Excellence in Research and Innovation for Humanity

International Science Index

Commenced in January 1999 Frequency: Monthly Edition: International Abstract Count: 40434

Mechanical and Mechatronics Engineering

Flow Structure Analysis Downstream the Front Wheel Arch of a Passenger Car
The flow around realistic passenger vehicles is highly complex and characterized by many different flow structure interactions. The flow behind the front wheel house is particularly complicated due to interactions among the wheelhouse, the underbody and the external flow. In addition, the rotation of the wheel creates extra difficulties. Therefore it is of high importance to increase the understanding of the occurring flow phenomena. In this work, time resolved surface pressure measurements are analyzed regarding the pressure distribution, standard deviation, cross correlations and frequency spectra of the structures immediately behind the front wheel arch of a full scale car. The study shows that two flow phenomena can be observed. One results from the flow over the hood and a second is created by a separation at the wheelhouse edge. It is discussed how these propagate over the investigated region and to what extent the flow through the rim and around the front of the car influences the structure development. To correlate the experimental findings with the structures occurring in the bulk flow, results from CFD computations are used to complement the work.
Establishment of Direct Relationships to Calculate Properties of Palm Biodiesel and Diesel Blends
Biodiesel, as an alternative for the conventional fossil fuel Diesel, has been given importance by the world of research. With a motive of improving certain properties of diesel, palm biodiesel has been blended in different volume proportions. Subsequently, with an intention of developing a better understanding of the effect of biodiesel proportion on the properties of diesel, properties like flash point, fire point, cloud point, pour point and heating value of the blends were determined. The properties determined for 9 blends of palm biodiesel and diesel were compared with those of petrodiesel. With the increasing palm biodiesel percentage, cloud point and pour point of the diesel are found to increase which is not preferable. Flash point and fire point of the blends are found to increase with increasing palm content. Well lying within the limits, heating value of the blends is found to decrease with the increasing biodiesel content. Based on the percentage of palm biodiesel added and the properties data, a multi linear regression approach is used to develop correlations to predict biodiesel and diesel blend properties based on the blend percentage. The developed regression correlations are validated using different biodiesel and diesel blends other than those used as an input to develop them. Neural networking analysis is performed using MATLAB nntool which predicts properties of biodiesel and diesel blends based on the blend percentage.
Application of Computational Fluid Dynamic to Predict NOx Formation in a Coal-Fired Industrial Boilers
Nowadays, Asia pacific region has become a promising market target in terms of power generation industry. Especially Indonesia plans to add 35000 MW of electricity by building new power plants which are mostly covered by coal-fired ones. The project is a very challenging task especially if the government plans to apply clean coal technology with regards to the pollutant emission regulation. Meanwhile, numerical modelling of combustion processes in conjunction with Computational Fluid Dynamics (CFD) has become a very efficient tool and is hence widely applied in predicting flow field, temperature, flue gas composition, and particle aerodynamics inside coal-fired furnaces achieving a high local resolution and reliability. An advanced CFD models in designing low-NOx burners can ensure an effective optimization of the combustion system. In this work, a commercial CFD code (FLUENT) has been extended via User Defined Function (UDF) to calculate NOx concentration in the flue gas of utility boiler. In addition to the pollutant formation, this paper covers also some aspects related to the other main combustion parameters such as: temperature and flue gas concentration. Capability of various NOx formation pathways is evaluated by using the existing experimental data from the International Flame Research Foundation (IFRF) combustion test facility. Furthermore, the applicability of the model is validated to the full-scale industrial combustion for power generation. The results show that the simulation results are in agreement with the values at the boiler outlet.
Result Analysis for the Accelerated Life Cycle Test of the Motor for Washing Machine by Using Acceleration Factor
Accelerated life cycle test is applied to various products or components in order to reduce the time of life cycle test in the industry. It must consider many test conditions according to the product characteristics of the test subject and selection of acceleration parameter is especially very important. We carried out the general life cycle test and the accelerated life cycle test by applying the acceleration factor (AF) considering the characteristics of brushless dc (BLDC) motor for washing machine. The final purpose of this study is to verify the validity by analyzing the results of the general life cycle test and the accelerated life cycle test. It will make it possible to reduce the life test time through the reasonable accelerated life cycle test.
Adjustable Aperture with Liquid Crystal for Real-Time Range Sensor
An adjustable aperture using a liquid crystal is proposed for real-time range detection and obtaining images simultaneously. The adjustable aperture operates as two types of aperture stops which can create two different Depth of Field images. By analyzing these two images, the distance can be extracted from camera to object. Initially, the aperture stop has large size with zero voltage. When the input voltage is applied, the aperture stop transfers to smaller size by orientational transition of liquid crystal molecules in the device. The diameter of aperture stop is 1.94mm and 1.06mm. The proposed device has low driving voltage of 7.0V and fast response time of 6.22m. Compact size aperture of 6×6×1.1 mm3 is assembled in conventional camera which contains 1/3” HD image sensor and focal length of 3.3mm that can be used in autonomous. The measured range was up to 5m. The adjustable aperture has high stability due to no mechanically moving parts. This range sensor can be applied to the various field of 3D depth map application which is the Advanced Driving Assistance System(ADAS), drones and manufacturing machine.
A Hybrid Analytical/Experimental Model for Evaluation of the Aerodynamic Noise in Fan Coil
This paper aims to investigate and minimize the negative effects of reversed flows and vortices on the aerodynamics and aeroacoustics performance of an open system consisting of an axial fan and a heat exchanger where hybrid method incorporating CFD and CAA is used to predict the noise behavior. To achieve this goal, the flow inside the system was refined by designing an air channel form which reduces the intensity of reversed flows and vortices. Thus, the Curle's boundary dipole noise contribution at low frequency and the quadrupolar aerodynamic noise contribution generated by the flow field could be reduced. Unsteady flow field of the original and air channel cases were obtained by using different turbulence models. The SAS model is capable of resolving large-scale turbulent structures without the time and grid-scale resolution restrictions of LES, often allowing the use of existing grids created for RANS simulations. For this reason, three different turbulence models, namely URANS, LES, SAS have been applied. Acoustic sources were computed based on the pressure fluctuations and sound pressure level and frequency dependent graphics were plotted with Fast Fourier Transform. On the other hand, acoustic measurements were performed in a semi-anechoic chamber for both of them. When the experimental and numerical results were compared with the previously determined receiver points, the accuracy rate was obtained as LES, SAS, URANS respectively. Besides, all over sound pressure level at low frequency was minimized with the aid of the new air channel design.
High Sensitivity Crack Detection and Locating with Optimized Spatial Wavelet Analysis
In this study, a spatial wavelet-based crack localization technique for a thick beam is presented. Wavelet scale in spatial wavelet transformation is optimized to enhance crack detection sensitivity. A windowing function is also employed to erase the edge effect of the wavelet transformation, which enables the method to detect and localize cracks near the beam/measurement boundaries. Theoretical model and vibration analysis considering the crack effect are first proposed and performed in MATLAB based on the Timoshenko beam model. Gabor wavelet family is applied to the beam vibration mode shapes derived from the theoretical beam model to magnify the crack effect so as to locate the crack. Relative wavelet coefficient is obtained for sensitivity analysis by comparing the coefficient values at different positions of the beam with the lowest value in the intact area of the beam. Afterward, the optimal wavelet scale corresponding to the highest relative wavelet coefficient at the crack position is obtained for each vibration mode, through numerical simulations. The same procedure is performed for cracks with different sizes and positions in order to find the optimal scale range for the Gabor wavelet family. Finally, Hanning window is applied to different vibration mode shapes in order to overcome the edge effect problem of wavelet transformation and its effect on the localization of crack close to the measurement boundaries. Comparison of the wavelet coefficients distribution of windowed and initial mode shapes demonstrates that window function eases the identification of the cracks close to the boundaries.
Investigation of Heat Loss from Pipes Buried in Seabed
Prediction and evaluation of heat loss from a pipeline is a major concern in most oil and gas operations. From a flow assurance point of view, accurate knowledge of the temperature distribution of the fluids being transported is invaluable in determining efficient and effective measures that ensure continuous operation of the pipeline. Pipe burial is a common practice in order to protect the pipeline against natural elements and accidental physical damages such as ice gouging. Heat loss from a buried pipeline is therefore an area of interest in both production and transportation of oil and gas. This is especially important in offshore and arctic environments where the extreme conditions make flow assurance that much more challenging. Most of the current practices are based on simple analytical models that are not always very accurate and can increase the flow assurance expenses exponentially with over-conservative predictions or worse, lead to pipeline failure. One of the most common caveats in these models is the assumption of pure conduction in the soil surrounding the pipe. This is distinctly observed in offshore pipe burials where the high saturation and low consolidation of the backfill soil increase the potential for convective heat transfer through the porous medium of the soil. The present work is aimed to address this gap. Numerical modeling is backed by experiments in order to determine the importance of natural convection in a saturated soil and predict the heat loss from and temperature distribution of a buried pipe more accurately.
Analysis of Mechanisms for Design of Add-On Device to Assist in Stair Climbing of Wheelchairs
In the present scenario, many motorized stair climbing wheelchairs are available in the western countries which are significantly expensive and hence are not popular in developing countries. Also, such wheelchairs tend to be bulkier and heavy which makes their use for normal conditions difficult. Manually operated solutions are rarely explored in this space. Therefore, this project aims at developing a manually operated cost effective solution for the same. Differently abled people are not required to climb stairs frequently in their daily use. Because of this, carrying a stair climbing mechanism attached to the wheelchair permanently adds redundant weight to the wheelchair which reduces ease of use of the wheelchair. Hence, the idea of add-on device for stair climbing was envisaged wherein the wheelchair is mounted onto add-on only at the time when climbing the stairs is required. This work analyses in detail the mechanism for stair climbing of conventional wheelchair followed by analysis and iterations on multiple mechanisms to identify the most suitable mechanism for application in the add-on device. Further, this work imparts specific attention to optimize the force and time required for stair climbing of wheelchairs. The most suitable mechanism identified was validated by building and testing a prototype.
Investigating the Effect of a Humanoid Robot's Gaze Direction on Imitating Human Emotions
Humans show their emotions with facial expressions. In this paper, we investigate the effect of a humanoid robot's gaze direction on imitating human emotions. In an Internet survey through animation, we asked participants to adjust the gaze of a robot to express six basic emotions: Anger, Disgust, Fear, Happiness, Sadness, and Surprise. We found that humans expect a robot to look straight down when it is angry or sad, to look straight up when it is surprised or happy, and to look down and to its right when it is afraid. We also found that when a robot is disgusted some humans expect it to look straight to its right and some expect it to look down and to its left. We found that humans expect the robot to use an averted gaze for all six emotions in contrast to other studies that showed approach-oriented (anger and joy) emotions being attributed to direct gaze and avoidance-oriented emotions (fear and sadness) being attributed to averted gaze.
Global Direct Search Optimization of a Tuned Liquid Column Damper Subject to Stochastic Load
In this paper, a global direct search optimization algorithm to reduce vibration of a tuned liquid column damper (TLCD), a class of passive structural control device, is presented. The objective is to find optimized parameters for the TLCD under stochastic load from different wind power spectral density. A verification is made considering the analytical solution of an undamped primary system under white noise excitation. Finally, a numerical example considering a simplified wind turbine model is given to illustrate the efficacy of the TLCD. Results from the random vibration analysis are shown for four types of random excitation wind model where the response PSDs obtained showed good vibration attenuation.
Direct Visualization of Shear Induced Structures in Wormlike Micellar Solutions by Microfluidics and Advanced Microscopy
In the last decades, wormlike micellar solutions have been extensively used to tune the rheological behavior of home care and personal care products. This and other successful applications underlie the growing attention that both basic and applied research are devoting to these systems, and to their unique rheological and flow properties. One of the key research topics is the occurrence of flow instabilities at high shear rates (such as shear banding), with the possibility of appearance of flow induced structures. In this scenario, microfluidics is a powerful tool to get a deeper insight into the flow behavior of a wormlike micellar solution, as the high confinement of a microfluidic device facilitates the onset of the flow instabilities; furthermore, thanks to its small dimensions, it can be coupled with optical microscopy, allowing a direct visualization of flow structuring phenomena. Here, the flow of a widely used wormlike micellar solution through a glass capillary has been studied, by coupling the microfluidic device with μPIV techniques. The direct visualization of flow-induced structures and the flow visualization analysis highlight a relationship between solution structuring and the onset of discontinuities in the velocity profile.
Linearization of Y-Force Equation of Rigid Body Equation of Motion and Behavior of Fighter Aircraft under Imbalance Weight on Wings during Combat
Y-force equation comprises aerodynamic forces, drag and side force with side slip angle β and weight component along with the coupled roll (φ) and pitch angles (θ). This research deals with the linearization of Y-force equation using Small Disturbance theory assuming equilibrium flight conditions for different state variables of aircraft. By using assumptions of Small Disturbance theory in non-linear Y-force equation, finally reached at linearized lateral rigid body equation of motion; which says that in linearized Y-force equation, the lateral acceleration is dependent on the other different aerodynamic and propulsive forces like vertical tail, change in roll rate (Δp) from equilibrium, change in yaw rate (Δr) from equilibrium, change in lateral velocity due to side force, drag and side force components due to side slip, and the lateral equation from coupled rotating frame to decoupled rotating frame. This paper describes implementation of this lateral linearized equation for aircraft control systems. Another significant parameter considered on which y-force equation depends is ‘c’ which shows that any change bought in the weight of aircrafts wing will cause Δφ and cause lateral force i.e. Y_c. This simplification also leads to lateral static and dynamic stability. The linearization of equations is required because much of mathematics control system design for aircraft is based on linear equations. This technique is simple and eases the linearization of the rigid body equations of motion without using any high-speed computers.
A Simulation Study of E-Glass Reinforced Polyurethane Footbed and Investigation of Some Parameters Effecting Elastic Behaviour of Footbed Material
In this study, we mainly focused on a simulation study regarding composite footbed in order to contribute to shoe industry. As a footbed, e-glass fiber reinforced polyurethane was determined since polyurethane based materials are already used for footbed in shoe manufacturing frequently. Ansys 14.0 APDL mechanical module is utilized in all simulations and analysed stress distributions for different fiber angles and amounts. Furthermore, young modulus of the composite was calculated theoretically and interpreted for mechanical aspects.
Design and Analysis of a Planetary Gearbox Used in Stirred Vessel
Gear in stirred vessel is one of the most critical components in machinery which has power transmission system and it is rotating machinery cost and redesign being the major constraints, there is always a great scope for a mechanical engineer to apply skills to improve the design. Gear will be most effective means of transmitting power in future machinery due to their high degree of compactness. The Galliard moved in the industry from heavy industries such as textile machinery and shipbuilding to industries such as automobile manufacture tools will necessitate the affable application of gear technology. The two-stage planetary reduction gear unit is designed to meet the output specifications. In industries, where the bevel gears are used in turret vessel to transmit the power, that unit is replaced by this planetary gearbox. Use of this type of gearbox is to get better efficiency and also the manufacturing of the bevel gear is more complex than the spur gears. Design a gearbox with the epicyclic gear train. In industries, the power transmission from gearbox to vessel is done through the bevel gears, which transmit the power at a right angle. In this work, the power is to be transmitted vertically from gearbox to vessel, which will increase the efficiency and life of gears. The arrangement of the gears is quite difficult as well as it needs high manufacturing cost and maintenance cost. The design is replaced by the planetary gearbox to reduce the difficulties, and same output is achieved but with a different arrangement of the planetary gearbox.
A Method of Drilling a Ground Using a Robotic Arm
Underground tunnel face bolting and pipe umbrella prereinforcement is one of the most challenging tasks in the construction industry. Through a variety of soil and rock, the cyclic Conventional Tunneling Method (CTM) excavation method remains the best one for projects with highly variable ground conditions or shapes and the only alternative for the renovation of existing tunnels and creating emergency exit. During the drilling process, a wide variety of nondesired vibrations may arise, and a method using a robot arm is proposed. The main kind of drilling through vibration here is the bit-bouncing phenomenon (resonant axial vibration). Hence, assist the task by a robot arm may play an important role on drilling performances and security. We propose to control the axial-vibration phenomenon along the drill-pipes at a practical resonant frequency, and transport the resonant sonic drilling head by a robot arm for the operation. Many questionable industry drilling criteria are discussed in this paper.
Experimental Validation of Computational Fluid Dynamics Used for Pharyngeal Flow Patterns during Obstructive Sleep Apnea
Obstructive sleep apnea (OSA) is a sleep disorder where the patient suffers a disturbed airflow during sleep due to partial or complete occlusion of the pharyngeal airway. Recently, numerical simulations have been used to better understand the mechanism of pharyngeal collapse. However, to gain confidence in the solutions so obtained, an experimental validation is required. Therefore, in this study an experimental validation of computational fluid dynamics (CFD) used for the study of human pharyngeal flow patterns during OSA is performed. A stationary incompressible Navier-Stokes equation solved using the finite element method was used to numerically study the flow patterns in a computed tomography-based human pharynx model. The inlet flow rate was set to 250 ml/s and such that a flat profile was maintained at the inlet. The outlet pressure was set to 0 Pa. The experimental technique used for the validation of CFD of fluid flow patterns is phase contrast-MRI (PC-MRI). Using the same computed tomography data of the human pharynx as in the simulations, a phantom for the experiment was 3 D printed. Glycerol (55.27% weight) in water was used as a test fluid at 25°C. Inflow conditions similar to the CFD study were simulated using an MRI compatible flow pump (CardioFlow-5000MR, Shelley Medical Imaging Technologies). The entire experiment was done on a 3 T MR system (Ingenia, Philips) with 108 channel body coil using an RF-spoiled, gradient echo sequence. A comparison of the axial velocity obtained in the pharynx from the numerical simulations and PC-MRI shows good agreement. The region of jet impingement and recirculation also coincide, therefore validating the numerical simulations. Hence, the experimental validation proves the reliability and correctness of the numerical simulations.
Investigation of Polymers and CuInS₂ Quantum Dots Heterojunction
CuInS₂ quantum dots have been synthesized successfully by hydrothermal process. The structural and morphological characteristics have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM). XRD study confirms the formation of chalcopyrite phase of CuInS₂. SEM and TEM analysis confirm the spherical shape particles of size in the range of 2-3 nm. X-ray photoelectron spectroscopy (XPS) shows the chemical composition of Cu and In elements in +1 and +3 oxidation state respectively. Raman spectroscopy, photoluminescence spectroscopy, and UV-Visible spectroscopy were also studied to investigate the optical properties of CuInS₂ quantum dots. ZnO nanoparticles have been fabricated by a chemical method with the size of 8-10 nm. In order to investigate the diode behavior, the heterojunction device ITO/PEDOT:PSS/P3HT:CuInS₂/ZnO/Al was designed by the spin casting process and thermal evaporation method. Atomic force microscopy was used to determine the thickness of various layers, and it was found to be 85 nm, 182 nm and 23 nm of PEDOT:PSS, P3HT:CuInS₂ and ZnO thin layers, respectively. The saturation current along with the turn-on voltage was measured and was found to be 1.04 µA and 0.28 V, respectively. Moreover, the ideality factor was calculated to be 5.3.
Finite Element Modeling of a Lower Limb Based on the East Asian Body Characteristics for Pedestrian Protection
Current vehicle safety standards and human body injury criteria were established based on the biomechanical response of Euro-American human body, without considering the difference in the body anthropometry and injury characteristics among different races, particularly the East Asian people with smaller body size. Absence of such race specific design considerations will negatively influence the protective performance of safety products for these populations, and weaken the accuracy of injury thresholds derived. To resolve these issues, in this study, we aim to develop a race specific finite element model to simulate the impact response of the lower extremity of a 50th percentile East Asian (Chinese) male. The model was built based on medical images for the leg of an average size Chinese male and slightly adjusted based on the statistical data. The model includes detailed anatomic features and is able to simulate the muscle active force. Thirteen biomechanical tests available in the literature were used to validate its biofidelity. Using the validated model, a pedestrian-car impact accident taking place in China was re-constructed computationally. The results show that the newly developed lower leg model has a good performance in predicting dynamic response and tibia fracture pattern. An additional comparison on the fracture tolerance of the East Asian and Euro-American lower limb suggests that the current injury criterion underestimates the degree of injury of East Asian human body.
Linear Evolution of Compressible Görtler Vortices Subject to Free-Stream Vortical Disturbances
Görtler instabilities generate in boundary layers from an unbalance between pressure and centrifugal forces caused by concave surfaces. Their spatial streamwise evolution influences transition to turbulence. It is therefore important to understand even the early stages where perturbations, still small, grow linearly and could be controlled more easily. This work presents a rigorous theoretical framework for compressible flows using the linearized unsteady boundary region equations, where only the streamwise pressure gradient and streamwise diffusion terms are neglected from the full governing equations of fluid motion. Boundary and initial conditions are imposed through an asymptotic analysis in order to account for the interaction of the boundary layer with free-stream turbulence. The resulting parabolic system is discretize with a second-order finite difference scheme. Realistic flow parameters are chosen from wind tunnel studies performed at supersonic and subsonic conditions. The Mach number ranges from 0.5 to 8, with two different radii of curvature, 5 m and 10 m, frequencies up to 2000 Hz, and vortex spanwise wavelengths from 5 mm to 20 mm. The evolution of the perturbation flow is shown through velocity, temperature, pressure profiles relatively close to the leading edge, where non-linear effects can still be neglected, and growth rate. Results show that a global stabilizing effect exists with the increase of Mach number, frequency, spanwise wavenumber and radius of curvature. In particular, at high Mach numbers curvature effects are less pronounced and thermal streaks become stronger than velocity streaks. This increase of temperature perturbations saturates at approximately Mach 4 flows, and is limited in the early stage of growth, near the leading edge. In general, Görtler vortices evolve closer to the surface with respect to a flat plate scenario but their location shifts toward the edge of the boundary layer as the Mach number increases. In fact, a jet-like behavior appears for steady vortices having small spanwise wavelengths (less than 10 mm) at Mach 8, creating a region of unperturbed flow close to the wall. A similar response is also found at the highest frequency considered for a Mach 3 flow. Larger vortices are found to have a higher growth rate but are less influenced by the Mach number. An eigenvalue approach is also employed to study the amplification of the perturbations sufficiently downstream from the leading edge. These eigenvalue results are compared with the ones obtained through the initial value approach with inhomogeneous free-stream boundary conditions. All of the parameters here studied have a significant influence on the evolution of the instabilities for the Görtler problem which is indeed highly dependent on initial conditions.
Towards a Complete Automation Feature Recognition System for Sheet Metal Manufacturing
Sheet metal processing is automated, but the step from product models to the production machine control still requires human intervention. This may cause time-consuming bottlenecks in the production process and increase the risk of human errors. In this paper we present a system, which automatically recognizes features from the CAD-model of the sheet metal product. By using these features, the system produces a complete model of the particular sheet metal product. Then the model is used as an input for the sheet metal processing machine. Currently the system is implemented, capable to recognize more than 11 of the most common sheet metal structural features, and the procedure is fully automated. This provides remarkable savings in the production time, and protects against the human errors. This paper presents the developed system architecture, applied algorithms and system software implementation and testing.
CFD Simulation of the Pressure Distribution in the Upper Airway of an Obstructive Sleep Apnea Patient
CFD simulations are performed in the upper airway of a patient suffering from obstructive sleep apnea (OSA) that is a sleep related breathing disorder characterized by repetitive partial or complete closures of the upper airways. The simulations are aimed at getting a better understanding of the pathophysiological flow patterns in an OSA patient. The simulation is compared to medical data of a sleep endoscopic examination under sedation. A digital model consisting of surface triangles of the upper airway is extracted from the MR images by a region growing segmentation process and is followed by a careful manual refinement. The computational domain includes the nasal cavity with the nostrils as the inlet areas and the pharyngeal volume with an outlet underneath the larynx. At the nostrils a flat inflow velocity profile is prescribed by choosing the velocity such that a volume flow rate of 150 ml/s is reached. Behind the larynx at the outlet a pressure of -10 Pa is prescribed. The stationary incompressible Navier-Stokes equations are numerically solved using finite elements. A grid convergence study has been performed. The results show an amplification of the maximal velocity of about 2.5 times the inlet velocity at a constriction of the pharyngeal volume in the area of the tongue. It is the same region that also shows the highest pressure drop from about 5 Pa. This is in agreement with the sleep endoscopic examinations of the same patient under sedation showing complete contractions in the area of the tongue. CFD simulations can become a useful tool in the diagnosis and therapy of obstructive sleep apnea by giving insight into the patient’s individual fluid dynamical situation in the upper airways giving a better understanding of the disease where experimental measurements are not feasible. Within this study, it could been shown on one hand that constriction areas within the upper airway lead to a significant pressure drop and on the other hand a good agreement of the area of pressure drop and the area of contraction could be shown.
Application of Fuzzy Logic to Design and Coordinate Parallel Behaviors for a Humanoid Mobile Robot
This paper presents a design and implementation of a navigation controller for a humanoid mobile robot platform to operate in indoor office environments. In order to fulfil the requirement of recognizing and approaching human to provide service while avoiding random obstacles, a behavior-based fuzzy logic controller was designed to simultaneously coordinate multiple behaviors. Experiments in real office environment showed that the fuzzy controller deals well with complex scenarios without colliding with random objects and human.
Analytical Technique for Definition of Internal Forces in Links of Robotic Systems and Mechanisms with Statically Indeterminate and Determinate Structures Taking into Account the Distributed Dynamical Loads and Concentrated Forces
The distributed inertia forces of complex nature appear in links of rod mechanisms within the motion process. Such loads raise a number of problems, as the problems of destruction caused by a large force of inertia; elastic deformation of the mechanism can be considerable, that can bring the mechanism out of action. In this work, a new analytical approach for the definition of internal forces in links of robotic systems and mechanisms with statically indeterminate and determinate structures taking into account the distributed inertial and concentrated forces is proposed. The relations between the intensity of distributed inertia forces and link weight with geometrical, physical and kinematic characteristics are determined in this work. The distribution laws of inertia forces and dead weight make it possible at each position of links to deduce the laws of distribution of internal forces along the axis of the link, in which loads are found at any point of the link. The approximation matrixes of forces of an element under the action of distributed inertia loads with the trapezoidal intensity are defined. The obtained approximation matrixes establish the dependence between the force vector in any cross-section of the element and the force vector in calculated cross-sections, as well as allow defining the physical characteristics of the element, i.e., compliance matrix of discrete elements. Hence, the compliance matrixes of an element under the action of distributed inertial loads of trapezoidal shape along the axis of the element are determined. The internal loads of each continual link are unambiguously determined by a set of internal loads in its separate cross-sections and by the approximation matrixes. Therefore, the task is reduced to the calculation of internal forces in a final number of cross-sections of elements. Consequently, it leads to a discrete model of elastic calculation of links of rod mechanisms. The discrete model of the elements of mechanisms and robotic systems and their discrete model as a whole are constructed. The dynamic equilibrium equations for the discrete model of the elements are also received in this work as well as the equilibrium equations of the pin and rigid joints expressed through required parameters of internal forces. Obtained systems of dynamic equilibrium equations are sufficient for the definition of internal forces in links of mechanisms, which structure is statically definable. For determination of internal forces of statically indeterminate mechanisms (in the way of determination of internal forces), it is necessary to build a compliance matrix for the entire discrete model of the rod mechanism, that is reached in this work. As a result by means of developed technique the programs in the MAPLE18 system are made and animations of the motion of the fourth class mechanisms of statically determinate and statically indeterminate structures with construction on links the intensity of cross and axial distributed inertial loads, the bending moments, cross and axial forces, depending on kinematic characteristics of links are obtained.
Heat and Mass Transfer of Triple Diffusive Convection in a Rotating Couple Stress Liquid Using Ginzburg-Landau Model
A nonlinear study of triple diffusive convection in a rotating couple stress liquid has been analysed. It is performed to study the effect of heat and mass transfer by deriving Ginzburg-Landau equation. Heat and mass transfer are quantified in terms of Nusselt number and Sherwood numbers, which are obtained as a function of thermal and solute Rayleigh numbers. The obtained Ginzburg-Landau equation is Bernoulli equation, and it has been elucidated numerically using Mathematica. The effect of couple stress parameter, solute Rayleigh numbers and Taylor number on the onset of convection and heat and mass transfer have been examined. It is found that the effects of couple stress parameter and Taylor number are to stabilize the system and increase the heat and mass transfer.
Numerical Investigation of Subcooled Boiling Flow at Elevated Pressure Using a Mechanistic Wall Heat Partitioning Model
The wide range of industrial applications involved with boiling flows promotes the necessity of establishing fundamental knowledge in boiling flow phenomena. For this purpose, a number of experimental and numerical researches have been performed to elucidate the underlying physics of this flow. In this paper, the improved wall boiling models, implemented on ANSYS CFX 14.5, were introduced to study subcooled boiling flow at elevated pressure. At the heated wall boundary, the Fractal model, Force balance approach and Mechanistic frequency model are proposed for predicting the nucleation site density, bubble departure diameter, and bubble departure frequency. The proposed wall heat flux partitioning closures were modified to consider the influence of bubble sliding along the wall before the lift-off, which usually happens in the flow boiling. The simulation was performed based on the Two-fluid model, where the standard k-ω SST model was selected for turbulence modelling. Existing experimental data at 4-5 bars were chosen to evaluate the accuracy of the proposed mechanistic approach. The results show that the void fraction and Interfacial Area Concentration (IAC) are in good agreement with the experimental data. However, the predicted bubble velocity and Sauter Mean Diameter (SMD) are over-predicted. This over-prediction may be caused by consideration of only dispersed and spherical bubbles in the simulations. According to the experiments, it is better to consider the mechanisms, such as merging of bubbles during sliding and shrinking of bubbles while growing due to the condensation, to enhance the mechanistic model capability for a wider range of flow prediction.
Numerical Investigation of Fluid Outflow Through a Retinal Hole After Scleral Buckling
Objectives of the study are i) to perform numerical simulations that permit an analysis of the dynamics of subretinal fluid when an implant has induced scleral intussusception and ii) assess the impact of the physical parameters of the model on the flow rate. Computer simulations were created using finite element method (FEM) based on a model that takes into account the interaction of a viscous fluid (subretinal fluid) with a hyperelastic body (retina). The purpose of the calculation was to investigate the dependence of the flow rate of subretinal fluid through a hole in the retina on different factors such as: viscosity of subretinal fluid, material parameters of the retina, and the offset of the implant from the retina’s hole. These simulations were performed for different speeds of eye movement that reflect the behavior of the eye when reading, REM, and saccadic movements. Similar to other works in the field of subretinal fluid flow, it was assumed stationary, single sided, forced fluid flow in the considered area simulating the subretinal space. Additionally, a hyperelastic material model of the retina and parameterized geometry of the considered model was adopted. The calculations also examined the influence the direction of the force of gravity due to the position of the patient’s head on the trend of outflow of fluid. The simulations revealed that fluid outflow from the retina becomes significant with eyeball movement speed of 100°/sec. This speed is greater than in the case of reading, but is four times less than saccadic movement. The increase of viscosity of the fluid increased beneficial effect. Further, the simulation results suggest that moderate eye movement speed is optimal and that the conventional prescription of the avoidance of routine eye movement following retinal detachment surgery should be relaxed. Additionally, to verify numerical results, some calculations were repeated with use of meshless method (method of fundamental solutions), which is relatively fast and easy to implement.
Study of the S-Bend Intake Hammershock Based on Improved Delayed Detached Eddy Simulation
Numerical investigation of hammershock propagation in the S-bend intake caused by engine surge has been conducted by using Improved Delayed Detach-Eddy Simulation (IDDES). The effects of surge signatures on hammershock characteristics are obtained. It was shown that once the hammershock is produced, it moves upward to the intake entrance quickly with constant speed, however, the strength of hammershock keeps increasing. Meanwhile, being influenced by the centrifugal force, the hammershock strength on the larger radius side is much larger. Hammershock propagation speed and strength are sensitive to the ramp upgradient of surge signature. A larger ramp up gradient results in higher propagation speed and greater strength. Nevertheless, ramp down profile of surge signature have no obvious effect on the propagation speed and strength of hammershock. Increasing the maximum value of surge signature leads to enhance in the intensity of hammershock, they approximate match quadratic function distribution law.
Design and Fabrication of Micro-Bubble Oxygenator
The present research applies the MEMS technology to design and fabricate a micro-bubble generator by a piezoelectric actuator. Coupled with a nickel nozzle plate, an annular piezoelectric ceramic was utilized as the primary structure of the proposed generator. In operations, the piezoelectric element deforms transversely under an electric field applied across the thickness of the generator. The surface of the nozzle plate can expand or contract because of the induction of radial strain, resulting in the whole structure to bend, and successively transport oxygen micro-bubbles into the blood flow for enhancing the oxygen content in blood. In the tests, a high magnification microscope and a high speed CCD camera were employed to photograph the time evolution of meniscus shape of gaseous bubbles dispensed from the micro-bubble generator for flow visualization. This investigation thus explored the bubble formation process including the influences of inlet gas pressure along with driving voltage and resonance frequency on the formed bubble extent.
Optimization and Simulation Models Applied in Engineering Planning and Management
Mathematical simulation and optimization models packaged within interactive computer programs provide a common way for planners and managers to predict the behaviour of any proposed water resources system design or management policy before it is implemented. Modeling presents a principal technique of predicting the behaviour of the proposed infrastructural designs or management policies. Models can be developed and used to help identify specific alternative plans that best meet those objectives. This study discusses various types of models, their development, architecture, data requirements, and applications in the field of engineering. It also outlines the advantages and limitations of each the optimization and simulation models presented. The techniques explored in this review include; dynamic programming, linear programming, fuzzy optimization, evolutionary algorithms and finally artificial intelligence techniques. Previous studies carried out using some of the techniques mentioned above were reviewed, and most of the results from different researches showed that indeed optimization and simulation provides viable alternatives and predictions which form a basis for decision making in building engineering structures and also in engineering planning and management.