课程文献中心 更多>>

关键词： 拉普拉氏变换   拉普拉斯逆变换   线性微分方程  

摘要： 拉普拉斯变换是一种具有广泛应用的积分变换.由于拉氏变换及其逆变换有一些简洁明了易于计算的性质,运用这些性质去解决较复杂的常系数非齐次线性微分方程的初值问题也成为解这一类特殊微分方程的好方法.文章比较了用拉氏变换法和微分方程的一般解法去解二阶常系数非齐次线性微分方程的初值问题的异同,发现用拉氏变换法更为简便.

关键词： China   Conservation messaging   Flagship species   Awareness raising   Interview survey   Protected area  

摘要： Conservation outreach is regularly conducted to increase support for conservation by altering local awareness and attitudes about species or environmental issues. However, there is often little assessment of the effectiveness of these activities. We investigated knowledge of past conservation outreach in 26 villages adjacent to Bawangling National Nature Reserve, Hainan, China, which contains the last population of the Hainan gibbon (Nomascus hainanus). The medium of past outreach activities was reported most frequently by interviewees, followed by who delivered them and the outreach topic, with the fewest interviewees reporting the specific messages being communicated (the consequences of following conservation management policies). Negativelyframed messages, emphasizing prohibited activities and associated punishments, were reported more than positively-framed messages that aimed to foster conservation support. Male interviewees and those with higher education levels reported more aspects of past activities. The Hainan gibbon had higher salience than other threatened native species, and reporting the occurrence (but not necessarily the content) of past outreach was associated with increased likelihood of knowing that gibbons were threatened. These findings highlight the need for conservation outreach to increase both exposure and retention of key messages among target audiences. Meaningful and concrete conservation benefits should be communicated to local communities, and the effectiveness of outreach using a flagship species could be expanded to also improve awareness of other conservationpriority species within the same landscape.

关键词： Abstract concepts   Grounded cognition   Mentalizing   Mental state concepts   Sensory-motor systems  

摘要： Refined grounded cognition accounts propose that abstract concepts might be grounded in brain circuits involved in mentalizing. In the present event-related potential (ERP) study, we compared the time course of neural processing in response to semantically predefined abstract mental states and verbal association concepts during a lexical decision task. In addition to scalp ERPs, source estimates of underlying volume brain activity were determined to reveal spatio-temporal clusters of greater electrical brain activity to abstract mental state vs. verbal association concepts, and vice versa. Source estimates suggested early (onset 194 ms), but short-lived enhanced activity (offset 210 ms) to verbal association concepts in left occipital regions. Increased occipital activity might reflect retrieval of visual word form or access to visual conceptual features of associated words. Increased estimated source activity to mental state concepts was obtained in visuo-motor (superior parietal, pre- and postcentral areas) and mentalizing networks (lateral and medial prefrontal areas, insula, precuneus, temporo-parietal junction) with an onset of 212 ms, which extended to later time windows. The time course data indicated two processing phases: An initial conceptual access phase, in which linguistic and modal brain circuits rapidly process features depending on their relevance, and a later conceptual elaboration phase, in which elaborative processing within feature-specific networks further refines the concept. This study confirms the proposal that abstract concepts are based on representations in distinct neural circuits depending on their semantic feature content. The present research also highlights the importance of investigating sets of abstract concepts with a defined semantic content.

关键词： cell morphometry   retinal degeneration   artificial intelligence   data science   AMD  

摘要： Regional phenotypic and functional differences in the retinal pigment epithelium (RPE) monolayer have been suggested to account for regional susceptibility in ocular diseases such as age-related macular degeneration (AMD), late-onset retinal degeneration (L-ORD), and choroideremia (CHM). However, a comprehensive description of human topographical RPE diversity is not yet available, thus limiting the understanding of regional RPE diversity and degenerative disease sensitivity in the eye. To develop a complete morphometric RPE map of the human eye, artificial intelligence-based software was trained to recognize, segment, and analyze RPE borders. Five statistically different, concentric RPE subpopulations (P1 to P5) were identified using cell area as a parameter, including a subpopulation (P4) with cell area comparable to that of macular cells in the far periphery of the eye. This work provides a complete reference map of human RPE subpopulations and their location in the eye. In addition, the analysis of cadaver non-AMD and AMD eyes and ultra-widefield fundus images of patients revealed differential vulnerability of the five RPE subpopulations to different retinal diseases.

关键词： differential phase contrast   quantitative phase imaging   deep learning  

摘要： Optical phase shifts generated by the spatial variation of refractive index and thickness inside the transparent samples can be determined by intensity measurements through quantitative phase contrast imaging. In this review, we focus on isotropic quantitative differential phase contrast microscopy (qDPC), which is a non-interferometric quantitative phase imaging technique that belongs to the class of deterministic phase retrieval from intensity. The qDPC is based on the principle of the weak object transfer function together with the first-order Born approximation in a partially coherent illumination system and wide-field detection, which offers multiple advantages. We review basic principles, imaging systems, and demonstrate examples of DPC imaging for biomedical applications. In addition to the previous work, we present the latest results for isotropic phase contrast enhancements using a deep learning model. We implemented a supervised learning approach with the U-net model to reduce the number of measurements required for multi-axis measurements associated with the isotropic phase transfer function. We show that a well-designed and trained neural network provides a fast and efficient way to predict quantitative phase maps for live cells, which can help in determining morphological parameters of cells for detailed study. The prospects of deep learning in quantitative phase microscopy, particularly for isotropic quantitative phase estimation, are discussed.

关键词： FPGA   瞬时测频   数字信道化   频率引导  

摘要： 本文针对某一设备的需求,设计了一种具有快速引导功能的高效数字信道化接收机。并利用Verilog语言在FPGA上完成了门电路实现。最终完成了2.5GHz采样率16子通道数字信道化接收机及其快速引导功能的板级实现,并验证了该结构的可靠性和高效性。

关键词： Jordan不等式   导数   应用  

摘要： 文章研究Jordan不等式在求解含有正弦、余弦形式的函数的导数压轴题中的应用。

关键词： Coupled mixed derivative nonlinear Schrodinger equation   Generalized Darboux transformation   Soliton   Inelastic colli-osions   Bound states  

摘要： In this paper,the dynamics of the higher-order soliton solutions for the coupled mixed derivative nonlinear Schrodinger equation¨are investigated via generalized Darboux *** a pair of linearly independent solutions of the Lax pair,the oneto three-soliton solutions are obtained via algebraic ***,two and three solitons are respectively displayed via numerical ***,the dynamics of solitons are illustrated with corresponding evolution plots,such as elastic collisions,inelastic collisions,and bound *** is found that there are some novel phenomena of interactions among solitons,which may provide a theoretical basis for studying optical solitons in experiments.

关键词： Electron beams  

摘要： Traditional x-ray sources used today for multiple applications, such as medical imaging (computed tomography, radiography, mammography, and interventional radiology) or industrial inspection, are vacuum based electron beam devices that include several key components, such as electron emitters, electron guns/cathodes, and anodes/targets. The associated electronics for electron beam generation, focusing and control, and beam acceleration are located outside the vacuum chamber. The general topology of these tubes has been directionally unchanged for more than 100 years;however, tube design remains a long, inefficient, tedious, and complex process;blind design of experiments do not necessarily make the process more efficient. As a case study, in this paper, we introduce the differential evolution (DE), an artificial intelligence-based optimization algorithm, for the design optimization of x-ray source beam optics. Using a small-scale design problem, we demonstrate that DE can be an effective optimization method for x-ray source beam optics design. Published under an exclusive license by AIP Publishing.