Average Coefficient Research Articles

Mitigating Low-Speed Crawling and Jitter in Telescopic Hydraulic Cylinders through Stick-Slip Dynamics Analysis and Friction Reduction Strategies

Abstract This study investigates the mechanisms of jittering in telescopic cylinders and proposes effective mitigation strategies. The focus is on the dynamic behavior of hydraulic cylinders under low-speed conditions, particularly the stick-slip phenomenon. Through finite element analysis using Abaqus and tribological tests, the impact of various factors on the friction and wear properties of cylinder components is examined. Findings reveal that optimizing the average friction coefficient, stick-slip amplitude, and stick-slip time can significantly reduce jitter and creep in hydraulic cylinders. The results provide valuable insights for improving the performance and longevity of hydraulic systems in engineering machinery.

Investigation on tribo‐properties of twaron pulp‐reinforced brake friction composites

AbstractDetermining the appropriate formulation in designing and developing brake friction materials is one of the most complex tasks. This study investigates the synergistic effect and optimization of twaron fiber on the fade and recovery performance of brake friction composites. For this purpose, a series of friction materials containing varying amounts of twaron between 1 and 9 wt% were developed, and their characterization and tribo evaluation were carried out. The tribo performance of the composites was evaluated in a Krauss‐type friction test machine in line with the ECE R90 procedure in terms of their fade and recovery behaviors. It was noted that the fade‐recovery friction response of composites was affected when fiber is added; that is, an increase in fiber content improved the fade performance, friction fluctuations decreased, and a higher recovery response was observed. The fade and average coefficient of friction were found to be the main determinants, while recovery was found to be the stabilizer. Analytical hierarchy process (AHP) was used to determine the priority of importance of criteria in the performance evaluation, and VIKOR (multi‐criteria optimization compromise solution) was used for ranking evaluation. The formulation with a concentration of twaron 7 wt% was found to have exhibited an optimal braking performance. The worn surfaces scanning electron microscope (SEM) study confirms the general friction and wear mechanisms of friction layers with fiber content.Highlights Development of twaron pulp‐reinforced eco‐friendly brake friction composites. Use of MCDM approach in the development of BFCs for braking applications. VIKOR optimization positioned 7 wt% twaron‐addition BFC as the optimal choice. It was observed that fiber amount is effective on the behaviors of composites.

Experimental and Simulation Investigation of J-shaped and Kammtail Virtual Airfoils in Small-Scale Horizontal Axis Wind Turbines

Abstract In this work, the performance of new wind blade designs for small-scale horizontal axis wind turbines (HAWTs) was studied and compared with the performance of a baseline design. The studied designs were J-shaped and Kammtail Virtual Foil profiles. Three J-shaped pressure-side truncation ratios and two KVF truncation ratios were studied. All proposed cases were first investigated in a two-dimensional simulation study to get the lift-to-drag ratio by applying different wind speeds and angles of attack. The baseline design was experimentally investigated. Output power was measured using a digital rotary torque sensor at three wind speeds. The tip speed ratio was calculated after measuring each wind speed's free rotating revolutions. Three wind speeds and experimental TSRs were used in three-dimensional simulations to capture the performances of the proposed cases and compare them with the baseline. The simulation investigation was carried out for lab-scale and scaled cases. The three-dimensional study found that the J-shaped blades enhanced the performance of the HAWTs for both lab-scale and scaled cases. J-shaped blades with a 1/3 opening ratio yielded an average power coefficient enhancement of around 1.56% and 4.16% for lab-scale and scaled cases, respectively. J-shaped blades with a 2/3 opening ratio enhanced the average power coefficient for lab-scale and scaled cases. Furthermore, it was found that the KVF blades diminished the performance for both lab-scale and scaled cases.

The thrust balance model during the dragonfly hovering flight

In recent years, the micro air vehicle (MAV) oscillations caused by thrust imbalances have received more attention. This paper proposes a dual-wing thrust balance model (DTBM) that can solve the above problem by iterating the modified rotation angle formula. The core control parameter of the DTBM model is the au angle, which refers to the angle between the wing surface and the stroke plane at the mid-stroke position during the upstroke. For each degree change in the au angle, the range of variation in the dimensionless average thrust coefficient is between 0.0225-0.0268. A thrust coefficient of 0.0225 causes the dragonfly to move forward by 9.037 cm in one second, which is equivalent to 1.29 times its body length. By using DTBM, the average thrust coefficient can be reduced to below 0.001 in just a few iterations. No matter how complex the motion pattern is, the DTBM can achieve thrust balance within 0.278 s. Through our research, when selecting the deviation angle motion of real dragonflies, the dual-wing au angles exhibit a highly linear correlation with wing spacing, called linear motion. In contrast, the nonlinear variation of the au angle appears in the hindwing of the no-deviation motion and the forewing of the elliptical deviation motion. All of the nonlinear changes are referred to as nonlinear motion. Nonlinear variation of the au angle arises from larger disturbances of the lateral force during the upstroke. The stronger lateral force is closely related to the flapping trajectory. When the flapping trajectory causes the dual-wing to closely approach each other in the mid-stroke, a continuous positive pressure zone forms between the dual-wing. The collision of the leading-edge vortex and the shedding of the trailing-edge vortex is the special flow field structure in the nonlinear motion. Guided by the DTBM, future designs of MAVs will be able to better achieve thrust balance during hovering flight, requiring only the embedding of the iteration algorithm and prediction function of the DTBM in the internal chip.

On the Influence of Microstructure and Properties of Direct Laser Deposited 50Cr6Ni2Y Coatings with Different TiC Contents

Three 50Cr6Ni2Y + x wt.% TiC (x = 1.5, 3.0, 4.5) alloy steel coatings were prepared using direct laser deposition (DLD) technology. The microstructure, microhardness, and wear resistance of DLD samples were studied. The results indicate that DLD coatings were composed of α-Fe (Fe-Cr-Ti), γ-Fe (Fe-Ni), and TiC. When the added TiC content was 3.0 wt.%, the DLD coating without cracks was fabricated, and TiC particles were well embedded in the sample. In addition, the coating demonstrated the best performance, with a microhardness of 758 ± 23.3 HV0.2, an average friction coefficient of 0.58, and a wear rate of 0.37 %. The addition of an appropriate amount of TiC as a reinforcing phase, on the one hand, had played a role in the second phase strengthening. On the other hand, the diffusion interfaces formed between TiC particles and the matrix allowed some Ti elements to melt into the matrix and formed a solid solution, playing a role in solid solution strengthening. The results could provide a reference for the preparation and repair of laser additive manufacturing high-performance wear-resistant parts.

An Investigation on the High-Temperature Stability and Tribological Properties of Impregnated Graphite

Impregnated graphite is a common material for friction pairs in aeroengine seals, especially at high temperatures. For the convenience of the application of graphite materials in aeroengines, an SRV-4 tribometer and a synchronous thermal analyzer are employed to study the tribological properties and thermal stability of pure, resin-impregnated, metal-impregnated, and phosphate-impregnated graphite against stainless steel from room temperature to 500 °C. The results indicate that impregnations can improve the wear resistance and thermal stability of graphite at high temperatures. Compared with other impregnated graphite materials, the resin-impregnated graphite shows a good friction coefficient and poor wear rate and thermal stability over 300 °C, due to the degradation and oxidation of the resin-and-graphite matrix. The metal- and phosphate-impregnated graphite materials exhibit excellent wear resistance and thermal stability under 500 °C as a result of the protection of the impregnations, while the average friction coefficient of the metal-impregnated graphite is much greater than the phosphate-impregnated graphite, and even reaches 2.14-fold at 300 °C. The wear rates for the graphite impregnated with resin, metal, and phosphate are 235 × 10−7, 7 × 10−7, and 16 × 10−7 mm3N−1m−1 at 500 °C, respectively. Considering all aspects, the phosphate-impregnated graphite exhibits excellent tribological properties and thermal stability.

African Schistosomiasis: A Framework of Indicators Assessing the Transmission Risk and Intervention Effectiveness

Schistosomiasis, a parasitic disease with a complex transmission mechanism, requiring a snail intermediate host, is influenced by biology, the environment, human behavior and the prevailing socioeconomic situation. This study aimed to systematically investigate the importance and feasibility of indicators related to the factors influencing transmission and intervention measures for Schistosoma mansoni and S. haematobium. Based on a literature review and group discussions according to the Delphi method, a framework questionnaire was designed. A total of 33 experts on schistosomiasis were invited, and 27 were accepted, to rate the importance and feasibility of indicators for transmission with and the control of schistosomiasis, with a focus on intervention measures for S. mansoni and S. haematobium infections in Zimbabwe. After two rounds of Delphi consultations with these experts, calculated to have a high average authority coefficient (0.88), a consensus was reached on a framework that included 2 primary, 6 secondary and 39 tertiary indicators. The Delphi–entropy method was applied to assess the weight of each indicator. The key influencing factors included hazardous water exposure, accessibility to safe drinking water, sanitary facilities and the contamination of water bodies by outdoor defecation/urinary habits. The intervention measures involved improved diagnostics, health education, preventive chemotherapy, the presence of national control plans and the implementation of the strategy on water, sanitation and hygiene (WASH). While these factors are already well known, their detailed order of importance could help to improve the allocation of specific control efforts.

Developing a quality indicator system for evaluating internet plus home care nursing services based on the SERVQUAL model: a Delphi-analytic hierarchy process study

Background In the context of global population aging and the rapid development of information technology, the demand for Internet Plus Home Care Nursing (Internet+ HCN) services have been on the rise, especially in China. Internet+ HCN services have the potential to maximize existing human resources to counter the shortage of medical healthcare services. However, at present, Internet+ HCN services are difficult to scale due to the lack of standardized service quality governance. Quality indicators for service evaluation of Internet+ HCN services are under-defined. Objective To develop a quality indicator system for evaluating Internet+ HCN services, and to shed theoretical light on assessing mHealth service quality from a user experience perspective. Methods An initial quality indicator system was established based on scenarios related to Internet+ HCN services. The Delphi Method was applied to modify the indicators according to experts’ opinions, and the analytic hierarchy process (AHP) was applied to calculate the indicator weight. Finally, a quality indicator system for evaluating Internet+ HCN services was developed based on the SERVQUAL model. Results Altogether, 17 experts from relevant fields such as nursing education, clinical nursing, health management, and health informatics were consulted through email surveys. The response rates in both rounds of Delphi and the AHP were 100%. The average expert authority coefficients were 0.912 and 0.925 respectively in the two rounds of Delphi. Kendall’s W, indicating variation coefficients, ranged from 0.262 to 0.265. Finally, a quality indicator system for evaluating Internet+ HCN services, comprising five primary indicators and 15 secondary indicators, was developed. Primary indicators and their AHP generated the following weights: assurance (0.245), reliability (0.240), tangibles (0.192), responsiveness (0.190), and empathy (0.132). Conclusions By measuring the services quality gap between user expectations and perceptions, the proposed SERVQUAL model-based quality indicator system shows potential in improving the quality of Internet+ HCN services through the perspective of user experiences.

Study on the skid resistance decay of submerged asphalt pavements based on texture parameters

AbstractIt is well known that prolonged rainwater erosion can adversely affect the surface texture of asphalt pavements, leading to a rapid decline in their skid resistance. This study utilized a small-scale accelerated loading device, a high-precision 3D scanner, and digital image processing technology to investigate the surface texture wear process and skid resistance decay trends of basalt asphalt pavement and steel slag asphalt pavement under water erosion and traffic load. The results indicate that under submerged conditions, the skid resistance (BPN) of asphalt pavement declines rapidly during the first 500,000 load cycles, and the rate of decline gradually stabilizes after 500,000 cycles. After 1.2 million load cycles, the BPN of basalt pavement decreased by 28.10%, while that of steel slag pavement decreased by 21.18%, indicating that the skid resistance of steel slag pavement is significantly better than that of basalt pavement. Texture parameters—namely, root mean square height, peak material volume, core material volume, void volume of the core, and valley void volume—exhibited the same decay trend as BPN. The average correlation coefficients between BPN and texture parameters were 0.846, 0.848, 0.898, and 0.916, respectively, indicating that texture parameters can be used as evaluation indicators for skid resistance decay. Finally, the decay of pavement skid resistance was predicted using an exponential decay equation.

Numerical Investigations on the Enhancement of Convective Heat Transfer in Fast-Firing Brick Kilns

In order to reduce CO2 emissions in the brick manufacturing process, the effectiveness of the energy-intensive firing process needs to be improved. This can be achieved by enhancing the heat transfer in order to reduce firing times. As a result, current development of tunnel kilns is oriented toward fast firing as a long-term goal. However, a struggling building sector and complicated challenges, such as different requirements for product quality, have impeded developments in this direction. This creates potential for the further development of oven designs, such as improved airflow through the kiln. In this article, numerical flow simulations are used to investigate two different reconstruction measures and compare them to the initial setup. In the first measure, the kiln height is reduced, while in the second measure, the kiln cars are adjusted to alternate the height of the bricks so that every other pair of bricks is elevated, creating a staggered arrangement. Both measures are investigated to determine the effect on the heating rate compared to the initial configuration. A transient grid independence study is performed, ensuring numerical convergence and the setup is validated by experimental results from measurements on the initial kiln configuration. The simulations show that lowering the kiln height improves the heat transfer rate by 40%, while the staggered arrangement of the bricks triples it. This leads to an average brick temperature after two hours which is around 130 °C higher compared to the initial kiln configuration. Therefore, the firing time can be significantly reduced. However, the average pressure loss coefficient rises by 70% to 90%, respectively, in the staggered configuration.

Litter Removal Counteracts the Effects of Warming on Soil Bacterial Communities in the Qinghai–Tibet Plateau

Climate warming and high-intensity human activities threaten the stability of alpine meadow ecosystems. The stability of the soil microbial community is crucial for maintaining ecological service function. However, the effects of warming and litter removal on microbial interactions, community-building processes, and species coexistence strategies remain unclear. In this study, we used a fiberglass open-top chamber to simulate global change, and moderate grazing in winter was simulated by removing above-ground litter from all plants in the Qinghai–Tibet Plateau, China, to investigate the effects of warming, litter removal, and interactions on soil microbial communities. The treatments included (1) warming treatment (W); (2) litter removal treatment (L); (3) the combined treatment (WL); and (4) control (CK). The results show that compared with the control treatment, warming, litter removal, and the combined treatments increased bacterial Shannon diversity but reduced fungal Shannon diversity, and warming treatment significantly changed the bacterial community composition. Warming, litter removal, and the combined treatments reduced the colinear network connectivity among microorganisms but increased the modularity of the network, and the average path distance and average clustering coefficient were higher than those in the control group. Stochastic processes played a more important role in shaping the microbial community composition, and soil–available phosphorus and soil ammonium contributed more to the βNTI of the bacterial community, while total phosphorus and NAG enzyme in the soil contributed more to the βNTI of the fungal community. Notably, litter removal counteracts the effects of warming on bacterial communities. These results suggest that litter removal may enhance bacterial community stability under warming conditions, providing insights for managing alpine meadow ecosystems in the context of climate change.

Investigation of aluminum-based mono and hybrid surface composites by incorporating SiC and graphene reinforcements using friction stir processing

The present investigation focuses on the synthesis of mono (AA5052/SiC and AA5052/graphene) and hybrid (AA5052/SiC/graphene) surface composites using friction stir processing (FSP). This work examines the synergistic effect of SiC and graphene on the fabricated surface composites. Macro/microstructure, microhardness, and wear test analysis were done on these samples, and the results were compared with the base material AA5052-H32. The microstructure analysis showed that the distribution of reinforcement particles in the aluminum matrix is made more uniform by adding hard SiC with graphene nanoparticles, which can reduce the occurrence of particle clustering and agglomeration. As a result, the smallest grain size of 11.2 µm and the highest microhardness obtained was 84.1 HV obtained in hybrid surface composites. Consequently, the hybrid surface composites obtained more improved wear properties than mono surface composites. Thus, the hybrid surface composites achieved the lowest average friction coefficient of 0.304.

Estimating Rainfall Anomalies with IMERG Satellite Data: Access via the IPE Web Application

This study assesses the possibilities of the Integrated Multi-satellite Retrievals for Global Precipitation Measurement (IMERG-GPM) to estimate extreme rainfall anomalies. A web application, the IMERG Precipitation Extractor (IPE), was developed which allows for the querying, visualization, and downloading of time-series satellite precipitation data for points, watersheds, country extents, and digitized areas. The tool supports different temporal resolutions ranging from 30 min to 1 week and facilitates advanced analyses such as anomaly detection and storm tracking, an important component for climate change study. To validate the IMERG precipitation data for anomaly estimation over a 22-year period (2001 to 2022), the Rainfall Anomaly Index (RAI) was calculated and compared with RAI data from 2360 NOAA stations across the conterminous United States (CONUS), considering both dry and wet climate regions. In the dry region, the results showed an average correlation coefficient (CC) of 0.94, a percentage relative bias (PRB) of −22.32%, a root mean square error (RMSE) of 0.96, a mean bias ratio (MBR) of 0.74, a Nash–Sutcliffe Efficiency (NSE) of 0.80, and a Kling–Gupta Efficiency (KGE) of 0.52. In the wet region, the average CC of 0.93, PRB of 24.82%, RMSE of 0.96, MBR of 0.79, NSE of 0.80, and KGE of 0.18 were computed. Median RAI indices from both the IMERG and NOAA indicated an increase in rainfall intensity and frequency since 2010, highlighting growing concerns about climate change. The study suggests that IMERG data can serve as a valuable alternative for modeling extreme rainfall anomalies in data-scarce areas, noting its possibilities, limitations, and uncertainties. The IPE web application also offers a platform for extending research beyond CONUS and advocating for further global climate change studies.

Achieving considerable wear resistance in new Ti-based high-entropy alloys through microstructural hardening by adding Nb

In this study, (CoCrNiMn)78Ti22−xNbx eutectic high-entropy alloys were successfully synthesised via an arc melting process under vacuum, and the phase structure, microstructure, mechanical properties and dry sliding tribological behaviour of the alloys were systematically investigated. The XRD results for the (CoCrNiMn)78Ti22−xNbx eutectic high-entropy alloys are almost in agreement with the JMatPro phase diagram simulations, and the volume fraction of the Laves phase increased with increasing Nb content. OM and SEM images revealed that the microstructure was composed of dendrites (BCC A2) and interdendrites (BCC B2 +Laves) and changed from a hypoeutectic to a eutectic to a BCC B2 +Laves dual-phase structure, with the average grain size decreasing from 6.715 µm to 6.391 µm. Ti promoted the growth of the layered Laves phase and provided the alloy with base hardness and wear resistance. The hardness of the alloy combination of 21 % Ti and 1 % Nb reached the maximum value of 707.04 HV, whereas the average coefficient of friction (COF) and wear rate reached the lowest values of 0.49 and 1.668 × 10−4 mm3/N·m, respectively. With increasing load, the wear mechanism was mixed fatigue, delamination wear, and abrasive wear accompanied by oxidation, and the possibility of three-body wear paths between compacted tribolayers cannot be excluded. The debris was mostly in the form of microclusters, and the particle size range was concentrated between 1 −2 µm; meanwhile, the shape of the debris tended to develop from lamellar to spherical with increasing hardness.

An automated pheochromocytoma and paraganglioma lesion segmentation AI-model at whole-body 68Ga- DOTATATE PET/CT.

Somatostatin receptor (SSR) targeting radiotracer 68Ga-DOTATATE is used for Positron Emission Tomography (PET)/Computed Tomography (CT) imaging to assess patients with Pheochromocytoma and paraganglioma (PPGL), rare types of Neuroendocrine tumor (NET) which can metastasize thereby becoming difficult to quantify. The goal of this study is to develop an artificial intelligence (AI) model for automated lesion segmentation on whole-body 3D DOTATATE-PET/CT and to automate the tumor burden calculation. 132 68Ga-DOTATATE PET/CT scans from 38 patients with metastatic and inoperable PPGL, were split into 70, and 62 scans, from 20, and 18 patients for training, and test sets, respectively. The training set was further divided into patient-stratified 5 folds for cross-validation. 3D-full resolution nnUNet configuration was trained with 5-fold cross-validation. The model's detection performance was evaluated at both scan and lesion levels for the PPGL test set and two other clinical cohorts with NET (n = 9) and olfactory neuroblastoma (ONB, n = 5). Additionally, quantitative statistical analysis of PET parameters including SUVmax, total lesion uptake (TLU), and total tumor volume (TTV), was conducted. The nnUNet AI model achieved an average 5-fold validation dice similarity coefficient of 0.84 at the scan level. The model achieved dice similarity coefficients (DSC) of 0.88, 0.6, and 0.67 at the scan level, the sensitivity of 86%, 61.13%, and 61.64%, and a positive predictive value of 89%, 74%, and 86.54% at the lesion level for the PPGL test, NET and ONB cohorts, respectively. For PPGL cohorts, smaller lesions with low uptake were missed by the AI model (p < 0.001). Anatomical region-based failure analysis showed most of the false negative and false positive lesions within the liver for all the cohorts, mainly due to the high physiologic liver background activity and image noise on 68Ga- DOTATATE PET scans. The developed deep learning-based AI model showed reliable performance for automated segmentation of metastatic PPGL lesions on whole-body 68Ga-DOTATATE-PET/CT images, which may be beneficial for tumor burden estimation for objective evaluation during therapy follow-up. https://www. gov/study/NCT03206060 , https://www. gov/study/NCT04086485 , https://www. gov/study/NCT05012098 .

A new reading of the relationship between financial development, trade openness, vulnerability and economic growth in Africa: New perspectives from method of moment’s quantile regression

One of the most frequently debated subjects in international forums is economic growth, which is regarded as a global priority. Consequently, researchers have turned their attention from conventional economic growth at a single average coefficient to divisible economic growth at levels of its value. Although the existing literature has discussed several determinants of economic growth, our article contributes to examining the sources of economic growth in African countries during the generations of reforms from 1990 to 2019 and in the context of economic vulnerability. The variables used in the analysis are gross domestic product, trade openness, financial development, and economic vulnerability. The study uses a quantile regression econometric model to examine these variables at different stages of reform. Quantile regression (QR) estimates for quantiles 0.05 to 0.95 showed mixed results: financial development is favorable to African economic growth at all quantile levels. However, economic vulnerability is a major impediment to economic growth at all quantile levels. In addition, it was found that a high degree of trade openness has a detrimental effect on African economic growth from quantile 0.5 of the dependent variable. Finally, another important result proves that financial development is a remedy for decision-makers against economic vulnerability.

Operation study of the photovoltaic thermal heat pump integrated energy system under trigeneration condition and harsh conditions

In recent years, the photovoltaic thermal heat pump has gained significant attention as a near zero-carbon energy technology, due to the comprehensive ability to provide heating in winter, cooling in summer, photovoltaic power generation and domestic hot water throughout the year. However, owing to the incomplete research on the system operating characteristics in trigeneration condition and harsh conditions, the production performance and operational stability of the photovoltaic thermal heat pump were not widely recognized. In view of the above problems, the following studies were conducted in this paper: First, the integrated energy system based on the modular photovoltaic thermal heat pump was designed and constructed. Then, the system operation in severe hot and cold season was carried out and the operational stability of the system under harsh operating conditions was demonstrated sufficiently. Afterwards, the operation of the system under the continuous trigeneration operation were analyzed. During the 7-day trigeneration operation, the average hot water output was 12.12 tons and the average photovoltaic power generation was 88.5 kWh in the daytime heating operation. Besides, the average coefficient of cooling performance was 2.32 in the nighttime cooling operation and the effective cooling-supply time of the system was approximately 4 h.

Experimental study on the aerodynamic characteristics and wake flow feature of triangular prisms with various round corner radius

In this work, particle image velocimetry (PIV) and wind pressure measurements are employed in the wind tunnel to investigate triangular prisms with different rounded corner radius. The effect of rounded corner radius on wind pressure distribution, aerodynamic force, and wake flow characteristics are analyzed. Results indicate that the surface wind pressure can be effectively reduced through filleting treatment, with an average drag coefficient decrease of 52.7% as the corner shape transitions from sharp to round. The continuous increase of the radius of the rounded corner causes an accretion of the fluctuating lift coefficient, and a slow decrease of the drag coefficient. The modification of the corner radius has a limited impact on the vortex shedding frequency, but the shedding vortex tend to gather the leeward side. Additionally, statistical analysis of wake flow shows that an increment in the rounded corner radius leads to a significant reduction in the wake recirculation region, amounting to 20.16%. Concurrently, the peak values of turbulent kinetic energy and Reynolds stress exhibit a pattern of initial increase followed by a decrease. On the other hand, results of proper orthogonal decomposition suggest that the spatial distribution of vortex structures becomes increasingly compact with the enlargement of the rounded corner radius.

Integrating material flow analysis into hydrological model for water environment management of large-scale urban-rural mixed catchment

Simultaneous simulation of urban and rural hydrological processes is important for water environment management of mixed land-uses catchments. However, the discharge paths of pollution in the urban drainage system are not described in traditional catchment hydrological models. In this study, an urban-rural water environment (URWE) model is developed through incorporating the material flow analysis (MFA) and the soil and water assessment tool (SWAT) into a general framework. The URWE model is an advancement with respect to traditional hydrological models in terms of simultaneously simulating the urban organized and rural decentralized discharges of pollution. Due to the low data requirement and high computational efficiency of MFA, URWE model is applicable to large-scale catchment with wide urban area. The URWE model is applied to a typical urban-rural mixed catchment, the Dianchi Catchment (China), where the pollution characteristics are analyzed and the pollution control measures are investigated. Results indicate that the URWE model outperforms the conventional SWAT model for both water quantity and quality simulations, with an 8.5 % improvement in average coefficient of determination (R2) and a 67.4 % improvement in average Nash coefficient (NSE). Rural best management practice, rainwater-sewage separation, and storage capacity expansion are identified as the most cost-effective measures for COD, TN, and TP reduction, respectively. Contributions of this study are to improve the accuracy of water environment simulation in urban-rural mixed catchment, as well as to help decision-makers develop synergistic urban-rural water environment management measures.

Development of a horizontal seepage test system of constructed wetland and research on the seepage characteristics based on micro-pollution water

Horizontal subsurface flow constructed wetlands (HSFCW) were widely used as an effective biotechnology for wastewater treatment. However, clogging of the substrate bed was a key factor restricting its application. In this study, a horizontal seepage test system was independently developed, which was used to reveal the development trends of hydraulic resistance in HSFCW, as well as changes in permeability coefficients with time. The relationship between the average permeability coefficient and purification effect was further analyzed. The results showed that the new test system has proved the law of resistance development in HSFCW. The distribution characteristics of the isobaric surface indicate that the blockage of the HSFCW gradually spreads from the lower part to the lower part. The seepage resistance of homogeneous subbed in HSFCW was mainly concentrated in the front end. The growth rate of hydraulic loss in the core zone ranged from 0.685 to 19.515 cm·month−1, the growth rate in the transition zone ranged from 0.223 to 0.695 cm·month−1, and little change occurred in the safety zone. At the end of the HSFCW operation, the widths of the core, transition, and safety zones account for approximately 20–30 %, 50–70 %, and 10–20 % of the entire wetland length, respectively. Meanwhile, the SS removal rate stabilized at over 92 %, when the average permeability coefficient reached 41.45 m·d−1. The removal rate of COD and TN was higher when the average permeability coefficient is between 59.45 and 41.45 m·d−1 and 27.08–59.45 m·d−1, respectively. This study provided a horizontal testing method to accurately understand the changes in the seepage field in HSFCW.