Validation gaps in Engineering

Representative open questions

Showing 30 of 108 — one per source paper, highest-quality first.

• Friction Stir Welding of Dissimilar Materials: A Comprehensive Study on Joining Stainless Steel to Ni, Ti, and NiTi Alloys (2026) · doi

  The critical reaction layer thickness threshold of approximately 1 μm for brittle intermetallic suppression (FeTi and Fe2Ti) in SS-Ti and SS-NiTi dissimilar FSW has only been established for thin-gauge configurations up to 3 mm under monotonic loading; validation of this threshold across thicker sections (6+ mm) and under cyclic/dynamic loading conditions is absent.

• 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.

• Electrically switchable continuous phase liquid crystal Fresnel zone plate (2026) · doi

  The rise time of the electrically switchable liquid crystal Fresnel zone plate is limited to 6.734 s due to the hybrid aligned nematic (HAN) configuration and 20 µm LC layer thickness. The authors propose laser writing at 0 Vpp to eliminate HAN formation and achieve conventional planar alignment, but have not yet experimentally validated whether active temperature control during fabrication (using a cooling stage) can sufficiently stabilize the LC director and suppress thermally driven pattern blurring to enable faster electro-optic response.

• 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.

• 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.

• 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.

• Mechanistic modeling of primary drying of frozen particulates (2026) · doi

  Temperature probe placement in poorly conducting particle beds causes significant measurement artifacts, with predicted product temperatures initially trending much lower than experimental probe readings. A comparative study using alternative temperature measurement techniques (e.g., thermal imaging, distributed fiber optics) across different particle bed configurations is needed to validate the model's temperature predictions.

• 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.

• A review: recent progress of piezoelectric effect coupled photocatalytic reaction: diverse mechanisms, system/structure design, characterization and application (2026) · doi

  Mott-Schottky analysis has revealed that excessively high ultrasonic power induces conduction band position shifts that suppress photocatalytic hydrogen evolution, but the quantitative relationships between ultrasonic power intensity and piezoelectric potential-induced band structure changes across different material compositions remain uncharacterized.

• Biosensors: Enzyme Immobilization Chemistry (2018) · doi

  Nanomaterials are stated to improve biosensor performance due to high surface-to-volume ratios and proximity to enzyme reaction centers, but the paper lacks specific quantitative comparisons of signal transduction efficiency between immobilization on nanomaterials (nanotubes, nanoparticles, nanofibers, nanocorals) versus conventional matrices under identical enzymatic and transducer conditions.

• 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.

• 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.

• Electron-donor/-acceptor ratio-guided molecular engineering for buried interface optimization in n-i-p perovskite solar cells (2026) · doi

  The stability tests are limited to 30 days ambient storage (20-25°C, 25%-30% RH) and 120 h thermal aging; accelerated aging protocols at elevated temperatures (60-85°C) and high humidity (>80% RH) for extended durations (>500 h) are not reported to validate long-term encapsulation-free performance claims.

• Transfer-learning guided design of high-performance conjugated polymers for low-voltage electrochemical transistors (2026) · doi

  The transfer-learning approach for conjugated polymer design has not been validated across different electrochemical transistor architectures (e.g., organic electrochemical transistors vs. organic field-effect transistors); the generalizability of the learned features to structurally diverse polymer systems operating at different voltage ranges requires systematic investigation.

• Unpacking Teachers’ Transformative Agency Following Digital Fabrication Workshops on Making Mathematical Manipulatives (2026) · doi

  The study identifies access to DF tools (laser cutters and 3D printers) as critical infrastructure but does not compare outcomes between teachers using school-based fabrication equipment versus external partnerships with university makerspaces or communal makerspaces in terms of sustained use, manipulative production rates, and long-term pedagogical integration.

• 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.

• Coal seam porosity and water resources estimation based on big data analysis and deep learning models: A case study in the Surat Basin, Australia (2026) · doi

  The joint spacing relationship shown in Figure 7.4 (spacing increases with bed thickness) is based on outcrop data from highwall photogrammetry and appears lithology-specific (coal vs. clastic units). The study does not validate whether this spacing-thickness relationship from outcrop measurements is consistent with subsurface image log data across different coal seams or depositional facies in the Surat Basin.

• 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.

• Integrating Deterministic and Monte Carlo Approaches to the Risk Reduction Index for Sustainable Urban Construction Projects (2026) · doi

  The Monte Carlo simulation framework generated probabilistic ranges (P5-P95) for 11 risk categories, but no validation protocol is presented for calibrating the likelihood and impact distributions used in the simulation. Future work must establish validation procedures comparing Monte Carlo RRI predictions against actual historical project outcome data from sustainable urban construction case studies to assess model calibration accuracy.

• How to improve the lifespan of electric vehicle batteries using chemistry? (2026) · doi

  Self-healing materials for lithium-ion batteries must simultaneously maintain electrochemical stability and preserve lithium-ion conductivity, but the paper provides no specific validation of how candidate self-healing materials achieve both crack-closure and unimpeded lithium transport without degrading cycle performance.

• Dynamic Chemistry of Anion Recognition (2011) · doi

  The combination of computational de novo design with dynamic self-assembly under thermodynamic control is presented as a hybrid approach for receptor optimization, but the paper does not quantitatively compare binding kinetics, thermodynamic stability, or practical assembly yields of computationally-designed self-assembled receptors versus those obtained through classical DCC methods on identical target anions.

• 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.