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排序方式: 共有93条查询结果,搜索用时 15 毫秒
1.
Sound pressure distributions in the human ear canal, whether unoccluded or occluded with ear molds, were studied using a probe tube technique. On average, for frequencies below 6 kHz, the measuring probe tube had to be placed within 8 mm of the vertical plane containing the top of the eardrum (TOD), determined optically, in order to obtain sound pressure magnitudes within 6 dB of "eardrum pressure." To obtain that accuracy in all of the eight subjects studied, the probe had to be within 6 mm of the TOD. Since probe location relative to the drum has to be known, a purely acoustic method was developed which can be conveniently used to localize the probe-tip position, utilizing the standing wave property of the sound pressure in the ear canal. The acoustically estimated "drum location" generally lay between the optically determined vertical planes containing the TOD and the umbo. On average, the "drum location" fell 1 mm medial to the TOD. Of the 32 estimates made acoustically in various occluded and unoccluded conditions in 14 subjects, 30 estimates lay within a +/- 2-mm range of this average. 相似文献
2.
A model of the cochlea is explored using as stimuli two simultaneously presented sinusoids of equal amplitude. The model consists of two stages: a linear bandpass filter, followed by a reservoir-type representation of the hair-cell/nerve-fiber complex. Fast Fourier transforms of the model's output were computed. While the amplitudes of the individual response components were strongly nonlinear functions of intensity, the ratio of the magnitudes of the response components at the frequencies of the two stimulating sinusoids was found to be nearly equal, over a wide intensity range, to the ratio of the amplitudes which those stimulating sinusoids possessed at the output of the filter. Thus the reservoir stage exerts "automatic gain control". 相似文献
3.
H. Schelhorn M. Geisler H. Gerstenberger 《Journal of Radioanalytical and Nuclear Chemistry》1980,58(1-2):239-246
A neutron activation analysis procedure was developed for the determination of osmium in geological materials. The method
consists in the measurement of the 129.4 keV γ-rays of191Os after radiochemical separation of osmium. The sample decomposition, the chemical separation process and the optimal measuring
conditions are described and discussed.
相似文献
4.
Hegedus LS Geisler L Riches AG Salman SS Umbricht G 《The Journal of organic chemistry》2002,67(22):7649-7655
Butenolides 5a and 13 were used as optically active templates in the de novo synthesis of 4'-disubstituted nucleoside analogues. The butenolides were reduced and acylated in situ to give acetates 10 and 14. Vorbrüggen coupling gave the protected nucleoside analogues 11 and 15. Reduction of 11 gave 4'-ethoxy-2',3'-dideoxythymidine (6) and deprotection of 15 gave 4'-ethoxy-2',3'-dideoxydidehydrothymidine (7). The cis-dihydroxylation of a variety of butenolides occurred with the major product formed from oxidation of the beta-face. 相似文献
5.
H. Gerstenberger H. -Ch Treutler M. Geisler 《Journal of Radioanalytical and Nuclear Chemistry》1982,74(1-2):181-189
In the bremsstrahlung field of the Microtron MT 22, copper foils (0.035 mm thick) positioned along beam direction and also
perpendicular to the beam at different distances from the bremsstrahlung target were irradiated. From these activated copper
foils autorodiograms were prepared. By means of a densitron and a microdensitometer, the autoradiograms were measured. The
densitron pictures give a qualitative impression of the geometry of the bremsstrahlung field, whereas the curves of optical
density yield quantitative values. From optical density curves, conclusions have been drawn about optimal geometry for irradiation
positions of samples in this bremsstrahlung field. A sample rotating device applicable for photon activation analysis by means
of the MT 22 is described.
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8.
M. Geisler 《Isotopes in environmental and health studies》2013,49(8):321-325
Es wird eine Anordnung beschrieben, die es gestattet, bis zu 7 Proben unter identischen Bedingungen rotationssymmetrisch zu aktivieren. Die Proben rotieren um zwei parallele Achsen. Es wird über Erprobungsmessungen durch Aktivierung von Cu-und N-haltigen Proben berichtet. 相似文献
9.
Synthesis of 2‐Unsubstituted 1,3‐Selenazoles by Cyclization of Selenoformamide with α‐Bromocarbonyl Compounds 下载免费PDF全文
Harald Below Wolf‐Diethard Pfeiffer Karlheinz Geisler Ashot S. Saghyan Christine Fischer Peter Langer 《Journal of heterocyclic chemistry》2015,52(2):592-596
2‐Unsubstituted 1,3‐selenazoles were prepared by cyclization of selenoformamide with α‐bromoacetophenones. Parent 1,3‐selenazole was prepared by cyclization of selenoformamide with α‐bromoacetaldehyde. 相似文献
10.