Comparative study of offshore spar-buoy oscillating water column dynamic models for captured power estimation

The prompt estimation of power and geometrical aspects enables faster and more accurate financial assessment of wave energy converters to be deployed. This may lead to better commercialisation of wave energy technologies, as they require location-based customisation, unlike the mature wind energy technologies with developed benchmark. The adopted approach provides simple and efficient modelling tool allowing the study of the system from different perspective. The aim of this study is to select the optimum dynamic model to predict the captured power of a spar-buoy Oscillating Water Column (OWC) wave energy converter. Four dynamic models were developed to predict the system dynamics and results were validated experimentally. In-depth investigations on the effect of the mass and damping ratios of the oscillating bodies on the accuracy of the adopted models were performed. Such investigations included the proposed one-way coupling model and three two-degree of freedom models and three reduced-scale models, in addition to analytical and numerical solutions. Pneumatic power was calculated for the reduced-scale model where orifices’ covers simulated the power take-off mechanism damping experimentally. Analysis and comparisons between the adopted models are finally provided.

Geotechnical characterization and modelling of the “Fallen Lands” phenomenon in the amazon environment

In many rivers of the Amazon, mainly along the Amazon River, the phenomenon of "fallen land" occurs at the time of the rivers' ebb, causing the erosion of river banks, resulting in major social and economic problems. The influence of saturation/percolation of soil layers on the shear resistance of the affected massifs is unknown. Thus, the main objective of the characterization and geotechnical modelling of these slopes is to determine the shear strength of the affected massifs. For this purpose, deformed and undeformed samples were collected from the various layers of the soil massif in a location where the phenomenon was under development. These samples were characterized physically, chemically, and mechanically. Subsequently, the massifs were recreated in reduced scale models, observing the critical conditions in which the disaster occurred, and qualitatively comparing them with slope stability computational models. The results showed that the layers are classified as silty and sandy soils, with a small fraction of clay, and that there are three types of movements associated with the fallen soils: the fall, overturning, and rotational landslide, all actively influenced by the effects of the river's ebb, saturation/percolation, and texture.

Endings (c. AD 380–400)

The evidence for London’s late fourth century decline is put under the microscope. The paucity and problematic interpretation of dating evidence is discussed, but it is concluded that important elements of London’s urban infrastructure were in serious disrepair from as early as the 380s. Some main roads could no longer have carried regular wheeled traffic. Sites of former public buildings on the margins of towns were converted into small cemeteries in the late fourth century, showing that the city was still populated but on a reduced scale and hinting at a closer relationship between communities of the living and communities of the dead. Rich assemblages recovered from within some wells within the town are thought likely to represent termination rituals, as properties were closed and households departed. Abandonment horizons can also be described from the finds left behind over the latest floors of some houses. These acts of closure and departure may also have begun in the 380s, perhaps under Magnus Maximus who had briefly revived London’s mint but also withdrew troops and administrators from Britain. Whilst the city may still have been occupied into the fifth century, this is far from certain, and there is no evidence of repair and refurbishment of urban properties beyond the last years of the fourth century. This evidence of redundancy and retreat seems consistent with the interrupted history of the diocesan administration. London had become marginal city of relatively little importance to Rome.

The Improved Motion Model of Particles in the Cone Crusher Considering the Spatial Compound Motion of the Mantle

The cone crusher is the main equipment in the particle crushing process. The productivity of the cone crusher is determined by the motion characteristics of particles passing through the crushing chamber. In order to accurately describe the motion characteristics of the particles, the influence of the spatial compound motion of the mantle rotates around the central axis of the cone crusher and its central axis on the motion characteristics of the particles is investigated, then the improved motion model is established. Through the coordinate system transformation matrix, the motion characteristics of the particles including spatial sliding, free-falling, and spatial compound falling are solved. The applicability and accuracy of the improved model in describing the motion characteristics of the particle were verified through the experiment using a reduced-scale experimental cone crusher to simulate the motion characteristics of the particle. Based on the improved model, the motion characteristics of the particles in the CF11 hydraulic cone crusher can be simulated. With the decrease in height, the motion characteristics of particles gradually change from spatial sliding to spatial compound falling and finally to free-falling. The particles deflect circumferentially around the central axis of the cone crusher. The circumferential deflection of particles is directly related to the motion characteristics including spatial sliding and spatial compound falling. The improved model provides a theoretical basis for the high energy design of the crushing chamber and productivity improvement of the cone crusher.

Marina el-Alamein as an Example of Painting Decoration of Main Spaces of Hellenistic-Roman Houses in Egypt

The article is based on the research conducted by the authors. The houses from the ancient town discovered in 1985 on the Mediterranean coast at the location of today’s Marina el-Alamein, are among the rare remains of Egyptian residential buildings from Hellenistic and Roman times. There are few remains of houses from this period in major cities, including the capital of Alexandria. The ancient town, which functioned under the influence of nearby Alexandria, developed from the second century BC to the sixth century AD. Various types of buildings, relatively well preserved here, provide information on a reduced scale about the architecture of Alexandria, as well as the lives of its inhabitants. This also applies in particular to residential houses, their décor and colours. The ancient town of Marina el-Alamein can be seen as demonstrating solutions that are more common. The present article aims to analyse the preserved remains of painting decoration in the main spaces of houses and attempts to reconstruct forms and the principles of their creation on the background of better-known solutions from other regions. Houses in Marina generally implemented layouts defined by flagstone-paved portico courtyards, sporadically taking the form of an incomplete peristyle, and reception halls oikos, which could be accompanied by smaller adjoining rooms. Both the columns and entablature with the cornices of the porticoes as well as the walls of the main rooms were painted. Wall decoration was organised by geometric partitions, filled in variously. The aedicula that served religious purposes, placed centrally in the rear walls of the main reception rooms, was also polychrome. The painted decoration can be reconstructed from the preserved remains, as rich and intensely colourful, similar to Hellenistic and Roman layouts from other regions, but differing in details.

Design of a radiant panel test at reduced scale for the high throughput development of artificial turf structures

Artificial turf structures are increasingly used in closed areas and have to comply with the European fire standard for building products (EN ISO 13501-1). The main test to evaluate the fire performance of flooring products is the EN ISO 9239-1 radiant panel test. The test principle is to determine the critical heat flux of floorings exposed to a forced ignition and a specific heat flux profile. As large amounts of material are needed to perform the test, the development of a radiant panel test at reduced scale was considered. The experimental design methodology was implemented to mimic the heat flux profile. The fire performance of artificial turf structures was evaluated at both scales and the results were compared. The burnt lengths of the specimens and thus the critical heat flux are similar for both scales. Thus, the downscaled device could advantageously be used for high throughput development of artificial turf structures.

Conceptualisation of an Efficient Particle-Based Simulation of a Twin-Screw Granulator

Discrete Element Method (DEM) simulations have the potential to provide particle-scale understanding of twin-screw granulators. This is difficult to obtain experimentally because of the closed, tightly confined geometry. An essential prerequisite for successful DEM modelling of a twin-screw granulator is making the simulations tractable, i.e., reducing the significant computational cost while retaining the key physics. Four methods are evaluated in this paper to achieve this goal: (i) develop reduced-scale periodic simulations to reduce the number of particles; (ii) further reduce this number by scaling particle sizes appropriately; (iii) adopt an adhesive, elasto-plastic contact model to capture the effect of the liquid binder rather than fluid coupling; (iv) identify the subset of model parameters that are influential for calibration. All DEM simulations considered a GEA ConsiGma™ 1 twin-screw granulator with a 60° rearward configuration for kneading elements. Periodic simulations yielded similar results to a full-scale simulation at significantly reduced computational cost. If the level of cohesion in the contact model is calibrated using laboratory testing, valid results can be obtained without fluid coupling. Friction between granules and the internal surfaces of the granulator is a very influential parameter because the response of this system is dominated by interactions with the geometry.