Search

Purpose - This paper aims to explore the affordances of Massive Open Online Practical (MOOP) platforms in individual and collaborative learning. The purpose of this exploration is to enhance our understanding of MOOP platforms in achieving success in individual and collaborative learning. Design/methodology/approach - Qualitative data is collected by a survey of 37 undergraduate students in China. This paper extracts the affordances of MOOP platforms identified from participant feedback. Findings - this paper identifies 8 themes of MOOP affordances for individual and collaborative learning, among which the affordances for individual learning includes: practicality, informing, motivation, and efficiency; The affordances of collaborative learning includes share resources, learning pathway, synthesis, monitoring and assessment. In addition, this study provides insights into the complexity of individual and collaborative learning, and also provides advice for the future of MOOP platforms. Originality/value - This study has analyzed a unique set of data to elucidate the experiences of participants in MOOP platforms and contributed by exploring future impacts. [ABSTRACT FROM AUTHOR]

Abstract Frequency control is the major concern for the integration of renewable energy into power systems. Electric vehicles (EV) are suggested to mitigate the system frequency deviation due to its vehicle-to-grid (V2G) capability and quick response characteristic. In this paper, the EVs are modeled by an EV aggregator and responded to the measureable states, such as system frequency, outputs of power plants and EV aggregator. Thus, a structure constrained feedback controller for the power plants and the EV aggregator is designed. However, the time delays during the transmission of control signal and state variable are inevitable. To deal with the time delays in the input and state variables, the Pade approximation is applied to construct the state space equations for the time delays. An equivalent augmented system without time delay is derived, in which the linear quadratic regulator (LQR) method is applied to derive the structure constrained feedback controller. Effectiveness and correctness of the proposed method are validated by a simple Great Britain power system in 2020. [ABSTRACT FROM AUTHOR]

Abstract A game-theory based trading analysis between distribution network operator (DNO) and multi-microgrids (multi-MGs) is proposed in this paper. Firstly, the model of DNO and MG are developed respectively. The operational objective of the DNO is trading profit (TP) maximization and the operational objective of the MGs are operation cost (OC) minimization. Secondly, a game composed of DNO and MGs is formulated and the Karush–Kuhn–Tucker (KKT) method is utilized to achieve the Nash Equilibrium (NE) point. Numerical results show that the proposed solution method is able to balance different interest of DNO and MGs simultaneously and the trading behaviors under different market prices are analyzed, which contributes to the optimal operation in aspect of payoff maximization. [ABSTRACT FROM AUTHOR]

Abstract With the rapid development of economy, the lack of freshwater resources has become increasingly urgent in many areas of China. Desalination can ease some of the pressure on freshwater supply, especially in coastal areas and isolated islands. The micro energy network is an efficient distributed energy supply system that can be used to supply electricity, cooling, heat and freshwater simultaneously. In this paper, wind turbine, photovoltaic(PV), combined cooling, heating and power(CCHP) system and desalination unit are integrated into the micro energy network. A multi-objective optimization research is conducted on the key equipment capacity and the operation of the desalination unit, with the goal of optimizing the life cycle cost and annual CO2 emissions simultaneously. And through the study of cases, the impact of the operation of desalination unit on the planning solutions of micro energy network is researched. [ABSTRACT FROM AUTHOR]

Based on the previous generation of yolk-shell nanostructured polyaniline@SiO 2 particles, a confined carbonization process followed by etching the SiO 2 layer is carried out to achieve carbon particles. The existence of the SiO 2 shell helps to preserve the original well-dispersed morphology of the polyaniline that retains amounts of active sites for oxygen reduction reaction. Furthermore, the CeO 2 oxidant and the SiO 2 shell lead to the increased amount of oxygen existing in the product and the oxygen reduction reaction results show the well-maintained nanostructure with mesopores and the effective O doping benefit for achieving enhanced catalytic activity. [ABSTRACT FROM AUTHOR]

A multi-objective optimal hybrid power flow algorithm was proposed for multi-objective scheduling and management of the integrated community energy system (ICES). Firstly, an energy conversion analysis model for the energy center was developed based on the energy hub model. Then, a multi-objective optimal hybrid power flow algorithm is proposed to minimize the operation cost and total emission of the ICES considering the constraints from unbalanced three-phase electric distribution network, the natural gas network and the energy centers. Numerical results showed that the proposed multi-objective optimal hybrid power flow algorithm can be further used in the optimal day-ahead scheduling for the ICES, which considers the ICES's multiple operation needs in aspects of security, economy and environmental friendliness. [ABSTRACT FROM AUTHOR]

A simple dynamic model to simulate heating/cooling energy consumption in a building was proposed in this paper. The model consists of several transient energy balance equations for external walls and internal air, in which the convective heat transfer, conductive heat transfer and heat storage in the heat transfer process are considered. The proposed model has been implemented utilizing the SIMULINK/MATLAB platform. Then, a model predictive control (MPC) approach for the building Microgrid considering the dynamic thermal characteristics of the building was proposed. The MPC approach aims to minimize the total energy consumption of the building Microgrid by combining the model predictive and the short-term control, and guarantees the customer temperature comfort level at the same time. Two comparative cases are presented to verify the effectiveness of the proposed MPC approach. [ABSTRACT FROM AUTHOR]

A heuristic planning method of electric vehicle (EV) fast charging station on a freeway considering the power flow constraints of the distribution network was proposed. Firstly, the spatial and temporal distribution of EV charging points was determined based on a spatial-temporal model (STM); then the charging demand of candidate fast charging stations was determined based on the Shared Nearest Neighbor (SNN) Clustering algorithm; finally, a heuristic principle was proposed to meet the power flow constraints of the distribution network and the final planning scheme (the location and capacity) was determined. A typical test system was used to verify the validity of the planning method. [ABSTRACT FROM AUTHOR]

This paper aims to develop a hierarchical management strategy for the building microgrid. The proposed hierarchical framework is presented as day-ahead scheduling stage and a two-layer intra-hour adjustment stage. Firstly, a virtual storage system (VSS) model is developed by utilizing the heat storage characteristics of a building. Then, the VSS model is integrated into the developed hierarchical management strategy of the building microgrid, which is presented as a day-ahead optimal economic scheduling stage for the minimum operation cost and an intra-hour adjustment stage to follow the tie-line power set-points. In the intra-hour real-time adjustment, a master–client structure is designed. The VSS and plug-in electric vehicles (EVs) are coordinated by a method with two different time scales in order to execute the schedule and handle uncertainties from the load demand, outdoor environment and the renewable generation in the intra-hour adjustment stage. Numerical studies demonstrate that the proposed strategy can contribute to the operation cost reduction in day-ahead scheduling stage and tie-line power smoothing in intra-hour adjustment stage, while guarantee the customer temperature comfort level and EVs travelling demands at the same time. [ABSTRACT FROM AUTHOR]

This study aimed to examine the potential association between low-level prenatal manganese (Mn) exposure and 1-year-old children's neurodevelopment quotient (DQ) by using the Gesell Developmental Inventory (GDI) (motor, adaptive, language, and social domains) and explored the role of brain-derived neurotrophic factor (BDNF) in Mn-induced cognitive impairments. A total of 377 mothers were recruited from a prospective birth cohort in rural northern China. Cord serum concentrations of Mn and BDNF were measured and children's DQ was evaluated. The median serum Mn concentration was 3.4 μg/L. After adjusting for confounding factors, Mn level was significantly associated with gross motor scores (β = −6.0, 95% CI: −11.8 to −0.2, p < 0.05) and personal–social scores (β = −4.2, 95% CI: −8.4 to 0.1, p < 0.05). BDNF level was positively correlated with personal–social score (β = 0.7, 95% CI: 0–1.4, p < 0.05). A significant correlation was found between Mn and BDNF (r = −0.13, 95% CI: −0.23 to −0.03, p < 0.01). Furthermore, the interaction between cord serum Mn and BDNF was significant ( p < 0.001). In conclusion, elevated low-level prenatal Mn exposure impaired infant's neurodevelopment, and BDNF plays an important role in cognitive impairment, especially in the personal–social ability. [ABSTRACT FROM AUTHOR]

Background: Dietary methylmercury intake can occur not only through fish ingestion but also through rice ingestion; however, rice does not contain the same beneficial micronutrients as fish.Objectives: In rural China, where rice is a staple food, associations between prenatal methylmercury exposure (assessed using maternal hair mercury) and impacts on offspring neurodevelopment were investigated.Methods: A total of 398 mothers were recruited at parturition at which time a sample of scalp hair was collected. Offspring (n=270, 68%) were assessed at 12 months using the Bayley Scales of Infant Development-II, yielding age-adjusted scores for the Mental Developmental Index (MDI) and Psychomotor Developmental Index (PDI).Results: Among 270 mothers, 85% ingested rice daily, 41% never or rarely ingested fish/shellfish and 11% ingested fish/shellfish at least twice/weekly. Maternal hair mercury averaged 0.41μg/g (median: 0.39μg/g, range: 0.079-1.7μg/g). In unadjusted models, offspring neurodevelopment (both MDI and PDI) was inversely correlated with hair mercury. Associations were strengthened after adjustment for fish/shellfish ingestion, rice ingestion, total energy intake (kcal), and maternal/offspring characteristics for both the MDI [Beta: -4.9, 95% Confidence Interval (CI): -9.7, -0.12] and the PDI (Beta: -2.7, 95% CI: -8.3, 2.9), although confidence intervals remained wide for the latter.Conclusions: For 12-month old offspring living in rural China, prenatal methylmercury exposure was associated with statistically significant decrements in offspring cognition, but not psychomotor development. Results expose potential new vulnerabilities for communities depending on rice as a staple food. [ABSTRACT FROM AUTHOR]

Background The increasing incidence of invasive Candida infections (ICIs) in preterm infants in the neonatal intensive care unit (NICU) of Xinhua Hospital aroused our concern. We undertook a retrospective study to evaluate the efficacy of different preventive measures for ICI in preterm infants. Methods Preterm infants with gestational age (GA) <33 weeks admitted between 2010 and 2013 were divided into 3 groups according to the preventive measures applied in different periods: the control group (CG), fluconazole group (FG), and integrated measures group (IMG). We analyzed the incidence of ICI and distribution of fungal pathogens in these 3 groups, and also evaluated the efficiency of various measures in preventing ICIs in preterm infants. Results The study sample comprised 261 preterm infants born at <33 weeks GA, including 94 in the CG, 99 in the FG, and 68 in the IMG. The differences among the groups were not significant at baseline. ICI developed in 41 of the 261 infants (15.7%). The incidence of ICI varied significantly among the groups: 22.3% in the CG (21/94), 18.2% in the FG (18/99), and only 2.9% in the IMG (2/68) ( P = .003). ICI was less frequent in the IMG compared with the CG ( P <.001) and the FG ( P = .003). Conclusions The integrated measures approach is meaningful for the prevention of ICIs in preterm infants in NICUs with many patients but inadequate medical resources in some developing countries. [ABSTRACT FROM AUTHOR]

To assess associations of single and combined exposures to lead and stress during different stages of pregnancy with offspring neurodevelopment. We measured prenatal lead (maternal blood-lead in early-pregnancy and umbilical-cord-blood-lead) and maternal stress levels in Shanghai-Birth-Cohort from 2013 to 2016. Maternal stress was assessed using Center-for-Epidemiological-Studies-Depression-Scale and Self-Rating-Anxiety-Scale during mid-pregnancy. The Ages-Stages-Questionnaires-3 (at 6/12-months-of-age) and Bayley-III (at 24-months-of-age) were both used to assess neurodevelopment. A total of 2132 mother-child pairs with both prenatal lead and stress measurements were included. The geometric-means of blood-lead in early-pregnancy and cord-blood-lead were 1.46 μg/dL and 1.33 μg/dL, respectively. Among the study women, 1.89 % and 0.14 % were screened positive for depression and anxiety. Adjusting for related confounders, the combined exposures had stronger adverse associations with offspring social-emotional skills than single exposures; and the combined exposure in early-pregnancy was associated with greater neurodevelopmental differences than combined exposure around-birth, especially in social-emotion at 24 months-of-age [β (95 %CI): − 10.48(−17.42, −3.54) vs. − 5.95(−11.53, −0.36)]. Both single and combined prenatal exposures to lead/stress impaired infant neuro-development, and the effects of combined exposure may be more profound than single exposures. Combined exposure in early-pregnancy may be associated with worse neurodevelopmental outcomes than combined exposure around-birth, especially in social-emotional development. • Effects of prenatal single and combined exposure to lead and stress were investigated using a large-scale birth cohort. • The overall levels of prenatal exposures to lead/stress were relatively low in the Shanghai study women. • Adverse effects of prenatal combined exposure on offspring neurodevelopment may be more profound than single exposure. • The impaired neurodevelopment domains in the offspring mainly include social-emotional development. • Higher levels of impairments were induced when the combined exposure occurred in an earlier stage of pregnancy. [ABSTRACT FROM AUTHOR]

Abstract: Maternal hair and blood were investigated as biomarkers for prenatal methylmercury (MeHg) exposure among seventeen mothers recruited at parturition in Wanshan, Guizhou Province, China, where rice ingestion was the primary MeHg exposure pathway and atmospheric mercury (Hg) levels were elevated. For all three trimesters (n = 51), hair total Hg (THg) and MeHg concentrations ranged from 0.27 to 4.9 μg/g (median: 0.96 μg/g) and 0.077 to 2.3 μg/g (median: 0.43 μg/g), respectively, while blood THg levels ranged from 1.7 to 11 μg/L (median: 3.0 μg/L, n = 17). Despite adequate hair washing procedures, median %MeHg (of THg) was 37% (range: 14–89%, n = 51), indicating exogenous inorganic Hg(II) contamination or incorporation of elemental Hg (Hgo) into the hair shaft were important. Rice MeHg levels (n = 17) were highly correlated with blood THg (r 2 = 0.66) compared to hair MeHg (r 2 = 0.31) (when variables were log10-transformed), suggesting blood THg was a more preferable biomarker for prenatal MeHg exposure within this population. [Copyright &y& Elsevier]

Abstract: The relationship between serum 25-hydroxyvitamin D and quantitative ultrasound bone mineral density in young children remains unclear. In addition, consensus has not been reached with regard to the concentration of 25(OH)D to define vitamin D deficiency for infants and children. In the present study, 203 children 0–6years old were recruited in Shanghai, China. The concentrations of serum 25(OH)D, weight, length, and quantitative ultrasound bone mineral density (BMD) of left mid-tibia were determined. Low BMD was defined as <20th percentile of given age and sex. Low 25(OH)D was defined as 25(OH)D<20ng/ml. The results showed that median serum 25(OH)D level was 19.0ng/ml, and 58.6% had a serum 25(OH)D below 20ng/ml. After adjusting for potential confounders, a linear relationship between serum 25(OH)D and BMD was observed. Serum 25(OH)D was positively associated with BMD (ß=323.3, 95% CI=201.0–445.7, p<0.001), and low 25(OH)D (<20ng/ml) had a high risk for low BMD (OR=5.5, 95% CI=2.5–12). In addition, there is a nonlinear relationship between 25(OH)D and low BMD, and a threshold for 25(OH)D of 20ng/ml existed for low BMD. The prevalence of low BMD was 47.1% in the group of 25(OH)D<20ng/ml, much higher than 16.7% in the group of 25(OH)D≥20ng/ml (p<0.05). The results suggested that quantitative ultrasound BMD could be an indicator for vitamin D status in young children, and also provided further evidence to define vitamin D deficiency for infants and children. [Copyright &y& Elsevier]

Abstract: Previous research has consistently shown that the left parietal cortex is critical for numerical processing, but the role of the right parietal lobe has been much less clear. This study used the intraoperative cortical electrical stimulation approach to investigate neural dissociation in the right parietal cortex for subtraction and multiplication. Results showed that multiplication (as well as picture naming) was not affected by the cortical electrical stimulation on all the targeted sites of the right parietal cortex as well as those of the right temporal cortex. In contrast, stimulation at three right parietal sites (two sites in the right inferior parietal lobule and one in the right angular gyrus) impaired performance on simple subtraction problems. This study provided the first evidence from an intraoperative cortical electrical stimulation study to show the dissociation of arithmetic operations in the right parietal cortex. This dissociation between subtraction and multiplication suggests that the right parietal cortex plays a more significant role in quantity processing (subtraction) than in verbal processing (multiplication) in numerical processing. [Copyright &y& Elsevier]