Varela Aldas, José

Preferred name

Varela Aldas, José

Main Affiliation

Centro de investigación en Mecatrónica y Sistemas Interactivos

Ambato

josevarela@uti.edu.ec

ORCID

0000-0002-4084-1424

Scopus Author ID

57192546163

Now showing 1 - 10 of 172

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Fiber–matrix interaction governs compressive strength in agave-bagasse-reinforced adobe: a factorial experiment with two-way ANOVA and competing mechanism analysis
(Frontiers Media SA, 2026-07-31)
De-Obaldia-Escalante, Marcela
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Del-Valle-Soto, Carolina
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Acevedo-Parra, H. R.
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Montoya-Márquez, Orlando
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Varela Aldas, José
Natural-fiber reinforcement is widely cited as a pathway to improve the mechanical performance of adobe, but reported effects on compressive strength are inconsistent across studies: some find improvement, others find degradation, and the choice of experimental conditions rarely disentangles the role of the fiber from that of the matrix. This study quantifies the coupling through a balanced factorial experiment. Forty-nine adobe specimens of (Formula presented) cm were manufactured with three granular compositions (sand-dominated, jal-dominated, and balanced, where jal is a regional non-plastic silt of Jalisco, Mexico) and four mass fractions of agave-bagasse fiber (0%, 0.5%, 1%, and 2%), and were tested under Mexican standard NMX-C-036-ONNCCE by an accredited external laboratory. Three complementary analytical tools are applied to the resulting dataset: (i) a two-way analysis of variance (ANOVA), (ii) a reinforcement efficiency index (Formula presented) with bootstrap confidence intervals, and (iii) a competing mechanism phenomenological descriptor (Formula presented) that separates a saturating reinforcement term from a linear disruption term. The two-way ANOVA reveals a highly significant mixture–fiber interaction ((Formula presented), (Formula presented), and partial (Formula presented)), which is stronger than either main effect and statistically demonstrates that the sign of the fiber effect is not an intrinsic property of the fiber but rather a property of the fiber–matrix pair. For sand-containing mixtures, the reinforcement efficiency index is (Formula presented) [M1, 95% bootstrap CI (0.96, 1.32)] and (Formula presented) [M3, (0.92, 1.59)] at the optimum (Formula presented); a non-parametric bootstrap over 5, 000 resamples places the optimum at (Formula presented) with posterior probability (Formula presented) (M1) and (Formula presented) (M3). For the jal-dominated mixture, fiber inclusion is net destructive [(Formula presented), (0.68, 0.95) at (Formula presented)], with Welch (Formula presented)-tests rejecting equivalence with the control at (Formula presented) (0.5%) and (Formula presented) (2%) and Cohen’s effect sizes (Formula presented). The best-performing conditions yield mean compressive strengths of 3.22 MPa, which exceeds the 2.0 MPa minimum required by NMX-C-441-ONNCCE-2011 for non-structural masonry by 60%. An immersion test shows that unstabilized specimens disintegrate within 2–3 min, bounding applications to non-exposed or externally protected uses and defining the primary direction for future work.
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Channel-Specific Stimulus Sensitivity, Reliability, and Complementarity of Multimodal Wearable Sensing During Short-Form Influencer Video Exposure
(MDPI AG, 2026-10-08)
Del-Valle-Soto, Carolina
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Corona, Violeta
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Gómez Padilla, Regina
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Walls Fernández, Fátima Sofía
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López-Pimentel, Juan-Carlos
Multimodal wearable sensing is increasingly used to quantify audience engagement with short-form video, yet it remains unclear which sensing channels actually carry stimulus-driven information at the exposure durations typical of this format. We recorded electrodermal activity, photoplethysmographic pulse, triaxial acceleration, video-based eye tracking, and automated facial expression analysis from 50 young adults while they viewed 20 short-form influencer clips (5.6–19.3 s) presented in individually randomized order, yielding 1000 participant × clip trials and 12 primary indices spanning four modalities. Using crossed random-effects variance partitioning, split-half reliability with Spearman–Brown projection, permutation-based multivariate testing, participant-wise decoding, and inter-subject correlation, we show that stimulus-driven variance is strongly channel-specific: it reaches 13.7% for fixation rate and 10.2% for facial engagement but only 0.11% for pulse rate and 0.23% for RMSSD. Clip-level estimates were highly reliable for facial and oculomotor indices ((Formula presented.) – (Formula presented.)) and poor for autonomic indices ((Formula presented.) – (Formula presented.)), which would require 134–370 participants to reach (Formula presented.). Between-modality dependence was almost six times weaker than within-modality dependence, and five components were retained by parallel analysis. Oculomotor and facial features jointly identified individual clips at 16.8% balanced accuracy against a 5% chance level, whereas electrodermal and pulse features, taken separately, did not exceed chance. Electrodermal responses were nonetheless stimulus-locked in 18 of 20 clips. A per-second re-analysis of nine channels showed that the ordering partly reverses for within-clip dynamics: tonic electrodermal and pupil time courses were reliable across viewers ((Formula presented.) and (Formula presented.)), facial time courses were not ((Formula presented.)), and pulse rate was unreliable under both treatments. We derive explicit design guidance for sensor selection and sample size in short-exposure multimodal engagement studies. © 2026 by the authors.
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From Simulation to Reality: A Digital Twin Implementation of a 4-DOF Robotic Manipulator
(2025)
Bryan S. Guevara
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Varela Aldas, José
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Viviana Moya
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Angéelica Veróonica Quito Carrióon
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Marcelo Ortiz
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Experimental and data-driven evaluation of transport-layer and application-layer security for MQTT-based IoT networks
(Elsevier BV, 2026-12)
Del-Valle-Soto, Carolina
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Alvarez-Garcia, Maria Fernanda
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Valdivia, Leonardo J.
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Del-Puerto-Flores, José A.
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Varela Aldas, José
The rapid expansion of Internet of Things (IoT) deployments has intensified the need for secure and efficient communication mechanisms tailored to resource-constrained devices. Message Queuing Telemetry Transport (MQTT) is widely adopted due to its lightweight design; however, it lacks native security support, requiring external protection mechanisms that may significantly affect system performance. This paper presents a comprehensive experimental and data-driven evaluation of two security paradigms for MQTT-based IoT networks implemented on ESP32 microcontrollers: transport-layer security using TLS and application-layer encryption based on elliptic curve cryptography (ECC) for key exchange combined with AES symmetric encryption. The analysis jointly evaluates memory utilization, end-to-end latency, energy consumption, and resistance to passive traffic interception under identical experimental conditions. In addition to conventional metric-based comparisons, multivariate statistical analysis and unsupervised learning techniques are employed as exploratory tools to characterize the system-level behavior induced by each security scheme. Results show that Transport Layer Security (TLS) offers stronger confidentiality guarantees at the cost of higher memory overhead, while the ECC–(Advanced Encryption Standard) AES approach significantly reduces memory footprint with moderate latency penalties and comparable energy consumption. Multivariate analysis further reveals that each security mechanism induces a distinct performance regime, providing a compact joint characterization of the security–performance trade-offs across the evaluated configurations.
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Does the use of dedicated mobile devices in magnetism classes improve student learning?
(Frontiers Media SA, 2026-04-21)
Varela Aldas, José
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Collay, Washington
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Del-Valle-Soto, Carolina
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Palacios-Navarro, Guillermo
Mobile devices have been evaluated from multiple perspectives as tools to support classroom learning; however, devices specifically dedicated to learning activities still require further research to elucidate their influence in the classroom. This study aimed to evaluate whether the use of dedicated mobile devices for teaching basic magnetism content improves learning among secondary school students. A quantitative, comparative quasi-experimental study with non-equivalent groups was conducted ((Formula presented)) with secondary school students in Ecuador. The experimental group used an educational application running on a dedicated mobile device (M5Stack Core2) and interacted with an electromagnet as a didactic peripheral, whereas the control group received a traditional teacher-centered lesson supported by slides. Learning outcomes were measured using a teacher-designed theoretical test administered at the end of a 90-min session. Mean scores were similar between groups (experimental: 7.32; control: 7.58). After verifying assumptions of normality and homogeneity of variance, an independent-samples t-test showed no statistically significant differences ((Formula presented)), and the effect size was small (Cohen’s (Formula presented)). Under the conditions evaluated, the dedicated mobile device did not produce measurable gains in knowledge performance compared to the traditional lesson. Longer interventions, larger samples, and longitudinal study designs are needed to clarify when and how this technology may provide educational benefits.
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INDI: A Low-Cost LLM-Enabled Multimodal Campus Guide Robot
(MDPI AG, 2026-09-03)
Varela Aldas, José
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Carvajal, Christian
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Cadena, Josue
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Del-Valle-Soto, Carolina
University technology campuses contain specialized laboratories, academic programs, and services that can be difficult for first-time visitors to identify. This paper presents INDI, a custom mobile campus guide robot that combines spoken interaction, synthesized speech, touchscreen feedback, animated facial states, head motion, and predefined mobile guidance behaviors. The platform retains the modular mechanical concept of an earlier prototype while replacing its Raspberry Pi and open-loop remote-control architecture with an NVIDIA Jetson Nano, an Arduino Uno motor-control bridge, ROS 1 nodes, encoder feedback, and dual PID speed loops. The robot weighs 2.37 kg, measures (Formula presented.) cm, reaches a software-limited maximum speed of 0.4 m/s, and provides 27 min of continuous operation in the reported tests. Ten repetitions of each motion test produced mean displacements of 1.058 m and 2.182 m for 1 m and 2 m commands, respectively, and mean rotations of 89.2° and 180.3° for 90° and 180° commands. Voice trials achieved 90% correct interaction in a quiet environment and 70% under nearby conversational noise. In an exploratory user study with 13 participants, 16 of 20 assigned tasks were completed and the mean overall rating was 4.31/5. The results demonstrate the feasibility of an integrated, modular, physically embodied information service, while also revealing accumulated linear-motion error, sensitivity to ambient speech, limited battery duration, and the need for grounded institutional knowledge and autonomous localization. These findings are presented as preliminary evidence of technical and interaction feasibility rather than as confirmatory evidence of usability or campus-scale autonomous navigation. © 2026 by the authors.
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Identifiability-Aware Virtual Force Sensing and Self-Calibration for Quadrotors
(Institute of Electrical and Electronics Engineers (IEEE), 2026)
Varela Aldas, José
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Quito, Angelica
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Andaluz, Victor H.
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Brandao, Alexandre Santos
Many aerial tasks, such as flying in wind or carrying a payload, require the external force on the airframe, yet quadrotors rarely carry a force sensor. We turn the onboard inertial measurement unit into a virtual force sensor: the external specific force is read directly from the accelerometer residual. The obstacle is calibration, since the reading needs the vehicle mass, which is unidentifiable near hover, where a mass error is indistinguishable from a vertical force; a standard extended Kalman filter then corrupts the mass. We make the sensor identifiability-aware and self-calibrating. An online identifiability measure, the Fisher information on the mass, gates the calibration and freezes the mass when it cannot be seen; and when the flight lacks the excitation to recalibrate, the controller injects a minimal probe that the same measure shapes. In simulation the sensor reads the external force with a per-axis correlation of 0.93 under continuous wind; the gate holds the mass calibration to 3 % through a windy hover where an ungated filter drifts to 7 %; the probe recovers the mass from a wrong prior that hover alone cannot identify; and feeding the sensed force to a model-predictive controller reduces the tracking error by 34 to 80 % under wind, most where the wind dominates the dynamics. The sensor degrades gracefully under injected accelerometer and thrust errors and runs in real time at 100 Hz. © 2013 IEEE.
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Multipath Routing Protocol: For Wireless Ad-hoc Networks Based on Fibonacci
(Zarqa University, 2026-07-04)
Sun, Haiyun
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Varela Aldas, José
A WANET, which stands for Wireless Ad hoc Network, is a temporary network in which nodes are connected to each other via wireless links and there is no central management. Due to its adaptive structure, WANET is very useful in situations when quick communication link setup is necessary. On the other hand, Channel Contention (CC), degrades the performance of WANET and is a major contributor to packet drops. To solve the CC problem, this paper proposes a routing protocol called Multipath Channel Contention Based Routing (MCCBR). Using MCCBR, several paths are discovered for data transmission that have minimal contention between the source and destination. Then the packets are distributed over the discovered routes based on the Fibonacci sequence. The process of searching for new paths for transmission is initiated when the number of found paths becomes less than 50%. The proposed routing protocol was tested and verified using NS2 simulator. The performance of MCCBR was evaluated against the Ad hoc On Demand Distance Vector (AODV) and Channel Contention Based Routing (CCBR) protocols. MCCBR outperformed AODV and CCBR in terms of Packet Delivery Ratio (PDR), End-to-End (E2E) delay, and normalized Media Access Control (MAC) overhead. © 2026, Zarka Private University. All rights reserved.
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Point Mass Planning and NMPC Tracking for Time-Optimal Agile Quadrotor Gate Navigation
(Institute of Electrical and Electronics Engineers (IEEE), 2026)
Guevara, Bryan S.
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Brandao, Alexandre Santos
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Varela Aldas, José
Time-optimal agile flight through a sequence of three-dimensional gates requires a consistent coupling between trajectory planning and tracking control. Point-mass planners offer fast numerical solutions for free-final-time optimisation, but the value of progressively enriching the reference fed to a nonlinear model predictive control (nmpc) tracker through a differential flatness bridge has not been clearly characterised on multi-gate circuits. This paper presents a modular three-stage pipeline: an offline time-optimal point-mass model (pmm) planner solved with CasADi and IPOPT; a differential flatness bridge that maps the flat outputs and their time derivatives to a full quadrotor reference comprising desired position, velocity, attitude quaternion, body angular rate, and collective thrust; and a body-rate nmpc tracker implemented on the acados SQP-RTI scheme with an SO(3) logarithmic-map external cost. Two reference configurations are compared in a software-in-the-loop setup that drives the MuJoCo physics engine through ROS 2 under a randomly seeded external-force disturbance. The baseline, nmpc-Att, uses only a yaw-only attitude reference derived from the velocity heading and carries no angular-rate or thrust feedforward. The proposed configuration, nmpc-Full, activates the complete flat reference, including the full attitude quaternion, body angular rate, and thrust feedforward. Results on a seven-gate figure-8 and an eight-gate vertical loop show that reference enrichment yields a categorical improvement in gate crossing and a systematic reduction of tracking error without increasing solver cost. The loop circuit further highlights a structural limitation of the common practice yaw-only reference: it cannot represent inverted attitudes, and only the flatness-based reference resolves this case
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From Simulation to Reality: A Digital Twin Implementation of a 4-DOF Robotic Manipulator
(2025)
Bryan S. Guevara
;
Varela Aldas, José
;
Viviana Moya
;
Angéelica Veróonica Quito Carrióon
;
Marcelo Ortiz

Varela Aldas, José

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