In terms of enhancing the mechanical properties of the com-posite material, we investigate the effect of different post-curing tem-peratures on the tensile strength, strain, and elastic modulus of carbon UD/Vinyl Ester composite. The performance of composite material can be developed by modifying the condition of manufacture to en-hance the bonding between resin and fibre. The best interlocking will occur upon the complete polymerization reactions of the resin. It was characterized by the formation of the polymer cross-link chain. These conditions are commonly called curing conditions. We did three dif-ferent post-curing treatments for this composite, they were conditioned at room temperature (approximately 25° C), 80° C, and 100 ° C, for 24 hrs, 4 hrs, and 4 hrs time respectively. The tensile properties have al-ready been tested for both composites that refer to ASTM D3039. The Ultimate Tensile Strength (UTS) of three different heat treatment composites was increased by increasing the heat temperature from 25° C to 80°C and 100° C, the increment is about 1.17% and 17.46% ap-proximately. Furthermore, still comparing with the 25° C post-curing treatment, the modulus of elasticity value with heat treatment in 80 ° C is a little bit decreased to 7.29% but it decreased significantly for 47.42% in 100° C heat treatment.
The hybridization of carbon fiber (CFRP) and glass fiber (GFRP) composites is required to overcome the disadvantages of GFRP composites and their commercial feasibility for marine applications. This study was conducted on a hybrid glass/carbon composite with a vinyl ester matrix made by vacuum-assisted resin infusion process with a stacking sequence of [GCG 2 CG 2 C] s. Composites are immersed in natural seawater for up to 6 months. The maximum weight gain of e-glass/carbon hybrid composite is 0.79%. The results showed that the tensile, shear and compressive strengths of the glass/carbon hybrid composite after immersion in natural seawater decreased to 19%, 13%, and 50%, respectively. The decrease in compressive strength is the highest compared to others. It indicates that compressive strength should be of more significant concern for marine environmental applications. SEM analysis exhibited that seawater absorption causes the matrix, fiber, and fiber/matrix interface degradation. It is indicated by the absence of a firm matrix fracture surface, the number of fractures in the thread, the presence of fiber/matrix debonding, and fiber pull-out in the specimen after immersion in seawater. It is the cause of the decrease in the mechanical properties of the hybrid composite.
Unusually long duration and heavy rainfall from 5 to 6 February 2021 caused widespread and devastating floods in Semarang, Central Java, Indonesia. The heavy rainfall was produced by two mesoscale convective systems (MCSs). The first MCS developed at 13Z on 5 February 2021 over the southern coast of Sumatra and propagated towards Semarang. The second MCS developed over the north coast of Semarang at 18Z on 5 February 2021 and later led to the first peak of precipitation at 21Z on 5 February 2021. These two MCSs eventually merged into a single MCS, producing the second peak of precipitation at 00Z on 6 February 2021. Analysis of the moisture transport indicates that the strong and persistent north-westerly wind near the surface induced by CENS prior to and during the event created an intensive meridional (southward) tropospheric moisture transport from the South China Sea towards Semarang. In addition, the westerly flow induced by low-frequency variability associated with La Nina and the tropical depression over the North of Australia produced an intensive zonal (eastward) tropospheric moisture transport from the Indian Ocean towards Semarang. The combined effects of the zonal and meridional moisture transport provided favorable conditions for the development of MCSs, and hence extreme rainfall over Semarang. These results provide useful precursors for extreme weather-driven hazard prediction in Semarang and the surrounding regions in the future.
The study of ionospheric disturbances associated with the two large strike-slip earthquakes in Indonesia was investigated, which are West Sumatra on 2 March 2016 (Mw = 7.8), and Palu on 28 September 2018 (Mw = 7.5). The anomalies were observed by measuring co-seismic ionospheric disturbances (CIDs) using the Global Navigation Satellite System (GNSS). The results show positive and negative CIDs polarization changes for the 2016 West Sumatra earthquake, depending on the position of the satellite line-of-sight, while the 2018 Palu earthquake shows negative changes only due to differences in co-seismic vertical crustal displacement. The 2016 West Sumatra earthquake caused uplift and subsidence, while the 2018 Palu earthquake was dominated by subsidence. TEC anomalies occurred about 10 to 15 min after the two earthquakes with amplitude of 2.9 TECU and 0.4 TECU, respectively. The TEC anomaly amplitude was also affected by the magnitude of the earthquake moment. The disturbance signal propagated with a velocity of ~1–1.72 km s−1 for the 2016 West Sumatra earthquake and ~0.97–1.08 km s−1 for the 2018 Palu mainshock earthquake, which are consistent with acoustic waves. The wave also caused an oscillation signal of ∼4 mHz, and their azimuthal asymmetry of propagation confirmed the phenomena in the Southern Hemisphere. The CID signal could be identified at a distance of around 400–1500 km from the epicenter in the southwestern direction.
Net primary productivity (NPP) and chlorophyll-a (Chl-a) are indicators of water productivity. This research aims to analyze the characteristics of NPP and Chl-a and their relationship to pelagic fish seasons in the Banda Sea. The methods used to analyze the data are Hovmoller diagram and Pearson's correlation. The NPP data used comes from Vertically Generalized Production Model (VGPM) and Chl-a from Aqua MODIS satellite. The results of data analysis from January 2003-December 2020, NPP and Chl-a reached highest concentration in dry season and lowest in wet season. The highest monthly concentration occurred in August and the lowest in April and December The Banda Sea include mesotrophic waters with monthly average of NPP 429 mg C/m2/day and Chl-a 0.24 mg/m(3). Spatially (longitude and latitude) and temporally (seasonal and monthly), the high concentrations of NPP and Chl-a are found in northern and eastern parts of study area. During La Nina and El Nino, there was a change (decrease/increase) the concentration of NPP and Chl-a in dry season and transition period II. NPP and Chl-a have a high correlation and a strong linear relationship. The change of NPP concentrations temporally corresponded to change of Chl-a concentrations. Seasonal factors, La Nina and El Nino have a strong influence in influencing the variability of NPP and Chl-a concentrations. Skipjack and tuna seasons occur in transition period II, wet season and La Nina. High productivity have an effect on the flying fish season which occurs in the dry season and El Nino.
