Theory gaps in Engineering

Representative open questions

Showing 30 of 46 — 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

  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.

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

  The hybrid SBR-200 + connector configuration shows improved energy dissipation and mixed-mode failure with partial cohesive involvement, but the mechanisms by which dowel action and chemical bonding interact at the meso-scale are not quantitatively characterized through fractography, microscopy, or strain analysis.

• Eutectogel-Based Drug Delivery Systems: Recent Advancements and Pharmaceutical Applications (2026) · doi

  Trade-offs between mechanical properties and ionic conductivity in eutectogels have been identified but not systematically characterized; quantitative structure-property relationship studies are needed to predict how DES composition affects both mechanical robustness and functionality in drug delivery applications.

• 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.

• Harnessing Surface Instabilities for Functional Materials: Mechanics, Morphology, and Emerging Applications (2026) · doi

  Self-wrinkling coating systems for impact resistance and mechanical enhancement have been developed, but the relationship between coating wrinkle morphology parameters (amplitude, wavelength, aspect ratio) and impact energy absorption, crack propagation resistance, and long-term durability under cyclic loading is incompletely understood.

• 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.

• Predicting rock strength anisotropy using a sensitivity-driven evolutionary polynomial regression (2026) · doi

  The EPR model failed to capture the non-monotonic behavior observed in Biotite Schist where anisotropy is quelled at σ₃ = 70 MPa, despite this stress-dependent anisotropy reduction being documented in experimental results. The paper does not specify which confining stress ranges or rock types exhibit this quenched-anisotropy phenomenon or propose modifications to EPR for capturing it.

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

  The strong collinearity between cutting velocity and thrust force (rs = +0.932) in this dataset is a consequence of CCD design structure; it is unclear whether this collinearity persists in factorial or random experimental designs, or whether PISRE-NF's superior performance is contingent on this specific design property.

• 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.

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

  The mechanism of viral inactivation involves ROS-mediated damage to envelope proteins, lipid membranes, and potential nucleic acid damage, plus direct interaction with thiol groups on viral surface proteins; the relative contribution of each mechanism and their dependence on microenvironment conditions in platinum nanoparticle systems requires quantitative mechanistic characterization.

• 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.

• 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.

• 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.

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

  While feature importance analysis (Fig. 15) identifies nanoparticle concentration, inlet temperature, and mass flow rate as input parameters, the paper does not investigate potential nonlinear interaction effects between these variables or their combined influence on radiator performance degradation at extreme nanoparticle concentrations (>5%) where agglomeration and viscosity penalties may dominate thermal gains.

• 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.

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

  Biofilm formation kinetics and optimization for enhanced electron transfer at electrodes lack quantitative characterization; systematic studies on biofilm thickness, density, and microbial composition effects on direct electron transfer (DET) and mediated electron transfer (MET) mechanisms are needed for MFC performance improvement.

• EFFECT OF MATERIAL COMPOSITION ON FREE VIBRATION OF BIDIRECTIONAL FUNCTIONALLY GRADED BEAM VIA A QUASI-3D THEORY (2026) · doi

  The convergence plateau observed at L/h ≥ 15 for all material types requires investigation into the physical mechanisms governing why stretching effects stabilize at this specific aspect ratio threshold in bidirectional FG beams.

• 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.

• Influence of Petrographic Properties on the Strength and Durability of Dolomite and Limestone for Infrastructure Development (2026) · doi

  The porosity and point load test correlation is weak for dolomite (R² = 0.42) compared to limestone (R² = 0.84), suggesting the need for further investigation into the mechanisms governing this relationship.

• Multifunctional PVC-based metal oxide/graphene composites for high-performance DSSC counter electrodes (2026) · doi

  The apparent IPCE extension beyond 700 nm does not originate from additional optical absorption of the Z907 dye, but this mechanism of enhanced internal quantum efficiency requires further investigation to fully understand the interplay between suppressed charge recombination and accelerated redox regeneration.

• Intrinsically stretchable organic light-emitting-diode with high brightness and stretchability via elastic-microphase-engineered emitter and dual-embedded electrode (2026) · doi

  Device failure at 120% strain is attributed to combined effects of resistance increase and charge transport pathway severance, but the exact mechanisms and relative contributions of each factor are not fully elucidated.

• 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.

• Exploiting the insulator–metal transition of VO2 in photocatalytic methane conversion (2026) · doi

  The biased VO2 system shows dramatically improved performance (2769 µmol.g-1h-1 for C2H6) compared to unbiased control, but the paper lacks detailed investigation of the bias mechanism and its interaction with the insulator-metal transition.

• 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.

• 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.

• Green Modified Graphene Oxide Nanoplatelets as Drug Adsorbents (2026) · doi

  While electrostatic attraction and dispersion interactions were identified as the basic interaction mechanisms, deeper mechanistic understanding of the non-covalent functionalization process between vitamin B3 and graphene oxide surfaces requires additional investigation.

• Coupled Electro-Elastic Dynamic Analysis of Two Fixed-End Macro Fiber Composite (MFC) Beams on the Same Side (2026) · doi

  Adhesive layer shear hysteresis and viscoelastic effects and interface damage evolution can be introduced to establish a beam-adhesive layer-MFC transmission mechanism model.

• Physics-Driven Linear Quantification of Matrix Crack Density in Composites via Continuous Centroid Analysis of FBG Sensors (2026) · doi

  The spatial randomness of matrix crack distribution is inherent to the physical model and inevitably introduces a certain degree of error into the results, contributing to the R² value of 0.83.