Resale and Bundling in Auctions

Allowing resale in multi-object auctions increases bidders. incentives to jointly reduce demand, because resale increases low-value bidders’ willingness to pay and reduces high-value bidders’ willingness to pay. Therefore (unlike in single-object auctions), resale may reduce the seller’s revenue in multi-object auctions. However, we show that, under reasonable conditions, allowing resale and bundling the objects on sale are “complement strategies” for the seller – by bundling and allowing resale the seller earns a higher revenue than by selling the objects separately and/or not allowing resale. We also analyze how resale affects a bidder’s incentive to unilaterally reduce demand, and we show why allowing resale may reduce efficiency.multi-object auctions, resale, bundling, demand reduction

Are Disadvantaged Bidders Doomed in Ascending Auctions?

A bidder is said to be advantaged if she has a higher expected valuation of the auction prize than her competitor. When the prize has a common-value component, a bidder competing in an ascending auction against an advantaged competitor bids especially cautiously and, hence, the advantaged bidder wins most of the time. However, contrary to what is often argued, a disadvantaged bidder still wins with positive probability, even if his competitor.s advantage is very large and even if the disadvantaged bidder has the lowest actual valuation ex-post. Therefore, the disadvantaged bidder has an incentive to participate in the auction, and the presence of a bidder with a small advantage does not have a dramatic e¤ect on the seller.s revenue.common-value auctions, asymmetric bidders

Bids as a Vehicle of (Mis)Information: Collusion in English Auctions with Affiliated Values

During an English auction, bidders' behaviour conveys information on their valuation of the prize. So whenever valuations are not independent, a bidder's strategy depends on the price at which his competitors drop out before he does. A ring of bidders can strategically manipulate the information reported through its members' bids, in order to mislead other bidders into bidding less aggressively and so allow a ring member to bid more aggressively. Collusion increases the probability that a ring bidder wins the auction and reduces the price he pays. The presence of a ring harms other bidders (as well as the seller) and reduces efficiency.auctions, collusion

Should Speculators Be Welcomed in Auctions?

The possibility of resale after an auction attracts speculators (i.e., bidders who have no use value for the objects on sale). In a multi-object auction, a high-value bidder may strictly prefer to let a speculator win some of the objects and then buy in the resale market, in order to keep the auction price low for the objects she wins in the auction. Therefore, although speculators increase competition in the auction, they also affect high-value bidders.incentives to .reduce demand..We show that the net e¤ect on the seller.s revenue of allowing resale to attract speculators depends on the heterogeneity of bidders.valuations. But the presence of speculators may increase the seller.s revenue only if speculators are eventually outbid. We also analyze the effect on the seller.s revenue of allowing resale in the absence of speculators, and we discuss the strategies that the seller can adopt to increase his revenue.multi-object auctions, speculation, resale, demand reduction

Planning natural repointing manoeuvres for nano-spacecraft

In this paper the natural dynamics of a rigid body are exploited to plan attitude manoeuvres for a small spacecraft. By utilising the analytical solutions of the angular velocities and making use of Lax pair integration, the time evolution of the attitude of the spacecraft in a convenient quaternion form is derived. This enables repointing manoeuvres to be generated by optimising the free parameters of the analytical expressions, the initial angular velocities of the spacecraft, to match prescribed boundary conditions on the final attitude of the spacecraft. This produces reference motions which can be tracked using a simple proportional-derivative controller. The natural motions are compared in simulation to a conventional quaternion feedback controller and found to require lower accumulated torque. A simple obstacle avoidance algorithm, exploiting the analytic form of natural motions, is also described and implemented in simulation. The computational efficiency of the motion planning method is discussed

Planning natural repointing manoeuvres for nano-spacecraft

In this paper the natural dynamics of a rigid body are exploited to plan attitude manoeuvres for a small spacecraft. By utilising the analytical solutions of the angular velocities and making use of Lax pair integration, the time evolution of the attitude of the spacecraft in a convenient quaternion form is derived. This enables repointing manoeuvres to be generated by optimising the free parameters of the analytical expressions, the initial angular velocities of the spacecraft, to match prescribed boundary conditions on the final attitude of the spacecraft. This produces reference motions which can be tracked using a simple proportional-derivative controller. The natural motions are compared in simulation to a conventional quaternion feedback controller and found to require lower accumulated torque. A simple obstacle avoidance algorithm, exploiting the analytic form of natural motions, is also described and implemented in simulation. The computational efficiency of the motion planning method is discussed

Computationally light attitude controls for resource limited nano-spacecraft

Nano-spacecraft have emerged as practical alternatives to large conventional spacecraft for specific missions (e.g. as technology demonstrators) due to their low cost and short time to launch. However these spacecraft have a number of limitations compared to larger spacecraft: a tendency to tumble post-launch; lower computational power in relation to larger satellites and limited propulsion systems due to small payload capacity. As a result new methodologies for attitude control are required to meet the challenges associated with nano-spacecraft. This paper presents two novel attitude control methods to tackle two phases of a mission using zero-propellant (i) the detumbling post-launch and (ii) the repointing of nano-spacecraft. The first method consists of a time-delayed feedback control law which is applied to a magnetically actuated spacecraft and used for autonomous detumbling. The second uses geometric mechanics to construct zero propellant reference manoeuvres which are then tracked using quaternion feedback control. The problem of detumbling a magnetically actuated spacecraft in the first phase of a mission is conventionally tackled using BDOT control. This involves applying controls which are proportional to the rate of change of the magnetic field. However, real systems contain sensor noise which can lead to discontinuities in the signal and problems with computing the numerical derivative. This means that a noise filter must be used and this increases the computational overhead of the system. It is shown that a timedelayed feedback control law is advantageous as the use of a delayed signal rather than a derivative negates the need for such a filter, thus reducing computational overhead. The second phase of the mission is the repointing of the spacecraft to a desired target. Exploiting the analytic solutions of the angular velocities of a symmetric spacecraft and further using Lax pair integration it is possible to derive exact equations of the natural motions including the time evolution of the quaternions. It is shown that parametric optimisation of these solutions can be used to generate low torque reference motions that match prescribed boundary conditions on the initial and final configurations. Through numerical simulation it is shown that these references can be tracked using nanospacecraft reaction wheels while eigenaxis rotations, used for comparison, are more torque intensive. As the method requires parameter optimisation as opposed to optimisation methods that require numerical integration, the computational effort is reduced

On-Net/Off-Net Price Discrimination and 'Bill-and-Keep' vs. 'Cost-Based' Regulation of Mobile Termination Rates

This paper surveys the recent literature on competition between mobile network operators in the presence of call externalities and network effects. It shows that the regulation of mobile termination rates based on “long-run incremental costs” increases networks’ strategic incentives to inefficiently set high on-net/off-net price differentials, thus harming smaller networks and new entrants. The paper argues in favor of a “bill-and-keep” system for mobile-to-mobile termination, and presents international evidence in support of this conclusion.mobile termination, network effects, call externalities, bill-and-keep

Functional proteomics.

Background: With the increase in the number of genome sequencing projects, there is a concomitant exponential growth in the number of protein sequences whose function is still unknown. Functional proteomics constitutes an emerging research area in the proteomic field whose approaches are addressed towards two major targets: the elucidation of the biological function of unknown proteins and the definition of cellular mechanisms at the molecular level. Methods: The identification of interacting proteins in stable complexes in vivo is essentially achieved by affinity-based procedures. The basic idea is to express the protein of interest with a suitable tag to be used as a bait to fish its specific partners out from a cellular extract. Individual components within the multi-protein complex can then be identified by mass spectrometric methodologies. Results and conclusions: The association of an unknown protein with partners belonging to a specific protein complex involved in a particular mechanism is strongly suggestive of the biological function of the protein. Moreover, the identification of protein partners interacting with a given protein will lead to the description of cellular mechanisms at the molecular level. The next goal will be to generate animal models bearing a tagged form of the bait protein

Vertical Separation with Private Contracts

We consider a manufacturer's incentive to sell through an independent retailer, rather than directly to final consumers, when contracts with retailers cannot be observed by competitors. If retailers conjecture that identical competing manufacturers always offer identical contracts (symmetry beliefs), vertical separation by all manufacturers is an equilibrium, and it results in higher consumers' prices and manufacturers' profits. Even with private contracts, vertically separated manufacturers reduce competition by inducing less aggressive behaviour by retailers in the final market. We characterize a condition for manufacturers' profits to be higher with private than with public contracts. Our results hold both with price and with quantity competition, and do not hinge on retailers' beliefs being perfectly symmetric.Delegation, vertical separation, private contracts, symmetry beliefs