A case study of process facility optimization using discrete event simulation and genetic algorithm

Optimization problems such as resource allocation, job-shop scheduling, equipment utilization and process scheduling occur in a broad range of processing industries. This paper presents modeling, simulation and optimization of a port facility such that effective operational management is obtained. A GA base approach has been integrated with the port system model to optimize its operation. A case study of bulk material port handling systems is considered

On the Gannon-Lee Singularity Theorem in Higher Dimensions

The Gannon-Lee singularity theorems give well-known restrictions on the spatial topology of singularity-free (i.e., nonspacelike geodesically complete), globally hyperbolic spacetimes. In this paper, we revisit these classic results in the light of recent developments, especially the failure in higher dimensions of a celebrated theorem by Hawking on the topology of black hole horizons. The global hyperbolicity requirement is weakened, and we expand the scope of the main results to allow for the richer variety of spatial topologies which are likely to occur in higher-dimensional spacetimes.Comment: 13 pages, no figures, to appear in Class. Quantum Gra

Semiconductor technology program: Progress briefs

Measurement technology for semiconductor materials, process control, and devices, is discussed. Silicon and silicon based devices are emphasized. Highlighted activities include semiinsulating GaAs characterization, an automatic scanning spectroscopic ellipsometer, linewidth measurement and coherence, bandgap narrowing effects in silicon, the evaluation of electrical linewidth uniformity, and arsenicomplanted profiles in silicon

Engaging for the future:challenge-based learning and stakeholder partnerships in sustainability education

This paper aims to illustrate a mechanism and the impact of collaboration between academia and external stakeholders using a challenge-based learning (CBL) approach, with ill-defined open challenges as the starting point of the learning journey. The context of the study is a sequence of three connected courses that enabled students to address pressing sustainability challenges both in the Global South and the Global North in a variety of fields, such as health, urban living, agriculture and waste management. The courses aimed to equip students with knowledge and skills on how to tackle the challenges and design responsible innovations, as well as inspire them to make an impact in the world, while collaborating with external stakeholders. The insights gained from this study are that the courses effectively fostered critical thinking, organizational skills, and teamwork capabilities among students. The collaboration with external partners was particularly valued by the students for its relevance to their learning and potential career progression, as it allowed them to take ownership of the challenges to tackle, thereby enhancing motivation and deepening their learning experience. Furthermore, the courses were successful in enabling students to apply knowledge to real-world cases and engage in meaningful debates on responsible innovation and SDGs

Uniqueness of de Sitter space

All inextendible null geodesics in four dimensional de Sitter space dS^4 are complete and globally achronal. This achronality is related to the fact that all observer horizons in dS^4 are eternal, i.e. extend from future infinity scri^+ all the way back to past infinity scri^-. We show that the property of having a null line (inextendible achronal null geodesic) that extends from scri^- to scri^+ characterizes dS^4 among all globally hyperbolic and asymptotically de Sitter spacetimes satisfying the vacuum Einstein equations with positive cosmological constant. This result is then further extended to allow for a class of matter models that includes perfect fluids.Comment: 22 pages, 2 figure

On the topology of stationary black holes

We prove that the domain of outer communication of a stationary, globally hyperbolic spacetime satisfying the null energy condition must be simply connected. Under suitable additional hypotheses, this implies, in particular, that each connected component of a cross-section of the event horizon of a stationary black hole must have spherical topology.Comment: 7 pages, Late

Holding Media Responsible for Deceptive Weight-Loss Advertising

In Fall 2002, the Federal Trade Commission held a Workshop exploring the problem of misleading weight-loss promotional pitches. After the agency spent decades cleaning up deceptive advertising, the weight-loss industry continues to be replete with such tactics. In an attempt to more aggressively attack those deceptions, the FTC used the Workshop as a forum to suggest that media should play a more active role in screening ads for diet products and programs. Some saw this as an implied threat that the agency may begin holding media liable for publishing those ads. Media protest that this forces them into the de facto role of regulators, and could create a chilling effect, leading fearful media to censor speech that is not deceptive. This article explores the FTC\u27s legal authority and the constitutional viability of making media responsible for the role they play in delivering these deceptive weight-loss messages to the public and finds no obstacles in the agency\u27s path

Small scale structures in three-dimensional magnetohydrodynamic turbulence

We investigate using direct numerical simulations with grids up to 1536^3 points, the rate at which small scales develop in a decaying three-dimensional MHD flow both for deterministic and random initial conditions. Parallel current and vorticity sheets form at the same spatial locations, and further destabilize and fold or roll-up after an initial exponential phase. At high Reynolds numbers, a self-similar evolution of the current and vorticity maxima is found, in which they grow as a cubic power of time; the flow then reaches a finite dissipation rate independent of Reynolds number.Comment: 4 pages, 3 figure

Visualisation of alternating shielding gas flow in GTAW

The alternating shielding gas technique is a method of achieving transient arc characteristics during arc welding; however the complex flow that occurs through its use has not been investigated previously. A schlieren system was used to image density gradients that arise when alternating argon and helium shield gases, under varying flow parameters, with gas tungsten arc welding (GTAW). A theoretical analysis was carried out to determine the conditions under which the technique facilitates arc pulsing, in particular to avoid mixing the shield gases in the delivery pipe prior to the welding nozzle. At appropriate pulsing frequency and flow rates, a stable horizontal region of helium was obseved in the weld region, maintained in position by the denser argon from the preceding pulse. This higher than average mass fraction of helium when applying the shielding gases alternately, compare to a premixed gas with the same volume of argon and helium, increased the weld penetration by 13% on average, suggesting a modest improvement in heat transfer