Points Of Curve Research Articles

Digital-image based performance analysis of CFRP–concrete interface bond under anchorage

This study investigated the bonding performance of Carbon fiber reinforced polymer (CFRP)-reinforced concrete interface under anchorage. The effect of positive compressive stress on the bonding performance of the interface was analysed using a single-sided shear test of the interface. The strain distribution on the CFRP surface during interface debonding was obtained using digital image technology. The shear-stress transfer law of the CFRP-concrete interface under anchorage was analyzed, and the bond-slip curve of the interface was obtained. Results showed that the increase in interfacial compressive stress improves the interfacial bearing capacity and slip behavior. After the interfacial compressive stress increases to a certain extent, the maximum strain of the CFRP specimens does not change with the positive stress. The principal model of bond slip in the anchorage zone under the anchoring action of the compressive steel plate was obtained; the models were tested and found to be consistent with the test results. The analytical solutions of the characteristic points of the interfacial load-slip curve in the anchorage zone under positive pressure were compared with the experimental values to prove the reliability of the fitted bond–slip intrinsic model.

Isomorphism classes of cut loci for a cube

We prove that a face of a cube can be optimally partitioned into 193 connected sets on which the cut locus, or ridge tree, is constant up to isomorphism as a labeled graph. These are 60 connected open sets, curves bounding them, and intersection points of curves. Polynomial equations for the curves are given. Sixteen pairs of sets support the same cut locus class. We present the 177 distinct cut locus classes.

Research on multi-model prediction of skeleton curves of prefabricated concrete columns based on Residual fusion Long Short-Term Memory -Transformer

This study aims to investigate a deep learning-based model that permits quick evaluation of the seismic performance of prefabricated concrete columns under bidirectional seismic influences. To capture the time-series properties of the skeleton curves and simultaneously solve the difficulty of predicting the randomness of the initial points of the curves, two models, the fusion model ResMLP-LSTM-Transformer and the single ResMLP, are used to predict the skeleton curves for different concrete columns. For this objective, a skeleton curve dataset of 300 concrete columns with 14 physical properties of each column as input parameters and coordinates of each point of the skeleton curve as output was created. In addition, after utilizing 10-fold cross-validation and hyper-parameter tuning to the models, the predictions of each model were compared with curve results obtained from experiments and finite elements, and the accuracy of the predictions from each model was quantified using RMSE, MSE, MAE, MAPE, and R2. Finally, a thorough investigation was conducted into the impact of the ResMLP sequence length on the fusion model's accuracy. The results demonstrate that despite the diverse and variable physical characteristics of concrete columns, both the fusion model and ResMLP are capable of producing accurate predictions, with the fusion model having a better prediction performance. In addition, the evaluation indexes demonstrate that the fusion model's prediction error increases as ResMLP's sequence length increases, while the RMLT_3 model's prediction performance at a sequence length of three is optimal.

An area-efficient and low-latency elliptic curve scalar multiplication accelerator over prime field

For the elliptic curve cryptography (ECC) over prime field, this paper presents an area-efficient and low-latency elliptic curve scalar multiplication (ECSM) accelerator, which supports to process any prime number p ≤ 256 bits. The proposed accelerator is based on a parallel hardware implementation of iterative digit-digit Montgomery multiplication and an optimized data flow architecture for elliptic curve point operations. The proposed design is implemented in Xilinx Virtex-7 FPGA. The experimental results show that the proposed architecture occupies 23.7k look-up tables (LUTs) and performs single 256-bit scalar multiplication in 0.56 ms. The area-time product of the proposed architecture is only 13.36. Compared with other state-of-the-art ECSM implementations, the proposed architecture has obvious advantage in terms of the area-time product.

Analysis of drug of abuse compounds using passive sampling and ultrahigh-liquid chromatography coupled to mass spectrometry

The present study proposes the monitoring of compounds of drugs of abuse through the use of passive samplers in water systems. Initially, four positive ion compounds of interest were determined according to national surveys, and then composite sampling and passive sampling were implemented using continuous-flow passive samplers containing two types of sorbents, the Empore disk and Gerstel Twister. Two study sites were established at the beginning and at the end of the middle Bogotá River basin. After 4 days, the sorbents were removed so that they could be desorbed and analyzed using UHPLC–MS in the laboratory. For the composite samples, the results were below the first calibration curve point (FCCP) of the chromatographic method, and for passive sampling, peaks of benzoylecgonine (BE) (21427.3 pg mL−1), methamphetamine (MET) (67101.5 pg mL−1), MDMA (ecstasy) (225844.8 pg mL−1) and 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) (15908.4 pg mL−1) were found. Therefore, passive sampling could be suggested as an alternative to composite sampling for the monitoring of compounds.

Investigation of time-dependent gate dielectric breakdown in recessed E-mode GaN MIS-HEMTs using ferroelectric charge trap gate stack (FEG-HEMT)

The aim of achieving E-mode operations has led to the proposal of novel hybrid ferroelectric charge trap gate stack schemes. These schemes involve utilizing a combination of the charge trapping layer (CTL) and the ferroelectric laminated layer to positively shift the threshold voltage to a normally-off margin after initializing the gate pulse, thus achieving the Enhancement-mode (E-mode) characteristic. This study focuses on the forward gate bias time-dependent dielectric breakdown (TDDB) gate reliability in the E-Mode GaN MIS-HEMTs using ferroelectric charge trap gate stack (FEG-HEMT) with and without recess and investigates the impact of temperature on TDDB. The gate voltages required for operation with a 1 % failure rate over a 10-year period are 12.95 V and 10.22 V at 25 °C and 150 °C for both samples, respectively. Also, the examination of the stability of the recessed process by calculating the activation energies (0.7 eV) of both samples are demonstrated. The article also investigates the relationship between long-term reliability and short-term initialization by examining the transition point of the time-dependent failure curve.

An Optimized Flexible Accelerator for Elliptic Curve Point Multiplication over NIST Binary Fields

This article proposes a flexible hardware accelerator optimized from a throughput and area point of view for the computationally intensive part of elliptic curve cryptography. The target binary fields, defined by the National Institute of Standards and Technology, are GF(2163), GF(2233), GF(2283), GF(2409), and GF(2571). For the optimization of throughput, the proposed accelerator employs a digit-parallel multiplier. The size of the digit is 41 bits. The proposed accelerator has reused the multiplication and squaring circuit for area optimization to compute modular inversions. Flexibility is included using three additional buffers on top of the proposed accelerator architecture to load different input parameters. Finally, a dedicated controller is used to optimize control signal handling. The architecture is modeled using Verilog and implemented up to the post-place-and-route level on a Xilinx Virtex-7 field-programmable gate array. The area utilization of our accelerator in slices is 1479, 1998, 2573, 3271, and 4469 for m=163 to 571. The time needed to perform one-point multiplication is 7.15, 10.60, 13.26, 20.96, and 30.42 μs. Similarly, the throughput over area figures for the same key lengths are 94.56, 47.21, 29.30, 14.58, and 7.35. Consequently, achieved results and a comprehensive performance comparison show the suitability of the proposed design for constrained environments that demand throughput/area-efficient implementations.

A comparison of methods for the calculation of all the key points of the PV single-diode model including a new algorithm for the maximum power point

In this paper we describe and compare the methods for the calculation of all the key points of the photovoltaic single-diode model. These include the short-circuit point, the open-circuit point, the maximum power point, the mean slope point, the maximum curvature point, and the jerk point. The main contribution of this paper is a new algorithm to obtain the maximum power point which is based on reducing its computation to solve a single-variable equation. Its unique solution leads to an explicit expression of the point by using a recent parametrization of the single-diode model current–voltage curve. In the numerical resolution of the previous equation, we will use as starting point the mean slope point which has been proved to be close to the maximum power point. Previously, we will provide for the first time in the literature an exact and explicit expression of the mean slope point. The new algorithm proposed reaches the accuracy of the best known numerical methods, but it is much faster, almost reaching the execution times of explicit formulas.

Dew point of the methane-ethanol system: Data via acoustic technique and modeling via CPA EoS

The use of gas-lift systems for chemical injection presents a smart solution in numerous cases, particularly when production wells are already equipped with such systems. However, ensuring optimal operating conditions demands a thorough understanding of the phase equilibria curves of natural gas - inhibitor mixtures. The primary objective of this study is to experimentally determine the dew point curve of the methane - ethanol mixture, with methane being a significant constituent of natural gases, and ethanol being one of the most widely utilized gas hydrate inhibitors. The experiments covered temperatures within the range of 313.15–353.15 K and pressures ranging from 1.2 MPa to 8.5 MPa. Both visual and acoustic techniques were applied as synthetic methods to obtain accurate data. Additionally, a thermodynamic model employing the Cubic-Plus-Association (CPA) equation of state, fine-tuned with the experimental bubble and dew point data, was utilized to establish the dew point curve under optimized conditions. An average absolute relative deviation of 4.4% was obtained between the experimental dew points obtained in this work and the thermodynamic model. Moreover, this study fills a noticeable gap in the literature by providing reliable experimental data, which had been scarce. Furthermore, the acoustic experimental technique showcased in this work presents a feasible option for determining dew points. By gaining deeper insights into the behavior of the methane - ethanol mixture, this research contributes to the enhancement of gas-lift systems' efficiency and reliability in chemical injection applications. The findings are expected to have a positive impact on flow assurance strategies and ensure safer and more efficient operations in oil and gas production.

AC-Faster R-CNN: an improved detection architecture with high precision and sensitivity for abnormality in spine x-ray images.

Objective.In clinical medicine, localization and identification of disease on spinal radiographs are difficult and require a high level of expertise in the radiological discipline and extensive clinical experience. The model based on deep learning acquires certain disease recognition abilities through continuous training, thereby assisting clinical physicians in disease diagnosis. This study aims to develop an object detection network that accurately locates and classifies the abnormal parts in spinal x-ray photographs.Approach.This study proposes a deep learning-based automated multi-disease detection architecture called Abnormality Capture-Faster Region-based Convolutional Neural Network (AC-Faster R-CNN), which develops the feature fusion structure Deformable Convolution Feature Pyramid Network and the abnormality capture structure Abnormality Capture Head. Through the combination of dilated and deformable convolutions, the model better captures the multi-scale information of lesions. To further improve the detection performance, the contrast enhancement algorithm Contrast Limited Adaptive Histogram Equalization is used for image preprocessing.Main results.The proposed model is extensively evaluated on a testing set containing 1007 spine x-ray images and the experimental results show that the AC-Faster R-CNN architecture outperforms the baseline model and other advanced detection architectures. The mean Average Precision at Intersection over Union of 50% are 39.8%, the Precision and Sensitivity at the optimal cutoff point of Precision-Recall curve are 48.6% and 46.3%, respectively, reaching the current state-of-the-art detection level.Significance.AC-Faster R-CNN exhibits high precision and sensitivity in abnormality detection tasks of spinal x-ray images, and effectively locates and identifies abnormal areas. Additionally, this study would provide reference and comparison for the further development of medical automatic detection.

Analysis and Optimized Design of Rigid–Flexible Coupling Characteristics of Crab Apple Picking Machines and Crab Apple Trees

In recent years, with the gradual expansion of the planting area for Chinese crab apple trees, the traditional method of picking crab apples has become inadequate due to its large workload, low efficiency, and high cost. To address this issue, this paper presents the design of a trunk-type vibration picker specifically for crab apple picking. The design process began with a modal analysis and a harmonic response analysis of a crab apple tree using Ansys Workbench. Through these analyses, the optimal excitation frequency for the crab apple tree was determined to be 12.7 Hz. Subsequently, the picker was designed, and its key components underwent modal and stress analyses. A comparison revealed no resonance between the picker and the key components, ensuring the feasibility of the picker. To further evaluate the performance of the picker, a rigid–flexible coupling analysis was conducted using Adams. This analysis determined the acceleration response curves of the lateral branch points of the crab apple tree at various excitation frequencies: 9.7 Hz, 12.7 Hz, 15.7 Hz, and 18.7 Hz. Finally, field trials were carried out to validate the reliability of the data obtained from Adams. The results showed that the lateral branch point acceleration increased with higher excitation frequencies. However, when the optimal excitation frequency of 12.7 Hz was reached, the lateral branch point acceleration decreased. This indicated that the most effective vibration frequency for picking crab apples was 12.7 Hz.

Partition of the space of planar quintic Pythagorean-hodograph curves

The quintics are the lowest–order planar Pythagorean–hodograph (PH) curves suitable for free–form design, since they can exhibit inflections. A quintic PH curve r(t) may be constructed from a complex quadratic pre–image polynomial w(t) by integration of r′(t)=w2(t), and it thus incorporates (modulo translations) six real parameters — the real and imaginary parts of the coefficients of w(t). Within this 6–dimensional space of planar PH quintics, a 5–dimensional hypersurface separates the inflectional and non–inflectional curves. Points of the hypersurface identify exceptional curves that possess a tangent–continuous point of infinite curvature, corresponding to the fact that the parabolic locus specified by the quadratic pre–image polynomial w(t) passes through the origin of the complex plane. Correspondingly, extreme curvatures and tight loops on r(t) are incurred by a close proximity of w(t) to the origin of the complex plane. These observations provide useful insight into the disparate shapes of the four distinct PH quintic solutions to the first–order Hermite interpolation problem.

MATHEMATICAL MODELLING AND OPTIMIZATION OF POLY-CRYSTALLINE PHOTOVOLTAIC MODULE

This work proposes modeling and optimization of poly-crystalline photovoltaic (PV) modules, validated with experiment, using single diode (SDM) and double diode model(DDM). The PV cell is treated as an equivalent electrical circuit with series and shunt resistance. The weather data like temperature and irradiance are used as input variables. The operating current and maximum power point are obtained using three variables: current, voltage, and power. An experiment was set up in Nagpur city, on the Deccan plateau situated in central India. This place is suited for PV installation due to the high average solar insolation period throughout the year. The outputs of the PV model are optimized using a genetic algorithm (GA) and simulated annealing (SA) algorithm and validated against the experiments with variable load conditions. The metaheuristics optimization techniques worked well for this model and improved the accuracy and precision of the current-voltage (I-V) and power voltage (P-V) curves. The present work compares the errors of the SA and GA algorithms used for extracting the five key points of (I -V) curves using the normalized sum of squared errors (NSSE). The proposed model optimization results are in close agreement with experimental results.

Elliptic Curve Implementation and its Applications: A Review

Encryption is regarded as essential within the safety measures used to protect data via unsafe transport methods. Elliptic Curve encryption (ECC), one of the several asymmetric encryption algorithms currently in use, has become popular because of its high level of security and small key sizes. In contrast to Rivest, Shamir and Adleman (RSA), for instance, ECC can keep security levels at a certain level with a smaller key. The primary purpose of ECC is elliptic curve point multiply (ECPM), which also has the largest hardware cost. Numerous hardware applications have been made to accelerate the calculus of the ECPM. This paper discusses the idea behind the cryptography of elliptic curves (ECC's) and the benefits it quicker, moreover believed way of encoding as compared to the RSA public_key encryption techniques that are currently used as standards. ECC's specifications encompass all relevant asymmetry cryptography elements, including electronic signatures & key negotiation processes. The scalar multiplication Key Point (K.P) function, which is the fundamental operation of ECCs, is utilized to accomplish this objective. Where P is a value and k represents an integer and is exists on an elliptic curve. This article explains how ECC contributes to system safety and applications of it in the field of security

An analytical method for the meshing performance of deviation surface of spiral bevel gear based on a one-dimensional probe

The meshing performance is a significant indicator for evaluating the machining quality of spiral bevel gear. The flank contact accuracy (FCA) and flank geometric accuracy (FGA) are important aspects of meshing performance, and both are indispensable. In the actual production process, due to the lack of professional meshing performance analysis (MPA) software, the flank geometric structure cannot be reflected based on the FCA, and the actual meshing state cannot be reflected by the FGA, which cannot meet the manufacturing requirements of high-quality gear. Therefore, a MPA method for deviation surface of spiral bevel gear is proposed based on the gear measuring center using a one-dimensional probe. By constructing the deviation surface, the flank meshing model is established, and the meshing parameters are determined. Aiming at the complexity of solving the meshing model, a method for decreasing the dimension of the meshing equations is proposed by establishing the mathematical relationship between the rotation angle and the normal vector, which improves the solution accuracy of the meshing point. The intersection points of the adjacent transmission error curves are taken as the meshing in and out points, and then the actual position of the contact pattern is accurately determined. The instantaneous contact ellipse is obtained by using the method of a cylindrical surface intercepting the deviation surfaces, which not only simplifies the solution algorithm, but also obtains the contact pattern more in line with the actual situation. Finally, the transmission error and contact pattern are digitally characterized. The experimental results show that the digital and actual patterns have good consistency. Flank geometry and gear meshing are organically linked based on the proposed method, and the actual meshing state can be predicted according to the flank topology deviation, which provides important theoretical support for the improvement of the machining quality and meshing performance of the spiral bevel gear.

Studying the effect of seasonal changes on the infrared radiation properties of the ground target using multi-physics simulation

The infrared radiation properties of ground targets are influenced by the surrounding environment, solar radiation and climate. Typically, the target and its environment exhibit different temperature distributions due to different thermodynamic characteristics. Coupled multi-physics field simulation methodare is used, and the infrared radiation characteristics of ground target is investigated under different seasons based on thermodynamics and computational fluid dynamics. The temperature contour plots are observed to find that the temperature distributions of the ground target and its background are closely related to the seasons. The temperature variation curves of different monitoring points are compared to obtain the temperature of the ground target with respect to ambient temperature, structures, materials and solar altitude angle.

A probabilistic framework for fatigue damage of lift based wave energy converters

Wave cycloidal rotors are lift based wave energy devices that have shown great potential to harness the energy of the waves through the use of submerged hydrofoils. Although the lift force of the foils can be controlled passively or actively to maximise power extraction, the foils of the rotor are subject to variable loading which can expose these components to premature mechanical failure. Therefore, it is important to develop novel fatigue analysis tools that help predicting the lifetime of this type of lift based devices. In this paper, we test the hypothesis that when cyclorotor operates at constant rotational velocity in irregular waves, the fatigue damage of the hydrofoil stress hot spot can be computed through a probabilistic approach. We compare our results to the fatigue damage computed with well established deterministic methods. We find that for both narrow and broad band stress energy spectra, the probabilistic method works well at high probability sea states, when the range of stresses does not exceed the inflection point of a double slope SN curve. This is a promising outlook since it confirms that the fatigue damage of these versatile lift based wave devices can be treated in a similar fashion to the fatigue damage of conventional offshore structures.

Learning curve of tibial cortex transverse transport: a cumulative sum analysis

ObjectiveThis study aimed to describe the learning curve of surgeons performing tibial cortex transverse transport (TTT) and explore its safety and effectiveness during the initial stages of surgeon’s learning.MethodsThe clinical data of patients with diabetic foot ulcers classified as Wagner grade ≥ 2, who underwent TTT at our hospital from January 2020 to July 2021, were included in this retrospective analysis. The same physician performed all procedures. Patients were numbered according to the chronological order of their surgery dates. The cumulative sum and piecewise linear regression were used to evaluate the surgeon's learning curve, identify the cut-off point, and divide the patients into learning and mastery groups. A minimum follow-up period of 3 months was ensured for all patients. Baseline data, perioperative parameters, complications, and efficacy evaluation indicators were recorded and compared between the two groups.ResultsSixty patients were included in this study based on the inclusion and exclusion criteria. After completing 20 TTT surgeries, the surgeon reached the cut-off point of the learning curve. Compared to the learning group, the mastery group demonstrated a significant reduction in the average duration of the surgical procedure (34.88 min vs. 54.20 min, P < 0.05) along with a notable decrease in intraoperative fluoroscopy (9.75 times vs. 16.9 times, P < 0.05) frequency, while no significant difference was found regarding intraoperative blood loss (P = 0.318). Of the patients, seven (11.7%) experienced complications, with three (15%) and four cases (10%) occurring during the learning phase and the mastery phase, respectively. The postoperative ulcer area was significantly reduced, and the overall healing rate was 94.8%. Significant improvements were observed in postoperative VAS, ABI, and WIFI classification (P < 0.05). There were no significant differences in the occurrence of complications or efficacy indicators between the learning and mastery groups (P > 0.05).ConclusionSurgeons can master TTT after completing approximately 20 procedures. TTT is easy, secure, and highly efficient for treating foot ulcers. Furthermore, TTT’s application by surgeons can achieve almost consistent clinical outcomes in the initial implementation stages, comparable to the mastery phase.

Failure characterization by pull-out test on structural inserts in sandwich panels used in the aerospace industry applying neutron imaging

In the present work, the failure of the inserts potted on the structural sandwich panel used in satellites was analysed. Inserts were tested by pull-out test to evaluate the strength of the joint between the potting mass and the sandwich panel. Neutron experiments were performed in NECTAR, the thermal neutron imaging facility at FRM II. Two series of specimens with dimensions of 10x10x2.5 cm3 and 5x5x2.5 cm3 were tested by applying different normal loads to detect singular points in the load-displacement curves. Images were acquired using thermal neutrons and filtering the beam obtaining images formed by gamma rays and epithermal neutrons. The filter was formed by a cadmiun (Cd) layer on the neutron beam. The results determined the usefulness of this characterization technique to analyse the dynamics failure of the insert union by the use of in-situ experiments in future studies.

Constructing geometrical models of spherical analogs of the involute of a circle and cycloid

The common properties of images on a plane and a sphere are considered in the scientific works by scientists-designers of spherical mechanisms. This is due to the fact that the plane and the sphere share common geometric parameters. They include constancy at all points of the Gaussian curve, which has a zero value for a plane and a positive value for a sphere. Figures belonging to them can slide freely on both surfaces. With unlimited growth of the radius of the sphere, its limited section approaches the plane, and the spherical shape transforms into a plane. Thus, a loxodrome that crosses all meridians at a constant angle is transformed into a logarithmic spiral that intersects at a constant angle the radius vectors that come from the pole. The tooth profile of cylindrical gears is outlined by the involute of a circle. A spherical involute is used for the corresponding bevel gears. Other spherical curves are also known, which are analogs of flat ones. The formation of a cycloid and an involute of a circle are associated with the mutual rolling of a line segment with each of these figures. If the segment is fixed and the circle rolls along it, then the point of the circle describes the cycloid. In the case of a stationary circle along which a segment is rolled, the point of the segment will execute the involute. To move to the spherical analogs of these curves, it is necessary to replace the circle with a cone, and the straight line with a plane. The spherical prototype of the cycloid will be the trajectory of the point of the base of the cone, which rolls along the plane, that is, along the sweep of the cone. The sweep of a cone is a sector, the radius of the limiting circle of which is equal to the generating cone. If this sweep, like a section of a plane, is rolled around a fixed cone, when its top coincides with the center of the sector, then the point of the limiting radius of the sector will execute a spherical involute. This paper analytically implements these two motions and reports the parametric equations of the spherical analogs of the circle involute and the cycloid