Platform Layout Research Articles

Efficient parts nesting schemes for improving stereolithography utilization

In the present paper, the platform layout optimization problem for the simultaneous fabrication of different parts, which is addressed in the batch planning of Stereolithography Additive Manufacturing technology, is studied. The methodology proposed in the paper employs a Genetic Algorithm technique for the 2D nesting of parts on the platform of the stereolithography machine. The build orientation of the parts is assumed fixed and is decided prior to layout optimization, according to part-specific quality and cost requirements. Three placement schemes, appropriately adapted to the problem, are considered for the parts nesting and fabrication layout definition. The algorithms and placement schemes developed are evaluated in several test cases/benchmarks involving parts with both simple and complex geometries. The computational results included in the paper indicate that the proposed methodology can lead to satisfactory layout/packing–nesting arrangements in a time efficient manner, leading, therefore, to substantial improvement of stereolithography machine utilization.

Quantitative assessment of hydrocarbon explosion and fire risks in offshore installations

A risk-based design framework should involve both risk assessment and risk management. This article introduces and describes a number of procedures for the quantitative assessment and management of fire and gas explosion risks in offshore installations. These procedures were developed in a joint industry project on the explosion and fire engineering of floating, production, storage and off-loading units (the EFEF JIP), which was led by the authors. The present article reports partial results, focussing on defining the frequency of fires and explosions in offshore installations. Examples of the aforementioned procedures’ application to a hypothetical floating, production, storage, and off-loading unit (FPSO) are presented. A framework for the quantitative risk assessment of fires and explosions requires the definition of both the frequency and consequences of such events. These procedures can be efficiently applied in offshore development projects, and the application includes the assessment of design explosion and fire loads as well as the quantification of effects of risk control options (RCO) such as platform layout, location and number of gas detectors, isolation of ignition sources etc.

A theory of platform-dependent low-level software

The C language definition leaves the sizes and layouts of types partially unspecified. When a C program makes assumptions about type layout, its semantics is defined only on platforms (C compilers and the underlying hardware) on which those assumptions hold. Previous work on formalizing C-like languages has ignored this issue, either by assuming that programs do not make such assumptions or by assuming that all valid programs target only one platform. In the latter case, the platform's choices are hard-wired in the language semantics. In this paper, we present a practically-motivated model for a C-like language in which the memory layouts of types are left largely unspecified. The dynamic semantics is parameterized by a platform's layout policy and makes manifest the consequence of platform-dependent (i.e., unspecified) steps. A type-and-effect system produces a layout constraint: a logic formula encoding layout conditions under which the program is memory-safe. We prove that if a program type-checks, it is memory-safe on all platforms satisfying its constraint. Based on our theory, we have implemented a tool that discovers unportable layout assumptions in C programs. Our approach should generalize to other kinds of platform-dependent assumptions.

Platform Layout for the New Britain to Hartford Busway

The New Britain to Hartford Busway is a two-lane, exclusive, bus-rapid-transit facility to be constructed along abandoned and active rail lines connecting the cities of New Britain and Hartford. The preliminary design and Environmental Impact Statement are currently being completed for this 15.1-km (9.4-mi), 12-station facility. As part of the preliminary design, a process of evaluating varying platform layout configurations was undertaken. To design the busway stations, many elements had to be taken into consideration. First, the busway is to provide multiple types of service, including express bus service, therefore requiring bus pull-offs. Second, the right-of-way along the busway corridor is narrow and the effect of this needs to be minimized; therefore, alternative platform layouts need to have a minimum width when possible. In addition, the busway operation and patron use had to be safe, secure, comfortable, and convenient while providing connectivity to the adjoining land use. Three platform configurations were investigated, including center platforms, traditional opposite platforms, and offset platforms. Although the offset platforms provided the narrowest design, their use was rare because they were perceived by many to be less safe for the rider than the opposite platform design. For most of the stations, a modified opposite platform design was chosen by the reviewing agencies and members of the public. The center platforms were eliminated because it was decided that the existing right-side-door fleet of buses would be used in conjunction with any new buses.

Testing schedule performance and reliability for train stations

On busy congested rail networks, randomdelays of trains are prevalent, and these delays have knock-on effects which result in a significant or substantial proportion of scheduled services being delayed or rescheduled. Here we develop and experiment with a simulation model to predict the probability distributions of these knock-on delays at stations, when faced with typical patterns of on-the-day exogenous delays. These methods can be used to test and compare the reliability of proposed schedules, or schedule changes, before adopting them. They can also be used to explore how schedule reliability may be affected by proposed changes in operating policies, for example, changes in minimum headways or dwell times, or changes in the infrastructure such as, layout of lines, platforms or signals. This model generates a reliability analysis for each train type, line and platform. We can also use the model to explore some policy issues, and to show how punctuality and reliability are affected by changes in the distributions of exogenous delays.

Unified stabilized platform for the international project (space solar patrol)

Unified stabilized platform (USP) is intended to point various instruments of space solar patrol (SSP) and to stabilize their axes toward the Sun irrespective of a space-craft or orbital station oscillations.The paper describes the platform layout and its interaction with scientific equipment: a spectrometer and two radiometers developed at the Vavilov State Optical Institute [1]. Principles of control structure development essentially depend on requirements of the USP operational accuracy taking into account dimensions and mass of the scientific payload. We propose a modular scheme for building stabilized platforms, which allow to unify them for various payloads to reduce the costs of the project considerably and to increase its scientific output.Since 1964 J.-S.Co. VNIITRANSMASH has been engaged in design, manufacture, tests, and delivery of space engineering products of various applications and also participates in their usage. Among the products are automatic chassis for Lunokhod-1 and 2, Mars rover M-71, PROP-FP apparatus intended to explore the Phobos surface, family of mini-and-micro planet rovers, manipulators for various applications, devices for studying of mechanical properties of the Moon and Venus soil.Since 1986 VNIITRANSMASH has been engaged in development and delivery of space stabilized platforms (with high and average accuracy of stabilization).

Modeling Decisions in Emergency Situations

Summary In this paper, we describe a methodology and supporting software tool that we developed for helping to model the decisions that people make in emergency situations offshore. We believe that this is the first time that people's decision-making has been incorporated into egress and evacuation models. Our work, therefore, is an important first step in the introduction of improved approaches to the evaluation of platform layout, facilities, and emergency procedures. We worked with our collaborators to integrate our model of people's decisions with their model of people's movement. Our result indicates that people's movements are modified by factors such as their reactions to alarms, their reactions to hazards, their familiarity with the installation, their training, and their roles. Our program has a generic architecture for modeling decisions. We used "scripts" to define typical actions or procedures associated with particular conditions: people in the computer simulation adopt particular scripts according to the situations in which they find themselves. In future developments, we would like to improve the decision model by incorporating communication between individuals as a scenario proceeds. This would be particularly useful in (1) scenarios that go beyond muster to evacuation, (2) scenarios where there is significant structural damage, (3) scenarios where there are casualties, and (4) scenarios that cannot be simulated realistically in exercises. The software runs on a 486 PC under Windows 3.1. Safety analysts can build floor plans and set up scenarios with different facilities, populations, or hazards to determine their various effects.