This paper proposes efficient fixed-point and floating-point implementations for radix-10 decimal logarithm on Xilinx FPGA devices. The technique is based on the digit-recurrence method, which supports the three decim...
详细信息
This paper proposes efficient fixed-point and floating-point implementations for radix-10 decimal logarithm on Xilinx FPGA devices. The technique is based on the digit-recurrence method, which supports the three decimal floating-point (DFP) types specified in the IEEE 754-2008 standard. The novelty of this proposal is that it avoids the implementation of redundant carry-save logic by direct selection (i.e. via scaling). The designs involve novel techniques based on efficient use of dedicated resources in the programmable devices. Implementations were made on Xilinx 7-series devices. For fixed-point logarithm, they are capable of operating up to 145 MHz for p= 7,124 MHz for p = 16 and 108 MHz for p= 34, and for DFP logarithm the operation frequency obtained was 123 MHz for p= 7,104 MHz for p=16 and 93 MHz for p=34. In contrast to other related works, the proposed architecture achieves better computation times and less occupation in area in terms of LUTs. (C) 2018 Elsevier B.V. All rights reserved.
Optoelectronic synapses have been attracting significant attention due to their important role in visual information processing. In this work, we fabricate an all-organic optoelectronic synaptic device with a double h...
详细信息
Optoelectronic synapses have been attracting significant attention due to their important role in visual information processing. In this work, we fabricate an all-organic optoelectronic synaptic device with a double heterojunction structure of PEDOT:PSS/poly(vinylidene fluoridetrifluoroethylene) (P(VDF-TrFE))/copper (II) phthalocyanine (CuPc) by a simple preparation process. The introduction of a dielectric P(VDF-TrFE) layer between PEDOT:PSS and CuPc layers benefits the trapping of charge carriers and slows down the electron-hole recombination rate. This two-terminal optoelectronic device is successfully applied to simulate synaptic functions of biological synapses by using optical pulses of 660 nm, including paired-pulse facilitation, spike-duration dependent plasticity, spike-rate dependent plasticity, spike-number dependent plasticity, and learning-experience behavior. Furthermore, the key characteristics of a nociceptor and the optical logic function of the "AND" and "OR" operations are also emulated. This work illustrates the potential of such device for constructing neuromorphic computing systems at the physical level.
Consider orbits O(z,kappa) of the fractal iterator f(kappa)(z) := z(2) + kappa, kappa is an element of C, that start at initial points z is an element of K-kappa((m)) subset of C, where C is the set of all rational co...
详细信息
Consider orbits O(z,kappa) of the fractal iterator f(kappa)(z) := z(2) + kappa, kappa is an element of C, that start at initial points z is an element of K-kappa((m)) subset of C, where C is the set of all rational complex numbers (their real and imaginary parts are rational) and K-kappa(m) consists of all such z whose complexity does not exceed some complexity parameter value m (the complexity of z is defined as the number of bits that suffice to describe the real and imaginary parts of z in lowest form). The set K-kappa((m)) is a bounded-complexity approximation of the filled Julia set K-kappa. We present a new perspective on fractals based on an analogy with Chaitin's algorithmic information theory, where a rational complex number z is the analog of a program p, an iterator f(kappa) is analogous to a universal Turing machine U which executes program p, and an unbounded orbit O(z,kappa) is analogous to an execution of a program p on U that halts. We define a real number Upsilon(kappa) which resembles Chaitin's Omega number, where, instead of being based on all programs p whose execution on U halts, it is based on all rational complex numbers z whose orbits under f(kappa) are unbounded. Hence, similar to Chaitin's Omega number, Upsilon(kappa) acts as a theoretical limit or a "fractal oracle number" that provides an arbitrarily accurate complexity-based approximation of the filled Julia set K-kappa. We present a procedure that, when given m and kappa, it uses Upsilon(kappa) to generate K-kappa(m). Several numerical examples of sets that estimate K-kappa(m) are presented.
In this paper we examine string block edit distance, in which two strings A and B are compared by extracting collections of substrings and placing them into correspondence. This model accounts for certain phenomena en...
详细信息
In this paper we examine string block edit distance, in which two strings A and B are compared by extracting collections of substrings and placing them into correspondence. This model accounts for certain phenomena encountered in important real-world applications, including pen computing and molecular biology. The basic problem admits a family of variations depending on whether the strings must be matched in their entireties, and whether overlap is permitted. We show that several variants are NP-complete, and give polynomial-time algorithms for solving the remainder.
The requirement of high memory bandwidth for next-generation computing systems moved the attention to the development of devices that can combine storage and logic capabilities. Domain wall-based spintronic devices in...
详细信息
The requirement of high memory bandwidth for next-generation computing systems moved the attention to the development of devices that can combine storage and logic capabilities. Domain wall-based spintronic devices intrinsically combine both these requirements making them suitable both for non-volatile storage and computation. Co\Pt and Co\Ni were the technology drivers of perpendicular Nano Magnetic Logic devices (pNML), but for power constraints and depinning fields, novel CoFeB\MgO layers appear more promising. In this paper, we investigate the Ta-2\CoFeB1\MgO2\Ta-3 stack at the simulation and experimental level, to show its potential for the next generation of magnetic logic devices. The micromagnetic simulations are used to support the experiments. We focus, first, at the experimental level measuring the switching field distribution of patterned magnetic islands, M-s via VSM and the domain wall speed on magnetic nanowires. Then, at the simulation level, we focus on the magnetostatic analysis of magnetic islands quantifying the stray field that can be achieved with different layout topologies. Our results show that the achieved coupling is strong enough to realize logic computation with magnetic islands, moving a step forward in the direction of low power perpendicularly magnetized logic devices.
The International Obfuscated C Code Contest was a programming contest for the most creatively obfuscated yet succinct C code. By contrast, an interest herein is in programs which are, in a sense, easily seen to be cor...
详细信息
The International Obfuscated C Code Contest was a programming contest for the most creatively obfuscated yet succinct C code. By contrast, an interest herein is in programs which are, in a sense, easily seen to be correct, but which cannot be proved correct in pre-assigned, computably axiomatized, powerful, true theories T. A point made by our first theorem, then, is that, then, unverifiable programs need not be obfuscated! The first theorem and its proof is followed by a motivated, concrete example based on a remark of Hilary Putnam. The first theorem has some non-constructivity in its statement and proof, and the second theorem implies some of the non-constructivity is inherent. That result, then, brings up the question of whether there is an acceptable programming system (numbering) for which some non-constructivity of the first theorem disappears. The third theorem shows this is the case, but for a subtle reason explained in the text. This latter theorem has a number of corollaries, regarding its acceptable programming system, and providing some surprises and subtleties about proving its program properties (including universality, and the presence of the composition control structure). The next two theorems provide acceptable systems with contrasting surprises regarding proving universality in them. Finally the next and last theorem (the most difficult to prove in the paper) provides an acceptable system with some positive and negative surprises regarding verification of its true program properties: the existence of the control structure composition is provable for it, but anything about true I/O-program equivalence for syntactically unequal programs is not provable.
Strain localization is one of the most challenging phenomena in solid mechanics. It occurs when strains concentrate in very narrow bands within a solid, typically referred to as localization bands. This behaviour is r...
详细信息
Strain localization is one of the most challenging phenomena in solid mechanics. It occurs when strains concentrate in very narrow bands within a solid, typically referred to as localization bands. This behaviour is related to different types of failure mechanisms: fracture, shear bands and slip lines. Being a dissipative process, the modelling of strain localization could seem to preclude the use of variational methods. However, a sound framework to deal with this issue has been developed in the last few decades. In this contribution, we review the modelling of strain localization by means of variational methods systematically, presenting the main underlying theoretical concepts. The issue of irreversibility is approached by means of the theory of generalized standard materials, which constitutes the basis for the variational approach. Then, typical problems occurring in the modelling of strain localization are analyzed: the tendency to localize in a band of zero thickness with no dissipation, the determination of the geometry of the localization band, and the orientation bias of such band with respect to mesh alignment in finite element discretizations. We discuss solutions for these problems, focusing on the approach that tackles the description of the localization band using phase fields.
We study nucleon-nucleon scattering on the lattice at next-to-leading order in chiral effective field theory. We determine phase shifts and mixing angles from the properties of two-nucleon standing waves induced by a ...
详细信息
We study nucleon-nucleon scattering on the lattice at next-to-leading order in chiral effective field theory. We determine phase shifts and mixing angles from the properties of two-nucleon standing waves induced by a hard spherical wall in the center-of-mass frame. At fixed lattice spacing we test model independence of the low-energy effective theory by computing next-to-leading-order corrections for two different leading-order lattice actions. The first leading-order action includes instantaneous one-pion exchange and same-site contact interactions. The second leading-order action includes instantaneous one-pion exchange and Gaussian-smeared interactions. We find that in each case the results at next-to-leading order are accurate up to corrections expected at higher order.
This paper analyzed the effects of setback micro-springs on a MEMS safety and arming (S&A) device. To make up for defects related to current methods of obtaining the elastic coefficients of micro-springs, a comput...
详细信息
This paper analyzed the effects of setback micro-springs on a MEMS safety and arming (S&A) device. To make up for defects related to current methods of obtaining the elastic coefficients of micro-springs, a computational formula for the elastic coefficients of S-shaped micro-springs was developed in accordance with Castigliano's second theorem and Hooke's law and verified for three types of setback micro-springs with different structures through finite element simulations and a self-designed testing system for the elastic coefficients of micro-springs. The testing values and the simulation values were in good agreement with the theoretical values. The results indicate that the precise measurement and calculation of the elastic coefficients of micro-springs in the transverse, longitudinal and vertical directions can be realized with the method presented in this paper. For the S-shaped setback micro-spring, the elastic coefficient in the transverse direction is the smallest and the most prone to fracture and plastic deformation. In the design of MEMS S&A devices, priority should be given to applying the deformation of the micro-spring in the longitudinal and vertical directions.
A new bisimulation based semantics, called performance equivalence, is proposed for a process algebra equipped with the TCSP parallel operator. This semantics relies on the basic assumption that actions are time-consu...
详细信息
A new bisimulation based semantics, called performance equivalence, is proposed for a process algebra equipped with the TCSP parallel operator. This semantics relies on the basic assumption that actions are time-consuming, where their duration is statically fixed. Performance equivalence equates systems whenever they perform the same actions in the same amount of time, thus introducing a simple form of performance evaluation in process algebras. A comparison with other equivalences is provided;in particular, we show that performance equivalence is strictly finer than step bisimulation equivalence and strictly coarser than partial ordering bisimulation equivalence.
暂无评论