Analysis Of Scale Effects Research Articles

Statistical analysis of scale effect on equivalent elastic modulus of jointed rock masses

The study of scale effects plays an important role in the evaluation of mechanical properties of rock masses. There have been many studies on this topic; however, few have been able to effectively analyze relationships between size and deformation properties analytically. This paper presents an investigation of scale effects on deformation properties of jointed rock masses by using analytical and statistical methods. First, the analytical formula for E eq (equivalent elastic modulus) of jointed rock with a parallel joint set was derived. This derivation is related to a geometrical parameter ρ’, defined as joint trace length per unit area. Second, model of a half-space rock with a parallel joint set was constructed and subsequently sampled to specimens with different locations and lengths. The expectation and standard deviation of the ρ’ of rock samples were derived to statistically describe scale effect of ρ’. Then, the scale effect of 1/E eq (equivalent elastic compliance) was analyzed. The investigation shows that expectation of 1/E eq is a constant with varying size and standard deviation of 1/E eq decreases and periodically fluctuates with increasing size. The applicability of the conclusions was discussed, and some extended studies on stochastic jointed rock masses were made. Finally, representative elementary volumes of the rock model were determined according to the analytical solutions.

耦合种群动态的生境格局变化分析粒度与景观因子选择——以盐城越冬丹顶鹤及其生境的变化为例

PDF HTML阅读 XML下载 导出引用 引用提醒 耦合种群动态的生境格局变化分析粒度与景观因子选择——以盐城越冬丹顶鹤及其生境的变化为例 DOI: 10.5846/stxb201412102450 作者: 作者单位: 南京农业大学 土地管理学院;College of Land Management;College of Land Management,南京农业大学 土地管理学院;College of Land Management;College of Land Management 作者简介: 通讯作者: 中图分类号: 基金项目: 江苏省青蓝工程项目 Grain size and landscape indices selection by coupling population dynamics and habitat pattern analysis: a case study of wintering red-crowned crane and its habitat in Yancheng Author: Affiliation: Nanjing Agriculture University,Nanjing agriculture 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:选择盐城珍禽国家级自然保护区,以丹顶鹤越冬生境景观与种群动态这一格局-过程关系为切入点,尝试从丹顶鹤最小存活面积特征与种群动态视角探讨一下最佳粒度、景观格局变化分析的指数遴选方法。结果发现:根据丹顶鹤最小生存面积确定200m为最大转换粒度,综合景观指数随空间粒度变化的规律和粒度转换精度损失评价的结果,确定最佳分析粒度为70m。在众多景观因子中,运用Spearman秩相关分析,再利用逐步回归分析建立起景观与丹顶鹤数量指标间的联系,最终筛选出反映景观面积(CA)和空间格局(IJI,ENN_MN)的3种影响显著景观因子,其解释贡献率(累计R2)达到70.5%,且其所代表的生境景观的组成和结构信息较为客观地反映出研究区丹顶鹤种群动态分布的显示状态。与纯粹的景观指数分析相比,这种方法更能反应景观格局演变特征的特定生态学意义。 Abstract:Landscape pattern is scale-dependent. Thus, understanding landscape structure and functioning requires multiscale information. Scaling functions are the most precise and concise methods for explicitly quantifying multiscale characteristics. If landscape indices are ecologically relevant and reflect important attributes of spatial pattern, they can functionally link the dynamics of ecological processes to landscape structure. Therefore, the selection of appropriate scale (e.g., grain size) and landscape indices are critical to landscape pattern analysis. The major objective of this study was to explore how optimal grain size and landscape indices can be selected for landscape pattern analysis, to improve our understanding and prediction of ecological processes. For this, we conducted a case study on wintering Red-crowned crane and its habitat in Yancheng. To obtain the optimal grain size for landscape pattern analysis of the wintering habitat of the Red-crowned crane, we followed two steps. The first step was scale (grain) effect analysis, to find a grain size that the test metrics could detect in case of any variation (sensitivity). In this step, the minimum survival area for the species was considered for identifying the maximum grain size for scaling. The second step was accuracy test by evaluating the loss of landscape area and patch numbers in each grain size level. The optimal grain size was obtained by integrated analysis of the results from the above two steps. In landscape indices selection, 19 landscape metrics (computed at the optimal grain size) were subjected to Spearman rank correlation analysis to assess the independence. Then, step-wise regressions were performed to evaluate the effects of the spatial attributes (landscape indices with higher independence) at three hotspots on the abundance of cranes (based on population dynamics of the past 12 years[1]). Variables with significance level above 90% were selected as the optimal landscape indices for pattern analysis. The results showed the following: (1) on the basis of the minimum survival area of the red-crowned crane, 200 m was the highest obtained grain size, and 70 m was the optimal grain size identified by integrating the results of scale (grain) effect and accuracy after assessing the grain conversion area loss. (2) Effects of landscape patterns at the hotspots were analyzed using 8 pairs of landscape indices (results of metrics for the most suitable and supplement habitat types for cranes were computed) as the independent variables. Three landscape indices (CA, IJI, ENN_MN) of two habitat types were found to be significant (R2 = 70.5%). (3) The selected optimal landscape indices of the supplement habitat showed positive effect for isolation and negative effect for area size on population abundance. Our results imply that supplement habitat may provide complementary resource sites for cranes, but continued species concentration at these habitats may negatively affect crane abundance and distribution due to induced human disturbance. Our combined findings on optimal grain size and landscape indices proved to be satisfactory for landscape pattern analysis, suggesting that our approaches are reasonable. Further, compared to landscape pattern analysis by using random grain size and simple landscape metrics, the results obtained using our approaches, as shown in this case study, are ecological relevant. 参考文献 相似文献 引证文献

Numerical identification of classical and nonclassical moduli of 3D woven textiles and analysis of scale effects

Homogeneous anisotropic couple-stress continuum model as substitutes of 3D woven textiles are presently developed. The architecture of the considered fabric preforms is obtained from an idealized geometry and organization of the yarns within a representative unit cell. The effective properties are obtained based on the finite element response of the representative volume element (RVE) under prescribed boundary conditions. Specific boundary conditions including both traction and displacement boundary conditions are applied on the structure boundaries. The effective classical and nonclassical mechanical moduli are deduced by an equivalent strain energy method. The characteristic bending lengths are identified from the resulting homogenized moduli. We model 2D and 3D textiles either as a one phase solid (dry textiles), or as a two-phase material consisting of the set of yarns and a softer surrounding phase representing the resin. The effects of scale on the predicted classical and nonclassical moduli of these textiles are investigated by varying the size of the textile unit cell over which the boundary conditions are applied. The analysis delivers classical moduli that are independent of unit cell size, whereas the couple stress moduli depend on the cell size. The developed approach is quite general and applicable to any composite materials.

The dynamics of productivity in Swiss universities

This paper analyzes the productivity of Swiss university departments between 1995 and 2012. Using a parametric input distance function we estimate and decompose the Malmquist productivity indexes in line with Fuentes et al. (J Product Anal 15:79–94, 2001) and Atkinson (J Bus Econ Stat 21:284–294, 2003). The adopted model is a mixed-effects model with department-specific fixed effects and random time trends. An autoregressive stochastic term is used to model inefficiency shocks with gradual dissipation by adaptation and learning. The results indicate a negative trend in Malmquist index starting from 2002, with an average rate of about 1 % per year. However, our analysis of scale effects indicates that this decline is more or less offset by universities’ constant expansion and the resulting economies of scale. The results point to various patterns of overall productivity change across scientific fields that are closely related to potential productivity gains due to scale economies. In contrast to some previous studies we do not find any significant relation between productivity development and the Bologna reform.

Extended Finite Element Numerical Analysis of Scale Effect in Notched Glass Fiber Reinforced Epoxy Composite

Abstract Nominal strength reduction in cross ply laminates of [0/90]2s is observed in tensile tests of glass fiber composite laminates having central open hole of diameters varying from 2 to 10 mm. This is well known as the size effect. The extended finite element method (XFEM) is implemented to simulate the fracture process and size effect (scale effect) in the glass fiber reinforced polymer laminates weakened by holes or notches. The analysis shows that XFEM results are in good agreement with the experimental results specifying nominal strength and in good agreement with the analytical results based on the cohesive zone model specifying crack opening displacement and the fracture process zone length

Application of bivariate mapping for hydrological classification and analysis of temporal change and scale effects in Switzerland

Hydrological classification schemes are important tools for assessing the impacts of a changing climate on the hydrology of a region. In this paper, we present bivariate mapping as a simple means of classifying hydrological data for a quantitative and qualitative assessment of temporal change. Bivariate mapping consists of classifying map objects into discrete classes based on the values of two variables. We demonstrate the application of bivariate mapping to distributed hydro-climatic model outputs for the whole of Switzerland with a cell size of 200m and compared the resulting bivariate maps with an existing classification of Swiss river regimes. The effects of scale were investigated by comparing these raster maps with a map showing the same variables aggregated to sub-basins with a mean area of 40km2. Finally, maps of the current state were compared with predictions for future periods based on various model chains and greenhouse gas emission scenarios. For the map comparisons, four measures of association and two measures of agreement were used.Of all the variable pairs tested, a bivariate map combining runoff and snowmelt contribution to runoff obtained the highest similarity scores with the map of river regimes, which suggests a strong link between the combination of these variables and intra-annual streamflow variations. Also, this classification offers new insights, as it includes absolute values of runoff, which are often ignored in classification schemes. Comparing current-state maps with future predictions indicated that the magnitude of change is reflected in the patterns of bivariate maps, with lower agreement scores for predictions further away in time or when higher greenhouse gas emissions are assumed. Furthermore, a visualization of the spatial distribution of agreement scores allows a qualitative assessment of the magnitude of change for different regions, and an analysis of the differences in spatial patterns of predictions based on different model chains or emission scenarios.

Dam-Break Flood Routing Simulation and Scale Effect Analysis Based on Virtual Geographic Environment

Because of the barrier lake affected by highly changing and complex environment, it is always a great challenge that proper actions must be performed within a limited amount of time. Thus, how to scientifically and efficiently analyze the dam-break risk of the barrier lake and its impact area is very important for barrier lake disposal and downstream communities transfer. To improve the efficiency and the accuracy of the dam-break flood routing simulation, this paper mainly focuses on the construction of the virtual geographic environment (VGE) system and the scale effect analysis. Unlike most of the current cellular automata (CA)-based flood simulation systems, the proposed VGE system can offer an intuitive, efficient, and interactive visualization environment through which users can explore complicated spatial information and conduct risk assessment work. Some key technologies including the CA model of dam-break flood, the VGE system framework, the impact analysis method, and the scale effect analysis method were discussed in detail. A prototype system was developed to support dam-break simulation and risk analysis of the Xiaojiaoqiao barrier lake in Anxian County, Sichuan Province of China. By means of a variety of cell scales effect analysis experiments, the adaptation scope and characteristics of multiscale cells were obtained to implement the simulation analysis of the dam-break flood routing better. The proposed VGE system can improve the efficiency of risk assessment and decision-making.

Taylor-plasticity-based analysis of length scale effects in void growth

We have studied the void growth problem by employing the Taylor-based strain gradient plasticity theories, from which we have chosen the following three, namely, the mechanism-based strain gradient (MSG) plasticity (Gao et al 1999 J. Mech. Phys. Solids 47 1239, Huang et al 2000 J. Mech. Phys. Solids 48 99–128), the Taylor-based nonlocal theory (TNT; 2001 Gao and Huang 2001 Int. J. Solids Struct. 38 2615) and the conventional theory of MSG (CMSG; Huang et al 2004 Int. J. Plast. 20 753). We have addressed the following three issues which occur when plastic deformation at the void surface is unconstrained. (1) Effects of elastic deformation. Elasticity is essential for cavitation instability. It is therefore important to guarantee that the gradient term entering the Taylor model is the effective plastic strain gradient instead of the total strain gradient. We propose a simple elastic–plastic decomposition method. When the void size approaches the minimum allowable initial void size related to the maximum allowable geometrically necessary dislocation density, overestimation of the flow stress due to the negligence of the elastic strain gradient is on the order of near the void surface, where l, εY and R0 are, respectively, the intrinsic material length scale, the yield strain and the initial void radius. (2) MSG intrinsic inconsistency, which was initially mentioned in Gao et al (1999 J. Mech. Phys. Solids 47 1239) but has not been the topic of follow-up studies. We realize that MSG higher-order stress arises due to the linear-strain-field approximation within the mesoscale cell with a nonzero size, lε. Simple analysis shows that within an MSG mesoscale cell near the void surface, the difference between microscale and mesoscale strains is on the order of , indicating that when , the higher-order stress effect can make the MSG result considerably different from the TNT or CMSG results. (3) Critical condition for cavitation instability. When Taylor plasticity replaces classical plasticity as the flow rule, the critical cavitation condition, appearing when the derivative of the externally imposed mean stress with respect to the current void radius becomes zero, is rewritten analytically according to the Leibniz relation and found to be very different from the classical counterpart.

Scale effect analysis of the relationships between urban heat island and impact factors: case study in Chongqing

Several indices, including the normalized difference vegetation index (NDVI), normalized difference build-up index (NDBI), and normalized difference water index (NDWI), were retrieved from the Landsat 5 Thematic Mapper (TM) images, and the land surface temperature (LST) was reversed by the thermal radiation transfer model. Next, with the help of the thermal field variance index from LST, characteristics of spatial distribution of urban heat island were analyzed. Then, the regression models between LST and the three indices were formed by the least-squares method after they were aggregated from 30 to 120, 240, 480, 960, and 1200 m, and the relationships between the accuracies of the regression models and spatial scales were analyzed quantitatively. Finally, results from the experiment exemplified by Chongqing show that at all these spatial scales, both NDVI and NDWI are negatively correlated with LST and NDBI is positively correlated with LST. At the same spatial scale, cooling effect by NDWI acting upon LST is superior to that by NDVI, while inferior to that by NDBI to enhance LST. The fitting determination coefficients (R 2 ) of the regression models of LST and NDVI, NDBI, and NDWI increase from 0.23 (30 m) to 0.57 (1200 m), from 0.34 (30 m) to 0.70 (1200 m), and from 0.31 (30 m) to 0.68 (1200 m), respectively. Further, the R 2 of all of the regression models and spatial scales have positive logarithmic function relations, while the standard deviation and spatial scale have negative logarithmic function relations correspondingly, and the R 2 of all of the logarithmic models are >0.95 . The heat islands of Chongqing are roughly along northeast–southwest directions, while the heat islands of the urban core area, such as Yuzhong district, are not obvious due to the influence of the Yangtze River and the Jialing River.

Analysis of Energy Consumption in China and the Driving Factors Based on MRCI

Using the complete structure of input output analysis theory and no residual decomposition method (MRCI) effect on the growth of energy consumption China and corresponding contribution rate of quantitative analysis of scale effect, the contribution rate of 100.99%, the structure of production effect, the contribution rate of 38.16%, per capita energy efficiency reached 9.05%, population scale contribution rate of 12.11%, the use of the structure effect reached 6.09%, distribution structure effect is up to 5.83%, pushing the energy consumption growth Chinese role; energy intensity effect contribution rate of-72.23% China, inhibit the growth of energy consumption, saving energy and reducing consumption of our country plays an important role.

Scale effect analysis of early-termination fixed-complexity sphere detector

In this paper, we show that the early-termination fixed-complexity sphere detector (ET-FSD) has a scale effect when being employed in multi-antenna systems that have to detect signals of multiple users under the constraint of sum complexity. The so-called scale effect stands for a kind of effect in which the complexity per user can be reduced as the number of users increases without loss of diversity order. The main contributions of this study are as follows: (1) we establish a mathematical model based on the large deviation principle to apply the concept of scale effect to ET-FSD; (2) we prove the existence of the scale effect of ET-FSD in a multi-user scenario; and (3) we demonstrate that within multi-user systems, the scale effect can be exploited to realize ET-FSD that has the optimal performance in the point view of diversity order under polynomial complexity constraint per user.

A trapezoidal flexoelectric accelerometer

In this article a new acceleration sensor using flexoelectric barium strontium titanate cantilever was designed, fabricated, and tested for vibration monitoring. The flexoelectric sensors were configured as a trapezoidal unimorph with a barium strontium titanate layer bonded onto a steel substrate. Seismic mass was attached to the unimorph tip to amplify the transverse flexoelectric response of the barium strontium titanate layer. The theoretical model was developed and validated by vibration tests using the prototyped flexoelectric unimorph. The prototyped accelerometer with thickness of 0.1 mm and length and width in millimeters showed a stable sensitivity of 0.84 pC/g over the frequency range of 100 Hz–1.6 kHz. The aging property of the flexoelectric material was demonstrated to be much better than that of the reported piezoelectric materials right after poling. Scaling effect analysis was also performed for flexoelectric unimorphs. The test results and initial scaling effect analysis indicate that micro/nano flexoelectric sensing holds promise for a broad range of applications.

Scaling effects of landscape metrics: a comparison of two methods

Scale and scaling are important conceptual and methodological issues in geography and ecology. Grain, one indicator of scale, is widely used to determine the scaling behaviors of landscape spatial patterns represented by landscape metrics. This study compared two strategies, including a high-resolution-data-based resampling (RS) approach and a multisource and multiresolution data (MSMRD) approach, to quantify the grain effects of nine commonly used landscape metrics determined by FRAGSTATS software. Three adjacent, small watersheds in the central Loess Plateau of China were selected as study sites. Using the RS and MSMRD approaches, five and seven landscape metrics, respectively, were detected to have significant and mostly linear grain effects. The MSMRD approach was more effective in detecting grain effects, and landscape areas were found to be important in the grain effects of landscape metrics. Changing grain means changing the spatial analysis or landscape observation scales and, thus, the quality of landscape pattern information acquired, without impacting the ground-surface landscape pattern. In this sense, the analysis of scale effects through the manipulation of grains can be practically implemented in spatial data processing and selection for landscape modeling tasks. This paper also highlights gaps in present scaling research on landscape metrics by their numerical responses to grain sizes, with the conceptual and mathematical formulations largely neglected. The latter, however, is more important in research concerning landscape metrics, such as scaling, correlation, and even the interaction between landscape patterns and ecological processes.

On Scale Correction Model of Coastline and its Application for Coastline Remote Sensing Monitoring

This paper focuses on the scale correction of coastline extracted from remote sensing images. Measurement of coastline is one of the basic and core work of coastal zone remote sensing monitoring projects. Based on analysis of coastline scale effect and multi-scale simulation of coastline, a scale correction method is presented for remote sensing coastline. This method can be used to correct remote sensing coastline to specified map scale, in order to obtain high-precision remote sensing monitoring results of coastline. The results of application example showed that the absolute error of coastline length is reduced to about one third of the original error after correction using the presented method. So the presented method can increase the accuracy of remote sensing coastline for specified scale substantially.

Combustion performance and scale effect from N2O/HTPB hybrid rocket motor simulations

HRM code for the simulation of N2O/HTPB hybrid rocket motor operation and scale effect analysis has been developed. This code can be used to calculate motor thrust and distributions of physical properties inside the combustion chamber and nozzle during the operational phase by solving the unsteady Navier–Stokes equations using a corrected compressible difference scheme and a two-step, five species combustion model. A dynamic fuel surface regression technique and a two-step calculation method together with the gas–solid coupling are applied in the calculation of fuel regression and the determination of combustion chamber wall profile as fuel regresses. Both the calculated motor thrust from start-up to shut-down mode and the combustion chamber wall profile after motor operation are in good agreements with experimental data. The fuel regression rate equation and the relation between fuel regression rate and axial distance have been derived. Analysis of results suggests improvements in combustion performance to the current hybrid rocket motor design and explains scale effects in the variation of fuel regression rate with combustion chamber diameter.

New Approach of Geomechanical Properties by Scale Effect and Fractal Analysis in the Kedougou-Kenieba Inlier (Senegal-West Africa)

This paper shows geometric aspects of rock masses in the Senegalese side of Kédougou-Kéniéba inlier. The studies are done in one part on sedimentary rocks (represented by sandstones) with stratification and on the other part in igneous rocks (represented by basalts). Geometric studies are the fractal configuration and the scale effect. Scale effect is stud- ied by comparing the results of mechanical tests done in the laboratory and on outcrops. For all samples, laboratory pa- rameters are higher than values of field. In this paper, scale effect is characterized by the decrease of mechanical pa- rameters from laboratory samples to field. The scale coefficient is defined and characterizes the relation between me- chanical properties. More importantly, the scale effect is more significant. This scale effect depends largely on the rock anisotropy. The anisotropy depends on the fracturation and the filling. The scale effect takes into account the fracturation, the filling minerals and their diversity which define the complexity of the rock. The anisotropy is complex; the impact of scale effect traduced by an increase of scale coefficient is the highest. Configuration of discontinuities also defines fractal geometry. This fractal aspect appears on the asperities, the spacing and the apertures of discontinuities. The fractal dimension is different from a parameter to another. All these two parameters estimate the stage of fracturation of the rock in a geological system and depend one on another if they are studied in the same element.

Using X-ray computed tomography in pore structure characterization for a Berea sandstone: Resolution effect

Summary X-ray computed tomography (XCT) is a powerful tool for detecting the micro-scale pore structure and has been applied to many natural and synthetic porous media. However, due to the resolution limitations, either non-representative view of the sample or inaccurate results can be produced from the XCT image processing. In this paper, two XCT (micro-CT and CT with synchrotron radiation) with different resolutions of 12.7 μm and 0.35 μm, as well as mercury intrusion porosimetry (MIP) with a minimum detection limit of 3 nm, were used for Berea sandstone to investigate the effect of detecting resolution on the pore structure. Several key pore structure parameters, including porosity, pore size distribution, pore connectivity, surface area, hydraulic radius, and aspect ratio were analyzed in a manner of quantitative comparison between different resolutions of XCT and MIP. The low resolution XCT can capture the large-pore porosity, while overestimates the pore size and pore connectivity. The high resolution XCT is more accurate in describing the pore shape, porosity, pore size; however, it is not representative since narrower detecting pore size range and small volume represented. A representative element volume related to large-pore porosity and probably large-pore connectivity with diameter and height of 2.8 mm is obtained through scale effect analysis. Therefore, selecting an appropriate resolution should be a compromise between the pore size and the representative element volume for the specific property or process of interest.

On the scale effects oriented MIMO detector: Diversity order, worst-case unit complexity and scale effects

In this paper, the insight into the scale effects oriented MIMO detector (SEOD) which is developed for the MIMO system that has to detect signals of multiple users, e.g., the multiple-antenna base-station (BS) system, is presented. The diversity order, complexity and scale effects of SEOD are investigated. The main contributions of this work can be listed as follows: (1) applying the concept of scale effects in microeconomics to MIMO detection and establishing the corresponding model for the analysis of scale effects; (2) presenting the complete proof of the existence of scale effects in our proposed SEOD scheme; (3) demonstrating that the scale effects can be utilized to realize MIMO detection that has the optimal performance in the sense of diversity order while keeping the worst-case unit complexity be polynomial in multiple-user system. Through the computer simulation, we obtain the numerical results which support the theoretical analysis.

Character Measurement of Flapping-Wing Mechanism

The characteristics and the application prospect are analyzed. It is concluded that bionic flapping-wing flying has better lift fore generation efficiency, which is the development trend of aerial vehicles. By the scaling effect analysis on bionic flying mechanism, it is presented that bionic flying could be realized more easily when the sizes are decreased. In this article, the flying mechanism of inset and Aves was studied and the high lift force mechanism of flapping-winging was concluded. In order to make the flapping-flying easier, we design a new type flapping-flying mechanism. A set of flapping-wing move comparatively. It can provide lift force all the time. We test the lift force in the condition of different speed and different frequency. The lift effect is validated on a simple suspend flight device. An experimental platform to measure the aerodynamic force is devised and developed by ourselves. On this equipment, the aerodynamics force of the prototype is test. The result is that enhancing speed or frequency can improve lift force in evidence

Endogenous problems in cross-sectional valuation models based on accounting information

The main purpose of this paper is to deal with the analysis of the scale effect in the value-relevance of accounting numbers. We examine the impacts of widely used deflators on the adjustment of scale effect. We find that most of the usual deflators employed in the literature generate endogeneity problems. In this paper we recommend the use of exogenous deflator such as the number of employees in market-based accounting research models. This alternative deflator produces, at least for the USA and Canada data, slightly better statistical results than other (endogenous) deflators such as the market value, the book value of equity, or the total assets.