EnDat2.2接口的新一代角度编码器

海德汉公司中心轴和内置轴承角度编码器已成为小至数角秒的小角度测量的标准设备.特别适用于机床旋转轴,例如回转工作台和铣床摆头,是位置控制和速度控制的最佳选择.     

未来机载雷达中具有高精度测距能力的新HPRF模式

已研究了一种新的雷达模式，它可以不模糊地估算目标速度并能通过IPRF模式中的脉冲时间延迟估算距离。要实现这点，距离门宽度要减至近乎机载目标（比如战斗机）的距离向长度。与普通HPRF模式不同的是，在不模糊距离中要有多个可辨别的距离门。距离模糊的分辨则由脉冲串至脉冲串间的脉冲重复频率变化来进行。模糊分辨的算法要考虑到这样一个事实，即在PRF变化期间，目标能移至下一个距离门或跨过一个或更多的相邻距离门。此外，可以在算法中采用不模糊速度测量来补偿目标距离徙动以减少虚警率。     

Xenopus laevis embryos can establish their spatial bilateral symmetrical body pattern without gravity.

One assumes that gravity cooperates with the sperm in the establishment of bilateral symmetry in the embryo, particularly in species with yolky eggs. However, only experiments under genuine microgravity can prove this. May 2nd 1988 on the TEXUS-17 Sounding Rocket, eggs of Xenopus laevis became the first vertebrate eggs ever successfully fertilized in Space. Fertilization was done in fully automated hardware; the experiment was successfully repeated and extended in 1989. Here we report a "Space First" from the IML-1 Space Shuttle mission (January 1992): In similar hardware and under microgravity, artificially fertilized Xenopus eggs started embryonic development. Histological fixation was pre-programmed at the time gastrulation would occur on Earth and indeed, gastrulae were fixed. Thus after fertilization in near weightlessness Xenopus embryos do develop bilaterally symmetrically, very probably cued by the sperm alone.     

Particle Scattering by Magnetic Fields

The need for a correct quantitative treatment of the interactions between cosmic rays and turbulent magnetic fields continues to be one of the fundamental problems of modern astrophysics. It is the aim of this paper to review new developments in the understanding of mechanisms involved in the scattering of charged particles by magnetic field fluctuations. Special emphasis is given to a comparison of transport parameters determined from the modeling of spacecraft and neutron monitor observation of solar particle events, with theoretical predictions derived from a spectral analysis of simultaneously measured fluctuation spectra. It appears that the traditional quasi-linear theory of particle scattering requires only a slight modification, and the major problem still is our lack of knowledge of the three-dimensional structure of the magnetic turbulence. Possibilities to better reconcile the theory with observations by properly taking into account the microphysics of wave and turbulence aspects of the fluctuations, and to use energetic particles as probes to study certain properties of the magnetic turbulence, are discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

A cost-engineered launch vehicle for space tourism

The paper starts with a set of major requirements for a space tourism vehicle and discusses major vehicle options proposed for this purpose. It seems that the requirements can be met best with a Ballistic SSTO Vehicle which has the additional advantage of lowest development cost compared to other launch vehicle options — important for a commercial development venture.

The BETA Ballistic Reusable Vehicle Concept is characterized by the plug nozzle cluster engine configuration where the plug nozzle serves also as base plate and re-entry heat shield. In this case no athmospheric turn maneuver is required (as in case-of the front-entry Delta-Clipper DC-Y concept). In our specific case for space tourism this mode has the avantage that the forces at launch and reentry are in exactly the same direction, easing passenger seating arrangements. The second basic advantage is the large available volume on top of the vehicle providing ample space for passenger accomodation, visibility and volume for zero-g experience (free floating), one of the major passenger mission requirements. An adequate passenger cabin design for 100 passengers is presented, as well as the modern BETA-STV Concept with its mass allocations.     

International space station: : Ready to fly

The International Space Station (ISS) is no longer a paper program, focused on design, development and planning. It is an operational program, with hardware soon to be launched and ground systems in place. Additional modules, components and elements are now under construction in almost all of the 16 ISS International Partner and Participant countries, with metal being bent, software being written, and testing ongoing. Crew members for the first four crews are in training in the U.S. and Russia, with the first crew launching in mid 1999. Mission control centers are fully functioning in Houston and Moscow, with operations centers in St. Hubert, Darmstadt, Tsukuba, Turino, and Huntsville going on line as they are required.

The International Space Station, as the largest international civil program in history, features unprecedented technical, managerial, and international complexity. Seven international partners and participants encompassing 15 countries are involved in the ISS. Each partner is contributing and will be operating separate pieces of hardware, to be integrated on-orbit into a single orbital station. Mission control centers, launch vehicles, astronauts/cosmonauts, and support services will be provided by partners across the globe, but must function in a coordinated, integrated fashion. This paper will review the accomplishments of the ISS Program and each of the Partners and Participants over the past year, focusing on completed milestones and hardware. It will also give a status report on the development of the remainder of the ISS modules and components by each Partner and Participant, and discuss upcoming challenges.