Judul: Analisis Struktur Horizontal Equatorial Planetary Waves (EPW) Menggunakan Teknik Empirical Orthogonal Function (EOF)
Abstrak: Empirical Orthogonal Function (EOF) adalah salah satu teknik untuk mendapatkan pola dan menduga kondisi cuaca dan iklim. Penelitian ini mengidentifikasi struktur horizontal EPW menggunakan teknik filter ganda yaitu menggunakan teknik STSA dan EOF. Beberapa leading mode EOF dari data Outgoing Longwave Radiation (OLR) digunakan untuk menggambarkan struktur horizontal gelombang Kelvin, MRG, ER, dan TD-type dengan lebih baik. Hasil analisis menunjukkan bahwa delapan EOF pertama mewakili sinyal gelombang Kelvin, pasangan mode EOF pertama, kedua, ketiga, dan keempat masing-masing mewakili gelombang Kelvin dengan bilangan gelombang zonal 2, 3, 4, dan 5. Karakteristik gelombang MRG dan ER dijelaskan oleh dua mode EOF pertama, sementara gelombang TD-type dijelaskan oleh mode EOF 1-4, 5-6, dan 9-10 yang masing-masing aktivitas terkuatnya terdeteksi di sekitar wilayah Cina, Afrika, dan Amerika Tengah. Hasil analisis EOF yang dibandingkan dengan teori menunjukkan bahwa gelombang Kelvin merambat ke arah timur dan hanya memiliki perturbasi angin zonal yang simetri terhadap ekuator. Gelombang MRG merambat ke arah barat dan hanya memiliki perturbasi angin meridional yang asimetri terhadap ekuator, sedangkan gelombang ER dan TD-type memiliki struktur horizontal yang mirip dengan gelombang MRG. Penelitian ini menunjukkan bahwa teknik filter ganda STSA dan EOF menunjukkan struktur horizontal EPW yang konsisten dengan teori. Selain itu diperoleh sinyal EPW yang lebih jelas dan tidak terdapat percampuran sinyal gangguan fenomena fisis atmosfer lain.
Keyword: EOF, EPW, struktur, horizontal, wavenumber, wilayah

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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