Judul: Identifikasi Gelombang Kelvin di Lapisan Tropouse Indonesia Bagian Barat dengan Menggunakan Data Sounding NOAA
Abstrak: Dinamika pada atmosfer menengah didominasi oleh QBO dimima QBO mempunyai pengaruh terhadap sistem sirkulasi secara global yang berkailan dengan berbagai masalah lingkungan. QBO dipercaya dibangkitkan dari hasil interaksi gelombang ekuatorial dengan aliran dasar. Salah satu gelombang ekuatorial yang berskala planeter adalah gelombang Kelvin. Gelombang Kelvin yang sebelumnya teramati pada lapisan stratosfer bawah berada di wilayah India dan Pasifik barat. Posisi Indonesia yang berada diantara dua wilayah tersebut memungkinkan terjadinya gelombang Kelvin di wilayah Indonesia. Namun, karakter yang teramati belum tentu sama. Kondisi aliran dasar dianalisis dengan menggunakan Time-Height Section pada semua val label sedangkan untuk mengidentifikasi gelombang digunakan analisis spektrum dan spektrum silang. Dinamika tropis yang teramati adalah monsun, sirkulasi Hadley, sirkulasi Walker dan pergeseran ITCZ yang mengikuti musimnya. Pada JJAS, ITCZ bergcser ke utara sedangkan pada DJFM ITCZ bergeser ke selatan. Pada troposfer atas, angin zonal yang dominan adalah angin timuran dimana kondisi ini metnenuhi syarat untuk terjadinya gelombang Kelvin.
Keyword: 

Judul: Analisis Penjalaran Gelombang Kelvin di Atas Kototabang Berbasis Data EAR (Equatorial Atmosphere Radar)
Abstrak: Indonesian geographical condition, maritime continent, contribute significant effects in atmosphere dynamics both macro and micro scale. One of equatorial atmospheric waves which play an important role is the Kelvin wave. It was suspected as the trigger of the Intraseasonal Variability phenomenon especially MJO (Madden Julian Oscillation). Studies on propagation and vertical structure of Kelvin wave were still limited on OLR data, GPS, RO, NCEP / NCAR reanalysis and radiosonde. EAR data were expected to explain about propagation and vertical structure of Kelvin wave better. To analyze the Kelvin wave propagation above Kototabang, spectral analysis method were used with both the FFT (Fast Fourier Transform) and the Wavelet technique. Statistical analysis was also done with cross-correlation technique (Cross Corelation Function) and cross Spectral (Cross Spectrum) to see the relevance between Kelvin wave and the KTTL (Kototabang Tropical Tropopause Layer). Based on EAR data over period of 1 December 2007 – 31 December 2008, Kelvin wave was detected above Kototabang with eastward zonal propagation and downwards vertically. Spectral analysis during this period showed that the Kelvin wave appeared periodic every 18 days at 17.41 km altitude near the Tropopause layer (~17 km). Power spectrum analysis indicate that the Kelvin wave energy was stronger during wet season than during dry season. During wet months, the Kelvin wave is dominant at 16.97 km in altitude and appear periodic every 15 days. While in dry months, it is more dominant at 16.52 km in altitude and appeared every 18 days. Statistical analysis results during wet and dry season indicate a correlation between zonal wind dynamics with the fluctuation of Tropopause height, spontaneously and inspontaneously. Cross-spectrum analysis showed that zonal wind dynamics activity affected the height fluctuation of the Tropopause where the Kelvin wave tend to rise the KTTL height during wet season, while in dry season it will lower the KTTL height. Keywords : Kelvin waves, Propagation, EAR, KTTL, Spectral analysis.
Keyword: 

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.
Keyword: