Key Engineering Materials Vols. 594-595

Abstract: Nowadays, most of asphalt used in pavement construction is produced from petrochemicals through refining process of crude oil. When evolves with time, asphalt become stiffer and brittle due aging process. In this paper, the rheological effect of short-term and long-term oxidative ageing of asphalt binder modified with montmorillonite (MMT) was studied using SuperpaveTM rotational viscometer (RV), dynamic shear rheometer (DSR) and Fourier transform infrared (FTIR) instruments. The results indicate the addition of MMT increased the viscosity. Based on dynamic mechanical analysis with DSR, MMT modified binder has a potential to increase rutting and fatigue resistance. In terms of FTIR test, it appears that the chemical bonding had changed in the asphalt binder before and after RTFO and PAV aging which suggest that the additional of MMT could delay the aging process.

Abstract: Hybrid silica xerogel mesoporous composite was synthesized by a low temperature acid catalysed sol-gel route where a natural copolymer; sodium alginate (Na-COOH) together with calcium oxide (CaO) powder were incorporated into silica sol precursor prior to gel formation. For this study, bulk xerogels samples were prepared with the amount of silica precursor and the natural copolymer was fixed meanwhile the loading of calcium oxide was varied at 10 and 20 wt%. The porous properties were studied and the comparison between the hybrid silica and monolith was made. The calcium oxide powder used in this study was prepared from calcium hydroxide, CaOH compound, which been calcined at 1000°C for 3 hours in normal air. Mesoporous structure with small particle size and glassy phase of matrixes are the main features of the prepared xerogels. The presence of sodium alginate and calcium oxide in silica matrixes produces a significant decrease especially in total surface area and porosity volume of the xerogel samples. Monolith silica xerogels exhibits a very large surface area approximately at 600 m²/g compared to the hybrid xerogels which showed 120m²/g and 25m²/g for the respective 10 and 20 wt.% of calcium oxide loading. Nevertheless, only a slight increased in pore size has been observed due to the increased amount of calcium oxide loading.

Abstract: Hybrid silica xerogel mesoporous composite was synthesized by a mild temperature acid catalysed sol-gel route where a natural copolymer; sodium alginate (Na-COOH) together with calcium oxide (CaO) powder were incorporated into silica sol precursor prior to gel formation. For this study, bulk xerogels samples were prepared with the amount of silica precursor and the natural copolymer was fixed meanwhile the loading of calcium oxide was varied at 10 and 20 wt%. The monolith silica was also synthesized as control parameter. The preliminary properties were investigated using XRD, FTIR and SEM together with EDS for elemental analysis. The calcium oxide powder used in this study was prepared from calcium hydroxide, CaOH compound, which was previously calcined at 1000°C for 3 hours in normal air. The component of calcium oxide and sodium alginate were found to be uniformly dispersed in matrixes without affecting the cross-linked silica formation. As the presence of the components in the silica matrixes, the synthesized hybrid xerogels were found to be crack-free, structurally amorphous and physically opaque. Furthermore, the hybrid xerogels samples were found to have denser bodies, smoother surface, and decreased in particle sizes and thus might produced less brittleness in nature compared to the monolith xerogels.

Abstract: Samples of concrete incorporate different waste materials such as iron filings, iron balls of used ball bearings and slags from steel industry were assessed for their anti-radiation attenuation coefficient properties. The attenuation measurements were performed using gamma spectrometer of NaI (Tl) detector. The utilized radiation sources comprised Cs¹³⁷ and Co⁶⁰ radioactive elements with photon energies of o.662 MeV for Cs¹³⁷ and two1.17 and 1.33 MeV energy levels for the Co⁶⁰. Likewise the mean free paths for the tested samples were obtained. The maximum linear attenuation coefficient values of 0.92±1.12×10^-3 for CS¹³⁷and 1.12±1.57×10^-3 for CO⁶⁰ attained, in this study were for concrete incorporate iron filling wastes of 30 wt. %. The iron balls and the steel slags gave much inferior values. The concrete incorporates iron filings provided the best shielding effect. The microstructure, concretefillings composite density, the homogeneity and particulate distribution were examined and evaluated using different metallographic, microscopic and measurement facilities.

Abstract: In this paper, the seismic performance of the insulated sandwich wall panel is studied. Two samples W1 and W2 of Insulated Sandwich Wall Panel (ISWP) were tested under in-plane lateral cyclic loading. The difference between W1 and W2 is the numbers of wall plug used in order to hold the specimen in standing parallel position. Four wall plugs used for W1 meanwhile eleven wall plugs used for W2. ISWP is placed axially on top of the foundation beam. The concrete block is slotted on top of the wall panel as load transfer from the roof. The aspect ratio of the specimen is Ar = H/B = 1.97 and slenderness ratio is λ = H/t = 36.92. The testing is conducted with small percent of drift which is 0.1% and continued with 0.2%. The drift was increased gradually about 0.2% until reach ±1.0%. Furthermore, the specimen was tested with an increment of ±0.2% drift until the specimens reach the strength capacity. The experimental results showed that for the first specimen, the wall panel behaves elastically up to 0.4% drift before yielding. Due to loading and unloading condition, the aluminium frame that used along the perimeter of the wall panel buckled at 1.2% drift. For the second specimen the wall panel behaves elastically up to 0.4% drift before yielding. Once 0.6% drift applied, crack started to appear at the connection joint between G.I channel and foundation beam. The analysis of the result from the graphs of hysteresis loop for both W1 and W2 were presented by considering the seismic parameter such as stiffness, ductility and equivalent viscous damping.

Abstract: This paper focus on mitigating the atmospheric turbulence effect in free space optical communication using dual diffuser modulation (DDM) technique. Phase screen diffuser located on transmitter create 'new' beam wave to propagate through turbulence more efficiently. This technique uses two transmitter and differential mode detection at the receiver. The numerical result show that the DDM produce better performance compare to conventional FSO that using intensity modulation/direct detection (IM/DD) for On-Off Keying Modulation (OOK). The reduction in the scintillation level also improve in DDM compare to conventional technique that using a perfectly coherence beam.

Abstract: This paper presents an investigation on the use of tomography system using using optical and electrodynamic sensors. The system obtains data from both sensors which detect the flow in a process pipe. Information on the flow is processed in order to display the image reconstruction of a solid flow.

Abstract: The integration of heterogeneous technologies promotes ubiquity and mobility. Optical code division multiple access (OCDMA) may be deployed in conjunction to SCM to improve the spectral efficiency and enhance the data rate of subscribers in a Local Area Network (LAN). This paper compares the performance of multimode fiber to single mode fiber in the deployment of a SCM-OCDMA system with multi-diagonal (MD) codes in a LAN.

Abstract: Hybrid optical OFDM/WDM system is proposed to provide longer reach and larger capacity comparing with existing PON systems in order to meet the ever increasing bandwidth demand and data rate of next generation optical access networks. In this paper, two channels using different modulation at 10 Gb/s are used for downstream link. OFDM signals occupy different portions of the available signal spectrum for signal transmissions by using WDM. As a result, the system has good performance based on SNR with 50 km distance and QAM modulation delivers better performance compared with PSK.

Abstract: This paper presented a new class of codes for Fiber-To-The-Home (FTTH) network design based on Spectral Amplitude Coding (SAC) - Optical Code Division Multiple Access (OCDMA) coding approaches. The FTTH SAC-OCDMA network is demonstrated by utilizing the Flexible Cross Correlation (FCC) code. The FCC code has an ability to suppress and cancels the effect of Multi Access Interference (MAI). The results indicated good performance whereas the FCC code offers 100%, 287% and 331% percentage larger cardinality compared to MDW W=4, MFH W=8 and Hadamard codes respectively. Finally, the FCC code accommodates low effective receive power P_sr = -23dBm which is expected to be more significant for future FTTH network development for future usages.