A note on optimization in deteriorating systems using scheduling problems with the aging effect and resource allocation models

AbstractThis paper concerns scheduling problems with the aging effect and additional resource allocation. A measurable result of the aging phenomenon is that the time required to perform a job increases whereas the additional resource allocation allows one to decrease it. As an example of a deteriorating system that can be described and optimized by the application of the models and algorithms considered, we choose the pickling process, where cleaning of metal items decreases the efficiency of the pickling (cleaning) bath (i.e., one containing an active substance), whereas heating it up can improve the efficiency. In particular, we focus on the optimization problems for such systems and model them as single-machine scheduling problems with job processing times dependent on the fatigue of a machine and on the allocation of additional resources. The objectives considered are the minimization of time criteria (the maximum completion time and the maximum lateness) under a given resource consumption as well as the minimization of the resource consumption under given time criteria. The computational complexity of the problems is determined and solution properties are proved. On the basis of these, we construct optimal polynomial time algorithms for some cases of the problems considered

Development and Validation of a Numerical Model of the CO2 Dry-ice Blasting Process for Aircraft Engine Cleaning Applications

On-wing cleaning of engine compressors for commercial aircraft is a required maintenance task which results in greater operating efficiency and lower emission rates. It is typically carried out by injection of water and detergents into the intake of an engine while the engine is being cranked by the starter. Two drawbacks of this process are the risk of icing in cold weather and the collection and treatment of the water effluent. The dry-ice blasting process, a cleaning system which uses pressurized air and CO2 dry-ice particles as cleaning agent, has been proposed as an alternative method which does not suffer the above drawbacks but is potentially capable of efficient cleaning. In this context, such a cleaning system is currently being developed by Lufthansa Technik in association with Hochschule Darmstadt and DIT. This work focuses on the development and validation of a numerical model of this process, which can be used to improve the understanding of the complex multiphase flow phenomena involved and to assess the cleaning physics. Appropriate multiphase flow set-ups and new particle breakup and erosion models are developed. These new models will facilitate the numerical prediction of particle behaviour and defouling erosion rates during the defouling process. An appropriate simulation set-up for the particle laden injection system flow simulations using the Euler-Lagrange method is investigated. Three possible injection systems with various air flow velocities and particle loading densities are considered. These systems are investigated by means of high-speed camera (HSC) experiments and the predicted results are compared to the experimental in order to find the best numerical set-up. An improvement to the particle drag force formulation is proposed for highly pressurized air-flows. A new particle breakup model for dry-ice in Euler-Lagrange simulations is developed. This model is theoretically derived from an energy balance and un-derpinned with data from HSC experiments. It includes velocity, impact angle and target temperature as factors determining breakup behaviour of dry-ice particles impinging solid walls. A new defouling erosion model utilizing an energy balance approach and based on a range of experiments with several types of actual and artificial fouling material is developed and tested. The particle breakup and the erosion model are implemented into the commercial CFD code Ansys CFX. Verification and validation studies of both new models are presented. The validation of the new models uses data acquired in a specially-designed wind-tunnel experiment. All main findings and models are used in a final application case study where the new dry-ice based cleaning procedure is applied to a GE-CF6-50 test engine. Comparison of numerical results to data from air-flow, particle tracking and defouling experiments is also presented for this case

Submersed sensing electrode used in fuel-cell type hydrogen detector

Electrode has silicone rubber diffusion barrier with fixed permeation constant for hydrogen. Barrier controls flow of hydrogen to anode and Faraday relationship establishes upper limit for current through cell. Electrode fabrication is described

Instructional Approaches That Increase Reading Achievement for Boys, Grades 3-6

An achievement gap persists in many educational settings with females outperforming males in reading. In a Southern California school district, reading scores for boys average 10 percentile points below those of girls. A qualitative case study was conducted to explore which instructional approaches can help close this gender gap. The conceptual framework for this study was based on engagement theory, which proposes that students who are engaged in learning tasks achieve at higher levels. The guiding question asked how reading achievement for boys in Grades 3-6 could be improved in the district under study. Semistructured individual interviews were conducted with 4 teachers from different schools and grade levels who\u27s boys, according to district officials, had demonstrated a strong increase in reading achievement. Content analysis of interview transcripts used a 2-cycle coding method to find emerging themes. Participants indicated 5 instructional approaches that contributed to an increase in reading achievement for boys: differentiated reading instruction, collaborative learning, motivation, goal setting and monitoring, and positive teacher-student relationships. Understanding how teachers can improve reading achievement for boys may contribute knowledge about how to improve achievement for all students in other grades in this district, help close achievement gaps, and improve the chance of getting into college for all students

Decision-making, emergence and narrative in Dragon Age: Origins, Mass Effect and Mass Effect 2

This article focuses on digital role-playing games produced by BioWare in which the decisions made by players can have a profound impact on the narrative of each game. My approach relies heavily upon the dissection of examples from Dragon Age: Origins, Mass Effect, and Mass Effect 2 as I found that scholarship about video games focused heavily on theory rather than analysis of in-game content, at least compared to the size and popularity of the genre. I work with key concepts such as narrative, simulation, and sideshadowing in order to analyse the dialogue options and scenarios presented to the player in these games. I claim that we can compare decision-making in real life and decision-making in role-playing games in order to examine the emotions and thoughts that go into the decision-making process. I task myself with discussing the implications of choosing one’s own narrative and analysing the mechanics of these games that urge players to make morality-based choices. I consider the ideas of Gary Saul Morson and Mikhail Bahktin as a way of using literary theory to deconstruct the complexities of navigating through these unique game worlds. My aim is to show that the multi-linear structures of modern, digital role-playing games represent simulators through which players can explore their own decision-making processes. BioWare constructs emotional and intellectual decision-making opportunities that entice players to consider their own morality in the face of life or death decisions. I argue that these role-playing games urge us to consider the ways we make decisions in our everyday lives and allow us to simulate how we might act given the chance to play hero or villain

Regenerable adsorbent study

Thin film solid regenerable adsorbent for use with sorber plate to determine gase

Improved fuel-cell-type hydrogen sensor

Modified hydrogen sensor replaces oxygen cathode with a cathode consisting of a sealed paste of gold hydroxide and a pure gold current collector. The net reaction which occurs during cell operation is the reduction of the gold hydroxide to gold and water, with a half-cell potential of 1.4 volts