The purpose of this study was to determine the displacement and dynamic distribution characteristics of the remaining oil in the two development stages of water flooding and subsequent alkaline surfactant polymer(ASP)...The purpose of this study was to determine the displacement and dynamic distribution characteristics of the remaining oil in the two development stages of water flooding and subsequent alkaline surfactant polymer(ASP) flooding. The well pattern types in the water and ASP flooding stages are a longdistance determinant well pattern and short-distance five-point well pattern, respectively. The type A displacement characteristic curve can be obtained using the production data, and the slope of the straight-line section of the curve can reflect the displacement strength of the oil displacement agent. A numerical simulation was carried out based on the geological model. The results revealed that the injected water advances steadily with a large-distance determinant water-flooding well pattern. The single-well water production rate increases monotonically during water flooding. There is a significant positive correlation between the cumulative water-oil ratio and the formation parameter. Differential seepage between the oil and water phases is the main factor causing residual oil formation after water flooding, while the residual oil is still relatively concentrated. The effect of the chemical oildisplacement agent on improving the oil-water two-phase seepage flow has distinct stages during ASP flooding. The remaining oil production is extremely sporadic after ASP flooding.展开更多
Static tests under cyclic loading were carried out on Populus alba var. pyramidalis to determine its characteristic curves of restoring forces. The results show that P alba var. pyramidalis had good elastic performanc...Static tests under cyclic loading were carried out on Populus alba var. pyramidalis to determine its characteristic curves of restoring forces. The results show that P alba var. pyramidalis had good elastic performance. There was degradation of strength and stiffness under cyclic loading and unloading, where characteristic curves of restoring forces ofP. alba var. pyrarnidalis assumed a ＂flat and contrary S-shape＂ form. Simultaneously, P alba vat. pyramidalis showed typical characteristics of brittle destruction under large high peak loading and unloading. Furthermore, dynamic tests were carried out under wind loads to obtain dynamic displacement curves and dynamic strain curves. P alba var. pyramidalis reflected its stochastic dynamic performance in building up its resistance to the stochastic wind loads and its dynamically hysteretic properties. The dynamic response of this species was random and fuzzy under stochastic wind loads. This study has theoretical significance and reference value to research on the static characteristics and wind-induced dynamic performance of forests.展开更多
This paper introduces horizon control, seismic control, logging control and facies control methods through the application of the least squares fitting of logging curves, seismic inversion and facies-controlled techni...This paper introduces horizon control, seismic control, logging control and facies control methods through the application of the least squares fitting of logging curves, seismic inversion and facies-controlled techniques. Based on the microgeology and thin section analyses, the lithology, lithofacies and periods of the Permian igneous rocks are described in detail. The seismic inversion and facies-controlled techniques were used to find the distribution characteristics of the igneous rocks and the 3D velocity volume. The least squares fitting of the logging curves overcome the problem that the work area is short of density logging data. Through analysis of thin sections, the lithofacies can be classified into eruption airfall subfacies, eruption pyroclastic flow subfacies and eruption facies.展开更多
A Receiver Operating Characteristic(ROC)analysis of a power is important and useful in clinical trials.A Classical Conditional Power(CCP)is a probability of a classical rejection region given values of true treatment ...A Receiver Operating Characteristic(ROC)analysis of a power is important and useful in clinical trials.A Classical Conditional Power(CCP)is a probability of a classical rejection region given values of true treatment effect and interim result.For hypotheses and reversed hypotheses under normal models,we obtain analytical expressions of the ROC curves of the CCP,find optimal ROC curves of the CCP,investigate the superiority of the ROC curves of the CCP,calculate critical values of the False Positive Rate(FPR),True Positive Rate(TPR),and cutoff of the optimal CCP,and give go/no go decisions at the interim of the optimal CCP.In addition,extensive numerical experiments are carried out to exemplify our theoretical results.Finally,a real data example is performed to illustrate the go/no go decisions of the optimal CCP.展开更多
BACKGROUND:The study aimed to evaluate the predictive role of interleukin-6(IL-6)and chronic obstructive pulmonary disease(COPD)assessment test(CAT)score in mechanical ventilation(MV)in COPD patients at the acute exac...BACKGROUND:The study aimed to evaluate the predictive role of interleukin-6(IL-6)and chronic obstructive pulmonary disease(COPD)assessment test(CAT)score in mechanical ventilation(MV)in COPD patients at the acute exacerbation stage in the emergency department(ED).METHODS:For a one-year period,among adult patients in the ED who met the criteria of acute exacerbation of COPD,158 who received MV within 48 hours after admission were compared to 294 who didn't require MV within the same period after admission.IL-6 level and CAT score were compared between the two groups.The predicted value of IL-6 and CAT score was assessed by logistic regression analysis and a receiver operating characteristic(ROC)curve.RESULTS:The IL-6 and CAT scores in the 158 MV patients were much higher than those without.IL-6 and CAT scores were independent predictors of MV within 48 hours using logistic regression analysis(IL-6:odds ratio[OR]1.053,95%confidence interval[CI]1.039–1.067,P<0.001;CAT score:OR 1.122,95%CI 1.086–1.159,P<0.001).The combination of IL-6 and CAT scores(area under ROC curve[AUC]0.826,95%CI 0.786–0.866,P<0.001)improved the accuracy of predicting MV within 48 hours when compared with IL-6(AUC 0.752,95%CI 0.703–0.800,P<0.001)and CAT scores alone(AUC 0.739,95%CI 0.692–0.786,P<0.001).The sensitivity and specificity were 69.6%,74.1%,75.32%and 63.6%,respectively.CONCLUSION:The combined of IL-6 and CAT scores is useful for evaluating the risk of COPD patients at acute exacerbation in ED,and can provide a predictive value for MV or not within 48 hours.展开更多
By introducing the coupling flow expressions of main fracture-matrix, secondary fracture-matrix and main fracture-secondary fracture into the traditional main fracture material balance equation, the “main fracture-se...By introducing the coupling flow expressions of main fracture-matrix, secondary fracture-matrix and main fracture-secondary fracture into the traditional main fracture material balance equation, the “main fracture-secondary fracture-matrix” leak-off coupling flow model is established. The pressure-dependent fracture width equation and the wellbore injection volume equation are coupled to solve the pressure-rate continuity problem. The simulation and calculation of the bottomhole pressure drop and fracture network closure after the pump stopping in slickwater volumetric fracturing treatment are realized. The research results show that the log-log curve of pump-stopping bottomhole pressure drop derivative presents five characteristic slope segments, reflecting four dominant stages, i.e. inter-fracture crossflow, fracture network leak-off, fracture network closure and residual leak-off, after pump shutdown. At the initial time of pump shutdown for volumetric fracturing treatment of horizontal well, the crossflow between main and secondary fractures is obvious, and then the leak-off becomes dominant. The leak-off of main and secondary fractures shows a non-uniform decreasing trend. Specifically, the leak-off of main fractures is slow, while that of secondary fractures is fast;the fracture network as a whole presents the leak-off law of fast first, then slow, until close to zero. The influence of fracture network conductivity on the shape of pressure decline curve is relatively weaker than that of fracture network size. The fracture network conductivity is positively correlated with leak-off volume and fracture closure. The secondary fracture size is positively correlated with leakoff volume and closure of the secondary fracture, but negatively correlated with closure of the main fracture. Field data validation proves that the proposed model and simulation results can effectively reflect the closure characteristics of the fracture network, and the interpretation results are reliable and can reflect the non-uniform stimulation performance of each fracturing stage of an actual horizontal well.展开更多
The prototype neutron flux monitor consists of a high purity ^(235)U fission chamber detector and a'blank'detector,which is a fissile material free detector with the same dimension as the fission chamber detec...The prototype neutron flux monitor consists of a high purity ^(235)U fission chamber detector and a'blank'detector,which is a fissile material free detector with the same dimension as the fission chamber detector to identify noise issues such as noise coming from gamma rays.The main parameters of the fission chamber assembly that have been measured in the laboratory are confirmed to approach the technological level of the International Thermonuclear Experimental Reactor(ITER)in the near future.This prototype neutron flux monitor will be further developed to become a neutron flux monitor suitable for the operation phase of D-D fusion on the ITER.展开更多
BACKGROUND:Spontaneous isolated superior mesenteric artery(SMA)dissection(SISMAD)is a rare cause of abdominal pain.The aim of the study is to investigate the role of a new parameter,the ratio of the SMA diameter to th...BACKGROUND:Spontaneous isolated superior mesenteric artery(SMA)dissection(SISMAD)is a rare cause of abdominal pain.The aim of the study is to investigate the role of a new parameter,the ratio of the SMA diameter to the superior mesenteric vein(SMV)diameter(SMA/SMV)based on non-enhanced computed tomography(CT),in the early diagnosis of SISMAD.METHODS:In a registry study from December 2013 to June 2021,97 abdominal pain SISMAD patients(SISMAD group)admitted to our hospital were enrolled.Meanwhile,the matched sex and age abdominal pain non-SISMAD patients at 1:2 were collected in reverse chronological order as the control group.Student’s t-test,Wilcoxon rank-sum test,and Chi-square test were used to compare differences between the SISMAD and control groups.Med Calc was used to generate receiver operating characteristic(ROC)curve.RESULTS:A total of 291 abdominal pain patients,including 97 SISMAD patients and 194 nonSISMAD patients,were included in the current study.The maximum SMA diameter,perivascular exudation,and SMA/SMV based on non-enhanced CT were significant between the two groups(all P<0.05).ROC curves showed that for the maximum SMA diameter,the area under the curve(AUC),cut-off,sensitivity,and specificity were 0.926,9.80,93.8%,and 79.4%,respectively.For SMA/SMV,its AUC,cut-off,sensitivity,and specificity were 0.956,0.83,88.7%,and 92.3%,respectively.The diagnostic efficiency of SMA/SMV was better than that of the maximum SMA diameter(P<0.05).The combined parameters of SMA/SMV and maximum SMA diameter had the best diagnostic efficiency(AUC=0.970).CONCLUSION:SMA/SMV may be a potential marker for SISMAD.展开更多
Objective： To assess the value of MR spectroscopy （MRS） in the diagnosis of prostate cancer by meta-analysis. Methods： Prospective studies were selected from the MEDLINE, Ovid, Embase databases, Springer, Elsevier...Objective： To assess the value of MR spectroscopy （MRS） in the diagnosis of prostate cancer by meta-analysis. Methods： Prospective studies were selected from the MEDLINE, Ovid, Embase databases, Springer, Elsevier, China National Knowledge Infrastructure. According to the suggestion, results were determined by the ratio of （Cho＋Cr）/Cit. If this ratio was less than 0.75, negative result was respectively determined, and the definitive tumor was diagnosed as this threshold. According to the assessment standard of Evidence-based Medicine, English and Chinese literature in Grade A and B on MRS imaging was included. According to homogeneity test, different effect models were chosen to calculate different pooled weighted values of sensitivity, specificity and the corresponding 95% confidence intervals （95% CI）. Summary receiver operating characteristic （SROC） curves were used to assess the results. Funnel plot was used to analyze publication bias. Results： According to the assessment standard of Evidence-based Medicine, only 5 papers in Grade B were included in this research. The pooled weighted sensitivity and its 95% confidence interval is 82% （73%, 89%） and the pooled weighted sensitivity and its 95% confidence interval is 68% （58%, 76%）. The AUC （area under curve） is 83.40%. An asymmetric funnel plot suggested two missing studies leading to publication bias. Conclusion： If the ratio of （Cho＋Cr）/Cit is regarded as the diagnostic criteria in detecting prostate cancer by MRS, meta-analysis suggests this method has a better diagnostic value to detect the malignant prostate mass but the sensitivity needs to be improved. We hope to support a method and requirement about diagnostic test. Performing perspective register and improving quality of study design is the only way to reduce the bias and get real information of disease.展开更多
Understanding the drivers of biological invasions in landscapes is a major goal in invasion ecology.The control of biological invasions has increasingly become critical in the past few decades because invasive species...Understanding the drivers of biological invasions in landscapes is a major goal in invasion ecology.The control of biological invasions has increasingly become critical in the past few decades because invasive species are thought to be a major threat to endemism.In this study,by examining the key variables that influence Acacia mearnsii,we sought to understand its potential invasion in eastern Zimbabwe.We used the maximum entropy(MaxEnt)method against a set of environmental variables to predict the potential invasion front of A.mearnsii.Our study showed that the predictor variables,i.e.,aspect,elevation,distance from streams,soil type and distance from the nearest A.mearnsii plantation adequately explained(training AUC=0.96 and test AUC=0.93)variability in the spatial distribution of invading A.mearnsii.The front of invasion by A.mearnsii seemed also to occur next to existing A.mearnsii plantations.Results from our study could be useful in identifying priority areas that could be targeted for controlling the spread of A.mearnsii in Zimbabwe and other areas under threat from A.mearnsii invasion.We recommend that the plantation owners pay for the control of A.mearnsii invasion about their plantations.展开更多
基金The authors would like to thank the National Science and Technology Major Project(2016ZX05054012)for funding.
文摘The purpose of this study was to determine the displacement and dynamic distribution characteristics of the remaining oil in the two development stages of water flooding and subsequent alkaline surfactant polymer(ASP) flooding. The well pattern types in the water and ASP flooding stages are a longdistance determinant well pattern and short-distance five-point well pattern, respectively. The type A displacement characteristic curve can be obtained using the production data, and the slope of the straight-line section of the curve can reflect the displacement strength of the oil displacement agent. A numerical simulation was carried out based on the geological model. The results revealed that the injected water advances steadily with a large-distance determinant water-flooding well pattern. The single-well water production rate increases monotonically during water flooding. There is a significant positive correlation between the cumulative water-oil ratio and the formation parameter. Differential seepage between the oil and water phases is the main factor causing residual oil formation after water flooding, while the residual oil is still relatively concentrated. The effect of the chemical oildisplacement agent on improving the oil-water two-phase seepage flow has distinct stages during ASP flooding. The remaining oil production is extremely sporadic after ASP flooding.
基金supported by the National Natural Science Foundation of China (Grant No. 30872071)
文摘Static tests under cyclic loading were carried out on Populus alba var. pyramidalis to determine its characteristic curves of restoring forces. The results show that P alba var. pyramidalis had good elastic performance. There was degradation of strength and stiffness under cyclic loading and unloading, where characteristic curves of restoring forces ofP. alba var. pyrarnidalis assumed a ＂flat and contrary S-shape＂ form. Simultaneously, P alba vat. pyramidalis showed typical characteristics of brittle destruction under large high peak loading and unloading. Furthermore, dynamic tests were carried out under wind loads to obtain dynamic displacement curves and dynamic strain curves. P alba var. pyramidalis reflected its stochastic dynamic performance in building up its resistance to the stochastic wind loads and its dynamically hysteretic properties. The dynamic response of this species was random and fuzzy under stochastic wind loads. This study has theoretical significance and reference value to research on the static characteristics and wind-induced dynamic performance of forests.
基金A Project Funded by National Science and Technology Major Project (2011ZX05001-002-003)the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)Key Laboratory for Coalbed Methane Resources and Reservoir formation Process, CUMT, Ministry of Education, China
文摘This paper introduces horizon control, seismic control, logging control and facies control methods through the application of the least squares fitting of logging curves, seismic inversion and facies-controlled techniques. Based on the microgeology and thin section analyses, the lithology, lithofacies and periods of the Permian igneous rocks are described in detail. The seismic inversion and facies-controlled techniques were used to find the distribution characteristics of the igneous rocks and the 3D velocity volume. The least squares fitting of the logging curves overcome the problem that the work area is short of density logging data. Through analysis of thin sections, the lithofacies can be classified into eruption airfall subfacies, eruption pyroclastic flow subfacies and eruption facies.
基金supported by the National Social Science Fund of China(Grand No.21XTJ001).
文摘A Receiver Operating Characteristic(ROC)analysis of a power is important and useful in clinical trials.A Classical Conditional Power(CCP)is a probability of a classical rejection region given values of true treatment effect and interim result.For hypotheses and reversed hypotheses under normal models,we obtain analytical expressions of the ROC curves of the CCP,find optimal ROC curves of the CCP,investigate the superiority of the ROC curves of the CCP,calculate critical values of the False Positive Rate(FPR),True Positive Rate(TPR),and cutoff of the optimal CCP,and give go/no go decisions at the interim of the optimal CCP.In addition,extensive numerical experiments are carried out to exemplify our theoretical results.Finally,a real data example is performed to illustrate the go/no go decisions of the optimal CCP.
基金supported by grants from Dongzhimen Hospital Fund of Special Talent(2018RC01)Beijing University of Chinese Medicine Fund of Project(2019-JYB-XJSJJ-025)
文摘BACKGROUND:The study aimed to evaluate the predictive role of interleukin-6(IL-6)and chronic obstructive pulmonary disease(COPD)assessment test(CAT)score in mechanical ventilation(MV)in COPD patients at the acute exacerbation stage in the emergency department(ED).METHODS:For a one-year period,among adult patients in the ED who met the criteria of acute exacerbation of COPD,158 who received MV within 48 hours after admission were compared to 294 who didn't require MV within the same period after admission.IL-6 level and CAT score were compared between the two groups.The predicted value of IL-6 and CAT score was assessed by logistic regression analysis and a receiver operating characteristic(ROC)curve.RESULTS:The IL-6 and CAT scores in the 158 MV patients were much higher than those without.IL-6 and CAT scores were independent predictors of MV within 48 hours using logistic regression analysis(IL-6:odds ratio[OR]1.053,95%confidence interval[CI]1.039–1.067,P<0.001;CAT score:OR 1.122,95%CI 1.086–1.159,P<0.001).The combination of IL-6 and CAT scores(area under ROC curve[AUC]0.826,95%CI 0.786–0.866,P<0.001)improved the accuracy of predicting MV within 48 hours when compared with IL-6(AUC 0.752,95%CI 0.703–0.800,P<0.001)and CAT scores alone(AUC 0.739,95%CI 0.692–0.786,P<0.001).The sensitivity and specificity were 69.6%,74.1%,75.32%and 63.6%,respectively.CONCLUSION:The combined of IL-6 and CAT scores is useful for evaluating the risk of COPD patients at acute exacerbation in ED,and can provide a predictive value for MV or not within 48 hours.
基金Supported by the National Natural Science Foundation of China (51974332)。
文摘By introducing the coupling flow expressions of main fracture-matrix, secondary fracture-matrix and main fracture-secondary fracture into the traditional main fracture material balance equation, the “main fracture-secondary fracture-matrix” leak-off coupling flow model is established. The pressure-dependent fracture width equation and the wellbore injection volume equation are coupled to solve the pressure-rate continuity problem. The simulation and calculation of the bottomhole pressure drop and fracture network closure after the pump stopping in slickwater volumetric fracturing treatment are realized. The research results show that the log-log curve of pump-stopping bottomhole pressure drop derivative presents five characteristic slope segments, reflecting four dominant stages, i.e. inter-fracture crossflow, fracture network leak-off, fracture network closure and residual leak-off, after pump shutdown. At the initial time of pump shutdown for volumetric fracturing treatment of horizontal well, the crossflow between main and secondary fractures is obvious, and then the leak-off becomes dominant. The leak-off of main and secondary fractures shows a non-uniform decreasing trend. Specifically, the leak-off of main fractures is slow, while that of secondary fractures is fast;the fracture network as a whole presents the leak-off law of fast first, then slow, until close to zero. The influence of fracture network conductivity on the shape of pressure decline curve is relatively weaker than that of fracture network size. The fracture network conductivity is positively correlated with leak-off volume and fracture closure. The secondary fracture size is positively correlated with leakoff volume and closure of the secondary fracture, but negatively correlated with closure of the main fracture. Field data validation proves that the proposed model and simulation results can effectively reflect the closure characteristics of the fracture network, and the interpretation results are reliable and can reflect the non-uniform stimulation performance of each fracturing stage of an actual horizontal well.
基金The project supported by the National Natural Science Foundation of China(No.10175021)the Retraining Foundation of the Southwestern Institute of Physics for Talented Personnel
文摘The prototype neutron flux monitor consists of a high purity ^(235)U fission chamber detector and a'blank'detector,which is a fissile material free detector with the same dimension as the fission chamber detector to identify noise issues such as noise coming from gamma rays.The main parameters of the fission chamber assembly that have been measured in the laboratory are confirmed to approach the technological level of the International Thermonuclear Experimental Reactor(ITER)in the near future.This prototype neutron flux monitor will be further developed to become a neutron flux monitor suitable for the operation phase of D-D fusion on the ITER.
基金supported by Clinical Scientific Research Fund of Zhejiang Medical Association(2021ZYC-A73)。
文摘BACKGROUND:Spontaneous isolated superior mesenteric artery(SMA)dissection(SISMAD)is a rare cause of abdominal pain.The aim of the study is to investigate the role of a new parameter,the ratio of the SMA diameter to the superior mesenteric vein(SMV)diameter(SMA/SMV)based on non-enhanced computed tomography(CT),in the early diagnosis of SISMAD.METHODS:In a registry study from December 2013 to June 2021,97 abdominal pain SISMAD patients(SISMAD group)admitted to our hospital were enrolled.Meanwhile,the matched sex and age abdominal pain non-SISMAD patients at 1:2 were collected in reverse chronological order as the control group.Student’s t-test,Wilcoxon rank-sum test,and Chi-square test were used to compare differences between the SISMAD and control groups.Med Calc was used to generate receiver operating characteristic(ROC)curve.RESULTS:A total of 291 abdominal pain patients,including 97 SISMAD patients and 194 nonSISMAD patients,were included in the current study.The maximum SMA diameter,perivascular exudation,and SMA/SMV based on non-enhanced CT were significant between the two groups(all P<0.05).ROC curves showed that for the maximum SMA diameter,the area under the curve(AUC),cut-off,sensitivity,and specificity were 0.926,9.80,93.8%,and 79.4%,respectively.For SMA/SMV,its AUC,cut-off,sensitivity,and specificity were 0.956,0.83,88.7%,and 92.3%,respectively.The diagnostic efficiency of SMA/SMV was better than that of the maximum SMA diameter(P<0.05).The combined parameters of SMA/SMV and maximum SMA diameter had the best diagnostic efficiency(AUC=0.970).CONCLUSION:SMA/SMV may be a potential marker for SISMAD.
文摘Objective： To assess the value of MR spectroscopy （MRS） in the diagnosis of prostate cancer by meta-analysis. Methods： Prospective studies were selected from the MEDLINE, Ovid, Embase databases, Springer, Elsevier, China National Knowledge Infrastructure. According to the suggestion, results were determined by the ratio of （Cho＋Cr）/Cit. If this ratio was less than 0.75, negative result was respectively determined, and the definitive tumor was diagnosed as this threshold. According to the assessment standard of Evidence-based Medicine, English and Chinese literature in Grade A and B on MRS imaging was included. According to homogeneity test, different effect models were chosen to calculate different pooled weighted values of sensitivity, specificity and the corresponding 95% confidence intervals （95% CI）. Summary receiver operating characteristic （SROC） curves were used to assess the results. Funnel plot was used to analyze publication bias. Results： According to the assessment standard of Evidence-based Medicine, only 5 papers in Grade B were included in this research. The pooled weighted sensitivity and its 95% confidence interval is 82% （73%, 89%） and the pooled weighted sensitivity and its 95% confidence interval is 68% （58%, 76%）. The AUC （area under curve） is 83.40%. An asymmetric funnel plot suggested two missing studies leading to publication bias. Conclusion： If the ratio of （Cho＋Cr）/Cit is regarded as the diagnostic criteria in detecting prostate cancer by MRS, meta-analysis suggests this method has a better diagnostic value to detect the malignant prostate mass but the sensitivity needs to be improved. We hope to support a method and requirement about diagnostic test. Performing perspective register and improving quality of study design is the only way to reduce the bias and get real information of disease.
文摘Understanding the drivers of biological invasions in landscapes is a major goal in invasion ecology.The control of biological invasions has increasingly become critical in the past few decades because invasive species are thought to be a major threat to endemism.In this study,by examining the key variables that influence Acacia mearnsii,we sought to understand its potential invasion in eastern Zimbabwe.We used the maximum entropy(MaxEnt)method against a set of environmental variables to predict the potential invasion front of A.mearnsii.Our study showed that the predictor variables,i.e.,aspect,elevation,distance from streams,soil type and distance from the nearest A.mearnsii plantation adequately explained(training AUC=0.96 and test AUC=0.93)variability in the spatial distribution of invading A.mearnsii.The front of invasion by A.mearnsii seemed also to occur next to existing A.mearnsii plantations.Results from our study could be useful in identifying priority areas that could be targeted for controlling the spread of A.mearnsii in Zimbabwe and other areas under threat from A.mearnsii invasion.We recommend that the plantation owners pay for the control of A.mearnsii invasion about their plantations.
