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11.
基于新课标对核心素养“科学探究与创新意识”的水平划分,分别选择旧教材的“科学探究”栏目和新教材的“探究”栏目作为分析单元,从内容对象、开放水平等2个维度对新旧教材科学探究内容进行分析。分析结果显示,新教材探究活动数目减少,但其开放水平整体提高,减少了无效探究,增加了结构化的探究活动。建议教师充分把握新教材“探究”栏目的新特征,开展素养为本的教学。  相似文献   
12.
Interference nanolithography techniques based on long-range surface plasmon polaritons (LR-SPP) are hardly ever achieved by experiments at present. One key reason is that suitable liquid materials are difflcult to find as the match layer connects the metal film and the resist. We redesign a Kretschmann-Raether structure for interference lithography. A polymer layer is coated under the metal film, and an air layer is placed between the polymer layer and the resist layer. This design not only avoids the above-mentioned question of the match layer, but also can form a soft contact between the polymer layer and the resist layer and can protect the exposure pattern. Simulation results confirm that a device with an appropriately thick polymer layer can form high intensity and contrast interference fringes with a critical dimension of about λ/7 in the resist. In addition, the fabrication of the device is very easy.  相似文献   
13.
A new type of meandering spiral pattern, in which the dense waves form groups while the sparse waves keep evenly spaced, is observed in a spatial open reactor using a ferroin-catalyzed Belousov-Zhabotinsky reaction. Such a phenomenon is related to both the Doppler effect of a meandering spiral and the oscillatory dispersion relation of the system. Simulation in the two-dimensional Oregonator reaction-diffusion model with an oscillatory dispersion relation gives very similar results.  相似文献   
14.
太阳直射光谱和天空光谱的测量与分析   总被引:4,自引:0,他引:4       下载免费PDF全文
在海拔9600m高空测量并获得了大气上界直射太阳光谱和天空光谱,测量了成都、丽江和玉龙雪山地表直射太阳光谱和天空光谱.结果表明:(西昌段)大气上界直射太阳光谱能量最大峰值对应的波长位于482.1nm,天空光谱能量分布相对于直射太阳光谱能量分布明显紫移,0.41—0.42μm波段成为天空光谱能量第一主峰区;地表晴天天空光谱中的能量分布与直射太阳光谱的能量分布区别很大,而有云时天空光谱中的能量分布和直射太阳光谱能量分布的差别比较小;玉龙雪山山峰积雪雪面在可见光波段对不同波长有不同的反照率. 关键词: 太阳直射光谱 天空光谱 大气上界  相似文献   
15.
西藏羊八井位于东经90.53°, 北纬30.11°, 海拔4310m, 垂直地磁截止刚度14.1GV. 2005年1月20日羊八井太阳中子望远镜和中子监测器探测到与X7.1/2b太阳耀斑相关的GLE事件, 其中太阳中子望远镜能量>40MeV的能道在5min(07:00—07:05UT)和20min(07:00—07:20UT)的时间间隔内计数率增长的统计显著性分别是3.7σ和6.0σ, 同时羊八井中子监测器也探测到计数率的增长,初始时间为06:51—06:52UT. 观测表明在这次GLE事件中太阳质子可被加速到能量大于10GeV.  相似文献   
16.
A focused gallium ion (Ga+) beam is used to fabricate micro/submicron spacing gratings on the surface of porous NiTi shape memory alloy (SMA ). The crossing type of gratings with double-frequency (25001/mm and 50001/mm) using the focused ion beam (FIB) milling are successfully produced in a combination mode or superposition mode. Based on the double-frequency gratings, high-quality scanning electron microscopy (SEM) Moird patterns are obtained to study the micro-scale deformation of porous NiTi SMA. The grating fabrication technique is discussed in detail. The experimental results verify the feasibility of fabricating high frequency grating on metal surface using FIB milling.  相似文献   
17.
Fourier transform profilometry based on composite structured light pattern   总被引:1,自引:0,他引:1  
In Fourier transform profilometry (FTP), the zero frequency of the imaged patterns will influence the measurement range and precision. The π phase shifting technique is usually used to eliminate the zero order component, but this method requires the capture of two fringe patterns with a π phase difference between them, which will impede the real time application of the method. In this paper, a novel method is proposed, in which a composite structured light pattern is projected onto the object. The composite structured light pattern is formed by modulating two separate fringe patterns with a π phase difference along the orthogonal direction of the two distinct carrier frequencies. This method can eliminate the zero frequency by using only one fringe pattern. Experiments show that there is no decrease in the precision of this novel method compared with the traditional π phase shifting technique.  相似文献   
18.
碳纳米管束中的正电子理论   总被引:1,自引:0,他引:1       下载免费PDF全文
陈祥磊  郗传英  叶邦角  翁惠民 《物理学报》2007,56(11):6695-6700
采用中性原子叠加模型和有限差分方法(SNA-FD)计算了大范围内不同管径的单壁碳纳米管束中的正电子情况,发现对于单壁碳纳米管束,正电子的主要湮没区域,湮没对象和正电子寿命随碳纳米管管径的不同而发生规律性变化.计算得到管径范围在0.8—1.6nm的碳纳米管束的正电子寿命范围为332—470ps,与实验测得的394ps符合较好.  相似文献   
19.
Mass analysis of proteolytic fragment peptides following hydrogen/deuterium exchange offers a general measure of solvent accessibility/hydrogen bonding (and thus conformation) of solution-phase proteins and their complexes. The primary problem in such mass analyses is reliable and rapid assignment of mass spectral peaks to the correct charge state and degree of deuteration of each fragment peptide, in the presence of substantial overlap between isotopic distributions of target peptides, autolysis products, and other interferant species. Here, we show that at sufficiently high mass resolving power (m/Δm50% ≥ 100,000), it becomes possible to resolve enough of those overlaps so that automated data reduction becomes possible, based on the actual elemental composition of each peptide without the need to deconvolve isotopic distributions. We demonstrate automated, rapid, reliable assignment of peptide masses from H/D exchange experiments, based on electrospray ionization FT-ICR mass spectra from H/D exchange of solution-phase myoglobin. Combined with previously demonstrated automated data acquisition for such experiments, the present data reduction algorithm enhances automation (and thus expands generality and applicability) for high-resolution mass spectrometry-based analysis of H/D exchange of solution-phase proteins.  相似文献   
20.
This paper reports that the synchronous integer multiple oscillations of heart-cell networks or clusters are observed in the biology experiment. The behaviour of the integer multiple rhythm is a transition between super- and sub- threshold oscillations, the stochastic mechanism of the transition is identified. The similar synchronized oscillations are theoretically reproduced in the stochastic network composed of heterogeneous cells whose behaviours are chosen as excitable or oscillatory states near a Hopf bifurcation point. The parameter regions of coupling strength and noise density that the complex oscillatory rhythms can be simulated are identified. The results show that the rhythm results from a simple stochastic alternating process between super- and sub-threshold oscillations. Studies on single heart cells forming these clusters reveal excitable or oscillatory state nearby a Hopf bifurcation point underpinning the stochastic alternation. In discussion, the results are related to some abnormal heartbeat rhythms such as the sinus arrest.  相似文献   
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