• Proceedings of the National Institute of Ecology of the Republic of Korea
• /
• v.3 no.1
• /
• pp.47-53
• /
• 2022

The escape behavior of prey fish to predator attack is directly linked to the survival of the fish. In this study, I explored the escape behavior of Medaka fish to bird attacks. To simulate the attack, I designed a model triangular-shaped bird to slide along a fishing line connected between rods at both ends of the tank. The triangular shape was set to 10×15 (S=1), 15×20 (S=2), and 20×25 cm (S=3) with base×height. The slope (θ) of the fishing line, which determines the attack speed of the model bird, was set to values of 15° (θ=1), 30° (θ=2), and 45° (θ=3). The escape behavior was characterized using five variables: escape speed (ν), escape acceleration (α), responsiveness (γ), branch length similarity entropy (ε), and alignment (ϕ). The experimental results showed when (S, θ)=(fixed, varied), the change in values of the five variables were not significant. Thus, the fish respond more sensitively to S than to θ In contrast, when (S, θ)=(varied, fixed), ν, α, and γ showed increasing trends but ε and ϕ did not change much. This indicates the nature of fish escape behavior irrespective of the threat is inherent in ε and ϕ. I found that fish escape behavior can be divided into two types for the five physical quantities. In particular, the analysis showed that the type was mainly determined by the size of the model bird.

• Journal of Power System Engineering
• /
• v.16 no.6
• /
• pp.24-29
• /
• 2012

In this study, the numerical simulation has been performed to investigate the hydrodynamic evaluation between double plate steel rudder and newly designed foil type rudder for small fishing boat. The simulations are carried out in 2 speed ranges with 7 variations of flow's angle of attack which is at intervals of about 5 degree respectively. As the well-known commercial code, FLUENT and CATIA are used as the solver. The simulation results show that new designed foil type rudder is better than conventional double plate rudder in terms of Lift and Drag of running boat in the water.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.22 no.5
• /
• pp.199-206
• /
• 2021

This paper describes the feasibility and reliability verification of installing a protective structure to protect attack periscopes. The attack periscope is the critical equipment of a submarine to enable the user to monitor surface and air activity, collect navigational data, and detect and identify targets. The attack periscope provides target information acquired through TV, IR camera, and laser range finder to the combat system. In the product improvement program, the upper part of the masts was exposed to the outside of the sail because the existing attack periscope was replaced with a new one. On the other hand, the head sensor can be damaged by floating objects, such as fishing nets, during sea navigation. Therefore, the installation of a protective structure for an attack periscope improved the equipment operation performance. The feasibility and reliability of the installation of the protective structure were verified by examining the influence of URN.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.39 no.4
• /
• pp.305-317
• /
• 2003

Underwater shape and hook depth in tuna longline gear are important factors to decide fishing performance. It also should be considered that management and analysis of hooked rate data from hooked fish species and sizes, and each fishing would be used as a reference data in the future fishing. In this research, after analyzing underwater shape of tuna longline gear by current direction and speed using simulation, experiments were executed in flume tank to verify accuracy of the analysis. Also using the depth of each hook from the simulation, a database system was setup to process the data of bait and hooked fish species. The results were as follows；1. When the attack angle and the shortening rate are fixed, a decrease of the hook depth is proportion to an increase of current speed. 2. When the shortening rate and current speed are fixed, a decrease of hook depth is proportion to an increase of attack angle. 3. When the attack angle and velocity of flow are fixed, a decrease of hook depth is proportion to an increase of shortening rate 4. As a result of comparison between the underwater shape by simulation and that by model gear, the result of the simulation was very close to that of model gear within $$ {\pm}3%$$ 3% error range. 5. In this research, hooked rate database system using hook depth of simulation can analyze the species and size of fish by the parameter; bait. hook depth, so It could be helpful to manage and analyze the hooked data on the field.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.16 no.2
• /
• pp.61-67
• /
• 1980

Previously, we had experimented on the model of stow net under the various combination including water velocity, spherical floats and elevating floats with the shearing hoods instead of the upper beam, however we couldn't concern with their characteristics. Spherical floats maintain their buoyancy at the same level when the speed increases, only the drag increases and effects some reduction in the fishing height. To eliminate this shortcoming, floats have to some hydrodynamic lifting force which increases with increasing speed. Phillips float with a dish-shaped metal plate welded on at the lower part and synthetic upthrusting float were used for the experiment to compare with their characteristics. Six kinds of model shearing hood depend on the angle of attack were used to test the characteristic of the shearing hood. According to their results, when the angle of attack is 30\ulcorner, the lift and drag coefficient reveal 1. 36, 0.84 respectively. And also experimented on the 5X8cm shearing hood to investigate the suitability for the model stow net.

• Convergence Security Journal
• /
• v.6 no.4
• /
• pp.171-177
• /
• 2006

The hacking aspect of recent times is changing, the phishing attack which uses a social engineering technique is becoming the threat which is serious in Information Security. It cheats the user and it acquires a password or financial information of the individual and organization. The phishing attack uses the home page which is fabrication and E-mail and acquires personal information which is sensitive and financial information. This study proposes the establishment of National Fishing Response Center, complement of relation legal system Critical intelligence distribution channel of individual and enterprise.

• Journal of Korea Society of Digital Industry and Information Management
• /
• v.10 no.3
• /
• pp.87-97
• /
• 2014

Pharming attack is a confidence trick that the hacker catch away customers financial information on Internet banking. At first, a hacker installs malicious execution code on customers PC in secret. As a customer tries to connect a Internet banking Web site, the malicious code changes it to phishing site in Internet explorer. The hacker catch away customers financial information in process of internet banking. The hacker steals money from customer's bank account using stolen information. PKI is a widespread and strong technology for providing the security using public key techniques. The main idea of PKI is the digital certificate that is a digitally signed statement binding an user's identity information and his public key. The Internet banking service stands on the basis of PKI. However, the bank is trusted in natural, the only customer is certified in the present Internet banking. In this paper, we propose a method of cross certification in Internet banking. The customer certify a bank and the bank certify the customer in proposed method. The method can service to customer the secure Internet banking about pharming attack. We compare the proposed method with other methods.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.42 no.4
• /
• pp.217-227
• /
• 2006

This research aims at establishing the application of canvas kite to the fishing gear through the analysis of the lift/drag tests of the kites have been performed in our previous finding. Now that several methodologies were designed to find the most effective triangular model as a buoyancy device applied to the fishing gear. Comparisons of drag/lift were made by installing the model in an installation frame instead of the prototype. Also, we have considered the application of canvas kite to the prototypic fishing gear by calculation using the result of this test. The results obtained from the above approaches are summarized as follows, where attack angle, lift coefficient, maximum lift coefficient and drag coefficient are denoted as $B,\;C_L,\;C_Lmax\;and\;C_D$ respectively. The camber showed a gradual increase with an increase of fluid velocity. There was a big discrepancy in B=20 unlike B=30. Even if the kite retreats along the fluid flow, there is little relationship with the velocity variation. Lifts calculated with the kites were bigger and drags were smaller than those of the calculations with the float only. The kite as the buoyancy device will be very useful when the appropriate applications and the stability are met.

• The Journal of the Korea Contents Association
• /
• v.12 no.5
• /
• pp.32-39
• /
• 2012

When you want to be given the on-line service, their homepage requires sign-up with detail personal information. This collected private information lead to mass data spill by hacking. Especially, this makes terrible social problems that the users who sign up their site are persistingly attacked and damaged by hackers using this information. As methods of the social technologic attacks are simple but based upon human psychology, it is easy that people become a victim in the majority of cases. There is a strategy blocking fishing sites by using the black list for defending these attacks. This tactic, however, has some problems that it isn't possible to handle new fishing sites having a short life-cycle. In this paper, we suggest two solutions to minimize data spill. One marks existing sites with the sign of a reliability measured by a comparison between black list and the white list; therefore, the user check the authenticity about the homepage. The other shut off previously the leaking of private information by sensing a entry of personal information into new sites.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.47 no.1
• /
• pp.1-9
• /
• 2011

In order to investigate the cause and magnitude of scale effect occurring in the model experiments of fishing nets, five pairs of Nylon pyramid nets and one pair of PE ones in which all the two nets paired were equal each other in the factors determining their flow resistance, i. e., the ratio d/l of diameter d to length l of bars, the angle f between two adjacent bars, the attack angle q of nettings to the water flow, and the wall area S of nets, and different in the values of d and l were prepared. Then, the nets were attached to the circular steel frame alternately and their flow resistances with shapes in water were measured on the sea ascribing no turbulent flows by using the tension meter made of a block bearing for the experiment. All the Nylon nets were spreads out easily in water to form a circular cone at relatively low velocity of water and showed the resistance smaller a little in the nets with larger d and l than them with smaller d and l, because the filtration of water through meshes become easier in nets especially with larger l. But PE nettings were not spread out sufficiently on account of their small flexibility and showed higher resistance especially in them with thicker twines. Therefore, the difference in bar length or mesh size and flexibility of nettings between prototype and model nets are regarded to become factors ascribing scale effect. Especially the influence of the difference in mesh size may become large significantly in actual model experiments because the mesh size of model nets is decided at much larger value than that given by scale ratio and so the difference of mesh size between the two nets become much larger than that between nets used in this experiment.