Line Method Research Articles

The impact of variable illumination on vegetation indices and evaluation of illumination correction methods on chlorophyll content estimation using UAV imagery

BackgroundThe advancements in unmanned aerial vehicle (UAV) technology have recently emerged as an effective, cost-efficient, and versatile solution for monitoring crop growth with high spatial and temporal precision. This monitoring is usually achieved through the computation of vegetation indices (VIs) from agricultural lands. The VIs are based on the incoming radiance to the camera, which is affected when there is a change in the scene illumination. Such a change will cause a change in the VIs and subsequent measures, e.g., the VI-based chlorophyll-content estimation. In an ideal situation, the results from VIs should be free from the impact of scene illumination and should reflect the true state of the crop’s condition. In this paper, we evaluate the performance of various VIs computed on images taken under sunny, overcast and partially cloudy days. To improve the invariance to the scene illumination, we furthermore evaluated the use of the empirical line method (ELM), which calibrates the drone images using reference panels, and the multi-scale Retinex algorithm, which performs an online calibration based on color constancy. For the assessment, we used the VIs to predict leaf chlorophyll content, which we then compared to field measurements.ResultsThe results show that the ELM worked well when the imaging conditions during the flight were stable but its performance degraded under variable illumination on a partially cloudy day. For leaf chlorophyll content estimation, The r^2 of the multivariant linear model built by VIs were 0.6 and 0.56 for sunny and overcast illumination conditions, respectively. The performance of the ELM-corrected model maintained stability and increased repeatability compared to non-corrected data. The Retinex algorithm effectively dealt with the variable illumination, outperforming the other methods in the estimation of chlorophyll content. The r^2 of the multivariable linear model based on illumination-corrected consistent VIs was 0.61 under the variable illumination condition.ConclusionsOur work indicated the significance of illumination correction in improving the performance of VIs and VI-based estimation of chlorophyll content, particularly in the presence of fluctuating illumination conditions.

ScrumOntoSPL: Collaborative Method of Agile Product Line Engineering for Software Resource Reuse

Agile Product Line Engineering (APLE), a relatively new approach combining the two successful methods of Agile Software Development (ASD) and Software Product Lines (SPLs), makes product lines more responsive to ever-changing customer needs or market changes. However, SPLs often fail to keep up with market demand due to high coordination costs, slow development processes, and long release cycles in the case of frequent changes in business requirements; in agile software projects, the lack of a unified specification for describing requirements leads to high coordination costs and inconvenient requirement management. Some studies in the literature have proposed optimized approaches to integrate ASD and SPLs, but they still have not covered all aspects of APLE’s characteristics, and software resource reuse is rarely considered in these approaches during product line development. In view of this, we propose a collaborative framework of agile product line engineering for software resource reuse, namely ScrumOntoSPL. The ScrumOntoSPL approach efficiently merges ASD and SPL based on the agile method Scrum, SPL architecture, and ontology technology. In ScrumOntoSPL, uniform requirement specification is constructed by utilizing ontology, and the Matching Requirement with Component (MRC) process is designed to match product new requirements and software resources stored in a resource pool. In addition, we evaluated the proposed framework and approach with CMMI. In the end, a case study of a software development tool called IMC-Tool based on ScrumOntoSPL for a universal Instrument Microcontroller Chip (IMC) is discussed. The IMC-Tool case illustrates that the ScrumOntoSPL has the advantages of dynamically managing demand changes, enhancing software resource reuse, reducing coordination costs, and reducing time to market.

Exploring UV-Laser Effects on Al-Implanted 4H-SiC

In this paper, we explore the effects of excimer laser irradiation on heavily Aluminum (Al)-implanted silicon carbide (4H-SiC) layer. 4H-SiC layers were exposed to UV-laser radiation (308 nm, 160 ns), at different laser fluences and the effects of the laser exposure surface were evaluated from morphological, micro-structural and nano-electrical standpoints. Depending on the irradiation condition, significant near-surface changes were observed. Moreover, the electrical characteristics of the implanted layer, evaluated by means of transmission line method, gave a sheet-resistance of 1.62×104 kW/sq for the irradiated layer, linked to a poor activation of the p-type dopant and/or a low mobility of the carriers in the laser-modified 4H-SiC layer. This study can be useful for a fundamental understanding of laser annealing treatments of 4H-SiC implanted layers.

Optimization Method of Transfer Streamlines in Integrated Passenger Hubs Based on 3D Spatial Perspective

To optimize the functional space layout of various transportation modes of the integrated passenger transport hub, and improve the transfer efficiency and service quality of the hub, a quantitative analysis of the transfer flow lines of the integrated passenger hub is carried out. The research clarifies the layout factors of the functional areas of the “get on and drop off areas” for each mode of transportation, generates a candidate set of the placement of each functional area, and determines the priority ranking of the candidate sets and the transfer starting and end locations. Based on the analysis of passenger route selection factors, the basic transfer streamline network is generated. The basic network is distributed according to the improved shortest path allocation algorithm, and the relevant parameters are calculated to simplify the initial transfer streamline network, generate and compare the initial network plan of the transfer streamline. Take Wuxi Integrated Passenger Transport Hub as an example to verify: when the weight coefficient λ = 0.65 and the number of allocations n = 207, the optimal solution T = 2,738,027 s is obtained. As the calculation is based on the 15,000 passenger transfer flow at Wuxi Station, the optimized average transfer time per person is 3 min 2 s. Compared with the current average transfer time per person at Wuxi Station of 4.5 min, the optimization effect of this paper is significant. The initial network generation and comparison method of the transfer flow line enables the space layout of the transportation modes of the hub to be coordinated with the transfer flow line design, and solves the problem of the transfer flow line design when the hub building space layout is determined. The hub is designed to meet the requirements of functional space layout, passenger transfer needs and interchange efficiency at the initial stage of architectural design.

Manufacturing of dies and an experimental study on the cold-press surface-texture forming process

Surface texturing can significantly improve the service performance of joint surfaces. However, the fabrication techniques for micro- and nanoscale structures require high-precision equipment and involve complicated processes. An efficient and practicable cold-press forming technique for surface-texture fabrication was proposed. First, the feasible methods for fabricating cold-pressed dies with surface textures were introduced. Three methods for preparing cold-pressing dies having microembossment arrays were explored. The preparation of dies via through-mask electrochemical machining on an alloy steel surface was deemed feasible. Then, the process parameters of cold-press surface-texturing were calculated using the sliding line method. The application of single microembossment to cold pressing of brass verified the validity of the models. Ultimately, cold-pressing experiments were performed using an array microembossment die. A surface texture of 1000 pits was formed in ∼3 s, and the desired quality was achieved. The experimental results showed that cold pressing of surface textures could be accomplished using the manufactured dies at a low cost and high efficiency.

Wireless Mesh Networking Tests and Evaluation in the Karst Natural Caves of Southwest China

Currently, the exploration and development of the Karst natural caves (KNCs) have become hot research topics, and flexible and reliable communication in the KNCs is very important. However, because of the inherent concavity and irregular limestone formations in the KNC, wireless signal propagation is sparse and unpredictable. In this paper, we explore the application of wireless mesh networking (WMN) in the KNC. First, by measuring the relative permittivity of the KNC using the transmission line method at 530 MHz, 670 MHz and 1.4 GHz, we segment the channel characteristics using classical free space propagation modeling, lossy waveguide modeling and bend modeling based on the geographical features of the KNC for reducing the complexity of channel modeling. The measured results are in good agreement with the segment model calculation. Second, we test and evaluate the network performance at 530 MHz, including multihop routings and multidata flows in static scenarios and mobile scenarios. The test results show that audio and video can be transmitted clearly below three hops, it is feasible to deploy WMN in an irregular KNC.

Study on Complex Wake Characteristics of Yawed Wind Turbine Using Actuator Line Method

In modern large-scale wind farms, power loss caused by the wake effect is more than 30%, and active yaw control can greatly reduce the influence of the wake effect by deflecting the wind turbine’s wake. The yawed wind turbine’s wake characteristics are complex, and a deep comprehension of a yawed turbine’s wake is necessary. The actuator line method combined with URANS (unsteady Reynold-averaged Navier–Stokes equations) is used to study the yawed wind turbine’s wake characteristics in this paper. Compared with an un-yawed wind turbine, a yawed one has two main characteristics, deflection and deformation. With an increasing yaw angle, turbine wake shows an increasing deflection. The results indicated that deflection at different height was different, the wake profile showed the biggest deflection at about the hub height, while the smallest deflection existed at the top and bottom of the yawed turbine’s wake. This can be visually demonstrated by the evolution of a kidney-shape velocity distribution at the vertical cross-section. Two-dimensional and three-dimensional presentations of velocity deficit distributions are presented in this paper. The evolution of an irregular kidney-shape distribution is discussed in this paper. It is formed by the momentum exchange caused by the counter-rotating vortex pair. The results indicated that the counter-rotating vortex pair was composed of the streamwise vortex flux brought by the tip vortex. Furthermore, when the wind turbine rotated clockwise and yawed clockwise, the negative vorticity of counter-rotating vortex first appeared in the upper left position.

Penerapan Metode Time Line Dalam Pembelajaran PAI di SMA N 1 Tanjung Mutiara

The background of this research is that some students have a low level of awareness in participating in PAI learning activities, especially about historical material. Students are less enthusiastic in participating in learning and students are less involved in the process of teaching and learning activities. From the problems that exist, researchers are interested in examining the application of the time line method in PAI learning at SMAN 1 Tanjung Mutiara and its inhibiting factors. This study aims to find out how the application of the Time line learning method and its inhibiting factors. This type of research is descriptive qualitative research which describes the application of the time line method in PAI learning at SMAN 1 Tanjung Mutiara. In collecting data researchers used observation techniques, interviews and documentation. Meanwhile, to analyze it, the researcher uses data reduction, data presentation and conclusion drawing. Researchers checked the data that had been obtained from various research instruments, namely teachers, principals and students using source triangulation, researcher triangulation and method triangulation. So as to produce a credible conclusion. From the research that has been done, it can be concluded that the application of the time line method in PAI learning at SMAN 1 Tanjung Mutiara starts with teacher planning in preparing lessons by making lesson plans which serve as teacher guidelines in teaching and learning activities carried out in the classroom. The application of the Time Line method in learning is carried out through three activities, namely preliminary activities, core activities and closing activities. The essence of applying the time line method is that students observe, analyze and discover for themselves related to learning in discussion activities. The inhibiting factors found were the short time allocation, the teacher's ability to link learning, students playing around during discussions, and female students being more active than male students.

Research on Arc Sag Measurement Methods for Transmission Lines Based on Deep Learning and Photogrammetry Technology

Arc sag is an important parameter in the design and operation and maintenance of transmission lines and is directly related to the safety and reliability of grid operation. The current arc sag measurement method is inefficient and costly, which makes it difficult to meet the engineering demand for fast inspection of transmission lines. In view of this, this paper proposes an automatic spacer bar segmentation algorithm, CM-Mask-RCNN, that combines the CAB attention mechanism and MHSA self-attention mechanism, which automatically extracts the spacer bars and calculates the center coordinates, and combines classical algorithms such as beam method leveling, spatial front rendezvous, and spatial curve fitting, based on UAV inspection video data, to realize arc sag measurement with a low cost and high efficiency. It is experimentally verified that the CM-Mask-RCNN algorithm proposed in this paper achieves an AP index of 73.40% on the self-built dataset, which is better than the Yolact++, U-net, and Mask-RCNN algorithms. In addition, it is also verified that the adopted approach of fusing CAB and MHSA attention mechanisms can effectively improve the segmentation performance of the model, and this combination improves the model performance more significantly compared with other attention mechanisms, with an AP improvement of 2.24%. The algorithm in this paper was used to perform arc sag measurement experiments on 10 different transmission lines, and the measurement errors are all within ±2.5%, with an average error of −0.11, which verifies the effectiveness of the arc sag measurement method proposed in this paper for transmission lines.

Sliding mesh simulations of a wind turbine rotor with actuator line lattice‐Boltzmann method

AbstractSimulating entire wind farms with an actuator line model requires significant computational effort, especially if one is interested in wake dynamics and wants to resolve the tip vortices. A need to explore unconventional approaches for this kind of simulation emerges. In this work, the actuator line method is implemented within a lattice‐Boltzmann flow solver, combined with a sliding mesh approach. Lattice‐Boltzmann solvers have advantages in terms of performance and low dissipation, while the sliding mesh allows for local refinement of the blade and tip vortices. This methodology is validated on a well‐documented case, the NREL Phase VI rotor, and the local refinement is demonstrated on the NREL 5 MW rotor. Results show good agreement with reference Navier–Stokes simulations. Advantages and limitations of the sliding mesh approach are identified.

A Few-Shot Defect Detection Method for Transmission Lines Based on Meta-Attention and Feature Reconstruction

In tasks of transmission line defect detection, traditional object detection algorithms are ineffective, with few training samples of defective components. Meta-learning uses multi-task learning as well as fine-tuning to learn common features in different tasks, which has the ability to adapt to new tasks quickly, shows good performance in few-shot object detection, and has good generalization in new tasks. For this reason, we proposed a few-shot defect detection method (Meta PowerNet) with a Meta-attention RPN and Feature Reconstruction Module for transmission lines based on meta-learning. First, in the stage of region proposal, a new region proposal network (Meta-Attention Region Proposal Network, MA-RPN) is designed to fuse the support set features and the query set features to filter the noise in anchor boxes. In addition, it has the ability to focus on the subtle texture features of smaller-sized objects by fusing low-level features from the query set. Second, in the meta-feature construction stage, we designed a meta-learner with the defect feature reconstruction module as the core to capture and focus on the defect-related feature channels. The experimental results show that under the condition, there are only 30 training objects for various types of component defects. The method achieves 72.5% detection accuracy for component defects, which is a significant improvement compared with other mainstream few-shot object detection. Meanwhile, the MA-RPN designed in this paper can be used in other meta-learning object detection models universally.

A novel representation of electromagnetic field interaction with vertically stratified structures

PurposeThe purpose of this study is to develop an efficient model to solve the electromagnetic forward problem using a novel semi-analytical approach to compute the electromagnetic fields because of the presence of a scatterer.Design/methodology/approachThe proposed model involves a novel formulation of a complete orthonormal set of radiating/nonradiating polarization currents. Furthermore, an integral equation-based representation is derived, and the appropriate boundary conditions are imposed to get the scattered electromagnetic field. An error term is introduced to evaluate the obtained results.FindingsThe proposed model was tested using several examples at different frequencies. The results of this study show that the novel representation exhibits fast convergence behavior and achieves highly accurate results, when compared to the results provided by the transmission line method.Originality/valueThe derived formulations presented in this study are significant in the electromagnetic forward modelling field because of the meaningful physical representation they provide. This is an important aspect that leads to precise calculation of electromagnetic fields for various applications.

Temperature measurement of SO2 based on mid‐infrared laser absorption spectroscopy

AbstractThe temperature measurement of Sulfur dioxide (SO2) is a crucial parameter for accurately determining its concentration, particularly in high‐temperature environment. Herein, it is realized by using three different techniques, which are direct absorption spectroscopy, wavelength modulation spectroscopy and non‐calibration wavelength modulation spectroscopy based on the bispectral lines temperature measurement method. The bispectral lines of SO2 locates at 1396.844 and 1396.921 cm−1, respectively. The gas temperature in the absorption cell was also measured with K‐type thermocouple and compared with these three spectral measurements. The linearities corresponding to these three techniques are 99.71%, 99.8%, and 99.88%, respectively. Their average relative error between the spectral measurement results and the linear fitting value of the three techniques is 1.15%, 0.86%, and 0.57%, respectively. It is illustrated the feasibility of the bispectral lines method for high‐temperature measurement. These investigations provide methods for temperature measurement in high‐temperature coal‐fired boilers, potentially for investigating other sulfide gas molecules such as SO3 and H2S.

Does a physiology-based interpretation of cardiotocography allow to dispense with second-line methods? A cross-sectional online survey.

Second line methods are used to help obstetricians to identify abnormalities that reflect fetal acidosis. Since the use of a new technique of cardiotocography (CTG) interpretation based on the pathophysiology of the fetal period, the use of second-line tests has been questioned. To evaluate the impact of specific training in CTG physiology-based interpretation on professional attitudes towards the use of second-line methods. This cross-sectional study included 57 French obstetricians divided into two groups: the trained group (obstetricians who had already participated in a training course in physiology-based interpretation of CTG) and the control group. Ten medical records of patients who had abnormal CTG tracings and underwent fetal blood sampling pH measurement during labour were presented to the participants. They were given three choices: use a second-line method, continue labour without using second-line method, or perform a caesarean section. The main outcome measures was the median number of decisions to use second-line method. Forty participants were included in the trained group and 17 in the control group. The median number of recourses to second-line method was significantly inferior for the trained group (4/10 second-line methods) than for the control group (6/10, p=0.040). Regarding the 4 records for which a caesarean section was the real outcome, the median number of decisions of continuing labour was significantly superior in the trained group than in the control group (p=0.032). Participation in a training course in physiology-based interpretation of CTG could be associated with a less frequent use of second-line method at the cost of more frequently continuing labour with the risk compromising fetal and maternal well-being. Additional studies are required to determine whether this change in attitude is safe for the fetal well-being.

Impact of the rotor blades elasticity on the loads and wake of the large IEA 15-MW wind turbine

This work presents an investigation of the aeroelastic effects occurring on the IEA 15-MW reference wind turbine in a turbulent atmospheric boundary layer. Large Eddy simulation is carried out using an actuator line method coupled to the finite element beam solver BeamDyn. The results show that the blades experience significant displacements, leading to an important variation of the loads along the blade span. The turbulence also interacts with the blades natural frequencies, resulting in a variation of the spectra of the various loads. The impact of the flexibility is also evaluated on the wake by comparing the undeformed configuration with a statically and dynamically deformed rotor. It appears that the mean deformation plays an important role in the wake development due to changes in the load distribution, but that the dynamic effects have minimal impact on the wake behavior.

Measurement and Evaluation Method Study of Alignment Deviation of Double-helical Gear

The alignment deviation of the V-vertex of two symmetrically arranged gears with different rotation directions is a unique geometric parameter of double helical gears, which has an important effect on the vibration, noise, and double helical gear service life. Aiming to more accurately represent the manufacturing accuracy of double helical gears and their transmission performance, this paper proposes the meaning of the v-vertex basis the contact line of tooth surface based on the apex characteristics of double helical gears. First, the mathematical model of tooth flank is established based on gear meshing theory. Secondly, a method for measuring and evaluating the alignment deviation of double helical gear v-vertex (full tooth contact line method) is proposed. Eventually, the validity and convenience of the proposed measurement method are verified by the experiment. Experimental results showed that the total alignment deviation of double helical gears evaluated by the full tooth contact line method is 0.0082 mm, which meets the design requirements in Reference 16. This paper provides a new measurement and evaluation method for the comprehensive and accurate evaluation of double helical gears, which has significant implications for the design and manufacture of high-precision double helical gears.

Dynamic Mode Decomposition of merging wind turbine wakes

The design and operation of wind farms is significantly affected by the impact that upstream turbine wakes have on the power production and fatigue loading of subsequent turbines; often called the wake effect. In this work, two types of flows are considered: the wake of a single turbine with a laminar inflow and the combined wake of two turbines operating in-line where the upstream wake results in an unsteady inflow for the downstream turbine. Those two scenarios are simulated using large eddy simulation (LES) and the actuator line method (ALM). The spatio-temporal velocity fields are analyzed by means of high order dynamic mode decomposition (HODMD), a well established variant of the DMD. The results show that most of the higher frequencies characterizing the laminar case are instead dominated by the lower frequency modes in the combined wake. This suggests that structures emerging from the blade rotations in a wind turbine wake may be less significant for describing the wake dynamics when the rotor is operating in the unsteady wake of an upstream rotor.

Low specific contact resistance between InAs/Ni–InAs evaluated by multi-sidewall TLM

The specific contact resistance ρint of the InAs/Ni–InAs interface was evaluated by the multi-sidewall transmission line method (MSTLM), where Ni–InAs was formed by alloying Ni and InAs-on-insulator substrates. The revised test structure for MSTLM has been proposed, which can be easily fabricated. By evaluating each component of the parasitic resistance separately, the specific contact resistance of the InAs/Ni–InAs was accurately extracted. As a result, the record low ρint of (4.3 ± 2.5) × 10−9 Ω cm2 among metal/III-V contacts was obtained for the 30-nm-thick InAs/Ni–InAs interface with the average electron concentration of 9.1 × 1018 cm−3 for InAs, which is close to the Landauer limit. The comparison of the experimental and theoretical ρint indicates that there is no potential barrier at the InAs/Ni–InAs interface, which is attributable to the negative Schottky barrier height for electrons of InAs.

A novel pilot protection method for UHVDC transmission lines based on U-I characteristics

As one of the principal protections of UHVDC transmission lines, pilot protection requires strict synchronization and small data flow by exchanging the current on both terminals under the limitation of DC protection action rapidity. To solve this problem, this paper finds that the DC voltage and current on both terminals of the line have different plane distribution characteristics when faults occur internally and externally in the system area, and then advances a novel pilot protection method for UHVDC transmission lines based on U-I characteristics. By setting up the U-I plane with DC voltage and current as variables, analyzing the dynamic trajectory of the real-time captured U-I plane, constructing protection criteria based on the U-I plane on the rectifier side and inverter side separately, and finally converting the judgment results into state information. Both terminals of the line identify the fault location by exchanging the longitudinal comparison of state information. This protection project only utilizes the instant tracks of voltage and current in the rectifier side and inverter side at the time of fault to judge. The principle is simple and can quickly locate faults. The state messages of the two terminals are not modified by the data asynchrony on both terminals. This protection method is convenient for setting, has high sensitivity, and can quickly identify interior and exterior faults. The results are testified by theoretical analysis and simulation verification.

The Analysis of Stress Raisers Affecting the GFRP Strength at Quasi-Static and Cyclic Loads by the Theory of Critical Distances, Digital Image Correlation, and Acoustic Emission.

The purpose of this work is to analyze the stress-raisers that affect the tensile strength and fatigue resistance of GFRP parts using the point and line methods of the theory of critical distances (TCD) to obtain a quantitative measure of the defect size that can be tolerated by the composite before it fails. In the course of the work, a method combining TCD and the Weibull function was developed. In the course of the work, GFRP structural fiberglass for electrical purposes was tested under uniaxial quasi-static and cyclic loading with digital image correlation (DIC) and acoustic emission (AE), as well as a numerical simulation of deformation. The studied specimens were plain (without a stress-raiser) and notched (V-shaped) with different notch root radii and depths. The results were used to determine the material critical distances. In this case, two approaches to TCD were used: line (LM) and point (PM) methods. To analyze the experimental results, finite element modeling was applied using the ANSYS software package. As a result, the linearized maximum principal stresses were obtained on the central line passing through the top of the stress raiser. Thus, the values of the critical distances of the material were determined by PM and LM. Based on the data obtained, the sizes of permissible defects in the studied fiberglass were established that do not affect the tensile and fatigue strength of the material. The paper illustrates the cumulative energy, peak amplitudes, and distributions of the frequency of the spectral maximum of acoustic emission signals obtained after the destruction of specimens by fatigue test. Evolutions of deformation fields on the specimen surface were recorded using a Vic-3D contactless optical video system and the DIC.