Inventions

A low-cost, automated surface tension analyzer was designed and developed based on the maximum bubble pressure method. The system measures the pressure required to form air bubbles through a capillary immersed in a liquid, allowing the surface tension to be determined from the pressure–depth relationship. The experimental setup integrates a pressure sensor solenoid valve, stepper-motor-controlled depth stage, and data acquisition unit. A Python-based software interface was developed for real-time signal processing. Validation was performed using several Newtonian liquids, including water, toluene, methanol, ethanol, and n-hexane, with experimental results showing strong agreement with theoretical values yielding a maximum deviation below 2%. The developed instrument demonstrates excellent repeatability and sensitivity confirming its suitability for research and industrial applications.

This study presents the design, construction, and evaluation of a modular chamber for the vegetative propagation of cuttings, capable of simultaneously accommodating three plant cuttings at equidistant positions within a compact volume of 40 cm × 45 cm × 15 cm. It integrates distributed sensing using DHT22 temperature and relative humidity sensors, a BH1750 light sensor, and an MQ-2 gas/smoke detection sensor; programmable lighting via four NeoPixel WS2812B boards arranged in two parallel rows; and an ESP32 microcontroller responsible for processing, wireless communication, and threshold-based feedback control of environmental variables. The system was continuously monitored for four weeks to characterize the internal foliar microclimate in relation to external environmental conditions. Internal temperatures ranged from a weekly average of 25.26 °C to 28.71 °C, while relative humidity in the foliar zone varied between 28.99% and 41.24%. The lighting system provided stable and repeatable illuminance conditions, with weekly averages reaching up to 111.10 lux, and the gas sensor enabled continuous detection of transient variations in gas concentration within the chamber. The results demonstrate the feasibility of the proposed chamber as a compact, modular, and replicable platform for environmental data acquisition and experimental control in future studies on plant cutting propagation, biological rooting performance was not evaluated in the present study, therefore, the reported results primarily validate the technical and environmental performance of the developed prototype.

This paper introduces a systematic weighted multi-objective approach for selecting the switching frequency (fs) of a parabolic-carrier-based pulse-width-modulated (PC-PWM) inverter in a solar microgrid. The MATLAB (Version 23.2.0) /Simulink (Version 23.2) model incorporates a 10 kW PV array, an incremental-conductance MPPT boost converter, a regulated 700 V DC link equipped with a 4700 µF capacitor, a 15 kVA three-level neutral-point-clamped (NPC) inverter, an LCL output filter, and an 8 kW nonlinear three-phase rectifier load. The inverter fs varies from 2 to 20 kHz in 1 kHz increments under otherwise fixed nominal operating conditions. For each fs, voltage total harmonic distortion (THD_V), current total harmonic distortion (THD_I), inverter loss, and efficiency are evaluated and integrated into a normalized weighted objective function. FFT-based THD is evaluated over the last five fundamental cycles using a 1 µs discrete simulation step and harmonic orders up to the 39th. For the stated model, candidate-frequency set, normalization, and baseline weights, 16 kHz is the best evaluated point, with THD_V = 1.44%, THD_I = 2.28%, inverter switching loss = 353 W, and inverter efficiency = 96.78%. The added weight-sensitivity analysis demonstrated that this optimum depends on the selected engineering priorities: stronger harmonic weighting shifts the optimum upward, whereas stronger loss weighting shifts it downward. Consequently, the proposed procedure is presented as an offline design method rather than a universal or adaptive optimal solution.