Basic Square Research Articles

Band engineering in two-dimensional porphyrin- and phthalocyanine-based covalent organic frameworks: insight from molecular design

Two-dimensional covalent organic frameworks (2D COFs) represent an emerging class of crystalline polymeric networks, characterized by their tunable architectures and porosity, synthetic adaptability, and interesting optical, magnetic, and electrical properties. The incorporation of porphyrin (Por) or phthalocyanine (Pc) core units into 2D COFs provides an ideal platform for exploring the relationship between the COF geometric structure and its electronic properties in the case of tetragonal symmetry. In this work, on the basis of tight-binding models and density functional theory calculations, we describe the generic types of electronic band structures that can arise in tetragonal COFs. Three tetragonal lattice symmetries are examined: the basic square lattice, the Lieb lattice, and the checkerboard lattice. The potential topological characteristics of each lattice are explored. The Por-/Pc-based COFs exhibit characteristic band dispersions that are directly linked to their lattice symmetries and the nature of the frontier molecular orbitals of their building units. We show that the band dispersions in these COFs can be tailored by choosing specific symmetries of the molecular building units and/or by modulating the relative energies of the core and linker units. These strategies can be extended to a wide array of COFs, offering an effective approach to engineering their electronic properties.

Hopf bifurcation of a non-parallel Navier-Stokes flow

A plane non-parallel flow in a square fluid domain exhibits an odd number of vortices. A spectral structure is found to have a non-real solution of the spectral problem linearized around the flow. With the use of this structure, Hopf bifurcation or secondary time periodic flows branching of a basic square eddy flow are found. In contrast to a square eddy flow involving an even number of vortices in earlier analytical and experimental investigations, instability of the flow leads to steady-state bifurcations.

A Novel Ultra-Miniaturized Angularly Stable Frequency Selective Surface for L-Band Shielding Applications

This paper presents a novel ultraminiaturized frequency selective surface (FSS) for L-band electromagnetic shielding applications. A basic square loop incorporated with folded arms in the top layer constructs the single-layer FSS design. Band-stop characteristics for the entire L-band operating frequency ranging from 1 GHz to 2 GHz are offered by the proposed design. An ultraminiaturized profile of 0.028λο × 0.028λο is achieved by the designed FSS, where λο corresponds to the lowest operating frequency, achieving at least 32.1% miniaturization when compared to the state-of-the-art FSS designs in the literature. Polarization insensitivity with a peak shielding effectiveness of 45.4 dB is manifested by the rotational symmetry of the proposed design. The proposed FSS exhibits excellent angular stability performance up to 80° with a frequency deviation of less than 1%. The equivalent circuit model helps to understand the working principle of the proposed FSS. The experimental results of the designed FSS prototype agree well with the simulation results. Hence, the proposed spatial filter is a suitable candidate for enhancing security in wireless communication at the carrier frequencies of GPS systems.

IEEE-754 Precision- p base-β Arithmetic Implemented in Binary

We show how an IEEE-754 conformant precision- p base-β arithmetic can be implemented based on some binary floating-point and/or integer arithmetic. This includes the four basic operations and square root subject to the five IEEE-754 rounding modes, namely the nearest roundings with roundTiesToEven and roundTiesToAway, the directed roundings downwards and upwards, as well as rounding towards zero. Exceptional values like ∞ of NaN are covered according to the IEEE-754 arithmetic standard. The results of the precision- p base-β operations are computed using some underlying precision- q binary arithmetic. We distinguish two cases. When using a precision- q binary integer arithmetic, the base-β precision p is limited for all operations by β 2 p ≤ 2 q , whereas using a precision- q binary floating-point arithmetic imposes stronger limits on the base-β precision, namely β 2 p ≤ 2 q for addition and multiplication, β 2 p ≤ 2 q-1 for division and β 2 p ≤ 2 q -3 for the square root. Those limitations cannot be improved. The algorithms are implemented in a Matlab/Octave flbeta-toolbox with the choice of using uint64 or binary64 as underlying arithmetic. The former allows larger precisions, the latter is advantageous for the square root, whereas computing times are similar. The flbeta-toolbox offers precision- p base-β scalar, vector and matrix operations including sparse matrices as well as corresponding interval operations. The base β can be chosen in the range β ∊ [2,64]. The flbeta-toolbox will be part of Version 13 of INTLAB [ 18 ], the Matlab/Octave toolbox for reliable computing.

Comparison and Analysis of Electromagnetic Characteristics of Basic Structure of Wireless Power Coil for Permanent Magnet Motors in Electric Vehicles

The purpose of this paper is to compare and analyze the electromagnetic characteristics of the basic structure of the coil in the electromagnetic coupling mechanism for the wireless power supply of permanent magnet motors in electric vehicles. The electromagnetic coupling mechanism is one of the key technologies for wireless power transmission and the coil structure plays a key role in the transmission performance of the coupling mechanism, and different structures can achieve different performances. The central objective of coil structure studies is to investigate how the coupling coefficient can be increased to achieve greater transmitted power and higher efficiency. In this paper, we investigate two basic coil configurations, circular and square, by studying their flux density variations when used as transmitting coils and their electromagnetic coupling characteristics when used as receiving coils. Three couplers consisting of circular and square coils are also analyzed in simulations and experiments are carried out on couplings containing circular and square coils of the same area. The results of the study show that the qualitative analysis, simulation analysis and experimental results are in high agreement. The results of this paper are an important reference for the design and optimization of wireless power coils for permanent magnet motors in electric vehicles.

A novel reduced instruction set computer-communication processor design using field programmable gate array

In this paper, a novel reduced instruction set computer (RISC)- communication processor (RCP) has been designed with 32-bit operations which access 64-bit instruction format and implemented using field programmable gate array (FPGA). The design of the RISC processor is facilitated with communication operations like basic signals sine, cosine, and square, and modulation schemes like amplitude modulation, amplitude shift keying, analog, and digital quadrature amplitude modulation. Additionally, application-oriented operations like a traffic light, digital clock, and linear feedback shift register are included in the design. The pipeline mechanism is incorporated in the design to enhance the performance characteristics of the processor, hence allowing the execution of the instructions more effectively. Also, the design is implemented with Xilinx Virtex 7 family FPGA. The device utilization analysis of the proposed FPGA along with different FPGA families is evaluated and compared.

An Effect of Layered Auxiliary Cathode on Thickness Uniformity in Micro Electroforming Process.

Thickness nonuniformity is a bottleneck in the micro electroforming process of micro-metal devices. In this paper, a new method of fabricating a layered auxiliary cathode is proposed to improve the thickness uniformity of a micro-electroforming layer. In order to analyze the general applicability of the proposed method, four basic microstructures, namely circular, square, regular triangular, and regular hexagonal were used to study the effect of a layered auxiliary cathode on thickness uniformity through simulation and experimentation. The simulation results showed that with the help of the proposed auxiliary cathode, the thickness nonuniformity of four microstructures should decrease due to the reduced edge effect of the current density. The experimental results showed that the thickness uniformity of four microstructures fabricated via the proposed method was improved by 190.63%, 116.74%, 80.43%, and 164.30% compared to that fabricated via the traditional method, respectively. Meanwhile, the micro-gear was fabricated and the nonuniformity was reduced by 101.15% using the proposed method.

Enhancing strontium clock atom interferometry using quantum optimal control

Strontium clock atom interferometry is a promising new technology, with multiple experiments under development around the world to explore its potential for dark matter and gravitational wave detection. In these detectors, large momentum transfer using sequences of many laser pulses is necessary, and thus high-fidelity pulses are important since small errors become magnified. Quantum optimal control (QOC) is a framework for developing control pulse waveforms that achieve high fidelity and are robust against experimental imperfections. Resonant single-photon transitions using the narrow clock transition of strontium involve significantly different quantum dynamics than more established atom interferometry methods based on far-detuned two-photon Raman or Bragg transitions, which leads to new opportunities and challenges when applying QOC. Here, we study in simulation QOC pulses for strontium clock interferometry and demonstrate their advantage over basic square pulses (primitive pulses) and composite pulses in terms of robustness against multiple noise channels. This could improve the scale of large momentum transfer in Sr clock interferometers, paving the way to achieving these scientific goals.

Cell‐based allometry: an approach for evaluation of complexity in morphogenesis

BackgroundMorphogenesis is a complex process in a developing animal at the organ, cellular and molecular levels. In this investigation, allometry at the cellular level was evaluated.MethodsGeometric information, including the time‐lapse Cartesian coordinates of each cell’s center, was used for calculating the allometric coefficients. A zero‐centroaxial skew‐symmetrical matrix ( CSSM), was generated and used for constructing another square matrix (basic square matrix: BSM), then the determinant of BSM was calculated ( d). The logarithms of absolute d (Lad) of cell group at different stages of development were plotted for all of the cells in a range of development stages; the slope of the regression line was estimated then used as the allometric coefficient. Moreover, the lineage growth rate (LGR) was also calculated by plotting the Lad against the logarithm of the time. The complexity index at each stage was calculated. The method was tested on a developing Caenorhabditis elegans embryo.ResultsWe explored two out of the four first generated blastomeres in C. elegans embryo. The ABp and EMS lineages show that the allometric coefficient of ABp was higher than that of EMS, which was consistent with the complexity index as well as LGR.ConclusionThe conclusion of this study is that the complexity of the differentiating cells in a developing embryo can be evaluated by allometric scaling based on the data derived from the Cartesian coordinates of the cells at different stages of development.

Categorizing Drunkard's Path type quilting patterns

The Drunkard's Path quilt block is a basic square quilt block consisting of a quarter circle in one corner on a square of some contrasting fabric. In this paper, we use symmetry to organize a library of quilting patterns using the Drunkard's Path quilt block. The organizational strategy begins by arranging the basic quilt blocks into squares that we call arrangements. We categorize these arrangements by symmetry type. We also act upon the arrangements by rotations, reflections, and colour exchanges, using the results to produce squares that we call tiles. These tiles are subsequently considered as tiles for quilt tops, thereby giving fodder for analysis of the underlying wallpaper symmetry groups and sometimes even two-colour symmetry patterns. Over 90 of the tiles are shown representing just a small number of the possible quilt patterns.

Amplitude expansion of the phase-field crystal model for complex crystal structures

The phase-field crystal (PFC) model describes crystal lattices at diffusive timescales. Its amplitude expansion (APFC) can be applied to the investigation of relatively large systems under some approximations. However, crystal symmetries accessible within the APFC model are limited to basic ones, namely triangular and square in two dimensions, and body-centered cubic and face-centered cubic in three dimensions. In this work, we propose a general, amplitudes-based description of virtually any lattice symmetry. To fully exploit the advantages of this model, featuring slowly varying quantities in bulk and localized significant variations at dislocations and interfaces, we consider formulations suitable for real-space numerical methods supporting adaptive spatial discretization. We explore approaches originally proposed for the PFC model which allow for symmetries beyond basic ones through extended parametrizations. Moreover, we tackle the modeling of non-Bravais lattices by introducing an amplitude expansion for lattices with a basis and further generalizations. We study and discuss the stability of selected, prototypical lattice symmetries. As pivotal examples, we show that the proposed approach allows for a coarse-grained description of the kagome lattice, exotic square arrangements, and the diamond lattice, as bulk crystals and, importantly, hosting dislocations.

Numerical analysis of the effectiveness of a unique roughened surface solar air heater

ABSTRACT The main goal of this study is to enhance the functionality of the solar air heater by adding unique roughened surfaces to the absorber section that disrupt the sluggish sub-layer. The roughened surfaces are created so that the depth of roughened surface’s dimension is constant for all the cases; there will not be any pressure difference lost. Initially, a square roughened surface is considered for the primary plain tube solar air heater. Later, the remaining roughened surfaces are created by removing some triangular portions from the basic square rib surfaces. The primary intention of creating surfaces like this is that the sharp edges facing the upwind stream disturb the viscous sub-layer at a greater level than the squared rib roughened surfaces. Using a computational fluid dynamics tool, this research problem has been investigated numerically by computing formula that controls the fluid flow with the RNG k-ε turbulence model. The functionality of solar-powered air heaters has been examined at different Reynolds numbers by studying temperature, turbulence, and the Nusselt number. Based on the overall comparison of the numerical results for the different roughened surfaces, Case 4 offers superior heat transmission performance compared to the simple tube solar air heater, which has 43.7% more turbulence. In the investigated range, the roughened surface solar air heater had a high Nusselt number 3.15 times more than the plain tube solar heater with a comparable roughness value of 7.14 at a Reynolds number (Re) of 15,000. Case-4 solar-powered air heater with roughened surfaces reached a maximum temperature of 406.4 K

Optimized Neural Network-Based Micro Strip Patch Antenna Design for Radar Application

Microstrip antennas are low-profile antennas that are utilized in wireless communication systems. In recent years, communication engineers have been increasingly interested in it. Because of downsizing, novelty, and cost reduction, the number of wireless standards has expanded in recent years. Wideband technologies have evolved in addition to analog and digital services. Radars necessitate antenna subsystems that are low-profile and lightweight. Microstrip antennas have these qualities and are suited for radars as an alternative to the bulky and heavyweight reflector/slotted waveguide array antennas. A perforated corner single-line fed microstrip antenna is designed here. When compared to the basic square microstrip antenna, this antenna has better specifications. Because key issue is determining the best values for various antenna parameters when developing the patch antenna. Optimized Neural Network (ONN) is one potential technique utilized to solve this issue, and this work also uses Particle Swarm Optimization (PSO) to enhance the antenna performance. Return loss (S11) and Voltage Standing Wave Ratio (VSWR) parameters are considered in all situations, developed with Advanced Design System (ADS) applications. The transmitters are made to emit in the Ku-band, which covers a wide range of wavelengths. From 5–15 GHz, it is used in most current radars. The ADS suite is used to create the simulation design.

Treatment of Extended Kalman Filter Implementations for the Gyroless Star Tracker.

The literature since Apollo contains exhaustive material on attitude filtering, usually treating the problem of two sensors, a combination of state measuring and inertial devices. More recently, it has become popular for a sole attitude determination device to be considered. This is especially the case for a star tracker given its unbiased stellar measurement and recent improvements in optical sensor performance. The state device indirectly estimates the attitude rate using a known dynamic model. In estimation theory, two main attitude filtering approaches are classified, the additive and the multiplicative. Each refers to the nature of the quaternion update in the filter. In this article, these two techniques are implemented for the case of a sole star tracker, using simulated and real night sky image data. Both sets of results are presented and compared with each other, with a baseline established through a basic linear least square estimate. The state approach is more accurate and precise for measuring angular velocity than using the error-based filter. However, no discernible difference is observed between each technique for determining pointing. These results are important not only for sole device attitude determination systems, but also for space situational awareness object localisation, where attitude and rate estimate accuracy are highly important.

A study on methods for detecting districts with locally significant population changes using the basic grid square statistics

A study on methods for detecting districts with locally significant population changes using the basic grid square statistics

Computational analysis of designing an improved coronary stents of biodegradable Poly-lactic Acid (PLA)

ABSTRACT The complications arising after the transplantation of conventional stents put atherosclerotic cardiovascular patients at high risk. Biodegradable poly-lactic acid (PLA) stents provide practical solutions for diseased vessels (atherosclerotic) and avoid the side complications of vessels and their incompatibility with permanent stents in the long term. PLA is a biodegradable and reliable material that is used for biodegradable stents designs to maintain natural mechanical behaviour in blood vessels. In this study, we suggest a new cross section ‘circular and elliptic’ that are proposed based on basic square shape cross section to study the mechanical behaviour of stents under pulsatile blood pressure in the blood vessels in order to choose the best shape to allow the biodegradability of Absorb stents with Poly-lactic Acid (PLA) material by numerical fatigue study. Three types of cross-sections stents struts have been analysed to compare their mechanical properties in terms of stress, strain, fatigue damage and life cycle. The numerical results obtained from the finite element analysis (FEA) method demonstrate that the elliptical and circular stents design has better efficiency in terms of stress and strain (16.66–33.33%) and fatigue damage (62.4–86.07%) compared to the square design.

Role of Heat Release from Inter-Electrode Chemical Crosstalk in Thermal Runaway Propagation Characteristics of Lithium-Ion Battery Modules

While lithium-ion batteries are continually increasing in energy and power density, thermal safety still remains a significant concern. In some thermal abuse scenarios, thermal runaway can be triggered by the exothermic reactions from inter-electrode chemical crosstalk between the cathode and the anode without an internal short circuit. Under these circumstances, the thermal runaway temperature is lower than the separator's thermal shrinkage temperature, implying that the cell's catastrophic thermal runaway occurs without a large-scale short circuit produced by separator failure. These cell failures must be managed such that the neighboring cells in a battery module are not affected, a phenomenon known as thermal runaway propagation. In the present work, we employed a high-resolution cell-level thermal runaway model constructed from the accelerating rate calorimetry data of a commercial Li-ion cell to characterize the cell-to-cell thermal runaway propagation behavior for a basic square arrangement of lithium-ion battery module connected by tabs. We determined safe practices under the effects of different ambient conditions, inter-cell spacing, trigger cell location, and external heating power. Additionally, we have identified the critical pathways for the thermal runaway propagation in the battery module and quantified their statistical distribution in terms of the thermal runaway propagation speed, heat release from exothermic reactions, and heat dissipation to the surroundings. The findings from the study are believed to be of immediate relevance for the safer design of lithium-ion battery packs.

Numerical Investigation of Photonic Crystal Fiber-Based Biosensor for Pathogens Detection in Water

In this paper, a Photonic Crystal Fiber (PCF) based Surface Plasmon Resonance (SPR) biosensor for the detection of four bacteria such as <i>Vibrio Cholera, Escherichia Coli (E. coli), Bacillus Anthracis, and Enterococcus Faecalis</i> is proposed and evaluated numerically using finite element method (FEM)-based simulation tool. The proposed sensor exhibits excellent performance characteristics and has the configuration of identifying analyte samples externally. The sensor is designed with a basic square lattice of PCF, covered with a thin chemically stable gold layer. The proposed sensor can detect these four bacteria from pure water and has the highest wavelength sensitivity of 5161 nm/RIU for <i>Enterococcus Faecalis</i>. Other critical parameters such as Signal to Noise Ratio, Detection Limit, Sensor Length, Quality Factor, and Detection Accuracy are also calculated and presented for the proposed PCF biosensor.

Low Complex Methods for Robust Channel Estimation in Doubly Dispersive Environments

Wireless communications play a significant role in facilitating several mobile applications like unmanned aerial vehicles, high-speed railway, and vehicular communications. Particularly, the concept of connected vehicles brings a new level of connectivity to vehicles. Along with novel on- board computing and sensing technologies, vehicular networks serve as a key enabler of intelligent transportation systems and smart cities. However, in such environments, the propagation medium between the network nodes is highly time-varying leading to considerable reliability challenges. Ensuring communication reliability by the means of accurate channel estimation in such environments is very important. Initially, vehicular communications standards apply the basic least square (LS) estimation that is not enough for the dynamic vehicular environment. Moreover, the frame structure has low pilot density, making channel tracking a difficult task to achieve, especially in high mobility scenarios. Conventional estimators either employ data subcarriers besides pilots in the estimation process, or the estimated channel and noise statistics. Therefore they suffer from significant performance degradation due to high error probability resulting from hard symbol demapping and the sensitivity against the change in the employed channel statistics. The motivation behind this paper is to overcome this challenge by proposing a low complex and robust channel estimation scheme based on truncated discrete Fourier transform (T-DFT) that updates the channel estimates using DFT interpolation without the need for data subcarriers decisions and the estimated channel statistics. Moreover, further performance improvement can be achieved by considering temporal averaging on top of T-DFT estimation. Analytical and simulation results carried out using different vehicular channel models reveal the performance superiority of the proposed schemes compared to conventional estimators while recording a significant decrease in computational complexity and execution time.

Study on biological control model of Empoasca onukii Matsuda ‐take tea garden ecology as an example

AbstractThe closeness of the spatial relationship between natural enemies and target pests directly affects the control effect of natural enemies on target pests. Therefore, we here use both geostatistics and cluster sample variance analysis methods to investigate the six kinds of natural enemies and pests in Huangshan large‐leaf tea garden at fall and winter of 2020. In this study, we firstly use the geostatistics method to calculate the geostatistical semivariogram variation range and then conduct the Grey correlation analysis on six main natural enemies of Empoasca onukii Matsuda. Our results indicate that the larger the correlation value is, the closer the natural enemy is to the target pest in space, and the top three natural enemies Clubiona japonicola, Oxyopes sertatus and Tetragnatha squamata are more closely related to Empoasca onukii Matsuda in space through the comprehensive judgment. Secondly, we use the cluster sample variance analysis method to calculate the basic sample square number and then perform the Grey correlation analysis on them. Our findings demonstrate that the top three natural enemies O. sertatus, T. squamata and Erigonidium graminicolum are more closely related to Empoasca onukii Matsuda in space via the comprehensive judgment. Remarkably, both O. sertatus and T. squamata have been revealed to be vital enemies of the Empoasca onukii Matsuda in tea garden. Overall, our study not only uncovers the spatial relationship between natural enemies and Empoasca onukii Matsuda, but also provides a scientific basis for further protecting and utilizing natural enemies to control pests in the tea garden.