Judul: Metode kuadrat terkecil pada analisis data dengan ulangan dan ukuran subsampling tidak sama
Abstrak: Penelitian ini bersumber dari percobaan yang dilakukan oleh seorang mahasiswa program S3 IPB dalam mempelajari pengaruh pemberian 3 taraf protein dan 3 taraf yodium pada kambing induk, serta diamati pula pengaruhnya pada kambing anak yang dilahirkannya. Pada penelitian ini terutama membahas aspek-aspek statistika yang timbul akibat keadaan struktur data pada percobaan tersebut, dimana banyaknya ulangan dan ukuran subsampling yang tidak sama besar. Permasalahan yang timbul adalah dalam penentuan nilai harapan kuadrat tengah perlakuan, penguraian jumlah kuadrat dalam analisis regresi polinomial ortogonal, dan statistik uji yang digunakan untuk menguji hipotesis linear. Untuk penentuan nilai harapan kuadrat tengah, diperkenalkan metode Doolittle dipersingkat, yang sangat berguna jika unit pengamatan dalam percobaan tidak sama. Kemudian dalam analisis regresi polinomial ortogonal, diperkenalkan metode pengortogonalan matriks dengan metode pengortogonalan Gram-Schmidt yang dapat digunakan secara umum. ...
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Judul: Perbandingan metode regresi kuadrat terkecil dengan metode kekar
Abstrak: Ordinary least squares method is generally used to estimate parameter of a linear model. However, ordinary least squares is vulnerable against outliers because this method treats every element of data with equal weight. To overcome this problem, several studies have been done to find methods that produce more robust estimator. The robust methods being studied in this paper are weighted least squares, least absolute deviations, least median squares, and least trimmed squares methods. The comparison among those methods indicates that the method of least absolute deviation and weighted least squares are more resistant in case of the presence of outliers in the dependent variable. Meanwhile, least median squares and least trimmed squares methods are resistant to the presence of outliers both in the dependent and independent variable.
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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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