Ambient Perturbations Research Articles

A REVIEW OF CONTROL METHODS FOR QUADROTOR UAV

This study reviews numerous control approaches utilized to address various issues encountered by unmanned aerial vehicles (UAVs). Specifically, focusing on the quadrotor system. Due to its versatility and compact size, quadrotors have gained popularity as UAVs in recent decades. Quadrotors face challenges such as ambient disturbances, impediments, non-parametric and parametric perturbations while performing tasks. Consequently, a robust and efficient control system is essential for such a system to ensure the stability and enhance their performance. It should be noted that, in this review, we have examined and analyzed the most recent highly cited papers selected from esteemed journals and magazines renowned for their exceptional quality and reputation.

The Secondary Sex Ratio and Male Mortality at Pre-Reproductive Ages: A Test of Selection In Utero.

The secondary sex ratio (i.e., the ratio of male to female live births; hereafter referred to as the SSR) falls in populations encountering ambient stressors. Much theory and some empirical work indicates that males born to low SSR cohorts may be "positively selected" in that excess culling in utero may correspond with greater than expected survival among live-born males in that cohort. We extend prior work by testing, in historical Utah, whether the SSR varies positively with male mortality at pre-reproductive ages. This study uses detailed records from the Utah Population Database to focus on Utahns born 1850-1940. We use rigorous time-series methods, which control for strong secular declines in mortality as well as ambient perturbations shared equally among males and females, to investigate the male culling inference. We observe a positive relation between the SSR and male mortality during youth (i.e., 5 to < 20 years; p < 0.05) but not in infancy or early childhood. In this historical population, the SSR appears to gauge hardiness of surviving male cohorts. However, whether the high fertility and/or family structure context of Latter-day Saints in historical Utah explains the age-specific pattern of male mortality warrants further scrutiny.

Dynamics and optimal therapy of a stochastic HTLV‐1 model incorporating Ornstein–Uhlenbeck process

As the prevalence of viral infection in body, human T‐cell leukemia virus type 1 (HTLV‐1) is receiving increasing attention. Research on the corresponding virus models is of great significance to tackle the challenges of understanding HTLV‐1 development and treatment. This paper focuses on the dynamic analysis for a stochastic model with nonlinear cytotoxic T lymphocyte (CTL) response, which is driven by Ornstein–Uhlenbeck (OU) process to model the progression of HTLV‐1 in vivo. Rich dynamic behaviors such as the extinction of infected CD4+ T cells (ITCs), stationary distribution (SD), probability density, and finite‐time stability (FTS) of the model are established to reveal the interaction of cell populations. The optimal therapeutic strategy based on the cost‐benefit viewpoint is further obtained. Finally, illustrative numerical simulations are represented to corroborate the effectiveness of treatment and the ambient perturbation's impact that strengthening the noise strength can lead to rapid virus clearance.

On the settling of a spherical particle in slightly perturbed ambient fluid

Direct numerical simulations of the settling of a spherical particle under the action of gravity in a slightly perturbed ambient fluid have been performed. The ambient perturbations are generated using a synthetic turbulence inflow generator method, and their length scale and intensity are varied to study their influence on the particle motion. The Galileo number is 151 and the solid-to-fluid density ratio is 1.5, so that in the absence of perturbations, the particle settles following a steady vertical trajectory. It has been found that the ambient perturbations trigger the formation of double-threaded vortical structures in the wake of the particle. These structures resemble those that appear in the oblique oscillating regime that is found in the absence of perturbations at higher Galileo numbers. Due to the flow perturbations the particle is pushed randomly in all directions, and this results in a combination of slow lateral drifts along fixed directions and relatively fast excursions in random directions. The particle response has been characterized using probability density functions of the velocity in the cross-plane and persistence probability. The slow drifts are strongly influenced by the size of the perturbations and by the rotational motion of the particle, while the intensity of the perturbations seems to play a minor role.

Electron Energization by Inertial Alfvén Waves in Density Depleted Flux Tubes at Jupiter

AbstractJuno satellite observations have illustrated substantial examples of broadband electron energization up to 105–106 eV levels. In order to explain these observations, we use a hybrid gyrofluid kinetic‐electron model in an untilted dipolar topology to illustrate energization to high levels in weak current conditions by inertial Alfvén waves close to the Jupiter ionosphere for ambient plasma densities and magnetic field perturbations inferred from Juno satellite observations. The key to the high energization is the extremely low densities evident in the observations which necessitates the acceleration of electrons to very high velocities in order to carry the field‐aligned current.

Non-Hermitian-enhanced topological protection of chaotic dynamics in one-dimensional optomechanics lattice

Chaotic dynamics in microcavity have promoted massive discoveries and applications ranging from decoherence suppression to broadband optical devices. However, a chaotic light source on the chip is more likely to suffer from the ambient randomness and perturbations than its bulk counterparts, vanishing chaotic dynamics. Topological protection provides a robust framework for manipulating the periodic wave dynamics, whereas the symmetric layout in topological protection poses a direct challenge to leveraging this notion in chaotic dynamics. Here, we discover that benefiting from an engineered exceptional point, the non-Hermitian-enhanced topological protection yields zero modes and switches the chaotic dynamics. As a result, this new effect significantly extends the topologically protected chaotic dynamics to a more general trivial phase beyond the constraint of the topological invariant. More importantly, the zero modes merit robust chaotic dynamics prevail with intentionally introduced perturbations. Moreover, we find that an extended photonics lattice composed of an increased number of microcavities not only offers a more robust topological protection but also can delay the chaos generation, providing a new degree of freedom to harness the chaos generation. This study presents a promising approach for robust on-chip chaotic light sources and advances various explorations on multibody non-Hermitian physics.

Cross-Axis Dynamic Field Compensation of Optically Pumped Magnetometer Arrays for MEG

We present dynamic field compensation (DFC), whereby three-axis field measurements from reference magnetometers are used to dynamically maintain null at the alkali vapor cells of an array of primary sensors that are proximal to a subject's scalp. Precision measurement of the magnetoencephalogram (MEG) by zero-field optically pumped magnetometer (OPM) sensors requires that sensor response is linear and sensor gain is constant over time. OPMs can be operated in open-loop mode, where the measured field is proportional to the output at the demodulated photodiode output, or in closed-loop, where on-board coils are dynamically driven to maintain the internal cell at zero field in the measurement direction. While OPMs can be operated in closed-loop mode along all three axes, this can increase sensor noise and poses engineering challenges. Uncompensated fluctuations in the ambient field along any statically nulled axes perturb the measured field by tipping the measurement axis and altering effective sensor gain – a phenomenon recently referred to as cross-axis projection error (CAPE). These errors are particularly problematic when OPMs are allowed to move in the remnant background field. Sensor gain-errors, if not mitigated, preclude precision measurements with OPMs operating in the presence of ambient field fluctuations within a typical MEG laboratory. In this manuscript, we present the cross-axis dynamic field compensation (DFC) method for maintaining zero field dynamically on all three axes of each sensor in an array of OPMs. Together, DFC and closed-loop operation strongly attenuate errors introduced by CAPE. This method was implemented by using three orthogonal reference sensors together with OPM electronics that permit driving each sensor's transverse field coils dynamically to maintain null field across its OPM measurement cell. These reference sensors can also be used for synthesizing 1st-gradient response to further reduce the effects of fluctuating ambient fields on measured brain activity and compensate for movement within a uniform field. We demonstrate that, using the DFC method, magnetic field measurement errors of less than 0.7% are easily achieved for an array of OPM sensors in the presence of ambient field perturbations of several nT.

Fiber-Integrated Tamm Plasmon Polariton System

Plasmonic devices have witnessed their success in optical applications due to the boosted light-matter interactions in the subwavelength scale. Among them, optical fiber-based configurations offer excellent portability and accessibility. Here, we report a novel kind of plasmonic fiber devices by introducing Tamm plasmon polaritons (TPPs) into the fiber-optic community. TPPs are cavity modes confined between a distributed Bragg reflector (DBR) and a metallic layer, resulting in high quality factor ∼100, strong field-intensity enhancement of 92, immunity to ambient perturbations, and flexible tunability. As the fabrication process only requires thin-film deposition, fiber-based TPP system is relatively low-cost and high-repeatability. This scenario extends the scope of plasmonic devices and open up new perspectives for active and passive fiber-optic systems.

Multigenerational inspections of environmental thermal perturbations promote metabolic trade-offs in developmental stages of tropical fish

Global warming both reduces global temperature variance and increases the frequency of extreme weather events. In response to these ambient perturbations, animals may be subject to trans- or intra-generational phenotype modifications that help to maintain homeostasis and fitness. Here, we show how temperature-associated transgenerational plasticity in tilapia affects metabolic trade-offs during developmental stages under a global warming scenario. Tropical tilapia reared at a stable temperature of 27 °C for a decade were divided into two temperature-experience groups for four generations of breeding. Each generation of one group was exposed to a single 15 °C cold-shock experience during its lifetime (cold-experienced CE group), and the other group was kept stably at 27 °C throughout their lifetimes (cold-naïve CN group). The offspring at early life stages from the CE and CN tilapia were then assessed by metabolomics-based profiling, and the results implied that parental cold-experience might affect energy provision during reproduction. Furthermore, at early life stages, progeny may be endowed with metabolic traits that help the animals cope with ambient temperature perturbations. This study also applied the feature rescaling and Uniform Manifold Approximation and Projection (UMAP) to visualize metabolic dynamics, and the result could effectively decompose the complex omic-based datasets to represent the energy trade-off variability. For example, the carbohydrate to free amino acid conversion and enhanced compensatory features appeared to be hypothermic-responsive traits. These multigenerational metabolic effects suggest that the tropical ectothermic tilapia may exhibit transgenerational phenotype plasticity, which could optimize energy allocation under ambient temperature challenges. Knowledge about such metabolism-related transgenerational plasticity effects in ectothermic aquatic species may allow us to better predict how adaptive mechanisms will affect fish populations in a climate with narrow temperature variation and frequent extreme weather events.

Instability and turbulent relaxation in a stochastic magnetic field

An analysis of instability dynamics in a stochastic magnetic field is presented for the tractable case of the resistive interchange. Externally prescribed static magnetic perturbations convert the eigenmode problem to a stochastic differential equation, which is solved by the method of averaging. The dynamics are rendered multi-scale, due to the size disparity between the test mode and magnetic perturbations. Maintaining quasi-neutrality at all orders requires that small-scale convective cell turbulence be driven by disparate scale interaction. The cells in turn produce turbulent mixing of vorticity and pressure, which is calculated by fluctuation-dissipation type analyses, and are relevant to pump-out phenomena. The development of correlation between the ambient magnetic perturbations and the cells is demonstrated, showing that turbulence will ‘lock on’ to ambient stochasticity. Magnetic perturbations are shown to produce a magnetic braking effect on vorticity generation at large scale. Detailed testable predictions are presented. The relations of these findings to the results of available simulations and recent experiments are discussed.

Sensing characteristics of grating assisted counterpropagating cladding modes in optical fibers.

In this paper, using full vector modal field analysis, we present physical parameter sensing, e.g., temperature, axial strain, bulk refractive index, and affinity sensing characteristics of counterpropagating cladding modes in optical fibers. Counterpropagating cladding modes (HEmn) are considered to be excited by resonant power coupling from the fundamental core mode using a suitably designed fiber Bragg grating (FBG). We show that for such couplings, the bandwidths of reflection spectra are much smaller than those obtained for conventional core mode reflecting FBGs. Next, we also show that the reflection bandwidth increases linearly with increasing grating strength, whereas it decreases exponentially with increasing grating length. The reflection spectra of such FBGs, as a function of different ambient physical perturbation parameters, are obtained, and then the grating sensitivity corresponding to those parameters is established. Interestingly, we have noticed that despite having the same evanescent field in the analyte region, unlike the long-period grating assisted co-propagating cladding modes (HEmn), the same cladding modes while propagating counter to the core mode are weakly sensitive to changes in the ambient refractive index. The reason behind this observation is discussed.

Monitoring Indoor People Presence in Buildings Using Low-Cost Infrared Sensor Array in Doorways.

We propose a device for monitoring the number of people who are physically present inside indoor environments. The device performs local processing of infrared array sensor data detecting people’s direction, which allows monitoring users’ occupancy in any space of the building and also respects people privacy. The device implements a novel real-time pattern recognition algorithm for processing data sensed by a low-cost infrared (IR) array sensor. The computed information is transferred through a Z-Wave network. On-field evaluation of the algorithm has been conducted by placing the device on top of doorways in offices and laboratory rooms. To evaluate the performance of the algorithm in varying ambient temperatures, two groups of stress tests have been designed and performed. These tests established the detection limits linked to the difference between the average ambient temperature and perturbation. For an in-depth analysis of the accuracy of the algorithm, synthetic data have been generated considering temperature ranges typical of a residential environment, different human walking speeds (normal, brisk, running), and distance between the person and the sensor (1.5 m, 5 m, 7.5 m). The algorithm performed with high accuracy for routine human passage detection through a doorway, considering indoor ambient conditions of 21–30 °C.

Axisymmetry breaking, chaos, and symmetry recovery in bubble film thickness profiles due to evaporation-induced Marangoni flows

Understanding the dynamics of evaporating thin liquid films is of practical and fundamental interest. Practically, this understanding is crucial for tuning bubble stability, while fundamentally thin films are an excellent platform to study the characteristics of evaporation-driven two-dimensional (2D) flows. Here, we experimentally study, across a wide range of volatile species concentrations (c0), the spatial and temporal dynamics of film thickness profiles [h(r, θ, t)] over bubbles in binary liquid mixtures subjected to evaporation-induced Marangoni flows. Initially, we probe the spatial structure and show that the spatial symmetry of the film thickness profiles is non-monotonic functions of volatile species concentration with profiles being axisymmetric for both very low (∼1%) and very high (∼90%) concentrations. The temporal evolution of the film thickness fluctuations reveals a similar non-monotonic dependence between the species concentration and the spatial prevalence of fluctuation stochasticity. At a tested intermediate species concentration of 50%, we observe a complete breakdown in spatial symmetry and obtain film thickness fluctuations that are chaotic everywhere in space with spatially invariant fluctuation statistics and rapidly decaying spatial correlation. The observed non-monotonic behavior is a result of the system sensitivity to ambient perturbations scaling as Δγc0(1 − c0)/μ, where Δγ is the difference in equilibrium surface tension between the two species in the mixture and μ is the dynamic viscosity. These insights along with the reported experimental setup serve as an excellent platform to further investigate evaporation-driven 2D chaotic flows.

Long-term estimates of ambient air pollution and perturbations in the peripheral blood transcriptome in a large Dutch twin cohort

Background/Aim Studying the internal exposome has the potential to provide insight into the biological pathways through which air pollutants affects disease risk. In this study we linked long-term estimates for seven air pollutants and their elemental composition to transcriptomics data collected in the Dutch Twin Register (NTR) cohort. In addition to standard regression techniques we exploited the twin design by comparing gene expression among pairs of monozygotic and dizygotic twins. Replication of findings will be conducted in the Dutch NESDA cohort. Methods In both discovery (NTR, n= 2438) and replication (NESDA, n= 2341) cohorts, long-term land use regression model estimates were generated for nitrogen oxides (NO2, NOx), particulate matter (PM2.5 (including elemental composition), PM2.5abs, PM10, PMcoarse), and ultrafine particles (UFP). Other covariates were assessed using geospatial methods or questionnaires. Gene expression was assessed using Affymatrix U219 arrays (n=44,241 probes). Multi-variable univariate mixed-effect models were used to assess the association between these air pollutants and the transcriptome. Functional analysis was conducted using DAVID (v6.8). Results In the NTR cohort long-term exposure to PM2.5 (and few of the other pollutants) was associated with 374 transcripts (Benjamini- Hochberg p&lt;0.05). Elemental Copper and Sulphur in PM2.5 significantly contributed to this signal. Associations were stronger among residents of less urban areas, with lower exposure levels, and weaker among men. Results were robust in a series of sensitivity analyses. Genes most significantly differentially expressed were ZNF791, BTBD1 and OSBPL8 (upregulated), and WIPF2 (downregulated). We observed strong evidence for enrichment of phosphoprotein and alternative splicing pathways. Twin-only models did not yield strong associations. Replication analyses in the NESDA cohort are ongoing. Conclusions Results from our analyses in the NTR cohort suggest a distinct PM2.5 signal in the peripheral blood transcriptome, primarily occurring in phosphoprotein and alternative splicing pathways.

Robust principal component analysis and support vector machine for detection of microcracks with distributed optical fiber sensors

Development of a method for distributed detection of microcracks on structural elements with very small crack opening displacements is described in this study. Robust principal component analysis (RPCA) and support vector machine (SVM) techniques were employed for denoising and classification of the signals. The objective was to detect microcracks in structural elements less than 30 µm in size. The viability of the method was accomplished by experiments involving a 15-meter steel beam with known microcracks. A distributed optical fiber sensor system based on the Brillouin scattering technology was employed for distributed measurement of strains along the length of the 15-m long beam. Distributed strain signals based on Brillouin based sensors possess inherent system noise and ambient perturbations which in turn reduce the signal-to-noise ratio of the measurements. Therefore, it is not possible to detect the smaller microcracks with small crack opening displacements. Smaller CODs are lost within the noisy distributed strain signal acquired by the Brillouin system. Undetected microcracks result in larger cracks, corrosion, and other anomalies with severe economical and safety ramifications.The method introduced for denoising and enhancement of the signal in the present study enables manifestation of the singularities on the distributed strain data and detection of microcracks. The significant component containing those singularities is effectively separated from the noise component by RPCA-based matrix decomposition. An SVM classifier with Gaussian kernel function was designed, through which the crack detections are realized by singular and nonsingular binary classification. The experimental results demonstrated that it was possible to detect microcracks with CODs as low as 23 µm without errors.

Distance versus Capillary Flow Dynamics-Based Detection Methods on a Microfluidic Paper-Based Analytical Device (μPAD).

In recent years, there has been high interest in paper-based microfluidic sensors or microfluidic paper-based analytical devices (μPADs) towards low-cost, portable, and easy-to-use sensing for chemical and biological targets. μPAD allows spontaneous liquid flow without any external or internal pumping, as well as an innate filtration capability. Although both optical (colorimetric and fluorescent) and electrochemical detection have been demonstrated on μPADs, several limitations still remain, such as the need for additional equipment, vulnerability to ambient lighting perturbation, and inferior sensitivity. Herein, alternative detection methods on μPADs are reviewed to resolve these issues, including relatively well studied distance-based measurements and the newer capillary flow dynamics-based method. Detection principles, assay performance, strengths, and weaknesses are explained for these methods, along with their potential future applications towards point-of-care medical diagnostics and other field-based applications.

Dynamic Physiological Phenotyping of Drought-Stressed Pepper Plants Treated With "Productivity-Enhancing" and "Survivability-Enhancing" Biostimulants.

The improvement of crop productivity under abiotic stress is one of the biggest challenges faced by the agricultural scientific community. Despite extensive research, the research-to-commercial transfer rate of abiotic stress-resistant crops remains very low. This is mainly due to the complexity of genotype × environment interactions and in particular, the ability to quantify the dynamic plant physiological response profile to a dynamic environment. Most existing phenotyping facilities collect information using robotics and automated image acquisition and analysis. However, their ability to directly measure the physiological properties of the whole plant is limited. We demonstrate a high-throughput functional phenotyping system (HFPS) that enables comparing plants’ dynamic responses to different ambient conditions in dynamic environments due to its direct and simultaneous measurement of yield-related physiological traits of plants under several treatments. The system is designed as one-to-one (1:1) plant–[sensors+controller] units, i.e., each individual plant has its own personalized sensor, controller and irrigation valves that enable (i) monitoring water-relation kinetics of each plant–environment response throughout the plant’s life cycle with high spatiotemporal resolution, (ii) a truly randomized experimental design due to multiple independent treatment scenarios for every plant, and (iii) reduction of artificial ambient perturbations due to the immobility of the plants or other objects. In addition, we propose two new resilience-quantifying-related traits that can also be phenotyped using the HFPS: transpiration recovery rate and night water reabsorption. We use the HFPS to screen the effects of two commercial biostimulants (a seaweed extract –ICL-SW, and a metabolite formula – ICL-NewFo1) on Capsicum annuum under different irrigation regimes. Biostimulants are considered an alternative approach to improving crop productivity. However, their complex mode of action necessitates cost-effective pre-field phenotyping. The combination of two types of treatment (biostimulants and drought) enabled us to evaluate the precision and resolution of the system in investigating the effect of biostimulants on drought tolerance. We analyze and discuss plant behavior at different stages, and assess the penalty and trade-off between productivity and resilience. In this test case, we suggest a protocol for the screening of biostimulants’ physiological mechanisms of action.

Performance and Applicability of Orbital Transfer with Bare Electrodynamic Tether

Electrodynamic tether technology is a novel way to perform spacecraft orbital transfers. This paper focuses on a bare electrodynamic tether (BEDT) system and evaluates its orbital transfer performance and mission applicability. A nonsingular dynamic model of the BEDT orbital transfer system is developed. In particular, the ambient perturbation forces, including the atmospheric drag and Earth oblateness effect, are taken into account. Numerical simulations are then performed to investigate the orbital transfer performance under various mission parameters involving the initial orbital altitude, initial orbital inclination, tether length, tether diameter, spacecraft mass, and power voltage. An orbital transfer scheme is designed to raise and regulate the orbit. Furthermore, to verify its practicability, the mission applicability of the BEDT system is analyzed for Ariane-4’s H10 upper stage by comparison with the conventional chemical propulsion method. Finally, the conclusions and some discussions are presented to support conducting BEDT-based orbital transfer mission planning in practice.

Evaluation of noise in measurements with speckle shearography

Abstract Speckle shearography has the advantage of allowing non-contact, full-field and high resolution measurements. Nevertheless, due to its nature and to its sensitivity to ambient perturbations, the measurements may present high levels of noise. The evaluation of the experimental noise is needed in order to assess the degree of accuracy of the measurements. This assessment is not straightforward since the measurements will involve resolving simultaneously the phase discontinuities and the phase fluctuations produced by the noise which are 2π wrapped. The phase discontinuities can be easily removed if the phase map is smooth and the phase jumps are not greater than 2π rad. However, this procedure cannot be directly applied for resolving the random phase fluctuations produced by the noise. In this work, a method is proposed to efficiently evaluate the noise in measurements with speckle shearography whenever it is in the range [−π, π]. The limits of the proposed method are assessed by applying it to phase maps with added noise, which are obtained through the numerical simulation of speckle shearography. The results show a very good evaluation of noise with low and moderate amplitudes. Finally, the proposed method is used to evaluate the experimental noise in rotation fields of a free-free aluminum beam measured with speckle shearography.

Simultaneous Measurement of Temperature and Pressure by Utilizing an Integrated Mach-Zehnder

A highly sensitive temperature and pressure sensor based on a cascade structure of an integrated Mach–Zehnder interferometer waveguide and an Fabry-Perot cavity is proposed and experimentally demonstrated. The waveguide is fabricated by the standard Planar Lightwave Circuit procedure, while the Fabry-Perot cavity is formed by a thin film layer made of a urethane-based UV-curable polymer. The ambient perturbations of temperature and pressure can be measured by monitoring the dip shifts of the Mach–Zehnder interference and the FP interference. The sensor can offer a high temperature sensitivity of ∼0.317 nm/°C and a pressure sensitivity of −199.0 pm/KPa. Such a cascaded sensor is the first step to approach to a fully-integrated dual-parameter sensor, which has not been reported yet within the scope of our knowledge. The proposed sensing system has promising applications in various conditions, such as stress environment, liquid condition and solid building.