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Determination of far-field characteristics of large underwater sound transducers from near-field measurements
OCEANOGRAPHIC ABSTRACTS This section contains the first group of abstracts of current papers on general oceanography and related subjects. Together with the oceanographic bibliography it will provide a comprehensive service to scientists engaged in deep-sea research and oceanography in general. For ease of reference the names of authors are arranged in alphabetical order.
AJBtrrALOV N., H. GRIESSEIER and I. SADRIN, 1962. Ktistendynamische Untersuchungen in der Uferzone der Anapa Nehrung. Acta Hydrophys. 7(2): 105-150. Deutsch-sowjetische Gemeinschaftsuntersuchungen bei Anapa im Herbst des Jahres 1960 werden zum AnlaB genommen, die wichtigsten Ergebnisse eines tiber 10jiihrigen Studiums der Hydrodynamik und der Lithodynamik der Uferzone der Anapa Nehrung zusammenzusteUen und zu verallgemeinern. ALGERIA, CENTRE DE GEOLOGIE MARINE ET DE SEDIMENTOLOGIE, 1962. Utilisation des radiotraceurs /t courbet-marine. Etude de l'ensablement d'un port du littoral algerois. Methodes sedimentologiques utilisation de traceurs radio-actifs. Cah. Oc6anogr., C.C.O.E.C., 14(8): 526-542, French conclusions p. 542. Les causes pratiques de l'ensablement de ce port sont: (1) d'une part, orientation N.NE de la passe qui laisse les boules N. NW, N e t N.NE p6n6trer dans le port, soit directement, soit indirectement; (2) d'autre part, la situation de la passe dans la zone de d6ferlement. Ces causes pratiques d6pendent d'une cause profonde, le d6s6quilibre apport6 par cet ouvrage dans le jeu des facteurs: conditionnant la raise en mouvement de s6diment. La m6thode des traceurs radio-actifs donne donc des r6sultats sur place et imm6diats et est, /~ ce point de vue, in6galable. EUe a, en revanche, le d6faut correspondant/t ces qualit6s, c'est-A-dire sa trop grande instantan6it6. Elle dolt doric 6tre appliqu6e plusieurs fois de suite au meme lieu et au m6me ph6nom6ne afin de constituer une 6tude compl6te.
ANANIADIS C. I. 1962. Ocean currents. (In Greek; English summary), Thal. Epiztn. Fulla, 6: 59-77. It is the purpose of this article to give a general account of the role which the currents play in the sea economy. The main features of the superficial water circulation in the various oceans, and a broad, generalized average current systems are described. In addition to the horizontal surface currents deeper ones and the ascending and descending currents were included. Water rises up from below in the Equatorial zones. Along the coasts of Western Africa and America there are regions where water upwells to replace that driven towards the West in the Equatorial Streams. There are also good biological reasons for studying currents because they generally control the distribution of marine life and affect the navigation and the sea fisheries. There is a brief description of the methods of investigating ocean currents, drifter observations, direct current measurements, salinity and temperature observations, etc. ATHAVALE V. T., C. V. KRISHNAN and A. R. SUaRAMA~AN, 1962. Determination of residual chlorine in chlorinated sea water. J. Soc. Analyt. Chem. Lond. 87(1038): 707-711. A spectrophotometric method is reported for determining residual chlorine in chlorinated sea water; it is based on the bleaching action of chlorine on methyl orange. Anions such as sulphate, acetate, phosphate and nitrate do not interfere. Large amounts of weak oxidizing agents, such as ferric iron, cupric copper and idodine in potassium idodide, do not oxidize the indicator under the given experimental conditions. Hydrogen peroxide, potassium dichromate and hydrated maganese dioxide react slowly, and bromine and permanganate react in the same way as chlorine. The method does not measure the combined residual chlorine in the absence of bromide ion in the sample. BAKER D. D. 1962. Determination of far-field characteristics of large underwater sound transducers from near-field measurements. J. Acous. Soc. Amer., 34(11): 1737-1744. It has recently become necessary to find a way to determine far-field characteristics of large underwater sound transducers from measurements made in the near field of the transducer (at ranges small compared to the transducer dimensions). It is possible to compute far-field directivity patterns and source levels from pressure amplitude and phase measurements made in the near field. This can be done by using Kirchhoff's formula with a simple approximation for the normal component of the 531
532
Oceanographic Abstracts
pressure gradient. Pattern computations were made on line, plane-array, dipole, and line-and-cone transducers from measurements made in open water. Extensive pattern and source level computations were made on a large, multistave cylindrical transducer from measurements made in open water and in a highly reflective tank. Agreement with measured far-field patterns and source levels was good throughout and was within 4-1 dB in the more recent work with the cylindrical transducer. Particularly significant is the fact that successful measurements were made in a tank of diameter only 2"9 times that of the transducer. These measurements were made near the leading edge of the received pulses in order to avoid interference due to reflections. Preliminary work on a simplified near-field test for a cylindrical transducer has also been done. Such a test would enable one to use near-field data to make certain judgments about the far-field performance of a transducer without computations. BARASrI M. S. 1962. Studies of the suspended matter in surface water North Atlantic in the R/V M. Lomonosov (microscopical method). (ln Russian). Trud. Inst. Okeanol., Akad. Nauk, SSSR, 56: 69-86. Suspended matter in the surface water of the North Atlantic Ocean was studied by the microscopical method of M. V. Klenova. The samples of water were successively filtered through three filters, separating the suspended particles being thus divided into three fraction: more than 5 micra, 5-1 micra and less than 1 micron. The number of particles were calculated under the microscope. Most of the suspension is organic detritus, the smallest is plankton, and less frequently mineral grains. The large amount of the suspension occurs naturally near a shoreline in small water depths. The suspension in the coastal waters is to a considerable degree terrigenous particles not only from the land but also from the bottom sediments at the time of storms etc. In the Azores at the time of the eruption of a new volcano, particles of ash predominated. The large amount of suspension in connection with the development of plankton was observed in zones of the "polar front". On banks the maximal suspension is above the slopes. The total content of the suspension and especially of the mineral particles increases above the Mid-Atlantic ridge and above others areas with a dissected deep-sea topography. The amount in suspension in waters of the Sargasso Sea is very. small. The different water masses are characterized by the mechanical composition of the suspension. The sorting of the suspension depends on the duration of the transportation of the material. The better sorted suspension is noted in the North Equatorial Current. The sorting of the suspension is worst in the Sargasso Sea. The small total amount of suspension and its poor sorting indicates the relative isolation of the Sargasso Sea. BARNES H. and M. BARNES, 1962. The growth rate of Elminius modestus (Crust., Cirripedia) in Scotland. Int. Rev. Ges. Hydrobiol., 47(3): 481-486. (1) Data are presented on the growth rate of Elminius modestus in,Scotland at three localities with contrasting conditions and at different intertidal levels. (2) Growth takes place in the summer and autumn following settlement, but there is little increase in size during the winter. (3) Growth is somewhat faster on complete submersion than at high intertidal levels but the contrast is less marked than in Balanus balanoids. The feeding efficiency of Elminius modestus may be greater. (4) Growth is as good in open as in turbid water. E. modestus is not, therefore, specifically adapted to a detrital diet; this does not rule out the possibility that some species may not thrive so well on detritus. (5) In the north, where winter temperatures are low and summer temperatures only moderate, brood production is relatively low and the indigenous competitor, Balanus balanoides is at an advantage in competition with the immigrant. Extension of the immigrant will probably be limited in the north rather by competition than by the physical conditions of the environment. BIEBL R. 1962. Temperaturresistenz tropischer Meeresalgen. (In German). Botanica Marina, 4(3/4): 241-254. Tropical marine algae from the south coast of Puerto Rico, and some from the east coast of Venezuela, were examined for heat and cold resistance. The resistance criterion was life after 12 hours' exposure to temperature. The results were compared with those of earlier investigations of the temperature resistance of algae of temperate seas (BIEBL 1939, 1958). Besides high desiccation and osmotic resistances, the tropical intertidal algae, without any ecological necessity, show a high degree of cold resistance (down to --2 °) C, sea water not yet frozen). This phenomenon is interpreted as a consequence of a particular quality of the proto ptasm, which is above all responsible for the drying resistance of the intertidal algae. Unlike the intertidal algae of temperate seas, however, the tropical algae will not tolerate freezing. The tropical submerged algae differ from those in temperate seas in their extremely high susceptibility to cold. The resistance limit is between × 5 ° and + 14° C, as compared with --2 ° to + 3°C for the submerged algae of temperate seas. The heat resistance of the tropical submerged algae extends up to 32 ° and 35 ° C that of the submerged algae of temperate seas to 27 ° and 30°C. Thus the difference between ecologically required heat resistance and actual heat resistance is considerably smaller in the tropics (sea temperature of
AJBtrrALOV N., H. GRIESSEIER and I. SADRIN, 1962. Ktistendynamische Untersuchungen in der Uferzone der Anapa Nehrung. Acta Hydrophys. 7(2): 105-150. Deutsch-sowjetische Gemeinschaftsuntersuchungen bei Anapa im Herbst des Jahres 1960 werden zum AnlaB genommen, die wichtigsten Ergebnisse eines tiber 10jiihrigen Studiums der Hydrodynamik und der Lithodynamik der Uferzone der Anapa Nehrung zusammenzusteUen und zu verallgemeinern. ALGERIA, CENTRE DE GEOLOGIE MARINE ET DE SEDIMENTOLOGIE, 1962. Utilisation des radiotraceurs /t courbet-marine. Etude de l'ensablement d'un port du littoral algerois. Methodes sedimentologiques utilisation de traceurs radio-actifs. Cah. Oc6anogr., C.C.O.E.C., 14(8): 526-542, French conclusions p. 542. Les causes pratiques de l'ensablement de ce port sont: (1) d'une part, orientation N.NE de la passe qui laisse les boules N. NW, N e t N.NE p6n6trer dans le port, soit directement, soit indirectement; (2) d'autre part, la situation de la passe dans la zone de d6ferlement. Ces causes pratiques d6pendent d'une cause profonde, le d6s6quilibre apport6 par cet ouvrage dans le jeu des facteurs: conditionnant la raise en mouvement de s6diment. La m6thode des traceurs radio-actifs donne donc des r6sultats sur place et imm6diats et est, /~ ce point de vue, in6galable. EUe a, en revanche, le d6faut correspondant/t ces qualit6s, c'est-A-dire sa trop grande instantan6it6. Elle dolt doric 6tre appliqu6e plusieurs fois de suite au meme lieu et au m6me ph6nom6ne afin de constituer une 6tude compl6te.
ANANIADIS C. I. 1962. Ocean currents. (In Greek; English summary), Thal. Epiztn. Fulla, 6: 59-77. It is the purpose of this article to give a general account of the role which the currents play in the sea economy. The main features of the superficial water circulation in the various oceans, and a broad, generalized average current systems are described. In addition to the horizontal surface currents deeper ones and the ascending and descending currents were included. Water rises up from below in the Equatorial zones. Along the coasts of Western Africa and America there are regions where water upwells to replace that driven towards the West in the Equatorial Streams. There are also good biological reasons for studying currents because they generally control the distribution of marine life and affect the navigation and the sea fisheries. There is a brief description of the methods of investigating ocean currents, drifter observations, direct current measurements, salinity and temperature observations, etc. ATHAVALE V. T., C. V. KRISHNAN and A. R. SUaRAMA~AN, 1962. Determination of residual chlorine in chlorinated sea water. J. Soc. Analyt. Chem. Lond. 87(1038): 707-711. A spectrophotometric method is reported for determining residual chlorine in chlorinated sea water; it is based on the bleaching action of chlorine on methyl orange. Anions such as sulphate, acetate, phosphate and nitrate do not interfere. Large amounts of weak oxidizing agents, such as ferric iron, cupric copper and idodine in potassium idodide, do not oxidize the indicator under the given experimental conditions. Hydrogen peroxide, potassium dichromate and hydrated maganese dioxide react slowly, and bromine and permanganate react in the same way as chlorine. The method does not measure the combined residual chlorine in the absence of bromide ion in the sample. BAKER D. D. 1962. Determination of far-field characteristics of large underwater sound transducers from near-field measurements. J. Acous. Soc. Amer., 34(11): 1737-1744. It has recently become necessary to find a way to determine far-field characteristics of large underwater sound transducers from measurements made in the near field of the transducer (at ranges small compared to the transducer dimensions). It is possible to compute far-field directivity patterns and source levels from pressure amplitude and phase measurements made in the near field. This can be done by using Kirchhoff's formula with a simple approximation for the normal component of the 531
532
Oceanographic Abstracts
pressure gradient. Pattern computations were made on line, plane-array, dipole, and line-and-cone transducers from measurements made in open water. Extensive pattern and source level computations were made on a large, multistave cylindrical transducer from measurements made in open water and in a highly reflective tank. Agreement with measured far-field patterns and source levels was good throughout and was within 4-1 dB in the more recent work with the cylindrical transducer. Particularly significant is the fact that successful measurements were made in a tank of diameter only 2"9 times that of the transducer. These measurements were made near the leading edge of the received pulses in order to avoid interference due to reflections. Preliminary work on a simplified near-field test for a cylindrical transducer has also been done. Such a test would enable one to use near-field data to make certain judgments about the far-field performance of a transducer without computations. BARASrI M. S. 1962. Studies of the suspended matter in surface water North Atlantic in the R/V M. Lomonosov (microscopical method). (ln Russian). Trud. Inst. Okeanol., Akad. Nauk, SSSR, 56: 69-86. Suspended matter in the surface water of the North Atlantic Ocean was studied by the microscopical method of M. V. Klenova. The samples of water were successively filtered through three filters, separating the suspended particles being thus divided into three fraction: more than 5 micra, 5-1 micra and less than 1 micron. The number of particles were calculated under the microscope. Most of the suspension is organic detritus, the smallest is plankton, and less frequently mineral grains. The large amount of the suspension occurs naturally near a shoreline in small water depths. The suspension in the coastal waters is to a considerable degree terrigenous particles not only from the land but also from the bottom sediments at the time of storms etc. In the Azores at the time of the eruption of a new volcano, particles of ash predominated. The large amount of suspension in connection with the development of plankton was observed in zones of the "polar front". On banks the maximal suspension is above the slopes. The total content of the suspension and especially of the mineral particles increases above the Mid-Atlantic ridge and above others areas with a dissected deep-sea topography. The amount in suspension in waters of the Sargasso Sea is very. small. The different water masses are characterized by the mechanical composition of the suspension. The sorting of the suspension depends on the duration of the transportation of the material. The better sorted suspension is noted in the North Equatorial Current. The sorting of the suspension is worst in the Sargasso Sea. The small total amount of suspension and its poor sorting indicates the relative isolation of the Sargasso Sea. BARNES H. and M. BARNES, 1962. The growth rate of Elminius modestus (Crust., Cirripedia) in Scotland. Int. Rev. Ges. Hydrobiol., 47(3): 481-486. (1) Data are presented on the growth rate of Elminius modestus in,Scotland at three localities with contrasting conditions and at different intertidal levels. (2) Growth takes place in the summer and autumn following settlement, but there is little increase in size during the winter. (3) Growth is somewhat faster on complete submersion than at high intertidal levels but the contrast is less marked than in Balanus balanoids. The feeding efficiency of Elminius modestus may be greater. (4) Growth is as good in open as in turbid water. E. modestus is not, therefore, specifically adapted to a detrital diet; this does not rule out the possibility that some species may not thrive so well on detritus. (5) In the north, where winter temperatures are low and summer temperatures only moderate, brood production is relatively low and the indigenous competitor, Balanus balanoides is at an advantage in competition with the immigrant. Extension of the immigrant will probably be limited in the north rather by competition than by the physical conditions of the environment. BIEBL R. 1962. Temperaturresistenz tropischer Meeresalgen. (In German). Botanica Marina, 4(3/4): 241-254. Tropical marine algae from the south coast of Puerto Rico, and some from the east coast of Venezuela, were examined for heat and cold resistance. The resistance criterion was life after 12 hours' exposure to temperature. The results were compared with those of earlier investigations of the temperature resistance of algae of temperate seas (BIEBL 1939, 1958). Besides high desiccation and osmotic resistances, the tropical intertidal algae, without any ecological necessity, show a high degree of cold resistance (down to --2 °) C, sea water not yet frozen). This phenomenon is interpreted as a consequence of a particular quality of the proto ptasm, which is above all responsible for the drying resistance of the intertidal algae. Unlike the intertidal algae of temperate seas, however, the tropical algae will not tolerate freezing. The tropical submerged algae differ from those in temperate seas in their extremely high susceptibility to cold. The resistance limit is between × 5 ° and + 14° C, as compared with --2 ° to + 3°C for the submerged algae of temperate seas. The heat resistance of the tropical submerged algae extends up to 32 ° and 35 ° C that of the submerged algae of temperate seas to 27 ° and 30°C. Thus the difference between ecologically required heat resistance and actual heat resistance is considerably smaller in the tropics (sea temperature of