Assessment of the accuracy of different standard methods for determining reservoir capacity and sedimentation     

Marcus Vinicius Estigoni  Artur José Soares Matos  Frederico Fabio Mauad 《Journal of Soils and Sediments》2014,14(7):1224-1234

Purpose

Determination of reservoir volume has been used in the calculation of sedimentation, hydrodynamic modelling, and dam safety assessment, among others, and the method used as well as its associated error play an important role in the quality of these studies. This study assessed the accuracy of reservoir volume calculations based on different standards for the definition of the spacing between bathymetric range lines. A technique for terrain modelling and a method for determining the survey accuracy are also proposed.

Materials and methods

The reference reservoir volume was based on highly detailed bathymetry (10 m resolution). Seven different spacings were selected, which generated 99 separate bathymetric data sets. For each data set, the volume was calculated based on a digital terrain model according to the usual model (triangular irregular network (TIN)) and according to the insertion of mesh points (IMP) method. This was then compared with the reference volume, and the accuracy of each survey was determined.

Results and discussion

Utilization of a highly detailed and reliable bathymetric survey allowed for the assessment of the associated error in each of the bathymetric data sets, as well as of the spacing standards analyzed. The accuracy of the standards analyzed using TIN modeling ranged from 0.31% to 14.40% (30 and 300 m, respectively). The high errors are attributed to the limitation of the TIN in representing regions near shores, producing incorrect shallow depth readings, resulting in a lower calculated volume than the real volume. IMP modeling exhibited great improvement in performance over the standard TIN (i.e., for 300 m accuracy of 5.51% for IMP and 14.40% for standard TIN), and in none of the cases were the generated volumes greater than the reference volume.

Conclusions

The IMP method proved to be consistent, improving quality of the data while reducing effort in field work. The low accuracies found showed that even surveys following the widely accepted standards contain errors of a magnitude that cannot be ignored. Thus, knowing and evaluating the survey accuracy is of fundamental importance. Definition of standard spacing for reservoirs proved to be unfeasible. This must be defined on a case-to-case basis, considering the error acceptable for the purpose of the survey.  相似文献   

A possible relativistic jetted outburst from a massive black hole fed by a tidally disrupted star     

Bloom JS  Giannios D  Metzger BD  Cenko SB  Perley DA  Butler NR  Tanvir NR  Levan AJ  O'Brien PT  Strubbe LE  De Colle F  Ramirez-Ruiz E  Lee WH  Nayakshin S  Quataert E  King AR  Cucchiara A  Guillochon J  Bower GC  Fruchter AS  Morgan AN  van der Horst AJ 《Science (New York, N.Y.)》2011,333(6039):203-206

Gas accretion onto some massive black holes (MBHs) at the centers of galaxies actively powers luminous emission, but most MBHs are considered dormant. Occasionally, a star passing too near an MBH is torn apart by gravitational forces, leading to a bright tidal disruption flare (TDF). Although the high-energy transient Sw 1644+57 initially displayed none of the theoretically anticipated (nor previously observed) TDF characteristics, we show that observations suggest a sudden accretion event onto a central MBH of mass about 10(6) to 10(7) solar masses. There is evidence for a mildly relativistic outflow, jet collimation, and a spectrum characterized by synchrotron and inverse Compton processes; this leads to a natural analogy of Sw 1644+57 to a temporary smaller-scale blazar.  相似文献   

Something in the eye of the beholder     

Blau H  Brazelton T  Keshet G  Rossi F 《Science (New York, N.Y.)》2002,298(5592):361-2; author reply 362-3

  相似文献   

Breakdown of cortical effective connectivity during sleep     

Massimini M  Ferrarelli F  Huber R  Esser SK  Singh H  Tononi G 《Science (New York, N.Y.)》2005,309(5744):2228-2232

When we fall asleep, consciousness fades yet the brain remains active. Why is this so? To investigate whether changes in cortical information transmission play a role, we used transcranial magnetic stimulation together with high-density electroencephalography and asked how the activation of one cortical area (the premotor area) is transmitted to the rest of the brain. During quiet wakefulness, an initial response (approximately 15 milliseconds) at the stimulation site was followed by a sequence of waves that moved to connected cortical areas several centimeters away. During non-rapid eye movement sleep, the initial response was stronger but was rapidly extinguished and did not propagate beyond the stimulation site. Thus, the fading of consciousness during certain stages of sleep may be related to a breakdown in cortical effective connectivity.  相似文献   

Pikeperch (Sander lucioperca) spermatozoa motility and volume regulation under different osmotic and ionic conditions     

Herrera  Fabio  Boryshpolets  Sergey  Mraz  Jan  Knowles  Jindriska  Bondarenko  Olga 《Fish physiology and biochemistry》2022,48(4):899-910

Fish Physiology and Biochemistry - Pikeperch (Sander lucioperca) is a highly profitable commercial species whose economic value has greatly increased in the last decade. As in other species, the...  相似文献