Efficient Electromagnetic Wave Absorption and Thermal Infrared Stealth in PVTMS@MWCNT Nano‑Aerogel via Abundant Nano‑Sized Cavities and Attenuation Interfaces

Pre-polymerized vinyl trimethoxy silane(PVTMS)@MWCNT nano-aerogel system was constructed via radical polymerization,sol-gel transition and supercritical CO_(2)drying.The fabricated organic-inorganic hybrid PVTMS@MWCNT aerogel structure shows nano-pore size(30-40 nm),high specific surface area(559 m^(2)g^(−1)),high void fraction(91.7%)and enhanced mechanical property:(1)the nano-pore size is beneficial for efficiently blocking thermal conduction and thermal convection via Knudsen effect(beneficial for infrared(IR)stealth);(2)the heterogeneous interface was beneficial for IR reflection(beneficial for IR stealth)and MWCNT polarization loss(beneficial for electromagnetic wave(EMW)attenuation);(3)the high void fraction was beneficial for enhancing thermal insulation(beneficial for IR stealth)and EMW impedance match(beneficial for EMW attenuation).Guided by the above theoretical design strategy,PVTMS@MWCNT nano-aerogel shows superior EMW absorption property(cover all Ku-band)and thermal IR stealth property(ΔT reached 60.7℃).Followed by a facial combination of the above nano-aerogel with graphene film of high electrical conductivity,an extremely high electromagnetic interference shielding material(66.5 dB,2.06 mm thickness)with superior absorption performance of an average absorption-to-reflection(A/R)coefficient ratio of 25.4 and a low reflection bandwidth of 4.1 GHz(A/R ratio more than 10)was experimentally obtained in this work.

Metal–Organic Gel Leading to Customized Magnetic‑Coupling Engineering in Carbon Aerogels for Excellent Radar Stealth and Thermal Insulation Performances

Metal–organic gel(MOG)derived composites are promising multi-functional materials due to their alterable composition,identifiable chemical homogeneity,tunable shape,and porous structure.Herein,stable metal–organic hydrogels are prepared by regulating the complexation effect,solution polarity and curing speed.Meanwhile,collagen peptide is used to facilitate the fabrication of a porous aerogel with excellent physical properties as well as the homogeneous dispersion of magnetic particles during calcination.Subsequently,two kinds of heterometallic magnetic coupling systems are obtained through the application of Kirkendall effect.FeCo/nitrogen-doped carbon(NC)aerogel demonstrates an ultra-strong microwave absorption of−85 dB at an ultra-low loading of 5%.After reducing the time taken by atom shifting,a FeCo/Fe3O4/NC aerogel containing virus-shaped particles is obtained,which achieves an ultra-broad absorption of 7.44 GHz at an ultra-thin thickness of 1.59 mm due to the coupling effect offered by dual-soft-magnetic particles.Furthermore,both aerogels show excellent thermal insulation property,and their outstanding radar stealth performances in J-20 aircraft are confirmed by computer simulation technology.The formation mechanism of MOG is also discussed along with the thermal insulation and electromagnetic wave absorption mechanism of the aerogels,which will enable the development and application of novel and lightweight stealth coatings.

Lightweight Dual‑Functional Segregated Nanocomposite Foams for Integrated Infrared Stealth and Absorption‑Dominant Electromagnetic Interference Shielding

Lightweight infrared stealth and absorption-dominant electromagnetic interference(EMI)shielding materials are highly desirable in areas of aerospace,weapons,military and wearable electronics.Herein,lightweight and high-efficiency dual-functional segregated nanocomposite foams with microcellular structures are developed for integrated infrared stealth and absorption-dominant EMI shielding via the efficient and scalable supercritical CO_(2)(SC-CO_(2))foaming combined with hydrogen bonding assembly and compression molding strategy.The obtained lightweight segregated nanocomposite foams exhibit superior infrared stealth performances benefitting from the synergistic effect of highly effective thermal insulation and low infrared emissivity,and outstanding absorption-dominant EMI shielding performances attributed to the synchronous construction of microcellular structures and segregated structures.Particularly,the segregated nanocomposite foams present a large radiation temperature reduction of 70.2℃ at the object temperature of 100℃,and a significantly improved EM wave absorptivity/reflectivity(A/R)ratio of 2.15 at an ultralow Ti_(3)C_(2)T_(x) content of 1.7 vol%.Moreover,the segregated nanocomposite foams exhibit outstanding working reliability and stability upon dynamic compression cycles.The results demonstrate that the lightweight and high-efficiency dual-functional segregated nanocomposite foams have excellent potentials for infrared stealth and absorption-dominant EMI shielding applications in aerospace,weapons,military and wearable electronics.

MTTSNet:Military time-sensitive targets stealth network via real-time mask generation

The automatic stealth task of military time-sensitive targets plays a crucial role in maintaining national military security and mastering battlefield dynamics in military applications.We propose a novel Military Time-sensitive Targets Stealth Network via Real-time Mask Generation(MTTSNet).According to our knowledge,this is the first technology to automatically remove military targets in real-time from videos.The critical steps of MTTSNet are as follows:First,we designed a real-time mask generation network based on the encoder-decoder framework,combined with the domain expansion structure,to effectively extract mask images.Specifically,the ASPP structure in the encoder could achieve advanced semantic feature fusion.The decoder stacked high-dimensional information with low-dimensional information to obtain an effective mask layer.Subsequently,the domain expansion module guided the adaptive expansion of mask images.Second,a context adversarial generation network based on gated convolution was constructed to achieve background restoration of mask positions in the original image.In addition,our method worked in an end-to-end manner.A particular semantic segmentation dataset for military time-sensitive targets has been constructed,called the Military Time-sensitive Target Masking Dataset(MTMD).The MTMD dataset experiment successfully demonstrated that this method could create a mask that completely occludes the target and that the target could be hidden in real time using this mask.We demonstrated the concealment performance of our proposed method by comparing it to a number of well-known and highly optimized baselines.

Aerodynamic/stealth design of S-duct inlet based on discrete adjoint method

It is a major challenge for the airframe-inlet design of modern combat aircrafts,as the flow and electromagnetic wave propagation in the inlet of stealth aircraft are very complex.In this study,an aerodynamic/stealth optimization design method for an S-duct inlet is proposed.The upwind scheme is introduced to the aerodynamic adjoint equation to resolve the shock wave and flow separation.The multilevel fast multipole algorithm(MLFMA)is utilized for the stealth adjoint equation.A dorsal S-duct inlet of flying wing layout is optimized to improve the aerodynamic and stealth characteristics.Both the aerodynamic and stealth characteristics of the inlet are effectively improved.Finally,the optimization results are analyzed,and it shows that the main contradiction between aerodynamic characteristics and stealth characteristics is the centerline and crosssectional area.The S-duct is smoothed,and the cross-sectional area is increased to improve the aerodynamic characteristics,while it is completely opposite for the stealth design.The radar cross section(RCS)is reduced by phase cancelation for low frequency conditions.The method is suitable for the aerodynamic/stealth design of the aircraft airframe-inlet system.

特异性stealth siRNA抑制小鼠肺成纤维细胞TGF-β_1表达的实验研究

目的设计特异性stealth siRNA并检测其对TGF-β1的抑制作用。方法针对BALB/c小鼠TGF-β1基因组,选择不同位点设计3套siRNA基因序列,并经化学修饰合成3种stealth siRNA,转染体外培养的小鼠肺成纤维细胞,免疫组化法检测其对TGF-β1表达的影响。结果3种stealth siRNA对TGF-β1表达在不同时间有不同程度的抑制作用,以stealth_166效果更为明显;抑制效果与转染时间长短相关,48h后就可检测出明显抑制,72h达到最高峰,96h后开始减弱。结论合成的特异性stealth siRNA可以抑制TGF-β1在小鼠肺成纤维细胞的表达,有望成为防治肺间质纤维化的一种手段。

Stealth siRNA对HBV复制和表达的抑制

目的设计siRNA并检测其对HBV的抑制作用。方法针对HBV基因组设计siRNA基因序列,化学修饰合成3种Stealth siRNA,转染带有HBV的2.2.15细胞,ELISA法检测其对HBV复制和表达的影响。结果3种Stealth siRNA对HBV的复制和表达在不同时间有不同程度的抑制作用。72 h后就可检测出抑制,其中siRNA508效果最显著。结论合成的Stealth siRNA可以抑制HBV的复制和表达,有望成为控制HBV感染的一种手段。

Pharmaceutical Characteristics of Daunorubicin Stealth Liposomes

This report studied on pharmaceutical characteristics of the stealth liposome containing dau-norubicin (DNR). The shape, size, entrapment efficiency and stability of the daunorubicin stealth liposomes (DNRSL) were examined. Visible spectrophotometry and the HPLC method were established for determination of the DNR in the DNRSL. The release of DNR from DNRSL in HBS (pH 7.5) and rat serum at 37 oC were examined. The results showed that the DNRSL had high entrapment efficiency (>85%), small size and slow release.

Investigation into wideband electromagnetic stealth device based on plasma array and radar-absorbing materials

Manipulation of electromagnetic waves is essential to various microwave applications,and absorbing devices composed of low-pressure gas discharge tubes and radar-absorbing materials(RAM)can bring new solutions to broadband electromagnetic stealth.The microwave transmission method is used to measure the physical parameters of the plasma unit.The designed structure exhibits superior absorption performance and radar cross-section(RCS)reduction capability in the 2–18 GHz band,with unique absorption advantage in the S and C frequency bands.It is found that the combination of the plasma and the RAM can significantly broaden the absorption frequency band and improve the absorption performance with excellent synergistic stealth capability.Experimental and simulation results present that broadband,wide-angle,tunable electromagnetic wave absorption and RCS reduction can be achieved by adjusting the spatial layout of the combined plasma layer and the type of RAMs,which creates opportunities for microwave transmission and selective stealth of equipment.Therefore,the wave manipulation by combined plasma array and RAM provides a valuable reference for developing numerous applications,including radar antenna stealth,spatial filter,and high power microwave shielding.

利用MAK Stealth进行视景仿真开发方法的研究

为了解决分布式仿真的可视化需求,提出了利用MAK Stealth进行视景仿真开发的方法。MAK Stealth以其具有完备的开发接口和良好的可扩展性,使得用户能方便的将其嵌入到自己的应用开发中。根据视景仿真系统的组成,结合MAKStealth进行视景仿真的开发方法,针对联邦通信和视景驱动控制分析了MAK Stealth的应用开发接口API,依照MAK Stealth的开发流程,实现了三维视景显示系统。系统运行结果表明了利用MAK Stealth进行视景仿真开发是十分方便快捷的。

Ni Flower/MXene-Melamine Foam Derived 3D Magnetic/Conductive Networks for Ultra-Efficient Microwave Absorption and Infrared Stealth

The development of multifunctional and efficient electromagnetic wave absorbing materials is a challenging research hotspot.Here,the magnetized Ni flower/MXene hybrids are successfully assembled on the surface of melamine foam(MF)through electrostatic self-assembly and dip-coating adsorption process,realizing the integration of microwave absorption,infrared stealth,and flame retardant.Remarkably,the Ni/MXene-MF achieves a minimum reflection loss(RLmin)of−62.7 dB with a corresponding effective absorption bandwidth(EAB)of 6.24 GHz at 2 mm and an EAB of 6.88 GHz at 1.8 mm.Strong electromagnetic wave absorption is attributed to the three-dimensional magnetic/conductive networks,which provided excellent impedance matching,dielectric loss,magnetic loss,interface polarization,and multiple attenuations.In addition,the Ni/MXene-MF endows low density,excellent heat insulation,infrared stealth,and flame-retardant functions.This work provided a new development strategy for the design of multifunctional and efficient electromagnetic wave absorbing materials.

Security information factor based airborne radar RF stealth

Radar radio frequency （RF） stealth is very important in electronic war （EW）, and waveform design and selection. Existing evaluation rules of radar RF stealth include too many parameters of radar and interceptors, such as Schleher interception factor, which makes it difficult to evaluate radar RF stealth technologies if interceptor parameters are unknown. In communication, security capacity has been presented to describe the possible ability to communicate in complete security. Since the essential of the secu- rity capacity is to have the interceptor get none valued information from the emitter, this paper is proposed to study security infor- mation factors taking advantage of mutual information to evaluate radar RF stealth under some conditions. Through analyzing mutual information obtained by the radar and the interceptor, this paper defines the security information factor with and without cooperative jamming. Furthermore, this paper deduces the ratio of the match filter to the match incoherent filter and discuss mutual information received by the interceptor. Numerical simulations illustrate radar RF stealth effects based on the security information factor concept under different conditions.

Ultrabroad Microwave Absorption Ability and Infrared Stealth Property of Nano-Micro CuS@rGO Lightweight Aerogels

Developing ultrabroad radar-infrared compatible stealth materials has turned into a research hotspot,which is still a problem to be solved.Herein,the copper sulfide wrapped by reduced graphene oxide to obtain three-dimensional(3D)porous network composite aerogels(CuS@rGO)were synthesized via thermal reduction ways(hydrothermal,ascorbic acid reduction)and freeze-drying strategy.It was discovered that the phase components(rGO and CuS phases)and micro/nano structure(microporous and nanosheet)were well-modified by modulating the additive amounts of CuS and changing the reduction ways,which resulted in the variation of the pore structure,defects,complex permittivity,microwave absorption,radar cross section(RCS)reduction value and infrared(IR)emissivity.Notably,the obtained CuS@rGO aerogels with a single dielectric loss type can achieve an ultrabroad bandwidth of 8.44 GHz at 2.8 mm with the low filler content of 6 wt%by a hydrothermal method.Besides,the composite aerogel via the ascorbic acid reduction realizes the minimum reflection loss(RL_(min))of−60.3 dB with the lower filler content of 2 wt%.The RCS reduction value can reach 53.3 dB m^(2),which effectively reduces the probability of the target being detected by the radar detector.Furthermore,the laminated porous architecture and multicomponent endowed composite aerogels with thermal insulation and IR stealth versatility.Thus,this work offers a facile method to design and develop porous rGO-based composite aerogel absorbers with radar-IR compatible stealth.

Design of synthetic aperture radar low-intercept radio frequency stealth

Not confined to a certain point,such as waveform,this paper systematically studies the low-intercept radio frequency(RF)stealth design of synthetic aperture radar(SAR)from the system level.The study is carried out from two levels.In the first level,the maximum low-intercept range equation of the conventional SAR system is deduced firstly,and then the maximum low-intercept range equation of the multiple-input multiple-output SAR system is deduced.In the second level,the waveform design and imaging method of the low-intercept RF SAR system are given and verified by simulation.Finally,the main technical characteristics of the lowintercept RF stealth SAR system are given to guide the design of low-intercept RF stealth SAR system.

Numerical Optimization on Aerodynamic/Stealth Characteristics of Airfoil Based on CFD/CEM Coupling Method

Based on computational fluid dynamics （CFD）/computational eleetromagnetics method （CEM） coupling method and surrogate model optimization techniques, an integration design method about aerodynamic/stealth characteristics of airfoil is established. The O-type body-fitted and orthogonal grid around airfoil is first generated by using the Poisson equations, in which the points per wave and the normal range satisfy the aerodynamic and electromagnetic calculation accuracy requirement. Then the aerodynamic performance of airfoil is calculated by sol- ving the Navier-Stokes （N-S） equations with Baldwin-Lomax （B-L） turbulence model. The stealth characteristics of airfoil are simulated by using finite volume time domain （FVTD） method based on the Maxwell＇s equations, Steger-Warming flux splitting and the third-order MUSCL scheme. In addition, based upon the surrogate model optimization technique with full factorial design （FFD） and radial basis function （RBF）, an integration design about aerodynamic/stealth characteristics of rotor airfoil is conducted by employing the CFD/CEM coupling meth- od. The aerodynamic/stealth characteristics of NACA series airfoils with different maximum thickness and camber combinations are discussed. Finally, by choosing suitable lift-to-drag ratio and radar cross section （RCS） ampli- tudes of rotor airfoil in four important scattering regions as the objective function and constraint, the compromised airfoil with high lift-to-drag ratio and low scattering characteristics is designed via systemic and comprehensive ana- lyses.

Inhibitory effect of humanized anti-VEGFR-2 ScFv-As_2O_3-stealth nanoparticles conjugate on growth of human hepatocellular carcinoma:in vitro and in vivo studies

Objective:To investigate the inhibitory effect of humanized anti-VEGFR-2 ScFv-As2O3-stealth nanoparticles conjugate on growth of human hepatocellular carcinoma both in vitro and in vivo,which may be a potential agents with sensitivity and targeting ability for human hepatocellular cancer.Methods:Humanized anli-VECFR-2 ScFv-As2O3-stealth nanoparticles conjugate was previously constructed using ribosome display technology and antibody conjugate technology.In this combined in vitro and in vivo study,the inhibitory effects of anti-VEGFR-2 ScFv-As2O3-stealth nanoparticles conjugate on tumor growth,invasion,and metastasis was observed with human liver carcinoma cell line Bel7402 and normal cell L02 by MTT assay,Tanswell assay,Hochest33258 staining,and DNA ladder analysis.The anticancer activity and distribution of anti-VEGFR-2 ScFv-As2O3-stealth nanoparticles was then verified in a mouse model of Bel7402xenografts.Results:Anti-VEGFR-2 ScFv-As2O3-stealth nanoparticles significantly inhibited the proliferation of Bel7402 in the 3-(4,5-dimethylthiazol-2-yh-2,5-diphenyltetrazolium bromide assay while had almost no effects on L02 cells.And the apoptosis inducing effects were proved by Hochest33258 staining and DNA ladder analysis.Transwell assay found that the drug also inhibited the metastasis ability of tumor cells.Furthermore,anti-VEGFR-2 ScFv-As^-stealth nanoparticles significantly delayed the growth of Bel7402 xenografts after administration（92.9%）,followed by As2O3-stealth nanoparticles,anti-VEGFR-2 ScFv,and As203（61.4%,58.8%,20.5%,P【0.05）.The concentration of As2O3 in anti-VEGFR-2 ScFv-As2O3-steallh nanoparticles group was more selectively.Conclusions:Anti-VEGFR-2 ScFv-As2O3-stealth nanoparticles is a potent and selective anti-hepatocellular carcinoma agent which could inhibit the growth of liver cancer as a targeting agent both in vitro and in vivo and also significantly inhibit angiogenesis.

Laser stealth absorbent of samarium oxysulfide prepared by flux method

A novel 1064 tun laser stealth absorbent of SmzO2S was prepared by flux method. The effects of different calcining temperatures and fluxes on the reflective property of Sm2O2S were investigated. The phase composition, morphology, and reflectivity of the powders were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and ultraviolet-visible spectrophotometer （UVPC）. The results showed that pure phase of Sm202S could be obtained with Na2CO3 as flux above 950~C, and the reflectivity decreased with the calcination temperature increasing. Compared with other samarium compounds, the reflectivity at 1064 nm of Sm2O2S was the lowest. Different fluxes had great impact on the phase composition, particle morphology, and reflectivity of the products. In short, Sm2O2S was suitable as a kind of absorbent against 1064 nm laser.

A thin radar-infrared stealth-compatible structure:Design,fabrication,and characterization

A thin radar-infrared stealth-compatible structure with reflectivity below -10 dB in the whole radar X wave band and infrared emissivity less than 0.3 in the infrared region of 8μm-14 μm is reported. The designed stealth-compatible structure consists of metallic frequency selective surface （MFSS）, resistive frequency selective surface （RFSS）, and metal backing from the top down, and it is only 2. l-mm thick. The MFSS is made up of some divided low infrared emissivity metal copper films, and the RFSS consists of a capacitive array of square resistive patches. They are placed close together, working as an admittance sheet because of a mutual influence between them, and the equivalent admittance sheet greatly reduces the thickness of the whole structure. The proposed stealth-compatible structure is verified both by simulations and by experimental results. These results indicate that our proposed stealth-compatible structure has potential applications in stealth fields.

Bayesian-MCMC-based parameter estimation of stealth aircraft RCS models

When modeling a stealth aircraft with low RCS（Radar Cross Section）, conventional parameter estimation methods may cause a deviation from the actual distribution, owing to the fact that the characteristic parameters are estimated via directly calculating the statistics of RCS. The Bayesian–Markov Chain Monte Carlo（Bayesian-MCMC） method is introduced herein to estimate the parameters so as to improve the fitting accuracies of fluctuation models. The parameter estimations of the lognormal and the Legendre polynomial models are reformulated in the Bayesian framework. The MCMC algorithm is then adopted to calculate the parameter estimates. Numerical results show that the distribution curves obtained by the proposed method exhibit improved consistence with the actual ones, compared with those fitted by the conventional method. The fitting accuracy could be improved by no less than 25% for both fluctuation models, which implies that the Bayesian-MCMC method might be a good candidate among the optimal parameter estimation methods for stealth aircraft RCS models.

Research on Stealth Assistant Decision System of Submarine Voyage Stage

Stealth security has always been considered as an important guarantee for the vitality and combat effectiveness of submarines.In accordance with the stealth requirements of submarines performing stealth voyage tasks,this paper proposes a stealth assistant decision system.Firstly,the submarine stealth posture is acquired.A fuzzy neural network inference engine based on improved simplified particle swarm optimization is designed.The auxiliary decision-making scheme for state control and maneuver avoidance of submarine and its equipment is automatically generated.Secondly,the simulation and deduction of the assistant decision-making scheme are realized by the calculation modules of sound source level,propagation loss,and stealth situation.The assistant decision-making scheme and simulation result provide decision support for the commander.Thirdly,the simulation experiment platform of the submarine stealth assistant decision system is constructed.The submarine stealth assistant decision system described in this paper can quickly and efficiently produce assistant decision-making schemes,including submarine and equipment control and maneuver avoidance.The scheme is in line with the combat experience and the results of the pre-model simulation experiments,whereas the simulation deduction evaluates the rationality and effectiveness of the selected scheme.The submarine stealth assistant decision system can adapt to a complex battlefield environment in addition to rapidly and accurately providing assistance in decision-making.