bluuebunny/crossref_metadata_2025_split huggingface dataset:
Random Forest Machine Learning Model for Predicting Combustion Feedback Information of a Natural Gas Spark Ignition Engine
Authors: Liu Jinlong , Ulishney Christopher , Dumitrescu Cosmin Emil 
Published: July 2020

AbstractEngine calibration requires detailed feedback information that can reflect the combustion process as the optimized objective. Indicated mean effective pressure (IMEP) is such an indicator describing an engine’s capacity to do work under different combinations of control variables. In this context, it is of interest to find cost-effective solutions that will reduce the number of experimental tests. This paper proposes a random forest machine learning model as a cost-effective tool for optimizing engine performance. Specifically, the model estimated IMEP for a natural gas spark ignited engine obtained from a converted diesel engine. The goal was to develop an economical and robust tool that can help reduce the large number of experiments usually required throughout the design and development of internal combustion engines. The data used for building such correlative model came from engine experiments that varied the spark advance, fuel-air ratio, and engine speed. The inlet conditions and the coolant/oil temperature were maintained constant. As a result, the model inputs were the key engine operation variables that affect engine performance. The trained model was shown to be able to predict the combustion-related feedback information with good accuracy (R2 ≈ 0.9 and MSE ≈ 0). In addition, the model accurately reproduced the effect of control variables on IMEP, which would help narrow the choice of operating conditions for future designs of experiment. Overall, the machine learning approach presented here can provide new chances for cost-efficient engine analysis and diagnostics work.
Anhydrite (Calcium Sulfate) Mineral as a Novel Weighting Material in Drilling Fluids
Authors: Murtaza Mobeen , Tariq Zeeshan , Mahmoud Mohamed , Kamal Muhammad Shahzad , Al-Shehri Dhafer 
Published: July 2020

AbstractDifferent additives such as barite, calcium carbonate, hematite, and ilmenite having high-density and fine solid materials are used to increase the density of drilling fluids. However, some of the weighting additives can cause some serious drilling problems such as barite (particle settling, formation damage, erosion, and insoluble filter cake). In this study and for the first time, anhydrite (calcium sulfate) is used as a weighting additive in the drilling fluids. Several laboratory experiments such as density, rheology, fluid loss, resistivity, and pH were carried out to assess the performance of calcium sulfate as a weighting additive in the drilling fluids. The performance of calcium sulfate as a weighting additive was compared with the commonly used weight enhancing additive calcium carbonate. The results showed that calcium sulfate has higher solubility than calcium carbonate. The fluid loss test showed that both additives lost the same volume of fluid and created the same thickness of filter cake; however, the solubility of calcium sulfate-based filter cake with organic and inorganic acids was higher compared with other weighting materials. Calcium sulfate-based filter cake was completely dissolved using a new formulation that consists of glutamic-diacetic acid (GLDA) chelating agent and potassium carbonate as a convertor. The removal efficiency after 10 h reached 100% in 20 wt% GLDA and 10 wt% potassium carbonate solution at 100 °C.
Experimental Investigation on Mixed Combustion Characteristics of Coal, Tobacco Straw, and Cinder in an Energy-Saving Bake Process
Authors: Yan Yunfei , Zhao Ting , Guo Hongliang , Xu Fulei , Zhang Li , Yang Zhongqing , Ran Jingyu 
Published: July 2020

Abstract
In view of high-energy consumption, high baking cost, and serious pollution emission during the baking process of tobacco leaves, thermogravimetric analysis is employed to investigate the combustion characteristics of coal, tobacco straw, and cinder. Analyzing thermogravimetric-derivative of thermogravimetric (TG-DTG) characteristics of samples with different blending ratios and based on the ignition temperature and burnout temperature, the combustion characteristics of the samples are obtained. Compared with the individual combustion of coal, the blending ratio of the optimal positive effect is obtained. It is illustrated that different blending ratios of coal, tobacco straw, and cinder result in different effects between promotion and inhibition. Tobacco straw is beneficial to burn on fire but adverse to keep combustion of fixed carbon. Compared with the TG and DTG characteristics in different blending ratios of coal, tobacco straw, and corresponding combustion characteristic parameter, it is illustrated that the best blending ratio of tobacco straw is 40%. According to the TG and DTG characteristics of different blending ratios of coal, cinder, and corresponding combustion characteristic parameter, it is shown that the more blending ratio of cinder, the more adverse effect to fixed carbon burning. The composite fuels with 40% tobacco straw, 10% coal cinder, and 50% coal have two obvious advantages. On the one hand, it can maintain quick burning and the volatile combustion of the tobacco straw at low-temperature stage. On the other hand, it can keep continuous combustion of the fixed carbon in coal at high-temperature stage.
Control Optimization of Pump Cycles in Onshore Oilfields With Network and Electric Power Constraints
Authors: Camponogara Eduardo , Seman Laio Oriel 
Published: July 2020

Abstract
In onshore oilfields, sucker rod pumps are deployed to lift fluids from wells to the surface, which are then transferred by a pipeline network to a central facility. Each pump operates according to a cyclic control policy that alternates between a period of production and a period of recess, allowing the reservoir to replenish the fluids. To minimize the peak in the electric power drawn by the sucker rods, previous works have considered the scheduling of the control policies over time. However, when the production system sprawls over a large area, the energy required to force the flow through the pipelines and the pressure drops are significant. To this end, this article develops mixed-integer nonlinear formulations and mixed-integer linear approximations for baseline control-policy scheduling and reconfiguration.
Modal Velocity-Based Multiaxial Fatigue Damage Evaluation Using Simplified Finite Element Models
Authors: Kersch Kurthan , Woschke Elmar 
Published: July 2020

Abstract
This work proposes a new method for the fatigue damage evaluation of vibrational loads, based on preceding investigations on the relationship between stresses and modal velocities. As a first step, the influence of the geometry on the particular relationship is studied. Therefore, an analytic expression for Euler Bernoulli beams with a non-constant cross section is derived. Afterward, a general method for obtaining geometric factors from finite element (FE) models is proposed. In order to ensure a fast fatigue damage evaluation, strongly simplified FE-models are used for the determination of both factors and measurement locations. The entire method is demonstrated on three mechanical structures and indicates a better compromise between effort and accuracy than existing methods. For all examples, the usage of velocities and geometric factors obtained from simplified FE models enables a sufficient fatigue damage calculation.
Properties of Porous PDMS and Stretchability of Flexible Electronics in Moist Environment
Authors: Pan Peng , Bian Zuguang , Song Xin , Zhou Xiaoliang 
Published: July 2020

Abstract
Polydimethylsiloxane (PDMS) is a good choice for the substrate and encapsulation of clinical flexible electronics, since it possesses some distinguished characteristics such as high elasticity, excellent optical characteristic, good biocompatibility, and stability. In the present study, the emulsion polymerization technique was used once more to fabricate porous PDMS, which is expected to assure the sweat penetration through the flexible electronics, and therefore to reduce the irritation to the skin due to the flexible electronics. To assess the mechanical performance of flexible electronics with moisture, the saturated moisture concentration, coefficient of moisture expansion, and elastic modulus of porous PDMS for different relative wetness fraction were measured in experiment. Meanwhile, an asymptotic homogenization method (AHM) was adopted to predict these parameters theoretically. Results indicate that the saturated moisture concentration is linear to the porosity, while the coefficient of moisture expansion is independent of the porosity, both of which are well verified by the experimental data. The fitted formula on the elastic modulus for different porosities suggested in our previous study was developed to take account of the relative wetness fraction based on the experimental data. These three parameters were finally applied in calculating the stretchability of a flexible electronic with serpentine interconnects in moist environment. Numerical stimulation reveals that the stretchability increases with the porosity and relative wetness fraction of the substrate and encapsulation. The present work is hoped to pave the way for flexible electronics in clinical applications.
A Review of Physically Based and Thermodynamically Based Constitutive Models for Soft Materials
Authors: Xiang Yuhai , Zhong Danming , Rudykh Stephan , Zhou Haofei , Qu Shaoxing , Yang Wei 
Published: July 2020

Abstract
In this paper, we review constitutive models for soft materials. We specifically focus on physically based models accounting for hyperelasticity, visco-hyperelasticity, and damage phenomena. For completeness, we include the thermodynamically based viscohyperelastic and damage models as well as the so-called mixed models. The models are put in the frame of statistical mechanics and thermodynamics. Based on the available experimental data, we provide a quantitative comparison of the hyperelastic models. This information can be used as guidance in the selection of suitable constitutive models. Next, we consider visco-hyperelasticity in the frame of the thermodynamic theory and molecular chain dynamics. We provide a concise summary of the viscohyperelastic models including specific strain energy density function, the evolution laws of internal variables, and applicable conditions. Finally, we review the models accounting for damage phenomenon in soft materials. Various proposed damage criteria are summarized and discussed in connection with the physical interpretations that can be drawn from physically based damage models. The discussed mechanisms include the breakage of polymer chains, debonding between polymer chains and fillers, disentanglement, and so on.
Probabilistic Finite Element Analysis of Cooled High-Pressure Turbine Blades—Part B: Probabilistic Analysis
Authors: Högner Lars , Voigt Matthias , Mailach Ronald , Meyer Marcus , Gerstberger Ulf 
Published: July 2020

Abstract
Modern high-pressure turbine (HPT) blade design stands out due to high complexity comprising three-dimensional blade features, multipassage cooling system (MPCS), and film cooling to allow for progressive thermodynamic process parameters. During the last decade, probabilistic design approaches have become increasingly important in turbomachinery to incorporate uncertainties such as geometric variations caused by manufacturing scatter. In Part B of this two-part article, real geometry effects are considered within a probabilistic finite element (FE) analysis that aims at sensitivity evaluation. The knowledge about the geometric variability is derived based on a blade population of more than 400 individuals by means of parametric models that are introduced in Part A. The HPT blade population is statistically assessed, which allows for reliable sensitivity analysis and robustness evaluation taking the variability of the airfoil, profiled endwalls (PEWs) at hub and shroud, wedge surfaces (WSFs), and the MPCS into account. The probabilistic method—Monte Carlo simulation (MCS) using an extended Latin hypercube sampling (eLHS) technique—is presented subsequently. Afterward, the FE model that involves thermal, linear-elastic stress, and creep analysis is described briefly. Based on this, the fully automated process chain involving computer-aided design (CAD) model creation, FE mesh morphing, FE analysis, and postprocessing is executed. Here, the mesh morphing process is presented involving a discussion of the mesh quality. The process robustness is assessed and quantified referring to the impact on input parameter correlation. Finally, the result quantities of the probabilistic FE simulation are evaluated in terms of sensitivities. For this purpose, regions of interest are determined, wherein the statistical analysis is conducted to achieve the sensitivity ranking. A significant influence of the considered geometric uncertainties onto mechanical output quantities is observed, which motivates to incorporate these in modern design strategies or robust optimization.
A Discrete Adjoint Method for Two-Phase Condensing Flows Applied to the Shape Optimization of Turbine Cascades
Authors: Pini M. , Azzini L. , Vitale S. , Colonna P. 
Published: July 2020

Abstract
This paper presents a fully turbulent two-phase discrete adjoint method for metastable condensing flows targeted to turbomachinery applications. The method is based on a duality preserving algorithm and implemented in the open-source CFD tool SU2. The optimization framework is applied to the shape optimization of two canonical steam turbine cascades, commonly referred to as White cascade and Dykas cascade. The optimization were carried out by minimizing either the liquid volume fraction downstream of the cascade or the total entropy generation due viscous effects and heat transfer. In the first case, the amount of condensate turned out to be reduced by as much as 24%, but without reduction of the generated entropy, while the opposite resulted in the second case. The outcomes demonstrate the capability and computational efficiency of adjoint-based automated design for the shape optimization of turbomachinery operating with phase change flow.
Black hole and naked singularity geometries supported by three-form fields
Authors: Barros Bruno J. , Dǎnilǎ Bogdan , Harko Tiberiu , Lobo Francisco S. N. 
Published: July 2020

AbstractWe investigate static and spherically symmetric solutions in a gravity theory that extends the standard Hilbert–Einstein action with a Lagrangian constructed from a three-form field $$A_{\alpha \beta \gamma }$$Aαβγ, which is related to the field strength and a potential term. The field equations are obtained explicitly for a static and spherically symmetric geometry in vacuum. For a vanishing three-form field potential the gravitational field equations can be solved exactly. For arbitrary potentials numerical approaches are adopted in studying the behavior of the metric functions and of the three-form field. To this effect, the field equations are reformulated in a dimensionless form and are solved numerically by introducing a suitable independent radial coordinate. We detect the formation of a black hole from the presence of a Killing horizon for the timelike Killing vector in the metric tensor components. Several models, corresponding to different functional forms of the three-field potential, namely, the Higgs and exponential type, are considered. In particular, naked singularity solutions are also obtained for the exponential potential case. Finally, the thermodynamic properties of these black hole solutions, such as the horizon temperature, specific heat, entropy and evaporation time due to the Hawking luminosity, are studied in detail.
Approximation of critical regularity functions on stratified homogeneous groups
Authors: Curcă Eduard 
Published: July 2020

Let [Formula: see text] be a stratified homogeneous group with homogeneous dimension [Formula: see text] and whose Lie algebra is generated by the left-invariant vector fields [Formula: see text]. Let [Formula: see text], [Formula: see text] and [Formula: see text]. We prove that for any function [Formula: see text] there exists a function [Formula: see text] such that [Formula: see text] [Formula: see text] where [Formula: see text] is the largest integer smaller than [Formula: see text] and [Formula: see text] is a positive constant depending only on [Formula: see text]. Here, [Formula: see text] is a homogeneous Triebel–Lizorkin type space adapted to [Formula: see text]. This generalizes earlier results of Bourgain, Brezis [New estimates for eliptic equations and Hodge type systems, J. Eur. Math. Soc. 9(2) (2007) 277–315] and of Bousquet, Russ, Wang, Yung [Approximation in fractional Sobolev spaces and Hodge systems, J. Funct. Anal. 276(5) (2019) 1430–1478] in the Euclidean case and answers an open problem in the latter reference.
Bromodomain-Selective BET Inhibitors Are Potent Antitumor Agents against MYC-Driven Pediatric Cancer
Authors: Slavish P. Jake , Chi Liying , Yun Mi-Kyung , Tsurkan Lyudmila , Martinez Nancy E. , Jonchere Barbara , Chai Sergio C. , Connelly Michele , Waddell M. Brett , Das Sourav , Neale Geoffrey , Li Zhenmei , Shadrick William R. , Olsen Rachelle R. , Freeman Kevin W. , Low Jonathan A. , Price Jeanine E. , Young Brandon M. , Bharatham Nagakumar , Boyd Vincent A. , Yang Jun , Lee Richard E. , Morfouace Marie , Roussel Martine F. , Chen Taosheng , Savic Daniel , Guy R. Kiplin , White Stephen W. , Shelat Anang A. , Potter Philip M. 
Published: July 2020

Abstract

Inhibition of members of the bromodomain and extraterminal (BET) family of proteins has proven a valid strategy for cancer chemotherapy. All BET identified to date contain two bromodomains (BD; BD1 and BD2) that are necessary for recognition of acetylated lysine residues in the N-terminal regions of histones. Chemical matter that targets BET (BETi) also interact via these domains. Molecular and cellular data indicate that BD1 and BD2 have different biological roles depending upon their cellular context, with BD2 particularly associated with cancer. We have therefore pursued the development of BD2-selective molecules both as chemical probes and as potential leads for drug development. Here we report the structure-based generation of a novel series of tetrahydroquinoline analogs that exhibit &gt;50-fold selectivity for BD2 versus BD1. This selective targeting resulted in engagement with BD-containing proteins in cells, resulting in modulation of MYC proteins and downstream targets. These compounds were potent cytotoxins toward numerous pediatric cancer cell lines and were minimally toxic to nontumorigenic cells. In addition, unlike the pan BETi (+)-JQ1, these BD2-selective inhibitors demonstrated no rebound expression effects. Finally, we report a pharmacokinetic-optimized, metabolically stable derivative that induced growth delay in a neuroblastoma xenograft model with minimal toxicity. We conclude that BD2-selective agents are valid candidates for antitumor drug design for pediatric malignancies driven by the MYC oncogene.

Significance:
This study presents bromodomain-selective BET inhibitors that act as antitumor agents and demonstrates that these molecules have in vivo activity towards neuroblastoma, with essentially no toxicity.
Nitrogen Trapping as a Therapeutic Strategy in Tumors with Mitochondrial Dysfunction
Authors: Madala Hanumantha Rao , Helenius Iiro Taneli , Zhou Wen , Mills Evanna , Zhang Yiyun , Liu Yan , Metelo Ana M. , Kelley Michelle L. , Punganuru Surendra , Kim Kyung Bo , Olenchock Benjamin , Rhee Eugene , Intlekofer Andrew M. , Iliopoulos Othon , Chouchani Edward , Yeh Jing-Ruey Joanna 
Published: July 2020

Abstract

Under conditions of inherent or induced mitochondrial dysfunction, cancer cells manifest overlapping metabolic phenotypes, suggesting that they may be targeted via a common approach. Here, we use multiple oxidative phosphorylation (OXPHOS)–competent and incompetent cancer cell pairs to demonstrate that treatment with α-ketoglutarate (aKG) esters elicits rapid death of OXPHOS-deficient cancer cells by elevating intracellular aKG concentrations, thereby sequestering nitrogen from aspartate through glutamic-oxaloacetic transaminase 1 (GOT1). Exhaustion of aspartate in these cells resulted in immediate depletion of adenylates, which plays a central role in mediating mTOR inactivation and inhibition of glycolysis. aKG esters also conferred cytotoxicity in a variety of cancer types if their cell respiration was obstructed by hypoxia or by chemical inhibition of the electron transport chain (ETC), both of which are known to increase aspartate and GOT1 dependencies. Furthermore, preclinical mouse studies suggested that cell-permeable aKG displays a good biosafety profile, eliminates aspartate only in OXPHOS-incompetent tumors, and prevents their growth and metastasis. This study reveals a novel cytotoxic mechanism for the metabolite aKG and identifies cell-permeable aKG, either by itself or in combination with ETC inhibitors, as a potential anticancer approach.

Significance:
These findings demonstrate that OXPHOS deficiency caused by either hypoxia or mutations, which can significantly increase cancer virulence, renders tumors sensitive to aKG esters by targeting their dependence upon GOT1 for aspartate synthesis.
Exploiting the Microhomology-Mediated End-Joining Pathway in Cancer Therapy
Authors: Patterson-Fortin Jeffrey , D'Andrea Alan D. 
Published: July 2020

Abstract
Repair of DNA double-strand breaks (DSB) is performed by two major pathways, homology-dependent repair and classical nonhomologous end-joining. Recent studies have identified a third pathway, microhomology-mediated end-joining (MMEJ). MMEJ has similarities to homology-dependent repair, in that repair is initiated with end resection, leading to single-stranded 3′ ends, which require microhomology upstream and downstream of the DSB. Importantly, the MMEJ pathway is commonly upregulated in cancers, especially in homologous recombination-deficient cancers, which display a distinctive mutational signature. Here, we review the molecular process of MMEJ as well as new targets and approaches exploiting the MMEJ pathway in cancer therapy.
Starvation-induced lipid reserve depletion in Pratylenchus brachyurus leads to decreased infectivity in maize roots
Authors: Alves Paula S. , Terra Willian C. , Pinto Giselle B. , Pacheco Paulo V.M. , Fatobene Bárbhara J.R. , Campos Vicente P. , de Souza Jorge T. 
Published: July 2020

Summary
Nematode body neutral lipid (triacylglycerol) content has been related to infectivity and has direct implications in control strategies. In this study, Pratylenchus brachyurus populations were split into two groups: i) freshly hatched second-stage juveniles (J2) containing lipids stored during embryogenesis; ii) third- and fourth-stage juveniles (J3/J4) plus females that replenished their lipid reserves by feeding on maize (Zea mays) roots. These groups were subjected to starvation to study their lipid consumption dynamics by staining with Oil Red O, which binds specifically to neutral lipids. Before starvation, freshly hatched J2 had 27% of their body area stained, whereas J3/J4 and females had 75%. Freshly hatched J2 starved for 28 days at 25°C in water lost 63.8% of the original neutral lipid content, which caused a reduction of 91% of infectivity in maize roots. By contrast, J3/J4 and females exposed to the same conditions lost 56.7% of the original neutral lipid content, which resulted in less than 50% reduction in infectivity. During the period of food deprivation, J2 had a mean daily neutral lipid consumption rate of 0.63% and the other infectious stages (J3/J4 and females) had a mean daily neutral lipid consumption rate of 1.46% per day. This study adds information on the dynamics of lipid utilisation that supports the use of longer waiting periods for planting crops after fallow in soils infested with P. brachyurus as compared to Meloidogyne spp.-infested soils.