Pricing in a duopoly with a lead time advantage

We analyze the price competition between two suppliers offering two different lead times and two different prices to a buyer. The buyer chooses its inventory replenishment policy in order to minimize its infinite-horizon average cost. In essence, the fast and expensive supplier is used only in emergencies, while the slow and cheap supplier receives the bulk of the orders. Thus, despite a higher price, the fast supplier is able to capture a part of the buyer's orders. We analyze the price competition between the asymmetric suppliers, where the market share of each supplier is derived from the buyer's inventory problem. We find equilibria that differ significantly from the Bertrand price-only competition. In particular, for some cost parameters, the fast supplier is able to charge a premium for faster delivery, and stay in business even with a higher production cost. We obtain in some cases closed-form formulas for the price difference in equilibrium. Hence, our results show that high cost suppliers may not be driven out of business if they can offer fast delivery.offshoring; dual sourcing;

Competing for shelf space

This paper studies competition for shelf space in a multi-supplier retail point. We consider a retailer that seeks to allocate her shelf space to maximize her profit. Because products associated with larger profit margin are granted more shelf space, suppliers can offer the retailer financial incentives to obtain larger space allocations. We analyze the competitive dynamics arising from the scarcity of space, and show existence and uniqueness of equilibrium. We then demonstrate that the inefficiencies from decentralizing decision-making are limited to 6% with wholesale-price contracts, and that full coordination can be achieved with pay-to-stay fee contracts. We finally investigate how competition is distorted under the practice of category management.Game theory; Supply chain competition; Price of Anarchy; Pricing; Supply contracts;

A capacitated commodity trading model with market power

In this paper we consider the problem of a trader who purchases a commodity in one market and resells it in another. The trader is capacitated: the trading volume is limited by operational constraints, e.g., logistics. The two markets quote different prices, but the spread is reduced when trading takes place. We are interested in finding the optimal trading policy across the markets so as to obtain the maximum profit in the long-term, taking into account that the trading activity influences the price processes, i.e., market power. As in the no-market-power case, we find that the optimal policy is determined by three regions, where 1) move as much as possible from one market to the other; 2) the same in the opposite direction; or 3) do nothing. Finally, we use the model to analyze kerosene price differences between New York and Los Angeles.commodity trading; price processes; inventory management;

Improving supply chain efficiency through wholesale price renegotiation

In a decentralized supply chain, double marginalization is an important source of inefficiency. We suggest in this paper a simple mechanism to reduce it that uses a wholesale price contract and renegotiation. Our mechanism only requires repeated interaction, and rational behavior from the players. Specifically, over T rounds of negotiation, the supplier proposes different prices in each round, and the buyer places orders at the quoted price. Even though prices are decreasing in time, the buyer places a positive order, to force the supplier to reduce its price in the following round. This interaction results in higher profits for both supplier and buyer. We solve the buyer and supplier problems and show that, as T increases, supply chain efficiency tends to 100%, and the sub-optimality gap decreases with 1/T. Finally, we discuss how these results can be applied to design negotiation processes.strategic customer; dynamic pricing; supply chain;

A Note on Shapleys Convex Measure Games

L. S. Shapley, in his paper Cores of Convex Games, introduces Convex Measure Games, those that are induced by a convex function on R, acting over a measure on the coalitions. But in a note he states that if this function is a function of several variables, then convexity for the function does not imply convexity of the game or even superadditivity. We prove that if the function is directionally convex, the game is convex, and conversely, any convex game can be induced by a directionally convex function acting over measures on the coalitions, with as many measures as players.supermodularity, multilinear extension, convex cooperative games, directional convexity

Myopic inventory policies using individual customer arrival information

We investigate optimality of myopic policies using the single-unit decomposition approach in inventory management. We derive, under certain conditions, closed-form replenishment decisions, which we call a base-probability policy. That is, the order associated with a given customer is placed if and only if its arrival probability within the lead-time is higher than a threshold.inventory management; base-stock policies; myopic policies;

Assignment markets with the same core

In the framework of bilateral assignment games, we study the set of matrices associated with assignment markets with the same core. We state conditions on matrix entries that ensure that the related assignment games have the same core. We prove that the set of matrices leading to the same core form a join-semilattice with a nite number of minimal elements and a unique maximum. We provide a characterization of the minimal elements. A sucient condition under which the join-semilattice reduces to a lattice is also given.core, semilattice, assignment game

Competition in the supply option market

This paper develops a multi-attribute competition model for procurement of short life cycle products. In such an environment, the buyer installs dedicated production capacity at the suppliers before the demand is realized. Final production orders are decided after demand materializes. Of course, the buyer is reluctant to bear all the capacity and inventory risk, and thus signs flexible contracts with several suppliers. We model the suppliers' offers as option contracts, where each supplier charges a reservation price per unit of capacity, and an execution price per unit of delivered supply. These two parameters illustrate the trade-off between total price and flexibility of the contract, and are both important to the buyer. We model the interaction between the suppliers and the buyer as a game in which the suppliers are the leaders and the buyer is the follower. Specifically, suppliers compete to provide supply capacity to the buyer and the buyer optimizes its expected profit by selecting one or more suppliers. We characterize the suppliers' equilibria in pure strategies for a class of customer demand distributions. In particular, we show that this type of interaction gives rise to cluster competition. That is, in equilibrium, suppliers tend to be clustered in small groups of two or three suppliers each, such that within the same group all suppliers use similar technologies and offer the same type of contract. Finally, we show that in equilibrium, the supply chain inefficiencies, i.e., the loss of profit due to competition, are in general at most 25% of the profit of a centralized supply chain, for a wide class of demand distributions.supplier portfolio; supplier competition;

Compósitos luminescentes baseados em celulose bacteriana e lantanídeos

Mestrado em QuímicaThe development of innovative bio-based materials has gained considerable attention during the last decades because of the increasing society awareness regarding environmental issues and sustainable development. Cellulose is the most abundant natural polymer and therefore represents one of the most relevant raw materials from renewable resources. For example, the combination of natural polymers, as cellulose, with inorganic compounds with specific properties is a quite interesting and versatile strategy for the design of novel functional materials. In this context, the aim of this work was to prepare and characterize novel luminescent organic-inorganic hybrid films obtained by combination of cellulose acetate (prepared by almost complete acetylation bacterial cellulose nanofibrils) and a lanthanide ß-diketone complex (Tb(acac)3). All the obtained films were very homogeneous and transparent and displayed improved thermal and mechanical properties, in comparison with the undoped cellulose acetate films. The photoluminescence analysis confirmed the high ability of lanthanides to provide luminescence properties to different materials. Finally, the addition of partially acetylated bacterial cellulose nanofibrils to the films improved the mechanical properties without affecting the transparency and luminescence in a great extent.O desenvolvimento de materiais inovadores baseados em biomassa tem ganho uma atenção considerável durantes as últimas décadas devido à crescente consciencialização da sociedade em relação às questões ambientais e de desenvolvimento sustentável. A celulose é o polímero natural mais abundante e, por conseguinte, representa uma das matérias primas provenientes de fontes renováveis mais relevantes. Por exemplo, a combinação de polímeros naturais, como a celulose, com compostos inorgânicos com propriedades específicas é uma estratégia interessante e versátil para a criação de novos materiais funcionais. Neste contexto, o objetivo deste trabalho foi preparar e caracterizar novos filmes híbridos orgânico-inorgânicos luminescentes obtidos pela combinação de acetato de celulose (preparado por acetilação completa de nanofibrilas de celulose bacteriana) e um complexo ß-dicetona de lantanídeo (Tb(acac)3). Todos os filmes obtidos eram bastantes homogéneos e transparentes e demonstraram propriedades mecânicas e térmicas melhoradas, em comparação com os filmes de acetato de celulose não dopados. A análise de fotoluminescência confirmou a elevada capacidade dos lantanídeos para proporcionar propriedades de luminescência quando combinados com outros materiais. Finalmente, a adição de nanofibrilas de celulose bacteriana parcialmente acetiladas aos filmes melhorou as suas propriedades mecânicas sem afectar extensivamente a sua transparência e luminescência

La trampa del antropomorfismo. Hacia una interfaz (más) compleja de lo social

La enseñanza de la sociología supone, hoy día, una cura de humildad. Por más que acudamos a sofisticados modelos teóricos (la sociedad líquida, la teoría de sistemas, la fluidez social, la teoría del actor-red), que cuestionan las bases fundacionales de la sociología clásica, la práctica docente evidencia que entre los estudiantes sigue imperando una imagen simple o esquemática de lo social. La sorpresa es mayor si asumimos que se trata de una generación que se ha socializado en el uso de herramientas digitales que facilitan, en principio,la elaboración de mapas más acordes con la complejidad que lo social reviste. El antropomorfismo, la idea de que la sociedad es ante todo un agrupamiento más o menos estable de individuos, es el límite infranqueable que sigue imponiéndose a la hora de entender lo social. Para minar esta visión hegemónica es preciso acudir a disciplinas como el arte (digital), las nuevas tecnología y, en general, las innovaciones estéticas, no tanto para destruir esa representación antropomórfica de lo social sino para desfigurándola prefigurar otras más acordes con una complejidad que ya no sólo intuimos y cuyo aliento sentimos muy cercaThe teaching of sociology is today a humbling experience. Although we use complex theoretical models (the liquid society, system theory, social fluidity or Actor-Network Theory) that question the foundational bases of classical sociology, teaching practice shows that a simple or schematic picture of the social continues to prevail among students. The surprise is even greater when we consider that this is a generation that has been socialized in the use of digital tools, a resource that, in principle, should facilitate a mapping of social reality more appropriate to its complexity. Anthropomorphism, the idea that society is primarily a more or less stable grouping of individuals, is the impassable limit that continues to be imposed when it comes to understanding society. To undermine this hegemonic vision one must to turn to fields such as (digital) art, the new technologies and, in general, aesthetic innovation, not so much to destroy the anthropomorphic representation of the social as to disfigure it, in order to obtain other representations more consistent with a social complexity that we not only intuit, but whose proximity we can fee