Theory gaps in Engineering

Representative open questions

Showing 30 of 39 — one per source paper, highest-quality first.

• Engineering of Asymmetric Dual-Atom Sites for Effective Oxygen Electrocatalysis (2026) · doi

  The adsorption strength of ADASCs toward key intermediates (e.g., *OOH, *O, *OH) tends to deviate due to insufficient precision in d-band center modulation.

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

  The asymmetric material flow caused by rheological mismatch between Nitinol and Stainless Steel (differing flow stresses and thermal conductivities) was identified as the root cause of tunnel defects, but no quantitative flow stress ratio thresholds or specific thermal conductivity differential limits are provided to predict when asymmetry will occur during parameter selection.

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

  The reactivity mechanism of basalt powder as a sole precursor remains poorly characterized across different geological origins. While crystalline BP showed only ~16 MPa compressive strength versus 47 MPa for reactive basaltic volcanic ash, the specific mineralogical and glass content thresholds that distinguish reactive from non-reactive basalt sources have not been systematically quantified or mapped.

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

  The paper demonstrates controller stability and tracking performance during voltage sags but does not analyze harmonic distortion, frequency response characteristics, or interactions with grid-connected harmonic impedance during the transient periods following voltage sag recovery.

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

  The study identified that beam reflection caused insufficient energy delivery at smooth interfaces (8.76 μm roughness), leading to defects such as partially melted powder and lack of fusion, but did not quantify the relationship between surface roughness and beam energy absorption or reflection coefficient in the hybrid additive manufacturing process.

• High-Entropy Catalysts for Biomass-Derived Chemicals Valorization: Mechanisms, Applications, and Opportunities (2026) · doi

  The selective oxidation mechanism of HMF using HEC catalysts remains unresolved: current designs achieve ~100% FDCA selectivity through consecutive aldehyde and hydroxyl oxidation, but designing HEC catalysts to selectively oxidize only the hydroxyl group or a single aldehyde group to produce HMCA, DFF, or FFCA intermediates instead of complete oxidation to carboxyl groups requires mechanistic clarification and rational catalyst design strategies.

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

  While the RSEI decreased from 64 to 33 Ω during lithiation in the MSi-C/PVDF-HFP/LATP system, the quantitative contribution of mechanical pressure-induced interfacial contact improvement versus LixSi conductivity enhancement to this impedance reduction has not been separated through controlled experimental design or mathematical modeling.

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

  The discrepancy between experimental and calculated dielectric permittivity values becomes substantial at nanoparticle volume fractions above 60% in BTO-doped P(VDF-HFP) nanocomposites, but the underlying mechanisms causing this model-data divergence have not been systematically investigated or explained.

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

  The interactions among multiple physical fields under diverse electric field distributions and multi-physical coupling in different classes of piezoelectric-photocatalytic material systems remain unclear; the commonalities and distinctive features across material systems have not been comprehensively elucidated.

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

  An unresolved tradeoff exists between minimizing false negatives (missed failures in nuclear systems with catastrophic consequences) and controlling false positives (operational disruption); tuning sensitivity to detect weak early-failure signals hidden in high-noise sensor streams requires development of domain-specific decision thresholds that balance safety and availability.

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

  The relationship between molecular planarity (quantified through computational descriptors) and charge transport mobility in low-voltage conjugated polymers has not been fully characterized in the transfer-learning framework; explicit inclusion of planarity metrics and their interaction with side-chain effects in the model requires further empirical validation.

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

  Advanced composite and metallic AM materials specifically optimized for wind turbine blade applications remain underdeveloped. Research is needed on material property characterization, process parameter optimization, and long-term performance validation for AM composites and metallic systems at blade-scale manufacturing.

• 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 study uses a power-law distribution (n3d(l) = a·l^-b) fitted to 69 mapped faults with R² = 0.9031, but does not investigate whether this single distribution adequately characterizes fracture size distributions across different coal seams (A4 to D8) with varying lithologies or whether separate distributions are needed for conductive versus mixed fractures identified in image logs.

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

  State of Charge (SoC) dynamics and battery degradation effects are monitored but not explicitly modeled; investigation into how the AHA controller performs under various battery aging states, depth of discharge cycles, and temperature-dependent battery efficiency changes is missing.

• IoT-Driven Transformer Health Monitoring and Fault Detection: Advancing Reliability in Emerging Power Systems (2026) · doi

  Humidity monitoring (≤60% RH threshold) is included as a parameter affecting insulation health, but the paper provides no data on the correlation between measured humidity levels and actual insulation degradation rates, dielectric strength loss timelines, or the relationship between ambient humidity and internal winding moisture accumulation in different transformer designs. Quantitative validation of humidity thresholds against insulation failure mechanisms is absent.

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

  Ionic liquid electrolytes show SEI layer stability and low evaporation but suffer from insufficient electrical conductivity at normal operating temperatures; the paper does not identify specific conductivity threshold targets or which ionic liquid chemical structures should be modified to meet EV operational requirements.

• Quantum simulation of single-server Markovian queues: a dynamic amplification approach (2026) · doi

  The paper identifies that moderate traffic conditions (λ = 5, µ = 10) show higher fluctuation in relative error (0.098% to 6.47%) compared to low and high traffic scenarios, but does not investigate the underlying mechanism causing this instability. A systematic study is needed to characterize why moderate traffic creates more challenges for quantum simulation stability than the extreme regimes.

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

  The comparison in Table 5 shows that SHFA with GF distinguisher achieves 34 fault injections for 99% key recovery, but there is no investigation of how the attack success rate degrades when fault injection success rates fall below 100%, which is critical for real-world applicability.

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

  The paper identifies that foundation properties significantly influence vibration suppression in height-sensitive systems but does not establish quantitative relationships or predictive models for designing CA-UHPC smart plate systems with pre-specified vibration characteristics for specific sports engineering applications.

• Chemical processing routes, crystal structure design and physical parameters of rare-earth doped Sm₂Zr₂O₇ for emerging applications (2026) · doi

  The ionic radius ratio (rA/rB) range of 1.46-1.78 governs pyrochlore formation and order-disorder transitions in rare-earth-doped Sm₂Zr₂O₇, but quantitative structure-property relationships linking specific radius ratios to thermal conductivity and ionic conductivity values have not been systematically mapped across the full compositional space.

• Strategies to enhance Biocompatibility via additive manufacturing for medical applications: A state-of-the-art review (2026) · doi

  Gap in understanding how surface modifications (such as anodization and nanostructuring) affect long-term biocompatibility and anti-fouling properties of AM-produced implants.

• The 2D materials roadmap (2026) · doi

  Interfacial layer formation between top metal and HfO2 layer during 2D transfer and processing (1.74nm additional CET) needs further understanding and process optimization.

• Temperature control performance change of EPS foam box with ice packing in aircraft cargo hold (2026) · doi

  After the foam box is packaged and sealed in a normal pressure environment on the ground, it is in a low-pressure environment during flight. The wall of the foam box is affected by the pressure difference between the inside and outside air, and there will inevitably be certain deformation. This factor also has a certain impact on the temperature control performance of the foam box and is worthy of further in-depth analysis and study in future research.

• Integrated experimental and statistical evaluation of hydraulic and strength behavior in compacted high-plasticity fine-grained soils (2026) · doi

  The relationship between AEV and breakpoint stress does not coincide perfectly for all soils (e.g., Sample 3 lies well above the 1:1 reference line), suggesting that structural rearrangement and pore-pressure buildup may dominate mechanical response independently of air entry onset in some cases.

• Enhanced electromechanical coupling in piezoelectric MEMS vibration energy harvesters via strain-induced phase transition in Mn-doped bismuth ferrite epitaxial films (2026) · doi

  The energy outputs under a single impulsive force were similar across all films (BFO, BFMO, and PZT), suggesting a need for further investigation into why sinusoidal vibration performance differs from impulsive force responses.

• Pavement Rutting and Deformation Performance Analysis through FEM (2026) · doi

  Future studies must incorporate more advanced constitutive models and environmental factors to enhance the predictive capability beyond the current simplified assumptions.

• Performance evaluation of the effect of tilt angle on a grid connected photovoltaic power plant using PVsyst (2026) · doi

  Thermal performance depends on both irradiance intensity and heat transfer conditions, but the study does not deeply investigate the interaction mechanisms between these factors.

• Observation of Raman anomaly and characterization of magnetic phases in van der Waals ferromagnet Fe 5 GeTe 2 (2026) · doi

  The relationship between the different exchange interactions and the observed magnetic anisotropy could be explored further through additional theoretical or computational studies.

• Large-range strain measurement and elastic-plastic loading analysis in liquid helium environments based on metallized fiber Bragg grating sensor (2026) · doi

  Theoretical modeling is referenced as part of the proposed framework, but detailed mathematical models describing the sensor behavior under elastic-plastic transitions are not elaborated in the excerpt.

• Tribological Characteristics of Nanocomposite Coatings Based On the Principle of Multielementality (2026) · doi

  The mechanisms by which Cr and Ni presence in amorphous carbon leads to changes in sp2 and sp3 bond ratios are assumed rather than experimentally validated: 'apparently', 'possibly', and 'can be assumed' indicate uncertainty.