Technical Relevance Research Articles

Retracted: “Symmetric and Asymmetric Disturbances in the Rayleigh Zone of an Air-Assisted Liquid Sheet: Theoretical and Experimental Analysis,” [ASME Journal of Fluids Engineering, 2020, 142(7), p. 071302; DOI: 10.1115/1.4045998

AbstractThe temporal analysis of symmetric (dilatational) and asymmetric (sinusoidal) perturbations at the interface of a water sheet in a coflowing air stream focuses on low gas Weber number region (Weg < 0.4), namely, Rayleigh breakup zone. The motive for this investigation is to acquire a better insight of breakup phenomena involved, rather than technical relevance, by utilizing Kelvin–Helmholtz instability. Accordingly, perturbations are introduced on the basic flow whose stability is to be examined by the method of normal (Fourier) modes. The temporal growth-rate of perturbations is traced to extract the wavenumber associated with maximum growth-rate. Thus, the critical wavelength, in conjunction with the phase velocity of the disturbance will facilitate to obtain the corresponding breakup frequency of the liquid sheet. The analytical findings on liquid sheet breakup frequency with increasing Weber number ratio exhibit the dominance of symmetric wave over asymmetric wave. It also shows independent evolution of breakup frequency with respect to Weber number ratio for the respective perturbation modes, which appears to be a pointed profile. That is, the frequency contour for dilatational mode dips, whereas it rises for the sinusoidal mode and at the Weber number ratio of 0.518 the crossover occur. The theoretical results were substantiated by high-speed flow visualization studies that discern the coexistence of low-frequency (primary) and high-frequency (intermediate) breakup events. Furthermore, the empirical average frequency data track reasonably well with the dilatational instability.

Thermal analysis: an effective characterization method of polyvinyl acetate films applied in corrosion inhibition field

To prepare a commercial product with economic and technical relevance, polyvinyl acetate (PVAc) was synthesized, under our laboratory conditions, updating an industrial prescription by emulsion polymerization of vinyl acetate using polyvinyl alcohol as emulsifier, Fenton reagent as reaction initiator and acetic acid as aqueous phase pH-regulator. A polymeric film (PSYF) was made and comparatively characterized with a standard PVAc film (PSTF) by scanning electron microscopy with energy-dispersive X-ray spectroscopy, Raman spectroscopy and simultaneous thermogravimetry and derivative thermogravimetry analysis. Similar vibration bands for PSTF and PSYF in the Raman spectra were identified which accurately reproduce the values reported in the literature. Thermal analysis was an efficient method to detect the compositional differences between the two polymeric films, precisely indicating that PSYF contained 92% PVAc and a mixture of 8% containing unreacted monomer, polyvinyl alcohol and humidity. Additionally, the PVAc film inhibitive properties on carbon steel corrosion in acid environments were investigated by potentiodynamic polarization and electrochemical impedance spectroscopy. A high inhibition efficiency of PVAc, ranging between 86.0 and 88.0%, was computed from electrochemical measurements, indicating the polymer adsorption ability on carbon steel surface.

Research on classification and similarity of patent citation based on deep learning

This paper proposes a patent citation classification model based on deep learning, and collects the patent datasets in text analysis and communication area from Google patent database to evaluate the classification effect of the model. At the same time, considering the technical relevance between the examiners’ citations and the pending patent, this paper proposes a hypothesis to take the output value of the model as the technology similarity of two patents. The rationality of the hypothesis is verified from the perspective of machine statistics and manual spot check. The experimental results show that the model effect based on deep learning proposed in this paper is significantly better than the traditional text representation and classification method, while having higher robustness than the method combining Doc2vec and traditional classification technology. In addition, we compare between the proposed method based on deep learning and the traditional similarity method by a triple verification. It shows that the proposed method is more accurate in calculating technology similarity of patents. And the results of manual sampling show that it is reasonable to use the output value of the proposed model to represent the technology similarity of patents.

MHD Rotating Fluid Flow past a Vertical Plate that Applies Arbitrary Shear Stress with Ramped Wall Temperature

Heat transfer in rotating, incompressible viscous ?‡uid near an in?…nite ver-tical plate that applies a time-dependent shear stress f(t) with ramped wall temperatureis investigated. Closed form exact solutions of the dimensionless governing equations alongwith imposed initial and boundary conditions are determined using the Laplace transformtechnique. These solutions are uncommon in literature and can generate exact solutions forany motion of problem with technical relevance of this type. The e?¤ects of di?¤erent systemparameters, such as Ekman number, Grashof number, Prandtl number, magnetic numberand time on the velocity is examined in detail. Its in?‡uence on the ?‡uid motion is graphicallydisplayed. Some special cases together with particular cases are considered.

Investigation on fatigue strength of cut edges produced by various cutting methods for high-strength steels

Due to the interest in effective light steel constructions, high-strength steels have gained importance. Different thermal cutting processes are frequently used in the metal processing industry. Besides the weld seams, free cutting edges gain technical and economic relevance as locations for potential fatigue cracks. In this investigation, fatigue tests were carried out on 8-mm-thick samples of S355M and S690Q steels at a stress ratio of R = 0.1. The cutting methods used were oxygen, plasma, laser, and waterjet cutting. Quality improvement methods, like shot peening, grinding, and cutting speed reduction, were applied for some series. The surface roughness was measured to classify the specimens into quality groups according to ISO 9013. The cut edge condition was also characterized by hardness and residual stress measurements. The investigation shows that all tested series exceed the FAT100 class and can be classified in FAT125. Specimens ranged in quality group 2 of ISO 9013 according to the roughness achieve FAT140 regardless of cutting technology or material. According to the ISO 9013, most of the specimens are classified in the quality group 2 and group 3. Fatigue strength results are significantly different in one quality group. No prediction can be made. ISO 9013 has a weak connection to fatigue strength. Quality improvement methods have a significant influence on the fatigue strength and can increase it. Due to reduced cutting speeds, the roughness decreases also. It results in an increase of the fatigue strength in all tested series in this study. In order to make a prediction of the fatigue performance, the standard has to be specified and the cutting process as well as the steel strength should be considered.

DNS study of the global heat release rate during early flame kernel development under engine conditions

Despite the high technical relevance of early flame kernel development for the reduction of cycle-to-cycle variations in spark ignition engines, there is still a need for a better fundamental understanding of the governing in-cylinder phenomena in order to enable resilient early flame growth. To isolate the effects of small- and large-scale turbulent flow motion on the young flame kernel, a three-dimensional DNS database has been designed to be representative for engine part load conditions. The analysis is focussed on flame displacement speed and flame area in order to investigate effects of flame structure and flame geometry on the global burning rate evolution. It is shown that despite a Karlovitz number of up to 13, which is at the upper range of conventional engine operation, thickening of the averaged flame structure by small-scale turbulent mixing is not observed. After ignition effects have decayed, the flame normal displacement speed recovers the behavior of a laminar unstretched premixed flame under the considered unity-Lewis-number conditions. Run-to-run variations in the global heat release rate are shown to be primarily caused by flame kernel area dynamics. The analysis of the flame area balance equation shows that turbulence causes stochastic flame kernel area growth by affecting the curvature evolution, rather than by inducing variations in total flame area production by strain. Further, it is shown that in local segments of a fully-developed planar flame with similar surface area as the investigated flame kernels, temporal variations in flame area rate-of-change occur. Contrasting to early flame kernels, these effects can be exclusively attributed to curvature variations in negatively curved flame regions.

Introduction to the Special Section on the 2019 IEEE S3S Conference

This special section of the IEEE JOURNAL OF ELECTRON DEVICES SOCIETY is dedicated to select papers presented at the 2019 IEEE S3S Conference, which was held Oct. 14– 17, 2019 in San Jose, CA, USA. The papers were selected based on their technical merits and relevance to the Journal and with the feedback from the Technical Committee of the conference and session chairs.

Robustness Against Indirect Invasions in Asymmetric Games

The concept of robustness against indirect invasions is well-known for symmetric games. We are concerned with the technical aspects and relevance of this concept for asymmetric games with continuous strategy space. For such games, we show that the set of all indirect neutral mutants of a robust profile is equivalent to a minimal evolutionarily stable set. It is also proved that a globally strong uninvadable profile is robust and the set of its indirect neutral mutants is a singleton. The results are illustrated using examples.

Entropy Generation and Heat Transfer in Drilling Nanoliquids with Clay Nanoparticles

Different types of nanomaterials are used these days. Among them, clay nanoparticles are the one of the most applicable and affordable options. Specifically, clay nanoparticles have numerous applications in the field of medical science for cleaning blood, water, etc. Based on this motivation, this article aimed to study entropy generation in different drilling nanoliquids with clay nanoparticles. Entropy generation and natural convection usually occur during the drilling process of oil and gas from rocks and land, wherein clay nanoparticles may be included in the drilling fluids. In this work, water, engine oil and kerosene oil were taken as base fluids. A comparative analysis was completed for these three types of base fluid, each containing clay nanoparticles. Numerical values of viscosity and effective thermal conductivity were computed for the nanofluids based on the Maxwell–Garnett (MG) and Brinkman models. The closed-form solution of the formulated problem (in terms of partial differential equations with defined initial and boundary conditions) was determined using the Laplace transform technique. Numerical facts for temperature and velocity fields were used to calculate the Bejan number and local entropy generation. These solutions are uncommon in the literature and therefore this work can assist in the exact solutions of a number of problems of technical relevance to this type. Herein, the effect of different parameters on entropy generation and Bejan number minimization and maximization are displayed through graphs.

Variables individuales, sociodemográficas e institucionales asociadas a la retención de estudiantes de primer año del Programa Académico de Bachillerato de la Universidad de Chile

La retención en Educación Superior Universitaria (ESUP) en América Latina y el Caribe (ALC) tiene importantes efectos sociales, económicos e individuales (Proyecto ALFA-GUIA, 2013; CINDA, 2006). La retención ha alcanzado relevancia técnica en los estudios de calidad en la educación, al mismo tiempo que aumenta su importancia en los rankings internacionales y en las acreditaciones de las instituciones universitarias. De acuerdo a un estudio del Banco Mundial (Ferreyra et al., 2017) la ESUP en la región se caracteriza por: 1) una tasa de finalización promedio de 46%, con importantes diferencias entre un país y otro; 2) la existencia de un aumento exponencial de las matrículas, duplicando la tasa regular de estudiantes; 3) el ingreso de “nuevos estudiantes”, anteriormente subrepresentados en la ESUP. Considerando que en la región son escasas las investigaciones que intentan predecir el fenómeno de la retención (Munizaga, Cifuentes & Beltrán, 2018), este estudio busca revisar la información reciente respecto a la retención en ALC, consensuar una definición sobre el fenómeno y ampliar la discusión sobre cómo garantizar la retención de estudiantes en una ESUP equitativa e inclusiva (Espinoza, González & Latorre, 2009). En concreto, este trabajo busca responder ¿Cuáles son las variables individuales, sociodemográficas e institucionales asociadas a la retención de estudiantes de primer año del Programa Académico de Bachillerato de la Universidad de Chile? A través de un modelo de regresión logística binaria, compuesto por ocho variables, se identificaron las siguientes seis variables significativas jerarquizadas: origen étnico de los estudiantes, aprobación de todos los créditos y gratuidad, con una relación positiva con la retención; y preferencia, género y puntaje de la prueba de selección universitaria, con una relación negativa. Las principales recomendaciones de este estudio son, a nivel institucional, ofrecer trayectorias académicas más amplias y, a nivel estatal, hacerse responsable del financiamiento de los estudiantes.

Lipase-Catalyzed Chemoselective Ester Hydrolysis of Biomimetically Coupled Aryls for the Synthesis of Unsymmetric Biphenyl Esters.

Lipases are among the most frequently used biocatalysts in organic synthesis, allowing numerous environmentally friendly and inexpensive chemical transformations. Here, we present a biomimetic strategy based on iron(III)-catalyzed oxidative coupling and selective ester monohydrolysis using lipases for the synthesis of unsymmetric biphenyl-based esters under mild conditions. The diverse class of biphenyl esters is of pharmaceutical and technical relevance. We explored the potency of a series of nine different lipases of bacterial, fungal, and mammalian origin on their catalytic activities to cleave biphenyl esters, and optimized the reaction conditions, in terms of reaction time, temperature, pH, organic solvent, and water–organic solvent ratios, to improve the chemoselectivity, and hence control the ratio of unsymmetric versus symmetric products. Elevated temperature and increased DMSO content led to an almost exclusive monohydrolysis by the four lipases Candida rugosa lipase (CRL), Mucor miehei lipase (MML), Rhizopus niveus lipase (RNL), and Pseudomonas fluorescens lipase (PFL). The study was complemented by in silico binding predictions to rationalize the observed differences in efficacies of the lipases to convert biphenyl esters. The optimized reaction conditions were transferred to the preparative scale with high yields, underlining the potential of the presented biomimetic approach as an alternative strategy to the commonly used transition metal-based strategies for the synthesis of diverse biphenyl esters.

Growth of Iron-Oxidizing Bacteria Gallionella ferruginea and Leptothrix cholodnii in Oligotrophic Environments: Ca, Mg, and C as Limiting Factors and G. ferruginea Necromass as C-Source

Iron-oxidizing bacteria (FeOB) can successively populate low-nutrient aquatic environments and adapt to a broad concentration range of alkaline earth metals, with optimum conditions widely differing from one species to another. For the most abundant known FeOB genera Gallionella and Leptothrix, there is a lack of reports on substrate affinity for calcium and magnesium and necromass assimilability. Single nutrient and combined affinity for Ca and Mg of a wild Gallionella ferruginea isolate and a Leptothrix cholodnii strain as well as growth of heterotrophic L. cholodnii on necromass of autotrophic G. ferruginea were determined by cell density measurements. G. ferruginea responds with Monod-shaped preferences and thus favors waters rich in Ca and Mg. Maximum growth occurred at Ca concentrations five times above those of commonly used modified mineral Wolfe’s medium. L. cholodnii showed a Monod-shaped preference in the low concentration range and an inhibitory response to increasing hardness: concentrations >2 mM Ca or >0.6 mM Mg allow only 50 or 75%, respectively, of maximum specific cell densities. Considering the concentration range with a Monod-shaped response (for L. cholodnii only lower concentration range), both FeOB show a type I independent colimitation for Ca and Mg with lower requirements of Mg than Ca. On a C-limited medium containing G. ferruginea necromass as the only C-source, L. cholodnii cell counts were higher by two orders of magnitude compared to pyruvate medium. Thus, the necromass may serve as a primary C-source for heterotrophic FeOB and other heterotrophic bacteria with technical and economical relevance.

X-Ray Phase Contrast Imaging of Liquid Film and Spray Development Inside an Aircraft Engine Swirler

Abstract Modern aircraft engines combine liquid fuel and air using an intricate flow device with many fuel and air flow passages. To date, the process by which the fuel atomizes within this swirler set has not been examined directly due to optical access limitations. In this work, high-speed X-ray phase-contrast imaging of a liquid spray inside a gas turbine engine swirler geometry is presented. Measurements were carried out at the 7-BM beamline of the Advanced Photon Source at Argonne National Laboratory using the high-energy broadband X-ray beam. The synchrotron X-ray source provides the necessary photon energy and flux to capture time-resolved fluid phenomena within the confines of the relevant geometry while liquid and air are flowing. Spray nozzle hardware and geometries were provided by the National Jet Fuels Combustion Program (NJFCP), allowing for characterization of the spray using a commercially relevant configuration. Modified swirlers were three-dimensional printed with acrylic to improve imaging access while maintaining influential internal features. Water was used as a surrogate fluid for these studies to demonstrate the visualization capabilities. The experiments were conducted at atmospheric exit pressure conditions with a pressure drop of 6% across the swirler. High-speed imaging of the pilot spray cone revealed sheet breakup several millimeters downstream of the orifice exit, upon interaction with the radial assist air flow. These droplets and ligaments were observed to impinge on the inner filming surface of the swirler and flow toward the exit while developing a tangential flow. Under these conditions, the liquid film grows up to several hundred microns in thickness on the filming surface, and subsequently forms ligaments up to several millimeters in length before breaking up. This work demonstrates the capability of X-ray diagnostics in visualizing liquid flows within solid geometries of technical relevance. Furthermore, the spatial quantification of filming flows and liquid interaction with the swirler air provides validation data for modeling of the multiphase flows and surface interactions within the swirler.

An alternative sequence of operation for Pumped-Hydro Compressed Air Energy Storage (PH-CAES) systems

In a previous publication, entitled “Experimental study of a PH-CAES system: Proof of concept”, we presented results of an innovative solution for energy storage that uses only air and water as working fluids, named PH-CAES (Pumped-Hydro Compressed Air Energy Storage). Differently from a conventional CAES that operates with air turbines and air compressors, the PH-CAES uses a pump to compress water against air, and a hydraulic turbine to generate power. In the time of the aforementioned publication, it was possible to see that with a suitable thermodynamic cycle the PH-CAES could reach a high round-trip efficiency. Since then, we have worked on this cycle, and in this article we share the progress we have made. We redefined the sequence of charging and discharging aiming to provide constant power output. We present here simulations based on the balance of energy and entropy for transient regime, also used datasheets to simulate the pump characteristics. The maximum round-trip efficiencies were approximately 42%. We show that this is a relatively high round-trip efficiency, when compared to other CAES systems, which usually depend on multiple heat exchangers, burning fuel or an external heat source, validating thus, the technical relevance of the proposed solution.

Maintaining interoperability in open source software: A case study of the Apache PDFBox project

Software interoperability is commonly achieved through the implementation of standards for communication protocols or data representation formats. Standards documents are often complex, difficult to interpret, and may contain errors and inconsistencies, which can lead to differing interpretations and implementations that inhibit interoperability. Through a case study of two years of activity in the Apache PDFBox project we examine day-to-day decisions made concerning implementation of the PDF specifications and standards in a community open source software (OSS) project. Thematic analysis is used to identify semantic themes describing the context of observed decisions concerning interoperability. Fundamental decision types are identified including emulation of the behaviour of dominant implementations and the extent to which to implement the PDF standards. Many factors influencing the decisions are related to the sustainability of the project itself, while other influences result from decisions made by external actors, including the developers of dependencies of PDFBox. This article contributes a fine grained perspective of decision-making about software interoperability by contributors to a community OSS project. The study identifies how decisions made support the continuing technical relevance of the software, and factors that motivate and constrain project activity.

Silicon(II) Cation Cp*Si:+ X–: A New Class of Efficient Catalysts in Organosilicon Chemistry

The catalytic activity of the pentamethylcyclopentadienylsilicon(II) cation Cp*Si:+ was investigated. It was shown that Cp*Si:+ efficiently catalyzes reactions of technical relevance in organosilicon chemistry: Cp*Si:+ proved to be a very efficient nonmetallic catalyst for the hydrosilylation of olefins at low catalyst amounts of <0.01 mol % and for the Piers–Rubinsztajn reaction in order to make controlled silicone topologies. The thermal induction of hydrosilylation which is important for the manufacturing of silicone rubber can be achieved by small amounts of alkoxysilanes.

Microstructural characterization of carrier-based dry powder inhalation excipients: Insights and guidance.

The growing interest in development of dry powder inhalation (DPI) products raises a need for development of standard testing methods and specifications for DPI excipients. The pharmaceutical industry, meanwhile, yet lacks compendial guidance on this topic. Despite of the complexity of interactions taking place in DPI systems and the large number and variety of interplaying factors, understanding of key determinants of performance (critical quality attributes) of DPI excipients have considerably developed over the past years. In light of the current knowledge in this area, this article provides technical guidance and insights on testing and quality control of carrier-based-DPI excipients. These excipients are, typically, blends of coarse, carrier particles and fine, performance-modulating particles. The article explores techniques used for measurement of key microstructural attributes, namely the particle size distribution, the porosity and the particle surface roughness, the particle shape, rheological properties, and the permeability, of these excipients. The technical relevance of each measurement to the functionality of the excipients is critically discussed. In this regard, caveats concerning use of some measurements and data analysis procedures are raised. The guidance lends itself for compendial adoption.

Chemo‐Enzymatic Dynamic Kinetic Resolution of Symmetric and Non‐Symmetric α‐Hydroxy Ketones for Industrial Application

Abstractα‐Hydroxy ketones are important intermediates in various drugs and fine chemicals. Stereoselective synthesis of both symmetric and asymmetric compounds is demonstrated involving benzoin, 2–2’‐furoin, phenylacetyl carbinol (PAC) and 2‐hydroxy‐1‐phenylpropan‐1‐one (HPP) as representatives. Dynamic kinetic resolution of the racemic preparations was achieved in one‐pot combining transesterification catalyzed by immobilized lipases from Pseudomonas stutzeri and Pseudozyma antarctica, respectively, and racemization mediated by the heterogeneous chemo‐catalyst Zr‐TUD‐1 in water‐free organic solvent. (S)‐benzoin, (S)‐2,2’‐furoin, (S)‐PAC and (R)‐HPP were obtained with both high efficiency and high enantiomeric excess. Within 90 minutes, 2,45 g (S)‐PAC butyrate (ee 88%) yielded from a 130 mL batch reaction demonstrating both technical feasibility and relevance for application.

Issue: Selected paper of OIPE 2016 on modeling and optimal design of electromagnetic and electronic devices

Issue: Selected paper of OIPE 2016 on modeling and optimal design of electromagnetic and electronic devices

Characterization of Residence Time Distribution in a Plug Flow Reactor

AbstractOne of the biggest advantages of plug flow reactors lies in their narrow residence time distribution. The pulse experiment, as a common method on acquiring that distribution, relies on the tracer injection being a perfect pulse. A deviation from a perfect pulse leads to erroneous results if not taken into account. With a numerical analysis of experimental data, this effect is quantified in turbulent and laminar flow regime and the results are compared to an analytical method. Significant deviations occur mostly in the turbulent regime, which has the greatest technical relevance.