Now showing 1 - 10 of 30
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Estimating freight rates in inventory replenishment and supplier selection decisions

2009 , Mendoza, Abraham , José A. Ventura

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Analytical models for supplier selection and order quantity allocation

2012 , Mendoza, Abraham , José A. Ventura

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MOBILITY OF BLIND PEOPLE USING THE SMARTPHONE’S GPS AND A WEARABLE TACTILE DISPLAY

2021 , Velázquez, Ramiro , EDWIGE PISSALOUX , Del-Valle-Soto, Carolina , MIGUEL ANGEL CARRASCO ZAMBRANO , Mendoza, Abraham , Varona, Jorge

This paper presents a novel wearable system devoted to assist the mobility of blind and visually impaired people in urban environments with the simple use of a smartphone and tactile feedback. The system exploits the positioning data provided by the smartphone’s GPS sensor to locate in real-time the user in the environment and to determine the directions to a destination. The resulting navigational directions are encoded as vibrations and conveyed to the user via an on-shoe tactile display. To validate the pertinence of the proposed system, two experiments were conducted with test users. The first one involved a group of 20 voluntary normally sighted subjects that were requested to recognize the navigational instructions displayed by the tactile-foot device. The results show high recognition rates for the task. The second experiment consisted of guiding two blind voluntary subjects along public urban spaces to target destinations. Results show that the task was successfully accomplished and suggest that the system enhances independent safe navigation of visually impaired and blind people. Moreover, results show the potentials of smartphones and tactile-foot devices in assistive technology. Keywords: assistive technology, GPS localization, mobility of blind people, tactile-foot stimulation, vibrotactile display, wearable system.

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Multi-period multi-product closed loop supply chain network design: A relaxation approach

2021 , Subramanian Pazhani , Mendoza, Abraham , Ramkumar Nambirajan , T.T. Narendran , K. Ganesh , Olivares-Benitez, Elias

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A serial inventory system with supplier selection and order quantity allocation

2010 , Mendoza, Abraham , José A. Ventura

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A methodology for increasing revenue in fashion retail industry

2018 , Nucamendi-Guillén, Samuel , Moreno, Miguel A. , Mendoza, Abraham

Purpose Fashion retail companies typically exhibit short life-cycles, high volatility and low predictability. Therefore, their success is largely determined by the organisation’s flexibility and responsiveness. The purpose of this paper is to present a methodology to facilitate inventory control to minimise both shortages and excess inventory for a multi-product, multi-period finite time horizon inventory problem by using statistical and stochastic analysis. Design/methodology/approach The proposed methodology operates in two phases: the first phase consists on determining an aggregate plan (AP) that will be used for monitoring the behaviour of the items during the time horizon. This plan is obtained by statistically analysing historical data related to sales and inventory shortages and is used to determine a demand forecast during the time horizon that allows to handle with potential disruptions derived from real demand variations. Finally, supply replenishment policies are defined to facilitate the monitoring process during the second phase. For the second phase, the behaviour of real demand for every item is captured into a database and compared against its projected demand (from the AP). If needed, adjustments are made in the procurement of future deliveries to reduce the probability of having shortages and/or excess inventory. Findings A case study in a Mexican fashion retail company was conducted to assess the performance of the methodology. Results indicate that shortage in early periods can be reduced totally for certain products while, for others, the reduction is about 90.5 per cent. In addition, the incomes of the company were increased over 57 per cent. Research limitations/implications Even when the success of the methodology has been shown, cultural and behavioural factors were not considered. An extensive study is suggested to determine if these factors should be included to enhance the performance of the methodology. Practical implications A case study of a Mexican fashion retail company was conducted to assess the performance of the proposed methodology. The methodology is easy to implement and effectively and quickly responds to disruptions in the demand and it also significantly reduces the level of shortages while increasing sales and revenue for the company. Originality/value This paper proposes a methodology that is able to anticipate product’s behaviour from early weeks. Additionally, replenishment policies allow to quickly adjust future orders to guarantee the availability of items and minimise overstock.

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Coordination of pricing and inventory replenishment decisions in a supply chain with multiple geographically dispersed retailers

2022 , Hamza Adeinat , Subramanian Pazhani , Mendoza, Abraham , Jose A. Ventura

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Differential Evolution Based Algorithm for Optimal Current Ripple Cancelation in an Unequal Interleaved Power Converter

2021 , Rosas-caro, Julio , Pedro M. García-Vite , Rodríguez Vázquez, Alma Nayeli , Mendoza, Abraham , Alejo-Reyes, Avelina , Erik Cuevas , Francisco Beltran-Carbajal

This paper proposes an optimal methodology based on the Differential Evolution algorithm for obtaining the set of duty cycles of a recently proposed power electronics converter with input current ripple cancelation capability. The converter understudy was recently introduced to the state-of-the-art as the interleaved connection of two unequal converters to achieve low input current ripple. A latter contribution proposed a so-called proportional strategy. The strategy can be described as the equations to relate the duty cycles of the unequal power stages. This article proposes a third switching strategy that provides a lower input current ripple than the proportional strategy. This is made by considering duty cycles independently of each other instead of proportionally. The proposed method uses the Differential Evolution algorithm to determine the optimal switching pattern that allows high quality at the input current side, given the reactive components, the switching frequency, and power levels. The mathematical model of the converter is analyzed, and thus, the decision variables and the optimization problem are well set. The proposed methodology is validated through numerical experimentation, which shows that the proposed method achieves lower input current ripples than the proportional strategy.

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Numerical Optimization of the Capacitors Selection in the MSBA Converter to Reduce the Output Voltage Ripple

2022 , Alejo-Reyes, Avelina , Rodríguez Vázquez, Alma Nayeli , Rosas-caro, Julio , Mendoza, Abraham

DC–DC power electronics converters are widely used in many applications, such as renewable energy systems. The multistage-stacked boost architecture (MSBA) converter is a large voltage gain converter whose PWM scheme may reduce a percentage of the output voltage ripple, taking advantage of the symmetry of the voltage signals in capacitors (they are triangular waveforms) to have a symmetry cancelation. The switching ripple is unavoidable; the correct selection of components can reduce it, but this may result in a large amount of stored energy (larger size). The selection of capacitors influences the output voltage ripple magnitude. This article proposes a design methodology that combines a recently introduced PWM scheme with a numerical optimization method to choose the capacitors for the MSBA converter. The objective is to minimize the output voltage ripple by choosing two capacitors simultaneously while ensuring the constraint of a certain (maximum) amount of stored energy in capacitors is not overpassed. The internal optimization was performed with the differential evolution algorithm. The results demonstrate that the proposed method that includes numerical optimization allows having a very low output voltage ripple with the same stored energy in capacitors compared to the traditional converter. In a design exercise, up to 60% reduction was observed in the output voltage ripple with the same stored energy in capacitors.

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A Memetic Algorithm for the Cumulative Capacitated Vehicle Routing Problem Including Priority Indexes

2020 , Nucamendi-Guillén, Samuel , Flores Díaz, Diego , Mendoza, Abraham , Olivares-Benitez, Elias

This paper studies the Cumulative Capacitated Vehicle Routing Problem, including Priority Indexes, a variant of the classical Capacitated Vehicle Routing Problem, which serves the customers according to a certain level of preference. This problem can be effectively implemented in commercial and public environments where customer service is essential, for instance, in the delivery of humanitarian aid or in waste collection systems. For this problem, we aim to minimize two objectives simultaneously, the total latency and the total tardiness of the system. A Mixed Integer formulation is developed and solved using the AUGMECON2 approach to obtain true efficient Pareto fronts. However, as expected, the use of commercial software was able to solve only small instances, up to 15 customers. Therefore, two versions of a Memetic Algorithm with Random Keys (MA-RK) were developed to solve the problem. The computational results show that both algorithms provided good solutions, although the second version obtained denser and higher quality Pareto fronts. Later, both algorithms were used to solve larger instances (20–100 customers). The results were mixed in terms of quality but, in general, the MA-RK v2 consistently outperforms the first version. The models and algorithms proposed in this research provide useful insights for the decision-making process and can be applied to solve a wide variety of business situations where economic, customer service, environmental, and social concerns are involved.