COMPONENT ALLEE EFFECTS AND STAGE‐SPECIFIC PREDATION: A BRIEF INSIGHT INTO CONSERVATION AND BIOLOGICAL CONTROL ISSUES

In this paper, we propose a two‐stage structured population model subject to component Allee effects in fecundity and maturation, and with two disturbances (predation only and harvest and predation) acting on both stages. It is shown that this combination leads to a demographic Allee effect—a characteristic that could be exploited in pest biological control, but on the other hand, it represents a bane in conservation biology. The analysis is performed for disturbances with functional responses type 2 and 3, and the models show that they yield qualitatively similar results. This characteristic is discussed from the species conservation and biological control point of view, together with possible extensions of this work.     

基于多分辨分析的沪深股市相关性分析

为了有效地揭示沪深股市不同交易周期股票交易的相关性,本文采用极大重叠离散小波变换,将上证指数和深圳成指高频收益率分解在不同的交易周期上,对各个周期的收益率采用semi-GPD模型作为其边缘分布分别进行拟合,在此基础上采用Copula函数方法建立同周期收益率的联合分布,度量了沪深两市同周期交易的相关性.实证表明,不同交易周期所表现出的相关性存在明显差异,并且随着交易期的增长,沪深两市非对称结构逐步明显。     

Experimental and density functional theoretical investigations of linkage isomerism in six-coordinate FeNO(6) iron porphyrins with axial nitrosyl and nitro ligands

A critical component of the biological activity of NO and nitrite involves their coordination to the iron center in heme proteins. Irradiation (330 < lambda < 500 nm) of the nitrosyl-nitro compound (TPP)Fe(NO)(NO(2)) (TPP = tetraphenylporphyrinato dianion) at 11 K results in changes in the IR spectrum associated with both nitro-to-nitrito and nitrosyl-to-isonitrosyl linkage isomerism. Only the nitro-to-nitrito linkage isomer is obtained at 200 K, indicating that the isonitrosyl linkage isomer is less stable than the nitrito linkage isomer. DFT calculations reveal two ground-state conformations of (porphine)Fe(NO)(NO(2)) that differ in the relative axial ligand orientations (i.e., GS parallel and GS perpendicular). In both conformations, the FeNO group is bent (156.4 degrees for GS parallel, 159.8 degrees for GS perpendicular) for this formally {FeNO}(6) compound. Three conformations of the nitrosyl-nitrito isomer (porphine)Fe(NO)(ONO) (MSa parallel, MSa perpendicular, and MSa(L)) and two conformations of the isonitrosyl-nitro isomer (porphine)Fe(ON)(NO(2)) (MSb parallel and MSb perpendicular) are identified, as are three conformations of the double-linkage isomer (porphine)Fe(ON)(ONO) (MSc parallel, MSc perpendicular, MSc(L)). Only 2 of the 10 optimized geometries contain near-linear FeNO (MSa(L)) and FeON (MSc(L)) bonds. The energies of the ground-state and isomeric structures increase in the order GS < MSa < MSb < MSc. Vibrational frequencies for all of the linkage isomers have been calculated, and the theoretical gas-phase absorption spectrum of (porphine)Fe(NO)(NO(2)) has been analyzed to obtain information on the electronic transitions responsible for the linkage isomerization. Comparison of the experimental and theoretical IR spectra does not provide evidence for the existence of a double linkage isomer of (TPP)Fe(NO)(NO(2)).     

凝胶型选择性堵水剂DQ-2的研制及应用

以改性聚丙烯酰胺为主要原料,配以交联剂和稳定剂,制得选择性堵水剂DQ-2.优选出选择性堵水剂DQ-2的最佳配方:0.6%改性聚丙烯酰胺+0.6%交联剂+0.03%稳定剂.采用瓶试法成胶实验和岩心流动实验评价了DQ-2体系的各项性能.实验结果表明:DQ-2堵水剂耐温30～70℃;抗矿化度性能良好,对K+和Na+的容忍度可以达到10 000 mg/kg,对Ca2+和Mg2+的容忍度可以达到5 000 mg/kg;对不同渗透率的岩心,堵水率达到90%,突破压力梯度大于10 MPa/m,堵油率小于30%,突破压力梯度低于1 MPa/m,具有较好的油水选择性.DQ-2体系的这些性能指标均达到了长庆油田现场应用的要求,实现了对水淹油井的有效治理,取得了较好的经济效益.     

抗多普勒频移的Ka频段FRFT-OFDM系统及其均衡

针对多普勒频移严重影响Ka频段正交频分复用(orthogonal frequency division multiplexing,OFDM)系统传输性能的问题,提出使用分数阶傅里叶变换(fractional Fourier transform,FRFT)的方法.将多普勒频移引入Ka频段移动卫星信道模型,通过选取不同环境...     

BLT方程在箱体屏蔽效能分析中的应用

根据Robinson算法和电磁拓扑理论,提出了一种基于BLT方程的有孔箱体屏蔽效能分析方法,介绍了BLT方程的基本原理,推导出了描述孔缝耦合的BLT方程,建立了屏蔽箱体、孔逢、入射波等参数与屏蔽效能的函数关系,并扩展到偏心孔以及任意极化角的情形,分析了孔缝形状、尺寸以及观测点位置等对屏蔽效能的影响。在0~1GHz范围,对中心开孔箱体的屏蔽效能进行仿真,并与CST仿真结果进行对比,验证了方法效性,数值计算结果表明:文中算法不仅能够准确的描述出箱体屏蔽效能随入射波频率的变化关系,而且能有效地估算出屏蔽箱体的谐振频率。     

科特勒的分销渠道理论在报业中的应用

科特勒的分销渠道理论对报业是非常适用的。该理论对如何选择与评价渠道成员以及如何激励渠道成员都提出了新颖独到的看法。这些策略和理论对报纸发行渠道的建立同样具有指导意义。我们应将其灵活地运用于报业的实践,使报业方面的理论研究能跟得上我国报业实践的发展。     

时滞控制理论的研究进展

时滞是自然界中广泛存在而又不可避免的一种现象。研究时滞现象,对于解决工程中的时延问题,提高控制系统性能,有着理论和实践意义。时滞控制基于内模原理,在控制器中引入时滞项以减少额外的干扰,从而提高控制系统的性能。本文概述了时滞控制理论的最新研究进展,包括:(1)时滞控制系统的数学模型及其分类,系统的鲁棒性与稳定性分析,最优与次优控制等;(2)时滞控制的基本原理与研究现状,时滞控制与其他控制方法的结合情况。最后指出了时滞控制系统需要进一步研究和解决的几个主要问题,并对其未来发展方向做了展望。     

The mass spectrometry of some aromatic azides

Bromophenyl azides provide the only exceptions to the observation that nitrogen (N₂) is eliminated from the molecular ions. Splitting out of HCN, C₂H₂ and (in the case of acyl or o-nitroaryl azides) CO are important processes.