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Measurement of the transverse energy flow in nucleus-nucleus collisions at 200 GeV per nucleon

During the last few years there has been considerable progress in the study of natural ecosystems. However, translation of the basic concepts system ecology into school curriculum is still in its early stages. Therefore the objectives of the present investigation were to study the structure and function of a desert ecosystem, to develop a desert ecology course and to evaluate it. The structure and function of the ecosystems were investigated in the Negev. Typical food chains were studied in two habitats. Laboratory work was carried out to obtain growth curves and oxygen consumption as a function of temperature. Compartment models were constructed to represent energy flow and energy exchange in the ecosystems.

Tailored time variations can enable efficient control over signal flows, giving rise to exotic wave phenomena. In this work, we demonstrate how abrupt temporal switching of the coupling between two cavities can tailor the energy flow between them beyond the limitations of static scenarios, enabling unitary excitation transfer. The proposed scheme is robust with respect to a wide range of nonidealities, with implications for classical and quantum phenomena, from computing to nanophotonic systems.

A study has been made of the vibrational energy flow mechanisms and time scales pertaining to the overtone stretch excitations of methyl and acetylenic CH stretches in propyne. Classical trajectories are used to interpret the experimental data for the overtone linewidths, as well as to analyze the role that individual modes play in determining energy flow. The full anharmonic potential surface for these calculations, including all modes, has been developed from spectroscopic and structural information, including the linewidth data. The principal results are: (1) The trajectory calculations show a localization transition, corresponding to a switch over from normal-mode behavior for CH3 excitations up to v≅3 to a local-mode CH excitation within the CH3 moiety for excitations of v≳6, with transition behavior for v=4,5. (2) The acetylenic CH shows local-mode behavior from v=1. Extremely long lifetimes are found for the excitations of this mode, and the trajectories indicate that the experimental width is predominantly rotational. (3) The rocking and deformation modes are dominant receiving modes in the relaxation of the methyl stretch. (4) A shorter lifetime is calculated for the v=6 vs the v=5 or v=7 overtones of the methyl C–H stretch. Experimental results are qualitatively consistent with this prediction. The origin of this shorter lifetime is a band of resonances between the stretch excitation and combinations of rocking, deformation, and pseudorotation modes. (5) CH3 internal rotation figures importantly in the relaxation of some levels (v=5, 8 of CH3) where it ‘‘closes the energy gap’’ for achieving resonant energy transfer. (6) For v=8 of the methyl CH, some direct energy transfer to both C–C≡C stretching modes is seen. The switching on of the stretches as receiving modes is a consequence of sufficiently strong interactions between the excited H and the C–C≡C chain, which take place at these high vibrational energies. (7) Evidence is found for long distance ‘‘through-space’’ energy transfer due to long-range dipole–dipole forces. This transfer occurs from the acetylenic to the methyl CH stretches. This result is illustrated for the v=2 excitation of the acetylenichydrogen, and constitutes a direct demonstration of intramolecular long-distance, through-space v–v energy transfer. These results demonstrate the potential importance of large amplitude modes such as rocking and deformation as initial receiving modes for vibrational energy from excited CH overtones. On the time scale probed here (∼1 ps), despite the availability of many degrees of freedom, the transfer process is dominated by specific energy transfer channels and by the specific behavior of individual modes, rather than by statistical considerations, which will certainly prevail on longer time scales.

Abstract In this review we will summarize new data on hardron-nucleus interactions. The possibility that quark-gluon plasma may be created in heavy ion collisions has led to renewed interest in hadron-nucleus collisions. In particular one hopes that understanding the energy loss of hadrons in h-A collissions will allow us to estimate the optimum energy in AA collisions in order to achieve maximum baryon and/or maximum energy density. This will allow us to choose the optimal experimental environment in the search for quark-gluon plasma. This review will thus omit many interesting results from hadron-nucleus collisions, such as the A dependence of lepton pair production, EMC effect and others. We will focus our attention on the following: (i) Estimating the rate of energy loss of the incident hadron as it propagates through the target. (ii) Determining where the enmergy is deposited in central hadron-nucleus collisions. It is clear that there is no direct or unique method of extrapolating our knowledge of h-A collisions to predict what will happen in AA-collisions. The knowledge and understanding of pp and pA collisions is, however, a useful and necessary guide to what one can expect in AA collisions. In this review we will concentrate on three experimental approaches to the study of h-A collisions. In Section 1 we will discuss the present status of pA → p + X inclusive measurements. In Section 2 measurements from visual detectors, in this case results from the 30″ hybrid spectrometer, which allows investigations of global event properties will be presented. In Section 3 data using 2π calorimeters, where one can trigger and measure transverse energy and energy flow over a given rapidity region, will be discussed. The conclusions will be given in Section 4.

This paper presents both criticism and suggested changes to boiler efficiency standards associated with fossil-fired steam generators. These standards include the widely used ASME PTC 4.1, PTC 4 and DIN 1942, and others. The chief criticism is inconsistent application of thermodynamic principles. Specifically, conceptual errors are made with application of reference temperatures and the treatment of shaft powers. When using computed fuel flow as a touchstone, it becomes obvious that arbitrary use of reference temperatures and/or use of capricious energy credits cannot dictate a system’s computed fuel flow. Efficiency, calorific value and fuel flow must have fixed definitions concomitant with a system’s useful energy flow. Thermodynamics is not an arbitrary discipline, the computed fuel needs of a system must describe the actual. Boiler efficiency requires the same treatment, as an absolute value, as actual fuel feed and emission flow. Boiler efficiencies and associated calorific values have obvious standing when judging contractual obligations, for thermal performance monitoring, and for confirming carbon emissions. Note that a 0.5 to 1% change in efficiency may well have significant financial consequences when testing a new unit, or the on-going costs associated with fuel and carbon taxes. This paper demonstrates that errors greater than 2% are entirely possible if following the current standards. This paper appeals to the resolution of efficiency at the 0.1% level. The power plant engineer is encouraged to read the Introduction and Summary & Recommendations sections while the thermodynamicist is requested to throughly review and critique the mid-sections. The author hopes such reviews will advocate for improvement of these important industrial standards.