14,542 research outputs found
Data highway terminal controller
A data highway terminal controller with transmission controllers assigned to each processor in a set of multiple processors is described. Shared-use terminals are loop connected to the processors via the controllers
Are Estimates of Asymmetric First-Price Auction Models Credible? Semi & Nonparametric Scrutinizations
Structural first-price auction estimation methods, built upon Bayesian Nash Equilibrium (BNE), have provided prolific empirical findings. However, due to the latent nature of underlying valuations, the assumption of BNE is not feasibly testable with field data, a fact that evokes harsh criticism on the literature. To respond to skepticism regarding credibility, we provide a focused answer by scrutinizing estimates derived from experimental asymmetric auction data in which researchers observe valuations. We test the statistical equivalence between the estimated and true value distributions. The Kolmogorov-Smirnov test fails to reject the distributional equivalence, strongly supporting the credibility of structural asymmetric auction estimates
Backbone colorings along perfect matchings
Given a graph and a spanning subgraph of (the backbone of ), a backbone coloring for and is a proper vertex coloring of in which the colors assigned to adjacent vertices in differ by at least two. In a recent paper, backbone colorings were introduced and studied in cases were the backbone is either a spanning tree or a spanning path. Here we study the case where the backbone is a perfect matching. We show that for perfect matching backbones of the number of colors needed for a backbone coloring of can roughly differ by a multiplicative factor of at most from the chromatic number . We show that the computational complexity of the problem ``Given a graph with a perfect matching , and an integer , is there a backbone coloring for and with at most colors?'' jumps from polynomial to NP-complete between and . Finally, we consider the case where is a planar graph
Toughness and hamiltonicity in -trees
We consider toughness conditions that guarantee the existence of a hamiltonian cycle in -trees, a subclass of the class of chordal graphs. By a result of Chen et al.\ 18-tough chordal graphs are hamiltonian, and by a result of Bauer et al.\ there exist nontraceable chordal graphs with toughness arbitrarily close to . It is believed that the best possible value of the toughness guaranteeing hamiltonicity of chordal graphs is less than 18, but the proof of Chen et al.\ indicates that proving a better result could be very complicated. We show that every 1-tough 2-tree on at least three vertices is hamiltonian, a best possible result since 1-toughness is a necessary condition for hamiltonicity. We generalize the result to -trees for : Let be a -tree. If has toughness at least then is hamiltonian. Moreover, we present infinite classes of nonhamiltonian 1-tough -trees for each $k\ge 3
Do Crime-Prone Areas Attract Gambling Shops? A Case of London Boroughs
We investigate a causal effect of crime on the number of betting shops by using annual data from London boroughs (2007-2015). Using an instrumental variable strategy, we estimate a panel model accounting for omitted variables and borough-level heterogeneity. Our estimation results show that a 1% increase in crime rate causes a 1.2% increase in the number of betting shops (per capita). Put differently, a new betting shop opens in a borough for every 1.4% increase in the local crime rate, on average. The causal effect is robust across a variety of specifications, although the magnitude varies across models
Risk- & Regret-Averse Bidders in Sealed-Bid Auctions
Overbidding, bidding more than risk-neutral Bayesian Nash Equilibrium, is a widely observed phenomenon in
virtually all experimental auctions. The scholars within the auction literature propose the risk-averse preference
model to explain overbidding structurally. However, the risk-averse preference model predicts underbidding in
such important classes of auctions as all-pay auctions. To solve this discrepancy, we construct a structural model
of bidding behavior in sealed-bid auctions, one in which bidders may regret their decisions. Our model nests both
risk-averse and regret-averse attitudes and aims to explain overbidding in a wider class of auctions. We first derive
equilibrium first-order conditions, which are used for estimation and calibration analyses, and show monotonic
increasing properties of equilibrium bidding functions. Second, we carry out structural estimation and calibration
analyses based on experimental data from Kagel and Levin (1993) and Noussair and Silver (2006). With these
structurally estimated parameters, we test the significance of bidders’ risk-averse and regret-averse attitudes.
The estimation results show that bidders exhibit weak risk-averse (close to risk-neutral) and strong regret-averse
attitudes. Furthermore, regret-averse attitudes are significant when bidders anticipate losing. Calibration results
demonstrate that our risk- & regret-averse model can explain overbidding across all of the above IPV auctions.
Third, we simulate our model with the estimated parameters and obtain revenue rankings numerically. This
allows us to confirm the revenue supremacy in all-pay auctions reported in experimental auction literature. We
discuss extensions to asymmetric and Common-Value (CV) auctions in our online appendix
Running performance of an aerodynamic journal bearing with squeeze film effect
Results of theoretical and experimental studies concerning the performance of an aerodynamic journal bearing which running is assisted by squeeze film ultrasonic levitation (SFUL) are presented in this paper. The SFUL mechanism not only can separate journal from the bearing at the start and stop phases of operation but also can significantly contribute to the dynamic stability of the bearing when it runs at speed. Computer calculations and validating experimental testing of a prototype device were carried out. It was found that that SFUL mechanism, when combined with aerodynamic lift, extends the threshold speed of bearing’s instability by almost four times comparing to that of a bearing operating without SFUL. Typically, the bearing running without SFUL became unstable at the speed of 300 rpm while with the SFUL the speed at which instability became apparent was 10,000 rpm (calculated result) or 13,200 (experimental result)
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