Geometrical Parameters Of Model Research Articles

In the name of art

In building a digital library of Chinese calligraphy, it is desirable to preserve the dynamic writing as well as the aesthetic properties of the masterpieces. Compared with the work on computer synthesis of Chinese calligraphy, we are dealing with the reverse problem; it can be achieved by performing image analysis on the archaic Chinese calligraphic images to obtain a model-based parametric representation. In this article, we introduce our methodology to preserve archaic Chinese calligraphic images by automatically estimating the set of three-dimensional (3-D) geometric and ink model parameters such as the properties of the brush hair and the variations of ink deposition along the stroke trajectory. The dynamic brush writing of the archaic Chinese characters can then be reproduced with various brush and ink effects so that the calligraphy generation process can be visualized and the masterpieces can be reproduced with high-quality printing in scalable resolution.

RESOURCESAT-1 LISS-4 MX bands onground co-registration by in-flight calibration and attitude refinement

RESOURCESAT-1 satellite was launched in October of 2003. Since then it has been consistently providing high quality 5m monochromatic and multispectral images of same resolution. LISS-4 MX sensor has complex acquisition geometry. It operates in three spectral bands imaged by 3 CCD arrays, which are separated by a finite time in imaging along the satellite track direction. Individual band data is acquired at different times while the satellite is driven by a pre-determined yaw profile. In addition, the odd–even pixels are too shifted by a small fixed delay in time. A unique challenge in LISS-4 MX Level-2 data processing sub-system is to autonomously rectify and additionally co-register the three bands data because of the influence of orbit and attitude in the time gap in the imaging sequence. In this paper, authors bring out details of in-flight calibration arrived for LISS-4 MX sensor. It addresses parameterization of co-registration problem by doing sensitivity analysis of the geometric model parameters to achieve co-registration among all bands. This approach can also be used for other sensor system having similar imaging geometry to achieve improved image co-registration among bands.

Self-Calibration of a Biologically Inspired 7 DOF Cable-Driven Robotic Arm

This paper presents the self-calibration of a novel biologically inspired 7 DOF cable-driven robotic arm. Similar to the human arm, the proposed robotic arm consists of three sequentially connected modules, i.e., a 3 DOF shoulder module, a 1 DOF elbow module, and a 3 DOF wrist module. Due to factors like manufacturing defects, assembly misalignments, compliance, and wear of connecting mechanisms, errors in the geometric model parameters always exist. Hence, the identification of such errors is critical for path planning and motion control tasks. Self-calibration models of the various modules in the robotic arm are formulated based on the differential change in the cable end-point distances. Due to the linear nature of these self-calibration models, an iterative least-squares algorithm is employed to identify the errors in the geometric model parameters. The calibration does not require any external pose measurement devices, because it utilizes the cable length data obtained from the redundant actuation scheme of the cable-driven arm. Computer simulations and experimental studies were carried out on both the 3 DOF and 1 DOF modules, to verify the robustness and effectiveness of the proposed self-calibration algorithm. From the experimental studies, errors in the geometric model parameters were precisely recovered after a minimum number of pose measurements.

Slab stiffness control of trench motion: Insights from numerical models

Subduction zones are not static features, but trenches retreat (roll back) or advance. Here, we investigate the dominant dynamic controls on trench migration by means of two‐ and three‐dimensional numerical modeling of subduction. This investigation has been carried out by systematically varying the geometrical and rheological model parameters. Our viscoplastic models illustrate that advancing style subduction is promoted by a thick plate, a large viscosity ratio between plate and mantle, and a small density contrast between plate and mantle or an intermediate width (w ∼ 1300 km). Advancing slabs dissipate ∼45% to ∼50% of the energy in the system. Thin plates with relatively low viscosity or relatively high density, or wide slabs (w ∼ 2300 km), on the other hand, promote subduction in the retreating style (i.e., slab roll‐back). The energy dissipated by a retreating slab is ∼35% to ∼40% of the total dissipated energy. Most of the energy dissipation occurs in the mantle to accommodate the slab motion, whereas the lithosphere dissipates the remaining part to bend and “unbend.” With a simple scaling law we illustrate that this complex combination of model parameters influencing trench migration can be reduced to a single one: plate stiffness. Stiffer slabs cause the trench to advance, whereas more flexible slabs lead to trench retreat. The reason for this is that all slabs will bend into the subduction zone because of their low plastic strength near the surface, but stiff slabs have more difficulty “unbending” at depth, when arriving at the 660‐km discontinuity. Those bent slabs tend to cause the trench to advance. In a similar way, variation of the viscoplasticity parameters in the plate may change the style of subduction: a low value of friction coefficient weakens the plate and results in a retreating style, while higher values strengthen the plate and promote the advancing subduction style. Given the fact that also on Earth the oldest (and therefore probably stiffest) plates have the fastest advancing trenches, we hypothesize that the ability of slabs to unbend after subduction forms the dominant control on trench migration.

Statistical Optimization for Geometric Fitting: Theoretical Accuracy Bound and High Order Error Analysis

A rigorous accuracy analysis is given to various techniques for estimating parameters of geometric models from noisy data. First, it is pointed out that parameter estimation for vision applications is very different in nature from traditional statistical analysis and hence a different mathematical framework is necessary. After a general framework is formulated, typical numerical techniques are selected, and their accuracy is evaluated up to high order terms. As a byproduct, our analysis leads to a hyperaccurate method that outperforms existing methods.

Shape Memory Alloy Hybrid Composite Plates for Shape and Stiffness Control

Shape memory alloy hybrid composite plates are `intelligent' structures whose shape or stiffness is actively modified by embedded shape memory alloy fibers. In this work, the behavior of such structures is investigated numerically and experimentally. A finite element model which separately represents the host structure and the fibers in a two-dimensional setting is proposed as a simple tool to predict the structural behavior in stiffness and shape control. The shape control configuration is used to validate the model experimentally since it is the most sensitive to the choice of the geometrical and mechanical model parameters.

Pore network modeling of fibrous gas diffusion layers for polymer electrolyte membrane fuel cells

A pore network model of the gas diffusion layer (GDL) in a polymer electrolyte membrane fuel cell is developed and validated. The model idealizes the GDL as a regular cubic network of pore bodies and pore throats following respective size distributions. Geometric parameters of the pore network model are calibrated with respect to porosimetry and gas permeability measurements for two common GDL materials and the model is subsequently used to compute the pore-scale distribution of water and gas under drainage conditions using an invasion percolation algorithm. From this information, the relative permeability of water and gas and the effective gas diffusivity are computed as functions of water saturation using resistor-network theory. Comparison of the model predictions with those obtained from constitutive relationships commonly used in current PEMFC models indicates that the latter may significantly overestimate the gas phase transport properties. Alternative relationships are suggested that better match the pore network model results. The pore network model is also used to calculate the limiting current in a PEMFC under operating conditions for which transport through the GDL dominates mass transfer resistance. The results suggest that a dry GDL does not limit the performance of a PEMFC, but it may become a significant source of concentration polarization as the GDL becomes increasingly saturated with water.

Control of vortex shedding-induced effects in a sectional bridge model by spanwise perturbation method

An experimental study was conducted to determine the effectiveness of the spanwise sinusoidal perturbation method (SPPM) in controlling vortex-induced vibrations (VIV) in a plate girder bridge section model. The geometric parameters of the plate girder section model were selected to give the maximum VIV response. A SPPM module was attached to both the leading and trailing edges of the section model. Two different SPPM configurations with two different wavelengths and the same amplitude were utilized. Vertical motion responses, surface pressure measurements, as well as hotwire measurements in the wake of the section model were taken. The results revealed that the SPPM with the higher wave steepness distinctively suppressed the VIV responses. The behavior of the model with the SPPM is remarkably different with a fixed section model. Generally, a reduction in the fluctuating surface pressure components is observed, indicating an increase in the degree of steadiness of the flow around the model with either of the two SPPM configurations. However, no qualitative difference could be observed between the effects of the low and high wave steepness configurations. Moreover, wake measurements did not show any distinctive effect for either configuration when compared to the base case.

Gyrokinetic electron acceleration in the force-free corona with anomalous resistivity

We numerically explore electron acceleration and coronal heating by dissipative electric fields. Electrons are traced in linear force-free magnetic fields extrapolated from SOHO/MDI magnetograms, endowed with anomalous resistivity ($\eta$) in localized dissipation regions where the magnetic twist $\nabla \times \bhat$ exceeds a given threshold. Associated with $\eta > 0$ is a parallel electric field ${\bf E} = \eta {\bf j}$ which can accelerate runaway electrons. In order to gain observational predictions we inject electrons inside the dissipation regions and follow them for several seconds in real time. Precipitating electrons which leave the simulation system at height $z$ = 0 are associated with hard X rays, and electrons which escape at height $z$ $\sim$ 3$\cdot 10^4$ km are associated with normal-drifting type IIIs at the local plasma frequency. A third, trapped, population is related to gyrosynchrotron emission. Time profiles and spectra of all three emissions are calculated, and their dependence on the geometric model parameters and on $\eta$ is explored. It is found that precipitation generally preceeds escape by fractions of a second, and that the electrons perform many visits to the dissipation regions before leaving the simulation system. The electrons impacting $z$ = 0 reach higher energies than the escaping ones, and non-Maxwellian tails are observed at energies above the largest potential drop across a single dissipation region. Impact maps at $z$ = 0 show a tendency of the electrons to arrive at the borders of sunspots of one polarity. Although the magnetograms used here belong to non-flaring times, so that the simulations refer to nanoflares and `quiescent' coronal heating, it is conjectured that the same process, on a larger scale, is responsible for solar flares.

Modelling a spatially heterogeneous biofilm and the bulk fluid: selected results from Benchmark Problem 2 (BM2)

The numerical simulation of mass transfer and conversion in spatially heterogeneous biofilms on the meso-scale requires an accurate description of the hydrodynamics in the biofilm systems and of spatial effects. This leads to systems of three-dimensional nonlinear partial differential equations that are numerically very expensive to solve and to data requirements that are not easy to meet. In this paper several modeling approaches to reduce the physical complexity and, hence, accelerate the computation are compared. They range from a mere reduction of dimensionality by lumping the problem along a secondary flow direction to global mass balances or empirical correlations, at the core of which a one-dimensional boundary value problem must be solved. It is found that even strongly simplified models can describe the qualitative behaviour of the model with regard to variations in the geometrical and hydrodynamic model parameters quite well. In order to obtain also quantitatively reliable results the hydrodynamics must be considered in an appropriate manner.

Improvements In Spaceborne Laser Altimeter Data Geolocation

For many science applications of laser altimetry, the preciselocation of the point on the Earth's surface from which the laser energy reflects is required.The laser surface return geolocation is computed from the laser altimeter's range observation in combinationwith precise knowledge of spacecraft position, instrument tracking points referenced to thespacecraft center of mass, spacecraft attitude, laser orientation, observation and attitude data timetags. An approach that simultaneously estimates the geometric and dynamic parameters of the orbit andlaser range measurement model by a combined reduction of both spacecraft tracking and laseraltimeter surface range residuals is applied to produce improved pointing, orbit and range bias solutionsand therefore improved geolocation. The data acquired by the Shuttle Laser Altimeter (SLA)-01 and 02missions constitute a valuable pathfinder data set to test algorithms in preparation for the upcoming VCL(Vegetation Canopy Lidar) and ICESat (Ice, Cloud and Elevation Satellite) missions. Results from apreliminary SLA-01 data analysis are presented along with a brief description of the methodology and itsapplication to future spaceborne missions.

Conditioning 3D Stochastic Channels to Pressure Data

Summary This work discusses the development and implementation of a procedure to condition a stochastic channel to well-test pressure data and well observations of the channel thickness and the depth of the top of the channel. The stochastic channel is defined by a set of geometric random variables (referred to as geometric model parameters) that describe the location, size, and shape. Channel and nonchannel permeability and porosity are treated as random variables. These four random variables plus the geometric parameters comprise the complete set of model parameters. Multiple conditional realizations of the geometric parameters and rock properties are generated to evaluate the uncertainty in model parameters and the reduction in uncertainty obtained by conditioning to well-test pressure data.

Quasi-dumbbell Structure of C70 Molecule

C70 should be a quasi-dumbbell molecule formed by dimerization of two 3/5 C60 spheres. This paper calculated the concave dihedral angle Lσ at the waist of C70 molecule, the distance of two spherical centres of the dumbbell and some other geometric parameters of C70 molecule model.

A Theoretical Analysis of CO2 Absorption in Sun Versus Shade Leaves

A one-dimensional, steady-state, constant temperature model of diffusion and absorption of CO2 in the intercellular air spaces of a leaf is presented. The model includes two geometrically distinct regions of the leaf interior, corresponding to palisade and spongy mesophyll tissue, respectively. Sun, shade, and intermediate light leaves are modeled by varying the thicknesses of these two regions. Values of the geometric model parameters are obtained by comparing geometric properties of the model with experimental data of other investigators found from dissection of real leaves. The model provides a quantitative estimate of the extent to which the concentration of gaseous CO2 varies locally within the leaf interior.