Improved Arithmetic Performance by Combining Stateful and Non‐Stateful Logic in Resistive Random Access Memory 1T–1R Crossbars

Computing-in-memory (CIM) is a promising approach for overcoming the memory-wall problem in conventional von-Neumann architectures. This is done by performing certain computation tasks directly in the storage subsystem without transferring data between storage and processing units. Stateful and non-stateful CIM concepts are recently attracting lots of interest, which are demonstrated as logical complete, energy efficient, and compatible with dense crossbar structures. However, sneak-path currents in passive resistive random access memory (RRAM) crossbars degrade the operation reliability and require the usage of active 1 Transistor–1 Resistance (1T-1R) bitcell designs. In this article, the arithmetic performance and reliability are investigated based on experimental measurements and variability-aware circuit simulations. Herein, it is aimed for the evaluation of logic operations specifically with fully integrated 1T–1R crossbar devices. Based on these operations, an N-bit full adder with optimized energy consumption and latency is demonstrated by combining stateful and non-stateful CIM logic styles with regard to the specific conditions in active 1T–1R RRAM crossbars

Exact results for hydrogen recombination on dust grain surfaces

The recombination of hydrogen in the interstellar medium, taking place on surfaces of microscopic dust grains, is an essential process in the evolution of chemical complexity in interstellar clouds. The H_2 formation process has been studied theoretically, and in recent years also by laboratory experiments. The experimental results were analyzed using a rate equation model. The parameters of the surface, that are relevant to H_2 formation, were obtained and used in order to calculate the recombination rate under interstellar conditions. However, it turned out that due to the microscopic size of the dust grains and the low density of H atoms, the rate equations may not always apply. A master equation approach that provides a good description of the H_2 formation process was proposed. It takes into account both the discrete nature of the H atoms and the fluctuations in the number of atoms on a grain. In this paper we present a comprehensive analysis of the H_2 formation process, under steady state conditions, using an exact solution of the master equation. This solution provides an exact result for the hydrogen recombination rate and its dependence on the flux, the surface temperature and the grain size. The results are compared with those obtained from the rate equations. The relevant length scales in the problem are identified and the parameter space is divided into two domains. One domain, characterized by first order kinetics, exhibits high efficiency of H_2 formation. In the other domain, characterized by second order kinetics, the efficiency of H_2 formation is low. In each of these domains we identify the range of parameters in which, the rate equations do not account correctly for the recombination rate. and the master equation is needed.Comment: 23 pages + 8 figure

Pitfalls in the diagnosis of acoustic neuroma

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71894/1/j.1365-2273.1984.tb01490.x.pd