Asymmetric Model Research Articles

The British Political Tradition and Constitutional Policy: The Offer of Deliberative Mini Publics

Abstract The Review of the UK Constitution was an eighteen-month project assessing the functioning of the UK constitution resulting in a set of practical, innovative, and robust recommendations. This article draws out one theme from this research, the offer of Deliberative Mini Publics (DMPs) in the process of constitutional change in the UK. Using Marsh, Richards, and Smith’s ‘Asymmetric Power Model’ as a mechanism for understanding the centralised and top–down nature of British democracy, we argue that the integration of DMPs can offer an opportunity to mitigate some of the core problems with the functioning of the UK constitution and produce better constitutional policy.

Scaling Properties of Liquid Dynamics Predicted from a Single Configuration: Pseudoisomorphs for Harmonic-Bonded Molecules.

Isomorphs are curves in the thermodynamic phase diagram of invariant excess entropy, structure, and dynamics, while pseudoisomorphs are curves of invariant structure and dynamics, but not of the excess entropy. The latter curves have been shown to exist in molecular models with flexible bonds [Olsen, A. E. J. Chem. Phys. 2016, 145, 241103]. We here present three force-based methods to trace out pseudoisomorphs based on a single configuration and test them on the asymmetric dumbbell and 10-bead Lennard-Jones chain models with bonds modeled as harmonic springs. The three methods are based on requiring that particle forces, center-of-mass forces, and torques, respectively, are invariant in reduced units. For each of the two investigated models we identify a method that works well for tracing out pseudoisomorphs, but these methods are not the same. Overall, we find that the more internal degrees of freedom there are in the molecule studied, the less they appear to affect the gross dynamical behavior. Moreover, the "internal" degrees of freedom (including rotation) do not significantly affect the scaling behavior of the dynamical/transport coefficients provided some 'quenching' is performed.

An unstable Union? The Conservative Party, the British Political Tradition, and devolution in Scotland and Wales 2010–23

Abstract While devolution in Scotland and Wales is often established as the settled will, it has been built on unsettled ground, lacking a robust system of intergovernmental relations, and sitting increasingly at odds with the central principle of parliamentary sovereignty. Examining successive UK Conservative-led governments, we evaluate devolution in Scotland and Wales through the lens of the Asymmetric Power Model and the British Political Tradition, documenting changes in the position of successive Conservative governments, from the more plurinationally sensitive respect agenda of David Cameron to the more assertive and intrusive Unionism advanced under those in post after 2016, notably Theresa May and Boris Johnson.

The challenge of devolved English governance and the rise of political spatial inequality

Abstract The UK is characterised by spatial inequality between and within regions, alongside an over-centralised asymmetric model of governance. In England especially, these features are stark, and throughout the last decade, politicians have responded by forging a distinctive programme of English devolution focused on city-regions. In this article, we analyse the core drivers of the English devolution agenda to understand its impact on the future trajectory of British politics. We identify the predominance of a narrow economic vision of devolution that systematically negates other agendas. The result is a failure to address the trade-offs inherent in the devolution process, alongside an inadequate engagement with the growing demand for democratic revitalisation. In the long-term, we argue that the empowerment of the largest cities in England and the relative neglect of non-urban areas will exacerbate power asymmetries within the UK political system in both centre-periphery and centre-local relations, a phenomenon we term ‘political spatial inequality’. There is a risk of resurgent ‘territorially based populism’ stemming from this uneven political geography which has the potential to exacerbate political instability and significantly reshape UK politics in the wake of Brexit. English devolution is a prescient example of how policy ‘solutions’ can in turn create new problems that pose major challenges for policymakers.

Comparative Analysis of GARCH-Based Volatility Models of Financial Market Volatility: A Case of Nairobi Security Market PLC, Kenya

This paper conducted a comprehensive comparative analysis of various GARCH (Generalized Autoregressive Conditional Heteroskedasticity) models to forecast financial market volatility, with a specific focus on the Nairobi Stock Exchange Market. The examined models include symmetric and asymmetric GARCH types, such as sGARCH, GJR-GARCH, AR (1) GJG-GARCH, among others. The primary objective is to identify the most suitable model for capturing the complex dynamics of financial market volatility. The study employs rigorous evaluation criteria, including the Akaike Information Criterion (AIC), Bayesian Information Criterion (BIC), Mean Error (ME), and Root Mean Absolute Error (RMAE), to assess the performance of each model. These criteria facilitate the selection of the optimal model for volatility forecasting. The analysis reveals that the GJR-GARCH (1,1) model emerges as the best-fit model, with AIC and BIC values of −5.5008 and −5.4902, respectively. This selection aligns with the consensus in the literature, highlighting the superiority of asymmetric GARCH models in capturing volatility dynamics. The comparison also involves symmetric GARCH models, such as sGARCH (1,1), and other asymmetric models like AR (1) GJG-GARCH. While these models were considered, the GJR-GARCH (1,1) model demonstrated superior forecasting capabilities. The study emphasizes the importance of accurate model selection and the incorporation of asymmetry in volatility modeling. The research provides essential insights into financial market volatility modeling and forecasting using both asymmetric and symmetric GARCH models. These findings have significant implications for government policymakers, financial institutions, and investors, offering improved tools for risk assessment and decision-making during periods of market turbulence.

Instability and inequality in the British state

Abstract The UK state has been through many periods of perceived crisis, but the instability of the last decade has shaken some of the foundational institutions of British politics. Our main argument is that the rise of political instability relates to the failure of British politics to respond to structural inequality in society and politics. This includes growing economic and geographic disparities, as well as destabilizing divisions over long-standing social injustices. The infusion of these trends into the political process is the subject of the ‘asymmetric power model (APM)’, which acts as the theoretical underpinning of this paper and the special issue it introduces. In this editorial to the Parliamentary Affairs Special Issue on ‘Instability and inequality in the British state’, we elaborate these arguments and provide a brief overview of the eight papers in the issue, which cover the APM, the constitution, the UK Union, the Conservative Party, public policymaking, gender inequalities, intersectional inequalities, and geographical inequalities. Together, the papers identify the causes and features of the UK’s troubling inequality-instability dialectic and offer various practical and theoretical ways forward.

Piezoelectric-based smart structures for aero-engine blade: Piezoelectric layout optimization and vibration suppression tests

To promote the use of piezoelectric smart structures in aero-engine blades, this paper introduces a novel method for optimizing the layout of piezoelectric elements on the blade's surface and an active vibration control method, along with vibration suppression tests. A preprocessing method is introduced for the point cloud data of in-service blades to reconstruct the blade surface. An improved parameter-adaptive differential evolution algorithm is proposed to optimize the layout of piezoelectric actuators and sensors and accurately identify the hysteresis nonlinear model of piezoelectric elements. A Hammerstein model is constructed by cascading an asymmetric Bouc-Wen model with an ARX model to describe the rate-dependent hysteresis nonlinear characteristics of piezoelectric elements. An improved variable step-size FxLMS algorithm is proposed to balance the relationship between convergence speed and steady-state error in the control algorithm. The proposed layout optimization and vibration control algorithm are validated experimentally on an experimental platform under various disturbances, with results showing improved performance of the proposed VSS-FxLMS algorithm in terms of convergence and efficiency.

Asymmetric triangular body-cover model of the vocal folds with bilateral intrinsic muscle activation.

Many voice disorders are linked to imbalanced muscle activity and known to exhibit asymmetric vocal fold vibration. However, the relation between imbalanced muscle activation and asymmetric vocal fold vibration is not well understood. This study introduces an asymmetric triangular body-cover model of the vocal folds, controlled by the activation of bilateral intrinsic laryngeal muscles, to investigate the effects of muscle imbalance on vocal fold oscillation. Various scenarios were considered, encompassing imbalance in individual muscles and muscle pairs, as well as accounting for asymmetry in lumped element parameters. Measurements of amplitude and phase asymmetries were employed to match the oscillatory behavior of two pathological cases: unilateral paralysis and muscle tension dysphonia. The resulting simulations exhibit muscle imbalance consistent with expectations in the composition of these voice disorders, yielding asymmetries exceeding 30% for paralysis and below 5% for dysphonia. This underscores the relevance of muscle imbalance in representing phonatory scenarios and its potential for characterizing asymmetry in vocal fold vibration.

Estimation of ultrasonic flight time based on SHADE algorithm and extended kalman filtering

Abstract Traditional methods of using ultrasound to measure oxygen concentration have the issue of inaccuracy and susceptibility to noise interference when measuring the time of flight (TOF) of ultrasonic echo signals. A proposed algorithm for ultrasonic parameter estimation, utilizing an asymmetric Gaussian model, aims to enhance the precision and reliability of TOF estimation, aiming to reduce the influence of noise interference. The algorithm combines an improved Self-Adaptive Differential Evolution (SHADE) algorithm based on successful historical records with an Extended Kalman Filter (EKF). The improved SHADE algorithm controls the degree of mutation strategy greediness during the mutation operation based on the number of iterations, thereby enhancing the algorithm’s iteration speed. Then, the obtained solution is used as the initial value for the EKF to estimate the model parameters, thus addressing the issue of EKF’s dependency on accurate initial values to obtain precise outputs. Through simulation and experimental measurements of ultrasonic oxygen concentration, several commonly used parameter estimation algorithms are compared with the proposed SHADE-EKF algorithm. Results demonstrate that the SHADE-EKF algorithm exhibits superior performance in estimating the TOF of ultrasonic waves.

Markets and Public Goods: Integrity, Trust, and Climate Change

Public goods are an anomaly in neoclassical economics, a form of ‘market failure’. They exist outside the efficient and equitable optimality of market exchange. It can be shown however that competitive markets are only efficient in short product cycles. Long-term objectives require social support. Corruption arises from the consequent private public interaction. Integrity, the absence of corruption, is a public good. Corruption has risen since the 1980s with privatization and outsourcing. How did European governments become honest in the first place? In the century after the 1770s, they moved from regarding public office as a form of private property to a conception of serving the public good. This integrity revolution was facilitated by Weberian bureaucracies, selected by academic merit and committed to impartiality by long-term incentives. The neoliberal revolution of the 1980s regarded bureaucracies as obstructive and slow. It admired the business corporation with its opaque procedures and charismatic leadership. Concurrently economics moved from neoclassical harmony theory to an asymmetric information model of ‘opportunism with guile’, providing doctrinal legitimacy for corruption. Corporate advertising is deliberately deceptive, and undermines the public good of trustworthiness. Digital platforms, powered by advertising, have subverted public discourse. Misinformation and disinformation have become prime risk factors for current societies. The practical operation of markets undermines the public goods of integrity and trustworthiness. The public good of a habitable climate cannot be achieved by market methods. For long-term payoffs, ‘free markets’ are a harmful delusion, inefficient, corrupt, impossible to achieve, and not sustainable.

Distributed fixed-time formation tracking control for multiple underactuated USVs with lumped uncertainties and input saturation

A fixed-time distributed formation control strategy is investigated for multiple underactuated unmanned surface vehicles (USVs) with unmeasured velocities and input saturation. Initially, a necessary coordinate transformation is applied to the mathematical model of USVs to address the underactuated issue. Subsequently, a fixed-time extended state observer (FESO) is constructed to estimate unmeasured velocities and lumped disturbances of USVs based on input and output data in the control loop. Meanwhile, the leader–follower approach is applied to achieve a preset formation. A fixed-time differentiator is utilized to compute real-time differential signals for virtual control laws, which simplifies the complexity of controller design. Furthermore, a fixed-time distributed formation controller is designed based on an asymmetric differentiable saturation model. The effects of input saturation are eliminated by a designed auxiliary system. Finally, the fixed-time stability of the closed-loop system is analyzed through the Lyapunov stability theory. The comparison simulation results verify the effectiveness and superiority of the proposed formation control scheme.

Volatility spillovers among economic policy uncertainty, energy and carbon markets—The quantile time-frequency perspective

As global uncertainty and trade tensions escalate, the world's economic stability faces growing risks. This study examines the volatility spillovers among economic policy uncertainty (EPU), energy, and carbon markets. We assume that returns in energy and carbon markets follow a Skew-t distribution and estimate volatility using an asymmetric EGARCH model. Then, we utilize methods developed by Diebold and Yilmaz (2012) and Barunik and Křehlík (2018), as well as a new quantile connectedness approach to investigate the directional and dynamic risk associations across different time frequencies and market environments. Our study first reveals that long-term volatility spillovers dominate normal periods, whereas medium-term spillovers become more pronounced in extreme cases. Second, EPU is a net receiver of risk in the short term but shifts to a risk transmitter in the medium and long term. Third, the solar energy market, a representative of new energy, drives spillover effects, while the carbon market is particularly susceptible to external influences. Fourth, the total risk spillovers exhibit a dynamic time-varying characteristic and are susceptible to extreme events. Finally, we observe an asymmetric distribution of risk spillovers among markets during extreme events. These findings offer valuable implications for policymakers and investors.

Asymmetric Effects of COVID-19 Deaths and Oil Price Shocks on Stock Market Returns in Some Selected African Countries: Evidence From Nonlinear ARDL Approach

This study investigates the asymmetric impact of oil price shocks and COVID-19 total deaths on Kenya, Morocco, Nigeria and South Africa stock market returns. To achieve this objective employing weekly time series data from March 13, 2020 to September 23, 2022, first, we apply the BDS test which confirm the nonlinearity of each series. Second, stationarity tests are used to investigate each series for unit root. The results show that series are stationary in level and in first difference. Third, the bounds test reveals that the series have a cointegration relationship and we apply the nonlinear autoregressive distributed lag (ARDL) ARDL framework to decompose oil price into positive and negative partial sum to investigate a possible asymmetric effect of oil price on stock market returns. The main findings of the asymmetric ARDL model reveal that, in the short-run dynamic, a positive shock in the oil price have a negative and positive effect on stock market returns in Morocco and South Africa respectively. The result is insignificant for Kenya and Nigeria. A negative shock in the oil price have a negative effect on the stock returns in Nigeria, South Africa and in Kenya, Morocco with one period lag. Furthermore, in the long-run, a positive shock in oil price exerts a negative effect on the stock market performance in Morocco and Nigeria while a negative shock in oil price leads to a negative effect also on the stock market returns. The total deaths present a counterintuitive result. Both in the long-run and short-run dynamic, the total number of deaths due to COVID-19 have a significant increasing effect on stock market returns in Kenya, Morocco and South Africa except for Nigeria.

Examining The Impact of Inflation on Financial Development in The Fragile Five Economies with Asymmetric Cointegration Tests

This study examines the relationship between inflation and financial development indicators for the Fragile Five countries between 1981 and 2021. The study analysed the relationship between symmetric and asymmetric distributed lag regression models. Inflation appears to have a negative impact on financial development in countries other than Brazil and India. The results prove that the most extended correction process was experienced in India, and the shortest was experienced in Indonesia among the Fragile Five countries. Research results emphasise that high inflation negatively affects financial development in these economies by increasing the cost of financial intermediation.

Modeling Exchange Rate of Naira to Euro with the APLSTAR-GARCH model

Application of the asymmetric power logistic smooth transition autoregressive (APLSTAR) model proposed by [1] to naira/Euro exchange rate spanning from January, 2006 to April, 2021, which is a nonlinear macroeconomic time series was considered. The APLSTAR model was justifiably fitted to the series and the fit of the APLSTAR model compared with the fits of the competing models revealed that the APLSTAR model fits the data exchange rate of naira to Euro better than the other asymmetric STAR models. Lagrange Multiplier tests for autoregressive conditional heteroscedastic (ARCH) effects were carried out and there was no substantial evidence to reject the presence of ARCH effects in the set of residuals used. Hence, we compared hybrid smooth transition autoregressive-generalized ARCH (STAR-GARCH) models using model evaluation criteria. On balance, the APLSTAR-GARCH (0, 1) model outperforms the other models under consideration.

Exploring the Macroevolutionary Signature of Asymmetric Inheritance at Speciation.

Popular comparative phylogenetic models such as Brownian Motion, Ornstein-Ulhenbeck, and their extensions, assume that, at speciation, a trait value is inherited identically by two descendant species. This assumption contrasts with models of speciation at a micro-evolutionary scale where descendants' phenotypic distributions are sub-samples of the ancestral distribution. Different speciation mechanisms can lead to a displacement of the ancestral phenotypic mean among descendants and an asymmetric inheritance of the ancestral phenotypic variance. In contrast, even macro-evolutionary models that account for intraspecific variance assume symmetrically conserved inheritance of ancestral phenotypic distribution at speciation. Here we develop an Asymmetric Brownian Motion model (ABM) that relaxes the assumption of symmetric and conserved inheritance of the ancestral distribution at the time of speciation. The ABM jointly models the evolution of both intra- and inter-specific phenotypic variation. It also infers the mode of phenotypic inheritance at speciation, which can range from a symmetric and conserved inheritance, where descendants inherit the ancestral distribution, to an asymmetric and displaced inheritance, where descendants inherit divergent phenotypic means and variances. To demonstrate this model, we analyze the evolution of beak morphology in Darwin finches, finding evidence of displacement at speciation. The ABM model helps to bridge micro- and macro-evolutionary models of trait evolution by providing a more robust framework for testing the effects of ecological speciation, character displacement, and niche partitioning on trait evolution at the macro-evolutionary scale.

Enhancing thermodynamic consistency: Clarification on the application of asymmetric activity model in multi-component chromatographic separation

The single-component Mollerup model, with over 40 direct applications and 442 citations, is the most widely used activity model for chromatographic mechanistic modeling. Many researchers have extended this formula to multi-component systems by directly adding subscripts, a modification deemed thermodynamically inconsistent (referred to as the reference model). In this work, we rederived the asymmetric activity model for multi-component systems, using the van der Waals equation of state, and termed it the multi-component Mollerup model. In contrast to the reference model, our proposed model accounts for the contributions of all components to the activity. Three numerical experiments were performed to investigate the impact of the three different activity models on the chromatographic modeling. The results indicate that our proposed model represents a thermodynamically consistent generalization of the single-component Mollerup model to multi-component systems. This communication advocates adopting of the multi-component Mollerup model for activity modeling in multi-component chromatographic separation to enhance thermodynamic consistency.

Cross-commodity market integration and price transmission in Thailand’s livestock sector

The ability to substitute goods and services is crucial for maintaining market stability during price fluctuations, particularly in the livestock market, where products are interchangeable. This study aimed to analyse market integration and asymmetric price transmission concerning livestock commodity prices in Thailand. Specifically, it focused on beef cattle, swine, broiler chicken, and chicken egg prices, using time-series data from January 2011 to December 2022. The analysis employed unit root tests to check if the time series data were stationary, Granger causality tests to determine the direction of relationships among livestock prices and an asymmetric price transmission model to examine short-term asymmetry and adjustment in cross-commodity prices. The findings indicate three directions of price integration in Thailand’s livestock market: from broiler chicken price to chicken egg price, from swine price to chicken egg price, and from swine price to broiler chicken price. The results suggest that price transmission in Thailand is symmetrical, demonstrating an efficient interdependent relationship. Thus, the findings indicate that chicken eggs are a substitute for broiler chickens and swine when prices fluctuate, while broiler chickens are a substitute for swine. The results reveal that chicken eggs can replace swine consumption more effectively than broiler chickens within Thailand. This study highlights that chicken eggs are the most effective substitute during livestock price fluctuations in Thailand, with broiler chickens being the second most effective. Consequently, stakeholders in the livestock supply chain, such as policymakers, entrepreneurs, and farmers, should understand the integration of different commodities and price transmission in Thailand’s livestock market. To guarantee market stability, stakeholders should manage the demand and supply of livestock commodities and acquire chicken eggs and broiler chickens during significant fluctuations in domestic livestock commodity prices

Model and performance analysis of energy conversion in functionally graded flexoelectric semiconductor nanostructures

Energy systems converting efficiently from surrounding environment for powering semiconductor electronic components at nanoscale has attracted intense research interests. Due to the strong size dependency, flexoelectricity has been demonstrated as an excellent candidate implemented as nanoscale piezoelectric semiconductor energy harvesters. In this work, through a judicious exploitation of structural symmetry and nonuniformity, we theoretically study the energy conversion behaviors of a novel asymmetric nanodisk model composed of functionally graded (FG) flexoelectric semiconductor (FS) (FG-FS) materials while being loaded with thickness-extensional mechanical vibration. In numerical analysis, the material parameters have been treated with a general variation method under the Cartesian coordinate systems for simplicity. Taking into accounts of the nonuniform structural form and multi-field coupling features, we derived an octic governing equation with variable coefficients for the current analyzed FG-FS nanodisk structure, which is, however, almost impossible to obtain analytical solutions. To successfully address this issue and also further explore the improved performance and new phenomena induced by the FG type of non-uniform structural profile, we specially proposed an efficient tensor algorithm and reduced the octic governing equation into one quartic equation with variable coefficients and other four common quadratic equations. Later, we explicitly explored the effect of each physical parameter on the energy conversion performance of the FS energy harvester by studying the variations of the output electric power density and the energy conversion efficiency. Results illustrated that the electromechanical energy conversion behaviors of the studied FG-FS nanodisk can be properly tuned by not only the related material parameters but also their gradations. We believe our work have the potential to pave new way for the designs and manufacture of novel nano-electronic semiconductor components for the future practical applications.

Time-Varying Correlations between JSE.JO Stock Market and Its Partners Using Symmetric and Asymmetric Dynamic Conditional Correlation Models

Time-Varying Correlations between JSE.JO Stock Market and Its Partners Using Symmetric and Asymmetric Dynamic Conditional Correlation Models