Aplikasi Transformasi Reduction to Pole (RTP) Menggunakan Matlab dalam Pengolahan Data Magnetik WDMAM pada Wilayah Tapal Kuda -Jawa Timur

Dalam metode magnetik, medan magnet anomali disebabkan oleh sumber medan magnet dipol. Setiap tempat memiliki sudut iklinasi dan deklinasi magnetik yang berbeda sehingga menyebabkan peta anomali magnetik bersifat kompleks dan interpretasinya menjadi relatif sulit. Untuk mengatasi kerumitan dalam interpretasi data magnetik, penggunaan transformasi reduksi ke kutub RTP sangat penting dilakukan. Tapis RTP dengan memanfaatkan fungsi-fungsi built in Matlab telah berhasil direalisasikan dan diaplikasikan pada data magnetik WDMAM wilayah Tapal Kuda-Jawa Timur. Nilai sudut inklinasi I = -32.82° dan sudut deklinasi D = 0.72° digunakan pada aplikasi RTP daerah ini. Anomali magnetik hasil RTP menunjukkan bahwa terjadi perubahan rentang nilai medan magnet yaitu dari -345.51 nT  s.d 282.30 nT menjadi -975.37 nT s.d 782.38 nT. Selain itu, terjadi pergeseran lokasi klosur anomali magnetik positif dan negatif. Anomali magnetik positif mendominasi di bagian tengah sampai utara Wilayah Tapal Kuda dan diduga berkaitan dengan Zona Vulkanik Kuarter. Klosur-klosur anomali positif mengalami pergeseran letak ke barat di sekitar Gunung Bromo dan Gunung Argopuro. Anomali magnetik negatif mendominasi tepi selatan  Wilayah Tapal Kuda dan diduga berkaitan dengan Zona Pegunungan Selatan. Klosur anomali negatif juga mengalami pergeseran letak yaitu ke barat daya mendekati gunung Semeru

Improvement of Fluid Simulation Runtime of Smoothed Particle Hydrodynamics by Using Graphics Processing Unit (GPU)

This study concerns an implementation of smoothed particle hydrodynamics (SPH) fluid simulation on a graphics processing unit (GPU) using the Compute Unified Device Architecture's (CUDA) parallel programming. A bookkeeping method for the neighbor search algorithm was incorporated to accelerate calculations. Based on sequence code profiling of the SPH method, particle interaction computation "“ which comprises the calculation of the continuity equation and the momentum conservation equation "“ consumes 95.2% of the calculation time. In this paper, an improvement of the calculation is proposed by calculating the particle interaction part on the GPU and by using a bookkeeping algorithm to restrict the calculation only to contributed particles. Three aspects are addressed in this paper: firstly, speed-up of the CUDA parallel programming computation as a function of the number of particles used in the simulation; secondly, the influence of double precision and single precision schemes on the computational acceleration; and thirdly, calculation accuracy with respect to the number of particles. Scott Russell's wave generator was implemented for a 2D case and a 3D dam-break. The results show that the proposed method was succesfull in accelerating the SPH simulation on the GPU

PEMODELAN ANOMALI SELF-POTENTIAL GEOMETRI TETAP DAN INVERSI GLOBAL OPTIMASI VERY FAST SIMULATED ANNEALING

Penelitian ini membahas interpretasi anomali self-potential (SP) berdasarkan asumsi model bergeometri sederhana yang tetap (fixed-geometry) berbentuk lempeng di bawah permukaan.  Inversi anomali SP berupa data sintetik untuk mendapatkan parameter-parameter model lempeng dilakukan dengan menggunakan metode global optimasi Very Fast Simulated Annealing (VFSA). Nilai parameter model hasil inversi memiliki nilai yang hampir sama dengan nilai parameter model yang membangkitkan data sintetik. Hal ini mengindikasikan validasi dan efektivitas skema inversi yang dibuat untuk diterapkan pada anomali SP hasil pengukuran sesungguhnya di lapangan

Gravity Inversion of Talwani Model using Very Fast Simulated Annealing

Global approaches for estimating geophysical model parameters have been proposed by several authors, including their application for gravity interpretation, which is currently limited to simple and fixed geometrical problems. This paper proposes implementation of Very Fast Simulated Annealing (VFSA) in two-dimensional gravity interpretation problems, which are still rarely addressed. The modeling domain was divided into smaller sub-domains and gravity anomaly calculation was carried out based on the Talwani formulation.  To improve the uniqueness of the solution of under-determined problems, specific constraints were added in addition to the assumed known symmetry axes. The inversion of VFSA was tested on synthetic data generated by simple models and on previously published real data to evaluate the applicability of the proposed approach to the interpretation of field data

KOREKSI STATIK DATA CSAMT (CONTROLLED SOURCE AUDIO-FREQUENCY MAGNETOTELLURIC) MENGGUNAKAN TEKNIK SPATIAL FILTERING

CSAMT adalah metoda elektromagnetik dengan domain frekuensi dengan menggunakan dipol yang ditanahkan sebagai sumber sinyal buatan. Pengukuran CSAMT dengan jarak sumber medan primer terhadap penerima yang berhingga menyebabkan gelombang yang ditangkap penerima bersifat kompleks. Pergeseran nilai medan listrik karena ada efek statik menyebabkan kurva resistivitas terangkat naik atau turun. sehingga mempengaruhi data hasil pengukuran. Tujuan penelitian ini untuk memperoleh data CSAMT yang sudah terkoreksi efek statik. Metode penelitian yang digunakan untuk menghilangkan efek statik digunakan teknik spatial filtering. Pada penelitian ini diperoleh data CSAMT yang sudah terkoreksi efek statik sehingga dapat diinterpretasikan dengan baik. Kata kunci : CSAMT; Efek Statik; Spatial Filtering

Prediction of Carbon Monoxide Concentration with Variation of Support Vector Regression Kernel Parameter Value

Human and industrial activities produce air pollutants that can cause a decline in air quality. In urban areas, transportation activities are the main source of air pollution. One of the emitted air pollutants produced by transportation is carbon monoxide (CO). The understanding of CO concentration is crucial since its overabundance beyond a certain limit will have a negative impact on human health and the environment. In this study, the support vector regression (SVR) method was used to predict CO concentration. The purpose of this study was to predict the hourly CO concentration in the Ujung Berung district, Bandung City, West Java, Indonesia with optimal prediction accuracy. An experiment was carried out by modeling the CO concentration with varying kernel parameter values to obtain accurate prediction results. The suitability of the values between error (ɛ), a trade-off constant (C), and variation mismatch (γ) is vital to obtain optimal prediction results. The results showed that the best prediction accuracy value was 97.68% with kernel parameter values ɛ = 0.02, γ = 30, and C = 0.006. These results may lead to proper decision making on environmental issues and can improve air pollution control strategies

STUDI GELOMBANG ULF: KORELASI PULSA MAGNET Pc3 DENGAN KECEPATAN ANGIN SURYA DAN MEDAN MAGNET ANTARPLANET (STUDY OF ULF WAVE: CORRELATION OF Pc3 MAGNETIC PULSATIONS WITH SOLAR WIND VELOCITY AND INTERPLANETARY MAGNETIC FIELD)

Energy for the Earth’s magnetospheric processes is provided by solar wind. Pc3 magnetic pulsation is one of geomagnetic ULF wave. Pc3 magnetic pulsation has been studied to understand the dynamic of magnetosphere. Geomagnetic pulsations are quasi-sinusoide variations in the Earth’s magnetic field in the period range of 10-45 seconds. The magnitude of these pulsations ranges from fraction of a nT (nano Tesla) to several nT. These pulsations can be observed in a number of ways such as applied of ground based magnetometer. We used the magnetometer data of Manado, Parepare, and Kupang stations to studied the effect of the solar wind and interplanetary magnetic field on these pulsations. To extract Pc3 magnetic pulsations we applied second order of Butterworth filter and using Hamming windowing. The result showed that Pc3 magnetic pulsation have correlation with increasing solar wind velocity and interplanetary magnetic field-IMF, it is mean that solar wind controls Pc3 magnetic pulsations occurrence. ABSTRAKAngin surya merupakan sumber energi bagi proses-proses fisis yang terjadi di magnetosfer Bumi. Untuk dapat memahami dinamika di magnetosfer Bumi dapat di tinjau dari gelombang ULF salah satunya pulsa magnet Pc3. Pulsa magnet Pc3 merupakan variasi quasi-sinusoide pada medan magnet Bumi dalam rentang periode 10 – 45 detik. Pulsa magnet Pc3 umumnya memiliki amplitudo rendah dengan rentang nT (nano Tesla). Terdapat beberapa cara yang dapat dilakukan untuk mengamati pulsa magnet Pc3 diantaranya dengan menggunakan magnetometer landas Bumi. Dalam makalah ini kami menggunakan data pengamatan magnetometer stasiun Kupang, Manado, dan Parepare untuk mempelajari hubungan pulsa magnet Pc3 terkait dengan angin surya dan medan magnet antarplanet. Pulsa magnet Pc3 diekstrak dari data variasi medan magnet dengan menggunakan Butterworth Filter dan Hamming windowing. Hasil yang diperoleh menunjukkan bahwa pulsa magnet Pc3 memiliki korelasi dengan peningkatan kecepatan angin surya dan medan magnet antarplanet. Hal ini mengindikasikan bahwa angin surya merupakan salah satu sumber yang mengontrol perubahan yang terjadi pada pulsa magnet Pc3

Comparing Electrical and Magnetic Properties of Soil Layer from Sag Pond near Lembang Fault, West Java, Indonesia

Electrical and magnetic properties have been used in soil characterization for various types of soils except for soil originated from sag pond sediment. Formed near fault line, sag pond provides a unique environment for sedimentation. In this study, electrical conductivity and magnetic susceptibility of soil samples obtained by coring process were measured to find out how these two properties were related. A 364 cm core was obtained in a sag pond located next to Lembang Fault in West Java, Indonesia. The core covers two different layers that are differ not only on their coloration and texture but also showed variations in their electrical conductivity and magnetic susceptibility. In the first layer, termed silty loam (above 165 cm), electrical conductivity correlates positively with magnetic susceptibility whereas in the second layer, termed silty-clay (below 165 cm) the correlation is negative. These differences are probably due content of magnetic minerals that is high in silt but low in clay. The results of this study infer that correlation between electrical conductivity and magnetic susceptibility could then be used as a tool to delineate soil layers.