Utilizing Iron's Attractive Chemical and Magnetic Properties in Microrocket Design,Extended Motion,and Unique Performance

All‐in‐one material for microrocket propulsion featuring acid‐based bubble generation and magnetic guidance is presented. Electrochemically deposited iron serves as both a propellant, toward highly efficient self‐propulsion in acidic environments, and as a magnetic component enabling complete motion control. The new microrockets display longer lifetime and higher propulsion efficiency compared to previously reported active metal zinc‐based microrockets due to the chemical properties of iron and the unique structure of the microrockets. These iron‐based microrockets also demonstrate unique and attractive cargo towing and autonomous release capabilities. The latter is realized upon loss of the magnetic properties due to acid‐driven iron dissolution. More interestingly, these bubble‐propelled microrockets assemble via magnetic interactions into a variety of complex configurations and train structures, which enrich the behavior of micromachines. Modeling of the magnetic forces during the microrocket assembly and cargo capture confirms these unique experimentally observed assembly and cargo‐towing behaviors. These findings provide a new concept of blending propellant and magnetic components into one, toward simplifying the design and fabrication of artificial micro/nanomachines, realizing new functions and capabilities for a variety of future applications.     

基于改进LSTM的航运物流路径轨迹修复研究

目的 提高航运物流路径轨迹信息的挖掘精度和安全效率。方法 对宁波舟山港条帚门水域窄口航道船舶的类型、数量、长度进行统计分析,对货运船AIS物流路径轨迹异常进行识别与修复。考虑船舶实际航行的环境因素,提出一种新的数据纠偏方法。考虑船舶属性与环境因素,以通航宽度和三自由度运动学的转向能力识别异常数据,然后运用Bi-LSTM法对筛选后航运物流路径进行轨迹修复。结果 所提筛选方法不需要轨迹聚类或建立额外的模型进行判别,筛选数据量占总数量的34.26%,修复后的AIS货船物轨迹数据量在原有基础上提升了115.34%。结论 使用文中方法可以有效纠偏和修复异常航运物流路径轨迹数据,为航运物流轨迹数据挖掘提供一定的基础方法。     

弹体头部形状对穿甲爆破弹穿甲性能影响的仿真

为给某穿甲爆破(Armor Piercing High Explosive, APHE)弹优化设计提供参考,运用ANSYS/LS DYNA对某小口径火炮穿甲爆破弹以不同着角、不同着速侵彻不同厚度均质钢靶板的过程进行仿真,得到弹丸穿靶过程中的速度变化规律以及穿靶后的形态、存速和剩余动能等.仿真结果表明：对弹体头部形状和尺寸进行优化设计可以提高弹丸的穿甲性能,其中将弹体头部改为截锥形,弹丸穿靶后剩余动能提高5.3％;弹体头部形状对弹丸穿甲强度也有影响,其中尖锥形最差,截锥形最优;随着着角的增大,弹丸剩余动能越来越小,当着角达到65°时会出现跳弹现象.     

警用刑事实验室枪弹测速系统设计及实现

针对警用刑事实验室对自制枪发射的弹丸速度测试需求,设计了一种区截光幕传感器测量系统.该系统以光幕靶或天幕靶作为区截光幕,配接数据采集卡和处理软件构建了完整的测速系统.针对获取的弹丸波形数据,经过软件处理得到弹丸穿靶速度,从而判定枪弹的杀伤力.实弹射击试验表明,该系统可以准确可靠地测量直径最小为2mm破片的速度,测试相对误差不超过0.1%,能够满足警用刑事实验室枪弹杀伤效果的检验要求.     

航空货运收益管理动态定价模型

结合国内航空货运的实际情况,应用价格需求弹性系数理论和博弈理论,考虑了货物体积、重量的约束及因定价差异引起的航空公司市场份额的变动,以航空公司利益最大化为目标,建立了在竞争市场环境下多家航空公司货物多级运价动态模型,探讨了模型求解的方法,求出航空货运定价的均衡解。通过数值算例的形式不仅展示了模型在实际操作中应用的流程,而且对比了均衡策略与其他策略,结果表明,均衡策略优于其他策略。     

Impact Dynamics of Supercavitating Projectile with Fluid/Structure Interaction

As supercavitating projectiles move at high speed, the periodic impacts ("tail-slap") on the interior surface of the cavity generally occur due to disturbances. The interactions between the projectile and the water/cavity interface are the sources of structural vibrations, which affect the guidance of the vehicle and undermine the structural reliability. The Fluid/Structure Interaction calculation procedure of the tail-slaps of supercavitating projectile is established, and the dynamic behaviours of the projectile operating in tail-slap conditions with and without considering Fluid/Structure Interaction are obtained and compared. The responses of the projectile riding a reducing cavity are studied, and the effect of Fluid/Structure Interaction is also analyzed. The results show that the angular velocity of projectile increases as the body slowing down, and the amplitude of the elastic displacement response decreases at the beginning and increases when the cavity size is close to the diameter of the tail of projectile. The effect of Fluid/Structure Interaction reduces the amplitudes and frequencies of the impact loads and the vibration responses of the body, and when the speed is higher, the effect is more apparent.     

片梭织机纬纱飞行速度分析

介绍了一种新的纱线速度传感器的使用方法．该传感器可通过滤波纱线上的静电测量纱线速度,借助于该传感器测量图表展示了片梭织机纬纱飞行速度的曲线．同时,探讨了片梭织机上纬纱飞行速度和纱线张力、纱线弹性等之间的关系以及影响片梭飞行的因素．     

基于PCA的神经网络在港口货物吞吐量中的预测

分析选取了可能影响港口货物吞吐量的因素,采用PCA技术提取关键因子,最后以提取的关键因子作为神经网络的神经输入元,分别建立BP神经网络预测模型和GRNN神经网络预测模型。以上海港口为例,对港口货物吞吐量进行预测并对预测结果给予分析。     

Experimental study of perforation and cracking of water-filled aluminum tubes impacted by steel spheres

Water-filled aluminum tubes were subjected to impact by six steel spherical projectiles of different diameters at impact velocities of 40–200 m/s. The effects of the diameter of the steel projectiles and of the material properties of the tubes on cracking and perforation were discussed. Water decreased the wall strength of the aluminum alloy tubes, and the impact velocity at which a steel projectile first passes through the tube wall decreased with increasing diameter of the steel projectile. Using the velocity at which the steel projectile perforates the tube wall, empirical equations of the energies required to perforate the tube wall were derived. Also, the energy balance in the steel projectile during a collision is discussed referring to the pressure history in the filled water and the velocities of the steel projectile before and after collision.