Search Results (13)

Most electrical energy generation systems are based on synchronous generators; as a result, their analysis always provides interesting findings, especially if an approach different to those traditionally studied is used. Therefore, an approach involving the modeling and simulation of a synchronous generator connected to an infinite bus through a transmission line in a bond graph is proposed. The behavior of the synchronous generator is analyzed in four case studies of the transmission line: (1) a symmetrical transmission line, where the resistance and inductance of the three phases $(a,b,c)$ are equal, which determine resistances and inductances in coordinates $(d,q,0)$ as individual decoupled elements; (2) a symmetrical transmission line for the resistances and for non-symmetrical inductances in coordinates $(a,b,c)$ that result in resistances that are individual decoupled elements and in a field of inductances in coordinates $(d,q,0)$; (3) a non-symmetrical transmission line for resistances and for symmetrical inductances in coordinates $(a,b,c)$ that produce a field of resistances and inductances as individual elements decoupled in coordinates $(d,q,0)$; and (4) a non-symmetrical transmission line for resistances and inductances in coordinates $(a,b,c)$ that determine resistances and inductance fields in coordinates $(d,q,0)$. A junction structure based on a bond graph model that allows for obtaining the mathematical model of this electrical system is proposed. Due to the characteristics of a bond graph, model reduction can be carried out directly and easily. Therefore, reduced bond graph models for the four transmission line case studies are proposed, where the transmission line is seen as if it were inside the synchronous generator. In order to demonstrate that the models obtained are correct, simulation results using the 20-Sim software are shown. The simulation results determine that for a symmetrical transmission line, currents in the generator in the d and q axes are −25.87 A and 0.1168 A, while in the case of a non-symmetrical transmission line, these currents are −26.14 A and 0.0211 A, showing that for these current magnitudes, the generator is little affected due to the parameters of the generator and the line. However, for a high degree of non-symmetry of the resistances in phases a, b and c, it causes the generator to reach an unstable condition, which is shown in the last simulation of the paper. Full article

Graph anomaly detection aims to identify unusual patterns or structures in graph-structured data. Most existing research focuses on anomalous nodes in ordinary graphs with pairwise relationships. However, complex real-world systems often involve relationships that go beyond pairwise relationships, and insufficient attention is paid to hypergraph anomaly detection, especially anomalous hyperedge detection. Some existing methods for researching hypergraphs involve transforming hypergraphs into ordinary graphs for learning, which can result in poor detection performance due to the loss of high-order information. We propose a new method for Anomalous Hyperedge Detection on Symmetric Line Expansion (AHD-SLE). The SLE of a hypergraph is an ordinary graph with pairwise relationships and can be backmapped to the hypergraph, so the SLE is able to preserve the higher-order information of the hypergraph. The AHD-SLE first maps the hypergraph to the SLE; then, the information is aggregated by Graph Convolutional Networks (GCNs) in the SLE. After that, the hyperedge embedding representation is obtained through a backmapping operation. Finally, an anomaly function is designed to detect anomalous hyperedges using the hyperedge embedding representation. Experiments on five different types of real hypergraph datasets show that AHD-SLE outperforms the baseline algorithm in terms of Area Under the receiver operating characteristic Curve(AUC) and Recall metrics. Full article

Product disassembly is an effective means of waste recycling and reutilization that has received much attention recently. In terms of disassembly efficiency, the number of disassembly skills possessed by workers plays a crucial role in improving disassembly efficiency. Therefore, in order to effectively and reasonably disassemble discarded products, this paper proposes a partial parallel disassembly line balancing problem (PP-DLBP) that takes into account the number of worker skills. In this paper, the disassembly tasks and the disassembly relationships between components are described using AND–OR graphs. In this paper, a multi-objective optimization model is established aiming to maximize the net profit of disassembly and minimize the number of skills for the workers. Based on the bat algorithm (BA), we propose an improved discrete bat algorithm (IDBA), which involves designing adaptive composite optimization operators to replace the original continuous formula expressions and applying them to solve the PP-DLBP. To demonstrate the advantages of IDBA, we compares it with NSGA-II, NSGA-III, SPEA-II, ESPEA, and MOEA/D. Experimental results show that IDBA outperforms the other five algorithms in real disassembly cases and exhibits high efficiency. Full article

The article presents an analysis of electromagnetic transient processes in long ultra-high voltage transmission lines, taking into account shield wires. It was shown that EMTP and Matlab/Simulink software are currently widely used in the study of transient processes in power lines. The EMTP software package uses the finite element method when integrating the equation that mathematically models the distributed parameter transmission line. The Matlab/Simulink software uses the d’Alembert method. In both cases, it is not known how the boundary conditions for the partial differential equation that mathematically models the transmission line are determined. The power line is analyzed as a distributed parameter system, described by a second-order partial differential equation. The advantage of the proposed method of calculating the boundary conditions for the abovementioned equation is the use of boundary conditions of the second and third types of Neumann and Poincaré, which allowed us to take into account the mutual influence of shield wires and phase conductors of the line in one power system. On this basis, the methodology for obtaining time domain graphs, spatial distributions, and traveling wave distributions of voltages and currents for phase conductors and line shielding wires is presented. The results of a computer simulation of transient processes when switching on the power line, taking into account controlled phase commutation and under single-phase earth fault conditions, are presented. All calculation results of transient processes presented in the article were obtained exclusively using numerical methods. Full article

The renewal and updating of the cadastre of real estate is a long and tedious task for land administration, especially for rural buildings that lack unified design and planning. In order to retain the required accuracy of all points in the register, huge extensive manual editing is often required. In this work, a precise cadastral survey approach is proposed using Unmanned Aerial Vehicle (UAV) imagery-based stereo point clouds. To ensure the accuracy and uniqueness of building outer walls, the non-maximum suppression of wall points that can separate noise and avoid repeated extraction is proposed. Meanwhile, the multiple cue weighted RANSAC, considering both point-to-line distance and normal consistency, is proposed to reduce the influence of building attachments and avoid spurious edges. For a better description of wall topology, the wall line segment topology graph (WLTG), which can guide the connection of adjacent lines and support the searching of closed boundaries through the minimum graph loop analysis, is also built. Experimental results show that the proposed method can effectively detect the building vector contours with high precision and correct topology, and the detection completeness and correctness of the edge corners can reach 84.9% and 93.2% when the mean square error is below 10 cm. Full article

Hypergraphs have become an accurate and natural expression of high-order coupling relationships in complex systems. However, applying high-order information from networks to vital node identification tasks still poses significant challenges. This paper proposes a von Neumann entropy-based hypergraph vital node identification method (HVC) that integrates high-order information as well as its optimized version (semi-SAVC). HVC is based on the high-order line graph structure of hypergraphs and measures changes in network complexity using von Neumann entropy. It integrates $s$-line graph information to quantify node importance in the hypergraph by mapping hyperedges to nodes. In contrast, semi-SAVC uses a quadratic approximation of von Neumann entropy to measure network complexity and considers only half of the maximum order of the hypergraph’s $s$-line graph to balance accuracy and efficiency. Compared to the baseline methods of hyperdegree centrality, closeness centrality, vector centrality, and sub-hypergraph centrality, the new methods demonstrated superior identification of vital nodes that promote the maximum influence and maintain network connectivity in empirical hypergraph data, considering the influence and robustness factors. The correlation and monotonicity of the identification results were quantitatively analyzed and comprehensive experimental results demonstrate the superiority of the new methods. At the same time, a key non-trivial phenomenon was discovered: influence does not increase linearly as the $s$-line graph orders increase. We call this the saturation effect of high-order line graph information in hypergraph node identification. When the order reaches its saturation value, the addition of high-order information often acts as noise and affects propagation. Full article

Climate change has become an increasingly intense global phenomenon in recent years. A great number of researchers support the idea that climate change is strongly connected to some environmental hazards, and specifically, those correlated to extreme weather events. Following the Paris Agreement, and due to the increased concern regarding climate change impacts, several indices have been established. The Climate Change Performance Index (CCPI) includes 59 countries and the EU, which cumulatively emit 92% of global greenhouse gases (GHGs), while the Global Climate Risk Index (CRI) analyzes to what extend countries have been affected by impacts of weather-related loss events. Both indices provide annual scores to each country and rank them based on those scores indicating the existing environmental situation. Our main purpose is to examine whether there is an interconnection between those two indices as well as testify whether economic growth is a great contributor to country’s environmental performance and as a result to climate risk. Using a sample of the reported countries for the year 2019, the latest reported year for both indices, and following a cross-sectional econometric analysis, we provide evidence regarding the connection of CCPI and CRI by using graphs, mapping visualization and econometric estimations in order to draw lines between indices. Moreover, we examine the interlinkages, and we estimate the influence caused by socio-economic factors and emissions levels per country. We provide evidence regarding the high-ranked and low-ranked countries and how they perform not only to an environmental base, but also to an economic base. Regarding the major finding, based on our analysis, no proven causality between CRI and CCPI was observed. Economic growth appears to have a significant impact on CRI but not on the CCPI, for the year 2019, while population density has an impact on both indices. Regarding greenhouse gas emissions, the econometric estimations provide evidence of significance for CRI but not for CCPI. An in-depth understanding of the current situation as well as of the factors affecting the climate conditions will give us the needed elements in order to minimize the adverse impact, if not improve the current situation. It is well known and stated that climate action should be taken so that we bequeath a safer and more sustainable planet to the next generations. Full article

This paper deals with the possibility of obtaining zinc from waste galvanic sludge, which is formed during galvanic plating. The aim of the experimental and practical part was to obtain zinc after the leaching of galvanic sludge. Leaching was performed in sulfuric acid, nitric acid and hydrochloric acid at different temperatures and time intervals with the addition of oxidizing agents as hydrogen peroxide or ozone. A separation of the leach and filtrate using filtration followed. The leach was further processed by a precipitation of iron and other metals using various agents. After a further filtration, the electrolysis was performed in order to obtain pure zinc on the cathode at the electrical voltage of approximately 3.5 V. Leaching using a solution of sodium hydroxide or potassium hydroxide was also performed when the prior dissolving of a major part of zinc into the leach occurred, while iron and non-ferrous metals remained in the leaching residue. After the filtration of the leach, the electrolysis with a high zinc yield of a purity of more than 99% followed. This way seems to be an optimal one for building a semi-industrial line for galvanic sludge recycling. All the partial products, i.e., the leach, the leaching residue, the filtrate, the solid precipitate and the separated metal on the cathode were subjected to chemical analyses. The analyses results are presented in tables and graphs. Full article

UAV may be limited by its flight height and camera resolution when aerial photography of a tea garden is carried out. The images of the tea garden contain trees and weeds whose vegetation information is similar to tea tree, which will affect tea tree extraction for further agricultural analysis. In order to obtain a high-definition large field-of-view tea garden image that contains tea tree targets, this paper (1) searches for the suture line based on the graph cut method in the image stitching technology; (2) improves the energy function to realize the image stitching of the tea garden; and (3) builds a feature vector to accurately extract tea tree vegetation information and remove unnecessary variables, such as trees and weeds. By comparing this with the manual extraction, the algorithm in this paper can effectively distinguish and eliminate most of the interference information. The IOU in a single mosaic image was more than 80% and the omissions account was 10%. The extraction results in accuracies that range from 84.91% to 93.82% at the different height levels (30 m, 60 m and 100 m height) of single images. Tea tree extraction accuracy rates in the mosaic images are 84.96% at a height of 30 m, and 79.94% at a height of 60 m. Full article

The current theories suggest the fundamental role of semantic memory in creativity, mediating bottom-up (divergent thinking) and top-down (fluid intelligence) cognitive processes. However, the relationship between creativity, intelligence, and the organization of the semantic memory remains poorly-characterized in children. We investigated the ways in which individual differences in children’s semantic memory structures are influenced by their divergent thinking and fluid intelligence abilities. The participants (mean age 10) were grouped by their levels (high/low) of divergent thinking and fluid intelligence. We applied a recently-developed Network Science approach in order to examine group-based semantic memory graphs. Networks were constructed from a semantic fluency task. The results revealed that divergent thinking abilities are related to a more flexible structure of the semantic network, while fluid intelligence corresponds to a more structured semantic network, in line with the previous findings from the adult sample. Our findings confirm the crucial role of semantic memory organization in creative performance, and demonstrate that this phenomenon can be traced back to childhood. Finally, we also corroborate the network science methodology as a valid approach to the study of creative cognition in the developmental population. Full article

Water distribution systems (WDSs) as critical infrastructures are subject to demand peaks due to daily consumption fluctuations, as well as long term changes in the demand pattern due to increased urbanization. Resilient design of water distribution systems is of high relevance to water suppliers. The challenging combinatorial problem of high-quality and, at the same time, low-cost water supply can be assisted by cost-benefit optimization to enhance the resilience of existing main line WDSs, as shown in this paper. A Mixed Integer Linear Problem, based on a graph-theoretical resilience index, is implemented considering WDS topology. Utilizing parallel infrastructures, specifically those of the urban transport network and the water distribution network, makes allowances for physical constraints, in order to adjust the existing WDS and to enhance resilience. Therefore, decision-makers can be assisted in choosing the optimal adjustment of WDS depending on their investment budget. Furthermore, it can be observed that, for a specific urban structure, there is a convergence of resilience enhancement with higher costs. This cost-benefit optimization is conducted for a real-world main line WDS, considering also the limitations of computational expenses. Full article

Glioblastoma multiforme (GBM) is a type of cancer which has the highest mortality rate among brain cancers (1–2). Momordica charantia, known as bitter melon, is a plant its pharmacological activities and nutritional properties. Due to contains bioactive compounds, M. charantia is used for cancer treatments, inflammation-related diseases and diabetes (3–4). In this study, it was aimed to investigate the effects of M. charantia extract on cell viability, cytotoxicity and migration capacity in U87G cell line. U87G was cultured in DMEM-high glucose containing FBS 10% (v/v) and penisillin-streptomicin 1% (v/v). Cells were incubated at 37 °C in a humidified 5% CO₂ incubator. The cytotoxic effect of M. charantia extract was determined by MTT analysis, cell viability by survival analysis and migration by wound-healing analysis. The results were evaluated by using ANOVA and GraphPad Prism7.0 program (GraphPad Software, La Jolla, CA, USA) in three replicates. IC₅₀ value of M. charantia extract was found 750 μg/mL which is statistically significant (* p < 0.05). The extract had an increasing lethal effect at the 16.6% (24 h), 42.6% (48 h), 79.3% (72 h) and 91.6% (96 h). According to the wound-healing analysis, the wound closed at 24 h in the control group and the wound gradually increased depending on time in the extract treated group. According to the results, M. charantia extract has a cytotoxic and a significant anti-proliferative effect on U87G. It might be used as therapeutic agent against to GBM. However, in order to understand the effect of M. charantia in living organisms, in vivo experiments must be determined. Full article

The increasing rate of heat in the climate in urban areas has become one of the striking problems in many developing countries. This study examined the relationships between the monthly temperature, rainfall and incidence of heat-rash between 2003 and 2012 in order to determine the impact of climate on occurrence of heat-rash in Akure, Ondo state, Nigeria. Data were obtained from Ondo State Specialist Hospital and Ondo State Meteorological Center. A line graph analysis was employed to identify the trend of the temperature, rainfall and incidence of this weather-based disease. Correlation analysis determined the relationship existing between the monthly temperature and the heat-rash. Tables and graphs were generally used for data presentation. The result shows that; the monthly temperature is low between the month of May and October when the minimum and maximum temperature is at 20.6 °C and 34.1 °C respectively; high temperature was recorded during the month of January, February, March and slightly different in April, November and December ranging from 24.6 °C to 35.1 °C.; the monthly temperature descends sharply during the month of March and remains low in April, May, June and July that characterized with high peak of rainfall; heat-rash has significant increase in 2003 (September), 2004 (September), 2007 (December), 2011 (November) and 2012 (October). The study recommends that people in this area and other related environments should engage in sensitizing the public on awareness of temperature—rash relationship and put up a measure of avoiding the heat effect during the periods of high temperature. Full article