Search Results (869)

This research explores a phase-shift-based discontinuous PWM method used for 24 V battery-powered onboard micro inverters, which are critical for thermally limited applications like micromachines, where efficient heat dissipation and compact size are paramount. Discontinuous pulse width modulation (DPWM) reduces switching losses by clamping the phase voltage to the DC bus in order to improve inverter efficiency. Due to the change in power factor at different operating points from motors or the inductor load, the use of only one DPWM method cannot achieve the optimal efficiency of a three-phase voltage source inverter (3ph-VSI). This paper proposes a generalized DPWM method with a continuously adjustable phase shift angle, which extends the six traditional DPWM methods to any type. According to different power factors, the proposed DPWM method is divided into five power factor angle intervals, namely [−90°, −60°], [−60°, −30°], [−30°, 30°], [30°, 60°], and [60°, 90°], and automatically adjusts the phase shift angle to the optimal-efficiency DPWM mode. The power factor is calculated by means of the Synchronous Reference Frame Phase-Locked Loop (SRF-PLL) method. The switching losses and harmonic characteristics of the proposed DPWM are analyzed, and finally, a 24 V onboard 3ph-VSI experimental platform is built. The experimental results show that the efficiency of DPWM methods can be improved by 3–6% and the switching loss can be reduced by 40–50% under different power factors. At the same time, the dynamic performance of the proposed algorithm with a transition state is verified. This method is particularly suitable for miniaturized inverters where efficiency and thermal management are critical. Full article

As a core functional device in microwave systems, attenuators play a crucial role in key aspects such as signal power regulation, amplitude attenuation, and impedance matching. Addressing the pressing technical issues currently exposed by attenuators in practical applications, such as excessive insertion loss, low attenuation accuracy, large physical dimensions, and insufficient process reliability, this paper proposes a design scheme for an RF three-bit reconfigurable stepped attenuator based on radio frequency micro-electromechanical systems (RF MEMS) switches. The attenuator employs planar integration of the T-type attenuation network, Coplanar Waveguide (CPW), Y-shaped power divider, and RF MEMS switches. While ensuring rational power distribution and stable attenuation performance over the full bandwidth, it reduces the number of switches to suppress parasitic parameters, thereby enhancing process feasibility. Test results confirm that this device demonstrates significant advancements in attenuation accuracy, achieving a precision of 1.18 dB across the 0–25 dB operational range from DC to 20 GHz, with insertion loss kept below 1.65 dB and return loss exceeding 12.15 dB. Additionally, the device boasts a compact size of merely 0.66 mm × 1.38 mm × 0.32 mm, significantly smaller than analogous products documented in existing literature. Meanwhile, its service life approaches 5 × 10⁷ cycles. Together, these two attributes validate the device’s performance reliability and miniaturization advantages. Full article

This paper introduces a power-driven systems engineering methodology for the early-phase design of highly miniaturized satellites: PlanarSats. We derive an analytical framework linking power requirements, contingency policies, solar-cell performance, and subsystem integration to determine the absolute minimum satellite size. Through idealized and detailed case studies, we explore the trade-offs inherent in subsystem selection and integration constraints. Sensitivity analysis identifies critical factors affecting minimum area and operational envelopes. Our framework provides a clear tool for balancing functionality, reliability, and physical limits in next-generation ultra-small satellite missions. Full article

Measurement While Drilling (MWD) systems require high-precision triaxial magnetometers for real-time downhole attitude sensing, yet conventional fluxgates fail to meet the stringent size, noise, bandwidth, and temperature demands of deep reservoirs (>175 °C). To bridge this gap, we present a miniaturized triaxial fluxgate magnetometer (23 × 23 × 21 mm³) leveraging Co-Fe-Si-B amorphous wire cores—a material selected for its near-zero magnetostriction and tunable magnetic anisotropy. The sensor achieves breakthrough performance: a 300 Hz bandwidth combined with noise levels below 200 pT/√Hz at 1 Hz when operating at 175 °C while maintaining full functionality with the probe surviving temperatures exceeding 200 °C. This advancement paves the way for more accurate wellbore positioning and steering in high-temperature hydrocarbon and geothermal reservoirs. Full article

Advancement of compact atomic clocks has centered on reducing footprint and power consumption. Such developments come at the cost of the clock’s stability performance. Various commercial and military applications demand reduced size, weight, and power (SWaP) requirements but desire an enhanced stability performance beyond what is achieved with the lower-profile standards, such as Microchip’s chip-scale atomic clock (CSAC) or miniature atomic clock (MAC). Furthermore, a high-performing space-rated clock will enhance small satellite missions by providing capability for alternate PNT, one-way radiometric ranging, and eventual lunar PNT purposes. The MAC is a strong candidate as it has modest SWaP parameters. Enhanced performance improvement to the MAC, particularly in the medium to long-term stability over a day and beyond will strengthen its candidacy as an on-board clock in small satellite missions and other ground-based applications. In this work, using external thermal control methods, we demonstrate an improvement of the MAC performance by at least a factor of five, showing a superior stability of σ_y = 4.2 × 10⁻¹³ compared to the best-performing miniaturized standard on the market for averaging intervals of τ > 10⁴ s up to 4 days. Full article

Purpose: Androgenetic alopecia (AGA) is a common, chronic, non-cicatricial dermatological condition characterized by progressive miniaturization of hair follicles. Although AGA is a benign disorder, it has a considerable impact on patients’ quality of life and psychological health. The current treatment options often demonstrate limited efficacy and are frequently associated with undesirable side effects. This study aimed to co-mill two natural compounds, quercetin (QT) and glycyrrhizic acid (GL), to develop follicle-targeted nanocrystals (NCs), thereby enhancing local accumulation, improving the pathological follicular microenvironment associated with AGA, and promoting hair regrowth. Methods: QT nanocrystals (QT-NCs) were fabricated using a top–down wet media milling technique with GL as a bioactive stabilizer. The resulting QT-NCs were characterized regarding their particle size, crystallinity, morphology, and stability. The skin permeation properties of the QT-NCs were further evaluated in vitro, and their therapeutic efficacy was assessed in a dihydrotestosterone (DHT)-induced AGA mouse model. Results: The QT-NCs exhibited an irregular structure with a particle size ranging from 200 to 300 nm, demonstrating uniform dimensions and excellent storage stability. In vitro permeation studies revealed a 2.27-fold increase in cumulative penetration and a 2.47-fold enhancement in skin retention compared to raw QT. In the DHT-induced AGA mouse model, QT-NCs significantly reduced local DHT levels while concurrently modulating the follicular microenvironment, resulting in markedly improved therapeutic outcomes. Notably, when co-administered, QT and GL demonstrated synergistic pharmacological effects, suggesting potential combinatory benefits. Conclusions: This study presents the first demonstration of QT-NCs for AGA treatment, establishing a novel therapeutic strategy with substantial potential for clinical translation. Full article

In modern laptops, antenna design for Wi-Fi 7 is constrained by limited space and reduced ground plane size, conditions under which many compact designs exhibit degraded bandwidth or efficiency or require large device grounds. This paper presents a miniaturized tri-band inverted-F antenna (IFA) that supports the 2.4, 5, and 6 GHz Wi-Fi 7 bands within a radiator area of 20 × 5 × 0.8 mm³ and a ground plane of 60 × 40 mm². The proposed design achieves wideband impedance matching and stable radiation efficiency under intentionally reduced grounding conditions, addressing a scenario rarely considered in prior studies where both radiator and ground plane miniaturization must be satisfied. Measurements confirm efficiencies of 74–81% at 2.4 GHz and 64–90% across 5–7 GHz, with performance in the lower band exceeding that of many compact designs and upper-band coverage comparable to structures requiring larger footprints. By demonstrating tri-band operation under simultaneous radiator and ground reduction, this work provides a practical antenna solution for next-generation Wi-Fi 7 laptop integration. Full article

In the context of increasingly stringent vehicle emission regulations, computer-aided engineering has been indispensable for optimizing the design and the operational strategies of emission control systems. This paper proposes a new filtration model for particulate filters that enables the accurate estimation of solid particle number emissions above 10 and 23 nm in diameter (SPN10 and SPN23, respectively). The model incorporates a persistent slip factor and a linear filtration efficiency of cake layers into the unit collector model proposed by Konstandopoulos and Johnson. This enhancement captures PM escape phenomena, such as a passage through interconnected large pores in filter walls. Simulations using a 1D + 1D two-channel framework with the proposed model successfully reproduced experimental results of SPN10 and SPN23 emissions downstream of a miniature gasoline particulate filter (GPF) tested with a synthetic particle generator. The model was also able to represent the observed continuous emissions during a cake filtration mode. Additional simulations using the same model parameters showed good agreement with experimental data of SPN10 and SPN23 emissions downstream of a full-size GPF tested with a gasoline direct injection (G-DI) engine under 5 steady-state operating conditions. The simulations revealed that particles in the 10–100 nm size range dominated the downstream SPN emissions despite their high filtration efficiency, whereas particles in the 100–200 nm size range were less significant. The proposed model is expected to contribute to the GPF developments to comply with the stringent emission regulations of the upcoming Euro 7. Full article

The constitutive modelling of granular soils has been a long-standing research subject in geotechnical engineering, and machine learning (ML) has recently emerged as a promising tool for achieving this goal. This paper proposes two recurrent neural networks, namely, the Gated Recurrent Unit Neural Network (GRU-NN) and the Long Short-Term Memory Neural Network (LSTM-NN), which utilize input parameters such as the initial void ratio, initial fabric anisotropy, uniformity coefficient, mean particle size, and confining pressure to establish the high-dimensional relationships of granular soils from micro to macro levels subjected to triaxial shearing. The research methodology consists of several steps. Firstly, 200 numerical triaxial tests on idealized granular soils comprising polydisperse spherical particles are performed using the discrete element method (DEM) simulation to generate datasets and to train and test the proposed neural networks. Secondly, LSTM-NN and GRU-NN are constructed and trained, and their prediction performance is evaluated by the mean absolute percentage error (MAPE) and R-square against the DEM-based datasets. The extremely low error values obtained by both LSTM-NN and GRU-NN indicate their outstanding capability in predicting the constitutive behaviour of idealized granular soils. Finally, the trained ML-based models are applied to predict the constitutive behaviour of a miniature glass bead sample subjected to triaxial shearing with in situ micro-CT, as well as to two extrapolated test sets with different initial parameters. The results show that both methods perform well in capturing the mechanical responses of the idealized granular soils. Full article

IP spoofing is a critical component in many cyberattacks, enabling attackers to evade detection and conceal their identities. This study rigorously compares eight deep learning models—LSTM, GRU, CNN, MLP, DNN, RNN, ResNet1D, and xLSTM—for their efficacy in detecting IP spoofing attacks. Overfitting was mitigated through techniques such as dropout, early stopping, and normalization. Models were trained using binary cross-entropy loss and the Adam optimizer. Performance was assessed via accuracy, precision, recall, F1 score, and inference time, with each model executed a total of 15 times to account for stochastic variability. Results indicate a powerful performance across all models, with LSTM and GRU demonstrating superior detection efficacy. After ONNX conversion, the MLP and DNN models retained their performance while achieving significant reductions in inference time, miniaturized model sizes, and platform independence. These advancements facilitated the effective utilization of the developed systems in real-time network security applications. The comprehensive performance metrics presented are crucial for selecting optimal IP spoofing detection strategies tailored to diverse application requirements, serving as a valuable reference for network anomaly monitoring and targeted attack detection. Full article

More and more chemosensors and biosensors are turning to electronic transistors, as they are ideal transducers, precise in current response, miniaturized in size and capable of providing sub-picomolar detection limits. Among these devices, ISFET transistors—Ion-Sensitive Field-Effect Transistors—have the capacity of integrating ion-sensitive layers together with field effect transistors of ultimate generations. Recent studies have indicated that nanoporous materials deposited or grown within the transistor gate space offer a dual advantage—a favorable environment for an optimal capture of liquid state receptors through capillary effects, but also of direct anchoring of these nanoporous structures on a Si wafer. This article aims to review the constructive evolutions of ISFET transistors, along with some newer nanowire devices, as well as their co-integration techniques with nanoporous materials, which are beneficial in the optimization of many chemosensors but of enzymatic biosensors in particular. Full article

This paper proposes a highly symmetrical miniaturized, frequency-selective surface (FSS) based on LC parallel resonance to optimize high-frequency passband characteristics, enhancing transmission efficiency under large-angle conditions. Through meandered design optimization, the device size is further reduced. Utilizing cell bending techniques and LC resonators, a single-layer FSS unit with parallel LC resonance is designed, achieving reflection and transmission peaks at approximately 1.56 GHz and 1.94 GHz, respectively. By employing co-planar and hetero-planar configurations to manipulate the effective capacitance through structural design, the reflection resonance frequency is effectively shifted beyond 0.7 GHz while preserving passband stability. The single-polarization characteristic is enhanced through cell arrangement. Experimental results validate the FSS’s transmission performance in the 1.71–2.2 GHz band under large-angle incidence (0–60°), with gain reduction not exceeding 1.2 dB. With a compact footprint (0.134λ × 0.134λ), a simple structure, and a stable angular response, the proposed FSS demonstrates strong potential for base station applications that require multi-band compatibility and spatial efficiency. Full article

The present study is a comprehensive experimental investigation of the uncertainties in the mechanical response of short fibre-reinforced composites. The reference material investigated is a short glass fibre-reinforced phenolic resin matrix material, manufactured in a thermoset injection-moulding process. The mechanical material response was investigated in experiments on three different scales, considering ISO-size, miniature, and micro tensile samples. Further to the tensile experiments, compressive and shear tests were performed on macroscopic samples. Experiments on breadboard samples featuring more complex stress and deformation states complete the study. The injection-moulding process was found to control the basic fibre orientation. However, the nominal local fibre orientation distribution is superimposed with a pronounced local uncertainty. This microstructural uncertainty strongly affects the uncertainty in the local mechanical properties as well as variations between samples taken from identical positions in different but nominally identical plates. Full article

Although the allocation of biomass among floral organs reflects critical trade-offs in plant reproductive strategies, the scaling relationships governing biomass allocations remain poorly resolved, particularly in flowers. Here, we report the fresh mass scaling allocation patterns among four floral organs (i.e., sepals, petals, stamens, and carpels), and the two subtending structural components (i.e., the pedicel and receptacle) of 497 flowers of the hypogynous Rosa chinensis var. minima (miniature rose) using reduced major axis protocols. The two-parameter Weibull probability density function was also applied to characterize the distributions of floral organ mass, and revealed skewed tendencies in all six measured traits. The results show that the numerical values of the scaling exponents (α) for all pairwise power-law relationships significantly exceeded unity (α > 1), indicating disproportionate investments in larger floral structures with increasing overall flower size. Specifically, the scaling exponent of corolla fresh mass vs. calyx fresh mass was α = 1.131 (95% confidence interval [CI]: 1.086, 1.175), indicating that petal investment outpaces sepal investment as flower size increases. Reproductive organs also exhibited significant disproportionate investments (i.e., allometry): the collective carpel (gynoecium) fresh mass scaled allometrically with respect to the collective stamen (androecium) mass (α = 1.062, CI: 1.028, 1.098). Subtending axial structures (pedicel and receptacle) also had hyperallometric patterns, with pedicel mass scaling at α = 1.167 (CI: 1.106, 1.235) with respect to receptacle mass. Likewise, the combined fresh mass of all four foliar homologues (sepals, petals, androecium, and gynoecium) scaled disproportionately with respect to the biomass of the two subtending axial structures (α = 1.169, CI: 1.126, 1.214), indicating a prioritized resource allocation to reproductive and display organs. These findings are in accord with hypotheses positing that floral display traits, such as corolla size, primarily enhance pollen export by attracting pollinators, while maintaining fruit setting success through coordinated investment in gynoecium development. The consistent hyperallometry across all organ pairwise comparisons underscores the role of developmental integration in shaping floral architecture in Rosaceae, as predicted by scaling theory. By integrating morphometric and scaling analyses, this study proposes a tractable methodology for investigating floral resource allocation in monomorphic-flowering species and provides empirical evidence consistent with the adaptive patterns of floral traits within this ecologically and horticulturally significant lineage. Full article

In this study, a novel direct laser beam turning (DLBT) approach is proposed for the precision machining of AISI 308L austenitic stainless steel, which eliminates the need for cutting tools and thereby eradicates tool wear and vibration-induced surface irregularities. A nanosecond-pulsed Nd:YAG fiber laser (λ = 1064 nm, spot size = 0.05 mm) was used, and Ø1.6 mm × 20 mm cylindrical rods were processed under ambient conditions without auxiliary cooling. The experimental framework systematically evaluated the influence of scanning speed, pulse frequency, and the number of laser passes on dimensional accuracy and material removal efficiency. The results indicate that a maximum diameter reduction of 0.271 mm was achieved at a scanning speed of 3200 mm/s and 50 kHz, whereas 0.195 mm was attained at 6400 mm/s and 200 kHz. A robust second-order polynomial correlation (R² = 0.99) was established between diameter reduction and the number of passes, revealing the high predictability of the process. Crucially, when the scanning speed was doubled, the effective fluence was halved, considerably influencing the ablation characteristics. Despite the low fluence, evidence of material evaporation at elevated frequencies due to the incubation effect underscores the complex photothermal dynamics governing the process. This work constitutes the first comprehensive quantification of pass-dependent diameter modulation in DLBT and introduces a transformative, noncontact micromachining strategy for hard-to-machine alloys. The demonstrated precision, repeatability, and thermal control position DLBT as a promising candidate for next-generation manufacturing of high-performance miniaturized components. Full article