1,741,033 research outputs found
ZHANG, F. & LIU, X-W. (2009) A review of the subgenus Diestrammena (Gymnaeta) from China (Orthoptera: Rhaphidophoridae Aemodogryllinae). Zootaxa, 2272, 21-36.
No full textZhang, F., Liu, X-W. (2009): ZHANG, F. & LIU, X-W. (2009) A review of the subgenus Diestrammena (Gymnaeta) from China (Orthoptera: Rhaphidophoridae Aemodogryllinae). Zootaxa, 2272, 21-36. Zootaxa 2288 (1): 68, DOI: 10.11646/zootaxa.2288.1.5, URL: http://dx.doi.org/10.11646/zootaxa.2288.1.
Influence of ac ageing on space charge dynamics in LDPE
No full textPolymeric materials have been widely used as insulation in power industry due to their excellent electrical properties. However, these properties deteriorate in time irreversibly when the material is subjected to electric stress. Although space charge is believed to play an important role in ac ageing, exact mechanisms are poorly understood due to very limited experimental data. In the present work efforts have been made to investigate the influence of ac ageing on space charge dynamics in low-density polyethylene (LDPE). LDPE films with 200mm were aged at 50 kV/mm at 50 Hz for various times at ambient temperature. Space charge dynamics in the samples prior to and after ageing were monitored using the pulsed electroacoustic (PEA) technique under dc electric stress. The results indicate that there is a significant amount of homocharge accumulation in the unaged sample due to charge injection. These injected charges are the captured by the deep traps originated from the interface between crystalline and amorphous regions in LDPE. Ageing under ac condition does not necessarily lead to an increase in amount of charge in the bulk but leads to an increase in mobility of charge carriers. Chemical analysis by infrared spectroscope (FTIR) reveals there are chemical changes taken place in the bulk of the material after ac ageing. It is believed that the chemical changes introduce shallow traps which promote the movement of charge carriers in the bulk. Consequently, the injected charges spread across the sample
Derivation of l-i SEIR model equations from l-i AIR model equations
No full textI presented a l-i SEIR epidemiological model recently (Liu X (2023) PloS one, 18(6): e0287196.). The l-i SEIR model was derived from the previously published l-i AIR model (a. Liu X (2021) Results Phys 20: 103712. b. Liu X & DeVries AC (2021) Research Square, https://wwwresearchsquarecom/article/rs-310822/v1). Here I describe the derivation process step by step in detail.THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV
Precise BER Formulas for Asynchronous QPSK-Modulated DS-CDMA Systems Using Random Quaternary Spreading Over Rayleigh Channels
No full textPrecise bit-error-ratio (BER) analysis of an asynchronous QPSK-modulated direct-sequence code-division multiple-access system using random quaternary spreading sequences for transmission over Rayleigh channels is performed based on the characteristic-function approach. Its accuracy is verified by our numerical simulation results and also compared with those of the Gaussian approximation. Index Terms—Asynchronous direct-sequence code-division multiple-access (DS-CDMA), bit-error-ratio (BER), precise, QPSK, quarternary spreading, Rayleigh
Effects of Rate Adaption on the Throughput of Random Ad Hoc Networks
No full textThe capacity of wireless ad hoc networks has been studied in an excellent treatise by Gupta and Kumar [1], assuming a fixed transmission rate. By contrast, in this treatise we investigate the achievable throughput improvement of rate adaptation in the context of random ad hoc networks, which have been studied in conjunction with a fixed transmission rate in [1]. Our analysis shows that rate adaptation has the potential of improving the achievable throughput compared to fixed rate transmission, since rate adaptation mitigates the effects of link quality fluctuations. However, even perfect rate control fails to change the scaling law of the per-node throughput result given in [1], regardless of the absence or presence of shadow fading. This result is confirmed in the context of specific adaptive modulation aided design examples
On the limits of application of mean motion resonant normal forms of the three-body problem for crossing orbits and close encounters
No full textIn this paper, we study the limits of application of canonical perturbation theory, specifically the validity of the normal form approximations, for the study of the mean motion resonances of the planar circular restricted three-body problem in the domain of orbits which cross, or are close to cross, the orbit of the secondary body. First, we discuss analytic issues related to the definition of a MMR normal form within a domain of the phase-space to which these orbits belong; then, we compute with a numerical method the canonical transformations defining the MMR normal forms. The limits of validity of the averaging method are studied by supplementing the information provided by the phase-portrait representations of the normal form Hamiltonian with analyses concerning the preservation of the quasi-integrals of motion obtained through one step of perturbation theory, and the computation of fast Lyapunov indicators regularized with respect to the close encounters with the secondary body. ..
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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