基于人眼视觉皮层系统的SAR图像目标识别

人眼的视觉系统是已知最复杂最精确的目标识别系统;针对现有浅层学习模型提取SAR图像目标特征效果不理想、普适性不强及目标识别精度不高等问题,参考人眼视觉系统的分层特征提取机制提出了一种深层特征提取目标识别算法;算法首先提出一种针对SAR图像的预处理方法,在特征提取阶段应用多层稀疏自动编码器,通过逐层减少神经元数目使编码器学习得到输入数据的压缩表示,从而提取得到更抽象更鲁棒的目标特征;采用MSTAR数据库3个目标进行实验,试验结果表明,算法能很好地对MSTAR目标进行特征提取和识别,类比原有的方法有较高的识别准确率,达到96.7%。具有较强的实用性。     

改进的双曲等效法用于双站合成孔径雷达前视成像

双站合成孔径雷达(SAR)前视成像有着很多的潜在应用,比如在能见度很低的天气实现飞机的导航和盲降,提高飞机飞行的安全度等.然而实现双站SAR前视成像的难点在于其距离历程的双根式性,直接采用驻定相位原理对其分解将得到复杂的解析式,从而后续算法的推导变得困难.现有的双曲等效法可以将双根式距离历程等效为单根式,但由于该方法为距离历程的二阶近似,当用于双站SAR前视成像时,由于其较大的前视角,未完全等效的距离历程高次项造成的误差已经超出可以接受的范围.针对以上问题,本文首先提出了一种改进的双曲等效法,该方法通过引入新的补偿变量来提高距离历程的等效精度;然后在此基础上推导回波信号的二维频谱解析式,并给出了一种适用于双站SAR前视成像的距离多普勒算法;最后通过仿真实验,将原双曲等效法与改进方法的等效误差以及成像结果做对比,验证了本文算法的有效性和优越性.     

Synthesis and Antifungal Activities of New Type β‐Methoxyacrylate‐Based Strobilurin Analogues

Strobilurins have become one of the most important classes of agricultural fungicides. To discover new strobilurin derivatives with high activity against resistant pathogens, a series of novel β‐methoxyacrylate analogues were designed and synthesized by integrating substituted pyrimidine with a strobilurin pharmacophore. The compounds were confirmed and characterized by infrared, ¹H nuclear magnetic resonance, elemental analysis and mass spectroscopy. The bioassays indicated that most of the compounds 1 exhibited potent antifungal activity against Colletotrichum orbiculare, Botrytis cinerea Pers and Phytophthora capsici Leonian at the concentration of 50 μg/mL. Exhilaratingly, compound 1a (R=methyl) showed better antifungal activity against all the tested fungi than the commercial strobilurin fungicide azoxystrobin.     

Synthesis,biological evaluation and SAR studies of benzimidazole derivatives as H1-antihistamine agents

A series of benzimidazole derivatives have been designed,synthesized and evaluated for H₁ antihistamine activity.Six compounds have showed potent antihistamine H₁ activity.The primary SAR analysis indicated that benzyl or benzylidinyl substituted on the exo-nitrogen atom and C2 of the benzimidazole were significant.Further experiments indicated that compound 17d displayed excellent activity to reduce mast cell degranulation,moderate anti-PAF activity and decreased potency on hERG compared to astermizole.Hence compound 17d could serve as anti-allergic agent for further development.     

Evaluation of MRI issues at 3-Tesla for a hospital identification (ID) wristband

Background and Purpose

A recent report suggested that a serious burn injury was due to the presence of the identification (ID) wristband. As such, in lieu of removing or padding hospital ID wristbands in all patients prior to magnetic resonance imaging (MRI), testing may be performed to characterize risks for ID wristbands. Therefore, the purpose of this investigation was to evaluate the magnetic field interactions, heating and artifacts at 3 T for a hospital ID wristband.

Materials and Methods

Standardized test methods were used to evaluate magnetic field interactions, MRI-related heating, and artifacts at 3 T for a hospital ID wristband.

Results

There were no magnetic field interactions. MRI-related heating evaluated at a relatively high, MR system-reported, whole body-averaged specific absorption rate (2.9 W/kg) did not increase above the background level. The artifacts related to the ink used for printing were “small” for one toner and “large” for the other in relation to the dimensions of the printing.

Conclusions

Based on the tests performed, this particular hospital ID wristband is considered MR safe and will not pose a hazard to a patient undergoing an MRI examination. Importantly, it is not necessary to remove this item for a patient referred for MRI.     

结合边缘信息和图像特征信息的曲波域遥感图像融合

曲波变换是一种更适合于图像处理的多尺度几何分析方法,具有比小波变换更强的方向选择和辨识能力,而且对图像边缘的表达更优于小波.结合色度-饱合度-亮度变换将其应用于合成孔径雷达图像和多光谱图像融合可以更好地表示图像中的有用特征.首先对多光谱图像进行色度-饱合度-亮度变换,得到亮度分量Ⅰ,对雷达图像和Ⅰ分量进行曲波变换得到粗尺度系数和细节尺度系数;将雷达图像的粗尺度系数和细节尺度系数进行叠加,计算归一化的曲波系数直方图,定义边缘有效因子,利用合成孔径雷达图像的特征信息将曲波变换系数分为均匀区、非均匀区和亮点目标区.然后采用相应的融合规则对融合图像的粗尺度系数进行处理,对细节尺度系数采用简单的直接取大方法,逆变换后得到新的亮度分量.用新的亮度分量替代原亮度分量进行逆色度-饱合度-亮度变换得到最终融合结果,利用统计类指标对融合结果进行评价.实验结果表明,该方法在保持光谱信息和提高空间分辨率上都有较好的效果.     

药物化学中构效关系的教学方法研究

构效关系是先导化合物修饰、新型药物设计的基础,在药物化学教学中具有至关重要的作用.由于其多样性和复杂性,学生的掌握情况不理想.本文针对这一问题对药物的构效关系进行归纳分类,总结为"三部分一核心多构型"三类,每一类都进行举例讲解,为学生更好地理解与掌握药物化学的构效关系提供一种可行的方式.     

INS／GPS／SAR组合系统白噪声误差特性的在线随机加权估计

首次把随机加权估计这一新兴的统计计算方法应用于导航系统的研究,证明用它进行INS/GPS/SAR组合系统误差特性的估计是可行的,仿真实验和计算结果表明,该方法明显地优于其它传统的统计估计方法。     

离子液体的毒性

离子液体因其特有的物化性质受到越来越多的关注,并被认为是环境友好的"绿色产品"。但是有关离子液体的潜在毒性一直被人们所忽视,直到最近才有少量报道。本文综述了离子液体毒性研究的相关情况：详细介绍了离子液体毒性研究的各种方法及优缺点;离子液体对各类生物的急性毒性和慢性毒性;离子液体的各部分组成,尤其是阳离子核种类、取代烷基碳链长度和阴离子种类对离子液体毒性的影响情况,以及SAR理论在离子液体毒性研究中的应用情况。在此基础上提出今后离子液体毒性研究的发展方向。     

ANALYSIS OF WAVEFORM ERRORS IN MILLIMETER-WAVE LFMCW SYNTHETIC APERTURE RADAR

In remote sensing applications, there is a special interest in the lightweight, cost effective, and high resolution imaging sensors. The combination of linearly frequency modulated continuous wave (LFMCW) technology and synthetic aperture radar (SAR) technique can lead to such a sensor. This paper concentrates on the analysis of waveform errors in millimeter-wave (MMW) LFMCW SAR. The generating scheme of millimeter-wave LFMCW waveforms with phase locked loop (PLL) and direct digital synthesizer (DDS) combined frequency synthesizer is investigated. The impacts of quantization errors, spurs, and frequency nonlinearities are analyzed. Simulation results show that the quality of LFMCW waveforms has a direct influence on the SAR images. Hence a scheme of frequency synthesizer to achieve high performance MMW LFMCW waveform is proposed. This synthesizer driven by a DDS array can adaptive suppress the spurious level without degradation of excellent frequency linearity and fast switching speed.