Research on High-Frequency Isolation Type of Dual-PWM Variable Frequency Speed Regulation

Liu Jiangong,Liu Wenzhuang,Wang Yiying,Zhang Guilin,Chen Longfei 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.4

Frequency converters are widely used in power grids, motor speed regulation, and other fields. When the voltage level is above low voltage and the workspace is limited, traditional frequency converters mostly adopt the power frequency transformer to connect to the power grid. But the structure has the problems of bigger volume and complexity. To solve these problems, this paper proposes a three-stage topology structure of high-frequency isolation type of dual-PWM variable frequency speed regulation based on three-phase rectification, single active isolated DC/DC converter, and three-phase inverter, and analyzes its power transmission characteristics in detail. And a new method that combines high-frequency electrical isolation and frequency conversion is discussed. Then, the control strategies of the new method are also described. Lastly, simulation and experiment are constructed to verify the new design method is correct and feasible, and that the steady and dynamic characteristics of the three-stage high-frequency isolated frequency converter are better.

Real-time life and degradation prediction of ceramic filter tube based on state-space model

Liu Longfei 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.10

Bayesian estimation theory was used in this study to establish a state-space model of the ceramic filter tube degradation process. The model continuously integrates the latest residual pressure drop to update its own parameters, then the change rate of the degradation state, remaining life, and failure probability density distribution of the tube in real time. The residual pressure drop of the Shell Coal Gas Process was analyzed to find that the model results converge to real values as the residual pressure drop increases. The change rate of the ceramic filter tube degradation state calculated by the model gradually decreases over time, which is consistent with the initial rapid increase in residual pressure drop followed by a slower increase in later stages of operation. The amount of particle deposition in the ceramic filter tube wall under different operating times was measured and predicted; the predictions are consistent with the state-space model results. The state-space model also reflects variations in filter tube performance degradation caused by emergent conditions such as leakage or fractures, as it does not make stationarity assumptions for the degradation process.

Multi-objective optimization model of high-temperature ceramic filter

Longfei Liu,Zhongli Ji,Xin Luan 한국화학공학회 2020 Korean Journal of Chemical Engineering Vol.37 No.5

Ceramic filters have been widely used in industrial engineering, such as the Shell coal gasification process (SCGP) and Integrated gasification combined cycle (IGCC), where the performance of the ceramic filter is achieved by the pulse jet. Residual pressure drop and gas consumption are directly related to reverse-flow pulse (RFP) pressure. However, in the process of operation, the RFP pressure is too large and gas consumption is too high. In this study, the effects of RFP pressures on filter’s cleaning efficiency, residual pressure drop, and gas consumption were investigated on a ceramic filter. Within a certain range, the cleaning efficiency gradually increased with increased RFP pressure. When the RFP pressure reached a certain value, the cleaning efficiency did not increase with increased pressure, showing a quadratic relationship between cleaning efficiency and RFP pressure. The residual pressure drop and RFP pressure were also in a quadratic relationship. Besides, the gas consumption increased linearly as increased RFP pressure according to the theoretical model. Based on the research results, a multi-objective optimization model of a ceramic filter was established with the cleaning efficiency as a constraint condition, gas consumption and residual pressure drop as the optimization objectives. A fuzzy decision-making method was used to solve the optimization model and calculate the residual pressure drop and gas consumption, from which the optimal RFP pressure was obtained.

Experimental study on vortex-induced motions of a semi-submersible with square columns and pontoons at different draft conditions and current incidences

Liu, Mingyue,Xiao, Longfei,Lu, Haining,Xiao, Xiaolong The Society of Naval Architects of Korea 2017 International Journal of Naval Architecture and Oc Vol.9 No.3

The Vortex-induced Motions (VIM) phenomenon of semi-submersibles is relevant for the fatigue life of moorings and risers. Model tests regarding the VIM behavior of a semi-submersible with four square columns were conducted in order to investigate the effects of the current incidence and the aspect ratio of the immerged column. The experimental results show that the largest transverse amplitudes are around 70% of the column width at $30^{\circ}$ and $45^{\circ}$ incidences in a range of reduced velocities from 5 to 8 when the aspect ratio of the immerged column is 1.90. The largest yaw motion occurs at $0^{\circ}$ incidence with the peak value around $4.5^{\circ}$. Similar characteristics of the VIM response are observed for the semi-submersible with aspect ratios of 1.90 and 1.73. When the aspect ratio decreases 50% to 0.87, 30% decrease in the peak transverse amplitudes can be seen.

Experimental investigation of flow characteristics around four square-cylinder arrays at subcritical Reynolds numbers

Liu, Mingyue,Xiao, Longfei,Yang, Lijun The Society of Naval Architects of Korea 2015 International Journal of Naval Architecture and Oc Vol.7 No.5

The Deep Draft Semi-Submersible (DDS) concepts are known for their favourable vertical motion performance. However, the DDS may experience critical Vortex-Induced Motion (VIM) stemming from the fluctuating forces on the columns. In order to investigate the current-induced excitation forces of VIM, an experimental study of flow characteristics around four square-section cylinders in a square configuration is presented. A number of column spacing ratios and array attack angles were considered to investigate the parametric influences. The results comprise flow patterns, drag and lift forces, as well as Strouhal numbers. It is shown that both the drag and lift forces acting on the cylinders are slightly different between the various L/D values, and the fluctuating forces peak at L/D = 4.14. The lift force of downstream cylinders reaches its maximum at around ${\alpha}=15^{\circ}$. Furthermore, the flow around circular-section-cylinder arrays is also discussed in comparison with that of square cylinders.

On the association analysis of CNV data: a fast and robust family-based association method

Liu, Meiling,Moon, Sanghoon,Wang, Longfei,Kim, Sulgi,Kim, Yeon-Jung,Hwang, Mi Yeong,Kim, Young Jin,Elston, Robert C.,Kim, Bong-Jo,Won, Sungho BioMed Central 2017 BMC bioinformatics Vol.18 No.1

<P><B>Background</B></P><P>Copy number variation (CNV) is known to play an important role in the genetics of complex diseases and several methods have been proposed to detect association of CNV with phenotypes of interest. Statistical methods for CNV association analysis can be categorized into two different strategies. First, the copy number is estimated by maximum likelihood and association of the expected copy number with the phenotype is tested. Second, the observed probe intensity measurements can be directly used to detect association of CNV with the phenotypes of interest.</P><P><B>Results</B></P><P>For each strategy we provide a statistic that can be applied to extended families. The computational efficiency of the proposed methods enables genome-wide association analysis and we show with simulation studies that the proposed methods outperform other existing approaches. In particular, we found that the first strategy is always more efficient than the second strategy no matter whether copy numbers for each individual are well identified or not. With the proposed methods, we performed genome-wide CNV association analyses of hematological trait, hematocrit, on 521 Korean family samples.</P><P><B>Conclusions</B></P><P>We found that statistical analysis with the expected copy number is more powerful than the statistic with the probe intensity measurements regardless of the accuracy of the estimation of copy numbers.</P><P><B>Electronic supplementary material</B></P><P>The online version of this article (doi:10.1186/s12859-017-1622-z) contains supplementary material, which is available to authorized users.</P>

A Gene Cluster for the Biosynthesis of Dibenzodioxocinons in the Endophyte Pestalotiopsis microspora, a Taxol Producer

( Yanjie Liu ),( Longfei Chen ),( Qiaohong Xie ),( Xi Yu ),( Anqing Duan ),( Yamin Lin ),( Biyun Xiang ),( Xiaoran Hao ),( Wanwan Chen ),( Xudong Zhu ) 한국미생물생명공학회(구 한국산업미생물학회) 2019 Journal of microbiology and biotechnology Vol.29 No.10

The fungal products dibenzodioxocinones promise a novel class of inhibitors against cholesterol ester transfer protein (CEPT). Knowledge as to their biosynthesis is scarce. In this report, we characterized four more dibenzodioxocinones, which along with a previously described member pestalotiollide B, delimit the dominant spectrum of secondary metabolites in P. microspora. Through mRNA-seq profiling in gα1Δ, a process that halts the production of the dibenzodioxocinones, a gene cluster harboring 21 genes including a polyketide synthase, designated as pks8, was defined. Disruption of genes in the cluster led to loss of the compounds, concluding the anticipated role in the biosynthesis of the chemicals. The biosynthetic route to dibenzodioxocinones was temporarily speculated. This study reveals the genetic basis underlying the biosynthesis of dibenzodioxocinone in fungi, and may facilitate the practice for yield improvement in the drug development arena.

Experimental investigation of flow characteristics around four square-cylinder arrays at subcritical Reynolds numbers

Mingyue Liu,Longfei Xiao,Lijun Yang 대한조선학회 2015 International Journal of Naval Architecture and Oc Vol.7 No.5

The Deep Draft Semi-Submersible (DDS) concepts are known for their favourable vertical motion performance. However, the DDS may experience critical Vortex-Induced Motion (VIM) stemming from the fluctuating forces on the columns. In order to investigate the current-induced excitation forces of VIM, an experimental study of flow characteristics around four square-section cylinders in a square configuration is presented. A number of column spacing ratios and array attack angles were considered to investigate the parametric influences. The results comprise flow patterns, drag and lift forces, as well as Strouhal numbers. It is shown that both the drag and lift forces acting on the cylinders are slightly different between the various L/D values, and the fluctuating forces peak at L/D = 4.14. The lift force of downstream cylinders reaches its maximum at around α = 15°. Furthermore, the flow around circularsection- cylinder arrays is also discussed in comparison with that of square cylinders.

Experimental study on vortex-induced motions of a semi-submersible with square columns and pontoons at different draft conditions and current incidences

Mingyue Liu,Longfei Xiao,Haining Lu,Xiaolong Xiao 대한조선학회 2017 International Journal of Naval Architecture and Oc Vol.9 No.3

The Vortex-induced Motions (VIM) phenomenon of semi-submersibles is relevant for the fatigue life of moorings and risers. Model tests regarding the VIM behavior of a semi-submersible with four square columns were conducted in order to investigate the effects of the current incidence and the aspect ratio of the immerged column. The experimental results show that the largest transverse amplitudes are around 70% of the column width at 30 and 45 incidences in a range of reduced velocities from 5 to 8 when the aspect ratio of the immerged column is 1.90. The largest yaw motion occurs at 0 incidence with the peak value around 4.5. Similar characteristics of the VIM response are observed for the semi-submersible with aspect ratios of 1.90 and 1.73. When the aspect ratio decreases 50% to 0.87, 30% decrease in the peak transverse amplitudes can be seen.

Numerical studies on flow-induced motions of a semi-submersible with three circular columns

Tian Chenling,Liu Mingyue,Xiao Longfei,Lu Haining,Wang Jin 대한조선학회 2021 International Journal of Naval Architecture and Oc Vol.13 No.1

The semi-submersible with three circular columns is an original concept of efficient multifunctional platform, which can be used for marginal oil, gas field, and Floater of Wind Turbines (FOWT). However, under certain flow conditions, especially in uniform current with specific velocities, the eddies will alternatively form and drop behind columns, resulting in the fluctuating lift force and drag force. Consequently, the semi-submersible will subject to the Flow-Induced Motions (FIM). Based on the Detached Eddy Simulation (DES) method, the numerical studies were carried out to understand the FIM characteristics of the three-column semi-submersible at two different parameters, i.e., current incidences (0, 30, and 60-incidences) and reduced velocities (4 Ur 14). The results indicate that the lock-in range of 6 Ur 10 for the transverse motions is presented, and the largest transverse nondimensional nominal amplitude is observed at 60-incidence, with a value of Ay=D ¼ 0:481. The largest yaw amplitude Ayaw is around 3.0 at 0-incidence in the range of 8 Ur 12. The motion magnitude is basically the same as that of a four-column semi-submersible. However, smaller responses are presented compared to those of the three-column systems revealing the mitigation effect of the pontoon on FIM.