景天三七水培营养液配方研究

为了研究景天三七水培营养液配方,并探讨(氮与钾)N,K元素对景天三七(Sedum.k.F)次生代谢产物积累的影响,以景天三七幼苗为试验材料,采用3种不同水培营养液配方培养景天三七,以Hoagland营养液(霍格兰配方)为对照,30 d后进行生长形态及黄酮含量的测定。结果表明:在配方B水培条件下,景天三七的茎粗较粗,根长最长、地上地下部分的鲜重最重,地上部干重最重,地下部干重较重,黄酮类物质含量也较高,该配方是最适合景天三七水培生长的营养液配方;且提高水培营养液中N、K元素的浓度对景天三七中的黄酮类物质的产生有促进作用。

Effects of porosity heterogeneity on chemical dissolution-front instability in fluid-saturated rocks

Homogeneity and heterogeneity are two totally different concepts in nature.At the particle length scale,rocks exhibit strong heterogeneity in their constituents and porosities.When the heterogeneity of porosity obeys the random uniform distribution,both the mean value and the variance of porosities in the heterogeneous porosity field can be used to reflect the overall heterogeneous characteristics of the porosity field.The main purpose of this work is to investigate the effects of porosity heterogeneity on chemical dissolution front instability in fluid-saturated rocks by the computational simulation method.The related computational simulation results have demonstrated that:1) since the propagation speed of a chemical dissolution front is inversely proportional to the difference between the final porosity and the mean value of porosities in the initial porosity field,an increase in the extent of the porosity heterogeneity can cause an increase in the mean value of porosities in the initial porosity field and an increase in the propagation speed of the chemical dissolution front.2) An increase in the variance of porosities in the initial porosity field can cause an increase in the instability probability of the chemical dissolution front in the fluid-saturated rock.3) The greater the mean value of porosities in the initial porosity field,the quicker the irregular morphology of the chemical dissolution front changes in the supercritical chemical dissolution systems.This means that the irregular morphology of a chemical dissolution front grows quicker in a porosity field of heterogeneity than it does in that of homogeneity when the chemical dissolution system is at a supercritical stage.

Effects of different numerical algorithms on simulation of chemical dissolution-front instability in fluid-saturated porous rocks

Many scientific and engineering problems need to use numerical methods and algorithms to obtain computational simulation results because analytical solutions are seldom available for them.The chemical dissolution-front instability problem in fluid-saturated porous rocks is no exception.Since this kind of instability problem has both the conventional(i.e.trivial)and the unconventional(i.e.nontrivial)solutions,it is necessary to examine the effects of different numerical algorithms,which are used to solve chemical dissolution-front instability problems in fluid-saturated porous rocks.Toward this goal,two different numerical algorithms associated with the commonly-used finite element method are considered in this paper.In the first numerical algorithm,the porosity,pore-fluid pressure and acid/solute concentration are selected as basic variables,while in the second numerical algorithm,the porosity,velocity of pore-fluid flow and acid/solute concentration are selected as basic variables.The particular attention is paid to the effects of these two numerical algorithms on the computational simulation results of unstable chemical dissolution-front propagation in fluid-saturated porous rocks.The related computational simulation results have demonstrated that:1)the first numerical algorithm associated with the porosity-pressure-concentration approach can realistically simulate the evolution processes of unstable chemical dissolution-front propagation in chemical dissolution systems.2)The second numerical algorithm associated with the porosity-velocity-concentration approach fails to simulate the evolution processes of unstable chemical dissolution-front propagation.3)The extra differential operation is the main source to result in the failure of the second numerical algorithm.

Finite element modeling of convective pore-fluid flow in fluid-saturated porous rocks within upper crust:An overview

Convective pore-fluid flow (CPFF) plays a critical role in generating mineral deposits and oil reservoirs within the deep Earth. Therefore, theoretical understanding and numerical modeling of the thermodynamic process that triggers and controls the CPFF are extremely important for the exploration of new mineral deposits and underground oil resources. From the viewpoint of science, the CPFF within the upper crust can be treated as a kind of thermodynamic instability problem of pore-fluid in fluid-saturated porous media. The key issue of dealing with this kind of problem is to assess whether a nonlinear thermodynamic system under consideration is supercritical. To overcome limitations of using theoretical analysis and experimental methods in dealing with the CPFF problems within the upper crust, finite element modeling has been broadly employed for solving this kind of problem over the past two decades. The main purpose of this paper is to overview recent developments and applications of finite element modeling associated with solving the CPFF problems in large length-scale geological systems of complicated geometries and complex material distributions. In particular, two kinds of commonly-used finite element modeling approaches, namely the steady-state and transient-state approaches, and their advantages/disadvantages are thoroughly presented and discussed.

气囊分离装置工作性能的影响规律仿真研究

气囊分离装置具有承载、分离和提供推力的功能,并且工作过程无污染,广泛用于运载火箭整流罩纵向分离。研究气囊分离装置工作性能的影响规律,对气囊分离装置的设计和应用具有重要指导意义。建立了非线性有限元模型,采用LS-DYNA对其工作过程进行仿真分析,研究炸药索装药量、铆钉失效应变、气囊初始缺陷等因素的影响规律。结果表明,炸药索装药量是影响气囊分离装置工作性能的主要因素,装药量越高,推冲速度越快,但可能造成局部结构破坏;铆钉失效应变的增加会延长气囊分离装置的分离时间;位于顶部的气囊缺陷对分离过程影响比较大。