A Primal DPG Method Without a First-Order Reformulation

We show that it is possible to apply the DPG methodology without reformulating a second-order boundary value problem into a first-order system, by considering the simple example of the Poisson equation. The result is a new weak formulation and a new DPG method for the Poisson equation, which has no numerical trace variable, but has a numerical flux approximation on the element interfaces, in addition to the primal interior variable

Gas permeation through a polymer network

We study the diffusion of gas molecules through a two-dimensional network of polymers with the help of Monte Carlo simulations. The polymers are modeled as non-interacting random walks on the bonds of a two-dimensional square lattice, while the gas particles occupy the lattice cells. When a particle attempts to jump to a nearest-neighbor empty cell, it has to overcome an energy barrier which is determined by the number of polymer segments on the bond separating the two cells. We investigate the gas current $J$ as a function of the mean segment density $\rho$, the polymer length $\ell$ and the probability $q^{m}$ for hopping across $m$ segments. Whereas $J$ decreases monotonically with $\rho$ for fixed $\ell$, its behavior for fixed $\rho$ and increasing $\ell$ depends strongly on $q$. For small, non-zero $q$, $J$ appears to increase slowly with $\ell$. In contrast, for $q=0$, it is dominated by the underlying percolation problem and can be non-monotonic. We provide heuristic arguments to put these interesting phenomena into context.Comment: Dedicated to Lothar Schaefer on the occasion of his 60th birthday. 11 pages, 3 figure

Peephole optimization of asynchronous macromodule networks

Journal ArticleAbstract- Most high-level synthesis tools for asynchronous circuits take descriptions in concurrent hardware description languages and generate networks of macromodules or handshake components. In this paper, we propose a peephole optimizer for these networks. Our peephole optimizer first deduces an equivalent blackbox behavior for the network using Dill's tracetheoretic parallel composition operator. It then applies a new procedure called burst-mode reduction to obtain burst-mode machines from the deduced behavior. In a significant number of examples, our optimizer achieves gate-count improvements by a factor of five, and speed (cycle-time) improvements by a factor of two. Burst-mode reduction can be applied to any macromodule network that is delay insensitive as well as deterministic. A significant number of asynchronous circuits, especially those generated by asynchronous high-level synthesis tools, fall into this class, thus making our procedure widely applicable

A correctness criterion for asynchronous circuit validation and optimization

technical reportIn order to reason about the correctness of asynchronous circuit implementations and specifications, Dill has developed a variant of trace theory [1]. Trace theory describes the behavior of an asynchronous circuit by representing its possible executions as strings called "traces" A useful relation defined in this theory is called conformance which holds when one trace specification can be safely substituted for another. We propose a new relation in the context of Dill's trace theory called strong conformance. We show that this relation is capable of detecting certain errors in asynchronous circuits that cannot be detected through conformance, Strong conformance also helps to justify circuit optimization rules where a component is replaced by another component having extra capabilities (e.g., it can accept more inputs). The structural operators of Dill's trace theory compose rename and hide - are shown to be monotonic with respect to strong conformance. Experiments are presented using a modified version of Dill's trace theory verifier which implements the check for strong conformance

Performance analysis and optimization of asynchronous circuits

Journal ArticleAsynchronous/Self-timed circuits are beginning to attract renewed attention as promising means of dealing with the complexity of modern VZSI designs. Very few analysis techniques or tools are available for estimating their performance. In this paper we adapt the theory of Generalized Timed Petri-nets (GTPN) for analyzing and comparing asynchronous circuits ranging from purely control-oriented circuits to those with data dependent control. Experiments with the GTPN analyzer are found to track the observed performance of actual asynchronous circuits, thereby offering empirical evidence toward the soundness of the modeling approach

Frustration and glassiness in spin models with cavity-mediated interactions

We show that the effective spin-spin interaction between three-level atoms confined in a multimode optical cavity is long-ranged and sign-changing, like the RKKY interaction; therefore, ensembles of such atoms subject to frozen-in positional randomness can realize spin systems having disordered and frustrated interactions. We argue that, whenever the atoms couple to sufficiently many cavity modes, the cavity-mediated interactions give rise to a spin glass. In addition, we show that the quantum dynamics of cavity-confined spin systems is that of a Bose-Hubbard model with strongly disordered hopping but no on-site disorder; this model exhibits a random-singlet glass phase, absent in conventional optical-lattice realizations. We briefly discuss experimental signatures of the realizable phases.Comment: 5 pages, 2 figure

Peephole optimization of asynchronous macromodule networks

Journal ArticleMost high level synthesis tools for asynchronous circuits take descriptions in concurrent hardware description languages and generate networks of macromodules or handshake components. In this paper we describe a peephole optimizer for such macromodule networks that often effects area and/or time improvements. Our optimizer first deduces an equivalent black-box behavior for the given network of macrmodules using Dill's trace-theoretic parallel composition operator. It then applies a new procedure culled Burst-mode reduction to obtain burst-mode machines, which can be synthesized into gate networks using available tools. Since burst-mode reduction can be applied to any macromodule network that is delay-insensitive as well as deterministic, our optimizer covers a significant number of asynchronous circuits especially those generated by asynchronous high level synthesis tools

Effect of Substrate Temperature on Spray Deposited Zinc Sulphide Thin Films

Thin films of Zinc sulphide (ZnS) on glass substrate were prepared by chemical spray pyrolysis technique using precursor solutions of zinc chloride and n–n dimethyl thiourea at substrate temperatures of 598 K and 623 K. X ray diffraction analysis exposed the polycrystalline nature with growing crystallinity with respect to substrate temperature. The preferential orientation growth of ZnS compound increased with relatively higher substrate temperature having hexagonal structure along (019) plane. At 623 K, The size of the Zinc sulphide crystallite with nano dimension was determined using the Full Width Half Maximum value of the Bragg peak. The surface morphology had been analyzed using scanning electron microscope. The compositional analysis had been observed by Energy Dispersive Analysis by X-ray spectrum. FTIR study had been carried out for the bond evaluation

Data storage lock algorithm with cryptographic techniques

The cloud computing had its impact far and wide, and Enterprise solutions are getting migrated to different types of clouds. The services are delivered from the data centers which are located all over the world. As the data is roaming with less control in any data centers, data security issues in cloud are very challenging. Therefore we need multi-level authentication, data integrity, privacy and above all encryption to safeguard our data which is stored on to the cloud. The data and applications cannot be relocated to a virtual server without much degree of security concern as there can be much confidential data or mission-critical applications. In this paper, we propose Data Storage Lock Algorithm (DSLA) to store confidential data thereby provides secure data storage in cloud computing based on cryptographic standards