Memristor MOS Content Addressable Memory (MCAM): Hybrid Architecture for Future High Performance Search Engines

Large-capacity Content Addressable Memory (CAM) is a key element in a wide variety of applications. The inevitable complexities of scaling MOS transistors introduce a major challenge in the realization of such systems. Convergence of disparate technologies, which are compatible with CMOS processing, may allow extension of Moore's Law for a few more years. This paper provides a new approach towards the design and modeling of Memristor (Memory resistor) based Content Addressable Memory (MCAM) using a combination of memristor MOS devices to form the core of a memory/compare logic cell that forms the building block of the CAM architecture. The non-volatile characteristic and the nanoscale geometry together with compatibility of the memristor with CMOS processing technology increases the packing density, provides for new approaches towards power management through disabling CAM blocks without loss of stored data, reduces power dissipation, and has scope for speed improvement as the technology matures.Comment: 10 pages, 11 figure

Fungal colonization of Douglas-fir sapwood

The fungi that cause mold and stain of freshly sawn lumber result in millions of dollars in losses to the forest products industry. Stain and mold are typically prevented by either kiln drying or by application of a topical fungicide. While these treatments are effective, kiln drying is costly and many mills object to use of chemicals. One alternative to conventional stain prevention is biological control. One problem with this approach on western wood species such as Douglas-fir is the lack of information on the target stain and mold fungi that colonize the sapwood of this species. The fungi colonizing freshly sawn Douglas-fir sapwood were isolated and identified by culturing lumber obtained from 4 different locations in the Willamette Valley in western Oregon using regular, streptomycin amended or streptomycin/cycloheximide amended malt extract agar. The ability of each taxa to cause discoloration was evaluated in a laboratory discoloration test. A total of 547 fungi were isolated from Douglas-fir sapwood, representing 24 genera and 45 species. Graphium species were the most frequently isolated fungi, representing 17.4 percent of all isolates. Most of these isolates were considered as anamorphs of Ophiostoma piceae. Other frequently isolated sapstaining fungi included Cephaloascus fragrans, Aureobasidium pullulans, Rhinocladiella cellaris, Cladosporium cladosporioides and Scytalidium lignicola. Molds, primary Penicillium and Trichoderma species, were frequently isolated, and may represent potential biological control organisms or competitors of biological control organisms because of their antagonistic characteristics. Many fungal species of unknown biological significance were also isolated from Douglas-fir sapwood, and their roles in the stain development merit further study. Media and lumber source both affected the fiingal flora isolated. Among stain fungi, Graphium species exclusively occurred on cycloheximide amended media. There was also close relationship between the degree of fungal colonization and the length of time after the lumber was cut. The degree of discoloration exceeded 70 percent in all Graphium species. Cephaloascus fragrans, Aureobasidium pullulans, Rhinocladiella cellaris, Cladosporium cladosporioides, Scytalidium lignicola and Thysanophora penicillioides also produced extensive staining of Douglas-fir sapwood. Mold isolates also caused discoloration of Douglas-fir sapwood wafers, although their discoloration could be easily removed. All Penicillium species produced over 90 percent discoloration, while Trichoderma species produced 80 to 86 percent discoloration. The results indicate that Graphium species are the primary stain fungi on Douglas-fir sapwood, however, other species were also capable of colonizing this material

Voice vs. silence: the role of cognitive appraisal of and emotional response to stressors

Stress is in the nature of work, employees, teams, and organizations. Some speak up under stress, whereas others keep silent. Given that employee voice has long been recognized to enhance high-quality decisions and organizational effectiveness, understanding conditions under which employees practice voice is important. In this article, we combine appraisal theory, prospect theory, and threat-rigidity thesis so as to enrich our understanding of the relationship between stressors and voice. In so doing, our theory paper integrates threat-rigidity thesis, prospect theory, and appraisal theory on the basis of the interaction between cognition and emotion, and it explores the detailed cognition-emotion-behavior (voice) relationship

Analog Weights in ReRAM DNN Accelerators

Artificial neural networks have become ubiquitous in modern life, which has triggered the emergence of a new class of application specific integrated circuits for their acceleration. ReRAM-based accelerators have gained significant traction due to their ability to leverage in-memory computations. In a crossbar structure, they can perform multiply-and-accumulate operations more efficiently than standard CMOS logic. By virtue of being resistive switches, ReRAM switches can only reliably store one of two states. This is a severe limitation on the range of values in a computational kernel. This paper presents a novel scheme in alleviating the single-bit-per-device restriction by exploiting frequency dependence of v-i plane hysteresis, and assigning kernel information not only to the device conductance but also partially distributing it to the frequency of a time-varying input. We show this approach reduces average power consumption for a single crossbar convolution by up to a factor of x16 for an unsigned 8-bit input image, where each convolutional process consumes a worst-case of 1.1mW, and reduces area by a factor of x8, without reducing accuracy to the level of binarized neural networks. This presents a massive saving in computing cost when there are many simultaneous in-situ multiply-and-accumulate processes occurring across different crossbars.Comment: 2019 IEEE International Conference on Artificial Intelligence Circuits and Systems, 5 pages, 4 figure

Gapped Nearly Free-Standing Graphene on an SiC(0001) Substrate Induced by Manganese Atoms

The electron band structure of manganese-adsorbed graphene on an SiC(0001) substrate has been studied using angle-resolved photoemission spectroscopy. Upon introducing manganese atoms, the conduction band of graphene completely disappears and the valence band maximum is observed at 0.4 eV below Fermi energy. At the same time, the slope of the valence band decreases, approaching the electron band structure calculated using the local density approximation method. While the former provides experimental evidence of the formation of nearly free-standing graphene on an SiC substrate, concomitant with a metal-to-insulator transition, the latter suggests that its electronic correlations can be modified by foreign atoms. These results pave the way for promising device applications using graphene that is semiconducting and charge neutral.Comment: 16 pages, 3 figure

Anti-reflective nano- and micro-structures on 4H-SiC for photodiodes

In this study, nano-scale honeycomb-shaped structures with anti-reflection properties were successfully formed on SiC. The surface of 4H-SiC wafer after a conventional photolithography process was etched by inductively coupled plasma. We demonstrate that the reflection characteristic of the fabricated photodiodes has significantly reduced by 55% compared with the reference devices. As a result, the optical response Iillumination/Idark of the 4H-SiC photodiodes were enhanced up to 178%, which can be ascribed primarily to the improved light trapping in the proposed nano-scale texturing

Nanopores of carbon nanotubes as practical hydrogen storage media

We report on hydrogen desorption mechanisms in the nanopores of multiwalled carbon nanotubes (MWCNTs). The as-grown MWCNTs show continuous walls that do not provide sites for hydrogen storage under ambient conditions. However, after treating the nanotubes with oxygen plasma to create nanopores in the MWCNTs, we observed the appearance of a new hydrogen desorption peak in the 300–350 K range. Furthermore, the calculations of density functional theory and molecular dynamics simulations confirmed that this peak could be attributed to the hydrogen that is physically adsorbed inside nanopores whose diameter is approximately 1 nm. Thus, we demonstrated that 1 nm nanopores in MWCNTs offer a promising route to hydrogen storage media for onboard practical applications