Discussion on the Core Strength Training Method for 100-Meter Event in Track and Field Sports

In track and field sports,the 100-meter race is an extremely intense sport that requires effective training of athletes’core strength.From the perspective of adolescents,in order to enhance core strength,it is necessary to effectively fix the pelvic position in the process of exercise,so that the core stability,balance,and coordination of athletes can be improved.The training process of the 100-meter event is mainly an anaerobic metabolic exercise,it is necessary to ensure that athletes maintain a high level of physical readiness during the exercises and concentrate highly on their core strength,so that they can achieve excellent results.This paper analyzes the core strength training for the 100-meter event in track and field sports,discusses its importance,and puts forward specific training methods,hoping to provide guidelines for relevant researchers.

Common Sports Injuries and Preventive Measures for Athletes—Take The Track and Field Team Athletes in Yushan County as an Example

Taking the common sports injuries and preventive measures of Yushan County middle school track and field athletes as the research object,the sports injuries of Yushan County middle school track and field athletes were investigated and analyzed from the angle,type,location and nature of sports injury.Research on sports injury problems,trying to find the causes of sports injuries in daily training of track and field athletes,and proposed targeted preventive measures based on the specific situation of Yushan County Middle School.The results show that 77.70%of track and field athletes have suffered sports injury and periostitis and ligament/muscle strains are the most common forms of injury,and lower limbs are more prone to sports injuries than upper limbs.

Study on Entertainment Teaching Experiment for Track and Field in Physical Education Major

By utilizing the method of documentation, experimental teaching in contrast, mathematical statistics to experimentally study on entertainment teaching experiment for track and field in physical education major, this paper puts forward that this teaching can not only creat the good teaching environment, effectively improve the teaching quality for track and field in P.E. major, but also effectively promote the process of popularity and socialization of track and field.

Investigation and Research on the Ordinary University High Level Track and Field Sports Teams in Sichuan Province

by using the method of literature, questionnaire and mathematical statistics and comparative analysis and ?research method of sichuan university high level survey of the Track and field team, sichuan university high level Track and field team and the analysis of existing problems and research, in order to sichuan university of high level Track and field teams development to provide the reference.

Apatite Fission Track Thermochronology of Granite from the Xiazhuang Uranium Ore Field,South China:Implications for Exhumation History and Ore Preservation

Xiazhuang uranium ore field,located in the southern part of the Nanling Metallogenic Belt,is considered one of the largest granite-related U regions in South China.In this paper,we contribute new apatite fission track data and thermal history modeling to constrain the exhumation history and evaluate preservation potential of the Xiazhuang Uranium ore field.Nine Triassic outcrop granite samples collected from different locations of Xiazhuang Uranium ore field yield AFT ages ranging from 43 to 24 Ma with similar mean confined fission track lengths ranging from 11.8±2.0 to 12.9±1.9μm and Dpar values between 1.01 and 1.51μm.The robustness time-temperature reconstructions of samples from the hanging wall of Huangpi fault show that the Xiazhuang Uranium ore field experienced a time of monotonous and slow cooling starting from middle Paleocene to middle Miocene(~60-10 Ma),followed by relatively rapid exhumation in the late Miocene(~10-5 Ma)and nearly thermal stability in the Pliocene-Quaternary(~5-0 Ma).The amount of exhumation after U mineralization since the Middle Paleogene was estimated as~4.3±1.8 km according to the integrated thermal history model.Previous studies indicate that the ore-forming ages of U deposits in the Xiazhuang ore field are mainly before Middle Paleocene and the mineralization depths are more than 4.4±1.2 km.Therefore,the exhumation history since middle Paleocene plays important roles in the preservation of the Xiazhuang Uranium ore field.

改进YOLOv7+Bytetrack的小目标检测与追踪

近年来,目标检测技术已经相当成熟,但小目标检测一直是目标检测领域的一大挑战。为了解决这一问题,设计一种名为MFF-YOLOv7的小目标检测算法,该算法旨在提高小目标检测的准确率。设计级联双向特征金字塔KBiFPN,以及联合提出的多级感受野特征聚合模块MFA,来聚合浅层特征并增强特征的信息表达能力。为了解决小目标漏检问题,设计了新的解耦头和新的注意力机制。新的解耦头对小目标的检测能力更强,新的注意力机制可以重点关注感兴趣的小目标区域。引入了一种新的损失函数ECIOU,旨在加快模型的收敛速度。为了验证模型的性能,分别在三个小目标数据集上进行了实验。实验结果表明,MFF-YOLOv7算法提高了检测精度。同时,使用多目标追踪Bytetrack算法在MOT17和VisDrone2019-MOT两个多目标追踪数据集上对新模型进行了验证,进一步证明了其有效性。此外,MFF-YOLOv7算法在动态视频追踪中表现出了良好的性能。

The training process： Planning for strength-power training in track and field. Part 2： Practical and applied aspects

Planning training programs for strength-power track and field athletes require an understanding of both training principles and training theory. The training principles are overload, variation, and specificity. Each of these principles must be incorporated into an appropriate system of training. Conceptually, periodization embraces training principles and offers advantages in planning, allowing for logical integration and manipulation of training variables such as exercise selection, intensification, and volume factors. The adaptation and progress of the athlete is to a large extent directly related to the ability of the coach/athlete to create and carry an efficient and efficacious training process. This ability includes： an understanding of how exercises affect physiological and performance adaptation （i.e., maximum force, rate of force development, power, etc.）, how to optimize transfer of training effect ensuring that training exercises have maximum potential for carryover to performance, and how to implement programs with variations at appropriate levels （macro, meso, and micro） such that fatigue management is enhanced and performance progress is optimized.

The training process： Planning for strength-power training in track and field. Part 1： Theoretical aspects

The process of strength-power training and the subsequent adaptation is a multi-factorial process. These factors range from the genetics and morphological characteristics of the athlete to how a coach selects, orders, and doses exercises and loading patterns. Consequently, adaptation from these training factors may largely relate to the mode of delivery, in other words, programming tactics. There is strong evidence that the manner and phases in which training is presented to the athlete can make a profound difference in performance outcome. This discussion deals primarily with block periodization concepts and associated methods of programming for strength-power training within track and field. 2015 Production and hosting by Elsevier B.V. on behalf of Shanghai University of Sport.

EFFECT OF ENVIRONMENTAL FIELD ON TROPICAL CYCLONE TRACK AFTER LANDFALL FROM EAST CHINA SEA

The past few years have seen work on the maintenance and decaying mechanisms of tropical cyclones （TCs） over land. Statistic study has been on the landfall frequency and location of TCs and their maintenance, decaying, transition, intensification and dissipation for the past 32 years and that （1） the deeper water accumulates on land, the more favorable it would be for the maintenance of low pressures and vast lakes, and the surface of large rivers and large- sized reservoirs can slow down the decaying of TC lows, （2） the descending and intrusion of cold air from mid- and upper- tropospheric and warm advection from lower troposphere are responsible for TCs transition; and （3） after landfall, TCs tend to accelerate towards areas of intense convection to the northwest, etc. Being mainly numerical simulation and diagnostic analyses for cases covering much detail and depth, most of the studies cannot tell anything in common about how TCs maintain and decay over land. There has been little work on the difference of land track of TCs, which travel with the underlying surface changing from sea to land. The energy supply from the tropical ocean is severely reduced or completely cut off on the one hand, rough land surface is both a blocking and frictional force for TCs to dissipate their energy on the other. In fact, landfall TCs can either maintain for only a few hours and cover a distance of less than 100 km or stay active tbr more than 100 hours and go as farther away as a few thousand km inland. Why do they differ so much？ Why do TCs follow routes that differ dramatically when they land at or near the same sites with identical or similar underlying surface？ It is obvious that the environmental field is one of the essential factors for TCs after landfall. The aim of this paper is to discuss the effect of the environmental field on TCs track over land and to know whicch, synoptic systems or factors play key roles in it so as to provide basis for the forecasting of land track of TCs after landfall.

Conditional Random Field Tracking Model Based on a Visual Long Short Term Memory Network

In dense pedestrian tracking,frequent object occlusions and close distances between objects cause difficulty when accurately estimating object trajectories.In this study,a conditional random field tracking model is established by using a visual long short term memory network in the three-dimensional(3D)space and the motion estimations jointly performed on object trajectory segments.Object visual field information is added to the long short term memory network to improve the accuracy of the motion related object pair selection and motion estimation.To address the uncertainty of the length and interval of trajectory segments,a multimode long short term memory network is proposed for the object motion estimation.The tracking performance is evaluated using the PETS2009 dataset.The experimental results show that the proposed method achieves better performance than the tracking methods based on the independent motion estimation.

Surface current field and seasonal variability in the Kuroshio and adjacent regions derived from satellite-tracked drifter data

The muhiyear averaged surface current field and seasonal variability in the Kuroshio and adjacent regions are studied. The data used are trajectories and （1/4） ° latitude by （1/4） ° longitude mean currents derived from 323 Argos drifters deployed by Chinese institutions and world ocean circulation experiment from 1979 to 2003. The results show that the Kuroshio surface path adapts well to the western boundary topography and exhibits six great turnings. The branching occurs frequently near anticyclonic turnings rather than near cyclonic ones. In the Luzon Strait, the surface water intrusion into the South China Sea occurs only in fall and winter. The Kuroshio surface path east of Taiwan, China appears nearly as straight lines in summer, fall, and winter, when anticyclonic eddies coexist on its right side; while the path may cyclonically turning in spring when no eddy exists. The Kuroshio intrusion northeast of Taiwan often occurs in fall and winter, but not in summer. The running direction, width and velocity of the middle segment of the Kuroshio surface currents in the East China Sea vary seasonally. The northward intrusion of the Kuroshio surface water southwest of Kyushu occurs in spring and fall, but not in summer. The northmost position of the Kuroshio surface path southwest of Kyushu occurs in fall, but never goes beyond 31 °N. The northward surface current east of the Ryukyu Islands exists only along Okinawa-Amami Islands from spring to fall. In particular, it appears as an arm of an anti- cyclonic eddy in fall.

Calculation and Analysis for Temperature Field of Tank Track and Wheels

To know the temperature status of track and wheels on tank,the finite element calculation of temperature field was implemented with ANSYS software.The detailed temperature distributions for road wheel,drive wheel,idle wheel and track loop were obtained.The effect of factors,such as tank speed,environment temperature,sun radiant energy,ground deformation resistant and tank load,on the temperature of road wheel was studied.The sensitivity analysis shows that the effect of tank load on the temperature is the most,and the effect of ground deformation resistant is the least.The temperature testing device for road wheel on tank was developed to perform the experiments in real time.The calculated temperatures are in accord well with the experimental values.

Analysis on Thermal Current Field in Powertrain Cabin of Tracked Vehicles With Electric Transmission System Configuration-2

The electric transmission system congfiguration-2 is one of the main electric drives for tracked vehicles. The geometrical model for the power-train cabin is established and the preliminary design for its cooling system is implemented. The mathematic model is established for thermal current field computation, simulation and analysis in the powertrain cabin. The three-dimensional structure of the powertrain cabin is optimized. The validity of the cooling system design is proved. The foundation for optimizing the whole electric transmission system configuration is laid.

Real-time localization for underwater equipment using an extremely low frequency electric field

A new real-time underwater equipment location method adopting an electric field induced by a standard current source is proposed.Our goals were real-time tracking and location of stationary or moving underwater equipment both in shallow and deep seas,under noisy conditions.The main features of this method are as follows:(1)a standard current source on the water surface,which can be towed by a vehicle,consisting of two electrodes,a signal generator,and a GPS unit;(2)measurement of the extremely low frequency(ELF)electric field emitted by the current source,made possible by electric field sensors on the underwater equipment;(3)position of the underwater equipment is estimated in real time based on a progressive update extended Kalman filter(PUEKF),which is carried out using the propagation model of an ELF electric field because the electric field at the position of the underwater equipment and the current source position are known.We verified the accuracy of our method and confirmed real-time location feasibility through numerical,physical scale,and real-time sea experiments.Through numerical experiments,we verified that our method works for underwater equipment location in real-world conditions,and the location error can be less than 0.2 m.Next,real-time location experiments for stationary underwater measuring equipment in water tank were conducted.The result shows that the location error can be less than 0.1 m.We also confirmed real-time location feasibility through the use of offshore experiment.We expect that our method will complement conventional underwater acoustic location methods for underwater equipment in acoustically noisy environments.

A prob of the effect of psychological suggestion in Track and Field Sports

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基于实测数据的高海拔大日温差地区拱上组合梁桥-无砟轨道体系温度场研究

温度作用是影响桥梁-轨道结构服役性能的重要因素之一。为探究高海拔大日温差地区拱上组合梁桥-无砟轨道体系的温度场变化规律,基于某拟建铁路上承式大跨拱桥桥址处的环境温度持续监测数据与卫星反演得到的太阳辐射数据,建立了考虑太阳辐射阴影遮挡效应的拱上组合梁桥-无砟轨道体系温度场模型,重点分析日温度变化规律和竖向温差分布规律,获得了考虑实测气温和太阳辐射逐时变化的全年日温度场;采用广义帕累托分布对竖向温差样本进行了极值分布估计,确定不同超越概率的竖向温差代表值,提出多折线形式的竖向温度梯度模式。研究结果表明,梯度相较于平原地区更为显著,无砟轨道的遮挡效应使得温度梯度分布上移,钢梁外侧腹板在冬季产生局部梯度作用;基于实测数据的温差极值估计方法考虑了环境温度和太阳辐射对结构温度场的随机影响,可为特殊地区桥梁设计阶段温度作用的计算提供参考。

重载列车编组与运行对双线桥动力响应的影响

研究目的:为研究重载列车编组与运行对双线桥梁动力响应的影响,以朔黄重载铁路线上一座32 m预应力混凝土双线简支T梁为研究对象,建立重载列车-轨道-桥梁耦合有限元模型,并通过现场试验验证有限元模型的准确性,研究重载列车通过双线桥梁时的动力响应,分析重载列车不同编组方式、重载列车双线对开运行等因素对双线桥梁动力响应的影响规律。研究结论:(1)动力响应计算结果与实测值吻合较好,表明所建立的重载列车-轨道-桥梁耦合有限元模型的可靠性高;(2)重车编组对桥梁的位移响应和动应变影响最大,对加速度的影响最小;空车编组对桥梁的加速度响应最大;空重混编次之,其中重车在前空车在后的混合编组对空车的位移响应影响较大,可能引起空车脱轨;(3)重车空车双线对开运行下桥梁的动力响应随着车速的提高而增加,与重车单线运行下桥梁的动力响应规律相似;在相同车速下,双线对开运行下桥梁的跨中竖向动力响应峰值均比重车单线运行下略大,而横向动力响应峰值比重车单线运行下小;(4)当重车与空车入桥距离差值为车体长度的整数倍时,桥梁的动力响应峰值与重车空车同时上桥时基本相等;当入桥距离差值为车体长度一半的整数倍时,桥梁的动力响应峰值有所降低;(5)本研究成果可为新建重载铁路双线桥梁的设计提供参考。

基于变前视距离的四轮同步转向农机改进纯跟踪控制

路径跟踪控制是提高自主导航系统控制精度的关键。针对在复杂农田作业环境下转弯时纯跟踪算法跟踪精度不高的问题,本文提出了一种基于改进纯追踪模型的四轮同步转向农机路径跟踪控制算法。建立了基于四轮同步转向农机的运动学模型和纯跟踪模型,在此基础上考虑航向误差得到改进纯跟踪模型,进行RTK定位坐标修正,根据量化误差的评价函数搜索前视区域最优目标点,得到最优前视距离。本文算法能实时确定四轮同步转向农机改进纯跟踪模型中的前视距离,使航向误差和横向误差最小化,实现目标点的自适应优化。仿真结果表明,本文方法转弯时平均绝对横向误差减至0.035 m,平均绝对航向误差减至0.212°;水田实验结果表明,当四轮同步转向农机作业速度为3.6 km/h时,四轮转向农机轨迹跟踪平均绝对横向误差减至0.109 m,平均绝对航向误差减至2.799°,转弯跟踪精度显著提高。

粤北长江铀矿田隆升剥露历史和矿床保存——来自磷灰石裂变径迹热年代学的启示

粤北长江铀矿田是中国南方最重要和最具代表性的花岗岩型铀矿田之一。前人关于长江铀矿田的研究工作主要涉及铀矿成因、成岩成矿时代和铀矿化机制等方面,关于控矿构造研究也集中在矿床形成过程方面(如导矿、运矿和储矿构造),对成矿后矿床的剥露历史和保存研究甚少。本文通过磷灰石裂变径迹测试,恢复了长江铀矿田热演化历史,结果显示晚白垩世末以来表现为单向隆升剥露降温过程,在约63~55 Ma和44~34 Ma存在两次快速隆升过程,约34~5 Ma冷却速率较慢,为构造平静期,5 Ma以来又发生了快速隆升。自75 Ma至今长江铀矿田的隆升剥蚀量为3 km左右。矿田内被NEE向棉花坑断裂和NWW向油洞断裂分割的书楼丘、棉花坑和长排三个矿区隆升剥蚀量差异非常微小,说明棉花坑断裂两侧和油洞断裂两侧在新生代时期没有明显的差异升降,也进一步佐证了棉花坑断裂和油洞断裂的活动性不大。结合控矿构造的发育特点、3.2~5.6 km的成矿深度以及相关的成矿温压条件,表明长江铀矿田深部资源保存良好,深部具有很大的找矿潜力。

应用于无人机全局航迹规划的改进双向RRTs算法

针对无人机复杂环境下的全局航迹规划问题,将人工势场法与双向RRTs(Rapidly-exploring random trees)算法结合,提出一种改进双向RRTs算法。首先,目标偏置策略引导采样点以一定概率顺着目标点生成,同时随机树新节点受到障碍物斥力和目标点引力的合力影响有效避开障碍物生长,提高航迹搜寻效率,其次对随机树的节点扩展考虑了无人机飞行性能约束条件,最后采用3阶贝塞尔函数进一步航迹优化。仿真结果表明:二维和三维复杂环境中改进双向RRTs算法相比传统RRT、双向RRTs算法航迹搜索耗时减少了71.3%、24.7%和41.0%、18.6%,验证了改进算法全局搜索能力的快速性和有效性,能很好的应用于无人机离线全局航迹规划场合。