On the estimation of Morison force coefficients and their predictive accuracy for very rough circular cylinders

This paper makes an assessment of the various method that may be used to analyse experiment data on the force experienced by a circular cylinder in waves and combined wave and current flows to estimate drag and inertia coefficients for use in Morison's equation. Most of the widely used techniques are considered together with a weighted least squares approach for time domain analysis. A set of data obtained from experiments on heavily roughened circular cylinders of diameters 0.513 and 0.216 m in the Delta wave flume at De Voorst in Holland in waves and simulated current has been analysed in turn by all these techniques. The experiment data was split into two halves. The first was used for the analyses and the second was used to assess the predictive accuracy of Morison's equation. Using the force coefficients obtained from the different analysis techniques corresponding predicted force time series were constructed using the particle kinematics measured in the second parts of the data sets. These predicted time series were then compared with the corresponding measured force time histories. The root mean square error and the bias in the estimation of maximum force in each wave cycle are used as measures of predictive accuracy and as a basis for comparing the efficiency of the different analysis techniques. It was found that the weighted least square method generally gave the best predictive accuracy, but only by a small margin.     

The effect of accelerated soil erosion on hillslope morphology

Intensive agricultural land use can have detrimental effects on landscape properties, greatly accelerating soil erosion, with consequent fertility loss and reduced agricultural potential. To quantify the effects of such erosional processes on hillslope morphology and gain insight into the underlying dynamics, we use a twofold approach. First, a statistical analysis of topographical features is conducted, with a focus on slope and gradient distributions. The accelerated soil erosion is shown to be fingerprinted in the distribution tails, which provide a clear statistical signature of this human-induced land modification. Theoretical solutions are then derived for the hillslope morphology and the associated creep and runoff erosion fluxes, allowing us to distinguish between the main erosional mechanisms operating in disturbed and undisturbed areas. We focus our application on the landscape at the Calhoun Critical Zone Observatory in the US Southern Piedmont, where severe soil erosion followed intensive cotton cultivation, resulting in highly eroded and gullied hillslopes. The observed differences in hillslope morphologies in disturbed and undisturbed areas are shown to be related to the disruption of the natural balance between soil creep and runoff erosion. The relaxation time required for the disturbed hillslopes to reach a quasi-equilibrium condition is also investigated. © 2019 John Wiley & Sons, Ltd.     

Access to fisheries in the maritime frontier of Palawan Province,Philippines

Globally, capital investments are intensifying extraction and contestation over resources in frontier spaces, yet most discussion has focused on terrestrial frontiers. This paper shifts this focus to bring a scaled political ecology approach to examine the access dynamics of fisheries trade in the maritime frontier of Palawan province, the Philippines. We adapt the linked concepts of access and exclusion to highlight how access dynamics unfold at multiple scales. At the local scale, social relations of class and ethnicity serve as important markers of difference that inform control over access to fisheries resources. At the regional scale, we show how engagement in fisheries trade is also shaped by broader historical and geographical contexts of migration and land use change. Access dynamics unfold at multiple inter‐related scales to heavily influence the differentiated social outcomes of expanded fisheries trade.     

Photoelectric and visual observations of AM Cas

According to statistical informations the orbital period of this cataclysmic binary of Z Camelopardalis type should be in the range between 0^d.10 and 0^d.19. A sole deep minimum was found photoelectrically. It lasted about 40 minutes and had an amplitude of nearly 2 mag in U. For reasons described in detail it can hardly be interpreted as an eclipsing one. Possibly there is no contribution to the light variation of AM Cas from orbital motion.     

Zur Abschätzung der Zyklenlänge bei langzyklischen U-Geminorum-Sternen

Several methods for estimating very long mean cycle lengths of U Geminorum type variables and the influence of observational gaps are discussed. The well-observed star SW UMa serves as an example for comparing statistical findings with more direct evalutions; the agreement is not bad.     

Density profiles of suspected optical counterparts of gamma-ray bursts

Four suspected optical flashes on archival plates with coordinates within or near to the error boxes of gamma-ray bursts, respectively, are investigated by surface photometry, Their density profiles are shown to be consistent with that of stars of similar magnitude. Hence, the suspected flashes are not likely to be plate defects but real objects on the sky.     

Astrophysical statistics of compact galaxies near the galactic north pole. Part II. Blue galaxies in the tautenburg catalogue of compact galaxies

Aus dem Tautenburger Katalog von 745 kompakten Galaxien in 4 Feldern um M3 wurden blaue Objekte selektiert. Dies geschah mit Hilfe des Farbenindex U – B ≧ −0.40 mag und durch spektroskopische Inspektion auf Objektivprismen-aufnahmen. Es wurden 45 Objekte als blau oder als emissionsverdächtig befunden.     

Search for Optical Identifications in the 5C3-Radio Survey II. Statistical Treatment and Results

On plates of the large Schmidt-telescope of Karl-Schwarzschild-Observatory Tautenburg, taken by F. BÖRNGEN, 139 radio sources of the ₅C₃ area were inspected for possible identifications with optical objects. The results are published in paper I and in the appendix of the present paper II. A detailed analysis of these objects showed a relatively large number of about 65 real identifications up to the utmost plate limit B ≈ 21^m.7, which corresponds to an identification rate of about 47%. The individual reliability of each possible optical identification is estimated (table 6). Apparently the identified objects (see tables 4 and 6) are galaxies, “blue” and “neutral” quasars, and one H II-region of the Andromeda nebula. It is of great cosmological interest that no “red” quasars could be found.     

Structural Investigations in the Central Part of the Coma Cluster on the Base of Equidensity Diagrams. I.

On the base of a photographic plate in system V, which was taken with the 134/200/400 cm Schmidt camera of the Karl-Schwarzschild-Observatorium Tautenburg maximal diameters of galaxies in the centre of the Coma cluster are determined by photographic equidensitometry. An other system of diameters is determined for medium densities of the objects. The results are compared with ROOD and BAUM'S who derived the diameters by visual measurements on plates taken with the 5-metre telescope of the Hale Observatories. Both statistics contain galaxies up to 19^m. They are complete up to 17^m.5. It is pointed out that the Tautenburg diameters are in the mean 3 times larger than those derived by ROOD and BAUM. Diameter-magnitude diagrams and ellipticities of the objects are derived, further photometric corrections for tilted objects. For describing the general structure of the cluster diameter functions are derived instead of magnitude functions. The accuracy of a brightness determination by the equidensity method from the diameter-magnitude diagrams is nearly twice better than according to ROOD and BAUM.