bluuebunny/crossref_metadata_2025 huggingface dataset:
U.S. Securities and Exchange Commission (SEC) Staff issues no-action relief to facilitate implementation of Markets in Financial Instruments Directive II (MiFID II) research provisions
Authors: Delligatti Paul J. , Lane William P.
Published: March 2018

Purpose

The purpose of this paper is to summarize and discuss the implications of three related U.S. Securities and Exchange Commission (SEC) no-action letters dated October 26, 2017 that seek to address the provisions of MiFID II related to “inducements”.

Design/methodology/approach

Provides background information regarding MiFID II and summarizes each of the three SEC Staff no-action letters: the SIFMA letter, the ICI letter and the AMG letter.

Findings

The no-action letters provide market participants with increased clarity as to how certain aspects of their business activities, in particular the “bundling” or “unbundling” of payments for research and execution, can comply with potentially competing systems of regulations.

Originality/value

Practical guidance from experienced financial industry and investment management lawyers.
Association between nonsteroidal anti‐inflammatory drugs and atrial fibrillation among a middle‐aged population: a nationwide population‐based cohort
Authors: Chuang Shao‐Yuan , Hsu Pai‐Feng , Lin Fang‐Ju , Huang Ya‐Wen , Wang Gou‐Zhau , Chang Wei‐Chiao , Tsai Hui‐Ju
Published: March 2018

Aims

It remains inconclusive whether the use of nonsteroidal anti‐inflammatory drugs (NSAIDs) increases the risk of atrial fibrillation (AF), especially in middle‐aged Asian populations. In this study, we evaluated the association between NSAID use and the risk of AF in a nationwide population‐based study of middle‐aged individuals in Taiwan.

Methods

A nested case–control study was conducted using the National Health Insurance Research Database (NHIRD) in Taiwan. We identified the cases with a diagnosis of AF (ICD‐9‐CM codes: 427.31) and the matched controls from three independent Longitudinal Health Insurance Databases (LHIDs) derived from the NHIRD from data collected from 2001 to 2013. Conditional logistic regression models with covariate adjustment were performed to evaluate the association between NSAID use and the risk of AF.

Results

A total of 57 058 participants (28 529 AF cases and 28 529 matched controls) were included. Participants with NSAID use had an elevated risk of AF compared to non‐users [adjusted odds ratio (AOR) = 1.18, 95% confidence interval (CI): 1.14–1.23]. When further assessing the effects of different classes of NSAIDs on the risk of AF, the results showed that participants who used non‐selective NSAIDs had a significantly elevated risk of AF (AOR = 1.18, 95% CI: 1.13–1.23), as did participants with a combined use of selective and non‐selective NSAIDs (AOR = 1.30, 95% CI: 1.21–1.39).

Conclusions

NSAID use was associated with an increased risk of AF occurrence among the participants included in our study cohort. Closely monitoring the adverse effects of NSAID treatment on the risk of AF will be important, particularly among individuals at high risk.
Increasing amphetamine use and forensic involvement among clients of three residential Indigenous alcohol and other drug services in Victoria, Australia
Authors: Goutzamanis Stelliana , Higgs Peter , Richardson Mike , MacLean Sarah
Published: March 2018

Introduction and Aims

Indigenous people seeking residential alcohol and other drug (AOD) rehabilitation in Victoria are most frequently referred to the Ngwala Willumbong Co‐operative (Ngwala). This study aimed to describe socio‐demographic changes in clients of Ngwala’s residential rehabilitation services between 2015 and 2016.

Design and Methods

Self‐assessment surveys completed upon screening for rehabilitation between May 2015 and November 2016 (n = 117) were analysed for socio‐demographic data, AOD use and mental health status. Ngwala’s monthly summary reports from January 2015 to December 2016 were analysed to compare primary drugs of concern, proportion of forensic clients assessed and admitted across 2015–2016. Independent t‐tests and tests of two proportions were used to compare variables between years, with differences considered significant when P < 0.05.

Results

Clients were predominantly Indigenous (n = 100, 91%), male (n = 92, 71%) and unemployed (n = 106, 93%). Most clients (n = 92, 88%) were at high risk of serious mental illness (by Kessler Psychological Distress Scale). A significantly higher proportion of forensic clients were admitted in 2016 (n = 221, 60%) compared to 2015 (n = 158, 43%; P < 0.001; 95% confidence interval −0.24, −0.10). The mean monthly number of clients listing amphetamines as their primary drug of concern upon assessment was greater in 2016 (21 ± 7.19 people) compared to 2015 (12 ± 2.78 people; P = 0.01; 95% confidence interval 3.13, 15.37).

Discussion and Conclusions

These findings suggest the proportion of Indigenous people in AOD treatment with amphetamine use problems or forensic involvement is increasing. These trends should be considered in service design and funding decisions.
Accountability y sociedad civil: el control político en la era digital
Authors: Ríos Ramírez Alejandra , Garro Jua Esteban
Published: March 2018

Este artículo tiene como objetivo exponer el peso que tienen actualmente las tecnologías de la información y la comunicación en el ejercicio del accountability societal. Para ello, se hace una reconstrucción del término accountability teniendo en cuenta sus dimensiones y tipologías. A continuación, se hace un contraste entre gobierno electrónico, gobierno abierto y el discurso de la transparencia. Concluimos que, aunque el análisis de los discursos y las propuestas que buscan ligar el uso de herramientas digitales a la promoción de la transparencia y el control político permite identificar avances significativos en lo concerniente al desarrollo de aplicaciones y portales para la liberación de datos estatales, no es muy clara la distinción entre las apuestas por la circulación libre de la información y las posibilidades reales de sanción y control sobre el Estado que aquellas promueven. Hemos hallado, mediante una exhaustiva revisión bibliográfica, que esa falta de claridad es un obstáculo para para conciliar el anhelo de gobiernos abiertos y transparentes con herramientas de fiscalización, monitoreo y sanción a la conducta de representantes y funcionarios públicos. A pesar de lo anterior, proponemos que dirigir la mirada de manera seria a las plataformas móviles como herramientas de control político posibilitaría una suerte de “gobernanza móvil” a partir de la cual se susciten prácticas de gobierno abierto articuladas a la real posibilidad de que los ciudadanos activos movilicen las agencias estatales orientadas a la sanción de aquellos funcionarios públicos que se excedan en sus ejercicios de administración y poder político.
Límites de responsabilidad de las convenciones internacionales de transporte de mercancías y posibilidad de reclamación bajo los seguros de transporte
Authors: García Luis Felipe , Gutiérrez Sokoloff Martín
Published: March 2018

El presente trabajo busca establecer, a partir de un análisis de las decisiones jurisprudenciales en diferentes países, cuál es el manejo que se le dá en cada una de estas jurisdicciones a la aplicación de los límites de responsabilidad establecidos en convenciones internacionales o en normativa interna. Con esto se busca crear un panorama para las compañías de seguros que explotan el ramo de seguros de transporte respecto de la posibilidad de recuperación cuando ejercen una acción de subrogación en contra del transportador.
El desafío de los daños colectivos y del riesgo del desarrollo en el derecho del consumo. Autonomía o dependencia. Sus contornos propios
Authors: Garrido Cordobera Lidia M. R.
Published: March 2018

Se aborda en este trabajo la situación que debe afrontar el derecho en una economía global y de traslación de riesgos en materia de consumo y la solución posible frente a daños masivos a consumidores no detectables por el estado de la ciencia en el momento de puesta en circulación y cuáles son los contornos que el tema presenta.
La declaración del riesgo en el Seguro de vida, deber de informar y de informarse
Authors: Rios Ossa Roberto
Published: March 2018

El deber de declaración del riesgo asegurado en el ordenamiento jurídico chileno transitó de un sistema de declaración espontáneo a uno guiado por cuestionario, según las nuevas exigencias legales introducidas por la ley 20.667 a la regulación del contrato de seguro, que recoge, además, el principio favor contractus.
Problemática en torno a la limitación de la prestación en los seguros de responsabilidad civil en Argentina
Authors: Compiani Maria Fabiana , Facal Carlos José María
Published: March 2018

El seguro contra la responsabilidad civil nació para proteger el patrimonio de quienes contratan este seguro. Como todo seguro, reconoce límites precisos: el daño causado, la suma asegurada y otras estipulaciones que fijan descubiertos a cargo del propio asegurado y exclusiones de cobertura. Pero al mismo tiempo, el seguro contra la responsabilidad civil contribuyó a la expansión de las indemnizaciones que acuerdan los tribunales. El derecho moderno pretende una reparación creciente de los damnificados y, en su afán de brindar soluciones satisfactorias a las víctimas, empiezan a dictarse algunas sentencias que pretenden desconocer los límites tradicionales y hasta la misma viabilidad del seguro contra la responsabilidad civil. Los autores dejan entrever que quizá haya llegado la hora de recurrir a otras herramientas para dar respuesta a quienes sufren daños.
Pipelines for War and Peace
Authors: Wicks Frank
Published: March 2018

This article demonstrates the inevitability of pipelines for the development and growth of a city, state, or a country. During the World War II, the United States government produced and distributed posters, pamphlets, and movies to feature the heroic efforts of the workers and success of the pipelines. It inspired Americans on the home front and overseas. The potential of delivering substantial amounts of natural gas to the North overwhelmed the obstacles and conversion costs. A small group of oil industry investors started to raise money and formed the Texas Eastern Transmission Corp. New York City received natural gas for the first time in 1952. Seattle in 1956 became the last major city to receive pipeline natural gas.
Gas Turbine Disc Resurrection?
Authors: Langston Lee S.
Published: March 2018

This article discusses various aspects and need for gas turbine disc resurrection. Depending on the record keeping system used by the government, airlines, OEMs, and users, gas turbine discs are retired before they reach a critical state that might lead to their failure. Experts have reviewed current approaches to gas turbine life management. They point out that the high reliability and safety of modern gas turbines is largely due to a combination of improved materials, conservative design and maintenance philosophies, and improved life prediction capabilities. However, there are significant safety and economic concerns involved in the use of life predictions applied to extend disc life. Another resurrection path is the question of appropriating used discs to manage safe continued operation from unexpected field damage until new discs become available. Disc resurrection may be an attractive prospect, but lots of questions need to be answered before gas turbine users adopt the practice.
The Nanoscale Frontier
Authors: Winters Jeffrey
Published: March 2018

This article presents an overview of various aspects of nanoscale technology. As opposed to the macroscale, where water molecules next to a pipe wall have zero velocity, in nanochannels, fluid molecules slip at the channel surface, experiencing an enhanced convective transport. Nanotechnology can also help us alter natural designs. Carbon nanotubes act like a reinforcement to give synthetic tissue the strength, stiffness, and viscoelastic performance of natural membranes. In order to store macroscopically significant amounts of energy, one needs to deform large numbers of carbon nanotubes. It is more challenging still to deform them in a way that maintains high-energy density of overall system. Micro- and nanoscale structures have given us capabilities to interact with cells and pathogens at their level as never before and helped us understand how they live, grow, multiply, differentiate, and die.
Safety Overhead
Authors: Hyam Kathryn , Reddington Patricia
Published: March 2018

This article emphasizes the importance of safety standards and codes developed by ASME for ensuring construction safety. Within the committee framework managed by ASME, the B30 standards committee is always looking to incorporate the industry's latest technological advances and best practices. While the basic principles of ancient machines are still applicable in many modern lifting devices, advances in materials and technology have allowed for cranes to be adapted to aid in accomplishing difficult and unusual tasks. Some cranes are even used to erect other cranes, which then go on to build the skyscrapers that dot our skyline. Even with all these changes, ensuring safety is just as important today as it was in 1916. ASME is leading the way in helping to ensure cranes can be a common and essential part of the everyday landscape.
Cycling
Authors: Dixon Warren , Bellman Matthew
Published: March 2018

This article presents an overview of a control systems perspective. An electric field when applied to yield functional tasks is called as functional electrical stimulation (FES). FES is commonly prescribed as a treatment for various neurological disorders. Given the existence of regions in the crank cycle where it is inefficient to produce torque, a motor can be included as another torque source. FES control of the muscles yields cadence tracking in torque efficient regions, while the motor yields cadence tracking when it is efficient for the limbs to produce torque. The inclusion of a motor enables switching between stable systems and eliminates the need for the development of sufficient dwell-time conditions. Hence, the development of adaptive switched controllers for motorized FES-cycling systems may have a closer horizon. The inclusion of a motor also expands the possible control objectives that can be pursued.
Large and Small Turbofans
Authors: Kroeger Jim
Published: March 2018

This article presents a study on common design challenges of large and small turbofans. Turbofan engines powering large transport aircraft have demonstrated much different design objectives than business-jet turbofans including thrust, range, mission type, development cost, unit price, maintainability standards, and production quantities. Prolific use of ‘thermal barrier coating’ has helped turbine designers compensate for the inability to distribute a large quantity of small diameter film holes over the turbine blade surface. The historical trends in overall pressure ratio observed for both large and small turbofans have parallel slopes. Small turbofans lag behind the larger engines due to the miniaturization required for low flowrates characteristic of the smaller engines. These trends are qualitatively demonstrated, showing the growth in both the overall engine pressure ratio and turbine inlet temperature for several decades. It has been noted in this paper that the importance of high-performance impeller designs and intricate turbine blade cooling concepts for very low compressor exit corrected flows has not yet been fully appreciated.
Thunder on the Horizon
Authors: Mintz Testa Bridget
Published: March 2018

This article discusses the advantageous usage of thorium-based breeder reactors in the nuclear industry. Since thorium is more abundant than uranium and can be turned into fuel without the enrichment process needed to concentrate U-235, experts believe that the thorium fuel cycle could be more sustainable than the uranium cycle. The addition of thorium to the fluid salt helps reduce uranium consumption. ThorCon, a Florida-based nuclear power startup, has developed the ThorCon reactor that will be breeding some of its own fuel by irradiating thorium. Thorium is about three times more abundant than uranium, and all of it can be used to create a fuel source for nuclear reactors. Thor Energy is developing two different families of thorium-based fuels with both U-235 and Pu-239 as the fissile driver material. The interest in thorium suggests that it is going to take an unconventional approach to lead to the much-anticipated Nuclear Renaissance.
The Merger of Technology & Talent
Authors: Goldsmith Marc
Published: March 2018

This article discusses various challenges faced by the utilities industry in retaining knowledge and important institutional awareness as trained engineers are closing their retirement age. Utilities need to find a way to hold onto critical knowledge and important institutional awareness of these long-time employees while letting go of the obsolete information that they also hold. However, through various technological innovations, the industry is trying to take full advantage of the Internet of Things (IoT) and the wired and wireless world. Advanced Meter Infrastructure—the so-called Smart Grid—and the suite of devices known as the IoT will play a key role in the transition to a new workforce, and change the types of workers utilities employ. This latest technology will require new skill sets to construct, operate, maintain, and decommission. Digital technology, combined with and contained in such devices as cameras, strain gauges, accelerometers, microphones, and the like, can replace the senses of workers. Software coupled with computing power can improve the speed and accuracy of the engineering calculations or better analyze risk. Robots or unmanned vehicles can carry tools and sensors where it is dangerous or uneconomical to send workers.
Modal Analysis of Fuel Injection Systems and the Determination of a Transfer Function Between Rail Pressure and Injection Rate
Authors: Ferrari A. , Paolicelli F.
Published: March 2018

A detailed analysis of a common rail (CR) fuel injection system, equipped with solenoid injectors for Euro 6 diesel engine applications, has been performed in the frequency domain. A lumped parameter numerical model of the high-pressure hydraulic circuit, from the pump delivery to the injector nozzle, has been realized. The model outcomes have been validated through a comparison with frequency values that were obtained by applying the peak-picking technique to the experimental pressure time histories acquired from the pipe that connects the injector to the rail. The eigenvectors associated with the different eigenfrequencies have been calculated and physically interpreted, thus providing a methodology for the modal analysis of hydraulic systems. Three main modal motions have been identified in the considered fuel injection apparatus, and the possible resonances with the external forcing terms, i.e., pump delivered flow rate, injected flow rate, and injector dynamic fuel leakage through the pilot valve, have been discussed. The investigation has shown that the rail is mainly involved in the first two vibration modes. In the first mode, the rail performs a decoupling action between the high-pressure pump and the downstream hydraulic circuit. Consequently, the oscillations generated by the pump flow rates mainly remain confined to the pipe between the pump and the rail. The second mode is centered on the rail and involves a large part of the hydraulic circuit, both upstream and downstream of the rail. Finally, the third mode principally affects the injector and its internal hydraulic circuit. It has also been observed that some geometric features of the injection apparatus can have a significant effect on the system dynamics and can induce hydraulic resonance phenomena. Furthermore, the lumped parameter model has been used to determine a simplified transfer function between rail pressure and injected flow rate. The knowledge obtained from this study can help to guide designers draw up an improved design of this kind of apparatus, because the pressure waves, which are triggered by impulsive events and are typical of injector working, can affect the performance of modern injection systems, especially when digital rate shaping strategies or closely coupled multiple injections are implemented.
Nonlinear Analysis of Rotordynamic Fluid Forces in the Annular Plain Seal by Using Extended Perturbation Analysis of the Bulk-Flow Theory (Influence of Whirling Amplitude in the Case With Concentric Circular Whirl)
Authors: Ikemoto Atsushi , Inoue Tsuyoshi , Sakamoto Kazukiyo , Uchiumi Masaharu
Published: March 2018

The bulk-flow theory for the rotordynamic (RD) fluid force has been investigated for many years. These conventional bulk-flow analyses were performed under the assumption and restriction that the whirl amplitude was very small compared to the seal clearance while actual turbomachinery often causes the large amplitude vibration, and these conventional analyses may not estimate its RD fluid force accurately. In this paper, the perturbation analysis of the bulk-flow theory is extended to investigate the RD fluid force in the case of concentric circular whirl with relatively large amplitude. A set of perturbation solutions through third-order perturbations are derived explicitly. It relaxes the restriction of conventional bulk flow analysis, and it enables to investigate the RD fluid force for the whirl amplitude up to about a half of the clearance. Using derived equations, the nonlinear analytical solutions of the flow rates and pressure are deduced, and the characteristics of the RD fluid force are investigated in both radial and tangential directions. The influence of the whirl amplitude on the RD fluid force is explained and validated by comparing with computational fluid dynamics (CFD) analysis. These results are useful for the analysis and prediction of frequency response of the vibration of the rotating shaft system considering the RD fluid forces.
Piecing Together Product Dissection: How Dissection Conditions Impact Student Conceptual Understanding and Cognitive Load
Authors: Starkey Elizabeth M. , McKay Alexander S. , Hunter Samuel T. , Miller Scarlett R.
Published: March 2018

Product dissection has been widely deployed in engineering education as a means to aid in student's understanding of functional product elements, development of new concept ideas, and their preparation for industry. However, there are large variations in the dissection activities employed in education with little research geared at understanding the impact of these variations on student cognitive load requirements and, ultimately, student conceptual understanding. This is problematic because without this knowledge, we do not know what components of product dissection impact (positively or negatively) conceptual understanding of the dissected product and how this is related to the cognitive requirements of the dissection activity. Therefore, the purpose of this study was to investigate how the type of product dissected (complexity and product power source), the virtuality of the product (physical or virtual), and the type of dissection activity performed impacted student conceptual understanding and cognitive requirements through a factorial experiment with 141 engineering students. While the type of cognitive load varied between virtually and physically dissecting products, no differences were found in subsequent levels of conceptual understanding. This indicates that virtual environments may be used as a proxy for physical environments without impacting the conceptual understanding of products by students. These results are used to develop recommendations for the use of product dissection in education and propel future research that investigates relationships between example-based design practices and student understanding outcomes.
Design of Powered Ankle-Foot Prosthesis With Nonlinear Parallel Spring Mechanism
Authors: Gao Fei , Liu Yannan , Liao Wei-Hsin
Published: March 2018

In this paper, a powered ankle-foot prosthesis with nonlinear parallel spring mechanism is developed. The parallel spring mechanism is used for reducing the energy consumption and power requirement of the motor, at the same time simplifying control of the prosthesis. To achieve that goal, the parallel spring mechanism is implemented as a compact cam-spring mechanism that is designed to imitate human ankle dorsiflexion stiffness. The parallel spring mechanism can store the negative mechanical energy in controlled dorsiflexion (CD) phase and release it to assist the motor in propelling a human body forward in a push-off phase (PP). Consequently, the energy consumption and power requirements of the motor are both decreased. To obtain this desired behavior, a new design method is proposed for generating the cam profile. Unlike the existing design methods, the friction force is considered here. The cam profile is decomposed into several segments, and each segment is fitted by a quadratic Bezier curve. Experimental results show that the cam-spring mechanism can mimic the desired torque characteristics in the CD phase (a loading process) more precisely. Finally, the developed prosthesis is tested on a unilateral below-knee amputee. Results indicate that, with the assistance of the parallel spring mechanism, the motor is powered off and control is not needed in the CD phase. In addition, the peak power and energy consumption of the motor are decreased by approximately 37.5% and 34.6%, respectively.
Determination of Optimum Preload Considering the Skidding and Thermal Characteristic of High-Speed Angular Contact Ball Bearing
Authors: Fang Bin , Zhang Jinhua , Wan Shaoke , Hong Jun
Published: March 2018

Skidding is a typical behavior of high-speed angular contact ball bearings. Studies show that the effect of preload on bearing skidding and thermal characteristic is essential but insufficient. This paper proposed a comprehensive mathematic model to predict the skidding behavior of ball bearing, and the influences of the interactions between ball and raceways, cage and lubricant have been taken into consideration. Based on the proposed model, the bearing heating generation was calculated and the effects of skidding on bearing heating and temperature rise were analyzed. For validation proposes, a hydraulic variable preload experimental setup has been built, and the temperature rise of bearing outer rings under different preloads and speeds was collected and analyzed. The results indicated that at high speeds, the skidding has a significant negative effect on bearing temperature rise, and a proper preload can effectively prevent skidding and decrease temperature rise. Therefore, for a high-speed spindle-bearing system, an optimum preload that produced the minimum temperature rise can be obtained.
The Sensitivity to the Lode Parameter in Ductile Failure of Tubular Steel Grades
Authors: Barsoum I. , Al-Khaled M. A.
Published: March 2018

Ductile failure in steels is highly controlled by the stress state, characterized by the stress triaxiality (T) and the Lode parameter (L). The ASME Boiler and Pressure Vessel Code requires pressure vessels to be designed to resist local ductile failure. However, the standard does not account for the Lode parameter dependence in its failure locus. In this study, the influence of the stress state, characterized T and L, on the ductility of ASME tubular product steel grades is investigated. Two seamless pipes of midstrength carbon steel SA-106 Gr. B and high-strength superduplex steel SA-790 were considered. Ring specimen geometries for plane strain (PS) stress state (L = 0) and tensile stress (TS) state (L = −1) are utilized to establish the ductile failure locus in terms of T and L for the two steels. The experimental results (EXP) show that the effect of the Lode parameter on the failure locus for the SA-106 Gr. B steel is insignificant, whereas for the SA-790 steel, the effect is rather significant. A parameter SL is introduced in order to quantify the sensitivity of the failure locus to the Lode parameter. It is found that for materials with ultimate strength lower than about 550 MPa, the sensitivity to L is insignificant (SL ≈ 1), whereas for materials with ultimate strength higher than 550 MPa, the sensitivity to L could be significant (SL > 1). Scanning electron microscopic (SEM) analysis of the fracture surfaces revealed that the sensitivity to L is closely associated with the rupture micromechanisms involved.
Aerothermal Characteristics of Solid and Slitted Pentagonal Rib Turbulators
Authors: Tariq Andallib , Sharma Naveen , Mishra Manish
Published: March 2018

This work is an experimental study of detailed aerothermal characteristics inside a duct carrying an array of solid and permeable pentagonal ribs with a parallel and inclined slit, mounted on the bottom wall. The rib height-to-hydraulic diameter ratio, the rib pitch-to-height ratio, and the open area ratio fixed during experiments are 0.125%, 12%, and 25%, respectively. The heat transfer coefficient (HTC) distribution is mapped by using transient liquid crystal thermography (LCT), while the detailed flow measurements are performed by using particle image velocimetry (PIV). The primary focus of the study is to assess the influence of inter-rib region flow characteristics on the local heat transfer fields. The heat transfer and friction factor measurements are evaluated along with thermohydraulic performances at different Reynolds numbers, i.e., 26,160, 42,500, and 58,850. Performance indexes show that the pentagonal ribs with the inclined-slit are superior to other configurations from both perspective. Aerothermal features within inter-rib region were elucidated by analyzing the time-averaged streamlines, mean velocities, fluctuation statistics, vorticity, turbulent kinetic energy (TKE) budget terms, and local and spanwise-averaged Nusselt number as well as augmentation Nusselt numbers. Critical flow structures and coherent structures were identified, which illustrate about different flow dynamic processes. The flow emanating out of the inclined-slit pentagonal rib significantly affects the magnitude of streamwise velocity, fluctuation statistics, vorticity, and TKE budget terms at the downstream corner, whereas the dissipation term of TKE budget correlates well with the surface heat transfer distribution.
Geometric Approach to the Realization of Planar Elastic Behaviors With Mechanisms Having Four Elastic Components
Authors: Huang Shuguang , Schimmels Joseph M.
Published: March 2018

This paper addresses the passive realization of any selected planar elastic behavior with redundant elastic manipulators. The class of manipulators considered are either serial mechanisms having four compliant joints or parallel mechanisms having four springs. Sets of necessary and sufficient conditions for mechanisms in this class to passively realize an elastic behavior are presented. The conditions are interpreted in terms of mechanism geometry. Similar conditions for nonredundant cases are highly restrictive. Redundancy yields a significantly larger space of realizable elastic behaviors. Construction-based synthesis procedures for planar elastic behaviors are also developed. In each, the selection of the mechanism geometry and the selection of joint/spring stiffnesses are completely decoupled. The procedures require that the geometry of each elastic component be selected from a restricted space of acceptable candidates.
Effectiveness of Bottom Insulation of a Salinity Gradient Solar Pond
Authors: Ganguly Sayantan , Date Abhijit , Akbarzadeh Aliakbar
Published: March 2018

This technical brief presents a study on the effectiveness of the bottom insulation of a salinity gradient solar pond (SGSP) in Melbourne, Australia. Insulation is applied at the bottom of a SGSP in order to minimize the heat loss from the SGSP to the ground underneath. But selection of optimum thickness of the insulation to extract the best thermal performance of an SGSP is a challenge as insulation involves significant investment. Hence, modeling heat loss from SGSP to the ground before and after applying the insulation is thus very essential. In this study, a layer of polystyrene is used as insulation at the bottom of SGSP. The temperature distribution in the SGSP and ground below it, the efficiency of the SGSP and the heat removal from SGSP are estimated for the SGSP without insulation and with insulation of different thicknesses. The results show that the insulation definitely reduces the heat loss from the SGSP to the ground, but to a certain extent. Insulation beyond a certain thickness is proved to be ineffective in increasing the efficiency or reducing the heat loss to ground and thus unable to enhance the thermal performance of the SGSP.
Iterative Multiscale Approach for Heat Conduction With Radiation Problem in Porous Materials
Authors: Haymes Ronen , Gal Erez
Published: March 2018

This paper describes a thermal homogenization approach to the application of a multiscale formulation for heat conduction with radiation problems in a porous material. The suggested formulation enables to evaluate the effective macroscopic thermal conductivity, based on the microscopic properties such as porosity, and can also provide the microscopic radiosity heat flux, based on the macroscopic temperature gradient field. This is done by scaling up and down between the microscopic and macroscopic models according to the suggested methodology. The proposed methodology involves a new iterative upscaling procedure, which uses heat conduction at macroscopic problem and heat transfer by conduction and radiation at microscopic problem. This reduces the required computational time, while maintaining the required level of accuracy. The suggested multiscale formulation has been verified by comparing its results with reference finite element (FE) solutions of porous (filled with air) materials examples; the results shows excellent agreement (up to 5% discrepancy) with reference solutions. The efficiency of the suggested formulation was demonstrated by solving a full-scale engineering transient problem.
Three Way Catalyst-Selective Catalytic Reduction Aftertreatment System Evaluation for a Lean Burn Gasoline Engine Operating in Homogenous Charge Compression Ignition, Spark-Assisted Compression Ignition, and Spark-Ignited Combustion Modes
Authors: Easter Jordan , Bohac Stanislav V.
Published: March 2018

Low temperature and dilute homogenous charge compression ignition (HCCI) and spark-assisted compression ignition (SACI) can improve fuel efficiency and reduce engine-out NOx emissions, especially during lean operation. However, under lean operation, these combustion modes are unable to achieve Environmental Protection Agency (EPA) Tier 3 emissions standards without the use of lean aftertreatment. The three way catalyst (TWC)-SCR lean aftertreatment concept investigated in this work uses periodic-rich operation to produce NH3 over a TWC to be stored on a selective catalytic reduction (SCR) catalyst for NOx conversion during subsequent lean operation. Experiments were performed with a modified 2.0 L gasoline engine that was cycled between lean HCCI and rich SACI operation and between lean and rich spark-ignited (SI) combustion to evaluate NOx conversion and fuel efficiency benefits. Different lambda values during rich operation and different times held in rich operation were investigated. Results are compared to a baseline case in which the engine is always operated at stoichiometric conditions. SCR system calculations are also presented to allow for comparisons of system performance for different levels of stored NH3. With the configuration used in this study, lean/rich HCCI/SACI operation resulted in a maximum NOx conversion efficiency of only 10%, while lean/rich SI operation resulted in a maximum NOx conversion efficiency of 60%. If the low conversion efficiency of HCCI/SACI operation could be improved through higher brick temperatures or additional SCR bricks, calculations indicate that TWC-SCR aftertreatment has the potential to provide attractive fuel efficiency benefits and near-zero tailpipe NOx. Calculated potential fuel efficiency improvement relative to stoichiometric SI is 7–17% for lean/rich HCCI/SACI with zero tailpipe NOx and −1 to 5% for lean/rich SI with zero tailpipe NOx emissions. Although the previous work indicated that the use of HCCI/SACI increases the time for NH3 to start forming over the TWC during rich operation, reduces NH3 production over the TWC per fuel amount, and increases NH3 slip over the SCR catalyst, if NOx conversion efficiency could be enhanced, improvements in fuel efficiency could be realized while meeting stringent tailpipe NOx standards.
To Demonstrate the Potential Application of “Low Temperature and High Performance Silicon Heterojunction Solar Cells Fabricated Using HWCVD” in Wireless Sensor Network: An Initial Research
Authors: Agarwal Mohit , Munjal Amit , Dusane Rajiv
Published: March 2018

Wireless sensor network (WSN) is widely used in a variety of applications including habitat monitoring, military surveillance, environmental monitoring, scientific applications, etc. The major limitation of WSN is that sometimes it is not feasible to replace or recharge the battery once it gets fully exhausted and thus, it limits the lifetime of WSN. One of the possible solutions to overcome this limitation is to incorporate any energy harvesting device, which can use the alternative energy sources to charge the battery. However, the processing temperature and the performance of energy harvesting devices limit their applications. In this paper, low temperature and high performance single-sided silicon heterojunction (SHJ) solar cells are fabricated with 13% efficiency using hot-wire chemical vapor deposition (HWCVD) method. This paper also describes an energy management model that successfully addresses the various issues in the existing energy harvesting models. In order to implement the proposed model, the results show that the high efficiency SHJ solar cells are best suitable candidate as an energy harvesting device that can be incorporated inside the node. The subsequent analysis shows that the consumed power per day by the node can be successfully recovered from the SHJ solar cells, if the sunlight is available only for 25 min in a day with 100 mW/cm2 intensity. This clearly indicates that the node's battery will remain fully charged if the above said condition is satisfied, which seems to be very feasible. Finally, one can conclude that the node functioning will remain active till the battery lifetime i.e., approximately 30 years for Li-ion battery.
Numerical and Experimental Analyses of Dynamic Characteristics for Liquid Annular Seals With Helical Grooves in Seal Stator
Authors: Nagai K. , Kaneko S. , Taura H. , Watanabe Y.
Published: March 2018

Numerical and experimental analyses were carried out to investigate the dynamic characteristics of liquid annular seals with helical grooves in the seal stator. In the numerical analysis, the governing equations were the momentum equations with turbulent coefficients and the continuity equation, all averaged across the film thickness and expressed using an oblique coordinate system in which the directions of coordinate axes coincided with the circumferential direction and the direction along the helical grooves. These governing equations were solved numerically to obtain the dynamic characteristics, such as the dynamic fluid-film forces, dynamic coefficients, and whirl-frequency ratio (WFR). The numerical analysis included the effect of both fluid inertia and energy loss at the steps between the helical groove and the land sections. In the experiments, the dynamic fluid-film pressure distributions, which were induced by a small whirling motion of the rotor about the seal center, were measured to obtain the dynamic characteristics. The equivalent numerical results reasonably agree with the experimental results, demonstrating the validity of the numerical analysis. The value of the tangential dynamic fluid force induced by the rotor whirling motion decreased with increasing the helix angle γ. Consequently, the values of the cross-coupled stiffness coefficient and WFR decreased with increasing γ and became negative for large γ. In general, pump rotors rotate with a forward whirling motion under normal operating conditions. Hence, the negative value of WFR for helically grooved seals contributes to rotor stability by suppressing the forward whirling motion of the rotor.
Fan Performance Scaling With Inlet Distortions
Authors: Defoe J. J. , Etemadi M. , Hall D. K.
Published: March 2018

Applications such as boundary-layer-ingesting (BLI) fans and compressors in turboprop engines require continuous operation with distorted inflow. A low-speed axial fan with incompressible flow is studied in this paper. The objectives are to (1) identify the physical mechanisms which govern the fan response to inflow distortions and (2) determine how fan performance scales as the type and severity of inlet distortion varies at the design flow coefficient. A distributed source term approach to modeling the rotor and stator blade rows is used in numerical simulations in this paper. The model does not include viscous losses so that changes in diffusion factor are the primary focus. Distortions in stagnation pressure and temperature as well as swirl are considered. The key findings are that unless sharp pitchwise gradients in the diffusion response, strong radial flows, or very large distortion magnitudes are present, the response of the blade rows for strong distortions can be predicted by scaling up the response to a weaker distortion. In addition, the response to distortions which are composed of nonuniformities in several inlet quantities can be predicted by summing up the responses to the constituent distortions.
Influence of the Operating Conditions of Two-Degree-of-Freedom Planetary Gear Trains on Tooth Friction Losses
Authors: Esmail Essam Lauibi
Published: March 2018

In a planetary gear train (PGT), the power loss by tooth friction is a function of the potential power developed within the gear train elements rather than that being transmitted through it. In the present work, we focus on the operating conditions of two-degree-of-freedom (two-DOF) PGTs. Any operating condition induces its own internal power flow pattern; this implies that tooth friction loss depends on the mechanism of power loss developed in the gearing that differs from one case to another over the entire range of operating conditions. The approach adopted in this paper stems from a unification of the kinematics and tooth friction losses of PGTs and is based on potential powers and power ratios. The range of applicability of the power relations is investigated and clearly defined, and tooth friction loss formulas obtained by their use are tabulated. A short comparison with formulas currently available in the literature is also made. The simplicity of the proposed method for analyzing two-input or two-output planetary gear trains is helpful in the design, optimization, and control of hybrid transmissions. It assists particularly in choosing correctly the appropriate operating conditions to the involved application.
Flow Field and Wall Temperature Measurements for Reacting Flow in a Lean Premixed Swirl Stabilized Can Combustor
Authors: Park Suhyeon , Gomez-Ramirez David , Gadiraju Siddhartha , Kedukodi Sandeep , Ekkad Srinath V. , Moon Hee-Koo , Kim Yong , Srinivasan Ram
Published: March 2018

In this study, we provide detailed wall heat flux measurements and flow details for reacting flow conditions in a model combustor. Heat transfer measurements inside a gas turbine combustor provide one of the most serious challenges for gas turbine researchers. Gas turbine combustor improvements require accurate measurement and prediction of reacting flows. Flow and heat transfer measurements inside combustors under reacting flow conditions remain a challenge. The mechanisms of thermal energy transfer must be investigated by studying the flow characteristics and associated heat load. This paper experimentally investigates the effects of combustor operating conditions on the reacting flow in an optical single can combustor. The swirling flow was generated by an industrial lean premixed, axial swirl fuel nozzle. Planar particle image velocimetry (PIV) data were analyzed to understand the characteristics of the flow field. Liner surface temperatures were measured in reacting condition with an infrared camera for a single case. Experiments were conducted at Reynolds numbers ranging between 50,000 and 110,000 (with respect to the nozzle diameter, DN); equivalence ratios between 0.55 and 0.78; and pilot fuel split ratios of 0 to 6%. Characterizing the impingement location on the liner, and the turbulent kinetic energy (TKE) distribution were a fundamental part of the investigation. Self-similar characteristics were observed at different reacting conditions. Swirling exit flow from the nozzle was found to be unaffected by the operating conditions with little effect on the liner. Comparison between reacting and nonreacting flows (NR) yielded very interesting and striking differences.
A Random Walk Model Approach for the Wheel-Rail Contact Force Estimation
Authors: Niola Vincenzo , Strano Salvatore , Terzo Mario
Published: March 2018

The wheel-rail contact strongly influences the dynamics of the railway vehicles. This interaction is affected by several conditioning factors such as vehicle speed, wear, and adhesion level, and, moreover, it is nonlinear. As a consequence, the modeling and the observation of this kind of phenomenon are complex tasks but, at the same time, they constitute a fundamental step for the estimation of the adhesion level or for the vehicle condition monitoring. This paper presents a novel technique for the real time estimation of the wheel-rail contact forces that allows an a priori no knowledge of this kind of mechanism because a random walk model (RWM) approach is adopted and integrated in a complete model based estimator for railway vehicle.
Optimal Design and Analysis of NIOFPID-Based Direct Power Control to Strengthen DFIG Power Control
Authors: Darvish Falehi Ali
Published: March 2018

A high-performance controller and strategy can significantly ameliorate the dynamic and transient capability of doubly fed induction generator (DFIG) based wind turbine. As regards, the wind speed has essentially defined the generated power by DFIG, thus, both the active and the reactive power must be followed out according to the entrance wind in the nominal and disturbance conditions. Toward this objective, noninteger order fuzzy proportional integral derivative (NIOFPID) controller based direct power control (DPC) strategy is proposed in this paper to minimize the deviation of both active and reactive power with the aim of accurate and speedy tracking of these powers. In the same vein, the aforementioned problem must be formulized in the form of the multi-objective optimization problem. Multi-objective particle swarm optimization (MOPSO) is here taken into account to intermingle with the simultaneous coordination of NIOFPIDs. The performance of held forth controller has been further evaluated under the affected power system caused by short circuit and flicker events. Eventually, the simulation results under transient and steady-state conditions demonstrate the dynamic and transient performance of NIOFPID-based DPC.