نشریه مهندسی شناورهای تندرو
پیاپی 46 (بهار و تابستان 1394)

In the current article, an efficient hull form is presented to achieve 80 knot speed and its initial conceptual design is carried out. Presented hull form is able to gain 80 knot in sea state 3 and capable to satisfy the requirements related to payload and operational range. In this regards, a hard chine, deep V, warped and two stepped hull form is taken from Southampton’s series and by scaling the model to a 16 meters hull, various steps of conceptual design phase are evaluated. First, calm water resistance is analyzed and consequently, by using existing experimental data, sea-keeping in irregular waves is studied. Longitudinal stability is another issue which is surveyed in this article and no porpoising behavior is observed. Moreover, transverse stability of presented hull form is checked based on Blount criteria. Engine selection and weight distribution are final issues which are presented. Finally, by performing various steps of conceptual design phase, it is obviously clear that hard chine, deep V, warp and stepped hull form can satisfy existing requirement.

Inability to timely detection of pre-engineered attacks are the most obvious weaknesses in cyber defense. The possession and efficient indigenous methods of intrusion detection in computer networks, defense against cyber attacks will increase. In this study, by using intrusion detection system based on the combination of data mining and clustering methods and artificial neural network is presented. Learning and assessment method using the training data set of Cambridge and by using software and Matlab been Weka. The results show that the three criteria of article Precision, Recall, F- value works better than other methods.

The purpose of this study was to test the resistance of planning vessels in a towing tank. The study is intended to float on the degrees of freedom of movement (Surge), perpendicular to the motion (Heave) and the plate of pitch. According to data obtained by the resistance curve speed can be divided into three areas. In the first and third speed is quite ascending. The second area is in the transition region, the exact behavior depends on geometric¡ stream and spray parameters of water and it encounters with a special complexity.

One of the tests that are done on helicopter rotor blades is modal analysis to obtain its natural frequencies and various modes of vibration. It is done periodically to ensure blades performance for non-occurrence of resonance obtained under various operating conditions. Therefore, in this paper the rotor modal analysis are discussed. Since metal or composite helicopter blades have a certain flexibility at different speeds in different planes can lead to deformation of the structure that can have a great effect on the aerodynamic performance of the helicopter.
In this paper, modal analysis of helicopter blade has been carried out by the finite element analysis and modal test on the rotor structure. The finite element analysis has been developed by two approach of analytical method of FORTRAN code, and the finite element software of ABAQUS. Modal testing was also performed in both static and dynamic states, with constant speed, to validate the finite element method. Finally, the results of both methods are compared with each other. After ensuring there correspondence between finite element analysis and experimental results, an analysis was done according to the operating conditions of the rotor and finally Spoke diagram has been generated. According to this diagram became clear there was not any problem with the resonance of the rotor blades, while the numerical result of case has an acceptable match with the experimental results.

One of the main problems of marine transportation is passengers and crew's seasickness due to longitudinal movement of vessels. When marine structures excited by waves, acceleration of heave and pitch motion will be exceeded. So vessel's motion should be reduced as much as possible to increase the comfort and safety of passengers. By Using appropriate control algorithms can be reduce ship movements in waves. Longitudinal motion control in waves for vessels such as catamaran is one of the main priorities of design. So, the control surfaces like interceptor and hydrofoil are used for reduce longitudinal motion of vessel. These control surfaces by applying variable forces against wave loading can reduce longitudinal motion.
Nowadays, artificial neural networks are used a lot in the design of control systems. Neural networks are able to model complex dynamics systems, and design appropriate controller them. In this study catamaran heave motion is modeled and then multilayer neural network is taught for control heave motion. As will be shown, designed neural network controller has acceptable accuracy for standard inputs.

A significant portion of the lift on the floor in front of Extremist vessels and 60 to 70 percent of the produced wet surface wet surface does not generate enough lift force, so remove the friction surfaces can be useful later because of low levels of the body, a significant uplift force not produced. It is possible to use the stairs to cross. In addition to the pressure distribution along the hull vessel after the first step produces a peak pressures that increase lift and float longitudinal balance A. In this paper, using Computational fluid dynamics, pressure distribution at the stairs to the first transverse By Hfty, porch and flat Extremist vessels without air injection has been studied. Among the outstanding results of this study, the higher the amount of lift and drag the vestibule of the two other samples is. To continue this research suggests Air injection is also modeled after the stairs.

In the high speed craft, the study of dynamic behavior is important issue. Always, stability and performance improvements are the main principles of design of the high speed craft in sea wave conditions. The complexity of the equations of motion will be increased by increasing boat velocity under wave force. In this paper, the boats behavior with planing form is investigated against irregular wave conditions. Due to nonlinearity and complexity of dynamic behavior under wave excitations, many limitations are imported in the analytical and numerical calculations. For this purpose, in this study, the behaviors of high speed craft are discussed by given the assumption to simplify the problem. Therefore, at first the equations of motion are modeled in regular waves, and then these equations will be developed for irregular waves so that nonlinear nature of motions has been maintained.