Suchergebnisse

ABSTRACTOne of the basic tenets of scheduling theory is that the SPT sequencing rule maximizes average production rates and minimizes average in‐process inventories. This paper shows that on single‐card kanban‐controlled lines FCFS often has greater average production rates than SPT. Further, the performance of SPT declines relative to FCFS for larger queue capacities and less frequent material handling. Results for the single‐card system are also compared to those of Berkley and Kiran [1]. In that article it was shown that for two‐card systems with periodic material handling, SPT has larger average inventories than FCFS. This paper shows that these surprising results can be attributed to Berkley and Kiran's material‐handling mechanism.

ABSTRACTThe kanban system is a pull method of production control in which the material‐handling operation between two stations is initiated by the downstream station. Most often, because of limited transportation resources, the physical distance separating workstations, or other factors, the material‐handling operation is performed periodically. The number of withdrawal kanbans must be set large enough to satisfy production requirements over the period between occurrences of the material‐handling operation‐the withdrawal cycle time. This paper presents a decomposition approximation for kanban‐controlled flow shops that explicitly considers the withdrawal cycle time. Several examples are given to show how the approximation method can be used to determine the required number of kanbans, the required withdrawal cycle time, or both.

ABSTRACTA recent Decision Sciences article by Jordan [9] presented a Markov‐chain model of a just‐in‐time (JIT) production line. This model was used to estimate average inventories and production rates to find the optimal number of kanbans. Results for expected production rate were found to be consistently lower than those obtained by Huang, Rees, and Taylor [8] in a previous Decision Sciences article. Jordan attributed this unexpected outcome to some procedural problems in Huang et al.'s simulation methodology. In this paper, Markov‐numerical analysis is used to compare the performance of Jordan's and Huang et al.'s methods of production control. Simulation analysis is then used to determine the effects of finite withdrawal cycle times. Results show that, for equal numbers of kanbans, Huang et al.'s two‐card method of production control provides substantially greater expected production rates than Jordan's method. These results suggest that the Jordan model should not be applied to the problem of setting kanban numbers on manual JIT lines. Finally, we comment on the efficiency of Jordan's iterative method to obtain performance measures of tandem queues.

This paper addresses the problem of sequencing in decentralized kanban‐controlled flow shops. The kanban production control system considered uses two card types and a constant withdrawal period. The flow shops are decentralized in the sense that sequencing decisions are made at the local workstation level rather than by a centralized scheduling system. Further, there are no material requirements planning (MRP)‐generated due dates available to drive dispatching rules such as earliest due date, slack, and critical ratio.Local sequencing rules suitable for the decentralized kanban production‐control environment are proposed and tested in a simulation experiment. These rules are designed so that they can be implemented with only the information available at the workstation level. Example sequencing problems are used to show why the shortest processing time rule minimizes neither average work‐in‐process inventory nor average finished‐goods withdrawal kanban waiting time. Further, it is shown how work station supervisors can use the withdrawal period, in addition to the number of kanbans, to manage work‐in‐process inventories.

AbstractInformal logic in philosophy and evaluation share considerable common ground and can offer each other various opportunities for meaningful cross‐fertilization that can lead to advancements in theory and practice in both fields.

Through analysis of Dayton's economic transformation, explores the importance of combining public sector, university, business and grass root community interests to arrive at a region-wide planning process in which all these disparate elements share responsibility and identify their goals for local development. (Abstract amended)

The approach that should be used by law enforcement officers in order to safely and effectively enter a room is a point of contention among many police trainers. Based on five experiments conducted over a two-year period, Evaluating Police Tactics demonstrates that the conventional wisdom is not optimal. Using the scientific method to systematically assess current room entry philosophies and techniques employed by police, Evaluating Police Tactics offers suggestions for examining the current philosophies and determining how patrol officers can enter scenes of ongoing violence, find the shoote

An experimental comparison of university versus newspaper sponsorship in a random digit dial telephone survey produced no significant response rate difference, but a clear difference in response distributions on one issue. Hypothesizes that the result was due to the newspaper having taken a clear position on the issue. (Abstract amended)

Non-native ambrosia beetles (Coleoptera: Curculionidae), especially Xylosandrus compactus (Eichhoff), Xylosandrus crassiusculus (Motschulsky) and Xylosandrus germanus (Blandford), are destructive wood-boring pests of trees in ornamental nurseries and tree fruit orchards. Previous studies have demonstrated the adults are repelled by verbenone and strongly attracted to ethanol. We tested a "push-pull" semiochemical strategy in Ohio, Virginia and Mississippi using verbenone emitters to "push" beetles away from vulnerable trees and ethanol lures to "pull" them into annihilative traps. Container-grown trees were flood-stressed to induce ambrosia beetle attacks and then deployed in the presence or absence of verbenone emitters and a perimeter of ethanol-baited interception traps to achieve the following treatment combinations: (a) untreated control, (b) verbenone only, (c) ethanol only, and (d) verbenone plus ethanol. Verbenone and ethanol did not interact to reduce attacks on the flooded trees, nor did verbenone alone reduce attacks. The ethanol-baited traps intercepted enough beetles to reduce attacks on trees deployed in Virginia and Mississippi in 2016, but not in 2017, or in Ohio in 2016. Xylosandrus germanus, X. crassiusculus and both Hypothenemus dissimilis Zimmermann and X. crassiusculus were among the predominant species collected in ethanol-baited traps deployed in Ohio, Virginia and Mississippi, respectively. Xylosandrus germanus and X. crassiusculus were also the predominant species dissected from trees deployed in Ohio and Virginia, respectively. While the ethanol-baited traps showed promise for helping to protect trees by intercepting ambrosia beetles, the repellent "push" component (i.e., verbenone) and attractant "pull" component (i.e., ethanol) will need to be further optimized in order to implement a "push-pull" semiochemical strategy. ; USDA Floriculture and Nursery Research Initiative (USDA/FNRI); Horticultural Research Institute (HRI); USDA-ARS National Program 304-Crop Protection and Quarantine [3607-22000-012-00D]; USDA-ARS National Program 305-Crop Production [6062-21430-002-00D]; USDA National Institute of Food and AgricultureUnited States Department of Agriculture (USDA) [SC-1700473] ; Funding for this project was provided by the USDA Floriculture and Nursery Research Initiative (USDA/FNRI); Horticultural Research Institute (HRI); USDA-ARS National Program 304-Crop Protection and Quarantine (Project 3607-22000-012-00D); USDA-ARS National Program 305-Crop Production (Project 6062-21430-002-00D); and USDA National Institute of Food and Agriculture (Project SC-1700473). We thank Jenny Barnett (USDA-ARS), Jenna Zhu (USDA-ARS) and Mary Seward (Hampton Roads AREC) for technical assistance. ; Public domain authored by a U.S. government employee

Medical assessments provide evidence of the negative impact of the UK's accommodation centres on the health of asylum seekers. A trauma-informed approach should underpin the government's future strategy in this area.