Machine learning for predicting the outcome of terminal ballistics events

Machine learning(ML) is well suited for the prediction of high-complexity,high-dimensional problems such as those encountered in terminal ballistics.We evaluate the performance of four popular ML-based regression models,extreme gradient boosting(XGBoost),artificial neural network(ANN),support vector regression(SVR),and Gaussian process regression(GP),on two common terminal ballistics’ problems:(a)predicting the V50ballistic limit of monolithic metallic armour impacted by small and medium calibre projectiles and fragments,and(b) predicting the depth to which a projectile will penetrate a target of semi-infinite thickness.To achieve this we utilise two datasets,each consisting of approximately 1000samples,collated from public release sources.We demonstrate that all four model types provide similarly excellent agreement when interpolating within the training data and diverge when extrapolating outside this range.Although extrapolation is not advisable for ML-based regression models,for applications such as lethality/survivability analysis,such capability is required.To circumvent this,we implement expert knowledge and physics-based models via enforced monotonicity,as a Gaussian prior mean,and through a modified loss function.The physics-informed models demonstrate improved performance over both classical physics-based models and the basic ML regression models,providing an ability to accurately fit experimental data when it is available and then revert to the physics-based model when not.The resulting models demonstrate high levels of predictive accuracy over a very wide range of projectile types,target materials and thicknesses,and impact conditions significantly more diverse than that achievable from any existing analytical approach.Compared with numerical analysis tools such as finite element solvers the ML models run orders of magnitude faster.We provide some general guidelines throughout for the development,application,and reporting of ML models in terminal ballistics problems.

A novel approach of jet polishing for interior surface of small-grooved components using three developed setups

It is a challenge to polish the interior surface of an additively manufactured component with complex structures and groove sizes less than 1 mm.Traditional polishing methods are disabled to polish the component,meanwhile keeping the structure intact.To overcome this challenge,small-grooved components made of aluminum alloy with sizes less than 1 mm were fabricated by a custom-made printer.A novel approach to multi-phase jet(MPJ)polishing is proposed,utilizing a self-developed polisher that incorporates solid,liquid,and gas phases.In contrast,abrasive air jet(AAJ)polishing is recommended,employing a customized polisher that combines solid and gas phases.After jet polishing,surface roughness(Sa)on the interior surface of grooves decreases from pristine 8.596μm to 0.701μm and 0.336μm via AAJ polishing and MPJ polishing,respectively,and Sa reduces 92%and 96%,correspondingly.Furthermore,a formula defining the relationship between linear energy density and unit defect volume has been developed.The optimized parameters in additive manufacturing are that linear energy density varies from 0.135 J mm^(-1)to 0.22 J mm^(-1).The unit area defect volume achieved via the optimized parameters decreases to 1/12 of that achieved via non-optimized ones.Computational fluid dynamics simulation results reveal that material is removed by shear stress,and the alumina abrasives experience multiple collisions with the defects on the heat pipe groove,resulting in uniform material removal.This is in good agreement with the experimental results.The novel proposed setups,approach,and findings provide new insights into manufacturing complex-structured components,polishing the small-grooved structure,and keeping it unbroken.

THE INTERIOR TRANSMISSION EIGENVALUE PROBLEM FOR AN ANISOTROPIC MEDIUM BY A PARTIALLY COATED BOUNDARY

We consider the interior transmission eigenvalue problem corresponding to the scattering for an anisotropic medium of the scalar Helmholtz equation in the case where the boundary?Ωis split into two disjoint parts and possesses different transmission conditions.Using the variational method,we obtain the well posedness of the interior transmission problem,which plays an important role in the proof of the discreteness of eigenvalues.Then we achieve the existence of an infinite discrete set of transmission eigenvalues provided that n≡1,where a fourth order differential operator is applied.In the case of n■1,we show the discreteness of the transmission eigenvalues under restrictive assumptions by the analytic Fredholm theory and the T-coercive method.

Simulation of two-dimensional interior ballistics model of solid propellant electrothermal-chem ical launch with discharge rod plasma generator

Instead of the capillary plasma generator(CPG),a discharge rod plasma generator(DRPG)is used in the30 mm electrothermal-chemical(ETC)gun to improve the ignition uniformity of the solid propellant.An axisymmetric two-dimensional interior ballistics model of the solid propellant ETC gun(2D-IB-SPETCG)is presented to describe the process of the ETC launch.Both calculated pressure and projectile muzzle velocity accord well with the experimental results.The feasibility of the 2D-IB-SPETCG model is proved.Depending on the experimental data and initial parameters,detailed distribution of the ballistics parameters can be simulated.With the distribution of pressure and temperature of the gas phase and the propellant,the influence of plasma during the ignition process can be analyzed.Because of the radial flowing plasma,the propellant in the area of the DRPG is ignited within 0.01 ms,while all propellant in the chamber is ignited within 0.09 ms.The radial ignition delay time is much less than the axial delay time.During the ignition process,the radial pressure difference is less than 5 MPa at the place 0.025 m away from the breech.The radial ignition uniformity is proved.The temperature of the gas increases from several thousand K(conventional ignition)to several ten thousand K(plasma ignition).Compare the distribution of the density and temperature of the gas,we know that low density and high temperature gas appears near the exits of the DRPG,while high density and low temperature gas appears at the wall near the breech.The simulation of the 2D-IB-SPETCG model is an effective way to investigate the interior ballistics process of the ETC launch.The 2D-IB-SPETC model can be used for prediction and improvement of experiments.

Mapping the Child’s Grey Interior:Authenticity of Plague Narrative in The Great Plague

The Great Plague:The Diary of Alice Paynton,London 1665-1666 adopts the realistic painting style and direct writing to the painful experience,describes the situation of the Great Plague in London truly from the perspective of children,and breaks people’s cognitive expectation of children’s literature,the construction of children’s Gray inner world is completed behind the true description of the Great Plague in London with the true brushwork,which presents a different world of childlike innocence.Despite the importance of epidemics writing in literature,the child’s diary perspective of them is one of the least developed of Plague Narrative.Only when authenticity and the child’s grey interior are integrated will we reveal a true picture of society as it was.

The Non-Singular Fast Terminal Sliding Mode Control of Interior Permanent Magnet Synchronous Motor Based on Deep Flux Weakening Switching Point Tracking

This paper presents a novel non-singular fast terminal sliding mode control(NFTSMC)based on the deep flux weakening switching point tracking method in order to improve the control performance of permanent interior magnet synchronous motor(IPMSM)drive systems.The mathematical model of flux weakening(FW)control is established,and the deep flux weakening switching point is calculated accurately by analyzing the relationship between the torque curve and voltage decline curve.Next,a second-order NFTSMC is designed for the speed loop controller to ensure that the system converges to the equilibrium state in finite time.Then,an extended sliding mode disturbance observer(ESMDO)is designed to estimate the uncertainty of the system.Finally,compared with both the PI control and sliding mode control(SMC)by simulations and experiments with different working conditions,the method proposed has the merits of accelerating convergence,improving steady-state accuracy,and minimizing the current and torque pulsation.

2023年国外航天领域发展综述

为及时、准确地了解2023年度国外航天领域的发展动向,对国外航天运输领域、弹道导弹领域以及高超声速技术领域的最新发展情况进行了全面梳理,涉及美、俄等各国航天领域的重点型号研发、飞行试验情况以及重大热点事件等,并通过综述分析对2024年国外航天领域的发展进行了展望。

一种双级弹射作动筒对抛分离输出特性研究

为满足武器系统低过载对抛分离功能要求,设计了一种对抛式双级弹射作动筒,基于零维内弹道理论建立了对抛式双级弹射作动筒内弹道模型,对其分离输出特性进行了仿真,并对内弹道模型的准确性进行了试验验证。结果表明,对抛式双级弹射作动筒内弹道模型准确可靠,压强仿真曲线与实测曲线基本吻合,分离输出参数仿真值与实测值基本一致,误差不超过5%。本研究能够为同类型对抛式双级弹射作动筒的设计提供理论指导。

Reform and Practice of Talent Training of Architectural Interior Design Professionals in Higher Vocational Skills Competition: Taking Chongqing Energy Vocational College as an Example

For higher vocational colleges,skills competition is an important indicator of professional personnel training quality.In this paper,the architectural interior design professional skills competition in Chongqing Energy Vocational College is taken as an example,the many years of teaching and competition experience are taken into account,the problems existing in the cultivation of architectural interior design professionals in higher vocational colleges are analyzed,and corresponding solutions are proposed.

Research on the Interior Decoration Characteristics of Peking Union Medical College Phase I Project

Peking Union Medical College was founded in the late Qing Dynasty and the early Republic of China.Since then,society and politics have been rapidly changing,and its architectural aesthetics reflect the idea of advocating the West and inheriting tradition.Through research and actual investigation,this paper summarizes the current status of its building from two aspects,interior decoration art and interior decoration technology,analyzes the interior decoration characteristics of Peking Union Medical College Phase I Project,and records the archives of Peking Union Medical College’s decoration technology.

Ideological and Political Integration Strategies in Interior Design Professional Courses Under the Background of Innovation and Entrepreneurship

Based on the ideological and political requirements of interior design professional courses,exploring the integrated education path of professional plus innovation and entrepreneurship requires first expanding the ideological and political content of professional introductory courses,core courses,and expanded courses.Then,we will reshape the curriculum system based on the principle of connecting professional teaching and ideological and political courses,focusing on the realistic principle of talent needs,striving for student growth,adjusting the course content,optimizing the teaching model,and transforming teaching through in-and out-of-class practice and counterpoint guidance.

Teaching Strategy of Higher Vocational Interior Design Based on “Internet Plus” Thinking

“Internet Plus”thinking has been widely adopted in the teaching of interior design in colleges and universities,and its application has significant implications that cannot be disregarded.“Internet Plus”thinking not only realizes the innovation of interior design teaching but also significantly improves the level and quality of teaching.Through an analysis of the advantages of“Internet Plus”education platform and the current situation of higher vocational interior design teaching,effective strategies for higher vocational interior design teaching based on“Internet Plus”thinking are proposed in this paper in hope that this study will contribute to the efficient development of interior design teaching activities.

基于场所精神的建筑室内空间设计研究

人与场所交互对话方式是近年来设计者研究的主要方向。建筑室内空间作为人们物质和精神生活的场所,传递着一种生活方式的态度。建筑室内空间的场所精神,映射出社会环境与生产方式多维度空间行为体验逻辑价值认同的特定意义。文章结合场所精神的行为体验研究,通过对“人”的需求尊重来诠释建筑室内空间场所设计的“内在精神气质”,强化人与环境互动的双向作用生成,实现场所空间营造内在价值的有效途径。

基于川南建筑特色的会馆室内装饰设计研究——以夕佳山民居为例

以夕佳山民居为代表的川南建筑具有独特的地域特色,其装饰元素往往具有平安吉祥、多福健康等美好寓意,代表着人们对美好生活的向往。对其地域文化和建筑艺术特征进行了分析叙述,将具有地域特色的夕佳山传统民居建筑元素和会馆室内设计相结合,从形、色、材几个方面进行装饰方法探讨。在设计应用中,根据会馆的文化属性,从消费者的实际需求出发,注重不脱离装饰外形所依附的内在文化和内在精神价值,利用新材料新技术作为突破点,以传承和创新两个方向探讨结合的设计策略,在会馆室内设计中传承创新川南地域文化。

杨燕教授从肺论治儿童功能性便秘的临床经验

儿童功能性便秘约占小儿便秘的95%以上,是小儿消化系统的常见病,病程迁延易对儿童的身心健康产生严重影响。文章总结杨燕教授治疗儿童功能性便秘的临床经验。杨燕教授认为便秘的病机主要是大肠的传导功能失常,但与肺脏密切相关。肺与大肠相表里,肺气亏虚或肺气郁闭,宣肃失职,气机不畅,津液疏布失常,肺热移于大肠,肠失濡润,均可导致便秘发生。从肺论治,临证采用塞因塞用之法补气启闭治虚秘,提壶揭盖之法理肺通腑治实秘,同时重视良好的饮食结构及日常护理,临床疗效显著。附验案1则以佐证。

地域文化影响下的乡村民宿室内设计探析

随着社会经济的飞快发展,人们的生活水平越来越高,对待生活的态度也随之转变。在此背景下,具有地域文化特色的休闲度假游备受人们青睐。乡村民宿设计作为展示地域文化的载体,承担着传播地域文化的责任和使命,在其室内设计中表达地域文化则尤为重要。因此,文章以地域文化为切入点,综合考虑乡村民宿室内设计的需求,探究两者之间的关系,不仅能够切实有效地满足游客的体验性需求,提升游客的满意度,又有利于地域文化的传承,同时还可以提高乡村民宿室内设计的文化底蕴。

基于“心肠合治法”论乌梅丸

“心肠合治法”理论起源可追溯至《黄帝内经》,阐释了心与小肠在生理和病理上的相互影响,近年来,研究者多从“颅脑肠脑说”“心与肠道菌群说”“肠道菌群-脑-肠轴”等方面进行研究,证实了“心与小肠相表里”学说的科学性,从而也证明了“心肠合治法”在临床中的可行性、重要性。该文中“心”即心、脑、血脉,包括现代医学中的心血管系统、神经系统等,“肠”即小肠,包括消化系统中的十二指肠、空肠、回肠等。“心肠合治法”是一种很重要但未被重视起来的治疗思路,而乌梅丸即“心肠合治法”的代表方剂,在临床中常被用来治疗心系与肠系病。故该文就“心肠合治法”理论渊源、现代研究机制及其临床运用的研究概况进行探讨,以期从更多角度探究乌梅丸的配伍规律及临床应用。

铝合金三角形波纹夹芯板抗平头弹冲击的损伤特性研究

为研究铝合金三角形波纹夹芯板受到平头弹冲击后的损伤形式与抗冲击性能,利用一级气炮对铝合金三角形波纹夹芯板的两种冲击位置进行冲击试验。根据试验数据,对比分析三角形波纹夹芯板及等面密度单层板的弹道极限速度与耗能,并结合有限元仿真分析夹芯板的动态损伤过程、动态载荷响应及损伤机理。研究结果表明,三角形波纹夹芯板损伤形式为剪切破坏、撕裂破坏与弯曲变形。波纹板的抗冲击性能低于等面密度的单层板,并且波纹板节点位置的抗冲击性能高于基座位置。当弹体冲击速度较低时,波纹板的耗能低于单层板,随着冲击速度增加,波纹板节点位置的耗能高于单层板,基座位置的耗能与单层板相近。此外,波纹板的动态载荷响应与失效机理均受到冲击位置与弹体冲击速度的影响。

芳纶平纹编织复合材料平板弹道冲击特性及损伤分析

为了研究1000D629T/EPMOLD110芳纶平纹编织复合材料平板抗冲击行为及损伤特性,采用真空辅助树脂灌注成型技术(VARI)和树脂传递模塑成型技术(RTM)加工不同厚度的平板试验件,通过空气炮装置进行弹道冲击试验。同时,基于芳纶平纹编织复合材料基础力学性能试验数据,建立经验证的细观代表体积单元(RVE)模型,通过拟合确定宏观模型的材料本构参数;建立芳纶平纹编织复合材料平板弹道冲击宏观有限元模型,结合CT扫描结果进一步分析其弹道极限特性及损伤形貌等。结果表明:芳纶平纹编织复合材料平板在圆柱弹体冲击试验下的失效模式主要为纤维拉伸断裂、纤维脱出、面外剪切与层间分离等;随着平板厚度增加,其弹道极限相应增加,且与VARI工艺相比,采用RTM工艺可将芳纶平纹编织复合材料平板的抗冲击性能提升5%;芳纶平纹编织复合材料平板宏观模型的弹道冲击仿真结果与试验结果吻合较好,弹道极限误差在1%以内。

采用生理响度感知机制的车内噪声声品质预测

现有车内噪声声品质预测的响度计算中没有考虑真实人耳生理解剖结构的传声特性,因此提出了一种基于生理响度感知模型的车内噪声声品质预估方法。首先,采集两款轿车的车内噪声样本,并通过主观评价试验得到车内噪声的主观评价烦恼度。之后,整合中耳集总参数模型与耳蜗传输线模型,构建生理响度模型。然后,以生理响度模型的响度计算值为主要参数,结合尖锐度、粗糙度与车内噪声的主观评价值,通过TabNet模型构建了车辆声品质预测模型。最终,对比分析了所构建声品质模型与基于现有标准响度模型所构建的声品质模型的预测效果。结果表明,采用生理响度模型的声品质预测平均误差百分比仅有4.73%,优于采用Moore响度(6.13%)与Zwicker响度(6.94%)的声品质预测结果。此外,所构建的TabNet声品质预测模型的平均误差百分比也低于基于BP神经网络模型的平均误差百分比(7.60%)。采用生理响度模型的TabNet声品质预测能够提高车内噪声声品质客观评价的准确率。