Judul: Seagrass Distribution Mapping Using Sentinel-2A Imagery in the Shallow Water of Lancang Island, Kepulauan Seribu
Abstrak: Wilayah pesisir Indonesia memiliki tiga tipe ekosistem penting yaitu mangrove, terumbu karang dan lamun. Lamun merupakan tumbuhan berbunga (Angiospermae) yang memiliki akar, rimpang, daun, bunga dan buah serta dapat berkembang biak secara penyerbukan bunga dan pertumbuhan tunas. Penelitian ini bertujuan mengetahui dan memetakan sebaran lamun di perairan dangkal Pulau Lancang, Kepulauan Seribu menggunakan citra satelit Sentinel-2A dengan pendekatan klasifikasi berbasis piksel dengan algoritma Maximum Likelihood (MLH) dan Support Vector Machine (SVM). Hasil klasifikasi menggunakan algoritma MLH dengan tiga kelas yaitu lamun padat, lamun sedang dan non lamun menghasilkan luasan masing-masing 27,46 ha, 25,41 ha dan 125,96 ha. Klasifikasi menggunakan algoritma SVM dengan tiga kelas yaitu lamun padat, lamun sedang dan non lamun menghasilkan luasan masing-masing 29,09 ha, 32,85 ha dan 116,89 ha. Akurasi keseluruhan dari klasifikasi dengan algoritma MLH dan SVM masing-masing sebesar 76,0% dan 78,6%., Indonesia has three important ecosystems in coastal areas: mangrove, coral reef and seagrass. Seagrass is a flowering plant (Angiospermae) with root, rhizome, leave, flower and fruit and it can be reproduced by pollinating flowers and growing shoots. This study aims to determine and map seagrass distribution in the shallow waters of Lancang Island, Kepulauan Seribu using Sentinel-2A satellite imagery by applying a pixel-based classification method with Maximum Likelihood (MLH) and Support Vector Machine (SVM) algorithms. The classification results using the MLH algorithm with three classes, dense seagrass, medium seagrass and non-seagrass, have an area of 27,46 ha, 25,41 ha and 125,96 ha. The SVM algorithm classification resulted in three classes, dense seagrass, medium seagrass and non-seagrass with an area of 29,09 ha, 32,85 ha and 116,89 ha. The overall accuracy of the classification using the MLH and SVM algorithms is 76,0% and 78,6%.
Keyword: Lancang Island, MLH, seagrass, sentinel-2A, SVM

Judul: Pemetaan Perubahan Luasan Padang Lamun Menggunakan Citra Satelit Sentinel-2A di Pulau Lancang
Abstrak: Lamun merupakan salah satu komponen utama penyusun ekosistem perairan laut dangkal. Tumbuhan lamun memiliki fungsi secara ekologis dan ekonomis diantaranya sebagai sumber utama produktivitas primer di laut dan bahan baku obat-obatan. Penyusutan areal padang lamun terjadi karena adanya aktivitas manusia di wilayah pesisir dan ancaman dari alam. Penelitian ini bertujuan memetakan dan mengetahui perubahan luasan lamun tahun 2017 dan 2022 menggunakan citra Sentinel-2A di Pulau Lancang, Kepulauan Seribu. Penelitian ini melalui beberapa tahapan seperti pengambilan data lapang, pra-pengolahan citra, koreksi kolom perairan, klasifikasi citra, dan deteksi perubahan luasan lamun. Klasifikasi lamun di Pulau Lancang terbagi menjadi tiga kelas yaitu lamun padat, lamun sedang, dan non lamun. Klasifikasi dengan metode maximum likelihood menghasilkan luas area lamun tahun 2017 sebesar 78.43 ha dan tahun 2022 sebesar 72.43 ha. Perubahan luasan lamun yang terjadi dari lamun menjadi non lamun adalah sebesar 26.78 ha. Sementara perubahan luasan dari non lamun menjadi lamun sebesar 20.78 ha., Seagrass is a crucial component of shallow marine ecosystems. These plants have ecological and economic functions, being the primary source of productivity in the sea and providing raw materials for medicine. Unfortunately, human activities in coastal areas and threats from nature cause the shrinkage of seagrass beds. The goal of this study is to map and analyze changes in the seagrass area on Lancang Island, Kepulauan Seribu, using Sentinel-2A imagery from 2017 and 2022. The research involved several stages, including field data collection, image pre processing, water column correction, image classification, and detection of changes in the seagrass area. The classification of seagrass on Lancang Island were divided into three classes, namely dense seagrass, medium seagrass, and non-seagrass. The maximum likelihood method was used for classification, resulting in an area of 78.43 ha for seagrass in 2017 and 72.43 ha in 2022. The detection of seagrass to non-seagrass area change resulted in a net loss of 26.78 ha. On the other hand, the change from non-seagrass to seagrass area was 20.78 ha.
Keyword: Lancang Island, sentinel-2, seagrass

Judul: Sintesis Paduan Ti-6Al-4Nb sebagai Matrial Implan Pengganti Komponen Tibial
Abstrak: Synthesis of Ti-6Al-4Nb alloy was done by melting using Tri Arc Melting Furnace. Each sample was remelted five times to ensure the homogenity. Aluminum and niobium addition were expected to stabilize α phase and β phase until the αβ-titanium alloy was resulted. Yet based on the experiment, it was α-titanium alloy resulted. α-titanium alloy was a Hexagonal Close Packed (HCP) crystalline structure which would be cracked if deformation non-uniaxial happens. The presence of oxygen in pure titanium significantly increased the hardness of titanium. The addition of aluminum was also able to increase the hardness of titanium alloy because aluminum more stabilize the α phase in the α-titanium alloy. The corrosion ressistance of titanium could be increased by adding aluminum and niobium. Titanium coating with HA/chitosan composite was also proved in decreasing the corrosion rate because it barried direct interaction between titanium alloy and corrotion solution.
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