A Multivariate GARCH Model with Time-Varying correlations

In this paper we propose a new multivariate GARCH model with time- varying correlations. We adopt the vech representation based on the conditional variances and the conditional correlations. While each conditional-variance term is assumed to follow a univariate GARCH formulation, the conditional-correlation matrix is postulated to follow an autoregressive moving average type of analogue. By imposing some suitable restrictions on the conditional-correlation-matrix equation, we construct a MGARCH model in which the conditional-correlation matrix is guaranteed to be positive definite during the optimisation. Thus, our new model retains the intuition and interpretation of the univariate GARCH model and yet satisfies the positive-definite condition as found in the constant-correlation and BEKK models. We report some Monte Carlo results on the finite-sample distributions of the MLE of the varying- correlation MGARCH model. The new model is applied to some real data sets. It is found that extending the constant-correlation model to allow for time-varying correlations provides some interesting time histories that are not available in a constant-correlation model.BEKK model, constant correlation, Monte Carlo method, multivariate GARCH model, maximum likelihood estimate, varying correlation

EM Scattering by a Conducting Sphere Coated with a Uniaxial Layer under Arbitrary Illumination Angle in a Fixed Laboratory Frame

Under a fixed laboratory frame, the electromagnetic theory of the scattering of a plane wave of arbitrary polarizations incidence from arbitrary angles by a uniaxial anisotropic medium was obtained for the first time, and could be solved analytically from an eigensystem determined by a uniaxial anisotropic medium. By applying the boundary conditions at respective interfaces of the coated spherical structure, the unknown expansion coefficients can be obtained from the incident field and the electromagnetic fields in the anisotropic medium, and from the scattered field. Not only did the numerical results demonstrate the validity of our proposed theory but this paper shall also provide discussions in relation to some general cases (under arbitrary incident angles) of bistatic radar cross section

Infrastructure Policy and Economic Growth: Case of Hong Kong

The article argues that in most infrastructure projects, the government has to take up aleading role in managing the development of strategic infrastructure. This article alsodiscusses the value of an integrated approach linking the public and private sectors ininfrastructure investment. Such an integrated approach reflects both the need to buildagreement between various interested parties, and also the strength of the privatesector, whose forces may be effectively combined with foreign ventures. By so doingthe investment risk can be minimised and maximum market efficiency can be achieve

Risk perception and decision making in the supply chain: theory and practice

For over sixty years, academics and practitioners from different backgrounds, including psychology, sociology, and management, have studied the perception of risk and how different decision making affects daily life and business activities. Although it is almost six hundred years since Machiavelli stressed the importance of calculation of risk and effective response to it, approaches to risk measurement and assessment, and to decision making in risky situations, continue to develop and evolve. In the business world, managers strive to find ways to understand how different internal and external factors influence risk, how to judge and interpret the available evidence on the possibility of loss, and how to take individual actions to manage the risk (Slovic 2000). In this decade, a number of risk management frameworks (e.g. IS031000) have been proposed and employed in different areas. These frameworks provide foundations and building blocks for managers to collect available data to analyse risk. Most importantly, such frameworks allow managers to gather knowledge intellectually, to properly judge their experience and to assess the current situation, so as to enter into the most appropriate decision

Effects of Two-Phase Treatment with the Herbst and Preadjusted Edgewise Appliances on the Upper Airway Dimensions

published_or_final_versio

Bioimpedance Sensing and Ablation Needles for Image-Guided Therapy

Sensing and ablation needles and catheter instruments combined with multimodal imaging, navigation and AI-assisted diagnosis have been increasingly utilised by interventional radiologists for image-guided therapy, emerging as an innovative tool for both diagnosis and treatment. This paper reviews the significant advancements in the field over the past decade, focusing on the development and refinement of both bioimpedance sensing needles and thermal ablation needles. Bioimpedance sensing needles differentiate pathological tissues by measuring impedance variations in biological tissues, offering a less invasive diagnostic approach. Thermal ablation needles, on the other hand, employ Radio Frequency (RF) techniques or Electrolytic Ablation (EA) to effectively target and treat lesions. This review covers the evolution of these needles, including advancements in materials, novel sensor technologies, impedance analysis methods, ablation catheter powering techniques, and needle design. It also provides insights into the needle structure, fabrication methods, and testing outcomes of these advanced sensing and ablation needles. Additionally, the paper presents an analysis of bioimpedance data across various pathological tissues and discusses innovative impedance analysis methodologies. The review concludes by presenting the current challenges in the field and discussing directions for future research, thereby providing an overview of the state-of-the-art in electronic technology for medical diagnosis and treatment needles

5W+1H pattern: A perspective of systematic mapping studies and a case study on cloud software testing

postprin