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Experimental investigation on weak shock wave mitigation characteristics of flexible polyurethane foam and polyurea

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Defence Technology（防务技术） 2024年第1期31卷 179-191页

作者： Shiyu Jia Cheng Wang Wenlong Xu Dong Ma Fangfang Qi state Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing100081China institute for Advanced Technology Shandong UniversityJinan250061China

In recent years,explosion shock wave has been considered as a signature injury of the current military *** strong shock wave is lethal to the human body,weak shock wave can cause many more lasting *** investigate the protection ability and characteristics of flexible materials and structures under weak shock wave loading,the blast wave produced by TNT explosive is loaded on the polyurethane foam with the density of 200.0 kg/m3(F-200)and 400.0 kg/m3(F-400),polyurea with the density of 1100.0 kg/m^(3)(P-1100)and structures composed of the two materials,which are intended for individual *** results indicate that the shock wave is attenuated to weak pressure disturbance after interacting with the flexible materials which are not *** shock wave protective capability of single-layer materials is dependent on their thickness,density and microscopic *** overpressure,maximum pressure rise rate and impulse of transmitted wave decrease exponentially with increase in sample *** the same thickness,F-400 provides better protective capability than F-200 while P-1100 shows the best protective capability among the three *** this study,as the materials are not destroyed,F-200 with a thickness more than10.0 mm,F-400 with a thickness more than 4.0 mm,and P-1100 with a thickness more than 1.0 mm can attenuate the overpressure amplitude more than 90.0%.Further,multi-layer flexible composites are *** layer layouts of designed structures and layer thickness of the single-layer materials can affect the protective *** the research range,the structure in which polyurea is placed on the impact side shows the optimal shock wave protective performance,and the thicknesses of polyurea and polyurethane foam are 1.0 mm and 4.0 mm *** overpressure attenuation rate reached maximum value of 93.3%and impulse attenuation capacity of this structure are better than those of s

关键词： Free-field explosion Weak shock wave mitigation Polyurea Polyurethane foam Multi-layered composites

Formation behaviors of rod-like reactive shaped charge penetrator and their effects on damage capability

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Defence Technology（防务技术） 2024年第2期32卷 242-253页

作者： Tao Sun Haifu Wang Shipeng Wang Chao Ge Die Hu Pengwan Chen Yuanfeng Zheng Beijing institute of Technology State Key Laboratory of Explosion Science and TechnologyBeijing100081China Xi'an institute of Electromechanical Information Technology Xi'an710065China

Formation behaviors of rod-like reactive shaped charge penetrator(RRSCP)and their effects on damage capability are investigated by experiments and numerical *** pulsed X-ray technology and a spaced aluminum/steel plate with the thicknesses of 5 mm/100 mm are *** types of sphericalsegment aluminum-polytetrafluoroethylene-copper(Al-PTFE-Cu)reactive liners with Cu contents of 0%,46.6%,and 66%are fabricated and *** experimental results show that the reactive liners can form excellent rod-shaped penetrators with tail skirts under the shaped charge effect,but the tail skirts disappear over ***,rupturing damage to the aluminum plate and penetration to the steel plate are caused by the RRSCP *** simulation analysis,the RRSCP is formed by a mechanically and chemically coupled response with the reactive liner activated by shock in its outer walls and bottom and then backward overturning,forming a leading reactive penetrator and a following chemical energy *** unique formation structure determines the damage modes of the aluminum plate and the steel *** analysis indicates that the formation behaviors and damage capability of Al-PTFE-Cu RRSCP strongly depend on Cu *** increasing Cu content,the velocity,activation extent,and reaction extent of Al-PTFE-Cu RRSCP decrease,which contribute to elongation and alleviate the negative effects of chemical reactions on elongation,significantly increasing the length-diameter ratio and thus enhancing the capability of steel plate ***,the lower activation extent and energetic density will weaken the RRSCP's capability of causing rupturing damage to the aluminum plate.

关键词： Reactive materials Al-PTFE composites Reactive liner X-ray Penetration

Receptivity of Mack modes to localized unsteady blowing and suction in a chemical non-equilibrium hypersonic boundary layer

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Acta Mechanica Sinica 2024年第7期40卷 1-18页

作者： Qingjiang Yuan Runjie Song Ming Dong state Key laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China

This paper studies the local receptivity of the Mack-mode instability to localized unsteady blowing and suction(UBS)in a chem-ical non-equilibrium(CNE)hypersonic boundary *** five-species CNE model is employed,and the receptivity efficiency is formulated by use of the residual *** with the results for the calorically perfect gas(CPG)model,we find that the real-gas effect enhances the receptivity efficiency remarkably in the majority of the second-mode frequency band,and the enhancement is mainly attributed to the modification of the base flow due to the CNE effect,which is akin to the cold-wall effect in hypersonic boundary *** with the destabilizing role of the CNE effect on the Mack second mode,it is concluded that the CNE effect would lead to a greater linearly accumulated perturbation amplitude,implying premature of transition to turbulence in a high-enthalpy hypersonic boundary layer subject to localized perturbations.

关键词： Chemical non-equilibrium flow Boundary-layer instability Hypersonic Receptivity Transition to turbulence

Effects of nano-metal oxide additives on ignition and combustion properties of MICs-boron rich fuels

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Defence Technology（防务技术） 2024年第9期39卷 157-167页

作者： Liang Hu Danyang Liu Kun Yang Jianying Lu Chao Shi Jianyu Wang Xinhang Liu Lang Chen state Key Laboratory of Explosion Science and Safety Protection Beijing Institute of TechnologyBeijing100081China

Boron has been considered a promising powdered metal fuel for enhancing composite propellants'energy output due to its high energy ***,the high ignition temperature and low combustion efficiency limit the application of boron powder due to the high boiling point of the boron oxide *** research is ongoing to overcome these shortcomings,and one potential approach is to introduce a small quantity of metal oxide additives to promote the reaction of *** study prepared boron-rich fuels with 10 wt%of eight nano-metal oxide additives by mechanical ball *** effect of metal oxides on the thermo-oxidation,ignition,and combustion properties of boron powder was comprehensively studied by the thermogravimetric analysis(TG),the electrically heated filament setup(T-jump),and the laser-induced combustion *** experiments at 5 K/min found that Bi_(2)O_(3),MoO_(3),TiO_(2),Fe_(2)O_(3),and CuO can promote thermo-oxidation of *** to pure boron,Tonsetcan be reduced from 569℃to a minimum of 449℃(B/Bi_(2)O_(3)).Infrared temperature measurement in T-jump tests showed that when heated by an electric heating wire at rates from 1000 K/s to 25000 K/s,the ignition temperatures of B/Bi_(2)O_(3) are the lowest,even lower than the melting point of boron *** images and SEM for the products further showed that the high heating rate is beneficial to the rapid reaction of boron powder in the single-particle combustion ***(B/Bi_(2)O_(3),B/MoO_(3),and B/CuO)were mixed with the oxidant AP and ignited by laser to study the combustion *** results showed that B/CuO/AP has the largest flame area,the highest BO_(2) characteristic spectral intensity,and the largest burn rate for powder *** combine the advantages of CuO and Bi_(2)O_(3),binary metal oxide(CBO,mass ratio of 3:1)was prepared and the test results showed that CBO can very well improve both ignition and combustion properties of *** B/CBO/AP has the h

关键词： Boron-rich fuel Mechanical ball milling Electrically heated filament Laser-induced combustion

Hemispherical resonator with low subsurface damage machined by small ball-end fine diamond grinding wheel:A novel grinding technique

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Chinese Journal of Aeronautics 2024年第5期37卷 570-585页

作者： Biao QIN Henan LIU Jian CHENG Jinchuan TIAN Jiangang SUN Zihan ZHOU Chuanzhen MA Mingjun CHEN state Key Laboratory of Robotics and System Harbin Institute of TechnologyHarbin 150001China Center for Precision Engineering Harbin Institute of TechnologyHarbin 150001China

As for the ultra-precision grinding of the hemispherical fused silica resonator,due to the hard and brittle nature of fused silica,subsurface damage(SSD)is easily generated,which enormously influences the performance of such ***,ultra-precision grinding experiments are carried out to investigate the surface/subsurface quality of the hemispherical resonator machined by the small ball-end fine diamond grinding *** influence of grinding parameters on the surface roughness(SR)and SSD depth of fused silica samples is then *** experimental results indicate that the SR and SSD depth decreased with the increase of grinding speed and the decrease of feed rate and grinding *** addition,based on the material strain rate and the maximum undeformed chip thickness,the effect of grinding parameters on the subsurface damage mechanism of fused silica samples is ***,a multi-step ultra-precision grinding technique of the hemispherical resonator is proposed based on the interaction influence between grinding depth and feed ***,the hemispherical resonator is processed by the proposed grinding technique,and the SR is improved from 454.328 nm to 110.449 nm while the SSD depth is reduced by 94%from 40μm to 2.379μ*** multi-step grinding technique proposed in this paper can guide the fabrication of the hemispherical resonator.

关键词： Fused silica Ultra-precision grinding Hemispherical resonator Subsurface damage Grinding technique

AP assembled on ultrafine aluminum particle and its application to NEPE propellant

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Defence Technology（防务技术） 2024年第6期36卷 20-29页

作者： Huixin Wang Qiang Li Hui Ren Liangjun Xie Tingting Liu Zhihong Chen state Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China Inner Mongolia institute of Synthetic Chemicals Hohhot 010010China

Coating modification is an important way to enhance the reactivity of aluminum *** this paper,ammonium perchlorate and aluminum powder were assembled into energetic microunits by liquid deposition *** particles with AP as shell and ultrafine aluminum powder as the core(Al@AP)were *** micromorphology results show that the coated particles are about 5μm,and the coating layer is evenly distributed on the outer surface of aluminum powder,indicating a complete *** energetic microunits were implanted into the nitrate ester plasticizing adhesive system(NEPE)as solid phase *** effect of filler on the rheological properties,safety,mechanical properties,thermal reaction and energy properties of the system was analyzed by comparing with the raw aluminum *** test results show that the rheological properties,mechanical properties and pressure index of NEPE containing system Al@AP meets the requirements of solid propellant *** with Al based propellant,the mechanical sensitivity and thermal sensitivity are decreased,the safety is better,and the explosion heat of the propellant is increased by 7.8%.The engine test shows that the specific impulse is increased by 1.2 ***@AP can improve the energy output and safety of NEPE propellant,and has potential application prospects in high-energy propellants.

关键词： Aluminum powder Coating NEPE propellant Energy output Applied research

Emergence of machine language: towards symbolic intelligence with neural networks

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National Science Review 2024年第4期11卷 27-30页

作者： Yuqi Wang Xu-Yao Zhang Cheng-Lin Liu Tieniu Tan Zhaoxiang Zhang state Key Laboratory of Multimodal Artificial Intelligence Systems Institute of AutomationChinese Academy of Sciences

Representation learning is a core issue in artificial intelligence (AI). Currently,there exists a disparity in the choice of representation between humans and machines. Humans rely on discrete language for communicati...

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Flexible resource allocation optimization model considering global K-means load clustering and renewable-energy consumption

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Clean Energy 2024年第5期8卷 129-143页

作者： Jie Jiao Puyu He Yuhong Zhang Jiyuan Zhang Zhuhan Long Hanjing Liu state Grid Sichuan Electric Power Company Economic Research institute ChengduChina

Vigorously developing flexible resources in power systems will be the key to building a new power system and realizing energy *** investment construction cost and operation cost of various flexible resources are different,and the adjustment ability is different in different ***,the optimization of complementary allocation of various resources needs to take into account the economy and adjustment ability of different *** this paper,the global K-means load clustering model is pro-posed and the 365-day net load is reduced to eight typical daily net loads by ***,a two-level optimization model of flexible resource complementary allocation considering wind power and photovoltaic consumption is *** flexible resources involved include the flexible transformation of thermal power,hydropower,pumped storage,energy storage,and demand *** upper-layer model optimizes the capacity allocation of various flexible resources with the minimum investment and construction cost as the goal and the lower layer optimizes the operating output of various units with the minimum operating cost as the *** results of the example analysis show that the flexible capacity of thermal power units has nothing to do with the abandonment rate of renewable *** the abandonment rate of renewable energy decreases,the optimal capacity of pumped storage,electrochemical energy storage,and hydropower units *** the power-abandonment rate of renewable energy is 5%,the optimal allocation capacity of thermal power flexibility transformation,pumped storage,electrochemical energy storage,hydropower unit,and adjustable load in Province A is 5313,17090,5830,72113,and 4250 MW,*** the condition that the renewable-energy abandonment rate is 0,5%,and 10%respectively,the configured capacity of pumped storage is 20000,17090,and 14847 MW,respectively.

关键词： wind power photovoltaic power K-means clustering algorithm flexible resources complementary configuration operation optimization

On a Formation of Singularities of Solutions to Soliton Equations Represented by L,A,B-triples

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Acta Mathematica Sinica,English Series 2024年第1期40卷 406-416页

作者： Iskander A.TAIMANOV Novosibirsk state University 630090 Novosibirskand Sobolev Institute of Mathematics630090 NovosibirskRussia

We discuss the mechanism of formation of singularities of solutions to the Novikov-Veselov,modified Novikov-Veselov,and Davey-Stewartson II(DSII)equations obtained by the Moutard type *** equations admit the L,A,B-triple presentation,the generalization of the L,Apairs for 2+1-soliton *** relate the blow-up of solutions to the non-conservation of the zero level of discrete spectrum of the *** also present a class of exact solutions,of the DSII system,which depend on two functional parameters,and show that all possible singularities of solutions to DSII equation obtained by the Moutard transformation are indeterminancies,i.e.,points when approaching which in different spatial directions the solution has different limits.

关键词： Soliton equation blow up Davey-Stewartson equation Moutard transformation