فصلنامه علوم و فناوری دریا
سال بیست و هفتم شماره 105 (بهار 1402)

Recently, different methods have been proposed for classifying and extracting features from passive sonar data. The main purpose of this paper is to present a feature extraction method from passive sonar data in the presence of noise. Then, the extracted features are used in the classification system and lead to increased efficiency of the classification system compared to previous works. In this paper, the features of the time and frequency domain have been used together. Short-time Fourier transforms with the cepstrum method are used to extract the frequency and time-domain features. The short-time Fourier transform method is used to extract the frequency and time domain features and the cepstrum method is used to extract the features of the time domain. The proposed method was evaluated and tested on the actual collected data of several vessels in the Caspian Sea and the results of the simulations show an improvement in the performance of the proposed method compared to other methods.

Implementing control and guidance systems on an autonomous underwater vehicle requires spending much money, which in case of failure, will suffer heavy losses. For this purpose, the complete method of evaluating an autonomous underwater vehicle's guidance, control, and navigation system is the hardware in the loop test before the diving and buoyancy so that the validation of the designed system can be evaluated in conditions close to reality.This research discusses the implementation of the hardware in the loop test to guide the path of a remotely operated vehicle. Considering the dynamics of the underwater robot - which is highly non-linear and dependent; First, the design of a free model sliding mode controller in the presence of underwater currents as a disturbance in the form of software in the loop is discussed. Second, the software in the loop test is performed by applying the control signal obtained from the proposed controller to the driver of the electric motor as the robot's proportion, whose mathematical model has been identified in the laboratory. Finally, by gradually replacing the hardware drives of the robot in the loop, the hardware in loop test of six degrees of freedom of the remotely operated vehicle is done in real-time in the presence of environmental disturbances. The proximity of the hardware in the loop test results with the software test in the loop shows the correctness of the work done. Meanwhile, the performance of the proposed controller is compared with the PID controller in trajectory tracking. In the end, the accuracy and validity of the implemented hardware table are examined by analyzing the frequency spectrum of the measurements of the hardware in the loop rig.

n general, the maximum practical transferable power is different from the theoretical power, and in most cases much less. This is due to the role of factors related to the geometric shape of the structure, the characteristics of the emitted wave and the propagation environment of the waves. This article deals with practical considerations in transmitting maximum power in waveguides. In this paper, the theoretical principles of electrical breakdown in gases and consequently the maximum power hanling in waveguides as well as the factors that affect the power handling in waveguides are stated. Finally, a rectangular waveguide in the X band with the given wave characteristics and environmental conditions is investigated.

Abstract In the northern basin of the Indian Ocean, including the Bay of Bengal and the Arabian Sea pre-monsoon (March–May) and post-monsoon (October–December) seasons (defined as the seasons before and after the summer monsoon season, Atmospheric conditions create a favorable environment for the formation and strengthening of tropical storms, which can cause human and financial damage if they reach the shores of the Indian Ocean. Various parameters are effective in creating and amplifying tropical storms, such as sea level pressure, sea surface temperature and wind speed. These parameters deepen with the development of the storm and become normal before the storm as the storm weakens. Surface pressure is a quantity that develops and weakens with the growth cycle of a tropical cyclone, and the most important feature of a tropical cyclone is the formation of closed compression lines around the center of low pressure, Which makes it possible to identify anomalies using the tools of statistics and probability and pressure of the rotating center. Statistical or percentage statistical technique has been used to identify low pressure centers.Mean sea level pressure data on the North Indian Ocean were available over a 41-year period, and one of the challenges of using a percentile or percentage on this data is the existence of temporal and spatial dimensions in the data. To overcome the problem of temporal and spatial dimensions of data and define a threshold value for anomalies that includes both time and place dimensions: A) Calculate the percentage index on spatial data in the North Indian OceanB) Calculation of percentage index in time dimension from spatial percentage indicators calculated The important point in identifying the anomalies of the North Indian Ocean is that the best monthly threshold is 97.5% with the identification of 94.5%, which was able to detect the most anomalies in the North Indian Ocean. Therefore, it is observed that the best result in identifying turbulence and rotational disorders by percentage thresholds is the monthly threshold of 97.5%, which is obtained by calculating the percentage threshold by temporal and spatial dimensions

The purpose of the present research is to present a pattern for predicting organizational innovative climate based on high -performance work systems, psychological empowerment and organizational commitment in Noshahr Marin Sciences University. The population included the whole employees of Noshahr Marin Sciences University. 200 employees were selected by simple random method. The research instruments were as follows: Chou and et al.(2010) organizational innovative climate questionnaire which consisted of 16 items with Cronbach’s Alpha of 0.92, Dimitrios and et al. (2016) high-performance work systems questionnaire which consisted of 31 items with Cronbach’s Alpha of 0.96, Mishra & Spreitzer (1997) psychological empowerment questionnaire which consisted of 12 items with Cronbach’s Alpha of 0.86, Allen & Meyer (1996) organizational commitment questionnaire which consisted of 12 items with Cronbach’s Alpha of 0.90. The results of multivariate regression indicated that there is meaningful relationship between High-performance work systems and its dimensions and psychological empowerment and its dimensions and also organizational commitment and its dimensions with organizational innovative climate. The pattern for predicting organizational innovative climate based on high-performance work systems, organizational commitment, psychological empowerment and their dimensions is presented.

The present study was conducted to rank the factors affecting attitudinal and behavioral loyalty in marine tourism in Mazandaran province with emphasis on the dimensions of tourism marketing mix (p8). The statistical population of this study includes all people active in travel agencies, museums, hotels, historical sites and experts in the field of management, tourism and marketing. The sample size is 384 people using Krejcie and Morgan table and the method of cluster random sampling. The method of data collection is a researcher-made questionnaire. In this study, structural equations and 22 SPSS statistical software were used to analyze the hypotheses to analyze the data. In addition, Cronbach's alpha criterion and convergent validity index (AVE) were used to determine reliability and validity. The results show that there is a positive and significant relationship between the dimensions of maritime tourism marketing mix and tourists' attitudinal loyalty. There is also a positive and significant relationship between the marketing mix of maritime tourism and the behavioral loyalty of tourists. Also, according to the research results, people have the highest priority and the process dimension has the lowest priority in creating tourist loyalty.

Passive Millimeter Wave (PMMW) imaging makes it possible to acquire images of objects that are concealed underneath clothing by measuring the radiometric temperatures of different objects on a human subject, that provides a great advantage for security systems in special places like airports. Due to the inherent physical properties of PMMW imaging and the associated hardware, images have poor contrast and low signal to noise ratio. The fundamental operation underlying the sensing operation is the low-pass filtering effect due to the finite size of the antenna lens. The image at the output of the imaging system is a low-pass filtered and blurred version of the original scene. In order to improve the resolution and the fusion quality of the image, some methods of image restoration, super-resolution and fusion will be needed. In the process of restoration, the point spread function is used for the inverse restoration of the original image. Image fusion is the technique of quality improvement that intelligently integrates and processes the multi-source images from various sensors and obtains more accurate, complete and dependable descriptions about the same scene compared with than any of the individual source images. In this paper, various methods for image restoration, super-resolution and fusion are reviewed. Then, appropriate methods in both contexts are selected and modified for the special considered usage. Also, an appropriate generic procedure is designed for PMMW quality improvement in concealed object detection applications. By implementing this procedure, noticeable visual improvement is found in the output image quality.