Field assessments of above ground biomass (AGB) of mangrove stand in Merbok, Malaysia

Mangroves are considered as unique and important ecosystems that occupy an intertidal zone of protected shorelines. The halophytic plants present in mangroves provide support not only for social economic needs but also for ecological roles which include carbon sinks. Above ground biomass (AGB) of mangroves was estimated in mangrove stands in Merbok, Kedah. Field data collection was conducted from January 2013 to May 2013. A total of 25 sites measuring 100 m x 100 m were surveyed in the study area. Within randomly selected plots, diameter at breast height (DBH), tree height and crown width were measured. Mangrove trees were identified at the species level. Published allometric functions were used to compute the AGB of mangroves. Rhizophoraapiculata was found to be the most abundant species followed by Bruguieraparviflora, Bruguieragymnorrhiza and Avicennia marina. An overall mean for AGB in study area was estimated to be 176 Mg/ha. From the analysis of variance (ANOVA), it was found that there is a significant different in the means of all mangrove variables measured between four mangrove species (p <0.0001). Positive relationships were found between DBH, height and crown width and AGB with r values of 0.88, 0.43 and 0.81 respectively. The subsequent analysis will involve a study of relationships between mangrove stand attributes with spectral radiance recorded from remote sensing

Atenuasi ultrasonik dan modulus ricih pada suhu genting superkonduktor terdop sederhana (Tl0.8Bi0.2)Sr2 (Ca0.9Cr0.1)Cu2 O7

Modulus ricih dan atenuasi ultrasonik superkonduktor suhu tinggi terdop sederhana (Tl0.8Bi0.2)Sr2 (Ca0.9Cr0.1)Cu2 O7 (Tl-1212) dengan suhu genting (Tc ) 98 K telah dikaji. Modulus ricih, G meningkat apabila suhu diturunkan daripada 240 K ke 80 K yang menunjukkan pengerasan kekisi. Walau bagaimanapun, pada suhu antara 160 K hingga 190 K modulus ricih menunjukkan anomali menandakan kecenderungan untuk kekisi melembut. Berhampiran suhu genting modulus ricih menunjukkan pelembutan kekisi iaitu ketakselanjaran pada cerun (dG/dT) dan ini sejajar dengan ciri peralihan fasa termodinamik tertib ke dua. Peratus perubahan modulus ricih antara 240 K dan 80 K ialah 5.5%. Atenuasi ultrasonik menunjukkan penurunan mendadak daripada 240 K ke 210 K diikuti dengan profil yang hampir mendatar sehingga 140 K. Puncak atenuasi dicerap berhampiran suhu genting dan ini menunjukkan penyerapan tenaga akustik meningkat apabila bahan memasuki fasa mensuperkonduksi. Anomali modulus ricih dan atenuasi ultrasonik ini dijelaskan melalui peralihan fasa tertib kedua dan tertiban oksigen jarak dekat dalam satah Cu-O unit sel bahan superkonduktor ini

Heat transfer enhancement in two-start spirally corrugated tube

Various techniques have been tested on heat transfer enhancement to upgrade the involving equipment, mainly in thermal transport devices. These techniques unveiled significant effects when utilized in heat exchangers. One of the most essential techniques used is the passive heat transfer technique. Corrugations represent a passive technique. In addition, it provides effective heat transfer enhancement because it combined the features of extended surfaces, turbulators and artificial roughness. Therefore, A Computational Fluid Dynamics was employed for water flowing at low Reynolds number in spiral corrugated tubes. This article aimed for the determination of the thermal performance of unique smooth corrugation profile. The Performance Evaluation Criteria were calculated for corrugated tubes, and the simulation results of both Nusselt number and friction factor were compared with those of standard plain and corrugated tubes for validation purposes. Results showed the best thermal performance range of 1.8–2.3 for the tube which has the severity of 45.455 × 10−3 for Reynolds number range of 100–700. The heat transfer enhancement range was 21.684%–60.5402% with friction factor increase of 19.2–36.4%. This indicated that this creative corrugation can improve the heat transfer significantly with appreciably increasing friction factor