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An Approach of Dimension Reduction in k-Nearest Neighbor Based Short-term Load Forecasting
Chu, FaZheng,Jung, Sung-Hwan Korea Multimedia Society 2017 멀티미디어학회논문지 Vol.20 No.9
The k-nearest neighbor (k-NN) algorithm is one of the most widely used benchmark algorithm in classification. Nowadays it has been further applied to predict time series. However, one of the main concerns of the algorithm applied on short-term electricity load forecasting is high computational burden. In the paper, we propose an approach of dimension reduction that follows the principles of highlighting the temperature effect on electricity load data series. The results show the proposed approach is able to reduce the dimension of the data around 30%. Moreover, with temperature effect highlighting, the approach will contribute to finding similar days accurately, and then raise forecasting accuracy slightly.
An Adaption of Pattern Sequence-based Electricity Load Forecasting with Match Filtering
Chu, Fazheng,Jung, Sung-Hwan Korea Multimedia Society 2017 멀티미디어학회논문지 Vol.20 No.5
The Pattern Sequence-based Forecasting (PSF) is an approach to forecast the behavior of time series based on similar pattern sequences. The innovation of PSF method is to convert the load time series into a label sequence by clustering technique in order to lighten computational burden. However, it brings about a new problem in determining the number of clusters and it is subject to insufficient similar days occasionally. In this paper we proposed an adaption of the PSF method, which introduces a new clustering index to determine the number of clusters and imposes a threshold to solve the problem caused by insufficient similar days. Our experiments showed that the proposed method reduced the mean absolute percentage error (MAPE) about 15%, compared to the PSF method.
Safety Evaluation In Vitro of Enterococcus durans from Tibetan Traditional Fermented Yak Milk
Jing Li,Fazheng Ren,Huiyong Gu,Xiaopeng Li,Bozhong Gan 한국미생물학회 2011 The journal of microbiology Vol.49 No.5
Despite its ubiquity in fermented dairy products, the safety of lactic acid enterococcal bacteria remains controversial. In this study, five Enterococcus durans strains – A1, A2, B1, B2, and C1 – were isolated from traditional fermented yak milk from Tibet. To evaluate the strains’ safety, biogenic amine production, antibiotic resistance and presence of known virulence determinants were investigated. Strain A1 can produce biogenic amines for histamine, spermine, and spermidine (mean values: 8.64, 8.31, and 0.30 mg/L, respectively). Polymerase chain reaction amplification for Strain A1 found genes involved in expression of gelatinase (gleE), cytolysin (cylA, cylB, and cylM), sex pheromones (ccf and cpd) and cell wall adhesion (efaA). Strain A2 showed sensitivity or intermediate resistance to all tested antibiotics, and no virulence determinants except gelE and ccf, but did produce tyramine at a relatively high level (912.02 mg/L). Both strains B1 and B2 could produce histamine (10.43 and 10.56 mg/L, respectively), and showed vancomycin resistance; B1 also produced tyramine (504.02 mg/L). Strain C1 could produce all five biogenic amines tested in the study – putrescine, histamine, tyramine, spermine, and spermidine; concentrations were 6.51, 9.59, 205.85, 5.55, and 5.39 mg/L, respectively. All E. durans strains found in Tibetan traditional fermented yak milk thus offer potential risk.
( Yunyun Jiang ),( Fazheng Ren ),( Songling Liu ),( Liang Zhao ),( Huiyuan Guo ),( Caiyun Hou ) 한국미생물 · 생명공학회 2016 Journal of microbiology and biotechnology Vol.26 No.3
Acid stress can affect the viability of probiotics, especially Bifidobacterium. This study aimed to improve the acid tolerance of Bifidobacterium longum BBMN68 using adaptive evolution. The stress response, and genomic differences of the parental strain and the variant strain were compared by acid stress. The highest acid-resistant mutant strain (BBMN68m) was isolated from more than 100 asexual lines, which were adaptive to the acid stress for 10th, 20th, 30th, 40th, and 50th repeats, respectively. The variant strain showed a significant increase in acid tolerance under conditions of pH 2.5 for 2 h (from 7.92 to 4.44 log CFU/ml) compared with the wildtype strain (WT, from 7.87 to 0 log CFU/ml). The surface of the variant strain was also smoother. Comparative whole-genome analysis showed that the galactosyl transferase D gene (cpsD, bbmn68_1012), a key gene involved in exopolysaccharide (EPS) synthesis, was altered by two nucleotides in the mutant, causing alteration in amino acids, pI (from 8.94 to 9.19), and predicted protein structure. Meanwhile, cpsD expression and EPS production were also reduced in the variant strain (p < 0.05) compared with WT, and the exogenous WT-EPS in the variant strain reduced its acid-resistant ability. These results suggested EPS was related to acid responses of BBMN68.
( Songling Liu ),( Fazheng Ren ),( Jingli Jiang ),( Liang Zhao ) 한국미생물 · 생명공학회 2016 Journal of microbiology and biotechnology Vol.26 No.6
The acid response of Bifidobacterium longum subsp. longum BBMN68 has been studied in our previous study. The fab gene, which is supposed to be involved in membrane fatty acid biosynthesis, was demonstrated to be induced in acid response. In order to investigate the relationship between acid response and cell membrane fatty acid composition, the acid adaptation of BBMN68 was assessed and the membrane fatty acid composition at different adaptation conditions was identified. Indeed, the fatty acid composition was influenced by acid adaptation. Our results showed that the effective acid adaptations were accompanied with decrease in the unsaturated to saturated fatty acids ratio (UFA/SFA) and increase in cyclopropane fatty acid (CFA) content, which corresponded to previous studies. Moreover, both effective and non-effective acid adaptation conditions resulted in decrease in the C18:1 cis- 9/C18:1 trans-9 ratio, indicating that the C18:1 cis-9/C18:1 trans-9 ratio is associated with acid tolerance response but not with acid adaptation response. Taken together, this study indicated that the UFA/SFA and CFA content of BBMN68 were involved in acid adaptation and the C18:1 cis-9/C18:1 trans-9 ratio was involved in acid tolerance response.
Liu, Songling,Ren, Fazheng,Jiang, Jingli,Zhao, Liang The Korean Society for Microbiology and Biotechnol 2016 Journal of microbiology and biotechnology Vol.26 No.7
The acid response of Bifidobacterium longum subsp. longum BBMN68 has been studied in our previous study. The fab gene, which is supposed to be involved in membrane fatty acid biosynthesis, was demonstrated to be induced in acid response. In order to investigate the relationship between acid response and cell membrane fatty acid composition, the acid adaptation of BBMN68 was assessed and the membrane fatty acid composition at different adaptation conditions was identified. Indeed, the fatty acid composition was influenced by acid adaptation. Our results showed that the effective acid adaptations were accompanied with decrease in the unsaturated to saturated fatty acids ratio (UFA/SFA) and increase in cyclopropane fatty acid (CFA) content, which corresponded to previous studies. Moreover, both effective and non-effective acid adaptation conditions resulted in decrease in the C<sub>18:1</sub> cis-9/C<sub>18:1</sub> trans-9 ratio, indicating that the C<sub>18:1</sub> cis-9/C<sub>18:1</sub> trans-9 ratio is associated with acid tolerance response but not with acid adaptation response. Taken together, this study indicated that the UFA/SFA and CFA content of BBMN68 were involved in acid adaptation and the C<sub>18:1</sub> cis-9/C<sub>18:1</sub> trans-9 ratio was involved in acid tolerance response.
Purification and properties of a milk-clotting enzyme produced by Bacillus amyloliquefaciens D4
Xiaoling He,Bozhong Gan,Fazheng Ren,Huiyuan Guo,Weibing Zhang,Xi Song 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.1
The milk-clotting enzyme from Bacillus amyloliquefaciens D4 was purified to 17.2-fold with 20% recovery by precipitation in ammonium sulfate and ion-exchange chromatography. The molecular mass of the enzyme was 58.2kDa as determined by SDS-PAGE, and it was proved to be a metalloprotease by EDTA inhibition. The enzyme was active in the pH range 5.5-7.0 and was inactivated completely by heating at 55℃ for 20 min. The highest level of enzyme activity was obtained at 65 ℃, pH 5.5, in the presence of 25mM CaCl_2. The milk-clotting activity was inhibited only slightly by Na^+ and K^+ and significantly by Cu^(2+), Zn^(2+) and Sn^(2+). The Km value of this enzyme was 0.471 mg/mL. The high level of milk-clotting activity coupled with a low level of thermal stability suggested that the milk-clotting enzyme from B. amyloliquefaciens D4 should be considered as a potential substitute for calf rennet.