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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Discrete event dynamic systems 5 (1995), S. 115-140 
    ISSN: 1573-7594
    Keywords: time-parallel simulation ; asynchronous transfer mode networks ; burst-level simulation ; statistical multiplexer ; cellloss ratio ; broadband integrated services digital network
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The simulation of high-speed telecommunication systems such as ATM (Asynchronous Transfer Mode) networks has generally required excessively long run times. This paper reviews alternative approaches using parallelism to speed up simulations of discrete event systems, and telecommunication networks in particular. Subsequently, a new simulation method is introduced for the fast parallel simulation of a common network element, namely, a work-conserving finite capacity statistical multiplexer of bursty ON/OFF sources arriving on input links of equal peak rate. The primary performance measure of interest is the cell loss ratio, due to buffer overflows. The proposed method is based on two principal techniques: (1) the derivation of low-level (cell level) statistics from a higher level (burst level) simulation and (2) parallel execution of the burst level simulation program. For the latter, atime-division parallel simulation method is used where simulations operating at different intervals of simulated time are executed concurrently on different processors. Both techniques contribute to the overall speedup. Furthermore, these techniques support simulations that are driven by traces of actual network traffic (trace-driven simulation), in addition to standard models for source traffic. An analysis of this technique is described, indicating that it offers excellent potential for delivering good performance. Measurements of an implementation running on a 32 processor KSR-2 multiprocessor demonstrate that, for certain model parameter settings, the simulator is able to simulate up to 10 billion cell arrivals per second of wallclock time.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0730-2312
    Keywords: IL-3-dependent FDC-P1 cells ; histone H4 gene ; cell cycle control ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: To evaluate transcriptional mechanisms during cytokine induction of myeloid progenitor cell proliferation, we examined the expression and activity of transcription factors that control cell cycle-dependent histone genes in interleukin-3 (IL-3)-dependent FDC-P1 cells. Histone genes are transcriptionally upregulated in response to a series of cellular regulatory signals that mediate competency for cell cycle progression at the G1/S-phase transition. We therefore focused on factors that are functionally related to activity of the principal cell cycle progression at the G1/S-phase transition. We therefore focused on factors that are functionally related to activity of the principal cell cycle regulatory element of the histone H4 promoter:CDC2, cyclin A, as well as RB-and IRF-related proteins. Comparisons were made with activities of ubiquitous transcription factors that influence a broad spectrum of promoters independent of proliferation or expression of tissue-specific phenotypic properties. Northern blot analysis indicates that cellular levels of cyclin A and CDC2 mRNAs increase when DNA synthesis and H4 gene expression are initiated, supporting invoulvement in cell cycle progression. Using gel-shift assays, incorporating factor-specific antibody and oligonucleotide competition controls, we define three sequential periods following cytokine stimulation of FDC-P1 cells when selective upregulation of a subset of transcription factors is observed. In the initial period, the levels of SP1 and HiNF-P are moderately elevated; ATF, AP-1, and HiNF-M/IRF-2 are maximal during the second period; while E2F and HiNF-D, which contain cyclin A as a component, predominate during the third period, coinciding with maximal H4 gene expression and DNA synthesis. Differential regulation of H4 gene transcription factors following growth stimulation is consistent with a principal role of histone gene promoter elements in integrating cues from multiple signaling pathways that control cell cycle induction and progression. Regulation of transcription factors controlling histone gene promoter activity within the context of a staged cascade of responsiveness to cyclins and other physiological mediators of proliferation in FDC-P1 cells provides a paradigm for experimentally addressing interdependent cell cycle and cell growth parameters that are operative in hematopoietic stem cells. © 1995 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2019-06-28
    Description: Emissions of nitrogen oxides NO(x) are a significant problem in the United States. NO(x) are formed in any combustion process, therefore it is not surprising that NO(x) are emitted from the boilers at KSC. Research at UCF has shown (in the laboratory) that injecting H2O2 into hot simulated flue gases can oxidize the NO and NO2 to their acid gas forms, HNO2 and HNO3, respectively. These acid gases are much more water soluble than their counterparts, and theoretically can be removed easily by wet scrubbing. This technology was of interest to NASA, both for their boilers at KSC, and for their combustion sources elsewhere. However, it was necessary to field test the technology and to provide pilot-scale data to aid in design of full-scale facilities. Hence this project was initiated in May of 1996.
    Keywords: Environment Pollution
    Type: NASA-CR-203718 , NAS 1.26:203718 , UCF-1620204
    Format: application/pdf
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