Judul: Sintesis Fluorapatit Nanopartikel Berbasis Cangkang Telur Ayam dengan Metode Sonokimia
Abstrak: Apatit alami yang ada dalam gigi berskala nanometer sehingga diperlukan fluorapatit nanopartikel agar sesuai dengan gigi alami manusia dan meningkatkan biokompatibilitasnya. Fluorapatit nanopartikel dalam penelitian ini disintesis menggunakan metode sonokimia dengan variasi molaritas kalsium oksida, asam fosfat, amonium fluorida, dan variasi amplitudo ultrasonikasi. Hasil karakterisasi XRD menunjukkan bahwa fluorapatit telah terbentuk pada setiap sampel. Meningkatkan molaritas kalsium oksida, asam fosfat, ammonium fluorida dan amplitudo ultrasonikasi dapat meningkatkan kristalinitas dan ukuran kristalit fluorapatit. Berdasarkan hasil karakterisasi FTIR dan EDX, sampel dengan perlakuan ultrasonikasi memiliki persentase fluor lebih banyak dibanding sampel tanpa perlakuan ultrasonikasi. Berdasarkan hasil SEM ukuran rata-rata partikel sampel tanpa ultrasonikasi cenderung lebih kecil daripada sampel dengan perlakuan ultrasonikasi.
Keyword: fluorapatit, metode sonokimia, nanopartikel

Judul: Sintesis Nanopartikel Ca(OH)2 dari Cangkang Telur Ayam dengan Metode Presipitasi Berbantukan Ultrasonik
Abstrak: Cangkang telur ayam berpotensi untuk dijadikan sumber kalsium pada gigi. Kalsinasi cangkang telur ayam pada suhu 1000 oC dapat membentuk senyawa CaO sebagai komponen utama untuk memperoleh senyawa Ca(OH)2. Komposisi kalsium tertinggi hasil kalsinasi yang diperoleh mencapai 63.21% dan data yang didapatkan sesuai dengan pola XRD CaO. Gelombang ultrasonik digunakan untuk membantu sintesis nanopartikel Ca(OH)2. Sampel yang diperoleh dikarakterisasi dengan XRD, FTIR, SEM, dan EDS. Gugus fungsi yang muncul pada spektra FTIR diantaranya karbonat (CO32-) dan hidroksil (-OH). Sonikasi dilakukan selama 2 jam untuk membentuk senyawa Ca(OH)2 yang berukuran nano. Endapan Ca(OH)2 disaring dan di sintering dengan variasi suhu 100 oC, 200 oC dan 400 oC. Variasi suhu saat sintering tidak terlalu mempengaruhi karakteristik sampel Ca(OH)2 yang terbentuk. Citra SEM menunjukkan bahwa nanopartikel Ca(OH)2 memiliki morfologi berbentuk hexagonal. Karakterisasi EDS menunjukkan bahwa terdapat kandungan unsur kimia pada sampel diantaranya oksigen, emas, dan kalsium.
Keyword: Cangkang telur ayam, Gelombang ultrasonik, Nanopartikel Ca(OH)2

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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