Acrylic acid (AAc) and styrene (St) were grafted onto poly(vinylidene fluoride) (PVDF) powder or membrane samples by pre-irradiation graft copolymerization.The grafted chains were proved by FT-IR spectroscopy analysis...Acrylic acid (AAc) and styrene (St) were grafted onto poly(vinylidene fluoride) (PVDF) powder or membrane samples by pre-irradiation graft copolymerization.The grafted chains were proved by FT-IR spectroscopy analysis.The degree of grafting (DG) of the grafted PVDF was determined by fluorine elemental analysis (FEA) method,and was compared with the DGs determined by weighing method,acid-base back titration method and quantitative FT-IR method.The results show that the FEA method is accurate,convenient and universal,especially for the grafted polymer powders.展开更多
目的了解重庆市溺水死亡率及疾病负担变化趋势,为开展溺水预防提供建议。方法收集分析2012—2018年重庆市溺水死亡个案信息(ICD-10编码:W65-W74),采用SPSS 25.0统计分析溺水死亡率、标化死亡率、伤残调整生命年(Disability adjusted lif...目的了解重庆市溺水死亡率及疾病负担变化趋势,为开展溺水预防提供建议。方法收集分析2012—2018年重庆市溺水死亡个案信息(ICD-10编码:W65-W74),采用SPSS 25.0统计分析溺水死亡率、标化死亡率、伤残调整生命年(Disability adjusted life years,DALYs)、早死所致的寿命损失年(Years of life lost,YLLs)、残疾所致寿命损失年(Year lived with disability,YLDs)等指标。男女、城乡之间溺水死亡率的比较采用卡方检验。率的趋势变化采用年度变化百分比(Annual percent change,APC),APC检验采用t检验,检验水准α=0.05。结果重庆市溺水死亡率与标化死亡率分别由2012年的4.90/10万、4.87/10万下降到2018年的3.85/10万、3.59/10万,APC分别为-3.34%与-4.59%,变化趋势差异均无统计学意义(t=2.34、2.42,P>0.05)。历年溺水死亡率男性高于女性,差异均有统计学意义(P>0.05)。历年农村地区溺水死亡率高于城市,差异均有统计学意义(P<0.05)。5岁以下年龄组溺水死亡率历年均是最高的。5岁以下年龄组溺水死亡率由2012年的14.47/10万下降到2018年的4.28/10万,APC为-17.06%,变化趋势差异有统计学意义(t=8.86,P<0.001)。65岁及以上年龄组溺水死亡率由2012年的8.14/10万上升至2018年的9.77/10万,APC为4.92%,变化趋势差异无统计学意义(t=2.56,P=0.051)。溺水的DALYs率、YLLs率分别由2012年的2.73千人年、2.70千人年下降到2018年的1.66千人年、1.64千人年,APC分别为-7.41%与-7.41%,变化趋势差异均有统计学意义(P均<0.05),YLDs率由2012年0.03千人年下降至2018年的0.02千人年,变化趋势差异无统计学意义(P>0.05)。结论重庆市溺水死亡率及疾病负担呈下降的趋势,低于全国的平均水平,儿童、男性与老年人是预防溺水发生的重点人群,农村是预防溺水的重点地区。展开更多
Machining of carbon/carbon （C/C） composite materials is difficult to carry out due to its high specific stiffness, brittleness, anisotropic, non-homogeneous and low thermal conductivity, which can result in tear, bu...Machining of carbon/carbon （C/C） composite materials is difficult to carry out due to its high specific stiffness, brittleness, anisotropic, non-homogeneous and low thermal conductivity, which can result in tear, burr, poor surface quality and rapid wear of cutters. Accurate and fast pre- diction of cutting forces is important for milling C/C composite materials with high quality. This paper presents an alternative cutting force model involving the influences of the directions of fiber. Based on the calculated and experimental results, the cutting forces＂ coefficients of 2.5D CC com- posites are evaluated using multiple linear regression method. Verification experiment has been car- ried out through a group of orthogonal tests. Results indicate that the proposed nmdel is reliable and can be used to predict the cutting forces in ball-end milling of 2.5D C/C composites.展开更多
目的评价肌少症筛查工具即简易五项评分问卷(SARC-F)对肌少症的诊断准确性和临床适用性,评估其诊断价值。方法计算机检索PubMed、The Cochrane Library、Wed of Science、EMBASE、MEDLINE、Ovid、中国知网、中国生物医学数据、维普数据...目的评价肌少症筛查工具即简易五项评分问卷(SARC-F)对肌少症的诊断准确性和临床适用性,评估其诊断价值。方法计算机检索PubMed、The Cochrane Library、Wed of Science、EMBASE、MEDLINE、Ovid、中国知网、中国生物医学数据、维普数据库和万方数据库,搜集自建库以来至2020年3月1日前所有与SARC-F对肌少症的诊断相关的研究。采用RevMan 5.3软件、Stata16.0软件综合评价SARC-F对肌肉减少症的诊断价值。结果总共纳入13项研究,包括8860例患者。Meta分析结果显示,应用欧洲肌少症共识、亚洲肌少症共识、国际肌少症共识制定的诊断标准作为金标准时,灵敏度都较低,而特异度相对较高。受试者工作特征曲线下面积分别为0.71、0.69、0.67,Q指数为0.6593、0.6509、0.6316。结论SARC-F在肌少症的筛查诊断中具有一定的价值,在日后的研究中,建议在此问卷的基础上加入对肌肉质量简易测量的内容,提高问卷筛查准确性。展开更多
基金Supported by National Natural Science Foundation of China (10875164,10805070)the Knowledge Innovation Project of Chinese Academy of Sciences,Shanghai Municipal Commission for Science and Technology (10ZR1436700),and SRF for ROCS of the Ministry of Education
文摘Acrylic acid (AAc) and styrene (St) were grafted onto poly(vinylidene fluoride) (PVDF) powder or membrane samples by pre-irradiation graft copolymerization.The grafted chains were proved by FT-IR spectroscopy analysis.The degree of grafting (DG) of the grafted PVDF was determined by fluorine elemental analysis (FEA) method,and was compared with the DGs determined by weighing method,acid-base back titration method and quantitative FT-IR method.The results show that the FEA method is accurate,convenient and universal,especially for the grafted polymer powders.
文摘目的了解重庆市溺水死亡率及疾病负担变化趋势,为开展溺水预防提供建议。方法收集分析2012—2018年重庆市溺水死亡个案信息(ICD-10编码:W65-W74),采用SPSS 25.0统计分析溺水死亡率、标化死亡率、伤残调整生命年(Disability adjusted life years,DALYs)、早死所致的寿命损失年(Years of life lost,YLLs)、残疾所致寿命损失年(Year lived with disability,YLDs)等指标。男女、城乡之间溺水死亡率的比较采用卡方检验。率的趋势变化采用年度变化百分比(Annual percent change,APC),APC检验采用t检验,检验水准α=0.05。结果重庆市溺水死亡率与标化死亡率分别由2012年的4.90/10万、4.87/10万下降到2018年的3.85/10万、3.59/10万,APC分别为-3.34%与-4.59%,变化趋势差异均无统计学意义(t=2.34、2.42,P>0.05)。历年溺水死亡率男性高于女性,差异均有统计学意义(P>0.05)。历年农村地区溺水死亡率高于城市,差异均有统计学意义(P<0.05)。5岁以下年龄组溺水死亡率历年均是最高的。5岁以下年龄组溺水死亡率由2012年的14.47/10万下降到2018年的4.28/10万,APC为-17.06%,变化趋势差异有统计学意义(t=8.86,P<0.001)。65岁及以上年龄组溺水死亡率由2012年的8.14/10万上升至2018年的9.77/10万,APC为4.92%,变化趋势差异无统计学意义(t=2.56,P=0.051)。溺水的DALYs率、YLLs率分别由2012年的2.73千人年、2.70千人年下降到2018年的1.66千人年、1.64千人年,APC分别为-7.41%与-7.41%,变化趋势差异均有统计学意义(P均<0.05),YLDs率由2012年0.03千人年下降至2018年的0.02千人年,变化趋势差异无统计学意义(P>0.05)。结论重庆市溺水死亡率及疾病负担呈下降的趋势,低于全国的平均水平,儿童、男性与老年人是预防溺水发生的重点人群,农村是预防溺水的重点地区。
基金supported by the National Natural Science Foundation of China(No.51105312)the Fundamental Research Funds for the Central University of China(No.3102015JCS05005)
文摘Machining of carbon/carbon （C/C） composite materials is difficult to carry out due to its high specific stiffness, brittleness, anisotropic, non-homogeneous and low thermal conductivity, which can result in tear, burr, poor surface quality and rapid wear of cutters. Accurate and fast pre- diction of cutting forces is important for milling C/C composite materials with high quality. This paper presents an alternative cutting force model involving the influences of the directions of fiber. Based on the calculated and experimental results, the cutting forces＂ coefficients of 2.5D CC com- posites are evaluated using multiple linear regression method. Verification experiment has been car- ried out through a group of orthogonal tests. Results indicate that the proposed nmdel is reliable and can be used to predict the cutting forces in ball-end milling of 2.5D C/C composites.
