基于非线性特征的旅游系统模型研究

对旅游系统模型的研究不同的学者切入点不同所建立的模型也有出入.现有的旅游系统模型主要包括三类:旅游功能系统模型、旅游混沌模型和旅游地理系统模型.但是,在建立模型时,对旅游系统的非线性这一主要特征的考虑还很欠缺.本文选取旅游系统的非线性特征这一切入点,在揭示非线性产生的原因后,以系统的信息反馈为基础建立了基于非线性特征的旅游系统模型.     

Characterization of the heteroepitaxial growth of 3C-SiC on Si during low pressure chemical vapor deposition

3C-SiC heteroepitaxial layers were grown on Si substrates using a horizontal, hot-wall low pressure chemical vapor deposition system. The crystal quality, surface morphology and thickness uniformity of the layers were characterized by X-ray diffraction, atomic force microcopy and Fourier transform infrared spectroscopy, respectively. Growth of the epitaxial layer was determined to follow a three-dimensional island mode initially and then switch to a step-flow mode as the growth time increases. Barrier epithelia, especially airway epithelial cells, are persistently exposed to micro-organisms and environmental factors. To protect the host from these microbial challenges, many immune strategies have evolved. The airway epithelium participates in the critical innate immune response through the secretion of immune effectors such as mucin, antimicrobial peptides (AMP), and reactive oxygen species (ROS) to entrap or kill invading microbes. In addition, airway epithelial cells can act as mediators connecting innate and adaptive immunity by producing various cytokines and chemokines. Here, we present an overview of the role of mucosal immunity in airway epithelium, emphasizing the framework of bacterial and viral infections along with regulatory mechanisms of immune effectors in human cells and selected animal models. We also describe pathophysiological roles for immune effectors in human airway disease.     

Effect of additive boron on type-Ib gem diamond single crystals synthesized under HPHT

The boron-doped type-Ib gem diamond crystals were synthesized successfully by adding amorphous boron into a system of graphite and Kovar catalyst under high pressure and high temperature (HPHT).The effect of additive boron on type-Ib gem diamond was extensively studied including the growth characteristic,morphology and nitrogen concentration.The synthesized boron-doped type-Ib gem diamond crystals were characterized by optical microscope (OM),scanning electron microscope (SEM) and infrared spectrometer (IR)...     

Effects of size variation and spatial structure on plastic response of plant height to light competition

Plants only interact with neighbors over restricted distances,so local conditions are of great significance for plants.In this study,a spatially-explicit,individual-based model was constructed to explore the effects of size variation and spatial structure on adaptive plasticity of plant height in response to light competition.In the model a plant maintains its height at an optimal value in order to maximize its growth rate,and this optimal height increases with the increase of the intensity of light competi...     

Solving surface plasmon resonances and near field in metallic nanostructures: Green’s matrix method and its applications

With the development of nanotechnology, many new optical phenomena in nanoscale have been demonstrated. Through the coupling of optical waves and collective oscillations of free electrons in metallic nanostructures, surface plasmon polaritons can be excited accompanying a strong near field enhancement that decays in a subwavelength scale, which have potential applications in the surface-enhanced Raman scattering, biosensor, optical communication, solar cells, and nonlinear optical frequency mixing. In the present article, we review the Green’s matrix method for solving the surface plasmon resonances and near field in arbitrarily shaped nanostructures and in binary metallic nanostructures. Using this method, we design the plasmonic nanostructures whose resonances are tunable from the visible to near-infrared, study the interplay of plasmon resonances, and propose a new way to control plasmonic resonances in binary metallic nanostructures.     

基于图像质量评估的MIMO-SAR等效相位中心误差界

受等效相位中心误差的影响,新体制的多输入多输出合成孔径雷达(MIMO-SAR)方位成像结果存在"假峰"而导致成像质量下降。该文提出基于虚假旁瓣比、积分旁瓣比及峰值能量损失等图像质量指标联合评价"假峰"对SAR成像质量的影响,进而确定MIMO-SAR等效相位中心误差界,为系统设计和信号处理提供了依据。结果表明:当等效相位中心误差超过0.2rad时,一般需要对其进行补偿以满足常规指标要求;星载系统较机载系统更适合等效相位中心处理,通常可忽略等效相位中心误差的补偿环节。     

大牛地气田泡沫排水工艺效果评价及影响因素分析

自大牛地气田气井投入开发以来,井筒积液严重影响了气井的正常生产,泡沫排水采气工艺以其设备简单、施工容易、见效快、成本低等特点,在气田内得到了广泛应用。详细分析了泡沫排水工艺的效果评价及影响因素,以期为现场生产提供指导。     

改进的粒子滤波算法在目标跟踪中的应用

粒子滤波算法中通常采用先验转移概率代替重要性函数,由此重要性密度函数对后验函数的偏差将增大。将小波去噪应用到粒子滤波过程中,降低了偏差,提高了粒子算法的滤波精度,并将该算法应用到目标跟踪的过程中,通过仿真证实该方法能够提高粒子滤波精度。     

公共图书馆的读者服务初探

分析了读者与图书馆之间存在的矛盾,提出了加强公共图书馆读者服务工作的几点建议,指出应加强读者沟通以提升图书馆服务质量。     

基于双目标规划和遗传算法的航线配船优化

为弥补目前航线配船问题研究存在的不足,以最大化船公司航线运营利润、最小化运力浪费为目标,建立双目标航线配船模型.同时为避免目前航线配船模型求解方式的繁琐,尝试将航线配船问题的可行解用染色体形式表示,通过遗传算法在解空间内的遍历和搜索,得到问题的满意解.实例分析证明了模型的可行性和算法的有效性.