King Abdullah University of Science and Technology

The Model-based Predictive Control (MPC) has gained popularity in the field of multiphase drives because of its high degree of flexibility and its robust dynamic response. However, the performance of Asymmetrical six-phase Machine (A6M) with low secondary subspace impedance has been reported to suffer from poor current quality under conventional MPC. Although, the Virtual Voltage Vectors (VVVs) concept has been proposed to address this issue, the current waveforms still exhibit high ripple content in the low-speed operating region. Although existing solutions in the literature manage to optimize the VVV amplitude based on loading conditions, they fall short in addressing the low-speed region with Light/high loading conditions. The proposed technique in this paper aims to improve the machine performance under low speeds over the full loading range by synthesizing the so called Optimized Virtual Voltage Vectors (OVVV). These OVVV are synthesized with variable amplitude based on the Constant Flux Scenario (CFS). The same concept is also extended to enhance the drive efficiency by adopting the Variable Flux scenario (VFS) in low-speed light-loading region. The proposed OVVV approaches show a significant enhancement in terms of current quality, current tracking, losses and torque ripple reduction as well as increased loading capability. The effectiveness of the proposed OVVV approach for different operating conditions is experimentally validated using a 1.5 Hp prototype A6M.

Wastewater treatment plants (WWTPs) are major contributors to global anthropogenic greenhouse gas (GHG) emissions, with China ranks among the leading emitters. In the context of China's "dual-carbon" journey, precision quantification and predictive forecasting of GHG fluxes, particularly methane (CH4) and nitrous oxide (N2O)—are crucial for developing advanced mitigation strategies of WWTPs. To accurately assess GHG emissions, this study firstly introduced customized emission factors (EFs) to precisely evaluate the GHG emissions of a full - scale A2O - based WWTP in Beijing. This approach addressed the overestimation of emissions when using the IPCC's standard EFs. Additionally, the study proposed machine learning (ML) techniques to predict GHG fluxes based on routine wastewater quality parameters. Specifically, Long Short-Term Memory (LSTM) and Random Forest (RF) models showed the strong performance in predicting CH4 and N2O emissions, respectively. Moreover, our findings revealed distinct spatiotemporal patterns of GHG emission: CH4 emissions peak during the summer solstice, while N2O emissions rise during the winter months. For the first time, this study identified the nitrification biofilter in the advanced treatment unit as a significant direct source of N2O emissions. Eventhough, indirect CO2 emissions account for a dominant 57%-90% of the total GHG emissions. Scenario analyses revealed a strategic mitigation approach. Energy conservation emerged as the most effective measure, capable of reducing emissions by 23.41%, followed by heat recovery, which could cut emissions by 10.15%. In practical applications, improving energy efficiency is of utmost importance in real - world mitigation strategies. This highlights the significance of integrated approaches for achieving the sustainable development of WWTPs in the "dual - carbon" background.

Metal catalysts for the CO2 reduction reaction (CO2RR) face challenges such as high cost, limited durability, and environmental impact. Although various structurally diverse and functional metal‐free catalysts have been developed, they often suffer from slow kinetics, low selectivity, and nonrecyclability, significantly limiting their practical applications. In this study, we introduce a recyclable nonmetallic polymer material (vitrimer) as a catalyst for a new platform in contact‐electrocatalysis. This approach harnesses the contact charges generated between water droplets and vitrimer to drive CO2RR, achieving methanol selectivity exceeding 90%. The imine groups within the vitrimer play a dual role, facilitating CO2 adsorption and enriching friction‐generated electrons, thereby mediating efficient electron transfer between the imine groups and CO2 to promote CO2RR. After 84 h of CO2RR, the system achieved a methanol production rate of 13 nmol·h⁻¹, demonstrating the excellent stability of the method. Moreover, the vitrimer retains its high‐performance electrocatalytic activity even after recycling. Mechanistic studies reveal that, compared to traditional metal catalysts, the N─O bond in the imine, which adsorbs the key intermediate *OCH3, breaks more readily to produce methanol, resulting in enhanced product selectivity and yield. This efficient and environmentally friendly contact‐electroreduction strategy for CO2 offers a promising pathway toward a circular carbon economy by leveraging natural water droplet‐based contact‐electrochemistry.

Despite recent progress in 3D covalent organic frameworks (3D‐COFs), their design and synthesis still pose significant challenges, mainly due to a limited mechanistic understanding of their synthesis. Herein, a linker exchange approach has been utilized to synthesize a series of new 3D‐COFs by first preparing an imine‐linked 3D‐COF followed by exchanging with selected linear diamine linkers. This approach can be widely applicable to different types of diamines, enabling rational‐designed synthesis of 3D frameworks that are previously inaccessible via direct polymerization in a one‐pot reaction. Mechanistic aspects associated with the improved 3D‐COF synthesis via the linker exchange approach, are investigated by density functional theory calculations, in which the possibility of the departure of the leaving linker is a spontaneous process with a decrease in enthalpy. Catalytic and computational results revealed that incorporating benzoxazole moiety into the 3D‐COF frameworks enables a significant increase in the capability of visible‐light‐driven catalysis. The overall findings of the present study will pave the way toward the development of 3D‐COFs with tunable structures and functions for other promising and challenging applications.

Despite the rapid efficiency increase, tin halide perovskite solar cells are significantly behind their lead‐based counterpart, with the highest reported efficiency of 15.38%. The main reason for this large difference is attributed to the instability of Sn²⁺, which easily oxidizes to Sn⁴⁺, creating Sn vacancies and increasing the open‐circuit voltage loss. In this work, we implemented tin thiocyanate (Sn(SCN)2) as an additive for passivating the bulk defects of a germanium‐doped tin halide perovskite film. Adding Sn²⁺ and SCN⁻ ions reduces the Sn and iodine vacancies, limiting non‐radiative recombination and favoring longer charge‐carrier dynamics. Moreover, the addition of Sn(SCN)2 induces a higher film crystallinity and preferential orientation of the (l00) planes parallel to the substrate. The passivated devices showed improved photovoltaic parameters with the best open‐circuit voltage of 0.716 V and the best efficiency of 12.22%, compared to 0.647 V and 10.2% for the reference device. In addition, the passivated solar cell retains 88.7% of its initial efficiency after 80 min of illumination under 100 mW cm‐2 and is substantially better than the control device, which reaches 82.6% of its initial power conversion efficiency only after 30 min. This work demonstrates the passivation potential of tin‐based additives, which combined with different counterions give a relatively large space of choices for passivation of Sn‐based perovskites.

The attenuation property of earth media can lead to amplitude loss and phase dispersion effects on multicomponent elastic data. Ignoring their impacts during imaging process will result in blurred and dislocated imaging profiles. To accurately characterize the attenuation effect in viscoelastic media, we first derive a new viscoelastic wave equation with decoupled fractional Laplacians. Numerical tests show that the proposed wave equation can accurately capture the propagation characteristics of seismic waves in viscoelastic media. Furthermore, our new wave equation can be modified to yield a decomposition equation, which enables the separated propagation of vector P‐ and S‐wavefields. Building on the derived viscoelastic forward propagator, we develop a stable Q ‐compensated viscoelastic reverse‐time migration approach. Usually, the inner product imaging condition is used to obtain imaging results. However, the result of inner product is affected by the angle between vectors, making the resulting images contaminated with the angle information. In this article, we introduce the magnitude‐ and sign‐based imaging condition for PS imaging and conduct a cross‐correlation imaging condition based on the scalar P‐wavefield for PP imaging. In contrast to the inner product imaging condition, our imaging scheme is capable of overcoming the contamination by the angle information. In addition, high‐frequency noise is amplified exponentially during the attenuation compensation process, affecting imaging precision. To address this problem, we derive the stabilized Q ‐compensation wave equations explicitly for vector‐ and scalar wavefields. Numerical examples demonstrate that the proposed Q ‐compensated viscoelastic reverse‐time migration method can effectively correct the viscoelastic effects, yielding high‐quality PP‐ and PS‐imaging profiles.

We define the operator $D^+_VD^-_W:=\Delta _{W,V}$ on the one-dimensional torus $\mathbb {T}$. Here, W and V are functions inducing (possibly atomic) positive Borel measures on $\mathbb {T}$, and the derivatives are generalized lateral derivatives. For the first time in this work, the space of test functions $C^{\infty }_{W,V}(\mathbb {T})$ emerges as the natural regularity space for solutions of the eigenproblem associated with $\Delta _{W,V}$. Moreover, these spaces are essential for characterizing the energetic space $H_{W,V}(\mathbb {T})$ as a Sobolev-type space. By observing that the Sobolev-type spaces $H_{W,V}(\mathbb {T})$ with additional Dirichlet conditions are reproducing kernel Hilbert spaces, we introduce the so-called W-Brownian bridges as mean-zero Gaussian processes with associated Cameron-Martin spaces derived from these spaces. This framework allows us to introduce W-Brownian motion as a Feller process with a two-parameter semigroup and càdàg sample paths, whose jumps are subordinated to the jumps of W. We establish a deep connection between W-Brownian motion and these Sobolev-type spaces through their associated Cameron-Martin spaces. Finally, as applications of the developed theory, we demonstrate the existence and uniqueness of related deterministic and stochastic differential equations.

Uncalibrated global hydrological models are primarily used to inform projections of flood and drought changes under global warming and their impacts, but it remains unclear how model calibration might benefit these projections. Using the Yangtze River Basin as a case study, we compare projected changes in flood and drought frequencies and their impacts—area, population, and gross domestic product affected—at various warming levels, from uncalibrated and calibrated simulations with the Community Water Model. These projections are driven by 10 General Circulation Models (GCMs) from Coupled Model Intercomparison Project Phase 6, within the Inter‐Sectoral Impact Model Intercomparison Project framework. Calibration significantly improves simulated discharge, yet the impact of calibration under climate change on projected increases in flood frequency and their associated impacts is minor, in contrast to its notable role in drought projections. We further quantify the relative contribution of GCMs, emission scenarios, and calibration approaches to the projected impacts, finding that GCMs primarily drive projected flood changes, while emission scenarios and calibration contribute more significantly to the variance in drought projections after 2050. The differing sensitivities to calibration are attributed to the dominance of extreme precipitation in flood generation and the influence of long‐term evapotranspiration trends on drought occurrence. The findings imply that future projections of relative changes in flood frequency and risks based on uncalibrated hydrological models are likely still quite reliable for warm and humid regions. However, careful calibration and model improvement is crucial for enhancing the reliability of future drought impact assessments.

Single-crystal SrTiO3 (STO) is an ultrahigh-κ insulator with an expected low interface trap density that promises high breakdown strength and has great potential to boost the reliability of two-dimensional (2D) field-effect transistors (FETs). Here we provide a detailed study of the performance, stability, and reliability of MoS2 FETs with STO gate insulators. Most importantly, we observe a small hysteresis for electric fields up to 8 MV cm−1 at a sweep rate range spanning 0.01−1 V s −1 and sweep times of kiloseconds. Interestingly, the hysteresis is counterclockwise and bias temperature instability (BTI) is often anomalous, both likely caused by the diffusion of oxygen vacancies. We also show that the hysteresis dynamics in MoS2/STO FETs are reproducible over a long time, which underlines their high reliability. Our findings show that STO is a promising gate insulator that might help overcome critical obstacles to highly reliable 2D nanoelectronics.

Since the recognition of the area of asymmetric synthesis in 2000, there has been a tremendous focus on the development of heterogeneous catalysts for asymmetric synthesis. Porous organic polymers (POPs) have emerged in recent years as inextricable materials of high physicochemical and hydrolytic stabilities, permitting infinite possibilities to modulate and tune reactivity, engineer porosity, regulate spatial environments and pore attributes, and manoeuver material transport. With a diligent design of building blocks and the exploitation of organic reactions judiciously, the synthesis of POPs with BET surface areas of the order of a few thousand cm3/g has been demonstrated. The incorporation of reactive functional groups and chiral centres into the porous matrices of polymers offers opportunities to conduct asymmetric synthesis. Very high enantioselectivities of the order of 99% ee have been exemplified in the reactions mediated by chiral POPs (CPOPs). The design‐driven tunability of POPs allows the development of catalytic materials for targeted applications in a tailor‐made fashion. This review, while placing the development of chiral materials for asymmetric synthesis in the right perspective, delves into different design principles to pave the way for continued research on futuristic CPOP materials by a creative design, limited by one’s imagination, for heretofore unprecedented results.

Hexameric helicases are nucleotide-driven molecular machines that unwind DNA to initiate replication across all domains of life. Despite decades of intensive study, several critical aspects of their function remain unresolved¹: the site and mechanism of DNA strand separation, the mechanics of unwinding propagation, and the dynamic relationship between nucleotide hydrolysis and DNA movement. Here, using cryo-electron microscopy (cryo-EM), we show that the simian virus 40 large tumour antigen (LTag) helicase assembles in the form of head-to-head hexamers at replication origins, melting DNA at two symmetrically positioned sites to establish bidirectional replication forks. Through continuous heterogeneity analysis², we characterize the conformational landscape of LTag on forked DNA under catalytic conditions, demonstrating coordinated motions that drive DNA translocation and unwinding. We show that the helicase pulls the tracking strand through DNA-binding loops lining the central channel, while directing the non-tracking strand out of the rear, in a cyclic process. ATP hydrolysis functions as an ‘entropy switch’, removing blocks to translocation rather than directly powering DNA movement. Our structures show the allosteric couplings between nucleotide turnover and subunit motions that enable DNA unwinding while maintaining dedicated exit paths for the separated strands. These findings provide a comprehensive model for replication fork establishment and progression that extends from viral to eukaryotic systems. More broadly, they introduce fundamental principles of the mechanism by which ATP-dependent enzymes achieve efficient mechanical work through entropy-driven allostery.

Understanding the relative influence of immigration and species sorting in wastewater treatment systems is essential, as bacteria in influent wastewater can significantly impact treatment system functionality. This study investigated the contribution of immigration to the community assembly of different-sized microbial aggregates in a full-scale aerobic granular sludge (AGS) system using genome-resolved metatranscriptomics. Our novel analysis revealed that negative-net-growth-rate populations, which persist due to immigration, can exhibit substantial activity and potentially contribute to the AGS system’s functionality. The results also highlighted that sulfate-reducing and fermenting bacteria, along with some nitrifiers and glycogen-accumulating organisms (GAOs), were more active in the influent wastewater, serving as a continuous source of both beneficial and competing immigrants to the AGS system. Granular sludge (size >0.2 mm) demonstrated a robust capacity to resist immigration effects from competing immigrants, whereas flocculent sludge (size <0.2 mm) was more susceptible. Importantly, flocculent sludge harbored functional microbial groups such as active nitrifiers and fermentative polyphosphate-accumulating organisms (PAOs) belonging to Ca. Phosphoribacter, while granular sludge enriched for active conventional PAOs such as Ca. Accumulibacter. These findings provide valuable insights for engineers to design and operate AGS systems by optimizing microbial aggregate sizes and emphasizing the importance of influent microbial characterization in the design of wastewater treatment plants to enhance the functionality and activity of AGS systems.

Reconfigurable intelligent surfaces (RISs) suffer from high switch costs and complex switch integration with electromagnetic (EM) structures. In this article, we propose solutions to both of the abovementioned problems by screen printing of low-cost vanadium-dioxide (VO2) switches. The VO2 ink has been prepared in-house and batches of switches have been printed and integrated with the resonator elements. Screen printing is suitable for low-cost and large-area manufacturing, and thus, these VO2 switches are a fraction of the cost of commercial switches. Furthermore, the printing of these switches directly on metal patterns negates the need for any minute soldering of the switches. To avoid the complications of multilayer printing and realizing the RIS without vias, the resonators and the biasing lines are realized on a single layer. However, this introduces the challenge of interference between the biasing lines and the resonators. We address this by integrating bias lines into the resonator design. By adjusting the unit cell periodicity and the dimension of the H-shaped resonator, we achieve a 220∘–170∘ phase shift from 23.5 to 29.5 GHz covering both 5G n257 and n258 bands. Inside the wide bandwidth, the maximum reflection magnitude in the on state is 74% and is 94% in the off state. The RIS array comprises 20 × 20 unit cells (4.54λ2 × 4.54λ2 at 29.5 GHz). Each column of unit cells is serially connected to a current biasing circuit. To validate the array’s performance, we conduct full-wave simulations as well as near-and far-field measurements. The fully printed array shows signal enhancements of around 8–10 dB, validating its effectiveness.

The upcoming sixth-generation (6G) communication system is set to operate in the Sub-THz band, which could provide substantially higher communication capacity. Meanwhile, the fifth-generation (5G) systems have already started to operate in the millimeter-wave (mm-Wave) bands. Therefore, dual-band antennas, which can operate for both 5G and 6G bands simultaneously, with circularly polarized (CP) radiation, are attractive for future wireless communication. However, achieving dual-band CP radiations, at frequencies as high as 100 GHz, is quite challenging. In this work, a novel dual-band, CP, eight-port multiple-input multiple-output (MIMO) antenna is presented. The proposed CP MIMO configuration comprises of orthogonally placed 4-element shared-aperture Vivaldi antenna and a linear-to-dual-circular polarization (LDCP) converter, operating at the frequencies of 40 GHz (5G mm-Wave band) and 110 GHz (6G sub-THz band). The shared-aperture Vivaldi antenna, proposed as the excitation source for the LDCP converter, demonstrates high gain, compact size, and end-fire linear polarization (LP) radiation for dual-wideband operation (5G/6G). The designed dual-band LDCP converter has a compact unit cell size (0.16λ at 40 GHz) and works for both horizontal and vertical polarizations. The fabricated prototype demonstrates a measured LHCP bandwidth from 39 to 45 GHz (14.2%) for the 5G band, and an RHCP bandwidth from 98 to 110 GHz (11.5%) for the 6G band. For the first time, we demonstrate a dual-band, dual-CP eight-port MIMO antenna with polarization (LHCP/RHCP) and spatial (30° incidence angle difference) diversity at the 5G/6G bands, making it a suitable candidate for future integrated 5G/6G communication systems.

Thin-film interferometry (type: Fabry–Pérot) with visible white-light illumination can detect sub-nanometer changes in optical path and, therefore, be utilized to study the thickness and refractive index (RI) of nano-confined fluids at a typical resolution ≤ λ/10⁴. This type of white light interferometry is understandably at the core of the surface forces apparatus technique, where two mica sheets with identical thickness (e.g., 1–5 µm) are used to confine a fluid between their surfaces at nanometer separations and measure surface forces as a function of surface separation. In this context, the absolute accuracy of white light interferometry has received little attention historically, although accuracy is the key limiting factor for certain types of experiments, such as the measurements of RI of nanometer thin fluid films. At its root, the accuracy of interferometric RI measurement critically depends on exactly detecting secondary spectral modulations. The following spectral evaluation requires a theory based on an interferometer definition that consists of accurate values for thickness and dispersive RI for all optical layers involved. This work aims at complementing the partially existing literature toward a systematic treatment of the most relevant accuracy-limiting factors; in addition, systematic errors in the interferometer definition include the choice of dispersive RI mathematical model or other experimentally variable factors like the mechanical deformations occurring inside the interferometer under the influence of surface forces. We conclude that an accurate optical description of the layers contributing most to the optical path (e.g., mica surfaces) is currently the leading source of systematic error and that the present methodology of thin film interferometry is not sufficiently accurate to detect and quantify a change of density <10% in a nanometer confined fluid.

Semiconductor lasers hold significant promise for space laser communication. However, excessive radiation in space can cause laser failures. In principle, quantum dot (QD) lasers are more radiation‐resistant than traditional semiconductor lasers because of their superior carrier confinement and smaller active regions. However, the multifaceted nature of radiation effects on QDs result in ongoing controversies. In this work, comprehensive radiation tests under simulated space conditions on InAs/GaAs QDs and lasers is conducted to validate their performance. The results reveal that InAs/GaAs QDs with filling factors exceeding 50% exhibit enhanced radiation hardness. The linewidth enhancement factor (LEF) of well‐designed QD lasers remains remarkably stable and nearly zero, even under proton irradiation at a maximum fluence of 7 × 10 ¹³ cm ⁻² , owing to their intrinsic insensitivity to irradiation‐induced defects. These QD lasers demonstrate an exceptional average relative intensity noise (RIN) level of −162 dB Hz ⁻¹ , with only a 1 dB Hz ⁻¹ increase at the highest fluence, indicating outstanding stability. Furthermore, the lasers exhibit remarkable robustness against optical feedback, sustaining stable performance even under a feedback strength as high as −3.1 dB. These results highlight the critical advantages of QD lasers for space laser communication applications, where high reliability and resilience to radiation and environmental perturbations are essential.

This study conducts a comprehensive metabolomic profiling of the Zygophyllum (Z) coccineum plant, a halophyte prevalent in Saudi Arabia and Egypt, employing gas chromatography-mass spectrometry (GC–MS), liquid chromatography-mass spectrometry (LC–MS), and nuclear magnetic resonance (NMR) spectroscopy. Recognizing the plant’s significance in traditional medicine, we explore its adaptative mechanisms and potential pharmacological applications through the identification of metabolites. Various solvents, namely acetonitrile–water (AcW), isopropanol-methanol–water (IMW), and methanol–water (MW) were utilized for metabolite extraction. Our results reveal a diverse spectrum of metabolites, including amino acids, sugars, organic acids, alkaloids, steroids, and terpenoids, with significant variations in extraction efficiency and metabolite composition across solvents. Identified metabolites indicate the reason for using Z. coccineum leaves as traditional medicine in Saudi Arabia, and Egypt because of consist of several phytochemical metabolites used for the treatment of diabetes, kidney diseases, cancer, urinary tract secretions, dental pain, tumors, stomach pain, smallpox, asthma, rheumatism, gout, infections, hypertension, burns, and blood pressure, found in the extractions by the three different solvents on the analysis through GC/LC–MS spectrometry. Identified metabolites and their statistical analyses, including principal component analysis (PCA) and variable importance in projection (VIP), indicated that AcW in GC–MS provides a superior number of metabolites, clustering, and variability statistical analysis, while MW excels in LC–MS metabolic profiling and their statistical analysis compared to other solvents. These multilayers of solvents and analytical techniques approach underscores the importance of solvents in enhancing metabolomic studies, thereby facilitating a deeper understanding of the phytochemicals within Z. coccineum and their medicinal potential. Enhancing our knowledge of the plant’s metabolomics may inform future applications in pharmacology and agriculture.

In layered two-dimensional (2D) perovskites, the inorganic perovskite layers sandwiched between cation spacers create quantum well (QW) structures, showing large exciton binding energies that hinder the efficient dissociation of excitons into free carriers. This leads to poor carrier transport properties and low-performance light-conversion-based devices, and the direct understanding of the underlying physics, particularly concerning surface states, remains extremely difficult, if not impossible, due to the challenges in real-time accessibility. Here, we utilized four-dimensional scanning ultrafast electron microscopy (4D-SUEM), a highly sensitive technique for mapping surface carrier diffusion that diverges from those in the bulk and substantially affects material properties. We directly visualize photo-generated carrier transport over both spatial and temporal dimensions on the top surface of 2D perovskites with varying inorganic perovskite layer thicknesses ( n = 1, 2, and 3). The results reveal the photo-induced surface carrier diffusion rates of ~30 cm ² ·s ⁻¹ for n = 1, ~180 cm ² ·s ⁻¹ for n = 2, and ~470 cm ² ·s ⁻¹ for n = 3, which are over 20 times larger than bulk. This is because charge carrier transmission channels have much wider distributions on the top surface compared to the bulk, as supported by the Density Functional Theory (DFT) calculations. Finally, our findings represent the demonstration to directly correlate the discrepancies between surface and bulk carrier diffusion behaviors, their relationship with exciton binding energy, and the number of layers in 2D perovskites, providing valuable insights into enhancing the performance of 2D perovskite-based optoelectronic devices through interface engineering.

Employing first‐principles calculations and the non‐equilibrium Green's function method, a hexa‐peri‐hexabenzocoronene nanoflake is investigated on an armchair graphene nanoribbon. It turns out that a current modulation of up to 25% can be achieved by twisting of the nanoflake due to modulated scattering as a consequence of changes in the orbital overlap. The effect of twist gating is reminiscent of current control by electrostatic gating with a large variety of potential applications.

We propose a method for estimation of a globally constant but unknown delay $\tau >0$ in a negative feedback loop, where only an upper bound on the possible values of $\tau$ is given. Also the initial datum is not revealed. The method is based on detecting the decay rate of the solution throughout its evolution and guarantees that the estimate converges to the true value of $\tau$ asymptotically for large times. In a second step, the estimated delay is used to adaptively control the sensitivity (feedback gain) of the loop with the goal of reaching optimal rate of convergence towards equilibrium. We stress that our approach is distinguished from traditional feedback control methods by leveraging the system’s sensitivity as a control parameter to achieve equilibrium. In the second part of the paper we adapt the method to estimate unknown delay and control the sensitivity in a linear opinion formation model. Here the estimation of the delay is based on the decay properties of the quadratic fluctuation of the agents’ opinions, employing appropriate approximations and some heuristic arguments. In both cases we present numerical examples illustrating the performance of the method.