bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of the Scientific Method to the Analyses in Forensic Science With Case Example
Authors: Wiechel John F. , Morr Douglas R. , Boggess Brian M.
Published: May 2012

Analysis of the failure of a mechanical device requires investigation of the circumstances surrounding the failure, inspection of the mechanical device, interpretation of the information gathered during that inspection, and reverse engineering of the incident, with the end goal of reaching a conclusion as to the cause and mechanism of the failure. Often during the process of post-failure forensic analysis, hypotheses are posited to explain the failure. As an investigative engineer, the formulation of hypotheses to explain the failure often occurs after the initial investigation is conducted and the engineer has a general understanding of the conditions present at the time of the failure. If hypotheses are developed before the investigation begins, there may be too many hypotheses to consider. The hypotheses are then tested to determine their strength and false hypotheses are discarded. True hypotheses are assembled into an explanation of the failure. There is often insufficient physical evidence available to establish the exact configuration of a device after a failure. Regardless of the reason why the failed part is not present, the parties involved may dictate a need to determine the cause of the failure. When the device or failed part is not available, other techniques in addition to a physical test of the failed part must be used to test hypotheses and evaluate the cause of the failure. Examples of such techniques are (1) using information on the performance of the machine to determine possible failure mechanisms and progressions and (2) reported accounts of the machine and its environment by operators or surrounding witnesses. The current study investigates the relationship of witness observations to the analysis of example mechanical failures. Various aspects of how witnesses observe and process their observations are discussed as well as the caution needed in considering witness observations due to incomplete observations or potential benefit to the witness. The use of Failure Mode Effects Analysis in determining the cause of a failure is discussed, most notably in an extension of this technique to analyzing operator error. One particular real world example where the allegedly failed part was not available throughout the investigation is discussed in detail. The results of this study show that witness accounts of a failure should be considered by the engineer when determining the cause of a failure and that ignoring witness accounts can lead to unsubstantiated and possibly incorrect conclusions.
Introducing Problem Based Learning in a Materials Science Course in the Undergraduate Engineering Curriculum
Authors: Henry Holly , Jonassen David H. , Winholtz Robert A. , Khanna Sanjeev K.
Published: May 2012

Problem solving is the primary intellectual activity of mechanical engineers. Therefore, enhancing problem-solving skills is essential for preparing mechanical engineering students for the workplace. The most powerful method for enhancing problem-solving skills is problem-based learning (PBL). This paper presents the design and construction of a PBL-based course in materials science at the junior level. We examine the ability of the course based on problems to enable students to learn both fundamental knowledge of the subject matter and also problem solving skills and contrast it with outcomes in a traditional lecture based course. The issues and challenges faced and qualitative evidence is presented.
Hydrophobicity of Electrospun Nanofibers Films Characterized by a Quartz Crystal Microbalance
Authors: Wang Pengtao , Song Minghao , Liu Sai , Sun Hongwei
Published: May 2012

The quartz crystal microbalance (QCM) sensor is used to study the dynamic characteristic of hydrophobic nanofiberous surfaces. The nanofibrous films of polymethyl methacrylate (PMMA), PMMA/ Polydimethylsiloxane (PDMS) and Polyacrylonitrile (PAN) were prepared with an electrospinning process for different hydrophobicity (wettability). The mechanical impedance analysis of DI water on a fibrous coated QCM surface is able to quantitatively characterize the hydrophobicity of these nanofibers surfaces. The two layers including a viscoelastic nanofiber film and a liquid layer result in a nonlinear combination of mechanical impedances. To simplify the analysis, an apparent viscosity was introduced in the analysis to account for the surfacial slip effect. The experimental results showed that the hydrophobic surface resulted in small mechanical impedance loading and low value of apparent viscosity, while the hydrophilic surface generated large mechanical impedance and gave high value of apparent viscosity.
Random Collocation Method (RCM)
Authors: Isshiki Hiroshi
Published: May 2012

Recently, young people’s concern on theory is becoming very poor. If there is a numerical procedure that is friendlier with theory, the distance between theory and calculation would be decreased much, and the interaction between them would become more active. When the geometry of the domain is simple, the traditional analytical method using function expansion is very convenient in many numerical problems. In many problems, it has given very useful solutions for various problems. However, its effectiveness is usually limited to simple geometries of the domain. In the past, a fusion of the analytical approach and computational one has not been pursued sufficiently. If it becomes possible, it may give a different paradigm for obtaining the numerical solution. In the present paper, an innovative idea named Random Collocation Method (RCM) is discussed on how to overcome the weak point of the traditional method by combining it with computational method. It is the purpose of the present paper to develop the simplest numerical method and to make the distance between the theory and numerical method as small as possible.
Submerged Jet Impingement Cooling of a Nanostructured Plate
Authors: Sesen Muhsincan , Kosar Ali , Demir Ebru , Kurtoglu Evrim , Kaplan Nazli , Erk Hadi Cagdas , Khudhayer Wisam , Karabacak Tansel
Published: May 2012

In this paper, the results of a series of heat transfer experiments conducted on a compact electronics cooling device based on single phase jet impingement techniques are reported. Deionized-water is propelled into four microchannels of inner diameter 685 μm which are used as nozzles and located at a nozzle to surface distance of 2.5mm. The generated jet impingement is targeted through these channels towards the surface of a nanostructured plate. This plate of size 20mmx20mm consisted of ∼600 nm long copper nanorod arrays with an average nanorod diameter of ∼150 nm, which were integrated on top of a silicon wafer substrate coated with a copper thin film layer (i.e. Cu-nanorod/Cu-film/Silicon-wafer). Heat removal characteristics induced through jet impingement are investigated using the nanostructured plate and compared to results obtained from a flat plate of copper thin film coated on silicon wafer surface. Enhancement in heat transfer up to 15% using the nanostructured plate has been reported in this paper. Heat generated by small scale electronic devices is simulated using a thin film heater placed on an aluminum base. Surface temperatures are recorded by a data acquisition system with the thermocouples integrated on the surface at various locations. Constant heat flux provided by the film heater is delivered to the nanostructured plate placed on top of the base. Volumetric flow rate and heat flux values were varied in order to better characterize the potential enhancement in heat transfer by nanostructured surfaces.
Diesel Active-Flow Aftertreatment Control on a Heated Flow Bench
Authors: Jeftic Marko , Yu Shui , Chen Xiang , Xu Xiaohong , Wang Meiping , Zheng Ming
Published: May 2012

Empirical investigations were carried out to explore the influence of parameters such as exhaust flow temperature, exhaust flow rate, and supplemental fuel amount on diesel aftertreatment devices. A heated flow-bench system was utilized in combination with a diesel lean NOx trap (LNT) and/or a diesel particulate filter (DPF). The heated flow bench had the capability of producing stable gas temperatures and pressure drop across these aftertreatment devices. Preliminary pressure drop diagnostics were conducted with unloaded substrates meant for LNT and DPF applications. Subsequently, the DPF was loaded with varying amounts of liquid water or liquid diesel fuel and pressure drop diagnostic tests were repeated to determine if the presence of liquid substances within the substrate could be detected. With the presence of a liquid substance, the DPF exhibited relatively flat and undetectable pressure drop variation up to a critical loading level. Once this level was reached, there was a sharp and sudden increase in pressure drop. Further tests investigated the effects of exhaust flow rate and supplemental fuel amount on raising the LNT substrate temperature as required for the LNT de-NOx regeneration process. The results suggested that the maximum substrate temperature was primarily dependant on the fuel amount. Although the exhaust flow rate had very little effect on the substrate’s maximum temperature, it was significant in determining how quickly the maximum temperature was reached.
Failure Analysis of a Double Rectangular Deep Drawn Part Using FEM: An Industrial Case
Authors: Garci´a Zugasti Pedro de Jesu´s , Medelli´n Castillo Hugo Iva´n , Cerino Zapata Abel , de Lange Dirk Frederik , Ca´rdenas Galindo Antonio
Published: May 2012

Complex shape deep drawn parts are more frequently used in many industrial applications. However, complex parts can be particularly difficult to form due to serious wrinkling and tearing problems associated to the different forming modes and complex material flow. Moreover, deep drawing depends highly on the part design, including radii, draw depths, wall angles, steps and transitions; these variables interact to affect the cost and quality of the drawing. Since there are not theoretical methods available in the literature yet, and because several factors affect the drawn, deep drawing of complex shapes is usually developed using the trial and error method. To increase the speed of the design process and the machine tuning, and to reduce the use of the trial and error method, computer-assisted analysis and simulations based on numerical approaches such as Finite Element Method (FEM), are more intensively used. By using these computerized methods, process parameters (sheet metal material, lubricants, forces, part geometry etc.) can be reproduced and modified, part defects can be also identified and, if possible, eliminated. This paper presents the analysis of an industrial double rectangular deep drawing kitchen sink using virtual prototyping based on FEM. In the original deep drawing process the part presented defects (cracks). A failure criterion was established to evaluate and reduce the stresses levels that were causing the cracks. An analysis procedure was then proposed and the optimal lubrication conditions were obtained to eliminate the cracks. FEM model, simulations and results, were validated by measuring the thickness of the actual fabricated part. The thickness of the sheet metal at the critical area was measured in the FEM simulation and compared with the thickness profile of the actual fabricated part before and after changes in the lubrication conditions. The results have shown that FEM can be effectively used as a design tool to eliminate part defects in complex shape deep drawing processes.
Viscoelastic Properties of Macaque Neural Tissue at Low Strain Rates
Authors: Bentil Sarah A. , MacLean Sean , Dupaix Rebecca B.
Published: May 2012

Increased knowledge of the mechanical properties of soft tissue subjected to low strain rates is beneficial to biomedical applications, such as designing bio-compatible implants, developing minimally invasive surgical techniques and surgical simulation devices for training surgeons. Unconfined compression and indentation experiments were conducted to extract macro- and micro-level mechanical properties of Macaque neural tissue. The tissues were placed in physiological saline solution and tested at room temperature within one hour post-sacrifice and three weeks post sacrifice using unconfined compression and indentation experiments. For each test, the temporal lobe was sectioned into 26 mm diameter disks that were subjected to 1%, 2%, 5%, and 10% strain at a loading rate of 5 mm per minute. The impermeable platen used in the unconfined compression test had a diameter equivalent to the tissue sample. The diameter of the flat tip used in the indentation experiment was 5 mm. Both test configurations utilized a ramp-and-hold strain input to capture the features of the tissue attributed to the stress-strain relationship (ramp) and stress-relaxation (hold). Viscoelastic theory was applied to the experimental data for the calculation of the secant and relaxation modulus, which correspond to the ramp and hold portion of the strain input, respectively. The resulting viscoelastic behavior of the Macaque brain at the macro- and micro-scale were compared with (i) bovine and porcine neural tissue, commonly found in the literature and (ii) viscoelastic models for neural tissue, which in the literature are generally applicable only to large deformations.
Mechanical Modeling and Design for Reduction of Parkinsonian Hand Tremor
Authors: Doughty Timothy A. , Bankus Nicholas
Published: May 2012

Most of the active research in reducing Parkinsonian tremor involves invasive surgeries or medical treatment. In this paper hand tremors associated with Parkinson’s Disease (PD) are studied and passive vibration control methods are developed and tested. Patients with PD are surveyed regarding difficulties with hand tremor during the act of eating. The result leads to design criteria for an enhanced eating utensil and the establishment of meaningful testing methods for measuring hand tremor. Tremor data collected from several PD patients provides insight into the nature of the motion and allows for the development of test fixture and prototypes. This experimental data is coupled with linear model identification testing for the free response of a “healthy” hand undergoing the same motions. The resulting differential equation model, where the system input is realized as actuation through the biomechanics of the forearm and wrist, is used in the design of an eating utensil for vibration reduction. With self-excitation and the existence of harmonics, the tremor data is also used to develop a nonlinear differential equation model, where the complete neurological/mechanical system is realized with an equivalent mechanical system. This nonlinear model is shown to mimic the tremor data and is used to enhance the development of the vibration absorber. A prototype of the vibration absorber is built, validated on the test fixture, and tremor reduction data is collected again with PD patients.
Aerosol Synthesis of Nano and Micro-Scale Zero Valent Nickel Particles From Oxide Precursors
Authors: Soliman Haytham , Phillips Jonathan , Luhrs Claudia , Zea Hugo , Leseman Zayd C.
Published: May 2012

In this work a novel aerosol method, derived from the batch Reduction/Expansion Synthesis (RES) method, for production of nano / micro-scale metal particles from oxides and hydroxides is presented. In the Aersosol-RES (A-RES) method, an aerosol, consisting of a physical mixture of urea and metal oxide or hydroxides, is passed through a heated oven (1000 °C) with a residence time of the order of 1 second, producing pure (zero valent) metal particles. It appears that the process is flexible regarding metal or alloy identity, allows control of particle size and can be readily scaled to very large throughput. Current work is focused on creating nanoparticles of metal and metal alloy using this method. Although this is primarily a report on observations, some key elements of the chemistry are clear. In particular, the reducing species produced by urea decomposition are the primary agents responsible for reduction of oxides and hydroxides to metal. It is also likely that the rapid expansion that takes place when solid/liquid urea decomposes to form gas species influences the final morphology of the particles.
An Experimental Study of Operational Parameters on the Performance of PEMFCs
Authors: Barakat Emad G. , Abdel-Rahman Ali K. , Ahmed Mahmoud A. , Ali Ahmed Hamza H.
Published: May 2012

The performance of Proton exchange membrane fuel cell (PEMFC) has been experimentally investigated. An experimental set-up was designed to study the effects of operating parameters such as cell temperature, gas humidification, and cell operating pressure on the performance of fuel cell. The results indicated that the output power increase with the increase of humidification ratio. Furthermore, an increase of cell pressure results in a significant increase of cell power. The results indicated that increasing of the temperature leads to a decrease of cell power. The results are explained and discussed in more details for different operational parameters.
Identifying Crack Parameters in Slow Rotating Machinery Using Vibration Measurements and Hybrid Neuro-Particle Swarm Technique
Authors: Senousy Mohamed S. , Khattab Tamer M. , Al-Qaradawi Mohamed , Gadala Mohamed S.
Published: May 2012

Low-cycle fatigue-initiated cracks may result in failure in slow-rotating equipments. Online monitoring to identify such fault/crack parameters, namely crack size and crack location, would be critical in providing an early warning signal to the operator and would be used in calculating estimate about the remaining safe life of the equipment in operation. In an earlier study, a scaled-down slow-rotating washer drum was constructed to experimentally investigate the vibrations of a cracked rotor and/or drums. Cracks were simulated using the bolt removal method (BRM), and the vibration signals identifying signatures of certain cracks were measured. Thereafter, a 3D finite element model was used to solve the forward analysis of the inverse problem of crack identification. In this paper, the scaled-down experimental setup is introduced to cracks at different locations of the drum/rotor. Vibration signals identifying signatures of such cracks are measured. Since noisy signals, similar patterns of faults, and similar vibration fault signals create particular challenges for feature extraction systems, two techniques for feature extraction are considered and compared in this work. The fast Fourier transform (FFT) of the vibration signals showing variation in amplitude of the harmonics as time progresses are presented for comparison with the full time signal feature extraction. A hybrid particle-swarm artificial Neural Networks (neuro-particle swarm) is used to identify both the crack size and crack location. The hybrid neuro-particle swarm technique is compared with the previously investigated fuzzy genetic algorithms.
Micro-PIV Measurements Near a Moving Contact Line
Authors: Zimmerman Jeremiah D. , Weislogel Mark M. , Tretheway Derek C.
Published: May 2012

The moving contact line is the line of intersection between two immiscible fluids as one displaces the other along a solid boundary (i.e. dynamic wetting). The displacement process has been the subject of a large amount of theoretical, numerical, and experimental research throughout the twentieth century [1], yet the fundamental mechanisms that govern contact line motion are not fully described. Theoretical study has dominated the published work on the moving contact line problem. This is due to the inability of previous experimental methods to elucidate flow behavior at small enough scales to differentiate between competing theories.
Orthogonal Frequency Ultrasound Vibrometry
Authors: Zheng Yi , Yao Aiping , Chen Shigao , Urban Matthew W. , Kinnick Randy , Greenleaf James F.
Published: May 2012

New vibration pulses are proposed to increase the power of shear waves induced by ultrasound radiation force in a tissue region with a preferred spectral distribution. The new pulses are sparsely sampled from an orthogonal frequency wave composed of several sinusoidal signals. Those sinusoidal signals have different frequencies and are orthogonal to each other. The phase and amplitude of each sinusoidal signal are adjusted to control the shape of the orthogonal frequency wave. Amplitude of the sinusoidal signal is increased as its frequency increases to compensate for higher loss at higher frequency in the tissue region. The new vibration pulses and detection pulses can be interleaved for array transducer applications. The experimental results show that the new vibration pulses significantly increases induced tissue vibration with the same peak ultrasound intensity, compared with the binary vibration pulses.
Computational Fluid Dynamics Simulations of an Inertance Type Pulse Tube Refrigerator
Authors: Antao Dion Savio , Farouk Bakhtier
Published: May 2012

A numerical study is reported here for the investigation of the fundamental flow and heat transfer processes found in an inertance type pulse tube refrigerator (IPTR). The general design of an IPTR incorporates a pressure wave generator, a transfer line, an aftercooler, a regenerator, a pulse tube, a pair of heat exchangers for the cold and hot ends of the pulse tube, an inertance tube and a reservoir. The performance of the IPTR system is simulated using computational fluid dynamics (CFD) using cylindrical co-ordinates (r–z) and applying the axisymmetric assumption. The IPTR is driven by a cyclically moving piston at one end of the system operating at a fixed frequency with helium as the working fluid. Both constant temperature and convective heat transfer boundary conditions are examined along the external walls of the hot heat exchangers. The simulations reveal interesting steady-periodic flow patterns that develop in the pulse tube due to the fluctuations caused by the piston and the presence of the inertance tube. The secondary-flow recirculation patterns in the pulse tube reduce the heat pumping effect from the low-temperature heat exchanger to the high-temperature heat exchangers.
Coupled Transverse and Axial Vibrations of Cracked Cantilever Beams With Roving Mass and Rotary Inertia
Authors: Hu Hurang , Ojetola Akindeji , Hamidzadeh Hamid
Published: May 2012

The vibration behavior of a cracked cantilever beam with a stationary roving mass and rotary inertia is investigated. The beam is modeled as an Euler-Bernoulli beam with rectangular cross section. The transverse deformation and axial deformation of the cracked beam are coupled through a stiffness matrix which is determined based on fracture mechanics principles. The analytical solutions are obtained for the natural frequencies and mode shapes of a cracked cantilever beam with a roving mass and rotary inertia. The effects of the location and depth of the crack, the location and the weight of the roving mass and rotary inertia on the natural frequencies and mode shapes of the beam are investigated. The numerical results show that the coupling between the transverse and axial vibrations for moderate values of crack depth and/or roving mass and rotary inertia is weak. Increasing the crack depth and the mass and rotary inertia will increase the coupling effect. Detection of the crack location using natural frequencies and mode shapes as parameters is also discussed.
A Simple Method for Adhesive Bonding of Capacitive Pressure Sensors
Authors: Mohammadi Abdolreza R. , Chiao Mu
Published: May 2012

We have developed a simple, low cost technique using new materials to bond capacitance pressure sensors. The old methods have difficult processes when a metal trace on the bonding area perturbs the sealing. The new method uses a polymeric gap-controlling block between glass and silicon wafers and a heat curing adhesive which penetrates between them due to capillary force. We used two different materials including SU-8™ and UV (ultraviolet) curing adhesive in order to control the gap. The technique allows us to generate a small gap between the chips due to low viscosity of the heat curing adhesive, align and bond chips immediately, make a strong bond, and easily seal the sensor. Also, the high temperature, strong heat curing adhesive makes the sensor suitable for high temperature and high pressure applications. The sensors were tested up to 2 MPa and 170°C in a nitrogen chamber. The maximum thermal error of ±1.74% and ±1% full scale output (FSO) were measured for SU-8 and UV sensors, respectively.
An Assignment of Methods to Analyze Uncertainty in Different Stages of the Development Process
Authors: Eifler Tobias , Engelhardt Roland , Mathias Johannes , Kloberdanz Hermann , Birkhofer Herbert
Published: May 2012

During its life cycle, each engineering product goes through different stages of planning, production and usage. Uncertainties occur in all of these phases. As defined, uncertainties in technical systems are present as far as product and process properties are not determined and deviations of these properties arise. They result either from imperfect information about output values of production processes (regarding product properties) or in terms of diverging uses of the products. Especially within the product development process, the occurring uncertainties have to be taken into account. During the early design stages, decisions that have a variously strong impact on the future product are made. Moreover, the knowledge about a future product is still low so that neither the expected processes nor the product’s properties are known. For this reason, well-known methods of probabilistic uncertainty analysis are not sufficient. They cannot be applied until the product is completely defined. A comprehensive uncertainly analysis in the product development process can be executed in an integrated process model with the Uncertainly Mode and Effects Analysis Methodology (UMEA) [1]. The underlying model of uncertainly is the basis for a comprehensive and consistent classification of uncertainly, a distinction comparable to concepts such as reliability, availability, error or risk. The model to analyze uncertainty has been exercised using the example of the product development process according to Pahl/Beitz [2]. It enables the assignment of suitable methods for the classification of uncertainty at different stages in the design process and thus different levels of abstraction. Based on this model, the quantitative methods of the probability theory are complemented by qualitative concepts such as risk analysis methods, for example, FailureMode and Effects Analysis (FMEA), Event Tree Analysis (ETA), or Hazard and Operability (HAZOP). The assignment of methods offers the possibility to analyze the classified uncertainties in the different phases of the product development process.
Electrowetting on Dielectric Based Droplet Transport Inside a Closed-Channel
Authors: Ahamed Mohammed Jalal , Ben-Mrad Ridha , Sullivan Pierre
Published: May 2012

The paper reports Electrowetting on Dielectric (EWOD) actuated droplet transport characteristics inside a closed-channel. Traditional EWOD devices are open-plane wall-less devices within which droplets are either sitting on a substrate or sandwiched between top and bottom substrates. We investigated droplet motion by EWOD actuation inside a sealed closed-channel. Closed-channel EWOD actuation is useful for interfacing open-plane EWOD (digital) designs to closed continuous (analog) microfluidic devices. Some transport characteristics of the closed-channel EWOD actuation were investigated. Actuation voltage was varied between 85–120 VRMS. Channel height was varied between 90–150 μm. The electrodes were square shaped and 2 mm across. Within these range of design parameters the droplet velocity profile showed no steady state constant velocity. And it accelerated to the peak value near the midpoint of the energized electrode then decelerated for the rest of the travel.
Application of New SEUMRE Global Optimization Tool in High Efficiency EV/PHEV/EREV Electric Mode Operations
Authors: Younis Adel , Zhou Leon , Dong Zuomin
Published: May 2012

Electric Vehicles (EV), Hybrid Electric Vehicles (HEV), Plug-in Hybrid Electric Vehicles (PHEV) and Extend Range Electric Vehicles (EREV) draw mechanical power or regenerate electric power using multiple electric motors and generators (M/Gs). Conventionally, heuristics and experience based control rules are used to guide the determination of powertrain component operation parameters to obtain good efficiency. To achieve optimal vehicles electrical/mechanical energy conversion efficiency and to prolong the pure electric range of these vehicles, the energy conversion efficiency is to be maximized against powertrain component operation parameters using high fidelity model and simulation. However, the energy conversion efficiency model using vehicle powertrain component model and simulation is complex, multimodal, and computationally intensive. An efficient global optimization tool is needed to produce the optimal efficiency look-up surface for real-time control system implementation, or to search for the optimal operation parameters in real time. In this work, the electrical/mechanical energy conversion efficiency of EV and PHEV/EREV in EV mode is modeled using MATLAB Simulink based powertrain component models. In particular, a new 2 mode-plus EREV design is used as a design example. The optimal vehicle electrical/mechanical energy conversion efficiency under various powertrain component operation parameters are obtained using three alternative global optimization tools, Genetic algorithm (GA), Particle Swarm Optimization (PSO) and Space Exploration and Unimodal Region Elimination (SEUMRE). The conventional GA and PSO tools, with less efficient search efficiency and requiring long search time, are used for benchmark comparisons. The new SEUMRE global optimization tool is used obtain equally accurate results much efficiently. A rough look-up surface is created to demonstrate the difference in computational efficiency. Application of the SEUMRE global optimization tool allow refined and more accurate vehicle electrical/mechanical energy conversion efficiency map being created for the optimal operation of the EV/PHEV/EREV Optimal vehicle control schemes can then be generated in determining the speed and torque of the M/Gs of the vehicle without violating their physical constraints and achieving the overall maximum efficiency of the hybrid powertrain system. Results of the design optimization are presented and compared. New design guidelines are provided.
Natural Convection in a Vertical Enclosure With Grooves
Authors: Takatsu Yasuyuki , Masuoka Takashi , Nomura Takahiro
Published: May 2012

The natural convection in a vertical enclosure with grooves has been numerically studied. To identify the structure of the thermal boundary layer along the discontinuous vertical surface, the iso-flux condition is imposed to each heating (or cooling) portion of the discontinuous vertical surface, and the adiabatic condition is applied to the other solid walls including the grooves. We focus on the behavior of the thermal boundary layer along the discontinuous vertical surface, and clarify the dual structure of the thermal boundary layer. The whole thermal boundary layer develops along the discontinuous vertical surface, while the internal thermal boundary layer forms on each solid portion of the discontinuous flat surface. We can recognize from the isotherms near the solid portion that the internal thermal boundary layer develops from the leading edge to the trailing edge of the solid portion. The internal thermal boundary layer plays an important role in the heat transfer enhancement. As the thin thermal boundary layer forms at the leading and trailing edges, the heat transfer coefficient near the leading and trailing edges takes higher values.
A Curl-Based Approach to Ultrasound Elastography
Authors: Baghani Ali , Zahiri Azar Reza , Salcudean Septimiu , Rohling Robert
Published: May 2012

The past two decades have witnessed the development of a new medical imaging modality: tissue elastography. The contrast in the images produced by an elastography system is based on the tissue elasticity, hence these images are called elastograms. Tissue elasticity is of clinical interest, because it is often correlated with pathology [1]. Different approaches to tissue elastography have emerged [2, 3]. In this article we report a tissue elastography system and its implementation on an ultrasound machine which provides consistent elastograms of a commercial quality assurance elastography phantom. The system uses our previously developed high frame rate sequencing and phase compensation techniques to measure axial and lateral motions at a typical frame rate of 1.25 kHz [4]. The system uses the curl of the displacements in a direct inversion algorithm to reconstruct elasticity. The most important benefit of this method is that the obtained elastograms are not dependent on the boundary conditions or the shape, size or position of the exciter, and as a result, the elastograms have fewer artifacts originating from these factors. The curl of the displacement has been used in magnetic resonance elastography (MRE) before, together with the direct inversion of the wave equation [5] and promising results have been obtained.
Effect of Interleaved Electrospun Nanofiber on Flexural Properties of Fiber Glass Composites
Authors: Shendokar Sachin , Kelkar Ajit , Mohan Ram , Bolick Ronnie
Published: May 2012

Electrospinning is regarded as one of the most efficient processes to generate one-dimensional nano structures. The electrospinning process is simple and provides consistent mass production of nanofibers. The scalability of the electrospinning process has an excellent potential to fulfill the high volume requirements of nanofibers in the infrastructure applications. The present work emphasizes the use of interleaved electrospun nanofibers in fiber glass composite beams. The Flexural behavior of a simply supported beam under a centrally concentrated loading is studied. Flexural properties of a fiber glass composite beam with interleaved electrospun nanofibers are compared with a fiber glass composite beam without electrospun nanofibers. The material configuration of the composite beams is: woven E-glass fabric prepregs with a low temperature molding resin. In addition, interleaved between the plies are TEOS (Tetra Ethyl Orthosilicate) electrospun nanofibers. The nanofibers were produced by developing optimized operating process parameters and a stabilized sintering temperature cycle to ensure consistency in the fiber morphology and pore structure. The successful integration of the electrospun nanofibers within the prepreg layers was obtained by pre-impregnation with a B-staged resin film and de-bulking to remove excessive resin prior to vacuum bagging. A series of mechanical Flexure tests were performed per the ASTM D7264 standard specification. Micrographs were obtained to study the progressive deformation and damage mechanics due to flexural loading in the specimens and clearly illustrate the differences in the failure mechanism with and without the electrospun interface layers.
Measurement of Tendon Excursion Using an Audio-Based Fourier Technique With Pulsed-Wave Doppler Ultrasound
Authors: Stegman Kelly J. , Dechev Nikolai , Park Edward J. , Podhorodeski Ronald
Published: May 2012

This work presents a feasibility study in estimating the displacement of a moving tendon using Pulsed-Wave Doppler ultrasound. The displacement estimation is accomplished using a tendon mimicking experiment, by performing a Fourier analysis of audio-based output signals from a commercial ultrasound scanner. The feasibility study shows that our proposed technique is better able to measure the actual tendon displacement, in comparison to the scanner’s onboard software, for the purposes of determining near-surface tissue excursion (i.e. displacement). The proposed technique also demonstrates that data acquisition from the audio output signal of a portable ultrasound scanner is possible, and can be processed with custom software to achieve our purpose. The motivation for this work is to noninvasively and dynamically monitor the displacement of the major tendons in the human lower arm. Such tendon displacement monitoring can provide an important diagnostic tool for people with hand injuries.
Dynamic Mechanism of a Train Suspension System
Authors: Luo Albert C. J. , O’Connor Dennis
Published: May 2012

Nonlinear dynamical behaviors of a train suspension system with impacts are investigated. The suspension system is modelled through an impact model with possible stick between a bolster and two wedges. Based on the mapping structures, periodic motions of such a system are described. To understand the global dynamical behaviors of the train suspension system, system parameter maps are developed. Numerical simulations for periodic and chaotic motions are performed from the parameter maps.
On the Utilization of Web-Based Collaboration Tools by Student Design Teams
Authors: Koch Michael D. , Tumer Irem Y. , Schulte Richard J.
Published: May 2012

Over the last couple decades, the engineering world has seen a steady increase in collaboration and knowledge sharing through predominantly web-based means. Facilitated by a growing number of tools that allow for data and knowledge to be easily transferred, the technological landscape that organizations operate in is completely different than even a couple years ago. Specifically for engineering design, mainstream tools such as email, forums and wikis have been researched in both a professional sense as well as in design education. The following paper looks to build off these studies by identifying and studying the wide range of tools that engineering students utilize on their own accord to collaborate and progress towards finishing a design project. Specifically, mechanical and industrial engineering students enrolled in introductory design courses at Oregon State University and Humboldt State University were observed, interviewed and surveyed regarding these topics. The following will outline the findings from this study, with hopes that this work can help others in the design education field better understand and make better use of the tools that students prefer to use. Also, as the next generation of engineers moves onto professional careers, the ability of engineering firms to understand how the younger generation collaborates and communicates will be important in shaping how engineering firms efficiently utilize new web-based tools in engineering design.
Multi-Physics, Multi-Scale Modeling in Polymer Electrolyte Fuel Cells
Authors: Wang Yun , Cho Sung Chan , Mukherjee Partha P.
Published: May 2012

In recent years, the polymer electrolyte fuel cell (PEFC) has emerged as a promising clean energy conversion device for various applications. One key research direction requiring significant breakthrough in order to alleviate performance limitations in PEFCs involves enhanced understanding of the coupled multi-physics transport phenomena and interfacial processes catering over multiple length scales in the constituent porous components. Multi-physics, multi-scale modeling is envisioned to hold the key toward enhanced understanding of the underlying structure-transport-performance interactions. In this article, a brief overview of several major aspects pertaining to the multi-physicochemical modeling of electrochemical reaction kinetics, species transport, two-phase heat and water transport, and phase change in the PEFC is presented.
Toward Understanding Collaborative Design Center Trade Study Software Upgrade and Migration Risks
Authors: Van Bossuyt Douglas L. , Tumer Irem Y.
Published: May 2012

Collaborative design centers often employ software tools to conduct trade studies. Commonly, this takes the form of a software program to aggregate and pass data between multiple computer workstations. This allows multiple people to concurrently create a conceptual design. Trade study software continues to evolve to meet the demands of modern collaborative design centers. However, the risks associated with moving from one trade study software tool to another are not well understood. Additionally, little is known about the software preferences of Collaborative Design Center (CDC) staff. This paper determines software preferences of two user groups consisting of graduate and undergraduate mechanical engineering students. This paper then explores the risks in deploying new trade study software in a collaborative design center. A method for estimating and mitigating risks with changing trade study software is presented. Recommendations for a smooth transition between software packages are given. The risk model developed in this paper offers a quick way of estimating and mitigating conversion risk for collaborative design centers.
Prediction of Turbulent Flow-Induced Noise in Aircraft Cabins
Authors: da Rocha Joana , Suleman Afzal , Lau Fernando
Published: May 2012

Flow-induced noise in aircraft cabins can be predicted through analytical models or numerical methods. However, the analytical methods existent nowadays were obtained for simple structures and cabins, in which, usually, a single panel is excited by the turbulent flow, and coupled with an acoustic enclosure. This paper discusses the development of analytical models for the prediction of aircraft cabin noise induced by the external turbulent boundary layer (TBL). The coupled structural-acoustic analytical model is developed using the contribution of both structural and acoustic natural modes. While, in previous works, only the contribution of an individual panel to the cabin interior noise was considered, here, the simultaneous contribution of multiple flow-excited panels is also analyzed. The analytical models were developed for rectangular and cylindrical cabins. The mathematical models were successfully validated through the good agreement with several independent experimental studies. Analytical predictions are presented for the interior sound pressure level (SPL) at different locations inside the cabins. It is shown that identical panels located at different positions have dissimilar contributions to the cabin interior noise, showing that the position of the vibrating panel is an important variable for the accurate prediction of cabin interior noise. Additionally, the results show that the number of vibrating panels significantly affects the interior noise levels. It is shown that the average SPL, over the cabin volume, increases with the number of vibrating panels. The space-averaged SPL is usually accepted to provide the necessary information for the noise prediction. However, in some real life applications, the local sound pressure may be desirable. To overcome this point, the model is also able to predict local SPL values, at specific locations in the cabin, which are also affected by number of vibrating panels, and often differ from the average SPL values. The developed analytical model can be used to study a wide range of different systems involving a cabin coupled with vibrating panels, excited by the TBL. The properties of the external flow, acoustic cabin, and panels, as well as the number of vibrating panels, can be easily changed to represent different systems. These abilities of the model make it a solid basis for future investigations involving the implementation of noise reduction techniques and multidisciplinary design optimization analyzes.
Vapor Trapping Membrane for Reverse Osmosis
Authors: Lee Jongho , O’Hern Sean , Karnik Rohit , Laoui Tahar
Published: May 2012

This paper presents a concept for desalination by reverse osmosis (RO) using a vapor-trapping membrane. The membrane is composed of hydrophobic nanopores and separates the feed salt water and the fresh water (permeate) side. The feed water is vaporized by applied pressure and the water vapor condenses on the permeate side accompanied by recovery of latent heat. A probabilistic model was developed for transport of water vapor inside the nanopores, which predicted 3–5 times larger mass flux than conventional RO membranes at temperatures in the range of 30–50°C. An experimental method to realize short and hydrophobic nanopores is presented. Gold was deposited at the entrance of alumina pores followed by modification using an alkanethiol self-assembled monolayer. The membranes were tested for defective or leaking pores using a calcium ion indicator (Fluo-4). This method revealed the existence of defect-free areas in the 100–200 μm size range that are sufficient for flux measurement. Finally, a microfluidic flow cell was created for characterizing the transport properties of the fabricated membranes.
Verifying the Usability of Failure-Based Computational Design Methods
Authors: Oman Sarah , Koch Michael , Tumer Irem Y. , Bohm Matt
Published: May 2012

In the early stages of the design process, there is a need to provide designers with tools to assess risks and possible failures so as to avoid costly redesigns, comply with established safety measures and to promote innovation throughout the design process. Recently, various methods have been proposed in research to accomplish such tasks, including the Risk in Early Design (RED) and the Function Failure Design Method (FFDM). This paper proposes a method for examining the utility of such failure-based computational design methods. Validation is accomplished by analyzing products with a known history of failure, decomposing these products into functional representations and performing both RED and FFDM analyses on these models to see how closely such methods are able to correctly identify the real-world failures. The goal of this work is to determine the effectiveness of both the RED and FFDM methods in order to suggest improvements for both methods. The results provide insight on the verification methodology in addition providing to prescriptive methods to increase the usefulness of early stage failure and risk assessment techniques.
Flow Characteristics in Helical Pipes of Various Coil Geometries With Rectangular Cross Section
Authors: Katinas Christopher , Fakheri Ahmad
Published: May 2012

Although curved pipes are commonly used in industrial operations, such as chemical reactors and heat exchangers, few investigations have been performed to develop an understanding of how tightly wound coils impact the heat transfer rate and friction factor in the laminar flow regime. Small coil radius geometries exhibit interesting characteristics that impact both Nusselt number and friction factor. Numerical solutions are presented for rectangular ducts of various coil diameters and aspect ratios which are compared with available experimental and analytical solutions to determine their applicabilty to tightly wound coils. A new non-dimensional parameter called the modified friction factor is presented and correlated to the results presented in this study. Additionally, a correlation for Nusselt number is presented for a variety of coil diameter ratios for curved square channels.