Transmission Studies of Left-handed Materials

Left-handed materials are studied numerically using an improved version of the transfer-matrix method. The transmission, reflection, the phase of the reflection and the absorption are calculated and compared with experiments for both single split-ring resonators (SRR) with negative permeability and left-handed materials (LHMs) which have both the permittivity and permeability negative. Our results suggest ways of positively identifying materials that have both permittivity and permeability negative, from materials that have either permeability or permittivity negative

The effects of win-win conditions on revenue-sharing contracts

This paper studies revenue-sharing contracts in distribution chains in the presence of win-win conditions. Revenue-sharing contracts are a mechanism to coordinate the firms in a distribution chain. Under these contracts the retailer shares its revenue with the supplier in exchange for a lower wholesale price. The win-win conditions are natural conditions requiring that the profit of any firm may not decrease after implementing the revenue-sharing contract. If these conditions are not met, that is, if at least one firm is confronted with decreased profits, the firms will not agree upon signing the contract and the revenue-sharing contract will not be implemented. We show that the win-win conditions result in a smaller range of contracts being offered by the supplier. More important, in case of multiple competing retailers there may be no revenue-sharing contract satisfying these conditions. Hence, in the presence of win-win conditions revenue-sharing contracts are not suitable for distribution chains with a supplier and multiple competing retailers. For these chains we present a simple alternative coordination mechanism that coordinates the chain and satisfies all win-win conditions. \u

When should you press the reload button?

While surfing on the Internet, you may have observed the following. If a webpage takes a long time to download and you press the reload button then often the page promptly appears on your screen. Hence, the download was not hindered by congestion — then you’d better try again later — but by some other cause.\ud If you do not know if some cause (like congestion) may hinder your download then what is a good strategy? When should you cancel the download and when should you press the reload button? Should you press it immediately or should you wait for a while? And how long should you wait before cancelling the download? We analyze these issues in this article, which is a non-technical impression of the paper “Efficiency of Repeated Network Interactions” [4] by Judith Timmer (UT) and Michel Mandjes (UvA).\u

Hemispheric Vision: Jackson School Revitalizes Ties through Latin American Forum on Energy and the Environment

Latin American Studie

The Quantum Mechanical Arrows of Time

The familiar textbook quantum mechanics of laboratory measurements incorporates a quantum mechanical arrow of time --- the direction in time in which state vector reduction operates. This arrow is usually assumed to coincide with the direction of the thermodynamic arrow of the quasiclassical realm of everyday experience. But in the more general context of cosmology we seek an explanation of all observed arrows, and the relations between them, in terms of the conditions that specify our particular universe. This paper investigates quantum mechanical and thermodynamic arrows in a time-neutral formulation of quantum mechanics for a number of model cosmologies in fixed background spacetimes. We find that a general universe may not have well defined arrows of either kind. When arrows are emergent they need not point in the same direction over the whole of spacetime. Rather they may be local, pointing in different directions in different spacetime regions. Local arrows can therefore be consistent with global time symmetry.Comment: 9 pages, 4 figures, revtex4, typos correcte

Interpreting Begay After Sykes: Why Reckless Offenses Should Be Eligible To Qualify as Violent Felonies Under the ACCA’s Residual Clause

Passed as part of the Armed Career Criminal Act, 18 U.S.C. § 924(e) subjects felons in possession of firearms to a strict mandatory minimum sentence if the offenders have three prior state or federal convictions that qualify as serious drug offenses or violent felonies. A crime qualifies as a violent felony under the residual clause, 18 U.S.C. § 924(e)(2)(B)(ii), if it is one of the enumerated offenses of burglary, arson, or extortion, involves use of explosives, or otherwise involves conduct that presents a serious potential risk of physical injury to another. Current federal circuit court interpretations of the Supreme Court\u27s decisions in Begay v. United States and Sykes v. United States exclude both crimes with lesser mens rea—recklessness or negligence—and strict-liability crimes from qualifying under the residual clause. This Note proposes that some reckless crimes, like drive-by shooting, would qualify if compared to their closest analogs among the enumerated offenses for purposes of determining similarity in kind, a requirement under Sykes and Begay. This proposed solution would bring some reckless offenses within the scope of the residual clause, allowing for increased, though narrow, targeting of the most dangerous felons: the armed career criminals