论文标题:科学假说探析
Studies on Data Transmission Techniques in Shallow Water Acoustic Channels
论文作者 陈海明
论文导师 潘世墨,论文学位 硕士,论文专业 科学逻辑
论文单位 厦门大学,点击次数 840,论文页数 38页File Size2044k
2002-06-01论文网 http://www.lw23.com/lunwen_1927282/ 科学假说;形成;检验
shallow water acoustic channels;data transmission;multi-path interference;channel model;FH communication;synchronization technique
《科学假说探析》一文主要从科学假说的形成和检验两个角度来对科学假说进行阐述。科学假说是科学家为了解决某一疑难问题而提出的一种尝试性理论，但是这一尝试性理论是如何形成的，或者说科学发现是如何产生的，却在科学家或者科学哲学家中存在一定的分歧。整的说来，关于科学假说的形成，通常存在三种方法论主张：归纳主义方法论、非逻辑主义方法论、整体主义方法论。归纳主义方法论认为，科学假说的形成是科学家遵循严密的逻辑步骤从具体经验观察数据中归纳出普遍性理论或定律的结果。相反，非逻辑主义方法论认为，科学假说的形成过程不存在严格的归纳方法，科学发现是灵感、想象、直觉等非理性因素作用的结果。整体主义方法论认为科学活动既有逻辑的因素，又有非逻辑因素，既有归纳活动，又有演绎活动：科学发现活动既有想象、灵感、直觉等非逻辑因素的作用，又有比较、分析、综合、概括、抽象、归纳、演绎等规范性逻辑因素。本文在第二部分对与科学假说检验有关的一些主要问题进行了阐述和分析。在科学假说的检验途径这一节，主要阐述了具有普遍性的科学假说通过与辅助假说相结合演绎出具体的检验推论，接受观察和实验的检验，本节还对检验途径的各种逻辑形式进行了列举。在科学假说的经验涵义及原则上的可检验性这一节，主要阐述了合格的科学假说必须具有经验内容，不具有经验内容的科学假说无法进行检验。在科学假说的支持这一节，主要阐述了科学假说所受支持力和确认度的大小与以下各种因素有关：检验证据的数量、证据种类的多样性、观察实验的精密度、证据的新颖程度。在简单性决定科学假说的取舍这一节，主要论述了相互竞争的科学假说在受到相同的经验数据支持时，也就是在其解释力和预测力大小均相等时，更简单的假说将优先被接受。在科学假说的证实和证伪这一节，主要阐述了科学假说接受检验后的结局问题，即证实和证伪问题，对证实主义和证伪主义观点进行了反驳。
Shallow water area is a very important strategic area for both military and nonmilitary purposes. People have applied the techniques of underwater acoustic communication to a variety of purposes in their use and exploration of the seas. In recent years, studies on data transmission in shallow water acoustic channels have attracted people"s wide interests and got a rapid development. It provides important techniques to solve the problems of the reliability of information exchange in the seas.On the basis of general analysis of the features of shallow water acoustic channels, the key techniques and the difficult points in underwater acoustic (UWA) communications, this dissertation proposes a simple but effective model for multi-path interference, which is then used to simulate the communication system for underwater acoustics. Associated with the experimental results of the field test, we present a data transmission technique using frequency-hopping communication in underwater acoustic channels.The main research contents in this dissertation are as follow:1. Discusses the unfavorable effects of the shallow water acoustic channels on data transmission, and objectively introduces recent certain advanced in UWA communication.2. Studies on the simulation of communication system for underwater acoustics. A UWA channel model has been developed based on the sound ray. Special emphasis has been given to the effects of the bottoms, the surfaces of the shallow sea, and the absorption of the signal caused by the shallow water. The dissertation introduces the impulse response of the shallow acoustic channel, utilizes windowing techniques to determine the effect of the signal-to corruptive multi-path signal ratio (SMR) on UWA communication in the observation window.3. Experimental studies on the statistical characteristics of the sound transmission in the shallow water in Xiamen Harbor. The dissertation gives the PDFs (probability density functions) of amplitude and time correlativity coefficient function of the direct-path signal and multi-pathinterference, measures the frequency spectra distribution of the noise in Xiamen Harbor. With these test results, we obtain correlate parameter for UWA communication system.4. Introduces the diversity methods and frequency hopping (FH) communication techniques to reduce the signal fading and eliminate inter-symbol interference (ISI) of multi-path interference. The dissertation analyses the principle of data transmission with FH communication to anti-multi-path in shallow water acoustic channels, and designs a method to implement data transmission in UWA.5. Synchronization is one of the key techniques of FH communication. A method of displacement waiting auto-synchronization with match filters is put forward to realize the synchronization of FH communication in UWA. We deduce from theory that this method can reduce the time of acquisition, then the dissertation designs and implements a method of synchronization with correlated detection for UWA FH communication.6. Based on basic research and experiments, a data transmission system in shallow water acoustic channels is designed and the field test is performed in Xiamen Harbor. Experimental results shows: a data rates of 600bits/s with the bit error rates on the order of 10"4 was demonstrated at distance 6000m in the shallow water channel of Xiamen harbor.The innovation of this dissertation is that:1. Both the channel model simulation and experimental study on the statistics characteristics of data transmission in shallow water channels are been obtained in this dissertation.2. The dissertation put forwards a method of displacement waiting auto-synchronization with match filters for UWA communication.3. The dissertation designs and implements the system of data transmission with FH communication in underwater seas, which is performed in field test in Xiamen Harbor.
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