bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Transient Laminar Forced Convection of Nanofluids in Circular Channels
Authors: Sert İsmail Ozan , Sezer-Uzol Nilay , Kakac Sadik
Published: October 2013

In this study, forced convection heat transfer characteristics of nanofluids are investigated by numerical analysis of incompressible transient laminar flow in a circular duct under step change in wall temperature and wall heat flux. The thermal responses of the system are obtained by solving energy equation under both transient and steady-state conditions for hydrodynamically fully developed flow. In the analyses, temperature dependent thermo-physical properties are also considered. In the numerical analysis, Al2O3/water nanofluid is assumed as a homogenous single-phase fluid. For the effective thermal conductivity of nanofluids, Hamilton-Crosser model is used together with a model for Brownian motion in the analysis which takes the effects of temperature and the particle diameter into account.

Temperature distributions across the tube for a step jump of wall temperature and also wall heat flux are obtained for various times during the transient calculations at a given location for a constant value of Peclet number and a particle diameter. Variations of thermal conductivity in turn, heat transfer enhancement is obtained at various times as a function of nanoparticle volume fractions, at a given nanoparticle diameter and Peclet number. The results are given under transient and steady-state conditions; steady-state conditions are obtained at larger times and enhancements are found by comparison to the base fluid heat transfer coefficient under the same conditions.
Experimental Investigation of a Jet and Vortex Actuator Using Particle Image Velocimetry
Authors: Cadirci Sertac , Gunes Hasan , Rist Ulrich , Peters Bernd
Published: October 2013

The Jet and Vortex Actuator (JaVA) is a zero-net-mass flux device for active flow control. JaVA was investigated experimentally using flow visualization and Particle Image Velocimetry (PIV) measurements and tested in still water instead of air to be able to make real-time observations with naked eye at an actuator plate frequency of f = 1 Hz. It has been already published that typical JaVA induced flow regimes are angled and vertical jets, wall jets and vortex flows. The flow types depend on the governing parameters including actuator plate width, the amplitude and the frequency of the actuator and the mean position of the actuator plate due to the JaVA cavity. First, we carried out extensive flow visualizations in an effort to observe flow dynamics qualitatively and describe the effect of governing parameters on JaVA induced flows. Then, we carried out PIV experiments and obtained quantitative data. We present results using velocity and vorticity fields for different types of jet flows. The suction and blowing phases of the jet flows, and mean jet flow rate and the jet momentum flux are investigated in detail. The vertical jet is found to have the maximum mean flow rate as well as the maximum jet momentum flux.
A Noise Evaluation Based Wiener Deconvolution Method for Contact Parameters Measurement Using Ultrasound
Authors: Du Fei , Hong Jun , Li Baotong , Luo Zeng , Wang Shaofeng , Xu Ying
Published: October 2013

Ultrasound method is an extremely useful tool in contact parameters identification for joint surface widely used in engineering product. Wiener filter is commonly used to ultrasonic reflection map to reduce the influences of the blurring effect introduced by ultrasonic beam size on the measurement accuracy, but the results are not good enough because it is difficult to estimate the signal-to-noise ratio of reflection map. In this paper, a noise evaluation based Wiener deconvolution approach is developed to handle this problem. The noise power spectrum of reflection map is estimated through the steel-air contact area of the joint surface, and an evaluation of the ratio of noise power spectrum and signal power spectrum is obtained based on the noise variance and the experimental reflection map. To verify the efficiency of the developed approach, a sphere-plate contact interface is selected as a concrete case in which different Wiener deconvolution approaches are applied for evaluation of contact parameters. The results are compared with simulation results produced by a finite element model (FEM). The comparisons show that the contact parameters obtained by the proposed approach are more accurate than that obtained by commonly used Wiener filter approaches.
Physical Sense of the Plastic Modulus of Metallic Materials at High Strain-Rates
Authors: Fan Ya-fu , Ning Jun-sheng , Chen Jie , Cui Xin-zhong
Published: October 2013

In this paper, impact experiments in nitrogen alloyed austenitic steel (high-N steel) and 685 steel were carried out with the split Hopkinson pressure bar (SHPB) apparatus. It can be found from the experiments that the plastic modulus and the strain-rate sensitivity exponent are two main factors of holding together materials dynamic steadiness at high strain-rates. In particular, the magnitude of plastic modulus indicated the ability with transferring stress-wave load in aspect of physical nature. The greater this value, the greater is absorbency of projectile dynamical energy for target material. This conclusion has been proved by fitting Johnson-Cook model parameters and correlative numerical calculation and microcosmic analysis. Continuing above thoughts, the estimation of terminal ballistics performance of target material using Johnson damage number and hardening damage number will be applied in engineering.
Modeling and Experiments on Fast Response Thermoelectric Co-Generation for Intermittent Renewable Energy Sources
Authors: Yazawa Kazuaki , Wong Vernon K. , Blarke Morten Boje , Shakouri Ali
Published: October 2013

We present preliminary proof-of-concept experimental results on a thermoelectric heat pump system. In our previous work we proposed a thermal battery which would benefit from state-of-the-art heat pumps in order to provide useful cooling and heating. The preliminary analysis demonstrated the benefit of using excess electricity from intermittent renewable power sources, e.g. solar or wind, and converting it into the hot and cold water storage tanks typically used for residential applications. The time response of mechanical heat pumps is slow and their efficiency suffers from fluctuating electricity supplies. To overcome this issue, we propose thermoelectric (TE) co-generation systems that benefit from their fast response and scalability. Modeling has been performed to optimize the TE module for the effective harvesting of both heat and electricity from intermittent solar energy with response times in minutes. Throughout the modeling and experiments, the combined coefficient-of-performance (COP) is found to be 1.6, while the hot water is 52.5°C and cold water is 16.5°C, both from 22.3°C. The COP is moderate, but due to its quick response, the accumulated energy harvested by this thermoelectric system could be comparable to mechanical compressor systems.
Design and Production of Wireless Micro Sensor Node Based on Printed Electronics Technology
Authors: Guo F. , Zhou H. , Wei J. , Wei Z.
Published: October 2013

With the wide applications of Internet of Things technology, the design and fabrication of small size sensor nodes with high sensitivity at low cost will be the main direction of development. In this paper, the important design requirements and design drivers for the manufacturing of wireless micro sensor node based on printed electronics technology are analysed and reviewed. The micro-sensor nodes fabricated can be powered with solar cell. The production cost could be effectively reduced and the life of the system is extended. The sensor nodes could be widely used for real-time monitoring in wide areas.
Nonlinear Vibration Absorber for Mitigation of Torsional Vibrations
Authors: Bin Tahir Ammaar , Shiryayev Oleg , Karki Hamad , Vahdati Nader
Published: October 2013

This work discusses the effects of utilizing a nonlinear energy absorber with linear and cubic stiffness characteristic in mitigating torsional vibrations in a 5 degrees-of-freedom (5-DOF) rotational system. Results comparing the effects of adding a linear TMD in the system with those obtained by adding an NES are presented which demonstrate the usefulness of an NES over a conventional TMD. Subsequently, a simpler translational system comprising of an NES is considered and an optimization-based tuning methodology is used in order to tune the NES for maximum dissipation of vibration energy. The results are compared with those obtained for the system with a linear absorber.
On the In-Pipe Measurements of Acoustic Signature of Leaks in Water Pipelines
Authors: Khulief Y. A. , Khalifa A.
Published: October 2013

Identification and localization of leaks in water pipelines using acoustic methods have been utilized for many years. Most of the existing acoustic leak detection techniques rely on external measurements of sound emitted from the turbulent jet of water escaping the pipe. Direct acoustic measurements via hydrophones, which travel inside the pipe with the flow, have been recently addressed as a viable complementary leak detection technique. This paper presents an experimental investigation that addresses the feasibility and potential of inpipe acoustic measurements for leak detection. An experimental water pipe circuit was constructed to permit different line pressures, flow rates and leak sizes. The leak acoustic signature was acquired at different proximities from the leak port for variations of the line parameters. The acquired acoustic signals are processed and analyzed to access the feasibility and point out the limitations of invoking in-pipe measurements for leak detection.
Modeling and Analysis of Solar Radiation Potentials on Building Rooftops
Authors: Omitaomu O. A. , Kodysh J. B. , Bhaduri B. L.
Published: October 2013

The active application of photovoltaic for electricity generation could effectively transform neighborhoods and commercial districts into small, localized power plants. This application, however, relies heavily on an accurate estimation of the amount of solar radiation that is available on individual building rooftops. While many solar energy maps exist at higher spatial resolution for concentrated solar energy applications, the data from these maps are not suitable for roof-mounted photovoltaic for several reasons, including lack of data at the appropriate spatial resolution and lack of integration of building-specific characteristics into the models used to generate the maps.

To address this problem, we have developed a modeling framework for estimating solar radiation potentials on individual building rooftops that is suitable for utility-scale applications as well as building-specific applications. The framework uses light detection and ranging (LIDAR) data at approximately 1-meter horizontal resolution and 0.3-meter vertical resolution as input for modeling a large number of buildings quickly. One of the strengths of this framework is the ability to parallelize its implementation. Furthermore, the framework accounts for building specific characteristics, such as roof slope, roof aspect, and shadowing effects, that are critical to roof-mounted photovoltaic systems. The resulting data has helped us to identify the so-called “solar panel sweet spots” on individual building rooftops and obtain accurate statistics of the variation in solar radiation as a function of time of year and geographical location.
Maximum Missile Velocity From Boiling-Liquid Expanding-Vapor Explosions (BLEVE) Using Exergy Analysis
Authors: Ramirez Juan C. , Smyth Suzanne A. , Ogle Russell A.
Published: October 2013

One of the hazards from a boiling liquid expanding vapor explosion (BLEVE) is the formation and projection of missiles. The design of safeguards for protection from missiles, such as barricades or buffer zones, requires an estimate of the maximum kinetic energy of the missiles. In this paper we demonstrate the use of exergy analysis to estimate the maximum available work of the explosion, and then use a modified Gurney method to estimate the partitioning of exergy into the kinetic energy of the saturated vapor, the saturated liquid, and the missiles. The advantage of using exergy analysis to evaluate the maximum work of an explosion is that exergy is a state variable: its value depends only on the initial conditions of the high pressure fluid and the specification of the dead state. The advantage of using the Gurney method for evaluating the kinetic energy of missiles is that it does not require the selection of an equation of state for the high pressure fluid. The methodology is illustrated for several pure component fluids, and is then compared with other estimation methods.
Elastic Property Monitoring by Radiation Force Impulse and Phase Contrast Imaging
Authors: Bawolin Nahshon K. , Chen Daniel X. B.
Published: October 2013

In tissue engineering, one promising methodology is the scaffold based approach, where an artificial construct is seeded with cells, which then proceed to organize and proliferate into new tissue. The scaffold then biodegrades, leaving behind the newly formed tissue that originally developed in the scaffold’s pores. The degradation behavior of the scaffold is critical to its performance during the treatment period, since the decline in scaffold mechanical properties influences the loading of the tissue developing in the scaffold pores, which is known to have an effect on cell behavior. To monitor the scaffold’s mechanical properties, soft scaffolds are deformed by the acoustic radiation force generated by an ultrasound source. Measuring the deflection the scaffold experiences from this ultrasound based radiation force is challenging, since the scaffold is surrounded by the living environment. In this paper, an in-vitro methodology is presented, proceeding from scaffold fabrication, scaffold imaging, image analysis, mathematical equations, and finally model implementation. The innovation comes from the author’s use of in-line phase contrast x-ray imaging at 20 KeV to characterize tissue scaffold deformation from ultrasound radiation forces, and the measured deformation is then compared with predictions given by the forward solution of a mathematical model.
The Friction Forces Between Si Tip and Multilayer Graphene
Authors: Zhang Yan , Wang Yingying , Chen Yunfei , Wang Yujuan
Published: October 2013

Mechanical peeling method is used to prepare multilayer graphene on silicon wafer with natural oxide, and the layer number of graphene is determined through atomic force microsopy (AFM) topography image and optical image. The friction force between Silicon tip and multilayer graphene and SiO2/Si substrates is measured with AFM. It is found that the friction force is reduced with the increase of the graphene layer number and approaches the value between the Si tip and graphite. Through comparing the tip sliding on graphene with different layers, the deformation of graphene is believed to be the main reason causing the decrease of the friction force with the layer number. When the normal load is much larger than the adhesion force, friction force increases with normal load linearly. However, while normal load closes to the adhesion force, friction force is independent of the normal load.
Leidenfrost Cart
Authors: Hashmi Ali , Coder Benjamin , Yu Gan , Xu Yuhao , Spafford Jonathon , Michael Grant E. , Osborne Paul A. , Xu Jie
Published: October 2013

Friction is a major inhibitor in almost every mechanical system. Enlightened by the Leidenfrost effect — a droplet can be levitated by a vapor layer on a hot surface — we demonstrate for the first time that a small cart also can be levitated by Leidenfrost vapor provided that the surface temperature is above the Leidenfrost point. The levitated cart can carry certain amount of load and move frictionless on the hot surface. The maximum load that the cart can carry is experimentally tested over a range of surface temperatures. We show that the Leidenfrost levitated cart can not only be propelled by gravitational force on a slanted flat surface, but also can be self-propelled on a ratchet shaped horizontal surface. In the end, we experimentally measured water consumption rate for the Leidenfrost levitated cart, and compared the results to theoretical calculations. If perfected, this frictionless Leidenfrost cart could be used in numerous applications.
Hybridization of Medium-Duty Tactical Truck Using Crankshaft-Integrated-Starter-Generator (C-ISG)
Authors: Liao Y. Gene , O’Malley Molly , Quail Allen M.
Published: October 2013

Fuel economy improvement on medium-duty tactical truck has and continues to be a significant initiative for the U.S. Army. The Crankshaft-Integrated-Starter-Generator (C-ISG) is one of the full hybrid propulsions to improve the fuel economy. The C-ISG configuration is attractive because one electric machine can be used to propel the vehicle, to start the engine, and to be function as a generator. The C-ISG has been implemented in one M1083A1 5-ton tactical cargo truck. This paper presents the experimental evaluation of the C-ISG hybrid truck performance characteristics compared to the conventional truck. The evaluated performance characteristics include all electric range for on- and off-road mission cycles, fuel consumption, as well as the battery charging profile and the silent watch time duration in the static tests.
On the Hybrid-Type Method of Brownian Dynamics and Lattice Boltzmann for Activating the Brownian Motion of Magnetic Particles
Authors: Ito Kana , Satoh Akira
Published: October 2013

We have discussed the feasibility of a method for activating the Brownian motion of dispersed particles in the lattice Boltzmann method. The method to be treated in the present study is a technique based on the Brownian dynamics method, in which the random forces in the Brownian dynamics are added to the equations of motion of magnetic particles. In order to activate the Brownian motion at a physically reasonable level, a viscosity-modifying method is introduced in adjusting the random displacements of the particles. The viscosity-modifying method is verified by comparing the present results with those of the Monte Carlo simulations. The main results obtained here are summarized as follows. The aggregate structures of magnetic particles are in good agreement with the results of the Monte Carlo method. Moreover, the pair correlation functions agree well with the Monte Carlo results quantitatively. The scaling coefficient of viscosity is seen to be constant and independent of the strengths of magnetic particle-field and particle-particle interactions. Also, it is independent of the volumetric fraction and the number of particles, if lattice system’s roughness is constant. We may conclude from these results that the hybrid-type method of lattice Boltzmann and Brownian dynamics combined with the viscosity-modifying procedure can be expected to be a hopeful technique for simulating a flow problem of magnetic particles under a non-uniform applied magnetic field.
Sensing Signal and Energy Generation Analysis on a Flexoelectric Beam
Authors: Hu S. D. , Li H. , Tzou H. S.
Published: October 2013

Flexoelectricity is known as an electromechanical gradient coupling effect. The direct flexoelectric effect that can convert mechanical strain gradient into electric polarization (or electric field) plays an important role in charge generation in the situation when piezoelectricity is absent. This study focuses on the application of the direct flexoelectric effect based on a flexoelectric cantilever beam to investigate its effectiveness of sensing signal and energy generation. The dielectric cantilever beam is deposited with electrodes both on top and bottom surfaces to generate an electric voltage. The sensing mechanism of flexo-piezo-electric effect is analyzed and the expression of sensing signal is derived. Results show that the output sensing signal is only contributed by the flexoelectric effect while the piezoelectric effect is eliminated due to the symmetric bending strains through the beam thickness. The spatial distribution of sensing signal when the fully covered electrode is uniformly segmented to 10 patches is evaluated as an illustration, and the flexoelectric sensitivity of about 0.15V/mm for the first mode and 4V/mm for the fourth mode is achieved. The optimal sensing position is dependent of the electrode size and the vibration mode and in general, it locates where the difference between the slopes at two ends of the electrode patch reaches maximum. Based on the flexoelectric voltage, the energy generation power is also conducted when the flexoelectric cantilever beam is treated as distributed energy harvesters. As a result, the maximal power of RMS is about 1.5×10−8W/mm for the first mode and increases to about 0.6mW/mm for the fourth mode. It provides an alternative way to harvest electric energy from the ambient vibration without using piezoelectricity.
International and Multidisciplinary Experiences in Engineering Courses at UNAM
Authors: Borja Vicente , Ramírez-Reivich Alejandro , López-Parra Marcelo , Treviño Arizmendi Arturo , Equihua Zamora Luis F.
Published: October 2013

A team of faculty members from the Universidad Nacional Autónoma de México (UNAM) has coordinated multidisciplinary courses in collaboration with universities from other countries. The team, who is composed by faculty from the School of Engineering and the School of Architecture, coordinates with pairs of Stanford University, the University of California at Berkeley, and the Technical University of Munich; to teach three particular design courses.

All three courses are related to product innovation but they have different emphasis depending on the collaborating partner. The focal points of each of the three courses are: (1) innovation, (2) user centered design and sustainability and (3) transport in megacities of the future.

Engineering and industrial design students are involved in the courses. They are organized in teams that include participants from the two collaborating universities. During the courses teams carry out projects working mostly at a distance; they use different means of communication and information sharing and also pay reciprocal visits between the universities involved in the collaboration.

This paper describes each of the three courses highlighting their particular characteristics. The outcomes and results of the courses and specific projects are commented. In the end of the paper lessons learned are discussed and final remarks are presented.
A Research on Drying Performance of Vertical Type Equipment for PCB Wet Process
Authors: Kim Jun Young , Jang Kyung-Min , Yoon Jong-Kuk , Kim Kwang-Sun
Published: October 2013

An etching equipment for a printed circuit board (PCB) sprays chemical and DI water through nozzles on the surface of a substrate. The horizontal type equipment moves the substrate between the upper and lower rollers and they cause the damage on the patterns and sagging of the substrate. The flow rate difference between the upper and lower air knives also causes the damage on the substrates when drying them after the end of etching and washing process. To prevent this problem, the forces of the upper and lower air knives should be compensated. The drying rates of the upper and lower sides of the substrate could still be different for the horizontal type because of difficult control of drying flow rates. The vertical type equipment that the rollers don’t contact to the circuits has recently been developed as an alternative to solve the problems. This equipment has advantages that the DI water flows on the both sides of the substrate in the direction of the gravity and the flow rate of the air from the knives can be balanced because of its structural distinction. They lead to the better drying performance without damage on the substrate. The drying process of the substrate consists of two stages which are removing the extra water by wind from the air knives and evaporating the remained moisture by the high temperature of the chamber. In this research, we selected two parameters to optimize the drying capability to the angles of air knives and the temperature in the chamber. We also investigated about the removal capability of the extra drop of water and the remained moisture by using CFD. The design conditions for the process the refore have been founded by analyzing the velocity vector of wind and the time to get the target temperature.
Dynamic Buckling Strength Assessment of Containership’s Bow Structures Subjected to Bow Flare Slamming
Authors: Yang Shun-Han , Lee Ya-Jung , Chien Hui-Lung , Chou Chih-Ming , Tseng Kuo-Cheng
Published: October 2013

The objective of this paper is to analyze the structural dynamic buckling strength of bow structure of a 1,700 TEU container vessel subjected to slamming impact force using finite element method (FEM). The slamming impact load formula suggested by Lloyd’s Register (LR) is used to assess the reliable value of impact force acting on the bow structure. To determine the critical buckling strength of a structure, two methods were developed—a one-time thickness deformation method and a buckling failure method—and are suggested to be used in the future as an industry standard. Various reasons for the causes of structure buckling damage are discussed, including magnitude of impact load, impact duration time and wave impact pattern. The result demonstrates that impact force integration under impact force-time curve is one of the crucial factors for structure dynamic buckling assessment. In the consideration of structure design optimization, this study compares efficient solutions to increase the structure buckling strength. Additionally, this study provides a clear picture of structure dynamic buckling behavior under variant impact force; moreover, it offers the designer solutions to prevent the structure from buckling damage.
Characteristics of Flow Past a Symmetric Airfoil at Low Reynolds Number: A Nonlinear Perspective
Authors: Khalid M. Saif Ullah , Akhtar Imran
Published: October 2013

Flow separation in airfoils have been extensively studied to analyze the underlying physics of the phenomenon. The phenomenon being nonlinear requires tools to reveal various features involving stall, bifurcation, and transition to chaos. In this study, we perform numerical simulations of the flow past a symmetric airfoil (NACA-0012) at 1,000 Reynolds number to compute the aerodynamic forces at different angles of attack (α). The time histories and spectral analysis reveal important features of nonlinear behavior in the flow around the airfoil. We find that the steady state temporal solutions for aerodynamic forces; lift and drag, contain both odd and even harmonics which indicate the presence of quadratic as well as cubic nonlinearity in the system. These results also help to understand nonlinear behavior of the system as a function of α. Considering the angle of attack for airfoil as a control parameter, we observe that to achieve the static stall, flow becomes chaotic adopting a route through period-doubling and quasi-periodic regimes. Using phase portraits and Poincare maps between the states of the system, period-doubling is observed in this nonlinear system at α = 22° leading to chaos at α = 27°.
Quantitative Evaluation of the Crystallinity of Grain Boundaries in Polycrystalline Materials
Authors: Murata Naokazu , Suzuki Ken , Miura Hideo
Published: October 2013

The effect of the crystllinity of electroplated copper thin films on their mechanical and electrical reliability was investigated experimentally. The crystallinity of grains and grain boundaries was evaluated by IQ (Image Quality) value of EBSD (Electron Back-Scattering Diffraction) analysis. Mechanical properties of thin electroplated films were measured by tensile test. The crystallinity of the thin film was improved by annealing. Therefore, yield stress decrease and fracture strain increase with increase of annealing temperature. Thin film interconnections for measurement of electrical properties were prepared based on damascene process. The crystallinity of the interconnection without annealing was low. The crystallinity of interconnection was improved by annealing at 400°C for 30minutes. Though the EM (Electro-Migration) resistance of the annealed film was improved drastically, SM (Stress-induced Migration) was activated even though interconnection was kept at room temperature without any application of electrical current after annealing. This is because high residual stress was caused by shrinkage of electroplated copper due to change of crystallinity. Thus the control of the crystallinity of the electroplated film was very important to improve the reliability of the interconnection.
An Analytical Model of Flow Boiling Heat Transfer for Slug Flow in a Single Circular Horizontal Micro-Channel
Authors: Younes Amen M. , Hassan Ibrahim
Published: October 2013

Slug flow is one of the most common flow patterns that occur during flow boiling in horizontal micro-channels. In the present work, an analytical model of flow boiling heat transfer is developed for slug flow in a single circular horizontal micro-channel under a uniform heat flux. The heat transfer is affected mainly by the liquid film thickness confined between the vapor slug and the channel wall. For more physical and reliable flow boiling heat transfer model, the liquid film thickness variation and pressure gradient effects on the flow boiling heat transfer coefficient are considered. The influence of vapor quality on heat transfer coefficient, vapor velocity and liquid film velocity is studied. The model is constructed based on the conservation equations of the separated two phase flow. The interphase surface is assumed to be smooth and the flow is a laminar flow. The obtained model applied for flow boiling of R-134a refrigerant in the slug flow at a narrow vapor quality range (0.0 < x < 0.1). The heat transfer coefficient showed a high increase close to the low vapor quality while decreases gradually after the peak. Furthermore, the vapor velocity increases linearly by increasing the vapor quality while, the liquid film velocity decreases.
Digital Control iBook: A Flashier Way to Study
Authors: Brito João , Soares Filomena , Leão Celina P.
Published: October 2013

Nowadays, the iPad tablet is the first choice by frequent users of new technologies. According to Nielsen Company, the iPad holds about 82% of tablet’s market share in the USA. Due to the multi-touch interface, the iPad can captivate the user since it allows interactivity, it is a friendly tool and the user’s interface is activated by our natural and most used pointer, the finger. The user easily learns how to work on this kind of technology because iPad has also an elegant and intuitive interface. These aspects, among others, make the iPad a relevant tool for work, study and leisure. Once Apple makes both hardware and operating system, it is possible to develop an application to take advantage of the iPad’s hardware. In this sense, the main idea of this project is to develop an iBook for iPad that will serve as a support tool to two Course Units of the MSc in Industrial Electronics and Computer Engineering (MIEEIC) at School of Engineering in University of Minho: Applied Mathematics (second year) and Digital Control (third year). A portable tool like the iPad is an asset to the student’s needs in learning process. In particular, the iBook for this project will really help and support the students and make their study easier when learning Digital Control and Applied Mathematics.
On the Use of the Proper Generalised Decomposition for Solving Nonlinear Vibration Problems
Authors: Grolet Aurelien , Thouverez Fabrice
Published: October 2013

This paper presents the use of the so called Proper Generalized Decomposition method (PGD) for solving nonlinear vibration problems. PGD is often presented as an a priori reduction technique meaning that the reduction basis for expressing the solution is computed during the computation of the solution itself. In this paper, the PGD is applied in addition with the Harmonic Balance Method (HBM) in order to find periodic solutions of nonlinear dynamic systems. Several algorithms are presented in order to compute nonlinear normal modes and forced solutions. Application is carried out on systems containing geometrical nonlinearity and/or friction damping. We show that the PGD is able to compute a good approximation of the solutions event with a projection basis of small size. Results are compared with a Proper Orthogonal Decomposition (POD) method showing that the PGD can sometimes provide an optimal reduction basis relative to the number of basis components.
Effect of Phonon Confinement on the Dispersion Relation and Heat Capacity in Nanoscale Si Membranes
Authors: Cuffe J. , Chávez E. , Shchepetov A. , Chapuis P.-O. , El Boudouti E. H. , Alzina F. , Pennec Y. , Djafari-Rouhani B. , Prunnila M. , Ahopelto J. , Sotomayor Torres C. M.
Published: October 2013

The effect of confinement on the acoustic phonon dispersion relation and heat capacity in free-standing silicon membranes is investigated, with thickness values down ∼ 8 nm. The discrete phonon branches are observed by angle-resolved inelastic light scattering spectroscopy. The fundamental flexural mode was observed to have a scattering intensity nearly two orders of magnitude larger than the fundamental dilatational mode, which is ascribed to its large out-of-plane density of states and quadratic dispersion. The quadratic dispersion also results in a reduction of the phase and group velocities of the fundamental flexural mode by more than one order of magnitude compared to bulk values. To investigate the effect of this behavior on the thermal conductivity, we perform calculations based on continuum elasticity theory to estimate corresponding changes in the heat capacity. This work provides a basis to investigate the effects of the frequency and dimension dependence of other phonon properties, in particular in the sub-20 nm regime, where phonon-phonon relaxation times, density of states and thermal conductivity are expected to possess different spectral dependencies than for bulk materials.
Hydro Turbine Load Optimization Using CFD Simulations
Authors: He Anpeng , Zhang Ning , Ballard Brent
Published: October 2013

The goal of the paper is to determine the optimal load on a special designed hydro turbine with various flow conditions and design configurations. Turbulent flows in the hydro turbine were simulated using the immersed-boundary method with LES turbulence model. Due to the use of the immersed-boundary method, the flow-induced turbine motions can be simulated and the transient turbine rotating speed (RPM) can be predicted. The power output based on the RPM can be calculated. Since the power output depends on both RPM and the load specified on the generator, the optimal load exists for the maximum power output. It is worth noting that the RPM changes as different loads are specified, thus numerous test cases were conducted to obtain the optimal values for one flow condition and design configuration. There are large number of cases required for various flow conditions and design configurations. Thanks to the immersed-boundary method, the computational cost for this complicated moving body problem has been reduced significantly comparing to the traditional CFD methods. Therefore, it allows a large number of cases to be simulated for the optimization purpose.
Shock Tube Autoignition Studies for Conventional and Alternative Transportation Fuel Components
Authors: Oehlschlaeger Matthew A.
Published: October 2013

Gas-phase autoignition, a fundamental indicator of fuel reactivity, and its underlying reaction kinetics are of importance to the operation of gas turbine and internal combustion engines, particularly in advanced engine concepts where kinetics may play a more important role than in legacy designs. The increasing significance of kinetics in modern engine operation and the rapid development of alternative fuels motivates an understanding of reaction kinetics and in particular the influence of fuel structure on oxidation and autoignition. A series of shock tube autoignition studies have been carried for pure fuel components found in conventional and alternative transportation fuels over the last five years. Results of these studies are summarized here. Measurements have been made for compounds found in or relevant to conventional gasoline, diesel, and jet fuels and alternative fuels including biodiesels, Fischer-Tropsch fuels, and hydroprocessed renewable fuels. Experiments were carried out for gaseous fuel/air mixtures in a heated shock tube facility. Fuel/air mixtures were studied for rich to lean conditions at high pressures (10–60 atm) and for a large range of temperatures spanning three distinct regions of reactivity from the high-temperature Arrhenius region, through the negative-temperature-coefficient region, and into the low-temperature region. The experimental results provide fundamental information about the structure-reactivity relationships for fuels and targets for the development of fuel oxidation kinetic models.
Investigation of Molten Salt Nanomaterial as Thermal Energy Storage in Concentrated Solar Power
Authors: Dudda Bharath , Shin Donghyun
Published: October 2013

It is a known fact that the solar energy is the most abundant form of renewable source of energy available abundantly in most of the areas. It is relatively the most promising form of renewable energy through which many developed countries like US, Spain are generating electricity using CSP, PV, and other forms of solar cells. This paper mainly focuses on the Concentrated Solar Power (CSP) and about the method of enhancing the Thermal Energy Storage (TES) capacity. Here, we use molten salt as the Heat Transfer Fluid (HTF) as an alternative to mineral oils and other commonly used HTF. The reasons behind using molten salts have also been listed in the paper. The major disadvantage in molten salts as a HTF is their low specific heat capacity compared to mineral oils. The low specific heat capacity of molten salt can be enhanced by dispersing oxide nanoparticles. In this paper, we synthesized molten salt nanomaterials by dispersing oxide nanoparticles in to selcte4d molten salts. Specific heat capacity measurement was performed using a modulated differential scanning calorimeter (MDSC). Hence, we evaluated the use of molten salt nanomaterials as HTF in CSP.
Stress Concentrations at the Rounded Edges of a Shaft-Hub Interference Fit Expressed in Terms of a Coefficient Normalizing the Coupling Geometry and the Young’s Modulus Effects
Authors: Strozzi Antonio , Baldini Andrea , Giacopini Matteo , Bertocchi Enrico , Bertocchi Luca
Published: October 2013

The elastic stress concentrations developed from the keyless, frictionless, static press-fit of a solid shaft into a hub with bore rounded edges are addressed. Derived from an analytical approach, a normalising parameter Φ is employed that accounts for the combined effects on the hub stress concentration of the fillet radius of the hub bore, the shaft radius, the interference, and the Young’s modulus. Compiled with the aid of Finite Elements, several design charts are presented that report the elastic stress concentrations within the hub versus the normalising parameter Φ. Each curve is valid for prescribed ratios of a) the hub inner radius to the outer radius, and b) the fillet radius to the shaft radius. An approximating expression of ample validity is also presented for a prompt evaluation of the hub stress concentration factor.
Space Cooling Using the Concept of Nanofluids-Based Direct Absorption Solar Collectors
Authors: Vishwakarma Vivek , Singhal Nitin , Khullar Vikrant , Tyagi Himanshu , Taylor Robert A. , Otanicar Todd P. , Jain Ankur
Published: October 2013

A solar-energy based vapor absorption refrigeration system is potentially an excellent alternative air-conditioning system. However, there are several research challenges to ensure sufficient efficiency and reliability for ensuring widespread implementation. Integration of a parabolic trough solar collector utilizing a mixture of nanoparticles and water with a vapor absorption system has the potential to significantly enhance the efficiency of the system. Such a system makes use of the superior thermo-physical properties of the nanofluid compared to the base fluid. Moreover, the direct absorption phenomenon of solar radiation through interaction with the participating medium (nanofluid) results in a higher temperature rise of the medium in conjunction with higher operating efficiencies as well. At the same time there are certain challenges that need to be identified and addressed in the implementation of this novel concept. For instance, to make it reliable, the system further needs to be integrated with a thermal storage system which facilitates air-conditioning even during non-sunshine hours. Integration of vapor absorption refrigeration technology, parabolic trough with water-nanoparticles mixture as the absorbing medium and a thermal storage facility is the uniqueness of this design which under certain conditions and locations may prove to be an efficient and reliable substitute to the conventional electrical air-conditioning systems. In this particular study a space cooling application for approximately 100 Tons of refrigeration is studied. Hourly variation in sunlight as well as seasonal changes for temperate climate conditions is considered. Parameters such as the cooling load of the space, and waste heat produced by electronics are evaluated. The cooling system driven by the nanofluid-based concentrated parabolic solar collector is mathematical modeled and then the optimization is done by varying the nanoparticle size and volume fraction in order to obtain the best result for collector outlet temperature, thermal efficiency and optical efficiency.
Design of DNA Origami Machines and Mechanisms
Authors: Marras Alex E. , Su Haijun J. , Castro Carlos E.
Published: October 2013

This research introduces DNA origami as a viable approach to design and fabricate nanoscale mechanisms and machines. DNA origami is a recently developed nanotechnology that has enabled the construction of objects with unprecedented nanoscale geometric complexity via self-assembly. These objects are made up of thousands of DNA base-pairs packed into 3D structures with typical dimensions of 10–100nm. The majority of DNA origami research to date focuses on assembly of static 2D or 3D structures. In this work, we aim to extend the scope of DNA origami to include design of objects with kinematically constrained moving parts. Borrowing concepts from macro-scale kinematic mechanisms, we propose the concept of DNA Origami Mechanisms and Machines (DOMM) comprised of multiple links connected by joints. The links are designed by bundling double stranded DNA (dsDNA) helices to achieve the desired geometry and stiffness. The joints are designed by combining links with strategic placement flexible single stranded DNA (ssDNA) to enable motion in specific degrees of freedom. We detail design approaches for links and common joints including revolute, prismatic, and spherical, and discuss their integration into higher order mechanisms. As a proof of concept, we built a nanoscale hinge (revolute joint) and integrated four of these hinges into a prototype DOMM, namely a Bennett 4-bar linkage, which can be completely folded into a closed bundle geometry and unfolded into an open square geometry with a specified kinematic motion path. A kinematic analysis shows that the DNA Bennett linkage closely follows the 3D motion path of the rigid body counterpart. Our results demonstrate that DNA origami has high potential for the design and assembly of nanoscale machines. The ultimate goal of this work is to develop a library of nanoscale DNA-based links and joints that can be widely used in the design and assembly of higher order mechanisms and machines. We anticipate that, in the future, these components can be used to build nanorobots for useful applications including drug delivery, nanomanufacturing, and biosensing.
Molecular-Based Theory for Drag on a Circular Cylinder by a Liquid
Authors: Wemhoff Aaron P.
Published: October 2013

A simple multiscale theory is presented that predicts the inertial drag on an infinite cylindrical rod in a homogeneous liquid. The theory essentially integrates the van der Waals molecular interactions between the rod molecules and the surrounding fluid molecules, where these integrated molecular forces are influenced by the bulk motion of the surrounding fluid. The theory suggests that the drag force exhibited by the fluid onto the rod is caused by the combination of leading-edge repulsive forces and trailing-edge attractive forces, and the predicted drag coefficient increases linearly with the rod diameter. An application of the theory to the endothelial glycocalyx layer (EGL), which contains an array of 20 nm diameter protein chain fibers lining the walls of human blood vessels, predicts a substantial difference in drag coefficient when compared to a continuum theory. This result shows that theory predicts a small inertial drag force compared to viscous force on the EGL, which provides some validation of the theory.
Turning Dynamics: Part 1 — Experimental Analysis
Authors: Halfmann Eric B. , Suh C. Steve , Hung N. P.
Published: October 2013

The workpiece and tool vibrations in a lathe are experimentally studied to establish improved understanding of cutting dynamics that would support efforts in exceeding the current limits of the turning process. A Keyence laser displacement sensor is employed to monitor the workpiece and tool vibrations during chatter-free and chatter cutting. A procedure is developed that utilizes instantaneous frequency (IF) to identify the modes related to measurement noise and those innate of the cutting process. Instantaneous frequency is shown to thoroughly characterize the underlying turning dynamics and identify the exact moment in time when chatter fully developed. That IF provides the needed resolution for identifying the onset of chatter suggests that the stability of the process should be monitored in the time-frequency domain to effectively detect and characterize machining instability. It is determined that for the cutting tests performed chatters of the workpiece and tool are associated with the changing of the spectral components and more specifically period-doubling bifurcation. The analysis presented provides a view of the underlying dynamics of the lathe process which has not been experimentally observed before.
Turning Dynamics: Part 2 — Stability at High Speed
Authors: Halfmann Eric B. , Suh C. Steve , Hung N. P.
Published: October 2013

A comprehensive 3D lathe cutting model is validated by comparing numerical simulations to the experimental data obtained in Part 1 using instantaneous frequency. Comparison of chatter-free cutting demonstrates that the model effectively captures the work-piece natural frequency, tool natural frequency, a nonlinear mode, and the spindle speed, which are main components of the underlying dynamics observed experimentally. The model accurately simulates chatter vibrations characterized as increased vibration amplitude and the appearance of coupled tool – work-piece vibrations at a chatter frequency. The stability diagram constructed by running the model at various spindle speeds and depth-of-cuts demonstrates a general increase in the chatter-free critical depth-of-cut as the spindle speed increased. This chatter-free limit begins to exponentially level out as the spindle speed exceeds 1500RPM. At high spindle speeds the work-piece motions dominate the cutting dynamics, resulting in cases of excessive work-piece vibration amplitude and highly nonlinear frequencies which affect the efficiency of the process. The excessive work-piece amplitude cases create a second stability limit to be considered as a result of imbalance and configuration of the work-piece. Thus, work-piece dynamics should not be neglected in mathematical and experimental analyses for the design of machine tools and robust cutting control law.