叶片光化学植被指数(PRI)的修正及其敏感性分析

光化学植被指数(PRI)被成功的应用于估算不同叶片生化组分的光能利用率(LUE),这些生化组分包括叶片含水量、氮元素浓度等。以往的研究中已经成功建立了叶片、冠层和景观尺度PRI和LUE的相关关系。但是,为了利用PRI更加准确地估算叶片LUE,很多问题仍然亟需解决,比如当LUE高于0.03 mol CO₂ mol-1 PPFD(photosynthetic photon flux density),PRI会出现一个明显的饱和区域以及PRI和LUE关系会随季节发生较大变化。文章对PRI进行了修正,并基于PROSPECT模型对这一修正形式进行了4个参数的敏感性分析。分析结果表明,叶片SR-PRI(Simple ratio PRI) 对叶肉结构参数(N)、叶绿素浓度(c_ab)敏感性要高于叶片的等效水厚(c_w) 和干物质浓度(c_m)。因此叶肉结构参数(N) 和叶绿素浓度(c_ab)的微小变化都会造成SR-PRI的较大变化,进而影响到LUE的估算精度。对SR-PRI的实证实验表明,这一指数也能够很好地用来估算叶片的光能利用率并且结果要优于PRI和LUE之间的相关关系。SR-PRI最重要的一方面在于其更清晰的物理意义和对531 nm处反射率变化的敏感性,因为这一波段位置的反射率变化是评价光能利用率的核心参数。     

水管冷却等效热交换系数及参数敏感性分析

为了更加精确的进行软水管冷却仿真分析,对第三类边界冷却水与混凝土间的等效热交换系数进行了研究,分析了其变量对冷却效果的影响,结果表明：增大管径,减小管壁厚度可以明显的加大水管冷却效果,流速变化对冷却效果影响不是很大,实际工程施工通水冷却要保证冷却水管流态为紊流。     

基于改进麻雀搜索算法和支持向量机的边坡稳定性

边坡失稳是由多种因素共同作用的结果,常规的数学模型难以准确预测。为提高边坡稳定性预测精度,采用多策略融合改进麻雀搜索算法（improved sparrow search algorithm,ISSA）优化支持向量机（support vector machine,SVM）,进而建立边坡稳定性预测模型（ISSA-SVM模型）。将重度、粘聚力、内摩擦角、边坡角、边坡高、孔隙压力比6项因素作为输入特征,将边坡稳定性状态作为输出结果,进而预测边坡稳定性。选取国内外工程实例建立边坡数据库,将ISSA-SVM模型与SSA-SVM模型进行对比分析,通过灰色关联度分析法（grey relation analysis,GRA）进行敏感性分析。结果表明：ISSA-SVM模型预测精度更高、泛化能力更强,粘聚力和内摩擦角是对边坡稳定性最为敏感的因子。所提ISSA-SVM模型不仅能够准确地预测边坡稳定状态,还可以为其他领域相关问题提供参考。     

采场底板岩体裂隙发育深度影响因素敏感性研究

底板突水过程实际上是水压驱动下岩层裂纹萌生、扩展、贯通,直到最后断裂导致失稳破裂的过程。本文通过正交试验法设计了9个计算模型,并对UDEC数值模拟结果进行极差分析,从而得出采场底板岩体裂隙发育深度影响因素的敏感性顺序为：隔水层强度〉原岩应力〉原生裂隙度〉采面长度〉承压水压〉采高。该结果对承压水体上采煤的底板裂隙发育能够...     

松树枯梢病菌对百菌清的敏感性研究

应用刹菌剂百菌清对从中国不同地理区域和不同针对树上收集的５５个松树枯梢病菌（Ｓｐｈａｅｒｏｐｓｉｓ ｓａｐｉｎｅａ）菌株进行孢子萌发敏感性及菌丝生长敏感性测定,并采用相对分生孢子萌发率（ＲＣＧ）和相对菌丝体生长量（ＲＭＧ）进行敏感性评估,结果表明,Ｓ．ｓａｐｉｎｅａ的分生孢子对百菌清极为敏感,且不同菌株间的敏感性差异很大（ＲＣＧ１％～１００％）;而菌丝对百菌清的敏感性较小,不同菌株间的敏感性差异不     

Mathematical modeling and solution trajectories of complex chemical mechanism based on Monte Carlo methods

The main purpose of this article is introducing the method of Spectral Quasi Equilibrium Manifold taking different model, simple and complex mechanism to find solution curve. Before that discussing reaction kinetic, reduction of system, chemical equilibrium, QEM technique. As in complex reaction we need to split reaction mechanism in different route to reduce the complexity of higher dimensional system.in this article SQEM technique is apply to different route and comparison of route is also discussed. In previous years, the depiction of existing method based on chemical reaction kinetics has become a standard approach, for which estimation of involved parameters become challenge. For the model developments and standardization, Sensitivity analysis is powerful tool. Influence of parameters on target output is discussed through graphical results.     

Unprecedented Relaxivity Gap in pH-Responsive FeIII-Based MRI Probes

Two mononuclear ferric complexes are reported that respond to a pH change with a 27- and 71-fold jump, respectively, in their capacity to accelerate the longitudinal relaxation rate of water-hydrogen nuclei, and this starting from a negligible base value of only 0.06. This unprecedented performance bodes well for tackling the sensitivity issues hampering the development of Molecular MRI. The two chelates also excel in the fully reversible and fatigue-less nature of this phenomenon. The structural reasons for this performance reside in the macrocyclic nature of the hexa-dentate ligand, as well as the presence of a single pendant arm displaying a five-membered lactam or carbamate which show (perturbed) pK_a values of 3.5 in the context of this N6 N5O1 coordination motif.     

Recent progress in nuclear magnetic resonance strategies for time-resolved atomic-level investigation of crystallization from solution

Crystallization underpins essential processes in our everyday life, creating exceptional materials. Yet, fundamental understanding of the mechanisms underlying crystallization processes is still lacking because of the scarcity of experimental approaches allowing atomic-level investigation of the sequence of intermediate phases formed during crystallization as a function of time.We review recent progress of Nuclear Magnetic Resonance (NMR) in tackling this challenge across the last four years. New in-situ and ex-situ strategies are discussed, in which cryogenic conditions are combined with dynamic nuclear polarization (DNP) NMR to monitor crystallization. Under these conditions, both the temporal and structural resolution of the analysis increase, enabling the detection of – previously elusive – transient forms. We conclude with suggestions of future directions that could extend the capabilities of NMR even further, bringing key mechanistic details of crystallization process that could expand our fundamental understanding of crystallization and improve control over crystallization outcome.     

多项式混沌展开的浅海水声环境参数敏感度分析

水下声场是海洋环境参数的非线性函数,因此环境参数的不确定性必然会引起水下声场预测的不确定性,从而导致与声场预测相关的声呐探测和水声通信等设备性能的下降.该文将Sobol敏感度指数的计算与多项式混沌展开方法相结合,将敏感度指数表达为环境条件的函数,利用Q范数约束的双曲截断方案来减少多项式项数,有效地分析了设定的"浅海负梯...