蒸发波导环境下雷达电磁盲区的分布特征

蒸发波导是近海面大气环境中出现概率最高的一种大气波导,利用蒸发波导可以实现雷达超视距探测.然而,由于蒸发波导的存在,雷达的电磁盲区也会发生不同的变化,从而对岸基、舰船雷达的探测性能产生极大的影响.基于射线追踪技术,构建了电磁波传播路径的微分计算方法,并对蒸发波导环境中的岸基、舰船雷达电磁盲区随雷达天线高度变化特征进行了...     

革命、寓言与历史意识——论作为现代文学“起源”的《狂人日记》

鲁迅的写作与中国革命之间的关系是一个经典话题,然而,已有阐释多以外在历史结论穿透鲁迅的文本却较为忽略其形式的意味。鲁迅的第一篇白话小说《狂人日记》就包含着重要的形式线索,远非从象征出发的阐释模式可以把握。作为文学的狂人日记建构出全新的吃人,动摇了旧有整全的意义世界,同时也付出了沉陷于寓言状态的代价。鲁迅以其写作承认了中国革命的吊诡之处及其寓言式的状态,也以此弃绝了诸种简单的进步或回退的历史意识与历史观念。在这个意义上,作为现代文学起源的《狂人日记》呈现出鲁迅关于中国革命及其历史展开的洞见。     

前馈型轨到轨恒跨导恒增益CMOS运算放大器

设计了一种恒跨导恒增益的轨到轨运算放大器.输入级采用一倍电流镜控制的互补差分对结构,实现轨到轨和恒跨导.通过分析运算放大器电压增益随共模电压变化的原因,提出了一种前馈型恒增益控制模块,可以根据共模电压开启或关闭附加电流源,使运算放大器电压增益保持恒定.输出级采用前馈型AB类输出结构,以达到轨到轨输出效果.采用Chartered公司0.35μm工艺进行流片,仿真及测试结果表明:该运算放大器的直流开环增益为125dB,单位增益带宽为8.879MHz,在整个共模范围内电压增益最大变化率为1.69%.     

多层电路结构微带天线的波概念迭代法分析

利用波概念迭代法结合传输线理论分析一种三层电路结构的超宽带微带贴片天线,通过与典型电磁场数值算法的计算复杂度对比,验证波概念迭代法在分析多层电路时计算效率高、计算速度快的优点;利用其计算该天线的回波损耗、方向图和增益等参数,通过与HFSS仿真结果对比,证明该方法在分析多层电路的正确性和有效性.     

基于LabVIEW的造气炉温度辨识系统的研究

通过对造气炉的结构特点和反应机理分析,以及对测温干扰的估计,采用带受控项自回归滑动平均模型(CARMA)来表征其温度特性较为理想,但这种算法复杂,较难实现。基于任何CARMA模型都可以用高阶带受控项的自回归模型(CAR)逼近到任何精度,实现起来却又相对简单的特点,以LabVIEW为平台来完成对气化层温度的任意高阶CAR建模,能够很好的解决气化层温度难以直接测量的问题。     

切眼过高冒区综合加固技术研究与应用

针对王庄煤矿在掘进煤柱工作面、边角煤工作面顺槽巷道时遇到的困难,为改进施工工艺、提高掘进效率,论述了切眼过高冒区综合加固技术的施工工艺、支护措施、安全技术措施,为今后类似的巷道掘进提供技术保障,     

Does flagship species tourism benefit conservation? A case study of the golden snub-nosed monkey in Shennongjia National Nature Reserve

Tourism has been widely used as a conservation strategy that directly compensates local people or management authorities, thereby contributing to development and creating incentives to preserve the landscape. Reserves or parks that are inhabited by flagship species may be able to generate more revenue through tourism than those without such species because flagship species have great potential for raising funds and creating publicity for conservation goals. In this paper, we examine flagship species tourism...     

Amplitudes, rates, periodicities and causes of temperature variations in the past 2485 years and future trends over the central-eastern Tibetan Plateau

Amplitudes, rates, periodicities, causes and future trends of temperature variations based on tree rings for the past 2485 years on the central-eastern Tibetan Plateau were analyzed. The results showed that extreme climatic events on the Plateau, such as the Medieval Warm Period, Little Ice Age and 20th Century Warming appeared synchronously with those in other places worldwide. The largest amplitude and rate of temperature change occurred during the Eastern Jin Event (343-425 AD), and not in the late 20th century. There were significant cycles of 1324 a, 800 a, 199 a, 110 a and 2-3 a in the 2485-year temperature series. The 1324 a, 800 a, 199 a and 110 a cycles are associated with solar activity, which greatly affects the Earth surface temperature. The long-term trends (>1000 a) of temperature were controlled by the millennium-scale cycle, and amplitudes were dominated by multi-century cycles. Moreover, cold intervals corresponded to sunspot minimums. The prediction indicated that the temperature will decrease in the future until to 2068 AD and then increase again.     

Photonic integrated technology for multi-wavelength laser emission

We summarized the design, fabrication challenges and important technologies for multi-wavelength laser transmitting photonic integration. Technologies discussed include multi-wavelength laser arrays, monolithic integration and modularizing coupling and packaging. Fabrication technique requirements have significantly declined with the rise of reconstruction-equivalent-chirp and second nanoimprint mask technologies. The monolithic integration problem between active and passive waveguides can be overcome with Butt-joint and InP array waveguide grating technologies. The dynamic characteristics of multi-factors will be simultaneously measured with multi-port analyzing modules. The performance of photonic integration chips is significantly improved with the autoecious factors compensation packaging technique.     

Ancient DNA sequences of rice from the low Yangtze reveal significant genotypic divergence

Rice (Oryza sativa) was first domesticated in the lower and middle Yangtze regions of China, and rice remains have been found in many Chinese archaeological sites. Until now, only phenotypic archeobotanical evidence, such as the spikelet bases of ancient grains, has been used to speculate on the domestication process and domestication rate of rice. In this study, we sequenced 4 genomic segments from rice remains in Tianluoshan, a site of the local Hemudu Neolithic culture in the low Yangtze and two other archaeological sites (~2400 and 1200 BC, respectively). We compared our sequences with those of the current domesticated and wild rice (O. rufipogon) populations. At least two genotypes were found in the remains from each site, suggesting a heterozygotic state of the rice seeds. One ancient genotype was not found in the current domesticated population and might have been lost. The rice remains belonged to the japonica group, and most if not all were japonica-type, suggesting that the remains might be at an early stage of indica-japonica divergence or an indica-japonica mixture. We also identified sequences with significant similarity to those from species of Sapindales, Zygophyllales, and Brassicales, which is consistent with the identification of other plant remains in the Tianluoshan site and the common rice field weeds such as mustards in southern China.