Velocity changes of the Giotto spacecraft during the comet flybys: on the interpretation of perturbed Doppler data

Upon developing a new theory for the analysis of one-way and two-way Doppler shifts of the radio carrier signal transmitted by interplanetary spacecraft, Porsche (1999) urges a reassessment of the radio science data obtained during the Giotto flybys at comets P/Halley and P/Grigg–Skjellerup. We explain again the Doppler recording method and the operational strategy of the flybys and present both the two-way and one-way data sets from Giotto's flyby at comet Grigg–Skjellerup as an example. We find no reason to change our most probable flyby scenarios. Furthermore, we assert that Porsche's treatment of the classical Doppler effect is in error. All quantities derived from his analysis are gross overestimates and incompliant with observations and cometary physics.     

《航空发动机》编辑委员会成员简介

<正>甘晓华,1957年1月出生,中国工程院院士,空军装备研究院总工程师。1989年北京航空航天大学博士毕业.担任中国航空学会浮空器分会主任委员,北京航空航天学会副理事长,任多所院校兼职教授,享受政府特殊津贴。第十、十一、十二届全国政协委员。长期从事航空发动机技术研究,开发了某型三代发动机关健部件的修复和改进技术;在发动机热负荷控制和单机定     

A Brief History of Radar

In his report about experiments with radio communication in the Baltic Sea in 1897, Russian scientist Alexander Popov reported the detection of a warship "Lieutenant Il'in" when it crossed the radio communication link between two other ships "Europe" and "Africa". This observation was the first mention about the possibility of object detection by means of radio waves. The first patent on the phenomena was obtained in 1904 by German engineer Christian Hiilsmeyer who called this device the "Telemobiloskop". However, neither A. Popov's observation nor C. Hulsmeyer's invention was the subject of any development up to the 1930s of the 20th century. This is a partial summary of the work done by the Soviet Union and Russia in the field of radar.     

Microwave landing system: a pilots point of view

The author describes the MLS installation on runway 19L at Mid-Continent Airport, Wichita, Kansas, which has been operational since mid-1987. He describes the MLS equipment installation in his aircraft, which is one of a number of aircraft in the Wichita area that have been equipped with MLS equipment and routinely utilize the system. He summarizes his operational experience with the system. He reports complete satisfaction and increased versatility as a result of the guidance information provided     

简谈子路

子路是孔子3000弟子中一个比较有个性特点的人物,他年龄与孔子相差不大,与孔子关系甚密。子路擅长军事,性格豪放,相关文献中请教孔子学问的记载也较全,这可以让我们多方面客观全面地认识子路。他的为政原则与他个人性格和孔子对其教化密不可分,因此研究子路不仅对其本人有更好的了解,而且对进一步了解儒家所提倡的道义具有一定意义。     

论陀思妥耶夫斯基《永久的丈夫》主人公的复调人格

陀思妥耶夫斯基试图探索人类心灵的谜题。《永久的丈夫》中主人公巴维尔·巴夫洛维奇的形象因其所具有的心理上的多元维度而令人印象深刻。作者将其置于精心安排臻于极致的情节中不断拷问人性,使其心灵世界逐渐展露。对复调人格的深刻揭示,是陀思妥耶夫斯基的对世界文学的伟大贡献。     

J.A. Pierce: pioneer award winner, 1961

A biography of John Alvin Pierce is given, starting with his early interest in radio. Pierce received his amateur license and operated a spark transmitter at the age of twelve. His amateur activities led to work at the Cruft Laboratory of Harvard University under the supervision of Professor H.R. Mimno. This association with the Cruft Laboratory has continued to the present day with few interruptions. Pierce's work with different groups and in various areas is sketched, focusing on his work with Loran     

从生态翻译学的角度看严复翻译

严复在中国翻译史上有着十分重要的地位,是我国第一个提出规范标准的翻译家,他所提出的"信、达、雅"翻译理论具有很强的指导意义。生态翻译学是对翻译活动进行研究的新视角,从生态翻译学的核心理论视角出发,对严复翻译进行探讨,可以看出,严复翻译遵从其所处的翻译生态环境的法则,受生态环境中各要素的制约,既促进了当时社会的科学发展,也与当时其所处的生态环境相融合。     

Computerizing the circuit board industry while reducing costs

The author examines a systems approach to automation that the printed circuit board (PCB) manufacturer can use in order to adapt today's technology for his or her individual needs. He begins with an overview of production functions. He then describes the subsystems approach, the steps leading to computerization, implementation, the bare board test system, and preprocessing     

陈乃兴先生的主要学术成就和对科技发展的重要贡献:隆重纪念陈乃兴先生逝世一周年

2019年8月6日是中国著名工程热物理学家陈乃兴先生逝世一周年的纪念日。从6个方面详细阐述了陈乃兴先生的主要学术成就和对科技发展的重要贡献。他一生献身祖国、献身科学研究的拼搏精神，将鼓舞大家砥砺奋进。     

Observed Long-Term Variations of Solar Irradiance at the Earth’s Surface

The variation of global radiation (sum of direct solar and diffuse sky radiation) at the Earth’s surface is examined based on pyranometer measurements at about 400~sites. The period of the study covers in general the last 50 years. For Europe the study is extended to the beginning of observations in the 1920s and 1930s. Global radiation generally increased in Europe from the 1920s to the 1950s. After the late 1950s and early 1960s global radiation began to decrease in most areas of the world at a mean rate of 0.7 Wm⁻²a⁻¹ until 1980s, thereafter 75%; of the stations showed a recovery at a mean rate of 0.7 Wm⁻²a⁻¹. All stations in the Polar region, which are far from aerosol sources, also show this pattern of change. At the remaining 25% of the stations the decrease has continued to present. These regions are a part of China, most of India, and Central Africa. Both during the declining and recovering phases global radiation observed under the cloudless condition also followed the same tendency, indicating the simultaneous and parallel changes of aerosol and cloud conditions. Long-term observations of total zenith transmittance of the atmosphere indicate a decrease in transmittance to the mid 1980s and an increase after this period. Since the brighter and darker periods correspond to relatively warmer and colder periods, the present study offers the possibility to quantitatively evaluate the mutual relationships between the solar irradiance, atmospheric transmittance, cloud conditions and air temperature.     

Johannes Geiss’ Investigations of Solar, Heliospheric and Interstellar Matter

Johannes Geiss is a world leader and foremost expert on measurements and interpretation of the composition of matter that reveals the history, present state, and future of astronomical objects. With his Swiss team he was first to measure the composition of the noble gases in the solar wind when in the late 1960s he flew the brilliant solar wind collecting foil experiments on the five Apollo missions to the moon. Always at the forefront of the art of composition measurements, he with his colleagues determined the isotopic and elemental composition of the solar wind using instruments characterized by innovative design that have provided the most comprehensive record of the solar wind composition under all solar wind conditions at all helio-latitudes. He discovered heavy interstellar pickup ions, from which the composition of the neutral gas of the Local Interstellar Cloud is determined, and the “Inner Source” of pickup ions. Johannes Geiss played a key role both in the in-situ measurements and modeling of molecular ions in comets, and the interpretation of these data. He and co-workers measured the composition of plasmas in the magnetospheres of Earth and Jupiter. Here we highlight Johannes Geiss’ many discoveries and seminal contributions to our knowledge of the composition of matter of the Sun, solar wind, interstellar gas, early universe, comets and magnetospheres.     

“觉世稗官”与“湖上笠翁”——李渔小说与传奇创作关系探究

李渔在《闲情偶寄》中对作品提出了"脱窠臼"的要求。他的小说创作确实遵照这一原则进行,但是他的传奇创作却不断出现直接借用自己已经出版的小说故事的情况。探究这种看似矛盾的行为,除了可以借体裁的转变谋取更大的经济利益之外,这种题材的借用也是明清传奇作者的共同习惯。而恰是从李渔对这种习惯的遵从中,我们更可以发现古代作者们对于小说与传奇两种不同体裁的文体认识的差异。     

Thermal radio emission from the major planets

The use of long-wavelength radio measurements of brightness temperature to remotely measure the thermal structure of the atmospheres of the major planets at great depths (>10 atm.) is discussed. Data are presented which show that the gross features of Jupiter's and Saturn's microwave spectra, as determined from ground based observations, can be explained in terms of thermal emission from ammonia in deep convective atmospheres of He and H₂.This is one of the publications by the Science Advisory Group.     

The Juno Waves Investigation

Jupiter is the source of the strongest planetary radio emissions in the solar system. Variations in these emissions are symptomatic of the dynamics of Jupiter’s magnetosphere and some have been directly associated with Jupiter’s auroras. The strongest radio emissions are associated with Io’s interaction with Jupiter’s magnetic field. In addition, plasma waves are thought to play important roles in the acceleration of energetic particles in the magnetosphere, some of which impact Jupiter’s upper atmosphere generating the auroras. Since the exploration of Jupiter’s polar magnetosphere is a major objective of the Juno mission, it is appropriate that a radio and plasma wave investigation is included in Juno’s payload. This paper describes the Waves instrument and the science it is to pursue as part of the Juno mission.     

Three R's of radar: recollections, remonstrances, and ruminations

The author describes his experiences in the early days in radar, working on a radar landing system called ground control approach (GCA). He discusses for the disparity between the short time from conception to worldwide deployment of that system and today's 10- to 15-year cycle, as well as GCA's high (100%) availability, and identifies the factors responsible. The author goes on to argue that the radar community has a history of overselling what radar can do. He forecasts future trends and concludes with a few things he has learned over the years     

深空导航无线电干涉测量技术的发展历程和展望

结合世界各航天大国和组织所开展的深空探测活动和深空测控系统建设中,对无线电干涉测量技术的开发、应用以及深空导航技术试验验证情况,系统地梳理和总结了深空导航无线电干涉测量技术的发展历程,并通过该技术未来在国际上几个主要深空探测任务中的应用规划,分析了无线电干涉测量领域未来的发展方向.该领域技术的最新发展对我国深空测控网无线电干涉测量系统的后续建设也具有重要的借鉴意义.     

玩票成大师

在我们周围多才多艺的人不计其数,但多才多艺到这样程序的人,据圈内人士说也许在全中国亦属风毛麟角,这个人就是邓廷毅。他擅长雕塑、陶艺、国画、油画、摄影、古玩修复、医学图谱绘制、医教模具设计等诸多艺术门类,且都卓有成绩。是什么使然?基因?天赋?聪敏?……邓廷毅却说,与玩票有关。     

无线电高度表信号模拟器射频信号延时/衰减模块设计

无线电高度表程控信号模拟器是无线电高度表自动测试系统（ATE,ATS）的重要组成部分,而射频信号延时/衰减模块则是无线电高度表程控信号模拟器3个功能模块组件中的核心模块。研制了一种采用声表面波（SAW）延迟线作为射频信号延时器件、射频衰减器作为射频信号功率衰减器件,通过程控射频开关控制不同声表面波延迟线的切换,包含射频信号变频、放大等结构电路的无线电高度表信号模拟器射频信号延时/衰减模块。经无线电高度表自动测试系统的实际工程应用表明,该无线电高度表射频信号延时/衰减模块对C波段（4.2～4.4 GHz）射频调制信号的延时精度高、衰减范围大,体小、质轻,适合置于无线电高度表测试适配器内部使用,具有较高的工程应用价值。     

Ionization processes in the heliosphere — Rates and methods of their determination

The rates of the most important ionization processes acting in interplanetary space on interstellar H, He, C, O, Ne and Ar atoms are critically reviewed in the paper. Their long-term modulations in the period 1974 – 1994 are reexamined using updated information on relevant cross-sections as well as direct or indirect data on variations of the solar wind/solar EUV fluxes based on IMP 8 measurements and monitoring of the solar 10.7 cm radio emission. It is shown that solar cycle related variations are pronounced (factor of 3 between maximum and minimum) especially for species such as He, Ne, C for which photoionization is the dominant loss process. Species sensitive primarily to the charge-exchange (as H) show only moderate fluctuations 20% around average. It is also demonstrated that new techniques that make use of simultaneous observations of neutral He atoms on direct and indirect orbits, or simultaneous measurements of He⁺ and He⁺⁺ pickup ions and solar wind particles can be useful tools for narrowing the uncertainties of the He photoionization rate caused by insufficient knowledge of the solar EUV flux and its variations.