The generalized constitutive model relating the resilient modulus (MR) of flexible pavement layer materials to stress state, adopted by the Mechanistic-Empirical Pavement Design Guide (MEPDG), contains a set of consta...The generalized constitutive model relating the resilient modulus (MR) of flexible pavement layer materials to stress state, adopted by the Mechanistic-Empirical Pavement Design Guide (MEPDG), contains a set of constants known as k-values (k1, k2, and k3) which are associated with the physical state of the layer materials. In Ghana, natural gravels constitute the predominant and sometimes the sole layer materials for most flexible pavements yet representative k-values of gravel materials, have not been determined to permit full application and implementation of the mechanistic-empirical design concept to pavements involving such materials. In this study, k-values characterising typical natural quartzitic gravels used for road construction in the country were derived by regression techniques from MR values determined using laboratory repeated load triaxial test. Using multiple linear regression technique, correlation relationships were then developed between the k-values and the physical properties of the gravels, namely, percentages of materials passing the 9.5 mm (P9.5) and 2.0 mm (P2.0) sieves, liquid limit (LL), maximum dry density (ρdmax), and optimum moisture content (wopt). The regression analysis returned k1 values which ranged between 441 and 958 with a mean of 516;k2 which varied between 0.0636 and 0.2168 with a mean value of 0.1216;and, k3 values which ranged between 0.1257 and 3.1590 with a mean value of 1.723. Contrary to what is mostly reported in literature, the analysis returned positive k3 values for all but one gravel material, suggesting stress hardening under octahedral shear stress for those materials. While an expanded sample base is required to fully characterize the whole gamut of natural gravels used in pavement construction in the country, this study on limited quartzitic gravel samples has given a good indication of strong linear correlations between the k-values and the index properties of the gravels, to permit estimates of the constants for such gravels be made where capability and opportunity for conducting resilient modulus tests do not exist.However, further work is recommended to fully characterise the exact nature of k3 values for quartzitic gravels in the country.展开更多
Context:Prevalence of nutritional anemia among Saudi female and children is evident and has been reflected in different studies,most of researchers conclude that there is a gap in dietary coun-seling in addition to th...Context:Prevalence of nutritional anemia among Saudi female and children is evident and has been reflected in different studies,most of researchers conclude that there is a gap in dietary coun-seling in addition to the poor awareness of community about appropriate dietary habits;this study is trying to assess counseling behavior and training competency of family physician at primary health centers with respect to nutritional anemia.Objective:Study objective is to assess general beliefs,practice,and level of training in coun-seling by family physician.Methodology:This is a cross-sectional study design;data collected using self-administered questionnaire provided to the doctor at clinic site.Results:The most commonly learned counseling technique in order as follows motivational interviewing(68%),cognitive behavioral therapy(58%),and 15-Minute Hour approach(53%).Conclusion:This study confirms the presence of positive counseling beliefs and practices by family physicians;however,the result is also reflects the current reluctant state of family physicians in devoting ample time for nutritional anemia counseling.展开更多
Traffic accident severity prediction is essential for dynamic traffic safety management.To explore the factors influencing the severity of traffic accidents on mountain freeways and to predict the severity of traffic ...Traffic accident severity prediction is essential for dynamic traffic safety management.To explore the factors influencing the severity of traffic accidents on mountain freeways and to predict the severity of traffic accidents,four models based on machine learning algorithms are constructed using support vector machine(SVM),decision tree classifier(DTC),Ada_SVM and Ada_DTC.In addition,random forest(RF)is used to calculate the importance degree of variables and the accident severity influences with high importance levels form the RF dataset.The results show that rainfall intensity,collision type,number of vehicles involved in the accident and toad section type are important variables influencing accident severity.The RF feature selection method improves the classification performance of four machine leaming algorithms,resulting in a 9.3%,5.5%,7.2% and 3.6% improvement in prediction accuracy for SVM,DTC,Ada_SVM and Ada_DTC,respectively.The combination of the Ada_SVM integrated algorithm and RF feature selection method has the best prediction performance,and it achieves 78.9% and 88.4% prediction precision and accuracy,respectively.展开更多
文摘The generalized constitutive model relating the resilient modulus (MR) of flexible pavement layer materials to stress state, adopted by the Mechanistic-Empirical Pavement Design Guide (MEPDG), contains a set of constants known as k-values (k1, k2, and k3) which are associated with the physical state of the layer materials. In Ghana, natural gravels constitute the predominant and sometimes the sole layer materials for most flexible pavements yet representative k-values of gravel materials, have not been determined to permit full application and implementation of the mechanistic-empirical design concept to pavements involving such materials. In this study, k-values characterising typical natural quartzitic gravels used for road construction in the country were derived by regression techniques from MR values determined using laboratory repeated load triaxial test. Using multiple linear regression technique, correlation relationships were then developed between the k-values and the physical properties of the gravels, namely, percentages of materials passing the 9.5 mm (P9.5) and 2.0 mm (P2.0) sieves, liquid limit (LL), maximum dry density (ρdmax), and optimum moisture content (wopt). The regression analysis returned k1 values which ranged between 441 and 958 with a mean of 516;k2 which varied between 0.0636 and 0.2168 with a mean value of 0.1216;and, k3 values which ranged between 0.1257 and 3.1590 with a mean value of 1.723. Contrary to what is mostly reported in literature, the analysis returned positive k3 values for all but one gravel material, suggesting stress hardening under octahedral shear stress for those materials. While an expanded sample base is required to fully characterize the whole gamut of natural gravels used in pavement construction in the country, this study on limited quartzitic gravel samples has given a good indication of strong linear correlations between the k-values and the index properties of the gravels, to permit estimates of the constants for such gravels be made where capability and opportunity for conducting resilient modulus tests do not exist.However, further work is recommended to fully characterise the exact nature of k3 values for quartzitic gravels in the country.
文摘Context:Prevalence of nutritional anemia among Saudi female and children is evident and has been reflected in different studies,most of researchers conclude that there is a gap in dietary coun-seling in addition to the poor awareness of community about appropriate dietary habits;this study is trying to assess counseling behavior and training competency of family physician at primary health centers with respect to nutritional anemia.Objective:Study objective is to assess general beliefs,practice,and level of training in coun-seling by family physician.Methodology:This is a cross-sectional study design;data collected using self-administered questionnaire provided to the doctor at clinic site.Results:The most commonly learned counseling technique in order as follows motivational interviewing(68%),cognitive behavioral therapy(58%),and 15-Minute Hour approach(53%).Conclusion:This study confirms the presence of positive counseling beliefs and practices by family physicians;however,the result is also reflects the current reluctant state of family physicians in devoting ample time for nutritional anemia counseling.
基金supported by the Science and Technology Innovation programme of the Department of Transportation,Yunnan Province,China(Grants No.2019303 and[2020]75)the general programme of key science and technology in transportation,the Ministry of Transport,China(Grants No.2018-MS4-102 and 2021-TG-005)the research fund of the Nanjing Joint Institute for Atmospheric Sciences(Grant No.BJG202101).
文摘Traffic accident severity prediction is essential for dynamic traffic safety management.To explore the factors influencing the severity of traffic accidents on mountain freeways and to predict the severity of traffic accidents,four models based on machine learning algorithms are constructed using support vector machine(SVM),decision tree classifier(DTC),Ada_SVM and Ada_DTC.In addition,random forest(RF)is used to calculate the importance degree of variables and the accident severity influences with high importance levels form the RF dataset.The results show that rainfall intensity,collision type,number of vehicles involved in the accident and toad section type are important variables influencing accident severity.The RF feature selection method improves the classification performance of four machine leaming algorithms,resulting in a 9.3%,5.5%,7.2% and 3.6% improvement in prediction accuracy for SVM,DTC,Ada_SVM and Ada_DTC,respectively.The combination of the Ada_SVM integrated algorithm and RF feature selection method has the best prediction performance,and it achieves 78.9% and 88.4% prediction precision and accuracy,respectively.
