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Wyświetlanie 1-4 z 4
Tytuł:
Test research on the resistance performance of high-speed trimaran planing hull
Autorzy:
Ma, W.
Sun, H.
Zou, J.
Yang, H.
Powiązania:
https://bibliotekanauki.pl/articles/259708.pdf
Data publikacji:
2013
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
trimaran planing hull
side hulls
high speed
step
resistance
model test
Opis:
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.
Źródło:
Polish Maritime Research; 2013, 4; 45-51
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Test studies of the resistance and seakeeping performance of a trimaran planing hull
Autorzy:
Ma, W.
Sun, H.
Zou, J.
Zhuang, J.
Powiązania:
https://bibliotekanauki.pl/articles/259495.pdf
Data publikacji:
2015
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
trimaran planing hull
appendix
resistance
seakeeping
model test
Opis:
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.
Źródło:
Polish Maritime Research; 2015, 1; 22-27
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The role of detoxifying enzymes in the resistance of the cowpea aphid (Aphis craccivora Koch) to thiamethoxam
Autorzy:
Abdallah, I.S.
Abou-Yousef, H.M.
Fouad, E.A.
El-Hady Kandil, M.A.
Powiązania:
https://bibliotekanauki.pl/articles/66085.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
detoxifying enzyme
resistance
cowpea aphid
Aphis craccivora zob.cowpea aphid
groundnut aphid zob.cowpea aphid
black legume aphid
true bug
Aphididae
synergism
thiamethoxam
insecticide
Opis:
The cowpea aphid (Aphis craccivora Koch) is considered a serious insect pest attacking several crops. We carried out biochemical studies to elucidate the role of the metabolising enzymes in conferring resistance to thiamethoxam, in two strains (resistant and susceptible) of the cowpea aphid. Bioassay experiments showed that the thiamethoxam selected strain developed a 48 fold resistance after consecutive selection with thiamethoxam for 12 generations. This resistant strain also exhibited cross-resistance to the tested carbamates; pirimicarb and carbosulfan, organophosphorus (malathion, fenitrothion, and chlorpyrifos-methyl), and the neonicotinoid (acetamiprid). Synergism studies have indicated that S,S,S-tributyl phosphorotrithioate (DEF), a known inhibitor for esterases, increased thiamethoxam toxicity 5.58 times in the resistant strain compared with the susceptible strain. Moreover, the biochemical determination revealed that carboxylestersae activity was 30 times greater in the resistant strain than in the susceptible strain. In addition, the enzyme activity of glutathione S-transferase (GST) and mixed function oxidases (mfo) increased only in the resistant strain 3.7 and 2.7 times, respectively, in relation to the susceptible (the control). Generally, our results suggest that the higher activity of the detoxifying enzymes, particularly carboxylesterase, in the resistant strain of the cowpea aphid, apparently have a significant role in endowing resistance to thiamethoxam, although additional mechanisms may contribute.
Źródło:
Journal of Plant Protection Research; 2016, 56, 1
1427-4345
Pojawia się w:
Journal of Plant Protection Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Role of metabolic enzymes in resistance to chlorpyrifos-methyl in the cowpea aphid, Aphis craccivora (Koch)
Autorzy:
Mokbel, E.M.S.
Swelam, E.S.H.
Radwan, E.M.M.
Kandil, M.A.-E.
Powiązania:
https://bibliotekanauki.pl/articles/66464.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
metabolic enzyme
resistance
chlorpyrifos-methyl insecticide
insecticide
cowpea aphid
aphid
Aphis craccivora
Opis:
The cowpea aphid, Aphis craccivora management relies mainly on chemical control. As a result extensive and repeated treatment of insecticides has led to the development of aphid resistance to commonly used insecticides. To investigate chlorpyrifos-methyl resistance in A. craccivora, a field strain was selected for 24-generations to achieve a resistance factor of 82.3 fold compared with a susceptible strain. In the resistant strain, malathion and lambda-cyhalothrin exhibited obvious cross-resistance; while fenvalerate and dinotefuran showed moderate cross-resistance. In contrast, slight or no cross-resistance was obtained with the other tested insecticides. To investigate metabolic resistance mechanisms, integration of biochemical and synergism assays was conducted. Results showed the key role of esterase (EST) and mixed function oxidases (MFO); however, glutathione-s-transferase (GST) contributed less to resistance. Cross-resistance studies showed the need for rotation with non-cross resistant insecticides as a resistance management tactic.
Źródło:
Journal of Plant Protection Research; 2017, 57, 3
1427-4345
Pojawia się w:
Journal of Plant Protection Research
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-4 z 4

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