bluuebunny/crossref_metadata_2025 huggingface dataset:
A Review of Anomaly Detection Strategies to Detect Threats to Cyber-Physical Systems
Authors: Jeffrey Nicholas , Tan Qing , Villar José R.
Published: July 2023

Cyber-Physical Systems (CPS) are integrated systems that combine software and physical components. CPS has experienced rapid growth over the past decade in fields as disparate as telemedicine, smart manufacturing, autonomous vehicles, the Internet of Things, industrial control systems, smart power grids, remote laboratory environments, and many more. With the widespread integration of Cyber-Physical Systems (CPS) in various aspects of contemporary society, the frequency of malicious assaults carried out by adversaries has experienced a substantial surge in recent times. Incidents targeting vital civilian infrastructure, such as electrical power grids and oil pipelines, have become alarmingly common due to the expanded connectivity to the public internet, which significantly expands the vulnerability of CPS. This article presents a comprehensive review of existing literature that examines the latest advancements in anomaly detection techniques for identifying security threats in Cyber-Physical Systems. The primary emphasis is placed on addressing life safety concerns within industrial control networks (ICS). A total of 296 papers are reviewed, with common themes and research gaps identified. This paper makes a novel contribution by identifying the key challenges that remain in the field, which include resource constraints, a lack of standardized communication protocols, extreme heterogeneity that hampers industry consensus, and different information security priorities between Operational Technology (OT) and Information Technology (IT) networks. Potential solutions and/or opportunities for further research are identified to address these selected challenges.
Spectral Clustering Approach with K-Nearest Neighbor and Weighted Mahalanobis Distance for Data Mining
Authors: Yin Lifeng , Lv Lei , Wang Dingyi , Qu Yingwei , Chen Huayue , Deng Wu
Published: July 2023

This paper proposes a spectral clustering method using k-means and weighted Mahalanobis distance (Referred to as MDLSC) to enhance the degree of correlation between data points and improve the clustering accuracy of Laplacian matrix eigenvectors. First, we used the correlation coefficient as the weight of the Mahalanobis distance to calculate the weighted Mahalanobis distance between any two data points and constructed the weighted Mahalanobis distance matrix of the data set; then, based on the weighted Mahalanobis distance matrix, we used the K-nearest neighborhood (KNN) algorithm construct similarity matrix. Secondly, the regularized Laplacian matrix was calculated according to the similarity matrix, normalized and decomposed, and the feature space for clustering was obtained. This method fully considered the degree of linear correlation between data and special spatial structure and achieved accurate clustering. Finally, various spectral clustering algorithms were used to conduct multi-angle comparative experiments on artificial and UCI data sets. The experimental results show that MDLSC has certain advantages in each clustering index and the clustering quality is better. The distribution results of the eigenvectors also show that the similarity matrix calculated by MDLSC is more reasonable, and the calculation of the eigenvectors of the Laplacian matrix maximizes the retention of the distribution characteristics of the original data, thereby improving the accuracy of the clustering algorithm.
Deep Reinforcement Learning for Dynamic Twin Automated Stacking Cranes Scheduling Problem
Authors: Jin Xin , Mi Nan , Song Wen , Li Qiqiang
Published: July 2023

Effective dynamic scheduling of twin Automated Stacking Cranes (ASCs) is essential for improving the efficiency of automated storage yards. While Deep Reinforcement Learning (DRL) has shown promise in a variety of scheduling problems, the dynamic twin ASCs scheduling problem is challenging owing to its unique attributes, including the dynamic arrival of containers, sequence-dependent setup and potential ASC interference. A novel DRL method is proposed in this paper to minimize the ASC run time and traffic congestion in the yard. Considering the information interference from ineligible containers, dynamic masked self-attention (DMA) is designed to capture the location-related relationship between containers. Additionally, we propose local information complementary attention (LICA) to supplement congestion-related information for decision making. The embeddings grasped by the LICA-DMA neural architecture can effectively represent the system state. Extensive experiments show that the agent can learn high-quality scheduling policies. Compared with rule-based heuristics, the learned policies have significantly better performance with reasonable time costs. The policies also exhibit impressive generalization ability in unseen scenarios with various scales or distributions.
Maritime Target Recognition and Location System Based on Lightweight Neural Network
Authors: Zhao Xiao , Chen Zhenjia , Wang Min , Wang Jingbo
Published: July 2023

China’s sea surface area is vast, the need to monitor the area is too large, and the traditional human monitoring method consumes a lot of manpower. Additionally, the monitoring period is too long; the monitoring efficiency is too low; and long-term human monitoring can easily cause visual fatigue, as well as missed detection and error detection. At present, the detection of sea surface targets generally includes infrared, visible light and other different means, which can obtain the image information of sea surface targets in different ways. The infrared target detection of the sea surface can be processed in the spatial domain and frequency domain, respectively, but the image resolution is not high in general, and the detection effect is not good because it is easily affected by weather. In this paper, we propose a maritime target detection method based on embedded vision. Based on visible video images, this paper realizes the rapid detection and recognition of sea surface targets. Clouds and waves in ocean images are filtered by adding an image preprocessing module. Compared with the traditional two-frame difference method, this algorithm has better detection capability for sea surface targets. Experiments were carried out in different weather conditions to detect moving ships at sea. By comparing the number of detection boxes and the detection accuracy, the accuracy of this method reaches 90.2 percent. By designing a single camera location algorithm for the marine environment, the world coordinate location of the marine target is realized. On this basis, the communication function is added to realize the intelligent monitoring of the sea surface without human intervention.
On the Efficiency of Mobile Hydraulic Power Packs Operating with New and Aged Eco-Friendly Fluids
Authors: Chiavola Ornella , Frattini Edoardo , Palmieri Fulvio , Fioravanti Ambra , Marani Pietro
Published: July 2023

With the increasing environmental awareness, in many applications, ranging from agriculture to industry and logistics, a wider and wider use of eco-friendly fluids is desirable. Although the chemical and biological aspects related to environmental compatibility have been extensively investigated by industries and researchers for obvious environmental reasons, not much literature is available on the performance of hydraulic components and systems operating with eco-friendly fluids, especially on the possible degradation of performance due to fluid aging. This work is aimed at studying the influence of eco-friendly fluids on the performance of external gear pumps for compact mobile hydraulic power units, which are among the most widespread hydraulic devices in the world, for their cost-effective and flexible construction. Once the experimental set-up is implemented to be well representative of the hydraulic power packs’ typical arrangement, pump performance is investigated. Pump energy performance is obtained in terms of volumetric efficiency and torque efficiency. Alongside the traditional fluid, two types of eco-friendly fluid available in the market are tested. Once the comparison is complete, the investigations are devoted to highlighting the impact of fluid aging on the pump performance. The fluids were aged through 2000 h operation under heavy-duty thermo-mechanical stress on a separate set-up and, afterwards, the pump performance was tested again with aged fluids. The results allow the assessment of the influence of different fluids on pump performance and a comparison of the impact of new versus aged eco-friendly fluids. The eco-friendly fluids exert a significant effect on the pump energy profile. The pump overall efficiency increases, marking an up to 5% improvement, depending on the cases. Fluid aging is found to reduce the pump’s overall performance. This paper addresses the key points defining the pump performance and provides new information on the topic. The results are original and represent a fundamental contribution to define the best practices for energy and maintenance management of hydraulic systems and to foster the deployment of further studies on models and simulation tools to catch the effect of the fluid condition.
Summary of Health-State Estimation of Lithium-Ion Batteries Based on Electrochemical Impedance Spectroscopy
Authors: Sun Xinwei , Zhang Yang , Zhang Yongcheng , Wang Licheng , Wang Kai
Published: July 2023

With the increasing application of lithium-ion batteries, accurate estimation of the state of health (SOH) of lithium-ion batteries is of great significance for the safe operation of lithium-ion battery systems and the reduction of operation and maintenance costs. The complex physical and chemical reactions inside the lithium battery and the complex external working conditions make it challenging to achieve an accurate health-state estimation and life prediction. Therefore, the accurate estimation of the SOH of lithium-ion batteries is an important issue. At present, electrochemical impedance spectroscopy (EIS) is widely used in the study of battery-power impedance characteristics and battery-state estimation due to its advantage of nondestructive measurement. For this reason, this paper summarizes the research progress of lithium-ion SOH estimation based on EIS in recent years and details it layer by layer, mainly from two aspects: first, the quantitative relationship model between the characteristic parameters and SOH is established by constructing a frequency domain-equivalent circuit model. Secondly, we construct a quantitative relationship model between EIS data and SOH using the data-driven method. Finally, the advantages and disadvantages of different methods and estimation accuracy are analyzed and compared, and the future estimation of SOH based on EIS is prospected.
A New Method for Comprehensive and Quantitative Characterization of Shale Microfractures: A Case Study of the Lacustrine Shale in the Yuanba Area, Northern Sichuan Basin
Authors: Li Pingping , Li Qianshen , Li Lei , Zou Huayao
Published: July 2023

Microfractures can connect isolated pores within shale, significantly increasing the shale’s storage capacity and permeability, and benefiting shale gas exploitation. Therefore, the quantitative characteristics of microfractures are important parameters for shale reservoir evaluation. In this paper, taking the Jurassic Da’anzhai Member (J1z4) lacustrine shale in the Yuanba area of the northern Sichuan Basin as an example, we propose a method for comprehensive and quantitative characterization of shale microfractures that combines rock thin section (RTS) and scanning electron microscopy (SEM) observations. The different magnifications of RTSs and SEM images lead to the identification and characterization of microfractures of different scales using these two methods. RTSs are mainly used to characterize microfractures with widths larger than 10 μm, while SEM is mainly used to characterize microfractures with widths smaller than 10 μm. These techniques can be combined to comprehensively and quantitatively characterize microfractures of different scales in shale. The microfracture characterization results show that the average total porosity of the J1z4 shale is 4.46%, and the average microfracture surface porosity is 1.20% in the Yuanba area. The calculated average percentage of microfracture porosity to total porosity is 21.09%, indicating that the J1z4 shale reservoir space is dominated by pores and has the conditions for stable shale gas production and potential for shale gas exploration. However, the percentage of microfracture porosity to total porosity of shale near faults and fold zones approaches or exceeds 50%, which may lead to the loss of shale gas. The new method proposed in this study is also useful for quantitative characterization of shale microfractures in the Sichuan Basin and other basins.
Is Banning Fossil-Fueled Internal Combustion Engines the First Step in a Realistic Transition to a 100% RES Share?
Authors: Danieli Piero , Masi Massimo , Lazzaretto Andrea , Carraro Gianluca , Dal Cin Enrico , Volpato Gabriele
Published: July 2023

Planning the best path for the energy system decarbonization is currently one of the issues of high global interest. At the European level, the recent policies dealing with the transportation sector have decided to ban the registration of light-duty vehicles powered by internal combustion engines fed by fossil fuels, from 2035. Regardless of the official positions, the major players (industries, politicians, economic and statistical institutions, etc.) manifest several opinions on this decision. In this paper, a mathematical model of a nation’s energy system is used to evaluate the economic impact of this decision. The model considers a superstructure that incorporates all energy conversion and storage units, including the entire transportation sector. A series of succeeding simulations was run and each of them was constrained to the achievement of the decarbonization level fixed, year by year, by the European community road-map. For each simulation, an optimization algorithm searches for a less costly global energy system, by including/excluding from the energy system the energy conversion units, storage devices, using a Mixed Integer Linear approach. Three optimization scenarios were considered: (1) a “free” scenario in which the only constraint applied to the model is the achievement of the scheduled decarbonization targets; (2) an “e-fuels” scenario, in which all new non-battery-electric light-duty vehicles allowed after 2035 must be fed with e-fuels; (3) a “pure electric” scenario, in which all new light-duty vehicles allowed after 2035 are battery-electric vehicles. The comparison of the optimum solutions for the three scenarios demonstrates that the less costly transition to a fully renewable energy system decarbonizes the transportation sector only when the share of renewable energy sources exceeds 90%. E-fueled light-duty vehicles always turn out to be a less expensive alternative than the electric vehicles, mainly because of the very high cost of the energy supply infrastructure needed to charge the batteries. Most of all, the costs imposed to society by the “e-fuels” and “pure electric” light-duty-vehicle decarbonizing scenarios exceed by 20% and 60%, respectively, the “free” transition scenario.
Feasibility Investigation of Attitude Control with Shape Memory Alloy Actuator on a Tethered Wing
Authors: Zhu Yufei , Tsuruta Ryohei , Gupta Rikin , Nam Taewoo
Published: July 2023

This study is aimed at assessing the feasibility of employing an innovative, smart-material-based control effector for an inflatable wing. A shape memory alloy (SMA) actuator is primarily investigated as a control effector in this work for its advantages of a simple actuation mechanism and a high force-to-weight ratio. This paper presents the design, control strategy and simulation results of the SMA actuator used as a stability augmentation system for a small-scale prototype kite. Stable flight of the kite is achieved during open wind tunnel tests using the SMA actuator. Based on experimental and simulation analyses, it is evident that the current SMA actuator is better for low-frequency actuations rather than stability augmentation purposes, as its performance is sensitive to practical conditions. The study also discusses potential improvements and applications of the SMA actuator.
Recent Trends in Real-Time Photovoltaic Prediction Systems
Authors: Gallardo Isaac , Amor Daniel , Gutiérrez Álvaro
Published: July 2023

Photovoltaic power forecasting is an important problem for renewable energy integration in the grid. The purpose of this review is to analyze current methods to predict photovoltaic power or solar irradiance, with the aim of summarizing them, identifying gaps and trends, and providing an overview of what has been achieved in recent years. A search on Web of Science was performed, obtaining 60 articles published from 2020 onwards. These articles were analyzed, gathering information about the forecasting methods used, the horizon, time step, and parameters. The most used forecasting methods are machine learning and deep learning based, especially artificial neural networks. Most of the articles make predictions for one hour or less ahead and predict power instead of irradiance, although both parameters are strongly correlated, and output power depends on received irradiance. Finally, they use weather variables as inputs, consisting mainly of irradiance, temperature, wind speed and humidity. Overall, there is a lack of hardware implementations for real-time predictions, being an important line of development in future decades with the use of embedded prediction systems at the photovoltaic installations.
Impact of Inter-Turn Short Circuit in Excitation Windings on Magnetic Field and Stator Current of Synchronous Condenser under Unbalanced Voltage
Authors: Li Junqing , Zhang Chengzhi , He Yuling , Hu Xiaodong , Geng Jiya , Ma Yapeng
Published: July 2023

Inter-turn short circuit in the excitation windings of synchronous condensers is a common fault that directly impacts their normal operation. However, current fault analysis and diagnosis of synchronous condensers primarily rely on voltage-balanced conditions, while research on short-circuit faults under unbalanced voltage conditions is limited. Therefore, this paper aims to analyze the fault characteristics of inter-turn short circuits in the excitation windings of synchronous condensers under unbalanced grid voltage. Mathematical models were developed to represent the air gap flux density and stator parallel currents for four operating conditions: normal operation and inter-turn short circuit fault under balanced voltage, as well as a process without fault and with inter-turn short circuit fault under unbalanced voltage. By comparing the harmonic content and amplitudes, various aspects of the fault mechanism of synchronous condensers were revealed, and the operating characteristics under different conditions were analyzed. Considering the four aforementioned operating conditions, finite element simulation models were created for the TTS-300-2 synchronous condenser in a specific substation as a case study. The results demonstrate that the inter-turn short circuit fault in the excitation windings under unbalanced voltage leads to an increase in even harmonic currents in the stator parallel currents, particularly the second and fourth harmonics. This validates the accuracy of the theoretical analysis findings.
A Systemic Comparison of Physical Models for Simulating Surfactant–Polymer Flooding
Authors: Alhotan Muhammad M. , Batista Fernandes Bruno R. , Delshad Mojdeh , Sepehrnoori Kamy
Published: July 2023

Three different reservoir simulators that utilize both two-phase and three-phase microemulsion phase behavior models are used to model surfactant–polymer flooding to determine and compare their results. Different models are used in each simulator to describe the physical behavior of injected chemicals into the reservoir, which raises the need to benchmark their results. The physical behavior models of polymer and surfactant were constructed and verified on a 1D scale reservoir model and further verified in a 3D model. Finally, simulations were conducted in a field-scale reservoir containing 680,400 grids, where results were compared and analyzed. The 1D and 3D model results suggest an excellent match between the different simulators in modeling surfactant–polymer floods. In the case of the field-scale model, the simulators matched in terms of oil recovery and total volumes produced and injected, while having similar reservoir pressure profiles but with significant discrepancies in terms of injected and produced chemicals. These results indicate that despite the differences in the calculated injected and produced chemicals due to the different models in the simulators, the effect of surfactant–polymer floods on oil recovery, total injected and produced fluids, and average pressure profiles can be comparably modeled in all of the three simulators.
A Special Issue: Electric Machinery and Transformers
Authors: Hiziroglu Huseyin R.
Published: July 2023

As the demand for electrical energy increases worldwide, engineers and scientists have been investigating new electrical systems and materials to meet this demand economically, having large-scale planning and employing environmentally friendly energy production and energy-efficient systems for consumption to minimize adverse environmental effects [...]
Polymeric Membranes for H2S and CO2 Removal from Natural Gas for Hydrogen Production: A Review
Authors: Rao Shraavya , Prasad Babul , Han Yang , Ho W.S. Winston
Published: July 2023

Natural gas, an important source of hydrogen, is expected to be crucial in the transition to a hydrogen-based economy. The landscape of the gas processing industry is set to change in the near future with the development of highly acidic sour gas wells. Natural gas purification constitutes a major share of the gas separation membrane market, and the shift to low-quality sour gas wells has been mirrored in the trends of membrane material research. Purification also constitutes the major portion of the cost of natural gas, posing implications for the cost of hydrogen production. This review provides an update on the current state of research regarding polymeric membranes for H2S removal, along with CO2 separation, from natural gas that is used for hydrogen production via steam methane reforming. The challenges of adapting polymeric membranes to ternary H2S/CO2/CH4 separations are discussed in detail. Key polymeric materials are highlighted, and the prospects for their application in H2S removal from natural gas are evaluated. Finally, the growing interest in H2 production from H2S is discussed. Advances in the membrane industry and the emergence of new membrane materials may significantly improve the commercial viability of such processes.
Numerical Simulation of Subcooled Flow Boiling in a Threaded Tube and Investigation of Heat Transfer and Bubble Behavior
Authors: Lei Ke , Wang Jinfeng , Xie Jing , Wang Bingjun
Published: July 2023

Three-dimensional subcooled flow boiling of R134a in a threaded tube was numerically simulated at the conditions of 200~400 kW/m2 heat flux, 3~20 K inlet subcooling, and 0.2~0.6 m/s inlet velocity. The bubble behavior in the horizontal threaded tube with 0.581 mm thread tooth height was observed. The effect of heat flux, inlet subcooling, and inlet velocity on bubble departure diameter and heat transfer coefficient were explored. The results presented the whole growth process of five kinds of bubbles. It was found that the bubbles either collapsed in cold liquid after leaving the heating wall or grew along the axial direction and contacted the heating wall. And there was no bubble sliding during the growth. In addition, the most important and special characteristic of bubble behavior in threaded tubes was the phenomenon of the bubble passing through the cavity. The coalescence and breakup behavior occurred after the bubble passed through the cavity. According to the discussions of the departure diameter and heat transfer coefficient, it was inferred that the bubble departure diameter increased with the increase of heat flux from 200~400 kW/m2 and subcooling from 3~20 K while decreasing with the increase of inlet velocity from 0.2~0.6 m/s. And due to the influence of the threaded tube structure, there are special points in the change of bubble departure diameter. The heat transfer coefficient of the bubbles in the threaded tube was higher than the smooth tube, which was increased by 1.5~12.5%. The heat transfer coefficient increased with the increase of heat flux and subcooling and is closely related to the bubble departure diameter.
Predicting Li-Ion Battery Remaining Useful Life: An XDFM-Driven Approach with Explainable AI
Authors: Nair Pranav , Vakharia Vinay , Borade Himanshu , Shah Milind , Wankhede Vishal
Published: July 2023

The accurate prediction of the remaining useful life (RUL) of Li-ion batteries holds significant importance in the field of predictive maintenance, as it ensures the reliability and long-term viability of these batteries. In this study, we undertake a comprehensive analysis and comparison of three distinct machine learning models—XDFM, A-LSTM, and GBM—with the objective of assessing their predictive capabilities for RUL estimation. The performance evaluation of these models involves the utilization of root-mean-square error and mean absolute error metrics, which are derived after the training and testing stages of the models. Additionally, we employ the Shapley-based Explainable AI technique to identify and select the most relevant features for the prediction task. Among the evaluated models, XDFM consistently demonstrates superior performance, consistently achieving the lowest RMSE and MAE values across different operational cycles and feature selections. However, it is worth noting that both the A-LSTM and GBM models exhibit competitive results, showcasing their potential for accurate RUL prediction of Li-ion batteries. The findings of this study offer valuable insights into the efficacy of these machine learning models, highlighting their capacity to make precise RUL predictions across diverse operational cycles for batteries.
Field Test Method and Equivalence Analysis of Delay Characteristics of DC Electronic Current Transformer
Authors: Zhu Mengmeng , Tang Hongda , He Zhaolei , Liao Yaohua , Tang Biao , Zhang Qunqun , Shu Hongchun , Deng Yaqi , Zeng Fang , Cao Pulin
Published: July 2023

DC electronic current transformer is the data source of the system control and protection device, so its measurement delay has always been concerned. In this paper, the DC current transformer is modelled equivalently and the key factors affecting the delay of shunt and the remote module are analyzed. A field test method for the delay characteristics of the DC electronic current transformer is proposed. Moreover, a complex multi-state large current generator and integrated test system are developed. On the basis of the IEC 60044-8 standard transmission protocol, the accuracy of standard signal acquisition with the shunt is better than 0.2%. The maximum output current of the established testing system is 600 A. Based on the field test in an actual HVDC project, transient step and various frequency signal components are applied for analyzing.
Modeling Height–Diameter Relationship Using Artificial Neural Networks for Durango Pine (Pinus durangensis Martínez) Species in Mexico
Authors: Ou Yuduan , Quiñónez-Barraza Gerónimo
Published: July 2023

The total tree height (h) and diameter at breast height (dbh) relationship is an essential tool in forest management and planning. Nonlinear mixed effect modeling (NLMEM) has been extensively used, and lately the artificial neural network (ANN) and the resilient backpropagation artificial neural network (RBPANN) approach has been a trending topic for modeling this relationship. The objective of this study was to evaluate and contrast the NLMEN and RBPANN approaches for modeling the h-dbh relationship for the Durango pine species (Pinus durangensis Martínez) for both training and testing datasets in a mixed-species forest in Mexico. The knowledge of this relationship is important for forest management and planning in Mexican Forestry. The total dataset considered 1000 plots (each plot 0.10 ha) (11,472 measured trees) randomly selected from 14,390 temporary forest inventory plots and the dataset was randomly divided into two parts: 50% for training and 50% for testing. An unsupervised clustering analysis was used to group the dataset into 10 cluster-groups based on the k-means clustering method. An RBPANN was performed for tangent hyperbolicus (RBPANN-tanh), softplus (RBPANN-softplus), and logistic (RBPANN-logistic) activation functions in the cross product of the covariate or neurons and the weights for the ANN analysis. Also, a different vector of hidden layers was used for training of ANNs. For both training and testing, 10 classical statistics (e.g., RMSE, AIC, BIC, and logLik) were computed for the residual values and to assess the approaches for the h-dbh relationship. For training and testing, the ANN approach outperformed the NLMEM approach, and the RBPANN-tanh had the best performance in both the training and testing of ANNs.
Artificial Weathering Effects on the Physical and Chemical Properties of Paulownia tomentosa and Pinus koraiensis Woods Heat-Treated in Oil and Air
Authors: Suri Intan Fajar , Purusatama Byantara Darsan , Kim Jong-Ho , Hidayat Wahyu , Iswanto Apri Heri , Park Se-Yeong , Lee Seung-Hwan , Kim Nam-Hun
Published: July 2023

This study evaluated the effect of artificial weathering on the surface characteristics, physical properties, and chemical compositions of oil heat-treated (OHT) and air heat-treated (AHT) Paulownia tomentosa and Pinus koraiensis woods. The untreated and heat-treated samples at 180, 200, and 220 °C for 2 h were exposed to ultraviolet (UV) and water for artificial weathering for 168 and 336 h, respectively, according to ASTM G53-96. The weathering experiment comprised 2 h of UV-light irradiation followed by 2 h of condensation cycles. Color change, volumetric swelling, and chemical components of weathered samples were determined. In both species, heat-treated woods showed a significantly lower total color change and volumetric swelling than the untreated woods. The total color change and VS of OHT woods were significantly lower than those of AHT. Fourier transform infrared spectra indicated that the lignin peaks in untreated and AHT woods decreased after weathering exposure, whereas the peaks were stable in OHT woods. Oil heat treatment is an effective method to stabilize dimensional change and color quality during weathering.
A Simulation Study on the Influence of Street Tree Configuration on Fine Particulate Matter (PM2.5) Concentration in Street Canyons
Authors: Liu Junyou , Zheng Bohong
Published: July 2023

Because motor vehicles emit a large amount of PM2.5 pollution, traffic-related emissions have always been an important part of PM2.5 pollution. To better understand the influence of street trees on traffic-related PM2.5 pollution, our study focused on camphor trees, common evergreen urban street trees in central and southern China. We used ENVI-met for the simulation of PM2.5 pollution and to build a model to show the distribution of PM2.5 pollution along a section of Xinyao North Road in downtown Changsha City in central China. Based on this model, we constructed four other models with different heights, quantities, and distances between street trees, where each model had high feasibility and aimed to determine how these affect the PM2.5 concentration on the designated block. We performed simulations within different time frames in the year. We found that the wind can promote the diffusion of PM2.5 in the street canyon. Too dense a distribution of tall street trees will have a negative impact on PM2.5 concentration in street canyons. A moderate distance between street trees is conducive to the dispersion of pollutants. Because the crown of 5 m high street trees is small, its negative impact on the dispersion of wind and PM2.5 is relatively small, so further increasing the number of 5 m high street trees in street canyons with densely distributed tall street trees will have only a little more negative impact on PM2.5 concentration in street canyons. The PM2.5 concentration in the street canyon is generally better when the street trees are 5 m long, even if the number of 5 m high street trees is relatively large. Although the crown size of 15 m high street trees is larger than that of 10 m street trees, the vertical distance between the canopy of 15 m high street trees and the ground is usually greater than that of 10 m high street trees. The distance between the canopy of 15 m high street trees and the breathing zone is usually greater than that of the 10 m street trees. Longer distances lead to a weakening of its impact on PM2.5. When the 15 m high and 10 m high street trees are more scattered in the street, their effects on the PM2.5 concentration at the height of the breathing zone (1.5 m) are generally similar.
New Technologies for Expedited Forest Inventory Using Smartphone Applications
Authors: Sandim André , Amaro Mariana , Silva Maria Emilia , Cunha Jorge , Morais Susana , Marques Alexandra , Ferreira André , Lousada José Luis , Fonseca Teresa
Published: July 2023

The forest inventory plays a crucial role in forest management planning, and it is the first step in planning actions for forest production. However, conducting an inventory can be expensive and complex. Forest inventory applications on smartphones have emerged as an alternative to traditional methods and they aim to make field data collection more accessible to non-professionals while ensuring accuracy in determining the volume of wood in a given area. This study evaluates the effectiveness of the Katam, Arboreal, and Trestima applications compared to traditional data collection methods. The study focuses on assessing the stand density and diameter of sampled trees—two key variables that are assessed in forest inventories. Two species, maritime pine (Pinus pinaster Aiton) and Eucalyptus spp. (mainly Eucalyptus globulus and Eucalyptus nitens), were used to evaluate the performance of the methods, with assessments performed in the stands of diverse dendrometric characteristics, specifically those regarding the tree age, stand density, and topographic conditions (flat or sloping terrain). For the purpose of comparison, goodness-of-fit statistics (R2, RMSE, and BIAS) were calculated, and an analysis of the diameter distribution and comparison of the mean diameter, number of trees per hectare, and basal area were performed. In general, the applications were accurate, and the average basal area did not differ significantly from the traditional method. The diameter measurements showed good accuracy. The accuracy of the applications varied depending on the terrain and forest characteristics, with the applications performing better in areas with flat terrain, as well as with older forests that were regular and had low under-cover density. In contrast, the applications performed worse in younger, irregular forests with sloping terrain, high tree density, and those with a great deal of understory vegetation. The applications still need to evolve in evaluating other important variables (such as tree height or volume) as they are currently estimated from auxiliary variables through mathematical equations.
Analysis of Selection-Cutting Silviculture with Thujopsis dolabrata—A Case Study from Japan Compared to German Plenter Forests
Authors: Műnzer Leonie , Masaka Kazuhiko , Takisawa Yuko , Hein Sebastian , End Christoph , Sugita Hisashi , Hoshino Daisuke
Published: July 2023

(1) Background: In Japan, single-tree selection-cutting silviculture with hiba (Thujopsis dolabrata var. hondai) is a traditional silvicultural system and is well documented. We evaluated an experimental forest regarding past structural dynamics and future development while comparing it to the German multilayer coniferous “Plenterwald/plenter forest”. (2) Methods: Classical growth and yield data were recorded since 1995 from two hiba-mixed species plots, one managed since Matsukawa’s (the founder) times in 1931 and the other unmanaged since 40–50 years before 1931. (3) Results: Clear structural differences appeared, with the managed plot having a reverse J-shaped DBH and tree height distribution curve, and a higher percentage of hiba, also typical for German plenter forests’ intensely multi-storied structure. The unmanaged plot was composed of trees with large stem diameters, even though they were more evenly distributed, together with less admixed species. In both plots, the growing stock increased in the past. While the managed plot’s growing stock in 2019 was 561 m3 ha−1, the unmanaged plot reached 982 m3 ha−1 with large portions accumulated in DBH classes >60 cm. (4) Conclusions: When compared to today’s clearcutting system in Japan, selection silviculture shows advantages and may thus serve as a valuable inspiration for silviculture in Japan as it was with plenter forestry for Germany.
Effects of Soil Arthropods on Non-Leaf Litter Decomposition: A Meta-Analysis
Authors: Cheng Wei , Tie Liehua , Zhou Shixing , Hu Junxi , Ouyang Shengnan , Huang Congde
Published: July 2023

According to the widely accepted triangle model, global litter decomposition is collectively controlled by climate, litter initial quality, and decomposers. However, the specific contribution of soil arthropods to litter, especially the non-leaf litter, the decomposition of terrestrial ecosystems and its drivers are still unclear. We conducted a global meta-analysis based on 268 pairs of data to determine the contribution and pattern of soil arthropods to branch, stem, and root litter decomposition in farmlands, forests, and grasslands and analyzed the relationship of soil arthropods’ decomposition effect and potential drivers. Our results showed that: (1) soil arthropods increased global non-leaf litter mass loss by 32.3%; (2) the contribution varied with climate zone and ecosystem type, with a value of subtropical (53.3%) > temperate (18.7%) > tropical (14.7%) and of farmlands (40.6%) > grasslands (34.3%) > forests (0.6%), respectively; (3) the soil arthropods’ decomposition effect gradually decreased with decomposition time, and it was higher in litterbags with a mesh size of 1–2 mm (65.4%) and >2 mm (49.8%) than that of 0.5–1 mm (13.6%); (4) the soil arthropods’ decomposition effects were negatively correlated with the litter initial C/N ratio, mean annual precipitation (MAP; p < 0.001), and elevation and was positively correlated with litter weight. In conclusion, soil arthropod promoted global non-leaf litter decomposition, and the contribution varied with climate zone, ecosystem type, and decomposition time as well as litterbag mesh size. Overall, this study improves the understanding of soil arthropods driving global non-leaf litter decomposition.
The Mechanical Stability of Pure Norway Spruce Stands along an Altitudinal Gradient in the Czech Republic
Authors: Dušek David , Novák Jiří , Černý Jakub
Published: July 2023

Norway spruce stands are established and managed along various site conditions in central Europe. Currently, spruce often grows at locations outside of its ecological optimum, resulting in extensive damage elicited by harmful abiotic and biotic factors, which relatively shortens the time to change this adverse status in the adaptation frame by foresters. Except for the rapid change in species composition through clear-cuts, another way is possible, i.e., stabilising current (especially young) spruce stands to extend the time required to implement adaptation measures. The assumption that different site conditions will have to be respected as part of this adaptation was confirmed by our study based on NFI data of the Czech Republic. A semiparametric generalized linear model (GAM) was used to model the relationship between the height-to-diameter ratio and forest stand age, differentially considering particular forest vegetation zones. Spruce stands with lower elevations attain a lower stability (expressed by their height-to-diameter ratio; HDR) than those in the mountains. The HDR culminated in lower and middle altitudes in the first half of the rotation period, representing the most critical timing and effectivity of silvicultural measures. Contrary to previous findings, we found higher HDR values at nutrient-rich sites than those at acid ones, especially up to 50–60 years old. Therefore, more research should be devoted to the issue concerning the same thinning regime under different site conditions.
Changes in Community Structure and Functional Characteristics of Soil Bacteria and Fungi along Karst Vegetation Succession
Authors: Li Yuanyong , Tang Qian , Yuan Congjun , Zhu Sixi , Ye Yuyan , Wu Peng , Cui Yingchun , Ding Fangjun
Published: July 2023

Soil microbes are a crucial component of karst ecosystems, and exploring their community changes during succession can help to elucidate the mechanisms driving succession dynamics. However, the variation of soil microbial communities during vegetation succession in karst ecosystems is still poorly understood. We studied the variations in community structure and potential functions of soil microbes within the four successional stages of grassland (GL), shrubland (SL), secondary forest (SF), and primary forest (PF) for the topsoil (0–10 cm) and subsoil (10–20 cm) in a karst area using high-throughput sequencing. The research findings showed that the bacterial and fungal community diversity and composition changed more obviously in the topsoil than in the subsoil across the succession. With vegetation succession, the structural and functional characteristics of soil bacterial and fungal communities show different trends, with soil fungal communities having a greater response to successional stage changes. Actinobacteria and Acidobacteria were dominant in secondary and primary forests, respectively, while Bacteroidetes was prevalent in grassland. However, the change in Proteobacteria was not significant at both soil depths. Ascomycota was the dominant phylum of soil fungi throughout the succession. The function of soil bacteria was mainly carbohydrate metabolism, which had the highest proportion in the shrubland at different soil depths. The dominant fungal functional groups were saprotroph, pathotroph, and pathotroph–saprotroph. The soil bacterial communities were observably affected by soil organic carbon, total nitrogen, total potassium, ammonia nitrogen, nitrate nitrogen, and leucine aminopeptidase, among which soil organic carbon, ammonia nitrogen, and leucine aminopeptidase mainly influenced the bacterial community in the topsoil, while nitrate nitrogen chiefly influenced the bacterial community in the subsoil. The soil fungal community was only significantly affected by soil organic carbon. Collectively, these results indicate that the effects of vegetation succession on soil microbial communities are largely driven by successional stage and soil properties, with soil fungi being more susceptible to the vegetation successional stage and soil bacteria being more sensitive to the soil properties. During this process, soil bacterial and fungal communities follow different succession patterns.
How Did the Southwest China Mountains Turn Green from 2000 to 2020? A Case Study in Chongqing
Authors: Cheng Jie , Qian Mingjie , Liu Junfang , Chen Xiaofeng , Zuo Yiting , Zhao Zhongqiu , Zhang Jianjun
Published: July 2023

Vegetation, as a comprehensive ecological indicator of environmental change, plays an essential role in terrestrial ecosystems. Dramatic climate change and increasing anthropogenic disturbances have led to a profound change in vegetation cover. This study employed Moderate Resolution Imaging Spectroradiometer (MODIS) and other relevant data in Southwest China mountains, using Chongqing as a case study, to explore the variation in Normalized Difference Vegetation Index (NDVI) and its spatial differentiation mechanisms, quantify the relative contributions of climate change and human activities to these variations, and assess the effects of ecological policies, including afforestation, mountain closure forestry and natural forest conservation, and agricultural improvement. Results showed that the spatial distribution of annual NDVI, on average, varied 0.109 to 0.929, with the rate varying from −0.033 to 0.017 yr−1. NDVI was improved in 83.4% areas of Chongqing, and human activities contributed 69.1% of revegetation, whereas climate contributed 30.9%. On the other hand, human activities and climate change contributed 76.3% and 23.7% to vegetation degradation in 17.6% areas, respectively. Moreover, the explanatory power of anthropogenic factors on spatial differentiation of NDVI were stronger than that of climatic factors, and land use type was the dominant factor. The cumulative afforestation area, effective irrigation rate, fertilizer application, and total agricultural machinery power of the whole city was extremely significantly correlated with NDVI (p < 0.01), and the vegetation cover fluctuation in the region affected by natural forest protection and mountain closure forestry project was much more stable than that in non-protected areas, which to a certain extent reflected the effective implementation of local ecological protection, agricultural improvement, and other related policies.
Evaluation of the 20-Year Restoration Process in an Air-Pollution-Damaged Forest near the Ulsan Industrial Complex, Korea
Authors: Kim Dong-Uk , Lim Bong-Soon , Seok Ji-Eun , Kim Gyung-Soon , Moon Jeong-Sook , Lim Chi-Hong , Lee Chang-Seok
Published: July 2023

A study was conducted to evaluate the effects of restoration practices in a forest ecosystem near the Ulsan Industrial Complex in southeastern Korea. The calcium and magnesium contents in the soil, as well as the soil pH, increased after the application of a soil ameliorator but decreased again after 20 years. Meanwhile, the aluminum content presented the opposite trend. After restoration, the species composition and diversity of vegetation tended to differ from that of the non-restored site over time while continuously becoming more similar to that of the reference site. The ratio of exotic plant species was lower than that at the non-restored site but higher than that at the reference site. The frequency distribution for the diameter class of oaks established through restoration presented a reverse J-shaped pattern, and thus, they can be maintained continuously; similar results were obtained for the reference site. In sum, the forest ecosystem near the industrial park—which had been severely degraded due to air pollution and soil acidification—was restored to a forest close to natural conditions through restorative treatments, including the neutralization of acidic soil and the introduction of tolerant species.