Wyniki wyszukiwania - BazTech

1

Vertical motions damping model test of a lifeboat lowered onto a flat sea surface

Kniat A., Dymarski P.

Polish Maritime Research

|

2018

|

S 1

51--55

EN

The article presents the experiment’s results of the lifeboat model lowered with an initial speed and then released to fall onto a flat water surface. The purpose of the research is to determine the trajectory of the vertical boat motion and describe it with a mathematical model. This is closely related to determining the damping factor since the vertical motion is damped and the lifeboat gets balanced and stops moving after some time. The procedure of selecting parameters in the mathematical model to adjust to the results of the experiment was described in details. The summary describes the imperfections of the presented damping model and their probable causes.

2

Czy BIM to tylko model 3D – o roli technologii BIM w procesie realizacji inwestycji

Fedko D., Dymarski P.

Materiały Budowlane

|

2018

|

nr 10

140--141

3

Steganografia akustyczna w tle sygnału mowy

Dymarski P., Markiewicz R.

Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

|

2017

|

nr 8-9

665--669

PL

Przedstawiono algorytmy umożliwiające zestawienie łącza steganograficznego w tle sygnału mowy, transmitowanego kanałem VolP Ukryta informacja jest wstawiana bezpośrednio do sygnału mowy, bez ingerencji w algorytm kodowania i protokoły transmisyjne. Szybkość transmisji steganograficznej wynosi 20 bit/s (bez zabezpieczenia kodem nadmiarowym) lub 10 bit/s (z zabezpieczeniem) . Łącze jest odporne na kompresję mowy (koder Speex 8000 bit/s), jej przepróbkowanie oraz (pod pewnymi warunkami) na utratę pakietów.

EN

Algorithms for acoustic steganography in speech signal, transmitted through VolP channel, are presented. Data are embedded directly in speech, without any modification of speech coder and transmission protocols. They are transmitted at 20 bps (without error correcting code) or 10 bps (with ECC). The steganographic link is resistant to speech compression (Speex coder 8000 bps), resampling and (under certain conditions) packet loss.

4

Technology concept of TLP platform towing and installation in waters with depth of 60 m

Dymarski C., Dymarski P., Żywicki J.

Polish Maritime Research

|

2017

|

S 1

59--66

EN

The article is part of the design and research work conducted at the Gdansk University of Technology, Faculty of Ocean Engineering and Ship Technology, in cooperation with a number of other research centres, which concerns offshore wind farms planned to be built in the Polish zone of the Baltic sea in the next years. One of most difficult tasks in this project is building suitable foundations for each power unit consisting of a tower and a wind turbine mounted on its top. Since the water regions selected for building those wind farms have different depths, there was need to study different possible technical variants of this task, with the reference to both the foundation structures themselves, and the technology of their transport and setting, or anchoring. The article presents the technology of towing, from the shipyard to the setting place, and installation of the foundation having the form of a floating platform of TLP (Tension Leg Platform) type, anchored by tight chains to suction piles in the waters with depth of 60 m.

5

Searching for critical conditions during lifeboat launching – simulations

Dymarski C., Dymarski P., Kniat A.

Polish Maritime Research

|

2017

|

S 1

53--58

EN

The article describes numerical simulations of the process of lifeboat launching at the ship’s side. The research aimed at finding the values of ship motion parameters which appear to be most dangerous for people in the lowered lifeboat due to the generated accelerations. The simplified model of ship hull motion adopted at this research stage bases on a superposition of harmonic motions with given amplitudes and periods in six degrees of freedom. The range of the amplitude of motion for each degree of freedom corresponds approximately to that of possible motion of the PANAMAX type ship on the Baltic sea. In total, 120 960 cases of ship hull motion were examined.

6

Design of structure of tension leg platform for 6 MW offshore wind turbine based on FEM analysis

Żywicki J., Dymarski P., Ciba E., Dymarski C.

Polish Maritime Research

|

2017

|

S 1

230--241

EN

The article presents the calculation and design stages of the TLP platform serving as a supporting construction of a 6 MW offshore wind turbine. This platform is designed to anchor at sea at a depth of 60 m. The authors presented the method of parameterization and optimization of the hull geometry. For the two selected geometry variants, the load and motion calculations of the platform subjected to wind, wave and current under 50-year storm conditions were performed. The maximum load on the structure was determined in these extreme storm conditions. For these loads, the MES calculation of the designed platform was performed for the selected variant. Authors have presented a method for calculating maximum wind, wave and current stresses on the structure during the worst storm in the past 50 years. For these loads the MES endurance calculations of the designed platform were made. Based on the results of these calculations, the required structural changes and recalculations have been made in succession to the structural design of the platform, which meets the design requirements and has the required ad hoc strength. The article contains stress analysis in „difficult” nodes of constructions and discusses ways of solving their problems. The work is part of the WIND-TU-PLA project from the NCBR Research Agreement (Agreement No. MARTECII / 1/2014).

7

Algorytmy dekodowania "rzadkich" sygnałów MIMO

Dymarski P.

Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

|

2016

|

nr 8-9

1138--1144, CD

PL

W referacie przedstawiono algorytmy dekodowania sygnałów MIMO w sytuacji, gdy liczba anten odbiorczych jest mniejsza od liczby anten nadawczych. Założono ograniczoną aktywność nadawców – większość anten nadawczych emituje symbol zerowy. W tych warunkach klasyczne algorytmy dekodowania nie sprawdzają się, należy stosować algorytmy „rzadkiej” aproksymacji. W pracy porównano szereg tego typu algorytmów, opartych na rzutowaniu ortogonalnym na podprzestrzeń i zaproponowano nowe warianty. Przeprowadzone symulacje wykazują zmniejszenie SER przy akceptowalnej złożoności obliczeniowej algorytmu dekodowania.

EN

Algorithms of MIMO signals decoding are analyzed under the following conditions: number of transmit antennas greater than number of receiving ones, low activity of transmitters. Sparse approximation algorithms are used to solve this kind of problems. New variants of such algorithms, based on orthogonal projection on the selected subspace, are proposed. Simulations show decrease of SER at acceptable complexity of decoding algorithm.

8

Effective method for determining environmental loads on supporting structures for offshore wind turbines

Dymarski P., Ciba E., Marcinkowski T.

Polish Maritime Research

|

2016

|

nr 1

52--60

EN

This paper presents a description of an effective method for determining loads due to waves and current acting on the supporting structures of the offshore wind turbines. This method is dedicated to the structures consisting of the cylindrical or conical elements as well as (truncates) pyramids of polygon with a large number of sides (8 or more). The presented computational method is based on the Morison equation, which was originally developed only for cylindrically shaped structures. The new algorithm shown here uses the coefficients of inertia and drag forces that were calculated for non-cylindrical shapes. The analysed structure consists of segments which are truncated pyramids on the basis of a hex decagon. The inertia coefficients, CM, and drag coefficients, CD, were determined using RANSE-CFD calculations. The CFD simulations were performed for a specific range of variation of the period, and for a certain range of amplitudes of the velocity. In addition, the analysis of influence of the surface roughness on the inertia and drag coefficients was performed. In the next step, the computations of sea wave, current and wind load on supporting structure for the fifty-year storm were carried out. The simulations were performed in the time domain and as a result the function of forces distribution along the construction elements was obtained. The most unfavourable distribution of forces will be used, to analyse the strength of the structure, as the design load.

9

Developing methodology for model tests of floating platforms in low-depth towing tank

Dymarski C., Dymarski P.

Archives of Civil and Mechanical Engineering

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2016

|

Vol. 16, no. 1

159--167

EN

The paper presents two different methods of physical modeling of semi-submersible platform mooring system for research in low depth towing tank. The tested model was made in the scale of 1:100 resembling the “Thunder Horse” platform moored in the Gulf of Mexico at a depth of 1920 m. Its mooring system consisted of 16 semi-taut mooring lines (chain-wire-chain) spaced star-shape and attached at the bottom to suction piles. The tests were performed in the towing tank of the Gdansk University of Technology (GUT). The tank depth is 1.5 m and which is about 13.5 times less than that required for typical model tests. This required the development and use of non-standard methods of mooring for the model, which was adapted to the technical conditions existing in the laboratory and material possibilities. Numerical calculations and characteristics of static displacement of the model as a function of the external horizontal load were carried out for both anchoring systems. These characteristics were scaled to the natural conditions and compared with the calculated characteristics of the reference platform. The second method of modeling proved to be much more accurate.

10

Design and strength calculations of the tripod support structure for offshore power plant

Dymarski C., Dymarski P., Żywicki J.

Polish Maritime Research

|

2015

|

nr 1

36--46

EN

The support structure being the object of the analysis presented in the article is Tripod. According to the adopted assumptions, it is a foundation gravitationally set in the water region of 60 m in depth, not fixed to the seabed, which can be used for installing a 7MW wind turbine. Due to the lack of substantial information on designing and strength calculations of such types of structures in the world literature, authors have made an attempt to solve this problem within the framework of the abovementioned project. In the performed calculations all basic loads acting on the structure were taken into account, including: the self mass of the structure, the masses of the ballast, the tower and the turbine, as well as hydrostatic forces, and aero- and hydrodynamic forces acting on the entire object in extreme operating conditions.

11

Computational simulation of motion of a rescue module during its launching from ship at rough sea

Dymarski C., Dymarski P.

Polish Maritime Research

|

2014

|

nr 3

54--60

EN

This paper is a continuation of the work titled : “A computational model for simulation of motion of rescue module during its launching from stern ramp of a ship at rough sea”. It presents results of computer simulations of motion of a rescue module with embarked persons during its launching on rollers along stern ramp of a ship at rough sea. The simulations were conducted for a selected ship fitted with a launching ramp , for a few selected scenarios of sea conditions. It was assumed that during this operation the ship drifts across direction of wave propagation.

12

A numerical model to simulate the motion of a lifesaving module during its launching from the ship’s stern ramp

Dymarski P., Dymarski C.

Polish Maritime Research

|

2014

|

nr 2

34--40

EN

The article presents a numerical model of object motion in six degrees of freedom (DoF) which is intended to be used to simulate 3D motion of a lifesaving module during its launching from a ship using a stern ramp in rough sea. The model, of relatively high complexity, takes into account both the motion of the ship on water in changing sea conditions, and the relative motion of the ramp with respect to the ship. The motion of the ramp changes and strongly depends on its constructional and geometrical parameters. The presented model takes into account the displacement of the submerged part of the ramp, as well as its damping in the water and the interaction with the module moving on it. The results of test simulation of a module launching from the ship in still water are included.

13

Robust Audio Watermarks in Frequency Domain

Dymarski P., Markiewicz R.

Journal of Telecommunications and Information Technology

|

2014

|

nr 2

12--21

EN

In this paper an audio watermarking technique is presented, using log-spectrum, dirty paper codes and LDPC for watermark embedding. This technique may be used as a digital communication channel, transmitting data at about 40 b/s. It may be also applied for hiding a digital signature, e.g., for copyright protection purposes. Robustness of the watermarks against audio signal compression, resampling and transmitting through an acoustic channel is tested.

14

Sygnatury cyfrowe sygnatów fonicznych

Dymarski P., Markiewicz R., Kopertowska A.

Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

|

2013

|

nr 8-9

650--655

PL

Omówiono metody wstawiania i detekcji sygnatur cyfrowych, umieszczanych w sygnałach fonicznych w celu zapewnienia ochrony praw autorskich, uwierzytelniania przekazu głosowego, znakowania emisji radiowych itp. Zaproponowano metodę wstawiania sygnatury w dziedzinie czasu i w dziedzinie zlogarytmowanego widma amplitudy. Wstawiane znaki wodne są odporne na przepróbkowanie i kompresję metodą MPE-G-audio. Ponadto są one trudne do wykrycia i usunięcia przez osoby niepowołane.

EN

Embedding and detection methods of digital signatutes in audio signal are considered These signatures (watermarks) may be applied to copyright protection, authentication of voice messages, broadcast watermarking etc. Two algorithms are analyzed: the first one embeds a watermark in time domain and the second one in log-spectrum domain. The hidden audio signatures are robust against audio signal resampling, MPEG-Audio compression and attacks of unauthorized persons.

15

Computational model for simulation of lifeboat motions during its launching from ship in rough seas

Dymarski P., Dymarski C.

Polish Maritime Research

|

2012

|

nr 3

45-52

EN

This paper presents a computational model which describes motion of an object of six degrees of freedom (DoF), intended for simulation of spatial motion of one- or two- rope-sling lifeboat or rescue boat during its launching from ship in rough sea. This is a complex model which accounts for sea conditions as well as elasticity and damping properties of davit’s elements and mechanisms, rope and boat hull. Also, are presented results of example calculations for an assumed set of technical parameters of davit and boat as well as sea conditions.

16

Design solution and selected research results of the sea-wave energy converter

Dymarski C., Dymarski P.

Journal of Polish CIMAC

|

2012

|

Vol. 7, no 1

45-56

EN

The paper presents a novel device, a special buoy, for capturing the energy of sea-waves and the design of its model for conducting test in a towing-tank. The paper also presents the research program and general analyses on selecting the turbine and hull form, systems of anchoring and propulsion. In addition, it includes some chosen results of model tests and numerical calculations. Model of the buoy at the scale of 1:5 was tested in the towing tank for some range of wave height and its frequency and for two value of column length, a few states of ballast and tension of the anchor ropes. Numerical calculations were conducted for the same conditions and additionally for several anchor systems as well.

17

QoS Conditions for VoIP and VoD

Dymarski P., Kula S., Huy T. N.

Journal of Telecommunications and Information Technology

|

2011

|

nr 3

29-37

EN

This paper concerns quality evaluation of the telecommunication services: VoIP (representing the RT interactive class) and VoD (representing the MM streaming class). Subjective and objective methods and tools for perceived quality measurement are analyzed and compared. Subjective tests are performed for selected video sequences using the Double-Stimulus Impairment Scale (DSIS) method. Thus the objective algorithms (VQM and VQmon) are calibrated. Speech quality is measured using the objective methods: PESQ and POLQA. Threshold values for network parameters (packet loss rate, delay jitter) are set, that guarantee the acceptable service quality.

18

Badanie jakości sygnałów i usług

Dymarski P., Kula S., Janicki A.

Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

|

2010

|

nr 4

118-120

19

A method for the accurate numerical prediction of the tip vortices shed from hydrofoils

Flaszyński P., Szantyr J. A., Dymarski P., Kraskowski M.

Polish Maritime Research

|

2010

|

nr 2

10-17

EN

The possibly accurate numerical prediction of the detailed structure of vortices shed from the tips of hydrofoils is an important element of the design process of marine propellers. The concentrated tip vortices are responsible for the propeller cavitation erosion and acoustic emission. The purpose of the project described in this paper was to develop the numerical method for prediction of the tip vortex structure. In the course of the project the numerical calculations were confronted with the results of experimental measurements. This led to creation of the specific method of construction of the computational grid and to selection of the optimum turbulence model. As a result the reliable method for the accurate numerical prediction of the concentrated tip vortices for different hydrofoil geometry and flow conditions has been developed and validated. This method enables elimination of the unfavourable phenomena related to the tip vortices in the course of the propeller design calculations.

20

Projekt i badania jednostki pływającej zasilanej energią słoneczną

Dymarski P., Grygorowicz M., Leśniewski W., Litwin W.

Napędy i Sterowanie

|

2010

|

R. 12, nr 2

68-73

PL

Rozwój najnowszych technologii, rosnące ceny surowców energetycznych oraz większa świadomość ekologiczna społeczeństwa stymulują rozwój coraz to nowych przyjaznych środowisku układów napędu i zasilania. Nowoczesne technologie nie ominęły również okrętownictwa. Ze względu na to, że w niektórych atrakcyjnych turystycznie rejonach świata zabroniono stosowania silników spalinowych do napędu jednostek pływających, krokiem naprzód może się okazać zainstalowanie na nich paneli fotowoltaicznych. W artykule opisano projekt i badania prowadzone w Centrum Techniki Okrętowej w Gdańsku w związku z katamaranem zasilanym energią słoneczną.

EN

Modern technology development, rising costs of primary energy resources and society higher environmental consciousness stimulate development of new and environment friendly drive and power supply systems. State of the art technologies are also applied in shipbuilding. Due to the fact that in many parts of the world vessels powered with combustion engines are not allowed, application of photovoltaic panels may be a step forward. The article describes project and studies carried out at Shipbuilding Technology Center in Gdansk related to catamaran powered with solar energy.