A Stochastic Dynamic Programming Approach to Revenue Management in a Make-to-Stock Production System

In this paper, we consider a make-to-stock production system with known exogenous replenishments and multiple customer classes. The objective is to maximize profit over the planning horizon by deciding whether to accept or reject a given order, in anticipation of more profitable future orders. What distinguishes this setup from classical airline revenue management problems is the explicit consideration of past and future replenishments and the integration of inventory holding and backlogging costs. If stock is on-hand, orders can be fulfilled immediately, backlogged or rejected. In shortage situations, orders can be either rejected or backlogged to be fulfilled from future arriving supply. The described decision problem occurs in many practical settings, notably in make-to-stock production systems, in which production planning is performed on a mid-term level, based on aggregated demand forecasts. In the short term, acceptance decisions about incoming orders are then made according to stock on-hand and scheduled production quantities. We model this problem as a stochastic dynamic program and characterize its optimal policy. It turns out that the optimal fulfillment policy has a relatively simple structure and is easy to implement. We evaluate this policy numerically and find that it systematically outperforms common current fulfillment policies, such as first-come-first-served and deterministic optimization.revenue management;advanced planning systems;make-to-stock production;order fulfillment

Revenue Management and Demand Fulfillment: Matching Applications, Models, and Software

Recent years have seen great successes of revenue management, notably in the airline, hotel, and car rental business. Currently, an increasing number of industries, including manufacturers and retailers, are exploring ways to adopt similar concepts. Software companies are taking an active role in promoting the broadening range of applications. Also technological advances, including smart shelves and radio frequency identification (RFID), are removing many of the barriers to extended revenue management. The rapid developments in Supply Chain Planning and Revenue Management software solutions, scientific models, and industry applications have created a complex picture, which appears not yet to be well understood. It is not evident which scientific models fit which industry applications and which aspects are still missing. The relation between available software solutions and applications as well as scientific models appears equally unclear. The goal of this paper is to help overcome this confusion. To this end, we structure and review three dimensions, namely applications, models, and software. Subsequently, we relate these dimensions to each other and highlight commonalities and discrepancies. This comparison also provides a basis for identifying future research needs.Manufacturing;Revenue Management;Software;Advanced Planning Systems;Demand Fulfillment

Malignant and noninvasive skin tumours in renal transplant recipients.

Background. Transplant recipients require immunosuppression to prevent graft rejection. This conveys an increased risk of malignancy, particularly skin tumours. There is a need for up-to-date data for the South of England. Method. Pathology records were reviewed for 709 kidney transplant recipients on immunosuppression at our hospital from 1995 to 2008. Skin tumours were recorded/analysed. Results. Mean age at transplant was 46 years. Mean length of follow-up was 7.2 years and total follow-up was 4926 person-years. 53 (7.5%) patients (39/458 (8.5%) males and 14/251 (5.6%) females) developed ≥1 skin malignancy. Cumulative incidences of 4.0%, 7.5%, and 12.2% were observed for those with <5, <10, and ≥10 years follow-up, respectively. The rate was 45 tumours per 1000 person-years at risk. Additionally, 21 patients (3.0%) only had noninvasive tumours. 221 malignant skin tumours were found: 50.2% were SCCs, 47.1% BCCs, and 2.7% malignant melanomas. Mean years to first tumour were 5.8. Mean number of tumours per patient was 4, with mean interval of 12 months. Conclusions. Despite changes in transplantation practice during the time since the last data were published in this region, these findings are similar to previous studies. This adds to the evidence allowing clinicians to inform patients in this region of their risk

Revenue Management and Demand Fulfillment: Matching Applications, Models, and Software

Recent years have seen great successes of revenue management, notably in the airline, hotel, and car rental business. Currently, an increasing number of industries, including manufacturers and retailers, are exploring ways to adopt similar concepts. Software companies are taking an active role in promoting the broadening range of applications. Also technological advances, including smart shelves and radio frequency identification (RFID), are removing many of the barriers to extended revenue management. The rapid developments in Supply Chain Planning and Revenue Management software solutions, scientific models, and industry applications have created a complex picture, which appears not yet to be well understood. It is not evident which scientific models fit which industry applications and which aspects are still missing. The relation between available software solutions and applications as well as scientific models appears equally unclear. The goal of this paper is to help overcome this confusion. To this end, we structure and review three dimensions, namely applications, models, and software. Subsequently, we relate these dimensions to each other and highlight commonalities and discrepancies. This comparison also provides a basis for identifying future research needs

A Stochastic Dynamic Programming Approach to Revenue Management in a Make-to-Stock Production System

In this paper, we consider a make-to-stock production system with known exogenous replenishments and multiple customer classes. The objective is to maximize profit over the planning horizon by deciding whether to accept or reject a given order, in anticipation of more profitable future orders. What distinguishes this setup from classical airline revenue management problems is the explicit consideration of past and future replenishments and the integration of inventory holding and backlogging costs. If stock is on-hand, orders can be fulfilled immediately, backlogged or rejected. In shortage situations, orders can be either rejected or backlogged to be fulfilled from future arriving supply. The described decision problem occurs in many practical settings, notably in make-to-stock production systems, in which production planning is performed on a mid-term level, based on aggregated demand forecasts. In the short term, acceptance decisions about incoming orders are then made according to stock on-hand and scheduled production quantities. We model this problem as a stochastic dynamic program and characterize its optimal policy. It turns out that the optimal fulfillment policy has a relatively simple structure and is easy to implement. We evaluate this policy numerically and find that it systematically outperforms common current fulfillment policies, such as first-come-first-served and deterministic optimization

Recognition and property in Hegel and the early Marx

The article attempts to show, first, that for Hegel the role of property is to enable persons both to objectify their freedom and to properly express their recognition of each other as free, and second, that the Marx of 1844 uses fundamentally similar ideas in his exposition of communist society. For him the role of ‘true property’ is to enable individuals both to objectify their essential human powers and their individuality, and to express their recognition of each other as fellow human beings with needs, or their ‘human recognition’. Marx further uses these ideas to condemn the society of private property and market exchange as characterised by ‘estranged’ forms of property and recognition. He therefore uses a structure of ideas which Hegel had used to justify the institutions of private property and market exchange in order to condemn those same institutions. It is concluded that Marx’s adoption from Hegel of the idea that property as the means of self-objectification and of expressed recognition, leaves his vision of communism open to the charge that in it, just as in market society, the relations between human beings are mediated by things

SMOKE for Europe – adaptation, modification and evaluation of a comprehensive emission model for Europe

The US EPA regional emission model SMOKE was adopted and modified to create temporally and spatially distributed emission for Europe and surrounding countries based on official reports and public domain data only. The aim is to develop a flexible model capable of creating consistent high resolution emission data for long-term runs of Chemical Transport Models (CTMs). This modified version of SMOKE, called SMOKE for EUROPE (SMOKE-EU) was successfully used to create hourly gridded emissions for the timespan 1970–2010. &lt;br&gt;&lt;br&gt; In this paper the SMOKE-EU model and the underlying European datasets are introduced. Emission data created by SMOKE-EU for the year 2000 are evaluated by comparison to data of three different state-of-the-art emission models. SMOKE-EU produced a range of values comparable to the other three datasets. Further, concentrations of criteria pollutants calculated by the CTM CMAQ using the four different emission datasets were compared against EMEP measurements with hourly and daily resolution. Using SMOKE-EU gave the most reliable modelling of O&lt;sub&gt;3&lt;/sub&gt;, NO&lt;sub&gt;2&lt;/sub&gt; and SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2&amp;minus;&lt;/sup&gt;. The amount of simulated concentrations within a factor of 2 (F2) of the observations for these species are: O&lt;sub&gt;3&lt;/sub&gt; (F2 = 0.79, &lt;i&gt;N&lt;/i&gt; = 329 197), NO&lt;sub&gt;2&lt;/sub&gt; (F2 = 0.55, &lt;i&gt;N&lt;/i&gt; = 11 465) and SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2&amp;minus;&lt;/sup&gt; (F2 = 0.62, &lt;i&gt;N&lt;/i&gt; = 17 536). The lowest values were found for NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt; (F2 = 0.34, &lt;i&gt;N&lt;/i&gt; = 7400) and NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt; (F2 = 0.25, &lt;i&gt;N&lt;/i&gt; = 6184). NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt; concentrations were generally overestimated, leading to a fractional bias (FB) averaged over 22 measurement stations of (FB = 0.83 ± 0.41) while better agreements with observations were found for SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2&amp;minus;&lt;/sup&gt; (FB = 0.06 ± 0.38, 51 stations) and NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt; (FB = 0.13 &amp;plusmn; 0.75, 18 stations). &lt;br&gt;&lt;br&gt; CMAQ simulations using the three other emission datasets were similar to those modelled using SMOKE-EU emissions. Highest differences where found for NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt; while O&lt;sub&gt;3&lt;/sub&gt; concentrations were almost identical

Relations between measures of executive functions and self-regulation in preschoolers

"Performance on different measures of executive functions (EF) and self-regulation (SR) does not always correspond to the behaviour children show in real-life situations. The present study assesses the relationships between performances on different EF and SR measures and teacher ratings of children’s selfcontrol and thoughtfulness. In total, 217 children between 34 and 72 months (54% boys) were assessed. Four tests measuring cognitive EF (Digit Span backward, Block Recall, Day-Night Stroop, Hearts and Flowers) and two tests measuring behavioural EF (Tower) and SR (Head-Toes-Knees-Shoulders [HTKS]) were administered. Additionally, teachers rated the dimension ‘self-control and thoughtfulness’ of the German observation scale ‘Social‐emotional well‐being and resilience of children in early childhood settings’ (PERiK). It was found that all measures differentiated with regard to age in the range of three to six years. Correlations between cognitive EF measures with the HTKS were almost twice as high as correlations with the Tower. This indicates that the HTKS taps similar processes as the cognitive EF measures. Teacher ratings did not show higher correlations with behavioural EF and SR than with cognitive EF measures. Also, behavioural EF and SR measures did not predict scores obtained on the teacher rating better than cognitive EF measure. This article discusses to what extent distinctions among measures of EF and SR are possible and useful." (author's abstract)"Die Leistung bei standardisierten Verfahren zur Erfassung der exekutiven Funktionen (EF) und Selbstregulation (SR) passt nicht immer zu dem Niveau an Selbstkontrolle, dass Kinder im Kindergartenalter in realen Situationen zeigen. Die vorliegende Studie untersucht die Zusammenhänge zwischen den Leistungen bei verschiedenen Tests zu EF und SR und der Fremdeinschätzung der Selbstkontrolle, die die Kinder im Kindergartenalltag zeigen, durch pädagogische Fachkräfte. Insgesamt 217 Kinder zwischen 34 und 72 Monaten (54% Jungen) nahmen an der Studie teil. Vier Tests zu Erfassung der kognitiven EF (Zahlen nachsprechen rückwärts, Block Recall, Day-Night Stroop, Hearts and Flowers) und zwei Tests zur Erfassung der behavioralen EF (Turmbau) und der behavioralen SR (Head-Toes-Knees-Shoulders [HKTS]) wurden durchgeführt. Darüber hinaus bewerteten pädagogische Fachkräfte die Kinder auf der Skala 'Selbstkontrolle und Rücksichtnahme' des deutschen Beobachtungsbogens 'Positive Entwicklung und Resilienz im Kindergartenalltag' (PERiK). Zusammenhänge zwischen den Messinstrumenten zur kognitiven EF mit den HKTS waren fast doppelt so hoch wie ihre Korrelationen mit dem Turmbau. Dieses Ergebnis weist darauf hin, dass der HTKS, ausgewiesen als Instrument zur Erfassung der behavioralen SR, ähnliche Konstrukte wie die Tests zur Erfassung der kognitiven EF misst. Die Bewertung des Kindesverhaltens durch die pädagogischen Fachkräfte zeigte keine höheren Korrelationen mit den behavioralen als mit den kognitiven Messinstrumenten. Auch die Einschätzung durch die pädagogischen Fachkräfte wird durch die behavioralen Messungen nicht besser vorhergesagt als durch die kognitiven Messungen, wie es erwartet wurde. Es wird diskutiert, inwieweit eine Unterscheidung in die beiden Kategorien von Messinstrumenten möglich und sinnvoll ist." (Autorenreferat

El concepto de acción en hegel

Trad. de Daniel Barreto González. México: Anthropos / Universidad autonoma metropolitana, 2010. 238 pp

GEWEX Cloud System Study (GCSS) cirrus cloud working group: development of an observation-based case study for model evaluation

The GCSS working group on cirrus focuses on an inter-comparison of model simulations ranging from very detailed microphysical and dynamical models through to general circulation models (GCMs). The past GCSS cirrus cloud inter-comparison highlighted the wide range in modelling results that was a surprise to the modelling community. That inter-comparison was idealised and, therefore, a key issue was that it did not benefit from observations to help distinguish between model performances. In this work, we aim to address this key issue by developing an observationally based case study to be used for the GCSS cirrus modelling inter-comparison study. We focused on developing a case that had sufficient observations with which to evaluate models, to help identify which models in the inter-comparison are performing well and highlight areas for model development. Furthermore, it will provide a base case for future model comparisons or testing of new or updated models. This paper outlines the modelling case development and the inter-comparison results will be presented in a follow-on paper. The case was based on the 9 March 2000 Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) during an intensive observation period (IOP). The case was developed utilising various observations including ARM SGP remote sensing including the Milli-Meter Cloud Radar (MMCR), radiometers, radiosondes, aircraft observations, satellite observations, objective analysis and complemented with results from the Rapid Update Cycle (RUC) model as well as bespoke gravity wave simulations used to provide the best estimate for large scale forcing. The retrievals of ice water content, ice number concentration and fall velocity provide several constraints to evaluate model performances. Initial testing of the case has been reported using the UK Met Office Large Eddy Simulation Model (LEM) which suggests the case is appropriate for the model inter-comparison study. To our knowledge, this case offers the most detailed case study for cirrus comparison available and we anticipate this will offer significant benefits over past comparisons which have mostly been loosely based on observations