Ideal Memory Research Articles

Shape Memory Behavior of a Polyethylene-Based Carboxylate Ionomer

Shape memory behavior of a partially zinc-neutralized, poly(ethylene-co-methacrylic acid) ionomer was investigated. The ionomer was a semicrystalline ionomer with a broad melting transition in the range 60–100 °C. Physical crosslinks in the ionomer due to an ionic nanodomain structure provided a “permanent” crosslinked network, while polyethylene crystallinity provided a temporary network. The broad melting transition allowed one to tune the dual-shape memory behavior by choosing a switching temperature, Tc, anywhere within the melting transition. Similarly, multiple-shape memory behavior was achieved by choosing two or more switching temperatures within the melting transition, though the effectiveness of fixing (F) depended on how much material was melted and recrystallized to support the specific temporary shape. Crosslinking improved the recovery efficiency (R), and the crosslinked ionomer exhibited nearly ideal shape memory behavior in the dual-shape memory cycle.

Quantum reading of digital memory with non-Gaussian entangled light

It has been shown recently S. Pirandola [Phys. Rev. Lett. 106, 090504 (2011)] that entangled light with Einstein-Podolsky-Rosen correlations retrieves information from digital memory better than any classical light. In identifying this, a model of digital memory with each cell consisting of a reflecting medium with two reflectivities (each memory cell encoding the binary numbers 0 or 1) is employed. The readout of binary memory essentially corresponds to discrimination of two bosonic attenuator channels characterized by different reflectivities. The model requires an entire mathematical paraphernalia of a continuous variable Gaussian setting for its analysis when arbitrary values of reflectivities $0\ensuremath{\le}{r}_{0},{r}_{1}\ensuremath{\le}1$ are considered. Here we restrict ourselves to a basic quantum readout mechanism with two different families of non-Gaussian entangled states of light, in which the binary channels to be discriminated are (i) ideal memory characterized by reflectivity ${r}_{1}=1$ (identity channel) and (ii) a thermal noise channel---where the signal light illuminating the memory location gets completely lost (${r}_{0}=0$) and only a white thermal noise hitting the upper side of the memory reaches the decoder. We compare the quantum reading efficiency of two families of non-Gaussian entangled light [($m,{m}^{\ensuremath{'}}$) family of path-entangled photon states and entangled state obtained by mixing a single photon with coherent light in a 50:50 beam splitter] with any classical source of light in this model. We identify that the classes of non-Gaussian entangled transmitters studied here offer significantly better reading performance than any classical transmitters of light in the regime of low signal intensity. We also demonstrate that the ($m,{m}^{\ensuremath{'}}$) family of entangled light exhibits better reading performance than NOON states.

Oxygen Ion Drift‐Induced Complementary Resistive Switching in Homo TiOx/TiOy/TiOx and Hetero TiOx/TiON/TiOx Triple Multilayer Frameworks

AbstractDeveloping a means by which to compete with commonly used Si‐based memory devices represents an important challenge for the realization of future three‐dimensionally stacked crossbar‐array memory devices with multifunctionality. Therefore, oxide‐based resistance switching memory (ReRAM), with its associated phenomena of oxygen ion drifts under a bias, is becoming increasingly important for use in nanoscalable crossbar arrays with an ideal memory cell size due to its simple metal–insulator–metal structure and low switching current of 10–100 μA. However, in a crossbar array geometry, one single memory element defined by the cross‐point of word and bit lines is highly susceptible to unintended leakage current due to parasitic paths around neighboring cells when no selective devices such as diodes or transistors are used. Therefore, the effective complementary resistive switching (CRS) features in all Ti‐oxide‐based triple layered homo Pt/TiOx/TiOy/TiOx/Pt and hetero Pt/TiOx/TiON/TiOx/Pt geometries as alternative resistive switching matrices are reported. The possible resistive switching nature of the novel triple matrices is also discussed together with their electrical and structural properties. The ability to eliminate both an external resistor for efficient CRS operation and a metallic Pt middle electrode for further cost‐effective scalability will accelerate progress toward the realization of cross‐bar ReRAM in this framework.

Combined mTOR Inhibition and OX40 Agonism Enhances CD8+ T Cell Memory and Protective Immunity Produced by Recombinant Adenovirus Vaccines

The memory CD8(+) T cell population elicited by immunization with recombinant human adenovirus serotype 5 (rHuAd5) vaccines is composed primarily of effector and effector memory cells (T(EM)) with limited polyfunctionality. In this study, we investigated whether treatment with immunomodulators could enhance and/or redistribute the CD8(+) memory population elicited by rHuAd5. Vaccination in combination with both rapamycin (to modulate differentiation) and an OX40 agonist (to enhance costimulation) increased both the quantity and polyfunctionality of the CD8(+) memory T cell population, with expansion of the T(EM) and memory precursor populations. Furthermore, this intervention enhanced protection against multiple virus challenges. Attenuation of adenovirus transgene expression was required to enable the combination rapamycin + OX40 agonist immunomodulatory treatment to further enhance skewing towards central memory formation, indicating that persistence of antigen expression ultimately limits development of this memory population following rHuAd5 immunization. These results demonstrate that during the expansion phase following adenovirus immunization, the level of mammalian target of rapamycin (mTOR) activity, the amount of costimulation and the duration of antigen availability act together to define the magnitude, phenotype, and functionality of memory CD8(+) T cells. Modulation of these factors can be used to selectively manipulate memory formation.

Characterization of Femtosecond laser-irradiation crystallization and structure of multiple periodic Si/Sb_80Te_20 nanocomposite films by coherent phonon spectroscopy

Multiple parameters of nanocomposite Si/Sb₈₀Te₂₀ multilayer films are possibly optimized simultaneously to satisfy the development of ideal phase-change memory devices by adjusting chemical composition and physical structure of multilayer films. The crystallization and structure of the films are studied by coherent phonon spectroscopy. Laser irradiation power dependence of coherent optical phonon spectroscopy reveals laser-induced crystallization of the amorphous multilayer film, while coherent acoustic phonon spectroscopy reveals the presence of folded acoustic phonons which suggests a good periodic structure of the multilayer films. Laser irradiation-induced crystallization shows applicable potentials of the multilayer films in optical phase change storage.

Discriminating quantum-optical beam-splitter channels with number-diagonal signal states: Applications to quantum reading and target detection

We consider the problem of distinguishing, with minimum probability of error, two optical beam-splitter channels with unequal complex-valued reflectivities using general quantum probe states entangled over M signal and M' idler mode pairs of which the signal modes are bounced off the beam splitter while the idler modes are retained losslessly. We obtain a lower bound on the output state fidelity valid for any pure input state. We define number-diagonal signal (NDS) states to be input states whose density operator in the signal modes is diagonal in the multimode number basis. For such input states, we derive series formulas for the optimal error probability, the output state fidelity, and the Chernoff-type upper bounds on the error probability. For the special cases of quantum reading of a classical digital memory and target detection (for which the reflectivities are real valued), we show that for a given input signal photon probability distribution, the fidelity is minimized by the NDS states with that distribution and that for a given average total signal energy N_s, the fidelity is minimized by any multimode Fock state with N_s total signal photons. For reading of an ideal memory, it is shown that Fock state inputs minimize the Chernoff bound. For target detection under high-loss conditions, a no-go result showing the lack of appreciable quantum advantage over coherent state transmitters is derived. A comparison of the error probability performance for quantum reading of number state and two-mode squeezed vacuum state (or EPR state) transmitters relative to coherent state transmitters is presented for various values of the reflectances. While the nonclassical states in general perform better than the coherent state, the quantitative performance gains differ depending on the values of the reflectances.

Synthesis and thermomechanical research of shape memory epoxy systems

Abstract Shape memory polymers (SMPs) and their composites are a class of novel smart materials. In order to achieve adjustable thermomechanical and shape memory properties, a series of shape memory epoxy systems were synthesized by varying the types of curing agents and their contents. Thermal frozen/recovery tests, differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) were performed to investigate shape memory behaviors and thermomechanical properties of fabricated specimens. The results show that thermomechanical properties and critical shape transition temperature of shape memory epoxy systems can be adjusted by changing types and contents of curing agents, but all specimens fabricated in this study exhibit ideal shape memory effects.

Memory systems in the many-core era

The memory subsystem is a fundamental performance and energy bottleneck in almost all computing systems. Recent trends towards increasingly more cores on die, consolidation of diverse workloads on a single chip, and difficulty of DRAM scaling impose new requirements and exacerbate old demands on the memory system. In particular, the need for memory bandwidth and capacity is increasing [14], applications' interference in memory system increasingly limits system performance and makes the system hard to control [12], memory energy and power are key design concerns [8], and DRAM technology consumes significant amount of energy and does not scale down easily to smaller technology nodes [7]. Fortunately, some promising solution directions exist. In this talk, we will examine recent technology, application, and architecture trends motivating a fundamental rethinking of the memory hierarchy. Based on this motivation, we will describe requirements from an ideal memory system suitable for the many-core era. The talk will examine questions one would need to answer in approximating the ideal memory system and possible avenues that seem promising for the research community to explore. In particular, we will focus on the problem of uncontrolled inter-application interference in the memory system and draw upon our experiences in solving it by designing quality-of-service (QoS) aware memory controllers [5, 6, 9, 10, 11, 12], interconnects [1 2 13], and entire memory systems. We will make a case forapplication- and QoS-aware design of memory systems and [3, 4]integrated/cooperative design of cores, interconnects, and memory components to optimize the overall system.

A cost-effective heuristic to schedule local and remote memory in cluster computers

Cluster computers represent a cost-effective alternative solution to supercomputers. In these systems, it is common to constrain the memory address space of a given processor to the local motherboard. Constraining the system in this way is much cheaper than using a full-fledged shared memory implementation among motherboards. However, memory usage among motherboards can be unfairly balanced. On the other hand, remote memory access (RMA) hardware provides fast interconnects among the motherboards of a cluster. RMA devices can be used to access remote RAM memory from a local motherboard. This work focuses on this capability in order to achieve a better global use of the total RAM memory in the system. More precisely, the address space of local applications is extended to remote motherboards and is used to access remote RAM memory. This paper presents an ideal memory scheduling algorithm and proposes a cost-effective heuristic to allocate local and remote memory among local applications. Compared to the devised ideal algorithm, the heuristic obtains the same (or closely resembling) results while largely reducing the computational cost. In addition, we analyze the impact on the performance of stand alone applications varying the memory distribution among regions (local, local to board, and remote). Then, this study is extended to any number of concurrent applications. Experimental results show that a QoS parameter is needed in order to avoid unacceptable performance degradation.

Nonvolatile semiconductor memory revolutionizing information storage

(1) NVSM has revolutionized the information-storage technology and has ushered in the mobile electronics era. (2) NVSM has enabled the development of numerous new electronic applications and has penetration rates of over 90% in electronic systems since 2005; it is ubiquitous. (3) Flash memory owns many good attributes for an almost ideal memory. Therefore, it is an inevitable key component in many applications. (4) NAND-based Flash is not only for memory use but is the best solution today for semiconductor digital-mass storage among all other semiconductor choices. Many exotic/emerging technologies are under research for the next-generation candidate, but as of today, none are ready to overtake the floating-gate NVSM- the gap is still quite large.

Statistical Mechanics of Neocortical Interactions: Nonlinear Columnar Electroencephalography

Columnar firings of neocortex, modeled by a statistical mechanics of neocortical interactions (SMNI), are investigated for conditions of oscillatory processing at frequencies consistent with observed electroencephalography (EEG). A strong inference is drawn that physiological states of columnar activity receptive to selective attention support oscillatory processing in observed frequency ranges. Direct calculations of the Euler-Lagrange (EL) equations which are derived from functional variation of the SMNI probability distribution, giving most likely states of the system, are performed for three prototypical Cases, dominate excitatory columnar firings, dominate inhibitory columnar firings, and in-between balanced columnar firings, with and without a Centering mechanism (CM) (based on observed changes in stochastic background of presynaptic interactions) which pulls more stable states into the physical firings ranges. Only states with the CM exhibit robust support for these oscillatory states. These calculations are repeated for the visual neocortex, which has twice as many neurons/minicolumn as other neocortical regions. These calculations argue that robust columnar support for common EEG activity requires the same columnar presynaptic parameter necessary for ideal short-term memory (STM). It is demonstrated at this columnar scale, that both shifts in local columnar presynaptic background as well as local or global regional oscillatory interactions can effect or be affected by attractors that have detailed experimental support to be considered states of STM. Including the CM with other proposed mechanisms for columnar-glial interactions and for glial-presynaptic background interactions, a path for future investigations is outlined to test for quantum interactions, enhanced by magnetic fields from columnar EEG, that directly support cerebral STM and computation by controlling presynaptic noise. This interplay can provide mechanisms for information processing and computation in mammalian neocortex.

Coherent optical pulse sequencer for quantum applications

The bandwidth and versatility of optical devices have revolutionized information technology systems and communication networks. Precise and arbitrary control of an optical field that preserves optical coherence is an important requisite for many proposed photonic technologies. For quantum information applications, a device that allows storage and on-demand retrieval of arbitrary quantum states of light would form an ideal quantum optical memory. Recently, significant progress has been made in implementing atomic quantum memories using electromagnetically induced transparency, photon echo spectroscopy, off-resonance Raman spectroscopy and other atom-light interaction processes. Single-photon and bright-optical-field storage with quantum states have both been successfully demonstrated. Here we present a coherent optical memory based on photon echoes induced through controlled reversible inhomogeneous broadening. Our scheme allows storage of multiple pulses of light within a chosen frequency bandwidth, and stored pulses can be recalled in arbitrary order with any chosen delay between each recalled pulse. Furthermore, pulses can be time-compressed, time-stretched or split into multiple smaller pulses and recalled in several pieces at chosen times. Although our experimental results are so far limited to classical light pulses, our technique should enable the construction of an optical random-access memory for time-bin quantum information, and have potential applications in quantum information processing.

P1-157: TICS-m and cantab PAL: The ideal telephone screen and memory test for selecting amnestic mild cognitive impairment cases for clinical trials: The oxford project to investigate memory and ageing (optima) vitacog trial experience

P1-157: TICS-m and cantab PAL: The ideal telephone screen and memory test for selecting amnestic mild cognitive impairment cases for clinical trials: The oxford project to investigate memory and ageing (optima) vitacog trial experience

Metal-Organic Chemical Vapor Deposition (MOCVD) of GeSbTe-based Chalcogenide Thin Films

AbstractChalcogenide Random Access Memory (C-RAM) has shown significant promise in combining the desired attributes of an ideal memory, including: nonvolatility, fast read/write/erase speed, low read/write/erase voltage/power, high endurance, and radiation hardness. Current C-RAM production technology relies on sputtering to deposit the active chalcogenide layer. The sputtering process leads to difficulties in meeting requirements for device conformality (in particular – filling vias), film adherence, compositional control, wafer yield, and surface damage. Ultimately, a viable CVD manufacturing process is needed for high-density products to realize the full potential of C-RAM. In this work, we discuss the Metal-Organic Chemical Vapor Deposition (MOCVD) tool technology used to produce the films and report the materials properties of GeSbTe-based chalcogenide thin films grown in small research scale and in large production scale MOCVD reactors. Films were grown at low pressures at temperatures ranging from 350 C to 600 C. X-Ray Fluorescence (XRF) and Auger Electron Spectroscopy (AES) were performed and determined that the film composition is controllable and uniform.

A linear optimization neural network for associative memory

Almost all the existing continuous neural networks now for associative memory are based on optimizing a quadratic function. The disadvantage is that the structure is complicated and implementation of circuit cannot coincide with the theoretical analysis. In this paper, a new linear neural network is presented for associative memory. Simple in nature, the proposed network is proved to be an ideal associative memory. Compared with other networks, the main difference is that each pattern to be recognized is used as a parameter of the network other than an initial point. The main advantage is that the theoretic analysis coincides precisely with the easy implementation and the network can explain clearly the meaning of each refused pattern. The model considered herein is intrinsically a neural network for solving linear optimization problems with hybrid constraints. But its state is allowed to lie in a general closed convex set spanned by the prototype patterns. The performance of the proposed network is demonstrated by means of simulation of one numerical example.

Observation of entanglement between a single trapped atom and a single photon.

An outstanding goal in quantum information science is the faithful mapping of quantum information between a stable quantum memory and a reliable quantum communication channel. This would allow, for example, quantum communication over remote distances, quantum teleportation of matter and distributed quantum computing over a 'quantum internet'. Because quantum states cannot in general be copied, quantum information can only be distributed in these and other applications by entangling the quantum memory with the communication channel. Here we report quantum entanglement between an ideal quantum memory--represented by a single trapped 111Cd+ ion--and an ideal quantum communication channel, provided by a single photon that is emitted spontaneously from the ion. Appropriate coincidence measurements between the quantum states of the photon polarization and the trapped ion memory are used to verify their entanglement directly. Our direct observation of entanglement between stationary and 'flying' qubits is accomplished without using cavity quantum electrodynamic techniques or prepared non-classical light sources. We envision that this source of entanglement may be used for a variety of quantum communication protocols and for seeding large-scale entangled states of trapped ion qubits for scalable quantum computing.

A fast and accurate method for determining a lower bound on execution time

AbstractIn performance critical applications, memory latency is frequently the dominant overhead. In many cases, automatic compiler‐based optimizations to improve memory performance are limited and programmers frequently resort to manual optimization techniques. However, this process is tedious and time‐consuming. Furthermore, as the potential benefit from optimization is unknown there is no way to judge the amount of effort worth expending, nor when the process can stop, i.e. when optimal memory performance has been achieved or sufficiently approached. Architecture simulators can provide such information but designing an accurate model of an existing architecture is difficult and simulation times are excessively long. In this article, we propose and implement a technique that is both fast and reasonably accurate for estimating a lower bound on execution time for scientific applications. This technique has been tested on a wide range of programs from the SPEC benchmark suite and two commercial applications, where it has been used to guide a manual optimization process and iterative compilation. We compare our technique with that of a simulator with an ideal memory behaviour and demonstrate that our technique provides comparable information on memory performance and yet is over two orders of magnitude faster. We further show that our technique is considerably more accurate than hardware counters. Copyright © 2004 John Wiley & Sons, Ltd.

Ferroelectric 1-T memory device—will it be viable for nonvolatile memory applications?

ABSTRACTThe quest for a nonvolatile memory FET based on the metal-ferroelectric-(insulator)-semiconductor (MF(I)S) gate stack concept has greatly intensified in recent years. In principle, such a memory device (MF(I)S) could be a building block of an ideal memory technology which offers random access, high speed, low power, high density and non-volatility. In practice, however, none of the reported ferroelectric memory transistors has achieved a memory retention time of more than a few days so far. These results are a far cry from the 10-year retention time requirement for non-volatile memory devices. This paper reveals progress and optimization that grain size, interfacial properties, and crystallinity of the annealed ferroelectric SrBi2Ta2O9 (SBT) films have a strong impact on the size of the memory window, as does the choice of the buffer layer material. The properties of SiN buffer layer sandwiched between SBT and Si are discussed. Switches in the polarization of the ferroelectric SBT play a key role for both the ferroelectric-polarization-dominated and the trapping-dominated memory windows. Preliminary results on MFIS capacitors and transistors are reviewed, limited retention time has been observed. A closer look at the physics of device operation reveals two major causes of the short retention time: (1) depolarization fields; (2) finite gate leakage current and the associated charge trapping. Here, the origins of these problems are analyzed and practical difficulties in attempting to realize nonvolatile ferroelectric 1-T memory devices are illustrated. Two possible solutions have been proposed to circumvent problems associated with the finite retention time in ferroelectric FETtype memories: (1) memory refreshes as done in the FEDRAM cell, (2) single-crystallize the ferroelectric film.

Prospect of Emerging Nonvolatile Memories

ABSTRACTConventional nonvolatile memories such as Flash and EEPROM memory have successfully evolved toward high density and low cost. Especially, the market and density of flash memories has grown rapidly which leads semiconductor technology. However, there have been concerns about whether this successful progress can be maintained in the future nano era and can satisfy the requirement of diversified future IT market. Flash memories have the advantage of high density with small cell size and by contraries the disadvantage of slow writing speed and limited endurance. This slow writing speed and limited endurance is not aligned with the trend of high speed and reliability for future semiconductor memories.The future for these conventional nonvolatile memories forces many research groups and companies to develop alternative memories with ideal memory characteristics such as non-volatility, high density, high speed, and low power, which none of the conventional memories can satisfy at the same time.In this article, I will evaluate the characteristics of future nonvolatile memories such as ferroelectric random access memory (FRAM), magnetoresistive random access memory (MRAM) and phase change random access memory (PRAM). These memories have been recently evaluated because of the possibility that they can overcome the challenges that conventional memories are facing. Finally we will review critical technology barriers in developing future memory and predict the promising technology to overcome the barriers in conventional and emerging new memories, which will be technology guidelines for future memory development.

Reading the cemetery, lieu de memoire par excellance

This work uses rhetoric's fourth canon to “read”; the cemetery, a bricolage that can tell us both how memory is shaped and some of what is forgotten. As ideal memory sites, cemeteries show how kairos merges with chronos as well as how memory is linked to power and truth. Looking most specifically at Mount Auburn Cemetery in Cambridge, Massachusetts, this work analyzes several gravesites as well as the cemetery itself to see how such readings of cemeteries might help us develop a more critical perspective on memory.