Search

Insulated plastic greenhouses (IPG) were a new type of facility emerging in production in China. The mechanism of construct parameters on the indoor solar radiation deserves further study. A mathematical model that can well describe the spatial and temporal distribution of solar radiation in the greenhouse was established. Based on this model, the effects of multiple construct parameters, such as insulation blanket shading, height–span ratio, greenhouse azimuth, and geographical latitude, on the indoor solar radiation of IPG were quantitatively specified. The results showed that the spatial and temporal distribution of inside solar radiation was highly variable along the span direction of IPG. And by analyzing the simulation data, it was found that for different heights of greenhouses, the corresponding optimal span is different. Therefore, in the construction of greenhouses, the appropriate height–span ratio should be selected according to the planting demand. And by simulating the inside solar radiation under different greenhouse azimuth angles, it was found that accumulated daily solar radiation in the greenhouse reaches the optimum value when the greenhouse azimuth angle is in the range of 0–20°. This paper can provide theoretical guidance for the design and optimization of structure parameters of IPG in China. [ABSTRACT FROM AUTHOR]

The prevention and control of the spread of Cystic Echinococcosis is an important public health issue. Health education has been supported by many governments because it can increase public awareness of echinococcosis, promote the development of personal hygiene habits, and subsequently reduce the transmission of echinococcosis. In this paper, a dynamic model of echinococcosis is used to integrate all aspects of health education. Theoretical analysis and numerical model fitting were used to quantitatively analysed by the impact of health education on the spread of echinococcosis. Theoretical findings indicate that the basic reproduction number is crucial in determining the prevalence of echinococcosis within a given geographical area. The parameters of the model were estimated and fitted by using data from the Ningxia Hui Autonomous Region in China, and the sensitivity of the basic reproduction number was analysed by using the partial rank correlation coefficient method. These findings illustrate that all aspects of health education demonstrate a negative correlation with the basic reproduction number, suggesting the effectiveness of health education in reducing the basic reproduction number and mitigating the transmission of echinococcosis, which is consistent with reality. Particularly, the basic reproduction number showed a strong negative correlation with the burial rate of infected livestock (b) and the incidence of infected livestock viscera that is not fed to dogs (q). This paper further analyzes the implementation plan for canine deworming rates and sheep immunity rates, as well as the transmission of infected hosts over time under different parameters b and q. According to the findings, emphasizing the management of infected livestock in health education has the potential to significantly reduce the risk of echinococcosis transmission. This study will provide scientific support for the creation of higher quality health education initiatives. [ABSTRACT FROM AUTHOR]

In order to advance the utilization rate of multi-source solid wastes in the Ningxia region of China, 16 groups of pavement base mixtures were designed with cement and fly ash (FA) as binders, steel slag (SS), silicon manganese slag (SMS), and recycled crushed stone (RCS) as composite aggregates. The evolution laws of mechanical and frost resistance properties of the mixture were investigated by unconfined compressive strength (UCS), indirect tensile strength (ITS), freeze–thaw (FT), and ultrasonic detection tests. Then, the strength formation mechanisms were revealed by microscopic characterization technology. The mathematical models between UCS-ITS, UCS-ultrasonic amplitude, FT cycles-UCS damage, and frost resistance coefficient-relative dynamic elastic modulus Er were established. The results show that cement content and curing age exhibited a positive effect on the mechanical strength and frost resistance of the mixture. When the replacement rate of SS was 60%, the mechanical strength and frost resistance were preferable. The R2 of the strength relationship models constructed was greater than 0.9, indicating high fitting accuracy. With the extension of the curing age, the cementitious products such as C-S-H (hydrated calcium silicate) and AFt (ettringite) developed entirely, and they were interlocked and cemented with each other, resulting in the micro-morphology developed from the three-dimensional network structure to the dense system. The macroscopic behavior incarnated that the mechanical strength and frost resistance of the mixture were significantly enhanced. [ABSTRACT FROM AUTHOR]

Based on the key module-lifting arm system, based on the principle of similarity and the hydrodynamic experimental method of a multi-dimension vibration test platform, an experimental platform for dismantling equipment is designed and built. Subsequently, the motion control model of the six-degrees-of-freedom platform is established. The three-ring control model of a servo electric cylinder is established, and the active heave compensation control of a servo electric cylinder is realized by combining position control theory. Based on the co-simulation of ADAMS and Simulink, the co-simulation system of the integrated dismantling equipment experimental platform is designed and built, and the simulation system is tested and verified. Finally, simulation and experimental verification are carried out based on the experimental platform and co-simulation system. The results show that the heave compensation rate reaches 58.3% in third-class sea conditions, 61.2% in fourth-class sea conditions, and 62.4% in fifth-class sea conditions. The integrated dismantling scheme of super large offshore oilfield facilities is feasible but, in order to ensure the safety and reliability of the operation, a heave compensation system needs to be added. The error between the simulation results and the experimental results is about 15%. Based on the analysis of external interference factors in the experiment, the error results are within a reasonable range, which proves that the experimental platform, the co-simulation system of the experimental platform, and the heave compensation strategy are accurate and effective. This study, for the first time in China, provides an effective experimental platform and co-simulation platform for the design and optimization of the integrated dismantling equipment of super large offshore oilfield facilities and lays a good research foundation for the construction and engineering demonstration of subsequent equipment. [ABSTRACT FROM AUTHOR]

In 2017, China began to comprehensively control rural water pollution in two steps, and aims to complete the purification of rural domestic sewage by the end of 2030. The short-term goal was to implement rural drinking water safety as soon as possible, and the medium-term and long-term goals were to completely block all kinds of pollution sources. Based on the field survey data, a variety of mathematical models were established to evaluate the progress of rural sewage treatment, the operation efficiency of sewage treatment facilities and the current situation of water pollution in China. The results show that the short-term goal has been basically achieved. The rural tap water penetration rate has reached 98%, and about 95% of the water has reached the drinking standard. About 70% of the groundwater is safe for bathing. However, the rural economy is weak, the residence is scattered and the unit sewage treatment cost is high, so it is very difficult to implement rural sewage treatment. The implementation of medium-term and long-term goals is slow, especially the treatment rate of agricultural non-point source sewage and domestic sewage is generally low, and surface water such as rural ponds and reservoirs basically belongs to Class IV or Class V. The study found that the key to the poor effect and slow progress of sewage treatment is the lack of economic support. It is suggested that the government should further increase investment in rural sewage treatment facilities. [ABSTRACT FROM AUTHOR]

Copyright of Oil Drilling & Production Technology / Shiyou Zuancai Gongyi is the property of Shiyou Zuancai Gongyi Bianjibu and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The logistics management of refined oil under a separation of production and transportation leads to high logistics costs and a mismatch between the supply and demand sides. This paper intends to develop a general framework to assess the impact of the integration of the production and transportation in terms of economic, environmental, and energy benefits. Firstly, this paper proposes a tactical-level mathematical model for optimizing the integration of production and transportation of refined oil to minimize the total cost. In the model, several factors, such as level of market demand, production capacity limits, transportation modes, and transportation capacity, are taken into consideration. Then, the energy, economy, and environment analysis method are applied to assess the impact of the integration on the field of refined oil logistics. Four scenarios are set up and a comparative analysis is carried out in detail in China. The optimal resource allocation scheme and production adjustment scheme for each scenario are obtained. The results show that after the integration, the logistics cost is reduced by 6.8 %− 11 %, the greenhouse gas emission is reduced by 7.3 %− 17.7 %, and the energy consumption per unit turnover is reduced by 4.4 %− 7.4 %. This proves that the integration of production and transportation guided by the proposed method performs positive economic, environmental, and energy benefits. Finally, policy implications are provided. • A framework is raised to assess the integration of oil production and transportation. • A logistics optimization model considering production adjustment is proposed. • The economic, environmental and energy benefits in a real case are identified. • Policy prescriptions are recommended for China. [ABSTRACT FROM AUTHOR]

This study used a calibrated mathematical model to evaluate age-specific tuberculosis (TB) vaccination strategies, for drug-resistant (DR)-TB management in China. Prioritizing elderly vaccination significantly reduced multidrug-resistant or rifampicin-resistant TB incidence and mortality, while avoiding the need for second-line treatment, offering a promising approach to mitigate DR-TB burden by 2050., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The mass vaccination program has been actively promoted since the end of 2020. However, waning immunity, antibody-dependent enhancement (ADE), and increased transmissibility of variants make the herd immunity untenable and the implementation of dynamic zero-COVID policy challenging in China. To explore how long the vaccination program can prevent China at low resurgence risk, and how these factors affect the long-term trajectory of the COVID-19 epidemics, we developed a dynamic transmission model of COVID-19 incorporating vaccination and waning immunity, calibrated using the data of accumulative vaccine doses administered and the COVID-19 epidemic in 2020 in mainland China. The prediction suggests that the vaccination coverage with at least one dose reach 95.87%, and two doses reach 77.92% on 31 August 2021. However, despite the mass vaccination, randomly introducing infected cases in the post-vaccination period causes large outbreaks quickly with waning immunity, particularly for SARS-CoV-2 variants with higher transmissibility. The results showed that with the current vaccination program and 50% of the population wearing masks, mainland China can be protected at low resurgence risk until 8 January 2023. However, ADE and higher transmissibility for variants would significantly shorten the low-risk period by over 1 year. Furthermore, intermittent outbreaks can occur while the peak values of the subsequent outbreaks decrease, indicating that subsequent outbreaks boosted immunity in the population level, further indicating that follow-up vaccination programs can help mitigate or avoid the possible outbreaks. The findings revealed that the integrated effects of multiple factors: waning immunity, ADE, relaxed interventions, and higher variant transmissibility, make controlling COVID-19 challenging. We should prepare for a long struggle with COVID-19, and not entirely rely on the COVID-19 vaccine. [ABSTRACT FROM AUTHOR]

The degree of informatization of coal mine safety management is becoming higher and higher, and a large amount of information is generated in this process. How to convert the existing information into useful data for risk control has become a challenge. To solve this challenge, this paper studies the mathematical model of coal mine risk early warning in China based on data mining. Firstly, the coal mine risk data was comprehensively analyzed to provide basic data for the risk prediction model of data mining. Then, the adaptive neuro-fuzzy inference system (ANFIS) was optimized twice to build the coal mine risk prediction model. By optimizing the calculation method of the control chart, the coal mine risk early warning system was proposed. Finally, based on the coal mine risk early warning model, the software platform was developed and applied to coal mines in China to control the risks at all levels. The results show that the error of the optimized ANFIS was reduced by 66%, and the early warning error was reduced by 57%. This study aimed to provide implementation methods and tools for coal mine risk management and control, and data collected has reference significance for other enterprises. [ABSTRACT FROM AUTHOR]

In this paper, the factors influencing the passenger flow of rail transit stations in Shanghai of China are studied by using the entropy weight-grey correlation model. The model assumptions and the corresponding variables are proposed, including traffic accessibility, built environment, regional characteristics of the district to which the rail transit station belongs, conditions of the station and spatial location, which affect the passenger flow of rail transit stations. Based on the assumptions and the variables, the entropy weight-grey correlation model for analyzing the passenger flow of urban rail transit stations is presented. By collecting the data of passenger flow of rail transit stations and corresponding influencing factors in Shanghai, the results of the entropy weight-grey correlation model are obtained. It is shown that the influencing factors, such as the distances from the rail transit station to the adjacent third-class hospital and the adjacent large commercial plazas, district committees, parking areas and the transaction price of important plots, and the gross output value of the tertiary industry, have significant impacts on the passenger flow of a subway station. Finally, some suggestions are proposed for the local governments to formulate improved policies for rail transit development. The conclusions can provide a reference for the development of rail transit in other large cities and countries. [ABSTRACT FROM AUTHOR]

The first case of Corona Virus Disease 2019 (COVID-19) was reported in Wuhan, China in December 2019. Since then, COVID-19 has quickly spread out to all provinces in China and over 150 countries or territories in the world. With the first level response to public health emergencies (FLRPHE) launched over the country, the outbreak of COVID-19 in China is achieving under control in China. We develop a mathematical model based on the epidemiology of COVID-19, incorporating the isolation of healthy people, confirmed cases and contact tracing measures. We calculate the basic reproduction numbers 2.5 in China (excluding Hubei province) and 2.9 in Hubei province with the initial time on January 30 which shows the severe infectivity of COVID-19, and verify that the current isolation method effectively contains the transmission of COVID-19. Under the isolation of healthy people, confirmed cases and contact tracing measures, we find a noteworthy phenomenon that is the second epidemic of COVID-19 and estimate the peak time and value and the cumulative number of cases. Simulations show that the contact tracing measures can efficiently contain the transmission of the second epidemic of COVID-19. With the isolation of all susceptible people or all infectious people or both, there is no second epidemic of COVID-19. Furthermore, resumption of work and study can increase the transmission risk of the second epidemic of COVID-19. [ABSTRACT FROM AUTHOR]

A groundwater drainage system comprising five drainage points and seven submersible pumps was designed to relieve the threat of flooding by 2.9 million m3 of mine water and a dynamic water supply volume of 718 m3/h in the Guhanshan Coal Mine. The key aim of the design was to ensure safe production. A mathematical model of the optimal scheduling of the water drainage system was constructed and solved using an improved particle swarm optimization algorithm to minimize long-term energy consumption. The algorithm had high convergence accuracy, and quickly and efficiently realized the optimal configuration of the pumping volume of the mine drainage system. When the Wucun mine was full of water, the flow of submersible pumps no. 1 (or 2) and nos. 3, 4, 5, and 6 were set to 58, 150, 150, 180, and 180 m3/h, respectively, and the energy consumption of the system was minimal. When the water level in the Wucun mine was less than − 40 m, the lowest energy consumption was found when the flow rates of pumps nos. 3, 4, 5, 6, and 7 were, respectively set to 150, 150, 180, 180, and 58 m3/h. This overcame the shortcomings of adjusting the submersible pump flow based only on past experience and should be useful for many future mine water drainage projects. [ABSTRACT FROM AUTHOR]

Traditional steganography methods are usually designed on a lossless channel; thus, messages are often not extracted correctly from an image transmitted over a lossy channel that includes attacks such as scaling. To address this issue, in recent years, the field of robust steganography has emerged. In this paper, the process of image scaling by interpolation is first observed and serves as the basis for proposing the idea of inverse interpolation. Subsequently, the idea of constructing an inverse interpolation equation set is proposed to solve the problem of intersectional blocks during the inverse interpolation process. Then, the scaling factor’s valid range of inverse interpolation is analyzed. Next, the inverse interpolation is successfully applied in robust image steganography. A method that combines antiscaling and antidetection is proposed. Afterward, actual tests on the top 9 mobile phone brands with 28 models and 2 social communication apps that are currently popular in China are done. The scaling factor’s valid range of the proposed method is verified to match the actual lossy channel. The experimental results show that the proposed method achieves a reliable extraction of embedded messages for common interpolation scaling attacks while maintaining high statistical detection resistance. [ABSTRACT FROM AUTHOR]

We conducted a comparative study of the COVID-19 epidemic in three different settings: mainland China, the Guangdong province of China and South Korea, by formulating two disease transmission dynamics models which incorporate epidemic characteristics and setting-specific interventions, and fitting the models to multi-source data to identify initial and effective reproduction numbers and evaluate effectiveness of interventions. We estimated the initial basic reproduction number for South Korea, the Guangdong province and mainland China as 2.6 (95% confidence interval (CI): (2.5, 2.7)), 3.0 (95%CI: (2.6, 3.3)) and 3.8 (95%CI: (3.5,4.2)), respectively, given a serial interval with mean of 5 days with standard deviation of 3 days. We found that the effective reproduction number for the Guangdong province and mainland China has fallen below the threshold 1 since February 8th and 18th respectively, while the effective reproduction number for South Korea remains high until March 2nd Moreover our model-based analysis shows that the COVID-19 epidemics in South Korean is almost under control with the cumulative confirmed cases tending to be stable as of April 14th. Through sensitivity analysis, we show that a coherent and integrated approach with stringent public health interventions is the key to the success of containing the epidemic in China and especially its provinces outside its epicenter. In comparison, we find that the extremely high detection rate is the key factor determining the success in controlling the COVID-19 epidemics in South Korea. The experience of outbreak control in mainland China and South Korea should be a guiding reference for the rest of the world. • We conducted a comparative study of the COVID-19 epidemic in three different settings: mainland China, the Guangdong province of China and South Korea. • We estimated the initial basic reproduction number for South Korea, the Guangdong province and mainland China as 2.6 (95% confidence interval (CI): (2.5, 2.7)), 3.0 (95%CI: (2.6, 3.3)) and 3.8 (95%CI: (3.5,4.2)). • A coherent and integrated approach with stringent public health interventions is the key to the success of containing the epidemic in China and especially its provinces outside its epicenter. • The extremely high detection rate of infected individuals is the key to the success in controlling the epidemics in South Korea. [ABSTRACT FROM AUTHOR]

Data-driven control without using mathematical models is a promising research direction for urban traffic control due to the massive amounts of traffic data generated every day. This article proposes a novel distributed model-free adaptive predictive control (D-MFAPC) approach for multiregion urban traffic networks. More specifically, the traffic dynamics of the network regions are first transformed into MFAPC data models, and then, the derived MFAPC data models instead of mathematical traffic models serve as the prediction models in the distributed control design. The formulated control problem is finally solved with an alternating direction method of multipliers (ADMM)-based approach. The simulation results for the traffic network of Linfen, Shanxi, China, show the feasibility and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Impedance modeling of a permanent magnet synchronous generator (PMSG)-based wind energy conversion system (WECS) usually ignores the machine-side dynamics, instead, the machine-side system is simplified as a constant power source, while merely keeping the detailed grid-side converter model. This simplification is mainly based upon the intuition that the dc-bus capacitor is large enough so that the machine- and grid-side dynamics can be decoupled. However, the simplification probably does not hold in practice since there is always a tendency to minimize the capacitor size to achieve a smaller package for installation. Therefore, the machine-side system should not be ignored, otherwise maybe leading to error for stability analysis. To address this issue, this paper developed a complete ac-side impedance model of the PMSG-based WECS. Then, impact factors about the coupling characteristics between machine- and grid-side systems of the PMSG-based WECS are discussed. Finally, a case study of sub/super synchronous oscillation is carried out on a practical offshore wind farm integrated with a modular multilevel converter based high-voltage dc (MMC-HVDC) transmission system in China. The results show that ignoring the machine-side system would lead to an optimistic stability judgement, which confirms the necessity of the complete model of PMSG-based WECS. Furthermore, the system can be stabilized by either changing the couplings between machine- and grid-side systems of PMSG-based WECS or implementing active damping in the wind farm side MMC. [ABSTRACT FROM AUTHOR]

Currently, the entire world is fighting against the Corona Virus (COVID-19). As of now, more than thirty lacs of people all over the world were died due to the COVID-19 till April 2021. A recent study conducted by China suggests that Chest CT and X-ray images can be used as a preliminary test for COVID detection. This paper propose a transfer learning-based mathematical COVID detection model, which integrates a pre-trained model with the Random Forest Tree (RFT) classifier. As the available COVID dataset is noisy and imbalanced so Principal Component Analysis (PCA) and Generative Adversarial Networks (GANs) is used to extract most prominent features and balance the dataset respectively. The Bayesian Cross-Entropy Loss function is used to penalize the false detection differently according to the class sensitivity (i.e., COVID patient should not be classified as Normal or Pneumonia class). Due to the small dataset, a pre-trained model like VGGNet-19, ResNet50 and Inception_ResNet_V2 were chosen to extract features and then trained them over the RFT for the classification task. The experiment results showed that ResNet50 gives the maximum accuracy of 99.51%, 98.21%, and 97.2% for training, validation, and testing phases, respectively, and none of the COVID Chest X-ray images were classified as Normal or Pneumonia classes. [ABSTRACT FROM AUTHOR]

Copyright of Environmental Science & Technology (10036504) is the property of Editorial Board of Environmental Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A 2-D beam scanning subsystem provides an effective means for a real-aperture microwave radiometer (MWR) to observe atmospheric events from a geostationary Earth orbit (GEO). However, it is practically difficult to achieve a high-quality and high-efficiency beam coverage in the specified regional target scene under different working modes of the MWR and their corresponding observation constraints. In this study, a scan planning model used by China's future GEO MWR is derived. This model is useful for achieving the optimal balance between the scan quality and time. Additionally, we establish a framework to compute the solution of our model. In the framework, we first present nominal-grid-based algorithms to numerically calculate the model constraints and objective function, and then introduce a multilevel neighbor search strategy to find the optimized solution. The significance of the framework lies in its capability to balance the tradeoffs between time consumption and global optimality. Preliminary test results demonstrate the validity and feasibility of the proposed model. The methods and results presented in this study are expected to provide constructive insights into the scanning scheme design of China's future GEO MWR and benefit the development of other similar 2-D beam scanning systems. [ABSTRACT FROM AUTHOR]

The ongoing coronavirus disease-2019 (COVID-19) pandemic caused by severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) has serious influences on human health and economy. The available clinical data suggest that patients infected by SARS-CoV-2 have the possibility of simultaneous infection of bacteria. In this study, we present a data-driven mathematical model for coinfection of SARS-CoV-2 and bacteria to investigate the dynamics of COVID-19 progress. Specifically, based on the statistical analysis of different clinical data from China and some other countries, a system model with ordinary differential equations (ODEs) in four variables, i.e. SARS-CoV-2, bacteria, neutrophils and lymphocytes, is established. We further validate our model through theoretical analysis and fitting of different clinical data. Moreover, through numerical simulations and bifurcation analysis, we find that bacterial infection and immune-related parameters in certain ranges lead to the system transitions among three steady states, i.e. mild, severe and death. We also analyzed the influence of the time it takes for patients to switch from a high-risk area to a low-risk area on the recovery time. These results reveal that the coinfection of viruses and bacteria can explain the changes in neutrophils and lymphocytes, and that initial bacterial infection and immune-related parameters have great influences on the severity degree and mortality in COVID-19 patients. Together, our model and quantitative analysis suggest that preventing bacterial infection and enhancing immune ability during the early phase of infections could be a potential treatment option for high-risk COVID-19 patients. [ABSTRACT FROM AUTHOR]

The four-stage fast linear transformer driver (FLTD) with sharing cavity shell, gas insulation, and pluggable main bricks is the fundamental building block of the next-generation China Z-pinch driver CZ34. This contribution presents the self-consistent electromagnetic (EM) field distributions of the four-stage FLTD using the field-circuit coupled time-domain finite integration technique. Principles and methods on establishing the 3-D EM numerical model are discussed. The first analysis on equivalent inductances of the 92 main discharging bricks in the induction cavity and bricks’ EM characteristics is implemented. Simulated and experimental results demonstrate good consistency in the electrical performance of the four-stage FLTD with sharing cavity shell. Comparisons between the sharing cavity shell and independent cavity shell structures are performed in terms of load current and voltage and EM field distributions. Thus, applicability of the newly developed sharing cavity configuration is confirmed. The EM-interference (EMI) inside the induction cavity of the two kinds of FLTDs is also expounded and compared for the first time. This article offers a novel viewpoint on the related problems and supports the subsequent research activity and efforts to improve the performance of FLTD and Z-pinch machine. [ABSTRACT FROM AUTHOR]

Precipitation plays a critical role in the water and energy cycle. The systematic and random errors of precipitation are usually estimated using the additive model. However, various studies have shown that the multiplicative model is more suitable to describe the errors of precipitation than the additive model. This study integrates the multiplicative model with the Willmott–AghaKouchak method to characterize the errors of four selected representative satellite precipitation products in China. Zero precipitation is addressed by adding a tiny increment, which is determined by a sensitivity analysis, enabling the examination of missed precipitation and false alarms compared with the traditional strategy that only considers hit events. The results show that the systematic errors based on the additive model are too sensitive to heavy precipitation, resulting in problems, such as unexpected fluctuations, regional biases, unsteady performance, and reverse seasonal and elevational trends in some cases. In contrast, the multiplicative model resolves these problems through balancing the contributions of light and heavy precipitation and is recommended for systematic and random error estimation. [ABSTRACT FROM AUTHOR]

Time delays are inevitable in the power systems with wide-area control signals, which may compromise the control pe-rformance and thus jeopardize the stability of the power systems. To analyze the impacts of system parameters on critical oscillation modes of a time-delayed power system (TDPS), a new method for eigenvalue trajectory tracking of TDPS is proposed in this paper based on the continuation theory of invariant subspaces. When small changes are imposed on system parameters, such as parameters of wide-area damping controllers (WADCs) and time delays, the invariant subspaces are continuously predicted and corrected, followed by the eigenvalues and eigenvectors. In the process, the predictor and corrector are computed by solving linear equations sparsely and in blocks, which is highly scalable and computationally efficient for large-scale power system applications. The 16-generator 68-bus test system and two real-world power grids in China are used to test and demonstrate the proposed method. The results show that the proposed method can accurately and efficiently track eigenvalue trajectories for TDPS, especially for large-scale power grids. In addition, the sensitivities of eigenvalues and eigenvectors with respect to WADCs’ parameters and time delays are obtained as by-products of the approach. [ABSTRACT FROM AUTHOR]

The aim of this contribution is the first numerical investigation on the electromagnetic (EM), thermal, and mechanical coupled fields of a newly developed single-stage fast linear transformer driver (FLTD) with 24-separate columns in the China Z-pinch driver CZ34. Considering the mutual influences of the EM, thermal, and mechanical fields during a pulsed current discharging process of the FLTD, the proposed numerical model is calculated using the field-circuit coupled time-domain finite integration technique (TD-FIT). By making reference to Tonti’s classification diagram, integral form state variables in the transient thermal field and mechanical field can be defined similar to those of the EM field. With appropriate time integration schemes, governing equations of different physical fields can be transformed to corresponding algebraic time-updating equations. The two-way interplays of the EM, thermal, and mechanical fields are performed with predefined coupling terms and time steps. The simulated results indicate that during one current discharging process, the temperature rise is less than 1 K and the maximum deformation generated by the Lorentz force is less than 0.1 mm. [ABSTRACT FROM AUTHOR]

• We developed a mobility network model for spatial epidemics. • The second outbreak occurred approximately on March 1, 2020. • By March 15, 2020, the cumulative cases increased by 70.6% without a travel ban. • The increase of cumulative cases is mainly caused by intra-province travel. • The strict travel ban successfully prevented a severe secondary wave in China. The ongoing COVID-19 pandemic expanded its geographic distribution through the movement of humans and caused subsequent local outbreaks. Hence, it is essential to investigate how human mobility and travel ban affect the transmission and spatial spread while minimizing the impact on social activities and national economics. We developed a mobility network model for spatial epidemics, explicitly taking into account time-varying inter-province and inner-province population flows, spatial heterogeneity in terms of disease transmission, as well as the impact of media reports. The model is applied to study the epidemic of the dynamic network of 30 provinces of mainland China. The model was calibrated using the publicly available incidence and movement data. We estimated that the second outbreak occurred approximately on February 24, 2020, and the cumulative number of cases as of March 15, 2020, increased by 290.1% (95% CI: (255.3%, 324.9%)) without a travel ban in mainland China (excluding Hubei and Tibet). We found that intra-province travel contributes more to the increase of cumulative number of cases than inter-province travel. Our quantitative and qualitative research results suggest that the strict travel ban has successfully prevented a severe secondary outbreak in mainland China, which provides solutions for many countries and regions experiencing secondary outbreaks of COVID-19. [ABSTRACT FROM AUTHOR]

With the increasing development of AC/DC hybrid power systems, local synchronous generators in receiving-end grids are being replaced by high-voltage direct current (HVDC) power. The risk of short-term voltage instability exists because of the decline in dynamic reactive power resources from generators, the presence of high-proportioned induction motors and the demand for vast reactive power of HVDC under AC faults. In this situation, unit commitment (UC) should take short-term voltage stability into account. Hence, crucial generators can be retained to provide sufficient dynamic reactive power. This paper proposes a UC model incorporating short-term voltage stability constraints (SVSCUC). Furthermore, a decomposition-based solution approach is presented, which involves an alternate iterative solving of UC and differential-algebraic equations (DAEs). Time-domain simulation (TDS) is utilized to quantify the stability with an indicator. Linear stable cuts are formulated through trajectory sensitivity analysis and added into the UC. The UC is decomposed into a master problem based on mixed-integer linear programming (MILP) and subproblems. The SVSCUC is illustrated using benchmark systems and a real system in eastern China. The results show the effectiveness and efficiency of the proposed methods. Violations of short-term voltage stability for credible contingencies are eliminated under the commitment of SVSCUC. [ABSTRACT FROM AUTHOR]

Incoherent scatter radar (ISR), as one of the most powerful ionospheric detection methods on the ground, can obtain a variety of important ionospheric parameters with high spatiotemporal resolution over the entire ionosphere. A high-power large-aperture phased array (PA) ISR, named Sanya ISR (SYISR), is under construction at Sanya (18.3°N, 109.6°E), China. Two remote receive-only arrays of SYISR will be built in the future to form a tristatic ISR system, which will be the only multistatic ISR in a low-latitude region. Estimating the signal-to-noise ratio (SNR) is the key task for analyzing the detection accuracy and evaluating the radar performance. In this article, the SNR of the SYISR tristatic system is simulated for the first time using a suitable PA bistatic radar equation. The parameters of the designed SYISR tristatic system are used in the simulation. Subsequently, the SNR spatial variability of the bistatic PA radar and bistatic equivalent parabolic dish (EPD) radar is analyzed and compared. The results show that the radar system constants, effective scattering volume, and spatial variable terms are the three different sources of factors affecting the SNR. They jointly determine the spatial distribution characteristics of the SNR. Moreover, the PA SNR is significantly different from the EPD SNR numerically and morphologically. The PA SNR is weaker than the EPD SNR in the whole observational space. In the horizontal direction, the PA SNR has a single-peak structure, while the EPD SNR has a double-peak structure. The root cause of these differences is that the beamwidth of a PA changes with the beam directions, while that of the EPD is fixed. This research provides a theoretical basis for the design of tristatic PA ISR in hardware optimization and error analysis, which will be shown in another article. [ABSTRACT FROM AUTHOR]

Recently, frequency coupling oscillation events, such as harmonic oscillations, subsynchronous and supersynchronous oscillations, driven by multiple converters with different switching frequencies have brought new challenges of ac/dc grid modeling, despite the traditional one of improving the accuracy and efficiency. There is an urgent requirement of practical engineering projects to produce a modeling method that can produce instantaneous and harmonic phasor waveforms simultaneously, dedicated to harmonic interaction analysis of large-scale ac/dc grids. To realize the above-mentioned targets, the harmonic phasor domain (HPD) modeling of power electronic based dc grids is proposed. The HPD modeling is then combined and coordinated with electromagnetic transient (EMT) based ac-grid models based on the proposed HPD transmission line model (HPD-TLM). The overall HPD cosimulation is realized by the EMT-based ac-grid models, HPD-based dc-grid models, and HPD-TLM, which is governed by the decoupled and coordinated time sequences. The performance (efficiency and accuracy of instantaneous and harmonic phasor waveforms) for the HPD cosimulations is validated on practical large-scale voltage source converter modular multilevel converter based ac/dc grids in China. [ABSTRACT FROM AUTHOR]

Xinjiang has been one of the high incidence areas of pulmonary tuberculosis (PTB) in China. Besides being infected by direct contacting with active PTB individuals (direct infection), the susceptible would be infected because of the exposure to the environment contaminated by Mycobacterium tuberculosis (indirect infection). Active PTB individuals include not only the smear-positive PTB (PTB+) but also the smear-negative PTB (PTB-) who are infectious due to their ability to release tiny Mycobacterium tuberculosis particles even in the absence of visible Mycobacterium tuberculosis in sputum. By taking account of direct/indirect infection and the difference between PTB+ and PTB- individuals in transmission capability, a periodic dynamical PTB transmission model is proposed. The model is fitted to the newly monthly PTB+ and PTB- cases in Xinjiang from 2008 to 2017 by Markov Chain Monte Carlo algorithm. Moreover, global sensitivity analysis is constructed to address the uncertainty of some key parameters by using Latin hypercube sampling and partial rank correlation coefficient methods. Basic reproduction number R 0 for PTB transmission in Xinjiang is estimated to be 2.447 (95% CrI:(1.203, 3.844)), indicating that PTB has been prevalent in Xinjiang over the study period. Our results suggest that reducing the direct/indirect transmission rates, early screening, isolating and treating the latent, PTB+ and PTB- individuals, and enhancing the clearance of Mycobacterium tuberculosis in the environment could more effectively control PTB transmission in Xinjiang. The model fits the reported PTB data well and achieves acceptable prediction accuracy. We believe that our model can provide heuristic support for controlling PTB transmission in Xinjiang., Competing Interests: Declaration of competing interest The authors declare that they have no conflict of interest., (Copyright © 2024. Published by Elsevier B.V.)

Background: Despite recent advances through the development pipeline, how novel tuberculosis (TB) vaccines might affect rifampicin-resistant and multidrug-resistant tuberculosis (RR/MDR-TB) is unknown. We investigated the epidemiologic impact, cost-effectiveness, and budget impact of hypothetical novel prophylactic prevention of disease TB vaccines on RR/MDR-TB in China and India.Methods: We constructed a deterministic, compartmental, age-, drug-resistance- and treatment history-stratified dynamic transmission model of tuberculosis. We introduced novel vaccines from 2027, with post- (PSI) or both pre- and post-infection (P&PI) efficacy, conferring 10 years of protection, with 50% efficacy. We measured vaccine cost-effectiveness over 2027-2050 as USD/DALY averted-against 1-times GDP/capita, and two healthcare opportunity cost-based (HCOC), thresholds. We carried out scenario analyses.Results: By 2050, the P&PI vaccine reduced RR/MDR-TB incidence rate by 71% (UI: 69-72) and 72% (UI: 70-74), and the PSI vaccine by 31% (UI: 30-32) and 44% (UI: 42-47) in China and India, respectively. In India, we found both USD 10 P&PI and PSI vaccines cost-effective at the 1-times GDP and upper HCOC thresholds and P&PI vaccines cost-effective at the lower HCOC threshold. In China, both vaccines were cost-effective at the 1-times GDP threshold. P&PI vaccine remained cost-effective at the lower HCOC threshold with 49% probability and PSI vaccines at the upper HCOC threshold with 21% probability. The P&PI vaccine was predicted to avert 0.9 million (UI: 0.8-1.1) and 1.1 million (UI: 0.9-1.4) second-line therapy regimens in China and India between 2027 and 2050, respectively.Conclusions: Novel TB vaccination is likely to substantially reduce the future burden of RR/MDR-TB, while averting the need for second-line therapy. Vaccination may be cost-effective depending on vaccine characteristics and setting. [ABSTRACT FROM AUTHOR]

Background: Due to an increase in mosquito habitats and the lack facilities to carry out basic mosquito control, construction sites in China are more likely to experience secondary dengue fever infection after importation of an initial infection, which may then increase the number of infections in the neighboring communities and the chance of community transmission. The aim of this study was to investigate how to effectively reduce the transmission of dengue fever at construction sites and the neighboring communities. Methods: The Susceptible-Exposed-Infectious/Asymptomatic-Recovered (SEIAR) model of human and SEI model of mosquitoes were developed to estimate the transmission of dengue virus between humans and mosquitoes within the construction site and within a neighboring community, as well between each of these. With the calibrated model, we further estimated the effectiveness of different intervention scenarios targeting at reducing the transmissibility at different locations (i.e. construction sites and community) with the total attack rate (TAR) and the duration of the outbreak (DO). Results: A total of 102 construction site-related and 131 community-related cases of dengue fever were reported in our area of study. Without intervention, the number of cases related to the construction site and the community rose to 156 (TAR: 31.25%) and 10,796 (TAR: 21.59%), respectively. When the transmission route from mosquitoes to humans in the community was cut off, the number of community cases decreased to a minimum of 33 compared with other simulated scenarios (TAR: 0.068%, DO: 60 days). If the transmission route from infectious mosquitoes in the community and that from the construction site to susceptible people on the site were cut off at the same time, the number of cases on the construction site dropped to a minimum of 74 (TAR: 14.88%, DO: 66 days). Conclusions: To control the outbreak of dengue fever effectively on both the construction site and in the community, interventions needed to be made both within the community and from the community to the construction site. If interventions only took place within the construction site, the number of cases on the construction site would not be reduced. Also, interventions implemented only within the construction site or between the construction site and the community would not lead to a reduction in the number of cases in the community. [ABSTRACT FROM AUTHOR]

Objective: To estimate the potential effects of an intense sex work crackdown on syphilis transmission in Guangdong Province, China.Methods: We developed a deterministic compartmental model of syphilis transmission among female sex workers (FSW) and their male clients in Guangdong Province, China. We based model assumptions on census data and scientific literature, and we fitted the model to sentinel surveillance estimates of syphilis prevalence (positive results in both treponemal and non-treponemal tests) among FSW between 2009 and 2013. We estimated the impact of an intense sex work crackdown in 2014 by comparing the number of new syphilis infections between 2014 and 2020 in crackdown versus basecase (no crackdown) scenarios. In modelling scenarios, we examined main crackdown mechanisms of impact, including changed number of FSW engaging in sex work, reduction of weekly transactions, condom usage rate and syphilis diagnosis rate.Results: In the basecase, predicted syphilis prevalence in FSW decreased from 2% in 2014 to 0.4% in 2020. In crackdown scenarios, syphilis incidence was predicted to transiently decrease and then to rebound relative to basecase levels a few years later. Shorter crackdowns led to higher, faster rebounds.Conclusions: Short-term intense crackdowns may exacerbate syphilis transmission among FSW and further marginalise an already vulnerable group. This study provides a quantitative, infection-related basis for changing sex work policies to reduce harms. [ABSTRACT FROM AUTHOR]

Rationale: Most U.S. residents who develop tuberculosis (TB) were born abroad, and U.S. TB incidence is increasingly driven by infection risks in other countries.Objectives: To estimate the potential impact of effective global TB control on health and economic outcomes in the United States.Methods: We estimated outcomes using linked mathematical models of TB epidemiology in the United States and migrants' birth countries. A base-case scenario extrapolated country-specific TB incidence trends. We compared this with scenarios in which countries achieve 90% TB incidence reductions between 2015 and 2035, as targeted by the World Health Organization's End TB Strategy ("effective global TB control"). We also considered pessimistic scenarios of flat TB incidence trends in individual countries.Measurements and Main Results: We estimated TB cases, deaths, and costs and the total economic burden of TB in the United States. Compared with the base-case scenario, effective global TB control would avert 40,000 (95% uncertainty interval, 29,000-55,000) TB cases in the United States in 2020-2035. TB incidence rates in 2035 would be 43% (95% uncertainty interval, 34-54%) lower than in the base-case scenario, and 49% (95% uncertainty interval, 44-55%) lower than in 2020. Summed over 2020-2035, this represents 0.8 billion dollars (95% uncertainty interval, 0.6-1.0 billion dollars) in averted healthcare costs and $2.5 billion dollars (95% uncertainty interval, 1.7-3.6 billion dollars) in productivity gains. The total U.S. economic burden of TB (including the value of averted TB deaths) would be 21% (95% uncertainty interval, 16-28%) lower (18 billion dollars [95% uncertainty level, 8-32 billion dollars]).Conclusions: In addition to producing major health benefits for high-burden countries, strengthened efforts to achieve effective global TB control could produce substantial health and economic benefits for the United States. [ABSTRACT FROM AUTHOR]

Accurate forecast of citywide crowd flows on flexible region partition benefits urban planning, traffic management, and public safety. Previous research either fails to capture the complex spatiotemporal dependencies of crowd flows or is restricted on grid region partition that loses semantic context. In this paper, we propose DeepFlowFlex, a graph-based model to jointly predict inflows and outflows for each region of arbitrary shape and size in a city. Analysis on cellular datasets covering 2.4 million users in China reveals dependencies and distinctive patterns of crowd flows in not only the conventional space and time domains, but also the speed domain, due to the diverse transportation modes in the mobility data. DeepFlowFlex explicitly groups crowd flows with respect to speed and time, and combines graph convolutional long short-term memory networks and graph convolutional neural networks to extract complex spatiotemporal dependencies, especially long-term and long-distance inter-region dependencies. Evaluations on two big cellular datasets and public GPS trace datasets show that DeepFlowFlex outperforms the state-of-the-art deep learning and big-data-based methods on both grid and non-grid city map partition. [ABSTRACT FROM AUTHOR]

Objective: The rapid expansion of the recreational drug market becomes a global health concern. It is worrying that the bacterial and viral infection epidemics linking to drug use may worsen accordingly. This study aimed to estimate the impacts of changing trend and behaviours of using heroin only, synthetic drug (SD) only and polydrug (using SD and heroin concurrently) on HIV, hepatitis C virus (HCV) and syphilis epidemics among people who use drugs in China by 2035.Methods: We constructed a compartmental model to estimate HIV, HCV and syphilis epidemics in the dynamic drug-use trend by three scenarios: SD-only use, heroin-only use and polydrug use based on Monte Carlo simulations. The parameters for the model were collected from a comprehensive literature search.Results: Our model estimated that polydrug use led to the highest HIV and HCV prevalence among three drug-use patterns. The prevalences were projected to increase from 10.9% (95% CI 10.2% to 11.5%) and 61.7% (95% CI 59.4% to 62.5%) in 2005 to 19.0% (95% CI 17.3% to 20.7%) and 69.1% (95% CI 67.3% to 69.5%), respectively, in 2035 among people using polydrug. Similarly, HIV and HCV prevalence in the SD-only group were projected to increase from 0.4% (95% CI 0.3% to 0.4%) and 19.5% (95% CI 19.4% to 21.7%) to 1.8% (95% CI 1.4 to 2.1%) and 33.7% (95% CI 33.2% to 34.9%) in 2005-2035. Conversely, HIV prevalence in the heroin-only group was projected to decrease from 8.0% (95% CI 7.6% to 8.1%) to 2.2% (95% CI 2.0% to 2.3%) in 2005-2035. Syphilis prevalence was estimated to remain unchanged in all population groups within this time frame. It was projected that the proportion of HIV transmitted by sexual transmission will increase compared with unsafe injection transmission in all people who use drugs from 2005 to 2035.Conclusion: Our modelling suggests that polydrug use is projected to lead to the highest HIV and HCV disease burden by 2035, and the proportion of HIV transmitted by sexual transmission will increase. Current HIV intervention among people using heroin seems effective according to our estimation. [ABSTRACT FROM AUTHOR]

An inverse mapping table (IMT) method is proposed in this article to retrieve the raindrop size distribution (RSD) parameters from X-band polarimetric weather radar data. In the IMT method, a forward mapping database from three parameters of a gamma-type RSD to polarimetric radar variables is first built based on the scattering simulations under ideal atmospheric conditions, and then an inverse mapping database is derived. In particular, given a fixed shape parameter ($\mu $) of RSD, the intersection of horizontal reflectivity ($Z_{\text {H}}$) and differential reflectivity ($Z_{\text {DR}}$) contour lines is first obtained in the domain of total number concentration ($N_{\text {T}}$) and median volume diameter (MVD) $D_{0}$ ; and the inverse mapping relationship between $Z_{H}$ and $Z_{\text {DR}}$ to $N_{T}$ and $D_{0}$ at a fixed $\mu $ value is derived to form a single layer of IMT. Then, the monotonic relationship between $\mu $ and the specific differential propagation phase shift ($K_{\text {DP}}$) or backscatter differential phase ($\delta _{\text {CO}}$) can aid in determining $\mu $ and a single layer of IMT. Thus, the inverse mapping database from polarimetric observations to the three gamma-type RSD parameters $\mu $ , $N_{\text {T}}$ , and $D_{0}$ can be established. Demonstration studies during a convective rainfall event and a large-scale rainfall event which occurred in northeastern China are carried out to examine the performance of this IMT method compared to a constrained-gamma (C-G) method that uses empirical relations between RSD parameters. The results show that the IMT method has a better performance in the convective case and similar performance in the large-scale continuous rainfall case. [ABSTRACT FROM AUTHOR]

In this paper, our objective is to propose a stability concept within the graph model for conflict resolution (GMCR) that does not require knowledge about preferences of other decision makers (DMs) in the conflict and is flexible to analyze the conflict with variable horizon. For that we propose the use of the maximin decision rule within the GMCR. More specifically, we consider a GMCR with two DMs and introduce the concept of Maximinh stability with horizon h for a given DM. The Maximinh stability concept was inspired by the notion of limited-move stability with horizon h present in the GMCR literature and it is adequate for modeling cautious DMs in conflicts where they have no knowledge about the other DM’s preferences. We establish what is the relationship among the Maximinhstabilities for different horizons and the relationship among Maximinh stability and other GMCR stability concepts. Finally, we present an application to illustrate the proposed stability concept, namely, a neuroscience technological selection conflict in China. [ABSTRACT FROM AUTHOR]

Human adenovirus infection is a common cause of upper and lower respiratory illness and easily breaks out in schools and the army. In an adenovirus epidemic, a large number of samples would be collected for laboratory diagnosis, and it is urgent to optimize the current sampling strategy. We researched the application of laboratory detection in the adenovirus epidemic and optimized the range of laboratory pathogen detection in the adenovirus epidemic by summarizing previous theoretical achievements, research reports, and experts' opinions and by using mathematical model tools. Under certain assumptions, a susceptible-infectious-quarantined-recovered (SIQR) model was established to describe the adenovirus epidemic and optimize the range of laboratory pathogen detection. Some standards and implementation rules suggest that when the number of cases is less than 10 or 20, all patients should be sampled for laboratory examination, and when the number of cases is more than 10 or 20, at least 10 or 20 samples should be collected. In practice, the sampling range can be appropriately expanded. A total of 21 studies were analyzed, and the sampling rate of adenovirus infection was 31% (95%CI: 24%~38%). The mathematical model suggested that the screening of asymptomatic people in the latent stage can slow the spreading of the epidemic, but the detection range will be too large. These findings may be helpful for policymaking during an adenovirus epidemic and to avoid proceeding with laboratory testing blindly. Furthermore, it may also provide some guidance for optimizing the sampling strategy of other diseases, especially for respiratory tract infections. [ABSTRACT FROM AUTHOR]

Regional wind power prediction (WPP) is conducive to achieving scientific dispatch of the power system as well as improving its reliability. Data mining based on a large number of samples is an effective way to improve the accuracy of WPP. A new regional power forecasting method in the context of data mining is proposed in the article. First, a previously described regional WPP method, single feature similarity matching (SFSM) method, is analyzed and a new multifeature similarity matching (MFSM) method is proposed. Second, the optimization and analysis processes of four key parameters in the MFSM method are proposed and the impact of each key parameter on prediction error and the applicability of the method under different regional scales is analyzed. Finally, the new method and the optimization and analysis processes are verified by wind farm clusters, composed of 52 wind farms in northeast China, and the new method is compared with the conventional method, such as additive method, statistical up-scaling method, and the SFSM method. The results show that the improved MFSM method is superior to the conventional prediction method, whereby the root mean square error (RMSE) of 0 to 2 h is reduced by 3.65% and the RMSE of 0 to 4 h is reduced by 1.56%. The new method has been proved to be an effective WPP method for wind farm clusters and has potential industrial application prospects. [ABSTRACT FROM AUTHOR]

One of biggest obstacles for the development of terahertz (THz) science and technology is the lack of the THz sources, especially, when the requirement of the power reaches to kilowatts. Among all the existing sources, the gyrotron is the most promising one which can generate high-power THz radiation. Recently, a THz detection system is under development in the THz Research Center, University of Electronic Science and Technology of China, Chengdu, China, which is applied for detecting radioactive material. Thus, a 0.68-THz second harmonic gyrotron has been simulated and tested in the center. In this article, we present the theoretical study on the designed gyrotron based on the linear and nonlinear theories. The influences of the different electron beam parameters on the beam–wave interaction are analyzed. The mode competition based on the time-dependent multimode nonlinear theory has also been investigated in the designed gyrotron; it is shown that the operating mode can dominate the mode competition when the gyrotron is working at the optimized operating point. The experiment results show that the output power can reach 3.25 kW with the efficiency 9.26%, at frequency 0.679 THz, when the beam voltage is 39 kV, the beam current is 0.9 A, and the magnetic field is 12.84 T. [ABSTRACT FROM AUTHOR]

• Since January 23 2020, stringent measures for controlling novel coronavirus epidemics have been enforced and strengthened in mainland China. • Most infected cases have been quarantined or put in suspected class, which had been ignored in existing models. • Results of our model show that the trend of the epidemics mainly depends on quarantined and suspected cases. • It is important to continue enhancing the quarantine and isolation strategy and improving the detection rate in mainland China. Since January 23, 2020, stringent measures for controlling the novel coronavirus epidemic have been gradually enforced and strengthened in mainland China. The detection and diagnosis have been improved, as well. However, the daily reported cases remaining at a high level make the epidemic trend prediction difficult. Since the traditional SEIR model does not evaluate the effectiveness of control strategies, a novel model in line with the current epidemic's process and control measures was proposed, utilizing multisource datasets including the cumulative number of reported, deceased, quarantined and suspected cases. Results show that the trend of the epidemic mainly depends on quarantined and suspected cases. The predicted cumulative numbers of quarantined and suspected cases nearly reached static states, and their inflection points have already been achieved, with the epidemic's peak coming soon. The estimated effective reproduction numbers using model-free and model-based methods are decreasing, as well as new infections, while newly reported cases are increasing. Most infected cases have been quarantined or put in the suspected class, which has been ignored in existing models. The uncertainty analyses reveal that the epidemic is still uncertain, and it is important to continue enhancing the quarantine and isolation strategy and improving the detection rate in mainland China. [ABSTRACT FROM AUTHOR]

Background: On December 31, 2019, the World Health Organization was alerted to the occurrence of cases of pneumonia in Wuhan, Hubei Province, China, that were caused by an unknown virus, which was later identified as a coronavirus and named the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We aimed to estimate the reproductive number of SARS-CoV-2 in the Hubei Province and evaluate the risk of an acute respiratory coronavirus disease (COVID-19) outbreak outside China by using a mathematical model and stochastic simulations. Results: We constructed a mathematical model of SARS-CoV-2 transmission dynamics, estimated the rate of transmission, and calculated the reproductive number in Hubei Province by using case-report data from January 11 to February 6, 2020. The possible number of secondary cases outside China was estimated by stochastic simulations in various scenarios of reductions in the duration to quarantine and rate of transmission. The rate of transmission was estimated as 0.8238 (95% confidence interval [CI] 0.8095–0.8382), and the basic reproductive number as 4.1192 (95% CI 4.0473–4.1912). Assuming the same rate of transmission as in Hubei Province, the possibility of no local transmission is 54.9% with a 24-h quarantine strategy, and the possibility of more than 20 local transmission cases is 7% outside of China. Conclusion: The reproductive number for SARS-CoV-2 transmission dynamics is significantly higher compared to that of the previous SARS epidemic in China. This implies that human-to-human transmission is a significant factor for contagion in Hubei Province. Results of the stochastic simulation emphasize the role of quarantine implementation, which is critical to prevent and control the SARS-CoV-2 outbreak outside China. [ABSTRACT FROM AUTHOR]

Line-commutated converter based high voltage direct current (LCC-HVDC) transmissions are widely applied in delivering large-capacity electricity in China. Multiple large-capacity LCC-HVDC transmissions strengthen dynamic coupling between AC and DC networks. Existing literature has reported some stability problems caused by dynamic interactions between AC and DC power grids, however, the mechanism behind these problems has not been totally understood and revealed. To analyze dynamic interactions between AC and DC power grids, this article presents a small-signal model to understand the external characteristics of LCC-HVDC stations based on the motion equation concept. Comparison of time-domain simulation response with the detailed switching model shows that the proposed model can hold main behaviors of concern. Dynamic interactions between AC and DC power grids are studied based on the proposed model in multi-infeed LCC-HVDC systems. Analytical results demonstrate that there exists power dynamics in receiving AC grid when sending AC grid subjects to a disturbance, and effects of converter stations’ controller parameters on power dynamics are explained by the physical relationship among state variables of the proposed model. [ABSTRACT FROM AUTHOR]

• The laboratory and full-scale prototypes of the novel solar air collector were tested. • Fuel economy achieved in tests varies from 11% to 81% depending on weather conditions. • The increased concentration ratio of about 1.4 was obtained without a sun-tracking device. • The mathematical model of the collector was validated against experimental results. • The model was used to define the rational design parameters of the full-scale prototype. The application of greenhouse technologies is rapidly expanding in China and other regions of the world with the continental climate. Such technologies are characterized by a considerable consumption of fossil fuels, especially in winter periods. Various renewable energy technologies are used to reduce the energy demand in greenhouses, including solar heating. Simpler designs of water or air solar collectors are preferred without sun-tracking devices and reduced dimensions and weight. In this work, a novel solar multi-surface air collector with double-receiver tubes, which does not require a sun-tracking device is proposed and has increased concentration ratio and sun rays convergence and reduced thermal losses. The laboratory and full-scale prototypes of the proposed novel collector were manufactured and tested in laboratory conditions during the December-January period as a part of the greenhouse with the active-passive ventilation wall and latent thermal storage, located in the Beijing Region. Results of experiments demonstrate that the solar collector increases the average temperatures of the greenhouse north wall inner surface by 7.5 °C, indoor air during the night-time by 1.8 °C and indoor soil by 1.5 °C. The novel collector provided active heat gains of 11.831 GJ during the December-January period and satisfied from 11% to 81% of the heat load. A lumped parameter mathematical model of the proposed collector was developed, and the comparison of simulation results and experimental data demonstrate its high accuracy in prediction of the collector performance. The model was used to study the influences of outdoor meteorological parameters, air velocity in the receiver tubes and their length on the performance of the collector. This data was used to determine the rational design parameters and air velocity of the full-scale collector. The model was also used to rationalize the variation of air velocity in the receiver tube during the day. [ABSTRACT FROM AUTHOR]

Gravity‐drainage‐assisted steam flooding is a new technology to improve the recovery factor after deep penetration in deep super‐heavy oil reservoirs. This study is based on a model of the 60‐H25 test well group in Block 59 in Liaohe Oilfield, China. The numerical model uses the C programming language to analyze the influence of change in the bottom water height on the drainage effect and provides a theoretical basis for physical model experiments and field production. The physical model experiment uses similar principles to describe the production characteristics at different stages in a short cycle. We combine the numerical model and the physical model experiment to analyze the production rule of the Wa59 block over a long time period. The results show that the physical model experiment and the actual production of the block reflect the productivity change law of the well group, the degree of production, and the productivity relationship of the well group over short cycles and long periods, respectively. The comparison showed that the actual production was consistent with the production model of the physical model test, and the drainage effect was verified. The study of gravity‐drainage‐assisted steam flooding provides a reliable basis for the next stage of oilfield production. [ABSTRACT FROM AUTHOR]

Background: Developing countries exhibit a high disease burden from shigellosis. Owing to the different incidences in males and females, this study aims to analyze the features involved in the transmission of shigellosis among male (subscript m) and female (subscript f) individuals using a newly developed sex-based model. Methods: The data of reported shigellosis cases were collected from the China Information System for Disease Control and Prevention in Hubei Province from 2005 to 2017. A sex-based Susceptible–Exposed–Infectious/Asymptomatic–Recovered (SEIAR) model was applied to explore the dataset, and a sex-age-based SEIAR model was applied in 2010 to explore the sex- and age-specific transmissions. Results: From 2005 to 2017, 130 770 shigellosis cases (including 73 981 male and 56 789 female cases) were reported in Hubei Province. The SEIAR model exhibited a significant fitting effect with the shigellosis data (P < 0.001). The median values of the shigellosis transmission were 2.3225 × 108 for SARmm (secondary attack rate from male to male), 2.5729 × 108 for SARmf, 2.7630 × 10-8 for SARfm, and 2.1061 × 10-8 for SARff. The top five mean values of the transmission relative rate in 2010 (where the subscript 1 was defined as male and age ≤ 5 years, 2 was male and age 6 to 59 years, 3 was male and age ≥ 60 years, 4 was female and age ≤ 5 years, 5 was female and age 6 to 59 years, and 6 was male and age ≥ 60 years) were 5.76 × 10-8 for β61, 5.32 × 10-8 for β31, 4.01 × 10-8 for β34, 7.52 × 10-9 for β62, and 6.04 × 10-9 for β64. Conclusions: The transmissibility of shigellosis differed among male and female individuals. The transmissibility between the genders was higher than that within the genders, particularly female-to-male transmission. The most important route in children (age ≤ 5 years) was transmission from the elderly (age ≥ 60 years). Therefore, the greatest interventions should be applied in females and the elderly. [ABSTRACT FROM AUTHOR]

Background: Shigellosis is one of the main diarrhea diseases in developing countries. However, the transmissibility of shigellosis remains unclear.Methods: We used the dataset of shigellosis cases reported between January 2005 and December 2017, from Hubei Province, China. A mathematical model was developed based on the natural history and the transmission mechanism of the disease. By fitting the data using the model, transmission relative rate from person to person (b) and from reservoir to person (bw), and the effective reproduction number (Reff) were estimated. To simulate the contribution of b and bw during the transmission, we performed a "knock-out" simulation in four scenarios: A) b = 0 and bw = 0; B) b = 0; C) bw = 0; D) control (no intervention).Results: A total of 130,770 shigellosis cases were reported in Hubei province, among which 13 cases were dead. The median annual incidence was 19.96 per 100,000 persons (range: 5.99 per 100,000 persons - 29.47 per 100,000 persons) with a decreased trend (trend χ2 = 25,470.27, P < 0.001). The mean values of b and bw were 0.0898 (95% confidence interval [CI]: 0.0851-0.0946) and 1.1264 × 10- 9 (95% CI: 4.1123 × 10- 10-1.8416 × 10- 9), respectively. The "knock-out" simulation showed that the number of cases simulated by scenario A was almost the same as scenario B, and scenario C was almost the same as scenario D. The mean value of Reff of shigellosis was 1.19 (95% CI: 1.13-1.25) and decreased slightly with a Linear model until it decreased to an epidemic threshold of 0.99 (95% CI: 0.65-1.34) in 2029.Conclusions: The incidence of shigellosis is still in high level. The transmissibility of the disease is low in Hubei Province. The transmission would be interrupted in the year of 2029. [ABSTRACT FROM AUTHOR]

Frequency drop due to loss of massive generation is a threat to power system frequency stability. Under-frequency load shedding (UFLS) is the principal measure to prevent successive frequency declination and blackouts. Based on traditional stage-by-stage UFLS scheme, a new continuous UFLS scheme is proposed in this paper to shed loads proportional to frequency deviation. The characteristic of the proposed scheme is analyzed with a closed-form solution of frequency dynamics. Frequency threshold and time delay are added to make the proposed scheme practical. A line-by-line scheme based on precise load control is introduced to implement the continuous scheme for systems without enough continuously controllable loads. The load shedding scale factor of the proposed scheme is tuned with an analytical method to achieve adaptability to different operating conditions. The adaptability of the proposed scheme is validated with 39-bus New England model and simplified Shandong Power Grid of China. [ABSTRACT FROM AUTHOR]