Center Of Ellipse Research Articles

Intrasubject and intersubject variability of stabilography parameters in normal conditions and simulated space mission isolation

The state of isolation and confinement causes several symptoms as a psycho-physiological stressor. The crew’s health and condition may play a crucial role in prolonged space sojourns success. However, it’s important to distinguish the role of microgravity from the distress aspect to better understand human physiology in training during space missions. Although stabilography is a commonly used biomechanical technique, there is not enough data on the measurement repeatability. It has already been proven that the stabilograms differ between subjects due to multiple anatomical and physiological characteristics but the intersubject variability remains unclear. The study provides statistical data on 10 different stabilography measurements of 18 participants performed on different days during an analog space mission (5 females and 4 males) and in normal conditions (5 females and 4 males). Descriptive statistics and interclass correlation were used to determine intra- and intersubject variability. Mann-Whitney test was used for group comparison. Isolation was found to significantly impact symmetry and forefoot/backfoot index in trials with eyes open and ellipse area and forefoot/backfoot index in trials with eyes closed. The results show a diverse level of stabilography parameters measurement repeatability. The least stable parameter was the ellipse area (%SD = 45.79 %) and the most stable stance symmetry (%SD = 4.60 %). The results confirm ellipse area and center of pressure path poor repeatability and relative stability of parameters describing load distribution. It also proves the importance of performing multiple trials in stabilography studies to reduce the risk of erroneous results caused by intersubject variability.

Research on Water Ecological Resilience Measurement and Influencing Factors: A Case Study of the Yangtze River Economic Belt, China

Industrial development and population expansion has had serious negative impacts on the water ecological environment, and enhancing water ecological resilience (WER) has become a new sustainable development goal. Current research on WER is mostly about ecological resilience assessment including water systems. In order to explore the WER of the Yangtze River Economic Belt (YREB), ecological resilience and water ecology were combined to form the concept of WER. Based on the “social-ecological” resilience perspective, a DCSMI (Driving Force—Carrying Capacity—State—Management—Innovation) WER evaluation index system was constructed, which consists of five subsystems. The WER of the YREB from 2011 to 2022 was measured by using game-theoretic combination weights and the comprehensive evaluation method, which were then combined with the kernel density (KD) estimation, the Thiel index, and the center of gravity-standard deviation ellipse (SDE) method to reveal the WER differences and spatial evolution characteristics of the YREB. Finally, the key factors influencing WER were explored using the BP-DEMATEL model. It was found that (1) the average value of WER in the YREB has declined from 0.4562 to 0.4442, the polarization of WER is obvious, the overall gap is on a widening trend, and the gap between different basins is the main reason for the differences in WER in the YREB. (2) The WER of the YREB presents an asymmetric U-shaped distribution pattern with the downstream optimal, upstream medium, and midstream worst, and the spatial evolution presenting a northwestern–southeastern pattern. (3) The key factors of the top-ranked provinces in the WER index are concentrated in the layer of the State (S) indicators, the middle-ranked provinces and the back-ranked provinces are more influenced by the Driving Force (D) and the Carrying Capacity (C) indicators, respectively, and the Management (M) and Innovation (I) indicators are distributed in several provinces. These results can provide theoretical support for the construction of “resilient cities” and water ecology optimization in the YREB.

View factor of a spheroid and an ellipse from a plate element

A view factor is a fundamental parameter for evaluating radiative heat transfer between two surfaces. View factors for various geometries have been investigated in the past studies. However, the view factors of a spheroid and an ellipse are known only for limited configurations. In this study, the analytical view factor expressions of an ellipse and a spheroid from a plate element are derived. The spheroid view factor solution applies to a plate element with any position and orientation, and the ellipse solution is valid when the plate element is on the perpendicular axis through the ellipse center. The derived analytical solutions are validated against the numerical results for various configurations, showing deviations of less than 0.0001 for all cases.

Spatiotemporal Evolution of Land Cover and Landscape Ecological Risk in Wuyishan National Park and Surrounding Areas

Previous studies on national park conservation have focused mainly on their internal areas, and few studies have focused on national parks and their surrounding areas as unified entities. Therefore, the investigation of land cover and landscape ecological risks in national parks and surrounding areas is essential for overall ecosystem protection and regional sustainable development. This study examines the spatiotemporal evolution of land cover and its landscape ecological risk in Wuyishan National Park, China, and its surrounding areas (WNPSA) from 1990 to 2020. The results show that (1) the land cover of WNPSA from 1990 to 2020 predominantly exhibited a consistent decline in forested areas, paralleled by an augmentation in farmland and impervious surface areas. The center of standard deviation ellipse of impervious surfaces has been progressively moving further south in tandem with the expansion of these surfaces, primarily located within the county town of Fujian Province. (2) The Wuyishan National Park (WNP) areas were dominated by low values of landscape index, and the high value areas in the park were mainly located at the provincial boundary area, with a gradual narrowing during 1990–2020, suggesting a decrease in landscape heterogeneity within the park. High value areas in the surrounding areas mainly occurred in areas with clustered impervious surfaces (e.g., the county town), where part of them located in Wuyishan City have spread to the edge area southeast of WNP. (3) From 1990 to 2020, the lowest-risk areas continue to expand. However, as the medium-risk zone of the adjacent region extends into the edge of the national park, the low risk zone within the national park exhibits a trend from continuous to separate with the neighboring low risk zone. This led to an escalating stress effect on the ecological security of both the adjacent regions and the national park’s boundary areas due to land cover changes.

Exact computation of projected sphere centres in cone beam x-ray projections

A method is presented for fitting the projected centres of spheres in cone beam x-ray imaging. By using a suitable coordinate system, the method allows direct and exact calculation of the sphere centre without fitting the projection shape with an ellipse and correcting from the ellipse centre to the sphere centre. Advantages in numerical implementation result from the number of unknown variables being reduced compared to ellipse fits. Additionally, the orientation of the detector relative to the x-ray source can be obtained from fitting the shapes of projections of multiple spheres without knowledge of the positions or dimensions of the spheres. The accuracy of the method is compared to other techniques using simulated x-ray projections.

Bone Density Distribution Pattern in the Lateral Wall of the Femoral Intercondylar Notch: Implications for the Direct Insertion of the Femoral ACL Attachment

Background: The ideal position of the femoral bone tunnel in the anterior cruciate ligament (ACL) is controversial. The functional importance of the ACL fiber varies depending on where it is attached to the femur. Functionally important fibers can cause high mechanical stress on the bone, and the Wolff law predicts that bone mineral density will increase at high mechanical stress sites. Purpose/Hypothesis: The purpose of this study was to use computed tomography imaging to determine the distribution pattern of bone density in the lateral intercondylar wall. It was hypothesized that the high-density area (HDA) of the lateral intercondylar wall would reflect the functional insertion of the ACL as reported in previous anatomic studies. Study Design: Descriptive epidemiology study. Methods: Data from 39 knees without ACL injuries were retrospectively collected. The HDA of the lateral intercondylar wall was defined as the region containing the top 10% of the radiodensity values. The shape of the HDA was approximated as an ellipse, and the quadrant method was used to determine the center of the ellipse. The association between the ratio of the minor axis to the major axis of the ellipse and background characteristics was investigated. Results: According to the quadrant method, the center of the HDA ellipse was 33.6% in the deep-shallow direction and 23.4% in the high-low direction. The center of the ellipse was comparable to the anatomic center of the ACL footprint, as previously reported. The ratio of the minor axis to the major axis of the ellipse was 0.58 (95% CI, 0.54-0.62). There was a significant negative correlation between the ratio of the minor axis to the major axis of the HDA ellipse and the posterior tibial slope ( r = −0.38, P = .02). Conclusion: The center of the HDA ellipse was found to be similar to the anatomic center of the ACL footprint. Considering the mechanical stress responses in bone, the HDA of the lateral intercondylar wall has the potential to represent the ACL insertion, especially functional insertion.

Time-lapse Very Long Baseline Interferometry Imaging of the Close Active Binary HR 1099

We report multiepoch astrometric very long baseline interferometry observations of the chromospherically active binary HR 1099 (V711 Tau, HD 22468) at six epochs over 63 days using the Very Long Baseline Array at 22.2 GHz. We determined hourly radio positions at each epoch with a positional uncertainty significantly smaller than the component separation. The aggregate radio positions at all epochs define an ellipse in the comoving reference frame with an inclination i=39.°5−3.°5+3.°6 and longitude of ascending node Ω = 212° ± 22°. The ellipse center is offset from the Third Gaia Celestial Reference Frame position by Δα = −0.81−0.37+0.25 , Δδ = 0.45−0.25+0.23 mas. All radio centroids are well displaced from the binary center of mass at all epochs, ruling out emission from the interbinary region. We examined the motion of the radio centroids within each epoch by comparing hourly positions over several hours. The measured speeds were not statistically significant for five of the six epochs, with 2σ upper limits in the range 200–1000 km s−1. However, for one flaring epoch, there was a 3σ detection v ⊥ = 228 ± 85 km s−1. This speed is comparable to the mean speed of observed coronal mass ejections on the Sun.

Hand-eye calibration of line structured-light sensor by scanning and reconstruction of a free-placed standard cylindrical target

This paper proposed a hand-eye calibration method for a line structured-light (LSL) scanner mounted on industrial robot. Unlike widely used spherical targets, the target used in our work is a cylinder, which is inexpensive and easy to be manufactured in larger size to cover a wider calibration space. In order to address the profile self-occlusion and drastically shape changing of conic section during calibration, an unconstrained dimensionality reduction method is proposed to fit the scanned profiles. Based on fitted ellipse centers under various robot poses, the hand-eye calibration model is developed based on the difference between cylinder radius and the distance from the profile point to the cylinder axis. Simulation and actual experiments have shown that the proposed ellipse fitting method is more accurate and robust, and the calibration method achieves higher reconstruction accuracy under the same robot positioning error, need less robot operations to obtain more accurate hand-eye parameters.

Design method of rack-and-pinion pair with pure rolling variable transmission ratio

Rack-and-pinion pair with variable transmission ratio can achieve the unity of vehicle steering portability and sensitivity, and effectively reduce vehicle steering energy consumption. Therefore, they have gradually become the standard core components of steering system. However, the gear surface of rack-and-pinion pair with variable transmission ratio is seriously worn under long-term service, which leads to the degradation of performance and cannot achieve the theoretically variable transmission ratio. To solve these problems, a new configuration of rack-and-pinion pair for commercial vehicle with herringbone pure rolling variable transmission ratio is proposed in this paper. The tooth surface mathematical model of the fully-conjugate variable transmission ratio is established based on the variable speed envelope principle, and the formula for calculating pure rolling point of tooth surface with variable transmission ratio is derived. The tooth point deviation equation of fully-conjugate variable transmission ratio is proposed, and the method of constructing pure rolling variable transmission ratio tooth surface is formed. The finite element analysis shows that the design of the pure rolling rack-and-pinion pair with variable transmission ratio has good tooth surface quality without the phenomenon of contact spot intermittent and edge contact during the meshing process, and the contact ellipse center of the tooth surface is located at the theoretical pure rolling point of the tooth surface. The measured transmission ratio curve of the samples is in good agreement with the theoretical variable transmission ratio curve, and the transmission ratio error is within a reasonable range. The contact strips of tooth surface impression test are consistent with those of finite element analysis, which indicates that the designed rack-and-pinion pair with variable transmission ratio has the characteristics of pure rolling and point contact. The tooth surface wear test shows that the wear of pure rolling gear surface with variable transmission ratio is obviously less than that of traditional gear surface with variable transmission ratio. The above tests and simulation indicate the correctness of the design method.

Diagnosis of Power Switch Faults in Three-Phase Permanent Magnet Synchronous Motors via Current-Signature Technique

The paper deals with the development of a model-based current-signature algorithm for the detection and isolation of power switch faults in three-phase Permanent Magnet Synchronous Motors (PMSMs). The algorithm, by elaborating the motor currents feedbacks, reconstructs the current phasor trajectories in the Clarke plane through elliptical fittings, up to detecting and isolating the fault depending on the characteristics of the signature deviation from the nominal one. As a rough approximation, as typically proposed in the literature, the fault of one out of six power switches implies that, at constant speed operation, the phasor trajectory deviates from the nominal circular path up to a semi-circular “D-shape” signature, the inclination of which depends on the failed converter leg. However, this evolution can significantly deviate in practical cases, due to the dynamics related to the transition of motor phase connections from failed to active switches. The study demonstrates that an online ellipse fitting of the current signature can be effective for diagnosis, through correlating the ellipse centre to the location of the failed switch. The performances of the proposed monitoring technique are here assessed via the nonlinear simulation of a PMSM employed for the propulsion of a lightweight fixed-wing Unmanned Aerial Vehicle (UAV), by quantifying the fault latencies and the related transients.

The attenuating effect of green finance on environmental quality and its mechanism: Spatial modified PTRM model

The traditional Panel Threshold Regression Model (PTRM) neglects spatial factors, causing model bias in prior research on green finance's environmental impact. To address this shortcoming, a Spatial Modified PTRM Model is constructed to investigate green finance's spatial threshold effects on the environment. Moreover, this study analyzes temporal and regional heterogeneities and explores the influence mechanisms underlying the observed attenuating in environmental effects. Results show that: (1) The "more developed, less effective" phenomenon in green finance's environmental impact is confirmed, instead of cumulative enhancement, as green finance intensity surpasses thresholds around −0.48 to −0.61, its effects decrease by approximately 66.3%–156.1% units. (2) Temporal and regional heterogeneities in the attenuating phenomenon are explored, in 2015, the attenuation phenomenon initiates, transitioning from statistical ''insignificance'' to ''significance'', from ''rapid development'' to ''plateau'', and from ''single high-value peak'' to ''single low-value peak'', also, developed green finance regions experience the most significant attenuation, up to 76.0% more pronounced than less developed regions. (3) The unbalanced regional distribution and the free-riding phenomenon are confirmed as two factors contributing to the attenuation, with the ellipse center shifting southward and the index deviating since around 2015, meanwhile, the free-riding intensity has increased over time, surging from around 0.10 in the early stages to approximately 0.40 in 2021.

Real-time pose correction and registration of complex workpiece in robotic machining considering normal consistency constrains

Efficient and precision model registration of complex workpiece with arbitrary pose is a challenging task that determines the effects of intelligent robotic machining. Aiming at the problems of limited field of view of 3D vision sensors such as surface structured light and the complexity of scanning-splicing-registration algorithm, in this paper a real-time pose correction and registration algorithm of complex workpiece in robotic machining considering normal consistency constrains is proposed. Specifically, the operations on ellipse feature detection and center point extraction are performed based on the arc-support line segment, and then the actual three-dimensional coordinate of the ellipse is obtained by the camera conversion matrix. Furthermore, considering the constrained normal consistency of the center points set of ellipses on the model surface, the pose of the target workpiece is corrected in real-time by the improved ICP registration algorithm. Taking the automotive flywheel shell as a typical application object, the experimental results demonstrate that the registration correction time of the proposed algorithm is 0.5 s, and the registration accuracy can reach 0.35 mm. The repetitive correction time of the algorithm after arbitrarily changing the workpiece pose is less than 1 s, and the positioning accuracy of the guiding robot is less than 1.5 mm. On the premise of satisfying the robotic machining quality requirements, the pose of the complex workpiece model can be corrected in real-time for subsequent robotic machining.

The spatial pattern of Scirpus mariqueter expansion and the associated mechanism of self-organization using unmanned aerial vehicles and its significance for coastal wetland restoration.

Understanding the spatial expansion process of salt marshes and quantifying the factors driving this expansion are crucial for the management and restoration of coastal wetlands. In this study, we aimed to illustrate the expansion process of Scirpus mariqueter using drone remote sensing and quantify its relationship with habitat quality. Our hypothesis was that landscape metrics could serve as valuable indicators for prioritizing habitat restoration efforts along the coast. We utilized drone remote sensing and adopted the simple Greenness Index to reflect the growth status of S. mariqueter. Using this index, we computed the standard deviation ellipse and growth center. To evaluate habitat quality, we developed a method based on our previous research and other relevant reports. We then conducted a quantitative analysis of the expansion process of S. mariqueter in areas with varying habitat quality. We found that S. mariqueter's optimal elevation was 3.7m, with a range of 2.5 to 4.3m. The threshold value for soil total nitrogen was 0.3g/kg, and the tolerance threshold for soil salinity was 2500ppm. These three factors, elevation, soil total nitrogen, and soil salinity, collectively influenced habitat quality, with weights of 0.68, 0.23, and 0.09, respectively, as determined through geodetector analysis. During the summer, we observed a dominance of dispersal in S. mariqueter, with the species primarily spreading to areas with increased habitat quality. Patch shapes tended to be compact and regular in this season. In contrast, during the autumn, a dominance of decline was observed, with S. mariqueter mainly distributing to areas exhibiting decreased habitat quality. Patch shapes tended to be complex and irregular in the autumn season. Eventually micro-geomorphic modification and patch shape filling methods based on UAV observations are proposed to aid wetland restoration. These findings are of utmost importance for the restoration of coastal wetlands and the enhancement of ecosystem resilience.

Analysis of spatial and temporal changes and driving forces of arable land in the Weibei dry plateau region in China

Arable land is the lifeblood of food production, it is of great significance to promote the protection of arable land and ensure national food security by accurately understanding the change law of cultivated land and its driving mechanism. This study takes the Weibei dry plateau region of China as an example, explores its spatial and temporal change characteristics through the center of gravity shift and land use shift matrix, and couples the geographic probe model to reveal the driving mechanisms affecting arable land change. The results show that in the past 25 years, the total arable land area in the Weibei Dry Plateau Region of China has decreased by 5.58%, and the stability of arable land resources in the whole region has weakened. The center of gravity of arable land shifts to the northeast, and the standard deviation ellipse of arable land mainly undergoes the change process of "increase (1995–2015)-decrease (2015–2020)", and the spatial distribution of arable land tends to be dispersed. In the LISA frequency mapping, the proportion of stable constant and low-frequency areas is as high as 89.58%, and the spatial pattern of cultivated land is relatively stable. Medium and high frequency areas. The transformation mode is mainly "low-low" aggregation, "low–high" aggregation is not significant, and the decline of cultivated land in the study area is more obvious. In the past 25 years, a total of 1017.26 km2 of arable land was converted to construction land. The explanatory power of the influencing factors varies in each period (0.299 to 0.731), with total agricultural machinery power has the strongest explanatory power of 0.694, 0.592, and 0.731, respectively. The interaction between slope and annual average temperature and other factors being the highest, both greater than 0.8. Through the construction of LISA frequency mapping, combined with the center of gravity model and standard deviation ellipse, the spatial evolution trend of regional arable land is more comprehensively and dynamically grasped. By using the geodetector model, the driving mechanism of the changes of arable land is revealed comprehensively, which provides a theoretical basis for the scientific management and effective protection of arable land resources and a basis for decision-making.

Using Medium-Resolution Remote Sensing Satellite Images to Evaluate Recent Changes and Future Development Trends of Mangrove Forests on Hainan Island, China

Mangroves are endemic forest communities in tropical and subtropical coastal zones. China’s Hainan Island is very rich in mangrove plant species. In recent years, due to climate change and human disturbance, the living environment of many mangrove distribution areas has been seriously threatened. This study used land satellite series remote sensing images from 1990 to 2020 to monitor the coverage and area changes of mangroves on Hainan Island. The spatial distribution pattern and change trend of mangroves were explored using the standard deviation ellipse method, and the CA–Markov model was used to predict the possible changes of mangroves in the study area in 2025 and 2030. The development trend of mangroves in the future and the driving factors affecting the evolution of mangroves were also analyzed. Over the past 30 years, the area of mangroves has witnessed fluctuations. It decreased from 4578 hectares in 1990 to its lowest at 3870 hectares in 2005 and then rebounded to 4474 hectares by 2020, indicating an initial decline followed by a gradual increase. Although conservation and restoration efforts have yielded success, specific areas have witnessed a decline in mangrove coverage. From 1990 to 2020, mangrove areas in Huiwen decreased from 1055 hectares to 904 hectares, areas in Guannan decreased from 227 hectares to 167 hectares, areas in Xinyinggang decreased from 328 hectares to 298 hectares, areas in Yangpugang decreased from 747 hectares to 682 hectares, areas in Huachangwan decreased from 355 hectares to 327 hectares, and areas in Puqian decreased from 170 hectares to 141 hectares. In particular, the growth in the Eastern and Mayao port areas is especially significant. Additionally, data analysis has revealed the spatial distribution characteristics of mangroves in different regions, such as the mangrove area in Dongzhaigang, which remained relatively stable from 1990 to 2020, while in other areas like Huiwen and Guannan, the mangrove area decreased during these 20 years. By calculating the standard deviation ellipse, we observed that the overall change of mangroves on Hainan Island from 1990 to 2020 was relatively slow, mainly distributed along the northern coastal area of Hainan Island. Furthermore, the standard deviation ellipse and SDE center point of each mangrove growth area have visualized the growth trends of the mangroves. The Markov chain simulation results show that future changes in mangroves will mainly be concentrated in the marginal areas of the mangroves. These areas may be affected by rising sea levels, climate change, soil salinity, and human activities. In the future, mangrove areas are expected to display a dynamic equilibrium, experiencing periods of expansion and reduction, ultimately moving towards a more consistent state. To protect and restore mangroves, it is necessary to strengthen the monitoring and management of their ecological environment and socio-economic factors and improve their stability and diversity.

Nonlinear characterization of enhanced and generalized Hjorth’s feature space for bearing condition monitoring

The degradation assessment of rolling bearings provides a reasonable maintenance plan for the safe operation of mechanical equipment. The general strategy for bearing condition monitoring is to construct a health indicator (HI) to characterize different degradation stages. A preferable HI that can sensitively detect initial faults and track machine degradation is crucial to developing timely maintenance strategies for mechanical equipment to avoid catastrophic accidents. However, many developed and reported HIs are still insensitive to early faults, resulting in delayed maintenance schedules. To identify the incipient defects as early as possible, a novel HI constructed by nonlinear characterization of enhanced and generalized Hjorth’s feature space based on extended probability entropy is proposed in this paper. Firstly, the time-frequency spectral amplitude modulation helps to enhance the characteristics of the original signal with the amplitude editing in the time-frequency domain. Then, three new features of generalized Hjorth’s parameter combinations are designed and combined with other similar feature combinations to construct a high-dimensional enhanced and generalized Hjorth’s feature space. On this basis, a set of low-dimensional sensitive features is obtained by nonlinearly characterizing high-dimensional features through extended probability entropy after these features are standardized. Finally, a novel HI is developed by calculating the distance between the minimum volume ellipse (MVE) center of the low-dimensional feature subspace based on nonlinear characterization and the low-dimensional feature vector of the real-time monitoring signal. The performance of the proposed approach is verified in three cases, whose experimental results indicate that the proposed HI is more sensitive and significant in detecting early faults compared to some current HIs.

Spatio-temporal dynamic evolution of carbon emissions from land use change in Guangdong Province, China, 2000–2020

Global warming caused by massive carbon emissions poses a serious threat to the environment and human beings. Dynamic monitoring of the spatio-temporal evolution of carbon emissions is an essential way to achieve carbon reduction goals, especially in coastal areas like Guangdong Province faced with dual challenges of massive carbon emissions and rigorous reduction targets. To reveal the spatio-temporal characteristics of carbon emissions and provide a basis for further fine-grained carbon emission reduction strategies, we analyzed spatio-temporal distribution characteristics of carbon emissions in Guangdong Province at the county-level scale from 2000 to 2020. Based on the land-use data obtained from the Data Center for Resources and Environmental Sciences of the Chinese Academy of Sciences and energy consumption data from the Statistical Yearbook, the carbon emission of each county is estimated, and the spatio-temporal evolutionary features of them are explored by a series of methods of the exploratory spatio-temporal data analysis (ESTDA). The shift of spatial distribution characteristics and gravity center is further revealed with the standard deviational ellipse and gravity center migration analysis.The results reveal that the net carbon emissions increased from 6179.229 × 104 tons to 20765.723 × 104 tons during 2000–2020. The net carbon emissions of county-level administrative regions show a significant positive spatial correlation, and the spatial convergence shows a trend of first decreasing and then increasing. The spatio-temporal pattern of carbon emissions has an obvious path dependence and locked spatial features, and shows a gradually strengthening trend. The spatial distribution of carbon emissions formed a stable “northeast-southwest” pattern, and the gravity center of carbon emissions in the past 20 years has been distributed between 113.208°–113.357°E and 22.760°–22.878°N, tending slightly shifting to the northeast. The results of the study can help understand the spatio-temporal evolution of carbon emissions in Guangdong, and provide a reference for formulating effective carbon reduction policies.

Spatial-temporal variation and driving forces of the synergy of “pollution reduction, carbon reduction, green expansion and economic growth”: evidence from 243 cities in China

IntroductionPollution reduction, carbon reduction, green expansion and economic growth—the synergistic effects of the four—have become essential in maintaining urban ecological security and promoting a green and low-carbon transition. And it is inherently consistent with the globally accepted concept of sustainable development. MethodsBased on the evaluation index system and the coupling mechanism of the four, we adopt the entropy method and the coupling coordination model to measure the synergistic level of “pollution reduction, carbon reduction, green expansion and economic growth” in 243 cities above prefecture level in China from 2005 to 2020. Furthermore, the study examined the temporal and spatial evolution and regional differences by utilizing the center of gravity-standard deviation ellipse, Dagum Gini coefficient method, Kernel density estimation, and Markov chain. In addition, the spatial econometric model was used to analyze the driving factors affecting the synergistic development.ResultsThe results show that the overall synergistic level is rising, the spatial distribution characteristics of “high in the east and low in the west.” The standard deviation ellipse shows a “northeast–southwest” pattern, and the center of gravity moves in a “southeast–northwest–southwest” migration trend. Regional differences are mainly rooted in inter-regional differences. The intra-regional differences are East > West > Central, with the most prominent East–West inter-regional differences. Without considering the spatial factor, the synergistic level shows a steady increase and has continuity. Under the spatial condition, the synergistic level has a positive spatial correlation. However, the positive spatial correlation decreases significantly as the years go by. Also, the probability of “rank locking” of synergistic development has been reduced, and there is a leapfrog shift. In terms of driving factors, the innovation level, level of external openness, population size, and industrial structure positively drive synergistic development. While government intervention negatively affects synergistic development. DiscussionsBased on the above findings,policy recommendations are proposed to strengthen the top-level design and build a policy system, play the radiation linkage, apply precise policies according to local conditions, and optimize the industrial structure fully. Which is of great significance for improving the urban ecological resilience and helping to achieve the “double carbon” target.

Research into the Spatiotemporal Characteristics and Influencing Factors of Technological Innovation in China’s Natural Gas Industry from the Perspective of Energy Transition

Promoting technological innovation in the natural gas industry is a feasible means of achieving energy transition. Guided by the geographic innovation theory, this article carries out research on the scale, technical fields, capabilities, and influencing factors of technological innovation in the natural gas industry of 312 Chinese prefecture-level cities, making use of the cusp catastrophe model, the center of gravity and standard deviational ellipse, exploratory spatial data analysis, and geographically and temporally weighted regression (GTWR). The research shows the following: (1) Technological innovation in China’s natural gas industry has continuously expanded in terms of scale, with the number of participating cities increasing, showing a spatially uneven pattern of local agglomeration and national diffusion. (2) There have been significant innovation achievements in natural gas equipment and engineering, but natural gas utilization is lagging in comparison, with drilling, new materials, environmental protection, pipe network engineering, and digital services becoming frontier fields, and collaborative innovation with the thermoelectric, metalworking, automotive, and other related industries having been initially established. (3) The unevenness of technological innovation capabilities is obvious, with the core advantages of Beijing–Tianjin being continuously strengthened and Sichuan–Chongqing, the Yangtze River Delta, the Pearl River Delta, Shandong Peninsula, and Liaodong Peninsula forming high-level technological innovation capability agglomerations. (4) The spatiotemporal pattern of technological innovation capability is the result of multiple factors, with northeastern cities mainly being affected by natural gas demands, northwestern cities being highly sensitive to capital strength, eastern cities mostly relying on urban development, and cities in North China mainly being bolstered by the strength of talent. (5) It is necessary to carry out further multi-agent and multi-scale future research on technological innovation in the natural gas industry and its relationship with the energy transition and to explore the interactivity of the influencing factors. This study may provide strategies for technological innovation in the natural gas industry from the perspective of the energy transition.

Tree Species Classification Based on ASDER and MALSTM-FCN

Tree species classification based on multi-source remote sensing data is essential for ecological evaluation, environmental monitoring, and forest management. The optimization of classification features and the performance of classification methods are crucial to tree species classification. This paper proposes Angle-weighted Standard Deviation Elliptic Cross-merge Rate (ASDER) as a separability metric for feature optimization. ASDER uses mutual information to represent the separability metric and avoids the difficulty of differentiation caused by multiple ellipse centers and coordinate origins forming straight lines by angle weighting. In classification method, Multi-head Self-attention Long Short-Term Memory—Full Convolution Network (MALSTM-FCN) is constructed in this paper. MALSTM-FCN enhances the global correlation in time series and improves classification accuracy through a multi-head self-attention mechanism. This paper takes Beijing Olympic Forest Park (after this, referred to as Aosen) as the research area, constructs a tree species classification dataset based on an actual ground survey, and obtains a classification accuracy of 95.20% using the above method. This paper demonstrates the effectiveness of ASDER and MALSTM-FCN by comparing temporal entropy and LSTM-FCN and shows that the method has some practicality for tree species classification.