bluuebunny/crossref_metadata_2025 huggingface dataset:
Exploding head syndrome is common in college students
Authors: Sharpless Brian A.
Published: March 2015

Exploding head syndrome is characterized by the perception of loud noises during sleep–wake or wake–sleep transitions. Although episodes by themselves are relatively harmless, it is a frightening phenomenon that may result in clinical consequences. At present there are little systematic data on exploding head syndrome, and prevalence rates are unknown. It has been hypothesized to be rare and to occur primarily in older (i.e. 50+ years) individuals, females, and those suffering from isolated sleep paralysis. In order to test these hypotheses, 211 undergraduate students were assessed for both exploding head syndrome and isolated sleep paralysis using semi‐structured diagnostic interviews: 18.00% of the sample experienced lifetime exploding head syndrome, this reduced to 16.60% for recurrent cases. Though not more common in females, it was found in 36.89% of those diagnosed with isolated sleep paralysis. Exploding head syndrome episodes were accompanied by clinically significant levels of fear, and a minority (2.80%) experienced it to such a degree that it was associated with clinically significant distress and/or impairment. Contrary to some earlier theorizing, exploding head syndrome was found to be a relatively common experience in younger individuals. Given the potential clinical impacts, it is recommended that it be assessed more regularly in research and clinical settings.
Pannexin‐2 is expressed in the human colon with extensive localization in the enteric nervous system
Authors: Diezmos E. F. , Sandow S. L. , Perera D. S. , King D. W. , Bertrand P. P. , Liu L.
Published: March 2015

Background

Pannexin‐2 (Panx2) is a member of the novel group of membrane spanning protein channels present in the central nervous system. Limited studies have examined Panx2 in the intestine, where it may have important physiological roles. The present study characterized Panx2 expression and localization in the human colon in health and disease states.

Methods

Immunofluorescence determined Panx2 localization and co‐localization, and quantitative real‐time PCR and Western blot determined gene and protein expression in ulcerative colitis (UC), Crohn's disease (CD), and control human colon.

Key Results

Panx2 was widely expressed in myenteric and submucosal ganglia, particularly in the cytoplasm of neurons. Panx2 was also expressed on smooth muscle of the muscularis and blood vessels, some non‐lymphoid leukocytes, mast cells, and mucosal epithelial cells. Co‐localization of Panx2 occurred with β‐tubulin, neuronal nitric oxide synthase, substance P, vesicular acetylcholine transporter, and calcitonin gene‐related peptide, indicating widespread Panx2 expression in extrinsic and intrinsic neurons. Molecular studies revealed a 3.4‐fold higher level of Panx2 mRNA in ascending compared to sigmoid muscularis (p < 0.05), despite similar protein levels. Similarly, UC muscularis showed a 35‐fold up‐regulation in Panx2 mRNA, but not in protein (p < 0.05).

Conclusions & Inferences

Here, we demonstrated the dense expression of Panx2 in the enteric nervous system and the co‐localization of Panx2 with a spectrum of neuronal markers, indicating that Panx2 may be involved in mediating neurotransmission in the colon. The substantial increase in Panx2 mRNA in UC muscle but not protein suggests that the Panx2 translation process may be disrupted in UC.
How Green are Exporters?
Authors: Girma Sourafel , Hanley Aoife
Published: March 2015

There is a well‐established theoretical and empirical literature that shows that exporters are more innovative than otherwise equivalent non‐exporters. In this article, we ask whether this is also true when it comes to the effects of adopting greener production techniques. Using an instrumental variables strategy based on UK firm level data, we find robust evidence that exporters are more likely to report their innovation as having a ‘high/very high’ environmental effect.
Stress, Coping, and Mental Health Differences among Homeless People
Authors: Lippert Adam M. , Lee Barrett A.
Published: March 2015

People who are chronically homeless are assumed to have higher rates of mental health problems than episodically or new‐entry homeless individuals. It is unclear to what extent early‐life and current stressors account for this disadvantage. Guided by cumulative disadvantage theory and stress research, we analyze data from a national study of theUShomeless population to examine how stressors and coping resources throughout the life course are implicated in differences among homeless people in psychiatric disorders and alcohol or other drug abuse disorders. Logistic regression analysis reveals that new‐entry homeless persons are less likely than their chronically and episodically homeless counterparts to have current psychiatric disorders. This is explained by stressors and coping resources experienced in childhood and during adult homeless spells. Alcohol and other drug abuse is common but comparable across the three homeless types and shares an association with selected stress and coping measures. Findings lend credibility to anaccumulation of risksperspective, highlighting how past as well as contemporaneous stressors are related to the mental health of homeless people.
Million Dollar Maybe? The Effect of Female Presence in Movies on Box Office Returns
Authors: Lindner Andrew M. , Lindquist Melissa , Arnold Julie
Published: March 2015

This study examines processes that contribute to the underrepresentation of women in film by linking the depiction of gender in film to its impact on domestic box office returns. Drawing on a sample of widely distributed movies from 2000 to 2009 (n = 974), we test whether the box office under‐performance of films with an independent female presence results primarily from “downstream” public rejection or from an gendered “upstream” division of resources that provides greater studio support to movies about men. Using a series of multivariate regression analyses and controlling for genre, critical appraisal, arthouse label, being a sequel, and including a popular star, films with a female presence earn less at the box office. This effect, however, appears to be largely the consequence of movies that feature women having smaller production budgets, suggesting that the underrepresentation of women in film stems from “upstream” routines of film industry gatekeepers, not a lesser interest in stories about women in the minds of the public.
Perceptions of Structural Injustice and Efficacy: Participation in Low/Moderate/High‐Cost Forms of Collective Action
Authors: Corcoran Katie E. , Pettinicchio David , Young Jacob T. N.
Published: March 2015

Prior studies on perceptions of structural disadvantage and injustice, efficacy, and collective action have suffered from two major limitations: (1) they have used single‐country samples, usually of economically advanced countries, and (2) generally theorized and investigated perceptions of structural injustice and efficacy separately. Drawing on value‐expectancy theory, we provide an integrated theory to predict direct and conditional effects of efficacy and perceptions of structural disadvantage and injustice on collective action within countries. To address the limitations of previous research, we use cross‐national data of 29 countries, including economically advanced and less advanced nations, to test how well these hypotheses explain within‐country variation in collective action. We find that internal efficacy is significantly and positively associated with low‐ and moderate‐cost collective action, whereas organizational embeddedness, a proxy for political efficacy, is significantly and positively associated with low‐, moderate‐, and high‐cost collective action. Perceptions of legitimate and unjust structural disadvantage are also positively associated with all types of collective action. Importantly, the positive effects of both types of efficacy on high‐cost collective action are conditional on perceptions of structural injustice. That is, participation in high‐cost collective action is more likely for those who are both efficaciousandperceive structural disadvantage as unjust.
Can Computational Goals Inform Theories of Vision?
Authors: Anderson Barton L.
Published: March 2015

One of the most lasting contributions of Marr's posthumous book is his articulation of the different “levels of analysis” that are needed to understand vision. Although a variety of work has examined how these different levels are related, there is comparatively little examination of the assumptions on which his proposed levels rest, or the plausibility of the approach Marr articulated given those assumptions. Marr placed particular significance on computational level theory, which specifies the “goal” of a computation, its appropriateness for solving a particular problem, and the logic by which it can be carried out. The structure of computational level theory is inherently teleological: What the brain does is described in terms of its purpose. I argue that computational level theory, and the reverse‐engineering approach it inspires, requires understanding the historical trajectory that gave rise to functional capacities that can be meaningfully attributed with some sense of purpose or goal, that is, a reconstruction of the fitness function on which natural selection acted in shaping our visual abilities. I argue that this reconstruction is required to distinguish abilities shaped by natural selection—“natural tasks” —from evolutionary “by‐products” (spandrels, co‐optations, and exaptations), rather than merely demonstrating that computational goals can be embedded in a Bayesian model that renders a particular behavior or process rational.
Use of enoxaparin in dogs with primary immune‐mediated hemolytic anemia: 21 cases
Authors: Panek Cynthia M. , Nakamura Reid K. , Bianco Domenico
Published: March 2015

Objective

To describe the complications and frequency of thrombosis associated with the use of enoxaparin, a low molecular weight heparin, in dogs with primary immune‐mediated hemolytic anemia (IMHA).

Design

Retrospective case series.

Setting

Two privately owned veterinary referral hospitals.

Animals

Twenty‐one client‐owned dogs with primary IMHA.

Interventions

Dogs were treated with enoxaparin (0.8 mg/kg subcutaneously every 6 h) as the sole anticoagulation therapy starting at admission to the hospital.

Measurements and Main Results

Only 2 dogs had minor hemorrhagic complications associated with enoxaparin therapy. Frequency of thrombosis was not assessed. Long‐term survival was comparable to other anticoagulation protocols reported for dogs with primary IMHA.

Conclusions

The use of enoxaparin was safe in a small group of dogs with primary IMHA. Whether enoxaparin therapy can reduce mortality and thrombotic complications in dogs with primary IMHA compared with other anticoagulation protocols remains unknown.
Evaluation of Electronic Prescription Implications in Turkey: An Investigation of the Perceptions of Physicians
Authors: Gіder Ömer , Ocak Saffet , Top Mehmet
Published: March 2015

Background

Electronic prescribing (e‐prescribing) is an evolving area of healthcare information technology that aims to support physician decision‐making by capturing, reviewing, and issuing medical prescriptions with high potential for improving the quality and safety of the process.

Purpose

To describe physician perception of e‐prescription use in healthcare organizations that work with social security and to evaluate their infrastructures for MEDULA (an information system for billing and other health informatics) in healthcare organizations in Turkey.

Methods

A cross‐sectional survey design was used for this study. A convenience sample of physicians in eight general hospitals and in two oral and dental health centers of the Ministry of Health in Turkey were surveyed.

Results

Survey response rate was 47% (248/425). The majority of physicians (62%) support e‐prescribing but have not used an electronic signature for prescriptions (78.2%). Almost half of them believe that e‐prescriptions would positively contribute to patient safety (43%)

Linking Evidence to Action

Our study provides a first look at the perceptions of physicians regarding the implications of e‐prescriptions, which became mandatory on January 15, 2013, in Turkey. Advocates of e‐prescribing have suggested that additional efforts are needed to strengthen clinical decision systems. Physicians and nurses are better able to adopt e‐prescribing systems and to view them positively if they recognize the limitations of paper‐based prescribing and understand the utility of electronic systems in addressing some of these limitations. This study represents a starting point for government and related organizations to improve their knowledge on how well the implied benefits of e‐prescriptions are realized in their acquisition, appraisal, and use in health policy decision‐making and health systems.
Addition of a Decision Point in Evidence‐Based Practice Process Steps to Distinguish EBP, Research and Quality Improvement Methodologies
Authors: Mick JoAnn
Published: March 2015

This column shares the best evidence‐based strategies and innovative ideas on how to facilitate the learning of EBP principles and processes by clinicians as well as nursing and interprofessional students. Guidelines for submission are available at http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1741‐‐6787
Systematic Review of Medical Home Models to Promote Transitions to Primary Adult Health Care for Adolescents Living With Autism Spectrum Disorder
Authors: Rogers Kathleen , Zeni Mary Beth
Published: March 2015

Background

There is a growing number of children diagnosed and living with autism spectrum disorders (ASDs) in the United States. This increasing incidence and prevalence of ASDs require care coordination within a medical home model, which needs to continue into adulthood.

Aim

This paper is an evidence review of medical home models for transitioning adolescents living with ASDs from pediatric primary healthcare practices to adult primary care practices.

Method

Databases were reviewed and articles selected based on inclusion and exclusion criteria.

Results

Nine articles were reviewed and four met criteria. None of the articles addressed medical home models to transition adolescents living with ASDs into adult primary healthcare services.

Linking Evidence to Action

There is a need for nursing to work within an interdisciplinary framework to educate adult healthcare providers on the needs of adolescents living with ASDs and to evaluate medical home transition models for this vulnerable population.
Crashworthy Landing Gear Design Using a Composite Tube by Extra Energy Absorber
Authors: Kim Tae-Uk , Kim Sung Joon , Lee Seunggyu
Published: March 2015

Landing gear is the one of the key components for improving aircraft crashworthiness because its primary function is the energy absorption. But, in general, the shock absorbers are designed to have best efficiency for normal landing cases and can be ineffective when faced with very high sink speed. Thus special design and implementation are necessary for landing gear to have crashworthiness. For this purpose, various concepts have been studied and put to practical use such as structural pin, pressure relief valve and additional energy absorbing devices, etc. In this paper, the composite tube is investigated as an extra energy absorber and adopted to landing gear to increase shock absorbing performance in case of crash. To do this, first the quasi-static and impact test of composite tubes are conducted and the analysis model is tuned to explain the test results. During the correlation process, the failure modes and the specific energy absorption of the composite tubes are analyzed and the optimal configurations are searched.

The overall performance of landing gear including the composite tube is analyzed by developing a simplified dynamic model. Each force-stroke relation of oleo-pneumatic shock absorber, tire and composite tube are modeled as spring and damper, then the equation of motion is solved to obtain the crash responses. In this model, after the bottoming of shock absorber, the crushing of composite tube is activated for additional energy absorption. Numerical solutions show that the enhanced shock absorbing capability in case of crash when the composite tube adopted. For practical use, the landing gear performance should be verified by drop tests and this is author’s future research project.
Chaotic Tool Wear During Machining of Titanium Metal Matrix Composite (TiMMCs)
Authors: Duong Xuan-Truong , Balazinski Marek , Mayer René
Published: March 2015

The initial tool wear during machining of titanium metal matrix composite (TiMMCs) is the result of several wear mechanisms: tool layer damage, friction - tribological wear, adhesion, diffusion and brace wear. This phenomenon occurs at the first instant and extends to only ten seconds at most. In this case the adhesive wear is the most important mechanism while the brace wear is considered as a resistance wear layer at the beginning of the steady wear period. In this paper, the effect of the initial tool wear and initial cutting conditions on tool wear progression and tool life is investigated. We proposed herein a new mathematical model based on the scatter wear and Lyapunov exponent to study quantitatively the “chaotic tool wear”. The Chaos theory, which has proved efficient in explaining how something changes in time, was used to demonstrate the dependence of the tool life on the initial cutting conditions and thus contribute to a better understanding of the influence of the initial cutting condition on the tool life. Based on the chaotic tool wear model, the scatter wear dimension and Lyapunov exponents were found to be positive in all case of the initial cutting conditions such as initial speed, feed rate and depth of cut. The initial cutting speed appears however to have the most significant impact on tool life. In particular, the mathematical model was successfully applied to the case of machining TiMMCs. It was clearly shown that changing the initial cutting speed by 20 m/min for the first two seconds of machining instead of keeping it constant at 60 m/min during the whole cutting process leads to an increase in the tool life (up to 24%).
Algorithm for Detecting and Solving the Problem of Under-Filled Pointed Ends Based on 3D Printing Plastic Droplet Generation
Authors: Prša Jelena , Irlinger Franz , Lueth Tim C.
Published: March 2015

In this paper the problem of under-filled pointed ends is introduced and mathematically defined. To tackle this problem, we present a new algorithm that detects and fills the critical areas, which arise at the 3D printed plastic parts. While printing the contours and/or infill lines, due to the limitations based on the width of the extruded material, narrow edges and pointed ends remain improperly filled. This eventually results in 3D printed objects with the final geometry that differs greatly from the initial geometry.

This paper presents the fundamentals for solving the problem of 3D printing of geometries which contain narrow pointed ends. The critical area of the pointed ends is mathematically defined and, depending on the angle, the formulae for the calculation of under-filled and over-filled areas are given. The newly developed algorithm, based on the 3D Printing plastic droplet generation process, assures that the droplets of the repeating contours are placed at the edges of the contour-segments and by that minimises the potential under-fills. Furthermore, an additional number of droplets is defined, that are either printed in or removed from the under-filled areas in the angle bisector.

The proposed algorithm is applied on parts, whose geometry describes pointed ends. The final 3D printed parts are very appealing and their shape resembles the original geometry more than the final shape of the parts without applying the algorithm.
Speed Function Effects in Electron Beam Additive Manufacturing
Authors: Cheng Bo , Price Steven , Gong Xibing , Lydon James , Cooper Kenneth , Chou Kevin
Published: March 2015

In this paper, the process parameter effects on the thermal characteristics in powder-bed electron beam additive manufacturing (EBAM) using Ti-6Al-4V powder were investigated. The machine-specific setting, called “speed function” (SF) index that controls the beam speed and the beam current during a build, was utilized to evaluate the beam scanning speed effects. EBAM parts were fabricated using different levels of SF index (20 to 65) and build surface morphology and part microstructures were examined. A near infrared (NIR) thermal imager was used for temperatures measurements during the EBAM process. In addition, a thermal model previously developed was employed for temperature predictions and comparison with the experimental results.

The major results are summarized as follows. The SF index noticeably affects the thermal characteristics in EBAM, e.g., a melt pool length of 1.72 mm vs. 1.26 mm for SF20 and SF65, respectively, at the 24.43 mm build height. This is because the higher the speed function index, the higher the beam speed, which reduces the energy density input and results in a lower process temperature. For the surface conditions and part microstructures, in general, a higher SF index tends to produce parts of rougher surfaces with more residual porosity features and large β grain columnar widths.
Conceptual Design of a 200 Passenger Blended Wing Body Aircraft
Authors: Ammar Sami , Trépanier Jean-Yves
Published: March 2015

The Blended Wing Body (BWB) aircraft is based on the flying wing concept. For this aircraft the literature has reported performance improvements compared to conventional aircraft. However, most BWB studies have focused on large aircraft and it is not sure whether the gains are the same for smaller aircraft. The main objective of this work is to perform the conceptual design of a 200 passengers BWB and compare its performance against an equivalent conventional A320 aircraft in terms of payload and range. Moreover, an emphasis will be placed on obtaining a stable aircraft, with the analysis of static and dynamic stability. The design of BWB was carried out under the platform called Computerized Environment for Aircraft Synthesis and Integrated Optimization Methods (CEASIOM). This design platform, suitable for conventional aircraft design, has been modified and additional tools have been integrated in order to achieve the aerodynamic analysis, performance and stability of the BWB aircraft.
Assessment of Restricted Contact Cutting Tool in Dry Machining of AISI 1045 Steel
Authors: Ma J. , Ge Xianchen , Duong Nick H. , Lei Shuting
Published: March 2015

This paper studies the performance of restricted cutting tool in dry orthogonal machining of mild steel (AISI 1045 steel) using finite element simulations. The rake face of cemented carbide (WC/Co) cutting inserts is designed and the rake face length is shortened. The purpose is to examine the effect of shortened tools on machining performance and to compare it with regular cutting tools. The following restricted tool parameters are examined: length of rake face, alpha angle (the angle between the rake face and the supporting face), and edge radius. Their effects are assessed in terms of the main force, thrust force, and chip-tool contact length. It is found that restricted cutting tools generate lower cutting force and thrust force and consequently lower the energy necessary for machining. The length of rake face, the angle between the rake face and the supporting face, and edge radius all have influence on cutting force in their own ways. The effects of these three parameters on the tool temperature distribution are also investigated.
Improved Turbulence and Transition Prediction for Turbomachinery Flows
Authors: Bode Christoph , Aufderheide Thorben , Friedrichs Jens , Kožulović Dragan
Published: March 2015

A correlation based approach for estimation of the turbulence length scale lT at the inflow boundary is proposed and presented. This estimation yields reasonable turbulence decay, supporting the transition model in accurately predicting the laminar-turbulent transition location and development. As an additional element of the approach, the sensitivity of the turbulence model to free stream values is suppressed by limiting the eddy viscosity in non-viscous regions. Therefore a criterion to detect those regions, based only on local variables, is derived. The method is implemented in DLR’s turbomachinery flow solver TRACE in the framework of the k–ω turbulence model by Wilcox 1988 [1] and the γ–Reθ transition model by Langtry and Menter [2] in combination with a cross flow (CF) induced transition criterion after Müller [3]. The improved model is tested to the T161 turbine test case [4], [5] and validated at the Durham turbine Cascade [6] and an outlet guide vane for low pressure turbine configurations [7].
Novel Active Control Strategy for LCO and Flutter Suppression by a Coordinated Use of Multiple Distributed Surface Actuators
Authors: Cassaro M. , Nágy A. , Marzocca P. , Battipede M. , Ahmadi G.
Published: March 2015

The effectiveness of a novel actuation architecture developed to control flutter and post-flutter is investigated in this paper. To this purpose, the performance of an active control strategy in various operational conditions is experimentally examined. A physical prototype, consisting of a wing section with multiple spoilers mounted on an aeroelastic apparatus, has been designed and assembled to carry out open- and closed-loop operations. Wind tunnel aeroelastic testing are performed with a plunging and pitching apparatus specifically designed to simulating wing sections with prescribed stiffness characteristics, including torsional structural nonlinearities responsible of a stable nonlinear post-flutter limit cycle behavior. Five surface mounted spoilers located at 15% of the chord from the leading edge are used to control aeroelastic vibrations in pre- and post-flutter. The spoilers design, including selection of best size and chord position and considering the geometrical constraints, has been carried out by CFD simulation, with the objective of maximizing the aerodynamic pitching moment used to stabilize the lifting surface at the various speeds. The spoiler actuations are commanded by an active control system as to extend the flight region in the natural post-flutter condition. A simple PID algorithm is implemented to test the efficiency of the control system design to suppress flutter oscillation. A trial and error tuning of the gain has been executed on-site during the experimental campaign. Only the pitch angle is used as state feedback in the control laws to stabilize the system above the open-loop flutter velocity. Results and pertinent conclusions are outlined.
Influence of Geometrical Parameters on the Maximum Deep Drawing Height of Rectangular Parts
Authors: Menchi Aarón Rivas , Medellín Castillo Hugo I. , de Lange Dirk F. , García Zugasti Pedro de J.
Published: March 2015

The deep drawing process is commonly used in the industry because its ability to produce parts with reduced weight and good mechanical properties at a high production rates. However, the elasto-plastic deformation mechanism of deep drawing is complex and difficult to analyse; this because there are many process parameters and variables involved that affect the quality of final products. Among these variables are the geometric parameters, which have been proved to have a great influence on the process. Theoretical and experimental analyses reported in the literature have been mainly focused on conventional cylindrical cup deep drawing. Few research works have dealt with the deep drawing analysis of non-cylindrical parts, particularly the influence of geometrical parameters on the deep drawing performance.

This paper presents an analysis of the effect of geometrical parameters on the allowable deep drawing height (DDH) of rectangular parts before fracture. The aim is to identify the influence of the main geometrical parameters on the DDH, Numerical analyses based on the Finite Element Method (FEM) were used to investigate the influence of geometrical parameters, such as the radii, the metal sheet thickness, and the aspect ratio, among others, on the DDH.
Structural Properties of Similar and Dissimilar Aluminum Alloy Joints by FSW
Authors: Ramaraju Ramgopal Varma , Ibrahim Abdullah Bin , Mansor Muhammed Arifpin Bin , Yattapu Yaswanth
Published: March 2015

The present study aims to predict the mechanical properties of similar and dissimilar aluminium alloy friction stir Welded joints. The present research also addresses the challenges in joining aluminium alloys Al5083 and Al6061 of 5mm thickness at varying process parameters. A total number of 24 joints have been fabricated with a set of eight joints each for Al6061 (similar), Al5083 (similar) and a combination of Al5083 × Al6061 (dissimilar alloy) as per the experimental plan by Taguchi technique using L8 orthogonal array. The dimensions of the plates are chosen in such a way that the weld length is fixed to 150 mm. The tensile strength and the micro hardness of the welded joints as well as micro structures have been examined. Taguchi technique has been utilized to study the optimized value of the process parameters. The process parameters for joining these have been identified as rotational speeds at 1000 and 1600 rpm, traverse speed 40 and 160mm/min and axial force of 2.5 and 3.5kn.
Converting Helicopter Rotor Blades From D-Spar to C-Spar: Allowing for Aeromorphing Structures
Authors: Hosking Nathan S. , Sotoudeh Zahra
Published: March 2015

Modern helicopter blades are designed as thin-walled hollow structures in form of either C-spar or D-spar cross-sections. With the advent of new materials hollow designs have been implemented to reduce the overall weight of the structure. A D-spar is a rotor blade cross-section that is hollow in nature with a single vertical spar used to carry a large portion of the stresses otherwise carried by the skin [1]. The vertical spar is normally located between the leading edge and half of the chord length. The remaining volume aft of the vertical spar can either be hollow or filled with a honeycomb structure. The honeycomb structure increases the cross-sectional stiffness. Figure 1. shows an example of a common D-spar with a honeycomb structure aft of the vertical spar [2]. Due to new manufacturing methods the D-spar has now become common place in helicopter design [3]. A C-spar cross-section is very similar to the D-spar cross-section in design and construction. The C-spar cross-section does not have the honeycomb structure and the spar. The structural load is offset by more lamina layers towards the leading edge of the cross-section [4,5]. The thin-walled structure is comprised of many layers of composite materials such as fiberglass or carbon fibers. There has been extensive research into D-spar cross-section while there is a lack of studies for C-spar cross-sections [1,3,4].
Load Detection and Fatigue Health Monitoring Equipment Design for Landing Gears
Authors: Jiménez Andrés , Novillo E. , Morante E. , Chamorro E.
Published: March 2015

The Weight on Wheel system on an aircraft gives an indication of whether the aircraft has weight on its wheels, meaning the airborne is on the ground.

This system monitors the loads appearing on each Landing Gear structure. It sends a status signal to Landing gear computer that manage the redundant signals coming from each WOW systems. The management of these signals gives the information needed to activate “on ground” configuration of aircraft for braking control laws. “On ground” configuration specifies maximum load conditions and requirements for shock absorbers design for each type of aircraft (heavy freighters, military transport …)

Based on CESA experience on this field, a new approach oriented to fatigue health monitoring, is presented here. Current WOW system could be modified allowing a continuous monitoring of loads experienced by Landing Gear structure. This will optimize the life cycle of the aircraft by checking individually the status of different structural parts of each Landing Gear. Therefore, it will improve maintenance actions that will be performed only when needed. Load detection and monitoring of landing gears provides a valuable and useful information data to predict accurately the accumulated fatigue damage on landing gear components.
Performance of Nitrogen and Liquid Nitrogen as Coolants in Orthogonal Machining of AISI 1020 Steel Alloy With Uncoated Carbide Tools
Authors: Chandrasekaran Vishnu Vardhan , Payton Lewis N. , Hunko Wesley Scott
Published: March 2015

The growing cost associated with insurance, handling and disposing of conventional metal working fluids (oil and water based) continues to drive a need for alternative metal working fluids. An orthogonal tube turning experiment was conducted to study the effects of nitrogen and liquid nitrogen in machining of AISI 1020 steel alloy on a HAAS CNC lathe along with a Kistler Dynamometer to record the force data. Two levels of uncut chip thickness, 0.002” and 0.004” per revolution are maintained with a constant feed and depth of cut of 0.125”. The tool used in this study is an uncoated carbide insert at three different rake angles of 0°, 7° and 15°, with no chip breaker. The statistical design of the experiment established the machining for a duration of 1 minute at each factor level combination. Force data from the dynamometer is analyzed along with wear of the tooling. Tool inserts were studied under a 3-dimensional optical microscope to measure the rake face tool wear. Simple nitrogen produced less wear than the more expensive liquid nitrogen setup.
Electrospray Ionization of Polymers: Evaporation, Drop Fission, and Deposited Particle Morphology
Authors: Merrill Marriner H. , Pogue William R. , Baucom Jared N.
Published: March 2015

The fundamental challenge of nanomanufacturing is to create, control, and assemble enormous quantities of nanoscale objects and distribute them over large surface areas. Electrospray ionization (ESI) has the potential to address this challenge due to its simplicity, applicability to a broad range of materials, and intrinsic scalability. ESI uses high voltages to electrically charge and disperse materials ranging in size from sub-nanometers to micrometers in diameter, which can then be guided and deposited on a substrate. However, the interactions between initial spray parameters and final deposited morphology are not well understood. In this study, we show that when electrospraying polymers, deposited particle size and morphology can be modified through the initial polymer concentration and nozzle-substrate distance. We report the results of electrospraying 0.1% and 0.5% concentrations of poly(acrylic acid) (PAA) onto substrates with 1, 3, and 5 cm nozzle-substrate distances. Scanning electron microscopy showed that deposited particles ranged from less than 10 nm to nearly 200 nm in diameter with tight, multi-modal size distributions. Particle shape and spread on the substrate were also examined. We use physics-based models to show that the size distributions are a function of the evaporation and drop fission during the spray along with the effect of solute concentration gradients within an evaporating drop. This work validates our previously developed models and will lead to future process guidelines.
Process Performance of Silicon Thin-Film Transfer Using Laser Micro-Transfer Printing
Authors: Al-okaily Ala’a , Ferreira Placid
Published: March 2015

Micro-transfer printing is rapidly emerging as an effective pathway for heterogeneous materials integration. The process transfers pre-fabricated micro- and nano-scale structures, referred to as “ink,” from growth donor substrates to functional receiving substrates. As a non-contact pattern transfer method, Laser Micro-Transfer Printing (LMTP) has been introduced to enhance the capabilities of transfer printing technology to be independent of the receiving substrate material, geometry, and preparation. Using micro fabricated square silicon as inks and polydimethylsiloxane (PDMS) as the stamp material. The previous work on the LMTP process focused on experimentally characterizing and modeling the effects of transferred inks’ sizes and thicknesses, and laser beam powers on the laser-driven delamination process mechanism. In this paper, several studies are conducted to understand the effects of other process parameters such as stamp post dimensions (size and height), PDMS formulation for the stamp, ink-stamp alignment, and the shape of the transferred silicon inks on the LMTP performance and mechanism. The studies are supported by both experimental data for the laser pulse duration required to initiate the delamination, and thermo-mechanical FEA model predictions of the energy stored at the interface’s edges to release the ink (Energy Release Rate (ERR)), stress levels at the delamination crack tip (Stress Intensity Factors (SIFs)), and interfacial temperature. This study, along with previous studies, should help LMTP users to understand the effects of the process parameters on the process performance so as to select optimal operation conditions.
“Cut-Glue” Approximation in Problems on Static and Dynamic Mathematical Model Development
Authors: Neydorf Rudolf
Published: March 2015

The solution to the problem on building mathematical models of technical objects through the approximation of various experimental dependences is offered in the paper. This approach is especially true for modeling aircraft because the aerodynamic coefficients of their models can be obtained either by full-scale study or by computer simulation only. Currently, the experimental simulation is performed either through the regression analysis (RGA) methods, or through spline approximation. However, the RGA has a significant disadvantage, namely a poor approximability of piecewise and multiextremal dependencies. The RGA gives a rough approximation of the experimental data for similar curves. Spline approximation is free from this disadvantage. However, a high degree of discretization, a strict binding to the number of spline points, and a large number of equations, make this approach inconvenient for application when a compact model building and an analytic transformation are required.

A problem solution combining the advantages of both approaches and clearing up the troubles is offered in the paper. The proposed approach is based on the regression construction of the mathematical models of the dependence fragments, the multiplicative excision of these fragments in the local functional form, and on the additive combining of these local functions into a single analytic expression. The effect is achieved by using special “selection” functions multiplicatively limiting a nonzero definition domain for each of the approximating functions. The method is named “cut-glue” by the physical analogy of the approximation techniques. The order and structure of the approximating function for each segment can be arbitrary. A significant advantage of the “cut-glue” approximation is in a single analytic expression of the whole piecewise function instead of a cumbersome system of equations. The analytical and numerical studies of the properties and operational experience of the proposed method are resulted.
The Dependence of 3D Surface Roughness Parameters on High-Speed Milling Technological Parameters and Machining Strategy
Authors: Torims Toms , Logins Andris , Rosado Pedro Castellano , Gutiérrez Santiago , Torres Rafael
Published: March 2015

High-speed milling is an effective machining method extensively used in modern material processing. This machining method offers increased efficiency, quality and accuracy of the machined surface as well as considerably reducing overall production costs and machining time. This paper outlines comprehensive research into the impact of the technological strategy and processed materials on carefully selected 3D surface roughness parameters. This research provides manufacturers who use high-speed milling with recommendations on how to better obtain the desired surface roughness parameters. More specifically, it covers multifactorial analysis of the following factors: feed rate, manufacturing strategy, overlap and material influences on the most characteristic 3D surface parameters. The results are based on ANOVA – analysis of variance, where differences between groups of means are analysed using a range of statistical models.

Subsequent analysis and respective conclusions identify the most significant factors as being the material and high-speed milling manufacturing strategy. Analytically justified recommendations for manufacturers regarding the preferred high-speed milling strategies are provided.

The research concluded that the values of the selected 3D surface roughness parameters in high-speed milling depend significantly on the type of material being machined, milling mode and cutting tool overlap as well as feed. In particular, Sa - the arithmetic mean height, is highly sensitive to the milling mode.
Mathematical Model of the Influence of Process Parameters on Geometrical Values and Shape in MIG/MAG Multi-Track Cladding
Authors: Ratkus Andris , Torims Toms
Published: March 2015

The cladding process in the present case contributes to a repair technology, in which a new layer of material is created by using Metal Inert Gas/Metal Active Gas technology on inner cylindrical surfaces, e.g. bucket bores or hydro cylinders. The cladded layer is subsequently subjected to mechanical processing. Although cladding technology itself is well known, its results are hardly ever predicted with regard to inner surface renewal. In this paper, we explore the influence of cladding technological process parameters on geometrical values: the thickness, cross-section areas and shape of the newly cladded layer are established. Current research provided significant information which enabled mathematical models to be developed for inner surface cladding. Polynomial regression was used to create a mathematical model, where coefficients established with the SYSTAT software and their adequacy was checked using the analysis of variance technique. Thus an equation was obtained to help identify the effects of parameters on the final result. The most significant factor identified in cladding geometry is the amount of material that is supplied to the melting pool, followed by the process speed and heat input. The obtained coefficient describing the amount of material is presented, together with equations for calculating minimal thickness, efficient thickness and the multi-track cladding shape.
Multi-Layer Computational Modeling of Selective Laser Sintering Processes
Authors: Moser Daniel , Fish Scott , Beaman Joseph , Murthy Jayathi
Published: March 2015

Selective laser sintering (SLS) is an additive manufacturing technique able to rapidly create parts directly from a CAD model using a laser to selectively fuse successive layers of powder. However, defects can arise in SLS parts due to incomplete fusion of the powder layers or thermal stresses introduced by large temperature gradients during the part build. Accurate models of the SLS process are needed to ensure that high quality parts are produced and to allow new materials and designs to be used without requiring extensive experimentation. Most existing models of the SLS process are very narrowly focused, predicting the temperature history of a single powder layer after a single laser pass or examining the impact of a few processing parameters on the properties of the produced part. A model capable of predicting a complete temperature history during an entire part build does not yet exist. Therefore, a new thermal model able to simulate multiple powder layers is proposed.

A transient, three-dimensional, finite volume model is developed and implemented in ANSYS Fluent. A domain of cells representing multiple layers of an SLS build is initialized, some with the properties of air and some with the properties of powder, depending on cell location. A Gaussian heat source representing the laser is applied to the top layer of powder cells. The center of the Gaussian is varied with time along an established path to simulate the motion of the laser along the powder bed. At all times the three-dimensional heat equation is solved to produce a temperature profile of the powder bed. When the laser completes a full scan of the powder layer, the air cells directly above the powder layer are re-initialized as powder cells and re-set to an initial temperature, representing the addition of a new powder layer. The process is repeated for each new layer. Temperature history results from the model are validated against experimental data available in the literature and good agreement is obtained. As the model accounts for multiple powder layers, it can be used to simulate an entire part build and predict the impact of any of the SLS processing parameters on part quality and thus enable better control and optimization of the SLS process.
Application of a Morphing Wing Technology on Hydra Technologies Unmanned Aerial System UAS-S4
Authors: Gabor Oliviu Şugar , Simon Antoine , Koreanschi Andreea , Botez Ruxandra
Published: March 2015

The paper describes the application of a morphing wing technology on the wing of an Unmanned Aerial System (UAS). The morphing wing concept works by replacing a part of the rigid wing upper and lower surfaces with a flexible skin whose shape can be dynamically changed using an actuation system placed inside the wing structure. The aerodynamic coefficients are determined using the fast and robust XFOIL panel/boundary-layer codes, as the optimal displacements are calculated using an original, in-house optimisation tool, based on a coupling between the relatively new Artificial Bee Colony Algorithm, and the classical, gradient-based Broyden-Fletcher-Goldfarb-Shanno (BFGS) method. All the results obtained by the in-house optimisation tool have been validated using robust, commercially available optimization codes. Three different optimization scenarios were performed and promising results have been obtained for each. The numerical results have shown substantial aerodynamic performance increases obtained for different flight conditions, using the proposed morphing wing concept.
Secondary Flow Control on Axial Flow Compressor Cascade Using Vortex Generators
Authors: Diaa Ahmed M. , El-Dosoky Mohammed F. , Abdel-Hafez Omar E. , Ahmed Mahmoud A.
Published: March 2015

Axial flow compressors have a limited operation range due to the difficulty controlling the secondary flow. Vortex generators are considered to control the secondary flow losses and consequently enhance the compressor’s performance. In the present work, a numerical simulation of three-dimensional unsteady compressible flow has been developed in order to gain insight into the nature of this flow. Based on the numerical simulation, the effects of vortex generators with variable geometrical parameters and their application inside the cascade are investigated. The predicted flow fields with and without the vortex generators are presented and discussed. For each configuration of vortex generator, the total pressure and loss coefficient are calculated. The predicted velocity and pressure distributions at different locations are compared with the predicted and measured values available in the literatures.