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.

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.

Implementation of a Stand-alone Photovoltaic Pumping System with Maximum Power Point Tracking

Zhao Zhengming,Chen Kunlun,Yuan Liqiang 전력전자학회 2001 ICPE(ISPE)논문집 Vol.2001 No.10

Photovoltaic (PV) pumping systems with maximum power point tracking (MPPT) technique aims at obtaining the highest possible power to the pump under various insolation and temperature, thus overcomes the mismatch between the photovoltaic panel and the pumping load. A simple method of tracking the maximum power points and forcing the system to operate close to these points is presented in this paper. The MC68HC908GP32 micro control unit (MCU) is employed to implement the proposed MPPT controller. Experimental results will also show the performances of the photovoltaic pumping system with the MPPT technique.<br/>

Research on impact isolation performance of cylindrical honeycomb pedestals considering gradient effect

Jiangcheng Huang,Zhengming Xiao,Tao Liu,Jiang Liu,Longlong Zhang 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.9

The porous honeycomb is widely used in the field of impact energy absorption due to its high porosity and low density. However, traditional honeycomb pedestals are mainly studied for the influence of the increase or decrease of uniform parameters on the impact isolation performance, and are prone to stress concentration, low in-plane stiffness and poor bearing capacity. Therefore, a cylindrical honeycomb pedestal is proposed, and its anti-deformation ability is analyzed. Through multiple sets of comparative simulations, the influence of the change of honeycomb core cell parameters on its impact isolation performance is discussed. On the premise of ensuring the mass and volume of the pedestals unchanged, honeycomb layers with positive thickness gradient, inverse thickness gradient, positive angle gradient and inverse angle gradient were designed with cell wall thickness and concave angle as independent variables, respectively. The effects of layered gradient design and gradient variation on the impact isolation performance of the pedestals were discussed. The results show that, on the one hand, the cylindrical honeycomb pedestal has higher specific stiffness and stronger bearing capacity than the regular square pedestal; on the other hand, the thinner the cell wall thickness, the greater the absolute value of the concave angle of the cell, and the better the impact isolation performance of the pedestal. The design of the thickness gradient has improved the impact isolation performance compared with the uniform parameter design. The positive thickness gradient design has the best effect, and the angle gradient design has no obvious effect on the impact isolation performance. At the same time, the greater the gradient change, the more significant the effect.

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.

A novel high-order multivariate Markov model for spatiotemporal analysis with application to COVID-19 outbreak

Elshehawey AM,Qian Zhengming 한국통계학회 2023 Journal of the Korean Statistical Society Vol.52 No.3

We propose a new strategy for analyzing the evolution of random phenomena over time and space simultaneously based on the high-order multivariate Markov chains. We develop a novel Markov model of order r for m chains consisting of s possible states to gather parsimony with realism. It can capture negative and positive associations among the chains with only a reduced number of parameters, rm^2 (s^2 + 2), remarkably lower than ms^(rm+1) required for the full parameterized model. Our model privileges are enhanced by a Monte Carlo simulation experiment, besides application to analyze the spatial–temporal dynamics for the risk level of a recently global pandemic (COVID-19) outbreak in world health organization (WHO) regions for predicting the risk state of epidemiological prevalence and monitoring infection control.

Transient Performance Improvement in the Boundary Control of Boost Converters using Synthetic Optimized Trajectory

Gaohui Feng,Liqiang Yuan,Zhengming Zhao,Junjie Ge,Xiuxi Ye,Ting Lu 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.2

This paper focuses on an improvement in the transient performance of Boost converters when the load changes abruptly. This is achieved on the basis of the nature trajectory in Boost converters. Three key aspects of the transient performance are analyzed including the storage energy change law in the inductors and capacitors of converters during the transient process, the ideal minimum voltage deviation in the transient process, and the minimum voltage deviation control trajectory. The changing relationship curve between the voltage deviation and the recovery time is depicted through analysis and simulations when the load suddenly increases. In addition, the relationship curve between the current fluctuation and the recovery time is obtained when the load suddenly decreases. Considering the aspects of an increasing and decreasing load, this paper proposes the transient performance synthetic optimized trajectory and control laws. Through simulation and experimental results, the transient performances are compared with the other typical three control methods, and the ability of proposed synthetic trajectory and control law to achieve optimal transient performance is verified.

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.

Tradeoff between the Output Voltage Deviation and Recovery Time of Boost Converters

Junjie Ge,Liqiang Yuan,Zhengming Zhao,Ting Lu,Fanbo He,Gaohui Feng 전력전자학회 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.2

The time-optimal control for boost converters can achieve the minimum recovery time. However, their output voltage deviation is quite large. Since the minimum output voltage deviation and minimum recovery time cannot be obtained at the same time, a novel energy control is proposed to achieve a superior tradeoff between them in this paper. The peak value of the inductor current can be decreased as well. Its control parameter is easy to choose. When compared with the conventional control methods, the proposed control shows a better dynamic performance. Experimental results, which are in agreement with the theoretical analysis, are provided to verify the proposed control method.