51 research outputs found

    Profit-oriented disassembly-line balancing

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    As product and material recovery has gained importance, disassembly volumes have increased, justifying construction of disassembly lines similar to assembly lines. Recent research on disassembly lines has focused on complete disassembly. Unlike assembly, the current industry practice involves partial disassembly with profit-maximization or cost-minimization objectives. Another difference between assembly and disassembly is that disassembly involves additional precedence relations among tasks due to processing alternatives or physical restrictions. In this study, we define and solve the profit-oriented partial disassembly-line balancing problem. We first characterize different types of precedence relations in disassembly and propose a new representation scheme that encompasses all these types. We then develop the first mixed integer programming formulation for the partial disassembly-line balancing problem, which simultaneously determines (1) the parts whose demand is to be fulfilled to generate revenue, (2) the tasks that will release the selected parts under task and station costs, (3) the number of stations that will be opened, (4) the cycle time, and (5) the balance of the disassembly line, i.e. the feasible assignment of selected tasks to stations such that various types of precedence relations are satisfied. We propose a lower and upper-bounding scheme based on linear programming relaxation of the formulation. Computational results show that our approach provides near optimal solutions for small problems and is capable of solving larger problems with up to 320 disassembly tasks in reasonable time

    Decentralized subcontractor scheduling with divisible jobs

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    Subcontracting allows manufacturer agents to reduce completion times of their jobs and thus obtain savings. This paper addresses the coordination of decentralized scheduling systems with a single subcontractor and several agents having divisible jobs. Assuming complete information, we design parametric pricing schemes that strongly coordinate this decentralized system, i.e., the agents’ choices of subcontracting intervals always result in efficient schedules. The subcontractor’s revenue under the pricing schemes depends on a single parameter which can be chosen to make the revenue as close to the total savings as required. Also, we give a lower bound on the subcontractor’s revenue for any coordinating pricing scheme. Allowing private information about processing times, we prove that the pivotal mechanism is coordinating, i.e., agents are better off by reporting their true processing times, and by participating in the subcontracting. We show that the subcontractor’s maximum revenue with any coordinating mechanism under private information equals the lower bound of that with coordinating pricing schemes under complete information. Finally, we address the asymmetric case where agents obtain savings at different rates per unit reduction in completion times. We show that coordinating pricing schemes do not always exist in this case

    Production of biogas - a manner of manufacturing

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    Advertising is commonly criticised for being pervasive, offensive, manipulative, harmful and irresponsible. This thesis focuses on the subjective criticisms and complex issues related to taste, decency, morality and offence, particularly as applied to, and understood within, the public and non-profit contexts. It is positioned at the intersection of marketing communications, marketing ethics, and social and non-profit marketing and explores how shocking, offensive and/or controversial (SOC) advertising appeals are interpreted, regulated and contested, by divergent groups of people. The approach taken is inspired by stakeholder theory and its focus on ethical decision-making for the betterment of all stakeholders. A mixed methods research design was adopted, resulting in three studies and these are presented as three discrete articles. Article I maps the field of existing research into SOC advertising and identifies gaps in our knowledge by means of a systematic literature review. It offers a critical appraisal of the field by highlighting definitional tensions, limited interdisciplinary work and an overdependence on student samples, on quantitative analysis and on non-longitudinal methodologies. It then proposes a series of remedies to these shortcomings. The second and third papers continue this reparative work by conceptualising and analysing actual SOC advertising interpretations and contestations. Article II explores the interpretations and experiences of SOC advertising within the regulatory context by analysing evidence from complainants, advertisers and regulatory bodies. It then proposes and develops an interpretation of the implicit power dynamics through which their contradictory interests overlap. The methodology underpinning this chapter combines a thematic content analysis of a substantial archive of complaints submitted to the Advertising Standards Authority (ASA) with an interpretation of case adjudication reports influenced by the work of Michel Foucault. The findings suggest that the regulation of SOC advertising prioritises the interests of firms and advertisers by relegating the role of complainant to that of merely registering complaints. The focus of Article III moves from the regulatory framework to the complained-about advertisements themselves. It provides an innovative theoretical and methodological approach to analysing SOC advertisements, rooted in the classic Aristotelian notion of rhetorical appeals and figuration, by developing and analysing a carefully selected example in detail. The analysis reveals an implicit NFP sector-specific appeal to ethos and the importance of a complex appeal to pathos. Each of the papers offers a different level of analysis of the often-contradictory viewpoints represented by stakeholder groups involved in, or affected by, the use of SOC advertising tactics. These viewpoints include academics, general consumers, the vocal minority of complainants, the advertisers including the non-profit and public organisations and the advertising creatives, and the advertising regulator. Taken together, the papers amount to a thesis that makes an important contribution to debates about the appropriateness, ethics, and application of SOC themes, formats and imagery in social and non-profit advertising. By exploring the regulatory processes of the ASA, an exemplary advertising self-regulatory body, it further contributes to the discourse on self-regulatory practices and highlights an NFP sector-specific consequentialist approach that appears to stifle the voice of the offended complainant. On a practical level, this work has implications for advertising practitioners and advertising regulators who are involved in producing and regulating advertising that uses SOC tactics

    Significant release of shear energy of the North Korean nuclear test on February 12, 2013

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    On February 12, 2013 the Democratic People\u27s Republic of Korea (DPRK) carried out an announced nuclear test, which was the third after tests conducted in 2006 and 2009. An important task in discriminating a man-made explosion and a natural tectonic earthquake is the analysis of seismic waveforms. To determine the isotropic and non-isotropic characteristics of the detonation source, I invert long-period seismic data for the full seismic moment tensor to match the observed seismic signals by synthetic waveforms based on a 3D earth model. Here, I show that the inversion of long-period seismic data of the 2013 test reveals a clear explosive (isotropic) component combined with a significant release of shear energy by the double-couple part of the moment tensor. While the isotropic part of the nuclear test in 2009 was similar to that in 2013, the double-couple part was lower by a factor of 0.55 compared to the explosion in 2013. Moreover, the ratio of the isotropic seismic moments of the 2013 and 2009 nuclear tests is 1.4±0.1 and lower than published estimations of the yield ratio, which indicates the importance of considering the release of shear energy. The determined orientation of the double-couple fault plane is parallel to the dominating geologic fault structures NNE-SSW to NE-SW, but the calculated normal faulting mechanism does not correspond to the general tectonic strike-slip regime. Thus, explanations for the enhanced release of shear energy might be induced dip-slip motion pre-stressed by the previous test or near source damaging effects due to a changed containment of the nuclear explosion

    Surface wave focusing effects: Numerical modeling and statistical observations

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    Most techniques used in seismological practice have been performed under the assumption that surface waves propagate along great circle arcs between the epicenter and the station. However, lateral variations of surface wave phase velocities should result in deviation of the wave paths from great circle arcs and in corresponding anomalies of geometrical spreading (so-called focusing effect). We performed numerical modeling of these effects using the ray approximation on the basis of recent global phase velocity maps for fundamental Rayleigh mode obtained by tomographic inversion in the period range from 60 to 150 s. The aim for such a modeling is to investigate where the conventional methods based on using great circles as paths fail, and to obtain quantitative characteristics for the effects of rays focusing. Predicted and observed focusing effects are analyzed from a statistical point of view on a dataset of real seismic data. Records of earthquakes in a wide magnitude range (6 < Ms < 7) and with epicenters in different seismic regions are used for the analysis (over 3000 measurements). Synthetic and observed Rayleigh wave amplitude spectra are found to be in better agreement when the focusing effect is taken into account: correction of spectra for predicted focusing effect significantly improves the fit of synthetics to observations at periods larger than 75 s. Calculation of focusing effect based on ray theory ignores the effects of wavefront smoothing which increases with increasing period. However, even this approximation gives considerable improvement of synthetics at periods up to 150 s and, therefore, can be used in many applications, such as seismic source studies, magnitude measurements, and Q estimates. We also demonstrated that the discrepancy between real data and synthetics cannot be explained by attenuation effects. It means that there is still large room for improvement of the existing tomographic models which, in order to correctly explain observed amplitudes, must include heterogeneity of anisotropy and anelasticity up to higher degree

    Integrated Assembly Line Balancing with Skilled and Unskilled Workers

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