Judul: Variation of seasonal, Trend and Ocean Health Index based on Oceanographic Parameter in the Natuna Sea
Abstrak: Laut Natuna merupakan salah satu laut Indonesia yang berbatasan langsung dengan Laut Cina Selatan dan Laut Jawa. Laut ini memiliki kelimpahan sumberdaya perikanan, migas, dan tambang. Sehingga dapat menimbulkan fenomena serta masalah terhadap kondisi kesehatan perairan. Tujuan dari penelitian ini adalah mengetahui variasi musiman, variabilitas, tren, serta indeks kesehatan Laut Natuna. Data model INDESO dengan resolusi 1/12° dan Marine Copernicus digunakan untuk studi dengan analisis data mencakup validasi, volume transport, karakteristik musiman oseanografi, variabilitas, tren, dan perhitungan Indeks Kesehatan Laut (IKL). Hasil penelitian menggambarkan validasi data model dengan satelit memiliki korelasi yang tinggi yaitu 0,94 (suhu permukaan laut/SPL), 0,70 (arus zonal), dan 0,95 (arus meridional). Siklus musiman SPL di Laut Natuna berkisar 27,21 sampai 32,00 °C, salinitas berkisar 32,00 sampai 34,00 PSU, oksigen terlarut (DO) berkisar 5,465 sampai 7,112 mg/L, dan nitrat berkisar 0,0005 sampai 0,0780 mg/L. Analisis Transformasi Wavelet Kontinu menunjukkan variabilitas parameter yaitu Semi Annual Variability (SAV), Intra Seasonal Variability (ISV), Annual Variability (AV), dan Inter Annual Variability (IAV). Tren per tahun menunjukkan nilai -0,05 °C (SPL), 0,07 PSU (salinitas), -0,002 mg/L (DO), dan -0,0002 mg/L (nitrat). Nilai IKLNatuna berkisar 71,54 dan tergolong dalam kategori cukup baik., The Natuna Sea is one of Indonesian seas that are contiguous with the South China Sea and the Java Sea. This sea has abundant resources of fish, oil and gas, and mines. Thus, the marine health in this sea is prone to problems. The aim of this study was to find out the seasonal variation, variability, trend, and Ocean Health Index of the Natuna Sea. INDESO data model with the resolution of 1/12° and Marine Corpernicus were used in this study with the scope of analysis covering validation, volume transport, seasonal oceanographic characteristic, variability, trend, and Ocean Health Index calculation. The results portray that the data model validation with the satellite shows a high degree of correlation which are 0,94 (sea surface temperature), 0,70 (zonal current), and 0,95 (meridional current). Seasonal SPL cycle in the Natuna Sea ranges from 27,21 °C to 32,00 °C, salinity ranges from 32,00 to 34,00 PSU, dissolved oxygen (DO) ranges between 5,465 and 7,112 mg/L, nitrate ranges from 0,0005 to 0,0780mg/L. Continuous Wavelet Transform analysis showed parameter variabilities which are Semi Annual Variability (SAV), Intra Seasonal Variability (ISV), Annual Variability (AV), and Inter Annual Variability (IAV). Annual parameter trend shows the value of -0,05°C (SPL), 0,07 PSU (salinity), -0,002 mg/L (DO), and -0,0002 mg/L (nitrate). The Natuna Sea’s IKL values around 71,54 and is considered good enough.
Keyword: IKL, INDESO, Natuna Sea, Trend, Variability

Judul: Oceanographic Characteristic, Trend Estimation and Ocean Health Index in Madura Strait
Abstrak: Selat Madura merupakan wilayah perairan yang banyak dimanfaatkan sebagai alur pelayaran, daerah penangkapan ikan, dan eksploitasi migas bumi. Kegiatan pemanfaatan tersebut berpengaruh pada kesehatan lingkungan laut. Tujuan dari penelitian ini adalah mendeskripsikan pola spasial dan variasi temporal dari beberapa parameter oseanografi, struktur vertikal arus, tren dan kondisi kesehatan laut berdasarkan parameter oseanografi yang diestimasi dari nilai IKL di Perairan Selat Madura. Data INDESO dan Marine Copernicus digunakan untuk penelitian dengan analisis data mencakup validasi, volume trasnport, EOF, CWT, tren, dan perhitungan IKL. Hasil penelitian menunjukkan siklus tahunan SPL laut berkisar 27,89 – 30,77 oC, salinitas berkisar 17,51 – 33,6 PSU, TPLberkisar 0,505 – 0,676 m, fosfat berkisar 0,00001 – 0,00978 mg/l, nitrat berkisar 0,00023 – 0,04225 mg/l , klorofil berkisar 0,107 – 1,196 mg/m3, dan DO berkisar 6,318 – 6,77 mg/l. Struktur vertikal arus zonal pada musim barat (musim timur), arus permukaan cenderung bergerak ke arah timur (ke arah barat), tetapi pada musim timur di kedalaman 6-36 m arus bergerak ke arah timur. Struktur vertikal arus meridional pada musim barat dan timur, arus cenderung bergerak ke utara. Tren 12 tahun menunjukkan pola kenaikan hanya pada parameter salinitas dan nitrat sedangkan pada parameter lain mengalami penurunan. Estimasi nilai IKL berkisar 0,63 sehingga Selat Madura tergolong dalam kondisi yang sedang., Madura Strait is a water area that is widely used as a shipping channel, fishing area, and oil and gas exploitation. These utilization activities affect the health of the marine environment. The study aimed to describe the spatial patterns and temporal variations of several oceanographic parameters, the vertical structure of currents, trends, and ocean health conditions based on oceanographic parameters estimated from the OHI value in the Madura Strait Waters. INDESO and Marine Copernicus data were used for the study with data analysis including validation, transport volume, EOF, CWT, trend, and calculation of OHI. The results showed the annual cycle of ocean SST ranged from 27,89 – 30,77 oC, salinity ranged from 17,51 – 33,6 PSU, SSH ranged from 0,505 – 0,676 m, phosphate ranged from 0,00001 – 0,00978 mg/l, nitrate ranged from 0,00023 – 0,04225 mg/l, chlorophyll-a ranged from 0,107 – 1,196 mg/m3, and DO ranged from 6,318 – 6,77 mg/l. In the vertical structure of zonal currents during the west monsoon (east monsoon), surface currents tended to move eastward (westward), but during the east monsoon at depths of 6-36 m, the currents move eastward. The vertical structure of meridional currents during the west and east monsoon showed that currents tended to move northward. The 12-year trend showed an increasing pattern only in the salinity and nitrate parameters while other parameters decreased. The estimated OHI value was around 0,63, so the Madura Strait was classified as being in a fair condition.
Keyword: Indeks Kesehatan Laut, INDESO, Oseanografi, Selat Madura, Tren

Judul: Grup dan Homomorfisma Grup pada Rubik Revenge
Abstrak: Rubik cube is a kind of puzzle game. A player must arrange rubik sides, which have been disordered, back to the position where every side has the same colour. This paper does not focus on the settlement solution, but instead on proving the existence of a group homomorphism between rubik movement group and S96 symmetric permutation group in rubik revenge. Firstly, it has been proved that rubik movement set is a group. Then, it also has been proved that the M set, which contains numeric labels of 1 until 96 in cubinos sides, is S96 symmetric permutation group.
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