The Estimation of the Mean Size of Ship Domains

1983 ◽  
Vol 36 (1) ◽  
pp. 130-136 ◽  
Author(s):  
W. G. P. Lamb
Keyword(s):  
Domain Size ◽  
Time Intervals ◽  
The North ◽  
Maximum Value ◽  
Nearest Point ◽  
The North Sea ◽  
Mean Size ◽  
Average Domain Size ◽  
The Mean ◽  
Average Domain

Efforts to determine the mean size of ship ‘domains’ from measurements of the distribution of ships in the vicinity of an individual ship have been made by several workers, particularly by Goodwin, who made extensive observations in the Sunk Lightship area of the North Sea. The work involved plotting the positions of vessels at time intervals of a few minutes to estimate the number of ships in an annulus about a central ship, or alternatively the number per unit area at various distances from a central ship. These figures were used to obtain distribution curves from which the average domain could be estimated. The work of Curtis and Barratt on the validation of simulator studies of passing manoeuvres in fog, in which the nearest point of approach of ship's tracks was determined, serves to illustrate an alternative method based on the distribution of the density of tracks. In both procedures use is made of the point at which the distribution function first returns to the value which would obtain if the distribution were uniform, that is, if ship domains were absent. Some doubts have been expressed as to the validity of using the position of the cross-over point as a measure of the average domain size, and also whether it would be more appropriate to employ the position of the maximum value of the functions.

Reproductive biology of Eledone moschata (Cephalopoda: Octopodidae) in the Aegean Sea (Izmir Bay, Turkey)

2007 ◽  
Vol 87 (4) ◽  
pp. 967-970 ◽  
Author(s):  
Okan Akyol ◽  
Halil Şen ◽  
H. Tuncay Kınacıgil
Keyword(s):  
Gonadosomatic Index ◽  
Aegean Sea ◽  
Monthly Basis ◽  
The North ◽  
Eastern Aegean ◽  
North Eastern ◽  
Winter Peak ◽  
Mean Size ◽  
The Mean ◽  
Two Peaks

Reproductive properties of Eledone moschata from the north-eastern Aegean Sea are reported for the first time. A total of 471 specimens was collected during monthly samplings from December 2004 to November 2005. The mantle lengths of the species were between 4.5 and 15.0 cm with an average of 8.1 cm ±0.15 for 204 males, and between 2.7 and 14.0 cm with an average of 7.8 cm ±0.12 for 267 females. The annual sex ratio (males: females) of the sampled specimens was 1:1.31. Maturity stages were recorded on a monthly basis in both sexes. The highest monthly percentage of mature females (21%) and males (46%) was recorded in January 2005 and June 2005, respectively. The monthly and seasonal gonadosomatic index (GSI) results indicated that E. moschata shows two annual reproduction peaks for each sex. For males, the first spring peak occurs in March–June and the second, autumn peak is in November. For females, the first summer peak occurs in May–June and the second, winter peak is in January, respectively. On the other hand, the reproductive season extends from November to July with two peaks in the Aegean Sea. Total oocyte stock varied from 273 to 2896 with a mean of 836 ±193 oocytes. The mean size of the oocytes was 6.26 ±0.10 mm. The maximum oocyte size found was 10.7 mm. The mean length of spermatophores was of 13.66 ±0.08 mm (range: 7.3–18.3) and their average number was 52 ±6 (range: 6–172).

Long-term variability in North Sea zooplankton off the Northumberland coast: productivity of small copepods and analysis of trophic interactions

1988 ◽  
Vol 68 (1) ◽  
pp. 143-164 ◽  
Author(s):  
John C. Roff ◽  
Ken Middlebrook ◽  
Frank Evans
Keyword(s):  
North Sea ◽  
Trophic Interactions ◽  
Growth Rates ◽  
Larval Fish ◽  
The North ◽  
The North Sea ◽  
The Mean ◽  
June July

All groups of meso- and macro-zooplankton in the North Sea off Northumberland, at a depth of 53 m, were studied during a 15-year period (1969–83); copepod productivity was estimated from biomass and growth rates. Phytoplankton were seasonally bi-modal with peaks in April and August–October; copepods were uni-modal peaking in June–July. The predatory zooplankters: larval fish, decapods, ctenophores, medusae (the summer-autumn predators) peaked between May and September, while chaetognaths and euphausiids (the winter predators) peaked in December–January. Copepods and the summer-autumn predators were seasonally and inter-annually positively correlated, and declined in abundance from 1974 to 1980. Euphausiids and chaetognaths on the contrary increased in abundance during these years, and were seasonally and inter-annually negatively correlated to the copepods. The mean annual abundance of copepods was positively related to the previous winter's minimum, and inversely related to the abundance of chaetognaths and euphausiids. Annual copepod productivity averaged 1260 kJ m-2 year-1, and showed no relationship to other groups of plankton.

scholarly journals Estimation of the age-specific rate of natural mortality for Shetland sandeels

2004 ◽  
Vol 61 (2) ◽  
pp. 159-164 ◽  
Author(s):  
R.M. Cook
Keyword(s):  
Survey Data ◽  
Population Analysis ◽  
Mean Value ◽  
Specific Rate ◽  
Natural Mortality ◽  
The North ◽  
Virtual Population ◽  
Stock Assessments ◽  
The North Sea ◽  
The Mean

Abstract It is generally difficult to obtain reliable direct estimates of natural mortality, M, from conventional fisheries data and stock assessments. However, as a result of the closure of the Shetland sandeel (Ammodytes marinus) fishery from 1991 to 1994 and in the absence of any significant fishery in other years, research vessel survey data offer a rare opportunity to obtain estimates of M directly. A model is described that assumes that M can be decomposed into an age effect and year effects. Application of the model to the survey data produces values of M that decline from 2.1 for 0-group fish to 0.6 at age 2. There is some indication of an increase for ages 4 and older. Although there does not appear to be an overall trend in the mean value of M for the period 1985–1999, the annual values change by up to 50%. The values calculated from the model are in line with estimates obtained for the North Sea from multispecies virtual population analysis (MSVPA).

scholarly journals Age and Growth in Phocoena Phocoena Linnaeus, 1758 (Cetacea, Odontoceti) from the North Sea

1978 ◽  
Vol 48 (1) ◽  
pp. 16-28 ◽  
Author(s):  
W.L. van Utrecht
Keyword(s):  
North Sea ◽  
Posterior Part ◽  
The Body ◽  
Age And Growth ◽  
Body Measurements ◽  
Lower Growth ◽  
The North ◽  
The North Sea ◽  
Lower Growth Rate ◽  
The Mean

Data and material are collected from 106 Harbour Porpoises (P. phocoena) from the southern part of the North Sea. All animals are accidentally caught or found stranded. The greatest length for males in the sample is 151 cm, for females 186 cm. For detailed analysis of body measurements, 30 males and 37 females are selected, while from 20 males and 34 females teeth are used for age analysis. The analysis of the body measurements shows sexual dimorphism in the anterior and posterior part of the back, in the flukes and flippers and in the position of the genital slit. The maximum number of dentinal layers found in the teeth is 12. Males attain sexual maturity after the deposition of 5 dentinal layers, females when 6 layers are formed, at a body length of about 135 cm and 150 cm, respectively. Some evidence is found that the population of P. phocoena from the North Sea has a lower growth rate than the population from Canadian waters. The gestation period is estimated to be eleven months, the peak of the birth period being in June. The animals are born at a length varying between 67 cm to 80 cm. Growth of the visceral organs is isogonic. The mean weight of the organs is greater in females than in males.

scholarly journals Size and Strength of Tropical Cyclones as Inferred from QuikSCAT Data

2012 ◽  
Vol 140 (3) ◽  
pp. 811-824 ◽  
Author(s):  
Kelvin T. F. Chan ◽  
Johnny C. L. Chan
Keyword(s):  
Tropical Cyclones ◽  
High Strength ◽  
Outer Core ◽  
The North ◽  
Large Size ◽  
Tangential Wind ◽  
Ocean Surface Winds ◽  
Mean Size ◽  
The Mean ◽  
Potential Factors

A comprehensive statistical climatology of the size and strength of the tropical cyclones (TCs) occurring over the western North Pacific (WNP; including the South China Sea) and the North Atlantic (NA; including the Gulf of Mexico and the Caribbean Sea) between 1999 and 2009 is constructed based on Quick Scatterometer (QuikSCAT) data. The size and strength of a TC are defined, respectively, as the azimuthally averaged radius of 17 m s−1 of ocean-surface winds (R17) and the azimuthally averaged tangential wind within 1°–2.5°-latitude radius from the TC center (outer-core wind strength, OCS). The mean TC size and strength are found to be 2.13° latitude and 19.6 m s−1, respectively, in the WNP, and 1.83° latitude and 18.7 m s−1 in the NA. While the correlation between size and strength is strong (r ≈ 0.9), that between intensity and either size or strength is weak. Seasonally, midsummer (July) and late-season (October) TCs are significantly larger in the WNP, while the mean size is largest in September in the NA. The percentage frequency of TCs having large size or high strength is also found to vary spatially and seasonally. In addition, the interannual variation of TC size and strength in the WNP correlate significantly with the TC lifetimes and the effect of El Niño over the WNP. TC lifetime and seasonal subtropical ridge activities are shown to be potential factors that affect TC size and strength.

Consistency of Towing Speed and Sampling Depth for the Continuous Plankton Recorder

1993 ◽  
Vol 73 (4) ◽  
pp. 967-970 ◽  
Author(s):  
G. C. Hays ◽  
A. J. Warner
Keyword(s):  
Time Series ◽  
North Atlantic ◽  
Data Sets ◽  
Sampling Depth ◽  
The North ◽  
The North Sea ◽  
The Mean ◽  
Towing Speed ◽  
Term Data

The mean annual towing speed of the Continuous Plankton Recorder (CPR) varied systematically between 1946 and 1991. By mounting a pressure transducer on the CPR to record towing depth, it was shown, however, that changes in towing speed did not cause a significant change in towing depth, although the mean towing depth (6–7 m, SD=l-7 m, N=77) was shallower than the previously assumed towing depth of 10 m. Thus the observed changes in towing speed are unlikely to have caused discontinuities in the CPR time-series by affecting sampling depth.Long-term data sets play an important role in attempts to understand the causes of fluctua- tions in plankton abundance. The Continuous Plankton Recorder (CPR) survey provides multi- decadal information on plankton abundance in the North Sea and North Atlantic (McGowan, 1990), and is one of the longest standing marine plankton abundance time-series. However, while the CPR time-series has great potential, as with all other data sets spanning many years, questions may be asked regarding the consistency with which the data have been collected and hence the true continuity of the time-series.

Reliability analysis of foundation stability for gravity platforms in the North Sea

1989 ◽  
Vol 26 (3) ◽  
pp. 359-368 ◽  
Author(s):  
Tien H. Wu ◽  
Oddvar Kjekstad ◽  
In-Mo Lee ◽  
Suzanne Lacasse
Keyword(s):  
North Sea ◽  
Reliability Index ◽  
Site Investigation ◽  
Offshore Structures ◽  
Material Strength ◽  
Strength Measurement ◽  
The North ◽  
The North Sea ◽  
Coefficients Of Variations ◽  
The Mean

The uncertainties encountered in the evaluation of foundation stability for four offshore gravity structures in the North Sea are reviewed. The uncertainties include those about the load, the material type, the material strength, and the analytical method. The means and coefficients of variations of these are used as inputs to compute the mean and coefficient of variation of the safety factor and the reliability index. The latter are used to assess the effect of various options in site exploration and strength measurement on foundation reliability. Key words: foundation, gravity platforms, offshore structures, probability, reliability, shear strength, site investigation, stability.

scholarly journals On the Torques Due to Tidal Friction of the Oceans and Adjacent Seas

1972 ◽  
Vol 48 ◽  
pp. 235-239 ◽  
Author(s):  
P. Brosche ◽  
J. Sündermann
Keyword(s):  
Bering Sea ◽  
Tidal Friction ◽  
The North ◽  
The Earth ◽  
Numerical Integrations ◽  
The North Sea ◽  
Frictional Forces ◽  
The Mean ◽  
Initial Results ◽  
The Bering Sea

The torques of the frictional forces on the bottoms of the seas are calculated in an approximate inertial system and not in the corotating system used hitherto. In this way, the loss of rotational energy of the Earth – corresponding to the mean torque – can be compared with the value obtained from astronomical observations. The calculations are based on velocities which are computed by numerical integrations of the hydrodynamical equations. Initial results are presented for the North Sea, the Bering Sea and rough models of theworld ocean.

Course, Management and Outcome of Oral-Anticoagulant-Related Intracranial Haemorrhages

2000 ◽  
Vol 45 (4) ◽  
pp. 105-109 ◽  
Author(s):  
J. Berwaerts ◽  
O. J. Robb ◽  
R. S. Dykhuizen ◽  
J. Webster
Keyword(s):  
Oral Anticoagulant ◽  
Large Scale ◽  
Tertiary Care ◽  
Tertiary Care Centre ◽  
Term Outcome ◽  
The North ◽  
Significant Difference ◽  
Anticoagulant Reversal ◽  
Mean Size ◽  
The Mean

The aim of this study was to compare the clinical course and radiological features of oral anticoagulant (OAC)-related intracranial haemorrhages with those of haemorrhages unrelated to OAC use admitted over the last six years to a tertiary care centre in the North of Scotland. We furthermore wished to determine the measures taken for reversal of OAC therapy and the resulting short-term outcome. Sixty-eight patients had been treated with OACs at the time of intracranial haemorrhage (32% subdural, 62% intracerebral). Patients admitted with OAC-related and unrelated haemorrhages did not differ significantly in any of the clinical features considered. On CT scan, there was no significant difference according to OAC use in the mean size of subdural (depth 15 ± 5 vs. 18 ±8mm, p=0.36), or intracerebral haematomas (max. diameter 40 ±21 vs. 41 ±20 mm, p=0.73). No reversal measures were taken in 38% of OAC-treated patients. In-hospital mortality was significantly higher for OAC-related haemorrhages compared to unrelated haemorrhages (38% vs. 18%), p=0.001). To further elucidate the effects of anticoagulant reversal on the outcome of OAC-related intracranial haemorrhages, a large-scale prospective study is warranted.

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