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"During the last decade, water scarcity in terms of quantity and quality degradation has become a major issue in Indonesia. In 2006, Universitas Indonesia (UI) supported by the Ministry of Public Works built a recharge pond as a field model to overcome flood and drought in Jakarta and its surroundings. However, since then, a lack of research has been conducted to monitor and analyze the rate of change in water quality in the UI recharge pond. The purposes of this study are to identify the characteristics of UI recharge pond and evaluate the surface water quality changes. Water samples were taken from the pond and analyzed in the laboratory for water quality tests. The evaluation method used for simulation of water quality was a numerical model using Runge-Katta Order 4. Laboratory analysis results show concentrations of Mn, Fe, BOD and COD are exceeding the water quality standards (GR No.82/2001). The water purification process in the pond was found to be faster in response to BOD (?= 0.5 d-1) and for Mn, Fe, and COD are found to have similar results at ?= 0.4 d-1. The 95% response time of the pond was found to be longer for Mn, Fe, and COD (t95 = 7.5 d) and the faster rate is BOD (t95 = 6.0 d). The result of numerical modeling demonstrates Mn concentration in the pond will be doubled (0.45 mg/L) on the day-15th and asymptotically converges on a steady state. The Fe, BOD, and COD reaches the steady state concentration around on the day-11th (0.95 mg/L), on the day-13th (56.6 mg/L), and on the day-17th (224 mg/L), respectively."

"Localized Surface Plasmon Resonance (LSPR) adalah fenomena eksitasi yang terjadi ketika cahaya datang berinteraksi dengan nanopartikel dari logam mulia (emas dan perak). Interaksi ini dapat teramati melalui absorpsi dan scattering oleh nanopartikel yang berosilasi. Dalam penelitian ini, metode yang digunakan untuk mengamati fenomena LPR ini adalah dengan melakukan simulasi. Dalam simulasi fenomena LPR, dapat diamati pengaruh bentuk, ukuran, material dan indeks bias terhadap kurva absorpsi, scattering, dan extinction. Simulasi ini dilakukan dengan metode elemen-hingga dengan pendekatan quasistatik terhadap material emas dan perak didalam tiga jenis dielektrik. Bentuk yang digunakan adalah bola, rod, dan triangle dengan variasi ukuran 10-100 nm. Hasil simulasi menunjukan bahwa bentuk, ukuran, jenis material, dan indeks bias mempengaruhi besarnya puncak cross section dan panjang gelombang dari setiap kurva dimana bentuk, ukuran, dan indeks bias mempengaruhi tinggi puncak, dan jenis material menentukan panjang gelombang dari puncak. Hasil juga menunjukan kesesuaian pendekatan quasistatik dengan teori Mie.

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Localized Surface Plasmon Resonance (LSPR) is an exitation phenomenon that occurs when nanoparticle of noble metal (gold and silver) interact with electromagnetic wave. These interactions can be observed through absorption and scattering by the nanoparticle oscillate. In this study, we performed some simulations of LSP phenomenon to observed the effect of shape and size of nanoparticle, materials, and refractive index toward absorption, scattering, and exitation. Simulation is done by finite element method with quasistatic approximation toward gold and silver in three types of dielectric. Shape variation that used in these simulation are sphere, rod, and triangle with size variation 10 - 100 nm. The result show that size, shape, material and refractive index affect the peak of extinction, scattering and absorption cross section curve and their wavelength. The result with quasistatic approximation show similiarity with Mie theory."