Search Results (14)

Natural ventilation is a common cooling strategy in open dairy barns, but its efficiency largely depends on external wind directions and speeds. Misalignment between external airflow and fan jets often led to non-uniform air distribution, reduced local cooling efficiency, and an elevated risk of heat stress in cows. However, few studies have systematically examined the combined effects of wind directions and speeds on airflow and heat dissipation. Most research isolates natural or mechanical ventilation effects, neglecting their interaction. Accurate computational fluid dynamics (CFD) modeling of the coupling between outdoor and indoor airflow is crucial for designing and evaluating mixed ventilation systems in dairy barns. To address this gap, this study systematically analyzed the effects of external wind directions (0°, 45°, 90°, 135°, 180°) and speeds (1, 3, 5, 7, 10 m s⁻¹) on fan jet distribution and convective heat transfer around dairy cows using the open-source CFD platform OpenFOAM. By evaluating body surface airflow and regional convective heat transfer coefficients (CHTCs), this study quantitatively linked barn-scale airflow to animal heat dissipation. Results showed that both wind directions and speeds markedly influenced airflow and heat exchange. Under 0° wind direction, dorsal airflow reached 6.2 m s⁻¹ and CHTCs increased nearly linearly with wind speeds, indicating strong synergy between the fan jet and external wind. Crosswinds (90° wind direction) enhanced abdominal airflow (approximately 5.2 m s⁻¹), whereas oblique and opposing winds (135–180°) caused stagnation and reduced convection. The dorsal-to-abdominal CHTCs ratio ($R_{d/a}$) increased to about 1.6 under axial winds but decreased to 1.1 under cross-flow, reflecting reduced thermal asymmetry. Overall, combining axial and lateral airflow paths improves ventilation uniformity in naturally or mechanically ventilated dairy barns. The findings provide theoretical and technical support for optimizing ventilation design, contributing to energy efficiency, animal welfare, productivity, and the sustainable development of dairy farming under changing climatic conditions. Full article

With the increasing maturity of renewable energy technologies and the pressing need to address climate change, urban power systems are striving to integrate a higher proportion of low-carbon renewable energy sources. However, the inherent variability and intermittency of wind and solar power pose significant challenges to the stability and reliability of urban power grids. Existing research has primarily focused on short-term energy storage solutions or small-scale integrated energy systems, which are insufficient to address the long-term, large-scale energy storage needs of urban areas with high renewable energy penetration. This paper proposes a mid-to-long-term capacity expansion model for hydrogen energy storage in urban-scale power systems, using Shanghai as a case study. The model employs mixed-integer linear programming (MILP) to optimize the generation portfolios from the present to 2060 under two scenarios: with and without hydrogen storage. The results demonstrate that by 2060, the installed capacity of hydrogen electrolyzers could reach 21.5 GW, and the installed capacity of hydrogen power generators could reach 27.5 GW, accounting for 30% of the total installed capacity excluding their own. Compared to the base scenario, the electricity–hydrogen collaborative energy supply system increases renewable penetration by 11.6% and utilization by 12.9% while reducing the levelized cost of urban comprehensive electricity (LCOUCE) by 2.514 cents/kWh. These findings highlight the technical feasibility and economic advantages of deploying long-term hydrogen storage in urban grids, providing a scalable solution to enhance the stability and efficiency of high-renewable urban power systems. Full article

Mixed municipal solid waste (MSW) of cities and tourist-heavy areas typically contains elevated amounts of recyclable materials. In Austria, numerous material recovery facilities exist for processing this waste; however, they primarily focus on separating metals, neglecting the recovery potential of other recyclables. To evaluate such potential for polyolefins and paper-based materials, two pilot-scale trials were conducted in a model region in Tyrol, Western Austria, accompanied by comprehensive sampling, waste characterisation, and material flow analysis. Pre-concentrates with up to 70% purity were obtained using two stages of near-infrared sorting, although challenges arose due to the presence of textiles and composite materials. This study found that separating polyolefins from mixed MSW could increase recycling rates in the region by up to 16% (absolute). Paper recovery also showed a modest increase. Polyolefin recovery slightly lowered, whereas paper recovery moderately raised the heating value. Recycling such materials is technically feasible, and forthcoming legislative changes are expected to create a market for these materials. Although fundamental questions remain regarding the optimal balance between recycling and refuse-derived fuel, as well as concerns about microbiological or chemical hazards, it can enhance resource efficiency, develop circularity, and aid comparison in regions with similar demographic and tourism characteristics. Full article

The transition to renewable energy has been recognized as a crucial step in addressing climate change and achieving greenhouse gas reduction targets, but it can also cause energy sprawl if not planned properly. Clean renewable energy communities (CREC) are emerging globally as an approach for decentralized energy systems and an alternative to traditional centralized energy systems. CREC aim to lower the energy carbon footprint, enhance local energy resilience, and improve the quality of life of residents. Through a comprehensive literature review, this study reviews metrics that can assess the impact of energy transition plans and support decision-making to select technologies that create efficient, reliable, and accessible energy systems. It classifies these metrics into a five-dimensional sustainability approach including environmental, technical, social, economic, and political and institutional dimensions. The paper proposes a conceptual framework to guide decision-makers in recognizing the role of sustainable land development, sustainable energy planning, and resiliency as an integrated approach to energy transition planning. This framework stresses mapping the place-based potential for clean renewable energy at various scales, highlights the importance of resilience in energy planning, and addresses challenges associated with energy source selection, built environment efficiency, and the energy trade. While the framework can serve as a starting point for evaluating energy transition plans, further work is needed to address the limitations of existing metrics and identify additional evaluations for mixed-energy land use that are critical to managing energy sprawl in terms of ecosystem services and other land uses. Full article

Biogas production by fermentation is a relatively low-cost and simple method for the transformation of a substrate into an energy carrier with a wide range of possible applications. The aim of this study was to determine the potential of Arthrospira platensis biomass as a source of bioenergy produced during anaerobic digestion (AD). The studies were carried out on a fractional-technical scale. Biogas yield and composition were analyzed as a function of the amount of biomass subjected to anaerobic digestion, the substrate dosing frequency in the digester and the use of biomass pre-hydrolysis in the mixing compartment. The energy efficiency of the process was also compared for each sample. In addition, a biomass conversion power index was developed and determined. It was found that A. platensis biomass had significant energy potential, and the amount of biogas obtained and its calorific value changed depending on the applied treatments. The maximum cumulative biogas production was 505 L kg⁻¹ volatile solids (VS), while the maximum average methane (CH₄) content was 67.32%. A two-fold increase in the organic loading rate from 1 g VS·L⁻¹ volatile solids (VS) to 2 g VS·L⁻¹ had a positive effect on methane concentration. The highest energy efficiency of the AD process was obtained for 2 g VS·L⁻¹, with a single feedstock input into the digester, in a single-stage process (2/s/-), while the highest conversion power ratio was for a feedstock of 1 g VS·L⁻¹, under the same process conditions (1/s/-). Moreover, the energy efficiency of the microalgae fermentation process obtained in the study is higher compared to conventional substrates used in biogas plants. This energy analysis can support the selection of cogeneration power engines in a biogas plant and help to determine the potential output of the biogas plant, especially with varying energy and heat demand. Full article

Forage grass is very important for food security. The development of artificial grassland is the key to solving the shortage of forage grass. Understanding the spatial distribution of forage grass in alpine regions is of great importance for guiding animal husbandry and the rational selection of forage grass management measures. With its powerful computing power and complete image data storage, Google Earth Engine (GEE) has become a new method to address remote sensing data collection difficulties and low processing efficiency. High-resolution mapping of pasture distributions on the Tibetan Plateau (China) is still a difficult problem due to cloud disturbance and mixed planting of forage grass. Based on the GEE platform, Sentinel-2 data and three classifiers, this study successfully mapped the oat pasture area of the Shandan Racecourse (China) on the eastern Tibetan Plateau over 3 years from 2019 to 2021 at a resolution of 10 m based on cultivated land identification. In this study, the key phenology windows were determined by analysing the time series differences in vegetation indices between oat pasture and other forage grasses in the Shandan Racecourse, and monthly scale features were selected as features for oat pasture identification. The results show that the mean Overall Accuracy (OA) of Random Forest (RF) classifier, Support Vector Machine (SVM) classifier, and Classification and Regression Trees (CART) classifier are 0.80, 0.69, and 0.72 in cultivated land identification, respectively, with corresponding the Kappa coefficients of 0.74, 0.58, and 0.62. The RF classifier far outperforms the other two classifiers. In oat pasture identification, the RF, SVM and CART classifiers have high OAs of 0.98, 0.97, and 0.97 and high Kappa values of 0.95, 0.94, and 0.95, respectively. Overall, the RF classifier is more suitable for our research. The oat pasture areas in 2019, 2020 and 2021 were 347.77 km² (15.87%), 306.19 km² (13.97%) and 318.94 km² (14.55%), respectively, with little change (1.9%) from year to year. The purpose of this study was to explore the identification model of forage grass area in alpine regions with a high spatial resolution, and to provide technical and methodological support for information extraction of the forage grass distribution status on the Tibetan Plateau. Full article

The mobile phone is a typical 3C electronic product characterized by frequent replacement, multiple product specifications, high flexibility, high-frequency production line switching, and urgent delivery time during production. Therefore, the optimized design of the mobile phone production workshop is crucial. This paper takes the assembly process of a specific type of mobile phone assembly as the research object and adopts the heuristic balance method to combine the production procedures. Moreover, it considers the automation degree of the process and the demand for production line rhythm to carry out station division and working hours design for the assembly process. The advantages and disadvantages of the plug-and-play production line and unit production line architecture are integrated, aiming at the production line’s construction cost and unit area capacity. A hybrid workshop with a mixed combination of two types of production lines is designed and an optimization model of hybrid workshop design is established. The semi-physical simulation technology of digital twins is utilized to verify the proposed design scheme to achieve the balance optimization of the production line, improve production efficiency, and reduce production costs. This work provides a technical scheme for designing and optimizing large-scale mobile phone assembly workshops with multi-batch and high-frequency production changes. Full article

Growth in total factor productivity (TFP) indicates the sustainable and/or judicious use of scarce resources, including non-renewables. This paper identifies sources of growth in global agricultural TFP and its finer components, ranging from climate, production environment, and socio-economic factors, using a panel data of 104 countries, covering a 45-year period (1969–2013); and, finally, projects changes in TFP from increased climate variability. The results revealed that global agricultural productivity grew consistently at a rate of 0.44% p.a., driven by technological progress and mix-efficiency change, with negligible contributions from technical- and scale-efficiency changes; albeit with variations across regions. Both long-term and short-term climatic factors and the natural production environment significantly reduce global agricultural productivity, whereas a host of socio-economic factors have a significant but varied influence. The projected increased level of future climate variability will significantly reduce future agricultural productivity. Policy implications include investments in crop diversification, education, agricultural spending, number of researchers, and country specific R&D. Full article

To deal with environmental uncertainty, organizations need resilience to respond to disruptions, such as changing market conditions or variations in demand or supply, while avoiding large scale adjustments. The concept of resilience is ambiguous, often explained as the capability of an organization or a supply chain to recover its original state, within an appropriate time frame, after being disrupted. Resilient supply chains have event handling capabilities, can provide efficient responses, and can return to their normal operating performance, after the disruptive event. To increase their resilience, companies often make changes or adjustments to their internal IT infrastructure, which may temporarily disrupt their smooth operation. As a result, contemporary IT infrastructures are mixed and include varied systems or technologies. Although new technologies, including blockchain, IoT and cloud-based solutions, may facilitate the handling of changes by providing secure, low cost and scalable solutions, more traditional systems may hinder such changes. Therefore, the relationship between IT and supply chain resilience is still unclear. The paper intends to examine the above issues by adopting a socio-technical approach to explain the concept of supply chain resilience and investigate the role of IT. More specifically, based on previous literature and on the appreciative systems thinking theoretical perspective, the paper develops a theoretical framework to analyse the organisational and/or supply chain resilience. It then uses this framework to examine and explain the impact of IT, by identifying important characteristics of an IT infrastructure and examining whether they may support or hinder business resilience. Full article

High-quality economic development and the realization of ecological civilization have become the main goals of China’s economic development. This study constructed a global reference Malmquist–Luenberger productivity index model of directional distance function from the perspective of mixed disposability and divided water resources green efficiency into pure technical efficiency change (PEC) index, scale efficiency change (SEC) index, pure technology change (PTC) index and scale technology change (STC) index. The results show the following: (1) The value of China’s water resources green efficiency increased by 1.1% from 2000 to 2016. The central region improved the most (1.4%), followed by the western (1%) and eastern (0.9%) regions. The water resources green efficiency improved in all provinces except Guangxi and Yunnan. (2) The water resources green efficiency is significantly affected by national policies, and there may not be a significant positive correlation with economic development. At present, the water resources green efficiency in most provinces still needs to be improved. (3) From 2000 to 2016, China’s water resources green efficiency decomposition index showed an upward trend except for SEC, and PTC was the main driving force for improving China’s water resources green efficiency. (4) The variation of PEC among provinces showed an inverted “N” trend, while the differences of SEC and STC showed an ascending trend, and PTC showed an inverted “U” trend. The proportions of provinces in which PEC, SEC, and STC indices improved were 40%, 46.67%, and 60%, respectively. Full article

The present study applied the Färe–Primont index approach to estimate the total factor productivity (TFP) growth of world agriculture, covering the period 1969–2013. Overall, the world agricultural TFP grew at a rate of 0.44% p.a. This growth was mainly contributed to by technological progress and mix efficiency changes, while the contributions of technical efficiency and scale efficiency changes were negligible. TFP growth varied across regions, with South Asia at the top of the list (1.05% p.a.), and East Asia and the Pacific (0.18% p.a.) at the bottom. TFP components exerted differential influences amongst regions. For instance, mix efficiency played a dominant role in Sub-Saharan Africa, the Middle East and North Africa, whereas it was technical efficiency change in Latin America and the Caribbean region. The paper argues for region specific policy interventions emphasizing technical progress through investment in R&D and price and non-price interventions to improve economies of scope and scale of operation in the agricultural sector. Full article

This paper presents the results of an efficiency study of Colombian public universities in 2012, conducted using the methodology of Data Envelopment Analysis (DEA) and the models CCR, BCC and SBM under output orientation. The main objective is to determine technical, pure technical, scale and mix efficiencies using data acquired from the Ministry of National Education. An analysis of the results shows the extent to which outputs of inefficient Higher Education Institutions (HEIs) could be improved and the possible cause of this inefficiency. The universities were also ranked using a Pareto efficient cross-efficiency model and a study was made of changes to overall productivity between 2011 and 2012. The results showed Tolima, Caldas and UNAD to be the best-performing universities, with Universidad del Pacífico as the worst performer. Malmquist index was applied to analyze the change in productivity from 2011 to 2012. The Universidad de La Guajira showed great improvement in technical efficiency between 2011 and 2012. Full article

Based on stochastic frontier analysis and translog input distance function, this paper examines the total factor energy efficiency of China’s industry using input-output data of 30 sub-industries from 2002 to 2014, and decomposes the changes in estimated total factor energy efficiency into the effects of technical change, technical efficiency change, scale efficiency change and input-mix effect. The results show that during this period the total factor energy efficiency in China’s industry grew annually at a rate of 3.63%; technical change, technical efficiency change and input-mix effect contributed positively to the change in total factor energy efficiency; while scale efficiency change contributed negatively to it. Full article

The study assessed agricultural sustainability in South Asia (i.e., Bangladesh, Pakistan, India and Nepal) by computing multi-lateral multi-temporal Total Factor Productivity (TFP) indices and their six finer components (technical change, technical-, scale- and mix-efficiency changes, residual scale and residual mix-efficiency changes) and examined the role of capital in driving TFP growth covering a 34-year period (1980–2013). Results revealed that all countries sustained agricultural productivity growth at variable rates with Bangladesh experiencing highest rate estimated @1.05% p.a. followed by India (0.52%), Pakistan (0.38%) and Nepal (0.06% p.a.). There were little or no variation in technical and scale efficiency changes among the countries. However, residual scale efficiency increased @0.44% p.a. in Bangladesh, 0.12% p.a. in Pakistan, remained unchanged in India and declined −0.39% p.a. in Nepal. Similarly, mix efficiency increased @0.44% in Bangladesh, remained unchanged in India and declined @−0.12% p.a.in Pakistan and −0.39% p.a. in Nepal. The major drivers of agricultural TFP growth were the levels of natural, human and technology capital endowments whereas financial capital and crop diversification had opposite effects. Policy implications include land and tenurial reforms aimed at consolidating farm operation size and smooth operation of the land rental market to improve natural capital, investments in education to improve human capital and agricultural R&D to enhance technology capital in order to boost agricultural productivity growth in South Asia. Full article