Judul: Modeling of Ocean Currents and Distribution of Total Suspended Solids in Citarum River Estuary
Abstrak: Sungai Citarum merupakan salah satu sungai penting di Jawa Barat yang bermuara ke Laut Jawa dengan membawa sedimen tersuspensi yang besar. Tujuan penelitian ini adalah mengkaji interaksi pola arus dan sebaran Total Suspended Solid (TSS) pada Musim Barat dan Musim Timur dengan pemodelan hidrodinamika. Model arus dan TSS yang digunakan merupakan model 2-dimensi dengan perangkat lunak OpenFlows FLOOD. Validasi hasil model pasang surut menggunakan metode Root Mean Square Error (RMSE) dengan nilai 0.10. Kecepatan arus pada Musim Barat dan Musim Timur berkisar antara 0.07 – 0.35 m/s. Arus bergerak ke arah utara dan timur laut pada saat kondisi pasang dan bergerak ke arah selatan dan barat daya pada saat kondisi surut pada kedua musim. Konsentrasi TSS tertinggi pada Musim Barat saat kondisi surut yaitu berkisar antara 560 – 575 mg/L. Konsentrasi TSS terendah pada Musim Timur saat kondisi pasang berkisar antara 80 – 120 mg/L. Tingginya konsentrasi TSS ini pada Musim Barat dipengaruhi oleh curah hujan yang lebih tinggi dengan rata-rata pada bulan Januari sebesar 23.2 mm/hari sementara pada Musim Timur hanya sebesar 7.8 mm/hari. Kata kunci: arus, curah hujan, pasang surut, Sungai Citarum, TSS., Citarum River is one of the important rivers in West Java which empties into the Java Sea carrying large suspended sediments. The purpose of this study was to examine the interaction of current patterns and distribution of Total Suspended Solid (TSS) in the West and East Monsoons with hydrodynamic modeling. The flow model and TSS used are 2-dimensional models with OpenFlows FLOOD software. Validation of the tidal model results using the Root Mean Square Error (RMSE) method with a value of 0.10. Current velocity in the West and East monsoons ranges from 0.07 – 0.35 m/s. Currents move north and northeast during high tide conditions and move south and southwest during low tide conditions in both seasons. The highest concentration of TSS is in the West Season at low tide, which is in the range of 560 – 575 mg/L. The lowest TSS concentration is in the East Season during high tide conditions ranging from 80 – 120 mg/L. The high concentration of TSS in the West Season is influenced by higher rainfall. The high concentration of TSS in the West Season is influenced by higher rainfall with an average in January of 23.2 mm/day while in the East Season it is only 7.8 mm/day. Keywords: Citarum River, current, rainfall, tide, TSS.
Keyword: Citarum River, current, rainfall, tide, TSS

Judul: Sebaran Konsentrasi Sedimen Tersuspensi di Teluk Jakarta
Abstrak: Jakarta Bay is the estuary for 13 rivers and the flow of water from all these rivers carries sediment from land to water. This will have an impact on the level of turbidity of the waters in Jakarta Bay.The purpose of this study was to determine the flow pattern and distribution of suspended solids in the West and East monsoons in Jakarta Bay in 2019 using numerical modeling and spatial imagery methods. The two-dimensional model development was carried out using MOHID 2016 for 14 days in 2 scenarios, West Season and East Season. The simulation model had an initial value of 45 mg/L. The image used is a Landsat 8 image with a collection time of 29 December 2018 and 25 July 2019. The validation model used the Root Mean Square Error (RMSE) method with a value of 0.0603 for the tides and 0.05 and 0.11 for the zonal- meridional current component. The surface current velocity in Jakarta Bay in the West Season was in the range of 1.03 – 10.75 cm/s while in the East Season it was in the range of 1.35 – 11.53 cm/s. The concentration of suspended sediment in the West Season was around 67 – 249.5 mg/L and in the East Season it had a concentration of 59 – 249.5 mg/L. The distribution of suspended sediment in both the West and East monsoons followed the pattern of surface currents. The model results showed that the highest suspended sediment concentration occured during the West Season. The image results had a higher suspended sediment concentration than the model results., Teluk Jakarta menjadi muara bagi 13 sungai dan aliran air dari seluruh sungai tersebut membawa sedimen dari darat menuju perairan. Hal ini akan berdampak pada tingkat kekeruhan perairan di Teluk Jakarta. Tujuan penelitian ini adalah mengetahui pola arus dan sebaran padatan tersuspensi pada Musim Barat dan Musim Timur di Teluk Jakarta pada tahun 2019 dengan metode pemodelan numerik dan spasial citra. Pembangunan model dua dimensi dilakukan menggunakan MOHID 2016 selama 14 hari dalam 2 skenario yaitu, Musim Barat dan Musim Timur. Simulasi model memiliki nilai awal (initial condition) sebesar 45 mg/L. Citra yang digunakan adalah Citra Landsat 8 dengan waktu pengambilan 29 Desember 2018 dan 25 Juli 2019. Validasi model menggunakan metode Root Mean Square Error (RMSE) dengan nilai 0.0603 untuk pasang surut serta 0.05 dan 0.11 untuk komponen arus zonal-meridional. Kecepatan arus permukaan di Teluk Jakarta pada Musim Barat berada pada rentang 1.03 – 10.75 cm/s sementara pada Musim Timur berada pada rentang 1.35 – 11.53 cm/s. Konsentrasi sedimen tersuspensi pada Musim Barat sekitar 67 – 249.5 mg/L dan pada Musim Timur memiliki konsentrasi sebesar 59 – 249.5 mg/L. Sebaran sedimen tersuspensi baik saat Musim Barat dan Musim Timur mengikuti pola arus permukaan. Hasil model menunjukan bahwa konsentrasi sedimen tersuspensi tertinggi terjadi saat Musim Barat. Hasil citra memiliki konsentrasi sedimen tersuspensi lebih besar dibandingkan dengan hasil model.
Keyword: current, distribution of sediment, Jakarta Bay, Landsat 8 imagery, modelling, suspended sediment

Judul: The Exploration of Discrete Logarithm over Finite Field GF(3m)
Abstrak: The security of many public~key algorithms is based on the problem of finding discrete logarithms. The generalized discrete logarithm problem is the following: given a finite cyclic group G of order n, a generator a of G, and an element fl E G, find the integer x, 0 ~ x ~ n - 1, such that 0: = fl. Algorithm for discrete logarithm problem focused on Menezes et al. (1997) that consist of exhaustive search algorithm, the baby-step giant-step algorithm, Pollard's rho algorithm, Pohlig-Hellman algorithm, and index-calculus algorithm. These algorithms are explorated to be used in discrete logarithm problem over finite field GF(3m ). The exploration also produces some algorithms, i.e. naif negative algorithm, baby-step mother-step algorithm, baby-step mother free-step algorithm, and baby-step free-step algorithm. All algorithms implemented using Maple 11. The Pohlig-Hellman and baby-step giant-step algorithms are efficient enough to be used in discrete logarithm problem over finite field GF(3m ) for m < 20.
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