On the behaviour of artificial head transfer system applied to acoustic evaluation researches for halls

The author has made tests for an artificial head transfer system whichis modelled on a Chinese male on its main physical behaviour such as frequencyresponses,frequency response differences between the front and the rear inci-dences,as will as on its important hearing behaviour such as localization,theperception of distance and room dimensions.The results verify that this kind ofartificial head transfer system can be used as one of effective tools of acousticevaluation researches for halls.     

人类对超声的听觉感知及应用前景

本文对人类通过骨传导所产生的超声听觉感知，就以下四方面进行介绍：１．感知的方法、频率和强度范围；２．感知机理；３．可能的应用；４．值得研究的问题。     

Effective tortuosity and different acoustic waves in porous media

Summary A simple method has been suggested to estimate the acoustic characteristics of porous structure from a hybrid model—a hybridisation of Biot's phenomenological model and the microscopic multiple-scattering theory which introduces the idea of an effective tortuosity. Without using any adjustable parameter this model may be used to provide rough estimates of the tortuosity, the fast, the shear and the slow sound speeds. The predictions are compared with observation on water-saturated glass bead samples. The author of this paper has agreed to not receive the proofs for correction.     

On the use of the Galerkin method for 3D numerical modelling of the general circulation: the South Atlantic eperiment

A linear three‐dimensional hydrodynamical numerical model, with the application of the Galerkin Method for the vertical dependence, is here presented. The spherical coordinate system is used, in order to allow large‐scale simulations. The equations and mathematical development of the model are shown in detail, together with the boundary and initial conditions, and the sequence of equations' solution. The model is applied to the South Atlantic Ocean, for estimating typical seasonal circulations, and the results are summarized in maps of currents at surface and 1000 m depth, and in transport values of the Brazil Current between 30°S and 40°S. Copyright © 2002 John Wiley & Sons, Ltd.     

水下噪声及其控制技术进展和展望

本文主要介绍近年来船舶行业水下噪声研究进展情况，包括水下噪声形成机理和预报；水下噪声控制技术；水下噪声近代测量分析技术，并提出对水下噪声研究工作的展望。     

On the baroclinic instability of nonplanar flows

Summary Different ocean models with one or two layers having constant static stability and supporting constant-shear flows, whose directions are allowed to change with depth, are examined in the frame-work of the linear nonzonal baroclinic stability theory and in the absence of the β-effect. The analysis is reduced to solving a simple Sturm-Liouville boundary value problem in one dimension. A fairly general dispersion relation is found which correctly reproduces several special cases analysed by other authors. This relation shows a fair variety of possible behaviours for stability curves of two-layer models. The results show that the presence of a nonplanar shear-flow may have profound consequences on the stability character of the stationary geostrophic flow. In fact, it appears that the stability properties are strongly dependent on the propagation angle of the disturbance so that wave numbers which appear stable in the usual zonal theory may result unstable on such a nonzonal flow andvice versa. Paper presented at the 1^o Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 19–22, 1984, Rome.     

The impact of higher-order bragg terms on radar sea return

Summary The possibility that radar sea return observed using aKu band fan beam Doppler airborne scatterometer flown over crude oil artificial spills might have been back-scattered via the second-order Bragg interaction is surmised. An attempt is made to justify the absence of the first-order Bragg term.

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Riassunto Prendendo in considerazione l'effetto dei primi ordini di Bragg e sopprimendo il ter mine di ordine 1, si mostra come l'inesplicato andamento dell'eco del mare in presenza di film di spandimento, rilevato con radar doppler in bandaKu montato su aereo, coincida con misure effettuate altrove in presenza di analogo film. Si propone una teoria secondo cui l'assenza del primo ordine è dovuta ad una carenza dell'onda capillare pertinente.

     

Sea level oscillations in the gulf of Trieste, the role of the atmospheric-pressure forcing and the tidal effect in the pressure and wind behaviour

Summary This paper is divided into three parts. The first one takes some cases of sea level perturbation (the tides being removed) at Trieste into account. The spectral analysis shows the occurring of the principal seiches of the Adriatic Sea together with oscillations believed as forced oscillations. In the second part the pressure oscillations have been examined and the same periods forcing the sea level have been found. Such oscillations appear very evident and stable, mostly in the summer months. In the third part of the work the tidal effect on the wind, derived from the atmospheric pressure, is tested. In the summer situations prevailing breezes are present and the spectral analysis of the records points out clearly the occurrence of some ?wind tides? both in the diurnal and semi-diurnal range.

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Riassunto Questo lavoro si articola in tre parti. Nella prima parte sono mostrati alcuni casi in cui il livello del mare a Trieste è perturbato da forti oscillazioni extramareali. I grafici della marea meteorologica registrati negli intervalli temporalit(1)…t(14) possono tipicizzare queste situazioni, essi riportano l'evoluzione del livello dopo che le maree sono state eliminate con calcoli di filtraggio dei dati osservati. Da queste serie temporali sono stati eseguiti gli spettri di ampiezza col metodo dei minimi quadrati. In questi si vedono due picchi, sempre presenti sui periodi di circa 11 e 21 ore che sono, mediamente e arrotondando, i periodi delle sesse principali (longitudinali) dell'Adriatico. Quando il livello è perturbato queste ultime sono sempre presenti, pur con ampiezza diversa, assieme ad altre di origine locale. Si rilevano anche onde forzate da oscillazioni barometriche. La seconda parte del lavoro esamina alcune onde barometriche forzanti. Si trova che le piú stabili onde barometriche presenti nell'evoluzione della pressione atmosferica a Trieste sono le cosiddette maree atmosferiche. Alcune considerazioni sono presentate su questo fenomeno. Data la persistenza delle maree atmosferiche nella pressione, un sincrono effetto viene cercato nel vento. Nella terza parte del lavoro si esamina questo effetto trovando che effettivamente, in regime di brezza, periodicità ?mareali? si trovano anche nell'evoluzione del vento. In altri regimi ?le maree del vento? sono completamente mascherate da altri effetti, come le maree marine quando si sovrappongono forti perturbazioni di carattere extramareale.

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Резюме Эта статья делится на три части. В первой части рассматриваются некоторые случаи колебания уровня моря (влияние прилива исключается) в заливе Триеста. Спектральный анализ показывает существование главных сейшей Адриатического моря вместе с другими осцилляциями, которые рассматриваются как вынужденные колебания. Во второй части исследуются осцилляции давления и обнаружены колебания уровня моря с такими же периодами. Такие осцилляции являются заметными и устойчивыми, особенно в летние месяцы. В третьей части работы исследуется влияние приливов на ветер, порожденный атмосферным давлением. В летний период превалируют бризы и спектральный анализ показывает в явном виде существование некоторых ?ветровых приливов? в суточных и полусуточных диапазонах измерений.

     

Sea-level response to impulsive north winds in the Gulf of Trieste. Event on 25th September 1987

Summary The detailed behaviour of the sea level in the Gulf of Trieste, in the presence of a sharp wind impulse at the first hours on 25th September 1987, is described. For the first time the data have been obtained by means of an ultrasound tide gauge, with a digital record and one minute scanning.

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Riassunto Il lavoro descrive il comportamento del livello del mare nel golfo di Trieste in relazione ad un impulso meteorologico che ha avugo luogo nelle prime ore del 25 Settembre 1987. Per la prima volta i dati sono stati ottenuti con un mareografo ad ultrasunoni, a registrazione digitale, con una frequenza di acquisizione di uno al minuto.

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Резюме Описывается подробнхое поведение уровня моря в заливе Триеста при наличии резкого импульса ветра в первые часы 25 сентября 1987 г. Впервые получены данные с помощью ультразвуковых приливных датчиков с цифровой регистрацией и с одноминутым сканированием.

     

A process of thermocline erosion on the Sicilian continental shelf

Summary We study a process of thermocline erosion measured in the Channel of Sicily in the period 16 November–December 1985. Evidence is presented that the transition from Summer to Winter stratification has been an impulsive process. We show that the erosion of the seasonal thermocline and the deepening of the surface mixed layer were stimulated by the action of two strong atmospheric perturbations. Possible relations between mixing events and internal wave breaking are discussed. Paper presented at the IV Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 22–24, 1987, Rome.