Validation gaps in Engineering

Representative open questions

Showing 30 of 140 — one per source paper, highest-quality first.

• Basalt powder as a sustainable precursor in alkali‑activated materials: a critical review of performance, mechanisms, and durability (2026) · doi

  Alternative pre-treatment strategies for basalt powder—including mechanical activation, acid leaching, and thermal shock—are mentioned as emerging approaches but lack detailed experimental validation, quantitative comparison of their relative efficacy, and assessment of their impact on the amorphous content and subsequent geopolymerization kinetics.

• Sophisticated control design for direct drive permanent magnet synchronous generator-based wind turbines under voltage sags (2026) · doi

  The paper relaxed MPPT strategies and protection systems to demonstrate controller robustness under voltage sags, but does not investigate how the optimized PMSG-based wind turbine controller performs when these critical subsystems are active during DC link voltage dips exceeding 50% of nominal value.

• A novel deep learning approach for accurate and efficient design of LNOI power splitters (2026) · doi

  The DNN-based inverse design framework constrains geometric parameters within LNOI fabrication tolerance ranges, but the paper does not specify how these constraint boundaries were determined or validated against actual LNOI etching and thin-film deposition process capabilities from specific foundries.

• Experimental evaluation of bond performance between substrate and overlay concrete using bonding agents and mechanical connectors (2026) · doi

  The paper reveals that uneven adhesive application or insufficient drying of the SBR-200 layer may impede mechanical interlock under slant shear conditions, yet no experimental protocol is established to quantify the minimum drying time requirements or acceptable adhesive uniformity tolerances for hybrid bonding systems.

• Metal repair using hybrid additive manufacturing process: A comparative study of interfacial surface roughness for improved mechanical strength (2026) · doi

  The study observed that interface roughening improved yield strength by 36.36% and UTS by 64.23% in one metal system, but reduced ductility in the dissimilar metal system (ASTM A36-SS316L) with only 25.06% elongation versus 41.16% in substrate. The trade-off mechanism between strength and ductility across different metal pairs requires investigation with additional dissimilar metal combinations beyond the two tested systems.

• A Review on Engineering Approaches to Reverse Osmosis Brine Management: Disposal, Volume Reduction and Emerging Resource Recovery (2026) · doi

  Pretreatment and fouling-resistant membrane material innovations for hypersaline brine treatment require validation data to establish conservative operating envelopes for multistage membrane-based concentration and thermal hybrid processes. Current material screening lacks standardized test protocols for high-salinity, high-fouling-potential brine conditions.

• Advancement in fusion welded aluminium alloy joints by friction stir processing technique: a critical review (2026) · doi

  Advanced tool geometries including scroll, triflute, stepped, and variable-profile pins have been proposed theoretically but lack comprehensive comparative experimental validation across different aluminium alloy systems to quantify their effectiveness in eliminating subsurface defects and controlling material flow during FSP of fusion-welded joints.

• Advances of artificial intelligence applications to low-carbon metallurgy of iron and steel (2026) · doi

  Deep learning frameworks for slab transverse crack prediction in continuous casting have been developed using LSTM-FCN architectures, but the generalization of these multivariate models across different casting conditions, steel grades, and industrial facilities with varying data distributions remains unexplored.

• Revisiting the Modification Strategies of Alloy-Base Anode for Solid-State Lithium-Ion Batteries Through Deconstructing Anode-Interface-Solid Electrolyte (2026) · doi

  The interfacial compatibility between Si@MOF anode and PPG electrolyte was demonstrated only at 60°C operating temperature; the thermal stability and interfacial contact maintenance of this system at elevated temperatures (80-100°C) and cryogenic conditions have not been evaluated for solid-state lithium-ion battery applications.

• Design Optimization of an Additively Manufactured Passive Vibration Isolator for an Inertial Measurement Unit for Enhanced Measurement Performance (2026) · doi

  The viscoelastic material damping behavior is currently modeled using a master curve constructed at a reference temperature of 25°C and extrapolated to 15°C and 35°C using the WLF function; however, experimental validation of the WLF-predicted mechanical properties (storage modulus E′ and loss modulus E″) of TPU85A elastomer at these extreme temperatures is not presented.

• Physics-Informed Symbolic Regression Ensemble (PISRE) for surface roughness prediction in Ti-6Al-4V dry turning (2026) · doi

  PISRE-NF was developed and validated exclusively on Ti-6Al-4V dry turning with a 19-sample CCD design; generalization to other titanium alloys (e.g., Ti-5Al-5V-5Fe-3Cr), different cutting fluids (wet/flood cooling), or alternative tool materials and geometries remains undemonstrated.

• Wind Tunnel Testing for Wind Energy: A State-of-the-Art Review (2026) · doi

  Wind tunnel wall corrections and viscous endwall effects have significant influence on separated flows in wind turbine testing facilities, but most correction methods have not been adequately validated for three-dimensional separated flow conditions near airfoil-wall junctions. Digital twin CFD simulations of wind tunnel facilities should be systematically developed and validated to predict mounting interference effects before actual wind turbine rotor tests.

• Multifunctional zinc-ion capacitors for energy storage (2026) · doi

  Long-term cycling stability of multifunctional zinc-ion capacitors under operating conditions shows only several hundred cycles achieved in working state, far below practical application requirements. The degradation mechanisms under operating conditions remain underexplored and must be systematically characterized through extended cycling studies.

• Functional nanocomposites for energy storage: chemistry and new horizons (2020) · doi

  Soft percolation in BTO nanoparticle networks causes breakdown strength reduction through ineffective surface modification and ionizable site passivation at 10-20% volume fraction, but the quantitative relationship between phosphonate layer coverage and percolation threshold has not been established.

• Automatic Car Parking System by using ESP 32 (2026) · doi

  The ESP32-based automatic car parking system uses ultrasonic sensors for vehicle detection, but the paper does not specify the sensitivity threshold or response time validation under varying environmental conditions (e.g., rain, fog, extreme temperatures) that would affect Time of Flight distance calculations in real-world parking facilities.

• Revolutionizing infection control in ICUs: photocatalytic binder materials with platinum nanoparticles (2026) · doi

  The platinum nanoparticle binder materials have been tested against only two viral pathogens (Influenza A and Feline Calicivirus); efficacy against clinically relevant drug-resistant bacterial species including MRSA, CRE, and VRE must be systematically evaluated to establish broad-spectrum antimicrobial potential in ICU settings.

• Telekit: a bilateral, teleoperated platform for hands-on learning (2026) · doi

  The spur gear system in the Telekit introduces backlash and reduced smoothness due to manufacturing tolerances, contributing to oscillations during contact experiments. The paper identifies that higher-precision machined gears and helical or herringbone gear implementations could reduce backlash, but these specific mechanical design alternatives have not been experimentally evaluated in the teleoperation platform.

• Piezoelectric stepped-plate resonators vibrating at lateral modes for direct viscosity determination in liquids (2026) · doi

  The current measurement range of the AlN piezoelectric resonator is limited to 0.3–4.5 mPa·s. To extend the sensor's applicability to highly viscous liquids, the paper identifies advanced piezoelectric materials (potassium sodium niobate KNN films and scandium-substituted AlN ScAlN films) as promising alternatives but provides no experimental validation of these materials in the laterally vibrating stepped-plate resonator geometry.

• Data-Driven Approaches to Reliability Modeling in Critical Energy Infrastructure: Analytical Perspectives on Early Failure Detection (2026) · doi

  Models trained on single-infrastructure datasets (e.g., wind turbine vibration monitoring) demonstrate poor transferability to heterogeneous resources and operating conditions; no systematic cross-domain validation or transfer learning framework has been established for multi-infrastructure energy reliability modeling despite emerging domain adaptation attempts.

• A review of additive manufacturing techniques for wind turbine blade production: capabilities, AI integration, and Scale-Up Potential (2026) · doi

  Multimodal sensing systems for AM process monitoring show approximately 22% relative improvement over single-sensor approaches in specific experimental setups, but unified validation protocols comparing multimodal versus single-sensor configurations across different AM techniques and defect types remain undeveloped.

• PF-Bearing Analyzer: algorithmic implementation of the peak factor method for diagnosing and predicting the technical condition of rolling bearings (2026) · doi

  The threshold model defines discrete peak factor ranges (Normal: 3.0, Initial wear: 5.0, Moderate defect: 8.0, Critical defect: 10.0) validated only on outer race defects with varying severity; the paper lacks experimental validation of these thresholds for inner race defects, rolling element defects, and lubrication failures in the same bearing equipment.

• Performance Evaluation of Electric Vehicles Using PSO and AHA Based Optimal Control Methodology (2026) · doi

  The AHA-based optimal control methodology was evaluated only on three discrete Artemis drive cycles (urban, rural, and motorway 150 kmph); validation across additional real-world driving conditions such as mixed urban-highway routes, aggressive acceleration patterns, and extreme temperature environments is absent.

• Elastic Property Anisotropy in Inconel 718 Alloy Specimens Fabricated by Wire Arc Additive Manufacturing (2026) · doi

  The study establishes a correlation between pole density distribution (along [001]–[111] crystallographic diagonal) and elastic anisotropy in WAAM-fabricated Inconel 718, but does not experimentally validate this predictive methodology across different deposition parameters, layer heights, or wire feed rates that could alter crystallographic texture development.

• Modelling the effect of the water evaporation rate on total shrinkage of blended cement concrete (2026) · doi

  The shrinkage model was calibrated exclusively using concretes with compressive strengths between 30-70 MPa incorporating fly ash and slag as supplementary cementitious materials with basalt aggregates. The model's applicability to alternative binder chemistries such as limestone calcined clay cement and high-alumina cement, different aggregate types, and concretes containing shrinkage-reducing agents has not been experimentally verified.

• Intelligent performance prediction of nanoparticle-enhanced automotive radiator cooling using CFD and machine learning (2026) · doi

  The paper reports a 5% average deviation between CFD-predicted and experimentally measured outlet temperatures but attributes this solely to steady-state assumptions and heat losses. The specific quantitative contribution of each neglected physical phenomenon (wind speed effects, radiation losses, conduction losses, convection losses) to the CFD-experimental discrepancy has not been decomposed through sensitivity analysis.

• Statistical fault analysis of Ascon: multiple distinguishers and impossible-state exploitation (2026) · doi

  The proposed statistical fault analysis methods for Ascon are primarily validated through software simulations; experimental validation on actual Ascon implementations running on constrained devices (microcontrollers, FPGAs) with precise S-box-level fault injection using voltage glitch generators or multi-spot lasers remains absent.

• Nuclear Reactor Chemistry (2017) · doi

  The retardation factor model (R ≈ 1 + 10Kd) for predicting radionuclide transport in geologic media has been validated primarily through theoretical calculations and limited site-specific data. Experimental validation of this retardation factor across different geologic host media (bedded salt, granite, basalt, welded volcanic tuff) under varying groundwater chemistry conditions and temperature regimes relevant to deep repository environments is needed to confirm its applicability.

• Translational dynamics of bridled kites: a reduced-order model in the course reference frame (2026) · doi

  Dynamic deviations from quasi-steady predictions become pronounced at higher wing loadings (rigid-wing cases show λLoyd ≈ −1 s⁻¹ versus soft kites at −4 to −5 s⁻¹), but the specific threshold wing loading at which quasi-steady assumptions fail for bridled kites in crosswind flight has not been quantified.

• AI-driven adaptive vibration control in smart plate systems: a sustainable approach for next-generation sports engineering (2026) · doi

  The study demonstrates that voltage control effectiveness varies significantly with width-to-height ratios in CA-UHPC smart plate systems, but does not provide empirical validation of optimal voltage adjustment strategies for momentary voltage conditions in actual sports engineering applications where rapid adaptability is required.

• Electron transfer mechanism in microbial fuel cells (2026) · doi

  The cathodic oxygen reduction reaction (ORR) kinetics remain poorly characterized due to high overpotential limitations; development and comparative evaluation of non-noble metal catalysts as alternatives to platinum must be systematically tested to reduce MFC system costs while maintaining electron transfer efficiency.