ARTICLE | doi:10.20944/preprints202203.0281.v1
Subject: Social Sciences, Econometrics & Statistics Keywords: COVID-19; GARCH; ARCH; MSDR; Volatility
Online: 21 March 2022 (09:14:26 CET)
COVID-19, a global health crisis, occurred unexpectedly and has led to global transformation over all countries in the world today. While COVID-19 had claimed lives and led to an economic crisis, the impacts on the financial market cannot be overemphasized. Considering the previous financial crisis, which occurred due to poor regulations and unchecked misconduct by financial market stakeholders, COVID-19 is the first to mention an indirect crisis that almost has no direct relationship to the financial system. Thus, this paper explores the impacts of COVID-19 from a stochastic approach on Local markets by applying the GARCH model to measure the level of volatility of two (2) US stock indexes (NASDAQ and NYSE) and a Europe index (EURONEXT). Our results show that volatility existed before COVID-19, but the volatility rate increased after COVID-19, possibly due to the COVID-19 shock. We also explore the Markov-Switching Dynamic Regression (MSDR) model to corroborate our findings. We validated that there is a very high persistent volatility for all the considered local markets at the early stage COVID-19 period.
ARTICLE | doi:10.20944/preprints202006.0036.v1
Online: 4 June 2020 (13:35:40 CEST)
The masonry building Heritage is appreciated for its aesthetic and historical value all around the world. The widespread presence of curved elements, such as arch, vault and dome express the relevant constructive abilities in the different historical epochs. These curved elements are characterized by architectural beauty, structural strength (especially against the gravity loads), thermal comfort and fire resistance. On the other hand, curved structures required scaffolding in order to be erected. The design, the construction and the dismantling of the scaffolds is typically time-consuming and expensive. In addition, the on-site working risk is related to time-interferences (e.g. in manpower working, at the same time, over and under scaffold). This technology dates back to the Era of the Roman Empire and it is currently still used, despite its limitations and disadvantages. In the present paper, an innovative technique (recently patented), aiming for the construction of a curved structural member without scaffolds, is proposed and illustrated. It consists in a Hinged Lifting Arch (HLA), using FRP (Fiber Reinforced Polymer) bonded strips. In details, a series of blocks are cut following an arch geometry and then aligned on the ground-floor in order to bond a composite on their top surface. Moreover, the impregnation of the polymeric adhesive is not allowed at the extremities of each block. The fiber sheet is applied continuously along the entire extrados. In this sense, hinges are introduced, in fact, the FRP-connected blocks are able to easily rotate, in the opposite direction, around the contact ends (i.e. hinge). Finally, the middle block is lifted-up and the arch takes the desiderated shape. In the first experimental demonstration, the natural calcareous stone was used, even if the proposed technique is totally material-independent. Moreover, an analytical model is proposed and discussed for designing the proper aspect ratio of the blocks in order to ensure the full mutual contact when the HLA is totally lifted up. The advantages of the proposed technique are related to the absence of scaffolds and improved seismic strength against horizontal loads thanks to the presence of the FRP, which limits the occurrence of hinges at the extrados.
ARTICLE | doi:10.20944/preprints202202.0324.v1
Subject: Engineering, Civil Engineering Keywords: curved link-slab; hingeless arch; theoretical derivation; parametric sensitivity analysis
Online: 25 February 2022 (07:45:06 CET)
This paper proposes a curved link-slab (CLS) structure, simplified into a hingeless-arch model, to address the current cracking phenomenon of CLS concrete. The stress formula of the hingeless arch under various loads is derived based on the classical mechanic's method. Based on an actual bridge example, the mechanical properties of CLS are analyzed under different loads and load combinations. The results show that: (1) the CLS stress is significantly lower than that of the flat link-slab structure (FLS), (2) its stress values are less than the concrete tensile limit, and (3) the CLS can effectively solve the concrete cracking phenomenon on the link-slab. The rationality of the stress formula derived from the simplified model of the hingeless arch is verified using the finite element method (FEM). The parametric sensitivity analysis shows that variation of the reinforcement ratio of the CLS has a limited impact on it. Considering both the concrete tensile and compressive limit, the thickness of the CLS should be 15 cm to 20 cm, and its design span should be about 5% to7.5% of the main beam length.
ARTICLE | doi:10.20944/preprints201904.0272.v1
Subject: Earth Sciences, Environmental Sciences Keywords: Coffee Output; Climate Change; Commodity Price Volatility; GARCH; ARCH; FMOLS
Online: 24 April 2019 (12:40:21 CEST)
Empirical evidence is lacking on the nexus between coffee commodity output, climate change and commodity price volatility of Africa’s most populous country, Nigeria and other developing countries. To fill this gap, this study analyzed the reaction of coffee output to climate change and commodity price volatility. We used secondary data from 1961 to 2015 from reliable sources for Nigeria. The study adopted GARCH, ARCH and FMOLS in analysis of coffee output reaction to climate change and commodity price volatility. The findings show that coffee output in Nigeria is influenced by climate change and the international commodity price of coffee. The study demonstrates the potential benefits of improving coffee output and export through climate mitigation and adaptation measures and revival of Agricultural Commodity Marketing in Nigeria and other developing countries.
ARTICLE | doi:10.20944/preprints202106.0444.v1
Subject: Social Sciences, Accounting Keywords: Stock Market; Financial Markets; News Model; KSE 100 Index; ARCH/GARCH; OLS
Online: 16 June 2021 (12:40:07 CEST)
This study will investigate different signals and events/news that determined the stock market's movements. As we know, many factors affect the stock market on a daily, weekly, and monthly basis, e.g., rate of interest, exchange rate, and oil prices, etc. Our research will investigate the impact of daily events/news in the KSE-100 index due to several policies announced and events/news in the country because the daily movements in the stock market can be determined only by different signals and events/news. Time series data is collected daily for particular reasons from "The News" (Daily Newspaper, Sunday edition) from 2010 to 2019. The results of this study show that political and global news affects the stock market index ferociously. For investors, the investment in blue chips is not less than a safe haven. When day-to-day transactions are concerned, there is always a higher panic attack than the herd behaviour in the stock exchange. Investors tend to make prompt responses to negative rather than positive news, which makes them risk averters. Our finding also confirmed that the ARCH/GARCH model is better than the simple OLS method concerning stock market upheaval.
ARTICLE | doi:10.20944/preprints201912.0163.v4
Subject: Mathematics & Computer Science, Probability And Statistics Keywords: ARCH; ARMA; functional data; functional principal components; functional time series; GARCH; invertible linear processes; parameter estimation; stationary solutions; Yule-Walker equation
Online: 23 September 2020 (04:32:09 CEST)
Conditional heteroskedastic financial time series are commonly modelled by (G)ARCH processes. ARCH(1) and GARCH were recently established in C[0,1] and L^2[0,1]. This article provides sufficient conditions for the existence of strictly stationary solutions, weak dependence and finite moments of (G)ARCH processes for any order in C[0,1] and L^p[0,1]. It deduces explicit asymptotic upper bounds of estimation errors for the shift term, the complete (G)ARCH operators and the projections of ARCH operators on finite-dimensional subspaces. The operator estimaton is based on Yule-Walker equations, and estimating the GARCH operators also involves a result estimating operators in invertible linear processes being valid beyond the scope of (G)ARCH. Moreover, our results regarding (G)ARCH can be transferred to functional AR(MA).
ARTICLE | doi:10.20944/preprints202210.0314.v1
Subject: Engineering, Biomedical & Chemical Engineering Keywords: Aortic surgery; Aortic arch; Three-way cannulation approach; Carotid artery perfusion; Pressure-volume loop; Lumped parameter model; Software simulation; Cardiovascular modelling.; CARDIOSIM
Online: 20 October 2022 (14:19:25 CEST)
Aortic disease has a significant impact on quality of life. Involvement of the aortic arch requires preservation of blood supply to the brain during surgery. Deep hypothermic circulatory arrest is an established technique for this purpose although neurological injury remains high. Additional techniques have been used to reduce the risk although controversy still remains. A three-way cannulation approach, including both carotid arteries and the femoral artery or the ascending aorta, has been used successfully for aortic arch replacement and redo procedures. We have de-veloped circuits of the circulation to simulate blood flow during this type of cannulation set up. The aim is to analyse using CARDIOSIM© cardiovascular simulation platform, how the haemodynamic and energetic parameters are affected and the benefit derived with particular reference to the cerebral circulation.
ARTICLE | doi:10.20944/preprints202108.0157.v1
Subject: Life Sciences, Cell & Developmental Biology Keywords: reptile, ventricular septation, endocardial cushions, semilunar valves, outflow tract, cartilage, foramen of Panizza, left aorta, right aorta, pulmonary trunk, pharyngeal arch arteries, coronary arter
Online: 6 August 2021 (11:08:56 CEST)
The outflow tract of crocodilians resembles that of birds and mammals as ventricular septation is complete. The arterial anatomy however, presents with a pulmonary trunk originating from the right ventricular cavum, and two aortae originating from either the right or left ventricular cavum. Mixing of blood in crocodilians cannot occur at ventricular level as in other reptiles, but instead takes place at aortic root level by a shunt, the Foramen of Panizza, the opening of which is guarded by two facing semilunar leaflets of both bicuspid aortic valves. Methods. Developmental stages of Alligator mississipiensis, Crocodilus niloticus and Caiman latirostris, have been studied. Results and Conclusions. The outflow tract septation complex can be divided into 2 components. The aorto-pulmonary septum divides the pulmonary trunk from both aortae, whereas the interaortic septum divides the systemic from the visceral aorta. Neural crest cells are most likely involved in the formation of both components. Remodeling of the endocardial cushions and both septa results in the formation of bicuspid valves in all three arterial trunks. The foramen of Panizza originates intracardially as a channel in the septal endocardial cushion.
ARTICLE | doi:10.20944/preprints201811.0335.v1
Subject: Engineering, Construction Keywords: 3D printing (3DP), Construction processes, Architectural design, Concrete Engineering, Numerical Modelling, Arch-Roof, High-density polyethylene (HDPE), Additive manufacturing (AM), Computer-aided design (CAD), Manufacture, Design, Sustainability
Online: 14 November 2018 (10:39:43 CET)
Three-dimensional (3D) printing technologies are transforming the design and manufacture of components and products across a variety of disciplines, however their application in the construction industry is still limited. Material deposition processes can achieve infinite geometries and have advanced from rapid prototyping and model-scale markets to their application in fabricating functional products, large objects and the construction of full-scale buildings. Many international projects have recently been realized and the construction industry is beginning to utilise these dynamic technologies. The potential advantages for integrating 3D printing into house construction are significant, these include the capacity for mass customization of designs and parameters for functional and aesthetic purposes, reduction in construction waste from highly precise material placement, and the use of recycled waste products in layer deposition materials. With the ultimate goal of improving construction efficiency and decreasing building costs, applying Strand7 Finite Element Analysis software, a numerical model was designed specifically for 3D printing in a cement mix incorporated with recycled waste product High Density Polyethylene (HDPE) and found that construction of an arched truss-like roof was structurally feasible without the need for steel reinforcements. The lab sizes prototypes were manufactured based on the destined numerical model by using a 3D printing technology. Currently available 3D printing technologies can be adopted for building construction and this paper discusses the applications, advantages, limitations and future directions of 3D printing as an innovative and viable solution for affordable house construction.