Judul: Penerapan Metode Prestack dan Poststack Time Migration Untuk Meningkatkan Kualitas Data Seismik Laut
Abstrak: Migration is the final and primary stages in seismic data processing. Migration was carried out because the results of the seismic stacked section was unable to describe the actual position of the reflector. In this research, Kirchhoff migration was conducted in time domain on seismic recording line-7 in Gulf of Bone, South Sulawesi. Data processing was conducted by migration processes namely poststack and prestack time migration. The succeded of this process is strongly influenced by the velocity model, aperture width, maximum dip to migrate and also frequency. The analysis result of cross section obtained showed that the cross section of prestack time migration had a better results in describing the pattern of reflectivity than poststack time migration. On the research area, normal faults event and the boundary sequences found were characterized by downlap, toplap and onlap field.
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Judul: Pengukuran Kecepatan Gelombang Seismik Laut 2D menggunakan Prestack Time Migration dengan Metode Kirchhoff
Abstrak: Seismic method is a method used in geophysics to study the structure of earth surface and below using sounds. Seismic waves are emitted by the transmitter into the sea to the subsurface ocean floor. Reflected wave is returned subbottom to the hydrophone and contains information on the elastic parameters of the subbottom. The method used in this study is using the Prestack Time Migration (PSTM) with the Kirchhoff method has the advantage to increase the Signal/Noise data and be able to improve data quality including time, angles, and distances. This study was conducted to analyze the speed of default parameters and the root mean square (rms) using Prestack Kirchhoff Time Migration method. Cross-sectional results of the two treatments were applied in seismic data line 13-1 in the Gulf of Bone waters, South Sulawesi. In the seismic section are sequence boundaries of toplap, downlap, normal and reverse faults event. Based on the results obtained, cross prestack time migration using the rms velocity analysis (picking velocity) gives better results compare to the cross section of prestack time migration using default parameters.
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Judul: Isolasi senyawa golongan flavonoid sebagai antioksidan dari daun dandang gendis (Clinacanthus nutans)
Abstrak: The leaves of dandang gendis (Clinacanthus nutans) exhibit antioxidant activity. The objective of this study is to investigate the highest antioxidant activity from flavonoid extract of the leaves. Antioxidant activities were determined by radical scavenging assay using 1,1-diphenyl-1-pycryl-hydrazyl radical. The result showed that ethyl acetate extract had antioxidant activity with IC50 value of 178.40 mg L-1. The ethyl acetate extract was fractionated further using preparative thin layer chromatography with eluent of n-buthanol:acetic acid: water (4:1:5) and produced 3 fractions. The most active fraction was fraction 2 with IC50 value of 52.93 mg L-1, which was lower than that of butylated hydroxy toluene (IC50 16.71 mg L-1). Flavonoid assay of fraction 2 showed that it contained flavonol and flavon. The ultraviolet-visible spectrum of fraction 2 in methanol solvent showed a maximum absorption at 332 in band 1 and 274 nm in band 2. In MeOH+MeONa and MeOH+AlCl3-HCl solvents there was a bathochromic shift, indicated the presence of 4'-OH and 5-OH. The new peak at 326.5 nm showed the presence of 7-OH substituent.
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