A NUMERICAL STUDY ON NATURAL CONVECTION IN A CLOSED CAVITY PARTIALLY FILLED WITH POROUS MEDIUM

The present paper decribes numerical analytical results of natural convection in a closed cavity partially filled with porous medium by means of Forchheimer-Brinkman model. The effects of heated rate,permeability,height of porous region,heat conduction coefficients and aspect ratio on flow and heat transfar in the cavity are systematically investigated. Velocity and temperature fields in the cavity are given and dependence of average Nu on time is obtained.     

Analysis on the stability of traffic flow with the information of two preceding cars

The stability analysis is one of the important problems in the traffic flow theory, where the congestion phenomena can be regarded as the instability and the phase transition of a dynamical system. An extended optimal velocity model is deduced by considering the effect of the information of two leader cars. The stability condition of the extended model is obtained by using the linear stability theory. The modified Korteweg-de Vries (mKdV) equation is derived to describe the traffic behavior near the critical point by applying the nonlinear analysis. The numerical simulation results demonstrate the analytical results and show that the traffic congests are suppressed more efficiently by considering two vehicles ahead. Therefore, the next-nearest-neighbor car has strong effects on traffic dynamics and plays an important role on stabilizing the traffic flow.     

‘杂选1号’苜蓿新品系抗旱性比较研究

为阐明‘杂选1号’苜蓿新品系的抗旱性,研究测定不同苜蓿品种的叶夹角、叶绿素相对含量（SPAD值）、细胞膜相对透性、过氧化物酶(POD)、过氧化氢酶(CAT)、脯氨酸含量及水分饱和亏(WSD)。采用聚类分析方法对不同苜蓿品种的抗旱性进行分析。研究结果表明,抗旱性从强到弱的顺序为：‘杂选1号’＞‘巨人’＞‘陇中’＞‘中兰1号’＞‘杜普梯’＞‘图牧’＞‘埃及’。     

一维稳态流非饱和土渗透系数垂直分布模型及其线性简化

渗透系数是控制地下水流动的重要参数,对渗透系数的空间分布规律进行研究具有重要的意义。基于Gardner模型获取了一维稳态流非饱和土渗透系数沿垂直分布模型,该模型用指数函数描述,受饱和渗透系数和无量纲的深度与流动率等因素的控制;该模型表明一维稳态流条件下均质典型土类的渗透系数其沿垂直方向变化趋势主要受比流量与饱和渗流系数的负数值二者之间的相对大小影响。分别采用泰勒级数方法和以地下水位处及地表处的渗透系数作为控制条件方法对一维稳态流非饱和土渗透系数沿垂直分布模型进行线性近似简化。采用泰勒级数方法获取的简化模型其计算误差随无量纲的深度增大而增大。简化后的模型具有形式简单、参数少等特点。通过算例对比简化模型与原模型的差异,计算结果表明:采用以地下水位处及地表处的渗透系数作为控制条件的方法进行线性近似简化的模型计算误差比采用泰勒级数方法获得的线性近似简化模型的计算误差小。     

Experimental Study of Flow and Heat Transfer in Heat Exchanger with Small Channels

The experimental study of the flow resistance and heat transfer characteristics are conducted for water and ethylene glycol solution (66% Wt) flowing in the heat exchanger with small rectangular microchannels . The heat exchanger having the channels of 0.4 mm in width, 2.0 mm in height, and 20 mm in length is heated by a hearing rod at the bottom surface, the upper and two side surfaces are adiabatic. During experiments, the Reynolds number are ranged from 2 to 2 500. The experimental results show that the flow friction factor decreases and Nusselt number increases with increasing Reynolds number for water and ethylene glycol solution. At a fixed Reynolds number, the Nusselt number for ethylene glycol solution with larger Prandtl number is greater than that for water. Meanwhile, the correlations of flow resistance and heat transfer in the heat exchanger with small channels are obtained for engineering application.     

Transpiration Dynamics in Cadmium-Treated Soybean (Glycine max L.) Plants

Soybean ( Glycine max L.) plants, cv Richland, were grown during 30 days in a nutrient solution. After this period the plants were treated with a 50 μM Cd(NO₃)₂ solution. Sap flow rate and stomatal conductance were monitored during 4 consecutive days; at the end of this period relative water content and stomatal width and length were determined on fully expanded leaves. On the second day from the Cd treatment sap, flow rate and stomatal conductance in the treated plants were reduced to 60% of the control plants. Stomatal conductance kept on decreasing up to the fourth day. Cadmium decreased the leaf relative water content and the reduction in the stomatal closure was supported by an increase in the L/W ratio of the stomata. Root water uptake should be the primary mechanism reduced by Cd stress in soybean, and this reduction is consistent with the decrease in transpiration rate and with the stomatal closure.     

水分供应和氮素形态对水稻一些水分生理特征的影响

为探明不同水分供应和氮素形态对水稻一些水分生理特征的影响,设正常水分及50 g L^-1 PEG模拟水分胁迫及3种不同NH₄⁺-N/NO₃^--N比例（75/25,50/50,25/75）的处理,测定了水稻叶片的NO₃^-、Ca²⁺和Mg²⁺含量,叶片浸出液电导率,叶片相对含水量,叶片水分临界饱和亏以及叶片水势。结果表明,在NH₄⁺-N/NO₃^--N比例较低时,模拟水分胁迫使广陵香粳水稻幼苗吸收更多的NO₃^--N。模拟水分胁迫条件下,水稻幼苗叶片浸出液电导率随NH₄⁺-N/NO₃^--N比例的降低呈下降趋势,且在NH₄⁺-N/NO₃^--N比例为25/75时,叶片浸出液电导率低于正常水分培养条件下的叶片浸出液电导率。而在正常水分培养条件下,水稻幼苗叶片浸出液电导率随NH₄⁺-N/NO₃^--N比例的降低呈上升趋势。水分胁迫使高NH₄⁺-N/NO₃^--N处理水稻叶片相对含水量降低、水分临界饱和亏上升,但对低NH₄⁺-N/NO₃^--N处理（25/75）水稻叶片相对含水量和水分临界饱和亏影响很小。同样,低NH₄⁺-N/NO₃^--N处理削弱了水分胁迫对水稻叶片水势的降低。总体上说,低NH₄⁺-N/NO₃^--N能减轻水分胁迫对水稻水分生理的不良影响。     

Analytical Solution for One Dimensional Contaminant DiffusionThrough Unsaturated Soils Beneath Landfills

A one-dimensional diffusion model was developed to investigate contaminant distributions in unsaturated soils beneath a landfill. On the basis of the assumption that the volume water content is a linear function of depth, the analytical solution of the model was obtained by using the method of separation of variables combined with generalized orthogonal theory. The results obtained by the proposed analytical solution agree well with those obtained by the finite element software COMSOL Multiphysics 4.2. The proposed analytical solution can be degraded to the steady-state solution. When the maximum volume water content of 0.6 and minimum volume water content of 0.3 is assumed for an unsaturated soil, the 100-year contaminant flux at the bottom of unsaturated soil was 91 g/ha/a, which is 1.4 times greater than that of the case assuming porosity of 0.3 for the saturated and 0.7 times less than that with a saturated volume water content of 0.6. When the sum of the top and bottom volume water content of the unsaturated soil remains constant, the relative concentration at the bottom of the soil will decrease with increase of the volume water content at the top of the soil. The bottom contaminant flux was not greatly affected by the variation of the distribution of volume water content when the sum of the top and bottom volume water content remains constant. The proposed analytical solution is relatively simple, and can be used for verification of complicated numerical models, experimental data fitting, and preliminary design of landfill liner systems.     

一种利用流式细胞术鉴定梨倍性的方法

流式细胞术鉴定植物染色体倍性的方法广泛应用于果树多倍体育种中,然而相关流式细胞术鉴定梨染色体倍性的方法还没有系统的研究。以梨树叶片为试材系统优化了各个流式细胞术关键实验节点,结果表明：实验材料选取当年春季新梢第3~5 片梨树嫩叶,尤其是大棚新梢嫩叶最好;叶片前处理时用蒸馏水、去离子水依次洗净叶片表面后,再用去离子水浸泡10 min;使用WPB解离液对梨叶片细胞核进行提取后,用500 目滤膜过滤2 次,离心1 次后用流式细胞仪进行检测可得到理想的实验结果。该方法步骤简单、结果可靠,是一种快速、高效的梨染色体倍性鉴定的方法,可广泛用于梨树多倍体鉴定。     

Modeling and Performance Analysis of Unglazed Solar Collector/Regenerator

An analytical model of the unglazed solar collector/regenerator(C/R) was presented. There was an optimum flow rate per unit collector area at normal temperature which led to the maximum evaporation rate. The inlet temperature of absorbent solution and the wind velocity are key parameters to determine the optimum flow rate, in addition, the concentration of solution and solar radiation intensity have obvious effects on the maximum evaporation rate. When the outlet temperature of solution is higher than the inlet temperature, there is not an optimum flow rate, which reflects that the more the flow rate of solution is, the better regeneration efficiency is. With the 2m/s of wind speed, the evaporation rate reaches the peak. In this paper, kinds of factors influencing the performance of solar C/R were evaluated as well.     

干旱胁迫下玉米根系活力和膜透性的变化

研究了干旱胁迫下盆栽玉米叶片含水量，根系活力和质膜透透性的变化，结果表明：干旱胁迫下，玉米叶片相对含水量下降，叶片及根系质膜透性上升，根系活力下降，并且，下部幼根的质膜透性比上部老根上升快，同时其活力下降也快于上部老根。     

Near Crack Line Elastoplastic Solution for an Eccentric Cracks Loaded by the Pore Water Pressure

By using near crack line analysis method and Mohr-Coulomb strength criterion,the elastic-plastic solution for near crack line of an eccentric cracks loaded by the pore water pressure under large scale yielding condition is analyzed.The elastic stress fields,the plastic stress field,the unit normal vector of the elastic-plastic boundary near the crack line,the elastic-plastic stress fields near crack line are identified.The change pattern of the length of the plastic zone and the pore water pressure is presented.Besides,the elastic-plastic analytical solution for an eccentric cracks loaded by the pore water pressure is obtained.     

番茄营养液深液流无限生长型栽培营养液的管理与调控

根据北京地区的水质特点和非常规栽培的特殊性,制定了在营养液深液流无限生长型栽培条件下使用的营养液配方。并根据番茄生长发育的不同时期和养分吸收特性,及时调整营养液的组成成分、浓度、酸碱度等,对营养液实行动态管理。栽培试验结果表明,该配方中的各种营养成分（N、P、K、Ca、Mg等）基本可以被番茄均衡地吸收,属于营养均衡的配方。     

Meta-analyses of oil yield in Cuphea PSR23

Oil content and composition of Cuphea seed are of special economic value as raw materials for industrial and food applications. The inherent unpredictability in determining and predicting Cuphea’s oil yield is attributed, in part, to the indeterminate growth habit and the persistence of the domestication syndrome of this semi-domesticated potential oilseed crop. Meta-analysis using multivariate statistical modeling, computer simulations, and custom profiling was carried out on a database collated from several studies carried out in growth chamber, greenhouse and field experiments. Meta-analyses identified the importance of, and quantified direct and indirect relationships and tradeoffs between and within functional traits classified within five interrelated plant modules. Several multivariate statistical analyses procedures were employed in predicting oil content and oil yield, as performance measures of Cuphea at the plant and population levels of integration. The most parsimonious partial least squares regression model identified plant-, capsule-, and seed-based traits that can be used in reconstructing the best configuration needed for high agronomic performance at the individual plant and population levels. Variance-based structural equation modeling suggested that the variation in relative growth rate was strongly linked to differences in specific leaf area and leaf mass ratio; both traits expressed large positive direct and indirect effects on oil yield, but not oil content. Results of custom profiling suggested that seed yield, oil% and oil yield can be optimized by trait adjustments within the phenotypic and metabolic modules. Adjustments to thousand-seed weight and protein content would influence seed yield, oil yield and oil%, in a decreasing order. Improvements in eco-physiological traits, nutrient ratios and structural traits would lead to a slightly higher oil% and eventually higher oil yield.     

Numerical Analysis of Viscous Fluid Flow past a Circular Cylinder near a Plane with Boundary Element Method

The boundary element method was used for incompressible viscous fluid flow past a circular cylinder near a plane. The various phases of the flow passing the cylinder are studied numerically with different g/d. The numerical simulation of velocity fields is in good agreement with Davis' theoretical results and Taneda's experiments. In particular, the distributive curves of the surface force and the pressure on the circular cylinder were calculated numerically.     

A calculation method for coalbed permeability by using drainage data

In order to more accurately calculate the changes in the permeability of coalbed during production process, a calculation method for coalbed permeability based on production data is established by combining with material balance equations and production equations, and it gives the fact that the output data can be a good reflection of the inner permeability of coalbed. The average pressure of coalbed in production process can be calculated through material balance equation. Dimensionless water production index is introduced into the production equation in the stage only with water production. In the next stage with both gas and water, gas and water production ratio is introduced to eliminate the influence of flush-flow radius, skin factor as well as other uncertain factors on the calculation of CBM permeability. The relationship between permeability and surface cumulative liquid production can be described as a single-variable cubic equation by derivation. There is a trend that the permeability declines firstly and then increases after wells in Qinshui CBM field are calculated. The results show that reservoir permeability increase after drainage stage, but the growth rate decrease gradually. The regression result of the permeability ratio and surface cumulative fluid production agrees with the theoretical mathematic relationship.     

Dynamics of oil and tocopherol accumulation in sunflower grains and its impact on final oil quality

Tocopherols are one of the most important bioactive compounds in vegetable oils. It is known that these antioxidants present a dilution like relationship with oil weight per grain but the mechanism underlying this relationship are unknown. The aim of this work was to analyze the dynamics of tocopherol accumulation in sunflower grains, its relationship with oil accumulation and its effects on final oil quality in genotypes with different fatty acid composition. Three field experiments were conducted with genotypes with different potential fatty acid composition (a traditional, a high oleic and a high stearic−high oleic) and treatments with different source (intercepted solar radiation) or sink (grains) during grain filling to obtain varied grain filling conditions and grains with different oil concentration and oil unsaturation. Intercepted solar radiation modified oil per grain but did not affect tocopherol per grain. The rate of accumulation explained 79% and 74% of the oil and tocopherol per grain variation, respectively. When intercepted solar radiation increased, the duration of the period of oil and tocopherols accumulation increased, being the first the most responsive. These differences in the duration of accumulation periods are reflected in a larger relative increase in oil than tocopherols per grain and thus a dilution of the latter in the oil. These differences in the dynamics of oil and tocopherol accumulation are common to genotypes with different level of unsaturation. These results help to understand the mechanism associated with the dilution curve of oil tocopherol concentration reported in the literature.     

Shear resistant performance of RC columns subjected to vertical near-fault velocity pulse-like earthquake actions

The aim is to evaluate the seismic properties of ancient timber structure after strengthening and analyze the failure process and corresponding failure state. Based on the hysteretic behavior and energy dissipation principle of the dovetail column-frame strengthened with CFRP and Arches Brackets under the low reversed cyclic loading, the “potential of destruction-resisting” of the two energy-consuming components is obtained. The dissipated energy of each energy-consuming component under the various earthquake conditions is calculated combining with the shaking table test of ancient timber structure. The model of seismic damage evaluation of the two energy-consuming components is established on the basis of the “potential of destruction-resisting” and the dissipated energy. By means of the energy distribution coefficient, the relationship of the failure state between energy-consuming components and overall strengthened structure is discovered, and the model of seismic damage evaluation of the overall structure under the various earthquake conditions is presented. With the derived model of seismic damage evaluation, the failure coefficient of the energy-consuming components and the overall strengthened structure is quantitatively calculated. According to the failure state, the corresponding damage grade of overall strengthened structure is obtained. The results can provide a reliable theoretical basis for predicting the destruction before earthquake and re-reinforcement to the strengthened ancient timber structures after earthquake.     

光照和水流阻力对小麦蒸腾波动的影响

生长在步入式植物生长箱中的小麦幼苗, 当光子流密度(PFD)下降时, 蒸腾速率发生了有规律的波动。 波动周期与下降幅度有关, 下降幅度越大, 周期越长。 在波动进行期间, 当再次降低PFD(100 μmol m-2s-1到30 μmol m-2s-1)后, 波动频率和振幅都有所降低。 通过外界压力使叶鞘部木质部变形, 以导致在变形区的水流阻力增     

Closed-form Analytical Solution for Beam on Elastic Foundation with Different Tension and Compression Modulus

On the basis of the theory of different modulus, the closed-form analytical solution for beams on elastic foundations with different modulus has been derived. A comparison is made between the results of the analytical solution and those calculated from the classic mechanic theories, in which the tension modulus are equal to the compression modulus. It is shown from the numerical results that the ratio of compressive modulus to tensile modulus will greatly affect the elastic characteristic values,internal forces and flexibilities. The present theory satisfies the mechanical behavior of materials. The amount of materials can be economized through rational design by using the elastic theory of different modulus.