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Solution-assisted Energy-savvy Synthesis of High-voltage Na2M2(SO4)(3) (M=3d metals) Alluaudite Family of Sodium Insertion Materials
No full textThe benchmarking of Fe3+/Fe2+ redox potential at 3.8 V (versus Na) in alluaudite-type Na2Fe2(SO4)(3), along with fast rate kinetics and excellent cycling stability (Nat. Commun., 5, 4358, 2014) has opened up new era of research in Na-ion research. Further insight to the reported material show synthesis is a careful solid-state method involving (a) formation of anhydrous FeSO4 from commercial FeSO4 center dot 7H(2)O, (b) prolonged milling and (c) longer annealing (350 degrees C, 24 h). Journey of such materials from laboratory to industry warrants economic, sustainable and scalable synthesis. Here, we report novel solution assisted-Ionothermal, aqueous spray-drying and pechini synthesis of Na2Fe2(SO4)(3), M = 3d metals] alluaudite cathodes. It will approach (i) salient feature of synthesis, (ii) structure/polymorphism, (iii) magnetic properties and (iv) electrochemical properties of Na2Fe2(SO4)(3) cathode materials. (C) 2018 Elsevier Ltd. All rights reserved
Preserving Semantic Relations for Zero-Shot Learning
No full textZero-shot learning has gained popularity due to its potential to scale recognition models without requiring additional training data. This is usually achieved by associating categories with their semantic information like attributes. However, we believe that the potential offered by this paradigm is not yet fully exploited. In this work, we propose to utilize the structure of the space spanned by the attributes using a set of relations. We devise objective functions to preserve these relations in the embedding space, thereby inducing semanticity to the embedding space. Through extensive experimental evaluation on five benchmark datasets, we demonstrate that inducing semanticity to the embedding space is beneficial for zero-shot learning. The proposed approach outperforms the state-of-the-art on the standard zero-shot setting as well as the more realistic generalized zero-shot setting. We also demonstrate how the proposed approach can be useful for making approximate semantic inferences about an image belonging to a category for which attribute information is not available
Disambiguation of Source and Trajectory Non-Stationarities of a Moving Acoustic Source
No full textIt is well known that when there is a relative motion between the transmitter (source) and receiver, a Doppler shift is observed in the spectral content of the received signal. In this paper, we investigate a scenario where the source signal itself has an innate spectral non-stationarity in addition to the non-stationarity introduced by the source motion relative to the receiver. Using only a single microphone recording, we show that these two kinds of non-stationarities are distinguishable and propose a method of separating them. Towards this, we propose a novel scheme of simulating the signal from a source traversing an arbitrary trajectory. The proposed simulation mechanism employs band-limited interpolation and non-uniform sampling to incorporate an acoustic source generating an arbitrary band-limited signal and moving along an arbitrary trajectory
Interference from GPU System Service Requests
No full textHeterogeneous systems combine general-purpose CPUs with domain-specific accelerators like GPUs. Recent heterogeneous system designs have enabled GPUs to request OS services, but the domain-specific nature of accelerators means that they must rely on the CPUs to handle these requests. Such system service requests can unintentionally harm the performance of unrelated CPU applications. Tests on a real heterogeneous processor demonstrate that GPU system service requests can degrade contemporaneous CPU application performance by up to 44% and can reduce energy efficiency by limiting CPU sleep time. The reliance on busy CPU cores to perform the system services can also slow down GPU work by up to 18%. This new form of interference is found only in accelerator-rich heterogeneous designs and may be exacerbated in future systems with more accelerators. We explore mitigation strategies from other fields that, in the face of such interference, can increase CPU and GPU performance by over 20% and 2 x, respectively, and CPU sleep time by 4.8 x. However, these strategies do not always help and offer no performance guarantees. We therefore describe a technique to guarantee quality of service to CPU workloads by dynamically adding backpressure to GPU requests
Gaze Controlled Interface For Limited Mobility Environment
No full textThis paper investigates design constraints for developing GUI (Graphical User Interfaces) in limited mobility environments. In particular, we have presented a gaze controlled interface for users with severe physical impairment and for pilots in military aviation who are constrained by situational impairment. We have developed and implemented algorithms to investigate visual search pattern and improve pointing and selection tasks in eye gaze controlled GUI. User studies in both environments show that for situational impaired users, there is improved flying performance and significant reduction in pointing and selection times for secondary mission control tasks compared to existing interaction systems
An Auxiliary-Capacitor-Based Active Phase Converter With Reduced Device Current Stress
No full textReduced switch active phase converters (APC) are cost-effective solutions for running three-phase loads from single-phase grids. This paper proposes a novel auxiliary-capacitor-based APC (AC-APC) for this application. The combination of the topological location of the auxiliary capacitor and the control of the AC-APC reduces current stress on the semiconductor devices. In this paper, a selection criterion for the optimal auxiliary capacitor value is formulated to reduce the device currents in such a way that the overall efficiency is enhanced. This paper presents a comparative analysis of converter volt-ampere (VA) rating and device power loss for conventional H-bridge active front-end and inverter-based topology, APC, and AC-APC. To evaluate the efficacy of the proposed AC-APC, an experimental study is conducted on the APC and the AC-APC feeding a 3-hp three-phase induction motor. At a full load of 2.5 kW and 0.8 power factor, the measured maximum efficiency of the AC-APC is 2% higher than that of the APC. Analytical evaluation of converter currents and device power loss are in close agreement with experimental observations
Mixing and warming of cryogenic hydrogen releases
No full textLaboratory measurements were made on the concentration and temperature fields of cryogenic hydrogen jets. Images of spontaneous Raman scattering from a pulsed planar laser sheet were used to measure the concentration and temperature fields from varied releases. Jets with up to 5 bar pressure, with near-liquid temperatures at the release point, were characterized in this work. This data is relevant for characterizing unintended leaks from piping connected to cryogenic hydrogen storage tanks, such as might be encountered at a hydrogen fuel cell vehicle fueling station. The average centerline mass fraction was observed to decay at a rate similar to room temperature hydrogen jets, while the half-width of the Gaussian profiles of mass fraction were observed to spread more slowly than for room temperature hydrogen. This suggests that the mixing and models for cryogenic hydrogen may be different than for room temperature hydrogen. Results from this work were also compared to a one-dimensional (streamwise) model. Good agreement was seen in terms of temperature and mass fraction. In subsequent work, a validated version of this model will be exercised to quantitatively assess the risk at hydrogen fueling stations with cryogenic hydrogen on-site
COLOR BILATERAL FILTERING USING STRATIFIED FOURIER SAMPLING
No full textBrute force implementation of the bilateral filter is known to be prohibitively slow. Several fast approximations have been proposed in the literature that are able to accelerate the filtering without perceptible loss of filtering quality. In particular, it has been shown that by replacing the range kernel (usually Gaussian) of the bilateral filter with its Fourier approximation, the filtering can be performed using fast convolutions. While an accurate Fourier approximation of a one-dimensional Gaussian (for grayscale filtering) can be obtained using N similar to 10 terms, a comparable approximation in three dimensions (for color filtering) requires N-3 Fourier terms, and proportionate number of convolutions. As shown in prior work, we can overcome this problem using Monte Carlo (MC) sampling. In this paper, we demonstrate that the variance of MC sampling can be reduced using stratified sampling, i.e., by conditionally sampling the low and high frequency terms. Importantly, we are able to cut down the pixelwise fluctuation of the filtered output as a result. We analytically compute the variances of MC and stratified sampling, whereby the variance reduction is evident. The PSNR fluctuation of our approximation is also shown to be smaller than existing Monte-Carlo algorithms
Fast Secure Computation for Small Population over the Internet
No full textSecure Multi-Party Computation (MPC) with small number of parties is an interesting area of research, primarily due to its ability to model most real-life MPC applications and the simplicity and efficiency of the resulting protocols. In this work, we present efficient, constant-round 3-party (3PC) and 4-party (4PC) protocols in the honest-majority setting that achieve strong security notions of fairness (corrupted parties receive their output only if all honest parties receive output) and guaranteed output delivery (corrupted parties cannot prevent honest parties from receiving their output). Being constant-round, our constructions are suitable for Internet-like high-latency networks and are built from garbled circuits (GC). Assuming the minimal model of pairwise-private channels, we present two protocols that involve computation and communication of a single GC-(a) a 4-round 3PC with fairness, (b) a 5-round 4PC with guaranteed output delivery. Empirically, our protocols are on par with the best known 3PC protocol of Mohassel et al. CCS 2015] that only achieves security with selective abort, in terms of the computation time, LAN runtime, WAN runtime and communication cost. In fact, our 4PC outperforms the 3PC of Mohassel et al. significantly in terms of per-party computation and communication cost. With an extra GC, we improve the round complexity of our 4PC to four rounds. The only 4PC in our setting, given by Ishai et al. CRYPTO 2015], involves 12 GCs. Assuming an additional broadcast channel, we present a 5-round 3PC with guaranteed output delivery that involves computation and communication of a single GC. A broadcast channel is inevitable in this setting for achieving guaranteed output delivery, owing to an impossibility result in the literature. The overall broadcast communication of our protocol is nominal and most importantly, is independent of the circuit size. This protocol too induces a nominal overhead compared to the protocol of Mohassel et al
Method to Model Input Voltage Ripple in Multi-Domain Fully Integrated Voltage Regulators
No full textThe on-chip power domains of the latest generation of high performance server microprocessors are generated using integrated switched mode dc-dc converters also known as Fully Integrated Voltage regulators (FIVR). The multi-domain FIVRs in the chip share a common input power supply and the input voltage ripple can be quite high when all of them switch together. The modeling of the input voltage ripple in multi-domain FIVRs using circuit simulation tools such as SPICE is a tedious task. This paper proposes a simple method to accurately model the steady state input voltage ripple using the Harmonic Domain (HD) method