12,814 research outputs found

    Effects of depolarizing quantum channels on BB84 and SARG04 quantum cryptography protocols

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    We report experimental studies on the effect of the depolarizing quantum channel on weak-pulse BB84 and SARG04 quantum cryptography. The experimental results show that, in real world conditions in which channel depolarization cannot be ignored, BB84 should perform better than SARG04.Comment: 4 pages, 4 figure

    Impact of Direct Income Payments on Productive Efficiency of Korean Rice Farms

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    This paper examines the impact of direct income payments on productive efficiency of Korean rice farms, using farm-level cross sectional data in 2006. For representation of efficiency and its determinants, this paper uses a model that estimates the deviations of farms from a translog distance function and the determinants of these deviations. This paper especially estimates a stochastic frontier production function to explain deviations from best-practice productivity with a two-part error term including statistical noise from measurement error and technical inefficiency arising from farms not reaching the production frontier boundary. The empirical evidence finds that farms that get a higher share of direct payments in farm revenue are less efficient than others. This inefficiency is reduced by increases in farm size. Another result indicates that farms received greater direct payments on aggregate are more efficient than other farms since fixed payment, one part of rice direct payment, is tied to the amount of a farm's cropland that has been enrolled in programs, as well as yield histories.direct income payments, productive efficiency, stochastic frontier production function, Korea, Agribusiness, Agricultural and Food Policy, Crop Production/Industries,

    The structure of gauge-invariant ideals of labelled graph CC^*-algebras

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    In this paper, we consider the gauge-invariant ideal structure of a CC^*-algebra C(E,L,B)C^*(E,\mathcal{L},\mathcal{B}) associated to a set-finite, receiver set-finite and weakly left-resolving labelled space (E,L,B)(E,\mathcal{L},\mathcal{B}), where L\mathcal{L} is a labelling map assigning an alphabet to each edge of the directed graph EE with no sinks. Under the assumption that an accommodating set B\mathcal{B} is closed under taking relative complement, it is obtained that there is a one to one correspondence between the set of all hereditary saturated subsets of B\mathcal{B} and the gauge-invariant ideals of C(E,L,B)C^*(E,\mathcal{L},\mathcal{B}). For this, we introduce a quotient labelled space (E,L,[B]R)(E,\mathcal{L},[\mathcal{B}]_R) arising from an equivalence relation R\sim_R on B\mathcal{B} and show the existence of the CC^*-algebra C(E,L,[B]R)C^*(E,\mathcal{L},[\mathcal{B}]_R) generated by a universal representation of (E,L,[B]R)(E,\mathcal{L},[\mathcal{B}]_R). Also the gauge-invariant uniqueness theorem for C(E,L,[B]R)C^*(E,\mathcal{L},[\mathcal{B}]_R) is obtained. For simple labelled graph CC^*-algebras C(E,L,Eˉ)C^*(E,\mathcal{L},\bar{\mathcal{E}}), where Eˉ\bar{\mathcal{E}} is the smallest accommodating set containing all the generalized vertices, it is observed that if for each vertex vv of EE, a generalized vertex [v]l[v]_l is finite for some ll, then C(E,L,Eˉ)C^*(E,\mathcal{L},\bar{\mathcal{E}}) is simple if and only if (E,L,Eˉ)(E,\mathcal{L},\bar{\mathcal{E}}) is strongly cofinal and disagreeable. This is done by examining the merged labelled graph (F,LF)(F,\mathcal{L}_F) of (E,L)(E,\mathcal{L}) and the common properties that C(E,L,Eˉ)C^*(E,\mathcal{L},\bar{\mathcal{E}}) and C(F,L,Fˉ)C^*(F,\mathcal{L},\bar{\mathcal{F}}) share

    Performance of SSE and AVX Instruction Sets

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    SSE (streaming SIMD extensions) and AVX (advanced vector extensions) are SIMD (single instruction multiple data streams) instruction sets supported by recent CPUs manufactured in Intel and AMD. This SIMD programming allows parallel processing by multiple cores in a single CPU. Basic arithmetic and data transfer operations such as sum, multiplication and square root can be processed simultaneously. Although popular compilers such as GNU compilers and Intel compilers provide automatic SIMD optimization options, one can obtain better performance by a manual SIMD programming with proper optimization: data packing, data reuse and asynchronous data transfer. In particular, linear algebraic operations of vectors and matrices can be easily optimized by the SIMD programming. Typical calculations in lattice gauge theory are composed of linear algebraic operations of gauge link matrices and fermion vectors, and so can adopt the manual SIMD programming to improve the performance.Comment: 7 pages, 5 figures, 4 tables, Contribution to proceedings of the 30th International Symposium on Lattice Field Theory (Lattice 2012), June 24-29, 201

    Thermomechanics of Solid Oxide Fuel Cell Electrode Microstructures Using Finite Element Methods: Progressive Interface Degradation under Thermal Cycling

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    The electrochemical performance of solid oxide fuel cell (SOFC) is significantly influenced by three-phase boundary (TPB) zones in the microstructure. TPB zones are locations where all three phases comprising the microstructure such as the two solid phases and the pore phase are present. Electrochemical reactions such as oxygen reduction occur near TPBs, and TPB density is believed to affect the polarization resistance of the cathode. In this regard, the effect of interface degradation under repeated thermal loading on the mechanical integrity and electrochemical performance of solid oxide fuel cell (SOFC) electrodes is studied through finite element simulations. Image-based 3-D models are used in this study, with additional interface zones at the boundaries between dissimilar solid phases. These interface zones are composed of 3-D cohesive elements of small thickness. The effect of interface degradation on mechanical integrity is studied by subjecting 50:50 LSM:YSZ wt.% cathode models to increasing levels of thermal load from room temperature (20°C) up to operating temperature (820°C). Energy quantities (e.g., strain energy and damage dissipation) for cathode models with and without cohesive interface zones are obtained through finite element analysis (FEA). These quantities are compared using energy balance concepts from fracture mechanics to gain insight into the effects of interface degradation on mechanical integrity
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