bluuebunny/crossref_metadata_2025 huggingface dataset:
Creep Damage of a Re/Ru-Containing Single Crystal Nickel-Based Superalloy at Elevated Temperature
Authors: Zhao Guo Qi , Tian Su Gui , Zhang Shun Ke , Tian Ning , Liu Li Rong
Published: March 2019

By means of creep properties measurement, microstructure observation and contrast analysis of dislocation configuration, the creep behavior of a 4.5%Re/3.0%Ru-containing single crystal nickel-based superalloy at elevated temperature is investigated. Results show that the creep life of the alloy at 1040°C/160MPa is measured to be 725h to exhibit a better creep resistance at high temperature. In the primary stage of creep at high temperature, the γ phase in alloy has transformed into the N-type rafted structure along the direction vertical to the stress axis, the deformation mechanism of alloy during steady state creep is dislocations slipping in γ matrix and climbing over the rafted γ phase. In the latter period of creep, the deformation mechanism of alloy is dislocations slipping in γ matrix and shearing into the rafted γ phase. Wherein the dislocations shearing into the γ phase may cross-slip from {111} to {100} planes for forming the K-W locks to restrain the slipping and cross-slipping on {111} plane, which is thought to be the main reason of the alloy having a better creep resistance. As the creep goes on, the alternate slipping of dislocations results in the twisted of the rafted γ phase to promote the initiation and propagation of the cracks along the interfaces of γ/γ phase up to creep fracture, which is thought to be the damage and fracture mechanism of alloy during creep at high temperature.
Determination of Ratio of Yield Strength and Reduced Modulus during Cold Work Processing in 304 Austenitic Stainless Steel
Authors: Li Kai , Xue He , Zhao Kuan , Wang Shuai , Wang Ting , Song Rui Han
Published: March 2019

304 austenitic stainless steel is a common structural material used in the nuclear power plant, and its basic mechanical property would be changed by work hardening, which seriously affects the evaluation of the integrity of the nuclear power structure. The relationships of between the yield strength and the reduced modulus ratio (σ0.2/Er) with the residual indentation depth and maximum depth ratio (hr/hm) during cold work processing of 304 austenitic stainless steel is analyzed by using theoretical analysis, experiment and finite element simulation, and an approximate analytical model to expressσ0.2/Erbyhr/hmis established in this paper. The investigating results indicate that yield strength, Vickers hardness, andσ0.2/Erwill increase, andhr/hmdecreases with the material deformation increasing, and the analytical result of theσ0.2/Erbasically consistent with the experiment result.
Effect of Pre-Strain on Small Punch Creep Test of 316L Stainless Steel at 373K
Authors: Li Kai Shang , Peng Jian
Published: March 2019

Creep does not only appear at high temperature, but also appears at low temperature for 316L stainless steel that threatens the safety of equipment. In this work, the creep behavior of as-received and pre-strained 316L stainless steel at 373K was investigated by uniaxial creep (UC) tests and small punch creep (SPC) tests. The parameters of power-law creep model were determined from stress dependence of UC tests. Then, the creep behavior of SPC test was analyzed by finite element (FE) simulation combined with power-law creep model. Comparing with experimental creep deflection, the results of FE simulation can reasonably reflect the creep behavior of as-received and pre-strained small punch specimens. Based on the comparison of as-received specimen and pre-strained specimen from UC test, SPC test and FE simulation, pre-strain significantly restrains creep behavior of 316L austenitic steel at 373K.
Creep Void Formation and Rupture Lifetime in Multiaxial Stress States
Authors: Sakane Masao , Kobayashi Hiroki , Ohki Ryohei , Itoh Takamoto
Published: March 2019

This paper discusses creep void formation and rupture lifetimes in multiaxial stress states for a SUS 304 stainless steel at elevated temperatures. Biaxial and triaxial tension creep tests were performed using a cruciform and a cubic specimen, respectively. These two types of the specimens were designed to achieve uniform equi-biaxial and equi-triaxial stress distributions by a finite element analysis in the gage parts. Void formation at grain boundaries was observed by intermitting biaxial creep tests and by interrupting triaxial creep tests. Creep rupture lifetimes were also obtained in biaxial and triaxial creep tests. Biaxial stresses increase the void formation but give a little influence on a creep rupture lifetime in the correlation with von Mises equivalent stress. Triaxial stresses also increase the void formation and drastically reduce a creep rupture lifetime in the correlation with von Mises equivalent stress. Evident void formation in an equi-triaxial stress condition demonstrates that von Mises equivalent stress is not a suitable measure to evaluate creep damage development in multiaxial stress states. A new equivalent stress is proposed to evaluate creep rupture lifetimes in biaxial and triaxial stress states.
Determination of Material Fracture Toughness by Circular Pre-Cracked Small Punch Test Specimens
Authors: Wang Wu Lin , Wang Du Wei , Guan Kai Shu
Published: March 2019

Fracture toughness empirical correlation between SPT(Small Punch Test) with non-crack sample and standard fracture toughness test has been established in recent years. In order to compensate the imperfection of empirical correlation, such as absence theoretical basis, poor repeatability and universality, in this paper, an O-type pre-cracked sample was adopted to evaluate fracture toughness. The mechanical model of the sample is in compliance with plane strain condition in the direction of crack propagation. In this paper a determination procedure was studied and established, and the J-integral of steel Q345R was calculated using the procedure.
Modelling of Hysteresis Behavior of Ceramic Matrix Composites
Authors: Teng Xue Feng , Shi Duo Qi , Yang Xiao Guang
Published: March 2019

Under cyclic loading, the fiber-reinforced ceramic matrix composites exhibits hysteresis behavior due to the friction stress. When the matrix/fiber debonding occurs, the shear stress is transferred by friction stress on the debond surface. The friction stress is derived from the equilibrium equation of debond fiber in the unit cell. The result indicates that friction shear stress of a single debond fiber can be described by bilinear law due to the static friction and sliding friction. The nonlinear characteristic of friction stress at macro scale attributes to the distribution of the fiber pullout length. The hysteresis loops arise due to the friction stress and the shape is dominated by the evolution of friction during loading/unloading process. The model decoupled the shear stress into two independent terms: the first term represents the shear stress on well bond interface and the second term represents friction shear stress on debond interface. The method developed in this paper is employed to study the hysteresis behavior of C/SiC composite subjected to arbitrary cyclic load. The hysteresis behavior of C/SiC composite is predicted and compared with experimental data.
Effects of Hydroforming Process on Fatigue Life of Reinforced S-Shaped Bellows
Authors: Yuan Zhe , Huo Shi Hui , Ren Jian Ting
Published: March 2019

Reinforced s-shaped bellows, which can withstand high pressure, is a kind of typical reinforced metal bellows. The reinforced s-shaped bellows mainly uses the hydroforming process, and the forming process is a severe plastic deformation process. The hydroforming process and its effects on the fatigue life of reinforced s-shaped bellows were discussed in the present study. Different levels of plastic strain and wall thickness thinning were detected in the hydroforming process. The maximum plastic strain can reached 32%, while the maximum wall thickness thinning ratio is 20%, which occurs on the wave peak. Mechanical characteristics of reinforced s-shaped bellows were discussed considering the effects of hydroforming process. The maximum stress appears on the upper and lower ends, which is the weak part of the structure. Fatigue life of the reinforced s-shaped bellows was analyzed based on the modified Manson-Coffin method. Mechanical properties of related materials, which can be more accurate consideration the effects of hydroforming process, were tested under the pre-plastic deformation. Fatigue life analysis of reinforced s-shaped bellows was carried out and the effects of hydroforming process were discussed. The hydroforming process will lead to a decline in fatigue life, which needs to be considered well in the structural design and analysis. Keywords: Reinforced s-shaped bellows, Hydroforming process, Fatigue life, Mechanical characteristics.
Research on Brittle Fracture of X70/X80 Line Pipes with Big Wall Thickness at Low Temperature
Authors: Wang Hai Tao , Li Shi Li , Luo Yan Long , Wang Jun Qiang , Zhang Hai Bin , Lin Nan
Published: March 2019

Based on research of the low temperature fracture property of high grade steel pipe, it shows that X70, X80 steel pipe and X80 tee have high Charpy impact toughness. However, as the wall thickness increases, the shear area of DWTT decreases rapidly, and the thickness effect is significant. The research results show that the original wall thickness impact specimen fracture of steel pipe may not be ductile, for design temperature less than -30°C and wall thickness greater than 40mm. The brittle fracture was caused by structural factors. The Charpy impact energy, which just reflects the toughness of materials, does not show the fracture appearance as it would occur in service, because of the different specimen geometry and high rate of impact. The brittle fracture can occur at low temperature and low stress even with a high Charpy impact energy, the conditions of brittle fracture should be established under combination of the wall thickness, temperature and other factors. In this work, it is clarified that measurement of the fracture toughness under service temperature should be used to control low stress brittle fracture, besides the Charpy impact energy to ensure the material toughness.
Effects of T-Stress on Fracture Behavior of Central-Cracked Stiffened Plate
Authors: Huang Xing Ling , Liu Ying Hua
Published: March 2019

Traditionally, the stress intensity factor (SIF) is solely focused on in the fracture analyses of stiffened plate, while the T-stress is usually ignored. However, the fracture toughness is influenced by T-stress and the effects need to be studied. By means of three-dimensional finite element method, the characteristics of mode I SIF and in-plane T-stress are investigated in the double symmetrical central stiffened plate (DSC-SP). Then the fracture toughness is corrected with in-plane T-stress based on the two-parameter model in the R6 assessment procedure. Lastly, the curves of corrected fracture toughness and crack arrest effect are obtained in the stiffened plate. The results show that the T-stress is dependent on the size and integrity of the stiffener, and has significant effects on the fracture toughness of stiffened plate. Compared with the traditional estimation of the crack arrest effect of the stiffener, the evaluation is more reasonable when the influences of in-plane T-stress are taken into account.
Research on the Micro-Mechanical State at Tip of Environmentally Assisted Cracking Based on Latin Hypercube Sampling Method
Authors: Zhao Kuan , Xue He , Zhao Ling Yan
Published: March 2019

Environmentally assisted cracking (EAC) of nickel-based alloys is one of the most significant potential safety hazards in the primary circuit of nuclear power plants. To understand the influence of randomness on micro-mechanical state at tip of EAC, Latin hypercube sampling method is applied to analyze the uncertainty of stress-strain in the oxide film at the EAC tip considering the uncertainties of load and material properties of base metal and oxide film. Meanwhile, to improve the efficiency of numerical analysis, MATLAB is employed in the secondary development for ABAQUS. With the help of finite element numerical simulation and Latin hypercube sampling method, the uncertainty of mechanical properties at tip of EAC in one-inch compact tension specimen is simulated and analyzed in this study. The results show that the randomness of material properties and load markedly affect the uncertainty of micro-mechanical state. Among the variables, The randomness of load has the greatest influence on uncertainty of strain, and Poisson`s ratio of oxide film is the smallest effect.
A more Accurate Constraint Parameter to Characterize the Creep Constraint Effect at Crack Tip of Cr-Mo-V Steel
Authors: Luo Yun , Zhang Qian , Jiang Wen Chun
Published: March 2019

A suitable constraint parameter is a key to quantify the creep crack tip constraint levels. In this study, a new more accurate creep constraint parameter As of brazed joint was proposed based on the existing constraint parameters R* and Ac. The CCG rate equation of Cr-Mo-V steel related to the constraint parameter As is obtained. The results show that the constraint parameter As is basically unchanged with the increase of creep time. The crack growth data predicted by the constraint dependent CCG rate equation are in good agreement with the experimental data. The established constraint dependent CCG rate equation can predict the CCG rate at other constraint levels very well.
Effects of Curing Temperature and Pressure on the Mechanical Properties of Gasket Material Used for Polymer Electrolyte Membrane Fuel Cells
Authors: He Ri Dong , Wang Zhi Qiang , Tan Jin Zhu , Yin Li , Liu Zeng Hui
Published: March 2019

The long-term mechanical stability of the gasket material is critical to sealing and electrochemical performance of the polymer electrolyte membrane (PEM) fuel cells. In this paper, the silicone rubber material, which is being considered as gasket material for PEM fuel cells, was fabricated at different curing temperatures and different curing pressures. Effects of the curing temperatures and curing pressures on the mechanical properties of the silicone rubber material were investigated. The tensile test results show that tensile strength of the specimen cured at the curing temperature of 160 was larger than that for the specimens cured at the curing temperature of 150 or 170 under the same curing pressure. The test results of the compression stress-strain, compression set and compression stress relaxation show that the curing temperature and curing pressure affected significantly the compression elastic modulus, compression set rate and compression stress relaxation behavior. It is found that the silicone rubber material cured at the curing temperature of 160 under the curing pressure of 10MPa had good compression mechanical properties compared to the materials cured at the other curing temperatures and curing pressure in this work.
Study on Anti-Tumor Activity of Novel 3-Substituted 4 Anilino-Coumarin Derivatives Using Quantitative Structure-Activity Relationship (QSAR)
Authors: Putri Daratu E.K. , Pranowo Harno Dwi , Haryadi Winarto
Published: March 2019

Study on anti breast cancer activity of 3-substituted 4-anilino coumarin derivatives by using quantitative structure-activity relationship (QSAR) has been performed. The structures and the activity data were literatured from Guoshun et al. experiment. The molecular and electronic molecule properties were obtained from DFT/BPV86 6-31G method calculation after was through methods validation. The QSAR analysis were shown by Multi Linear Regression method (MLR). The best model of obtained for 3-substituted 4-anilino coumarin derivatives is: Log IC50 = 5.905 + (0.936 x qC1) + (-8.225 x qC8) + (-0.582 x qC13) + (11.273 x qC15) + (0.869 x ∆E) ; n = 26; r2= 0.704; Fcal/Ftab = 2.462; SEE = 0.184.
Polyacrylamide Coated on Quartz Crystal Microbalance Electrodes for Highly Sensitive Sensor of Acetic Acid
Authors: Rizani Ahmad , Winingsih Sulis Setyawati , Rianjanu Aditya , Julian Trisna , Nur Hidayat Shidiq , Kusumaatmaja Ahmad , Roto Roto , Triyana Kuwat
Published: March 2019

In many cases, acetic acid is categorized as hazardous to health. A high-performance sensor for detecting acetic acid is urgently required. This study aims to observe the characteristics of quartz crystal microbalance (QCM) coated with polyacrylamide as an acetic acid sensor. For this purpose, we prepared the sensor by firstly coating with 1-dodecanethiol (using self-assembled-monolayers or SAM technique) followed subsequently by glutaraldehyde and polyacrylamide (PAM).As results, the sensors showed less sensitivity to humidity changes, which is one of the basic prerequisites for a stable sensor to an environment. We also obtained that the sensor showed relatively fast response time and high sensitivity to acetic acid vapor of about 96 seconds and 12.9 Hz/(mgL-1), respectively. Further research, however, is still required to improve the sensitivity and specificity by choosing more selective polymers.
Antibacterial Activity of TiO2-Ag-Nanoparticle under Visible Light
Authors: Wahyuni Endang Tri , Roto Roto , Prameswari Mirma
Published: March 2019

A visible active antibacterial agent, namely TiO2-Ag-Nanoparticle has been prepared, characterized, and examined to combat E.coli bacteria in the present of the visible light. The preparation was carried out by reduction of AgNO3solution over TiO2photocatalyst under UV light exposure. TiO2-Ag nanoparticle was characterized using XRD, SEM and DRS instruments. The activity as an antibacterial agent has been tested for disinfection of E. coli bacteria in the contaminated well water. The antibacterial assay was carried out by visible light irradiation of the contaminated well water in the present of TiO2-Ag, as well as TiO2for comparison, for the various period. The antibacterial performance was represented as the number of the bacteria determined by colony counting method. Their XRD patterns probe that the Ag doping leads to the crystalline of TiO2partially destroyed and the average particle size of TiO2in TiO2-Ag is larger thanTiO2bare, and no peaks of Ag metal appeared, implying that the Ag silver is very small(nanoparticle) that may be inserted into the TiO2crystal lattice. Based on the DRS spectra it is observed that TiO2-Ag has visible light absorption meanwhile TiO2only can absorb the UV light. The antibacterial assessment demonstrates that the TiO2-Ag has high performance in the bacterial inactivation under visible light. Meanwhile, very low activity is shown by TiO2. Moreover, the increase of Ag loaded gives rise in the bacterial inactivation, but further increase leads to the inactivation slightly reduced. The extension time of the visible light exposure is found to promote more effective antibacterial process up to maximum level, and no effect was observed with the much longer time. It is also confirmed that a small amount of Ag is dissolved from TiO2-Ag NP during the antibacterial testing.
Synthesis and Characterization of Mg(OH)2-Impregnated Activated Carbon Adsorbent from Coconut Shell
Authors: Saputra Andri , Sulistyo Hary , Swantomo Deni
Published: March 2019

Introducing or impregnating Mg(OH)2onto activated carbon is a promising path for wastewater treatment of uptake (removal) uranium from aqueous solution. The present study aims to synthesize and characterize Mg(OH)­2-impregnated activated carbon from coconut shell. The introducing or impregnating Mg(OH)2into treated biochar by activation method using various impregnation ratio (IR) of MgCl2(IR = 0.5; 1.0; 2.0). Characterization of functional groups in produced activated carbon was conducted with the aid of FTIR spectroscopy. The presence of O-H or Mg(hydroxyl) bond was confirmed by FTIR analysis at 3343.50 cm-1with the highest intensity of the obtained peak at impregnation ratio (IR) 2.0. Due to the surface area is one of the important factors that control a material’s ability to adsorb contaminations, the surface area of activated carbon was measured about 353-358 m2/g by BET method. To indicate that introducing or impregnating Mg(OH)2or Mg(hydroxyl) into treated carbon is successfully work, the presence of Mg (%w) in activated carbon was performed using X-Ray Fluorescence Analysis with the highest Mg presence about 28.587 (%w) at impregnation ratio (IR) 2.0.
Effect of SiH4 Flow Rates on the Structures and Properties of Si-Rich Silicon Nitride Films Prepared by Hot Wire Chemical Vapor Deposition
Authors: Tian Yan Sai , Gao Ai Ming , Zhou Bing Qin
Published: March 2019

Silicon-rich silicon nitride thin films were deposited on the P type (100) of silicon and Corning7059 glass by hot-wire chemical vapor deposition method using SiH4 and NH3 as reaction gas source. The effects of SiH4 flow rate on the structures and optical properties of the thin films were studied under optimizing other deposition parameters. The structures, band gap width and surface morphology of the thin films were characterized by Fourier transform infrared absorption spectroscopy (FTIR), ultraviolet-visible (UV-VIS) light transmittance spectra and scanning electron microscope (SEM), respectively. The experiment results show that, with increasing of the SiH4 flow rate, the content of N and Si atoms in the thin films increases, and the Si-N bond density increases gradually, and the optical band gap of the films shows a trend of increasing. When the silane flow rate is less than 0.9sccm, there is no Si-H bond stretching vibration absorption peak, and silicon atoms mainly bond with nitrogen atoms. As the SiH4 flow rate decreases, silicon clusters embedded in silicon nitride matrix gradually become smaller. When SiH4 flow rate is 0.4sccm, we prepared the silicon cluster nanoparticles with an average diameter of about 50nm embedded in silicon nitride thin films matrix. Therefore, properly reduction of the SiH4 flow rate is favorable for preparing the smaller silicon cluster nanoparticles in silicon rich silicon nitride thin films. The results lay the foundation for the preparation of silicon quantum dots thin film materials.
Organic Field-Effect Transistors Based on 3’-Flouro-2,2',6,6'-Tetraphenyl-4,4'-Dipyranylidene
Authors: Bolag Altan , Yamashita Yoshiro
Published: March 2019

In this work, 3’-flouro-2,2',6,6'-tetraphenyl-4,4'-dipyranylidene (3FDP) was originally synthesized and investigated with density functional theory (DFT) calculations, ultraviolet–visible spectroscopy (UV–Vis) and cyclic voltammetry (CV) in comparison with 2,2',6,6'-tetraphenyl-4,4'-dipyranylidene (DP) and 4’-flouro-2,2',6,6'-tetraphenyl-4,4'-dipyranylidene (4FDP). 3FDP-based organic field-effect transistors (OFETs) were fabricated with bottom contact configuration on bare SiO2/Si substrate, 1,1,1,3,3,3-hexamethyldisilazane (HMDS) and octadecyltrichlorosilane (OTS) treated substrate, respectively. The HMDS-treated device showed highest mobility of 4 × 10−4 cm2 V−1 s−1, on/off ratio of 4 × 103 and threshold voltage of −10 V. Finally, vacuum deposited 3FDP films morphology was investigated by X-ray diffraction (XRD) analyses and the results showed higher crystallinity of HMDS-treated 3FDP film compared to the OTS-treated film, leading to a better FET performance.
Estimation of the Critical Temperatures of Order-Disorder Phase Transitions in Cu-Au Alloys Using Short-Range Order Parameters
Authors: Enkhtor Lhkamsuren , Silonov Valentin
Published: March 2019

An expression for calculating the critical temperature of order-disorder transition in face-centered cubic alloys is developed with accounting of pairwise interatomic potential in the first eleven shells. Obtained expression was applied for the estimation of critical temperatures at Cu3Au, CuAu, and CuAu3 alloys in comparison with experimental data from phase diagram of Cu-Au system. Magnitudes of the pairwise interatomic potential in considered alloys was computed using values of the short-range order parameters which were experimentally obtained from X-ray diffuse scattering intensity. In this computation, the Krivoglaz-Clapp-Moss approximation and Cowley equations were applied.
Structural Features of Products Formed during DC Arc Discharge in Water
Authors: Vanchinkhuu Jigmeddorj , Bat-Erdene Baasandorj , Bayanjargal Erdene , Gerelmaa Orgilsaikhan
Published: March 2019

Products formed in the discharge region of the DC arc between graphite electrodes in water were studied. Whereas one of them was grown on a cathode and kept whole, the other is arose by erosion of electrodes in powder form and sank or floated in the surrounding water. The structure of the products was studied by SEM and SEM EDX analysis. The whole parts grown on the cathode were made up three different components: (i) almost spherical tiny particulates; (ii) long and narrow linear parts; and (iii) macro particulates of gigantic size. We have identified the size distributions and the number densities for these component parts in the sample as well their mechanical features. The powder samples included bulk particulates of carbon sheets and linear structures, like a thread. The study shows that the long linear structures in the powder sample are formed by the scrolling of carbon layers whereas the ones deposited are formed by a growth mechanism
Notch Signaling Controls Transcription via the Recruitment of RUNX1 and MYB to Enhancers during T Cell Development
Authors: Rodríguez-Caparrós Alonso , García Vanina , Casal Áurea , López-Ros Jennifer , García-Mariscal Alberto , Tani-ichi Shizue , Ikuta Koichi , Hernández-Munain Cristina
Published: March 2019

Tcrd and Tcrg display identical developmental programs that depend on the activity of the enhancers Eδ and Eγ being “on” in pre–β-selection thymocytes to activate transcription and V(D)J recombination of the unrearranged genes and “off” in post–β-selection CD4+CD8+ double-positive thymocytes to inhibit transcription of the rearranged genes and avoid the expression of TCR δ- and TCR γ-chains in αβ T lymphocytes. Eδ and Eγ activity depends on transcription factor binding to essential Runx and Myb sites and parallels that of Notch signaling. We performed Notch gain- and loss-of-function experiments and found that Notch signaling activates Tcrd and Tcrg transcription by favoring the recruitment of RUNX1 and MYB to the enhancers. Our results suggest that the dissociation of RUNX1 and MYB from Eδ and Eγ chromatin in double-positive thymocytes, which results in enhancer inactivation, is caused by decreased Notch signaling triggered by pre-TCR signaling, thereby deciphering the molecular mechanism of Tcrd and Tcrg silencing during β-selection. These findings reveal a novel molecular mechanism for gene regulation via Notch signaling through the recruitment of RUNX1 and MYB to enhancer chromatin during thymocyte development.
Real Hypersurfaces in the Complex Quadric with Lie Invariant Structure Jacobi Operator
Authors: Suh Young Jin , Kim Gyu Jong
Published: March 2019

We introduce the notion of Lie invariant structure Jacobi operators for real hypersurfaces in the complex quadric$Q^{m}=SO_{m+2}/SO_{m}SO_{2}$. The existence of invariant structure Jacobi operators implies that the unit normal vector field$N$becomes$\mathfrak{A}$-principal or$\mathfrak{A}$-isotropic. Then, according to each case, we give a complete classification of real hypersurfaces in$Q^{m}=SO_{m+2}/SO_{m}SO_{2}$with Lie invariant structure Jacobi operators.
La criminalización mediática en los discursos sobre la escuela argentina
Authors: Saez Virginia
Published: March 2019

Este artículo presenta un estudio exploratorio que analiza la criminalización mediática en los discursos sobre episodios de violencia en las escuelas, en la prensa argentina durante el período 1993-2011. Dadas las características del objeto de indagación, el abordaje metodológico fue cualitativo y la información se analizó en el marco del análisis socioeducativo del discurso. Entre los resultados observamos que la presentación de los episodios se limita a los estudiantes como responsables de las situaciones de violencia,  se propone soluciones punitivas y se describe la institución escolar como incapaz de resolver los conflictos que allí se mencionan. Las estrategias comunicacionales utilizadas por la prensa coinciden en naturalizar el accionar de las fuerzas de seguridad.  Concluimos que la criminalización mediática forma parte de una dinámica de estigmatización social. Por su originalidad, este estudio constituye un antecedente para futuras indagaciones sobre las representaciones mediáticas del espacio escolar.
Traduciendo políticas de convivencia escolar: Análisis de dispositivos sociotécnicos en Argentina y Chile
Authors: López Verónica , Litichever Lucía , Valdés René , Ceardi Andrea
Published: March 2019

Los dispositivos sociomateriales son claves para comprender la traducción de políticas públicas en prácticas locales. En este artículo describimos y analizamos comparativamente políticas y prácticas de abordaje de la convivencia escolar en Chile y Argentina, desde una perspectiva de la Teoría de Actor Red (ANT), con foco en dos dispositivos sociotécnicos: el libro de clase y sus respectivas anotaciones positivas y negativas; y la nota de cargo, utilizados en Chile y Argentina respectivamente para la implementación y regulación de la convivencia. La metodología incluyó observaciones no participantes, entrevistas en profundidad y análisis comparativo de los dispositivos y las regulaciones sociales que éstos proponían. Se consideraron cuatro ejes de análisis: la resolución de los conflictos, la participación de los estudiantes, la formación para la ciudadanía, y la construcción de estudiantes como sujetos. Los resultados indican que ambos dispositivos conforma una red de relaciones sociomateriales que posicionan a los estudiantes de forma distinta con implicancias también distinguibles en cuanto a su participación en la (auto versus hetero) regulación del comportamiento y la construcción de estudiantes-sujetos dentro del sistema escolar.
Respeto docente y convivencia escolar: Significados y estrategias en escuelas chilenas
Authors: Carrasco-Aguilar Claudia , Luzón Trujillo Antonio
Published: March 2019

En la actualidad, el profesorado chileno se encuentra atravesando una crisis de devaluación de su rol producto de múltiples políticas neoliberales, aunque muchos se consideren al mismo tiempo, como valorados por su estudiantado y comunidad cercana. La pérdida del respeto a su autoridad debido a esta devaluación, es enfrentada a través de estrategias con múltiples enfoques y consecuencias, lo que deja en evidencia cómo el rol docente tiene un profundo impacto en la convivencia escolar. Este estudio buscó describir y analizar significados y estrategias en torno al respeto docente, y su relación con la convivencia escolar. Se realizó un estudio basado en la Teoría Fundamentada, entrevistando a docentes, estudiantes, familias y personal escolar. El análisis de contenido mostró diversidad de significados de respeto docente, y un continuo de estrategias que se ubican en dos polos: obediencia-autoritarismo, y reconocimiento-valoración-cercanía. Los resultados se discuten en torno a las políticas actuales, el contexto de vulnerabilidad socioeducativa en el que trabaja el profesorado de este estudio, y las consecuencias que estas estrategias tienen para una convivencia escolar amónica.
Polyols and glucose particulate species as tracers of primary biogenic organic aerosols at 28 French sites
Authors: Samaké Abdoulaye , Jaffrezo Jean-Luc , Favez Olivier , Weber Samuël , Jacob Véronique , Albinet Alexandre , Riffault Véronique , Perdrix Esperanza , Waked Antoine , Golly Benjamin , Salameh Dalia , Chevrier Florie , Oliveira Diogo Miguel , Bonnaire Nicolas , Besombes Jean-Luc , Martins Jean M. F. , Conil Sébastien , Guillaud Géraldine , Mesbah Boualem , Rocq Benoit , Robic Pierre-Yves , Hulin Agnès , Le Meur Sébastien , Descheemaecker Maxence , Chretien Eve , Marchand Nicolas , Uzu Gaëlle
Published: March 2019

Abstract. A growing number of studies
are using specific primary sugar species, such as sugar alcohols or primary saccharides,
as marker compounds to characterize and apportion primary biogenic organic aerosols
(PBOAs) in the atmosphere. To better understand their annual cycles, as well as their
spatiotemporal abundance in terms of concentrations and sources, we conducted a large
study focusing on three major atmospheric primary sugar compounds (i.e., arabitol,
mannitol, and glucose) measured in various environmental conditions for about 5300 filter
samples collected at 28 sites in France. Our results show significant atmospheric
concentrations of polyols (defined here as the sum of arabitol and mannitol) and glucose
at each sampling location, highlighting their ubiquity. Results also confirm that polyols
and glucose are mainly associated with the coarse rather than the fine aerosol mode. At
nearly all sites, atmospheric concentrations of polyols and glucose display a well-marked
seasonal pattern, with maximum concentrations from late spring to early autumn, followed
by an abrupt decrease in late autumn, and a minimum concentration during wintertime. Such
seasonal patterns support biogenic emissions associated with higher biological metabolic
activities (sporulation, growth, etc.) during warmer periods. Results from a previous
comprehensive study using positive matrix factorization (PMF) based on an extended
aerosol chemical composition dataset of up to 130 species for 16 of the same sample
series have also been used in the present work. The polyols-to-PMPBOA ratio
is 0.024±0.010 on average for all sites, with no clear distinction between traffic,
urban, or rural typology. Overall, even if the exact origin of the PBOA source is still
under investigation, it appears to be an important source of particulate matter (PM),
especially during summertime. Results also show that PBOAs are significant sources of
total organic matter (OM) in PM10 (13±4 % on a yearly average, and up to
40 % in some environments in summer) at most of the investigated sites. The mean PBOA
chemical profile is clearly dominated by contribution from OM (78±9 % of the mass
of the PBOA PMF on average), and only a minor contribution from the dust class
(3±4 %), suggesting that ambient polyols are most likely associated with
biological particle emissions (e.g., active spore discharge) rather than soil dust
resuspension.
The interference of tetrachloromethane in the measurement of benzene in the air by a gas chromatography–photoionisation detector (GC-PID)
Authors: Romero-Trigueros Cristina , González María Esther , Doval Miñarro Marta , González Ferradás Enrique
Published: March 2019

Abstract. The European Union requires that benzene in the air is continuously measured due
to its toxicity and widespread presence in the population nuclei, mainly
motivated by vehicle emissions. The reference measuring technique is gas
chromatography (GC). Automatic chromatographs used in monitoring stations
must verify the operating conditions established in Standard EN 14662 part 3,
which includes a type approval section with a number of tests that analysers
must pass. Among these tests, the potential interference of a number of
compounds is evaluated. The 2005 version of the mentioned standard requires
the evaluation of the potential interference of tetrachloromethane (TCM). The
2015 version eliminates TCM as a potential interferent. Although most
consumer uses of TCM have been banned, recent studies have measured
significant concentrations of TCM in the air. In this paper, the potential
interference of TCM in benzene measurements obtained with gas chromatography
coupled to a photoionisation detector (GC-PID) has been investigated. Our study
shows that the simultaneous presence of benzene and TCM causes a significant
decrease in benzene readings. For TCM concentrations of 0.7 µg m−3
(typical of urban areas) and 4.5 µg m−3 (detected in the vicinity
of landfills), the relative errors in benzene measurements were 34 % and 70 %, respectively, which are far too high compared to the maximum overall
uncertainty allowed for benzene measurements (25 %). Possible mechanisms
to qualitatively and quantitatively explain the behaviour of the PID when
measuring benzene with and without TCM have been proposed.
Fluvial sedimentary deposits as carbon sinks: organic carbon pools and stabilization mechanisms across a Mediterranean catchment
Authors: Martínez-Mena María , Almagro María , García-Franco Noelia , de Vente Joris , García Eloisa , Boix-Fayos Carolina
Published: March 2019

Abstract. The role of fluvial sedimentary areas as organic carbon sinks
remains largely unquantified. Little is known about mechanisms of organic
carbon (OC) stabilization in alluvial sediments in semiarid and subhumid
catchments where those mechanisms are quite complex because sediments are
often redistributed and exposed to a range of environmental conditions in
intermittent and perennial fluvial courses within the same catchment. The
main goal of this study was to evaluate the contribution of transport and
depositional areas as sources or sinks of CO2 at the catchment
scale. We used physical and chemical organic matter fractionation techniques
and basal respiration rates in samples representative of the three phases of
the erosion process within the catchment: (i) detachment, representing the
main sediment sources from forests and agricultural upland soils, as well as
fluvial lateral banks; (ii) transport, representing suspended load and
bedload in the main channel; and (iii) depositional areas along the channel,
downstream in alluvial wedges, and in the reservoir at the outlet of the
catchment, representative of medium- and long-term residence deposits,
respectively. Our results show that most of the sediments transported and
deposited downstream come from agricultural upland soils and fluvial lateral
bank sources, where the physicochemical protection of OC is much lower than
that of the forest soils, which are less sensitive to erosion. The protection
of OC in forest soils and alluvial wedges (medium-term depositional areas)
was mainly driven by physical protection (OC within aggregates), while
chemical protection of OC (OC adhesion to soil mineral particles) was
observed in the fluvial lateral banks. However, in the remaining sediment
sources, in sediments during transport, and after deposition in the reservoir
(long-term deposit), both mechanisms are equally relevant. Mineralization of
the most labile OC (the intra-aggregate particulate organic matter
(Mpom) was predominant during transport. Aggregate formation and OC
accumulation, mainly associated with macroaggregates and occluded
microaggregates within macroaggregates, were predominant in the upper layer
of depositional areas. However, OC was highly protected and stabilized at the
deeper layers, mainly in the long-term deposits (reservoir), being even more
protected than the OC from the most eroding sources (agricultural soils and
fluvial lateral banks). Altogether our results show that both medium- and
long-term depositional areas can play an important role in erosive areas
within catchments, compensating for OC losses from the eroded sources and
functioning as C sinks.
Taking a Breath of the Wild: Are geoscientists more effective than
non-geoscientists in determining whether game-world landscapes
are realistic?
Authors: Hut Rolf , Albers Casper , Illingworth Sam , Skinner Chris
Published: March 2019

Abstract. From the wilderness of Hyrule, the entire continent of Tamriel, to Middle Earth, players of videogames are exposed to wonderous, fantastic, but ultimately fake, landscapes. Given the time people may spend in these worlds, compared to the time they spend being trained in geoscience, we wondered if expert geoscientists would differ from non-geoscientists in whether they judge the landscapes in these games to be realistic. Since games have a great opportunity for tangential learning it would be a missed opportunity if it turns out that features obviously fake to geoscientists are perceived as plausible by non-geoscientists. To satisfy our curiosity and answer this question we conducted a survey where we asked people to judge both photos from real landscapes as well as screenshots from the recent The Legend of Zelda: Breath of the Wild videogame on how likely they thought the features in the picture were to exist in the real world. Since game-world screenshots are easily identified based on their rendered, pixaleted nature, we pre-processed all pictures with an artistic Van Gogh filter that removed the rendered nature, but retained the dominant landscape features. We found that there is a small but significant difference between geoscientists and non-geoscientists with geoscientists being slightly better at judging which pictures are from the real world versus from the game world. While significant the effect is small enough to conclude that fantastical worlds in games can be used for tangential learning on geoscientific subjects.
Testing of photogrammetry for differentiation of soil organic carbon and biochar in sandy substrates
Authors: Fister Wolfgang , Goldman Nina , Mayer Marius , Suter Manuel , Kuhn Nikolaus J.
Published: March 2019

Abstract. Landforms in different environmental ecosystems are formed
through selective erosion and transport mechanisms by wind and water. To
understand their development, biochemical composition, and effect on
neighbouring ecosystems, it is essential to better understand the forming
processes and to be able to monitor the behaviour and transport of particles
through the landscape. Conventional methods to track and differentiate
between organic and inorganic particles usually involve extensive sampling
campaigns that disturb the processes themselves. Therefore, this study aimed
to prove that the method of photogrammetry, which is non-contact and
non-invasive, is able to quantify erosion rates and can also be used to
differentiate between organic and inorganic material. To prove this concept,
a bottom-up experimental rainfall simulation set-up was conducted with sieved
sand substrates of very narrow particle size distribution and biochar under
highly controlled conditions. By using two-dimensional index and reflectance
maps of the surface computed with the software Pix4D, the erosion of biochar
was estimated and compared to the actual erosion amount that was transported
along the plot. The results show that photogrammetry has the potential to
distinguish between a sandy substrate and biochar. An approximate decrease of
5 % in biochar on the plot surfaces was detected in three out of four
rainfall experiments within the first 30 s. After these 30 s, the quality
of detection was significantly reduced due to shadow effects, which were
falsely classified as biochar as well. For future investigations on this
topic, it will be necessary to improve the lighting of the plot and the
post-processing of the images to reduce the error caused by shadows.
Additional approaches that should be taken into account for further test
experiments are the full exclusion of external light, which means working in
the dark, and the use of hyperspectral cameras to detect different carbon
types.
Global assessment of how averaging over land-surface heterogeneity affects modeled evapotranspiration rates
Authors: Rouholahnejad Freund Elham , Fan Ying , Kirchner James W.
Published: March 2019

Abstract. The major goal of large-scale Earth System Models (ESMs) is to understand and predict global change. However, computational constraints require ESMs to operate on relatively large spatial grids (typically ~1 degree or ~100 km in size) with the result that the heterogeneity in land surface properties and processes at smaller spatial scales cannot be explicitly represented. Averaging over this spatial heterogeneity may lead to biased estimates of energy and water fluxes in ESMs. For example, evapotranspiration rates and the properties that regulate them are spatially heterogeneous at scales orders of magnitude smaller than typical ESM grid cells. Here we quantify the effects of spatial heterogeneity on grid-cell-averaged evapotranspiration (ET) rates, as seen from the atmosphere over heterogeneous landscapes across the globe. In an earlier study, we used a Budyko framework to functionally relate ET to precipitation (P) and potential evapotranspiration (PET), and used a sub-grid closure relation to quantify the effects of sub-grid heterogeneity on average ET at 1° by 1° grid cells- the scale of typical ESM. We showed that because the relationships driving ET are nonlinear, averaging over sub-grid heterogeneity in P and PET leads to overestimation of average ET. In this study, we extend that work to the globe and examine the global distribution of this bias, its scale dependence, and the underlying mechanisms. Our analysis shows that this heterogeneity bias is more pronounced in mountainous terrain, in landscapes where P is inversely correlated with PET, and in regions with temperate climates and dry summers. We also show that the magnitude of this heterogeneity bias grows on average, and expands over larger areas, as the size of the grid cell increases. Correcting for this overestimation of ET in ESMs is important for modeling the water cycle, as well as for future temperature predictions, since current overestimations of ET rates imply smaller sensible heat fluxes, and potential underestimation of dry and warm conditions in the context of climate change. Our work provides a basis for translating the heterogeneity bias into correction factors in large-scale ESMs, and highlights the regions where more detailed mechanistic modeling is needed.