Search results for "Hard"
showing 10 items of 2294 documents
Magnetic domain-wall racetrack memory for high density and fast data storage
2012
The racetrack memory device is a new concept of Magnetic RAM (MRAM) based on controlling domain wall (DW) motion in ferromagnetic nanowires. It promises ultra-high storage density thanks to the possibility to store multiple narrow DWS per memory cell. By using read and write heads based on magnetic tunnel junctions (MTJ) with perpendicular magnetic anisotropy (PMA) fast data access speed can also be achieved. Thereby the racetrack memory can be used as universal storage to address both embedded and standalone applications. In this paper, we present the device physics, integration circuit and architecture designs of a racetrack memory based on MTJs with PMA. Mixed SPICE simulations at 65 nm …
Lone Star Stack: Architecture of a Disk-Based Archival System
2014
The need for huge storage systems rises with the ever growing creation of data. With growing capacities and shrinking prices, "write once read sometimes" workloads become more common. New data is constantly added, rarely updated or deleted, and every stored byte might be read at any time - a common pattern for digital archives or big data scenarios. We present the Lone Star Stack, a disk based archival storage system building block that is optimized for high reliability and energy efficiency. It provides a POSIX file system interface that uses flash based storage for write-offloading and metadata and the disk-based Lone Star RAID for user data storage. The RAID attempts to spin down disks a…
LoneStar RAID
2016
The need for huge storage archives rises with the ever growing creation of data. With today’s big data and data analytics applications, some of these huge archives become active in the sense that all stored data can be accessed at any time. Running and evolving these archives is a constant tradeoff between performance, capacity, and price. We present the LoneStar RAID, a disk-based storage architecture, which focuses on high reliability, low energy consumption, and cheap reads. It is designed for MAID systems with up to hundreds of disk drives per server and is optimized for “write once, read sometimes” workloads. We use dedicated data and parity disks, and export the data disks as individu…
Importance of the Window Function Choice for the Predictive Modelling of Memristors
2021
Window functions are widely employed in memristor models to restrict the changes of the internal state variables to specified intervals. Here, we show that the actual choice of window function is of significant importance for the predictive modelling of memristors. Using a recently formulated theory of memristor attractors, we demonstrate that whether stable fixed points exist depends on the type of window function used in the model. Our main findings are formulated in terms of two memristor attractor theorems, which apply to broad classes of memristor models. As an example of our findings, we predict the existence of stable fixed points in Biolek window function memristors and their absenc…
Branch-and-cut algorithms for the vehicle routing problem with trailers and transshipments
2013
This article studies the vehicle routing problem with trailers and transshipments VRPTT, a practically relevant, but challenging, generalization of the classical vehicle routing problem. The article makes three contributions: i Building on a nontrivial network representation, two mixed-integer programming formulations for the VRPTT are proposed. ii Based on these formulations, five different branch-and-cut algorithms are developed and implemented. iii The computational behavior of the algorithms is analyzed in an extensive computational study, using a large number of test instances designed to resemble real-world VRPTTs.Copyright © 2013 Wiley Periodicals, Inc. NETWORKS, Vol. 631, 119-133 20…
An Efficient Implementation of Distributed Routing Algorithms for NoCs
2008
The design of NoCs for multi-core chips introduces new design constraints like power consumption, area, and ultra low latencies. Although 2D meshes are preferred, heterogeneous blocks, fabrication faults, reliability issues, and chip virtualization may lead to the need of irregular topologies or regions. In this situation, efficient routing becomes a challenge. Although the use of routing tables at switches is flexible, it does not scale in terms of latency and area due to its memory requirements. LBDR (logic-based distributed routing) is proposed as a new routing method that removes the need of using routing tables at all. LBDR enables the implementation of many routing algorithms on most …
Simulating spin models on GPU
2010
Over the last couple of years it has been realized that the vast computational power of graphics processing units (GPUs) could be harvested for purposes other than the video game industry. This power, which at least nominally exceeds that of current CPUs by large factors, results from the relative simplicity of the GPU architectures as compared to CPUs, combined with a large number of parallel processing units on a single chip. To benefit from this setup for general computing purposes, the problems at hand need to be prepared in a way to profit from the inherent parallelism and hierarchical structure of memory accesses. In this contribution I discuss the performance potential for simulating…
Atypical transistor-based chaotic oscillators: Design, realization, and diversity
2017
In this paper, we show that novel autonomous chaotic oscillators based on one or two bipolar junction transistors and a limited number of passive components can be obtained via random search with suitable heuristics. Chaos is a pervasive occurrence in these circuits, particularly after manual adjustment of a variable resistor placed in series with the supply voltage source. Following this approach, 49 unique circuits generating chaotic signals when physically realized were designed, representing the largest collection of circuits of this kind to date. These circuits are atypical as they do not trivially map onto known topologies or variations thereof. They feature diverse spectra and predom…
Covid-19 in Italy: Modelling, Communications, and Collaborations
2022
Abstract When Covid-19 arrived in Italy in early 2020, a group of statisticians came together to provide tools to make sense of the unfolding epidemic and to counter misleading media narratives. Here, members of StatGroup-19 reflect on their work to date
Step-by-Step Control of the Dynamics of a Superconducting QED-like System
2007
We discuss the modus operandi of a theoretical scalable coupling scheme to control step by step the time evolution of a pair of flux qubits embedded in a lossy resonant cavity. The sequential interaction of each qubit with the quantized cavity mode is controlled by externally applied magnetic fluxes. Our analysis indicates that indirect qubit-qubit interactions, with the electromagnetic mode acting as a data bus, can be selectively performed and exploited both for the implementation of entangling gates and for the generation of states with a priori known characteristics.