In this paper, ultrasonic C-scan test of spot welds for stainless steel has been studied. It is concluded that large scanning step length contributes to high testing efficiency, however, the low-resolution C-scan imag...In this paper, ultrasonic C-scan test of spot welds for stainless steel has been studied. It is concluded that large scanning step length contributes to high testing efficiency, however, the low-resolution C-scan image generated cannot be used to assess spot welding quality reliably. Based on bicubic image interpolation, the C-scan image in low resolution with the large step length 1 000 ~xm is subdivided and reconstructed. By this means, the C-scan image resolution is greatly enhanced and testing results obtained are satisfactory, realizing rapid assessment of spot welds. The results of rapid ultrasonic C-scan test fit the actual metallographic measured value well. Mean value of normal distribution of error statistics is O. 006 67, and the standard deviation is O. 087 11. Rapid ultrasonic C-scan test based on image interpolation is of high accuracy and excellent stability.展开更多
A capsulated microdose 14C-urea breath test (14C-UBT) was developed to detect Helicobacter pylori (HP) infection in 137 patients (54 HP negative and 83 HP positive individuals)to whom a single dose of 3. 7ｘ 104 Bq of...A capsulated microdose 14C-urea breath test (14C-UBT) was developed to detect Helicobacter pylori (HP) infection in 137 patients (54 HP negative and 83 HP positive individuals)to whom a single dose of 3. 7ｘ 104 Bq of 14C-urea in a capsule was given. Samples of exhaled gas were collected at the sib, 10th, 15th. 20th, 25th, 30th, 45th and 60th minute after the administration and the peak value of exhaled 14CO2 was found in the samples collected at the 25th minute. This peak value was taken as the measuring point and directly expressed as Bq/mmol CO2 to develop a new detecting method. Then its results were compared with those of HP culture and histological examination. It was found that the samples collected on the 25th minute showed a sensitivity of 97. 06%, specificity of 95. 12%, positive predictive value of 97. 06% and negative predictive value of 95. 12% respectively when the mean value of 14CO2 in HP negative subjects ±3s on the 25th minute was taken as the critical value. This suggests that the capsule-based microdose 14C-UBT may replace conventional 14C-UBT using a larger dose of (1. 85-3. 7)ｘ 105 Bq for it is non-invasive, safe, rapid, accurate, simple and economic.展开更多
为实现XML数据库的性能评测,提出基于TPC-C的XML数据库测试方案。针对XML数据库特性,对其数据结构、查询事务语句进行定制,将原有9张表映射成5个XML Schema文件,按照SQL/XML标准重写负载事务。应用该方案对SQL Server 2005数据库进行测...为实现XML数据库的性能评测,提出基于TPC-C的XML数据库测试方案。针对XML数据库特性,对其数据结构、查询事务语句进行定制,将原有9张表映射成5个XML Schema文件,按照SQL/XML标准重写负载事务。应用该方案对SQL Server 2005数据库进行测试,结果表明显示的各项事务特征均与TPC-C基准相同。展开更多
提出了疲劳寿命预腐蚀影响系数曲线(C- T 曲线)通用性分析的 C值直接对比法和C -T 曲线参数统计对比法,并进行相关试验研究,得到了 C -T 曲线和载荷谱、应力水平以及裂纹尺寸基本无关的结论。C- T曲线是进行腐蚀条件下飞机结构疲劳寿命...提出了疲劳寿命预腐蚀影响系数曲线(C- T 曲线)通用性分析的 C值直接对比法和C -T 曲线参数统计对比法,并进行相关试验研究,得到了 C -T 曲线和载荷谱、应力水平以及裂纹尺寸基本无关的结论。C- T曲线是进行腐蚀条件下飞机结构疲劳寿命评定和分析的基础,为验证分析 C- T 曲线和载荷谱、应力水平以及裂纹尺寸的相关性,从C的定义和分布规律出发,提出了 C值直接对比法和C -T 曲线参数统计对比法,近似谱、不同恒幅应力水平以及不同指定裂纹尺寸下的预腐蚀疲劳寿命数据均表明了 C- T 曲线基本具有通用性;并进行了某型飞机结构主梁模拟试件在随机谱及恒幅谱下的预腐蚀疲劳试验,试验结果同样验证了上述结论,从而说明了C- T 曲线的通用性。展开更多
文摘In this paper, ultrasonic C-scan test of spot welds for stainless steel has been studied. It is concluded that large scanning step length contributes to high testing efficiency, however, the low-resolution C-scan image generated cannot be used to assess spot welding quality reliably. Based on bicubic image interpolation, the C-scan image in low resolution with the large step length 1 000 ~xm is subdivided and reconstructed. By this means, the C-scan image resolution is greatly enhanced and testing results obtained are satisfactory, realizing rapid assessment of spot welds. The results of rapid ultrasonic C-scan test fit the actual metallographic measured value well. Mean value of normal distribution of error statistics is O. 006 67, and the standard deviation is O. 087 11. Rapid ultrasonic C-scan test based on image interpolation is of high accuracy and excellent stability.
文摘A capsulated microdose 14C-urea breath test (14C-UBT) was developed to detect Helicobacter pylori (HP) infection in 137 patients (54 HP negative and 83 HP positive individuals)to whom a single dose of 3. 7ｘ 104 Bq of 14C-urea in a capsule was given. Samples of exhaled gas were collected at the sib, 10th, 15th. 20th, 25th, 30th, 45th and 60th minute after the administration and the peak value of exhaled 14CO2 was found in the samples collected at the 25th minute. This peak value was taken as the measuring point and directly expressed as Bq/mmol CO2 to develop a new detecting method. Then its results were compared with those of HP culture and histological examination. It was found that the samples collected on the 25th minute showed a sensitivity of 97. 06%, specificity of 95. 12%, positive predictive value of 97. 06% and negative predictive value of 95. 12% respectively when the mean value of 14CO2 in HP negative subjects ±3s on the 25th minute was taken as the critical value. This suggests that the capsule-based microdose 14C-UBT may replace conventional 14C-UBT using a larger dose of (1. 85-3. 7)ｘ 105 Bq for it is non-invasive, safe, rapid, accurate, simple and economic.
文摘为实现XML数据库的性能评测,提出基于TPC-C的XML数据库测试方案。针对XML数据库特性,对其数据结构、查询事务语句进行定制,将原有9张表映射成5个XML Schema文件,按照SQL/XML标准重写负载事务。应用该方案对SQL Server 2005数据库进行测试,结果表明显示的各项事务特征均与TPC-C基准相同。
文摘提出了疲劳寿命预腐蚀影响系数曲线(C- T 曲线)通用性分析的 C值直接对比法和C -T 曲线参数统计对比法,并进行相关试验研究,得到了 C -T 曲线和载荷谱、应力水平以及裂纹尺寸基本无关的结论。C- T曲线是进行腐蚀条件下飞机结构疲劳寿命评定和分析的基础,为验证分析 C- T 曲线和载荷谱、应力水平以及裂纹尺寸的相关性,从C的定义和分布规律出发,提出了 C值直接对比法和C -T 曲线参数统计对比法,近似谱、不同恒幅应力水平以及不同指定裂纹尺寸下的预腐蚀疲劳寿命数据均表明了 C- T 曲线基本具有通用性;并进行了某型飞机结构主梁模拟试件在随机谱及恒幅谱下的预腐蚀疲劳试验,试验结果同样验证了上述结论,从而说明了C- T 曲线的通用性。
