Recycled aggregates(RA)are frequently obtained from various unknown sources,which caused variation in properties among recycled aggregates concrete(RAC).This paper investigated the macro and microscopic properties o...Recycled aggregates(RA)are frequently obtained from various unknown sources,which caused variation in properties among recycled aggregates concrete(RAC).This paper investigated the macro and microscopic properties of RAC prepared with RAs originated from different parent concretes with 90-day strength ranging from 30 MPa to 100 MPa.These parent concretes were prepared in advance and crushed to produce RA of distinct qualities.The attached mortar content can reach up to 69%in the concrete with highest strength grade.The microscopic investigation on different RAC was conducted with the X-ray Micro-Computed Tomography scanning technique and image process.Experimental results showed that the properties of RA derived from various parent concrete varied because of the amount of residual mortar.The development of mechanical properties and chloride-ion penetration of RACs all followed a binomial trend with the strength grades of the parent concrete because of the different quantity and quality of RAs.展开更多
An orchard-lifting platform is a type of mechanical equipment to assist growers in fruit picking,fruit tree pruning,flower thinning,and other operations.In its operational processes,the tilting stability directly affe...An orchard-lifting platform is a type of mechanical equipment to assist growers in fruit picking,fruit tree pruning,flower thinning,and other operations.In its operational processes,the tilting stability directly affects the operational safety and adaptability under complex terrain conditions,while critical tilting angle is an important criterion to evaluate the tilting stability.Based on the structure and the operating characteristics of the three degree of freedom(3-DOF)lifting platform for hilly orchards,the tilting stability was analyzed in different parked states,and the theoretical expressions of critical tilting angle were obtained;in the theoretical expressions,the influencing factors on tilting stability were determined as the parked positionβ1,the manned worktable rotary positionβ2,the lifting height h,and the load m.Based on the multi-body dynamics principle,the tilting stability simulation was carried out.The relative error of tilting angles was approximately 4.6%between simulation and tilting verification experiment,which indicated that the results of tilting stability simulation were reliable.Therefore,the multi-body dynamics simulation was used for further clarifying the influencing factors on tilting stability.A virtual orthogonal test was designed,and the results showed that critical tilting angle ranged from 20°to 44°when the factors were at different values,which indicated that the 3-DOF lifting platform for hilly orchards had a high tilting stability performance and could adapt to the operating conditions of hills with slope angles from 5°to 20°.The results of the range analysis and ANOVA showed that the influence intensity of factors on tilting stability wasβ1>h>m>β2;at the same time,β1,h,and m exerted significant effect on tilting stability.The tilting stability first decreased and then either increased or decreased with the increasing lifting height;it gradually decreased with the increasing load.It also showed that the position of the manned worktable along the slope down always had the lowest tilting stability.This research can provide a theoretical basis and reference for the analysis of tilting stability of the lifting machinery for hilly orchards.展开更多
On April 26,2021,a 33-year-old male Chinese sailor returning from India via Kathmandu,Nepal,tested positive for the coronavirus disease 2019(COVID-19)by Chengdu Customs and was confirmed positive by Chengdu CDC(Case A...On April 26,2021,a 33-year-old male Chinese sailor returning from India via Kathmandu,Nepal,tested positive for the coronavirus disease 2019(COVID-19)by Chengdu Customs and was confirmed positive by Chengdu CDC(Case A).On May 2,2021,a housewife in the same flight tested positive for COVID-19 by Pengzhou CDC in Sichuan Province during her quarantine period and was confirmed positive by Chengdu CDC the next day(Case B).展开更多
The development of types is an important but challenging issue in temporal logic programming. In this paper, we investigate how to formalize and implement types in the temporal logic programming language MSVL, which i...The development of types is an important but challenging issue in temporal logic programming. In this paper, we investigate how to formalize and implement types in the temporal logic programming language MSVL, which is an executable subset of projection temporal logic （PTL）. Specifically, we extend MSVL with a few groups of types including basic data types, pointer types and struct types. On each type, we specify the domain of values and define some standard operations in terms of logic functions and predicates. Then, it is feasible to formalize statements of type declaration of program variables and statements of struct definitions as logic formulas. As the implementation of the theory, we extend the MSV toolkit with the support of modeling, simulation and verification of typed MSVL programs. Applications to the construction of AVL tree and ordered list show the practicality of the language.展开更多
基金This research was funded by the National Natural Science Foundation of China[Grant Number 51708419].
文摘Recycled aggregates(RA)are frequently obtained from various unknown sources,which caused variation in properties among recycled aggregates concrete(RAC).This paper investigated the macro and microscopic properties of RAC prepared with RAs originated from different parent concretes with 90-day strength ranging from 30 MPa to 100 MPa.These parent concretes were prepared in advance and crushed to produce RA of distinct qualities.The attached mortar content can reach up to 69%in the concrete with highest strength grade.The microscopic investigation on different RAC was conducted with the X-ray Micro-Computed Tomography scanning technique and image process.Experimental results showed that the properties of RA derived from various parent concrete varied because of the amount of residual mortar.The development of mechanical properties and chloride-ion penetration of RACs all followed a binomial trend with the strength grades of the parent concrete because of the different quantity and quality of RAs.
基金The research was financially supported by Co-Innovation Center of the Intelligent Management and Equipment for Orchard on the Hilly Land in south China(JX2014XCHJ02).
文摘An orchard-lifting platform is a type of mechanical equipment to assist growers in fruit picking,fruit tree pruning,flower thinning,and other operations.In its operational processes,the tilting stability directly affects the operational safety and adaptability under complex terrain conditions,while critical tilting angle is an important criterion to evaluate the tilting stability.Based on the structure and the operating characteristics of the three degree of freedom(3-DOF)lifting platform for hilly orchards,the tilting stability was analyzed in different parked states,and the theoretical expressions of critical tilting angle were obtained;in the theoretical expressions,the influencing factors on tilting stability were determined as the parked positionβ1,the manned worktable rotary positionβ2,the lifting height h,and the load m.Based on the multi-body dynamics principle,the tilting stability simulation was carried out.The relative error of tilting angles was approximately 4.6%between simulation and tilting verification experiment,which indicated that the results of tilting stability simulation were reliable.Therefore,the multi-body dynamics simulation was used for further clarifying the influencing factors on tilting stability.A virtual orthogonal test was designed,and the results showed that critical tilting angle ranged from 20°to 44°when the factors were at different values,which indicated that the 3-DOF lifting platform for hilly orchards had a high tilting stability performance and could adapt to the operating conditions of hills with slope angles from 5°to 20°.The results of the range analysis and ANOVA showed that the influence intensity of factors on tilting stability wasβ1>h>m>β2;at the same time,β1,h,and m exerted significant effect on tilting stability.The tilting stability first decreased and then either increased or decreased with the increasing lifting height;it gradually decreased with the increasing load.It also showed that the position of the manned worktable along the slope down always had the lowest tilting stability.This research can provide a theoretical basis and reference for the analysis of tilting stability of the lifting machinery for hilly orchards.
基金Non-Profit Central Research Institute Fund of Chinese Academy of Medical Sciences(2020-PT330-005).
文摘On April 26,2021,a 33-year-old male Chinese sailor returning from India via Kathmandu,Nepal,tested positive for the coronavirus disease 2019(COVID-19)by Chengdu Customs and was confirmed positive by Chengdu CDC(Case A).On May 2,2021,a housewife in the same flight tested positive for COVID-19 by Pengzhou CDC in Sichuan Province during her quarantine period and was confirmed positive by Chengdu CDC the next day(Case B).
文摘The development of types is an important but challenging issue in temporal logic programming. In this paper, we investigate how to formalize and implement types in the temporal logic programming language MSVL, which is an executable subset of projection temporal logic （PTL）. Specifically, we extend MSVL with a few groups of types including basic data types, pointer types and struct types. On each type, we specify the domain of values and define some standard operations in terms of logic functions and predicates. Then, it is feasible to formalize statements of type declaration of program variables and statements of struct definitions as logic formulas. As the implementation of the theory, we extend the MSV toolkit with the support of modeling, simulation and verification of typed MSVL programs. Applications to the construction of AVL tree and ordered list show the practicality of the language.
