Judul: Mesin Pencari Dokumen Bahasa Indonesia Menggunakan Latent Semantic Indexing dengan Pembobotan Global
Abstrak: Current users tend to like search engine based on semantic of word. This is caused by the existence of synonymy and polysemy problems in the selection of the use of the word. One technique to resolve these issue is Latent Semantic Indexing (LSI). LSI has the ability to find relevant documents even if the word of the query are not written in the document. Currently, TF-IDF term weight algorithm is widely applied in search engines. Xia and Chai (2011) stated that, in a document collection, the term with higher frequency and hypo-dispersion distribution usually contains less information. The purpose of this research is to implement LSI using Singular Value Decomposition (SVD) method with term distribution based global term weight. This research used 1000 Indonesian agricultural documents. The performance of search engine using LSI with term-distribution-based global term weight gave highest average precision around 40.47%. The test result also showed that LSI with term-distribution-based global term weight gives better acuracy than LSI with TF-IDF.
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Judul: Pengindeksan Ontologi Dokumen Bahasa Indonesia Menggunakan Latent Semantic Analysis
Abstrak: Ontology is a collection of concepts that can be applied to the information retrieval system that is able to represent knowledge of a document in a specific domain, so that ontology is considered to improve the performance of information retrieval systems. Therefore the construction of ontology concept must be able to solve semantic problem in corpus. This research proposes ontology indexing of document Bahasa Indonesia using latent semantic analysis. Latent semantic analysis (LSA) is a theory and method which can be considered to solve the problem of semantic words in the corpus by extracting and representing contextual usage meaning of the word by using statistical method. In this research, ontology which has been constructed is applied to the information retrieval systems and evaluated using 20 pairs of queries. As the result of this experiment a recall value of 96.5% and average precision value of 83.4% were obtained.
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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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