1,841 research outputs found

    PETRI NET BASED MODELING OF PARALLEL PROGRAMS EXECUTING ON DISTRIBUTED MEMORY MULTIPROCESSOR SYSTEMS

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    The development of parallel programs following the paradigm of communicating sequen- tial processes to be executed on distributed memory multiprocessor systems is addressed. The key issue in programming parallel machines today is to provide computerized tools supporting the development of efficient parallel software, i.e. software effectively har- nessing the power of parallel processing systems. The critical situations where a parallel programmer needs help is in expressing a parallel algorithm in a programming language, in getting a parallel program to work and in tuning it to get optimum performance (for example speedup). . We show that the Petri net formalism is higly suitable as a performance modeling technique for asynchronous parallel systems, by introducing a model taking care of the parallel program, parallel architecture and mapping influences on overall system perfor- mance. PRM -net (Program-Resource- Mapping) models comprise a Petri net model of the multiple flows of control in a parallel program, a Petri net model of the parallel hardware and the process-to-processor mapping information into a single integrated performance model. Automated analysis of PRM-net models addresses correctness and performance of parallel programs mapped to parallel hardware. Questions upon the correctness of parallel programs can be answered by investigating behavioural properties of Petri net programs like liveness, reachability, boundedness, mutualy exclusiveness etc. Peformance of parallel programs is usefully considered only in concern with a dedicated target hard- ware. For this reason it is essential to integrate multiprocessor hardware characteristics into the specification of a parallel program. The integration is done by assigning the concurrent processes to physical processing devices and communication patterns among parallel processes to communication media connecting processing elements yielding an in- tegrated, Petri net based performance model. Evaluation of the integrated model applies simulation and markovian analysis to derive expressions characterising the peformance of the program being developed. Synthesis and decomposition rules for hierarchical models naturally give raise to use PRM-net models for graphical, performance oriented parallel programming, support- ing top-down (stepwise refinement) as well as bottom-up development approaches. The graphical representation of Petri net programs visualizes phenomena like parallelism, syn- chronisation, communication, sequential and alternative execution. Modularity of pro- gram blocks aids reusability, prototyping is promoted by automated code generation on the basis of high level program specifications

    Irradiance calibration with solar diffuser

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    The sun's energy is used in combination of movable and fixed diffuser plates, windows and apertures which are positioned in a series of test sequences (modes) for reflectance monitoring and calibration without the use of man-made sources. There are three embodiments, or implementations, of the invention--one embodiment uses two diffusers--a working diffuser and a secondary diffuser--the second embodiment uses three diffusers, a working diffuser, a secondary diffuser and a reference diffuser--and the third embodiment uses two diffusers--a working diffuser and a secondary diffuser, the latter also functioning as a cover for the working diffuser. The movable diffusers are mounted on rotatable cones and, in all embodiments, the sun is blocked from reaching the diffusers when not in use. Thus, the sun is used as a stable source for calibration and monitoring and the sun/diffuser combination is used in such a way that the response of all elements of the optical subsystem of the TOMS can be unambiguously and efficiently characterized with high accuracy and precision

    PERTUMBUHAN DAN PRODUKSI TIGA VARIETAS BAWANG MERAH (Allium ascalonicum L.) PADA BERBAGAI KONSENTRASI BIOSLURRY CAIR

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    Penelitian  bertujuan untuk mempelajari pengaruh bioslurry cair terhadap pertumbuhan dan produksi tiga varietas bawang merah. Penelitian ini dilaksanakan di kebun percobaan Fakultas Pertanian Universitas Hasanuddin, Makassar dimulai pada bulan Juni sampai Agustus 2020. Penelitian ini dilaksanakan dalam bentuk percobaan menggunakan rancangan petak terpisah (RPT). Petak utama adalah varietas yang terdiri atas 3 varietas yaitu: varietas bima, varietas super philip dan varietas tajuk. Sedangkan anak petak adalah konsentrasi bioslurry cair terdiri dari 4 taraf, yaitu: konsentrasi 0 mL.L-1; konsentrasi 50 mL.L-1; konsentrasi 100 mL.L-1 dan konsentrasi 150 mL.L-1. Hasil penelitian menunjukkan bahwa terjadi interaksi antara varietas tajuk dengan konsentrasi bioslurry cair 100 mL.L-1 menghasilkan produksi umbi per hektar terbaik (13,61 ton ha-1). Konsentrasi 100 mL.L-1 menunjukkan hasil terbaik pada parameter pengamatan tinggi tanaman (39,37 cm), jumlah daun (42,53 helai), diameter umbi (29,31 mm), jumlah umbi per tanaman (8,52 umbi), bobot basah umbi per tanaman (51,41 g), bobot basah umbi per petak (1,79 kg), bobot kering umbi per tanaman (44,85 g), bobot kering umbi per petak (1,57 kg), dan produksi umbi per hektar (11,50 ton ha-1). Varietas Tajuk menghasilkan rata-rata tanaman tertinggi yaitu 37.33 cm. Semua karakter pengamatan berkorelasi sangat kuat terhadap produksi umbi per hektar yaitu tinggi tanaman (0,72**), jumlah daun (0,88**), diameter umbi (0,82**), jumlah umbi per tanaman (0,88**), bobot basah umbi per tanaman (0,97**), bobot basah umbi per petak (0,97**), bobot kering umbi per tanaman (0,95**), dan bobot kering umbi per petak (0,95**)

    VLT Diffraction Limited Imaging and Spectroscopy in the NIR: Weighing the black hole in Centaurus A with NACO

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    We present high spatial resolution near-infrared spectra and images of the nucleus of Centaurus A (NGC 5128) obtained with NAOS-CONICA at the VLT. The adaptive optics corrected data have a spatial resolution of 0.06" (FWHM) in K- and 0.11" in H-band, four times higher than previous studies. The observed gas motions suggest a kinematically hot disk which is orbiting a central object and is oriented nearly perpendicular to the nuclear jet. We model the central rotation and velocity dispersion curves of the [FeII] gas orbiting in the combined potential of the stellar mass and the (dominant) black hole. Our physically most plausible model, a dynamically hot and geometrically thin gas disk, yields a black hole mass of M_bh = (6.1 +0.6/-0.8) 10^7 M_sun. As the physical state of the gas is not well understood, we also consider two limiting cases: first a cold disk model, which completely neglects the velocity dispersion; it yields an M_bh estimate that is almost two times lower. The other extreme case is to model a spherical gas distribution in hydrostatic equilibrium through Jeans equation. Compared to the hot disk model the best-fit black hole mass increases by a factor of 1.5. This wide mass range spanned by the limiting cases shows how important the gas physics is even for high resolution data. Our overall best-fitting black hole mass is a factor of 2-4 lower than previous measurements. With our revised M_bh estimate, Cen A's offset from the M_bh-sigma relation is significantly reduced; it falls above this relation by a factor of ~2, which is close to the intrinsic scatter of this relation. (Abridged)Comment: 12 pages, 14 figures, including minor changes following the referee report; accepted for publication in The Astrophysical Journa

    First Observation of 15Be

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    The neutron-unbound nucleus 15Be was observed for the first time. It was populated using neutron transfer from a deuterated polyethylene target with a 59 MeV/u 14Be beam. Neutrons were measured in coincidence with outgoing 14Be particles and the reconstructed decay energy spectrum exhibits a resonance at 1.8(1) MeV. This corresponds to 15Be being unbound by 0.45 MeV more then 16Be thus significantly hindering the sequential two-neutron decay of 16Be to 14Be through this state

    Tomato linalool synthase is induced in trichomes by jasmonic acid

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    Tomato (Lycopersicon esculentum) plants emit a blend of volatile organic compounds, which mainly consists of terpenes. Upon herbivory or wounding, the emission of several terpenes increases. We have identified and characterized the first two tomato monoterpene synthases, LeMTS1 and LeMTS2. Although these proteins were highly homologous, recombinant LeMTS1 protein produced (R)-linalool from geranyl diphosphate (GPP) and (E)-nerolidol from farnesyl diphosphate (FPP), while recombinant LeMTS2 produced β-phellandrene, β-myrcene, and sabinene from GPP. In addition, these genes were expressed in different tissues: LeMTS1 was expressed in flowers, young leaves, stems, and petioles, while LeMTS2 was strongest expressed in stems and roots. LeMTS1 expression in leaves was induced by spider mite-infestation, wounding and jasmonic acid (JA)-treatment, while LeMTS2 did not respond to these stimuli. The expression of LeMTS1 in stems and petioles was predominantly detected in trichomes and could be induced by JA. Because JA treatment strongly induced emission of linalool and overexpression of LeMTS1 in tomato resulted in increased production of linalool, we propose that LeMTS1 is a genuine linalool synthase. Our results underline the importance of trichomes in JA-induced terpene emission in tomato

    Nondisturbing extremum seeking control for multi-agent industrial systems

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    Industrial applications of extremum seeking control (ESC) can be a hit and miss affair. Although a gain in performance can be achieved, the dither applied to excite the system causes unwanted fluctuations in the performance of the system. The fluctuations in systems with a single extremum seeking loop are generally small. However, for systems with many extremum seeking loops, the fluctuations in each loop may add up to an intolerable amount of fluctuation in the total performance. In this article, we propose a method to cancel the dither-induced fluctuations in the overall system performance to a large extent by smartly constructing the dither signals in each extremum seeking loop using a centralized coordinator. The novelty of our method lies in the direct calculation of the dither signals that avoids the heavy computations required by other methods. Moreover, we provide a solvability analysis for the problem of cancelling dither-induced fluctuations in the total performance of the system. Furthermore, a complete stability analysis of the overall ESC scheme with dither coordination is given.publishedVersio
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