Rectangular Notch Research Articles

Design and kinematics analysis of a cable-stayed notch manipulator for transluminal endoscopic surgery

The friction between the joints of the continuum manipulator with discrete joints brings great difficulties to kinematic modeling. The traditional driving wire arrangement limits the load capacity of the manipulator. A cable-stayed notch manipulator for transluminal endoscopic surgery is proposed, and a driving force coupling kinematic mode is established. The manipulator is fabricated from a superelastic Nitinol tube with bilaterally cut rectangular notches and is actuated by a stay cable. By applying the comprehensive elliptic integral solution (CEIS) for large deformation beams, the bending angle of each elastic beam is obtained, and the kinematics from the driving space to the joint space is formed. According to the bending angle of each elastic beam, the expression of the manipulator in Cartesian space can be obtained by geometric analysis. The kinematics from the joint space to the Cartesian space is established. The outer diameter of the manipulator is only 3.5 mm, and the inner diameter can reach 2 mm, allowing instruments to pass through. The maximum error of the manipulator movement is less than 5%. The load capacity of the manipulator has been verified through the stiffness experiments, and the maximum load of the manipulator can reach 400 g. The cable-stayed notch manipulator can be accurately modeled on the base of CEIS, and its motion accuracy can meet the needs of engineering applications. The compact size and excellent load capacity of the manipulator make it potential for application in transluminal endoscopic surgical robots.

Investigating the impact of notch shapes on oxide–oxide ceramic matrix composites strength: A computational approach

AbstractThis study utilizes finite element analysis (FEA) to explore the effect of standardized notch shapes—triangular, circular, and rectangular on the tensile behavior of oxide–oxide (O–O) ceramic matrix composites (CMCs) across various temperature ranges. Findings reveal that unnotched samples exhibited a superior equivalent stress of ∼425 MPa, closely aligning with experimental values. However, under elevated temperatures of 1000°C and 1200°C, degradation occurs, reaching up to 54% decrease at 1200°C. Notched samples demonstrate similar behavior, with all notches acting as stress concentrators. Analysis of single and double notches highlights that circular notches have the most significant stress concentrators due to their smooth surfaces and lack of sharp edges, in contrast to rectangular and triangular notches. Although all notch types influence stress concentration, the absence of non‐sharp corners in circular notches limit stress dissipation, resulting in higher stress concentrations. This trend persists under high temperature as well. The study emphasizes the critical need for a thorough assessment of notch effects, considering their position, orientation, shape, and size, as they significantly affect the mechanical properties of O–O CMCs.

Development of a Test Rig for a New Vertical Ultra-Low-Head Hydro Turbine with Calibration of Rectangular Notch for Discharge Measurement

Development of a Test Rig for a New Vertical Ultra-Low-Head Hydro Turbine with Calibration of Rectangular Notch for Discharge Measurement

Wide‐angle band‐pass FSS with high‐frequency selectivity based on SIW cavity technology

AbstractThis work proposes and investigates a wide‐angle band‐pass frequency selective surface (FSS) with two sharp sidebands. The presented FSS element is made up of three metallic layers and two substrate layers in between, which are surrounded by a substrate‐integrated waveguide (SIW) cavity. The top metallic layer is identical to the bottom layer, composed of a square patch etched with a hexagonal groove, while the middle layer is a similar patch but with rectangular notch edges. This structure achieves a second‐order band‐pass response with highly frequency selectivity on either side of the passband. At the same time, this FSS demonstrates excellent stability for both transverse electric and transverse magnetic polarizations with incident angles between 0° and 60°. The electric current and field distributions are demonstrated for deep analysis. Furthermore, an equivalent circuit model is developed to further understand the operating mechanisms. To verify the validity of the design, we construct a prototype of the SIW‐based FSS (SIW‐FSS) and measured it. There is a fair degree of agreement between the measured and simulated results. Finally, we loaded it onto the horn antenna and tested its application in filtering antennas.

Vibration-based structural damage detection strategy using FRFs and machine learning classifiers

In this paper, a damage detection strategy for beam-type structures based on frequency response functions (FRFs) is presented. Five aluminum beams of equal nominal dimensions are used in an experimental program under laboratory conditions to obtain experimental FRF data from both undamaged and damaged conditions. Damages are induced by creating rectangular notches on the beams using saw-cutting. A stochastic finite element model of the beam is developed in MATLAB to construct several training datasets. The damages are modeled by reducing the cross-sectional area at the corresponding damaged elements. Simple damage indexes are proposed as damage-sensitive features. Decision Tree, Support Vector Machines, and Artificial Neural Networks classifiers are trained in the first stage to perform damage detection and localization. Single and multiple damages located in a single zone and more than one zone simultaneously are considered. In the second stage, experimental data not used for training are used for validation. The results from the first stage suggest that the proposed damage indexes can effectively detect and locate structural damage in beams. Among all classifiers, Artificial Neural Networks is the classifier that best performed. High accuracy is achieved to identify the presence of damage (99.3%) and detecting its location on the beam for some of the training datasets (from 80.0% to 97.1%). In the second stage of validation, accuracy, as expected, decreased. However, misclassifications occur mainly for FRF samples in the impact zone, which indicates that the proposed strategy can be efficient to detect damages at locations other than the excitation zone.

Bandwidth enhancement of compact and wideband square microstrip patch antenna for WLAN/WiMAX applications in C‐band

AbstractThis paper presents a compact and wideband square microstrip patch antenna using low cost and easy available FR‐4 substrate of ground size 30 mm × 30 mm (0.51 × 0.51 at lowest resonant frequency 5.07 GHz). The radiating patch of antenna is designed by embedding three T‐shape notches of same dimension formed by two rectangular notches of size 6 mm × 5 mm and 3 mm × 2 mm. The radiating patch is optimized by parametric variation of notches and feed line. The wideband fractional bandwidth (S11 < −10 dB) of 47.2% (2810 MHz) is achieved from 4.55 to 7.36 GHz with good return loss of −47.27 dB at 5.07 GHz for an optimized dimension of notches and feed line. However, the measured fractional bandwidth of 43.9% (2340 MHz) is achieved from 4.16 to 6.50 GHz with return loss of −37.34 dB at 5.14 GHz. A stable simulated gain of 4.69 to 5.93 dBi and measured gain of 4.4 to 5.9 dBi is observed in complete resonating band. The antenna is excited by line feed of 50 Ω and simulated by IE3D simulation tool. The entire resonating band 4.55–7.36 GHz is suitable for different applications in C‐band (4–8 GHz).

Sensitivity analysis of notch shape on brittle failure by using uni-bond dual-parameter peridynamics

The brittle failure of components weakened by sharp or blunt notches is a topic of active and continuous research. Notches created during the design and manufacturing of structural components give rise to localized stress concentrations, which can generate a crack leading to catastrophic failure or to a shortening of the assessed structural life. To investigate how notches influence the fracture and bearing capacity of brittle materials by using peridynamics (PD), an extended uni-bond dual-parameter peridynamic (UDPD) model that can overcome the fixed Poisson’s ratio in bond-based PD and address the attenuation effect of the nonlocal PD force is developed. The expressions of normal stiffness and tangential stiffness with elastic modulus and Poisson’s ratio are derived and rewritten. Additionally, the critical microstrain energy density for the extended UDPD model is given to judge the fracture initiation, and the validity and accuracy of the proposed model are verified by four examples. Ultimately, six typical types of notches, i.e., rectangular notches, sharp V notches, U notches, blunt V notches, keyhole notches, and VO notches, were selected and investigated in brittle plates with four different tip radii to study the notch sensitivity of brittle failure to notch shape by using the extended UDPD model. The results show that the crack path and bearing capacity of the structure are sensitive to the notch shape and the tip radius of the notch, and a blunt notch with a larger tip radius (U notch, blunt V notch, keyhole notch, and VO notch, tip radius ρ⩾2mm) offers better performance in terms of structural safety than a sharp notch or a notch with a smaller tip radius.

Impact analysis and optimization of notched high-gain Antipodal Vivaldi antenna using machine learning

Optimizing antenna parameters without knowing their impact on the gain is a time-consuming and iterative process. This article shows how the Classification and Regression Tree (CART) technique, the Random Forest (RF) algorithm, and the Principal Component Analysis (PCA) method is used to study the effect of geometrical parameters of rectangular notches of the Antipodal Vivaldi antenna on gain. Carving out the notches is a general approach for end-fire antenna design. Integrating the EM simulation with machine learning could reduce the time spent on AVA design. In this approach, the gain category of the antenna under design: Low, Medium, and High, is first classified by the three multiclass machine learning models, K-Nearest Neighbor (KNN), Artificial Neural Network (ANN), and Support Vector Machine (SVM). When the predicted category of gain belongs to the High class, in that case, the four regression models, Polynomial, SVM, ANN, and RF, predict the gain value to anticipate the antenna gain according to the notch dimensions to reduce the optimization time of the simulation-driven antenna. In this work, the band-limited approach of notches on gain is also been validated using simulation before fabrication. Machine learning models are optimized the antenna parameters to achieve a high gain within the frequency range of 20 to 40 GHz. A peak simulated gain of 19 dB is achieved at the frequency of 27 GHz. The proposed structure is fabricated utilizing a single-layer Rogers substrate (RO4003C) with a dielectric constant of 3.38 and compact dimensions of 96 mm × 174 mm × 0.508 mm, i.e., 0.32 × 0.58 × 0.0017 λ03; here the symbol λ0 denotes the wavelength of free space at the minimum operating frequency.

Equivalent circuit model‐based design and analysis of microstrip line fed electrically small patch antenna for sub‐6 GHz 5G applications

SummaryIn this paper, an equivalent circuit model‐based electrically small patch antenna is designed for sub‐6 GHz 5G application (3.5 GHz) using 50‐Ω microstrip line feed. The overall size of the proposed antenna is 0.33λ0 × 0.4λ0 × 0.019λ0 (28 × 34 × 1.6 mm3) at 3.50 GHz frequency. The proposed antenna has a tilted Y‐shape slot, two rectangular shape slots, and two rectangular shape notches in the radiating patch. The proposed antenna is resonating from 3.21 to 3.74 GHz covering the entire sub‐6 GHz 5G band (3.3–3.8 GHz). The impedance bandwidth (simulated) of the proposed antenna has been obtained 530 MHz resonating at 3.50 GHz frequency. The good return loss of −23.62 dB is also obtained at 3.50 GHz resonant frequency. The simulation results and geometry of the proposed antenna are validated with equivalent circuit model and experimental measurement of prototype antenna using vector network analyzer (VNA) and anechoic chamber. In the whole operating frequency range, the measured findings show reasonable agreement with the simulated ones. The measured impedance bandwidth of the proposed antenna has been obtained 480 MHz (3.21–3.69 GHz) resonating at 3.48 GHz frequency with a return loss of −21.61 dB, while the theoretical impedance bandwidth of the proposed antenna has been obtained 720 MHz (3.18–3.90 GHz) resonating at 3.58 GHz frequency with a return loss of −21.5 dB. The peak gain of 3.39 (simulated) and 3.2 dB (measured) is obtained at 3.50 GHz frequency. Moreover, the antenna shows 97% (simulated) and 95% (measured) efficiency at 3.50 GHz frequency.

Numerical analysis and optimization of adhesively-bonded single lap joints by adherend notching using a full factorial design of experiment

The objective of this study is to carry out experiments using the experimental design methodology to determine the optimal geometric configuration which improves the resistance of a single-lap joint with notched adherends subjected to uniaxial tensile load. On the sides of the adherends in contact with the adhesive layer, a longitudinal rectangular notch is introduced. A complete experimental design (15) of three factors at two levels: the adhesive thickness (tA), depth (dN) and extended length (LE) of the notch was used to determine their effects on strength of an adhesive joint. The response or dependent variable used was the resistance of a single lap joint (SLJ). Finite element (FE) analysis was conducted to investigate the effect of different notch parameters on the strength enhancement of the SLJs. A quadratic regression model with interaction is developed to relate the strength of an adhesive joint and the variables (tA, dN and LE). The regression model was validated using various statistical approaches. According to the ANOVA results, the model is highly significant and in good agreement with the experimental results. The quadratic regression model suggested was used for optimizing the resistance of the joint. The maximum joint strength occurs when the adhesive thickness is the smallest (left end) and when the adhesive thickness is the largest (right end) of the validated domain. The strength of SLJ increases when the notching parameters (dN and LE) increase in the validation zone. The numerical results show that to improve the resistance of an adhesive joint with notched adherend, it is necessary to minimize the thickness of the adhesive layer and to use notch with the highest depth and extension equal or greater than the overlap. The results show that using the adherend notching can significantly improve the load bearing capacity of SLJs.

Reconstructing the fallen arch of Notre-Dame. New insights into Gothic vault-building

During the fire in April 2019, part of the central vaulting of the nave of Notre-Dame de Paris collapsed beneath the impact of the fallen spire. The blocks composing the transverse arch were decontaminated, then subjected to archeological examination prior to attempting to dry-mount them (i.e., without mortar) on the ground. The purpose was to collect as much information as possible about the arch itself (its state of conservation, geometry, fashioning of the blocks, assembly, etc.), to consider the possibility of putting the fallen stones back in their original places, and more broadly to improve knowledge about mediaeval cathedral vaulting.This article describes the method used during this mounting, which took place in winter 2020/21. Five criteria of differing kind and importance guided decisions on where to place the voussoirs, which way round to position them, and which to associate with which. Three were taken into consideration from the outset, with the interpretation of two of these changing over time: the non-standardized dimension of the voussoirs (their thickness), the presence of a cross mark on one of the joint faces, and the presence of rectangular notches on the extrados of the blocks for housing the end of a centering system for constructing the vault compartments. Two other criteria were incorporated as work progressed, pertaining to the order in which the blocks were collected after the fire, and the geological facies of the stones, thus introducing the idea of degree of confidence.By the end of this operation, only four blocks had been placed with certainty. Nevertheless, the criteria thereby defined and their weighting have been used as a starting point for other investigation methods. In terms of archaeology, the observations carried out on this arch in these exceptional conditions suggest we should reconsider the dating of the nave vaulting, while throwing light more broadly on the relative chronology of building works on this landmark monument of Gothic architecture.

Influence of notched baffles on aerothermal performance behaviors in a channel

The proper designs of modified heat transfer surfaces or turbulence enhancement inserts for heat transfer augmentation are extremely important for improving overall aerothermal performances relating to the energy-saving capabilities of thermal systems. A major challenge is to control friction loss as little as possible while maintaining reasonable heat transfer enhancement. Transverse baffles with rectangular notches or notched baffles (NBs) were applied for improving aerothermal performance in a channel with a constant aspect ratio of 3.75 while notch height-to-baffle height ratio (a/e) ranged from 0.125 to 0.5. Reynolds number ranged from 6000 to 24,000, in experiments. Heat transfer enhancement, pressure loss, and aerothermal performance in a rectangular channel with notched baffles were examined. Compared to the solid transverse baffle (SB, a/e = 0), the NBs with a/e = 0.125 increased the heat transfer rate while lessening the pressure loss, as shown by the experimental findings. Obviously, Nusselt number, friction factor and aerothermal performance increased as the a/e ratio decreased. The NBs with the smallest notch height-to-baffle height ratio (a/e = 0.125) exhibited the highest aerothermal performance of 1.17, which can be attributed to the efficient heat transfer enhancement by the strong multi-jet impingements and the moderate friction loss penalty resulting from the presence of notches (spaces) on the baffles.

Characterization of glass fiber reinforced polymer via digital volume correlation: Quantification of strain activity and damage growth

Strain and damage distributions within a dogbone specimen containing a rectangular notch were assessed in-situ via X-ray computed tomography coupled with digital volume correlation. The specimen cut from a continuous glass fiber mat reinforced polyester resin composite plate was subjected to cyclic tensile loading. The strain–damage interplay was evaluated by analyzing major eigen strain and correlation residual fields. The horizontal strained band emanating from the notch root was present from the beginning of loading. The final failure proceeded along this strained band. The first cracks did not initiate in the notched region, despite high strain gradients. Strain activity and damage growth were quantified by analyzing the cumulative probabilities of major eigen strains. The comparison was made between the notched region and the remaining part of the inspected specimen. It is shown that, although the mean levels were higher in the notched region, the standard deviations of the major eigen strain distributions were higher in the remaining part of the specimen.

Prediction of the discharge coefficient for the rectangular notch with different hydraulic and geometric properties

Abstract This study aims to investigate experimentally the variation of the coefficient of discharge Cd with the rectangular notch hydraulic and geometric parameters such as water head h, notch height p, notch width B, and notch thickness t. The results show that the coefficient of discharge Cd increases with an increase of h and B while it decreases with t. There are no changes in the variation of actual discharge Qact and consequently the discharge coefficient Cd with h for notch height p more than 6 cm. An empirical formula was developed based on the dimensional analysis principle that can be used to predict the coefficient of discharge Cd value for the rectangular notch with known hydraulic and geometric data (h, B, p, and t).

Skyrmion-based reconfigurable logic gates and diodes in a racetrack with hard magnetic material and a notch

Due to the good stability and high mobility, magnetic skyrmions are considered for information carriers in future racetrack memory and spintronic devices. Here, we study the effect of the barrier at the edges on the dynamics of skyrmions in the Co/Pt bilayer racetrack, where the barrier is induced by a higher perpendicular magnetic anisotropy due to the hard magnetic material attached to the racetrack edges. In particular, we study the dynamics of skyrmions in the racetrack with a rectangular notch on one side of the boundary barrier. We systematically investigate the effect of the boundary barrier on the longitudinal velocity of the skyrmion. Compared with the model with no boundary force, it is found that when the repulsive effect of the boundary barrier just overcomes the Magnus force, the longitudinal velocity of the skyrmion can be increased significantly. We also find that a rectangular notch at the edge can be used to enrich the dynamics of the skyrmion. Based on the dynamic behaviors of skyrmions, we realize the skyrmion-based logic AND, OR, NOT, NAND and NOR gates and the diode in the same racetrack. In particular, the logic NOT, NAND and NOR gates are implemented in a reconfigurable way. Our results may be helpful for understanding the dynamics of skyrmions and may contribute to the design of non-volatile spintronic devices with integrated multiple functions and ultra-low energy consumption.

Characterization of glass fiber reinforced polymer via Digital Volume Correlation: Investigation of notch sensitivity

The results of in-situ cyclic tensile experiments performed on two dogbone specimens made of glass fiber mat reinforced polyester resin are presented (the second specimen contains a machined rectangular notch). The experimental data were obtained by using X-ray Computed Tomography. The reconstructed volumes were analyzed via Digital Volume Correlation. The investigated material was notch-insensitive since both specimens failed at equal stress levels. To further confirm this hypothesis, and to study strain–damage interactions, the major eigen strain and correlation residual maps of both specimens were analyzed. Even in the first loading cycle, an inner strained band extending through the whole ligament area developed within both specimens, already indicating the path to final fracture. It is shown that the final failure of the studied material was primarily driven by the yarn mesostructure, i.e., the influence of the underlying heterogeneities prevailed over the effects due to specimen machining and/or geometric singularity.

Bandwidth Enhancement of a Compact Slot Antenna with Frequency Scale Up/down Capability

In this paper, a printed wideband slot antenna is proposed and investigated. The antenna geometry consists of a 45° rotated square slot and a circular parasitic patch situated at its center. In addition, the slot consists of four rectangular notches at every corner. It brings close the resonances of both slot and circular patches and enhances bandwidth. The antenna achieved the measured impedance bandwidth of 111.7% from 2.24 to 7.91 GHz, with almost stable pattern. Furthermore, a comprehensive parametric study has been carried out to prepare a set of guidelines to scale up or down the antenna for a specified impedance bandwidth (111.7%) between different frequency ranges. The frequency scaling feature has been verified by simulating a set of antennas for different frequency bands. The result demonstrates that all antennas under test yield almost equal impedance bandwidth.

C‐band high purity circularly polarized array with modified radial slots and electromagnetic band‐gap substrate configuration

AbstractNovel broadband circularly polarized (CP) electromagnetic band‐gap (EBG) antenna array was proposed in this paper. The antenna's radiating element is utilized by a microstrip‐fed circular patch, radial slot, and three rectangular notches. The proposed antenna elements are fed by feeding network comprised form four hybrid couplers and microstrip lines with appropriate lengths to support desired phase difference at output ports. Radiating patches are sequentially rotated to enhance CP property and form a 4 × 4 array. Finally, the novel scheme of electromagnetic structure (EBG) was inserted among radiating elements to decrease the mutual coupling. Using these structures results in the improvement of antenna bandwidth to cover the entire C‐band. In addition, CP purity is increased at the implicational band. Measured results indicate that the array has an impedance bandwidth of 4 GHz covering the C‐band totally and 3 dB axial‐ratio bandwidth of 2.6 GHz that is between 4.9 and 7.5 GHz (~42%). The antenna array has a peak gain of 8dBi at 6 GHz.

A Wideband Endfire Dual Circularly Polarized Antenna for 5G Millimeter-Wave Applications

In this letter, an all-metallized wideband dual circularly polarized antenna with endfire radiation is proposed for fifth-generation (5G) millimeter-wave applications. By introducing two rectangular notches on the side walls of open-ended waveguide, the vertical components are increased and close to the horizontal components in the broadband range so that the axial ratio (AR) bandwidth is enhanced. The simulated results show that the proposed antenna excited by wave port has 63.9% operation bandwidth (22.7–44.0 GHz), where reflection coefficients less than −10 dB, isolations greater than 20 dB, and AR less than 3 dB are achieved. To verify the design, the proposed antenna excited by coaxial connectors is fabricated and measured. Based on the measurement results, the reflection coefficients less than −10 dB, isolations greater than 20 dB, and AR less than 3 dB are achieved from 23.0–40.0 GHz, the endfire gain varies from 5.1 to 8.5 dBic at the frequencies mentioned above.

Realization of the skyrmionic logic gates and diodes in the same racetrack with enhanced and modified edges

Magnetic skyrmions are topological quasiparticles with nanoscale size and high mobility, which have potential applications in information storage and spintronic devices. Here, we computationally investigate the dynamics of isolated skyrmions in a ferromagnetic racetrack, where magnetic properties of the edges are enhanced and modified, forming a channel with lower magnetic anisotropy for skyrmion motion. It is found that the rectangular notch at the edge can have a pinning effect on the skyrmion and enrich the dynamics of the skyrmion. Based on the racetrack with modified edges and the notch, we design a racetrack that realizes the skyrmionic logic AND, OR, and NOT gates as well as the diode in the same magnetic racetrack. It is found that the driving current density could be much smaller than those used in previous designs of skyrmion-based logic gates. By slightly altering the shape of the racetrack, we also design the NAND and NOR gates. Finally, we study the feasibility of our design at finite temperatures. Our results may contribute to the design of nonvolatile spintronic devices with integrated multiple functions and ultra-low energy consumption.