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    "label": "Report, OSI - 1/49, Central Intelligence Agency, An Estimate of Swedish Capabilities in Science",
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    "title": "Report, OSI - 1/49, Central Intelligence Agency, An Estimate of Swedish Capabilities in Science",
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        "President's Secretary's Files (Truman Administration)",
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{
    "seq": 52,
    "pageIndex": 0,
    "type": "photo",
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    "ocrText": "SECRET\ncent experience has shown that at 200-400 km d-c transmission becomes more economi-\ncal than a-c.\nA new magnetometer for measurement of the z-component of the earth's field has\nbeen developed by G. Ising. A fine galvanometer coil is suspended so as to be movable\naround a horizontal axis. It is fed with low-frequency current from a battery and\ncommutator. The coil oscillates under the action of the terrestrial field. The oscilla-\ntions are quenched by a movable control magnet and a compensating coil (fine adjust-\nment) supplied with d-c. The compensation measures the z-component. The instru-\nment has been successfully used in mining and surveying.\nIn the field of acoustics, U. Ingard, Division of Electronics, Chalmers Institute of\nTechnology, has investigated the radiation into a circular tube from sound sources of\ncircular symmetry. Both in precision measurements of acoustic impedance and in\nanalogy studies referring to the electromagnetic case, the intensive study of the propa-\ngation and attenuation of the higher-order waves near the discontinuity is of great\nimportance. Formulas that modify the resonant frequency of a cylindrical resonator\non the basis of these higher-order attenuated waves have been derived and these for-\nmulas, and also the expressions for input impedence, were checked by means of probe\nmeasurements in various cylindrical tubes and resonators terminated in several dif-\nferent ways.\nAt present virtually no research in acoustics has been reported, but an increasing\nemphasis is indicated by a recent article by P. V. Bruel, Chalmers Institute, giving\nstandards for acoustical definitions and measurements methods. The measurement\nfrequencies are determined from International Standard figures and measurement of\nnoise level is given in phons. Definitions are also given for reverberation time, absorp-\ntion, and absorption coefficient. Further defined are: airborne sound insulation; air-\nborne sound insulation figure; and effective airborne sound insulation. The last is an\nentirely new concept which indicates that the sound insulating qualities of a completed\nbuilding are independent of the paths taken by the sound from one room to another.\n45\nSECRET"
}