Hydrothermal Synthesis of La-Mn-hexaaluminates for the Catalytic Combustion of Methane

Xu, Jinguang,Zhijian Tian,Wang, Junwei,Yunpeng Xu,Zhusheng Xu,Lin, Liwn 한국화학공학회 2003 Korean Journal of Chemical Engineering Vol.20 No.2

Hydrothermal synthesis by using urea hydrolysis at 1.0~3.0MPa and 120~130℃ was employed to prepare Mn-substituted hexaaluminate catalysts for methane combustion. The results from DTA-MS demonstrated that CO^2-_3 and OH^- anions co-exist in the hydrothermal reaction. XRD reveals that the components of carbonates of carbonates and hydroxides in the hydrothermal reaction are more favorable than those in the(NH_4)_2CO_3 co-precipitation for the formation of the Mn-substituted hexaaluminate phase. After calcination at 1,200℃ for 2h, LaMnAl_11O_19 is the major phase of the catalyst prepared by the hydrothermal synthesis method while LaAlO_3 is the major one of the catalysts prepared by NH_4OH and (NH_4)_2CO_3 co-precipitation. The catalyst prepared by hydrothermal synthesis has higher activity than that prepared by NH_4OH and (NH_4)CO_3 co-precipitation. The major reason is that more Mn^2+ ions have incorporated into the hexaaluminate lattice. The effect of drying methods on the formation of hexaaluminate phase was also discussed.

GOP Adaptation Coding of H.264/SVC Based on Precise Positions of Video Cuts

( Yunpeng Liu ),( Renfang Wang ),( Huixia Xu ),( Dechao Sun ) 한국인터넷정보학회 2014 KSII Transactions on Internet and Information Syst Vol.8 No.7

Hierarchical B-frame coding was introduced into H.264/SVC to provide temporal scalability and improve coding performance. A content analysis-based adaptive group of picture structure (AGS) can further improve the coding efficiency, but damages the inter-frame correlation and temporal scalability of hierarchical B-frame to different degrees. In this paper, we propose a group of pictures (GOP) adaptation coding method based on the positions of video cuts. First, the cut positions are accurately detected by the combination of motion coherence (MC) and mutual information (MI); then the GOP is adaptively and proportionately set by the analysis of MC in one scene. In addition, we propose a binary tree algorithm to achieve the temporal scalability of any size of GOP. The results for test sequences and real videos show that the proposed method reduces the bit rate by up to about 15%, achieves a performance gain of about 0.28-1.67 dB over a fixed GOP, and has the advantages of better transmission resilience and video summaries.

A Novel Compensator for Eliminating DC Magnetizing Current Bias in Hybrid Modulated Dual Active Bridge Converters

Yunpeng Yao,Shen Xu,Weifeng Sun,Shengli Lu 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.5

This paper proposes a compensator to eliminate the DC bias of inductor current. This method utilizes an average-current sensing technique to detect the DC bias of inductor current. A small signal model of the DC bias compensation loop is derived. It is shown that the DC bias has a one-pole relationship with the duty cycle of the left side leading lag. By considering the pole produced by the dual active bridge (DAB) converter and the pole produced by the average-current sensing module, a one-pole-one-zero digital compensation method is given. By using this method, the DC bias is eliminated, and the stability of the compensation loop is ensured. The performance of the proposed compensator is verified with a 1.2-㎾ DAB converter prototype.

Variable speed sliding mode control of magnetic suspension linear synchronous motor based on feedback linearization

Yunpeng Sun,Yipeng Lan,Xiaolei Shi,Zelai Xu,Cheng Lei 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.11

In the high-speed and high-precision magnetic suspension linear synchronous motor, the non-linear coupling between armature current, suspension height and horizontal velocity, as well as the uncertain factors such as load disturbance, which will have many adverse effects on the control system. To solve these problems, this paper uses a feedbacklinearized control method. Through coordinate transformation and state feedback, the nonlinear model of motor affine is decoupled and linearized into three independent linear subsystems of straight axis current subsystem, horizontal speed subsystem and suspension height subsystem. In order to reduce the dependence of feedback linearization control on linear motor mathematical model and improve the robustness of servo system, so as to realize decoupling control of magnetic suspension linear synchronous motor, a variable speed reaching law sliding mode controller is designed on the basis of linearization model. Simulation and experimental results show that the dynamic and static performance of the system is enhanced significantly by using the proposed control strategy.

A Novel Compensator for Eliminating DC Magnetizing Current Bias in Hybrid Modulated Dual Active Bridge Converters

Yao, Yunpeng,Xu, Shen,Sun, Weifeng,Lu, Shengli The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.5

This paper proposes a compensator to eliminate the DC bias of inductor current. This method utilizes an average-current sensing technique to detect the DC bias of inductor current. A small signal model of the DC bias compensation loop is derived. It is shown that the DC bias has a one-pole relationship with the duty cycle of the left side leading lag. By considering the pole produced by the dual active bridge (DAB) converter and the pole produced by the average-current sensing module, a one-pole-one-zero digital compensation method is given. By using this method, the DC bias is eliminated, and the stability of the compensation loop is ensured. The performance of the proposed compensator is verified with a 1.2-kW DAB converter prototype.

Two-Dimensional POMDP-Based Opportunistic Spectrum Access in Time-Varying Environment with Fading Channels

Wang, Yumeng,Xu, Yuhua,Shen, Liang,Xu, Chenglong,Cheng, Yunpeng The Korea Institute of Information and Commucation 2014 Journal of communications and networks Vol.16 No.2

In this research, we study the problem of opportunistic spectrum access (OSA) in a time-varying environment with fading channels, where the channel state is characterized by both channel quality and the occupancy of primary users (PUs). First, a finite-state Markov channel model is introduced to represent a fading channel. Second, by probing channel quality and exploring the activities of PUs jointly, a two-dimensional partially observable Markov decision process framework is proposed for OSA. In addition, a greedy strategy is designed, where a secondary user selects a channel that has the best-expected data transmission rate to maximize the instantaneous reward in the current slot. Compared with the optimal strategy that considers future reward, the greedy strategy brings low complexity and relatively ideal performance. Meanwhile, the spectrum sensing error that causes the collision between a PU and a secondary user (SU) is also discussed. Furthermore, we analyze the multiuser situation in which the proposed single-user strategy is adopted by every SU compared with the previous one. By observing the simulation results, the proposed strategy attains a larger throughput than the previous works under various parameter configurations.

Two-Dimensional POMDP-Based Opportunistic Spectrum Access in Time-Varying Environment with Fading Channels

Yumeng Wang,Yuhua Xu,Liang Shen,Chenglong Xu,Yunpeng Cheng 한국통신학회 2014 Journal of communications and networks Vol.16 No.2

In this research, we study the problem of opportunisticspectrum access (OSA) in a time-varying environment with fadingchannels, where the channel state is characterized by bothchannel quality and the occupancy of primary users (PUs). First,a finite-state Markov channel model is introduced to represent afading channel. Second, by probing channel quality and exploringthe activities of PUs jointly, a two-dimensional partially observableMarkov decision process framework is proposed for OSA. In addition,a greedy strategy is designed, where a secondary user selects achannel that has the best-expected data transmission rate to maximizethe instantaneous reward in the current slot. Compared withthe optimal strategy that considers future reward, the greedy strategybrings low complexity and relatively ideal performance. Meanwhile,the spectrum sensing error that causes the collision betweena PU and a secondary user (SU) is also discussed. Furthermore,we analyze the multiuser situation in which the proposed singleuserstrategy is adopted by every SU compared with the previousone. By observing the simulation results, the proposed strategy attainsa larger throughput than the previous works under variousparameter configurations.

Neutron-irradiated effect on the thermoelectric properties of Bi2Te3-based thermoelectric leg

Zhao Huanyu,Liu Kai,Xu Zhiheng,Liu Yunpeng,Tang Xiaobin 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.8

Thermoelectric (TE) materials working in radioisotope thermoelectric generators are irradiated by neutrons throughout its service; thus, investigating the neutron irradiation stability of TE devices is necessary. Herein, the influence of neutron irradiation with fluences of 4.56 1010 and 1 1013 n/cm2 by pulsed neutron reactor on the electrical and thermal transport properties of n-type Bi2Te2.7Se0.3 and ptype Bi0.5Sb1.5Te3 thermoelectric alloys prepared by cold-pressing and molding is investigated. After neutron irradiation, the properties of thermoelectric materials fluctuate, which is related to the material type and irradiation fluence. Different from p-type thermoelectric materials, neutron irradiation has a positive effect on n-type Bi2Te2.7Se0.3 materials. This result might be due to the increase of carrier mobility and the optimization of electrical conductivity. Afterward, the effects of p-type and n-type TE devices with different treatments on the output performance of TE devices are further discussed. The positive and negative effects caused by irradiation can cancel each other to a certain extent. For TE devices paired with p-type Bi0.5Sb1.5Te3 and n-type Bi2Te2.7Se0.3 thermoelectric legs, the generated power and conversion efficiency are stable after neutron irradiation.

Expression of Human FGF18 by Fusion with Oleosin in Arabidopsis thaliana Seeds

Chao Jiang,Xiaokun Li,Feng Zhai,Nuo Xu,Jing Yang,Yunpeng Wang,Libo Jin,Haiyan Li 한국식물학회 2018 Journal of Plant Biology Vol.61 No.3

Expression of recombinant human fibroblast growthfactor 18 (hFGF18) in mammalian cells and Escherichia colihas been extensively used for fundamental research andclinical applications, but they are difficult, expensive. Theexpression of recombinant proteins fused to oleosin proteinhave distinct advantages, such as safety, ease, low cost. Sowe have expressed hFGF18 fused to oleosin protein in the oilbodies of Arabidopsis thaliana (A. thaliana) and screen theproliferation effect of NIH3T3 cells. The vector of oleosinhFGF18fusion gene was constructed and transformed intowild A. thaliana. Transformed A. thaliana lines were obtainedby the floral dip method and confirmed using polymerasechain reaction (PCR). The PCR results indicated that theoleosin-hFGF18 fusion gene was integrated into the A. thaliana genome. The oil bodies expression of oleosin-hFGF18was confirmed by sodium dodecyl sulfate polyacrylamidegel electrophoresis and western blotting. The biologicalactivity showed that oil bodies expressing oleosin-hFGF18could stimulate the proliferation of NIH3T3 cells.

A Bacillus coagulans and its Application in Pine Pollen Fermentation

Shanyan Yang,Yaoyao Wu,Chubo Luo,Zhihong Di,Yunpeng Wu,Jie Zhang,Yaomei Xu 한국식품과학회 2015 Food Science and Biotechnology Vol.24 No.6

In the study, a potential L-lactic acid-producing bacillus-strain LT1 was isolated. It was identified as Bacillus coagulans based on its morphological, physiological, biochemical properties, and phylogenetic similarity of 16S rDNA. The fermentation conditions of pine pollen by strain LT1 were optimized using Box-Behnken design and response surface methodology. Optimum values of the tested variables for production of viable counts were an inoculum size of 9.22%, temperature= 49.21℃, and an initial pH of 6.82. Under optimized conditions, the viable count was 5.49×109 CFU/mL. Finally, the single factor experiment as preliminary research for fermentation product treatment was performed.