

Articles
by
Z. Ibrahim 
Total Records (
4 ) for
Z. Ibrahim 





H. Hashamdar
and
Z. Ibrahim


Problem statement: The Trujillo algorithm is indirect method and has been used in this study. The approach is based upon the principle of conservation of energy. Approach: Cable structures are very light and flexible and they undergo appreciable deflections when subjected to external loading. Results: Since all the main loadcarrying members in cable structures are usually in tension, there are no stability problems and the strength of high tensile steel used for cables can be rationally utilized. Conclusion/Recommendations: In order to define the position of equilibrium the method of analysis should, therefore, cater for the change in geometry caused by any form of applied load. Hence the classical linear theories of structural mechanisms cannot be used for the solution of cable assemblies. 





H. Hashamdar
and
Z. Ibrahim


Numerical methods such as Finite Elements (FE) resulted in a large set of simultaneous linear equations, which are generally solved by the direct stiffness approach. The DavidonFletcherPowell (DFP) is indirect methods which are often employed for the solution. Solutions through the direct minimization of the Total Potential Energy (TPE) became extremely efficient and economical in the sense of storage requirements of the solution algorithm, in comparison with the FE packages. The DavidonFletcherPowell algorithm is applied to calculate the set of displacements that minimize the energy in this study. 





A. Abdu
,
S. Tanaka
,
S. Jusop
,
N.M. Majid
,
Z. Ibrahim
,
K. Sakurai
and
M.E. Wasli


A study was conducted in the rehabilitation of degraded
forestland in the Bukit Kinta Forest Reserve, Perak, Peninsular Malaysia
with two main objectives: (1) to assess the growth performance of two
indigenous dipterocarp species, Shorea pauciflora (King) and S.
macroptera (Dyer) planted under various line planting widths and gap
planting openings and (2) to examine soil fertility status and site quality
of the study area using two indices; Soil Fertility Index (SFI) and Soil
Evaluation Factor (SEF), which are commonly used for estimating soil fertility
of secondary forest in humid tropical regions. The survival rate of the
two species was not affected by line planting width and gap planting opening.
However, its effect on the tree growth was very clear probably due to
preference of light intensity under the canopy, which in turn can be controlled
by line planting widths and gap planting openings. Principal component
analysis categorized the soil properties into three principal components
which explained 70% of the total variation. The First Component Score
(PC1) was related to cation retention capacity with a high contribution
of soil organic matter. The linear regression analysis indicated that
there were positive correlations between PC1 score and the proposed SFI
and SEF for both soil depths (p < 0.01). The SFI and SEF were also
highly correlated with height, dbh (diameter at breast height) and tree
volume, while PC1 score was only correlated with dbh and tree volume for
the surface soils. This shows that the SFI and SEF can be used as indices
to predict soil fertility and site quality of rehabilitated degraded forestland. 





M. Azri
,
M.H. Bahrom
,
N.H.A. Khanipah
,
Z. Ibrahim
,
N.A. Rahim
and
S.R.S. Raihan


This study presents the optimization of parameter operation in (PEMFC) Proton Exchange of Fuel cell
using the electrical model and the mathematical model. The parameters of the fuel cell are hard to be determine
since, the developer did not provides their parameter in details. The modelling of thermodynamic mathematical
model and the electrical model is model based on a dynamic model and both is modeled using Matlab/Simulink
simulation software by following the Horizon500 specification. The analysis of the model is model based on
the losses of the system. The cell temperature plays a role in affecting the value of losses in the model. The
input pressure plays part in affecting the stack output of the mathematical model where it is proven that a higher
pressure will produce large difference in the stack output. The efficiency for both mathematical and electrical
is below 10% less compared to the specification of Horizon500 specification thus the model parameter is
verified. 





