No 1/1995

        The essence of the effective mean velocity definition is analysed by the author. This definition is indivisibly connected with the effective velocity field being in interaction with the ship screw propeller. The effective mean velocity is set against the mean value of the isolated effective velocity field. The differences in the relations between criterional quantities in the averaging process in both cases are specified. These differences make the necessity of introduction of a new effective mean velocity definition to the model propulsion tests and to the numerical simulation procedures well justified.
(POLISH MARITIME RESEARCH, No 1/1995)

        The paper shortly presents model test results of hydrodynamic characteristics of hull shapes adapted to fast passenger catamaran with the speed of 40 knots. This work, realized within the framework of a project sponsored by The State Committee for Scientific Research, comprises investigations of planing and "wave piercing" hull shapes. Ship resistance was tested in calm water and in regular and irregular head waves. Model tests of propulsive and manoeuvring characteristics were carried out on a lake using large self propelled models.(POLISH MARITIME RESEARCH , No 1/1995)

        Operating principles of GPS global navigation system and its use possibilities for ship manoeuvre testing are presented in this paper. The system is based on MX200 receiver, manufactured by Magnavox company, and a complemen-tary system, worked out by Ship Design and Research Centre (CTO).
(POLISH MARITIME RESEARCH, No 1/1995)

        The paper presents general possibilities of identification of technical state of the flow elements in a marine gas turbine. The identification was set on the basis of relative change of gas thermodyna-mical parameters. The paper contains some results of the research on the flow elements of a marine gas turbine in operation. The research contained maesurements of thermodynamical parameters in a marine gas turbine and endoscopic inspection of its passagas.
(POLISH MARITIME RESEARCH, No 1/1995)

        The article presents a model of the steam superheater installed in the main propulsion boilers on board t/t GIEWONT. The model structure is non-linear with time-lags. The correction of model static and dynamic properties was carried out in view of adapting it to optimal control synthesis. The correction includes the compensation of measurable and non-measurable disturbances. The compensation of measurable disturbances was based on the condition of total invariance, while the compensation of non-measurable disturbances was done on the basis of a formulated principle of an internal model for SISO linear stationary time-lag systems. (POLISH MARITIME RESEARCH , No 1/1995)

        In the paper general considerations on possible ways of controlling ships operation costs by a carrier are presented. Relationships of all important components of ship operation costs versus different internal and external factors are shortly described and possibly ways of controlling the cost components are indicated. At this stage of the study only the qualitative aspects of the subject are considered.(POLISH MARITIME RESEARCH , No 1/1995)

        The essence of the effective mean velocity definition is analysed by the author. This definition is indivisibly connected with the effective velocity field being in interaction with the ship screw propeller. The effective mean velocity is set against the mean value of the isolated effective velocity field. The differences in the relations between criterional quantities in the averaging process in both cases are specified. These differences make the necessity of introducing a new effective mean velocity definition to the model propulsion tests and to the numerical simulation procedures well justified.
(POLISH MARITIME RESEARCH, No 2/1995) * Part I of the paper was published in No 1 (1995) of this journal

        The paper deals with the stress-based fatigue analysis of beams fabricated from constructional steels and subjected to combined bending, tension-compression, and twisting. A complex state of stress with sinusoidal components of equal frequency and arbitrary phase angles is considered. Two functionals of safety are defined the minimum values of which in the time domain determine the safety factor in the safe range of the basic variable space and the number of stress cycles to failure in the high-cycle fatigue range. As an example the influence of the phase shift between bending moment and axial force on the safety factor and the number of cycles to failure is analyzed. It is shown that the more pronounced is the effect, the closer to p/2 is the phase shift, the smaller is the difference in values of the partial safety factors and the higher are the exponents in equations of S-N curves.
(POLISH MARITIME RESEARCH, No 2/1995)

        In the paper results of investigations on corrosion and stress corrosion resistance of Al-Mg and Al-Zn-Mg alloys, applicable for ship structures, in different treatment states and test conditions are reported. Influence of chemical composition, heat treatment, load (stress) and electric potential applied on the mechanical and corrosion properties of the alloys are demonstrated and discussed.
(POLISH MARITIME RESEARCH, No 2/1995)

        The new starting method of asynchronous motor driving the ship bow thruster when the motor rated power and the generator output are comparable is described. The AVR (Automatic Voltage Regulator) of the generator is fitted with an additional current regulator which keeps adjusted value of motor starting current. The principles of operation and site test results are given.
(POLISH MARITIME RESEARCH, No 2/1995)

        The paper presents the Data Bank containing information on stress factors dominating in ship's environment and samples of information collected in the bank . Proposals on how to apply the degradation prediction method to materials used in ship equipment are given in Part II of the paper. The presented method could be helpful in environment aggressiveness assessment, degradation, failure or damage risk assessment, selection of laboratory test type and time for an equipment guaranteed period or required durability, material durability prediction etc.
(POLISH MARITIME RESEARCH, No 2/1995)

        In the paper applicability of different methods to determination of critical (FMP) and permissible (TML) moisture content in coarse-grained ore concentrates are discussed from the point of view of safe shipment in bulk of such cargoes. Test results for three different coarse-grained materials, obtained with the use of four various methods, are presented.
(POLISH MARITIME RESEARCH, No 2/1995)

        Operating problems connected with improper reactive power distribution between parallelly working marine electric generators are presented in this article. Reactive power distribution mechanism in electric power system is discussed. Methods of identifying proper reactive power distribution in the ship power plant depending on main switchboard measuring equipment are shown. Reactive power distribution corrective algorithm for selected excitation systems and voltage regulators is formuled.
(POLISH MARITIME RESEARCH, No 2/1995)

        This paper presents some aspects of active stopping manoeuvre simulation in which a mathe-matical model of ship motion is applied. Results of several simulations performed with the use of PC version of the authors' computer program are included and compared with some results of full scale trials. Both results are reasonably convergent.
(POLISH MARITIME RESEARCH, No 3/1995)

        To apply classification society survey to coastal fishing boats it is necessary to elaborate a simple but rational method for their stability assessment. The paper presents an approach to the stability assessment of such boats which can be applied in boat design and control in operation.
(POLISH MARITIME RESEARCH, No 3/1995)

        The paper deals with modelling the state of stress in beams subjected to complex loadings. The cases of periodic and stationary random stress produced by simultaneous bending, twisting and tension-compression are considered under assumption that the stress components are physically and statistically independent. Using Cempel's theory of energy transforming systems and Rice's concept of an equivalent frequency an equivalent state of stress with synchronous components is determined.
(POLISH MARITIME RESEARCH, No 3/1995)

        In the paper the effect of the operation and initial costs on choice of ship propulsion plant is analysed. Attention is paid to the optimum engine selection criteria. Two economic criteria are applied: Net Present Value (NPV) and Real Payback Time (RPT). The applied computer program and the numerical example computed with its use are based on the technical data of the MAN-B&W MC engine family.
(POLISH MARITIME RESEARCH, No 3/1995)

        In this paper an autonomous, mobile, multipurpose measuring system designed as an integral part of the SWOT Engineering Objects Detection System applicable in deep water exploration is presented. Its measuring characteristics related to some possible tasks of the underwater instrument carrier, KRAB, are described. Motion qualities of the vehicle are determined more pracisely with regard, in particular, to motion parameters stabilization. (POLSH MARITIME RESEARCH, No 3/1995)

        In the paper applicability of different methods for determination of critical (FMP) and permissible (TML) moisture content in fine-grained ore concentrates are discussed from the point of view of safe shipment in bulk of such cargoes. Test results of several floatation and sedimentation ore concentrates and coal samples of Polish as well as foreign origin, obtained with the use of four various methods, are presented. Results of earlier tests of ore concentrates and coal samples are also given for comparison. On this basis the methods are critically evaluated and the ranges of applicability of each of them stated.
(POLISH MARITIME RESEARCH, No 3/1995)

        In this paper the external and internal interferences which may disturb proper operation of the Global Maritime Distress and Safety System are discussed. All potential sources of the inter-ferences are specified and classified. To find appropriate remedies an analysis of mechanisms of the generation of interferences is still needed. (POLSH MARITIME RESEARCH, No 3/1995)

        Taking advantage of the equivalent state of stress in beams determined in [2], in this paper the limit-state design criteria in fatigue design for infinite life and a finite life till crack initiation are formulated. The cases of periodic and stationary random stress produced by simultaneous bending, twisting and tension-compression are considered.
(POLISH MARITIME RESEARCH, No 4/1995 )

        This paper presents results of the research on determination of the daily catch rate of vessel-trawl system. Mean, long-term catch rates and peak catch coefficients are expressed in function of trawl towing horsepower and vessel's ability to untilize the caught raw materials, viz. hold capacity - for wet fish trawlers, or processing and freezing capacity - for factory and freezing trawlers. Daily catch rate statistics and measurements of trawling system characteristics, carried out on some Polish fishing cutters (small trawlers), were used to determine the above mentioned relationships for the Polish cutter fleet in the Baltic Sea. Results of measurements of trawl resistance and catch rates of Polish trawlers used in the North and Southern Atlantic and the North Pacific are presented elswhere [2].
(POLISH MARITIME RESEARCH, No 4/1995)

        This paper presents a theoretical investigation of the boat davit construction and pivoting mechanism designs which comply with current provisions of the International Convention for the Safety of Life at Sea - SOLAS. The analysis is based on two main types of the mechanisms applied also in the davits produced by FAMA Marine Machinery Works, Gniew, Poland.
(POLISH MARITIME RESEARCH, No 4/1995)

        The paper presents an automatic computer-aided system applicable to remote monitoring physical and chemical parameters of the water and air environment. The measurement data are transmitted by radio. The system was designed and tested by the authors' team of Faculty of Maritime Technology, Technical University of Szczecin.
(POLISH MARITIME RESEARCH, No 4/1995)

        In the paper the present state of NOx emission from marine diesel engines is evaluated. IMO proposals of NOx limitation for new ships and the relevant engine test cycles are reviewed. The NOx emission level at maximum continous rating of different two-stroke and four-stroke diesel engines, currently avaiable on the market, are presented. The weighted specific NOx emission from those engines is estimated in accordance with the ISO 8178 test cycles and compared with the IMO new draft limitations.
(POLISH MARITIME RESEARCH, No 4/1995)

        The paper discusses the problem of improving the anti-interference ability of transducers applicable to automated ship's systems, especially to those of marine engine room. A variety of detection methods and types of sensors for some physical quantities is presented and illustrated by examples. Mechanisms of interference penetration into measuring circuits of automatic control loops and main reasons of disturbing factors generation under ship's conditions are shortly pointed out. Some methods and technical means to eliminate them, such as a choice of appropriate measurement method, a way of signal processing and also constructional and technological solutions are discussed. Special attention is paid to integrated and smart sensors and their application in ship's hostile environment. Finally, some conditions concerning the use of such transducers in microcomputer monitoring systems are formulated.
(POLISH MARITIME RESEARCH, No 4/1995)

        The problem of the overloading of steering gears controlled by an automatic pilot is presented. The paper also describes basic causes of the phenomenon, applied methods of limiting the signals sent to the steering gear under such conditions and prospects of solving the problem by introduction of an optimum multicriterion control system.
(POLISH MARITIME RESEARCH, No 4/1995)

        In this paper a preliminary analysis of extending application (mainly in marine industry) of diagnostic strategy based on technical state assessment is presented. It is proposed to use portable diagnostic systems for implementation of this strategy which is hoped to be more effective than the service life strategy, widely and almost exclusively used in ship exploitation. Scope of necessary research to make using these systems possible and justifiable is also given.
(POLISH MARITIME RESEARCH, No 4/1995)