Browse

81 - 90 of 234 items :

  • Electrical Engineering x
  • Geosciences x
Clear All
Methods for determining mechanical losses of marine diesel engines

Abstract

The paper presents based on literature critical evaluation of commonly known methods for determining the mechanical losses of a piston engine. Their advantages and disadvantages were pointed out also the possibility of their use in a marine propulsion system was assessed.

Open access
An operational calculus model for the central difference and exponential-trigonometric and hyperbolic fibonacci sequences

Abstract

In the paper, there has been constructed such a non-classical Bittner operational calculus model, in which the derivative is understood as a central difference Dn{x(k)}:= {x(k+n)–x(k-n)}. The discussed model has been generalized by considering the operation Dn,b{x(k)}:= {x(k+n)–bx(k-n)}, where b∈𝕔\{0}. In the D 1-difference model exponential-trigonometric and hyperbolic Fibonacci sequences have been introduced.

Open access
Radio link system solutions for mobile platforms operatingin sea environment

Abstract

In this paper radio link system solutions operating in 300 MHz — 3000 MHz range and sea environment were described. Solutions with more than one frequency and wave propagation models for horizontal not more than 50 km and far range were described. In the paper the results of actions taken design and construction solutions adopted were presented, aimed to contribute to ensure the reliability of the system, among other things, by implementing mechanisms for collecting and processing information. This solutions allow resources management to automatically adjust the transmission parameters configuration to the bitrate and range requirements. Available configurations can be extended with active part and electronic beam steering with one or more beams. The paper describes antenna systems ability of transmission parameters adaptation to get the range required.

Open access
An underwater spoiler on a warship: why, when and how?

Abstract

There are a lot of energy saving devices for ships on the market, but few have seen wide adoption on naval ships, with one exception: the bulbous bow. The bulbous bow was developed for naval ships in the early 20th century and is now widespread on a variety of ship designs. Many have wondered if the effect of the bulbous bow — reducing the resistance of a ship by reducing the bow wave — could be replicated somehow at the stern — by reducing the stern wave. This is exactly what is done by a novel and patented energy saving device called Hull Vane®.

Invented by Dutch hydrodynamicist Dr Peter van Oossanen for an America’s Cup sailing yacht in the early 21st century, research over the years has shown that this wing-shaped appendage works best on ships that combine a relatively high displacement with a relatively high top speed requirement — even if most sailing hours are done at half speed. Examples are certain offshore vessels, superyachts, patrol vessels and naval ships. On offshore patrol vessels, the resistance reduction from the Hull Vane® ranges typically from 10 to 20% over the entire useful speed range.

In this paper, the working principles of the Hull Vane® will be described to give a better under-standing of the device. An overview will be given of the work carried out on naval ships and coastguard ships (25 to 142 m), based on Computational Fluid Dynamics studies, model tests and full-scale applications. The question ‘Why?’ will be answered by translating the hydrodynamic effects to concrete capability improvements for naval ships: a lower fuel consumption, a longer range, reduced signature, a higher top speed and improved seakeeping.

The question ‘When?’ will zoom in on whether a Hull Vane® is something to be included in a newbuild or if it is something to be retrofitted to an existing ship. Finally the answer to the question ‘How?’ will explain the process of either integrating a Hull Vane® in a newbuild project or retrofitting it during a midlife upgrade of an existing ship.

Open access
Determination of Dynamic Characteristics of Austenitic Steel to be Utilized in Fem Simulation and its Verification

Abstract

This paper presents the dynamic mechanical properties of austenitic steel with improved durability, which is used in the construction of hulls of minesweepers, mine destroyers, submarines and other naval vessels. Dynamic tensile tests performed on the steel samples using a rotary hammer with a strain rate of up to 1000 s-1 allowed determination of elastic-plastic characteristics of the material in the form of a polynomial of Johnson-Cook constitutive model, taking into account the influence of strain rate and temperature. A characteristic of this type is utilized in numerical calculations in the CAE software. The obtained characteristics were experimentally verified by bending tests of flat samples with a drop-weight type impact hammer. Simultaneously numerical calculations were performed in order to compare the deformation state.

Open access
Nonhomogeneous Stochastic Processes Connected to Poisson Process

Abstract

Some generalizations of the Poisson process and their properties are presented in the paper. The non-homogeneous Poisson process allows to construct a probabilistic model describing the different kinds of accidents number. The nonhomogeneous compound Poisson process enables to describe mathematically the various types of accidents consequences. Theoretical results give possibility to anticipate the accidents number and their consequences.

Open access
Report on Research with Biomimetic Autonomous Underwater Vehicle — Navigation and Autonomous Operation

Abstract

The paper presents the second part of the final report on all the experiments with biomimetic autonomous underwater vehicle (BAUV) performed within the confines of the project entitled ‘Autonomous underwater vehicles with silent undulating propulsion for underwater ISR’, financed by Polish National Center of Research and Development. The report includes experiments on the swimming pool as well as in real conditions, that is, both in a lake and in the sea. The tests presented in this part of the final report were focused on navigation and autonomous operation.

Open access
Selected Decompression Procedures for Survivors Who Became Saturated in a Sunken Wreck

Abstract

This article is one of the series dedicated to the DiveSMART Baltic project conducted to better coordination of international underwater rescue operations in the Baltic Sea. The project DiveSMART Baltic has received Flagship status.

The article is the forth in the planned cycle of articles referring tasks realised in the Naval Academy in the framework of DiveSMART Baltic project. This article describes selected decompression procedures for victims who became saturated by air at maximum depth to H =30 mH 2 O in the air pockets of the hull of a sunken wreck. This subject is associated with the work package four ‘Medical treatment’ of the DiveSMART Baltic project: Identifies methods for different medical treatments in operational areas.

Open access
Static Analysis of the Tubular Electromagnetic Linear Actuator with Permanents Magnets

Abstract

In this paper a results of a static analysis of the tubular linear electromagnetic actuator is presented. The linear actuator consist of two parts: a cylindrical unmovable coils surrounded by a soft ferromagnetic case, and a runner made from sequence of permanent magnet with a soft ferro-magnetic gasket. In the first part of the paper the analytical method was performed for preliminary analysis. In the second part of the paper the more detailed analysis was depicted with using finite element method (FEM). The magnetic circuit shape and impact of selected dimensions on static characteristics is presented. Then the axial and radial electromagnetic force as a function of the runner dimensions were analysed.

Open access
Thrust Measurement of Biomimetic Underwater Vehicle with Undulating Propulsion

Abstract

In the recent years, a dynamical development of an underwater robotics has been noticed. One of the newest group of underwater robots are biomimetic underwater vehicles. These vehicles are driven by undulating propulsion imitating fins of underwater creatures, e.g. a fish, a seal, etc.

This paper undertakes problem of thrust measurement of new biomimetic underwater vehicle equipped with undulating propulsion. At the beginning, the stand for thrust measurement is described. Then, two constructions of BUVs imitating a fish and a seal are presented. Further, the results of thrust measurement for two different undulating propulsions are inserted. At the end of the paper containing conclusions from performed measurements and foreseen research is included.

Open access