Search Results (5,864)

Conventional inverse synthetic aperture radar (ISAR) imaging techniques can produce high-resolution imagery from complete observation data. However, in practical scenarios, incomplete data caused by undersampling or missing data often leads to defocused results with traditional methods. While compressive sensing or low-rank reconstruction approaches have been proposed to address this challenge, existing techniques frequently fail to fully exploit both the sparsity and low-rank properties inherent in ISAR scenes. Moreover, they typically rely on convex approximations that introduce estimation bias, weaken sparsity promotion, and increase computational complexity, ultimately degrading imaging performance. To overcome these limitations, this work presents an enhanced sparse ISAR imaging method that jointly enforces non-convex sparsity and low-rank constraints for incomplete data recovery. The imaging model incorporates both inherent sparsity priors and a low-rank constraint. The resulting non-convex optimization problem is solved via an efficient iterative algorithm based on the alternating direction method of multipliers, where the sparse component is reconstructed using an iterative reweighted scheme with a regularizer and the low-rank component is recovered through truncated singular value decomposition. Experimental results on both simulated and measured data demonstrate the efficacy and superior performance of the proposed method. Full article

Polarization-encoded detector multiplexing has recently shown promise for compact wide-field infrared imaging, where multiple field-of-view (FOV) regions are mapped onto a shared detector area and distinguished through Stokes-vector decoding. The practical implementation of this architecture, however, requires reflective folding components for optical path compression and detector reuse. Oblique metallic reflection introduces unequal amplitude attenuation and phase retardation between the p- and s-polarized components, which can deform the designed polarization code before it reaches the polarization-resolved detector. This work establishes a coordinate-consistent Jones–Mueller model for eight peripheral reflections from the internal octagonal mirror and one central direct path. The model distinguishes deterministic polarization-state transport from true depolarization and compares detector-side calibration, encoder pre-compensation, one shared liquid-crystal polarization retarder (LCPR), and a segmented-LCPR upper bound. Using a unified aluminum model at 4.0 um, the mirror displaces the encoded states by several degrees but does not depolarize a fully polarized monochromatic ray. Across 60 Monte Carlo trials with 2000 samples per channel, all principal methods remain approximately 100% accurate at an additive Gaussian-noise standard deviation of σ = 0.02, normalized relative to unit S₀. At σ = 0.15, the ideal-codebook, calibrated-codebook, and pre-compensated decoders achieve 90.87%, 91.24%, and 89.87%, respectively. A shared LCPR provides little global benefit, whereas segmented settings recover individual states at the cost of channel-resolved hardware. The results show that mirror-aware calibration, code-space separation, and physically implementable compensation must be considered jointly. Full article

The hot deformation behavior and microstructure evolution of a novel near-α Ti65 titanium alloy with an initial lamellar microstructure were investigated by isothermal compression. Compression tests were conducted at 950–1010 °C in the α + β phase region and 1050–1110 °C in the β phase region, with strain rates of 0.01–10 s⁻¹ and deformation amounts of 30–75%. The flow behavior, strain-compensated Arrhenius constitutive model, processing map and microstructural evolution were systematically analyzed. The results indicate that the flow stress decreases with increasing temperature and decreasing strain rate, while flow softening is more pronounced in the α + β region than in the β region. The apparent activation energies are 1050.27 kJ/mol for the α + β region and 203.51 kJ/mol for the β region, indicating distinct deformation mechanisms. The established constitutive models exhibit high prediction accuracy, with R and AARE values of 0.98 and 5.97% in the α + β region and 0.99 and 4.29% in the β region, respectively. Processing-map analysis identifies two instability domains at high strain rates: 990–1020 °C/3.5–10 s⁻¹ in the upper α + β region and 1060–1110 °C/1.65–10 s⁻¹ in the β region. Microstructural observations reveal that dynamic spheroidization of lamellar α dominates deformation in the α + β region, whereas dynamic recovery accompanied by limited β dynamic recrystallization occurs in the β region. Increasing deformation amount at 980 °C and 0.01 s⁻¹ promotes α-lamella fragmentation, spheroidization, grain refinement and texture weakening. The maximum pole density decreases to 6.23 mrd at a high deformation amount. By directly correlating strain-dependent processing-map characteristics with quantitative microstructural and crystallographic evolution, this work provides a microstructure-based basis for optimizing the hot-working window of Ti65 alloy with an initial lamellar microstructure. Full article

Novel steel composite metal foams (CMFs) are lightweight materials made from stainless-steel hollow spheres, with entrapped air suspended within the stainless-steel matrix. In this work, the performance of CMF-core front rails, containing steel CMF within an aluminum 6061 alloy double tube, is compared against rectangular high-strength low-alloy (HSLA) 350 steel and double-octagon aluminum 6061 alloy front rails of equivalent masses and lengths. Explicit finite element models of different front rails are subjected to frontal impact with entrapped air within the CMF core modeled using the pneumatic fluid cavity technique. The inclusion of a steel CMF-core within the double-tube structure results in plateauing vehicle deceleration instead of pulsating behavior observed during the buckling of tube-only structures. CMFs containing pressurized air and core–tube interactions enhance the compressive resistance of front rails to prevent localized bucking. The CMF-core front rail increases the accident velocity required to exceed the critical accident severity and head injury criterion (HIC) by 33.73% and 39.50%, respectively, when compared to an equivalent double-octagon front rail and by 31.93% and 48.24%, respectively, when compared to an equivalent rectangular front rail. The research demonstrates that utilizing novel energy-absorbing steel CMFs within automotive front rail structures helps improve occupant safety for crashworthiness applications. Full article

This article provides a detailed analysis of ballasted and ballastless railway subgrade structures. The advantages and disadvantages of each structure are identified, and a solution is given for the use of an alternative option—application of sub-ballast with Hot-Mix Asphalt (HMA). The purpose of this study is to determine the strength and deformability parameters of the reinforced subgrade based on the results of numerical simulation of the stress–strain state. Based on the real parameters of the subgrade, a finite element model with sub-ballast is created. It is determined that the maximum value of the vertical displacement of the structure without sub-ballast is 12.5% greater than that of the option with sub-ballast. It is found that the sub-ballast blocks the ingress of a more stressed field into the subgrade and redistributes the vertical stresses. Accordingly, the obtained maximum stress in the middle of the sub-ballast does not cause even local failure in it. Experimental studies of HMA specimens under uniaxial compression conditions were conducted. The experimental results confirm the results of numerical simulation of the subgrade and prove that HMA in the sub-ballast clearly works in the elastic stage, effectively reducing the stresses (in percentage terms, 38.8 … 72.3%). Full article

Silicon photomultipliers (SiPMs) are widely used in high-energy physics, medical imaging, and other photon-counting applications. While their nonlinear response at high light intensities is well known, its impact on the statistical fluctuations of the detector output remains much less understood. In this work, we develop an analytical framework for the variance of the charge response of passive-quenching SiPMs in the two limiting cases of instantaneous light pulses and pulses much longer than the pixel recovery time. Based on these exact results, we propose a phenomenological model that describes the variance of the SiPM charge response for arbitrary pulse durations while accounting for pixel recovery and correlated noise. The resulting framework is then used to predict the photon-counting resolution over the full dynamic range of the detector. The model is validated through Monte Carlo simulations and experimental measurements performed with laser, LED, and scintillation light sources. The results show that the optimal photon-counting resolution is generally reached well beyond the onset of nonlinear response, since pixel saturation introduces sub-Poissonian fluctuations that partially compensate for the nonlinear compression of the SiPM response. These findings provide a practical framework for predicting photon-counting resolution and optimizing the operation of passive SiPMs over a wide dynamic range. Full article

Grouted anchors made of glass fiber-reinforced polymer (GFRP) have gained popularity in cold-region construction projects, primarily owing to their resistance to corrosion and low density. Although prior research has addressed the bond–slip characteristics of FRP-to-concrete joints, a theoretical formulation that links cumulative freeze–thaw damage of the mortar matrix to the progressive loss of bond strength at the GFRP bar–mortar interface is still lacking. This work provides a combined experimental and theoretical examination of how the bonding capacity of ribbed GFRP bars in cement mortar declines after 0, 30, 60, and 90 FTCs. Compression and splitting tension tests were carried out on mortar cubes, while pullout specimens were used to assess the interfacial bond strength. Two mortar grades commonly used in anchorage practice (M25 and M35) and two bar diameters (12 mm and 16 mm) were selected as test variables. After 90 FTCs, the maximum bond strength fell by as much as 64.1%, whereas the post-peak residual bond strength suffered an even more pronounced drop of up to 79.3%. Meanwhile, the residual-to-peak-bond-strength ratio decreased steadily with the number of FTCs, marking a shift from a mechanically interlocked interface to a friction-governed one. The higher-grade mortar (M35) experienced clearly superior resistance to freeze–thaw attack compared to M25, while the larger-diameter bars (16 mm) degraded faster. An analytical model for estimating the bond-strength degradation is proposed, where an exponential environmental factor was introduced and the decay constants were calibrated via nonlinear regression against the bond-strength retention ratios at 0, 30, 60, and 90 FTCs. The proposed models are calibrated empirical relationships that reproduce the measured degradation well within the tested parameter ranges and indicate reasonable internal stability under leave-one-group-out cross-validation. This study provides two theoretical provisions: the freeze–thaw degradation of the GFRP–mortar bond can be effectively described by a single exponential damage law whose decay constant quantifies the rate at which the interfacial capacity is exhausted, and the residual-to-peak-bond-strength ratio serves as a mechanistic indicator of the transition from mechanical interlock to friction-controlled failure. These provisions quantitatively link mortar degradation to interfacial capacity loss, thereby providing a theoretical basis for durability design of GFRP grouted anchors in cold regions. Full article

Green hydrogen production through water electrolysis is a key pathway to the decarbonization of future energy systems. However, part of the electrical input is transformed into waste heat. In this study, alkaline, proton-exchange membrane, anion-exchange membrane, and solid oxide electrolysis systems are compared in terms of operating temperature, heat generation, heat transfer medium, and integration constraints. Reported COP values for commercial high-temperature vapour-compression heat pumps range from 2.4 to 5.8, depending on operating conditions. The heat-pump technologies reviewed include vapour-compression systems with single-stage, multistage, cascade, and transcritical configurations, together with absorption and adsorption systems, with a focus on suitable working fluids and practical limitations. The review distinguishes between direct heat recovery and heat recovery assisted by heat pumps, and it identifies two main areas of application: external supply for district heating, industrial consumers, and energy communities; and internal support for feedwater preheating, water cycle integration, and steam generation. A selection framework is proposed in which source- and sink-temperature compatibility determines thermodynamic feasibility, COP characterizes heat-pump performance, and LCoH supports techno-economic comparison. Direct heat recovery should be preferred when temperatures are compatible, while heat pumps can operate as enabling technologies when temperature upgrading is required and system-level economic and environmental performance remains advantageous. Full article

Complex patient-specific bone defects remain difficult to reconstruct because the regenerative capacity of bone is limited and prefabricated implants cannot readily match defect geometry. In this work, methylcellulose-gelatin-hydroxyapatite (MC/GEL/HA) inks were formulated with varying methylcellulose content and hydroxyapatite incorporation, crosslinked with EDC/NHS, and 3D-printed into porous scaffolds with defined square-pore architectures. Inks were evaluated by oscillatory and steady-shear rheology, and printed scaffolds were characterized for morphology, chemical composition, mechanical performance, physicochemical stability, wettability, apatite-forming bioactivity, and osteogenic responses of human bone marrow mesenchymal stem cells. Methylcellulose content primarily governed ink rheology and printability, and increased compressive strength (up to ~0.38 MPa for 15MC/10GEL/30HA), whereas hydroxyapatite enhanced surface hydrophilicity, promoted apatite nucleation within 7 days in simulated body fluid, and markedly increased alkaline phosphatase activity (>10-fold over HA-free scaffolds), mineralization (~2-fold by Alizarin Red), and the highest osteocalcin expression among the HA-containing formulations (~2.45-fold at day 14). The 15MC/10GEL/30HA formulation showed the most favorable balance of printability, mechanical performance, and osteogenic performance. These complementary functions reconciled structural stability with osteogenic performance, supporting the MC/GEL/HA system as a tunable bioink platform for non-weight-bearing bone regeneration, while warranting further in vivo validation. Full article

For hydrogen refueling stations, metal hydride compressors offer a safe and efficient alternative to mechanical systems. This work systematically investigates Ti_0.94Zr_0.08Cr_1.0Mn_0.6−xFe_0.4+x (x = 0, 0.1, 0.2, 0.3, 0.4) alloys for primary hydrogen compression targeting 25 MPa. All alloys crystallize as a single C14 Laves phase, with Fe substitution causing negligible lattice changes but leading to linearly increased particle size due to solid-solution strengthening. In the testing temperature range of −80 to −50 °C, the hydrogen storage capacity decreases with increasing Fe, whereas the effective desorption capacity improves. Pressure–composition isotherms exhibit single plateaus with elevated plateau pressures at higher Fe/Mn ratios. In the range of x = 0–0.4, the enthalpy of desorption decreases in magnitude with Fe content. Using Van’t Hoff extrapolations to 30 °C absorption and 80 °C desorption, the compression factor shows a non-monotonic trend, reaching a maximum of 1.99 at x = 0.2. This composition provides nearly a two-fold pressure boost, demonstrating promise for low-grade heat driven hydrogen compression in refueling infrastructure. Full article

Municipal solid waste incineration fly ash (MSWIFA) poses environmental risks due to high chloride and heavy metal contents. This study solidified MSWIFA via geopolymerization with coal fly ash (CFA), using low-temperature calcination and water washing to remove dioxins and chlorides, respectively. All formulations effectively immobilized heavy metals below regulatory limits. Increasing addition of calcined-washed fly ash (CWFA) from 0% to 25% reduced the 28 d compressive strength from 32.5 MPa to 4.8 MPa and fluidity from 185 mm to 128 mm, while increasing the content and modulus of alkali activator both enhanced these properties. The incorporation of moderate Ca(OH)₂ promoted the substitution of Na⁺ by Ca²⁺ within the gel framework under the combined action of the alkaline activator, thereby favoring the formation of gel network. When the dosage of Ca(OH)₂ increased to 7.5%, the 28 d compressive strength increased from 45.75 MPa to 53.33 MPa. However, excessive Ca(OH)₂ resulted in more unreacted residues and accelerated carbonation, which occupied active sites and disrupted gel continuity, leading to a slight decrease in strength to 49.85 MPa. This work provided a viable pathway for the utilization of MSWIFA into geopolymer, especially for optimizing Ca regulation to modify compressive strength, fluidity, and heavy metals toxicity. Full article

This article reconsiders Pjetër Budi’s Christian Doctrine as a formative work of early Albanian literature in which biblical reception, vernacular writing, and communal address become mutually constitutive. Rather than treating Budi’s poetry as a derivative versification of Scripture or as a document whose religious purpose excludes literary analysis, the article argues that biblical material is transformed through poetic re-creation in Albanian. Budi receives Scripture as a narrative sequence, moral pattern, image, voice, and rhetorical authority. His retellings of the Fall, Cain and Abel, the Flood, the Passion, and Resurrection preserve recognizable biblical structures while changing their mode of address through rhythm, compression, repetition, dramatic speech, and collective exhortation. The article further argues that vernacularization is itself a literary event. Budi’s insistence that prayer must be understood in the language of the community, together with his invocation for divine illumination so that he may sing a “new song” in Albanian, makes language part of the work’s theology and poetics. Scripture thus becomes more than a source behind the poems: it becomes a medium through which Albanian acquires spiritual, poetic, and public authority. Budi’s work offers a significant case for biblical literary studies because it shows how a small vernacular literary culture with limited institutional infrastructure can convert inherited sacred forms into an instrument of literary formation and communal self-recognition. Note on translations: Unless otherwise indicated, English translations of quotations from Albanian sources are the author’s. Full article

Off-grid agricultural cold chains suffer from high energy conversion losses due to intermediate electrical stages in traditional refrigeration. This study addresses the lack of empirical quantification by comparing Direct Mechanical Drive (DMD) and Electrical Power Generation (EPG) drive trains for an R-134a vapor compression refrigeration system. Under steady-state conditions (randomized block design), DMD achieved a statistically significant 13.89% reduction in biomass consumption over EPG (1840.0 vs. 2136.7 g/h; p < 0.001). The biomass consumption was evaluated based on the measured charcoal mass flow under the same lower heating value basis. Conversely, refrigeration COP was statistically equivalent (2.74 vs. 2.73; p = 0.815), confirming that drive-train architecture does not alter internal vapor compression thermodynamics. Only 19.6% of the compressor shaft power appeared as useful fluid-side compression work under this fractional-load operating condition, a volumetric rather than mechanical deficiency arising from operation at 7.7–15.5% of the compressor’s rated capacity. Referenced consistently to the primary biomass chemical energy input, the First-Law biomass-to-cooling system efficiency was 3.66% (equivalent to 5.34% when referenced to the syngas delivered to the engine), with a corresponding biomass-referenced exergy efficiency of 0.44%. Component exergy analysis revealed that the internal combustion engine (59.13% of total exergy destruction, ε = 13.1%) and the gasifier (32.4%, ε = 67.7%) dominated total system exergy destruction (15.49 kW). Furthermore, a 10-year life-cycle cost (LCC) analysis indicates DMD-Syngas yields net present value savings of 21,071.57 USD over gasoline-EPG, yielding a 0.14-year (~50-day) simple payback period on the 400.12 USD net incremental hardware capital cost (the gasification subsystem less the alternator–motor drive train that the direct-drive configuration does not require, and excluding one-time installation and training costs). When the fully installed cost is accounted for—including site preparation, process-water supply and effluent handling, low-voltage provision, installation labor, operator training and contingency—the incremental investment rises to 1298–2405 USD and the payback period extends to approximately 162–301 days. Under the least favorable combination examined, in which commercially purchased charcoal is imposed simultaneously with the upper installed-cost bound, capital recovery extends to approximately 1.4 years; the base case nevertheless recovers the incremental investment within the first operating year. An operational-phase (gate-to-gate) carbon assessment indicates near parity with the gasoline baseline on a strictly attributional basis (+120 to +1200 kg CO₂e yr⁻¹); a net saving of 8880–13,320 kg CO₂e yr⁻¹ arises only under the consequential scenario in which open-field burning of orchard residues is displaced and is further contingent on including black carbon in the accounting basket. This is not a full ISO 14040/44 life-cycle assessment, and the environmental outcome is therefore scenario-dependent rather than intrinsic to fuel substitution. These results demonstrate that mechanical drive-train optimization substantially enhances fuel economy without compromising refrigeration performance, providing a rigorous evidence base for scalable biomass-powered off-grid cold chains. Full article

In the industrial edge-to-cloud continuum, data is often privacy-sensitive and spans multiple organizations that do not fully trust one another, making central aggregation of raw data undesirable and often non-compliant with regulations such as the General Data Protection Regulation (GDPR). Federated Learning (FL) addresses this by sharing model updates rather than raw data, but conventional FL assumes a central coordinator, leaving it exposed to poisoning and inference attacks and to a single point of trust and failure. Decentralized Federated Learning (DFL) couples FL with Distributed Ledger Technologies (DLTs), removing the coordinator and enabling verifiable aggregation in trustless, cross-organizational environments. In this work, we assess the applicability of DFL to on-device spoken-command recognition—a representative edge audio task underpinning voice-driven industrial interfaces—by comparing decentralized and centralized training under idealized and adversarial conditions. Using a Convolutional Neural Network (CNN) replicated across edge nodes, we evaluate resilience to inter-node data imbalance, to poisoning attacks, and to a privacy-preserving noise-injection defense against inference attacks, together with model compression for resource-constrained edge devices. The system pairs this comparison with a validation-based poisoning defense in which each node scores its peers’ updates on its own held-out data, and an update is aggregated only if a majority of nodes report a weighted F1-score above a threshold—requiring neither a shared validation set nor a trusted validator. Our results indicate that the DFL system achieves accuracy comparable to centralized baselines in most scenarios (weighted F1-score 0.762 across nine nodes, against 0.896 centralized), and that a cross-node validation mechanism reliably excludes poisoned updates as long as fewer than half of the nodes are compromised (within 3.54% of the unpoisoned model). Noise-based inference defenses reduce accuracy substantially (44.7% on average at a noise standard deviation of 1.0), exposing a sharp privacy–utility trade-off, whereas model compression preserves performance (0.765 against 0.762 for pruning and format conversion, with 8-bit quantization costing up to a further 13.3%). These findings clarify both the promise and the current limitations of decentralized, privacy-preserving learning for the industrial edge-to-cloud continuum. Full article

Synthesizing realistic radio-frequency signals is important for data augmentation in wireless systems, yet labeled in-phase/quadrature (I/Q) measurements are expensive to collect, and diffusion models typically demand large per-class training sets. This paper studies whether a diffusion model trained on one modulation scheme can be transferred to unseen schemes with minimal data and a minimal parameter budget. We formulate the adaptation as a minimal-cardinality parameter-increment problem and adapt a conditional diffusion transformer, pretrained on QPSK signals from the RML2018.01a corpus, to three target modulations (OQPSK, 16PSK, and 32QAM) through low-rank adaptation (LoRA) of its attention projections under a composite objective that couples waveform reconstruction with spectral and autocorrelation constraints, updating only 0.496% of the 9.9-million-parameter backbone. With only 50 target signals, the adapted models attain a periodogram cosine similarity of 0.985 against 0.705 for from-scratch training and match from-scratch models given 1000 signals: a twenty-fold gain in sample efficiency. The transferred models also match or exceed reference target experts trained on up to 333 times more target data on every spectral and autocorrelation metric. Ablations on two target schemes show that sources with dense phase manifolds transfer best irrespective of family labels and that the generation quality is insensitive to the LoRA rank between 1 and 16, pointing to a low-dimensional adaptation subspace. Downstream classifier experiments confirm that the synthetic signals help few-shot modulation classification, and they also bound the claim: conventional label-preserving transforms remain stronger at very small sample sizes, downstream utility does not track spectral fidelity, and the generated signals under-represent the noise floor in the low-SNR regime. The main study uses RML2018.01a; a cross-corpus check on the independently generated Sig53 corpus reproduces the transfer advantage with compressed margins, and validation on over-the-air recordings remains future work. Full article