小学教育专业“基础化学-倾向生活化学”教学探索与实践

课程教学与改革须融合知识更新,立足专业培养目标,将课堂真正落实到所需之处。因此笔者在小学教育专业开设“基础化学”教学时,重构课程内容,将基础化学知识融合于日常生活中;构建实验平台,提供学生动手实践的机会;体现师范教育,注重培养学生实施科教活动的素养和技能,取得了较好的教学效果。

无机化学四个易混淆基本概念的讲授建议

化学概念模糊表述容易导致学生学习障碍,不利于培养学生严密的逻辑思维。无机化学是化学及近化学专业的基础课之一,教授对象多为大学一年级本科生,清晰讲授基本概念的重要性不言而喻。本文通过对无机化学四个常见易混淆的概念进行分析,指出了产生错误结论的原因,并给予了一些讲授建议。

Convolutional neural networks for time series classification

Time series classification is an important task in time series data mining, and has attracted great interests and tremendous efforts during last decades. However, it remains a challenging problem due to the nature of time series data: high dimensionality, large in data size and updating continuously. The deep learning techniques are explored to improve the performance of traditional feature-based approaches. Specifically, a novel convolutional neural network (CNN) framework is proposed for time series classification. Different from other feature-based classification approaches, CNN can discover and extract the suitable internal structure to generate deep features of the input time series automatically by using convolution and pooling operations. Two groups of experiments are conducted on simulated data sets and eight groups of experiments are conducted on real-world data sets from different application domains. The final experimental results show that the proposed method outperforms state-of-the-art methods for time series classification in terms of the classification accuracy and noise tolerance. ? 1990-2011 Beijing Institute of Aerospace Information.

Micro-motion dynamics analysis of ballistic targets based on infrared detection

The dynamic characteristics related to micro-motions, such as mechanical vibration or rotation, play an essential role in classifying and recognizing ballistic targets in the midcourse, and recent researches explore ways of extracting the micro-motion features from radar signals of ballistic targets. In this paper, we focus on how to investigate the micro-motion dynamic characteristics of the ballistic targets from the signals based on infrared (IR) detection, which is mainly achieved by analyzing the periodic fluctuation characteristics of the target IR irradiance intensity signatures. Simulation experiments demonstrate that the periodic characteristics of IR signatures can be used to distinguish different micro motion types and estimate related parameters. Consequently, this is possible to determine the micro-motion dynamics of ballistic targets based on IR detection.

Design and Verification of High Attenuation Vibration Isolation Damper in Remote Sensing Satellite Transport

To solve the safe horizontal transportation by rail&road of remote sensing satellite problem in the process of unpredictable dynamic load,a high attenuation vibration isolation damper(hereinafter referred to as vibration isolation damper)was developed.By simulation analysis and transportation test using satellite structural model and engineering prototype,validity and reliability of the vibration isolation damper was verified,which can meet the requirements of vibration and shock from various transportation conditions.

低能强流混合离子束空间电荷补偿度研究

空间电荷效应是影响束流传输和束流品质的一个重要因素,特别是对于低能量强流离子束来说。离子束与束流传输线中的剩余气体分子通过电离反应等产生大量二次电子,受离子束的空间电势约束,可以部分补偿空间电荷效应。为了深入研究强流束在低能段的传输,需要准确测量束流的空间电荷补偿度(SCCD),尤其是混合束流的SCCD。利用一台三栅网式能量分析仪和一台基于128通道皮安表系统构成的束流剖面探测器,分别测量了不同流强和束流分布下的混合O离子束的二次离子能量分布和束流流强分布,从而计算得出SCCD。实验结果表明,在1.0×10^(−5) Pa的真空度下,不同流强的混合O离子束的SCCD基本在70%左右;不同束流分布对空间电势分布影响较大,对离子束的SCCD也会有一定程度的影响。

Bi_(2)O_(2)Se nanoplates for broadband photodetector and full-color imaging applications

Broadband light detection and sensing are widely applied in modern technology.As a promising candidate for next-generation two-dimensional(2D)optoelectronic material,bismuth oxyselenide(Bi_(2)O_(2)Se)nanoplates exhibit many prospects in the application of visible light detection due to their peculiar properties.In this work,we report the photodetection performance of single-crystal 2D Bi_(2)O_(2)Se nanoplates grown on SiO_(2)based on a ternary-alloy growth model by utilizing chemical vapor deposition(CVD).The Bi_(2)O_(2)Se nanoplates were found to have an even and uniform square shape with side lengths up to 15μm and an approximate thickness of 15 nm.A visible-light photodetector was fabricated based on a CVD-grown Bi_(2)O_(2)Se nanoplate,and characterized by a set of illumination experiments using a 400 nm laser at temperatures ranging from 77 to 370 K.The device exhibited superior performance at the temperature of 77 K,with a responsivity of 523 A/W,a specific detectivity of 1.37×10^(11)Jones,a response time of 0.2175 ms,an external quantum efficiency of 162,119.44%,resulting in high-quality and fullcolor imaging in the visible spectrum.These results indicate that the single-crystalline Bi_(2)O_(2)Se nanoplates have excellent potential in broadband photodetection and non-cryogenic imaging.

Large area van der Waals epitaxy of II-VI CdSe thin films for flexible optoelectronics and full-color imaging

The demand for future semiconductor devices with enhanced performance and lower cost has driven the development of epitaxial growth of high quality,free-standing semiconductor thin film materials without the requirement of lattice matching to the substrate,as well as their transfer to other substrates and associated device processing technology.This work presents a study on the van der Waals epitaxy based molecular beam epitaxy of CdSe thin films on two-dimensional layered mica substrates,as well as related etch-free layer transfer technology of large area,free-standing layers and their application in flexible photodetectors for full-color imaging.The photoconductor detectors based on these flexible CdSe thin films demonstrate excellent device performance at room temperature in terms of responsivity(0.2 A·W^(-1))and detectivity(1.5×10^(12)Jones),leading to excellent full-color imaging quality in the visible spectral range.An etch-free and damage-free layer transfer method has been developed for transferring these CdSe thin films from mica to other substrate for further device processing and integration.These results demonstrate the feasibility of van der Waals epitaxy method for growing high quality,large area,and free-standing epitaxial layers without the requirement for lattice matching to substrate for applications in low-cost flexible and/or monolithic integrated optoelectronic devices.

Self-polymerization and co-polymerization kinetics of gadolinium methacrylate

Gadolinium methacrylate（Gd（MAA）3） was synthesized by using gadolinium oxide and methacrylic acid as the starting materials and its self-polymerization kinetic was studied based on non-isothermal and isothermal analysis. Moreover, the monomer reactivity ratios of methyl methacrylate（MMA） and Gd（MAA）3 were evaluated by using Kelen-Tiidos method. The thermal neutron shielding properties of PMMA and poly（MMA-co-Gd（MAA）3） were calculated by MCNP program. The results show that the selfpolymerization of Gd（MAA）3 can be initiated by thermal and free radical and its activation energy is103.35 kJ/mol or 58.55 kJ/mol correspondingly in the solid state or aqueous solution. The polymerization rate,Rp,under low conversion at 65 ℃ is expressed as Rp = K[M]^（1.05）[I]^（0.60）. The reactivity ratios of r1（MMA） and r2（Gd（MAA）3） are 0.225 and 1.340, respectively. The ability of thermal neutron shielding of poly（MMA-co-Gd（MAA）3） is increased by gadolinium contents and is far better than PMMA.

Effect of Boron Compounds on Properties of Chinese Fir Wood Treated with PMUF Resin

Plantation Chinese fir wood was modified by low molecular weight phenol melamine urea formaldehyde(PMUF)resin and boron compounds(BB)through a progressive gradual infiltration process.The results showed that the limiting oxygen index(LOI)values,density,dimensional stability and static flexural properties of the PMUF resin treated wood gradually improved with the increase of resin solid content.When boron compounds were additionally introduced into the PMUF resin,the density and the LOI values of the samples of compound modification increased,whereas the anti-swelling efficiency,the modulus of rupture and impact toughness decreased by more than 17.6%,10.1%and 42.9%,respectively.It was demonstrated by X-ray diffraction and Fourier transform infrared spectroscopy that boron compounds could improve the crystallinity of resin modified samples and did not have a chemical reaction with resin or wood.Scanning electron microscope analysis indicated boron compounds made the microstructure of the resin polymers loose,influencing the mechanical properties and dimensional stability of resin modified wood.

A Model Study on the Generation of Internal Tides by Tidal Flows Over a Submerged Seamount in the Channel

It is known that the submerged seamount/ridge is a source for the generation of internal tides.In this paper,a three-dimensional two-layer model is set up to study the generation of internal tides by tidal flows over a submerged seamount/ridge in the channel.Several numerical experiments with different topographic features,upper layer depths,tidal flows and background currents are carried out to study the variations of the induced internal tides.It is shown that,for the specific stratification,the seamount feature,the slope,the initial upper layer depth and the imposing driven force determine the Froude number near the seamount peak.Once when the Froude number is supercritical,the associated maximum amplitude of the induced internal tide is so large that the internal tide begins to disintegrate,which brings about severe variations of the current velocity and the water elevation fields,and the associated induced baroclinic tidal energy around the seamount peak is much larger than the barotropic one.The Richardson number greater than 1/4 is a criterion for stability of shear flow.Since the maximum tidal velocity changes within 0∼360◦with time in a period around the seamount peak,the induced internal tide does not stride the seamount peak before it disintegrates,which is different from the two-dimensional modeled results.The asymmetrical slope of the submerged seamount is a mechanism for the asymmetrical internal tide generation.