Hot tearing is often a major casting defect in magnesium alloys and has a significant impact on the quality of their casting products.Hot tearing of magnesium alloys is a complex solidification phenomenon which is sti...Hot tearing is often a major casting defect in magnesium alloys and has a significant impact on the quality of their casting products.Hot tearing of magnesium alloys is a complex solidification phenomenon which is still not fully understood,it is of great importance to investigate the hot tearing behaviour of magnesium alloys.This review attempts to summarize the investigations on hot tearing of magnesium alloys over the past decades.The hot tearing criteria including recently developed Kou’s criterion are summarized and compared.The numeric simulation and assessing methods of hot tearing,factors influencing hot tearing,and hot tearing susceptibility(HTS)of magnesium alloys are discussed.展开更多
By solving steady model of air flow diffusion and chemical reaction in loose coal, distribution of oxygen concentration and flow velocity magnitude were obtained. Compared the simulating results with critic value as w...By solving steady model of air flow diffusion and chemical reaction in loose coal, distribution of oxygen concentration and flow velocity magnitude were obtained. Compared the simulating results with critic value as well as duration of spontaneous combustion from large-scale spontaneous combustion experiment, 'three zones' of spontaneous combustion were partitioned and mining conditions to avoid spontaneous combustion were obtained. The above method was employed to partition 'three zones' in gob of fully mechanized top-coal caving long wall face and got fairly good result. Calculation of the above method is much smaller than simulating the whole process of coal spontaneous combustion, but the prediction precision can satisfy the demand of predicting and extinguishing spontaneous combustion in mining.展开更多
The motion of a surface vehicle on/above an irregular object is inv.estigated for a potential interest in the insitu explorations to asteroids of the solar system. A global valid numeric method, including detailed gra...The motion of a surface vehicle on/above an irregular object is inv.estigated for a potential interest in the insitu explorations to asteroids of the solar system. A global valid numeric method, including detailed gravity and geo- morphology, is developed to mimic the behaviors of the test particles governed by the orbital equations and surface cou- pling effects. A general discussion on the surface mechanical environment of a specified asteroid, 1620 Geographos, is presented to make a global evaluation of the surface vehicle＇s working conditions. We show the connections between the natural trajectories near the ground and differential features of the asteroid surface, which describes both the good and bad of typical terrains from the viewpoint of vehicles＇ dynamic performances. Monte Carlo simulations are performed to take a further look at the trajectories of particles initializing near the surface. The simulations reveal consistent conclusions with the analysis, i.e., the open- field flat ground and slightly concave basins/valleys are the best choices for the vehicles＇ dynamical security. The dependence of decending trajectories on the releasing height is studied as an application; the results show that the pole direction （where the centrifugal force is zero） is the most stable direction in which the shift of a natural trajectory will be well limited after landing. We present this work as an example for pre-analysis that provides guidance to engineering design of the exploration site and routing the surface vehicles.展开更多
Finite element method is employed to calculate the temperature fields for two kinds of steel concrete composite slabs: composite slab with profiled steel sheeting and LJMB composite slab. The calculated results are in...Finite element method is employed to calculate the temperature fields for two kinds of steel concrete composite slabs: composite slab with profiled steel sheeting and LJMB composite slab. The calculated results are in good agreement with those of tests. Fire resistance of the two kinds of composite slabs is calculated by using a numeric method. The results show that: due to heat absorbing of concrete, the performance of composite slabs under fire is better than that of unprotected steel structure, and fire resistance of composite slabs mentioned in this paper is at least 30 min subjected to standard fire. Parameters related to the fire resistance are discussed. It was found that with increasing of concrete strength and thickness of slab, fire resistance increases, and with increasing of steel strength and steel ratio, fire resistance decreases. Also thickness of fire proof is calculated by a numeric method. The results obtained in this paper may be referenced for practical engineering.展开更多
Objective:Vulvar lichen planus(VLP),especially erosive VLP(EVLP),seriously affects women’s physiological function and quality of life.A retrospective analysis of erosive vulvar lichen planus(EVLP)was performed to rai...Objective:Vulvar lichen planus(VLP),especially erosive VLP(EVLP),seriously affects women’s physiological function and quality of life.A retrospective analysis of erosive vulvar lichen planus(EVLP)was performed to raise awareness on this chronic,deforming,and painful vulvar disease.Methods:This observational retrospective study involved 40 patients with EVLP among 1,368 patients with vulvar disease from 2017 to 2020.The patients’vulvar clinical features and extravulvar mucosal involvement were investigated.The patients’pain and quality of life were evaluated with the numeric rating scale and the Dermatology Life Quality Index(DLQI),respectively.Clinical characteristics were reported using frequencies and proportions for categorical variables.Continuous variables are expressed as mean±standard deviation.The association between NRS score for pain and DLQI score was analyzed by Pearson’s correlation test.Results:EVLP accounted for 2.9%(40/1,368)of all cases of vulvar disease,and the median age at onset was 42 years.Erosion mostly occurred on the labia minora and introitus.Half(20/40)of the patients had extravulvar mucosal involvement.Seventeen(42.5%)patients had oral lichen planus,and seven(17.5%)patients were diagnosed with vulvovaginal-gingival syndrome.The numeric rating scale score showed that 47.5%(19/40)of patients experienced mild pain,whereas 12.5%(5/40)described the pain as severe.Thirty-one patients(77.5%,31/40)had dyspareunia,and nine patients had aggravated pain after sexual intercourse.The mean DLQI score was 9.1±6.0,with 37.5%(15/40)of patients indicating that EVLP had severely affected their lives.The numeric rating scale score for pain was significantly correlated with the DLQI score(P=0.007).Conclusion:EVLP can affect the quality of women’s lives and cause severe deformations and painful architectural changes.The description of the characteristics of EVLP in this report will benefit the diagnosis and early treatment of this disease.展开更多
Probabilistic inflow forecasts can quantify the uncertainty involved in the forecasting process and provide useful risk information for reservoir management.This study proposed a probabilistic inflow forecasting schem...Probabilistic inflow forecasts can quantify the uncertainty involved in the forecasting process and provide useful risk information for reservoir management.This study proposed a probabilistic inflow forecasting scheme for the Three Gorges Reservoir(TGR)at 1-3 d lead times.The post-processing method Ensemble Model Output Statistics(EMOS)is used to derive probabilistic inflow forecasts from ensemble inflow forecasts.Considering the inherent skew feature of the inflow series,lognormal and gamma distributions are used as EMOS predictive distributions in addition to conventional normal distribution.Results show that TGR's ensemble inflow forecasts at 1-3 d lead times perform well with high model efficiency and small mean absolute error.Underestimation of forecasting uncertainty is observed for the raw ensemble inflow forecasts with biased probability integral transform(PIT)histograms.The three EMOS probabilistic forecasts outperform the raw ensemble forecasts in terms of both deterministic and probabilistic performance at 1-3 d lead times.The EMOS results are more reliable with much flatter PIT histograms,coverage rates approximate to the nominal coverage 89.47%and satisfactory sharpness.Results also show that EMOS with gamma distribution is superior to normal and lognormal distributions.This research can provide reliable probabilistic inflow forecasts without much variation of TGR5s operational inflow forecasting procedure.展开更多
A mathematical model with cytotoxic cells of hepatitis B virus (HBV)infection is set up based on a basic model of virus dynamics without cytotoxic cells andexperimental observation of anti-viral drag therapy for HBV i...A mathematical model with cytotoxic cells of hepatitis B virus (HBV)infection is set up based on a basic model of virus dynamics without cytotoxic cells andexperimental observation of anti-viral drag therapy for HBV infection patients. A quantitativeanalysis of dynamic behaviors shows that the model has three kinds of equilibrium points, whichrepresent the patient's complete recovery without immune ability, complete recovery with immuneability, and HBV persistent infection at the end of the treatment with drag lamivudine,respectively. Our model may provide possible quantitative interpretations for the treatments ofchronic HBV infections with the drag lamivudine, in particularly explain why the plasma virus ofNowak et al. 's patients turnover the original level after stopping the lamivudine treatment.展开更多
Cancer is a major public health problem worldwide and finding a total cure or eradication of the disease has been the expectations of medical researchers and medical practitioners in the recent times. In this paper, i...Cancer is a major public health problem worldwide and finding a total cure or eradication of the disease has been the expectations of medical researchers and medical practitioners in the recent times. In this paper, invasion of normal cells by carcinogens is considered. The purpose of the research is to study the dynamic evolutions of cancer and immune cells with the view finding most effective strategic way to control or eradicate cancer growth in human beings. We proposed five growths and mitigate models for benign and malignant cancer which are coupled ordinary differential equations and partial differential equations and Numerical simulations are made for the models. Analytic and Numerical solutions and sensitivity analysis of the models to parameters are obtained. It is found that the benign and malignant cancer cells displayed out of control growth and hence unstable in nature and the immune cells depreciated to the point of immune collapse. By the use of energy function it is established that staving of cancer cells of oxygen or use of drugs are strategic ways of combating cancer disease. Moreover, if the cancer cells are starved of basic nutrients or some basic enzymes inhibited it is expected that similar effect can also be achieved. The starvation of cancer cells should focus on oxygen, nutrients and vital enzymes. However, it is hoped that drugs developers and bioengineers will come up with means to achieve the starvation strategies to combat cancer disease.展开更多
Few experimental studies have evaluated the efficacy of continuing educational programs aimed at the improvement of nurses’ pain-management skills. This study assessed whether a standardized educational program aimed...Few experimental studies have evaluated the efficacy of continuing educational programs aimed at the improvement of nurses’ pain-management skills. This study assessed whether a standardized educational program aimed at nurses could increase the use of the Numeric Rating Scale-11 in both documenting and reducing postoperative pain-intensity levels in hospitalized surgical patients. The study had a quasi-experimental pre- and post-intervention design. Data were collected from records of surgical patients prior to and after the standardized educational program was completed. There were no significant differences between pre- and post-intervention groups in terms of either pain-documentation frequency or pain-intensity level. The study showed no increase in the frequency of postoperative pain documentation and no reduction of surgical patients’ postoperative pain-intensity level. This finding indicates that the standardized educational program on postoperative pain management was insufficient to bring about changes in clinical practice.展开更多
In many database applications, ranking queries may reference both text and numeric attributes, where the ranking functions are based on both semantic distances/similarities for text attributes and numeric distances fo...In many database applications, ranking queries may reference both text and numeric attributes, where the ranking functions are based on both semantic distances/similarities for text attributes and numeric distances for numeric attributes. In this paper, we propose a new method for evaluating such type of ranking queries over a relational database. By statistics and training, this method builds a mechanism that combines the semantic and numeric distances, and the mechanism can be used to balance the effects of text attributes and numeric attributes on matching a given query and tuples in database search. The basic idea of the method is to create an index based on WordNet to expand the tuple words semantically for text attributes and on the information of numeric attributes. The candidate results for a query are retrieved by the index and a simple SQL selection statement, and then top-N answers are obtained. The results of extensive experiments indicate that the performance of this new strategy is efficient and effective.展开更多
In order to simulate the recovery of groundwater funnels under the condition of reducing groundwater abstraction, hydrogeological conditions of recoverability construction of Shijiazhuang groundwater funnel were analy...In order to simulate the recovery of groundwater funnels under the condition of reducing groundwater abstraction, hydrogeological conditions of recoverability construction of Shijiazhuang groundwater funnel were analyzed, and a numerical simulation method was used based on the change of various parameters. The results show that the groundwater flow model can accurately reflect groundwater hydrogeological characteristics, and can guarantee the reliability of groundwater restoration prediction. The research has set up four schemes for rural water-saving, planting structure adjustment, urban reducing abstraction and integrated method. The effect of four restoration schemes on the restoration of groundwater funnels was compared with water table variations of two observation well. Comparison results show that the level changes of plan Three and Four are different from the other two kinds of exploitation and the drop trend of water table in the funnel area is flat. So we can conclude that Plan Three and Four have significant effect on the groundwater funnel restoration of Shijiazhuang.展开更多
A numeric reasoning method is proposed in this paper. It transforms the step--by-step matching reasoning method into computations of logical values. The reasoning time of this model is at most O(n2).
基金the National Natural Science Foundation of China(Project 51531002,51474043)the Ministry of Science&Technology of China(2013DFA71070)+1 种基金the Ministry of Education of China(SRFDR 20130191110018)Chongqing Municipal Government(CSTC2013JCYJC60001,CEC project,Two River Scholar Project and The Chief Scientist Studio Project).
文摘Hot tearing is often a major casting defect in magnesium alloys and has a significant impact on the quality of their casting products.Hot tearing of magnesium alloys is a complex solidification phenomenon which is still not fully understood,it is of great importance to investigate the hot tearing behaviour of magnesium alloys.This review attempts to summarize the investigations on hot tearing of magnesium alloys over the past decades.The hot tearing criteria including recently developed Kou’s criterion are summarized and compared.The numeric simulation and assessing methods of hot tearing,factors influencing hot tearing,and hot tearing susceptibility(HTS)of magnesium alloys are discussed.
基金Supported by Natural Science Program of Shaanxi Province Education Department (05JK261)
文摘By solving steady model of air flow diffusion and chemical reaction in loose coal, distribution of oxygen concentration and flow velocity magnitude were obtained. Compared the simulating results with critic value as well as duration of spontaneous combustion from large-scale spontaneous combustion experiment, 'three zones' of spontaneous combustion were partitioned and mining conditions to avoid spontaneous combustion were obtained. The above method was employed to partition 'three zones' in gob of fully mechanized top-coal caving long wall face and got fairly good result. Calculation of the above method is much smaller than simulating the whole process of coal spontaneous combustion, but the prediction precision can satisfy the demand of predicting and extinguishing spontaneous combustion in mining.
基金supported by the National Basic Research Program of China(973 Program)(2012CB720000)the National Natural Science Foundation of China(11372150)
文摘The motion of a surface vehicle on/above an irregular object is inv.estigated for a potential interest in the insitu explorations to asteroids of the solar system. A global valid numeric method, including detailed gravity and geo- morphology, is developed to mimic the behaviors of the test particles governed by the orbital equations and surface cou- pling effects. A general discussion on the surface mechanical environment of a specified asteroid, 1620 Geographos, is presented to make a global evaluation of the surface vehicle＇s working conditions. We show the connections between the natural trajectories near the ground and differential features of the asteroid surface, which describes both the good and bad of typical terrains from the viewpoint of vehicles＇ dynamic performances. Monte Carlo simulations are performed to take a further look at the trajectories of particles initializing near the surface. The simulations reveal consistent conclusions with the analysis, i.e., the open- field flat ground and slightly concave basins/valleys are the best choices for the vehicles＇ dynamical security. The dependence of decending trajectories on the releasing height is studied as an application; the results show that the pole direction （where the centrifugal force is zero） is the most stable direction in which the shift of a natural trajectory will be well limited after landing. We present this work as an example for pre-analysis that provides guidance to engineering design of the exploration site and routing the surface vehicles.
文摘Finite element method is employed to calculate the temperature fields for two kinds of steel concrete composite slabs: composite slab with profiled steel sheeting and LJMB composite slab. The calculated results are in good agreement with those of tests. Fire resistance of the two kinds of composite slabs is calculated by using a numeric method. The results show that: due to heat absorbing of concrete, the performance of composite slabs under fire is better than that of unprotected steel structure, and fire resistance of composite slabs mentioned in this paper is at least 30 min subjected to standard fire. Parameters related to the fire resistance are discussed. It was found that with increasing of concrete strength and thickness of slab, fire resistance increases, and with increasing of steel strength and steel ratio, fire resistance decreases. Also thickness of fire proof is calculated by a numeric method. The results obtained in this paper may be referenced for practical engineering.
文摘Objective:Vulvar lichen planus(VLP),especially erosive VLP(EVLP),seriously affects women’s physiological function and quality of life.A retrospective analysis of erosive vulvar lichen planus(EVLP)was performed to raise awareness on this chronic,deforming,and painful vulvar disease.Methods:This observational retrospective study involved 40 patients with EVLP among 1,368 patients with vulvar disease from 2017 to 2020.The patients’vulvar clinical features and extravulvar mucosal involvement were investigated.The patients’pain and quality of life were evaluated with the numeric rating scale and the Dermatology Life Quality Index(DLQI),respectively.Clinical characteristics were reported using frequencies and proportions for categorical variables.Continuous variables are expressed as mean±standard deviation.The association between NRS score for pain and DLQI score was analyzed by Pearson’s correlation test.Results:EVLP accounted for 2.9%(40/1,368)of all cases of vulvar disease,and the median age at onset was 42 years.Erosion mostly occurred on the labia minora and introitus.Half(20/40)of the patients had extravulvar mucosal involvement.Seventeen(42.5%)patients had oral lichen planus,and seven(17.5%)patients were diagnosed with vulvovaginal-gingival syndrome.The numeric rating scale score showed that 47.5%(19/40)of patients experienced mild pain,whereas 12.5%(5/40)described the pain as severe.Thirty-one patients(77.5%,31/40)had dyspareunia,and nine patients had aggravated pain after sexual intercourse.The mean DLQI score was 9.1±6.0,with 37.5%(15/40)of patients indicating that EVLP had severely affected their lives.The numeric rating scale score for pain was significantly correlated with the DLQI score(P=0.007).Conclusion:EVLP can affect the quality of women’s lives and cause severe deformations and painful architectural changes.The description of the characteristics of EVLP in this report will benefit the diagnosis and early treatment of this disease.
基金This study is supported by the National Key Research and Development Plan of China(No.2016YFC0402206)the National Natural Science Foundation of China(Grant Nos.51879192,91647106).Thanks are also given to CWRC for providing necessary data and the three anonymous reviewers’valuable suggestions to improve our manuscript.
文摘Probabilistic inflow forecasts can quantify the uncertainty involved in the forecasting process and provide useful risk information for reservoir management.This study proposed a probabilistic inflow forecasting scheme for the Three Gorges Reservoir(TGR)at 1-3 d lead times.The post-processing method Ensemble Model Output Statistics(EMOS)is used to derive probabilistic inflow forecasts from ensemble inflow forecasts.Considering the inherent skew feature of the inflow series,lognormal and gamma distributions are used as EMOS predictive distributions in addition to conventional normal distribution.Results show that TGR's ensemble inflow forecasts at 1-3 d lead times perform well with high model efficiency and small mean absolute error.Underestimation of forecasting uncertainty is observed for the raw ensemble inflow forecasts with biased probability integral transform(PIT)histograms.The three EMOS probabilistic forecasts outperform the raw ensemble forecasts in terms of both deterministic and probabilistic performance at 1-3 d lead times.The EMOS results are more reliable with much flatter PIT histograms,coverage rates approximate to the nominal coverage 89.47%and satisfactory sharpness.Results also show that EMOS with gamma distribution is superior to normal and lognormal distributions.This research can provide reliable probabilistic inflow forecasts without much variation of TGR5s operational inflow forecasting procedure.
文摘A mathematical model with cytotoxic cells of hepatitis B virus (HBV)infection is set up based on a basic model of virus dynamics without cytotoxic cells andexperimental observation of anti-viral drag therapy for HBV infection patients. A quantitativeanalysis of dynamic behaviors shows that the model has three kinds of equilibrium points, whichrepresent the patient's complete recovery without immune ability, complete recovery with immuneability, and HBV persistent infection at the end of the treatment with drag lamivudine,respectively. Our model may provide possible quantitative interpretations for the treatments ofchronic HBV infections with the drag lamivudine, in particularly explain why the plasma virus ofNowak et al. 's patients turnover the original level after stopping the lamivudine treatment.
文摘Cancer is a major public health problem worldwide and finding a total cure or eradication of the disease has been the expectations of medical researchers and medical practitioners in the recent times. In this paper, invasion of normal cells by carcinogens is considered. The purpose of the research is to study the dynamic evolutions of cancer and immune cells with the view finding most effective strategic way to control or eradicate cancer growth in human beings. We proposed five growths and mitigate models for benign and malignant cancer which are coupled ordinary differential equations and partial differential equations and Numerical simulations are made for the models. Analytic and Numerical solutions and sensitivity analysis of the models to parameters are obtained. It is found that the benign and malignant cancer cells displayed out of control growth and hence unstable in nature and the immune cells depreciated to the point of immune collapse. By the use of energy function it is established that staving of cancer cells of oxygen or use of drugs are strategic ways of combating cancer disease. Moreover, if the cancer cells are starved of basic nutrients or some basic enzymes inhibited it is expected that similar effect can also be achieved. The starvation of cancer cells should focus on oxygen, nutrients and vital enzymes. However, it is hoped that drugs developers and bioengineers will come up with means to achieve the starvation strategies to combat cancer disease.
文摘Few experimental studies have evaluated the efficacy of continuing educational programs aimed at the improvement of nurses’ pain-management skills. This study assessed whether a standardized educational program aimed at nurses could increase the use of the Numeric Rating Scale-11 in both documenting and reducing postoperative pain-intensity levels in hospitalized surgical patients. The study had a quasi-experimental pre- and post-intervention design. Data were collected from records of surgical patients prior to and after the standardized educational program was completed. There were no significant differences between pre- and post-intervention groups in terms of either pain-documentation frequency or pain-intensity level. The study showed no increase in the frequency of postoperative pain documentation and no reduction of surgical patients’ postoperative pain-intensity level. This finding indicates that the standardized educational program on postoperative pain management was insufficient to bring about changes in clinical practice.
文摘In many database applications, ranking queries may reference both text and numeric attributes, where the ranking functions are based on both semantic distances/similarities for text attributes and numeric distances for numeric attributes. In this paper, we propose a new method for evaluating such type of ranking queries over a relational database. By statistics and training, this method builds a mechanism that combines the semantic and numeric distances, and the mechanism can be used to balance the effects of text attributes and numeric attributes on matching a given query and tuples in database search. The basic idea of the method is to create an index based on WordNet to expand the tuple words semantically for text attributes and on the information of numeric attributes. The candidate results for a query are retrieved by the index and a simple SQL selection statement, and then top-N answers are obtained. The results of extensive experiments indicate that the performance of this new strategy is efficient and effective.
基金supported by Public Welfare Project of Ministry of Water Resources(201501008)Natural Science Foundation of Hebei Province(D2015504019)
文摘In order to simulate the recovery of groundwater funnels under the condition of reducing groundwater abstraction, hydrogeological conditions of recoverability construction of Shijiazhuang groundwater funnel were analyzed, and a numerical simulation method was used based on the change of various parameters. The results show that the groundwater flow model can accurately reflect groundwater hydrogeological characteristics, and can guarantee the reliability of groundwater restoration prediction. The research has set up four schemes for rural water-saving, planting structure adjustment, urban reducing abstraction and integrated method. The effect of four restoration schemes on the restoration of groundwater funnels was compared with water table variations of two observation well. Comparison results show that the level changes of plan Three and Four are different from the other two kinds of exploitation and the drop trend of water table in the funnel area is flat. So we can conclude that Plan Three and Four have significant effect on the groundwater funnel restoration of Shijiazhuang.
文摘A numeric reasoning method is proposed in this paper. It transforms the step--by-step matching reasoning method into computations of logical values. The reasoning time of this model is at most O(n2).
