Judul: Pelapisan Komposit Hidroksiapatit-gelatin pada Paduan Logam CoCrMo dengan Metode Dip Coating yang Dimodifikasi
Abstrak: Hidroksiapatit (HAp) dengan rumus kimia Ca10(PO4)6(OH)2 merupakan salah satu senyawa anorganik penyusun jaringan keras pada tubuh manusia seperti tulang dan gigi. Tujuan penelitian ini adalah menyintesis HAp dari cangkang keong sawah yang dikompositkan dengan gelatin dan melapisinya pada permukaan paduan CoCrMo dengan metode dip coating yang dimodifikasi untuk meningkatkan bioaktivitas kerekatan antara logam dan HAp. Kadar Ca yang terkandung dalam sampel CaO sebesar 44.73%. Analisis pola difraksi menggunakan difraksi sinar-X menunjukkan adanya fase HAp. Pelapisan komposit HAp-gelatin pada paduan CoCrMo dilakukan dengan ragam waktu perendaman, 6, 12 dan 24 jam. Konsentrasi gelatin yang ditambahkan adalah 1%, 2% dan 3%. Berdasarkan hasil analisis morfologi pelapisan terbaik dihasilkan pada waktu perendaman selama 24 jam dengan tambahan gelatin 3%. Hasil pengukuran pelepasan ion Ca2+ menunjukkan bahwa tambahan gelatin dapat meningkatkan bioaktivitas kerekatan antara HAp dan loga
Keyword: CoCrMo, modified dip coating method, gelatin, hydroxyapatite

Judul: Hydroxyapatite coating on metal alloys CoCrMo-TiN with Sol-Gel method
Abstrak: Hidroksiapatit (HAp) disintesis dengan metode presipitasi-sonikasi menggunakan sumber kalsium dari serbuk cangkang keong sawah dan sumber fosforus dari (NH4)2HPO4. Kadar kalsium diukur menggunakan spektofotometer serapan atom sebesar 82.82%. Suhu diragamkan pada 600, 800, dan 1000 oC untuk menentukan suhu terbaik pelapisan. Suhu terbaik tersebut digunakan untuk melapiskan HAp pada paduan logam CoCrMo-TiN menggunakan metode sol-gel termodifikasi. Lapisan yang menempel pada paduan logam diidentifikasi dengan diffraksi sinar X (XRD) dan uji korosi. Hasil XRD menunjukkan sebagian besar permukaan paduan logam CoCrMo-TiN terlapisi oleh HAp. Selain HAp, terdapat fase lain seperti kalsium fosfat, apatit karbonat tipe A dan tipe B. Hasil uji korosi paling baik ditunjukkan pada paduan logam CoCrMo-TiN yang terlapisi HAp dengan laju korosi paling kecil, yaitu 0.0082 mpy., Hydroxyapatite is synthesized by precipitation-sonification using calcium from field snail shell powder phosphorus from (NH4)2HPO4. The calcium level measured by atomic absorption spectrophotometer was 82.82%. The temperatures were varied on 600, 800, and 1000 oC to determine the best temperature of the coating. The best temperature was used to superimpose the HAp on the CoCrMo-TiN metal alloy using the modified sol-gel method. The layer on the metal alloy was identified with x-ray diffraction (XRD) and corrosion test. The XRD result showed that most of the CoCrMo-TiN metal alloy surface was coated by HAp. Beside HAp, there were several other phases such as calcium phosphate, carbonate apatite type A and type B. The best result of the corrosion test was showed in CoCrMo-TiN metal alloy coated with HAp with the smallest corrosion rate 0.0082 mpy. Key words: hydroxyapatite, metal alloys CoCrMo-TiN, precipitation-sonification, sol-gel modified
Keyword: hidroksiapatit, paduan logam CoCrMo-TiN, presipitasi-sonikasi, sol-gel termodifikasi

Judul: Thermal Characteristics and Dynamics of Tropical Cyclone over Western North Pacific Ocean: A Case Study of Typhoon Songda (Chedeng) 2011
Abstrak: The frequent occasion of Tropical Cyclone (TC) over Western North Pacific (WNP) Ocean lies from 10˚N to 26˚N and 121˚E to 170˚E. Sources of TC development come from warm ocean temperature where latent heat is released during condensation processes and subsequently concentrated in the boundary layer. Relative humidity at 850-700 hPa is responsible to produce the most intense storm. Meanwhile, weak vertical wind shear between 850-200 hPa is one of the dynamical factors that lead to the development of TC. Pressure level of 850-200 hPa is chosen to minimize the thermodynamic effect in the lower troposphere. Typhoon Songda (Chedeng in the Philippines) or TSC lasted from May 18th to 30th, 2011 and strengthened into powerful Super Typhoon stage between May 24th and 27th. Long curving track and the exhibition of all sequences of TC life cycle, TSC is then considered as an ideal case of TC. The objective of the study with case of TSC is to investigate the role of thermal characteristics and dynamics on TC intensity. The research is carried out by using Advanced Research of Weather Research and Forecasting model (WRF ARW model) version 3.3. Two domains are employed in the model. The first domain situate from 02˚N to 40˚N and 118˚E to 149˚E and cover spatial resolution () of 33.1 km. The second domain situate from 09˚N to 27˚N and 119˚E to 132˚E with of 11 km. Timestep of the model () is 120 seconds. The model is supported by the following physical parameterization, i.e., Yonsei University Scheme (YSU) in the boundary layer, Kain-Fritsch scheme (KF) in the cumulus, and WRF Single-Moment 3-class scheme in the microphysics. Initial meteorological condition prior to the formation of the cyclone is generated using WRF ARW standard-release model. Sensitivity of the model output is obtained from a selected single-parameter change scenarios, namely, 10 % to 20 % decrease and increase of wind shear initial data at 850-200 hPa, and by 10 % to 20 % decrease of relative humidity initial data at 850-700 hPa. The result showed that the negative correlations between wind shear and intensity are found in wind shear scenarios. Wind shears of 10 ms-1 which lead to strengthening of the wind intensity in the early period of Typhoon development are found in wind shear scenarios. The effect of wind shear changes on wind intensity is statistically significant in the 20 % wind shear scenarios. During mature stage, weak wind intensity occurred when wind shear increase as given in the WRF standard-release and the 20 % decreasing scenario. Different situation is found in the 20 % increasing scenario where wind shear tend to weak and lead to strong wind intensity at this stage. Meanwhile, the reduction of moisture supply at 850-700 hPa resulting from 20 % decreasing relative humidity play a major role in the weakening of wind intensity and reduces mechanical energy of the cycle process as much as 300 J kg-1.
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