Scheduling a general flexible manufacturing system to minimize tardiness related costs

Includes bibliographical references (p. 59-60)

A Symmetry for the Cosmological Constant

We study a symmetry, schematically Energy -> - Energy, which suppresses matter contributions to the cosmological constant. The requisite negative energy fluctuations are identified with a "ghost" copy of the Standard Model. Gravity explicitly, but weakly, violates the symmetry, and naturalness requires General Relativity to break down at short distances with testable consequences. If this breakdown is accompanied by gravitational Lorentz-violation, the decay of flat spacetime by ghost production is acceptably slow. We show that inflation works in our scenario and can lead to the initial conditions required for standard Big Bang cosmology.Comment: 18 pages, 3 figures, References correcte

Cluster Interpretation of Properties of Alternating Parity Bands in Heavy Nuclei

The properties of the states of the alternating parity bands in actinides, Ba, Ce and Nd isotopes are analyzed within a cluster model. The model is based on the assumption that cluster type shapes are produced by the collective motion of the nuclear system in the mass asymmetry coordinate. The calculated spin dependences of the parity splitting and of the electric multipole transition moments are in agreement with the experimental data.Comment: 29 pages, 10 figure

Extended M1 sum rule for excited symmetric and mixed-symmetry states in nuclei

A generalized M1 sum rule for orbital magnetic dipole strength from excited symmetric states to mixed-symmetry states is considered within the proton-neutron interacting boson model of even-even nuclei. Analytic expressions for the dominant terms in the B(M1) transition rates from the first and second $2^+$ states are derived in the U(5) and SO(6) dynamic symmetry limits of the model, and the applicability of a sum rule approach is examined at and in-between these limits. Lastly, the sum rule is applied to the new data on mixed-symmetry states of 94Mo and a quadrupole d-boson ratio $nd(0^+_1)/nd(2^+_2) \approx 0.6$ is obtained in a largely parameter-independent wayComment: 19 pages, 3 figures, Revte

Potential Application of Solid Free-Form Fabrication (SFF) Process in Ceracon P/M Forging

The Ceracon Process is a patented[ll, low cost powder metallurgy process for achieving near-net-shape, full density parts. It. isasimple.·consolidation.technique which utilizes conventionalpowder metallurgyequipmenfand set-up. The Cetacon Process is a quasi-isostatic,hot consolidation technique, that utilizes a ceramic particulate material as a pressure transmitting medium instead ofagasmedia as is used in. hipping. Pressures up to 200 K.si can be used and a broad range ofmetallic, ceramic, and polymeric materials and composites have been successfully processed£2-6] .Mechanical Engineerin

Potential Application of Solid Free-Form Fabrication (SFF) Process in Ceracon P/M Forging

The Ceracon Process is a patented[ll, low cost powder metallurgy process for achieving near-net-shape, full density parts. It. isasimple.·consolidation.technique which utilizes conventionalpowder metallurgyequipmenfand set-up. The Cetacon Process is a quasi-isostatic,hot consolidation technique, that utilizes a ceramic particulate material as a pressure transmitting medium instead ofagasmedia as is used in. hipping. Pressures up to 200 K.si can be used and a broad range ofmetallic, ceramic, and polymeric materials and composites have been successfully processed£2-6] .Mechanical Engineerin

Due date based scheduling in a general flexible manufacturing system

Dynamic scheduling of manufacturing systems for due date based objectives has received considerable attention from practitioners and researchers due to the importance of meeting due dates in most industries. Research investigations have focused primarily on the relative effectiveness of various dispatching rules in job shops. These rules operate by prioritizing jobs using a “criticality index” based on job and system status. Jobs are then scheduled from most critical to least, with the indexes typically being updated as the system changes.This study considers two important issues which have not been addressed previously in the literature. First, we investigate the impact of unequal machine workloads on the relative effectiveness of dispatching rules. This is significant because workloads are likely to be unbalanced in most real systems. While it is clear, intuitively, that this imbalance in machine workloads is likely to deteriorate system performance, it is not obvious whether the superiority of certain dispatching rules established in earlier studies for balanced workloads is carried forward to this case. We show that the performance of different dispatching rules does indeed depend upon the degree of workload imbalance. We also propose and test a scheduling procedure which performs well in both balanced and unbalanced systems.Next, we develop a scheduling approach which shows promise as being an improved alternative to the use of dispatching rules. This approach decomposes the dynamic scheduling problem into a series of static problems.These static problems are then solved using an optimum‐seeking method, and the solutions are implemented on a rolling basis. We show through a simulation experiment that adopting this approach over dispatching rules leads to an improvement in the overall solution quality, even in a dynamic environment.The two very practical implications of our study are: (1) that commonly used dispatching rules in job shops or automated manufacturing systems may not be the best approach when capacity utilization is unbalanced (2) a job shop or automated manufacturing system would likely benefit from implementing optimal‐seeking scheduling rules instead of the traditional job dispatching rules.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146830/1/joom115.pd