Position Of Patch Research Articles

基于图论的景观连接度量化方法应用研究——以福建省闽清县自然森林为例

PDF HTML阅读 XML下载 导出引用 引用提醒 基于图论的景观连接度量化方法应用研究——以福建省闽清县自然森林为例 DOI: 10.5846/stxb201507301599 作者: 作者单位: 复旦大学环境科学与工程系,复旦大学环境科学与工程系 作者简介: 通讯作者: 中图分类号: 基金项目: 国家社科基金重大资助项目（14ZDB140） Evaluation method for landscape connectivity based on graph theory: a case study of natural forests in Minqing County, Fujian Province Author: Affiliation: Department of Environmental Science and Engineering,Fudan University,Department of Environmental Science and Engineering,Fudan University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:气候变化和人类活动导致的自然生境丧失和生境片断化使全球生物多样性面临威胁，而有效缓解这类问题的手段之一是维持自然生境的景观连接度。图论分析法作为景观连接度研究的新途径成为研究领域热点，但仍然存在提高距离阈值取值的科学性、充分解读图论连接度指数等有待探究的问题。以闽清县自然森林为对象使用图论分析方法进行了景观连接度的量化研究，提出并使用了距离阈值综合取值方法，联合使用了多种景观连接度指数。研究结果表明，距离阈值综合取值方法能够提高取值的准确性并具有广泛适用性，二进制连接度指数与概率连接度指数能够从不同角度指示景观结构和斑块重要性格局。研究区域90%以上的景观连接度由主要景观组分维持，数量很少的极高重要值斑块数能够对整体连接度水平产生显著影响。面积越大的斑块重要性指数越高，但是极高重要值斑块的重要性指数并不完全取决于斑块面积，而更多的与斑块位置等因素相关。本研究进一步完善图论分析法在景观连接度研究方面的应用，对生物多样性保护工作具有参考价值。 Abstract:The loss of natural habitat and habitat fragmentation, caused by climate change and human activities is a seriously threat global biodiversity. Maintaining landscape connectivity of natural habitats is one of the most effective methods for alleviating these related problems. Landscape connectivity describes the degree to which the landscape facilitates or impedes ecological flow and movement among habitat patches. By integrating information related to landscape structure and ecological processes, landscape connectivity describes the effects of habitat fragmentation on the organisms living within the landscape. Graph theory provides powerful tools for assessing landscape connectivity, and has become a popular research method in recent years. However, some issues related to the application of graph-based methods still need to be discussed and analyzed, such as choosing a proper threshold distance and gaining an understanding of various connectivity indices. This study used the graph theory method to assess the landscape connectivity of natural forest in Minqing County, Fuzhou City, China. A comprehensive method was utilized to assign a reasonable threshold distance, which consisted of three steps:namely, determining the range of the maximum dispersal distance of a focal species, enumerating a gradient distance value, and an experiment using link thresholding. Six indices were used to assess the landscape connectivity of the study area:number of links (NL), number of components (NC), Harary index (H), area-weighted flux (AWF), integral index of connectivity (ⅡC), and probability of connectivity (PC). We harvested data related to the natural commonweal forests of Mingqing County from the data of 2010 National Forest Resource Inventory using ArcGIS 10.2 to define habitat patches in the study area. The six landscape connectivity indices were calculated using Conefor Sensinode 2.6 software. Using the comprehensive method, 1 km was found to be the optimal threshold distance that best presented the structure of the landscape. A medium-level structure, consisting of 56 components was detected using the NL and NC indices. Based on the binary (H, ⅡC) and probability (AWF, PC) indices, the level of landscape connectivity of the natural forests in Minqing is comparatively low. The patch importance indices (dIs) aided in identifying the most important patches that could potentially affect the overall level of connectivity. We determinded that the main component provided 90% of the connecting functions in maintaining the landscape connectivity; however, losing a single critical patch could significantly reduce overall connectivity. The results indicated that this new method involving evaluation of the threshold distance could help researchers determine more accurate distance values for landscape connectivity, and therefore, this method would be applicable for both scientific research and planning. In addition, binary and probability indices could be used together to reveal landscape structure and the spatial patterns of patch importance. In our analysis, we found that the values of dI are generally proportional to the area of patches; however, patch area is not the dominate element that determines the dI values of the most critical patches. Other patch features, such as patch position, may have greater influence on the dI values for the extremely important patches. This may be caused by a commonly used but inaccurate method of evaluating patch attributes. This topic required further investigation and improvement in future studies. In conclusion, this study will help promote the application of graph theory in research studies related to landscape connectivity, and can provide guidance for land managers tasked with conserving biodiversity. 参考文献 相似文献 引证文献

Active Vibration Control of Smart Structure Using PZT Patches

The assembly that serves an engineering function is called as structure and structure that exhibits intelligence, efficiency, adaptability, accurate response and optimum performance is termed as a smart structure. Though, due to these advantages smart structures are used in many high end applications like aerospace engineering, microelectronics productions, precise positioning and automation industries, active vibration control of these structures is extremely important. This is because; mechanical vibrations in the structure can have detrimental effects as they can damage sensitive components of the structure or even the whole structure. Vibration control basically suppresses the effect of external disturbances and keeps the structure in its equilibrium position. In this paper, vibration control analysis of the structure for forced vibrations is carried out. The smart structure considered here, is a finite and flat beam-like fiber cantilever structure with PZT patches attached to its surface. Along with vibration control analysis effect of changing positions of PZT patches on this analysis is also discussed in this paper.

Optimal Placement of Piezoelectric Patches on Cantilever Beam for Voltage Generation: Experimental Study

The paper presents design, development and testing of piezoelectric material based energy harvesting devices as energy generators. In general, a common energy harvesting device uses piezoelectric patch on a cantilever beam with a tip mass. Most of these devices use a rectangular piezoelectric patch covering all position or part of the beam. The voltage generated by the piezoelectric patches are depends upon position on the cantilever beam. In this paper, a prototype harvester has been designed as per aforementioned structure and the output voltage was found experimentally. The piezoelectric patches were placed at different positions on the rectangular cantilever beam and generated ac output voltage was measured. In addition, by changing the tip mass we examine the appearance of different solutions. Identification of optimum place for patches and tip mass on the vibrating structure for the energy harvester is important as each solution may provide a difierent magnitude of ac output voltage. Based on the results, the optimal position of piezoelectric patches for energy harvester is predicted, which gives a way to increase its output voltage.

Computation of aerothermoelastic properties and active flutter control of CNT reinforced functionally graded composite panels in supersonic airflow

This paper presents an aerothermoelastic analysis of carbon nanotube (CNT) reinforced functionally graded composite panels in supersonic airflow. Meanwhile, the active flutter control of CNT reinforced functionally graded composite panels is also carried out using the piezoelectric actuator and sensor. Reddy’s third-order shear deformation theory is applied in the structural modeling. The equation of motion of the structural system is formulated using Hamilton’s principle and the assumed mode method. The displacement feedback algorithm is used to design the controller. The frequency domain method is applied to investigate the aerothermoelastic properties and active flutter control effects of the panels. The influences of CNT distribution, aspect ratio and thickness-to-length ratio on the aerothermoelastic properties of the CNT reinforced functionally graded composite panels are analyzed. Active flutter control effects under different thicknesses of CNT reinforced functionally graded composite panels are investigated. The optimal area and position of piezoelectric patches are also obtained by the genetic algorithm.

Spatial Distribution Patterns of Weed Communities in Corn Fields of Central Spain

The overall objective of this study was to identify common patterns in the spatial distribution of the major weed species present in the corn-growing region of central Spain, exploring the scale dependence of these patterns and the possible associations or dissociations between individual species. Weed density was assessed in 16 commercial fields using digital images acquired in a 9-m by 9-m sampling grid. A set of six species was found in all the fields: black nightshade, common cocklebur, fierce thornapple, johnsongrass, purple nutsedge, and velvetleaf. Spatial analysis by distance indices and inverse distance weighting interpolation methods were performed to create weed distribution maps. The results showed aggregated spatial distribution patterns for all individual species regardless their life cycle, annual or perennial. Some associations and dissociations among species were found in the analysis of interactions. Nevertheless, the spatial patterns of co-occurrence of weed species were field-specific and therefore cannot be considered general patterns of weed co-occurrence. In order to explore the scale dependence of these results, an additional study was conducted in an experimental field located in the same area using a 1.0-m by 0.75-m sampling grid. Although this resolution allowed for a better definition of the positions of the weed patches and weed-free gaps, the results obtained revealed similar patterns to those observed with a coarser sampling resolution.

Patch-based vehicle logo detection with patch intensity and weight matrix

A patch-based method for detecting vehicle logos using prior knowledge is proposed. By representing the coarse region of the logo with the weight matrix of patch intensity and position, the proposed method is robust to bad and complex environmental conditions. The bounding-box of the logo is extracted by a thershloding approach. Experimental results show that 93.58% location accuracy is achieved with 1100 images under various environmental conditions, indicating that the proposed method is effective and suitable for the location of vehicle logo in practical applications.

Robust single object tracker based on kernelled patch of a fixed RGB camera

One of the weaknesses of the mean-shift tracker is its limited ability to track a fast-moving object. Not only does the captured image look blurred but the object will often be out of the search window. Moreover, blur issue is a normal occurrence for a fast-moving object by using a commercially available camera due to a low frame rate. This paper aims to develop a robust observation detector for a single object tracker, especially for blurred image, fast-moving and non-rigid object. We propose a fusion of a kernel-based histogram and feature detector based approach. The measurement input is selected from candidate patches that will be generated by matching the vector descriptor. These vectors are built based on the detected points of interest. Two colour spaces are considered where all three channels of RGB are used, while only the hue channel of the HSV space is utilized. The kernel method is employed for better histogram accumulation. The output patch of the previous frame will be the target model where histogram similarity is measured based on Gaussian distribution. The selected output of the patch matching will undergo position smoothing for better precision. Maximum likelihood approach is used to iterate the patch position until the best match is found. The results indicate that our algorithm has a good detection for challenging surroundings and environments. In some cases, our algorithm may have less accuracy but in no case did it failed to detect.

Optimal placement of piezoelectric actuators on plate structures for active vibration control via modified control matrix and singular value decomposition approach using modified heuristic genetic algorithm

ABSTRACTThe present work deals with the optimal placement of piezoelectric actuators on a thin plate using modified control matrix and singular value decomposition (MCSVD) approach. The MCSVD is considered as the fitness function and optimal positions of the actuators are obtained by maximizing it with MHGA (modified heuristic genetic algorithm). Vibration suppression has been studied for simply supported plate with piezoelectric patches in optimal positions to suppress first specified modes using LQR (linear quadratic regulator) controller. It is observed that the positions of patches obtained with this approach give greater vibration suppression, reduced computational requirements, and provide global optimum solution only.

Clonal Patch Size and Ramet Position of Leymus chinensis Affected Reproductive Allocation.

Reproductive allocation is critically important for population maintenance and usually varies with not only environmental factors but also biotic ones. As a typical rhizome clonal plant in China's northern grasslands, Leymus chinensis usually dominates the steppe communities and grows in clonal patches. In order to clarify the sexual reproductive allocation of L. chinensis in the process of the growth and expansion, we selected L. chinensis clonal patches of a range of sizes to examine the reproductive allocation and allometric growth of the plants. Moreover, the effects of position of L. chinensis ramets within the patch on their reproductive allocation were also examined. Clonal patch size and position both significantly affected spike biomass, reproductive tiller biomass and SPIKE/TILLER biomass ratio. From the central to the marginal zone, both the spike biomass and reproductive tiller biomass displayed an increasing trend in all the five patch size categories except for reproductive tiller biomass in 15–40m2 category. L. chinensis had significantly larger SPIKE/TILLER biomass ratio in marginal zone than in central zone of clonal patches that are larger than 15 m2 in area. Regression analysis showed that the spike biomass and SPIKE/TILLER biomass ratio were negatively correlated with clonal patch size while patch size showed significantly positive effect on SEED/SPIKE biomass ratio, but the reproductive tiller biomass and SEED/TILLER biomass ratio were not dependent on clonal patch size. The relationships between biomass of spike and reproductive tiller, between mature seed biomass and spike biomass and between mature seed biomass and reproductive tiller biomass were significant allometric for all or some of patch size categories, respectively. The slopes of all these allometric relationships were significantly different from 1. The allometric growth of L. chinensis is patch size-dependent. This finding will be helpful for developing appropriate practices for the management of L. chinensis-dominant grasslands.

Symmetrical Slot on C-Shape Microstrip Patch for Tri-band Application

A new triple band microstrip patch antenna is presented in this paper for wireless communication. By adjusting the dimension of ground plane and patch, its fractional bandwidth at primary resonance mode can increased sufficiently to achieve desired bandwidth of proposed antenna. In proposed design, it has been found that the symmetrical position of patch over ground plane have clear impact on overall antenna performance. Many antenna structures have been modeled to demonstrate the effects of these parameters on the resulting triple band response. We design antenna for (1.07-1.75GHz), (3.22-4.35) and (5.78-6.5GHz).

C-Shape Microstrip Patch for Dual Band on Different Shape Ground Plane

The objective of this paper is to design an inset fed dual band rectangular microstrip patch antenna symmetrical ground plane. In this paper we simulated our design by using the electromagnetic solver, simulator (IE3D), was used to numerically investigate and optimize the proposed antenna configuration. Besides the structure external dimensions, the influence of the various antenna parameters on the resonant behavior have been observed. It has been found that the symmetrical position of patch over ground plane have clear impact on overall antenna performance. Many antenna structures have been modeled to demonstrate the effects of these parameters on the resulting dual band response. we design antenna for (1.85-2.05GHz) and upper band (2.352.44GHz).

Finite Element Simulation of Electro-Mechanical Impedance Technique

Electro-mechanical impedance method is emerging as an important and powerful technique for structural health monitoring (SHM). Active elements of the technique are Piezoelectric Wafer Active Sensor (PWAS) bonded on the structure. Modeling and simulation of PWAS and host structure play an important role in the SHM applications with PWAS. For decades finite element method has been extensively applied in the analysis of piezoelectric materials and structures. In this paper, piezoelectric element and a host metallic structure were modeled using Ansys finite element software to find the Electromechanical Impedance (EMI) according to the signal frequency. After that, the EMI signature of the beam was found for different position of the PWAS patch. The study shows that sensor position may directly control the EMI signature.

Rotation and translation covariant match kernels for image retrieval

Most image encodings achieve orientation invariance by aligning the patches to their dominant orientations and translation invariance by completely ignoring patch position or by max-pooling. Albeit successful, such choices introduce too much invariance because they do not guarantee that the patches are rotated or translated consistently. In this paper, we propose a geometric-aware aggregation strategy, which jointly encodes the local descriptors together with their patch dominant angle or location. The geometric attributes are encoded in a continuous manner by leveraging explicit feature maps. Our technique is compatible with generic match kernel formulation and can be employed along with several popular encoding methods, in particular Bag-of-Words, VLAD and the Fisher vector. The method is further combined with an efficient monomial embedding to provide a codebook-free method aggregating local descriptors into a single vector representation. Invariance is achieved by efficient similarity estimation of multiple rotations or translations, offered by a simple trigonometric polynomial. This strategy is effective for image search, as shown by experiments performed on standard benchmarks for image and particular object retrieval, namely Holidays and Oxford buildings.

Features of change of permanent snow patches in the Mongun-Taiga Massif, 1966–2011

The article is dedicated to perennial snow patches of Mongun-Taiga mountain massif (south-western Tuva), their morphology, present state and dynamics over the last 45 years. We created a scheme of snow patch classification with regard to genesis of relief and position on the slopes. Dynamics of snow patches is analyzed for periods between several time points – 1966 (on basis of aerial photos), 2000, 2007–2008 and 2011 (on basis of field measurements and observations). From 1966 to 2008 the number of snow patches decreased by 4 times, the total area – by 15 times, the altitudinal zone of snow patches moved 250–300 m up. In 2008–2011 the altitudinal zone of snow patches partly recovered, its lower limit moved 250 m down, periglacial snow patches recovered, a new type – snow patches of buried ice and debris-covered glaciers appeared. It could be the first face of the process of small glaciers recovery in the massif. Using the changes of the altitudinal position of snow patches in comparison with data of the closest meteorological station we estimated the amount of annual precipitation, critical for the existence of local snow patches.

Method for an Automated Optimization of Fiber Patch Placement Layup Designs

The manufacturing of composite structures is expensive due to high material cost and the amount of manual labor needed. Current manufacturing technologies, e.g. filament winding, braiding or fiber placement technologies are offering a possibility of automated manufacturing to lower these costs. Nevertheless, these technologies are limited when it comes to structures with complex fiber architecture and small geometries. A new approach to overcome these limitations is the fiber patch placement technology. The preform of a composite structure is built up with small and dry fiber patches in a sequential order. Fiber discontinuities are necessarily occurring between two patches and are influencing the mechanical properties. To optimize strength of the composite those discontinuities have to be distributed within the preform. With increased number of patches, the number of combinations of patch positions is increasing significantly. This paper presents a method based on an ant colony algorithm for an efficient calculation of an optimized distribution, which enables to use the potential of patched laminates.

Active vibration control of a sandwich plate by non-collocated positive position feedback

The active vibration control of a free rectangular sandwich plate by using the Positive Position Feedback (PPF) algorithm was experimentally investigated in a previous study. Four normal modes were controlled by four nearly collocated couples of piezoelectric sensors and actuators. The experimental results of the control showed some limitation, especially in the Multi-Input Multi-Output (MIMO) configuration. This was attributed to the specific type of sensors and their conditioning, as well as to the phase shifts present in the vibration at different points of the structure. An alternative approach is here undertaken by abandoning the configuration of quasi-perfect collocation between sensor and actuator. The positioning of the piezoelectric patches is still led by the strain energy value distribution on the plate; each couple of sensor and actuator is now placed on the same face of the plate but in two distinct positions, opposed and symmetrical with respect to the geometric center of the plate. Single-Input Single-Output (SISO) PPF is tested and the transfer function parameters of the controller are tuned according to the measured values of modal damping. Then the participation matrices necessary for the MIMO control algorithm are determined by means of a completely experimental procedure. PPF is able to mitigate the vibration of the first four natural modes, in spite of the rigid body motions due to the free boundary conditions. The amplitude reduction achieved with the non-collocated configuration is much larger than the one obtained with the nearby collocated one. The phase lags were addressed in the MIMO algorithm by correction phase delays, further increasing the performance of the controller.

Inverted E-Shape Micro Strip Patch for Dual Band

The objective of this paper is to design, and fabricate an inset fed rectangular microstrip patch antenna. In this paper we tested our design by using the electromagnetic solver, simulator (IE3D), was used to numerically investigate and optimize the proposed antenna configuration. Besides the structure external dimensions, the influence of the various antenna parameters on the resonant behavior have been observed. It has been found that the symmetrical position of patch over ground plane have clear impact on overall antenna performance. Many antenna structures have been modeled to demonstrate the effects of these parameters on the resulting dual band response. We design antenna for lower band (2.642.85GHz) and upper band (7.03-7.21GHz).

Autonomous buckling of micrometer-sized lipid-protein membrane patches constructed by Dictyostelium discoideum.

BackgroundThe cytosol of amoeba cells controls the membrane deformation during their motion in vivo. To investigate such ability of the cytosol of amoeba cell, Dictyostelium discoideum (Dictyostelium), in vitro, we used lipids extracted from Dictyostelium and commercially available phospholipids, and prepared substrate-supported lipid membrane patches on the micrometer scale by spin coating.ResultsWe found that the spin coater holder, which has pores (pore size = 3.1 mm) of negative pressure to hold the cover glass induced the concave surface of the cover glass. The membrane lipid patches were formed at each position in the vicinity of the holder pores and their sizes were in the range of 2.7 to 3.2 × 104 μm2. After addition of the cytosol extracted from Dictyostelium to the lipid membrane patches, through time-lapse observation with a confocal laser scanning fluorescence microscope, we observed an autonomous buckling of the Dictyostelium lipid patches and localized behaviours of proteins found within.ConclusionThe current method serves as the novel technique for the preparation of film patches in which the positions of patches are controlled by the holder pores without fabricating, modifying, and arranging the chemical properties of the solution components of lipids. The findings imply that lipid-binding proteins in the cytosol were adsorbed and accumulated within the Dictyostelium lipid patches, inducing the transformation of the cell-sized patch.Electronic supplementary materialThe online version of this article (doi:10.1186/1754-1611-9-3) contains supplementary material, which is available to authorized users.

Novel Absorber Based on Pixelated Frequency Selective Surface Using Estimation of Distribution Algorithm

A novel design method for absorber is presented, based on pixelated FSS with common effect of metallic pixels and lumped resistors. Considering the relative position of resistors and pixelated patches, the estimation of distribution algorithm is firstly employed to optimize the absorbing performance. Optimization process demonstrates its availability and high-efficiency. An absorption band (3.08-6.00 GHZ) below -6 dB formed with two strong absorption peaks is achieved, compared with the poor absorption performance in pixelated FSS without resistors. The simulated surface current distributions suggest that the loaded resistors are the main source for energy loss of incident electromagnetic wave, and provide an intuitive explanation to the correlation of optimized unit cell geometry and corresponding absorption peaks. The designed absorber is fabricated and the measured reflectivity curve fits well with the simulated results, which indicates that the availability of novel design method.

Soft-patchy nanoparticles: modeling and self-organization.

We consider a novel class of patchy particles inspired by polymer-based complex units where the limited valence in bonding is accompanied by soft interactions and incessant fluctuations of the patch positions, possibly leading to reversible modifications of the patch number and size. We introduce a simple model that takes into account the aforementioned features and we focus on the role played by the patch flexibility on the self-organization of our patchy units in the bulk, with particular attention to the connectivity properties and the morphology of the aggregated networks.