Judul: Characteristics of carbon fluxes and catchment health from Java Major Rivers in Java.
Abstrak: Carbon derived from land, whether from natural or the result of human production and consumption will partially be dissolved by surface flow into the river and flows into the sea. Forms of carbon in the rivers are organic and inorganic in the form of dissolved and particulate matter. Watershed condition has great influenced on the river carbon fluxes. Carbon is very important as energy source for life in coastal waters and for the process of photosynthesis. There has not been extensive research yet on the relationship between the condition of watershed and carbon. Changes in river flow patterns have significant influence on the carbon cycle, particularly the flux of carbon from rivers. With regards to the above issue, this study aims to: a) assess characteristics of carbon flux from rivers in Java; b) identify trends and patterns in hydrological character; and c) identify level of catchment health as indicator of environmental degradation. This research is both exploratory and investigative to obtain facts of phenomena that exist, locate and disclose information in a factual, and compare with other research objects. The research on carbon flux is a kind of basic research conducted to address environmental problems, particularly in explaining state of knowledge of the carbon cycle that is always developing. Concentration of carbon and the dissolved organic carbon yield of rivers in Java is higher compared with the rivers in the world. The average concentration of dissolved organic carbon in Java about 11.15 mg/l, while the rivers in the world of 5.62 mg/l. This is influenced by a large population and watershed conditions that have degraded. Catchment health index shows most of the watersheds in Java are in critical condition. River which flows into the north of Java is in more critical condition than that into the south of Java. This phenomenon is also reflected in the distribution of carbon flux, where the flux of carbon going to the north of Java greater than that to the south. Some of the factors that cause smaller carbon export to the south of Java are among others: lower carbon concentration, river flow, watershed area, population density, and number of industries. The rivers in Java contributes dissolved organic carbon to the sea about 6.58% of the rivers in Indonesia, or about 0.66% of the rivers in the world. Export of carbon to the north of Java Island is greater than that to the south of Java Island. Based on calculations by the method of partial pressure of CO2 (pCO2), the rivers in Java has less than 4259 μatm. pCO2 of rivers in Java is greater than the rivers in the world, as an example of the Yangtze in China 1125 μatm, the Rhine in Europe 1268 μatm, and Amazon 3067 μatm. While the influence of carbon on the quality of river waters in the Java environment is still very difficult to determine. Up to now there has been unknown quality standard for carbon in the waters in the world. Carbon in the river can not be used as an indicator of the watershed health. To overcome
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Judul: Spatial and Temporal Distribution of Dissolved Oxygen  and Nutrients in the Ciliwung River, DKI Jakarta
Abstrak: Masukan limbah organik dan anorganik dari kegiatan antropogenik di sekitar sungai berpotensi menyebabkan penurunan kualitas perairan dan pengayaan nutrien. Penelitian ini bertujuan menganalisis dan mendeskripsikan sebaran oksigen terlarut dan nutrien (amonia, nitrit, nitrat, nitrogen total, dan fosfat total) di Sungai Ciliwung, DKI Jakarta, secara spasial dan temporal. Pemantauan kualitas air dilakukan pada bulan Februari-September 2021 dari 18 stasiun pengamatan. Secara spasial, kandungan oksigen Sungai Ciliwung tergolong rendah di Jakarta Pusat dan Jakarta Utara, kandungan nitrogen total, nitrat, dan fosfat total memenuhi baku mutu di seluruh wilayah sungai, sementara kandungan amonia dan nitrit cenderung tinggi dan tidak memenuhi baku mutu di seluruh wilayah Sungai Ciliwung, DKI Jakarta. Secara temporal, konsentrasi oksigen terlarut, nitrit, nitrogen total, dan fosfat total cenderung tidak berbeda antarmusim, sedangkan konsentrasi amonia lebih tinggi di musim kemarau dan nitrat lebih tinggi di musim hujan. Status kualitas air Sungai Ciliwung, DKI Jakarta, berada pada kondisi tercemar sedang hingga berat., The input of organic and inorganic waste from anthropogenic activities around the river causes a decrease in water quality and nutrient enrichment. This study aims to analyze and describe the distribution of dissolved oxygen and nutrients (ammonia, nitrite, nitrate, total nitrogen, and total phosphate) in the Ciliwung River, DKI Jakarta, spatially and temporally. Water quality monitoring was carried out in February-September 2021 from 18 observation stations. Spatially, the oxygen content of the Ciliwung River is low in Central Jakarta and North Jakarta, the total nitrogen, nitrate, and total phosphate content meets the quality standards in the entire river area, while the ammonia and nitrite content tend to be high and do not meet the quality standards in the entire Ciliwung River area, DKI Jakarta. Temporally, concentrations of dissolved oxygen, nitrite, total nitrogen, and total phosphate tended not to differ between seasons, while ammonia concentrations were higher in the dry season and nitrate was higher in the rainy season. The water quality status of the Ciliwung River, DKI Jakarta, is in moderate to extremely polluted condition.
Keyword: dissolved oxygen, nutrients, river, spatial, temporal

Judul: Konstruksi aritmetika kurva eliptik F(2m) supersingular dan non-supersingular untuk skema kunci publik ElGamal
Abstrak: Algoritme ElGamal adalah salah satu algoritme kunci publik dengan aritmetik modular p yang mempunyai struktur grip siklik Z(p). Tingkat keanaman algoritme ini terletak pada pemecahan masalah logaritme diskret dari Z(p). Akan tetapi, tingkat keamanan tadi tahun ke tahun semakin menurun yang disebabkan kemampuan pemecahan algoritme diskret semakin meningkat. Untuk memenuhi tingkat keamanan yang memadai dibutuhkan p yang cukup besar yang menyebabkan proses enkripsi dan dekripsi menjadi lambat.
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