Effect Of Various Designs Research Articles

Mechanics Comparison of Various Designs of Implant-supported Mandibular Restoration

The purpose of this study was to compare the effects of various designs of implants' placement on stress distribution in bone around the implants supporting one-unit fixed complete dentures. A computer tomography image was redrawn to reconstruct a digital three-dimensional solid model of a mandible including the cortical bone and cancellous bone. Moreover, the reverse engineering method and computer-aided design were employed to construct a digital three-dimensional solid model of fixed complete dentures as well as implant and abutment. All of the digital three-dimensional solid models were combined and transformed to the FE models, and they were classified into 7 configurations according to the number and location of the implants. The MSC/Patran software was used to develop the FE mesh comprising of 1101954 elements with 252693 nodes. The MSC/Nastran software was utilized as pre and post-processor for all mathematical calculations necessary to evaluate dental and mandibular biomechanics. One set of multiple vertical loads was used to simulate the possibility of occlusion status. And the von Mises stress values in the cortical bone, cancellous bone and implants were evaluated. The simulated results indicated that the stress distributions for FE models were largely affected by the number and location of implants. In the bone, similar to the single-tooth case, the von Mises stresses were all concentrated toward the cortical bone around the collar of the implants for FE models. By increasing the thickness of each connector of complete dentures, the stress distribution for cortical bone around implants could be decreased.

Steels with Ferrite-Bainite Microstructure with Improved Weldability and Cold Resistance for Main Pipelines

The required complex of properties of modern pipe steels, including improved weldability and cold resistance, can be achieved due to formation of fine-grained ferrite-bainite microstructure of steel. Effect of various designs of additional alloying of steel on phase transformations with use of deformation CCT diagrams is investigated. Key parameters of TMCPtechnology, necessary for obtaining the best complex of properties of plate and strip products are determined. Results of industrial trials in production of steel with ferrite-bainite microstructure of Russian steel manufacturers are presented.

Part 3: Pavement Surface Properties-Vehicle Interaction: Analysis of Effectiveness of Longitudinal Grooving Against Hydroplaning

Longitudinal pavement grooving has been applied in highways to reduce the occurrence of hydroplaning at accident-prone locations. However, to date there has not been a systematic study of its effectiveness against hydroplaning. This lack can be attributed to the difficulty in conducting such experiments and the extreme complexity of the theoretical analysis involved. A numerical model was developed to simulate the hydroplaning phenomenon. Then a systematic study was conducted on the effectiveness of various designs of longitudinal grooving against hydroplaning. The analysis covers groove widths of 2 to 10 mm, groove depths of 1 to 10 mm, and groove center-to-center spacing of 5 to 25 mm. Groove dimensions were found to have significant effects on the effectiveness of a grooving design against hydroplaning. The results show quantitatively how the use of larger groove width and depth and smaller groove spacing reduces hydroplaning risk, by computation of the changes in the expected hydroplaning speed. For t...

Analysis of Effectiveness of Longitudinal Grooving against Hydroplaning

Longitudinal pavement grooving has been applied in highways to reduce the occurrence of hydroplaning at accident-prone locations. However, to date there has not been a systematic study of its effectiveness against hydroplaning. This lack can be attributed to the difficulty in conducting such experiments and the extreme complexity of the theoretical analysis involved. A numerical model was developed to simulate the hydroplaning phenomenon. Then a systematic study was conducted on the effectiveness of various designs of longitudinal grooving against hydroplaning. The analysis covers groove widths of 2 to 10 mm, groove depths of 1 to 10 mm, and groove center-to-center spacing of 5 to 25 mm. Groove dimensions were found to have significant effects on the effectiveness of a grooving design against hydroplaning. The results show quantitatively how the use of larger groove width and depth and smaller groove spacing reduces hydroplaning risk, by computation of the changes in the expected hydroplaning speed. For the range of groove dimensions studied, the expected hydroplaning speed for a typical passenger car increased by approximately 2.8 km/h for every mm increase of groove depth, by approximately 3.5 km/h for every mm increase of groove width, and by approximately 1.0 km/h for every mm decrease of groove spacing. The model also was applied to evaluate the hydroplaning potential of different grooving designs used in practice and past studies and to explain the conflicting findings of past studies on whether longitudinal pavement grooving does improve traction and reduce hydroplaning risk.

Finite element analysis of bridge approach slabs considering soil – structure interaction

The objective of this paper is to present results of a study employed to identify the probable causes and location of cracking in bridge approach and transition slabs and the factors influencing the crack development. A finite element (FE) model has been developed to study the cracking phenomenon in bridge approach and transition slabs under vehicular live load and soil settlement. A field survey was conducted to determine the extent and probable causes of crack development in these slabs at various bridge sites in the State of New Jersey, USA. The data collected from field observations were compared with those predicted by the FE model to determine its reliability and consistency. The FE model was employed in conducting a parametric study to evaluate the effect of various designs as well as soil parameters on the cracking behavior of the slabs. The results from the parametric study showed that increasing the slab thickness would significantly increase the cracking load carrying capacity of the approach s...

Utility of deep sea CO2 release experiments in understanding the biology of a high‐CO2 ocean: Effects of hypercapnia on deep sea meiofauna

Oceanic CO2 levels are expected to rise during the next 2 centuries to levels not seen for 10–150 million years by the uptake of atmospheric CO2 in surface waters or potentially through the disposal of waste CO2 in the deep sea. Changes in ocean chemistry caused by CO2 influx may have broad impacts on ocean ecosystems. Physiological processes animals use to cope with CO2‐related stress are known, but the range of sensitivities and effects of changes in ocean chemistry on most ocean life remain unclear. We evaluate the effectiveness of various designs for in situ CO2 release experiments in producing stable perturbations in seawater chemistry over experimental seafloor plots, as is desirable for evaluating the CO2 sensitivities of deep sea animals. We also discuss results from a subset of these experiments on the impacts of hypercapnia on deep sea meiofauna, in the context of experimental designs. Five experiments off central California show that pH perturbations were greatest for experiments using “point source” CO2 pools surrounded by experimental plots. CO2 enclosure experiments with experimental plots positioned within a circular arrangement of CO2 pools had more moderate pH variation. The concentration of dissolution plumes from CO2 pools were related to the speed and turbulence of near‐bottom currents, which influence CO2 dissolution and advection. Survival of meiofauna (nematodes, amoebae, euglenoid flagellates) was low after episodic severe hypercapnia but lower and variable where pH changes ranged from 0 to 0.2 pH units below normal.

Adsorption performance of powdered activated carbon-ultrafiltration systems

The use of powdered activated carbon in combination with ultrafiltration membranes is attracting increasing interest for the removal of organic compounds in drinking water treatment. The overall adsorption efficiency of this hybrid membrane process strongly depends on the reactor configuration and its operating conditions. Identification of the operating conditions yielding optimum carbon performance can be facilitated by the use of mathematical models describing the adsorption process. In this study, the effect of various designs and operating parameters on the efficiency of the adsorption process is discussed using an adsorption model previously developed and verified by the authors. This discussion includes the effect of filtration time, membrane reactor volume, carbon dosing procedure, carbon dose and carbon particle size on the adsorption removal of two selected micropollutants and dissolved organic matter.

Application of solar assisted heating and desiccant cooling systems for a domestic building

The performance of solar assisted heating and desiccant cooling systems for a domestic two story residence located in Baghdad was evaluated. A computer simulation was developed to assess the effects of various designs and operating conditions on the performance of the system and its components. The solar air heating system included a V corrugated solar air heater array, a rock bed storage unit and an auxiliary heat source. A rotary silica gel desiccant dehumidifier, a sensible cooler and an evaporative cooler were added to the above system to form an open cycle solar assisted desiccant cooling system. The variable base degree-day method was employed in order to incorporate the hourly variations of solar heat gain and internal heat gains of the space in the estimation of the heating load. The transfer function method was used to evaluate the hourly variation of the cooling load. Only two collector rows in series were employed to provide the required supply air temperature for the heating system and the required regeneration temperature for the desiccant cooling system. This array gave an air outlet temperature of approximately 62°C at an air mass flux of 0.06 kg/s m 2 at midday in July, while a 36°C outlet air temperature was achieved for the same array and mass flux in January. The results of simulation of the solar air heating system indicated that the major design parameter is the collector area. The effect of air mass flux through the collector array was not significant. Also, increasing the rock bed storage volume produces only slight improvements in the solar fraction. Simulation of the open cycle solar assisted desiccant cooling system showed that the ambient temperature, regeneration temperature, heat exchanger effectiveness and evaporative cooler effectiveness have major influences on the system performance, whereas the dehumidifier has a minor effect. Also, the simulated system was capable of providing a cool supply of air at acceptable comfort conditions for various summer days in Baghdad.

Comparison of Parameter Estimation Design Criteria Using a Solute Transport Model with Matrix Diffusion

AbstractThree criteria for the experimental design of parameter estimation are compared by using the criteria to develop sampling patterns for determining parameter values in one‐dimensional transport models. The models include advection, dispersion, and matrix diffusion, the latter being an important process for nuclear waste isolation. The effectiveness of various designs is assessed by studying expected errors of parameter estimates and correlation between parameters. The correlations and expected errors are computed using parameter sensitivities, and the results demonstrate that the choice of design criterion can make a significant difference in the expected estimation error of parameter values in sparse designs. The best overall choice is D‐optimality, which is a measure of the volume of the joint confidence ellipsoid of the parameter estimates. E‐optimality, which minimizes the longest axis of the confidence ellipsoid, gives somewhat similar results but is not as robust for all of the estimated parameters. It is also shown that approaches that consider parameter sensitivities, but not correlation between parameters, may result in inferior designs.

The use of particle image velocimetry in the physical modeling of flow in electromagnetic or direct-chill casting of aluminum part II. Results of the physical model, including bag geometry, blockage, and nozzle placement

This second part of a two-part article describes the application of the physical model and particle image velocimetry (PIV) system, treated in Part I, to studying the flows in the pool at the top of the casters used for semicontinuous casting of aluminum. The effects of various designs of “bags” that are used in the industry to modify the flow were determined, as were the effects of blocking the outflow “windows” of the bag and the effects of varying the submergence of the nozzle delivering metal into the bag. The flows were found to be strongly dependent on bag design; for example, on the length of the bag and the presence of windows in the bottom of the bag. Flows in the vicinity of the (simulated) solidification front were greatly changed by such apparently small changes in design as lengthening the bag by 50 mm. A qualitative explanation is offered for some of these effects, and the article ends with a discussion of what might be the best flow from the viewpoint of caster operability or ingot structure.

Gas-particle interaction in detonation spraying systems

A model is developed to describe dynamic interaction of particles with the carrier gas during detonation spraying. Equations of mass, energy, and momentum conservation are integrated numerically for the two-phase particle-gas flow with the Hugoniot boundary conditions at the detonation wave front. Velocity and temperature of the sprayed powder and the gas parameters are calculated self-consistently, taking into account effects of friction and cooling of the gas in the vicinity of the gun barrel and effects of particle-gas interaction on the parameters of the gas phase. Calculations are performed for tungsten carbide particles of 30 μm diam and a 1.8 m long detonation gun using a stoichiometric mixture of oxygen and propane. Distributions of gas and particle parameters along the barrel are calculated for various moments of time. Tungsten carbide particles of 30 μm reach an exit velocity of 1278 m/s and a temperature of 1950 K. Exit particle velocity is a nonmonotonic function of the loading distance,L, with a distinct maximum atL = 75 cm. The proposed model can be applied to a broad range of problems related to detonation coating technology and allows evaluation of the effectiveness of various designs and optimization of operational parameters of detonation spraying systems.

Reactor tests and postirradiation examination of htgr fuel elements and coated particles

An extensive series of irradiation tests have been carried out on HTGR spherical fuel elements and coated particle fuels. The effects of various designs and fabrication processes on the irradiation stabilities of the fuel elements have been determined. The behavior of the fuel elements and coated particle fuels under design basis accidents and severe accident conditions has been examined.

Measurement of environmental vibrations in Langmuir films

Several methods of measuring vibrations in monolayer films were used to evaluate the effectiveness of various designs of vibration isolation tables. Both a recording seismograph and a Langmuir film balance interfaced to a microcomputer (IBM-PC) were used to monitor vibrations in the film for each of the designs which were studied. A correlation between the film balance measurements and the seismographic results was shown. It was concluded that the film balance itself can be used as a sensitive indicator of environmental vibrations in monolayer films. A preferred method of vibration isolation was determined from these results.

Mass transfer at the surface of a rotating cylinder

The effect of various designs of cylinder and cylinder mounting on the equiaccessibility of the cylinder surface is described. It is shown that unless proper care is taken by the fitting of inert end sections to the cylinder, there can be a substantial increase in mass transfer near the cylinder ends. Using such properly designed cylinders, the empirical equation for mass transfer to the surface of rotating cylinder was redetermined for the range of Reynolds numbers 10 3–10 5. The expression for k, the mass transfer coefficient is ▪ Complications caused by surface roughening are also considered.

A Radiant Heated Titanium Sublimator

A new radiant heated sublimator is described which employs an approximately spherical shell of titanium enclosing a tungsten filament heater. The sublimator is relatively simple in construction and can dispense ∼37 g of titanium at sublimation rates up to 0.5 g/h. The sublimation rate at a given power input remains relatively constant throughout the life of the sublimator, making it very simple and reliable to operate. Comparative experiments are described with both spherical and cylindrical sublimators which illustrate the effect of various designs on the sublimation rate versus power and time characteristics. The operating characteristics of this device are discussed relative to other sublimation sources in common use in the field of titanium sublimation pumping.