فصلنامه علوم و فناوری دریا
سال بیست و هفتم شماره 108 (زمستان 1402)

In the spoofing attack, the attacker sends his fake request messages to the destination server computer and pretends that the requests were sent from a source that is a node in the network with a valid and reliable IP address. In this article, an intelligent method is introduced to detect the presence of several fake users. Evolutionary processing has also been used to improve the accuracy and precision of detecting the number of attackers. The artificial neural network reveals the spoofing attack by detecting the change in the signal pattern of the IP packets received from a node in the access point. The metaheuristic algorithm of imperial competition also determines the number of attackers using clustering. By extracting the features of signal strength, signal phase, and received signal energy, this algorithm can cluster the signal pattern of users with a specific IP address. In the worst case, it correctly detects attacks with a probability of 98. As a result, if the number of clusters is more than the number of active IP addresses of the wireless network, this number of excess clusters shows the number of attackers. The simulation results of the proposed algorithm show that it has 99% precision and 98% accuracy in detecting attacks.

In this article, a microstrip antenna with suitable dimensions and wide circular polarization bandwidth has been designed, simulated, and built. This antenna is designed with an incomplete ground plane and dual feeding. Also, this antenna has an incomplete ground plane in a creative way, which is removed from the ground plane, in the proposed antenna with dual input and a quarter circular patch, which is presented with wide changes in the ground plane with the aim of creating a wide bandwidth and a suitable axial ratio. The antenna includes two long transmission lines and two ports in the antenna patch. The fabricated antenna has external antenna dimensions of 40 × 50 mm2 and FR4 substrate height of 1.6 mm. Using the incomplete ground plane in the proposed antenna improves the impedance matching and increases the parameters S and axial ratio (AR). The measurement results show that the proposed antenna with an incomplete ground plane can reduce the coupling and improve the circular polarization. The measurement and simulation results show that the proposed antenna has a wide bandwidth from 4.89 to 6.85 GHz for return loss.

In this paper, an ultra wideband amplifier is proposed applying for the frequency range 3.1 to 10.6 GHz. The structure of this circuit is defined as differential and common-gate. A standard 0.18 CMOS technology is used for simulation. Amplifier has a good stability thorough the frequency range of operation. The power consumption is 11 mw from a 1.8V supply. The simulation results show that the LNA achieved the maximum gain of 15 dB, input and output return loss lower than -10 dB and -8 dB respectively, A minimum noise figure is less than 4 dB in 3.1-10.6 GHz. Techniques used in the proposed circuit is using capacitive cross coupling circuits used in the conventional structure of wideband circuits that makes noise figure and gain improve the entire frequency range.

This article proposes a three-effect system based on diesel engine to increase efficiency and reduce environmental pollution. An organic Rankine cycle to produce power, an ejector refrigeration cycle to produce cold and a heat exchanger to produce heat. 12 biofuels are produced based on vegetable oils and compared with the performance of pure diesel. Mass, energy, exergy, economic and environmental analyzes are performed for the produced biofuels. In this regard, canola biofuel B20 has been selected as the best fuel for the designed system, which has a net power of 7468 kW with an exergy efficiency of 37.96%, an environmental sustainability index of 1.611 and an environmental impact index of 1.635 at an engine speed of 1700 rpm and load. It provides 100 percent. The exergy efficiency of the engine is influenced by the engine load, while the exergy efficiency of the proposed system is influenced by the engine speed. Also, the exergy efficiency of the system and the unit product cost are 37.96% and 11.196 $/GJ, respectively, in the optimal state.

The Awt terminal is suitable for all weather conditions and is suitable for goods whose unloading and loading operations depend on weather conditions. The purpose of this research is to investigate the impact of the feasibility study of setting up an all-season terminal with an emphasis on the increase in sea traffic in Astarami port. In terms of the purpose of this qualitative research, the strategy of content analysis with specific related principles has been used. The information required for the research was collected in the field by referring to the personnel of the Ports and Shipping Department, Astara Customs and Kaveh Company. The findings of the research show that the establishment of an all-season terminal in Astara port has a positive effect on the flexibility of transportation and the increase of sea traffic, but this action is carried out if the communication links such as road and rail, as well as the rules and regulations governing transportation Comply with global standards.

The purpose of this research is to design a capacitive wave recorder and evaluate the risk of its design and extract critical levels to prevent its occurrence in the capacitive wave recorder. In this research, designed circuits were simulated in Proteus environment and Arduino board and C software were used to write the necessary programs.Also, the error mode analysis method was used to evaluate failure modes. All parts of the capacitive wave recorder were evaluated and states, effects and causes of failure were calculated and evaluated. Then the risk number of each failure was calculated and its crisis level was prioritized.Failure analysis documentation can only include a brief statement of proposed exposures or design changes: replacing elements with more reliable ones, introducing backup systems, and new or improved methods that limit damage.Critical situations were extracted and countermeasures were suggested to improve performance. Two methods of observation and interview were considered to collect information.

Paying attention to export is considered as one of the main actions of developing countries for economic growth and development. Considering the importance of small and medium-sized companies in the economy of developed countries, as well as the geographical conditions of the country in terms of access to sea routes, export is of particular importance for these companies in this way. Therefore, the purpose of this research is to design a model for the characteristics of decision makers of small and medium companies that make decisions in the development of sea-based exports.

This research is applied in terms of purpose and descriptive-exploratory in terms of execution method and it is among the qualitative researches of the foundation data method and it was carried out through the Strauss-Corbin systematic method. The data collection tool was a semi-structured interview and the information was analyzed using open coding, axial coding and selective coding. The participants were qualified subject matter experts in companies that are effectively involved in marine exports, which achieved theoretical data saturation through snowball sampling of up to 11 people.

The central phenomenon is management characteristics, which explains the management characteristics effective on export development activities in a process of underlying and intervening factors and relying on a group of causal factors.

The results of the research showed that management ability, management records, management commitment, management scientific capacity and the purposefulness of management actions are effective in the development of sea-based exports of small and medium-sized companies.

Law of the seas always provides the possibility of resolving conflicting approaches to issues at sea and guarantees legal certainty in the freedom of shipping lines in the high seas. Although some governments have a conflicting approach in this matter, in the end they must respect the legal rules, both contractual and customary. Strategic Navy of the Army of the Islamic Republic of Iran in the direction of securing national and international interests and providing maritime security , supporting the commercial shipping lines of the country, etc. and also based on the strategy determined in the governance structure of the Iran has been present in the field of international waters based on upstream documents and within the framework of the international law of the seas. But in the meantime, some countries such as; America, Australia, France, etc. have tried to prevent the presence of the army navy in international waters, especially the mission of the 360 fleet with a double interpretation of the rules of international law of the seas and the application of policies Sanction to prevent this presence. Therefore, the purpose of this research is to examine the rules governing the freedom of navigation in the open sea, and to examine the performance of the Islamic Republic of Iran Navy from the Indian Ocean to the implementation of the 360 flotilla mission, which briefly tries to answer the question that Has the performance of the Navy of the Islamic Republic of Iran from the Indian Ocean to the mission of the 360 flotilla been within the framework of the international law of the seas? to answer The research method of this article is descriptive analytical method, and the method of collecting information is library-reference method. According to the findings of the research, despite the unsuccessful efforts and violation of the rules of international law by the United States and other allied countries, the performance of the Islamic Republic of Iran has been in compliance with and respect for the rules of international law of the seas, and the aforementioned missions has implemented with authority in the international arena.