Judul: DEVELOPMENT AND FIELD TEST OF IOT-BASED DRIFTING BUOY INSTRUMENTS FOR COASTAL WATERS
Abstrak: Data spasial arus pesisir umumnya diperoleh dari satelit altimetri. Namun data yang diperoleh masih memiliki kekurangan yaitu rendahnya tingkat resolusi dan perlunya validasi lapangan (ground truth). Electronic drift buoy (GPS- GPRS) adalah instrumen akuisisi data oseanografi yang menggunakan sistem Internet of Things (IoT) dan bergerak mengikuti pergerakan air di sekitar instrumen. Penerapan sistem IoT pada pelampung elektronik akan memudahkan akuisisi data dari pelampung hanyut karena data akan langsung masuk ke database, dikirimkan melalui sistem GPRS sehingga dapat dipantau secara real-time melalui website. Tujuan penelitian ini yaitu: (1) Menghasilkan prototipe instrumen pelampung hanyut pesisir dengan menggunakan sistem IoT; (2) Menganalisis data suhu dan konsentrasi fitoplankton di lokasi uji coba pelampung hanyut (perairan pulau Panggang Kepulauan Seribu). Perancangan instrument berbasis mikrokontroler ESP32 ini dilengkapi dengan modul GPS untuk akuisisi data lokasi dan modul GPRS untuk transmisi data ke database. Hasil rancang bangun instrument terdiri dari tiga bagian yaitu bagian pelampung apung memiliki dimensi tinggi 52 cm dan lebar 30 cm, bagian perangkap arus memiliki dimensi tinggi 25 cm dan lebar 25 cm untuk setiap sayap yang terbuat dari besi, serta bagian wahana sensor memiliki dimensi 20 cm dengan lebar 8.3 cm terbuat dari PVC dan diikatkan pada perangkap arus menggunakan tali. Uji lapang dilakukan di Perairan Kepulauan Seribu dengan melepas 3 buah pelampung buoy secara bersamaan. Data hasil pengambilan data oleh instrument kemudian dikirim ke database untuk bisa ditampilkan dalam bentuk ploting data pada website. Website yang dibangun digunakan untuk melihat hasil pengambian data instrument pelampung hanyut secara real-time. Website yang dibangun terdiri dari tiga halaman yaitu halaman beranda, halaman plot data drifter dan halaman setting waktu. Setiap halaman website terdiri dari tiga bagian utama yaitu header, content dan footer. Berdasarkan hasil uji lapang, didapatkan kecepatan arus berkisar 0,038 m/s hingga 0,35 m/s dan kecepatan arus rata-rata 0,19 m/s, sedangkan suhu permukaan berkisar 26,37 hingga 27,83 °C dengan nilai rata-rata 26,75 °C. Adapun konsentrasi fitoplankton di lokasi uji lapang berkisar antara 673.299 ind/l sampai 1,024.456 ind/l dengan nilai rata-rata sebesar 836.312 ind/l. Berdasarkan hasil uji coba ini dapat disimpulkan bahwa alat pelampung drifter telah berfungsi sesuai dengan tujuan pengembangannya.
Keyword: arus, GPS-GPRS, IoT, pelampung hanyut, suhu permukaan laut, konsentrasi fitoplankton

Judul: Design and Performance Test of Drifter Buoy
Abstrak: The modern drifter buoy is a high-tech version of the "message in a bottle". It consists of a surface buoy and a subsurface drogue, attached by a long, thin tether. The buoy measures temperature and other sea/air properties, and has a transmitter to send the data to passing satellites. Drifters buoy for oceanographic research in the field had long been developed, but the design and construction of this instrument is still on going process. The major goal of the drifter intended by the designers of the drifter are cheap, lightweight and stable on several conditions. This study attempted to produce a drifter system capable of measuring position, speed and direction of surface current using a microcontroller, GPS and GSM technology as the data transmitter and receiver. There are 3 main parts of the drifter. They are the electronic systems, software and vehicles. Electronic systems are built from the microcontroller ATmega32, storage SD / MMC cards, transmission using GSM modem, GPS as a sensor position and velocity, and DALLAS DS18B20 as temperature sensors. The software is divided into 2 parts: software that is embedded into vehicle and software to control and receiving data in ground segment. Vehicle is divided into 2 main parts, first is float to house electronics system and drogue to maintain a position of drifter from the influence of surface wind. GPS used has a precision of 10 m, therefore the determination of position requires a certain time interval, this interval is very dependent on the speed of surface currents in the area. The results of performance test systems in the field showed that the design is able to record 95% -99% of the data successfully at 64 bps transfer speed. Field trial results also showed 85% and 93% successful data transmission using the GSM network with the power used in these systems totaling approximately 541-544 mW. The value of drag area ratio is 53.38, greater than 40 indicates that the drifter is produced has a pretty good ability to follow the movement of the water. In Pelabuhan Ratu, a different current direction at the center and edge of the bay. In the middle of the bay, when the water toward to lowest ebb the current direction towards to west and then silently at the lowest ebb. Finally, when water level increase the curent direction toward to the north. On the eastern edge of the bay, when the water toward to the lowest ebb, the direction of ocean surface current sheading out the bay.
Keyword: 

Judul: Penentuan Nilai Eigen dan Vektor Eigen dari Matriks Tridiagonal 2-Toeplitz dengan Pendekatan Polinomial Chebyshev
Abstrak: The eigenvalues and eigenvectors of a matrix can be determined by finding its characteristic polynomials. The characteristic polynomials of a tridiagonal 2-Toeplitz matrix is shown to be closely connected to polynomials which satisfy the Chebyshev recurrence relationship. If the order of the matrix is odd, then the eigenvalues are found explicitly in terms of the Chebyshev zeros and the eigenvectors are found in terms of the polynomials satisfying the recurrence relationship. For even ordered matrices, the situation is more complicated. The problem in these cases is that although the Chebyshev recurrence formula is still applied, its initial values are not generating Chebyshev polynomials
Keyword: