Set Of Geometrical Parameters Research Articles

SENSITIVITY ANALYSIS OF LIGHT INTERCEPTION TO GEOMETRICAL TRAITS OF APPLE TREES: AN IN SILICO STUDY BASED ON MAPPLET MODEL

The efficiency of light interception is a driving factor for plant transpiration and photosynthesis, and contributes greatly to plant growth. For a fruit tree, the efficiency of light interception is also a key factor to improve yield quality. Such efficiency is highly dependent on the tree geometrical and topological organisation which may vary between genotypes, or as a result of agronomic practices such as pruning. The purpose of this study was to use a functional-structural plant model, in order to find out the major geometrical traits that influence the efficiency of light interception in apple trees. MAppleT, an architectural model of apple tree, and VPlants, a software library that includes functionalities to simulate light environment, provided the basis for this work. The STAR, namely the silhouette to total area ratio of leaves, was used to evaluate the light interception efficiency. The general methodology contained three steps: (1) manipulation of a set of geometrical parameters in MAppleT, such as those related to internode elongation, leaf area expansion, and branching angle; (2) integration of the resulting tree architecture within the simulated light environment for calculation of STAR values at the whole tree scale; (3) analysis of the influence of the variation of each geometrical trait on the variance of STAR outputs. As expected, leaf area manipulation had the highest impact on STAR values. Interactions between input parameters were also found, and are illustrated in the case of leaf area versus internode length. This suggests that optimal combination(s) of the corresponding traits could be found, setting a target for genetic improvement, as well as physiological studies on real apple trees.

Parameters for Molecular Dynamics Simulations of Manganese-Containing Metalloproteins.

A set of geometrical parameters has been determined for single manganese metalloproteins for the AMBER force field, and ultimately to other force fields with a similar philosophy. Twelve (12) models from 9 different single-cluster manganese proteins were optimized and parametrized, using a bonded model approach. Mn-ligand bonds, Mn-ligand angles, and Restrained Electrostatic Potential charges for all the 74 residues in the first metal coordination sphere of each Mn metalloprotein were parametrized. The determined parameters were validated with molecular dynamics simulations and several statistics strategies were used to analyze the results. In addition, to validate the parametrized models, frequency and normal mode calculations were performed and comparisons were obtained for the overall structures both with quantum mechanics and molecular mechanics calculations. Linear and polynomial fittings were performed to estimate Mn-ligand bond force constants for generic manganese centers. Furthermore, averages are proposed for the main Mn-ligand angle interactions of typical manganese coordination centers: axial, square and triangular equatorial planes, and tetrahedral positions, for the different combinations of donor atoms from waters and hard ligands.

Geometric calibration of a terrestrial laser scanner with local additional parameters: An automatic strategy

Terrestrial laser scanning systems are steadily increasing in many fields of engineering, geoscience and architecture namely for fast data acquisition, 3-D modeling and mapping. Similarly to other precision instruments, these systems provide measurements with implicit systematic errors. Systematic errors are physically corrected by manufacturers before delivery and sporadically afterwards. The approach presented herein tackles the raw observables acquired by a laser scanner with additional parameters, a set of geometric calibration parameters that model the systematic error of the instrument to achieve the most accurate point cloud outputs, improving eventual workflow owing to less filtering, better registration and best 3D modeling. This paper presents a fully automatic strategy to calibrate geometrically terrestrial laser scanning datasets. The strategy is tested with multiple scans taken by a FARO FOCUS 3D, a phase-based terrestrial laser scanner. A calibration with local parameters for datasets is undertaken to improve the raw observables and a weighted mathematical index is proposed to select the most significant set of additional parameters. The improvements achieved are exposed, highlighting the necessity of correcting the terrestrial laser scanner before handling multiple data sets.

Impact vibration characteristics of a shrouded blade with asymmetric gaps under wake flow excitations

The vibro-impact mechanism of a rotating shrouded blade with asymmetric gaps is investigated. The Frobenius method is employed to determine the dynamic frequencies and corresponding mode functions of the shrouded blade under the action of dynamic stiffness. The mode functions are used to truncate the governing partial differential equation of the shrouded blade to ordinary differential equations by using the Galerkin method. Taking into account the influence of the rotating speed, the contact stiffness of adjacent blades is assumed to be an equivalent contact spring stiffness which is determined by the bending dynamic stiffness of the blade. Then the average method is employed to obtain the dynamic responses of the primary, the sub-harmonic and the super-harmonic resonances of the shrouded blade with wake flow excitation, respectively. Finally, the dynamical responses of a shrouded blade with a set of typical material constants and geometrical parameters are given to illustrate the influence of the blade shroud gaps on the vibration amplitude.

Crystalline Structural Intermediates of a Breathing Metal–Organic Framework That Functions as a Luminescent Sensor and Gas Reservoir

A rod-packing, breathing MOF (1), with two crystalline structural intermediates (1 a and 1 b; H(2) btca = benzotriazole-5-carboxylic acid) has been investigated. An underlying net approach for analyzing possible breathing MOFs, and a set of geometric parameters that can quantitatively describe such a breathing structural feature, are suggested. The 3D luminescent MOF is a promising candidate for specific sensors with exceptional sorption capacity.

FEA based investigation of the magnetic forces developed by fractional slot PM synchronous machines

Purpose – The paper is aimed at the investigation of the magnetic forces generated by fractional slot surface mounted PM machines, considering a comparative study between two topologies: a 9 slot/10 pole machine and a 12 slot/10 pole machine.Design/methodology/approach – Following the distribution of the armature windings using the star of slots approach, an investigation of the magnetic forces developed by both machines under study, using 3D finite element analysis (FEA). Prior to such investigation, a 2D FEA based sizing procedure is carried out in order to select a set of suitable geometrical parameters. Then, the comparison between both machines is extended to the torque production capability.Findings – It has been found that the 9 slot/10 pole machine has a pic value of the average magnetic force reaching almost 40N which is located in one side of the air gap. Such a peak does not exceed 7N in the 12 slot/10 pole machine and is located in two diametrically‐opposite areas of the air gap.Research limit...

A methodology for the geometric design of heat recovery steam generators applying genetic algorithms

This paper shows how the geometric design of heat recovery steam generators (HRSG) can be achieved. The method calculates the product of the overall heat transfer coefficient (U) by the area of the heat exchange surface (A) as a function of certain thermodynamic design parameters of the HRSG. A genetic algorithm is then applied to determine the best set of geometric parameters which comply with the desired UA product and, at the same time, result in a small heat exchange area and low pressure losses in the HRSG.In order to test this method, the design was applied to the HRSG of an existing plant and the results obtained were compared with the real exchange area of the steam generator. The findings show that the methodology is sound and offers reliable results even for complex HRSG designs.

3D Spirals with Controlled Chirality Fabricated Using Metal-Assisted Chemical Etching of Silicon

The ability to fabricate 3D spiraling structures using metal-assisted chemical etching (MaCE) is one of the unique advantages of MaCE over traditional etching methods. However, control over the chirality of the spiraling structures has not been established. In this work, a systematic parametric study was undertaken for MaCE of star-shaped catalysts, examining the influence of arm shape, arm length, number of arms, center core diameter, and catalyst thickness on the rotation direction. This data was used to identify a set of geometric parameters that reliably induce rotation in a predefined direction such that large arrays of 3D spiraling structures can be fabricated with the same chirality. Electroless deposition into the MaCE template was used to examine the full etch path of the catalyst and an experimental fit was established to control rotation angle by adjusting the catalyst's center core diameter. The ability to fabricate large arrays of 3D spiraling structures with predefined chirality could have important applications in photonics and optoelectronics.

Characterization of sand lenses embedded in tills

Tills dominate large parts of the superficial sediments on the Northern hemisphere. These glacial diamictons are extremely heterogeneous and riddled with fractures and lenses of sand or gravel. The frequency and geometry of sand lenses within tills are strongly linked to glaciodynamic processes occurring in various glacial environments. This study specifically focuses on the appearance and spatial distribution of sand lenses in tills. It introduces a methodology on how to measure and characterize sand lenses in the field with regard to size, shape and degree of deformation. A set of geometric parameters is defined to allow characterization of sand lenses. The proposed classification scheme uses a stringent terminology to distinguish several types of sand lenses based on the geometry. It includes sand layers, sand sheets, sand bodies, sand pockets and sand stringers. The methodology has been applied at the Kallerup field site in the Eastern part of Denmark. The site offers exposures in a number of till types that underwent different levels of glaciotectonic deformation. Sand lenses show high spatial variability and only weak uniformity in terms of extent and shape. Secondly, the genesis of the various types of sand lenses is discussed, primarily in relation to the depositional and glaciotectonic processes they underwent. Detailed characterization of sand lenses facilitates such interpretations. Finally, the observations are linked to a more general overview of the distribution of sand lenses in various glacial environments. Due to the complex and mutable appearance of sand lenses, geometric descriptions can reveal the deformation history and even give indications on the palaeo-glaciological conditions during the deposition of the surrounding tills. This information can support the understanding of till genesis and further inform till classifications. In this regard, structural heterogeneity such as sand lenses can supplement traditional directional element analysis to identify till types and may be used as a novel tool in till investigations.

ROBOT WORKSPACE OPTIMIZATION USING A NOVEL MODIFIED DIFFERENTIAL EVOLUTIONARY TECHNIQUE

Robotic manipulators with three-revolute (3R) family of positional configurations are very common in the industrial robots (IRs). The capability of a robot largely depends on the workspace (WS) of the manipulator apart from other parameters. With the constraints in mind, the optimization of the workspace is of prime importance in designing the manipulator. The problem is formulated as a constrained optimization problem with workspace volume as objective function. It is observed that the previous literature is confined to use of conventional soft computing algorithms only, while a new search algorithm is conceptualized and proposed to improve the computational time. The proposed algorithm differs from the conventional differential evolutionary (DE) algorithm only in the place of initialization and selection. The algorithm gives a good set of geometric parameters of manipulator within the applied constrained limits. The availability of such an algorithm for optimizing the workspace is important, especially for highly constrained environments. The efficiency of the proposed approach to optimize the workspace of 3R manipulators is exhibited through diverse cases.

TU-A-218-10: Design and Characterization of TiO2 Nanotube Based X-Ray Tube with Single Focusing Electrode

Purpose: To study the effect of geometrical and electrical parameters on focal spot size (FSS) of TiO2 nanotubefield emission X‐ray tube. The X‐ray tube parameters were optimized to achieve the smallest FSS for different cathode sizes and anode voltages. Methods: The simulations were performed using the industry standard commercial software SIMION 80.1 3D. FSS was simulated as a function of the distance between gate electrode and focusing electrode (dG‐L), focusing electrode opening diameter (dL), thickness of the focusing electrode (HL), distance between focusing electrode and anode (dL‐A), and anode diameter (dA). The anode voltage was varied between 20‐120 kV. dL was varied from 4 to 24 mm with 4 mm increments, and at each dL value FSS and focusing voltage (Vf) were studied as a function of TiO2 nanotube sample size dS. Simulations were followed by experiments to build X‐ray tube with optimized parameters. Results: The effect of various X‐ray tube parameters on the focusing properties of electron optics system was investigated in the search for the smallest FSS for different TiO2 nanotube sample sizes. In particular, it is found that FSS grows with dS for all dL values. FSS grows fast at the beginning with the average growth rate of 183 μm/mm until dS reaches approximately 1 mm for all dL values. Then, FSS becomes weekly dependent on dS and later, as dS approaches dL, it starts growing fast again with average growth rate of 193 μm/mm. An X‐ray tube was built with optimized from simulations parameters and its performance was tested. Conclusions: A set of geometrical and electrical parameters have been established for different anode voltages and cathode sizes that provide the smallest focal spot size. An X‐ray tube has been built and tested with optimized parameters.

Numerical modeling of Knudsen's thermal creep experiment

In his study of thermal creep phenomena in 1910, M. Knudsen build a construction that was composed of 10 pairs of cylindrical tubes of different diameters heated at its junctions. He observed that at some conditions the construction worked as a gas compressor and he was able to obtain the pressure ratio at the ends of the device up to 10. The aim of the present work was to model the experiment using the power of modern computers and the efficient method for solving the Boltzmann kinetic equation. The computations were made for the same set of temperatures, gas pressures and geometrical parameters of the installation as in the experiment, and for molecular hydrogen with real Lenard-Jones potential and realistic rotational energy relaxation time. The Boltzmann equation was solved by the conservative projection method. The computations were carried out with the use of specially developed by the authors program-solving environment for modeling of rarefied gas flows with arbitrary geometry and real gas parameters. The obtained results are in reasonable good agreement with the experimental data.

Revisiting the inverse dynamics of the Gough–Stewart platform manipulator with special emphasis on universal–prismatic–spherical leg and internal singularity

This article discusses the dynamic modeling for control of Gough–Stewart platform manipulator with special emphasis on universal–prismatic–spherical leg kinematics. Inverse dynamic model of these six degrees of freedom parallel manipulator robots is reviewed, while complete dynamics with true kinematics of universal–prismatic–spherical legs is compared with several models found in the literature. Most existing models have not taken into account some of the legs kinematical effects, namely the legs angular velocity around their axes and the internal singularities due to passive joints; some other used a simplified parameterization to describe the leg kinematics. Furthermore, some kinetic assumption can be used to reduce the computational burden. This article shows the effect of all these simplifications on the driving forces by simulating the different dynamic models for a commercial manipulator and for different sets of geometric and dynamic parameters of manipulator.

Electron energy and geometry parameters of InGaAs/GaAs quantum rings: an interpretation of C-V data

ABSTRACTWe investigate the electronic properties of InAs/GaAs quantum rings (QRs) in a magnetic field using an original effective potential model based on a single band kp-approximation with an energy dependent effective mass. We used two sets of geometrical parameters for the selfassembled QRs. The first is the experimentally proposed geometry; the second follows from the oscillator model due to the relation between the model parameters and the real sizes of the quantum objects. The energy of an electron in a magnetic field, calculated for each of the geometries, is compared with C-V experimental data. We show that the results of the calculation obtained for the second geometry fit the experimental data rather well. Interpretation of the recent C-V data given by W. Lei et al. (Appl. Phys. Lett. 96 (2010) 033111) on the basis of the oscillator model is discussed.

Stability of accretionary wedges based on the maximum strength theorem for fluid-saturated porous media

Accretionary wedges are idealized as triangular-shaped regions, the top surface corresponding to the topography, the bottom surface to the weak, frictional contact (décollement) with the subducting plate and the last side, the back-wall, to the contact with the continent. New critical stability conditions are obtained and defined by the sets of geometrical and material parameters for which the deformation occurs concurrently in two regions of the wedge e.g., the front and the rear. They extend the classical critical stability conditions, restricted to triangular regions of infinite extent and composed of frictional materials, by accounting for arbitrary topography, finite geometry and cohesive materials. They are obtained by the application of the kinematic approach of limit analysis, referred to as the maximum strength theorem, which is first extended to fluid-saturated porous media. The basic failure mode used to defined these stability conditions consists of two reverse faults intersecting the décollement at a common point, the root. The décollement is activated from the back wall to the root. The root position is indeterminate for our extended critical stability conditions. The proposed theory predicts the classical stability conditions as a special case. A first application to the Barbados prism is proposed accounting for a non-linear gradient in fluid pressure within the décollement. The details of the topography is responsible for several sets of critical stability conditions. Our pressure predictions necessary to explain the activation of the frontal thrust are significantly less than the estimates done during the drilling on site. Finally, the theory is applied to a wedge with the décollement partitioned into two regions, the deepest corresponding to the seismogenic zone. The associated failure modes include one composed of two blocks sliding at different velocities over the décollement and separated by a single discontinuity, dipping either towards the front or towards the rear of the wedge. This special mode dominance is facilitated by large pressures and small friction coefficients in the shallowest region of the décollement.

Electronic and dynamics properties of a molecular wire of graphane nanoclusters

In this work we study the electronics and dynamical properties of an array of graphane nanoclusters. The electronic properties are obtained from first principles calculations. The dynamical study is performed by solving the time-dependent Schrödinger equation, adopting the occupation number Hamiltonian and using parameters obtained with first principles calculations. The thermal behavior is simulated by a stochastic algorithm. Our results show that for a set of geometric parameters of the array of nanoclusters, the system exhibits bi-stability in the charge configuration, excitation energies that allow operation at room temperature, operation times below the picosecond and scalability.

Franck-Condon simulation, including anharmonicity, of the photodetachment spectrum of P2H−: Restricted-spin coupled-cluster single-double plus perturbative triple and unrestricted-spin coupled-cluster single-double plus perturbative triple -F12x potential energy functions of P2H and P2H−

Geometry optimization and harmonic vibrational frequency calculations have been carried out on the X̃(2)A(') state of P(2)H and the X̃(1)A(') state of P(2)H(-) using the restricted-spin coupled-cluster single-double plus perturbative triple excitation [RCCSD(T)] and explicitly correlated unrestricted-spin coupled-cluster single-double plus perturbative triple excitation [UCCSD(T)-F12x] methods. For RCCSD(T) calculations, basis sets of up to the augmented correlation-consistent polarized valence quintuple-zeta (aug-cc-pV5Z) quality were employed, and contributions from extrapolation to the complete basis set limit and from core correlation of the P 2s(2)2p(6) electrons were also included. For UCCSD(T)-F12x calculations, different atomic orbital basis sets of triple-zeta quality with different associated complementary auxiliary basis sets and different geminal Slater exponents were used. When the P 2s(2)2p(6) core electrons were correlated in these F12x calculations, appropriate core-valence basis sets were employed. In addition, potential energy functions (PEFs) of the X̃(2)A(') state of P(2)H and the X̃(1)A(') state of P(2)H(-) were computed at different RCCSD(T) and UCCSD(T)-F12x levels, and were used in variational calculations of anharmonic vibrational wavefunctions, which were then utilized to calculate Franck-Condon factors (FCFs) between these two states, employing a method which includes allowance for anharmonicity and Duschinsky rotation. The photodetachment spectrum of P(2)H(-) was then simulated using the computed FCFs. Simulated spectra obtained using the RCCSD(T)/aug-cc-pV5Z and UCCSD(T)-F12x(x = a or b)/aug-cc-pCVTZ PEFs are compared and found to be essentially identical. Based on the computed FCFs, a more detailed assignment of the observed vibrational structure than previously reported, which includes "hot bands," has been proposed. Comparison between simulated and available experimental spectra has been made, and the currently most reliable sets of equilibrium geometrical parameters for P(2)H and its anion have been derived. The photodetachment spectrum of P(2)D, yet to be recorded, has also been simulated.

Transport Physics and Device Modeling of Zinc Oxide Thin-Film Transistors—Part II: Contact Resistance in Short Channel Devices

Short-channel zinc oxide (ZnO) thin-film transistors (TFTs) are investigated in a wide range of temperatures and bias conditions. Scaling down the channel length, the TFT performance is seriously affected by contact resistances, which depend on gate voltage and temperature. To account for the contact resistances, the transistor is ideally split in three parts. The contact regions are modeled as two separate transistors with a fixed channel length and an exponential distribution of localized states, whereas the channel is treated as reported in Part I. The overall model reproduces the measured characteristics at different channel length, with a single set of physical and geometrical parameters. It can be readily implemented in a circuit simulator. Numerical simulations confirm the validity of the model approach and are used to evaluate the impact of nonidealities at the electrode/semiconductor interface.

Interfacial flows in corrugated microchannels: Flow regimes, transitions and hysteresis

We report simulations of gas–liquid two-phase flows in microchannels periodically patterned with grooves and ridges. A constant effective body force is applied on both fluids to simulate a pressure-driven creeping flow, and a diffuse-interface model is used to compute the interfacial evolution and the contact line motion. Depending on the body force, capillary force and the level of liquid saturation, a number of flow regimes may appear in the corrugated microchannel: gas flow, blockage, liquid flow, bubble–slug flow, droplet flow, annular flow and annular-droplet flow. A map of flow regimes is constructed for a set of geometric and flow parameters starting from a prescribed initial configuration. Some of the regimes are new, while others have been observed before in straight tubes and pipes. The latter are compared with previous experiments in terms of the regime map and the holdup ratio. The transition among flow regimes shows significant hysteresis, largely owing to the pinning of the interface at sharp corners in the flow conduit. Hysteresis is reduced if the sharp corners are rounded. Under the same operating conditions, different flow regimes can be realized from different initial conditions. The roles of geometry and wettability of the channel walls are also elucidated.

Numerical Simulation for Composite Wing Structure Design Optimization of a Minitype Unmanned Aerial Vehicle

To improve performances of minitype unmanned aerial vehicle (UAV) wing, numerical simulation and optimization design principle was carried out for designing best composites wing structure. Thus tradeoff can be obtained between general performance and weight of wing. Advanced composite material has its own outstanding features, such as high specific strength, high specific modulus, designable performance and integral forming easily. The application of advanced composite material on aerocraft can significantly reduce weight, and improve aerodynamic and flight performances. In this paper, parametric finite element model is established using parametric modeling technique for stress and stain analysis. Given any set of geometric parameters, geometric modeling, meshing, strain and stress analysis can be automatically carried out in sequence. The global optimal solution is guaranteed by proposed two-step optimization search strategy combing genetic algorithm (GA) and sequential quadratic programming (SQP). Comparative studies show that optimization efficiency can be greatly improved with two-step optimization search strategy. As a kind of new material, advanced composite material brings about great revolution to aerocraft industry since it was introduced in 1960s. With its wide application in aerospace structure, advanced composite material is named as the four main materials of aerospace structure along with aluminum alloy, titanium alloy, and alloy steel. The advanced composite material has its own prominent features, such as high specific strength, high spe- cific modulus, designable performance and integral forming easily, etc. With application of advanced composites, weight of aerocraft can be reduced by about 25% ~ 30% compared to conventional metal structures. Moreover, aerodynamic and flight performances can be improved to levels that conventional materials can hardly achieve. The extensive application of advanced composites is also able to promote some further technology development of stealth and intelligent design. The aerocraft performance is significantly dependent on part and quality of advanced compo- sites used in aerocraft. However, it is difficult to achieve good designs of composites in aerocraft to guarantee requirements for different missions. Therefore, to fully explore directional properties of composites, designable ability of performance and excellent manufacturability of large component integral forming, it is necessary to introduce principle of optimization to composite design (1-6). In this paper, optimization design and numerical simulation for composite of wing on a UAV is