bluuebunny/crossref_metadata_2025 huggingface dataset:
Improvement of Constant Temperature Anemometer and Measurement of Energy Spectra in a Plane Turbulent Jet
Authors: Terashima Osamu , Onishi Kazuhiro , Sakai Yasuhiko , Nagata Kouji
Published: October 2013

A constant temperature anemometer (CTA) is a useful instrument for measuring the velocity fluctuations in turbulent flow. However, in our calibration test, the actual frequency response of a typical CTA was no more than 5 kHz under normal laboratory conditions: for example, the diameter of the hot wire is 5 μm and the free stream velocity is 20 m/s. Therefore, in some cases, a typical CTA is not enough to measure accurately turbulent velocity fluctuations for fine scale structures. In this paper, we present a rearranged CTA circuit to obtain a faster frequency response so that in turn fine-scale structures can be more accurately investigated.

A typical CTA circuit consists of a Wheatstone bridge and a feed back circuit. To improve the frequency response, the ratio of the electrical resistance of the Wheatstone bridge is set to 1 and two operational amplifiers with a gain-band width product of 100 MHz and a slew rate of 20 V/μs are used in the feedback circuit.

An experiment to estimate the frequency response of the rearranged CTA circuit is performed with a free stream velocity of 20 m/s and using hot wires of diameter 5 μm and 3 μm. Experimental results show that the roll-off frequency of the rearranged CTA circuit is improved from 5 kHz to 20 kHz for the 5 μm hot wire and from 6 kHz to 40 kHz for the 3 μm hot wire.

Velocity measurements are made using the rearranged CTA circuit in a plane turbulent jet where the value of the Taylor microscale λ is 3.2 mm and the Taylor-scale Reynolds number Reλ is 440. Measurements shows that the power spectrum obeys the reliable numerical profile derived by a LDIA (Lagrangian Direct-Interaction Approximation) theory until more than 0.20 of the non-dimensional wave number κ1η, which is a wider range in comparison with the results obtained when using a typical CTA circuit. Here, κ1 is the axial wave number and η is the Kolmogorov microscale.

Further, velocity measurements are performed taken using the rearranged CTA circuit with a square jet where the value of λ is 6.3 mm and Reλ is 1,720. Measurements shows that the power spectrum obeys the numerical profile by the LDIA theory in the range 0.04 < κ1η < 0.20, which is a much wider range than the results obtained when using a typical CTA circuit (0.04 < κ1η < 0.08).

These results indicate that the rearranged CTA circuit can be used to investigate fine-scale structures in turbulent flows more accurately.
Stick-Slip Motion of a Resin-Steel Contact at Low Speeds
Authors: Hou Zhichao , Wang Xiangwu , Liao Tao , Yano Akihiko , Akiyama Yo
Published: October 2013

Low speed sliding bearings are widely used in many industrial engineering fields. Friction induced vibration sometimes occurs, which decreases the performance and the life of machines besides introducing heavy noise. It is still quite difficult however, to predict the occurrence of the frictional vibration due to the nonlinearity of the system. This paper tries to address the occurrence of stick-slip motion by means of experiments and simulations. With a specially designed test device, extensive tests were carried out on face-to-face contact specimens of a resin material (Polyamide 6) that rotates against steel specimens, to understand the occurrence of stick-slip motion. Math models have been employed to describe the discontinuous transition between the static and the kinetic friction coefficient of the rubbing pairs. Based on the transition law, two contact models were employed to describe the dynamic interaction between the resin and the steel specimens. A special subroutine was then implemented in Adams by C-language. Simulations were conducted for the influence of contact pressure and relative speed on the occurrence of the stick-slip motion. Comparisons show the applicability and accuracy of the models.
Research on Fluctuating Forces Occurred in Components of Reciprocating Hydrogen Compressors
Authors: Mori Yoshifumi , Saito Takashi , Aoki Takehisa , Fujita Katsuhide
Published: October 2013

This paper treats dynamic analysis about reciprocating compressors used in a petroleum refining plant and a petrochemical plant. In order to clarify the cause of damage occurred as a result of long-term operation, we investigated the effects of deterioration around the connecting parts and the sliding parts on the dynamics of the system. Introducing the rigid body model with eleven degrees of freedom, we have determined the model parameters based on beam theory and the Hertz contact theory. By comparison with experimental results, we showed validity of the proposed model. Thus, changes in the characteristics of the middle spring piston rod were found to be a major impact on the dynamics of the system [1].
On the Dynamics of Fractional Visco-Elastic Beams
Authors: Di Lorenzo Salvatore , Pinnola Francesco P. , Pirrotta Antonina
Published: October 2013

With increasing advanced manufacturing process, visco-elastic materials are very attractive for mitigation of vibrations, provided that you may have advanced studies for capturing the realistic behavior of such materials.

Experimental verification of the visco-elastic behavior is limited to some well-known low order models as the Maxwell or Kelvin models. However, both models are not sufficient to model the visco-elastic behavior of real materials, since only the Maxwell type can capture the relaxation tests and the Kelvin the creep tests, respectively. Very recently, it has been stressed that the most suitable model for capturing the visco-elastic behavior is the spring-pot, characterized by a fractional constitutive law.

Based on this assumption, the quasi-static behavior has been investigated very recently, however for noise control there is a need of exploiting the dynamic behavior of such a fractional visco-elastic beam.

The present paper introduces the dynamic response of fractional visco-elastic Euler-Bernoulli beam under dynamic loads.
Formulation for Static Behavior of the Viscoelastic Euler-Bernoulli Micro-Beam Based on the Modified Couple Stress Theory
Authors: Taati E. , Nikfar M. , Ahmadian M. T.
Published: October 2013

In this work an analytical solution is presented for a viscoelastic micro-beam based on the modified couple stress theory which is a non-classical theory in continuum mechanics. The modified couple stress theory has the ability to consider small size effects in micro-structures. It is strongly emphasized that without considering these effects in such structures the solution will be wrong and not suitable for designing systems in micro-scales. In this study correspondence principle is used for deriving constitutive equations for viscoelastic material based on the modified couple stress theory. Governing equilibrium equations are obtained by considering an element of micro-beam. Closed-form solution for the static deflection of simply supported micro-beam is presented. Numerical results show that when the size of system is near the length scale parameter, the classical response will intensely be deviated from the correct solution observed in laboratories contrary to the modified couple stress which reflects the size effects.
Advances in Aerosol Direct-Write Technology for Fine Line Applications
Authors: Hoey Justin , Lutfurakhmanov Artur , Robinson Michael , Swenson Orven , Schulz Doug
Published: October 2013

Aerosol deposition tools including Aerosol Jet™ and Collimated Aerosol Beam Direct-Write (CAB-DW™) have been used to create fine metallic traces with line widths as thin as 5 μm by focusing and accelerating aerosol particles through a nozzle and onto a substrate. These tools excel at applications requiring a non-contact method of rapid prototyping. We developed the CAB-DW system after an understanding of the fluid-particle interactions inside the Aerosol Jet system was realized. CAB-DW offers both narrower line widths and reduced overspray due to its 3-component converging-diverging-converging nozzle system. The details behind how this system was designed, subsequent progress in aerosol focusing designs, and applications of aerosol deposition systems will be discussed. In addition, a comparison of these aerosol direct-write systems to other direct-write systems and the future prospects of these tools will be presented.
Micro Cold Spray Direct Write Process
Authors: Bhattacharya Sourin , Lutfurakhmanov Artur , Hoey Justin M. , Swenson Orven F. , Sailer Rob
Published: October 2013

Gas dynamic cold spray was first discovered in the 1980s and has since been used as a surface coating process for depositing metals, metal-ceramic composites, metal-carbon nanotube composites and other composite materials onto both flexible and rigid substrates. We recently developed a focused cold spray material deposition tool termed Micro Cold Spray (MCS). MCS is a direct-write tool applicable for printed electronics and has been used to print conductive trace patterns as thin as 50 μm wide using copper, aluminum and tin micro powders. Unlike conventional aerosol processing at 10–100 m/s, aerosol particles in the MCS process are accelerated to speeds greater than 500 m/s. In this paper the possibility to accelerate, focus, collimate, and deposit aerosol particles is theoretically explored using a finite difference approximation method to simulate the flow of Helium through a symmetric converging-diverging nozzle of throat diameter 200 μm. A Lagrangian particle tracking algorithm is used to calculate the particle trajectories and corresponding velocities. This paper presents a comparison of the effect of Stoke’s drag force and Saffman’s lift force on the trajectory and velocity of copper particles 3 μm in diameter.
Fine Line Metallization of Silicon Solar Cells via Collimated Aerosol Beam Direct Write
Authors: Fink Jacob , Hoey Justin M. , Schulz Douglas L.
Published: October 2013

The global push for affordable sources of renewable energy has sparked rapid growth in photovoltaic research directed at improving the efficiency of the overall cells. Efficiency gains related to the optimization of the top metallization layer and current collector are largely limited by the minimum collector line width (∼100 μm) that can be printed using industrial processes such as screen printing. An alternative direct-write process termed Collimated Aerosol Beam Direct-Write (CAB-DW) is capable of depositing collector lines as thin as 15μm wide while still allowing heights up to 7 μm. In this paper we present data demonstrating improvements to efficiency of silicon solar cells with optimized grid designs along with a theoretical/experimental comparison confirming these results. Finally, results demonstrating collector grid induced light trapping possible with direct-written traces which reduces shadowing and further increases collection efficiency are presented.
Dispersion Flow in Microchannels
Authors: Akhmetov Alfir T. , Mavletov Marat V. , Sametov Sergey P. , Rakhimov Artur A. , Valiev Azat A. , Akhatov Iskander S.
Published: October 2013

The work is devoted to experimental investigations of the features of flow of dispersions in microchannels. The paper consists of three parts. In the first part the flow of emulsions in smooth contracting cylindrical microchannels is investigated. It is received that a significant role at dynamic blocking of channels is played by the inclusions comparable by size to the diameter of a narrowing. This is in spite of the fact that their influence on the change of a flow rate of emulsion before blocking is insignificant. In the second part the generation of emulsion in a complex structure of microchannels (micromodels) when water is displaced by composition of hydrocarbon with surfactants is investigated. The experimental dependences of the rheological characteristics of emulsions based on the composition of SAS and water at different concentrations of the aqueous phase can explain blocking of a porous structure by generated emulsion. In the third part a comparison of flow of water-in-oil emulsions with the suspension which was obtained by freezing the microdroplets of the aqueous phase of emulsions was studied. It was found that the blocking of suspension is not as complete as in the case of emulsion. It is explained by deformation of the droplets and by formation of a dense structure, as opposed to suspension of beads, through which hydrocarbon phase is filtered. A small increase in effective viscosity due to solidification of freezing droplets of the dispersed phase was found.
Wave Energy Extraction Maximization Using Direct Transcription
Authors: Allison James T. , Kaitharath Allen , Herber Daniel R.
Published: October 2013

Wave energy converters (WECs) extract energy from the motion of ocean waves. A variety of different WEC devices have been studied over the past several decades, with emphasis on cost-effective energy extraction. Active control has been shown to improve energy production significantly. Here we investigate energy extraction potential of a tethered heaving cylinder WEC using direct transcription (DT), an open-loop optimal control strategy. This enables direct inclusion of asymmetric constraints on power and tether force, practical considerations not considered in previous studies, and opens the door to WEC optimal control problems with more realistic nonlinear models and integration of control design with physical system design.
Liquid Attachment and Momentum Transfer by Collisions Between Free-Fall Solids and Liquid Spray Droplets
Authors: He Pengfei , Patel Raivat , Zhang Bo , Zhu Chao
Published: October 2013

Understanding the solids wetting by collisions between flowing solids and spray droplets is essential to optimizing the design and operation of related industrial processes. This paper presents an innovative experimental method to identify the statistical distributions of liquid attachment and collision probability of the impingement of a liquid spray onto free-fall particles. To separate the liquid attachment from other contributions to the mass measurements of particles and liquids, individual impingement experiment with hydrophobic or hydrophilic particles of the same otherwise properties is respectively performed under the same conditions. In addition, a series of collection bins are distributed along the spray path to determine the statistical probability of collision properties including coating thickness. Based on these measurements, the collision-induced momentum transfer and velocity redistribution of solids and droplets can be estimated with the aid of a Lagrangian trajectory model. Consequently a general two-parameter of collision probability density function is proposed.
3D Reconstruction Based on Single Defocused Microscopic Image
Authors: Xing Z. G. , Zhao C. M. , Wei J. , Wei Z.
Published: October 2013

Microscope has being limited by the depth of focus, while the focused image is clear, the defocused images are fuzzy and fuzzy degree of the object images vary with different defocused distances. This paper presented a 3D reconstruction method based on a defocused microscopic image. After the defocused microscopic image is divided the microscopic into M × N regions, the fuzzy degree of each region is quantitatively evaluated. A corresponding curve of the relation between fuzzy degree and defocus distance is drawn by the presented algorithm in this paper, and then the three-dimensional characteristics of objects are reconstructed. This method has the merits of little computation, low cost and high speed. And M and N values can be changed according to the needs of the measurement accuracy.
Experimental Study and High Speed Visualization of Flow Boiling Characteristics in Silicon Microgap Heat Sink
Authors: Alam Tamanna , Lee Poh Seng , Yap Christopher R. , Jin Liwen
Published: October 2013

Flow boiling in microgap heat sink is very attractive for high-performance electronics cooling due to its high heat transfer rate and easy fabrication process. In absence of thermal interface material between the active electronic component and a microgap cold plate, significant reduction in interface thermal resistance and enhancement in heat transfer rate can be achieved. In earlier studies by these authors, encouraging results have been obtained using microgap heat sink as it can potentially mitigate flow instabilities, flow reversal and maintain uniform wall temperatures over the heated surface. So, more work should be carried out to advance the fundamental understanding of the two-phase flow heat transfer associated with microgap heat sink and the underlying mechanisms. In this study, local flow boiling phenomena in different microgap sizes have been investigated experimentally. Experiments are performed in silicon based microgap heat sink having microgap depth ranging from 80 μm to 500 μm, using deionized water with 10 °C subcooled inlet temperature. The effects of mass flux and heat flux on heat transfer coefficient and pressure drop characteristics are examined by using different mass fluxes ranging from 400 kg/m2s to 1000 kg/m2s and effective heat flux varying from 0 to 100 W/cm2. Apart from these experimental investigations, simultaneous high speed visualizations are conducted to observe and explore the mechanism of flow boiling in microgap. Confined slug and annular boiling are observed as the two main heat transfer mechanisms in microgap. Moreover, experimental results show that flow boiling heat transfer coefficients are dependent on gap size, and the lower the gap size, higher the heat transfer coefficient.
Heat Transfer in a Long, Thin Tube Section of an Air Compressor: An Empirical Correlation From CFD and a Thermodynamic Modeling
Authors: Zhang Chao , Saadat Mohsen , Li Perry Y. , Simon Terrence W.
Published: October 2013

Heat transfer during compression of air in a long, thin tube is studied by CFD. The tube represents one of the many in a honeycomb geometry inserted in a liquid piston air compressor to minimize temperature rise. A dimensionless number for the heat flow rate that includes the changing heat transfer area between the tube wall and air during compression is used. From the CFD results, alinear relation between the inverse of this dimensionless heat flow rate and the Stanton number is found. Using thisrelation, the transient volume-averaged temperature, and heat flow rate from the air can be well predicted by thermodynamic modeling.With the heat transfer model, a non-linear ODE is solved numerically todetermine the average temperature and pressure. The application of this study can be found in liquid piston air compressors for compressed air energy storage systems.
Teaching Classical Control System Course With Portable Student-Owned Mechatronic Kits
Authors: Enikov Eniko T. , Eke Estelle
Published: October 2013

Teaching classical controls systems design to mechanical engineering students presents unique challenges. While most mechanical engineering programs prepare students to be well-versed in the application of physical principles and modeling aspects of physical systems, implementation of closed loop control and system-level analysis is lagging. It is not uncommon that students report difficulty in conceptualizing even common controls systems terms such as steady-state error and disturbance rejection. Typically, most courses focus on the theoretical analysis and modeling, but students are left asking the questions…How do I implement a phase-lead compensator? …What is a non-minimum phase system? This paper presents an innovative approach in teaching control systems design course based on the use of a low-cost apparatus that has the ability to directly communicate with MATLAB and its Simulink toolbox, allowing students to drag-and-drop controllers and immediately test their effect on the response of the physical plant. The setup consists of a DC micro-motor driving a propeller attached to a carbon-fiber rod. The angular displacement of the rod is measured with an analog potentiometer, which acts as the pivot point for the carbon fiber rod. The miniature circuit board is powered by the USB port of a laptop and communicates to the host computer using the a virtual COM port. MATLAB/Simulink communicates to the board using its serial port read/write blocks to command the motor and detect the deflection angle. This presentation describes a typical semester-long experimental protocol facilitated by the low-cost kit. The kit allows demonstration of classical PID, phase lead and lag controllers, as well as non-linear feedback linearization techniques. Comparison between student gains before and after the introduction of the mechatronic kits are also provided.
A Study of the Performance Emission and Combustion Characteristics of a DI Diesel Engine Using Waste Cooking Oil Methyl Ester-Ethanol Blends
Authors: Anand R. , Kannan G. R. , Karthikeyan P.
Published: October 2013

The growing environmental concerns and the depletion of petroleum reserves have caused the development of alternative fuels. Biodiesel and alcohols are receiving increasing attention as alternative fuels for diesel engines due to well oxygenated, renewable fuels. In this study, a single cylinder, naturally aspirated, direct injection diesel engine has been experimentally investigated using ethanol-blended waste cooking oil methyl ester. Various proportion of biodiesel-ethanol blends were used in stability test at the different temperatures from 10 °C to 40 °C in the increment of 10°C. Based on the stability tests and improvement in fuel properties, B90E10 (90% biodiesel and 10% ethanol) and B80E20 (80% biodiesel and 20% ethanol) were selected for this investigation. Test results revealed that the improved engine characteristics with the use of B9E10 especially in comparison with B80E20. Reduction in brake thermal efficiency by 3.8% and slightly higher brake specific energy consumption of 15.1% were observed with B90E10 when compared to diesel at 100% load condition. Carbon monoxide, unburnt hydrocarbon, nitric oxide and smoke emission of B90E10 were reduced by 0.09% by vol., 10 ppm, 187 ppm and 12.9%, respectively compared to diesel. B90E10 exhibited lower peak pressure of 70.5 bar, slightly longer ignition delay of 14.2 °CA, and combustion duration of 43.3 °CA was also observed at 100% load condition.
Preliminary Results for Forecasting the Oil Price Evolution With Negative Inflation Rate
Authors: Gori Fabio
Published: October 2013

Mass conservation equation is employed to study the time evolution of the mass of oil remaining in a reservoir, according to the mass flow rate of extraction, and to define the critical mass flow rate of extraction, which is the value exhausting the reservoir in an infinite time. The price evolution with time of the resource sold to the market is investigated in case of no-accumulation and no-depletion of the resources; i.e. when the resources are extracted and sold to the market at the same mass flow rate. The energy conservation equation is transformed into an energy-capital conservation equation, which allows to study the oil price evolution with time, dependent on the following parameters. The parameter PIFE, “Price Increase Factor of Extracted resource”, is the difference between the basic interest rate of the capital, e.g. inflation rate, and the mass flow rate of extraction. The parameter PIFS, “Price Increase Factor of Sold resource”, is the difference between the interest rate of the capital, e.g. prime rate, and the mass flow rate of extraction. The parameter CIPS, “Critical Initial Price of Sold resource”, depends on the initial price of the extracted resource, the interest rate of non-extracted resource, and the difference between PIFS and PIFE. The parameter CIPES, “Critical Initial Price Extreme of Sold resource”, depends on the initial price of the extracted resource, the interest rate of non-extracted resource, and PIFS. The present theory is applied to the time evolution of the oil price during the years following the economic crisis of 2008, introducing the new category of cases with a negative inflation rate, that was registered during 2009. The present theory can be applied also to the months with negative inflation rate with a reasonable fair agreement.
Experimental and Numerical Heat Transfer on a Cylinder Cooled by Two Rectangular Jets of Different Heights
Authors: Gori Fabio , Petracci Ivano , Angelino Matteo
Published: October 2013

The present paper presents experimental measurements of heat transfer on a cylinder, cooled by two rectangular jets of the same width but different height, H, in order to investigate the influence of the jet height on the local and the average cooling rates, because one of the problems in the heat transfer with jet flow is the convenience to choose the height of the jet in comparison to the height of the impinged object. The cylinder, heated by electric current, is set at several distances from the jet exit, x, on the symmetrical plane of symmetry, i.e. in a two-dimensional geometry, in order to find the optimal position which realizes the maximum heat transfer. The experimental heat transfer on the impingement shows that the local Nusselt number, defined with the cylinder diameter, D, is greater for the smaller slot because velocity is slightly higher but the average Nusselt numbers, defined with the cylinder diameter, D, are quite similar because the higher slot has a greater surface of impingement. Local and average Nusselt numbers are in qualitative agreement only if are compared with the same dimensionless distance, x/H, which can be interpreted as the ratio Rex/ReH, which is per unit of mass flow rate or is independent of the mass flow rate. Numerical simulations are carried out with a two-equations turbulent model using the RNG k-ε approach, on a cylinder with the same thickness of the experiments or without thickness. The numerical simulations of the cylinder without thickness are in acceptable agreement for what concern the average Nusselt numbers. The local Nusselt numbers are in fair agreement only if the cylinder has the thickness of the experiments, independently of the heat flow conditions, i.e. uniformly throughout the thickness or from the inner surface.
Benefic Effect of Conservative Treatments on Patients Diagnosed With Osteoporosis
Authors: Pop Petru A. , Lazar Liviu , Marcu Florin M.
Published: October 2013

Osteoporosis (OP) represents the most common metabolic bone disease, characterized by the shrinkage in bone mass and the destruction of bone quality, thus conferring a higher risk for micro-fractures and injuries. The goal of treatment in OP is to grow-up the bone mineral density of the skeleton and to increase resorption of formed bone, due to improving the quality life of patients. The methods are diverse, such as medications, conservative measures, weight reduction, physical and occupational therapy, mechanical support devices and surgery. This paper presents a balneal-conservative treatment of patients diagnosed with OP from Rehabilitation Clinical Hospital of Felix Spa. The treatment is complex and involves balneal-physical-kinetic therapy or balneal-physical-kinetic recovery treatment, which must be periodical repeated every six months to obtain good results. The study has been applied to two separate groups of patients with OP between 2009–2011. The first group of 100 subjects, presented clinical symptomatology, as pain of variable types like backaches, fragility fractures or deformation of bone shape that resulted from fractures or alterations of weakens bones. A second group of 80 subjects, received the balneal-rehabilitation treatment combined, or not with physical exercises. DEXA and SF-36 scores, using statistical analysis, performed the evaluation of OP treatment. The results of experiment emphasized the efficiency of balneal-rehabilitation treatment applied patients with OP. The future research will be focused upon the implementation of vibration therapy with balneal-conservative treatment on patients with osteoporosis and osteoarthritis to reduce the therapy time and improving the quality life of patients.
Testing of Sonic-Absorbent Panels’ Behavior in Open-Air Environment
Authors: Pop Petru A. , Ungur Patricia A. , Lazar Liviu , Gordan Mircea , Marcu Florin M.
Published: October 2013

One wildly used method to reduce and control the noise pollution in green city’s buildings is using sonic-absorbent panels. Their applications can be multiple, such as the insulation of buildings, acoustic barriers and fences along the highway or in front of supermarkets, hospitals and other public buildings. This paper presents a method for testing the behavior of sonic-absorbent panels in open-air environment. The work represents a carrying on of previous research about absorbent materials from gypsum family, tested in lab conditions. The experiment setup used a dynamic installation and as a sample a stand formed by six sonic-absorbent panels from special modeling alpha-gypsum plaster. This installation has been composed of two loudspeakers for emitting the sound at a well-defined frequency by the first laptop, the microphone for detecting and transmitting the signal to the second laptop for analyzing and processing the data. All operations were performed using MATLAB Programs, while a Data Logger Sound Level Meter type CENTER 332 was put on near the microphone to compare both results. The first experiment of acoustic stand has been realized by setting up the installation at a frequency from 50 Hz to 1250 Hz and altering the distance between loudspeakers and stand at 0.5m to 1m and 1.5m, respectively. The second experiment kept the same test’s conditions, while two and three layers of sonic-absorbent panels formed the stand, respectively, but at same distance from source of 0.5 m. In both tests, the results underlined the good sonic-absorbent properties of these panels, especially at medium and high frequency, which can recommend using the panels for multiple outside applications.
Numerical Optimization of Ejector Geometry Based on Non-Dimensional Parameters
Authors: Sharifi Navid , Boroomand Masoud , Sharifi Majid
Published: October 2013

Supersonic steam ejectors are simple devices which can be used to compress a low pressure flow by a pressurized motive flow. “Compression ratio” and “entrainment ratio” are two major characteristics of the ejectors. One of the current challenging issues in ejector design is the correct size selection for different dimensions of ejectors to achieve the maximum entraining capability at a given compression ratio. The conventional design methods are based on varying shape parameters such as lengths, angles and diameters and pick a particular geometry which yields the best performance under a given boundary conditions.

In the current study, a new method of size selection for different geometrical parameters of ejectors will be introduced. The basis of this method is to define a non-dimensional volume in terms of ejector dimensions. The effect of varying this parameter on the characteristics of ejectors has been studied numerically via a CFD method. The numerical simulation has been performed on more than 400 ejector models with different geometries according to the finite-volume steady-state method. Steam was taken as the working fluid and it was assumed a real gas with a nonlinear relationship between pressure and density. The numerical results verified with experimental measurements obtained from a pilot model of steam ejector. This method enables us to develop the practical characteristic curves based on non-dimensional parameters which further leading to achieve an optimized size selection for design purposes.
Investigating a Framework for Modeling and Analysis for Wound Progression
Authors: Chin Jessica , Zeid Abe , Kamarthi Sagar
Published: October 2013

Wounds are as unique as a fingerprint. A wound can be a tear, scrape or cut — simply anything that damages the protective layer of skin. Wounds occur anywhere on the body from a small paper cut to a large gash. Because the topology of a wound varies so significantly, current tracing and modeling methods fail to adapt to the changing environment. Similarly, traumatic wounds are a greater challenge to heal without infection due to their nature, size, depth and moisture. Presently, tracing and modeling methods are inaccurate and unreliable for wounds that exceed a certain depth. With any wound, non-invasive, full field methods are necessary to effectively measure and assess the severity of the wound. Due to lack of diagnosis options, wounds are expensive to treat and heal. There are few methodologies that exist to help affect the decision for clinicians regarding wound care, how wounds are evaluated, and how wounds are created. In the U.S., there are an estimated 2.5 million pressure ulcers treated each year in acute care facilities. The epidemiology of pressure wounds result in particular physiological principles that we can use to quantify and determine a baseline wound condition. At the moment, the physician and his experience rather than a standard diagnostic system determines the wound condition. This paper presents methods of quantifying wound progression and their impact thus far on patient care. It also provides open-ended research issues that support the need for a structured, systematic methodology for the modeling and analysis of wound progression. The purpose of this paper is also to disseminate a preliminary epistemology on wound progression and modeling in a quantifiable manner.
Application of a Constitutive Modeling for Light Activated Shape Memory Polymer to Circular Shear
Authors: Cui Fangda , Rao I. J.
Published: October 2013

Shape memory polymers (SMP’s) are polymers that have the ability to retain a temporary shape, which can revert back to the original shape on exposure to specific triggers such as increase in temperature or exposure to light at specific wavelengths. A new type of shape memory polymer, light activated shape memory polymers (LASMP’s) have been developed in the past few years. In these polymers the temporary shapes are fixed by exposure to light at a specific wavelength. Exposure to light at this wavelength causes the photosensitive molecules, which are grafted on to the polymer chains, to form covalent bonds. These covalent bonds are responsible for the temporary shape and act as crosslinks. On exposure to light at a different wavelength these bonds are cleaved and the material can revert back to its original shape. A constitutive model of LASMP’s which based on the notion of multiple natural configurations has been developed (see Sodhi and Rao[1]). In this work we use this model to analyze the mechanical behavior of LASMP’s under a specific boundary value problem, namely, the problem of circular shear. We use this model problem to study the behavior of the LASMP’s when a temporary configuration is formed by exposing the polymer to light. In addition we show that these materials are able to undergo complex cycles of deformation due to the flexibility with which these temporary configurations can be formed and removed by exposure to light.
Hybridization Between Classroom and On-Line Teaching: An Alternative Teaching Approach
Authors: Duan Shanzhong (Shawn) , Bassett Kurt
Published: October 2013

Though face to face class is still a dominant-teaching approach in most higher educational institutes, with the development of internet technology, on-line teaching has been increasingly popular. This paper intends to share experiences, myths, and lessons that the authors have learned during exploration of hybridization between classroom and on-line teaching of an undergraduate course in the area of mechanical engineering. Several key factors have been used to determine effectiveness and efficiency of this blended teaching approach. The paper will also discuss how the hybridization takes advantage and avoids disadvantages of both traditional classroom teaching and on-line teaching. The hybridization approach is also compared with traditional classroom teaching. The current student survey and course assessment indicates that the approach provides a promising alternative for teaching an undergraduate course.
Effects of Biased AC Electroosmotic Micro-Pumping on Symmetric and Asymmetric Electrode Arrays
Authors: Islam Nazmul
Published: October 2013

This paper presents an analysis and experiment results that were conducted to assess the effect of combining an AC signal with a DC bias when generating the electric field on electrode arrays needed to impart electroosmosis within a microchannel. The analysis was done using COMSOL 3.5a in which currently available theoretical models for EO flows were embedded in the software and solved numerically. The simulation evaluate the effects of channel geometry, frequency of excitation, electrode array geometry, and AC signal with a DC bias on the flow imparted on an electrically conducting fluid.

For the AC driven flow, the simulation results indicate the existence of an optimized frequency of excitation and an optimum geometry that lead to the maximum net forward flow of the pump. No relevant net flows were generated with the symmetric electrode arrays with a constant magnitude of AC voltage applied to both electrodes. However, superimposing a DC signal over the AC signal on the same symmetric electrode array lead to a noticeable net forward flow of 18.70 μL/min. On the other hand asymmetric electrode pattern can generate flow in both cases and can improve the microflow inside the micro-channel. Experimental flow measurements were performed on several electrode array configurations manufactured using typical MEMS fabrication techniques. The experimental results are in good agreement with the simulation data. They confirm that using an asymmetric electrode array excited by an AC signal with a DC bias leads to a significant improvement in flow rates in comparison to the flow rates obtained in an asymmetric electrode array configuration excited just with an AC signal.
Integration of a Real-Time Remote Experiment Into a Multi-Player Game Laboratory Environment
Authors: Tumkor Serdar , Zhang Mingshao , Zhang Zhou , Chang Yizhe , Esche Sven K. , Chassapis Constantin
Published: October 2013

While real-time remote experiments have been used in engineering and science education for over a decade, more recently virtual learning environments based on game systems have been explored for their potential usage in educational laboratories. However, combining the advantages of both these approaches and integrating them into an effective learning environment has not been reported yet. One of the challenges in creating such a combination is to overcome the barriers between real and virtual systems, i.e. to select compatible platforms, to achieve an efficient mapping between the real world and the virtual environment and to arrange for efficient communications between the different system components.

This paper will present a pilot implementation of a multi-player game-based virtual laboratory environment that is linked to the remote experimental setup of an air flow rig. This system is designed for a junior-level mechanical engineering laboratory on fluid mechanics. In order to integrate this remote laboratory setup into the virtual laboratory environment, an existing remote laboratory architecture had to be redesigned. The integrated virtual laboratory platform consists of two main parts, namely an actual physical experimental device controlled by a remote controller and a virtual laboratory environment that was implemented using the ‘Source’ game engine, which forms the basis of the commercially available computer game ‘Half-Life 2’ in conjunction with ‘Garry’s Mod’ (GM). The system implemented involves a local device controller that exchanges data in the form of shared variables and Dynamical Link Library (DLL) files with the virtual laboratory environment, thus establishing the control of real physical experiments from inside the virtual laboratory environment. The application of a combination of C++ code, Lua scripts [1] and LabVIEW Virtual Instruments makes the platform very flexible and expandable. This paper will present the architecture of this platform and discuss the general benefits of virtual environments that are linked with real physical devices.
Numerical Study of a Non-Linear Model for the Heat Flux Vector for Granular Materials
Authors: Yang Hyunjin , Aubry Nadine , Massoudi Mehrdad
Published: October 2013

The two important constitutive relations needed for the study of flow and heat transfer in granular materials, where the effects of radiation are ignored, are the stress tensor and the heat flux vector. Massoudi [1, 2] derived a constitutive model that reflects the dependence of the heat flux vector on the temperature gradient, the density gradient and the velocity gradient, in an appropriate frame-invariant formulation. In this paper we use a simplified version of this model and consider the one dimensional fully developed flow of granular materials down a heated inclined plane, subject to a constant temperature boundary condition. The equations are made dimensionless and a parametric study is performed in order to examine the effects of the additional parameters on the heat flux vector. The derived governing equations are coupled non-linear second order ordinary differential equations which are solved numerically and the results are shown for the temperature, volume fraction and velocity profiles.
The Effect of Insulation on Energy Savings and Costs for the Current Building Inventory in Turkey
Authors: Erdem Serkan , Onan Cenk , Özkan Derya B. , Bedirli S. Eray
Published: October 2013

The current building inventory in Turkey includes a large number of uninsulated buildings. By insulating these buildings, the required heating energy is decreased, and significant energy savings are achieved. Within the country, the standard “Thermal Insulation Requirements for Buildings” was placed into effect in buildings in the year 2000 and divided the country into four climatic regions. The optimum insulation thickness in buildings changes as a function of the region, type of insulation material and fuel. In this study, the implemented insulation thickness according to the “Thermal Insulation Requirements for Buildings” standard is calculated for the four different regions of Turkey for expanded polystyrene insulation material. The current building inventory in Turkey was taken from the State Institute of Statistics (Prime Ministry, Republic of Turkey). Energy savings, costs and payback period are calculated by the P1-P2 method for the current building inventory, using XPS insulation in all buildings and natural gas as the fuel for the heating energy requirements. The results are shown in the figures for the four different climatic regions, and the effect of the current building inventory distribution around the country is determined.
Finite Element Analysis for Nonlinear Time Dependent Response of Piezoelectric Materials
Authors: Sohrabi Amir , Muliana Anastasia
Published: October 2013

Piezoelectric materials show nonlinear response under high electric field. In addition, recent experiments showed that the electromechanical coupling coefficients of polarized piezoelectric materials, such as PZT ceramics, change with time, leading to history dependent and hysteretic responses in these materials. In this study, the coupling behavior of piezoelectric material under high electric field is investigated. The electromechanically coupled constitutive equation that accounts for history of mechanical loading and electric field is used for the piezoelectric materials. Effect of high electric field which causes nonlinearity in response of piezoelectric material is modeled by taking the material’s electromechanical coupling coefficients to be dependent on applied electric field and single time integration model is employed to incorporate history-dependent behavior. A continuum finite element with displacement and electric potential degrees of freedom that incorporates nonlinear history dependent effect is developed. Nonlinear finite element solver is formulated by using direct iteration method at element level and recursive iterative method at material (Gaussian) integration points. Nonlinear time-dependent finite element formulation is validated by comparing its response with experimental data on PZT ceramics. History dependent and nonlinear response of PZTs due to electric field and stress is discussed. Developed finite element is capable of modeling behavior of smart structures with piezoelectric sensors and actuators.
An Overall Analysis of Servo Control System Influence on Frequency Spectrum Structure of Linear Motor Thrust
Authors: Yang Xiaojun , Cao Kun , Liu Hui , Zhao Wanhua , Zhang Jun
Published: October 2013

Servo control system in CNC machine tools is crucial for machining accuracy. In order to obtain good dynamic precision, the in-depth analysis of the output torque of the servo motor should be a prerequisite. In this paper the servo control system including CNC, electromagnetic noise and feedback information disturbance, are analyzed in frequency domain, to study their individual influence on the frequency spectrum of the linear motor thrust. The following work has been done: 1) the control-related modules in CNC, i.e., the interpolator and the Acceleration/Deceleration Control (ADC) module are studied by analytic method to reveal their impact on the command signal used to control the servo motor. 2) The influence of the servo drive circuit on the frequency components of the motor current as well as the mechanism of PWM module & power amplifier is investigated. 3) The electromagnetic conversion inside the servo motor is analyzed to explore the energy flow of the motion inside the mechatronic system. 4) The influences of the electromagnetic noise and feedback information disturbance on the thrust spectrum are analyzed. The results show that, the frequency spectrum distribution of the motor thrust is decentralized and complicated, and each part is influenced by certain module of the servo control system respectively. It is also found that the thrust spectrum varies with the feed speeds.
A Numerical Approach for Mechanics of Soil-Tool Interaction for a Robotic Assistant Farmer
Authors: Armin Ahad , Szyszkowski Walerian , Fotouhi Reza
Published: October 2013

Use of mobile robots in farm setting may result in lowering production costs, reducing the manual labors, and may be essential in the future due to a potential shortage of farmers. The conditions, such as blade geometry, soil conditions, and cutting depth, have been shown to have great effects on power consumption and on efficiency of particular farm machineries. In this paper, a 3-dimensional nonlinear finite element analysis (FEA) is developed to analyze behavior of a blade moving in a block of soil, and to find force reactions on the blade. This FEA model resulted in accurately predicting draft forces developed on the blade when it moves through the soil. The deformation of soil in front of the blade during soil-blade interaction is also studied. The FEA results are compared with analytical soil mechanics results which show good agreement.
Simulations of Droplet Collisions in Shear Flow
Authors: Shardt Orest , Derksen J. J. , Mitra Sushanta K.
Published: October 2013

When droplets collide in a shear flow, they may coalesce or remain separate after the collision. At low Reynolds numbers, droplets coalesce when the capillary number does not exceed a critical value. We present three-dimensional simulations of droplet coalescence in a simple shear flow. We use a free-energy lattice Boltzmann method (LBM) and study the collision outcome as a function of the Reynolds and capillary numbers. We study the Reynolds number range from 0.2 to 1.4 and capillary numbers between 0.1 and 0.5. We determine the critical capillary number for the simulations (0.19) and find that it is does not depend on the Reynolds number. The simulations are compared with experiments on collisions between confined droplets in shear flow. The critical capillary number in the simulations is about a factor of 25 higher than the experimental value.