FMR Study of Co/Ti Bilayer Thin Films

. We focused on the interaction between two ferromagnetic cobalt layers through a non-magnetic titanium layer. The magnetic properties of the structure were characterized by ferromagnetic resonance technique (FMR). The data were collected as a function of non-magnetic titanium layer thickness. Co/Ti multilayer (Ti (50 {\AA})/Co(45 {\AA})/Ti(2-40 {\AA})/Co(40 {\AA})/Ti(100 {\AA}))films were grown onto naturally oxidized p-type single crystal Si (100) substrate at UHV condition with magnetron sputtering system at room temperature. The thickness of Ti spacer layer ranges from 2 to 40 {\AA} with 2 {\AA} steps. We did not observe usual optic and acoustic modes; instead we had two broad overlapped peaks for the films ranged from 6 {\AA} to 40 {\AA}. One interesting result was the high anisotropic resonance field values for these films. Exchange coupling between ferromagnetic layers causes shift on resonance field values but these shifts in our samples were much larger than expected. This large anisotropic behavior is not clear at the moment. Our theoretical model was not able to determine a value for the exchange coupling parameter. One reason can be the close thickness values for Co sublayers. The other reason can be the Ti non-magnetic layer. If titanium did not grow layer by layer on cobalt, the cobalt ferromagnetic layers may behave as a single layer. As a result one cannot observe exchange interaction between ferromagnetic layers through non-magnetic spacer.Comment: 6 pages, 5 figure

Data locality and parallelism optimization using a constraint-based approach

Cataloged from PDF version of article.Embedded applications are becoming increasingly complex and processing ever-increasing datasets. In the context of data-intensive embedded applications, there have been two complementary approaches to enhancing application behavior, namely, data locality optimizations and improving loop-level parallelism. Data locality needs to be enhanced to maximize the number of data accesses satisfied from the higher levels of the memory hierarchy. On the other hand, compiler-based code parallelization schemes require a fresh look for chip multiprocessors as interprocessor communication is much cheaper than off-chip memory accesses. Therefore, a compiler needs to minimize the number of off-chip memory accesses. This can be achieved by considering multiple loop nests simultaneously. Although compilers address these two problems, there is an inherent difficulty in optimizing both data locality and parallelism simultaneously. Therefore, an integrated approach that combines these two can generate much better results than each individual approach. Based on these observations, this paper proposes a constraint network (CN)-based formulation for data locality optimization and code parallelization. The paper also presents experimental evidence, demonstrating the success of the proposed approach, and compares our results with those obtained through previously proposed approaches. The experiments from our implementation indicate that the proposed approach is very effective in enhancing data locality and parallelization. © 2010 Elsevier Inc. All rights reserved

Multicore education through simulation

Cataloged from PDF version of article.A project-oriented course for advanced undergraduate and graduate students is described for simulating multiple processor cores. Simics, a free simulator for academia, was utilized to enable students to explore computer architecture, operating systems, and hardware/software cosimulation. Motivation for including this course in the curriculum is provided along with a detailed syllabus and an assessment demonstrating its successful impact on the students. © 2011 IEEE

A novel queue-aware wireless link adaptation mechanism and its fixed-point analytical model

A point-to-point (PTP) wireless link is studied that carries long-lived TCP flows and is controlled with active queue management (AQM). A cross-layer queue-aware adaptive modulation and coding (AMC)-based link adaptation (LA) mechanism is proposed for this wireless link to improve the TCP-level throughput relative to the case where AMC decisions are made based solely on the physical layer (PHY) parameters. The proposed simple-to-implement LA mechanism involves the use of an aggressive modulation and coding scheme (MCS) with high spectral efficiency and high block error rates when the queue occupancy exceeds a certain threshold, but otherwise a relatively conservative MCS with lower spectral efficiency and lower block error rates. A fixed-point analytical model is proposed to obtain the aggregate TCP throughput attained at this wireless link and the model is validated by ns-3 simulations. Numerical experimentation with the proposed analytical model applied to an IEEE 802.16-based wireless link demonstrates the effectiveness of the proposed queue-aware LA (QAWLA) mechanism in a wide variety of scenarios including cases where the channel information is imperfect. The impact of the choice of the queue occupancy threshold of QAWLA is extensively studied with respect to the choice of AQM parameters in order to provide engineering guidelines for the provisioning of the wireless link. © 2015, Ozturk and Akar

Compiler-directed energy reduction using dynamic voltage scaling and voltage Islands for embedded systems

Cataloged from PDF version of article.Addressing power and energy consumption related issues early in the system design flow ensures good design and minimizes iterations for faster turnaround time. In particular, optimizations at software level, e.g., those supported by compilers, are very important for minimizing energy consumption of embedded applications. Recent research demonstrates that voltage islands provide the flexibility to reduce power by selectively shutting down the different regions of the chip and/or running the select parts of the chip at different voltage/frequency levels. As against most of the prior work on voltage islands that mainly focused on the architecture design and IP placement related issues, this paper studies the necessary software compiler support for voltage islands. Specifically, we focus on an embedded multiprocessor architecture that supports both voltage islands and control domains within these islands, and determine how an optimizing compiler can automatically map an embedded application onto this architecture. Such an automated support is critical since it is unrealistic to expect an application programmer to reach a good mapping correlating multiple factors such as performance and energy at the same time. Our experiments with the proposed compiler support show that our approach is very effective in reducing energy consumption. The experiments also show that the energy savings we achieve are consistent across a wide range of values of our major simulation parameters

Scalar f0 and a0 mesons in radiative ϕ→K+K−γ decay

AbstractWe study the radiative ϕ→K+K−γ decay within a phenomenological framework by considering the contributions of the f0(980) and a0(980) scalar resonances. We consider the kaon-loop model and the no-structure model to evaluate these contributions and compare the results obtained in two models

Job promotion in midcareer: gender, recession, and “crowding”

Data from the National Longitudinal Survey of Youth 1979 indicate that, between 1996 and 2010, women, on average, lost some of the promotion momentum they had achieved at the beginning of midcareer, although they outperformed men in this regard. For both genders, the economic downturn of 2001 and the Great Recession of 2007–2009 contributed to reduced promotion probabilities. In the case of women, however, cohort effects, rather than the business cycle, seem to explain the promotion experience during the Great Recession. Promotions translate into higher real-wage increases, especially when coupled with growth in job responsibilities. Crowding effects, if not necessarily a thing of the past, are no longer manifested in reduced female promotion rates or earnings

The thickness of pitch: Crossmodal metaphors in Farsi, Turkish and Zapotec

Speakers use vocabulary for spatial verticality and size to describe pitch. A high–low contrast is common to many languages, but others show contrasts like thick–thin and big–small. We consider uses of thick for low pitch and thin for high pitch in three languages: Farsi, Turkish, and Zapotec. We ask how metaphors for pitch structure the sound space. In a language like English, high applies to both high-pitched as well as high-amplitude (loud) sounds; low applies to low-pitched as well as low-amplitude (quiet) sounds. Farsi, Turkish, and Zapotec organize sound in a different way. Thin applies to high pitch and low amplitude and thick to low pitch and high amplitude. We claim that these metaphors have their sources in life experiences. Musical instruments show co-occurrences of higher pitch with thinner, smaller objects and lower pitch with thicker, larger objects. On the other hand bodily experience can ground the high–low metaphor. A raised larynx produces higher pitch and lowered larynx lower pitch. Low-pitched sounds resonate the chest, a lower place than highpitched sounds. While both patterns are available from life experience, linguistic experience privileges one over the other, which results in differential structuring of the multiple dimensions of sound