A new approach is presented for deriving the residence time distribution(RTD)in open-type reactors with exclusion of residence in the fore section.Inasmuch as failure to predict the con-version of chemical reactions h...A new approach is presented for deriving the residence time distribution(RTD)in open-type reactors with exclusion of residence in the fore section.Inasmuch as failure to predict the con-version of chemical reactions has been evidenced in many occasions,numerical solution of tracerdispersion in the presence of background concentration gradient of reactant is given to demonstratethe strong effect of background reactant on the true RTD a reactant molecule experiences.Withinthe error of computation,the conversion of a first-order chemical reaction under steady state is shownto be equal in both closed and open reactors,despite difference in relevant展开更多
The paradox is well known that the residence time distribution(RTD)is not valid forthe estimation of the conversion of a first order reaction in an open tubular reactor.A casc ofδ injection of reactive species into a...The paradox is well known that the residence time distribution(RTD)is not valid forthe estimation of the conversion of a first order reaction in an open tubular reactor.A casc ofδ injection of reactive species into an open flow system is investigated theoretically in this paper.The analytical solution with the Laplace transform demonstrated that the conversion of a first orderreaction is identical to that in a closed reactor under steady state.The effect of the backgroundreactant concentration gradient addressed by the authors in a previous paper was employed to thiscase.and the numerical solution of the tracer dispersion based on this novel argument gave rise to asimilar value of conversion.suggesting the validity of the concept and the significance of the subtledifference between RTDs determined with or without the presence of a background reactant in anopen flow system.展开更多
The living circumstances of human beings are closely related to the geological environment. As exemplified by the Zhangjiakou-West Beijing region, this paper describes the intensive mantle-crust uplift, which led to a...The living circumstances of human beings are closely related to the geological environment. As exemplified by the Zhangjiakou-West Beijing region, this paper describes the intensive mantle-crust uplift, which led to anomalous element background values for regional rocks (ores) and soils. As a result, some agricultural crops, and forests and fruits are of “super-quality and high yield” or of “poor quality and low yield”. The anomalous elements can find their way into grains, fruits, vegetables and drinking water and then will be taken by human beings, constituting a food chain, which would directly impact human health and lead to the spread of some endemic diseases. Studies have shown that the geomorphological features in the Zhangjiakou-West Beijing region are the outcome of geotectonic evolution since the Mesozoic. Mantle-crust movement is the key factor leading to the evolution and change of the regionally geological environment.展开更多
This paper analyses and summarizes the natural radionuclide contents of soil and building materials, radon concentrations and the penetrating radiation levels in Hong Kong. From these, a thorough and objective assessm...This paper analyses and summarizes the natural radionuclide contents of soil and building materials, radon concentrations and the penetrating radiation levels in Hong Kong. From these, a thorough and objective assessment for the terrestrial background irradiation level of Hong Kong was made. Finally, the annual effective dose equivalent received by Hong Kong people due to the natural background irradiation was calculated to be 3.2 mSv.展开更多
文摘A new approach is presented for deriving the residence time distribution(RTD)in open-type reactors with exclusion of residence in the fore section.Inasmuch as failure to predict the con-version of chemical reactions has been evidenced in many occasions,numerical solution of tracerdispersion in the presence of background concentration gradient of reactant is given to demonstratethe strong effect of background reactant on the true RTD a reactant molecule experiences.Withinthe error of computation,the conversion of a first-order chemical reaction under steady state is shownto be equal in both closed and open reactors,despite difference in relevant
文摘The paradox is well known that the residence time distribution(RTD)is not valid forthe estimation of the conversion of a first order reaction in an open tubular reactor.A casc ofδ injection of reactive species into an open flow system is investigated theoretically in this paper.The analytical solution with the Laplace transform demonstrated that the conversion of a first orderreaction is identical to that in a closed reactor under steady state.The effect of the backgroundreactant concentration gradient addressed by the authors in a previous paper was employed to thiscase.and the numerical solution of the tracer dispersion based on this novel argument gave rise to asimilar value of conversion.suggesting the validity of the concept and the significance of the subtledifference between RTDs determined with or without the presence of a background reactant in anopen flow system.
文摘The living circumstances of human beings are closely related to the geological environment. As exemplified by the Zhangjiakou-West Beijing region, this paper describes the intensive mantle-crust uplift, which led to anomalous element background values for regional rocks (ores) and soils. As a result, some agricultural crops, and forests and fruits are of “super-quality and high yield” or of “poor quality and low yield”. The anomalous elements can find their way into grains, fruits, vegetables and drinking water and then will be taken by human beings, constituting a food chain, which would directly impact human health and lead to the spread of some endemic diseases. Studies have shown that the geomorphological features in the Zhangjiakou-West Beijing region are the outcome of geotectonic evolution since the Mesozoic. Mantle-crust movement is the key factor leading to the evolution and change of the regionally geological environment.
文摘This paper analyses and summarizes the natural radionuclide contents of soil and building materials, radon concentrations and the penetrating radiation levels in Hong Kong. From these, a thorough and objective assessment for the terrestrial background irradiation level of Hong Kong was made. Finally, the annual effective dose equivalent received by Hong Kong people due to the natural background irradiation was calculated to be 3.2 mSv.
