Purpose: The purpose of this study was to test a model that proposes that innovative cognitive style and self-regulation (setting priorities, planning work activities, and monitoring time and task ...progress) are related to the selfreported success of architects. We investigated two aspects of the success: as designers and as business people. To this end, we examined the mediating role of self-efficacy in these relationships. Data/Methodology/Approach: We collected data using a web-based survey among 276 architects in the Netherlands. These were architects that either managed and/or owned a company, including freelance architects. Findings: Innovative cognitive style was related directly and indirectly, via design self-efficacy, to the self-rating of being a successful designer. Self-regulation, via self-efficacy, was indirectly related to being a successful designer, and directly related to being a successful businessperson. In addition, design success was related to success as a businessperson. Implications: This study shows that self-regulation at work is related to self-rated success in design and business. We regard self-regulation to be a form of actively managing work tasks, identified as an increasingly important type of behavior at work. Originality/Value: This study is one of the first to investigate the self-regulation of creative professionals that included both design and business aspects. We focused on three aspects of self-regulation, and tested our model using structural equation modeling.
Gives an overview of quantitative model-based research in operations management, focusing on research methodology. Distinguishes between empirical and axiomatic research, and furthermore between ...descriptive and normative research. Presents guidelines for doing quantitative model-based research in operations management. In constructing arguments, builds on learnings from operations research and operations management research from the past decades and on research from a selected number of other academic disciplines. Concludes that the methodology of quantitative model-driven empirical research offers a great opportunity for operations management researchers to further advance theory.
Dunes on Pluto Telfer, Matt W; Parteli, Eric J R; Radebaugh, Jani ...
Science (American Association for the Advancement of Science),
06/2018, Letnik:
360, Številka:
6392
Journal Article
Recenzirano
Odprti dostop
The surface of Pluto is more geologically diverse and dynamic than had been expected, but the role of its tenuous atmosphere in shaping the landscape remains unclear. We describe observations from ...the New Horizons spacecraft of regularly spaced, linear ridges whose morphology, distribution, and orientation are consistent with being transverse dunes. These are located close to mountainous regions and are orthogonal to nearby wind streaks. We demonstrate that the wavelength of the dunes (~0.4 to 1 kilometer) is best explained by the deposition of sand-sized (~200 to ~300 micrometer) particles of methane ice in moderate winds (<10 meters per second). The undisturbed morphology of the dunes, and relationships with the underlying convective glacial ice, imply that the dunes have formed in the very recent geological past.
We study a maintenance organization serving industrial customers operating a commoditized capital good. The maintenance organization provides for availability of the capital good. Upon failure, a ...substitute good rented from a third party is installed. A logistics service provider picks up the failed good and delivers it to the repair shop. On arrival at the repair shop the failed good is repaired, returned, and installed for use. Rent for the substitute ends at installation of the repaired good. Idle repair shop capacity can be used for other revenue generating tasks, depending on the time the capacity is available. We consider three failed good collection modes. First, a failed good is immediately collected, transported, and immediately admitted to the repair shop. Second, the logistics service provider is allowed a certain slack time for the delivery of the failed good to the repair shop. Third, a failed good is only admitted periodically to the shop and collection and transportation ensures that the failed good is available in the repair shop at the start of the first period possible. We ask under what conditions a transportation slack time, either as a constant slack or as a periodic admission to the repair shop, can be beneficial. We present analytical solutions for immediate transportation and transportation with a constant time slack considering costs. We find that (some) transportation time slack can be beneficial for high failure rates and high transportation costs.
In this paper, we study the capacity flexibility problem of a maintenance service provider, who is running a repair shop and is responsible for the availability of numerous specialized systems which ...contain a critical component that is prone to failure. Upon a critical component failure, the component is sent to the repair shop and the service provider is responsible for the repair as well as the down-time costs resulting from the system unavailability. In order to decrease the down-time costs, the repair shop keeps an inventory for the critical components, such that a failed critical component can be replaced with a spare one immediately, if it is available. The component inventory stock level and the repair shop capacity level decisions have to be taken jointly by the service provider. The shop floor manager resorts to two different capacity modes in order to make use of capacity flexibility. First one is the single-level capacity mode, in which the capacity level is fixed and is the only capacity related decision. The best results in this mode serve as a reference to the two-level capacity mode, in which there are low (permanent) and high (permanent plus contingent) capacity levels. In this mode, the permanent capacity is always available in the shop, whereas the deployment of the contingent capacity is decided at the start of each period based on the number of components waiting to be repaired in the shop. The relevant capacity decisions of this mode are the permanent and contingent capacity levels, the period length and the states (in terms of number of failed components waiting) where the contingent capacity is deployed. We develop quantitative models based on queuing theory that integrate the inventory level decision with the capacity related decisions for the repair shop, in each of the two capacity modes, in order to minimize the total cost rate of the service provider. Our numerical results suggest that two-level capacity mode can bring substantial savings compared to the best fixed capacity mode and these savings are mostly resulting from lower repair shop capacity usage. Moreover, we find that the system, in most cases, chooses the shortest period length possible, indicating the overarching importance of a fast response to the system state. The system switches to the high capacity mode if the spare part stock is just one or two, then it uses a quite high contingent capacity level, in order to avoid out of stock. If contingent capacity costs are high, system chooses a high level of permanent capacity to prevent frequent capacity switches.
In this paper, we study a production system that operates under a lead-time performance constraint which guarantees the completion of an order before a pre-determined lead-time with a certain ...probability. The demand arrival times and the service requirements for the orders are random. To reduce the capacity-related operational costs, the production system under study has the option to use flexible capacity. We focus on periodic capacity policies and model the production system as a queuing system that can change its capacity periodically and choose to operate in one of the two levels: a permanent capacity level and a permanent plus contingent capacity level. Contingent capacity is supplied if needed at the start of a period, and is available during that period, at a cost rate that is decreasing in period length in different functional forms. Next, we propose a search algorithm that finds the capacity levels and the switching point that minimizes the capacity-related costs for a given period length. The behaviour of the capacity-related costs changes drastically under different period lengths and cost structures. In our computational study, we observe that the periodic capacity flexibility can reduce the capacity-related operational costs significantly (up to 35%). However, in order to achieve these savings, the period length must be chosen carefully depending on ambition level and capacity-related costs. We also observe that the percentage savings are higher for more ambitious lead-time performance constraints. Moreover, we observe that the use of contingent capacity makes the total system costs more insensitive to the lead-time performance requirements.
In this paper, we study a make-to-order production system with parallel, identical processing units. Each order needs to be satisfied on a single processing unit that is run by a crew. The ...inter-arrival time and the service time for each order are random variables. The system operates under a lead time performance constraint, which demands the completion of each order within a pre-determined lead time with a certain probability. The minimum number of processing units needed to satisfy this constraint is determined at the tactical level. Our research focuses on the cost savings that can be realized with the use of flexible crews via contractual hiring agreements with an External Labor Supply Agency (ELSA). The ELSA can periodically provide an agreed number of crews. The cost incurred for a flexible crew is higher than that for a permanent crew, and is decreasing in the period length. We model and analyze this system using the transient behavior analysis of multi-server queues and propose several empirically testable functions for the cost of flexible crews. In our computational study, we demonstrate possible cost savings of 2-level, threshold type hiring policies, relative to the fixed capacity system, under 9 scenarios with three demand-to-processing rate ratios and three lead time performance constraints, each of which reflects a different level of ambition. We observe that the maximum savings occur when the cost of a flexible crew is same as that of a permanent crew, and range from 29.38% to 50.56%. However, as the flexible crews become more expensive, the system may choose to employ permanent crews only. We observe that cost savings consist of two parts: savings due to the cancellation of the sclerosis of capacity discreteness, and savings due to the use of workload information in hiring actions. The latter part is higher for more ambitious lead time performance constraints, and for higher mean processing times. Finally, when there is an additional cost for transacting an agreement with the ELSA, we observe that the capacity flexibility option loses its charm, especially if the transaction cost is higher than the cost of a permanent crew.
In this paper we study the capacity investment decision for make-to-order manufacturing firms that utilize a fixed capacity, operate in a stochastic, stationary market, and can influence their demand ...rate by increasing or decreasing their sales effort. We consider manufacturing situations that differ in sales contribution, in market elasticity to sales effort, work-in-process costs, and demand sensitivity to lead time.
If demand is insensitive to lead time we find that for situations with a low sales contribution and high work-in-process costs (for example the manufacturing of capacity equipment that is at the end of the innovative life cycle, such as food processing machines and textile printing machines), using a dynamic demand rate policy can bring substantial improvements in profit. Moreover, when using the optimal demand rate policy, the profit is quite insensitive to the initial capacity investment. If demand is sensitive to lead time, using a dynamic demand rate policy brings substantial increases in profit in all situations considered. The profit again is quite insensitive to the initial capacity investment.
Consequently, without much loss in profit, for all cases the capacity investment decision can be based on the stochastic model with stationary demand, neglecting the possibility of influencing the demand rate. However, the profit that results from this investment, and the return-on-investment, should be determined from a model that includes the optimal demand rate policy, since the stationary stochastic model can significantly underestimate the profit and could lead to the abandonment of the investment.
Pluto's haze as a surface material Grundy, W.M.; Bertrand, T.; Binzel, R.P. ...
Icarus (New York, N.Y. 1962),
11/2018, Letnik:
314
Journal Article
Recenzirano
Odprti dostop
•Haze settles rapidly onto Pluto's surface, yet there is color diversity.•Interaction of haze is explored for three distinct surface units.•Haze particles could evolve differently in different ...regions or haze particles with different characteristics arrive in different regions.
Pluto's atmospheric haze settles out rapidly compared with geological timescales. It needs to be accounted for as a surface material, distinct from Pluto's icy bedrock and from the volatile ices that migrate via sublimation and condensation on seasonal timescales. This paper explores how a steady supply of atmospheric haze might affect three distinct provinces on Pluto. We pose the question of why they each look so different from one another if the same haze material is settling out onto all of them. Cthulhu is a more ancient region with comparatively little present-day geological activity, where the haze appears to simply accumulate over time. Sputnik Planitia is a very active region where glacial convection, as well as sublimation and condensation rapidly refresh the surface, hiding recently deposited haze from view. Lowell Regio is a region of intermediate age featuring very distinct coloration from the rest of Pluto. Using a simple model haze particle as a colorant, we are not able to match the colors in both Lowell Regio and Cthulhu. To account for their distinct colors, we propose that after arrival at Pluto's surface, haze particles may be less inert than might be supposed from the low surface temperatures. They must either interact with local materials and environments to produce distinct products in different regions, or else the supply of haze must be non-uniform in time and/or location, such that different products are delivered to different places.
•The geology of Sputnik Planitia on Pluto is mapped at 1:2M scale.•All mapped units are presently being affected by the action of flowing N2 ice.•Sputnik Planitia is experiencing convection, glacial ...flow, and sublimation.•Condensation of N2 onto much of Sputnik Planitia creates a bright mantle.•Blocky H2O ice mountains and hills have been mobilized by flow of N2 ice.
The geology and stratigraphy of the feature on Pluto informally named Sputnik Planitia is documented through geologic mapping at 1:2,000,000 scale. All units that have been mapped are presently being affected to some degree by the action of flowing N2 ice. The N2 ice plains of Sputnik Planitia display no impact craters, and are undergoing constant resurfacing via convection, glacial flow and sublimation. Condensation of atmospheric N2 onto the surface to form a bright mantle has occurred across broad swathes of Sputnik Planitia, and appears to be partly controlled by Pluto's obliquity cycles. The action of N2 ice has been instrumental in affecting uplands terrain surrounding Sputnik Planitia, and has played a key role in the disruption of Sputnik Planitia's western margin to form chains of blocky mountain ranges, as well in the extensive erosion by glacial flow of the uplands to the east of Sputnik Planitia.
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