bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamics of Single-Hit Pneumatic Test Drill for Pulse-Shaping Analysis of Impacting Waves
Authors: Montonen Jori , Keskinen Erno , Cotsaftis Michel , Miettinen Juha , Seeman Wolfgang
Published: April 2014

Rock drilling is one of the elementary processes in mining industry. As larger diameter holes are drilled by hitting with units attached to the crone adapter down in the hole, the smaller blast holes are hit with units impacting the rod neck at rock surface. Key question in the performance and energy efficiency of the blast-hole drilling process is then, how completely the impact energy can be transmitted to the crone over the relatively long wave guide. There have been discussions about the effect of wave length and shape on to the penetration dynamics of rock drills. As the drilling process is a continuous set of hits following each other at relatively high constant period and the response is a random overlapped mixture of coming waves and returning reflected waves from multiple delayed hits, a detailed analysis of penetration dynamics is rather a complex problem. To overcome this difficulty, a full-scale half-manual test-drill has been designed and built to produce single hits for a systematic production and analysis of optimally shaped stress waves. The test-drill is an air-powered pneumatic gun, whose impact energy can be adjusted by setting the initial pressure level to correspond the desired end velocity of the piston. The design parameters, by which the pulse shape can be modified, are the length and the geometric profile of the piston body. The first problem to be faced is then to determine the optimal pulse shape for maximized penetration depth and the second one is to produce such desired shape by an optimal choice of the design parameters. The rig has been modelled using finite elements for the rod system and adiabatic state equations for the compressed and expanding air volumes. By modifying the design parameters, different penetration responses can be produced. In the first step, the model has been updated by means of experimental response measurements. The second step has been to modify the geometrical profiles of the piston body by starting from piece-vice linear and parabolic cross-sectional distributions. The output of the numerical analysis is to evaluate the penetration depth pro hit for different geometrical profiles. The most promising geometry has then been selected for the fabrication of the prototype piston. An experimental hitting test then completes the analysis, whose repeatability showed to be limited due to the random variation of the rock properties in the test bed. Test results obtained by using more regular concrete specimens exhibited reduced deviations in the responses, but the weakness in the test is the different damaging mechanism during the penetration. Another option is the use of an artificial load-sensing endsupport in order to produce a known boundary condition to replace the tool-rock resistance in the model-updating phase.
Size-Dependent Antibacterial Behavior of Graphene Quantum Dots
Authors: Su Siheng , Shelton Carla B. , Qiu Jingjing
Published: April 2014

In this study, the antibacterial behavior of differing sized graphene quantum dots (GQDs) was studied. The gram negative bacteria, Escherichia coli (E. coli), were used as the bacteria mode. Different sized GQDs with tunable fluorescent colors were acquired by a gel-filtration method. The size, surface chemistry, and photoluminescence properties of GQDs were characterized, respectively. The viability of GQDs treated bacteria was determined by the standard plate counting method. Moreover, the reactive oxidative species (ROS) level was detected by the 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) method. The integrality of the bacteria membrane was observed under the scanning electron microscopy (SEM). The experimental results indicated that GQDs demonstrated size-dependent and surface chemistry-dependent antibacterial behaviors. This research provided insightful guidelines in the selection of suitable GQDs for their potential bioapplications.
Flash Boiling and Desorption From a Macroporous Carbon-Boron-Nitrogen Foam
Authors: Engerer Jeffrey D. , Jackson Galen R. , Paul Rajib , Fisher Timothy S.
Published: April 2014

This paper presents a tunable cooling technology befitting fast transient thermal events. In this approach, the rapid depressurization of the working fluid triggers coincident flash-boiling and desorption events, thereby achieving very high cooling rates for short periods of time. Carbon-boron-nitrogen foam, derived through the chemical modification of a highly graphitized carbon precursor, is utilized because of its excellent thermal conductivity, adsorptive properties and open macroporous structure. Preliminary results indicate a bulk fluid temperature change of 45 °C in less than one second, with a corresponding 26 °C temperature drop of the baseplate during a controlled ten-second flash boiling process with no external heating.
Expanding Helmet Design Methodologies Through Brain Functional Area Representative Threat Models
Authors: Ford Matthew , Matic Peter , Leung Alan
Published: April 2014

In combat zones, warfighters may be exposed to multiple threat types that can result in impacts to the head. These head impacts can lead to traumatic brain injury (TBI) or other functional or cognitive impairments, depending on the impact location, duration, and severity. Personal protective equipment mitigates the damage to the head, and current equipment design efforts focus on high-level protective metrics such as local helmet deformations and penetrations, as well as global accelerations or rotations of the head. Advances in brain imaging and mapping have made it possible to couple brain regions with specific functions, which could lead to higher resolution injury models and a more integrated helmet design process.

The Naval Research Laboratory has developed a design tool to relate cognitive and functional brain regions from the literature to representative threat models for a head-helmet system. In this study, the philosophy and methods behind this augmented design tool and some of its applications are discussed. Through surveying detailed brain mappings and Brodmann functional areas, spatial coordinates for a coarse and a fine brain model were identified, scaled, and positioned within a three-dimensional model of the head. Projectile threats to the brain from all directions were simulated to evaluate the vulnerability of specific brain regions for a given protective helmet geometry. Using this platform, a variety of design tools were developed to investigate the functional effects of making geometric changes to the helmet.
Design and Path Planning for a Spherical Rolling Robot
Authors: Lee Jaeyeon , Park Wooram
Published: April 2014

Several designs for a spherical rolling robot have been suggested and some of them were implemented. The kinematics and dynamics study as well as the path planning for the rolling robot are based on the assumption that the deterministic model describes the actual rolling robot successfully. However, due to the high mobility of the sphere, the stochastic behavior is obviously observed. In this paper, we first build a rolling robot to confirm the stochasticity. The robot is actuated by a mass-shifting mechanism where an unbalanced weight inside the spherical robot is rotated by two motors, and the imbalance induced by the weight makes the robot roll. After confirming that this actual rolling robot shows the stochastic behavior, we propose a path planning method for the spherical robot rolling on the plane. The path-of-probability method is applied to generate the most probable path from starting location to destination. This planning method uses the stochasticity of the system to produce the probability density function, and generates the piece-wise short steps for the robot move, which construct the whole trajectory that the robot should follow.
Characterizing Suitability of Wearable Sensors for Movement Analysis Using a Programmed Robotic Motion
Authors: Martori Amanda L. , Carey Stephanie L. , Alqasemi Redwan , Ashley Daniel , Dubey Rajiv V.
Published: April 2014

Wearable sensor systems have the potential to offer advancements in the study of motion disorders, particularly outside of a laboratory setting during activities of daily living or on a football field. Advantages like portability and the capability to gather real-world data have resulted in the rapid adoption of these sensors in various studies for gait analysis, balance control evaluation, physical activity recognition and fall prevention. However, before using wearable sensors in long-term acquisition studies, it is necessary to quantify and analyze errors and determine their sources. In this study, the accuracy of joint angles and velocities measured with the wearable inertial measurement unit (IMU) sensors were compared to both measurements from an optical motion-tracking system and from encoders on a robotic arm while it completed various predetermined paths. The robotic arm uses incremental encoders at each joint to measure and calculate its Cartesian motion relative to a reference frame using inverse kinematics. Motion profiles of the robotic arm were tracked using the onboard encoders, an eight-camera Vicon (Oxford, UK) motion-tracking system with passive retro-reflective markers, and four wearable IMUs by APDM (Portland, OR). In order to better isolate various types of contributing errors, linear, planar, and 3-dimensional robot motions were used. Data were collected from the sensors over several hours, which provided insight into time-based effects as well as management of large amounts of data for future long-term tracking applications. In addition, the authors have previously seen acquisition errors with high-speed gaits, thus robotic arm trajectories of varying velocities were used to provide further insight into these rate-based effects. Angular velocity and joint angles were compared for all three systems and used to investigate the hysteresis, drift and time-based effects on the IMUs as well as their accuracy during motion tracking. Effects on IMU performance due to the application of filtering algorithms were not investigated. The results show that the IMUs were able to calculate the joint angles within a clinically acceptable range of the gold standard optical motion-tracking system. The IMUs also provided accurate trajectory recognition and angular velocity measurements relative to the known motion input of the robotic arm. Future work will include the development of algorithms to detect gait abnormalities such as those seen in patients with mild traumatic brain injury (mTBI). To complement human subject testing with gait pathology, controlled introduction of gait deviations into this robotic testing framework will allow for well-characterized unit testing, providing more robust algorithm development.
Computational Comparison of Shock Wave Propagation in Explosive Blast and Shock Tube Experiments
Authors: Laksari Kaveh , Assari Soroush , Darvish Kurosh
Published: April 2014

In this study, detonation of TNT was simulated using an FE code and the resulting mechanical behavior of air, in which the explosion took place, was studied as a function of distance. Incident and reflected pressure and impulse profiles were compared with published data. In addition, an FE model of a shock tube setup at Temple University was developed using equations of state for Helium and air as the driver and driven fluids. The characteristics of the shock wave developed from explosive blast and shock tube were compared. It was shown that merely the two variables commonly used in the literature to compare the results from a shock tube to that of blast, i.e., peak incident pressure and positive duration, could not thoroughly include all the characteristics of the shock wave. Other parameters such as reflected pressure and impulse, which includes the velocity of the particles in addition to the pressure, are also needed to describe the shock wave.
Exergy Efficiency Optimization for Gas Turbine Based Cogeneration Systems
Authors: Ferreira Ana C. , Teixeira Senhorinha F. , Teixeira José C. , Nunes Manuel L. , Martins Luís B.
Published: April 2014

Energy degradation can be calculated by the quantification of entropy and loss of work and is a common approach in power plant performance analysis. Information about the location, amount and sources of system deficiencies are determined by the exergy analysis, which quantifies the exergy destruction. Micro-gas turbines are prime movers that are ideally suited for cogeneration applications due to their flexibility in providing stable and reliable power. This paper presents an exergy analysis by means of a numerical simulation of a regenerative micro-gas turbine for cogeneration applications. The main objective is to study the best configuration of each system component, considering the minimization of the system irreversibilities. Each component of the system was evaluated considering the quantitative exergy balance. Subsequently the optimization procedure was applied to the mathematical model that describes the full system.

The rate of irreversibility, efficiency and flaws are highlighted for each system component and for the whole system. The effect of turbine inlet temperature change on plant exergy destruction was also evaluated. The results disclose that considerable exergy destruction occurs in the combustion chamber. Also, it was revealed that the exergy efficiency is expressively dependent on the changes of the turbine inlet temperature and increases with the latter.
The Role of Water in the Hygro-Thermo-Mechanical Behavior of Wood
Authors: Derome Dominique , Patera Alessandra , Rafsanjani Ahmad , Abbasion Saeed , Carmeliet Jan
Published: April 2014

Wood, due to its biological origin, has the capacity to interact with water. Sorption/desorption of moisture is accompanied with swelling/shrinkage and softening/hardening of its stiffness. The correct prediction of the behavior of wood components undergoing environmental loading or industrial process requires that the hygric, thermal and mechanical (HTM) behavior of wood are considered in a coupled manner. In addition, we propose a comprehensive framework using a fully coupled poromechanical approach, where its multiscale implementation provides the capacity to take into account, directly, the exact geometry of wood cellular structure, using computational homogenization. A hierarchical model is used to take into account the subcellular composite-like organization of the material. Such advanced modeling requires high resolution experimental data for the appropriate determination of inputs and for its validation.
Measurement of Electrical Impedance and Eddy Currents in Tissue Phantoms
Authors: Sequin Emily , Bellman Karen , Koch Scott , West Joseph , Prakash Shaurya , Subramaniam Vish
Published: April 2014

Measurement of the electromagnetic (EM) properties of tissue such as electrical conductivity, permittivity, and eddy current characteristics can be used in clinical medicine for characterizing and distinguishing soft tissue morphology. Such measurements can yield complementary information to what can be obtained using analysis with an optical microscope. An example is the assessment of margins during the surgical resection of occult tumors. In current practice, the surgeon relies on pre-operative imaging modalities, sight and palpation to locate and attempt to fully resect the tumor(s). Frozen section pathological assessment offers the only other resource available to the surgeon for margin analysis, but it is incomplete because only a small fraction of the resected tissue is examined and it is often not feasible to wait for the results of the frozen section analysis before completing the surgery. This paper describes a characterization and imaging method based on variations in electromagnetic tissue properties to assess the surgical margins of resected tissues. This is noteworthy because accurate margin assessment has been shown to significantly improve long term patient outcomes[1].
AC Electrothermal Pumping Improvement by Biocompatible Nanocomposite Surface Modification
Authors: Islam Nazmul , Askari Davood
Published: April 2014

The AC electrothermal effect can improve the pumping rate by multiple folds compared to other eletrokinetic techniques in micro/nano scale. In this research, the AC electrothermal micropump velocity will be optimized by surface modification using a biocompatible hydrophobic nanocomposite monolayer. This coating will modify the micropump surface to a hydrophobic surface and reduce the friction losses at the liquid-solid interface, and eventually increase the micropumping velocity. The advent of microfabrication and integrated miniature pumps has applications on biomedical devices such as implantable glucose sensors. These micropumps require the transport of small amounts of fluids (μL range). When utilized in biomedical applications, micropumps can be used to administer small amounts of medication (e.g. insulin) at regular time intervals. These micropumps can also be integrated with the lab-on-a-chip devices and can provide inexpensive disposable devices. To demonstrate the fluid manipulation in high conductive bio-fluids, we have developed an optimized AC electrothermal micropump using symmetrical electrode arrays.
An Analytical Study of Skull Deformation During Head Impacts
Authors: Mansoor-Baghaei Shahab , Sadegh Ali M.
Published: April 2014

Spherical shells have been employed to model impacts to human heads; however, an ellipsoidal shell is that is more realistic model of the head has not fully investigated. In this paper, impact of an elastic ellipsoidal shell with an elastic flat half space is analytically analyzed and a closed-form solution is derived which led to a complex differential equation. Due to the complexity of the impact equation it could not be solved by standard solutions. Therefore, the Newtonian method and a linearization scheme are employed to simplify this equation in order to obtain the response of the impact problem and the closed-form solution. The analytical solutions are validated by finite element method. Good agreement between the closed form solution and the FE results is observed. To show the difference, the ellipsoidal solutions are also compared to the spherical solutions. To the best of our knowledge, this method and its closed-form solution have not been addressed in the literature. It is concluded that the closed-form solution is trustworthy and can be used to investigate the impact of the skull (as an elastic ellipsoidal shell) with a rigid or elastic plate, including the skull deformation and parametric studies. This solution could be expanded to include the brain materials inside the ellipsoidal shell.
Modeling Hazard and Threat Risks to Populations Surrounding Public-Use, Non-Towered Airports due to General Aviation Operations
Authors: Salmon Christian , Motevalli Vahid
Published: April 2014

This paper considers the potential future wherein the General Aviation (GA) infrastructure of airports and aircraft becomes an integral part of the commercial aviation transportation network. Further, this paper discusses inherent individual and societal risks sourced in the very characteristic that makes the GA infrastructure attractive: accessibility and ubiquity.

Air traffic controller furloughs, mergers, surface transportation congestion and infrastructure degradation are a few examples of system discontinuities that have led to increased travel time for short and medium air travel (200–500 miles). These, amongst other constraints, are drivers of various initiatives that seek to mitigate these delays via transfer of travel demand from larger towered airport infrastructure to the General Aviation infrastructure via development of aircraft, business plans, operation oversight processes. An example being the nascent air taxi industry coupled with the development of the Very Light Jet designed to operate on 3,000 ft runways.

The development of High Volume Operations (HVO) capability in the GA infrastructure (specifically non-towered airports) will subsequently increase risks to communities situated in the vicinity of GA airports via increased potential for accidents. Modeling and understanding these inherent risks in is important if public safety and negative reaction to operational changes, particularly at community airports, is to be avoided; a negative public opinion that could forestall the development of HVO.

Similarly, the potential for security threats (i.e. use of aircraft as a missile) from unsecured community airports are greater, but qualitatively less severe than TSA regulated commercial airports.

With the potential of 4,000+ additional airports being added to the national commercial air transportation infrastructure, a risk-based allocation of security resources would need to be implemented for efficient allocation of scarce resources.
Thermal Predictions of the AGR-3/4 Experiment
Authors: Hawkes Grant L. , Sterbentz James W. , Maki John T.
Published: April 2014

A thermal analysis was performed for the Advanced Gas Reactor test experiment number three/four (AGR-3/4) irradiated at the Advanced Test Reactor (ATR) at the Idaho National Laboratory (INL). Several fuel irradiation experiments are planned for the AGR Fuel Development and Qualification Program which supports the development of the Very-High-Temperature gas-cooled Reactor (VHTR) under the Next-Generation Nuclear Plant (NGNP) project.

AGR-3/4 combines two tests in a series of planned AGR experiments to test tristructural-isotropic (TRISO)-coated, low-enriched uranium oxycarbide fuel. The AGR-3/4 test was designed primarily to assess fission product transport through various graphite materials. The AGR-3/4 test was inserted in the ATR beginning in 2011 and is currently still in the reactor. Forty-eight (48) TRISO fueled compacts were inserted into twelve separate capsules for the experiment.

The purpose of this analysis was to calculate the temperatures of each compact and graphite layer to obtain daily average temperatures and to compare with experimentally measured thermocouple data. Heat rates were input from a detailed physics analysis using the MCNP code for each day during the experiment. Individual heat rates for each non-fuel component were input as well. A steady-state thermal analysis was performed for each daily calculation. A finite element model was created for this analysis using the commercial finite element heat transfer and stress analysis package ABAQUS. The fission and neutron gamma heat rates were calculated with the nuclear physics code MCNP. ATR outer shim control cylinders and neck shim rods along with driver fuel power and fuel depletion were incorporated into the daily physics heat rate calculations. Compact and graphite thermal conductivity were input as a function of temperature and neutron fluence with the field variable option in ABAQUS. Surface-to-surface radiation heat transfer along with conduction heat transfer through the gas mixture of helium-neon (used for temperature control) was used in these models. The kinetic theory of gases was used to correlate the thermal conductivity of the gas mixture. Model results are compared to thermocouple data taken during the experiment. Future thermal analysis models will consider control temperature gas gaps and fuel compact–graphite holder gas gaps varying from the original fabrication dimensions as a function of fast neutron fluence.
Study of Part-Site Interactions in Microscale Capillary Self Assembly
Authors: Carballo Jose M. , Crane Nathan B.
Published: April 2014

Most common microscale assembly strategies are serial based, such as robotic grasp-and-release systems. Regardless of their high cost and limited throughput, these systems are well developed and thus are easily commercialized [1]. Self-assembly (SA) is a parallel process that, when adapted to microscale, offers high throughput. Furthermore, SA eliminates the need for expensive tooling [2–4]. Yet the lack of SA process knowledge hinders its commercial implementation.
Integration of Carbon Nanotubes Into a Fiberglass Reinforced Polymer Composite and its Effects on Electromagnetic Shielding and Mechanical Properties
Authors: Tehrani Mehran , Boroujeni Ayoub Y. , Manteghi Majid , Zhou Zhixian , Al-Haik Marwan
Published: April 2014

Electromagnetic (EM) waves, such as electronic noise and radio frequency interference can be regarded as an invisible electronic pollution which justifies a very active quest for effective electromagnetic interference (EMI) shielding materials. Highly conductive materials of adequate thickness are the primary solutions to shield against EMI. Equipment cases and basic structure of space aircraft and launch vehicles have traditionally been made of aluminum, steel and other electrically conductive metals. However, in recent years composite materials have been used for electronic equipment manufacturing because of their lightweight, high strength, and ease of fabrication. Despite these benefits, composite materials are not as electrically conductive as traditional metals, especially in terms of electrical grounding purposes and shielding. Therefore, extra effort must be taken to resolve these shortcomings. The present work demonstrates a study on developing hybrid composites based on fiberglass with surface grown carbon nanotubes (CNTs) for EMI applications. The choice of fiberglass is primarily because it naturally possesses poor electrical conductivity, hence growing CNTs over glass fiber surface can significantly improve the conductivity. The fabrics were sputter-coated with a thin layer of SiO2 thermal barrier prior to growing of CNTs. The CNTs were grown on the surface of woven fiberglass fabrics utilizing a relatively low temperature technique. Raw fiberglass fabric, SiO2 coated fabric, and SiO2 coated fabric which was subjected to the identical heat treatment as the samples with CNTs were also prepared. Two-layers composite specimens based on different surface treated fiberglass fabrics were fabricated and their EMI shielding effectiveness (SE) was measured. The EMI SE of the hybrid CNT-fiberglass composites was shown to be 5–10 times of the reference samples. However, the tensile mechanical properties of the composites based on the different above mentioned fibers revealed significant degradation due to the elevated CNT growth temperature and the addition of coating layer and CNTs. To further probe the structure of the hybrid composites and the inter-connectivity of the CNTs from one interface to another, sets of 20-layers composites based on different surface treated fabrics were also fabricated and characterized.
Enhancement of the Computation of Common Normal Between Wheel and Rail Surface
Authors: Fallahi Behrooz , Ballamudi Sunil K.
Published: April 2014

Simulations are playing an important role to predict derailment, switching, wheel climbing and curving in the study of dynamics of railroad vehicles. For a successful simulation, a robust and efficient approach for computation of all common normal between wheel and rail surface is needed. In a previous work, the authors had devised an approach based on sign distant function to compute all common normal between a pair of wheel and surface. As part of this approach, two major computational tasks were formulated. They were computation of cauchy index around a cell (a closed curve) and computation of the zero’s of the gradient of the signed distance function. In this study, a bookkeeping technique is devised to compute the cauchy index more efficiently. Also the performance of trust region method as a solver for a set of nonlinear equation is compared to Newton’s method.
Vibration Suppression Drafting Arm for Tremor Patients
Authors: Mojica Jose W. , Kumagai Akihiko , Marsh Steven
Published: April 2014

Essential Tremor (ET) is a progressive neurological condition that affects over 10 million Americans. It causes a rhythmic trembling of the body that is most pronounced in the hands. Many ET patients lose the ability to perform simple yet vital tasks, such as writing. Current writing assisting devices are not able to efficiently cancel or restrict the trembling experienced by these patients when they write. We have developed a drafting arm that diminishes the arm and hand vibrations of ET patients by dampening the motion of the pen. Our design incorporates a two-segment arm with variable dampers at its joints. One end of the arm attaches to any table while the other holds a writing device. The two dampers resist the rotation at each joint. ET patients using this tool have shown significant improvement in their writing ability in comparison to using other consumer devices available today. As the final development stage, considerable effort is being put into engineering the device to be of practical use and to function well in the everyday lives of people.
Dynamic Response of Biomimetic Hair Receptors in Both Steady and Unsteady Flow Environment
Authors: Chidurala Manohar , Dickinson Benjamin T. , Chakravarty Uttam K.
Published: April 2014

The high performance of nature’s creations and biological assemblies has inspired the development of engineered counter parts that may outperform or provide new capabilities to conventional systems. In particular, the wings of bats contain distributed arrays of micro-scaled flow sensitive hair receptors over their surface, which inspires artificial hair sensors (AHS) development in aerodynamic feedback control designs using the micro-electro-mechanical systems (MEMS). One approach investigates the possibility of installing AHS on the leading edges of the wings of small-scaled unmanned aerial vehicles (UAVs) to improve the aerodynamic control. Our major motivation for the present study is that current mathematical models have limited relevance to aerodynamic situations because they are analyzed in steady or purely oscillatory flows. Our overall objective is to understand AHS fluid-structure interaction (FSI) in flow regimes relevant to small-scaled UAVs, for which we speculate a steady baseline flow perturbed by an oscillatory component is an appropriate flow reference condition. Towards understanding the AHS in this situation, we investigate the dynamic response of a hair receptor in a creeping flow environment with a steady and oscillatory component. We present time varying deflection and bending moment of the artificial hair sensors at different freestream velocities. For this, a three-dimensional FSI model is developed for the flexible hair-structure in the airflow, which is coupled with a finite element model using the computational fluid dynamics (CFD). The Navier-Stokes equations including continuity equation are solved numerically for the CFD model. To describe the dynamic response of the hair receptors, the natural frequencies and mode shapes of the hair receptors, computed from the FSI model, are compared with the excitation frequencies of the surrounding airflow. This model also describes both the boundary layer effects and effects of inertial forces due to FSI of the hair receptors. For supporting the FSI model, the dynamic response of the hair receptor is also validated considering the Euler-Bernoulli beam theory including the steady and unsteady airflow.
A Virtual Tool for Wear Simulation of Plastic Gear Pairs
Authors: Karpat F. , Ekwaro-Osire S. , Yüce C. , Karpat E.
Published: April 2014

Currently plastic gears are widely used in industry, and not only for lightly loaded applications like household appliances, tools, and toys, but also in the more demanding areas of machinery in automotive applications. However there is a need to investigate important properties such as load capacity, endurance, cost, life, stiffness and wear. Tooth wear is one of the major failure modes in plastic gears just like with steel gears. This paper focuses on the simulation of wear for standard and non-standard gears using an analytical approach. A numerical model for wear prediction of gear pairs is developed. A wear model based on Archard’s equation is employed to predict wear depth. The variation of the contact load generated by the cumulative tooth profile wear is simulated and examined. A MATLAB-based virtual tool is developed to analyze wear behavior of standard and non-standard spur gears depending on various gear parameters. In this paper, this virtual tool is introduced with numerical examples.
Development of a New Hydraulic Power Control Course in the Mechanical Engineering Program at SDSU
Authors: Duan Shanzhong (Shawn) , Bassett Kurt
Published: April 2014

The national Fundamentals of Engineering (FE) Exam is a critical assessment measure used by some ABET-accredited Mechanical Engineering programs to evaluate quality of their programs and report to ABET. Fluid power transmission and control is one key subject area covered in the FE exam. Before 2012, there was no course in the Mechanical Engineering (ME) curriculum to address this at South Dakota State University (SDSU). This had a direct impact on the metrics used for program evaluation. An instructional project was carried out to meet this need. This paper presents design and implementation of the instructional project. The project includes development of a new hydraulic power control course and establishment of new hydraulic power control lab. The authors intend to share experiences, myths, and lessons learned during this project. The paper also presents the steps taken by the authors to accomplish this instructional project from start to the final course delivery. It includes students’ learning experiences, pedagogical concepts, development of lab assignments, difficulties faced and how they were handled, software used, and existing issues for future work.
How Does Concrete Affect Evaporation of Cryogenic Liquids: Evaluating LNG Plant Safety
Authors: Ibarreta Alfonso , Hart Ryan J. , Ponchaut Nicolas , Morrison Delmar (Trey) , Kytömaa Harri
Published: April 2014

With the impending natural gas boom in the U.S., many companies are pursuing DOE approval for exporting liquefied natural gas (LNG), which is a cryogenic liquid. The next decade also promises to demonstrate growth in LNG-fueled fleets of vehicles and marine vessels, as well as growth in other natural gas uses. The future expansion in the LNG infrastructure will lead to an increased focus on managing the risks associated with spills of LNG.

Risk analysis involving LNG spill scenarios and their consequences requires the determination of the size of resulting ignitable flammable vapor clouds. This in turn depends strongly on the rate of evaporation of the spilled LNG. The evaporation of a cryogenic LNG spill (and thus the flammable vapor cloud hazard) can be quite a complex process, and it is primarily controlled by the rate of spreading of the pool and by the transient conductive heat transfer from the ground to the spilled liquid. Radiative and convective heat transfer are also present, but the conductive heat transfer rate dominates in the evaporation of a cryogenic liquid spilled into a trench or sump initially at ambient temperature.

The time dependent evaporation rate can be calculated using a variety of models, such as the built-in model in PHAST (DNV) or other proprietary models that account for pool spreading, heat conduction within the substrate, and phase change. Trenches and sumps used to contain LNG spills are normally lined with various types of concrete, including insulated or aerated concrete. We have found that for a cryogenic liquid, the choice of thermal properties for concrete can greatly affect the source term.

In this work, we perform a sensitivity study of the effects of substrate properties on the evaporation rate of LNG. The study will look at the dependence for a range of sump diameters. The PHAST model results will be compared to results obtained using an in-house Shallow Water Equation (SWE) liquid propagation and heat transfer model. The results of this work will provide guidance for the selection of substrate properties during modeling; as well as a comparison of the relative evaporation rates expected for different surfaces, such as regular concrete and insulated concrete.
Variational Integrators for Piezoelectricity
Authors: Nasiri P. , Dargush Gary F.
Published: April 2014

Variational integrators have been used to study the transient response of a number of dynamical problems, while displaying superior conservation characteristics. The purpose of this paper is to develop variational integrators for linear piezoelectric problems. A two-field piezoelectric functional is first discretized in space and time and the coupled discrete Euler-Lagrange equations for displacement and electrical potential are then derived. Afterwards, to validate this new formulation, the numerical results for two initial/boundary value problems involving a piezoelectric plate are compared to the corresponding analytical solutions and finite element results obtained from a commercial software package. The excellent correlation of these solutions indicates the capability of variational integrators in modeling transient piezoelectric behavior. Finally, the superior energy conservation behavior of the developed method is demonstrated.
Simultaneous Time-Frequency Synchronization of Non-Autonomous Chaotic Systems
Authors: Liu Meng-Kun , Suh C. Steve
Published: April 2014

A novel chaos control concept is presented for the synchronization of a non-autonomous chaotic circuit system in the time and frequency domains concurrently. The controller effectively eliminates the differences between two chaotic circuits in the time domain and at the same time restores the characteristics of the driving response in the frequency domain. The simultaneous time-frequency control is achieved through manipulating wavelet coefficients, thus not limited by the increasing bandwidth of the chaotic system — a fundamental restraint that deprives contemporary controller designs of validity and effectiveness. The feedforward feature of the control concept prevents errors from re-entering the control loop and inadvertently perturbing the sensitive chaotic system. Because neither closed-form nor linearization is required, the innate, genuine features of the chaotic response are faithfully retained. The on-line identification feature allows the response system to start at arbitrary initial conditions and to be driven by the sinusoidal forcing term of different amplitudes and phases requiring no knowledge of the system parameters.
Mechanotransduction in Corneal Epithelial Cells
Authors: Molladavoodi Sara , Medley John B. , Gorbet Maud , Kwon H. J.
Published: April 2014

Mechanical properties of the cornea can be affected by diseases such as keratoconus. In keratoconus, a decrease in both thickness and rigidity of the cornea is observed. It is currently not clear whether and how changes in mechanical properties of the cornea are associated with corneal epithelial cell behavior.

In the present study, polyacrylamide (PAA) gels with different elastic moduli have been prepared and human corneal epithelial cells (HCECs) have been cultured on them. To investigate the effect that changes in elastic modulus may have on adhesion and migration of corneal epithelial cells, actin filament organization and expression of adhesion molecules were characterized. It was found that HCECs actin filament organization improves with increasing substrate stiffness and integrin α3 expression significantly increases on more compliant substrates.
Modeling the Effect of the Leidenfrost Vapor Coat Behavior on the Vitrification in Micro-Droplets Using the Cryogenic Droplet Levitation Time
Authors: Katkov Igor I. , Bolyukh Vladimir F. , Yakhnenko Ilya
Published: April 2014

The levitation (“hovering”) of a liquid droplet on the surface of the coolant such as liquid nitrogen (LN2) is a useful model for studying the Leidenfrost effecr (LFE), that is formation of a vapor film of boiling coolant around the surface of a relative,ly hotter sample, at cryogenic temperatures. Several models of the cryogenic droplet levitation (CDL) have been proposed but no experimental verifications had been proposed for this model in earlier papers. Utkan Demirci’s group has recently developed fast ice-free cooling (vitrification) of microdroplets formed by an ink-jet printer. The group proposed a combination of a theoretical model of film boiling on a hot sphere with the zone theory of non-isothermal kinetic ice propagation within an initially liquid levitating droplet, and they gave theoretical predictions and experimental evaluations of the CDL (Leidenfrost) time tLF of droplets hovering on the surface of LN2 [6]. Here, we report our own experiment results of verification of the data and predictions reported in [6] and describe a thermodynamical model that for elucidating the fate of the levitating droplets. This model adequately explains our experimental results on measuring tLF but almost predicts somewhat 4-fold departure from the numbers claimed by Demirci’s group. We also discuss possible flaws of the model and, especially, experimental claims presented in [6].
Computational Fluid Dynamics and Structural Finite Element Analysis of a Micro Hydro Turbine
Authors: Riglin Jacob D. , Schleicher W. Chris , Kraybil Zackary , Klein Robert C. , Oztekin Alparslan
Published: April 2014

Performance characteristics of a micro hydro turbine are determined through the use of computation fluid dynamics (CFD) and finite element analysis (FEA). CFD is used to optimize a portable micro hydro turbine. The runner geometry is designed as a non-uniform Archimedean Spiral. The transient 3D turbulent flow simulation is conducted for various runner designs to determine power generation and the efficiency. The equations governing the fluid motion through the turbine are solved in a frame of reference change between time-steps. A multiphase flow model is employed to study the cavitation for various flow rates and rotation rates to determine the onset of the cavitation. It was determined that the onset of cavitation occurred between inlet flow rates of 0.0625 m3/s and 0.075 m3/s for the 1.5 pitch Archimedean spiral at a rotation rate of 250 RPM. When the rotation rate is increased to 500 RPM, vapor formation within the flow exists between a flow rate of 0.05 m3/s and 0.0625 m3/s. The occurrence of cavitation was predicted using Cavitation number, with the critical number being approximately −10,000. The presence of cavitation caused the efficiency to drop up to 10%. Basic structural analysis of the Archimedean blade yielded a maximum von Mises stress of 143.67 MPa at flow rate of 0.1 m3/s and a rotation rate of 1000 RPM. From the von Mises stress obtained, aluminum alloy is the best material to be used based on the importance of material strength and weight.
Numerical Analysis on the Development of the Large-Scale Showerhead for Depositing AlGaInN Films
Authors: Byun Chulsoo , Kim Dae Hyeon , Joo Kang Woo , Kim Kwang-Sun
Published: April 2014

The metal organic chemical vapor deposition (MOCVD) process is widely used to form a multi-layered structure with thin films for diverse semiconductor materials. The MOCVD process is the most promising method for manufacturing chips that are based on the compound semiconductor, but its technology is partly still insufficient. If a device, for example, lacks a non-uniformity related to the composition and thickness of the film, it decreases the reliability of the final product and affects the economics. To ensure that the equipment is competitive in the worldwide markets, a high reliability including the controllability of compositions is required for the equipment. In this study the CFD analysis was used to investigate the behavior of the process gas in a MOCVD reactor where the process gases including the component of the GaN films are injected as separated through a multi-module showerhead for eventually targeting multi-component films such as AlGaInN materials. After applying of Porous Media, a stabilization of process gas was confirmed from the results of pressure distribution.
Multiplex Single Molecule Detection Module for Stroke Diagnosis
Authors: Park D. S. , Lowrey B. B. , Brown C. R. , You B. H. , Singh V. , Soper S. A. , Baird A. , Murphy M. C.
Published: April 2014

A polymer-based, multiplex single molecule detection module (SMD) was developed with a fluidic substrate and a cover plate. The fluidic substrate was fabricated using a single-step, double-sided hot embossing in poly(methyl methacrylate) (PMMA) with sampling zone microchannels on the bottom side and microlenses on the top. Shallow sampling zone microchannels (5 μm deep and 100 μm wide) were made to improve sampling efficiency and microlenses were adopted to collect the fluorescent radiation from the sampling zone microchannels. A cyclic olefin copolymer (COC) embedded waveguide in PMMA along with an integrated coupling prism was fabricated using polydimethylsiloxane (PDMS) stencils and melted COC (40% w/v in toluene) on the cover plate. The COC waveguide with a COC integrated coupling prism will be used for evanescent excitation of fluorescent samples in the sampling zone microchannels. The fluidic substrate was bonded with the cover plate using thermal fusion bonding based on a pressure-assisted boiling point control system. This approach allowed for sealing of shallow microchannels without observable sagging of the cover plate, which was confirmed by leakage testing with fluorescent dyes. The completed SMD module will be tested for characterization of the optical performances such as signal-to-noise ratio and sampling efficiency and it will provide the capability for rapid screening of stroke at low cost.
Analysis and Design of Active Morphing Units Based on SMA Actuators
Authors: Yue Hong-Hao , Liu Zhan-Qiu , Yuan Han , Long Yu-Fei , Tzou Horn-Sen
Published: April 2014

Morphing wings can change their shapes in flight to optimize aircraft’s aerodynamics, which increases aircraft’s performance for a given flight stage. This paper introduces an active morphing unit (AMU) which can deform by the two-way actuator comprising two one-way shape memory alloy (SMA) elements. The mathematical model and the forward kinematics of AMU are established. The structure of AMU is design. Then, the paper demonstrates that the combination of AMUs can function as the main spar of distributed multi-freedom active morphing wing. Three different combination strategies of AMUs are analyzed by forward kinematics and realizable variable geometries of wing. A configuration sample of one-dimension morphing wing is presented to demonstrate a combination strategy. The rotation function and stiffness of AMU prototype are tested. Experimental results illustrate that AMU can realize desired deformation and has high stiffness. This research will lay the foundations of next generation morphing aircrafts.
Teaching Neural Network Control System Design Using a Low-Cost Rapid Control Prototyping Platform
Authors: Franquiz Francisco , Hurst Alecia , Tang Yan
Published: April 2014

This paper presents the use of a low-cost rapid control prototyping platform, HILINK, in teaching a graduate course on neural network control system design for mechanical engineering students. The HILINK platform offers a seamless interface between physical plants and Simulink for implementation of hardware-in-the-loop real-time control systems. With HILINK, student can quickly build a neural network controller for applications using Neural Network Toolbox in Simulink. As a result, students can use one single environment for both computer simulation and hardware implementation to understand theories and tackle practical issues in a limited time frame. The paper presents the experimental setup and implementation process of the NARMA-L2 controller for DC motor speed control, and demonstrates the convenience and effectiveness of using HILINK in developing a neural network controller.