Effect of flash processing on recrystallization behavior and mechanical performance of cold-rolled IF steel

Flash processing(FP)has attracted considerable attention due to its high efficiency,economic advantages,and the extraordinary opportunity if offers to improve the mechanical properties of steel.In this study,we investigated the influences of FP on the recrystallization(REX)behavior and mechanical performance of cold-rolled IF steel.Using a thermomechanical simulator,we performed both single-stage FPs,at heating rates of 200℃/s and 500℃/s,and two-stage FP,with an initial preheating to 400℃ at a rate of 5℃/s and then to peak temperatures at a rate of 200℃/s.In comparison to continuous annealing(CA),single-stage FP can effectively refine the recrystallized grain sizes and produce a similar or even sharperγ(ND(normal direction)//{111})texture component.In particular,the heating rate of 500℃/s led to an increase in the yield strength of about 23.2%and a similar ductility.In contrast,the two-stage FP resulted in a higher REX temperature as well as a certain grain refinement due to the stored strain energy,i.e.,the driving force of REX,which was largely consumed during preheating.Furthermore,both stronger{110}<110>and weakerγtexture components appeared in the two-stage FP and were believed to be responsible for the early necking and deterioration in ductility.

Coherent and incoherent theories for photosynthetic energy transfer

自然界的光合作用有一个显著的特点,即能量传递效率近乎100%.近年来,由于光合作用实验技术的飞速发展,譬如二维光谱实验和单分子泵浦探测实验,其能量传输过程中的量子相干效应已经在实验上得到了证实.传统的非相干理论能够有效计算能量转移效率,如广义的F?rster理论和修正的Redfield理论.然而,为了描述光合作用中的量子相干效应,人们必须利用量子相干理论.例如,除了传统的Redfield理论之外,还有级联运动方程、量子路径积分、相干修正的Redfield理论、小极化子量子主方程、广义Bloch-Redfield理论等.本文综述了上述方法的主要内容,不仅有助于对自然界光合作用中激子能量转移的量子动力学进行有效的量子模拟,并对人工太阳能收集装置的设计提供了一定的指导作用.

Experimental demonstration of mode-matching and Sagnac effect in a millimeter-scale wedged resonator gyroscope

The highly efficient coupling of light from conventional optical components to optical mode volumes lies in the heart of chip-based micro-devices,which is determined by the mode-matching between propagation constants of fiber taper and the whispering-gallery-mode(WGM)of the resonator.Optical gyroscopes,typically realized as fiber-optic gyroscopes and ring-laser gyroscopes,have been the mainstay in diverse applications such as positioning and inertial sensing.Here,the mode-matching is theoretically analyzed and experimentally verified.We observe the Sagnac effect in a millimeter-scale wedged resonator gyroscope,which has attracted considerable attention and has been rapidly promoted in recent years.We demonstrate a bidirectional pump and probe scheme,which directly measures the frequency beat caused by the Sagnac effect.We establish the linear response between the detected beat frequency and the rotation velocity.The clockwise and counterclockwise rotation can also be distinguished according to the value of the frequency beat.The experimental results verify the feasibility of developing the gyroscope in a WGM resonator system and pave the way for future development.

A thermodynamic model on predicting density of medium-Mn steels with experimental verification

A new model on predicting the density of hot-rolled multi-phased medium-Mn steel has been presen ted on the basis of thermodynamic calculations. This is an integrated model, which includes one for calculating the retained austenite （RA） fraction and the other for volume expansion during the aus tenite-to martensite transformation, because both of them are key parameters for calculating the den- sity of steel at ambient temperature. The existing empirical equations for calculating Mx temperature and lattice constants of both martensite and austenite have been all rcassessed by the XRD measure ments on the microstructures of seven hot-rolled medium-Mn steels. Finally, the densities ot seven steels were calculated merely from compositions and compared with the measured ones. The differ ence between them is no more than 1 %, suggesting that the presented model should be of good value in designing the low density steels.