A tight lower bound for an online hypercube packing problem and bounds for prices of anarchy of a related game

We prove a tight lower bound on the asymptotic performance ratio $\rho$ of the bounded space online $d$-hypercube bin packing problem, solving an open question raised in 2005. In the classic $d$-hypercube bin packing problem, we are given a sequence of $d$-dimensional hypercubes and we have an unlimited number of bins, each of which is a $d$-dimensional unit hypercube. The goal is to pack (orthogonally) the given hypercubes into the minimum possible number of bins, in such a way that no two hypercubes in the same bin overlap. The bounded space online $d$-hypercube bin packing problem is a variant of the $d$-hypercube bin packing problem, in which the hypercubes arrive online and each one must be packed in an open bin without the knowledge of the next hypercubes. Moreover, at each moment, only a constant number of open bins are allowed (whenever a new bin is used, it is considered open, and it remains so until it is considered closed, in which case, it is not allowed to accept new hypercubes). Epstein and van Stee [SIAM J. Comput. 35 (2005), no. 2, 431-448] showed that $\rho$ is $\Omega(\log d)$ and $O(d/\log d)$, and conjectured that it is $\Theta(\log d)$. We show that $\rho$ is in fact $\Theta(d/\log d)$. To obtain this result, we elaborate on some ideas presented by those authors, and go one step further showing how to obtain better (offline) packings of certain special instances for which one knows how many bins any bounded space algorithm has to use. Our main contribution establishes the existence of such packings, for large enough $d$, using probabilistic arguments. Such packings also lead to lower bounds for the prices of anarchy of the selfish $d$-hypercube bin packing game. We present a lower bound of $\Omega(d/\log d)$ for the pure price of anarchy of this game, and we also give a lower bound of $\Omega(\log d)$ for its strong price of anarchy

Origin of Tc Enhancement Induced by Doping Yttrium and Hydrogen into LaFeAsO-based Superconductors: 57Fe, 75As, 139La, and 1H-NMR Studies

We report our extensive 57Fe-, 75As-, 139La-, and 1H-NMR studies of La_{0.8}Y_{0.2}FeAsO_{1-y} (La_{0.8}Y_{0.2}1111) and LaFeAsO_{1-y}H_{x}(La1111H), where doping yttrium (Y) and hydrogen (H) into optimally doped LaFeAsO_{1-y} (La1111(OPT)) increases T_c=28 K to 34 and 32 K, respectively. In the superconducting (SC) state, the measurements of nuclear-spin lattice-relaxation rate 1/T_1 have revealed in terms of a multiple fully gapped s_\pm-wave model that the SC gap and T_c in La_{0.8}Y_{0.2}1111 become larger than those in La1111(OPT) without any change in doping level. In La1111H, the SC gap and T_c also increase slightly even though a decrease in carrier density and some disorders are significantly introduced. As a consequence, we suggest that the optimization of both the structural parameters and the carrier doping level to fill up the bands is crucial for increasing T_c among these La1111-based compounds through the optimization of the Fermi surface topology.Comment: 4 pages, 4 figures, 1 table, to be published in J. Phys. Soc. Jpn, Vol. 79, No. 1

NASDA Space Program In Japan

The National Space Development Agency of Japan, NASDA, was established on October 1, 1969, under the NASDA Law as the nucleus of the nation\u27s space development effort in order to promote space development and utilization for peaceful purposes. NASDA, in a sense, is the equibalent of NASA in the United States, or ESA ( European Space Agency ) in Europe. In accordance with the basic program for space development decided by the Prime Minister, NASDA is undertaking (1) the development, launching and tracking of satellites and satellite launch vehicles and (2) the development and consolidation of software, equipment and facilities needed for launching and tracking. So far, NASDA has succeeded in launching four satellites by means of its N Launch vehicle from the Tanegashima Space Center, three of them into 1,000 km circular orbit and one into geosynchronous orbit. NASDA succeeded also in the insertion of three satellites into geosynchronous orbits at their projected positions after having been launched by US NASA\u27s Delta 2914 from ETR under the reimbursable launch contract. NASDA activities in general will be overviewed in this report

Make-up Fabrication of Big or Complex Parts Using the SLA Process

Rapid prototyping is a highly flexible manufacturing technology which can produce big or complex parts without any special fixtures and tools. But it is often a costly and time consuming process to produce big and complex parts. To solve this problem, this paper proposes the makeup fabrication process. The process cuts the CAD models of big or complex parts into several small components. optimizes the building orientation and the layout of the multiple objects and then uses theSLA process to build. The paper discusses the basic process, the discretion rules of the CAD models and the optimization of the layout of multiple objects in the simultaneous buildingMechanical Engineerin

Bipyridyl substituted triazoles as hole-blocking and electron-transporting materials for organic light-emitting devices

ArticleORGANIC ELECTRONICS. 9(1): 77-84 (2008)journal articl