耦合气动参数与车身姿态变化的圈速仿真

以大学生方程式赛车为对象展开圈速仿真研究,综合考虑离地间隙和偏航角与阻力系数、升力系数之间的关系,采用试验和数值仿真相结合的方法,研究行驶中车身姿态变化对方程式赛车气动特性的影响。首先,对现有车辆气动模型进行修正,再利用龙格库塔方法对速度积分进行圈速仿真,并与商业软件Optimumlap的仿真结果进行对比。结果表明,基于气动参数与车身姿态耦合关系建立的模型对于圈速仿真有着更为准确的描述;忽略气动变化影响会高估过弯时轮胎的抓地力,且在不考虑载荷转移的同时低估赛车的加速性能,从而高估阻力对于圈速的影响;考虑载荷转移的模型,不同赛道对阻力的敏感程度不同。为改进赛车空气动力学设计提供参考。

追赶罗西的乐趣

早在1998年,第一代RSV Mille推出时就配置了圈速计,它成为最早配置圈速计的跑车之一。

Nonlinear Control of Beam Halo-Chaos in Accelerator-Driven Clean Nuclear Power System

Beam halo-chaos in high-current accelerators has become a key concerned issue because it can cause excessive radioactivity from the accelerators therefore significantly limits their applications in industry,medicine,and national defense.Some general engineering methods for chaos control have been developed in recent years,but they generally are unsuccessful for beam halo-chaos suppression due to many technical constraints.Beam halo-chaos is essentially a spatiotemporal chaotic motion within a high power proton accelerator.In this paper,some efficient nonlinear control methods,including wavelet function feedback control as a special nonlinear control method,are proposed for controlling beam halo-chaos under five kinds of the initial proton beam distributions (i.e.,Kapchinsky-Vladimirsky,full Gauss,3-sigma Gauss,water-bag,and parabola distributions) respectively.Particles-in-cell simulations show that after control of beam halo-chaos,the beam halo strength factor is reduced to zero,and other statistical physical quantities of beam halo-chaos are doubly reduced.The methods we developed is very effective for suppression of proton beam halo-chaos in a periodic focusing channel of accelerator.Some potential application of the beam halo-chaos control in experiments is finally pointed out.

Filtering algorithm and direction identification in relative position estimation based on induction loop-cable

A filtering algorithm and direction identification method are presented for the positioning system of the mid-speed maglev train. Considering the special structure of the mid-speed maglev train, the ground position estimation method is adopted for its traction system. As the train is running, the induction loop-cable receives the signal sent by the on-board antenna to detect the position and direction of the train. But the height of the on-board antenna relative to the loop-cable is highly vulnerable to the change of the suspension height and the magnetic field produced by the traction during traveling, which may lead to amplitude fluctuation of the received signal. Consequently, the position estimation may be inaccurate. Therefore, a discrete second-order nonlinear trackdifferentiator is proposed based on the boundary characteristic curves, and the new differentiator could also extract the running direction of the train for the traction system. The experimental results show that the tracking differentiator can effectively filter out the signal interference and can provide accurate direction signal.

Deduction of Design Equations for Durability Performance Improvement of Voice Coil Type Linear Actuator for Servo Valve Operation

The precise hydraulic valve is widely used in various industrial fields like aircraft, automobile and general machinery. Linear actuator is the most important device for driving the precise hydraulic valve. The reliable operation of linear actuator has effects on the overall hydraulic system. The performance of linear actuator relies on frequency response and step response according to arbitrary input signal. In this paper, the analysis for the components of linear actuator is performed to satisfy the reliable operation and response characteristics through the reliability analysis, and also deducted the design equations to realize the reliable operation and fast response characteristics of voice coil type linear actuator for servo valve operation through the empirical knowledge of experts and electromagnetic theories. The design equations are suggested to determine the values of design parameters of linear actuator as like bobbin size, length of yoke and plunger and turn number of coil, and calculated the life test time of linear actuator for verification of reliability of the prototype. In addition, for reducing the life test time, the acceleration model of linear actuator is proposed and the acceleration factor is calculated considering the field operating conditions. And then, the achieved design values are verified through accelerated life test and performance tests using some prototypes of linear actuators adapted in servo valve.

Trend in Coral-Algal Phase Shift in the Mandapam Group of Islands, Gulf of Mannar Marine Biosphere Reserve, India

The present study revealed proliferation of macro-algae modifying coral reef ecosystems in a different manner due to diseases and sedimentations in the Mandapam group of islands in the Gulf of Mannar. Benthic surveys were conducted with major attack of seven coral reefs diseases with high sedimentation rate, nine species of fleshy macro-algae(Turbinaria ornata, Turbinaria conaides, Caulerpa scalpelliformis, Caulerpa racemosa, Kappaphycus alvarezii, Padina gymnosphora, Sargassum wightii, Ulva reticulata and Calurpa lentillifera) proliferation against major corals life forms(Acropora branching, Acropora digitate, Acropora tabulate, coral massive, coral submassive, coral foliose and coral encrusting). The results confirm that diseased corals most favor to macro-algae growth(15.27%) rather than the sedimentation covered corals(8.24 %). In the degradation of coral life forms, massive corals were more highly damaged(7.05%) than any other forms. Within a short period of time(May to September), coral coverage shrank to 17.4% from 21.9%, macro-algae increased 23.51% and the average sedimentation rate attained 77.52 mg cm^(-2) d^(-1) with persisting coral reef diseases of 17.59%. The Pearson correlation showed that the coral cover decreased with increasing macro-algae growth, which was statistically significant(r =-0.774, n = 100, P < 0.0005). The proliferation of the various macro-algae C. scalpellifrmis, T. ornata, C. racemosa, T. conaides, U. reticulata, S. wightii, K. alvarezii, P. gymnosphora and C. lentillifera increased with percentages of 6.0, 5.8, 5.7, 4.9, 4.2, 3.7, 2.7 and 1.9, respectively. If this trend continues, the next generation of new recruit corals will undoubtedly lead to a phase shift in Gulf of Mannar corals.

乐高新超跑迈凯伦塞纳

乐高在打造了一款可以真的缓慢前行的全尺寸布加迪Chiron后,又把视线瞄向了去年刚刚推出的顶级超跑迈凯伦塞纳。迈凯伦塞纳算得上近两年推出的最强劲的超级性能车之一,去年接连刷新了数个赛道的圈速记录,加上车神名号加成,成为了真正的梦想神车。此次乐高通过经典积木打造出了一台完全1:1 还原的乐高版塞纳。

Dynamics of unstable continental subduction:Insights from numerical modeling

Numerical experiments are used in this study to systematically investigate the effects of convergence rate,crustal rheological strength,and lithospheric thermal structure on the dynamics of continental collision.The study focuses on the types,conditions and processes of unstable continental subduction.Modelling results suggest that the development of unstable continental subduction can be promoted by conditions that tend to decrease rheological strength of the lithosphere,such as low crustal rheological strength,"hot"thermal structure of the lithosphere,or low convergence rate.Unstable subduction mode can be further categorized into three types:(1)multi-stage slab breakoff,(2)continuously"flowing"of fluid-like slab into the upper mantle,and(3)large-scale detachment of the thickened orogenic root.These three types of unstable continental subduction are respectively associated with(1)a low convergence rate,(2)"hot"thermal structure of the lithosphere with a high convergence rate,and(3)moderate-high crustal rheological strength with a low convergence rate.It is also revealed that the evolution of crustal melting is dominated by the deformation pattern of continental collision,which is mainly controlled by crustal rheological strength.The modelling results have important implications for understanding of continental subduction mode selection under specific geodynamic conditions.

2-D P-wave velocity structure of lithosphere in the North China tectonic zone: Constraints from the Yancheng-Baotou deep seismic profile

We obtained the 2-D P-wave velocity structure of the lithosphere in the eastern North China Craton, Shanxi fault subsidence zone, and Yinchuan-Hetao fault subsidence zone by ray tracking technology based on six groups of clearly identified crustal phases and one group of lithospheric interface reflection phases from seismic recording sections of 21 shots along the 1300-km-long Yancheng-Baotou deep seismic wide-angle reflection/refraction profile. The results indicate significant differ- ences between the lithospheric structure east and west of the Taihang Mountains, which is a gravity-gradient zone as well as a zone of abrupt change in lithospheric thickness and a separation zone of different rock components. East of the Taihang Mountains, the Mesozoic and Cenozoic lithospheric structure of the North China Craton has undergone strong reformation and destruction, resulting in the lithosphere thickness decreasing to 70-80 km. The North China Basin has a very thick Cenozoic sedimentary cover and the deepest point of crystalline basement is about 7.0 kin, with the crustal thickness decreasing to about 31.0 kin. The crystalline basement of the Luxi uplift zone is relatively shallow with a depth of 1.0-2.0 km and crustal thickness of 33.0-35.0 km. The Subei Basin has a thicker Cenozoic sedimentary cover and the bottom of its crystalline basement is at about 5.0-6.0 km with a crustal thickness of 31.0-32.0 km. The Tanlu fault is a deep fracture which cuts the lithosphere with a significant velocity structure difference on either side of the fault. The Tanlu fault plays an important role in the lithospheric destruction in the eastern part of the North China Craton. West of the Taihang Mountains, the crustal thickness increases sig- nificantly. The crust thickness beneath the Shanxi fault depression zone is about 46 km, and there is a low-velocity structure with a velocity of less than 6.1 km s-~ in the upper part of the middle crust. Combined with other geophysical study results, our data shows that the lithospheric destruction at the Shaanxi-Shanxi fault depression zone and the Yinchuan-Hetao rift surround- ing the Ordos block is non-uniform. The lithosphere thickness is about 80-90 km in the Datong-Baotou area, 75-137 km at the Dingxiang-Shenmu region, and about 80-120 km in the Anyang-Yichuan area. The non-uniform lithospheric destruction may be related to the ancient tectonic zone surrounding the Ordos block. This zone experienced multi-period tectonic events in the long-term process of its tectonic evolution and was repeatedly transformed and weakened. The weakening level is related to the interactions with the Ordos block. The continental collision between the Cenozoic India and Eurasia plates and N-E thrust- ing by the Qinghai Tibet Plateau block is causing further reformation and reduction of the lithosphere.