Sutawanir Darwis
Statistics Research Division, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Bandung,

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DERAJAT KETAKSESUAIAN DAN DERAJAT KEDIVERGENAN KALMAN FILTER Darwis, Sutawanir; Mutaqin, Aceng Komarudin; Karyana, Yayat; Sobri, Mohammand
STATISTIKA: Forum Teori dan Aplikasi Statistika Vol 14, No 2 (2014)
Publisher : Program Studi Statistika Unisba

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29313/jstat.v14i2.1208

Abstract

Tulisan ini membahas beberapa ukuran derajat ketaksesuaian dan derajat kekonvergenan Kalmanfilter yang didefinisikan melalui matriks kovariansi. Pencilan mempengaruhi kinerja penaksiranstate. Dijabarkan pengaruh pencilan terhadap taksiran state dan kovariansi error.
ESTIMASI KERNEL FUNFSI INTENSITAS KEMUNCULAN GEMPA Kurniandi, Ocke; Darwis, Sutawanir
STATISTIKA: Forum Teori dan Aplikasi Statistika Vol 3, No 1 (2003)
Publisher : Program Studi Statistika Unisba

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29313/jstat.v3i1.553

Abstract

Topik yang dibahas dalam tulisan ini adalah estimasi kernel untuk fungsi intensitas kemunculan gempa bumi dilingkungan sekitar pulau Jawa. Kemunculan gempa dapat dimodelkan sebagai proses Poisson spasial-waktu inhomogen dalamtulisan ini dibatasi pada masalah kemunculan gempa bumi dengan intensitas kekuatan gempa lebih dari 4 skala righter padadaerah domain suatu himpunan kompak di R2 (longitude dan Latitude). Estimasi kernel di R2 ini menghasilkan suatu peta konturintensitas kemunculan gempa yang berguna untuk prediksi daerah gempa.
UPDATING RESERVOIR MODELS USING ENSEMBLE KALMAN FILTER Darwis, Sutawanir; GUNAWAN, AGUS YODI; WAHYUNINGSIH, SRI; SUNUSI, NURTITI; MUTAQIN, ACENG KOMARUDIN; FITRIYATI, NINA
STATISTIKA: Forum Teori dan Aplikasi Statistika Vol 10, No 1 (2010)
Publisher : Program Studi Statistika Unisba

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29313/jstat.v10i1.1007

Abstract

The Ensemble Kalman Filter (EnKF) has gain popularity as a methodology for real time updates ofreservoir models. A sample of models is updated whenever observation data available. Successfulapplication of EnKF to estimate reservoir properties has been reported. A flow modeling is missing inthis research area. This paper presents the applicability of EnKF in flow modeling for three cases:infinite reservoir, bounded reservoir and one dimensional composite reservoir. The solution of flowequation was derived and used as a modeling component of state space modeling of Kalman filterupdating formula. This three reservoir models shows that the EnKF methodology can be used forupdating the reservoir models.
NONLINEAR LEAST SQUARES (NLS) TRACER MODEL Rahmawati, Siti; Darwis, Sutawanir
STATISTIKA: Forum Teori dan Aplikasi Statistika Vol 9, No 1 (2009)
Publisher : Program Studi Statistika Unisba

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29313/jstat.v9i1.992

Abstract

Tracer test is used to study possible temperature decline and cooling of production well during longtermre-injection through studying connection between injection and production well. Tracer testinvolve injecting a chemical tracer into a hydrological system and monitoring it?s recovery throughtime. Concentration tracer in production well is nonlinear model. Nonlinear Least Squares Method isproposed to estimate the tracer parameter, i.e. average fluid velocity in the channel and dispersioncoefficient, by using simulation data tracer concentration from production wells AH-4bis, AH-19, andAH-22 in Ahuacapan, Elsavador. The results of estimation are used for predicting thermalbreakthrough and cooling production well during long term re-injection.
The consistency between professed teaching practices and assessment practices: A case in mathematics class Purnomo, Yoppy Wahyu; Kaur, Amrita; Ismail, Siti Noor Binti; Suryadi, Didi; Darwis, Sutawanir
Beta: Jurnal Tadris Matematika Vol 11 No 2 (2018): Beta November
Publisher : Universitas Islam Negeri (UIN) Mataram

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.20414/betajtm.v11i2.223

Abstract

[English]: The purpose of this research was to (1) develop scales for measuring teaching practices and assessment practices in mathematics class; (2) identify the profile of teaching practices and assessment practices in mathematics class; and (3) examine the consistency between relevant factors in teaching practices and assessment practices in mathematics class. The methods of cross-sectional surveys and a scale development study were used to achieve that purpose. The participants in this research included two sample groups of primary school teachers in Jakarta. The first sample consisted of 252 teachers and the second sample consisted of 325 teachers. This research found that there were two factors in each dimension of teachers’ practices in mathematics class. Teaching practices included the relational and instrumental practices, while the assessment practices included the assessment for learning and assessment of learning. This research also found that most of the teachers leaned toward traditional practices for both teaching practices and assessment practices, and that there was a consistency between relevant factors in those teaching and assessment practices. A more detailed discussion can be found in the findings and discussion section. Keywords: Assessment practices, Teaching practices, Mathematics class, Scale development study, Cross-sectional Survey [Bahasa]: Penelitian ini bertujuan untuk (1) mengembangkan sebuah skala untuk mengukur praktik mengajar dan penilaian di kelas matematika; (2) mengidentifikasi profil praktik mengajar dan praktik penilaian di kelas matematika; dan (3) mengkaji konsistensi antar faktor-faktor yang bersesuaian pada praktik mengajar dan penilaian di kelas matematika. Metode survei cross-sectional dan studi pengembangan skala digunakan untuk menggapai tujuan tersebut. Partisipan dalam penelitian ini mencakup dua kelompok sampel guru sekolah dasar di Jakarta. Sampel pertama adalah 252 guru dan sampel kedua adalah 325 guru. Temuan penelitian ini mendapati terdapat dua faktor di setiap dimensi praktik guru di kelas matematika. Praktik mengajar mencakup faktor praktik relasional dan instrumental, sedangkan praktik penilaian mencakup faktor praktik assessment for learningdan assessment of learning. Penelitian ini juga menemukan bahwa sebagian besar guru mengarah pada praktik-praktik tradisional baik praktik mengajar maupun praktik penilaian, dan terdapat konsistensi antar faktor yang bersesuaian pada praktik mengajar dan penilaian tersebut. Diskusi lebih detail dapat ditemukan pada bagian hasil dan pembahasan. Kata kunci: Praktik penilaian, Praktik mengajar, Kelas Matematik, Studi Pengembangan Skala, Survei cross-sectional
RUN-OFF TRIANGLE DATA DAN PERMASALAHANNYA Mutaqin, Aceng Komarudin; Tampubolon, Dumaria R.; Darwis, Sutawanir
STATISTIKA: Forum Teori dan Aplikasi Statistika Vol 8, No 1 (2008)
Publisher : Program Studi Statistika Unisba

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29313/jstat.v8i1.975

Abstract

Run-off triangle data sering digunakan sebagai dasar untuk menaksir cadangan kerugian dari suatuperusahaan asuransi umum kelas bisnis long-tail. Run-off triangle data memuat gambaran klaimkeseluruhan (aggregate), dan merupakan ringkasan dari suatu data set klaim-klaim individu.Makalah ini mengupas run-off triangle data tersebut bersama-sama dengan permasalahan yang adadi dalamnya. Dalam makalah ini dikemukakan dua masalah, yaitu pertama untuk kasus-kasustertentu, tidak semua data dalam run-off triangle teramati. Kemudian masalah yang kedua adalahadanya nilai-nilai incremental data yang negatif dalam run-off triangle terutama dalam incurred claimsdata.
ROBUST DECLINE CURVE ANALYSIS Darwis, Sutawanir; Ruchjana, Budi Nurani; Permadi, Asep Kurnia
Journal of the Indonesian Mathematical Society Volume 15 Number 2 (October 2009)
Publisher : IndoMS

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22342/jims.15.2.50.105-111

Abstract

Empirical decline curve analysis of oil production data gives reasonable answer in hyperbolic type curves situations; however the methodology has limitations in fitting real historical production data in present of unusual observations due to the effect of the treatment to the well in order to increase production capacity. The development ofrobust least squares offers new possibilities in better fitting production data using declinecurve analysis by down weighting the unusual observations. This paper proposes a robustleast squares fitting lmRobMM approach to estimate the decline rate of daily production data and compares the results with reservoir simulation results. For case study, we usethe oil production data at TBA Field West Java. The results demonstrated that theapproach is suitable for decline curve fitting and offers a new insight in decline curve analysis in the present of unusual observations.DOI : http://dx.doi.org/10.22342/jims.15.2.50.105-111
INTERPOLASI DECLINE RATE MENGGUNAKAN KRIGING SEKUENSIAL Darwis, Sutawanir; Saefullah, Gan Gan
STATISTIKA: Forum Teori dan Aplikasi Statistika Vol 6, No 2 (2006)
Publisher : Program Studi Statistika Unisba

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29313/jstat.v6i2.941

Abstract

Kriging sebagai metode interpolasi membutuhkan proses inversi matriks korelasi antar sample.Secara empiris, observasi yang berada jauh dari titik interpolasi cenderung memiliki bobot nol ataunegative (screen effect). Tulisan ini mengusulkan metode kriging sekuensial untuk interpolasi lajupenurunan (decline rate) laju alir (mass flow) sumur produksi disekitar sumur produksi.Krigingsekuensial merupakan proses updating penambahan data disekitar titik interpolasi. Laju penurunanproduksi ditaksir melalui regresi ln(mass flow) terhadap waktu menggunakan model laju alireksponensial. Korelasi spatial laju alir penurunan mass flow interpolasi kriging sekuensialmengikuti pola sperikal. Interpolasi kriging sekuensial menghasilkan kontur merepresentasikandistribusi laju penurunan disekitar sumur produksi. Hasil interpolasi dapat digunakan untukmemperkirakan cadangan (energi) lapangan panas bumi.
ANALYZING PATTERN OF MUTATION IN MTDNA USING MARKOV CHAIN Adiyani, Lira; Darwis, Sutawanir; Noer, Achmad Saifuddin
STATISTIKA: Forum Teori dan Aplikasi Statistika Vol 8, No 2 (2008)
Publisher : Program Studi Statistika Unisba

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29313/jstat.v8i2.982

Abstract

Mutation in mtDNA becomes an interesting topic that needed to discuss. If someone has a mutationin his mtDNA, then it might be affect his health. Those effects could be some diseases or anothervariation that gives different characteristics. In study of mutation, there are two such things becomethe main problems: (1) does mutation occur dependently? and (2) what is the pattern? From theresearch (by 9 degrees of freedom ?2), DNA sequence shows a positional dependence. In addition, wecan also see a positional dependence in mtDNA sequence clearly (position i-1, i, i+1 are dependentwith i define as mutation) by sign test, which means, it is possibly that there is a pattern of mutation.This paper uses Markov chain to quantify the pattern and as results all bases will mutate if positioni+1 is C or cytosine (±40%). Moreover, A, C, and G will mutate (become T) if position i-1 is A oradenine (54.5%).
SECOND ORDERMEASUREMENT MODEL OF TEACHING PERFORMANCE Darwis, Sutawanir; Soleh, A Zanbar; Lacutonsina, Roslan
STATISTIKA: Forum Teori dan Aplikasi Statistika Vol 5, No 2 (2005)
Publisher : Program Studi Statistika Unisba

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29313/jstat.v5i2.919

Abstract

This paper uses second order measurement model to analyse teaching performance. Theinstrument comprising lecturer competency, lecturer attitude, lecturer organization, and studentmotivation. A survey of first year calculus student was used to test the relationships between theconstructs in the model. Students were ask to evaluate the teaching activities using a 15 itemsquestionaire on a five point Likert scale ranging from strongly agree to strongly disagree. In general,the survey results supported the proposed second order measurement model. The data showed thatthe latent construct were strongly correlated and significantly affected the quality teaching strategy.