Mechanism of Cloud Cavitation Generation on a 2-D Hydrofoil

When a sheet cavity on a hydrofoil section attains a certain size, it starts violent periodical oscillation shedding a harmful cloud cavity downstream at each oscillation cycle. This phenomenon is due to the occurrence of the re-entrant jet. In this paper, the behavior of the re-entrant jet was observed in detail using a transparent foil section model and a high-speed video camera. Time variation of pressure distribution on the foil was measured simultaneously. It was found that the re-entrant jet can start at any point in sheet cavity elongating stage. Even two re-entrant jets can appear in one cycle. When a re-entrant jet is generated upstream, the jet velocity is lower compared to the case when a re-entrant jet is generated downstream. The jet velocity is almost constant at the value determined by the location of the generation. As a result, the cavity oscillation cycle becomes constant when it is normalized by the sheet cavity surface velocity and the maximum sheet cavity length. The jet velocity is calculated from the pressure gradient at the sheet cavity T.E., using a simple theoretical model. The calculated jet velocity agrees with the measurement, showing that the jet velocity increases as its generation point shifts downstream. It is possible that pressure gradient at the sheet cavity T.E. is the driving force of re-entrant jet

Entry Deterrence and Signaling in Markets for Search Goods

This paper studies entry in markets for search goods. Signaling through prices is studied when an entrant s quality is (i) private information; and (ii) common information of entrant and incumbent. When consumers visit a store, they observe quality and can switch before purchasing. When switching costs are low, an entrant can signal high quality by setting a sufficiently high price; consumers who find out that quality is low switch to the incumbent. Entry may be facilitated when switching costs are sufficiently low, or when the incumbent knows the entrant s type.

License auctions with exit (and entry) options: Alternative remedies for the exposure problem

Inspired by some spectrum auctions, we consider a stylized license auction with incumbents and one entrant. Whereas the entrant values only the bundle of several units (synergy), incumbents are subject to non-increasing demand. The seller proactively encourages entry and restricts incumbent bidders. In this framework, an English clock auction gives rise to an exposure problem that distorts efficiency and impairs revenue. We consider three remedies: a (constrained) Vickrey package auction, an English clock auction with exit option that allows the entrant to annul his bid, and an English clock auction with exit and entry option that lifts the bidding restriction if entry failed

Product innovation and market acquisition of firms

The paper explores the incentives for an incumbent firm to acquire an entrant willing to sell a product innovation, rather than openly compete with this entrant and, in case of acquisition, the incentives to sell simultaneously both the existing products and the new one, rather than specializing on a single variant. We prove that, in some circumstances, an incumbent firm can find it profitable to make an acquisition proposal to the entrant in order to deter entry. Nevertheless, in this acquisition scenario, a product proliferation strategy is never observed at equilibrium. Rather, the incumbent restricts itself to offer either its own variant or the product innovation produced by the entrant, depending on the quality differential existing between them. It follows that, while being available for sale, sometimes the innovation simply remains unexploited

Re-entrant resonant tunneling

We study the effect of electron-electron interactions on the resonant-tunneling spectroscopy of the localized states in a barrier. Using a simple model of three localized states, we show that, due to the Coulomb interactions, a single state can give rise to two resonant peaks in the conductance as a function of gate voltage, G(Vg). We also demonstrate that an additional higher-order resonance with Vg-position in between these two peaks becomes possibile when interactions are taken into account. The corresponding resonant-tunneling process involves two-electron transitions. We have observed both these effects in GaAs transistor microstructures by studying the time evolution of three adjacent G(Vg) peaks caused by fluctuating occupation of an isolated impurity (modulator). The heights of the two stronger peaks exibit in-phase fluctuations. The phase of fluctuations of the smaller middle peak is opposite. The two stronger peaks have their origin in the same localized state, and the third one corresponds to a co-tunneling process.Comment: 9 pages, REVTeX, 4 figure

Entry into a network industry: consumers’ expectations and firms’ pricing policies

This paper presents a model of entry into a network industry. The entrant tries to attract the customer base of the incumbent service provider. While the entrant is more efficient, the incumbent enjoys an advantage thanks to a bias in consumers’ expectations. Buyers enter the game with heterogenous beliefs as to which of the two firms is going to win competition. Then expectations converge - through higher order beliefs - and select one winner, who ends up being the single supplier. The path of expectations convergence crucially depends on the pricing policy followed by firms: so equilibrium beliefs are endogenous. Depending on parameter values, one of two outcomes obtains: (i) the incumbent is able to exclude the entrant, by lowering his price below the monopoly level; (ii) the entrant is successful, by undercutting the incumbent price. Productive efficiency and consumers’ welfare are hurt by exclusion; the entry threat is beneficial to consumers anyway. Imposing compatibility among networks is welfare improving, as it removes the exclusionary potential enjoyed by the incumbent.network industries, critical mass, entry, exclusion, higher order beliefs

Would you like to enter first with a low-quality good?

Using a two-period duopoly model with vertical differentiation, we show that there exists a unique subgame perfect equilibrium where the first entrant supplies a lower quality and gains higher profits than the second entrant. We also prove that this entry sequence is socially efficient.entry, vertical differentiation

Interplay between dipole and quadrupole modes of field influence in liquid-crystalline suspensions of ferromagnetic particles

In the framework of continuum theory we study orientational transitions induced by electric and magnetic fields in ferronematics, i.e., in liquid-crystalline suspensions of ferromagnetic particles. We have shown that in a certain electric field range the magnetic field can induce a sequence of re-entrant orientational transitions in ferronematic layer: nonuniform phase --- uniform phase --- nonuniform phase. This phenomenon is caused by the interplay between the dipole (ferromagnetic) and quadrupole (dielectric and diamagnetic) mechanisms of the field influence on a ferronematic structure. We have found that these re-entrant Freedericksz transitions exhibit tricritical behavior, i.e., they can be of the first or the second order. The character of the transitions depends on a degree of redistribution of magnetic admixture in the sample exposed to uniform magnetic field (magnetic segregation). We demonstrate how electric and magnetic fields can change the order of orientational transitions in ferronematics. We show that electric Freedericksz transitions in ferronematics subjected to magnetic field have no re-entrant nature. Tricritical segregation parameters for the transitions induced by electric or magnetic fields are obtained analytically. We demonstrate the re-entrant behavior of ferronematic by numerical simulations of the magnetization and optical phase lag.Comment: 12 pages, 9 figures, to be published in Soft Matte

Re-entrant hidden order at a metamagnetic quantum critical end point

Magnetization measurements of URu2Si2 in pulsed magnetic fields of 44 T reveal that the hidden order phase is destroyed before appearing in the form of a re-entrant phase between ~ 36 and 39 T. Evidence for conventional itinerant electron metamagnetism at higher temperatures suggests that the re-entrant phase is created in the vicinity of a quantum critical end point.Comment: 8 pages, including 3 figures (Physical Review Letters, in press) a systematic error in the field calibration has been fixed since the original submission of this manuscrip