Polynomial cubic splines with tension properties

In this paper we present a new class of spline functions with tension properties. These splines are composed by polynomial cubic pieces and therefore are conformal to the standard, NURBS based CAD/CAM systems

VELOS: A VR Platform for Ship-Evacuation Analysis

“Virtual Environment for Life On Ships” (VELOS) is a multi-user Virtual Reality (VR) system that aims to support designers to assess (early in the design Process) passenger and crew activities on a ship for both normal and hectic Conditions of operations and to improve ship design accordingly. This paper focuses On presenting the novel features of VELOS related to both its VR and Evacuation-specific functionalities. These features include: i) capability of multiple Users’ immersion and active participation in the evacuation process, ii) Real-time interactivity and capability for making on-the-fly alterations of environment Events and crowd-behavior parameters, iii) capability of agents and Avatars to move continuously on decks, iv) integrated framework for both the Simplified and the advanced method of analysis according to the IMO/MSC 1033 Circular, v) enrichment of the ship geometrical model with a topological model Suitable for evacuation analysis, vi) efficient interfaces for the dynamic specification and handling of the required heterogeneous input data, and vii) post Processing of the calculated agent trajectories for extracting useful information For the evacuation process. VELOS evacuation functionality is illustrated using Three evacuation test cases for a ro-ro passenger ship

A discrete methodology for controlling the sign of curvature and torsion for NURBS

This paper develops a discrete methodology for approximating the so-called convex domain of a NURBS curve, namely the domain in the ambient space, where a user-specified control point is free to move so that the curvature and torsion retains its sign along the NURBS parametric domain of definition. The methodology provides a monotonic sequence of convex polyhedra, converging from the interior to the convex domain. If the latter is non-empty, a simple algorithm is proposed, that yields a sequence of polytopes converging uniformly to the restriction of the convex domain to any user-specified bounding box. The algorithm is illustrated for a pair of planar and a spatial Bézier configuration

Use of VELOS platform for modelling and accessing crew assistance and passenger grouping in ship-evacuation analysis

VELOS, which stands for “Virtual Environment for Life On Ships”, is a multi-user VR system that aims to support designers, early in the design process, to assess passenger and crew activities on ship and improve ship design accordingly. VELOS functionalities provide design aids required for both normal and hectic operational conditions. This has been accomplished by integrating a broad range of software components in VELOS platform which includes tools targeting geometric and VR modelling, crowd microscopic modelling based on steering behaviours technology, as well as communication interfaces with external computational software packages. In the present work, we focus on the evacuation-specific functionality of VELOS by enhancing it with passenger-grouping and crew-assistance behaviour. This is mainly achieved by combining and extending steering behaviours, already used within VELOS, for crowd modelling, as, e.g., Leader-Follow and Cohere behaviour. This enhancement allows simulating the evacuation process more realistically and comparing results acquired for the scenarios prescribed by the IMO, with and without the consideration of grouping and crew-assistance behaviour

Shape-optimization of 2D hydrofoils using an Isogeometric BEM solver

In this paper, an optimization procedure, based on an Isogeometric BEM solver for the potential ow, is developed and used for the shape optimization of hydrofoils. The formulation of the exterior potential- ow problem reduces to a Boundary-Integral Equation (BIE) for the associated velocity potential exploiting the null-pressure jump Kutta condition at the trailing edge. The numerical solution of the BIE is performed by an Isogeometric Boundary-Element Method (BEM) combining a generic B-splines parametric modeler for generating hydrofoil shapes, using a set of eight parameters, the very same basis of the geometric representation for representing the velocity potential and collocation at the Greville abscissas of the knot vector of the hydrofoil's B-splines representation. Furthermore, the optimization environment is developed based on the geometric parametric modeler for the hydrofoil, the Isogeometric BEM solver and an optimizer employing a controlled elitist genetic algorithm. Multi-objective hydrofoil shape optimization examples are demonstrated with respect to the criteria i) maximum lift coefficient and ii) minimum deviation of the hydrofoil area from a reference area

VELOS : a VR platform for ship-evacuation analysis

Virtual Environment for Life On Ships (VELOS) is a multi-user Virtual Reality (VR) system that aims to support designers to assess (early in the design process) passenger and crew activities on a ship for both normal and hectic conditions of operations and to improve ship design accordingly. This article focuses on presenting the novel features of VELOS related to both its VR and evacuation-specific functionalities. These features include: (i) capability of multiple users’ immersion and active participation in the evacuation process, (ii) real-time interactivity and capability for making on-the-fly alterations of environment events and crowd-behavior parameters, (iii) capability of agents and avatars to move continuously on decks, (iv) integrated framework for both the simplified and advanced method of analysis according to the IMO/MSC 1033 Circular, (v) enrichment of the ship geometrical model with a topological model suitable for evacuation analysis, (vi) efficient interfaces for the dynamic specification and handling of the required heterogeneous input data, and (vii) post-processing of the calculated agent trajectories for extracting useful information for the evacuation process. VELOS evacuation functionality is illustrated using three evacuation test cases for a ro–ro passenger ship

Ship-Hull Shape Optimization with a T-spline based BEM-Isogeometric Solver

In this work, we present a ship-hull optimization process combining a T-spline based parametric ship-hull model and an Isogeometric Analysis (IGA) hydrodynamic solver for the calculation of ship wave resistance. The surface representation of the ship-hull instances comprise one cubic T-spline with extraordinary points, ensuring C2C2 continuity everywhere except for the vicinity of extraordinary points where G1G1 continuity is achieved. The employed solver for ship wave resistance is based on the Neumann–Kelvin formulation of the problem, where the resulting Boundary Integral Equation is numerically solved using a higher order collocated Boundary Element Method which adopts the IGA concept and the T-spline representation for the ship-hull surface. The hydrodynamic solver along with the ship parametric model are subsequently integrated within an appropriate optimization environment for local and global ship-hull optimizations against the criterion of minimum resistance

Naval ship design-process analysis through dynamic social networks

Modern naval ship design is increasing in complexity as more and more systems are incorporated into the design process, leading to an increase in the number (and interdependence) of tasks that designers need to complete and progress through the design stages. This work develops a dynamic bipartite social network representation, separating the nodes in activities and individuals, with the aim to analyse and draw conclusions regarding the design process. A dynamic time-dependent graph (TDG) is constructed with the use of a presence function for the edges. Network properties (density, clustering, active tasks/designers) are expressed as functions of time, and node-wise metrics (centralities) reveal the key role of individuals in the naval ship design process, which is heavily-crowded with respect to tasks. Furthermore, application of the model to naval ship design data reveals interesting insights regarding the impact of COVID-19 and the design company’s adopted hiring policy

Parametric Analysis of Rib Pillar Stability in a Longitudinal Sublevel Open Stoping Operation in an Underground Copper Mine in Southern Africa

The pillar stability factor (PSF) is calculated in three different mining stages for a sublevel open stoping mining project located in northern Botswana. Several three-dimensional finite element models were developed by varying the stope span. Pillar strength was estimated using the Lunder and Pakalnis equation and pillar stress was obtained from the numerical models. As mining progresses, both the first and second mining stages meet the rib pillar stability factor requirement for safe extraction. Geometrical improvements are suggested in the mining layout for the third mining stage to achieve the required PSF, which is based on international practices