On the minimum orbital intersection distance computation: a new effective method

The computation of the Minimum Orbital Intersection Distance (MOID) is an old, but increasingly relevant problem. Fast and precise methods for MOID computation are needed to select potentially hazardous asteroids from a large catalogue. The same applies to debris with respect to spacecraft. An iterative method that strictly meets these two premises is presented.Comment: 13 pages, 10 figures, article accepted for publication in MNRA

Mixing in convective thermal fluxes in unsteady nonhomogeneous flows generating complex three dimensional vorticity patterns

Diffusion and scaling of the velocity and vorticity in a thermoelectric driven heating and cooling experimental device is presented in order to map the different patterns and transitions between two and three dimensional convection in an enclosure with complex driven flows. The size of the water tank is of 0.2 x 0.2 x 0.1 m and the heat sources or sinks can be regulated both in power and sign [1-3]. The thermal convective driven flows are generated by means of Peltier effects in 4 wall extended positions of 0.05 x 0.05 cm each. The parameter range of convective cell array varies strongly with the Topology of the boundary conditions. Side heat and momentum fluxes are a function of Rayleigh, Peclet and Nusselt numbers, [4-6] Visualizations are performed by PIV, Particle tracking and shadowgraph. The structure of the flow is shown by setting up a convective flow generated by buoyant heat fluxes. The experiments described here investigate high Prandtl number mixing using brine and fresh water in order to form a density interface and low Prandtl number mixing with temperature gradients. The evolution of the mixing fronts are compared and the topological characteristics of the merging of the convective structures are examined for different configurations. Based on two dimensional Vorticity spectral analysis, new techniques can be very useful to determine the evolution of scales considering the multi-fractal structure of the convective flows.Peer ReviewedPostprint (published version

Congruences on monoids of order-preserving or order-reversing transformations on a finite chain

Glasgow Mathematical Journal, nº 47 (2005), pg. 413-424This paper is mainly dedicated to describing the congruences on certain monoids of transformations on a finite chain Xn with n elements. Namely, we consider the monoids ODn and PODn of all full, respectively partial, transformations on Xn that preserve or reverse the order, as well as the submonoid POn of PODn of all its order-preserving elements. The inverse monoid PODIn of all injective elements of PODn is also considered. We show that in POn any congruence is a Rees congruence, but this may not happen in the monoids ODn, PODIn and PODn. However in all these cases the congruences form a chain.This work was developed within the activities of Centro de ´Algebra da Universidade de Lisboa, supported by FCT and FEDER, within project POCTI ”Fundamental and Applied Algebra

Congruences on monoids of transformations preserving the orientation on a finite chain

Journal of Algebra, 321 (2009), p. 743–757Congruences on monoids of transformations preserving the orientation on a finite chai

The cardinal and the idempotent number of various monoids of transformations on a finite chain

Bulletin of the Malaysian Mathematical Sciences Society, 2, 34 (1),(2011), p. 79–85We consider various classes of monoids of transformations on a finite chain, in particular transformations that preserve or reverse either the order or the orientation. Being finite monoids we are naturally interested in computing both their cardinals and the number of their idempotents. In this note we present a short survey on these questions which have been approached by various authors and close the problem by computing the number of idempotents of those monoids not considered before. Fibonacci and Lucas numbers play an essential role in the last computations

KPI tree - a hierarchical relationship structure of key performance indicators for value streams

Performance Measurement Systems (PMS) have been a potential answer to problems related to production systems monitoring, allowing the management and manipulation of data collected at various levels in organizations. PMS can be defined as a group of indicators in an information system. There are several types of PMS, however, the relationship between indicators in a PMS is still an issue that needs to be explored, as the KPIs in a production system are not independent and may have an intrinsic relationship. The purpose of this paper is to present a multilevel structure and its intrinsic structural relation for managing and analysing KPIs for a value stream production system. This hierarchical structure has different KPI levels such as Improvement KPIs, Monitoring KPIs, and Results KPIs or KPR (Key Performance Results), intrinsically related from the strategic levels to the operational levels. This provides a useful tool for the management of production systems, being used to analyse, and support the organization's continuous improvement processes.This Work was supported by the FCT – Fundação para a Ciência e Tecnologia, Portugal, within the Project Scope UIDB/00319/2020. C.J. has been supported by operation NORTE-06-3559-FSE-000226, funded by Norte Portugal Regional Operational Program (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Social Fund (ESF)

Green façades and in situ measurements of outdoor building thermal behaviour

Using green façades in large cities with hot climates has been introduced in the search for more sustainable solutions for urban development. This paper presents the data collected in situ and quantifies the thermal external behaviour of a green wall and a bare one in the same surrounding environment in the city centre of Madrid, Spain. The methodological approach helps to assess the impacts of both walls on the variation of the urban temperature range at the microclimate scale in accordance with environmental physical data at different seasons and times of the day. In the summer campaign, the maximum values of air temperature reduction as measured in situ range between 2.5 °C and 2.9 °C which confirmed the values of various other studies using similar measurements. In the autumn campaign, the maximum values were half of the ones obtained for the summer, not exceeding 1.5 °C. However, these values increased after calculating similar conditions of sunlight in both façades. This comparative analysis of the experimental results on a green wall and a bare wall demonstrates that green façades can have a significant temperature reduction potential in the surrounding microclimate.The authors are grateful to the European Union Erasmusþ Program for funding the Portuguese researchers' trips and visits to Madrid

Asphalt mixtures produced with 100% reclaimed materials

The environmental and economic benefits of using Reclaimed Asphalt Pavement (RAP) material in hot mix asphalt (HMA) applications could be pushed up to the limit, by producing totally recycled HMAs (100% RAP), but the performance of this alternative must be satisfactory. In fact, these mixtures could possibly present a lower performance due to the behaviour of the aged binder, which loses its lighter fractions with time. In order to improve the mixture properties, a binder rejuvenator should be used. Thus, in the present study, the utilization of a used motor oil as a rejuvenator was evaluated. This would allow the modification of the aged binder, restoring some of its original properties and promoting an adequate performance of the mixture. The optimal amount of oil was determined by conventional bitumen tests, using the achievement of a bitumen with a penetration grade above, as the selection criterion for the definition of the amount of oil. Once the amount of rejuvenator (oil) was defined, laboratory specimens were prepared and tested for water sensitivity, permanent deformation, stiffness and fatigue, in order to confirm that the totally recycled mixture will perform as good as a conventional mixture used for comparison purposes.Fundação para a Ciência e a Tecnologia (FCT