Judul: Pembobotan RIDF pada Mesin Pencari Bahasa Indonesia untuk Ekspansi Kueri Menggunakan Analisis Konteks Lokal
Abstrak: Automatic query expansion is a technique for dealing with the fundamental issue of word mismatch between queries and documents in information retrieval. A number of approaches on query expansion have been studied, especially on techniques that analyze the corpus to discover word relationships (global technique) and those that analyze documents retrieved by initial query (local technique). Both techniques have their own advantages and limitations. Local context analysis is an automatic query expansion which is a combination of global and local techniques. The purpose of this research is to implement query expansion with local context analysis using TF (Term Frequency) RIDF (Residual Inverse Document Frequency) weighting method, a variation of IDF (Inverse Document Frequency) that assigns weights to terms according to the difference between the logs of the actual IDF and its prediction by Poisson model. The obtained performance of information retrieval was 15% average precision. The results also showed that the number of top-ranked documents and passages did not significantly affect the average precision. The more influential factor was the number of query expansions.
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Judul: Ekspansi Kueri pada Sistem Temu Kembali Informasi Berbahasa Indonesia Menggunakan Analisis Konteks Lokal
Abstrak: Users express their needs in a query to get information using a information retrieval system. However, many are not able to compose appropriate queries as the average length of their queries were too short. Another problem is word mismatch, which refers to the phenomenon that the users of information retrieval systems often use words to describe the concept in their queries which are different from words that authors use to describe the same concept in their documents. Local context analysis is an automatic query expansion which is a combination of global and local techniques. Like global techniques, local context analysis select expansion features based on their co-occurrences with the query terms. Like local techniques, it selects expansion features from the top retrieved documents for a query. Local context analysis ranks the concept by their co-occurrences with the query term in the top ranked documents and uses the highest ranked concepts for query expansion. Basically, a document consists of topics, so in this research, the top ranked documents are divided into passages which represent topics in the relevant document. The highest ranked concepts are then taken from top ranked passages. The purpose of this research is to implement query expansion with local context analysis. The performance of information retrieval system with local context analysis gave good result with around 60% average precision. The results showed that the retrieval performance using local context analysis was significantly higher based on statistical analysis using t-test. The average precision increased by 6.07% compared to retrieval without local context analysis, indicating relevant documents occur higher in the retrieval result. The results also showed that the number of top-ranked documents and passages did not significantly affect the average precision. The more influential factor was the number of query expansions added. Local context analysis is quite suitable for collection of relatively similar documents.
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Judul: Hydroxyapatite-Chitosan Composite Coating on Stainless Steel 316 to Improve Corrosion Resistance
Abstrak: Metals that were used in bone implantation should have good corrosion resistance that were not easily corroded when implanted into the body. Metal corrosion resistance of stainless steel 316 can be enhanced through the metal coating by hydroxyapatite-chitosan composite with composition ratio of hydroxyapatite (gram) and chitosan 3% (mL) 0.2:0, 0.2:0.1, 0.2:0.5, 0.2:1.0, and 0.2:1.5. Besides improving the corrosion resistance of metal, the presence of chitosan also maintain the position of hydroxyapatite on metal surfaces. Corrosion resistance increases with increasing amount of chitosan added and the best composition of hydroxyapatite-chitosan composite was 0.2:1.0.
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