Judul: Penyelesaian Masalah Integer Programming dengan Metode Relaksasi Lagrange
Abstrak: Masalah integer programming (IP) dapat diselesaikan dengan menggunakan metode relaksasi Lagrange. Ide dari permasalahan relaksasi Lagrange berawal dari metode penalti yang merupakan suatu metode yang digunakan untuk mencari solusi hampiran dari masalah pemrograman berkendala. Dalam formulasi masalah relaksasi Lagrange terkait dengan pengali Lagrange. Nilai pengali Lagrange pada masalah relaksasi Lagrange dapat ditentukan dengan menggunakan metode subgradien atau metode branch and bound. Pada karya ilmiah ini, nilai pengali Lagrange diperoleh dengan menggunakan metode subgradien. Pada karya ilmiah ini juga dilakukan pembandingan antara penyelesaian IP dengan relaksasi Lagrange dan penyelesaian IP dengan pemrograman linear relaksasi. Dalam karya ilmiah ini digunakan software LINDO 6.1 untuk memperoleh solusi dari masalah pemrograman linear relaksasi dan masalah relaksasi Lagrange.
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Judul: Pemrograman Integer dengan Fungsi Objektif Linear Sepotong- Sepotong
Abstrak: Integer Linear Programming (ILP) tidak dapat digunakan untuk menyelesaikan permasalahan yang mengandung fungsi objektif linear sepotong-sepotong, karena pada dasarnya fungsi linear sepotong-sepotong bukan merupakan fungsi linear. Tulisan ini memberikan suatu metode untuk menyatakan fungsi linear sepotong-sepotong sebagai fungsi linear, sehingga masalah ILP dengan fungsi objektif linear sepotong-sepotong dapat dinyatakan sebagai ILP dalam bentuk standar. Hal ini dapat dilakukan dengan dua langkah, langkah pertama adalah merubah fungsi objektif linear sepotong-sepotong ( f(x) ) menjadi z1f(b1)+z2f(b2)+...+ znf(bn), dimana , , ..., 1 2 b b bn merupakan break point. Kemudian langkah kedua menambahkan kendala-kendala baru sedemikian sehingga formula pada langkah satu dapat berfungsi.
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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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