Endogenous Information Acquisition on Opponents' Valuations in Multidimensional First Price Auctions

This paper investigates bidder's covert behavior of endogenous information acquisition on her opponents' valuations in first price auction model with independent private values. Such an information acquisition setting leads to bidimensional type space and bidimensional strategy space. We consider two different specifications of the environments: the ex ante information acquisition setting and the interim information acquisition setting. In equilibria the expected payoffs of the bidder under these specifications could exceed the counterpart payoffs of the corresponding standard sealed-bid auctions without information acquisition as long as the cost is small, but the auctioneer has lower payoffs in these models than those of the standard ones. Moreover, the incurred information cost becomes the deadweight loss, resulting in ine±cient outcomes

Vickrey Auctions with Sequential and Costly Participation

This paper investigates the cutoff strategies and the effects of sequential and costly participation in Vickrey auctions with independent private value settings. It demonstrates a Stackelberg version of participation decision in auctions, while simultaneous participation can be regarded as a Cournot version in auctions. Buyers adopt cut-off participation strategies. In two-buyer case, the cutoff strategy equilibrium is unique. The follower's critical values are always monotonic in participation cost in both symmetric and asymmetric settings. This is also true for the leader with mild conditions on c.d.fs. We also characterize equilibria in three-buyer and more general n-buyer environments. We then study buyer's preference to be a leader or a follower. Comparison with simultaneous model shows that the driven-out effect is much stronger in our sequential participation model, which implies the simultaneous specification might not be desirable

Log-Less Metadata Management on Metadata Server for Parallel File Systems

This paper presents a novel metadata management mechanism on the metadata server (MDS) for parallel and distributed file systems. In this technique, the client file system backs up the sent metadata requests, which have been handled by the metadata server, so that the MDS does not need to log metadata changes to nonvolatile storage for achieving highly available metadata service, as well as better performance improvement in metadata processing. As the client file system backs up certain sent metadata requests in its memory, the overhead for handling these backup requests is much smaller than that brought by the metadata server, while it adopts logging or journaling to yield highly available metadata service. The experimental results show that this newly proposed mechanism can significantly improve the speed of metadata processing and render a better I/O data throughput, in contrast to conventional metadata management schemes, that is, logging or journaling on MDS. Besides, a complete metadata recovery can be achieved by replaying the backup logs cached by all involved clients, when the metadata server has crashed or gone into nonoperational state exceptionally

Phase Changes in the Evolution of the IPv4 and IPv6 AS-Level Internet Topologies

In this paper we investigate the evolution of the IPv4 and IPv6 Internet topologies at the autonomous system (AS) level over a long period of time.We provide abundant empirical evidence that there is a phase transition in the growth trend of the two networks. For the IPv4 network, the phase change occurred in 2001. Before then the network's size grew exponentially, and thereafter it followed a linear growth. Changes are also observed around the same time for the maximum node degree, the average node degree and the average shortest path length. For the IPv6 network, the phase change occurred in late 2006. It is notable that the observed phase transitions in the two networks are different, for example the size of IPv6 network initially grew linearly and then shifted to an exponential growth. Our results show that following decades of rapid expansion up to the beginning of this century, the IPv4 network has now evolved into a mature, steady stage characterised by a relatively slow growth with a stable network structure; whereas the IPv6 network, after a slow startup process, has just taken off to a full speed growth. We also provide insight into the possible impact of IPv6-over-IPv4 tunneling deployment scheme on the evolution of the IPv6 network. The Internet topology generators so far are based on an inexplicit assumption that the evolution of Internet follows non-changing dynamic mechanisms. This assumption, however, is invalidated by our results.Our work reveals insights into the Internet evolution and provides inputs to future AS-Level Internet models.Comment: 12 pages, 21 figures; G. Zhang et al.,Phase changes in the evolution of the IPv4 and IPv6 AS-Level Internet topologies, Comput. Commun. (2010

Elliptical ring distribution probability-based damage imaging method for complex aircraft structures

In engineering applications, the robustness and effectiveness of damage diagnostic imaging for guided wave-based structural health monitoring could be affected by the complexity of structures. In this study, an elliptical ring distribution probability-based diagnostic imaging algorithm is proposed to mitigate this effect using the estimated wave velocity and damage index. This algorithm improves the ability of damage localization by modifying the defect distribution probability of probability-based diagnostic imaging. The elliptical ring distribution probability of the presence of defect is used for each sensing path in the algorithm. The width of the elliptical ring distribution probability is determined by the range of estimated wave velocity. The amplitude of the elliptical ring distribution probability is determined by the damage index. The damage location is determined by the cross region of different elliptical rings for different sensing paths. The capability of the algorithm is validated by identifying damages at different locations on a complex composite fuselage panel. The results show that the proposed algorithm can identify a single damage accurately and it can identify multiple damages effectively as well