Judul: The using of CART and CHAID’s method in finding factors that affect students’ achievement of STAKPN Tarutung
Abstrak: Students’ learning achievement is one of indicators that can be used to determine the study quality that conducted by the college. Therefore, to assess the learning quality improvement can be done by investigating the factors that affect students’ achievement. Generally, these factors consist of two parts: internal factors and external factors. Internal factors consist of health, learning interest, learning attitude and religiosity. While external factors consist of campus environment and family environment. The aim of this study is to determine the factors that influence students’ achievement of STAKPN Tarutung by using Classification and Regression Tree (CART) and Chi-square method Automatic Interaction Detection (CHAID). These methods are tree structure methods were used to examine the relationship between the response variable with explanatory variable that influence it. Learning achievement is response variable which is measured by students’ value (GPA). CART method was used when the performance index value used as continuous data, while CHAID method was used when the performance index value used as ordinal data. While the explanatory variables were analyzed consist of 21 variables, such as: origin of school, status of school, majoring, illness, disability, suitability majors, number of siblings, father's education, mother's education, parental income, study schedules, long time to learn, creativity to seek support lecture material, creativity to do assignments, calssroom conditions, facilities and means of lectures, ideological dimensions of religiosity, ritualistic dimension of religiosity, experiential dimension of religiosity, intellectual dimensions of religiosity, and consequential dimension of religiosity. The object of this study is the students of STAKPN (Sekolah Tinggi Agama Kristen Negeri) Tarutung. The source of were got from primary data and secondary data. Primary data was collected by using a questionnaire research instruments. The questionnaire contained a list of questions to determine the identity, educational background, health condition, family situation, campus environment, learning attitude, learning motivation, and the religiosity of the respondent. While secondary data was got from a list of values (GPA) of respondents were obtained from academic section of STAKPN Tarutung. Data collection was conducted in May 2013. The total number of respondents was 176 students. The result of CART analysis showed that variables influence student’s achievement of STAKPN Tarutung row were students’ major in high school, number of students’ siblings, intellectual dimension of religiosity and long time student studying at home. The first variable that splits was high school majors. The respondent was split into 2 groups based on their majoring. Students’ majoring from science consist of 75 respondents and students from social and vocational consist of 101 respondents. Students from science related to the number of siblings. Variable number of siblings split science graduate students group into two groups, namely the number of students who have siblings >3 consist of 59 respondents and students who have a number of relatives ≤3 consist of 16 respondents. Groups of undergraduate students majoring in social studies and related to the intellectual dimension of religiosity. This variable split groups and undergraduate students majoring in social studies into two groups, namely group of students with the intellectual dimension of religiosity categories of never or rarely consist of 25 respondents
Keyword: CART’s method, CHAID’s method, students’ achievement

Judul: Faktor-Faktor yang Memengaruhi Keberhasilan Studi Mahasiswa IPB Jalur Ketua OSIS dengan Metode Pohon Regresi
Abstrak: Keberhasilan studi seorang mahasiswa IPB dapat dilihat dari indeks prestasi yang diperoleh setiap akhir semester. Sementara itu, tingkat keberhasilan studi seseorang secara umum dipengaruhi oleh dua faktor yaitu, faktor internal dan faktor eksternal. Faktor internal terdiri dari kecerdasan (intelektual), jasmaniah, sikap, minat, bakat, dan motivasi, sedangkan faktor eksternal terdiri dari keadaan keluarga, keadaan sekolah, dan lingkungan masyarakat. Oleh karena itu, penelitian ini menggunakan metode analisis pohon regresi untuk mengetahui faktor-faktor apa saja yang memengaruhi keberhasilan studi mahasiswa jalur ketua OSIS. Pohon regresi merupakan salah satu metode dari classification and regression trees (CART) untuk melakukan analisis klasifikasi baik pada peubah yang bersifat kategorik maupun kontinu. Peubah respon yang bersifat kontinu akan menghasilkan pohon regresi atau kelompok data berhirarki yang dimulai dari akar dan diakhiri dengan kelompok kecil yang relatif homogen. Adapun peubah respon yang digunakan dalam penelitian ini adalah nilai IP semester 1 mahasiswa. Penelitian ini menggunakan data sekunder dari 493 mahasiswa IPB jalur ketua OSIS tahun 2018-2020 yang masih aktif hingga sekarang. Selanjutnya, analisis pohon regresi dilakukan terhadap empat model yang berbeda, yaitu untuk masing-masing angkatan dan keseluruhan angkatan dengan menyesuaikan peubah yang tersedia. Adapun, pembentukan pohon regresi dilakukan dengan 10 kali pengulangan dan hasil pembentukan pohon regresi yang diambil adalah pohon yang memiliki nilai perkiraan risiko terkecil. Kemudian, akhir hasil yang didapatkan dari analisis pohon regresi terdapat peubah-peubah yang berbeda pada model setiap angkatan dan keseluruhan angkatan dalam memengaruhi keberhasilan studi mahasiswa jalur ketua OSIS, tetapi jika diperhatikan lebih lanjut terdapat dua peubah yang sama dalam memengaruhi keberhasilan studi mahasiswa jalur ketua OSIS, yaitu peubah asal provinsi SLTA dan program studi mahasiswa., The success of IPB student's study can be seen from the achievement index obtained at the end of each semester. Meanwhile, the success rate of one's study is generally influenced by two factors, internal factors and external factors. Internal factors consist of intelligence (intellectual), physical, attitudes, interests, talents, and motivations, while external factors consist of family circumstances, school conditions, and the community environment. Therefore, this study uses the analysis method of classification and regression trees (CART) to find out what factors influenced the success of the Student Council (OSIS) university students. Regression tree it is one of the methods of classification and regression trees (CART) to perform classification analysis on both categorical and continuous response variables. Continuous response variables will produce a regression tree or hierarchical data group that starts at the root and ends with a relatively homogeneous small group. The response variable used in this study is the Achievement Index of first semester students. The results obtained from the analysis showed that there are several different variables in each class in influencing the success of the student council (OSIS) university students, but if we look further, there are two variables that are the same in influencing the success of the student council (OSIS) university students, which are variables from high school province and student study programs. This study uses secondary data from 493 IPB students track the chairman of the student council of the year 2018-2020 which is still active until now. Furthermore, the analysis of the
Keyword: achievement in study, CART, regression trees, student council president's path

Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
Keyword: