Judul: Remote Sensing Reflektansi pada Berbagai Musim dan Tipe Air Laut.
Abstrak: Pengukuran nilai spektral remote sensing reflektansi (Rrs) dilakukan untuk melakukan kajian pada warna perairan, estimasi kandungan suatu perairan melalui pemodelan algoritma bio-optik, dan dapat digunakan untuk kalibrasi dan validasi hasil pengukuran citra satelit. Warna perairan dipengaruhi oleh kandungan zat terlarut dalam perairan seperti fitoplankton, colored dissolved matter (CDOM), dan partikel. Penentuan nilai Rrs ini dapat membantu mengetahui sebaran secara spasial dan temporal kandungan penting suatu kolom perairan. Nilai Rrsumumnya dipengaruhi oleh kandungan materi yang terdapat dalam kolom air maupun intensitas dan geometris radiasi matahari yang sampai kedalam kolom air tersebut. Dengan demikian penelitian terkait penentuan nilai Rrs pada berbagai musim dan tipe air yang berbeda sangat perlu dilakukan. Penelitian ini bertujuan untuk mengetahui kisaran dari nilai remote sensing reflectance (Rrs) di permukaan perairan timur laut Teluk Meksiko pada berbagai musim dan tipe perairan. Pengolahan data radiansi dan irradiansi dilakukan di Laboratorium Remote Sensing dan GIS Kelautan, Departemen Ilmu dan Teknologi Kelautan, FPIK, IPB berupa penentuan nilai radiansi, irradiansi, water leaving radiance, dan nilai Rrs. Data tersebut selanjutnya diplotkan berdasarkan posisi stasiun pengambilan data kemudian membandingkan nilai Rrsberdasarkan tipe perairan dan musim yang berbeda. Hasil penelitian secara umum menunjukkan bahwa nilai Rrs di daerah dekat muara sungai maksimum pada gelombang hijau dan di daerah offshoreRrs tertinggi berada pada kisaran gelombang biru, hal ini dikarenakan konsentrasi klorofil di daerah muara sungai relatif lebih tinggi, sedangkan konsentrasi klorofil yang rendah terdapat pada laut lepas. Pada gelombang merah yang relatif mudah terserap oleh air, nilai Rrspada gelombang ini secara umum relatif rendah. Kisaran nilai Rrs pada gelombang biru yakni 2 x 10-3 – 1,2 x 10-2 sr-1, untuk gelombang hijau dengan kisaran 1,8 x 10-3– 5,5 x 10-3 sr-1, sedangkan untuk gelombang merah adalah 0,1 x 10-3 – 1,8 x 10-3sr-1. Berdasarkan pengolahan data yang dilakukan menunjukkan daerah muara Sungai Suwannee, Mississippi, Mobile, Chochawatchee, Apalachicola, dan Teluk Tampa memiliki nilai Rrsyang relatif tinggi pada gelombang hijau, sedangkan daerah laut lepas memiliki reflektansi tertinggi pada panjang gelombang biru. Akan tetapi, pada musim panas, nilai Rrs pada panjang gelombang hijau relatif lebih tinggi dan relatif terdistribusi hingga daerah offshore jika dibanding dengan musim gugur maupun semi. Relatif tingginya nilai Rrspada gelombang hijau sampai perairan offshore pada musim panas, disebabkan adanya pengaruh loop current yang menyeret air dengan kandungan nutrien relatif tinggi dari muara sungai Mississippi ke arah offshore.
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Judul: Distribusi Spasial dan Variabilitas Koefisien Total Hamburan di Permukaan Perairan Berbagai Musim
Abstrak: The optical properties of the waters are affected by the intensity and angle of incidence light and material contained in the water column. The optical properties are divided into two categories i.e., apparent optical properties (AOP) influenced by the intensity and angle of incident light and the amount of material in the water, and the inherent optical properties (IOP) affected only by the content of the material in the column water such as phytoplankton, suspended solid materials, organic matter, and colored dissolved organic matter (colored dissolved organic matter (CDOM). Scattering is the process of radiation deflection by the water column and the material contained in the water column. Scattering is divided into two categories i.e., backscattering and forward scattering. Total scattering is a combination of backscattering and forward scattering. The Northeastern Gulf of Mexico waters (NEGOM) contains type-1 waters (offshore) and type-2 (coastal waters). The NEGOM waters are also influenced by the Loop Current, upwelling, wind, and freshwater discharge of several rivers. Currently, few studies were conducted related variability and spatial distribution of the total scattering in NEGOM waters especially in tropical waters. Standard facilities and bio-optical equipment are also minimal to none in Indonesia. Therefore, this research is very important to be conducted. The purpose of this study was to determine the variability of the spatial and temporal distribution of the total scattering coefficient (scattering) in 9 wavelength (λ) in different seasons in the NEGOM. The result was expected to obtain information about the value, variability, and the spatial distribution of the total scattering coefficient (scattering) which will be utilized in the development of bio-optical algorithms satellite ocean color. The results showed that the total scattering coefficient in 1999 (average of 0.26(±0.05)-0.37(± 0.07) m-1), was generally higher in the summer than that in spring and winter (average of 0.09(±0.002)-0.23(±0.04) m-1). Except in the Mississippi region, the total scattering coefficient in spring 1999 (average of 1.54(±0.94)-2.01(±1.03) m-1) was higher than that in summer and winter. In 2000, total scattering coefficient values were also generally higher in summer (average of 0.21(±0.02)-0.32(±0.02) m-1) than that in spring and winter (average of 0.03(±0.003)-0.21(±0.01) m-1. These results showed that particles and suspended matter in summer were generally higher than that in spring and winter. In general, total scattering coefficients were relatively high especially in the coastal waters near the reiver mouth and relatively low in offshore waters in every season except during the summer the total scattering coefficients were relatively high in offshore waters. The relatively high total scattering coefficients found in offshore during summer was caused by the intrusion of the Mississippi river flow toward offshore containing high nutrients that can enhance the growth of phytoplankton in the waters offshore, increase suspended matter, and reduce salinity. The average value of total scattering coefficients at each local coastal and offshore waters in the NEGOM each season were also showed significantly different results.
Keyword: spatial distribution, variability, total scattering coefficient, various seasons

Judul: Sintesis Paduan Ti-6Al-4Nb sebagai Matrial Implan Pengganti Komponen Tibial
Abstrak: Synthesis of Ti-6Al-4Nb alloy was done by melting using Tri Arc Melting Furnace. Each sample was remelted five times to ensure the homogenity. Aluminum and niobium addition were expected to stabilize α phase and β phase until the αβ-titanium alloy was resulted. Yet based on the experiment, it was α-titanium alloy resulted. α-titanium alloy was a Hexagonal Close Packed (HCP) crystalline structure which would be cracked if deformation non-uniaxial happens. The presence of oxygen in pure titanium significantly increased the hardness of titanium. The addition of aluminum was also able to increase the hardness of titanium alloy because aluminum more stabilize the α phase in the α-titanium alloy. The corrosion ressistance of titanium could be increased by adding aluminum and niobium. Titanium coating with HA/chitosan composite was also proved in decreasing the corrosion rate because it barried direct interaction between titanium alloy and corrotion solution.
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