Optimum Area Ratio Research Articles

Optimizing mangrove afforestation: Mollusc biodiversity comparisons reveal optimal mudflat-mangrove area ratio.

In recent decades, mangrove wetlands globally have suffered from human activities and climate change, leading to issues like area reduction, degraded ecological functions and declining biodiversity. Restoration efforts, primarily through mangrove afforestation (i.e. mangrove plantation in mudflats), have been widespread, yet they often overlook the significance of unvegetated mudflats. In addition, under the condition that the total area of suitable mudflats is limited, the problem of what is the threshold of mangrove forests and unvegetated mudflats to better protect mangrove biodiversity has not been solved. Therefore, this study conducted a field survey of molluscs in mangrove wetlands in Hainan Island in China and explored the relative importance of mangroves and unvegetated mudflats through taxonomic alpha diversity and functional diversity. The results showed that (1) mollusc abundance of unvegetated mudflats was notably higher than this of mangrove forests, and the species richness, functional richness and functional vulnerability were significantly lower than those of mangrove forests; (2) the abundance and functional vulnerability of molluscs were mainly affected by sediment properties (pH, interstitial water salinity, median diameter, total nitrogen, C/N ratio), while the species richness and functional richness of molluscs were primarily influenced by vegetation structure (plant density); and (3) retaining at least 20% of the unvegetated mudflat area could well protect the biodiversity of mangrove wetlands. To our knowledge, our study is the first to propose the proportion of mangrove forests and unvegetated mudflats on the basis of benthic biodiversity, providing theoretical support and decision-making reference for mangrove protection and restoration.

Shifts of the pond area ratio for lowland polders: Implication for nutrient control

Shifts for natural ecosystems were increasingly concerned due to its profound impacts on ecosystem services. Ponds within lowland artificial watersheds (polders) play a critical role in nitrogen (N) and phosphorus (P) cycling. From the perspective of N & P control in management practices, it is needed to determine an optimal pond area ratio for polders. For this purpose, our study proposed a process-based modelling framework to investigate the response of polder N & P loss to pond area, and thus to determine the threshold value of pond area ratio to achieve maximum N & P reduction for polders. The proposed framework included two process-based models (NDP and PDP) specially developed to describe N & P dynamics in lowland polders. To evaluate the proposed performance of the framework, it was applied to 171 polders in Zhong River Watershed in Lake Taihu Basin, eastern China. Our investigation results revealed that the correlation between polder N & P reduction rate and pond area ratio had an abrupt shift of 13.6 %, 14.7 % for N & P, respectively. Therefore, polders with a pond area ratio of 13.6–14.7 % had the largest N & P reduction (5.27 and 0.19 kg/ha). Polder size affected P reduction rate, with smaller polders (<200 ha) showing a higher P reduction rate, while it did not affect N reduction rate. Compared with annual precipitation, rainy-season precipitation more significantly (P<0.01) determined polder N & P reduction. This study demonstrated the use of our process-based framework in characterizing the shifts for the pond area ratio for polders, and thus provided technical support for N & P control of lowland areas in water management practices.

Influence of Inlet and Outlet Area Ratio on Intake Port Flow Capacity

The flow capacity of the intake port has a great influence on the charging efficiency of the internal combustion engine, affecting the engine’s performance, so it is critical to improve the intake port flow capacity. In this paper, the intake port numerical model was established, and the influence of the inlet and outlet area ratio on intake port flow capacity was studied. The results show that, under the same condition of relative pressure difference, the intake port discharge coefficient increases sharply and then slowly with an increase in area ratio. Under the same condition of area ratio, the discharge coefficient is only determined by relative pressure difference and decreases with an increase of relative pressure difference when the inlet and outlet area ratio&gt;1. The optimal area ratio decreases and then converges with an increase in relative pressure difference. When the intake port is designed, the optimal area ratio under the working condition of a smaller relative pressure difference should be applied in order to ensure the discharge coefficient is optimal under all working conditions.

Experimental and numerical investigation on the impact of MS2AF on local scour protection performance

Suction anchor foundations are widely used in the offshore wind power industry. The installation of suction caissons alters the near-bed flow field and leads to local scour. This study proposes a novel integrated design for the scour protection of suction anchor foundations, known as the multihole sector suction anchor foundation (MS2AF). Through indoor flume experiments and numerical flume simulations, the local scour protection performances of MS2AFs with different design parameters under the action of steady flow were investigated. The results showed that the scour evolution of MS2AFs can be divided into three stages: slow scour, rapid scour, and scour equilibrium. The MS2AF reduced the flow shear stress on the sediment bed, thereby decreasing the depth and range of the local scour. The maximum scour depth, width, and length of the scour hole exhibited negative linear relationships with the width and thickness of the sector and decreasing-then-increasing relationships with the diameter and area ratio of the holes. Among these factors, the sector's thickness had the most significant impact. There existed an optimal diameter and area ratio that maximized the stratification effect and deceleration effect of the multihole sector.

Efficient waste heat recovery from molten carbonate fuel cells through graphene-collector thermionic generators

The waste heat released by molten carbonate fuel cells (MCFCs) contains considerable energy that can be captured for electric power generation. Nonetheless, the current high-grade heat harvesting devices for the MCFC cogeneration of electrical power are still constrained by low power output or energy conversion. To address this challenge, we present a novel hybrid system that combines an MCFC and a graphene-collector thermionic generator (GCTG), in which the GCTG can efficiently harness the exhaust heat released from the MCFC and generate additional electricity. The results show that the hybrid system’s maximum power density reaches 0.298 W/cm2, which is 1.6 times that of the sole MCFC at 923 K, demonstrating that the hybrid system delivers a significant boost in output performance. Furthermore, finite-time thermodynamics estimates the hybrid system’s optimal operating regions and key parameter designs. The optimal performance of the hybrid system can be further improved by selecting the optimal area ratio, raising the MCFC operating temperature, strengthening the heat transfer coefficient, lowering the thermal emissivity of the thermionic emitter, and manufacturing the perfect optical reflector. The MCFC-GCTG outperforms other MCFC-based hybrid systems regarding output performance, demonstrating that GCTG can more effectively exploit the waste heat released from MCFCs than other heat recovery devices. This study offers valuable theoretical guidance for the strategic optimization of the MCFC-GCTG hybrid system, thereby paving a constructive strategy towards realizing advanced, high-performance MCFC cogeneration systems.

Research on Internal Flow Field Characteristics of Straight-Groove Texture Using Three-Dimensional Modeling

Surface texture modification is a reasonable strategy for improving the tribological property of friction pairs. The internal flow behavior of the surface texture significantly impacts its performance. In this study, a three-dimensional computational fluid dynamics (CFD) model is constructed to explore the internal flow behavior of the straight-groove texture in the thrust bearing. The influences of the Reynolds number, depth ratio, and area ratio of the straight-groove texture on the internal flow behavior are systematically investigated. Furthermore, the streamline and tribological performance parameters are checked to reveal the mechanism of the groove texture influencing the tribological properties. It is found that the vortex and cavitation significantly affect the tribological performance of textured surfaces under hydrodynamic lubrication. The cavitation and upstream vortex areas increase with the Reynolds number, while the downstream vortex area shows a reverse trend. The increase in depth ratio strengthens the upstream and downstream vortexes while reducing the cavitation area. Additionally, a method is proposed to determine the location of the cavitation within the groove texture. Certain operating conditions create the optimal texture depth ratio and area ratio, which could maximize the load-carrying capacity (LCC) of the oil film, and the friction coefficient is relatively small.

Numerical simulation on startup performance of thrust bearing under different acceleration scenarios

PurposeThis paper aims to study the startup performance of thrust bearing. The effects of acceleration scenarios, roughness, the area ratio of texture and texture depth on the transient startup performance of the thrust bearing were analyzed.Design/methodology/approachThe lubrication model is solved by the Reynolds equation with the mass-conservation boundary condition. The Greenwood and Tripp contact model is used to predict asperity contact load. The finite volume method is used to discretize the governing equations.FindingsBy studying the bearing performance with different acceleration functions, it was found that the higher the acceleration at the beginning of the startup, the faster the thrust bearing operates under the hydrodynamic lubrication regime in the start stage. It appears that the friction and contact time of asperity increase with the increasing roughness. The optimal area ratio of texture is within 30%–50%. The depth of texture ranging from 1 to 2 is the best.Originality/valueThis paper proposes a transient mixed lubrication analysis model of the thrust bearing. This model can be used to analyze the variations of tribological performance and lubrication regime of the thrust bearing under different acceleration scenarios.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-09-2022-0268/

Thermodynamic analysis and parameter optimization of a hybrid system based on SOFC and graphene-collector thermionic energy converter

The exhaust heat released from SOFCs (solid oxide fuel cells) possesses tremendous energy that can be recovered for energy cascade utilization. Nevertheless, low conversion efficiency or power density limits the SOFC’s high-grade waste heat recovery capabilities for the cogeneration of electric power. To address this challenge, a novel hybrid system coupling a SOFC with a GTEC (graphene-collector thermionic energy converter) is proposed, where the GTEC harvests the high-grade exhaust heat produced by the SOFC and generates extra electricity. It is found that the maximum power density of the hybrid system can reach 0.774 W/cm2 at 1073 K, which is 1.20 times higher than that of the sole SOFC, indicating that the hybrid system offers a considerable improvement in output performance. Additionally, the optimal operating conditions and major parameter designs of the hybrid system are determined from the perspective of finite-time thermodynamics. Choosing the optimal area ratio, increasing the SOFC operating temperature, enhancing the heat transfer coefficient, decreasing the thermal emissivity, and fabricating the perfect optical reflector can further improve the optimal performance of the hybrid system. Compared with other SOFC-based hybrid systems, the SOFC-GTEC provides better output performance, proving that the GTEC can more efficiently utilize the exhaust heat produced by SOFC than other energy harvesting devices. This work provides crucial theoretical guidance on the optimal designs and parametric analysis of SOFC-GTEC hybrid systems, thus paving the way towards developing high-performance SOFC cogeneration systems.

Optimal cross-sectional area ratio between porous material and resonance tube for the onset of self-excited oscillations in standing-wave thermoacoustic engines

Optimal cross-sectional area ratio between porous material and resonance tube for the onset of self-excited oscillations in standing-wave thermoacoustic engines

The potential of a retractable roof of the natatorium on the indoor environmental improvement: Taking Jiading natatorium of Tongji University as an example

The Star-ccm + multiphysics simulation software was used to perform Computer Fluid Dynamic (CFD) simulation on the five operating conditions of a swimming pool at the Jiading Swimming Hall of Tongji University in Shanghai, to determine the energy efficiency of these operations. The indoor environment of each working condition was evaluated. The relationship between the opening and closing area ratio and the indoor environment was also evaluated and obtained the optimal opening area ratio for the Jiading Swimming Hall. The simulation research of the open–closed roof further confirmed that the open–closed roof technology can effectively adjust the internal environment of the swimming pool in summer. The open–closed roof could improve the indoor comfort and reduce the summer energy consumption of the swimming pool and could also provide an organically integrate architectural art feature and technology to create a new stadium design.

Maximizing energy generation: A study of radiative cooling-based thermoelectric power devices

In the present study, a continuous thermoelectric power generation device (CTEGRC) has been fabricated by combining the recently proposed radiative cooling paint with a commercially available thermoelectric generator (TEG) to achieve continuous power generation throughout the day. The CTEGRC has been modeled and the results have been verified through experiments, and then the effects of structural and environmental parameters on the performance of the CTEGRC have been discussed in detail. The annual performance of the CTEGRC has been evaluated for five different weather conditions (five cities in China) based on the established model. It has been shown that an annual power generation of 241.46 Wh/m2-423.86 Wh/m2 can be achieved for the applications of the CTEGRC in the five climate zones of China based on an optimal area ratio of 11 for the radiative cooling module to the TEG.

Hydrodynamic performance study of a dimple textured surface at various area ratios and sliding speeds using CFD

A three dimensional computational fluid dynamic (CFD) analysis was conducted to understand the hydrodynamic performance of a dimple texture produced using recently invented low-cost dynamic-assisted tooling (DAT) in the machining process. Five different area ratios, αr of 0%, 1.63%, 3.26%, 6.53%, and 9.80%, and three different sliding speeds represented by Reynolds number, Re of 10, 45, and 80 were analyzed. From the study, there existed an optimum area ratio of 3.26%, which generated up to 290% higher load-carrying capacity compared to a fully textured surface. These findings revealed the benefits of dimple texture produced using DAT, as well as proposing the optimum area ratio needed to be considered in order to optimize the dimple performance for actual application on piston engine surfaces in the near future.

Nitrogen source recovery efficiency in the catfish farming zero emission integrated system in Mekong delta, Viet Nam

The purpose of this study is to optimize the nitrogen recovery efficiency in the catfish farming agro-based zero emission integrated system (AZEIS) in Mekong delta, Vietnam with special focuses on limiting the nitrogen loss into the environment, as well as on saving cost for other agriculture activities. Nitrogen source was recovered from catfish wastewater, sediment and dead fish bodies. Optimal nitrogen recovery system was estimated based on the amount of waste and nitrogen concentration in the treatment processes within the integrated system. In this study, LINGO software was used to estimate nitrogen recovery efficiency, and the construction area for the system. In addition, Material Flow Analysis (MFA) technique was used to monitor the transportation and accumulation ratio of nitrogen circulating within the integrated zero emission system. This study results indicate that a high nitrogen recovery efficiency was obtained in the study system which helps to reduce nitrogen discharging rate into the environment. The total nitrogen quantity of 12,049.9 KgN was recovered for the total designed farming area of 120,062 m2, and the optimal area ratio between fish ponds and other treatment components (composting area, grass garden, water hyacinth pond, cow breeding cage etc) in the integrated system was also obtained. This designed system has been successfully applied to a local catfish farm with an area of 10,000 m2 which produced valuable by-products such as organic fertilizer (with 1.7% total Nitrogen), hydrolyzed protein solution (with 3.08% total Nitrogen). Moreover, the nitrogen recovery efficiency from catfishpond wastewater for further supply to corn cultivation and water hyacinth were 47.9% and 79.5%, respectively.

Synergistic effect of adjustable ejector structure and operating parameters in solar-driven ejector refrigeration system

The ejector has a substantial impact on the performance of the solar-driven ejector refrigeration system. This work designs an adjustable ejector without disassembly and performs numerical modeling of the geometric model to enhance the ejector capacity to adapt to various operating conditions; the simulations dependability was also validated using experimental evidence. The findings indicate that within the given operating conditions, the adjustable ejector efficiency increased by an average of 82.4 %; the COP of the system increased by an average of 72.8 %. It is also found that the adjustable ejector has a saturation region, where the ejector performance rapidly declines as the nozzle exit position increases. Under the given operating conditions, the functional relationship between the optimal area ratio and nozzle exit position is obtained. By defining the operating condition coefficient (Γ), the function of the Γ and optimal area ratio is obtained, which provides the adjustable ejector control logic. From the energy perspective, the influence of structural changes on the vortex near the premixing chamber wall is analyzed, and the basic internal reasons for how structural alterations affect the ejector performance are initially revealed.

Performance assessment of a perovskite solar cell-driven thermionic refrigerator hybrid system

To develop a high-performance solar refrigeration technology, a novel refrigeration system composed of a perovskite solar cell (PSC) and a thermionic refrigerator (TIR) is constructed. Based on theories of photovoltaic effect, thermionic emission and non-equilibrium thermodynamics, the coefficient of performance (COP) and refrigerating capacity of the integrated system are mathematically expressed, in which the various irreversible losses are taken into consideration. The integration characteristics and coupling relationships between the PSC and TIR are investigated, and the working voltage regions for the combined operation of the subsystems are determined. Furthermore, the impacts of the area ratio, the work function, the environment temperature, the cold reservoir temperature and the heat transfer coefficient on systemic performance are evaluated in detail. Numerical calculation examples illustrate that the maximum COP and maximum refrigerating capacity of the integrated system are 0.81 and 81.2 W, respectively. Analysis results show that there exist optimal area ratio and work function to optimize the system performance. The present study may offer some fresh perspectives on the evolution of the solar refrigeration system.

Experimental Study on the Axial Compression Performance of Glued Wood Hollow Cylinders Reinforced with BFRP

The present paper investigates the impact of basalt fiber reinforced polymer (BFRP) on the axial compression performance of glued wood hollow cylinders. This study aims to facilitate the application of BFRP in the field of structural reinforcement of glued wood hollow columns. Ten glued laminated wood hollow columns of the same size were designed and placed into five groups (ZC1 and ZRC2 to ZRC5), of which one group (ZC1), with a total of two pure wooden columns, was not arranged with BFRP, and the remaining two wooden columns in each group were arranged with BFRP at different distances. The destruction mode, ultimate load capacity, load–displacement curve, load–strain curve, and ultimate load capacity–total area of the BFRP paste curve of each specimen were obtained by conducting axial compression tests on five groups of wood columns reinforced with different basalt fiber cloths, which revealed the damage mechanism, the relationship between the ultimate load capacity and total area of BFRP paste, and pointed out the most effective area ratio. The test results show that the destruction mode of axially pressed, glued, laminated wood hollow columns is typical compression buckling damage, mainly manifested as follows: the wood at the middle or end of the specimen under pressure first buckles; then, with the increase in load, the specimen is crushed; at this time, the maximum ultimate bearing capacity of each specimen is in the range of 296.77~375.85 kN, the maximum longitudinal displacement is in the range of 2.77~3.38 mm, and longitudinal cracks appear at the end. It is worth noting that the growth rate of the ultimate bearing capacity varies with the increase in the total area of the BFRP paste. When the total area of the BFRP paste is less than a 3.2 × 105 mm2 range value, the growth rate of the ultimate bearing capacity is faster, and then, the growth rate gradually becomes slower. The optimum BFRP paste area ratio can be taken as k = 0.59. The ultimate bearing capacity after reinforcement increases from 11.06% to 26.65% compared with the pure wood column. According to GB50005-2017, “wood structure design standards” improve the hollow wood column bearing capacity calculation method and fit the BFRP reinforced hollow wood column’s ultimate bearing capacity calculation formula; the errors are within ±10%, which can provide a reference for the practical application of BFRP in the field of reinforcing glued wood hollow cylindrical structures.

An approach to optimize building area ratios scheme of urban complex in different climatic conditions based on comprehensive energy performance evaluation

In the context of the global energy shortage, urban complexes have attracted more and more attention from energy-saving research due to their large number and great energy-saving potential. While, the energy performance factors are rarely considered in the function scheme decision of urban complex in the recent pre-programming process. Optimizing the building area ratio scheme of urban complex is the key link to improve the comprehensive energy utilization efficiency. This paper proposes an approach to optimize building area ratio scheme of urban complex from energy performance perspective by energy simulation, scenario analysis and demand side management methods, and provides a data set of rankings of urban complex function combination schemes by evaluating the performance of energy load leveling and the degree of load stability of each building area ratio scheme in different climatic conditions, respectively. The results indicate that: 1) the different building area ratios notably affect the integrated operating energy performance of urban complexes with a maximum evaluation indexes difference of more than 85%; 2) the evaluating and optimizing results of the building area ratio schemes show broadly similarity in different climate conditions; 3) the optimal building area ratio scheme of urban complex is usually with less “shopping mall” (0 ∼ 10%), more “residence” (more than 35%), and floating ratio of “office” and “hotel” (0 ∼ 35%). The main findings of this study provide a quantitative basis for the architectural pre-programming and function scheme decision-making of urban complex by demand-side energy management to improve the energy efficiency, so as to guarantee the energy supply security.

A Study on the Influence of Bolt Arrangement Parameters on the Bending Behavior of Timber–Steel Composite (TSC) Beams

The present paper investigates the impact of bolt distance, bolt diameter, and the number of bolt rows on the bending performance of timber–steel composite (TSC) beams. This study aims to facilitate the application of bolt connections in assembled TSC structures. Composite steel I-beams were designed with timber boards connected in the upper section with bolts. Three-point static bending tests were conducted on nine timber–steel composite beams divided into four groups (L1, L2, L3, and L4) with varying bolt arrangements. The destruction mode, ultimate bearing capacity, ductility coefficient, load–midspan deflection curve, and load–midspan strain curve of each specimen were obtained. In addition, the destruction mechanism, the quantitative relationship between the bolt area ratio and interfacial slip, and the ideal bolt area ratio were identified. It was found that when the midspan deflection of the timber–steel composite beam approached the prescribed limit, the main failure mode can be explained as follows: The top surface of the boards of all the specimens had longitudinal local splitting, except L1, which had fewer bolts and no obvious damage. Moreover, due to compression and because the stress at the lower edge of the I-beam entered the flow amplitude stage, some of the specimens were crushed but were not pulled off. The composite beams had high flexural load capacity and ductility coefficient, and the maximum relative slips of the timber–steel interfaces were in the range of 2–6 mm. It was also found that the maximum slip of the interface and the ductility coefficient decreased steadily as the bolt area ratio increased, while the specimen’s flexural bearing capacity increased. The optimal bolt area ratio was determined to be 8 × 10−3. Using the total bolt area, we designed the arrangement of the bolts on the board. For convenience, multiple bolt variables were converted into one bolt variable. The longitudinal distance of the bolts had a greater impact on the slip, and the bolt diameter had a smaller impact. The theoretical values of total relative slip were found to be in good agreement with the experimental results, which were based on the superposition of the relative slip equations with varying bolt distances. The effective bolt area ratio and the formula of the relative slip of each segment can provide instructions for the arrangement of bolts and the control of the relative slip of intersections in engineering practices.

On the optimal texture shape with the consideration of surface roughness

The optimal texture shape considering surface roughness is determined by solving the average Reynolds equation, selecting Jakobsson–Floberg–Olsson boundary conditions, and using a genetic algorithm. The effects of surface roughness as indicated by the combined root-mean-square (RMS), surface pattern parameter, and operating parameters on the friction coefficient, area ratio, and depth of the optimal self-defined shape and optimal dimple were studied. Results show that the friction coefficient will be significantly reduced during the shape optimization considering the effect of surface roughness. The variation laws of the optimal dimple area ratio with the combined RMS, surface pattern parameter, minimum film thickness, sliding speed and the variation law of the optimal depth of the optimal self-defined shape with surface roughness and working parameters are obtained. Finally, this study concludes that the influence of roughness parameters on the optimal dimple shape is greater than that on the optimal self-defined shape under different sliding speeds.

Integrated evaluation and optimization on building area ratios of urban complex with distributed energy resource system in different climatic conditions

As the main construction type in urban centers, urban complex has become the focus of energy-saving and emission-reducing studies facing the severe challenges of energy crisis and environmental problems. However, the current energy-saving design is usually carried out after the layout design of buildings, which limits the energy-saving effect. This study supposes to improve the integrated energy performance of urban complex before the architectural design. Based on the operating characteristics of distributed energy resource system, we study the reasonable building area ratios of urban complex in different climate zones in China by the energy simulation, scenario analysis and multi-criteria assessment methods. Primary energy consumption saving rate, carbon dioxide emission reduction rate and operating cost saving rate are selected to assess the integrated energy performance of urban complex. The results indicate that (1) building area ratios have an appreciable impact on the integrated energy benefits of urban complex, while the climatic conditions have less impact on the optimization of its building area ratio scheme; (2) area ratio scheme with more “residence” and balanced ratio of other basic functions show the optimal integrated energy benefits of the urban complex with DER system; (3) optimal building area ratio scheme of urban complexes in different types and different climate conditions achieve an integrated saving rate of 22.2%∼46.5%. The main findings of this study could be a useful quantitative reference for the pre-planning of urban complex, which also contribute to the energy conservation and pollution reduction of urban area in the future.