Short channel effects in graphene-based field effect transistors targeting radio-frequency applications

Channel length scaling in graphene field effect transistors (GFETs) is key in the pursuit of higher performance in radio frequency electronics for both rigid and flexible substrates. Although two-dimensional (2D) materials provide a superior immunity to Short Channel Effects (SCEs) than bulk materials, they could dominate in scaled GFETs. In this work, we have developed a model that calculates electron and hole transport along the graphene channel in a drift-diffusion basis, while considering the 2D electrostatics. Our model obtains the self-consistent solution of the 2D Poisson's equation coupled to the current continuity equation, the latter embedding an appropriate model for drift velocity saturation. We have studied the role played by the electrostatics and the velocity saturation in GFETs with short channel lengths L. Severe scaling results in a high degradation of GFET output conductance. The extrinsic cutoff frequency follows a 1/L^n scaling trend, where the index n fulfills n < 2. The case n = 2 corresponds to long-channel GFETs with low source/drain series resistance, that is, devices where the channel resistance is controlling the drain current. For high series resistance, n decreases down to n= 1, and it degrades to values of n < 1 because of the SCEs, especially at high drain bias. The model predicts high maximum oscillation frequencies above 1 THz for channel lengths below 100 nm, but, in order to obtain these frequencies, it is very important to minimize the gate series resistance. The model shows very good agreement with experimental current voltage curves obtained from short channel GFETs and also reproduces negative differential resistance, which is due to a reduction of diffusion current.Comment: 27-pages manuscript (10 figures) plus 6 pages of supplementary information. European Union Action H2020 (696656) / Department d'Universitats, Recerca i Societat de la Informaci\'o of the Generalitat de Catalunya (2014 SGR 384) / Ministerio de Econom\'ia y Competitividad of Spain (TEC2012-31330 and TEC2015-67462-C2-1-R) / MINECO FEDE

Rock Characterization Through Physical Properties and Their Relationship to Simple Compressive

This work proposes a simple methodology and practical application in the field for the approximate determination of the Unconfined Compressive Strength (UCS) in rocks, property or characteristic that is important in mining, since through it analyzes are carried out to the assessment of security and stability factors and/or possible fortification systems in the works or mining structures, in addition to the characterization of the UCS is also influential in the use of explosives for the exploitation or extraction of materials from a quarry or mine. This estimate is proposed based on the determination of the following three properties of the rock, which in this investigation we call density, porosity and absorption ‘in mine’. These physical properties can be obtained in a simple, but methodical way and in this work, tests have been carried out on the same material or rock from the Cojitambo area, Cañar province (Ecuador) and on the basis of 60 samples or test tubes. The results obtained allow a correlation between the properties described above and the UCS, in addition to a calculation methodology for the proposed objective. Keywords: compression, rock, density, porosity, absorption, fortification. Resumen En este trabajo se propone una metodología sencilla y de aplicación práctica en campo para la determinación aproximada de la Resistencia a la Compresión Simple (RCS) en rocas, propiedad o característica que es importante en minería, ya que mediante la misma, se ejecutan análisis para la valoración de factores de seguridad y estabilidad y/o posibles sistemas de fortificación en las obras o estructuras mineras, a más de que la caracterización de la RCS es también influyente en el uso de explosivos para la explotación o extracción de materiales de una cantera o mina. Esta estimación se la propone en base a la determinación de las siguientes tres propiedades de la roca, que en esta investigación las denominamos densidad, porosidad y absorción ‘en mina’. Estas propiedades físicas se las puede obtener de una forma simple, pero metódica y en este trabajo se han ejecutado ensayos sobre un mismo material o roca proveniente de la zona de Cojitambo, provincia del Cañar (Ecuador) y sobre una base de 60 muestras o probetas. Los resultados obtenidos permiten una correlación entre las propiedades antes descritas y la RCS, a más que se ha estructurado una metodología de cálculo para el objetivo planteado. Palabras Clave: compresión, roca, densidad, porosidad, absorción, fortificación

When mobile advertising is interesting: interaction of minors with ads and influencers’ sponsored content on social media

Social ads, along with apps, display and geolocation are the most used actions in the context of mobile marketing. Adolescents are also identified as the main target audience for mobile marketing because they are very active users, they have a sound command of technology and their role as prescribers, especially in social networks. For this reason, the interaction between advertising on social networks among minors (10-14 years) was studied, differentiating between those standard format ads and those commercial content published by influencers. To this avail, more than 2,400 ads were analyzed after monitoring for a week the commonly used device of a sample of minors from the Metropolitan Area of Santiago de Chile. Standard formats, despite being the most used, they hardly generated interaction, unlike commercial content by influencers, which achieved a higher level of interaction (visual and click interaction), although they were less employed. These results open the door to question the advertising management of a digital space which was created for dialogue such as social networks, in which advertisers prioritize selling products and services.La publicidad en redes sociales, junto con las apps, display y geolocalización, son las acciones más recurrentes de las marcas en el contexto del marketing móvil. Igualmente, se identifica a los adolescentes como el principal público objetivo del marketing móvil por ser usuarios muy activos, por sus conocimientos en tecnología y por su papel de prescriptores, especialmente en redes sociales. Por ello, se ha propuesto analizar qué interacción despierta la publicidad en redes sociales entre los menores de edad (10-14 años), tanto aquellos anuncios en formato estándar como los contenidos comerciales publicados por influencers. Para ello se analizaron más de 2.400 anuncios registrados tras monitorizar durante una semana los móviles de uso común de una muestra de menores del Área Metropolitana de Santiago de Chile. Se pudo comprobar que los formatos estándares, a pesar de ser de uso recurrente, apenas generaron interacción en los usuarios, a diferencia de los contenidos comerciales de la mano de influencers que sí lograron un mayor nivel de interacción (tanto visual como en forma de clic), aunque tuvieran una presencia más anecdótica en el conjunto de la muestra. Estos resultados abren la puerta a cuestionar el uso publicitario que se realiza de un espacio concebido para el diálogo, como son las redes sociales, en el que los anunciantes tienen como principal objetivo la venta de productos y servicios

When ads become invisible: minors’ advertising literacy while using mobile phones

It has been traditionally estimated that children begin to understand the persuasive intent of advertising at about the age of 8 which is when they acquire the skills of adult consumers. The ability to identify and interpret the persuasive content that minors are exposed to via mobile phones was analyzed through semi‐structured interviews of children aged 10 to 14 years along with their parents in 20 households. Although minors seem to be able to recognize the persuasive intent of advertising, this does not necessarily mean that they have a deep understanding of the new digital formats that combine persuasion and entertainment. Data analysis of the interviews shows low recognition of the persuasive intent of commercial messages that are not explicitly identified as such, particularly on social networks. Data collected after minors viewing of different examples allowed researchers to conclude that standardized advertising is mainly identified by its format. Three levels of advertising processing were detected in minors: the liking of the advertisement, the affinity for the advertised product, and the ability to contrast the claims with searches for comments, forums or opinions of influencers. Recent research verified that conceptual knowledge of the persuasive intention of the advertising does not suffice for minors to interpret the message, a fact that must be taken into account when developing advertising literacy. For parents, the amount of time spent on these devices and the type of use minors make of their cellphones or the relationships they establish on them are more relevant than exposure to advertising itself

To Search or not to Search: Where is the Mobile Search Market Heading? Results from a Survey with Experts

Web search providers have a highly successful business model in place, which has rendered them amongst the most profitable companies on the internet. The mobile sector is expanding rapidly with the number of worldwide subscribers estimated to reach 5 billions by 2012 and with two-digit growth rates in the number of mobile internet connections. Consequently, many observers consider mobile search as the 'next big market'. However, there is little evidence so far to support such high expectations. In addition, we spot a general lack of studies based on large public data sets, which employ reproducible methods to forecast the evolution of trends in the sector. Surprisingly, whereas some market research reports dedicated solely to mobile search were published a few years ago, just when mobile search is moving to become a mainstream application, there appear to be no comprehensive recent studies about where the mobile search market is going. In this paper we report and analyse the collective opinions of a group of experts on the prospects of mobile search. The research we present is based on a two-round Delphi exercise. The first round of such exercise was conducted online in order to reach a wide community of experts and to cover a broad range of expertise. The second round was carried out face-to-face with a selection of respondents to discuss in depth the results of the online questionnaire. To get the prospective dimension into the Delphi discussion, we proposed seven distinct scenarios. This set a common ground for participants to engage into a forwardlooking debate and to focus their attention onto prospective drivers and barriers rather than solely onto today's landscape. Our Delphi study confirms the high expectations and bright future experts see for the mobile search market, but with noteworthy nuances. We found that the experts' optimism is rooted in the conviction that all critical technological components are already available and that only some system integration is missing. Our paper argues that there is no adequate market pull response to such technology push. Undeniably some (trial) applications are under way, but their business models are still insufficiently defined and companies are experimenting with different business ideas. Irrespectively of the business model, however, experts single out user-centric interfaces as the most The manuscript was submitted on 15th February 2010. This work was supported in part by the European Commission's coordination action CHORUS+ (ICT-2009.1.5 Grant 249008). Corresponding author: [email protected] critical element for increased mobile search take up. Today's interfaces and applications are not satisfactory in terms of users' needs and desires, which is delaying massive adoption. Another essential component for adoption is trust in the service provider. The liability and responsibility of the different players (telecom operators, search engine providers, device manufacturers, etc) needs to be scrutinized. Our study also presents the views of experts on how privacy and personal data usage are influencing the evolution of mobile search. The paper concludes with some suggestions for fostering the evolution of the mobile search domain by increasing the interoperability of services, assuring the openness and mash-ups of content and services, developing personal identity data management systems to improve user acceptance and enhance trust and by supporting research, both on the technologies that are required to enable more advanced used of mobile search applications, and supporting living labs a experimental platform to test new application and innovative business models

Screening of white rot fungal species for their capacity to degrade lindane and other isomers of hexachlorocyclohexane (HCH)

White-rot fungi have demonstrated a high capacity to degrade organic pollutants, including the insecticide lindane (y-HCH). The purpose of this study was to evalúate the degradative capacities of several white rot fungi species, Bjerkandera adusta, Irpex lacteus, Lentinus tigrinus, Phanerochaete chrysosporium, Phanerochaete sórdida, Phlebia radiata, Pleurotus eryngii, Poliporus cialatus, and Stereum hirsutum. Fungal tolerance to various concentrations of a-, (3-, y- and 8 isomers of hexachlorocyclohexane (HCH) was studied in both liquid and soil media samples. 8- and y-HCH isomers showed the highest inhibition of fungal growth of all HCH isomers. P. chrysosporium and B. adusta exhibited a high tolerance to HCH pollution. The 8- and y-HCH isomers were degraded between 15.1 and 70.8% by six of the nine fungal species, B. adusta, P. ciliatus, L. tigrinu, S. hirsutum, P. eryngii, and I. lacteus; [3-HCH was 56.6, 26.5 and 23.9% degraded by B. adusta, P. ciliatus and P. eryngii, respectively In non-sterile soil, all the HCH isomers were degraded between 8.2 and 17.5% by B. adusta immobilized on corncobs or woodchips. In nonsterile soil, other soil microflora showed an antagonistic effect on white-rot fungi catalyzed degradation of HCH isomersLos hongos de la pudrición blanca de la madera han demostrado una alta capacidad para degradar contaminantes orgánicos y entre ellos el insecticida lindane (y-HCH). Sin embargo, no se conoce su capacidad para degradar los demás isómeros presentes en la formulación de este insecticida, altamente tóxico y recalcitrante en el ambiente. El objetivo de este estudio fue evaluar la sensibilidad de diferentes especies de hongos de la pudrición blanca de la madera a los isómeros de a-, (3-, y- y o de hexachlorociclohexane (HCH), así como su capacidad para degradarlos en medios líquidos y sólidos. Los hongos evaluados fueron: Bjerkandera adusta, Irpex lacteus, Lentinus tigrinus, Phanerochaete chrysosporium, Phanerochaete sórdida, Phlebia radiata, Pleurotus eryngii, Poliporus cialatus y Stereum hirsutum. Los resultados mostraron que o- y y-HCH fueron los isómeros que presentaron mayor grado de inhibición en el crecimiento a concentraciones entre 5 y 10 mgL1. Además, P. chrysosporium and B. adusta fueron los que mostraron mayor tolerancia a altas concentraciones de los contaminantes. Los isómeros o- and y-HCH fueron considerablemente degradados en medio líquido entre 15,1 and 70,8% por B. adusta, P. ciliatus, L. tigrinu, S. hirsutum, P. eryngii and /. lacteus. Mientras que (3-HCH solamente fue degradado por B. adusta, P. ciliatus and P. eryngii, en proporciones de 56,6; 26,5 and 23,9%, respectivamente. En suelo esterilizado B. adusta degradó parcialmente todos los isómeros entre 8,2 and 17,5%, mientras que en suelo no esterilizado se observó un efecto antagonista que impidió la acción del hongoS

Plataforma Hardware-Software para el desarrollo de habilidades STEM

Robotics not only play a significant role in medicine, manufacturing, or aerospace industry, but also in education. According to governmental studies carried out in the United States and Europe, careers related to STEM skills like engineering, are constantly increasing worldwide. Due to this, several countries have been implementing STEM education. But, in Colombia this initiative just recently started to take place. Currently, it is possible to find several STEM educational robotic kits on the market such as boost from Lego, Cozmo from Anki, Mbot from Makeblocks and Dash from Make wonder. In this trend, the STEM robotic kit proposed in this document, pretends to be a hardware grounding to implement a whole STEAM program. It intends to encourage children to develop their science, tech, math, and artistic outcomes. Also, the kit offers a differential plus from others because it has two interactive components: an elephant-bot called Eli, a robot easy to assemble inspired in the protection of African elephants; and, an intuitive user interface, called "Experiencia Chamali" made up of three modules. The first one consists of assembly the robot, the second one is designed for developing of spatial perception throughout maze challenges, and the last one is made for test the robot's movements live. Two groups of children between 6 and 11 years old tested the robotic platform. During the activity, the groups reinforced STEM skills such as teamwork, communication, and problem-solving as a conclusion of test results. The children divided the assembly of the elephant-bot into several tasks on their initiative to make an agile construction. Also, in the challenge of the labyrinth, they worked collaboratively on the spatial location. Finally, the members of each group worked as a team decorating the physical labyrinth freely and observing the movements of the "elephant-bot" in this environment