting Na₂CsC₆₀ at 20K and at room temperature. We have found that Cs⁺ ion is located at not only the octahedral site but also the tetrahedral site.     

Highly practical fiber squeezer polarization controller

The authors developed a fiber squeezer polarization controller satisfying these requirements: (1) stable endless operation, (2) high response speed in the endless operation, and (3) protection from fiber break, a particular problem in a fiber squeezer polarization controller. The developed controller realized a stable endless operation with less than 0.1-dB power penalty under 40°C fiber squeezer temperature change. In addition, a practically sufficient response speed of 15 π rad/s was obtained in an endless operation. A metal-coated fiber used in the fiber squeezers was confirmed to be effective in preventing fiber break by a repetitive load application test (5-10 kg, one million times) to the metal-coated fiber. These techniques could realize a practical and high performance polarization controller for a coherent transmission system     

A Comparison of Normal Approximation Rules for Attribute Control Charts

Control charts, known for more than 80 years, have been important tools for business and industrial manufactures. Among many different types of control charts, the attribute control chart (np‐chart or p‐chart) is one of the most popular methods to monitor the number of observed defects in products, such as semiconductor chips, automobile engines, and loan applications. The attribute control chart requires that the sample size n is sufficiently large and the defect rate p is not too small so that the normal approximation to the binomial works well. Some rules for the required values for n and p are available in the textbooks of quality control and mathematical statistics. However, these rules are considerably different, and hence, it is less clear which rule is most appropriate in practical applications. In this paper, we perform a comparison of five frequently used rules for n and p required for the normal approximation to the binomial. With this result, we also refine the existing rules to develop a new rule that has a reliable performance. Datasets are analyzed for illustration. Copyright © 2013 John Wiley & Sons, Ltd.     

Group signature implies public-key encryption with non-interactive opening

In this paper, we show that public-key encryption with non-interactive opening (PKENO) can be constructed from an arbitrary group signature (GS) scheme which is secure in the dynamic group setting and provides opening soundness. Moreover, the resulting PKENO construction is efficient if the underlying GS scheme is efficient and the message space of the PKENO scheme is restricted to short messages. Hence, our result not only shows that the existence of this type of GS implies the existence of PKENO, but also that designing a practical GS scheme is as difficult as designing a practical PKENO scheme. Our transform is constructed by carefully investigating the relationship between the functionalities of GS and that of PKENO, and developing a novel (but specific) multiple encryption technique. This multiple encryption technique plays an important role for simultaneously achieving both practical efficiency and security.     

Behaviors of Bellows-Like Origami Patterned Tubes with Trapezoidal Patterns

In this paper, we show one of the possibility utilizing typical origami structures for civil engineering fields such as the bridge bearing support. We numerically investigate axial spring constants and buckling behaviors of bellows-like origami tube structures. The bellows-like origami tube structures, which can be folded because of elastic deformations, work as a kind of spring. If the initial heights of the bellows-like origami tubes are less than 90% of the height of the prismatic tubes without bellows-like folded lines, the spring constants of the bellows-like tubes are very low compared with those of the prismatic tubes. The buckling loads and patterns of the bellows-like tubes vary depending on the initial heights of the tubes.