Electric Car Chassis for Shell Eco Marathon Competition: Design, Modelling and Finite Element Analysis

The increasing demand for energy efficient electric cars, in the automotive sector, entails the need for improvement of their structures, especially the chassis, because of its multifaceted role on the vehicle dynamic behaviour. The major criteria for the development of electric car chassis are the stiffness and strength enhancement subject to mass reduction as well as cost and time elimination. Towards this direction, this work indicates an integrated methodology of developing an electric car chassis considering the modeling and simulation concurrently. The chassis has been designed in compliance with the regulations of Shell Eco Marathon competition. This methodology is implemented both by the use of our chassis load calculator (CLC) model, which automatically calculates the total loads applied on the vehicle&rsquo s chassis and by the determination of a worst case stress scenario. Under this extreme stress scenario, the model&rsquo s output was evaluated for the chassis design and the FEA method was performed by the pre-processor ANSA and the solver Ansys. This method could be characterized as an accurate ultrafast and cost-efficient method. Document type: Articl

Effect of Irrigation Scheduling on Gerbera Flower Yield and Quality

Better understanding of the effects of irrigation frequency and dose on flower production of gerbera plants (Gerbera jamesonii) can lead to optimal water management and crop yield. Measurements of greenhouse microclimate and production and quality characteristics of a gerbera crop were carried out under two irrigation frequency regimens in soilless cultivation in a greenhouse located in Arta, Greece. Irrigation scheduling was based on solar radiation and performed whenever accumulated solar radiation energy outside the greenhouse reached 1650 kJ.m(-2) [high irrigation frequency (HIF)] or 3300 kJ.m(-2) [low irrigation frequency (LIF)I. The amount of water applied was 0.125 mm and 0.250 mm for HIF and LIF, respectively. Stem fresh length and thickness, and number of harvested gerbera flowers IN-ere measured along with crop evapotrarispiration, crop leaf area, and greenhouse microclimate variables. Measurements started 8 months after transplanting and lasted 90 days (May to July). Leaf area, fresh weight, harvested cut flowers, and the main quality characteristics of gerbera flowers (stein length and flower diameter) were unaffected by file irrigation frequency. In the framework of the experiment, simple formulas for calculation of leaf area index were developed. Finally, a first approach study of an alternative remote sensing irrigation control method using a reflectance index was made and the results are presented

Efficient computation of popular phylogenetic tree measures

Given a phylogenetic tree T of n nodes, and a sample R of its tips (leaf nodes) a very common problem in ecological and evolutionary research is to evaluate a distance measure for the elements in R. Two of the most common measures of this kind are the Mean Pairwise Distance (MPD) and the Phylogenetic Diversity (PD). In many applications, it is often necessary to compute the expectation and standard deviation of one of these measures over all subsets of tips of T that have a certain size. Unfortunately, existing methods to calculate the expectation and deviation of these measures are inexact and inefficient. We present analytical expressions that lead to efficient algorithms for computing the expectation and the standard deviation of the MPD and the PD. More specifically, our main contributions are • We present efficient algorithms for computing the expectation and the standard deviation of the MPD exactly, in Θ(n) time. • We provide a Θ(n) time algorithm for computing approximately the expectation of the PD and a O(n 2) time algorithm for computing approximately the standard deviation of the PD. We also describe the major computational obstacles that hinder the exact calculation of these concepts. We also describe O(n) time algorithms for evaluating the MPD and PD given a single sample of tips. Having implemented all the presented algorithms, we assess their efficiency experimentally using as a point of reference a standard software package for processing phylogenetic trees. © 2012 Springer-Verlag

Fast computation of categorical richness on raster data sets and related problems

In many scientific fields, it is common to encounter raster data sets consisting of categorical data, such as soil type or land usage of a terrain. A problem that arises in the presence of such data is the following: given a raster G of n cells storing categorical data, compute for every cell c in G the number of different categories appearing within a window centered at c. The window can either be a (2r+1)x(2r+1) square or a disk of radius r for a positive integer parameter r. We call this the categorical richness problem, and we present two algorithms for it: one for square windows that runs in O(n) time and one for circular windows that runs in O((1+K/r)n) time, where K is the number of distinct categories in G. The algorithms are not only efficient in theory, but also in practice: our experiments show that our algorithms can handle raster data of hundreds of millions of cells. The categorical richness problem is related to colored range counting, where the goal is to preprocess a colored point set such that we can efficiently count the number of colors appearing inside a query range. We present a data structure for colored range counting in R2 for the case where query ranges are squares. Our structure uses O(n polylog n) storage and has O(polylog n) query time, which is significantly better than what is known for arbitrary rectangular ranges

Evaluation of crop reflectance indices for greenhouse irrigation scheduling

Development of direct, non-contact, non-destructive methods for irrigation control purposes is of great interest. The present work deals with the evaluation of reflectance indices for irrigation control in greenhouse environment. On this purpose, measurements were carried out on a gerbera cultivation (Gerbera jamesonii) grown hydroponically in a greenhouse located at Arta, Greece. Radiation reflected by the plant canopy - in 8 narrow wavelength bands, centered at 460, 510, 560, 610, 660, 710, 760 and 810 nm - was monitored under different irrigation regimes at selected days during one year. Additionally, greenhouse microclimate variables, plant water use, substrate moisture, leaf temperature and stomatal resistance, were measured. Crop Water Stress Index (CWSI) and leaf stomatal resistance (rl) were used as reference indicators of plant water status in order to evaluate reflectance indices. The difficulties to apply remote sensing methods inside a greenhouse are related to noise removal such as interferences from greenhouse structure and machinery shadows, effects from heating systems, floor and substrate reflectance, distinction between different types of stress and definition of threshold values for irrigation scheduling. The presented results are expected to assist at the design of protocols for further research as they are promising regarding the development of reflectance indices for determination of irrigation events timing

Effects of planting and structural configurations on human thermal comfort in a schoolyard

Schoolyards are places where children spend a lot of their day. In highly populated Greek cities, schoolyards are usually surrounded by dense and elevated buildings, while the grounds are largely hard surfaces comprising asphalt, concrete, bricks and stone paving. This combination creates considerable thermal discomfort, especially in hot or Mediterranean-type climates. A study exploring the redesign of schoolyards to improve thermal comfort and heat stress conditions is presented in this paper. This included use of a microclimate model ENVI-met (V4), first validated using experimental data and then later applied to different case studies in schoolyards of Volos, a coastal city in central Greece. Microclimate measurements were carried out and thermal comfort and heat stress conditions evaluated by means of the physiologically equivalent temperature (PET, °C). The impact of materials, structures, obstacles, and different tree species on thermal comfort was also assessed. The results of the measured and simulated values were similar, including air temperature, relative humidity, solar radiation and mean radiant temperature (Tmrt). ENVI-met was then used to evaluate different landscape design proposals to improve outdoor human thermal comfort that prevail in schoolyards. © 2017 ISHS

Response of an eggplant crop grown under Mediterranean summer conditions to greenhouse fog cooling

The effects of greenhouse cooling using a high-pressure fog system on greenhouse microclimate and on eggplant (Solanum melongena) crop response were studied at the coastal area of western Greece. Measurements were carried out in two distinct greenhouse compartments involving: (1) no air humidity control and (2) a fog system operating in order to obtain a greenhouse air relative humidity of 80%. Fog cooling reduced mean fruit temperature by about 3 degrees C and maintained greenhouse air temperature below 32 degrees C, while maximum temperature without cooling reached 40 degrees C. Furthermore, fogging reduced air vapor pressure deficit by about 55% and increased crop stomatal conductance by about 73%. These changes, in combination with alterations in crop aerodynamic conductance, resulted in around 31% decrease of crop transpiration rate. Fog system cooling efficiency was relatively low (46%) resulting in relatively high water consumption for fog cooling, reaching an equivalent to about 60% of crop water uptake. Nevertheless, since fog cooling decreased crop water needs, total greenhouse water consumption with fog cooling was only 19% higher than with no air humidity control. These results indicate the need to increase the cooling efficiency of fog systems in order to reduce greenhouse water consumption. Furthermore, the fog system enhanced mean fruit weight and marketable fruits, but appreciably reduced total fruit number per plant. Finally, fog cooling did not affect fruit quality characteristics such as fruit resistance to penetration, skin colour, fruit titratable acidity and total soluble solids. (C) 2009 Elsevier B.V. All rights reserved

Design of extensive green roofs for the major school plants of Piraeus

Despite the increase of global awareness regarding environment related issues and the development of relevant international policies; effective activities to conserve open space remain inconsistent in Mediterranean cities. Additionally as urban areas continue to expand and free space at street level becomes more and more limited there is a greater need for innovative green technologies which could contribute to the creation of sustainable urban ecosystems. Green roofs on buildings have already proved valuable for storm water management, energy conservation, microclimate mitigation, pollution remediation and biodiversity restoration, but their spreading in Mediterranean cities is still very limited. The shallow-substrate extensive type of green roofs is of great interest for massive application, which would lead to great scale positive effects in urban ecosystems. In Greece, in the framework of a relevant initiative called "Green roofs on public buildings", pilot extensive green roofs for the four major school plants of the city of Piraeus were designed. These green roofs which have a total area of about 0.6 ha are located in highly populated districts with negligible green spaces. This presentation is focusing on the decision making processes during the design and the selection of the growing medium and the planting material. The methods and the parameters of the relevant landscape, bioclimatic, hydrologic, irrigation and drainage studies are also presented. It is expected that the construction of these green roofs will improve the life quality of the school communities and more generally of the citizens of Piraeus

Measurements and simulation of microclimatic effects of a horizontal hydroponic pergola

The microclimate model ENVI-met (V4) was used for predicting the effects of different systems of planted pergolas on the microclimate of an atrium. The model was firstly validated using experimental data and then used for different cases studies. The microclimate measurements were carried in a real construction project of a hydroponic pergola at Kostakii Campus of the Technological Education Institute of Epirus (Arta, Greece). The validation results showed a very good agreement between measured and simulated values of air temperature. The model was used to predict the effects on air temperature (Tair), relative humidity (RH), mean radiant temperature (Tmrt) and Physiologically Equivalent Temperature (PET) when of 0%, 50% and 100% of the atrium horizontal plane area was covered by the planted pergola. The results showed that compared to the case with no pergola in the atrium, covering 100% the atrium area with a planted pergola reduced average Tair up to 0.78 and 1.3 °C during the day and night, respectively, while at the hottest time of day, Tmrt was lowered 29.4 °C and the PET was lowered up to 17.9 °C. © 2015 for this paper by its authors