Flexible Matrix Research Articles

Stabilization Design of Three-Phase LCL-Filtered Grid-Connected Inverter Using IDA-PBC Controller

With the aim of improving the stability of renewable energy system with high permeability in the weak grid, a modified passivity-based control based on interconnection and damping assignment (IDA) is presented for LCL-filtered grid-connected inverters to eliminate the interactive resonances. The object is modeled in the form of port-controller Hamiltonian, including the partial differential of stored energy function. On the premise of ensuring Lyapunov stability, a more flexible interconnection matrix design method is applied to simplify the design process. The closed-loop stability is ensured with the selected Hamiltonian energy function at the desired balanced point. Moreover, a step-by-step design process for damping gains is provided to guarantee stable operation and fast dynamic response under variation of complex grid impedance. With the designed injected damping parameters, considering the effect of delay, it is possible for the real part of the inverter output admittance to be positive within the switching frequency. The performance and robustness of the proposed method for LCL-filtered inverter system are validated via simulated and experimental results under both unbalanced and balanced grid conditions.

Cationic Zr-based metal-organic framework via post-synthetic alkylation for selective adsorption and separation of anionic dyes

Adsorption and separation of toxic organic dyes are of great importance in wastewater treatment and dye recycling. In this work, cationic metal-organic framework MIL-140C–2NMe+ with triangular hydrophobic channels was prepared in which methyl groups were added to the pyridyl sites of the ligand [2,2'-bipyridine]-5,5'-dicarboxylic acid (H2bpydc) via post-synthetic alkylation reaction. MIL-140C–2NMe+ can be used as an efficient adsorbent for the selective adsorption and separation of anionic dyes in the aqueous mixture of cationic/anionic dyes. Specifically, the adsorption capacities of MIL-140C–2NMe+ for anionic methyl orange can reach 310 mg/g in 10 min. With a facile doctor-blading process, we have also polymerized the MIL-140C–2NMe+ nanocrystals and polyvinylidene fluoride (PVDF) polymer to fabricate a flexible and self-supporting mixed matrix membrane (MMM), which can selectively capture and separate the anionic organic dyes from the binary dye mixtures.

Evaluation of flexible multi-claw and multi-channel semi-dry electrodes for evoked electroencephalography recording

Polydimethylsiloxane (PDMS) filled with copper sulphate crystals, TiO2 nanoparticles, and carbon nanotubes (CNTs) were used as flexible matrices to fabricate semi-dry multi-claws and 19-channel electrodes for electroencephalography (EEG) recording. Good adhesion of the flexible Cu-TiO2-CNT@PDMS substrate and internal CNT conductive network together reduce the contact resistance between EEG electrode and the scalp. The scalp-contact impedance of the flexible matrix was < 5 kΩ when coated with conductive gel, whereas the poured semi-dry electrodes were < 20 kΩ in the hair area. The correlation coefficient between the spontaneous EEG signals synchronously collected by commercial Ag/AgCl and the semi-dry electrodes was greater than 99.3%. With these flexible electrodes, the amplitude of the α-rhythm reached 6 μV in the frequency domain, the service life was more than 3 months, and the SNR of the EEG signal reached 8–12 dB in steady-state visual evoked potential. For the 19-channel high-density electrode, the real-time EEG impedance of each channel was < 26.3 kΩ, and the SNR of the EEG at rest was 6.3 dB. The high-density electrode showed the response of α- and β-rhythms in auditory evoked EEG, and the regularity of these two rhythms was extracted from feedback EEG signals of speech and semantic stimuli. The Cu-TiO2-CNT@PDMS matrix and its semi-dry electrodes provide new materials and new processes for the preparation of flexible semi-dry electrodes and offer a new strategy for the preparation of integrated high-density electrodes.

Proportional flexibility-based damage detection for buildings in unknown mass scenarios: The case of severely truncated modal spaces

Modal flexibility-based methods are recognized in the literature as effective methods for detecting damage in structures using vibration measurements. However, the application of such methods with output-only data (as is the case of civil structures tested under ambient excitations) is challenging, because the mass normalization factors required for assembling the modal flexibility matrix cannot be estimated directly from the data. To address this issue, a method for output-only damage detection and localization in building structures that can be applied with minimal or no a-priori information about the structural masses has been proposed in a previous work by the authors. In the method, to estimate the mass distribution and to assemble the proportional flexibility matrices, the modal orthogonality relationships that involve the mode shapes and the structural masses are used to form a system of equations, and through that system of equations, an inverse problem is solved for the estimation of the mass distribution. Reducing the number of available modes, however, reduces the number of available equations, while the number of unknowns (i.e., the number of degrees of freedom) stay the same; hence, the approach cannot be applied when the modal space is severely truncated. This paper proposes a technique for estimating the mass distribution and assembling proportional flexibility matrices from output-only vibration data that overcomes the mentioned limitations and that can be applied for any number of identified modes, including the case in which the modal space is severely truncated. The proposed technique is then integrated into the above-mentioned method for output-only damage detection in building structures, to verify the applicability of the whole procedure when considering the case of severely truncated modal spaces. Numerical simulations and experimental vibration tests were used to demonstrate the validity and effectiveness of the approaches proposed in this paper.

Novel computational mathematical algorithms for structural optimization using graph-theoretical methods

PurposeThe purpose is to reduce round-off errors in numerical simulations. In the numerical simulation, different kinds of errors may be created during analysis. Round-off error is one of the sources of errors. In numerical analysis, sometimes handling numerical errors is challenging. However, by applying appropriate algorithms, these errors are manageable and can be reduced. In this study, five novel topological algorithms were proposed in setting up a structural flexibility matrix, and five different examples were used in applying the proposed algorithms. In doing so round-off errors were reduced remarkably.Design/methodology/approachFive new algorithms were proposed in order to optimize the conditioning of structural matrices. Along with decreasing the size and duration of analyses, minimizing analytical errors is a critical factor in the optimal computer analysis of skeletal structures. Appropriate matrices with a greater number of zeros (sparse), a well structure and a well condition are advantageous for this objective. As a result, a problem of optimization with various goals will be addressed. This study seeks to minimize analytical errors such as rounding errors in skeletal structural flexibility matrixes via the use of more consistent and appropriate mathematical methods. These errors become more pronounced in particular designs with ill-suited flexibility matrixes; structures with varying stiffness are a frequent example of this. Due to the usage of weak elements, the flexibility matrix has a large number of non-diagonal terms, resulting in analytical errors. In numerical analysis, the ill-condition of a matrix may be resolved by moving or substituting rows; this study examined the definition and execution of these modifications prior to creating the flexibility matrix. Simple topological and algebraic features have been mostly utilized in this study to find fundamental cycle bases with particular characteristics. In conclusion, appropriately conditioned flexibility matrices are obtained, and analytical errors are reduced accordingly.Findings(1) Five new algorithms were proposed in order to optimize the conditioning of structural flexibility matrices. (2) A JAVA programming language was written for all five algorithms and a friendly GUI software tool is developed to visualize sub-optimal cycle bases. (3) Topological and algebraic features of the structures were utilized in this study.Research limitations/implicationsThis is a multi-objective optimization problem which means that sparsity and well conditioning of a matrix cannot be optimized simultaneously. In conclusion, well-conditioned flexibility matrices are obtained, and analytical errors are reduced accordingly.Practical implicationsEngineers always finding mathematical modeling of real-world problems and make them as simple as possible. In doing so, lots of errors will be created and these errors could cause the mathematical models useless. Applying decent algorithms could make the mathematical model as precise as possible.Social implicationsErrors in numerical simulations should reduce due to the fact that they are toxic for real-world applications and problems.Originality/valueThis is an original research. This paper proposes five novel topological mathematical algorithms in order to optimize the structural flexibility matrix.

THE LOOP RESULTANT METHOD FOR STATIC STRUCTURAL ANALYSIS

This work deals with the loop resultant method applied to linear static response of statically indeterminate rod-systems. The method uses the representation of this system in the form of a union of statically indeterminate loops. An algorithm for construction the flexibility matrix of the system is proposed. The unknowns of a system are the loop resultants. This method is based on the use of compatibility equations of deformations, the general solution of homogeneous equations of equilibrium is obtained by transposition of the compatibility matrix. The advantages of this method are the number and location of zero blocks and non-zero blocks of the system flexibility matrix depend only on the numbering of loops. Application of this method is considered for analysis of structural frame.

Mixture of non-ionic and organic ionic plastic crystals immobilized in poly(vinylidene fluoride-co-hexafluoropropylene): A flexible gel polymer electrolyte composition for high performance carbon supercapacitors

Flexible and quasi-solid-state gel polymer electrolytes (GPEs) comprising plastic crystals are emerged as new class of materials for the energy storage applications. Here, a novel composition of a flexible matrix of GPEs comprising a mixture of a non-ionic plastic crystal (succinonitrile) and an organic-ionic plastic crystal 1-ethyl-1-methyl-pyrrolidinium bis(trifluoromethyl sulfonyl)imide, immobilized in a polymer poly(vinylidine fluoride-co-hexafluoropropylene) for application in carbon supercapacitors. Different structural, thermal and electrochemical properties including high ionic conductivity (σ ~3.3 × 10−3 S cm−1 at room temperature) and a wide electrochemical stability window (~3.1 V versus Ag) make the GPE films attractive as potential electrolyte for supercapacitors. Effect of addition of Li-salt (lithium bis(trifluoromethanesulfonyl)imide, LiTFSI) in GPE is also studied and found improvement in supercapacitors' performance. Supercapacitors are fabricated using the mixed plastic crystals-based GPE films separated by activated carbon electrodes, optimized via different techniques namely cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge-discharge measurements. The optimized capacitor with GPE containing LiTFSI offers the specific capacitance of ~370.7 F g−1 with specific energy and maximum power density of ~80.5 Wh kg−1 and ~70.6 kW kg−1, respectively. The supercapacitor offers stable cyclic performance for ~10,000 charge-discharge cycles with ~93% of retention and safe performance over a temperature range from −40 to 80 °C.

Effect of Transfer Film on Tribological Properties of Anti-Friction PEI- and PI-Based Composites at Elevated Temperatures.

The structure, mechanical and tribological properties of the PEI- and PI-based composites reinforced with Chopped Carbon Fibers (CCF) and loaded with commercially available micron-sized solid lubricant fillers of various nature (polymeric-PTFE, and crystalline-Gr and MoS2) were studied in the temperature range of 23–180 (240) °C. It was shown that tribological properties of these ternary composites were determined by the regularities of the transfer film (TF) adherence on their wear track surfaces. The patterns of TFs formation depended on the chemical structure of the polymer matrix (stiffness/flexibility) as well as the tribological test temperatures. Loading with PTFE solid lubricant particles, along with the strengthening effect of CCF, facilitated the formation and fixation of the TF on the sliding surfaces of the more compliant PEI-based composite at room temperature. In this case, a very low coefficient of friction (CoF) value of about 0.05 was observed. For the more rigid identically filled PI-based composite, the CoF value was twice as high under the same conditions. At elevated temperatures, rising both CoF levels and oscillation of their values made it difficult to retain the non-polar PTFE transfer film on the sliding surfaces of the PI-based composite. As a result, friction of the ceramic counterpart proceeded over the composite surface without any protecting TF at T ≥ 180 °C. For the sample with the more flexible PEI matrix, the PTFE-containing TF was retained on its sliding surface, providing a low WR level even under CoF rising and oscillating conditions. A similar analysis was carried out for the less efficient crystalline solid lubricant filler MoS2.

Bridge Flexibility Identification through a Reference-Free Substructuring Integration Method Driven by Mode Fitting

Flexibility plays an important role in bridge load-carrying capacity assessment. The flexibility of bridges has been extracted from the measured data of numerical impact testing and in laboratory experiments. Recently, substructuring impact testing has been increasingly investigated and developed because it avoids deploying sensors throughout bridges while obtaining the same results as full-structure testing. However, most substructuring testing methods require overlapping transition areas between the divided substructures, thereby affecting the operability and efficiency of the test. This study proposes a novel substructuring flexibility integration method that uses limited instruments to sequentially test different substructures subdivided from the whole girder bridge structure without requiring the overlapping reference points of adjacent substructures. Using the basis that the structural mode shapes satisfy the orthogonality and mode node theorem, the parameters of each substructure can be efficiently integrated and the entire flexibility matrix can be identified from the sparse flexibility matrices of the substructures. Case studies using experimental data from a cantilever beam and a continuous girder bridge are considered to verify the availability and effectiveness of the proposed method.

Flexible strain sensor based on CNT/TPU composite nanofiber yarn for smart sports bandage

As people pay more attention to physical health, smart textiles with motion detection functions are favored by consumers. Up to now, developing conductive composite yarns with high strain sensing performance that can be directly integrated into fabrics through textile technology is still a challenge. Here, we prepared a highly-stretchable carbon nanotube (CNT)/thermoplastic polyurethane (TPU) composite nanofiber yarn with a breaking elongation of up to 476% by dispersing CNTs uniformly into flexible TPU matrix and multi-needle liquid-bath electrospinning. The parameters about the preparation of the composite solution, electrospinning, and twisting were discussed and analyzed. On this basis, a highly-conductive dip-coating CNT/TPU composite nanofiber yarn (1.02 kΩ/cm) was developed by simply dip-coating CNT ink. The effects of coating methods on strain sensing performance and mechanism were explored according to the twisting structure of the yarn. This yarn-based strain sensor exhibited a high relative resistance change (440%) under 140% strain with satisfactory linearity and repeatability (1250 cycles). Finally, a smart sports bandage with sports auxiliary functions for badminton, basketball, running, and medical monitoring functions for heartbeat, respiration was developed by directly sewing the composite yarn into an elastic self-adhesive bandage. In the future, this yarn will be able to endow ordinary sportswears “intelligence” through simple sewing or embroidery.

Enzyme-Mimetic Molecular Selective Catalysis via Single Zr Atom Catalysis in Chelated Cage Embedded in a Flexible Piezoelectrical Matrix.

The molecularly selective catalysis in enzyme is central to life. However, their functioning mechanism remains elusive. We propose here that the synergistic effects from (i) effective orbital hybridizing and energy gap decreasing via chelating on single Zr atom as the catalytic center, (ii) selective supramolecular encapsulation in the cage, and (iii) piezoelectrical field motivation are able to achieve the enzyme-mimetic molecular selective high performance catalysis. Metal-organic polyhedra (MOPs) are added into a piezoelectrical polymer matrix to achieve the composite structure where ultrasonic treatment motivates redox reactions in the MOP-guest complex. Encapsulated and chelated guest such as Rhodamine B (RhB) is effectively converted with ratios higher than 90 % after 100 min. In comparison, molecules inefficient in either cage encapsulation or chelating with the Zr center can not be converted. This study first proposes a synergistic plot for enzyme-mimetic catalyst realization and is expected to inspire new mentality in efficient catalyst designing.

A Biomimetic Polymer-Based Composite Coating Inhibits Zinc Dendrite Growth for High-Performance Zinc-Ion Batteries.

Because of their low cost, safety, and green nature, aqueous Zn-ion batteries are promising candidates for energy storage. However, the appearance of Zn dendrites, hydrogen evolution reaction (HER), and corrosion limit the development of the aqueous Zn-ion batteries. Here, inspired by fibrous cartilage, a biomimetic poly(vinylidene fluoride) (PVDF)-based composite polymer coating layer, including aramid nanofiber (ANF) and zinc trifluoromethanesulfonate [Zn(CF3SO3)2], called ANFZ, was designed and fabricated. The high ionic conductivity (3.84 mS cm-1) of the flexible PVDF matrix, optimized by Zn(CF3SO3)2, combined with the highly mechanical ANF network can effectively guide the rate of Zn stripping/plating, homogenize the Zn2+ distribution, and suppress the dendrites. In addition, the high Coulombic efficiency is obtained due to the suppression of HER and corrosion by the biomimetic coating layer. Symmetric ANFZ@Zn//ANFZ@Zn can steadily work over 1000 h at 1 mA cm-2 with a high degree of reversibility, which is greater than that of bare Zn//bare Zn. Furthermore, the ANFZ@Zn//MVO batteries show a high specific capacity (400.2 mAh g-1, 0.1 A g-1) and a long cycle life. This work presents a novel method combined with bionics for designing and assembling Zn anodes without dendrites for zinc-ion batteries.

A Wearable System Composed of FBG-Based Soft Sensors for Trunk Compensatory Movements Detection in Post-Stroke Hemiplegic Patients.

In this study, a novel wearable system for the identification of compensatory trunk movements (CTMs) in post-stroke hemiplegic patients is presented. The device is composed of seven soft sensing elements (SSEs) based on fiber Bragg grating (FBG) technology. Each SSE consists of a single FBG encapsulated into a flexible matrix to enhance the sensor’s robustness and improve its compliance with the human body. The FBG’s small size, light weight, multiplexing capability, and biocompatibility make the proposed wearable system suitable for multi-point measurements without any movement restriction. Firstly, its manufacturing process is presented, together with the SSEs’ mechanical characterization to strain. Results of the metrological characterization showed a linear response of each SSE in the operating range. Then, the feasibility assessment of the proposed system is described. In particular, the device’s capability of detecting CTMs was assessed on 10 healthy volunteers and eight hemiplegic patients while performing three tasks which are representative of typical everyday life actions. The wearable system showed good potential in detecting CTMs. This promising result may foster the use of the proposed device on post-stroke patients, aiming at assessing the proper course of the rehabilitation process both in clinical and domestic settings. Moreover, its use may aid in defining tailored strategies to improve post-stoke patients’ motor recovery and quality of life.

A fluid-driven soft robotic fish inspired by fish muscle architecture

Artificial fish-like robots developed to date often focus on the external morphology of fish and have rarely addressed the contribution of the structure and morphology of biological muscle. However, biological studies have proven that fish utilize the contraction of muscle fibers to drive the protective flexible connective tissue to swim. This paper introduces a pneumatic silicone structure prototype inspired by the red muscle system of fish and applies it to the fish-like robot named Flexi-Tuna. The key innovation is to make the fluid-driven units simulate the red muscle fiber bundles of fish and embed them into a flexible tuna-like matrix. The driving units act as muscle fibers to generate active contraction force, and the flexible matrix as connective tissue to generate passive deformation. Applying alternant pressure to the driving units can produce a bending moment, causing the tail to swing. As a result, the structural design of Flexi-Tuna has excellent bearing capacity compared with the traditional cavity-type and keeps the body smooth. On this basis, a general method is proposed for modeling the fish-like robot based on the independent analysis of the active and passive body, providing a foundation for Flexi-Tuna’s size design. Followed by the robot’s static and underwater dynamic tests, we used finite element static analysis and fluid numerical simulation to compare the results. The experimental results showed that the maximum swing angle of the tuna-like robot reached 20°, and the maximum thrust reached 0.185 N at the optimum frequency of 3.5 Hz. In this study, we designed a unique system that matches the functional level of biological muscles. As a result, we realized the application of fluid-driven artificial muscle to bionic fish and expanded new ideas for the structural design of flexible bionic fish.

Flexible multi-walled carbon nanotubes/polyvinylidene fluoride membranous composites with weakly negative permittivity and low frequency dispersion

Flexible composites with negative permittivity have great potentials in flexible electronics and wearable devices. To improve their working performance, it is critical to search for such materials that possess weakly and stable negative permittivity in a wide frequency range. In this work, the polyvinylidene fluoride (PVDF) was selected as the flexible matrix and the modified multi-walled carbon nanotubes (MWCNTs) were used as functional fillers to prepare MWCNTs/PVDF membranous composites with a weakly negative permittivity. When the content of MWCNTs exceeded 13 wt%, the negative permittivity conforming to Drude model appeared. The absolute value of negative permittivity can be as low as approximately 10 in the whole test frequency range, presenting a low frequency dispersive behavior. It demonstrated that the weakly negative permittivity was ascribed to the dilution of electrons in the resulting composites, and the high electron mobility in MWCNTs was responsible for the low frequency dispersion. The MWCNTs/PVDF membranous metacomposites with a twisted and foldable flexibility can contribute to the development of flexible metamaterials and enrich their significant applications.

A new effective mesh stiffness calculation method with accurate contact deformation model for spur and helical gear pairs

This paper proposes a new effective mesh stiffness calculation method for spur and helical gear pairs, which is explicitly formulated by an original FE-analytical slice model for tooth local contact deformation, efficient FE model for gear global deformation and mathematical programming approach for gear contact. The original FE-analytical slice model comprehensively integrates the advantages of FE method, Hertz contact theory and slice approach, which can address the displacement datum and elastic interaction of tooth slices effectively, so that tooth contact deformation is determined accurately. The geometry modeling of tooth slices is established and the pressure configuration in the contact region of each slice is prescribed by Hertz distribution. A specified FE programming is developed to derive the tooth contact flexibility matrix accurately. Thus, the mesh stiffness can be effectively calculated by using the proposed method with the FE-analytical slice model. The local contact deformation of gear tooth and mesh stiffness of gear pairs under ideal and error conditions are simulated. The accuracy and efficiency of the proposed method are validated against the ANSYS benchmark and common existing methods.

Performance evaluation on particle‐reinforced rigid/flexible composites via fused deposition modeling3Dprinting

AbstractThe diversity of filament consumables is the basis for developing of fused deposition modeling (FDM) 3D printing industry. At the same time, the blending of matrix materials and the addition of reinforcing materials are the manufacturing difficulties of this composite 3D printing consumable. In this article, poly(lactic acid) (PLA)/thermoplastic polyurethane (TPU)/organic montmorillonite (OMMT) composites were manufactured to systematically study the characteristics and laws of these composites. Both the rigid matrix PLA and the flexible matrix TPU played advantages in multi‐component composites, while the blended matrix balanced their characteristics. OMMT added with 5% wt not only improved the mechanical and thermal properties of matrix materials but also affected the processability and practicability of composite consumables. The distribution of OMMT particles in the composites was quantitatively analyzed through image processing technology. PLA/TPU/OMMT FDM 3D printed samples as a representative composite system were selected to evaluate the general performance of particle‐reinforced 3D printed composites, and to provide reference for the research and development based on this type of 3D printed products.

Влияние жесткой и пластичной матриц на предельную прочность и механизмы разрушения полимерных композиционных материалов при ударе и в статике

An universal method “Break upon Impact and Static” (RUS) has been developed for the experimental determination of the ultimate strength properties of polymer composite materials based on multifilament nanocrystalline ultra-high molecular weight polyethylene (UHMWPE) fibers, which differs in the method of fixing the sample in a testing machine.The method is carried out using a uniform BIS-sample with an intermediate matrix at the ends and equipment for its attachment to the platforms of testing machines. The sample is a round composite rod composed of the fibers and matrices under investigation, which is held in the tooling by an additional matrix that fixtures it under various loading rates. The RUS method was used to study the properties and mechanisms of destruction upon impact and in a static situation of anisotropic polymer and hybrid composite materials (PCM and HCM) based on flexible and rigid matrices reinforced with hybrid fibers of carbon, aramid, and UHMWPE-fibers activated by non-equilibrium low-temperature plasma. The breaking loads under low-velocity impact and static bending conditions, relative deformation, specific absorbed-in-fracture energy, work of adhesion, shear strength, and other properties are determined. It was found out that the plasticity of the matrix and the hybrid fiber composition affect the properties and fracture mode of PCM and HCM. For the destruction of HCM with a flexible matrix upon impact, a load twice as large as for composites with a rigid matrix is required. HCMs have the highest strength, in which at all stages of loading up to failure, joint deformation of the matrix and the reinforcing fiber occurs. The mechanism of deformation and destruction of anisotropic HCM upon impact is stepwise, while the nature of the deformation curve is zigzag. In statics, the deformation proceeds smoothly. By changing the ratio of carbon and UHMWPE-fibers during hybridization, it is possible to control the properties of HCM and improve its specific properties. The combination of carbon and UHMWPE-fibers in a hybrid fiber for reinforcing a flexible matrix makes it possible to create a material with a delayed fracture. It has been established that for HCM based on a flexible matrix reinforced with a hybrid fiber combining 20 % carbon and 80 % UHMWPE fiber, the fracture load increases by factor 2, the specific fracture work by 42 %, relative deformation by 68 %.

Влияние гибридизации углеродных волокон арамидными и СВМПЭ-волокнами на ударные свойства гибридных углепластиков

The properties and mechanisms of destruction of hybrid composite materials (HCMs) based on flexible and brittle matrices, reinforced with hybrid fibers made of carbon, aramid and ultra-high molecular weight polyethylene (UHMWPE) fibers were investigated by the method of “impact break” (IB) upon low-velosity impact. The composition of the hybrid fiber and the plasticity of the matrix affect the properties and fracture mode of the HCM. It is discovered that the combination of carbon and aramid fibers in a hybrid fiber for reinforcing a flexible matrix (FM) makes it possible to create a material with delayed fracture. It has been shown that upon impact for the destruction of HCM with a flexible matrix, a load twice as large as for specimens with a brittle matrix is required. The highest strength have hybrids, in which, at all stages of loading, up to fracture, there is a joint deformation of the matrix and the reinforcing fiber. The mechanism of deformation and destruction of anisotropic HCMs upon impact has a stepwise character.

Multi-Target Track Initiation in Heavy Clutter

In the heavy clutter environment, the information capacity is large, the relationships among information are complicated, and track initiation often has a high false alarm rate or missing alarm rate. Obviously, it is a difficult task to get a high-quality track initiation in the limited measurement cycles. This paper studies the multi-target track initiation in heavy clutter. At first, a relaxed logic-based clutter filter algorithm is presented. In the algorithm, the raw measurement is filtered by using the relaxed logic method. We not only design a kind of incremental and adaptive filtering gate, but also add the angle extrapolation based on polynomial extrapolation. The algorithm eliminates most of the clutter and obtains the environment with high detection rate and less clutter. Then, we propose a fuzzy sequential Hough transform-based track initiation algorithm. The algorithm establishes a new meshing rule according to system noise to balance the relationship between the grid granularity and the track initiation quality. And a flexible superposition matrix based on fuzzy clustering is constructed, which avoids the transformation error caused by 0–1 voting method in traditional Hough transform. In addition, the algorithm allows the superposition matrixes of nonadjacent cycles to be associated to overcome the shortcoming that the track can’t be initiated in time when the measurements appear in an intermittent way. And a slope verification method is introduced to detect formation-intensive serial tracks. Last, the sliding window method is employed to feedback the track initiation results timely and confirm the track. Simulation results verify that the proposed algorithms can initiate the tracks accurately in heavy clutter.