Judul: Trophic States of Situ Patenggang, Bandung Regency, West Java
Abstrak: Situ Patenggang is managed as a recreation area in the form of Natural Tourism Park. Human activities around it can provide organic and inorganic materials which cause changes in lake’s trophic states. Utilization potential of water bodies can be measured by trophic state level that consider the presence of nutrients and phytoplankton. This study aims to determine the trophic states of Situ Patenggang, Bandung Regency, West Java. Sampling of water and phytoplankton were conducted at Situ Patenggang with four observation stations for three times of collections. Trophic index (TRIX) approach is used to analyzed the trophic state of Situ Patenggang. Concentration of total phosphate ranged from 0.20 – 0.64 mg/L. Dissolved inorganic nitrogen concentration ranged from 0.20 – 0.64 mg/L. Chlorophyll-a concentration ranged from 10.08 – 33.83 µg/L. Trophic states of Situ Patenggang is classified as eutrophic waters with values ranging from 4.25-6.54 according to the TRIX approach. These information can be used to anticipate trophic level increase for sustainable utilization of Situ Patenggang’s ecosystem., Situ Patenggang dikelola sebagai tempat rekreasi berupa Taman Wisata Alam Situ Patenggang. Aktivitas masyarakat di sekitar perairan dapat memberikan masukan bahan organik dan anorganik yang berpotensi meningkatkan kesuburan perairan. Tingkat kesuburan perairan erat kaitanya dengan potensi pemanfaatan perairan yang ditinjau dari keberadaan unsur hara dan kelimpahan fitoplankton. Penelitian ini bertujuan menentukan status kesuburan perairan Situ Patenggang, Kabupaten Bandung, Jawa Barat. Pengambilan contoh air dan fitoplankton dilakukan pada empat stasiun pengamatan selama tiga kali waktu pengambilan. Status kesuburan perairan dianalisis menggunakan pendekatan trophic index (TRIX). Konsentrasi fosfat total berkisar antara 0,04 – 0,19 mg/L. Konsentrasi nitrogen anorganik terlarut berkisar antara 0,20 – 0,64 mg/L. Konsentrasi klorofil-a berkisar antara 10,08 – 33,83 µg/L. Status kesuburan perairan Situ Patenggang berdasarkan pendekatan TRIX secara umum tergolong ke dalam perairan eutrofik dengan nilai berkisar antara 4,25 – 6,54. Hasil penelitian ini dapat digunakan sebagai informasi pendukung bagi pengelola dalam mengantisipasi terjadinya peningkatan status kesuburan perairan guna pemanfaatan perairan Situ Patenggang yang lebih optimal dan berkelanjutan.
Keyword: eutrophic, phytoplankton, nutrients, trophic states, TRIX

Judul: Phosphorus Dynamic Model of Situ Patenggang, Bandung Regency, Jawa Barat
Abstrak: Fosfor merupakan elemen yang biasa digunakan untuk menggambarkan kesuburan perairan. Namun, upaya mengkaji dinamika fosfor perairan tawar Indonesia menggunakan model relatif masih belum banyak dilakukan. Penelitian ini bertujuan membangun model dinamika fosfor di badan air Situ Patenggang. Contoh air dan sedimen diambil pada bulan Juni, Juli, dan Agustus 2022 di empat stasiun pengambilan. Berdasarkan potensi pengadukan, Situ Patenggang merupakan danau polymictic yang sering mengalami pengadukan massa air hingga ke dasar perairan. Rasio parameter besi dengan fosfat total, serta besi dengan sulfat menunjukkan bahwa desorpsi dan absorpsi fosfor kurang dipengaruhi oleh elemen besi dalam air. Hasil regresi linear menunjukkan bahwa oksigen terlarut dan alkalinitas di hipolimnion merupakan parameter kunci primer, serta oksigen terlarut epilimnion, curah hujan, dan kecepatan angin merupakan parameter kunci sekunder. Parameter kunci primer dan sekunder tersebut menjadi acuan dalam pembangunan model. Model dijalankan untuk mengekstrapolasi dinamika oksigen terlarut, alkalinitas, dan fosfat total untuk satu tahun berikutnya berdasarkan curah hujan dan kecepatan angin rata-rata yang telah dijadikan normal iklim. Hasil pemodelan menunjukkan bahwa dinamika fosfor secara tidak langsung ditentukan oleh fluktuasi curah hujan dan kecepatan angin., Phosphorus has been widely used to describe a water body’s trophic level. However, there are still few efforts to study the phosphorus dynamic of freshwater ecosystems in Indonesia by modeling. This study aims to build Situ Patenggang’s phosphorus dynamic model. Water and sediment samples were taken in June, July, and August 2022 with four sampling sites. Based on mixing potential, Situ Patenggang is a polymictic lake that frequently experiences entire water mixing from bottom to surface. Iron-total phosphate ratio and iron-sulfate ratio show that the phosphorus dynamic is not dependent on iron availability. Linear regression shows that primary key parameters consist of dissolved oxygen and alkalinity in the hypolimnion, on the other hand, secondary key parameters consist of dissolved oxygen in the epilimnion, rainfall, and wind speed. Model creation is based on primary and secondary key parameters. The model was run to approximate dissolved oxygen, alkalinity, and phosphorus data for the coming year based on rainfall and average wind speed that has been converted into climate normal. The simulation results show that the phosphorus dynamic is indirectly related to rainfall and wind speed fluctuations.
Keyword: meteorology, modeling, phosphorus dynamic, Situ Patenggang

Judul: Algoritme LLL dan Aplikasinya dalam Pembongkaran Sistemkripto Knapsack Merkle-Hellman
Abstrak: LLL algorithm is an algorithm that can be used to determine an approximation of the shortest vector in a lattice. Size reduction algorithm is an important step of LLL algorithm. The LLL algorithm can be applied in many elds. This paper shows how LLL algorithm can be used in breaking one of the famous cryptosystem, namely the Merkle-Hellman knapsack cryptosystem. Merkle-Hellman knapsack cryptosystem is an asymmetric cryptosystem using the subset sum problem as the support of security. Subset sum problem can be transformed into the problem of determining shortest vector in a lattice, so that LLL algorithm can also be used to solve the subset sum problem. Since the subset sum problem can be easily solved by applying LLL algorithm, then the Merkle-Hellman knapsack cryptosystem can also be easily be destructed.
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