Judul: Klasifikasi Debitur Kartu Kredit Menggunakan Algoritme K-Nearest Neighbor untuk Kasus Imbalanced Data
Abstrak: Data is said to suffer the class imbalanced problem when the class distribution are highly imbalance. In this case, minority class is more difficult to predict then the majority class. Though the minority class sometime has important information. In this paper, classification analysis of credit card debtors is conducted by using k-nearest neighbor that can classify debtors into two categories, good or bad. Analysis of a prospective debtor is essential to minimize credit risk. One approach taken to overcome imbalanced data problems is to modify instance distribution using oversampling and undersampling method. The evaluation is conducted by comparing the value of parameter k, accuracy, precision, recall, and F-measure. The evaluation results show that oversampling technique gives the best result of 96.24% with k = 3, 99.23% recall with k = 2, 95.21% precision with k = 1, and 96.30% F-measure with k = 3.
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Judul: Classification of imbalanced data using weighted k-nearest neighbor in data bank credit card debtors
Abstrak: Manajemen risiko kredit bertujuan untuk meminimalkan potensi kerugian dari kredit macet. Analisis data debitur bermasalah yang sudah ada dapat menjadi model dalam kualifikasi pemberian kredit selanjutnya. Data debitur bank termasuk kasus data tidak seimbang. Proses klasifikasi menjadi tidak optimal karena kelas dengan jumlah data lebih banyak memberikan pengaruh yang sangat besar dalam hasil klasifikasi. Penelitian ini bertujuan untuk mengembangkan model klasifikasi data debitur kartu kredit menggunakan algoritme weighted k-nearest neighbor dan metode sampling yang bertujuan meningkatkan kualitas klasifikasi pada data tidak seimbang. Metode sampling yang digunakan yaitu oversampling dan undersampling. Metode oversampling acak menghasilkan nilai f-measure terbaik sebesar 86.51%. Metode oversampling duplikasi menghasilkan nilai recall terbaik sebesar 100%., Credit risk management aims to minimize potential losses of non-performing loans. The classification results of existing data debtors can be referred for credit qualifications. The debtors data, most likely, are imbalanced due to the good debtors dominated the bad one. Classification process could not be optimum because of the class with more data had tremendous influence in the classification result. This research aims to develop a data classification model based on credit card debtors using weighted k-nearest neighbor and sampling method which aimed to improve the quality of classification on the imbalanced data. The sampling methods used are the oversampling and undersampling. The random oversampling method obtains the best performance with F-measure of 86.51%. Moreover, the duplication oversampling can obtain 100% recall. Keywords: imbalanced data, oversampling, undersampling, weighted k-nearest neighbor
Keyword: data tidak seimbang, oversampling, undersampling, weighted k-nearest neigbor

Judul: Extracellular Expression of thermostable Geobacillus stearothermophilus T1.2RQ Lipase for Biodiesel Production
Abstrak: The extracellular expression of enzymes in an excellent secretion host such as Bacillus subtilis is a useful strategy for making enzymes of industrial significance more affordable by lowering the cost of its downstream processing. Lipases are a category of hydrolases that catalyze the hydrolysis of triglycerides to glycerol and free fatty acids. Also, lipases catalyze the hydrolysis and transesterification of other esters as well as the synthesis of esters. They can perform very specific biotransformation reactions and are widely used in food, organic synthesis, detergents, cosmetic, and pharmaceutical industries. Geobacillus stearothermophilus T1.2RQ lipase is an industrially-desired thermostable lipolytic enzyme with an excellent hydrolytic and transesterification activity. This study aimed to express T1.2RQ lipase, in B. subtilis WB800 and ensure its secretion into the extracellular medium. Three signal peptides (AmyQ, Epr, LipA) and two promoters (Pgrac01 and Pgrac100) were used in the secretory-expression of T1.2RQ lipase, based on five constructed expression vectors constructed by restriction cloning and PCR mutagenesis. Sangers sequencing was used to verify constructs to ensure they are in the correct reading frame. Recombinants vectors, pHT43 (plasmid control), pHT43-T1.2RQ, pHT43- T1.2RQ_AmyQ, pHT43-T1.2RQ_Epr, and pHT43-T1.2RQ_LipA, were transformed by electroporation into Bacillus subtilis WB800. The electroporation was successful with the optimum condition of 2500V, 200 ohms, 25µF, and 5milliseconds. Recombinant B. subtilis pHT43 (negative control) and pHT43-T1.2RQlip + signal peptides were streaked on the lipidic agar, LA+TBN. All four recombinants, including the negative control (B. subtilis WB800-pHT43), produced clear zones on the TBN agar plate after overnight incubation (fig 2), indicating the presence of a lipolytic enzyme in all of the recombinant B. subtilis cells. pHT43-T1.2RQlip + signal peptides (AmyQ, Epr, and LipA) have clear zones with significantly higher diameters than B. subtilis WB800-pHT43 (negative control). This phenomenon suggests that the recombinant thermostable lipase T1.2RQ introduced into these cells was successfully expressed, thereby increasing the lipolytic capability of its host cells T1.2RQ lipase was expressed in 50ml terrific broth medium (TB) and the expression induced with 1mM IPTG. Lipase activity assay using p-nitrophenyl esters showed that all three signal peptides directed the secretion of T1.2RQ lipase into the extracellular medium. Signal peptide, LipA, resulted in the highest extracellular activity of 5.6 U/mL, which corresponds to a 6-fold increase over the parent B. subtilis WB800 strain. Meanwhile, signal peptides, AmyQ and Epr produced 4.2 U/mL and 3.4 U/mL activity respectively. SDS-Zymogram analysis confirmed that T1.2RQ lipase was correctly processed and secreted in its original size of 44 kDa. An attempt to further increase lipase expression level by promoter optimization showed that, contrary to expectation, promoter Pgrac100 exhibited similar expression levels as the original Pgrac01. Nevertheless, the demonstration of the successful secretion of T1.2RQ lipase in this work confirms the latter as a promising approach for the industrial production of the enzyme
Keyword: Bacillus subtilis, Expression, Extracellular, Heterologous, Lipase, Thermostable