165 research outputs found
PERMEABILITY TO RESIDUAL WATER SATURATION IN OIL SATURATED PLUGS
ABSTRACT A series of laboratory experiments have been conducted to determine the permeability of brine close to irreducible water saturations with varying rock types, capillary pressures, saturations and permeabilities. X-ray tomography (CT) was used in one experiment as a quality assurance measure, visualizing the distribution of the flow of S wi phase in the sample. Water-saturated plugs attached to a water-wet ceramic membrane were drained by oil to S wi . Oil was then substituted by water at the inlet keeping both the water-and the oilsaturations in the plug constant. This was done in order to allow for water to flow through the plug and the membrane. A subsurface analogue to this laboratory experiment is a hydrocarbon-filled reservoir that is leaking water through a cap rock or a fault -keeping the hydrocarbons in place. The CT scan images showed that, although the overall flow rate was very low, the injected water moved quickly through the S wi -phase. Only a small fraction of the S wi volume contributed to this flow. The CT experiment also revealed some experimental artefacts such as spontaneous imbibition and gravity effects, which warrants further investigation. The result of the experiments verified that water could flow through different core plugs with varying S wi -phase permeability without forcing the oil through the membrane or changing the water saturation. The residual water permeability was dependent on the water saturation (S wi ) and the core plug permeability. Lowering the absolute permeability does not give a similar reduction in water permeability at S wi . The water permeability at S wi ranged from 0.02 ”D to 1 ”D. The absolute permeability for the different plugs ranged from approximately
Search for Direct CP Violation in Non-Leptonic Decays of Charged and Hyperons
A search for direct CP violation in the non-leptonic decays of hyperons has
been performed. In comparing the product of the decay parameters,
, in terms of an asymmetry parameter,
, between hyperons and anti-hyperons in the charged and decay sequence, we found no evidence of
direct CP violations. The parameter was measured to be .Comment: Submitted for publication; RevTex, 13 pages, 4 figure
Incremental bounded model checking for embedded software
Program analysis is on the brink of mainstream usage in embedded systems development. Formal verification of behavioural requirements, finding runtime errors and test case generation are some of the most common applications of automated verification tools based on bounded model checking (BMC). Existing industrial tools for embedded software use an off-the-shelf bounded model checker and apply it iteratively to verify the program with an increasing number of unwindings. This approach unnecessarily wastes time repeating work that has already been done and fails to exploit the power of incremental SAT solving. This article reports on the extension of the software model checker CBMC to support incremental BMC and its successful integration with the industrial embedded software verification tool BTC EMBEDDED TESTER. We present an extensive evaluation over large industrial embedded programs, mainly from the automotive industry. We show that incremental BMC cuts runtimes by one order of magnitude in comparison to the standard non-incremental approach, enabling the application of formal verification to large and complex embedded software. We furthermore report promising results on analysing programs with arbitrary loop structure using incremental BMC, demonstrating its applicability and potential to verify general software beyond the embedded domain
Preliminary results from E756 on the Îâ and Ωâ magnetic moments
We have used the spin precession technique to measure the Îâ and Ωâ magnetic moments. The preliminary results are ÎŒ(Îâ)=â0.64±0.02 nuclear magnetons and ÎŒ(Ωâ)=â2.0±0.2 nuclear magnetons where the error for both measurements is statistical. The polarization of Îââs produced at 2.5 mr by 800 GeV protons on a Be target was 11% while the polarization of Ωââs was consistent with zero. Polarized Îââs and Ωââs were produced using spin transfer from a polarized neutral hyperon beam. The Ωâ polarization at 325 GeV/c was 6.5%.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87375/2/374_1.pd
Polarization and spin transfer of Ωâ and Îâ hyperons at 800 GeV
Fermilab experiment E756 has measured the polarization of Wâ hyperons produced by 800 GeV protons to be small compared to that of Îâ hyperons. When produced by a neutral beam containing polarized Î and Î0 hyperons, both the Ωâ and the Îâ have a significant polarization indicating a large spin transfer at high energies.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87380/2/80_1.pd
Weak Hyperon Decays: Quark Sea and SU(3) Symmetry Breaking
An explanation of the difference in the values of the apparent ratios
for the S- and P- wave amplitudes of nonleptonic hyperon decays is proposed.
The argument is formulated in the framework of the standard pole model with
ground-state and excited baryons as intermediate
states for the P- and S- waves respectively. Under the assumption that the
dominant part of the deviation of from is due to large
quark sea effects, symmetry breaking in energy denominators is shown to
lead to a prediction for which is in excellent agreement with
experiment. This corroborates our previous unitarity calculations which
indicated that the matrix elements of the parity
conserving weak Hamiltonian between the ground-state baryons are characterized
by or more. A brief discussion of the problem of the
relative size of S- and P- wave amplitudes is given. Finally, implications for
weak radiative hyperon decays are also discussed.Comment: 26 pages, LATEX, 1647/PH IFJ Krako
Study of the Decay phi --> eta pi0 gamma with the KLOE detector
In a sample of 5.3x10^7 phi-decays observed with the KLOE detector at the
Frascati phi-factory Dafne we find 605 eta pi0 gamma events with eta -->
gamma\gamma and 197 eta pi0 gamma events with eta --> pi+ pi- pi0. The decay
phi --> eta pi0 gamma is dominated by the process phi --> a0 gamma. From a fit
to the eta pi0 mass spectrum we find BR(phi --> ao(980) gamma)= (7.4 +-
0.7)x10^-5.Comment: 12 pages, 6 figures, submitted to Phys.Lett.
Measurement of Decay Parameters for Decay
Based on 1.35 million polarized events, we measure the parameter
to be for
decay. New results for the parameters
and are also presented. Assuming that the
CP-violating phase-shift difference is negligible, we deduce the strong
phase-shift difference between the P-wave and S-wave amplitudes of the
final state to be . This strong phase-shift difference reduces the theoretical
uncertainty in estimating the level of CP violation in -hyperon decay.Comment: To be published in Physical Review Letter
Adjustment of photosynthetic activity to drought and fluctuating light in wheat
Drought is a major cause of losses in crop yield. Under field conditions, plants exposed to drought are usually also experiencing rapid changes in light intensity. Accordingly, plants need to acclimate to both, drought and light stress. Two crucial mechanisms in plant acclimation to changes in light conditions comprise thylakoid protein phosphorylation and dissipation of light energy as heat by non-photochemical quenching (NPQ). Here, we analyzed the acclimation efficacy of two different wheat varieties, by applying fluctuating light for analysis of plants, which had been subjected to a slowly developing drought stress as it usually occurs in the field. This novel approach allowed us to distinguish four drought phases, which are critical for grain yield, and to discover acclimatory responses which are independent of photodamage. In short-term, under fluctuating light, the slowdown of NPQ relaxation adjusts the photosynthetic activity to the reduced metabolic capacity. In long-term, the photosynthetic machinery acquires a drought-specific configuration by changing the PSII-LHCII phosphorylation pattern together with protein stoichiometry. Therefore, the fine-tuning of NPQ relaxation and PSII-LHCII phosphorylation pattern represent promising traits for future crop breeding strategies
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