This paper presents the sequence of activities to improve the thermal hydraulic analysis of the IEA-R1 research reactor to operate in safe conditions after power upgrade from 2 to 5 MW and core size reduction from 30 ...This paper presents the sequence of activities to improve the thermal hydraulic analysis of the IEA-R1 research reactor to operate in safe conditions after power upgrade from 2 to 5 MW and core size reduction from 30 to 24 fuel assemblies. A realistic analysis needs the knowledge of the actual operation conditions (heat flow, flow rates) beyond the geometric data and the uncertainties associated with manufacturing and measures. A dummy fuel assembly was designed and constructed to measure the actual flow rate through the core fuel assemblies and its pressure drop. First results showed that the flow distribution over the core is nearly uniform. Nevertheless, the values are below than the calculated ones and the core bypass flow rate is greater than those estimated previously. Based on this, several activities were performed to identify and reduce the bypass flow, such as reduction of the flow rate through the sample irradiators, closing some unnecessary secondary holes on the matrix plate, improvement in the primary flow rate system and better fit of the core components on the matrix plate. A sub-aquatic visual system was used as an important tool to detect some bypass flow path. After these modifications, the fuel assemblies flow rate increased about 13%. Additional tests using the dummy fuel assembly were carried out to measure the internal flow distribution among the rectangular channels. The results showed that the flow rate through the outer channels is 10% - 15% lower than the internal ones. The flow rate in the channel formed between two adjacent fuel assemblies is an estimated parameter and it is difficult to measure because this is an open channel. A new thermal hydraulic analysis of the outermost plates of the fuel assemblies takes into account all this information. Then, a fuel design modification was proposed with the reduction of 50% in the uranium quantity in the outermost fuel plates. In order to avoid the oxidation of the outermost plates by high temperature, low flow rate, a reduction of 50% in the uranium density in the same ones was shown to be adequate to solve the problem.展开更多
This article analyzes 186 hospitality reports from the Center of Hospitality Research in Cornell University. Objectives of the study are to (a) profile the content of hospitality report of the Center of Hospitality Re...This article analyzes 186 hospitality reports from the Center of Hospitality Research in Cornell University. Objectives of the study are to (a) profile the content of hospitality report of the Center of Hospitality Research;(b) identify differences between the findings of hospitality journals research and the results of hospitality reports in the Center of Hospitality Research;and (c) derive emerging trends and make suggestions on future directions regarding hospitality research with industry professionals in the Center of Hospitality Research. Content analysis results showed that the differences between hospitality reports in the Center of Hospitality Research and other journal exit in the research theme and unit of analysis. Finance in the Center of Hospitality Research was increasingly popular, while human resources in other journal were emphasized. The Center of Hospitality Research focused on individual behavior, as well as organizational behavior, while other journal mainly focused on individual behavior. According to the results, hospitality reports in the Center of Hospitality Research will lay more emphasis on finance and decline the research of human resources. Multiple-authorship and collaboration with industry professionals and scholars from other universities will be popular in the Center of Hospitality Research.展开更多
冻土路基的稳定性对于寒区公路与铁路的安全运营至关重要。为全面了解冻土路基领域的研究现状及发展趋势,利用知识图谱工具CiteSpace对中国知网和Web of Science数据库中冻土路基相关文献进行了可视化分析。检索时间范围为2000年1月1日...冻土路基的稳定性对于寒区公路与铁路的安全运营至关重要。为全面了解冻土路基领域的研究现状及发展趋势,利用知识图谱工具CiteSpace对中国知网和Web of Science数据库中冻土路基相关文献进行了可视化分析。检索时间范围为2000年1月1日—2023年8月31日,共纳入1 027篇中文文献和854篇英文文献。结果表明:自2000年以来,冻土路基研究的发文量总体呈增长趋势;从2017年开始,英文文献的发布数量逐渐超过中文文献,其中我国学者在国际期刊的发文量占到80%左右;国内研究机构之间合作较为密切,以中国科学院西北生态环境资源研究院和北京交通大学为核心的科研机构及院校在冻土路基的研究中起着主导作用,而国际机构间的合作还有待加强。关键词聚类与突现图谱表明,冻土路基的研究主要围绕多年冻土路基的稳定性、路基病害与补强措施、季节冻土路基的病害防治展开。近几年,冻土专家学者们聚焦于新型路基稳定措施,路基的水、汽迁移机理,以及高铁路基的冻胀防治研究,新材料、新技术及新结构不断被引入到冻土路基研究。未来随着新能源、材料学、人工智能、合成孔径雷达干涉测量(InSAR)等新一代技术与机械化的融合,冻土路基的稳定性补强措施和季节冻土路基的防冻胀措施会在提高效果的同时更加注重环保理念,冻土路基的施工、管理及监测也会不断向着数字化和智能化发展。展开更多
目的定量测度我国城市在药学基础研究国际合作中的参与度。方法通过Web of Science数据库检索2021年1月至2023年8月我国发表的药学基础研究相关论文,提取发文机构及其所在城市,统计发文量排名前列的城市和机构的国际合作论文数量及占比...目的定量测度我国城市在药学基础研究国际合作中的参与度。方法通过Web of Science数据库检索2021年1月至2023年8月我国发表的药学基础研究相关论文,提取发文机构及其所在城市,统计发文量排名前列的城市和机构的国际合作论文数量及占比,构建全球合作网络,计算其在国际合作网络中的度、加权度、接近中心性、中介中心性和聚类系数,并采用优劣解距离(TOPSIS)法将上述指标汇总生成综合指标,比较不同城市和机构的重要性。结果北京、上海和广州的国际合作论文数量及TOPSIS得分连续3年全国排名前3,其次是南京、杭州、武汉、成都等城市;深圳是我国非港澳台地区国际合作论文占比最高的城市,但缺乏实力相对突出的机构;苏州和西安近几年的TOPSIS得分排名逐年提升。浙江大学、复旦大学、首都医科大学、上海交通大学、广州医科大学、北京大学等为国际合作中表现较好的机构。结论我国不同城市在药学研究国际合作中的参与度存在明显差异,以北京、上海、广州、南京、杭州、武汉、成都、深圳等城市表现较突出,苏州和西安也处于上升趋势。展开更多
The Tropical Rainfall Measuring Mission （TRMM） Multi-satellite Precipitation Analysis （TMPA） and National Oceanic and Atmospheric Administration （NOAA） Climate Prediction Center （CPC） morphing technique （CMO...The Tropical Rainfall Measuring Mission （TRMM） Multi-satellite Precipitation Analysis （TMPA） and National Oceanic and Atmospheric Administration （NOAA） Climate Prediction Center （CPC） morphing technique （CMORPH） are two important multi-satellite precipitation products in TRMM-era and perform important functions in GPM-era. Both TMPA and CMORPH systems simultaneously upgraded their retrieval algorithms and released their latest version of precipitation data in 2013. In this study, the latest TMPA and CMORPH products （i.e., Version-7 real-time TMPA （T-rt） and gauge-adjusted TMPA （T-adj）, and Version- 1.0 real-time CMORPH （C-rt） and Version-l.0 gauge-adjusted CMORPH （C-adj）） are evaluated and intercompared by using independent rain gauge observations for a 12-year （2000--2011） period over two typical basins in China with different geographical and climate conditions. Results indicate that all TMPA and CMORPH products tend to overestimate precipitation for the high-latitude semiarid Laoha River Basin and underestimate it for the low-latitude humid Mishui Basin. Overall, the satellite precipitation products exhibit superior performance over Mishui Basin than that over Laoha River Basin. The C-adj presents the best performance over the high-latitude Laoha River Basin, whereas T-adj showed the best performance over the low-latitude Mishui Basin. The two gauge-adjusted products demonstrate potential in water resource management. However, the accuracy of two real-time satellite precipitation products demonstrates large variability in the two validation basins. The C-rt reaches a similar accuracy level with the gauge-adjusted satellite precipitation products in the high-latitude Laoha River Basin, and T-rt performs well in the low-latitude Mishui Basin. The study also reveals that all satellite precipitation products obviously overestimate light rain amounts and events over Laoha River Basin, whereas they underestimate the amount and events over Mishui Basin. The findings of the precision characteristics associated with the latest TMPA and CMORPH precipitation products at different basins will offer satellite pre- cipitation users an enhanced understanding of the applicability of the latest TMPA and CMORPH for water resource management, hydrologic process simulation, and hydrometeorological disaster prediction in other similar regions in China. The findings will also be useful for IMERG algorithm development and update in GPM-era.展开更多
This study explored and reviewed the logistic regression (LR) model, a multivariable method for modeling the relationship between multiple independent variables and a categorical dependent variable, with emphasis on m...This study explored and reviewed the logistic regression (LR) model, a multivariable method for modeling the relationship between multiple independent variables and a categorical dependent variable, with emphasis on medical research. Thirty seven research articles published between 2000 and 2018 which employed logistic regression as the main statistical tool as well as six text books on logistic regression were reviewed. Logistic regression concepts such as odds, odds ratio, logit transformation, logistic curve, assumption, selecting dependent and independent variables, model fitting, reporting and interpreting were presented. Upon perusing the literature, considerable deficiencies were found in both the use and reporting of LR. For many studies, the ratio of the number of outcome events to predictor variables (events per variable) was sufficiently small to call into question the accuracy of the regression model. Also, most studies did not report on validation analysis, regression diagnostics or goodness-of-fit measures;measures which authenticate the robustness of the LR model. Here, we demonstrate a good example of the application of the LR model using data obtained on a cohort of pregnant women and the factors that influence their decision to opt for caesarean delivery or vaginal birth. It is recommended that researchers should be more rigorous and pay greater attention to guidelines concerning the use and reporting of LR models.展开更多
文摘This paper presents the sequence of activities to improve the thermal hydraulic analysis of the IEA-R1 research reactor to operate in safe conditions after power upgrade from 2 to 5 MW and core size reduction from 30 to 24 fuel assemblies. A realistic analysis needs the knowledge of the actual operation conditions (heat flow, flow rates) beyond the geometric data and the uncertainties associated with manufacturing and measures. A dummy fuel assembly was designed and constructed to measure the actual flow rate through the core fuel assemblies and its pressure drop. First results showed that the flow distribution over the core is nearly uniform. Nevertheless, the values are below than the calculated ones and the core bypass flow rate is greater than those estimated previously. Based on this, several activities were performed to identify and reduce the bypass flow, such as reduction of the flow rate through the sample irradiators, closing some unnecessary secondary holes on the matrix plate, improvement in the primary flow rate system and better fit of the core components on the matrix plate. A sub-aquatic visual system was used as an important tool to detect some bypass flow path. After these modifications, the fuel assemblies flow rate increased about 13%. Additional tests using the dummy fuel assembly were carried out to measure the internal flow distribution among the rectangular channels. The results showed that the flow rate through the outer channels is 10% - 15% lower than the internal ones. The flow rate in the channel formed between two adjacent fuel assemblies is an estimated parameter and it is difficult to measure because this is an open channel. A new thermal hydraulic analysis of the outermost plates of the fuel assemblies takes into account all this information. Then, a fuel design modification was proposed with the reduction of 50% in the uranium quantity in the outermost fuel plates. In order to avoid the oxidation of the outermost plates by high temperature, low flow rate, a reduction of 50% in the uranium density in the same ones was shown to be adequate to solve the problem.
文摘This article analyzes 186 hospitality reports from the Center of Hospitality Research in Cornell University. Objectives of the study are to (a) profile the content of hospitality report of the Center of Hospitality Research;(b) identify differences between the findings of hospitality journals research and the results of hospitality reports in the Center of Hospitality Research;and (c) derive emerging trends and make suggestions on future directions regarding hospitality research with industry professionals in the Center of Hospitality Research. Content analysis results showed that the differences between hospitality reports in the Center of Hospitality Research and other journal exit in the research theme and unit of analysis. Finance in the Center of Hospitality Research was increasingly popular, while human resources in other journal were emphasized. The Center of Hospitality Research focused on individual behavior, as well as organizational behavior, while other journal mainly focused on individual behavior. According to the results, hospitality reports in the Center of Hospitality Research will lay more emphasis on finance and decline the research of human resources. Multiple-authorship and collaboration with industry professionals and scholars from other universities will be popular in the Center of Hospitality Research.
文摘冻土路基的稳定性对于寒区公路与铁路的安全运营至关重要。为全面了解冻土路基领域的研究现状及发展趋势,利用知识图谱工具CiteSpace对中国知网和Web of Science数据库中冻土路基相关文献进行了可视化分析。检索时间范围为2000年1月1日—2023年8月31日,共纳入1 027篇中文文献和854篇英文文献。结果表明:自2000年以来,冻土路基研究的发文量总体呈增长趋势;从2017年开始,英文文献的发布数量逐渐超过中文文献,其中我国学者在国际期刊的发文量占到80%左右;国内研究机构之间合作较为密切,以中国科学院西北生态环境资源研究院和北京交通大学为核心的科研机构及院校在冻土路基的研究中起着主导作用,而国际机构间的合作还有待加强。关键词聚类与突现图谱表明,冻土路基的研究主要围绕多年冻土路基的稳定性、路基病害与补强措施、季节冻土路基的病害防治展开。近几年,冻土专家学者们聚焦于新型路基稳定措施,路基的水、汽迁移机理,以及高铁路基的冻胀防治研究,新材料、新技术及新结构不断被引入到冻土路基研究。未来随着新能源、材料学、人工智能、合成孔径雷达干涉测量(InSAR)等新一代技术与机械化的融合,冻土路基的稳定性补强措施和季节冻土路基的防冻胀措施会在提高效果的同时更加注重环保理念,冻土路基的施工、管理及监测也会不断向着数字化和智能化发展。
文摘目的定量测度我国城市在药学基础研究国际合作中的参与度。方法通过Web of Science数据库检索2021年1月至2023年8月我国发表的药学基础研究相关论文,提取发文机构及其所在城市,统计发文量排名前列的城市和机构的国际合作论文数量及占比,构建全球合作网络,计算其在国际合作网络中的度、加权度、接近中心性、中介中心性和聚类系数,并采用优劣解距离(TOPSIS)法将上述指标汇总生成综合指标,比较不同城市和机构的重要性。结果北京、上海和广州的国际合作论文数量及TOPSIS得分连续3年全国排名前3,其次是南京、杭州、武汉、成都等城市;深圳是我国非港澳台地区国际合作论文占比最高的城市,但缺乏实力相对突出的机构;苏州和西安近几年的TOPSIS得分排名逐年提升。浙江大学、复旦大学、首都医科大学、上海交通大学、广州医科大学、北京大学等为国际合作中表现较好的机构。结论我国不同城市在药学研究国际合作中的参与度存在明显差异,以北京、上海、广州、南京、杭州、武汉、成都、深圳等城市表现较突出,苏州和西安也处于上升趋势。
基金Under the auspices of Programme of Introducing Talents of Discipline to Universities by Ministry of Education and the State Administration of Foreign Experts Affairs, China (the 111 Project, No. B08048)National Natural Science Foundation of China (No. 41501017)Natural Science Foundation of Jiangsu Province (No. BK20150815)
文摘The Tropical Rainfall Measuring Mission （TRMM） Multi-satellite Precipitation Analysis （TMPA） and National Oceanic and Atmospheric Administration （NOAA） Climate Prediction Center （CPC） morphing technique （CMORPH） are two important multi-satellite precipitation products in TRMM-era and perform important functions in GPM-era. Both TMPA and CMORPH systems simultaneously upgraded their retrieval algorithms and released their latest version of precipitation data in 2013. In this study, the latest TMPA and CMORPH products （i.e., Version-7 real-time TMPA （T-rt） and gauge-adjusted TMPA （T-adj）, and Version- 1.0 real-time CMORPH （C-rt） and Version-l.0 gauge-adjusted CMORPH （C-adj）） are evaluated and intercompared by using independent rain gauge observations for a 12-year （2000--2011） period over two typical basins in China with different geographical and climate conditions. Results indicate that all TMPA and CMORPH products tend to overestimate precipitation for the high-latitude semiarid Laoha River Basin and underestimate it for the low-latitude humid Mishui Basin. Overall, the satellite precipitation products exhibit superior performance over Mishui Basin than that over Laoha River Basin. The C-adj presents the best performance over the high-latitude Laoha River Basin, whereas T-adj showed the best performance over the low-latitude Mishui Basin. The two gauge-adjusted products demonstrate potential in water resource management. However, the accuracy of two real-time satellite precipitation products demonstrates large variability in the two validation basins. The C-rt reaches a similar accuracy level with the gauge-adjusted satellite precipitation products in the high-latitude Laoha River Basin, and T-rt performs well in the low-latitude Mishui Basin. The study also reveals that all satellite precipitation products obviously overestimate light rain amounts and events over Laoha River Basin, whereas they underestimate the amount and events over Mishui Basin. The findings of the precision characteristics associated with the latest TMPA and CMORPH precipitation products at different basins will offer satellite pre- cipitation users an enhanced understanding of the applicability of the latest TMPA and CMORPH for water resource management, hydrologic process simulation, and hydrometeorological disaster prediction in other similar regions in China. The findings will also be useful for IMERG algorithm development and update in GPM-era.
文摘This study explored and reviewed the logistic regression (LR) model, a multivariable method for modeling the relationship between multiple independent variables and a categorical dependent variable, with emphasis on medical research. Thirty seven research articles published between 2000 and 2018 which employed logistic regression as the main statistical tool as well as six text books on logistic regression were reviewed. Logistic regression concepts such as odds, odds ratio, logit transformation, logistic curve, assumption, selecting dependent and independent variables, model fitting, reporting and interpreting were presented. Upon perusing the literature, considerable deficiencies were found in both the use and reporting of LR. For many studies, the ratio of the number of outcome events to predictor variables (events per variable) was sufficiently small to call into question the accuracy of the regression model. Also, most studies did not report on validation analysis, regression diagnostics or goodness-of-fit measures;measures which authenticate the robustness of the LR model. Here, we demonstrate a good example of the application of the LR model using data obtained on a cohort of pregnant women and the factors that influence their decision to opt for caesarean delivery or vaginal birth. It is recommended that researchers should be more rigorous and pay greater attention to guidelines concerning the use and reporting of LR models.
