货运动车组装载门凹陷对隧道内会车压力波的影响

随着我国技术经济水平的提高，电子商务产业快速发展，货运动车组应运而生。采用有限体积方法和重叠网格方法，以及SST k-ω高雷诺数湍流模型，数值模拟研究时速350 km的货运动车组在隧道内交会的压力波，探究货运动车组车体结构即装载门凹陷对隧道内交会压力波的影响。实车试验结果验证了本文数值模拟方法的准确性。研究结果表明，凹陷的装载门使平直车身处的最大正压值增大约20%~30%，且有无凹陷的装载门中心最大正压值的差异百分比维持在35%~80%，最大负压值差异百分比在20%~25%。     

DYNAMIC RESPONSE OF HIGH SPEED TRAIN MEETING IN OPEN AIR,MEETING IN TUNNEL AND PASSING TUNNEL1)

明线会车、隧道会车和过隧道工况下的气动压力波对高速列车的动力响应和运行安全产生很大影响,本文建立了三辆编组的高速列车动力学模型,通过数值仿真得到了列车在三种工况下的车体所受的气动力,基于数值积分分析了列车的动力响应和脱轨系数。研究发现：明线会车和隧道会车工况相比,车辆的侧向运动相反。 明线会车和过隧道时,气动载荷对列车的脱轨系数影响较小,而隧道会车时,气动载荷作用对尾车的安全性影响较大。     

Nucleon effective mass splitting and density-dependent symmetry energy effects on elliptic flow in heavy ion collisions at E_(lab)= 0.09 ～ 1.5 GeV/nucleon

By incorporating an iso spin-dependent form of the momentum-dependent potential in the ultra-relativistic quantum molecular dynamics(UrQMD) model,we systematically investigate effects of the neutron-proton effective mass splitting m*_(n-p)=m*_n-m*_p/m and the density-dependent nuclear symmetry energy E_(sym)(ρ) on the elliptic flow v_2 in~(197)Au+~(197) Au collisions at beam energies from 0.09 to 1.5 GeV/nucleon.It is found that at higher beam energies(≥0.25 GeV/nucleon) with the approximately 75 MeV difference in slopes of the two different E_(sym)(ρ),and the variation of m*_(n-p) ranging from-0.03 to 0.03 at saturation density with isospin asymmetry δ=(ρ_n-ρ_p)/ρ-0.2,the E_(sym)(ρ) has a stronger influence on the difference in v_2 between neutrons and protons,i.e.,v_2~n-v_2~p,than m*_(n-p) has.Meanwhile,at lower beam energies(≤0.25 GeV/nucleon),v_2~n-v_2~p is sensitive to both the E_(sym)(ρ) and the m*_(n-p).Moreover,the influence of m*_(n-p) on v_2~n-v_2~p is more evident with the parameters of this study when using the soft,rather than stiff,symmetry energy.     

三色圆偏振激光组合脉冲驱动氦原子产生椭圆偏振的阿秒脉冲

我们提出利用频率为ω,3ω和强度较弱的2ω组成的三色圆偏振激光组合脉冲驱动氦原子能够得到椭偏率较大的阿秒脉冲链的一种方法.通过强场近似方法,计算了氦原子在两色和三色圆偏振激光组合脉冲驱动下发射高次谐波谱及其合成阿秒脉冲链,比较了氦原子(初态为s态)在这两种情况下发射高次谐波谱的特点及其合成阿秒脉冲链椭偏率的大小,结果发现,在反旋的两色ω,3ω激光脉冲基础上加入了频率为2ω的第三色激光脉冲联合作用到氦原子上,所得到的阿秒脉冲链的椭偏率相对于双圆场情况下有所增加,通过调整ω,3ω激光的强度比,并且选择适当的第三色激光的强度,对初态为s态的原子,仍能够得到具有较大椭偏率的阿秒脉冲链.     

A novel rigid wheel for agricultural machinery applicable to paddy field with muddy soil

The working performance of agricultural machinery is largely determined by the walking performance of the wheel when driving in complex unstructured soil. However, the driving performance of existing wheels is not satisfactory for paddy field with muddy soil. The purpose of the current study is therefore to propose a novel rigid wheel for agricultural machinery which is applicable to paddy field with muddy soil. Firstly, a novel arc edge shaped wheel was designed based on the principles of mechanics on the ground. Then the driving performance of this arc edge shaped wheel was evaluated using FE modeling of interaction between rigid wheel and soil. Finally, the structure originally designed arc edge shaped wheel was improved according to FE modeling results, and this improved design was further evaluated by both FE simulation and prototype experiments. Both FE modeling and experimental results indicate that the improved arc edge shaped wheel proposed in this study has a good driving performance with regarding to wheel sinkage and soil reaction force. The proposed arc edge shaped wheel could be used as an effective component of rice harvester for paddy field with muddy soil.     

Parameter-dependent synchronization of coupled neurons in cold receptor model

In this paper, synchronization in two coupled neurons with spiking, bursting and chaos firings is investigated as the coupling strength gets increased. Synchronization state can be identified by means of the bifurcation diagram, the correlation coefficient and ISI-distance. It is illustrated that the coupled neurons can exhibit different types of synchronization state when the coupling strength increases. The different synchronization processes appear similar, but their detailed processes are different depending on the parameter values. The synchronization of neuronal network with two different network connectivity patterns is also studied. It is shown that chaotic and high period pattern are more difficult to get complete synchronization than the situation in single spike and low period pattern. It is also demonstrated that the synchronization status of multiple neurons is dependent on the network connectivity patterns. These results may be instructive to understand synchronization in neuronal systems.     

Development of in-wheel sensor system for accurate measurement of wheel terrain interaction characteristics

Planetary rovers need high mobility on a rough terrain such as sandy soil, because such a terrain often impedes the rover mobility and causes significant wheel slip. Therefore, the accurate estimation of wheel soil interaction characteristics is an important issue. Recent studies related to wheel soil interaction mechanics have revealed that the classical wheel model has not adequately addressed the actual interaction characteristics observed through experiments. This article proposes an in-wheel sensor system equipped with two sensory devices on the wheel surface: force sensors that directly measure the force distribution between the wheel and soil and light sensors that accurately detect the wheel soil surface boundary line. This sensor design enables the accurate measurement of wheel terrain interaction characteristics such as wheel force distribution, wheel–soil contact angles, and wheel sinkage when the powered wheel runs on loose sand. In this article, the development of the in-wheel sensor system is introduced along with its system diagram and sensor modules. The usefulness of the in-wheel sensor system is then experimentally evaluated via a single wheel test bench. The experimental results confirm that explicit differences can be observed between the classical wheel model and practical data measured by the in-wheel sensor system.     

Probe chiral magnetic effect with signed balance function

In this paper a pair of observables are proposed as alternative ways,by examining the fluctuation of net momentum-ordering of charged pairs,to study the charge separation induced by the Chiral Magnetic Effect(CME)in relativistic heavy ion collisions.They are,the out-of-plane to in-plane ratio of fluctuation of the difference between signed balance functions measured in pair’s rest frame,and the ratio of it to similar measurement made in the laboratory frame.Both observables have been studied with simulations including flow-related backgrounds,and for the first time,backgrounds that are related to resonance's global spin alignment.The two observables have similar positive responses to signal,and opposite,limited responses to identifiable backgrounds arising from resonance flow and spin alignment.Both observables have also been tested with two realistic models,namely,a multi-phase transport(AMPT)model and the anomalous-viscous fluid dynamics(AVFD)model.These two observables,when cross examined,will provide useful insights in the study of CME-induced charge separation.     

Effects of nuclear charge fluctuations on dilepton photoproduction

Fluctuations of dilepton production from two photon interactions γγ→l~+l~- are studied in semicentral and peripheral nuclear collisions.Based on the Weizsacker-Williams approach,electromagnetic(EM) fields generated by moving nuclear charges are approximated as quasi-real photons.As fluctuating EM fields in each collision event are hard to be measured directly in experiments due to its short lifetime,we study the dilepton photoproduction with fluctuating EM fields,which are crucial for the EM fields induced chiral and charged particle evolutions,and calculate the relative standard deviation of the dilepton mass spectrum with the event-by-event fluctuating nuclear charge distributions.This fluctuation effect becomes smaller in more peripheral collisions where the shift of proton positions is implicit for EM fields outside the nucleus.The uncertainty of effective impact parameter △b on the standard deviation is also studied,and its effect is around one-third of the effect of nuclear charge fluctuations when △b is taken as～1 fm.