On the postulation of s^d fat points in P^d

In connection with his counter-example to the fourteenth problem of Hilbert, Nagata formulated a conjecture concerning the postulation of r fat points of the same multiplicity in the projective plane and proved it when r is a square. Iarrobino formulated a similar conjecture in any projective space P^d. We prove Iarrobino's conjecture when r is a d-th power. As a corollary, we obtain new counter-examples modeled on those by Nagata.Comment: 14 page

Simulation of a flowing snow avalanche using molecular dynamics

This paper presents an approach for the modeling and simulation of a flowing snow avalanche, which is formed of dry and liquefied snow that slides down a slope, using molecular dynamics and the discrete element method. A particle system is utilized as a base method for the simulation and marching cubes with real-time shaders are employed for rendering. A uniform grid-based neighbor search algorithm is used for collision detection for interparticle and particleterrain interactions. A mass-spring model of the collision resolution is employed to mimic the compressibility of the snow and particle attraction forces are put into use between the particles and terrain surface. In order to achieve greater performance, general purpose GPU language and multithreaded programming are utilized for collision detection and resolution. The results are displayed with different combinations of rendering methods for the realistic representation of the flowing avalanche. © TÜB̄TAK

Improved quantum efficiency in InGaN light emitting diodes with multi-double-heterostructure active regions

InGaN light emitting diodes(LEDs) with multiple thin double-heterostrucutre (DH) active regions separated by thin and low energy barriers were investigated to shed light on processes affecting the quantum efficiency and means to improve it. With increasing number of 3 nm-thick DH active layers up to four, the electroluminescence efficiency scaled nearly linearly with the active region thickness owing to reduced carrier overflow with increasing total thickness, showing almost no discernible efficiency degradation at high injection levels up to the measured current density of 500 A/cm2. Comparison of the resonant excitation dependent photoluminescence measurements at 10 K and room temperature also confirmed that further increasing the number of DH layers beyond six results in degradation of the material quality, and therefore, increasing nonradiative recombination. Using multiple DH active regions is shown to be a superior approach for quantum efficiency enhancement compared with simply increasing the single DH thickness or the number of quantum wells in LED structures due to better material quality and larger number of states available

Worthy Transfers? A Dynamic Analysis of Turkey's Accession to the European Union

We build a two-country dynamic general equilibrium model to study whether European citizens would benet from the eventual accession of Turkey to the European Union. The results of the simulations show that Turkey's accession to the European Union is welfare enhancing for Europeans, provided that Turkish total factor productivity (TFP) increases suciently after enlargement. In the model with no capital mobility, the Europeans are better o if the Turkish TFP increase bridges more than 31% of the initial TFP gap between Turkey and the European Union. That gure becomes 45% when capital mobility is introduced.European Union, Turkey, Enlargement, Dynamic General Equilibrium, Open Economy Macroeconomics

The effect of stair case electron injector design on electron overflow in InGaN light emitting diodes

Effect of two-layer (In0.04Ga0.96N and In0.08Ga0.92N) staircase electron injector (SEI) on quantum efficiency of light-emitting-diodes (LEDs) in the context of active regions composed of single and quad 3 nm double heterostructures (DHs) is reported. The experiments were augmented with the first order model calculations of electron overflow percentile. Increasing the two-layer SEI thickness from 4 + 4 nm up to 20 + 20 nm substantially reduced, if not totally eliminated, the electron overflow in single DH LEDs at low injections without degrading the material quality evidenced by the high optical efficiency observed at 15K and room temperature. The improvement in quad 3 nm DH LEDs with increasing SEI thickness is not so pronounced as the influence of SEI is less for thicker active regions, which in and of themselves necessarily thermalize the carriers. (C) 2013 AIP Publishing LLC

Worthy Transfers ? A Dynamic Analysis of Turkey’s Accession to the European Union

In this paper, we build a two-country dynamic general equilibrium model to study whether European citizens would benefit from the eventual accession of Turkey to the European Union. The results of the simulations show that Turkey's accession to the European Union is welfare enhancing for Europeans, provided that Turkish total factor productivity (TFP) increases sufficiently after enlargement. In the model with no capital mobility, the Europeans are better off it the Turkish TFP increase bridges more than 31% of the initial TFP gap between Turkey and the European Union. That figure becomes 45% when capital mobility is introduced.European Union, Turkey, Enlargement, Dynamic General Equilibrium, Open Economy Macroeconomics