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: Karakteristik Oseanografi dan Estimasi Indeks Kesehatan Laut di Kawasan Teluk Palabuhanratu dan Sekitarnya
Abstrak: Teluk Palabuhanratu dikenal sebagai salah satu daerah utama penangkapan ikan di perairan Selatan Jawa yang memiliki potensial perikanan pelagis dan sumber daya laut lainnya. Wilayah ini berpotensi terancam oleh kualitas air yang dapat mempengaruhi kesehatan lingkungan laut. Tujuan dari penelitian ini adalah mendeskripsikan karakteristik oseanografi secara spasio-temporal, variasi volume transpor, serta tren dan estimasi indeks kesehatan laut berdasarkan parameter oseanografi di Teluk Palabuhanratu. Dataset rataan harian dari keluaran model INDESO dan MARINE COPERNICUS (2008-2019) digunakan untuk penelitian ini. Data deret-waktu tersebut divalidasi dan dianalisis dengan metode Empirical Orthogonal Function (EOF), metode Power Spectral Density (PSD), serta estimasi tren dan indeks kesehatan laut. Hasil penelitian menunjukkan pola arus pada musim barat (musim timur) bergerak mendekati (menjauhi) teluk dengan pola sebaran suhu yang semakin rendah (tinggi) ke arah laut lepas sedangkan salinitas sebaliknya. Variasi suhu pada musim barat lebih tinggi (rendah) dibandingkan pada musim timur dan saat terjadi IOD negatif suhu lebih rendah. Struktur vertikal arus zonal pada musim barat (musim timur) arus permukaan dominan bergerak ke arah timur (ke arah barat), tetapi pada kedalaman 20-100 m pada musim barat (musim timur) terdapat arus yang bergerak ke arah barat (ke arah timur). Tren parameter selama 12 tahun menunjukan pola penurunan pada parameter suhu dan oksigen, sedangkan pada parameter lainnya mengalami kenaikan. Estimasi indeks kesehatan laut memiliki nilai 0.66 yang tergolong dalam kondisi cukup baik., The Palabuhanratu Bay is well known as one of the main fishing regions in the southern Java waters that has potential pelagic fisheries and other marine resources. This region may be potentially threatened by suitable water quality that may affects the health of the marine environment. The aim of this research is to describe the spatio-temporal oceanographic characteristics, transport volume variability, as well as trends and estimation of marine health indices based on oceanographic parameters in Palabuhanratu Bay. Daily averaged datasets from INDESO and MARINE COPERNICUS model outputs (2008-2019) were used for this study. The time-series data were validated and analyzed by Empirical Orthogonal Function (EOF) method, Power Spectral Density (PSD) method, and trend estimation and ocean health index. The results showed that the current pattern in the west season (east season) moves closer to (away from) the bay with a lower (higher) sea water temperature distribution pattern towards the open sea while salinity is the opposite. Variability of seawater temperature in the western season are higher (lower) than in the eastern season and during negative IOD temperatures are lower. The vertical structure of zonal currents in the west season (east season) dominant surface currents move eastward (westward), but at a depth of 20-100 m in the west season (east season) there are currents that move westward (eastward). The trend of parameters for 12 years shows a decreasing pattern in temperature and oxygen parameters, while other parameters have increased. The estimated ocean health index has a value of 0.66, which is classified as in fairly good condition
Keyword: Analisis data deret-waktu, dataset INDESO, indeks kesehatan laut, karakteristik oseanografi, Teluk Palabuhanratu

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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