用于经济型使用的多轴加工中心

作为世界最大的汽车供应厂商之一的大陆公司(Continental)要按照他们全球顾客的需求生产,将来的生产设备也同样必须灵活地适应客户需求的变化。从这个意义来说,SW公司已经为大陆公司开发了一种"世界机床"。作为全球汽车供应的重要厂商,大陆公司远远超出了车辆构件的制造和按时交货的能力。这里,专有的组件和标准部件的OEM方式(来件组装)摆脱了开发和生产各种成套汽车部件的困境。这样,在46个国家约有173000员工的情况下,     

Structure and importance of logspace-MOD class

We refine the techniques of Beigelet al. [4] who investigated polynomial-time counting classes, in order to make them applicable to the case of logarithmic space. We define the complexity classes and demonstrate their significance by proving that all standard problems of linear algebra over the finite ringsZ/kZ are complete for these classes. We then define new complexity classes LogFew and LogFew and identify them as adequate logspace versions of Few and Few. We show that LogFew is contained in and that LogFew is contained in for allk. Also an upper bound for in terms of computation of integer determinants is given from which we conclude that all logspace counting classes are contained in.     

Beam plasma neutron sources based on beam-driven mirror

The design and performance of a relatively low-cost, plasma-based, 14-MeV D-T neutron source for accelerated end-of-life testing of fusion reactor materials are described in this article. An intense flux (up to 5×10¹⁸ n/m²·s) of 14-MeV neutrons is produced in a fully-ionized high-density tritium target (n _e 3×10²¹ m^–3) by injecting a current of 150-keV deuterium atoms. The tritium plasma target and the energetic D⁺ density produced by D⁰ injection are confined in a column of diameter 0.16 m by a linear magnet set, which provides magnetic fields up to 12 T. Energy deposited by transverse injection of neutral beams at the midpoint of the column is conducted along the plasma column to the end regions. Longitudinal plasma pressure in the column is balanced by neutral gas pressure in the end tanks. The target plasma temperature is about 200 eV at the beam-injection position and falls to 5 eV or less in the end region. Ions reach the walls with energies below the sputtering threshold, and the wall temperature is maintained below 740 K by conventional cooling technology.     

In utero exposure to extra vitamin D from food fortification and the risk of subsequent development of gestational diabetes: the D-tect study

Background

The primary aim of this study was to assess whether exposure during fetal life to extra vitamin D from food fortification was associated with a reduction in the risk of subsequently developing gestational diabetes mellitus (GDM). Furthermore, we examined whether the effect of the vitamin D from fortification differed by women’s season of birth.

Methods

This semi-ecological study is based on the cancellation in 1985 of the mandatory policy to fortify margarine with vitamin D in Denmark, with inclusion of entire national adjacent birth cohorts either exposed or unexposed to extra vitamin D in utero. The identification of GDM cases later in life among both exposure groups was based on the Danish national health registers. Logistic regression analyses generating odds ratios (ORs) and 95% confidence intervals (95% CIs) were performed.

Results

Women who were prenatally exposed to the extra vitamin D from fortification tended to have a lower risk of subsequently developing GDM than unexposed women (OR 0.87, 95%CI 0.74,1.02, P?=?0.08). When analyses were stratified by women’s season of birth, exposed women born in spring had a lower risk of developing GDM compared to unexposed subjects (OR 0.68, 95%CI 0.50,0.94, p?=?0.02).

Conclusion

This study suggests that prenatal exposure to extra vitamin D from mandatory fortification may lower the risk of developing gestational diabetes among spring-born women.

Trial registration

This study is part of the D-tect project, which is registered on clinicaltrials.gov: NCT03330301.

     

The influence of water air content on cavitation erosion in distilled water

The influence of increased air content of the cavitating liquid (distilled water) was studied in rotating disk test rig. A rise in the total air content (including dissolved and entrained air) of the water in the undersaturated range resulted in bubble collapse cushioning and reduction of cavitation damage. When the water was oversaturated with air, large air bubbles formed and cavitation damage was drastically reduced, probably due to both bubble collapse cushioning and shock wave attenuation.     

MIMO conditional integrator control for unmanned airlaunch

A nonlinear MIMO controller based on the conditional integrator technique is designed for the robust stabilization of a new satellite launching strategy called (unmanned) airlaunch. This control technique concerns an integrator performing similar to a sliding mode controller when the system is outside a boundary layer defined by the controller, and performing as a linear controler that provides the integral term when the system enters into the boundary layer. Satellite airlaunch strategy consists in using a two‐stage launching system. The first stage is composed of an airplane (manned or unmanned) that carries a rocket launcher, which constitute the subsequent stages. The control objective is to stabilize the aircraft in the launch phase. It is developed separately for the two nonlinear (one MIMO and one SISO) motion modes of the model, the longitudinal mode and lateral mode, and is then applied to the full model of the aircraft. The considered system is highly nonlinear, mostly as a consequence of a possible large angle of attack, sideslip, and roll angle. Finally, the present work illustrates through simulations, the good performance of the proposed control algorithm. Copyright © 2013 John Wiley & Sons, Ltd.