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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Information storage at the molecular level - The design of a molecular shift register memory

The control of electron transfer rates is discussed and a molecular shift register memory at the molecular level is described. The memory elements are made up of molecules which can exist in either an oxidized or reduced state and the bits can be shifted between the cells with photoinduced electron transfer reactions. The device integrates designed molecules onto a VLSI substrate. A control structure to modify the flow of information along a shift register is indicated schematically.

Beratan, David N.↗
NASA NTRS1989

Electronic shift register memory based on molecular electron-transfer reactions

The design of a shift register memory at the molecular level is described in detail. The memory elements are based on a chain of electron-transfer molecules incorporated on a very large scale integrated (VLSI) substrate, and the information is shifted by photoinduced electron-transfer reactions. The design requirements for such a system are discussed, and several realistic strategies for synthesizing these systems are presented. The immediate advantage of such a hybrid molecular/VLSI device would arise from the possible information storage density. The prospect of considerable savings of energy per bit processed also exists. This molecular shift register memory element design solves the conceptual problems associated with integrating molecular size components with larger (micron) size features on a chip.

Hopfield, J. J.↗
NASA NTRS1988

A molecular shift register based on electron transfer

An electronic shift-register memory at the molecular level is described. The memory elements are based on a chain of electron-transfer molecules and the information is shifted by photoinduced electron-transfer reactions. This device integrates designed electronic molecules onto a very large scale integrated (silicon microelectronic) substrate, providing an example of a 'molecular electronic device' that could actually be made. The design requirements for such a device and possible synthetic strategies are discussed. Devices along these lines should have lower energy usage and enhanced storage density.

Hopfield, J. J.↗
DOE OSTI2015

Shift Register Clock Rate Effects on Coincidence Collection 50MHz versus 4MHz Comparison Tests

The following report identifies and quantifies the timing differences between the older slower Shift Register Coincidence/Multiplicity modules and today’s modern higher speed devices. Modern high speed Shift Register Coincidence/Multiplicity instruments employ high speed internal clocks that run at frequencies more than ten times the older units, typically 50MHz. These higher speed clocks allow for a finer time resolution when recording input pulses.

Nuclear Disarmament, Safeguards, & Physical Protec↗
DOE OSTI2019

Methods for diagnosing and quantifying double pulsing in a Uranium Neutron Collar system using shift register logic

Double pulsing in neutron coincidence counters is the result of a pulse processing chain-3He proportional counter timing incompatibility known to nondestructive assay system designers. It is not currently widely acknowledged, or accounted for, in the user community. However, it is gaining attention as list mode data acquisition and analysis becomes more commonly used for system diagnostics, revealing features that have been overlooked by historic timing gate selection using traditional shift register data acquisition methods. Double pulsing increases the apparent number of measured neutron events from a source. Therefore, it may contribute to a falsely increased count rate if present at the operational high voltage used when assaying samples, even with set predelays. The authors have previously studied the effects of double pulsing, using list mode data acquisition and analysis on neutron pulse trains in three common neutron coincidence counting systems used in routine measurements for international safeguards: a Canberra Industries JCC-71 Neutron Coincidence Collar, a variant on the Canberra Industries JCC-51 Active Well Neutron Coincidence Counter (the Large Volume Active Well Neutron Coincidence Counter), and an AnTech Inc. N2071 Neutron Coincidence Collar. We find that this non-ideal behavior was isolated to the Amptek A111 Charge Sensitive Preamplifier & Discriminator chip used in both the Canberra Industries and Antech systems. The double pulsing fraction was calculated in post-analysis for various high voltage settings in these A111-based systems, assuming no predelay settings. In this work, the authors expand upon this identification and analysis to make it more translatable between list mode data acquisition and analysis and shift register-based analysis. By investigating the double pulsing fractions in a JCC-71 Uranium Neutron Collar as a function of predelay settings, as well as describing and performing alternative tests and analyses to diagnose and quantify the double pulsing using shift register logic, this work hopes to complete the picture of double pulsing identification and analysis.

Safeguards↗
NASA NTRS1974

Families of shift-register sequences with impulsive correlation properties

A study of the linear feedback shift registers corresponding to a subset of nonprimitive irreducible polynomials over GF(2) has uncovered a class of sequences with interesting structures and cyclic correlation properties. These families of sequences are made up of interleaved identical sequences which are from primitive irreducible polynomials. Furthermore, they have correlation functions which are two or three valued, being constant at zero or a small value throughout most of their length with the exception of a small number of impulses. Each interval between such impulses on the correlograms uniquely corresponds to (and thus uniquely identifies) the member sequence or sequences producing it. It is shown that these families of sequences have direct application as error-correcting codes.

Lee, J.-J.↗
NASA NTRS1976

M-ary shift register

Binary devices are used to construct an m-ary linear feedback shift register.

Perlman, M.↗
NASA NTRS1977

Continuous data stream FIFO magnetic bubble domain shift register

There is described a simple first-in, first out (FIFO) magnetic bubble domain shift register which has continuous data storage capability. In a preferred embodiment, two parallel detector branches are associated with a main storage loop. The bubbles in the storage loop are replicated toward each detector branch by passive replicators in the storage loop. Annihilators associated with each of the replicators and each of the detectors are arranged an appropriate distance from the replicators so that selective energization of the annihilators permits certain bits to propagate to one detector and other bits to propagate to the other detector. Connection of the detectors in an appropriate bridge circuit permits full data rate reclamation.

Chen, Thomas T.↗