Interpretation of acceleration measurements in inertial navigation

It is shown that, when the absolute and apparent accelerations are measured simultaneously, the problem of autonomous inertial navigation is reduced to the solvable inverse problem. Physical and geometrical (kinematic) conditions for solvability are formulated.     

Three-dimensional gravimetry based on the inertial navigation method

A technique with which the gravimetry problem is embedded in the problem of disposition of a three-component (three-dimensional) inertial navigation system on a stationary base is substantiated. Results of numerical simulation are presented.     

Mobile gravitoinertial system based on the three-component method of inertial navigation

A model of a ballistically unperturbed (stable) gravimetric system is suggested, the functioning of which is based on conversion of inertial information and (radial) position information about the object’s motion.     

Effect of headphone position on absolute threshold measurements

Pure-tone audiometry (measurement of absolute thresholds using pure tones) is the main test for the diagnosis of hearing loss. The aim of the present study is to determine whether the headphone placement over a listener’s ears has an influence on pure-tone audiometric tests, for a large frequency range, for Sennheiser HD600 and Telephonics TDH39 headphones. Audiograms (with 1 dB step, and including 10 frequencies up to 14 kHz) were performed several times on normal-hearing subjects, for different – or not different – headphone positions (allowing to dissociate between effects of headphone position and cognitive factors). Globally, the results seem to indicate that the reliability without headphone removing was quite close to the one observed with removing. The influence of removing did not appear more crucial for high frequencies. The rare frequencies for which a removing effect was seen seem to be function of the headphone model. Finally the results were quite different among the subjects.     

The absolute flatness measurements of two aluminum coated mirrors based on the skip flat test

Two methods based on the skip flat test are proposed to understand the absolute flatnesses of two aluminum coated mirrors, one with a circular aperture of 69 mm diameter, and the other with an elliptical aperture whose major and minor axes are 60 mm and 42 mm, respectively. For the mirror with the circular aperture, three measurements including one cavity measurement and two skip flat measurements are conducted. The measuring results are 0.079λ (PV) and 0.019λ (RMS). For the mirror with the elliptical aperture, two cavity measurements and one skip flat test are used. The measured results are 0.059λ (PV) and 0.014λ (RMS). The results agree well with those obtained with the mirrors measured at normal incidence, using high precision transmission flat as the reference. The agreements of the results indicate that the new methods could be used as two reliable ways to understand the absolute flatnesses of the aluminum coated mirrors.     

Review of absolute neutrino mass measurements

The discovery of neutrino flavor oscillations has firmly established that at least two of the three known neutrino mass eigenstates possess a non-vanishing rest mass. Complementary to cosmology and the search for neutrino-less double beta decay laboratory-based measurements of low-energy beta decays provide a direct and model-independent approach to measure the effective electron (anti-)neutrino mass. I have reviewed the recent progress of the field starting from the first molecular tritium spectrum measured with the current state of the art KATRIN experiment before discussing the development of new approaches to achieve the sensitivity required to cover the full neutrino mass parameter range allowed in the inverted mass ordering scheme. The new avenues opened by micro-calorimeteric measurements of the electron capture decay spectrum of ¹⁶³Ho (ECHo, Holmes and Numecs) and by the new technology of cyclotron radiation emission spectroscopy in combination with molecular and atomic tritium sources have been presented.     

Sounding rocket measurements of suprathermal ion acceleration

Transverse ion acceleration has been observed at rocket altitudes between 500 and 1000 km due to the injection of 100-200-eV argon plasma, auroral electron precipitation, and the injection of electromagnetic waves. Field-aligned currents necessary to neutralize the plasma injection payloads and those naturally occurring in the aurora could be responsible for the ions observed in the first two observations. Associated with the aurora, both bulk heating and tail heating are observed, sometimes simultaneously. In this case, either different masses are accelerated and/or different mechanisms are responsible. The bulk heating is closely correlated with the aurora structure while tail heating is not so well correlated. High-time-resolution rocket ion data have revealed that the transverse acceleration process is of very short duration (~100 ms) and occurs in a very limited volume (a few hundred kilometers along B and on the order of the ion gyrodiameter across B). Such impulse acceleration events are correlated with waves near the lower hybrid resonance. Wave injections of electromagnetic waves near the lower hybrid frequency result in the transverse acceleration of ambient ions     

First absolute mass measurements of short-lived isotopes

Absolute mass measurements of short-lived isotopes have been performed at the on-line mass separator ISOLDE at CERN by determining the cyclotron frequencies of ions confined in a Penning trap. The cyclotron frequencies for^{77,78,85,86,88}Rb and⁸⁸Sr ions could be determined with a resolving power of 3×10⁵ and an accuracy of better than 10⁻⁶, which corresponds to 100 keV for massA=100. The shortest-lived isotope under investigation was⁷⁷Rb with a half-life of 3.7 min. The resonances obtained for the isobars⁸⁸Rb and⁸⁸Sr were clearly resolved.     

Split-pulse spectrometer for absolute XUV frequency measurements

A split-pulse spectrometer based on pairs of time-delayed femtosecond pulses can give access to accurate frequency measurements in the extreme ultraviolet (XUV) spectral domain. We demonstrate this approach by measuring the absolute frequency of a single-XUV-photon transition to a bound state of atomic argon excited with the ninth harmonic of an amplified Ti:sapphire laser.     

Carbon clusters for absolute mass measurements at ISOLTRAP

The cyclotron frequencies of singly charged carbon clusters C_n ⁺ (n ≥ 2) were measured with the Penning-trap mass spectrometer ISOLTRAP at ISOLDE/CERN. The present limit of mass accuracy δm/m = 1.2 ^. 10^-8 and the extent of the mass-dependent systematic shift (δm/m)_sys = 1.7(0.6) ^. 10^-10/u ^. (m - m _ref) of the setup were investigated for the first time. In addition, absolute mass measurements by use of pure clusters of the most abundant carbon isotope ¹²C are now possible at ISOLTRAP. Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002 RID="a" ID="a"Present address: CERN, CH-1211 Geneva 23, Switzerland; e-mail: klaus.blaum@cern.ch     

A null method for making absolute measurements of the reflectivity of transparent solids with high precision

A null method is described for making absolute measurements of the surface reflectivity of transparent solids with high precision ( ≈ 1 part in 10⁴). The phase sensitivity of a two beam interferometer is used to separate signatures of different order produced by multiple reflections in the air gap of a Fabry-Perot etalon constructed from the specimen. Then, by using two apertures in front of the etalon and two moving mirrors, signatures of different order are brought simultaneously to the output port of the interferometer. A difference signal is produced by subtracting the two signatures either optically or electronically, and the apertures are adjusted to produce a null output. The experimental value of the reflectivity is determined by the ratio of the areas of the two apertures and is independent of the photometric accuracy of the detector. The method should also be suitable for investigating weak structure in the reflectivity of transparent solids at the level of ≈ 10⁻⁵ or less.     

Possible measurements of the gravitational acceleration with neutral antimatter

The interest in measuring the gravitational acceleration using neutral antimatter is discussed as well as the advantages compared with using charged antimatter, and a few possible experimental schemes are briefly discussed.     

Total emissivity measurements without use of an absolute reference

Total emissivity measurement by ordinary steady state radiometric methods are difficult at low temperature; besides, those methods require an emissivity reference. In this paper, several new periodic methods suitable for total emissivity measurements are presented. First it is shown that the thermal modulation of a sample allows direct emissivity measurements, even at low temperature, with an ordinary equipment involving no cooled vessel. Very accurate measurements have been performed within a few minutes at room temperature, on reflective materials. Second, it is shown that indirect total emissivity measurements are also feasible, provided source and sample temperatures are equal. This condition can be fulfilled with a modulated temperature hemispherical gray surface as IR source, or in a simpler way, with a mobile part of a hemisphere. Third, it is shown that if both sample and source temperatures are modulated, simultaneous direct and indirect measurements can be carried out. This results in an absolute emissivity measurement without reference. As an experimental validation, simultaneous direct and indirect measurements of the total directional emissivity are carried out on three samples at room temperature. Periodic radiometry methods are found to be reliable and accurate, emission and reflection measurements giving the same result.     

基于激光多普勒测速仪的车载组合导航

 针对车载纯捷联惯性导航系统(SINS)导航精度随时间增长而降低的不足,提出了基于激光多普勒测速仪（LDV）这一新型速度传感器的组合导航方案。通过建立SINS/LDV组合导航系统的状态方程和量测方程,设计了系统的卡尔曼滤波器,并对组合导航系统进行了仿真模拟。结果表明：SINS/LDV组合方案能够有效减小SINS导航参数随时间的累积误差,可以实现全自主、高精度导航;当LDV测速精度为0.1%时,组合导航系统的位置精度提高了2个数量级,速度精度提高了1个数量级。     

Study on autonomous navigation based on pulsar timing model

The basic principle of pulsar timing model was introduced, and the general relativistic corrections were analyzed when pulse time of arrival (TOA) was transferred to coordinate TOA at the Solar System Barycentre. Based on the shifting, an iterative method of autonomous position determination for spacecraft was developed. Accordingly, the linear form of the position offset equation was evolved. Using the initial estimated value of spacecraft’s position as the input of pulsar timing equation, through calculation of the offset between measured or transferred and predicted TOA, the position offset can be solved by Least Squares. At last, the main error sources including modeling error and parameters error were discussed. Supported by the National Defence Laboratory Foundation of China (Grant No. 9140C3601010901) and Science Foundation of Shaanxi Province (Grant No. 2007F12) and the Technology Specialism Foundation of Shaanxi Education Department of Shaanxi Province (Grant No. 07JK332), and the Innovative Research Plan of Xi’an University of Technology (Grant No. 105-210714)     

捷联惯导/北斗高精度组合导航方法研究

提出采用紧组合方式进行捷联惯导/北斗组合导航设计,首先对捷联惯导与北斗系统进行误差分析与建模,将捷联惯导系统误差、北斗等效时钟误差相应的距离(伪距误差)以及等效时钟频率误差相应的距离率(伪距率误差)作为组合导航系统状态;利用捷联惯导位置输出与北斗接收机星历输出构造获得等效伪距,将其与北斗接收机测量的伪距对应相减作为量测,推导建立对应的量测方程,采用卡尔曼滤波设计捷联惯导/北斗组合导航滤波算法。仿真结果表明,该组合导航方法的速度精度达到±0.05m/s,位置精度达到±3.2m,水平姿态精度达到±0.4′,航向精度达到±1.6′。     

Predictive visual tracking based on least absolute deviation estimation

To cope with the occlusion and intersection between targets and the environment, location prediction is employed in the visual tracking system. Target trace is fitted by sliding subsection polynomials based on least absolute deviation （LAD） estimation, and the future location of target is predicted with the fitted trace. Experiment results show that the proposed location prediction algorithm based on LAD estimation has significant robustness advantages over least square （LS） estimation, and it is more effective than LS-based methods in visual tracking.     

一种基于光学倍乘原理的绝对距离干涉测量系统

介绍了一个基于光学倍乘原理的绝对距离干涉测量系统。系统包括两个干涉仪:采用半导体激光器作为光源的定位干涉仪和测量位移的外差干涉仪。介绍了光源的选择,系统的设计以及信号的采集和处理方案。采用这套绝对测量系统,可以实现长度为2m以内的绝对距离测量,定位精度可以达到±0.5μm。     

基于绝对差度量的灰阶图像光学匹配运算

讨论了基于绝对差度量的灰阶图像识别问题;利用光学相关原理和循环编码方法实现了基于绝对差度量的灰阶图像快速匹配处理;基于差异度矩阵和λ截集的概念来描述匹配结果,提高了灰阶目标识别抵抗各种畸变干扰的稳定性。此方法可以适用于任何的相干光和非相干光相关系统,给出了实验示例。