Excellence in Research and Innovation for Humanity

International Science Index

Commenced in January 1999 Frequency: Monthly Edition: International Abstract Count: 44166

Mechanical and Mechatronics Engineering

An Experimental Study of Diffuser-Enhanced Propeller Hydrokinetic Turbines
Wind tunnel experiments of horizontal axis propeller hydrokinetic turbines model were carried out, in order to determine the performance behavior for different configurations and operational range. The present experiments introduce the use of two different geometries of rear diffusers to enhance the performance of the free flow machine. The present paper reports an increase of the power coefficient about 50%-80%. It represents an important feature that has to be taken into account in the design of this kind of machine.
Numerical Study on Enhancement of Heat Transfer by Turbulence
This paper scrutinizes the influences of turbulence on heat transport rate, Nusselt number. The subject matter of this investigation also deals with the improvement of heat transfer efficiency of the swirl flow obtained by rotating a twisted tape in a circular pipe. The conditions to be fulfilled to observe the impact of Reynolds number and rotational speed of twisted tape are: a uniform temperature on the outer surface of the pipe, the magnitude of velocity of water varying from 0.1 m/s to 0.7 m/s in order to alter Reynolds number and a rotational speed of 200 rpm to 600 rpm. The gyration of twisted tape increase by 17%. It is also observed that heat transfer is exactly proportional to inlet gauge pressure and reciprocally proportional to increase of twist ratio.
An Experimental Investigation of Hydrodynamic Effects on the Heat Transfer and Scale Mitigation in Agitation Tank
Scale formation on the process equipment is a major problem as it leads to reduced plant efficiency and high operational cost. Its mechanism is not well undertsood, therefore, elucidating the process is important for its mitigation. The effective scale mitigation techniques will reduce energy consumption in high energy demand industry. Crystallisation scale occurs when dissolved minerals precipitate out from an aqueous solution. To investigate this scale growth, a lab-scale agitation tank with and without baffles were used as a benchmark using normal solubility salt of potassium nitrate solution as a process fluid. Potassium nitrate (KNO3) solution in this test leads to crystallisation scale formation on the low-temperature heat exchange surfaces. This experimental investigation has focused on the effect of surface crystallisation of potassium nitrate on the low-temperature heat exchange surfaces on the wall of the agitation tank. The impeller agitation rate affects the scaling rate at the low-temperature agitation wall, and it shows a decreasing scaling rate with an increasing agitation rate. It was observed that there was a significant variation of heat transfer coefficients and scaling thermal resistance coefficients with different agitation rate as well as with varying impeller size, tank with and without baffles and solution concentration.
Mechanism Design and Dynamic Analysis of the Active Independent Front Steering System
Active Independent Front Steering system is a steering system which can according to vehicle driving situation adjusts the relation of steering angle between inner wheel and outer wheel. In low-speed cornering, AIFS sets the steering angles of inner and outer wheel into Ackerman steering geometry to make vehicle has less cornering radius. Besides, AIFS changes the steering geometry to parallel or even anti-Ackerman steering geometry to keep vehicle stability in high-speed cornering. Therefore, based on the analysis of the vehicle steering behavior from different steering geometries, this study develops a new screw type of active independent front steering system to make vehicles best cornering performance at any speeds. The screw type of active independent front steering system keeps the pinion and separates the rack into main rack and second rack. Two racks connect by a screw. Extra screw rotated motion powered by assistant motor through coupler makes second rack move relative to main rack, which can adjust both steering ratio and steering geometry. First of all, this study distinguishes the steering geometry by using Ackerman percentage and utilizes the software of ADAMS/Car to construct diverse steering geometry models. The different steering geometries are compared at low-speed and high-speed cornering, and then control strategies of the active independent front steering systems could be formulated. Secondly, this study applies closed loop equation to analyze tire steering angles and carries out optimization calculations to make the steering geometry from traditional rack and pinion steering system near to Ackerman steering geometry. Steering characteristics of the optimum steering mechanism and motion characteristics of vehicle installed the steering mechanism are verified by ADAMS/Car models of front suspension and full vehicle respectively. By adding dual auxiliary rack and dual motor to the optimum steering mechanism, the active independent front steering system could be developed to achieve the functions of variable steering ratio and variable steering geometry. At last, this study uses ADAMS/Car and Matlab/Simulink to co-simulate the cornering motion of vehicles confirms the vehicle installed the Active Independent Front Steering (AIFS) system has better handling performance than that with Active Independent Steering (AFS) system or with Electric Power Steering (EPS) system. At low-speed cornering, the vehicles with AIFS system and with AFS system have better maneuverability, less cornering radius, than the traditional vehicle with EPS system because that AIFS and AFS systems both provide function of variable steering ratio. However, there is a slight penalty in the motor(s) power consumption. In addition, because of the capability of variable steering geometry, the vehicle with AIFS system has better high-speed cornering stability, trajectory keeping, and even less motor(s) power consumption than that with EPS system and also with AFS system.
Experimental Investigation of Flow Boiling Heat Transfer Characteristics of R134a Flowing in Smooth and Microfin Tubes
Evaporators are one of the important equipment of refrigeration systems, so it is important to determine design parameters which are heat transfer rate and pressure drop. In the study, heat transfer and pressure drop of R134a flowing in smooth and microfin tubes are experimentally investigated, and the effect of operational parameters such as mass flux, saturation pressure and vapor quality on them is determined during flow boiling conditions. Moreover, heat transfer improvement and pressured drop increment are compared for smooth and microfin tubes for different vapor qualities and the effect of the microfin tube usage instead of smooth one is presented for tested conditions.
Analysis of Radial Pulse Using Nadi-Parikshan Yantra
Diagnosis according to Ayurveda is to find the root cause of a disease. Out of the eight different kinds of examinations, Nadi-Pariksha (pulse examination) is important. Nadi-Pariksha is done at the root of the thumb by examining the radial artery using three fingers. Ancient Ayurveda identifies the health status by observing the wrist pulses in terms of 'Vata', 'Pitta' and 'Kapha', collectively called as tridosha, as the basic elements of human body and in their combinations. Diagnosis by traditional pulse analysis – NadiPariksha - requires a long experience in pulse examination and a high level of skill. The interpretation tends to be subjective, depending on the expertise of the practitioner. Present work is part of the efforts carried out in making Nadi-Parikshan objective. Nadi Parikshan Yantra (three point pulse examination system) is developed in our laboratory by using three pressure sensors (one each for the Vata, Pitta and Kapha points on radial artery). The radial pulse data was collected of a large number of subjects. The radial pulse data collected is analyzed on the basis of relative amplitudes of the three point pulses as well as in frequency and time domains. The same subjects were examined by Ayurvedic physician (Nadi Vaidya) and the dominant Dosha - Vata, Pitta or Kapha - was identified. The results are discussed in details in the paper.
An Experimental Investigation of Hydrodynamic Effects on Scale Growth and Mitigation in Agitation Tank
Mineral scale formation is undoubtedly a more serious problem in the mineral industry than other process industries and its mechanism is not well understood. To better understand scale growth and suppression, an experimental model is proposed in this study for supersaturated crystallised solutions commonly found in mineral process plants. In this experiment, surface crystallisation of potassium nitrate (KNO3) on the wall of the agitation tank and agitation effects on the scale growth and suppression are studied. The new quantitative scale suppression model predicts that at lower agitation speed, the scale growth rate is enhanced and at higher agitation speed, the scale suppression rate increases due to the increased flow erosion effect. A lab-scale agitation tank with and without baffles were used as a benchmark in this study. The fluid dynamic effects on scale growth and suppression in the agitation tank with three different size impellers (diameter 86, 114, 160 mm and model A310 with flow number 0.56) at various rotational speeds (up to 700 rpm) and solutions with different concentration (4.5, 4.75 and 5.25 mol/dm3) were investigated. For more elucidation, the effects of the different size of the impeller on the wall surface scale growth and suppression rate as well as the bottom settled scale accumulation rate are also discussed. Emphasis was placed on applications in the mineral industry, although results are also relevant to other industrial applications.
Autonomous Flight Control for Multirotor by Alternative Input Output State Linearization with Nested Saturations
Multirotor is one of the most popular types of small unmanned aircraft systems and has already been used in many areas including transport, military, surveillance, and leisure. Together with its popularity, the needs for proper flight control is growing because in most applications it is required to conduct its missions autonomously, which is in many aspects based on autonomous flight control. There have been many studies about the flight control for multirotor, but there is still room for enhancements in terms of performance and efficiency. This paper presents an autonomous flight control method for multirotor based on alternative input output linearization coupled with nested saturations. With alternative choice of the output of the multirotor flight control system, we can reduce computational cost regarding Lie algebra, and the linearized system can be stabilized with the introduction of nested saturations with real poles of our own design. Stabilization of internal dynamics is also based on the nested saturations and accompanies the determination of part of desired states. In particular, outer control loops involving state variables which originally are not included in the output of the flight control system is naturally rendered through this internal dynamics stabilization. We can also observe that desired tilting angles are determined by error dynamics from outer loops. Simulation results show that in any tracking situations multirotor stabilizes itself with small time constants, preceded by tuning process for control parameters with relatively low degree of complexity. Future study includes control of piecewise linear behavior of multirotor with actuator saturations, and the optimal determination of desired states while tracking multiple waypoints.
Managing Uncertainty in the Unmanned Aircraft System Safety Performance Requirements Compliance Process
The Unmanned Aircraft System (UAS) industry is rapidly evolving the aviation sector. However, as with any new technology, there are associated safety risks. Till date, these risks have largely been managed through the imposition of significant restrictions on the operation of these systems, including prohibiting their flight over populated areas. It is now broadly recognised that airworthiness regulations should be tailored to the different UAS types and their Concepts of Operations, based on the level of risk posed. Consequently, UAS are likely to require certification against a prescriptive code of airworthiness requirements, which includes showing compliance to system safety regulations (Part 1309 regulations). The challenge, however, lies in applying the system safety process to UAS, which lack the data and operational heritage of conventionally piloted aircraft. The part of the system safety regulations that is of relevance to this research is the System Safety Performance Requirements (SSPR). The low data and high uncertainty associated with UAS make showing compliance to the SSPR a challenge. The current System Safety Assessment (SSA) process as used for conventional civil aviation systems does not address this uncertainty. A more comprehensive treatment of uncertainty is required for more rational, objective, and consistent compliance decision making. A fundamentally new approach to system safety, which aims to address these challenges, has already been proposed by the authors. It proposes a significant change to how aviation safety practitioners currently undertake regulatory compliance activities and is in line with contemporary decision making approaches first proposed by the nuclear industry (also suffers from low data and high risk and uncertainty). The objective of this paper is to provide a description of the overall SSPR framework and extend the existing approach by showing how uncertainties in the assignment of consequence severities to failure modes can be considered. The basic principles of Bayesian analysis, coupled with Bayesian inference techniques, Bayesian Belief Networks and normative decision making will be employed while developing the model. Some of the advantages of the new approach include, 1) providing a mathematically robust method for systematically combining subjective and objective data sources used in the SSA process (e.g., accident and incident reports and expert judgement); 2) providing a mathematically robust means for updating SSA as new technical or operational data is obtained; 3) supporting inductive and deductive reasoning in relation to the system safety of UAS (e.g., predictive assessments or incident analysis); 4) being compatible with existing system safety modelling and analysis tools (e.g., Functional Hazard Assessments (FHA)) 5) supporting more justifiable and systematic compliance findings; 6) facilitating compliance findings to be made on the basis of compliance risk; 7) reducing the need for conservative assumptions and the subsequent impost of unnecessary costs on the UAS industry. This paper describes a fundamentally new approach to system safety compliance, which can be applied to UAS (or other aviation systems, where there is high uncertainty). The approach is particularly suited to 'new aviation systems', where the state of knowledge and availability of data to support system safety assessments is evolving.
Optimum Design of Hybrid (Metal-Composite) Mechanical Power Transmission System under Uncertainty by Convex Modelling
The design models dealing with flawless composite structures are in abundance, where the mechanical properties of composite structures are assumed to be known a priori. However, if the worst case scenario is assumed, where material defects combined with processing anomalies in composite structures are expected, a different solution is attained. Furthermore, if the system being designed combines in series hybrid elements, individually affected by material constant variations, it implies that a different approach needs to be taken. In the body of literature, there is a compendium of research that investigates different modes of failure affecting hybrid metal-composite structures. It covers areas pertaining to the failure of the hybrid joints, structural deformation, transverse displacement, the suppression of vibration and noise. In the present study a system employing a combination of two or more hybrid power transmitting elements will be explored for the least favourable dynamic loads as well as weight minimization, subject to uncertain material properties. Elastic constants are assumed to be uncertain-but-bounded quantities varying slightly around their nominal values where the solution is determined using convex models of uncertainty. Convex analysis of the problem leads to the computation of the least favourable solution and ultimately to a robust design. This approach contrasts with a deterministic analysis where the average values of elastic constants are employed in the calculations, neglecting the variations in the material properties.
Experimental Investigation of Flat Plate Closed Loop Pulsating Heat Pipe
Electronic devices are shrinking in their form factor every passing day on the one hand, while their functionality is increasing, on the other hand. This has certainly increased heat dissipation due to more functions and also made the heat flux severe due to the shrinking sizes. In this scenario, the thermal management of the devices need mechanisms for diffusion of these high heat fluxes. These mechanisms are supposed to be competitive from the economic point of view as well. Pulsating heat pipes (PHPs) have promised to be effective heat spreaders (more or less like the conventional heat pipes). Also from the point of view of fabrication, PHPs are less intensive than their conventional counter-parts. Despite these advantages, there still exists shortage of data both experimental and analytical, to predict and design PHPs with certainty. In this study, a flat plate configuration closed loop PHP of aluminium alloy has been experimentally verified for its thermal performance. The PHP with 12 channels, each 2.2 mm deep x 2.0 mm wide, was tested with deionized water and methanol for a fill ratio of 70% by volume for various orientations staring from Evaporator below Condenser (90°) to near horizontal (7.5°) for its thermal performance for a single heat load of 50 W. The PHP performance as expected was best at the 90° orientation with very little deterioration up to 45°. An attempt has been made to ascertain/resolve the critical angle after which the PHP ceases to perform. The overall thermal resistances were estimated for each orientation. The results also indicate that at smaller angles of inclination (near horizontal) methanol performed better than water.
Effect of Cellular Water Transport on Deformation of Food Material during Drying
Drying is a food processing technique where simultaneous heat and mass transfer take place from surface to the center of the sample. Deformation of food materials during drying is a common physical phenomenon which affects the textural quality and taste of the dried product. Most of the plant-based food materials are porous and hygroscopic in nature that contains about 80-90% water in different cellular environments: intercellular environment and intracellular environment. Transport of this cellular water has a significant effect on material deformation during drying. However, understanding of the scale of deformation is very complex due to diverse nature and structural heterogeneity of food material. Knowledge about the effect of transport of cellular water on deformation of material during drying is crucial for increasing the energy efficiency and obtaining better quality dried foods. Therefore, the primary aim of this work is to investigate the effect of intracellular water transport on material deformation during drying. In this study, apple tissue was taken for the investigation. The experiment was carried out using 1H-NMR T2 relaxometry with a conventional dryer. The experimental results are consistent with the understanding that transport of intracellular water causes cellular shrinkage associated with the anisotropic deformation of whole apple tissue. Interestingly, it is found that the deformation of apple tissue takes place at different stages of drying rather than deforming at one time. Moreover, it is found that the penetration rate of heat energy together with the pressure gradient between intracellular and intercellular environments is the responsible force to rupture the cell membrane.
Economic Optimization of Shell and Tube Heat Exchanger Using Nanofluid
Economic optimization of shell and tube heat exchanger (STHE) is presented in this paper. To increase the rate of heat transfer, copper oxide (CuO) nanoparticle is added into the tube side fluid, and their optimum results are compared with the case of without nanoparticle additive. Total annual cost (TAC) is selected as fitness function and nine decision variables related to the heat exchanger parameters as well as concentration of nanoparticle are considered. Optimization results reveal the noticeable improvement in the TAC and in the case of heat exchanger working with nanofluid compared with the case of base fluid (8.9%). Comparison of the results between two studied cases also reveals that the lower tube diameter, tube number, and baffle spacing are needed in the case of heat exchanger working with nanofluid compared with the case of base fluid.
To Study the Effect of Optic Fibre Laser Cladding of Cast Iron with Silicon Carbide on Wear Rate
The study investigates the effect on wear rate of laser clad of cast iron with silicon carbide. Metal components fail their desired use because they wear, which causes them to lose their functionality. The laser has been used as a heating source to create a melt pool over the surface of cast iron, and then a layer of hard silicon carbide is deposited. Various combinations of power and feed rate of laser have experimented. A suitable range of laser processing parameters was identified. Wear resistance and wear rate properties were evaluated and the result showed that the wear resistance of the laser treated samples was exceptional to that of the untreated samples.
An Interpolation Method Using Spatial Principal Component Analysis and Modulation Transfer Functions for Pan-Sharpening
In remote sensing, there is a physical trade-off between the spatial and the spectral resolutions of electro-optical sensors. This implies that acquired multispectral (MS) images have a coarser spatial resolution than the corresponding panchromatic (PAN) images. Pan-sharpening, or image fusion, refers to the research field of using mutually complementary images to generate images of high spatial and spectral resolution. For effective image fusion, there are three principal issues to address. The first issue is effectively extracting the high-frequency component injected into the MS images from a spatially detailed PAN image. The second issue is selecting the appropriate injection gain to decide on the degree of injecting the high-frequency components. The last issue is generating the MS images to the same size as that of the PAN image using interpolation techniques. In particular, the last issue can be influenced more significantly by image fusion methods such as multiresolution analysis (MRA) methods in contrast to the component substitution (CS) methods. For instance, since WorldView-3 short-wave infrared (SWIR) images holds a 25-times coarser spatial resolution over its panchromatic image, this extreme ratio is being perceived as a hindrance for effective image fusion. To address the last issue, this paper proposes an algorithm to interpolate the coarser SWIR images to match its PAN image using the spatial principal component analysis (SPCA) and modulation transfer functions (MTF). In this paper, the proposed interpolation scheme, bilinear and bicubic interpolation methods were applied to the pre-processing stage for image fusion. Finally, the CS-based fusion technique termed the Gran-Schmidt adaptive method, and the MRA-based additive wavelet luminance proportional method was compared, and the proposed interpolation scheme demonstrated better results for all the tested evaluation indices.
Numerical Simulation of Lifeboat Launching Using Overset Meshing
Lifeboat launching from marine vessel or offshore platform is one of the important areas of research in offshore applications. With the advancement of computational fluid dynamic simulation (CFD) technology to solve fluid induced motions coupled with Six Degree of Freedom (6DOF), rigid body dynamics solver, it is now possible to predict the motion of the lifeboat precisely in different challenging conditions. Traditionally dynamic remeshing approach is used to solve this kind of problems, but remeshing approach has some bottlenecks to control good quality mesh in transient moving mesh cases. In the present study, an overset method with higher-order interpolation is used to simulate a lifeboat launched from an offshore platform into calm water, and volume of fluid (VOF) method is used to track free surface. Overset mesh consists of a set of overlapping component meshes, which allows complex geometries to be meshed with lesser effort. Good quality mesh with local refinement is generated at the beginning of the simulation and stay unchanged throughout the simulation. Overset mesh accuracy depends on the precise interpolation technique; the present study includes a robust and accurate least square interpolation method and results obtained with overset mesh shows good agreement with experiment.
Analyzing the Effect of Design of Pipe in Shell and Tube Type Heat Exchanger by Measuring Its Heat Transfer Rate by Computation Fluid Dynamics and Thermal Approach
Shell and tube type heat exchangers are predominantly used in heat exchange between two fluids and other applications. This paper projects the optimal design of the pipe used in the heat exchanger in such a way to minimize the vibration occurring in the pipe. Paper also consists of the comparison of the different design of the pipe to get the maximize the heat transfer rate by converting laminar flow into the turbulent flow. By the updated design the vibration in the pipe due to the flow is also decreased. Computational Fluid Dynamics and Thermal Heat Transfer analysis are done to justifying the result. Currently, the straight pipe is used in the shell and tube type of heat exchanger where as per the paper the pipe consists of the curvature along with the pipe. Hence, the heat transfer area is also increased and result in the increasing in heat transfer rate. Curvature type design is useful to create turbulence and minimizing the vibration, also. The result will give the output comparison of the effect of laminar flow and the turbulent flow in the heat exchange mechanism, as well as, inverse effect of the boundary layer in heat exchanger is also justified.
Numerical Investigation of Dynamic Stall over a Wind Turbine Pitching Airfoil by Using Openfoam
Computations for two-dimensional flow past a stationary and harmonically pitching wind turbine airfoil at a moderate value of Reynolds number (400000) are carried out by progressively increasing the angle of attack for stationary airfoil and at fixed pitching frequencies for rotary one. The incompressible Navier-Stokes equations in conjunction with Unsteady Reynolds Average Navier-Stokes (URANS) equations for turbulence modeling are solved by OpenFOAM package to investigate the aerodynamic phenomena occurred at stationary and pitching conditions on a NACA 6-series wind turbine airfoil. The aim of this study is to enhance the accuracy of numerical simulation in predicting the aerodynamic behavior of an oscillating airfoil in OpenFOAM. Hence, for turbulence modelling, with low-Reynolds correction is employed to capture the unsteady phenomena occurred in stationary and oscillating motion of the airfoil. Using aerodynamic and pressure coefficients along with flow patterns, the unsteady aerodynamics at pre-, near- and post-static stall regions are analyzed in harmonically pitching airfoil and the results are validated with the corresponding experimental data possessed by the authors. The results indicate that implementing the mentioned turbulence model leads to accurate prediction of the angle of static stall for stationary airfoil and flow separation, dynamic stall phenomenon and reattachment of the flow on the surface of airfoil for pitching one. Due to the geometry of the studied 6-series airfoil, the vortex on the upper surface of the airfoil during upstrokes is formed at the trailing edge. Therefore, the pattern flow obtained by our numerical simulations represents the formation and change of the trailing-edge vortex at near- and post-stall regions where this process determines the dynamic stall phenomenon.
A Numerical Study on the Influence of Co2 Dilution on Combustion Characteristics of a Turbulent Diffusion Flame
The objective of the present study is to numerically investigate the effect of CO2 replacement with N2 in air stream on the flame characteristics of the CH4 turbulent diffusion flame. The Open Field Operation And Manipulation (OpenFOAM) has been used as the computational tool. In this regard, laminar flamelet and modified k-ε models have been utilized as combustion and turbulence models respectively. Results reveal that the presence of CO2 in air stream changes the flame shape and maximum flame temperature. Also CO2 dilution causes an increment in CO mass fraction.
Fatigue Life Estimation Using N-Code for Drive Shaft of Passenger Vehicle
The drive shaft of passenger vehicle has its own function such as transmitting the engine torque from the gearbox and differential gears to the wheels. It must also compensate for all variations in angle or length resulting from manoeuvring and deflection for perfect synchronization between joints. Torsional fatigue failures occur frequently at the connection parts of the spline joints in the end of the drive shaft. In this study, the fatigue life of a drive shaft of passenger vehicle was estimated by using the finite element analysis. A commercial software of n-Code was applied under twisting load conditions, i.e. 0~134kgf•m and 0~188kgf•m, in which the shear strain range-fatigue life relationship considering Signed Shear method, Smith-Watson-Topper equation, Neuber-Hoffman Seeger method, size sensitivity factor and surface roughness effect was taken into account. The estimated fatigue life was verified by a twisting load test of the real drive shaft in a test rig. (Human Resource Training Project for Industry Matched R & D, KIAT, N036200004).
Feasibility Study on Hybrid Multi-Stage Direct-Drive Generator for Large-Scale Wind Turbine
Direct-drive generators for large-scale wind turbine, which are divided into AFPM(Axial Flux Permanent Magnet) and RFPM(Radial Flux Permanent Magnet) type machine, have attracted interest because of a higher energy density in comparison with gear train type generators. Each type of the machines provides distinguishable geometrical features such as narrow width with a large diameter for the AFPM-type machine and wide width with a certain diameter for the RFPM-type machine. When the AFPM-type machine is applied, an increase of electric power production through a multi-stage arrangement in axial direction is easily achieved. On the other hand, the RFPM-type machine can be applied by using its geometric feature of wide width. In this study, a hybrid two-stage direct-drive generator for 6.2MW class wind turbine was proposed, in which the two-stage AFPM-type machine for 5 MW was composed of two models arranged in axial direction with a hollow shape topology of the rotor with annular disc, the stator and the main shaft mounted on coupled slew bearings. In addition, the RFPM-type machine for 1.2MW was installed at the empty space of the rotor. Analytic results obtained from an electro-magnetic and structural interaction analysis showed that the structural weight of the proposed hybrid two-stage direct-drive generator can be achieved as 155tonf in a condition satisfying the requirements of structural behaviors such as allowable air-gap clearance and strength. Therefore, it was sure that the 6.2MW hybrid two-stage direct-drive generator is competitive than conventional generators. (NRF grant funded by the Korea government MEST, No. 2017R1A2B4005405).
Regulation, Co-Regulation and Self-Regulation of Civil Unmanned Aircrafts in Europe
Safety and security concerns play a key role during the design of civil UAs (aircraft controlled by a pilot who is not on-board it) by the producers and the offer of different services by the operators. At present, European countries have fragmented regulations about the manufacture and use of civil drones, therefore the European institutions are trying to approach all these regulations into a common one by 2019. In this sense, not only Law but also Ethics can give guidelines to the industry in order to obtain better reports from their clients. Moreover, the European Aviation Safety Agency (EASA), as an Agency of the European Union, promotes the highest common standards of safety and develops common safety rules at the European level. This Agency and their National equivalents monitor the activity of producers and operators, but depending on the size of the drone this activity could cover regulation measures or ethical recommendations. In this sense, the aim of our analysis is to categorize the concerns, measures and types of hard-soft regulations that we find in the European Union. Our study is based on a content analysis from three sources of information: academic papers, policies and regulation proposals from the European Union, and the regulation of some European countries. From a comparative analysis of the results, we evaluate the different concerns, regulations, and solutions of the National Laws and the European proposal. Taking into account the different regulation systems of the European members, we can find two groups of countries: countries regulation-centered, where legal regulation covers the majority of cases, and countries jurisprudence-centered, where co-regulation is enhanced. After this evaluation, and applying benchmarking, we can classify the best practices that could fit better with each type of regulation: legal regulation, co-regulation, and self-regulation. We show how technology is very difficult to regulate and, for this reason, other tools, such as co-regulation and self-regulation, although soft instruments are useful alternatives for the manufacturers and operators of civil drones. In general, few countries have taken self-regulation as a solution for some problems although in other industry sectors it has positive experiences. With these results, we would like to give advice to the European industry, as well as give new insights to the academia and policymakers.
Unsteady Temperature Distribution in a Finite Functionally Graded Cylinder
In the current study, two-dimensional unsteady heat conduction in a functionally graded cylinder is studied, analytically. The temperature distribution is in radial and longitudinal directions. Heat conduction coefficients are considered a power function of radius both in radial and longitudinal directions. The proposed solution can exactly satisfy the boundary conditions. Analytical unsteady temperature distribution for different parameters of the functionally graded cylinder are investigated. The achieved exact solution is useful for thermal stress analysis of functionally graded cylinders. Regarding the analytical approach, this solution can be used to understand the concepts of heat conduction in functionally graded materials.
Rheological Evaluation of Various Indigenous Gums
In the present investigation, rheology of the three different natural gums has been evaluated experimentally using MCR 102 rheometer. Various samples based on the variation of the concentration of the solid gum powder have been prepared. Their non-Newtonian behavior has been observed by the consistency plots and viscosity variation plots with respect to different solid concentration. The viscosity-shear rate curves of gums are similar and the behavior is shear thinning. Gums are showing pseudoplastic behavior. The value of k and n are calculated by using various models. Results show that the Herschel–Bulkley rheological model is reliable to describe the relationship of shear stress as a function of shear rate. R² values are also calculated to support the choice of gum selection.
Navigation Support System for Blind People Using Arduino Based Obstacle Detection and Voice Signal Indication
A navigation support system is introduced in this article, that enables the localization of obstacles for visually impaired people using cost-effective tools, thus helping them in independent moving. The navigation support is implemented on an Arduino and Android based system, which notifies the user in the form of voice feedbacks about the position and distance of detected objects, and also about the detected depth changes on the pavement in front of the user. The study introduces the system’s structure, its performance, and test results.
Hand Controlled Mobile Robot Applied in Virtual Environment
By the development of IT systems, human-computer interaction is also developing even faster, and newer communication methods become available in human-machine interaction. In the article, the application of a hand gesture controlled human-computer interface is being introduced through the example of a mobile robot. The control of the mobile robot is implemented in a realistic virtual environment, that is advantageous regarding the aspect of different tests, parallel examinations, so purchase of expensive equipment is unnecessary. The usability of the implemented hand gesture control has been evaluated by test subjects. According to the opinion of testing subjects, the system can be well used, its application would be recommended on other application fields too.
Numerical Investigations on Dynamic Stall of a Pitching-Plunging Helicopter Blade Airfoil
Effect of plunging motion on the pitch oscillating NACA0012 airfoil is investigated using computational fluid dynamics (CFD). A simulation model based on overset grid technology and k-ω shear stress transport (SST) turbulence model is established, and the numerical simulation results are compared with available experimental data and simulated results. Two cases of phase angle φ= 0, π which represents the phase difference between the pitching and plunging motions of an airfoil are performed. Airfoil vortex generation, moving, and shedding are discussed in details. Good agreements have been achieved with the available literature. The upward plunging motion made the equivalent angle of attack less than the actual one during pitching analysis. It observed that the formation of the stall vortex is suppressed, resulting in a decrease in the lift coefficient and a delay of the stall angle. In contrast, the downward plunging motion made the equivalent angle of attack more than the actual one.
Numerical Simulation of Store Separation Trajectories for Eglin Test Case Using Overset Mesh
Overset Mesh with higher order interpolation is applied for transient store separation from air vehicles and validated with the experimental data. Numerical methods with dynamic mesh are traditionally used in computational fluid dynamic simulations (CFD) for store separation problems, which cuts down the need of expensive and dangerous testing approaches like Wind Tunnel and Flight Testing. However, dynamic mesh generation is time consuming and provides limited control on maintaining desirable mesh quality during simulation. Overset mesh on the other hand allows complex geometries to be meshed easily using a series of overlapping component meshes without compromising on mesh quality. In the present study, a most commonly used Eglin test case is validated for transonic flow (M=0.95) and supersonic flow (M=1.2) using overset mesh. Density based flow solver coupled with Six Degree of Freedom (6DOF) rigid body dynamics solver is used for solving compressible Reynolds averaged Navier Stokes (RANS) equations to predict projectile motion of store. An accurate second order least square method is applied for overset boundary interpolation achieving very satisfactory results.
Modeling of Austenitic Stainless Steel during Face Milling Using Response Surface Methodology
The objective of this work is to model the output responses namely; surface roughness (Ra), cutting force (Fc), during the face milling of the austenitic stainless steel X2CrNi18-9 with coated carbide tools (GC4040). For raison, response surface methodology (RMS) is used to determine the influence of each technological parameter. A full factorial design (L27) is chosen for the experiments, and the ANOVA is used in order to evaluate the influence of the technological cutting parameters namely; cutting speed (Vc), feed per tooth, and depth of cut (ap) on the out-put responses. The results reveal that (Ra) is mostly influenced by (fz) and (Fc) is found considerably affected by (ap).
Mass Transfer Studies of Carbon Dioxide Absorption in Sodium Hydroxide in Millichannels
In this work, absorption studies are done by conducting experiments of 99.9 (v/v%) pure CO₂ with various concentrations of sodium hydroxide solutions in a T-junction glass circular milli-channel. The gas gets absorbed in the aqueous phase resulting in the shrinking of slugs. This phenomenon is used to develop a lumped parameter model. Using this model, the chemical dissolution dynamics and the mass transfer characteristics of the CO₂-NaOH system is analysed. The liquid side mass transfer coefficient is determined with the help of the experimental data.