哨声波的自聚焦

本文分析和计算了由于有质动力所导致的哨声波的自聚焦现象。结果表明,对磁层内的中等强度哨声和强哨声自聚焦是可能的。从而这种自聚焦现象可能是哨声导管传播的一种非线性机制。      

武昌哨声的传播特征及其与地磁活动的相关

本文利用武昌(磁纬19.2°N)连续三年的哨声观测资料,研究了武昌地区哨声传播的一般特征。着重对武昌哨声的传播路径进行了分析推断,并讨论了它们与地磁活动的相关特性。发现:武昌哨声的显著特征是色散与电离层f₀F₂有明显的正相关关系;其次常出现一类色散值稳定、出现率也很高的哨声。此外,对典型事件的分析及统计分析都表明武昌哨声出现率在地磁扰动时明显增高;哨声色散在磁暴急始后不久即有一个急剧的上升,上升幅度达18%至37%。      

海南岛三亚哨声观测资料的初步分析

本文主要介绍1983年初在海南岛三亚观测哨声的部分结果.记录到大量哨声,其中包括短哨、多源哨和多路哨;约有10%的哨声下截频在0.8kc/s左右.经分析发现:(1)三亚哨声几乎全部出现在f₀F₂下降的过程中,哨声出现率的峰值在f₀f₂下降最快处,即电子浓度下降变化急剧处;(2)哨声活动和磁暴的关系与中高纬有所不同,存在明显的相反情况.      

哨声显示电路

哨声接收机的终端一般都采用监听的方法,没有终端显示装置。最近我们设计了一种能连续显示哨声的电路,电路结构简单,配接低频示波器就可以用来作为哨声接收机的终端显示,克服了人耳监听的缺点。      

南极长城站的哨声定向观测

在中国首次南极考察期间,使用我们研制的GM型接收机对哨声进行了连续的定向观测,本文介绍了仪器性能和一些初步的观测结果,并对哨声导管在本地上空的形成过程做了分析和讨论。      

哨声模波通过低纬电离层传播的某些特征

本文采用IGRF(1980)模型进行了哨声模三维射线跟踪计算, 研究了夜间哨声通过低纬电离层传播的射线与波法的特征.着重讨论了形成非导管哨声可透射路径的条件、射线的聚焦效应及射线的低纬截止.数值计算得到路径终纬度截止约在倾角纬度10.7°N.      

1981年7月31日漠河地区日食的外电离层效应

本文利用漠河(磁径190°17′E, 磁纬42°18′N)地区接收的哨声和同时观测的电离层资料, 采用南北半球电子浓度不一定对称的假设, 以电离层垂测资料和哨声联合换算的模式法, 得到了1981年7月31日哨声色散常数的日食效应;并粗略地测定了日食期间, 漠河上空沿磁力线分布的电子浓度剖面, 磁通量管电子含量和等效标高的部分结果;此外, 还初步讨论了日食的外电离层效应.      

磁暴期间甚低纬哨声的导管传播

对磁暴期间甚低纬哨声导管传播的机理进行了初步的讨论，根据暴时低纬哨声的特点，认为暴时出现的扩展哨、多跳回波是沿东向扰动电场导致的场列电离增强路径传播的。对在东向电场影响下低纬Ｆ层的数值模拟表明，东向电场导致的场列电离增强结构有利于哨声的捕获和传播。     

电离层离子丰度对哨声传播经度效应的影响

Iss-b卫星探测结果表明,|电离层离子丰度呈现经度变化.本文选取较真实的电离层模型参数,对130°E和114°E两个子午面内传播的低纬哨声进行了射线跟踪.我们发现,由于[O~+],[He~+]和[H~+]决定的电子浓度垂直梯度的经度变化,导致哨声传播特性的经度效应,使得130°E比114°E内传播的低纬哨声更好地满足透射条件:|μsinδ|≤1.与电子浓度的水平梯度的影响比较,离子丰度决定的电子浓度垂直梯度随经度的变化使哨声传播产生的经度效应明显得多.武昌(地理30.5°N,114.6°E;地磁19.3°N).和鹿儿岛(31.5°N,130.8°E;20.5°N)两台站观测到的哨声出现率的经度效应证实了本文的理论预言.     

相对论电子束的哨声不稳定性

本文根据相对论粒子与电磁波的共振特性, 讨论了相对论电子束的反常迴旋共振产生的哨声不稳定性.满足共振条件的粒子在动量空间位于一组双曲线上.对于具有损失锥分布的相对论电子束, 相对论效应的共振特性提高了哨声不稳定性的阈值, 对ω～0.5Ω_e频段的哨声影响最大.这种作用在背景参数ω_e～Ω_e时最为显著, 并随ω_e/Ω_e增大而减小.      

One-to-one relationship between low latitude whistlers and conjugate source lightning discharges and their propagation characteristics

One-to-one relation with its causative lightning discharges and propagation features of night-time whistlers recorded at low-latitude station, Allahabad (geomag. lat. 16.05°N, L = 1.08), India, from continuous observations made during 1–7 April, 2011 have been studied. The whistler observations were made using the Automatic Whistler Detector (AWD) system and AWESOME VLF receiver. The causative lightning strikes of whistlers were checked in data provided by World-Wide Lightning Location Network (WWLLN). A total of 32 whistlers were observed out of which 23 were correlated with their causative lightnings in and around the conjugate location (geom. lat. 9.87°S) of Allahabad. A multi-flash whistler is also observed on 1 April with dispersions 15.3, 17.5 and 13.6 s^1/2. About 70% (23 out of 32) whistlers were correlated with the WWLLN detected causative lightnings in the conjugate region which supports the ducted mode of propagation at low latitude. The multi-flash and short whistlers also propagated most likely in the ducted mode to this station.     

Possible influence of cosmic rays on climate through thunderstorm clouds

With decreasing of cosmic ray (CR) intensity caused by increasing of solar activity (SA) or in some short periods of Forbush-decreases, the intensity of secondary CR relativistic electrons decreases and the probability of formation of thunderstorm clouds and discharges between clouds or between clouds and ground is also expected to decrease. This will influence on weather and climate. In this case is very important to have more detail information on the atmospheric electric field distribution in the atmosphere, additional to information what gave now electric field sensors (EFS) only in about one point near the ground. We show that CR not only influenced on atmospheric electric field phenomenon, but can give practically continuous information on the atmospheric electric field distribution in the atmosphere. We extend our theory of CR atmospheric electric field effect on electron–photon, muon and neutron component including different multiplicities. We take into account that about 0.07 of neutron monitor counting rate caused by negative soft muons captured by lead nucleons and formed mesoatoms with generation of several MeV energy neutrons from lead. In this case the neutron monitor or neutron super-monitor works as analyzer that detects muons of only one, negative sign. It is very important because the atmospheric electric field effect have opposite signs for positive and negative muons that main part of this effect in the muon telescope or in ionization chamber is compensated and we can observe only small part of total effect of one sign muons. On the basis of our general theory of CR atmospheric electric field effects with taking into account of negative soft muon acceleration and deceleration in the Earth atmosphere (in dependence of direction and intensity of electric field) we discuss the possibility of existing this effect in CR neutron monitor counting rate and in different multiplicities and calculate the expected effects in dependence of atmospheric electric field distribution in the atmosphere. We show that the comparison of observed effects with theoretically expected will give important information on the value of atmospheric electric field and its distribution in the atmosphere. We consider also the possible influence of secondary relativistic electrons of CR and relativistic electrons precipitated from the Earth’s radiation belts on thunderstorms and lightnings, and through this – on climate change.     

计算机虚拟北航的建造与人机交互的实现

提出了虚拟北航校园场景数据库的层次结构,给出了基于碰撞检测的模型控制面场景调度控制方法,实现了冗余建模数据删减、纹理映射、多级层次细节模型三种场景复杂度消减策略,着重讨论了基于标准二维输入设备的实体选择算法并实现了对受限运动实体的操纵,最后简要介绍了一个通用的、与模型无关的漫游引擎框架结构的实现.     

高精度的连续电离层延迟建模研究

在多项式电离层模型确定过程中, 针对实测数据出现空白区域的问题, 提出了以GIM 数据作为背景场, 联合实测数据进行多项式电离层模型确定的方法, 分析了两种数据的权重, 建立了相应的数学模型; 另外对模型在时段间的连续性问题, 提出了利用相邻两组系数进行时间加权计算电离层延迟的平滑方法; 最后通过算例验证了建模和平滑方法的有效性.      

具有良好压控特性的压控晶体振荡器的设计

介绍了一种具有良好压控特性的晶体振荡器的设计方法。阐述了产生压控晶体振荡器压控特性非线性的原因,介绍了VCXO设计过程中主要元件的选择和设计,并且设计和制作了一个工作频率为10MHZ,具有一个粗调节压控端和一个微调节压控端的压控晶体振荡器。该电路通过MAX828来改善VCXO的电压控制范围及压控线性。实验证明了该设计的正确性。     

特种风洞试验中气动伺服弹性失稳故障分析

在某带飞行控制系统的特种风洞试验中,试验模型在闭环大增益情况下出现了振动发散现象。为分析故障原因,对试验数据进行了频谱分析并检验了无风情况下伺服稳定性;同时,将风洞试验动力学系统简化为数学模型,并建立相应的运动微分方程进行分析,得到以下结论:加入支持结构后整个系统的弹性影响较大,并与控制及气动力发生耦合出现气动伺服弹性失稳。进一步针对以上简化模型,进行数值仿真,其结果验证了以上机理。为解决此失稳问题,对控制系统提出了2种改进方案:增加结构陷波器或更改操纵面偏转比例参数,2种方案亦得到仿真验证。最后,将增加结构陷波器的改进方案应用到试验中,达到了预期的效果。      

计算机辐射测量的内容,方法和意义

为了防止计算机辐射的危害,深入分析了计算机辐射的成因、危害、限额值、测量方法等问题。指出:这一研究作为电磁兼容学的一个分支,国内外正加强重视并扩大研究规模。文末指出了当前进一步研究的方向。     

Fluence-based relative biological effectiveness for charged particle carcinogenesis in mouse Harderian gland.

Neoplasia in the rodent Harderian gland has been used to determine the carcinogenic potential of irradiation by HZE particles. Ions from protons to lanthanum at energies up to 670 MeV/a have been used to irradiate mice, and prevalence of Harderian gland tumors has been measured 16 months after irradiation. The RBE for tumor induction has been expressed as the RBEmax, which is the ratio of the initial slopes of the dose vs prevalence curve. The RBEmax has been found to be approximately 30 for ions with LET values in excess of 100 keV/micrometer. Analysis on the basis of fluence as a substitute for dose has shown that on a per particle basis all of the ions with LET values in excess of 100 keV/micrometer have equal effectiveness. An analysis of the probabilities of ion traversals of the nucleus has shown that for these high stopping powers that a single hit is effective in producing neoplastic transformation.     

Experimental and mathematical modeling of the consumer's influence on productivity of algae in a model aquatic ecosystem.

A "producer-consumer" (Chlorella vulgaris-Paramecium caudatum) closed aquatic system has been investigated experimentally and theoretically. It has been found that there is a direct relationship between the growth of the paramecia population and their release of ammonia nitrogen, which is the best form of nitrogen for Chlorella growth. The theoretical study of a model of a "producer-consumer" aquatic biotic cycle with spatially separated compartments has confirmed the contribution of paramecia to nitrogen cycling. It has been shown that an increase in the concentration of nitrogen released as metabolites of paramecia is accompanied by an increase in the productivity of microalgae.     

空间交会对接中Hill方程的计算误差特性研究

比较详细地分析了航天器在空间所受的各种摄动力,建立了航天器空间轨道的精确计算模型,进而建立了空间交会接中两航天器相对运动的精确计算模型,并以此作为精度基准,对Ｈｉｌｌ方程的计算结果进行了误差分析。