bluuebunny/crossref_metadata_2025 huggingface dataset:
Catching the Sun
Authors: Crawford Mark
Published: July 2018

This article discusses various aspects of concentrating solar power (CSP) systems. CSP system ensures that more solar energy reaches the earth in one hour than the combined worldwide consumption of energy by human activities in one year. The article also focuses on various challenges posed by the CSP systems as alternative energy sources. Some CSP systems focus sunlight onto a line, where tubes contain a working fluid, such as synthetic oil, which is heated and pumped to heat exchangers to produce high-pressure steam. These systems are oriented north–south and track on a single axis from east to west over the course of a day. Technological improvements have been made in nearly all the sub-components of CSP systems over the past few years. Research efforts include developing novel materials and heat-transfer fluids, designing receivers that can achieve high temperatures, and building higher efficiency heat collectors. The study shows that nearly every part of the CSP system presents rich opportunities for mechanical engineers to contribute their expertise. In particular, the challenging SunShot Initiative goals call for innovations and ingenious system designs to drive costs down, while improving efficiencies.
Cars Without Combustion
Authors: Crawford Mark
Published: July 2018

This article discusses the use of fuel cell-powered vehicles that aim to change the face of transportation. These fuel cell-powered vehicles are expected to have a significant impact on reducing both the emissions implicated in global climate change and those that cause local smog. Fuel cells electrochemically oxidize a fuel without burning, thereby avoiding the inefficiencies and pollution associated with the traditional combustion technologies. The U.S. Department of Energy is working with researchers at the University of Waterloo in Ontario and elsewhere to develop non-precious materials to replace the platinum catalysts in fuel cells. European scientists have developed a material for converting hydrogen and oxygen to water that uses only 10% of the amount of platinum that is normally required. The researchers discovered that the efficiency of the nanometer-sized catalyst particles is greatly influenced by their geometric shape and atomic structure. Mechanical engineers play a crucial role in the development of both fuel cell and hydrogen production technologies.
Emerging Nexis of Cyber, Modeling, and Estimation in Advanced Manufacturing
Authors: Beaman Joseph , Lopez Felipe
Published: July 2018

This article describes opportunities for exploiting cyber, modeling, and estimation technical areas for advanced manufacturing in small lots. In particular, Cyber Enabled Manufacturing Systems (CeMs) for small lot manufacturing that incorporates a model of the process directly into the control algorithm are presented and discussed. The model enables the manufacturing monitoring and control algorithm to accommodate changing conditions without extensive additional experiments. One of the manufacturing processes currently being studied with this methodology is Vacuum Arc Remelting (VAR). Similar to Additive Manufacturing, VAR is a small lot, high-value manufacturing process. There is great opportunity for the control community to have a major impact on advanced manufacturing. This includes increasing the performance of mature manufacturing processes such as VAR or developing the critical control of emerging manufacturing processes like 3D printing. This opportunity is especially timely because of a nexus of multi-physics simulation software, modern estimation methods, and real-time computer architecture and hardware.
Certified Quality
Authors: Pang Joseph , Mähler Chris
Published: July 2018

This article discusses various aspects of a new ASME program that seeks to support a robust global supply chain for the nuclear industry. Under the program, an ASME audit team will assess a company’s quality assurance program. It will make an accurate assessment of a supplier’s capability in implementing its QA program in compliance with the NQA-1 standard and will issue a certificate affirming that the company has been found in compliance. Safeguards are in place for companies to receive a fair and unbiased evaluation. Conflicts of interest are removed by having the ASME Conformity Assessment Department develop and administer the program. The ASME audit team will visit all locations where the nuclear quality assurance program is being implemented and will require a company to implement or demonstrate all aspects of its program. The review of the supplier’s QA manual and the on-site audit will be the basis of the team’s report in conveying to ASME the company’s capabilities, knowledge, and understanding of its program and of the ASME NQA-1 standard.
Nanotechnology for the Brain
Authors: Brown Alan S.
Published: July 2018

This article explores various nanotechnology-based programs conducted by different teams to study the brain. In the United States, the National Institutes of Health is leading the Brain Research through Advancing Innovative Neurotechnologies (BRAIN) Initiative, a public–private program that will spend millions on research. The European Union has also proposed a similar effort that will focus on simulating the entire brain on supercomputers. Hongkun Park is developing nanowire arrays that can inject neurons with chemicals or measure electrical activity as it develops in the cell. Weiss and Anne Andrews, a professor of psychiatry at UCLA, have developed sensors that detect the important neurotransmitter, serotonin, by engineering surfaces that bond with it exclusively and not with related molecules. The next step is to create transducers that signal when sensors capture a serotonin molecule. Nanotechnology will play a vital role in that advance.
Earth Battery
Authors: Buscheck Thomas A.
Published: July 2018

This article elaborates the features of Multi-Fluid/CO2 Plume Geothermal (CPG) energy storage system. This system provides utility-scale diurnal and seasonal energy storage and dispatchable power, while permanently sequestering carbon dioxide (CO2) from industrial-scale fossil-energy power plants. Operationally, a Multi-Fluid/CPG system is radically different from traditional power plants or energy storage systems, such as pumped hydroelectric. Most of the system resides below the ground surface, consisting of horizontal injection and production wells arrayed in concentric rings that could be five miles or more across. This ring configuration is used to pressurize and confine CO2 in the region in the center of the array and to pressurize brine between the outer two rings. Because the Multi-Fluid/CPG system relies on the injection of carbon dioxide, the cost of sequestration is turned into an operational investment. Just as enhanced oil recovery has made geological CO2 sequestration economically viable in the petroleum industry. Multi-Fluid/CPG can make it profitable to lock away CO2 that would otherwise be emitted.
Insights of Wormhole Propagation During Carbonate Acidizing: A Comparison Between Constant Injection Pressure Versus Constant Volumetric Rate
Authors: Gomaa Ahmed M. , Nino-Penaloza Andrea , Cutler Jennifer , Chaudhary Saleem
Published: July 2018

Acidizing of carbonate reservoirs is a common technique used to restore and enhance production by dissolving a small fraction of the rock to create highly conductive channels. Literature review reveals that most acidizing studies are focused on acid injection at a constant volumetric rate (CVR) instead of at a constant injection pressure (CIP). Therefore, the primary objective of the present work is to investigate the benefits and recommended applications of each technique. The study analyzes dissolution patterns and wormhole propagation rate. A coreflood study was conducted using different Indiana limestone cores to assess both techniques. Additionally, a two-dimensional (2D) wormhole model was used to mathematically describe the acidizing phenomena. The algorithm is based on a 2D radial flow system that iterates time to quantify wormhole propagation and injection rate. Wormhole velocity is calculated by an empirical laboratory model that depends on two parameters measured from core flow testing. Therefore, the algorithm captures the essential physics and chemistry of the acid reaction in a carbonate porous medium. The study confirmed that conical, wormhole, and branched types of acid dissolution patterns exist for both techniques (CVR or CIP). Unlike in the CVR technique, dissolution patterns during the CIP technique can change and tend toward a branched dissolution regime. The CIP technique required a lower acid volume to achieve a breakthrough in the conical dissolution regime and a higher acid volume to achieve a breakthrough in the branched dissolution regime compared to the CVR technique. In a dominant wormhole pattern, both techniques required nearly the same acid volume for a breakthrough. A computed tomography (CT) scan confirmed that the CIP technique developed a uniform wormhole at a low initial injection rate. For the CIP technique, the acid injection rate increased exponentially with the volume of the acid injected. The CIP technique is recommended for a low-permeability reservoir where acid injection at a high rate is not possible to avoid face dissolution wormhole patterns. On the other hand, the CVR technique is recommended for a medium—to the high-permeability reservoir where high acid injection rate can be achieved.
Development and Analysis of a Three-Dimensional Printed Miniature Walking Robot With Soft Joints and Links
Authors: DeMario Anthony , Zhao Jianguo
Published: July 2018

Miniature robots have many applications ranging from military surveillance to search and rescue in disaster areas. Nevertheless, the fabrication of such robots has traditionally been labor-intensive and time-consuming. This paper proposes to directly leverage multimaterial 3D printing (MM3P) to fabricate centimeter-scale robots by utilizing soft materials to create not only soft joints to replace revolute joints but also soft links to replace rigid links. We demonstrate the capability of MM3P by creating a miniature, four-legged walking robot. Moreover, we leverage a three-spring rotational-prismatic-rotational (RPR) model to approximate the motion of soft joints or links, which is further utilized to numerically predict the motion of the leg mechanism with multiple soft joints and links. The accuracy of the proposed numerical method is validated with experimental results, and outperforms the results from using a psuedorigid-body (PRB) 1R model to approximate the motion of soft joints/links of the same mechanism. Meanwhile, a functional walking robot actuated by a single DC motor is demonstrated with a locomotion speed of 5.7 cm/s. We envision that the concept of employing both soft joints and links will inspire the design and realization of novel miniature mechanisms for a wide range of applications including robotics, deployable structures, or mechanical metamaterials. The proposed numerical method can also be readily applied to analyze other mechanisms with soft joints and links.
Analysis for Combustion Instability and Stabilization Characteristics in a Swirled Premixed Combustor With a Slotted Plate
Authors: Oh Seungtaek , Kim Jaehyeon , Kim Yongmo
Published: July 2018

In this study, new methodologies are introduced to analyze combustion instability in a lab-scale swirled combustor. First, with the help of radial basis function neural network (RBFNN), the flame describing function (FDF) is effectively modeled from a limited number of experimental data. This neural-network-based FDF method is able to generate more refined FDF data in an extended range. In addition, instead of a perforated plate with round holes, a slotted plate is utilized as a stabilization device. In this approach, the acoustic impedance of a slotted plate is modeled by the Dowling approach, and the dimensions of a slotted plate are optimized by simulated annealing (SA) algorithm to get the highest average absorption coefficient in a given frequency range. The present RBFNN-based FDF approach yields the reasonably good agreements with the measurements in terms of the limit-cycle velocity perturbation ratio and resonant frequency. It is also found that a slotted plate optimized by SA algorithm is quite effective to attenuate combustion instability. Numerical results obtained in this study confirm that these new methodologies are quite reliable and widely applicable for the analysis of combustion instability encountered in practical combustion systems.
Dynamics Analysis of the Triangular Rotary Engine Structures
Authors: Hsieh Chiu-Fan
Published: July 2018

A triangular rotary engine includes several main components such as an eccentric shaft, a sun gear, a triangular rotor, a chamber, and apex seals. This study constructs the mathematical models for the chamber and triangular rotor profiles in a rotary engine, as well as for the kinematics and contact force of its apex seals by using the epitrochoid and envelope principles. The chamber profile is represented by design parameter, trochoid ratio, whose limitations are investigated together with the volume ratio. To simplify the calculation, the dynamics analysis model ignores the effects of combustion and thermal conditions in rotary engines. Gas force effect is taken into account by first constructing a fluid analysis model that measures the gas fluid moment on the triangular rotor. Then, based on the mathematical models of chamber and rotor, a systematic dynamics analysis model for a rotary engine is built. It allows analyzing the kinematics and the stress variations in all components of the engine. The dynamics model considers both output shaft torsion and fluid moment. The dynamics analysis then uses three cases of trochoid ratio to illustrate the effects of chamber profile design on the system dynamics properties of rotary engines. The results not only show the dynamic properties and differences in various mechanism designs but also indicate the stability and stress level in the components. In conclusion, the higher trochoid ratio with a larger variation in the chamber profile curvature reduces system stability and increases vibrations, stress fluctuations, and large stress peaks risk.
High-Performance Computing and Analysis-Led Development of High Efficiency Dilute Opposed Piston Gasoline Engine
Authors: Banerjee Siddhartha , Naber Clayton , Willcox Michael , Finney Charles E. A. , Edwards Dean K.
Published: July 2018

Pinnacle is developing a multicylinder 1.2 L gasoline engine for automotive applications using high-performance computing (HPC) and analysis methods. Pinnacle and Oak Ridge National Laboratory executed large-scale multidimensional combustion analyses at the Oak Ridge Leadership Computing Facility to thoroughly explore the design space. These HPC-led investigations show high fuel efficiency (∼46% gross indicated efficiency) may be achieved by operating with extremely high charge dilution levels of exhaust gas recirculation (EGR) at a light load key drive cycle condition (2000 RPM, 3 bar brake mean effective pressure (BMEP)), while simultaneously attaining high levels of fuel conversion efficiency and low NOx emissions. In this extremely dilute environment, the flame propagation event is supported by turbulence and bulk in-cylinder charge motion brought about by modulation of inlet port flow. This arrangement produces a load and speed adjustable amalgamation of swirl and counter-rotating tumble which provides the turbulence required to support stable low-temperature combustion. At higher load conditions, the engine may operate at more traditional combustion modes to generate competitive power. In this paper, the numerical results from these HPC simulations are presented. Further HPC simulations and test validations are underway and will be reported in future publications.
Stability Issues of Fuel Cell Models in the Activation and Concentration Regimes
Authors: Beale S. B. , Reimer U. , Froning D. , Jasak H. , Andersson M. , Pharoah J. G. , Lehnert W.
Published: July 2018

Code stability is a matter of concern for three-dimensional (3D) fuel cell models operating both at high current density and at high cell voltage. An idealized mathematical model of a fuel cell should converge for all potentiostatic or galvanostatic boundary conditions ranging from open circuit to closed circuit. Many fail to do so, due to (i) fuel or oxygen starvation causing divergence as local partial pressures and mass fractions of fuel or oxidant fall to near zero and (ii) nonlinearities in the Nernst and Butler–Volmer equations near open-circuit conditions. This paper describes in detail, specific numerical methods used to improve the stability of a previously existing fuel cell performance calculation procedure, at both low and high current densities. Four specific techniques are identified. A straight channel operating as a (i) solid oxide and (ii) polymer electrolyte membrane fuel cell is used to illustrate the efficacy of the modifications.
Study on Radial Temperature Distribution of Aluminum Dispersed Nuclear Fuels: U3O8-Al, U3Si2-Al, and UN-Al
Authors: Ranasinghe Jayangani I. , Jossou Ericmoore , Malakkal Linu , Szpunar Barbara , Szpunar Jerzy A.
Published: July 2018

The understanding of the radial distribution of temperature in a fuel pellet, under normal operation and accident conditions, is important for a safe operation of a nuclear reactor. Therefore, in this study, we have solved the steady-state heat conduction equation, to analyze the temperature profiles of a 12 mm diameter cylindrical dispersed nuclear fuels of U3O8-Al, U3Si2-Al, and UN-Al operating at 597 °C. Moreover, we have also derived the thermal conductivity correlations as a function of temperature for U3Si2, uranium mononitride (UN), and Al. To evaluate the thermal conductivity correlations of U3Si2, UN, and Al, we have used density functional theory (DFT) as incorporated in the Quantum ESPRESSO (QE) along with other codes such as Phonopy, ShengBTE, EPW (electron-phonon coupling adopting Wannier functions), and BoltzTraP (Boltzmann transport properties). However, for U3O8, we utilized the thermal conductivity correlation proposed by Pillai et al. Furthermore, the effective thermal conductivity of dispersed fuels with 5, 10, 15, 30, and 50 vol %, respectively of dispersed fuel particle densities over the temperature range of 27–627 °C was evaluated by Bruggman model. Additionally, the temperature profiles and temperature gradient profiles of the dispersed fuels were evaluated by solving the steady-state heat conduction equation by using Maple code. This study not only predicts a reduction in the centerline temperature and temperature gradient in dispersed fuels but also reveals the maximum concentration of fissile material (U3O8, U3Si2, and UN) that can be incorporated in the Al matrix without the centerline melting. Furthermore, these predictions enable the experimental scientists in selecting an appropriate dispersion fuel with a lower risk of fuel melting and fuel cracking.
The Study of Nanosized Cu–Mn Precipitates Contribution to Hardening in Body Centered Cubic Fe Matrix
Authors: Dou YanKun , He XinFu , Wang DongJie , Shi Wu , Jia LiXia , Yang Wen
Published: July 2018

In order to study the contribution of manganese (Mn) atoms in copper (Cu) precipitates to hardening in body centered cubic (BCC) structure iron (Fe) matrix, the interactions of a 1/2 〈111〉 {110} edge dislocations with nanosized Cu and Cu–Mn precipitates in BCC Fe have been investigated by using molecular dynamics method (MD). The results indicate that the critical resolved shear stresses (τc) of the Cu–Mn precipitates are larger than that of Cu precipitates. Meanwhile, τc of the Cu–Mn precipitates show a much more significant dependence on temperature and size compared to Cu precipitates. Mn atoms exhibit strong attraction to dislocation segment in Cu precipitate and improve the fraction of transformed atoms from BCC phase to nine rhombohedron (R) phase for big size precipitates. Those all lead to the higher resistance to the dislocation glide. Eventually, these features confirmed that the appearance of Mn atoms in Cu precipitates greatly facilitates the hardening in BCC Fe matrix.
Analysis of Nanofluid-Based Parabolic Trough Collectors for Solar Thermal Applications
Authors: Freedman Justin P. , Wang Hao , Prasher Ravi S.
Published: July 2018

Solar-to-thermal energy conversion technologies are an important and increasingly promising segment of our renewable energy technology future. Today, concentrated solar power (CSP) plants provide a method to efficiently store and distribute solar energy. Current industrial solar-to-thermal energy technologies employ selective solar absorber coatings to collect solar radiation, which suffer from low solar-to-thermal efficiencies at high temperatures due to increased thermal emission from selective absorbers. Solar absorbing nanofluids (a heat transfer fluid (HTF) seeded with nanoparticles), which can be volumetrically heated, are one method to improve solar-to-thermal energy conversion at high temperatures. To date, radiative analyses of nanofluids via the radiative transfer equation (RTE) have been conducted for low temperature applications and for flow conditions and geometries that are not representative of the technologies used in the field. In this work, we present the first comprehensive analysis of nanofluids for CSP plants in a parabolic trough configuration. This geometry was chosen because parabolic troughs are the most prevalent CSP technologies. We demonstrate that the solar-to-thermal energy conversion efficiency can be optimized by tuning the nanoparticle volume fraction, the temperature of the nanofluid, and the incident solar concentration. Moreover, we demonstrate that direct solar absorption receivers have a unique advantage over current surface-based solar coatings at large tube diameters. This is because of a nanofluid's tunability, which allows for high solar-to-thermal efficiencies across all tube diameters enabling small pressure drops to pump the HTF at large tube diameters.
Edge Trimming Induced Defects on Direct Bonded Wafers
Authors: Inoue Fumihiro , Jourdain Anne , Peng Lan , Phommahaxay Alain , Kosemura Daisuke , De Wolf Ingrid , Rebibis Kenneth June , Miller Andy , Sleeckx Erik , Beyne Eric
Published: July 2018

The diamond abrasive process which is applied onto the silicon wafer edge, the so called “edge trimming,” is an important step in three-dimensional microelectronics processing technology, due to the significant thickness reduction of the wafer after thinning. Nevertheless, the wafer edge defects caused by edge trimming have often been overlooked. Although the mechanisms of the formation of the defects in Si due to trimming may be similar to the ones caused by grinding, an in-depth study and risk assessment have not been done yet. In addition, the variety of stress relief processing options can give different morphology and defect removal behavior on the edge trimmed Si sidewall. In a first study, we used transmission electron microscopy and Raman spectroscopy to analyze the defects caused by edge trimming. We show the presence of a continuous layer of amorphous Si and of different phases of Si, caused by edge trimming. A comparison of the damage induced in the Si by two different integration schemes is also discussed. When polishing is used for stress release, the observed sidewall defects stay, since the polishing force is only applied on the top surface of the wafer. On the other hand, the damage is completely removed for the case of wet and dry etching. The surface chemical reactions occurring at the surface during these processes are also acting on the Si sidewall. These findings provide a workable edge trimming and stress relief method for permanently bonded wafers, with many industrial applications.
Large Eddy Simulation of a Pressurized, Partially Premixed Swirling Flame With Finite-Rate Chemistry
Authors: Jella Sandeep , Gauthier Pierre , Bourque Gilles , Bergthorson Jeffrey , Bulat Ghenadie , Rogerson Jim , Sadasivuni Suresh
Published: July 2018

Finite-rate chemical effects at gas turbine conditions lead to incomplete combustion and well-known emissions issues. Although a thin flame front is preserved on an average, the instantaneous flame location can vary in thickness and location due to heat losses or imperfect mixing. Postflame phenomena (slow CO oxidation or thermal NO production) can be expected to be significantly influenced by turbulent eddy structures. Since typical gas turbine combustor calculations require insight into flame stabilization as well as pollutant formation, combustion models are required to be sensitive to the instantaneous and local flow conditions. Unfortunately, few models that adequately describe turbulence–chemistry interactions are tractable in the industrial context. A widely used model capable of employing finite-rate chemistry is the eddy dissipation concept (EDC) model of Magnussen. Its application in large eddy simulations (LES) is problematic mainly due to a strong sensitivity to the model constants, which were based on an isotropic cascade analysis in the Reynolds-averaged Navier–Stokes (RANS) context. The objectives of this paper are: (i) to formulate the EDC cascade idea in the context of LES; and (ii) to validate the model using experimental data consisting of velocity (particle image velocimetry (PIV) measurements) and major species (1D Raman measurements), at four axial locations in the near-burner region of a Siemens SGT-100 industrial gas turbine combustor.
On the Development of Incompressible Round and Equilateral Triangular Jets Due to Reynolds Number Variation
Authors: Aleyasin Seyed Sobhan , Fathi Nima , Tachie Mark Francis , Vorobieff Peter , Koupriyanov Mikhail
Published: July 2018

The aim of this study is to examine the effects of Reynolds number (Re = 6000–20,000) on mean and turbulent quantities as well as turbulent structures in the near and intermediate regions of equilateral triangular and round sharp contraction jets. The results show shorter potential core length, faster growth of turbulence intensity, and faster diffusion of turbulent structures to the centerline of the triangular jets, implying enhanced mixing in the near field of these jets. On the other hand, the velocity decay and jet spread rates are higher in the round jets. The obtained data in the round jets show that the jet at Re = 6000 has the most effective mixing, while an increase in Reynolds number reduces the mixing performance. In the triangular jets, however, no Reynolds number effects were observed on the measured quantities including the length of the potential core, the decay and spread rates, the axis-switching locations, and the value of the Reynolds number. In addition, the asymptotic values of the relative turbulence intensities on the jet centerline are almost independent of the Reynolds number and geometry. The ratios of transverse and spanwise Reynolds stresses are unity except close to the jet exit where the flow pattern in the major plane of the triangular jet deflects toward the flat side. Proper orthogonal decomposition (POD) analysis revealed that turbulent structures in minor and major planes have identical fractional kinetic energy. The integral length scales increased linearly with the streamwise distance with identical slope for all the test cases.
Adjoint- and Hybrid-Based Hessians for Optimization Problems in System Identification
Authors: Nandi Souransu , Singh Tarunraj
Published: July 2018

An adjoint sensitivity-based approach to determine the gradient and Hessian of cost functions for system identification of dynamical systems is presented. The motivation is the development of a computationally efficient approach relative to the direct differentiation (DD) technique and which overcomes the challenges of the step-size selection in finite difference (FD) approaches. An optimization framework is used to determine the parameters of a dynamical system which minimizes a summation of a scalar cost function evaluated at the discrete measurement instants. The discrete time measurements result in discontinuities in the Lagrange multipliers. Two approaches labeled as the Adjoint and the Hybrid are developed for the calculation of the gradient and Hessian for gradient-based optimization algorithms. The proposed approach is illustrated on the Lorenz 63 model where part of the initial conditions and model parameters are estimated using synthetic data. Examples of identifying model parameters of light curves of type 1a supernovae and a two-tank dynamic model using publicly available data are also included.
Performance Assessments of Organic Rankine Cycle With Internal Heat Exchanger Based on Exergetic Approach
Authors: Yamankaradeniz Nurettin , Bademlioglu Ali Husnu , Kaynakli Omer
Published: July 2018

This study makes energy and exergy analysis of a sample organic Rankine cycle (ORC) with a heat exchanger which produces energy via a geothermal source with a temperature of 140 °C. R600a is preferred as refrigerant to be used in the cycle. The changes in exergy destructions (of irreversibility) and exergy efficiencies in each cycle element are calculated in the analyses made based on the effectiveness of heat exchanger used in cycle and evaporator temperature changing between 60 and 120 °C for fixed pinch point temperature differences in evaporator and condenser. Parameters showing system performance are assessed via second law approach. Effectiveness of heat exchanger and temperature of evaporator are taken into consideration within the scope of this study, and energy and exergy efficiencies of cycle are enhanced maximum 6.87% and 6.21% respectively. Similarly, exergy efficiencies of evaporator, heat exchanger, and condenser are increased 4%, 82%, and 1.57%, respectively, depending on the effectiveness of heat exchanger and temperature of evaporator.
Nonlinear Analysis for Influence of Parametric Uncertainty on the Stability of Rotor System With Active Magnetic Bearing Using Feedback Linearization
Authors: Kato Junya , Inoue Tsuyoshi , Takagi Kentaro , Yabui Shota
Published: July 2018

Active magnetic bearing (AMB) is the device to support and control rotating shaft. Feedback linearization is one of the methods to compensate the system nonlinearity, and it is often used in the control of AMB. Some parameters in the electromagnetic force model have often been ignored or their parametric uncertainty from the nominal values has been calibrated; however, their influence on the stability has not been investigated. In this paper, the influence of the parametric uncertainty in the electromagnetic force model on the stability of AMB is investigated. The equilibrium positions and their stability are investigated and clarified analytically. Furthermore, the choice of the parameter value for improving the stability of AMB with feedback linearization is proposed, and its effectiveness is explained analytically. It is shown that the proposed choice of the parameter value also reduces the remained nonlinearity significantly. The validity of theoretical results and proposed choice of the parameter value are confirmed by experiment.
Buoyancy Induced Convection From Biheaters in a Cavity: A Numerical Study
Authors: Giri Asis , Patel Swastika
Published: July 2018

A computational study of natural convection from biheaters of finite thickness and finite conductivity placed on a finite thickness and a finite conductive bottom plate of a cavity is performed under constant heat input condition. Cavity is cooled by the sidewalls, while the top and backside of the bottom plate are insulated. Streamline, isotherms, and local heat flux distribution of the sidewalls are discussed. Base Grashof number is chosen as 2.5 × 106. Biheater maintains a nondimensional distance of 0.4 between them. The left heater is placed at a nondimensional distance of 0.2 from the left wall. Heater length ratio is varied from 0.4 to 1.7, while heater strength ratio is varied from 0.25 to 7.0. Optimum operating temperature condition is found from the analysis.
Numerical Analysis of the Contact Pressure in a Quasi-Static Elastomeric Reciprocating Sealing System
Authors: Tsala Serge , Berthier Yves , Mollon Guilhem , Bertinotti Aude
Published: July 2018

In this technical brief, we present detailed finite element simulations of a sealing system operating in quasi-static conditions, in the framework of the real piston actuator of a landing gear braking system. Numerical results show two peaks of the contact pressure on the rod, and demonstrate that this contact pressure remains larger than that in the fluid chamber. These numerical results are qualitatively validated by scanning electron microscopy (SEM) observations of a worn sealing system. Overall, this study shows the benefits of numerical simulation in geometrical design of sealing systems targeting a given contact pressure at the rod/seal interface.
A Conceptual Design and Modeling Framework for Integrated Additive Manufacturing
Authors: Mokhtarian Hossein , Coatanéa Eric , Paris Henri , Mbow Mouhamadou Mansour , Pourroy Franck , Marin Philippe René , Vihinen Jorma , Ellman Asko
Published: July 2018

Modeling and simulation for additive manufacturing (AM) is commonly used in industry. Nevertheless, a central issue remaining is the integration of different models focusing on different objectives and targeting different levels of details. The objective of this work is to increase the prediction capability of characteristics and performances of additively manufactured parts and to co-design parts and processes. The paper contributes to this field of research by integrating part's performance model and additive technology process model into a single early integrated model. The paper uses the dimensional analysis conceptual modeling (DACM) framework in an AM perspective to generate causal graphs integrating the AM equipment and the part to be printed. DACM offers the possibility of integrating existing knowledge in the model. The framework supported by a computer tool produces a set of governing equations representing the relationships among the influencing variables of the integrated model. The systematic identification of the weaknesses and contradictions in the system and qualitative simulation of the system are some of the potential uses of the model. Ultimately, it is a way to create better designs of machines and parts, to control and qualify the manufacturing process, and to control three-dimensional (3D) printing processes. The DACM framework is tested on two cases of a 3D printer using the fused filament fabrication (FFF) powder bed fusion. The analysis, applied to the global system formed of the 3D printer and the part, illustrates the existence of contradictions. The analysis supports the early redesign of both parts and AM process (equipment) and later optimization of the control parameters.
Experimental Investigation of Amine-Surfactant CO2 Foam Stability Enhanced by Silica Nanoparticles
Authors: Zhang Liang , Kang Jun , Zhang Yin , Zhang Panfeng , Ren Shaoran , Khataniar Santanu , Guo Xinyang
Published: July 2018

The CO2 foam generated by the conventional surfactants usually does not show long-term stability due to the substantial solubility and diffusivity of CO2 in water. Silica nanoparticles with different wettability and high adsorption energy on the gas–water interface can be used as a stabilizer to enhance the stability of the CO2 foam. In this study, nine kinds of nonionic amine surfactants were employed to generate the CO2 foam, while three kinds of silica nanoparticles were selected and added to improve the CO2 foam stability. The influences of various factors, including pressure, temperature, pH, surfactant, and nanoparticle, on the CO2 foam stability have been investigated. The experimental results show that without nanoparticles, the CO2 foam stability decreases with the increase of the number of EO groups in the ethoxylated amine surfactant, especially under high-temperature and high-pressure (HTHP) conditions. In general, the nanoparticles with a low concentration (<0.5 wt %) have little influence on the CO2 foam stability, but when the concentration of nanoparticle is enhanced high enough (1.0 wt %), the CO2 foam stability can be improved significantly. In particular, by adding 1.0 wt % nanoparticle of QS-150 to 0.5 wt % surfactant of C18N(EO)2/10, the CO2 foam stability has been increased 5–6 times, while the volume of generated CO2 foam has been increased by 17–31%. Therefore, in this study, the synergetic mechanisms between the amine surfactants and the silica nanoparticles to generate and stabilize CO2 foam have been identified.
Adaptive Discrete Second-Order Sliding Mode Control With Application to Nonlinear Automotive Systems
Authors: Amini Mohammad Reza , Shahbakhti Mahdi , Pan Selina
Published: July 2018

Sliding mode control (SMC) is a robust and computationally efficient model-based controller design technique for highly nonlinear systems, in the presence of model and external uncertainties. However, the implementation of the conventional continuous-time SMC on digital computers is limited, due to the imprecisions caused by data sampling and quantization, and the chattering phenomena, which results in high-frequency oscillations. One effective solution to minimize the effects of data sampling and quantization imprecisions is the use of higher-order sliding modes. To this end, in this paper, a new formulation of an adaptive second-order discrete sliding mode controller (DSMC) is presented for a general class of multi-input multi-output (MIMO) uncertain nonlinear systems. Based on a Lyapunov stability argument and by invoking the new invariance principle, not only the asymptotic stability of the controller is guaranteed but also the adaptation law is derived to remove the uncertainties within the nonlinear plant dynamics. The proposed adaptive tracking controller is designed and tested in real time for a highly nonlinear control problem in spark ignition (SI) combustion engine during transient operating conditions. The simulation and real-time processor-in-the-loop (PIL) test results show that the second-order single-input single-output (SISO) DSMC can improve the tracking performances up to 90%, compared to a first-order SISO DSMC under sampling and quantization imprecisions, in the presence of modeling uncertainties. Moreover, it is observed that by converting the engine SISO controllers to a MIMO structure, the overall controller performance can be enhanced by 25%, compared to the SISO second-order DSMC, because of the dynamics coupling consideration within the MIMO DSMC formulation.
An Ergonomic Testing System for the First Metatarsophalangeal Joint Stiffness
Authors: Farhadi Fatemeh , Faraz Muhammad , Heng Marabelle , Johnson Shane
Published: July 2018

Osteoarthritis sufferers commonly have first metatarsophalangeal joint (MTPJ) problems in which articular surfaces are changed permanently due to fatigue. Therefore, medical devices for early diagnosis would increase the opportunity for prevention of disease progression. In previous studies on stiffness of the first MTPJ many details, although functionally of great importance, have not been fully considered including: design and size of the device, tribology consideration, and errors from device. Therefore, the motivation of our research was to enhance the device design by reducing the size of the device, and device design was enhanced by minimizing measurement errors through development of a new ergonomic left and right foot instrument located medial to the first MTPJ (instead of beneath the foot). The first MTPJ stiffness (N mm/kg radian) measurement was taken on 28 subjects with two replicates per subject by the same tester. The first MTPJ stiffness ranged from 3.49 to 14.42 N mm/kg radian with the mean (SD) value of 8.28 (3.15) N mm/kg radian for the left feet and 3.91 to 11.90 N mm/kg radian with the mean (SD) value of 7.65 (2.07) N mm/kg radian for the right feet. Reliability evaluation was measured using intraclass correlation coefficient and described an excellent reliability between two tests.
Modeling of Solid-State Hot Press Bonding and Its Application to the Fabrication of Titanium Alloy Joints
Authors: Zhang C. , Li H. , Li M. Q.
Published: July 2018

Solid-state hot press bonding is an advanced joining process wherein two specimens can be joined under high pressure for a period of time at an elevated temperature. The main step in hot press bonding is the void closure process. In the present study, a three-dimensional theoretical model for describing the void closure process is developed. In the model, the void closure process is divided into two stages: in the first stage, surface asperities are flattened by the time-independent local plastic flow mechanism, and isolated voids form at the bonding interface; in the second stage, the void closure is accomplished by three time-dependent mechanisms, namely, the viscoplastic flow mechanism, surface source diffusion mechanism, and interface source diffusion mechanism. The initial and ending conditions of these mechanisms are proposed. The model also includes an analysis of the effect of macroscopic deformation on void closure. Hot press bonding experiments of Ti–6Al–4V alloy are conducted to validate the model. The modeling predictions show good agreement with the experimental results.
Seismic Vulnerability Assessment of Fuel Storage Tanks in Italy
Authors: De Biagi Valerio , Chiaia Bernardino , Fiorentini Luca , Quirini Cristina Zannini
Published: July 2018

Seismic hazard represents one of the possible triggering causes for NaTech accidents in refineries and production plants. The vulnerability of steel storage tanks was evaluated within the framework of a rapid risk assessment. Tanks dataset is composed of 70 refinery items in located in various parts of Italy and the seismic calculations are performed in accordance to API 650 Annex E Standard. The paper summarizes the results of the investigation through two normalized parameters related to the masses and to the seismic load. Some trends in the solution are highlighted. The empirical fragility curve obtained from the analysis is compared with similar curves found in the literature and the resulting similarities (and dissimilarities) are critically discussed.
Fully-Developed Flow in Semicircular and Isosceles Triangular Ducts With Nonuniform Slip
Authors: Wang C. Y.
Published: July 2018

A modified Ritz method for solving nonuniform slip flow in a duct is applied to the semicircular duct and the isosceles triangular duct. These ducts are important in microfluidics. Detailed flow fields and Poiseuille numbers show the large effects of nonuniform slip. A rare exact solution for the semicircular duct with nonzero slip is also found.
Research on the Application of Fen for Environmentally Assisted Fatigue Evaluation of the Austenitic SS Pipe Under Combined Transient Loads
Authors: Liang Bingbing , Zhang Xu , Yin Haifeng , Dai Yang
Published: July 2018

Accumulative test data indicate that the effects of the light water reactor (LWR) environment could cause the fatigue resistance of primary pressure boundary components materials to be significantly reduced. Environmentally assisted fatigue (EAF) is the abbreviation of the environmentally assisted fatigue. In 2007, Nuclear Regulatory Commission (NRC) issued RG. 1.207. It was updated in 2014. And, it requires that the effects of LWR environment on the fatigue life reduction of metal components should be considered for new design plants. And it suggests to use environmental correction factor, Fen, to account for EAF. NRC regulation (NUREG), NUREG/CR-6909 (NRC, 2013, “Effect of LWR Coolant Environments on the Fatigue Life of Reactor Materials,” U.S. Nuclear Regulatory Commission, Argonne, IL, Standard no. NUREG/CR-6909), presents the detail Fen calculation formula. Fen is a function of temperature, strain rate, dissolved oxygen level in water, and sulfur content of the steel. Accordingly, Fen calculation will present a comparatively conservative result. Depending on the experience of the primary pressure boundary piping transient operation, Fen varies during each transient. More uncertainty and confusion are raised during the application of the Fen method. The research work in this paper includes: first, the typical character of piping thermal transient is derived based on the existing experience. Second, small specimen EAF tests are conducted depending on the above derived combined loading characters. Then effort is taken to improve the application of the Fen method for the combined multitransient loading conditions. And the results are compared with those of the lowest instantaneous Fen method and equalization of the weighted Fen method. Finally, a designed test plan is presented.
Sensitivity of Arterial Hyperelastic Models to Uncertainties in Stress-Free Measurements
Authors: Emuna Nir , Durban David , Osovski Shmuel
Published: July 2018

Despite major advances made in modeling vascular tissue biomechanics, the predictive power of constitutive models is still limited by uncertainty of the input data. Specifically, key measurements, like the geometry of the stress-free (SF) state, involve a definite, sometimes non-negligible, degree of uncertainty. Here, we introduce a new approach for sensitivity analysis of vascular hyperelastic constitutive models to uncertainty in SF measurements. We have considered two vascular hyperelastic models: the phenomenological Fung model and the structure-motivated Holzapfel–Gasser–Ogden (HGO) model. Our results indicate up to 160% errors in the identified constitutive parameters for a 5% measurement uncertainty in the SF data. Relative margins of errors of up to 30% in the luminal pressure, 36% in the axial force, and over 200% in the stress predictions were recorded for 10% uncertainties. These findings are relevant to the large body of studies involving experimentally based modeling and analysis of vascular tissues. The impact of uncertainties on calibrated constitutive parameters is significant in context of studies that use constitutive parameters to draw conclusions about the underlying microstructure of vascular tissues, their growth and remodeling processes, and aging and disease states. The propagation of uncertainties into the predictions of biophysical parameters, e.g., force, luminal pressure, and wall stresses, is of practical importance in the design and execution of clinical devices and interventions. Furthermore, insights provided by the present findings may lead to more robust parameters identification techniques, and serve as selection criteria in the trade-off between model complexity and sensitivity.
Acoustic Journal Bearing With Changeable Geometry and Built-in Flexibility
Authors: Stolarski T. A. , Miyatake M.
Published: July 2018

The influence of embodiment flexibility on the performance of an acoustic journal bearing is presented. Two completely different embodiments of the bearing were investigated using three criteria of performance assessment that is torque at the start-up, amount of separation due to squeeze film pressure, and motion stability of the shaft running at speed. The embodiment with built-in flexibility proved to perform far better than the bearing for which overall flexibility was much less. However, considerations pertinent to the easy of machining and fatigue endurance mitigate the ranking of performance of the two embodiments investigated.
A Novel Underactuated Tetrahedral Mobile Robot
Authors: Wang Zhirui , Tian Yaobin , Yao Yan-an
Published: July 2018

This paper presents a novel underactuated tetrahedral mobile robot with 12 degrees-of-freedom (DOFs). The robot contains four vertices and six URU chains (where U represents a universal joint and R represents an actuated revolute joint). The tetrahedral structure makes the robot have continuous mobile ability at any posture. The mobility analysis has been made and demonstrates the feasibility of underactuated which demands fewer devices and low costs. A kind of rolling locomotion of the robot is proposed, and the feasibility of the locomotion is proved by the kinematic and locomotion analysis based on an equivalent planar mechanism. Finally, a prototype is manufactured and a series of experiments are performed to verify the mobile capability of the robot.