BUKU ABSTRAK - Universiti Putra Malaysia

Analytical Evaluation of Unfairness Problem in Wireless LANs
Prof. Dr. Mohamed Othman
Ahmed Mohamedou
Faculty of Computer Science and Information Technology, University Putra Malaysia,
43400 UPM Serdang, Selangor, Malaysia.
+603-8946 6535; mothman@fsktm.upm.edu.my
Keywords: Access point, buffer size, congestion window, TCP, wireless LAN
The Production of Biohydrogen from Renewable Sources Towards Green Energy
Development
Prof. Dr. Mohd. Ali Hassan
Mohd. Zulkhairi Mohd. Yusoff, Nazlina Haiza Mohd. Yasin, Nor’ Aini Abdul Rahman, Suraini Abd. Aziz and
Yoshihito Shirai
Faculty of Biotechnology and Biomolecular Sciences, University Putra Malaysia,
43400 UPM Serdang, Selangor, Malaysia.
+603-8946 7590; alihas@biotech.upm.edu.my
Keywords: Biohydrogen, POME, biofuels, waste water treatment
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Science, Technology & Engineering
The number of users using wireless Local Area Network is increasing exponentially and their behaviour
is changing day after day. Nowadays, users of wireless LAN are using huge amount of bandwidth because of
the explosive growth of some services and applications such as video sharing. This situation imposes massive
pressure on the wireless LAN performance especially in terms of fairness among wireless stations. The limited
resources are not distributed fairly in saturated conditions. One of the most important resources is the access
point buffer space. This importance is a result of access point being the bottleneck between two different types
of networks. These two types are wired network with relatively huge bandwidth and wireless network with much
smaller bandwidth. Also the unfairness problem keeps getting worse because of the greedy nature Transmission
Control Protocol (TCP). In this research, we conducted a comprehensive study on wireless LAN dynamics and
proposed a new mathematical model that describes the performance and effects of its behavior. We validated
the proposed model by using the simulation technique. The proposed model was able to produce very good
approximation in most of the cases. It also gave us a great insight into the effective variables in the wireless LAN
behavior and what are the dimensions of the unfairness problem.
Oil palm is the highest oil crop in Malaysia, making palm oil the cheapest edible oil for the world market.
However, during palm oil processing, a lot of biomass produced as waste materials. The wastes have shown a
great potential substrate available for further conversion. Indeed, the production of biohydrogen from palm oil
mill effluent (POME) shows an innovative idea since it could couple the production of biohydrogen and partial
treatment of the waste before it goes to another process, i.e methane production or organic acids production.
Biohydrogen is the second generation of biofuel and it is one of alternative fuel, which can replace fossil fuel.
Biohydrogen known as environmental friendly biofuel since it only produces pure water when combusted. In the
present study, improved conditions of biohydrogen production have been performed using POME as a substrate
and heat-treated POME sludge as seed culture. Fermentation was carried out at ambient temperature (24 - 26°C)
and pH was controlled at 5.5. Total gas produced was free from methane due to heat treatment of POME sludge at
80°C, 20 min. The experiment was conducted using 150 mL serum bottle and then upgraded to a 50 L continuous
stirred tank reactor (CSTR). Impressive result has been shown with a maximum yield of biohydrogen at 1054
NmL/L-POME and biohydrogen content in biogas mixture is 30 - 60%. In another study, a total of 3 L biohydrogen
could be produced from 1 L of POME to use culture strain as inoculum. This study successfully demonstrated
the feasibility of biohydrogen production from POME as a carbon source. This findings are applicable at palm
oil industries since fermentation has been conducted under non-sterile condition and POME is used as a carbon
source.