Universidad del Norte, Colombia

About: Universidad del Norte, Colombia is a education organization based out in Barranquilla, Colombia. It is known for research contribution in the topics: Population & Context (language use). The organization has 3562 authors who have published 4355 publications receiving 37861 citations. The organization is also known as: University of the North, Colombia & Uninorte.

Iriarteeae palms tracked the uplift of Andean Cordilleras

Abstract: Aim: The high biodiversity of northern South America is unparalleled and includesseveral centres of diversity such as Amazonia, the Andes and the Choco. Movementof lineages amongst and within these bioregions is thought to be rare, and theeffect of those dispersals on the distribution, diversity, and community assemblyremains poorly understood. Here we address these effects by studying divergencetimes, biogeographical history, and species diversification of the palm tribe Iriar-teeae, an ecologically dominant forest component. Location: Central and South America. Methods: We developed a calibrated phylogeny and a spatially explicit diversifica-tion model that incorporates molecular and fossil data. In these analyses, weincluded a new fossil Iriartea species Gemmamonocolpites galeanoana, derived fromnew samples of Miocene deposits in western Amazonia. We also estimated the geo-graphical range evolution of lineages and tested whether speciation and extinctionrates were affected by dispersal events using a simulation approach in ClaSSE. Results: Dispersal amongst bioregions was not evenly distributed across the topol-ogy. We found that Amazonian communities are overdispersed across the phy-logeny, whereas Andean taxa are clustered. Dispersal events were associated withincreases in species diversification and were concomitant with periods of Andeanuplift. Migration into montane areas occurred several times from lowland Amazonianancestors, and montane taxa subsequently recolonized the Amazonian bioregion. Main conclusions: Our results suggest that the diversification of Iriarteeae palmsclosely followed the west-to-east surface uplift history of the Northern Andes. Froman early, lowland Amazonian ancestor, the first diversification events took place inthe earliest emerging mountain chain, the Western Cordillera. From there multiplerange expansions followed eastwards and back into the lowlands. This study demon-strates how geological events within a single mountain range can affect the geo-graphical expansion and diversification of lineages.

Evaluation of the Effect of Pavement Roughness on Skid Resistance

Abstract: Roughness of a pavement surface is commonly correlated to its serviceability. On the other hand, on many occasions, investigators have attributed pavement roughness to inadequate skid resistance (friction) as well. However, current pavement friction evaluation and standardization models have yet to incorporate effects of pavement roughness. Hence a study was conducted to investigate and quantify the effects of pavement roughness on the skid number (SN) (or 100 coefficient of friction). First, an experimental program was executed to evaluate SN measured from a locked wheel tester (LWT) on pavement sections with similar micro- and macrotexture conditions but different levels of roughness. The measured average SN was seen to be significantly lower on relatively rougher pavement sections. To explain the above observations, a second set of experiments was conducted to study the effect of the normal load on the LWT tire on SN. Statistical analysis including regression and ANOVA was used to validate the nonlinear reciprocal relationship found between SN and the normal load which contradicts the general perception of constant SN with respect to the normal load. Then, a one-dimensional two-degrees-of-freedom vibration model was formulated to incorporate the significant dynamic fluctuations of the normal load of the LWT induced by pavement roughness and the vehicle speed. The variation of the normal load and its nonlinear relation to SN was used to explain lower SN values measured on relatively rougher surfaces. The feasibility of using the international roughness index and the dynamic load coefficient as predictors of the reduction in SN due to pavement roughness was also investigated. Assurance of adequate skid resistance is a vital factor considered in allocating pavement rehabilitation funds at the network level. Since excessively rough pavements also create skid hazards, it is concluded that roughness effects must be considered in pavement management systems not only for serviceability purposes, but also in safety evaluations.

A method for designing strategy maps using DEMATEL and linear programming

Abstract: Purpose The purpose of this paper is to propose a quantitative methodology for the identification of the causal relationships between strategic objectives in a strategy map of a balanced scorecard. This is done to face the possible weaknesses described in the literature regarding the causal links and the difficulty in validating the relationships. Design/methodology/approach The proposed method combines the multi-criteria decision-making method called decision-making trial and evaluation laboratory (DEMATEL) and an optimization model. DEMATEL is used to establish the importance of the strategic relations between strategic objectives, and the optimization model is used to find the relations that are more “important” and should be included in the strategy map. The method was created by reviewing the existing literature, modeling the problem, and applying it in a company. Findings The most important results of applying this methodological design include that the proposed method maintains the BSC classical structure; it also enables the generation of several alternatives to support the decision-making process in terms of strategic objectives for a better organizational performance. Practical implications The method facilitates the decision-making process by presenting several alternatives of strategy maps according to different levels of organizational criteria. In fact, these alternatives help the organization in focusing on the most important aspects of the strategy map. Consequently, managers may identify where to pay more attention and resources in order to achieve the most important objectives of the company. Hence, this method, as a support for decision makers, enables (and requires) the active participation of senior managers and any kind of decision makers in creating and valuating objectives, relations, constraints, importance, and parameters of the optimization model. Originality/value DEMATEL has been used to design strategy maps. The contribution of the paper is the use of a linear programming model to select those relationships that should be included in the strategy map. It allows manager to focus on those strategic elements that are important from a strategic point of view. The application in a company showed that the contribution is not only theoretical but practical as well.

On the Use of LoRaWAN in Smart Cities: A Study With Blocking Interference

Abstract: Low-power wide-area network technologies allow sending sensor information through long distances with low data rates. Long Range (LoRa) is one of these technologies, which is less susceptible to noise and interference. This technology operates in unlicensed bands, increasing the chances of having interfering devices in the communication link. The issue of LoRa jamming with external interference and the effect of such interference in radio range has not been addressed in the literature. Therefore, tests measured packet loss, received signal strength, and signal-to-noise ratio with one end node located kilometers away from a gateway. Data were measured with and without external interference, to establish system robustness. This article computes an empirical model of the immunity region, where the level of interference does not affect LoRa communication. Results show that LoRa devices required interference levels up to 14 dBm to have total packet losses. These results are relevant for implementing LoRa systems, motivating researches to perform site surveys of interference and to account for range reduction in network design.