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Articles 421 - 450 of 15614

Full-Text Articles in Engineering

Assessment And Comparison Of Aviation Manufacturing Industries Throughout Mexico And Brazil, Omar E. Morsi, Kelly A. Whealan-George, Aaron D. Clevenger Aug 2018

Assessment And Comparison Of Aviation Manufacturing Industries Throughout Mexico And Brazil, Omar E. Morsi, Kelly A. Whealan-George, Aaron D. Clevenger

Aaron D. Clevenger

This literature review serves to provide insight and understanding in regards to the evolving aviation manufacturing industry throughout the globe and more specifically, Mexico and Brazil. Increased demand for aircraft units both in the commercial and private sectors have led to unprecedented expansions in aircraft manufacturing across the industry. In order to illuminate certain potentials and current growth levels of such industries, this review will delve into an array of information and specifications in regards to economic, political, and cultural influences throughout both Mexican and Brazilian markets respectively. In conclusion, the review will identify the transformation of an aviation manufacturing …

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Semi-Transparent Energy-Harvesting Solar Concentrator Windows Employing Infrared Transmission-Enhanced Glass And Large-Area Microstructured Diffractive Elements, Mikhail Vasiliev, Kamal Alameh, Mohsin Ali Badshah, Seok-Min Kim, Mohammad Nur-E-Alam Aug 2018

Semi-Transparent Energy-Harvesting Solar Concentrator Windows Employing Infrared Transmission-Enhanced Glass And Large-Area Microstructured Diffractive Elements, Mikhail Vasiliev, Kamal Alameh, Mohsin Ali Badshah, Seok-Min Kim, Mohammad Nur-E-Alam

Mikhail Vasiliev

We report on the study of energy-harvesting performance in medium-size (400 cm2)
glass-based semitransparent solar concentrators employing edge-mounted photovoltaic modules.
Systems using several different types of glazing system architecture and containing embedded
diffractive structures are prepared and characterized. The technological approaches to the rapid
manufacture of large-area diffractive elements suitable for use in solar window-type concentrators
are described. These elements enable the internal deflection and partial trapping of light inside
glass-based concentrator windows. We focus on uncovering the potential of pattern-transfer
polymer-based soft lithography for enabling both the improved photon collection probability at solar
cell surfaces, and the up-scaling of …

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Ultrasonic Techniques For Air Void Size Distribution And Property Evaluation In Both Early-Age And Hardened Concrete Samples, Shuaicheng Guo, Qingli Dai, Xiao Sun, Ye Sun, Zhen Liu Aug 2018

Ultrasonic Techniques For Air Void Size Distribution And Property Evaluation In Both Early-Age And Hardened Concrete Samples, Shuaicheng Guo, Qingli Dai, Xiao Sun, Ye Sun, Zhen Liu

Zhen Liu

Entrained air voids can improve the freeze-thaw durability of concrete, and also affect its mechanical and transport properties. Therefore, it is important to measure the air void structure and understand its influence on concrete performance for quality control. This paper aims to measure air void structure evolution at both early-age and hardened stages with the ultrasonic technique, and evaluates its influence on concrete properties. Three samples with different air entrainment agent content were specially prepared. The air void structure was determined with optimized inverse analysis by achieving the minimum error between experimental and theoretical attenuation. The early-age sample measurement showed …

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Lowest Matric Potential In Quartz: Metadynamics Evidence, Chao Zhang, Yi Dong, Zhen Liu Aug 2018

Lowest Matric Potential In Quartz: Metadynamics Evidence, Chao Zhang, Yi Dong, Zhen Liu

Zhen Liu

The lowest matric potential is an important soil property characterizing the strength of retaining water molecules and a key parameter in defining a complete soil water retention curve. However, the exact value of the lowest matric potential is still unclear and cannot be measured due to the limitation of current experimental technology. In this study, a general theoretical framework based on metadynamics was proposed to determine the lowest matric potential in quartz minerals. The matric potential was derived from partial volume free energy and can be further calculated by the difference between the adsorption free energy and self‐hydration free energy. …

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Atomistic‐Scale Investigation Of Effective Stress Principle Of Saturated Porous Materials By Molecular Dynamics, Chao Zhang, Zhen Liu, Peng Deng Aug 2018

Atomistic‐Scale Investigation Of Effective Stress Principle Of Saturated Porous Materials By Molecular Dynamics, Chao Zhang, Zhen Liu, Peng Deng

Zhen Liu

The effective stress principle is one of the most fundamental concepts in the mechanics of porous materials. Several mathematical expressions have been proposed for this fundamental principle, leading to unsettled debates on the validity and applicability of the principle and its mathematical descriptions. Recent developments in atomistic modeling techniques make it possible to understand multiphase systems at the atomistic scale. In this paper, molecular dynamics simulation is explored as a tool to investigate the stress formulation in porous materials. A molecular dynamics framework, including molecular models of phases, interatomic potentials, initial configuration, and simulation procedure, is presented. Numerical simulations based …

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Gnygrens18.Pdf, Garrett Nygren Aug 2018

Gnygrens18.Pdf, Garrett Nygren

Garrett Nygren

The finite element method was used to evaluate microstructural strengthening and toughening effects in nanoparticulate reinforced polymer composites (nanocomposites) and in short aligned discontinuous fiber reinforced polymer composites. Nanoparticulate reinforcement is a well-known method of polymer toughening which can greatly expand the range of engineering applications for polymers. However, the mechanisms of nanoparticulate toughening, as well as complementary sub-micron fracture processes, are not well understood. Short, aligned, discontinuous carbon fiber reinforced thermoplastics show promise as a versatile, inexpensive material system with favorable manufacturability, but failure of the associated morphologies is also not yet well explored.
In nanocomposites, two microstructural effects …

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Sbaigs18.Pdf, Sarfaraz Niaz Ali Baig Aug 2018

Sbaigs18.Pdf, Sarfaraz Niaz Ali Baig

Sarfaraz Baig

No abstract provided.

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نمرات نهایی.Pdf, Mahdi Abaszadeh Aug 2018

نمرات نهایی.Pdf, Mahdi Abaszadeh

mahdi abaszadeh

No abstract provided.

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2018-19 Tla Application - Thermal Fluid Sequence, M. A. Rafe Biswas Jul 2018

2018-19 Tla Application - Thermal Fluid Sequence, M. A. Rafe Biswas

M. A. Rafe Biswas

No abstract provided.

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Trust Development In Swift Starting Action Teams: A Multilevel Framework, Jessica Wildman, Marissa Shuffler, Elizabeth Lazzara, Stephen Fiore, C. Shawn Burke, Eduardo Salas, Sena Garven Jul 2018

Trust Development In Swift Starting Action Teams: A Multilevel Framework, Jessica Wildman, Marissa Shuffler, Elizabeth Lazzara, Stephen Fiore, C. Shawn Burke, Eduardo Salas, Sena Garven

Elizabeth Lazzara

Swift starting action teams (STATs) are increasingly prevalent in organizations, and the development of trust is often a critical issue for their effectiveness. However, current theory and research do not provide a clear picture regarding how trust toward the team (i.e., the team as the target) is developed in these settings. The primary contribution of this article is to present a theoretical framework describing how individual-level trust toward one’s team is developed in STAT contexts. This article integrates several existing trust theories into one comprehensive context-specific multilevel theory of how trust develops in STATs from cognitive, affective, behavioral, and contextual …

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Advances In Composite Manufacturing Of Helicopter Parts, Tobias A. Weber, Hans-Joachim K. Ruff-Stahl Jul 2018

Advances In Composite Manufacturing Of Helicopter Parts, Tobias A. Weber, Hans-Joachim K. Ruff-Stahl

Hans-Joachim Ruff-Stahl

This study investigates and compares different methods for improving standard autoclave composite manufacturing in order to find suitable approaches to a more efficient composite production. The goal is not only a reduction in manufacturing times and costs but also quality enhancement. Improved part quality while decreasing costs enables a manufacturer of composite parts to expand its market share, especially in the helicopter market, which has been constantly shrinking over the last two years. Various approaches such as improved tooling technology, the use of automated systems for lamination as well as outsourcing are examined to provide an overview of possible advancements …

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Not-So-Risky Business? Assessing The Risk Of Integrating Large Rpvs Into The Current Air Traffic System, Hans-Joachim K. Ruff-Stahl, Steven Esser, Dirk Farsch, Thomas Graner, Robert Klein, Christian Schneidt, Stefan Schoenborn Jul 2018

Not-So-Risky Business? Assessing The Risk Of Integrating Large Rpvs Into The Current Air Traffic System, Hans-Joachim K. Ruff-Stahl, Steven Esser, Dirk Farsch, Thomas Graner, Robert Klein, Christian Schneidt, Stefan Schoenborn

Hans-Joachim Ruff-Stahl

In spite of considerable efforts to commercialize large remotely piloted vehicles (RPV), an integration of these RPVs into the existing Air Transportation System (ATS) and Airspace Structure is pending. The purpose of this paper was to assess the risks of an exemplary integration of a Heron 1 type RPV into the existing European air space structure within the current regulatory framework and without the availability of sense and avoid technology. Six incident occurrence scenarios were investigated, based on a modified Fault Tree Analysis and Eurocontrol’s risk matrix. It was found that without the implementation of technological or procedural changes, an …

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Competitiveness Of Hybrid Electric Aircraft On Short Range Scheduled Flights, Johannes Anton, Hans-Joachim K. Ruff-Stahl Jul 2018

Competitiveness Of Hybrid Electric Aircraft On Short Range Scheduled Flights, Johannes Anton, Hans-Joachim K. Ruff-Stahl

Hans-Joachim Ruff-Stahl

Hybrid electric aircraft are expected to enter the small regional aircraft market within the next two decades. The aim of this study was to investigate if a hybrid electric passenger aircraft with 50 seats can be competitive against the established 100 seat aircraft on short range scheduled flights. The Embraer EMB 145 and EMB 190 regional jets were chosen as benchmarks for that market. A hypothetical hybrid version of the EMB 145 with increased fuel efficiency was tested on a cost per available seat mile (CASM) basis. The t tests confirmed significant (p < 0.05) competitiveness of the hybrid version, while in contrast the conventional 50-seater was significantly more expensive compared to the 100seat aircraft. This indicates that hybrid aircraft could enter the short haul market with a competitive advantage, even against the established 100 seat regional jets.

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Emerging Trends And New Frontiers In Community Operational Research, Michael P. Johnson Jr., Gerald Midgley, George Chichirau Jul 2018

Emerging Trends And New Frontiers In Community Operational Research, Michael P. Johnson Jr., Gerald Midgley, George Chichirau

Michael P. Johnson

Community operational research (Community OR), and its disciplinary relation, community-based operations research, has an increasingly high profile within multiple domains that benefit from empirical and analytic approaches to problem solving. These domains are primarily concentrated within nonprofit services and local development. However, there are many other disciplinary and application areas for which novel applications and extensions of COR could generate valuable insights. This paper identifies a number of these, distinguishing between ‘emerging trends’ (mostly in well-studied areas of operations research, management science and analytics) and ‘new frontiers’, which can be found in traditions not commonly oriented towards empirical and analytic …

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Investigation Of Zebrafish Larvae Behavior As Precursor For Suborbital Flights: Feasibility Study, Pedro Llanos, Kristina Andrijauskaite, Mark Rubinstein, Sherine S.L. Chan Jul 2018

Investigation Of Zebrafish Larvae Behavior As Precursor For Suborbital Flights: Feasibility Study, Pedro Llanos, Kristina Andrijauskaite, Mark Rubinstein, Sherine S.L. Chan

Pedro J. Llanos (www.AstronauticsLlanos.com)


Suborbital spaceflights, carrying scientific payloads, allow scientists not only to test the feasibility of their payloads, but they also provide the basis for refining scientific hypotheses to be later tested on the International Space Station (ISS). Therefore, it is essential to establish robust pre-flight procedures in order to take advantage of this unique research platform to facilitate payload delivery. In the present study, we assessed zebrafish larvae behavior as a precursor for the future suborbital spaceflight involving research on the musculoskeletal system. Zebrafish larvae were exposed to the same physiological stressors they would encounter during suborbital spaceflight: alterations in light, …

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Agonabadietal_2018_Eduexoemgdelaytutorial_13.Pdf, Arash Mohammadzadeh Gonabadi, Philippe Malcolm Jul 2018

Agonabadietal_2018_Eduexoemgdelaytutorial_13.Pdf, Arash Mohammadzadeh Gonabadi, Philippe Malcolm

Philippe Malcolm

No abstract provided.

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Fedsm 2018 Presentation, Nima Fathi, Peter Vorobieff, Seyed Sobhan Aleyasin, Goodarz Ahmadi Jul 2018

Fedsm 2018 Presentation, Nima Fathi, Peter Vorobieff, Seyed Sobhan Aleyasin, Goodarz Ahmadi

Nima Fathi

Horizontal linear shear stress apparatus offers a convenient way to study the rheology of rigid particles suspended in viscous shear flows in the laboratory. The single particle trajectories of a buoyant spherical solid particle in a linear shear flow are investigated. Reynolds numbers less than 0.1 are considered to provide the creeping flow in this investigating. The experimental apparatus provides a linear stress, Stokes, Couette flow where the wall boundary conditions of the set up can change. The two-dimensional CFD analysis is performed to simulate the primary and secondary phases of the domain. Our numerical assessment, discrete phase element method, is applied to simulate the fluid …

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Method For Radon Measurement In Residential Sewer Connections, David Yuill Jul 2018

Method For Radon Measurement In Residential Sewer Connections, David Yuill

David Yuill

Radon gas is the most deadly indoor air pollutant. In the US, it is responsible for over 20,000 deaths per year. Residential exposure is typically the largest portion of a person’s annual exposure, so a great deal of research has been done to understand the pathways that radon can follow to enter a house. Since radon emanates from the ground, it is present in high concentration in soil gas. Recent research on the vapor intrusion of volatile organic compounds from subsurface sources into a test house concluded that the sewer line is an important preferential pathway. Despite the potential for …

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Evaluation The Effect Of Washing On The Heat Transfer Capacity And Air-Side Flow Resistance Of Air Cooled Condensers, Mehdi Mehrabi, David Yuill Jul 2018

Evaluation The Effect Of Washing On The Heat Transfer Capacity And Air-Side Flow Resistance Of Air Cooled Condensers, Mehdi Mehrabi, David Yuill

David Yuill

Air cooled condensers are commonly used in rooftop units and residential air-conditioners to reject heat outdoors. Airborne particles in the environment, such as dust, grass, leaves, seeds, and anthropogenic agents, can foul the air side of the condensers. Therefore, it is common practice to regularly clean the air side of condensers. Seven fouled wavy fin, and two fouled spine fin condensers from residential condensing units were collected at the end of their service lives, and examined in the laboratory to study the effect of the fouling on heat transfer capacity and air-side flow resistance. A test apparatus was designed and …

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Effects Of Aspect Ratio On Laboratory Simulation Of Tornado-Like Vortices Jul 2018

Effects Of Aspect Ratio On Laboratory Simulation Of Tornado-Like Vortices

Changda Feng

No abstract provided.

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Titan Gel Gold Asli 082223118446, Tunggal Solusi Jul 2018

Dynamical Thermal Conductivity Of Suspended Graphene Ribbons In The Hydrodynamic Regime, Zlatan Aksamija, Arnab K. Majee Jul 2018

Dynamical Thermal Conductivity Of Suspended Graphene Ribbons In The Hydrodynamic Regime, Zlatan Aksamija, Arnab K. Majee

Zlatan Aksamija

The steady-state behavior of thermal transport in bulk and nanostructured semiconductors has been widely
studied, both theoretically and experimentally. On the other hand, fast transients and frequency dynamics of
thermal conduction has been given less attention. The frequency response of thermal conductivity has become
more crucial in recent years, especially in light of the constant rise in the clock frequencies in microprocessors
and terahertz sensing applications. Thermal conductivity in response to a time-varying temperature field starts
decaying when the frequency exceeds a cutoff frequency Omega_c, which is related to the inverse of phonon relaxation time τ, on the order of …

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Numerical Simulation Of Fault Impacts For Commercial Walk-In Freezers, Alireza Behfar, David Yuill Jun 2018

Numerical Simulation Of Fault Impacts For Commercial Walk-In Freezers, Alireza Behfar, David Yuill

David Yuill

Refrigeration systems can undergo many faults that could negatively affect their operation and performance. This paper describes a modeling process to simulate the fault impacts on the operation of a commercial walk-in freezer using semi-empirical models. These models often require less modeling effort than full forward models and could be used in scenarios where detailed information is missing, such as in field-measured systems. An important characteristic of a typical walk-in refrigeration system is the existence of a liquid-line receiver after the condenser, which significantly changes the behavior of the cycle, in comparison to a receiver-less system. Component models described in …

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Power Dissipation Of Wse2 Field-Effect Transistors Probed By Low- Frequency Raman Thermometry, Zlatan Aksamija, Cameron J. Foss, Arnab K. Majee, Amin Salehi-Khojin Jun 2018

Power Dissipation Of Wse2 Field-Effect Transistors Probed By Low- Frequency Raman Thermometry, Zlatan Aksamija, Cameron J. Foss, Arnab K. Majee, Amin Salehi-Khojin

Zlatan Aksamija

The ongoing shrinkage in the size of two-dimensional (2D) electronic circuitry results in high power densities during device operation, which could cause a significant temperature rise within 2D channels. One challenge in
Raman thermometry of 2D materials is that the commonly used high-frequency modes do not precisely represent the temperature rise in some 2D materials because of peak broadening and intensity weakening at elevated temperatures. In this work, we show that a low-frequency E2g 2 shear mode can be used to accurately extract temperature and measure thermal boundary conductance (TBC) in backgated tungsten diselenide (WSe2) field-effect transistors, whereas the high-frequency …

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Validation And Verification Flight Tests Of Fixed-Wing Collaborative Uass With High Speeds And High Inertias, A Ram (Bella) Kim Jun 2018

Validation And Verification Flight Tests Of Fixed-Wing Collaborative Uass With High Speeds And High Inertias, A Ram (Bella) Kim

A Ram (Bella) Kim

The research objective for this work is to validate and verify guidance, navigation, and control algorithms that are designed for fixed-wing collaborative unmanned aerial systems (UASs) in unstructured environments. A biologically-inspired swarm control theory provides a framework to distribute sensor payloads between several smaller and less complex agents that have local interactions. Controller design and flight testing of large UASs with high speeds and high inertias holding a formation in a dynamically changing environment and in the presence of external disturbances is complex and requires advanced planning and safety measures. Verification and validation flight tests were conducted using a fixed-wing …

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Engaged Student Learning In Dynamics Of Flight And Control Classes, A Ram (Bella) Kim Jun 2018

Engaged Student Learning In Dynamics Of Flight And Control Classes, A Ram (Bella) Kim

A Ram (Bella) Kim

The next big challenge in STEM education is envisioned to come from curricular change. This paper aims to assess the best-practice model in student learning that was developed and demonstrated in Flight Dynamics and Control courses between 2011 and 2014 and 2017. The best practice model was developed when a team research component was included into the undergraduate aerospace engineering courses of Flight Dynamics and Control I and II. By taking
advantage of the unmanned aerial system fleet owned by the Department of Aerospace Engineering at the University of Kansas (KUAE), students were tasked with developing a physics-based model for …

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Community-Based Participatory Research Through The Lens Of Decision Science, Michael P. Johnson Jr. Jun 2018

Community-Based Participatory Research Through The Lens Of Decision Science, Michael P. Johnson Jr.

Michael P. Johnson

This is a brief introduction to community-focused and community-engaged research through the perspective of the decision sciences. It is intended as a complement to similar approaches more generally situated in the social sciences.

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Reconsidering Downwind Operation By Analysis Of The Nrel Phase Vi Data, Scott Larwood, Raymond Chow Jun 2018

Reconsidering Downwind Operation By Analysis Of The Nrel Phase Vi Data, Scott Larwood, Raymond Chow

Scott M. Larwood

Data are presented comparing upwind versus downwind operation of the National Renewable Energy Laboratory’s Phase VI wind turbine. Power was not reduced as expected for downwind, which may be attributed to inboard three-dimensional effects. Average flap bending loads were reduced with downwind coning and compared well with prediction. Fatigue loads were increased with downwind; however, fatigue was mitigated with a tower shroud. The shroud needs to align with the freestream, demonstrated by an increase in fatigue loads from a 10° shroud misalignment. Pressure data were acquired in the tower wake at the rotor location with and without the shroud. The …

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Control Of Multi-Agent Collaborative Fixed-Wing Uass In Unstructured Environment, A Ram (Bella) Kim Jun 2018

Control Of Multi-Agent Collaborative Fixed-Wing Uass In Unstructured Environment, A Ram (Bella) Kim

A Ram (Bella) Kim

Swarms of unmanned aircraft are the inevitable future of the aerospace industry. In recent years, swarming robots and aircraft have been a subject of much interest; however, many research projects make impractical assumptions such as point mass dynamics with no aerodynamic effects for aircraft models, and most works stop short of fully validating their methods via flight testing. This work presents a proximity based guidance, navigation, and control of multi-agent fixed-wing unmanned aerial systems in an unstructured environment. A scalable swarm navigation method is developed using adaptive moving mesh partial differential equations controlled by the free energy heat flow equation. …

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Validation And Verification Of Gnc For Large Fixed-Wing Unmanned Aerial System In Unstructured And Noisy Environment, A Ram (Bella) Kim Jun 2018

Validation And Verification Of Gnc For Large Fixed-Wing Unmanned Aerial System In Unstructured And Noisy Environment, A Ram (Bella) Kim

A Ram (Bella) Kim

The impact of high update rate on the disparity in eigenvalues of the auto-correlation matrix, along with slow convergence and reduced stability of numerical analysis are well studied. However, the impact of high update rates of autopilots on the performance of unmanned aircraft has been ignored due to the intrinsic limitations of COTS autopilots
computation power. Although MEMS based IMUs have very high update rates, the majority of existing UAS autopilot system processing power is limited to 20 Hz. In this work, the challenges and processes for developing and flight test validating an autonomous flight controller for a large 30-kg …

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