In this study, acoustic signal fluctuation in a continental shelf break is analyzed to examine the effects of detection probability and false alarm probability due to internal waves frequently observed on the east coast of Korea. Internal waves induce ocean temperature changes with time and space, and thus cause acoustic signal fluctuation. Internal waves are analyzed by measuring vertical ocean temperature changes with time using three thermister chains placed at three different positions. An acoustic signal is also measured during internal wave events. The observed internal waves have the following characteristics: a typical period of 25 min, a wavelength of 1,200 m, and an average amplitute of 5 m. The acoustic fluctuation parameters are estimated to be 3.7, 3.9, and 4.8 at frequencies of 300, 500, and 700 Hz, respectively. As a result, using a modified receiver operating characteristic curve, it is concluded that the detection probability decreases from 95 to 64% at a false alarm probability of 1% and increases from 23 to 44% at a false alarm probability of 10−4% at a frequency of 300 Hz.

An approximate form of three-dimensional Cartesian split-step marching solution for the acoustic parabolic equation is derived in order to obtain the efficient algorithm for sound propagation in the three-dimensional ocean. The operator splitting method is used to split the full exponential operator into three exponential operators for depth, cross-range, and the combination of the two. The first two terms are implemented with the split-step Padé algorithm and the final term is implemented with the Taylor series expansion in depth and cross-range operator. In order to resolve the divergence of Taylor approximation out of the interval of convergence, the rational filter of rectangular type is applied to the depth and cross-range operator. The use of the filter improves the stability of the solution but requires extra numerical burdens. Numerical issues involving the accuracy, efficiency, and stability of the proposed model are discussed and illustrated in an ocean wedge environment.

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In counterfire warfare, it is important to detect and attack enemy targets faster than the enemy using sensingThe grided environmental data is usually provided by the numerical simulation coupled with a data assimilation technique and various inter-or extrapolation algorithms, both of which are based on the observation spanning from simple equipments to satellites. In order to employ the gridded environmental data in the M&S system frequently cutting area and changing its resolution, interpolation algorithms such as linear, cubic spline, IDW, and Kriging methods are necessary to apply. These methods, however, require much time in the M&S system. This paper introduces a technic to reduce time to change the resolution of data. using the binary search method, which finds a point to interpolate quickly and interpolate data in the vicinity of. We also show the efficiency of proposed methods by way of measuring the respective elapsed times.

It is well known that warm eddy is frequently developed through the year in the East Sea. The warm eddy may affect sound propagation due to changes of sound velocity structures in the sea water. To verify the effects of the warm eddy for long-range sound propagation, transmission loss and performance surface, which were used mean direct signal excess range generated by sound propagation modeling using re-analyzed climatology data on March 23th in 2007 were analysed. From these analyses, we found that characteristics of sound propagation in the sea water are changed by the warm eddy, and boundaries of the warm eddy act as a barrier for long-range sound propagation. Furthermore, these disadvantages of the eddy related to sound propagation were increased when the sea bottom depth is shallow.