bluuebunny/crossref_metadata_2025_split huggingface dataset:
On Numerical Investigation of Water Injection to Screw Compressors
Authors: Rane Sham , Kovačević Ahmed , Stošić Nikola , Stupple Graham 
Published: January 2019

Oil injection is widely used in screw compressors for lubrication, sealing and cooling purposes. More recently other, mainly lower viscosity fluids are used for the purpose, for example water. Water introduces new phenomena into the screw compressor process, one among them is evaporation. 3D numerical modelling is employed and presented in this paper for the detailed analysis of flow and thermodynamics process during injection of water in screw compressors. The advantage of such simulations is that realistic geometry of the rotors and the ports can be captured. In addition, the physical effects of fluid thermal interactions and leakage are directly taken into account by these models. Recent studies have shown that for oil free and oil injected air compressors a good agreement is achieved with measurements, in prediction of performance parameters. In these simulations the Eulerian-Eulerian multiphase modelling has been applied. To implement the same model for water injected compressors presents an additional challenge as the liquid water injected into the compression chamber changes phase and evaporates depending on the local saturation and thermodynamic conditions. Water also forms liquid film on the rotors and housing and thereby influences thermal changes.
In this paper a numerical model for water injected screw compressor that accounts for evaporation effects has been presented. Empirical form of the Lee (9) evaporation-condensation model for phase change has been applied in the compression chamber using the phase specific mass and energy sources. Calculation of the amount of water required to just saturate the compressed air at delivery pressure is used to set the mass flow rate of water at two operating speeds. The effect of the suction air temperature and relative humidity is studied. Evaporation inside compression chamber has two important physical effects, one is that the latent heat of evaporating water lowers the gas temperature and the other is the change of state from water to vapour. Including vapour as a third phase adds complexity to already challenging deforming grids required for screw domains. Hence a mass and energy source formulation is proposed in the presented study to account for the vapour phase change and evaporation effects, thus limiting the number of phases to be modelled. Local drop in gas temperature, distribution of water and regions of evaporation were identified by the simulations. Thermal hot spots on the rotor were located. Reduction in the leakage of gas and its exit temperature was well predicted by the model. Such simplified evaporation model can be further used in the design of water injected screw compressors and extended to predict thermal deformation of the rotors and the housing.
Flow Characteristics of Nitrogen (N2) in Micro-Channels of Printed Circuit Heat Exchanger (PCHE)
Authors: Shin Jeong-Heon , Yoon Seok Ho , Choi Jun Seok 
Published: January 2019

Experiment and simulation studies were performed to investigate the flow characteristics of pressure-driven Nitrogen flow in the micro-channels of Printed Circuit Heat Exchanger (PCHE). The core of the PCHE was made using diffusion bonding method with ten stainless steel 316L plates, where hemispherical 1 mm in diameter channels were chemically etched. On one of the plates, four-teen more channels, 1 mm in diameter, were milled to make pressure taps to measure local pressure drops. Then, one inlet tube and four-teen tubes for pressure tabs were attached by welding on the top and sides of PCHE core, respectively. The PCHE was connected to Nitrogen tank with pressure regulator, Coriolis flowmeter and differential pressure gauge, and data was acquired with DAQ system.
By varying the velocity of Nitrogen gas from 1 to 35 m/s, differential pressure drops were measured between two different locations. The local pressure drops were analyzed theoretically and pressure loss coefficients could be calculated in straight and serpentine channels, respectively. In addition, simulation work using ANSYS Fluent was also performed to understand flow characteristics especially at corners of channels.
Cellular Automaton and Finite Element Hybrid Simulation to Predict Axonal Extension Enhancement of Nerve Cell Under Mechanical Stimulation
Authors: Takeda Shota , Tomita Yoshihiro , Nakamachi Eiji 
Published: January 2019

In the clinical application, the mechanical stimulation against the damaged brain tissue is adopted as the kinesitherapy for the nerve regeneration. Nevertheless, the fundamental mechanism to repair the damaged nerve cell has not been revealed yet. Recently, the cyclic stretch stimulation has been reported as the efficacious treatment method to enhance the axonal extension for regenerative therapy of injured nerve cell. Therefore, we try to develop a new cellular automaton (CA) finite element (FE) hybrid method to predict the axonal extension and nerve network generation, which can evaluate the effect of stretch stimulation on the cell body, axon and dendrites.
In the FE results, the stress concentration occurred at the junction of the axon and cell body. The maximum stress value in the axon was 8.2 kPa which is about twice as large as that of the cell body. CA adopted to predict the morphological evolution of nerve cells under the mechanical stimulation. It was confirmed that the stress affects to accelerate the axonal extension as experimentally suggested. As a result, our CAFE can be employed to simulate the axonal extension and generation of nerve network system under the condition of extra cellular mechanical stimulation.
Development of Telepresence Teaching Robots With Social Capabilities
Authors: Zhang Mingshao , Duan Pengji , Zhang Zhou , Esche Sven 
Published: January 2019

A telepresence robot is a device that allows people to participate in video conferences on a moveable platform from a remote location. The users can remotely control the robot’s motion and interact with each other through a video screen. Such systems, which were originally designed to promote social interaction between people, have become popular in various application areas such as office environments, health care, independent living for the elderly, and distance learning. Although there is ample published empirical work surrounding the use of telepresence and computer-mediated communication in education, few studies have examined telepresence robots in the classroom. Although some studies have indicated positive learning experiences and outcomes in education facilitated by telepresence robots, further research is needed to better identify the possible effects such approaches have on student learning and perceptions of instructor credibility.
In order to maximize the students’ learning outcomes, it is very important to improve the usability of the telepresence robot platform for both the instructors and the students. In addition, the instructor credibility is also crucial to the overall learning experience. In the research presented here, an innovative remote teaching platform, which includes features of telepresence robots and social robots (which are autonomous robots that interact and communicate with humans by following social behaviors and rules associated with their roles), is developed. It is believed that telepresence robots equipped with the capabilities provided by social robots can improve the credibility of the instructor and the usability of the education platform, both of which contribute to the students’ overall learning outcomes.
Defects Evaluation of Selective Laser Melting Stainless Steel 316 Parts Using Positron Annihilation Lifetime Measurement
Authors: Yao Hong , Katona Ryan , Zhou Jianren , Islam Md I , Raush Jonathan , Lu Fengyuan , Guo Shengmin 
Published: January 2019

Alloy parts fabricated by the selected laser melting (SLM) additive manufacturing process generally contain many defects. Non-destructive Positron Annihilation Lifetime Spectroscopy (PALS) measurements were applied to evaluate these defects. The two-component positron lifetime method was used to analyze the evolution of two types of defects, mono-vacancy and vacancy cluster.
Stainless steel 316 SLM samples were prepared using two sets of SLM processing parameters. For SLM samples, the temperature effect of heat treatment was examined by PALS. The effect of plastic deformation is also examined using PALS.
Improvement of Joint Integrity in MIG Welded Steel: A Review
Authors: Odiaka Timothy , Madushele Nkosinathi , Akinlabi Stephen 
Published: January 2019

Metal Inert Gas Welding is one of the most widely used welding methods in manufacturing industries. A significant challenge in any welding process is the achievement of high quality welds. This has led to a host of welding techniques designed with the goal of maintaining weld integrity by improving its mechanical and structural properties.
This study looks at the application of various methods to improve the integrity of welded steel joints with attention to MIG welding. The systematic approach to the review considered in detail, the works done by numerous researchers in improving the integrity of welded steel joints through parametric optimization. This included several research works which adopted Taguchi’s Design of Experiment method. A few other notable methods of improving weld quality apart from parametric optimization were also reviewed and were not exclusive to MIG welding.
The study showed that the bulk of research embarked on, in the improvement of weld integrity involved parametric optimization. This also proved to be the simplest method. However, some other suggestions such as Post Weld Heat Treatment, Pulsed Current, Hybrid welding and Vibratory Welding were discovered to be alternative means of improving weld integrity. The use of reinforcing powders was also discovered, and it was suggested that the quality of MIG welded steel joints could be improved by using titanium alloy powder as weld joint reinforcement.
Real Time Loading Test Rig for Flight Control Actuators Under PHM Experimentation
Authors: Chiavaroli P. , De Martin A. , Evangelista G. , Jacazio G. , Sorli M. 
Published: January 2019

The article deals with the architecture, performance, and experimental tests of a test bench for servo-actuators used in flight controls. After the state of the art on the subject, the innovative architecture of the built bench is described, in which flight control actuator under test and load actuator are not in line but mounted perpendicularly.
The model of the bench actuating systems is then presented, consisting of the servo-controlled hydraulic actuator, load cell, speed transducer, angular position transducer of the coupling and pressure transducers. For each of these components the nonlinear multi-physics mechatronic model is described, according to the adopted solutions. The adopted force control algorithm is discussed, showing the integrative compensation on the action line and proportional-derivative on the feedback, with speed feedforward.
The experimental tests carried out on the bench under stalled conditions are also presented, whose results concerning time and frequency responses are compared with those obtained through the linearized and non-linear numerical model.
Finally, the non-linear models of the flight control actuator under test, controlled in position, and of the loading servo-actuator of the bench are joined together, and the results of various simulations are described.
Experimental Investigation on Flow Field in a Rotating Channel With a New TR-PIV System
Authors: Zhou Shengjun , Li Haiwang , Tao Zhi , You Ruquan , Duan Haoyu 
Published: January 2019

In the current study, the influence of different rotation conditions on the flow behavior is experimentally investigated by a new system which is designed for time-resolved PIV measurements of the smooth channels at rotation conditions. The Reynolds number equals 15000 and the rotation number ranges from 0 to 0.392 with an interval of 0.098.
This new time-resolved Particle Image Velocimetry system consists of a 10 Watts continuous laser diode and a high-speed camera. The laser diode can provide a less than 1mm thickness sheet light. 6400 frames can be captured in one second by the high-speed camera. These two parts of the system are fixed on a rotating disk. In this case, the relative velocity of flows in the rotating smooth square channel can be measured directly to reduce the measurement error. This system makes high-speed camera close to the rotating channel, which allows a high resolution for the measurements of main stream. In addition, high accuracy and temporal resolution realize a detailed analysis of boundary layer characteristics in rotation conditions. Based on this system, experimental investigation has been undertaken. Results are presented of the evolution of velocity and boundary layer thickness at various rotation numbers and different circumferential positions.
Development of a Low-Cost Mechanical Model of a Human Head
Authors: Foltz Grace , Tillotson Elizabeth , Todd Beth A. 
Published: January 2019

In recent years, interest has developed in Chronic Traumatic Encephalopathy (CTE) and the related concussions that occur in sports at both professional and amateur levels. Subsequently there is interest in developing new types of athletic helmets to both absorb energy to detect and reduce concussions. To test these helmets, an appropriate head form must be used that will fit the helmet and also exhibit the dynamic properties of the human head. While much effort has gone into creating biofidelic heads containing instrumentation for automotive crash testing, these heads can cost upwards of $10,000. The goal of this project is to create a head form for a few hundred dollars with the appropriate dynamic properties for testing linear and angular accelerations of a helmet.
The specific goals of this project are to create a head form with the following characteristics: 1) External size and shape that will properly fit a hockey helmet; 2) Weight representative of an adult head; 3) Robust enough to withstand a thousand impact tests. The manufacture of the head form and the verification that the design goals are described.
The Positive Effects on Student Performance of Using Social Networks in Courses of Applied Mechanics
Authors: Rodríguez-Paz Miguel X. , González-Mendivil Jorge A. , Zárate-García J. Asunción , Peña-Ortega Luis O. 
Published: January 2019

Digital Social Networks such as Facebook, Twitter, Instagram and Youtube are part of the lives of most students nowadays. Generally, lecturers and teachers do not allow the use of mobile devices during class time. In this work, some results are shown of the positive effects that the allowance of such devices, as well as the interaction between professor-students through social networks can have on students grades compared to previous semesters where no use of social networks was included in class. The main objective of this work is to show that, if digital social networks interaction between professor and class is included, the overall confidence of the group increases as well as the grade results in their examinations versus previous groups of similar sizes where there was no such interaction. Feedback from students is analyzed to show the perception of students on the use of the Youtube channel and how it has positively affected their performance in the course by increasing the reviewing options they get before an exam.
Another aspect also discussed in this work, is the importance of the personal branding the professor should develop so that he/she gets easily recognized across the different social networks.
Shape Memory Alloy Based Rotational Actuator
Authors: Hofmann Nick , Hennessey Michael P. 
Published: January 2019

Due to recent technological developments in advanced materials, the integration of shape memory alloys (SMAs) into new machines and mechanisms is becoming more common and it offers tremendous potential for the future. Using currently available properties of common SMA materials, the paper’s contribution is to: Study through dynamic simulation the potential offered by SMA springs to serve as the basis for rotary actuation. In the process, the SMA displaces a rocker arm rotating about an axis to induce rotational motion of a driveshaft, in effect converting a force into rotational motion. When embedded in a cycle with heating & cooling phases and a resetting mechanism, unidirectional rotational motion can be achieved.
Regarding heating and cooling cycles, forced air convection is used to reduce thermal cycle cooling and is calculated via transient thermal analyses. Using typical parameter values for the representative design considered, through forced air convection, cooling cycles are reduced from approximately 30 seconds (natural) to 5.5 seconds (forced) and as a result, a complete system cycle can occur in 10 seconds, with the applied inertial load of 2.0 kg-m2.
Using MATLAB and Simulink, a nonlinear 3rd order dynamic system model was created and simulations were performed. One complicating factor concerned angular limits and the necessary thermal cycling, which was solved through appropriate sequencing and resetting of integrators for different phases. Simulation results for the design considered show that a peak torque of 1.72 N-m is possible and that relatively smooth motion and approximately constant torque output is also possible through the addition of a few more rocker arm systems, properly commutated. Lastly, the design analysis framework and results may inspire future realization of actual devices.
Seismic Probabilistic Risk Assessment of Nuclear Power Plants: 10 CFR 50.69 Assumptions and Sources of Uncertainty
Authors: Lyons Sara , Vasavada Shilp 
Published: January 2019

The U.S. Nuclear Regulatory Commission (NRC) promulgated Part 50.69 to Title 10 of the Code of Federal Regulations (CFR), “Risk-informed categorization and treatment of structures, systems and components for nuclear power reactors,” in November 2004 (hereafter referred to as 10 CFR 50.69). The rule provides a voluntary alternative to compliance with many regulations which require “special treatment,” or regulatory requirements which go beyond industrial controls, including: specific inspection, testing, qualification, and reporting requirements. The voluntary alternative includes a process for categorization of structures, systems, and components (SSCs) as having either low safety significance (LSS) or high safety significance (HSS). The categorization process can result in increased requirements for HSS SSCs which were previously treated as non-safety-related, and reduced requirements for LSS SSCs which were previously treated as safety-related.
The categorization process includes plant-specific risk analyses which are used in combination with an integrated decision-making panel (IDP) to determine whether the SSC has a low or high safety significance. Seismic probabilistic risk assessment (SPRA) is one of the risk analyses options to account for the seismic risk contribution. Because the 10 CFR 50.69 rule has currently not been implemented widely, the significance of various SPRA assumptions and sources of uncertainty to the categorization process has had limited evaluation for a broad spectrum of U.S. nuclear power plants.
This paper will assess the importance of certain aspects of the seismic risk contribution to the categorization process. NRC Standardized Plant Analysis Risk (SPAR) models will be used to perform sensitivity studies to quantify the impact of various assumptions and sources of uncertainty on the outcome of the categorization process.
Numerical Analysis of the Contribution of Shot Peening in the Fatigue Strength of Multipass Welded Joints
Authors: Etxeberria U. , Esnaola J. A. , Ulacia I. , Ugarte D. , Llavori I. , Larrañaga M. , Lopez-Jauregi A. 
Published: January 2019

Tensile residual stress (RS) peaks near the weld toe accelerate crack generation and propagation stages reducing dramatically the life of welded components. In order to relief RS, components are typically heat-treated. However, heat treatments can affect the microstructure compromising mechanical properties. In addition, their application in big structures is complex due to size limitations. As an alternative, mechanical treatments such as shot peening can be locally applied. Moreover, they generate local compressive stresses in the treated surfaces, which present beneficial effect in the fatigue strength of treated components.
In the present work, the contribution of shot peening in the fatigue strength of multipass welded joints is numerically evaluated. For that purpose, first the RS stress pattern of a 3 pass butt weld of 10mm thick, 50mm length S275JR plates is calculated. Following, the application of shot peening in the tensile RS area is modelled and the evolution of RS pattern is analyzed. Finally, the fatigue strength of treated and non-treated butt welds is evaluated.
Active Acoustic Metamaterials With Programmable Densities Using an H-∞ Controller
Authors: Baz Amr 
Published: January 2019

Various types of acoustic metamaterials have been developed to control the flow of acoustical energy through these materials. Most of these metamaterials are passive in nature with pre-tuned and fixed material properties. In this paper, the emphasis is placed on the development of a class of one-dimensional acoustic metamaterials with programmable densities in order to enable the control the acoustic wave propagation in these media. With such unique capabilities, the proposed active acoustic metamaterials (AAMM) can be utilized to physically realize, for example, acoustic cloaks, wave shifters and focusers, tunable acoustic absorbers and reflectors, as well as non-reciprocal acoustic media.
The theoretical analysis of this class of AAMM with programmable effective dynamical densities is presented for an array of cavities separated by piezoelectric boundaries. These boundaries provide means for controlling the stiffness of the individual cavity and, in turn, its dynamical densities. In this regard, a disturbance rejection strategy is considered which is based on an H-∞ robust controller. The time and frequency response characteristics of a unit cell of the AAMM are investigated for various parameters of the controller in an attempt to optimize the performance characteristics.
Extension of this study to include active control capabilities of the bulk modulus of the metamaterials would enable the development of wide classes of AAMM that are only limited by our imagination.