bluuebunny/crossref_metadata_2025 huggingface dataset:
Research on the Tooth Modification in Gear Skiving
Authors: Zheng Fangyan , Zhang Mingde , Zhang Weiqing , Guo Xiaodong
Published: July 2018

As a prospective machining method for cylindrical gear, gear skiving has been promoted by many commercial companies, such as Gleason, Mitsubishi, and Prawema recently. Although the principle and mathematical model for gear skiving has been discussed by many works, the tooth modification was left behind in the literature. In fact, machine kinematics correction and tooth contact analysis (TCA) are widely used for tooth modification in gear processing, such as hobbing, grinding, and milling. Focusing on this, the paper generalizes machine kinematics correction and TCA to gear skiving. The influence of the modification parameters on tooth deviation, contact path, and transmission error are all investigated, showing that localized contact pattern and polynomial transmission error can be realized through cutter offset correction for one gear and cutter tilted (or crossed angle) correction for the other gear.
Organ-on-Chip Devices Toward Applications in Drug Development and Screening
Authors: Uhl Christopher , Shi Wentao , Liu Yaling
Published: July 2018

As a necessary pathway to man-made organs, organ-on-chips (OOC), which simulate the activities, mechanics, and physiological responses of real organs, have attracted plenty of attention over the past decade. As the maturity of three-dimensional (3D) cell-culture models and microfluidics advances, the study of OOCs has made significant progress. This review article provides a comprehensive overview and classification of OOC microfluidics. Specifically, the review focuses on OOC systems capable of being used in preclinical drug screening and development. Additionally, the review highlights the strengths and weaknesses of each OOC system toward the goal of improved drug development and screening. The various OOC systems investigated throughout the review include, blood vessel, lung, liver, and tumor systems and the potential benefits, which each provides to the growing challenge of high-throughput drug screening. Published OOC systems have been reviewed over the past decade (2007–2018) with focus given mainly to more recent advances and improvements within each organ system. Each OOC system has been reviewed on how closely and realistically it is able to mimic its physiological counterpart, the degree of information provided by the system toward the ultimate goal of drug development and screening, how easily each system would be able to transition to large scale high-throughput drug screening, and what further improvements to each system would help to improve the functionality, realistic nature of the platform, and throughput capacity. Finally, a summary is provided of where the broad field of OOCs appears to be headed in the near future along with suggestions on where future efforts should be focused for optimized performance of OOC systems in general.
Two-Dimensional Flow Passage Through a Hot Ribbed Channel: Effect of First Rib Width
Authors: Omari Boudjemaa , Mataoui Amina , Salem Abdelaziz
Published: July 2018

This work investigates numerically by finite volume method using Low k–ω model, the forced turbulent convection through a channel roughened by seven heated ribs arranged transversely. These ribs of rectangular cross section have a blocking ratio H/h = 10 and pitch ratio λ/h = 3. The modeling the problem parameters are Reynolds number, ranging from 5480 to 68500, and the width of the first rib L1 ranging from 0.5h to 15h. The objective of this study is to look for the width of the first rib L1 which induces the best heat transfer. The flow configurations of identical ribs from the first one generate a large eddy spreading along the top of the two first ribs, blocking the flow of the first cavity. The widening of the first rib may solve this problem. This flow configuration is required in several engineering applications necessitating the flow periodicity starting from the first cavity. The streamlines show that the first rib acts as a forward facing step when L1 > 5h. The effect of the width of the first rib is highlighted by velocity, pressure, turbulent kinetic energy and temperature profiles. Nusselt number distributions confirm that the widening of the heated surface is not recommended for improving heat transfer in spite of flow periodicity in all cavities (roughness d-type). The best improvement in heat transfer of 18%, compared to a smooth wall is obtained for thinnest first rib of L1/h = 0.5. However, this configuration provides a minor heat exchange at the first pitch and the second rib, which might be a disadvantage for the material structure.
Numerical
Simulation of Temperature Field in Indirect Thermal Washing for Wax
Cleaning
Authors: Ligang Zhang , Fei
Fu Xiao , Sining Qu , Shibin Li , Bing Guan
Published: July 2018

Wax deposition in oil pipelines brings a critical operational challenge in the oil development, and the indirect thermal washing is a most common and effective method of wax cleaning. The temperature field in thermal washing is the basis for making a reasonable plan to wash and remove wax well. In this paper, the wells of sucker rod pump in Da Qing oil field are selected as research objects, a new method which is based on heat-fluid coupling method is proposed for predicting temperature field during the thermal washing process. The temperature field of the annulus of tubing and casing and the temperature field of the annulus of rod and tubing are simulated with different thermal washing parameters. In the indirect thermal washing, the temperature in annulus of tubing and casing gradually decreases from wellhead to the bottom, while the temperature in the annulus of rod and tubing increases from bottom to the wellhead. With the increase of temperature and flow rate of thermal washing fluid, the temperature in annulus of tubing and casing and the temperature in annulus of rod and tubing are both increasing, but the rise rate is different at different depths. Compared to the measured results, the coincidences rate is in the range of 93.67%–99.31%. The research results can guide effectively the thermal washing operation.
Adaptive Thermal Conductivity Metamaterials: Enabling Active and Passive Thermal Control
Authors: Phoenix Austin A. , Wilson Evan
Published: July 2018

The novel adaptive thermal metamaterial developed in this paper provides a unique thermal management capability that can address the needs of future spacecraft. While advances in metamaterials have provided the ability to generate materials with a broad range of material properties, relatively little advancement has been made in the development of adaptive metamaterials. This metamaterial concept enables the development of materials with a highly nonlinear thermal conductivity as a function of temperature. Through enabling active or passive control of the metamaterials bulk effective thermal conductivity, this metamaterial that can improve the spacecraft's thermal management systems performance. This variable thermal conductivity is achieved through induced contact that results in changes in the F path length and the conductive path area. The contact can be generated internally using thermal strain from shape memory alloys, bimetal springs, and mismatches in coefficient of thermal expansion (CTE) or it can be generated externally using applied mechanical loading. The metamaterial can actively control the temperature of an interface by dynamically changing the bulk thermal conductivity controlling the instantaneous heat flux through the metamaterial. The design of thermal stability regions (regions of constant thermal conductivity versus temperature) into the nonlinear thermal conductivity as a function of temperature can provide passive thermal control. While this concept can be used in a wide range of applications, this paper focuses on the development of a metamaterial that achieves highly nonlinear thermal conductivity as a function of temperature to enable passive thermal control of spacecraft systems on orbit.
Energy Efficiency and Tracking Performance Evaluation for Dual-Mode Model Predictive Control of HVAC Systems
Authors: Cai Zicheng , Ul Haq Asad A. , Cholette Michael E. , Djurdjanovic Dragan
Published: July 2018

This paper presents evaluation of the energy consumption and tracking performance associated with the use of a recently introduced dual-mode model predictive controller (DMMPC) for control of a heating, ventilation, and air conditioning (HVAC) system. The study was conducted using detailed simulations of an HVAC system, which included a multizone air loop, a water loop, and a chiller. Energy consumption and tracking performance are computed from the simulations and evaluated in the presence of different types and magnitudes of noise and disturbances. Performance of the DMMPC is compared with a baseline proportional-integral-derivative (PID) control structure commonly used for HVAC system control, and this comparison showed clear and consistent superiority of the DMMPC.
Magnetic Field and Thermal Radiation Effects in Peristaltic Flow With Heat and Mass Convection
Authors: Hayat T. , Bibi Aneela , Yasmin H. , Alsaadi Fuad E.
Published: July 2018

This paper scrutinizes the impact of thermal radiation and applied magnetic field on Jeffrey fluid with peristalsis. The effects of Joule heating and viscous dissipation are retained. Convective conditions are imposed for the heat and mass transfer analysis. Lubrication approach is considered for the analysis. Expressions for pressure gradient, stream function, temperature, concentration, and heat transfer coefficient are developed and physically interpreted through illustrations. It is revealed that temperature enhances for higher estimation of Brinkman and Hartmann numbers, while it decays for larger Biot number. Furthermore, the concentration decreases for varying Schmidt number. Heat transfer coefficient has an oscillatory behavior for larger estimation of radiation parameter.
Analysis of Heat Transfer Through Optically Participating Medium in a Concentric Spherical Enclosure: The Role of Dual-Phase-Lag Conduction and Radiation
Authors: Mukherjee Aritra , Mondal Pranab Kumar
Published: July 2018

This paper deals with the analysis of the effects of combined dual-phase-lag (DPL) heat conduction and radiation in a concentric spherical enclosure with diffuse-gray surfaces. The enclosed medium is optically participating, i.e., it is radiatively absorbing, emitting, and scattering. Lattice Boltzmann method (LBM) is used to solve the energy equation, and finite volume method (FVM) is used to compute the radiative information. To establish the accuracy of this approach, the combined energy equation is also solved with the finite difference method. Radial temperature profiles and energy contributions by conduction and radiation at various instances and prior to steady-state are elaborated for different kind of thermal perturbations Influence of numerous conductive and radiative parameters over the heat transport process have been investigated in detail. It is observed that higher contribution of radiation to the heat transport process can destroy the thermal wave in the medium completely. Sample results for pure non-Fourier heat conduction, pure radiation, and steady-state response of combined Fourier conduction and radiation in spherical geometry are compared with the results available in literature. In all the cases, comparison shows good agreement with the reported results.
Numerical Analysis of Natural Convection and Radiation for Tube Solar Receiver With Glass Window
Authors: Guojun Zhang , Changyu Liu , Dong Li
Published: July 2018

Conjugate laminar natural convection heat transfer and air flow with radiation of tube solar receiver with glass window were numerically investigated. The discrete ordinate method was used to solve the radiative transfer equation. And the three-dimensional steady-state continuity, Navier–Stokes, and energy equations were solved. The temperature difference based on environment and high temperature surface of receiver is varied from 100 K to 1000 K. The influence of the surface emissivity, heating temperature, convective coefficient, and convective temperature of environment on the heat transfer from the receiver with glass window has also been investigated. The numerical results indicated that the highest temperature of glass window increases and the high temperature area becomes wide, with the temperature of heating wall and surface emissivity increasing. Adopting higher convective coefficient of glass window can reduce the peak magnitude of temperature distribution on glass window of tube receiver up to 45%.
Seizure Improved Lead-Free Electroplated Bearing Overlay System for Heavy-Duty Truck and Off-Highway Applications
Authors: Jupe Kevin , Gorges Roger , Rathod Anil , Carey John , Stearns John
Published: July 2018

The move to lead-free bearing materials is well known, and upcoming legislation, such as the restriction of hazardous substances, is increasing the drive to extend this trend toward heavy-duty diesel truck and off-highway applications. During the development of lead-free systems, new electroplated overlays and bronze-based substrates have been developed by various suppliers, but little attention has been given to the interlayer or diffusion barrier between the overlay and substrate materials. This interlayer is particularly necessary for tin-based solutions as it prevents the rapid diffusion of overlay species into the bronze substrate. The present development focuses on improving this often overlooked element in the system and provides a further robustness that could even be adapted to lead-based systems where increased performance is required. The incorporation of hexagonal boron nitride (hBN) as a solid lubricant in the nickel interlayer changes dramatically the interlayer properties and provides more typical bearing-like behavior for seizure resistance and scuff performance compared to nickel alone. The paper details the findings of respective rig tests as well as an actual engine test supporting the change in material characteristics and the associated improvement in seizure resistance.
Interfacial Compounds Characteristic and Its Reliability Effects on SAC305 Microjoints in Flip Chip Assemblies
Authors: Tian Ye , Ren Ning , Jian Xiaoxia , Geng Tie , Wu Yiping
Published: July 2018

This study mainly focuses on site effects of the Ni pad interface on intermetallic compounds (IMCs) characteristic during assembly reflowing, and attempts to provide a reasonable explanation for this particular finding. Besides, the changes of the resulting IMCs characteristic are characterized during thermal shock (TS) cycling, and their potential influences on thermal–mechanical reliability of microjoints are evaluated experimentally and numerically. The results show that the site on the Ni pad interface of silicon chip has great influence on interfacial reaction products, i.e., interfacial IMCs. After bumps soldering, a great amount of larger diamond-shaped (Cu, Ni)6Sn5 compounds were densely packed at the edge region, while some smaller ones were only scattered at the center region. Moreover, substantial particle-shaped (Ni, Cu)3Sn4 compounds as well as some rod-shaped ones emerged at the spaces between the (Cu, Ni)6Sn5 compounds of the center region. More importantly, such site effects were remained in the microjoints during TS cycling, which induced the formation of larger protruding (Cu, Ni)6Sn5 compounds. Finite element (FE) simulation results showed that the stress was mainly concentrated at the top of the protruding (Cu, Ni)6Sn5 compounds, which can be a critical reason to cause the crack occurrence. Furthermore, the underlying mechanism of the interfacial IMCs characteristic induced by the site effects was attempted to propose during bumps soldering.
On Importance of the Surface Charge Transport Equation in Numerical Simulation of Drop Deformation in a Direct Current Field
Authors: Alidoost Mohammadali , Reza Pishevar Ahmad
Published: July 2018

In the present study, the deformation of a droplet is numerically modeled by considering the dynamic model for electric charge migration at the drop interface under the effect of a uniform electric field. The drop and its ambient are both considered behaving as leaky dielectric fluids. Solving the charge conservation equation at the interface, which is the most important part of this study, the effect of conduction and convection of charges on different deformation modes will be explored. In this work, the interface is followed by the level set method and the ghost fluid method (GFM) is used to model the jumps at the interface. Physical properties are also chosen in a way that solving the charge conservation equation becomes prominent. The small drop deformation is investigated qualitatively by changing various effective parameters. In cases, different patterns of charges and flows are observed indicating the importance of electric charges at the interface. It is also shown that the transient behavior of deformation parameter can be either a monotonic or a nonmonotonic approach toward the steady-state. Moreover, large drop deformations are studied in different ranges of capillary numbers. It will be shown that for the selected range of physical parameters, considering the dynamic model of electric charges strongly affects the oblate deformation. Nevertheless, for the prolate deformation, the results are approximately similar to those obtained from the static model.
Finite Element Analysis Simulation of the Effect of Induction Hardening on Rolling Contact Fatigue
Authors: Hoa Ngan Nguyen , Bocher Philippe
Published: July 2018

The objective of this research is to conduct a finite element analysis to better understand the effects of induction hardening on rolling contact fatigue (RCF). The finite element analysis was developed in three-dimensional to estimate the maximal loading and the positions of the crack nucleation sites in the case of cylinder contact rolling. Rolling contact with or without surface compressive residual stress (RS) were studied and compared. The RS profile was chosen to simulate the effects of an induction hardening treatment on a 48 HRC tempered AISI4340 steel component. As this hardening process not only generates a RS gradient in the treated component but also a hardness gradient (called over-tempered region), both types of gradients were introduced in the present model. RSs in compression were generated in the hard case (about 60 HRC); tension values were introduced in the over-tempered region, where hardness as low as 38 HRC were set. In order to estimate the maximal allowable loadings in the rotating cylinders to target a life of 106 cycles, a multiaxial Dang Van criterion and a shear stress fatigue limit were used in the positive and negative hydrostatic conditions, respectively. With the proposed approach, the induction hardened component was found to have a maximal allowable loading significantly higher than that obtained with a nontreated one, and it was observed that the residual tensile stress peak found in the over-tempered region could become a limiting factor for fatigue rolling contact life.
Experiments and Finite Element Simulation of Ultrasonic Assisted Drilling
Authors: Paktinat Hossein , Amini Saeid
Published: July 2018

In this study, ultrasonic assisted drilling (UAD) is performed to investigate the effect of ultrasonic vibrations on common difficulties existed in conventional drilling (CD). UAD is a promising and advanced technique by which a harmonic movement with high frequency and low amplitude is superimposed on the movement of work material or cutting tool. The study is conducted both experimentally and numerically; at first, a UAD system is designed, manufactured, and carried out on a milling machine and then experimental tests are accomplished. In the following, experimental results are supported by the help of three-dimensional (3D) finite element simulation. Finally, the dependent parameters such as the burr height and cylindricity of the ultrasonically and conventionally drilled workpiece are measured and compared. Briefly, it was proved that the intermittent movement of drill bit in the direction of feed rate results in broken and discontinuous chips by which built-up-edge (BUE) is reduced and hole quality is improved. In addition, the burr height, which is known as unwanted projection of material at the exit surface of pieces, can notably decrease, if UAD is considered.
Formation Tracking Control of Second-Order Multi-Agent Systems With Time-Varying Delay
Authors: Li Tao , Li Zhipeng , Zhang Haitao , Fei Shumin
Published: July 2018

This paper considers the problem on formation tracking control of second-order multi-agent systems (MASs) with communication time-varying delay. Sufficient conditions on the directed interaction topology and existence of the feedback gains to ensure the desired control are presented. Through choosing two augmented Lyapunov–Krasovskii (L–K) functionals and using some novel Wirtinger-based integral inequalities, the previously ignored information can be reconsidered and the application area of derived results can be greatly extended. Moreover, a novel constructive technique is given to compute out the controller gain by resorting to solving the achieved linear matrix inequalities (LMIs). Finally, a numerical example with comparisons and simulations is provided to illustrate the obtained results.
Membrane-Less Hydrogen Iron Redox Flow Battery
Authors: Marma Kyamra , Kolli Jayanth , Cho Kyu Taek
Published: July 2018

In this study, a new type of redox flow battery (RFB) named “membrane-less hydrogen-iron RFB” was investigated for the first time. The membrane is a cell component dominating the cost of RFB, and iron is an abundant, inexpensive, and benign material, and thus, this iron RFB without the membrane is expected to provide a solution to the challenging issues of current battery systems such as high cost and safety concerns. The research focus in this study was placed on defining key design parameters to make this new system promising as an RFB. Crossing rate of reactants over carbon porous electrode (CPE) was controlled by modifying its pore structure with Teflon impregnation, and the effects of the Teflon on crossover, kinetic, Ohmic, and mass transfer was investigated by cell-based test and one-dimensional computational model. It was found that the cell performance (i.e., charge and discharge polarization) of the new membrane-less system was equivalent to that of the conventional membrane-system (i.e., RFB having a membrane). Especially, the Ohmic properties of the new system were constant and stable, while in the conventional membrane system, they were significantly varied and deteriorated as cell tests were continued, indicating that degradation or contamination of membrane affecting Ohmic properties could be mitigated effectively in the membrane-less system, which was found first in this research. The modeling analysis provided insight into the system, showing that the effect of reactant crossover on performance decay was not significant, and Teflon impregnation in the CPE caused significant kinetic and Ohmic losses by impeding ion transport and reactant access to reaction sites. From this study, it was found that the membrane-less H2-iron system is feasible and promising in resolving the challenge issues of the conventional systems. And the results of this study are expected to provide guidelines for research and development of flow battery systems without having a membrane.
Discrete Loading Ring-Core Method for Nonuniform In-Plane Residual Stress Analysis in Micro Area
Authors: Jin Peng , Li Xide
Published: July 2018

The ring-core method is often used in residual stress analysis. It is applied to macro- and microscale stress analysis and has a unique advantage of releasing the residual stress across the core instead of at a single point, which makes it possible to measure an uneven residual stress field within a limited area, especially when the area is too small to be measured by other techniques. We developed a new layer-by-layer stress analysis method based on the ring-core method to retrieve the uneven in-plane stress, in which a nonuniform load that surrounds the core is approximated by discrete loading and then used to reveal the stress distribution within the core. The displacement–stress relationship is calibrated through finite element simulation. Because of the difficulty of preparing a standard specimen with an accurate high-gradient in-plane field stress in an area of several micrometers, the performance of the method was tested by a finite element simulation experiment. Good matches were achieved when comparing the calculated stress fields and the stress fields in the simulation experiments, including the biaxial, uniaxial and high-gradient cases. The method was applied to a piece of superconductor stand with a highly nonuniform stress by using a 4 μm-diameter-area ring core cut with focused ion beam.
A Higher-Order Theory for Open and Closed Curved Rods and Tubes Using a Novel Curvilinear Cylindrical Coordinate System
Authors: Arbind A. , Srinivasa A. R. , Reddy J. N.
Published: July 2018

In this study, the governing equation of motion for a general arbitrary higher-order theory of rods and tubes is presented for a general material response. The impetus for the study, in contrast to the classical Cosserat rod theories, comes from the need to study bulging and other deformation of tubes (such as arterial walls). While Cosserat rods are useful for rods whose centerline motion is of primary focus, here we consider cases where the lateral boundaries also undergo significant deformation. To tackle these problems, a generalized curvilinear cylindrical coordinate (CCC) system is introduced in the reference configuration of the rod. Furthermore, we show that this results in a new generalized frame that contains the well-known orthonormal moving frames of Frenet and Bishop (a hybrid frame) as special cases. Such a coordinate system can continuously map the geometry of any general curved three-dimensional (3D) structure with a reference curve (including general closed curves) having continuous tangent, and hence, the present formulation can be used for analyzing any general rod or pipe-like 3D structures with variable cross section (e.g., artery or vein). A key feature of the approach presented herein is that we utilize a non-coordinate “Cartan moving frame” or orthonormal basis vectors, to obtain the kinematic quantities, like displacement gradient, using the tools of exterior calculus. This dramatically simplifies the calculations. By the way of this paper, we also seek to highlight the elegance of the exterior calculus as a means for obtaining the various kinematic relations in terms of orthonormal bases and to advocate for its wider use in the applied mechanics community. Finally, the displacement field of the cross section of the structure is approximated by general basis functions in the polar coordinates in the normal plane which enables this rod theory to analyze the response to any general loading condition applied to the curved structure. The governing equation is obtained using the virtual work principle for a general material response, and presented in terms of generalized displacement variables and generalized moments over the cross section of the 3D structure. This results in a system of ordinary differential equations for quantities that are integrated across the cross section (as is to be expected for any rod theory).
A New Growth Model for Aortic Valve Calcification
Authors: Halevi Rotem , Hamdan Ashraf , Marom Gil , Lavon Karin , Ben-Zekry Sagit , Raanani Ehud , Haj-Ali Rami
Published: July 2018

Calcific aortic valve disease (CAVD) is a progressive disease in which minerals accumulate in the tissue of the aortic valve cusps, stiffening them and preventing valve opening and closing. The process of valve calcification was found to be similar to that of bone formation including cell differentiation to osteoblast-like cells. Studies have shown the contribution of high strains to calcification initiation and growth process acceleration. In this paper, a new strain-based calcification growth model is proposed. The model aims to explain the unique shape of the calcification and other disease characteristics. The calcification process was divided into two stages: Calcification initiation and calcification growth. The initiation locations were based on previously published findings and a reverse calcification technique (RCT), which uses computed tomography (CT) scans of patients to reveal the calcification initiation point. The calcification growth process was simulated by a finite element model of one aortic valve cusp loaded with cyclic loading. Similar to Wolff's law, describing bone response to stress, our model uses strains to drive calcification formation. The simulation grows calcification from its initiation point to its full typical stenotic shape. Study results showed that the model was able to reproduce the typical calcification growth pattern and shape, suggesting that strain is the main driving force behind calcification progression. The simulation also sheds light on other disease characteristics, such as calcification growth acceleration as the disease progresses, as well as sensitivity to hypertension.
Development of a Key Performance Indicator Assessment Methodology and Software Tool for Product-Service System Evaluation and Decision-Making Support
Authors: Mourtzis Dimitris , Papatheodorou Anna-Maria , Fotia Sophia
Published: July 2018

During the last decade, as a result of their constant urge to retain sustainability, companies have shifted to the product-service system (PSS) business model, in an effort to gain competitive advantages. PSS providers have realized the importance of offering highly perceived solutions; thus, the necessity of monitoring the performance of PSSs and evaluating them has intensified. However, not much work has been conducted toward that direction, especially focusing on its practical application. In the current work, a holistic approach for PSS evaluation using key performance indicators (KPIs) is proposed, extending to all its lifecycle phases and covering aspects from both provider's and customer's perspectives. A software tool was developed to assist the decision maker in the selection of appropriate KPIs to monitor for PSS evaluation and additionally, to offer KPIs data collection, storage, processing, and visualization capabilities. The proposed methodology was applied in a real industrial case of the mold making area to validate its results.
Precise Foot Positioning of Walking Robot for Paraplegic Patient Wearing Exoskeleton by Using Electrical Stimulation Feedback
Authors: Li Mengze , Yuan Zhaofan , Aoyama Tadayoshi , Hasegawa Yasuhisa
Published: July 2018

The research and development of powered exoskeletons is expected to support the walking of paraplegic patients. At the current stage, exoskeletons do not allow patients to voluntarily control their gait, nor do they provide sensory feedback to compensate for the loss of lower-body sensation. This paper proposes a wearable walking control interface to achieve voluntary gait control, and an electrical stimulation method to inform the patients about their foot position for voluntary gait control. In this study, a walking robot that simulated a paraplegic patient wearing an exoskeleton was used to investigate the performance of the proposed interface and stimulation method. We confirmed that, by using the interface, the subjects were able to control the robot gait for a distance of 3 m. Moreover, the accuracy of the electrical stimulation feedback was confirmed to approximate the visual feedback achieved through the human eyes. The experimental results revealed that the proposed interface and electrical stimulation feedback could be applied to a walking support system for patients with complete paraplegia.
Optimization of Operation Parameters for Direct Spring Loaded Pressure Relief Valve in a Pipeline System
Authors: Kim Hyunjun , Kim Sanghyun , Kim Youngman , Kim Jonghwan
Published: July 2018

A direct spring loaded pressure relief valve (DSLPRV) is an efficient hydraulic structure used to control a potential water hammer in pipeline systems. The optimization of a DSLPRV was explored to consider the instability issue of a valve disk and the surge control for a pipeline system. A surge analysis scheme, named the method of characteristics, was implemented into a multiple-objective genetic algorithm to determine the adjustable factors in the operation of the DSLPRV. The forward transient analysis and multi-objective optimization of adjustable factors, such as the spring constant, degree of precompression, and disk mass, showed substantial relaxation in the surge pressure and oscillation of valve disk in a hypothetical pipeline system. The results of the regression analysis of surge were compared with the optimization results to demonstrate the potential of the developed method to substantially reduce computational costs.
Linear Shear Flow Past a Rotating Elliptic Cylinder
Authors: Naik Sandeep N. , Vengadesan S. , Arul Prakash K.
Published: July 2018

Simulations are carried out for linear shear flow past a rotating elliptic cylinder to investigate the effect of shear flow on hovering vortex. An in-house fluid solver that is based on immersed boundary method (IBM) is used to study the flow features and variation in aerodynamic forces. The simulations are carried out for various nondimensional rotation rates, axis ratio (AR) of the cylinder, and shear parameter. In shear flow past rotating elliptic cylinder, the negative vortices are sustained for longer distances in the downstream of the cylinder, and due to the velocity gradient, the sequence of the vortex street changes. It also has significant effect on the formation and composition of hovering vortex. To capture these features, each vortex is tracked as they form, detach, and move in the wake of the cylinder. Hovering vortex, formed due to coalescing of multiple vortices near the cylinder, is subdued for smaller rotation rates at moderate shear. It is also observed that lift forces increase linearly with shear, while the frequency of shedding shows no dependency on shear parameter.
The Need for Integrated Cybersecurity and Safety Training
Authors: Gupta Deeksha , Bajramovic Edita , Hoppe Holger , Ciriello Antonio
Published: July 2018

Companies involved in the nuclear energy domain, like component and platform manufacturers, system integrators, and utilities, have well-established yearly trainings on Nuclear Safety Culture. These trainings are typically covered as part of the annual quality assurance-related refresher trainings, introductory courses for new employees, or indoctrinations of temporary staff. Gradually, security awareness trainings are also addressed on a regular basis, typically with a focus on information technology, the daily office work, test bay, or construction site work environment, and some data protection and privacy-related topics. Due to emerging national nuclear regulation, steadily but surely, specialized cybersecurity trainings are foreseen for integrators and utilities. Beyond these safety, physical security and cybersecurity specific trainings, there is a need to address the joint part of these disciplines, starting from the planning phase of a new nuclear power plant (NPP). The engineers working on safety, physical protection, and cybersecurity must be aware of these interrelations to jointly elaborate a robust instrumentation and control architecture (defense-in-depth, design basis events, functional categorization and systems classification) and a resilient security architecture (security by design, security grading, zone model or infrastructure domain, security conduits, forensic readiness, security information, and event management). This paper provides more in-depth justification of when and where additional training is needed, due to the ubiquitous deployment of digital technology in new NPPs. Additionally, for existing NPPs, the benefits of conveying knowledge by training on specific interfaces between the involved disciplines will be discussed. Furthermore, the paper will address the need of focused training of management stakeholders, as eventually, they must agree on the residual risk. The decision-makers are in charge of facilitating the interdisciplinary cooperation in parallel to the allocation of resources, e.g., on security certifications of products, extended modeling-based safety and security analyses and security testing coverage.
Penetration of Elliptical Liquid Jets in Low-Speed Crossflow
Authors: Morad M. R. , Khosrobeygi H.
Published: July 2018

Trajectory and penetration of elliptical liquid jets emerged into a low-speed crossflow of air are studied. The jets are introduced to the crossflow at different momentum ratios ranging from 1 to 300. The images are analyzed to obtain the trajectories of the outer boundary of the jets for two different aspect ratios. An empirical correlation is proposed for the present injector geometries and for the range of momentum ratio, Weber, and Reynolds numbers used in this study. Finally, a theoretical model for the trajectory of the liquid column for an initially elliptical liquid emerging into a crossflow is presented, and the associated drag coefficients are obtained for a precise trajectory prediction.
Hydrodynamic Cavitation Downstream a Micropillar Entrained Inside a Microchannel—A Parametric Study
Authors: Nayebzadeh Arash , Tabkhi Hanieh , Peles Yoav
Published: July 2018

Hydrodynamic cavitation downstream a range of micropillar geometries entrenched in a microchannel were studied experimentally. Pressurized helium gas at the inlet tank and vacuum pressure at the outlet propelled distilled water through the device and trigger cavitation. The entire process from cavitation inception to the development of elongated attached cavity was recorded. Three modes of cavitation inception were observed and key parameters of cavitation processes, such as cavity length and angle of attachment, were compared among various micropillar geometries. Cavitation downstream of a triangular micropillar was found to have a distinct inception mode with relatively high cavitation inception numbers. After reaching its full elongated form, it prevailed through a larger system pressures and possessed the longest attached cavity. Cavity angle of attachments was predominantly related to the shape of the micropillar. Micropillars with sharp vertex led to lower cavity attachment angles close to the flow separation point, while circular micropillars resulted in higher angles. Twin circular micropillars have a unique cavitation pattern that was affected by vortex shedding. Fast Fourier transformation (FFT) analysis of the cavity image intensity revealed transverse cavity shedding frequencies in various geometries and provided an estimation for vortex shedding frequencies.
Effect of Slick Water on Permeability of Shale Gas Reservoirs
Authors: Yuan Bin , Wang Yongqing , Shunpeng Zeng
Published: July 2018

In this study, we analyzed the flow-back resistance of slick water fracturing fluid in shale reservoirs. The flow-back resistance mainly includes capillary force, Van der Waals (VDW) force, hydrogen bond force, and hydration stress. Shale of Lower Silurian Longmaxi Formation (LSLF) was used to study its wettability, hydration stress, and permeability change with time of slick water treatment. The results reveal that wettability of LSLF shale was more oil-wet before immersion, while it becomes more water-wet after immersion. The hydration stress of the shale increased with increasing immersion time. The permeability decreased first, then recovered with increasing immersion time. The major reason for permeability recovery is that the capillary effect (wettability) and the shale hydration make macrocracks extension and expansion and hydration-induced fractures formation.
Artificial Neural Network-Based Prediction of Performances-Exhaust Emissions of Diesohol Piloted Dual Fuel Diesel Engine Under Varying Compressed Natural Gas Flowrates
Authors: Paul Abhishek , Bhowmik Subrata , Panua Rajsekhar , Debroy Durbadal
Published: July 2018

The present study surveys the effects on performance and emission parameters of a partially modified single cylinder direct injection (DI) diesel engine fueled with diesohol blends under varying compressed natural gas (CNG) flowrates in dual fuel mode. Based on experimental data, an artificial intelligence (AI) specialized artificial neural network (ANN) model have been developed for predicting the output parameters, viz. brake thermal efficiency (Bth), brake-specific energy consumption (BSEC) along with emission characteristics such as oxides of nitrogen (NOx), unburned hydrocarbon (UBHC), carbon dioxide (CO2), and carbon monoxide (CO) emissions. Engine load, Ethanol share, and CNG strategies have been used as input parameters for the model. Among the tested models, the Levenberg–Marquardt feed-forward back propagation with three input neurons or nodes, two hidden layers with ten neurons in each layer and six output neurons, and tansig-purelin activation function have been found to the optimal model topology for the diesohol–CNG platforms. The statistical results acquired from the optimal network topology such as correlation coefficient (0.992–0.999), mean square error (MSE) (0.0001–0.0009), and mean absolute percentage error (MAPE) (0.09–2.41%) along with Nash–Sutcliffe coefficient of efficiency (NSE), Kling–Gupta efficiency (KGE), mean square relative error, and model uncertainty established itself as a real-time robust type machine learning tool under diesohol–CNG paradigms. The study also incorporated a special type of measure, namely Pearson's Chi-square test or goodness of fit, which brings up the model validation to a higher level.
An Analytical Dynamic Model of a Hollow Cylindrical Roller Bearing
Authors: Liu Jing , Shao Yimin
Published: July 2018

Hollow cylindrical roller bearings (HCRBs) have obtained much attention from design engineers in bearing industries since they can perform better than solid cylindrical roller bearings (SCRBs) in centrifugal forces, contact stiffness, cooling ability, fatigue life, etc. In this study, an analytical dynamic model of a lubricated HCRB is presented to analyze the influences of the radial load, the shaft speed, and the hollowness percentage of the roller on the bearing vibrations, which cannot be formulated by the methods in the reported literature. Both the support stiffness of the shaft and the roller mass are formulated in the presented dynamic model. The hollow hole in the roller is modeled as a uniform one. Numerical results show that the hollowness percentage of the roller has a great influence on the vibrations of the roller and the inner race of the HCRB. Moreover, the vibrations of the components of the HCRB are not only determined by the hollowness percentage of the roller, but also depended on the external radial load and shaft speed. Therefore, during the design process for the hollowness percentage of the roller, the influences of the radial load and the shaft speed on the vibrations of the bearing components should be considered, except for the fatigue life. The results show that this work can give a new dynamic method for analyzing the vibrations of the HCRBs. Moreover, it can give some guidance for the design method for the HCRBs.
Effect of Mn Modification on the Tribological Properties of In Situ Al-15Mg2Si Composites Containing Fe as an Impurity
Authors: Nadim A. , Taghiabadi R. , Razaghian A.
Published: July 2018

The effect of Mn modification on the tribological properties of Al-15Mg2Si-(0.5-2)Fe composites was investigated. The sliding wear tests were conducted under the applied pressures of 0.25, 0.5, and 1.0 MPa at the constant sliding speed of 0.13 m/s. According to the results, the behavior of FeMn-rich intermetallics against the strains induced by sliding wear has an important role in the wear behavior of composites. In low-Fe composites (0.5–1 wt % Fe), Mn promotes the formation of Chinese script α-Al15(Fe,Mn)3Si2 phases instead of harmful β-Al5FeSi platelets. The formation of these compounds strengthens the substrate and decreases its microcracking tendency giving rise to a more stable tribolayer and improved wear properties. At the higher Fe contents, Mn modification leads to the formation of primary polyhedral or star-like α-Al15(Fe,Mn)3Si2 compounds in the microstructure and substantially neutralizes the harmful effect of the primary β-Fe crystals on the wear behavior. However, when subjected to the friction-induced surface plastic strains, the near-surface α-FeMn particles fracture and incorporate into the tribolayer making it unstable and less protective. The tribolayer stability in Mn-modified composites decreases the chance of adhesion between contacting surfaces, and, under low applied pressures, lowers the average friction coefficient (AFC) and its fluctuation. At higher applied pressures, however, the nonmodified composites exhibit lower AFC, which is probably due to the negative impact of β-Fe fragments on the tribolayer shear strength.
Experimental Investigation of Second-Harmonic Lamb Wave Generation in Additively Manufactured Aluminum
Authors: Vien Benjamin Steven , Chiu Wing Kong , Francis Rose L. R.
Published: July 2018

The correlation between the nonlinear acousto-ultrasonic response and the progressive accumulation of fatigue damage is investigated for an additively manufactured aluminum alloy AlSi7Mg and compared with the behavior of a conventional wrought aluminum alloy 6060-T5. A dual transducer and wedge setup is employed to excite a 30-cycle Hann-windowed tone burst at a center frequency of 500 kHz in plate-like specimens that are 7.2 mm thick. This choice of frequency-thickness is designed to excite the symmetric Lamb mode s1, which, in turn, generates a second-harmonic s2 mode in the presence of distributed material nonlinearity. This s1-s2 mode pair satisfies the conditions for internal resonance, thereby leading to a cumulative build-up of amplitude for the second-harmonic s2 mode with increasing propagation distance. Measurements of a nonlinearity parameter β derived from the second-harmonic amplitude are plotted against propagation distance at various fractions of fatigue life under constant amplitude loading, for three different stress levels corresponding to low-cycle fatigue (LCF), high-cycle fatigue (HCF), and an intermediate case. The results show both qualitative and quantitative differences between LCF and HCF, and between the additively manufactured specimens and the wrought alloy. The potential use of this nonlinearity parameter for monitoring the early stages of fatigue damage accumulation, and hence for predicting the residual fatigue life, is discussed, as well as the potential for quality control of the additive manufacturing (AM) process.
Dynamic Performance of Annular Blowout Preventer Hydraulic Seals in Deepwater Environments
Authors: Mutlu Mete , Tang Yingjie , Franchek Matthew A. , Turlak Rob , Gutierrez Jose A.
Published: July 2018

Presented is the performance analysis of annular blowout preventer (BOP) reciprocating elastomer hydraulic seals operating in subsea environments. The method is based on a systems-level model that combines the effects of friction, material mechanical properties of the seal, installation compression, subsea hydrostatic pressure, and control system dynamics into one model. The model is calibrated using data from tests conducted on the surface and then validated on subsea operational data. Through model simulations, it will be shown that insufficient installation squeeze of the seal in combination with low elasticity seal material results in cases where the seal does not leak at the surface but show substantial internal leakage in subsea conditions. Leakage is also observed under dynamic operation when the walls of the seal groove do not energize the seal. The proposed model-based analysis method in conjunction with surface level testing offers a new paradigm in evaluating reciprocating seal subsea performance a priori of subsea operation thereby avoiding costly downtimes and subsea failures.