Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

On the search of lightweight lightning protection materials that can be used as part of Lightning Protection Systems (LPS), we investigate some types of electroconductive fabrics by applying several high lightning impulse currents in laboratory. Samples of four commercially available electroconductive textiles were analyzed: two rip-stop, a plain-weave, a non-woven, and additionally a carbon-impregnated polymeric film. Under laboratory conditions, each sample was subject to several subsequent lightning-like currents, recording both voltage and current signals. Optical and scanning electron microscope observations were performed after tests, revealing some patterns or morphological changes on the fabric surface. Despite these changes, the investigated conductive textiles withstand the several lightning impulse currents applied. Results suggest that some conductive fabrics could be used in personal mobile shelters, to protect human beings against the earth potential rise caused by a close lightning discharge.

— Electricity generation has to be increased to meet various type of future load demand like LED lightning, Electrical Vehicles, mobiles, communication network, non linear load etc. Automation is essential requirement now a days in each sector. To provide automation at residential, commercial and industrial sectors electrical energy is required. To meet energy requirement of various sector utility grid is integrated with DG Sources, which mainly include renewable energy sources like solar, wind and other environment friendly sources either in large scale or small scale depends on the location and availability. This type of technology leads power system to era of smart grid. Smart grid technology provides features like digitization, two way communication, distributed generation, adaptive islanding, self monitoring and self mitigating, fully controllable compare to conventional Grid. Though smart grid technology is advantageous but due to integration of distributed generation at transmission and distribution system will increase protection challenges in the power network. This paper gives an insight of different protection issues which occur at transmission, distribution and Micro grid network. The paper also focuses on the techniques and solution of the various protection challenges.

Objectives: Modern data centers serving web and mobile applications employ distributed load balancers. The Join Idle Queue (JIQ) algorithm is ideally suited for load balancing in a distributed setup. It attains fast response time by directing service requests to idle servers which can immediately process them. However, JIQ is not optimal in tracking idle servers leaving room for improvement. Methods: We observed that JIQ assigns idle servers non-uniformly to load balancers leaving some load balancers with no access to idle servers. We propose a variant of the JIQ algorithm, Join Idle Queue Dispatcher I-queue Optimization (JIQ-DIO), which increases the probability of load balancers having access to idle servers without additional communication overhead leading to improved response time. Findings: We simulated JIQ-DIO on CloudSim Plus 3.0 and compared it with standard JIQ and its different variants. JIQ-DIO was found to increase the probability of incoming requests being directed to idle servers and lead to more than two-fold improvement in response time across a broad range of parameters.

A modified master-slave scheme to look for synchronization, based on a general combination of elastic and dissipative couplings, is presented. We focus on solutions according the scheme presented, illustrating the method we use, by employing the van der Pol and Duffing oscillators and analyzing three different ways of coupling. We find synchronization in the oscillators.

The objective of this research is to verify the relationship between institutional pressures, green logistics activities and impacts on logistics performance. A survey of 56 logistics service providers was conducted. In relation to the data acquired, the return of 138 questionnaires answered by the middle/tactical managers of the 56 logistics service providers in Brazil was received. Institutional Pressures were the antecedents capable of explaining the corresponding variation in the Green Logistics construct (green packaging) in R2 = 0.3750, Green Logistics (green transport) in R2 = 0.9909 and Green Logistics (green warehousing and buildings) in R2 = 0.0389. Similarly, all Green Logistics constructs were able to explain the variation corresponding to a value observed in R2 = 0.5442 referring to Efficiency Perfor-mance (costs). The results demonstrate the influence of Institutional Pressures on Green Logistics activities as well as the impact of Green Logistics on Efficiency Performance (costs).

Currently, weather forecasting is the most commonly discussed topic by social and economic activists. It is also attracting widespread interest due to its application in various public and private sectors that include marine, agriculture, air traffic, and forestry. Recent developments have made climatic changes happen at a dramatic rate, making old methods of weather forecasting less effective, more hectic, and unreliable. Improved and efficient methods of weather prediction are needed to overcome these difficulties. This paper describes machine learning approaches using artificial neural networks to predict the weather of a particular city and compare the different weather conditions in different cities. We demonstrate empirically that Artificial Neural Networks produce very low deviations hence providing nearly accurate results for weather forecasts on a daily basis.

Heavy Metals (HMs) concentrations in a sediment sample from Habbaniyah Lake (HL), Iraq (Cr, Cd, Ni, Fe, Co, Zn, Pb, and Cu). 33 locations have been selected in the field of study from October 2020 to April 2021 to evaluate the contamination of HMs in sediments by using pollution load index (PLI), contamination factor (CF), Contamination degree (CD), and geo-accumulation index (I-geo). Atomic Absorption Spectrometer AAS was used to determine heavy metal concentrations (USA Phoenix-986). The following are the average concentrations: 2152.97 mg/kg for Fe, 47.35 mg/kg for Pb, 25.18 mg/kg for Cr, 18.00 mg/kg for Ni, 10.60 mg/kg for Co, 9.57 mg/kg for Zn, 4.53 mg/kg for Cu and 3.53 mg/kg for Cd during the research time. The average concentration of Pb, Ni, Fe, and Cd surpassed the USEPA recommendation. Cd is responsible for extremely high contamination; Pb is responsible for moderate pollution and severe contamination at some places based on the contamination factor (CF). According to contamination degree (CD), The Lake is classified as significant pollution degree and very pollution degree in some sites. Results indicated that HL is not contaminated with HMs according to geo-accumulation index and PLI for all sample locations during the study period. The lake is unpolluted by Fe, Cr, Co, Ni, Zn, and Cu according to contamination factor (CF), geo-accumulation index (I-geo), pollution load index (PLI), and Contamination degree (CD).

Sickle cell disease is a group of health disorders that affect hemoglobin in red blood cells. Sickle cell disease causes multiple manifestations and complications, including infections, delayed growth, pain crisis, and multi-organs damage. These complications can disturb the patients' vital signs, including body temperature, heart rate, and oxygen saturation. The decline in hemoglobin level is another indication of sickle cell disease due to abnormal hemoglobin that distorts red blood cells resulting in sickle cell anemia. RBCs, also called erythrocytes, are found in the blood and responsible for carrying oxygen to the body tissues attached to the hemoglobin. Optical microscopy can detect and monitor sickle cell disease, but it requires a blood sample and offline analysis, which is a time-consuming process. There is currently no known technology available to provide non-invasive monitoring solutions for sickle cell disease patients' health. Therefore, a need arises for a non-invasive and continuous monitoring solution to continuously check on sickle cell disease patients, which can be transformed into a wearable monitoring device. The proposed optical wristband consists of optical sensors that provide non-invasive and continuous health status monitoring of sickle cell disease patients using key vital signs and hemoglobin levels. A comparative study was performed among 21 participants and equally divided into three groups (non-anemic, anemic, and sickle cell disease patients). The data was collected from optical sensors, Arduino used as a processor, and continuously monitors the patient's vital signs and hemoglobin levels. Abnormal reading of any parameter alerts the user of any unhealthy status, and the parameter's trend assists the clinician in patient assessment. The body temperature and oxygen saturation levels of the anemic patients were found in the normal ranges, but the heart rate of three patients and hemoglobin of all the participants were found in aberrant ranges. The vital signs and hemoglobin levels of all sickle cell disease patients were beyond the normal ranges and significantly different (p>0.001) than non-anemic and anemic groups. Therefore, these physiological parameters monitoring has clinical importance for sickle cell disease management and early treatment.

Recently, direct power control (DPC) based proportional-integral (PI) controllers have become dominant for doubly fed induction generators (DFIGs) due to its simplicity and good dynamic response. But this strategy gives a high total harmonic distortion (THD) of the voltage and a large power ripple. In this paper, a new DPC method (called as NDPC-4L-NSVPWM) is proposed based on a four-level neural space vector pulse width modulation (4L-NSVPWM) and neural PI controllers for direct active and reactive powers command (DRAPC) of a DFIG integrated in a dual-rotor wind turbine (DRWT). This control scheme is based on direct reactive and active powers estimation. Theoretical principles of this strategy are presented along with simulation results. The advantages and robustness of NDPC-4L-NSVPWM control over other DPC with PI controllers (DPC-PI) are presented. The main advantages of NDPC-4L-NSVPWM strategy are relative to its good dynamic response, simplicity of the algorithm and operation at a constant switching frequency. Analysis of NDPC-4L-NSVPWM strategy based DFIG-DRWT has been done in MATLAB/Simulink software. Simulation results validate the performance of the NDPC-4L-NSVPWM strategy by evaluating the THD of current and the reduction of the ripples for the active/reactive power of DFIG-DRWTs.

The human resource assignment usually considers the search, qualification, selection, and allocation of human resources commonly based on their experience and professional development into different areas of a company. Rarely, the residence location and other characteristics of the personnel are considered.This paper takes a real case allocation problem from a public university social service program in Mexico City where the assignment process is restarted every six months. The lack of consideration of the personnel physical and functional attributes, led to an inefficient allocation process, increasing desertion of the program. To solve this problem, we propose a new methodology built on hexagonal tessellation capable of allocating personnel based on distance, schedules, and skills, which is later improved using simulation, reducing total travel distance in 585 km, improving matching schedules in 26%, matching skills in 37% and reduced the time dedicated to the allocation process from 5 days to 90 minutes.