Judul: Ekstraksi alumina dari limbah Coal Fly Ash sebagai bahan dasar prostetik tempurung lutut
Abstrak: Aluminium oksida (ahumina/Al₂O) merupakan material biokeramik yang dapat digunakan sebagai bahan dasar prostetik tempurung lutut. Ekstraksi alumina dari limbah Coal Fly Ash telah dilakukan dengan metode asam basa. Bahan yang digunakan dalam penelitian ini adalah limbah Coal Fly Ash, larutan NaOH dan HCI (Merck 37%). Ekstraksi alumina dilakukan dengan variasi konsentrasi 6 M dan 8 M larutan NaOH dan HCl dengan suhu sintering 900 °C dan 1200 °C Karakterisasi XRD menunjukkan alumina memiliki struktur kristal yaitu heksagonal (a = b + c) dengan parameter kisi a = b sebesar 4.759 A dan e sebesar 12.990 A. Fasa yang terbentuk pada 6 M suhu sintering 1200 °C adalah o-alumina (konumdum). Fasa yang terbentuk pada 8 M suhu sintering 1200 °C adalah bavenite dan mullite. Derajat kristanilitas yang dihasilkan sebesar 85.33%. Hasil uji analisis AAS menyatakan bahwa senyawa alumina sebesar 26.88% pada konsentrasi 6 M dan sebesar 6.00% pada konsentrasi 8 M. Hasil uji analisis SEM memperlihatkan morfologi berupa butiran halus dari senyawa yang bergabung membentuk sebuah partikel halus dan partikel padatan…
Keyword: Alumina, Asam-basa, Coal Fly Ash, Struktur kristal, XRD, Hasil analysis dengan XRF, Hasil analisis dengan AAS, Pengaruh konsentrasi

Judul: Ekstraksi Alumina dari Lumpur Sidoardjo sebagai Bahan Dasar Prostetik Tempurung Lutut
Abstrak: Alumina yang berasal dari lumpur Sidoardjo telah dibuat dengan menggunakan metode asam-basa. NaOH dengan konsentrasi 6 M dan 8 M digunakan sebagai pelarut. HCl digunakan sebagai koagulan dengan konsentrasi yang sama. Koagulan adalah sampel, dipanaskan pada suhu 105 °C untuk menghilangkan uap air. Selanjutnya disintering pada suhu 1200 °C untuk membentuk fasa alumina. Sebelum ekstraksi hasil uji AAS menyatakan kadar alumina dalam lumpur Sidoardjo sebesar 7.01%, setelah ekstraksi kadar alumina pada lumpur Sidoardjo 6 M sebesar 2.41% dan pada konsentrasi 8 M sebesar 3.95%. Berdasarkan analisis XRD didapatkan derajat kristalinitas pada lumpur Sidoardjo 6 M sebesar 99.86% sedangkan derajat kristalinitas lumpur Sidoardjo 8 M sebesar 100%.
Keyword: Alumina, Biomaterial, CFA, Lumpur Sidoardjo, Prostetik tempurung lutut, Alumina extruction, XRD analysis, Biomaterial lutut, Proses ekstraksi

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.
Keyword: