Satellite Observations of Natural and Anthropogenic Aerosol Effects on Clouds and Climate

Anthropogenic aerosols affect the climate system and the hydrological cycle. The net effect of aerosols is to cool the climate system, directly by reflecting sunlight to space, and indirectly by increasing the brightness and cover of clouds that in turn also reflect more sunlight to space. The uncertainty in the aerosol effect on climate is 5 times greater than that of the greenhouse gases. The reason for this is the short aerosol lifetime and chemical complexity, that makes it difficult to represent the global aerosol budget from surface or aircraft measurements. Satellites provide daily global information about the aerosol content, generating large statistics with excellent regional and global representation of the aerosol column concentration, and differentiating fine from coarse aerosol. Here we use observations performed with the MODIS instrument onboard the Terra and Aqua satellites to differentiate natural from anthropogenic aerosols, and to measure the aerosol effect on cloud properties and on the reflectivity of sunlight.     

鸟击的因素及防治策略

机鸟相撞,一直是困扰着各国航空安全的重大问题,轻则鸟死机伤,重则机毁人亡。本文从机场环境、飞机设计、飞行速度、飞行高度和季节时间等五个方面对鸟击因素特点进行了综合分析,并提出了以鸟情调查为基础,加强机场环境治理和鸟类食物链控制的鸟击防治策略。     

浅谈高校突发事件的成因及有效防范

高校突发事件是指那些发生在高校内或虽未发生在高校,却与高校中的人或事有相当联系,事前难以预测,对学校正常秩序造成一定影响、冲击乃至危及社会安定和政治稳定的公共事件,它具有严重危害性、社会敏感性、主体活跃性的特点。从学生、学校、社会三方面分析了高校突发事件的产生原因,并提出了相应的有效防范措施。     

航班延误原因解析

航班延误,作为航空运输服务纠纷的焦点,近几年随着中国民航运输量的不断增长,这个问题受到越来越多的关注。本文对航班延误的原因进行了深入的解析,以具体的数据来说明造成航班延误各种原因的比例,让大众对此有     

高温壁面热流与温度一体化测量传感器研究

为了测量超燃冲压发动机燃烧室的热环境,从Gardon热流计原理出发,发展了一套水冷热流/壁温一体化测量技术。采用热阻分析方法,对传感器的热结构进行了分析与优化设计。测试了多种隔热与外壳材料对传感器响应特性的影响。通过辐射加热方式对传感器进行了标定,获得了热流/电压、壁温/热流的标定曲线。采用该传感器,在模拟马赫数6、总温1800K的来流条件下,对超声速燃烧室的热环境进行了初步测量,获得了与传热分析相一致的结果。     

US government policies and hypersonic flight in the 21st century

The author examines the potentially negative impact of the US regulations on the development of advanced materials, components, and systems. He gives high priority to modification of US antitrust laws if the US is to have the best possible opportunity to compete with more aggressive economies abroad. He identifies export controls as limiting the availability of data to US firms engaged in developing commercial applications. He asserts that policies must also be enacted to better protect intellectual property rights     

Navigation and landing [A century of powered flight 1903-2003]

Navigation and landing for the first half century of aviation fundamentally relied on radio-based electronic aids. The military began serious investigation of radio navigation during World War I. Up until WW II map reading, dead reckoning, and various means of radio direction finding were the primary methods of determining aircraft position. Since WWII a number of other navigation techniques, such as Doppler radar, radio inertial, pure inertial, aided inertial, and today's integrated GPS inertial, have been developed. Most of the inertial systems evolved from the military ICBM and subsequent space programs.     

Stability and control [A century of powered flight 1903-2003]

Aircraft stability and control has evolved from stick and rudder through stability augmentation to redundant digital flight control systems (FCS) and finally to digital fly-by-wire (FBW). Substantial advances in avionics have occurred as aviation progressed from biplanes to civil transports to sub/supersonic military craft and finally the Space Shuttle. Aircraft stability can be defined as aircraft control by maintaining a favorable relationship between center of gravity (CG) and the center of pressure (CP).     

社会技术与自然技术的和谐图景

技术是人的本质存在形式。技术范畴已发生本体论上的外延,除自然技术外,还必然涵括社会技术范畴。社会技术的存在毋庸置疑,自学界提出社会技术的概念后,社会技术与自然技术的关系便成为技术哲学研究的崭新视角。和谐技术观是社会技术与自然技术关系之基。社会技术和自然技术在消解与融合、界限、可逆性等诸方面显现出和谐图景。     

探析新世纪反舰导弹的发展趋势

通过对面向新世纪反舰导弹作战需求的分析,从导弹射程实现中远程化,飞行速度实现超音速及亚超结合,精确制导技术、隐身技术和导弹目标参数实现信息化等方面,探讨了反舰导弹的发展趋势,为反舰导弹武器发展研究提供参考.     

Multi-experiment determination of plasma density and temperature

An attempt has been made to combine data from five instruments on GEOS-1 in order to determine the characteristics of the ambient cold plasma, assess the effects of spacecraft sheaths on the different techniques and establish cross calibration criteria. In addition to measuring plasma density and temperature it is necessary to consider the influence of satellite potential and motion, ionic composition, ion drifts (electric fields), electrons emitted from spacecraft surfaces and any consequent departures from isotropy or Maxwellian distribution.9 October 1977 was selected for the study, the orbit covers a range of L-values between 3.5 and 7.5 giving outbound and inbound plasmapause crossings with plasma densities spanning more than two orders of magnitude. Eclipse data from 7 February 1978 is used to determine the influence of photoelectron emission.Three techniques — active sounding of the plasma frequency resonance (S-301), a mutual impedance measurement (S-304) and DC electric field probe determination of floating potential (S-300) — utilize the long boom sensors in either AC or DC modes. Electrons and ions are measured directly by electrostatic analysers (S-302), mounted on one short radial boom. On the day chosen for study here ions are predominantly protons as determined by the body mounted ion composition experiment (S-303).The techniques using the 20 m long booms agree well in determining density whereas the short boom and body mounted ion detectors are seriously compromised when satellite potential becomes several volts positive. Measurements of satellite potential and plasma temperature agree within 20% among the several instruments making these measurements. Data obtained during the transition from eclipse to sunlight conditions show no discontinuity in the long boom instruments caused by the sudden appearance of photoelectrons.     

Flywheel technology: past, present, and 21st century projections

This paper describes the present status of flywheel energy storage technology, or mechanical batteries, and discusses realistic future projections that are possible based on stronger composite materials and advancing technology. The origins and use of flywheel technology for mechanical energy storage began several hundred years ago and was developed throughout the Industrial Revolution. One of the first “modern” dissertations on the theoretical stress limitations of rotational disks (isotropic only) is the seminal work by A. Stodola whose first translation to English was made in 1917. The next big milestones were during the 1960s and 1970s when NASA sponsored programs proposed energy storage flywheels as possible primary sources for space missions. However, it was not until the 1980's when microelectronics, magnetic bearing systems and high power density motor-generators became enabling technologies. The next decade proved that a mechanical battery could surpass chemical batteries for many applications     

数字温度传感器在多点温度测量系统中的应用

传统的温度测量系统,输出信号必须经过放大、A/D转换等处理之后才能送微控制器进行相应的处理,硬件电路设计复杂,成本较高。而由DALLAS公司生产的新型数字温度传感器DS18B20,能直接读出被测温度,并以串行数字信号传送给单片机进行处理。每片DS18B20都有唯一的ROM编码,使一根口线可接多片DS18B20。因而使用DS18B20构建多点温度测量系统可使测温系统结构更趋简单,成本更低、可靠性更高。本文介绍了DS18B20的特点、工作原理及由DS18B20构建的多点温度测量系统的硬软件设计。     

Introduction [A century of powered flight:1903-2003]

The term Avionics is used loosely to identify that electronic equipment necessary to fly an aircraft. The term is nearly 50 years old with origins in military electronics. With the increasing dependence of aviation on electronics the amount of equipment that falls into this category has skyrocketed. This issue is intended to commemorate the Wright Brothers' Centennial of Powered Flight. It emphasizes aviation-related electrical/electronic advances for the years 1903 to 1953. The following paragraphs highlight some of the major topics discussed in this special issue.     

Aviation Radio [A century of powered flight 1903-2003]

The following topics are dealt with: electron tubes; World War I efforts; post WWI radio advances; airmail; antenna developments; weather; and WWII and after.     

雷达自然寿命初探

通过对雷达失效物理机制的分析,根据雷达首翻期数据,在限定的维修方式下,建立了雷达的自然寿命模型并针对某型雷达进行了计算,这种方法对确定雷达的自然寿命有一定的参考作用.     

Cockpit Instruments [A century of powered flight:1903-2003]

Since nearly the beginning airplanes were flown using only the stick or control column, rudder pedals, dials, and switches. There were as many control arrangements (sticks, wheels, and levers) as there were pioneer airmen. The 1903 Wright Flyer was far from conventional in many ways. Their only instruments were a stopwatch and prop revolution counter. Instruments were of little interest for about a decade after the Wright Brother's flight. Just getting off and back onto the ground safely was the primary concern. Controls have evolved, but not changed as much as instrument displays. The stick/control column is beginning to be replaced by hand controllers in some fly-by-wire (FBW) aircraft (e.g., Airbus A-320 and up). Servo feedback provides the necessary hand controller "feel" as a function of the aerodynamic pressure expected on the control surface.