Correction of seabed layer thickness in processing subbottom profile data

The subbottom profiling is an important means of marine engineering survey, hazardous geology study and continental shelf scientific research. The accuracy of subbottom profile data interpretation has a direct impact on the research and investigation results. Because some of profilers’ transducer and hydrophone are separately installed, when the survey area is very shallow, distortion of shallow layers will be caused if it is seen as a self-excited and self-collected single-channel seismic system. According to the principle of subbottom profiler, the distortion correction formula is deduced and analyzed, providing actual value to using C-View software to interpret such subbottom profile data more accurately. In addition, the seabed sediments sound velocity is one of the key parameters when acquiring and processing the subbottom profile data. On the basis of comparing some sound velocity forecasting empirical equations, the LU Bo’s equation was considered the most appropriate to predict the seabed sediments, sound velocity at near-shore of China. In a survey of an artificial island site, the LU Bo’s equation and the porosity data obtained from geological drilling were utilized to predict the sediments sound velocity, and the sound velocity structure profile was plotted, which was applied in processing the subbottom profile data of the artificial island investigation. The method of using porosity data to predict sediments sound velocity in processing subbottom profile data can improve the interpretation accuracy and it’s of practical significance.

Depth Classification of Underwater Targets Based on Complex Acoustic Intensity of Normal Modes

In order to solve the problem of depth classification of the underwater target in a very low frequency acoustic field, the active component of cross spectra of particle pressure and horizontal velocity （ACCSPPHV） is adopted to distinguish the surface vessel and the underwater target. According to the effective depth of a Pekeris waveguide, the placing depth forecasting equations of passive vertical double vector hydrophones are proposed. Numerical examples show that when the sum of depths of two hydro- phones is the effective depth, the sign distribution of ACCSPPHV has nothing to do with horizontal distance; in addition, the sum of the first critical surface and the second critical surface is equal to the effective depth. By setting the first critical surface less than the difference between the effective water depth and the actual water depth, that is, the second critical surface is greater than the actual depth, the three positive and negative regions of the whole ocean volume are equivalent to two positive and negative regions and therefore the depth classification of the underwater target is obtained. Besides, when the 20 m water depth is taken as the first critical surface in the simulation of underwater targets （40 Hz, 50 Hz, and 60 Hz respectively）, the effectiveness of the algorithm and the cor- reemess of relevant conclusions are verified, and the analysis of the corresponding forecasting performance is conducted.

Relationship of Cardiovascular and Cerebrovascular Diseases to Meteorological Conditions and Forecast Method in Nanjing City

[Objective] The study aimed to discuss the relationship of cardiovascular and cerebrovascular diseases to meteorological conditions and forecast method in Nanjing City. [Method] Based on daily cases of cardiovascular and cerebrovascular diseases from a hospital in Nanjing City as well as daily meteorological data from Nanjing Meteorological Station from January 2003 to July 2008, the monthly and seasonal variations in quantity of patients suffedng from cardiovascular and cerebrovascular diseases in Nanjing City were analyzed firstly, and then the relationship between mete- orological elements and incidence of the diseases was discussed, finally the forecast model for the incidence of the diseases was established using the stepwise regression method. [Result] Cardiovascular and cerebrovascular diseases in Nanjing City happened all the year round, and the inci- dance was high in the seasonal transition phase from autumn to winter. Daily incidence of the diseases in Nanjing City correlated negatively with dai- ly maximum, minimum and average vapor pressure, daily minimum relative humidity and so forth, but their incidence had positive correlations with diumal range of daily temperature, daily maximum, minimum and average pressure. Daily average number of patients suffering from the diseases obviously correlated with daily average temperature, daily maximum vapor pressure and daily average relative humidity. [ Conclusion] The research could provide scientific references for the prevention and forecast of cardiovascular and cerebrovascular diseases in future.

Characteristics Analysis and Forecast of Fogin Changzhi Region

By analyzing meteorological data during 2000 -2009, the characteristics of fog in Changzhi region and weather situation of fog weather occurrence were summarized, and forecast equation was established.