油井磁防蜡技术中的Halbach型磁场的设计

设计用于油田开采防蜡技术中的两种永磁体磁场结构.一般地,好的磁场设计需具备两个特点：结蜡区内的磁感应强度强和油路轴向上磁感应强度的梯度大.为此,以Halbach型永磁磁场为基础,设计了两种“螺旋形”的防蜡磁场结构.通过数值模拟研究它们的磁场分布特点.结果表明：两种磁场均具备上述两个特点.     

Dynamics of submaximal effort soccer instep kicking

During a soccer match, players are often required to control the ball velocity of a kick. However, little information is available for the fundamental qualities associated with kicking at various effort levels. We aimed to illustrate segmental dynamics of the kicking leg during soccer instep kicking at submaximal efforts. The instep kicking motion of eight experienced university soccer players (height: 172.4 ± 4.6 cm, mass: 63.3 ± 5.2 kg) at 50, 75 and 100% effort levels were recorded by a motion capture system (500 Hz), while resultant ball velocities were monitored using a pair of photocells. Between the three effort levels, kinetic adjustments were clearly identified in both proximal and distal segments with significantly different (large effect sizes) angular impulses due to resultant joint and interaction moments. Also, players tended to hit an off-centre point on the ball using a more medial contact point on the foot and with the foot in a less upright position in lower effort levels. These results suggested that players control their leg swing in a context of a proximal to distal segmental sequential system and add some fine-tuning of the resultant ball velocity by changing the manner of ball impact.     

110m栏攻栏腿最佳下压时机探讨

用文献参阅、录象资料观察和理论分析的方法研究了优秀运动员和普通水平运动员110m栏中蹬地腿和攻栏腿下压时机的配合,并将配合分为三种情况：1.蹬地腿离地瞬间攻栏腿继续上摆;2.蹬地腿离地前攻栏腿开始下压;3.蹬地腿离地的瞬间攻栏腿开始下压。结果表明：蹬地腿离地瞬间攻栏腿继续上摆,拉长了过栏时间,造成压栏过晚;蹬地腿离地前攻栏腿开始下压,造成跳栏,影响了水平速度;蹬地腿离地的瞬间攻栏腿开始下压是最佳的下压时机。希望通过该研究能给跨栏训练者提供一些理论参考。     

增强现实系统中基于神经网络的磁力跟踪器校正

Nonlinear errors always exist in data obtained from tracker in augmented reality （AR）, which badly influence the effect of AR. This paper proposes to rectify the errors using BP neural network. As BP neural network is prone to getting into local extrema and convergence is slow, genetic algorithm is employed to optimize the initial weights and threshold of neural network. This paper discusses how to set the crucial parameters in the algorithm. Experimental results show that the method ensures that the neural network achieves global convergence quickly and correctly. Tracking precision of AR system is improved after the tracker is rectified, and the third dimension of AR system is enhanced.     

综合法快速绘制静定梁的剪力图和弯矩图

剪力图和弯矩图是工程力学中材料力学部分基本计算的重要内容之一,是准确确定梁危险截面的重要手段。综合法绘制剪力图弯矩图与其它方法相比,快速准确,易被学生掌握,值得推广．     

有限元法计算惯性矩及转动惯量

利用有限元法的原理,应用面积坐标和体积坐标的性质,分别计算任意多边形的惯性矩和任意多面体的转动惯量,方法简单,易于编制通用程序,准确性较好。     

近十年来国内多层膜巨磁电阻效应研究

近十年来国内对多层膜巨磁电阻效应的研究主要从金属多层膜、纳米颗粒膜、磁隧道结、氧化物薄膜四个方面展开，侧重研究了多层膜巨磁电阻效应产生的机理、各种膜的结构、影响巨磁电阻大小的因素，同时还引发了多层膜材料在温度大小、磁性(或合金)成份多少和种类、颗粒膜尺寸大小何种情况为最佳的思考。     

圆形载流线圈沿一直径折成直角可看作磁偶极子

从磁偶极子的特点出发，用毕奥一萨伐尔定律、安培力公式和力矩的定义，推导出用磁矩表示的圆形载流线圈沿一直径折成直角的远场及其在均匀磁场中所受的磁力和磁力矩，指出此非平面栽流线圈可看作磁偶极子．     

等离子体共振表面波的分析

研究具有轴向线性密度特性的非均匀圆柱冷等离子体的表面波,得到了碰撞等离子体时纯表面波在横磁模式下的实频率、衰减速率和特征函数,并且考虑了等离子体共振的情况.结果表明,在等离子体共振时的位置处,特征函数有极大值.     

Reducing 0s bias in video moment retrieval with a circular competence-based captioner

The current study addresses the problem of retrieving a specific moment from an untrimmed video by a sentence query. Existing methods have achieved high performance by designing various structures to match visual-text relations. Yet, these methods tend to return an interval starting from 0s, which we named “0s bias”. In this paper, we propose a Circular Co-Teaching (CCT) mechanism using a captioner to improve an existing retrieval model (localizer) from two aspects: biased annotations and easy samples. Correspondingly, CCT contains two processes: (1) Pseudo Query Generation (captioner to localizer), aiming at transferring the knowledge from generated queries to the localizer to balance annotations; (2) Competence-based Curriculum Learning (localizer to captioner), training the captioner in an easy-to-hard fashion guided by localization results, making pairs of the false-positive moment and pseudo query become easy samples for the localizer. Extensive experiments show that our CCT can alleviate “0s bias” with even 4% improvement for existing approaches on average in two public datasets (ActivityNet-Captions, and Charades-STA), in terms of R@1,IoU=0.7. Notably, our method also outperforms baselines in an out-of-distribution scenario. We also quantitatively validate CCT’s ability to cope with “0s bias” by a proposed metric, DM. Our study not only theoretically contributes to detecting “0s bias”, but also provides a highly effective tool for video moment retrieval by alleviating such bias.