Design and Research on Transmit Waveform of LPI Active Sonar

随着海洋探测精度、检测概率、通信性能等军事和民用方面的需求，声呐系统从被动方式转变为主动方式。这种转变一方面提高了目标检测概率和水下通信的性能，另一方面也增加了信息被截获或解调的概率。被动声呐只有接受机，而主动声呐系统包括声呐信号波形、声呐信道和声呐接收机三部分。在工作时，系统要先发射探测波形，这一过程将极有可能导致信号被敌方截获并解调，造成信息泄漏。所以如何隐藏信息不被敌方截获或解调是现代主动声呐的重要研究方向。 波形设计是主动声呐系统中一个极为重要的环节，研究表明：对主动声呐来说，声呐发射波形体制既决定了接收系统如何进行信号处理，又直接影响了系统的距离分辨力、速度分辨力、目标探测精度、对...The demands for marine exploration precision, detection probability, the communication performance in the military and civilian are increasing. The sonar system began to change from passive mode to active mode. On the one hand, the change increases the probability of target detection and performance of underwater sonar communication. On the other hand, it increases the probability of information b...学位：工学硕士院系专业：信息科学与技术学院_通信与信息系统学号：2332013115323

Estimating parameters of hyperbolic modulation frequency signal based on cascade dictionary

为降低水下通信中出现的多径和多普勒效应,提高水下目标探测精度,采用双曲调频信号作为探测信号,利用双曲调频信号(hyperbolic modulation frequency,HFM)时频变化具有双曲线的特征,通过建立HFM信号时间-尺度级联原子库模型,在原子库中寻找最优解,进而对HFM信号的两个频率变化因子进行估计。计算机仿真和水池实验的结果均证明,相较于现在常用的小波-拉东变换(wavelet-Radon)估计方法,本方法的均方根误差小于1%,因此在水下目标探测中有较大的应用价值。To reduce the multi-path and Doppler effects occurring in underwater communications and to increase the precision of underwater target detection,we employ a modulation frequency signal as the detection signal. A hyperbolic modulation frequency( HFM) signal is hyperbolic in the time-frequency domain. In view of this feature,we establish a time-scale cascade dictionary model to find the optimal solution; furthermore,two frequency variation factors of the HFM signal are estimated. The simulation results and the pool trials show that the proposed algorithm performs well,and its accuracy is superior to that of the commonly used wavelet-Radon transform. The root mean square error of the frequency variation factors is 1% lower than that achieved using the wavelet Radon transform.This demonstrates the potential of the suggested algorithm for underwater target detection.国家自然科学基金项目(61471309,61107023);; 国家教育部博士点基金项目(20110121120020);; 福建省自然科学基金项目(2013J01258);福建省自然科学基金项目(2010J01344);; 福建省重点基金项目(2012H1012

Lesson study of geography on junior high social studies education : focused on the argument-activity of discussion, aim to educate students for knowledge of society and its citizenship

本稿は，別稿（川口ほか, 2018）に続き，中学校社会科地理的分野の授業研究を進め，その授業改善を図り，併せて，授業研究の方法論の意義を確認した。授業研究としては，4ステップ6活動に定式化し，それに従い，取り上げた地理授業を検討し，課題を明らかにし，その改善を行った。その方策として，自らの考えを他人の考えと交流させ，その上で自らの考えの変容を確認する討議活動の構造を提案した。また，本稿の意義として，次の2つを指摘した。（1）社会科授業研究の方法論の意義である。中学校社会科地理的分野の授業を取り上げ，その単元や授業の各部分におけるエビデンスを用い，相互に照合して，授業の内的改善と外的改善を進める4ステップ6活動の社会科授業研究のあり方を示したことである。（2）中学校社会科授業の課題解決方法を示したことである。すなわち，地理授業において「知識の構造化という社会認識」と「自らの見方・考え方を成長させ，目標の達成へと繋がる他者との討議活動を尊重する態度という市民的資質」を一体的に育成することが可能な「討議の構造」を見いだしたことである。The aim of this paper is to advance the lesson study of geography in the junior high social studies education and to plan the class improvement and confirm the significance of our methodology of the lesson study. As a lesson study, we formulated 4 steps in 6 activities, examined the geography class, clarified some problems and performed the improvement. We made his/her idea be exchanged with others\u27 idea as the plan, and proposed the structure of the discussion/argumentation activity that the change in his/her idea is confirmed on it. As results of this paper, we pointed out the following: (1) The significance of the methodology of lesson research of social studies. We took up the geography class of the junior high social studies education, and checked mutually using evidence in each part of its unit and class according to our methodology of the lesson study on social studies, 4 steps 6 activities to push forward the internal improvement of the class and external improvement. (2) Showing the solution of some problems on junior high school social studies class. Based on a geography class, we brought up the knowledge of society called being structured of the knowledge and own viewpoint, way of thinking of each student and are to have found "structure of the discussion/argumentation" that can bring up the nature of the citizen of the manner to respect the discussion/argumentation activity with others, as the overall upbringing of the knowledge of society and the citizen-like quality