Minimum Line Research Articles

Fault characteristics and protection methods for long distribution lines with grid-forming IBDG integration

Grid-forming inverter-based distributed generation (IBDG) is an effective means to address low voltage issues at the end of long distribution lines in remote areas. However, existing distribution protection methods are not suitable for this scenario. By analyzing the voltage phase angles of grid-forming IBDG that meet low voltage remediation requirements, the boundary phase angle conditions corresponding to ”minimum line loss” and ”minimum inverter current” are derived. Based on this, the distribution characteristics of short-circuit currents in long distribution networks are analyzed, and the limitations of traditional three-stage current protection methods are revealed through a regional discussion.An adaptive current protection method is proposed, which automatically adjusts protection device parameters by real-time calculation of regional intersection positions and currents. The effectiveness of this method is verified through simulations. The simulation results confirm the accuracy of the proposed boundary conditions and fault characteristic analysis, demonstrating that the proposed adaptive current protection method can effectively address short-circuit scenarios in long distribution networks with grid-forming IBDG integration.

Impact of anthropogenic activities and the associated heavy metal pollution in Sundarbans waterways: threats to commercial fish and human health.

The exposure of fish to heavy metals is a significant concern for human health and natural ecosystems. Despite being a critical issue, the extent of contamination in tropical fish from developing countries like Bangladesh remains somewhat unexplored. In this study, ten economically vital fish species (Osteogeneiosus militaris, Arius gagora, Harpadon nehereus, Mugil ephalus, Pseudapocryptes elongates, Apocryptes bato, Labeo bata, Tenualosa toil, Notopterus notopterus, and Pampus chinensis) from the Pasur River, Bangladesh, were analyzed by atomic absorption spectrometer for the concentrations of four concerned heavy metals, viz., As, Cr, Cd, and Pb, and the associated human health risks. The mean concentrations (mg/kg) followed the order of As (3.30 ± 1.43) > Pb (2.32 ± 0.73) > Cr (0.63 ± 0.29) > Cd (0.37 ± 0.24). Additionally, the bioaccumulation factor of the metals in the investigated fish species followed a decreasing trend of As (824.75) > Cr (781.25) > Cd (744) > Pb (385.83). While most species fell below the minimum bioaccumulation line, a few exceptions were noted for some species specific to metals. Health risk assessments indicated no significant carcinogenic and non-carcinogenic risks for both children and adults, although children exhibited greater vulnerability to both types of health effects. Multivariate analysis and local perceptions supported the conclusion that heavy metals primarily originated from anthropogenic sources related to development activities adjacent to the riverine areas.

Development and application of a quadruplex TaqMan fluorescence quantitative PCR typing method for Streptococcus suis generalis, type 2, type 7 and type 9.

Streptococcus suis (SS) is one of the most important pathogens causing major economic losses in the global pig farming industry and is a serious threat to public health safety. It has multiple serotypes, with poor cross-protection between serotypes, and effective typing methods are lacking. In this study, a quadruplex TaqMan fluorescence quantitative PCR assay that can differentiate between Streptococcus suis types 2, 7 and 9 was developed using the gdh gene, a generic gene for Streptococcus suis, and cps2J, cps7H and cps9J, genes encoding podocarp-associated genes for types 2, 7 and 9, respectively, as targets. The method is specific enough to accurately type Streptococcus suis pigmentosus without detecting non-target pathogens (Escherichia coli, Pasteurella multocida, Staphylococcus aureus, Streptococcus agalactiae, Streptococcus pneumoniae and etal). The sensitivity was high, with a minimum lower detection line of 10 copies for P-SS and P-SS9, and 100 copies for P-SS2 and P-SS7. The standard curves generated showed good linearity with R2 of 0.999, 0.999, 0.997 and 0.998 respectively. The repeatability was good, with coefficients of variation between batch to batch and batch to batch tests ranging from 0.21% to 1.10%. Testing of 156 samples yielded 68 positive and 88 negative samples, of which the positive rate of SS was 5.77% (9/156), SS2 was 20.51% (32/156), SS7 was 8.33% (13/156) and SS9 was 9.6% (15/156), which was in line with the existing fluorescent quantitative PCR assay of 93.75%~100%, which was higher than the detection rate of conventional PCR. The quadruplex TaqMan fluorescence quantitative PCR method of Streptococcus suis generic, type 2, 7 and 9 established in this study can accurately differentiate the three serotypes of Streptococcus suis that currently have high prevalence and pathogenicity, which is of great importance for accurate clinical prevention and treatment, epidemiological investigation and vaccine development.

Theory and field tests of innovative cut blasting method for rock roadway excavation

The primary factor influencing the blasting excavation speed of coal mine rock roadways is cut blasting. Traditionally, cut holes are positioned at the lower part of the section, leading to uneven minimum resistance lines for the subsequent row of auxiliary holes after blasting, which results in poor rock fragmentation. In this paper, an innovative concept that cutting area is similar to the rock roadway cross-sectional contour (CSRC) for cut blasting is proposed, which is composed of two parts: layout of cutting holes and charging structure. Firstly, the concept of CSRC is introduced and relevant theoretical models are established. Then, the CSRC cut blasting is studied through numerical simulation and model testing methods. Finally, the CSRC cut blasting and digital electronic detonators are applied on site. The results indicate that arranging cut holes using this method makes the shape of the cutting cavity similar to the cross-sectional profile. And the resistance line of the next row of auxiliary holes becomes uniform, thereby enhancing rock fragmentation near adjacent auxiliary holes. Additionally, the use of discontinuous charges in deep hole excavation significantly improves excavation efficiency and increases the extent of rock damage. The industrial test results further validate that adjusting the layout of cut holes mainly affects rock fragmentation uniformity, the number of boreholes, and the quality of the surrounding formation. Adjusting the charging structure mainly influences the efficiency and depth of blasting excavation. Compared to traditional methods, employing CSRC cut blasting technology significantly reduces the number of boreholes, improves production efficiency, and lowers costs.

An improved k-means cluster method based on partial correlation coefficient for line-transformer connectivity identification in distribution network

Abstract The accurate identification of line-transformer connectivity of the distribution network is very important for load balancing and line loss management. The electric quantity data can be used to identify the relationship, but the recognition accuracy is limited. The essence of relation recognition is unsupervised classification, but as there is no direct center of mass and distance, the traditional mainstream clustering method cannot be applied. Therefore, this paper proposes an improved K-means clustering algorithm based on a partial correlation coefficient. Firstly, spectrum analysis is carried out for the collected power data of the distribution transformer and the 10 kV line, and the high-frequency component of the data is obtained by the high-pass filter. Then, the K-means clustering algorithm improved by the partial correlation coefficient is used to set the electric energy data of each line as the initial centroid. The correlation between the station area and the line is calculated by using the concept of the partial correlation coefficient, and the station area represented by the minimum line distance is assigned to the corresponding line. The results show that this method can improve the accuracy of linear relation identification based on electric quantity data.

A Model for Dry Electron Beam Etching of Resist

This paper presents a detailed physical model for a novel method of two- and three-dimensional microstructure formation: dry electron beam etching of the resist (DEBER). This method is based on the electron-beam induced thermal depolymerization of positive resist, and its advantages include high throughput and relative simplicity compared to other microstructuring techniques. However, the exact mechanism of profile formation in DEBER has been unclear until now, hindering the optimization of this technique for certain applications. The developed model takes into account the major DEBER phenomena: e-beam scattering in resist and substrate, e-beam induced main-chain scissions of resist molecules, thermal depolymerization of resist, monomer diffusion, and resist reflow. Based on the developed model, a simulation algorithm was implemented, which allowed simulation of the profile obtained in resist by DEBER. Experimental verification of the DEBER model was carried out, which demonstrated the reliability of the model and its applicability for theoretical study of this method. The ultimate DEBER characteristics were estimated by simulation. The minimum line width and the maximum profile slope that could be obtained by DEBER were approximately 300 nm and 70°, respectively.

Investigation of Railway Network Capacity by Means of Dynamic Flows

Capacity calculations are essential for the long-term planning of railway infrastructure. Many of the methods currently used in practice calculate characteristic capacity values separately for the single elements (mainly lines and nodes) of a railway network. Approaches that consider the entire network to account for interactions between the elements often rely on many assumptions, which renders a direct practical application difficult. This paper therefore introduces a linear optimization model that comprises railway-specific constraints such as minimum headway times, line capacities, and route conflicts. Under the consideration of these constraints, the developed model permits the calculation of a network-wide capacity. The model is validated on a sample network that is based on a real network of the German railway infrastructure.

Micromechanical investigation of the aging mechanism in sand

The current mechanisms and factors influencing soil aging remain inconclusive and incomplete. Discrete element method (DEM) is adopted to investigate the responses of irregularly shaped granular assemblies subjected to creep and post-creep triaxial shear. The simulated creep and aging behaviours are generally in line with those observed in existing laboratory tests and numerical investigations. In addition to an increase in soil stiffness, the DEM analyses predict an enhanced soil strength as a result of the prolonged interlocking between sand particles during the relatively long creep duration. It is demonstrated that the creep-induced interlocking is directly manifested as a shear resistance above the minimum energy line. The development of interlocking explains the overshooting behaviour observed in post-creep shear. The microscopic responses do not support the aging mechanism based on the buckling of strong force chains. A new hypothesis, termed ‘microstructure evolution by stability selection’, is proposed to explain soil aging. This hypothesis suggests that interlocking between particles develops naturally during the creep process because interlocked particle clusters generally have a greater chance to survive the particle rearrangement induced by creep, leading to an increased number of interlocked particle clusters in aged soils.

Agricultural path detection systems using Canny-edge detection and Hough transform

Navigation is one of the crucial aspects of automation technology within the field of agriculture, such as robotics systems or autonomous agricultural vehicles. Despite many navigation systems having been developed for agricultural land, due to their high development and component costs, these systems are difficult to access for farmers or organizations with limited capital. In this study, the Canny-edge detection and Hough transform methods are implemented in a path detection system on agricultural land to find an alternative, cost-effective navigation system for autonomous farming robots or vehicles. The system is tested on ground-level view images, which are captured from a low perspective and under three different lighting conditions. The testing and experimentation process involves adjusting the parameters of the Canny-edge detection and Hough transform methods for different lighting conditions. Subsequently, an evaluation is conducted using Intersection over Union to obtain the best accuracy results, followed by fine-tuning of the canny-edge detection and Hough transform method parameters. The identified parameters, specifically a 15×15 Gaussian kernel, low threshold of 50, high threshold of 150, Hough threshold, minimum line length of 150, and maximum line gap, have been discerned as optimal for the canny-edge and Hough transform algorithms under medium lighting conditions (G=1.0). The observed efficacy of these parameter configurations suggests the method’s viability for implementation in path detection systems for agricultural vehicles or robots. This underscores its potential to deliver reliable performance and navigate seamlessly across diverse lighting scenarios within the agricultural context.

Optimal configuration of hydrogen storage capacity of hybrid microgrid considering peak regulation and frequency modulation requirements

This study proposes an innovative hydrogen storage capacity optimization configuration method that considers multiple demand factors, addressing the issue that traditional methods for optimizing hydrogen storage capacity in hybrid microgrids cannot simultaneously balance economic efficiency and grid connection quality. This method breaks through the traditional optimization framework and adopts a double-layer optimization model, combining the peak shaving operation cost of the hybrid microgrid with the interactive power deviation and power fluctuation penalty terms of the interconnection line during the frequency regulation stage, achieving dual optimization of economy and grid connection quality. Through precise mathematical modeling and efficient optimization algorithms, we have successfully obtained the minimum operating cost corresponding to the minimum power fluctuation, the minimum interconnection line interactive power deviation penalty term, and the optimal hydrogen storage capacity configuration scheme. Identify two typical days through cluster analysis. Option 1 (considering peak shaving, frequency regulation, and hydrogen electrolysis) has the lowest net load and a total operating cost of 3.0331 million yuan, which is better than Option 2 (3.0973 million yuan) and Option 3 (5.0398 million yuan). This plan effectively reduces wind and solar power waste, shortens the operating time of thermal power units, and demonstrates the rationality and economy of optimizing hydrogen storage capacity configuration.

Micropatterning of LaCoO3 thin films through a novel photosensitive sol-gel lithography technique and their magnetic properties

This paper presents a study on the microstructure and magnetic properties of LaCoO3 (LCO) thin films, and also the micropatterning of LCO thin films using a novel photo-sensitive sol-gel lithography method. It is found that higher heat-treatment temperature can promote the healing of cracks and filling of pores, resulting in refining the grains, and improving the density of LCO film. The film treated at 850 °C has a larger nucleation energy, which makes the distribution of nucleation sites more uniform, promoting the healing of cracks and filling of pores, refining the grains, and improving the density of LCO film. LCO precursor sol, metal chelates with UV photosensitivity were synthesized by adding BzAcH photosensitizer. LCO micro-arrays with diameters of 50 μm, as well as other fine patterns with a minimum line width of about 2 μm were successfully prepared by a UV mask lithography technique. In contrast, our novel lithography method eliminates the need for photoresist, as the fine pattern is formed during the preparation of the LCO gel film, which is the advantages of our lithography method over traditional techniques.

The hybrid approach of genetic algorithm and particle swarm optimization on reduced weld line defect in plastic injection molding

Weld lines are a serious defect observed in plastic injection molded parts, impacting both their cosmetic appearance and mechanical properties. Controlling the conditions of plastic injection is crucial to mitigate these weld lines. This study introduces a novel approach to identify polypropylene injection molding (PIM) conditions aimed at reducing weld lines in polypropylene parts. The PIM conditions considered in this study include melt temperature, injection pressure, packing pressure, packing time, and cooling time. An orthogonal array Taguchi L27 design was employed for the experimental setup, producing 27 polypropylene parts with varying combinations of process conditions. The width of weld lines generated on the parts’ surfaces was measured using an optimum microscope for all trials. Parametric analysis was conducted using response surface plots and contour plots to estimate the process conditions yielding minimum weld lines. Analysis of variance and regression analysis were employed to interpret the experimental data, with the resulting regression equation used to predict weld lines for a set of PIM process conditions. Finally, two efficient optimization algorithms, genetic algorithm (GA), and particle swarm optimization (PSO), were implemented using MATLAB programming to estimate the optimum process conditions for minimizing weld lines. The GA and PSO predicted weld line widths of 6.12302 μm and 6.123 μm, respectively, representing an 18.51% improvement in results. These findings demonstrate that the novel approach presented in this study can be effectively and reliably applied to address plastic product defects in the industry.

Line optimization of multi-beam sonar sounding technology in ocean surveying and mapping

Abstract In this paper, the problem of line optimization existing in the practical application of multi-beam sonar-sounding technology is studied. Firstly, by analyzing the working principle of multi-beam sonar, the multi-beam coverage width model and the overlap rate model between adjacent strips are established considering the slope of seabed terrain. Then, a more general parameterized multi-beam coverage width formula with an adjustable azimuth angle of the line is derived under three-dimensional space coordinates. Then, the minimum total line length is defined as the objective function, and the constraint conditions of overlap rate and complete coverage are added to establish the mathematical model of line planning. Then, an iterative algorithm is designed to quickly determine the line spacing, and an improved particle swarm optimization algorithm, including a trigonometric function change learning factor, is used to search for the optimal line layout. Finally, the simulation results show that the optimized scheme can reduce the total line length by 2% compared with the unoptimized line layout, which verifies the effectiveness of the established model and algorithm. This study provides a theoretical basis for navigation planning and shipboard system optimization of multi-beam sonar survey. Subsequent work taking into account the influence of complex sea conditions, efforts were made to expand the model’s applicability.

Hybrid additive-subtractive manufacturing of high-density copper-based flexible transparent circuits based on side-etch process

High-density flexible transparent circuits (FTCs) are widely used in 5G/6G flexible transparent antennas, wearable devices, flexible transparent electronics and other fields. However, the rapid iteration and upgrading of electronic circuits present significant challenges to the manufacturing of both high-density and high-precision circuits (especially copper-based circuits) at room temperature, in an efficient and flexible manner. Here, we employ the side-etching phenomenon, which is typically avoided, to propose a novel method for hybrid additive-subtractive fabricating high-density copper-based FTCs that combines electric field-driven (EFD) microjet printing and wet etching technology. Firstly, the customized photoresist mask was flexibly printed on the copper-clad flexible substrate by EFD microjet printing, and then the copper circuit with less than the mask resolution was obtained by the side etching process of the wet etching process. By optimizing process parameters and precisely controlling the speed of the side etching stage during the etching process, the manufacturing of high-precision copper-based FTCs with a minimum line width of 2.4 μm and a minimum pitch of 4 μm was achieved. The typical sample is manufactured with a resistivity of 4 × 10−6 Ω·cm, a sheet resistance of 3.58 Ω/sq at a transmittance of up to 87.65 % (including the substrate), and it exhibits excellent mechanical stability. The prepared high-density flexible transparent interdigital electrode has excellent sensitivity, and can detect the concentration change of dilute H2SO4 solution at a minimum of 1 nmol/L at a frequency of 100–10,000 Hz. This method provides a new solution for the fabrication of copper-based FTCs at room temperature with high efficiency and low cost, and shows a good prospect for industrial application.

Automatic Defect Detection Instrument for Spherical Surfaces of Optical Elements

In order to realize automatic surface defect detection for large aperture precision spherical optical elements, an automatic surface defect detection instrument has been designed. The instrument consists of a microscopic imaging system, illumination system, motion scanning system, and a software algorithm system. Firstly, a multi-angle channel illumination source and a coaxial illumination source were designed. Bright and dark field images of surface defects were captured by cooperating with an automatic zoom microscope. Then, algorithms for scanning trajectory planning, image stitching, and intelligent defect recognition were designed to achieve full-aperture surface image acquisition and defect quantification detection. The automated defect detection process of the instrument is summarized and introduced. Finally, the experimental platform was constructed, which can work well for the optical elements with a maximum diameter of 400 mm and a relative aperture R/D value of 1. It takes about 15 min to detect an optical element with a diameter of 200 mm in dark-field imaging mode. As a result, the minimum line width of scratch detectable is 2 μm and the minimum diameter of pitting detectable is 4 μm. Clearly, the instrument can realize the automatic detection of surface defects of spherical optical elements, and has the advantages of a high efficiency, stability, reliability, quantification, and data traceability.

Transmission line earthing system; Advanced design diagram for safety compliance

An electrical high-voltage power system is essential to support everyday electrical demands. Due to the increase in electrical loads, a more rigid design is required to ensure system compliance with standards and policies. High-voltage safety is the number one priority when it comes to the design, installation, commissioning, and operation of the electrical power system network. Safety compliance is getting more complex due to the joining infrastructure between residential and high-voltage projects. Nowadays, high-voltage infrastructure, including substations and transmission lines, is constructed near residential properties. This neighboring setup increased the safety concerns of high voltage systems, especially under fault or system malfunction situations. Safety concerns are addressed during the design stage and verified during the commissioning stages.The paper discusses the minimum transmission line earthing system requirements. This document provides a clear and consistent approach to assess transmission line earthing system design. The work contents comply with current IEEE standards including rigid author research outcomes. The works reduce the complexity of the assessment and explain the critical role of different sectors within the transmission line network. The work introduces the boundaries when the fault current analysis should include the earth grid resistance. A case study is also included.

Investigations on tip-based large area nanofabrication and nanometrology using a planar nanopositioning machine (NFM-100)

This paper explores large area application of tip-based nanofabrication by field emission scanning probe lithography and showcases the simultaneous possibility of atomic force microscopy on macroscopic scales. This is made possible by the combination of tip-based technology and a planar nanopositioning and nanomeasuring machine. Using long range atomic force microscopy measurement of regular grating structures, the performance of the machine is thoroughly characterized over the full 100 mm range of motion of the positioning machine, which was confirmed by repeated measurements. After initially focussing on achieving the minimum line width of < 40 nm in microscopic areas, a grating with a pitch of 1 μm is additionally fabricated over a total length of 10 mm, whereby the dimensions and deviations are also considered.

Precisely Patterned Channels in a Vertical Organic Electrochemical Transistor with a Diazirine Photo‐Crosslinker

AbstractOrganic electrochemical transistors (OECTs) rely on both efficient ionic doping/de‐doping process and carrier transport in the mixed ionic‐electronic channel under the modulation of gate bias. Moreover, channels that hold photopatterning capability are highly desired to minimize parasitic capacitance and simplify the fabrication process/cost. However, yielding photo‐patternable channels with both precise/robust patterning capability and controllable ionic‐electronic coupling is still challenging. Herein, double‐end trifluoromethyl diazirines (DtFDA) with different chain lengths are introduced in the OECT channel to act as both photo‐crosslinker and medium to regulate ionic‐electronic transport. Specifically, high‐resolution patterns with a minimum line width/gap of 2 μm are realized in p(g2T‐T) or Homo‐gDPP based channels by introducing DtFDA. Maximum transconductances of 68.6 mS and 81.6 mS, current on/off ratio of 106 and 107 (under a drain voltage of only ±0.1 V), are achieved in p‐ and n‐type vertical OECTs (vOECTs), respectively, along with current densities exceeding 1 kA cm−2 and good cycling stability of more than 100,000 cycles (2000 seconds). This work provides a new and facile strategy for the fabrication of vOECT channels with high resolution and high performance via the introduction of a simple and efficient crosslinker.

Precisely Patterned Channels in a Vertical Organic Electrochemical Transistor with a Diazirine Photo-Crosslinker.

Organic electrochemical transistors (OECTs) rely on both efficient ionic doping/de-doping process and carrier transport in the mixed ionic-electronic channel under the modulation of gate bias. Moreover, channels that hold photopatterning capability are highly desired to minimize parasitic capacitance and simplify the fabrication process/cost. However, yielding photo-patternable channels with both precise/robust patterning capability and controllable ionic-electronic coupling is still challenging. Herein, double-end trifluoromethyl diazirines (DtFDA) with different chain lengths are introduced in the OECT channel to act as both photo-crosslinker and medium to regulate ionic-electronic transport. Specifically, high-resolution patterns with a minimum line width/gap of 2 μm are realized in p(g2T-T) or Homo-gDPP based channels by introducing DtFDA. Maximum transconductances of 68.6 mS and 81.6 mS, current on/off ratio of 106 and 107 (under a drain voltage of only ±0.1 V), are achieved in p- and n-type vertical OECTs (vOECTs), respectively, along with current densities exceeding 1 kA cm-2 and good cycling stability of more than 100,000 cycles (2000 seconds). This work provides a new and facile strategy for the fabrication of vOECT channels with high resolution and high performance via the introduction of a simple and efficient crosslinker.

Direct in Situ Fabrication of Multicolor Afterglow Carbon Dot Patterns with Transparent and Traceless Features via Laser Direct Writing.

Multicolor afterglow patterns with transparent and traceless features are important for the exploration of new functionalities and applications. Herein, we report a direct in situ patterning technique for fabricating afterglow carbon dots (CDs) based on laser direct writing (LDW) for the first time. We explore a facile step-scanning method that reduces the heat-affected zone and avoids uneven heating, thus producing a fine-resolution afterglow CD pattern with a minimum line width of 80 μm. Unlike previous LDW-induced luminescence patterns, the patterned CD films are traceless and transparent, which is mainly attributed to a uniform heat distribution and gentle temperature rise process. Interestingly, by regulating the laser parameters and CD precursors, an increased carbonization and oxidation degree of CDs could be obtained, thus enabling time-dependent, tunable afterglow colors from blue to red. In addition, we demonstrate their potential applications in the in situ fabrication of flexible and stretchable optoelectronics.