Higher Energy Research Articles

Management of Hybrid Hydropower and Floating Solar Systems at Num Ngum 1 in Lao PDR

The integration of a hybrid hydro-floating solar power (HPP-FPV) system is covered in this study with the goal of improving energy management and producing more electricity. The production capacity of the hybrid system is almost twice as high as that of the original HPP system, demonstrating its potential for higher energy generation. Because it forecasts weather and modifies electricity generation accordingly. The analysis highlights how crucial it is to make sure that the hybrid system's electricity generation doesn’t go beyond the current power grid's maximum transmission capacity. This is essential to preserving the consistency and caliber of the power that is provided. The research's overall goal of increasing the output of renewable energy through creative system integration and practical management techniques is captured in the abstract.

Evidence for a Fast Soft X-Ray Wind in M82 from XMM-RGS

Abstract Starburst wind models predict that metals and energy are primarily carried out of the disk by hot gas (T > 106 K), but the low energy resolution of X-ray CCD observations results in large uncertainties on the mass and energy loading. Here, we present evidence for a fast soft X-ray wind from the prototypical starburst galaxy M82 using deep archival observations from the Reflection Grating Spectrometer on XMM-Newton. After characterizing the complex line-spread function for the spatially extended outflow ( ≈ 4 ′ ), we perform emission-line fitting to measure the velocity dispersion, σ v , from O viii (0.65, 0.77 keV), Ne x (1.02 keV), and Mg xii (1.47 keV). For the T ≈ 3 × 106 K gas, O viii yields a velocity dispersion of σ v = 1160 − 90 + 100 km s−1, implying a wind speed that is significantly above the escape velocity (v esc ≲ 450 km s−1). Ne x ( σ v = 550 − 150 + 130 km s−1) and Mg xii (σ v < 370 km s−1) show less velocity broadening than O viii, hinting at a lower wind speed or smaller opening angle on the more compact spatial scales traced by the T ≈ (0.6−1) × 107 K gas. Alternatively, these higher energy emission lines may be dominated by shock-heated gas in the interstellar medium. Future synthesis of these measurements with performance verification observations of the E = 2−12 keV wind in M82 from the Resolve microcalorimeter on the X-ray Imaging and Spectroscopy Mission will inform the phase structure and energy budget of the hot starburst wind.

Vibration Suppression and Energy Harvesting of Nonlinear Energy Sink-Based Piezoelectric System with Combined Damping and Bistability Properties for Nonlinear Oscillator

Nonlinear energy sink (NES) as a new type of dynamic absorber has received widespread attention due to its broadband vibration suppression capability, but it has a certain requirement of energy triggering threshold. In this work, a bistable NES-based piezoelectric system with combined damping (BCPNES) and low threshold requirement is proposed. Electromechanical-coupled equations for the nonlinear oscillator coupled with BCPNES (NO-BCPNES) are established. The vibration suppression and vibration energy harvesting performance for the coupled system are investigated numerically and analytically. The frequency–energy plots of the conservative system are investigated using the complex-variable averaging method and the electromechanical decoupling method. The influence of circuit parameters on the target energy transfer threshold and harvested energy is discussed through the equivalent stiffness and damping of the circuit. The vibration suppression performance and the target energy transfer characteristics are analyzed in terms of the time–history response, the time–frequency response and the slowly varying dynamic flow, respectively. The results show that the electromechanical coupling coefficient affects the skeleton curve of frequency–energy plots in the form of equivalent stiffness. The NO-BCPNES system exhibits higher energy dissipation performance and better targeted energy transfer form under various excitations. From the phase perspective, NES-based piezoelectric system achieves vibration suppression of the main structure through the phase locking phenomenon. The mechanism of the influence of piezoelectric device parameters on the energy harvesting performance of the systems is clarified.

3D-printable Kresling-embedded honeycomb metamaterials with optimized energy absorption capability

Abstract Kresling origami structure has attracted significant interest for achieving extraordinary mechanical properties. In this study, we proposed a new strategy to develop 3D-printable Kresling-embedded honeycombs (KEHs) based mechanical metamaterials and achieve optimized mechanical energy absorption capability. By exploiting the twisted deformation modes and boundary constraints, various KEH reinforced metamaterials were designed, where their deformation behaviors and energy absorption properties were investigated using finite element analysis and quasi-static compression tests. Effects of orientation twisting angle, boundary constraint and crease tilting angle on the deformation behaviors of these KEH reinforced metamaterials were studied to optimize their energy absorption properties. Finally, deformation behaviors and energy absorption properties of KEH reinforced metamaterials incorporated of KEH arrays in both 2D structure and 3D structures were studied. Both experimental and simulation results showed that the proposed KEH reinforced metamaterials achieved much more stable compression behaviors and higher energy absorption capabilities than those of the traditional honeycomb structures. This study provides a novel KEH reinforcement strategy for 3D printed metamaterials with optimized energy absorption capabilities to dramatically expand their practical applications.

Continuous transcranial ultrasound in large vessel stroke: Image guidance for high-intensity focused sonothrombolysis.

Sonothrombolysis is a potential adjunctive therapy for large vessel occlusion (LVO) stroke. Bedside ultrasound image-guided high-intensity focused ultrasound (HIFU) therapy could deliver higher energy therapeutic ultrasound to the thrombus with higher precision than what was previously accomplished in human trials. The aim is to test the feasibility of diagnostic transcranial contrast-enhanced ultrasound (CEUS) to image the occlusion site and continuously maintain the guidance image on-target for a sufficient exposure time for HIFU to be effective during LVO stroke evaluation and treatment. This prospective, single center, observational cohort study included adult patients, presenting within 6 hours of stroke symptom onset, with LVO identified on computed tomography angiography (CTA). A hand-held CEUS imaging study was initiated following CTA and lasted up to 30 minutes. The primary outcome is the proportion of patients where a guidance CEUS image of the occlusion was achieved. A CEUS image of the occluded artery was obtained in 32/35 of the included patients. The median total imaging time was 23 minutes (interquartile range 15-30). Patients undergoing thrombectomy had a lower total imaging time (17 vs. 29.5 minutes, p=.002). When imaging was successful, on-target image was maintained for only 58% (standard deviation 23.8%) of total imaging time. No complications related to CEUS were observed. This feasibility study explored the use of diagnostic transcranial CEUS for continuous imaging of occlusion sites in LVO strokes. Challenges in maintaining target image during HIFU were identified, highlighting the need for technical advances for clinical application.

Energy Consumption, Emission, Transportation Sector in Malaysia: Review on Malaysia’s Road Transport

Transportation is a major challenge for energy conservation, with road transport in Malaysia being a significant contributor to greenhouse gas (GHG) emissions. In Malaysia, traditional fossil fuels such as gasoline and diesel dominate the transportation sector, which has become the second-largest source of GHG emissions, accounting for 20% in 2014. This increase in CO2 emissions, driven by rising vehicle ownership and economic growth, underscores the urgent need for effective emission reduction strategies. The rapid growth in road transportation in Malaysia is linked to socioeconomic factors, including rising incomes and urbanization, leading to higher energy consumption and pollution. Data indicates a significant increase in vehicle registrations from 1990 to 2018, with motorcars and motorcycles being the most common. This growth, fueled by subsidies and decentralization, has exacerbated the sector’s environmental impact. The Green Technology Master Plan Malaysia 2017–2040 aims to address these issues by setting ambitious targets to enhance renewable energy, improve energy efficiency, and promote eco-friendly fuels. Key strategies include expanding public transportation, increasing the adoption of electric vehicles (EVs), and introducing alternative fuels like hydrogen. Malaysia has substantial potential to reduce CO2 emissions through initiatives such as expanding EV infrastructure, promoting natural gas vehicles, and improving public transit. Effective implementation of these strategies can significantly lower the transportation sector’s carbon footprint, contributing to a more sustainable future.

Design of a Bionic Spider Robot with a Two-Degrees-of-Freedom Leg Structure and Body Frame

Spiders have unique biological characteristics and excellent maneuverability, making them an ideal model for bionic robot design. However, traditional bionic spider robot designs usually have multiple degrees of freedom and confront many challenges. These challenges include complex control requirements, higher energy consumption, larger size and weight, higher risk of failure, and higher cost. This study proposes a leg design with two degrees of freedom to reduce its control and manufacturing costs. It can better control leg movement and improve leg force through a multi-link mechanism and a dual-motor system. In addition, the triangular gait and hexagonal body structure align the weight of the body with the support point, thereby enhancing stability. This study offers a comprehensive and organized approach to bio-inspired robot design, providing a valuable reference for future bionic robot development.

Investigation of Laser Ablation Quality Based upon Entropy Analysis of Data Science

Laser ablation is a vital material removal technique, but current methods lack a data-driven approach to assess quality. This study proposes a novel method, employing information entropy, a concept from data science, to evaluate laser ablation quality. By analyzing the randomness associated with the ablation process through the distribution of a probability value (reb), we quantify the uncertainty (entropy) of the ablation. Our research reveals that higher energy levels lead to lower entropy, signifying a more controlled and predictable ablation process. Furthermore, using an interval time closer to the baseline value improves the ablation consistency. Additionally, the analysis suggests that the energy level has a stronger correlation with entropy than the baseline interval time (bit). The entropy decreased by 6.32 from 12.94 at 0.258 mJ to 6.62 at 0.378 mJ, while the change due to the bit was only 2.12 (from 10.84 at bit/2 to 8.72 at bit). This indicates that energy is a more dominant factor for predicting ablation quality. Overall, this work demonstrates the feasibility of information entropy analysis for evaluating laser ablation, paving the way for optimizing laser parameters and achieving a more precise material removal process.

Enhancing Vanadium Redox Flow Battery Performance with ZIF-67-Derived Cobalt-Based Electrode Materials

Vanadium redox flow batteries (VRFBs) have emerged as a promising energy storage solution for stabilizing power grids integrated with renewable energy sources. In this study, we synthesized and evaluated a series of zeolitic imidazolate framework-67 (ZIF-67) derivatives as electrode materials for VRFBs, aiming to enhance electrochemical performance. Four materials—Co/NC-700, Co/NC-800, Co3O4-350, and Co3O4-450—were prepared through thermal decomposition under different conditions and coated onto graphite felt (GF) electrodes. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analyses confirmed the structural integrity and distribution of the active materials. Electrochemical evaluations revealed that electrodes with ZIF-67-derived coatings exhibited significantly lower charge transfer resistance (Rct) and higher energy efficiency (EE) compared to uncoated GF electrodes. Co/NC-800//GF delivered the highest energy efficiency and discharge capacity among the tested configurations, maintaining stable performance over 100 charge–discharge cycles. These results indicate that Co/NC-800 holds great potential for use in VRFBs due to its superior electrochemical activity, stability, and scalability.

Carvacrol enhances antioxidant activity and slows down cell wall metabolism by maintaining the energy level of 'Guifei' mango.

Postharvest mango fruit are highly susceptible to rapid ripening, softening and senescence, greatly limiting their distribution. In this study, we evaluated the potential effects of carvacrol (0.06 g L-1) on mango (25 ± 1 °C) and the mechanisms by which it regulates antioxidant activity, energy and cell wall metabolism. The results showed that carvacrol treatment delayed the 'Guifei' mango color transformation (from green to yellow) and the decrease in firmness, titratable acidity, weight loss and soluble solids content, and suppressed the increase in relative conductivity, malondialdehyde content and reactive oxygen species (H2O2 and O2 ·-) as well as enhancing antioxidant activity. In addition, carvacrol treatment increased ascorbic acid and reduced glutathione levels, ascorbate peroxidase, glutathione reductase, monodehydroascorbate reductase and dehydroascorbate reductase activities in mango. Meanwhile, energy level (adenosine triphosphate, adenosine diphosphate, adenosine monophosphate and energy charge) content and energy metabolizing enzyme activities (H+-ATPase, Ca2+-ATPase, succinate dehydrogenasepears and cytochrome C oxidase) were increased on carvacrol treatment, which resulted in the maintenance of higher energy levels. Finally, the application of carvacrol was effective in maintaining firmness and cell wall components by inhibiting the activities of polygalacturonase, cellulase, pectin methyl esterase and β-galactosidase. The current study demonstrates that carvacrol effectively delays the ripening and softening of mangoes by modulating energy metabolism and cell wall dynamics through the attenuation of oxidative stress. © 2024 Society of Chemical Industry.

Impacts of Protein and Energy Levels on Rumen Fermentation and Microbial Activity Under Different Incubation Temperatures

This study aimed to explore the effects of different incubation temperatures on ruminal fermentation and rumen microorganisms and determine the appropriate protein and energy levels to enhance microbial protein synthesis using an in vitro system. Rumen inoculum was collected from two fistulated Holstein heifers (trial 1: BW: 652.3 kg ± 25.2; trial 2: BW: 683.3 kg ± 30.2) and assessed using a closed-batch culture system. The experimental model employed a 2 × 5 factorial arrangement using incubation temperatures set to 39 and 41 °C, with protein levels set to 12.0, 13.5, 15.0, 16.5, and 18.0% of DM in trial 1 or with energy levels set to 2.4, 2.5, 2.6, 2.7, and 2.8 Mcal/kg of DM in trial 2. The data were analyzed using the MIXED procedure. The results showed increased (p < 0.05) NH3-N concentrations and total volatile fatty acids (TVFAs) with higher incubation temperatures, while the liquid-associated bacterial (LAB) amounts decreased (p < 0.05) in trials 1 and 2. The interaction between the energy level and incubation temperature affected (p < 0.05) the LAB protein levels in trial 2. Higher protein levels led to increased (p < 0.05) NH3-N and acetate concentrations, but it decreased (p < 0.05) the propionate percentage. Conversely, higher energy levels decreased (p < 0.05) the amount of acetate and increased the propionate concentration, altering the acetate-to-propionate ratio. However, no interaction involving TVFA and LAB was observed between the incubation temperature and the protein or energy levels. Changes in the NH3-N, TVFAs, and LAB protein amounts were observed under different incubation temperatures and energy levels. In conclusion, these findings provide insight into the metabolic adaptation under different ruminal temperatures and the impacts of dietary adjustments on rumen fermentation and microbial activity. However, there are limitations to replicating the complex physiological responses that occur within the whole body solely through in vitro experiments.

Enhancing burning rate of ammonium nitrate by ammonia borane: Mechanism from reactive molecular dynamics simulation.

The development of ammonium nitrate (AN)/ammonia borane (AB) as a green propellant is crucial for their applicability in different engines. This study investigates the release patterns of small products, particularly nitrogen-containing molecules, during the initial pyrolysis of AN/AB at low and high pressures using ReaxFF MD simulations. Compared with pure AN, the addition of AB gives the hybrid system enhanced reactivity, leading to faster decomposition and higher energy release. The results show that the consumption of AN in the S13 system (AB with a mass ratio of 12.6 %) is accelerated at 1.47 MPa. NO2 and NO are produced through HNO3 and NO3. At 6.89 MPa, AN exhibits the fastest decomposition rate in the S15 system. The high pressure enhances more reactions of NO with free radicals such as NH and accelerates the release of N2. As the percentage content of AB increases to 15.3%, more H2O while more NO2 is generated. The effect of AB on the generation of radicals such as H2 and H, is analyzed. AB not only promotes the initial pyrolysis of AN but also accelerates the conversion of intermediates.

Comparison of nutritional value of the wild and cultivated spiny loaches at three growth stages.

Environmental pollution and overfishing of wild spiny loach have led to the increased demand for breeding the fish. However, the nutritional value between the wild and cultivated spiny loaches was unknown. Therefore, this study aimed to evaluate the nutritional components among the wild and cultivated spiny loaches at different growth stages by analyzing and comparing the proximate compositions, fatty acids, amino acids and volatile compounds. Results showed that the cultivated ones had significantly higher energy and fat contents than the wild. Particularly, the cultivated second-age spiny loach contained the highest contents of polyunsaturated fatty acids (4.83 ± 0.01%) and EPA + DHA (0.85 ± 0.02%). Besides, the total essential amino acid content of cultivated second-age spiny loach was 2201.28, exceeding that recommended in the FAO/WTO scoring pattern (2,190). And it had the highest flavor amino acid (6.24 ± 0.04 g/100 g), essential amino acid index value (71.82) and higher contents of volatile compounds. Overall, the cultivated spiny loach, especially that at the second growth stage, displayed the highest nutritional value. The findings of this study would help farmers to harvest the suitable breeding stage of spiny loaches from the perspective of nutritional value, which is beneficial to the sustainable fish farming.

Enhanced Electrocatalytic Urea Synthesis over Iron-Doped InOOH Nanosheets under Ambient Conditions.

Ambient urea synthesis via C-N coupling from CO2 and nitrate reduction offers an attractive alternative to the Bosch-Meiser route, but it is hindered by the lack of efficient catalysts. Herein, we report that Fe-doped InOOH nanosheets effectively catalyze the coreduction of CO2 and nitrate, giving a high Faradaic Efficiency of 26.9%, a yield rate of 980.6 μg h-1 mgcat.-1, and a good durability. Theoretical calculations further elucidate that iron dopants can tailor the reactivity of the In site, facilitating the hydrogenation of the key *CO2NH2 intermediate and suppressing the hydrogen production with a higher energy barrier.

Facts and Fictions About Photocatalytic CO2 Reduction to C2+ Products.

In response to carbon neutrality, photocatalytic reduction of CO2 has been the subject of growing interest for researchers over the past few years. Multi-carbon products (C2+) with higher energy density and larger market value produced from photocatalytic reduction of CO2 are still very limited owing to the low photocatalytic productivity and poor selectivity of products. This review focuses on the recent progress on photocatalytic reduction of CO2 towards C2+ products from the perspective of performance evaluation and mechanistic understanding. We first provide a systematic description of the entire fundamental procedures of photocatalytic reduction of CO2. An in-depth strategy analysis for improving the selectivity of photocatalytic reduction of CO2 to C2+ products is then addressed. Then the focus was on summarizing the ways to improve C2+ selectivity. The intrinsic mechanisms of photocatalytic reduction of CO2 to C2+ products are summarized in the final. Combining the foundation of photocatalysis with promising catalyst strategies, this review will offer valuable guidance for the development of efficient photocatalytic systems for the synthesis of C2+ products.

Sputtered Zero‐Excess Electrodes with Metallic Seed Layers for Solid‐State Sodium Batteries

Zero‐excess sodium metal solid‐state batteries offer improved safety, lower cost, higher energy density, and reduced resource dependency compared to today’s lithium‐ion technology. This study demonstrates the fabrication of zero‐excess electrodes with unprecedented stability during plating/stripping cycles. The fabrication process involves the sputter deposition of 20 nm metallic seed layers – zinc, silver, indium, or tin – onto NASICON (Na3.4Zr2Si2.4P0.6O12) ceramic separators, followed by the sputter deposition of a 30 µm copper current collector. The favorable influence of these seed layers on the in‐situ formation of the sodium|NASICON interface is examined through nucleation and cycling experiments, with a sodium metal reservoir serving as the non‐limiting counter electrode. Due to alloy formation the seed layers – particularly tin – stabilize sodium nucleation and cycling substantially and reduce dendrite formation compared to reference cells with bare copper current collectors. Sodium loss during cycling is primarily attributed to local cracking of the current collector and its partial delamination from the NASICON. Compared to polished NASICON, a roughened surface reduces the resistance e.g. of the counter electrode 200‐fold to approx. 1 Ωcm² at 3 MPa and suppresses delamination further.

Linking sustainability reporting and energy use through global reporting initiative standards and sustainable development goals

AbstractThis paper addresses the critical need for an integrated approach to sustainability reporting by examining the transition from internal combustion engine vehicles to electric vehicles within the automotive industry. By focusing on the top 8 highest-revenue global automakers in 2022, the study utilizes the Global Reporting Initiative (GRI) standards and United Nations Sustainable Development Goals to assess contributions to SDG 7 (affordable and clean energy) and other pertinent indicators. A comprehensive content analysis and logistic regression analysis are employed to explore the correlation between energy use and compliance with GRI standards from 2018 to 2022. The findings reveal significant trends in sustainability reporting, with a noted decrease in quality in the final year analyzed. Specifically, GRI 302-3 (energy intensity) shows a significant negative relationship with energy consumption, indicating higher energy usage correlates with lower compliance. The study reinforces the necessity for more transparent and effective sustainability reporting frameworks to enhance corporate practices and drive progress toward sustainability goals. Graphical abstract

Fabrication of solid-state plasmonic solar cell device using FTO|TiO2|Ag-nanoparticle assembly to generate hot electrons surpassing Schottky barrier

This work presents a detailed investigation into the fabrication and performance evaluation of plasmonic solar cells, where a thin film of silver nanoparticles is deposited onto a TiO₂ layer, with the silver film itself functioning as the active layer for light absorption and energy conversion. The study compares two deposition techniques—DC Magnetron Sputtering and Thermal Vapor Deposition (TVD)—revealing significant differences in the resulting device performance. The device fabricated using TVD demonstrated a significantly higher open circuit voltage of 440.3 mV and short circuit current density of 1.6 mA/cm² compared to the device fabricated via DC Magnetron Sputtering, which recorded an open circuit voltage of 56.92 mV and a short circuit current density of 0.03 mA/cm². These results indicate that TVD offers superior electron-hole separation, reduced recombination losses, and enhanced light absorption efficiency. The main contribution of this work lies in demonstrating that the TVD technique significantly improves the photovoltaic performance of plasmonic solar cells compared to DC Magnetron Sputtering. The study validates the hot-electron mechanism at the TiO2|Ag junction using Kelvin probe force microscopy, contributing valuable insights into the role of plasmonic effects in enhancing solar cell efficiency. Additionally, it underscores the potential of TVD for developing advanced solar cell technologies with higher energy conversion efficiency.

Energy, environmental footprints and economic benefit of substituting inorganic fertilizer with organic manure for winter wheat in Huanghuaihai Plain

Manure substitution shows promise for nitrogen (N) management, food security, energy balance and environmental costs reduction. However, there is limited research on this practice in the Huanghuaihai Plain. This study aimed to investigate the energy use efficiency, economic benefits, carbon and nitrogen footprint under two types of N fertilizer (U, urea and M, organic manure), two application rates of N (180 kg N ha−1, U1 for 100 % urea and M1 for 100 % organic manure; 90 kg N ha−1, U2 for 50 % urea and M2 for 50 % organic manure) and no fertilizer application treatment (CK) for winter wheat from 2017 to 2019. Results showed that grain yield and agricultural input cost under N application rate of 90 kg N ha−1 was 15.5 % and 7.8 % lower than that of 180 kg N ha−1, respectively, leading to a significant decrease in economic benefit. Under the same N rate, M1 obtained higher grain yield than U1, grain yield of M2 did no differ in that of U2. Total energy inputs and agricultural input costs of M were 9.5 % and 3.6 % lower than U, resulting in higher energy use efficiency and economic benefit. The reduced agricultural input for M was primarily due to a decrease in the application of inorganic fertilizer. Compared with other treatments, U2+M2 obtained higher grain yield, energy use efficiency, and economic benefit. The carbon and nitrogen footprint on unit grain yield of U1 was increased by 13.7 %-24.1 % and 3.9 %-19.6 %, which was attributed to the increase in direct N2O emissions, indirect carbon emission and losses of reactive N from agricultural inputs. Overall, U2+M2 sustained high productivity and reduced the environmental impact. Substituting inorganic fertilizer with organic manure was a promising strategy to improve agricultural production with less agricultural inputs and environmental footprints in the Huanghuaihai Plain.

Heart Rate Estimation Considering Reconstructed Signal Features Based on Variational Mode Decomposition via Multiple-Input Multiple-Output Frequency Modulated Continuous Wave Radar

Accurate heart rate estimation using Doppler radar and Frequency Modulated Continuous Wave (FMCW) radar is highly valued for privacy protection and the ability to measure through clothing. Conventional methods struggle to isolate the heartbeat from respiration and body motion. This paper introduces a novel heart rate estimation method using Variational Mode Decomposition (VMD) via Multiple-Input Multiple-Output (MIMO) FMCW radar. The proposed method first estimates human positions within the radar’s coverage, reducing noise by focusing on signals from these positions. The signal is then decomposed into multiple Intrinsic Mode Function (IMF) signals using VMD, and the heartbeat-specific IMF is extracted based on its center frequency. The heart rate signal is reconstructed using weighted addition of IMF signals for each radar cell, with cells defined by specific angles and distances within the coverage area. Peak detection is used to estimate heart rate from these reconstructed signals. To ensure accuracy, the method selects the heart rate estimate with the highest energy and periodicity for the first four time windows. From the fifth time window onward, it selects the estimate closest to the average of the previous four, minimizing extraneous variations. Experiments conducted with one and two subjects showed promising results. In case 1, with one subject, the method achieved a Mean Absolute Error (MAE) of 2.54 BPM and an exclusion rate of 0.94% using MIMO FMCW radar, compared to 4.72% with Doppler radar. In case 2, with two subjects, the method achieved an MAE of 2.28 BPM, confirming accurate simultaneous heart rate estimation.