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•Various water saturations simulate Classes I and II hydrate deposits in nature.•Ambient temperature controls periphery dissociation in excess-gas hydrate deposits.•Sensible heat ...dominates spatially uniform dissociation in excess-water deposits.•Secondary hydrate formation are prevented by adjusted gas production pressure.•Optimized depressurization is crucial to improve water production and CH4 recovery.
Depressurization is considered as the most promising technique for hydrate exploitation, as it achieves the highest energy profit ratio and is the most technologically feasible. However, the exploitation of excess-water hydrate accumulations generates high water production, leading to increased cost, poor energy efficiency, and problems with sand during operation. Thus, water management is crucial to gas recovery by the depressurization of different classes of hydrate accumulations, yet relevant studies remain limited. In this study, synthetic hydrate samples were prepared to simulate two types of natural methane hydrate sediments: Class 1 accumulations (excess-gas hydrate) and Class 2 accumulations (excess-water hydrate). Hydrate dissociation was conducted using a variety of depressurization approaches, and MRI imaging was employed to characterize water performance and methane recovery. Methane hydrate preferentially dissociated along the peripheries of the excess-gas samples due to more efficient heat dissipation. Methane hydrate dissociated more uniformly in the excess-water samples because the high specific heat capacity of water enabled the supply of extra heat. Furthermore, pressure histories, mean intensity change in MRI images, and water variations were monitored to analyze the characteristics of hydrate dissociation, changes in porosity, intrinsic permeability and reservoir heat, water and gas production rates, and possible secondary hydrate formation. The results of this study suggest that an optimized depressurization approach, such as stepwise depressurization, could improve methane recovery from Class 1 and Class 2 methane hydrate accumulations.
Corporate water performance and sustainable development are currently vital focus areas for scholars. Therefore, this paper investigates the experience of Chief Executive Officers (CEOs) with water ...shortage influences corporate water performance by focusing on listed companies in water-intensive and high-water-risk industries in China between 2014 and 2019. This paper manually collected information relative to the cities and provinces where CEOs grew up to evaluate their early exposure to water shortages. Furthermore, this paper develops an evaluation scale, based on the Enterprise Water Conservation Evaluation Guide (GB/T 7119-2006), to compute the enterprise water management practices scores. These results will constitute the enterprise water performance evaluation score. Moreover, this paper focuses on CEOs who have experienced water resource shortages through a positive impact on the water resource performance of their companies. As for the findings, they demonstrate that CEOs who grew up in regions with higher water scarcity have a more pronounced positive effect on their water shortage experience through corporate water performance. Furthermore, CEO power intensity positively moderates the relationship between the CEO's water shortage experience and corporate water resource performance. Further investigation reveals generational differences in the impact of CEO water shortage experience on company water performance. CEOs, who grew up during periods with a higher incidence of droughts, demonstrate a more significant promoting effect on corporate water performance. To sum up, this study expands the understanding of factors influencing corporate water resource performance and deepens the knowledge of the early life experiences of CEOs.
•We construct a set of scales to measure corporate water performance.•We explore the relationship between CEO water shortage experience and corporate water resource performance.•CEO water shortage experience has a positive effect on corporate water performance.•CEO power intensity plays a positive moderating role.
The crossover of nitrogen and oxygen from cathode to anode aggravates the non-uniformity inside dead-end anode proton exchange membrane fuel cell (DEA-PEMFC), inducing some other effects, such as ...carbon corrosion, to cause irreversible damage to catalyst. Therefore, developing a purge strategy according to the non-uniformity is necessary to improve its stability. In this study, the effects of operating parameters on the uneven electrical-thermal-water performance are investigated based on a three-dimensional transient model of DEA-PEMFC. Afterwards, a purge optimization is carried out based on the uneven distribution of field variables. The results show that the calculated standard deviation (STDEV) of overvoltage is reduced first and then increased quickly for all the cases. Therefore, the purge should be started when the STDEV approaches the minimum value, to avoid the irreversible damage to DEA-PEMFC, achieving high-stability output performance meanwhile. On this basis, the purge interval is optimized to 100 s, which is suitable for almost all the discussed cases. The purge duration is reduced to 0.2 s. In this situation, the minimum voltage is decreased by about 0.95% compared with the maximum value, indicating a good voltage stability. This study is beneficial to provide guidance for the efficient and long-term operation of DEA-PEMFC.
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•3D DEA-PEMFC transient model is integrated with the crossover of nitrogen and oxygen.•A uniformity-based purge optimization is conducted to avoid local damage to DEA-PEMFC.•A good voltage stability with fluctuation of 0.95% only is achieved.•Internal uniformity and stable output help to achieve the high stability of DEA-PEMFC.
The transfer of ship ballast water poses significant risks to the aquatic ecosystem and human health. To mitigate the influences of non-native species, ballast water management systems (BWMS) have ...been installed on international ships to ensure proper treatment of ballast water before discharge. This study investigates whether ballast water discharges managed by BWMS meet the requirements of the D-2 standard for organisms in different size classes. Representative ballast water samples were collected from 28 ships (a total of 20 different BWMS) arriving in Shanghai during the period 2020–2022. Results have shown that two samples (7.1 %) exceeded the D-2 Standard. The compliance rates varied among different vessel types, with cargo vessels achieving a compliance rate of 81.8 %, while LNG vessels and container vessels achieved 100 % compliance. The potential to achieve higher levels of ballast water management will increase as crews improve their skills in operating BWMS and BWMS is further developed.
•Investigate ballast water from Cargo, LNG, and Container to determine compliance with the D-2 standard.•The compliance with the D-2 standard for ballast water after treatment on different ship types is different.•Non-compliant samples with ≥ 50 um living organisms had the lowest compliance rate with the D-2 standard.•The study reveals that non-compliance with the D-2 standard is mainly due to misuse of ballast water management systems.
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•The properties of stone pine wood were assessed.•Due to the high amount of extractives present, P. pinea heartwood good water performance.•Water performance and durability results in ...good service life as calculated by the Meyer-Veltrup model.•Model indicate that the service life of P. pinea hardwood in above ground uses is 14× longer than spruce.•Heartwood could be used in above ground applications.
Relevant properties of stone pine (Pinus pinea) wood have been only fragmentarily addressed in the past, which has been recognized as a limiting factor for its potential applications. The sorption properties, permeability to water, extractives content and durability against fungi of Pinus pinea sapwood and heartwood were therefore determined in the present research. A SEM analysis was also performed. The Meyer-Veltrup model for material resistance was used to test relevant data. The results showed that sapwood of P. pinea fits into durability class 5 (very susceptible wood), while heartwood meets the requirements of durability class 2 (durable wood), if the mass loss after fungal exposure is considered as the sole criteria for classification. Heartwood contains up to 15% of lipophilic compounds, contributing to its hydrophobicity and influencing its sorption properties. In contrast, sapwood is very permeable and hence takes up a lot of water, while heartwood, with a higher resin content, exhibits better water performance. The higher durability of stone pine heartwood against wood decaying fungi can be linked to the presence of phenolic extractives and hydrophobic properties.
Water savings of LEED-certified buildings Luo, Kaifang; Scofield, John H.; Qiu, Yueming (Lucy)
Resources, conservation and recycling,
December 2021, 2021-12-00, Volume:
175
Journal Article
Peer reviewed
•Water performance gap refers to the gap between designed and actual water savings.•We find evidence of the water performance gap for LEED buildings.•LEED buildings do not save water usage compared ...to similar non-LEED buildings.•The largest LEED water study sample is used for statistical analysis.•Propensity score matching and weighted regressions are used.
The LEED rating system awards credits for a variety of criteria, including water efficiency. LEED certification indicates that the building is designed to conserve water. Given freshwater supply shortages and sustainable goals, the purpose of this paper is to investigate whether LEED buildings suffer from the water performance gap. The water performance gap is the difference between planned and actual water savings. Compared with previous studies, we analyze a substantially larger sample of 10,557 buildings in six U.S. cities covering 162 million square meters; 354 of those buildings are LEED certified. In particular, we focus on three types of buildings: offices, K-12 schools, and multifamily housing. First, we identify comparable non-LEED buildings with propensity score matching. Second, we apply weighted regression to estimate the effect of LEED certification on water savings using matched samples. Statistical analysis indicates no significant differences in water consumption between LEED and non-LEED buildings. LEED-certified buildings use no less water than non-LEED buildings, suggesting a water performance gap for LEED buildings. A 10-fold cross-validation method has been applied to validate the generalization accuracy of the established models. Based on our results, we propose that LEED system should secure more points for water efficiency and apply weights based on local conditions and building attributes. Moreover, the government should incentivize facility managers to reduce technology failure, promote long-term monitoring, and raise public awareness regarding water conservation.
The purpose of this systematic review with meta-analysis was to examine the effects of strength training (ST) on selected components of physical fitness (e.g., lower/upper limb maximal strength, ...muscular endurance, jump performance, cardiorespiratory endurance) and sport-specific performance in rowers. Only studies with an active control group were included if they examined the effects of ST on at least one proxy of physical fitness and/or sport-specific performance in rowers. Weighted and averaged standardized mean differences (SMD) were calculated using random-effects models. Subgroup analyses were computed to identify effects of ST type or expertise level on sport-specific performance. Our analyses revealed significant small effects of ST on lower limb maximal strength (SMD = 0.42, p = 0.05) and on sport-specific performance (SMD = 0.32, p = 0.05). Non-significant effects were found for upper limb maximal strength, upper/lower limb muscular endurance, jump performance, and cardiorespiratory endurance. Subgroup analyses for ST type and expertise level showed non-significant differences between the respective subgroups of rowers (p ≥ 0.32). Our systematic review with meta-analysis indicated that ST is an effective means for improving lower limb maximal strength and sport-specific performance in rowers. However, ST-induced effects are neither modulated by ST type nor rowers' expertise level.
CON: control group; ICC: intraclass correlation coefficient; CRE: cardiorespiratory endurance; F: female; IG: intervention group; INT: intervention group; M: male; Sets: number of sets per exercise; SMD: standardized mean differences; SMD
wm
: weighted mean SMD; ST: strength training; RCT: randomized controlled trial; Reps: repetitions; RM: repetition maximum; TF: training frequency (times per week); TI: training intensity (eg., % of 1 repetition maximum); TP: training periods (weeks)
•Metabolism model evaluates regional water management patterns and performance.•Seoul relies on abstracting surface water and shows a low level of internal water cycling.•Ulsan often relies on water ...imports but has high wastewater recycling potential.•Jeju takes water mainly from internal sources but shows high water use intensity.
As climatic and societal changes increase the prominence of water insecurity, sustainable urban water management focusing on water efficiency and reuse is an increasingly significant issue in Korea and elsewhere. This study uses the urban water metabolism framework to examine patterns of water flows in urbanized areas and evaluate water management performance in three Korean regions: Seoul (a metropolitan city), Ulsan (an industrial city), and Jeju (an urbanized agricultural province). Constructed water metabolism models showed distinct water use patterns and performance across each region in 2015. Seoul largely relied on surface water, while the residential sector’s dominant use of water implies high greywater use and wastewater recycling potential. Ulsan relied on abstracting river water, with lower water availability of the river making Ulsan’s water system less self-sustaining and more vulnerable to climatic risks than Seoul’s. Facing higher water use intensity due to high industrial demand, Ulsan actively promotes industrial wastewater recycling. Jeju showed the highest water use intensity because of the presence of intensive agricultural activities. Nonetheless, Jeju sourced 76% of its water from internal sources, with its water system considered to be the most self-sustaining. These results suggest that the water metabolism framework helps facilitate more holistic understandings and evaluations of the water performance of cities.
To estimate the performance of ships in waves, there have been studies on propeller performance in various operating environments. In previous studies, it was confirmed that propeller open water ...performance is diminished by ventilation when the propeller operates near the free surface. However, most of these studies were focused on the change in the advance ratio at the same immersion depth and the effect of varying the immersion depth with the same advance ratio. In this study, the propeller open water performance due to the variation of immersion depth in waves was calculated using computational fluid dynamics, and the POW characteristics due to immersion depth in calm water were compared with the POW characteristics in waves. As a result, it was concluded that the tendency of propeller performance by variation of immersion depth due to wave elevation is similar to the tendency of propeller performance due to a change of immersion depth in calm water. Also, the effect of water particle velocity due to the wave phase is similar to the variation of propeller performance due to the changing of advance ratio in calm water.
•Propeller open water performance in deep water.•Propeller open water performance prediction due to immersion depth and wave.•CFD analysis of propeller open water performance.
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