Watermarking FPGA Bitfile for Intellectual Property Protection

Intellectual property protection (IPP) of hardware designs is the most important requirement for many Field Programmable Gate Array (FPGA) intellectual property (IP) vendors. Digital watermarking has become an innovative technology for IPP in recent years. Existing watermarking techniques have successfully embedded watermark into IP cores. However, many of these techniques share two specific weaknesses: 1) They have extra overhead, and are likely to degrade performance of design; 2) vulnerability to removing attacks. We propose a novel watermarking technique to watermark FPGA bitfile for addressing these weaknesses. Experimental results and analysis show that the proposed technique incurs zero overhead and it is robust against removing attacks

Effects of Cutoff Functions of Tersoff Potentials on Molecular Dynamics Simulations of Thermal Transport

Past molecular dynamics studies of thermal transport have predominantly used Stillinger-Weber potentials. As materials continuously shrink, their properties increasingly depend on defect and surface effects. Unfortunately, Stillinger-Weber potentials are best used for diamond-cubic-like bulk crystals. They cannot represent the energies of many metastable phases, nor can they accurately predict the energetics of defective and surface regions. To study nanostructured materials, where these regions can dominate thermal transport, the accuracy of Tersoff potentials in representing these structures is more desirable. Based upon an analysis of thermal transport in a GaN system, we demonstrate that the cutoff function of the existing Tersoff potentials may lead to problems in determining the thermal conductivity. To remedy this issue, improved cutoff schemes are proposed and evaluated

Nuclear dipole polarizability from mean-field modeling constrained by chiral effective field theory

We construct a new Skyrme interaction Sk$\chi$m$^*$ by fitting the equation of state and nucleon effective masses in asymmetric nuclear matter from chiral two- and three-body forces as well as the binding energies of finite nuclei. Employing this interaction to study the electric dipole polarizabilities of $^{48}$Ca, $^{68}$Ni, $^{120}$Sn, and $^{208}$Pb in the random-phase approximation, we find that the theoretical predictions are in good agreement with experimentally measured values without additional fine tuning of the Skyrme interaction, thus confirming the usefulness of the new Skyrme interaction in studying the properties of nuclei. We further use this interaction to study the neutron skin thicknesses of $^{48}$Ca and $^{208}$Pb, and they are found to be consistent with the experimental data.Comment: Significantly revised, 7 pages, 4 figures. Published version in PL

Probing the equation of state of neutron-rich matter with intermediate energy heavy-ion collisions

Nuclear reactions induced by stable and/or radioactive neutron-rich nuclei provide the opportunity to pin down the equation of state of neutron-rich matter, especially the density ($\rho$) dependence of its isospin-dependent part, i.e., the nuclear symmetry energy $E_{\rm sym}$. A conservative constraint, $32(\rho /\rho_{0})^{0.7} < E_{\rm sym}(\rho ) < 32(\rho /\rho _{0})^{1.1}$, around the nuclear matter saturation density $\rho_0$ has recently been obtained from the isospin diffusion data in intermediate energy heavy-ion collisions. We review this exciting result and discuss its consequences and implications on nuclear effective interactions, radii and cooling mechanisms of neutron stars.Comment: 10 pages. Invited talks at (1) International Workshop on Nuclear Multifragmentation, Nov. 28-Dec. 1, 2005, Catania, Italy and (2) XXIX Symposium on Nuclear Physics, Jan. 3-6, 2006, Cocoyoc, Morelos, Mexic

Effects of nano-void density, size, and spatial population on thermal conductivity: a case study of GaN crystal

The thermal conductivity of a crystal is sensitive to the presence of surfaces and nanoscale defects. While this opens tremendous opportunities to tailor thermal conductivity, a true "phonon engineering" of nanocrystals for a specific electronic or thermoelectric application can only be achieved when the dependence of thermal conductivity on the defect density, size, and spatial population is understood and quantified. Unfortunately, experimental studies of effects of nanoscale defects are quite challenging. While molecular dynamics simulations are effective in calculating thermal conductivity, the defect density range that can be explored with feasible computing resources is unrealistically high. As a result, previous work has not generated a fully detailed understanding of the dependence of thermal conductivity on nanoscale defects. Using GaN as an example, we have combined physically-motivated analytical model and highly-converged large scale molecular dynamics simulations to study effects of defects on thermal conductivity. An analytical expression for thermal conductivity as a function of void density, size, and population has been derived and corroborated with the model, simulations, and experiments

Constraining the Skyrme effective interactions and the neutron skin thickness of nuclei using isospin diffusion data from heavy ion collisions

Recent analysis of the isospin diffusion data from heavy-ion collisions based on an isospin- and momentum-dependent transport model with in-medium nucleon-nucleon cross sections has led to the extraction of a value of $L=88\pm 25$ MeV for the slope of the nuclear symmetry energy at saturation density. This imposes stringent constraints on both the parameters in the Skyrme effective interactions and the neutron skin thickness of heavy nuclei. Among the 21 sets of Skyrme interactions commonly used in nuclear structure studies, the 4 sets SIV, SV, G$_\sigma$, and R$_\sigma$ are found to give $L$ values that are consistent with the extracted one. Further study on the correlations between the thickness of the neutron skin in finite nuclei and the nuclear matter symmetry energy in the Skyrme Hartree-Fock approach leads to predicted thickness of the neutron skin of $0.22\pm 0.04$ fm for $^{208}$Pb, $0.29\pm 0.04$ fm for $^{132}$Sn, and $0.22\pm 0.04$ fm for $^{124}$Sn.Comment: 10 pages, 4 figures, 1 Table, Talk given at 1) International Conference on Nuclear Structure Physics, Shanghai, 12-17 June, 2006; 2) 11th China National Nuclear Structure Physics Conference, Changchun, Jilin, 13-18 July, 200

Entry, reputation and intellectual property rights enforcement

We examine how reputation concerns induce a multinational to partly withhold its entry into a developing country under weak intellectual property rights (IPR) enforcement. Equilibrium IPR violations are shown to arise only in the presence of such concerns. Holding constant a multinational's incentive to innovate, better IPR enforcement encourages entry but reduces social welfare. The multinational's incentive to innovate may be inversely U-shaped in the strength of IPR enforcement. If timed properly, however, stronger IPR enforcement can foster innovation without compromising social welfare. Testable implications concerning observable IPR violations are derived.postprin

Self-assembled functional molecular materials for optoelectronic applications

There has been a growing interest to develop functional organic and organometallic materials in nano-scale by self assembly reactions as these materials could have unique electronic properties and applications. We have found that functionalized organometallic nano-wires which the formations are directed by weak Pt⋯Pt interactions along the dimension of the aggregates can be readily obtained by self-assembly reactions. These platinum(II) nano-wires exhibit interesting photophysical properties, vapochromic behavior, and could be used in the fabrication of organic (light-emitting) field-effect transistors.1,2 We have also found that thermally stable coordination polymers (with decomposition temperature up to 490°C), employing Zn 2+ as template metal ion and Schiff base or terpyridine as repeating chelating units, could be easily synthesized by self-assembly reactions. 3,4 These zinc (II) coordination polymers exhibit intense blue to green photoluminescence, and their thin-film samples have PL quantum yields up to 0.55. Polymer light-emitting devices (PLEDs) employing these coordination polymers as emitters give blue and green EL with turn-on voltage as low as 5 V and maximum efficiency up to 2.0 cd A-1. © 2009 Materials Research Society.published_or_final_versionThe 2008 Fall Meeting of the Materials Research Society, Boston, MA., 1-5 December, 2008. In Materials Research Society Symposium Proceedings, 2008, v. 1149, p. 1-1

Modelling Heat Transfer of Carbon Nanotubes

Modelling heat transfer of carbon nanotubes is important for the thermal management of nanotube-based composites and nanoelectronic device. By using a finite element method for three-dimensional anisotropic heat transfer, we have simulated the heat conduction and temperature variations of a single nanotube, a nanotube array and a part of nanotube-based composite surface with heat generation. The thermal conductivity used is obtained from the upscaled value from the molecular simulations or experiments. Simulations show that nanotube arrays have unique cooling characteristics due to its anisotropic thermal conductivity.Comment: 10 pages, 4 figure