Wyniki wyszukiwania - BazTech

1

Motion prediction of catamaran with a semisubmersible bow in wave

Sun H., Jing F., Jiang Y., Zou J., Zhuang J., Ma W.

Polish Maritime Research

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2016

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nr 1

37--44

EN

Compared with standard vessels, a slender catamaran with a semi-submerged bow (SSB) demonstrates superior seakeeping performance. To predict the motion of an SSB catamaran, computational fluid dynamics methods are adopted in this study and results are validated through small-scale model tests. The pitch, heave, and vertical acceleration are calculated at various wavelengths and speeds. Based on the overset grid and motion region methods, this study obtains the motion responses of an SSB catamaran in regular head waves. The results of the numerical studies are validated with the experimental data and show that the overset grid method is more accurate in predicting the motion of an SSB catamaran; the errors can be controlled within 20%. The movement data in regular waves shows that at a constant speed, the motion response initially increases and then decreases with increasing wavelength. This motion response peak is due to the encountering frequency being close to the natural frequency. Under identical sea conditions, the motion response increases with the increasing Froude number. The motion prediction results, that derive from a shortterm irregular sea state, show that there is an optimal speed range that can effectively reduce the amplitude of motion.

2

Test studies of the resistance and seakeeping performance of a trimaran planing hull

Ma W., Sun H., Sun H., Zou J., Zhuang J.

Polish Maritime Research

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2015

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nr 1

22—27

EN

Towing tank tests in calm water were performed on a trimaran planing hull to verify its navigational properties with different displacements and centres of gravity, as well as to assess the effects of air jets and bilge keels on the hull’s planing capabilities, and to increase the longitudinal stability of the hull. Hydrostatic roll tests, zero speed tests, and sea trials in the presence of regular waves were conducted to investigate the hull’s seakeeping ability. The test results indicate that the influence of the location of the centre of gravity on the hull resistance is similar to that of a normal trimaran planing hull; namely, moving the centre of gravity backward will reduce the resistance but lower the stability. Bilge keels improve the longitudinal stability but slightly affect the resistance, and the presence of air jets in the hull’s channels decreases the trim angle and increases heaving but has little effect on the resistance. Frequent small-angle rolling occurs in waves. The heaving and pitching motions peak at the encounter frequency of , and the peaks increase with velocity and move towards greater encounter frequencies. When the encounter frequency exceeds, the hull motion decreases, which leads to changes in the navigation speed and frequency.

3

Test research on the resistance performance of high-speed trimaran planing hull

Ma W., Sun H., Zou J., Yang H.

Polish Maritime Research

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2013

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nr 4

45--51

EN

In order to identify high-speed navigation ability of trimaran planing hull, as well as investigate the characteristics of its resistance and hull form, ship model tests were conducted to measure resistance, trim and heaving under different displacements and gravity centre locations. The test results were then used to study the influence of spray strips on resistance and sea-keeping qualities. Moreover, different planning surfaces were compared in the model tests which helped to look into influence of steps on hull resistance and its moving position. Also, the resistance features of monohull and trimaran planing hulls, both with and without steps, were compared to each other. From the tests it can be concluded that: the two auxiliary side hulls increase aerodynamic lift at high-speed motion, which improves the hydrodynamic performance; the trimaran planing hull has also excellent longitudinal stability and low wave-making action; when Fr∇> 8, its motion is still stable and two distinct resistance peaks and two changes of sailing state (the second change is smaller) appear; spray strips are favourable for sea-keeping qualities at high speed. The change trends before the second resistance peak as to the resistance and sailing behaviour of trimaran planing hull without steps are the same as for monohull planing hull without steps. but when steps in both hulls exist the change trends are different; more specifically: trimaran planing hull with steps has only one resistance peak and its resistance increases along with its speed increasing, and the resistance is improved at the increasing speed as the number of steps increases.

4

Research on Angle Measurement Model of Anti-radiation

Zou J., Gao K., Zhang E.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 3b

18-21

EN

How the monopulse passive radar seeker (PRS) of anti-radiation missiles (ARM) works in tracking radars is explained and demonstrated in this paper. The performance of PRS that the tracking location can fall at a point completely outside the decoys under coherent decoy jamming by using phase-amplitude sensing model, angle measurement error with different SNR compared with theoretic calculation results is given. The numerical results are presented to verify the effectiveness of this model and the coherent decoys jamming ARM theory.

PL

W artykule zaprezentowano jednopulsowy pasywny poszukiwacz radaru PRS w broni anty-radiacyjnej. Właściwości systemu PRS są analizowane przy wykorzystaniu modelu amplitudowo-fazowego, na podstawie którego obliczany jest błąd pomiaru kąta.

5

An Effective Hybrid Particle Swarm Optimization with Decline Disturbance Index for Expanded Job-shop Scheduling Problem

Zhao F., Tang J., Zou J., Di J.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 1b

34-38

EN

In this paper, an improved particle swarm optimization with decline disturbance index (DDPSO), is proposed for expanded job-shop scheduling problem (EJSSP). To balance the exploration and exploitation abilities of DDPSO, both PSO-based global search and an adaptive local search are designed and applied simultaneously in the proposed DDPSO. An index was added when the velocity of the particle is prone to stagnation in the middle and later evolution periods. The modification improves the ability of particles to explore the global and local optimization solutions, and reduces the probability of being trapped into the local optima. Theoretical analysis, which is based on stochastic processes, proves that the trajectory of particle is a Markov processes and DDPSO algorithm converges to the global optimal solution with mean square merit. After the exploration based on DDPSO, neighborhood search strategy is used in a local search and an adaptive Meta-Lamarckian strategy is employed to dynamically decide which neighborhood should be selected to stress exploitation in each generation. Simulation results and comparisons with typical algorithms show the effectiveness and robustness of the proposed DDPSO.

PL

Opisano ulepszony al;gorytm mrówkowy z indeksem DDPSO do rozwiązywania problemu EJSSP (expanded job-shop scheduling problem). Dodano indeks kiedy szybkość cząstki jest podatna na stagnację w środku i końcowej części procesu ewolucji. Analiza teoretyczna bazująca na ;procesach stochastycznych dowodzi że trajektoria cząstki jest procesem Markova i algorytm DDPSO pokrywa się z rozwiązaniem globalnego optimum metodą średniokwadratową.