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.
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Judul: Analisis Gelombang Atmosfer Ekuatorial Planeter (EPW) di Lapisan Tropopause dan Stratosfer Bawah Indonesia dengan Menggunakan Data NCEP/NCAR Reanalysis I.
Abstrak: Equatorial Atmospheric Planetary Waves (EPW) in the Tropopause and Lower Stratosphere of Indonesia are discussed. This research is motivated by complete unsolved problems relating to evidence of existence, behavior, propagation (horizontal and vertical structure), and periodicity of EPW as well as interconnected to other equatorial atmospheric oscillations in Indonesia. Based on linearized equations of EPW in β-plane, EPW n=0 mode has greatest meridional wind amplitude in Equator and decays exponentially when away from the Equator (Gaussian Decay). EPW n=1 mode has greatest amplitude of meridional wind pertubation (v’) at latitude y= ± 1 (dimensionless) and v’ equal to zero in Equator. For EPW n=2 mode, amplitude of v’ equal to zero at latitude y = ±1/2√2 and greatest amplitudes outside the Tropics. Simulation of mixed Rossby Gravity wave results that either zonal wind or geopotential field has greatest pertubation amplitudes at latitudinal domain y= ±1 (u’=0 in Equator). Pertubation of zonal wind (u’) and geopotential field (Ф’) be in geostrophic balance at latitude y>1 and y<-1 (dimensionless) or -(β-1√gH)1/2 < y < (β-1√gH)1/2 (length dimension unit). Simulation of Kelvin wave results that either zonal wind or geopotential field has symmetric amplitude and symmetric pertubation relative to Earth latitude. Based on spectral and kinetic energy (KE) analysis, Kelvin waves in the tropopause of Western Indonesia are found in the 15 days in wet season and 18 days in dry season. Energy of Kelvin wave in this region is stronger than others. In the Middle of Indonesia, these waves are found in a period of about 12.9-18 days in wet season and do not appear in dry season. While in Eastern Indonesia, this wave appears in period of 10-12.9 days (wet season) and 11.3-18 days (dry season). Their presence in transition season is not clearly found. KE response for Kelvin waves oscillations in 10- 18 days will exhibit when monsoon strengthened in the tropopause of Southeast Asia. In the Stratosphere of Indonesia Kelvin wave appears only in wet season. Presumably, existence of Kelvin wave in the lower stratosphere is produced by vertically propagation of Kelvin wave in the tropopause.
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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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