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迈特纳(Lise Meitner)是奥地利物理学家,她1878年11月7日出生于奥地利的维也纳,父母都是犹太人血统,父亲是一位律师、自由思想家.迈特纳从少年起就对物理学发生兴趣,1901年进入维也纳大学学习,受到著名物理学家玻尔兹曼的重视和鼓励.1905年,迈特纳完成关于非均匀物质中热传导的博士论文,并获得了博士学位. 相似文献
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迈特纳(Lise Meitner)是奥地利物理学家,她1878年11月7日出生于奥地利的维也纳,父母都是犹太人血统,父亲是一位律师、自由思想家.迈特纳从少年起就对物理学发生兴趣,1901年进入维也纳大学学习,受到著名物理学家玻尔兹曼的重视和鼓励.1905年,迈特纳完成关于非均匀物质中热传导的博士论文,并获得了博士学位. 相似文献
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用密度可变的连续介质模型计算了A≥100区域β稳定核宏观位能曲面,得到了合理的裂变位垒高度,预言了鞍点态裂变核电荷的双重心分布. 相似文献
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一、引言目前利用原子能有两条途径:一是很轻原子核的聚变反应,一是最重原子核的裂变反应,都会释放出大量的能量。到目前为止,聚变反应尚不能人为地控制,因此,目前利用原子能主要是重原子核的裂变反应。自1938年发现原子核裂变以来,在实际中已经得到极为广泛的应用,但是这一学科的理论研究却远远地落在实际的后面。近几年来,裂变物理学在实验方面取得了 相似文献
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本文在核裂变统计理论基础上应用微观方法计算了235U热中子裂变的质量分布、动能分布及其它物理量.即用BCS哈密顿计算了断点组态碎块的量子态密度,碎块的变形对量子态密度的贡献也被考虑了.用斯图廷斯基(Strutinski)方案计算了碎块的势能,因而在断点组态的激发能中引入了壳效应和对关联.断点两碎块间的距离被处理为一个可调节的参数. 计算结果和实验值符合的程度比其它统计理论计算有改善. 相似文献
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尼尔斯·玻尔对原子核物理的最直接、最重要的贡献,是他创立了核反应复合核模型与原子核的裂变理论. 原子核裂变是指一个重核自发地或者通过中子或其它带电粒子打进原子核产生的核反应,使这个核分裂成两个质量相差不多的碎片.这一现象是哈恩(Hahn)和斯塔兹曼(Stra-ssmann)于193 相似文献
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“发现教学法”的再发现 总被引:1,自引:0,他引:1
把改进教学方法,使教育的重点从传授知识转向培养能力作为一个研究课题,多年以前就引起了一些有识之士的高度重视。人们逐渐形成了一个共识:由于科学技术的发展导致知识在日新月异地更新. 相似文献
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Carl A. Batt Anna M. Waldron Natalie Broadwater 《Journal of nanoparticle research》2008,10(7):1141-1148
Nanotechnology will be an increasing part of the everyday lives of most people in the world. There is a general recognition
that few people understand the implications of the technology, the technology itself or even the definition of the word. This
lack of understanding stems from a lack of knowledge about science in general but more specifically difficulty in grasping
the size scale and symbolism of nanotechnology. A potential key to informing the general public is establishing the ability
to comprehend the scale of nanotechnology. Transitioning from the macro to the nanoscale seems to require an ability to comprehend
scales of one-billion. Scaling is a skill not common in most individuals and tests of their ability to extrapolate size based
upon scaling a common object demonstrates that most individuals cannot scale to the extent needed to make the transition to
nanoscale. Symbolism is another important vehicle to providing the general public with a basis to understand the concepts
of nanotechnology. With increasing age, individuals are able to draw representations of atomic scale objects, but these tend
to be iconic and the different representations not easily translated. Ball and stick models are most recognized by the public,
which provides an opportunity to present not only useful symbolism but also a reference point for the atomic scale. 相似文献
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前期的研究报道了红外光谱能够监测水果变质产生的挥发物质,其方法是将挥发物收集在气室中,利用多次反射的结构来增强光信号。实验中,我们使用开放光程傅里叶变换红外光谱法监测葡萄变质挥发物,尝试了主动和被动两种测量模式。根据红外光谱特征对葡萄品劣变过程中产生的挥发物进行了定性分析,并在研究中测量了葡萄储藏期间挥发物质的红外光谱特征的强度变化,并且根据这种变化规律建立了不同变质阶段的分类方法。此外,还尝试直接从原始光谱中分析挥发物质,证明了挥发物在原始光谱上仍然具有明显的光谱特征。这一研究证实了现场开放式傅里叶变换红外光谱法监测水果变质的可行性。开放光程傅里叶变换红外光谱法所具有的灵活使用性和非接触式在线测量的优点,使其有可能应用于大面积监测储藏中的水果变质问题,并具有进一步定位劣变源的潜力。 相似文献
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EAST���弰��������ϵͳ��� 总被引:1,自引:1,他引:0
EAST运行中的温度改变会导致磁体及冷屏产生形变和位移。为了测量此位移的变化,利用一个延长臂,把位移转移到较易测量的位置,然后采用直滑式电位器把位移变化转换成电压变化并测量出其值,最终转换成位移的变化值。该测量系统解决了EAST装置中磁体和冷屏位移测量的难题。 相似文献
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M. Campbell J. A. Cosgrove C. A. Greated S. Jack D. Rockliff 《Optics & Laser Technology》2000,32(7-8):629-639
A review of laser Doppler anemometry (LDA) and particle image velocimetry (PIV) with their application to the measurement of sound is presented. The fundamental principles behind LDA and PIV are discussed and extended to the application of sound measurement. Special attention is paid to analysis of LDA signals including the Hilbert transform, which enables amplitude information to be obtained about various frequency components of a signal and wavelet analysis, which allows non-stationary signals to be accurately analysed. The influence of the refractive index variations in a medium due to a sound wave on the laser beams of an LDA signal is discussed. Attention is also paid to acoustic streaming which arises due to high-intensity sound, and PIV results are presented to demonstrate the effect. 相似文献
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The work relates to the effect of temperature on the model parameters in local approaches (LAs) to cleavage fracture. According to a recently developed LA model, the physical consensus of plastic deformation being a prerequisite to cleavage fracture enforces any LA model of cleavage fracture to observe initial yielding of a volume element as its threshold stress state to incur cleavage fracture in addition to the conventional practice of confining the fracture process zone within the plastic deformation zone. The physical consistency of the new LA model to the basic LA methodology and the differences between the new LA model and other existing models are interpreted. Then this new LA model is adopted to investigate the temperature dependence of LA model parameters using circumferentially notched round tensile specimens. With the published strength data as input, finite element (FE) calculation is conducted for elastic-perfectly plastic deformation and the realistic elastic-plastic hardening, respectively, to provide stress distributions for model calibration. The calibration results in temperature independent model parameters. This leads to the establishment of a ‘master curve’ characteristic to synchronise the correlation between the nominal strength and the corresponding cleavage fracture probability at different temperatures. This ‘master curve’ behaviour is verified by strength data from three different steels, providing a new path to calculate cleavage fracture probability with significantly reduced FE efforts. 相似文献
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A hardware–software apparatus for food inspection capable of realizing multispectral NIR laser imaging at four different wavelengths is herein discussed. The system was designed to operate in a through-transmission configuration to detect the presence of unwanted foreign bodies inside samples, whether packed or unpacked. A modified Lock-In technique was employed to counterbalance the significant signal intensity attenuation due to transmission across the sample and to extract the multispectral information more efficiently. The NIR laser wavelengths used to acquire the multispectral images can be varied to deal with different materials and to focus on specific aspects. In the present work the wavelengths were selected after a preliminary analysis to enhance the image contrast between foreign bodies and food in the sample, thus identifying the location and nature of the defects. Experimental results obtained from several specimens, with and without packaging, are presented and the multispectral image processing as well as the achievable spatial resolution of the system are discussed. 相似文献