As a mesoscale phenomenon of the ocean, the ocean front can directly affect the structural characteristics of sound speed profiles and further affect the acoustic propagation characteristics of the ...sea area. In this paper, we use the fuzzy C-means (FCM) algorithm to cluster the surface sound speed in the sea area of the Kuroshio Extension (KE) and detect the frontal zone of Kuroshio Extension (KEF). At the same time, the sound speed profile (SSP) is used instead of the temperature profile to establish the model of the sound speed field in the front area of the Kuroshio Extension and to improve the theoretical model of the ocean front. Compared with the actual ocean front calculated by reanalysis data, the root means square error (RSME) of the transmission loss (TL) calculated by the model is controlled below 6 dB, which proves the validity of the model. Finally, we propose the melt function in the model to forecast the depth change of the acoustic convergence area. Compared with the actual calculation result based on reanalysis data, the root means square error (RSME) of the depth forecasting after the frontal zone is 43.3 m. This reconstruction method does not rely on the high spatial resolution data of the whole sea depth and can be of referential significance to acoustic detection in the ocean front environment.
The study focuses on the contemporary ethnolinguistic situation in Kupwar at the Maharashtra-Karnataka border. Gumperz and Wilson (1971)'s classic study of language contact in this village predicted ...that multilingualism would be maintained as long as the ethnic (i.e. religious) separateness of home life remained important in the contact situation. This paper examines the influence of religion and regional identity on language choices, especially among the newly created linguistic minority communities. The paper suggests that Kupwar is characterised today by both accentuated religious differentiation and growing linguistic assimilation. Present-day patterns of language choice are interpreted in the light of the changed ethno-social context and the perceived role of religious identity in the region.
•This study revisits Gumperz and Wilson's (1971) classic study of language contact in the border village of Kupwar.•Linguistic reorganisation has impacted this multi-religious, multi-lingual village.•Increased awareness of religious identities and assimilation towards the state language were observed.•Different religious groups have differing relations with new language of opportunity.•Acceptance of new state language as language of religious practice paves path for language change.
In Gao and Huang Z.X. Gao, T.Z Huang, Convergence of AOR method, Appl. Math. Comput. 176 (2006) 134–140 some practical sufficient conditions for the convergence of the AOR (accelerated ...overrelaxation) method for solving linear system
Ax
=
b
, with
A being doubly diagonally dominant matrix, are presented. Using a different approach we will give some improvements in both cases, when the matrix
A is either strictly diagonally dominant (SDD) or doubly diagonally dominant. Using the same simple example as in Gao and Huang (2006), we will illustrate how the new approach can significantly improve convergence area.
As the Kuroshio front which is greatly affected by the seasonal variation, its sound field distribution also presents different characteristics in different seasons. In this paper, the sound speed ...profiles of the Kuroshio front are classified via fuzzy C-means clustering algorithm, and we use the BELLHOP ray model to calculate the sound field under the Kuroshio front environment in winter and summer. The results show that the Kuroshio front is strong in winter, and its location is southward, which has a great impact on the distribution of convergence area after passing through the frontal zone; In summer, the Kuroshio front is relatively weak, and the location of Kuroshio front is northward. When the location of the sound source is the same as that in winter, the frontal zone has a greater impact on the distribution of convergence area near the sound source. We also calculate and analyze the three-dimensional sound field under the Kuroshio front environment in different periods, which shows that there are obvious differences in winter and summer.
The propagation mode based on the convergence zone in the deep sea is an important method for long-distance detection. In order to effectively identify the deep-sea convergence area, this paper ...proposes a method for identifying the deep-sea convergence area and shadow area based on the correlation matrix eigenvalue decline index of the horizontal array. The eigenvalue decline index of the correlation matrix refers to the ratio of the maximum eigenvalue to the second largest eigenvalue of the receiving signal correlation matrix, which is calculated to characterize the oscillation properties of the correlation coefficient matrix. The index can effectively characterize the oscillation characteristics of the correlation matrix in convergence area and shadow area which can be used to convergence zone and shadow zone discrimination. Simulation experiments show that setting a reasonable threshold of the eigenvalue decline index can effectively distinguish the convergence area from the shadow area.
In the ocean front environment, the existence of ocean front has an important impact on sound propagation due to the obvious change of sound speed profile. According to the two-dimensional ...parameterized model of ocean temperature front constructed by Olivier et al, we build a two-dimensional parameterized feature model of ocean front based on sound speed profile, calculate and compare the influence of ocean front on convergence area by setting different ocean front environment. The results show that when the sound wave propagates from the warm water mass to the cold water mass, the convergence area moves forward, and the degree of the forward movement changes with the intensity of the ocean front; when the sound wave propagates from the cold water mass to the warm water mass, the convergence area moves backward, and the degree of the backward movement changes with the intensity of the ocean front. We also analyze the reasons for the formation of the acoustic shadow area at a specific location under the condition of strong ocean front when the sound wave propagates from the warm water mass to the cold water mass, which may provide a reference for the acoustic concealment of the target under the environment of ocean front.
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