97,244 research outputs found
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
Regularity points and Jensen measures for R(X)
No full textWe discuss two types of `regularity point', points of continuity and R-points for Banach function algebras, which were introduced by the first author and Somerset in [16]. We show that, even for the natural uniform algebras R(X) (for compact plane sets X), these two types of regularity point can be different. We then give a new method for constructing Swiss cheese sets X such that R(X) is not regular, but such that R(X) has no non-trivial Jensen measures. The original construction appears in the first author's previous work. Our new approach to constructing such sets is more general, and allows us to obtain additional properties. In particular, we use our construction to give an example of such a Swiss cheese set X with the property that the set of points of discontinuity for R(X) has positive area
The studies on structural and thermal properties of delithiated LixNi1/3Co1/3Mn1/3O2 (0 < x ≤ 1) as a cathode material in lithium ion batteries
No full textThe structural and thermal properties of the delithiated LixNi1/3Co1/3Mn1/3O2 (0 < x ≤ 1) material have been investigated by using diffraction and thermoanalytical techniques such as XRD and TG-DSC methods. XRD result shows that the delithiated materials maintain the O3-type structure with defined stoichiometric number at the range of 0.24 < x ≤ 1, exhibiting good crystal structural stability. The cobalt and nickel ions in the delithiated materials change their valence state (i.e. Co3+ to Co4+ and Ni3+ to Ni4+) when x < 0.49; the irreversible changes of the transformation may affect the first cycle of charge-discharge efficiency of the materials. A comparison of the results of TG-DSC with TPD-MS shows that the irreversible change of oxygen species during the delithiation process of LixNi1/3Co1/3Mn1/3O2 have great influence on the structural and thermal stability and reversibility of the materials. © 2006
NO(x) emission control technologies in sludge pyrolysis and combustion
No full textThe characteristic of NOx emission in sludge pyrolysis and sludge combustion has been carried out in the fixed bed reactor. The influence factors including final temperatures, the heating rates, types of sludge were studied on the effects of the NOx emissions. The results showed that CaO, MgO can lead to the reduction of NO. Staged combustion and injection of NH(3) have been performed to study the effects on NOx release.Engineering, EnvironmentalCPCI-S(ISTP)
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Joint Iterative Decoding of Trellis-Based VQ and TCM
No full textA joint video and channel coded system employing an iteratively decoded serial concatenation of a Vector Quantization (VQ) based video codec and a Trellis-Coded Modulation (TCM) scheme is proposed. The video codec imposes VQ-induced code constraints, which may be completely described by a trellis structure, which is employed as the basis for optimal minimum mean-squared-error VQ-encoding and -decoding. In the latter case, the Bahl-Cocke-Jelinek-Raviv (BCJR) algorithm is employed to facilitate the iterative exchange of soft information between the VQ and TCM decoder. An error-free video reconstruction quality is supported using 16-level Quadrature Amplitude Modulation (16QAM) based TCM for transmission over Rayleigh-fading channels at a Signal-to-Noise Ratio (SNR) per bit of 5.25 dB. This value is within 1.29 dB of the Rayleigh channel’s capacity at our system’s effective bandwidth-efficiency of 2 bits/s/Hz. Owing to its ability to exploit the VQ-induced code constraints during iterative decoding, the joint video and channel coding approach is found to consistently outperform the Shannonian source and channel separation philosophy. This is achieved at the cost of a 1.6 times higher computational complexity. Finally, the convergence of the iterative decoder is investigated with the aid of a novel so-called EXtrinsic Information Transfer (EXIT) chart
Intersystem soft handover for converged DVB-H and UMTS networks
No full textDigital video broadcasting for handhelds (DVB-H) is the standard for broadcasting Internet Protocol (IP) data services to mobile portable devices. To provide interactive services for DVB-H, the Universal Mobile Telecommunications System (UMTS) can be used as a terrestrial interaction channel for the unidirectional DVB-H network. The converged DVB-H and UMTS network can be used to address the congestion problems due to the limited multimedia channel accesses of the UMTS network. In the converged network, intersystem soft handover between DVB-H and UMTS is needed for an optimum radio resource allocation, which reduces network operation cost while providing the required quality of service. This paper deals with the intersystem soft handover between DVB-H and UMTS in such a converged network. The converged network structure is presented. A novel soft handover scheme is proposed and evaluated. After considering the network operation cost, the performance tradeoff between the network quality of service and the network operation cost for the intersystem soft handover in the converged network is modeled using a stochastic tree and analyzed using a numerical simulation. The results show that the proposed algorithm is feasible and has the potential to be used for implementation in the real environment
One step preparation of pure tau-MnAl phase with high magnetization using strip casting method
No full textFerromagnetic phase of Mn-Al exhibits great potential in the rare-earth free permanent magnetic materials due to its high magnetocrystalline anisotropy, high magnetization, high Curie temperature and low cost. In this work, the strip casting technique was applied to prepare MnAl magnetic phase. X-ray diffraction and energy dispersive X-ray analyses indicate that the as-prepared Mn54Al46 strip sample consists of pure tau-MnAl magnetic phase. It is found that the composition of Mn54Al46 is suitable to prepare tau-MnAl phase during the strip casting process. The Mn54Al46 strip sample synthesized through the strip casting exhibits a fairly high magnetization of 114 emu/g under a field of 5 T, while the coercivity of iHc = 2.8 kOe, magnetization of M-5T = 63.9 emu/g at room temperature can be obtained for Mn54Al46 powder sample. This preparation method can produce a large amount of tau-phase MnAl alloy and promote mass industrialized production. (C) 2017 Author(s)
Iteratively Decoded Irregular Variable Length Coding and Trellis Coded Modulation
No full textIn this paper we propose a novel Irregular Variable Length Coding (IrVLC) scheme for near-capacity joint source and channel coding. We employ a number of Variable Length Coding (VLC) component codebooks having different coding rates for encoding appropriately chosen fractions of the input source symbols. These fractions may be designed With the aid of EXtrinsic Information Transfer (EXIT) charts so that the EXIT curve shape of the IrVLC codec may be matched to that of a serially concatenated channel codec as closely as possible. In this way, an open EXIT chart tunnel may be created even at low SNR values that are close to the channel capacity. We detail the proposed serially concatenated and iteratively decoded IrVLC and Trellis Coded Modulation (TCM) designs that are capable of operating within 0.6 dB of the uncorrelated narrowband Rayleigh fading channel’s capacity at an effective bandwidth efficiency of 1.56 bit/s/Hz, assuming ideal Nyquist filtering. By contrast, the equivalent-rate VLC-based bench-marker schemes were found to be capable of operating at 1.1 dB from capacity, which is nearly double the discrepancy of the proposed IrVLC-TCM scheme
Air cathode of zinc-air batteries: A highly efficient and durable aerogel catalyst for oxygen reduction
No full textIn this communication, N-doped carbon shell encapsulated Co3O4@Co nanoparticles (NPs) were assembled on N-doped reduced graphene oxide to form non-precious metal aerogels (Co3O4@Co/N-r-GO) for oxygen reduction. In an alkaline medium, the aerogels exhibit comparable oxygen reduction reaction (ORR) performances to the commercial Pt/C with respect to half-wave potential, current density and durability. Zn–air batteries (ZABs) assembled with Co3O4@Co/N-r-GO as the air cathode display high average voltages of ∼1.38 and ∼1.3 V at a current density of 1 and 5 mA cm−2, respectively, and show a specific capacity of ∼800 mA h g−1. These results demonstrate that Co3O4@Co/N-r-GO materials are highly active and durable ORR catalysts for ZABs. The unique structure of the composite aerogel, i.e. the carbon shell encapsulated Co3O4@Co NPs and the 3D interconnected macroporous N-r-GO matrix, is responsible for its high ORR activity and stability.No Full Tex
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