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Electron-related nonlinear optical properties of cylindrical quantum dot with the Rosen-Morse axial potential
No full textWe present a theoretical study on the effects of intense laser field (ILF) and static electric field on the linear and nonlinear optical properties of a cylindrical quantum dot with Rosen-Morse axial potential under the framework of effective mass and parabolic band approximations. This study also takes into account the effects of the structure parameters (η, V 1, and R). The analytical expressions of the linear, third-order nonlinear and total optical absorption coefficients (TOACs) and the relative refractive index changes (RRICs) are obtained by using the compact-density-matrix approach. The results of numerical calculations show that the resonant peak position of the TOACs and RRICs shifts towards lower energies and the magnitude of the peak increases with the effect of the static electric field and ILF. In addition, it is observed that while the resonant energies of the TOACs and RRICs of system shift towards the higher (lower) energies with the enhancement of η, V 1, they decrease with the augmentation of R. Thus, the findings of this study show that the optical properties of the structure can be adjusted by changing the magnitude of structure parameters and applied external fields. © 2020 Chinese Physical Society and IOP Publishing Ltd
Opto-electronic properties of twisted bilayer graphene quantum dots
No full textThe electronic and interband optical properties of vertically coupled stacked graphene quantum dots are investigated using the tight-binding method. Both zigzag and armchair edge configurations are taken into account. In particular, the effect of the geometrical shape (triangular or circle-like) and, most prominently, of the angle of twisting between layers is mainly addressed. The optical response is analyzed from the calculated imaginary part of the dielectric function. It is found that the interband absorption threshold is highly dependent on the dot size and geometry: For armchair triangular bilayer graphene dots the optical gap exhibits a moderate increase for smaller angles of twisting, and the structure behaves as an intermediate to a wide gap semiconductor; whereas zigzag triangular bilayer graphene dots are small gap systems in which the twisting causes the appearance of zero-gap states associated with the variation of HOMO and LUMO states resulting from the breaking of zero-energy degeneracy. In the latter case, it is shown that the low-energy transitions between those states are responsible for the main optical response of the structures which indicates possible applications in the THz optoelectronics. Circular dots are chosen in commensurable configurations and also show stronger low-energy absorption thresholds. A particular feature appearing in this case is the presence of Bravais-Moiré patterns in the two-dimensional probability density distributions for large enough dot radii. © 2019 Elsevier B.V
Removal of Cr (VI) from an aqueous solution using an activated carbon obtained from teakwood sawdust: Kinetics, equilibrium, and density functional theory calculations
No full textBecause of its acute toxicity and high mobility, the hexavalent chromium [Cr (VI)] found in wastewater is a risk to the environment. In this study, activated carbon was produced from teakwood sawdust, which was chemically modified using ZnCl2 (AT) as an efficient adsorbent for Cr (VI) removal from aqueous systems. Batch experiments were conducted to identify kinetic, diffusional, and equilibrium parameters. In addition, to better understand the adsorption process, computer calculations were conducted based on the density functional theory (DFT). A maximum adsorption capacity of 72.46 mg g-1 was achieved by adapting experimental data to the Langmuir isotherm model. Intraparticle diffusion was further identified through a three-dimensional diffusion model, which revealed that it was ruled by intraparticular diffusion based on surface diffusion, with surface diffusion coefficient (Ds) values ranging from 1.29 × 10-10 to 0.78 × 10-10 cm2 s-1. Finally, computational chemistry calculations and an FTIR analysis determined that oxygenated functional groups, lactone, semiquinone, phenols, and carboxylic acids were involved in the process of Cr (VI) adsorption on AT. Moreover, the main adsorption mechanisms were found to be complexation, electrostatic interaction, and reduction of Cr (VI) to Cr (III). © 2020 Elsevier Ltd
A new way for comparing solutions to non-technical electricity losses in South America
No full textNon-technical losses are a component of energy losses associated with energy theft and fraud by the final consumers, hindering revenues of distribution utilities. This paper aims to compare the implemented solutions in the countries of South America to reduce non-technical losses. In this comparison, we introduce a new indicator based on the World Bank's database as input information. Considering that some regulatory agencies take policy actions related to non-technical losses to improve the quality of the electricity supply, we also present a correlation analysis of the proposed indicator and the electricity supply quality index. This analysis shows that in most of South America's countries, there is a high correlation within the studied horizon. An adequate characterization of the temporal variation in the proposed indicator can characterize the evolution of the consumers' perception of the quality in the electricity supply. This indicator allows each country's regulatory agency to analyze how the performed action is reducing non-technical losses concerning neighboring countries. © 2020 Elsevier Lt
A Kinetic Modelling of the Growth Rate of Lolium perenne for Phytotoxicity Bioassays
No full textPlant growth rate represents one of the main factors in the vegetal-model bioassays design and the development of phytoremediation technologies. Lolium perenne is a promising plant to heavy metals monitoring and phytoremediation, but bioassays protocols and toxicity limits are needed. In this research, the effects of cadmium and mercury on germination time and emergence as toxicity markers of Lolium perenne plants were determined. Seeds were exposed to increasing concentrations in the range of 0 to 25 mg/L of cadmium (Cd2+) and mercury (Hg2+) in Petri dishes, by independent experiments carried out for 14 d. Emergence, root and shot length were assessed and kinetic parameters of growth were calculated. After 14 d, the maximum germination index of control seeds was 78.7 ± 4.8 %. The treatment of 25 mg/L Cd2+ posed an inhibitory effect on the seeds emergence of 24.7 %, and reduced the velocity germination Index (VGI). The maximum germination index of Hg2+ treated seeds had not significant differences to control. Toxic effects of Cd2+ and Hg2+ were found on the development of stem and roots of Lolium perenne, however, the range of concentrations which the plant grows well, is considered a suitable condition to potentially act as a phytoremediator. The kinetic parameters of growth are useful to perform toxicity tests and phytoremediation protocols of Lolium perenne. Copyright © 2019, AIDIC Servizi S.r.l
On the Optimal Robust Time-Delay Robot Dynamics
No full textOur paper is devoted to a specific class of Optimal Control Problems (OCPs) in theoretical mechanics. We consider a minimax-Type optimal control processes governed by dynamic systems with randomly varying time delays. In particular we deals with the minimax-Type OCPs associated with a family of delayed Lagrange differential equations for the robot dynamics. The mathematical abstractions under consideration provide an adequate approach to many real-world robotic systems. Moreover, the proposed minimax dynamic optimization approach has a fundamental interpretation as a system robustness with respect to the unavoidable delays in robot control. The obtained convex structure of a linearized robot dynamics makes it possible to reduce the originally given delayed OCP to an auxiliary convex program in a suitable Euclidean space. The equivalent transformation we propose involves the wide range of effective algorithms for an effective computational treatment of the resulting convex OCP. We finally propose a concrete gradient based computational approach for the optimal control design of the controlled Lagrange-Type robot dynamics. © 2018 IEEE
Distribution of chemical forms of mercury in sediments from abandoned ponds created during former gold mining operations in Colombia
No full textTotal mercury (THg) and methylmercury (MeHg) were studied in sediments from 27 abandoned gold mining ponds (AGMPs) through small-scale artisanal gold mining in the district of San Juan in Chocó region of Colombia. The AGMPs were abandoned in the last century (1997) and were grouped into three distinct groups (2–6; 7–12; 13–20 years). Overall concentration (in ng g−1) pattern of THg in sediments varied from 39.06 to 1271.32 (avg. 209.57) with 174.81 (13–20 years), 205.56 (7–12 years) and 248.33 (2–6 years) respectively. MeHg concentrations accounted for 3.3–10.9% (avg. 6.5%) of THg and were significantly correlated with THg during all periods. Correlations between organic matter (OM) vs MeHg and THg were negative in the oldest pools, signifying a “dilution effect” or “natural burial” of THg and MeHg. Results for sequential extraction indicate that the fraction of elemental Hg (Hg-e) and organo chelated Hg (Hg-o) represent the main chemical forms of Hg in the sediments, regardless of the abandonment period, whereas the bioavailable fraction was only 0.12–1.65% of THg. The significant statistical relationship between MeHg, THg and OM suggests that these parameters control the distribution, mobility, toxicity and bioavailability of Hg in the sediments of these abandoned ponds. Evaluation of THg with sediment quality guidelines indicates that the values are on the higher side for Threshold effect concentration and Upper continental crust. Comparing of MeHg with many other regions outside Colombia is a worrying factor and needs immediate attention to protect the human health. © 2020 Elsevier Lt
The family model of the concubinage: A jurisprudential recognition in colombia [La estructura familiar del concubinato: Un reconocimiento jurisprudencial en Colombia] [A estrutura familiar do concubinato: Um reconhecimento jurisprudencial na colômbia]
No full textIntroduction. The family is considered as an institution in constant change. In spite of this, the legislator intends to maintain its structure from a religious, traditional, conservative, matrimonial perspective and based on monogamous and heterosexual couple relationships. However, social and cultural manifestations have achieved the recognition of family structures different from those regulated, in application of the principles of equality and equity, and in guarantee of patrimonial and personal rights, as in the case of concubinage. Objective. Establish the development and jurisprudential evolution in Colombia of the Supreme Court of Justice and the Constitutional Court that led to the concubinage from illegality to its recognition as a family structure with legal protection. Materials and methods. The jurisprudence on the concubinage of both Courts was reviewed and classified into three categories: those that began to recognize it as a family and established requirements for it, those that changed these requirements and those that established differences with the marital union in fact. Research result: It demonstrates how to change from an illegal situation to a family structure with legal recognition, although not legal and, once again, how family law in Colombia is ineffective when recognizing the personal and patrimonial rights that derive from emerging family relationships. Conclusion: The results are framed in the current discussions of the social sciences on the family as an institution in permanent change, without implying that it is in crisis, because it is an understanding from the ends, roles and functions that the family fulfills in society and not from its structure. © 2018, Corporacion Universitaria Lasallista.Introdução: A família é considerada como uma instituição em constante mudança. Apesar disso, o legislador pretende manter sua estrutura a partir de uma posição religiosa, tradicional, conservadora, matrimonial e baseada em relacionamentos monogâmicos e heterossexuais nos casais. No entanto, as manifestações sociais e culturais tem conseguido o reconhecimento de estruturas familiares diferentes às normalizadas na aplicação dos princípios de igualdade e equidade e, na garantia dos direitos patrimoniais e pessoais, como é o caso do concubinato. Objetivo: Estabelecer o desenvolvimento e evolução jurisprudencial na Colômbia do Tribunal Supremo da Justiça e do Tribunal Constitucional que levaram ao concubinato da ilegalidade ao seu reconhecimento como estrutura familiar com proteção jurídica. Materiais e métodos: Revisou-se a jurisprudencia sob o concubinato de ambos os Tribunais e classificaram-se em três categorias: aqueles que começaram a reconhecer-lo como família e estabeleceram requisitos para isso; aqueles que mudaram estes requisitos e aqueles que estabeleceram diferenças com a união conjugal de fato. Resultados: demonstra-se como mudar de uma situação ilegal para uma estrutura familiar com reconhecimento jurídico, embora não seja legal e, mais uma vez, o direito de família na Colômbia é ineficaz para reconhecer os direitos pessoais e patrimoniais que derivam das relações familiares emergentes. Conclusão: Os resultados são enquadrados nas discussões atuais das ciências sociais sob a família como uma instituição em constante transformação, sem implicar que está em crise, pois trata-se de uma compreensão dos propósitos, papéis e funções que a sociedade cumpre e não de sua estrutura. © 2018, Corporacion Universitaria Lasallista.La familia es considera como una institución en constante cambio. A pesar de ello el legislador pretende mantener su estructura desde una posición religiosa, tradicional, conservadora, matrimonial y basada en relaciones de pareja monogámica y heterosexual. No obstante, las manifestaciones sociales y culturales han logrado el reconocimiento de estructuras familiares diferentes a las normativizadas, en aplicación de los principios de igualdad y equidad, y en garantía de derechos patrimoniales y personales, como en el caso del concubinato. Objetivo: Establecer el desarrollo y evolución jurisprudencial en Colombia de la Corte Suprema de Justicia y la Corte Constitucional que llevaron al concubinato de la ilegalidad a su reconocimiento como estructura familiar con protección jurídica. Materiales y métodos: Se revisó la jurisprudencia sobre el concubinato de ambas Cortes y se clasificaron en tres categorías: las que comenzaron a reconocerla como familia y establecieron requisitos para ello; las que cambiaron estos requisitos y las que establecieron diferencias con la unión marital de hecho. Resultados: Se demuestra cómo se cambió de una situación ilícita a una estructura familiar con reconocimiento jurídico, aunque no legal y, una vez más que, el derecho de familia en Colombia es ineficaz para reconocer los derechos personales y patrimoniales que se derivan de las relaciones familiares emergentes. Conclusión: Los resultados se enmarcan en las discusiones actuales de las ciencias sociales sobre la familia como una institución en permanente cambio, sin que ello implique que se encuentre en crisis, debido a que se trata de una comprensión desde los fines, roles y funciones que aquella cumple en la sociedad y no desde su estructura. © 2018, Corporacion Universitaria Lasallista
Economic openness and trade policy: Struggles of the dairy sector in colombia [Apertura económica y política comercial: Estudio del sector lácteo y sus dificultades en colombia]
No full textSince the economic openness in Colombia, some economic sectors have experienced significant challenges to compete with foreign products, as is the case of the dairy sector. Thus, this article provides an analysis between economic openness and the behavior of the dairy sector in Colombia, considering that many products in this industry have applied prohibitive custom rates and bound tariffs, making the dairy sector the one with the highest level of tariff protectionism. Therefore, variables such as exports, imports, productive capacity, consumption, among others, were analyzed at the national level and in Latin America-The Caribbean. The results show that in Colombia there are excessive levels of tariff protectionism and a growth in imports in the dairy sector, reflecting internal problems of productive efficiency and competitiveness. In conclusion, it is proposed to focus Colombian exports on products with higher added value and continue with the efforts to modernize and capitalize the dairy supply chain, to offer competitive national prices and satisfy domestic demand. © 2020, Universidad del Zulia. All rights reserved
Resettlement processes in Colombia: Is this a measure of both adaptation and the protection of the human rights of communities affected by climate change? [Procesos de reasentamiento en Colombia: ¿una medida de adaptación y protección de derechos humanos de las víctimas del cambio climático?]
No full textThis article presents the deficiencies of the legal system in relation to resettlement of communities as an exceptional measure of climate change adaptation and protection of human rights. Among the deficiencies under analysis: the lack of an adequate conceptualization of resettlement, lack of public policy regarding resettlement and its relation to climate change adaptation, and the granting of broad discretional powers to municipal governments to undertake resettlement process that, in practice, are implemented through informal actions - with out specific regulation and protocols that guide its implementation - that have caused violations of human rights. This document is the result of an investigation that supported the construction of a report to the Inter-American Commission of Human Rights, through both exploratory and analytical documentary research and the study of and intervention in real cases. © 2018 Pontificia Universidad Javeriana. All rights reserved