Judul: Identifikasi Fluktuasi Ketinggian Tropopause di Kawasan Pasifik Tropis
Abstrak: The 30-years (January 1981 – December 2010) ERA-Interim data issued by ECMWF (Europe Center for Medium Range Weather Forecasting) is used for identifying tropopause height fluctuation in tropical Pacific region. Principle component and spectral analysis is done in order to identify the main pattern of tropopause height fluctuation as generator in the region. The result has shown that the predominant fluctuation trigger is periodical 45-month ENSO. Meanwhile insolation fluctuation due to earth orbital position has placed second with 12- month period after ENSO occurrence. The 20-month oscillation period of QBO (Quasi Biennial Oscillation), periodical 6-month variation of SAO (Semi Annual Oscillation), and 6-month period of MJO (Madden Jullian Oscillation) give weaker influence on tropopause height fluctuation in the region than that of ENSO and insolation. Eigen vector distribution from principle component shows that these five oscillations are very influential and dominant in tropical west Pacific as response of interaction of the five oscillations with Walker circulation in tropical Pacific.
Keyword: Bogor Agricultural University (IPB), Spectral, Walker circulation, Tropopause height fluctuation, Principle component analysis

Judul: Identifikasi Pola Medan Suhu di Lapisan Tropopause Kawasan Pasifik Tropis
Abstrak: Fluktuasi suhu tropopause di kawasan pasifik tropis dianalisa dengan menggunakan analisis komponen utama (PCA) dan analisis spektrum. Analisis Komponen utama menunjukkan bahwa 2 komponen utama mempresentasikan 93.1% dari total variabilitas fluktuasi suhu tropopause di kawasan kajian. PCA 1 memiliki osilasi 12 bulan dan 6 bulan sedangkan PCA 2 memiliki osilasi dominan 45 bulan. Osilasi 12 bulan dipengaruhi oleh variasi insolasi akibat orbital bumi, osilasi 6 bulan disebabkan oleh SAO (Semi Annual Oscillation), dan osilasi 45 bulan oleh fenomena ENSO (El-Nino Southern Oscillation). Distribusi vektor eigen PCA 1 menunjukkan bahwa fenomena osilasi 12 bulan dan 6 bulan berinteraksi dengan sel Hadley sehingga fluktuasi suhu tropopause lebih dominan di wilayah Pasifik Tropis bagian Timur namun adanya pengaruh ENSO yang berinteraksi dengan sirkulasi Walker mengakibatkan distribusi vektor eigen PCA lebih berfluktuasi di Pasifik Tropis bagian Barat. Suhu tropopause akan merespon insolasi setelah 1 bulan kemudian.
Keyword: Suhu tropopause, Analisis komponen utama, Spektral, Sirkulasi Walker, Sel Hadley

Judul: Hydroxyapatite-Chitosan Composite Coating on Stainless Steel 316 to Improve Corrosion Resistance
Abstrak: Metals that were used in bone implantation should have good corrosion resistance that were not easily corroded when implanted into the body. Metal corrosion resistance of stainless steel 316 can be enhanced through the metal coating by hydroxyapatite-chitosan composite with composition ratio of hydroxyapatite (gram) and chitosan 3% (mL) 0.2:0, 0.2:0.1, 0.2:0.5, 0.2:1.0, and 0.2:1.5. Besides improving the corrosion resistance of metal, the presence of chitosan also maintain the position of hydroxyapatite on metal surfaces. Corrosion resistance increases with increasing amount of chitosan added and the best composition of hydroxyapatite-chitosan composite was 0.2:1.0.
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