Stability Parameters Research Articles

On possibility of anomalous microwave power absorption and gyrotron frequency sub-harmonics emission in X2-mode ECRH experiments at the TCV tokamak

In this paper, we analyze theoretically the low-threshold parametric decay instability (PDI) that can be excited at the tokamak à configuration variable (TCV tokamak, Lausanne, Switzerland) during X2 electron cyclotron resonance heating experiments producing a two-dimensionally localized upper hybrid (UH) wave and a daughter extraordinary wave running from the decay layer outward to the plasma edge. The primary instability is then saturated due to the cascade of secondary decays into two-dimensionally localized UH and ion Bernstein waves. The level of plasma microwave emission in the frequency range substantially below half the pump wave frequency and of anomalous power losses of the pump are predicted.

Poster 289: Impact of Graft Selection on Clinical Outcomes following Isolated MPFL Reconstruction in Adolescent and Young Adult Athletes

Objectives: Patellofemoral instability (PFI) commonly requires surgical intervention in adolescent and young adult athletes. However, the clinical impact of graft selection, which may vary amongst surgeons, has not been well studied. The purpose of this study was therefore to compare clinical outcomes, including recurrent instability reoperations and complications, of medial patellofemoral ligament reconstruction (MPFLR), based on graft type. Methods: Electronic medical records of patients who underwent primary MPFLR surgery for PFI over a 10-year period between 2010 and 2019 at a single center were retrospectively reviewed. Collected data included demographic, clinical, and radiologic parameters of instability and post-operative clinical outcomes. Exclusion criteria included concomitant extensor realignment procedures (tibial tubercle osteotomy, patellar tendon transfer procedures) and factors that would alter routine surgical indications or technical approaches, such as fixed or syndromic PFI, osteochondral shear fractures undergoing fixation or >1 cm in diameter, and prior ipsilateral knee surgery. Results: One-hundred and one patients (average age 15.2 years, 63% female), underwent primary isolated MPFLR with an average follow up time of 2.87 years. There were no significant differences in demographic and radiographic parameters between autograft and allograft, other than more semitendinosus grafts, increased number of pre-op dislocation events, and higher sulcus angle in autograft (Table 1). The autograft group had a higher rate of recurrent instability (41% vs 14%, p = 0.01) but no significant difference in return to sport, complications, and reoperations (Table 2). Reoperations for recurrent instability were performed in 9% of all patients (Table 3). Subgroup analysis of allograft tendon type demonstrated more dislocations and recurrent instability in gracilis than semitendinosus, though these differences were not statistically significant, and there was no difference in recurrent instability surgery or complications (Table 4). Conclusions: In adolescent and young adult athletes undergoing isolated primary MPFLR for PFI, allograft may be associated with decreased rates of recurrent instability compared to autograft. While trends towards higher recurrent instability were detected with gracilis allograft, compared to semitendinosus allograft, the precise role of allograft tendon type would benefit from future studies with larger sample size to better elucidate its impact on clinical outcomes.

Early internal detection of magnetic tearing and implications for tokamak magnetohydrodynamic stability

Internal fluctuation measurements with Faraday-effect polarimetry in the DIII-D tokamak reveal the onset of a tearing mode with toroidal mode number n = 3 well before it is detected by the sensing coils external to the plasma. This mode appears before the n = 2, 1 modes and is first detected with internal measurements at a lower value of the ideal-wall kink beta limit than is indicated at the time of first detection by the sensing coils. When the mode is first detected, the linear resistive stability parameter, Δ′, indicates marginal stability and continues to do so until later when the mode amplitude begins increasing linearly with time—together suggesting a neoclassical origin for this mode.

Properties of spring wheat varieties yield formation by plasticity and stability parameters

Properties of spring wheat varieties yield formation by plasticity and stability parameters

Assessment of samples of Phléum praténse L. by the parameters of ecological plasticity and stability in the conditions of Precarpathia

Assessment of samples of Phléum praténse L. by the parameters of ecological plasticity and stability in the conditions of Precarpathia

Thermoacoustic parametric instability of premixed ammonia flames propagating downwards in an open-closed tube

This work investigates the self-excited thermoacoustic parametric instability of downward propagating laminar premixed ammonia flames in an open-closed combustion tube. NH3/O2/N2 flames were propagated at different laminar burning velocities at equivalence ratios of ɸ = 0.8 and ɸ = 1.2. Different unstable flame regimes were observed through pressure fluctuation measurements and synchronized high-speed imaging capturing the lateral and longitudinal perspectives of flame propagation. The observed propagation speed of quasi-planar flames showed a strong correlation with the calculated laminar burning velocities of NH3/O2/N2 mixtures. For the first time, the cellular structures of laminar premixed ammonia flames at the onset of parametric instability were clearly observed from the present experimental approach. The experimental cellular flame wavenumbers and acoustic velocity fluctuation amplitudes at the onset of parametric instability are in qualitative agreement with the theory of stability of laminar flames under acoustic excitation. Experiments have shown that NH3/O2/N2 flames are more unstable than CH4/O2/N2 flames at the same laminar burning velocity independent of Lewis number within the range of tested conditions. The influence of activation energy on parametric instability is investigated through a comparative thermoacoustic analysis between two different fuels at varied equivalence ratios. Ammonia flames are characterized by large overall activation energy and Zeldovich numbers compared to hydrocarbon flames. This work elucidates how this unique property characterizes the acoustic instability of downward propagating premixed ammonia flames in a tube based on classical theories on acoustic instability of laminar premixed flames.

A three-step subgrid stabilized Oseen iterative method for Navier–Stokes type variational inequality

This work is devoted to developing a two-grid subgrid stabilized Oseen iterative finite element method for the convection dominated Navier–Stokes problem with friction boundary conditions whose weak form is the variational inequality of the second kind. This method inherits the best algorithmic advantages of each and involves three steps. Specifically, in the first step, a nonlinear Navier–Stokes type variational inequality is solved by applying m steps Oseen iterations to approximate the low frequencies of the solution on a coarse grid (H mesh), and then in the second and third steps, two subgrid stabilized and Newton-linearized Navier–Stokes type variational inequalities are solved to attain the high frequencies on a fine grid (h mesh). The developed method is easily implementable since there have identical stiffness matrices with only various right-hand sides in the second and third steps. Error bounds of the approximate velocity and pressure with regard to the mesh sizes h and H, stabilization parameters αH and αh and iteration step m are estimated, and new termination condition for nonlinear iterations is derived. The scalings both for the coarse grid and fine grid sizes as well as fine grid stabilization parameter obtained by our present method are improved in comparison with the developed method that only stays in the second step. Performance and effectiveness of the developed method are illustrated through a series of numerical experiments, which show that the accuracy of the calculated velocity and pressure of each step is higher than that of the previous step.

Interconnected pyrolysis and activation with in-situ H3PO4 activation of biochar from pear wood chips in a pilot scale dual fluidized bed

Interconnected pyrolysis and activation is a novel technology for combustible gas and biochar production in dual fluidized bed (DFB). The study proposed one-step and two-step methods for pyrolysis and activation of biomass in a pilot scale DFB with capacity of 100 kg/h. Physical and chemical activation occurred simultaneously in DFB system by phosphoric acid (H3PO4) impregnation pretreatment of pear wood chips, and flowing hot flue gas and steam. Stable operating parameters were observed for both methods. The one-step method was superior to the two-step method in terms of the pyrolysis gas quality, biochar pore distribution, micro- and meso-pores structures of biochar, while one-step method reduced the biochar yields. As an activation agent, H3PO4 increased the yields of biochar and pyrolysis gas, promoted formation of micropores and enriched the surface functional groups of biochar with increasing ratio of H3PO4. H3PO4 to biomass ratio of 1:5 reached the maximum biochar yield of 42.3 wt% and highest iodine adsorption value of 648.5 mg/g, increasing by 70.6 % and 90.3 % compared to the biochar without H3PO4 pretreatment, respectively. This DFB system facilitated the diversified use of fluidized beds and the co-production of biochar and product gas with energy saving and CO2 emission reduction.

The diagnosis of worn texture in urban villages—Case study: Lalejin urban village

The present study examines the effectiveness of the physical parameters of micro-density, impermeability, and instability in the diagnosis of worn texture in urban villages. The transformation of every village into a city causes hundreds of small and large changes in the urban space and the lifestyle of its inhabitants. With the increasing influx of migrants from surrounding villages into urban villages, there is an urgent need for more accurate management of deteriorating areas. To preserve the character of such places as a heritage and examine their condition and the damage incurred, it is necessary to precisely identify the worn textures as a first step towards addressing these challenges. The urban village of Lalejin, as the statistical population of the study, is a clear example of such failed transformation, as it has lost most of its agricultural land and yet has remained underdeveloped in urban construction. While there have been several studies on the status of the worn texture, there are major concerns regarding the validity of the physical parameters involved. This research aims to take a strategic approach to studying the desired texture and to investigate the three parameters of micro-density, impermeability, and instability. Subsequently, the strategy to recognize the worn-out texture in rural–urban regions was extrapolated. The developed strategy in this study can be further generalized to all urban villages and shows how to determine the degree of deterioration in rural–urban areas using three physical parameters: micro-density, impermeability, and instability. The results specify the conditions and formulas necessary for such assessment.

Effects of multicollinearity and data granularity on regression models of stream temperature

Water temperature is a key factor influencing biota of stream ecosystems. Hence, it is important to comprehend the environmental drivers of stream temperature for robust prediction of conditions and effective management of stream communities. Linear regression models are commonly used for predictive purposes, but their predictive capacity and interpretability can be significantly affected by their complexity and the structure of input data. In some cases, researchers may be obligated to favor prediction power or interpretability while compromising the other. Therefore, insight into relationships between model fit, correlation among predictor variables (i.e., multicollinearity), and level of temporal aggregation of data (i.e., data granularity) may be helpful to reduce such trade-offs. In this paper, we investigated these relationships within a hierarchical set of multiple linear regression (MLR) models examining environmental factors influencing stream temperature dynamics. Our findings showed that as the number of predictor variables (i.e., model complexity) increased, the magnitude of multicollinearity in MLR models increased, but model fit also increased. The results also revealed that using data averaged over longer time frames (i.e., coarser data granularity) yielded high multicollinearity, as indexed by variance inflation factor values (VIF) for all model predictors. This led to higher variance in parameter estimates (i.e., parameter instability) and potential challenges in model interpretation as the sign of parameter estimates changed in many streams examined. Multicollinearity was not the only reason for these changes in the sign of parameter estimates as they were also observed in simple linear regression models across varying levels of data granularity. Based on our findings, we conclude that the selection of data granularity is an important consideration in multiple regression modeling, with profound implications for model interpretability.

Estimating substance use disparities across intersectional social positions using machine learning: An application of group-lasso interaction network.

An aim of quantitative intersectional research is to model the joint impact of multiple social positions on health risk behaviors. Although moderated multiple regression is frequently used to pursue intersectional research hypotheses, such parametric approaches may produce unreliable effect estimates due to data sparsity and high dimensionality. Machine learning provides viable alternatives, offering greater flexibility in evaluating many candidate interactions amid sparse data conditions, yet remains rarely employed. This study introduces group-lasso interaction network (glinternet), a novel machine learning approach involving hierarchical regularization, to assess intersectional differences in substance use prevalence. Utilizing variable selection and parameter stabilization functionality for main and interaction effects, glinternet was employed to examine two-way interactions between three primary social positions (gender, sexual orientation, and race) predicting heavy episodic drinking, cannabis use, and cigarette use prevalence. Analyses were conducted using the All of Us Research Program (N = 283,403), a national sample with high representation from populations historically underrepresented in biomedical research. Results were replicated using holdout cross-validation and compared against logistic regression estimates. Glinternet prevalence estimates were more stable across discovery and replication samples relative to logistic regression, particularly among sparsely represented groups. Prevalence estimates for cigarette and cannabis use were elevated among sexual minority and White cisgender women compared to heterosexual and non-White women, respectively. Glinternet may improve upon traditional moderated multiple regression methods for pursuing intersectional hypotheses by improving model parsimony and parameter stability, providing novel means for quantifying health disparities among intersectional social positions. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Active filter parameter tuning method for harmonic voltage mitigation in wind power plants

It is challenging to determine the active filter control factors in wind power plants (WPP) to obtain effective harmonic voltage mitigation and avoid over-modulation or system instability problems caused by overlarge feedforward or feedback gains. To address this issue, an active filter tuning (AFT) method is proposed in this paper to offer a common parameter tuning and stability assessment strategy for both current-controlled and voltage-controlled harmonic impedance reshaping (HIR) methods by introducing a coordination factor including different weight coefficients for system stability margin, wind turbine (WT) harmonic suppression, and grid harmonic mitigation. The superiority of the proposed method is verified in a 20 MW WPP with four cases considering both WT harmonic voltage amplification and grid voltage amplification. Compared to previous methods, the AFT-based HIR method achieves a more flexible balance between system stability and harmonic voltage mitigation, obtaining better performance in WT harmonic suppression, grid harmonic suppression, system robustness, and transient response.

An NMPC-Based Integrated Longitudinal and Lateral Vehicle Stability Control Based on the Double-Layer Torque Distribution.

With the ongoing promotion and adoption of electric vehicles, intelligent and connected technologies have been continuously advancing. Electrical control systems implemented in electric vehicles have emerged as a critical research direction. Various drive-by-wire chassis systems, including drive-by-wire driving and braking systems and steer-by-wire systems, are extensively employed in vehicles. Concurrently, unavoidable issues such as conflicting control system objectives and execution system interference emerge, positioning integrated chassis control as an effective solution to these challenges. This paper proposes a model predictive control-based longitudinal dynamics integrated chassis control system for pure electric commercial vehicles equipped with electro-mechanical brake (EMB) systems, centralized drive, and distributed braking. This system integrates acceleration slip regulation (ASR), a braking force distribution system, an anti-lock braking system (ABS), and a direct yaw moment control system (DYC). This paper first analyzes and models the key components of the vehicle. Then, based on model predictive control (MPC), it develops a controller model for integrated stability with double-layer torque distribution. The required driving and braking torque for each wheel are calculated according to the actual and desired motion states of the vehicle and applied to the corresponding actuators. Finally, the effectiveness of this strategy is verified through simulation results from Matlab/Simulink. The simulation shows that the braking deceleration of the braking condition is increased by 32% on average, and the braking distance is reduced by 15%. The driving condition can enter the smooth driving faster, and the time is reduced by 1.5 s~5 s. The lateral stability parameters are also very much improved compared with the uncontrolled vehicles.

Investigation into the Potential Use of Damping Plates in a Spar-Type Floating Offshore Wind Turbine

Spar is one of the promising floating platforms to support offshore wind turbines. Wind heeling moment is large in the case of floating offshore wind turbines and, therefore, it is important to reduce the pitch motion of the floating platform. To address this issue, a spar platform with damping plates is proposed and investigated in this study. (i) Type-A, (ii) Type-B, and (iii) Type-C models of 1/120 scale were fabricated with similar stability parameters. Type-A is a classic spar, Type-B and Type-C are spar with damping plates by replacing the ballast water part with horizontal plates and vertical plates, respectively. The rotor model consists of (i) no disk and (ii) with disk conditions. A series of model scale experiments were carried out in the water tank in regular waves, and motion response was measured. A calculation method based on classic frequency-domain was developed to incorporate damping plates and validated with the experiment results in no disk and with disk conditions. When pitch response of Type-B and Type-C were compared with respect to Type-A, it was found that the spar platform with damping plates reduced the pitch response in most wave frequencies.

Formulation and Comparative Evaluation of Herbal Shampoo Powder with marketed preparation

Hair have been associated with beauty since time immemorial. A number of natural and synthetic hair cleansers are available in the market. The challenges associated with hair and scalp health are increasing day by day. Aside from the fast life, stress, dietary issues; the increasing temperature, dust, pollution, erratic climate changes, the sulphates and parabens included in synthetic hair cleansers and conditioners are majorly responsible for deterioration of hair strands and scalp. The aim of the current work was to combine trichologically beneficial herbal ingredients and prepare a formulation that would serve for conditioning and cleaning the hair and scalp effectively. Three herbal hair shampoo powder formulations containing the same ingredients in varying proportions were prepared and evaluated for their physicochemical and stability parameters. The formulation F1 showed better results when evaluated for the physicochemical and stability parameters as compared to formulations F2 and F3.

Time-varying equivalent circuit for dynamically modulated dielectric slabs and its implications for stability analysis.

Equivalent circuits (ECs) have played an instrumental role in analyzing and modeling distributed electromagnetic structures for many decades, owing to their intrinsic simplicity and the valuable intuition and physical insights they provide. Here, we envision what we believe to be a novel class of ECs featuring linear time-varying (LTV) circuit elements to harness the power of EC analysis for studying LTV structures, particularly LTV dielectric slabs. Our time-varying equivalent circuit (TVEC)-consisting of infinitely many time-varying LC resonators interconnected in either series or parallel-is rigorously derived and exact, with closed-form expressions for the circuit elements. Its convenient form, enabled by a judicious use of Mittag-Leffler expansion, simplifies the analysis of LTV slabs experiencing various resonant and harmonic phenomena. We demonstrate this point by applying our TVEC to the problem of parametric instability in linear time-periodic slabs. Despite its immense importance, instability has been largely neglected in the literature on periodically modulated structures, mainly due to the inherent complexity of problems involving partial differential equations with time-periodic coefficients. Time-periodic circuits, on the other hand, enjoy an abundance of mathematical tools and methods in the form of the theory of Hill's equation. We utilize this rich theory to investigate the nature of parametric instability in linear time-periodic slabs. Numerical results are then presented to verify these findings. Our TVEC is simple, applicable to any form of temporal modulation (not just periodic), and potentially extensible to other geometries, making it likely to have a significant impact on a multitude of hotly researched LTV topics.

Intereye Asymmetry as a Predictor of Progression in Patients With Untreated Keratoconus: Findings From a Longitudinal Study.

The purpose of this study was to evaluate interocular predictors of progression in patients with untreated keratoconus. This is a multicenter longitudinal observational study with real-world data collected through the Save Sight Keratoconus Registry. Patients between the period of June 2000 and September 2022 were included in this study. Parameters such as patient age, sex, ocular history, visual acuity, K2, Max-K, and thinnest corneal thickness pachymetry (TCT) were analyzed. There were 4342 untreated eyes from 2171 patients with keratoconus. A total of 333 patients showed progression of either Max-K, TCT, or both, whereas 1838 patients showed stable parameters. Factors associated with a higher incidence of progression in Max-K were younger baseline age (HR 0.96 per year older; 95% CI 0.95-0.98, P < 0.0001) and a higher baseline intereye asymmetry in Max-K (HR 1.02 per higher diopter; 95% CI 1.00-1.04, P = 0.04). A younger baseline age was the only predictor of progression in TCT (HR 0.97 per year older; 95% CI 0.95-0.99, P = 0.001). Age is the most significant predictor of progression for both corneal thinning and progression of Max-K. Interocular asymmetry in Max-K at baseline could be used as part of an algorithm for determining the risk of keratoconus progression. It is recommended that patients with higher interocular asymmetry in Max-K have a closer follow-up of both eyes as they are at a higher risk of progression.

Expansion of measurement capabilities of the bolometric sensor of the terahertz wave power based on an inexpensive and stable measuring system

The paper discusses the results of a joint work of the Central Office of Measures in the Republic of Poland and the Military University of Technology in Warsaw within the framework of the project “Measurement Consistency in Electromagnetic Power Measurements in the Sub-THz Band”. The main problems in the study of electromagnetic radiation power in the terahertz range using a bolometric detector are considered. The design and parameters of the measuring system based on the use of a resistive bolometric detector, own signal amplifier, and measuring converter, which were designed and implemented at the Central Office of Measures in the Republic of Poland, are described. The results of metrological traceability to the SI units are presented. This paper is dedicated to expanding measurement capabilities of the bolometric detector based on a highly stable and inexpensive measuring system in the terahertz range. As a result of the joint work, a measuring system characterized by high parameter stability and a gain of more than 20 000 V/V was developed and tested.

Effect of Energy Utilization on Pakistan’s Economic Development: A Time Series Analysis

The present research has been conducted to study the causal relation among GDP, electricity utilization, exports, real capital and labor force for Pakistan. Time dependent data for the mentioned parameters have been used for the time period of 1980 to 2022. Inter-relations among the above-mentioned variables have been studied in this work by the method of cointegration using bounds test. The results illustrate that there is an existence of long run relation among the parameters where GDP has been taken into consideration as the dependent variable. Granger causation analysis has also been performed for the variables. Results show that Granger causality between GDP and electricity utilization runs in both directions. Moreover, the study discloses that Electricity utilization granger cause exports and per capita real capital. Exports granger cause per capita real capital. Per capita real capital granger cause GDP. Labor force granger cause GDP and exports. The long run relation equation of GDP, Electricity utilization, exports, real capital and labor force has also been examined for parameter stability. The parameters are found to be stable with the significance level of 5%. The research also suggests some significant strategy recommendations.

Performance Analyzes of Thermodynamic Indices and Atmospheric Parameters in Thunderstorm and Non-thunderstorm Days in Istanbul, Turkey

This study aims to analyze the thunderstorm (TS) events in the megacity Istanbul by using thermodynamic indices and atmospheric stability parameters for the period of 2001–2022. It was determined that TS events did not show any trend on an annual basis, mostly (%69) occurred in the warm season (May–September), and mostly (%93) lasted for a few hours (0–3 h). The thermodynamic indices and atmospheric stability parameters used in the study are Showalter Index (SI), Lifted Index (LI), Severe Weather Threat Index (SWEAT), K-Index (KI), Totals Totals Index (TTI), Convective Available Potential Energy (CAPE), Convective Inhibition (CIN), and Bulk Richardson Number (BRN). Annual and seasonal analyzes of all indices and parameters were performed for TS and non-TS events. Significant differences were found in both average, maximum, and minimum values. The Probability of Detection (POD), False Alarm Ratio (FAR), Miss Rate (MR), Critical Success Index (CIS), Hiedke Skill Score (HSS), and True Skill Score (TSS) were used to analyze the success of the threshold values presented in the literature in detecting TS events. Then, the seasonal successes of these threshold values were tested. It was observed that the performance of the selected indices varied across seasons. The highest predictive skill was generally observed during the summer season, with the POD value ranging between 0.58 and 0.97 and the TSS value varying between 0.32 and 0.57. Conversely, the lowest predictive skill was typically observed during the winter season, where the POD value ranged from 0.00 to 0.75 and the TSS value varied between 0.00 and 0.40. The ideal threshold values were determined for indices and parameters by increasing or decreasing the existing threshold values at certain rates. Success increases of up to 15% in skill scores for the proposed threshold values.