中法激光时间比对和探测基本物理的相关空间计划

激光时间比对T2L2(Time Transfer by Laser Link)是法国蔚蓝海岸天文台(OCA)和法国空间中心(CNES)进行的新一代的时间传递计划,将于2008年年中随Jason-2卫星发射上天,并开始观测。它利用激光脉冲在空间的传播来实现地面—卫星,地面—地面远距离时钟的同步,精度比现有的微波比对方式提高1~2个数量级。中国拥有5个固定激光测距站和2个流动激光测距站,基于良好的地理位置和中法双方比较成熟的激光测距技术,中法激光站之间的时间比对和中国内部激光站之间的时间比对是该计划的重要内容。本文系统描述了T2L2的主要内容和关键技术,初步估算了该计划的精度和稳定度,对中法之间的时间比对做出了初步的观测规划。同时,简单介绍了目前世界上精密时钟的发展现况、T2L2的应用前景及正在研究中的TIPO、ASTRODⅠ、ACES、EGE等探测基本物理的相关空间计划。     

Probing the Microscopic Origin of Gravity via Precision Polarization and Spin Experiments

As in other parts of physics, we advocate the interaction approach: experiments ←→ (… are influenced and their importance is determined by … and vice versa) phenomenology ←→ low-energy effective (field) theory ←→ microscopic theory to probe the microscopic origin of gravity, Using the X-g phenomenological framework, we discuss the tests of equivalence principles. The only experimentally unconstrained degree of freedom is the axion freedom. It has effects on the long-range astrophysical/cosmological propagation of electromagnetic waves and can be tested/measured using the future generation of polarization measurement of cosmic background radiation.The verification or refutal of this axionic effect will be a crucial step for constructing an effective theory and probing the microscopic origin of gravity. The interaction of spin with gravity is another important clue for probing the microscopic origin of gravity. The interplay of experiments, phenomenology and effective theory are expounded. An ideal way to reveal the microscopic origin of gravity is to measure the gyrogravitational ratio of particles, Three potential experimental methods are considered.     

我们所认识的宇宙

本银系是指我们所在的银河系，所有肉眼可见的星体及天上的银河（见图1）都属于这一银河系，直到1918年以前，天学家还认为太阳系在我们银河系的中心。从可观察到的星之分布来说的确如此；这是因为大部分的星集中在银河系盘面附近，而盘面上有许多尘埃可以吸收、散射可见光，以致离我们较远的星我们看不到。     

超高增压发动机系统性能优化

一、前言 超高增压系统的原理方案是七十年代初提出的,经过十几年的研究,已应用于坦克和机车。我国自一九七八年开始这方面研究,北京工业学院已联合研制出原理样机。 超高增压发动机与普通增压发动机相比增加了旁通补燃装置,并采用低气缸压缩比等技术手段,这样,发动机在体积和机械、热负荷不显著增加的情况下,整机功率     

电厂热力计算可视化研究

1研究背景发电厂原则性热力系统是以汽轮机及其原则性回热系统为基础，考虑锅炉与汽轮机的匹配及辅助热力系统与回热系统的配合而形成的，可以细分为几个子系统：新蒸汽及再热蒸汽系统、给水回热加热及除氧器系统、补充水引人系统、轴封汽和其它废热回收系统以及热电厂的对外供热系统等［‘］。进行发电厂原则性热力计算的主要目的有：（1）确定电厂在若干工况下的热经济性指标；（2）提供全厂热力系统的主要参数；（3）为电厂各种热力设备的选型提供依据；（4）合理安排热力设备的检修。因此，无论对电厂设计部门还是运行部门，原则性热力…     

中法激光时间比对和探测基本物理的相关空间计划

激光时间比对T2L2(Time Fransfer by Laser Link)是法国蔚蓝海岸天文台(OCA)和法国空间中心(CNES)进行的新一代的时间传递计划,将于2008年年中随Jason-2卫星发射上天,并开始观测.它利用激光脉冲在空间的传播来实现地面-卫星,地面-地面远距离时钟的同步,精度比现有的微波比对方式提高1～2个数量级.中国拥有5个固定激光测距站和2个流动激光测距站,基于良好的地理位置和巾法双方比较成熟的激光测距技术,中法激光站之间的时间比对和中国内部激光站之间的时间比对是该计划的重要内容.本文系统描述了T2L2的主要内容和关键技术,初步估算了该计划的精度和稳定度,对中法之间的时间比对做出了初步的观测规划.同时,简单介绍了目前世界上精密时钟的发展现况、F2L2的应用前景及正在研究中的TIPO、ASTRODI、ACS、EGE等探测基本物理的相关空间计划.     

Extra dimensions and atomic transition frequencies

New unification theories predict large extra dimensions （LEDs）. If that is the case, gravity would be stronger at short ranges than what Newtonian gravity predicts. LEDs could also have effects at atomic level. In this paper we propose a new method to constrain the size of ‘gravity-only’ LEDs by analysing how these LEDs modify the energy of the atomic transitions 1s-2s and 2s-2p （Lamb shift）, in the particular case of the hydrogen and muonium atoms. We estimate these effects by using Bethe＇s non-relativistic treatment of Lamb shift. In the particular case of three LEDs, which may be a candidate to explain the interaction mechanism of dark matter particles, we have found that current knowledge in atomic spectroscopy could constrain their sizes to less than 10 μm. Although our contributions do not reach the sensitivity given by SN1987a, they are still slightly better than recent constraints given by Inverse Square Law tests of the Eoet-Wash group at Washington University, which gave R3 〈 36.6 μm.     

外差式激光干涉仪光学读出的两种新算法的设计与实现

纳米级和皮米级激光测距是光学技术中的重要一环,同时也是深空引力波探测实验所必须的技术。德国汉诺威的爱因斯坦研究所为此提出并实现了一种基于相位深度调制技术的外差式激光干涉仪,作为LISA计划测距系统的后备方案,在数值处理过程中使用了Levenberg-Marquardt非线性拟合方法作为干涉仪光学读出算法。探讨并展示了另外两种新的外差干涉仪光学读出拟合算法。第一种算法采用近似并迭代的数值方法将拟合过程分为两次迭代:第一次估算干涉仪的调制深度和调制相位,第二次线性迭代拟合干涉仪的相位和振幅。另外一种算法首先利用离散傅里叶变换计算频谱,然后从频谱中拟合出干涉仪的调制相位,之后采用高斯-牛顿迭代方法线性拟合调制深度、相位和振幅。在空气中长时间运行的结果显示,第一种拟合算法的连续测距误差小于0.24nm,第二种算法的误差在0.19nm左右,比原来的非线性拟合算法分析得到的误差小了5～6倍。     

Orbit optimization for ASTROD-GW and its time delay interferometry with two arms using CGC ephemeris

Astrodynamical space test of relativity using optical devices optimized for gravitation wave detection (ASTROD- GW) is an optimization of ASTROD to focus on the goal of detection of gravitation waves. The detection sensitivity is shifted 52 times toward larger wavelength compared with that of laser interferometer space antenna (LISA). The mission orbits of the three spacecrafts forming a nearly equilateral triangular array are chosen to be near the Sun-Earth Lagrange points L3, L4, and L5. The three spacecrafts range interferometrically with one another with an arm length of about 260 million kilometers. In order to attain the required sensitivity for ASTROD-GW, laser frequency noise must be suppressed to below the secondary noises such as the optical path noise, acceleration noise, etc. For suppressing laser frequency noise, we need to use time delay interferometry (TDI) to match the two different optical paths (times of travel). Since planets and other solar-system bodies perturb the orbits of ASTROD-GW spacecraft and affect the TDI, we simulate the time delay numerically using CGC 2.7 (here, CGC stands for center for gravitation and cosmology) ephemeris framework. To conform to the ASTROD-GW planning, we work out a set of 20-year optimized mission orbits of ASTROD-GW spacecraft starting at June 21, 2028, and calculate the differences in optical path in the first and second generation TDIs separately for one-detector case. In our optimized mission orbits of 20 years, changes of arm lengths are less than 0.0003 AU; the relative Doppler velocities are all less than 3m/s. All the second generation TDI for one-detector case satisfies the ASTROD-GW requirement.     

燃气轮机二次型调节的仿真研究

一、引言 线性二次型调节反馈增益为常数,易于实现,且具有较大的稳定裕度和鲁棒性,因而得到广泛应用.在应用于燃气轮机系统时,系统的状态变量太多,有的难以测量,调节器不易实现.为此,我们用模态分析和灵敏度分析相结合的方法,来确定哪些变量最宜作为反馈变量;进而,本文用部分状态反馈和全部状态反馈比较,得到既具有良好的闭环性能,又易于实现的次最优调节器.