Search

This paper presents a two-dimensional (2D) numerical model of soil erosion and sediment transport resulting from rainfall induced overland flow. It is a spatial and temporal dynamic model combining physical and empirical laws and comprises: i) An overland flow module that solves the two-dimensional unsteady water flow equations on an infiltrating surface; ii) A soil infiltration module that uses a combined Horton-SCS scheme; and iii) A soil erosion and sediment transport module that solves the two-dimensional sediment transport equation, distinguishing between rill erosion, interrill erosion and sediment deposition.

3D printing (3DP) presents great potential for automation, sustainability, and quality control in the construction sector. However, research on 3DP in Construction has been carried out primarily from a structural standpoint, and information on the thermal performance, comfort and energy efficiency of these solutions remains very limited. Given the importance of assessing how printed walls perform when subjected to hygrothermal solicitations, this work experimentally analyses a cement-based mortar specially developed for 3DP. An extensive laboratory campaign was carried out, and the following set of physical, hygric and thermal properties was obtained: the dry bulk density, saturation moisture content, specific heat capacity, porosity, water absorption due to capillary action, water vapour permeability, thermal conductivity (dry and moisture-dependent), and the sorption isotherm. The results show that the 3D printed cement-based mortar, which presents a dry density of 2060kg/m3and a thermal conductivity of 1.33 W/(mK), has a hygrothermal performance comparable to that of traditional cast concrete. This indicates that additional thermal insulation materials are required for appropriate thermal performance through the building envelope. Moreover, this detailed hygrothermal characterisation is suitable for design purposes, allowing the use of the obtained properties in future numerical simulations, important for studying the hygrothermal performance of printed building elements in service.

Nowadays, getting data remotely in a secure way, becomes critical and of utmost importance. The simple task of data transfer can be a problem in remote environments, where the network connectivity is unstable and can be unavailable for some period of times. In this paper is proposed a secure remote monitoring system with data encryption, which collects data from diverse sensors and display them to authenticated users, through charts in a website, with the option of exporting data using an Excel file format. The system created was tested with a hydraulic laboratory setup, where data is collected by a remote Data Logger, transmitted to a server and stored in a non-relational database by an encrypted data transmission that protects its integrity. The results obtained with the developed tests, regarding the success in data transmission, give good perspectives for its usability at a larger scale.

Insulating glasses (IGs) are composed by glass plates entrapping a cavity filled with a gas sealed by perimeter spacers. This composition pretends to guarantee higher energy efficiency and airborne sound insulation in buildings. The structural performances achieved by these IGs is not normally considered in detail. In fact, in codes there is no specific mechanical model for structural IGs under different loadings and boundary conditions, namely to estimate the vertical deflections when applied horizontally. For this, here a specific model, by combining some existing approaches, was proposed for two or four side supported IG under distributed/linear loadings. The main goal is to quantify if an IG follows a monolith or layered behaviour. Several analytical and numerical analyses using a finite element method (FEM) have been carried out. Then, the results have been validated against experimental laboratory measurements. Two specific IGs with different sizes have been used as case studies. Results show that FEM analyses of IGs are in close agreement with experimental measurements, whereas analytical code models are not as accurate as the numerical approach, in particular for two side supported IGs under linear loadings. Also, the effects of the gas and the interactions between superior and bottom glasses for a large IG are more relevant than for a small IG.

Improvement of the energy efficiency of residential buildings must ensure compliance with cost optimality criteria, assuming a specific lifespan of the building. At the same time, the energy retrofit of buildings ought to preserve their intrinsic architectural and heritage value. Portuguese residential buildings constructed before 1960 did not follow any energy efficiency rules. They represent 29% of the housing stock in the country and there is a high potential for increasing their energy efficiency. However, it costs more to implement envelope energy efficiency measures through retrofitting works than to provide for them in new buildings. An evaluation based on cost optimality criteria should therefore be performed. This work evaluates the energy performance of a Portuguese reference building typical of the pre-1960 building stock for different thicknesses of thermal insulation retrofit solutions (roof, facade, and ground floor) and systems. The study describes a sensitivity analysis that took a range of climate data, intervention costs, energy prices, discount rates, and energy needs into account. An energy needs factor dealt with the occupants’ habits and the effective reduction of energy consumption compared with the estimated energy needs.

Parasitic isopods, particularly members of the Bopyridae that infest crustacean hosts, have received scant study in many geographic regions. As part of a project aimed at documenting parasites of fish and invertebrates from the coast of Yucatán, Mexico, 2,467 individuals of the fiddler crab Uca spinicarpawere collected from March 2002 to July 2007. Based on the sampled specimens, we report the presence of Leidya distortain the branchial chamber of U. spinicarpafor the first time. We found a prevalence of 3.77%, mean intensity of 1.47, and mean abundance of 0.06 for this parasite. With the addition of L. distorta, the number of bopyrids reported from Mexican coasts increases to 44 species. Males of U. spinicarpawere more often infested than females, which could be due to the sex ratio being strongly skewed towards males in the host sample studied (0.85:0.15M:F). Morphological differences between males and juveniles, as well as between sub-adult and adult females of L. distortaare described.

Two specimens of Ophioderma ensiferumHendler and Miller, 1984 were collected at 2 different localities in the Yucatán Peninsula, Mexico. The first one collected at Alacranes Reef, Yucatán, a transition zone between the Gulf of Mexico and the Caribbean, and the second one in an anchialine cave located in Cozumel Island, Quintana Roo. These records expand the known distribution of the species to the southern part of the continental shelf of the Gulf of Mexico. This finding represents the first record of this ophiuroid on the continental shelf of Mexico, and also the first record of this species in an anchialine cave.

Abstract: This paper presents analytical Green''s functions for the transient heat transfer phenomena by conduction, for an unbounded medium, half-space, slab and layered formation when subjected to a point heat source. The transient heat responses generated by a spherical heat source are computed as Bessel integrals, following the transformations proposed by Sommerfeld [Sommerfeld A. Mechanics of deformable bodies. New York: Academic Press; 1950; Ewing WM, Jardetzky WS, Press F. Elastic waves in layered media. New York: McGraw-Hill; 1957]. The integrals can be modelled as discrete summations, assuming a set of sources equally spaced along the vertical direction. The expressions presented here allow the heat field inside a layered formation to be computed without fully discretizing the interior domain or boundary interfaces. The final Green''s functions describe the conduction phenomenon throughout the domain, for a half-space and a slab. They can be expressed as the sum of the heat source and the surface terms. The surface terms need to satisfy the boundary conditions at the surfaces, which can be of two types: null normal fluxes or null temperatures. The Green''s functions for a layered formation are obtained by adding the heat source terms and a set of surface terms, generated within each solid layer and at each interface. These surface terms are defined so as to guarantee the required boundary conditions, which are: continuity of temperatures and normal heat fluxes between layers. This formulation is verified by comparing the frequency responses obtained from the proposed approach with those where a double-space Fourier transformation along the horizontal directions [Tadeu A, António J, Simões N. 2.5D Green''s functions in the frequency domain for heat conduction problems in unbounded, half-space, slab and layered media. CMES: Computer Model Eng Sci 2004;6(1):43–58] is used. In addition, time domain solutions were compared with the analytical solutions that are known for the case of an unbounded medium, a half-space and a slab. [Copyright &y& Elsevier]

Abstract: Analytical Green''s functions in the frequency domain are presented for the three-dimensional diffusion equation in an unbounded, half-space, slab and layered media. These proposed expressions take into account the conduction and convection phenomena, assuming that the system is subjected to spatially sinusoidal harmonic heat line sources and do not require any type of discretization of the space domain. The application of time and spatial Fourier transforms along the two horizontal directions allows the solution of the three-dimensional time convection-diffusion equation for a heat point source to be obtained as a summation of one-dimensional responses. The problem is recast in the time domain by means of inverse Fourier transforms using complex frequencies in order to avoid aliasing phenomenon. Further, no restriction is placed on the source time dependence, since the static response is obtained by limiting the frequency to zero and the high frequency contribution to the response is small. The proposed functions have been verified against analytical time domain solutions, known for the case of an unbounded medium, and the Boundary Element Method solutions for the case of the half-space, slab and layered media. [Copyright &y& Elsevier]

This work describes an iterative technique for the definition of condensation across two-dimensional elements via the boundary element method (BEM). Initially, the BEM is used to calculate the steady-state conduction of heat and vapour diffusion, discretizing only the boundary materials'' discontinuities. Then, a small sub-domain is defined, where condensation develops; that is, where the vapour pressure exceeds the vapour saturation pressure. Using the Glaser approach, the vapour pressure is equalised to the vapour saturation pressure, and then the vapour equilibrium is redefined by means of the BEM solution. This process is repeated until all sub-domains where vapour pressure exceeds vapour saturation pressure are eliminated.The method is first implemented and validated by applying it to a simple one-dimensional hygrothermal problem, for which the solution is calculated analytically. The applicability of the proposed method is then illustrated by computing the two-dimensional condensation across a T shaped element, for different boundary conditions. [Copyright &y& Elsevier]

This paper presents the solution for transient heat conduction around a cylindrical irregular inclusion of infinite length, inserted in a homogeneous elastic medium and subjected to heat point sources placed at some point in the host medium. The solution is computed in the frequency domain for a wide range of frequencies and axial wavenumbers, and time series are then obtained by means of (fast) inverse Fourier transforms into space–time.The method and the expressions presented are implemented and validated by applying them to a cylindrical circular inclusion placed in an infinite homogeneous medium and subjected to a point heat source, for which the solution is calculated in closed form.The boundary elements method is then used to evaluate the temperature field generated by a point source in the presence of a cylindrical inclusion, with a non-circular cross-section, inserted in an unbounded homogeneous medium. Simulation analyses using this model are then performed to study the transient heat conduction in the vicinity of these inclusions. [Copyright &y& Elsevier]