bluuebunny/crossref_metadata_2025 huggingface dataset:
FORMAS DE ORGANIZAÇÃO DA DEMANDA DE FIRMAS DE TI NO MERCADO DE TRABALHO
Authors: Rodrigues Azambuja Lucas
Published: June 2019

Este artigo propõe compreender o comportamento das firmas no mercado de trabalho, através da análise de redes sociotécnicas. Evidenciamos que algumas características dessas redes dependem de aspectos organizacionais das empresas que, por sua vez, estão relacionados ao contexto mais amplo da chamada nova economia. Foi analisada a inter-relação entre redes sociotécnicas e características organizacionais na nova economia, com o objetivo de compreender o processo de construção social sobre o qual assenta a ida das empresas como demandantes no mercado de trabalho. Procedeu-se à realização de quatro estudos de casos em empresas de tecnologias da informação, situadas em Porto Alegre (RS) e Região Metropolitana. Com base na análise dos dados levantados através de entrevistas, observação e coleta de documentos, constatou-se que quanto mais uma firma apresenta características organizacionais típicas da nova economia, maior é o número de agentes integrados em sua rede sociotécnica e mais intensas serão as relações entre eles. Palavras-chave: Sociologia Econômica; Sociologia dos Mercados; Sociologia das Organizações
A classe trabalhadora tem cor: democracia racial e desenvolvimentismo em Volta Redonda (1946-1987).
Authors: Silva Leonardo Ângelo
Published: June 2019

A proposta deste trabalho é a análise da relação entre o discurso desenvolvimentista com o de democracia racial. Para tanto nosso recorte espacial é a região de Barra Mansa e Volta Redonda (região localizada no sulfluminense do Estado do Rio de Janeiro) e o recorte cronológico vai de 1946 (ano da primeira corrida do aço em Volta Redonda), a 1987 (ano de divulgação da primeira pesquisa sobre discriminação e racismo que teve Volta Redonda como uma das cidades base). Na construção de nossos argumentos nos pautamos na experiência dos trabalhadores da Companhia Siderúrgica Nacional (CSN) o que captamos através do cruzamento analítico de fotos originárias da própria empresa (mais de 900), entrevistas realizadas pelo autor e por outros grupos de pesquisadores, registros de atas da Câmaras Municipais e de periódico da própria CSN (O lingote). Destes cruzamentos podemos destacar a evidente contradição entre a estrutura de trabalho, claramente desigual, encontrada pelos trabalhadores negros e o forte discurso desenvolvimentista e trabalhista, no qual os trabalhadores não tinham cor ou eram de todas as cores.
Programa de Integração e Inclusão étnico-racial e cotas para negros na Universidade do Estado de Mato Grosso: uma breve análise sobre a primeira década (2005-2015)
Authors: Teixeira Laudiceia Fagundes , Vieira Paulo Alberto Dos Santos
Published: June 2019

Em setembro de 2015, em reunião ordinária, o Conselho de Ensino, Pesquisa e Extensão da Universidade do Estado de Mato Grosso prorrogou por mais dez anos o Programa de Integração e Inclusão Étnico-racial (Piier/Unemat), que se traduz nas cotas para negros desta universidade.  Nesta reunião chamou a atenção algumas situações, dentre as quais merecem destaque: a. posição da maioria do pleno, amplamente favorável à prorrogação; b mudança de posição em relação às cotas, na medida em que alguns atores que eram contrários em 2005 discursaram em prol da continuidade do programa; e c. absoluta ausência de qualquer tipo de dado e/ou informação oficial referente ao Programa. Neste artigo, pretende-se desenvolver argumentação que demonstre que a aprovação da prorrogação do Piier/Unemat não significou que as políticas de ação afirmativa, com recorte étnico-racial, sejam apoiadas. Buscar-se-á demonstrar que, paradoxalmente, a prorrogação pode ter por base a consolidação de práticas acadêmicas que tendem a dificultar, e no limite impedir, a presença negra no interior da universidade.  Para tanto o texto possui uma introdução, uma sessão acerca do conceito e histórico, outra relativa à Unemat e observações à guisa de conclusões.Palavras-Chave: Cotas para negros; Unemat; Mato Grosso.
Possibilidades de apropriação do habitat em assentamentos rurais no Brasil
Authors: Borges Amadja Henrique , Rego de Medeiros Cecília Marilaine , Silva de Oliveira Márcia , De Andrade e Andrade Sarah
Published: June 2019

Este artigo aborda a participação de arquitetos e urbanistas na assessoria aos movimentos sociais do campo, especificamente em assentamentos rurais chamados de “Reforma Agrária”, vinculados ao Movimento dos Trabalhadores Rurais Sem Terra (MST). Assim, tem como principal objetivo refletir acerca dos principais limites e possibilidades de parcela desta categoria profissional, desde a concepção do espaço construído, ao mesmo tempo em que envolvida com seu compromisso social. Trata dos métodos utilizados na produção coletiva da habitação social, por meio da troca de saberes científicos e tradicionais, de forma que lideranças e bases do Movimento se apropriem de seus habitats, concebidos e construídos a partir de parâmetros técnicos baseados na sua organização política e cultural, e desenvolvidos com sua participação. A experiência apresentada é a do grupo estudo dos autores, cuja parceria com o MST – e em alguns momentos com o Instituto Nacional de Colonização e Reforma Agrária (INCRA) – remonta a 1994. Tem como principais referências teórico-metodológicas o filósofo e sociólogo francês Henri Lefebvre e os educadores brasileiros Paulo Freire e Carlos Brandão. Como campo empírico, atua, sobretudo, junto aos assentamentos do estado do Rio Grande do Norte (RN), Brasil.
Role of ovarian sympathetic nerves and cholinergic local system during cold stress
Authors: Riquelme Raul , Ruz Freddy , Mayerhofer Artur , Lara Hernán E
Published: June 2019

An increase in the sympathetic tone in the rat ovary induces a polycystic ovary (PCOS-like) phenotype. No information exists about its impact on fertility. In contrast, increased follicular development and improved fertility in rats were found after pharmacological inhibition of acetylcholinesterase, which increased intraovarian acetylcholine (ACh). Now, we studied the impact of sympathetic stress, followed by a recovery period without stress, on the cholinergic and noradrenergic systems of the rat ovary and on fertility. To activate ovarian sympathetic nerves, female Sprague–Dawley rats were exposed to cold stress (4°C/3 h day for 28 days; first period), followed by a 28-day period without cold stress (second period). No changes in estrous cyclicity during the first period was found. At the end of this period, ovarian levels of NA and ACh were increased. Morphometric analysis showed lower numbers of secondary and antral follicles, enhanced follicular atresia and fewer corpora lutea. Plasma progesterone was lower and testosterone was higher than that in controls. At end of the second period, ovarian ACh levels had returned to control levels, but NA levels remained elevated. The second period was also characterized by the presence of cystic follicles in the ovary, by elevated plasma testosterone and estradiol levels, while progesterone levels were decreased. Estrous cyclicity and ovulation during that period were irregular and fertility decreased. Thus, cold stress initially activated both ovarian noradrenergic and cholinergic system. After stress, the ovary did not fully recover and activation of the noradrenergic system persisted and correlated with cystic ovarian morphology and decreased fertility.
Genomic Selection with Allele Dosage in Panicum maximum Jacq.
Authors: de C. Lara Letícia A , Santos Mateus F , Jank Liana , Chiari Lucimara , Vilela Mariane de M , Amadeu Rodrigo R , dos Santos Jhonathan P R , Pereira Guilherme da S , Zeng Zhao-Bang , Garcia Antonio Augusto F
Published: June 2019

Genomic selection is an efficient approach to get shorter breeding cycles in recurrent selection programs and greater genetic gains with selection of superior individuals. Despite advances in genotyping techniques, genetic studies for polyploid species have been limited to a rough approximation of studies in diploid species. The major challenge is to distinguish the different types of heterozygotes present in polyploid populations. In this work, we evaluated different genomic prediction models applied to a recurrent selection population of 530 genotypes of Panicum maximum, an autotetraploid forage grass. We also investigated the effect of the allele dosage in the prediction, i.e., considering tetraploid (GS-TD) or diploid (GS-DD) allele dosage. A longitudinal linear mixed model was fitted for each one of the six phenotypic traits, considering different covariance matrices for genetic and residual effects. A total of 41,424 genotyping-by-sequencing markers were obtained using 96-plex and Pst1 restriction enzyme, and quantitative genotype calling was performed. Six predictive models were generalized to tetraploid species and predictive ability was estimated by a replicated fivefold cross-validation process. GS-TD and GS-DD models were performed considering 1,223 informative markers. Overall, GS-TD data yielded higher predictive abilities than with GS-DD data. However, different predictive models had similar predictive ability performance. In this work, we provide bioinformatic and modeling guidelines to consider tetraploid dosage and observed that genomic selection may lead to additional gains in recurrent selection program of P. maximum.
Large posterior perforation of duodenal ulcer: A rare surgical emergency
Authors: Alaswad Faris
Published: June 2019

A 20-year-old man was admitted with a complaint of a constant dull aching pain in the epigastrium and back for five days, with subsequent worsening and generalization of the pain. Clinically the abdomen was tender all over with board-like rigidity. Chest radiography revealed pneumoperitoneum, and a decision was made to explore the patient. During laparotomy, we found a peritoneal collection with no perforation in the anterior surface of the stomach, duodenum, or the entire gastrointestinal tract. After opening the lesser sac, we found a large perforation of the posterior wall of the duodenum. After direct repair with stitching through duodenotomy and duodenoplasty also done, the patient recovered and was discharged after 14 days. Posterior perforation of a duodenum ulcer is a very rare condition.
New records and an updated map of distribution of Micrurus camilae Renjifo & Lundberg, 2003 (Elapidae) for Colombia
Authors: Meneses-Pelayo Elson , Caballero Diana
Published: June 2019

Camila’s Coral Snake, Micrurus camilae Renjifo & Lundberg, 2003, is known only by 3 collected specimens. In this work, we report for the first time the presence of M. camilae in the middle Magdalena Valley, and we add data about color variation in the species. The new record extends the distributional range of M. camilae by nearly 200 km in a straight line from Vereda El Rayo, Tarazá, Antioquia, which is the nearest point previously reported.
Instability formation in epitaxial SiGe lines under hydrogen annealing
Authors: Seiss Birgit , Brémond Georges , Dutartre Didier
Published: June 2019

The influence of film thickness and line width on the morphology of epitaxial SiGe was studied after an annealing step. The morphology of 5 nm and 19 nm thick SiGe was characterized in 60-490 nm wide lines which were oriented along <100> on Si (001) substrates. We have shown that the annealed SiGe morphology changed significantly as a function of line width and film thickness. Wide lines of 19 nm thick SiGe showed ridge formation; as the line width was decreased the morphology stabilized and then became unstable with the formation of bulges. The morphology of 5 nm thick SiGe consisted of ridges in wide lines, changed to faceted islands in narrower lines and was stable in the narrowest lines.
In situ X-ray Studies of (La,Sr)MnO3_δ, (La,Sr)CoO3_δ, and La0.6Sr0.4Co0.2Fe0.8O3-δ Thin Film SOFC Cathodes Grown by Pulse Laser Deposition
Authors: Chang Kee-Chul , Ingram Brian , Salvador Paul , Yildiz Bilge , You Hoydoo
Published: June 2019

We will briefly review in situ synchrotron x-ray investigation of model thin film cathode systems for solid oxide fuel cells. The film cathodes examined in this study are (La,Sr)MnO3_δ (LSM), (La,Sr)CoO3_δ (LSC), and La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) thin films epitaxially grown on YSZ single crystal substrates by the pulse laser deposition technique. We find in all cases that Sr is enriched or segregated to the surface of the film cathodes. We concluded that the Sr enrichments or segregations are mainly the results of annealing because they do not depend on whether the cathodes are electrochemically biased or not during annealing. However, at least in the case of LSCF, we find that B-site Co segregates rather uniformly to the surface and the segregation responds sensitively and reversibly to the electrochemical bias.
Ab initio Simulation of 1D Pattern Formation of Adsorbates on the Ge(100)-2 × 1 Surface
Authors: Shong Bonggeun , Bent Stacey F.
Published: June 2019

It is known that methanol and ethylene form distinct one-dimensional patterns along the dimer row on the Ge(100)-2 × 1 surface. A unified explanation for the pattern formation is attempted in this study through theoretical methods. Kinetic parameters of the precursor-mediated adsorption of the two molecules are calculated using density functional theory methods. The potential energy surface along the reaction channel was found to vary according to nearest-neighbor occupation. Monte Carlo simulations were performed with calculated kinetic coefficients and assumptions of a one-dimensional lattice with nearest neighbor interactions. The simulation results effectively reproduce the coverage-dependent evolution of longer-range adsorption patterns.
Modeling and Fabrication of Quantum Dot Channel Field Effect Transistors Incorporating Quantum Dot Gate
Authors: Kondo Jun , Lingalugari Murali , Chan Pik-Yiu , Heller Evan , Jain Faquir
Published: June 2019

Quantum dot gate (QDG) field-effect transistors (FET) have shown three-state transfer characteristics. Quantum dot channel (QDC) field-effect transistors (FET) have exhibited fourstate ID-VG characteristics. This project aims at studying the effect of incorporating cladded quantum dot layers in the gate region of QDC-FET. Four-state characteristics are explained by carrier transport in narrow energy mini-bands which are manifested in a quantum dot superlattice (QDSL) channel. QDSL is formed by an array of cladded quantum dots (such as SiOx-Si and GeOx-Ge). Multi-state FETs are needed in multi-valued logic (MVL) that can reduce the number of gates and transistors in digital circuits. The fabricated device showed the four-state characteristic (OFF, ‘I1’, ‘I2’, ON).
Thermoelectric Properties of Some Cobalt Phosphide-Arsenide Compounds
Authors: Watcharapasorn Anucha , DeMattei Robert C. , Feigelson Robert S. , Caillat Thierry , Borshchevsky Alexander , Jeffrey Snyder G. , Fleurial Jean-Pierre
Published: June 2019

Samples of CoP3, CoAs3 and CoP1.5As1.5 have been synthesized and their thermoelectric properties measured. All three samples show semiconducting behavior. The Seebeck coefficients of CoP3 and CoAs3 are weakly dependent on temperature and are relatively small with maximum values of about 40 and 50 μV/K, respectively. The Seebeck coefficient of the solid solution gradually decreases with increasing temperature and the values are larger than those of CoP3 and CoAs3 in the temperature range investigated, with a maximum value of about 89 μV/K near room temperature. The thermal conductivity of CoP3 and CoAs3 are higher than that of CoSb3, as can be expected from the effect of anionic size on lattice vibration. A substantial reduction in thermal conductivity was observed for the solid solution compared to the constituent binary compounds due to additional phonon scattering from lattice disorder and other possible point defects such as vacancies. Other compositions in the CoP3-xAsx system have also been synthesized and their thermoelectric properties are currently being investigated to provide essential information about lattice thermal conductivity reduction by point defect scattering and to further develop strategies for optimizing the thermoelectric properties of skutterudite materials.
Bulk Synthesis of Completely and Partially Sn filled CoSb3 Using the Multilayer Repeat Method
Authors: Sellinschegg Heike , Johnson David C. , Kaeser Michael , Tritt Terry M. , Nolas George S. , Nelson E.
Published: June 2019

Filled skutterudite compounds possess very low thermal conductivities due to the scattering of a wide range of phonon modes caused by a loosely bound cation incorporated in a cavity of the structure. The inclusion of such a filler cation causes several synthetic difficulties since the desired compounds are thermodynamically unstable with respect to disproportionation. Modulated elemental reactants were used in this study to circumvent these difficulties. SnxCo4Sb12 samples with x=0.5 and nearly 1.0 were synthesized using this method. To prevent nucleation of unwanted binary compounds, the repeat unit made up of elemental layers was less than 20 angstroms 500mg of each sample were produced, allowing for the samples to be hot pressed into a pellet. Structural analysis as well as measurements of the physical properties are presented.
Thermal Conductiviy of type I and II Clathrate Compounds
Authors: Nolas G.S. , Cohn J.L. , Kaeser M. , Tritt T.M.
Published: June 2019

Compounds with clathrate-hydrate type crystal lattice structures are currently of interest in thermoelectric materials research. This is due to the fact that semiconducting compounds can be synthesized with varying doping levels while possessing low, even ‘glass-like’, thermal conductivity. Up to now most of the work has focused on type I Si and Ge clathrates. Sn-clathrates however are viewed as having the greatest potential for thermoelectric cooling applications due to the larger mass of Sn and the expected small band-gap, as compared to Si and Ge clathrates. Transport properties on type I Sn-clathrates has only recently been reported [1–3]. In this report we present ongoing experimental research on both type I and II clathrates with an emphasis on the thermal transport of these novel materials. We present thermal conductivity data Si-Ge and Ge-Sn alloys as well as on a type II Ge clathrate for the first time, and compare these data to that of other clathrate compounds.
Epitaxial Growth and Thermoelectric Properties of Bi2Te3 Based Low Dimensional Structures
Authors: Nurnus Joachim , Beyer Harald , Lambrecht Armin , Böttner Harald
Published: June 2019

Bi2Te3 based low dimensional structures are interesting material systems to increase the thermoelectric figure of merit ZT by either the expected reduction of the thermal conductivity or by a possible power factor enhancement due to quantum confinement. Due to low lattice mismatch Bi2(Te1-xSex)3, PbSe1-xTex, as well as Pb1-xSrxTe, and BaF2 are suitable for Bi2Te3 based low dimensional structures. Especially due to their significantly enhanced band gap lead chalcogenide compounds like Pb1-xSrxTe (Pb0.87Sr0.13Te: 0.6 eV) are well-suited barrier materials in MQW structures. Alternatively the insulator BaF2 can be used for that purpose.

Here we report mainly on results of different superlattice structures mentioned above grown by molecular beam epitaxy (MBE) on BaF2(111). The structural properties of these layers were investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and secondary ion mass spectroscopy (SIMS). Structural performance and thermoelectric properties of different Bi2Te3 based superlattices were reported and compared with regard to their superlattice parameters.
Enhancement Of Power Factor In A Thermoelectric Composite With A Periodic Microstructure
Authors: Fel Leonid G. , Strelniker Yakov M. , Bergman David J.
Published: June 2019

The thermoelectric power factor has been calculated for a two-constituent composite medium, where one constituent is a “high quality thermoelectric” while the other constituent is a “benign metal”, with large electrical and thermal conductivities but poor thermoelectric properties. It was recently discovered that, in such a mixture, the power factor could be greatly enhanced by an appropriate choice of microstructure. Here we report on a study of three periodic microstructures with cubic point symmetry under rotations: simple cubic (SC), body centered cubic (BCC), and face centered cubic (FCC) arrays of identical spheres of the benign metal embedded in the high quality thermoelectric host. We show detailed results for these microstructures in the case where the benign metal constituent is Copper, while the high quality thermoelectric constituent is the thermoelectric alloy (Bi2Te3)0.2 (Sb2Te3)0.8.
Doping Studies of n-Type CsBi4Te6 Thermoelectric Materials
Authors: Lane Melissa A. , Ireland John R. , Brazis Paul W. , Kyratsi Theodora , Chung Duck-Young , Kanatzidis Mercouri G. , Kannewurf Carl R.
Published: June 2019

We have previously reported the successful p-type doping of CsBi4Te6 which had a high figure of merit at temperatures below 300 K. In this study, several dopants were explored to make n-type CsBi4Te6. A program of measurements was performed to identify the optimum doping concentration for several series of dopants. The highest power factors occurred around 125 K for the 0.5% Sn doped CsBi4Te6 sample which had a power factor of 21.9 μW/cm•K2 and 1.0% Te doped CsBi4Te6 which had a power factor of 21.7 μW/cm•K2.
Jamming in Liquids and Granular Materials
Authors: O'Hern C. S. , Langer S. A. , Liu A. J. , Nagel S. R.
Published: June 2019

Many systems can develop a yield stress while in an amorphous state. For example, a supercooled liquid, when cooled sufficiently, forms a glass - an amorphous solid with a yield stress. Another common example is a granular material which will remain solid and not move even under the influence of moderate stresses. This accounts for why piles of grain or sand can exist with a non-zero slope even though gravity is acting to flatten out the upper surface. The solidity in that case is due to the system having become jammed. Similar jamming often inhibits flow out of a hopper or in conduits transporting material across a factory floor. Jamming is a ubiquitous phenomenon occurring in many different systems such as colloidal suspensions, foams and, of course, traffic. We tend to think of the jamming transition as being stress-induced. A “fluid” at constant density (or under a confining pressure) flows if the stress is above the yield stress but becomes stuck in an amorphous configuration if the stress is too low. The idea of temperature, per se, does not seem to be crucial to the transition. This makes it seems quite different from the formation of a glass out of a supercooled liquid by lowering the temperature. However, there are similarities between these two types of transitions, aside from the obvious fact that they both have to do with the complete arrest of dynamics and flow. An exploration of these similarities was the subject of a program at the Institute for Theoretical Physics in Santa Barbara held in the Autumn of 1997. A synopsis of this program was published that details some of the interesting ideas now current in that field.[1]
A Simple Description of Thick Avalanches at the Surface of a Granular Material
Authors: Aradian Achod , Raphaël Elie , de Gennes Pierre-Gilles
Published: June 2019

Some years ago, Bouchaud et al. introduced a phenomenological model to describe surface flows of granular materials [J. Phys. Fr. I 4, 1383 (1994)]. According to this model, one can distinguish between a static phase and a rolling phase that are able to exchange grains through an erosion/accretion mechanism. Later, Boutreux et al. [Phys. Rev. E 58, 4692 (1998)] proposed a modification of the exchange term in order to describe thicker flows where saturation effects are present. However, these two approaches assumed that the downhill convection velocity of the grains is constant inside the rolling phase, a hypothesis that is not verified experimentally. We have recently modified the above models by introducing a velocity profile in the flow, and analyzed the physical consequences of this modification in the simple situation of an avalanche in an open cell. We here emphasize the physical predictions of our model, and show, in particular, that the thickness of the avalanche depends strongly on the velocity profile.
Impulse acoustics based ejection of ferrofluid grains from a ferrofluid: the blueprint of a concept for a nozzle-free inkjet printer
Authors: Manciu Felicia S. , Manciu Marian , Sen Surajit
Published: June 2019

We present numerical simulations to demonstrate that it may be possible to eject ferrofluid grains from a ferrofluid using non-linear acoustic impulses. The study considers a container with some dilute ferrofluid that is placed in a strong, vertical, homogeneous magnetic field. The field induces the formation of magnetic dipoles into vertical chains that approximately span the region between the base and the surface of the container. We use particle dynamical simulations to show that an impulse generated at the base of any chain, will typically travel as a weakly dispersive bundle of energy. When the impulse magnitudes are appropriate (typically ∼60 m/s or more) the ferrofluid grain nearest to the surface of the liquid may be ejected by the impulse. Since all ferrofluid grains possess a coating of the liquid host, the ejected grain can be used as an ink-drop, with typical diameter of 15 or so nanometers. The velocities of the ejecting grains can be controlled and hence the method, if experimentally feasible, may have wide ranging applications. One of these applications is likely to be in designing special-purpose nozzle-free inkjet printers of unprecedented resolution.
Rheology of a granular column
Authors: Kolb Evelyne , Ovarlez Guillaume , Sausse Pascal , Clément Eric
Published: June 2019

We study the rheology of a granular material in a confined geometry. The grains are stacked in a vertical cylinder and pushed at different driving velocities. The resistance force encountered by the bottom piston is monitored while the piston is pushing the granular column upwards. Above a critical velocity, the motion is characterized by a steady sliding and by a force level increasing rather slowly with the pushing velocity. For driving velocities under this threshold, the system undergoes a dynamic instability and then, a stick-slip motion occurs. The amplitude of the slipping events, and thus, the elastic energy release, increase strongly when the velocity decreases. The critical velocity depends on the stiffness of the driving system and on the height of the granular column. This transition can be shifted towards higher velocity values by increasing the friction at the walls of the cylinder. It is also very sensitive to the state of compaction of the grains. Moreover, the mean energy release during a stick-slip motion seems to increase as a power-law when the pushing velocity is decreased. We also show that the distribution of energy release is strongly dependent on the level of disorder in the grains (polydispersity, friction, etc.). We argue that this complex phenomenology characterizes confined granular packing in connection with arching and aging phenomena.
Flow of Granular Material through Rotating Cylinders: Modelling Transients
Authors: Spurling Richard J. , Davidson John F. , Scott David M.
Published: June 2019

Granular material, fed continuously into the top of a slowly rotating, slightly inclined cylinder, forms a moving bed. Much of the bed rotates with the cylinder in solid body motion. When particles reach the surface of the bed, they move rapidly down it, and are absorbed once more into the solid body motion. Such cylinders are used in calcining, pharmaceutical manufacture, and drying. A steady state transport model, applicable when the bed depth varies slowly along the cylinder, has existed for around 50 years. The bed surface is considered locally flat, and particles in it fall along the line of steepest descent, inclined to the horizontal at the angle of repose. There is reasonable agreement with experiment.

We propose a quasi-steady state dynamical model, in which the steady state model is coupled with a volume balance across an axial element. The model takes the form of a nonlinear diffusion equation which was solved numerically. The parameters of the dynamic model are the dimensions of the cylinder and outlet dam, the inclination of the axis of the cylinder, its rotational speed, the angle of repose of the granular material and its feed volumetric flow rate: the dynamic model has no free parameters. Experiments were conducted using sand, mean particle size 490 μm, in a perspex tube of length 1 m, radius 0.0515 m, lined with sandpaper, with a feed end dam of height 0.029 m, and with no exit dam, or an exit dam of height 0.0105 m. With the system initially in steady state, step changes in feed flow rate, rotational speed or axis inclination were imposed, and the resulting discharge flow rate and bed depth axial profile measured as functions of time. Good agreement is found between model and experiment.
Dislocation Exhaustion During Plastic Deformation
Authors: Couteau Olivier , Charbonnier Corinne , Kruml Tomas , Martin Jean-Luc
Published: June 2019

Repeated stress-relaxation experiments are used to characterize the deformation parameters in 3 types of single crystals (Cu, Ni3Al and Ge) in which different dislocation mechanisms are known to operate. Mobile dislocation exhaustion rates and the amplitude of the yield point at reloading after stress-relaxation are measured. These two parameters are discussed in terms of the work-hardening coefficient in monotonic tests.
New Line Model for Optimized Dislocation Dynamics Simulations
Authors: Madec Ronan , Devincre Benoit , Kubin Ladislas P.
Published: June 2019

A new model for the discretisation of dislocation lines is presented, which is optimised for mesoscale simulations of dislocation dynamics. By comparison with the existing edge-screw model, the present one provides a better description of the stress field close to the dislocation lines. It simplifies the modelling of dislocation reactions and accelerates computations by allowing to make use of larger time steps. An application to attractive junctions and forest hardening is briefly sketched.
Coarse Slip Bands in a Single-Crystalline Aluminum Alloy
Authors: Yang Seung-Yong , Li Xianghong , Alloy Aluminum
Published: June 2019

The effect of crystal orientation on the discontinuous deformation and coarse slip bands in aluminum single crystals has been investigated by finite element simulation. The numerical analysis is based on a rate-dependent crystal plasticity model recently formulated by us with modifications made here that explicitly accounts for the three strain hardening stages and the effect of the interaction of dislocations and alloying elements on setting the hardening rules on the individual slip systems of the aluminum alloy crystal. The dependence of the magnitude of the serrations of tensile stress-strain curves on orientation and its evolution over the three strain hardening stages of Al-0.3%Mg single crystals observed experimentally has been successfully explained in this investigation.
Lattice Trapping of Cracks in Fe Using an Interatomic Potential Derived from Experimental Data and Ab Initio Calculations
Authors: Farkas D. , Mehl M. J. , Papaconstantopoulos D. A.
Published: June 2019

A recent approach which combines first-principles and experimental data to produce highly accurate and reliable interatomic potentials is tested for the case of bcc and fcc Fe. The Embedded-Atom-like potential accurately reproduces the basic equilibrium properties of bcc Fe, including elastic constants, phonon properties, and vacancy formation energies, as well as the correct relative stability of structures with coordination numbers ranging from 12 to 4. This potential was used in a simulation study of lattice trapping effects during the cleavage fracture of bcc Fe. A strong directional anisotropy for crack propagation was observed due to lattice trapping effects. The strongest trapping effects were observed for cleavage along the {110} planes and it was found that lattice trapping strongly favors cleavage along the {100} planes.
Self-Affinity Analysis of the Fracture Surfaces of Polypropylene and Opal Glass.
Authors: Hinojosa M. , Reyes E. , Guerrero C. , Ortiz U.
Published: June 2019

In this work we report the self-affinity analysis of the fracture surfaces of a polymeric semicrystalline material and an opal glass. In the case of the plastic material, samples of isotactic polypropylene (i-PP) were prepared by varying the cooling rate from the melt; this resulted in different spherulite sizes. Samples were then broken in bend test after being immersed in liquid nitrogen. In the case of the opal glass, samples with different sizes of the opacifying particles, obtained by different thermal treatments, were broken in a punch test. In both cases the fracture surfaces were analyzed by both Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) in the contact mode. Self-affinity analysis was performed by the variable bandwidth method, covering a range of length scales spanning from a few nanometers up to ten micrometers. The roughness exponents are found to be of similar values close to ζ = 0.8 with the correlation length corresponding to the size of the spherulites in the plastic material and to the size of the opacifying particles in the opal glass. These results should be taken into account in the development of multiscale models and simulations of the fracture process of real heterogeneous materials.
Cosserat Modeling of Size Effects in Crystalline Solids
Authors: Forest Samuel
Published: June 2019

The mechanics of generalized continua provides an efficient way of introducing intrinsic length scales into continuum models of materials. A Cosserat framework is presented here to descrine the mechanical behavior of crystalline solids. The first application deals with the problem of the stress field at a crak tip in Cosserat single crystals. It is shown that the strain localization patterns developping at the crack tip differ from the classical picture : the Cosserat continuum acts as a bifurcation mode selector, whereby kink bands arising in the classical framework disappear in generalized single crystal plasticity. The problem of a Cosserat elastic inclusion embedded in an infinite matrix is then considered to show that the stress state inside the inclusion depends on its absolute size lc. Two saturation regimes are observed : when the size R of the inclusion is much larger than a characteristic size of the medium, the classical Eshelby solution is recovered. When R is much small than the inclusion, a much higher stress is reached (for an inclusion stiffer than the matrix) that does not depend on the size any more. There is a transition regime for which the stress state is not homogeneous inside the inclusion. Similar regimes are obtained in the study of grain size effects in polycrystalline aggregates of Cosserat grains.
Coupling of Length Scales: Hybrid Molecular Dynamics and Finite Element Approach for Multiscale Nanodevice Simulations
Authors: Lidorikis Elefterios , Bachlechner Martina E. , Kalia Rajiv K. , Voyiadjis George Z. , Nakano Aiichiro , Vashishta Priya
Published: June 2019

A hybrid molecular-dynamics/finite-element simulation scheme is applied to describe multiscale phenomena in nanodevices. The quality of both static and dynamic coupling between atomistic and continuum regions is studied. The hybrid scheme is used for the Si/Si3N4 interface problem (static coupling), and for the projectile impact on Si problem (dynamic coupling). Excellent agreement is found between hybrid and full molecular dynamics simulation results in the static case, and no wave reflections are found at the atomistic/continuum hand-shake in the dynamic case. The hybrid scheme is thus validated a powerful and cost effective method for performing multiscale simulations of nanodevices.
Microstructure and optical properties of GaN films grown on porous SiC substrate by MBE
Authors: Yun F. , Reshchikov M. A. , He L. , King T. , Huang D. , Morkoç H. , Inoki C. K. , Kuan T. S.
Published: June 2019

GaN thin films were grown on porous SiC substrates using reactive molecular beam epitaxy with ammonia as the nitrogen source. Microstructure analysis and optical characterization were performed to assess the quality of the effect of pores on the growth and the quality of the GaN films. Results indicate that the GaN films on porous SiC are slightly less defective and more strain-relaxed (some completely relaxed) when grown on porous SiC substrate, as compared to growth on standard 6H-SiC substrates. Rocking curve FWHMs of 3.3 arcmin for (0002) diffraction and 13.7 arcmin for (1012) diffraction were obtained for sub-micron thick GaN films. Excitonic transition with FWHM as narrow as 9.5 meV was observed at 15K on the GaN layer grown on porous SiC without a skin layer.
Influence of Be Doping on Material Properties of Low-Temperature-Grown GaAs
Authors: Marcinkevièius Saulius , Gaarder Andreas , Siegert Jörg , Roux Jean-Fraņois , Coutaz Jean-Louis , Wolos Agnieszka , Kaminska Maria , Adomavičius Ramūnas , Bertulis Klemensas , Krotkus Arunas
Published: June 2019

A number of experimental techniques were used to characterize structural quality, ultrafast carrier dynamics and deep center properties of low-temperature-grown GaAs doped with Be. GaAs layers grown at 280 °C, doped with the Be concentration from 5×1017 cm-3 to 2×1019 cm-3 and annealed at temperatures between 500 and 800 °C were studied. Electron trapping times in these samples varied from hundreds of femtoseconds to several picoseconds. A non-monotonous electron trapping time dependence on Be doping level is explained by the influence of triple-charged gallium vacancies and single-charged Be-acceptors on the number of ionized As antisite defects.
Charges and Dipoles at Semiconductor Interfaces
Authors: Tung Raymond T.
Published: June 2019

The formation of the Schottky barrier height at metal-semiconductor interfaces has often been discussed in terms of interface states. This paper examines theoretical models that specifically relate defects and other interface states (such as MIGS) to the interface dipole. These models usually rely on the assumption, which is also invoked in most experimental determination of interface state distribution, that the interface dipole can be broken up into the product of an interface charge and an interface distance/width. Various inconsistencies associated with this assumption are discussed, suggesting that the formation of the interface dipole is an integral process which cannot be divided. It is shown that the inclusion of the bond polarization at semiconductor interfaces, proposed in recent work, gives quantitative account of experimental Fermi level pinning effect. In addition, the bond polarization concept can be extended to the theoretical description of band offsets at epitaxial semiconductor heterojunctions. These results underscore the importance of correctly handling the chemistry at semiconductor interfaces in order to understand their electronic properties.
Injection of point defects by oxidation of AlGaAs
Authors: Chamberlin Danielle R. , McHugo Scott A. , Burak Dariusz , Burke Deyon , Osentowski Tim , Rosner S. Jeffrey
Published: June 2019

Injection of point defects into GaAs/AlxGa1-xAs heterostructures by oxidation of AlxGa1-xAs is investigated. The blueshift of the PL emission from GaAs quantum wells is measured as a function of rapid thermal annealing conditions in as-grown and thermally oxidized samples. Contrary to published data for point defect injection by oxidation of GaAs, oxidation of AlxGa1-xAs appears to reduce the interdiffusion of the quantum wells. The PL peak shifts after annealing have been fit assuming Al diffusion in the quantum wells and solving the singleparticle Schrödinger equation. These fits show a reduction in group-III diffusivity of over an order of magnitude with an oxidized layer of AlxGa1-xAs on the surface.
Laser Engineering of Barrier Structures Based on Solid Solution ZnCdHgTe.
Authors: Khlyap Galina
Published: June 2019

Room-temperature electric investigations carried out in CO2-laser irradiated ZnCdHgTe epifilms revealed current-voltage and capacitance-voltage dependencies typical for the metal-semiconductor barrier structure. The epilayer surface studies had demonstrated that the cell-like relief has replaced the initial tessellated structure observed on the as-grown samples. The detailed numerical analysis of the experimental measurements and morphological investigations of the film surface showed that the boundaries of the cells formed under the laser irradiation are appeared as the regions of accumulation of derived charged defects of different type of conductivity supplying free charge carriers under the applied electric field.
An Study of Influence of Imperfections on the Delamination of Diamond-Like Carbon Films
Authors: Moon Myoung-Woon , Lee Kyang-Ryel , Chung Jin-Won , Oh Kyu Hwan
Published: June 2019

The role of imperfections on the initiation and propagation of interface delaminations in compressed thin films has been analyzed using experiments with diamond-like carbon (DLC) films deposited onto glass substrates. The surface topologies and interface separations have been characterized by using the Atomic Force Microscope (AFM) and the Focused Ion Beam (FIB) imaging system. The lengths and amplitudes of numerous imperfections have been measured by AFM and the interface separations characterized on cross sections made with the FIB. Chemical analysis of several sites, performed using Auger Electron Spectroscopy (AES), has revealed the origin of the imperfections. The incidence of buckles has been correlated with the imperfection length.
First-Principles Simulation of Hydrogen Interaction in Amorphous Silicon Nitride
Authors: Kroll Peter
Published: June 2019

Structure and properties of amorphous hydrogented silon nitride (a- SiNx:H) are studied using density functional methods. Models of a-SiNx:H were generated using a random network algorithm. In addition we investigarted the N-H terminated surfaces of β-Si3N4.

A comparison between the vibrational spectra of the surface and of the bulk models shows that within the bulk the frequency of N-H bond stretching (≈ 3150 cm-1) is lower than at the surface (≈3300 cm-1). Both spectra show an asymmetric form of the principal peak tailing towards space of hydrogen with nearby atoms. Car-Parrinello moleculat dynamic simulations at elevated temperatures show hopping of bulk hydrogen between different two bonding sites. Moreover, hydrogen acts as network transformer releasing internal stresses.
Modeling Growth Directional Features of Silicon Nanowires Obtained Using SiO
Authors: Tan T. Y. , Lee S. T. , Gösele U.
Published: June 2019

Silicon nanowires (SiNW) grown using Si monoxide source materials are mainly oriented in the <112> direction, and some in the <110> direction. These directional features may be understood by postulating that growth of the SiNW is governed by lateral advancement of {111} plane layers that are stepped, and the role of particular kinds of dislocations providing perpetuate steps.
Understanding the Formation Energy of Transition Metal Hydrides
Authors: Smithson Huw J. , Morgan Dane , Ven Anton Van der , Marianetti Chris , Pedith Ashley , Ceder Gerbrand
Published: June 2019

A detailed analysis of the formation energies of transition metal hydrides is presented. The hydriding energies are computed for various crystal structures using Density Functional Theory. The process of hydride formation is broken down into three consecutive, hypothetical reactions in order to analyse the different energy contributions, and explain the observed trends. We find that the stability of the host metal is very significant in determining the formation energy, thereby providing a more fundamental justification for Miedema's “law of inverse stability” [1] (the more stable the metal, the less stable the hydride). The conversion of the host metal to the structure formed by the metal ions in the hydride (fcc in most cases) is only significant for metals with a strong bcc preference such as V and Cr - this lowers the driving force for hydride formation. The final contribution is the chemical bonding between the hydrogen and the metal. This is the only contribution that is negative, and hence favourable to hydride formation. We find that it is dominated by the position of the Fermi level in the host metal.
Electrical and Optical characteristics of ZnO:Al Thin Films
Authors: Keum M.J. , Yang J.S. , Son I.H. , Shin S.K. , Choi H.W. , Lee W.S. , Choi M.K. , Chu S.N. , Kim K.H.
Published: June 2019

ZnO with hexagonal wurzite structure is a wide band gap n-type semiconductor. ZnO films can be prepared to obtain high transparency in the visible range, low resistivity, chemical stability and stability in hydrogen plasma including many foreign materials such as Al, In. In this work, we prepared ZnO:Al thin film by Facing Targets Sputtering system with Zn metal target and ZnO:Al(Al2O3 2wt%, 4wt%) ceramic target at total working gas pressure 1mTorr, substrate temperature R.T.. We evaluated the crystallographic, electrical and optical characteristics of the ZnO:Al films.
A Grain Boundary Engineering Approach to Promote Special Boundaries in a Pb-base Alloy
Authors: Lee D.S. , Ryoo H.S. , Hwang S.K.
Published: June 2019

A grain boundary engineering approach was employed to improve the microstructure of a commercial Pb-base alloy for better performance in automobile battery application. Through a combination of cold working, recrystallization and subsequent thermomechanical-processing, it was possible to increase the fraction of the low ∑ coincidence site lattice boundaries up to 91% in addition to the substantial grain refinement. A preliminary electrochemical evaluation indicated a better corrosion resistance in the experimental material laden with the special boundaries. The high frequency of the coincidence site lattice boundaries in the specimens was interpreted in terms of the '∑3 regeneration' model proposed in previous works.
Ultralight Amorphous Silicon Alloy Photovoltaic Modules For Space Applications
Authors: Beernink Kevin , Pietka Ginger , Noch Jeff , Younan Kais , Wolf David , Banerjee Arindam , Yang Jeffrey , Jones Scott , Guha Subhendu
Published: June 2019

Results for solar cells with high specific power (W/kg) using amorphous silicon alloy technology are reported. Currently available roll-to-roll production technology capable of high volume has been used to form cells on thinned stainless steel with high specific power. Results of cells on thinned stainless steel formed in batch mode in research and development (R&D) machines are also presented. Cells on polyimide in the early R&D stage have also been formed and are described. An analysis of cell component material and dimension changes to increase specific power shows that specific power ∼2000 W/kg is possible as a long-term goal. Cells with specific power ranging from 300 to 400 W/kg for production cells with 8.5 % beginning of life AM0 efficiency to over 1200 W/kg for R&D cells on polyimide substrates are presented.