AIM:To evaluate the natural history of subepithelial lesions.METHODS:We reviewed the medical records of 104 159 patients who underwent upper gastrointestinal endoscopy at the Center for Health Promotion of Samsung Med...AIM:To evaluate the natural history of subepithelial lesions.METHODS:We reviewed the medical records of 104 159 patients who underwent upper gastrointestinal endoscopy at the Center for Health Promotion of Samsung Medical Center between 1996 and 2003.Subepithelial lesions were detected in 795 patients(0.76%);252 patients were followed using upper gastrointestinal endoscopy for 82.5 ± 29.2 mo(range,12-160 mo;median,84 mo;1st quartile,60 mo;3rd quartile,105 mo).The median interval of follow-up endoscopy was 12 mo(range,6-105 mo;1st quartile,12 mo;3rd quartile,24 mo).RESULTS:The mean patient age was 53 years(range,22-80 years),and the male-to-female ratio was 2.36:1(177/75).The lesion size at initial measurement averaged 8.9 mm(range,2-25 mm;median,8 mm;1st quartile,5 mm;3rd quartile,10 mm).Of the 252 lesions,244(96.8%) were unchanged and 8(3.2%) were significantly increased in size(from 12.9 ± 6.0 to 21.2 ± 12.2 mm) after a mean interval of 59.1 ± 27.5 mo(range,12-86 mo).Surgical resection of lesions was performed when the lesions were ≥ 3 cm in diameter.Two lesions were diagnosed as gastrointestinal stromal tumors with an intermediate or high risk of malignancy and one lesion was classified as a schwannoma.CONCLUSION:Most small subepithelial lesions do not change as shown by endoscopic examination,and regular follow-up with endoscopy may be considered in small,subepithelial lesions,especially lesions < 1 cm in size.展开更多
Solid backfill mining(SBM)is a form of green mining,the core of which is to control and minimize the deformation and movement of strata above longwall coal mines.Establishing a mechanical model that can reliably descr...Solid backfill mining(SBM)is a form of green mining,the core of which is to control and minimize the deformation and movement of strata above longwall coal mines.Establishing a mechanical model that can reliably describe roof deformation by considering the viscoelastic properties of waste gangue is important as it assists in improving mine designs and reducing the environmental impact on the surface.In this paper,the time-dependent deformation characteristics of gangue under different stress levels were obtained by using lateral confinement compression,that reliably represents the compaction of goaf.The viscoelastic foundation model for gangue mechanical response is different from the traditionally used elastic foundation model,as it considers the time factor and viscoelasticity.A mechanical model using a thin plate on a fractional viscoelastic foundation was established,and the roof deflection,bending moment,time-dependent,viscous and other characteristics of SBM were included and analyzed.Compared with the existing elastic foundation model,the proposed fractional order viscoelastic foundation model has higher accuracy with laboratory data.The plate deflection increases by 50.9%and the bending moment increases by 37.9%after 100 days,which the elastic model would not have been able to predict.展开更多
Existing algorithms of news recommendations lack in depth analysis of news texts and timeliness. To address these issues, an algorithm for news recommendations based on time factor and word embedding(TFWE) was propose...Existing algorithms of news recommendations lack in depth analysis of news texts and timeliness. To address these issues, an algorithm for news recommendations based on time factor and word embedding(TFWE) was proposed to improve the interpretability and precision of news recommendations. First, TFWE used term frequency-inverse document frequency(TF-IDF) to extract news feature words and used the bidirectional encoder representations from transformers(BERT) pre-training model to convert the feature words into vector representations. By calculating the distance between the vectors, TFWE analyzed the semantic similarity to construct a user interest model. Second, considering the timeliness of news, a method of calculating news popularity by integrating time factors into the similarity calculation was proposed. Finally, TFWE combined the similarity of news content with the similarity of collaborative filtering(CF) and recommended some news with higher rankings to users. In addition, results of the experiments on real dataset showed that TFWE significantly improved precision, recall, and F1 score compared to the classic hybrid recommendation algorithm.展开更多
Rainfed agricultural systems in semiarid Mediterranean environments are subject to erratic but often heavy rainfall events.As an agronomic practice,fallow periods can be included even within the existing European Unio...Rainfed agricultural systems in semiarid Mediterranean environments are subject to erratic but often heavy rainfall events.As an agronomic practice,fallow periods can be included even within the existing European Union common policy for crop diversification.This study aimed to quantify the effects of previous mineral fertilization on soil mineral nitrogen(N_(min))content and potential nitrate leaching during no-till fallow periods of crop rotation.The Leaching Estimation and Chemistry Model(LEACHM)was used for soil N_(min)prediction after fallow.During fallow periods,N_(min)measured in the soil profile increased by an average of 125 kg N ha^(-1),whereas the model showed an average increase of 95 kg N ha^(-1).The amount of nitrogen(N)leached was estimated to be 11–38 kg N ha^(-1).The N balance simulated using LEACHM might differ from the actual situation.The calibrated LEACHM underestimated soil N_(min)after a drought period followed by soil water replenishment,probably due to a pulse in soil C and N mineralization caused by the wetting of dry soil,but overestimated soil N_(min)after occasional rainy spells when soil quickly became saturated,probably due to occasional nitrous oxide emissions not being fully accounted for by the model and specific preferential water flow,which might lead to greater nitrate leaching than that simulated by LEACHM using the convection-dispersion equation.The results show that soil N_(min)measurements after fallow periods cannot be well predicted by LEACHM.The findings of this study provide a support for fertilization planning for crop rotation systems including a fallow period to avoid overfertilization in the following cropping season and reduce N environmental impacts.展开更多
The growth of COVID-19 pandemic throughout more than 213 countries around the world have put a lot of pressures on governments and health services to try to stop the rapid expansion of the pandemic.During 2009,H1N1 In...The growth of COVID-19 pandemic throughout more than 213 countries around the world have put a lot of pressures on governments and health services to try to stop the rapid expansion of the pandemic.During 2009,H1N1 Influenza pandemic,statistical and mathematical methods were used to track how the virus spreads around countries.Most of these models that were developed at the beginning of the XXI century are based on the classical susceptible-infected-recovered(SIR)model developed almost a hundred years ago.The evolution of this model allows us to forecast and compute basic and effective reproduction numbers(R_(t) and R_(0)),measures that quantify the epidemic potential of a pathogen and estimates different scenarios.In this study,we present a traditional estimation technique for R_(0) with statistical distributions by best fitting and a Bayesian approach based on continuous feed of prior distributions to obtain posterior distributions and computing real time R_(t).We use data from COVID-19 officially reported cases in Ecuador since the first confirmed case on February 29th.Because of the lack of data,in the case of R_(0) we compare two methods for the estimation of these parameters below exponential growth and maximum likelihood estimation.We do not make any assumption about the evolution of cases due to limited information and we use previous methods to compare scenarios about R_(0) and in the case of R_(t) we used Bayesian inference to model uncertainty in contagious proposing a new modification to the well-known model of Bettencourt and Ribeiro based on a time window of m days to improve estimations.Ecuadorian R_(0) with exponential growth criteria was 3.45 and with the maximum likelihood estimation method was 2.93.The results show that Guayas,Pichincha and Manabíwere the provinces with the highest number of cases due to COVID-19.Some reasons explain the increased transmissibility in these localities:massive events,population density,cities dispersion patterns,and the delayed time of public health actions to contain pandemic.In conclusion,this is a novel approach that allow us to measure infection dynamics and outbreak distribution when not enough detailed data is available.The use of this model can be used to predict pandemic distribution and to implement data-based effective measures.展开更多
文摘AIM:To evaluate the natural history of subepithelial lesions.METHODS:We reviewed the medical records of 104 159 patients who underwent upper gastrointestinal endoscopy at the Center for Health Promotion of Samsung Medical Center between 1996 and 2003.Subepithelial lesions were detected in 795 patients(0.76%);252 patients were followed using upper gastrointestinal endoscopy for 82.5 ± 29.2 mo(range,12-160 mo;median,84 mo;1st quartile,60 mo;3rd quartile,105 mo).The median interval of follow-up endoscopy was 12 mo(range,6-105 mo;1st quartile,12 mo;3rd quartile,24 mo).RESULTS:The mean patient age was 53 years(range,22-80 years),and the male-to-female ratio was 2.36:1(177/75).The lesion size at initial measurement averaged 8.9 mm(range,2-25 mm;median,8 mm;1st quartile,5 mm;3rd quartile,10 mm).Of the 252 lesions,244(96.8%) were unchanged and 8(3.2%) were significantly increased in size(from 12.9 ± 6.0 to 21.2 ± 12.2 mm) after a mean interval of 59.1 ± 27.5 mo(range,12-86 mo).Surgical resection of lesions was performed when the lesions were ≥ 3 cm in diameter.Two lesions were diagnosed as gastrointestinal stromal tumors with an intermediate or high risk of malignancy and one lesion was classified as a schwannoma.CONCLUSION:Most small subepithelial lesions do not change as shown by endoscopic examination,and regular follow-up with endoscopy may be considered in small,subepithelial lesions,especially lesions < 1 cm in size.
基金funded by the National Science Fund for Distinguished Young Scholars(No.51725403)the National Natural Science Foundation of China(No.52004271)+1 种基金the China PostdoctoralScienceFoundation(Nos.2019M661990and 2018M632410)the Fundamental Research Funds for the Central Universities(No.2020QN05)。
文摘Solid backfill mining(SBM)is a form of green mining,the core of which is to control and minimize the deformation and movement of strata above longwall coal mines.Establishing a mechanical model that can reliably describe roof deformation by considering the viscoelastic properties of waste gangue is important as it assists in improving mine designs and reducing the environmental impact on the surface.In this paper,the time-dependent deformation characteristics of gangue under different stress levels were obtained by using lateral confinement compression,that reliably represents the compaction of goaf.The viscoelastic foundation model for gangue mechanical response is different from the traditionally used elastic foundation model,as it considers the time factor and viscoelasticity.A mechanical model using a thin plate on a fractional viscoelastic foundation was established,and the roof deflection,bending moment,time-dependent,viscous and other characteristics of SBM were included and analyzed.Compared with the existing elastic foundation model,the proposed fractional order viscoelastic foundation model has higher accuracy with laboratory data.The plate deflection increases by 50.9%and the bending moment increases by 37.9%after 100 days,which the elastic model would not have been able to predict.
基金supported by the Research Program of the Basic Scientific Research of National Defense of China (JCKY2019210B005, JCKY2018204B025, and JCKY2017204B011)the Key Scientific Project Program of National Defense of China (ZQ2019D20401 )+2 种基金the Open Program of National Engineering Laboratory for Modeling and Emulation in E-Government (MEL-20-02 )the Foundation Strengthening Project of China (2019JCJZZD13300 )the Jiangsu Postgraduate Research and Innovation Program (KYCX20_0824)。
文摘Existing algorithms of news recommendations lack in depth analysis of news texts and timeliness. To address these issues, an algorithm for news recommendations based on time factor and word embedding(TFWE) was proposed to improve the interpretability and precision of news recommendations. First, TFWE used term frequency-inverse document frequency(TF-IDF) to extract news feature words and used the bidirectional encoder representations from transformers(BERT) pre-training model to convert the feature words into vector representations. By calculating the distance between the vectors, TFWE analyzed the semantic similarity to construct a user interest model. Second, considering the timeliness of news, a method of calculating news popularity by integrating time factors into the similarity calculation was proposed. Finally, TFWE combined the similarity of news content with the similarity of collaborative filtering(CF) and recommended some news with higher rankings to users. In addition, results of the experiments on real dataset showed that TFWE significantly improved precision, recall, and F1 score compared to the classic hybrid recommendation algorithm.
基金supported by Spanish Ministry of Economy and Competitiveness and Spanish National Institute for Agricultural Research and Experimentation(MINECOINIA)(No.RTA2017-88-C3-3).
文摘Rainfed agricultural systems in semiarid Mediterranean environments are subject to erratic but often heavy rainfall events.As an agronomic practice,fallow periods can be included even within the existing European Union common policy for crop diversification.This study aimed to quantify the effects of previous mineral fertilization on soil mineral nitrogen(N_(min))content and potential nitrate leaching during no-till fallow periods of crop rotation.The Leaching Estimation and Chemistry Model(LEACHM)was used for soil N_(min)prediction after fallow.During fallow periods,N_(min)measured in the soil profile increased by an average of 125 kg N ha^(-1),whereas the model showed an average increase of 95 kg N ha^(-1).The amount of nitrogen(N)leached was estimated to be 11–38 kg N ha^(-1).The N balance simulated using LEACHM might differ from the actual situation.The calibrated LEACHM underestimated soil N_(min)after a drought period followed by soil water replenishment,probably due to a pulse in soil C and N mineralization caused by the wetting of dry soil,but overestimated soil N_(min)after occasional rainy spells when soil quickly became saturated,probably due to occasional nitrous oxide emissions not being fully accounted for by the model and specific preferential water flow,which might lead to greater nitrate leaching than that simulated by LEACHM using the convection-dispersion equation.The results show that soil N_(min)measurements after fallow periods cannot be well predicted by LEACHM.The findings of this study provide a support for fertilization planning for crop rotation systems including a fallow period to avoid overfertilization in the following cropping season and reduce N environmental impacts.
基金The author(s)disclosed receipt the financial support for the research and publication of this article from Universidad de Las Americas through their annual general research projects funds.
文摘The growth of COVID-19 pandemic throughout more than 213 countries around the world have put a lot of pressures on governments and health services to try to stop the rapid expansion of the pandemic.During 2009,H1N1 Influenza pandemic,statistical and mathematical methods were used to track how the virus spreads around countries.Most of these models that were developed at the beginning of the XXI century are based on the classical susceptible-infected-recovered(SIR)model developed almost a hundred years ago.The evolution of this model allows us to forecast and compute basic and effective reproduction numbers(R_(t) and R_(0)),measures that quantify the epidemic potential of a pathogen and estimates different scenarios.In this study,we present a traditional estimation technique for R_(0) with statistical distributions by best fitting and a Bayesian approach based on continuous feed of prior distributions to obtain posterior distributions and computing real time R_(t).We use data from COVID-19 officially reported cases in Ecuador since the first confirmed case on February 29th.Because of the lack of data,in the case of R_(0) we compare two methods for the estimation of these parameters below exponential growth and maximum likelihood estimation.We do not make any assumption about the evolution of cases due to limited information and we use previous methods to compare scenarios about R_(0) and in the case of R_(t) we used Bayesian inference to model uncertainty in contagious proposing a new modification to the well-known model of Bettencourt and Ribeiro based on a time window of m days to improve estimations.Ecuadorian R_(0) with exponential growth criteria was 3.45 and with the maximum likelihood estimation method was 2.93.The results show that Guayas,Pichincha and Manabíwere the provinces with the highest number of cases due to COVID-19.Some reasons explain the increased transmissibility in these localities:massive events,population density,cities dispersion patterns,and the delayed time of public health actions to contain pandemic.In conclusion,this is a novel approach that allow us to measure infection dynamics and outbreak distribution when not enough detailed data is available.The use of this model can be used to predict pandemic distribution and to implement data-based effective measures.
