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51.
Infrastructure-as-a-Service (IaaS) cloud computing is gaining significant interest in industry and academia as an alternative platform for running HPC applications. Given the need to provide fault tolerance, support for suspend–resume and offline migration, an efficient Checkpoint-Restart mechanism becomes paramount in this context. We propose BlobCR, a dedicated checkpoint repository that is able to take live incremental snapshots of the whole disk attached to the virtual machine (VM) instances. BlobCR aims to minimize the performance overhead of checkpointing by persisting VM disk snapshots asynchronously in the background using a low overhead technique we call selective copy-on-write. It includes support for both application-level and process-level checkpointing, as well as support to roll back filesystem changes. Experiments at large scale demonstrate the benefits of our proposal both in synthetic settings and for a real-life HPC application. 相似文献
52.
The present study focuses on stiffness properties of woven textile reinforced polymeric composites with respect to hybridization, and geometry of reinforcement. The analyzed composites represent combinations of different fibre materials (E-glass, Kevlar 49, carbon HM) in a predetermined fabric geometry (a plane weave embedded in thermosetting polymeric resin) serving controlled properties and required performance. The effects of hybridization on the stiffness properties of woven textile composites have been studied with respect to the fibres materials, the unbalancing degree of fabrics, and the variation of compactness and undulation of yarns. Some undesirable effects in fabric geometry can be overcome by the combined effects of hybridization and compactness. 相似文献
53.
Constantin Claudiu Văduva Nicolae Vaszilcsin Andrea Kellenberger Mihai Medeleanu 《Journal of Applied Electrochemistry》2012,42(4):217-224
To improve the quality requirements for copper deposits, the influence of some inhibition agents added to the acidic copper bath has been studied. Several aromatic nitrogen compounds have been tested as inhibition agents, such as aniline, N-methylaniline, N-ethylaniline, N,N-dimethylaniline (DMA), and N,N-diethylaniline (DEA). The electrochemical behavior of these organic additives and the most relevant aspects of the electrochemical behavior of copper in acid solutions have been analyzed by cyclic voltammetry. At the same time, a correlation between voltammetric data and molecular properties of protonated amines obtained by molecular modeling has been performed. The morphology of the copper deposits obtained in the absence and presence of organic compounds has been studied by scanning electron microscopy. An improvement of the roughness degree and crystallite size upon addition of aromatic amine has been found. Best results were obtained for DMA and DEA working at room temperature (25 ± 0.1 °C) and 200 A m−2 current density, in 1 mol L−1 sulfuric acid solution with 50 g L−1 Cu2+. 相似文献
54.
Christo Angelov Wei Guan Nicolae Marian Feng Zhou Krzysztof Sierszecki S?ren Top 《Innovations in Systems and Software Engineering》2012,8(1):79-92
The widespread use of embedded systems requires the creation of industrial software technology that will make it possible to engineer systems being correct by construction. That can be achieved through the use of validated (trusted) components, verification of design models, and automatic configuration of applications from validated design models and trusted components. This design philosophy has been instrumental for developing COMDES—a component-based framework for distributed embedded control systems. A COMDES application is conceived as a network of embedded actors that are configured from instances of reusable, executable components—function blocks (FBs). System actors operate in accordance with a timed multitasking model of computation, whereby I/O signals are exchanged with the controlled plant at precisely specified time instants, resulting in the elimination of I/O jitter. The paper presents an analysis technique that can be used to validate COMDES design models in SIMULINK. It is based on a transformation of the COMDES design model into a SIMULINK analysis model, which preserves the functional and timing behaviour of the application. This technique has been employed to develop a feasible (light-weight) analysis method based on runtime observers. The latter are conceived as special-purpose actors running in parallel with the application actors, while checking system properties specified in Linear Temporal Logic. Observers are configured from reusable FBs that can be exported to SIMULINK in the same way as application components, making it possible to analyze system properties via simulation. The discussion is illustrated with an industrial case study—a Medical Ventilator Control System, which has been used to validate the developed design and analysis methods. 相似文献
55.
Virgil Gabriel Teodor Ionuţ Popa Nicolae Oancea 《The International Journal of Advanced Manufacturing Technology》2010,51(5-8):439-452
Generation of helical surfaces with cylinder-frontal tools (end mill tool or grinding wheels) as so as with cylindrical tools (planing tools) are proceedings used in the small lot productions manufacturing or for reparations. In many situations, the surfaces to be generated are known by measuring on three-dimensional measuring machines. In this way, is possible to define a generatrix expressed by sampled points, which impose specifically algorithms for the end mill tool’s profiling. In this paper, specifically proposed are algorithms for end mill tool and planing tool profiling, designated to generate helical surfaces known in discrete form. More is assumed that the helical surface’s generatrix may be expressed only by few points, three or four, so the helical surfaces generatrix may be expressed by inferior degree Bezier polynomials using topological geometry. One of the goals of this paper is to compare the numerical results obtained by the proposed algorithm with the results obtained from profiling theoretically methods, for the same surfaces types, in order to proof the new method quality. 相似文献
56.
This paper presents and investigates a novel approach for constructing a family of intersymbol interference (ISI)-free pulses that shows comparable or better ISI performance in the presence of sampling errors, compared with some recently proposed pulses. We propose and discuss a new parametric method for the design of Nyquist filter characteristics using constraints in frequency characteristics construction. The method for constructing the filter characteristics uses a piecewise polynomial approximation of an ideal optimized staircase characteristic by spline functions. The spline polynomials are used to approximate a function that must pass through specified points. The performances of new ISI-free pulses are studied with respect to the ISI error probability. This family provides flexibility in designing an appropriate pulse even after the roll-off factor has been chosen. The results for error probability outperform the fourth-degree polynomial pulse [4]. 相似文献
57.
Constantin Claudiu Văduva Nicolae VaszilcsinAndrea Kellenberger 《International Journal of Hydrogen Energy》2012
The catalytic effect of some aromatic amines towards hydrogen evolution reaction on copper in diluted sulfuric acid solution has been studied. Since amines facilitate the transport of protons from the solution bulk to the interface in the cathodic hydrogen evolution reaction, they are known as proton carriers. The catalytic effect of aniline, N-methylaniline, N-ethylaniline, N,N-dimethylaniline, N,N-diethylaniline, o-toluidine, m-toluidine and p-toluidine has been highlighted by linear sweep voltammetry. The kinetic parameters for the hydrogen evolution reaction (cathodic transfer coefficient 1-α and exchange current density io) in the presence of the studied aromatic amines were derived from the Tafel plots. It has been found that the catalytic effect of amines is active even at low concentration. Thus, in 0.5 mol L−1 H2SO4 solution the exchange current density increases by two orders of magnitude, from 2.01⋅10−5 A m−2 in the absence of aniline to 2.85⋅10−3 A m−2 in the presence of 10−4 mol L−1 aniline. The influence of amines concentration on the catalytic effect is described in detail for the case of m-toluidine. The results obtained by voltammetry have been compared with electrochemical impedance spectroscopy data. Furthermore, the kinetic parameters for the hydrogen evolution reaction have been determined as a function of temperature and amines concentration. 相似文献
58.
Ion Sava Liviu Sacarescu Iuliana Stoica Ileana Apostol Victor Damian Nicolae Hurduc 《Polymer International》2009,58(2):163-170
BACKROUND: One of the most important properties of the azobenzene chromophores is the photochemical trans–cis isomerization induced by UV or visible light. In azopolymers, the photoisomerization induces conformational changes in the polymer chains, which in turn lead to macroscopic variations in the chemical and physical properties of the surroundings and media. RESULTS: This work reports the photochromic behaviour and surface structuring capacity of azopolymers having rigid polyimide and flexible polysiloxane structures, respectively. These polymers have good thermostabilities, with the degradation process starting above 315 °C. The glass transition temperature of the azopolyimide is 228 °C, while that of the azopolysiloxane modified with thymine is 34 °C. CONCLUSION: The experiments show that the azobenzene groups can isomerize even in the case of the rigid polyimide, but the maximum degree of conversion to the cis isomer is less than in the case of the flexible polysiloxane. This behaviour is reversed in solution, probably due to both the thymine and azo group interactions and for conformational reasons. The azopolymers show a good surface structuring capacity. The polysiloxane is more sensitive in the case of low irradiation energy and irradiation time. By increasing the irradiation time for both polymers, the modulation depth increases and has comparable values. Copyright © 2008 Society of Chemical Industry 相似文献
59.
Anis Nurashikin Nordin Ioana Voiculescu Mona Zaghloul 《Microsystem Technologies》2009,15(8):1187-1193
Due to the sensitivity of the piezoelectric layer in surface acoustic wave (SAW) resonators to temperature, a method of achieving
device stability as a function of temperature is required. This work presents two methods of temperature control for CMOS
SAW resonators using embedded polysilicon heaters. The first approach employs the oven control temperature stabilization scheme.
Using this approach, the device’s temperature is elevated using on-chip heaters to Tmax = 42°C to maintain constant device temperature. Both DC and RF measurements of the heater together with the resonator were
conducted. Experimental results have indicated that the TCF of the CMOS SAW resonator of −97.2 ppm/°C has been reduced to
−23.19 ppm/°C when heated to 42°C. The second scheme uses a feedback control circuit to switch the on-chip heaters on and
off depending on the ambient temperature. This method provided reduction of the TCF from −165.38 ppm/°C, to −93.33 ppm/°C.
Comparison of both methods was also provided. 相似文献
60.
Predrag Lazi? Nicolae Atodiresei Mojtaba Alaei Stefan Blügel 《Computer Physics Communications》2010,181(2):371-3755
Nowadays the state of the art Density Functional Theory (DFT) codes are based on local (LDA) or semilocal (GGA) energy functionals. Recently the theory of a truly nonlocal energy functional has been developed. It has been used mostly as a post-DFT calculation approach, i.e. by applying the functional to the charge density calculated using any standard DFT code, thus obtaining a new improved value for the total energy of the system. Nonlocal calculation is computationally quite expensive and scales as N2 where N is the number of points in which the density is defined, and a massively parallel calculation is welcome for a wider applicability of the new approach. In this article we present a code which accomplishes this goal.