Search Results (195)

Under the dual pressures of rapid urbanization and intense human socioeconomic activities, habitat fragmentation and poor landscape connectivity have become critical issues in cities. Constructing ecological networks is essential for maintaining urban ecosystem health and promoting sustainable environmental development. It represents an effective approach to balancing regional economic growth with ecological conservation. This study focused on the Shenzhen Special Economic Zone. Ecological sources were identified using Morphological Spatial Pattern Analysis (MSPA) and landscape connectivity assessment. Circuit theory was applied to extract ecological corridors, ecological pinch points, and ecological barriers. The importance levels of ecological corridors were classified to form an ecological network. The network was optimized by adding ecological sources, stepping stones, and restoring breakpoints. Its structure and functionality were evaluated before and after optimization. The results indicate the following: (1) The core area in Shenzhen City Area covers 426.67 km², the largest proportion among landscape types. It exhibits high fragmentation, low connectivity, and a spatial pattern characterized as “dense in the east and west, sparse in the center.” (2) Seventeen ecological sources were identified, consisting of 8 key sources, 5 important sources, and 4 general sources, accounting for 17.62% of the total area. Key sources are mainly distributed in forested regions such as Wutong Mountain, Maluan Mountain, Paiya Mountain, and Qiniang Mountain in the southeast. (3) Twenty-six ecological corridors form a woven network, with a total length of 127.44 km. Among these, 13 key corridors are concentrated in the eastern region, while 7 important corridors and 6 general corridors are distributed in the western and central parts. Few corridors exist in the southwest and southeast, leading to ecological flow interruption. (4) The optimized ecological network includes 12 newly added ecological source areas, 20 optimized ecological corridors, 120 ecological pinch points, and 26 ecological barriers. The maximum current value increased from 10.60 to 20.51, indicating significantly enhanced connectivity. The results provide important guidance for green space planning, biodiversity conservation, and ecosystem functionality enhancement in Shenzhen City Area. Full article

The stability of a circular vortex is studied in the thermal quasi-geostrophic (TQG) model. Several radial distributions of vorticity and buoyancy (temperature) are considered for the mean flow. First, the linear stability of these vortices is addressed. The linear problem is solved exactly for a simple flow, and two stability criteria are then derived for general mean flows. Then, the growth rate and most unstable wavenumbers of normal-mode perturbations are computed numerically for Gaussian and cubic exponential vortices, both for elliptical and higher mode perturbations. In TQG, contrary to usual QG, short waves can be linearly unstable on shallow vorticity profiles. Linearly, both stratification and bottom topography (under specific conditions) have a stabilizing role. In a second step, we use a numerical model of the nonlinear TQG equations. With a Gaussian vortex, we show the growth of small-scale perturbations during the vortex instability, as predicted by the linear analysis. In particular, for an unstable vortex with an elliptical perturbation, the final tripolar vortices can have a turbulent peripheral structure, when the ratio of mean buoyancy to mean velocity is large enough. The frontogenetic tendency indicates how small-scale features detach from the vortex core towards its periphery, and thus feed the turbulent peripheral vorticity. We confirm that stratification and topography have a stabilizing influence as shown by the linear theory. Then, by varying the vortex and perturbation characteristics, we classify the various possible nonlinear regimes. The numerical simulations show that the influence of the growing small-scale perturbations is to weaken the peripheral vortices formed by the instability, and by this, to stabilize the whole vortex. A finite radius of deformation and/or bottom topography also stabilize the vortex as predicted by linear theory. An extension of this work to stratified flows is finally recommended. Full article

In this study, a mathematical model was proposed for a continuous, multistage, industrial-scale alcoholic fermentation process, comprising four vats in series with volumes equal to 600 m³, with separation, acid treatment, and cell recycling from the fourth to the first vat. The system was operated daily under variable volumetric flow rates and substrate concentrations in the feed stream, i.e., F₀ = 93–127 m³/h and S₀ = 210–238 g/L. The mathematical model consisted of mass balance equations for cells, substrate, and product in the vats, the separator, and the acid treatment unit. An unsegregated and unstructured approach was used to describe the microbial population, with the kinetics of cell growth, substrate consumption, and product formation represented by equations generally adopted for alcoholic fermentation. The model parameters were estimated by nonlinear regression, providing typical values for alcoholic fermentation. Model predictions agreed well with both the experimental data used in the parameter estimation step and those used in the model validation step. Full article

Hydrocarbon fuels are extensively employed as coolants in the regenerative cooling systems of scramjet engines. However, the pyrolytic coking of hydrocarbon fuels at high temperatures introduces complex adverse effects on the flow and cooling processes. In this study, a numerical model was developed to investigate the coupling processes of fluid flow, heat transfer, pyrolysis and pyrolytic coking in the heated tube, under both a constant outer wall heat flux of 1.8 MW/m² and a constant outer wall temperature of 1150 K. The multi-step pyrolytic reaction mechanism and the kinetic coking model were applied to simulate the pyrolytic coking processes of RP-3. The results reveal that the amounts of catalytic coking and lateral growth exhibit significant differences in magnitude, as well as in their spatial and temporal variations. Under a constant outer wall heat flux, coking evidently increases the outer wall temperature and thermal resistance, leading to a narrowed flow passage and a reduction in the residence time and RP-3 conversion rate. Under a constant outer wall temperature, coking decreases the heat absorption flux, resulting in a lower fluid temperature, which primarily affects the efficiency of the endothermic pyrolytic reaction. The results obtained in this research can provide practical insights for the development of regenerative cooling technology. Full article

Population growth drives increasing energy demands, agricultural production, and organic waste generation. The organic waste contributes to greenhouse gas emissions and increasing landfill burdens, highlighting the need for novel closed-loop technologies that integrate water, energy, and food resources. Within the context of the Water–energy–food Nexus (WEF), wastewater can be recycled for food production and food waste can be converted into clean energy, both contributing to environmental impact reduction and resource sustainability. A novel household-scale, closed-loop WEF system was designed, installed and operated to manage organic waste while retrieving water for irrigation, nutrients for plant growth, and biogas for energy generation. The system included a biodigester for energy production, a sand filter system to regulate nutrient levels in the effluent, and a hydroponic setup for growing food crops using the nutrient-rich effluent. These components are operated with a daily batch feeder coupled with automated sensors to monitor effluent flow from the biodigester, sand filter system, and the feeder to the hydroponic system. This novel system was operated continuously for two months using typical household waste composition. Controlled experimental tests were conducted weekly to measure the nutrient content of the effluent at four locations and to analyze the composition of biogas. Gas chromatography was used to analyze biogas composition, while test strips and In-Situ Aqua Troll Multi-Parameter Water Quality Sonde were employed for water quality measurements during the experimental study. Experimental results showed that the system consistently produced biogas with 76.7% (±5.2%) methane, while effluent analysis confirmed its potential as a nutrient source with average concentrations of phosphate (20 mg/L), nitrate (26 mg/L), and nitrite (5 mg/L). These nutrient values indicate suitability for hydroponic crop growth and reduced reliance on synthetic fertilizers. This novel system represents a significant step toward integrating waste management, energy production, and food cultivation at the source, in this case, the household. Full article

The rapid growth in the number of motor vehicles has exacerbated traffic congestion. The occurrence of congestion not only poses significant challenges for traffic management authorities but also severely impacts residents’ travel and daily routines. Against this backdrop, predicting traffic flow can provide crucial insights for anticipating changing traffic patterns. Therefore, this paper proposes a novel hybrid deep learning architecture (CNN-LSTM-GRU) for highway traffic flow prediction that integrates spatiotemporal and meteorological dimensions. Our approach constructs a multidimensional feature matrix encompassing temporal sequences, spatial correlations, and weather conditions. Convolutional Neural Networks (CNN) are employed to capture spatial patterns, while Long Short-Term Memory (LSTM) and Gated Recurrent Unit (GRU) networks jointly model temporal dependencies. Through systematic hyperparameter tuning and step-length optimization, we validate the model using real-world traffic data from a provincial highway network. The experimental evaluation analyzes the following two critical dimensions: (1) holiday vs. non-holiday traffic patterns, and (2) the impact of weather data integration. Comparative analysis reveals that our hybrid model demonstrates superior prediction accuracy over standalone LSTM, GRU, and their CNN-based counterparts (CNN-LSTM, CNN-GRU). Full article

Surface modification of carbon fibers (CFs) is a critical step in preparing carbon fiber-reinforced composites. This study developed a continuous experimental process that integrates electrochemical anodic oxidation and chemical vapor deposition to fabricate carbon nanotubes/carbon fiber (CNTs/CF) reinforcements. The effects of temperature and hydrogen flow rate during CNT growth on the resulting reinforcements were systematically investigated. The surface morphology and mechanical properties of the modified materials were characterized using scanning electron microscopy, Raman spectroscopy, and single-fiber tensile testing. Employing an Fe_0.5Ni_0.5 bimetallic catalyst under optimized conditions (550 °C, H₂ flow rate: 0.45 mol/min, C₂H₂ flow rate: 0.30 mol/min), the resulting reinforcement exhibited an 8.7% increase in tensile strength compared to as-received CF. Full article

This essay focuses on the Greek adoptees’ search for identity and on the agrafa, or the “unwritten” territories, into which this search penetrates. The Greek adoptees represent an underresearched case study of the postwar intercountry adoption movement (1950–1975). Creating a narrative of the self is key to the adoptees’ identity formation, but their personal narrative is often undermined by stereotypes and denunciations that stunt its development. The research presented here has been guided by questions that interrogate the verdict-making or “sentencing” associated with the adoptees’ identity-shaping process: their sentencing to subjugation by stock opinions, the denouncing of their alternative viewpoints about “rescue” adoptions, and the verdict of their entrapment in feel-good master narratives. This essay also explores broader research questions pertaining to modes of interrogating “historic” adoptions from Greece. It is concerned with the why rather than with the how or the who of the oldest, post-WWII intercountry adoption flows. In what forums and genres (narrative, visual, journalistic, scholarly) are Greek adoption facts and legacies articulated, mediated, and/or materialized? How do memories, both positive and negative, underpin current projects of self-identification and transformation? What are the adoptees’ preferred outlets to speak about embodied experiences, and are those satisfactory? Based on a mixed methods approach, the essay ties these steps in identity growth to the Adoptee Consciousness Model, illustrating the five phases of consciousness that the adoptees may experience throughout their lives. Full article

Calcium (Ca²⁺) is a macronutrient essential for the growth, development, yield, and quality of vegetables and fruits. It performs structural, enzymatic, and signaling functions in plants. This review examines Ca²⁺ translocation from soil to the fruit via the plant xylem network, emphasizing the importance of Ca²⁺ compartmentalization within fruit cell organelles in the development of calcium deficiency disorders such as blossom-end rot (BER). The underlying causes of BER and potential control measures are also discussed. Soil-available Ca²⁺, transported by water flow, enters the root apoplast through membrane channels and moves toward the xylem via apoplastic or symplastic routes. The transpiration force and the growth of organs determine the movement of Ca²⁺-containing xylem sap to aerial plant parts, including fruits. At the fruit level, the final step of Ca²⁺ regulation is intracellular partitioning among organelles and cellular compartments. This distribution ultimately determines the fruit’s susceptibility to Ca²⁺-deficiency disorders such as BER. Excessive sequestration of Ca²⁺ into organelles such as vacuoles may deplete cytosolic and apoplastic Ca²⁺ pools, compromising membrane integrity and leading to BER, even when overall Ca²⁺ levels are adequate at the blossom end. Effective BER management requires cultural and physiological practices that promote Ca²⁺ uptake, translocation to the fruit, and appropriate intracellular distribution. Additionally, the use of BER-resistant and Ca²⁺-efficient cultivars can help mitigate this disorder. Therefore, a comprehensive understanding of Ca²⁺ dynamics in plants is critical for managing BER, minimizing production loss and environmental impacts, and maximizing overall crop productivity. Full article

Water, an essential asset for life and growth, is under growing pressure due to climate change, overpopulation, pollution, and industrialization. At the same time, water distribution within cities relies on piping networks that are over 30 years old and thereby prone to leaks, cracking, and losses. Taking this into account, non-revenue water (i.e., water that is distributed to homes and facilities but not returning revenues) is estimated at almost 50%. To this end, intelligent water management via computational advanced tools is required in order to optimize water usage, to mitigate losses, and, more importantly, to ensure sustainability. To address this issue, a case study was developed in this paper, following a step-by-step methodology for the city of Heraklion, Greece, in order to introduce an intelligent water management system that integrates advanced technologies into the aging water distribution infrastructure. The first step involved the digitalization of the network’s spatial data using geographic information systems (GIS), aiming at enhancing the accuracy and accessibility of water asset mapping. This methodology allowed for the creation of a framework that formed a “digital twin”, facilitating real-time analysis and effective water management. Digital twins were developed upon real-time data, validated models, or a combination of the above in order to accurately capture, simulate, and predict the operation of the real system/process, such as water distribution networks. The next step involved the incorporation of a hydraulic simulation and modeling tool that was able to analyze and calculate accurate water flow parameters (e.g., velocity, flowrate), pressure distributions, and potential inefficiencies within the network (e.g., loss of mass balance in/out of the district metered areas). This combination provided a comprehensive overview of the water system’s functionality, fostering decision-making and operational adjustments. Lastly, automatic meter reading (AMR) devices could then provide real-time data on water consumption and pressure throughout the network. These smart water meters enabled continuous monitoring and recording of anomaly detections and allowed for enhanced control over water distribution. All of the above were implemented and depicted in a web-based environment that allows users to detect water meters, check water consumption within specific time-periods, and perform real-time simulations of the implemented water network. Full article

In this paper, we study the convergence and complex dynamics of a novel higher-order multipoint iteration scheme to solve nonlinear equations. The approach is based upon utilizing cubic interpolation in the second step of the King–Werner method to improve its convergence order from $2.414$ to 3 and the efficiency index from $1.554$ to $1.732$, which is higher than the efficiency of optimal fourth- and eighth-order iterative schemes. The proposed method is validated through numerical and dynamic experiments concerning the absolute error, approximated computational order, regions of convergence, and CPU time (sec) on the real-world problems, including Kepler’s equation, isentropic supersonic flow, and law of population growth, demonstrating superior performance compared to some existing well-known methods. Commonly, regions of convergence of iterative methods are investigated and compared by plotting attractor basins of iteration schemes in the complex plane on polynomial functions of the type $z^n-1$. However, in this paper, the attractor basins of the proposed method are investigated on diverse nonlinear functions. The proposed scheme creates portraits of basins of attraction faster with wider convergence areas outperforming existing well-known iteration schemes. Full article

This study investigated nutrient removal in tubular photobioreactors (PBR) illuminated by Light-Emitting Diodes (LEDs), treating the effluent from an Up-Flow Anaerobic Sludge Blanket (UASB) system followed by a Biological Percolator Filter (BPF). Designed as a tertiary treatment step, the PBRs aimed to minimize eutrophication while promoting microalgal growth through CO₂ assimilation released by bacterial activity—resulting in biomass with potential for value-added applications. The objective of this study was to elucidate the mechanisms responsible for nitrogen and phosphorus removal under a controlled environment. A key novelty of this work lies in the comparative evaluation of red and blue LED illumination in the pilot-scale PBRs used for wastewater treatment. All systems achieved >99% ammoniacal nitrogen removal, while soluble phosphorus removal achieved up to 95%. The highest nitrogen removal rate was observed under red light (10.60 mg L⁻¹ d⁻¹), although there was no difference for blue light, while blue light was more effective for phosphorus removal (3.28 mg L⁻¹ d⁻¹). Assimilation was the primary removal mechanism, supported by microalgae–bacteria interactions and artificial CO₂ injection. The research highlights distinct advantages of each light illumination: the blue-light photobioreactor was more suitable for tertiary treatment, whereas the red-light system showed potential for microalgal biomass-based co-product generation. Full article

Vibrio natriegens is widely used as a production host for biotechnological processes due to its superior maximum glucose consumption rate, high growth rate, and abundant ribosomes. Most bioprocesses also need a scalable biomass separation step. This can be achieved by cross-flow filtration with ceramic membranes, although the membrane pores are susceptible to fouling. However, the fouling characteristics of V. natriegens culture broth have not been investigated in detail. We therefore characterized membrane fouling during the separation of V. natriegens biomass from culture broth using a cross-flow filtration plant with ceramic membranes. The resistance in series model was used to quantify the fouling-induced resistance caused by the different components of the culture broth. The total fouling resistance was 4.1·10⁹ ± 0.6·10⁹ m⁻¹ for the culture broth and 5.4·10⁹ ± 0.7·10⁹ m⁻¹ for the summed broth components. Reversible resistance accounted for 86% and 81% of these totals, respectively. We then applied Hermia’s adapted filtration laws to determine the dominant fouling mechanism induced by the different broth components. In a further step, we established a setup to determine the compressibility index of the cells during cross-flow filtration, resulting in an estimated value of 0.55 ± 0.04. These results will facilitate the design of economic filtration plants and will help to establish V. natriegens as a production host for large-scale industrial processes. Full article

The Yangtze River Delta region is facing the demand for high-quality economic development, and the study of urban network as a manifestation of the interaction between cities is becoming increasingly important. This study focused on the node structure of the urban network in the Yangtze River Delta urban agglomeration from 2010 to 2021, used the modified gravity model to construct a polycentric city network from the perspective of economic flow, used the spatial Durbin model for spatial econometric analysis, and identified the conduction path through the two-step method of causal stepwise regression mediating effect test. The results show that Shanghai, as the core node city, has significantly promoted the economic development of Hangzhou, Nanjing, Hefei, and other cities and formed a metropolitan network structure characterized by “one core and five circles”. Under different spatial weight matrices, the polycentric city network has a significant positive impact on economic growth, and its impact is not only related to the economic level of the city itself but also closely related to the economic status of its neighboring cities. The polycentric city network significantly enhances economic growth by accelerating the flow of regional factors, promoting regional industrial division of labor and cooperation, and enhancing regional innovation capabilities. Full article

For effective transportation planning, land use, travel behavior, and infrastructure capacity should be optimized to support sustainable urban growth and reduce congestion. Every new site development generates traffic volume, which can affect the quality of traffic flow in the surrounding road network. Therefore, trip generation, which predicts future travel demand, is a crucial step in the traditional four-step transportation model. In this context, the main objective of this study is to develop a model for estimating vehicle trip generation due to the construction of a shopping center, which is a significant traffic generator. The survey was conducted in Split (Croatia) at five existing locations, and linear regression analysis was used to develop models for different time periods. The results indicated that vehicle trips are strongly correlated with the gross floor area of shopping centers, with a high coefficient of determination. Additionally, this study presents a comparison of measured traffic volumes with estimates using ITE Trip Generation Manual equations. The findings suggest that these vehicle trip estimates should be reduced by approximately 40%. Since no previous studies have been conducted on the impact of land use on trip generation in the Republic of Croatia, the developed models represent a first step in creating a database that should be expanded with new data. Estimating the traffic generated by a new site development is a crucial component of traffic management, as it helps planners and engineers assess its impact on the surrounding road network and implement necessary measures to ensure efficient and safe traffic flow. Full article