Superposition Analysis Research Articles

Energy coupling and surge wave superposition of upstream series double surge tanks of pumped storage power station

Pumped storage power station with surge tank is common, and surge wave superposition can cause more dangerous water levels. This paper aims to study the energy coupling and surge wave superposition of upstream series double surge tanks of pumped storage power station. Firstly, the simulation model of pumped storage power station based on method of characteristics is established. Combined operating conditions are illuminated. Then, surge wave control strategies coupling gravitational search algorithm, relative objective proximity and marginal analysis principle are designed. Coupling control domains are determined to perform surge wave superposition analyses under single objective and multi-objective. Finally, the energy coupling and conversion mechanisms are revealed. The results show that the coupling control domains of combined operating conditions with same initial operating condition are the same. Control domains for undamped and damped systems contain two and three sub control domains, respectively. Based on energy conversion mechanisms between discharges and water levels, the number of discharge superposition points of pipelines affects energy coupling strength by changing coupling oscillations of water levels in surge tanks, which is related to the pipeline parameters, surge tank parameters and system damping. Energy coupling affects surge wave superposition by changing the actual control water level.

Evaluation of soil erosion in the Changhua River Basin on Hainan Island based on the Chinese soil loss equation model

Soil erosion is one of the most serious ecological and environmental problems facing southern China. The Changhua River Basin on Hainan Island is affected by soil erosion, which is causing the soil environment to become more fragile. Compared with the Revised Soil Erosion Equation (RUSLE), the Chinese Soil Loss Equation (CSLE) is based on a large amount of Chinese local data and research results, which more accurately reflect the actual situation of soil erosion in China and therefore have better accuracy and applicability in the Chinese region. By combining GIS and RS technologies, this study establishes the CSLE model of the Changhua River Basin, quantifies the soil erosion data via image elements from 2020 to 2022 using the spatial interpolation method, classifies the erosion intensity, and analyzes the spatial and temporal change characteristics of soil erosion. The statistical results show that, during the period from 2020 to 2022, the area of slight erosion in the Changhua River Basin increased by 553.25 km2, with a rate of change of 15.83 %, and the areas of mild erosion, moderate erosion, intense erosion, very intense erosion, and severe erosion decreased by 446.42 km2, 64.4 km2, 25.73 km2, 11.25 km2, and 5.45 km2, respectively, with rates of change of −31.05 %, −30.08 %, −36.58 %, −18.02 %, and −13.85 %, respectively. Slight erosion is defined as soil erosion less than the permissible soil loss and is not regarded as soil erosion, and the other erosion intensities showed a yearly decreasing trend, indicating that the soil erosion control was effective during this three-year period. In the work of soil and water conservation, it is especially necessary to determine the main factors influencing soil erosion and predict the areas that may be prone to such erosion. Therefore, on the basis of establishing a characteristic model using land use type, slope and soil type, and through superposition analysis, we obtained the spatial and temporal change characteristics of soil erosion. The research results are as follows: (1) slight erosion is mainly concentrated in forested areas, and forested land has a better capacity for soil and water conservation; (2) mild, moderate, and strong erosion mainly occur in cultivated areas and areas with a slope of 0–5°; (3) areas of built land and areas with a slope of 8°–15° are more prone to intense erosion, although they cover a smaller area; (4) when the slope is greater than 15°, the overlap range with the forest area is larger and the slope is no longer the main factor leading to soil erosion. Thus, it can be seen that forest land significantly reduces the impact of soil erosion. (5) among the different soil types, Technosol, Ferralsol and Fluvisol all have less than 55 per cent uneroded area and are generally less erosion-resistant, while Lixisol and Acrisol are relatively more susceptible to a high degree of erosion hazard (Extremely strong erosion, severe erosion).

Multi-parameter viscoelastic material model for denture adhesives based on time-temperature superposition and multiple linear regression analysis

BackgroundRestorative solutions designed for edentulous patients such as dentures and their accompanying denture adhesives operate in the complex and dynamic environment represented by human oral physiology. Developing material models accounting for the viscoelastic behavior of denture adhesives can facilitate their further optimization within that unique physiological environment. This study aims to statistically quantify the degree of significance of three physiological variables - namely: temperature, adhesive swelling, and pH - on denture adhesive mechanical behavior. Further, based on these statistical significance estimations, a previously-developed viscoelastic material modelling approach for such denture adhesives is further expanded and developed to capture these variables’ effects on mechanical behavior.MethodsIn this study a comparable version of Denture adhesive Corega Comfort was analysed rheologically using the steady state frequency sweep tests. The experimentally derived rheological storage and loss modulus values for the selected physiological variables were statistically analyzed using multi parameter linear regression analysis and the Pearson’s coefficient technique to understand the significance of each individual parameter on the relaxation spectrum of the denture adhesive. Subsequently, the parameters are incorporated into a viscoelastic material model based on Prony series discretization and time-temperature superposition, and the mathematical relationship for the loss modulus is deduced.ResultsThe results of this study clearly indicated that the variation in both the storage and loss modulus values can be accurately predicted using the oral cavity physiological parameters of temperature, swelling ratio, and pH with an adjusted R2 value of 0.85. The R2 value from the multi-parameter regression analysis indicated that the predictor variables can estimate the loss and storage modulus with a reasonable accuracy for at least 85% of the rheologically determined continuous relaxation spectrum with a confidence level of 98%. The Pearson’s coefficient for the independent variables indicated that temperature and swelling have a strong influence on the loss modulus, whereas pH had a weak influence. Based on statistical analysis, these mathematical relationships were further developed in this study.ConclusionsThis multi-parameter viscoelastic material model is intended to facilitate future detailed numerical investigations performed with implementation of denture adhesives using the finite element method.

Construction and optimization of wilderness network connectivity to address landscape fragmentation in Zhejiang Province, China

Wilderness areas provide important ecosystem services for human being, and as crucial habitats for diverse species. Human activities have led to the fragmentation of wilderness landscapes, posing a significant challenge to biodiversity conservation. Identifying wilderness areas and assessing their network connectivity is fundamental for developing strategies to address this fragmentation. This study used Zhejiang Province, China, which is in the process of rapid urbanization as a case study. We identified the spatial distribution of wilderness by combing the index system and its weights of wilderness identification, using Boolean superposition analysis and the multi-criteria evaluation method, and tested the ecological sensitivity. Additionally, the connectivity of the wilderness network was assessed using the wilderness identification results in Zhejiang Province as ecological sources. The results indicate that: (1) 50% of Zhejiang Province still maintains relatively good wilderness integrity. (2) The wilderness network can cover 82% of highly fragmented habitats and currently unallocated potential natural reserves. (3) In areas not designated as nature reserves but experiencing frequent species movement as well as in identified wilderness regions, robust wilderness networks may play a crucial role in biodiversity conservation. The findings provide quantitative evidence for biodiversity-oriented wilderness network protection and landscape fragmentation management. The results also aid in selecting specific areas for rewilding and ecological restoration, thereby enhancing the overall robustness of the wilderness network.

Revealing the Impact of Viscoelastic Characteristics on Performance Parameters of UV-Crosslinked Hotmelt Pressure-Sensitive Adhesives: Insights from Time-Temperature Superposition Analysis.

This study emphasizes the influential role of rheology in decoding the viscoelastic properties of pressure-sensitive adhesives (PSAs) vital to predicting key application features such as shear, tack, and peel, depending on the flow characteristics of PSAs during bonding and debonding processes. By applying the principle of time-temperature superposition (TTS), we extend the scope of our frequency analysis, surpassing the technical constraints of the available apparatus. Our exploration aims to uncover the general correlations between PSAs' viscoelastic properties and their performance in end-use applications. Initially, the adhesive performance and viscoelastic properties of a UV-crosslinkable styrene-butadiene-styrene (SBS) model adhesive prior and subsequent to UV irradiation were examined. The subsequent crosslinking reaction increased cohesive strength and heat resistance, although tack and peel strength observed a substantial decline. We successfully demonstrated these effects by logging the viscoelastic properties, specifically the storage modulus G' at lower frequencies, which mirrors the shear strength at higher temperatures and the shift in the tan δ peak to represent each PSA's tack. These correlations were partially reflected in three commercial UV crosslinkable acrylic PSA products, although the effect of UV irradiation was less distinctive. This study also revealed the challenges in predicting tack and peel strength, which result from a complex interplay of bonding and debonding processes. Our findings reinforce the necessity for more sophisticated analysis techniques and models that can accurately predict the end-use performance of PSAs across different physical structures and chemical compositions. Further research is needed to develop these predictive models, which may reduce the need for labor-intensive testing under real-life conditions.

Frequency switching leads to distinctive fast–slow behaviors in Duffing system

The slowly forced Duffing system has been found to exhibit unique fast–slow behaviors in descending frequency switching scheme, the typical of which is the sliding bursting, which is instructive for understanding the dynamics of ubiquitous frequency switching systems in scientific research and practical engineering. This paper is devoted to further refining the fast–slow dynamics of the slowly forced Duffing system with another commonly encountered frequency switching scheme, i.e., the ascending frequency switching, characterized by switching the frequency synchronously according to the increase or decrease of state variable values. Taking the forcing amplitude as an example, this paper provides a theoretical way to fully summarize the fast–slow behaviors in frequency switching systems with the variation of parameter values based on the proposed superposition analysis of one- and two-parameter bifurcations of subsystems. As a result, two typical bifurcation structures and eight threshold windows with distinct switching vector fields therein are identified, inducing up to ten different bursting patterns. Among them, several novel fast–slow dynamics, such as multiple jumps hysteresis loop formed by boundary equilibrium bifurcations and the switching failure phenomena, are presented and investigated. In particular, the underlying mechanism of threshold modulation, i.e., the evolution of unconventional bifurcations, is also found. These findings contribute to complementing and contrasting the existing studies on the fast–slow dynamics of frequency switching systems.

A novel multi-step superposition model for the dispersion analysis of multiaxial prestressed plate-like structures

Understanding the dispersion characteristics of multi-axial prestressed plate-like structures is crucial for the engineering application of guided wave non-destructive testing. However, existing analytical and semi-analytical models neglect both constitutive and geometric nonlinearities induced by the prestress and require tedious theoretical derivation and coding, which may not achieve accurate predictions. To address these issues, a convenient model based on the multi-step superposition analysis was proposed to investigate the effects of an arbitrary multiaxial prestress on the dispersion characteristics of plate-like structures. The core idea of this model involves introducing an initial configuration to describe the static pre-deformation between undeformed and final states; then, the dynamic wave motion was superimposed on the initial pre-deformation for the eigenfrequency analysis. Additionally, the strain energy density of the hyperelastic material was implanted and set as the relevant variable between the two steps by the inheritance of the solution. This model significantly improved the accuracy compared to the conventional method, as validated through biaxial acoustoelastic experiments. Subsequently, the acoustoelastic responses of the multiaxial prestressed 6061-T6 aluminum plate were investigated. The results reveal that the non-uniform in-plane prestress leads to the coupling of guided wave modes propagating along non-principal directions. Furthermore, the effects induced by multiaxial prestress in the frequency bands with low dispersion could be decomposed into the sum of the effects induced by three uniaxial prestresses with a very small deviation. This work provides new insights into the acoustoelastic behavior and a theoretical basis to optimize the guided wave mode and frequency.

Shopping Mall Site Selection Based on Consumer Behavior Changes in the New Retail Era

As a product of the development of e-commerce over a specific period of time, the “new retail model” breaks the barriers between the traditional retail industry and e-commerce. Supported by Internet technology, it builds a new business model of “physical store + e-commerce + logistics” through the integration of online, offline, and logistics, which also leads to a great change in consumer behavior. Therefore, in order to meet consumer demand and achieve the long-term development of shopping malls, while taking into account the fair allocation of urban space resources, the indicators and methods of shopping mall site selection evaluation in the new retail era will be significantly different from traditional shopping mall site selection decisions. In this paper, the Wuhan East Lake Hi-Tech Zone is selected as the research object, and a comprehensive AHP-GIS assessment model is proposed. By investigating the impact of consumers’ behavioral changes on shopping mall location in the new retail era, a suitability evaluation system containing eight evaluation indicators is constructed, and the weights of each factor are determined using hierarchical analysis. At the same time, GIS is used to process the spatial analysis of the indicators, and combined with the weights of the factors, superposition analysis and quantitative research are carried out. Finally, based on the correlation analysis between ratings and customer flow, the suitability evaluation results are further supported in order to provide a more objective and scientific basis for the location of shopping malls from the perspective of the change in consumer behavior under the new retail model, and to put forward universal suggestions for the construction and development of shopping malls in the future.

Dynamics of transformed nonlinear waves for the (2+1)-dimensional pKP-BKP equation: interactions and molecular waves

In this paper, the dynamical behaviors of transformed nonlinear waves for the (2+1)-dimensional combined potential Kadomtsev-Petviashvili and B-type Kadomtsev-Petviashvili (pKP-BKP) equation are investigated, which can be used to reveal the nonlinear wave phenomena in nonlinear optics, plasma physics and hydrodynamics. The breath-wave and the lump solutions are constructed by means of the soliton solutions. The conversion mechanism for the breath-wave is systematically analyzed, which leads to several new kink-shaped nonlinear waves. The gradient relationships of these transformed waves are revealed by a Riemannian circle. Through the analysis of the nonlinear superposition between the periodic wave component and the kink solitary wave component, the dynamical characteristics including the formation mechanism, oscillation and locality for the nonlinear waves are investigated. The time-varying properties of transformed waves are shown by the study of time variables. By virtue of the two breath-wave solutions, several interactions including elastic and inelastic collisions between two nonlinear waves are studied. In particular, some transformed molecular waves encompassing the non-, semi- and full-transition modes are presented with the aid of velocity resonance. The results can help us further understand the complex nonlinear waves existing in the integrable systems.

Allergenicity and Linear Epitope Analysis of Scy p 8, an Allergen from Mud Crab.

Scy p 8 (triosephosphate isomerase) as a crab allergen in inducing distinct T-helper (Th) cell differentiation and a linear epitope associated with allergenicity remain elusive. In this study, mice sensitized with Scy p 8 exhibited significantly upregulated levels of IgE, IgG1, and IL-4 release, inducing a Th2 immune response. Moreover, the release of IFN-γ (Th1) and the levels of Treg cells were downregulated, while IL-17A (Th17) was upregulated, indicating that Scy p 8 disrupted the Th1/Th2 balance and Th17/Treg balance in mice. Furthermore, bioinformatics prediction and serum samples from crab-allergic patients and mice enabled the discovery of 8 linear epitopes of Scy p 8. Meanwhile, the analysis of peptide similarity and tertiary superposition revealed that 8 epitopes of Scy p 8 exhibited conservation across various species, potentially resulting in cross-reactivity. These findings possess the potential to enhance the comprehension of crab allergens, thereby establishing a foundation for investigating cross-reactivity.

Analysis of Spatial and Temporal Dynamics of Finland’s Boreal Forests and Types over the Past Four Decades

In the context of global warming, the study of the long-term spatial change characteristics of boreal forest cover is not only important for global climate change and sustainable development research but can also provide support for further research on the response of boreal forest changes to climate change. Using Landsat TM/OLI images from 1980 to 2020 as the data source and Google Earth Engine (GEE) as the platform, Finland was selected as the study area of boreal forests, and typical sample points of different features were chosen to classify forested and non-forested land using the random forest algorithm combined with spectral indices and classified feature sets of tasseled cap transform to obtain the four-phase forest cover change maps of the region. GEE test sample points and random selection points of images from the GF-2 and GF-7 satellites were used for verification. The classification accuracy was 97.17% and 88.9%. The five-phase forest cover images were segmented by a 2° latitude zone, and the spatial and temporal dynamic changes in forest cover in the whole area and each latitude zone were quantified by pixel superposition analysis. The results showed that, in the past 40 years, the boreal forest cover in Finland changed significantly, and the forest cover decreased from 75.79% to 65.36%, by 10.43%. Forest change mainly occurs in coniferous forests, whereas broadleaf forests are more stable. The forest coverage in each latitude zone decreased to varying degrees, with higher changes occurring in high-latitude areas above 64° N between 1980 and 2000, and higher and more severe changes occurring in low-latitude areas below 64° N between 2000 and 2020. Coniferous forests are the dominant type of forest in Finland, and the degradation of coniferous forests in the south is likely to become more severe, whereas the north and above is likely to become more favorable for coniferous forests. More monitoring and research are needed to follow up on the very different changes in the north and south regions.

Noise Analysis and Optimization Design of an Electric–Mechanical–Hydraulic Power Coupler for the Vehicle

This article proposes a new electric–mechanical–hydraulic power coupler (EMHPC). The EMHPC is integrated by a swash plate axial piston pump and permanent magnet synchronous motor, which can realize the conversion of electric, mechanical, and hydraulic energy. To analyze the noise characteristics of the EMHPC, the mathematical models of fluid noise and electromagnetic noise are established, respectively. An optimization model is built based on Isight, and the multi‐island genetic algorithm is used to optimize the triangular groove structure. The optimization results show that the sound pressure level of sound field monitoring points decreases at different frequencies, and the vibration displacement of the cylinder block decreases. The maximum sound pressure level of the directivity curve of the radiated sound field decreases by 9 dB. For the electrodynamic structure optimization of the EMHPC, this article establishes a combination approximation model with higher accuracy. The structure of the stator and rotor is optimized based on the combined approximate model. The optimization results show that the sinusoidal property of the radial air‐gap magnetic density curve is better after optimization, and the harmonic amplitude of the radial electromagnetic force decreases. The maximum sound pressure level in the air domain of the external sound field is reduced from 69 to 60 dB. Moreover, the superposition analysis of fluid noise and electromagnetic noise is carried out, and the main noise sources of the EMHPC in different working modes are determined.

GIS-based intelligent planning approach of child-friendly pedestrian pathway to promote a child-friendly city.

Pedestrian safety, particularly for children, relies on well-designed pathways. Child-friendly pathways play a crucial role in safeguarding young pedestrians. Shared spaces accommodating both vehicles and walkers can bring benefits to pedestrians. However, active children playing near these pathways are prone to accidents. This research aims to develop an efficient method for planning child-friendly pedestrian pathways, taking into account community development and the specific needs of children. A mixed-methods approach was employed, utilizing the Datang community in Guangzhou, China, as a case study. This approach combined drawing techniques with GIS data analysis. Drawing methods were utilized to identify points of interest for children aged 2-6. The qualitative and quantitative fuzzy analytic hierarchy process assessed factors influencing pathway planning, assigning appropriate weights. The weighted superposition analysis method constructed a comprehensive cost grid, considering various community elements. To streamline the planning process, a GIS tool was developed based on the identified factors, resulting in a practical, child-friendly pedestrian pathway network. Results indicate that this method efficiently creates child-friendly pathways, ensuring optimal connectivity within the planned road network.

Enhancing heat modification efficiency of Chinese fir wood through fly ash impregnation: A comprehensive evaluation using time-temperature superposition and cluster analysis

Catalytic degradation via fly ash impregnation (Im) has proven effective in reducing the heat modification (HM) temperature required for wood. To accurately gauge the intensity of HM on wood following Im, the physiomechanical properties of Im-HM treated wood were investigated across various treatment conditions (temperature: 80–140°C, duration: 1–4 h, and fly ash concentration: 2–8%), and compared them to conventional HM (CoHM) wood. Two mathematical methods (time-temperature superposition and cluster analysis) were employed to elucidate the relationships between treatment conditions and resulting properties. Results indicated that Im-HM treated wood exhibited comparable dimensional stability and visual appearance to CoHM wood, while retaining superior mechanical properties. The acid-catalyzed effect of Im-HM demonstrated significant dependence on treatment temperature, duration, and concentration, providing an avenue to regulate catalytic intensity. Employing the time-temperature superposition principle, master curves for weight percentage loss (WPL), modulus of elasticity (MOE) and anti-swelling efficiency (ASE) were constructed under a reference condition (80°C and 2% concentration), covering processing duration up to 20 hours. These master curves facilitated understanding the relationship between temperature, duration and concentration when evaluating catalytic intensity. Cluster analysis, based on the physiomechanical properties of Im-HM and CoHM wood, offered a clear interpretation of HM intensity. Notably, Im-HM treatment at 140°C for 4 hours with an 8% concentration exhibited HM intensity similar to CoHM treatment at 200°C. Through the integration of time-temperature superposition and cluster analysis, this study assesses Im-HM intensity, providing a valuable reference for the industrial application of Im-HM treatment.

Remote Sensing Ecological Quality and Its Response to the Rocky Desertification in the World Heritage Karst Sites

Clarifying the spatial and temporal evolution characteristics of the ecological environment quality of World Heritage Karst Sites (WHKSs) and its response to different rocky desertification grades at spatial scales is crucial for the monitoring and protection of WHKSs as well as the implementation of ecological and environmental policies in karst regions. The ecological evaluation model of Remote Sensing Ecological Index (RSEI) was used to evaluate the ecological environment of Libo–Huanjiang World Heritage Karst site and Shibing World Heritage Karst site, and then the spatial autocorrelation and geo-detection model was used to further analyze the ecological environment, and final spatial overlay of RSEI and rocky desertification by year to analyze the linkage relationship between RSEI and rocky desertification. The results showed that (1) in the three-phase ecological environmental quality evaluation of the two heritage sites, the RSEI in 2010, 2016, and 2022 reached 0.60, 0.67, and 0.64 for the Libo–Huanjiang heritage site, and RSEI in 2010, 2016, and 2022 for the Shibing heritage site reached 0.60, 0.74, and 0.70, respectively; (2) the RSEI of both heritage sites show a gradually increasing positive spatial correlation, and has significant spatial aggregation characteristics, with both heritage sites dominated by the high-high and low-low spatial aggregation categories; (3) both heritage sites have the highest degree of explanation of changes in ecological quality by the NDBSI factor, indicating that this factor plays a key role in changes in ecological quality at heritage sites; (4) the response of the RSEI mean value of Libo–Huanjiang in each grade of rocky desertification area is, from high to low, no rocky desertification, non-karst, potential rocky desertification, mild rocky desertification, moderate rocky desertification, intensive rocky desertification, and extreme intensity rocky desertification, and the response of the RSEI mean value of Shibing is, from high to low, non-karst, no rocky desertification, potential rocky desertification, mild rocky desertification, and moderate rocky desertification. The spatial superposition analysis of the RSEI index and rocky desertification index can quantitatively study the changing status of the ecological environment in different rocky desertification areas, and the results of the study can provide theoretical references for the environmental monitoring and the prevention and control of rocky desertification in the karst areas and WHKSs.

Ecological Vulnerability Assessment and Spatiotemporal Characteristics Analysis of Urban Green-Space Systems in Beijing–Tianjin–Hebei Region

The evaluation and analysis of the ecological vulnerability of urban green-space systems are conducive to the sustainable development of urban green-space systems. Taking the urban green-space system in the Beijing–Tianjin–Hebei region in 2010, 2015, and 2020 as the research object, an ESSR model was first constructed, and a total of ten types of impact factors were integrated into the four dimensions of “Exposure, Sensitivity, State and Response”. The weight of the impact factors was objectively determined via spatial principal component analysis, and the ecological vulnerability of the urban green-space system was evaluated via superposition analysis; the evaluation’s results were graded. Moreover, the transfer matrix, center-of-gravity migration model, standard deviation ellipse, and spatial autocorrelation analysis were used to study the temporal and spatial variation characteristics of the evaluation results; then, the driving force of impact factors was analyzed based on a geographical detector. Finally, the rationality of the evaluation results was verified using the changing trend of the remote sensing ecological index (RSEI). The results show that the ecological vulnerability of the urban green-space system in the Beijing–Tianjin–Hebei region has decreased year by year for the past ten years. The distribution law of “Hebei surrounds Beijing and Tianjin” is presented in this space, and 2015 is the mutation node. In 2010, the moderately and severely vulnerable areas of Hebei surrounded the mildly vulnerability areas of Beijing and Tianjin. Moreover, in 2015 and 2020, the mildly vulnerable areas of Hebei surrounded the severely vulnerable areas of Beijing and Tianjin. Vulnerability expands slightly in the east–west direction and shrinks slightly in the north–south direction, and the center of gravity shifts towards Beijing year by year along the northeast direction. Moreover, the spatial distribution of vulnerability shows significant positive spatial autocorrelations and exhibits very obvious agglomeration. In addition, vulnerability is the result of the combined effect of various factors, and education degree, human disturbance index, and annual average precipitation are the dominant factors. The analysis results provide a reference for the effective application and sustainable development of urban green-space ecological functions.

Assessment of the Impact of Basic Public Service Facility Configuration on Social–Spatial Differentiation: Taking the Zhaomushan District of Chongqing, China

Objectively assessing the impact of various basic public service facilities on social–spatial differentiation has become a prerequisite for promoting urban social integration and development. However, in practice, the configuration of basic public service facilities is not always conducive to social integration, especially at the microscale. Effectively measuring the inhibitory or aggravating effects of various basic public service facility configurations on social–spatial differentiation has become a challenge. Based on the assumption that the configuration of basic public service facilities has inhibitory and aggravating effects on social–spatial differentiation, this study selected two types of objects: social space and basic public service facilities to refine the research elements. Using spatial and statistical analysis methods such as ecological factors, clustering, correlation, mediation, and superposition analysis, a framework was constructed to evaluate the impact of basic public service facility configuration on social–spatial differentiation and take the Zhaomushan area in Chongqing, China, as a typical case for verification. The study found that registered residence, income, employment location, and residential density are still the main factors of social–spatial differentiation in the study area. The main factors contributing to the differentiation of basic public service facilities are elderly care and housing security, public transportation and green space access, education and employment security, and small-scale medical and health facilities in the study area. In the eight principal factor pairs after the superposition of two differentiation spaces, six pairs showed weakened spatial differentiation, while two pairs showed intensified spatial differentiation. This indicates that the allocation of basic public service facilities will simultaneously inhibit and exacerbate social–spatial differentiation, but the inhibitory effect is significantly stronger than the exacerbating effect. Among them, public transportation and green parks are the main types of facilities that mainly exacerbate social–spatial differentiation. This dual effect is specifically reflected in the change in the spatial adaptation position of social space and basic public services, the weakening of the original social space differentiation boundary and the emergence of new differentiation boundaries simultaneously, and the multicenter composite form of social space. In the future, quantitative evaluation based on research frameworks can provide scientific basis for constructing spatial adaptability strategies for the supply of basic public service facilities and social production and life, such as adjusting the distribution, scale, and spatiotemporal relationship between basic public service facilities and residential communities in a reasonable manner. This is crucial for promoting social integration.

Brownian dynamics simulation on the parallel superposition rheology of a colloidal gel

Parallel superposition rheology has been explored using Brownian dynamics simulations on a model colloidal gel by imposing a small amplitude probing oscillation parallel to the main shear flow. This study aims to investigate the constituting principles behind the material functions in parallel superposition rheometry (PSR) and to elucidate the principles behind the structure responses. The viscoelastic spectra under frequency sweeps show that in a high-frequency region, each curve can be superimposed onto a single master curve using horizontal shift factors equal to viscosity which is a reminiscence of time-shear rate superposition in orthogonal superposition rheometry. This corresponds to the region where a parallel superposition analysis can be adequately performed as the shear rate controls the viscoelastic spectra of the gel independently from probing perturbation. On the other hand, in the low-frequency region, this principle breaks down and even negative storage modulus is observed due to the strong flow coupling effect, which is also found in experiments. By introducing the spatial moduli, it is found that the negative modulus originates from the attractive potential region. In the flow conditions where negative modulus occurs, the shear force is strong enough to break down every surface bond between the particles. In this state, the increase in structural factor in response to the rise in the shear rate dominates particle stress, even within the attractive potential region. This arises because the isolated particles have more opportunities to interact with other particles as the shear rate of the imposed perturbation increases. This structural response, influenced by the attractive potential, results in a negative storage modulus and a positive loss modulus after performing Fourier transformation. This paper, for the first time by a simulation approach, demonstrates the essential characteristics of the material functions obtained using PSR. Also, this study is expected to enhance our understanding on the flowing materials and suggest a criterion for the reliable application of superposition rheology using a viscoelastic master curve.

New Mathematical Technique for Step Rate Test Analysis Aids Determination of Fracture Pressure and Overcomes the Uncertainty of Conventional Analysis.

Experience in the oil industry has shown that it is challenging to sustain successful long-term matrix injection, as injection water quality cannot be maintained rigorously due to facility hiccups and membrane clogging. Most oil field operators have resolved this problem of injectivity decline by increasing the surface injection pressure to part the formation and inject just above the fracture gradient with strict offtake management for zonal conformance. This is not an easy task as injection much above fracture opening pressure can lead to water fingering and poor sweep that results in uneconomical waterflood recovery. The operators, thus, strive to inject at a pressure just above the fracture opening pressure so that the fracture opens near the wellbore but does not extend and then maintain the pressure just above the fracture closing pressure. Therefore, determination of the fracture opening pressure and fracture closing pressure has remained critical data for the success of waterflood projects. The most reliable industry approach to estimating fracture opening and fracture closing pressures comes from the step rate test (SRT). This traditional approach of Cartesian analysis of pressure-rate plot fits straight lines through the data in a plot of injection pressure against injection rate and then estimates the fracture pressure from the intersection of these lines having different slopes. The data received often do not exhibit one clear change in slope, thus resulting in multiple possible solutions, making it difficult for the operator to use the data for high CAPEX facilities design. Most past studies indicate the subjectivity of this Cartesian slope fitting technique. Alternative solutions through multirate superposition analysis found limited application in the analysis of SRT data due to considerable sensitivity to the value of initial pressure used for superposition and lack of stability of rate and pressure data. In this article, a new technique of SRT analysis is presented, which provides a unique solution for fracture opening and fracture closing pressures. It helps to overcome the limitations of the traditional technique of arbitrary fitting of straight lines. It uses the mathematical understanding of cumulative derivatives to recognize that the matrix opens when the cumulative growth of the rate of injectivity shows a change. It estimates the derivative of the injection rate with respect to injection pressure at each step. Then, it estimates the fracture pressure from the plot of the cumulative of this derivative against pressure at each step. It helps to overcome the challenge SRT solutions posed by the nonlinear trend of pressure data at each injection step both before fracture and after fracture is initiated. It also overcomes the limitations of the multirate superposition technique, as it is not sensitive to the value of initial pressure used for superposition.

Forest Resource Quality and Human Activity Intensity Change and Spatial Autocorrelation Analysis in Yulin City, China

With the rapid development of society and the economy, human activities are increasing, which often brings potential threats such as a decline in forest resource quality and ecological function. In order to investigate the change in forest resource quality and human activity intensity, this study constructed a calculation model for a forest resource quality index and a human activity intensity index and conducted a quantitative analysis of the temporal and spatial changes in forest resource quality and human activity intensity in Yulin City based on sub-compartment data in 2017 and 2020. By combining spatial autocorrelation analysis, the changes in human activity intensity and spatial forest resource quality were explored, and key areas such as the prominent contradictions between humans and the land were superimposed and coupled as potential areas of concern. The results show the following: From 2017 to 2020, the forest resource quality in Yulin City improved as a whole, especially in Zizhou County, but there were increases and decreases in other regions. Human activity intensity increased as a whole, and the most obvious increase was in Hengshan District. Both the forest resource quality and human activity intensity indexes had spatial aggregation, the differences in forest resource quality between regions were reduced, and human activity intensity showed a trend towards aggregated development. The high–high cluster area for human activity intensity showed a decreasing trend, but it expanded outward in urban areas and other human-gathering areas, such as the surrounding area of Yulin City, Jingbian County, and Shenmu City. The high–high cluster area for forest resource quality showed a shrinking trend. Four specific regions were identified through a spatial coupled superposition analysis to reveal the dynamic relationship between forest resource quality and human activity intensity. The most obvious region was the Yuyang District, where the forest resource quality improved because of a reduction in the pressure of human activities on the natural environment.