Large-scale Spatial Structure Research Articles

Fourier Image Analysis of Multiphase Interfaces to Quantify Primary Atomization

This work describes a post-processing scheme for multiphase flow systems to characterize primary atomization. The scheme relies on the 2D fast Fourier transform (FFT) to separate the inherently multi-scale features present in the flow results. Emphasis is put on the robust quantitative analysis enabled by this scheme, with this work specifically focusing on comparing atomizer nozzle designs. The generalized finite difference (GFD) method is used to simulate a high pressure gas injected into a viscous liquid stream. The proposed scheme is applied to time-averaged results exclusively. The scheme is used to evaluate both the surface and volume features of the fluid system. Due to the better recovery of small-scale features using the proposed scheme, the benefits of post-processing multiphase surface information rather than fluid volume information was shown. While the volume information lacks the fine-scale details of the surface information, the duality between interfaces and fluid volumes leads to similar trends related to the large-scale spatial structure recovered from both surface- and volume-based data sets.

Modeling Features of Field Line Resonance Observable by a Single Spacecraft at Saturn

AbstractThe observations of Southwood et al. (2021, https://doi.org/10.1029/2020JA028473), using data from the Cassini magnetometer from the final (proximal) orbits of the mission at Saturn, show large scale azimuthally polarized magnetic signals are always present near periapsis. The signals were attributed to standing Alfvén waves excited on the magnetic shells planetward of the Saturn D‐ring. The apparent absence of any systematic variation in frequency as the spacecraft crossed magnetic shells, implied that the signals were not simply locally excited standing Alfvén modes, but were pumped by coupling to global compressional eigenmodes excited in a cavity formed in the dayside magnetosphere. In this study, we use a numerical magnetohydrodynamic (MHD) model to test such theoretical explanations for the observations, by examining in detail the MHD wave coupling and large scale spatial structure of the signals. The modeling not only shows good agreement with the data but further provides new insight into features previously overlooked in the data. In particular, we show how the apparent frequency of a single spacecraft observation is affected by the phase variation present in a local field line resonance.

Spotted-wing drosophila, Drosophila suzukii (Diptera: Drosophilidae), exhibits large-scale spatial genetic structure across Canada but not fruit host–associated genetic structure

Abstract Spotted-wing drosophila, Drosophila suzukii, is a global pest of soft fruits that is capable of reproducing on a wide range of cultivated and wild plant species. In Canada, D. suzukii was first reported in British Columbia in 2009 and is now widespread across the country. Understanding the genetic structure of D. suzukii populations could be important for pest management if there are phenotypic differences between genetically distinct populations. For example, insect pest populations could respond differently to directional selection imposed by insecticides, differ in their host plant preferences, and vary in their susceptibility to biological control agents. Here, we used double-digest restriction site–associated DNA sequencing to examine large- and fine-scale patterns of the genetic structure of D. suzukii reared from fruit hosts in Canada. We found that this species has a large-scale spatial genetic structure; the flies collected formed two distinct genetic clusters, one of which was distinct to western Canada and the other to eastern Canada. At the local scale, D. suzukii populations showed no evidence of host-associated structuring in British Columbia, suggesting that pest management tactics may be best applied at the landscape level. Our results highlight the need to investigate phenotypic differences between western and eastern D. suzukii populations in Canada.

Accounting for spatial dependence improves relative abundance estimates in a benthic marine species structured as a metapopulation

Sea urchin (Loxechinus albus) is one of the most important benthic resource in Chile. Due to their large-scale spatial metapopulation structure, sea urchin subpopulations are interconnected by larval dispersion, so the recovery of local abundance depends on the distance and hydrodynamic characteristics of their spatial domain. Currently, this resource is evaluated with classical stock assessment models, using standardized catch per unit effort (an index of relative abundance) as a key piece of information to determine catch quotas and achieve sustainability. However, these estimates assume hyperstability for the total population, ignoring spatial dependence among fishing sites, which is a fundamental concept for populations structured as metapopulation. We develop a Bayesian catch standardization model with explicit spatial dependence to better address the structure of this population. The proposed model performs statistically better compared to a model without spatial dependence, based on leave-one-out cross-validation, and predictive distributions also show that parameter estimation is consistent with the data. We argue that incorporating spatial structure improves the estimated relative abundance index in a population structured as a metapopulation. Our improved index of abundance will lead to better assessments and management advice, thus improving the sustainability of the stock.

Field measurement of wind pressure on a large-scale spatial structure and comparison with wind tunnel test results

Due to the features of light weight, high flexibility, and slight damping, large-scale spatial structures are very sensitive to wind load. Thus, special attention must be paid to wind effect on large-scale spatial structures. A wind pressure field measurement was carried out to characterize the actual wind pressure of a large-span spatial structure. Meanwhile, it is also intended to provide reliable full-scale measurements for verification of wind tunnel test results widely used in the design and construction of structure. In this study, both wind tunnel test and field measurement are utilized to investigate the properties of the wind pressure acting on a typical large-scale spatial structure. Specifically, wind pressure coefficients, spatial distribution, probability density distribution (PDF), non-Gaussian characteristics, and power spectral density (PSD) are fully compared and discussed based on the results of the wind tunnel test and long-term field measurement. The comparison results show that generally the results of the wind tunnel test have good agreement with those of the field measurement. In the meanwhile, the discrepancies between them are also observed. This study aims to fully investigate the wind effects on large-scale spatial structure and enhance the understanding of wind loads.

Co-occurrence patterns and the large-scale spatial structure of benthic communities in seagrass meadows and bare sand

BackgroundSpecies distribution models are commonly used tools to describe diversity patterns and support conservation measures. There is a wide range of approaches to developing SDMs, each highlighting different characteristics of both the data and the ecology of the species or assemblages represented by the data. Yet, signals of species co-occurrences in community data are usually ignored, due to the assumption that such structuring roles of species co-occurrences are limited to small spatial scales and require experimental studies to be detected. Here, our aim is to explore associations among marine sandy-bottom sediment inhabitants and test for the structuring effect of seagrass on co-occurrences among these species across a New Zealand intertidal sandflat, using a joint species distribution model (JSDM).ResultsWe ran a JSDM on a total of 27 macrobenthic species co-occurring in 300,000 m2 of sandflat. These species represented all major taxonomic groups, i.e. polychaetes, bivalves and crustaceans, collected in 400 sampling locations. A number of significant co-occurrences due to shared habitat preferences were present in vegetated areas, where negative and positive correlations were approximately equally common. A few species, among them the gastropods Cominella glandiformis and Notoacmea scapha, co-occurred randomly with other seagrass benthic inhabitants. Residual correlations were less apparent and mostly positive. In bare sand flats shared habitat preferences resulted in many significant co-occurrences of benthic species. Moreover, many negative and positive residual patterns between benthic species remained after accounting for habitat preferences. Some species occurring in both habitats showed similarities in their correlations, such as the polychaete Aglaophamus macroura, which shared habitat preferences with many other benthic species in both habitats, yet no residual correlations remained in either habitat.ConclusionsFirstly, analyses based on a latent variable approach to joint distributions stressed the structuring role of species co-occurrences beyond experimental scales. Secondly, results showed context dependent interactions, highlighted by species having more interconnected networks in New Zealand bare sediment sandflats than in seagrass meadows. These findings stress the critical importance of natural history to modelling, as well as incorporating ecological reality in SDMs.

Processes shaping wintering waterbird communities in an intensive modified landscape: Neutral assembly with dispersal limitation and localized competition

• Processes structuring wintering waterbird communities use 2 complementary approaches. • Dispersal limitation maybe the main force shaping wintering waterbird community. • Dispersal constraints lead to competitive exclusion in isolated communities. Better understanding of the mechanisms structuring ecological communities is not only a long-term theoretical pursuit in ecology but also critical for biodiversity conservation. Here, we used two complementary approaches (β-diversity partitioning, and phylogenetic and functional null models) to explore the processes structuring wintering waterbird communities in the floodplain lakes of middle-lower Yangtze River (MLYR), China. We found that 1) neutral assembly might be the predominant process shaping the composition of wintering waterbird communities in MLYR; 2) compared to environmental factors, spatial variables, in particular those describing the large scale spatial structure among lakes, contributed more in explaining the functional and phylogenetic composition variations across the region, indicating dispersal constraints might strongly mediate neutral processes. The dispersal constraint could be imposed by movement barriers caused by anthropogenic landscape modification, site fidelity, or both; and 3) strong dispersal constraints could lead to competitive exclusion superimposed over neutrally assembly isolated communities, a hypothesis confirmed by the α- and β-null models. These findings provide strong support for the importance of conserving and improving ecological connectivity at the regional scale as well as habitat quality enhancement at lake scale.

Damage Detection for Large-Scale Grid Structure Based on Virtual Axial Strain

To identify the damaged beams in large-scale spatial structure, a damage indicator based on virtual axial strain calculated from mode shape vectors was proposed. The damage detection process was performed based on the dynamic simulation flowchart. Firstly, random signals were used for excitation and the damage was simulated by decreasing beam elasticity modulus. Then, the NEWMARK-β precision direct integral method was appreciated for calculating time history response. Finally, the frequency-domain decomposition method only using output response signal was selected for modal parameter estimation. A double-layer grid structure was taken as example for verifying the damage detection method. Results indicate that the proposed indicator was insensitive to environmental noise and capable of localizing multiple damaged members in space structure without the baseline data.

Local contribution to beta diversity is negatively linked with community-wide dispersal capacity in stream invertebrate communities

It is increasingly well understood that stream communities are regulated by both local niche and regional dispersal processes, but comprehensive tests of these factors with datasets that cover extensive spatial and temporal scales are rare. Based on 1180 benthic invertebrate community samples from 2005 to 2012 in central low mountain streams of Germany, we tested the hypotheses that: 1) local contribution to beta diversity (LCBD: a measure of the uniqueness of communities) would decline with increasing average community dispersal capacity; and 2) owing to the relatively large spatial extent of the study region, regional dispersal processes would override local niche controls in structuring community composition. We found considerable temporal variation in LCBD and a negative correlation between LCBD and community dispersal capacity. However, no statistically significant correlation between species contribution to beta diversity (SCBD) and species dispersal capacity was observed. The large-scale spatial structure among locations (representative of dispersal limitation) was important in structuring benthic communities. Although much of the variation was explained by the shared effects of local processes and large-scale spatial variables, environmental controls were stronger than regional processes in few cases in the variance partitioning analysis, with the annual mean temperature and mean diurnal range of temperature being the important drivers. Given the highly varied correlates of beta diversity over time, we urge researchers to focus on not only spatial variation in diversity, but also the context of temporal variation.

Effects of solid particles and wall roughness on turbulent boundary layer in a two-phase horizontal channel flow

Particle image velocimetry (PIV) is used to study the horizontal channel flow over smooth and rough walls, and single-phase flow and particle-laden flow with two different particle diameters are analyzed. The phenomenon of the wall similarity hypothesis is verified in single-phase flow but affected by particles in particle-laden flows. The pyramidal rough elements cause a velocity defect and shorten the length scale of the vortex. The streamwise and wall-normal Reynolds stresses are enhanced by wall roughness. Two kinds of particles with different Stokes numbers are used in the experiment. The collision and dragging effect of particles in the inner region offset the influence of wall roughness on the mean velocity profile. The introduction of particles tends to increase the streamwise Reynolds stress, but makes the peak of the Reynolds stress move to a higher wall-normal position, which is contrary to the effect of wall roughness. Quadrant analysis indicates that the wall roughness and particles show a converse effect on quadrant events, but neither change the majority of second and forth quadrant events. The analysis of the spatial structure of turbulence shows that the small scale spatial structure is less affected by wall roughness compared with the large scale spatial structure. According to the statistics of the particle distribution, it was found that particles with a larger Stokes number show a more distinct prioritized deposition in the inner region, and the deposition of particles is reduced due to the existence of rough elements.

Voyager Evidence for Large-Scale Structure in Plasma and Energetic Particle Behavior Beyond the Termination Shock

Voyager 1 crossed the termination shock at the end of 2004, more than a full solar cycle ago. Similarly, Voyager 2 crossed it and entered the heliosheath at the end of August, 2007, which was before the beginning of SC 24. Voyager 1 crossed the heliopause in August, 2012, when solar activity was high. Thus, at each spacecraft changing readings over time in the heliosheath could be due either to the increasing solar distance or to changing solar activity. Comparing energetic particle observations by the two spacecraft at corresponding distances shows cases for which distance is more important. In particular, at both spacecraft the spectral index of protons in the anomalous cosmic ray energy range shows corresponding variations with distance, despite the differing times and the great separation between the spacecraft, and so do ratios of electron count rates in differential energy bands. These comparisons provide insight into the expectation that Voyager 2 will soon cross the heliopause. Consideration of the large-scale spatial structure of moving flare-generated disturbances also provides insight into particle behaviour associated with the plasma wave events observed by Voyager 1 since it crossed the heliopause. We discuss a variety of observations of these phenomena from the heliosheath and the local interstellar medium and suggest a possibility for future simulations.

Greenland Ice Sheet Surface Topography and Drainage Structure Controlled by the Transfer of Basal Variability

Ice flow can transfer variations in basal topography and basal slipperiness to the ice surface. Recent developments in this theory have made it possible to conduct numerical experiments to predict mesoscale surface topographical undulations and surface relief on an ice sheet-scale. Focussing here on the contemporary Greenland Ice Sheet (GrIS), we demonstrate that the theory can be used to predict the surface relief of the ice sheet from bed topography, ice thickness and basal slip ratio datasets. In certain regions of the GrIS our approach overestimates, while in others underestimates, the observed surface relief. The magnitude and spatial pattern of these mismatches correspond with the theory’s limitations and known uncertainties in the bed topography and basal slip ratio datasets. Our prediction experiment establishes that the first-order control on GrIS surface relief is basal topography modulated by ice thickness, surface slope and basal slip ratio. Additional analyses show that the surface relief, which is controlled by the bed-to-surface transfer of basal topography, preconditions the large scale spatial structure of surface drainage, with other factors such as surface runoff modulating the actual drainage system through influencing the temporal evolution of meltwater features. It follows that the spatial structure of surface drainage depends strongly on the transfer of basal topography to the ice surface. These findings represent an important step towards investigating and understanding the net long-term (>102 years) effect of surface drainage on ice sheet mass balance and dynamics during deglaciation events.

Genetic structure and genetic diversity of the endangered grassland plant Crepis mollis (Jacq.) Asch. as a basis for conservation management in Germany

Plant diversity is decreasing mainly through anthropogenic factors like habitat fragmentation, which lead to spatial separation of remaining populations and thereby affect genetic diversity and structure within species. Twenty populations of the threatened grassland species Crepis mollis were studied across Germany (578 individual plants) based on microsatellite genotyping. Genetic diversity was significantly higher in populations from the Alpine region than from the Central Uplands. Furthermore, genetic diversity was significantly positively correlated with population size. Despite smaller populations in the Uplands there were no signs of inbreeding. Genetic differentiation between populations was moderate (F ST = 0.09) and no isolation by distance was found. In contrast, large-scale spatial genetic structure showed a significant decrease of individual pairwise relatedness, which was higher than in random pairs up to 50 km. Bayesian analyses detected three genetic clusters consistent with two regions in the Uplands and an admixture group in the Alpine region. Despite the obvious spatial isolation of the currently known populations, the absence of significant isolation by distance combined together with moderate population differentiation indicates that drift rather than inter-population gene flow drives differentiation. The absence of inbreeding suggests that pollination is still effective, while seed dispersal by wind is likely to be impaired by discontinuous habitats. Our results underline the need for maintaining or improving habitat quality as the most important short term measure for C. mollis. For maintaining long-term viability, establishing stepping stone habitats or, where this is not possible, assisted gene flow needs to be considered.

Activation of the alpha-globin gene expression correlates with dramatic upregulation of nearby non-globin genes and changes in local and large-scale chromatin spatial structure

BackgroundIn homeotherms, the alpha-globin gene clusters are located within permanently open genome regions enriched in housekeeping genes. Terminal erythroid differentiation results in dramatic upregulation of alpha-globin genes making their expression comparable to the rRNA transcriptional output. Little is known about the influence of the erythroid-specific alpha-globin gene transcription outburst on adjacent, widely expressed genes and large-scale chromatin organization. Here, we have analyzed the total transcription output, the overall chromatin contact profile, and CTCF binding within the 2.7 Mb segment of chicken chromosome 14 harboring the alpha-globin gene cluster in cultured lymphoid cells and cultured erythroid cells before and after induction of terminal erythroid differentiation.ResultsWe found that, similarly to mammalian genome, the chicken genomes is organized in TADs and compartments. Full activation of the alpha-globin gene transcription in differentiated erythroid cells is correlated with upregulation of several adjacent housekeeping genes and the emergence of abundant intergenic transcription. An extended chromosome region encompassing the alpha-globin cluster becomes significantly decompacted in differentiated erythroid cells, and depleted in CTCF binding and CTCF-anchored chromatin loops, while the sub-TAD harboring alpha-globin gene cluster and the upstream major regulatory element (MRE) becomes highly enriched with chromatin interactions as compared to lymphoid and proliferating erythroid cells. The alpha-globin gene domain and the neighboring loci reside within the A-like chromatin compartment in both lymphoid and erythroid cells and become further segregated from the upstream gene desert upon terminal erythroid differentiation.ConclusionsOur findings demonstrate that the effects of tissue-specific transcription activation are not restricted to the host genomic locus but affect the overall chromatin structure and transcriptional output of the encompassing topologically associating domain.

Assessment of the Uncertainties in Arctic Low-Level Temperature Inversion Characteristics in Radio Occultation Observations

The variation of low-level inversion characteristics is one of the important factors for Arctic amplification. Radiosonde (RS) observations are one of the reliable tools to study Arctic inversions. However, they provide limited information on the spatial distribution of temperature inversions. The radio occultation (RO) technique can provide accurate, all-weather, high vertical resolution atmospheric parameter profiles over both land and ocean. In this paper, the RO technique is investigated to estimate the inversions, and their uncertainties are assessed via comparing with the RS inversions. Results show that the inversions (base, depth, and strength) from RS and RO observations are lower, deeper, and stronger in winter than in autumn, spring, and summer. Moreover, comparisons of spatiotemporally synchronized RO and RS inversions (i.e., Scheme I) during 2007–2013 reveal that the former are higher, deeper, and weaker than the latter. Further comparisons of RS and $5 {^{\circ }} \times 5 {^{\circ }}$ gridded RO inversions (i.e., Scheme II) show smaller overall standard deviations than Scheme I, indicating that the gridded RO observations can better describe the large-scale spatial structure of temperature inversions. Furthermore, corrections of the observed remarkable systematic differences between RO and RS inversions in both the schemes are also made. The results show that the RO inversions can be well calibrated, and that greater improvements in RO inversions calibration are achieved in Scheme II than in Scheme I. Therefore, the RO technique could be a potential tool to study the Arctic low-level temperature inversions as well as improve our understanding of Arctic climate change.

Coupling the Permeability and Permittivity of Space to the Electron Orbital Time: Potential Phase Shift Between Entanglement Latency and the Universe’s Final Epoch

The strength of the magnetic field for different ratios of matter densities relative to the permittivity of a vacuum solves for values approaching the velocity of light. When the strength of the field associated with densities similar to liquid water, ice, or stars (such as the Sun) is considered with respect to the magnetic permeability and average mass density of the universe, the emergent velocity is ~10²³ m•s^-1. This value has been derived from several approaches as the latency for excess correlation or “entanglement” and is consistent with a process that might explain the integrity of large-scale spatial structure over distances that are within fractions of the universe’s present diameter. The estimated latency to traverse this diameter with this velocity relative to the total duration of the universe (the final epoch) when considered as an Aharanov-Bohm type phase shift, results in an energy quantum that is convergent with Planck’s constant. One interpretation is that the duration of a single electron’s orbit is the phase shift between duration (latency) to traverse the universe and its total duration (final epoch). If this approach is valid then non-local effects and related excess correlations (Schrödinger’s “entanglement”) between photon emissions and specific dynamics of densities similar to liquid water may be a property of these conditions immersed within an average universal mass density of about one proton per cubic meter. It may also accommodate the challenges of understanding the apparent homogeneity across large scale space.

Geographic distribution, large-scale spatial structure and diversity of parasitoids of the seed-feeding beetle Acanthoscelides macrophthalmus.

Bruchine beetles are highly host-specific seed feeders during the larval stage. Although some specific parasitoid families have been recorded attacking bruchine beetles, most studies have been done at small spatial scales. Therefore, the current knowledge about the diversity and the geographic distribution of parasitoid species parasitizing bruchines is scarce, especially at a wide geographic area that extends over large distances through a latitudinal cline (i.e. large-scale spatial structure). The present study determined the species richness and evenness of parasitoids attacking the bruchine beetle Acanthoscelides macrophthalmus feeding on Leucaena leucocephala seeds, examined their geographic distribution, and characterized the large-scale spatial structure in parasitoid species composition. A total of 1420 parasitoids (all Hymenoptera) belonging to four families, five subfamilies and eight species were collected (genera: Horismenus, Paracrias, Urosigalphus, Stenocorse, Chryseida, Eupelmus). Most parasitoid species showed wide spatial distribution, high evenness in species abundance and the species richness estimators were close to stabilization (approximately eight species). Overall, greater similarity was observed in the species composition of plant populations near to each other than those farther apart, revealing a large-scale spatial structure in parasitoid species composition.

Genome-environment association study suggests local adaptation to climate at the regional scale in Fagus sylvatica.

The evolutionary potential of long-lived species, such as forest trees, is fundamental for their local persistence under climate change (CC). Genome-environment association (GEA) analyses reveal if species in heterogeneous environments at the regional scale are under differential selection resulting in populations with potential preadaptation to CC within this area. In 79 natural Fagus sylvatica populations, neutral genetic patterns were characterized using 12 simple sequence repeat (SSR) markers, and genomic variation (144 single nucleotide polymorphisms (SNPs) out of 52 candidate genes) was related to 87 environmental predictors in the latent factor mixed model, logistic regressions and isolation by distance/environmental (IBD/IBE) tests. SSR diversity revealed relatedness at up to 150m intertree distance but an absence of large-scale spatial genetic structure and IBE. In the GEA analyses, 16 SNPs in 10 genes responded to one or several environmental predictors and IBE, corrected for IBD, was confirmed. The GEA often reflected the proposed gene functions, including indications for adaptation to water availability and temperature. Genomic divergence and the lack of large-scale neutral genetic patterns suggest that gene flow allows the spread of advantageous alleles in adaptive genes. Thereby, adaptation processes are likely to take place in species occurring in heterogeneous environments, which might reduce their regional extinction risk under CC.

Temporal evolution of soil moisture statistical fractal and controls by soil texture and regional groundwater flow

Soil moisture statistical fractal is an important tool for downscaling remotely-sensed observations and has the potential to play a key role in multi-scale hydrologic modeling. The fractal was first introduced two decades ago, but relatively little is known regarding how its scaling exponents evolve in time in response to climatic forcings. Previous studies have neglected the process of moisture re-distribution due to regional groundwater flow. In this study we used a physically-based surface-subsurface processes model and numerical experiments to elucidate the patterns and controls of fractal temporal evolution in two U.S. Midwest basins. Groundwater flow was found to introduce large-scale spatial structure, thereby reducing the scaling exponents (τ), which has implications for the transferability of calibrated parameters to predict τ. However, the groundwater effects depend on complex interactions with other physical controls such as soil texture and land use. The fractal scaling exponents, while in general showing a seasonal mode that correlates with mean moisture content, display hysteresis after storm events that can be divided into three phases, consistent with literature findings: (a) wetting, (b) re-organizing, and (c) dry-down. Modeling experiments clearly show that the hysteresis is attributed to soil texture, whose “patchiness” is the primary contributing factor. We generalized phenomenological rules for the impacts of rainfall, soil texture, groundwater flow, and land use on τ evolution. Grid resolution has a mild influence on the results and there is a strong correlation between predictions of τ from different resolutions. Overall, our results suggest that groundwater flow should be given more consideration in studies of the soil moisture statistical fractal, especially in regions with a shallow water table.

Optimal Sensor Placement for the Tower Structure Based on Key Components

In order to improve the large-scale complex spatial structure sensor placement, this paper puts forward an optimal sensor placement method for the tower structure based on key components. According to this method, different probabilities of the structure system’s reliability degree caused by the same damage degree of components are firstly calculated; then component weight coefficients are introduced to measure the relative importance of various components in the whole structure system; the key components of the structure system are defined according to the value of weight coefficients; then modal parameters are adopted to analyze the damage sensitivity of the key components and to find out the vibration modes and measuring points sensitive to the damage of key components, thus to finish the sensor placement. Fully considering the structure characteristics, this method can solve the optimization issues, including the quantity of measurement points and the position, and avoid the complex iterative algorithm and modal expansion error, so it contributes to better controlling the structure state. Finally, through the calculation example of a communication tower, the feasibility and the validity of the method are proved.