Search

ABSTRACT: Gopher tortoise (Gopherus polyphemus) populations are declining throughout their range and recovery requires management intervention to alleviate losses. Population augmentation strategies may prove useful in recovery of depleted populations once threats are mitigated. We head‐started and soft‐released hatchlings produced from robust donor populations and evaluated their post‐release survivorship and movement for the first year following their release. During 2014 and 2015, we head‐started and released 145 tortoises, of which we radio‐tracked a subset of 41 individuals, from 2 cohorts at 2 release areas within Yuchi Wildlife Management Area in Burke County, Georgia, USA. Movement and mortality of gopher tortoises was highest in the first month after release but declined soon after. Estimated annual survivorship of our first cohort was 60.6%. Annual survivorship of our second cohort was low (7.1%) at the southeast release area but much higher (75.0%) at the northwest release area because of spatial variation in predation. Although survivorship was variable, site fidelity remained high throughout the study and no tortoise moved >122.0 m from its release location. Initial results suggest that head‐starting could prove effective as a population recovery tool, but that release strategy and predator mitigation, especially within the first month, are critical to success. © 2018 The Wildlife Society. [ABSTRACT FROM AUTHOR]

ABSTRACT Gopher tortoises ( Gopherus polyphemus) are among the most frequently translocated herpetofauna; yet, determining translocation success is difficult because tortoises are slow-growing, long-lived organisms with low reproductive potential. Comparing behavioral traits of translocated individuals with those of sympatric or nearby resident individuals can provide an ecologically relevant baseline to determine if translocated individuals show behavioral traits consistent with those of long-term residents. We used radio telemetry to concurrently monitor 21 translocated and 15 resident gopher tortoises across 2 sites in southern Georgia and compared movement patterns, body weights, and multi-scale habitat selection between treatments. Translocated tortoises moved farther and had larger home ranges than resident tortoises but showed similar patterns of site fidelity. We observed no differences in body weight change between treatments. Patterns of habitat selection were similar between treatments in that tortoises selected structurally open habitats at all scales. Our study suggests that more extensive post-release movements compared to resident individuals may not necessarily lead to lower site fidelity in translocated individuals. We suspect that the presence of structurally suitable habitat within the release area and retaining translocated individuals within a pre-release enclosure for 10 months contributed to high site fidelity. Although comparing translocated and resident individuals can help inform translocation efforts, we caution that using resident individuals from ecological sinks may lead to misleading results. © 2014 The Wildlife Society. [ABSTRACT FROM AUTHOR]

The article offers description on the use of spreadsheets to improve a flow line models operable by operations management students. Simplifying assumptions are made to build a useful, yet simple model of flow line behavior. Assumptions that the processing times and interarrival of jobs are generally disseminated, the mean and standard deviation of which are offered as model inputs.

Juvenile trees of temperate and boreal regions cease growth and set buds in autumn in response to short day-lengths (SD) detected by phytochrome. Growth cessation and bud set are prerequisites for the development of winter dormancy and full cold hardiness. In this study we show that the SD-requirement for bud set and cold hardening can be overcome in hybrid aspen ( Populus tremula L. × tremuloides Michx.) by low night temperature and inhibition of gibberellin (GA) biosynthesis. Bud set and increased cold hardiness were observed under normally non-inductive long day-length (LD) in wild-type plants, when exposed to low night temperature and paclobutrazol. In addition, the effect of PHYA overexpression could be overcome in transgenic plants, producing bud set and cold acclimation by treatment with: SD, low night temperature and paclobutrazol. After cold acclimation, the degree of bud dormancy was lower for wild-type plants prior treated with LD and transgenic plants (overexpressing PHYA), than SD-treated, wild-type plants. Thus, low night temperature in combination with reduced GA content induced bud set and promoted cold hardiness under normally non-inductive photoperiods in hybrid aspen, but was unable to affect development of dormancy. This might suggest separate signalling pathways from phytochrome regulating the induction of cold/cold hardiness and bud dormancy in hybrid aspen or alternatively, there might be one pathway that fails to complete its action in the transgenic and paclobutrazol treated plants. [ABSTRACT FROM AUTHOR]

Statistical tools found in the service quality assessment literature—theT2 statistic combined with factor analysis—can enhance the feedback instructors receive from student ratings.T2 examines variability across multiple sets of ratings to isolate individual respondents with aberrant response patterns (i.e., outliers). Analyzing student responses that are outside the“normal” range of responses can identify aspects of the course that cause pockets of students to be dissatisfied. This fresh insight into sources of student dissatisfaction is particularly valuable for instructors willing to make tactical classroom changes that accommodate individual students rather than the traditional approach of using student ratings to develop systemwide changes in course delivery. A case study is presented to demonstrate how the recommended procedure minimizes data overload, allows for valid schoolwide and longitudinal comparisons of correlated survey responses, and helps instructors identify priority areas for instructional improvement. [ABSTRACT FROM AUTHOR]

This paper considers the application of cellular manufacturing (CM) to batch production by exploring the shop floor performance trade-offs associated with shops employing different levels of CM. The literature has alluded to a continuum that exists between the purely departmentalized job shop and the completely cellular shop. However, the vast majority of CM research exists at the extremes of this continuum. Here, we intend to probe performance relationships by comparing shops that exist at different stages of CM adoption. Specifically, we begin with a hypothetical departmentalized shop found in the CM literature, and in a stepwise fashion, form independent cells. At each stage, flow time and tardiness performance is recorded. Modeling results indicate that, depending on shop conditions and managerial objectives, superior shop performance may be recorded by the job shop, the cell shop, or by one of the shops between these extreme points. In fact, under certain conditions, shops that contain partially formed cells perform better than shops that use completely formed cells. Additional results demonstrate that in order to achieve excellent performance, managers investigating specific layouts need to pay especially close attention to changes in machine utilization as machine groups are partitioned into cells. [ABSTRACT FROM AUTHOR]

This study investigates changes in inventory and customer service performance of a job-shop that desires to adopt a Group Technology (GT) philosophy in its shop floor operations. Simulation methodology is pursued to explore tradeoffs in shop performance between the routing flexibility of non-dedicated machines in a functional job-shop and the setup efficiency of dedicated machines in shops that have machine cell layouts. Further, traditional and GT-based scheduling procedures are investigated in these different shops to determine the conditions under which a GT philosophy may be profitably employed only in layout decisions, only in scheduling decisions, or in both layout and scheduling decisions. Results from this study show that shop layout choice is not a simple decision that can capitalize either on the high routing flexibility of the functional job-shop or on the setup efficiency advantages of a cell shop. The tradeoffs between routing flexibility and setup efficiency must be made carefully. The impact of demand variability on performance is also dependent on the type of layout. In general, product volume variability more adversely affects the performance of functional job-shops, while product mix variability has greater impact on the performance of cell shops. Finally, sensitivity analysis is performed to show that maintaining balance between the utilization of machines is a major determinant of performance, and consequently the best layout. [ABSTRACT FROM AUTHOR]

Much of the existing job shop scheduling literature has focussed on scheduling rules and heuristics that typically do not incorporate customer specific characteristics into their scheduling decisions. This paper specifically considers the situation in which depending upon the identity of the customer, different jobs have different tardiness penalties associated with them. In addition, the tardiness penalties associated with different customers are comparable in magnitude with one another. We propose here and test four different types of scheduling rules which utilize the jobs' tardiness penalty information, and show that the performance of the shop is only mildly affected by the shape and dispersion of the weighting scheme used in determining the tardiness penalties. The performance of scheduling rules is however contingent on due-date tightness. In general, apart from the traditionally well performing shortest processing time rule, the ATC rule works well on the mean flow time measure in loose due-date situations, while COVERT performs well on mean flow time under tight due-date conditions. Lesser differences are seen to exist between mean tardiness and root mean square tardiness (TRMS) performance of different scheduling rules. Weighted mean tardiness deteriorates with increasing due-date tightness and coefficient of variation of job tardiness penalties. Finally, customer service performance worsens considerably with weighted dispatching rules when the performance criteria are not weighted by each job's tardiness penalty. Implications of our results for providing more effective management of job shops, and exploring future research directions in this area are also presented and discussed. [ABSTRACT FROM AUTHOR]

We present a framework for managing vital customer priorities in job-shop manufacturing environments. We introduce the notion of attaining near-perfect on-time delivery service to a small portion of the firm's customers who contribute to a substantial portion of its sales revenue and profits. Consequently we postulate that appropriate order review and release (ORR) policies, along with the dispatching rules used to schedule customer orders, can be combined effectively to achieve the desired customer service results. Several dispatching rules specifically designed for this study are tested under different operating environments in order to derive the recommended set of ORR and dispatching rule policies. Capacity-based ORR procedures, in conjunction with dispatching rules that pace a job's progress through different operations in its route, provide the best overall performance. The nature of trade-offs inherent in managing the priorities of vitally important customers are also identified and presented in the form of managerial recommendations that can be used to enhance a job shop's overall performance. [ABSTRACT FROM AUTHOR]

We investigate the performance of capacity-sensitive order review and release (ORR) procedures in job shop environments that have not been previously explored. Previous research has ignored the case of job shops which must perform to very tight due-dates because of time-sensitive customers! We propose and test a new capacity sensitive ORR procedure called path based bottleneck (PBB) in such environments, along with the modified infinite loading (ML) procedure which has been shown to work well in several studies. We compare the performance of these two controlled release rules with that of immediate release rule under different conditions of capacity utilization and customer specified exogenous due- dates. Our results indicate that PBB performs well in lowering total costs when due-dates are fight, while MIL is a better procedure with relatively loose to medium due-dates. We also show that in many cases, the shortest processing time (SF1) dispatching rule is a superior performer than a due-date based rule like critical ratio (CR); a conclusion which is contrary to the existing research in this area. In addition, the shop floor control policies recommended are shown to be sensitive to the cost structure of the firm. The managerial implications of this research in providing effective shop floor control in job shops operating under fight due-date conditions are also discussed. [ABSTRACT FROM AUTHOR]