Engineering Archive
type: channel
description: engrXiv (Engineering Archive) is dedicated to the dissemination of engineering knowledge quickly and efficiently. The server is directed by Devin R. Berg and Open Engineering Inc., a 501(c)(3) non-profit. Follow us on Mastodon or Facebook or watch the engrXiv blog for updates.
language: en-US
publication name: Engineering Archive
items: Physics-informed multiscale modelling of tunnelling-governed percolation and conductivity evolution in carbon black modified cementitious composites
items: Global tree forecasters collapse at the hierarchical aggregate: a scale-aware, library-agnostic correction
items: An area-weighted particle-size peak from image analysis predicts total dissolved solids across grinder types
items: Forward Flight Study of a Power-efficient Disc-shaped UAV: a Computational Approach
items: Evaluating real-time particulate matter instruments against gravimetric and size-resolved references to advance residential wood heater development
items: Design of a Wearable Three-Channel Transthoracic Bioimpedance Spectroscopy Front-End with Synchronized ECG Acquisition
items: The Information Dilution Paradox in Low-Dimensional Thermodynamic Manifolds
items: Radiation-Hardened FPGA Architectures and Design Techniques for Space Applications: A Comprehensive Review.
items: Iterative droop control strategy for microgrids
items: A 2-D Subthreshold Analytical Model for Short Channel Effects in Nanowire MOSFETs (Si, Ge)
items: Mixedmode Circuit Simulation of Silicon and Germanium Nanowire MOSFETs – A Comparative Study
items: Constructal design of glider wings: the intersection of aerodynamic and structural asymptotes
items: A Mobile Feedback Framework for Pose-Based Cricket Fielding Technique Analysis
items: A Simulation-Ready Framework for Electric-Vehicle Gearbox NVH
items: Chemicals in Potable Reuse: Prioritizing and Controlling a Wide Universe of Compounds
items: Onsite Water Systems: An Expanding Reuse Paradigm
items: Tapping into untapped potential: Three approaches to develop new pathogen crediting frameworks
items: Pathogen Reduction Crediting for Reverse Osmosis: Getting Credit where Credit is Due with Good Surrogates
items: TinyFER-Lite: A Small-Data and Lightweight Attention-Based Architecture for Real-Time Facial Emotion Recognition
items: An Analytical Theory of Harmonic Distortion in RC Networks with Voltage-Dependent Capacitance
items: Prediction-Based Adaptive Control of Haptic Devices Under Communication Time Delay and Human Hand Interference
items: https://engrxiv.org/preprint/view/7459
items: Voltage-Dependent Ceramic Capacitors as a Source of Dynamic Error in SAR ADC Front Ends
items: Pathogen Reduction Crediting: Its not what you can remove, it's what you can prove
items: Direct Potable Reuse at the Global Scale: Regulations or Bust?

Physics-informed multiscale modelling of tunnelling-governed percolation and conductivity evolution in carbon black modified cementitious composites
type: item
description: Self-sensing cementitious composites (SSCCs) containing conductive nanofillers enable structural health monitoring through measurable electrical responses. However, conventional numerical models generally assume homogeneous interphase conductivity, neglecting the distance-dependent quantum tunnelling that governs conductive network formation near the percolation threshold. This study presents a physics-informed multiscale framework for predicting the effective electrical conductivity (EEC) and percolation threshold (PT) of carbon black nanoparticle (CBN) modified cementitious composites. Stochastic representative volume elements were coupled with finite element simulations, while the tunnelling region surrounding each particle was discretized into concentric layers with exponentially decaying conductivity derived from Simmons’ tunnelling theory. The framework reproduced the experimentally observed percolation threshold near 2 wt.% CBN and captured the conductivity increase from approximately 10⁻⁶ to 10⁻¹ S/m. Compared with the homogeneous interphase model, the discretized tunnelling formulation substantially improved prediction accuracy, with the ten-layer model reducing the logarithmic root mean square error (RMSE) from 0.520 to 0.132. The proposed framework provides a physically realistic and computationally efficient approach for modelling tunnelling-mediated transport and optimizing self-sensing cementitious composites.
subject: Preprints
  topic: section
creator: Jeslin Thalapil
rights: Copyright (c) 2026 Jeslin Thalapil https://creativecommons.org/licenses/by/4.0
date: 2026-07-06
publication date: 2026-07-06
doi: 10.31224/7509

Global tree forecasters collapse at the hierarchical aggregate: a scale-aware, library-agnostic correction
type: item
description: Global gradient-boosted-tree forecasters, trained by pooling series, are a workhorse of demand forecasting and reported accurate across hierarchy levels. We document a deployment-blocking exception. On a production panel of monthly gross transaction value from a business-to-business service marketplace, a global tree scored at the marketplace aggregate—far outside its per-buyer training support—collapses, under-predicting the total by an order of magnitude. We trace this to the constant extrapolation of trees beyond their training range: the failure is fundamentally one of scale, curable along either of two axes. One restores scale, via per-series scaling or a single-model cohort-weighted aggregate training row, both library-agnostic. The other renders the target stationary by seasonal differencing, which uniquely remains stable under recursive multi-step forecasting. The failure is structural—reproducing on synthetic data and three public datasets (M5, Tourism, B2B)—and seed-invariant, situated within a twenty-three-method benchmark documenting a unit-of-analysis dichotomy.
subject: Preprints
  topic: section
subject: gross transaction value
  topic: keywords
subject: global forecasting models
  topic: keywords
subject: gradient boosting
  topic: keywords
subject: hierarchical forecasting
  topic: keywords
subject: foundation models
  topic: keywords
subject: two-sided marketplaces
  topic: keywords
subject: time series forecasting
  topic: keywords
subject: machine learning
  topic: keywords
subject: Data Science
  topic: disciplines
subject: Operations Research
  topic: disciplines
subject: Computer Engineering
  topic: disciplines
subject: Statistics and Probability
  topic: disciplines
subject: Artificial Intelligence and Machine Learning
  topic: disciplines
subject: Industrial Engineering
  topic: disciplines
creator: Md Rezwanul Islam
creator: Wael Mohammed
rights: Copyright (c) 2026 Md Rezwanul Islam, Wael Mohammed https://creativecommons.org/licenses/by/4.0
date: 2026-07-06
publication date: 2026-07-06
doi: 10.31224/7508

An area-weighted particle-size peak from image analysis predicts total dissolved solids across grinder types
type: item
description: Coffee extraction is rate-limited by solute diffusion from particle surfaces, yet the particle size distribution (PSD) is commonly summarized by a single central value such as D50, which discards information about the shape of the distribution. Image analysis now enables inexpensive acquisition of the full PSD, but it remains unclear which of the many computable features best predicts total dissolved solids (TDS). In this study, 12 samples from two grinders (conical burr and flat burr, six settings each) were imaged and processed through a pipeline based on Fiji/ImageJ and Python. Spearman rank correlations between PSD features and TDS were compared. The area-weighted KDE peak (area_weighted_peak), defined as the mode of a kernel density estimate weighted by each particle's measured projected area, yielded the strongest and most consistent correlation (pooled ρ = −0.949; |ρ| > 0.94 for both grinders). Other features, including volume-weighted D50 (Dv50), De Brouckere mean diameter (D43), and count-weighted KDE peak (kde_peak), showed weaker or grinder-dependent correlations, whereas the Sauter mean diameter (D32) and area-weighted D50 (Da50) — the area-weighted mean and median of the same distribution — performed nearly as well as the area-weighted KDE peak (its mode). Among the evaluated descriptors, the area-weighted KDE peak showed the strongest and most consistent performance. It is independent of grinder geometry and can be computed from low-cost imaging equipment.
subject: Preprints
  topic: section
subject: coffee extraction
  topic: keywords
subject: particle size
  topic: keywords
subject: Extraction
  topic: keywords
subject: image analysis
  topic: keywords
subject: total dissolved solids
  topic: keywords
subject: Kernel density estimator (KDE)
  topic: keywords
subject: coffee extraction
  topic: subjects
subject: particle size distribution
  topic: subjects
subject: image analysis
  topic: subjects
subject: total dissolved solids
  topic: subjects
subject: kernel density estimation
  topic: subjects
subject: grind size
  topic: subjects
subject: coffee grinder
  topic: subjects
subject: Feret diameter
  topic: subjects
subject: particle size analysis
  topic: subjects
subject: Food Engineering
  topic: disciplines
subject: Food Science
  topic: disciplines
subject: Image Processing
  topic: disciplines
creator: Naoya Oec
rights: Copyright (c) 2026 Naoya Oec https://creativecommons.org/licenses/by/4.0
date: 2026-07-06
publication date: 2026-07-06
doi: 10.31224/7507

Forward Flight Study of a Power-efficient Disc-shaped UAV: a Computational Approach
type: item
description: This study investigates a disc-shaped unmanned aerial vehicle (UAV) engineered with a contoured upper surface to improve forward-flight efficiency. A three-dimensional CFD model, validated through mesh-sensitivity analysis, is used to quantify aerodynamic performance across forward speeds of 25–100 km/h and varying rotor and tilt configurations. The curved body generates up to 80.5% of total lift in level flight, reducing power demand by as much as 66.42% relative to hover. Maximum efficiency occurs at small negative angles of attack, where body inclination and surface geometry enhance the lift-to-drag ratio. Power savings increase from 48.31% at 25 km/h to 80.26% at 100 km/h. These results demonstrate how geometric shaping and attitude control can be leveraged to improve the aerodynamic and energy performance of non-conventional UAV platforms.
subject: Preprints
  topic: section
subject: Aerodynamics
  topic: keywords
subject: Computational Fluid Dynamics
  topic: keywords
subject: UAV
  topic: keywords
subject: Drones
  topic: keywords
subject: Aircraft Design
  topic: keywords
creator: Samia Shahrin Ahmed Snikdha
creator: Shih-Hsiung Chen
rights: Copyright (c) 2026 Samia Shahrin Ahmed Snikdha, Shih-Hsiung Chen https://creativecommons.org/licenses/by/4.0
date: 2026-07-06
publication date: 2026-07-06
doi: 10.31224/7506

Evaluating real-time particulate matter instruments against gravimetric and size-resolved references to advance residential wood heater development
type: item
description: Residential wood heater certification testing relies on time-integrated gravimetric filters that obscure the transient particulate matter (PM) generation events central to heater certification. Continuous PM instruments could support advancement of heater technologies, but most are developed for ambient air and may struggle under the high concentrations, dynamic transients, and variable aerosol properties of wood combustion. This study evaluated five continuous particulate matter (PM) instruments spanning light scattering (TSI DustTrak II 8530, Thermo MIE pDR-1500, Particles Plus 8306), inertial mass (Thermo Scientific 1405-D TEOM), and triboelectric charge (Sintrol S203) against gravimetric filters and size-resolved reference concentrations across three heater types and two operating phases. No single instrument performed well across all conditions. The DustTrak II and pDR-1500 demonstrated the most consistent temporal tracking (r ≥ 0.87 and r ≥ 0.79, respectively) but substantially overestimated integrated PM mass during cordwood combustion and require gravimetric correction for quantitative use. The TEOM performed closest to the gravimetric reference during pellet high-burn phases but exhibited sustained negative cumulative mass during cordwood tests. The Particles Plus and Sintrol showed the weakest overall performance across all conditions. These results support the continued advancement of residential wood heater technologies by identifying conditions under which each instrument provides more or less reliable PM data, and may help inform instrument selection for laboratory testing for product development and field studies for verification.
subject: Preprints
  topic: section
subject: wood smoke aerosol
  topic: keywords
subject: TEOM
  topic: keywords
subject: optical particle counter
  topic: keywords
subject: triboelectric monitor
  topic: keywords
subject: biomass
  topic: keywords
subject: light-scattering photometer
  topic: keywords
subject: Residential Wood Heating
  topic: subjects
subject: Biomass Combustion
  topic: subjects
subject: Certification
  topic: subjects
creator: Vi Rapp
creator: Brett Singer
creator: Rebecca Trojanowski
creator: Sharon Chen
creator: Dylan Anacleto-Black
creator: William Delp
creator: Eric Adair
creator: John Crouch
rights: Copyright (c) 2026 Vi Rapp, Brett Singer, Rebecca Trojanowski, Sharon Chen, Dylan Anacleto-Black, William Delp, Eric Adair, John Crouch https://creativecommons.org/licenses/by/4.0
date: 2026-07-03
publication date: 2026-07-03
doi: 10.31224/7502

Design of a Wearable Three-Channel Transthoracic Bioimpedance Spectroscopy Front-End with Synchronized ECG Acquisition
type: item
description: Transthoracic bioimpedance spectroscopy is a promising wearable sensing modality for tracking impedance based physiological changes, but practical wearable acquisition is limited by the lack of synchronized cardiac electrical information. This paper presents a portable three-channel thoracic bioimpedance front-end with synchronized electrocardiogram acquisition. The system integrates a DDS based sinusoidal excitation source, single-supply analog conditioning, a Tietze-type VCCS, multiplexed tetrapolar electrode selection, lead-off detection, GPD, an ECG analog front-end, microcontroller control, Bluetooth communication, and battery-powered operation. The excitation circuit generates 100 frequency points from 1 kHz to 1 MHz with an approximately 290μA current and less than 5 percent variation across the measured band. Based on the evaluated data, the impedance mean absolute percentage errors were 3.9±0.24%, 5.2±0.32%, and 5.72±0.5% for Channels 1–3, respectively. The corresponding phase mean absolute errors were 1.12±0.5◦, 1.08±0.7◦, and 1.4±0.65◦. Position-matched Nyquist trajectories further confirmed preservation of the resistive and reactive impedance components for all three channels. The integrated ECG path produced clearly identifiable R−peaks over a 30s recording. These results demonstrate a compact, single supply platform capable of acquiring validated multi-frequency BioZ data from all three transthoracic paths together with synchronized cardiac electrical timing.
subject: Preprints
  topic: section
creator: Abu Bony Amin
creator: Ebenezer Asabre
creator: Yeonsik Noh
rights: Copyright (c) 2026 Abu Bony Amin, Ebenezer Asabre, Yeonsik Noh https://creativecommons.org/licenses/by/4.0
date: 2026-07-03
publication date: 2026-07-03
doi: 10.31224/7501

The Information Dilution Paradox in Low-Dimensional Thermodynamic Manifolds
type: item
description: Predicting net hourly electrical energy output (PE) in Combined Cycle Power Plants (CCPP) is fundamental to grid dispatch optimization, typically addressed through tree-based ensembles. Recently, hybrid architectures incorporating Transformer-based self-attention have been proposed to enhance tabular regression by capturing latent feature interactions. This study empirically evaluates a Residual Hybrid Transformer-GBDT architecture against a standalone LightGBM baseline using the UCI CCPP dataset. Contrary to the prevailing hypothesis that latent embedding expansion improves predictive accuracy, our results reveal a performance degradation, with Root Mean Squared Error (RMSE) increasing from 3.2777 (Baseline) to 3.2853 (Hybrid). Detailed error segmentation identifies a significant performance collapse during low-load operational regimes (< 430 MW), where the Mean Absolute Error (MAE) increased by 36.5% compared to the baseline. We characterize this phenomenon as the 'Information Dilution Paradox', wherein mapping a low-dimensional physical manifold (d=4) into a high-dimensional latent space (d=16) introduces stochastic noise and feature redundancy rather than discriminative signal. These findings provide a critical counter-narrative to the adoption of high-capacity deep learning for low-cardinality tabular data, suggesting that raw physical feature representations remain superior for thermodynamic manifolds governed by strong intrinsic correlations.
subject: Preprints
  topic: section
subject: biology computation
  topic: disciplines
creator: Zulman Arif
rights: Copyright (c) 2026 Zulman Arif https://creativecommons.org/licenses/by/4.0
date: 2026-07-03
publication date: 2026-07-03
doi: 10.31224/7499

Radiation-Hardened FPGA Architectures and Design Techniques for Space Applications: A Comprehensive Review.
type: item
description: Field-Programmable Gate Arrays (FPGAs) have become an important technology in modern space systems because of their flexibility, reconfigurability, high processing power, and shorter development time. They are commonly used in satellite payloads, onboard data processing, communication systems, autonomous navigation, and scientific tools. However, the extreme radiation conditions found in space create significant reliability issues for FPGA-based systems. Radiation-related problems such as Total Ionizing Dose (TID), Single Event Upsets (SEUs), Single Event Transients (SETs), Single Event Latchups (SELs), and Single Event Functional Interrupts (SEFIs) can reduce performance, damage data, and lead to mission failures.To tackle these issues, various radiation-hardening methods have been developed at the device, circuit, architecture, and system levels. This review offers a detailed survey of radiation effects in FPGAs and looks at the latest methods used to reduce radiation impact in space applications. The paper covers radiation-hardened FPGA technologies, circuit-level hardening techniques, fault-tolerant design strategies like Triple Modular Redundancy (TMR) and configuration scrubbing, along with their use in actual space missions. It also discusses new trends such as adaptive fault tolerance, artificial intelligence-based onboard processing, and next-generation radiation-tolerant FPGA designs. By gathering recent developments and pointing out existing research gaps, this review gives researchers and engineers a clear understanding of radiation-hardened FPGA design practices and future paths for reliable reconfigurable computing in space settings.
subject: Preprints
  topic: section
creator: Keerthanaa Karthikeyan
rights: Copyright (c) 2026 Keerthanaa Karthikeyan https://creativecommons.org/licenses/by/4.0
date: 2026-07-03
publication date: 2026-07-03
doi: 10.31224/7500

Iterative droop control strategy for microgrids
type: item
description: In this technical report, we will apply the droop control strategy to a microgrid with N sources. In addition, to accommodate optimized reference values provided by a higher level controller, the droop gains are updated at a fixed/periodic interval.
subject: Preprints
  topic: section
subject: Power systems
  topic: keywords
subject: Power converters
  topic: keywords
subject: Droop control
  topic: keywords
subject: Microgrids
  topic: keywords
subject: Electrical Engineering
  topic: disciplines
creator: Kaushik K Gajula
rights: Copyright (c) 2026 Kaushik K Gajula https://creativecommons.org/licenses/by/4.0
date: 2026-07-03
publication date: 2026-07-03
doi: 10.31224/7493

A 2-D Subthreshold Analytical Model for Short Channel Effects in Nanowire MOSFETs (Si, Ge)
type: item
description: The present analysis proposes a 2D analytical model of potential and current for Nanowire MOSFETs in the subthreshold region for a moderately doped channel. The analytical expression for subthreshold current has been used to investigate the short channel parameters such as threshold voltage roll off and subthreshold slope. The model has been validated for Silicon and Germanium Nanowire MOSFETs by verifying the analytical results obtained with simulated results using Device3D.
subject: Preprints
  topic: section
subject: Nanowire MOSFET
  topic: keywords
subject: Gate-All-Around MOSFET
  topic: keywords
subject: Short Channel Effects
  topic: keywords
subject: Subthreshold Current
  topic: keywords
subject: Subthreshold Slope
  topic: keywords
subject: Threshold Voltage Roll-Off
  topic: keywords
subject: Device Modeling
  topic: keywords
subject: Analytical Modeling
  topic: keywords
subject: Semiconductor Devices
  topic: keywords
subject: TCAD Simulation
  topic: keywords
subject: CMOS Scaling
  topic: keywords
subject: Nanoelectronics
  topic: keywords
subject: Semiconductor Devices, Nanoelectronics, VLSI Technology, Device Physics, Microelectronics, Computational Electronics
  topic: subjects
subject: Electrical & Computer Engineering
  topic: disciplines
creator: Gaurav Mahajan
creator: Rakhi Narang
creator: Manoj Saxena
creator: V.K. Chaubey
rights: Copyright (c) 2026 Gaurav Mahajan, Rakhi Narang, Manoj Saxena, V.K. Chaubey https://creativecommons.org/licenses/by/4.0
date: 2026-07-01
publication date: 2026-07-01
doi: 10.31224/7486

Mixedmode Circuit Simulation of Silicon and Germanium Nanowire MOSFETs – A Comparative Study
type: item
description: Nanowire MOSFETs have been recognized as one of the possible choices to continue the scaling of CMOS beyond conventional scaling limits. In present study we study various aspects of device characteristics and Mixedmode circuit behavior of Silicon and Germanium Nanowire MOSFETs. The various parameters determining the behavior of device in the analog/digital circuits is studied and compared for Nanowire MOSFET with Si and Ge as channel material. Important parameters such as transconductance, output conductance, Ion/Ioff ratio and short channel parameters have been extracted and compared for Silicon and Germanium. The Mixed mode circuit simulation has been done for Inverter (VTC and transient analysis) and 3 stage Ring Oscillator (transient analysis). Results of these simulations give insights into the in-circuit behavior of these future generation devices.
subject: Preprints
  topic: section
subject: Nanowire MOSFETs
  topic: keywords
subject: Silicon Nanowire MOSFETs
  topic: keywords
subject: Germanium Nanowire MOSFETs
  topic: keywords
subject: Mixed-Mode Simulation
  topic: keywords
subject: CMOS Inverter
  topic: keywords
subject: Ring Oscillator
  topic: keywords
subject: Short Channel Effects
  topic: keywords
subject: Nanoscale CMOS
  topic: keywords
subject: Semiconductor Devices
  topic: keywords
subject: Device Modeling
  topic: keywords
creator: Gaurav Mahajan
creator: V. K. Chaubey
creator: Rakhi Narang
creator: Manoj Saxena
rights: Copyright (c) 2026 Gaurav Mahajan, V. K. Chaubey, Rakhi Narang, Manoj Saxena https://creativecommons.org/licenses/by/4.0
date: 2026-07-01
publication date: 2026-07-01
doi: 10.31224/7485

Constructal design of glider wings: the intersection of aerodynamic and structural asymptotes
type: item
description: When designing an aircraft, aerodynamic efficiency must be taken into account as well as structural integrity. While high-aspect-ratio wings minimize induced drag, they exponentially increase the bending moment and the required structural weight at the root of the wings. In this paper, “Constructal Theory” is applied to theoretically predict the optimal wing span for a glider. Instead of using complex and high-cost approaches such as “Fluid-Structure Interaction” to predict the optimal wing span, in this paper aerodynamic drag and structural weight are treated as two competing flow resistances that restrict the movement of the flying system. By formulating the total resistance function and applying the principle of the intersection of asymptotes, we analytically derive the geometric configuration that minimizes the global resistance. This mathematical optimization process shows that the geometry of an optimal wing is not a random occurrence, but it is a deterministic physical phenomenon driven by the equipartition of imperfection.
subject: Preprints
  topic: section
subject: Constructal Law
  topic: keywords
subject: Wing Optimization
  topic: keywords
subject: Intersection of Asymptotes
  topic: keywords
subject: Fluid-Structure Interaction
  topic: keywords
subject: Aspect Ratio
  topic: keywords
subject: Mechanical Engineering
  topic: disciplines
subject: Aeronautics / Aerospace Engineering
  topic: disciplines
creator: Tunç Güreşçi
rights: Copyright (c) 2026 Tunç Güreşçi https://creativecommons.org/licenses/by/4.0
date: 2026-07-01
publication date: 2026-07-01
doi: 10.31224/7482

A Mobile Feedback Framework for Pose-Based Cricket Fielding Technique Analysis
type: item
description: Cricket fielding analysis is a fine-grained sports action recognition problem because several techniques contain similar upper-body configurations but differ in posture transition, hand position, and movement timing. This paper proposes a mobile feedback framework for pose-based cricket fielding technique analysis. The framework connects video capture, prototype processing, pose extraction, fixed-length landmark representation, hybrid CNN–LSTM inference, confidence reporting, and recommendation delivery. MediaPipe Pose represents each video as a temporal landmark sequence, and the classifier recognizes five techniques: High Catch, Orthodox Cup, Reverse Cup, Short Barrier, and Long Barrier. The prototype is evaluated through functional, timing-related, and model-performance evidence. Beyond reporting model accuracy, the paper clarifies the architectural bridge between isolated action-recognition models and deployable mobile feedback systems, while identifying the additional ablation, deployment-latency, biomechanical-feedback, and user-study evidence required for stronger empirical validation.
subject: Preprints
  topic: section
subject: pose-based action recognition
  topic: keywords
subject: MediaPipe Pose
  topic: keywords
subject: CNN-LSTM
  topic: keywords
subject: mobile sports feedback system
  topic: keywords
subject: sports performance analysis
  topic: keywords
subject: Cricket
  topic: keywords
subject: Mobile Application
  topic: keywords
creator: Himashi Kodithuwakku
creator: Nishantha Janith Chandrasena
rights: Copyright (c) 2026 Himashi Kodithuwakku, Nishantha J. Chandrasena https://creativecommons.org/licenses/by/4.0
date: 2026-07-01
publication date: 2026-07-01
doi: 10.31224/7475

A Simulation-Ready Framework for Electric-Vehicle Gearbox NVH
type: item
description: Electric-vehicle (EV) gearboxes operate in an acoustic environment in which gear whine, motor orders, inverter-related harmonics, and structure-borne responses are readily perceived. Existing research often treats manufacturing variation, transmission error, multibody simulation, housing radiation, condition monitoring, and psychoacoustic assessment as separate topics. This review develops a simulation-ready framework that connects these domains in a single source-path-response-perception chain. The framework maps gear and assembly deviations, including pitch error, run-out, flank waviness, tooth-to-tooth microgeometry variation, bearing preload, misalignment, and housing stiffness, to intermediate quantities such as kinematic and dynamic transmission error, gear-mesh orders, shaft-order sidebands, structural vibration, sound-pressure bands, diagnostic indicators, and psychoacoustic metrics. A structured narrative synthesis of 38 sources combines 21 external publications with 17 representative publications from the author's research program to clarify which physical inputs and validation evidence are required for different engineering claims. Four simulation-readiness levels are proposed: nominal, tolerance-based, measurement-based, and variability-aware. These levels distinguish early concept screening from tolerance robustness, as-built unit reconstruction, and production-scatter prediction. The review also introduces a machine-readable source-claim representation to support transparent reuse of the cited evidence. The resulting framework provides practical guidance for robust EV gearbox NVH modeling, data-driven screening, root-cause analysis, end-of-line interpretation, and perception-oriented validation.
subject: Preprints
  topic: section
subject: electric vehicle gearbox
  topic: keywords
subject: NVH; gear whine
  topic: keywords
subject: transmission error
  topic: keywords
subject: manufacturing variability
  topic: keywords
subject: pitch error
  topic: keywords
subject: flank waviness
  topic: keywords
subject: tooth-to-tooth variability
  topic: keywords
subject: multibody dynamics
  topic: keywords
subject: structural acoustics
  topic: keywords
subject: machine learning
  topic: keywords
subject: psychoacoustics
  topic: keywords
subject: condition monitoring
  topic: keywords
subject: simulation readiness
  topic: keywords
subject: variability-aware simulation
  topic: keywords
creator: Krisztian Horvath
rights: Copyright (c) 2026 Krisztian Horvath https://creativecommons.org/licenses/by/4.0
date: 2026-06-30
publication date: 2026-06-30
doi: 10.31224/7477

Chemicals in Potable Reuse: Prioritizing and Controlling a Wide Universe of Compounds
type: item
description: Key Takeaways: While pathogens can cause health impacts after even short-term exposures, most chemicals of concern in potable reuse only impact public health after long-term, chronic exposures. Experts agree that potable reuse should focus on a wider diversity of chemicals than those regulated in traditional drinking water sources. One challenge is to identify which compounds should be prioritized. A commonly used risk-based approach prioritizes compounds that are frequently detected and at concentrations above their health thresholds. Lists of relevant compounds can be further refined through the selection of conservative indicators and surrogates. Multiple strategies are needed to control the ever-evolving universe of chemicals including robust and diverse treatment, source control, monitoring, and, in the case of indirect potable reuse, the environmental buffer.
subject: Preprints
  topic: section
subject: water reuse
  topic: keywords
subject: potable reuse
  topic: keywords
subject: chemical control
  topic: keywords
subject: indicator
  topic: keywords
subject: surrogate
  topic: keywords
subject: environmental engineering
  topic: disciplines
creator: Anya Kaufmann
creator: Brian Pecson
creator: Sarah Philo
creator: Shane Trussell
creator: Amy Childress
rights: Copyright (c) 2026 Anya Kaufmann, Brian M. Pecson, Sarah E. Philo, Shane Trussell, Amy E. Childress https://creativecommons.org/licenses/by/4.0
date: 2026-07-01
publication date: 2026-07-01
doi: 10.31224/7473

Onsite Water Systems: An Expanding Reuse Paradigm
type: item
description: Key Takeaways: The growth of onsite water reuse (OWR) is clear: 19 US states have regulations or guidelines that allow the practice An onsite water system is a decentralized system that collects, treats, and reuses water at the property where it is generated, rather than sending it to a centralized facility Stakeholders interviewed for this issue view OWR as an additional tool to support reuse and conservation goals Drivers for OWR include: (1) water scarcity, (2) lack of centralized wastewater capacity, and (3) economic advantages Key challenges for implementation include: (1) cost, (2) lack of public health requirements and program organization, and (3) stepping out of the “municipal mindset” Top solutions to address challenges: (1) legislation and regulations, (2) mandates and incentives, and (3) experience The rapid development of OWR across the US shows that the practice is moving into the mainstream
subject: Preprints
  topic: section
subject: onsite water systems
  topic: keywords
subject: water reuse
  topic: keywords
subject: forward operating base
  topic: keywords
subject: Environmental engineering
  topic: disciplines
creator: Brie Post
creator: Brian Pecson
creator: Anya Kaufmann
creator: Sarah Philo
creator: Shane Trussell
creator: Amy Childress
rights: Copyright (c) 2026 Brie Post, Brian M. Pecson, Anya Kaufmann, Sarah E. Philo, Shane Trussell, Amy E. Childress https://creativecommons.org/licenses/by/4.0
date: 2026-07-01
publication date: 2026-07-01
doi: 10.31224/7472

Tapping into untapped potential: Three approaches to develop new pathogen crediting frameworks
type: item
description: Key Takeaways: Potable reuse requires high levels of pathogen reduction, but many treatment processes do not have frameworks for claiming pathogen credits. There are three approaches that can be used to develop pathogen crediting frameworks: Modeling Approach: used for treatment processes whose mechanisms of pathogen reduction are well understood and whose performance can be accurately predicted using a model (e.g., an equation) with inputs that can be continuously measured. Surrogate Approach: relies on a parameter that: a) can be continuously monitored at the influent and effluent of the treatment process; and b) correlates well with the amount of pathogen reduction provided by the treatment. Operational Envelope Approach: establishes pathogen credits based on empirical studies conducted at one or multiple facilities. Credits are based on log reductions observed during the studies but requires the system to operate within the specific limits (i.e., the operational envelope) used during the study. The recently-developed frameworks for pathogen reduction crediting in membrane bioreactors provide an example of how new crediting frameworks can provide many benefits for the reuse industry.
subject: Preprints
  topic: section
subject: water reuse
  topic: keywords
subject: pathogen reduction crediting
  topic: keywords
subject: crediting frameworks
  topic: keywords
subject: membrane bioreactor
  topic: keywords
subject: Environmental engineering
  topic: disciplines
creator: Matthew Verbyla
creator: Anya Kauffman
creator: Brian Pecson
creator: Nicholas Babcock
creator: Mitchel Bartolo
creator: Jacob Newman
creator: Sarah Philo
creator: Shane Trussell
creator: Amy Childress
rights: Copyright (c) 2026 Matthew E. Verbyla, Anya Kauffman, Brian M. Pecson, Nicholas Babcock, Mitchel Bartolo, Jacob Newman, Sarah E. Philo, Shane Trussell, Amy E. Childress https://creativecommons.org/licenses/by/4.0
date: 2026-06-30
publication date: 2026-06-30
doi: 10.31224/7471

Pathogen Reduction Crediting for Reverse Osmosis: Getting Credit where Credit is Due with Good Surrogates
type: item
description: Key Takeaways Reverse osmosis (RO) is an excellent barrier against pathogens (e.g., 6-log10 virus reduction), but is under-credited for pathogen reduction due to the lack of good surrogates. Conductivity and total organic carbon, the most common surrogates, only provide log reduction credits of 1.5 to 2 log10. Other naturally occurring ions provide opportunity to increase RO credits up to 3-log10 . Alternative approaches—such as the use of spiked surrogates—have the potential to provide 4- or 5-log10, but more research is needed for implementation. This issue shows practitioners and regulators how to extend RO crediting with existing surrogates and points to the need for further research to maximize RO’s full potential.
subject: Preprints
  topic: section
subject: Water reuse
  topic: keywords
subject: pathogen reduction crediting
  topic: keywords
subject: reverse osmosis
  topic: keywords
subject: surrogates
  topic: keywords
subject: Environmental Engineering
  topic: disciplines
creator: Matthew Verbyla
creator: Brian Pecson
creator: Anya Kaufmann
creator: Jacob Newman
creator: Rodrigo Tackaert
creator: Sarah Philo
creator: Shane Trussell
creator: Amy Childress
rights: Copyright (c) 2026 Matthew E. Verbyl, Brian M. Pecson, Anya Kaufmann, Jacob Newman, Rodrigo A. Tackaert, Sarah E. Philo, Shane Trussell, Amy E. Childress https://creativecommons.org/licenses/by/4.0
date: 2026-06-29
publication date: 2026-06-29
doi: 10.31224/7451

TinyFER-Lite: A Small-Data and Lightweight Attention-Based Architecture for Real-Time Facial Emotion Recognition
type: item
description: Facial emotion recognition is useful for affective computing, education, human–computer interaction, and assistive systems, but practical models must balance accuracy with model size, latency, and reproducibility. This paper presents TinyFER-Lite, a compact PyTorch pipeline for FER2013-style small and imbalanced facial-expression datasets. The model combines a MobileNetV3-Small feature extractor, Efficient Channel Attention, ImageNet normalization, conservative augmentation, class-weighted focal loss, mixed precision training, and deployment-focused evaluation. On FER2013, the best checkpoint selected by validation macro-F1 obtains 67.07% accuracy, 67.18% macro-F1, and 67.09% weighted-F1 on the held-out PrivateTest split. The trained model has 932,202 trainable parameters, an estimated 3.61 MB size, and measured single-image latency of 8.85 ms on CPU and 7.04 ms on an RTX 3050 GPU in the local evaluation environment. The project does not claim state-of-the-art performance; it provides a reproducible lightweight baseline and a clear foundation for future FER ablations.
subject: Preprints
  topic: section
subject: facial emotion recognition
  topic: keywords
subject: FER2013
  topic: keywords
subject: lightweight neural networks
  topic: keywords
subject: MobileNetV3-Small
  topic: keywords
subject: Efficient Channel Attention
  topic: keywords
subject: imbalanced learning
  topic: keywords
subject: real-time inference
  topic: keywords
subject: computer vision
  topic: keywords
subject: Computer Vision
  topic: disciplines
subject: Artificial Intelligence
  topic: disciplines
subject: Machine Learning
  topic: disciplines
subject: Computer Engineering
  topic: disciplines
subject: Human-Computer Interaction
  topic: disciplines
creator: Nouman Khalid
rights: Copyright (c) 2026 Nouman Khalid https://creativecommons.org/licenses/by/4.0
date: 2026-06-29
publication date: 2026-06-29
doi: 10.31224/7466

An Analytical Theory of Harmonic Distortion in RC Networks with Voltage-Dependent Capacitance
type: item
description: Class II ceramic capacitors, including X7R and X5R MLCCs, are widely used in compact analog and mixed-signal hardware. Their main advantage is high volumetric capacitance, but that advantage comes from nonlinear dielectric materials. As a result, the effective capacitance depends on the applied voltage. In decoupling and bulk filtering applications, this effect is often treated mainly as a loss of capacitance under DC bias [4], [5], [6]. In signal-path circuits, however, voltage-dependent capacitance has a deeper consequence: the capacitor becomes a nonlinear charge-storage element and can generate harmonic distortion [1], [2], [3]. This paper studies the simplest circuit in which the mechanism appears clearly: a first-order RC low-pass network with a voltage-dependent shunt capacitor. Despite its simplicity, this network is a useful model for many practical nodes, including anti-alias filters, ADC input networks, AC-coupling stages, and local analog filters. The central question is practical: why does the distortion peak near the transition region of the filter rather than at the highest signal frequency? The analysis is based on a charge-conserving capacitor model. The nonlinear capacitor is described by its charge-voltage relation Q(V), not by an instantaneous capacitance value inserted into an otherwise linear current law. The differential capacitance is Cd(V)=dQ/dV, and the capacitor current is i=dQ(V)/dt. This distinction matters because the common shortcut Q=C(V)V can describe a different physical component when C(V) is actually a differential capacitance [7], [8], [9]. The resulting small-nonlinearity RC equation contains nonlinear terms of the form v dv/dt, v^2 dv/dt, v^3 dv/dt, and v^4 dv/dt. This structure explains the frequency dependence of the distortion. At low frequencies, the voltage across the capacitor is large, but its time derivative is small. At high frequencies, the derivative can be large, but the capacitor voltage and the generated harmonics…
subject: Preprints
  topic: section
subject: voltage-dependent capacitance
  topic: keywords
subject: Class II ceramic capacitors
  topic: keywords
subject: MLCC
  topic: keywords
subject: X7R
  topic: keywords
subject: X5R
  topic: keywords
subject: RC low-pass filter
  topic: keywords
subject: harmonic distortion
  topic: keywords
subject: charge-conserving model
  topic: keywords
subject: differential capacitance
  topic: keywords
creator: Boris Kuznetsov
rights: Copyright (c) 2026 Boris Kuznetsov https://creativecommons.org/licenses/by/4.0
date: 2026-06-30
publication date: 2026-06-30
doi: 10.31224/7464

Prediction-Based Adaptive Control of Haptic Devices Under Communication Time Delay and Human Hand Interference
type: item
description: This paper presents a predictor-based adaptive con trol framework to improve the performance of haptic interaction in the presence of time delay, sampling effects, and uncertain human hand dynamics. In haptic systems, computational delays, zero-order hold effects, and variations in hand impedance can de grade stability and prevent the device from accurately following the continuous trajectory generated by the virtual environment. To address these challenges, the predictor is designed to generate a delay-free trajectory for the adaptive controller, while the adap tive controller estimates uncertain hand impedance parameters and compensates for non-passive forces exerted by the user in real time. To reduce implementation complexity, the effects of sampling and zero-order hold are represented using Taylor series approximations, leading to a more practical theorem for predictor design. The stability of the proposed predictor is established using the linear matrix inequality (LMI) method, and its performance is evaluated in MATLAB/Simulink by comparing it with the widely used Smith predictor.
subject: Preprints
  topic: section
subject: Haptic feedback
  topic: keywords
subject: Adaptive Controller
  topic: keywords
subject: Model based Predictors
  topic: keywords
subject: Time Delay Compensation
  topic: keywords
creator: Khosro Ghorbani Zadeh
creator: Soroush Izadan
creator: Saeed Behbahani
rights: Copyright (c) 2026 Khosro Ghorbani Zadeh, Soroush Izadan, Saeed Behbahani https://creativecommons.org/licenses/by/4.0
date: 2026-06-29
publication date: 2026-06-29
doi: 10.31224/7460

https://engrxiv.org/preprint/view/7459
type: item
title: Damage-State Threshold Definitions in Analytical Fragility Assessment of Non-Ductile and Code-Deficient RC Buildings: A Systematic Review of Framework Origins, Inter-Study Divergence, and Transferability
description: Damage-state thresholds are the primary numerical input governing fragility curve position, yet their definition receives substantially less methodological scrutiny than ground-motion selection or structural modelling in seismic fragility assessment. This review systematically examines how damage-state thresholds are sourced, applied, and justified in analytical fragility studies of non-ductile and code-deficient reinforced concrete buildings. Five major threshold frameworks, HAZUS, EMS-98, ASCE 41, Eurocode 8 Part 3, and FEMA P-58, are classified by calibration basis and embedded structural assumptions; none was developed for a non-ductile, gravity-load-designed, or pre-code population as its primary target. Reported values for nominally equivalent damage states diverge substantially across structural classes, with the spread appearing to increase as damage severity increases. Transfer of thresholds from an external framework occurs in the majority of reviewed studies, yet full structural justification accompanies fewer than a third of these transfers. Controlled comparisons in which authorship and archetype basis are held constant demonstrate that divergence of comparable magnitude can arise from methodological choice alone. Detailing quality, governing failure mechanism, and demand-parameter compatibility are identified as the variables that determine whether a transferred threshold retains its physical validity. The evidence establishes that damage-state threshold definition functions as a primary determinant of fragility predictions and that current practice does not treat it accordingly, with direct consequences for seismic risk assessment of the non-ductile building stock that dominates seismically active regions worldwide.
subject: Preprints
  topic: section
subject: damage-state thresholds
  topic: keywords
subject: seismic fragility
  topic: keywords
subject: non-ductile reinforced concrete buildings
  topic: keywords
subject: threshold transferability
  topic: keywords
subject: interstorey drift ratio
  topic: keywords
subject: performance-based earthquake engineering
  topic: keywords
subject: Civil Engineering
  topic: disciplines
subject: Structural Engineering
  topic: disciplines
subject: Earthquake Engineering
  topic: disciplines
subject: Seismic Risk Assessment
  topic: disciplines
subject: Reinforced Concrete Structures
  topic: disciplines
creator: Muhammad Abubakar
creator: Muhammad Awaib
creator: Faheem Butt
creator: Ibrahim Sadiq
rights: Copyright (c) 2026 Muhammad Abubakar, Muhammad Awaib, Faheem Butt, Ibrahim Sadiq https://creativecommons.org/licenses/by/4.0
date: 2026-06-29
publication date: 2026-06-29
doi: 10.31224/7459

Voltage-Dependent Ceramic Capacitors as a Source of Dynamic Error in SAR ADC Front Ends
type: item
description: Multilayer ceramic capacitors based on Class II dielectrics, such as X7R and X5R, are widely used in compact analog front ends because they provide high capacitance density at low cost. However, their capacitance is not constant. It depends strongly on applied voltage, temperature, package size, dielectric formulation, and DC bias. In low-accuracy circuits this effect is often acceptable. In precision data acquisition systems, especially in front ends driving high-resolution SAR analog-to-digital converters, the same effect can become a significant source of deterministic nonlinear error. This article examines how voltage-dependent capacitance can degrade the dynamic performance of an ADC input path. The focus is not merely on the loss of nominal capacitance under DC bias, but on the distortion mechanism created when a nonlinear capacitor is charged and discharged by a time-varying input signal. In a sample-and-hold system, the final voltage captured at the end of the acquisition interval can deviate from the ideal sampled value in an amplitude-dependent and history-dependent manner. This error appears in the digitized spectrum as harmonic distortion and reduces SINAD and ENOB. A second topic is the modeling method itself. A nonlinear capacitor should be represented through a physically consistent charge-voltage relationship, Q(V), rather than through a naive time-step update of an instantaneous capacitance value C(V). Incorrect behavioral models may inject or remove charge numerically and can produce distortion components that are artifacts of the simulation rather than properties of the physical circuit. A charge-conserving formulation avoids this failure mode and allows the designer to estimate ADC degradation with better confidence. Representative simulations show that distortion is most severe under large-signal operation and can peak near the transition band of the input RC network rather than at the highest signal frequency. For a 16-bit, 100 kS/s acquisition…
subject: Preprints
  topic: section
subject: Analog-to-Digital Converters (ADC)
  topic: keywords
subject: Successive Approximation Register (SAR)
  topic: keywords
subject: Ceramic Capacitors
  topic: keywords
subject: Nonlinear Distortion
  topic: keywords
subject: Charge-Conserving Modeling
  topic: keywords
subject: Harmonic Distortion (THD)
  topic: keywords
subject: Effective Number of Bits (ENOB)
  topic: keywords
subject: MLCC (Multilayer Ceramic Capacitors)
  topic: keywords
subject: X7R / X5R Dielectrics
  topic: keywords
creator: Boris Kuznetsov
rights: Copyright (c) 2026 Boris Kuznetsov https://creativecommons.org/licenses/by/4.0
date: 2026-06-27
publication date: 2026-06-27
doi: 10.31224/7456

Pathogen Reduction Crediting: Its not what you can remove, it's what you can prove
type: item
description: Key Takeaways Potable water reuse requires much higher pathogen reduction than conventional drinking water treatment. As with drinking water treatment, potable reuse is regulated by comparing the log10 reduction value (LRV) requirements for pathogens with the LRV credits that can be achieved by the individual treatment processes in the facility. This LRV crediting approach is used because we are technically incapable of measuring pathogens in treated water down to the very low levels needed. Frameworks exist to assign pathogen LRV credits for some treatment processes; many other processes remain under-credited or entirely uncredited. To improve the efficiency and economics of potable reuse, existing crediting frameworks need to be expanded for under-credited processes and new frameworks need to be created for uncredited processes.
subject: Preprints
  topic: section
subject: Pathogen reduction crediting
  topic: keywords
subject: water reuse
  topic: keywords
subject: log reduction value
  topic: keywords
subject: Environmental Engineering
  topic: disciplines
creator: Matthew Verbyla
creator: Brian Pecson
creator: Anya Kaufmann
creator: Mitchel Bartolo
creator: Sarah Philo
creator: Shane Trussell
creator: Amy Childress
rights: Copyright (c) 2026 Matthew E. Verbyla, Brian M. Pecson, Anya Kaufmann, Mitchel Bartolo, Sarah E. Philo, Shane Trussell, Amy E. Childress https://creativecommons.org/licenses/by/4.0
date: 2026-06-27
publication date: 2026-06-27
doi: 10.31224/7450

Direct Potable Reuse at the Global Scale: Regulations or Bust?
type: item
description: Key Takeaways Potable reuse regulations are not being prioritized at the international scale for several reasons: The urgent need for water supplies can leave insufficient time for regulatory development. The effort to develop regulations is not justified by the low number of anticipated projects. Some countries do not have a culture that favors regulatory development and enforcement. Use of an environmental buffer provides an avenue for pursuing reuse without additional regulatory development. In many countries, existing drinking water frameworks do not explicitly prohibit potable reuse. Multiple strategies are used for protecting public health in the absence of potable reuse regulations: leveraging existing frameworks, building off precedents from existing projects, employing risk management approaches and demonstration facilities, and engaging experts. Three different regulatory approaches are discussed based on the urgency of water supply, the number of projects, and the availability of resources: (1) permitting projects on a case-by-case basis without uniform requirements, (2) developing non-enforceable guidelines, and (3) enacting regulations.
subject: Preprints
  topic: section
subject: Water Reuse
  topic: keywords
subject: direct potable reuse
  topic: keywords
subject: regulations
  topic: keywords
subject: Environmental Engineering
  topic: disciplines
creator: Anya Kaufmann
creator: Brian Pecson
creator: Sarah Philo
creator: Daniel Druhora
creator: Shane Trussell
creator: Amy Childress
rights: Copyright (c) 2026 Anya Kaufmann, Brian M. Pecson, Sarah E. Philo, Daniel Druhora, Shane Trussell, Amy E. Childress https://creativecommons.org/licenses/by/4.0
date: 2026-06-27
publication date: 2026-06-27
doi: 10.31224/7449