Judul: Karakteristik Gelombang Kelvin Ekuatorial Atmosferik pada Kondisi Normal (1990), La Nina (1988–1989), dan El Nino (1997–1998)
Abstrak: The purpose of this research is to analyze the characteristics of atmospheric equatorial Kelvin waves using spectral technique of upper winds in the level of 100 mb (tropopause) and 50 mb (lower-stratosphere) in Normal (1990), La Nina (1988–1989) and El Nino (1997–1998) condition. In tropopause, Kelvin waves are predominantly excited by deep tropical convections. Generally, behavior of Kelvin waves in the Normal condition is similar to those observed during the La Nina condition, namely the energy of waves is substantially strong over the maritime continent (Indonesia), but during the La Nina condition the energy of waves is also strong over Pasific ocean. Whereas the energy of waves over Indonesia is low during the El Nino condition because strong energy of the waves moves to western Pasific ocean following deep tropical convections. Kelvin waves have an upward energy propagation. The observed energy of the waves over Indonesia in the level of 100 mb is strong, thus, Indonesian region becomes a favorable region to induce the equatorial stratosphere circulation, especially on the quasi-biennial oscillation (QBO). In the lower-stratospher, we indetify the QBO during the period of 24 and 28 months. In the level of 50 mb the energy of Kelvin waves is strong when phase of QBO changes from easterly to westerly and westerly momentum increases. This is caused by easterly QBO phase dominates layer under the level of 50 mb, so the energy of Kelvin waves can penetrate to the level of 50 mb. The energy of Kelvin waves in tropopause is stronger than in lower-stratosphere due to distance from the forcing (tropical convection centre).
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: