毕奥萨伐尔定律建立的探讨

毕奥萨伐尔定律是电磁学中一个重要的定律。它是法国科学家毕奥和萨伐尔合作研究发现载流长直导线对磁极作用反比于距离的实验结果,并确定了电流对磁极作用力为横向力。该定律是由实验方法得到的,为了能够更好掌握毕萨定律的建立过程,我们尝试根据电磁场理论,应用电磁场变换的关系式推导运动电荷产生的磁场。进而得出经典物理学上的重要电磁规律---毕奥萨伐尔定律。在该条件下求出的毕萨定律,不仅适用条件清晰明了,同时为应用相对性原理解决问题做了充足准备。     

新文化偶像的塑造：胡适及其受众

胡适在新文化运动期间逐渐成名,之后他又借五四运动的影响和杜威访华带来的人气迅速跃升为当时思想界、学术界的要角。从传播学或阅读史的角度检视“五四”运动后胡适偶像地位的塑造过程和他所依赖的周边社会条件,不难发现胡适极高的情商和处世能力发挥了重要作用−他善于利用传媒发声,并具有与各方受众展开良性互动的本领,这为其“暴得大名”和吸引受众认可打下了良好基础。概言之,胡适新文化偶像地位的确立,与胡适自身的刻意经营表演密切相关,同时也是其受众包括其论敌积极参与塑造的结果。揭示这一过程,有助于我们更深刻认识新文化运动中的“互动”和“运动”因素的意义和影响。     

Synchronization of permanent magnet electric motors: New nonlinear advanced results

The nonlinear learning control techniques, based on Fourier approximation theory and used by Verrelli (2011) [2] to solve the synchronization problem for uncertain permanent magnet synchronous motors (performing repetitive tasks of uncertain repetition period), are considered in this paper. We show that, if the exogenous rotor position reference signal (which is to be globally tracked without assuming its foreknowledge) is restricted to the class of sinusoidal signals with uncertain bias, amplitude, frequency and phase, a stronger result can be derived by resorting to nonlinear advanced identification techniques. In contrast to Verrelli (2011) [2], neither availability of the rotor speed reference signal is required nor infinite memory identification schemes are used. The application to the problem of synchronizing a drumming robotic arm with a drumming human arm is presented: simulation results show satisfactory closed loop performances and confirm the effectiveness of the proposed solution.     

Movement measurement with a grating interferometer using sinusoidal phase-modulation

Movements of a surface profile are measured with a two-grating interferometer using sinusoidal phase-modulation. Since sinusoidal phase-modulating (SPM) interferometry can record a phase change due to the movement of an object in the interference signal, the SPM interferometer is suitable for measuring the movement of the object. Some experiments show that the two-grating interferometer can measure a sinusoidal vibration with amplitude of several tens of microns and a step movement with a magnitude of several microns.     

无气动腔型气动分置式斯特林制冷机推移活塞位移研究

涉及的气动分置式斯特林制冷机没有气动腔,依靠蓄冷器两端的压差提供推移活塞运动推力,目前还没有人对这种气动膨胀机的位移进行过测试和研究。建立了数学模型对推移活塞进行受力分析,并给出其运动方程及其求解方法。最后,用实验测量数据对其进行验证。     

Determination the ability of military vehicles to override vegetation

Military operations usually include movement over existing roads and also through natural terrain. Wooded terrain is one of the most challenging environments which affect vehicle mobility. The ability of a vehicle to cross a forest area depends on the possibility of determining if the vehicle is able to manoeuvre between tree stems or can override individual trees. Overriding tree obstacles can be more effective if a vehicle needs a shorter time to cross some tree stems rather than manoeuvring around them. Vehicle movement to cross a forest stand depends on vegetation factors as the stem diameter, stem spacing, and also on tree root parameters, which determine the mechanical tree stability, and a vehicle’s ability to override the trees. Also, the technical parameters (width, length, turning radius, weight, traction force) of the selected military vehicle are important to classify the cross-country movement options. This study describes both the theoretical predictions of the movement of vehicles in forest stands and summarizes the results of one of the most extensive testing of vehicles’ ability to cross individual trees.     

分业：“五四”后关于文化运动的反思

“五四”学生运动多被视作文化运动向政治运动转向的开端,从长时段来看,这一判断应无疑义。若从短程视野观察,“五四”运动结束后一段时间内,或出于反思性目的,不少青年学生在原有文化运动道路上有继续深入与前行的倾向,主要表现为越来越多的人抱持一种文化运动的分工意识,“分业”渐成一时流行的口号。这一倾向在少年中国学会内部表现尤为明显,不少学会成员在分工原则的指导下,自觉担负起思想学术方面的使命,在既有的社会运动之外,明确宣告“力学救国”。