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This paper presents the development of the utilization of solar energy in Colombia and discusses its development prospects. [ABSTRACT FROM AUTHOR]

This contribution gives up-to-date information on the use of wind generated electricity worldwide. It also describes the most immediate investment plans in the increase of wind as an alternative, non polluted energy source in Europe, as well as in the Latin America region. Based upon recent studies, carried out by the author, the paper assesses the wind energy potential for electricity generation in Colombia. At the end, some comments are made on developments and wind energy use in Colombia. [ABSTRACT FROM AUTHOR]

This paper presents a mathematical model of the problem of the planning of systems of electrical distribution which considers the location and sizing of new feeders and substations, and the reconductorazing of existing feeders. The mathematical model used is of the type Lineal Mixed Integer Programming (LMIP) and to solve it, an algorithm of Branch and Bound is used. In order to test the proposed algorithm, the electrical system of the city of Pereira is used. [ABSTRACT FROM AUTHOR]

This paper presents the main findings of the work carried out by Universidad de los Andes and Universidad Nacional de Colombia, with support from Colciencias -- the Colombian National Science Development Institution) and ISAGEN, a power generation company. These results are briefed in the following items: i) The main drivers for penetration of new energy sources and cleaner Technologies (not only for electricity) in the country, will be in its order: energy basket diversification, reduction of dependence on fossil fuels (as it is the case of biofuels), minimization of environmental impact, and support to technology and industrial development. ii) Current regulation of the energy market is not explicitly against the development of these power sources and technologies, however the market architecture and rules were made thinking in conventional sources and technologies, then some adjustments should be carried out to "level de playing field" for renewable in the country, this should aim to include all external cost and benefits from its installation and operation, as well as from the participation of distributed generation in grids. iii) It is indispensable to have appropriate financial schemes for longer pay-back periods with these technologies, investors should be aware of the benefits and complementarities that can be achieved in power markets, such as emission reduction. In addition, governments should give some priority to in-country technology development and to the adoption of some of these sources when conditions are the most favourable. [ABSTRACT FROM AUTHOR]

The main objective of this paper is to explore the incidence of the bidding processes, in civil engineering practice, that are producing the suspension of many consulting and construction projects. New circumstances involve low bidding cost evaluation and shorter times for project completion. This affects the possible training of young engineers. [TRANSLATION]

The present paper describes the work carried out in the development of a pump system for water desalination in a small reverse osmosis plant. The system must satisfy high pressure (4.8 MPa) and low flow rates (3.78 L/min) to operate the reverse osmosis membrane in its minimum energy consumption range. In order to achieve this objective, a positive displacement pump system (single action double effect) driven by a cycloidal speed reduction was developed. The system was tested under laboratory conditions. The analysis of the results shows high energy conversion efficiencies throughout the pumping cycle. The equipment was validated based on the acceptable flow and permeates concentration results. This design is capable of replacing actual pump systems that are technologically complex and at the same time more expensive. [ABSTRACT FROM AUTHOR]

EIn 1997 the Ministry of Environmental Affairs of Colombia adapted its National Cleaner Production Policy as a complementary environmental strategy to introduce prevention oriented approach into management practices of industry. Since then a range of different initiatives have been developed, all focused on the improvement of the environmental performance of companies. The results of the demonstration projects, voluntary agreements, capacity buildings programs among others, sustain the potential of this strategy to combine the reduction of environmental contamination with cost reductions and competitiveness improvement. Now, ten years after its expedition, Cleaner Production (CP) is still an emergent strategy for environmental management and industrial development in Colombian, even when the context of the time period and the main drivers, have changed. When in the early year's incentives to participate and contribute to CP initiatives were closely related to the new developed environmental regulation in Colombia and responses of industry towards those. Now, ten years later, the globalization of the economy and the integration of environmental variables in competitiveness make CP an important strategy to assume corporate social responsibility and respond to market and trade requirements. Taking into account this importance, this article proposes new ideas and strategies for the renovation of the National Cleaner Production Policy in Colombia. The proposed ideas and strategies are based on a: (i) historical review of the different CP initiatives in Colombia, (ii) the experience of the authors who have participated in a broad range of CP initiatives during the last ten years, and (iii) a literature review of CP initiatives and developments mainly published in the Journal of Cleaner Production. The conclusions of this paper show how the Cleaner Production Policy in Colombia has to develop towards an innovative business development strategy, changing its early emphasis of optimizing of existing processes and the implementation of best practices towards the innovation and promotion of cleaner technologies and sustainable business. Also the integration of the National Green Marketing Strategy with the Cleaner Production Policy opens up new perspectives to integrate environmental strategy with business development. [ABSTRACT FROM AUTHOR]

This paper presents the results of a consulting project in which a linear programming model was developed for establishing optimal packaging and delivery policies in a Colombian food company. The problem consists in minimizing transportation costs subject to capacity and packaging constraints and demand satisfaction. A sensitivity analysis showing possible future scenarios is also presented. Currently the company uses the model for optimizing its logistics operations. [ABSTRACT FROM AUTHOR]

This paper has as objective to model the principal Interlocking Schemes of switching, that belongs to Substation configurations of the Colombian Electric System for a voltage level of 230 KV. The modeling of the Interlocking Scheme will be used in a mathematic formalism such as Hierarchical High Level Petri Nets (H.H.L.P.N.). Once having obtained the model in the (H.H.L.P.N.) it's simulated in STATEFLOW computational toolbox of MATLAB designed to work with state finite machines, that required translate the H.H.L.P.N. to automata finite. [ABSTRACT FROM AUTHOR]

This paper presents the long term planning analysis of a power transmission system as a nonlinear integer mixed optimization problem that includes in the objective function the expected power not served as index that explicitly measures the reliability. This problem is solved combining the techniques of genetic algorithms for the optimization part and the state space enumeration for the reliability. As a real example, an expansion study of the power transmission system that serves the city of Pereira in Colombia is presented. [ABSTRACT FROM AUTHOR]

The access control systems (ACS) are useful to improve the Quality of Service solutions. These systems are generally based on delay, jitter or packet loss, employing more of these criteria to maintain the required quality of service requiring for voice or video sessions. We propose an ACS that employs packet loss between probes that send an end-to-end test stream before accepting additional sessions. We used Ethernet as our transport network because the 803.3ae is widely used in metropolitan area networks. This paper presents how the ACS will interoperate with MPLS and describe the improvements related to its use in a metropolitan Ethernet network. [ABSTRACT FROM AUTHOR]

Always have been told that: there is not tiny enemies, this statement couldn't be more true when we are talking about the fight between the body and different pathogen agents, cellular mutations, and dangerous substances. Right now our knowledge allow us to handle the matter at nanoscale (1/1.000'000.000 m) sizes. The nanotechnology develop this knowledge and be able to improve things as new materials, small amount of material to build devices, better performance with maximal efficiency of devices, and others [1], [2]. Using nanotechnology to solve health problems is call nanomedicine [2], [3]. This paper review nanotechnologic develops apply to diseases with high mortality and treatments that doesn't solve the problem deeply they just handle the disease with partial solutions. Therefore, nanomedicine will have greater impact in the future, improving the health issues of humanity. [ABSTRACT FROM AUTHOR]

In this paper we describe the application of discrete event simulation for analyzing queues in a school restaurant. From these results we determine quantitative requirements for restaurant design including the randomness of each process and their interaction. Furthermore the use of graphic tools allowed a fruitful interaction with the team in charge of the architectural design. We show the model construction process, the diverse scenarios analyzed, and the selected configuration, which shows strong advantages against the current design. [ABSTRACT FROM AUTHOR]

Many three-phase distribution feeders are unbalanced because, first, they serve their customers by means of single-phase distribution transformers; second, they use components which operate in single-phase manner; third, most of the failures that affect their components are single-phase. This important fact must be included in reliability studies because, as shown in this paper, when the contrary is assumed pessimistic assessments of the reliability indices are obtained which could lead to erroneous investment decisions. [ABSTRACT FROM AUTHOR]

This paper presents the results of the construction of a computing and architectural information system for a building solution catalog, CatArSis. The project's objective is the development of a systematized catalog of home solutions for low income population, assuring architectural quality, legal issues and appropriate technical conditions. We choose SVG (Scalable Vector Graphics) as the basic representation for architectural information, in order to generate customized documentation appropriate to demand building licenses and apply to government subsidies. [ABSTRACT FROM AUTHOR]

In this paper we present an algorithm of binary classification based on Support Vector Machines. It is combined with a modified Boosting algorithm. It run faster than the original SVM algorithm with a similar generalization error and equal complexity model but it has more compact representation. [ABSTRACT FROM AUTHOR]

In the first part of this paper the basics of the estimation of the stochastic production function is discussed. In the second part an application of the former is presented aimed at the hierarquization of the educational institutions which depend of the District of Bogotá, according to a measure of the technical efficiency --using inputs to maximize the output. For the present, a Cobb-Douglas production function is assumed with a symmetric noise and a semi-normal efficiency perturbations. Using maximum likelihood the parameters are obtained and the efficiency for each institution is calculated. [ABSTRACT FROM AUTHOR]

The work that is presented in this paper is comprised of two studies, carried out on the ISM, UNII I and UNII II bands, in the Hospital Universitario de la Samaritana. In the first study, measurements of the level of interference and electromagnetic noise were carried out on the 3 mentioned bands. The objective of this study was to have indications on the electromagnetic environment in: the ISM band, in which operates the wireless network that is installed in the hospital and on the UNII I and UNII II bands, in which some wireless local area networks can operate. It was found that microwave ovens emit radiation on the ISM band, the greater power registered was -52.48dBm. Additionally sporadic and short term radiation was found on the ISM band, although the source could not be determined. It was found convenient that the Access Points that operate near microwave ovens were configured in the channel 1. In the UNII I and UNII II bands, it was not found levels of power greater that the noise floor of the employed system. In the second study narrow band statistical path loss models were developed. The objective of this study was to adjust path loss models to the particular characteristics of the hospital's facilities. Such models constitute a starting point in the design of a wireless network, however it is clarified explicitly that the design of the wireless network does not do part of this work. It was found that in the new renal unit the electromagnetic energy is confined due to its architecture and to the materials with which it was built, this fact probably can be employed to achieve a convenient reassignment of frequencies. [ABSTRACT FROM AUTHOR]

This paper shows the study of the hydrolysis reaction of crude palm oil giving by lipase from Candida rugosa. The studied factors were agitation level, bleaching effect and lipase concentration. Experimentally 79 - 93% hydrolysis were achieved in 2 and a half hour. The reaction rate was increased with the increment of the impeller rotational speed as well as increasing the lipase concentration. Although the literature cites bleaching as a beneficial advantages to enzymatic hydrolysis, this procedure do not have a significant beneficial effect on the reaction. [ABSTRACT FROM AUTHOR]

The present paper will show that throughout the development of a deterministic algorithm the uniformity of the pressure service level in the Water Distribution Network (WDN) can be maximized. To obtain this in an optimal way, one must maximize an Index that relates the power by unit of weight dissipated by the network and the power by unit of weight available to dissipate by the same one (Resilience Index [2]), it improves the ability of the WDN to cope with possible failures in the system, slows down the pipes renovation processes and diminishes the level of leaks in the network. [ABSTRACT FROM AUTHOR]

This paper presents preliminary results from an on-going research project on the governance of water and sanitation services in the PUI of five metropolitan areas in three continents. It explores differences and similarities in the formal and informal practices in the delivery and consumption of these services. It deals with issues of access to decision-making, exploring the role that different actors, including state institutions, play in the political process. [ABSTRACT FROM AUTHOR]

Colombia has lacked an adequate planning process for the design, construction, and operation of wastewater treatment facilities in most of the municipalities. National, regional and local agencies have conflicting criteria for managing this sector. Furthermore, there is a lack of adequate tools to support decisions with appropriate environmental, financial, social, and technical information. In this paper, a computer model is presented as a tool to support at a national level the decision making process for planning municipal wastewater treatment facilities in Colombia. A geographical information system was used to obtain a structured river network from a digital elevation model. Modeling flows, dissolved oxygen, biochemical oxygen demand, and coliform bacteria throughout the entire national drainage network allowed the analysis of several wastewater treatment scenarios, using bacteriological contamination (i.e.: coliform bacteria) as the main indicator of public health risks resulting from wastewater pollution. Total length of oxygen deprived river reaches in the hydrological network was much less than the length of the bacteriological degraded reaches. Using multivariate analysis, different wastewater treatment scenarios were analyzed to determine their effectiveness to mitigate wastewater pollution, based on environmental, socioeconomic and infrastructure criteria. As a result, prioritizations for investment in wastewater treatment plants were obtained at municipal and basin levels. The decision making tool integrates the objectives of the national agencies involved in wastewater management policies, solving the conflicts between agencies and optimizing the use of financial resources for the sector. [ABSTRACT FROM AUTHOR]

Páramos are vulnerable zonal ecosystems located in the tropical mountains of Central and South America, approximately between 3000 and 4500 meters above the sea level. Their special characteristics generate particular floral, ecological, edaphological, geomorphological and climatic typologies. Páramos have great ecologic, genetic and scientific importance due to their endemic flora and landscapes, as well as their socio-economical functions, represented by their fundamental roll in water regulation for water supply in some cities downstream. Some efforts have been done to quantify the water balance in these special hydrosystems. This paper presents an approximation to the hydrologic modeling of these hydrosystems, based on the integration of the AvSWAT model, a horizontal precipitation model, and a geographic information system. As a case study, the upper Blanco river basin was analyzed. This basin is one of the principal areas of the Chingaza páramo, the main Bogotá City water supply source. Protection of these ecosystems is stressed in order to preserve flow regimes, mainly those associated with dry conditions. [ABSTRACT FROM AUTHOR]

On December 19th 2002 the accusatory system was formally introduced in the Colombian Constitution. This is, perhaps, the most complex change that our judicial system has undergone in the last decade. The implementation of the new criminal system implied a profound change in several institutions: a) the criminal courts, b) the general prosecution office; c) the national defense office; and d) all other state agencies that support criminal investigations. In order to design this transition the Comisión Interinstitucional para la Implantación del Sistema Penal Acusatorio (a governmental Commission responsible for the implementation of the accusatory system) open up a bidding. Uniandes in a temporal Union with the Instituto SER de Investigación, won this call for tenders. This paper briefly describes the way this multidisciplinary effort was done under the direction of the industrial engineering department. [ABSTRACT FROM AUTHOR]

This paper proposes an approaching focus from systems point of view, and empirical observation from the social networks design for the National Innovation System (NIS), through a typological and situational mapping that illustrate the articulation degree in the system, which from build a system dynamics model for the policy exploration, pointed to stimulate systemic efficiency of NIS. [ABSTRACT FROM AUTHOR]

The computational cost and complexity level of multiphysics analysis used in microsystems have demanded the creation of methodologies to create simplified models that provide accurate results in a fast and efficient way. These simplifications are known as the reduced order model (ROM) extraction. The ROM model captures lineal and nolineal behaviors accurately, in addition such a model is generated in a form that can be integrated into system level simulators. This paper introduces perhaps the most famous method to generate ROM models at the present. The method is applied to the analysis of a micro clamped-clamped beam electrostatically actuated, for this structure different simulations are performed; these analyses characterize the deflection of the structure for different kinds of voltage excitations. The outcomes demonstrate that sophisticated analysis can be carried out almost immediately once the ROM model is created. [ABSTRACT FROM AUTHOR]

In this paper we describe the implementation of a single-route city-bus timetabling LP model proposed by Riaño [15]. The aforementioned model considers stochastic issues like travel time and demand. A simulation model is also described, which was used to compare results from this model with others proposed in the literature. Preliminar results are promising. [ABSTRACT FROM AUTHOR]

This paper shows a review of studies comparing particulate emissions from diesel engines running on diesel, biodiesel and their blends, based not only on particle mass concentrations, but also on particle number concentrations and particulate chemical composition. Finally, it summarizes the need for thoroughly characterizing particulate matter emissions in studies comparing Colombian diesel and biodiesel from palm oil (or other oil-producing Colombian species). [ABSTRACT FROM AUTHOR]

This paper is focused on the extraction of myocardial borders (septum, endocardium and epicardium) on M-mode echocardiograms. The proposed method combines two algorithms, each developed specially to extract certain borders. The extraction of the epicardium is done by means of a basic maximum tracking algorithm [8]. For the extraction of the endocardium and the left wall of the interventricular septum, a 2 stages discontinuity detector [6] is used. In the first stage the local mean of the image is calculated, and for the second stage the local variance is used. The output of this detector represents the discontinuities in the M-mode echocardographic image. Additionally, the method allows for manually correction of errors in the detection. Experimental examples are presented to test the performance of the methodology. [ABSTRACT FROM AUTHOR]

Hybrid systems arise by the interaction between continuous dynamical systems and Discrete-event systems. This paper presents two modeling frameworks for this type of systems, in particular Mixed and Logical Dynamical (MLD) systems is explained. Then, model predictive control using MLD models is presented. The results are applied to a three-tank benchmark system as example. [ABSTRACT FROM AUTHOR]

Data and information analysis, together with the representation and modeling of the uncertainties associated with real world phenomena and reality perception are fundamental tasks in any engineering work. Traditionally, uncertainty has been represented by the probability theory. However, there are uncertainty types which could be better represented by other theories like fuzzy sets, possibility theory and Depster-Shafer theory, among others. This paper describes uncertainty types and the use of fuzzy sets, fuzzy inference and fuzzy reasoning as alternative to well known techniques of probabilistic inference and reasoning when vagueness is present and expert knowledge and experience is to be included in the reasoning system. [ABSTRACT FROM AUTHOR]

Vehicle performance road testing is based on international standards, particularly those developed by SAE. The Centro de Investigación en Control Ambiental, Vehículos y Combustibles -- CICOM designed a system capable of testing vehicles according to those standards. The system has already been used on different vehicles. This paper describes the procedure followed in order to perform vehicles tests, the equipment used to perform it, and results from a study done on a vehicle converted to natural gas. [ABSTRACT FROM AUTHOR]

Language capacity, acquiring and learning of other symbolic systems and the development of more elaborate thinking behaviors seem to be improving due to technology that constitutes a platform which allows research and problem resolution for disabled people with communication problems. This paper outlines the results of a interdisciplinary project experience between the Electric Engineering and Industrial Design department of the Los Andes University, and the Pedagogy department of the Pedagogic National University, which focuses on generating functional tool prototypes for people with disabilities. [ABSTRACT FROM AUTHOR]

This paper summarizes the main results of a research project carried out to determine the main characteristics and mechanical properties of the structural elements that conform the earth made constructions, and to propose seismic rehabilitation alternatives according to the seismic hazard and characteristics of this kind of structures in Colombia. The proposed seismic rehabilitation alternatives consist of reinforcement with wire mesh covered with lime based mortar, and confining reinforcement with wooden elements. These alternatives were subjected to a series of tests on small specimens, full scale walls loaded on both directions, shaking table tests on 1:5 scale models and cyclic horizontal loading on 1:1.5 house models. The results of the research allow to establish advantages and disadvantages for the rehabilitation alternatives studied. Considering the high seismic vulnerability of earth made constructions, the confining reinforcement with wooden elements was found to be a promising alternative to reduce the seismic risk of this type of constructions. [ABSTRACT FROM AUTHOR]

The use of virtual media as a support to formal higher education requires a methodology able to support the teacher's specific educative needs and the pedagogical requirements of diverse subjects and knowledge areas. This paper presents the methodology used on the construction of Learning Virtual Environments as a complement to the face to face activities of ten different disciplines courses on the Universidad de los Andes, at Bogotá (Colombia). The procedure and balance of this methodology are part of the reflection contained in this document. [ABSTRACT FROM AUTHOR]

This paper presents the common elements of the multivariate multiple regression, multivariate analysis of variance (manova), canonical correlation analysis and discriminant analysis of canonical variates focusing on the statistical tests and, in some extent, on the mathematics behind the techniques [ABSTRACT FROM AUTHOR]

This paper presents a rigorous mathematical method -created by the author- to calculate accurately the optimal size (or capacity) of an industrial plant while it is beeing planned and evaluated. Text-books on Proyect Evaluation, Financial Mathematics and connected subjects do not mention this method neither any othe for solving this important problem in Industrial Engineering. [ABSTRACT FROM AUTHOR]

In this paper we present a method, which has been denominated off/on-line, its objective is to calculate the reserve of resources (optimal bandwidth) in an ATM network, based on the characteristics of the traffic (MPEG-I video traces with category VBR), the characteristics of the network and certain parameters of quality of service: maximum delay between emitter and receiver and the cell loss rate in the transmission. [ABSTRACT FROM AUTHOR]

The main purpose of this paper is developing and applying a methodology based on multivariate statistical procedures to endorse a classification of certain rural regions in Colombia. In order to achieve the aims, cluster analyses were the basic procedures made. The techniques of principal components, canonical variates, discriminant analysis and Andrews' plots were used to validate the cluster analyses results. [ABSTRACT FROM AUTHOR]

This paper presents results of experimental tests of thin walled steel columns under pure axial loading. Twelve different elements in terms of slender factors were tested. Typical failure modes correspond to expected ones such as global or local buckling. Ultimate axial compression stresses were compared with analytical expressions given by the national building code, Norma Colombiana de Diseño y Construccion Sismo Resistente, NSR-98, presenting a relatively good agreement of results. Fabrication details as well as residual stresses play an important role when estimating axial strength of thin walled steel columns. [ABSTRACT FROM AUTHOR]

Auctions are price setting mechanisms that reduce transaction costs. In addition, auctions are efficient mechanisms because the winner will have the object to its best use. This paper presents the results of extensive simulated experimentation to observe and test the results given by the Revenue Equivalence Theorem. The Theorem says that all members of a certain family of auctions with some defined properties yield the same expected revenue to the seller. The auctions studied are Sad Losers, Santa Claus, All Pay, and Last Pay; these auctions satisfy the assumptions needed for the results of the Theorem to be valid. [ABSTRACT FROM AUTHOR]

The present article, briefly, describes the theoretical design procedure of Wells turbines, typically utilized in Pneumatic Wave Energy Conversion Systems (PWECS). The principle behind the PWECS consists of extracting the pneumatic energy caused by an oscillating water column by the entrance of water waves in enclosed spaces. The paper establishes the design and experimental testing of a small permanent magnet generator suited for the wells turbine under development. The adequate matching between the Wells turbine and the generator has been conceived as a portable 50w d.c. electricity generation device; to be used, either, to powering telecommunications systems in military operations or to power navigation aids in rivers or at sea [ABSTRACT FROM AUTHOR]

This paper presents a methodology for implementation of synthetic of VBR MPEG video traffic, that also of model the marginal distribution capture in a high grade the pres ent correlations in the empirical video traffic traces. It realizes an statistical and simulation comparison with empirical and synthetic traces. In the simulation its compare the parameters of performance of a system conformed for a buffer finite and an ATM link of output with empirical and synthetic traffic input. Its evidence that temporal dependence is the characteristic limitative of the models of generation of synthetic traffic. [ABSTRACT FROM AUTHOR]

Human wastes constitute an evergrowing by-product of civilization. Several catastrophic landslides have taken place in these so-called sanitary land fills. It is apparent that geotechnical and environmental engineers follow divergent paths to solve the related technical problems. Part I of this paper addresses the development of mechanical sciences leading to Soil Mechanics (1925) and Rock Mechanics (1960). Part II is dedicated to show how these sciences and arts are applied to huge accumulations of garbage of what could be referred to as anthropic wastes. [ABSTRACT FROM AUTHOR]

Seismic surveying for hydrocarbon detection is done in several ways; perhaps the most extended procedure is the reflection method where small charges of seimigel are detonated and reflections are gathered in geophones. The analysis of the records allow the geophysicist to estimate the spatial position of geologic formations that may accumulate hydrocarbons. There is the concern if detonations have some environmental impact. This paper explores it and concludes that if some minimum distances from the explosion to constructions and the like are maintained, there is no possibility to affect the environment. [ABSTRACT FROM AUTHOR]

Human wastes constitute an evergrowing by-product of civilization. Several catastrophic landslides have taken place in these so-called sanitary land fills. It is apparent that geotechnical and environmental engineers follow divergent paths to solve the related technical problems. Part I of this paper addresses the development of mechanical sciences leading to Soil Mechanics (1925) and Rock Mechanics (1960). Part II is dedicated to show how these sciences and arts or geomechanics are applied to huge accumulations of garbage of what could be referred to as anthropic waste deposits. [ABSTRACT FROM AUTHOR]

Solid waste collection problems are of increasing concern to expanding cities and sectors with high volumes of waste generation. This paper deals with the optimization of a collection system in the sidewalk for urban sectors. This is a combinatorial problem in which all arcs of a mixed network are traversed, subject to vehicle capacity and time restrictions. A flexible formulation is proposed which works with separate collection and transportation networks. A sequencing scheme to assign routes is also proposed. The performance of the model is analyzed under different scenarios and applied to a collection zone of Bogotá with satisfactory results. [ABSTRACT FROM AUTHOR]