知识传递与内化的过程反转——“翻转课堂”的教学模式设计与应用的关键

翻转课堂教学理论作为一种全新的教学理念,其在具体应用过程中发生了重大变化,但我们应该认识到老师和学生之间的互动关系不仅没有发生变化,从某种程度上看,其内涵更深刻。因此,这一教学模式在设计和应用过程中,必须针对学生学习的知识点,进行深化。该文拟从翻转课堂教学模式的定义和内涵入手,结合该教学模式应用的具体作用,从而分析知识传递和内化在该模式应用中的价值。

雨刮反转过程振动冲击特性实验研究

汽车雨刮反转时产生的振动冲击是引起雨刮噪声的主要因素之一。近年来,雨刮运动学及动力学性能得到广泛研究。为了研究雨刮反转过程的振动冲击特性,搭建一种基于平动测试系统的雨刮反转实验台,开展不同工况下雨刮反转过程中振动冲击实验与分析。结果表明,雨刮反转实验台能够实现对应实车各挡位调速功能,实验结果与实车测试在方向上具有一致性;其能够区分和模拟玻璃表面的不同干湿状态,并进行刮片力学状态分析;对于所测工况,刮刷速度与加减速对振动冲击的影响呈正相关,而相比刮刷速度,加减速时间对刮片反转过程中的振动冲击影响较小。实验研究结果对进一步分析雨刮噪声产生机理及噪声控制等具有一定意义与价值。

雨刮-风窗接触系统摩擦振动分析

针对雨刮-风窗接触系统在工作中的摩擦振动问题,首先建立雨刮-风窗接触系统的动力学理论模型,并推导出解析式以研究接触系统的振动;其次,利用Runge-Kutta法在MATLAB中计算出理论模型的非线性动态响应;最后,用雨刮-风窗接触系统的实验阐明雨刮片的振动行为。通过对比实验与仿真结果,验证了理论模型的有效性,可为雨刮-风窗接触系统的振动噪声控制提供参考。

Cloning and Expression Analysis of vasa During the Reproductive Cycle of Korean Rockfish, Sebastes schlegeli

Vasa, which is a conserved member of the DEAD-box protein family, plays an indispensable role in primordial germ cell proliferation. However, the expression ofvasa gene during the reproductive cycle in ovoviviparous fish has not been documented. In this study, the full-length sequence of vasa was obtained from the ovary of Korean rockfish （Sebastes schlegeli） using reverse transcription-PCR and rapid amplification of cDNA ends. The Vasa with a mature protein of 650 amino acids showed greatest homology （84%） with giant gourami （Osphronemus gorarny） and Pacific bluefin tuna （Thunnus orientalis）. The expression of vasa mRNA in Korean rockfish was detected in gonads only, suggesting its specific role in gonadal development. In addition, seasonal changes in the vasa expression levels were examined in gonads by quantitative real-time PCR. The vasa transcript levels in adult testis were found higher during spermatogenesis than during spermiation. The vasa transcript levels remained relatively high at the early ovary stage but declined during ovary maturation in adult female fish. These results suggest that the vasa gene play an important role in spermatogenesis and early oogenesis during the reproductive cycle of Korean rockfish.

Reaction mechanism of roasting Zn_2SiO_4 using NaOH

The reaction kinetics of roasting zinc silicate using NaOH was investigated.The orthogonal test was employed to optimize the reaction conditions and the optimized reaction conditions were as follows:molar ratio of NaOH to Zn2SiO4 of 16:1,reaction temperature of 550°C,and reaction time of 2.5 h.In order to ascertain the phases transformation and reaction processes of zinc oxide and silica,the XRD phase analysis was used to analyze the phases of these specimens roasted at different temperatures.The final phases of the specimen roasted at 600°C were Na2ZnO2,Na4SiO4,Na2ZnSiO4 and NaOH.The reaction kinetic equation of roasting was determined by the shrinking unreacted core model.Aiming to investigate the reaction mechanism,two control models of reaction rate were applied:chemical reaction at the particle surface and diffusion through the product layer.The results indicated that the diffusion through the product layer model described the reaction process well.The apparent activation energy of the roasting was 19.77 kJ/mol.

Extracting the Subsonic Anti-Symmetric Lamb Wave from a Submerged Thin Spherical Shell Backscattering Through Iterative Time Reversal

The extraction of the weakly excited anti-symmetric Lamb wave from a submerged thin spherical shell backscattering is very difficult if the carrier frequency of the incident short tone burst is not at its frequency of greatest enhancement. Based on a single channel iterative time reversal technique, a method for isolating the subsonic anti-symmetric Lamb wave is proposed in this paper. The approach does not depend on the form function of a thin shell and any other priori knowledge, and it is also robust in the presence of some stochastic noise. Both theoretical and numerical results show that the subsonic anti-symmetric Lamb wave can be identified, even when the carrier frequency of the incident short tone burst is away from the frequency of greatest enhancement. The phenomenon may also be observed even in the case that the subsonic anti-symmetric Lamb wave is submerged in the noise, other than the case with the Signal to Noise Ratio being less than 10 d B, when the amplitude of the noise is comparable with the specular wave. In this paper, each iteration process contains a traditional transmission and time reversal transmission steps. The two steps can automatically compensate the time delay of the subsonic anti-symmetric Lamb wave relative to the specular wave and within-mode dispersion in the forward wave propagation.

Atomistic simulations of interactions between screw dislocation and twin boundaries in zirconium

Molecular statics was employed to simulate interaction between screw dislocation and twin boundaries（TB） in hexagonal close-packed zirconium. In the moving TB model, the interaction of a moving {10ˉ12} TB with a static 1/311ˉ20{10ˉ10} screw dislocation was investigated. Twinning dislocation（TD） nucleation and movement play an important role in the interaction. The screw dislocation passes through the moving TB and changes to a basal one with a wide core. In the moving dislocation model, a moving 1/31120{1010} dislocation passes through the TB, converting into a basal one containing two partial dislocations and an extremely short stacking fault. If the TB changes to the {1011} one, the moving1/31120{1010} prismatic screw dislocation can be absorbed by the static TB and dissociated into two TDs on the TB. Along with the stress-strain relationship, results reveal the complicated mechanisms of interactions between the dislocation and TBs.

Dual function of Arabidopsis A TAF1 in abiotic and biotic stress responses

NAC family genes encode plant-specific transcription factors involved in diverse biological processes. In this study, the Arabidopsis NAC gene ATAF1 was found to be induced by drought, high-salinity, abscisic acid （ABA）, methyl jasmonate, mechanical wounding, and Botrytis cinerea infection. Significant induction of ATAF1 was found in an ABA-deficient mutant aba2 subjected to drought or high salinity, revealing an ABA-independent mechanism of expression. Arabidopsis ATAFl-overexpression lines displayed many altered phenotypes, including dwarfism and short primary roots. Furthermore, in vivo experiments indicate that ATAF1 is a bonafide regulator modulating plant responses to many abiotic stresses and necrotrophic-pathogen infection. Overexpression of ATAF1 in Arabidopsis increased plant sensitivity to ABA, salt, and oxidative stresses. Especially, ATAF1 overexpression plants, but not mutant lines, showed remarkably enhanced plant tolerance to drought. Additionally, ATAF1 overexpression enhanced plant susceptibility to the necrotrophic pathogen B. cinerea, but did not alter disease symptoms caused by avirulent or virulent strains of P. syringae pv tomato DC3000. Transgenic plants overexpressing ATAF1 were hypersensitive to oxidative stress, suggesting that reactive oxygen intermediates may be related to ATAFl-mediated signaling in response to both pathogen and abiotic stresses.

Numerical study on catalytic combustion of methane with ozone using Pd-exchanged zeolite X

A steady-state ID macro-homogeneous model is developed to illustrate the combustion process of methane with ozone in the reactor composed of Pd-exchanged zeolite X. The model is validated by comparing the predicted results with the measured data. The methane conversion increases with decreasing the inlet methane concentration and gas space velocity and increasing the inlet ozone concentration and temperature. As the reactor length reduces, the methane conversion varies little if the reactor is too long but decreases when the reactor is too short. Therefore, the reactor should he properly designed to balance costs and the methane-conversion efficiency.

Photosensitized oxidation of tryptophan and tyrosine by aromatic ketones:A laser flash photolysis study

Photochemical processes of benzophenone （BP） and xanthone （XT） with tryptophan （TrpH） and tyrosine （TyrOH） were stud- ied using the laser flash photolysis technique. It has been observed that the triplet state of BP and XT reacted with TrpH and TyrOH by hydrogen transfer with the formation of BP and XT ketyl radicals and oxidized radicals of Trp＂ and TyrO＇. The re- lated rate constants of these reactions were determined in this paper. The free energy changes （AG） of these reactions suggested that the proposed hydrogen transfer mechanism was thermodynamically feasible. These results provide theoretical foundation for further studying structural effects on the photochemical behaviors of proteins with triplet state BP and XT.