Atmospheric Electrification in the Solar System

Atmospheric electrification is not a purely terrestrial phenomenon: all Solar System planetary atmospheres become slightly electrified by cosmic ray ionisation. There is evidence for lightning on Jupiter, Saturn, Uranus and Neptune, and it is possible on Mars, Venus and Titan. Controversy surrounds the role of atmospheric electricity in physical climate processes on Earth; here, a comparative approach is employed to review the role of electrification in the atmospheres of other planets and their moons. This paper reviews the theory, and, where available, measurements, of planetary atmospheric electricity which is taken to include ion production and ion–aerosol interactions. The conditions necessary for a planetary atmospheric electric circuit similar to Earth’s, and the likelihood of meeting these conditions in other planetary atmospheres, are briefly discussed. Atmospheric electrification could be important throughout the solar system, particularly at the outer planets which receive little solar radiation, increasing the relative significance of electrical forces. Nucleation onto atmospheric ions has been predicted to affect the evolution and lifetime of haze layers on Titan, Neptune and Triton. Atmospheric electrical processes on Titan, before the arrival of the Huygens probe, are summarised. For planets closer to Earth, heating from solar radiation dominates atmospheric circulations. However, Mars may have a global circuit analogous to the terrestrial model, but based on electrical discharges from dust storms. There is an increasing need for direct measurements of planetary atmospheric electrification, in particular on Mars, to assess the risk for future unmanned and manned missions. Theoretical understanding could be increased by cross-disciplinary work to modify and update models and parameterisations initially developed for a specific atmosphere, to make them more broadly applicable to other planetary atmospheres.     

甘肃西北部黑河流域水资源对下游生态环境变化的影响阈

从流域尺度水资源承载能力及其有限性、可变性和上下游关联性的角度,探讨了黑河流域下游区生态环境变化的影响阈,阐明了不同水文年中游区的安全引水量和不同目标下下游区的生态环境修复对水资源的需求阈.基于多年平均地表径流量37.8×108m3/a的安全引水量为13.97×108m3/a和枯水年份(95%保证率)的安全引水量为10.14×108m3/a,下游区初步改善生态环境的生态需水量为8.01×108m3/a.提出了中游区经济社会可持续发展的水资源保障阈,即未来20年生产生活安全需水量介于22×108～23×108m3/a之间.在此基础上,阐明了在中游区经济社会稳定持续发展目标约束下确保黑河流域下游区生态环境不断改善的流域水资源优化配置模式及对策.     

强夯引起的振动规律及环境效应分析

强夯法是地基处理的一种常用方法,而强夯施工振动往往是制约强夯法应用的关键。综合国内外的研究成果,重点分析强夯引起的振动规律及振动对环境的影响,并结合某沿海地基处理中的强夯振动工程实例,根据实测结果,分析振动速度随距离的衰减规律及强夯安全距离的确定。     

水库渗流影响文物遗址安全发掘研究——以湖南里耶秦代古城遗址为例

与古遗址相邻的江、河由于后期的工程活动,如水库、大坝的修建和蓄水,水位上升,将对遗址区地下水的运动规律及渗流场产生较大影响。在其影响下,古遗址可能产生各种环境地质灾害并对其发掘安全产生不利影响。论文以国家重点文物——湖南里耶秦代古城遗址安全发掘深度研究为例,在分析水库蓄水诱发的环境地质灾害的基础上,对遗址在不同库水位下的安全发掘深度及发掘方案进行了研究,提出了保障发掘安全的工程措施。研究成果为国家重点文物的保护和进一步发掘提供了科学依据。对类似文物工程的保护和发掘具有借鉴意义。     

计算机跟踪伺服系统的保护电路

本文介绍了为紫台13.7米射电望远镜跟踪系统设计制造的一套的简单实用的保护电路。实验证明该电路性能可靠、效果显著。     

Renewable, controlled and environmentally safe phosphorus release in soils from mixtures of NH4 +-phillipsite tuff and phosphate rocks

 The renewable and controlled-release fertilization system investigated here uses NH₄ ⁺-exchanged phillipsite tuff, from Jordan, to help in the dissolution of phosphate rock. Accordingly, controlled and renewable soluble nitrogen, phosphate and Ca are released as nutrients for plants. NH₄ ⁺ phillipsite can sequester Ca ions released by the dissolution of phosphate rock, therefore, leading to further phosphate rock dissolution. In this study the results show that the amount of phosphate released is more than that released by phosphate rock alone. This method offers an alternative to the use of highly soluble fertilizers and may avoid environmental problems associated with their extensive use in agriculture. Received: 22 May 1997 · Accepted: 12 August 1997     

Problems in the calibration of an acoustic device for the observation of bedload transport

Developments in theoretical and empirical modelling of bedload transport processes are hindered by the lack of an adequate data base for testing or establishing the models. Conventional methods of measuring bedload transport rates fail to provide the necessary continuous or frequent record of variations at a single section. Acoustic techniques have the potential to overcome this deficiency, but their application has been very limited. Some of the problems of calibrating an acoustic device in the field and in a laboratory flume are discussed, and a possible circuit design described which might minimize calibration difficulties by automatically subtracting the noise generated by flow turbulence.     

同幅双速跟踪成像CCD相机模拟电路系统设计

讨论了同幅双速跟踪成像技术对CCD相机系统的特殊要求,详细地介绍了该相机前端模拟系统的设计思想、系统结构和主要的电路模块。对系统中一些关键电路模块进行了仿真和测试,并对仿真和测试结果进行比较分析,以检验电路系统设计的合理性。     

山西新阳矿太原组下组煤层底板岩溶水突水安全性评价

新阳矿9-10-11号煤层底板低于奥灰岩溶水位,承受水压较高,存在带压开采问题。依据矿区水文地质勘查资料,通过对9-10-11号煤层底板隔水岩层隔水性能、奥灰岩溶水富水程度、底板断裂构造发育情况、煤层底板承压大小以及采煤扰动底板破坏深度等突水因素分析,表明井田西南部断裂构造发育地段为突水危险区。分别采用突水系数法和突水危险度法对全井田9-10-11号煤层底板突水危险性进行评价,评价结果显示井田南部及断裂构造发育地段为突水危险区。理论分析与定量评价结果基本一致。针对9-10-11号煤层底板突水安全评价结果,提出了相应的防突水对策。     

基于CPLD的高精度门控电路的设计

距离门控制电路是卫星激光测距(SLR)系统的一个重要组成部分,高精度距离门控制可有效提高卫星测距探测成功概率。介绍了一种基于CPLD(复杂可编程逻辑器件)的高精度门控电路的设计。在该设计中,采用硬件描述语言VHDL对CPLD进行编程,使其与单片机、PC机协调工作,从而实现高精度的距离门控制电路。