bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydraulic Accumulator as Energy Storage
Authors: Juhala Jyri , Pietola Matti
Published: August 2012

Most of the hydraulically operated systems have potential to improve the energy efficiency of the system by using energy regeneration. The recovered energy can be stored in various ways. However, previous studies made by the authors have shown that in hydraulically operated regenerative systems a pressure accumulator seems to be potential option as energy storage. Hydraulic accumulator has also some disadvantages, e.g., energy losses in form of heat transfer. The efficiency can be improved by using different heat recovery methods. To compare these methods numerically, a reliable model of an accumulator is needed. The primary aim of this study is to build a multidisciplinary model of a basic piston type hydraulic accumulator and to validate the model with experimental measurements. The second aim is to experimentally test the effects of a honeycomb heat regenerator by efficiency point of view. The results manifest that multidisciplinary modeling is useful and valid tool for modeling the piston type hydraulic accumulator. The results also indicate that the heat regenerator attached inside the accumulator’s gas volume improves energy efficiency significantly.
Development of an “S.M.A.R.T.” Assessment System for Accreditation and Continuous Program Improvement
Authors: Karunamoorthy Swami
Published: August 2012

Development and implementation of an educational program in engineering or technology is not something new to Colleges and Universities; however periodic assessment of a program for the purpose of accreditation by ABET as well as to demonstrate the continuous improvement remains a challenge for most of the programs. The design of a successful assessment system is open ended similar to any engineering design problem. In addition to that, the design guidelines are not well defined resulting in difficulties to develop an effective assessment system. There is a need for a framework to develop a good assessment system for program evaluation. An emphasis is given in this paper to explore such a framework. Assessment based on SMART system is suggested as a viable system with S – Sustainable Process; M – Measurable Performance Criteria; A – Actionable Feedback; R – Robust Methods; and T – Team Work of Constituents.
A System-Level Generic Model of Water Use at Power Plants and its Application to Regional Water Use Estimation
Authors: Rutberg Michael J. , Delgado Anna , Herzog Howard J. , Ghoniem Ahmed F.
Published: August 2012

The withdrawal and consumption of water at electricity generation plants, mainly for cooling purposes, is a significant component of the energy water nexus in the US. The existing field data on US power plant water use, however, is of limited granularity and poor quality, hampering efforts to track industry trends and project future scenarios. Furthermore, there is a need for a common quantitative framework on which to evaluate the potential of the many technologies that have been proposed to reduce water use at power plants. To address these deficiencies, we have created a system-level generic model (S-GEM) of water use at power plants that applies to fossil, nuclear, geothermal and solar thermal plants, using either steam or combined cycles. The S-GEM is a computationally inexpensive analytical model that approximately reflects the physics of the key processes involved and requires a small number of input parameters; the outputs are water withdrawal and consumption intensity in liters per kilowatt-hour. Data from multiple sources are combined to characterize value distributions of S-GEM input parameters across the US, resulting in refined estimates of water use with quantified uncertainties. These estimates are then validated against typical values from the literature and against an existing field data set. By adjusting S-GEM input values or value distributions, any number of hypothetical scenarios can be rapidly evaluated. As an example, we focus here on technology evaluation, expressing proposed technological improvements in terms of S-GEM input parameters, then comparing their projected effects on overall water withdrawal and consumption intensities.
Unilateral Impact and Contact of Elastic Structures Using Lagrangian Multipliers
Authors: Tatzko Sebastian
Published: August 2012

This paper deals with linear elastic structures exposed to impact and contact phenomena. Within a time stepping integration scheme contact forces are computed with a Lagrangian multiplier approach. The main focus is turned on a simplified solving method of the linear complementarity problem for the frictionless contact. Numerical effort is reduced by applying a Craig-Bampton transformation to the structural equations of motion.
Investigation of a Nonlinear Control Model for Marine Propulsion Power-Plants
Authors: Xiros Nikolaos I.
Published: August 2012

A cycle-mean-value, quasi-steady, thermodynamic model of slow-speed, two-stroke marine Diesel engines, used for performance prediction and engine-propeller/turbocharger matching, is converted into a power-plant analytic model. The dynamic part of the cycle-mean model consists of the two first-order differential equations for the cycle-mean crankshaft and turbocharger shaft rotational accelerations. This form implies a state-space formulation of the power-plant modeling approach. However, engine, turbine and compressor torques have to be calculated through the solution of the algebraic part of the model, which consists of a nonlinear, perplexed algebraic system of equations not analytically solvable. This inhibits the formulation of the power-plant state-space description. By approximating the torque maps, generated by the thermodynamic model, with neural nets, explicit functional relationships are obtained. Identification of the power-plant operating regimes through linearization and decomposition is performed. In effect, a supervisory power-plant controller structure, applicable to real-time control and diagnostics, is proposed, incorporating the nonlinear state-space description of the plant.
Reciprocating Steam Turns 300
Authors: Carr Matthew A.
Published: August 2012

The year 2012 marks the 300th anniversary of the first successful reciprocating steam engine, which was built by Thomas Newcomen of Dartmouth, England to dewater a coal mine near Tipton, West Midlands, England. With over 1400 built during the 18th Century, Newcomen engines enabled the Industrial Revolution. This paper: (1) commemorates this achievement through an overview of the development of this remarkable machine; (2) describes the operation of the Newcomen steam engine; and, (3) provides modern thermo-fluids analyses using authentic historical data of the Westfield Engine at Parkgate, an engine that was constructed in 1823 and dismantled in 1934. The overarching goal of this paper is to encourage teaching about this fascinating historical technology in today’s classrooms by providing the background knowledge and pertinent calculations for integration into current thermo-fluids courses.
A Method of Measuring the Temperature Profile of a Thermal Barrier Coating Using Inverse Radiative Heat Transfer Methods
Authors: Moore Travis J. , Jones Matthew R.
Published: August 2012

Ceramic thermal barrier coatings (TBCs) are used in power generation and aerospace turbines to protect superalloy components from large and extended heat loads. These coatings allow for increased inlet temperatures, thereby increasing efficiency and reducing air cooling requirements. Knowledge of the temperature profile in a thermal barrier coating is critical for evaluating the TBC performance and monitoring its health, as well as for accurate simulation and modeling. Non-contact, non-destructive techniques for finding these temperature profiles are highly desirable. Current techniques are limited in that they cannot measure the entire temperature profile of the TBC along with its radiative properties. An inverse radiative heat transfer method capable of determining the temperature profile, as well as the spectral absorption coefficient and spectral emittance at various wavenumbers, of a TBC using non-contact techniques was developed. A model of the measurements of the intensity exiting the TBC, which account for the emission from the substrate as well as the emission and absorption of the TBC itself, was developed. The TBC was approximated as a one-dimensional, plane-parallel, non-scattering medium. Optimization methods were used to determine the desired parameters by minimizing the error between actual intensity measurements and those calculated from the model. This method was tested for a number of simulated measurements with and without measurement error. Even with 10% measurement error introduced, the base temperature of the TBC was determined with only 0.45% error while the error in the TBC surface temperature measurement was 3.36% and that in the spectral emittance of the bondcoat was 12%. The error in the spectral absorption coefficient was significant.
Fiber Pull-Out Strength of Single-Walled Carbon Nanotube Reinforced Polypropylene (PP) Composite Using Molecular Dynamics Simulation
Authors: Mandal A. , Singh S. P. , Prasad R.
Published: August 2012

Polymer crystallization has been studied to explore the bulk behavior of polymers and polymeric materials. Computer simulation has been widely used as a powerful tool for investigating the microscopic behavior of materials. Here a similar attempt has been made to investigate, how the polymer chains interact with single walled carbon nanotube (SWCNT). The physical interaction of polymer and CNT has been established. With computer simulation, the physical interactions have been examined in terms of pull-out strengths of reinforcement. All the simulations are performed in full atom configuration with DREIDING potential for both the polymer and the nanotube. Isothermal crystallization process is modeled with NVT ensemble at room temperature and atmospheric pressure. During initial relaxation process, the adsorption and orientation of polymer chain is observed and the total interaction energy of composite is minimized. Non-bond van der Waals interactions between the polymer and CNT are the main contributor for the adsorption and orientation of polymer. This aspect is explored in the paper, for its subsequent use in nano-composites with a large number of polymer chains. Finally the pull-out effect of the nanotube is simulated and the fiber pull-out phenomenon is examined in detail.
Process Improvement of Brake Lever Production Using DMAIC (+)
Authors: Sahay Chittaranjan , Ghosh Suhash , Bheemarthi Pradeep Kumar
Published: August 2012

This work describes a strategy to reduce the cost associated with poor quality, by reducing the parts per million defects by Defining, Measuring, Analyzing, Implementing and Controlling (DMAIC) the production process. The method uses a combination of principles of Six Sigma applications, Lean Manufacturing and Shanin Strategy. The process has been used in analyzing the manufacturing lines of a brake lever at a Connecticut automotive components manufacturing company for reducing the cost associated with the production of nonconforming parts. The analysis was carried out with the help of the data collected on nonconformance parts and the application of phase change rules from DMAIC (+). Data analysis was carried out on statistical process control softwares, MINITAB and SPC XL 2000. Although, the problem of tight bushing existed on only one line of the brake lever assembly, this problem solving approach has solved the tight bushing problems on all assembly and alternates lines in a time- and cost-effective way.
An Optical Tomography Reconstruction Algorithm With the Discontinuous Galerkin Method
Authors: Balima Olivier , Favennec Yann , Boulanger Joan , Charette Andre´
Published: August 2012

In optical tomography, the optical properties are recovered through an iterative scheme, which consists in minimizing the errors between the measurements and the predications of a forward model. Traditionally, finite volumes or continuous finite elements formulations of light transport are used as a forward model for the predictions. we have introduced an integral form of the objective function that takes into account the surface of the detectors, and thus making compatible the inverse approach with all finite elements formulations (continuous and discontinuous). This present paper illustrates this novel approach by developing a Discontinuous Galerkin formulation as a forward model. Numerical tests are performed to gauge the accuracy of the method with a gradient-based algorithm. The results show that the reconstruction is accurate and can be affected by noise on the measurements as expected. A filtering of the gradient improves the quality and the accuracy of the reconstruction.
Experimental Parametric Analysis of Water-Mist Sprays: An Investigation on Coalescence and Initial Dispersion
Authors: Santangelo Paolo E. , Tartarini Paolo , Valdiserri Paolo
Published: August 2012

An experimental approach and parametric analysis are here presented to investigate some dynamic aspects of water-mist sprays operating at high supply pressure. An already proposed methodology (P.E. Santangelo, 2010, Exp. Therm. Fluid Sci., 34, pp. 1353–1366) has been extended to a three-dimensional analysis, that emphasizes the characteristic drop-size evolution along the axial coordinate of the spray. Therefore, an evaluation of coalescence and secondary-atomization phenomena along the spray axis results as the ultimate scope of this study. With regard to dispersion, the initial-velocity field has been experimentally determined both as a contour/vector map and as magnitude profiles at different distances from the injector outlet. In addition, some evaluation of the spray-cone angle has been proposed, resulting from a simple geometric approach to the already mentioned maps. Advanced laser-based diagnostics has been employed to perform experimental measurements: a Malvern Spraytec device has been used to measure drop-size distribution and Particle Image Velocimetry has been chosen to evaluate both velocity and cone angle. Moreover, a mechanical patternator has been employed to introduce flux measurements as an averaging quantity. Two nozzles having different orifice diameter have been employed and operative pressure has been set at a value of interest for fire-protection applications.
Towards a Failure Criterion for Microtubules Based on Matching Strength Analysis in Finite Element Models to AFM Loads
Authors: Taylor William , Shepard W. Steve , Floyd Candace L.
Published: August 2012

In previous research studies, the geometric and elastic properties for a critical component of axon health, the microtubule (MT), have been determined using lateral indentation with the tip of an atomic force microscope (AFM). Although the response due to the indentations caused by the AFM was observed to be linear for most of the tests, forces greater than 300pN would result in a permanent irreversible collapse of the MT’s structure. While the intent of those researchers was not to evaluate microtubule strength properties, that load can be used as a starting point to evaluate internal stress failure criterion for such structures. To that end, the current research is investigating MT strength by replicating the loading and boundary conditions in a finite element model. This work is an extension of previous work aimed at using this 300 pN point load to develop failure criteria for MTs under more realistic loading conditions. In the present work, modeling has been used to correlate the AFM point load response with the more realistic distributed loading conditions that would result during a brain injury event. Furthermore, the impact of nearby MTs on the stresses that occur under similar loading conditions is also examined. These results are being used to analytically determine a stress threshold related to MT structural failure. Correspondingly, models that include dynamic wave propagation through the microtubule will be studied. The failure criterion determined in both cases would aid in evaluating brain injury studies that involve pressure wave propagation in whole-head finite element models, even when such models represent the white matter using homogeneous properties.
Flammability of Solid Materials: An Experimental Calorimetric Approach
Authors: Santangelo Paolo E. , Ryder Noah L. , Marshall Andre´ W. , Schemel Christopher F.
Published: August 2012

Flammability properties of solid materials are necessary to be a known parameter for many purposes: among them, forensic investigations of fire and explosion events, fire risk or hazard analysis, design and development of combustion-based systems. However, despite the large quantity of data in the literature, the flammability properties of many materials still appear not to be available or show a degree of uncertainty associated with them, which makes their value limited. The present work is aimed at proposing a calorimetric-based approach to determine some flammability and thermophysical properties of solids, with specific regard to time-to-ignition as a function of the imposed heat flux. Plastic materials have been here chosen as test cases, even though this approach has a general applicability. The two mentioned parameters have been analyzed to provide a quantitative estimation of the critical heat flux (minimum heat flux resulting in ignition). A cone calorimeter has been employed to conduct the experiments: the facility complies with standard ASTM E 1354; the related uncertainty and validity range has been evaluated through an appropriate error analysis. Finally, thermal inertia has been thereby calculated for the considered materials through a simple thermodynamic model, which is based upon critical heat flux and energy conservation.
Wireless Nerve Positional Control of Prosthetic Device
Authors: Loker David R. , Wu Yi , Voss Margaret A. , Roth John T. , Strom Stephen A.
Published: August 2012

Artificial limb control is an active area of research, and the control of prosthetic devices using electromyographic (EMG) interfaces is well established. The authors have previously performed a feasibility study which demonstrated that wireless nerve control of a prosthetic device is possible. This is critical for injuries that result in the loss of muscle which prevent EMG control. The purpose of this study is to extend the authors’ current research by providing enhancements to the system designed in the feasibility study. The objective of this current study is to take simulated nerve signals and transform them into corresponding positional motion control realized by a servo motor. The system designed has four functioning blocks: artificial nerve signal generation, wireless transmitter, wireless receiver, and servo motor. The artificial nerve generator used a PIC microcontroller to simulate and apply the signals directly to the wireless transmitter. A one-byte message, that indicated when the appropriate signal characteristics were met, was wirelessly transmitted. After receiving the message, the wireless receiver sent a corresponding pulse-width modulated (PWM) signal to the servo motor for positional control. Various input signal combinations were used to test the system.
Synthesis and Implementation of Advanced Controllers for a Novel Pneumatic Semi-Active Wheelchair Suspension
Authors: Smith David , Porumamilla Hemanth
Published: August 2012

Present within the medical literature are numerous studies which indicate the negative effects of the vibration environment encountered by a wheelchair passenger with regard to human health and comfort (Wolf, Cooper, Pearlman, Fitzgerald, & Kelleher, 2007). In the regard, the accelerations due to road variations have been documented to cause numerous health effects in the human body, such as chronic back, increased need for medication and painkillers, and aggravation of the primary disease, thereby illustrating a need for improvement of the vibration environment (Weisman & Huston, 1995). The current state of the art for wheelchair suspensions is very basic with vast majority of wheelchairs having no suspension of any kind (Cooper, Wolf, Fitzgerald, Bonninger, Ulerich, & Ammer, 2003), some that do offer suspensions use simple off-the-shelf components and are not tuned, reducing performance (Wolf, Cooper, Pearlman, Fitzgerald, & Kelleher, 2007) (Hostens, Papaioannou, Spaepen, & Ramon, 2003). This research study was conducted to design and implement a new semi-active suspension system utilizing the combination of purely pneumatic system components comprising of an airspring and an electronically controlled, high-fidelity, electro-mechanical valve to achieve variable pneumatic damping in real time. Three semi-active controller types were designed and tested in this research, viz. Skyhook control, Acceleration driven damping control, and a combined control law using a time domain frequency selector to determine which of the above two laws to choose at any given instant. The evaluation of the vibration environment was analyzed with respect ISO 2631, in order assess the performance of each controller. The three controllers were tested and implemented on the hardware. It was noticed that each of the three semi-active suspensions utilizing the different controllers showed a distinct improvement in the ride quality over the basic wheelchair configurations (Wheelchairs with no suspension) that are widely used. Furthermore, each controller design outperformed the passive suspension (current state-of-the-art) by two orders of magnitude. It was also shown that implementation of a passive suspension was counter-productive to system performance.
Passive Control of a Wind Turbine Blade Using Composite Material
Authors: Aziz Saad , Gale John , Ebrahimpour Arya , Schoen Marco P.
Published: August 2012

The weight and the cost of a wind turbine are two important factors that make wind energy competitive with other energy sources. The weight of the rotor is typically 40–80% of the total weight of the system. Thus, lowering cost by reducing the weight of the blade is an important consideration. Another significant factor is the operational life of the machine. At present, a wind turbine’s life span is about 108 cycles or 20 years of continuous service. Innovative design solutions are needed in order to meet the criteria of improved stiffness, fatigue life, reliability, and efficiency. The directional property of an anisotropic composite material can be used to passively control wind turbine blade geometry in fluctuating wind speeds. Anisotropic materials show various levels of elastic coupling, based upon the ply angle in the layers. Structural behavior that exhibits both bending and twisting due to a pure bending load is known as twist-bend coupling. This type of behavior can be used for load reductions, particularly fatigue loads. The idea is to allow the blade to unload (reducing the speed) by allowing the wind induced bending moment to twist the blade. Increments in bending moment produce an increment in the twist that lowers the aerodynamically produced load. Higher blade stiffness can be achieved by full or partial replacement of glass fiber with carbon fiber. Carbon fibers are not used extensively on commercial wind turbine blades as they are more costly than glass fiber. The main objectives of this work are: (1) design a baseline model (made from glass fibers) of the wind turbine blade in accordance with published airfoil data; (2) conduct a finite element analysis of the blade and determine stresses, and strain within the blade; (3) develop a hybrid blade design by replacing the glass fibers with carbon fibers in the spar cap; and (4) validate the feasibility of implementing bend-twist coupling in the wind turbine blade by studying stresses, and strain behavior. By giving different orientation in the carbon fiber and changing the fiber layer, different designs are analyzed with regard to the above listed criteria.
Parametric Stability Analysis of Nonlinear Rotating Blades
Authors: Wang Fengxia
Published: August 2012

The role of the “geometric stiffening” nonlinearities played in the stability analysis of a rotating beam is investigated. It is a well established fact that nonlinear theory must be employed to capture geometric stiffening effect, which has been extensively investigated. In this work, two models are built for a rotating blade with periodically perturbed rotation rate, one is the “effective load” linear model and the other is “geometric stiffening” nonlinear model. Both of these two models are discretisized via Galerkin’s method and a set of parametric excited gyroscopic equations are obtained. The dynamic stability of these two models are studied and compared by the generalized harmonic balance method.
Modeling of Serrated Chip Formation With a Fracture Locus Approach
Authors: Abushawashi Yalla , Xiao Xinran , Astakhov V. P.
Published: August 2012

A fracture model is of great concern when it comes to chip formation and simulation of localized shear bands that take place in serrated chip formation. Considering the special loading characteristics of the cutting regime, the present paper is intended to evaluate the equivalent fracture strain to be used in the prediction of segmented chip formation and energy evaluation. It is assumed that both the equivalent strain rate and stress triaxiality define the material fracture locus. The stress triaxiality analysis was based on the fracture experiments using flat-grooved specimen conducted by Bai et al. [1]. The effect of the strain rate was estimated based on the strain energy density and stress triaxiality. To ensure model completeness and solution stability, damage evolution was modeled based on the material fracture energy. Numerical simulations of machining AISI steel 1045 with and without friction model were performed. The physical and morphological characteristics of the chip formation were analyzed. The results were found to be in agreement with the experimental data of the actual segmented chip obtained from the literature. The anticipated fluctuation of the cutting force caused by the chip segmentation was observed. It is noted that up to 25% reduction of the total energy required by the system may be achieved by minimizing tool friction using tribological coating and/or metal working fluids.
Dynamic Balancing Analysis of the Armature in an Automobile Starting Motor: An Industrial Case Study
Authors: Medelli´n Castillo Hugo I. , Mendoza Lo´pez Edgar A.
Published: August 2012

It is a common design practice to balance all rotating members of a machine. Rotating parts can be designed to be inherently balanced by their geometry. However, due to production tolerances there will be some small unbalance in each part. Therefore a balancing operation may be required for each part after manufacture. In the case of electrical motors the major source of vibration and noise is unbalance in the armature. In the motor manufacturing industry, this problem is generally corrected by removing material from the armature. However, the number of unbalance armatures is generally high and therefore the balance operation is usually a bottleneck in the production line. As a result, the manufacturing process becomes inefficient and costly. Based on the fact that a motor manufacturing company is facing balancing problems in its production line, this paper presents a dynamic balancing analysis of the armature in an automobile starting motor. A theoretical balancing analysis is carried out using the design and manufacture information. Balancing is also experimentally studied at the assembly line by measuring the unbalance through the whole manufacturing process. Both analysis, theoretical and experimental, and then compared. From this comparison several external factors that affect the unbalance in the real assembly process are identified. As a result, design changes and production process modifications are proposed to reduce the armature unbalance.
Computational and Experimental Investigation of Heat Transfer Within a Column Photobioreactor
Authors: Mortuza S. M. , Gent Stephen P. , Kommareddy Anil , Anderson Gary A.
Published: August 2012

The goal of this research is to investigate heat transfer effects of two phase gas-liquid flows in a column photobioreactor (PBR) experimentally as well as computationally using Computational Fluid Dynamics (CFD). The authors have completed a preliminary study on bubble formation, rise and resulting circulation patterns using lab-scale experiments and CFD simulations. This study extends on this previous work by investigating the relationships of bubble drag coefficient and bubble Reynolds number with superficial gas velocity and a study of heat transfer within the PBR. It is hypothesized that a greater understanding the bubble movement patterns will aid in predicting heat transfer rates within the PBR. Dispersed gas–liquid flow in the rectangular column PBR are modeled using the Eulerian–Lagrangian approach. The heat transfer process has been considered for the case of a steady state three dimensional PBR. A low Reynolds number k–epsilon CFD model is used for the description of flow pattern near the wall. The velocity profiles and eddy diffusivity obtained by the model are utilized to predict heat transfer coefficients for different superficial gas velocities. The information on heat transfer effects between cooling or heating surfaces and a gas-liquid dispersed bed is essential for designing a PBR. Carbon dioxide, which is necessary for photosynthetic microalgae growth, is added to the system. Bubble size distribution measurements are carried out using a high-speed digital camera. The main interaction forces, i.e. the drag force, the added mass force, and lift force are considered. Heat transfer and internal hydrodynamics of a column reactor are studied and the numerical simulations results are presented for heat transfer and hydrodynamics in column PBRs. The results are validated with experimental data and with data from current literature.
Far Infrared Thermal Radiative Properties of Polar Materials From First-Principle Simulations
Authors: Bao Hua , Qiu Bo , Ruan Xiulin , Zhang Yu
Published: August 2012

The Lorentz oscillator model is well-known for its effectiveness to describe the far infrared optical properties of ionic materials. The parameters including oscillator strength and damping factor in the model are usually obtained by fitting to experimental results. In this paper, a new method, based on static and dynamic first-principle simulations, is developed to parameterize the Lorentz oscillator model with the initial atomic structure as the only input parameter. This method is then applied to predict the far infrared reflectance of GaAs, which shows excellent agreement with experimental measurements.
Finite Element Analysis of a Highly Parallel Robotic Surface
Authors: Salisbury Chris , Yim Woosoon
Published: August 2012

A novel three-dimensional robotic surface is devised and implemented using triangular modules. Each module is connected by a passive sixbar mechanism that mimics the constraints of a spherical joint at each triangle intersection. The finite element method (FEM) is applied to the static loading of this device using linear three dimensional (6 degrees of freedom) beam elements to calculate the cartesian displacement and force and the angular displacement and torque at each joint. In this way, the traditional methods of finding joint forces and torques are completely bypassed. An effiecient algorithm is developed to linearly combine local stiffness matrices into a full structural stiffness matrix for the easy application of loads. This is then decomposed back into the local matrices to easily obtain joint variables used in the design and open-loop control of the surface.
Analytical Solutions of Structural Response of Cylindrical Shells Subjected to Detonation Loading
Authors: Hu Hurang , Hamidzadeh Hamid
Published: August 2012

Cylindrical shells under a moving internal pressure has wide applications such as oil, gas, and water transmission and distribution pipelines, gun tubes, pressured aircraft fuselages, rocket casings, space station modules, and pulse detonation engines. As a moving load produces larger deformations and higher stresses than does an equivalent static load, the study of this kind of problems has significant importance in design and optimization of such structures. The problem of a cylindrical shell subjected detonation loading has been studied by many researchers, but there are still some problems that need to be further investigated, especially in the application aspect. In this work, analytical solutions for cylindrical shells under detonation loading are developed. The analytical solutions include static state and transient state. For transient state, three analytical models are presented. Numerical results show these analytical solutions are reliable and stable.
Thermoelectric Coolers for Hotspot Thermal Management of 3D Stacked Chips
Authors: Redmond Matthew , Manickaraj Kavin , Sullivan Owen , Kumar Satish
Published: August 2012

Three dimensional (3D) technologies with stacked chips have the potential to provide new chip architecture, improved device density, performance, efficiency, and bandwidth. Their increased power density also can become a daunting challenge for heat removal. Furthermore, power density can be highly non-uniform leading to time and space varying hotspots which can severely affect performance and reliability of the integrated circuits. Thus, it is important to mitigate thermal gradients on chip while considering the associated cooling costs. One method of thermal management currently under investigation is the use of superlattice thermoelectric coolers (TECs) which can be employed for on demand and localized cooling. In this paper, a detailed 3D thermal model of a stacked electronic package with two dies and four ultrathin integrated TECs is studied in order to investigate the efficacy of TECs in hot spot cooling for a 3D technology. We observe up to 14.6 °C of cooling at a hot spot inside the package by TECs. A strong vertical coupling has been observed between the TECs located in top and bottom dies. Bottom TECs can detrimentally heat the top hotspots in both steady state and transient operation. TECs need to be carefully placed inside the package to avoid such undesired heating. Thermal contact resistances between dies, inside the TEC module, and between the TEC and heat spreader are shown to have a crucial effect on TEC performance inside the package. We observed that square root current pulse can provide very efficient short-duration transient cooling at hotspots.
Thermal Energy Storage Using Zinc as Encapsulated Phase Change Material
Authors: Zhao Weihuan , Zheng Ying , Sabol Joseph C. , Oztekin Alparslan , Neti Sudhakar , Tuzla Kemal , Misiolek Wojciech M. , Chen John C.
Published: August 2012

Concentrating solar power is inherently intermittent and thus thermal energy storage is an essential component of a successful baseload solar power plant. Phase change materials (PCM) have the potential to decrease the cost of thermal energy storage systems for these plants since the latent heat contribution can be significant. The present work deals with certain aspects of using zinc as PCM for storing solar energy at high temperatures from 300°C to 500°C. The objective is the storage of hundreds of mega-watt-hours equivalent of solar energy in systems using zinc as encapsulated phase change materials (EPCM). Stainless steel and nickel have been considered as encapsulation materials for zinc. The present work describes several aspects of this technology that need consideration in designing the EPCM; such as thermal analysis, materials issues, proof of storage and retrieval of energy and cost analysis. EPCM of several sizes and shapes subjected to many cycles of energy storage/retrieval have been considered as part of the calorimetry tests here. Thanks to the large thermal conductivities of the metals involved, storing and retrieving energy into/out of the PCM is not an impediment. Potential interaction of PCM with encapsulation materials and their impact on storage capabilities are also discussed. Lastly the cost estimates ($/kWhth) of these large thermal storage systems based on procedures used by NREL are presented. Though zinc based EPCM storage systems can be expensive at around $54/kWhth, they are more economical than the current two-tank storage systems that use sensible heat only for thermal energy storage.
Predicting the Properties of Nanostructured Metamaterials: Vertically Aligned Single-Walled Carbon Nanotube Arrays
Authors: Sisto A. , Ruan X. , Fisher T. S. , Neaton J. B.
Published: August 2012

Recent advances in nanofabrication technology have facilitated the development of single-walled carbon nanotube (SWCNT) arrays with long-range order across macroscopic dimensions. However, an accurate generalized method of modeling these systems has yet to be realized. A multiscale computational approach combining first principles methods based on density functional theory (DFT) and extensions thereof to account for excited electron states, and classical electrodynamics simulations is described and applied to calculations of the optical properties of macroscopic SWCNT arrays. The first-principles approach includes the use of the GW and Bethe-Saltpeter methods, and the accuracy of these approximations is assessed through evaluation of the absorption spectra of individual SWCNTs. The fundamental mechanisms for the unique characteristics of extremely low reflectivity and high absorptance in the near IR are delineated. Furthermore, opportunities to tune the optical properties of the macroscopic array are explored.
Carbon Management Microfluidics
Authors: Fadaei Hossein , Sell Andrew , Sinton D.
Published: August 2012

In this paper we describe our current work in studying the fundamental transport properties of carbon dioxide and geological reservoir fluids using microfluidic systems. Small scale analysis systems are well suited to determining the transport parameters that govern much larger scale processes, such as enhanced oil recovery and carbon geosequestration.
Electron Beam Characterization via Infrared Pyrometry of Thin Tungsten Foil
Authors: Marquard Kirk , Robinson Vance , Zhang Xi
Published: August 2012

A method is explored for characterizing the energy distribution of an electron beam in vacuum. A thin (125 μm) tungsten foil intercepts the beam causing its temperature to rise. An infrared camera images the opposite side of the foil to map the temperature distribution. To the extent the thermal conduction can be neglected, the temperature distribution serves as a representation of the energy distribution of the incident electron beam. Design of experiments (DOE) methodology is used to develop an equation for predicting the shape of the temperature distribution based on the potential of a single electrostatic lens (−1000 V to 0 V) and that of the tungsten foil (0 V to 2000 V). An assessment of this technique’s utility for future electron beam characterization experiments is included.
Preliminary Studies of Stand-Alone Lance Concepts for Nanoinjection of DNA
Authors: Fernelius Mark H. , Toone Nathan C. , Jensen Brian D. , Burnett Sandra H. , Howell Larry L.
Published: August 2012

Nanoinjection is an innovative approach for the electromechanical injection of DNA into cells, in which DNA is electrically attracted to a lance, inserted into a cell, and repelled by reversing the electrical polarity. In previous work, the lance has been micromachined as part of an on-chip microelectromechanical system. This work investigates a Stand-Alone Lance concept, where the lance and other components are independent of a common substrate. The Stand-Alone Lance may make nanoinjection more accessible to researchers and be more compatible with lab equipment commonly available in transgenic facilities. Required parameters for the electrode are investigated using a mathematical computer model. Different materials and fabrication processes for the metal lance are also considered. Additional testing was performed using tungsten probes, including mock injections on mouse egg cells. Based upon the optimistic cell viability rate, it is recommended to further investigate the use of the Stand-Alone Lance to perform nanoinjections.
Wave Propagation in One-Dimensional Structure of Periodic Inelasticity Composites
Authors: Navarro Helio Aparecido , de Souza Braun Meire Pereira
Published: August 2012

This study involves the analysis of elastic-plastic-damage dynamics of one-dimensional structures comprising of periodic materials. These structures are composed by multilayer unit cells with different materials. The dynamical characteristics of the composite material present distinct frequency ranges where wave propagation is blocked. The steady-state forced analyses are conducted on a structure constructed from a periodic inelasticity material. The material models have a linear dependence for elasticity problems and non-linear for elastoplasticity-damage problems. This paper discusses the pass and stop-band dispersive behavior of material models on temporal and spatial domains. For this purpose, some structural problems are composed of periodic and damping materials for analysis of vibration suppression have been simulated. This work brings a formulation of Galerkin method for one-dimensional elastic-plastic-damage problems. A time-stepping algorithm for non-linear dynamics is also presented. Numerical treatment of the constitutive models is developed by the use of return-mapping algorithm. For spatial discretization the standard finite element method is used. The procedure proposed in this work can be extended to multidimensional problems, analysis of strain localization, and for others material models.
Novel Power Electronics Overload and Temperature Rise and Time Interval Prediction Based on Dynamic Thermal Modeling
Authors: Dutta Sumit , Karimi Moghaddam Giti , Bhattacharya Subhashish , Gould Richard
Published: August 2012

In this digest an overload predicting algorithm is proposed based on the converter operating point and the thermal model of a 6.5 KV Silicon IGBT module. This algorithm can predict both the overload and the time interval for overload and hence can be used for thermal cycle performance evaluation for converters.
Vibrational Contribution to Thermal Conductivity of Silicon Near Solid-Liquid Transition
Authors: Baker Christopher H. , Wu Chengping , Salaway Richard N. , Zhigilei Leonid V. , Norris Pamela M.
Published: August 2012

Although thermal transport in silicon is dominated by phonons in the solid state, electrons also participate as the system approaches, and exceeds, its melting point. Thus, the contribution from both phonons and electrons must be considered in any model for the thermal conductivity, k, of silicon near the melting point. In this paper, equilibrium molecular dynamics simulations measure the vibration mediated thermal conductivity in Stillinger-Weber silicon at temperatures ranging from 1400 to 2000 K — encompassing the solid-liquid phase transition. Non-equilibrium molecular dynamics is also employed as a confirmatory study. The electron contribution may then be estimated by comparing these results to experimental measurements of k. The resulting relationship may provide a guide for the modeling of heat transport under conditions realized in high temperature applications, such as laser irradiation or rapid thermal processing of silicon substrates.
Tractor Run Over: History and Design Considerations
Authors: Sevart Kevin B.
Published: August 2012

This paper will present a brief history of accidents in which a person was run over by an agricultural tractor, without an operator present at the controls. Circumstances which are common in these accidents will be described. Design considerations intended to prevent or reduce injuries and deaths associated with tractor run over will also be described.
Towards a System Analysis and Integration Framework for Early Design Trades in Sustainable Building Design
Authors: Piacenza Joseph , Tumer Irem Y. , Stone Robert B. , Knighton Jeffrey , Elzeyadi Ihab
Published: August 2012

The design and implementation of net-zero energy and water commercial buildings is a high-performance alternative to traditional structures. The complexity of engineering and architectural design strategies required to achieve post-construction net-zero standing requires an integrated design approach, utilizing an array of novel sustainable building design technologies. Here, we document the schematic design timeline of the Oregon Sustainability Center (OSC), a 150,000 ft2 net-zero energy commercial “smart” building slated for construction in Portland, Oregon. The design of the OSC is constrained around guidelines described in the Living Building Challenge (LBC), a building standard for sustainable, net-zero energy and water design in modern construction. This paper identifies the primary OSC design considerations, mechanical subsystems required to achieve these goals, as well the various stakeholders associated with the project. A correlation between stakeholder influences on design decisions is mapped demonstrating the relevance of peripheral effects on the design process. The intent of this case study documentation is to work toward an integrated approach to sustainable building design based on the goal of making critical design decisions strategically during the design process, conserving both financial and temporal resources. An integrated design framework for net-zero energy and water subsystems will assist in creating replicable sustainable building designs.
Numerical Investigation of Transient Marangoni Effects on Weld Pool Dynamics in Gas Tungsten Arc Welding of Stainless Steel
Authors: Sen Debamoy , Ball Kenneth S. , Pierson Mark A.
Published: August 2012

In this study, the fluid flow, heat transfer, and phase change occurring during the Gas Tungsten Arc (GTA) welding of stainless steel are numerically analyzed. Of all the driving forces involved during GTA welding, the Marangoni convection due to surface tension gradient is the most dominant. The amount of surfactant present in the metal strongly influences the strength, location, and direction of the Marangoni convection. Limited work has been done in the study of transient Marangoni convection behavior in the regime where a significant amount of surfactant is present, and depending on the thermal distribution in the molten metal pool, the surface tension gradient undergoes inflection, resulting in a flow reversal. The present investigation aims to address the complex relationship among the flow reversal, surfactant activity, and thermal pattern in the weld pool.