Judul: Deteksi Turbidity Front menggunakan Citra Satelit Sentinel-2 Hubungannya dengan Kondisi Oseanografi di Estuari Bengawan Solo
Abstrak: Turbidity front merupakan fenomena terbentuknya batas air tawar dan air laut akibat adanya pertemuan dua massa air yang berbeda antara massa jenis air estuari dan massa jenis air laut. Area pertemuan kedua massa air ini terjadi pengadukan (mixing) yang menyebabkan substansi-substansi yang ada di dasar perairan menjadi naik ke permukaan sehingga konsentrasi nutrien tinggi. Deteksi turbidity front menggunakan data citra satelit dilakukan karena terbatasnya penggunaan data in situ. Beberapa parameter yang penting digunakan untuk deteksi turbidity front yaitu salinitas, kekeruhan, konsentrasi klorofil-a, suhu, pasang surut dan curah hujan. Parameter ini memiliki keterkaitan secara langsung dan tidak langsung terhadap terjadinya turbidity front estuary. Penelitian menggunakan data in situ dan citra satelit untuk mengetahui lokasi terjadinya turbidity front estuary. Pengambilan data in situ (salinitas, kekeruhan, suhu dan konsentrasi klorofil-a) menggunakan alat water quality checker digunakan untuk mengetahui distribusi parameter lingkungan secara vertikal. Data citra Sentinel-2 digunakan untuk deteksi distribusi Total Suspended Solid (TSS) estuari dan lokasi terjadinya turbidity front dengan menerapkan algoritma dari perbandingan rasio band citra satelit sehingga diperoleh algoritma empiris lokal pada wilayah penelitian. Selanjutnya, di lokasi terjadinya turbidity front dilakukan analisis statistik dan spasial terhadap beberapa parameter yaitu intensitas curah hujan, pasang surut dan arus untuk mengetahui pengaruh dari masing-masing parameter pada area turbidity front. Hasil penelitian menunjukkan bahwa berdasarkan data in situ diketahui adanya perubahan drastis parameter salinitas, kekeruhan dan suhu pada jarak 2 – 4 km (turbidity front estuary) dari pantai di estuari Bengawan Solo. Hasil rasio band terbaik untuk deteksi distribusi TTS di estuari Bengawan Solo adalah band merah (B4)/ band biru (B2) + band hijau (B3) + band merah (B4). Hasil rasio band ini memiliki nilai koefisien determinasi (R2) = 0,7409 antara data in situ dan citra satelit. Berdasarkan citra satelit, turbidity front estuary terjadi pada jarak 1,6 – 2,8 km dari pantai. Adanya perbedaan nilai TSS 1,92 mg/L antara data in situ dengan citra satelit di daerah turbidity front estuary. Musim, curah hujan dan pasang surut memiliki pengaruh terhadap jarak turbidity front dari pantai. Ketika musim hujan jarak turbidity front semakin jauh dari pantai. Pola pergerakan arah dari distribusi dari turbidity front estuary dipengaruhi oleh arus di sekitar estuari Bengawan Solo., Turbidity front is a phenomenon of the formation of freshwater and seawater boundaries due to the meeting of two different water masses between estuary water density and seawater density. The area where the two water masses meet is mixing, causing the substances at the bottom of the water to rise to the surface so that the concentration of nutrients is high. Front turbidity detection using satellite image data is carried out due to the limited use of in situ data. Several critical parameters used to detect turbidity are salinity, turbidity, chlorophyll-a, temperature, tides, and rainfall. This parameter has a direct and indirect relationship to the occurrence of turbidity in the Estuary Bengawan Solo. The research method used is in situ data and satellite imagery to determine the location of the estuary front turbidity. In situ data retrieval (salinity, turbidity, temperature, and chlorophyll) using the AAQ tool is used to determine the environmental parameters vertically. Meanwhile,
Keyword: coastal turbidity, estuaries, GIS, remote sensing, suspended solids

Judul: Analisis Spasial dan Temporal Kualitas Perairan (Muatan Padatan Tersuspensi dan Klorofil-a) di Teluk Jakarta pada Tahun 2002-2012 menggunakan Citra Satelit LANDSAT-7 ETM.
Abstrak: Total suspended solid and chlorophyll-a are water quality parameter which can be studied using remote sensing method. The purpose of this study was to analyzing spatially and temporally water quality (total suspended solid and chlorophyll-a) in Jakarta Bay during 2002-2012 using LANDSAT-7 ETM satelite imageries. In situ measurement of total suspended solid and chlorophyll-a sample is taken from 20 station in July 2012. Analysis of spatial and temporal distribution of the water quality parameters is then done using the satellite imageries. Algorithms used in the analysis are the Tassan for total suspended solid concentration and the Pentury algorithm for chlorophyll-a concentration. The result of this study shows that the concentrations of the total suspended solid and chlorophyll-a tend to be higher in southern and eastern parts of the bay rather then other parts of the bay during the period of 2002-2012.
Keyword: Jakarta Bay, Total suspended solid, Chlorophyll-a, Tassan, Pentury, LANDSAT-7 ETM

Judul: Truncated Stop Loss as a Optimal Solution of Reinsurance Agreement in One-Period Model
Abstrak: Reinsurance is one of risk management efforts of an insurance company, which is called the cedent. Similar with insurance, reinsurance constitutes the cedent to pay the premium. We consider one-period reinsurance model and derive a rule which minimizes the ruin probability of the cedent for a fixed reinsurance premium. Therefore, it is needed to construct an optimal reinsurance agreement for the cedent. The premium is calculated according to four different principles, i.e. economic, generalized zero-utility, Esscher, and mean-variance principles. Stop loss is a reinsurance contract which protect the insurance company for losses that exceed a certain amount. The result of this research shows that a truncated stop loss is an optimal agreement in the class of all reinsurance contracts with various premiums calculated using above mentioned principles.
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