جستجوی مقالات مرتبط با کلیدواژه "do" در نشریات گروه "مهندسی دریا"

One of the most important things in a tropical storm that causes its intensity and weakening is the physical exchanges between the storm and the ocean surface. To study surface exchange, two very important quantities latent heat flux and momentum flux are considered. The momentum flux is related to the frictional velocity. Therefore, the frictional velocity has been used to study the momentum flux. The study of latent heat flux in tropical storms shows that this physical quantity has many changes in the tropical storm growth cycle in the central and peripheral parts of the storm. These fluctuations show that the latent heat flux plays a large and colorful role in the development of tropical storms. In all of this research, ERA5 data with spatial resolution accuracy of 0.25 degrees has been used in longitude and latitude data. The results of this research regarding the latent heat flux show that this flux reaches its maximum in accordance with the pressure of the central core at the peak of storm intensity and this flux will start to decrease during the weakening stage of the storm. A good coincidence is seen between the maximum latent heat flux and the minimum pressure drop in tropical storms. Based on the calculation of the latent heat flux for the internal part (radius less than 0.75 degrees) and the peripheral part (between 3 and 5 degrees), it indicates the horizontal flux exchange between the core and the surrounding environment. Actually, as the flux in the environment decreases, the flux in the inner core increases.

Today, navigation systems play a prominent role in modern life. They have various applications in different fields such as information security, marketing, transportation, energy resource management, and so on. Among satellite navigation systems, GPS and GLONASS are very common and widely used. However, satellite navigation systems are vulnerable to a wide range of spoofing attacks and interferences, making the detection of spoofing attacks a crucial challenge. In such a way that using simple methods without artificial intelligence, it is not possible to detect the presence of malicious spoofing attacks. With the advancement of science and technology, spoofing equipment is also evolving. In this article, five effective spoofing methods are introduced. These methods are validated by a Software Defined Radio (SDR) receiver. Then, using a weighted decision function, the overall performance of the five methods is evaluated, and the decision function will determine the presence of a spoofing scenario. These methods along with the decision function will be implemented on hardware consisting of a commercial receiver and an ARM processor. Furthermore, the results indicate that the performance of the detector is acceptable in various generated spoofing scenarios. The receiver's detector accuracy in detecting Spoofing attacks in this work is calculated to be 98.9 percent.

The formation and development of a breach in an embankment can dramatically affect the rate of an unplanned release of water from the reservoir and change the downstream area to a floodplain landscape. Furthermore, the failure of a landslide dam is considered one of the most serious natural hazards around the world, which has increased significantly due to the effects of climate change, frequent earthquakes, and population growth. Dam failure parameters, such as the width and height of the breach, are considered key variables for estimating the peak outflow discharge (Q_p). Determining the breach characteristics during the failure event has an important role in the estimation of flood hydrograph and the Q_p. Therefore, the failure characteristics, including average breach width (B_ave) in embankments and landslides are studied separately and outcomes are compared together. Additionally, new and unique relationships are developed based on the top width (B_t), the bottom width (B_b) of the breach, as well as the dam height (H_d), using artificial intelligence. To investigate the breach development process, laboratory data with granular materials obtained from the instantaneous failure of physical models have also been employed, and the time series variations of the dimensionless ratios of B_ave/B_t and B_ave/B_b are presented for a better evaluation of the erosion process. In this study, the dimensionless ratios obtained from the overtopping of the experimental models have also been compared with the historical records of the failure of existing prototypes derived from the breached embankments and landslides. Considering irregular compaction, lack of coherent structure, and the wide range of erosion in landslides, a new and accurate range of variation has been introduced using multiple regression for B_ave determination in both kinds of the dams in framework of the dimensionless ratios. The application of performance indices describes the high accuracy in the proposed relationships.

Due to the population increase and consequently rising energy demand and attempts to replace fossil fuels with clean energies, wave energies have been considered a dominant source of energy. Different types of wave energy converters for producing electricity have been made up to now. Several parameters affect the efficiency of these devices, like the related geometries. The research aim is to investigate the effect of the buoy geometry on the performance of such devices. These geometries are single-cylinder, cone cylinder, and hemisphere cylinder. After simulating of three models in AQWA the related power is calculated and the optimum one is defined. As the damping and stiffness coefficients of the PTO system cannot be modeled in AQWA the hydrodynamic coefficients are derived in Aqwa based on the frequency analysis and then the equation of motion is separately solved in Matlab. These three different types of geometries are analyzed under regular and irregular waves of the Makran sea. The results show that the cone cylinder results in higher averaged power compared to the –single-cylinder and hemisphere-cylinder under both the regular and irregular waves.

The dynamics of many mobile devices in water are interactive and none linear. In particular, due to the assignment of incomplete and insufficient actuators, complex dynamics can be seen clearly in the Hovercraft. In this device, the dynamics changes greatly in each maneuver (different speeds). By turning the rudder for lateral movement, the longitudinal channel is affected and also by changing the longitudinal speed, the dynamics of the lateral channel is completely transformed. In this research, by identifying the dynamics of the system, a non-interference linear model is first extracted. For the obtained transfer function, with certain requirements, the controller is designed for the longitudinal, lateral velocity channel and angular velocity channel. As stated, this controller is designed for a specific situation and does not necessarily behave optimally for all maneuvers or uncertainties in the Hovercraft's system specifications. Inevitably, with the reinforcement learning method and specifically with the Monte-Carlo learning algorithm, the primary controller gains are adjusted offline for all possible situations (maneuvers and uncertainties). It should be mentioned that all the calculation load is done off-line, the result is applied to the primary control system as correction gains and is used on-line for the control process. The research results show that by adjusting the controller with the help of machine learning, at least %25 improvement in the tracking error is prosecuted.

In this paper, simulation and modeling of Quantum Dot (QD) laser with planar cavity is implemented based on a set of rate equations for carriers and photons. This modeling is done with the purpose of using quantum dot lasers with different wavelengths in submarine and fiber optical communications with high security. The rate equations are solved in five energy states using 4th order Runge-Kutta method. It can be seen that increase in injected current of the laser active region results in decrease of switching time and stability time of the system and power peak and stationary state powers will be increased. By computing P-I curve, it is recognized that by decreasing carrier relaxation times to lower states, injection current can be decreased. Also, exponential dependence of laser switching time to injection current is shown.

The transfer of energy, momentum and mass that occurs between the atmosphere and the ocean and the interaction between them affects the circulation of the atmosphere and the ocean on a very large scale. Physical knowledge of these processes is necessary for their correct parameterization. It is necessary to determine the relationships required to investigate these interactions and calculate them in studies such as sea level energy budget, sea state forecasting, ocean boundary layer modeling and sea surface currents.In this research, using the bulk model based on semi-empirical relationships, the interaction between the atmosphere and the ocean and the stability of the environment in high-speed wind (tropical storm) have been studied. Real data related to the tropical cyclone Gono that occurred in the Indian Ocean and the Sea of ​​Oman have been used as inputs to the model. Important parameters such as the roughness of the water surface Zo, the frictional speed of the atmosphere on the water surface, the drag coefficient, the stability of Monin Abukov and the surface momentum flux in this environment have been calculated for the days of June 1 to 7, 2007. The graphs of these parameters are drawn according to the change in wind speed. The estimation of these parameters using different parametrization formulas presented shows different results, which is due to the difference of views about the physics of the interaction between the atmosphere and the sea. Also, for very high speed winds, we should be more careful in using the bulk model in order to estimate the fluxes between the atmosphere and the sea.

The three-dimensional reconstruction of the underwater environment for the exploration and exploitation of the oceans and seas in terms of transportation, trade, food and medicine resources, mineral resources and the security of coastal countries is very important in today's world. For this reason, various researches have been carried out in this area and it is still one of the important research areas for research groups in research centers and universities. Obviously, to conduct new research in this field, it is necessary to be familiar with the methods that have been presented up to now. Therefore, in this research, the various methods that researchers have presented for the reconstruction of the three-dimensional surface of seas and oceans and underwater objects have been reviewed. For this purpose, the content is presented in three categories. In the first category, the optical methods, the second category, the reconstruction of the underwater 3D surface using acoustic methods, and the third category, the 3D underwater reconstruction based on the combination of optical-acoustic images have been investigated and evaluated. Finally, potential future developments in this field are considered.

Analytical modeling in the early stages of designing electric machines has a significant value in terms of time and accuracy. In this article, an analytical method for modeling the magnetic field distribution in the air gap and magnets of a permanent magnet synchronous motor based on the calculation of the scalar potential vector is presented. In this modeling, which is presented based on the sub-domain modeling method, to reduce the complexity of the problem, the motor under study is divided into two sub-domains, including magnets and air gap, and Maxwell's equations are solved within these sub-domains with specific boundary conditions, and finally, two analytical relationships dependent on the geometrical variables and materials used in the motor under study was presented to estimate the size of the field density in the subdomains. The modeling method is based on the calculation of the scalar potential vector and the estimation of the magnetic field density distribution in each subdomain, which is based on solving the equations of the Laplacian/Poisson field obtained in polar coordinates. The obtained results are important from two points of view, firstly, in the modeling done, the effect of changing the geometrical parameters and materials on the distribution of the magnetic field density in a permanent magnet synchronous motor can be easily investigated, and on the other hand, due to the complex and time-consuming calculations Finite element simulation software in calculating the distribution of magnetic fields in electric machines. The obtained results show that the modeling done is suitable for use in design programs, to avoid long-term calculations by finite element simulations.

In today's knowledge-based economy, knowledge and virtual assets of the company, which are considered as intangible financial assets, are considered as the main factor of wealth production in comparison with other tangible assets of the company. In today's competitive markets, where the goal of companies, whether knowledge-based companies or other companies that have significant virtual assets, is to gain more market share by creating competitive advantages, the success of companies depends on the organization's virtual asset management because it is parallel to the growth of technology. Gradually, companies' assets are moving towards virtual assets. Today, with the advancement of technology, virtual assets have found a special place in various forms in the process of economic, managerial, technological and social development. Therefore, it is important in applied research to value the virtual assets of knowledge-based companies using information technologies, and the results are available to the stakeholders and managers of knowledge-based companies. For this reason, in this research, 92 knowledge-based companies cooperate with defense organizations. was evaluated by using structural equations and mediating role of information technology to examine the level of access, confidentiality and integrity of virtual assets of knowledge-based companies, and the results revealed that availability is 0.193, confidentiality is 0.363, and integrity is 0.061 variables of information technology. As a mediating variable, it influences and also the information technology variable predicts the intention by 0.717 of virtual assets.

Image fusion is an important technique in image processing with the aim of producing a single image containing salient features and complementary information from source images, using appropriate feature extraction methods and fusion strategies. In recent years, methods based on deep learning have shown great potential in image integration applications, and many researchers are trying to provide better quality of the integrated image using deep learning methods. In this research, a multi-scale convolutional neural network is proposed to integrate visible and infrared images called MSCNN-VIF, in which the various features and information in the images are integrated using convolutional blocks. In addition, the proposed model includes a multi-scale (MS) architecture for better scanning of different parts of the image, whose main goal is to improve the performance of the proposed image integration system. In general, the proposed model consists of an encoder and a decoder and includes three main parts: feature extraction, integration and reconstruction of visible image and infrared image. In this method, infrared and visible images are given to the encoder and background maps and details of feature maps are produced. Then, the network connects two types of layers along the channels. Finally, the concatenated feature maps are passed through the decoder to recover the original image. Different from the training phase, in the testing phase, an integration layer is placed that integrates background maps and detail features separately. Also, the proposed method has been tested on three known and available databases. The obtained results show that the proposed method has performed better than other methods based on different evaluation criteria.

Reducing the resistance force in order to access more power, higher speed, and less fuel consumption is one of the various goals in scientific research. Considering that the main important problem for a vessel moving in a fluid is the drag force, the tools for reducing drag has attracted the researchers.In this study, the researchers sought to find the mathematical relationship for predict sawtoothed riblets percentage of drag reduction. For this purpose, first, by investigating the result of scientific researches, they are determined the effective variables on drag reduction. Then, by anlyzing the relationship between drag reduction and these variable, fit the curve of the three-dimensional shape of the obtained function, and matching the spatial shape of the relationship with the equations of quadratic procedures, the closest shape that has the ability to match the relationship according to the limits was calculated. it determined elliptic paraboloid relationship. which had a good agreement with the experimental results.

n this research, in order to evaluate the ecological assessment of Safarod River sediments and environmental effects, 8 sediment samples were collected from river bed and the concentration of heavy metals (iron, arsenic, cobalt, chromium, nickel, lead, copper and zinc) was determined by ICP-OES method. Based on the degree of contamination (Cd), sediments of the Safarod River are classified in the range of moderate pollution. Also, based on the modified pollution degree index (mCd), it was determined that all the samples except for 3 stations are polluted and they are in the range of low to medium pollution degree. The pollution load coefficient (PLI) was obtained in most stations, especially in the end sections, in the range of more than 1 (slightly polluted to polluted), but in terms of the ecological risk (RI) of the river, it is in the low risk range. Based on these results, the key solutions to prevent further pollution of this river are continuous management, control of erosion of upstream sediments, reduction and treatment of industrial and domestic effluents and preventing them from entering the river.

Nowadays, comprehensive research is done on the hydrodynamic analysis of oil tankers to reduce their resistance. Most of these studies have focused on drag reduction in calm water and design conditions, and have rarely evaluated the ship's behavior under real operational conditions at sea. For this reason, in the current paper, using a practical and effective method, the dynamic behavior of an oil tanker has been studied in real conditions. To this accomplishment, the KVLCC2 tanker was selected, its resistance in calm water, dynamic behavior, and added resistance in the wavy condition were measured and the results obtained were compared with the experimental database. The numerical simulation shows the acceptable accuracy of the present method compared to the experimental results. After ensuring the accuracy of the results, a wide range of ship working conditions and exposure to waves, as well as different loading conditions have been studied. Based on the obtained results, it can be seen that the strip theory method is more accurate in estimating the added resistance of such a vessel compared to predicting its dynamic behavior. Also, the angle of impact of the waves on the vessel does not have a significant effect on the maximum range of the vertical displacement. In addition, the maximum added resistance at all wave impact angles is directly proportional to the ship draft.

A hotel barge is a barge that has been converted into a hotel or other types of accommodation to provide services. In Europe, hotel barges are commonly found on rivers and canals and may be used for domestic travel or permanently docked in an area. There are not many resources available regarding the interior architecture of the Hotel barge, and this article intends to cover a part of it in this field. The hotel barge has many advantages, such as the northern and southern cities in Iran, due to the location of the land, they are very affordable. They don't stay in one place forever and they can be moved by tug boat, they are environmentally friendly and they are quick and easy to build. In this article, first, some rules of the rules of the international convention on the safety of life at sea, and then the cross-sections of three famous floating hotels in the world have been examined, and some points related to the stability of the hotel have been presented. In the second step, the internal architecture of these hotels were examined and finally it was concluded that attention to the floating center of gravity is very important in the placement of different parts of a floating hotel. In the investigated floating hotels, the area of the rooms starts from 14 square meters and reaches 65 square meters. The minimum service area is 3 square meters and the maximum area is 8.8 square meters. The ratio of room area to room area with service is 0.73-0.91 and the ratio of room area to service area is from 2.64-9.7. The space allocated to each person in a room is also 5.5-28.25 square meters.