氮素穗肥对杂交籼稻籽粒灌浆影响及其与淀粉合成关键酶活性间关系

【目的】为明确氮素穗肥对杂交稻籽粒灌浆和淀粉合成关键酶活性的影响。【方法】选用两个直链淀粉含量差异较大的杂交稻品种锦优1319(高直链淀粉)和蓉优702(低直链淀粉),在不同的氮素穗肥处理下(设0、60、90和120 kg/hm^(2)4个纯氮水平,分别用CK、N1、N2、N3表示)研究氮素穗肥水平对籽粒灌浆和淀粉合成关键酶活性的影响。【结果】不同穗肥处理下杂交稻籽粒灌浆特性差异显著,且不同类型品种表现各异,其中氮素穗肥的施用显著降低了稻米的直链淀粉含量。锦优1319的Gmax和Gmean随氮素穗肥水平的变化均表现为N2>CK>N1>N3,而蓉优702则表现为N3>N2>CK>N1;施用氮素穗肥显著增加了花后5~25 d籽粒腺苷二磷酸焦磷酸化酶(ADPG)和淀粉分支酶(DBE)的活性,降低了花后5~15 d籽粒GBSS活性,降低了花后5~25 d籽粒淀粉合成酶(SSS)和SBE活性。【结论】高直链淀粉品种锦优1319籽粒灌浆的最佳氮素穗肥施用量低于低直链淀粉品种蓉优702:其中锦优1319的最佳氮素穗肥施用量为90 kg/hm^(2),蓉优702为120 kg/hm^(2)。施用氮素穗肥显著降低了GBSS、SSS的活性,加之SBE活性下降,DBE活性提高,最终降低稻米直链淀粉含量。本研究条件下,籽粒ADPG活性未对稻米直链淀粉含量产生显著影响。

与气动噪声相关的湍流模型及计算方法

针对气动噪声计算问题,经过两年的研究,主要进展如下:(1)研究了高精度湍流模拟技术的数值方法。首先发展了一套基于高阶有限差分格式的流场求解器,并进行了系统测评;在此基础上,针对激波模拟精度,提出了带宽耗散优化方法(BDOM),发展了MP-LD格式,结果表明MP-LD格式对小尺度流动结构的捕捉能力以及对湍流的模拟效率要显著优于常规的高阶激波捕捉格式。(2)采用高精度湍流模拟技术研究了复杂流动机理。利用MP-LD格式和ASTR程序,对激波/各向同性湍流干涉(SITI)和激波/湍流边界层干涉(SBLI)等进行了DNS和机理性的研究。结果表明:湍流脉动之间的非线性作用使得大尺度湍流结构向各向同性恢复的过程更加复,而小尺度脉动结构则更容易恢复各向同性;由于来流速度脉动的影响,激波表面形状会发生变形,较高的来流速度脉动会导致当地激波位置更靠近下游,并增加激波的强度。(3)研究了压气机三维角区分离流动机理和湍流模型改进。针对角区分离流动,首先开展了先进实验测量和高精度数值模拟,为机理研究和湍流模型改进提供丰富的数据库。其次,提出了基于湍流非平衡输运特性改进湍流模型的新方法,并针对SA湍流模型,提出了两种改进方法:一是修正模型系数Cb1;二是基于当地螺旋度计入湍流能量反传物理机制。其中,基于螺旋度改进可以"自适应"计入湍流非平衡输运特性,可以"自适应"实现对不同工况下压气机三维角区分离流动的准确模拟。(4)研究了压气机转静干涉机理和时均模拟方法。针对转静干涉噪声,团队提出了时均模拟技术和线性谐波法相结合的快速非定常数值模拟思路。该课题首先采用非定常数值模拟技术,研究了转静干涉机理。其次改进了交界面处理方法,深入分析了确定性相关项的分布特点和对时均流场的影响特性,发展了确定性相关项模型,发展完善了时均模拟技术,为下一步和线性谐波法相结合,实现对转静干涉噪声源的快速非定常计算,提供坚实的基础。(5)建立了气动声学知识库系统和噪声机理知识。首先建立了国际上首套气动声学知识库系统;其次对大攻角超音速流动,发现了机翼上表面存在一种激波/滑移面共存结构,发现了一种新的气动噪声来源;最后针对气动声学重要来源之一的点涡与物体的相互作用,建立了一套点涡群对多物体受力影响的基本理论。

基于改进多种群遗传算法的光伏阵列多峰值MPPT研究

光伏阵列在实际工作条件下因灰尘、受照不均匀等影响而功率输出呈现多峰特性,传统的最大功率点跟踪(maximum power point tracking,MPPT)算法不能实现全局寻优,无法精确跟踪到最大功率点。遗传算法可以有效解决多峰寻优问题,但一般遗传算法在跟踪过程中会出现早熟、准确率较低等问题,为此,提出一种多种群遗传算法(multiple population genetic algorithm,MPGA)与扰动法相结合的算法来解决此类问题。在光伏电池拓扑模型中,采用优化双二极管代替单二极管模型,并在Matlab/Simulink下进行建模仿真。结果表明:该算法可以准确快速高效地找到局部阴影条件下光伏阵列的最大功率点。

基于C#语言的ABAQUS二次开发及其在边坡稳定性计算中的应用

ABAQUS软件界面操作复杂,且前后数据处理需花费大量时间,针对以上问题,采用C#语言对ABAQUS进行二次开发,突破传统的单纯使用Python脚本配合ABAQUS内置GUI插件工具箱开发的局限性,利用C#语言编写程序,直接调用ABAQUS求解器,实现在不打开软件界面的情况下进行计算并读取结果,并将强度折减系数显示在WinForm窗体程序上。开发后的系统大大简化了ABAQUS中求解特定岩土边坡工程问题的复杂操作,降低了软件操作难度。

Review of shock wave detection method in CFD post-processing

In the present computational fluid dynamics （CFD） community, post-processing is regarded as a procedure to view parameter distribution, detect characteristic structure and reveal physical mechanism of fluid flow based on computational or experimental results. Field plots by contours, iso-surfaces, streamlines, vectors and others are traditional post-processing techniques. While the shock wave, as one important and critical flow structure in many aerodynamic problems, can hardly be detected or distinguished in a direct way using these traditional methods, due to possible confusions with other similar discontinuous flow structures like slip line, contact discontinuity, etc. Therefore, method for automatic detection of shock wave in post-processing is of great importance for both academic research and engineering applications. In this paper, the current status of methodologies developed for shock wave detection and implementations in post-processing platform are reviewed, as well as discussions on advantages and limitations of the existing methods and proposals for further studies of shock wave detection method. We also develop an advanced post-processing software, with improved shock detection.

A hypersonic lift mechanism with decoupled lift and drag surfaces

In the present study, we propose a novel lift mechanism for which the lifting surface produces only lift. This is achieved by mounting a two-dimensional shock-shock interaction generator below the lifting surface. The shock-shock interaction theory in conjunction with a three dimensional correction and checked with computational fluid dynamics (CFD) is used to analyze the lift and drag forces as function of the geometrical parameters and inflow Mach number. Through this study, though limited to only inviscid flow, we conclude that it is possible to obtain a high lift to drag ratio by suitably arranging the shock interaction generator.

Hypersonic starting flow at high angle of attack

Compressible starting flow at small angle of attack （AoA） involves small amplitude waves and time-dependent lift coefficient and has been extensively studied before. In this paper we consider hypersonic starting flow of a two-dimensional flat wing or airfoil at large angle of attack involving strong shock waves. The flow field in some typical regions near the wing is solved analytically. Simple expressions of time-dependent lift evolutions at the initial and final stages are given. Numerical simulations by compuational fluid dynamics are used to verify and complement the theoretical results. It is shown that below the wing there is a straight oblique shock （OSW） wave, a curved shock wave （CSW） and an unsteady horizontal shock wave （USW）, and the latter moves perpendicularlly to the wing. The length of these three parts of waves changes with time. The pres- sure above OSW is larger than that above USW, while across CSW there is a significant drop of the pressure, making the force nearly constant during the initial period of time. When, however, the Mach number is very large, the force coefficient tends to a time-independent constant, proportional to the square of the sine of the angle of attack.

Generalized Kutta–Joukowski theorem for multi-vortex and multi-airfoil flow(a lumped vortex model)

For purpose of easy identification of the role of free vortices on the lift and drag and for purpose of fast or engineering evaluation of forces for each individual body, we will extend in this paper the Kutta-Joukowski （K J） theorem to the case of inviscid flow with multiple free vortices and multiple airfoils. The major simplification used in this paper is that each airfoil is represented by a lumped vortex, which may hold true when the distances between vortices and bodies are large enough. It is found that the Kutta-Joukowski theorem still holds provided that the local freestream velocity and the circulation of the bound vortex are modified by the induced velocity due to the out- side vortices and airfoils. We will demonstrate how to use the present result to identify the role of vortices on the forces according to their position, strength and rotation direction. Moreover, we will apply the present results to a two-cylinder example of Crowdy and the Wagner example to demon- strate how to perform fast force approximation for multi-body and multi-vortex problems. The lumped vortex assumption has the advantage of giving such kinds of approximate results which are very easy to use. The lack of accuracy for such a fast evaluation will be compensated by a rig- orous extension, with the lumped vortex assumption removed and with vortex production included, in a forthcoming paper.

Modelling the spreading rate of controlled communicable epidemics through an entropy-based thermodynamic model

A model based on a thermodynamic approach is proposed for predicting the dynamics of communicable epidemics assumed to be governed by controlling eforts of multiple scales so that an entropy is associated with the system.All the epidemic details are factored into a single and time-dependent coefcient,the functional form of this coefcient is found through four constraints,including notably the existence of an inflexion point and a maximum.The model is solved to give a log-normal distribution for the spread rate,for which a Shannon entropy can be defined.The only parameter,that characterizes the width of the distribution function,is uniquely determined through maximizing the rate of entropy production.This entropy-based thermodynamic(EBT)model predicts the number of hospitalized cases with a reasonable accuracy for SARS in the year 2003.This EBT model can be of use for potential epidemics such as avian influenza and H7N9 in China.

Generalized Kutta–Joukowski theorem for multi-vortex and multi-airfoil flow with vortex production——A general model

By using a special momentum approach and with the help of interchange between singularity velocity and induced flow velocity, we derive in a physical way explicit force formulas for twodimensional inviscid flow involving multiple bound and free vortices, multiple airfoils, and vortex production. These force formulas hold individually for each airfoil thus allowing for force decomposition, and the contributions to forces from singularities（such as bound and image vortices,sources, and doublets） and bodies out of an airfoil are related to their induced velocities at the locations of singularities inside this airfoil. The force contribution due to vortex production is related to the vortex production rate and the distance between each pair of vortices in production, thus frameindependent. The formulas are validated against a number of standard problems. These force formulas, which generalize the classic Kutta–Joukowski theorem（for a single bound vortex） and the recent generalized Lagally theorem（for problems without a bound vortex and vortex production） to more general cases, can be used to identify or understand the roles of outside vortices and bodies on the forces of the actual body, optimize arrangement of outside vortices and bodies for force enhancement or reduction, and derive analytical force formulas once the flow field is given or known.

Kutta-Joukowski force expression for viscous flow

The Kutta Joukowski(KJ) theorem, relating the lift of an airfoil to circulation, was widely accepted for predicting the lift of viscous high Reynolds number flow without separation. However, this theorem was only proved for inviscid flow and it is thus of academic importance to see whether there is a viscous equivalent of this theorem. For lower Reynolds number flow around objects of small size, it is difficult to measure the lift force directly and it is thus convenient to measure the velocity flow field solely and then, if possible, relate the lift to the circulation in a similar way as for the inviscid KJ theorem. The purpose of this paper is to discuss the relevant conditions under which a viscous equivalent of the KJ theorem exists that reduces to the inviscid KJ theorem for high Reynolds number viscous flow and remains correct for low Reynolds number steady flow. It has been shown that if the lift is expressed as a linear function of the circulation as in the classical KJ theorem, then the freestream velocity must be corrected by a component called mean deficit velocity resulting from the wake. This correction is small only when the Reynolds number is relatively large. Moreover, the circulation, defined along a loop containing the boundary layer and a part of the wake, is generally smaller than that based on inviscid flow assumption. For unsteady viscous flow, there is an inevitable additional correction due to unsteadiness.