bluuebunny/crossref_metadata_2025 huggingface dataset:
Emerging roles for carbonic anhydrase in mesophyll conductance and photosynthesis
Authors: Momayyezi Mina , McKown Athena D. , Bell Shannon C. S. , Guy Robert D.
Published: December 2019

Carbonic anhydrase (CA) is an abundant protein in most photosynthesizing organisms and higher plants. This review paper considers the physiological importance of the more abundant CA isoforms in photosynthesis, through their effects on CO2 diffusion and other processes in photosynthetic organisms. In plants, CA has multiple isoforms in three different families (α, β and γ) and is mainly known to catalyze the CO2 equilibrium. This reversible conversion has a clear role in photosynthesis, primarily through sustaining the CO2 concentration at the site of ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco). Despite showing the same major reaction mechanism, the three main CA families are evolutionarily distinct. For different CA isoforms, cellular localization and total gene expression as a function of developmental stage are predicted to determine the role of each family in relation to the net assimilation rate. Reaction–diffusion modeling and observational evidence support a role for CA activity in reducing resistance to CO2 diffusion inside mesophyll cells by facilitating CO2 transfer in both gas and liquid phases. In addition, physical and/or biochemical interactions between CAs and other membrane‐bound compartments, for example aquaporins, are suggested to trigger a CO2‐sensing response by stomatal movement. In response to environmental stresses, changes in the expression level of CAs and/or stimulated deactivation of CAs may correspond with lower photosynthetic capacity. We suggest that further studies should focus on the dynamics of the relationship between the activity of CAs (with different subcellular localization, abundance and gene expression) and limitations due to CO2 diffusivity through the mesophyll and supply of CO2 to photosynthetic reactions.
Students’ Self-reflections of Own Participation in English Language Oral Class
Authors: Han Lin , Md Yusof Masdinah Alauyah
Published: December 2019

The English language learners’ needs changes from time to time. In Malaysia, the focus of English teaching and learning has shifted from accuracy to fluency; the effective usage of the language. Learners are expected to use the English language in daily communication and to learn the workplace English language communication skill. Due to this demand, language lecturers at higher institutions are expected to assist English language learners to use the language fluently rather than to concentrate heavily on form. Nevertheless, instigating speaking activities in Malaysian classrooms has never been easy and successful. This research was conducted with an aim to identify the underlying factors that motivate or demotivate students’ participation in an English oral classroom. The data were qualitatively collected via students’ self-reflection reports on their own participation in the English language oral class. It was found that teacher’s personality traits, students’ communication skills, learning environment, students’ motivation, self-confidence and topical knowledge, and fascinating discussion topics play significant roles in students’ participation in the English oral class. Thus, these findings could guide language teachers to consider relevant and creative oral activities to encourage students’ active classroom participation.
Reviewer Acknowledgements
Authors: Smith Robert
Published: December 2019

Journal of Education and Training Studies (JETS) would like to acknowledge the following reviewers for their assistance with peer review of manuscripts for this issue. Many authors, regardless of whether JETS publishes their work, appreciate the helpful feedback provided by the reviewers. Their comments and suggestions were of great help to the authors in improving the quality of their papers. Each of the reviewers listed below returned at least one review for this issue.Reviewers for Volume 7, Number 10Dare Azeez, Obafemi Awolowo University, NigeriaFathia Lahwal, Elmergib University, LibyaGianpiero Greco, University of Study of Bari, ItalyGuilherme Tucher, Universidade Federal do Rio de Janeiro (UFRJ), BrazilHenry D. Mason, Tshwane University of Technology, South AfricaJane Liang, California Department of Education, USAJohn Bosco Azigwe, Bolgatanga Polytechnic, GhanaJohn Cowan, Edinburgh Napier University, UKJongho Park, University of Michigan, USALaura Bruno, The College of New Jersey, USALisa Marie Portugal, American College of Education, USALorna T. Enerva, Polytechnic University of the Philippines, PhilippinesMaría Jesús Fernández, University of Extremadura, SpainMassimiliano Barattucci, Ecampus University, ItalyMatt Varacallo, University of Kentucky, USAMehmet Galip Zorba, Akdeniz University, TurkeyMeral Seker, Alanya Alaaddin Keykubat University, TurkeyMichael Wall, Independent Researcher in Music and Music Education, USANiveen M. Zayed, MENA College of Management, JordanOzgur Demirtas, Inonu University, TurkeyRichard Penny, University of Washington Bothell, USASamah El-Sakka, Suez University, EgyptSandro Sehic, Oneida BOCES, USASayim Aktay, Mugla Sitki Kocman University, TurkeyThada Jantakoon, Rajabhat Maha Sarakham University, ThailandVjacheslav Ivanovich Babich, Luhansk Taras Shevchenko National University, UkraineWenjuan Sang, Indiana University, USAYalçın Dilekli, Aksaray University, TurkeyYuxi Qiu, University of Florida, USA  Robert SmithEditorial AssistantOn behalf of,The Editorial Board of Journal of Education and Training StudiesRedfame Publishing9450 SW Gemini Dr. #99416Beaverton, OR 97008, USAURL: http://jets.redfame.com
A Pressurized High-Flux Solar Reactor for the Thermochemical Gasification of Charcoal Slurry—Two-Phase Flow and Heat Transfer Analysis
Authors: Müller F. , Steinfeld A.
Published: December 2019

A pressurized solar reactor for effecting the thermochemical gasification of carbonaceous particles driven by concentrated solar energy is modeled by means of a reacting two-phase flow. The governing mass, momentum, and energy conservation equations are formulated and solved numerically by finite volume computational fluid dynamics (CFD) coupled to a Monte Carlo radiation solver for a nongray absorbing, emitting, and scattering participating medium. Implemented are Langmuir–Hinshelwood kinetic rate expressions and size-dependent properties for charcoal particles undergoing shrinkage as gasification progresses. Validation is accomplished by comparing the numerically calculated data with the experimentally measured temperatures in the range 1283–1546 K, chemical conversions in the range 32–94%, and syngas product H2:CO and CO2:CO molar ratios obtained from testing a 3 kW solar reactor prototype with up to 3718 suns concentrated radiation. The simulation model is applied to identify the predominant heat transfer mechanisms and to analyze the effect of the solar rector's geometry and operational parameters (namely: carbon feeding rate, inert gas flowrate, solar concentration ratio, and total pressure) on the solar reactor's performance indicators given by the carbon molar conversion and the solar-to-fuel energy efficiency. Under optimal conditions, these can reach 94% and 40%, respectively.
Cavitation-Vortex-Pressure Fluctuation Interaction in a Centrifugal Pump Using Bubble Rotation Modified Cavitation Model Under Partial Load
Authors: Sun Weihua , Tan Lei
Published: December 2019

Cavitation is a complicated phenomenon in the centrifugal pump. In this work, the improved unsteady calculation model based on bubble-rotation-based Zwart–Gerber–Belamri (BRZGB) cavitation model is used to investigate the cavitation-vortex-pressure fluctuation interaction in a centrifugal pump under partial load with experimental validation. Spatial–temporal evolution of cavitation can be classified into three stages: developing stage, shedding stage, and collapsing stage. The cavitation evolution period is found as 1/4T (T is impeller rotation period), corresponding to the frequency 4fi (fi is impeller rotation frequency). On the analysis of the relative vorticity transport equation, it is revealed that the cavity is stretched by the relative vortex stretching term (RVS) and developed by the relative vortex dilation term (RVD), and they have great influence on the cavity shedding. The peak value of pressure fluctuation intensity occurs near the vapor–liquid interface at cavity rear, and shifts downstream with the cavitation development. The hysteresis between the vapor volume fraction, vorticity, and pressure fluctuation is observed, and the variation of vapor volume fraction is the source of cavitation-vortex-pressure interaction.
Supercritical and Subcritical Hopf Bifurcations in a Delay Differential Equation Model of a Heat-Exchanger Tube Under Cross-Flow
Authors: Vourganti Varun , Kandala Shanti Swaroop , Meesala Vamsi C. , Vyasarayani C. P.
Published: December 2019

Nonlinear vibrations of a heat-exchanger tube modeled as a simply supported Euler–Bernoulli beam under axial load and cross-flow have been studied. The compressive axial loads are a consequence of thermal expansion, and tensile axial loads can be induced by design (prestress). The fluid forces are represented using an added mass, damping, and a time-delayed displacement term. Due to the presence of the time-delayed term, the equation governing the dynamics of the tube becomes a partial delay differential equation (PDDE). Using the modal-expansion procedure, the PDDE is converted into a nonlinear delay differential equation (DDE). The fixed points (zero and buckled equilibria) of the nonlinear DDE are found, and their linear stability is analyzed. It is found that stability can be lost via either supercritical or subcritical Hopf bifurcation. Using Galerkin approximations, the characteristic roots (spectrum) of the DDE are found and reported in the parametric space of fluid velocity and axial load. Furthermore, the stability chart obtained from the Galerkin approximations is compared with the critical curves obtained from analytical calculations. Next, the method of multiple scales (MMS) is used to derive the normal-form equations near the supercritical and subcritical Hopf bifurcation points for both zero and buckled equilibrium configurations. The steady-state amplitude response equation, obtained from the MMS, at Hopf bifurcation points is compared with the numerical solution. The coexistence of multiple limit cycles in the parametric space is found, and has implications in the fatigue life calculations of the heat-exchanger tubes.
Effect of In Situ Post Weld Heat Treatment on Mechanical Behavior and Austenite–Ferrite Phase Balance of Fe-Cr-Ni/Fe-Cr Stainless Steels Upset Resistance Dissimilar Weld
Authors: Ozlati Ashkaan , Movahedi Mojtaba
Published: December 2019

Effect of the in situ post weld heat treatment (PWHT) was investigated on the flash profile, austenite/ferrite phase balance, and mechanical properties of the upset resistance dissimilar weld between Fe-Cr-Ni and Fe-Cr stainless steels rods. In order to explore the effect of the heat treatment on the joint strength, two as-welded samples with low strength (116 MPa) and high strength (372 MPa) were used. The results showed that in situ PWHT was beneficial for both welded samples, though in different ways. For the weld with low strength, PWHT improved the joint strength (∼130% increase in the optimum condition compared with the as-welded sample) due to the increase in the size of the flash and the related bonded area at the joint interface. However, ferrite percent in the weld zone increased from ∼50% up to ∼70%. For the sample with the high strength, ferrite/austenite phase balance was restored at an optimum condition of PWHT. However, the joint strength decreased slightly (less than 5%) due to the grain growth in the Fe-Cr rod, i.e., the fracture location. Fracture analysis was used for justification of the variations in the joint strength. For both Fe-Cr-Ni side and Fe-Cr side of the welds, in situ PWHT generally reduced the hardness. This observation is discussed in light of the simultaneous effects of the grain growth and formation of little martensite.
Validation Studies of Linear Oscillating Compressor Cascade and Use of Influence Coefficient Method
Authors: Phan H. M. , He L.
Published: December 2019

Advanced predictions of blade flutter have been continually pursued. It is noted however that validation cases of unsteady CFD methods against experimental cases with detailed 3D unsteady pressures are still rather lacking. The main objectives of the present work are two-folds. First, validate and understand the characteristics of blade tip clearance, as well as a bubble-type flow separation for an unsteady CFD solver against a 3D oscillating cascade experiment. And second, examine the applicability of the influence coefficient method (ICM) as widely used in an oscillating linear cascade setup. In the first part, the capability of a widely used commercial solver (CFX) for unsteady flows induced by a 3D oscillating compressor cascade is examined. The present computations have shown consistently a destabilizing effect of increasing blade tip clearance, in agreement with the experiment. More remarkably, the computational analyses reveal a distinctive interplay between the inlet endwall boundary layer and the tip clearance in relation to the aerodynamic damping. Different inlet endwall boundary layer thicknesses are shown to lead to qualitatively different aeroelastic stability characteristics in relation to tip clearance. The aero-damping variation with the tip clearance under the influence of the inlet endwall boundary layer seems to correlate closely to a balancing act between the passage vortex and the tip leakage vortex. The tip clearance aeroelastic behavior seems also in line with a simple quasi-steady analysis. On the other hand, the mid-chord laminar bubble separation on suction surface, though with a clear signature in the local aero-damping, has negligible effects on the overall stability. The second part aims to examine computationally the applicability of the influence coefficient method in a linear cascade setup. The comparison between the cascade-based ICM data and a baseline “tuned cascade” shows that the differences in the sensitivity to the far-field treatment can be significant, depending on inter-blade phase angles. On the other hand, non-linearity effects closely relevant to the basic linear assumption of the ICM are shown to only have a small influence. The present results suggest that extra caution should be exercised when comparing a CFD-based tuned cascade model with a finite cascade-based ICM model, at conditions close to acoustic resonance. The resultant discrepancies may well arise from the inherently different far-field sensitivities between the two models, rather than those typical numerical and physical modeling aspects of interest (e.g., meshing, spatial and temporal discretization errors as well as turbulence modeling).
Modification of Shear Stress Transport Turbulence Model Using Helicity for Predicting Corner Separation Flow in a Linear Compressor Cascade
Authors: Liu Yangwei , Tang Yumeng , Scillitoe Ashley D. , Tucker Paul G.
Published: December 2019

Three-dimensional corner separation significantly affects compressor performance, but turbulence models struggle to predict it accurately. This paper assesses the capability of the original shear stress transport (SST) turbulence model to predict the corner separation in a linear highly loaded prescribed velocity distribution (PVD) compressor cascade. Modifications for streamline curvature, Menter’s production limiter, and the Kato-Launder production term are examined. Comparisons with experimental data show that the original SST model and the SST model with different modifications can predict the corner flow well at an incidence angle of −7 deg, where the corner separation is small. However, all the models overpredict the extent of the flow separation when the corner separation is larger, at an incidence angle of 0 deg. The SST model is then modified using the helicity to take account of the energy backscatter, which previous studies have shown to be important in the corner separation regions of compressors. A Reynolds stress model (RSM) is also used for comparison. By comparing the numerical results with experiments and RSM results, it can be concluded that sensitizing the SST model to helicity can greatly improve the predictive accuracy for simulating the corner separation flow. The accuracy is quite competitive with the RSM, whereas in terms of computational cost and robustness it is superior to the RSM.
Reduced Chemical Kinetic Models of C1 - C4 Alcohols Using the Alternate Species Elimination Approach
Authors: Zhou Apeng , Jouzdani Shirin , Akih-Kumgeh Ben
Published: December 2019

This study presents four separate reduced chemical kinetic models of methanol/ethanol, propanol isomers, n- and iso-butanol, and n- and s-butanol isomers, derived from a comprehensive chemical kinetic model of C1-C5 alcohols using the Alternate Species Elimination approach. It is motivated by complexity of the detailed model (comprising 600 species and 4100 elementary reactions) and the need for simpler kinetic models for analysis of combustion of smaller alcohols. The reduced models are obtained on the basis of ignition delay time simulations with imposed thresholds on the resulting normalized changes in ignition delay times. The following reduced models are obtained: methanol/ethanol: 38 species and 197 reactions; propanol isomers: 68 species and 419 reactions; n- and iso-butanol: 140 species and 745 reactions; and n- and s-butanol: 134 species and 739 reactions. Predictions of ignition delay times by the reduced models are found to be in good with the detailed models. The reduced models are further tested against other relevant combustion properties. These properties include burning velocities of laminar premixed flames, global pyrolysis time scales, and heat release timing in Homogeneous Charge Compression Ignition engines. This verification shows that reduced models can replace the comprehensive model in combustion analysis without loss of predictive performance. The reduced models can also serve as starting models for developing combined chemical kinetic models of gasoline/diesel and alcohol blends.
Development of an Artificial Neural Network Model for the Performance Prediction of a Variable Compression Ratio Gasoline Spark Ignition Engine
Authors: Tripathy Srinibas , Sahoo Sridhar , Srivastava Dhananjay Kumar
Published: December 2019

The purpose of this study is to develop an artificial neural network (ANN) model for performance prediction of a variable compression ratio gasoline port fuel injection spark ignition engine. For ANN modeling, a large experimental data set was generated in which at random 85% was assigned for training the network, and 15% that are not included during the training process was used for testing the network. A multilayer perception feed forward neural network was used to predict the correlation between input and output layer. The input layer consists of engine speed, throttle position, spark timing, and compression ratio. Whereas, the output layer consists of torque, brake power and indicated mean effective pressure (IMEP). Neurons in the hidden layer were varied and optimized based on a specified goal error. A standard supervised back propagation learning algorithm was used in which the error between the target and network output was calculated and minimized. In the hidden and output layers, a non-linear tan-sigmoid and a linear transfer function were used, respectively, for input-output mapping. The performance of the network was evaluated by statistical parameters like correlation coefficient (R), mean relative error (MRE) and root mean square error (RMSE). It was found from the test data that the R and MRE values are lies in between 0.99853 to 0.99875 and 0.42% to 0.58%, respectively. Whereas, RMSE value for all performance parameters was found to be very low. Hence, this study reveals that the application of ANN modeling has the ability to predict the performance of a variable compression ratio gasoline engine and is the best alternative tool over all classical modeling techniques.
Implementing Natural Gas in a Compression Ignition Cycle Using Noble Gas Addition
Authors: Shahsavan Martia , Morovatiyan Mohammadrasool , Baghirzade Mammadbaghir , Mack J. Hunter
Published: December 2019

Natural gas is known as a relatively clean fossil fuel due to its low carbon to hydrogen ratio compared to other transportation fuels, which yields a reduction of carbon monoxide, carbon dioxide, and unburned hydrocarbons emissions. However, it has a low cetane number, which makes it a difficult fuel for use in compression ignition engines. A potential solution for this issue can be adding small amounts of argon, as a noble gas with a low specific heat to modify the intake conditions. In this numerical study, a commercial compression ignition engine has been modeled to evaluate the auto-ignition of natural gas with the modified intake conditions. Different amounts of argon added to the intake air are examined in order to attain the optimal operating conditions. A detailed chemistry solver is implemented on a 53-species chemical kinetics mechanism to calculate the rate constants. The results show that compression ignition of natural gas can be achieved by adding small amounts of argon to the intake air. It drastically increases the in-cylinder temperature and pressure near TDC, which enables the auto-ignition of the injected natural gas. Moreover, it leads to the reduction in ignition delay and heat release rate, and expands the combustion duration. Emissions analysis indicates that NOx and CO2 can be significantly diminished by increasing the amount of argon in the intake composition. This study introduces an efficient and clean compression ignition engine fueled with natural gas running in optimal operating conditions using argon addition to the intake.
A Study on the Distribution of Oil Film Thickness in the Circumferential Direction of Oil Ring in a Gasoline Engine
Authors: Ito Akemi , Hakkaku Tadatsugu , Mochiduki Kazuya , Tomotsune Keita , Inui Masatsugu , Akamatsu Hirotaka
Published: December 2019

Oil traveling upward through the sliding surface of a piston ring causes oil consumption of an engine. Piston rings are designed considering conformability to deformed cylinder bore. However, cylinder deformation sometimes affects strongly oil consumption. It suggests that a piston ring cannot conform dynamically to the cylinder bore. In this study, distribution of oil film thickness of an oil ring was measured for investigating the dynamic conformability. An optical fiber has embedded in the sliding surface of the lower rail of the oil ring, and oil film thickness was measured by laser induced fluorescence method. The measuring point was rotated in the circumferential direction, so the distribution in both the circumferential and the axial direction could be measured. Thick oil films partially were found and it was found that the oil ring did not conformed to the deformed cylinder bore dynamically. Furthermore, such oil film showed thicker value than those expected theoretically. It was showed that dynamic conformability must be considered for piston ring design for reducing oil consumption.
Investigation of the Effect of Plume Number on Spray Collapse
Authors: Sphicas Panos
Published: December 2019

The plumes of a gasoline spray collapse into a single entity under the influence of ambient pressure, ambient temperature and injection duration. Previous work by the author studied experimentally [1] and numerically [2] the phenomenon of spray collapse. It was observed that the entrained air from every single plume, accumulatively creates a recirculation zone in the middle of the spray. The recirculation zone of high velocity, creates a low pressure region, which causes the collapse of the spray. In this paper, the influence of the number of plumes in the spray, is investigated numerically. The plume angle and ambient conditions matched Spray G, but the number of plumes was varied from two to eight. The effect of the plume number on the spray collapse was investigated numerically. It was evident that increased number of plumes in the spray promotes spray collapse.
Optimization of the Mechanical and Thermodynamic Efficiency Loss Dynamic in a Lean Single Cylinder Natural Gas-Fueled Jet Ignition Engine
Authors: Peters Nathan , Subramanyam Sai Krishna Pothuraju , Bunce Michael , Blaxill Hugh
Published: December 2019

In an effort to reduce fuel consumption and lower emissions output, there is a growing need for high efficiency engines in power generation. Ultra-lean (λ > ∼1.6) combustion via air dilution is an enabling technology for achieving high efficiencies while simultaneously reducing emissions of nitrogen oxides (NOx). Jet ignition is a pre-chamber-based combustion system that enables ultra-lean operation beyond what is achievable with traditional spark ignition engines. In this paper, results and analyses related to the downspeeding of a 390cc, high efficiency low-output single cylinder jet ignition engine operating ultra-lean are presented. The engine was developed as part of the US Department of Energy’s Advanced Research Projects Agency–Energy (DOE ARPA-E) GENSETS program1. The purpose of the program is to develop technologies for use in high efficiency combined heat and power generator sets.

Due to the intended application of power generation, optimization of the engine for a specific operating condition is critical. An efficiency loss breakdown based on the Thermodynamic First Law is used to analyze the interdependent trends of engine speed, brake power, and normalized air-fuel ratio, lambda, with the aim of optimizing these parameters for brake thermal efficiency. The general trends of efficiency loss pathways with enleanment are found to be relatively insensitive to speed and load although the magnitude of the loss pathways changes. As the relative importance of the efficiency loss pathways changes with operating condition, so too does the lambda at which peak brake thermal efficiency occurs. The “peak efficiency lambda” was found to be at its leanest at low speed and high power where the influence of heat transfer is greatest and mechanical losses are minimized.
Engine Combustion System Optimization Using CFD and Machine Learning: A Methodological Approach
Authors: Badra Jihad , Khaled Fethi , Tang Meng , Pei Yuanjiang , Kodavasal Janardhan , Pal Pinaki , Owoyele Opeoluwa , Fuetterer Carsten , Brenner Mattia , Farooq Aamir
Published: December 2019

Gasoline compression ignition (GCI) engines are considered an attractive alternative to traditional spark-ignition and diesel engines. In this work, a Machine Learning-Grid Gradient Algorithm (ML-GGA) approach was developed to optimize the performance of internal combustion engines. Machine learning (ML) offers a pathway to transform complex physical processes that occur in a combustion engine into compact informational processes. The developed ML-GGA model was compared with a recently developed Machine learning Genetic Algorithm (ML-GA). Detailed investigations of optimization solver parameters and variables limits extension were performed in the present ML-GGA model to improve the accuracy and robustness of the optimization process. Detailed descriptions of the different procedures, optimization tools and criteria that must be followed for a successful output are provided here. The developed ML-GGA approach was used to optimize the operating conditions (case 1) and the piston bowl design (case 2) of a heavy-duty diesel engine running on a gasoline fuel with a Research Octane Number (RON) of 80. The ML-GGA approach yielded > 2% improvements in the merit function, compared to the optimum obtained from a thorough computational fluid dynamics (CFD) guided system optimization. The predictions from the ML-GGA approach were validated with engine CFD simulations. This study demonstrates the potential of ML-GGA to significantly reduce the time needed for optimization problems, without loss in accuracy compared to traditional approaches.
An Experimental Study on the Effects of Intake Charge and Pilot Injection on Premixed Burn Fraction and NOx Emission Characteristics of a CRDI Turbocharged Diesel Engine
Authors: Chacko Nivin , Jeyaseelan Thangaraja , Premnath Vijay Anirudh
Published: December 2019

The engine-out NOx emission from the combustion process depends on the fraction of premixed fuel burned. Hence, the study of the premixed combustion phase provides the flexibility to understand the NOx and other emissions. Here we performed an experimental study by modifying the intake charge along with pilot fueling on a twin-cylinder turbocharged CRDi diesel engine. The operating parameters, exhaust gas recirculation (EGR) and pilot injection were controlled to study about the premixed combustion phase, which gives minimum NOx emission without compromising other emissions particularly smoke. The results indicate that the premixed burn fraction decreased with an increase in pilot fuel quantity, dwell period and increased with higher EGR percentage. The optimum pilot sequences yielded a 41% reduction in NOx and 60% with smoke emissions. Also, the combination of pilot injection and EGR resulted in a drastic reduction of HC and CO emissions ∼54%.
A Computational Study of the Thermodynamic Conditions Leading to Autoignition in Nanosecond Pulsed Discharges
Authors: Gururajan Vyaas , Scarcelli Riccardo , Karpatne Anand , Breden Douglas , Raja Laxminarayan , Biswas Sayan , Ekoto Isaac
Published: December 2019

Nanosecond pulsed discharges have attracted the attention of engine manufacturers due to the possibility of attaining distributed ignition sites that accelerate burn rates while resulting in very little electrode erosion. Multidimensional modeling tools currently capture the electrical structure of such discharges accurately, but resolving the chemical structure remains a challenging problem owing to the disparity of time-scales in streamer propagation (nanoseconds) and ignition phenomena (microseconds). The purpose of this study is to extend multidimensional results towards resolving the chemical structure in the wake of streamers (or the afterglow) by using a batch reactor model. This can afford the use of very detailed chemical kinetic information. The full non-equilibrium nature of the electrons is taken into account, along with fast gas heating, shock wave propagation, and thermal diffusion. The results shed light on ignition phenomena brought about by such discharges.
Numerical Investigation of a Central Fuel Property Hypothesis Under Boosted Spark-Ignition Conditions
Authors: Pal Pinaki , Kalvakala Krishna , Wu Yunchao , McNenly Matthew , Lapointe Simon , Whitesides Russell , Lu Tianfeng , Aggarwal Suresh K. , Som Sibendu
Published: December 2019

In the present work, a central fuel property hypothesis (CFPH), which states that fuel properties are sufficient to provide an indication of a fuel’s performance irrespective of its chemical composition, was numerically investigated. In particular, the objective of the study was to determine whether Research Octane Number (RON) and Motor Octane Number (MON), as fuel properties, are sufficient to describe a fuel’s knock-limited performance under boosted spark-ignition (SI) conditions within the framework of CFPH. To this end, four TPRF-bioblendstock surrogates having different compositions but matched RON (= 98) and MON (= 90), were first generated using a non-linear regression model based on artificial neural network (ANN). Three unconventional bioblendstocks were included in the analysis: Di-isobutylene (DIB), Isobutanol and Anisole. Skeletal reaction mechanisms were generated for the TPRF-DIB, TPRF-isobutanol and TPRF-anisole blends from a detailed kinetic mechanism. Thereafter, numerical simulations were performed for the fuel surrogates using the skeletal mechanisms and a virtual cooperative fuel research (CFR) engine model, under a representative boosted operating condition. In the computational fluid dynamics (CFD) model, the G-equation approach was employed to track the turbulent flame front and the well-stirred reactor model combined with multi-zone binning strategy was used to capture auto-ignition in the end-gas. In addition, laminar flame speed was tabulated for each blend as a function of pressure, temperature and equivalence ratio a priori, and the lookup tables were used to prescribe laminar flame speed as an input to the G-equation model. Parametric spark timing sweeps were performed for each fuel blend to determine the corresponding knock-limited spark advance (KLSA) and 50% burn point (CA50) at the respective KLSA timing. It was observed that despite same RON, MON and engine operating conditions, the TPRF-Anisole blend exhibited markedly different knock-limited performance from the other three blends. This deviation from the octane index (OI) expectation was shown to be caused by differences in laminar flame speed (LFS). However, it was found that relatively large fuel-specific differences in LFS (> 20%) would have to be present to cause any appreciable deviation from the OI framework. Otherwise, RON and MON would still be robust enough to predict a fuel’s knock-limited performance.
Numerical Analysis of Pulse Laser Assisted Curing Region of Photocurable Resins
Authors: Nakamura Yuta , Fushinobu Kazuyoshi , Tamura Asato
Published: December 2019

AM (Additive manufacturing) technology has huge demand from industry for its high-speed fabricating, ability of fabricating complex shapes and low-cost fabrication which does not require expensive equipment such as molds. In particular, resolution of stereolithography technology is reaching to nanometer scale, and it is also expected to be utilized for nanodevice modeling.

One reason for stereolithography reaching to nanometer scale high resolution is due to the development of TPP (two-photon polymerization) technology.

As TPP requires advanced knowledge of optical, chemical and physical phenomena it is difficult to create a practical numerical method. On the other hand, there is a huge demand for prediction of curing range of resin from these parameters manufacturing of final products.

In this research, we discuss on numerical model which calculates curing region of photocurable resin by using short pulsed laser. The calculation will be conducted for line fabrication which will be more useful for practical use.
Prediction and Control Technique of the Paper Media Temperature After Fusing in Electrophotographic Process
Authors: Kawasaki Shunsuke , Kuramoto Shinichi , Fushinobu Kazuyoshi , Kato Koichi , Yamazaki Kimiharu , Hemmi Kaori
Published: December 2019

The production printer market is expected to increase due to the demand in high speed printing. In electrophotographic (EP) process, the printing speed is restricted by the toner cooling time. During continuous printing, if the printing speed is too high, following paper is printed before the toner on previous paper is solidified, which results in the adhesion of the toner on previous paper to the next paper. Therefore, it is important to reduce the toner cooling time to improve the printing speed. From the viewpoint of printing quality, although toner temperature is important in EP process, paper temperature is not. Therefore, to improve the printing speed without worsening printing quality, this report focuses on suppressing paper temperature rise after fusing, which means a method to predict paper temperature after fusing is required.

As one of effective approaches to predict paper temperature after fusing, numerical calculation based on physical model has been deployed. Constructing a physical model, however, has some problems such as complexity and uncertainty in particular parameter such as the thermal resistance. Printers have three dimensional and complex structure. The printing process itself is also a complex sequence to be appropriately modeled. It is also difficult to measure the thermal resistance and other properties due to the high speed motion of papers inside the machine. Therefore, as an alternative approach, machine learning can be used to correlate known inputs to the output temperature without relying on these uncertain parameters.

The objective of this research is to propose a new method for predicting and controlling the paper media temperature after fusing in electrophotographic process by machine learning.

Sensors are attached to the printer for the research. By using these sensors, temperature when printing is obtained. By using these data, machine learning is carried out to predict paper temperature after fusing.

This report constructs a new method to predict paper temperature after fusing. Our study demonstrates machine learning is an effective method for predicting and controlling the paper temperature after fusing.
Additive Manufactured, Low EMI, Non-Metallic Convective Heat Spreader Design and Optimization
Authors: Whitt Reece , Huitink David , Hudson Skyler , Nafis Bakhtiyar , Yuan Zhao , Narayanasamy Balaji , Deshpande Amol , Luo Fang , Imran Asif , Clarke Zion , Smith Sonya
Published: December 2019

With the increase of electronic device power density, thermal management and reliability are becoming increasingly important. First, increased density challenges the capability of conventional heat sinks to adequately dissipate heat. Secondly, higher frequency switching in wide bandgap power modules is introducing new issues in electromagnetic interference (EMI) in which metallic heat removal systems will couple and create damaging current ringing. Lastly, lightweight heat removal is required to meet the increasing needs of mobile power systems. In this effort we introduce an additive manufacturing pathway to produce custom-tailored heat removal systems using non-metallic materials, which take advantage of convective heat transfer to enable efficient thermal management. Herein, we leverage the precision of AM techniques in the development of 3D optimized flow channels for achieving enhanced effective convective heat transfer coefficients. The experimental performance of convective heat removal due to liquid impingement is compared with conventional heat sinks, with the requirement of simulating the heat transfer needed by a high voltage inverter. The implementation of non-metallic materials manufacturing is aimed to reduce EMI in a low weight and reduced cost package, making it useful for mobile power electronics.
Nanoindentation Testing of SAC305 Solder Joints Subjected to Thermal Cycling Loading
Authors: Fahim Abdullah , Hasan S. M. Kamrul , Suhling Jeffrey C. , Lall Pradeep
Published: December 2019

Solder joints in electronic packages are frequently exposed to thermal cycling environment. Such exposures can occur in real life application as well as in accelerated thermal cycling tests used for the fatigue behavior characterization. Because of temperature variations and CTE mismatches of the assembly materials, cyclic temperature leads to damage accumulation and material property evolution in the solder joints. This eventually results in crack initiation, and subsequent crack growth and failure.

In this study, the nanoindentation technique was used to understand the evolution of mechanical properties (modulus, hardness and creep behavior) of SAC305 BGA solder joints and Cu pad subjected to thermal cycling loading for various durations. In addition, microstructural changes in those joints that occur during thermal cycling were observed using both SEM and optical microscopy. BGA solder joint strip specimens were first prepared by cross sectioning BGA assemblies followed by surface polishing to facilitate SEM imaging and nanoindentation testing. The strip specimens were chosen to contain several single grain solder joints. This enabled large regions of solder material with equivalent mechanical behavior, which could then be indented several times after various durations of cycling.

After preparation, the solder joint strip samples were thermally cycled from T = −40 to 125 °C in an environmental chamber. At various points in the cycling (e.g. after 0, 50, 100, and 250 cycles), the package was taken out from the chamber, and nanoindentation was performed on each single grain joint and joint Cu pads to obtain the modulus, hardness, and creep behavior at 25 °C. This allowed the evolution of the mechanical properties with the duration of thermal cycling to be determined. Moreover, microstructural changes were also observed after various durations of cycling using optical microscopy. From the nanoindentation test results, it was found that the modulus and hardness of the SAC305 solder joints dropped significantly with thermal cycling. However, the Cu pad did not show any change in the mechanical behavior during cycling. Moreover, the nanoindentation creep test results showed significant increases in the creep deformation for solder joints whereas Cu pad did now show any significant changes in creep behavior when both of them were subjected to thermal cycling up to 250 cycles.
Application of Electronics Packaging Fundamentals to Photovoltaic Interconnects and Packaging
Authors: Spinella Laura , Bosco Nick
Published: December 2019

The energy capacity of photovoltaic (PV) installations worldwide has increased significantly in the last decade, increasing the demand for rigorous investigation of the physical phenomena causing degradation and failures in PV modules. As PV reliability science develops, established methods and approaches from longer-standing industries can inform and expedite PV reliability advances. This work demonstrates how thermomechanical solder bond fatigue models derived for electronics packaging applications can be applied to both standard and emerging PV interconnect designs. This expertise cannot be directly translated to PV however, as target PV module lifetimes are significantly longer than most electronics and the modules must withstand the natural climate wherever they are deployed. Verification of analytical reliability models is then an additional challenge, due to model size, test time, and climate variability. Furthermore, unconventional materials, such as low-temperature solders, are now being integrated into PV designs, for which appropriate material models must be selected and material parameters derived. In this paper, the current state of PV interconnect research is explored, with an emphasis on the experimental and simulation approaches and models being used for this work. Recent results for standard module architectures as well as emerging interconnect schemes are discussed.
Numerical Investigation on Electromigration Oriented Failure of Lead Free Solder Joints With Aging Effects
Authors: Ahmed Tusher , Motalab Mohammad , Suhling Jeffrey C.
Published: December 2019

Lead free solder materials have replaced lead based solder materials nowadays for increased environmental concern. Further miniaturization of electronic solder joints in packages has caused electromigration to dominate among all the reliability issues found in electronic packages. This current investigation deals with the review of mechanical property degradations of SAC305(Sn-96.5Ag-3.0Cu-0.5) solder materials due to thermal aging and their effects on electromigration oriented failure of small scale flip chip solder bumps. Thermal aging causes significant degradation of ultimate strength as well as elastic modulus of the SAC solder material. This degradation in stress-strain relationship plays an utterly important role in electromigration oriented mass diffusion and subsequent failure in the solder joints. This research highlights the linkage between thermal aging oriented strength degradation and its effect on electromigration oriented void propagation rate and time to failure. Structural-electric diffusion analyses with a finite element analysis software have been performed and results derived from different aging conditions (1 to 60 days of aging at 100 °C) at different electromigration temperatures have revealed that mass diffusion due to electromigration and associated stress migration actually reduces with the increment of aging time and thus increases time to failure in case of a flip chip solder joint. Simulation results have been found to be in good agreement with the experimental results available in literatures. These results can pave way to further detailed experimental investigation on effect of thermal aging on electromigration.
Effects of Shear Cycling on the Mechanical Properties of SAC and SAC+X Lead Free Solder Joints
Authors: Hoque Mohd Aminul , Chowdhury Md Mahmudur , Hamasha Sa’d , Suhling Jeffrey C. , Lall Pradeep
Published: December 2019

Solder joint reliability is a chief concern in electronic assemblies. Electronic packages consist of various materials, each having their own Coefficient of Thermal Expansion (CTE). When assembled packages experience high temperature gradients and thermal cycles, a mismatch in the CTE values brings about cyclic shear strains in the solder joints, which can ultimately lead to failure. Thus, it is important to understand the effects of shear cycling on the damage accumulated in solder joints.

Previous studies conducted on the effect of mechanical cycling on the material behavior of lead free solders have been performed on bulk samples subjected to tension and compression. Our goal in this study was to determine the evolution of the mechanical properties of doped lead free solder joints when subjected to mechanical shear cycling. Experiments conducted on actual solder joints would help us gain a better understanding on the real life effects of shear cycling. The test specimens consisted of a 3 × 3 array of nine solder joints of approximately 0.75 mm diameter. With the aid of specially designed test fixtures, the specimens were gripped and then subjected to mechanical cycling in the shear using an Instron Micromechanical tester. Testing was performed on both SAC305 and SACX (SAC+Bi) solder joints. The joints were cycled for certain durations, and a nanoindentation system was used to measure the evolution of the mechanical properties (elastic modulus, hardness, creep rate) as a function of the number of shear cycles.
Fatigue Delamination Crack Growth of Potting Compounds in PCB/Epoxy Interfaces Under Flexure Loading
Authors: Lall Pradeep , Dornala Kalyan , Suhling Jeff , Deep John , Lowe Ryan
Published: December 2019

Electronics components operating under extreme thermo-mechanical stresses are often protected with underfills and potting encapsulation to isolate the severe stresses. By encapsulating the entire PCB, the resin provides complete insulation for the unit thereby combining good electrical properties with excellent mechanical protection. In military and defense applications these components are often subjected to mechanical shock loads of 50,000g and are expected to perform with reliability. Due to the bulk of material surrounding the PCB, potting and encapsulation resins are commonly two-part systems which when mixed together form a solid, fully-cured material, with no by-products. The cured potting materials are prone to interfacial delamination under dynamic shock loading which in turn potentially cause failures in the package interconnects. The study of interfacial fracture resistance in PCB/epoxy potting systems under dynamic shock loading is important in mitigating the risk of system failure in mission critical applications. In this paper, three types of epoxy potting compounds were used as an encapsulation on PCB samples. The potting compounds were selected based on their ultimate elongation under quasi-static loading. Potting compound, A is a stiffer material with 5% of ultimate elongation before failure. Potting compound, B is a moderately stiff material with 12% ultimate elongation. Finally, potting compound C is a softer material with 90% ultimate elongation before failure. The fracture properties and interfacial crack delamination of the PCB/epoxy interface were determined using three-point bend loading with a pre-crack at the interface. The fatigue crack growth of the interfacial delamination was characterized for the three epoxy systems. A prediction of number of cycles to failure and the performance of different epoxy system resistance under cyclic bending loading was assessed.