bluuebunny/crossref_metadata_2025 huggingface dataset:
An ultra-incompressible Mn3N compound predicted by first-principles genetic algorithm
Authors: Zhang Chao , Sun Yang , Zhang Feng , Ho Kai-Ming , Wang Cai-Zhuang
Published: August 2020

Using genetic algorithms for an unbiased structure search and first-principles total-energy calculations, a stable manganese nitride, Mn3N, is discovered. Mn3N is a nonmagnetic metal and isostructural to superhard Re3N. Mn3N exhibits a large bulk modulus and incompressibility comparable to that of the ultra-incompressible OsB. We show that the large bulk modulus can be attributed to the strong covalent bonding in this system. Phonon calculations and analysis confirm the dynamical stability of the Mn3N compound. We also show that weak electron–phonon coupling leads to a small superconducting transition temperature for Mn3N.
Understanding nano-modification in liquid dielectric from coefficient of viscosity
Authors: Li Diangeng , Zhang Zicheng , Liu Shifei , Li Song
Published: August 2020

The breakdown experiments were conducted on the castor oil and Midel 7131 nano-liquids under microsecond pulse. The breakdown strength of the castor oil nano-liquid with 1% volume fraction was over 50% higher than its base liquid, while the breakdown strength of the Midel 7131 nano-liquid with 0.3% volume fraction was 10% higher than its base liquid. A high viscosity base liquid would help increase the optimal volume fraction of the nano-particles because the nano-particles in a high viscosity liquid are harder to polymerize. This study proposed new ideas for the mechanism of nano-modification and extended the scope of liquid nano-modification.
Energy transfer between vibrationally excited carbon monoxide based on a highly accurate six-dimensional potential energy surface
Authors: Chen Jun , Li Jun , Bowman Joel M. , Guo Hua
Published: August 2020

Energy transfer between vibrational modes can be quite facile, and it has been proposed as the dominant mechanism for energy pooling in extreme environments such as nonthermal plasmas and laser cavities. To understand such processes, we perform quasi-classical trajectory studies of CO(v) + CO(v) collisions on a new full-dimensional potential energy surface fit to high-level ab initio data using a neural network method and examine the key vibrational energy transfer channels. In addition to the highly efficient CO(v + 1) + CO(v − 1) channel, there exists a significant, sometimes dominant, CO(v + 2) + CO(v − 2) channel for large v states at low collision energies. The latter is shown to stem from the substantially increased interaction between highly vibrationally excited CO, which has a much larger dipole moment than at its equilibrium bond length. Finally, the vibrational state-specific cross sections and their energy dependence on the thermal range are predicted from a limited dataset using Gaussian process regression. The relevance of these results to plasma chemistry and laser engineering and the recently observed flipping of highly vibrationally excited CO adsorbates on a cold NaCl surface is discussed.
Application of XDM to ionic solids: The importance of dispersion for bulk moduli and crystal geometries
Authors: Otero-de-la-Roza A. , Johnson Erin R.
Published: August 2020

Dispersion corrections are essential in the description of intermolecular interactions; however, dispersion-corrected functionals must also be transferrable to hard solids. The exchange-hole dipole moment (XDM) model has demonstrated excellent performance for non-covalent interactions. In this article, we examine its ability to describe the relative stability, geometry, and compressibility of simple ionic solids. For the specific cases of the cesium halides, XDM-corrected functionals correctly predict the energy ranking of the B1 and B2 forms, and a dispersion contribution is required to obtain this result. Furthermore, for the lattice constants of the 20 alkali halides, the performance of XDM-corrected functionals is excellent, provided that the base functional’s exchange enhancement factor properly captures non-bonded repulsion. The mean absolute errors in lattice constants obtained with B86bPBE-XDM and B86bPBE-25X-XDM are 0.060 Å and 0.039 Å, respectively, suggesting that delocalization error also plays a minor role in these systems. Finally, we considered the calculation of bulk moduli for alkali halides and alkaline-earth oxides. Previous claims in the literature that simple generalized gradient approximations, such as PBE, can reliably predict experimental bulk moduli have benefited from large error cancellations between neglecting both dispersion and vibrational effects. If vibrational effects are taken into account, dispersion-corrected functionals are quite accurate (4 GPa–5 GPa average error), again, if non-bonded repulsion is correctly represented. Careful comparisons of the calculated bulk moduli with experimental data are needed to avoid systematic biases and misleading conclusions.
Terahertz oscillations in gallium nitride quantum-well channels predicted by hot-electron noise temperature behavior at microwave frequency
Authors: Ramonas M. , Liberis J. , Šimukovič A. , Šermukšnis E. , Matulionis A. , Avrutin V. , Özgür Ü. , Morkoç H.
Published: August 2020

The almost periodic streaming motion of accelerated electrons under moderate electric fields coupled with almost periodic emission of longitudinal optical (LO) phonons is studied in a gallium nitride quantum-well—a promising pathway for terahertz (THz) oscillations. The optimal conditions for the LO-phonon-terminated streaming depend, among others, on the density of the electron gas, the low-field electron mobility, the lattice temperature, and the electric field in a very specific way. The present manuscript exploited the electron noise temperature measured at an X band frequency as a marker for the oscillations at THz frequencies. The idea was tested on a deterministic model for a GaN two-dimensional electron gas (2DEG) through calculation of the electron noise temperature spectra in the Langevin approach for the frequency range from 1 GHz to 10 THz. The noise temperature at 10 GHz was found to be in a strong anticorrelation with the THz peaks in the noise temperature spectrum. In particular, a weaker dependence on the applied electric field at 10 GHz implies stronger THz oscillations. In an experiment, the microwave hot-electron noise measurements were carried out for AlGaN/AlN/GaN heterostructures with the 2DEG channel at 10 GHz under pulsed electric field conditions in order to mitigate the effect of Joule heating of the channel. The plateau-like behavior of the noise temperature, in its dependence on the electric field, was obtained for the 2DEG channels with rather low electron densities (2.5×1012 cm−2) in a good agreement with the model. The aforementioned plateau in the electron noise temperature observed at 10 GHz can be used as an indicator for the THz oscillations.
Analytical solutions to shock and expansion waves for non-ideal equations of state
Authors: Wang Jeremy C. H. , Hickey Jean-Pierre
Published: August 2020

We present analytical solutions to the stationary normal shock and centered rarefaction waves, which are valid for arbitrary non-ideal equations of state (EOS). Generalized shock functions are defined, which are shown to be well-behaved and locally convex, facilitating rapid and exact computation of shock ratios. For rarefactions, a novel domain mapping is used to derive flow variables as closed-form analytical functions in space and time, independent of the EOS. Results are discussed for transcritical and supercritical CO2. The solutions enable researchers to test shock-capturing codes designed for non-ideal flows, and the derivation strategy opens possibilities to revisit nonlinear hyperbolic conservation problems that traditionally lack analytical solutions.
Self-organization of zonal flows and isotropic eddies in toroidal electron temperature gradient driven turbulence
Authors: Kawai C. , Idomura Y. , Ogawa Y. , Yamada H.
Published: August 2020

Self-organization in the toroidal electron temperature gradient driven (ETG) turbulence is investigated based on a global gyrokinetic model in a weak magnetic shear configuration. Because of global profile effects, toroidal ETG modes with a higher toroidal mode number n are excited at the outer magnetic surfaces, leading to strong linear wave dispersion. The resulting anisotropic wave turbulence boundary and the inverse energy cascade generate the self-organization of zonal flows, which is the unique mechanism in the global gyrokinetic model. The self-organization is confirmed both in the decaying turbulence initialized by random noises and in the toroidal ETG turbulence. It is also shown that the self-organization process generates zonal flows and isotropic eddies depending on a criterion parameter, which is determined by the ion to electron temperature ratio and the turbulence intensity.
Steady-state multiple near resonances of periodic interfacial waves with rigid boundary
Authors: Li Jiyang , Liu Zeng , Liao Shijun , Borthwick Alistair G. L.
Published: August 2020

Steady-state resonant interfacial waves in a two-layer fluid within a frictionless duct are investigated theoretically. A combination of the homotopy analysis method (HAM) and Galerkin’s method is used to search for accurate steady-state resonant solutions with multiple near resonances. In the HAM, a piecewise parameter in the auxiliary linear operators is introduced to remove the small divisors caused by nearly resonant components. Convergent series solutions are then provided to the Galerkin iterations to accelerate the convergence rate. It is found that weakly nonlinear steady-state resonant waves form a continuum in the parameter space. As nonlinearity (wave steepness) increases, energy appears to be progressively shifted to sideband frequency components, effectively broadening the spectrum. The corresponding interfacial wave profile exhibits an almost fixed spatial pattern of repeated relatively high frequency, high-amplitude bursts followed by low-amplitude, longer waves. On examining the influence of density ratio, though changing slightly, the upper layer enlarges the amplitude of components near primary ones, which reduces the amplitude of higher frequency components, enlarges the wave steepness, and reduces the horizontal velocity in the wave field. Our results indicate that steady-state systems with resonant interactions among periodic interfacial wave components could occur naturally in the ocean. All these should enhance our understanding of periodic resonant interfacial waves.
Approach and breakup of Taylor bubble and Taylor drop in a Hele-Shaw cell
Authors: Chauhan Subhav , Kumar Parmod
Published: August 2020

The collision dynamics of a Taylor drop and a Taylor bubble is investigated in an immiscible surrounding liquid. The interaction of both the fluidic entities is studied using experiments and simulation in a vertically aligned Hele-Shaw cell. The steady rise of the bubble and fall of the drop are followed by a deceleration regime where their velocity has decreased due to the pressure imposed by the leading interfaces, indicated by the change in the curvature of their tip. Subsequently, the rapid outward expansion of the bubble has caused the swelling of the tip of the drop. The drop swell has then grown exponentially similar to Rayleigh–Taylor instability and resulted in a split of the bubble into two volumes.
Success rate analysis of the response of an excitable laser to periodic perturbations
Authors: Tiana-Alsina Jordi , Garbin Bruno , Barland Stephane , Masoller Cristina
Published: August 2020

We use statistical tools to characterize the response of an excitable system to periodic perturbations. The system is an optically injected semiconductor laser under pulsed perturbations of the phase of the injected field. We characterize the laser response by counting the number of pulses emitted by the laser, within a time interval, ΔT, that starts when a perturbation is applied. The success rate, SR(ΔT), is then defined as the number of pulses emitted in the interval ΔT, relative to the number of perturbations. The analysis of the variation of SR with ΔT allows separating a constant lag of technical origin and a frequency-dependent lag of physical and dynamical origin. Once the lag is accounted for, the success rate clearly captures locked and unlocked regimes and the transitions between them. We anticipate that the success rate will be a practical tool for analyzing the output of periodically forced systems, particularly when very regular oscillations need to be generated via small periodic perturbations.
Giant reversible magnetostriction in a ferromagnet–polymer composite
Authors: Richardson Thomas I. , Schleusner Austin , Dahlberg E. Dan
Published: August 2020

A magnetostrictive ferromagnet–polymer composite consisting of steel wires suspended in a polymer matrix has been developed that exhibits large reversible magnetostrictive strain in relatively low magnetic fields. The strain for a fixed field is a nonmonotonic function of wire loading for the longer wires investigated, and the strain for a given wire loading increases with decreasing the wire length. Within the limits of this study, a maximum saturation strain of 60.2% in a 7.5 kOe field was observed with a wire length of 0.50 cm and a wire volume fraction of approximately 0.2. No degradation in strain was observed over the maximum number of 50 expansion cycles.
Demonstration of GaN-based metal–insulator–semiconductor junction by hydrogen plasma treatment
Authors: Yang Chen , Fu Houqiang , Su Po-Yi , Liu Hanxiao , Fu Kai , Huang Xuanqi , Yang Tsung-Han , Chen Hong , Zhou Jingan , Deng Xuguang , Montes Jossue , Qi Xin , Ponce Fernando A. , Zhao Yuji
Published: August 2020

We demonstrate a nickel/insulating-GaN (i-GaN)/p-type GaN junction and investigate its electrical properties. The i-GaN is formed by exposure to a low-power hydrogen plasma to passivate the p-GaN layer. Cathodoluminescence spectroscopy of the i-GaN is used to understand the passivation effect of the hydrogen plasma on p-GaN. The junction shows very low leakage (<10−9 A at −50 V), excellent rectifying properties (∼107), high temperature stability, and blue light electroluminescence at forward bias. A bandgap model is proposed to illustrate the electrical properties of hydrogenated p-GaN and to understand the device characteristics.
Numerical analysis of temperature and current distributions in large-size intrinsic Josephson junctions with self-heating
Authors: Oikawa Dai , Mitarai Haruki , Tanaka Hiromi , Tsuzuki Keita , Kumagai Yuki , Sugiura Toko , Andoh Hiroya , Tsukamoto Takehiko
Published: August 2020

In this study, we focused on temperature and current distributions in voltage-state large-size intrinsic Josephson junction (IJJ) mesas with a self-heating effect. Because it is difficult to experimentally obtain temperature and current distributions in IJJ mesas, we numerically computed these distributions by solving non-linear diffusion and temperature dependence circuit equations. The local temperature in the mesa exceeded the critical temperature, and a normal-state appeared in the high bias region. Non-uniform temperature and current density distributions were obtained for each bias point of the current–voltage (I–V) characteristics. Normalized c-axis current distributions decreased with an increase in the bias current in the high bias regions. These results were explained using temperature dependent c-axis resistivity.
The histone methyltransferase DOT1L prevents antigen-independent differentiation and safeguards epigenetic identity of CD8
+
T cells
Authors: Kwesi-Maliepaard Eliza Mari , Aslam Muhammad Assad , Alemdehy Mir Farshid , van den Brand Teun , McLean Chelsea , Vlaming Hanneke , van Welsem Tibor , Korthout Tessy , Lancini Cesare , Hendriks Sjoerd , Ahrends Tomasz , van Dinther Dieke , den Haan Joke M. M. , Borst Jannie , de Wit Elzo , van Leeuwen Fred , Jacobs Heinz
Published: August 2020

Significance

Cytotoxic CD8
+
T cells control infectious diseases as well as cancer. Memory T cells are a subset of CD8
+
T cells that have previously encountered and rapidly responded to a specific antigen. Here we identified the epigenetic writer DOT1L as a central regulator of T cell physiology. In the absence of DOT1L, which methylates histone H3K79 at active genes, cytotoxic T cells prematurely acquired memory features without having encountered an antigen. However, loss of DOT1L in the T cell lineage led to a compromised immune response. Our findings highlight the importance of epigenetic signals in regulating T cell differentiation. Understanding these epigenetic signals is important for developing strategies to modulate T cell immunity.
PIP2: A critical regulator of vascular ion channels hiding in plain sight
Authors: Harraz Osama F. , Hill-Eubanks David , Nelson Mark T.
Published: August 2020

Significance

Phosphatidylinositol 4,5-bisphosphate (PIP2), a plasma membrane lipid, is hydrolyzed by Gq-protein–coupled receptor (GqPCR) signaling into inositol 1,4,5-trisphosphate and diacylglycerol—extensively studied second messengers with profound regulatory effects in the vasculature. However, there is extensive evidence that PIP2directly regulates ion channels, a finding with significant implications for vascular function. Beyond providing a previously unexplored perspective on how vascular GqPCR signaling influences vascular function, the concept of PIP2-mediated ion channel regulation helps to explain how vascular cell excitability is coordinated to support cerebral blood flow control mechanisms. Importantly, the link between the metabolic state of vascular cells and PIP2content may provide insight into how metabolism affects vascular ion channel activity and, ultimately, vascular function in health and disease.
Inhibition of PIKfyve kinase prevents infection by Zaire ebolavirus and SARS-CoV-2
Authors: Kang Yuan-Lin , Chou Yi-ying , Rothlauf Paul W. , Liu Zhuoming , Soh Timothy K. , Cureton David , Case James Brett , Chen Rita E. , Diamond Michael S. , Whelan Sean P. J. , Kirchhausen Tom
Published: August 2020

Significance

The membrane fusion proteins of viral pathogens as diverse in their replication strategies as coronaviruses and filoviruses depend, for their functional activity, on proteolytic processing during cell entry. Endosomal cathepsins carry out the cleavages. We have constructed chimeric forms of vesicular stomatitis virus (VSV) bearing the fusion proteins of Zaire ebolavirus (ZEBOV) or SARS coronavirus 2 (SARS-CoV-2) and shown that two small-molecule inhibitors of an endosomal lipid kinase (PIKfyve) inhibit viral infection by preventing release of the viral contents from endosomes. Both inhibitory compounds cause distension of Rab5 and Rab7 subcompartments into small vacuoles. One of them (Apilimod) also inhibits infection of cells by authentic SARS-CoV-2. The results point to possibilities for host targets of antiviral drugs.
Poly-procedural meaning and rhetoric
Authors: Bardzokas Valandis
Published: August 2020

The current paper aims to explore the meaning of one of the most elusive discourse markers in Modern Greek rhetorical discourse:afu. To address the challenge of a thorough and parsimonious account, the relevance-theoretic model of meaning analysis is deployed. The analysis undertaken ultimately reveals that the marker at hand encodes procedural meaning in standard relevance-theoretic terms. However, unlike traditional relevance-theoretic approaches linking a marker to a single procedural function, the current one proposes thatafuencodes a poly-procedural constraint on the implicated content of the utterance containing the marker. Moreover, it is argued that this poly-procedural constraint is rhetorically exploited by the speaker in the interest of convincing argumentation.
Identity studies and identity construction
Authors: Chen Rong
Published: August 2020

In this paper, I report on a quasi-case study of U.S. presidential identity based on Donald J. Trump’s presidency, demonstrating that Trump is considered by the American public as an antithesis of presidentiality. I then discuss the insights from this study on several critical issues that face identity studies, an expansive area of investigation which has attracted the attention of students from a diverse range of disciplines. I demonstrate that identity is a set of attributes the formation of which is based on the mission of the group and the expected behaviors of members of that group, that the construction of identity is largely a bottom-up and gradual process, and that identity is both preexisting and emergent.
Constituency and coincidence in Chácobo (Pano)
Authors: Tallman Adam J. R.
Published: August 2020

This paper provides a detailed description of the results of 24 constituency diagnostics, both morphosyntactic and phonological, to Chácobo, a southern Pano language of the northern Bolivian Amazon. While it is often assumed that misalignments across the domains that emerge from constituency diagnostics can be resolved by reference to a distinction between phonological and morphosyntactic words, I argue that this is not true of Chácobo. Divergence is at least as high within phonological domains and morphosyntactic domains as it is across them. While it is often assumed that domains tend to converge overall on a single wordhood candidate or that domain divergence is marginal, I argue that this is not true of Chácobo. I present a cluster of methodologies that assess the motivation for a word constituent as an empirical hypothesis, rather than treating it as an a priori assumption. No strong evidence for a word constituent emerges from the Chácobo data. Theoretical and methodological implications are discussed.
A fragile shield for protecting civil rights: The European Union in the eyes of Italian feminists
Authors: Chironi Daniela
Published: August 2020

The article explores how feminist and LGBTQI organisations frame the European Union (EU), the claims they address to the EU institutions, and the actions they put in place at the continental level. Challenging previous beliefs of a linear increase in the Europeanisation of progressive social movements, this study reveals a more complex picture. Heavily affected by the economic and political crises, Italian women and LGBTQI activists share the radical criticism of EU austerity policies put forward by labour and youth movements. Nonetheless, they reject any option for breaking down the EU, as they conceive of it as a source of multilevel opportunities and a field for struggles from below, in which mechanisms of cross-national horizontal diffusion have facilitated the return of mass protest. While chances to realise the ‘other Europe’ project are perceived as low, activists hope that the EU is a potential ally against domestic conservatism.
Multigap superconductivity in the Mo5PB2 boron–phosphorus compound
Authors: Shang T , Xie W , Gawryluk D J , Khasanov R , Zhao J Z , Medarde M , Shi M , Yuan H Q , Pomjakushina E , Shiroka T
Published: August 2020

The tetragonal Mo5PB2 compound was recently reported to show superconductivity with a critical temperature up to 9.2 K. In search of evidence for multiple superconducting gaps in Mo5PB2, comprehensive measurements, including magnetic susceptibility, electrical resistivity, heat capacity, and muon-spin rotation and relaxation measurements were carried out. Data from both low-temperature superfluid density and electronic specific heat suggest a nodeless superconducting ground state in Mo5PB2. Two superconducting energy gaps Δ0 = 1.02 meV (25%) and 1.49 meV (75%) are required to describe the low-T electronic specific-heat data. The multigap features are clearly evidenced by the field dependence of the electronic specific-heat coefficient and the Gaussian relaxation rate in the superconducting state (i.e., superfluid density), as well as by the temperature dependence of the upper critical field. By combining our extensive experimental results with numerical band-structure calculations, we provide compelling evidence of multigap superconductivity in Mo5PB2.
Geological and physical-chemistry characterization of asphaltite from Colombian Middle Magdalena region
Authors: Bustos N , Jerez E , Paez L , Roa M
Published: August 2020

The massive consumption of fossil hydrocarbons and the absence of new conventional oil reserves, research on unconventional resources is prevalent. The Asphaltite is a substance with high energy value thanks to its composition of high molecular weight hydrocarbons, becomes an energy alternative in the future. In Middle Magdalena region of Colombia, Luna formation emerges with its members Salada, Pujamana, and Galembo of Upper Cretaceous age, which contains a deposit of this type of substances, which can become an economic and energy engine for the region. A representative sample of this asphaltite was taken in the Galembo Member (Top of Luna formation) and a geological description was made about its formation and occurrence in the area. The solubility of asphaltite was evaluated in two characteristic solvents for hydrocarbons, toluene and heptane, the first of aromatic character, with which it was possible to solubilize probably corresponding to the light fractions, while solubilization with heptane generated a precipitate Asphaltene, a nature that was corroborated by tests of visible infrared and ultraviolet spectroscopy, additionally an elementary analysis was performed to determine the concentrations of carbon, hydrogen, sulphur and oxygen. Finally, by means of thermogravimetry and differential scanning calorimetry an analysis was carried out to evaluate its energy potential, according to the results obtained, asphaltite samples are a promising energy resource.
Evaluation of a hyperbranched polyester polyol as plasticizing agent for composites of recycled polystyrene and rice husk
Authors: Sandoval N A , Cruz A P , Murillo E A
Published: August 2020

This study makes a contribution to the preparation of composites from recycled polystyrene and rice husk (it is mainly incinerated producing environmental contamination in Norte de Santander department-Colombia), which will contribute to reduce the accumulation of waste derivatives from polymeric and rice industries in this region. Hence, the aim of this work was to use a hyperbranched polyester as plasticizing agent and to evaluate its influence on the properties of the composites. The proportions of the recycled polystyrene and rice husk were 60 wt% and 40 wt% respectively. In the case of the polyester, were employed amount of 10 wt%, 20 wt%, 30 wt% and 40 wt%. Also was prepared a control sample (0 % of polyester). The results of infrared analysis evidenced changes in the absorption of the hydroxy groups. The thermogravimetric analysis showed that the first thermal decomposition of the composites decreased with the polyester content, but it did not follow the same trend on mechanical properties. The results of scanning electronic microscopy analysis allowed evidence that the fracture mechanism of the composite was fragile. The viscosity of the control sample was lower than that of the composites obtained with the polyester.
Applications of the Poisson and diffusion equations to materials science
Authors: Nolasco C , Jácome N J , Hurtado-Lugo N A
Published: August 2020

The scope of a variety of experiments involving the transfer of heat in engineering applications is evident in research on thermal studies throughout the department of Norte de Santander, Colombia. From the energy optimization processes in the brickworks of the province of Ocaña to the didactic use in the Universidad Francisco Santander, Ocaña, Colombia. In this sense, mathematical models will be a fundamental tool in the understanding of thermal transfer processes. The aim of this work is to establish a mathematical model by numerical methods to determine the physical process of heat transfer in liquid crystal. For the data acquisition, an experiment that measures thermal properties on an aluminum plate was designed. We proceed to propose a mathematical model that uses the Poisson equation. Also, we proceed to calculate the solution of the equation by the finite difference method and then make a comparison with the analytical solution and the experimental data.
A computational model of a natural language processing system for architectural technical debt management
Authors: Perez B , Castellanos C , Correal D
Published: August 2020

Technical debt is a concept applied to decisions taken to favor rapid production, at the expense of future capacities to evolve or improve the product or service. This concept is transversal to all sciences, especially in experimental physics and systems. However, technical debt is difficult to manage because there is a lack of time, expertise, or knowledge on how to perform it. This paper proposes a computational model of technical debt management in software architecture, based on observations made in software teams in their daily work. This computational model exploits natural language processing and model-testing techniques on software project artifacts to build a model that allows localizing and visualizing the impact produced by the technical debt and its payment strategies. This proposal aims to support teams of architects to explain the current and future impact of the debt injected as a result of decisions made.
Developing a theory based on the causes of technical debt injection into software projects in Colombia
Authors: Perez B , Castellanos C , Correal D
Published: August 2020

Engineering, like sciences such as physics, seeks to ensure that the conclusions reached can be verified through experiments, and that subsequent theories allow predictions to be made in future observations. This procedure is applied in this article, whose objective is the identification of the causes that favor the injection or presence of technical debt, and its application in software projects in Colombia, to build a theory that allows explaining this behavior. In turn, these causes could be also extrapolated to physical research projects. Results showed that “focus on producing more at the expense of quality” is the most cited cause in general. Conversely, “planning and management” is the most cited category of causes of technical debt. The concept of technical debt is well understood by software practitioners and that most efforts need to be invested by researchers on offering strategies and tools to support technical debt management.
Analysis of caffeine in energy drinks by ultra-fast liquid chromatography
Authors: Medina I Y , Rodríguez D C , Parra J W
Published: August 2020

The objective of this work was to standardize the method of analysis of caffeine and determine its content in three energy drinks (Vive 100, Peak and Red Bull) consumed in the Colombian market, which were selected based on the results of a significant survey conducted to 384 people in the metropolitan area of “San José de Cúcuta, Colombia”, from each energy drink two production lots were taken and in turn from each lot three drinks were taken for a total of 18, each one was analyzed in triplicate; caffeine concentration was determined on a Shimadzu Prominence ultra-fast liquid chromatograph. The average concentrations in mg of caffeine/L, for lot 1 were 256.96, 218.10 and 235.73 for drinks Vive 100, Peak and Red Bull, respectively and for lot 2, the respective values were 229.30, 233.86 and 238.33. As established in Resolution 4150 of 2009, the maximum limit allowed is 320 mg of caffeine/L, it was observed that the concentrations in all the energy drinks analyzed are lower, therefore, they are complying with the provisions of the law.
Evaluation of the influence of calcium carbonate on the firing process and sintering time
Authors: Guerrero-Gómez G , Afanador-García N , Noriega-Sánchez C J
Published: August 2020

This paper presents the use of calcium carbonate as an additive in the manufacturing process of ceramic bricks, in order to reduce the temperature and sintering time of the clays and to improve the quality of the products. In the study, samples of solid bricks with two different proportions were made. One was composed of 100% clay and the other of 70% clay and 30% calcium carbonate, which were fired in an intermittent kiln. The temperatures of the firing process were recorded using a virtual instrument. The samples manufactured were tested for water absorption and strength. The addition of calcium carbonate brought advantages such as an 8.66% decrease in fuel consumption, a 23.88% decrease in firing time, a 12.11% and 26.67% decrease in the firing temperature and gases released into the environment, respectively, as well as improvements in the quality of the product. The use of calcium carbonate as an additive decreased the time and temperature of ceramic firing and fuel consumption and increased energy efficiency, productivity and product quality, as well as reduced gas emissions into the environment.
Genetic Algorithm 3D Trajectory Planning Based on Digital Map Pre-processing for Tilt-rotor Aircraft
Authors: Gao Jiaxin , Zhang Qian , Yu Zelong
Published: August 2020

Tilt-rotor aircraft is a new type of aircraft which can take off and land vertically and cruise at high speed. It can be used to perform specific tasks by special departments such as public security or fire rescue. The terrain environment and threat of tasks are complex and changeable. In order to ensure flight safety, the flight trajectory should be planned in advance. As a global optimization algorithm simulating biological evolution process, genetic algorithm is mostly used in two-dimensional flight path planning. In this paper, the three-dimensional digital map is preprocessed according to the actual mission environment and constraints of the tiltrotor aircraft. The related genetic operators and individual evaluation function of the genetic algorithm are improved to reduce the calculation of the trajectory planning and effectively avoid the partial optimal solution. The simulation results show that after preprocessing the 3D digital map, a 3D mission trajectory with the best cost in the complex mission environment can be successfully planned by the improved genetic algorithm.
Experimental and Simulation Study on the Pool Fire of Low Pressure Atomizing Nozzle
Authors: Chen Jian , Fan Enxi
Published: August 2020

Bubble atomization technology, originated in the 1990s, has the advantages of simple structure, good atomization effect, low influence of liquid viscosity on atomization effect and low energy consumption. At present, it is widely used in the fields of combustion, spraying and fire fighting. In order to further expand the application field of bubble atomization, the possibility of applying bubble atomization to cooling and cooling is studied in this paper. In this paper, six types of bubble atomization nozzles with different structures are designed and a special experimental platform is built to measure the data of six types of nozzle. The flow characteristics, droplet size distribution, droplet velocity distribution and other parameters of six kinds of bubble atomizing nozzles were studied, and the experimental results were compared and analyzed. On this basis, Fluent simulation software was used in this paper to simulate the gas-liquid two-phase distribution, velocity distribution and spray velocity distribution at the nozzle outlet of the mixing chamber structure, so as to supplement and verify the experimental results. Different nozzle structures have great influence on the atomization effect of the bubble atomization nozzle. This conclusion will play a certain role in the design of the bubble atomization nozzle in the future.
Calculation Method of Aerodynamic Performance of Small Propeller with Serrated Trailing Edge
Authors: Lan Tian , Li Guoxi , Zhang Meng
Published: August 2020

The small propeller with serrated trailing edge of the UAV has the characteristics of low aerodynamic noise. In this paper, based on the momentum-leaf theory and modified the airfoil parameters, the aerodynamic performance calculation method of the propeller with a serrated tail structure is put forward. Combined with the CDF technology of three-dimensional aerodynamic performance analysis of small propeller blades at low Reynolds number, this method was used to calculate the aerodynamic performance of the small propeller with serrated tail structure, and the calculation results were experimentally verified. The experimental results show that, using the modified airfoil parameters, the established aerodynamic performance calculation method of the tail serrated structure propeller hover state has a good effect.
Current Situation and Prospect of Erosion Wear
Authors: Liang Na , Yuan Zhaohui , Wang Jiangtao , Kang Jian , Chu Yuanbo
Published: August 2020

The material loss and equipment failure caused by erosion wear is a serious problem in solid-liquid mixture flow in the mechanical, metallurgy, energy, building materials, transportation, aviation, aerospace, military and other industrial departments. Therefore, understanding the erosion wear mechanism, the influencing factors, and how to set up mathematical model are very important. Since the 1950s, the research on the erosion wear made great development. The purpose of this paper is to give a comprehensive review about previous research work of erosion wear. Firstly, the mechanism and influencing factors of erosion wear are introduced. Secondly, the forces of particle caused by fluid are analysed and several erosion models which tested by experimental with good results are introduced. Thirdly, the method of erosion numerical simulation combining computer software and CFD theory is introduced. Finally, based on the conclusion, some useful conclusions are drawn and the future research direction is prospected.
An Adaptive Searching Kriging Surrogate Model for Aerodynamic Optimization
Authors: Xu Liang , Tang Zhili , Feng Wenliang
Published: August 2020

The Kriging-based genetic algorithm applied to aerodynamic optimization design encounters a problem of unexpected sample size. In this paper, an adaptive method is proposed that the search space moves with the local optimum. The automatic division and hierarchical approximation of search space are realized by taking the selection of refinement samples into account. The typical function optimization and transonic supercritical airfoil drag reduction design are performed using this method. Results show that the number of samples required is greatly reduced, and the aerodynamic performance of the airfoil is efficiently improved.
Study of flow through and around a square cylinder array
Authors: Fang Yuhao , Yang Zhigang , Ma Yuan , Li Qiliang
Published: August 2020

This paper performs the effect of solid volume fractions (0.09< SVF<0.64) on the flow through and around a square cylinder array at Re=63832. A delayed vortex shedding occurs in 8x8 array (SVF) while the Strhoul number is slightly higher than the solid one. For the intermediate SVF (0.25<SVF<0.49), the separated shear layers (SSLs) contain large-scale turbulent eddies but their ends cannot interact to generate wake billows. The maximum of root mean square of transverse velocity along wake center-line decreases monotonously as SVF decreases, and several ways of defining the spatial extent of the wake region are discussed.
Experimental Research on Detection of Internal leakage of Valves in Pressure Air Pipes based on Acoustic Emission Technology
Authors: Wu Mengmeng , Dong Xiuchen , Yang Jiaxuan , Xue Shunyan
Published: August 2020

Valve leakage is a very important factor affecting the normal operation of pressure piping system. In this paper, based on the analysis of the mechanism of acoustic emission detection in the valve, under the condition of laboratory, the experimental platform and acoustic emission detection devices are designed and built. The experimental results show that acoustic emission technique can be used to detect leakage and evaluate leakage rate, which is very important for the real-time monitoring and quantitative detection of leakage in the pressure pipeline valve.
Experimental Equipment for Forced Convection Heat Transfer with Equilibrium Tracking
Authors: Zhang Zhigang , Sun Xiaoqin , Tang Lijun
Published: August 2020

Based on the principle of forced convection heat transfer in a single tube with air transverse sweep, an experimental device of forced convection heat transfer with equilibrium point tracking was developed. The device controls wind speed, heating power and other experimental working parameters by MCU, synchronously adjusting, collecting and analyzing working parameters in real time, to realize the tracking of thermal balance point. Newton cooling formula and criterion relation are adopted to calculate Nusselt number and Reynolds number automatically, to fit criterion relation and to display correlation curve automatically, and to realize automatic data analysis. The test results show that the experimental results are in good agreement with the empirical correlation formula within the Reynolds number range of 40 ~ 4000, which realizes the automatic tracking of thermal equilibrium point and meets the requirements of real-time automatic measurement in forced convection heat transfer experiment.
Effect of suction and blowing control on NACA 0012 airfoil at low Reynolds number
Authors: Zhang Zhiyong , Wang Tuantuan , Wang Yafei , Guo Hao
Published: August 2020

To control the separation of flow past an airfoil with a simple jet mechanism, based on the Large Eddy Simulation from Favre, a suction-blowing combined jet is studied with holes placed on a NACA0012 airfoil’s upper surface and Re = 104 attack angle α = 6°. The results show the control mode of front-hole suction and back-hole blowing is effective. It can suppress the disturbance in the flow field and increase the lift-to-drag ratio of the airfoil at the same time.
Validation of momentum source method in the analysis and prediction of the rotor finite ground effect in hover
Authors: Li Huan , Li Bin , Chen Jiangtao , Cui Pengcheng , Zhang Yaobing
Published: August 2020

Aiming at the complex flow phenomena with multiple speed scales and the high computational cost constraints of the rotor’s finite ground effect, the momentum source methods to satisfy the computational accuracy and efficiency are developed. Combined with the preconditioning methods, which cope with multiple speed scales, a numerical simulation method for the finite ground effect of the rotor is presented. On this basis, the validity of the numerical method is verified by hovering case firstly. The thrust only slightly increases by 3.26% compared with the experiment. Then, the effects of rotor deviation and height on the aerodynamic performance of the rotor are studied, and a surrogate mode with finite ground effect is established, which is tested by the testing samples on its prediction accuracy. The conclusion shows that the momentum source method can be applied to the analysis and prediction of the finite ground effect of rotor hovering, and the finite ground effect has a significant impact on the overall aerodynamic performance of the rotor.
Research on Stepless Force Control Strategy of Multistage Force Cylinder Based on Simulation
Authors: Bao Zhongfu , Zeng Dejiang
Published: August 2020

Aiming at the problem that the output force of the cylinder is small, this paper studies a method based on the simulation technology to obtain the larger output force and realize the stepless control of the output force. Through the simulation analysis, it can be seen that the system can achieve a more stable output force control when the system damping is large. There will be a certain amount of impact when each stage of cylinder is started.
Investigation on Battery Thermal Management of Power Battery Based on Environmental Impact of Electric Vehicle
Authors: Xiong Fei , Ouyang Chenzhi , Zeng Junxiong , Zhu Linpei , Li Gang
Published: August 2020

The present study on battery thermal management performance is mainly based on the research conducted in a single-pack environment, without considering the impact of the vehicle driving environment on the thermal performance of the power battery. Therefore, this paper conducts a research on the thermal management performance of the power battery and considers the effect of heat exchange under the driving conditions of the whole vehicle. In addition, the ohmic heat generation method of a battery pack in the process of charging and dis-charging is established in this paper. The complete heat exchange condition of a liquid cooling power battery is obtained and the research of thermal management performance is carried out. The results indicated that the tested temperature values at sensor NTC position are in good agreement with the predicted data. The maximum temperature deviation between numerical results and experiment data at the same temperature sensor (NTC) position is 1.4 °C, which demonstrates that the prediction accuracy of numerical simulation methods adopted in this paper is significantly high.
Design and optimization of air intake system based on FSC
Authors: Guo Huali , Fu Baogui , Huang Zitao , Zhang Ruibin
Published: August 2020

Based on the requirements of Formula Student China racing rules, the maximum diameter of the restrictor valve is 20mm in the intake system. In order to improve the engine charge coefficient and reduce the impact on performance caused by uneven air intake of each cylinder, it is quite necessary to redesign and analyse the air intake system under. Firstly, we calculate the volume of the pressure stabilizing chamber and the length of the intake manifold applied theoretical knowledge. Secondly, we redesign the model of intake system using UG software, which includes the parameter of the throttle angles for inlet and outlet, the intake manifold length, the volume of the pressure stabilizing chamber. By comparing and analysing the different data of inlet-outlet angles for the restrictor valve and the height of the baffle located in the stabilizing chamber, we can came to a conclusion after using CFD software that it is the optimal value when the inlet angle for throttle is 14 degree, the outlet angle is 22 degree and the height of the baffle is 10mm, the intake unevenness of each cylinder is 1.4%, and the total intake air is increased by 5.5%.
Sustainable Development Indicators in Benchmarks of Russia’s Regional Policy
Authors: Tyrsin Alexander N , Vasilyeva Elena V
Published: August 2020

We have considered the problem concerning the substantiation of sustainable development indicators and the improvement of the standard of living of the population in Russian regions. To quantify the standard of living of the population, we have used a common indicator such as the Human Development Index. The authors present an approach to managing the region in the form of optimization problems aimed at improving the standard of living of the region’s population by increasing the probability of its classification as a region with a higher standard of living. The optimization problem is solved based on the identified relationship between the standard of living of the region’s population and its socioeconomic indicators.
Assessment of energy efficiency of initiative budgeting projects in the Yamalo-Nenets Autonomous district
Authors: Tsurkan Marina , Serditova Natalia , Vorotnikov Aleksandr
Published: August 2020

Some approaches to evaluating energy-efficient initiative budgeting projects are presented on the example of Yamalo-Nenets Autonomous district, the region of the Arctic zone of the Russian Federation. Formulas and an algorithm for evaluating the effectiveness of budgeting initiative project implementation to improve the energy efficiency of housing and communal complex are developed. An evaluation approach for energy efficiency of street lighting systems is proposed based on basic and optional criteria.