加性高斯白噪声信道中典型信号的信噪比估计

信噪比是衡量通信质量的重要参数,正确估计出信号的信噪比能为后续信号的研究提供重要信息。现结合多种信噪比估计的方法,在仅需调制方式的先验信息下,对不同种类的调制信号有针对性地进行信噪比估计,能够有效估计6种典型信号。其中包括调幅信号AM和2ASK,调相信号BPSK、QPSK,调频信号MSK、2FSK。仿真实验表明,该法对信噪比在0¹8dB的信号能有效进行估计,估计偏差在0.5dB以内。     

鸭式客机气动布局特性研究

采用CFD技术对鸭翼布局和常规布局飞机进行气动特性估算。利用计算机辅助软件对缩比飞机模型进行流体计算,通过对计算数据的处理,获得两种布局飞机在升力系数、阻力系数、升阻比、俯仰力矩等多个方面的典型气动特征参数,再对这些特征参数进行比对,最终得出两种布局飞机在气动方面的优缺点。     

几种形状规则刚体转动惯量的计算

转动惯量即刚体绕轴转动惯性的度量,是刚体力学中的重要概念。本文从刚体转动的动量矩和转动动能定义出发,推导计算了几种形状规则刚体的转动惯量,推导过程通俗易懂,便于学生理解和掌握,并且有助于学生寻求创新途径去巧解各类刚体的转动惯量。     

预应力混凝土槽形板桩截面优化分析

通过分析高强预应力混凝土板桩截面的抗弯系数的3种不同计算方法,探讨了板桩截面形状、尺寸与抗弯系数之间的关系。与现有的其它类似板桩产品相比,新研发的高强预应力槽形板桩有效提升了截面抗弯系数,提高了混凝土板桩的抗弯弯矩和抗裂弯矩。研究成果将对高性能预应力混凝土板桩优化设计和施工具有指导意义。     

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.     

船体在腐蚀损伤下随时间变化的可靠性分析

分析一种船体腐蚀影响下随时间变化的船体结构可靠性计算方法.通过可靠性函数对船舶于规定运用期限内的不同时段的状况进行计算,并以一艘散货船为例,与传统的方法进行计算和比较,得出较为实时精确的结论.     

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.