Recent Brazilian research on thunderstorm winds and their effects on structural design

Riera, Jorge D.,Ponte, Jacinto Jr. Techno-Press 2012 Wind and Structures, An International Journal (WAS Vol.15 No.2

Codes for structural design usually assume that the incident mean wind velocity is parallel to the ground, which constitutes a valid simplification for frequent winds caused by sypnoptic events. Wind effects due to other phenomena, such as thunderstorm downbursts, are simply neglected. In this paper, results of recent and ongoing research on this topic in Brazil are presented. The model of the three-dimensional wind velocity field originated from a downburst in a thunderstorm (TS), proposed by Ponte and Riera for engineering applications, is first described. This model allows the generation of a spatially and temporally variable velocity field, which also includes a fluctuating component of the velocity. All parameters are related to meteorological variables, which are susceptible of statistical assessment. An application of the model in the simulation of the wind climate in a region sujected to both EPS and TS winds is discussed next. It is shown that, once the relevant meteorological variables are known, the simulation of the wind excitation for purposes of design of transmission lines, long-span crossings and similar structures is feasible. Complementing the theoretical studies, wind velocity records during a recent TS event in southern Brazil are presented and preliminary conclusions on the validity of the proposed models discussed.

Recent Brazilian research on thunderstorm winds and their effects on structural design

Jorge D. Riera,Jacinto Ponte Jr. 한국풍공학회 2012 Wind and Structures, An International Journal (WAS Vol.15 No.2

Codes for structural design usually assume that the incident mean wind velocity is parallel to the ground, which constitutes a valid simplification for frequent winds caused by sypnoptic events. Wind effects due to other phenomena, such as thunderstorm downbursts, are simply neglected. In this paper, results of recent and ongoing research on this topic in Brazil are presented. The model of the threedimensional wind velocity field originated from a downburst in a thunderstorm (TS), proposed by Ponte and Riera for engineering applications, is first described. This model allows the generation of a spatially and temporally variable velocity field, which also includes a fluctuating component of the velocity. All parameters are related to meteorological variables, which are susceptible of statistical assessment. An application of the model in the simulation of the wind climate in a region sujected to both EPS and TS winds is discussed next. It is shown that, once the relevant meteorological variables are known, the simulation of the wind excitation for purposes of design of transmission lines, long-span crossings and similar structures is feasible. Complementing the theoretical studies, wind velocity records during a recent TS event in southern Brazil are presented and preliminary conclusions on the validity of the proposed models discussed.

Instability of pipes and cables in non-homogeneous cross-flow

Riera, Jorge D.,Brito, J.L.V. Techno-Press 1998 Wind and Structures, An International Journal (WAS Vol.1 No.1

The vibrations of bodies subjected to fluid flow can cause modifications in the flow conditions, giving rise to interaction forces that depend primarily on displacements and velocities of the body in question. In this paper the linearized equations of motion for bodies of arbitrary prismatic or cylindrical cross-section in two-dimensional cross-flow are presented, considering the three degrees of freedom of the body cross-section. By restraining the rotational motion, equations applicable to circular tubes, pipes or cables are obtained. These equations can be used to determine stability limits for such structural systems when subjected to non uniform cross-flow, or to evaluate, under the quasi static assumption, their response to vortex or turbulent excitation. As a simple illustration, the stability of a pipe subjected to a bidimensional flow in the direction normal to the pipe axis is examined. It is shown that the approach is extremely powerful, allowing the evaluation of fluid-structure interaction in unidimensional structural systems, such as straight or curved pipes, cables, etc, by means of either a combined experimental-numerical scheme or through purely numerical methods.

The Calibration of Instrumented Dies for Powder Compaction

Marba I.,Riera M.D.,Prado J.M. 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1

The correct computer simulation of the powder compaction stage requires the determination of the elastoplastic parameters which characterize its mechanical behavour. Instrumented dies are frequently used to monitor the longitudinal and radial stress occurring during powder compaction. When strain gages are employed a previous calibration is needed. Many sources of error exist that can lead to the incorrect calibration of the instrumented die. By means of a FEM simulation some of these problems are analysed. The effect of die wall thickness, compression length, and strain location are studied.

Wind velocity field during thunderstorms

Ponte, Jacinto Jr.,Riera, Jorge D. Techno-Press 2007 Wind and Structures, An International Journal (WAS Vol.10 No.3

Wind action is a factor of fundamental importance in the structural design of light or slender constructions. Codes for structural design usually assume that the incident mean wind velocity is parallel to the ground, which constitutes a valid simplification for frequent winds caused by meteorological phenomena such as Extratropical Storms (EPS) or Tropical Storms. Wind effects due to other phenomena, such as thunderstorms, and its combination with EPS winds in so-called squall lines, are simply neglected. In this paper a model that describes the three-dimensional wind velocity field originated from a downburst in a thunderstorm (TS) is proposed. The model is based on a semi empirical representation of an axially-symmetrical flow line pattern that describes a stationary field, modulated by a function that accounts for the evolution of the wind velocity with time. The model allows the generation of a spatially and temporally variable velocity field, which also includes a fluctuating component of the velocity. All parameters employed in the model are related to meteorological variables, which are susceptible of statistical assessment. A background wind is also considered, in order to account for the translational velocity of the thunderstorm, normally due to local wind conditions. When the translation of the TS is caused by an EPS, a squall line is produced, causing the highest wind velocities associated with TS events. The resulting vertical velocity profiles were also studied and compared with existing models, such as the profiles proposed by Vicroy, et al. (1992) and Wood and Kwok (1998). The present model predicts horizontal velocity profiles that depend on the distance to the storm center, effect not considered by previous models, although the various proposals are globally compatible. The model can be applied in any region of interest, once the relevant meteorological variables are known, to simulate the excitation due to TS winds in the design of transmission lines, long-span crossings, cable-stayed bridges, towers or similar structures.

Production of high-quality water by reverse osmosis of milk dairy condensates

Adrián Suárez,Francisco A. Riera 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.21 No.1

Low-pollution flash cooler (FC) condensates from the direct heat treatment of milk and milk-basedproducts were treated by means of reverse osmosis (RO) in order to obtain high-quality water for use inboilers. The behaviour of the spiral-wound membranes at the pilot-plant scale (8.2m2 surface area) wastested in terms of the permeate flow rate (J) and quality (conductivity and chemical oxygen demand(COD)) as a function of the operation conditions, including the pressure, temperature and volumeconcentration rate (VCR). Response surfaces were drawnwith the aim of obtaining information regardingthe permeate flow rate as well as conductivity and COD reduction in the range of the studied parameters. Based on the experimental data, a plant with a 90% recovery rate (RR)was proposed with the objective ofcarrying out a preliminary economic assessment, which yielded a payback of 1.16 years.

The Elastic Behaviour of Metal Powder Compacts

Prado J. M.,Riera M. D. 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1

Cylindrical specimens with different levels of density have been submitted to uniaxial compression tests with loading and unloading cycles. The analysis of the elastic loadings shows a non linear elasticity which can be mathematically represented by means of a potential law. Results are explained by assuming that the total elastic strain is the contribution of two terms one deriving from the hertzian deformation of the contacts among particles and another that takes into account the linear elastic deformation of the powder skeleton. A simple model based in an one pore unit cell is presented to support the mathematical model.

Plastic Behaviour of Green Powder Metallurgical Compacts

Prado J. M.,Riera M. D. 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1

The results of monotonic and cyclic uniaxial compression tests, in which the deviatoric component of the stress is predominant, carried out on green and recrystallized iron compacts with different levels of density are presented and discussed in order to analyse the macro and micro-mechanisms governing the mechanical behaviour of non-sintered PM materials. The plastic deformation of the particles, especially at the contact areas between neighbouring grains, produces an internal friction responsible for the main features observed in the behaviour of green metallic compacts. These results show important discrepancies with the plasticity models, Cam-Clay and Drucker-Prager Cap.

Real Exchange Rate Volatility, Economic Growth and the Euro

( Thorsten Janus ),( Daniel Riera Crichton ) 세종대학교 경제통합연구소 2015 Journal of Economic Integration Vol.30 No.1

This paper studies the impact of real effective exchange rate volatility on economic growth as well as the euro’s impact on real effective exchange rate volatility. We first show that after a plausible endogeneity correction, real effective exchange rate volatility is negatively associated with growth in a 1980~2011 panel of the OECD (Organization for Economic Cooperation and Development) countries. A one standard deviation volatility decrease is associated with a two percentage points growth increase. Second, we find that the euro adoption was associated with a decline of 0.4 standard deviations in long-run real effective exchange rate volatility before the Great Recession in 2008~2009. Moreover, while the Great Recession increased real effective exchange rate volatility by 38~189% of the sample mean for the countries outside the eurozone, the real effective exchange rate of the euro adopters were almost completely insulated. We conclude that real effective exchange rate stability may be growth-enhancing in the OECD countries and that the euro have played a growth-enhancing role at least before the recent eurozone debt crisis.

New-onset type 1 diabetes mellitus in the Paediatric Emergency Department: impact of the COVID-19 pandemic

Romero Raquel García,Riera Laia Baleta,Marcos Nuria Sanz,Constanti Vanessa Arias,Maza Victoria Trenchs Sainz de la,Luaces Carles 대한소아내분비학회 2023 Annals of Pediatirc Endocrinology & Metabolism Vol.28 No.3

Purpose: On the 14th of March 2020, the Spanish government decreed a state of alarm due to the coronavirus disease 2019 (COVID-19) pandemic, directly affecting healthcare. This situation led to delayed diagnosis of several serious diseases, and its impact on many diseases such as the onset of type 1 diabetes mellitus (T1DM) remains unknown. The aim of this study is to determine the impact of the COVID-19 pandemic on the onset of T1DM in children. Methods: A descriptive-observational study was performed using data from children younger than 18 years (n=115) admitted with diagnosis of T1DM. We compared the 8 months from May–December 2020 to the same timeframe in 2019. Results: Our data show an increase of newly attended cases of T1DM in 2020, due to referral of Catalan children with onset of diabetes to our centre. Moreover, fewer patients presented with simple hyperglycaemia at the onset of the COVID-19 period. Delay in consulting the hospital, decreased access to the healthcare system, and avoidance of hospitals to minimize exposure to COVID-19 could have contributed to this finding. There were no differences in the number of days of hospitalization (including days in the paediatric intensive care uniy) between the years. Conclusion: The effects of the lockdown during the COVID-19 pandemic not only delayed the diagnosis of diabetes, but also its allowed time for its severity to increase. Future studies should focus on the influence of new variants of COVID-19 on the onset of T1DM during the postvaccination period.