This research examines age differences in the use and value of memory compensation strategies for everyday memory tasks. Chapter 1 reviews the literature on memory compensation and aging. According to Selective Optimization with Compensation (SOC) model, older adults may be more likely than younger adults to take advantage of memory compensation strategies when they are available. Chapter 2 describes a diary study in which older and younger participants rated the extent to which they use compensation strategies in everyday life and reported everyday memory errors over the course of a week. Older adults reported fewer memory errors than younger adults and more use of memory aids. However, use of memory aids was unrelated to frequency of memory errors in either age group. Chapter 3 reports a laboratory experiment on the use of memory aids for recalling phone messages. Participants listened to phone messages while simultaneously completing a seating chart, and were asked to report the content of the messages to the experimenter. Participants were either allowed to use a memory aid for the phone message task, or not. Older participants reported using compensation strategies more frequently in everyday life, but they were no more likely than younger participants to search for or employ an aid in the phone message task. Using a memory aid was differentially beneficial, improving performance more for older than younger participants. In Chapter 4, participants completed two phone message recall and two seating plan tasks. Participants were encouraged to use whatever in the room that they might find helpful. On one round of tasks a pen was tied to a clipboard and participants could use it to write down the phone messages. On the other round no pen was available. The order of the trials was counterbalanced across participants. This design examined the calibration between participants’ use of memory aids and their performance on the recall task – whether participants’ performance on the first trial predicted their subsequent use of memory aids, and whether participants who chose to use a memory aid when it was available on the first trial performed particularly poorly on the second trial when no aid was present. As in Study 1, older adults reported using memory aids more frequently in everyday life but age was unassociated with whether or not participants used the pen when one was available. There was little evidence of calibration. Participants’ memory performance on an initial trial had little impact on their use of a memory aid on a subsequent trial. Participants who used a memory aid on the first trial actually recalled more phone message details on the second trial (without the aid) than those who did not. This was true for both age groups. Chapter 5 reflects on older and younger adults self-reported and observed uses of memory compensation strategies. Across all 3 studies older adults reported using external memory aids more frequently in everyday life. However, contrary to the SOC model, in Studies 2 and 3 there were no age differences in older and younger adults’ use of a pen to write down phone messages on the lab task. Nor was participants’ choice to use the memory aid associated with their unaided performance on the task. These results do not support the prediction derived from SOC that older adults use compensation strategies more frequently or more sensitively than younger adults. However, using the memory did improve performance on the task more for older than for younger adults. These results support the hypothesis that external memory aids are a particularly valuable strategy for older adults and suggest the need to better understand why some individuals engage in compensation use and others do not.

Although forgetfulness is a common and naturally occurring phenomenon, research suggests that it can be intentionally induced using several experimental paradigms. For some individuals, the ability to forget negative thoughts, images, or memories is problematic. That is, the inability to forget may be a source of significant psychological distress (e.g., post-traumatic stress, obsessive-compulsiveness, and depressed mood) that contributes to the maintenance of symptoms of various mental health disorders. The schema-activation hypothesis from Becks (1987) Cognitive Theory of Depression suggest that memories should be more readily brought to mind because they are more readily available through associated activation. Thus, negative memories may be difficult to inhibit (forget), for individuals who are depressed compared to non-depressed counterparts. <p> Indeed, suppression effort (the intentional mental effort to not think about something) often leads to an increase in the very cognitive content targeted for forgetting. For individuals who experience depression or dysphoria, suppression is not effective because the negative cognitive content, which is the hallmark the depressed mood state only serves to maintain or exacerbate the mood state. This raises the question of whether there are alternatives to suppression-like paradigms that may be more efficacious for those who are dysphoric or depressed. Investigating the efficacy of induced-forgetting of negative memories may provide researchers and clinicians with additional avenues to explore the therapeutic potential of induced forgetting as an intervention or preventive strategy in combating depressed mood states. <p>The purpose of the present study was threefold: first, this study examined whether individual differences (e.g., mood state) in a persons ability to call to mind (remember) negative self-relevant memories would affect memory generation time. Second, the implications of differences in mood for the efficacy of two experimental forgetting paradigms Directed Forgetting (DF) and Retrieval Induced Forgetting (RIF) were explored. Finally, individual differences in mental control (i.e., perceived mental controllability, mental control strategies, and rumination as a coping response) were examined in terms of their ability to predict who would be better at remembering and forgetting. <p>University students (N = 103) with high and low levels of symptoms of dysphoria were asked to generate a set of 32 negative memories using cue words. After rating their memories for clarity and negative valance, each set of memories was subject to either a Directed Forgetting or Retrieval-Induced Forgetting procedure. Participants also completed self-report measures of mental control and rumination. Individuals who were dysphoric were similar to those who were non-dysphoric in the amount of time it took to generate a set of 32 negative memories. These results failed to support the tenets of the Schema Activation Hypothesis of Becks (1967) Cognitive Theory of Depression. Subsequent analysis revealed that the act of generating negative memories was mood-inducing, which may have negated the effect of mood on generation time. In terms of the effect of mood on induced-forgetting paradigm efficacy, the analysis yielded several null findings. The insufficient power prohibited the ability to detect small effects. <p>Dysphoric individuals evidenced deficits in forgetting for the directed-forgetting but not the retrieval-induced forgetting paradigm, but only when separate analysis of individual paradigms was undertaken. In this case, the effect of mood on forgetting approached significance for the directed-forgetting paradigm but not the retrieval-induced forgetting paradigm. This suggests that inducing forgetting for those who are dysphoric is more likely to be successful if there is no instruction to forget. Finally, it was predicted that poor perceived mental control, a tendency to ruminate, and the use of mental control strategies would correlate with induced-forgetting. Results suggest that individuals who perceive themselves as poor at controlling mental content, and ruminate about their internal experience of sadness are impaired on recall of negative autobiographic memories when asked to forget them. In contrast, mental control variables were not related to the degree of forgetting using retrieval-practice methodology. The results of this study have implications for future research designed to further explore the therapeutic value of induced-forgetting, particularly for the RIF paradigm. That is, the presence of a retrieval-induced forgetting effect for those who are dysphoric could prove to be a beneficial coping strategy to combat unwanted negative memories. It may be important to study the longitudinal value, as well as explore the potential benefits for other psychologically distressing phenomena in which negative memories are a part (e.g., post-traumatic stress). That cognitive factors, such as mental control and ruminative coping, do not share a relationship with degree of forgetting in the RIF paradigm also bodes well in demonstrating a possible therapeutic advantage for RIF compared to DF. Researchers are advised to consider mood and mental control variables in terms of their potential effects on forgetting paradigm efficacy when selecting their methodology in studies of intentional forgetting. This is particularly important when using a university sample of participants. It is often the case with experimental research, that a university sample is used. Given the higher rates of dysphoria and self-reported depressive symptoms that tend to typify university students and therefore, may be higher than in community-based samples, researchers are cautioned to consider the implications of dysphoria on research outcomes when testing induced-forgetting paradigms.

Människor tenderar att minnas utförda uppgifter och återkalla dem bättre än när de enbart kodar samma uppgifter muntligt, även känd som enactment effekt. Syftet med den här studien var att undersöka om enactment effecten ökar under en ny inkodning som aldrig tidigare utförts inom paradigmet – Subject-Experimenter-Performed-Task. Sammanlagt medverkade 56 personer i studien, 32 killar och 24 tjejer i åldrarna 10-18. En grupp lågstadiebarn och en grupp gymnasieungdomar testades i VT, EPT, SPT och SEPT betingningar. Effekten av enactment har visat sig vara tydligast i SEPT inkodningen i både free och cued recall. Resultaten och eventuella köns- och åldersskillnader diskuteras utifrån episodic integration teorin.

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The cyclic instability in shape memory characteristics of NiTi-based shape memory alloys (SMAs), such as transformation temperatures, transformation and irrecoverable strains and transformation hysteresis upon thermal and mechanical cycling limits their applications requiring high number of cycles. The main reasons for these instabilities are lattice incompatibility between transforming phases and relatively low lattice resistance against dislocation motion. The objective of this study is to increase the slip resistance and thus, to minimize the plastic accommodation upon phase transformation in NiTi and TiNiPd SMAs. The effects of grain refinement down to submicron to nanorange through Equal Channel Angular Extrusion (ECAE) on the cyclic stability were investigated as potential remedies. The influence of ECAE parameters, such as processing temperature and strain path on the microstructural refinement was explored as well as the corresponding evolution in the stress differential between the yield strength of martensite and the critical stress to induce martensite and SMA characteristics of Ni49.7Ti50.3, Ti50Ni30Pd20, and Ti50.3Ni33.7Pd16 SMAs. Severe plastic deformation via ECAE at temperatures from 300°C up to 450°C refined the grains from 50μm down to a range between 0.03μm and 0.3μm in Ni49.7Ti50.3 and 0.5μm and 1μm in TiNiPd alloys. Regardless of the material, the lower the ECAE temperature and the higher the ECAE strain path, the better the cyclic stability. ECAE led to an increase in the stress differential between the yield strength of martensite and critical stress to induce martensite due to observed microstructural refinement and this increase is responsible for the improvement in the cyclic stability of the aforementioned SMA characteristics in all investigated materials. Addition of Pd to the NiTi alloy reduced the thermal hysteresis from 36°C down to 11°C, and enhanced the cyclic stability of the SMA characteristics. In additions to positive influence of ECAE on cyclic stability, it also led to an increase in the fracture stress levels of the TiNiPd alloys due to the fragmentation or dissolution of the precipitates responsible for the premature failures. ECAE caused a slight reduction in the work output; however it was possible to obtain large stable work outputs under higher stress levels than unprocessed materials.

The effects of crystallographic orientation, temperature and heat treatment on superelastic response of Ni45Mn36.5Co5In13.5 single crystals were investigated. Superelastic experiments with and without various magnetic field were conducted under compression on a custom built magneto-thermo-mechanical test setup. Magnetostress, which is the difference in critical stress levels for the martensitic transformation with and without magnetic field, was determined as a function of crystallographic orientation, heat treatment and temperature parameters. Magnetostress of [111] crystals was observed to be much higher than that of [001] crystals with same heat treatment. Water quenched samples have the highest magnetostress among other samples with the same orientation that were oil quenched and furnace cooled. Crystal structure and atomic ordering of the samples were examined using Synchrotron High-Energy X-Ray Diffraction to rationalize observed differences. Magnetostress levels were also traced at various temperatures. A Quantum Design superconducting quantum interference device (SQUID) was utilized to examine the magnetic properties of the material. The difference in saturation magnetization at various temperatures was analyzed to explain the temperature effect on magnetostress. Calculations based on the energy conversion from available magnetic energy to mechanical work output were used to predict the magnetic field dependence of magnetostress, which provides a guideline in material selection for the reversible magnetic field induced martensitic phase transformation. Isothermal superelastic response and load-biased shape memory response of Co48Ni33Al29 single crystals were determined as a function of temperature and stress, respectively. The aim of the work is to provide a new direction to understand the anomaly of transformation strain and hysteresis for ferromagnetic shape memory alloys. Thermo-mechanical behavior of Co48Ni33Al29 single crystal was determined by a custom built thermo-mechanical compression setup based on an electromechanical test frame made by MTS. Transformation strain was observed to decrease with increasing applied stress in isothermal tests or increasing temperature in superelastic experiments. The variation in the lattice constant in martensite and austenite was verified to account for such a trend. It was also discovered that both thermal and stress hysteresis decreased with increasing applied stress and temperature, respectively. Multiple factors may be responsible for the phenomenon, including the increase of dislocation, the compatibility between martensite and austenite phase.

The use of nanostructures has become very common throughout high-tech industries. In order to enhance the applicability of Shape Memory Alloys (SMAs) in systems such as Nano-Electromechanical Systems, the phase transformation behavior of SMA nanostructures should be explored. The primary focus of this work is on the fabrication of metallic nanowires and the characterization of the phase transformation of SMA nanowires. Various metallic nanowires are fabricated through the use of the mechanical pressure injection method. The mechanical pressure injection method is a template assisted nanowire fabrication method in which an anodized aluminum oxide (AAO) template is impregnated with liquid metal. The fabrication procedure of the AAO templates is analyzed in order to determine the effect of the various fabrication steps. Furthermore, metallic nanowires are embedded into polymeric nano bers as a means to incorporate nanowires within other nanostructures. The knowledge obtained through the analysis of the AAO template fabrication guides the fabrication of SMA nanowires of various diameters. The fabrication of SMA nanowires with di fferent diameters is accomplished through the fabrication of AAO templates of varying diameters. The phase transformation behavior of the fabricated SMA nanowires is characterized through transmission electron microscopy. By analyzing the fabricated SMA nanowires, it is found that none of the fabricated SMA nanowires exhibit a size eff ect on the phase transformation. The lack of a size e ffect on the phase transition of SMA nanowires is contrary to the results for SMA nanograins, nanocrystals, and thin films, which all exhibit a size eff ect on the phase transformation. The lack of a size eff ect is further studied through molecular dynamic simulations. These simulations show that free-standing metallic nanowires will exhibit a phase transformation when their diameters are sufficiently small. Furthermore, the application of a constraint on metallic nanowires will inhibit the phase transformation shown for unconstrained metallic nanowires. Therefore, it is concluded that free-standing SMA nanowires will exhibit a phase transformation throughout the nanoscale, but constrained SMA nanowires will reach a critical size below which the phase transformation is inhibited.

In deep submicron region, scaling the sizes of devices and chips down is indispensable. The silicide at ultra-shallow extension area is used in order to keep low sheet resistance while junction depth is scaled. To introduce the implant between source and channel keeps high saturation current. Furthermore, we put two blocks of oxide between source and channel to suppress the short channel effect, which are able to resist depletions. We also demonstrate the capacitor-less memory cell. We use the variation of the charge and bias replacing the real capacitor. The device is promising candidate for reduced chip size. According to the simulation results of ISE TCAD, the device with silicide at ultra-shallow extension area and the implantation between source and channel provide higher saturation current. The MOS with block oxide has high Ion/Ioff and low DIBL. We simulate different materials, different high and width of the block oxide, and discuss the effects of those device¡¦ characteristics. We show two methods of the implantation which can improve the charge density of pseudo neutral region. Those three structures provide an solution to make device and chip be scaled down easily.

As the complexity of System-on-a-Chip (SoC) designs increases, embedded memory components gradually occupy a significant portion of the total area cost, and the reusable memory Intellectual Property (IP) design becomes a critical issue. In this thesis, an automatic cache generator is developed which can be easily integrated into the current cell-based design flow. The generated cache contains both hard IP and soft IP. The storage array circuits are implemented as hard IP to reduce the area cost. The cache control unit is realized as soft IP. The hard IP of the core memory circuits mainly store data and tag information. The implementations of tag arrays can be divided into two categories: RAM-tag design and CAM (Content Addressable Memory)-tag design. We adopt the CAM-tag style in our cache design because CAM cells have the functions of storage as well as data-matching, and thus can be easily used to realize the tag function in cache. The soft IP of cache controller implements the different writing strategies and block replacement methods. The input parameters of the cache generator include cache size, block size, information on set-associativity, writing strategy, replacement methods, etc. The output of the cache generator contains the RTL code for the soft IP and other necessary Models for the hard IP so that the generated cache can be mixed with other pure cell-based design modules during synthesis and placement-and-routing.

In recent years, the fundamental researches on nanocrystals have been received increasing attentions for the novel applications, especially the nonvolatile memory technology. Adoption of nanocrystals technology could solve the serious limitation suffered by the conventional nonvolatile memory, flash, while scaling down. Once the thin tunneling oxide of flash device has been created a leaky path, all the stored charge in the floating gate will be lost after numerous counts of data reading and writing. Hence, the thinning of tunneling oxide will become one of important keys to the scaling limitation. Furthermore, if the tunneling oxide can not be thinned any more, both the operation voltage and speed of memory can not be improved. These drawbacks will restrict the development of nonvolatile memory. Replacement of floating gate structure with nanocrystals could effectively avoid the data losing due to the leaky path in the thin tunneling oxide. All stored charges can¡¦t be lost through the few leaky paths since the charges are stored in distributed nanocrystals. The charges stored nearby the leaky path will be lost, but others are still kept in the distributed and independent nanocrystals. The advantages of metal nanocrystals has have higher density of states around Fermi level, stronger coupling with conduction channel, wide range of available work functions and smaller energy perturbation due to carrier confinement. So metal nanocrystals can reduce operate voltage, and increase write/erase speed and endurance. In this thesis, we will study of cobalt and cobalt-silicide as the memory storage element. The nanocrystals were formed by high temperature oxidation or metal rapid thermal annealing with all kinds of conditions. And we analyze the effect of electron storage at metal nanocrystals by means of material and electrical analysis.