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Dual feedback control algorithm has proved to allow the base station to respond quickly and efficiently to the uplink bandwidth request in broadband wireless access (BWA) networks. In this algorithm the bandwidth request is calculated based on both the length of the backlogged queue and the mismatch between packet arrival and service rates. However, the physical channel quality, SNR, does not play any role in the algorithm, therefore the algorithm is sub optimal with respect to bandwidth utilization. Under fading conditions modern BWA networks employ adaptive modulation and coding (AMC) which has only a finite number of discrete service rates to grant to subscribers. In this paper, we examine the effect of AMC in WiMAX using the Finite State Markov Channel model on the practicality and efficiency of the dual feedback bandwidth request control algorithm.

It is well known that exploiting spatial diversity via cooperation of many cognitive radios leads to an increase in energy detection reliability. This is because the probability that many radio channels concurrently experience the worst shadowing and fading channel conditions decreases as the number of cooperative CRs increases. Compared to multipath fading, shadowing effects tend to produce weak and correlated received signals, hence reducing spatial diversity gain over a much larger distance, depending on the characteristics and the size of the obstruction. The motivation of our paper is that because signals received by neighboring CRs subject to shadowing by the same obstacle or cluster of obstacles are highly correlated, these CRs should be excluded from the cooperative sensing group. In this paper we present a technique to successfully identify those CRs and how to quantify justification for their exclusion.

A highly active photocatalyst based on Fe doped nano-sized TiO2 was successfully synthesized by chemical vapor deposition (CVD) using FeCl3 as iron source. The CVD was carried out by evaporating FeCl3 at 350 °C in nitrogen flow. The samples were characterized by AAS, XRD, XPS, UV-vis and FTIR. The photocatalytic activity of samples with different Fe contents obtained after different treatment times were tested in the oxidation of i-propanol in liquid phase using visible light. Titania and high Fe loaded TiO2 samples showed very low photo catalytic activity. In contrast, low loaded Fe doped TiO2 sample exhibited high photo catalytic activity. The high catalytic activity of this sample could be related to the presence of lattice defects (Ti-OH groups).

In order for the base station to respond quickly and efficiently to the uplink bandwidth request in broadband wireless access (BWA) networks using time-division duplex (TDD), a dual feedback control algorithm has recently been proposed [3]. In this algorithm the bandwidth request is adjusted in accordance with both the length of the backlogged queue and the mismatch between packet arrival and service rates. This paper presents a thorough study of the stability of the dual feedback algorithm in both continuous-time and discrete-time domains. It turns out that the stability condition in [3] is necessary but not sufficient to guarantee the stability of its discrete-time implementation.

Nano TiO 2 was synthesized by hydrothermal method. The sa mple was modified by doping transition metal ion (V, Cr and Fe) and non metal (N). Doped TiO 2 samples were characterized by XRD (X-ray diffraction), FE-SEM (Field-emission scanning electron microscopy) and UV-Vis (UV-Vis diffuse reflectance spectroscopy ). Photocatalytic activity in mineralization of xylene (vapor phase), methylene blue and active dyer PR (liquid phase) were tested. In comparison to non-doped TiO 2 , V-,Cr-,Fe-doped TiO 2 and N-doped TiO 2 samples exhibited much higher photocatalytic activity using visible light instead of UV . Keywords : Nano TiO 2 , doped TiO 2 , photocatalytic, non-doped TiO 2 , visible light. 1. INTRODUCTION In the past decades, TiO 2 has been the most widely used and investigated photocatalyst because of its non toxicity, inexpensiveness, chemical stability and favorable opto-electro nic properties. However, it can only work under ultraviolet (UV) light (wave length < 388nm) due to its wide band gap of 3.2 eV. More than 96% solar light reaches earth surface is in the range of visible light (mostly 400-600nm) since most UV is filtered by ozone layer. Therefore, a visible light response photocalyst becomes a recent trend in order to take full advantage of visible light [12]. The modification with the goal of improving the optical absorption and photocatalytic performances, e.g. extending spectral response into visible region and enhancing photocatalytic activity, seem to be the most important interest [6,7]. TiO

Users mobility in wireless networks has the obvious effect of increasing the channel fading fluctuation rate, hence the efficiency of opportunistic scheduling algorithms. In time-slotted wireless systems, the chosen slot size has to be compatible with the average channel access time (AAT) in order to preserve the multiuser diversity gain of the scheduling algorithm. This paper proposes to determine the slot size for max CNR and normalised CNR scheduling algorithms taking into account the distribution of users mobility in a wireless cell.

Within the frame of the National Strategy for Environmental Protection 2010/ 2020 for Vietnam an Air Quality Management (AQM) action plan was developed for Hanoi. The work was carried out in cooperation with Hanoi DONREH and the Swiss-Vietnamese Clean Air Program, a project under a bilateral agreement of the two governments.The plan represents a systematic and integral approach, which provides the base for a comprehensive AQM with a long-term view. It systematically addresses the major air quality concerns in Hanoi, in particular e.g. the dust and micro-dust problem, direct vehicular emissions, pollution from the industry, and growing small and medium enterprise's in the residential areas. The action plan includes a sound situation analysis (based on reliable data), defines air quality/emission targets and prioritizes a set of feasible measures to achieve targets.Implementation of the AQM plan is expected to offer "co-benefits", as the proposed measures will not only result in the reduction of air pollution in Hanoi and associated health risks, but also reduce substantial green house gas emissions from the transport and industrial sectors and reduce environmental damage costs. The SIM-air (Simple Interactive Model) analytical tool, was developed to support planning a comprehensive and systematic knowledge base, a shared-vision among the stakeholders involved, for informed decision making.

We present the results of investigation for influence of amplified spontaneous emission (ASE) noise, noise figure (NF) and chromatic dispersion on the performance of middle-distance Dense-wavelength-division-multiplexing (DWDM) networks using low-power pumped distributed Raman amplifiers (DRAs) in two different pump configurations, i.e., forward and backward pumping. We found that the pumping configurations, ASE noise, and dispersion play an important role for improving network performance by decrease of noise figure and bit error rate (BER) of the system. Simulation results show that the lowest bit error rate and low noise figure were obtained, when using forward pumping configuration. Moreover, we have also compared ASE noise powers of the simulation with these of the experiment. These results conclude that DRA with low pump power ($

Novel nano-structured materials: nano-particle materials like V-SiO2, TiO2 and nano-sized pore materials like Si-MCM-41, Ti-MCM-41 and Al-MCM-41Analogues were successfully synthesised using different methods: precipitation, sol-gel, micro-emulsion and hydrothermal treatment. These obtained nano-structured materials were characterised by using different physico-chemical methods: FE-SEM, TEM, XRD, IR, UV-vis and nitrogen adsorption/desorption (BET). These materials were examined to investigate adsorptive and catalytic properties of the materials. Nano TiO2 exhibited highly photocatalytic activity in the degradation of methyl red (MR). Pure silica form MCM-41 (Si-MCM-41Analogue) was a selective absorbent for VOCs (m-xylene) removal. Ti substituted MCM-41Analogue exhibited highly photocatalytic activity in the degradation of red phenol (RP) while Al substituted MCM-41Analogue showed high catalytic cracking of petroleum residue (Bach Ho oil field – Vietnam). The obtained results are discussed and rationalised.

The radiolysis of n-hexaneCCl4 mixtures has been studied as a function of temperature and concentration. A reaction scheme is proposed to calculate the concentration dependence by using either known rate constants or by determining them by a curve fitting procedure.

The radiolysis of the liquid binary mixture n-hexane-dichloromethane has been studied as a function of temperature and concentration. A reaction scheme has been proposed, and with its help several rate constants have been determined, either in comparison with known reactions or by a curve fitting procedure.

In modern broadband wireless access systems such as mobile worldwide interoperability for microwave access (WiMAX) and others, repetition coding is recommended for the lowest modulation level, in addition to the mandatory concatenated Reed-Solomon and convolutional code data coding, to protect vital control information from deep fades. This paper considers repetition coding as a time-diversity technique using maximum ratio combining (MRC) and proposes techniques to define and to calculate the repetition coding gain G r and its effect on bit error rate (BER) under the two fading conditions: correlated lognormal shadowing and composite Rayleigh-lognormal fading also known as Suzuki fading. A variable-rate, variable-power 10-state finite-state Markov channel (FSMC) model is proposed for the implementation of the adaptive modulation and coding (AMC) scheme in mobile WiMAX to maximize its spectral efficiency under constant power constraints in the two fading mechanisms. Apart from the proposed FSMC model, the paper also presents two other significant contributions: one is an innovative technique for accurate matching of moment generating functions, necessary for the estimation of the probability density function of the combiner's output signal-to-noise ratio, and the other is efficient and fast expressions using Gauss-Hermite quadrature approximation for the calculation of BER of QPSK signal using MRC diversity reception.