Short Term Prediction of Photovoltaic Power Based on FCM and CG‑DBN Combination

ZhengMing Li,ShiQuan Bao,ZhaoLiang Gao 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.1

Afected by many factors, the photovoltaic output power is characterized by nonlinearity, volatility and instability. Therefore, short-term forecasting models are required to have multiple inputs, levels, and categories. In order to solve the above problems and improve the accuracy of predictions, this paper proposes a combined model prediction method based on similar-day clustering and the use of Conjugate Gradient (CG) to improve Deep Belief Network (DBN). The initial method uses fuzzy C-Means Clustering Algorithm (FCM) to perform similar-day clustering on the original data according to the degree of membership. The CG-DBN prediction model is then designed according to the category, with the model ultimately being used to perform the short-term prediction of the PV output power. The proposed scheme uses data from Zhejiang Longyou power station for experimental analysis and verifcation, and the results were compared with the back propagation neural networks model, Support Vector Machine (SVM) model, and traditional deep belief network. The model’s predicted results are compared. Finally, it is concluded that, in the short-term PV power load forecasting, the prediction performance of the FCM and CG-DBN combination forecast model is better than the above three models and has strong feasibility in short-term PV power forecasting.

The Acetylation Level of rDNA in Brassica campestris

Zhengming Qiu,Lu Zhang, Yong Hu,Shibin He,Lijia Li 한국식물학회 2012 Journal of Plant Biology Vol.55 No.4

Ribosomal DNA is an important repeated sequence that forms the nucleolus at the interphase. Its transcription into ribosomal RNA for ribosome biogenesis also represents a transitional point for several cellular processes, including cell-cycle progression, gene-silencing,and formation of the ribonucleoprotein complex. The levels of rDNA acetylation have an important role in regulating structural changes in rDNA chromatin and transcriptional activity. Using root-tip samples from Brassica campestris, we determined that some rDNA chromatin is located in the heterochromatin regions while some is de-condensed and found in euchromatin regions. Immuno-staining results showed that histone H4K5acetylation and H4 tetra-acetylation signals are dispersed within the euchromatin. Analysis of the promoter and exon regions of rDNA via chromatin immuno-precipitation (ChIP) revealed a connection between histone acetylation and rDNA conformation.

Purification of naphthalene from eutectic mixture by continuous column crystallization

Zhengming Yi,Qunsheng Li,Xufeng Sun,Minggao Su 한국화학공학회 2010 Korean Journal of Chemical Engineering Vol.27 No.2

To obtain highly purified naphthalene, a column crystallizer was employed and operated in the continuous multistage countercurrent fractional mode. The principles and characteristics of the process are introduced. A large amount of experimental work has been done on the crystallization process in a D=50 mm×1,350 mm column. The effects of operation conditions including the composition of feed, reflux ratio, stirring speed and the bed height of crystal on crystallization were systematically studied. The experiments showed that over 99.0% of the purity of product can be easily achieved in such conditions: feed composition among w=85.462-95.894%, reflux ratio among 1.42-4.04,the crystal bed height among 400-900 mm. The purity of product even reaches 99.996% in experiment.

Design Methodology for Optimal Phase-Shift Modulation of Non-Inverting Buck-Boost Converters

Bingqing Shi,Zhengming Zhao,Kai Li,Gaohui Feng,Shiqi Ji,Jiayue Zhou 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.5

The non-inverting buck-boost converter (NIBB) is a step-up and step-down DC-DC converter suitable for wide-input-voltagerange applications. However, when the input voltage is close to the output voltage, the NIBB needs to operate in the buck-boost mode, causing a significant efficiency reduction since all four switches operates in the PWM mode. Considering both the current stress limitation and the efficiency optimization, a novel design methodology for the optimal phase-shift modulation of a NIBB in the buck-boost mode is proposed in this paper. Since the four switches in the NIBB form two bridges, the shifted phase between the two bridges can serve as an extra degree of freedom for performance optimization. With general phase-shift modulation, the analytic current expressions for every duty ratio, shifted phase and input voltage are derived. Then with the two key factors in the NIBB, the converter efficiency and the switch current stress, taken into account, an objective function with constraints is derived. By optimizing the derived objective function over the full input voltage range, an offline design methodology for the optimal modulation scheme is proposed for efficiency optimization on the premise of current stress limitation. Finally, the designed optimal modulation scheme is implemented on a DSPs and the design methodology is verified with experimental results on a 300V-1.5kW NIBB prototype.

Design Methodology for Optimal Phase-Shift Modulation of Non-Inverting Buck-Boost Converters

Shi, Bingqing,Zhao, Zhengming,Li, Kai,Feng, Gaohui,Ji, Shiqi,Zhou, Jiayue The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.5

The non-inverting buck-boost converter (NIBB) is a step-up and step-down DC-DC converter suitable for wide-input-voltage-range applications. However, when the input voltage is close to the output voltage, the NIBB needs to operate in the buck-boost mode, causing a significant efficiency reduction since all four switches operates in the PWM mode. Considering both the current stress limitation and the efficiency optimization, a novel design methodology for the optimal phase-shift modulation of a NIBB in the buck-boost mode is proposed in this paper. Since the four switches in the NIBB form two bridges, the shifted phase between the two bridges can serve as an extra degree of freedom for performance optimization. With general phase-shift modulation, the analytic current expressions for every duty ratio, shifted phase and input voltage are derived. Then with the two key factors in the NIBB, the converter efficiency and the switch current stress, taken into account, an objective function with constraints is derived. By optimizing the derived objective function over the full input voltage range, an offline design methodology for the optimal modulation scheme is proposed for efficiency optimization on the premise of current stress limitation. Finally, the designed optimal modulation scheme is implemented on a DSPs and the design methodology is verified with experimental results on a 300V-1.5kW NIBB prototype.

Study of N-lauroylethanolamine Delaying Senescence of Cut Carnation ‘Red Barbara’ Flowers via Regulating Lipid Peroxidation and Antioxidation Level during Vase

Yun Zhang,Wei-ming Guo,Liang Han,Zhengming Li,Fadi Chen 한국원예학회 2006 한국원예학회 기타간행물 Vol.- No.-

A Harmonic Detection Method for Distributed Generation Connected Grid System Using DWT and HHT

Min Xu,Tianhong Pan,Jiao Chen,Zhengming Li 대한전기학회 2019 Journal of Electrical Engineering & Technology Vol.14 No.4

In distributed generation (DG) connected grid system, there is serious harmonic pollution caused by the wide use of inverter units and nonlinear loads. The traditional detection methods (such as Fast Fourier Transform and wavelet analysis) heavily depend on synchronous signal detection or basis functions selection, which don’t satisfy the requirements of the harmonic detection of the micro-grid environment. Therefore, a novel method combining discrete wavelet transform (DWT) with Hilbert–Huang transform (HHT) is proposed to detect and analyze the harmonic. The method uses multi resolution analysis of DWT to process the original signal. Then, a series of intrinsic mode function (IMF) components are obtained from the processed signal by using Empirical Mode Decomposition (EMD) algorithm. Thirdly, the fundamental component and harmonic are extracted from the IMF components. Finally, the frequency and amplitude of the signal are calculated by using the HHT. Simulation results demonstrate that the proposed algorithm has high precision and good real-time characteristics. Furthermore, the proposed algorithm satisfi es the requirements of the harmonic detection of the DG connected grid system.

Assembly mechanisms of soil bacterial communities in subalpine coniferous forests on the Loess Plateau, China

Pengyu Zhao,Jinxian Liu,Tong Jia,Zhengming Luo,Cui Li,Bao-Feng Chai 한국미생물학회 2019 The journal of microbiology Vol.57 No.6

Microbial community assembly is affected by trade-offs between deterministic and stochastic processes. However, the mechanisms underlying the relative influences of the two processes remain elusive. This knowledge gap limits our ability to understand the effects of community assembly processes on microbial community structures and functions. To better understand community assembly mechanisms, the community dynamics of bacterial ecological groups were investigated based on niche breadths in 23 soil plots from subalpine coniferous forests on the Loess Plateau in Shanxi, China. Here, the overall community was divided into the ecological groups that corresponded to habitat generalists, ‘other taxa’ and specialists. Redundancy analysis based on Bray-Curtis distances (db-RDA) and multiple regression tree (MRT) analysis indicated that soil organic carbon (SOC) was a general descriptor that encompassed the environmental gradients by which the communities responded to, because it can explain more significant variations in community diversity patterns. The three ecological groups exhibited different niche optima and degrees of specialization (i.e., niche breadths) along the SOC gradient, suggesting the presence of a gradient in tolerance for environmental heterogeneity. The inferred community assembly processes varied along the SOC gradient, wherein a transition was observed from homogenizing dispersal to variable selection that reflects increasing deterministic processes. Moreover, the ecological groups were inferred to perform different community functions that varied with community composition, structure. In conclusion, these results contribute to our understanding of the trade-offs between community assembly mechanisms and the responses of community structure and function to environmental gradients.

Self-Rated Health Status and Risk of Incident Stroke in 0.5 Million Chinese Adults: The China Kadoorie Biobank Study

Wenhong Dong,Xiong-Fei Pan,Canqing Yu,Jun Lv,Yu Guo,Zheng Bian,Ling Yang,Yiping Chen,Tangchun Wu,Zhengming Chen,An Pan,Liming Li 대한뇌졸중학회 2018 Journal of stroke Vol.20 No.2

Background and purpose Self-rated health (SRH) is a consistent and strong predictor of all-cause and cardiovascular mortality in various populations. However, the associations between SRH measures and risk of first-ever or recurrent stroke were rarely explored. We thus aim to prospectively investigate the associations between SRH measures and risk of total and subtypes of stroke in Chinese population. Methods A total of 494,113 participants from the China Kadoorie Biobank without prior heart diseases or cancer (486,541 without stroke and 7,572 with stroke) were followed from baseline (2004 to 2008) until December 31, 2013. General and age-comparative SRH were obtained from baseline questionnaires. First-ever stroke or recurrent events were ascertained through linkage to disease registry system and health insurance data. Results We identified 27,662 first-ever stroke and 2,909 recurrent events during an average of 7.0 years of follow-up. Compared with excellent general SRH, the hazard ratios (HRs) and 95% confidence intervals (CIs) for first-ever stroke associated with good, fair, and poor general SRH were 1.04 (1.00 to 1.08), 1.19 (1.15 to 1.23), and 1.49 (1.42 to 1.56) in the multivariate model, respectively. Compared with better age-comparative SRH, the HRs (95% CIs) of same and worse age-comparative SRH were 1.13 (1.10 to 1.17) and 1.51 (1.45 to 1.58), respectively. The relations of SRH measures with ischemic stroke, hemorrhagic stroke, and recurrent stroke were similar to that with total first-ever stroke. However, the magnitude of associations was much stronger for fatal stroke than for non-fatal stroke. Conclusions This large-scale prospective cohort suggests that self-perceived health status is associated with incident stroke, regardless of stroke subtype.

Family History, Tobacco Smoking, and Risk of Ischemic Stroke

Mengyu Fan,Jun Lv,Canqing Yu,Yu Guo,Zheng Bian,Songchun Yang,Ling Yang,Yiping Chen,Feifei Li,Yaoming Zhai,Ping Wang,Junshi Chen,Zhengming Chen,Lu Qi,Liming Li 대한뇌졸중학회 2019 Journal of stroke Vol.21 No.2

Background and Purpose Both genetic factors and smoking are associated with ischemic stroke (IS) risk. However, little is known about the potential interaction of these factors. We aimed to assess whether smoking and a positive family history interact to increase the risk of IS. Methods The nationwide prospective study recruited 210,000 men and 300,000 women in 2004 to 2008 at ages 30 to 79 years. During 9.7 years of follow-up, we documented 16,923 and 20,656 incident IS cases in men and women without major chronic diseases at baseline, respectively. Multivariable Cox regression models were used to examine associations between family history and IS. Likelihood ratio tests were used to test the smoking-family history interactions on IS. Results About 67.8% (n=135,168) of men ever smoked regularly compared with 2.7% (n=7,775) of women. Among men, a significant interaction between family history and smoking on IS was observed (P for interaction=0.03), with more pronounced association between family history and IS among ever-regular smokers (hazard ratio [HR], 1.21; 95% confidence interval [CI], 1.16 to 1.27) than among never-smokers (HR, 1.11; 95% CI, 1.01 to 1.23). The association between family history and IS among ex-smokers after more than 10 years of cessation (HR, 1.01; 95% CI, 0.85 to 1.20) appeared similar to that among never-smokers. Among women, a similar but not significant interaction between family history and smoking on IS was observed. Ever-regular smokers who had a family history of stroke had the highest risk of IS. Conclusions Among Chinese men, the association of family history with IS was accentuated by smoking, and such accentuation tended to be lowered by cessation.