An Empirical Analysis of the Determinants of Success of Food and Agribusiness E-Commerce Firms

E-commerce's value creation in agricultural and food markets will only occur to the extent that e-commerce firms exist throughout the supply chain. The problem is that e-commerce firms throughout the agricultural and food supply chain have faced a serious challenge in staying in business. Many have been forced to exit the market, and only a few have survived to develop into functional web-based businesses. The objective of this research study is to identify characteristics that are associated with successful e-commerce firms throughout the agricultural and food supply chain. Relevant e-commerce and agricultural e-commerce literature suggests several characteristics that influence the success for agricultural and food e-commerce firms. A limited-dependent variable technique, logistic regression, is used to relate websites' characteristics to their probability of survival.e-commerce, food chains, survival probability, logistical regression, Agribusiness,

Geometric classical and total correlations via trace distance

We introduce the concepts of geometric classical and total correlations through Schatten 1-norm (trace norm), which is the only Schatten p-norm able to ensure a well-defined geometric measure of correlations. In particular, we derive the analytical expressions for the case of two-qubit Bell-diagonal states, discussing the superadditivity of geometric correlations. As an illustration, we compare our results with the entropic correlations, discussing both their hierarchy and monotonicity properties. Moreover, we apply the geometric correlations to investigate the ground state of spin chains in the thermodynamic limit. In contrast to the entropic quantifiers, we show that the classical correlation is the only source of 1-norm geometric correlation that is able to signaling an infinite-order quantum phase transition.Comment: v2: published versio

Community detection in complex networks by dynamical simplex evolution

We benchmark the dynamical simplex evolution (DSE) method with several of the currently available algorithms to detect communities in complex networks by comparing correctly identified nodes for different levels of fuzziness of random networks composed of well-defined communities. The potential benefits of the DSE method to detect hierarchical substructures in complex networks are discussed

Propuesta did?ctica para la construcci?n del concepto de variable como n?mero general basada en el modelo 3UV

156 p. Recurso Electr?nicoEn este proyecto se presentan algunos aspectos fundamentales en los procesos de ense?anza-aprendizaje del concepto de la variable como n?mero general en estudiantes pertenecientes a cinco grados diferentes de ense?anza media del instituto t?cnico Benjam?n Herrera de la ciudad de Ibagu?, teniendo como referentes principales el modelo 3UV (3 Usos de la Variable) Trigueros y Ursini, (2003); Ursini, et al., (2005) y el aprendizaje instrumental y relacional planteado por (Skemp, 1978). Para lo cual se han realizado una secuencia de actividades encaminadas a estos educandos por medio de una metodolog?a apropiada, de tal manera que les permita apropiarse del concepto en distintas facetas, interpretativa, aplicativa, anal?tica, y reflexiva que conlleve a un aprendizaje con comprensi?n y significado; no simplemente reducido a la aplicaci?n de reglas o algoritmos sin sentido. En este proyecto se hace una invitaci?n a la reflexi?n sobre c?mo se est? ense?ando las matem?ticas en nuestro contexto colombiano, sobre la importancia de generar un desarrollo del pensamiento Variacional desde edades tempranas, para fortalecer el paso de la aritm?tica al algebra; en cuanto a esto, es muy importante integrar al curr?culo actividades que pensadas desde lo aritm?tico y geom?trico potencialicen el razonamiento algebraico. Palabras claves: patr?n, ?lgebra, generalidad, unidad did?ctica, variable, modelo 3UV.In this Project are presented some fundamental aspects in the teaching ? learning process from the concept of the variable as a general number in students belonging to five different middle school grades from the Technical Institute Benjam?n Herrera from the city of Ibagu?, taking as principal referents the Model 3UV (3 Uses of the Variable) Trigueros and Ursini, (2003); Ursini, et al., (2005) and the instrumental and relational learning proposed by (Skemp, 1978). For which it has been executed a sequence of activities directed to these students by means of an appropriate methodology, in such a way that allows them to appropriate the concept in different facets, interpretative, applicative, analytical and reflective that lead to a learning with comprehension and meaning; not simply reduced to the application of rules or algorithms with no sense. In this project is made an invitation to the reflection on how mathematics is being taught in our Colombian context, about the importance of generate a development of variational thinking since early ages, to strengthen the passage from arithmetic to algebra; in terms of this, is very important to integrate into the curriculum, activities that thought from the arithmetic and geometric, potentiate the algebraic reasoning. Key words: pattern, algebra, generality, didactic unit, variable, Model 3UV

Functional morphology of tegmina-based stridulation in the relict species Cyphoderris monstrosa (Orthoptera: Ensifera: Prophalangopsidae)

Male grigs, bush-crickets and field crickets produce mating calls by tegminal stridulation: the scraping together of modified forewings functioning as sound generators. Bush- (Tettigoniidae) and field-crickets (Gryllinae) diverged some 240 million years ago, with each lineage developing unique characteristics in wing morphology and the associated mechanics of stridulation. The grigs (Prophalangopsidae), a relict lineage more closely related to bush crickets than to field-crickets, are believed to retain plesiomorphic features of wing morphology. The wing cells widely involved in sound production, such as the harp and mirror, are comparatively small, poorly delimited and/or partially filled with cross-veins. Such morphology is similarly observed in the earliest stridulating ensiferans, for which stridulatory mechanics remains poorly understood. The grigs, therefore, are of major importance to investigate the early evolutionary stages of tegminal stridulation, a critical innovation in the evolution of the Orthoptera. The aim of this study is to appreciate the degree of specialisation on grig forewings, through identification of sound radiating area areas and their properties. For well-grounded comparisons, homologies in wing venation (and associated areas) of grigs and bush-crickets are re-evaluated. Then, using direct evidence, this study confirms the mirror cell, in association with two other areas (termed ‘neck’ and ‘pre-mirror’), as the acoustic resonator in the grig Cyphoderris monstrosa. Despite the use of largely symmetrical resonators, as found in field-crickets, analogous features of stridulatory mechanics are observed between C. monstrosa and bush-crickets. Both morphology and function in grigs represents transitional stages between unspecialised forewings and derived conditions observed in modern species

Wing mechanics, vibrational and acoustic communication in a new bush-cricket species of the genus Copiphora (Orthoptera: Tettigoniidae) from Colombia

Male bush-crickets produce acoustic signals by wing stridulation to call females. Several species also alternate vibratory signals with acoustic calls for intraspecific communication, a way to reduce risk of detection by eavesdropping predators. Both modes of communication have been documented mostly in neotropical species, for example in the genus Copiphora. In this article, we studied vibratory and acoustic signals and the biophysics of wing resonance in C. vigorosa, a new species from the rainforest of Colombia. Different from other Copiphora species in which the acoustic signals have been properly documented as pure tones, C. vigorosa males produce a complex modulated broadband call peaking at ca. 30 kHz. Such a broadband spectrum results from several wing resonances activated simultaneously during stridulation. Since males of this species do rarely sing, we also report that substratum vibrations have been adopted in this species as a persistent communication channel. Wing resonances and substratum vibrations were measured using a μ-scanning Laser Doppler Vibrometry. We found that the stridulatory areas of both wings exhibit a relatively broad-frequency response and the combined vibration outputs fits with the calling song spectrum breadth. Under laboratory conditions the calling song duty cycle is very low and males spend more time tremulating than singing

Observation of environment-induced double sudden transitions in geometric quantum correlations

Correlations in quantum systems exhibit a rich phenomenology under the effect of various sources of noise. We investigate theoretically and experimentally the dynamics of quantum correlations and their classical counterparts in two nuclear magnetic resonance setups, as measured by geometric quantifiers based on trace-norm. We consider two-qubit systems prepared in Bell diagonal states, and perform the experiments in decohering environments resulting from Bell diagonal-preserving Markovian local noise. We then report the first observation of environment-induced double sudden transitions in the geometric quantum correlations, a genuinely nonclassical effect not observable in classical correlations. The evolution of classical correlations in our physical implementation reveals in turn the finite-time relaxation to a pointer basis under nondissipative decoherence, which we characterize geometrically in full analogy with predictions based on entropic measures.Comment: 5 pages, 2 figures. v2: Minor corrections. Published versio

Energy Self-Sufficiency Urban Module (ESSUM): GIS-LCA-based multi-criteria methodology to analyze the urban potential of solar energy generation and its environmental implications

The concentration of the population in cities has turned them into sources of environmental pollution, however, cities have a great potential for generating clean energy through renewable sources such as a responsible use of solar energy that reaches its rooftops. This work proposes a methodology to estimate the level of energy self-sufficiency in urban areas, particularly in a district of the city of Zaragoza (Spain). First, the Energy Self-Sufficiency Urban Module concept (ESSUM) is defined, then the self-sufficiency capacity of the city or district is determined using Geographical Information Systems (GIS), Light Detection and Ranging (LiDAR) point clouds and cadastral data. Secondly, the environmental implications of the implementation of these modules in the rooftops of the city using the LCA methodology are calculated. The results obtained show that total self-sufficiency of Domestic Hot Water (DHW) can be achieved using 21 % of available rooftop area, meanwhile the rest of rooftop area, dedicated to photovoltaic (PV), can reach 20 % of electricity self-sufficiency, supposing a final balance of a reduction in CO2 emissions of 12,695.4 t CO2eq/y and energy savings of 372,468.5 GJ/y. This corresponds to a scenario where full self-sufficiency of DHW was prioritized, with the remaining roof area dedicated to PV installation. In addition, other scenarios have been analyzed, such as the implementation of the energy systems separately

Heating energy consumption and environmental implications due to the change in daily habits in residential buildings derived from COVID-19 crisis: The case of Barcelona, Spain

The COVID-19 crisis has changed daily habits and the time that people spend at home. It is expected that this change may have environmental implications because of buildings’ heating energy demand. This paper studies the energy and environmental implications, from a Life Cycle Assessment (LCA) approach, due to these new daily habits in residential buildings at their current level of thermal insulation, and in different scenarios of thermal retrofit of their envelope. This study has a building-to-building approach by using Geographical Information Systems (GIS) for the residential housing stock in the case of Barcelona, Spain. The results show that a change in daily habits derived from the pandemic can increase the heating energy consumption and carbon dioxide emission in residential buildings by 182%. Retrofitting all buildings of Barcelona, according to conventional energy renovation instead of nearly Zero Energy Buildings (nZEB), will produce between 2.25 × 107 and 2.57 × 107 tons of carbon dioxide. Retrofitting the building stock using energy recovery is the option with better energy and emission savings, but also is the option with higher payback time for buildings built until 2007. The methodology presented can be applied in any city with sufficient cadastral data, and is considered optimal in the European context, as it goes for calculating the heating energy consumption