bluuebunny/crossref_metadata_2025 huggingface dataset:
Global Occupational Hazard: Silica Dust
Authors: Cooper Jennifer
Published: October 2013

One of the oldest industrial diseases, silicosis, results from exposures to respirable crystalline silica, also known as silica dust. Workers worldwide exposed to silica dust span a variety of industries from construction, mining, sandblasting, to masonry, and machinery. In the United States alone 1.7 million workers are exposed to crystalline silica, which can also lead to lung cancer, tuberculosis, and other chronic airway diseases [1].

This paper will examine the health effects of silica dust on the worker, discussing exposure paths, work groups affected, occupational safety measures, worker health policies, and compare these among the developed and developing world. Implementing worker safety programs, which include wearing Personal Protective Equipment (PPE) and health monitoring and developing exposure limits, can help mitigate the adverse health risks of working with silica dust. A comparison of the successes and limitations of several programs from around the world will show that strong national occupational safety programs can reduce the mortality and illness rates of silicosis due to occupational silica dust exposure.

Without a strong national occupational safety program history shows that workers will remain unprotected until they rally together under tragedy to fight for safety. Before more workers suffer and die tragically and unnecessarily, global safety policy makers can take a lesson from history, examine and compare current programs, and implement strong national occupational safety programs that save lives.
Fabrication and Thermal Conductivity Characterization of Polyetherimide Nanofoam
Authors: Sundarram Sriharsha S. , Jiang Wei , Li Wei
Published: October 2013

A number of analytical models exist to predict the thermal conductivity of foams; however, they do not consider the effect of pore size on the effective thermal conductivity. It is speculated that foams with smaller pore sizes would have much lower thermal conductivity owing to the Knudsen effect. This study aims at fabricating polymer nanofoams with pore sizes on the level of nanometers and to characterize their thermal conductivity. Polyetherimide (PEI) foams were fabricated using solid state foaming. Process parameters such as saturation pressure and duration, desorption time and foaming temperature were varied to obtain foams with pore sizes ranging from a few hundred nanometers to two microns. The microstructures of the samples were characterized using scanning electron microscopy. Throughout the cross section of the foams, there exist regions with varying pore size and porosity. The effective porosity and thermal conductivity of the individual regions were determined based on a series model for effective thermal conductivity. It is confirmed that as the pore size is reduced while maintaining a fixed porosity, the thermal conductivity also decreases.
Effect of Controlled Rate Freezing on the Microstructural Properties of Poly (L-lactic Acid) Scaffolds
Authors: Chinnasami Harish , Idicula George , Hayes Daniel , Devireddy Ram
Published: October 2013

Bio-degradable poly (l-lactic acid) (PLLA) scaffolds were prepared by using thermally induced phase separation (TIPS) method. A solution of PLLA-Dioxane was formed by dissolving PLLA in dehydrated 1,4-Dioxane at three wt/vol percentages, specifically 3, 7 and 10%. This PLLA-Dioxane solution was then frozen in borosilicate glass vials (5mL) at three cooling rates (1, 10 and 40 °C/min) in a commercially available controlled rate freezer (CRF). The frozen solution was freeze-dried to sublimate the dioxane. The microstructural properties of the resulting PLLA scaffolds were determined utilizing Scanning Electron Microscopy (SEM) images and uniaxial compressive testing. The relationship between the wt/vol ratio of PLLA and Dioxane and the imposed cooling rates on the structural properties of PLLA scaffolds was determined.
Ceiling-Mounted Fresh Air Personalized Ventilator System for Occupant-Controlled Microenvironment
Authors: Makhoul Alain , Ghali Kamel , Ghaddar Nesreen
Published: October 2013

The aim of this work is to develop an effective coaxial personalized ventilator nozzle as add-on to ceiling diffuser to localize the air conditioning and fresh air needs of occupants in a space. The ceiling diffusers supply the space with circulated conditioned return air while the personalized coaxial ventilators supply fresh air directly to the breathing zone of occupants. The coaxial nozzle minimizes air entrainment between the fresh air stream and the space contaminated air and allows the effective delivery of fresh air from a substantial distance with lower amounts than what is required by ASHRAE standards. A detailed 3D CFD model was developed and used to optimize the nozzles dimensions and outlet flow characteristics. The CFD model numerical findings were then validated against experimental data where flow field measurements involving the flow rate and air quality were taken. The proposed air delivery system (coaxial personalized ventilator and angled ceiling diffuser) has substantially reduced air conditioning system energy consumption (up to 28%) when it was compared with conventional overhead mixing systems. Meanwhile, it permitted to obtain equivalent thermal comfort conditions and achieve higher breathing air quality (45% ventilation effectiveness at 10 L/s.person fresh air flow rate) compared to conventional mixed air systems with the privilege of the occupant being able to control his own microclimate.
Effect of Altitude and Temperature on Volume Control of an Hydrogen Airship
Authors: Dumas Antonio , Trancossi Michele , Madonia Mauro
Published: October 2013

This paper analyses the model of volume control of an innovative stratospheric airship concept designed to use hydrogen as a buoyant gas. This paper presents a mathematical model which allows modelling the airship volume changes with altitude. CFD evaluation at different altitudes has been performed. CIRA and Standard Atmosphere models have been compared.
Exergetic Analysis of a Maisotsenko-Process-Enhanced Cooling Tower
Authors: Morosuk T. , Tsatsaronis G. , Maisotsenko V. , Kozlov A.
Published: October 2013

The Maisotsenko-process (M-process or M-cycle) is a complex process associated with humid air. Heat transfer and evaporative cooling occur in a unique indirect evaporative cooler resulting in product temperatures that approach the dew point temperature. This process utilizes the enthalpy difference between air at its dew point temperature, and air saturated at a higher temperature. This enthalpy difference is used to reject heat from the air stream with the high temperature. The different applications of the M-process contribute to effective energy savings. The M-process technology was realized initially in the year 1984. By enhancing cooling towers with the M-process it is possible to (a) cool water to dew point temperature; (b) reduce pressure drop and required fan power, and (c) modify existing cooling towers to substantially decrease cooled water temperature. An exergetic analysis identifies the real thermodynamic inefficiencies and the potential of improvement for the M-process. This paper demonstrates the detailed exergetic analysis of the M-process with separate consideration of the thermal and mechanical exergies (as two parts of the physical exergy) and the chemical exergy.
Modeling the Mechanics of Crystallizable Shape Memory Polymers With Two Crystallizing Phases for Crystallization Under Constant Strain
Authors: Moon Swapnil , Rao I. Joga
Published: October 2013

Shape Memory Polymers are a promising class of smart materials with applications ranging from biomedical devices to aerospace technology. SMPs have a capacity to retain complex temporary shapes involving large deformations and revert back to their original shape when triggered by external stimuli such as heat. Crystallizable SMPs are a subclass of SMPs where the transient shape is retained by formation of a crystalline phase and return to the original shape is due to melting of this crystalline phase [1]. Recently CSMPs with multiphase polymer networks containing two different crystallizable segments have been reported which have the capability to switch between three shapes when stimulated by changes in temperature [2,4]. These properties open up many new possibilities for applications. Our research is focused upon modeling the mechanics associated with these CSMPs. The model is developed using a framework based upon theory of multiple natural configurations [3]. The developed model is then used to simulate results for typical boundary value problems.
Integration of Carbon Fiber Composite Materials Into Air-Cooled Reciprocating Piston Engines for UAV Applications
Authors: Trunzo Mark , Schubbe Joel , Graham Stephen M. , Caton Patrick
Published: October 2013

The United States Navy (USN) has shown an interest in the development of small displacement, reciprocating piston diesel engines for Unmanned Aerial Vehicles (UAVs). These engines avoid the logistic challenges of relying on gasoline-fueled UAVs, and have relatively low fuel consumption, but suffer from poor power-to-weight ratios. Reducing weight is of significant importance to UAVs to allow sufficient range and loitering times. Carbon fiber composites offer strength-to-weight benefits over the metal components currently used in piston engines. However, composite components have more restrictive operating temperatures. None of the known previous efforts aimed at integration of composites into engines has focused on air-cooled engines and on their potential benefits for UAVs. A small, single-cylinder air-cooled gasoline engine was chosen as a convenient test platform and surrogate for an air-cooled UAV engine. The crankcase and connecting rod from this engine were redesigned using a high fraction of carbon fiber in order to reduce weight. To develop the designs, steady-state temperature profiles were measured both internally and externally. The steady state temperatures for the crankcase ranged between 93°C and 124°C while the connecting rod ranged roughly between 120°C and 160°C. Carbon fiber composite test specimens were tested for strength at a comparable range of temperatures to demonstrate thermal viability. The tensile and compressive tests showed the carbon fiber to be comparable to all aluminum material properties, if not better. Stress was modeled on the stock engine at the worst-case operating condition and used to design the composite crankcase and connecting rod to ensure sufficient strength to survive at this extreme condition. The modeled stresses resulted in a factor of safety of 1.5 for the connecting rod and 3.8 for the crankcase, although internal adhesion of bearing surfaces to fiber was noted as a problem for the connecting rod in the initial prototype, and ultimately led to premature failure. These composite components were integrated and tested, for various lengths of time, on the engine and indicate a potential weight savings of approximately 80% for the crankcase and 26% for the connecting rod. The composite case failed after approximately 20 minutes (O(104) cycles) of operation at the best torque condition (worst-case in terms of mechanical stress) due to manufacturing deficiency at the corners and base; the connecting rod failed after approximately 2 minutes (O(103) cycles) of worst-case operation due to separation of the bearing surface from fiber. Both sets of failures point to simple remedies for follow-on work. The initial prototypes resulted in an overall weight savings of 8.1%. Using commercially available data for small propeller-driven aircraft, this weight savings could be expected to result in a similar relative improvement in aircraft range.
Linear Heat Conduction Equation Based Filtering Iteration for Topology Optimization
Authors: Zhao Qing-hai , Chen Xiao-kai , Lin Yi , Ma Zheng-Dong
Published: October 2013

This paper deals with an alternative approach to density and sensitivity filtering based on the solution of the linear heat conduction equation which is proposed for eliminating checkerboard patterns and mesh dependence in topology optimization problems. In order to guarantee the existence, uniqueness and stability of the solution of PDE, Neumann boundary conditions are introduced. With the help of the existing computational framework of FEM, boundary points have been extended to satisfy Neumann boundary conditions, and together with finite difference method to solve this initial boundary value. In order to guarantee the stability, stability factor is introduced to control the deviation for the solution of the finite difference method. Then the filtering technique is directly applied to the design variables and the design sensitivities, respectively. Especially, different from previous methods based on convolution operation, filtering iteration is employed to ensure the function to eliminate numerical instability. When the value of stability factor is changed at setting range, the number of times of filtering is manually corresponding set. At last, using different test examples in 2D show the advantage and effectiveness of filtering iteration of the new filter method in compared with previous filter method.
In-Situ Resistance Coefficient Curve and Experimental Analysis of a Virtual Chilled Water Flow Meter at Air Handling Unit Level
Authors: Song Li , Wang Gang , Swamy Atul , Shim Gyujin
Published: October 2013

In this paper, a virtual Air handling unit (AHU) level water flow meter using a control valve as a measurement device is experimentally validated through two different sizes of control valves on cooling coils. The flow through the valve is indirectly calculated using in-situ valve resistance coefficient curve, differential pressure over both the valve and its associated coil and valve stem positions. It was concluded in previous studies that the in-situ valve resistance coefficient curve is critical for determining the accuracy of the virtual valve flow meter. In this paper, an experimental approach and a theoretical approach of obtaining the in-situ valve resistance coefficient curve are introduced and as a result, accuracy of the virtual valve flow meters, using two different sizes of control valves: a smaller valve with design water flow rate of 25GPM and a larger valve with design water flow rate of 300GPM, is compared with an ultrasonic meter. The comparison show less than 4% of error over the full measurement range.
Detailed Investigation on Rib Turbulated Flow Inside a Rectangular Duct
Authors: Ali Md. Shaukat , Tariq A. , Gandhi B. K.
Published: October 2013

Rib turbulators are the most intensively studied passive technique, which promotes near wall turbulence in the internal cooling passages of heat transfer devices. However, there exists the tradeoff between the pressure penalty and heat transfer enhancement. For suggesting a correct rib configuration for particular application, it is necessary to understand the flow mechanism behind rib tabulators. For this purpose an experimental setup has been designed to investigate the detailed flow field and corresponding effect on heat transfer characteristics using Particle Image Velocimetry and Liquid Crystal Thermography respectively. In the literature the detailed flow field investigation as well as the thermal characterizations behind the rib other than rectangular/square cross sectional shape is found to be limited. The present work is an experimental investigation inside a rectangular duct for flow behind the trapezoidal type of rib with changing angle at different Reynolds numbers. The emphasis is towards assessing the potential impact of varying chamfering angle over the flow structures and its subsequent effect on heat transfer enhancement as well as in obviating the hot spots in the vicinity behind the chamfered rib turbulators.
Multiple Grid and Multiple Time-Scale (MGMT) Simulations in Continuum Mechanics
Authors: Ruparel Tejas , Eskandarian Azim , Lee James
Published: October 2013

The work presented in this paper describes a general formulation for implementation of Multiple Grid and Multiple Time-scale (MGMT) simulations in continuum mechanics. Using this method one can solve problems in structural dynamics in which the domain under consideration can be selectively discretized (spatially and temporally) in critical and remote regions, hence allowing the user to obtain a desired level of accuracy and save computational time. The formulation is based upon the fundamental principles of Domain Decomposition Methods (DDM) used to obtain the semi-discrete equation of motion for coupled sub-domains augmented with interface energy. Lagrange Multipliers, based on Schur’s dual formulation, are used to enforce interface conditions since they not only ensure energy balance but also enforce continuity of kinematic quantities across the interface. The Finite Element Tearing and Interconnecting (FETI) based Multi Time-step (MTS) coupling algorithm proposed by Prakash and Hjelmstad [1] is then used to obtain the evolution of unknown quantities in respective sub-domains using different time-steps and/or different variants of the Newmark Implicit Method. Our work is in the direction of coupling this MTS algorithm with multiple grid discretizations in respective subdomains. We propose using coarse grid discretization to define the mortar space between non-conforming sub-domains and show that this particular choice when combined with the implicit integration scheme yields a stable algorithm for MGMT simulations.

The formulation is implemented, comprehensively, using Finite Element Methods and programming in FORTRAN 90. Several scenarios with different mesh densities and time-steps are evaluated to analyze the efficiency of MGMT simulations. The purpose of this paper is to study and evaluate its accuracy and stability by looking at evolution and distribution of quantities across the connecting interface. Results show that the interface coupling for non-conforming sub-domains with distinct integration time-steps can be efficiently modeled using this approach.
Operational Characteristic of Planar Steam Reformer Thermally Coupled With Catalytic Burner
Authors: Lee Kanghun , Yu Sangseok , Kang Sang gyu , Ahn Kook Young , Lee Sang Min
Published: October 2013

High efficiency reforming is a key parameter of high temperature stationary fuel cell system. In this study, a planar heat exchanger steam reformer (PHESR) was integrated with catalytic combustor in order that the unused energy of anode off-gas is delivered for heat of reforming. The PHESR was designed to use the anode-off gas of externally reformed SOFC system because it has an efficiency problem. In the PHESR reactor, the heat is transferred from catalytic burner to reformer that has weak gradient of temperature difference between two reactors.

The thermal behaviors of exothermic and endothermic reactions between reactors were investigated experimentally. The parameters of investigation were fuel utilization, inlet temperature, and air excess ratio. Comparison parameter was volume fraction of hydrogen at the exit of reforming side. The temperature gradients in longitudinal direction of two reactors were measured. As expected, temperature differences between two reactors were crucial factors that required optimization. Furthermore, the geometric aspects between the finned and un-finned reactors were also investigated. The results demonstrate that the volume fraction of hydrogen at the exit is closely coupled with the geometric constraints and the operating parameters.
The Effect of Cell-Phone User on Driver Attention
Authors: Yang Cheng-Ken , Langari Reza
Published: October 2013

Driving safety is increasingly a major issue in transportation systems. One of major culprits in this respect is driver distraction or inattention. Driving inattention, which can be caused by drowsiness as well as the use of devices such as cell-phones while driving increases crash/near-crash risk [1]. In fact among all causes of distraction, cell phone driving continues to be a major issue that impacts transportation safety since this is a matter that can be regulated through policy decisions. The empirical evidence in this regard continues to underline the gravity of the situation. In 2009, there were 5474 people (or approximately 12% of all traffic fatalities) killed by distracted drivers, and 995 of them were considered to have been killed by those drivers who were using cell phone during driving [2].

This paper considers the relation between driving safety and cell-phone using. We propose a way to estimate drivers’ attention by measuring their electroencepholography (EEG) signal to estimate the inattention index.
Molecular Dynamics Study of Anatase TiO2 Nanoparticles in Water and Vacuum Environments
Authors: Okeke George , Hammond Robert B. , Antony S. Joseph
Published: October 2013

Nanoparticles are nanometer sized metallic oxides which possess enhanced properties that are desirable to a wide range of industries. In this study, we investigate structural and surface properties of anatase TiO2 nanoparticles in vacuum and water environments using molecular dynamics simulations. The particle sizes ranged from 2 to 6 nm and simulations were performed at 300 K. Surface energy of the particles in vacuum was seen to be higher than that of the particles in water by about 100% for the smaller particles (i.e. 2 and 3nm) and about 60% for the larger particles (i.e. 4 to 6 nm). Surface energy of the particles in both environments, is seen to increase to a maximum (optimum value) as the particle size increases after which no further significant increase is observed. In vacuum, studies carried out at temperatures ranging from 300–2500 K showed a high dependence of surface energy on temperature. The estimated surface tension of water is seen to agree quite well with that of experiments.
Increasing the Accuracy of Positive Displacement Meters for the Measurement of Volume in Liquid Hydrocarbon Logistics
Authors: García-Berrocal Agustín , Montalvo Cristina , Balbás Miguel , Blázquez Juan , De Lis Fernando
Published: October 2013

Accuracy in the liquid hydrocarbons custody transfer is mandatory because it has a great economic impact. By far the most accurate meter is the positive displacement (PD) meter. Increasing such an accuracy may adversely affect the cost of the custody transfer, unless simple models are developed in order to lower the cost, which is the purpose of this work. PD meter consists of a fixed volume rotating chamber. For each turn a pulse is counted, hence, the measured volume is the number of pulses times the volume of the chamber. It does not coincide with the real volume, so corrections have to be made. All the corrections are grouped by a meter factor. Among corrections highlights the slippage flow. By solving the Navier-Stokes equations one can find an analytical expression for this flow. It is neither easy nor cheap to apply straightforward the slippage correction; therefore we have made a simple model where slippage is regarded as a single parameter with dimension of time. The model has been tested for several PD meters. In our careful experiments, the meter factor grows with temperature at a constant pace of 8×10−5 °C−1. Be warned because the equipment manuals cite half of the pace.
Comparing Mentor and Mentee Perspectives in a Research-Based Undergraduate Mentoring Program
Authors: Tsai Janet Y. , Kotys-Schwartz Daria , Louie Beverly , Ferguson Virginia , Berg Alyssa
Published: October 2013

At the University of Colorado Boulder (CU), a research-based undergraduate mentoring program is now in its second year of implementation. The program, Your Own Undergraduate Research Experience (YOU’RE@CU) has three main goals: improve the retention rate of diverse groups in undergraduate engineering, build undergraduate interest in engineering research, and prepare graduate students to take on leadership roles in either academia or industry-based research careers. In YOU’RE@CU, undergraduate students are paired with a graduate mentor and work in the graduate student’s lab several hours a week. Undergraduate mentees enroll in a one-credit seminar course focusing on research and graduate school opportunities, and are assessed via pre- and post-surveys to gauge their excitement and interest in engineering. The undergraduates also respond to biweekly qualitative reflective questions while participating in the program. Graduate mentors complete several reflective questions about their experiences and are required to complete pre- and post-assessments.

Adopting a person-centered, case study approach, this paper focuses on two telling examples of research-based mentoring relationships in the YOU’RE@CU program. Given identical mentor training through YOU’RE@CU, two graduate students start the Spring 2012 semester by meeting with their mentees to launch a research project. By examining application, pre-survey, reflective questions, and post-survey responses from these four participants, the differences in the trajectory of the two paired mentoring relationships can be clearly seen over the course of one semester. This close examination of two disparate mentoring relationships is instructive in understanding the subtle details that create either a positive learning environment or an uncomfortable lab situation for young engineers, and assists program administrators in making improvements in subsequent years.
Thermodynamic Analysis of an Integrated Solar-Based Multi-Stage Flash Desalination System
Authors: Abueidda Diab W. , Gadalla Mohamed
Published: October 2013

Worldwide concern about the scarcity of global water resources is increasing day by day. In Gulf countries, most power plants are co-generation power desalting plants (CPDP) that generate electric energy and also produce fresh water through the desalination of seawater. Nowadays, renewable energy provides a viable solution to the scarcity of energy resources and an environmental friendly option of global economy. In this paper, thermodynamic analyses have been performed on an integrated solar-based multi-stage flash desalination/Rankine cycle system. The respective losses as well as the first-law and second-law efficiencies for the system have been evaluated. The first-law and second-law efficiencies of the solar field were found to be 61.70% and 31.74%, respectively. The solar thermal field is based on direct steam generation method. Moreover, the mass flow rate through the Rankine cycle has been optimized to produce the maximum power. The optimal mass flow rate through the Rankine cycle found to be 51 kg/s. Furthermore, this paper presents and investigates a model of distillation plant that can use the heat rejected from the condenser of the Rankine cycle. The model is analyzed and validated with other results gained from literature. It found that the highest exergy destruction through the distillation unit occurs within the stages of the MSF unit. The percentage of exergy destruction in the MSF stages was found to be 75.41% of the total exergy destruction in the distillation unit. Additionally, this study verifies that increasing number of MSF stages decreases the percentage of exergy destruction.
Inverse Derivation of Constants for the Constitutive Equation and Fatigue Model of Pb-Free Solder Joints Based on Experiment Results, Finite Element Simulation and Virtual Optimization Methodology
Authors: Xie Weidong , Ahmad Mudasir
Published: October 2013

Solder joint reliability of Pb-free ball grid array (BGA) components, one of the most commonly used microelectronic devices, is one of the major concerns in product development and qualification. Accelerated Thermal Cycling (ATC) testing, though very time consuming and costly, remains the most prevalent means to evaluate solder joint reliability under certain end-use conditions. Wherever the test results are not readily available, a fine-tuned and well-benchmarked modeling methodology is of significance in producing quick-turn judgments and risk assessments to expedite product development.

The two most critical elements in simulating solder joint reliability are 1) the solder constitutive equations, which describe the solder creep behavior under different working conditions, and 2) the fatigue model which ties the damage index from finite element modeling together with the experimental results. In this study, a novel approach has been explored in which the constants of the constitutive equation and fatigue model for Sn-based Pb-free solder joints were derived inversely based on ATC results of a ceramic BGA test vehicle. In order to cover the typical end-use conditions of the targeted products, the test vehicle was assembled onto PCBs with two different thicknesses and then thermal cycled under three different temperature profiles. The basic idea was that all of the constants, both for the constitutive equation and the fatigue life prediction model, were initially given as a range. Then by utilizing modeFrontier®, a multi-objective optimization software, the finite-element model was coupled with the virtual optimization algorithm to derive simultaneously all the constants that yielded the best fatigue life predictions compared to the test results. To simplify the problem without compromising the generality, a hyperbolic sine creep constitutive equation and Coffin-Manson fatigue model were selected in the analysis. There were a total of 6 constants to be determined; the initial ranges of the constants were defined by fitting the creep experimental data for a variety of Sn-based solder materials. Available in other publications, the selected solder materials cover a wide range of both Ag and Cu content which therefore represent the typical behavior of the most commonly adopted solder materials by the industry. To reduce the computational cost and enable fast convergence of multiple-generation iterations required by the multiple objective optimization algorithms, a very-well benchmarked submodel has been employed. Furthermore, by utilizing ANSYS® high performance computing (HPC) capability and cloud computing, the computational time was reduced significantly. An overall good correlation was achieved between the fatigue life prediction using the constants derived by this approach and the test characteristic life.
Small Wind Turbine Tower Structural Vibration
Authors: Mollasalehi Ehsan , Wood David H. , Sun Qiao
Published: October 2013

A major barrier to the acceptance of small wind turbines is that they are perceived to be noisy particularly when mounted on monopole towers rather than traditional guy-wired ones. This paper discusses an aspect of noise propagation that has not been studied previously: vibration of the tower. To start studying the tower’s behavior, twenty four accelerometers were attached in two orthogonal lines along the 10 m tower of Southwest Windpower Skystream 2.4 kW wind turbine located at the edge of the city of Calgary. About 15 minutes of data were recorded in order to extract natural frequencies and corresponding mode shapes while the turbine was in operating. Operational modal analysis (OMA), in which input loads are considered the ambient input, is conducted to identify dominant modes up to 100 Hz. This range covers the infrasound region (<20 Hz) that might be perceived at sufficiently high sound pressure levels. The captured modal frequencies and modal shapes compared favorably to those predicted by a finite element analysis. Results indicate that a cluster of modes located around 10 Hz show significantly higher magnitude than other modes. This corresponds to the second bending mode. Short-time Fourier transform was used to distinguish natural and forced frequencies. It was seen that higher modes were exited less than lower ones. Original signals were decomposed using discrete wavelet transform to obtain different frequency bands. Relative root mean square values for each frequency band were calculated to determine the contribution to the vibration energy. It was observed that most of vibration energy occurs in the lowest frequency band which is in the infrasound region. The accelerometers were monitored while the blades and generator accelerated and decelerated as the wind speed changed, and only the first bending mode was excited significantly which apparently generates most of noise emission.
Wind Flow Regime Around a 3 Dimensional Helical Structure
Authors: Rashidi Majid , Kadambi Jaikrishnan R. , Kerze David
Published: October 2013

A three dimensional heliacal structure is modeled as a wind deflecting structure in this work. The purpose of the structure is to increase the natural wind speed and direct the follow of the wind toward two columns of horizontal-axis rooftop-size wind turbines that are installed in the grooves of the helical structure, diametrically opposed to each other. Computational Fluid Dynamics (CFD) analyses were conducted to determine the influence of the helical structure on the wind speed reaching the turbines. A wind speed amplification coefficient was determined for a helical structure of 6.7 m outer diameter. The velocity profiles of the wind flow around the helical structure were determined under a postulated wind speed of 4.47 m/s. The flow was modeled as turbulent with a Reynolds Number of 2,052,167. Standard “k-ἐ” turbulent model with “near wall treatment” and “standard wall function” were adapted in all analysis. A “y+” value of 50 was held constant in all simulation. The grid-size effects on the accuracy of the results were examined. Convergence criterion was satisfied in each case. This study shows that the helical structure having an outer diameter of 6.7 m results in an average wind speed increase factor of 1.52.
Shape Stabilized Bio-Based PCMs Formed by Coaxial Electrospinning Technique
Authors: Hu Wen , Yu Xun
Published: October 2013

Shape stabilized phase change materials was successfully prepared by encapsulating natural soy wax into polyurethane nanofibers. Coaxial electrospinning technique was used in this study. The morphology of the composites were characterized through environmental scanning electron microscopy (ESEM), Transmission electron microscopy (TEM), the thermal behaviors of the composites were also investigated. The results indicated that coaxial electrospinning resulted in a uniform fiber morphology with a core-shell structure, and a homogeneous wax distribution throughout the core of the fibers. Thermal analysis results show that the enthalpy increase with wax content. The fibrous structures exhibited balanced thermal storage and releasing properties for thermo-regulating function. The thermal properties were unaltered after 100 heating-cooling cycles tests, demonstrating that the composite fibers had good thermal stability and reliability. Tensile tests also indicate that the presence of wax enhanced the modulus and lowered the tensile strain.
Experimental Observations on the Central Nervous System’s Governing Strategies on the Arm Reaching With Reduced Mobility
Authors: Moon Hyosang , Robson Nina P. , Langari Reza , Buchanan John J.
Published: October 2013

For the motion planning of a point–to–point reaching task with a healthy arm, the CNS tends to plan the shortest hand path between two task points with a bell–shaped velocity profile. If any kinematic or dynamic constraints are imposed on the arm, the CNS adapts to the changes by incorporating learning mechanism into the motion planning. This paper seeks to identify the modified motion planning strategies of the CNS when the elbow joint is constrained to move. We present an experimental protocol, where subjects perform point–to–point reaching tasks with a lightweight elbow brace to restrict the joint kinematics with a minimal effect on the arm dynamics. From the experimental observations, the human strategies on each aspect of motion planning (i.e. hand path geometry, speed of the motion, and the arm posture selection) are hypothesized. The hypothesized strategies are developed as models and compared with the experimental data. As a result, we found that the hand path follows the rhumb line on the constraint workspace while the speed profile preserves a bell–shape, which can be roughly approximated by the minimum jerk model. In addition, by comparing the joint contributions data with and without the elbow constraint, it is hypothesized that the CNS resolves the redundancy of the inverse kinematics problem by reducing the kinetic energy of the limbs.
Ultrasound Hyperthermia: Dose Estimation and Device Design
Authors: Gordon Danica , Thamire Chandrasekhar
Published: October 2013

As a cancer treatment modality, thermal ablation offers the advantages of being less invasive and posing fewer post-procedural complications compared to traditional cancer therapies. It involves destroying cancerous cells by subjecting them to the appropriate amount of heat dose. In the present study, high frequency ultrasound (US) ablation is theoretically examined for effectiveness as a treatment modality for intraluminal and extracorporeal cancer treatment. Objectives of this study are to 1) develop thermal-damage correlations for a variety of cancer cells and 2) design US treatment devices, based on thermal damage correlations developed, and treatment planning protocols. To achieve these goals, thermal damage information for different cell types is first determined from earlier studies or pilot experiments. Required US doses for specific tissues are determined next through numerical experiments. Device design and estimation of thermal coagulation contours is then performed by comparing temperature-history data against the thermal-damage data for a range of device parameters. Treatment protocols are finally developed based on the analysis of the results for a range of applicable device parameters. Results are presented in terms of correlations for the volume and location of ablated tissue corresponding to a range of operating parameter values.
The Inter-Laminar Fracture and Mechanical Behavior of Nano-Alumina Modified Glass Fiber/ Epoxy Composite
Authors: John Mathew , Prakash Raghu V. , Velmurugan Raman
Published: October 2013

This paper presents the effect of addition of nano-alumina particles on the fracture properties of glass fiber reinforced plastic (GFRP) composite laminates. Epoxy resin is the most commonly used polymer matrix for advanced composite materials in view of its ability to adhere to a wide variety of fillers; on curing, they provide excellent stiffness and dimensional stability. However the highly cross linked epoxy often behaves undesirably brittle, because, plastic deformation is constrained, leading to poor resistance to crack initiation and propagation. Hence it is necessary to improve the toughness without sacrificing the other important mechanical and thermal properties. In this work, glass-fiber-reinforced composite with nano-alumina modified epoxy matrix was successfully produced with a hand lay-up process and characterized by EDAX and XRD technique for its composition. The experimental results show that the composites exhibited improvements in inter-laminar toughness values (GIC and GIIC) along with improvements in other mechanical properties, especially in toughness related properties. The Mode-I interlaminar fracture toughness for 2 phr (per hundred gram resin) nano-alumina was 2.5 times higher than that of unfilled epoxy and the Mode-II inter-laminar fracture toughness improved by 37%. The significant increase in Mode-I fracture toughness and improvement in Mode II inter-laminar fracture toughness resulting from the nano-particle modification, indicates a pronounced increase in matrix toughness. Impact tests suggest that the energy absorption capability of the GFRP considerably improved with the addition of equi-axed nano-alumina particles with epoxy resin. The laminate and fracture surface morphology analysis was done to understand the fracture and toughening mechanisms behind these property changes. The bending characteristic such as ILSS and Flexural properties recorded the maximum improvements of 14% and 17% respectively for the laminate with nano-alumina modified epoxy. A significant improvement in flexural modulus of over 37% was noticed with respect to unmodified epoxy. The experimental results show that the tensile modulus exhibited 15% improvement compared to laminate without nano-alumina, while, a modest change was observed in the tensile strength.
On the Nonlinear Multi-Physics Dynamics of a Mechanical Oscillator Coupled to an Electro-Magnetic Circuit
Authors: Georgiou Ioannis T. , Romeo Francesco
Published: October 2013

The dynamics of a nonlinear electro-magneto-mechanical coupled system is addressed. Such a system exhibits a rich dynamic behavior arising from the involved quadratic nonlinearities that can be explored by relying on both analytical and numerical tools. It will be shown that the global multi-physics dynamic can be effectively handled to make the system functioning either as a sensor or an actuator for applications in the micro electromechanical context. Towards this goal, the roles played by the electro-magnetic and mechanical components in the resulting complex response, encompassing bifurcations as well as possible transitions from regular to chaotic motion, will be highlighted by means of Poincaré sections. Moreover, when the linear frequency of the circuit is larger than that of the mechanical oscillator, the dynamics exhibits slow and fast time scales. Therefore we analyze the mechanical oscillator forced (actuated) via harmonic voltage excitation of the electric circuit; when the forcing frequency is close to that of the mechanical oscillator, the long term dynamics are expected to evolve in a purely slow timescale, in the presence of dissipation, with no interaction with the fast time scale. We show this by assuming the existence of a slow invariant manifold, computing it analytically, and verifying its existence via numerical experiments on both full- and reduced-order systems.
Steam-Side Characterisation of a Modular Air-Cooled Condenser
Authors: O’Donovan A. , Grimes R. , Walsh E. J. , Moore J. , Reams N.
Published: October 2013

Diminishing fossil fuel reserves and a growing collective environmental awareness has led to the development of alternative methods of power generation such as Concentrated Solar Power (CSP). Although almost all existing CSP plants currently use water-cooled condensers, limited water supplies in the designated desert regions for such power plants, the high costs associated with providing cooling water and environmental considerations will all restrict the future use of water-cooled condensers. Air-cooled condensers (ACCs) are therefore proposed, despite evidence to suggest that they suffer from significant inefficiencies [1]. It has been suggested that a modular design, addressed in this paper, could offer solutions to issues with current ACC technologies. To fully characterise the modular ACC design it is necessary to quantify the steam-side characteristics. A series of tests were performed under vacuum conditions representative of an operational condenser. The condenser vacuum was measured for a series of incremental fan rotational speeds, to determine both the qualitative and quantitative relationship between fan speed and condenser pressure. Results indicate that for a given steam mass flow rate, the condenser pressure decreases with increasing fan rotational speed. Furthermore, the choice of vacuum pump, used to displace air leakages, was shown to have a significant influence on the steam-side response. Larger displacement-capacity vacuum pumps permit lower condenser pressures. The steam condensation pressure drop through the condenser tubes was also measured. Results for the measured pressure drop revealed a large level of momentum recovery, which is not uncommon in steam condensation processes. Experimental frictional pressure drops were determined and these compared favourably with certain two-phase frictional pressure drop correlations. In particular, the Lockhart & Martinelli correlation was found to be most capable of predicting the frictional pressure drop trends encountered during testing. The large level of agreement between the measurements and predictions provide confidence in future use of the Lockhart & Martinelli correlation to predict frictional pressure losses.
Modeling of Transport Phenomena in Gas Tungsten Arc Welding Arc
Authors: Yang X. , Hu J. , Pallis J.
Published: October 2013

This paper developed a mathematical model to simulate the transport phenomena in the arc plasma of a gas tungsten arc welding (GTAW) process. The arc model simulated the electromagnetic field in three regions — cathode, arc plasma, and anode; and heat transfer and fluid flow in the arc region. The temperature, velocity, pressure, current density and electromagnetic fields are explored in the arc plasma region to study the arc plasma characteristics. The distributions of heat flux, current density, arc pressure and plasma shear stress at the anode surface are obtained as boundary conditions for weld pool models. The predicted results are compared with published results. The developed arc model will be coupled with a weld pool model to study the interaction between arc plasma and weld pool.
Effects of Within Part Variation on Measurement System Analysis
Authors: Sahay Chittaranjan , Ghosh Suhash , Haja Mohideen Syed Mohammed
Published: October 2013

Inherent variation of the measurement system, part-to-part variation and variation arising due to the operator are considered to be the most common sources of variation in a measurement system analysis (MSA). Often errors due to within part variation are overlooked, or even worse, are assumed to be from the inherent variation of the measurement system. Understanding the sources of variation in a measurement system is important for all measurement applications. It becomes even more critical when the part used to evaluate a gage has a significant within part variation. This is an important source of measurement system error that the current procedures followed for MSA studies do not clearly or adequately address. The primary reason for this is a lack of awareness, and there are no clear guidelines on conducting a MSA study under these circumstances. A detailed analysis of the effects of within part variation on MSA is described in this paper. An improved method for conducting the MSA under these circumstances is also presented. This improved and more effective MSA takes all sources of variations into consideration.
Design of Experiments: An Integral Part of a Thermal/Fluids Laboratory Course
Authors: Leylegian John C. , Naraghi Mohammad H.
Published: October 2013

Laboratory courses can be, and are often used to provide practical demonstrations of physical phenomena studied in various lecture courses. At Manhattan College, a senior-level Thermal-Fluids Laboratory incorporates a Design of Experiments (DoE) component into the syllabus, in which students learn about development of a text matrix, construction of an experiment to fulfill that matrix, and statistical analyses to confirm hypotheses. This paper describes the entire course syllabus, the portions of the course relevant to DoE, and some of the experiments conducted in recent years.