Deflection Area Research Articles

Numerical Simulation of Moving Load on Concrete Pavements

Abstract The knowledge of the development with time of the strain and stress states in pavement structures is needed in the solution of various engineering tasks as the design fatigue lifetime reliability maintenance and structure development. The space computing model of the truck TATRA 815 is introduced. The pavement computing model is created in the sense of Kirchhof theory of the thin slab on elastic foundation. The goal of the calculation is to obtain the vertical deflection in the middle of the slab and the time courses of vertical tire forces. The equations of motion are derived in the form of differential equations. The assumption about the shape of the slab deflection area is adopted. The equations of the motion are solved numerically in the environment of program system MATLAB. The dependences following the influence of various parameters (speed of vehicle motion, stiffness of subgrade, slab thickness, road profile) on the pavement vertical deflections and the vertical tire forces are introduced. The results obtained from the plate computing model are compared with the results obtained by the FEM analysis. The outputs of the numerical solution in the time domain can be transformed into a frequency domain and subsequently used to solve various engineering tasks.

Relationship between Deflection and Contact Area of Drive Tire

Relationship between Deflection and Contact Area of Drive Tire

Latitudinal gradient and spatial covariance in species richness of tropical Lepidoptera in the Andes

Abstract We investigated whether Lepidoptera species richness in the tropical Andes is distributed evenly across the latitudinal gradient, explored the spatial correlations between different taxonomic groups, and investigated historical and ecological factors responsible for shaping the observed patterns. We interpolated species richness from collecting records of nine ecologically diverse taxa of montane Lepidoptera, eight of butterflies (Ithomiini, Acraeini, Callicorini, Pronophilina, Aporiina, Leptophobia, Penaincisalia, and Forsterinaria) and one of moths (Geometridae: Erateina) along elevational transects from 1000 to 3500 m every two degrees in latitude between 11°N and 27°S. We used multiple regression to assess the role of climatic and historical variables in shaping their species richness patterns, and Spearman's correlation coefficient to examine the correlation of species richness gradients between pairs of taxa. We found that Lepidoptera species richness in the tropical Andes is distributed unevenly across the latitudinal gradient, differing considerably between the least and the most diverse transects, with a peak at 3–11°S, and is strongly correlated among all nine taxa. Geological age of the Andes, area and climatic seasonality explained the most variation in species richness, with age dominating in the north and seasonality in the south. The latitudinal gradient in east Andean Lepidoptera species richness is likely a result of historical and contemporary factors, in particular temperature seasonality and the greater age of the Andes south of the Equator. Local aspects of species richness patterns are due to small‐scale geological or climatic phenomena, for example, the peak at 3–5°S which results from local mixing of east‐west Andean faunas in the Huancabamba Deflection area.

Three dimensional finite element model of soil compaction caused by agricultural tire traffic

Most of the finite element models of soil compaction do not represent the tire, only the effect of a uniform ground stress is distributed on a soil area with a preset form. It constitutes an oversimplification of the problem and it would yield erroneous contact conditions, because the tire–soil contact stress distribution is the result of simultaneous tire and soil deformation. This research was carried out with the objective of developing a model, valid for soil compaction simulation caused by agricultural tire traffic that allows research factors that cause soil compaction of a Rhodic Ferralsol soil. The tire was developed as a unique solid layer, which represents its mean properties with a linear elastic constitutive model. Predictions of deflection and tire contact area in rigid surface were compared with experimental results and the tire model was validated. A three dimensional model of the soil was created and the soil properties were represented with an Extended Drucker Prager material model. ABAQUS/STANDARD 6.8-1 code was used to develop the tire–soil interaction model. A tire traffic experiment was carried out at a soil bin to two soil water conditions, tire inflation pressures and tire load. Triaxial and direct shear tests were used to obtain soil properties and constitutive parameters. Predictions were compared with experimental results to verify the validity of the model in each soil water content. Simulated and observed stresses after wheel traffic under different inflation pressures and tire loads agree well. The model predicts the effect of inflation pressures, ground pressure and tire load on the stresses on the contact and the soil profile, it can be used in both teaching and research. The model was used to predict the depth at which soil compaction was produced for each combination of tire inflation pressure and tire load, and the relationship between the tire inflation pressure, contact stress and tire load with soil compaction. The model showed that magnitudes of vertical stresses transmitted to soil are independent to water content and that more soil compaction in wet soils depends on the less yield stresses in those conditions. Besides, the good agreement of the model with experimental results demonstrates the validity of using the Extended Drucker Prager model to represent the mechanical response of the Rhodic Ferralsol soil.

NONLINEAR INSTABILITY OF DISHED SHALLOW SHELLS UNDER UNIFORMLY DISTRIBUTED LOAD

In this paper, the nonlinear instability of dished shallow shells under a uniformly distributed load is investigated. The dimensionless governing differential equations for the problem are derived and the equations solved by using the Free-Parameter Perturbation Method with the Spline Function Method. By analyzing the instability modes of dished shallow shells, we obtain the variation rules of the maximum deflection area of initial instability of the uniformly loaded dished shallow shell, and discuss the relationship between the initial instability area and the maximum deflection area of initial instability. These results provide some theoretical basis for engineering design and instability prediction and control of shallow shell structures.

Effect of Tai Chi on Body Balance: Randomized Controlled Trial in Elderly Men with Dizziness

The purpose of this study was to assess the effect of 18-week Tai Chi training on body balance in a dynamic trial among elderly men with dizziness. The study covered subjects aged 60 to 80 years. We identified 40 men who reported a history of dizziness. The subjects were recruited using direct mailings and a community information campaign. The participants were randomly assigned to either the exercise intervention (n = 20) or control group (n = 20). The Tai Chi group participated in an 18-week exercise class held for 45 minutes twice a week. Body balance was studied in two ways: using the "8 foot up and go test" (Rikli and Jones 2001) and using a Computer Posturographic System PE 90 (manufactured by Military Institute of Aviation Medicine in Warsaw and outfitted with Pro-Med modified software). The ability to perform specific tasks (maximal deflections in four directions) was measured on the posturographic platform. The variation in results obtained on the first and second date of tests in the experimental and control groups was confirmed statistically using four parameters, i.e. "8 foot up to and go test (H = 8.21;p = 0.003), forward deflection (H = 3.70;p = 0.050), backward deflection (H = 5.04;p = 0.024) and maximum sway area (H = 8.86;p = 0.002). Consequently, we found that the 18-week period of Tai-Chi exercises, with a frequency of twice a week for 45 minutes, is beneficial for dynamic balance, which is important for the reduction of fall risk factors among elderly men with dizziness.

The Nonlinear Instability Modes of Dished Shallow Shells under Circular Line Loads

This paper investigated the nonlinear stability problem of dished shallow shells under circular line loads. We derived the dimensionless governing differential equations of dished shallow shell under circular line loads according to the nonlinear theory of plates and shells and solved the governing differential equations by combing the free‐parameter perturbation method (FPPM) with spline function method (SFM) to analyze the nonlinear instability modes of dished shallow shell under circular line loads. By analyzing the nonlinear instability modes and combining with concrete computational examples, we obtained the variation rules of the maximum deflection area of initial instability with different geometric parameters and loading action positions and discussed the relationship between the initial instability area and the maximum deflection area of initial instability. The results obtained from this paper provide some theoretical basis for engineering design and instability prediction and control of shallow‐shell structures.

Visualization RCD (reinforced concrete design) table advisor for decision support activity

Reinforced concrete design (RCD) activity requires the services of design table to pick bar sizes and area of specific bar groups. This allow reinforced concrete (RC) designers to use their intuition to pick the right bar size for detailing of RC Structures which virtually enhance reliable and satisfactory answers to RCD problems. With the advent of computer with its powerful memory, most RCD software available automatically generates Steel Properties thus, jeopardising user’s contribution in terms of their perception. RCD Tables are conventionally small but not limited in use. By the skilful and innovative integration of available concepts and techniques, the power of the RCD Tables are enhanced to check for deflection, minimum and maximum area of steel, and display alert to users. Visualization RCD Table interface was designed as a dialog box. Simply Supported Reinforced Concrete Beam Structure (SSRCBS) tool was modified to accommodate the new tool. Statistical analysis revealed that the significance of time was borderline between SSRCBS tool and the modified tool. It was also found that as the tasks became more complex, the modified tool advantage increases in terms of task-by-task satisfaction and users understanding of the logic behind RCD. Key words: RCD visualization, RC, PDAs, SSRCBS, visRCD table advisor, DSS.

Impact characterization of glass/epoxy composite plates: An experimental and numerical study

This study presents the effects of impact energy, impactor mass and impact velocity on the maximum contact force, maximum deflection, contact time, absorbed energy, and overall damage area of glass/epoxy laminated composites, experimentally and numerically. The stacking sequence of the composite plates was chosen as [0°/30°/60°/90°] S. The impact event was simulated and analyzed by using 3DIMPACT finite element code. The overall delamination area obtained from experimental study and numerical analyses were also examined. It is seen that the numerical results are in good agreement with experimental results.

LOW FREQUENCY DAMPER

The low frequency damper is an autonomous equipment for damping vibrations with the 1-20Hz range. Its autonomy enables the equipment to be located in various mechanical systems, without requiring special hydraulic installations. The low frequency damper was designed for damping the low frequency oscillations occurring in the circuit controls of the upgraded IAR-99 Aircraft. The low frequency damper is a novelty in the aerospace field ,with applicability in several areas as it can be built up in an appropriate range of dimensions meeting the requirements of different beneficiaries. On this line an equipment able to damp an extended frequency range was performed for damping oscillations in the pipes of the nuclear power plants. This damper, tested in INCAS laboratories matched the requirements of the beneficiary. The low frequency damper is patented – the patent no. 114583C1/2000 is held by INCAS. Introduction Low frequency vibrations or infrasound occur in the aircraft system control. They operate permanently causing the pilot fatigue, discomfort, and in some cases induce a delay between the pilot reaction and the deflection of the control area. The analysis and synthesis of a low frequency damper came as a necessity for the IAR-99 aircraft. At longitudinal controls the pilot is subject to tiring efforts in the small and medium deflection area of the control surface. The designed equipment was studied in the laboratory through numerical simulations by the INCAS specialists which made evident the decrease and/or elimination of these vibrations. It is also useful to install in the mechanical circuits of the automatic systems of various complex installations from different activity fields a 1÷20 Hz range frequency damper. This equipment contributes substantially to the increase of the operating life of those installations. Construction The low frequency damper shown in Fig.1 consists of two modules designed independently: a hydrostatic module and a mechanical module. These modules are assembled inside a common cylinder. The hydrostatic module – located in the central area of the equipment provides the vibrations damping and the damage function. The elements of this module form a compact construction as follows: double -acting hydraulic cylinder; Supply valve; Piston hydraulic accumulator; Throttle; Relief valves to overpressure; Bleeder utilised only when loading the module with hydraulic fluid. The mechanical module – developed in cascade, from the exterior surface of the hydrostatic module to the common cylinder of the equipment, maintains the neutral position of the equipment and implicitly of the aircraft control circuit, giving an extra effort to the stick which is proportional to its stroke, thus, generating a sensibility decrease of the control in the small deflection area. The elements of this module are concentrically assembled with the hydraulic module in the following configuration: Special bush; Spring operating beakers Compression spring; The ends of the common cylinder are provided with arc limiting caps and installation elements. 64 INCAS BULLETIN No 1/ 2009 DOI: 10.13111/2066-8201.2009.1.1.12

The relationship between body balance function and occlusal function during the mixed dentition period

The aim of this study was to investigate the relation between body balance and occlusal balance during the mixed dentition stage. Fifty-six healthy children with Hellman's Dental Age IIIA: (31 boys and 25 girls) with an average age of 8.1 years, were selected from an elementary school. The body balance, distance and area of gravity center movement (GCM) were measured with automatic posture analytical devices. Occlusal abilities were measured with pressure-sensitive sheets (Dental Prescale ® ), including occlusal contacts area, average occlusal pressure, maximum occlusal pressure, occlusal force and occlusal balance. Analysis of occlusal balance was determined by separating the middle group (| x | ≤ 5 mm) from the deflection group (| x | > 5 mm) based on the position of occlusal balance center. Similarly, the children were instructed to perform the GCM area of eyes-closed exercise. The first 25% of the participants with the best balance were grouped as the good balance group; and the last 25% with the worse balance were grouped as the bad balance group. Results showed that occlusal contact area and occlusal force of the middle group were more than the deflection group, GCM distance and area of the middle group were less than the deflection group. occlusal contacts area and occlusal force of the good balance group were more than the bad group. Body balance function and occlusal balance function were observed to have mutual influence during Hellman's Dental Age IIIA stage in this study.

Model-Independent Extraction of Adhesion Energy from Indentation Experiments

We present a model-independent method for extraction of adhesion energy from indentation experiments in which force, deflection, and contact area are measured. It is based on calculating the difference between external work supplied and stored strain energy, the deficit, which is assigned as work expended in opening (or closing) an interface. The critical step in the method is determination of the elastic indentation response without adhesion, using measured compliance. We show that this model-independent method accurately reproduces results obtained using the Johnson-Kendall-Roberts theory when it is applicable, and is particularly useful when an analytical contact mechanics solution is unavailable.

Dynamic and not static change in ventricular repolarization is a substrate of ventricular arrhythmia on chronic ischemic myocardium.

The restitution mechanism has been the focus of attention as the possible mechanism behind ventricular fibrillation (VF). However, its contribution in chronic ischemic heart has not been established. We investigated chronic ischemic dogs with occlusion of left anterior descending artery. Sixty unipolar electrograms were simultaneously recorded from an entire cardiac surface. Activation-recovery intervals (ARIs) and QRST deflection area (AQRST) were measured during constant atrial pacing. The ischemic dogs were divided into two groups, five dogs in VF(+) group or seven dogs in VF(-) group, according to VF occurrence by programmed electrical stimulation. When investigating ARI dispersions on an epicardium, there was no difference between VF(+) and VF(-) groups. The relationship between ARIs and diastolic intervals was quantified as an electrical restitution curve. The slopes of the ARI restitution curve for the anterior left ventricle in VF(+) dogs were significantly steeper than those of VF(-) dogs. The amplitude of AQRST alternans were significantly greater in VF(+) dogs than VF(-) dogs. Combined observation of steep restitution slopes and increased electrical alternans supported the restitution mechanism as being involved in the arrhythmia. Dynamic restitution properties and not static single-beat ARI dispersion may play an important role in the VF arrhythmia in the chronic ischemic heart.

Correcting deviations in the shape of projected images in the electron beam block exposure column

The block exposure column has a mask with one hundred stencils in a deflection area. Each mask pattern projected by electron beams is reduced in size to 1/60th and imaged onto a wafer. Deviations in image shapes are dependent on deflected beam trajectories and imaging beam currents. We show techniques to measure the image shapes using reflected electron signals. Correction methods are proposed to reduce the deviations. After the corrections, the block exposure can expose images of every mask pattern of the size 5×5 μm with the image size deviation less than 11 nm, which includes 5.8 nm of an isotropic expansion and 9.6 nm of distortions.

Electron optical image correction subsystem in electron beam projection lithography

To obtain ultimate image fidelity in the PREVAIL electron beam projection lithography system (EB stepper) [Pfeiffer et al., J. Vac. Sci. Technol. B 17, 2840 (1999)], precise dynamic corrections [Zhu et al., Proc. SPIE 2522, 66 (1995)] of an exposed reticle subfield image on the wafer are required. The electron beam column for the EB stepper covers a large deflection area by a curvilinear variable axis lens (CVAL) [Stickel and Langner, J. Vac. Sci. Technol. B 17, 2847 (1999)] type deflection with high current, and very large 0.25 mm square beam. Because of these features together with tighter specifications for electron optics in below 70 nm node, aberrations which can be negligible in prior art electron beam lithography systems, can no longer be ignored. Therefore the electron optical image correction subsystem in the EB stepper is required to precisely correct the increased numbers of possible measurable aberrations caused by deflection as well as by space charge effects. In this article, a systematic overview of beam corrections is described.

Value of magnetocardiographic QRST integral maps in the identification of patients at risk of ventricular arrhythmias.

It has been shown that regional ventricular repolarization properties can be reflected in body surface distributions of electrocardiographic QRST deflection areas (integrals). We hypothesize that these properties can be reflected also in the magnetocardiographic QRST areas and that this may be useful for predicting vulnerability to ventricular tachyarrhythmias. Magnetic field maps were obtained during sinus rhythm from 49 leads above the anterior chest in 22 healthy (asymptomatic) control subjects (group A) and in 29 patients with ventricular arrhythmias (group B). In each subject, the QRST deflection area was calculated for each lead and displayed as an integral map. The mean value of maximum was significantly larger in the control group A than in the patient group B (1,626+/-694 pTms vs. 582+/-547 pTms, P<0.0001). To quantitatively assess intragroup variability in the control group A and intergroup variability of the control and patient groups, we used the correlation coefficient r and covariance sigma. These indices showed significantly less intragroup than intergroup variation (e.g., in terms of sigma, 28.0x10(-6)+/-12.3x10(-6) vs. 3.4x10(-6)+/-12.5x10(-6), P<0.0001). Each QRST integral map was also represented as a weighted sum of 24 basis functions (eigenvectors) by means of Karhunen-Loeve transformation to calculate the contribution of the nondipolar eigenvectors (all eigenvectors beyond the third). This percentage nondipolar content of magnetocardiographic QRST integral maps was significantly higher in the patient group B than in the control group A (13.0%+/-9.1 % vs. 2.6%+/-2.0%, P<0.0001). Discriminations between control subjects and patients with ventricular arrhythmias based on magnitude of the maximum, covariance sigma, and nondipolar content were 90.2%, 90.2%, and 86.3% accurate, with a sensitivity of 89.7%, 93.1%, and 75.9%, and a specificity of 90.9%, 86.4%, and 100%. We have shown that magnitude of the maximum and indices of variability and nondipolarity of the magnetocardiographic QRST integral maps may predict arrhythmia vulnerability. This finding is in agreement with earlier studies that used body surface potential mapping and suggests that magneticfield mapping may also be a useful diagnostic tool for risk analysis.

Structural Performance of Inservice Flexible Pavements

Due to the combined influence of traffic loading and environment, the structural condition of pavement deteriorates with time. Studies on structural damage, which usually results in functional deterioration, is important for the highway engineer to plan the maintenance/strengthening strategies to extend the life of pavements. In the present investigation, the data collected under the R-6 research project of the Ministry of Surface Transport, India, has been used to develop prediction models and growth curves for rebound deflection, rut depth, and crack area of pavements considering two types of surfacing: BM (bituminous macadam) + PC (premix carpet) and BM + AC (asphaltic concrete), commonly practiced in India. The performance of the pavements were studied and comparative analysis was made in terms of growth in deflection, rut depth, and crack area. An attempt has been made to develop failure envelopes based on selected critical rut depth criteria. The results are useful to decide the timing for maintenance/rehabilitation programs.

Ophthalmic tonometer with silicon micromachined structure

An electromechanical transducer with silicon micromachined die is described. The transducer is designed according to the Mackay-Marg principle of intraocular pressure (IOP) measurement. The transducer contains a 1 mm diameter SS 316 central movable plunger attached to the silicon die of a piezoresistive pressure sensor for the 100 kPa pressure region. The 2 mm×2 mm×0.38 mm die has a 1 mm× 1 mm×0.015 mm membrane with four piezoresistors in a Wheatstone bridge configuration. The plunger and die are packaged to the SS 316 body by means of standard IC mounting techniques. The transducer shows good static parameters with an output signal typically up to 40 mV of FSO for 60 mmHg of IOP. A very small deflection area of the cornea is obtained. The temperature characteristics are equal to a temperature coefficient of sensitivity (TCS) of −0.21% °C −1 per FSO. The dynamic output signal of the transducer versus time has a typical shape, well known from the Mackay-Marg description. An electronic system of the tonometer analyses the output dynamic, identifies the correct measurements, counts the IOP value, mean value and standard deviation of the measurement series.

Repetitive One-Tenth Micron Pattern Fabrication Using An EB Block Exposure System

Beam calibration techniques of an EB block exposure system (NOWEL 3) are developed to determine deflection and correction data to deflect beams through each mask pattern. After the calibration, the current densities in a deflection area differ less than 1.6% from the mean value. The exposure positioning errors are below 0.03 µ m in magnitude. The calibration results are used to expose a repetitive pattern of DRAM storage capacitors. The block mask has doughnut-type structures held by 2 µ m-wide bridges. Rectangular 0.45×0.85 µ m2 resist patterns with clear edges are resolved at 0.11 µ m intervals. Repetitive patterns in a logic LSIC are also exposed with the block exposure. We extract mask patterns from the cache memory and shift register regions. The number of exposure spots is decreased to about 1/5 of that used in conventional rectangular shaped beam methods. The stitching errors between the mask patterns are measured from the exposure results, which are less than 0.04 µ m.

Deflector and correction coil calibrations in an electron beam block exposure system

Mask deflectors and correction coils in an electron beam block exposure system are calibrated to expose 48 mask patterns in a deflection area with the same current density and at the same position on a wafer. The calibration has six measurement steps. When a mask stage changes area positions on a mask, only the last step needs to be executed during exposure. This last step takes about 2 s for measurement. Calibration results show that the current density through each mask pattern differs less than 1.6% from the mean value. Exposed position errors on a wafer are below 0.04 μm for 48 mask patterns. These position errors are corrected by additional deflections with an electrostatic minor deflector. To improve stitching accuracies between exposed patterns, we discuss another routine to adjust beam sizes and rotations of spots on a wafer.