bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Novel High Performance Lubricants
Authors: Matczak Leah , Smith Thomas W. , Schertzer Michael J. , Iglesias Patricia
Published: February 2017

This work will provide a method to characterize a variety of novel high performance lubricants. In particular, surface tension and evolution of the contact angle on a variety of surfaces over one hour were recorded. Contact angles were measured using a ramé-hart Goniometer. Surface tension is measured with the same device using the pendant drop method. Fluids studied here include: trihexyltetradecylphosphonium bis(trifluoromethyl-sulfonyl) amide ([THTDP][NTf2]), trihexyltetradecyl-phosphonium decanoate ([THTDP][Deca]), 1-ethyl-3-methyl imidazolium trifluorosulfonyl imide ([EMI][NTf2]), and 1-ethyl-3-methyl imidazolium trifluoromethanesulfonate ([EMI][FMS]). Contact angles were measured on the following surfaces: AISI 52100 stainless steel disks polished to 0.01–0.05 μm, Kapton, SU-8, Teflon, and glass slides. The resultant change in roughness on 52100 steel disks was measured to provide insight into the corrosive properties of each liquid.
Temporal Case-Based Reasoning for Personalized Hypertensive Treatment
Authors: Jalali Niloofar , Agboola Stephen , Jethwani Kamal , Zeid Ibrahim , Kamarthi Sagar
Published: February 2017

Most of the current problems can be solved by referring to the solutions of the previous problems. Case Based reasoning (CBR) is one of the methods that solves a problem by retrieving the similar problems from the past and adapting the solutions of the past problems to solve the new problem. Recent studies that apply CBR include time as a parameter to retrieve most effective solutions that vary with time. This approach is more helpful in healthcare area in which one needs to look at historical evidence to find an accurate diagnostic or treatment regime. Hence, in this study, a time-based CBR is applied to track the outcomes of the drug therapy on hypertensive patients and find the most effective drug as a prescription. Initially, episodes in each patient’s medical records are chronologically ordered such that the oldest episode is placed first in the episode sequence and the latest episode is placed the last. It is assumed that the first episode of each patient is the first instance of diagnose; so when a new patient comes for checkup, his/her state (health condition) is compared with the initial state of the past patients. Therefore, the retrieval process calculates the similarity between the new patient’s current state and the most similar patients at their first episodes in the patient records. Due to the diversity of therapies for matching patients, the best treatment couldn’t be determined without knowing the efficacy of the different treatments. Therefore, the subsequent episodes of matching patients are examined to find the best treatment for the new patient. This might even require using a combination of treatments from all matching patients to find a good treatment for the new patient.

After the treatment is defined for the first visit, the record of the new patient is stored in the library for future case retrieval. This method is a novel approach to personalized treatment of patients having chronic disease by tracking the medical records past patients over a long period of time.

The current approach for treating the hypertensive patients uses evidence-based guidelines for managing the disease. However, this approach is more general and doesn’t take into account all the patient characteristics such as lab results and physical examination parameters. In the current approach the similarity between patients can’t be leveraged; the change of the treatment regime is based only on the risk parameter. However, in this method several parameters are being checked for efficiency of the medication. In contrast, the proposed CBR-based method personalizes the treatment based on what worked well for similar patients.

In this paper, the clinical records of hypertensive patients are provided by a Boston based hospital. The preliminary results confirm that the proposed approach will give good recommendation for hypertension treatment.
A Reduced-Order Model for Annular Labyrinth Seals Based on Proper Orthogonal Decomposition
Authors: Jin Hanxiang , Untaroiu Alexandrina
Published: February 2017

Labyrinth seals are commonly used in pumps, compressors, and turbines to minimize the leakage of working fluid. They typically have a series of circular or rectangular shaped grooves designed to enhance the kinetic energy dissipation, consequently reducing the leakage rate. In this study a reduced order model is proposed for non-contacting annular labyrinth seals to describe leakage phenomenon and better understand the flow pattern as well as the energy distribution.

Both 2D and 3D reduced order models (ROM) were developed based on the transient CFD simulation results for a labyrinth seal with 20 rounded grooves circumferentially distributed. The matrix of cases analyzed consists of full order 2D and 3D models, as well as reduced order 2D and 3D models. The eigenvalues from the ROM matrix derived using Proper Orthogonal Decomposition (POD) and Snapshot techniques includes the relative energy of the flow field, however most of energy is related to only the very first few modes and corresponding eigenvalues.

The results show that 2D ROM models are more computationally efficient and can accurately reconstruct the flow field details. This method proves to have the ability to properly identify the flow characteristics, such as the recirculation flow pattern in the seal cavity.
Cooling of Concentrated Photovoltaic System Using Various Configurations of Phase-Change Material Heat Sink
Authors: Emam Mohamed , Ahmed Mahmoud , Ookawara Shinichi
Published: February 2017

In the current work, a hybrid system including Concentrated photovoltaic (CPV) and phase change material (PCM) as a heat sink is considered as a single module to achieve high solar conversion efficiency. The main objective is to accelerate the thermal dissipation with a longer thermal regulation period. Thus, a new CPV-PCM system using various configurations of the PCM heat sink and different combinations of PCMs is investigated. This study presents a numerical simulation of the effects of PCM materials and designs on the CPV-PCM system performance. To estimate the thermal performance of the new CPV-PCM system, a comprehensive 2-D model for CPV layers integrated with PCMs is developed. This model couples a thermal model for CPV layers and a thermo-fluid model that considers the phase-change phenomenon using the enthalpy method. The model is numerically simulated at different configurations and combinations of PCM with various ranges of phase transition temperatures. Three different configurations of PCMs are investigated: one with a single cavity, and two with parallel arrangements including three and five cavities. Results indicate that the use of PCM heat sinks with three and five cavities increases the heat transfer inside the PCM and achieves a significant reduction of the solar cell temperature compared with a single cavity CPV-PCM system. Furthermore, thermal regulation effect and temperature uniformity of the CPV-PCM system is enhanced by using various combinations of PCMs.
Small Arrays of Single Beam Laser Sensors as Effective LiDAR Obstacle Detection Systems for Autonomous Vehicles
Authors: Soloiu Valentin , Ibru Bernard , Beyerl Thomas
Published: February 2017

Ground vehicles with autonomous navigation require medium range external sensing for early obstacle detection and terrain mapping. Both are essential for path planning. The conventional method for accomplishing this is achieved by very complex and expensive LiDAR sensors with 32 to 64 individual lasers rotating rapidly and taking readings from the top of the vehicle. Our most pertinent research question however is to ascertain if a less cumbersome and cost effective setup of a small number of single beam laser rangefinder sensors can accomplish the same task. Our current method to achieve this is to sweep the sensors a variable number of steps along a predetermined angle. The information obtained is used to develop a complete and detailed view of the world around the autonomous vehicle.

This paper is focused on a small laser ranger finder attached to a programmable pan-tilt mount positioned at the front of the autonomous vehicle. These were chosen as they are the most viable type of sensors for this process due to low interference and also because long range accuracy data can be obtained with reasonable power consumption. The sensors and mount are connected to a microcontroller which gathers position and distance information of significant objects in the path of the vehicle, in polar coordinates. This information is then converted to more useful Cartesian coordinates and plotted on a point cloud which is then used for path planning in real time.

Future work will include sensor fusion of this system and an image sensor for detection of relevant objects such as traffic signs. Such systems establish a distance from the vehicle as well as distinguish them by shape and color.
Characterization of Bulk and Thin Film Fracture in Electronic Packaging
Authors: Subramanian Vijay , Alazar Tsgereda , Yazzie Kyle , Penmecha Bharat , Liu Pilin , Bai Yiqun , Malatkar Pramod
Published: February 2017

As semiconductor packaging technologies continues to scale, it drives the use of existing and new materials in thin layer form factors. Additionally, packaging technologies continue to increase in complexity such as multi-chip packages, 3D packaging, embedded dies/passives, and system in package. This increasing packaging complexity implies that materials in thin layers are subject to non-trivial loading conditions, which may exceed the toughness of the material, leading to cracks. Furthermore, the continued focus on cost leads to a growing interest in novel, low-cost materials. It is important to ensure that the reliability of these low-cost materials is at par or better than currently used materials. This in turn, leads to significant efforts in the area of material characterization at the lab level to speed up the development process. The chosen test methods must not only provide accurate and consistent data, but they must also be applicable across a suitably wide range of materials to aid in the optimization process.

Methods for testing and characterizing fracture induced failures in various material systems in electronic packaging are investigated in this paper. The learnings from the different tests methods are compared and discussed here. More specifically, different fracture characterization techniques on (a) freestanding ‘thin’ solder resist films, and (b) filled ‘bulk’ epoxy materials like underfills and epoxy mold compounds are investigated. For thin films, learnings from different test methods for measuring fracture toughness, namely, uniaxial tension (with and without an edge pre-crack) and membrane penetration tests, are discussed. The test methods are compared by characterizing several different thin films, to gauge how well each method could distinguish differences in material (and thickness). Reasonably good agreement was found between the various thin film toughness test methods; however, ease of sample preparation, fixture, and adaptability to environmental testing will be discussed. In the case of filled epoxy resin systems, the single-edge-notch bending (SENB) technique is utilized to obtain the fracture toughness of underfills and mold compounds with filler materials. Learnings on different methods of creating pre-cracks in SENB samples are also investigated and presented. Two methods are explored in this study, namely, razor blade and laser milling. Good agreement in fracture toughness values was obtained with the two precracking methods, along with considerations about ease of sample preparation and consistency of pre-crack dimensions also examined. Morphology of the pre-cracks obtained by these methods, and their effects on fracture toughness measurements, are also discussed.
The Behavior of Impurities During Producer Gas Implementation as Alternative Fuel in Steel Reheating Furnaces: A CFD and Thermo-Chemical Study
Authors: Saffari Pour M. , Andersson N. Å. I. , Ersson M. , Jonsson L. T. I. , Niska J. , Rensgard A. , Jönsson P. G.
Published: February 2017

The use of available and cheap industrial producer gases as alternative fuels for the steel reheating furnaces is an attractive topic for steel industry. The application of producer gases for such furnaces introduces not only the complicated combustion system of Low Calorific Value (LCV) gases, but also several impurities that could be problematic for the quality of final steel products. The quality of steel can be highly affected by the interaction of impurities with iron-oxides at hot slab surfaces. In this research, the combustion of producer gases and the behavior of impurities at the steel slab surface are studied by aid of a novel coupled computational fluid dynamics (CFD) and thermodynamics approach. The impurities are introduced as mineral ash particles with the particle size distributions of 15–100 μm. The CFD predicted data regarding the accumulation of ash particles are extracted from an interface layer at the flaring gas media around the steel slab surface. Later on, these predicted data are used for the thermo-chemical calculations regarding the formation of sticky solutions and stable phases at the steel slab surface. The results show that the particles are more likely follow the flow due to the high injection velocity of fuel (70 m/s) and the dominant inertial forces. More than 90 percent of particles have been evacuated through the exhaust pipes. The only 10 percent of remaining particles due to the high recirculation zones at the middle of furnace and the impinging effect of front walls tend to stick to the side wall of slab in the heating zone more than the soaking zone.
Design of an Efficient Catalytic Converter Using CFD Techniques
Authors: Warner Brent L. , Tegegne Ayele A. , Akbar Muhammad K.
Published: February 2017

This study presents the design of an efficient catalytic converter with increased flow rate and minimum pressure drop using Computational Fluid Dynamics (CFD) techniques. Automobile engines produce undesirable emissions during the combustion process, such as NOx, CO, and unburned hydrocarbons. In addition to these harmful gases, particulate matter, such as lead and soot, is created. As a countermeasure, automobiles are equipped with catalytic converters, which are designed to play a vital role in eradicating emissions. However, due to the catalyst and filler materials found inside the converters, an increase in backpressure develops which leads to an increase in fuel consumption. The gas must pass through a low-porosity substrate to increase the reaction rate, which was simulated using parametric geometry. In this study, parametric simulations of the fluid flow were conducted, utilizing CFD techniques, to determine the optimum parameters that would create a minimal pressure drop while maintaining a high chemical reaction rate.
Characterization of Materials Fabricated by Additive Manufacturing Method Using Line Focused Ultrasonic Transducer
Authors: Li Qiuyan , Zhang Xuande , Wang Yuxiang , Wang Qing-Ming
Published: February 2017

In this paper, we present our recent study on the characterization of the elastic properties of several metal alloys fabricated by additive manufacturing method using the line-focus ultrasonic transducer technique. Line-focused ultrasonic transducer has been used to measure leaky surface wave velocity based on the time-resolved defocusing method in recent years. Elastic properties of the materials can be calculated based on the velocities of leaky Rayleigh wave and longitudinal bulk wave, which are generated and detected by the ultrasonic transducer. In this work, a line focus ultrasonic testing system was constructed, using a PVDF thin film piezoelectric transducer, a computer controlled z-stage and a rotary stage, and data acquisition software for precision measurement of the propagation velocity of surface wave in the test materials. The transducer system was calibrated by testing the commercial stainless steel, aluminum, and copper. The surface roughness of the testing samples was measured to eliminate the possible effect on the surface wave velocity. Finally, the transducer system was used to characterize the elastic properties of specimens of nickel alloy and stainless steel which were built by additive manufacturing instruments. The results indicate good agreement with the data measured by traditional method.
Review and Comparison of Buckling Methodologies for ASME B&PV Code, Section III, Subsection NF Linear Piping Restraints
Authors: Nargund Shrikant , Williams Dennis K.
Published: February 2017

Piping supports and restrains are required to follow the design requirements as mentioned in ASME B&PV Code, Section III, Subsection NF. One of the requirements indicates the necessity of calculating the critical buckling stresses for the members that are subjected to a compressive loading. This paper discusses the prescribed requirements in the Code that specifically address the considerations of the stability and buckling load capacities of linear piping restraints (i.e., struts). The finite element modeling of various strut geometries and the results of the buckling analyses of a slender (slenderness ratio Kl/r greater than or equal to 100) structural members using various finite element solution techniques are presented herein. Specifically, three types of finite element analysis are conducted in an effort to define the critical buckling load for the subject structural member, and include the traditional linear (Eigen value) Euler method; the nonlinear, second order large deformation method; and finally, the nonlinear large deformation method that incorporates nonlinear elastic-plastic material behavior. These techniques are employed for a hollow cylindrical structural member (i.e., a strut assembly) with varying cross sections along its length. Finite element model consists of three dimensional hexahedral elements in combination with beam elements for the general purpose a finite element solver ANSYS. The critical buckling load is calculated in each case, thereby predicting the load at which instability will occur in the structural member. The results obtained from the aforementioned techniques are then compared both numerically and qualitatively with an appropriate explanation of the purpose and usefulness of each particular result with respect to the intent of the ASME B&PV Code, Section III, Subsection NF requirements. The results show significant variations (as expected) based on differences in the assumptions and techniques employed in the respective analyses.
Inkjet Printing of Carbon Nanotube-Polyimide Nanocomposite Strain Sensor
Authors: Li Qiuyan , Wang Qing-Ming
Published: February 2017

Inkjet printing has become a promising way to fabricate electrical mechanical devices and it has become a tool for rapid manufacturing technology. In this paper, the fabrication procedure and the characterization of the piezoresistive properties of Carbon nanotube (CNT) - Polyimide (PI) nanocomposites are presented. The suspensions of CNT-PI nanocomposites of five different CNT weight concentration based on the percolation threshold were fabricated, and the suspensions were then deposited on the polyimide substrate by a drop-on-demand piezoelectric inkjet printer. This makes it possible for the uniformity and geometry of the thin film to be highly controlled. Once the nanocomposites were fully cured, the strain sensors were ready for calibration. Under uniaxial tension, the strain and resistance change of the strain sensors were measured, and the gauge factors could be calculated. The temperature and humidity are two potential factors to effect the performance of the strain sensors. The temperature coefficients of the CNT-PI nanocomposites were measured and the temperature compensation methods were proposed. The humidity effect on the nanocomposites was also monitored, and a thin layer of Parylene-C was coated on the surface of the nanocomposites thin film and the effect of the coating was tested. In general, the inkjet printing technique was proved to be a convenient way to fabricate flexible nanocomposites thin film with uniform thickness and precise geometry control. The CNT-PI nanocomposite has good performance as piezoresistive strain sensor.
Uncertainty Analysis of Nondeterministic Multibody Systems
Authors: Sabet Sahand , Poursina Mohammad
Published: February 2017

This paper presents the method of polynomial chaos expansion (PCE) for the forward kinematic analysis of non-deterministic multibody systems. Kinematic analysis of both open-loop and closed-loop systems are presented. The PCE provides an efficient mathematical framework to introduce uncertainty to the system. This is accomplished by compactly projecting each stochastic response output and random input onto the space of appropriate independent orthogonal polynomial basis functions. This paper presents the detailed formulation of the kinematics of constrained multibody systems at the position, velocity, and acceleration levels in the PCE scheme. This analysis is performed by projecting the governing kinematic constraint equations of the system onto the space of appropriate polynomial base functions. Furthermore, forward kinematic analysis is conducted at the position, velocity, and acceleration levels for a non-deterministic four-bar mechanism with single and multiple uncertain parameters and a SCARA robot. Also, the convergence of the PCE and Monte Carlo methods is analyzed in this paper. Time efficiency and accuracy of the intrusive PCE approach are compared with the traditionally used Monte Carlo method. The results demonstrate the drastic increase in the computation time of Monte Carlo method when analyzing complex systems with a large number of uncertain parameters while the intrusive PCE provides better accuracy with much less computational complexity.
Entropy Generation for Forest Fire Propagation Prediction Through Preferential Direction Analysis
Authors: Guelpa Elisa , Verda Vittorio
Published: February 2017

Physical models of wildfires have been widely applied for evaluating the fire front evolution in order to obtain useful information for fire management. The main drawback in adopting such models for predicting fire propagation concerns the high computational resources that are required, especially when the analysis involves large areas or when multiple scenarios are investigated, e.g. for risk analysis purpose. This is mainly due to the complexity of phenomena involved and the necessity to use multi-dimensional approaches for the reconstruction of the fire front in the landscape. Complete two dimensional analyses can be avoided provided that possible preferential paths can be identified. Once this result is obtained, the analysis is reduced to one dimensional simulations, which can be made faster through the use of reduced models, such as POD models.

In this paper, an entropy generation analysis is proposed as approach to identify preferential paths for fire propagation analysis. The analysis of the effects due to wind and slope as well as the heat transfer mechanisms, including radiation, is performed. The different contributions to the local entropy generation rate are computed in a complex scenario and the areas involving minimum and maximum total amount of entropy generation are considered for evaluating the preferential directions.
Shellside Vacuum Condensation With a Noncondensable Gas
Authors: Ritchey Susan N.
Published: February 2017

Shell-and-tube vacuum condensers are present in many industrial applications such as chemical manufacturing, distillation, and power production [1–3]. They are often used because operating a condenser under vacuum pressures can increase the efficiency of energy conversion, which increases the overall plant efficiency and saves money. Typical operating pressures in the petrochemical industry span a wide range of values, from one atmosphere (101.3 kPa) down to a medium vacuum (1 kPa). The current shellside condensation methods used to predict heat transfer coefficients are based on data collected near or above atmospheric pressure, and the available literature on shellside vacuum condensation generally lacks experimental data. The accuracy of these methods in vacuum conditions well below atmospheric pressure has yet to be validated.

Recently, HTRI designed and constructed the Low Pressure Condensation Unit (LPCU) with a rectangular shellside test condenser. To date, heat transfer data have been collected in the LPCU for shellside condensation of a pure hydrocarbon and of a hydrocarbon with noncondensable gas at vacuum pressures ranging from 2.8 to 45 kPa (21 to 338 Torr). Traditional condensation literature methods underpredict the overall heat transfer coefficient by 20.8% ± 20.4% for the pure condensing fluid; whereas they overpredict heat transfer by 36.8% ± 40.0% with the addition of the noncondensable gas.

Over or under predicting the overall heat transfer coefficient in the presence of noncondensable gases leads to inefficient condenser designs and the inability to achieve desired process conditions. With the addition of the noncondensable gas, the measured heat exchanger duty was significantly reduced compared to the pure fluid, even at inlet mole fractions below 5%. In one case, a noncondensable inlet mole fraction of 0.63% was estimated to reduce the duty by approximately 10%.

Analysis of the acquired high-speed videos shows that the film thickness changes significantly from the top row to the bottom. The videos also display condensate drainage patterns and droplet interactions. The ripples and splashing of the condensate observed in the videos indicates that the Nusselt idealized model is not appropriate for analysis of a real condenser. This article presents the collected heat transfer data and high-speed images of shellside vacuum condensation flow patterns.
Numerical Investigation on Thermal and Fluid Dynamics Behaviors of the Exit Section Effect in Inclined Ventilated Roofs
Authors: Bianco Vincenzo , Buonomo Bernardo , Diana Alessandra , Manca Oronzio , Nardini Sergio
Published: February 2017

One of the most important requirements for building performance is energy saving and recovering and they are chased developing new strategies for the reduction of energy consumption, due to the heat flux transmitted through buildings envelopes. This work examines a prototypal ventilated roof numerically using a two-dimensional model in Ansys Fluent. Only a single flap of the roof is analyzed because its structure is geometrically and thermally symmetrical. The objective of this work is to study the thermal and fluid dynamic behaviors of a ventilated roof for different configurations of the exit section of the ventilated channel. The model is evaluated in air flow, considering a k-ε turbulence model to give the governing equations. Results are a function of an assigned heat flux on the top wall of the ventilation layer. They are analyzed studying temperature and air velocity distributions. The profiles of wall temperature and air velocity along the cross sections and longitudinal sections of the ventilated layer consider the different effects of the various geometric configurations. The results for different considering configuration detect that the ridge form and the outlet reservoir dimensions do not influence the thermal behavior inside the channel whereas a smaller outlet section determines higher wall temperature and lower air velocity in the channel.
Compressible 2D Flow Field Interaction of Two Contra-Rotating Blades
Authors: Barbely Natasha L. , Komerath Narayanan M.
Published: February 2017

The blades of coaxial, contra-rotating rotor systems cross each other in close proximity and at high relative speeds. This crossing event is a potential source of noise and severe blade loads. Effects of compressibility can aggravate the interaction and significantly alter the pressure field signature and phase relationships. A 2-D analysis of this phenomenon is performed by simulating two airfoils passing each other at specified speeds and vertical separation distances. Several test cases spanning a relevant range of Reynolds numbers, angles of attack, and relative Mach number are considered. The Mach number is varied to simulate the radial variation of velocity from the root to tip of a rotor blade to capture the pressure signature, lift, and drag of the airfoils. The velocity and pressure distributions on the airfoils, and in the space between the airfoils are computed before, at, and after airfoil crossing. The variations of lift and drag coefficients through the interaction are captured. The upper airfoil experiences an increase in lift followed by a very sharp drop in lift during the interaction. When relative Mach numbers are transonic, the region of interaction is greatly extended, with shock interactions occurring. The results show the complex nature of the aerodynamic and fluid dynamic impulses generated by blade-blade interactions, with implications to aeroelastic loads and aeroacoustic sources.
Study of Condensation Flow Patterns and Heat Transfer Characteristic on a Horizontal Tube Bundle
Authors: Gu Hongfang , Chen Qi , Zhang Zhe , Guo Haiyang
Published: February 2017

The numerous studies on condensation flow patterns and heat transfer were focused on the horizontal inside single tube. A number of heat and mass transfer correlations are used for design of shellside condensers based on tubeside condensation flow regimes. Due to a complex geometry and measurement difficulty in a tube bundle, there are few publications reported on shellside condensation flow regime and heat transfer characteristics. To investigate the condensation flow patterns and heat and mass transfer mechanism at the different flow regimes, a horizontal shellside condenser was tested from a multipurpose condensation rig recently. The horizontal test bundle is made of 36 tubes with the staggered tube layout. The tube OD is 19 mm and the tube length is 1.0 m using stainless steel. Four visualization windows were placed on the front and back sides on the shell for photographing condensation flow patterns. Steam and steam/air mixture were used as the test fluids. The condensation flow patterns, condensate film thickness and droplets distribution were recorded using a high-speed digital camera at a wide range of condensation process conditions. The experimental data show that the condensation flow regime changes from the shear-controlled flow to gravity-controlled flow depending on the vapor and condensate loads, bundle location and the concentration of the non-condensable gas. These experimental data provide a fundamental approach for developing the heat and mass transfer correlateons at different shellside condensation patterns. This paper presents the experimental result on shellside condensation patterns associated with heat transfer characteristics.
Development and Validation of an In-Situ Utility Pole Simulation Model for Virtual Modal Testing
Authors: Ferreira Pinto Plinio , Rideout Geoff
Published: February 2017

Modal testing is being investigated as a non-destructive test (NDT) method for wood poles. Modal properties of the pole must be extracted from sensor data containing frequency content associated with the interaction of the pole with its conductors. A dynamic model of a utility pole with attached conductors has been developed and validated through experimentation. The model will allow controlled, repeatable simulations of modal hammer hits for preliminary verification of pole property identification methods. The cable is modeled as a series of point masses connected by translational springs. The pole is represented by a modal expansion based on separation of variables. To facilitate creating and connecting the pole and cable models, scaling the model to represent longer pole lines, and introducing modal hammer inputs; the bond graph formalism was employed. To validate the model, an instrumented reduced-scale pole and cable system was built and tested in the laboratory. Time series measurements of cable tension and transverse motion, along with frequency-domain accelerometer data, show that the simulation model has sufficient fidelity to predict the effect of conductors on a pole’s response spectrum over the frequency range of interest.
Mechanisms for Kink Band Evolution in Polymer Matrix Composites: A Digital Image Correlation and Finite Element Study
Authors: Patel Jay , Peralta Pedro
Published: February 2017

Polymer matrix composites (PMCs) are attractive structural materials due to their high stiffness and low weight to strength ratio. However, unidirectional PMCs have low shear strength and failure can occur along kink bands that develop on compression due to plastic microbuckling that carry strains large enough to induce nonlinear matrix deformation. The study of kink band nucleation and evolution in unidirectional composites (UDCs) is an active area of research. In the last five decades, a large body of research has been done to understand kink band mechanisms using theory and experiments. However, a large fraction of the existing work is for uniaxial compression. The effects of stress gradients, such as those present during bending, have not been as well explored, and these effects are bound to make difference in terms of kink band nucleation and growth. Furthermore, reports on experimental measurements of strain fields leading to and developing inside these bands in the presence of stress gradients are also scarce. This need to be addressed to gain a full understanding of their behavior when UDCs are used under bending and other spatially complex stress states, particularly given that the compressive strength of these composites is a function of stress-gradient. Therefore, the primary focus of this work is to understand mechanisms for kink band evolution under an influence of stress-gradients induced during bending. Digital image correlation (DIC) is used to measure strains inside and around the kink bands during 3-point bending of samples with 0°/90° stacking made of Dyneema HB80, a trademark of DSM. Measurements indicate bands nucleate at the compression side and propagate into the sample carrying a mixture of large shear and normal strains, while also decreasing its bending stiffness. Failure was produced by a combination of plastic microbuckling and axial splitting. The microstructure of the kink bands was studied and used in a microstructurally explicit finite element model (FEM). It has been used to analyze stresses and strains at ply level in the samples during kink band evolution, using cohesive zone elements to represent the interfaces between plies. Cohesive element properties were deduced by a combination of delamination, fracture and three-point bending tests used to calibrate the FEMs. Modeling results show that progressive buckling of plies leads to kink band nucleation and propagation and that the band morphology is sensitive to the shear and opening properties of the interfaces between the plies.
Thermal Driven Dispersion of Smoke in a Parking Space
Authors: Teixeira José C. F. , Teixeira Senhorinha F. C. F. , Cunha Pedro , Silva Angela M.
Published: February 2017

Multi store parking spaces are complex buildings that pose specific problems to hazard management resulting from fire and pollutant release from the exhaust gases of automobiles. They are often characterized by large open spaces which do not prevent the spread of fire and smoke. The presence of large quantities of fuel just adds to the risk. In addition, the random occupancy of the space and existence of large openings make difficult the hazard containment. Structural details such as columns and beams can facilitate the accumulation of smoke in pockets. A combination of fire resistant doors and forced ventilation are the usual methods for smoke/fire mitigation.

The current legislation defines the acceptable limits for CO concentration for both continuous (50 ppm over 8 hours) and peak (200 ppm) conditions. If the parking space is above ground and has side openings, forced ventilation is not mandatory and it is acceptable that risk prevention and management can be dealt by natural ventilation only.

The commissioning of the space often requires that tests are carried out in which a smoke tracer is released into the space in order to evaluate its dispersion over time. This is performed at ambient temperature and the thermal effects on the plume are not taken into account resulting in a lower dispersion rate.

The objective of the present work is to evaluate the influence of the temperature of the release source into the smoke dispersion in a parking space. This is a large public space 113 m long, 76 m wide and 3 m in height. The computational model is implemented within the Ansys Fluent. In this, the continuity, momentum, energy and species equations are solved for the physical model which includes the building structural details and vehicles. The fluid is assumed as a mixture of CO, N2 and O2. The boundary conditions assume various conditions for the external wind through the side openings and the heat source is modeled as that resulting from the combustion of gasoline from an open fire. The time dependent variation of the heat load is assumed with a peak of 8 MW.

The results show that the temperature at the source promotes a stratification of the plume to the ceiling of the building leaving the occupied (lower) levels with a much clear atmosphere. Beams also facilitate the concentration of high levels of CO in isolated pockets. These proved to be stable while the atmosphere temperature remains high; subsequent cooling drives the smoke/pollutants to the power levels. Such behavior is also dependent upon the entrance of fresh air through the lateral openings.
Licensing Basis Event Selection Framework for Advanced Reactors
Authors: Holbrook Mark R. , Kinsey Jim C. , Moe Wayne L.
Published: February 2017

This paper describes key aspects of the risk-informed, performance-based licensing methodology as developed by the Department of Energy (DOE) for the Next Generation Nuclear Plant (NGNP) project. The discussion focuses on an event selection process using modular high temperature gas-cooled reactor (HTGR) design attributes and identifies how top-level regulatory criteria can be placed on a frequency-consequence curve. Preliminary Nuclear Regulatory Commission (NRC) staff evaluations concluded that the proposed approach is generally reasonable and responsive to the Commission’s Policy Statement on advanced reactors. However, the NRC deferred issuing any final assessments of the proposed approach due to other agency actions that were under consideration in response to the accident at Fukushima-Daiichi. In addition, important lessons learned during the NGNP prelicensing effort and their potential applications to alternative advanced reactor designs are presented.
Optimization Design of Anti-Dust Accumulation Centrifugal Fan Using Genetic Algorithm
Authors: Xiong Jin , Cui Haoyu , Li Jing-yin
Published: February 2017

Centrifugal fans are widely used in different fields. The working fluid with high concentration of dust or coal ash could result in accumulations of dust or ash on the surface of impellor. Consequently, the fan or process system often has to be shut down unplanned to clean the dust or ash, to prevent harmful vibration of the rotor. In this paper, the main accumulating positions of dust and ash in impellor were firstly summarized. Then, a model of dust particle adhesion force judgment was established on the basis of static force analysis. Base on the analysis result, the influences of blade angle and blade radii on the dust-accumulating positions were discussed, which conformed to practical observations. After that, there introduces a low flow rate fan which cannot even be used in practical applications due to its inferior dust anti-adhesion ability. For this case, an optimization design with eight control variables was proposed to improve its anti-adhesion ability and efficiency. After six generations of optimization, the optimized results were clustered to two domains. Therefore, the searching areas were limited down to two areas which are determined by using clustering method in order to speed up the optimization process. The results of the numerical simulation of the gas-solid two-phase flow based on discrete phase model (DPM) showed that the new fan can run stably for a long-term.
Graphene/Sulfur and Graphene Oxide/Sulfur Composite Cathodes for High Performance Li-S Batteries: A Molecular Dynamics Study
Authors: Dive Aniruddha , Gonzalez Ramiro , Banerjee Soumik
Published: February 2017

Lithium – sulfur (Li-S) battery, with theoretical capacity (∼1675 mAh/g) and energy density comparable to that of gasoline, is a promising technology meeting the demands of next-generation electric vehicles. However, the Li-S battery hasn’t been able to reach the theoretically predicted capacity due to several limitations, which include low electrical conductivity of pure sulfur cathode and loss of active material due to dissolution of intermediate polysulfides from the cathode during repetitive charge – discharge cycling referred commonly as “polysulfide shuttle”. Graphene/Graphene oxide (GO) are being explored as cathodes/cathode supports for Li-S batteries to alleviate these problems. We have employed molecular dynamics simulations to calculate the density distributions of polysulfides (S82−) in dimethoxy ethane (DME) – 2, 4 – dioxalane (DOL) electrolyte (1:1 v/v) in the vicinity of different graphene and GO structures, in order to study the impact of hydroxyl functional groups in GO on anchoring polysulfides. Density distribution of polysulfides provides valuable insight on the role of functional groups in successful anchoring of polysulfides onto the GO cathode supports structures.
Effects of Structure and Property Variations Within Hierarchal Biomineralized Composites Using Finite Element Methods
Authors: Nelms Matt , Livi Ken , Crawford Bryan , Rajendran A. M. , Hodo Wayne
Published: February 2017

Biological materials (biomaterials) have had a marked increase in interest from the material science and engineering community due to unique characteristics and properties that are typically sought after in traditional engineering materials. During the last few decades, research on biomineralized composites such as abalone shell, fish armor, turtle shell, and human bone revealed that those biological systems possess a carefully arranged multilayered composite structure. Unlike metals, ceramics, and traditional composite materials; biomineralized composites often possess enhanced characteristics such as, penetration resistance high toughness, flaw tolerance energy dissipation, damage mitigation, and delamination resistance all while achieving high strength-to-weight ratios. In this research experimentally driven finite element modeling was used to investigate the elastic response for the biocomposite structure. The Atractosteus spatula (Alligator gar) was used as the model structure for determining the elastic properties.
Mixed Convection Characteristic Inside a Thermal Cycling Chamber With Nonuniform Perforated Plate
Authors: Huang Y. Y. , Yang G. , Wu J. Y.
Published: February 2017

The steady-state flow field and temperature distribution inside a thermal cycling test chamber with nonuniform perforated plate are investigated both numerically and experimentally. Porous zones are set up by pressure loss analogy to simplify the perforated plate. Boussinesq approximation and low-Re model are used in the simulation. The numerical result shows both forced convection and natural convection contribute to the fluid flow and heat transfer. For uniform perforated plate, the temperature at the given height always increases from the center line to the walls. And from top to bottom of the cycling chamber, temperature increases around the center line while decreases near the walls. Based on that, two cases of nonuniform perforated plates with the same ratio of open area and different holes distribution are examined to improve the temperature uniformity in test chamber. The results show that both average temperature and standard temperature deviation are effected significantly by nonuniform perforated plate. The latter experiment is performed with the optimal perforated plate under the same condition of Re = 4.1 × 104, Gr = 1.8 × 1011. The experiment results are obtained by Constant Temperature Anemometry and agree with the numerical simulation.
Strain Sensing Using Hybrid Nanocomposite Membrane
Authors: Shang Wanru , Liu Yingtao
Published: February 2017

Damage and load sensing is rapidly advancing as driven by vast applications in aerospace and mechanical structures. Recently significant amount of efforts have been reported to develop new piezo-resistive strain sensor made from polymers with carbon nanoparticles, such as carbon nanotubes, carbon nanofibers, and graphene. These nanoparticles with advanced mechanical, electrical, and thermal properties are recognized as potential materials which can enhance mechanical performance and provide beneficial functionalities in polymers and composites. However, most previous research focused on the improvement of material properties for sensing applications. Limited work balanced the sensor design and material innovation for real time strain sensing. In this paper nanocomposite membranes are proposed to accurately measure local strain, especially for the strain sensing and health monitoring in composites. The micro-scale morphology and structures are first experimentally characterized. Both the fabrication process and the nanoparticle concentration are investigated to obtain the optimal sensing capabilities. The sensing function is achieved by correlating the piezoresistance variations to the stress or strain applied on the sensing area. Due to the conductive network formed and the tunneling resistance change in neighboring nanoparticles, the electrical resistance measured will show a clear correlation with the load conditions. The characterized membrane structures have the potential to be further applied to continuously monitor impact loads, especially focusing on low velocity barely visible damage in composites.