A specially developed ultrasonic measurement apparatus (UMA) was used to in situ monitor the setting process of fly ash blended cement paste. Combined with the results of Vicat Needle tests, isothermal calorimetric me...A specially developed ultrasonic measurement apparatus (UMA) was used to in situ monitor the setting process of fly ash blended cement paste. Combined with the results of Vicat Needle tests, isothermal calorimetric measurement, XRD analysis, SEM morphology and compressive test, the influence of curing temperature (20, 40, 60, and 90 ℃) and fly ash content (0,10%, 20% and 30%) on the setting and hydration process of fly ash blended cement paste was analyzed. The results show that setting and hardening process of fly ash blended cement paste at elevated temperature can be clearly identified into three stages including dormant stage, acceleration stage and deceleration stage. The increasing of curing temperature greatly accelerates the setting and hardening process. However, the content of fly ash does not have significant effect on the setting in condition of 90 ℃. Besides, the initial and final setting time of cement paste is correspondent with the time of duration of dormant stage and the time of UPV value is 1500 m/s (T1500), respectively. Thus, the UMA can be used to determine the initial and final setting time of cementitious material under different curing temperatures. The compressive test results indicate that the paste with 20% fly ash presents higher compressive strength than the plain paste at curing temperatures of 90 ℃. Therefore, appropriate amount of fly ash is beneficial for concrete in the high temperature curing conditions.展开更多
This paper investigates online scheduling problems with processing set restrictions.There is a sequence of jobs that are revealed one by one over list,where each job has unit processing time.A job can only be processe...This paper investigates online scheduling problems with processing set restrictions.There is a sequence of jobs that are revealed one by one over list,where each job has unit processing time.A job can only be processed by a subset of the machines,namely the processing set of the job.The objective is to minimize the makespan.For m machines with two different processing sets,we propose an optimal algorithm with a competitive ratio of 3/2.For three machines with inclusive processing sets,an optimal algorithm with competitive ratio 5/3 is provided.展开更多
Alkene cross-coupling provides a simple and efficient approach for constructing C-C bonds using readily accessible alkene feedstocks.Despite significant progress in C-C bonds formation through the difunctionalization ...Alkene cross-coupling provides a simple and efficient approach for constructing C-C bonds using readily accessible alkene feedstocks.Despite significant progress in C-C bonds formation through the difunctionalization of alkenes,analogous reaction involving two distinct alkenes remains extremely limited.Herein,we report the excited-state palladium(0)catalyzed alkenylcarboxylation of two distinct alkenes with CO_(2),delivering a variety of carboxylic acids in moderate to excellent yields.This reaction features high regio-&chemoselectivity,broad substrate scope(>70 examples),and facile derivatization of products.Mechanistic studies indicate that the key step for this new strategy lies in the reductive activation of electron-defficient alkenes with the excited-state palladium complex to generate alkene radical anions.The current single-electron reduction strategy for alkenes catalyzed by photoexcited palladium(0)not only broadens the scope of excited palladium chemistry but also provides a mild approach for alkenes activation.Furthermore,this method serves as an efficient tool for the rapid construction of multiple C-C bonds in a one-pot operation using two distinct alkenes.展开更多
基金Funded by the National Natural Science Foundation of China (Nos.51678309,51978339)973 Program (No.2015CB655102)+4 种基金Natural Science Foundation of Jiangsu Province of China (No.BK20161529)China Postdoctoral Science Foundation (No.2016M600351)Jiangsu Province Postdoctoral Science Foundation (No.1601028B)State Key Laboratory of Silicate Materials for Architectures (Wuhan University of Technology)Priority Academic Program Development Jiangsu Higher Education Institutions (PDPA)
文摘A specially developed ultrasonic measurement apparatus (UMA) was used to in situ monitor the setting process of fly ash blended cement paste. Combined with the results of Vicat Needle tests, isothermal calorimetric measurement, XRD analysis, SEM morphology and compressive test, the influence of curing temperature (20, 40, 60, and 90 ℃) and fly ash content (0,10%, 20% and 30%) on the setting and hydration process of fly ash blended cement paste was analyzed. The results show that setting and hardening process of fly ash blended cement paste at elevated temperature can be clearly identified into three stages including dormant stage, acceleration stage and deceleration stage. The increasing of curing temperature greatly accelerates the setting and hardening process. However, the content of fly ash does not have significant effect on the setting in condition of 90 ℃. Besides, the initial and final setting time of cement paste is correspondent with the time of duration of dormant stage and the time of UPV value is 1500 m/s (T1500), respectively. Thus, the UMA can be used to determine the initial and final setting time of cementitious material under different curing temperatures. The compressive test results indicate that the paste with 20% fly ash presents higher compressive strength than the plain paste at curing temperatures of 90 ℃. Therefore, appropriate amount of fly ash is beneficial for concrete in the high temperature curing conditions.
基金Guang-Ting Chen was supported by the National Natural Science Foundation of China(No.11571252)Long-Cheng Liu was supported by the China Scholarship Council Grants(No.201706315073)+4 种基金the Fundamental Research Funds for the Central Universities(No.20720190068)Yi-Wei Jiang was supported by the National Natural Science Foundation of China(No.11571013)Zhi-Yi Tan was supported by the National Natural Science Foundation of China(Nos.11471286,11671356)the Natural Science Foundation of Zhejiang Province(No.LR12A01001)An Zhang was supported by the National Natural Science Foundation of China(No.11771114).
文摘This paper investigates online scheduling problems with processing set restrictions.There is a sequence of jobs that are revealed one by one over list,where each job has unit processing time.A job can only be processed by a subset of the machines,namely the processing set of the job.The objective is to minimize the makespan.For m machines with two different processing sets,we propose an optimal algorithm with a competitive ratio of 3/2.For three machines with inclusive processing sets,an optimal algorithm with competitive ratio 5/3 is provided.
基金the financial support from the Fundamental Research Funds for the Central Universities(No.PA2020GDKC0021)the National Natural Science Foundation of China(No.21971051)the Hefei University Talent Research Fund(No.24RC31)。
文摘Alkene cross-coupling provides a simple and efficient approach for constructing C-C bonds using readily accessible alkene feedstocks.Despite significant progress in C-C bonds formation through the difunctionalization of alkenes,analogous reaction involving two distinct alkenes remains extremely limited.Herein,we report the excited-state palladium(0)catalyzed alkenylcarboxylation of two distinct alkenes with CO_(2),delivering a variety of carboxylic acids in moderate to excellent yields.This reaction features high regio-&chemoselectivity,broad substrate scope(>70 examples),and facile derivatization of products.Mechanistic studies indicate that the key step for this new strategy lies in the reductive activation of electron-defficient alkenes with the excited-state palladium complex to generate alkene radical anions.The current single-electron reduction strategy for alkenes catalyzed by photoexcited palladium(0)not only broadens the scope of excited palladium chemistry but also provides a mild approach for alkenes activation.Furthermore,this method serves as an efficient tool for the rapid construction of multiple C-C bonds in a one-pot operation using two distinct alkenes.
