Judul: Bogor Daily Rainfall Fluctuations in 1987-2017 Using Spectral Analysis
Abstrak: Salah satu alasan utama untuk mempelajari dan menyelidiki data curah hujan di suatu wilayah adalah untuk mengetahui apakah ada sinyal berulang yang membentuk pola/siklus. Siklus didefinisikan sebagai peristiwa gelombang naik (trough) dan turun (ridge) dalam suatu periode runtun waktu curah hujan. Curah hujan harian Bogor periode tahun 1987-2017 dianalisis menggunakan metode analisis spektral. Penelitian ini bertujuan mengetahui periodisitas tersembunyi dalam rentang waktu 31 tahun dan pengaruhnya terhadap fluktuasi curah hujan. Periodisitas tersembunyi ini penting untuk diketahui karena diperlukan dalam prakiraan cuaca dan analisis data di bidang terkait. Fluktuasi curah hujan Bogor mendapat pengaruh signifikan dari adanya sirkulasi atmosfer wilayah tropis serta moda variabilitas iklim yang memiliki periode ulang dan siklusnya masing-masing. Siklus skala bulanan didominasi oleh monsun dengan periode 12 bulan sekali, sehingga pola curah hujan Bogor termasuk tipe monsunal. Adapun sinyal dari fenomena Semi Annual Oscillation (SAO) dengan periode 6 bulanan juga teridentifikasi namun densitas spektrumnya tidak setinggi monsun. Aktivitas monsun ini ditandai dengan adanya satu puncak hujan tiap tahunnya yang dominan terjadi di bulan November dan jelasnya perbedaan musim antara musim basah (wet season) yang terjadi pada periode Desember-Januari-Februari (DJF) dan musim kering (dry season) yang terjadi pada periode Juni-Juli-Agustus (JJA), sedangkan SAO berkaitan dengan peristiwa equinox dan pergerakan Intertropical Convergence Zone (ITCZ). Sinyal dari kekuatan moda variabilitas iklim skala musiman dan harian juga turut mempengaruhi fluktuasi curah hujan di Bogor. Keberadaan sinyal Madden-Julian Oscillation (MJO) diketahui lebih kuat pada periode September-Oktober-November (SON), sedangkan gelombang Kelvin dan MRG memiliki aktivitas yang kuat pada bulan Maret-April-Mei (MAM) terutama saat kondisi La Nina. Sebesar 50% fluktuasi curah hujan di wilayah Bogor selama 31 tahun (1987-2017) disebabkan oleh adanya pengaruh dari dominansi aktivitas gelombang Mixed Rossby-Gravity (MRG) dengan rataan nilai spectral density 1324 mm2, sedangkan dua gelombang lainnya yaitu gelombang Kelvin dan MJO aktivitasnya tidak sekuat gelombang MRG dimana pengaruhnya terhadap fluktuasi curah hujan <50% dengan rataan nilai spectral density berturut-turut 755 mm2 dan 501 mm2., One of the main reasons to study and investigate rainfall data in a region is to find out whether it has recurring signals that form patterns or cycles. A cycle is defined as the occurrence of a single trough and ridge in the perturbation of rainfall time series. Daily rainfall of Bogor for the period of 1987-2017 is analyzed using spectral analysis method. This study aims to discover the hidden periodicity in the 31-year-long time series and its impacts on the rainfall fluctuation. The hidden periodicity is important to find out as it is needed in the weather forecast and analysis. Rainfall fluctuations in Bogor have a significant effect from the tropical atmospheric circulation and climate variability modes that have their respective return periods and cycles. The monthly cycle is dominated by the monsoon with a period of once every 12 months, so the rainfall pattern in Bogor is a monsoon type. The signal from the Semi Annual Oscillation (SAO) phenomenon with a 6-month period was also identified, but the spectrum density was not as high as the monsoon. This monsoon activity is characterized by the existence of one peak of rain each year which dominantly occurs
Keyword: deindustrialisasi, formasi sosial, garam, Madura

Judul: Analisis Curah Hujan Harian Maksimum dan Ekstrim di Kabupaten Bogor
Abstrak: The impact of extreme rainfall often cause serious problems for human being. However, the study of extreme rainfall is needed, so the impact of such extreme events can be anticipated as early as possible. This research aims to know the changes of extreme and maximum daily rainfall at some stations of Bogor Regency, and analyze the relationship between maximum daily rainfall with IOD condition (Indian Ocean Dipole) and SOI (Southern Oscillation Index). The analysis which used in this study are trend test using the Spearman Rank statistics and the probability distribution to acquire the probability of extreme rainfall and analyze maximum daily rainfall data with exceedence probability 5%, 10%, 25% and 50%. Correlation analysis was used to test the relationship between maximum daily rainfall with SOI and IOD. The results show that extreme rainfall occur in January, February and March, even occur in April. The most statistical distribution describes the maximum daily rainfall data in Bogor regency is Normal and Lognormal distribution. In some stasion, 3-Parameter Lognormal distribution, Gamma and Weibull can describes maximum daily rainfall data in dry season. The probability of extremes rainfall based on consecutively three day rainfall in region of this study is high enough, that is 0.80 at Gunung Mas, 0.23 at Katulampa, and 0.13 at Empang stasion. Generally, SOI and IOD significantly correlated and consistent on the maximum daily rainfall patterns in Bogor area in dry season and inconsistent in rainy season.
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Judul: Synthesis of Apatite - Chitosan Composite Using Duck Eggshell and Chitosan with Temperature and pH Control
Abstrak: Composite of apatite-chitosan was prepared by using chitosan as polymer matrix. Calcium phosphate was prepared from CaO and (NH4)2HPO4, which the ratio Ca : P had to be 1.67. Chitosan is produced by deacetilase from biopolymer chitin. Duck eggshell (95% CaCO3) as starting material was converted to be calcium oxide (CaO) through calcinations with temperature 1000oC for 5 hours. In-situ and ex-situ methods were prepared from apatite and chitosan (dissolved with acetate acid 2%). Calcium phosphate prepared for bone implantation, but it is too fragile and brittle to be implant into the body. So addition of chitosan can decrease crystalinity and increase mechanic characteristic (tougher). Composite apatite-chitosan was resulted by fast precipitation. Fast precipitation was held in a breaker glass with nitrogen atmosphere, under controlled temperature at 37oC and pH 7, in order to increase amount of hydroxyapatite. Precipitation with CaO which was dropped by (NH4)2HPO4. Hydroxyapatite and chitosan were appearing at samples with in-situ and ex-situ methods which indicating by peak matching of XRD (closed lattice parameter, crystal size), overlapping at FTIR spectra and supporting by SEM picture (homogenous and agglomerated particle). However, it still needs further research to examine biocompatibility osteoconductive degree of sample by in-vivo and in-vitro test.
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