模拟淋溶条件下亚热带不同性状凋落叶DOM的溶出量特征

亚热带区域丰沛的降雨可导致森林凋落叶可溶性有机质(Dissolved Organic Matter,DOM)大量淋溶溶出,成为地表和土壤活性有机质的重要来源,但凋落叶性状可能显著影响DOM溶出特征。本研究选取具有明显性状差异的8种亚热带森林典型树种凋落叶为研究对象,采用模拟淋溶实验方法,分析淋溶后凋落叶可溶性有机质(包括碳、氮和磷元素)的溶出量与化学计量特征及其与性状的关系。结果发现,相较于其他树种,淋溶前DOM含量较高、持水能力较高的杜英凋落叶淋溶后碳、氮、磷的溶出量以及质量损失均大于其他树种。不同性状凋落叶可溶性有机碳、氮、磷的溶出率也表现出显著差异,且磷的溶出率明显高于碳和氮的溶出率。相关性分析表明,凋落叶可溶性有机碳溶出率主要受淋溶前可溶性有机碳和氮含量以及最大持水力的影响,但凋落叶的叶面积和淋溶前可溶性有机磷含量是影响可溶性有机磷溶出率的最重要因子。此外,凋落叶性状也可显著影响溶出DOM的DOC/DOP,DON/DOP和DOC/DON,改变从凋落物进入土壤的DOM质量。这些结果充分表明亚热带森林凋落叶DOM的迁移过程与凋落叶持水能力密切相关,为区域生态系统结构优化和可持续经营管理提供了科学依据。

城市景观水体中水岸绿化植物凋落叶的分解及养分释放特征

植物凋落叶既可以在水体中快速释放养分,也可以通过吸附作用富集水体中的氮磷等养分元素,但可能受到凋落叶性状的影响,对此仍缺乏必要的认识。因此,以福建省福州市3种具有代表性的城市绿化植物小叶榕(Ficus concinna)、泰竹(Thyrsostachys siamensis)和黄葛树(Ficus virens)凋落叶为研究对象,采用分解袋法开展水体分解试验,研究凋落物在城市景观水体中的分解速率以及碳(C)、氮(N)、磷(P)和钾(K)元素动态变化规律。结果表明,小叶榕、泰竹和黄葛凋落叶在城市景观水体中质量损失表现为慢-快-慢的分解趋势;凋落叶的质量损失与长宽比、比叶面积以及P含量和C/N呈正相关,但与叶面积、N含量呈负相关。整体而言,C和K表现为明显的释放现象:3种凋落叶C均为直接释放模式;小叶榕和黄葛凋落叶K为直接释放模式,泰竹凋落叶K为富集-释放模式。N和P表现为明显的富集现象:小叶榕和泰竹凋落叶N为富集-释放模式,而黄葛凋落叶N为释放-富集-释放模式;3种凋落叶P均为富集-释放模式。其中,小叶榕凋落叶富集N,P的效果最好。相关性分析表明,不同分解阶段的凋落叶失重受到不同元素释放的影响,分解前期主要与K释放有关,中期主要与N释放有关,后期与C,N,P释放有关,且元素的释放与叶面积、比叶面积、长宽比以及初始C,N,P含量存在显著的相关关系。可见,水岸绿化植物凋落叶可在一定程度上富集水体氮磷,且受到凋落叶性状的影响,为景观水体岸边绿化植物选择与管理提供了一定的科学依据。

潮虫消耗木本植物凋落物的可选择性试验

近年来,越来越多的学者关注外来植物入侵对土壤生态功能的影响效应及其相应反馈机制的探索与研究,然而本地原生土壤生物群落对不同入侵程度下的外来植物种以及本地原生植物种之间是否存在消耗差异却尚不明了。通过等足目潮虫的选择性喂养试验来测试10个本地种、5个非入侵性外来种和5个强入侵性外来种之间的适口性差异,试图求证外来植物的入侵性是否与植物落叶被消耗率呈现必然联系。数据分析结果显示潮虫对本地种、非入侵性外来种和入侵性外来种的消耗并无显著差异;而潮虫对不同生活型下木本植物的取食却存在显著差异,即灌木消耗率显著高于乔木。其次,通过植物初始性状指标(包括木质素、纤维素、半纤维素、碳、氮含量)与相应消耗率的相关比较,消耗量总体上与植物凋落物的氮含量呈正相关关系(R2=0.358)。由此,研究结论强调植物落叶的降解速率并不一定与植物入侵性或入侵阶段呈绝对相互关连,但是氮含量,抑或各种形式的植物氮元素成分都可能在一定程度上参与并影响着外来植物的入侵进程。

Shape-sizing nested optimization of deployable structures using SQP

The potential role of formal structural optimization was investigated for designing foldable and deployable structures in this work.Shape-sizing nested optimization is a challenging design problem.Shape,represented by the lengths and relative angles of elements,is critical to achieving smooth deployment to a desired span,while the section profiles of each element must satisfy structural dynamic performances in each deploying state.Dynamic characteristics of deployable structures in the initial state,the final state and also the middle deploying states are all crucial to the structural dynamic performances.The shape was represented by the nodal coordinates and the profiles of cross sections were represented by the diameters and thicknesses.SQP(sequential quadratic programming) method was used to explore the design space and identify the minimum mass solutions that satisfy kinematic and structural dynamic constraints.The optimization model and methodology were tested on the case-study of a deployable pantograph.This strategy can be easily extended to design a wide range of deployable structures,including deployable antenna structures,foldable solar sails,expandable bridges and retractable gymnasium roofs.

Entropy of Field Interacting With Two Atoms in Bell State

In this paper, we investigate entropy properties of the single-mode coherent optical field interacting with the two two-level atoms initially in one of the four Bell states. It is found that the different initial states of the two atoms lead to different evolutions of field entropy and the intensity of the field plays an important role for the evolution properties of field entropy.

Node scattering manipulation based on trajectory model in wireless sensor network

To deploy sensor nodes over the area of interest,a scheme,named node scattering manipulation,was proposed.It adopted the following method:during node scattering,the initial states of every node,including the velocity and direction,were manipulated so that it would land in a region with a certain probability;every sensor was relocated in order to improve the coverage and connectivity.Simultaneously,to easily analyze the process of scattering sensors,a trajectory model was also proposed.Integrating node scattering manipulation with trajectory model,the node deployment in wireless sensor network was thoroughly renovated,that is,this scheme can scatter sensors.In practice,the scheme was operable compared with the previous achievements.The simulation results demonstrate the superiority and feasibility of the scheme,and also show that the energy consumption for sensors relocation is reduced.

On the Regional Enlarged Observability for Linear Parabolic Systems

In this paper, we study the notion of the enlarged observability for distributed parabolic systems, where the aim is to reconstruct the initial state between two prescribed profiles P1 and P2 in an internal subregion c0 of the evolution domain f2. We give some definitions and properties of this concept, and then we solve the problem of the reconstruction of initial state using the Hilbert Uniqueness Method （HUM）. This leads to several interesting results which are performed through numerical example and simulations.

Riemann boundary value problems and reflection of shock for the Chaplygin gas

In this paper,we study two-dimensional Riemann boundary value problems of Euler system for the isentropic and irrotational Chaplygin gas with initial data being two constant states given in two sectors respectively,where one sector is a quadrant and the other one has an acute vertex angle.We prove that the Riemann boundary value problem admits a global self-similar solution,if either the initial states are close,or the smaller sector is also near a quadrant.Our result can be applied to solving the problem of shock reflection by a ramp.

GLOBAL STABILITY OF SOLUTIONS WITH DISCONTINUOUS INITIAL DATA CONTAINING VACUUM STATES FOR THE RELATIVISTIC EULER EQUATIONS

The global stability of Lipschitz continuous solutions with discontinuous initial data for the relativistic Euler equations is established in a broad class of entropy solutions in L∞ containing vacuum states. As a corollary, the uniqueness of Lipschitz solutions with discontinuous initial data is obtained in the broad class of entropy solutions in L∞.

Dynamics analysis of chaotic circuit with two memristors

Based on Chua’s chaotic oscillation circuit, a fifth-order chaotic circuit with two memristors is designed and its corresponding dimensionless mathematic model is established. By using conventional dynamical analysis methods, stability analysis of the equilibrium set of the circuit is performed, the distribution of stable and unstable regions corresponding to the memristor initial states is achieved, and the complex dynamical behaviors of the circuit depending on the circuit parameters and the memristor initial states are investigated. The theoretical analysis and numerical simulation results demonstrate that the proposed chaotic circuit with two memristors has an equilibrium set located on the plane constituted by the inner state variables of two memristors. The stability of the equilibrium set depends on both the circuit parameters and the initial states of the two memristors. Rich nonlinear dynamical phenomena, such as state transitions, transient hyperchaos and so on, are expected.