Materials Science and Engineering Commons^™

Sustainability And Waste Diversion At Tva Shawnee "Project Phoenix", Bryan Jacob, Shane Harris

World of Coal Ash Proceedings

An engineered turf closure system can serve as an ideal foundation for a solar energy system to be installed atop coal combustion residual (CCR) impoundments. This approach not only enables productive power generation during the post-closure period, it also preserves opportunities for recovery and beneficial use of CCR material in the future. “Project Phoenix” at TVA’s Shawnee Fossil Plant offers an illustrative example. This paper will cover the sustainability benefits of the companion ClosureTurf® and PowerCap® systems installed at that site as well as waste diversion activities undertaken during construction to recycle as much as practical and minimize waste destined …

Expert Perspectives On The U.S. Coal Combustion Products Market – Now, Then, And The Future, Mark Rokoff, David Cox, Walter Lemaire, John Ward

World of Coal Ash Proceedings

This panel discussion will explore the continued evolution of the U.S. coal combustion products market, with a focus on the impacts of dynamic regulatory and market forces. Invited expert panelists will share perspectives on developments over the past several years (building on discussions from WOCA 2022 and WOCA 2024), current conditions, and expected future trends—particularly those likely to shape the market between 2026 and 2030. The discussion will address the interrelated markets for engineering, construction, and beneficiation of ash from both operating and inactive plants. Panelists will offer perspectives relevant to the full coal ash industry, from owner/operator organizations to …

Demystifying Large Language Models: How Ai Is Transforming Data, Compliance, And Decision-Making In Coal Ash And Environmental Management, Scott Pfeiffer

World of Coal Ash Proceedings

The environmental and coal combustion residuals (CCR) industries generate vast amounts of information—from groundwater monitoring reports and RCRA documentation to closure plans and analytical data. Managing, interpreting, and communicating this information is a growing challenge for utilities, regulators, and consultants alike. Large Language Models (LLMs), such as OpenAI’s GPT architecture, represent a breakthrough in how organizations can interact with their technical data. These models use deep neural networks trained on billions of words to understand, summarize, and generate language with human-like accuracy. When securely adapted for enterprise use, LLMs can automate routine reporting, extract data from technical documents, generate regulatory …

Subsurface Delineation Of Coal Combustion Residuals Using Multiple Geophysical Methods, Eric Hageman, Adam Rak, Thomas Jordan, Kate Mckinley

World of Coal Ash Proceedings

Geophysical techniques provide alternative methods of Coal Combustion Residual (CCR) delineation and characterization to supplement more invasive boring programs used for beneficial reuse planning. A demonstration project was designed to characterize the electromagnetic and seismic stratigraphy of CCR material and test the effectiveness of three geophysical techniques: Electrical Resistivity Imaging (ERI), Transient Electromagnetic (TEM) induction, and Multi-channel Analysis of Surface Wave (MASW). The demonstration project was completed at a dry-stack CCR unit containing a variety of CCR ash, gypsum, and thin layers of drainage aggregate (limestone). During a single-day deployment, several geophysical survey tests were conducted in specific areas of …

Design Of Air-Entrained Concrete For Airport Pavements Through Local Aggregate Utilization: Performance Optimization And Economic Analysis, Li Wentao, Rizwan Qadir, Arslan Mushtaq, Hilal Khan, Kamran Jillani

Journal of Sustainable Construction Materials and Technologies

Airport pavement construction in developing countries faces critical challenges balancing international performance standards with economic constraints, while limited research exists on optimizing air-entrained concrete mixes using locally sourced materials for cost-effective solutions. This study investigated the development of economical air-entrained concrete mix designs for airport pavements utilizing Pakistani aggregates and systematic cement content optimization. Comprehensive experimental evaluation included material characterization through petrographic analysis, alkali-aggregate reactivity assessment via accelerated mortar bar testing, and mechanical property development across cement contents from 360-450 kg/m3. Air entrainment was achieved through controlled admixture dosing while maintaining target slump of 50mm. Results demonstrated that locally sourced …

Development Of Hybrid Self-Cleaning Coating Using Lanthanide-Based Light Spectral Response Material To Enhance Photovoltaic (Pv) Panel Efficiency In Operational Environment, Khishn Kumar Kandiah

Student Works (2020-2029)

The efficiency of photovoltaic (PV) panels is crucial, as solar energy has become an alternative energy source that meets today’s global energy demands. Hence, dust accumulation and spectral mismatch have major effects on the efficiency of PV panels, around 20 %, but in extreme situations, this can reach up to 64 %. Therefore, initiatives are underway to address these issues, including PV cooling systems, conventional cleaning methods, and various coatings to enhance efficiency. In this work, a novel coating is fabricated with high transparency, excellent self-cleaning properties, and good spectral-modifying properties. Two types of powder composites are employed in this …

Designing Enhanced Nonlinearity In Plasmonic Devices With Epsilon-Near-Zero Films, Kevin Tran Le

Electrical Engineering and Computer Science (MS) Theses

The growing demand for energy-efficient optical information processing motivates compact nonlinear photonic devices that can operate at low power. Silicon photonics is a mature platform for linear optical functions, but nonlinear operation remains challenging because of its weak Kerr response, two-photon absorption at telecommunication wavelengths, and limited compatibility with deeply subwavelength plasmonic confinement. This thesis computationally investigates epsilon-near-zero thin films integrated into plasmonic waveguide architectures as a route toward stronger light–matter interaction in compact nonlinear devices.

Two waveguide geometries are examined: a hybrid metal-insulator-metal plasmonic slab waveguide incorporating an ultrathin indium tin oxide epsilon-near-zero layer (5–50 nm), and a dielectric-loaded …

Atom Probe Tomography Investigation Of Gas And Solid Fission Product Superlattice In Neutron Irradiated U-10 Wt.% Mo Fuel, Maalavan Arivu, Andrew Hoffman, Anish Ranjan, Assel Aitkaliyeva, Yaqiao Wu, Brandon Miller, Mukesh Bachhav, Dennis Keiser, Jian Gan, Haiming Wen

Materials Science and Engineering Faculty Research & Creative Works

Body-centered cubic structured γ U-Mo fuels have been developed for high performance research reactors. The formation of Xe gas bubble superlattice (GBS) in irradiated U-Mo fuels reduces the volumetric swelling of the fuels. In this study, atom probe tomography (APT) was used to measure the characteristics of the Xe GBS, including chemical composition, number density, and volume fraction of the gas bubbles, as well as the characteristics of the solid fission products, in neutron irradiated U-10 wt.% Mo fuel. It was found that in the bubbles (∼2 nm in diameter) that form the GBS are enriched with Xe with depletion …

Physical And Optical Properties Of The Germanium-Arsenic-Selenium Glass Forming Region For Precision Glass Molding And Infrared Optics, Peter F. Wachtel Ii

All Dissertations

The growth and advancement of infrared optical systems for thermal imaging, multi-band imaging, hyperspectral imaging, medical diagnostics, and chemical sensing are pushing the material science community to better understand existing materials while also developing new materials. Additionally, the thermal imaging market continues to grow, and system designers are continually being asked to reduce size, weight, and power while reducing costs (SWaP-c). Market growth has shifted optics manufacturing towards higher volume processes such as precision glass molding, but this does require most materials to be recharacterized due to property changes resulting from the process. Affecting the SWaP-c requirements, manufacturing tolerances are …

Adsorption Of Pfas On Bridged Functionalized Organosilica Materials, Elisha Lawerh Kabutey

Electronic Theses and Dissertations

PFAS are hazardous contaminants that have a devastating impact on human health and the environment. Their hazardous nature has led to the development of various adsorption methods for removing these contaminants from water sources. In this study, functionalized organosilica materials were synthesized from bis[3-(trimethoxysilyl)propyl] amine using the sol-gel method. The surface amino groups of the organosilica were converted into amine hydrochloride groups. Their adsorption properties were evaluated using salts of perfluorooctanoic acid, perfluorooctanesulfonic acid, and perfluorobutanesulfonic acid. Results showed excellent adsorption capacity of the materials. Adsorption of PFAS leads to particle agglomeration and flotation of the spent material. A column …

In-Operando Imaging For Mechanistic Insights And Process Optimization In The Biofuel-Driven Combustion Synthesis Of Cement And Precursor Phases, Shubham Agrawal, Jeffrey J. Long, Aditya Kumar, Narayanan Neithalath

Materials Science and Engineering Faculty Research & Creative Works

Biofuel-based combustion synthesis (BCS) is a promising low-carbon pathway for decarbonizing cement production, providing an alternative to the fossil-fuel-driven clinkering process typically conducted at ∼1450 °C. Understanding microscale combustion mechanisms is essential to efficiently transfer biofuel-generated heat to cement precursors for targeted phase formation. Unlike previous studies focusing on macro-scale parameters such as fuel content/type, porosity, and holding temperature, this work provides mechanistic insights into microscale combustion behavior, linking microstructural phenomena with macro-scale processing conditions to guide parameter optimization. In-operando microscale imaging was employed to examine combustion wave propagation, spatio-temporal temperature evolution, and microstructural transformations within reactive pellets. Two combustion …

Evaluation Of Iron-Phosphate Glass–Ceramic Waste Form For Electrorefiner Salt Waste Simulant Dechlorinated With Phosphoric Acid, Harmony Werth, Paige Murray, Lucas Greiner, Jade Beland, Charmayne Lonergan, Brian Riley, Krista Carlson

Materials Science and Engineering Faculty Research & Creative Works

The importance of glass and glass–ceramic nuclear waste forms has been reaffirmed in recent years by the growing interest in nuclear power as a reliable energy source. Determination of processing methods for the disposal of halide-containing wastes will be essential for the advancement of nuclear technologies such as non-aqueous fuel reprocessing. Phosphate-based dechlorination and subsequent vitrification of radioactive salt waste into an iron-phosphate waste form have been identified as a potential processing scheme for electrochemical processing waste. The impact of H₃PO₄-based dechlorination of complex salt mixtures on the vitrification process and structure of the final iron-phosphate …

Effect Of Composition On Grain-Boundary Chemistry And Fracture Behavior In High-Entropy Carbides, Caleb Schenck, Marium Mostafiz Mou, Elizabeth Pritchett, Fu Yun Tsai, Josephine Hartmann, Michael Lastovich, Sam Daigle, Kayla Yano, Matthew J. Olszta, Sanjit Bhowick, Elizabeth Kautz, Gregory E. Hilmas, William G. Fahrenholtz, Donald W. Brenner

Materials Science and Engineering Faculty Research & Creative Works

High-entropy carbides (HECs) are often treated as a single material class defined by configurational entropy; however, their properties are governed by composition-specific defects and grain-boundary chemistry. This study demonstrates that substituting a single element can qualitatively change grain-boundary structure and fracture behavior in HEC ceramics. Two HECs, (Cr,Hf,Ta,Ti,Zr)C (HEC-Cr) and (Hf,Ta,Ti,W,Zr)C (HEC-W), were examined via electron microscopy, atom probe tomography, and molecular dynamics simulations. Simulations predict preferential segregation of Cr, W, and Zr to grain boundaries. Experiments confirmed Cr enrichment at grain boundaries and the formation of W-rich nanograins along boundary networks. Mechanical testing revealed that these compositional differences translated …

Recovery And Evaluation Of A Germanium Infrared Camera, Michael Paszek

Graduate Theses and Dissertations

Short-wave infrared imagers made of germanium are a promising way to extend silicon-compatible imaging beyond the visible spectrum. They also use mature CMOS fabrication and readout electronics. This thesis details the recovery, initialization, and evaluation of a germanium focal plane array (FPA) infrared camera system using both a sealed TriWave camera and a modular prototype platform. Functionality was restored to this legacy hardware, and repeatable testing workflows were established for evaluating packaged infrared imagers under controlled indoor and outdoor conditions. The prototype used a custom software interface named Merlott for evaluation, and it followed a standard sequence that included checking …

Study On The Effects Of Molecular Layer Deposition Coating And Mechanical Pressure On Lithium Metal Anodes, Cameron Mondl

Graduate Theses and Dissertations

Lithium (Li) metal is a highly promising anode material for next-generation energy storage systems due to its outstanding theoretical capacity and low electrochemical potential. However, its commercialization implementation has been hindered due to interfacial instability and uncontrollable dendrite formation, leading to poor cycling efficiency and thermal runaway. Among the most promising stabilization strategies, protective interfacial coatings have emerged as an effective solution to promote more uniform Li deposition and suppress erratic morphological inconsistencies. In particular, molecular layer deposition (MLD) enables uniform film thickness through layer-by-layer deposits, offering a highly versatile approach to protective interfacial layers. In addition to interfacial engineering, …

Strong And Ductile Additively Manufactured Ti-6al-4v Through Yttrium Inoculation, Saeid Alipour, Ji Young Kim, Min Seok Kim, Arezoo Emdadi, Ju Li

Materials Science and Engineering Faculty Research & Creative Works

The unique microstructural features and thermal cycles in alloys produced by additive manufacturing (AM) techniques have led to the emergence of a new paradigm in the design and development of alloys for performance-critical applications. Despite the inherent microstructural features of AMed parts, optimizing the porosity-microstructure while acquiring desired mechanical performance has been crucial yet challenging. Hence, in many legacy alloys, achieving a strength-ductility synergy in the as-built condition without applying post-heat treatment or hybrid processes is considered an arduous task. In this research, we aimed to tailor the microstructure of the legacy Ti-6Al-4V alloy in the as-built condition by implementing …

Evaluating The Integration Of Bio-Based Waste Into Cement Production: A Pathway To Sustainable Building, Anja Terzić, Suzana Filipović, Adriana Peleš Tadić, Jelena Živojinović, Ivana N. Jelić, Nina Obradović, William G. Fahrenholtz

Materials Science and Engineering Faculty Research & Creative Works

Rapid urbanization has increased the demand for building materials, depleting natural resources used in cement production and prompting the use of alternative and waste materials. This research verifies that eggshell powder waste can fully replace limestone in clinker synthesis. Five clinkers were produced using eggshell powder, aluminum sources (bentonite, zeolite, fly ash, and kaolinitic–illitic clay), Fe-slag, and quartz sand, with mechanical preprocessing (10–30 min) before sintering at 1300 °C. Experimental tests assessed the effects of mix design and mechanical activation on clinkerization, phase formation, temperature, and mechanical properties. XRD, FTIR, and SEM/EDS confirmed consistent phase compositions and primary cement minerals. …

Computer Vision And Machine Learning Approaches For Defect Detection In 3d-Printed Cementitious Materials: A Systematic Review, Muhammad Ali Musarat, Ruben Paul Borg, Jingjie Wei, Carl James Debono, Kamal Khayat

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

3D printing is evolving at a fast pace in both the manufacturing and construction sectors. These advancements can greatly benefit these industries. However, the 3D printing of concrete structures presents some challenges due to defects in the 3D concrete printed elements. Hence, this study systematically reviews Artificial Intelligence (AI)-driven techniques, such as Computer Vision and Machine Learning, to identify surface defects that can occur in 3D-printed cementitious material structures. The adopted methodology was the PRISMA statement with the aim of reporting the systematic review and meta-analysis. Two well-known databases, Web of Science and Scopus, were utilised for data extraction of …

Moon Adaptive Technology For Extraterrestrial Architectural Robotics (Matear), Candela Noemi Solis Zampini

Theses and Dissertations

The Moon Adaptive Technology for Extraterrestrial Architectural Robotics (MATEAR) focuses on the development of an autonomous robotic system capable of providing structural building blocks directly from lunar regolith. As a sustained human presence on the Moon becomes a necessity, the costly and limited payload capacity associated with transporting construction goods from Earth creates a critical challenge. MATEAR addresses this problem through in-situ resource utilization (ISRU), integrating a regolith processing system onto a remote operated vehicle. The proposed system is designed to collect lunar dust, mechanically compact the material, and apply thermal treatment to enhance cohesion through sintering. These regolith-made bricks …

Engineering Silicone Magnetic Fluids For Localized Radiation Attenuation During Ocular Melanoma Brachytherapy, Zachary L. Caprow

All Dissertations

Ocular melanoma is commonly treated using plaque brachytherapy; however, radiation-induced damage to healthy ocular tissues frequently results in partial or complete vision loss. This work investigates the development of an injectable, magnetically responsive silicone magnetic fluid designed to localize adjacent to the tumor and attenuate low-energy gamma radiation during treatment.

The material system consists of iron oxide nanoparticles surface-functionalized with a siloxane polymer, in which the nanoparticles provide magnetic responsiveness and radiation attenuation, while the polymer coating ensures colloidal stability, injectability, and biocompatibility. A one-pot synthetic approach was developed wherein a functionalized siloxane polymer containing iron-affinitive groups was reacted with …

Enameling Coating Of Pipes: Thermal Proprieties And Corrosion Tests, Signo Reis, Genda Chen, Mike Koenigstein, Liang Fan

Materials Science and Engineering Faculty Research & Creative Works

Enamel coating on pipelines can be done in several ways such as the wet process, plasma spray, and electrostatic process. Wet process requires little capital expenses and provides an acceptable finish for industrial applications particularly when the part to be coated is small. Electrostatic process of enamel powder is most promising to coating large pipelines in field conditions. The enamel coating applied by the electrostatic process is very consistent and smooth since each particle is glass only. However, the powder is very fragile until fired and the charge retention is lowered in high humidity conditions. Coupons cut from a full-size …

A Maintenance-Aware Machine Learning Framework For Network-Level Highway Pavement Condition Prediction, Jin Hwan Kim, Guk Gon Song, Youngguk Seo

Faculty Articles

This study develops and validates maintenance-aware machine learning models for predicting the Highway Pavement Condition Index (HPCI) on the Korean expressway network. Multiple regression and tree-based models were trained and tested using the pavement condition surveys archived in the Highway Pavement Management System (HPMS). A stacking regressor that integrates random forest, gradient boosting, and extreme gradient boosting as base learners exhibited the most robust predictions. Performance metrics indicated that the stacking ensemble achieved a mean absolute error of 0.21, a root mean square error of 0.31, and a coefficient of determination exceeding 0.73 on the testing dataset. Also, the residuals …

Interplay Between Phase Instability And Deformation Mechanisms In Beta Titanium Alloys In Aggressive Environments, Benjamin Elbrecht

All Dissertations

Modern designs, such as commercial jet turbines, are reliant on the high temperature performance of their constituent materials. Improvements to the strength-at-temperature of materials are critical to the continued advancement of efficiency and payload capacity in these advanced applications. This dissertation presents studies that progress towards this goal through the construction of a new experimental setup for complex temperature and force profiles that also accurately captures deformation behavior through non-contact measurements. Using this setup, studies into two specialty titanium alloys were executed: discovering the microscopic mechanisms responsible for the macroscale behavior and testing in conditions closely replicating aircraft turbine operating …

The Influence Of Composition On Porosity And Strength In Planetary Analog Saline Ices, Tara C. Tomlinson

Dartmouth College Ph.D Dissertations

This thesis investigates how composition influences the physical structure and mechanical behavior of saline ice, with implications for both terrestrial sea ice and the ice shells of ocean worlds such as Europa and Enceladus. This is done through a multi-pronged approach of both numerical modeling and laboratory experiments. Modeling results re- veal that small-scale parameter variations in porosity, permeability, and permeability fac- tor may produce large discrepancies when extrapolated to planetary scales, underscoring the need for improved experimental constraints on pore connectivity and thermochemical conditions. Laboratory analyses show that while total porosity is relatively uniform with depth, it varies strongly …

The Impact Of People Interests In Evaluating The Open Public Spaces' Quality In The City Centre, Hasan Hadi, Adil Al-Saidi, Haitham Alshamari

HBRC Journal

The quality of open public spaces in city centres significantly affects people's satisfaction and responses to their built environment. The significance of these areas allow people to assess their performance. this paper addresses the issue of People's interests that affect their evaluation of public urban spaces in city centres. The research applied an ontological methodology that is people's experiences determine the spatial quality of the public spaces in city centres. In order to discover and assess the seven value variables, it recommended diagnosing a random sample of users as a group (A) and (B). The urban space in the historic …

Optimized Bombax Ceiba/Jute Hybrid Epoxy Composites For Enhanced Thermal Insulation Performance, Shadman Ahmed Khan, Naeem Ahmmed, Md Tanvir Hossain, Abdullah Ibn Asheque, Md Ariful Islam, Md Abdul Kader, Md Sohel Rana, Sakib Masud

Michigan Tech Publications

The development of sustainable hybrid natural-fiber composites provides a practical way toward lightweight materials with tailored mechanical and thermal performance. In this study, Bombax ceiba (BC)/jute hybrid epoxy composites were fabricated using a stacked preform followed by compression molding, and the effect of fiber blending ratio on mechanical, thermal, and microstructural properties was systematically investigated. Three compositions-40/60, 50/50, and 60/40 BC/jute by weight-were evaluated. Mechanical testing showed that the J50 composite, with a balanced fiber ratio, exhibited superior flexural strength and impact resistance, indicating effective hybrid synergy and improved stress transfer between fibers and the matrix. Thermogravimetric analysis showed that …

Molecular Catalysts For Electrochemical Nitrogen Activation Toward Sustainable Ammonia Synthesis, Jin-Xiu Han, Hao Xue, Xian-Biao Fu

Journal of Electrochemistry

Homogeneous electrocatalytic nitrogen reduction reaction (NRR) provides a powerful framework to interrogate molecular nitrogen-fixation pathways under mild conditions. By tuning the metal center, ligand architecture, and reaction medium, these systems enable capturing key intermediates and delivering mechanistic insight at the molecular-level resolution. Nevertheless, advances remain constrained by highly reduced operating potentials, intense competition from the hydrogen evolution reaction (HER), limited durability in turnover, and inadequate long-term stability.

In this review, we take electron delivery to the molecular active site as the guiding principle for organizing homogeneous electrochemical N₂ activation and transformation. We classify reported systems into direct electron transfer …

Water-Driven Solid Electrolyte Interphase Governs Continuous-Flow Ammonia Electrosynthesis, Peng-Bo Liu, Sheng-Liang Zhai, Ji Huang, Zhong-Shuo Zhang, Jie Zeng, Shao-Feng Li

Journal of Electrochemistry

Flow-cell architectures have emerged as a powerful platform for continuous and stable lithium-mediated nitrogen reduction (Li-NRR), enabling ambient-condition electrochemical ammonia synthesis and offering a promising alternative to Haber-Bosch processes. However, Li-NRR is exceptionally sensitive to trace water, and even minor variations in water content can profoundly alter interfacial chemistry. Here, we systematically investigate how initial water concentration affects Li-NRR performance in a continuous-flow cell. Excess water drives the formation of a thick solid electrolyte interphase (SEI) layer, which may impede nitrogen access to metallic lithium and hinder lithium-ion transport. As a result, the ammonia Faradaic efficiency collapses from ~61% to …

Insertion Of Noble Metal Free Cathodic Catalyst Layer With Fe-N-C Catalyst For Boosted Performance Of Pemfc, Shi Zhou, Muhammad Tariq, Asif Nadeem Tabish, Muhammad Salman, Fan-Di Ning, Muhammad Rayyan Tayyab, Ran-Ran Peng, Meng-Geng Hao, Wen-Mu Li, Xiao-Chun Zhou

Journal of Electrochemistry

Economical Fe-N-C catalysts are considered as promising alternatives to platinum group metal catalysts for proton exchange membrane fuel cells (PEMFCs). Despite exhibiting robust activity on rotating disk electrodes, their performance within membrane electrode assemblies often experiences limitations, such as decreased O₂ diffusion, high H₂O₂ formation, low proton conduction, and a lower electron transfer number. In this study, key factors, including proton transport, electron conduction, and gas diffusion within air-breathing PEMFCs, have been investigated by adjusting cathode catalyst layer (CCL) compositions. From the experimental results, the optimal peak power density was obtained when the loading of Fe-N-C …

A Comparative Study Of Tin Electrorefining In Molten Licl–Kcl–Cacl₂: Experimental Two-Electrode Current Control And Theoretical Three-Electrode Potential Control, Bryant Johnson, George Ankrah, Ander Fuller, Devin Rappleye

Reviews, Analyses, and Instructional Studies in Electrochemistry (RAISE)

Molten salt electrorefining is a mature technology for metal recovery, yet conventional current‑controlled, two‑electrode operation provides limited electrochemical selectivity and restricted insight into electrode‑specific behavior. In this work, a simplified model is developed to compare current‑controlled two‑electrode electrorefining data with a potential‑controlled three‑electrode electrorefining simulation using tin in molten LiCl–KCl–CaCl₂ as a surrogate for plutonium processing. The model examines anodic and cathodic limitations under fixed‑potential operation and evaluates implications for selectivity, efficiency, and runtime relative to experimentally demonstrated two‑electrode performance. Results indicate that independent potential control enables operation closer to thermodynamic selectivity limits, with the potential to suppress impurity oxidation …