Numerical simulation of long and slender cylinders vibrating in axial flow applied to the Myrrha reactor

Flow induced vibrations are an important concern in the design of nuclear reactors. One of the possible designs of the 4th generation nuclear reactors is a lead-cooled fast reactor of which MYYRHA is a prototype. The combination of high liquid density, flow velocity, low pitch-to-diameter ratio and the absence of grid spacers makes this design prone to flow induced vibrations. Although most vibrations are induced by cross flow, axial flow around this slender structure could also induce vibrations. In order to gain insight in the possible vibrations (either induced by cross flow, axial flow or an external excitation) this study examines the change of eigenmodes and frequencies of a bare rod due to the lead-bismuth flow. To do so partitioned simulations of the fluid structure interaction are performed in which the structure is initially perturbed according to an in-air eigenmode

Design an Optimum Highway Route using Remote Sensing Data and GIS-Based Least Cost Path Model, Case of Minya-Ras Ghareb and Minya-Wahat-Bawiti Highway Routes, Egypt

The traditional method of aligning highways is a tedious, time-consuming process, and needs a lot of manual work, expensive consuming and complicated process, where numerous environmental issues need to be addressed. The problem is exacerbated where the alignment is influenced by the location of services, existing roads, and buildings. Therefore, there is a great need to adopt new technologies that save time and money in designing and assessment of highway paths. Remote Sensing and GIS make the highway alignment most appropriate avoiding vulnerable high-risk zones such as sand dunes, stream crossing, fault zones, etc….in addition to considering environmental protection constraints and cost savings. It needs less manpower, less time consuming and less cost. In this context, a survey was conducted to determine the factors that affect the process of choosing the path of roads through the previous literature and a panel of experts. Minya Ras-Gharib road in the Eastern Desert of Egypt and Minya Wahat Bawiti road in the Western Desert of Egypt as a case study. Remotely sensing techniques, Landsat 8 and digital elevation models were used to produce land use maps, sand dunes, existing roads, slopes, and flood sites. In addition, thematic maps such as rock type, faults, protectorates. Cost factors were determined and cost surface for each factor was established, standardized, weighed and aggregated based on previous literature. A pairwise comparison is used to determine the weight of factors. These weighted factors /criteria maps were combined to create the least cost surface map. Four visions were modeled: an economic vision, an environmental vision, an equal vision, and economy only vision. A comparison was made between the four-route using the DEFINITE software.The equal-weights route was the best route. A comparison was made between the equal-weight route and the existing route.The results of the comparison show that the recommended route save about 48% for the road of Minya Ras Gharib and save about 33 % for the road of Minya Wahat Bawiti compared to the existing road, in addition to saving the time, effort and cost

Cooling towers influence in an urban environment: A predictive model to control and prevent Legionella risk and Legionellosis events

Cooling towers (CTs) are used to dissipate excess heat from water by evaporation, common in large facilities as hospital, companies, and hotels. The main risk attributed to CTs is represented by Legionella, a Gram-negative bacterium associated with a severe form of pneumonia known as Legionnaires' disease (LD). The infection route is by inhalation of aerosols reaching the lower respiratory tract. Despite several events associated with CTs, the knowledge in this field is still limited. The aim of this study was to develop a predictive model of bioaerosol dispersion using PM10 particles as a proxy, to generate risk maps of Legionella spread in the surrounding area in several weather and microbiological conditions. The Legionella contamination in the CT basin was 40938 ± 24523 cfu/L, with four peaks independent of the season, associated with an increase in air minimum temperature values (+1–2 °C) and a high relative humidity (66–100%) preceded by rainfall (0.2–30.6 mm/day). The model revealed that the most extensive bioaerosol spread is predicted in winter and summer, with an increase in Legionella risk at a distance of up to 1.5 km from the CT. This method represents a novel integrated approach for the prevention and management of LD risk in CTs

POVEĆANJE IZOLACIJSKIH SVOJSTAVA FILTARSKIH RESPIRATORA ZA ZAŠTITU DIŠNIH ORGANA RUDARA OD PRAŠINE

To increase the insulating properties of elastomeric half-masks, it is suggested to perforate the obturator in the area of the nasal bridge, chin and cheeks, which allows for adjustment in its size, thus preventing the occurrence of wrinkles on the user’s face in the areas which are the individual features of a particular user’s face. Three versions of the perforated filter respirator obturator have been proposed: in the first, the holes are made along the entire perimeter of the obturator; in the second, the holes are only in the area of the cheeks and nasal bridge; in the third, incisions with a diameter of 5 mm are made in the area of the nasal bridge and cheeks. The result of modelling a set of alternative solutions taking into account the coefficient of protection of filter respirator half-masks, the distribution of compressive forces, which are determined in the environment of the packages “ANSYS” and “Solid works”, has been obtained on the basis of main indicators of the proposed models. To make a decision on choosing the best model, the mass of the elastomeric half mask, its dimensions and the complexity of the design were additionally considered. On the basis of expert evaluation, according to the described procedure for determining the utility function of the factors from their values, it has been defined that the second model of the half-mask is characterized by the best parameters. Conducted laboratory studies to determine the aerosol absorption coefficient by the obturation line showed the lowest indicator in the second option.Kako bi se povećala izolacijska svojstva elastomernih polumaski, predlaže se perforacija brtve u području hrpta nosa, brade i obraza, što omogućuje promjenu njezine veličine i sprječava pojavu bora na licu korisnika na mjestima gdje su specifične značajke lica određenoga korisnika. Predložene su tri inačice perforiranih brtvi filtarskoga respiratora: u prvoj su rupe napravljene po cijelome obodu brtve, u drugome su rupe samo u području obraza i nosnoga mosta, a u trećemu se rade rezovi promjera 5 mm u području nosnoga hrpta i obraza. Alternativna rješenja razvijena su temeljem glavnih pokazatelja dobivenih modeliranjem u programskim paketima „ANSYS” i „Solid works”, uzimajući u obzir koeficijent zaštite filtarskoga respiratora polumaski, raspodjelu tlačnih sila. Za donošenje odluke o odabiru najboljega modela dodatno su u obzir uzeti: masa elastomerne polumaske, njezine dimenzije i složenost dizajna. Na temelju ekspertne ocjene, prema opisanome postupku određivanja funkcije korisnosti faktora iz njihovih vrijednosti, utvrđeno je da drugi model polumaske karakteriziraju najbolji parametri. Provedene laboratorijske studije za određivanje koeficijenta apsorpcije aerosola linijom začepljenja pokazale su najniže vrijednosti u drugoj inačici

Computational design of an automotive twist beam

International audienceIn recent years, the automotive industry has known a remarkable development in order to satisfy the customer requirements. In this paper, we will study one of the components of the automotive which is the twist beam. The study is focused on the multicriteria design of the automotive twist beam undergoing linear elastic deformation (Hooke's law). Indeed, for the design of this automotive part, there are some criteria to be considered as the rigidity (stiffness) and the resistance to fatigue. Those two criteria are known to be conflicting, therefore, our aim is to identify the Pareto front of this problem. To do this, we used a Normal Boundary Intersection (NBI) algorithm coupling with a radial basis function (RBF) metamodel in order to reduce the high calculation time needed for solving the multicriteria design problem. Otherwise, we used the free form deformation (FFD) technique for the generation of the 3D shapes of the automotive part studied during the optimization process

Effect of atmospheric aging on volatility and reactive oxygen species of biodiesel exhaust nano-particles

In the prospect of limited energy resources and climate change, effects of alternative biofuels on primary emissions are being extensively studied. Our two recent studies have shown that biodiesel fuel composition has a significant impact on primary particulate matter emissions. It was also shown that particulate matter caused by biodiesels was substantially different from the emissions due to petroleum diesel. Emissions appeared to have higher oxidative potential with the increase in oxygen content and decrease of carbon chain length and unsaturation levels of fuel molecules. Overall, both studies concluded that chemical composition of biodiesel is more important than its physical properties in controlling exhaust particle emissions. This suggests that the atmospheric aging processes, including secondary organic aerosol formation, of emissions from different fuels will be different as well. In this study, measurements were conducted on a modern common-rail diesel engine. To get more information on realistic properties of tested biodiesel particulate matter once they are released into the atmosphere, particulate matter was exposed to atmospheric oxidants, ozone and ultra-violet light; and the change in their properties was monitored for different biodiesel blends. Upon the exposure to oxidative agents, the chemical composition of the exhaust changes. It triggers the cascade of photochemical reactions resulting in the partitioning of semi-volatile compounds between the gas and particulate phase. In most of the cases, aging lead to the increase in volatility and oxidative potential, and the increment of change was mainly dependent on the chemical composition of fuels as the leading cause for the amount and the type of semi-volatile compounds present in the exhaust

On the temporal modelling of solar photovoltaic soiling: energy and economic impacts in seven cities

This work developed a framework to predict the energy and economic impacts of solar photovoltaic soiling. This framework includes the effects of relative humidity, precipitation and tilt angle on solar photovoltaic soiling. A concept of relative net-present value change was introduced to determine the optimal cleaning interval. The uncertainties in the economic analysis were accounted for using a Monte Carlo simulation method. The framework was used to study the soiling-induced efficiency and economic losses of solar photovoltaic modules in seven cities (i.e. Taichung, Tokyo, Hami, Malibu, Sanlucar la Mayor, Doha, and Walkaway). Overall, the efficiency loss (in ascending order) for Tokyo/Walkaway < Taichung < Sanlucar la Mayor < Malibu/Hami < Doha for a one-year study period. Doha experiences an efficiency loss over 80% for a 140-day exposure, while Tokyo has an efficiency loss less than 4% for a one-year exposure. Malibu has longest optimal cleaning intervals (70 days for manual cleaning and 49 days for machine-assisted cleaning) that leads to the relative net-present value changes of 1.7% and 1.1%. Doha has the shortest optimal cleaning intervals (23 days for manual cleaning and 17 days for machine-assisted cleaning) that leads to the relative net-present value changes of 21% and 19%. The work serves as an effective tool for designing optimal cleaning protocols for solar photovoltaic systems