A separation phenomenon occurring during the drop weight tear test of commercial thick-walled API （American Petroleum Institute） X80 strip steel was investigated in this work. Microstructural analysis showed that th...A separation phenomenon occurring during the drop weight tear test of commercial thick-walled API （American Petroleum Institute） X80 strip steel was investigated in this work. Microstructural analysis showed that the band structure of bainite elongated along the rolling direction works as the initiation sites of separation. The propagation of separation can be promoted not only by the occurrence of the band structure of martensite/austenite constituent, prior austenite grain boundaries, and elongated bainite, but also by fine acicular ferrite and bainite. Wide separation formed in the former case, while the narrow one appeared in the latter case. acicular ferrite in thick-walled X80 pipeline steel in order Some methods were proposed to obtain fine and homogeneous to minimize the occurrence of separation.展开更多
BACKGROUND Gestational diabetes mellitus(GDM) is a common metabolic derangement in pregnant women. In the women identified to be at high risk of GDM, a 75 g oral glucose tolerance test(OGTT) at 24-28 wk gestation is t...BACKGROUND Gestational diabetes mellitus(GDM) is a common metabolic derangement in pregnant women. In the women identified to be at high risk of GDM, a 75 g oral glucose tolerance test(OGTT) at 24-28 wk gestation is the recommended screening test in the United Kingdom as per National Institute for Health and Care Excellence(NICE). Hypoglycaemia following the glucose load is often encountered and the implication of this finding for the pregnancy, fetus and clinical care is unclear.AIM To determine the prevalence of hypoglycaemia at any time during the screening OGTT and explore its association with birth weight.METHODS All deliveries between 2009 and 2013 at the local maternity unit of the University hospital were reviewed. Of the total number of 24,154 women without preexisting diabetes, those who had an OGTT for GDM screening based on NICE recommended risk stratification, who had a singleton delivery and had complete clinical and demographic data for analysis, were included for this study(n =3537). Blood samples for fasting plasma glucose(FPG), 2-hour plasma glucose(2-h PG) and HbA1 c had been obtained. Birth weight was categorised as low(≤ 2500 g), normal or Macrosomia(≥ 4500 g) and blood glucose ≤ 3.5 mmol/L was used to define hypoglycaemia. Binary logistic regression was used to determine the association of various independent factors with dichotomized variables; the differences between frequencies/proportions by χ~2 test and comparison between group means was by one-way ANOVA.RESULTS Amongst the study cohort(3537 deliveries), 96(2.7%) women had babies with LBW(< 2500 g). Women who delivered a LBW baby had significantly lower FPG(4.3 ± 0.6 mmol/L, P = 0.001). The proportion of women who had a 2-h PG ≤ 3.5 mmol/L in the LBW cohort was significantly higher compared to the cohorts with normal and macrosomic babies(8.3% vs 2.8% vs 4.2%; P = 0.007). The factors which predicted LBW were FPG, Asian ethnicity and 2-h PG ≤ 3.5 mmol/L,whereas maternal age, 2-h PG ≥ 7.8 mmol/L and HbA1c were not significant predictors.CONCLUSION A low FPG and 2-h PG ≤ 3.5 mmol/L on 75-gram OGTT are significantly associated with low birth weight in women identified as high risk for GDM.Women of ethnic backgrounds(Asians) appear to be more susceptible to this increased risk and may serve as a separate cohort in whom we should offer more intensive follow up and screening for complications. Cost implications and resources for follow up would need to be looked at in further detail to support these findings.展开更多
This study was designed to examine the effects of dietary energy levels on some growth and reproductive parameters of local barred chickens in Cameroon. For this purpose, One hundred and forty four day-old barred male...This study was designed to examine the effects of dietary energy levels on some growth and reproductive parameters of local barred chickens in Cameroon. For this purpose, One hundred and forty four day-old barred male chicks, weighing 28.33 g in average were randomly divided into 12 groups of 12 chicks each. Three feeding programs (FP) comprising each a starter diet from day old to 12 weeks (S0: 2800 Kcal/Kg;S1: 2900 Kcal/Kg;S2: 3000 Kcal/Kg) and grower diet from 13 to 20 weeks (G0: 2900 Kcal/Kg;G1: 3000 Kcal/ Kg;G2: 3100 Kcal/Kg) were used and designated FP1, FP2 and FP3 respectively. Each of the FP was randomly allotted of 4 groups of 12 birds in a completely randomized design. Throughout experiment (1 day old to 20 weeks), body weight was recovered every 2 weeks. At 20 weeks of age, roosters were sacrificed;semen characteristic was analyzed and testes were characterized. Between 2 to 10 weeks old, body weight of cocks fed with FP3 was significantly higher (P < 0.05) as compared to others FP. Inversely, from 12 to 20 weeks, body weight of cocks receiving FP1 was significantly higher (P < 0.05) than that of cocks receiving feeding programs 2 and 3. At 20 weeks, 100% of cocks fed on FP3 produced semen versus 66.66% and 16.66% respectively for those on FP1 and FP2. Semen volume and mass motility of cocks fed on FP3 or FP1 were significantly (P < 0.05) higher than FP2. It was concluded that FP1 had more suitable dietary energy levels for growth and reproduction of local barred cocks.展开更多
The weight loss of cement slurry is the main cause of early annular air channeling and accurate experimental evaluation of the law of loss change is the key to achieve compression stability and prevent this undesired ...The weight loss of cement slurry is the main cause of early annular air channeling and accurate experimental evaluation of the law of loss change is the key to achieve compression stability and prevent this undesired phenomenon.Typically,tests on the pressure loss of cement slurry are carried out for temperature smaller than 120°C,and this condition cannot simulate effectively the situation occurring in high temperature wells.For this reason,in this study a series of experimental tests have been conducted considering a larger range of temperatures,different retarders and fluid loss additives.The results show that with an increase in the temperature,the weight loss curve of cement slurry changes from a“two-stage”to a“three-stage”behavior,and the risk of channeling increases accordingly.On increasing the amount of retarder and fluid loss additive,the transition time of cement slurry displays a non-monotonic behavior(it decreases first and then increases).It is found that the optimized retarder and fluid loss additive dosage are 0.2%and 2.5%,respectively.展开更多
This paper is concerned with the application of weighted least square method in change point analysis. Testing shift in the mean normal observations with time varying variances as well as of a GARCH time series are co...This paper is concerned with the application of weighted least square method in change point analysis. Testing shift in the mean normal observations with time varying variances as well as of a GARCH time series are considered. For both cases, the weighted estimators are given and their asymptotic behaviors are studied. It is also described that how the resampling methods like Monte Carlo and bootstrap may be applied to compute the finite sample behavior of estimators.展开更多
Having studied the property of compare matrix, this paper establishes a mathematical model of minimizing the sum of Euclidean norm (SEN) by means of the least square method. It is proved that the non linear program ...Having studied the property of compare matrix, this paper establishes a mathematical model of minimizing the sum of Euclidean norm (SEN) by means of the least square method. It is proved that the non linear program model can be transformed into linear a展开更多
In diagnostic trials, clustered data are obtained when several subunits of the same patient are observed. Within-cluster correlations need to be taken into account when analyzing such clustered data. A nonparametric m...In diagnostic trials, clustered data are obtained when several subunits of the same patient are observed. Within-cluster correlations need to be taken into account when analyzing such clustered data. A nonparametric method has been proposed by Obuchowski (1997) to estimate the Receiver Operating Characteristic curve area (AUC) for such clustered data. However, Obuchowski’s estimator gives equal weight to all pairwise rankings within and between cluster. In this paper, we modify Obuchowski’s estimate by allowing weights for the pairwise rankings vary across clusters. We consider the optimal weights for estimating one AUC as well as two AUCs’ difference. Our results in this paper show that the optimal weights depends on not only the within-patient correlation but also the proportion of patients that have both unaffected and affected units. More importantly, we show that the loss of efficiency using equal weight instead of our optimal weights can be severe when there is a large within-cluster correlation and the proportion of patients that have both unaffected and affected units is small.展开更多
The flat cylindrical indentation tests with different sizes of punch radius were investigated using finite element method （FEM） aimed to reveal the effect of punch size on the indentation behavior of the film/substr...The flat cylindrical indentation tests with different sizes of punch radius were investigated using finite element method （FEM） aimed to reveal the effect of punch size on the indentation behavior of the film/substrate system. Based on the FEM results analysis, two methods was proposed to separate film＇s reduced Young＇s modulus from a film/substrate system. The first method was based on a new weight function that quantifies film＇s and substrate＇s contributions to the overall mechanical properties of the film/substrate system in the flat cylindrical indentation test. The second method, a numerical approach, including fitting and extrapolation procedures was put forward. Both of the results from the two methods showed a reasonable agreement with the one input FE model. At last, the effect of maximum indentation depth and the surface micro-roughness of the thin film on the reduced Young＇s modulus of the film/substrate system were discussed. The methods proposed in the present study provide some new conceptions on evaluating other properties of thin films, e.g. creep, for which a flat-ended punch is also employed.展开更多
文摘A separation phenomenon occurring during the drop weight tear test of commercial thick-walled API （American Petroleum Institute） X80 strip steel was investigated in this work. Microstructural analysis showed that the band structure of bainite elongated along the rolling direction works as the initiation sites of separation. The propagation of separation can be promoted not only by the occurrence of the band structure of martensite/austenite constituent, prior austenite grain boundaries, and elongated bainite, but also by fine acicular ferrite and bainite. Wide separation formed in the former case, while the narrow one appeared in the latter case. acicular ferrite in thick-walled X80 pipeline steel in order Some methods were proposed to obtain fine and homogeneous to minimize the occurrence of separation.
文摘BACKGROUND Gestational diabetes mellitus(GDM) is a common metabolic derangement in pregnant women. In the women identified to be at high risk of GDM, a 75 g oral glucose tolerance test(OGTT) at 24-28 wk gestation is the recommended screening test in the United Kingdom as per National Institute for Health and Care Excellence(NICE). Hypoglycaemia following the glucose load is often encountered and the implication of this finding for the pregnancy, fetus and clinical care is unclear.AIM To determine the prevalence of hypoglycaemia at any time during the screening OGTT and explore its association with birth weight.METHODS All deliveries between 2009 and 2013 at the local maternity unit of the University hospital were reviewed. Of the total number of 24,154 women without preexisting diabetes, those who had an OGTT for GDM screening based on NICE recommended risk stratification, who had a singleton delivery and had complete clinical and demographic data for analysis, were included for this study(n =3537). Blood samples for fasting plasma glucose(FPG), 2-hour plasma glucose(2-h PG) and HbA1 c had been obtained. Birth weight was categorised as low(≤ 2500 g), normal or Macrosomia(≥ 4500 g) and blood glucose ≤ 3.5 mmol/L was used to define hypoglycaemia. Binary logistic regression was used to determine the association of various independent factors with dichotomized variables; the differences between frequencies/proportions by χ~2 test and comparison between group means was by one-way ANOVA.RESULTS Amongst the study cohort(3537 deliveries), 96(2.7%) women had babies with LBW(< 2500 g). Women who delivered a LBW baby had significantly lower FPG(4.3 ± 0.6 mmol/L, P = 0.001). The proportion of women who had a 2-h PG ≤ 3.5 mmol/L in the LBW cohort was significantly higher compared to the cohorts with normal and macrosomic babies(8.3% vs 2.8% vs 4.2%; P = 0.007). The factors which predicted LBW were FPG, Asian ethnicity and 2-h PG ≤ 3.5 mmol/L,whereas maternal age, 2-h PG ≥ 7.8 mmol/L and HbA1c were not significant predictors.CONCLUSION A low FPG and 2-h PG ≤ 3.5 mmol/L on 75-gram OGTT are significantly associated with low birth weight in women identified as high risk for GDM.Women of ethnic backgrounds(Asians) appear to be more susceptible to this increased risk and may serve as a separate cohort in whom we should offer more intensive follow up and screening for complications. Cost implications and resources for follow up would need to be looked at in further detail to support these findings.
文摘This study was designed to examine the effects of dietary energy levels on some growth and reproductive parameters of local barred chickens in Cameroon. For this purpose, One hundred and forty four day-old barred male chicks, weighing 28.33 g in average were randomly divided into 12 groups of 12 chicks each. Three feeding programs (FP) comprising each a starter diet from day old to 12 weeks (S0: 2800 Kcal/Kg;S1: 2900 Kcal/Kg;S2: 3000 Kcal/Kg) and grower diet from 13 to 20 weeks (G0: 2900 Kcal/Kg;G1: 3000 Kcal/ Kg;G2: 3100 Kcal/Kg) were used and designated FP1, FP2 and FP3 respectively. Each of the FP was randomly allotted of 4 groups of 12 birds in a completely randomized design. Throughout experiment (1 day old to 20 weeks), body weight was recovered every 2 weeks. At 20 weeks of age, roosters were sacrificed;semen characteristic was analyzed and testes were characterized. Between 2 to 10 weeks old, body weight of cocks fed with FP3 was significantly higher (P < 0.05) as compared to others FP. Inversely, from 12 to 20 weeks, body weight of cocks receiving FP1 was significantly higher (P < 0.05) than that of cocks receiving feeding programs 2 and 3. At 20 weeks, 100% of cocks fed on FP3 produced semen versus 66.66% and 16.66% respectively for those on FP1 and FP2. Semen volume and mass motility of cocks fed on FP3 or FP1 were significantly (P < 0.05) higher than FP2. It was concluded that FP1 had more suitable dietary energy levels for growth and reproduction of local barred cocks.
基金The authors gratefully acknowledge the research project from“Research and test on optimization of calculation model for cementing engineering of high temperature and high pressure wells”(Grant No.CQCJ-2020-06).
文摘The weight loss of cement slurry is the main cause of early annular air channeling and accurate experimental evaluation of the law of loss change is the key to achieve compression stability and prevent this undesired phenomenon.Typically,tests on the pressure loss of cement slurry are carried out for temperature smaller than 120°C,and this condition cannot simulate effectively the situation occurring in high temperature wells.For this reason,in this study a series of experimental tests have been conducted considering a larger range of temperatures,different retarders and fluid loss additives.The results show that with an increase in the temperature,the weight loss curve of cement slurry changes from a“two-stage”to a“three-stage”behavior,and the risk of channeling increases accordingly.On increasing the amount of retarder and fluid loss additive,the transition time of cement slurry displays a non-monotonic behavior(it decreases first and then increases).It is found that the optimized retarder and fluid loss additive dosage are 0.2%and 2.5%,respectively.
文摘This paper is concerned with the application of weighted least square method in change point analysis. Testing shift in the mean normal observations with time varying variances as well as of a GARCH time series are considered. For both cases, the weighted estimators are given and their asymptotic behaviors are studied. It is also described that how the resampling methods like Monte Carlo and bootstrap may be applied to compute the finite sample behavior of estimators.
文摘Having studied the property of compare matrix, this paper establishes a mathematical model of minimizing the sum of Euclidean norm (SEN) by means of the least square method. It is proved that the non linear program model can be transformed into linear a
文摘In diagnostic trials, clustered data are obtained when several subunits of the same patient are observed. Within-cluster correlations need to be taken into account when analyzing such clustered data. A nonparametric method has been proposed by Obuchowski (1997) to estimate the Receiver Operating Characteristic curve area (AUC) for such clustered data. However, Obuchowski’s estimator gives equal weight to all pairwise rankings within and between cluster. In this paper, we modify Obuchowski’s estimate by allowing weights for the pairwise rankings vary across clusters. We consider the optimal weights for estimating one AUC as well as two AUCs’ difference. Our results in this paper show that the optimal weights depends on not only the within-patient correlation but also the proportion of patients that have both unaffected and affected units. More importantly, we show that the loss of efficiency using equal weight instead of our optimal weights can be severe when there is a large within-cluster correlation and the proportion of patients that have both unaffected and affected units is small.
基金supports from National Natural Science Foundation of China (Nos.50775183 and 50805118)Research Fund for Doctoral Programof higher Education (N6CJ0001)National High Technical Research and Development Programme of China (No.2009AA04Z418)
文摘The flat cylindrical indentation tests with different sizes of punch radius were investigated using finite element method （FEM） aimed to reveal the effect of punch size on the indentation behavior of the film/substrate system. Based on the FEM results analysis, two methods was proposed to separate film＇s reduced Young＇s modulus from a film/substrate system. The first method was based on a new weight function that quantifies film＇s and substrate＇s contributions to the overall mechanical properties of the film/substrate system in the flat cylindrical indentation test. The second method, a numerical approach, including fitting and extrapolation procedures was put forward. Both of the results from the two methods showed a reasonable agreement with the one input FE model. At last, the effect of maximum indentation depth and the surface micro-roughness of the thin film on the reduced Young＇s modulus of the film/substrate system were discussed. The methods proposed in the present study provide some new conceptions on evaluating other properties of thin films, e.g. creep, for which a flat-ended punch is also employed.
