| 1. |
- You, H., et al.
(författare)
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Study on the Factors Associated with Postpartum Visits in Rural China
- 2013
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:2, s. Artnr. e55955-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Postpartum visits (PPVs) have been advocated as a way to improve health outcomes for mothers and their infants, but the rate of PPVs is still low in rural China. This study aims to investigate the utilization of PPVs and to explore the factors associated with PPVs in rural China. Parity is the most concerned factor in this study. Methods: A cross-sectional household survey was performed in two counties of Zhejiang province. Questions include socio-economic, health services and women's delivery data. Chi-square tests and multivariate logistic regression analyses were performed to identify factors associated with PPVs. Results: 223 women who had a delivery history in the recent five years were enrolled in analyses. 173 (78%) of them were primiparous. Among the primiparous women, 43 (25%) had not received any PPVs. The majority, 27 (55%) of the 49 multiparous women, had not received any PPVs. Multiparous women were less likely to receive PPVs than primiparous women. Among 223 puerperal women, 47 (21%) had been compensated for delivery fee expenses. Women who received compensation were found to be more likely to receive standard (at least 3) PPVs. Conclusions: It was found that women with "second babies" were less likely to use PPVs. This could be an unintended consequence of the "one-child policy", due to fear that contact with public health facilities could result in sanctions. This phenomenon should be taken seriously by government in order to improve the health of babies and their mothers. Financial compensation for delivery fee charges can improve the use of PPVs, thus free-of-charge delivery should be promoted. © 2013 You et al.
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| 2. |
- Chen, S., et al.
(författare)
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Operational flexibility of active distribution networks with the potential from data centers
- 2021
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Ingår i: Applied Energy. - : Elsevier Ltd. - 0306-2619 .- 1872-9118. ; 293
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Tidskriftsartikel (refereegranskat)abstract
- With the development of information technology, the scale and quantity of internet data centers (IDCs) are expanding rapidly. IDCs have emerged as the major electricity consumers in active distribution networks (ADNs), which dramatically increase the electricity load and have a significant impact on the operational flexibility of ADNs. Geographically distributed IDCs can participate in the operation of ADNs with the potential for spatio-temporal load regulation. This paper proposes flexible dispatch strategies of data centers to improve the operational flexibility of ADNs. First, a data-power model of IT equipment is proposed based on piecewise linearization to describe the power consumption characteristics of data centers. The flexible dispatch strategies for the delay-tolerant workload are further proposed from two aspects of temporal transfer and spatial allocation. Then, considering the potential for spatio-temporal load regulation, the operational flexibility analysis model with data centers is formulated to adapt to the operational requirements of ADNs in complex environments. Case studies show that through the spatio-temporal regulation of workload, the energy efficiency of IDCs can be effectively improved. The flexible dispatch of IDCs can also reduce the voltage violation and feeder load imbalance of ADNs, which can facilitate providing the high-quality power supply for IDCs.
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| 3. |
- Ji, H., et al.
(författare)
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Robust operation for minimizing power consumption of data centers with flexible substation integration
- 2022
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Ingår i: Energy. - : Elsevier Ltd. - 0360-5442 .- 1873-6785. ; 248
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Tidskriftsartikel (refereegranskat)abstract
- The rapid development of digital economy has led to a dramatic increasement of internet data centers (IDCs), which consume a large amount of electricity. The diverse data-processing demands, high power consumption and workload uncertainty put forward a high requirement for the economical and secure operation of IDCs. As information technology (IT) devices are driven by direct current (DC), flexible substation (FS) has been gradually utilized to provide DC power for IDCs. This paper proposes robust operation strategies for minimizing IDC power consumption with FS integration. First, the linearized IDC power consumption model based on the technology of dynamic voltage and frequency scaling (DVFS) is proposed to describe the operating state of IT devices. Then, considering the FS-based coordinated operation of IDC, photovoltaic (PV) station and energy storage system (ESS), the deterministic power consumption minimization model of IDCs is established. Considering the workload uncertainty, the operation strategies based on distributionally robust optimization (DRO) for IDCs are further proposed. Finally, the effectiveness of proposed method is validated on a modified practical network with IDCs integrated. Results show that through the dispatch of workload and power flow regulation of FS, the power consumption and dropping workload of IDCs are effectively reduced.
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| 4. |
- Xu, B., et al.
(författare)
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Dynamic regulation reliability of a pumped-storage power generating system : Effects of wind power injection
- 2020
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Ingår i: Energy Conversion and Management. - Oxford : Elsevier Ltd. - 0196-8904 .- 1879-2227. ; 222
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Tidskriftsartikel (refereegranskat)abstract
- Multi-energy integrated sources are increasingly being used as the bundling-sale for electric systems. Estimating the power supply reliability and regulation performance of the fixed-speed Pumped-Storage Generation Systems (PSGSs) in suppressing power fluctuations of intermittent energy is essential to the operational safety and reliability of a system. However, the regulation process relates to the coupling fluctuations of hydraulic-mechanical-electrical factors, leading to a multiple time-scale effect to the whole hybrid power system. This makes the PSGS's power response lagging behind the wind power fluctuation and further impacts the power supply reliability of the hybrid power system. To enable the analysis, a numerical model which describes operating states of the presented integrated system, including wind energy and PSGS, is developed in MATLAB/Simulink. Then, ten wind scenarios are selected to study complementation and regulation ability of the PSGS based on a framework of evaluation indicators. The results show that longer power response delay and larger guide vane distance opening result in weaker complementary response of PSGS to wind disturbances. It is also shown that the PSGS provides good complementary capability at lower random wind standard deviation (0.5 vs 1.5), larger wind speed mean value (15 m/s vs 13 m/s) and lower wind speed deviation (5 m/s vs 12 m/s). Furthermore, an unexpected regulation behavior is demonstrated: fast settling and peak times coincide with large variation in overshoot, undershoot and peak value of the power response. This presents a challenge in assessing performance of the integrated generation system. The proposed evaluation method and presented results are important steps to increasing the national power grid capability to accept high integration of multiple energy sources.
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| 5. |
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| 6. |
- Li, W., et al.
(författare)
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Methane production through anaerobic digestion : Participation and digestion characteristics of cellulose, hemicellulose and lignin
- 2018
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Ingår i: Applied Energy. - : Elsevier Ltd. - 0306-2619 .- 1872-9118. ; 226, s. 1219-1228
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Tidskriftsartikel (refereegranskat)abstract
- Lignocellulosic biomass is the most abundant natural resource with high biomethane potential. However, complex structure of lignocellulosic biomass has hampered the efficient utilization of this bioresource. Previous studies have investigated the overall anaerobic digestion performance of lignocellulosic biomass, but the individual participation of each lignocellulosic component during anaerobic digestion remained unclear. Thus, this study investigated the methane production characteristics of cellulose, hemicellulose, lignin and their mixtures along with the microbial communities involved in anaerobic digestion. The results showed that the biomethane potential of cellulose was higher than that of hemicellulose; however, hemicellulose was hydrolysed more quickly than cellulose, while lignin was very difficult to be digested. The higher concentrations of acetic, n-butyric and n-valeric acids hydrolysed from the hemicellulose resulted in a lower pH and more severe inhibition on methane production than that of cellulose, and the methanogenesis gradually recovered after pH adjustment. The co-digestion of cellulose and hemicellulose increased the methane yield and biodegradability compared to mono-digestions. The addition of lignin to cellulose brought more significant decrease in the methane yield of cellulose than that of hemicellulose. Substrate-related bacteria such as Clostridium sensu stricto, Lutaonella, Cloacibacillus and Christensenella showed higher relative abundance in cellulose digestate, and sugar-fermenting bacteria such as Saccharofermentans, Petrimonas and Levilinea were more rich in the digestate of hemicellulose. Moreover, methanogenic Methanospirillum and Methanothrix likely contributed to the methane production of cellulose, while aciduric methanogens from Methanobrevibacter, Methanomassiliicoccus, Methanobacterium and Methanoculleus contributed to that of hemicellulose. This study provides a deeper understanding of the mechanism in the bioconversion of lignocellulosic biomass during anaerobic digestion.
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| 7. |
- Sun, H., et al.
(författare)
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Methane hydrate re-formation and blockage mechanism in a pore-level water-gas flow process
- 2023
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Ingår i: Energy. - : Elsevier Ltd. - 0360-5442 .- 1873-6785. ; 263
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Tidskriftsartikel (refereegranskat)abstract
- Hydrate re-formation increases blockage risk and further reduces gas production efficiency. Considering the huge water production and gas migration, it is essential to determine the key parameters that control hydrate re-formation and blockage in the two-phase flow process. However, little research reveals the mechanism of hydrate re-formation in the water-dominated two-phase flow system. In this study, two-phase flow in hydrate sediment is simulated by controlling the water-gas flow rate, and the effect of effective sectional velocity on hydrate re-formation characteristics is analyzed. The experimental results showed that temperature and pressure followed a three-stage change trend in the water-dominated two-phase flow process: including hydrate re-formation induction stage I, mass hydrate re-formation and agglomeration stage II, and pore gas consumption stage III. Moreover, a lower effective sectional velocity of water (WESV) would reduce the gas concentration gradient between water and hydrate to enhance the hydrate re-formation process. Meanwhile, the gas phase impeded the mass transfer on the water-hydrate interface and acted as the nucleation site to promote hydrate re-formation. Furthermore, it was noticed that the relationship between the onset time of flow blockage and WESV was linearly positive, however, the amount of hydrate re-formation reduced with increasing WESV.
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| 8. |
- Tan, Sieting, et al.
(författare)
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A holistic low carbon city indicator framework for sustainable development
- 2017
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Ingår i: Applied Energy. - : Elsevier. - 0306-2619 .- 1872-9118. ; 185, s. 1919-1930
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Tidskriftsartikel (refereegranskat)abstract
- Many cities are pursuing the low-carbon practices to reduce CO2 and other environmental emissions. However, it is still unclear which aspects a low-carbon city (LCC) covers and how to quantify and certify its low carbon level. In this paper, an indicator framework for the evaluation of LCC was established from the perspectives of Economic, Energy pattern, Social and Living, Carbon and Environment, Urban mobility, Solid waste, and Water. A comprehensive evaluation method was employed for LCC ranking by using the entropy weighting factor method. The benchmark values for LCC certification were also identified. The framework was applied to 10 global cities to rank their low-carbon levels. The comparison of cities at different levels of economic, social, and environmental development enhances the holistic of the study. The results showed that Stockholm, Vancouver, and Sydney ranked higher than the benchmark value, indicating these cities achieved a high level of low-carbon development. São Paulo, London, and Mexico City are still in the slow transition towards LCC. Beijing and New York each has much lower LCC level than the benchmark value due to the poor environmental performance and infrastructure supports caused by intensive human activities. The proposed indicator system serves as a guideline for the standardization of LCC and further identifies the key aspects of low-carbon management for different cities.
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| 9. |
- Zhang, Kai, et al.
(författare)
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Power generation assessment of photovoltaic noise barriers across 52 major Chinese cities
- 2024
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Ingår i: Applied Energy. - : Elsevier Ltd. - 0306-2619 .- 1872-9118. ; 361
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Tidskriftsartikel (refereegranskat)abstract
- Photovoltaic noise barriers (PVNBs) have the potential to contribute to sustainable urban development by increasing the supply of renewable energy to cities while decreasing traffic noise pollution. However, estimating the power generation of PVNBs at the city or national scale remains a challenge due to the complexities of the urban environment and the difficulties associated with collecting data on road noise barriers (RNBs) and radiation. This study used RNBs, 2.5-dimensional (2.5D) buildings, and hourly time resolution radiation data, to estimate the power generation of PVNBs in 52 of China's major cities. First, hourly building shadows were estimated for each day of the year, covering the period from sunrise to sunset, to identify areas of RNB that are shaded at any given time. Second, hourly clear-sky radiation data were collected and corrected using a radiation correction model to simulate real weather radiation. Finally, utilizing an inclined surface radiation estimation model, the photovoltaic (PV) potential both inside and outside RNBs affected by building shadows was assessed. Subsequently, the power generation of PVNB was estimated based on parameters of mainstream PV systems in the market. The results show that the RNB mileage in 52 selected cities represents 87.7% of China's total RNB mileage. Building shadows often result in a radiation loss of approximately 30% for RNBs reception. The installed capacity and annual power generation of PVNBs in all investigated cities are 2.04 GW and 690.74 GWh, respectively. This study estimates the comprehensive PV potential of potentially exploitable PVNBs in China, offering essential scientific insights to inform and facilitate the strategic development of PVNB projects at both the national and municipal levels.
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