Accidents caused by hazardous materials released in an urban environment: a numerical and experimental approach.

This research studies the transport and dispersion of hazardous materials after a fire accident in an urban setting and the unpredictable threats provoked for the population and the environment. A fire accident may result, inter alia, from industrial activity or during the transportation of hazardous materials, such as diesel, petrol or kerosene liquids. In the current research, mineral oil pool fire accidents are examined in order to define the toxic smoke zones at different urban scale geometries. Three different urban scale geometries are examined: a) an isolated building, b) a street canyon and c) a staggered array of urban blocks. The fluid flow, the hazardous dispersion and the safety limits are studied using the Computational Fluid Dynamics (CFD) techniques and wind tunnel experiments. The Computational simulations were conducted using the CFD solver of Fluent and the Fire Dynamic Simulator (FDS). Both Reynolds-average Navier-Stokes (RANS) modes and Large Eddy Simulations (LES) methods were applied. Wind tunnel experiments were conducted in order to better understand the flow around these geometries and evaluate them with LES models. The numerical models were validated with wind tunnel experiments and with additional experimental data selected from the bibliography. The numerical results defined the toxic smoke limits and allowed the creation of simplified risk maps. The latter can define the mitigation measures after a fire accident.PhD in Aerospac

Essays in macroeconomics and finance

This thesis comprises three essays in macroeconomics and finance. In the first chapter we investigate the business cycle, property-price and investment dynamics when there is competition between households and firms for real estate. We introduce a construction sector into a RBC framework, which uses land, capital and labour to produce both commercial and residential real estate. This market structure activates a ‘real estate substitution channel’, where economic disturbances which alter the demand for one type of real estate, by affecting the overall costs of real estate production, endogenously create a substitution with its counterpart. For example, an increase in demand for residential real estate, also increases the cost of producing commercial structures which reduces the amount demanded by firms. In turn, this crowds out commercial real estate which affects the goods market in a similar way to an adverse aggregate supply shock. The estimated model reveals that housing preference shocks explain the largest part of the variation in property prices and residential investment, while commercial real estate prices are primarily driven by technology shocks. The second topic proposes a novel approach for testing for rational speculative bubbles in segmented capital markets. The basic idea is that, under capital controls, heterogeneity of speculative expectations across international equity markets causes financial assets with identical cash flow promises to trade at different prices. Because these deviations from the law of one price inherit the properties of the speculative bubble process, they display periods of explosive dynamics and have predictive power for future movements in equity prices in sample. These two hypotheses can be examined empirically using sequential unit root tests and predictive regressions. An attractive feature of this approach for bubble detection is that it does not require the specification of a model for market fundamentals, thus mitigating the well-known joint hypothesis problem. The focus of the paper is on mainland Chinese companies that cross list shares in Hong Kong. China is an ideal setting for our analysis because of the significant restrictions on capital movements imposed by the authorities and the turbulent behaviour of its stock market over the last decades. Finally, the third chapter investigates the causal effect of consumer confidence on the housing market dynamics, using narrative evidence. We adopt an external instrument approach that is using mass fatalities to identify exogenous variations in consumer confidence. We find that adverse sentiment shocks can negatively affect housing demand with a strong and prolonged reduction of house prices and new houses sold. The deterioration of sentiments worsens homeownership conditions, causes a response of monetary policy, and exacerbates real consumption spending. In a counterfactual experiment, we assess the importance of the housing market by restricting the response of the housing market variables to sentiment shock to be zero. We find that, the housing market can propagate the effect of the sentiment shock to the rest of the economy. The effect becomes particularly evident in longer horizons, specifically after one year, where the deviation from the unrestricted model becomes substantial

exuber:Recursive Right-Tailed Unit Root Testing with R

This paper introduces the R package exuber for testing and date-stamping periods of mildly explosive dynamics (exuberance) in time series. The package computes test statistics for the supremum ADF test (SADF) of Phillips, Wu, and Yu (2011), the generalized SADF (GSADF) of Phillips, Shi, and Yu (2015a,b), and the panel GSADF proposed by Pavlidis, Yusupova, Paya, Peel, Martinez-Garcia, Mack, and Grossman (2016); generates finite-sample critical values based on Monte Carlo and bootstrap methods; and implements the corresponding date-stamping procedures. The recursive least-squares algorithm that we introduce in our implementation of these techniques utilizes the matrix inversion lemma and in that way achieves significant speed improvements. We illustrate the speed gains in a simulation experiment, and provide illustrations of the package using artificial series and a panel on international house prices

Assessment of air flow distribution and hazardous release dispersion around a single obstacle using Reynolds-averaged Navier-Stokes equations

The flow around a cubical building, with a pollution source at the central point of the top of the cube, is studied. The Reynolds-averaged Navier-Stokes and species concentration equations are solved for Reynolds number, Re = 40,000, is based on the height of the cube. The predictions obtained with the standard, the Kato-Launder, and the low-Reynolds number k-epsilon models are examined with various wall functions for the near wall treatment of the flow. Results are compared against Martinuzzi and Tropea measurements (J. of Fluids Eng., 115, 85–92, 1993) for the flow field and against Li and Meroney (J. of Wind Eng. and Industrial Aerodynamics, 81, 333–345, 1983) experiments and Gaussian models for the concentration distribution. It is found that the present unstructured mesh model performs similarly to the structured mesh models. Results from the Kato-Launder model are closer to the experimental data for the flow patterns and contaminant distribution on the cube's roof. However, the Kato-Launder model has an over-prediction for the recirculation zone and the contaminant distribution windward of the cube. The standard k-epsilon and the low-Reynolds number k-epsilon models predict similar flow patterns and are closer to the experimental data of the cube's windward and side face

Real Estate and Construction Sector Dynamics Over the Business Cycle

This paper explores the property prices and investment dynamics over the business cycle when there is competition between households and firms for real estate. We introduce a construction sector into an RBC framework, which uses land, capital and labour to produce both commercial and residential real estate. This market structure activates a real estate substitution channel, where an increase in demand for residential real estate also increases the cost of producing commercial structures, which crowds out commercial real estate investment. In general, we find that the residential/commercial land allocation acts as an anchor for the allocation of its real estate investment counterpart; however, there are notable separations, particularly following the financial crisis where there was a simultaneous fall in residential and commercial investment. Our results indicate that whilst residential real estate prices were predominately driven by increases in its demand in the buildup to the financial crisis, the fall in demand for commercial real estate played a significant role in generating price falls for both types of real estate in the aftermath. Furthermore, falls in the overall supply of real estate played an important role in reducing real estate investment which put upward pressure on prices throughout the past two decades

Speculative Bubbles in Segmented Markets:Evidence from Chinese Cross-Listed Stocks

We propose a novel approach for testing for rational speculative bubbles in segmented capital markets. The basic idea is that, under capital controls, heterogeneity of speculative expectations across international equity markets causes financial assets with identical cash flow promises to trade at different prices. Because these deviations from the law of one price inherit the properties of the speculative bubble process, they display periods of explosive dynamics and have predictive power for future movements in equity prices in sample. These two hypotheses can be examined empirically using sequential unit root tests and predictive regressions. An attractive feature of this approach for bubble detection is that it does not require the specification of a model for market fundamentals, thus mitigating the well-known joint hypothesis problem. The focus of the paper is on mainland Chinese companies that cross list shares in Hong Kong. China is an ideal setting for our analysis because of the significant restrictions on capital movements imposed by the authorities and the turbulent behaviour of its stock market over the last decades

Computational assessment of the hazardous release dispersion from a diesel pool fire in a complex building’s area

A hazardous release accident taking place within the complex morphology of an urban setting could cause grave damage both to the population’s safety and to the environment. An unpredicted accident constitutes a complicated physical phenomenon with unanticipated outcomes. This is because, in the event of an unforeseen accident, the dispersion of the hazardous materials exhausted in the environment is determined by unstable parameters such as the wind flow and the complex turbulent diffusion around urban blocks of buildings. Our case study focused on a diesel pool fire accident that occured between an array of nine cubical buildings. The accident was studied with a Large eddy Simulation model based on the Fire Dynamics Simulation method. This model was successfully compared against the nine cubes of the Silsoe experiment. The model’s results were used for the determination of the immediately dangerous to life or health smoke zones of the accident. It was found that the urban geometry defined the hazardous gasses dispersion, thus increasing the toxic mass concentration around the buildings

Large eddy simulation of dispersion of hazardous materials released from a fire accident around a cubical building

The turbulent smoke dispersion from a pool fire around a cubical building is studied using large eddy simulation at a high Reynolds number, corresponding to existing experimental measurements both in laboratory and field test scales. Emphasis of this work is on the smoke dispersion due to two different fuel pool fire accident scenarios, initiated behind the building. For the setup of fire in the first case, crude oil was used with a heat release rate of 7.8 MW, and in the second, diesel oil with a heat release rate of 13.5 MW. It is found that in both fire scenarios, the downstream extent of the toxic zone is approximately the same. This is explained in terms of the fact that the smoke concentration and dispersion are influenced mainly by the convective buoyant forces and the strong turbulence mixing processes within the wake zone of the building. It is suggested that wind is the dominating factor in these accident scenarios, which represent the conditions resulting in the highest toxicity levels

The Effect Of Family And Social Environment On Smoking Behaviour In Adolescence

Background: Parental and peer smoking are considered major predictors of smoking in adolescence. We investigate the impact of family and social environment and parental anti-smoking socialization on the intensive and extensive margins of smoking for Greek adolescents. Method and Material: Information on 873 adolescents was collected through a self-reported survey and regression analysis examined associations with five different smoking outcomes (current/lifetime smoking status/intensity and onset). Subgroup analyses and interactions provided further insights. Results: Prevalence of adolescent smoking is high. Family and peer smoking habits and smoking restrictions at home reduce probability and intensity of smoking. Parental smoking increases probability of current smoking by 5% (95% CI: 0.01-0.09) as does having all your friends smoking by 30% (95% CI: 0.16-0.45). Parental anti-smoking advice delays onset of smoking by 0.76 years (95% CI: 0.15-1.39) but does not affect current smoking. Conclusion: Family and social environments play a significant role in preventing or promoting smoking and should be regarded as crucial factors when devising policy to curb adolescent smoking

Uterine Embolization as a New Treatment Option in Adenomyosis Uteri

Adenomyosis is characterized by the development of endometrial ectopic glands and tissue in the myometrium layer in depth greater than 2.5 mm from the endometrial surface of the separative area by -myomas well as by hypertrophy and hyperplasia of the smooth muscles of the myometrium. This is filtration, not mere displacement, of the myometrium, from the endometrium. Clinical symptoms include dysmenorrhea and menorrhagia. It is diffuse (adenomyosis) or focal (adenomyoma), asymmetrically affects the uterine wall of premenopausal women (usually the posterior) and often coexists with myomas. The pathogenesis of adenomyosis remains unknown. The treatment options are: drug therapy, invasive treatment of fibroids: myomectomy (open—intra-abdominal, laparoscopic, hysteroscopic), hysterectomy, myolysis—cryocatalysis, microwave or radiofrequency thermal catalysis (RF-ablation), ultrasound focus catalysis (FUS), laser photocatalysis and percutaneous selective uterine artery embolization (UAE). Embolization remains an alternative and not a substitute of hysterectomy. The medical indication is made on a case-by-case basis, depending on age, desire for pregnancy and the clinical symptoms of adenomyosis