有结果:(1)收敛(发散)当且仅当部份和S_N=sum from k=1 to a_k有界(无界)。但是,仅据此尚不能直接得到一个有效的判别法,下面我们介绍Kummer判别法(由德国数学家Ernst E.Kummer在1835年最先给出),它较[1]中结果更为丰满,那里只给出了充...有结果:(1)收敛(发散)当且仅当部份和S_N=sum from k=1 to a_k有界(无界)。但是,仅据此尚不能直接得到一个有效的判别法,下面我们介绍Kummer判别法(由德国数学家Ernst E.Kummer在1835年最先给出),它较[1]中结果更为丰满,那里只给出了充分条件。 定理 ①(1)收敛,当且仅当存在正项级数Σp_k及实数c】0。展开更多
Aim: A population-based survey was conducted in Tuoketuo and Shangdu Counties in Inner Mongolia Autonomous Region, China, in the Autumn of 2010, to assess the prevalence and causes of blindness and visual impairment o...Aim: A population-based survey was conducted in Tuoketuo and Shangdu Counties in Inner Mongolia Autonomous Region, China, in the Autumn of 2010, to assess the prevalence and causes of blindness and visual impairment of people aged 50 years and over. Methods: Random cluster sampling was used to select 82 clusters of 50 residents in the 2 counties. Each survey team included an ophthalmologist, a nurse and a coordinator, who went to door to door in each cluster to identify eligible people. A torch, direct ophthalmoscope and portable slit lamp were used for eye examination. Visual acuity (VA) was tested for each eye of every subject. Those with VA below 6/18 in either eye were examined and causes identified. Results: The survey identified a prevalence of blindness in people aged 50+ in Tuoketuo of 1.2% (95% Confidence Interval: 0.7% - 1.7%) and in Shangdu of 1.4% (95% CI: 1.0% - 1.9%). Cataract was identified as the leading cause of blindness (BL) and severe visual impairment (SVI), and uncorrected refractive errors were the major causes of moderate visual impairment (MVI) in both counties. Over two thirds of blindness, SVI and MVI were identified as avoidable. Conclusions: The prevalence of blindness in people aged 50+ in Tuoketuo and Shangdu was low compared to other studies conducted in China [1] [2]. The prevalence of blindness of people aged 50 years and over could be reduced by up to two thirds through better eye services in the two study areas.展开更多
文摘有结果:(1)收敛(发散)当且仅当部份和S_N=sum from k=1 to a_k有界(无界)。但是,仅据此尚不能直接得到一个有效的判别法,下面我们介绍Kummer判别法(由德国数学家Ernst E.Kummer在1835年最先给出),它较[1]中结果更为丰满,那里只给出了充分条件。 定理 ①(1)收敛,当且仅当存在正项级数Σp_k及实数c】0。
文摘Aim: A population-based survey was conducted in Tuoketuo and Shangdu Counties in Inner Mongolia Autonomous Region, China, in the Autumn of 2010, to assess the prevalence and causes of blindness and visual impairment of people aged 50 years and over. Methods: Random cluster sampling was used to select 82 clusters of 50 residents in the 2 counties. Each survey team included an ophthalmologist, a nurse and a coordinator, who went to door to door in each cluster to identify eligible people. A torch, direct ophthalmoscope and portable slit lamp were used for eye examination. Visual acuity (VA) was tested for each eye of every subject. Those with VA below 6/18 in either eye were examined and causes identified. Results: The survey identified a prevalence of blindness in people aged 50+ in Tuoketuo of 1.2% (95% Confidence Interval: 0.7% - 1.7%) and in Shangdu of 1.4% (95% CI: 1.0% - 1.9%). Cataract was identified as the leading cause of blindness (BL) and severe visual impairment (SVI), and uncorrected refractive errors were the major causes of moderate visual impairment (MVI) in both counties. Over two thirds of blindness, SVI and MVI were identified as avoidable. Conclusions: The prevalence of blindness in people aged 50+ in Tuoketuo and Shangdu was low compared to other studies conducted in China [1] [2]. The prevalence of blindness of people aged 50 years and over could be reduced by up to two thirds through better eye services in the two study areas.
