Search

In High-Temperature Gas-cooled Reactor (HTGR)s, coated fuel particles are dispersed in a graphite matrix, which forms both compact and spherical fuel elements. As for the post irradiation examination (PIE) of HTGR irradiated fuels, the electrochemical deconsolidation method in which graphite matrix is disintegrated into graphite powder is one of the feasible processing methods. The graphite matrix is composed of natural graphite, artificial graphite and glassy carbon from carbonized resin, which have different effects on electrochemical deconsolidation. In this work, synthesized graphite matrix specimens were produced by intentionally varying the resin binder content in the graphite matrix raw materials from 5% to 50%, in order to investigate the electrochemical deconsolidation mechanism of graphite matrix in HTGR fuel elements. The results showed that increasing the glassy carbon content increased the degree of chemical oxidation, with more pronounced production of graphite oxide. The driving force for graphite matrix deconsolidation is proposed to be a synergetic effect of the expansion stress around closed- and through-hole microstructure originating from oxidatively destroyed graphite layers. This work will not only help to more thoroughly understand the electrochemical deconsolidation procedure of HTGR fuels, but also contribute to the development of a feasible method to manage radioactive graphite waste.

The core components of HTR mainly consist of graphite, which is an excellent solid moderating material and structure material with good irradiation performance. However, graphite is easier to be oxidized at high temperature. It is important to improve the anti-oxidation performance of graphite substrate to enhance the safety of HTR. Anti-oxidation coating has been proved that it can effectively improve the oxidation resistance of graphite substrate. The selection of coating includes the coating materials system and the preparation techniques. In addition, attention also should be paid to the anti-oxidation mechanism. SiC based coating system is most commonly used in HTR and some other coating systems such as zirconium compounds coating, noble metal coating also can be used in nuclear. However, some coating systems are not suitable in HTR because the elements contained cannot be used in high irradiation environment. The emphasis is on the antioxidant mechanism of different coating systems. Some anti-oxidation coating techniques for graphite substrate are also reviewed in this paper, such as PC, CVD, PS and slurry. Finally, the existing problems of the oxidation resistance coating are proposed and an outlook is made for the development of the protection coating system for graphite substrate used in nuclear.

In this paper, distributed power flow controller (DPFC) constraints are analyzed. The energy balance relationship between fundamental wave and third harmonic in series and shunt-side converter is deduced. A proportional integral (PI) controller of the DPFC is constructed. The PI controller uses the voltage amplitude and phase angle injected into the system in the series side, along with the modulation ratio of the three-phase converter on the shunt side as the control variables. A multi-objective coordinated control equation is proposed, which factors the constraints of the energy balance between series and shunt side, device capacity limit, safe operation limit, fundamental component, as well as third harmonic component of the injection voltage at the series side. The equation minimizes the variance between the actual value of the control target and its given value to ensure that the DC capacitor voltage, both in the series and shunt side, is stable at target value. Simulations are conducted to verify correctness and effectiveness of the proposed control method.

BACKGROUND: Ventilation practice may be affected by economic variations, which might result in different outcomes to mechanically ventilated patients. We aimed to investigate the important effect of economic variations in patients with mechanical ventilation (MV) in China. METHODS: We carried out a national prospective multicentre cross-sectional observational study over 1 month of all patients receiving invasive MV for more than 24 hours in 20 intensive care units (ICUs), including patient characteristics, practice of MV, weaning modalities and outcomes, including probability of weaning and survival. Based on the 2012 World Bank classification of counties, patients were divided into high-income and middle-income groups according to gross domestic product per capita in their province of origin. RESULTS: Of the 483 patients enrolled, 291 (60.2%) were from high-income provinces and 192 (39.8%) were from middle-income provinces. Tidal volume, peak pressure, plateau and driving pressure were significantly lower, and the proportion of patients receiving protective ventilation (71.1% vs. 59.9%, P=0.014) was significantly higher in the high-income group than in the middle-income group. The probability of weaning within 28 days was significantly greater in the high-income group than in the middle-income group (P=0.046). Patients in the high-income group had significantly higher median numbers of ventilator-free days within 14 and 28 days than those in the middle-income group (P

This paper presents a control strategy of multi-terminal HVDC transmission system (MTDC) using voltage source converters (VSCs) based on voltage margin, a four-terminal VSC-MTDC system with two transmitting ends and two receiving ends is established and the framework and operation principles of the proposed system are described. The control strategy proposed in this paper adopts constant AC voltage and constant frequency control for the sending-end converter stations. The voltage step difference is formed by setting different voltage reference values for the receiving end converter stations. The relationship between the maximum limit of the d-axis current in the controller and the active power absorbed by the converter station is obtained by deduction. Simulation results by PSCAD/EMTDC under normal and abnormal operation conditions verifies the correctness of the control strategy and the simulation shows that the control method has good steady-state characteristics and dynamic performance.

While it is widely recognized that exposure to residential greenness is beneficial to older adults’ health and wellbeing, surprisingly few studies have examined whether the health-promoting effect of residential greenness varies between urban and rural populations in China, a rapidly urbanizing country. In addition, most previous studies on residential greenness-health associations in China have used data collected in a particular city instead of the entire country, resulting in insufficient statistical power and inadequate generalizability. This study assessed the relationship between the amount of surrounding greenness at the township-level and self-rated general health at the individual-level among older adults across the entire country of China, using the geo-referenced micro-data sample of the 2010 China population census and multilevel logistic models. Results indicated that Normalized Difference Vegetation Index (NDVI) was positively associated with self-rated health among all older people, and that the NDVI-health association was stronger in high-density urban areas relative to low-density urban areas and rural areas. Furthermore, the association was stronger for participants who were younger, higher-educated, and non-agricultural hukou holders. Our findings provide evidence in support of China’s recent endeavour to promote an eco-friendly and greener development strategy.

Einstein equivalence principle (EEP), as one of the foundations of general relativity, is a fundamental test of gravity theories. In this paper, we propose a new method to test the EEP of electromagnetic interactions through observations of black hole photon rings, which naturally extends the scale of Newtonian and post-Newtoian gravity where the EEP violation through a variable fine structure constant has been well constrained to that of stronger gravity. We start from a general form of Lagrangian that violates EEP, where a specific EEP violation model could be regarded as one of the cases of this Lagrangian. Within the geometrical optical approximation, we find that the dispersion relation of photons is modified: for photons moving in circular orbit, the dispersion relation simplifies, and behaves such that photons with different linear polarizations perceive different gravitational potentials. This makes the size of black hole photon ring depend on polarization. Further assuming that the EEP violation is small, we derive an approximate analytic expression for spherical black holes showing that the change in size of the photon ring is proportional to the violation parameters. We also discuss several cases of this analytic expression for specific models. Finally, we explore the effects of black hole rotation and derive a modified proportionality relation between the change in size of photon ring and the violation parameters. The numerical and analytic results show that the influence of black hole rotation on the constraints of EEP violation is relatively weak for small magnitude of EEP violation and small rotation speed of black holes., 16 pages, 6 figures

Background Although some evidence suggests that residential greenness may prevent hypertension in urban areas, limited attention has been paid to urban-rural disparities in the association of greenness with hypertension in rapidly urbanizing developing countries. Objectives The current study investigated the association between the amount of neighbourhood greenness and hypertension among middle and older aged people in Chinese urban and rural areas. It further examined whether PM2.5 (particulate matter ≤2.5 μm in aerodynamic diameter) concentrations, physical activity, and body mass index (BMI) mediated the association of greenness with hypertension. Methods We used data from 11 486 adults aged 50 years or above within the first wave of the Study on Global Ageing and Adult Health in China during 2007–2010. Hypertension was assessed by criterion-based measures of blood pressure. Residential greenness was characterized by satellite-derived Normalized Difference Vegetation Index. We employed multilevel generalized structural equation models to estimate the association between neighbourhood greenness and hypertension in urban and rural areas. Serial mediation models have been performed to test potential pathways linking greenness to hypertension. Results In rural areas, a greater amount of residential greenness was directly associated with a decrease in the odds of hypertension (odds ratio = 0.51, 95% confidence interval 0.29–0.89). No direct association was observed in urban areas (odds ratio = 1.33, 95% confidence interval 0.94–1.89). Serial mediation models showed that the association of greenness with hypertension was completely mediated by PM2.5 concentrations in urban areas, while the association of greenness with hypertension was only partially mediated by PM2.5 concentrations and serial PM2.5 concentrations-physical activity path in rural areas. There was no evidence that physical activity, air pollution-BMI path, air pollution-physical activity-BMI path, and physical activity-BMI path mediated the association in both urban and rural areas. Conclusions Higher neighbourhood greenness was directly associated with a lower prevalence of hypertension among middle and older aged adults in rural China but not in urban areas. The association of greenness with hypertension was completely mediated by air pollution (without any mediation effect of physical activity and BMI) in urban areas. In contrast, the association was partly mediated by air pollution, physical activity, and other unobservables in rural areas. Further longitudinal studies are warranted to prove a cause-and-effect association, which may help policymakers and practitioners to conduce effective interventions to prevent and control the prevalence of hypertension and the attendant disease burden.

Asymptomatic SARS-CoV-2-infected individuals are thought to play major roles in virus transmission. This study aimed to analyze the characteristics of asymptomatic carriers with COVID-19 to control the spread of the virus. We retrospectively investigated the clinical characteristics of 648 consecutive subjects who were enrolled in the study and were divided into asymptomatic carriers, mild cases, ordinary cases, severe or critical cases, and evaluated their impact on disease severity by means of Spearman correlation and multiple regression analyses. Receiver operating characteristic curve analysis was conducted to determine the optimum cutoff levels of laboratory findings for diagnostic predictors of asymptomatic carriers of COVID-19. In our study, a total of 648 subjects on admission with a mean age of 45.61 y including 345 males and 303 females were enrolled in our study. The leukocyte, lymphocyte, eosinophil, platelet, C-reactive protein, interleukin-6, CD3+, CD4+, and CD8 + T lymphocyte levels, and the erythrocyte sedimentation rate differed significantly among the groups (all p ≤ 0.05). Disease severity was negatively associated with the CD3+ (r = −0.340; p

Theories of gravity that incorporate new scalar degrees of freedom typically require screening mechanisms to ensure consistency with Solar System tests. One widely-studied mechanism -- the chameleon -- can lead to violations of the equivalence principle (EP), as screened and unscreened objects fall differently. If the stars are screened but the surrounding dark matter is not, this leads to asymmetry between leading and trailing streams. We provide analytic estimates of the magnitude of this effect for realistic Galactic mass distributions. Using a restricted N-body code, we simulate 4 satellites with a range of masses and orbits, together with a variety of strengths of the fifth force and screening levels of the Milky Way and satellite. The ratio of the cumulative number function of stars in the leading and trailing stream as a function of longitude from the satellite is computable from simulations, measurable from the stellar data and can provide a direct test. We forecast constraints for streams at large Galactocentric distances, using the specific example case of Hu-Sawicki gravity. Streams with apocentres between 100 and 200 kpc provide attainable constraints at the level of $|f_{R0}| = 10^{-7}$. Still more stringent constraints at the level of $10^{-7.5}$ or even $10^{-8}$ are plausible provided the environmental screening of the satellite is accounted for. These would be among the tightest astrophysical constraints to date. We note further signatures of chameleon gravity: (i) the trailing stellar stream may become detached from the dark matter progenitor if all the stars are lost, (ii) in the extreme fifth force regime, striations in the stellar trailing tail may develop, (iii) if the satellite is fully screened, its orbital frequency is lower than that of the associated dark matter, which is preferentially liberated into the leading tidal tail., PRD, 22 pages, 14 figures

We study the equivalence principle, regarded as the cornerstone of general relativity, by analyzing the deformation observable of black hole shadows. Such deformation can arise from new physics and may be expressed as a phenomenological violation of the equivalence principle. Specifically, we assume that there is an additional background vector field that couples to the photons around the supermassive black hole. This type of coupling yields impact on the way the system depends on initial conditions, and affects the black hole shadow at different wavelengths by a different amount, and therefore observations of the shadow in different wavelengths could constrain such couplings. This can be tested by future multi-band observations. Adopting a specific form of the vector field, we obtain constraints on model parameters from Event Horizon Telescope observations and measurements of gas/stellar orbits., Comment: 10 pages, 3 figures

Background: Patients with coronavirus disease 2019 (COVID-19) infected by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) which originated in Wuhan, China, and spreading over the country including Jiangsu Province. Our study aimed to study the epidemiological, clinical characteristics and therapies of these severe cases in Jiangsu Province.Methods: A multicenter retrospective cohort study was conducted to extract and analyze epidemiological, clinical, laboratory data and treatment of 60 severe cases with COVID-19 infection from 12 large hospitals in Jiangsu Province between Jan 24 and Feb 23, 2020. Cases were identified by real-time reverse transcription polymerase chain reaction (RT-PCR). The improvement and deterioration subgroups were compared to identify predictors of disease progression. Clinical outcomes were followed up until Feb 23, 2020.Results: A total of 631 infected cases with COVID-19 in Jiangsu Province, 60 of which were severe cases. Up until Feb 23, 2020, the mortality rate of these severe patients was 0%. The median age was 57 years (range, 26 to 97), and 58.3% were man. The body mass index (BMI) of these patients was higher, with an average of 25 kg/m². More than 90 percent of the patients had a history of contact with an infected patient or dined together, and two patients were infected while staying in the same train compartment with a confirmed patient. 51.7% of severe cases had at least one underlying disease, and low fever (80.0%) and dry cough (51.7%) were the most common symptoms. Mean acute physiology and chronic health evaluation (APACHE) II score on admission was 14±5. Acute respiratory distress syndrome (ARDS) appeared in 15% of the patients. White blood cell counts decreased in 45.0% of patients, lymphopenia in 63.3%, thrombocytopenia in 13.3%, and procalcitonin levels in 88.3% of the patients were less than 0.5 ng/mL. There were no statistically significant differences in immunoglobulin therapy and glucocorticoids therapy between the improvement and deterioration subgroups (P>0.05). Logistic regression analysis indentified higher levels of troponin T (odds ratio [OR]: 1.04; 95% confidence interval [CI]: 1.00-1.08; P=0.04), antiviral therapy with interferon (OR: 6.33; 95% CI: 1.18-33.98; P=0.03), and the application of non-invasive mechanical ventilation (OR: 1.99; 95%CI: 1.17-3.41; P=0.01) as predictors of disease progression, whereas higher lymphocyte count (OR: 0.11; 95% CI: 0.02-0.57; P=0.01) and early prone ventilation were associated with improvement (OR: 0.11; 95% CI: 0.01-0.98; P=0.04).Conclusions: The COVID-19 infection had a low mortality rate in Jiangsu Province, China. The higher levels of troponin T and lower lymphocyte count were predictors of disease progression. Antiviral therapy with interferon was not recommended. The early prone ventilation may be an effective treatment for severe cases.

The cloze test for Chinese idioms is a new challenge in machine reading comprehension: given a sentence with a blank, choosing a candidate Chinese idiom which matches the context. Chinese idiom is a type of Chinese idiomatic expression. The common misuse of Chinese idioms leads to error in corpus and causes error in the learned semantic representation of Chinese idioms. In this paper, we introduce the definition written by Chinese experts to correct the misuse. We propose a model for the Chinese idiom cloze test integrating various information effectively. We propose an attention mechanism called Attribute Attention to balance the weight of different attributes among different descriptions of the Chinese idiom. Besides the given candidates of every blank, we also try to choose the answer from all Chinese idioms that appear in the dataset as the extra loss due to the uniqueness and specificity of Chinese idioms. In experiments, our model outperforms the state-of-the-art model.

Background Early recognition of the risks of acute respiratory distress syndrome (ARDS) and prevention of the development of ARDS may be more effective in improving patient outcomes. We performed the present study to determine the ARDS risk factors in a Chinese population and validate a score to predict the development of ARDS. Methods This was an observational multicenter cohort study performed in 13 tertiary hospitals in China. Patients admitted into participating intensive care units (ICUs) from January 1 to January 31, 2012, and from January 1 to January 10, 2013, were enrolled in a retrospective derivation cohort and a prospective validation cohort, respectively. In the derivation cohort, the potential risk factors of ARDS were collected. The confirmed risk factors were determined with univariate and multivariate logistic regression analyses, and then the modified ARDS prediction score (MAPS) was established. We prospectively enrolled patients to verify the accuracy of MAPS. Results A total of 479 and 198 patients were enrolled into the retrospective derivation cohort and the prospective validation cohort, respectively. A total of 93 (19.4%) patients developed ARDS in the derivation cohort. Acute pancreatitis, pneumonia, hypoalbuminemia, acidosis, and high respiratory rate were the risk factors for ARDS. The MAPS discriminated patients who developed ARDS from those who did not, with an area under the curve (AUC) of 0.809 [95% confidence interval (CI), 0.758-0.859, P

Background: Although acute respiratory distress syndrome (ARDS) has been recognized for more than 50 years, limited information exists about the incidence and management of ARDS in mainland China. To evaluate the potential for improvement in management of patients with ARDS, this study was designed to describe the incidence and management of ARDS in mainland China. Methods: National prospective multicenter observational study over one month (August 31st to September 30th, 2012) of all patients who fulfilled the Berlin or American European Consensus Conference (AECC) definition of ARDS in 20 intensive care units, with data collection related to the management of ARDS, patient characteristics and outcomes. Results: Of the 1,814 patients admitted during the enrollment period, 149 (8.2%) and 147 (8.1%) patients were diagnosed by AECC and Berlin definition, respectively. Lung protective strategy with low tidal volume (Vt) (≤8 mL/kg) and limitation of the plateau pressure (Pplat) (≤30 cmH 2 O) was performed in 75.2% patients. And, 36%, 21.1% and 4.1% patients with severe, moderate and mild ARDS had the driving pressure more than 14 cmH 2 O (P 0.05). In severe ARDS, patient median positive end expiratory pressure (PEEP) was 10.0 (8.0–11.3) cmH 2 O and median FiO 2 was 90%. A recruitment maneuver was performed in 35.5% of the patients, and 8.7% of patients with severe ARDS received prone position. Overall hospital mortality was 34.0%. Hospital mortality was 21.8% for mild, 31.1% for moderate, and 60.0% for patients with severe ARDS (P=0.004). Conclusions: Despite general acceptance of low Vt and limited Pplat, high driving pressure, low PEEP and low use of adjunctive measures may still be a concern in mainland China, especially in patients with severe ARDS. Trial Registration: ClinicalTrials.gov NCT01666834; date of registration release: August 14th 2012.

Properties of SiC coating layer in the postulated accident condition of air and water ingress is crucial to the in-pile safety of tristructural-isotropic (TRISO) coated fuel particles of high temperature gas-cooled reactors (HTR). Particles of ZrO 2 kernels coated with low-density pyrolytic carbon buffer layer, high-density pyrolytic carbon layer and SiC layer fabricated by fluidized-bed chemical vapour deposition (FBCVD) were used to simulate real fuel particles in this research. The coated particles were tested at 1673 K in a certain flowing air with different water content between 0 and 100 g/m 3 for 10 h. Analysis results show that the corrosion reaction took place mainly on the outer surface of SiC layer with changing infiltration depth according to the flowing gas compositions. Steam content was controlled according to the relationship between saturated water vapour pressure and environment temperature. SiO 2 layer was the main product formed on the surface with thickness increase from 1.5 µm to 3 µm along with the content of water vapour in air. Formation of two types of micro-cracks after oxidation are observed: micro-cracks on spherulitic SiO 2 and penetrating micro-cracks on flat SiO 2 . Micro-stress generation mechanism is illustrated. Three are also some bubbles are observed either in SiO 2 layer or between SiO 2 and SiC layers. Results showed that no fracture occurred in the SiC layer after wet oxidation.

BACKGROUND. Data are limited on the impact of neuraminidase inhibitor (NAI) treatment on avian influenza A(H7N9) virus RNA shedding. METHODS. In this multicenter, retrospective study, data were collected from adults hospitalized with A(H7N9) infection during 2013–2017 in China. We compared clinical features and A(H7N9) shedding among patients with different NAI doses and combination therapies and evaluated factors associated with A(H7N9) shedding, using Cox proportional hazards regression. RESULTS. Among 478 patients, the median age was 56 years, 71% were male, and 37% died. The median time from illness onset to NAI treatment initiation was 8 days (interquartile range [IQR], 6–10 days), and the median duration of A(H7N9) RNA detection from onset was 15.5 days (IQR, 12–20 days). A(H7N9) RNA shedding was shorter in survivors than in patients who died (P < .001). Corticosteroid administration (hazard ratio [HR], 0.62 [95% confidence interval {CI}, .50-.77]) and delayed NAI treatment (HR, 0.90 [95% CI, .91-.96]) were independent risk factors for prolonged A(H7N9) shedding. There was no significant difference in A(H7N9) shedding duration between NAI combination treatment and monotherapy (P = .65) or between standard-dose and double-dose oseltamivir treatment (P = .70). CONCLUSIONS. Corticosteroid therapy and delayed NAI treatment were associated with prolonged A(H7N9) RNA shedding. NAI combination therapy and double-dose oseltamivir treatment were not associated with a reduced A(H7N9) shedding duration as compared to standard-dose oseltamivir.

ZrSi2-SiC/SiC coating was prepared on the surface of high temperature gas-cooled reactor (HTR) matrix graphite spheres by two-step pack cementation and sintering process. The microstructure, oxidation resistance and thermal shock resistance properties of the as-prepared coatings with different original powder mixtures were investigated. Results show that dense microstructure of the ZrSi2-SiC/SiC coating and continuous ZrSiO4-SiO2-ZrO2 glass phase generated during the oxidation process were the key factors for the outstanding thermal properties. When the mole ratio of Zr:Si:C reaches 1:7:3 in the second pack cementation powders, the coated graphite spheres have optimum oxidation resistant ability. The weight gain is only 0.6 wt% after 15 times thermal shock tests and 0.12 wt% after isothermal oxidation test at 1500 °C for 20 h in air. The oxidation resistant mechanism of the coating was also discussed. The dense inner SiC layer and the outer glass layer generated during the oxidation process could protect the ZrSi2-SiC/SiC coating from further oxidation.

Graphite dust can impact the operation of pebble-bed high-temperature gas-cooled reactors. Wear of fuel elements during collisions in the transport pipes of fuel handling and storage systems is a significant source of graphite dust generation; however, very little work on the wear behavior of this scenario has previously been reported. The present work investigated high contact loads of spherical fuel elements during collisions against pipe inner surfaces. Friction and wear tests, with the graphitic material sliding against steel, in a similar loading range were carried out. The coefficients of friction (COF) and wear rates were systematically investigated as a function of the sliding speed, applied load, steel surface roughness, and atmosphere. The COFs were found to be independent of the sliding speed and applied load, but initially decreased and then increased with increasing steel surface roughness; the wear rate of graphitic material increased with increasing load and steel surface roughness. Test results also showed that helium caused higher COFs and wear rates than air. Microscopic observations showed that the nature of the atmosphere can affect the generation of a lubrication layer at the contact area. These results could be applied in developing quantitative predictive models of dust generation during fuel handling and storage processes.

According to the ideas of risk assessment, the theory of support vector regression is introduced to forecast the ice thickness distribution and achieve the ice extreme value of the wire. Combined with the exponential function of failure rate when the line is under stress, the failure rate model of the line is established in the particular icing condition. The ice strengthening standard is developed by the icing thickness of transmission line, which is used to strengthen lines differentially. Especially, the lines that cross different meteorological conditions are strengthened by the method of segmentation. Finally, the method of economic assessment based on the total life cycle cost is improved, and the comprehensive failure rate is used to calculate differentiated “impairment” benefits. Different lines are made differentiated planning through the simulation example. Various economic indicators are comprehensively compared, in that case, economic assessment results of lines under different strengthening schemes are obtained, which proves the effectiveness of the proposed method.

The change of cultivated land pattern (CLP) has a significant impact on cultivated land system security (CLSS), and is the foundation of ensuring adequate provision of cultivated land, and the premise of achieving sustainable development of the society. While there is a lack of research on the CLP optimization with the goal of achieving CLSS, particularly lacking research that taking the main grain production areas at the provincial scale as a study area. Hence, taking Heilongjiang Province in China as the study area, this paper uses the regional interpolation of ArcGIS spatial analysis and Auto-Logistics method to diagnose the common driving factors of CLSS and CLP change, and further sets up different development scenarios with the goal of CLSS to carry out the study of CLP optimization through the introduction of Future Land Use Simulation (FLUS) model. The results showed that: Firstly, the dynamic changes of paddy field, dryland and cultivated land were the most intense in the eastern Sanjiang Plain, the second in the western Songnen Plain, the weakest in the north-south axis, and the changes of paddy field and dryland were more intense in the later period (2010–2015) than in the earlier period (1995–2010); Secondly, regional interpolation in ArcGIS and Auto-Logistics method can effectively and reasonably spatialize, and diagnose the key factors (terrain and geomorphology including elevation and slope, socio-economic (distance to residential area, agricultural three wastes index) and farmland productivity potential) which affect the change of CLSS and CLP; Thirdly, the Kappa test coefficient of CLP optimization based on FLUS model is 0.898, with good simulation accuracy, meaning the combination of Auto-logistic and FLUS can achieve high-precision simulation of CLP. The simulation results that under the integrated control scenarios of food security, ecological protection and economic development, the regional food security, ecological protection and economic development are considered comprehensively, and the contradictions among the three are coordinated, which is more reasonable and conducive to the improvement of CLSS. Fourthly, the policies on controlling the growth rate of paddy fields, rationally reducing rural residential areas and decreasing agricultural three wastes should be strengthened to implement the optimal CLP and improve CLSS. The results bestow convincing insights on decision-making for the implementation of the optimal distribution of cultivated land resources and the compilation of the national land space plan, and also provide an important reference for the study area to improve CLSS by optimizing CLP.

A ZrSi2-SiC/SiC double layer was fabricated on the surface of graphite spheres by two-step pack cementation with zirconium, silicon, and graphite powders as mainly raw materials. The microstructure, phase, oxidation behavior, and thermal shock resistance of the ZrSi2-SiC/SiC composite coatings were studied. The results show that the outer coating is composed of ZrSi2 and SiC and the inner coating is composed of SiC, of which the thickness is 450 μm. Isothermal oxidation test was conducted in air at 1773 K for 20 h and a weight increase of 1.69% were recorded. After 10 times of thermal shock tests between 1473 K and room temperature, the weight of the coated specimens decreased by only 1.14%. The excellent oxidation resistance is due to the production of SiO2 and ZrSiO4 in the process of the oxidation of SiC and ZrSi2, forming a glass phase that can effectively prevent further oxidation.

In this paper, a simulation model of the distributed power flow controller is established by PSCAD/EMTDC, where the shunt converter is equivalent to the current source when the interaction between the shunt and series converters is ignored. The coordinated control strategy for the multiple single phase converters in the series side is proposed. The interaction of the series of converters through the line is studied from the three aspects: switching on/off at the same time, switching on/off at the same interval, and being installed in different electrical distance. The simulation results show that the proposed control strategy is the best switching on/off at the equal interval, and there is a short negative interaction among the converters. The increase of the electrical distance will weaken the interaction of converters.

The interaction among control objectives of distributed power flow controller (DPFC) series-side converter is transformed into a multi-objective optimization problem. The variance between the three control objectives of active power, reactive power and DC capacitor voltage controller and the corresponding reference value is taken as the performance index to design the multi-objective function. The Pareto solution set is obtained by optimizing the objective function using multi-objective particle swarm optimization algorithm, and the best compromise solution based on membership function is adopted to select the best parameter solution. Finally, it is verified that the controller parameters designed by multi-objective particle swarm optimization algorithm can reduce the interaction between DPFC series-side multi-converters in PSCAD/EMTDC.

Based on the analysis of the interaction between multi-converters of distributed static synchronous series compensator (DDSC), a coordinated control strategy based on multi-objective optimization immune algorithm is proposed, which converts the interaction between DSSC into multi-objective optimization of controller. Firstly, the objective function of coordinated control of DSSC is established, and the immune algorithm is used to screen the antibody fitness, and the Pareto optimal solution set of controller parameters is obtained. Then the simulation model is established and analyzed. Finally, the effectiveness of the coordination strategy is verified by comparing the power flow parameters before and after optimization.

The possibility that ultra-diffuse galaxies lacking dark matter has recently stimulated interest to check the validity of Modified Newton Dynamics (MOND) predictions on the scale of such galaxies. It has been shown that the External Field Effect (EFE) induced by the close-by galaxy can suppress the velocity dispersion of these systems, so that they appear almost dark matter free in the Newtonian context. Here, following up on this, we are making a priori predictions for the velocity dispersion of 22 ultra-diffuse galaxies in the nearby Universe. This sample can be used to test MOND and the EFE with future follow-up measurements. We construct a catalog of nearby ultra-diffuse galaxies in galaxy group environments, and set upper and lower limits for the possible velocity dispersion allowed in MOND, taking into account possible variations in the mass-to-light ratio of the dwarf and in the distance to the galaxy group. The prediction for the velocity dispersion is made as a function of the three dimensional separation of the dwarf to its host. In 17 out of 22 cases, the EFE plays a crucial role in the prediction., Comment: 9 pages, 3 figures, 2 tables, accepted for publication in A&A

Nutrition therapy is considered an important treatment of burn patients. The aim of the study was to delineate the nutritional support in severe burn patients and to investigate association between nutritional practice and clinical outcomes. Severe burn patients were enrolled (n 100). In 90 % of the cases, the burn injury covered above 70 % of the total body surface area. Mean interval from injury to nutrition start was 2·4 (sd 1·1) d. Sixty-seven patients were initiated with enteral nutrition (EN) with a median time of 1 d from injury to first feed. Twenty-two patients began with parenteral nutrition (PN). During the study, thirty-two patients developed EN intolerance. Patients received an average of about 70 % of prescribed energy and protein. Patients with EN providing

The ultra-diffuse dwarf galaxy NGC 1052-DF2 (DF2) has ten (eleven) measured globular clusters (GCs) with a line-of-sight velocity dispersion of $\sigma=7.8^{+5.2}_{-2.2}\,$km/s ($\sigma=10.6^{+3.9}_{-2.3}\,$km/s). Our conventional statistical analysis of the original ten GCs gives $\sigma=8.0^{+4.3}_{-3.0}\,$km/s. The overall distribution of velocities agrees well with a Gaussian of this width. Due to the non-linear Poisson equation in MOND, a dwarf galaxy has weaker self-gravity when in close proximity to a massive host. This external field effect is investigated using a new analytic formulation and fully self-consistent live $N$-body models in MOND. Our formulation agrees well with that of Famaey and McGaugh (2012). These new simulations confirm our analytic results and suggest that DF2 may be in a deep-freeze state unique to MOND. The correctly calculated MOND velocity dispersion agrees with our inferred dispersion and that of van Dokkum et al. (2018b) if DF2 is within 150 kpc of NGC 1052 and both are 20 Mpc away. The GCs of DF2 are however significantly brighter and larger than normal GCs, a problem which disappears if DF2 is significantly closer to us. A distance of 10-13 Mpc makes DF2 a normal dwarf galaxy even more consistent with MOND and the 13 Mpc distance reported by Trujillo et. al. (2019). We discuss the similar dwarf DF4, finding good agreement with MOND. We also discuss possible massive galaxies near DF2 and DF4 along with their distances and peculiar velocities, noting that NGC 1052 may lie at a distance near 10 Mpc., Comment: 14 pages, 9 figures, 2 Tables, accepted for publication in MNRAS

A multi-layered SiC coating was prepared on graphite spheres to improve its antioxidant performance. The oxidation behaviour of the coating prepared on graphite sphere in static air was studied systematically for the first time. As an antioxidant layer, the dense block layer is effective in protecting the internal transition layer and refined grain layer from oxidation in static air at 1773 K. An amorphous SiO2 layer developing on the surface acts as a protective shell, while some carbon particles developed at the interface of oxide layer and SiC coating. As for the oxidation process of the SiC coated graphite sphere, it is comprised of three stages. Stage I (0−6 h) is characterized by a rapid weight gain, which follows a linear model, and the passive oxidation of SiC occurs in this stage. Stage II (6−50 h) is characterized by a slow weight gain, which follows the parabolic oxidation model. Stage III (50−200 h) is characterized by an invariable weight gain of merely 0.52%, which is accompanied with the interface reaction of SiC and the self-healing of oxide layer.

A two-step pack cementation technique was applied to synthesize the TiSi2–Si–SiC/SiC bilayer coating on the surface of graphite spheres for improving its antioxidant performance. Then, an investigation was conducted into the microstructure, phase composition, formation mechanism, and the isothermal oxidation behavior in static air of the coating. According to the research results, the coating consists of an internal SiC layer and an external TiSi2–Si–SiC layer. In the external layer, the gap between SiC particles filled with Si phase ensures the sufficient compactness of the as-prepared coating, while the small TiSi2 particles are embedded in SiC particles. In the oxidizing environment, TiSi2 is preferentially oxidized to reduce the consumption of SiC, thus ensuring the stability of the coating. The structure of the external layer is capable to ensure the excellent antioxidant performance of the coating. After being oxidized in static air at 1500 °C for 200 h, the weight gain of the coated graphite sphere reached merely 0.96 w.t.% and the thickness of the oxide layer was approximately 20 μm.

A micro four-layer SiC coating, which includes inner transition layer, fine-grained layer, dense bulk layer, and outer loose layer, was fabricated on the matrix graphite spheres of high-temperature gas-cooled reactor fuel elements to improve the oxidation-resistant property by a two-step pack cementation process. According to the experiment results, the micro four-layer can be differentiated by SiC grain size and microstructure variation. The oxidation tests at 1773 K for 200 h reveal that the coating structure could effectively improve the oxidation resistance of matrix graphite spheres with a weight gain of 0.52 wt%, and the fine-grained and dense bulk layers are evidenced as two main antioxidation layers. Although the thermal expansion coefficients of SiC and matrix graphite do not match each other so well, no obvious stress cracking was observed after thermal shocking tests from 1773 K to room temperature for 100 times.

Pack cementation is an effective method in the manufacture of SiC coating on carbon material substrate surface, which is a controllable and simple process. Meanwhile, due to the reactive infiltration process of powder mixture into the substrate, a gradient transition structure layer is formed between the substrate and outer layer. In this paper, SiC was coated on the spherical substrates taken from the matrix graphite pebbles of high temperature gas-cooled reactor (HTR) fuel element. Relations between the Si/C content ratio of the pack mixture and the thickness of SiC layer were studied. Analysis found that Si/C content ratio, powder size and sintering time are factors influenced the thickness of the coating layers. When the Si/C content ratio was higher than 3:1, a uniform thickness coating bonded well with the substrate was obtained. The composition phases and thickness of coating layer etc. also had obvious changes along with the change of the Si/C content ratio in this research.Results also show that sintering atmosphere and particle size of powders are important factors affecting coating microstructure, while a vacuum atmosphere can smaller powder size can help to get a dense structure.

Graphite is one of the most important material for the reactor core and fuel elements of high temperature gas-cooled reactor (HTR). Improving the oxidation resistance of graphite is very essential for the research of new fuel elements and the development of HTR. In this study, a gradient SiC layer of 500~700 μm was prepared on matrix graphite spheres by a two-step pack cementation, and the outer SiO2 layer prepared by the high-temperature oxidation process. The phases, microstructure, bonding strength and oxidation resistance of SiC/SiO2 coated matrix graphite spheres were investigated. The SiC/SiO2 coated matrix graphite spheres were carried on rapid thermal shocking tests from 1773 K to room temperature for 50 times without any cracks. The SiC/SiO2 coated matrix graphite spheres exhibits excellent anti-oxidation properties. No obvious weight loss was found after isothermal oxidation in air at 1273 K for 50 h and the weight gain was less than 1% at 1773 K in air for 50 h due to the oxidation of SiC layer.

BACKGROUND: The aim of the study was to identify the clinical features and the factors associated with burn induced mortality among young adults after exposure to indoor explosion and fire. METHODS: This is an observational study which included burn patients who were admitted to eighteen ICUs after a fire disaster. Epidemiologic and clinical characteristics, as well as therapy were recorded. The primary outcome was 90-day mortality. The mortality-related factors were also analyzed. RESULTS: There were 167 burn patients enrolled in the study, the median age was 38 years, 62 (37.1%) patients died within 90 days. Seventy-one percent of patients had a burn size ≥90% TBSA, and 73.7% of patients had a full-thickness burn area above 50% TBSA. The survivors had lower Baux scores, and received earlier escharectomy and autologous skin grafts. The 50% mortality rates (LA50s) for burn size and full-thickness burn area were 95.8% and 88.6% TBSA, respectively. The multivariate analysis showed that full-thickness burn area over 50% TBSA and residual burned surface area (RBSA)/TBSA at 28 days were strong predictors of mortality among burn patients (odds ratio 2.55; 95% CI, 1.01 to 6.44, P=0.047; odds ratio 1.07; 95% CI, 1.04 to 1.09, P

Distributed Power Flow Controller (DPFC) is expected to be used for improving the performance of power flow control in AC transmission power system. In this paper, a two-level control scheme for DPFC series units is proposed. The two-level control system consists of an upper-level controller, multiple lower-level series unit controllers and unidirectional power line carrier (PLC) communication link. The reference value of series compensated voltage is calculated by the top-level controller according to the power flow ordered by dispatch center and transferred to series units via PLC communication link. A corresponding compensated voltage will then be generated in series units. Comparing the reference value of the compensated voltage with actual value, the modulation signal of converter in series unit will be modified through PI control. The model of an AC transmission system at high-level voltage involved with DPFC is built in PSCAD/EMTDC. The simulation results indicate that the proposed two-level control method for DPFC series units is flexible and effective.

A great challenge in present-day physics is to understand whether the observed internal dynamics of galaxies is due to dark matter matter or due to a modification of the law of gravity. Recently, van Dokkum et al. reported that the ultra-diffuse dwarf galaxy NGC1052-DF2 lacks dark matter, and they claimed that this would -- paradoxically -- be problematic for modified gravity theories like Milgromian dynamics (MOND). However, NGC1052-DF2 is not isolated, so that a valid prediction of its internal dynamics in MOND cannot be made without properly accounting for the external gravitational fields from neighbouring galaxies. Including this external field effect following Haghi et al. shows that NGC1052-DF2 is consistent with MOND., 15 pages, including supplementary information (the external field formulae), published by Nature: https://rdcu.be/6uZn

To improve the anti-oxidation ability of graphite, Al2O3 and SiC as additives, a uniform SiC coating was prepared on the surface of HTR graphite spheres by the pack cementation and sintering process. The microstructure of SiC coating was characterized by XRD, Raman spectroscopy, scanning electron microscopy, and the effect of Si/C ratio, Al2O3 and SiC content in the starting powder, sintering process conditions on the microstructure of SiC coating was also analyzed. The results show that the SiC coating on the surface of spherical graphite sample can be obtained with Si/C ratio higher than 3: 1, and the SiC coatings with different raw materials possess different microstructure and phase constitutes. The SiC coating is a kind of clear porous microstructure, while the main composition of the coating is β-SiC with some α-SiC and unreacted graphite. It is found that the content of Al2O3 has a significant influence on the penetration into the SiC coating, while the SiC content has a great influence on the microstructure between SiC coating and the substrate. When Al2O3 content is 10%, the bonding between the SiC coating and the substrate is better. When SiC content is 20%, the SiC coatings obtained have good densification and less lamellar accumulation of on the surface of the coatings. The SiC coatings sintered in Ar gas at 1750 °C have larger thickness and porous porosity microstructure, and the maximum thickness, about 400 ∼ 600 μm, can be achieved with the 2h of sintering time. The obtained SiC coatings sintered in vacuum at 1750 °C have a plate-like dense microstructure, in which the main composition of the coating is free Si, α-SiC and β-SiC, and the transitional area between SiC coating and the substrate is not obvious.

During the medium and short term transmission network planning process, the planning department of power grid will get a large number of planning projects to be selected. These projects have passed the feasibility study. However, it is necessary to select some projects in case of the limited investment funds. At present, the selection of the projects basically relies on expert experience in practical engineering. However, with the increasing number of the projects to be selected, it is more and more difficult to select the projects scientifically and reasonably only relying on expert experience. To date, the existing research methods are not enough to cope with the optimization of the planning projects. In view of the existing problems, this paper puts forward two concepts, Reliability Benefit Coefficient and Project Urgency, to measure the Reliability Benefit of the projects. Combine Reliability Benefit with Economic Benefit as the Comprehensive Benefit, based on which a new combinatorial optimization model of transmission network planning projects is established. It provides a scientific and reasonable method for the combinatorial optimization of the transmission network planning projects. The validity of the method is verified in a case finally.

We consider the feasibility of testing Newtonian gravity at low accelerations using wide binary (WB) stars separated by $\ge 3$ kAU. These systems probe the accelerations at which galaxy rotation curves unexpectedly flatline, possibly due to Modified Newtonian Dynamics (MOND). We conduct Newtonian and MOND simulations of WBs covering a grid of model parameters in the system mass, semi-major axis, eccentricity and orbital plane. We self-consistently include the external field (EF) from the rest of the Galaxy on the Solar neighbourhood using an axisymmetric algorithm. For a given projected separation, WB relative velocities reach larger values in MOND. The excess is ${\approx 20\%}$ adopting its simple interpolating function, as works best with a range of Galactic and extragalactic observations. This causes noticeable MOND effects in accurate observations of ${\approx 500}$ WBs, even without radial velocity measurements. We show that the proposed Theia mission may be able to directly measure the orbital acceleration of Proxima Centauri towards the 13 kAU-distant $\alpha$ Centauri. This requires an astrometric accuracy of $\approx 1 \, \mu$as over 5 years. We also consider the long-term orbital stability of WBs with different orbital planes. As each system rotates around the Galaxy, it experiences a time-varying EF because this is directed towards the Galactic Centre. We demonstrate approximate conservation of the angular momentum component along this direction, a consequence of the WB orbit adiabatically adjusting to the much slower Galactic orbit. WBs with very little angular momentum in this direction are less stable over Gyr periods. This novel direction-dependent effect might allow for further tests of MOND., Comment: 31 pages, 20 figures, 6 tables. Fixed typo in equation 11

Background We evaluated factors associated with mortality in patients with moderate/severe generalized tetanus. Methods This retrospective study included patients with moderate/severe generalized tetanus admitted to the Affiliated Hospital of Nantong University (China) between January 2005 and January 2017. Clinical data were extracted from medical records. Patients were divided into two groups based on outcome (survival or death). Factors associated with mortality were analyzed using univariate and multivariate logistic regression. Results Seventy-five patients were included (57.3% male; age, 57.9 ± 18.4 years; APACHE II score, 10.6 ± 3.4; severe tetanus, 49.3%; mortality, 25.3%). Multivariate analysis identified severe tetanus (odds ratio [OR], 30.364; 95% confidence interval [CI], 2.459–374.896) and APACHE II score (OR, 1.536; 95%CI, 1.051–2.243) as positively associated with mortality, whereas high-calorie nutrition (OR, 0.027; 95%CI, 0.002–0.359) and dexmedetomidine use (OR, 0.035; 95%CI, 0.003–0.467) were negatively associated with mortality (all P Conclusion Tetanus severity and APACHE II score were associated with mortality in patients with generalized tetanus, whereas high-calorie nutrition and dexmedetomidine use reduced the odds of death. High-calorie nutrition and dexmedetomidine administration may improve prognosis in adult patients with moderate/severe generalized tetanus.

Background Evidence concerning the efficacy and safety of extracorporeal membrane oxygenation (ECMO) in patients with influenza A (H7N9) has been was limited to case reports. Our study is aimed to investigate the current application, efficacy and safety of ECMO in for severe H7N9 pneumonia-associated acute respiratory distress syndrome (ARDS) in the Chinese population. Methods A multicentre retrospective cohort study was conducted at 20 hospitals that admitted patients with avian influenza A (H7N9) viral pneumonia patients’ admission from 9 provinces in China between October 1, 2016, and March 1, 2017. Data from the National Health and Family Planning Commission of China, including general conditions, outcomes and ECMO management, were analysed. Then, successfully weaned and unsuccessfully weaned groups were compared. Results A total of 35 patients, aged 57 ± 1 years, were analysed; 65.7% of patients were male with 63% mortality. All patients underwent invasive positive pressure ventilation (IPPV), and rescue ventilation strategies were implemented for 23 cases (65.7%) with an average IPPV duration of 5 ± 1 d, PaO2/FiO2 of 78 ± 23 mmHg, tidal volume (VT) of 439 ± 61 ml and plateau pressure (Pplat) of 29 ± 8 cmH2O pre-ECMO. After 48 h on ECMO, PaO2 improved from 56 ± 21 mmHg to 90 ± 24 mmHg and PaCO2 declined from 52 ± 24 mmHg to 38 ± 24 mmHg. Haemorrhage, ventilator-associated pneumonia (VAP) and barotrauma occurred in 45.7%, 60% and 8.6% of patients, respectively. Compared with successfully weaned patients (n = 14), the 21 unsuccessfully weaned patients had a longer duration of IPPV pre-ECMO (6 ± 4 d vs. 2 ± 1 d, P

We attempt to understand the planes of satellite galaxies orbiting the Milky Way (MW) and M31 in the context of Modified Newtonian Dynamics (MOND), which implies a close MW-M31 flyby occurred ${\approx 8}$ Gyr ago. Using the timing argument, we obtain MW-M31 trajectories consistent with cosmological initial conditions and present observations. We adjust the present M31 proper motion within its uncertainty in order to simulate a range of orbital geometries and closest approach distances. Treating the MW and M31 as point masses, we follow the trajectories of surrounding test particle disks, thereby mapping out the tidal debris distribution. Around each galaxy, the resulting tidal debris tends to cluster around a particular orbital pole. We find some models in which these preferred spin vectors align fairly well with those of the corresponding observed satellite planes. The radial distributions of material in the simulated satellite planes are similar to what we observe. Around the MW, our best-fitting model yields a significant fraction (0.22) of counter-rotating material, perhaps explaining why Sculptor counter-rotates within the MW satellite plane. In contrast, our model yields no counter-rotating material around M31. This is testable with proper motions of M31 satellites. In our best model, the MW disk is thickened by the flyby 7.65 Gyr ago to a root mean square height of 0.75 kpc. This is similar to the observed age and thickness of the Galactic thick disk. Thus, the MW thick disk may have formed together with the MW and M31 satellite planes during a past MW-M31 flyby., Comment: 26 pages, 12 figures, 10 tables. Revised in response to referee comments and submitted to the Monthly Notices of the Royal Astronomical Society in this form

Blood flow during ECMO, changes in IPPV parameters and physiological indicators pre-ECMO and during ECMO. (DOCX 107Â kb)