Influence of the Fluctuation on the Property of the Interface in Molecular Dynamics Simulation

The paper advances a new calculation method improved by using(2~5)/1.2rm rule which concerns the influence of the fluctuation of molecules on the results of molecular dynamics simulation of the interface.The densities of saturated vapor and liquid of homogeneous phase and the surface tension of inhomogeneous phase of CH4 are obtained by applying this new calculation method.Compared with the traditional molecular dynamics simulation,this method has less error in calculating the surface tension of inhomogeneous phase and takes less calculating time.     

Molecular Dynamics Simulation of Ni Cluster Depositing on Cu Surface in Cold Spray

Cold gas spray is a relatively new coating technique by which coatings can be formed without significant heating of the sprayed powder.In contrast to the conventional thermal spray processes,such as flame,arc,and plasma spraying,in cold spraying there is no melting of particles prior to impact on the substrate.In cold spray,particles are accelerated to a very high velocity by a flowing gas with supersonic speed and the temperature of spray particles is much lower than its melting point.However,being accomplished in so short an interval,the impact and deposition processes are difficult to be observed by experimental ways.Using molecular dynamics simulation,the deposition of nano-scale Ni clusters on Cu(001) surface was studied.The many-body potential is used to simulate the interatomic force between the atoms.By taking "snapshot",the impact,deposition process and the final appearances of the cluster and the substrate were observed directly.It is found that both the substrate and the cluster deform and lose the crystalline structure.But after reconstruction and relaxation,both of them recover the crystalline structure.In addition,the influence factors on deposition,such as incident velocity and the size of the cluster,are discussedr.Simulation results show that the higher incident velocity or the larger size of the cluster could result in stronger interaction between the substrate and the cluster owing to the higher kinetic energy of the cluster.     

Experimental Study for the Movement of Liquid Droplets on the Surface with Gradient Surface Energy

By using the chemical vapor deposition (CVD), a surface with gradient surface energy is fabricated based on the treated silicon chip. The dodecyltrichlorosilane (C_(12)H_(25)Cl_3Si) and Octrytrichlorosilane (C_(8)H_(17)Cl_3Si) are used as the source of silanization. By using the measurement of sessile drop method, the surface with gradient surface energy was characterized by measuring the contact angle of small water which lied on the surface of the treated silicon chip. The experiment shows the liquid droplets are driven to move from hydrophobic to hydrophilic zone on the gradient surface which is placed horizontally, the diameter of the droplets are 1~3 mm, and the single droplet reached the maximum velocity of up to 0.9 m/s. Based on the experimental results, the mechanical of the movement of the liquid droplet on the gradient surface is researched.     

Numerical Simulation of the Solidification Process Under the Effect of Nature Convection

The process of solidification is numerically simulated with control volume method. The authors study the nature convection in the liquid phase and flow pattern of nature convection during the process of solidification. The result of simulation shows that there are the global flow cells inside the liquid phase, and the local circumfluence exists in the global cells. Especially, the authors analyze transformation of the interface between phases under the effect of free convection on the process of solidification.     

Effect of Dynamic Viscosity on Marangoni Convection in Liquid Bridge With Liquid Encapsulation

The authors establish the physical and mathomatical model of the Marangoni convection in liquid bridge with liquid encapsulation (or two immiscible coaxial liquid columns). A Numerical simulation of the Marangoni convection in liquid bridge with liquid encapsulation is performed by employed vorticity-streamfunction method and the Alternative Direction Implicit scheme in finite difference. The distribution of temperature and flow in two liquid columns is then obtained. The influence law of the dynamic viscosity ratio of the inner liquid to the outer liquid to the Marangoni convection in liquid bridge with liquid encapsulation is obtained.     

不同温湿度下乙烯在纤维素中扩散行为的分子模拟

乙烯是影响果蔬采后保鲜的重要因素之一,果蔬企业一般通过设置保鲜环境和使用包装来缓解乙烯的影响.利用分子模拟技术,模拟计算不同温度(273、283、293、303、313 K)和不同空气相对湿度(20％、60％、100％)条件对乙烯在纤维素中扩散行为的影响,通过均方位移(Mean Square Dis-placement,MSD)数据计算出扩散系数.结果表明,温度和相对湿度对乙烯在纤维素内的扩散系数的影响显著(P<0.05).在273～313 K的温度范围内,乙烯在纤维素中扩散系数随着温度的升高而增大;在20％～100％的空气相对湿度范围内,随着湿度的增加而增大.     

AFLP标记技术在甘薯育种中的应用进展

近年来,AFLP分子标记技术已经逐步应用于甘薯的遗传育种研究中。本文简要概述了AFLP技术在甘薯的起源、进化与亲缘关系研究、遗传多样性分析、连锁图谱构建及基因定位和分子标记辅助育种等的应用进展,并对其发展前景进行了展望。     

河南省2018年1月3—4日暴雪天气的诊断分析与数值模拟

为进一步探讨河南省暴雪天气过程的成因和机理,分析WRF模式对暴雪过程的模拟效果,提高预报准确率,笔者利用NCEP 1°×1°再分析资料和常规观测资料,对2018年1月3—4日河南省大范围的暴雪天气过程进行诊断分析,并对WRF模式模拟结果进行分析。结果表明,高空槽、低层的切变和急流、地面冷空气是这次暴雪的主要影响系统。水汽条件好,水汽通量低层辐合,高层辐散,伴有较强的上升运动,更有利于暴雪天气的发生。WRF模式模拟的降雪量范围和强度都与实况较为一致,表明模式对暴雪天气的预报有一定的参考价值。     

Effect of Different Levels of Wheat Straw Soil Surface Coverage on Weed Flora in Vicia faba Crops

The crop system implemented on organic farms requires that crop residues are incorporated into the soil following the end of wheat cultivation. This system leads to a reduction in soil moisture and the creation of favourable conditions for the emergence of weeds. In contrast, covering the soil with 60 % crop residues was found to maintain soil moisture and lead to a reduction in dry weed mass, population density and population frequency as well as a reduction in population diversity, regardless of the initial weed flora before the implementation of different soil tillage systems. Finally, an increase in the prevalence of broad‐leafed weeds was observed as the level of soil cover increased.     

基于响应面设计的小白菜氮磷钾肥料效应研究

进行小白菜田间施肥试验,采用响应面分析法,通过3因素3水平响应面优化试验,研究施氮量(N)、施磷量(P2O5)和施钾量(K2O)对小白菜产量的影响,建立小白菜产量的二次回归方程,分析小白菜最佳施肥条件。响应面分析表明,回归模型显著,施磷量对产量有极显著影响,施氮量、施钾量的影响不显著,施磷量与施氮量、施钾量之间的交互作用较强,施氮量与施钾量之间交互效应较弱;各因素对产量的影响顺序为施磷量>施氮量>施钾量。经过统计分析,最佳施肥组合为施氮量100.70 kg/hm²、施磷量98.7 kg/hm²、施钾量123.2 kg/hm²,通过模型推算在此条件下小白菜产量为37.899 t/hm²。研究结果可为高产优质小白菜生产提供技术支持。     

生态条件对籼粳稻杂交F2代亚种特性分化与经济性状的影响

以籼粳稻杂交F2代群体(七山占/秋光)为供试材料,2010年分别在广东省与辽宁省同年种植,研究籼粳亚种属性和经济性状的分化规律以及两者之间的相互关系.结果表明,广东和辽宁2个生态地区群体,亚种特性呈相似正态分布,未出现偏分现象,说明在F2群体中遗传重组对群体的作用呈主导性.经济性状发生较显著的分化,穗数、千粒重、1次枝梗数及粒数辽宁地区显著高于广东,而产量、穗粒数及结实率呈现相应生态条件的偏向性,籼型及偏籼型在广东地区较高,粳型及偏粳型在辽宁地区较高,说明在籼粳交F2代中不同的籼粳类型存在较为显著的生态适应性,并且该结果在相关性分析也得了验证.此外,对进一步研究籼粳分化机制的相关问题进行了讨论.     

Simulation of growth and development processes of spring wheat in response to CO2 and ozone for different sites and years in Europe using mechanistic crop simulation models

The response of crop growth and yield to CO₂ and ozone is known to depend on climatic conditions and is difficult to quantify due to the complexity of the processes involved. Two modified mechanistic crop simulation models (AFRCWHEAT2-O3 and LINTULCC), which differ in the levels of mechanistic detail, were used to simulate the effects of CO₂ (ambient, ambient ×2) and ozone (ambient, ambient ×1.5) on growth and developmental processes of spring wheat in response to climatic conditions. Simulations were analysed using data from the ESPACE-wheat project in which spring wheat cv. Minaret was grown in open-top chambers at nine sites throughout Europe and for up to 3 years at each site.

Both models closely predicted phenological development and the average measured biomass at maturity. However, intermediate growth variables such as biomass and leaf area index (LAI) at anthesis, seasonal accumulated photosynthetically active radiation intercepted by the crop (ΣIPAR), the average seasonal light use efficiency (LUE) and the light saturated rate of flag leaf photosynthesis (A_sat) were predicted differently and less accurately by the two models. The effect of CO₂ on the final biomass was underestimated by AFRCWHEAT2-O3 due to its poor simulation of the effect of CO₂ on tillering, and LAI.LINTULCC overestimated the response of biomass production to changes in CO₂ level due to an overprediction of the effect of CO₂ on LUE. The measured effect of ozone exposure on final biomass was predicted closely by the two models. The models also simulated the observed interactive effect of CO₂ and ozone on biomass production. However, the effects of ozone on LAI, ΣIPAR and A_sat were simulated differently by the models and less accurately with LINTULCC for the ozone effects on LAI and ΣIPAR. Predictions of the variation between sites and years of growth and development parameters and of their responses to CO₂ and ozone were poor for both AFRCWHEAT2-O3 and LINTULCC. It was concluded that other factors than those considered in the models such as chamber design and soil properties may have affected the growth and development of cv. Minaret. An analysis of the relationships between growth parameters calculated from the simulations supported this conclusion. In order to apply models for global change impact assessment studies, the difficulties in simulating biomass production in response to CO₂ need to be considered. We suggest that the simulation of leaf area dynamics deserves particular attention in this regard.