Judul: Tuning Parameter dalam Fungsi Okapi BM25 pada Mesin Pencari Teks Bahasa Indonesia
Abstrak: Information retrieval system was developed using various models, such as probabilistic models, language models, boolean models, vector-space models and many more. Thus, it’s problematic to determine which models is the best and the most efficient in every search condition. In this study, two models were developed and compared: probabilistic model and vector-space model. The probabilistic model has Okapi BM25 similarity function with parameters that are subject to fine tuning to seek for better performance. Fine tuning the parameters has made the probabilistic model’s average precision increases from 0.5885 to 0.5901. Further, this model also outperformed the vector-space model with average precision 0.5327.
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Judul: Ukuran kemiripan BM25 pada Model Ontologi Mesin Pencari Produk Online Shop
Abstrak: Penelitian ini membangun mesin pencari berbasis Apache Solr menggunakan informasi hierarki dari ontologi untuk mengekspansi query yang diberikan oleh pengguna. Mesin pencari ini menggunakan BM25Similarity dengan memodifikasi tuning parameter (k1 dan b) yang ada di dalamnya. Mesin pencari ini menggunakan 76 518 data produk milik Blibli.com. Hasil evaluasi terhadap mesin pencari ini menunjukkan bahwa BM25Similarity yang telah dituning (k1 = 2.0 dan b = 1.00) memberikan kinerja yang relatif lebih baik dibandingkan DefaultSimilarity (model Boolean dan ruang vektor) untuk evaluasi dengan menggunakan query uji pada pencarian produk online shop Blibli.com. BM25Similarity yang telah di-tuning pada penelitian ini dapat meningkatkan nilai MAP sebesar 0.0138.
Keyword: Apache Solr, BM25, mesin pencari, online shop, ontologi, tuning parameter

Judul: Growth, Concentration Chlorophyll-a, and Structure of Macroalgae Gracilaria edulis in the Culture Media Containing Copper
Abstrak: The physiological responses (specific growth rate, concentration of chlorophyll-a, morphological and anatomical structure of the vegetative cells) of the marine macroalga Gracilaria edulis at the different concentrations of copper (0.01 as control, 0.04, 0.06 and 0,5 ppm) delivered continuously for 28 days under controlled laboratory conditions were investigated. Result showed that the degree of copper toxicity depends on both factor the concentration and exposure time. Copper concentration and day of exposure decreased significantly the specific growth rate (SGR) of the Gracilaria edulis but only 0,5 ppm Cu decreased the chlorophyll-a content when compared to control. Of the various physiological end points measured, growth proved to be the most sensitive response than chlorophyll-a with reductions in specific growth rate (SGR). The reason for this could be related to a greater sensitivity of the enzymes involved in growth than those related to chlorophyll-a or a greater energy needs to maintain cellular integrity and metabolic processes under sublethal Cu stress. In all cases, the main effect on vegetative cells were structure changes in cortex and subcortex cells, compared to control, macroalgae exposed to copper showed depigmentation and blending in the lateral branches, heavy staining of the cell wall and severe damage of cell membrane, while the mucilage and the cell walls was densely fibrillar, thick and heavily stained, the cortex cell was clearly vacuolated, the presence of endophytic on the cell wall and endophytic spores in the mucilage. The presence vacuoles should be related to a metal immobilization mechanism, minimizing the Cu toxicity for cells. The epiphytic bacteria can act as a biofilter diminishing the availability of Cu for macroalgae accumulation.
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