Engineering

Abstract: An Almen strip verifies intensity, but the limits of what it can show are rarely stated. The ±0.0015 in tolerance of SAE J443 tests that a strip repeats its reference reading, not that the intensity is correct. This paper derives, in closed form and by simulation, the smallest change that strip verification can reveal, how long a fault goes undetected, and what tolerance on intensity that supports. For a process at 0.01265 in A, with four strips and a calibrated lot response, charted strips at the most sensitive exposure detect a 9.3% loss of exposure rate and a 4.4% change of intensity nine times in ten in one check (10.3% and 4.8% with the fitting uncertainty of the reference curve). Without lot calibration the intensity limit is 13%, no better than the tolerance. Under a screening rule introduced here, a justified tolerance lies between the smallest half-band that verification can assure and the largest change that the claim can tolerate. Under current practice ±0.002 in lies below the first (±0.0028 in) and above the second (±0.0017 in), so no tolerance can be both verified and protective. Under recommended practice, on one machine, ±0.0015 in lies inside the window. When the J443 test signals a slow drift, in 63% of runs the process has already passed a limit 0.00132 in away. The documents read give no derivation of any tolerance. At the common nozzle replacement limit of 1/16 in the modelled loss of intensity is 0% to 19%: the J443 test signals after the margin has gone, and a chart on four strips signals before. All results are model values for one process, and no prospective test has been run.

Abstract: Generative artificial intelligence (GenAI) is increasingly being explored for construction safety; however, its maturity and practical reliability remain unclear. This study systematically reviews GenAI applications in construction safety and assesses whether existing evidence supports reliable, source-grounded, human-supervised, and deployable applications. The review followed a predefined protocol and PRISMA 2020. Scopus, Web of Science, IEEE Xplore, and Google Scholar were searched in May 2026 for studies published from 2019 to August 2026. After duplicate removal and screening, sixty-five studies were included. Data on GenAI methods, safety applications, validation, deployment, and limitations were extracted and synthesized thematically. Six application areas were identified: safety knowledge retrieval and decision support; incident report analysis and risk prediction; multimodal hazard reasoning; synthetic data generation; worker-centered training, communication and behavior support; and generative optimization, monitoring, and safety control. Several studies provided proof-of-concept evidence using historical datasets, simulations, laboratory experiments, or expert assessments, while evidence of generalizability, field deployment, hazard-exposure reduction, and incident prevention remained limited. GenAI showed potential to support hazard recognition, decision support, and compliance-related safety tasks, but field validation, source grounding, and integration with preventive controls are needed for reliable deployment. A conceptual framework linking GenAI capabilities, and preventive safety controls is proposed.

Abstract: Presliding friction in ball-screw drives produces multivalued force–displacement hysteresis. This study uses a normalized path coordinate u to represent an ordered cycle through the single-valued mappings x(u) and F_eq(u), where F_eq is the motor-equivalent axial force. Four first-order Takagi–Sugeno fuzzy architectures are compared using a 600-point F200, 0.5 Hz experimental loop. Across ten leakage-controlled 70/‌30 t‍r‌a‌in–test par‍titions, SC16‌–TS ac‍hieved the lowest mean test NRMSE among the fuzzy models (0.01054), closely fo‍llowed by ANFIS–TS (0.01073), with n‌o significant difference after multiplicity correct‌ion‍ (p=0.064). Leave-one-complicate-cycle-out validatio‍n‌ yielded mean NRMSEs of 0.0‍1312 and 0.‍01357, respectively. A same-input RBF–SVR benchmark achieved a slightly lower NRMSE of 0.‌01028, whereas the fuzzy models retaine‌d exp‌li‍cit local rule bases. F‍C‍M–TS showed the greatest robustness under strong‍er synthetic training-noise contami‌nati‌on.‍ Phase-aligned transfer from‌ 0.5 t‍o 1.‌0 Hz increased NRMS E to approximately‍ 0.034 a‍nd loop-area error to approximat‌el‌y 25%, demo‍nstrating th‍at the normalized path coordinate alone does not capture frequency-dependent chan‌g‌es‌ in the hysteretic res‌ponse. Overall, normalized-path fuzzy modeli‍ng provi‌d‌es‍ an accurate‍ and i‍nterpre‍table r‍e‍prese‍ntation o‍f ex‍perimental presl‍iding history whil‌e identif‍yi‍ng the need for a‍‍n explicit frequency-aware state for cross-condit‌ion predic‌tion.

Abstract: Wearable sensing technologies have enabled continuous, non-invasive monitoring of physiological signals, accelerating advances in neuromuscular assessment, rehabilitation, and human–machine interaction. Among these technologies, surface electromyography (sEMG) has become a cornerstone for decoding muscle activity. However, the reliability of sEMG remains highly dependent on user–device interaction factors—including skin–electrode impedance, contact pressure, and skin temperature—that introduce signal variability, degrade long-term stability, and limit the generalizability of machine learning models. Despite their importance, these interaction variables are rarely acquired synchronously with sEMG in existing wearable systems, limiting systematic investigation of their influence on signal quality. Here, we present MyoProBand, a compact multimodal forearm wearable that records multichannel sEMG along with skin–electrode impedance, contact pressure, skin temperature, and inertial measurements. By combining neuromuscular, physiological, and mechanical sensing within a synchronized acquisition framework, the platform enables the characterization of the factors governing sEMG reliability during prolonged use. The MyoProBand incorporates custom analog front-end electronics, multimodal sensor conditioning, and embedded signal synchronization while maintaining a lightweight form factor suitable for experimental and translational research. We evaluated the system in healthy participants to assess hardware performance, multimodal signal synchronization, and operational stability during forearm muscle activity. The results show that the sensing modalities can be recorded within the same experimental session while preserving the primary sEMG acquisition and provide initial observations of how interface variables change during use. MyoProBand is intended as a research platform for collecting multimodal datasets that can support later studies of sEMG variability and robust myoelectric control.

Abstract: Background: Stem cell bioprocessing requires timely assessment of cell state and control over variable expansion and differentiation. Automated culture can execute predefined steps, whereas adaptive manufacturing uses observations to guide decisions during an ongoing batch.Objective: This review examines how artificial intelligence and machine learning connect process monitoring to prediction and feedback control, and assesses which links have been demonstrated in stem cell systems.Key Content: This topic covers image-based phenotyping, physical and multimodal sensing, growth and differentiation forecasts, process optimization, hybrid models, and proposed digital twins. A descriptive Level 0–6 continuum distinguishes endpoint assessment, monitoring, state estimation, prediction, operator decision support, within-run feedback, and coordinated workflow autonomy. Reported studies demonstrate image-guided adjustments to differentiation, robotic optimization across experiments, and rule-based feedback within a culture. However, these capabilities do not demonstrate autonomous production of a clinically releasable cell product. Translation is further limited by reduced model performance when entire experiments are withheld from training, fragmented datasets, variation across donors and processes, uncertain links between surrogate measures and potency, and the need for model governance.Conclusion: Supervised adaptation and supervised autonomy are credible near-term targets, characterized by bounded, traceable interventions with human oversight and a defined response to uncertainty. Prospective studies should compare adaptive and fixed processes across independent batches and assess cell identity, relevant function, safety-related attributes, and resource use. Claims of full autonomy require verified performance across the manufacturing workflow.

Abstract: Streamflow projections under climate and land-use change rarely state which results are robust to model uncertainty. This study developed a hybrid QSWAT-ANN workflow with a built-in verification system of four criteria, namely model performance (C1), signal direction (C2), spatial ranking (C3), and reference-series sensitivity (C4), for the Huai Luang River Basin (HLRB) in Northeast Thailand. It used six CMIP6 trajectories (three climate models under SSP2-4.5 and SSP5-8.5) and a single land use pathway to 2070. The corrected model passed C1 with overall NSE of 0.80 and 0.79. Ensemble precipitation increases of 10.5–13.7% were amplified into annual streamflow increases of 32.0–49.9%t, concentrated in the monsoon season, while paddy rice decreased by 55.1% toward cash crops. Within-trajectory Standardized Streamflow Index (SSFI) signals agreed in direction in at least four of six trajectories in all cases (C2 passed); the GCM model, ACCESS-CM2 was the only dissenting trajectory, with an explainable cause. The Drought Hazard Index (DHI) and Flood Hazard Index (FHI) classifications of 31 sub-basins gave rank agreement (Spearman p) of 0.545–0.646 and 0.570–0.811, passing the 0.60 threshold in three of six cases (C3). Screening still identified non-overlapping robust cores of eight (DHI) and ten (FHI) sub-basins at agreement of at least five of six trajectories. C4 confirmed complete rank preservation (p = 1.000), while index magnitudes shifted by typically 1.2–1.5 SD and more than 7 SD in extreme drought months. The workflow identified signal direction, seasonal structure, and upper-tier spatial cores as robust enough for Huai Luang reservoir management and sub-basin drought and flood targeting, whereas absolute index magnitudes should not be used as design values. This framework transfers directly to other monsoon basins.

Abstract: Velocity tracking is a fundamental task in reinforcement learning for quadruped locomotion. Conventional velocity-tracking rewards are typically formulated in terms of the squared error between commanded and actual velocities. In this study, we propose a velocity-tracking reward from the controllability Gramian of center-of-mass (CoM) dynamics, with ground reaction forces (GRFs) as control inputs. The proposed reward dynamically scales the velocity error according to recent contact history. It is defined as a quadratic form of the translational velocity-error vector and the inverse controllability Gramian, thereby embedding CoM controllability through GRFs into the velocity-error metric. We compared policies trained using the proposed reward with those trained using a conventional squared-error-based velocity-tracking reward. When used as the translational velocity-tracking term, the proposed reward reduced the cost of transport (CoT) by approximately 29% and the time-averaged squared vertical velocity by approximately 93.4%. In addition, increasing the weight of the proposed reward tended to shift the learned gait from bound to trot. These results suggest that incorporating CoM controllability into velocity tracking suppresses unnecessary vertical motion and promotes the learning of body states suitable for forward locomotion.

Abstract: A designer who takes credit for shot peening needs a residual stress, not only a depth. This paper builds a candidate screening envelope for the as-peened stress profile from the qualified process-and-witness record (Almen intensity, shot size and media, and process conditions) and the tensile strength, and tests what published data can and cannot support. The strip is read through a moment-equivalent eigenstrain whose bending moment gives the arc height; its magnitude is 1.6–2.6 times a synchrotron measurement, so no physical eigenstrain transfer is claimed. With each laboratory withheld, the peak is predicted to 13.5% (7.6% with one profile of the material) but the complete profile only to 23.5% of peak, and the predicted shape is no better than a median shape. The principal result is therefore the screening construction; the eigenstrain profile model is a conditional interpretation and a hypothesis for experiment. The screening envelope multiplies a cavity-law depth factor, a peak factor and a lower shape envelope. In laboratory-withheld tests it was the only fixed-factor rule tried that stayed conservative; at matched conservatism, a strength-aware depth is essential, and the cavity law and an empirical four-constant power law perform equally. Within normal SAE practice it was empirically conservative on all 36 profiles tested from 12 laboratories (22 development, 13 locked in advance, one unblinded), but with measurement uncertainty it was non-conservative for a soft carbon steel and a stretched aluminium alloy, so its evidence domain is high-strength steels and IN718. It covers about a quarter of the measured compressive area and, used as a mean stress in illustrative fatigue checks, about a third of the amplitude benefit of a measured profile. Twelve measurement-chain conditions show that unstated layer-removal corrections, not reading precision, limit what published profiles support. A frozen-rule prospective test is specified. The P0 construction is a candidate screening envelope that was empirically conservative on the stated test profiles; it is not a statistical lower bound, design allowable or authority-approved structural credit.

Abstract: Stone columns mitigate earthquake-induced liquefaction through three mechanisms: densification, shear-stress redistribution, and radial drainage. The first two are established at installation and are permanent; the third is not. Fines migrate into the column under cyclic hydraulic gradients, permeability falls, drainage resistance rises, and the pore pressure the design was intended to suppress re-accumulates. An improved site therefore migrates from a three-mechanism to a two-mechanism system during its service life, a transition current design practice does not recognize. This paper synthesizes that degradation quantitatively: a structured database of test configurations was extracted from a corpus of 188 records and pooled using a study-clustered random-effects procedure. The pooled bearing capacity ratio is 1.52 and the pooled settlement ratio 0.75, but every contributing configuration was tested statically, so the quantities the literature reports densely are not the quantities seismic design depends upon. That mismatch between what the literature measures densely and what seismic design actually requires is the principal empirical finding of this synthesis. Shaking table evidence shows ordinary columns clogging so rapidly that liquefaction onset is delayed by about one second relative to untreated ground at low base acceleration, after which the columns punch 26 to 43 percent of their length into the deposit; encased and sand-filtered columns settle with the ground by 9 percent and prevent liquefaction at four times that acceleration. Analytical models admitting clogging report post-earthquake settlement increases up to 229 percent and second-event pore-pressure ratios more than 36 percent higher. Against this, every fully coupled numerical framework in current use holds column permeability constant by assumption. The paper formalizes a clogging-induced hydro-mechanical deterioration framework with governing equations, shows the classical filter rule and the seismic drainage requirement to be mutually incompatible, and specifies the falsifiable experiment that would close the gap. Two limitations bound these pooled values and are stated here rather than buried: the bearing capacity ratio rests on three independent studies and the settlement ratio on one, so neither should be read as a stable population estimate, and both derive from static tests and therefore cannot be transferred to seismic drainage durability.

Abstract: Direct formic acid fuel cells (DFAFCs) offer a liquid-fuel alternative to hydrogen-fed proton-exchange membrane fuel cells, but inconsistent designs and operating conditions hinder performance comparison. This review benchmarks experimentally tested single-cell DFAFCs across Pt-, Pd-, Pt–Pd-, and non-noble-metal catalyst systems by peak power density, catalyst loading, durability, and operating conditions. Reported peak power densities range from 20 to 550 mW cm⁻². Pd–Ni₂P/C achieved 550 mW cm⁻², while PtBiPbNiCo reached 321.2 mW cm⁻². FeTSPc-promoted Pt increased peak power density from 76.3 to 126.6 mW cm⁻² and suppressed CO-forming pathways; a Co–NCNT cathode achieved 160.7 mW cm⁻², exceeding the corresponding Pt/C reference. However, inconsistent durability tests and cell configurations prevent reliable cross-study ranking and commercial-readiness assessment. A baseline protocol is proposed, specifying operation at 60 °C with 3 M formic acid, controlled oxidant supply, defined membrane-electrode assembly geometry, liquid-compatible anode diffusion layers, and at least 100 h of durability testing. The protocol is designed to generate interoperable, machine-readable datasets, which are a prerequisite for digital twins, predictive degradation assessment and real-time energy management of DFAFC-based hybrid transport power systems. Standardized full-cell testing can distinguish catalyst improvements from configuration effects and support reproducible DFAFC development.

Abstract: Introduction: Occupational health and safety (OHS) is governed by mandatory national regulations, whereas ISO 45001, the international standard for OHS management systems (OHSMS), is adopted voluntarily; yet the scientific literature on OHSMS remains insufficiently mapped. This study analyzed the scientific output and academic impact of research on OHSMS and ISO 45001 between 2018 and 2026. Method: A descriptive bibliometric study was conducted, adapted from PRISMA 2020 and PRISMA-S. Scopus was searched using ("Occupational Health and Safety Management Systems" AND "ISO 45001") up to 24 August 2026; of 496 records identified, 350 documents were analyzed with Python and Bibliometrix. Results: Articles represented 64.9% of documents and 87.7% were in English. Annual output rose from 16 documents in 2018 to 67 in 2025; Indonesia, Portugal, and the Russian Federation were the most productive countries. Engineering predominated (40.6%), and 70% of documents reported no funding. Management systems and risk assessment were the main thematic axes, while safety culture, certification, and artificial intelligence appeared in the most recent period. Impact was moderate (7.36 citations per document; maximum author h-index = 5 within the corpus); the most cited document received 89 citations, and Safety Science (h-index = 9) was the most influential journal. Collaboration networks were fragmented. Conclusions: Research on OHSMS and ISO 45001 is growing but shows moderate academic impact and weak articulation of international collaboration. Practical Applications: Findings can help researchers and funders prioritize collaborative, funded studies on ISO 45001 implementation and the empirical evaluation of emerging digital and artificial intelligence applications.

Abstract: Polymer composites show complex, nonlinear mechanical behaviour. This makes their rational design hard. Running tests or high-fidelity simulations for every candidate design is slow and costly. Purely data-driven models are fast, but they can break basic mechanics outside the training range. Most physics-informed (PI) models, on the other hand, target a single constitutive law or failure mode, and their loss weights are set by hand. This study presents a DBN-GJO-PI-RNN surrogate that links deep feature learning, physics-constrained learning and failure screening in one workflow. A Deep Belief Network (DBN) learns compact latent features from the material and loading inputs. A PI Recurrent Neural Network (PI-RNN) then predicts the mechanical response under a composite loss with data, constitutive, equilibrium and boundary terms. Golden Jackal Optimization (GJO) tunes the network settings and the three loss weights together. Its fitness function rewards both accuracy and physical consistency. The predicted failure index is then checked against the onset criterion (FI ≥ 1). We tested the framework on a public dataset of 5,000 polymer-composite samples with six response targets. On the test set, it reached an MAE of 1.1132, an RMSE of 1.3962 and an R² of 0.9932. Its RMSE was 38.3% lower than that of the best purely data-driven baseline (TCN) and 50.6% lower than that of a standard RNN. The ablation study showed that each module reduced the error. The framework offers a fast, physics-aware surrogate for screening polymer-composite designs before costly tests or simulations.

Abstract: Circular architecture increasingly treats existing buildings as resources whose value can be prolonged through maintenance, adaptation and successive cycles of use. In historic public buildings, however, material retention must be reconciled with heritage significance, functional change, safety, technological upgrading and future adaptability. This study investigates selective conservation as a framework for making these decisions explicit within adaptive reuse. The framework combines four intervention modes—retain, adapt, integrate and replace—with seven whole-life criteria and a four-level evidence code. It is tested on Buildings 5 and 15 within the regeneration of the former Sant’ Osvaldo Psychiatric Hospital in Udine, Italy, using project documentation as empirical evidence. The application shows that circularity cannot be reduced to maximum material retention: selective replacement and new additions can extend the useful life of retained building resources when they are compatible, maintainable and appropriately documented. The framework therefore reads selective conservation as a decision logic linking treatment of existing resources to their consequences over time, without collapsing heterogeneous design choices into a single circularity score.

Abstract: The increasing use of lithium-ion batteries (LIBs) has increased the need for physical pre-treatment methods capable of recovering electrode materials prior to downstream recycling processes. Mechanical separation can provide an effective initial removal of electrode coatings; however, residual active material may remain attached to the metallic current collectors, limiting the recovery of clean electrode fractions. In this work, a sequential mechanical–ultrasonic approach is investigated for the recovery of electrode materials from spent commercial 18650 lithium-ion battery cells. The proposed approach combines an initial mechanical removal step with short ultrasonic treatment cycles applied to the residual electrode coating. Mechanical activation between ultrasonic cycles was used to promote the detachment of remaining material while limiting prolonged exposure of the metallic current collectors to ultrasonic treatment. Preliminary continuous ultrasonic experiments showed that extended treatment increased degradation of the current collectors without producing a proportional improvement in coating removal, providing the basis for the sequential procedure. The recovered fractions were characterized to evaluate their composition, structural characteristics, and degree of separation from the metallic current collectors. A mass balance accounted for 14.58 g of recovered cathode material, while a 0.28 g difference remained unaccounted for and could not be experimentally assigned to a specific loss mechanism. X-ray diffraction confirmed chemically distinguishable cathode fractions, while energy-dispersive spectroscopy of the ultrasonic-recovered fraction showed a low average aluminum content of 0.21 wt.%. The results demonstrate that short, mechanically assisted ultrasonic treatments can effectively remove residual electrode material while limiting collector deterioration. These findings support the use of ultrasound as an assisting step following mechanical separation, rather than as a standalone delamination process, for the physical recovery of electrode materials from spent lithium-ion batteries.

Abstract: We present a rigorous parameter-free derivation of the scaling exponents for turbulent longitudinal structure functions, based on angular displacement spacetime framework φ(τ) and the physical upper bound of Lagrangian micro-rotation velocity (Ω_FluidMAX): ζp=p/3+p(3−p)/8π²+ max (0, p−6)/4π². For the low-order regime (p≤6), the derived strict quadratic formula reads: ζ_p=p/3+p(3−p)/8π². This formula contains zero adjustable parameters, with the correction term stemming solely from the universal topological constant 1/(4π²) intrinsic to rotational motion. It automatically satisfies the exact Kolmogorov 4/5 law at p=3 and is intrinsic physical consistency p=3, naturally explaining from first principles the ubiquitous experimental observation that “scaling exponents exceed K41 values for p<3 and fall below them for p>3”. Remarkably, it reduces to a form mathematically identical to Kolmogorov-Obukhov (K62) log-normal model, p= p/3 - (μ/18)·p(p−3), with the effective intermittency parameter fixed at μ= 9/4π² ≈0.228. The log-normal formulation is therefore not a competing model, but is subsumed as the p≤6 continuum approximation within the present geometric framework. We further predict that a physical phase transition occurs at p=6, corresponding to the breakdown of the continuum hypothesis. For 7≤p≤13, the scaling exponents deviate from the quadratic law due to the dominance of high-order nonlinear terms. Crucially, this high-order deviation is not a “fitting residual,” but the inevitable consequence of a hard-truncation phase transition (nonlinear breakdown): as the local micro-rotation velocity approaches Ω_FluidMAX , the hard-wall truncation of rotational kinetic energy causes a δ-function accumulation in the probability density at the threshold (angular condensation), thereby exciting a linear additional term ((p−6)/4π²) in the high-order moments. A complete set of zero-parameter predicted values for p=1 to 13 is provided for independent experimental verification—the predictions for ζ₁−ζ₁₁ already agree with the existing experimental/DNS data), whereas no DNS data exist for ζ₁₃—prior to the release of the R_λ≈2500 DNS data. This constitutes a blind test: the predictions are fixed, and the data will provide an independent verdict.

Abstract: This preliminary computational assessment examines an electromechanical carbody tilting concept (Kazakhstan Patent No. 37405): the carbody rotates on bogie-mounted rollers about a roll centre above its centre of gravity, driven by a servo pinion and an arc-shaped rack. A quasi-static model links seven design variables and ten vehicle, track and gear-load parameters, from 1520 mm rules, published data or assumptions, to the model speed limit, gauge clearance, actuator demand and ISO 6336 safety factors. Morris and Sobol' analyses, a two-stage design (NSGA-II layout, reliability-constrained gear sizing), Monte Carlo, drive-failure, wheel-unloading and rack-fastening estimates and a finite element cross-check were performed. In a first-order gauge check, a full-width coach can tilt at most 2.95°. A candidate layout with a 3.00 m carbody and a 2.8 m rack radius reaches a model-limited 130 km/h (conventional 101 km/h), or 116 km/h with a 100 mm lateral gauge allowance. Its conditional gear failure probabilities stay below 1% under the assumed uniform distributions but not under assumed correlations, wider load-factor ranges or model-error factors. After a drive failure the undamped carbody exceeds the gauge; an end stop, damper and brake are required. All speeds are model-limited, not operational limits, and require experimental validation.

Abstract: Traditional seismic excitation sources often perform poorly in complex urban settings. In this study, an innovative portable electromagnetic impact source is introduced. The design and manufacturing principles are detailed, and the performance is verified through comprehensive simulations. Furthermore, field experiments are conducted to assess the device's energy output, frequency range, and imaging accuracy in real-world engineering surveys. Experimental results show that compared with the traditional sledgehammer source, the electromagnetic impact seismic source has stronger excitation energy (the impact kinetic energy is about 1218 J, which is about 5 times that of the 24-pound sledgehammer source), and a wider frequency band (the widest range is 0.1–1200 Hz), which is critical for detection depth and accuracy. The obtained seismic data have a wider frequency band and a higher reflected wave signal-to-noise ratio, which effectively improves the resolution and detection depth of underground anomalies. The spatial distribution of air-raid shelters can be clearly identified based on the transient amplitude profile, which verifies the applicability and reliability of the electromagnetic impact source in seismic engineering surveys and demonstrates its good application prospects in the field of underground space detection. It is especially suitable for accurately detecting caves and air-raid shelters that are prone to collapse in urban road environments.

Abstract: This paper presents a compact coupled-line Marchand balun with symmetric inductive compensation for high-impedance transformation. The proposed circuit transforms a 50-Ω unbalanced input into a 300-Ω differential balanced output for S-band RF applications. The structure consists of two coupled-line sections, an input reactive matching network, and two identical compensation inductors placed symmetrically at the balanced output paths. The input matching network is used to support the impedance transformation at the unbalanced port, while the symmetric inductive compensation is introduced to adjust the effective modal response of the coupled-line paths and improve the output balance. The design is analyzed using even- and odd-mode circuit representation and optimized using ADS circuit-level simulation. A prototype was fabricated and measured, and its performance was compared with that of a conventional coupled-line Marchand balun under the same port-reference condition. At the design frequency of 2.25 GHz, the proposed balun achieved a measured input reflection coefficient of |S₁₁|=−28.05 dB. The measured transmission magnitudes were |S₂₁|=−3.11 dB and |S₃₁|=−3.05 dB, corresponding to an amplitude imbalance of 0.052 dB. The measured output phase difference was 180.52^∘, giving a phase error of 0.52^∘. Compared with the conventional prototype, the proposed balun provides improved input matching, smaller amplitude imbalance, and an output phase response closer to the ideal 180^∘ balanced condition. The measured results indicate that symmetric inductive compensation is a practical approach for improving compact high-impedance coupled-line Marchand baluns.

Abstract: The stability of hollow-section columns remains a central issue in structural engineering because they are widely used in buildings, bridges, industrial frames, and offshore systems. This study investigates the buckling resistance of square hollow section columns (SHS) made of S235, EN 1.4401/1.4404, and EN 1.4462 steels at ambient temperature and under elevated temperatures up to 800°C. A Eurocode-based analytical framework was employed to evaluate elastic buckling, plastic resistance, and buckling resistance for fixed-free members with varying cross-section size, thickness, and length. The results show that stainless steels retain a much larger proportion of their original resistance at elevated temperatures than S235 carbon steel. At 800°C, the mean normalized buckling resistance at elevated temperature to plastic resistance at ambient temperature was 2.56% for S235, 13.59% for EN 1.4401/1.4404, and 8.52% for EN 1.4462. Among the stainless steels studied, EN 1.4401/1.4404 exhibited the best normalized resistance retention at 800°C. The transition between elastic-buckling and plastic resistance dominated regimes was strongly influenced by both temperature and slenderness, with S235 exhibiting non-monotonic behavior due to the competing effects of stiffness degradation and strength loss, while stainless steels showed more gradual and favorable transitions.

Abstract: Traditional wireless sensor network (WSN) localization methods require at least 3 real anchors within the communication range of each node, resulting in extremely low coverage rates under sparse deployment. This paper proposes 2ACG-Loc, a method that uses only 2 real anchors to achieve 100% full-network coverage localization through dual-circle intersection geometric positioning, TDOA residual disambiguation, and hop-by-hop cascaded propagation. Based on Cramér-Rao lower bound (CRLB) theoretical analysis, we prove the bounded error condition for cascaded localization (nr + nv ≥ 5) and derive a closed-form solution for the WLS refinement improvement factor. Experiments show that the disambiguation accuracy reaches 97%–99% under Medium noise, and WLS refinement reduces the coarse localization error from 3.86 m to 1.46 m (62% improvement), achieving a 10-fold accuracy improvement over DV-Hop with 60% less communication overhead.