Special Array Research Articles

Reduced-dimension STAP method for conformal array based on sequential convex programming

Compared with the uniform arrays, the conformal array can effectively reduce the radar cross section and improve the utilization of the limited space in the aircraft. However, the special array structure aggravates the non-stationarity of the clutter, and the typical blocking matrix construction method in the space–time adaptive processing (STAP) is not appropriate any more. To address these issues, a reduced dimension STAP algorithm based on penalty sequential convex programming in the generalized sidelobe cancellation structure is proposed. The blocking matrix, channel selection vector and STAP weights can be optimized simultaneously in the algorithm framework. To tackle the resultant nonconvex problem, we formulate the original optimization function as a quasi-convex form and solve these parameters alternately within an iterative framework. Numerical simulations are provided to validate the proposed method and demonstrate its high performance.

A simple approach to design fabric with flame-retardant and pattern function

The study of fabrics’ flame retardant properties has always been a hot topic in the field of textiles. In this paper, a flame-retardant fabric with a sandwich structure was obtained by combining hydrogel patch method and in-situ polymerization technology via a two-step method. The thermogravimetric analysis (TGA) showed that the hydrogel could improve PLA materials’ thermal stability effectively. The hydrogel treated fabrics’ limiting oxygen index (LOI) value increased from 21.05 % to 80.00 %. The cone calorimeter test demonstrated that the pHRR and THR of the hydrogel treated fabrics decreased to 51.48 % and 55.97 %, respectively. After adding a mixture of ferric oxide and mica during the in-situ polymerization of the hydrogel, the pHRR and THR of the obtained fabric decreased to 43.77 % and 46.00 %, respectively, compared to the original PLA fabric. Furthermore, the mechanical strength test showed that the introduction of hydrogel patch had almost no effect on the mechanical properties of PLA materials. In addition, by using the way that metal ions can be arranged into a special array on the magnetic induction line, under the synergistic effect between ferric oxide and mica, the array formed by the ferric oxide particles on the magnetic induction line was designed with a series of patterns on its surface. Finally, a kind of textile with flame retardant properties and different patterns was obtained.

Neutronic simulation of Traveling Wave Reactor (TWR) core in multi-cycles using Monte Carlo method

Abstract An ingenious design, Traveling Wave Reactor (TWR) has been suggested for full exploitation of uranium resources in next generation of nuclear reactors. This design involves the slow propagation of a nuclear fission wave through a long initially subcritical core and the transmutation of nuclear fuel. It has been widely proven that the initiation and propagation of fission waves are feasible prompting the Terra Power Company to conduct preliminary commercialization studies on this project. In equilibrium state, the shapes of the neutron flux, nuclide densities and power density distribution remain constant but the burning region moves in axial (or radial) directions. In this case the in situ fissile material production and consumption drives the operation. Only natural or depleted uranium is required for fresh fuel region. However, in equilibrium state, the burning region contains a spectrum of fission products as well as higher actinides whose are not easily available for initial TWR core construction. One solution is based on the use of enriched uranium in the first cycle to ignite the fission wave and then employment of the composition in subsequent cycles up to the equilibrium state. The main objective of this work is the feasibility study of forming a fission wave as well as the neutronic analysis of a Gas-Cooled Traveling Wave Reactor in various cycles up to the equilibrium one. The MCNP Monte Carlo code was utilized for the analysis of criticality and burn-up calculation. In each cycle, the axial fresh fuel loading and spent fuel discharge, were subjected to analysis. Results showed that the equilibrium state can be obtained by using special arrays of absorbers, from the third cycle where the shape of neutron flux and the power density distribution in axial direction remain unchanged.

New Series of D-efficient Covariate Designs under BIBD set-up

In the present study, an effort has been made to construct D-efficient covariate designs in BIB design (v, b, r, k and λ) set-up when either one of k and r is odd or both k and r are odd numbers and Hadamard matrix of order k i.e., Hk does not exist. For all the developed D-efficient designs, the covariates are mutually orthogonal to each other. The methods of construction of D-efficient covariate designs are developed with the help of a new matrix viz., Special Array (Das et. al., 2020). In this article, the series of developed D-efficient covariate designs are not available in the existing literature. International Journal of Statistical Sciences, Vol.24(1), March, 2024, pp 15-30

On Some Properties of Bihyperbolic Numbers of The Lucas Type

To date, many authors in the literature have worked on special arrays in various computational systems. In this article, Lucas type bihyperbolic numbers were defined and their algebraic properties were examined. Bihyperbolic Lucas numbers were studied by Azak in 2021. Therefore, we only examined bihyperbolic Jacobsthal-Lucas and Pell-Lucas numbers. We also gave properties of bihyperbolic Jacobstal-Lucas and bihyperbolic Pell-Lucas numbers such as recursion relation, derivation function, Binet formula, D'Ocagne identity, Cassini identity and Catalan identity.

Fabrication of wear-resistant and superhydrophobic aluminum alloy surface by laser-chemical hybrid methods

To achieve rapid, efficient, and low-cost preparation of large-scale stable aluminum alloy superhydrophobic surfaces, a new preparation method is proposed. The outer surface of the array micro-protrusions was coated with a layer of armor, which was the molten spatter produced during picosecond laser processing. The molten sputters and micro-protrusions combined to form micro–nano composite multi-layer structures. Through these special array micro–nano composite multi-layer structures and chemical modification, the wear-resistant and superhydrophobic properties of aluminum alloy surfaces were realized. According to test results, the array micro–nano composite structures prepared by picosecond laser and chemical modification had a water drop contact angle of 154.6° and a water drop rolling angle of 2°, exhibiting excellent superhydrophobic and anti-adhesion properties. Its self-cleaning, corrosion resistance and friction and wear behavior were systematically analyzed. The analysis results showed that the rolling droplets on the prepared surface could easily take away contaminants. The corrosion voltage and corrosion current density of the prepared superhydrophobic surface are significantly lower than that of the raw surface. In addition, a water drop contact angle of the aluminum alloy sample maintained at 145.1° after five wear tests, indicating the prepared surface after wear testing still had hydrophobic performance. The innovative method proposed in this study provides a simple and effective method for preparing large-scale wear-resistant superhydrophobic surface of aluminum alloy.

Encryption Methods and Algorithms Based on Domestic Standards in Open-Source Operating Systems

The paper describes the principles and methods underlying the creation of an application in secure operating systems, which provides reliable data encryption. The research aims to analyze and indicate the specifics of encryption methods and algorithms based on domestic standards in open-source operating systems. Cryptanalysis was used in the article, as this avoids vulnerabilities identified in previously created implementations. In the article, the authors draw attention to the fact that 7-Zip uses CBC encryption (concatenation of encrypted text blocks), but the Counter Mode is supported. The same support was provided in the encrypt implementation. Since the key expansion function initially fills the special array created by p7zip with round keys using a unique property of the domestic standard, only one round encryption function was created (performed both during encryption and decryption). This method is also used in various modes. In many cases, initialization time deviations depending on the selected mode are insignificant. The created cryptographic module was tested to meet the domestic standard, which contains several test cases. It was confirmed during the tests that the created module implements the algorithm of the domestic standard. The article shows a way to implement a fairly convenient graphical interface for accessing the cryptographic module, which enables the user not to call the command line and remember the sequence and types of parameters passed to p7zip. This implementation also takes into account the verification of the correctness of decryption and the reading of other error codes.

A Novel Baseline-Free Method for Damage Localization Using Guided Waves Based on Hyperbola Imaging Algorithm.

Most imaging methods based on ultrasonic Lamb waves in structural health monitoring requires reference signals, recorded in the intact state. This paper focuses on a novel baseline-free method for damage localization using Lamb waves based on a hyperbolic algorithm. This method employs a special array with a relatively small number of transducers and only one branch of the hyperbola. The novel symmetrical array was arranged on plate structures to eliminate the direct waves. The time difference between the received signals at symmetrical sensors was obtained from the damage-scattered waves. The sequence of time difference for constructing the hyperbolic trajectory was calculated by the cross-correlation method. Numerical simulation and experimental measurements were implemented on an aluminum plate with a through-thickness hole in the current state. The imaging results show that both the damages outside and inside the diamond-shaped arrays can be localized, and the positioning error reaches the maximum for the diamond-shaped array with the minimum size. The results indicate that the position of the through-hole in the aluminum plate can be identified and localized by the proposed baseline-free method.

Top-k Self-Adaptive Contrast Sequential Pattern Mining.

For sequence classification, an important issue is to find discriminative features, where sequential pattern mining (SPM) is often used to find frequent patterns from sequences as features. To improve classification accuracy and pattern interpretability, contrast pattern mining emerges to discover patterns with high-contrast rates between different categories. To date, existing contrast SPM methods face many challenges, including excessive parameter selection and inefficient occurrences counting. To tackle these issues, this article proposes a top- k self-adaptive contrast SPM, which adaptively adjusts the gap constraints to find top- k self-adaptive contrast patterns (SCPs) from positive and negative sequences. One of the key tasks of the mining problem is to calculate the support (the number of occurrences) of a pattern in each sequence. To support efficient counting, we store all occurrences of a pattern in a special array in a Nettree, an extended tree structure with multiple roots and multiple parents. We employ the array to calculate the occurrences of all its superpatterns with one-way scanning to avoid redundant calculation. Meanwhile, because the contrast SPM problem does not satisfy the Apriori property, we propose Zero and Less strategies to prune candidate patterns and a Contrast-first mining strategy to select patterns with the highest contrast rate as the prefix subpattern and calculate the contrast rate of all its superpatterns. Experiments validate the efficiency of the proposed algorithm and show that contrast patterns significantly outperform frequent patterns for sequence classification. The algorithms and datasets can be downloaded from https://github.com/wuc567/Pattern-Mining/tree/master/SCP-Miner.

Collaborative Direction of Arrival estimation by using Alternating Direction Method of Multipliers in distributed sensor array networks employing Sparse Bayesian Learning framework

In this paper, we present a new method for Direction of Arrival (DoA) estimation in distributed sensor array networks by using Alternating Direction Method of Multipliers (ADMM) in Sparse Bayesian Learning (SBL) framework. Our proposed method, CDoAE, has certain advantages compared to previous distributed DoA estimation methods. It does not require any special array geometry and there is no need for inter-array frequency and phase matching. CDoAE uses the distributed ADMM to update the parameter set extracted by the SBL frameworks in the local arrays to minimize a common objective function. This update process is implemented in the master-node and the result is distributed back to the slave nodes. It is shown that the performance of the local arrays can be improved significantly in this distributed DOA estimation framework. Moreover, we present a method, CDoAE-TVR, to reduce the number of parameters transmitted from the local arrays to the master array which is important for the networks with limited bandwidth and energy. Several simulations have been performed including the cases with coherent sources. It is shown that the use of ADMM in a distributed fashion improves the SBL output efficiently and effectively. In addition, proposed CDoAE-TVR method reduces the transmitted parameters in the network with a small sacrifice on the DoA estimation performance.

Self-powered photodetectors with a position-controlled array based on ZnO nanoclusters.

A self-powered ultraviolet (UV) photodetector (PD) with a position-controlled array based on zinc oxide (ZnO) nanoclusters (NCs) has been proposed. The structure of the special array makes it possible to reduce the light loss and improve the light trap. The PD innovatively modifies the structure of ZnO PDs, which is distinguished from other traditional devices. The results demonstrate that the ZnO NC array can spontaneously generate the carrier and successfully achieve the detection at zero bias under the radiation of UV light. In this study, the structure is fabricated with two different substrates of silicon (Si) and GaN. At zero bias voltage, the Si-based PD under 365 nm shows the responsivity and external quantum efficiency (EQE) reaching up to 14.1 mA/W and 4.79%, respectively, and the responsivity of the GaN-based detector can be obtained up to 59.9 mA/W; its parameter of EQE is 20.04%, the photocurrent is 10-5A, and the on/off ratio is 174. Our findings indicate that this structure of the device has potential for applications that require detection of light.

N-Terminus-Mediated Solution Structure of Dimerization Domain of PRC1.

Simple SummaryThe solution structure of the N-terminal domain of Protein Regulator of Cytokinesis 1 (PRC1) was determined, and compared with the previously published crystal structure, significant differences were found. Extensive analyses were carried out to find the true reason for the differences between the solution and crystal structures, we discovered that this might be related to the conformation of residue M1, which is buried in the protein core of the solution structure, while situated outside of the hydrophobic core in the crystal structure. In this study, we have carried out a series of examinations using various methods and confirmed that the N terminal conformation is the key point in better describing the structure of PRC1 dimerization domain under solution conditions.Microtubule-associated proteins (MAPs) are essential for the accurate division of a cell into two daughter cells. These proteins target specific microtubules to be incorporated into the spindle midzone, which comprises a special array of microtubules that initiate cytokinesis during anaphase. A representative member of the MAPs is Protein Regulator of Cytokinesis 1 (PRC1), which self-multimerizes to cross-link microtubules, the malfunction of which might result in cancerous cells. The importance of PRC1 multimerization makes it a popular target for structural studies. The available crystal structure of PRC1 has low resolution (>3 Å) and accuracy, limiting a better understanding of the structure-related functions of PRC1. Therefore, we used NMR spectroscopy to better determine the structure of the dimerization domain of PRC1. The NMR structure shows that the PRC1 N terminus is crucial to the overall structure integrity, but the crystal structure bespeaks otherwise. We systematically addressed the role of the N terminus by generating a series of mutants in which N-terminal residues methionine (Met1) and arginine (Arg2) were either deleted, extended or substituted with other rationally selected amino acids. Each mutant was subsequently analyzed by NMR spectroscopy or fluorescence thermal shift assays for its structural or thermal stability; we found that N-terminal perturbations indeed affected the overall protein structure and that the solution structure better reflects the conformation of PRC1 under solution conditions. These results reveal that the structure of PRC1 is governed by its N terminus through hydrophobic interactions with other core residues, such hitherto unidentified N-terminal conformations might shed light on the structure–function relationships of PRC1 or other proteins. Therefore, our study is of major importance in terms of identifying a novel structural feature and can further the progress of protein folding and protein engineering.

Hetero-epitaxy growth of cobalt oxide/nickel oxide nanowire arrays on alumina substrates for enhanced ethanol sensing characteristics

In this work, Co3O4 nanowire arrays are prepared in-situ on the flat alumina substrates via a simple hetero-epitaxial growth without adding seed layers. It is found that the density of Co3O4 nanowires can be regulated by varying the concentration of NH4F that acts as substrate activation promoting the formation of nuclei on alumina substrate. In order to improve the gas-sensing performance, porous NiO nanosheets are anchored on the surface of Co3O4 nanowire arrays to form a novel heterostructure (Co3O4/NiO). Gas-sensing tests indicate a higher response value of these array composites towards ethanol (Rg/Ra = 4.26) than that of pristine Co3O4 nanowire arrays (Rg/Ra = 1.27) and NiO nanosheets (Rg/Ra = 1.89). The improved gas-sensing performances resulting from the special array structures and novel heterojunctions can provide abundant diffusion channels for gas molecules as well as a synergistic effect between Co3O4 and NiO.

Mechanically excellent nacre-inspired protective steel-concrete composite against hypervelocity impacts

Steel–concrete (SC) composite widely used in military defensive project is due to its impressive mechanical properties, long-lived service, and low cost. However, the growing use of hypervelocity kinetic weapons in the present war puts forward higher requirements for the anti-explosion and penetration performance of military protection engineering. Here, inspired by the special ‘brick-and-mortar’ (BM) structural feature of natural nacre, we successfully construct a nacre-inspired steel–concrete (NISC) engineering composite with 2510 kg/m3, possessing nacre-like lamellar architecture via a bottom-up assembling technique. The NISC engineering composite exhibits nacreous BM structural similarity, high compressive strength of 68.5 MPa, compress modulus of 42.0 GPa, Mohs hardness of 5.5, Young’s modulus of 41.5 GPa, and shear modulus of 18.4 GPa, higher than pure concrete. More interestingly, the hypervelocity impact tests reveal the penetration capability of our NISC target material is obviously stronger than that of pure concrete, enhanced up to about 46.8% at the striking velocity of 1 km/s and approximately 30.9% at the striking velocity of 2 km/s, respectively, by examining the damages of targets, the trajectories, penetration depths, and residual projectiles. This mechanically integrated enhancement can be attributed to the nacre-like BM structural architecture derived from assembling the special steel-bar array frame-reinforced concrete platelets. This study highlights a key role of nacre-like structure design in promoting the enhanced hypervelocity impact resistance of steel–concrete composites.

Magic phononic structures

To alter the dynamical response of a structure, engineers must alter its overall mass or stiffness, frequently at the expense of functional performance. Here, borrowing from the field of recreational mathematics, we propose the idea of magic structures—a new class of structures with invariant global mass and stiffness properties, but varying dynamical response. A magic square is a special array of numbers where all individual rows, columns, and diagonals sum up to the same constant value, called the magic number. Here, working within the context of phononic structures, we treat the total mass of the structure as its magic property. We study the dispersion behavior of an infinite, periodic spring-mass system with a 3 × 3 square unit cell with the magic mass property. While maintaining the magic mass, we study the effect of various mass distributions on the dispersion bands and phononic bandgaps. Our analysis shows that the frequency and width of the phononic bandgaps occurring in such structures can be altered while maintaining the total mass of the structure at a constant magic value. Finally, we present a practical application by altering the density distribution of a 2D plate to create low-frequency bandgaps without altering its global mass.

Comparative genomic hybridization (CGH) in molecular diagnostics

Comparative genomic hybridization (CGH) is a powerful molecular cytogenetic approach for identifying chromosomal abnormalities. CGH allows researchers to scan whole genomes for changes in DNA copy numbers. Starting in 2004, the array CGH became an irreplaceable method for the detection of gene mutations in people with congenital and developmental abnormalities, such as intellectual disability, dysmorphic characteristics, developmental delay, or several congenital deformities without an obvious syndrome pattern. This review focuses on the evolution of array CGH technology and its use in molecular diagnostics and its advantages over older cytogenetic tools. This review further highlights special arrays developed in the past decade which detect small intragenic copy number changes as well as large DNA segments for the region of heterozygosity.

Layered SnO2 nanorods arrays anchored on reduced graphene oxide for ultra-high and ppb level formaldehyde sensing

Three-dimension (3D) hierarchical SnO2@rGO nanocomposites (SRGNC) of layered SnO2 nanorods arrays anchored on reduced graphene oxide were fabricated by a hydrothermal approach. The layered SnO2 nanorods arrays were employed in-situ growth mechanism via a straightforward nanocrystal-seeds-directing on reduced graphene oxide. The 3D hierarchical structure of the SRGNC demonstrated a unique brush-like SnO2 arrayed nanorods with a diameter of approximately 7 nm and a length of several hundred nanometers. Applied as a gas sensing material, the SnO2@2.5 %rGO nanocomposite demonstrated ultra-high performance for formaldehyde gas that the gas response toward 50 ppm formaldehyde is up to 5437 at the lower optimal operating temperature of 50 °C. Not only that, the sensor based on SnO2@2.5 %rGO nanocomposite exhibited good selectivity, reproducibility, long term stability, and ultralow-limit gas detection (as low as 500 ppb). The perfect sensing performances could be attributed to the electronic coupling effect, the enlarged specific surface with abundant active sites and the special array structure of SnO2 nanorods.

2D DOA Estimation of Coherently Distributed Sources for Planar Arrays Based on Blind Signal Separation

A novel method is presented to estimate the direction-of-arrival (DOA) of coherently distributed (CD) sources for planar arrays. In the proposed method, the two-dimensional (2D) angular parameters are obtained by making use of the estimated generalized array manifold matrix, which is separated from the received observation data based on blind signal separation algorithm. The proposed method offers a number of advantages. First, the 2D central DOAs and angular spread variances can be estimated simultaneously. Second, the deterministic angular distributed functions (DADFs) of the CD sources do not need to know. Third, the special array geometries are not required, as the method is applicable to planar arrays. Computer simulations are shown to verify the efficacy of the proposed method.

Source Localization Using Distributed Electromagnetic Vector Sensors

Electromagnetic vector sensor (EVS) array has drawn extensive attention in the past decades, since it offers two‐dimensional direction‐of‐arrival (2D‐DOA) estimation and additional polarization information of the incoming source. Most of the existing works concerning EVS array are focused on parameter estimation with special array architecture, e.g., uniform manifold and sparse arrays. In this paper, we consider a more general scenario that EVS array is distributed in an arbitrary geometry, and a novel estimator is proposed. Firstly, the covariance tensor model is established, which can make full use of the multidimensional structure of the array measurement. Then, the higher‐order singular value decomposition (HOSVD) is adopted to obtain a more accurate signal subspace. Thereafter, a novel rotation invariant relation is exploited to construct a normalized Poynting vector, and the vector cross‐product technique is utilized to estimate the 2D‐DOA. Based on the previous obtained 2D‐DOA, the polarization parameter can be easily achieved via the least squares method. The proposed method is suitable for EVS array with arbitrary geometry, and it is insensitive to the spatially colored noise. Therefore, it is more flexible than the state‐of‐the‐art algorithms. Finally, numerical simulations are carried out to verify the effectiveness of the proposed estimator.

A frequency-domain beamforming for rotating sound source identification.

Identifications of rotating sound sources are of interest in many industrial applications. Nowadays, almost all frequency-domain rotating beamformings are based on the concept of virtual rotating array (VRA), and consequently, have one constraint that microphones must constitute a ring around the rotation axis of a sound source. This constraint greatly restricts the wide application of these beamformings in industrial experiments. To overcome this constraint, this paper proposed a frequency-domain rotating beamforming (mode composition beamforming, MCB). Without using the concept of VRA, MCB directly uses the concept of delay-and-sum with the mode composition of rotating sound. MCB has the same ability to rotate sound source identification as the famous time-domain rotating source identifier (ROSI) proposed by Sijtsma et al. (2001) and generally has a much higher computational speed than ROSI, especially when a large number of samplers are used. Special arrays, such as rotational symmetry array, with respect to the rotation axis with a high order of rotational symmetry, are recommended to compensate for the ghost contributions in MCB induced by the Doppler effect.