The helium abundance on Jupiter

Methods of determining helium on Jupiter (and the Jovian planets) are critically surveyed. Current information is consistent with solar abundance, He/H₂ = 0.11 by number. The available lines of evidence are the mean density, spectral-line broadening, and stellar occultations. Methods usable from spacecraft flying by are discussed. Observation of far-infrared emission has great promise, but we may have to await the development of entry probes for the greatest assurance.This is one of the publications by the Science Advisory Group.     

The synthesis of helium and CNO isotopes in massive stars

We present helium and CNO isotopic yields for massive mass-losing stars in the initial mass range 15M M _i 50M . We investigate their dependence on assumptions about mass loss rates, internal mixing processes, and metallicity, and specify the contributions from stellar winds and from supernova ejecta.     

The mass and helium discrepancy in massive stars: The case Vela X-1

A NLTE-analysis is presented of high S/N spectra of the optical component of the standard massive X-ray binary Vela X-1. In combination with the orbital parameters we conclude that the optical star is highly helium enriched and is significantly overluminous compared to standard evolutionary tracks of massive accretion stars. We then propose a new accretion model able to explain these features.     

Solar wind helium isotopic composition from SWICS/ULYSSES

This is the first study of the isotopic composition of solar wind helium with the SWICS time-of flight mass spectrometer. Although the design of SWICS is not optimized to measure³He abundances precisely,⁴He/³He flux ratios can be deduced from the data. The long term ratio is 2290±200, which agrees with the results obtained with the ICI magnetic mass spectrometer on ISEE-3 and with the Apollo SWC foil experiments.The ULYSSES spacecraft follows a trajectory which is ideal for the study of different solar wind types. During one year, from mid-1992 to mid-1993, it was in a range of heliographic latitudes where a recurrent fast stream from the southern polar coronal hole was observed every solar rotation. Solar wind bulk velocities ranged from 350 km/s to 950 km/s which would, in principle allow us to identify velocity-correlated compositional variations. Our investigation of solar wind helium, however, shows an isotopic ratio which does not depend on the solar wind speed.     

Observation of the interstellar helium cone by the NOZOMI spacecraft

‘The Japanese Mars probe, NOZOMI, is staying in the interplanetary space (1–1.5 AU) until its Mars’ orbit insertion scheduled in early 2004. Every 16 months on this interplanetary orbit the spacecraft crosses around 1 AU the ‘gravitational focusing cone’ of the interstellar helium, which are penetrating into the inner heliosphere under the solar gravity. During the first crossing of the cone in the season of March–May 2000, we observed these helium particles after the solar wind pickup process with an E/q type ion detector aboard NOZOMI. We have estimated the original temperature of the interstellar helium as 11 000 K. This revised version was published online in August 2006 with corrections to the Cover Date.     

Double-zone model with diffusive mixing and the mass and helium discrepancies in OB-stars

A model for massive main sequence (MS) stars is proposed that quantitatively accounts for the mass and helium discrepancies in luminous OB stars. The radiative envelope of the model consists of two zones being mixed by rotationally induced turbulent diffusion during the star's evolution on the MS. The rate of the mixing in the outer zone is assumed to be substantially lower than that in the inner zone. Both, the mass and helium discrepancy, are shown to be due to helium enrichment in the envelope produced by turbulent diffusion. Some arguments to support this double-zone stellar model are given.Alexander von Humboldt Fellow     

Analysis of Chang’e-5 lunar core drilling process

Chang’e-5 explorer successfully acquired lunar regolith core samples from depths of greater than 1 m of lunar surface. This study analyzed the lunar core drilling process based on the telemetry data, image information, and returned samples to optimize the sampling device design and enhance the understanding of the lunar regolith. In particular, a prediction method for the projected drilling path and local terrain fitting of drilling dip angle was proposed based on the flight events recorded during the core drilling process and the image information acquired before, during, and after sampling. The results revealed that the drilling dip angle of Chang’e-5 was approximately 2.3°, and the deviation of the drilling length and depth was less than 2 mm. For continuous drilling, a fusion method based on telemetry data and image information was applied to determine the demarcation point of drilling with and without the lunar soil. The position of the demarcation point implied that the drilling point remained at approximately 6 mm loose soil, thereby lagging the action of the force response. Additionally, a characteristic parameter comparison method was proposed for the lunar and ground drilling to analyze the status of the lunar soil. Furthermore, the analysis results revealed that the majority of the Chang’e-5 drilling samples were derived from 0–73.8 cm below the lunar surface and few samples were extracted below 73.8 cm, as the drilling encountered several rocky regions. Moreover, the drilling point exhibited two prominent stratification variations at ～28.7 cm and ～70 cm below the lunar surface. Ultimately, the preliminary relationship between sample dissected position in soft tube and drilling displacement was analyzed. The segmented estimation results can support research on subsurface lunar soil.     

Recent results on the parameters of the interstellar helium from the ULYSSES/GAS experiment

Velocity and direction of the flow of the interstellar helium and its temperature and density have been determined from the measurements of the ULYSSES/GAS experiment for two different epochs: during the in-ecliptic path of ULYSSES, representing solar maximum conditions, and during the south to the north pole transition (11/94-6/95), close to the solar minimum conditions. Within the improved error bars the values are consistent with results published earlier.The determination of the density n of the interstellar helium at the heliospheric boundary from observations in the inner solar system requires knowledge about the loss processes experienced by the particles on their way to the observer. The simultaneous observation of the helium particles arriving on direct and indirect orbits at the observer provides a tool to directly determine the effects of the loss processes assumed to be predominantly photoionization and — for particles travelling close to the Sun — electron impact ionization by high-energy solar wind electrons.Such observations were obtained with the ULYSSES/GAS instrument in February 1995, before the spaceprobe passed its perihelion. From these measurements values for the loss rates and the interstellar density could be derived. Assuming photoionization to be the only loss process reasonable fits to the observations were obtained for an ionization rate = 1.1 · 10^–7 s^–1 and a density n 1.7 · 10^–2 cm^–3. Including, in addition, electron impact ionization, a photoionization = 0.6 · 10^–7 s^–1 was sufficient to fit both observations, resulting in a density n 1.4 · 10^–2 cm^–3.On leave from Space Research Centre, Warsaw, Poland.     

Theater battle management core system lessons for systems engineers

The difficulties encountered during development of the theater battle management core system (TBMCS) provide lessons for systems engineering of large-scale, software-intensive systems. The absence of formal requirements and oversight, coupled with strong pressure for rapid deployment, caused the program to fail its first operational tests and actually delayed its deployment to the Held. The lack of measurable requirements and the need to integrate multiple third-party products and systems made it impossible to establish a system baseline and to test TBMCS in realistic conditions. Thus, significant problems manifested themselves only during official government tests. Moreover, despite nominal authority, the lead contractor had little or no control over the government-furnished elements and commercial off-the-shelf products that TBMCS was to incorporate. Experience with TBMCS leads to several conclusions. First, the more complex a system, the greater the need for rigor and discipline in engineering processes. Second, well-defined requirements are essential. Third, mandating the incorporation of specific third-party hardware or software may create severe problems for system development. Other lessons highlight the importance of open standards in a heterogeneous information technology environment and of layering with well-defined interfaces to facilitate integration and system evolution     

企业核心竞争力评价方法研究及应用

针对目前有关核心竞争力评价研究的现状，分析了综合评价中主、客观定权方法的优缺点，提出了主客观定权相结合的核心竞争力的组合评价方法。然后，对组合评价方法中主客观评价方法的选择，主客观定权方法中权重的确定方法，主客观权重的结合原则及方法，给出了作者自己的见解。以此方法为基础，选取了17家制造企业，进行了企业核心竞争力的评价。     

加强信息化营造企业核心竞争力

本文通过对企业信息化与核心竞争力之间关系的描述，指出如何加强企业信息化，改造传统产业，提高人世后我国企业的核心竞争力，从而迎接经济全球化的挑战。     

激波与氦气泡相互作用的实验与数值研究

提出了一种在激波管中实现运动激波与球形气一气界面相互作用的研究方案。以肥皂膜作为气体交界面,高压火花为光源,采用阴影法,在马赫数M=1．2的情况下,在矩形激波管中开展了一系列的实验研究,获得了激波作用下球形氦气泡界面发展变化的相关实验结果。还通过求解二维轴对称的Euler方程,结合网格自适应策略,对实验过程进行了数值模拟。通过与实验结果的对比分析,证实了涡量的产生和分布对于界面的变形和发展有着重要意义。     

金属梯度多孔夹芯板振动特性分析

金属梯度多孔材料芯层的胞孔壁厚度及半径沿芯层厚度方向逐渐变化,使得芯层的材料参数如密度和弹性模量等逐渐变化;采用金属梯度多孔材料代替传统均质多孔芯层会影响夹芯板的振动特性。基于高阶夹芯板理论且考虑梯度多孔芯层密度和弹性模量的耦合影响,建立了复合材料面层-金属梯度多孔夹芯板的振动方程。分析了3种密度的梯度芯层:单向分布、正梯度对称分布和负梯度对称分布对夹芯板固有频率的影响;最后讨论了3种梯度夹芯板在相同三角脉冲载荷作用下的振动响应。计算结果表明梯度芯层密度对称分布的夹芯板固有频率大于单向分布的夹芯板固有频率。     

On the derivation of empirical limits on the helium abundance in coronal holes below 1.5R s

We present a simple technique describing how limits on the helium abundance, , the ratio of helium to proton number density, can be inferred from measurements of the electron density, temperature and their gradients below 1.5R _s. As an illustration, we apply this technique to emission line intensities in the extreme ultraviolet, measured in polar coronal holes. The example indicates that can be significantly large in the inner corona. This technique could be applicable to the more extensive data to be obtained from coordinated ground and space-based observations during the Ulysses south polar passage and the Spartan flight, and subsequently during the SOHO mission. Limits on the helium abundance in the solar wind can thus be derived from its source region and compared to interplanetary values.     

基于力约束的空心涡轮叶片陶芯定位方法

精铸蜡型作为空心涡轮叶片精铸过程重要的前期工艺转接件,其壁厚精度主要由蜡型模具型腔与内部陶芯的位置匹配关系决定。由于陶芯在模具内完全依靠定位元件实现空间定位,为减小由定位误差引起的陶芯位姿漂移,提出了一种基于力平衡约束的空心涡轮叶片精铸模具陶芯定位布局优化方法。首先,通过建立陶芯定位误差传递模型,揭示了定位误差与陶芯空间位姿扰动量之间的映射关系;其次,根据力平衡原理构建了基于力约束的陶芯定位布局优化模型;之后,针对陶芯表面定位候选点的离散分布特性,结合遗传算法给出了陶芯定位布局点的详细求解策略。最后,仿真对比证明了利用本文所提方法获得的陶芯定位方案可以在保证陶芯定位稳定性的同时提高陶芯定位精度,此外,按照优化后的定位方案压制实际蜡型,壁厚检测结果也进一步表明所提方法的有效性。     

Influence of coating thickness on geometric parameters of a chevron core

A comparative analysis of folded cores by the strength criterion and volume density was carried out. The analytical dependences that make it possible to optimize the strength and mass characteristics of sandwich panels are proposed.     

蜂窝夹芯结构面内等效弹性参数的分析研究

针对Bernoulli Euler梁法计算蜂窝夹芯等效弹性参数的不足,利用3D有限元数值模拟技术,通过对不同材料、不同尺寸的正六边形蜂窝夹芯弹性参数进行数值模拟,给出了芳纶纸面内等效刚度和Poisson比随蜂窝夹芯几何参数变化关系,提出了等效弹性参数的计算公式和一种循环优化设计蜂窝夹芯板厚度的新思想,得到了一些Bernoulli Euler梁法无法得到的重要结论:正六边形蜂窝夹芯结构y方向的弹性模量大于x方向的1.5倍;等效Poisson比仅与蜂窝夹芯几何参数有关,而与材料常数无关等。最后通过与文献[11]铝质蜂窝夹芯的压缩实验结果比较,证实了本文所使用方法的有效性和部分公式的正确性。     

Theoretical and experimental technique of determining the mechanical characteristics of folded structure core in the form of Z-crimp. Theoretical foundations and core compression in transverse direction

The analytical formulas to determine the averaged elastic and strength characteristics of the folded structure core in the form of Z-crimp are obtained based on the assumption that the work of its elements (walls) at loading is momentless and they are eliminated from the work after buckling under bilateral tension-compression with shear. It is necessary to determine the dimensionless coefficients of the structural formulas obtained, that appear in solving the problems formulated, based on the data of the specially performed tension, compression and simple shear tests in two planes.