Grid Frame Research Articles

Research on the Reliability Evaluation Method for DC Grid

The reliability indexes and evaluation methods of AC transmission system and high voltage direct current (HVDC) transmission system were introduced. According to the characteristics of the DC grid, whether the above methods could be applied to DC grid reliability evaluation was analyzed, and the reasons and applications were also presented. The results show that state enumeration method, Monte Carlo method, and hybrid method can be applied to the large scale DC grid reliability assessment, based on either the grid frame structure or the power flow calculation; and the FD (frequency and duration)-FTA (fault tree analysis) method and FD-model combination method are more suitable for simple DC grid reliability assessment based on grid frame structure.

Experimental Study on Seismic Performance of the Reinforced Concrete Grid-Mesh Frame Wall

In order to validate the seismic performance of reinforced concrete grid-mesh frame wall , four grid frame walls in half size is made with different height-width ratios and different grid forms in the paper. Two of them are filling with cast-in-place plaster as filling material. According to the experimental results of these four walls subjected to horizontal reciprocating loads, we know that the grid-mesh frame wall's breaking form are in stages and multiple modes, and the main influencing factors are height-width ratio and grid form, what's more, with cast-in-place plaster as fill material, could not only improve the level of the wall bearing capacity and stiffness, but also improve the ductility and seismic energy dissipation capacity.

The Parallel Research of MP Sparse Decomposition in Grid Environment

Signal sparse representation in signal processing has many important applications, but the calculation amount of sparse decomposition is difficult to spread to realize industrialization because of its enormous calculation amount. At present, most of us make efforts to shorten the time of sparse decomposition calculation and improve the algorithm in order to make sparse decomposition feasible in its actual application. Although we make great achievements, the time cost by these improved algorithms is still difficult to be accepted. With the rapid development of internet in recent years, cloud computing and grid computing improve the computational ability so greatly that it can make a large amount of data calculation possible in reality. We introduce the grid computing into the sparse calculation so as to make its applicability possible in the practice. The thesis is to build a grid frame work. The performance of sparse decomposition is greatly improved by its calculating allocation to each node of grid computing, which makes it possible in its practical application.

The low frequency performance of metamaterial barriers based on cellular structures

The high sound transmission loss (STL) metamaterials that have been suggested to-date commonly require the introduction of relatively heavy resonating or constraining components which limit the applicability of these solutions in typical noise control applications where it is desirable to minimize the treatment mass at a given STL. Here it is proposed that a panel consisting of an array of cellular unit structures can possess a high STL within a specified low frequency range without an undue mass penalty. The cellular acoustical metamaterial considered comprises a periodic arrangement of unit cells consisting of plates held in a grid-like frame (which itself is unsupported). It is suggested here that such a cellular panel can yield enhanced STL if the unit cell mass is apportioned appropriately between the unit cell plate and the surrounding grid-like frame, the effect being similar to the high STL observed in the low frequency range for a plate clamped along its edges. A finite element-model of a single unit cell was used to predict the normal incidence transmission loss of the periodic array by imposing boundary conditions that enforce spatial periodicity. Two material designs were compared: one in which the densities of the materials used for the unit plate panel and the grid were changed relative to each other, and a second where the relative thicknesses of the unit plate panel and the grid frame were varied. The numerical simulations indicate that benefits can be achieved in either case. However, the design based on density variations appears to be more effective than the approach based on geometry alteration in creating a relatively broad range of low frequency transmission loss enhancement.

Numerical simulation of three-dimensional flow field of a paddle-spiral ribbon impeller

Impeller is the core component of stirrer, which is widely applied in many industrial fields, therefore more and more endeavor is made to design and optimize its structure, in order to improve the efficiency and reliability of stirrer. In this paper, a paddle-spiral ribbon impeller is introduced. 3-D numerical simulation is carried out to study the mixing performances of four different combined forms of this kind of impeller. In the numerical studies, unstructured grid and multi-reference frame (MRF) are used; standard k-ε turbulent model and mixture model are adopted to simulate the mixing process of solid-liquid two-phase flow. From the non-steady state simulations, velocity field, mixing time and power consumption are obtained. The results indicate that this kind of impeller is effective for stirring serious fluid. The fist combination form of paddle-spiral ribbon impeller has the best stirring performance.

Optimal Structural Frequency Design of Stiffened Shell

Frequency-aimed optimal structural design of stiffened shell is concerned. It is a reverse design problem for the first several modal frequencies to converge to a set of target value. A design method combined modified bi-directional evolutionary structural optimization (BESO) and size optimization is presented. Optimization model consists of skin and regular grid frame structure. To solve irregular branches and holes that often exist in ordinary topology optimization results, instead of elements, the existence states of ribs in the frame are used as design variables and sensitivity of the rib is discussed. Detailed design is conducted by size optimization. Example shows that frequency requirements are achieved. And the optimum structure is regular and clear, the localized modes problem is avoid. This is very suitable for designing airplane wind tunnel flutter test models.

Comparison of Mechanical Properties between Grid Frame Core-Tube Structure and Tube Structure

Reinforced concrete grid frame core-tube structure system is a new system. This article draws the conclusion that grid frame core-tube has high stiffness and obvious space affection, and that its basic mechanics properties is better than frame core-tube structure and similar to tube structure through the comparison of two tube structure systems, which the Inner tube is similar to grid frame core-tube and the outer tubes respectively are frame and high beam - column frame tube. It puts forward some reasonable suggestions for the future designation of this structural system.

Comparison of Mechanical Properties between Grid Frame Core-Tube Structure and Tube Structure

Reinforced concrete grid frame core-tube structure system is a new system. This article draws the conclusion that grid frame core-tube has high stiffness and obvious space affection, and that its basic mechanics properties is better than frame core-tube structure and similar to tube structure through the comparison of two tube structure systems, which the Inner tube is similar to grid frame core-tube and the outer tubes respectively are frame and high beam - column frame tube. It puts forward some reasonable suggestions for the future designation of this structural system.

A Topology Optimization Method in Fuselage Flutter Model Design

Airplane flutter scale model should maintain the load transfer characteristics of the original structure. It is a structural inverse problem for proper natural frequencies as well as structural simplification. This inverse problem could be solved by topology optimization. So based on bi-direction evolutionary structural optimization (BESO) method, a topology method for designing fuselage flutter model is presented. Facing porous and irregular shape often appears in topology optimization, a regular shaped grid frame structure consisted of the finite elements is discussed, including its internal mapping relationship and boundary conditions. The ratio criterion for structural modification is raised in this structural topology optimization using frequency sensitivity. Finally, this topology optimization method is applied to cylindrical fuselage flutter model design, result shown that the proposed approach is feasible to achieve given natural frequencies, maintains the character of inner frame structure completely, and the similarity between optimized structure and original structure is achieved.

Heterogeneous meshing and biomechanical modeling of human spine

We aim to develop a patient-specific biomechanical model of human spine for the purpose of surgical training and planning. In this paper, we describe the development of a finite-element model of the spine from the VHD™ Male Data. The finite-element spine model comprises volumetric elements suitable for deformation and other finite-element analysis using ABAQUS. The mesh generation solution accepts segmented radiological slices as input, and outputs three-dimensional (3D) volumetric finite element meshes that are ABAQUS compliant. The proposed mesh generation method first uses a grid plane to divide the contours of the anatomical boundaries and its inclusions into discrete meshes. A grid frame is then built to connect the grid planes between any two adjacent planes using a novel scheme. The meshes produced consist of brick elements in the interior of the contours and with tetrahedral and wedge elements at the boundaries. The nodal points are classified according to their materials and hence, elements can be assigned different properties. The resultant spine model comprises a detailed model of the 7 cervical vertebrae, 12 thoracic vertebrae, 5 lumbar vertebrae, and S1. Each of the vertebrae and intervertebral disc has between 1200 and 6000 elements, and approximately 1200 elements, respectively. The accuracy of the resultant VHD™ finite element spine model was good based on visual comparison of volume-rendered images of the original CT data, and has been used in a computational analysis involving needle insertion and static deformation. We also compared the mesh generated using our method against two automatically generated models; one consists of purely tetrahedral elements and the other hexahedral elements.

EFFECT OF MOON PHASE ON THE EFFICACY OF CHLORPYIFOS BAIT AND BIFENTHRIN FOR CONTROLLING NYMPH AND ADULT MOLE CRICKETS ON A GOLF COURSE, 1998

EFFECT OF MOON PHASE ON THE EFFICACY OF CHLORPYIFOS BAIT AND BIFENTHRIN FOR CONTROLLING NYMPH AND ADULT MOLE CRICKETS ON A GOLF COURSE, 1998: chlorpyrifos (Snare Mole Cricket Bait) and bifenthrin (Talstar) were applied at three different moon phases for controlling nymphs and adults of the mole crickets Scapteriscus vicinus and S. borellii) on a fairway of Angel's Trace Golf Links in Brunswick County, NC. Plots 20 ft x 20 ft were established in an areas showing relatively uniform mole cricket damage. Chlorpyrifos and bifenthrin were applied on 14 Aug (quarter moon), 21 Aug (new moon), and 4 Sep (full moon) 1998 using a Turf Gator boom sprayer delivering 23 gpa at 50 psi with ten 8003vs nozzles. Irrigation was applied to the plots after treatment with bifenthrin only. Soapy water flush sampling indicated that the population was approximately 89% TMC and 11% MC. Air and soil temperature at the time of application for new moon, quarter moon, and full moon were 90°F and 87°F, 92°F and 87°F, and 84° F and 80°F, respectively. Soil at the test site was classified as mineral soil with pH 6.5 and 0.41% humic matter. Mole cricket damage was rated at five randomly selected spots per replicate before and after insecticide application. Damage was rated on a 0-9 scale based on the occurrence of fresh damage in the nine subgrids of 1 x 1 m grid frame, where 0 = no damage and 9 = severe damage. The five grid ratings per replicate were averaged. All data were transformed (square root of X + 0.5 or arcsine for percentage data) prior to ANOVA and Waller-Duncan K-ratio T test.

Research on valve-regulated lead/acid batteries for automobiles

This paper introduces design technology for automotive valve-regulated lead/acid (VRLA) batteries, such as grid alloy separator, container, positive and negative plate additives, and grid frame. Compared with conventional flooded-electrolyte lead/acid batteries, automotive VRLA batteries are influenced by high charge voltage and by high temperature. If the voltage of the automotive charging system is reduced and the battery is located outside the engine compartment of the automobile, VRLA batteries will enjoy longer service lives than flooded-electrolyte counterparts. The same assembly line can produce both automotive VRLA batteries and polyethylene envelope batteries. This reduces the production costs for automotive VRLA batteries.

Torsion of Concrete Beams with Large Openings

The grid frame approach for analyzing reinforced concrete beams with large openings has been developed in this paper. In this approach, the beam with large web openings is visualized as a grid frame comprising two longitudinal stringers connected by posts between consecutive openings. For analyzing the grid frame, the twisting couple at each end of the beam is replaced by a statically equivalent system comprising two equal and opposite forces. The ultimate torsional strength computing using the grid frame approach has been compared with the observed ultimate strength of 25 specimens tested by the writers and other investigators.

Free vibrations of square plantes with stiffened square openings

A grid frame work model is extended to obtain the natural frequencies of square plates with stiffened square openings. This technique eliminates the use of fictitious points at the re-entrant corner point, junction point, etc. on the stiffened opening. Numerical results are presented for the first time for the cases of plates with simply supported and clamped boundary conditions in order to show the convergence and versatility of the method. Also, this investigation provides a general feeling about the changes in fundamental frequencies that occur when stiffeners are introduced.

A new method of making accurate fine-wire grids for use in radio valves

New techniques are described for the manufacture of very accurate planar fine-wire grids for radio valves. A polygonal mandrel is used, at each corner of which is a rod, screw-cut to the pitch of the grid to be made. The grid wire is wound on to this mandrel so that each groove of the screw thread locates one turn of the wire. A grid frame is then brazed to each face of the winding in turn, by eddy-current heating in a reducing atmosphere. The method is especially suitable for grids made from wire of 10? diameter or less, and wound at 400 turns/in or more. It not only simplifies manufacture, but also produces grids more accurately than any other known method. These techniques can also be applied to the manufacture of double-sided grids by clamping two planar grids back-to-back. The method has been further extended to the automatic accurate alignment of grids of 500 turns/in, to an accuracy of about ±5?.