Today,urban traffic,growing populations,and dense transportation networks are contributing to an increase in traffic incidents.These incidents include traffic accidents,vehicle breakdowns,fires,and traffic disputes,re...Today,urban traffic,growing populations,and dense transportation networks are contributing to an increase in traffic incidents.These incidents include traffic accidents,vehicle breakdowns,fires,and traffic disputes,resulting in long waiting times,high carbon emissions,and other undesirable situations.It is vital to estimate incident response times quickly and accurately after traffic incidents occur for the success of incident-related planning and response activities.This study presents a model for forecasting the traffic incident duration of traffic events with high precision.The proposed model goes through a 4-stage process using various features to predict the duration of four different traffic events and presents a feature reduction approach to enable real-time data collection and prediction.In the first stage,the dataset consisting of 24,431 data points and 75 variables is prepared by data collection,merging,missing data processing and data cleaning.In the second stage,models such as Decision Trees(DT),K-Nearest Neighbour(KNN),Random Forest(RF)and Support Vector Machines(SVM)are used and hyperparameter optimisation is performed with GridSearchCV.In the third stage,feature selection and reduction are performed and real-time data are used.In the last stage,model performance with 14 variables is evaluated with metrics such as accuracy,precision,recall,F1-score,MCC,confusion matrix and SHAP.The RF model outperforms other models with an accuracy of 98.5%.The study’s prediction results demonstrate that the proposed dynamic prediction model can achieve a high level of success.展开更多
Seismic force reduction factor(SFRF) spectra of shear-type multi-degree-of-freedom(MDOF) structures are investigated. The modified Clough model, capable of considering the strength-degradation/hardening and stiffnessd...Seismic force reduction factor(SFRF) spectra of shear-type multi-degree-of-freedom(MDOF) structures are investigated. The modified Clough model, capable of considering the strength-degradation/hardening and stiffnessdegradation, is adopted. The SFRF mean spectra using 102 earthquake records on a typical site soil type(type C) are constructed with the period abscissa being divided into three period ranges to maintain the peak features at the two sitespecific characteristic periods. Based on a large number of results, it is found that the peak value of SFRF spectra may also exist for MDOF, induced by large high-mode contributions to elastic base shear, besides the mentioned two peak values. The variations of the stiffness ratio λk and the strength ratio λF of the top to bottom story are both considered. It is found that the SFRFs for λF ≤λk are smaller than those for λF > λk. A SFRF modification factor for MDOF systems is proposed with respect to SDOF. It is found that this factor is significantly affected by the story number and ductility. With a specific λF(= λk0.75), SFRF mean spectra are constructed and simple solutions are presented for MDOF systems. For frames satisfying the strong column/weak beam requirement, an approximate treatment in the MDOF shear-beam model is to assign a post-limit stiffness 15%-35% of the initial stiffness to the hysteretic curve. SFRF spectra for MDOF systems with 0.2 and 0.3 times the post-limit stiffness are remarkably larger than those without post-limit stiffness. Thus, the findings that frames with beam hinges have smaller ductility demand are explained through the large post-limit stiffness.展开更多
We study a nonlinear periodic problem driven by the p(t)-Laplacian and having a nonsmooth potential (hemivariational inequalities). Using a variational method based on nonsmooth critical point theory for locally L...We study a nonlinear periodic problem driven by the p(t)-Laplacian and having a nonsmooth potential (hemivariational inequalities). Using a variational method based on nonsmooth critical point theory for locally Lipschitz functions, we first prove the existence of at least two nontrivial solutions under the generalized subquadratic and then establish the existence of at least one nontrivial solution under the generalized superquadratic.展开更多
A novel spatial domain method--soft morphology filter is presented for reducing the periodic noise in image processing. The simulation results are presented to demonstrate the effectiveness of the method in comparison...A novel spatial domain method--soft morphology filter is presented for reducing the periodic noise in image processing. The simulation results are presented to demonstrate the effectiveness of the method in comparison with a frequency domain method and other spatial domain filters.展开更多
The change in rainfall pattern and intensity is becoming a great concern for hydrologic engineers and planners. Many parts of the world are experiencing extreme rainfall events such as experienced on 26<sup>th&l...The change in rainfall pattern and intensity is becoming a great concern for hydrologic engineers and planners. Many parts of the world are experiencing extreme rainfall events such as experienced on 26<sup>th</sup> July 2005 in Mumbai, India. For the appropriate design and planning of urban drainage system in an area, Intensity Duration Frequency (IDF) curves for given rainfall conditions are required. The aim of the present study is to derive the IDF curves for the rainfall in the Mumbai city, Maharashtra, India. Observed rainfall data from 1901 pertaining to Colaba and from 1951 of the Santacruz rain gauge stations in Mumbai are used in the present study to derive the IDF curves. Initially, the proposed IDF curves are derived using an empirical equation (Kothyari and Garde), by using probability distribution for annual maximum rainfall and then IDF curves are derived by modifying the equation. IDF curves developed by the modified equation gives good results in the changing hydrologic conditions and are compatible even with the extreme rainfall of 26<sup>th</sup> July 2005 in Mumbai.展开更多
Background: The practice of exclusive breastfeeding (EB) in Morocco has witnessed a worrying decline in recent decades, contrary to the recommendations of the World Health Organization (WHO) which advocates it during ...Background: The practice of exclusive breastfeeding (EB) in Morocco has witnessed a worrying decline in recent decades, contrary to the recommendations of the World Health Organization (WHO) which advocates it during the first six months as a significant public health tool. The present study aims to assess the impact of educational materials on mothers’ behaviour with regard to keeping up EB as long as six months, at least. Methods: This is a cohort study with a prospective collection of data over a period of one year, through a questionnaire-based survey of 500 women who delivered at the Souissi Maternity Hospital in Rabat. The subjects were divided into an intervention group sensitized, during the medical visit, by means of information delivered orally about breastfeeding and a booklet containing instructions on breastfeeding management and the benefits of EB, especially when extended for the first six months;and a control group attending the same operation with no awareness-rising through educational materials. To assess EB rates, the subjects had been followed for six months through telephone. Results: 372 women who delivered were followed, 194 from the intervention group and 178 from the control group. The remaining 128 women not followed were lost sight of. A higher percentage of mothers in the intervention group exclusively breastfed their babies up to the age of six months compared to the control group, 55.2% against 38.8% (p = 0.002). The main reason produced by most mothers who ceased to exclusively breastfeed their babies is milk insufficiency. Conclusion: The postnatal nutritional education strategy based on the distribution of educational materials has considerably raised the number of women who exclusively breastfed their babies until the age of six months.展开更多
BACKGROUND As a highly contagious disease,coronavirus disease 2019(COVID-19)is wreaking havoc around the world due to continuous spread among close contacts mainly via droplets,aerosols,contaminated hands or surfaces....BACKGROUND As a highly contagious disease,coronavirus disease 2019(COVID-19)is wreaking havoc around the world due to continuous spread among close contacts mainly via droplets,aerosols,contaminated hands or surfaces.Therefore,centralized isolation of close contacts and suspected patients is an important measure to prevent the transmission of COVID-19.At present,the quarantine duration in most countries is 14 d due to the fact that the incubation period of severe acute respiratory syndrome coronavirus type 2(SARS-CoV-2)is usually identified as 1-14 d with median estimate of 4-7.5 d.Since COVID-19 patients in the incubation period are also contagious,cases with an incubation period of more than 14 d need to be evaluated.CASE SUMMARY A 70-year-old male patient was admitted to the Department of Respiratory Medicine of The First Affiliated Hospital of Harbin Medical University on April 5 due to a cough with sputum and shortness of breath.On April 10,the patient was transferred to the Fever Clinic for further treatment due to close contact to one confirmed COVID-19 patient in the same room.During the period from April 10 to May 6,nucleic acid and antibodies to SARS-CoV-2 were tested 7 and 4 times,respectively,all of which were negative.On May 7,the patient developed fever with a maximum temperature of 39℃,and his respiratory difficulties had deteriorated.The results of nucleic acid and antibody detection of SARS-CoV-2 were positive.On May 8,the nucleic acid and antibody detection of SARS-CoV-2 by Heilongjiang Provincial Center for Disease Control were also positive,and the patient was diagnosed with COVID-19 and reported to the Chinese Center for Disease Control and Prevention.CONCLUSION This case highlights the importance of the SARS-CoV-2 incubation period.Further epidemiological investigations and clinical observations are urgently needed to identify the optimal incubation period of SARS-CoV-2 and formulate rational and evidence-based quarantine policies for COVID-19 accordingly.展开更多
Objective:To analyze the syndrome characteristics in patients with chronic persistent asthma.Methods:365 patients(121 males,244 females,60.829.1 years old)with chronic persistent asthma were enrolled in this cross-sec...Objective:To analyze the syndrome characteristics in patients with chronic persistent asthma.Methods:365 patients(121 males,244 females,60.829.1 years old)with chronic persistent asthma were enrolled in this cross-sectional study.The information of syndrome,symptoms,signs,tongue coating and pulse were collected from all patients.The syndrome characteristics of chronic persistent asthma were examined through the multifactor dimensionality reduction(MDR)analysis and the results were verified by the Chi-square test.Results:The results of the MDR analysis and the Chi-square test showed the following positive correlation of the interaction among:the deficiency syndrome of the lung and spleen and deep pulse,disinclination to talk due to lack of qi,fatigue,lassitude and thick tongue coating;the deficiency syndrome of the lung and kidney and dizziness and disinclination to talk due to lack of qi,fatigue,lassitude and pallid complexion;the syndrome of phlegm-heat obstructing the lung and rapid pulse,abdominal distension,disinclination to talk due to lack of qi,frequent urination and lassitude;the syndrome of phlegm-dampness obstructing the lung and disinclination to talk due to lack of qi,greasy coating,fatigue and lassitude.(P<.05 for all).Conclusion:The syndrome of chronic persistent asthma is characterized by fatigue and lassitude due to dysfunction of the lung,spleen and kidney.展开更多
Objective:To study the nursing effect of liposuction and volume reduction in the treatment of lymphedema during the perioperative period.Method:A total of 68 patients treated with liposuction volume reduction surgery ...Objective:To study the nursing effect of liposuction and volume reduction in the treatment of lymphedema during the perioperative period.Method:A total of 68 patients treated with liposuction volume reduction surgery for pseudo-lymphedema of lower limbs admitted from May 2019 to May 2020 in a tertiary hospital in Xi’an,Shaanxi Province were selected,and they were divided into observation group and control group by random grouping method.There were 34 cases in each group.The control group took routine care during the perioperative period,while the observation group performed full care during the perioperative period.The complication rate and pain degree of the two groups were compared.Results:The complication rate of the study group was 5.88%,while that of the control group was 26.67%.Compared with the study group,the complication rate was significantly higher than that of the control group,and the gap was statistically significant(P>0.05).The pain scores of patients in the study group were significantly lower than those in the control group at 3 and 6 days after surgery,and the gap was statistically significant(P>0.05).Conclusion:Lymphedema should be taken care of during the perioperative period of liposuction and volume reduction,which can effectively reduce the occurrence of pain and complications.It is worthy of extensive clinical promotion.展开更多
The introduction of defects can adjust the activity of graphene-based single-atom catalysts for oxygen reduction reactions(ORR).Herein,we for the first time investigate the ORR catalytic activity of FeN_(4)sites embed...The introduction of defects can adjust the activity of graphene-based single-atom catalysts for oxygen reduction reactions(ORR).Herein,we for the first time investigate the ORR catalytic activity of FeN_(4)sites embedded on graphene with four types of line-defective boundary via density functional theory calculations.Our results show that periodic line defects consisting of pentagon-pentagon-octagon(C_(585))or quad-octagon chains(C_(484))can significantly enhance ORR activity,owing to the optimized electronic structures of FeN_(4)sites.The spin magnetic moment and the valence state of the Fe atom are both well correlated with the ORR overpotential.Experimental investigations further corroborate that FeN_(4)with a high degree of defects exhibits better ORR activity and stability compared to FeN_(4)sites of pristine graphene and commercial Pt/C.This work unravels the influence of the periodic defect boundary on the ORR performance of Fe-N-C catalysts and paves the way towards the rational design of highly effective single-atom electrocatalysts.展开更多
Winter North Atlantic Oscillation(NAO)indexes from observations based on various winter durations are compared.Results show that there are significant differences in the interannual and decadal variations of these NAO...Winter North Atlantic Oscillation(NAO)indexes from observations based on various winter durations are compared.Results show that there are significant differences in the interannual and decadal variations of these NAO indexes.For the same data source,a different definition of winter duration can lead to different signs of NAO index in some years,which mainly appear to be in the period of decadal phase transition.The different winter durations induce different cycles of the observation-based NAO.The longer the winter duration,the stronger the decadal variation.The NAO defined by different winter durations also can generate different descriptions of the NAO action centers,including the position and movement.The longer the winter duration,the more southerly action centers appear to be.The movement of the action centers affects not only site-based NAO indexes but also those defined by other methods,such as empirical orthogonal function(EOF)analysis.The length of time used in EOF analysis has a great influence on the spatial pattern of the NAO mode,which results in a considerable difference between the corresponding NAO indexes.Regardless of which NAO index is used,the NAO-related SST anomalies show the same tripole pattern.The longer the winter duration,the more significant the relationship between the NAO and SST affected by the timescale of sea-air interaction.展开更多
Taking the multi-component system as research object, a maintenance optimization model based on the unequal inspection period and imperfect repair is established by considering the requirement of expected availability...Taking the multi-component system as research object, a maintenance optimization model based on the unequal inspection period and imperfect repair is established by considering the requirement of expected availability for improving the system's availability. An age reduction factor is used to describe the effect of imperfect repair, and the modelling approach for the unequal inspection period is proposed. Unavailable situations are classified into three kinds of independent cases, and the availability is calculated accordingly. Based on the analysis of the relationship between the unavailable cases and the unequal inspection period, an optimization model under imperfect repair is established to optimize the system's expected availability. A case study of a wind turbine is provided, and three key components, i.e. gearbox, generator and spindle, are considered. The optimization results of the unequal inspection period model and the equal inspection period model are compared. The results show that the unequal inspection period model based on availability can update the maintenance plan so as to optimize maintenance activities and improve the system's availability.展开更多
Fluctuating snow-covered elevation (FSCE) was conceptualized and proposed to characterize within-year variation of the border between snow-covered and snow-free area in mountainous regions. Two parameters, namely me...Fluctuating snow-covered elevation (FSCE) was conceptualized and proposed to characterize within-year variation of the border between snow-covered and snow-free area in mountainous regions. Two parameters, namely median of snow flee period (Tm) and snow free duration (AT), were defined to quantify FSCE. A regression model of FSCE was developed for the Lhasa River Basin, Niyang River Basin, and Changdu region in eastern Tibet. Statistical analysis of the snow-products data with a spatial resolution of 25km×25km shows that: (1) Tm correlates weakly with geographical and topographic factors, having the yearly mean value of July 31; (2) △T correlates significantly with the average elevation of the snow-products cell, having the yearly mean value of nearly five months (i.e., 151 days); (3) the region begins snow disappearance in late April and finishes snow coverage in mid November, being snow-free from late June to mid September and snow-covered from December to March in the next year. In addi- tion, snow-products with higher spatial resolution will be helpful to characterize FSCE in smaller spatial scales.展开更多
In this paper, the analysis of ground motions (displacements, velocities and accelerations) has been performed focused to the seismic design. The relationships between the peak ground acceleration (PGA), the peak grou...In this paper, the analysis of ground motions (displacements, velocities and accelerations) has been performed focused to the seismic design. The relationships between the peak ground acceleration (PGA), the peak ground velocity (PGV), the peak ground displacement (PGD) and the bracketed duration, with the earthquake magnitude, are presented and their validity and applicability for seismic design is discussed. Finally, the dominant periods of the ground motions (displacement, velocity and acceleration) are obtained from their Fourier Spectrum. Their validity and applicability for the seismic design is discussed also. The results presented in this paper show that the relationships that exist between the important parameters: PGA, PGV, PGD and duration;and the earthquake magnitude, allow the prediction of the values for these parameters, in terms of the magnitude for future strong motions. These predictions can be very useful for seismic design. Particularly, the prediction of the magnitude associated to the critical acceleration, because the earthquakes with magnitude greater than this critical magnitude can produce serious damages in a structure (even its collapsing). The application of the relationships obtained in this paper must be very careful, because these equations are dependent on the source area, location and type of structure. The dominant periods of the ground motions (displacement, velocity and acceleration) that are computed and presented in this paper, are also important parameters for the seismic design, because recent studies have shown that the earthquake shaking is more destructive on structures having a natural period around some of these dominant periods. These parameters must also be handled with caution, because they show dependence with the source area, location and type of structure.展开更多
This article describes an analysis of the energy and economic impacts of possible energy efficiency standards for room air conditioners on both U.S. consumers and the nation as a whole. We used two metrics to determin...This article describes an analysis of the energy and economic impacts of possible energy efficiency standards for room air conditioners on both U.S. consumers and the nation as a whole. We used two metrics to determine the effect of standards on a representative sample of U.S. consumers: life-cycle cost change and payback period. For the national impact analysis, we evaluated national energy savings attributable to each potential standard, the monetary value of the energy savings to consumers of room air conditioners, the increased total installed costs because of standards, and the net present value of the difference between the value of energy savings and increased total installed costs. Our analysis indicates that standards for room air conditioners at efficiency level 3, which is 17% more efficient than today’s typical unit in the case of room air conditioners less than 6000 Btu/h with louvers and 12% more efficient in the case of room air conditioners 8000 - 13,999 Btu/h with louvers, would save close to one quad of energy over 30 years and have a net present value of consumer benefit of between ?$0.14 billion and $1.82 billion, depending on the discount rate. In addition, such standards would reduce carbon dioxide emissions and NOx emissions.展开更多
文摘Today,urban traffic,growing populations,and dense transportation networks are contributing to an increase in traffic incidents.These incidents include traffic accidents,vehicle breakdowns,fires,and traffic disputes,resulting in long waiting times,high carbon emissions,and other undesirable situations.It is vital to estimate incident response times quickly and accurately after traffic incidents occur for the success of incident-related planning and response activities.This study presents a model for forecasting the traffic incident duration of traffic events with high precision.The proposed model goes through a 4-stage process using various features to predict the duration of four different traffic events and presents a feature reduction approach to enable real-time data collection and prediction.In the first stage,the dataset consisting of 24,431 data points and 75 variables is prepared by data collection,merging,missing data processing and data cleaning.In the second stage,models such as Decision Trees(DT),K-Nearest Neighbour(KNN),Random Forest(RF)and Support Vector Machines(SVM)are used and hyperparameter optimisation is performed with GridSearchCV.In the third stage,feature selection and reduction are performed and real-time data are used.In the last stage,model performance with 14 variables is evaluated with metrics such as accuracy,precision,recall,F1-score,MCC,confusion matrix and SHAP.The RF model outperforms other models with an accuracy of 98.5%.The study’s prediction results demonstrate that the proposed dynamic prediction model can achieve a high level of success.
基金Supported by:National Key Research and Development Program of China under Grant No.2016YFC0701201
文摘Seismic force reduction factor(SFRF) spectra of shear-type multi-degree-of-freedom(MDOF) structures are investigated. The modified Clough model, capable of considering the strength-degradation/hardening and stiffnessdegradation, is adopted. The SFRF mean spectra using 102 earthquake records on a typical site soil type(type C) are constructed with the period abscissa being divided into three period ranges to maintain the peak features at the two sitespecific characteristic periods. Based on a large number of results, it is found that the peak value of SFRF spectra may also exist for MDOF, induced by large high-mode contributions to elastic base shear, besides the mentioned two peak values. The variations of the stiffness ratio λk and the strength ratio λF of the top to bottom story are both considered. It is found that the SFRFs for λF ≤λk are smaller than those for λF > λk. A SFRF modification factor for MDOF systems is proposed with respect to SDOF. It is found that this factor is significantly affected by the story number and ductility. With a specific λF(= λk0.75), SFRF mean spectra are constructed and simple solutions are presented for MDOF systems. For frames satisfying the strong column/weak beam requirement, an approximate treatment in the MDOF shear-beam model is to assign a post-limit stiffness 15%-35% of the initial stiffness to the hysteretic curve. SFRF spectra for MDOF systems with 0.2 and 0.3 times the post-limit stiffness are remarkably larger than those without post-limit stiffness. Thus, the findings that frames with beam hinges have smaller ductility demand are explained through the large post-limit stiffness.
基金supported by the National Science Foundation of China (11001063, 10971043)the Fundamental Research Funds for the Central Universities (HEUCF 20111134)+2 种基金China Postdoctoral Science Foundation Funded Project (20110491032)Heilongjiang Provincial Science Foundation for Distinguished Young Scholars (JC200810)Program of Excellent Team in Harbin Institute of Technology and the Natural Science Foundation of Heilongjiang Province (A200803)
文摘We study a nonlinear periodic problem driven by the p(t)-Laplacian and having a nonsmooth potential (hemivariational inequalities). Using a variational method based on nonsmooth critical point theory for locally Lipschitz functions, we first prove the existence of at least two nontrivial solutions under the generalized subquadratic and then establish the existence of at least one nontrivial solution under the generalized superquadratic.
基金Supported by the National Natural Science Foundation of China (No.60373084)
文摘A novel spatial domain method--soft morphology filter is presented for reducing the periodic noise in image processing. The simulation results are presented to demonstrate the effectiveness of the method in comparison with a frequency domain method and other spatial domain filters.
文摘The change in rainfall pattern and intensity is becoming a great concern for hydrologic engineers and planners. Many parts of the world are experiencing extreme rainfall events such as experienced on 26<sup>th</sup> July 2005 in Mumbai, India. For the appropriate design and planning of urban drainage system in an area, Intensity Duration Frequency (IDF) curves for given rainfall conditions are required. The aim of the present study is to derive the IDF curves for the rainfall in the Mumbai city, Maharashtra, India. Observed rainfall data from 1901 pertaining to Colaba and from 1951 of the Santacruz rain gauge stations in Mumbai are used in the present study to derive the IDF curves. Initially, the proposed IDF curves are derived using an empirical equation (Kothyari and Garde), by using probability distribution for annual maximum rainfall and then IDF curves are derived by modifying the equation. IDF curves developed by the modified equation gives good results in the changing hydrologic conditions and are compatible even with the extreme rainfall of 26<sup>th</sup> July 2005 in Mumbai.
文摘Background: The practice of exclusive breastfeeding (EB) in Morocco has witnessed a worrying decline in recent decades, contrary to the recommendations of the World Health Organization (WHO) which advocates it during the first six months as a significant public health tool. The present study aims to assess the impact of educational materials on mothers’ behaviour with regard to keeping up EB as long as six months, at least. Methods: This is a cohort study with a prospective collection of data over a period of one year, through a questionnaire-based survey of 500 women who delivered at the Souissi Maternity Hospital in Rabat. The subjects were divided into an intervention group sensitized, during the medical visit, by means of information delivered orally about breastfeeding and a booklet containing instructions on breastfeeding management and the benefits of EB, especially when extended for the first six months;and a control group attending the same operation with no awareness-rising through educational materials. To assess EB rates, the subjects had been followed for six months through telephone. Results: 372 women who delivered were followed, 194 from the intervention group and 178 from the control group. The remaining 128 women not followed were lost sight of. A higher percentage of mothers in the intervention group exclusively breastfed their babies up to the age of six months compared to the control group, 55.2% against 38.8% (p = 0.002). The main reason produced by most mothers who ceased to exclusively breastfeed their babies is milk insufficiency. Conclusion: The postnatal nutritional education strategy based on the distribution of educational materials has considerably raised the number of women who exclusively breastfed their babies until the age of six months.
基金Supported by National Natural Science Foundation of China,No.81772045Scientific Research Project of Heilongjiang Health and Family Planning Commission,No.2018086.
文摘BACKGROUND As a highly contagious disease,coronavirus disease 2019(COVID-19)is wreaking havoc around the world due to continuous spread among close contacts mainly via droplets,aerosols,contaminated hands or surfaces.Therefore,centralized isolation of close contacts and suspected patients is an important measure to prevent the transmission of COVID-19.At present,the quarantine duration in most countries is 14 d due to the fact that the incubation period of severe acute respiratory syndrome coronavirus type 2(SARS-CoV-2)is usually identified as 1-14 d with median estimate of 4-7.5 d.Since COVID-19 patients in the incubation period are also contagious,cases with an incubation period of more than 14 d need to be evaluated.CASE SUMMARY A 70-year-old male patient was admitted to the Department of Respiratory Medicine of The First Affiliated Hospital of Harbin Medical University on April 5 due to a cough with sputum and shortness of breath.On April 10,the patient was transferred to the Fever Clinic for further treatment due to close contact to one confirmed COVID-19 patient in the same room.During the period from April 10 to May 6,nucleic acid and antibodies to SARS-CoV-2 were tested 7 and 4 times,respectively,all of which were negative.On May 7,the patient developed fever with a maximum temperature of 39℃,and his respiratory difficulties had deteriorated.The results of nucleic acid and antibody detection of SARS-CoV-2 were positive.On May 8,the nucleic acid and antibody detection of SARS-CoV-2 by Heilongjiang Provincial Center for Disease Control were also positive,and the patient was diagnosed with COVID-19 and reported to the Chinese Center for Disease Control and Prevention.CONCLUSION This case highlights the importance of the SARS-CoV-2 incubation period.Further epidemiological investigations and clinical observations are urgently needed to identify the optimal incubation period of SARS-CoV-2 and formulate rational and evidence-based quarantine policies for COVID-19 accordingly.
基金This project is supported by the State Administration of Traditional Chinese Medicine(No.7-21).
文摘Objective:To analyze the syndrome characteristics in patients with chronic persistent asthma.Methods:365 patients(121 males,244 females,60.829.1 years old)with chronic persistent asthma were enrolled in this cross-sectional study.The information of syndrome,symptoms,signs,tongue coating and pulse were collected from all patients.The syndrome characteristics of chronic persistent asthma were examined through the multifactor dimensionality reduction(MDR)analysis and the results were verified by the Chi-square test.Results:The results of the MDR analysis and the Chi-square test showed the following positive correlation of the interaction among:the deficiency syndrome of the lung and spleen and deep pulse,disinclination to talk due to lack of qi,fatigue,lassitude and thick tongue coating;the deficiency syndrome of the lung and kidney and dizziness and disinclination to talk due to lack of qi,fatigue,lassitude and pallid complexion;the syndrome of phlegm-heat obstructing the lung and rapid pulse,abdominal distension,disinclination to talk due to lack of qi,frequent urination and lassitude;the syndrome of phlegm-dampness obstructing the lung and disinclination to talk due to lack of qi,greasy coating,fatigue and lassitude.(P<.05 for all).Conclusion:The syndrome of chronic persistent asthma is characterized by fatigue and lassitude due to dysfunction of the lung,spleen and kidney.
文摘Objective:To study the nursing effect of liposuction and volume reduction in the treatment of lymphedema during the perioperative period.Method:A total of 68 patients treated with liposuction volume reduction surgery for pseudo-lymphedema of lower limbs admitted from May 2019 to May 2020 in a tertiary hospital in Xi’an,Shaanxi Province were selected,and they were divided into observation group and control group by random grouping method.There were 34 cases in each group.The control group took routine care during the perioperative period,while the observation group performed full care during the perioperative period.The complication rate and pain degree of the two groups were compared.Results:The complication rate of the study group was 5.88%,while that of the control group was 26.67%.Compared with the study group,the complication rate was significantly higher than that of the control group,and the gap was statistically significant(P>0.05).The pain scores of patients in the study group were significantly lower than those in the control group at 3 and 6 days after surgery,and the gap was statistically significant(P>0.05).Conclusion:Lymphedema should be taken care of during the perioperative period of liposuction and volume reduction,which can effectively reduce the occurrence of pain and complications.It is worthy of extensive clinical promotion.
文摘The introduction of defects can adjust the activity of graphene-based single-atom catalysts for oxygen reduction reactions(ORR).Herein,we for the first time investigate the ORR catalytic activity of FeN_(4)sites embedded on graphene with four types of line-defective boundary via density functional theory calculations.Our results show that periodic line defects consisting of pentagon-pentagon-octagon(C_(585))or quad-octagon chains(C_(484))can significantly enhance ORR activity,owing to the optimized electronic structures of FeN_(4)sites.The spin magnetic moment and the valence state of the Fe atom are both well correlated with the ORR overpotential.Experimental investigations further corroborate that FeN_(4)with a high degree of defects exhibits better ORR activity and stability compared to FeN_(4)sites of pristine graphene and commercial Pt/C.This work unravels the influence of the periodic defect boundary on the ORR performance of Fe-N-C catalysts and paves the way towards the rational design of highly effective single-atom electrocatalysts.
基金supported jointly by the National Key Research and Development Program of China [grant number 2016YFB02008001]the National Natural Science Foundation of China [grant number 41530426]
文摘Winter North Atlantic Oscillation(NAO)indexes from observations based on various winter durations are compared.Results show that there are significant differences in the interannual and decadal variations of these NAO indexes.For the same data source,a different definition of winter duration can lead to different signs of NAO index in some years,which mainly appear to be in the period of decadal phase transition.The different winter durations induce different cycles of the observation-based NAO.The longer the winter duration,the stronger the decadal variation.The NAO defined by different winter durations also can generate different descriptions of the NAO action centers,including the position and movement.The longer the winter duration,the more southerly action centers appear to be.The movement of the action centers affects not only site-based NAO indexes but also those defined by other methods,such as empirical orthogonal function(EOF)analysis.The length of time used in EOF analysis has a great influence on the spatial pattern of the NAO mode,which results in a considerable difference between the corresponding NAO indexes.Regardless of which NAO index is used,the NAO-related SST anomalies show the same tripole pattern.The longer the winter duration,the more significant the relationship between the NAO and SST affected by the timescale of sea-air interaction.
基金The National Natural Science Foundation of China(No.71671035)Open Fund of Jiangsu Wind Power Engineering Technology Center,China(No.ZK15-03-01,ZK16-03-07)
文摘Taking the multi-component system as research object, a maintenance optimization model based on the unequal inspection period and imperfect repair is established by considering the requirement of expected availability for improving the system's availability. An age reduction factor is used to describe the effect of imperfect repair, and the modelling approach for the unequal inspection period is proposed. Unavailable situations are classified into three kinds of independent cases, and the availability is calculated accordingly. Based on the analysis of the relationship between the unavailable cases and the unequal inspection period, an optimization model under imperfect repair is established to optimize the system's expected availability. A case study of a wind turbine is provided, and three key components, i.e. gearbox, generator and spindle, are considered. The optimization results of the unequal inspection period model and the equal inspection period model are compared. The results show that the unequal inspection period model based on availability can update the maintenance plan so as to optimize maintenance activities and improve the system's availability.
基金supported by the National Natural Science Foundation of China under Grant No.50221903by the Ministry of Science and Technology of China under Grant No.2007BAC06B06
文摘Fluctuating snow-covered elevation (FSCE) was conceptualized and proposed to characterize within-year variation of the border between snow-covered and snow-free area in mountainous regions. Two parameters, namely median of snow flee period (Tm) and snow free duration (AT), were defined to quantify FSCE. A regression model of FSCE was developed for the Lhasa River Basin, Niyang River Basin, and Changdu region in eastern Tibet. Statistical analysis of the snow-products data with a spatial resolution of 25km×25km shows that: (1) Tm correlates weakly with geographical and topographic factors, having the yearly mean value of July 31; (2) △T correlates significantly with the average elevation of the snow-products cell, having the yearly mean value of nearly five months (i.e., 151 days); (3) the region begins snow disappearance in late April and finishes snow coverage in mid November, being snow-free from late June to mid September and snow-covered from December to March in the next year. In addi- tion, snow-products with higher spatial resolution will be helpful to characterize FSCE in smaller spatial scales.
文摘In this paper, the analysis of ground motions (displacements, velocities and accelerations) has been performed focused to the seismic design. The relationships between the peak ground acceleration (PGA), the peak ground velocity (PGV), the peak ground displacement (PGD) and the bracketed duration, with the earthquake magnitude, are presented and their validity and applicability for seismic design is discussed. Finally, the dominant periods of the ground motions (displacement, velocity and acceleration) are obtained from their Fourier Spectrum. Their validity and applicability for the seismic design is discussed also. The results presented in this paper show that the relationships that exist between the important parameters: PGA, PGV, PGD and duration;and the earthquake magnitude, allow the prediction of the values for these parameters, in terms of the magnitude for future strong motions. These predictions can be very useful for seismic design. Particularly, the prediction of the magnitude associated to the critical acceleration, because the earthquakes with magnitude greater than this critical magnitude can produce serious damages in a structure (even its collapsing). The application of the relationships obtained in this paper must be very careful, because these equations are dependent on the source area, location and type of structure. The dominant periods of the ground motions (displacement, velocity and acceleration) that are computed and presented in this paper, are also important parameters for the seismic design, because recent studies have shown that the earthquake shaking is more destructive on structures having a natural period around some of these dominant periods. These parameters must also be handled with caution, because they show dependence with the source area, location and type of structure.
文摘This article describes an analysis of the energy and economic impacts of possible energy efficiency standards for room air conditioners on both U.S. consumers and the nation as a whole. We used two metrics to determine the effect of standards on a representative sample of U.S. consumers: life-cycle cost change and payback period. For the national impact analysis, we evaluated national energy savings attributable to each potential standard, the monetary value of the energy savings to consumers of room air conditioners, the increased total installed costs because of standards, and the net present value of the difference between the value of energy savings and increased total installed costs. Our analysis indicates that standards for room air conditioners at efficiency level 3, which is 17% more efficient than today’s typical unit in the case of room air conditioners less than 6000 Btu/h with louvers and 12% more efficient in the case of room air conditioners 8000 - 13,999 Btu/h with louvers, would save close to one quad of energy over 30 years and have a net present value of consumer benefit of between ?$0.14 billion and $1.82 billion, depending on the discount rate. In addition, such standards would reduce carbon dioxide emissions and NOx emissions.