Search Results (320)

Power converters in the smart grid systems are essential to link renewable energy sources with all grid appliances and equipment. However, this raises the possibility of electromagnetic interference (EMI) between the smart grid elements. Hence, spread spectrum (SS) modulation techniques have been used to mitigate the EMI peaks generated from the power converters. Consequently, the performance of the nearby communication systems is affected under the presence of EMI, which is not covered in many situations. In this paper, the behavior of the G3 Power Line Communication (PLC) channel is evaluated in terms of the Shannon–Hartley equation in the presence of SS-modulated EMI from a buck converter. The SS-modulation technique used is the Random Carrier Frequency Modulation with Constant Duty cycle (RCFMFD). Moreover, The analysis is validated by experimental results obtained with a test setup reproducing the parasitic coupling between the PLC system and the power converter. Full article

Parameterization of SWMM subcatchments is labor-intensive and a major source of model uncertainty. This study presents the Rapid Catchment Generator (RCG), a fuzzy logic framework that derives hydraulic width, average slope, and impervious fraction from three easily accessible descriptors—area, landform type, and land cover type—and inserts them directly into SWMM input files. A sensitivity analysis of 116,640 synthetic simulations confirmed that width, slope, and imperviousness are the dominant controls on runoff and infiltration. Their relationships are encoded in triangular membership functions covering nine geomorphic classes and twelve imperviousness classes, linked through expert-calibrated Mamdani rules. Validation on a calibrated 37-subcatchment, 10-hectare urban basin in Wrocław, Poland, showed Mean Absolute Percentage Errors of 15.9–16.0% for total runoff, 19% for infiltration, and 29–37% for peak flow, while preserving hydrograph shape. RCG thus reduces model setup time and provides a transparent, reproducible starting point for rapid scenario screening and subsequent fine-scale calibration. Full article

This study investigates the electromagnetic performance of two carbon fiber monopole antennas integrated into a UAV copter frame, with emphasis on design adaptation, impedance matching, and propagation behavior. A comprehensive experimental campaign was conducted to characterize key parameters such as center frequency, bandwidth, gain, VSWR, and S₁₁. Both antennas exhibited dual-band resonance at approximately 381 MHz and 1.19 GHz, each achieving a 500 MHz bandwidth where VSWR ≤ 2. The modified antenna achieved a minimum reflection coefficient of –14.6 dB and a VSWR of 1.95 at 381.45 MHz, closely aligning with theoretical predictions. Gain deviations between measured (0.15–0.19 dBi) and calculated (0.19 dBi) values remained within 0.04 dB, while received power fluctuations did not exceed 1.3 dB under standard test conditions despite the composite material’s finite conductivity. Free-space link-budget tests at 0.5 m and 2 m of separation revealed received-power deviations of 0.9 dB and 1.3 dB, respectively, corroborating the Friis model. Radiation pattern measurements in both azimuth and elevation planes confirmed good directional behavior, with minor side lobe variations, where Antenna A displayed variations between 270° and 330° in azimuth, while Antenna B remained more uniform. A 90° polarization mismatch led to a 15 dBm signal drop, and environmental obstructions caused losses of 9.4 dB, 12.6 dB, and 18.3 dB, respectively, demonstrating the system’s sensitivity to alignment and surroundings. Additionally, signal strength changes observed in a Two-Ray propagation setup validated the importance of ground reflection effects. Small-scale fading analysis at 5 m LOS indicated a Rician-distributed envelope with mean attenuation of 53.96 dB, σ_dB = 5.57 dB, and a two-sigma interval spanning 42.82 dB to 65.11 dB; the fitted K-factor confirmed the dominance of the LOS component. The findings confirm that carbon fiber UAV frames can serve as effective directional antenna supports, providing proper alignment and tuning. These results support the future integration of lightweight, structure-embedded antennas in UAV systems, with potential benefits in communication efficiency, stealth, and design simplification. Full article

Free-Space Optical (FSO) communication systems operating in arid regions, especially those envisioned for current and future 5G/6G networks, are significantly affected by dust storms, which cause signal attenuation and service disruptions. While previous studies have proposed deterministic models to characterize attenuation in both controlled and real environments, probabilistic modeling approaches remain largely unexplored, particularly for capturing the variability of FSO signal attenuation under dust conditions. This study proposes a probabilistic model for FSO signal attenuation developed from experiments conducted in a repeatable and well-characterized controlled dust chamber. The chamber-based setup allowed precise manipulation of dust visibility levels and consistent data collection, serving as a benchmark for statistical modeling. We analyzed the measurements to fit appropriate probability distributions for modeling the signal attenuation as a random variable. The empirical data were fitted to several candidate distributions, and the Johnson SB distribution consistently achieved superior performance with $R^2\ge 0.95$ and RMSE and MAE values close to zero across all dust conditions. The results offer a foundational framework for modeling dust-induced attenuation as a random process, providing statistical bounds for FSO link planning in desert environments. Full article

Background/Objectives: This in vitro study investigated the retention of three different geometrical designs of short titanium base (Ti-base) abutments used in implant-supported zirconia crowns. The advent of digital technology has facilitated the integration of Ti-base abutments into implant dentistry by improving time efficiency, precision, and patient comfort. Methods: Three types of short Ti-base abutments were evaluated: Geo SRN multibase^® (Group A), Herilink^® (Group B), and TS Link^® (Group C), each with a height of 4 mm and gingival height of 1 mm (n = 20 per group). Zirconia crowns (LUXEN^® Smile S2, DentalMax, Republic of Korea) were modified for the testing setup and fabricated using CAD/CAM technology, then bonded to the abutments with RelyX^® Luting 2 resin-modified glass ionomer cement. Pull-out tests were conducted at a crosshead speed of 1 mm/min to assess retention. Results: One-way ANOVA and post hoc Tukey tests revealed significant differences in retention values among the different abutment shapes (p < 0.05). The mean retention forces were 194.65 N for Group A, 241.33 N for Group C, and 360.20 N for Group B. Conclusions: The geometrical design of Ti-base short abutments significantly affects the retention of CAD/CAM zirconia crowns, with hexagonal shapes (Group B) demonstrating superior retention. Clinically, selecting an abutment design with enhanced mechanical retention may improve the long-term success of implant-supported restorations. Full article

With advancing age, blood vessels undergo deterioration that causes structural and functional changes, including a progressive increase in arterial wall stiffness. Since arterial stiffness is closely linked to the potential risks of cardiovascular diseases, which remains the leading cause of global mortality, it has become essential to develop effective techniques for early diagnosis and continuous monitoring over time. Photoplethysmography, a low-cost and non-invasive technology that measures blood volume changes, has gained increasing popularity in recent years and has proven to be a potential valuable tool for estimating arterial stiffness. This study employs an in vitro experimental setup designed to simulate the cardiovascular system performing under controlled velocity and pressure conditions, in which silicone phantom models with different geometric and mechanical properties were implemented to evaluate their stiffness using a pair of photoplethysmographic sensors. These were employed to measure the pulse wave velocity, currently considered the reference technique for estimating arterial stiffness, correlated through the well-known Moens–Korteweg equation. Photoplethysmographic sensors were placed at three specific distances to determine an optimal configuration for assessing arterial stiffness. Results showed the best performance for softer vascular models at a 15 cm sensor distance, with measurements demonstrating satisfactory accuracy. Variability and standard deviation values increased with model stiffness. The aim of this study is to improve the use of photoplethysmographic sensors for monitoring the mechanical properties of blood vessels and, therefore, to prevent potential cardiovascular diseases. Full article

In this paper, we propose a grouping-based dynamic routing, core, and spectrum allocation (RCSA) method for preventing spectrum fragmentation and inter-core crosstalk in elastic optical path networks based on multi-core fiber environments. Multi-core fibers enable us to considerably enhance the transmission capacity of optical links; however, this induces inter-core crosstalk, which degrades the quality of optical signals. We should thus avoid using the same frequency bands in adjacent cores in order to ensure high-quality communications. However, this simple strategy leads to inefficient use of frequency-spectrum resources, resulting in spectrum fragmentation and a high blocking probability for lightpath establishment. The proposed method allows one to overcome this difficulty by grouping lightpath-setup requests according to their required number of frequency slots. By assigning lightpath-setup requests belonging to the same group to cores according to their priority, the proposed method aims to suppress inter-core crosstalk. Furthermore, the proposed method is designed to mitigate spectrum fragmentation by determining the prioritized frequency bandwidth for lightpath-setup requests according to their required number of frequency slots. We show that the proposed method reduces the blocking of lightpath establishment while suppressing inter-core crosstalk through simulation experiments. Full article

Mammalian fertilization depends on sperm successfully navigating a spatially and chemically complex microenvironment in the female reproductive tract. This process is often conceptualized as a competitive race, but is better understood as a collective random search. Sperm within an ejaculate exhibit a diverse distribution of motility patterns, with some moving in relatively straight lines and others following tightly turning trajectories. Here, we present a two-state random walk model in which sperm switch from high-persistence-length to low-persistence-length motility modes. In reproductive biology, such a switch is often recognized as “hyperactivation”. We study a circularly symmetric setup with sperm emerging at the center and searching a finite-area disk. We explore the implications of switching on search efficiency. The first proposed model describes an adaptive search strategy in which sperm achieve improved spatial coverage without cell-to-cell or environment-to-cell communication. The second model that we study adds a small amount of environment-to-cell communication. The models resemble macroscopic search-and-rescue tactics, but without organization or networked communication. Our findings provide a quantitative framework linking sperm motility patterns to efficient search strategies, offering insights into sperm physiology and the stochastic search dynamics of self-propelled particles. Full article

To address the challenges linked to climate change, rapidly increasing urbanization, and food security necessity, this study explores the potential of smart, low-cost innovative cultivation systems for modules on facades as nature-based solutions (NBSs) to improve building energy efficiency, urban food production, and sustainability. Innovative cultivation systems were studied and implemented in the horizontal experimental setup, with a focus on sub-irrigation techniques with terracotta pots, ozonated water, and IoT use. The best eco-smart irrigation system was selected considering both plant growth and the water savings obtained (up to 57.14%) in comparison to the traditional method. With the implementation of this system, a vertical green module (VGM) was designed, allowing for efficient distribution and water savings. The positive effects in terms of temperature reduction and energy behavior were validated by comparing two office rooms: one without VGM and the other with VGM in a Mediterranean city. The drop in internal temperatures achieved was up to 3–4 °C during the hot days of the experimental campaign. The uptake of this low-cost and smart prototype can be useful to support the enhancement of energy-efficient, eco-sustainable, and self-sufficient buildings and urban spaces, contributing to creating more climate-resilient cities and promoting sustainable urban agriculture. Full article

Variable stiffness actuators (VSAs) have attracted considerable attention in wearable robotics and soft exoskeletons due to their ability to adapt to various load conditions. This study presents a modular design for VSAs that incorporates a chain mail structure with various link topologies, allowing for a reconfiguration of stiffness. The proposed VSA consists of three main parts: the vacuum chamber, the VSA actuator, and the chain mail structure. The VSA fabrication process was carried out in five stages: (1) mold fabrication by 3D FDM printing, incorporating a film of oil to facilitate easy demolding; (2) mold preparation using silicone, with a precise ratio of 1:1 weight-based mixture to optimize material utilization; (3) silicone pouring into molds while applying vibration to eliminate air bubbles; (4) curing for four hours to achieve optimal mechanical properties; and (5) careful demolding to prevent damage. Experimental tests were conducted to characterize the stiffness of actuators with different chain mail fabric configurations, using an experimental setup designed to securely fix the actuator and accurately measure the pneumatic pressure and the angle of deformation after applying weights at its end. The European 6-in-1 and rounded square configurations were shown to be the most effective, increasing stiffness up to 382% compared to the chain mail-free configuration, highlighting the positive impact of these structural designs. Full article

The main purpose of this research is to develop an improved space vector pulse-width modulation (SVPWM) algorithm for three-level (3L) neutral point clamped (NPC) voltage source inverters (VSIs). The results of experiments conducted on the three-level power converter laboratory setup showed that the proposed SVPWM algorithm with a seven-stage switching sequence (SS) can reduce a VSI’s switching frequency by 43.48% compared to the SVPWM algorithm with the base SS. It also improves the neutral point (NP) voltage balance in the VSI DC link by 4.2% by controlling the duty factor of distributed base vectors in each SVPWM period based on phase load currents. It reduced the values of the 5th- and 7th-order harmonics of the VSI output voltage by 19% and 15.7%, respectively. The results show that the usage of the improved SVPWM algorithm helps increase the efficiency of a 3L NPC VSI by 0.6% and reduce the higher harmonics. The obtained results confirm the efficiency of the suggested algorithm and its great potential for power converters in industry. Full article

Submerged vegetation plays a crucial role in influencing flow hydrodynamics, generating turbulence, and shaping velocity distributions in aquatic environments. This study investigates the hydrodynamic effects of submerged rigid vegetation, specifically focusing on the local flow and turbulence alterations resulting from the removal of a single stem from an otherwise uniform vegetation array under controlled laboratory conditions. Experiments were conducted in a flume using Acoustic Doppler Velocimetry (ADV) to measure 3D (three-dimensional) flow characteristics, turbulence intensities, Reynolds shear stress (RSS), and quadrant analysis. In the fully vegetated scenario, vegetation significantly modified flow conditions, creating inflexion points and distinct peaks in velocity profiles, turbulence intensity, and RSS—particularly near two-thirds of the vegetation height—due to wake vortices and flow separation. The removal of a single stem introduced a localised gap, which redistributed turbulent energy, increased RSS and near-bed turbulent interactions, and disrupted the organised vortex structures downstream. While sweep and ejection events near the gap reached magnitudes similar to those in the fully vegetated setup, they lacked the characteristic coherent peaks linked to vortex generation. Overall, turbulence intensities and RSS were reduced, indicating a smoother flow regime and weaker energy redistribution mechanisms. These findings critically impact river restoration, flood management, and habitat conservation. By understanding how vegetation gaps alter flow hydrodynamics, engineers and ecologists can optimise vegetation placement in waterways to enhance flow efficiency, sediment transport, and aquatic ecosystem stability. This study bridges fundamental fluid mechanics with real-world applications in environmental hydraulics. Full article

This research presents a novel approach to 28 $\mathrm{GHz}$ impulse radio ultra-wideband (IR-UWB) transmission using pulse position modulation (PPM) over an analog radio-over-fiber (ARoF) link, investigating the impact of fiber-based fronthaul on the overall performance of the communication system. In this setup, an arbitrary waveform generator (AWG) is employed for PPM signal generation, while demodulation is performed with a commercial time-to-digital converter (TDC) based on an event timer. To enhance the reliability of transmitted reference PPM (TR-PPM) signals, the transmission system integrates Gray coding and Consultative Committee for Space Data Systems (CCSDS)-standard-compliant Reed-Solomon (RS) error correcting code (ECC). System performance was evaluated by transmitting pseudorandom binary sequences (PRBSs) and measuring the bit error ratio (BER) across a 5-m wireless link between two 20 $\mathrm{d}\mathrm{B}\mathrm{i}$ gain horn (Ka-band) antennas, with and without a 20 $\mathrm{k}\mathrm{m}$ single-mode optical fiber (SMF) link in transmitter side and ECC at the receiver side. The system achieved a BER of less than 8.17 × 10⁻⁷, using a time bin duration of 200 $\mathrm{p}\mathrm{s}$ and a pulse duration of 100 $\mathrm{p}\mathrm{s}$, demonstrating robust performance and significant potential for space-to-ground telecommunication applications. Full article

Conceptually, this paper aims to help reduce the communication blind spots originating from the design of millimeter-wave (mmW) beamforming by deploying radio units of an open radio access network (O-RAN) with free-space optics (FSOs) as the backhaul and the fiber-optic link as the fronthaul. At frequencies exceeding 24 GHz, the transmission reach of 5G/6G beamforming is limited to a few hundred meters, and the periphery area of the sector operational range of beamforming introduces a communication blind spot. Using FSOs as the backhaul and a fiber-optic link as the fronthaul, O-RAN empowers the radio unit to extend over greater distances to supplement the communication range that mmW beamforming cannot adequately cover. Notably, O-RAN is a prime example of next-generation wireless networks renowned for their adaptability and open architecture to enhance the cost-effectiveness of this integration. A 200 meter-long FSO link for backhaul and a fiber-optic link of up to 10 km for fronthaul were erected, thereby enabling the reach of communication services from urban centers to suburban and remote rural areas. Furthermore, in the context of beamforming, reinforcement learning (RL) was employed to optimize the error vector magnitude (EVM) by dynamically adjusting the beamforming phase based on the communication user’s location. In summary, the integration of RL-based mmW beamforming with the proposed O-RAN communication setup is operational. It lends scalability and cost-effectiveness to current and future communication infrastructures in urban, peri-urban, and rural areas. Full article

In this study, a novel fully compliant four-bar-based universal joint is introduced. The difference between the angular positions of the input and output shafts is obtained by two equivalent fully compliant four-bar mechanisms that operate simultaneously by sharing the same input link. During the design phase of the mechanism an iterative method for determining the optimum angular position of the links is proposed and applied. The proposed design is a single-piece mechanism that is produced from polypropylene and compatible with both additive manufacturing and injection molding techniques. The scalability of compliant mechanisms allows for a wide range of size options during the design process. An extensive survey of the current literature reveals that the design proposed is without precedent, marking it as both novel and inventive. In this study, the design procedure of the proposed universal joint, stress analysis of the links, the torque capacity of the joint, and an experimental setup are presented. The produced prototype demonstrates the functionality of the proposed design. In addition, it should be noted that the prototype production of the proposed design was conducted using the additive manufacturing method. This production technique is a significant motivation behind the design of the mechanism as a single piece. Additionally, the proposed mechanism in its current form is also suitable for production using the injection molding method which is widely used in the industry. Full article