bluuebunny/crossref_metadata_2025 huggingface dataset:
Adjunctive nutrients in first‐episode psychosis: A systematic review of efficacy, tolerability and neurobiological mechanisms
Authors: Firth Joseph , Rosenbaum Simon , Ward Philip B. , Curtis Jackie , Teasdale Scott B. , Yung Alison R. , Sarris Jerome
Published: March 2018

Aim

The effects of nutrient‐based treatments, including adjunctive vitamin or antioxidant supplementation, have been explored extensively in long‐term schizophrenia. However, no systematic evaluation of trials in “first‐episode psychosis” (FEP) has been conducted, despite the potential benefits of using these treatments during the early stages of illness. Therefore, we aimed to review all studies examining efficacy, tolerability and the biological mechanisms of action, of nutrient supplementation in FEP.

Methods

A systematic review of electronic databases was conducted from inception to July 2017. All information on feasibility, clinical outcomes and mechanistic findings from nutrient supplementation clinical trials was extracted and systematically synthesized.

Results

Eleven studies with a total of 451 patients with FEP (from 8 independent randomized controlled trials) were eligible for inclusion. Six studies examined omega‐3 fatty acids, with inconsistent effects on psychiatric symptoms. However, mechanistic studies found significant improvements in hippocampal neuronal health and brain glutathione. Antioxidants “n‐acetyl cysteine” (n = 1) and vitamin C (n = 2) also improved oxidative status in FEP, which was associated with reduced psychiatric symptoms. No benefits were found for vitamin E (n = 1). Finally, one study trialling the amino acid taurine, showed significant improvements in positive symptoms and psychosocial functioning.

Conclusion

There is preliminary evidence that taurine improves outcomes in FEP, whereas effects of omega‐3 and antioxidant vitamins/amino‐acids are inconsistent; perhaps mainly benefitting patients with high levels of oxidative stress. Future studies should evaluate multifaceted dietary and supplementation interventions in FEP; targeting‐specific nutritional deficits and the range of aberrant biological processes implicated in the disorder.
Reviewer Acknowledgements
Authors: Young James
Published: March 2018

International Journal of Social Science Studies (IJSSS) would like to acknowledge the following reviewers for their assistance with peer review of manuscripts for this issue. Many authors, regardless of whether IJSSS publishes their work, appreciate the helpful feedback provided by the reviewers. Their comments and suggestions were of great help to the authors in improving the quality of their papers. Each of the reviewers listed below returned at least one review for this issue.Reviewers for Volume 6, Number 4Agboola O. Paul, Universiti Teknologi Malaysia, MalaysiaAhmet Yıkmış, Abant Izzet Baysal Univeersity, TurkeyAmanda ElBassiouny, Spring Hill College, USAAntónio Calha, Polytechnic Institute of Portalegre, PortugalBegoña Montero-Fleta, Universitat Politécnica de València, SpainEnzo Loner, University of Trento, ItalyHenry Poduthas, West Texas A&M University, USAJehu Onyekwere Nnaji, University of Naples II,Italy and Globe Visions Network Italy, ItalyJohn Boulard Forkuor , Kwame Nkrumah University of Science and Technology (KNUST), GhanaKatja Eman, Univerza v Mariboru, SloveniaKim L. Stansbury, Eastern Washington University, USAMałgorzata Haładewicz, Opole University of Technology, PolandMichael Brooks, North Carolina A&T State University, USAMickey Langlais, University of Nebraska – Kearney, USAMohammad Naji Shah Mohammadi, Kuala Lumpur, MalaysiaRasa Poceviciene, Siauliai University, LithuaniaSudershan Pasupuleti, The University of Texas, USA
La desintermediación en el contrato de seguro. De la bancaseguros al uso de red
Authors: Mejía Aramburo Sebastián
Published: March 2018

En este trabajo nos proponemos desarrollar los antecedentes normativos para llegar a lo que hoy en día se tiene, y hacer recomendaciones acerca de lo que hace falta para propiciar canales más flexibles, e incluyentes, que generen soluciones efectivas a las necesidades de todos los sectores de la economía, y de todos los estratos socio económicos, en la totalidad del territorio nacional.

Hoy en día, la omnicanalidad del sector asegurador es una realidad creciente, lo cual ha desencadenado en el fortalecimiento del canal directo, y de las alianzas estratégicas para la comercialización de seguros, lo que a su vez ha desencadenado ampliar la penetración del sector asegurador, y una mayor inclusión financiera; esto ha generado, que el otorgamiento de productos y servicios sean cada vez más acordes a las necesidades de los asegurados.

De acuerdo con este panorama regulatorio internacional, hay una tendencia desintermediadora en la comercialización de seguros, en búsqueda de una mayor inclusión del sector aseguradora, y a su vez este pueda generar una mayor penetración en el PIB de los países, el cual es bastante bajo en nuestros países latinoamericanos.

Dentro del panorama colombiano encontramos avances regulatorios que permiten la democratización del contrato de seguro, en donde cada vez una mayor cantidad de personas, de todos los estratos socioeconómicos han tenido mayores posibilidades de adquirir un seguro, no solo por sus costos, sino también por la posibilidad de adquirirlo en una gama de lugares cada vez más amplia. No obstante consideramos que falta, sin desconocer los pasos que en la materia se han hecho, así como la buena labor que ha sido desarrollada por parte del Gobierno Nacional y de los reguladores.
Seguro decenal: Reflexión sobre el seguro decenal como oportunidad del mercado asegurador colombiano ante las necesidades del sector constructor
Authors: Lombana Silva Fernando , González Triviño Carlos Eduardo
Published: March 2018

Historia, reflexiones y estudio técnico de la póliza decenal como una oportunidad para el mercado colombiano en búsqueda de posible solución para los compradores de soluciones de vivienda, para dar tranquilidad y garantizar la estabilidad de la construcción, encaminado a mitigar los errores de diseño, deficiencia de materiales y fallas en la estructura en la iniciativa de la ley 1796 de 2016 “ley de vivienda segura”.
Los seguros de vida en el marco de las actividades financieras
Authors: Rabosto Antonio
Published: March 2018

El seguro de vida en las actividades financieras, tiene como una de sus aplicaciones el seguro de vida de deudores o de saldos deudores, cuyo objetivo es amparar contra el riesgo muerte o incapacidad total y permanente del deudor, cubriendo la aseguradora en caso de siniestro una suma equivalente al saldo adeudado. Análisis descriptivo de las características y funcionamiento de este seguro.
Análisis estadístico del envejecimiento en España. Principales indicadores demográficos para el periodo 1975-2016
Authors: Pérez-Fructuoso María José
Published: March 2018

El envejecimiento de la población es un fenómeno que afecta a todos los países desarrollados aunque en el caso de España se presenta con 10 años de retraso respecto al resto de Europa. Dicho envejecimiento se debe fundamentalmente a que el número de nacimientos que se producen no garantiza el reemplazo generacional, lo que da lugar a una disminución de la población a medio plazo, y, simultáneamente, la esperanza de vida es mayor. Desde un punto de vista económico, esto implica que los gastos en pensiones serán mayores, ya que la población de 65 años y más, aumentará y además vivirá durante más años. En este artículo se analizan los factores demográficos que afectan en mayor medida a la situación de envejecimiento de la población española a lo largo de los últimos 41 años.
Accelerated Evolution
Authors: Bejan Adrian
Published: March 2018

This paper describes human application of their knowledge and technological ability to fly and continue to enhance that power. Through application of their knowledge and technological ability, human beings have evolved the ability to fly and continue to enhance that power. Aircraft technology evolution is about the evolving design of the human movement on the Earth’s surface: people, goods, materials, and everything else. As the whole vehicle or animal evolves toward becoming better at moving mass on the landscape, the organs remain imperfect, because each represents a compromise. The whole vehicle or animal is a construct of organs that are ‘imperfect’ only when examined in isolation. The vehicle design evolves over time and becomes a better construct for moving the vehicle mass on the world map. Flow architectures are evolving right now, throughout nature and in technologies. The legacy of all flow systems (animate and inanimate) is: they have moved weight horizontally and improved the efficiency of that movement because of design evolution.
The Rise of the DNA Nanorobots
Authors: Su Hai-Jun , Castro Carlos E.
Published: March 2018

This article is a study of various aspects of design of DNA nanorobots. When designed properly, DNA folds into tiny devices that move like macroscopic machines. Researchers have built a large and growing variety of complex DNA origami structures, including nanotubes; nanopores; and templates for proteins, nanoparticles, small molecules, and carbon nanotubes. In order to design the motion of a robotic arm or other macroscopic mechanism, engineers use the principles of kinematics; the same principles have been used to design DNA origami mechanisms. The design process for DNA origami mechanisms is still too cumbersome and error-prone, often requiring costly design iterations. New software that combines the capabilities of Computer Aided Engineering for DNA Origami (CANDO) and CANDO would streamline the process, creating a CAD-like program that would allow mechanical engineers untrained in biology to design DNA origami parts and mechanisms. Researchers envision a nanoscale equivalent of a walking robot that can travel from one position to another, a robotic manipulator or Stewart-Gough six-axis platform to precisely position molecules for specific tasks, and a mechanism like the crank-slider for injecting drugs into individual cells.
A Flipped Lab Experience for Mechatronics Education
Authors: Hurst Joshua , Mishra Sandipan
Published: March 2018

This article discusses different lab experiences for mechatronics education. Integrated software tools like MATLAB and Simulink and the availability of low-cost hardware are enabling technologies for the development of innovative laboratory and curriculum paradigms. An example of this is the laboratory curriculum developed for the Mechatronics course at Rensselaer, consisting of the Rensselaer Mechatronics Hardware Kit and the associated RASPLib software package, which allow the students to take the laboratory experience out of the classroom and into their dorm rooms. This has created unique opportunities for learning and pedagogy. The Mini Inverted Pendulum project provides students a complete Mechatronics design experience. The end objective is clear: use the motor and sensors in the Mechatronics Kit to balance the pendulum.
Signals and Systems II
Authors: Lygeros John , Sutter Tobias
Published: March 2018

This article discusses the concept of flipped classroom. The flipped classroom concept aims to make the most of the personal contact between students and instructor, using online tools to carry some basic material that can be consulted at all times and releasing contact hours for a more creative, dynamic exchange. Creating intelligent, yet empathetic, digital technology to guide students along a personal, enjoyable, and, most importantly, effective learning experience is difficult and expectedly so. Beyond their use as teaching and learning media, online tools also serve to monitor class progress, both at the level of individual students and at the level of the class. This information allows the instructor to tailor subsequent material to the current state of learning of the class as a whole. The researchers hope that with a blended learning approach, and with digital solutions for lecture preparation, classroom engagement, and personalized learning, each student has the opportunity to obtain the best learning experience for him or herself.
Trial By Ice
Authors: Zeldovich Lina
Published: March 2018

This article explores the experiments, use, and advantages of a next-generation ocean robot that would be used to explore oceans. Nereid Under Ice has been designed specifically for exploring the underside of Arctic sea ice, an area so far off-limits to scientists. As Nereid also must withstand extreme Arctic temperatures, its materials had to be tested even before it was assembled. In one flight, Nereid travelled over the fairly unexplored Arctic Gakkel Ridge system and its hydrothermal vents – fissures in sea floor that shoot up hot water – allowing scientists to survey life over these unique environs. Researchers hope it can also bring back fluid samples from the hydrothermal vents to offer insights into their ecosystems that sometimes host unique bacteria and life forms. The ability to explore these previously unreachable places opens new frontiers for polar science.
Reading the Big Picture
Authors: Skakoon James G.
Published: March 2018

This article presents views and experiences of several engineers. Experts point out that books about the nature and history of technology can help round out an engineering education. Spencer Bondhus, a B.S.M.E degree holder, has been developing new products in the medical device industry. Adam Leemans has completed a Master of Science degree in energy and sustainability. Jill Hershman, another B.S.M.E graduate, finds Fearless Leadership: High-Performance Lessons From the Flight Deck by Carey D. Lohrenz very helpful in broad engineering thinking. Maxim Budyansky, the chief technology officer and co-founder of Avitus Orthopaedics, likes to learn about different ways of thinking as in The Four Agreements: A Practical Guide to Personal Freedom by Don Miguel Ruiz and Become What You Are by Alan W. Watts and also from self-improvement books like Carnegie’s How to Win Friends and Influence People.
Talk to me
Authors: Brown Alan S.
Published: March 2018

This article explores the collaboration of artificial intelligence and voice recognition in day-to-day living. As everyday products grow smarter and more capable, voice promises to simplify how we communicate with smart cars, smart homes, smart offices, and smart factories. Instead of mastering one new app after another, voice could make it simpler to command them all. Incorporating voice interfaces is expected to transform product design. Voice recognition is also expanding its beachhead in physical products. Many new cars use voice to place calls, set the GPS, write and receive texts, change radio stations, and adjust the temperature. The machine learning software behind voice recognition analyzes data from actual interactions to improve its performance. It is expected that by coupling natural language requests to the deepest workings of the operating system, we may soon have new types of products that will give anyone access to features that only a professional could manipulate.
Manufacturing Gets Smart
Authors: Brown Alan S.
Published: March 2018

This article explores impact and advantages of information technology on manufacturing industry. Information technology on the factory floor promises a revolution in productivity. The industrial hype machine is among the favorites because of its full-on mashup of manufacturing with modern information technologies. There is use of intelligent software and machines to interact with one another (and with people) autonomously, both in the factory and through the cloud. According to the experts, this new combination of brains and muscle will revolutionize manufacturing in ways that rival the introduction of steam, electricity, and automation. It is foreseen that factory machines and logistics equipment would communicate with one another autonomously to assign and route jobs through the factory – and reroute them when unexpected problems arise. Cloud-based artificial intelligence would constantly compare parts and processes to optimize performance. As software gets better at communicating, ubiquitous sensors are adding more data to the mix.
Clean Power from Burning Trash
Authors: Kitto John B. , Hiner Larry A.
Published: March 2018

This study presents an overview of distinctive features of America’s first new waste-to-energy plant, which is a source of renewable energy and reduces greenhouse gas emission. With combustion and air pollution equipment designed and supplied by The Babcock & Wilcox Co. (B&W), the new facility addresses the pollution and cost issues that stopped municipalities from building waste-to-energy plants. It eliminates the burial of problematic wastes that routinely emit tons of volatile organic compounds and problematic chemicals. Waste-to-energy plants produce lower net greenhouse gas emissions than any landfill option. Not only do they displace fossil fuels to produce electricity, but also they effectively eliminate methane landfill emissions by burning the biodegradable landfill waste that forms methane. Test results show that the facility’s emissions are, at their maximum, an order of magnitude lower than those limits. This makes it the best in class of any waste-to-energy plant in the world. Waste-to-energy plants give municipalities facing rising landfill costs an economically and environmentally sound alternative to consider.
Brave New Road
Authors: Johnson Brian David
Published: March 2018

This article discusses the future of autonomous cars and its impact on the society in the future. The engineering community is building a future and is focused on making autonomous vehicles safe, efficient, and attractive to use. Autonomous transport of goods will allow a complete reimagination of the future of the global supply chain. AARP’s interest is important for another reason: the elderly vote; and if they want self-driving cars, lawmakers will quickly tackle some of the thorniest policy hurdles—such as regulation, local traffic laws, and insurance. The future of autonomous cars is expected to change lives in both dramatic and subtle ways, but the ways that will be most interesting are the things that are forgotten, the things that the next generation deem useless and frivolous. Google's self-driving car is a street-legal vehicle; however, autonomous golf carts might be more practical. Experts believe that the most interesting changes that will be brought by autonomous cars will be the cultural shifts.
Teaching Cyber-Physical Systems
Authors: Zivi Edwin
Published: March 2018

This article discusses various aspects of a course on cyber-physical systems (CPS) in the educational programs of defense organizations. CPS are engineered systems that are built from, and depend upon, the seamless integration of computational algorithms and physical components. The article also highlights various objectives of the CPS course. A central challenge to deploying resilient CPSs involves the appreciation for the multi-disciplinary challenges and the lack of a unified framework for CPS analysis, design and implementation. A significant part of the course focuses on a case study in industrial control of a Vinyl Acetate (VAc) chemical plant. The course described herein presents fundamental concepts within the rapidly expanding field of CPS and has been tailored to and is well received by U.S. Naval Academy Systems Engineering senior level engineering students. The U.S. Naval Academy thrust in cyber security studies includes a new major, Cyber Sciences, and construction of a new facility, Hopper Hall, to house the assembled multi-disciplinary teaching and research team.
Demystifying Advanced Persistent Threats for Industrial Control Systems
Authors: Keliris Anastasis , Maniatakos Michail
Published: March 2018

This article discusses a comprehensive methodology for designing an Advanced Persistent Threat (APT), which is a stealthy and continuous type of cyberattack with a high level of sophistication suitable for the complex environment of Industrial Control Systems (ICS). The article also explains defensive strategies that can assist in thwarting cyberattacks. The APT design process begins with Reconnaissance, which is continuously undertaken throughout the lifetime of a cyberattack campaign. With regard to securing the network infrastructure of an ICS, best practices for network security should be enforced. These could include the use of firewalls, Intrusion Detection or Prevention Systems (IDS/IPS), and network separation between corporate and field networks. A new field of research for securing ICS relates to process-aware defense mechanisms. These mechanisms analyze information directly from the field and try to detect anomalies specific to the physical characteristics of an ICS process.
Design and Fabrication of a Multistage Solar Still With Three Focal Concentric Collectors
Authors: Abed Fayadh M.
Published: March 2018

This research is intended to design and manufacture a multilayer solar distiller at a promising cost. The solar distiller manufactured has the same design as simple water distillers, which are based on the principle of evaporation and condensation with a different energy cycle, where the processes of evaporation and condensation are completely isolated. The obtained results showed that the amount of produced water has increased by 60% compared to the traditional solar distillers, where the system is not isolated. No catalysts were used, and the areas of the evaporation and condensation have also been increased leading to the production of distilled water under natural conditions and low cost. A comparison between the theoretical and experimental results is performed. The productivity was as follows: 8.45, 11.04, 12.20, 21.44, 18.69, 16.15, and 14.49 L/day in January, February, March, September, October, November, and December, respectively.
The Antifouling Effects of Copper-Oxide Filler Incorporated Into Paint-Based Protective Films Applied to Steam Surface Condenser Tubes
Authors: Reuter H. C. R , Owen M. , Goodenough J. L.
Published: March 2018

Paint-based protective films (PPFs) are used to protect condenser tubes from corrosion and erosion but have been shown to be susceptible to biofouling. Here, the biocidal properties of copper-oxide fillers incorporated into PPFs are explored in this paper. Specifically, two PPFs filled with 20% and 50% filler (by weight) are tested in parallel with a nonbiocidal ordinary epoxy PPF, and bare stainless steel tube. Using double-pipe co-current flow heat exchangers installed at a thermal power plant, actual cooling water exiting the condenser is evenly distributed between the test tubes. Heat transfer in the condenser is simulated by heated water flowing through each annulus of the double-pipe heat exchangers, thereby maintaining repeatable outer convection conditions. An exposure test of 125 days shows that the 50% biocide-filled PPF has the lowest fouling factor of all the tubes. The nonbiocidal epoxy has the highest fouling factor and the 20% filled PPF behaves similarly. Both of these are greater than the bare stainless steel control tube. The 50% filled PPF is compared to the fouling of an existing admiralty brass tube and the shapes of the fouling curves are similar. This evidence suggests that provided the filler concentration is sufficiently high, there is the potential for the copper-oxide filler to reduce the asymptotic composite fouling factor by virtue of its antibacterial properties.
Aerodynamic Performance of Turbine Center Frames With Purge Flows—Part I: The Influence of Turbine Purge Flow Rates
Authors: Zerobin Stefan , Peters Andreas , Bauinger Sabine , Bhadravati Ramesh Ashwini , Steiner Michael , Heitmeir Franz , Göttlich Emil
Published: March 2018

This two-part paper deals with the influence of high-pressure turbine (HPT) purge flows on the aerodynamic performance of turbine center frames (TCF). Measurements were carried out in a product-representative one and a half-stage turbine test setup. Four individual purge mass flows differing in flow rate, pressure, and temperature were injected through the hub and tip, forward and aft cavities of the unshrouded HPT rotor. Two TCF designs, equipped with nonturning struts, were tested and compared. In this first part of the paper, the influence of different purge flow rates (PFR) is discussed, while in the second part of the paper, the impact of the individual hub and tip purge flows on the TCF aerodynamics is investigated. The acquired measurement data illustrate that the interaction of the ejected purge flow with the main flow enhances the secondary flow structures through the TCF duct. Depending on the PFR, the radial migration of purge air onto the strut surfaces directly impacts the loss behavior of the duct. The losses associated with the flow close to the struts and in the strut wakes are highly dependent on the relative position between the HPT vane and the strut leading edge (LE), as well as the interaction between vane wake and ejected purge flow. This first-time experimental assessment demonstrates that a reduction in the purge air requirement benefits the engine system performance by lowering the TCF total pressure loss.
Hydrodynamic Investigation of a Wafer Rinse Process Through Numerical Modeling and Flow Visualization Methods
Authors: Chen Chia-Yuan , Panigrahi Bivas , Chong Kok-Shen , Li Wei-Hsien , Liu Yi-Li , Lu Tsung-Yi
Published: March 2018

In the current semiconductor industrial scenario, wafers are rinsed in an overflow rinsing tank while being mounted on several lifters prior to most of its manufacturing processes. However, a major drawback of this overflow rinsing methodology is that some of the processing fluid stagnates due to the generated vortices in the regions between the side and middle lifters which entrap some of the flushed particles that further adhere and deteriorate the surface of the wafers. In this work, the hydrodynamics of the flow field inside the wafer rinsing tank with this original lifter orientation setup was studied and compared through numerical simulation and flow visualization using particle image velocimetry (PIV) method, and a strong agreement was found between them in terms of velocity calculation. A new lifter orientation setup was initiated and it was evidenced by the numerical simulation that with this new setup, the generated vortices which are situated opposite to the lifters tilting direction can be displaced significantly in terms of magnitude and distribution. This work presents a new wafer cleaning concept which shows its great potentials in improvement and implementation to the current in-line wafer batch fabrication process without modifying the original design of the rinsing tank.
Three-Dimensional Numerical and Experimental Simulation of Wave Run-Up Due to Wave Impact With a Vertical Surface
Authors: Bodaghkhani Armin , Muzychka Yuri S. , Colbourne Bruce
Published: March 2018

This paper describes a numerical simulation of the interaction of a single nonlinear wave with a solid vertical surface in three dimensions. A coupled volume of fluid (VOF) and level set method (LSM) is used to simulate the wave-body interaction. A Cartesian-grid method is used to model immersed solid boundaries with constant grid spacing for simplicity and lower storage requirements. Mesh refinement is implemented near the wall boundaries due to the complex behavior of the free surface around the body. The behavior of the wave impact, the water sheet, and the high-speed jet arising from the wave impact are all captured with these methods. The numerical scheme is implemented using parallel computing due to the high central processing unit and memory requirements of this simulation. The maximum wave run-up velocity, instant wave run-up velocity in front of the vertical surface, the sheet break-up length, and the maximum impact pressure are computed for several input wave characteristics. Results are compared with a laboratory experiment that was carried out in a tow tank in which several generated waves were impacted with a fixed flat-shaped plate model. The numerical and experimental data on sheet breakup length are further compared with an analytical linear stability model for a viscous liquid sheet, and good agreement is achieved. The comparison between the numerical model and the experimental measurements of pressure, the wave run-up velocity, and the break-up length in front of the plate model shows good agreement.
Analysis and Modifications of Turbulence Models for Wind Turbine Wake Simulations in Atmospheric Boundary Layers
Authors: Antonini Enrico G. A. , Romero David A. , Amon Cristina H.
Published: March 2018

Computational fluid dynamics (CFD) simulations of wind turbine wakes are strongly influenced by the choice of the turbulence model used to close the Reynolds-averaged Navier-Stokes (RANS) equations. A wrong choice can lead to incorrect predictions of the velocity field characterizing the wind turbine wake and, consequently, to an incorrect power estimation for wind turbines operating downstream. This study aims to investigate the influence of different turbulence models, namely the k–ε, k–ω, SSTk–ω, and Reynolds stress models (RSM), on the results of CFD wind turbine simulations. Their influence was evaluated by comparing the CFD results with the publicly available experimental measurements of the velocity field and turbulence quantities from the Sexbierum and Nibe wind farms. Consistent turbulence model constants were proposed for atmospheric boundary layer (ABL) and wake flows according to previous literature and appropriate experimental observations, and modifications of the derived turbulence model constants were also investigated in order to improve agreement with experimental data. The results showed that the simulations using the k–ε and k–ω turbulence models consistently overestimated the velocity and turbulence quantities in the wind turbine wakes, whereas the simulations using the shear-stress transport (SST) k–ω and RSMs could accurately match the experimental data. Results also showed that the predictions from the k–ε and k–ω turbulence models could be improved by using the modified set of turbulence coefficients.
Surgical Robot With Variable Remote Center of Motion Mechanism Using Flexible Structure
Authors: Yoshida Sho , Kanno Takahiro , Kawashima Kenji
Published: March 2018

Remote center of motion (RCM) mechanisms are often used in surgical robots for laparoscopic surgery. In this paper, a RCM mechanism for holding a robotic forceps that facilitates adjustment using a flexible structure is proposed. The flexible structure is designed and manufactured with polypropylene-like resin material using a three-dimensional (3D) printer. Super elastic NI-Ti rods are inserted in the structure to have elasticity for bending and have rigidity for twisting. The structure achieves pitch motion around the remote center with two pneumatic cylinders. One cylinder drives the position and the other cylinder controls the bending radius of the structure. Therefore, the location of the remote center can be variable. This allows easier adjustment of the remote center before or during operation. The holder robot including the mechanism has four degrees-of-freedom (DOFs) in total, consisting of the pitch, a rotation around yaw axis, a translation in the direction of forceps insertion and a rotation of the forceps. Pneumatic rotary actuators are used for rotations and a cylinder is used for the translational motion. The model of the flexible structure is derived experimentally to design a controller for the pitch motion. A pneumatically driven robotic forceps is mounted on the holder to construct a master–slave control system. Experimental results show that the proposed control law achieves the desired rotational pitch motion. We compare the holder with a rigid link RCM holder and confirm the robustness of the proposed holder for variable remote center. Finally, the effectiveness of the system is confirmed with suturing tasks using a phantom tissue.
Flutter Limit Investigation for a Horizontal Axis Wind Turbine Blade
Authors: Abdel Hafeez Mennatullah M. , El-Badawy Ayman A.
Published: March 2018

This work presents a new aeroelastic model that governs the extensional, chordwise, flapwise, and torsional vibrations of an isolated horizontal axis wind turbine blade. The model accounts for the sectional offsets between the shear, aerodynamic, and mass centers. The centrifugal stiffening effects are also accounted for by including nonlinear strains based on an ordering scheme that retains terms up to second-order. Aerodynamic loading is derived based on a modified Theodorsen's theory adapted to account for the blade rotational motion. A set of four coupled nonlinear partial differential equations are derived using the Hamiltonian approach that are then linearized about the steady-state extensional position. The finite element method (FEM) is then employed to spatially discretize the resulting equations with the aim of obtaining an approximate solution to the blade's dynamic response, utilizing state space techniques and complex modal analysis. Investigation of the blade's flutter stability limit is carried out. Effects of parameters such as wind speed and blade sectional offsets on the flutter limit and dynamic response are also investigated.
Nonlinear Dynamic Modeling of the Cracked Rotor Ball Bearing System With Emphasis on Damage Detection Capabilities
Authors: Kumar Vashisht Rajiv , Peng Qingjin
Published: March 2018

It is confirmed experimentally that in case of a rotor with crack, multiple harmonics are generated when the rotor revolves at a particular frequency. Only few modeling techniques successfully predict this particular behavior of the cracked rotor. It is observed in this research that modeling cracked rotors using conventional finite element methods cannot predict this particular behavior successfully. A nonlinear dynamic model of the flexible rotor with ball bearings is developed using discrete mass spring damper elements combined with an existing model of the crack to truly predict this confirmed experimental behavior. Certain crack detection techniques based on the steady-state response work well on this basic concept of the multiharmonics generation due to nonlinearities caused by cracks in the rotor. The presence of ball bearings, rotor-coupling misalignment, rotor-stator rub, and rotor bow can also cause significant nonlinearities in the overall system. These additional nonlinearities render these crack detection techniques to lose their effectiveness. Our work justifies through simulations that the Jeffcott rotors are the over simplified version of real-life rotor-bearing systems. Hence, these crack detection techniques cannot be efficiently applied for condition monitoring of real-life rotor-bearing systems. The proposed model also helps to understand that the presence of flexible bearing supports affects the dynamics of the system considerably and negatively affects the effectiveness of these crack detection techniques.
A Frequency Domain Method for Calculating the Failure Probability of Nonlinear Systems With Random Uncertainty
Authors: Liao Haitao , Wu Wenwang
Published: March 2018

A hybrid approach is proposed to evaluate the probability of unacceptable performance with respect to uncertain parameters. The evaluation of structural reliability and the solution of maximum vibration response are performed simultaneously. A constrained optimization problem is deduced for which several techniques have been developed to obtain the reliability index. The nonlinear equality constraints of the optimization problem are constructed based on the harmonic balance equations, the optimality condition of the maximum vibration response with respect to the vibration frequency and the limit state failure function. With the nonlinear equality constraints imposed on the harmonic balance equations and the derivative of the maximum vibration response with respect to the vibration frequency, the inner loop for solving the maximum vibration response is avoided. The sensitivity gradients are derived by virtue of the adjoint method. The original optimization formulation is then solved by means of the sequential quadratic programming method (SQP) method. Finally, the developed approach has been verified by comparison with reference values from Monte Carlo simulation (MCS). Numerical results reveal that the proposed method is capable of predicting the failure probability of nonlinear structures with random uncertainty.
Vibration Control of a Floating Raft System by Synchrophasing of Electrical Machines: An Experimental Study
Authors: Yang Tiejun , Huang Di , Li Xinhui , Brennan Michael J. , Zhou Liubin , Zhu Minggang , Liu Zhigang
Published: March 2018

This paper describes an experimental investigation into the vibration control of multiple electrical machines installed on a large-scale floating raft system. Vibration transmission to a flexible hull-like structure that supports the floating raft is controlled by adjusting the phases of the electrical power supply to the machines—a technique known as synchrophasing. Each machine is driven by a phase asynchronous motor and has two counter rotating shafts with adjustable eccentric masses, which allows the dynamic force generated by each machine to be set independently. Up to four rotating machines are considered. A genetic algorithm is used in the search for the optimum relative phases between each machine, because it is impractical to carry out an exhaustive search of the huge number of possible phase combinations. It is demonstrated that vibration control using synchrophasing is feasible in a marine environment, and can achieve significant vibration reduction, by simply adding some sensors and a control system. Reduction in the total transmitted vibration, as measured by the sum of the squared accelerations from 22 error sensors on the hull-like structure, was found to be up to 13 dB, and vibration reduction at higher harmonic frequencies was found to be up to 51 dB.
Investigations Into the Flow Behavior in a Nonparallel Shrouded Diffuser of a Centrifugal Fan for Augmented Performance
Authors: Madhwesh N. , Vasudeva Karanth K. , Yagnesh Sharma N.
Published: March 2018

It is a well-known fact that the diffuser of a centrifugal fan plays a vital role in the energy transformation leading to better static pressure rise and efficiency. Many researchers have worked on modified geometry with respect to both impeller and diffuser so as to extract better efficiency of the fan. This paper highlights a unique numerical study on the performance of a centrifugal fan, which has a diffuser having nonparallel shrouds. The shroud geometry is parametrically varied by adopting various convergence ratios (CR) for the nonparallel shrouds encompassing the diffuser passage. It is revealed in the study that there exists an optimal CR for which the performance is improved over the regular parallel shrouded diffuser passage (base model). It is observed from the numerical analysis that for a nonparallel convergent shroud corresponding to a CR of 0.35, a relatively higher head coefficient of 3.6% is obtained when compared to that of the base model. This configuration also yields a higher theoretical efficiency of about 2.1% corroborating the improvement in head coefficient. This study predicts a design prescription for nonparallel diffuser shrouds of a centrifugal fan for augmented performance due to the fact that the converging region accelerates and guides the flow efficiently by establishing radial pressure equilibrium.
Limitation on Increasing the Critical Speed of a Spinning Disk Using Transverse Rigid Constraints, An Application of Rayleigh's Interlacing Eigenvalues Theorem
Authors: Mohammadpanah Ahmad , Hutton Stanley G.
Published: March 2018

It can be predicted by Rayleigh's interlacing eigenvalue theorem that structural modifications of a spinning disk can shift the first critical speed of the system up to a known limit. In order to corroborate this theorem, it is shown numerically, and verified experimentally that laterally constraining of a free spinning flexible thin disk with tilting and translational degree-of-freedom (DOF), the first critical speed of the disk cannot increase more than the second critical speed of the original system (the disk with no constraint). The governing linear equations of transverse motion of a spinning disk with rigid body translational and tilting DOFs are used in the analysis of eigenvalues of the disk. The numerical solution of these equations is used to investigate the effect of the constraints on the critical speeds of the spinning disk. Experimental tests were conducted to verify the results.
The Effect of Different Sterilization Methods on Polypropylene Syringes
Authors: Selcan Turker N. , Yekta Özer A. , Kutlu Burak , Nohutcu Rahime , Colak Seyda , Ekizoglu Melike , Özalp Meral
Published: March 2018

This presents the influence of gamma irradiation on Pharmacopeia specifications, mechanical and flow parameters of polypropylene (PP) syringes. There has been significant progress in the terminal sterilization of single-use, disposable medical devices with gamma radiation sterilization due to the growing awareness of toxic residues during the ethylene oxide (EtO) sterilization. PP is a widely used polymer for the production of syringes because of its excellent mechanical and thermal properties and has expanded continuously over the last decade. Although 25 kGy was generally recommended for the gamma radiation sterilization of medical products, this radiation dose is high enough to produce substantial damage. Electron spin resonance (ESR) characteristics of irradiated syringes were also studied at normal (25 °C, 60% relative humidity) and accelerated (40 °C, 75% relative humidity) stability test conditions. It was found that the chemical and radiolytic changes and sterility assurance levels (SAL) after gamma radiation sterilization were different in PP syringes. It was shown that for two commercial syringes, E1 and E3, a SAL of 10−4 could be attained with only 10 kGy, with there being less detrimental radiation effects on E1. The differences in the radiosensitivity of the propylene syringes could be due to the different formulations and manufacturing processes. The results indicated that a commercial syringe, identified as E1 could be safely sterilized with gamma irradiation as the radicals decay over a period of days under normal conditions and quenched much faster under stability conditions. Furthermore, ESR technique could be used successfully in monitoring the radiosterilization of this material. Additionally, the confirmation and validation of the SAL doses which are below 25 kGy, will decrease the time and cost of the sterilization with less damaging effects of ionizing irradiation.
Air-Diffusion-Channel Constrained Surface Based Stereolithography for Three-Dimensional Printing of Objects With Wide Solid Cross Sections
Authors: He Haiyang , Pan Yayue , Feinerman Alan , Xu Jie
Published: March 2018

Oxygen inhibition has been proved capable of reducing the separation force and enabling successful prints in constrained surface vat photopolymerization (CSVP) based three-dimensional (3D) printing processes. It has also been demonstrated as a key factor that determines the feasibility of the newly developed CSVP-based continuous 3D printing systems, such as the continuous liquid interface production. Despite its well-known importance, it is still largely unknown regarding how to control and enhance the oxygen inhibition in CSVP. To close this knowledge gap, this paper investigates the constrained surface design, which allows for continuous and sufficient air permeation to enhance the oxygen inhibition in CSVP systems. In this paper, a novel constrained surface with air-diffusion-channel is proposed. The influences of the air-diffusion-channel design parameters on the robustness of the constrained surface, the light transmission rate, and light intensity uniformity are studied. The thickness of the oxygen inhibition layer associated with the proposed constrained surface is studied analytically and experimentally. Experimental results show that the proposed air-diffusion-channel design is effective in maintaining and enhancing the oxygen-inhibition effect, and thus can increase the solid cross section size of printable parts.
Multiple Surrogate-Assisted Many-Objective Optimization for Computationally Expensive Engineering Design
Authors: Bhattacharjee Kalyan Shankar , Singh Hemant Kumar , Ray Tapabrata
Published: March 2018

Engineering design often involves problems with multiple conflicting performance criteria, commonly referred to as multi-objective optimization problems (MOP). MOPs are known to be particularly challenging if the number of objectives is more than three. This has motivated recent attempts to solve MOPs with more than three objectives, which are now more specifically referred to as “many-objective” optimization problems (MaOPs). Evolutionary algorithms (EAs) used to solve such problems require numerous design evaluations prior to convergence. This is not practical for engineering applications involving computationally expensive evaluations such as computational fluid dynamics and finite element analysis. While the use of surrogates has been commonly studied for single-objective optimization, there is scarce literature on its use for MOPs/MaOPs. This paper attempts to bridge this research gap by introducing a surrogate-assisted optimization algorithm for solving MOP/MaOP within a limited computing budget. The algorithm relies on principles of decomposition and adaptation of reference vectors for effective search. The flexibility of function representation is offered through the use of multiple types of surrogate models. Furthermore, to efficiently deal with constrained MaOPs, marginally infeasible solutions are promoted during initial phases of the search. The performance of the proposed algorithm is benchmarked with the state-of-the-art approaches using a range of problems with up to ten objective problems. Thereafter, a case study involving vehicle design is presented to demonstrate the utility of the approach.
Automatic Generation of Design Space Conversion Maps and Its Application for the Design of Compound Split Hybrid Powertrains
Authors: Barhoumi Toumadher , Kim Hyunjun , Kum Dongsuk
Published: March 2018

Most of the prior design studies on compound split hybrids focused on the selection of optimal configurations through evaluating their performance within the physical design space, i.e., powertrain configurations. However, the authors revealed that using the compound lever for the performance analysis dramatically reduces the design space as redundant configurations exist for a single compound lever design, resulting in computational load reduction. Nevertheless, using the compound lever results in the loss of information required to realize the given configurations as these two configurations are represented by two different sets of variables. The powertrain configuration is defined by two physical design variables, i.e., gear ratios of the two planetary gears. However, the compound lever design is defined by two nonphysical design variables, α and β, which are the vertical bar lengths between the output node (vehicle) and the two motor/generators' (MG) nodes. Thus, if the compound lever is used as a design tool, the selected designs should be converted into powertrain configurations. This paper introduces an automatic methodology to generate feasible powertrain configurations for any given compound lever using generic conversion equations that express the relationship between the nonphysical design variables, α and β, and the physical design variables, gear ratios. Conversion maps relating the 252 powertrain configurations to the compound lever design space were generated, and the results confirmed that the compound lever removes the redundancy existing in the physical design space.