Logic Sum Research Articles

All‐optical 2's complement number conversion scheme without binary addition

In conventional method, 2's complement number conversion can be easily done by adding a binary bit ‘1’ with 1's complement of any binary number. In this study, the authors have proposed a new method where no addition is required. Also, an all-optical n-bit conversion circuit has been proposed here. The authors have used logic sum and binary XOR operation to build their design. Optical logic sum circuit can be easily designed with an N × 1 beam combiner. Also, binary XOR operation has been designed with a Mach–Zehnder interferometer (MZI) having quantum dot semiconductor optical amplifier placed in each arm. The novelty of this circuit is that they required only one MZI to design it. To get the proper result and performance of the circuit, numerical simulations have been done.

Simple novel all-optical half-adder

On the basis of Sagnac interferometric structure, a simple novel ultrafast scheme of all-optical half-adder is proposed. The structure comprises two of the same balanced terahertz optical asymmetric demultiplexers (TOADs). One TOAD is utilized to achieve an all-optical XOR gate, which is logic SUM. The other is utilized to obtain an all-optical AND gate, which is logic CARRY. Logical SUM and CARRY are simultaneously realized at 80 Gbit/s. Through numerical analysis, the operating characteristics of the scheme are illustrated at 80 Gbit/s. Furthermore, the carrier recovery time of the semiconductor optical amplifier is no longer a crucial parameter to restrict the operation speed of this scheme.

Absolute radioactivity measurements by the use of a 4 πβ–4 πγ detector configuration

The radioactivity of 60Co and 134Cs sources were measured using a 4 πβ–4 πγ detector configuration with a well-type NaI(Tl) crystal and a sandwich type 4 πβ detector composed of two sheets of NE102A plastic scintillator coupled to a slender photomultiplier tube. The β-detector was inserted into the well of the γ-detector. Since counting efficiencies in both the β- and γ-channels can be kept high, excellent counting statistics were attainable even when weak sources were measured. This configuration can also be used for radioactivity measurements based upon the direct integral counting of 4 πβ+4 πγ logic sum signals, and two independent results can be obtained for every measurement. This technique is especially useful for the standardization of complex decaying nuclides.

Synthesis of spp three-level logic networks using affine spaces

Recently defined, three-level logic sum of pseudo-products (SPP) forms are EXOR-AND-OR networks representing Boolean functions, and are much shorter than standard two-level sum of products (SOP) expressions (Luccio and Pagli, 1999). The main disadvantages of SPP networks are their cumbersome theory in the original formulation and their high minimization time. In addition, the current technology cannot efficiently implement the unbounded fanin EXOR gates of SPP expressions. In this paper, we rephrase SPP theory in an algebraic context to obtain an easier description of the networks. We define a new model of SPP networks (k-SPP) with bounded fanin EXOR gates, whose minimization time is strongly reduced and whose minimal forms are still very compact. In the Boolean space {0,1}/sup n/, a k-SPP form contains EXOR gates with at most k literals, where 1 /spl les/ k /spl les/ n. The limit case k = n corresponds to SPP networks and k = 1 to SOPs. Finally, we perform an extensive set of experiments on classical benchmarks. In order to validate our approach, the results are compared with those obtained for the major two- and three-level forms using standard metrics.

All-optical half adder using semiconductor optical amplifier based devices

An all-optical half adder using semiconductor optical amplifier based devices is suggested and demonstrated at 10 Gbit/s. Boolean A B and AB out of two semiconductor optical amplifiers have been obtained and combined to achieve an all-optical XOR gate, which is logic SUM. Also, an all-optical XPM wavelength converter has been utilized to obtain an all-optical AND gate, which is logic CARRY. Logic SUM and CARRY are simultaneously realized. No additional input beam such as clock signal or continuous wave light other than input signals A and B is used in this new design, which is required in many other all-optical logic gates.

Sequential Logic and its Application to the Synthesis of Finite Automata

Three logic functions are introduced, two of which are functions in two-variables, named sequential logic product and sequential logic sum, while the third, depending on only one variable, is termed sequential logic negation. An algebraic theory is developed for logic processes where time plays an essential part; the connection is pointed out between sequential logic and the algebraic theory of multiple-state finite automata. This connection finally leads to new methods of analysis, as well as of synthesis, for finite automata operating according to given sequential equations; these methods offer certain advantages over standard procedures. Results obtained are likely to be useful in the theory of digital computers.