Price Strategy Implementation

Consider a situation in which a company sells several different items to a set of customers. However, the company is not satisfied with the current pricing strategy and wishes to implement new prices for the items. Implementing these new prices in one single step mightnot be desirable, for example, because of the change in contract prices for the customers. Therefore, the company changes the prices gradually, such that the prices charged to a subset of the customers, the target market, do not differ too much from one period to the next. We propose a polynomial time algorithm to implement the new prices in the minimum number of time periods needed, given that the prices charged to the customers in the target market increase by at most a factor 1 + δ, for predetermined δ > 0. Furthermore, we address the problem to maximize the revenue when also a maximum number of time periods is predetermined. For this problem, we describe a dynamic program if the numberof possible prices is limited, and a local search algorithm if all prices are allowed. Also, we present the integer program that models this problem. Finally, we apply the obtained algorithms in a practical study.operations research and management science;

Bladder cancer recurrence patterns after robotic radical cystectomy with completely intracorporeal urinary diversion : a contemporary comparison with open radical cystectomy at a high-volume academic center

Background: There is some debate about patterns of recurrence after robotic radical cystectomy (RARC) for bladder cancer compared to open radical cystectomy (ORC). Objective: To compare rates and patterns of recurrence after RARC with completely intracorporeal urinary diversion (ICUD) and ORC. Design, Setting and Participants: Between August 2009 and June 2016, 837 consecutive patients underwent RARC with ICUD or ORC for localized BC at a single high-volume academic cancer center. Intervention: RARC and ICUD was performed in 237 patients, while ORC was performed in 598 patients. Outcome Measurements and Statistical Analysis: The outcomes of interest were recurrencefree survival (RFS), overall survival (OS) and distrubtion of local and distant recurrence. The patterns of local and distant recurrences within 2 years were tabulated. Kaplan-Meier analysis, the log rank test, and Cox regression analyses were used to compare RFS and OS between the two groups. All data was collected prospectively within an IRB-approved database and analysed retrospectively. All statistical analyses were performed using SAS software. Results and limitations: Both groups were comparable with respect to age, BMI, ASA, neoadjuvant chemotherapy status, CIS, LVI, positive soft-tissue margins and node-positive disease. RARC and ICUD patients were more likely to have an ileal conduit (64% vs 29%, p0.05). Median time to recurrence was 6.9 months in RARC arm and 7.7 months in the ORC arm. On multivariable regression analysis, RARC was not an independent predictor of recurrence after adjusting for confounders (HR 1.05, 95%CI 0.75–1.48; p=0.8). There were no differences in the number or patterns of recurrences, in particular, with respect to peritoneal carcinomatosis and extra-pelvic lymph node metastasis. The main limitation of this study is the retrospective analysis. Conclusions: These contemporary data show no differences in the rates or patterns of local or distant bladder cancer recurrence between ORC and RARC with ICUD. Patient summary: Radical cystectomy and urinary diversion for bladder cancer using the robotic platform is not associated with differences in the rates or patterns of recurrence compared to traditional open surgical techniques

Contributions and Solutions Using Small Hydro Power in Advanced Energy Recovery Strategies on WWTPs

Small Hydropowe

Monads with arities and their associated theories

After a review of the concept of "monad with arities" we show that the category of algebras for such a monad has a canonical dense generator. This is used to extend the correspondence between finitary monads on sets and Lawvere's algebraic theories to a general correspondence between monads and theories for a given category with arities. As application we determine arities for the free groupoid monad on involutive graphs and recover the symmetric simplicial nerve characterisation of groupoids.Comment: New introduction; Section 1 shortened and redispatched with Section 2; Subsections on symmetric operads (3.14) and symmetric simplicial sets (4.17) added; Bibliography complete

Online railway delay management: Hardness, simulation and computation

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Delays in a railway network are a common problem that railway companies face in their daily operations. When a train is delayed, it may either be beneficial to let a connecting train wait so that passengers in the delayed train do not miss their connection, or it may be beneficial to let the connecting train depart on time to avoid further delays. These decisions naturally depend on the global structure of the network, on the schedule, on the passenger routes and on the imposed delays. The railway delay management (RDM) problem (in a broad sense) is to decide which trains have to wait for connecting trains and which trains have to depart on time. The offline version (i.e. when all delays are known in advance) is already NP-hard for very special networks. In this paper we show that the online railway delay management (ORDM) problem is PSPACE-hard. This result justifies the need for a simulation approach to evaluate wait policies for ORDM. For this purpose we present TOPSU—RDM, a simulation platform for evaluating and comparing different heuristics for the ORDM problem with stochastic delays. Our novel approach is to separate the actual simulation and the program that implements the decision-making policy, thus enabling implementations of different heuristics to ‘‘compete’’ on the same instances and delay distributions. We also report on computational results indicating the worthiness of developing intelligent wait policies. For RDM and other logistic planning processes, it is our goal to bridge the gap between theoretical models, which are accessible to theoretical analysis, but are often too far away from practice, and the methods which are used in practice today, whose performance is almost impossible to measure.EU/FP6/021235-2/EU/Algorithms for Robust and on-line Railway optimisation: Improving the validity and reliability of large-scale systems/ARRIVA

Lucie Rault-Leyrat. La cithare chinoise zheng, un vol d’oies sauvages sur les cordes de soie...

Cet ouvrage tout à fait remarquable — issu d’une thèse de 3e cycle soutenue en 1973 à l’Université de Paris X — porte sur un instrument fort peu connu en Occident, alors qu’il semble être à l’heure actuelle de plus en plus pratiqué en République populaire de Chine et à Taïwan. En effet, le zheng, cithare à chevalets mobiles, a tendance à rester dans les pays occidentaux dans l’ombre du qin, cette autre cithare bien connu des amateurs de musique chinoise. Lucie Rault-Leyrat donne l’impression ..

Entwicklung supraleitender, strombegrenzender Transformatoren

Durch den Einsatz von Hochtemperatursupraleitern (HTSL) können Verluste, Volumen und Gewicht von Transformatoren reduziert werden, zudem werden diese aktiv Fehlerstrom begrenzend. In dieser Arbeit wurde die Rückkühlung von YBCO-Bandleitern nach einer Strombegrenzung untersucht. Weiterhin wurde ein Entwurfsgang für HTSL-Transformatoren erstellt und ein 60 kVA-Transformator entworfen und getestet. Darüber hinaus wurde eine Fallstudie zur Energieeinsparung durch HTSL-Transformatoren erstellt

Degree-bounded generalized polymatroids and approximating the metric many-visits TSP

In the Bounded Degree Matroid Basis Problem, we are given a matroid and a hypergraph on the same ground set, together with costs for the elements of that set as well as lower and upper bounds $f(\varepsilon)$ and $g(\varepsilon)$ for each hyperedge $\varepsilon$. The objective is to find a minimum-cost basis $B$ such that $f(\varepsilon) \leq |B \cap \varepsilon| \leq g(\varepsilon)$ for each hyperedge $\varepsilon$. Kir\'aly et al. (Combinatorica, 2012) provided an algorithm that finds a basis of cost at most the optimum value which violates the lower and upper bounds by at most $2 \Delta-1$, where $\Delta$ is the maximum degree of the hypergraph. When only lower or only upper bounds are present for each hyperedge, this additive error is decreased to $\Delta-1$. We consider an extension of the matroid basis problem to generalized polymatroids, or g-polymatroids, and additionally allow element multiplicities. The Bounded Degree g-polymatroid Element Problem with Multiplicities takes as input a g-polymatroid $Q(p,b)$ instead of a matroid, and besides the lower and upper bounds, each hyperedge $\varepsilon$ has element multiplicities $m_\varepsilon$. Building on the approach of Kir\'aly et al., we provide an algorithm for finding a solution of cost at most the optimum value, having the same additive approximation guarantee. As an application, we develop a $1.5$-approximation for the metric Many-Visits TSP, where the goal is to find a minimum-cost tour that visits each city $v$ a positive $r(v)$ number of times. Our approach combines our algorithm for the Bounded Degree g-polymatroid Element Problem with Multiplicities with the principle of Christofides' algorithm from 1976 for the (single-visit) metric TSP, whose approximation guarantee it matches.Comment: 17 page