Abstract: This paper presents a comprehensive study on the design and implementation of Finite Impulse Response (FIR) and Infinite Impulse Response (IIR) digital filters tailored for low-power modem applications. With the increasing demand for energy-efficient digital communication systems in Internet of Things (IoT) and mobile technologies, optimizing filters for power and performance is vital. FIR filters were designed using the windowing method, particularly the Hamming window, while IIR filters employed the bilinear transformation method to ensure stability and spectral accuracy. MATLAB was used for algorithmic design and frequency response analysis, whereas SIMULINK provided a dynamic environment to simulate real-time performance under varying signal conditions. The hardware realization was accomplished using VHDL, with synthesis and implementation carried out on FPGA platforms using Xilinx ISE. FIR filters were structured around a tap delay line architecture, offering inherent stability and linear phase characteristics, while IIR filters, though more complex due to feedback components, demonstrate superior power efficiency and sharper frequency cutoff characteristics. This study further explores the trade-offs between signal fidelity, computational complexity, and power consumption, providing insights through mathematical formulations, simulation results, and FPGA synthesis reports. Results indicate that FIR filters are advantageous in applications where linear phase response and stability are crucial, whereas IIR filters are preferable for constrained environments demanding minimal power usage. The comparative analysis suggests that filter selection should be application-specific, and future work may explore hybrid implementations that combine the advantages of both architectures for enhanced performance in next-generation communication systems.

Abstract: First demonstrated in 1942, subcritical and zero-power critical assemblies, also known as piles, are a fundamental tool for research and education at universities. Traditionally, their role has been primarily instructional and for measuring fundamental properties of neutron diffusion and transport. However, these assemblies could hold potential for modern applications and nuclear research. The Purdue University subcritical pile previously lacked a substantial testing volume, limiting its utility to simple neutron activation experiments for the purpose of undergraduate education. Following the design and addition of a mechanical and electrical testbed, this paper aims to provide an overview of the testbed design and characterize its neutron and gamma flux of the rearranged Purdue subcritical pile, justifying its use as a modern scientific instrument. The newly installed 1.5*10^5 cubic-centimeter volume testbed enables a systematic investigation of neutron and gamma effects on materials and the generation of a comprehensive dataset with the potential for machine learning applications. The neutron flux throughout the pile is measured using gold-197 and indium-115 foil activation alongside cadmium-covered foils for two-group neutron energy classification. The neutron flux measurements are then used to benchmark a detailed geometrically and materialistic accurate Monte-Carlo model using OpenMC and MCNP6.3. The experimental measurements reveal the testbed has a neutron environment with a total neutron flux approaching 9.5*10^3 n/cm^2*s and a thermal flux of 6.5*10^3 n/cm^2*s. This work establishes the modified Purdue subcritical pile can provide fair neutron and gamma fluxes within a large volume to enable radiation testing of integral electronic components and as a versatile research instrument with the potential to support material testing and limited isotope activation, while generating valuable training datasets for machine learning algorithms in nuclear applications.

Abstract: The increasing frequency and intensity of heat waves, combined with urban heat islands (UHI), pose significant public health challenges. Implementing low-cost, real-time moni-toring networks with distributed stations within the Smart city framework faces obstacles in transforming urban spaces. However, accurate data is essential for assessing these ef-fects. This paper compares different network types in a medium sized city in West Spain and their implications for UHI identification quality. The study first examines a pur-pose-built monitoring network using Open-Source platforms, IoT technology, and Lo-RaWAN communications, adhering to World Meteorological Organization guidelines. Additionally, it evaluates two citizen weather observer networks (CWON): one from a commercial smart device company and another from a global community connecting en-vironmental sensor data. The findings highlight several advantages of bespoke monitor-ing networks over CWON. These networks offer enhanced data accessibility and greater flexibility to meet specific requirements, facilitating adaptability and scalability for future upgrades. However, specialization is crucial for effective deployment and maintenance. Conversely, CWON faces limitations in network uniformity, data shadow zones, and in-sufficient knowledge of real sensor situations or component characteristics. Furthermore, CWON exhibits some data inconsistencies in probability distribution and scatter plots during extreme heat periods, as well as improbable UHI temperature values.

Abstract: To investigate the fracture crack in the rear axle of a certain passenger car during accelerated life testing, a comparative testing analysis was conducted on this car after replacing its new rear axle and on a comparative car. Strain on the rear axle, vibration acceleration, and vehicle speed signal were measured for both cars. Using the cyclic stress-strain hysteresis loop equation and Neuber's Rule, the nominal strain histories obtained from tests were converted to local stress-strain responses at the fracture crack locations. Subsequently, the fatigue damage to the rear axles of both the target car and comparative car was calculated based on Morrow's mean stress correction model and Miner's linear cumulative damage rule. The frequency sweeping of vibration mode was performed on the car bodies and rear axles of both cars using electromagnetic exciters to establish the correlation between the vibration frequency of rear axle, the excitation frequency of PG durability road, and the body vibration frequency. The calculations of fatigue damage and the frequency sweep testing results indicated that the accumulated damage to the rear axle of the target car was primarily concentrated on the washboard road of the PG. On this road surface, the standard deviation of rear axle strain and the RMS value of acceleration were higher than those observed in the comparative car. At a test speed of 65 km/h, the excitation frequency of forced vibration caused by the washboard road was 24.1 Hz, which was close to the natural frequency of the vibration modes of target car's rear axle, leading to resonance. This resulted in the rear axle experiencing significant amplitude alternating stress, thereby causing the crack initiation of vibration fatigue.

Abstract: A novel photonic-aided approach for generating flexible frequency hopping (FH) signals using optical comb filtering (OCF) is proposed and investigated. Wavelength selection, controlled by an intermediate-frequency (IF) signal, is achieved by leveraging the arithmetic progression of frequency differences between the OCF passband and the OFC comb lines. After optical heterodyne mixing of the selected wavelengths with the IF-FH signals, ultra-wideband and flexible FH signals are generated. Theoretical analysis and simulations are carried out to demonstrate the generation of 5-level, 10-level, and 25-level stepped frequency and Costas FH signals, as well as more complex signals like a 30 GHz LFM signal and a 24 GHz sinusoidal chirped signal. The effects of laser frequency offset and system parameter selection are also discussed. This approach, offering wide bandwidth, flexible tuning, good stability, and integration potential, is promising for applications in cognitive radio, modern radar systems, and electronic warfare.

Abstract: This research presents a comprehensive experimental investigation into the incorporation of recycled denim fibers into concrete as a sustainable reinforcement alternative. With the fashion industry generating substantial volumes of denim waste annually, particularly from post-consumer garments, the need for eco-conscious reuse strategies has become critical. Recycled denim fibers, rich in cellulose and blended synthetics, offer tensile properties that may enhance concrete’s mechanical behavior. Concrete mixes were prepared with incremental fiber dosages (0%, 0.5%, 1.0%, and 1.5% by weight of cement) and tested for workability, compressive strength, flexural strength, and durability through a battery of standardized tests. The findings indicate that denim fiber reinforcement improves the flexural strength and crack resistance of concrete, especially at 1.0% fiber content, with acceptable compromises in workability. This approach supports circular economy goals and presents a novel route for textile waste valorization in construction.

Abstract: Existing stellar map simulators lack color temperature information, have a complex system structure, and cannot independently control the color temperature of stars. Therefore, this study developed an OLED-based semi-physical simulation method and a simulation algorithm for the stellar map with color temperature information to realize a semi-physical simulation of the stellar map close to the real situation in space. The study also aimed to independently control the color temperature of each star. The simulation effect of the stellar map with color temperature information was verified using four stellar maps. The developed simulator achieved independent and controllable color temperature information for each star in the stellar map.

Abstract: For the long-term conductivity degradation of acid-etched fractures in ultra-deep carbonate reservoirs,a fracture permeability evolution model incorporating creep and stress sensitivity effects was established.Building upon this,a numerical simulation model for ultra-deep carbonate reservoirs was developed to quantitatively analyze the impacts of creep,stress sensitivity,and production strategies on well productivity.The research revealed that the creep and stress sensitivity characteristics of acid-etched fracture had a significant impact on the well productivity for ultra-deep carbonate oil reservoir.The larger the creep coefficient and stress sensitivity coefficient,the lower the oil well productivity;the larger the initial reservoir pressure and drawdown pressure,the higher the daily production and cumulative production of the oil well,but the cumulative production growth rate decreased;the cumulative production in the early stage of the release pressure production was significantly higher than that of the pressure controlled production,but with the increase of the pressure controlled time,the cumulative production reversed.When the pressure controlled for three years,the cumulative production increased by 5952 m3(38.8%);as the creep coefficient increased,the cumulative production increased by greater than the pressure released production.It shows that the larger the creep coefficient,the better the effect of controlling pressure production.The research results can provide theoretical basis and technical support for the efficient development of ultra-deep carbonate reservoirs.

Abstract: Thanks to Light Detection and Ranging (LiDAR), autonomous vehicles are able to detect different objects in their environment and measure the distance between them. This device gives an un-manned ground vehicle the ability to see its surroundings in real time. However, the accuracy of LiDAR can be reduced, especially in rainy weather, fog, urban smog and the like. These factors can have disastrous consequences as it increases errors in the vehicle's control computer. The aim of this research was to determine the most appropriate LiDAR frequency for autonomous vehicles, depending on the distance to them and scanning frequency in various weather conditions, therefore it is based on empiric data obtained by using the RoboPeak A1M8 LiDAR. The results obtained in rainy conditions are compared with the same ones in clear weather, using stochastic methods. A direct influence of both the frequencies used and the rain on the accuracy of the LiDAR measurements was found. Range measurement errors increase in rainy weather; as the scanning frequency increases, the results become more accurate but capture a smaller number of object points. The higher frequencies lead to about five times less error at the farthest distances compared to the lower frequencies.

Abstract: In this investigation, different natural by-products were used to modify the Particle Size Distribution (PSD) of a soil to evaluate their potential in Stabilized Rammed Earth (SRE) building. Three different mixes were manufactured; (i) a mix composed entirely of a clayey soil, (ii) a mix consisted of mining by-products and clayey soil and (iii) a mix entirely based on mining by-products. Unstabilized and stabilized samples of the mixes were manufactured, using two cement dosages (2.5% and 5%) and the samples were tested to Unconfined Compressive Strength (UCS), soaked UCS and wetting and drying tests. Mining by-products demonstrated significant potential in SRE building, as their addition to the clayey soil resulted in higher UCS values compared to the UCS obtained from clayey soil alone. Unstabilized samples lost their integrity during exposure to water. The inclusion of mining by-products also showed its potential, as although the mixes did not fully meet the requirements of the soaked UCS and the wetting and drying tests, the mix containing both mining by-products and clayey soil retained its integrity in water, unlike the samples composed solely of clayey soil. M3C5 successfully met the requirements of the soaked UCS and the wetting and drying tests, further highlighting the great potential of mining by-products in SRE building.

Abstract: The circular economy is becoming an increasingly important part of development strategies in various sectors, as it responds to critical challenges related to environmental protection, the rational use of natural resources and sustainable development. The transition from a linear to a circular model requires changes on many levels, both technological and social. In the circular model, it is crucial to design products with a view to their longer use and easier recycling and reuse. The aim of the research was to determine the physical and mechanical parameters of mortars with the addition of recycled material. The effect of the additive on the compres-sive and flexural strength, water absorption and capillary suction of mortars was inves-tigated. The rheological properties of mortars, i.e. consistency, bulk density and setting time, were also studied. The internal structure of the samples was examined using an industrial computer tomograph Nikon XT H 225 ST and the microstructure of the mortars was analysed. Thermal conductivity coefficients for mortars were estimated. The analysis of the conducted tests shows that the addition of recycled material affects the rheological properties of mortars, causing an increase in the flow of fresh mortars, an extension of the setting time and a reduction in bulk density. The recycled material affects the parameters of the hardened mortar, resulting in a reduction in compressive and flexural strength. The biocomponent causes the cement matrix to seal, resulting in a reduction in weight gain in the water absorption and capillary rise tests.

Abstract: Currently, the Ultra-Wide Band (UWB) technology commercialized in smartphones and smart keys is a High Rate Pulse repetition frequency (HRP) UWB of the IEEE 802.15.4z standard, which aims to accurately determine the distance between UWB devices located within tens of meters using Two Way Ranging (TWR). However, in order for UWB ranging technology to be spread to various location-based services or positioning services, it must be able to measure the distance between UWB devices that are hundreds of meters apart. Fortunately, UWB technology can freely change physical layer parameters as long as it complies with the UWB local regulation worldwide. Therefore, in this study, we analyzed the method of configuring packet structure, length, and transmission power from the link budget perspective to enable longer UWB ranging of hundreds of meters within UWB local regulations. As a result of the analysis, we theoretically confirmed that UWB ranging is possible even at hundreds of meters by selecting the optimal physical layer parameters. In addition, the experimental results using the Qorvo DW3000 module were confirmed to be consistent with the results analyzed in this study. The results of this study can be used as a basic data for the introduction of wide-area UWB technology and services in the future.

Abstract: Wave energy converters (WECs) have gained significant attention as a promising renewable energy source. Optimal control strategies, crucial for maximizing energy extraction, have traditionally relied on linear models based on small motion assumptions. However, recent studies indicate that these models do not adequately capture the complex dynamics of WECs, especially when large motions are introduced to enhance power absorption. The nonlinear Froude-Krylov (FK) forces, particularly in heaving point absorbers with varying cross-sectional areas, are acknowledged as key contributors to this discrepancy. While high-fidelity computational models are accurate, they are impractical for real-time control applications due to their complexity. This paper presents a parameterized approach for expressing nonlinear FK forces across a wide range of point absorber buoy shapes inspired by implementing real-time, model-based control laws. The model was validated using measured force data for a stationary spherical buoy subjected to regular waves. The FK model was also compared to a closed-form buoyancy model, demonstrating a significant improvement, particularly with high-frequency waves. Incorporating a scattering model further enhanced force prediction, reducing error across the tested conditions. The outcomes of this work contribute to a more comprehensive understanding of FK forces across a broader range of buoy configurations, simplifying the calculation of the excitation force by adopting a parameterized algebraic model and extending this model to accommodate irregular wave conditions.

Abstract: Hydrogen fuel cell vehicles are one of the most promising alternatives to achieve transport decarbonization targets thanks to their moderately high efficiency and low refueling time combined with zero exhaust emissions operation. In order to reach reasonable power density figures, fuel cell systems are generally supercharged by radial compressors, which can encounter significant limitations associated to surge and choke operation especially in high altitude. Alternatively, the current paper explores the altitude operation of a fuel cell system combined with a roots compressor. First, the balance of plant model is build in Simscape platform combining a physical and chemical 1D fuel cell model for the stack, calibrated against literature data at different pressure and temperature values, and the characteristic maps of the roots compressor. Then, the model is used to explore the balance of plant operation in a working range between 10 and 200 kW and an altitude range between sea level and 5 km. The results show that the compressor is capable to operate around the highest efficiency area (between 60 and 70%) for a wide range of altitude and power conditions, limiting the negative impact of the altitude in the system efficiency up to 3%. However, once the compressor efficiency falls below 60% the balance of plant performance rapidly drops, overcoming the benefits of the working pressure on the fuel cell stack operation and limiting the peak net power produced.

Abstract: Commercial automotive radar systems for ADAS have relied on FMCW waveforms for years due to their low-cost hardware, simple signal processing, and established academic and industrial expertise. However, FMCW systems face challenges, including limited unambiguous velocity, restricted multiplexing of transmit signals, and susceptibility to interference. This work introduces a unified automotive radar signal model and reviews alternative modulation schemes such as PC-FMCW, PMCW, OFDM, OCDM, and OTFS. These schemes are assessed against key technological and economic criteria and compared with FMCW, highlighting their respective strengths and limitations.

Abstract: The future fusion power plant EU DEMO will generate its own tritium fuel through the use of segmented breeding blankets (BBs), which must be replaced from time to time due to material damage caused by high-energy neutrons from the plasma. A vertical maintenance architecture has been proposed, using a robotic remote handling tool (transporter) to disengage the 125t and 180t outboard and inboard segments and manipulate them through an upper port. Safe disengagement without damaging the support structures requires the use of high-capacity tilting joints in the transporter. The trolley tilting mechanism (TTM) is proposed as a novel, compact, high-capacity robotic joint consisting of a 5-bar spatial mechanism integrated in the BB transporter trolley link. A kinematic model of the TTM is established, and the analytical input-output relationships, including position-dependent transmission ratio, are derived and used to guide the design and optimization of the mechanism. The model predictions are compared to an ADAMS multibody simulation, and to the results of an experiment conducted on a down-scaled prototype, both of which validate the model accuracy.

Abstract: The Volume-of-Fluid (VOF) method is widely used for multiphase flow simulations, where the VOF function implicitly represents the interface through the volume fraction field. The height function (HF) method on a Cartesian mesh integrates the volume fractions of a column of cells across the interface. A stencil of three consecutive heights and centered finite differences computes the unit normal n and the curvature κ with second-order convergence with grid refinement. The interface line can cross more than one cell of the column and the value of the geometrical properties of the interface should be interpolated in the cut cells. The continuous height function is used to show that a constant approximation of the two geometrical properties across the column provides first-order convergence, while linear or quadratic interpolations provide second-order convergence. The numerical results agree with the theoretical development presented in this study.

Abstract: The phase fraction plays a critical role in determining the solidification characteristics of metallic alloys. In this study, we propose a simplified method for estimating phase fraction based on the solidification time in cooling curves. The method was validated through experimental analysis of Al-18wt%Cu and Fe42Ni42B16 alloys, where phase fractions derived from cooling curves were compared with quantitative microstructure evaluations using computer-aided image analysis and the box-counting method. Results demonstrate strong consistency between the estimated phase fractions and experimental measurements, confirming the method’s reliability. The present method is easier operating, since it does not need derivative and integrals operations compared to Newtonian thermal analysis and Fourier thermal analysis methods. Furthermore, two key relationships deduced from the cooling curves were identified and analyzed: V/Rc=D/ΔT and RΔt=constant. These findings establish an operational framework for quantifying phase fractions and solidification rates in rapid solidification.

Abstract: Air assistance and electrical charge transfer to droplets can optimize pesticide applications and reduce losses in sweet pepper cultivation. The objective of this study was to evaluate the effects of spray rate and pneumatic spraying with and without an electrostatic charge on spray deposition, spray coverage, and ground losses in sweet pepper crops. Four application techniques were employed: standard farmer hydraulics (SFH), reduced volume hydraulics (RVH), pneumatic with air and electrostatic assistance (PAEA), and pneumatic with air assistance (PAA). The effects of the application techniques on spray deposition varied as a function of plant height, canopy depth, and leaf surface. The SFH resulted in the greatest amounts of spray deposition on adaxial leaf surface. In contrast, PAEA resulted in the greatest amounts of deposition on the abaxial leaves. The PAEA treatment improved spray coverage on abaxial leaves of the external canopy but did not improve spray coverage on the internal canopy. Compared to the SFH treatment, the 50% reduction in the spray rate of the RVH treatment decreased deposition and spray coverage. The pneumatic treatments, regardless of electrostatic charges, resulted in a lower spray lost to the ground.

Abstract: This research models a 20 MW PEM hydrogen plant. PEM units operate in the range of 60 to 80 ⁰C based on their locations and sizes. This study aims to recover the waste heat from modules to enhance the efficiency of the plant. In order to recover the heat, two systems are implemented: (a) recovering the waste heat from each PEM module and (b) recovering the heat from hot water for producing electricity using an organic refrigerant cycle (ORC). The model is made by ASPEN®, and the ORC is optimized using Python. The ORC module is optimized to maximize the produced electricity and enhance the cycle's efficiency. The system is a closed-loop cycle operating at 25 ⁰C and ambient pressure. The 20 MW PEM electrolyzer model produces 363 kg/hr of hydrogen and 2877 kg/hr of oxygen. Based on the higher heating value (HHV) of hydrogen, the plant produces 14302.2 kWh of hydrogen energy equivalent. The ORC is being maximized by increasing the electricity output from the turbine and reducing pump work while maintaining energy conservation and the mass balance. Solving equation 6 resulted in the electricity power output reaching 555.88 kW and the pump power reaching 23.47 kW.