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In adapting to the double-high development trend of high-voltage direct current (HVDC) receiving-end power systems and solving optimization problems in emergency frequency control (EFC) supporting virtual power plants (VPPs) in large-scale power systems, a parameter estimation method for a VPP frequency response model based on a successive linear programming (SLP) method is proposed. First, a “centralized/decentralized” hierarchical control architecture for VPP participation in EFC is designed. Second, the frequency response characteristics of multiple flexible resources are scientifically analyzed, and the system frequency response (SFR) model and equivalent model of VPP are constructed. Subsequently, parameter estimation of the VPP frequency response model is carried out based on the SLP method, aiming to balance the accuracy and computational efficiency of the model. Finally, the effectiveness of the proposed methodology is verified by using PSD-BPA to simulate and test the three-zone HVDC recipient area grid.

In this paper, controllable wind turbines are employed for emergency frequency control to reduce cost. However, controllable wind turbines introduce significant modeling uncertainties in the form of uncertain environmental factors and model aggregation into the system. To pre-generate feasible emergency control strategies at the lowest cost, a robust optimization model is constructed for a potentially serious fault in power systems, which is a mixed-integer nonlinear robust programming issue with non-analytical calculation (for post-event system frequency). Therefore, this study proposes to first quantify the impact of modeling uncertainties on wind turbine regulation and find the most unfavorable uncertain scenarios for emergency frequency control. Then, based on the above-filtered scenarios, the original problem is transformed into mixed-integer nonlinear programming. A novel simplified algorithm is proposed to solve the above problem efficiently. Finally, a case study is conducted on a real regional power system. It is proved effective in reducing costs by regulating wind turbines for emergency control, and the proposed method is effective in dealing with the impact of modeling uncertainties. Also, high solving efficiency (12 s in case study) meets the demand for efficient online pre-decision-making for emergency control. The research is meaningful in the promotion of secure access to power systems for sustainable power.

High-voltage direct current (HVDC) blocking disturbance leads to large power losses in the receiving-end power grid, and the event-driven emergency frequency control (EFC) is an important measure to prevent large frequency deviation. By aggregating controllable distributed energy resources (DERs) on the demand side, a virtual power plant (VPP) could quickly reduce its power and can be a new fast response resource for EFC. Considering both the VPP and the traditional control resources, this paper proposes an optimized EFC strategy coordinating multiple resources for the receiving-end power grid with multi-infeed HVDC. The approximate aggregation model of the VPP response process is constructed, based on which the EFC strategy, aiming at minimizing the total control cost while meeting constraints on rotor angle stability and frequency deviation security, is proposed. The electromechanical transient simulation combined with particle swarm optimization (PSO) is utilized to solve the model, and parallel computation is utilized to accelerate the solving process. The effectiveness of the proposed EFC strategy is verified by a provincial receiving-end power grid with multi-infeed HVDC. The detailed simulation results show that VPP could dramatically reduce the control cost of EFC while maintaining the same stability margin.

In response to flood risk, design flood estimation is a cornerstone of planning, infrastructure design, setting of insurance premiums, and emergency response planning. Under stationary assumptions, flood guidance and the methods used in design flood estimation are firmly established in practice and mature in their theoretical foundations, but under climate change, guidance is still in its infancy. Human-caused climate change is influencing factors that contribute to flood risk such as rainfall extremes and soil moisture, and there is a need for updated flood guidance. However, a barrier to updating flood guidance is the translation of the science into practical application. For example, most science pertaining to historical changes to flood risk focuses on examining trends in annual maximum flood events or the application of non-stationary flood frequency analysis. Although this science is valuable, in practice, design flood estimation focuses on exceedance probabilities much rarer than annual maximum events, such as the 1 % annual exceedance probability event or even rarer, using rainfall-based procedures, at locations where there are few to no observations of streamflow. Here, we perform a systematic review to summarize the state-of-the-art understanding of the impact of climate change on design flood estimation in the Australian context, while also drawing on international literature. In addition, a meta-analysis, whereby results from multiple studies are combined, is conducted for extreme rainfall to provide quantitative estimates of possible future changes. This information is described in the context of contemporary design flood estimation practice to facilitate the inclusion of climate science into design flood estimation practice.

When the main grid of the power grid malfunctions undergoes emergency repairs, the microgrid is in off-grid operation. At this time, the microgrid in an isolated state must have self-frequency regulation capability. This article proposes a frequency control strategy for isolated microgrids, which can improve their ability to resist frequency interference. The proposed control strategy considers the different characteristics and capabilities of various micro-sources for frequency regulation. It classifies the frequency modulation micro-sources in the microgrid. Judgment conditions and parameters are set to determine whether each micro-source participates in frequency modulation and the participating components. The isolated microgrid has an economical and fast frequency modulation strategy. Finally, a microgrid simulation model is established using Matlab/Simulink simulation software to verify the effectiveness of the proposed frequency modulation strategy.

Since the coronavirus disease (COVID-19) epidemic in China in December 2019, information and discussions about COVID-19 have spread rapidly on the internet and have quickly become the focus of worldwide attention, especially on social media. This study aims to investigate and analyze the public's attention to events related to COVID-19 in China at the beginning of the COVID-19 epidemic (December 31, 2019, to February 20, 2020) through the Sina Microblog hot search list. We collected topics related to the COVID-19 epidemic on the Sina Microblog hot search list from December 31, 2019, to February 20, 2020, and described the trend of public attention on COVID-19 epidemic-related topics. ROST Content Mining System version 6.0 was used to analyze the collected text for word segmentation, word frequency, and sentiment analysis. We further described the hot topic keywords and sentiment trends of public attention. We used VOSviewer to implement a visual cluster analysis of hot keywords and build a social network of public opinion content. The study has four main findings. First, we analyzed the changing trend of the public's attention to the COVID-19 epidemic, which can be divided into three stages. Second, the hot topic keywords of public attention at each stage were slightly different. Third, the emotional tendency of the public toward the COVID-19 epidemic-related hot topics changed from negative to neutral, with negative emotions weakening and positive emotions increasing as a whole. Fourth, we divided the COVID-19 topics with the most public concern into five categories: the situation of the new cases of COVID-19 and its impact, frontline reporting of the epidemic and the measures of prevention and control, expert interpretation and discussion on the source of infection, medical services on the frontline of the epidemic, and focus on the worldwide epidemic and the search for suspected cases. Our study found that social media (eg, Sina Microblog) can be used to measure public attention toward public health emergencies. During the epidemic of the novel coronavirus, a large amount of information about the COVID-19 epidemic was disseminated on Sina Microblog and received widespread public attention. We have learned about the hotspots of public concern regarding the COVID-19 epidemic. These findings can help the government and health departments better communicate with the public on health and translate public health needs into practice to create targeted measures to prevent and control the spread of COVID-19.

Emergency departments (EDs) play a critical role in the US healthcare system. As freestanding EDs (FSEDs) are integrated into the acute care landscape, local EMS providers are transporting to these facilities, which may be closer in proximity and provide faster turnaround times. We hypothesized that patients transported via EMS to a freestanding ED required fewer tests and are admitted less frequently than those transported to a HBED. Our objective was to compare testing frequency and admission rates between patients transported via EMS to a FSED vs. HBED. This was a retrospective cohort study of all patients who presented within a large integrated hospital system via EMS to one of 10 HBEDs or one of 6 FSEDs between April 1, 2020 – May 1, 2021. Categorical variables are presented as frequencies and percentages and comparisons between groups were obtained using chi squared tests. Continuous variables are presented as mean and standard deviation and p-values comparing groups were obtained using t-tests. Multiple logistic regression was used to assess the effect of ED type on admission status, labs ordered, and testing performed. A total of 123,120 encounters were included in our study. Mean age at the FSEDs was 59.9 vs. 61.3 at the HBEDs. At the FSEDs 55.6% (n = 4675) were female vs. 53.0% (n = 60,809) at the HBEDs. At the FSEDs 82.0% (n = 6805) were White vs. 60.7% (n = 68,430) at the HBEDs. We found 50.0% (n = 3974) had Medicare at the FSEDs vs 50.9% (n = 55,372) at the FSEDs. At the FSEDs, 69.5% (n = 5846) had bloodwork vs. 82.4% (n = 94,512) at the HBEDs; 68.3% (n = 5745) had an x-ray at the FSEDs vs. 70.7% (n = 81,089) at the HBEDs; 40.1% (n = 3370) had a CT scan at the FSEDs vs. 44.9% (n = 51,503) at the HBEDs; and 40.6% (n = 3412) were admitted at the FSEDs vs. 56.1% (n = 64,355) at the HBEDs. After controlling for Charlson Comorbidity Index, acuity, age, gender, sex, insurance and race, patients in FSEDs were 35% less likely to be admitted as compared to HBEDs. Patients brought in via EMS to a FSED were less likely to have blood work, x-ray, or CT scan, and were less likely to be admitted to the hospital than those transported to a HBED.

Understanding the attribution of urban extreme precipitation is vital for disaster warning and emergency management. However, present attribution analysis mostly applies factors with interaction within drive forces and little consideration on larger-scale teleconnection. In this study, the annual 1-day (AM1X) and 3-day mean (AM3X) maximum precipitation in Zhengzhou city were focused. First, the driving forces for extreme precipitation are identified by correlation trails and Granger causality test from 130 teleconnection factors. Then, the reconstructed series by regression models and observed series are contrasted to distinguish the attributions considering four return periods. Final, quantitative attribution and the variation with frequencies are obtained. The results show that (1) Western Pacific Subtropical High Area Index (WPSHAI) and Western Pacific Subtropical High Intensity Index (WPSHII) are the dominant teleconnection factors. (2) The point estimation under climate control corresponding to 10%, 1%, 0.1%, and 0.01% is 110.95, 141.40, 166.45, and 189.13 mm for AM1X and 37.10, 46.66, 53.51, and 59.17 mm for AM3X, and the interval estimation is 8.28 ~ 44.92 mm and 2.97 ~ 12.94 mm correspondingly. (3) Extreme precipitation corresponding to 10%, 1%, 0.1%, and 0.01% is governed by climatic control, 70.78% ~ 88.02% for AM1X and 50.72% ~ 67.73% for AM3X. The contribution of human activities increases with increasing return period. It is hoped that this study could provide a new theoretical framework to quantify attribution of urban extreme precipitation.

Background High-flow nasal cannula (HFNC) oxygen therapy is being increasingly used to prevent post-extubation hypoxemic respiratory failure and reintubation. However, evidence to support the use of HFNC in chronic obstructive pulmonary disease (COPD) patients with hypercapnic respiratory failure after extubation is limited. This study was conducted to test if HFNC is non-inferior to non-invasive ventilation (NIV) in preventing post-extubation treatment failure in COPD patients previously intubated for hypercapnic respiratory failure. Methods COPD patients with hypercapnic respiratory failure who were already receiving invasive ventilation were randomized to HFNC or NIV at extubation at two large tertiary academic teaching hospitals. The primary endpoint was treatment failure, defined as either resumption of invasive ventilation or switching to the other study treatment modality (NIV for patients in the NFNC group or vice versa). Results Ninety-six patients were randomly assigned to the HFNC group or NIV group. After secondary exclusion, 44 patients in the HFNC group and 42 patients in the NIV group were included in the analysis. The treatment failure rate in the HFNC group was 22.7% and 28.6% in the NIV group—risk difference of − 5.8% (95% CI, − 23.8–12.4%, p  = 0.535), which was significantly lower than the non-inferior margin of 9%. Analysis of the causes of treatment failure showed that treatment intolerance in the HFNC group was significantly lower than that in the NIV group, with a risk difference of − 50.0% (95% CI, − 74.6 to − 12.9%, p  = 0.015). One hour after extubation, the mean respiratory rates of both groups were faster than their baseline levels before extubation ( p  < 0.050). Twenty-four hours after extubation, the respiratory rate of the HFNC group had returned to baseline, but the NIV group was still higher than the baseline. Forty-eight hours after extubation, the respiratory rates of both groups were not significantly different from the baseline. The average number of daily airway care interventions in the NIV group was 7 (5–9.3), which was significantly higher than 6 (4–7) times in the HFNC group ( p  = 0.006). The comfort score and incidence of nasal and facial skin breakdown of the HFNC group was also significantly better than that of the NIV group [7 (6–8) vs 5 (4–7), P  < 0.001] and [0 vs 9.6%, p  = 0.027], respectively. Conclusion Among COPD patients with severe hypercapnic respiratory failure who received invasive ventilation, the use of HFNC after extubation did not result in increased rates of treatment failure compared with NIV. HFNC also had better tolerance and comfort than NIV. Trial registration chictr.org ( ChiCTR1800018530 ). Registered on 22 September 2018, http://www.chictr.org.cn/usercenter.aspx

Infectious individuals in an emergency department (ED) bring substantial risks of cross infection. Data about the complex social and spatial structure of interpersonal contacts in the ED will aid construction of biologically plausible transmission risk models that can guide cross infection control. We sought to determine the number and duration of contacts among patients and staff in a large, busy ED. This prospective study was conducted between 1 July 2009 and 30 June 2010. Two 12-hour shifts per week were randomly selected for study. The study was conducted in the ED of an urban hospital. There were 81 shifts in the planned random sample of 104 (78%) with usable contact data, during which there were 9183 patient encounters. Of these, 6062 (66%) were approached to participate, of which 4732 (78%) agreed. Over the course of the year, 88 staff members participated (84%). A radiofrequency identification (RFID) system was installed and the ED divided into 89 distinct zones structured so copresence of two individuals in any zone implied a very high probability of contact <1 meter apart in space. During study observation periods, patients and staff were given RFID tags to wear. Contact events were recorded. These were further broken down with respect to the nature of the contacts, i.e., patient with patient, patient with staff, and staff with staff. 293,171 contact events were recorded, with a median of 22 contact events and 9 contacts with distinct individuals per participant per shift. Staff-staff interactions were more numerous and longer than patient-patient or patient-staff interactions. We used RFID to quantify contacts between patients and staff in a busy ED. These results are useful for studies of the spread of infections. By understanding contact patterns most important in potential transmission, more effective prevention strategies may be implemented.