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1

Limit cycle oscillation prediction based on Finite Element-Modal approach

100%

Ahmad K. , Wu Z. , Rahman H.

Archive of Mechanical Engineering

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2018

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tom Vol. LXV, nr 4

497--514

EN

The central theme of this work was to analyze high aspect ratio structure having structural nonlinearity in low subsonic flow and to model nonlinear stiffness by finite element-modal approach. Total stiffness of high aspect ratio wing can be decomposed to linear and nonlinear stiffnesses. Linear stiffness is modeled by its eigenvalues and eigenvectors, while nonlinear stiffness is calculated by the method of combined Finite Element-Modal approach. The nonlinear modal stiffness is calculated by defining nonlinear static load cases first. The nonlinear stiffness in the present work is modeled in two ways, i.e., based on bending modes only and based on bending and torsion modes both. Doublet lattice method (DLM) is used for dynamic analysis which accounts for the dependency of aerodynamic forces and moments on the frequency content of dynamic motion. Minimum state rational fraction approximation (RFA) of the aerodynamic influence coefficient (AIC) matrix is used to formulate full aeroelastic state-space time domain equation. Time domain dynamics analyses show that structure behavior becomes exponentially growing at speed above the flutter speed when linear stiffness is considered, however, Limit Cycle Oscillations (LCO) is observed when linear stiffness along with nonlinear stiffness, modeled by FE-Modal approach is considered. The amplitude of LCO increases with the increase in the speed. This method is based on cantilevered configuration. Nonlinear static tests are generated while wing root chord is fixed in all degrees of freedom and it needs modification if one requires considering full aircraft. It uses dedicated commercial finite element package in conjunction with commercial aeroelastic package making the method very attractive for quick nonlinear aeroelastic analysis. It is the extension of M.Y. Harmin and J.E. Cooper method in which they used the same equations of motion and modeled geometrical nonlinearity in bending modes only. In the current work, geometrical nonlinearities in bending and in torsion modes have been considered.

2

Okra-leaf accessions of the upland cotton [Gossypium hirsutum L.]: genetic variability in agronomic and fibre traits

100%

Rahman H. , Bibi A. , Latif M.

Journal of Applied Genetics

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2005

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tom 46

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nr 2

EN

Okra-leaf types of the upland cotton have the potential to be competitive to the normal-leaf types in yield and fibre quality, in addition to its potential resistance to insect pests and drought. Okra-leaf cotton accessions, collected at Cotton Research Institute, Faisalabad, Pakistan, were evaluated in respect of genetic variance and relative performance in half- and full-sib crosses (combining ability) for 2 years. Variation due to parents x years interaction was significant for lint percentage, seed weight and earliness index, resulting in moderately low but significant genetic variance across environments (years) for these traits. Interaction of environment with general combining ability was significant for seed yield, seed weight, and earliness index. General combining ability variation, contributed by females and males together, accounted for 71% of the total variation available for seed cotton yield, 60% of that for seed weight and height to node ratio each, and 75% of that for earliness index. Specific combining ability variation accounted for 85% and 51% of the total variation available for lint percentage and staple length, respectively. The contribution of female parents to general combining ability variation was higher than that of male parents for seed cotton yield, seed weight, height to node ratio, and earliness index. Okra-leaf accessions HR-VO-MS and HR107-NH were predicted to produce progenies having high yield, HR109-RThigh lint percentage, while HR100-Okra, Gambo-Okra and HR-VO-1 were predicted to impart early crop maturity to their progenies by reason of their good general combining ability for these traits. The results also provided evidence that genes controlling high yield in HR-VO-MS and HR107-NH were different from those controlling high yield in HR109-RT. The set of genes controlling the high earliness index in HR100-Okra and that in HR-VO-MS also appeared to differ in expression.

3

Mix cropping of legume (Vigna Radiata) and non-legume (Zea Mays) crops alleviates water stress as revealed by growth and biochemical parameters

88%

Khan K. U. , Murad W. , Azizullah A. , Rahman H. , Khan M. D.

Acta Physiologiae Plantarum

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2017

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tom 39

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nr 01

4

Determination of critical limit of soil phosphorous for mustard (Brassica napus L.) and maize (Zea mays L.) in different agroecological zones of Bangladesh

63%

Khan M. R. , Rahman H. , Tarafder M. A. , Hague A. , Hossain B. , Islam T. , Skalicka J. , Skalicky M. , Hossain A.

Acta Agrobotanica

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2024

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tom 77

5

Soil and foliar zinc application techniques influence the productivity, zinc concentration, and protein content in the grains of bread wheat varieties

63%

Khan M. R. , Akram S. , Moonmoon J. F. , Tarafder M. A. , Rahman H. , Das S. , Skalicka E. , Skalicky M. , Hossain A.

Acta Agrobotanica

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2023

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tom 76