Two-dimensional Curves Research Articles

Multidimensional Seismic Fragility Study of Intake Towers Based on Incremental Dynamic Analysis

Assessing the fragility of intake towers using a single damage index does not allow for accurate evaluation of the potential for structural damage under seismic conditions. In this study, based on the probabilistic seismic demand analysis method, the effects of ground motion intensity on maximum displacement, local damage index, and global damage index are considered, and the seismic fragility of an intake tower structure is analyzed. First, 10 natural ground motion records were selected from the ground motion database (PEER) and 2 artificial seismic waves were synthesized. These seismic waves were amplitude-modulated for incremental dynamic analysis (IDA). The trends of the IDA curves were analyzed to divide the performance levels of the intake tower structure. Furthermore, a two-dimensional fragility curve for the intake tower structure was plotted in this study. The maximum displacement in the direction of parallel flow and the damage index were taken into account in the two-dimensional fragility curve. The results show that, under the designed seismic acceleration, the two-dimensional fragility curve for the intake tower structure was lower than the one-dimensional curve. This indicates that the seismic design based on the one-dimensional performance index was unstable. This provides a theoretical reference for seismic optimization design and the strengthening of intake towers. Therefore, it is recommended to use multidimensional fragility analysis to study the seismic performance of intake tower structures in seismic design.

Exploring Innovative Methods in Maritime Simulation: A Ship Path Planning System Utilizing Virtual Reality and Numerical Simulation

In addressing the high costs, inefficiencies, and limitations of purely digital simulations in maritime trials for unmanned vessel path planning, this paper introduces a ship virtual path planning simulation test system. This system, unbound by temporal and spatial constraints, vividly showcases the navigational performance of vessels. After analyzing the virtual testing requirements for the autonomous navigation performance of unmanned surface vehicles (USVs), we established the overall framework of this system. Data-driven by a numerical simulation platform, the system achieves synchronized operation between physical and virtual platforms and supports interactive path planning simulations between USVs and the virtual testing system. Furthermore, to address the limitations of traditional ship trajectory planning evaluation, this paper develops a global path planning fitness evaluation function that comprehensively considers trajectory safety, navigation distance, and vessel stability, achieving optimal comprehensive routes through the particle swarm optimization algorithm. Test results indicate an average roll reduction of 14.31% in the planned routes, with a slight increase in navigation distance. By integrating two-dimensional curve simulation with three-dimensional visualization, this paper not only overcomes the limitations of purely physical and purely virtual simulations but also enhances the overall credibility and intuitiveness of the simulation. Experimental results validate the system’s effectiveness, providing a novel method for autonomous navigation testing and evaluation of USVs.

Accuracy compensation method for 2D curve reconstruction of torsional FBG shape sensor of scraper conveyor

The straightness perception of scraper conveyor is a technology that helps to achieve intelligent operation of coal mine working faces. However, there is a problem of accuracy degradation caused by sensor torsion based on fiber Bragg grating (FBG) shape sensing technology. This paper proposes an accuracy compensation method based on torsion angle, and verifies the effectiveness of accuracy compensation through simulation and experimental research. Experimental tests have shown that when the torsion angle of the sensing substrate is 10° and 20°, the end accuracy of the reconstructed curve after accuracy compensation is increased by 2.77% and 1.93% compared to before compensation, respectively. This study indicates that compensation based on the torsion angle can significantly improve the accuracy of two-dimensional (2D) curve reconstruction, and it has broad engineering application prospects in fields such as straightness perception of scraper conveyors and monitoring of underwater pipelines.

Design of a three-frequency Rayleigh lidar for simultaneous temperature and wind measurements

This study proposes what we believe to be a novel high-spectral-resolution three-frequency Rayleigh lidar for simultaneously measuring middle atmosphere temperature and wind. The temperature and wind could be retrieved without assuming an external reference temperature, as typical for a traditional Rayleigh Doppler lidar. Adopting a similar idea used in sodium temperature/wind lidar, this system alternatively emits laser pulses at three frequencies. It receives the corresponding Rayleigh backscattered signals filtered by an iodine cell as a frequency discriminator. The three frequencies are optimized based on the spectral characteristics resulting from the convolution of the pulse laser lineshape convolved Rayleigh scattering signal with iodine molecular absorption spectrum. A two-dimensional calibration curve for temperature and wind ratio is then generated from the theoretical calculation of the final convoluted spectra and used to retrieve temperature and wind simultaneously. Simulated with the return signals collected by a current broadband Rayleigh lidar (30-inch telescope and 15 W output laser power), the temperature and wind uncertainties with resolutions of 1 km and 1 hr are estimated to be 0.4 K and 0.35 m/s, respectively, at 30 km and increase to 16.3 K and 8.1 m/s at 70 km.

A three-dimensional extension of the slope chain code: analyzing the tortuosity of the flagellar beat of human sperm

In the realm of 3D image processing, accurately representing the geometric nuances of line curves is crucial. Building upon the foundation set by the slope chain code, which adeptly represents intricate two-dimensional curves using an array capturing the exterior angles at each vertex, this study introduces an innovative 3D encoding method tailored for polygonal curves. This 3D encoding employs parallel slope and torsion chains, ensuring invariance to common transformations like translations, rotations, and uniform scaling, while also demonstrating robustness against mirror imaging and variable starting points. A hallmark feature of this method is its ability to compute tortuosity, a descriptor of curve complexity or winding nature. By applying this technique to biomedical engineering, we delved into the flagellar beat patterns of human sperm. These insights underscore the versatility of our 3D encoding across diverse computer vision applications.

Fretting wear behaviour of high strength alloy steel induced by plasma nitriding and post-oxidation

Fretting wear is caused by a relative movement of the material surface on a small scale. Finding ways to reduce fretting wear is of great importance for extending equipment life and reducing maintenance costs. With the increase of load, the effecrt of fretting wear adhesion of surface treated material becomes more obvious. The materials treated with post-oxidation have stronger wear adhesion than those treated only with plasma nitriding, but the total wear volume is reduced. In this paper, the fretting wear of high strength steel alloy with different surface treatments is simulated by the finite element method. The coefficient of friction and wear volume can be obtained from the experimental results, and the wear coefficient is calculated using the wear energy model. The predicted two-dimensional wear profile curves (U-shape and W-shape wear profiles) under different wear conditions are compared with the experimental results. The W-shape wear profile is used to describe the adhesion state of the worn surface. In addition, the surface deformation and mechanical properties of U-shape and W-shape wear profiles are analysed. The simulation results show that double-sided wear and the addition of adhesive layer is important for the prediction of wear characteristics.

Practical fracture limit function considering data flexibility under plane-stress conditions in Lagrangian formulation

Ductile fracture limits have been extensively studied from the perspectives of material science and mechanics. While these studies have provided scientifically significant insights into ductile fracture limits, the influence of the evolution of anisotropy observed in actual experimental data suggests a need to account for diversity in the experimental data. To address this, it may be possible to further develop the model by investigating more influences from the field of materials science. However, from an engineering perspective, it can be effective to represent the diversity of acquired experimental data as practical functions for use, rather than solely focusing on the material science aspect. This paper presents mathematical formulations representing the strain- and stress-based fracture limit surfaces of ductile materials, to consider diverse data set for the evolution of anisotropy, under plane-stress conditions within the framework of the Lagrangian formulation. The model introduces a strain-based fracture limit surface (FLS), which has an additional anisotropic profile function based on the commonly used two-dimensional strain-based fracture limit curve (FLC). The anisotropic profile function is capable of capturing the evolving anisotropic profile based on the deformation mode and principal loading direction to represent more flexible shapes. With this function, a three-dimensional strain-based FLS, which can present the variation in fracture strains in the space of the deformation mode and principal loading direction, can be constructed. Then, the proposed model transformed this strain-based FLS into a stress-based FLS by converting the presented state vector in the former into the corresponding vector in the latter in the Lagrangian formulation. To achieve this, this study developed a formulation that considers the nonlinear evolution of stress anisotropy independent of the strain anisotropy during stress evolution. The two proposed models were validated by experimental results on a dual-phase steel. These models provide flexible fracture limit functions for ductile materials under varying stress and strain conditions in engineering applications.

Anomaly Identification for Photovoltaic Power Stations Using a Dual Classification System and Gramian Angular Field Visualization

With the increasing scale of photovoltaic (PV) power stations, timely anomaly detection through analyzing the PV output power curve is crucial. However, overlooking the impact of external factors on the expected power output would lead to inaccurate identification of PV station anomalies. This study focuses on the discrepancy between measured and expected PV power generation values, using a dual classification system. The system leverages two-dimensional Gramian angular field (GAF) data and curve features extracted from one-dimensional time series, along with attention weights from a CNN network. This approach effectively classifies anomalies, including normal operation, aging pollution, and arc faults, achieving an overall classification accuracy of 95.83%.

Investigation of LAS-based fatigue evaluation methods for high-viscosity modified asphalt binders with high-content polymers

The objective of this paper is to investigate the microstructure of high-viscosity modified asphalt binder (HVA) containing high-content polymers and its effect on fatigue performance, as well as the applicability of different analytical methods and failure criteria of linear amplitude sweep (LAS) test to HVA. In this paper, two types of HVAs with different polymer contents, a commercial HVA, a conventional polymer-modified asphalt binder, and a base asphalt binder were first prepared or selected. Fluorescence microscopy tests, time sweep tests, and LAS fatigue tests were then performed on these binders. Finally, the fatigue properties of the different binders were analyzed in depth using different analytical methods and failure criteria. The results show that the polymers in HVA crosslink with each other to form a strong cross-linking structure, and the phase inversion of the polymers renders them into a continuous phase, which significantly improves the fatigue damage resistance of the HVA; moreover, the evolutions of stress with shear strain for the fatigue process of HVAs is related to the polymer network. Besides, the two-dimensional damage characteristic curve (DCC) cannot accurately reflect the evolution of the fatigue performance of HVA, and this paper suggests the use of a three-dimensional DCC curve with strain information. Furthermore, the 35% reduction in C0 in the dissipative energy method is not a suitable failure criterion, a more accurate fatigue performance ranking can be obtained by using the yield stress as the failure criterion. Although the fatigue resistance of HVA after yield stress is theoretically considered using the pseudo-strain energy approach, HVA does not show a peak of stored pseudo-strain energy even when the strain is increased to 60% in the LAS test. Therefore, the maximum strain value (30%) in the standard LAS test is not sufficient in characterizing high-polymer HVAs because there is not enough fatigue accumulation of HVAs in this range, consequently, the maximum shear strain parameter in the LAS experiment needs to be reconsidered.

Optimization of Dualistic Reservoir System Two-Dimensional Rule Curve with Three Allocation Rules

A two-dimensional operation chart is commonly used to manage the operation of a dual-reservoir system, where the water storage in each reservoir is accurately considered in the water-supply decision. The dual reservoir chart should be combined with one allocation rule to better represent water supply distribution between reservoirs. In this study, the 2D rule curve was coupled with three allocation rules: variable allocation ratios, fixed allocation ratios, and compensation regulation, to identify the efficiency of using these rules with the 2D rule curve in operating the dual reservoirs. Mosul-Dukan dual reservoirs in Iraq were implemented as a study area using monthly data extended from 2001 to 2020. The Shuffled Complex Evolution Algorithm was used to optimize the water allocation ratios. The results revealed that the variable allocation ratios were superior to the other two rules in terms of water deficit, in which the total water shortage of the variable allocation ratios rule was 56590 Mm3. The total shortage was less than that obtained by the fixed allocation ratio and compensation regulation rules by 0.9% and 56%, respectively. Finally, the variable allocation ratio was more suitable for application with a 2D reservoir rule curve than the two remaining rules (fixed allocation ratio and compensation regulation rules). The variable allocation ratios sustainably manage reservoirs in the regions that suffer from water scarcity and represent the most vulnerable to the impact of climate change. Doi: 10.28991/CEJ-2024-010-02-04 Full Text: PDF

Gas concentration monitoring based on the two-dimensional reflection intensity curve of Bloch surface wave

Proposed is a gas concentration monitoring method that is based on the dispersion of Bloch surface wave. Different from the conventional sensing method using a single parameter such as wavelength or angle, all measured data was fully analyzed from a two-dimensional reflection intensity curve of a Bloch surface wave by mutual reflection intensity, which can reflect changes in either the refractive index or the airflow motion. This method does not require recording specific wavelength or incidence angles and measurement of small wavelengths or angle deviations. Our airflow monitoring device has a detection limit of 1.14 × 10−4RIU and good linearity in an open environment with high noise levels. However, in a closed environment, we achieved stable monitoring of the dry ice sublimation process and prediction.

Earthquake Economic Loss Assessment of Reinforced Concrete Structures Using Multiple Response Variables

For buildings that meet the requirements of current seismic design codes, damage to nonstructural components and the internal objects of buildings often become the main source of the seismic economic losses of these buildings. However, the current specifications only consider the safety of ‘no collapse under strong earthquake’ and do not consider ‘functional recoverability’. In this paper, a six-story frame building was taken as an example. Four joint performance limit states were proposed, as per FEMA 273, to establish a two-dimensional probabilistic seismic demand model that considers parameter correlations. The limit state function was established, and the two-dimensional seismic vulnerability curve was calculated. The seismic intensity–economic loss curve and the annual average economic loss established by one-dimensional and two-dimensional seismic vulnerability curves were compared. The results showed that the seismic performance of the structure was lower than expected when using only a one-dimensional seismic vulnerability curve. However, the situation was more serious under high-intensity earthquake and high-performance levels.

Derivation of Optimal Two Dimensional Rule Curve for Dualistic Reservoir Water-Supply System

In arid and semi-arid regions particularly vulnerable to climate change, optimizing the long-term operation of multi-purpose reservoirs is paramount. This study derived an optimum two-dimensional rule curve to jointly operate the parallel reservoirs of Mosul and Dukan, Northern Iraq. A hybridized optimization technique combining conventional dynamic programming with the shuffled complex evolution algorithm (SCE-UA) was developed to solve this problem. The results showed that the proportion of normal water supply areas increased from the beginning of the flood season (October) to its highest levels in April (58.77% of the total water supply area). The proportion decreased to its lowest in September (25.04% of the total water supply area). The newly derived 2D rule cure was compared with the current operation policy and was found to optimize the amount of water shortage by 21.1% during the operational period. It also reduced the shortage period and avoided catastrophic water shortages during droughts. In addition, the developed model optimized the amounts of water more than the joint water requirements, suffering from a significant deficit in meeting the demand during some months of the operational years. As a result, the storage in each reservoir was improved and thence can be adapted to face water shortages during future climate changes. This study proved the new hybridized model's applicability and can serve as a tool for sustainable water management. Doi: 10.28991/CEJ-2023-09-07-016 Full Text: PDF

Retention Time Trajectory Matching for Peak Identification in Chromatographic Analysis.

Retention time drift caused by fluctuations in physical factors such as temperature ramping rate and carrier gas flow rate is ubiquitous in chromatographic measurements. Proper peak matching and identification across different chromatograms is critical prior to any subsequent analysis but is challenging without using mass spectrometry. The purpose of this work was to describe and validate a peak matching and identification method called retention time trajectory (RTT) matching that can be used in targeted analyses free of mass spectrometry. This method uses chromatographic retention times as the only input and identifies peaks associated with any subset of a predefined set of target compounds. An RTT is a two-dimensional (2D) curve formed uniquely by the retention times of the chromatographic peaks. The RTTs obtained from the chromatogram of a sample under test and those pre-installed in a library are matched and statistically compared. The best matched pair implies identification. Unlike most existing peak-alignment methods, no mathematical warping or transformation is involved. Based on the experimentally characterized RTT, an RTT hybridization method was also developed to rapidly generate more RTTs and expand the library without performing actual time-consuming chromatographic measurements, which enables successful peak matching even for chromatograms with severe retention time drifts. Additionally, 3.15 × 105 tests using experimentally obtained gas chromatograms and 2 × 1012 tests using two publicly available fruit metabolomics datasets validated the proposed method, demonstrating real-time peak/interferent identification.

On the Wave Structures to the (3+1)-Dimensional Boiti–Leon–Manna–Pempinelli Equation in Incompressible Fluid

In the present study, two effective methods, the Exp-function method and He’s frequency formulation, are employed to investigate the dynamic behaviors of the (3+1)-dimensional Boiti–Leon–Manna–Pempinelli equation, which is used widely to describe the incompressible fluid. A variety of the wave structures, including the dark wave, bright-dark wave and periodic wave solutions, are successfully constructed. Compared with the results attained by the methods, the obtained solutions are all new and have not been presented in the other literature. The diverse wave structures of the solutions are presented through numerical results in the form of three-dimensional plots and two-dimensional curves. It reveals that the proposed methods are powerful and straightforward, which are expected to be helpful for the study of travelling-wave theory in fluid.

Gap Detection in Pairs of Ultrasound Mid-air Vibrotactile Stimuli

Ultrasound mid-air haptic (UMH) devices are a novel tool for haptic feedback, capable of providing localized vibrotactile stimuli to users at a distance. UMH applications largely rely on generating tactile shape outlines on the users’ skin. Here we investigate how to achieve sensations of continuity or gaps within such two-dimensional curves by studying the perception of pairs of amplitude-modulated focused ultrasound stimuli. On the one hand, we aim to investigate perceptual effects that may arise from providing simultaneous UMH stimuli. On the other hand, we wish to provide perception-based rendering guidelines for generating continuous or discontinuous sensations of tactile shapes. Finally, we hope to contribute toward a measure of the perceptually achievable resolution of UMH interfaces. We performed a user study to identify how far apart two focal points need to be to elicit a perceptual experience of two distinct stimuli separated by a gap. Mean gap detection thresholds were found at 32.3-mm spacing between focal points, but a high within- and between-subject variability was observed. Pairs spaced below 15 mm were consistently (>95%) perceived as a single stimulus, while pairs spaced 45 mm apart were consistently (84%) perceived as two separate stimuli. To investigate the observed variability, we resort to acoustic simulations of the resulting pressure fields. These show a non-linear evolution of actual peak pressure spacing as a function of nominal focal point spacing. Beyond an initial threshold in spacing (between 15 and 18 mm), which we believe to be related to the perceived size of a focal point, the probability of detecting a gap between focal points appears to linearly increase with spacing. Our work highlights physical interactions and perceptual effects to consider when designing or investigating the perception of UMH shapes.

Visualization method for multidimentional random processes

The article proposes a method for visualizing multidimensional random process realizations using the example of the concentrations of harmful gases emitted into the atmosphere from a thermal power plant. The method is based on the transformation of gas concentration values in one point of multidimensional space at the same time into a two-dimensional curve, which is described by the sum of products of normalized concentrations by orthogonal Legendre functions of the corresponding order. The combination of such curves on a two-dimensional plane at discrete times creates a characteristic image that can be used to visually detect features of gas concentrations over time by a human operator.

FEATURES OF THE IMPLEMENTATION OF THE SPEAKER IDENTIFICATION SOFTWARE SYSTEM

The proposed architecture of the identification software system in the form of class and sequence diagrams. The main criteria for assessing the accuracy of speaker identification were studied and possible sources of loss of speaker identification accuracy were identified, which can be used when building a speaker identification system. A software system based on the proposed architecture and previously developed identification algorithms and methods was created.
 The following conclusions can be drawn on the basis of the performed research: approaches to the construction of existing announcer identification systems are considered; the main criteria for assessing the accuracy of announcer identification were investigated and the main sources of loss of accuracy during announcer identification were identified; the structural construction of the announcer identification system is considered, taking into account the identified sources of loss of accuracy during announcer identification; the proposed architecture of the speaker identification system in the UML language in the form of class and sequence diagrams; a software system was built that implements the functions of speech signal identification according to the methods and algorithm proposed in previous works.
 The software system uses a ranking method based on three different criteria. These include: calculation of the proximity of two-dimensional probability density function curves for the frequency of the main tone and the location in the spectrum of three frequency ranges that are extracted from the speech recorded in the speech signal; calculation of the proximity of the probability density function curves for each of these features separately; calculation of the degree of closeness of the absolute maxima of the formant spectra extracted from the speech recorded in the speech signal.

Tunable trimetallic TM-NiFe catalysts for enhancing the products selectivity of CO2 electroreduction

The synergistic effect of muti-metallic catalysts, possessing noticeable potential in tuning the physicochemical properties, provides a promising strategy to boost the electrocatalytic performance of catalysts for electrochemical CO2 reduction reaction (CO2RR). Herein, a series of trimetallic TM-NiFe (TM = first-row transition metals) catalysts were designed and screened by creating a two-dimensional active volcano curve. Moreover, the catalytic performance of TM-NiFe catalysts for converting CO2 to CO and HCOOH were evaluated via the density functional theory. The results indicate that Zn-NiFe presents better CO2RR-to-CO performance with a low overpotential of 0.697 V. The slightly weak adsorption strength of CO* on Zn-NiFe surface facilitates the kinetics of the potential-determining step (CO* → CO). V-NiFe is an ideal catalyst to produce syngas (CO and H2) due to the equivalent activity of CO2RR and hydrogen evolution reaction (HER). The Cr-NiFe catalyst favors the COOH* pathway over HCOO* pathway in the process of HCOOH generation. The negative charge on the catalyst surface and the low d-band center of Cr atoms promote the production of HCOOH over the Cr-NiFe catalyst at an exceptionally low overpotential of 0.080 V. Furthermore, Cr-NiFe catalyst significantly inhibits its competitive reactions (HER and CO2RR-to-CO). This work lays a reliable foundation for improving the activity and selectivity of trimetallic catalysts in CO2 conversion to essential chemical feedstocks.

Optimal selection of scalar and vector-valued intensity measures for improved fragility analysis in cross-fault hydraulic tunnels

Seismic intensity measures (IMs) are crucial because they are significantly connected to earthquake hazards and structural responses. It means that selecting appropriate IMs is necessary for underground structures under unfavourable earthquake hazard conditions. The seismic design code and dynamic analysis have conventionally employed the peak ground acceleration (PGA) as an optimal IM, mainly referring to the seismic design code of aboveground structures. However, seismic investigation of underground structures using PGA is still controversial. Simultaneously, directly employing the PGA as an ideal IM may increase the uncertainty associated with ground motions, which in turn increases the uncertainty for probabilistic seismic demand analysis of hydraulic tunnels. As a result, it is important to understand the roles played by different IMs while analyzing the fragility of hydraulic tunnels. This work aims to conduct a comprehensive analysis to identify the optimal scalar- and vector-valued IMs for fragility investigation of cross-fault hydraulic tunnels. Therefore, the 1080 complete nonlinear dynamic time history analysis by surrounding rock-concrete lining-fluid interaction system is conducted to express the earthquake-induced drift ratio of a cross-fault hydraulic tunnel by incremental dynamic analysis. Subsequently, a refinement process is performed to determine the optimal scalar-valued IMs by comparing the correlation, efficiency, practicality, and proficiency of the 7 examined IMs. Meanwhile, the probabilistic seismic demand model of optimum vector-valued IMs is also developed and compared, followed by the three scalar IMs. Eventually, the difference between the fragility curves of the tunnel produced using the optimal scalar- and vector-valued IM is compared. The results demonstrate that compared with scalar two-dimensional fragility curves, the vector three-dimensional fragility surface may increase the reliable probability and minimize the uncertainty in analyzing the structural response hazard curve. The generated vector fragility surface can also estimate the seismic fragility of identical cross-fault hydraulic tunnels in an approximative manner.