Spectrum measurement modelling and prediction based on wavelets

Chen, Yunfei,Oh, Hee-Seok IET 2016 IET COMMUNICATIONS Vol.10 No.16

<P>In this study, a new spectrum measurement modelling method is proposed for several important frequency bands by using the Daubechies wavelets. On the basis of this method, spectrum measurement prediction is also proposed by using regression. Unlike most previous works that model or predict the occupancy rate of the frequency band of interest, this study models and predicts the power measurements directly to remove the dependence of the model on the challenging detection threshold and also to provide more comprehensive descriptions of the licenced user signals for performance improvement in cognitive radios (CRs). Numerical results show that the new spectrum models have acceptable accuracies. They also show that the proposed spectrum measurement prediction method tracks the trend of the true values well. Therefore, these results are very useful in CR designs.</P>

The stacked over-expression of FPS, CYP71AV1 and CPR genes leads to the increase of artemisinin level in Artemisia annua L.

Yunfei Chen,Qian Shen,Yueyue Wang,Tao Wang,Shaoyan Wu,Ling Zhang,Xu Lu,Fangyuan Zhang,Weimin Jiang,Bo Qiu,Erdi Gao,Xiaofen Sun,Kexuan Tang 한국식물생명공학회 2013 Plant biotechnology reports Vol.7 No.3

Artemisinin is an endoperoxide sesquiterpenelactone isolated from the aerial parts of Artemisia annua L.,and is presently the most potent anti-malarial drug. Owingto the low yield of artemisinin from A. annua as well as thewidespread application of artemisinin-based combinationtherapy recommended by the World Health Organization,the global demand for artemisinin is substantially increasingand is therefore rendering artemisinin in short supply. An economical way to increase artemisinin production is toincrease the content of artemisinin in A. annua. In thisstudy, three key genes in the artemisinin biosynthesispathway, encoding farnesyl diphosphate synthase, amorpha-4, 11-diene C-12 oxidase and its redox partner cytochromeP450 reductase, were over-expressed in A. annuathrough Agrobacterium-mediated transformation. Thetransgenic lines were confirmed by Southern blotting andthe over-expressions of the genes were demonstrated byreal-time PCR assays. The HPLC analysis showed that theartemisinin contents in transgenic lines were increasedsignificantly, with the highest one found to be 3.6-foldhigher (2.9 mg/g FW) than that of the control. Theseresults demonstrate that multigene engineering is aneffective way to enhance artemisinin content in A. annua.

The Optimization of Genetic Algorithm in Wireless Sensor Network Coverage

Wengen Gao,Qigong Chen,Ming Jiang,Yunfei Li,Shinong Wang 보안공학연구지원센터(IJSIP) 2015 International Journal of Signal Processing, Image Vol.8 No.1

According to the maximum coverage problem in wireless sensor networks, GA algorithm combined with the standard processing method can improve the network coverage based on, but there is a risk of falling into local optimum, and costs more computation time. On the condition of analysis and proof of the effectiveness by the employment of normalization processing to resolve coding redundancy of MCSDP, further details of the evaluate conditions are proposed, and new parent selection mechanism is introduced, which both are verified by compared experiments. The experiment results show that the optimization processing method proposed in this paper retains the characteristics of existing methods, and has better optimization performance and improves the network coverage rate as well as calculation speed, which verifies the effectiveness and superiority of the method proposed in this paper.

Running safety of metro train over a high-pier bridge subjected to fluctuating crosswind in mountain city

Yunfei Zhang,Jun Li,Zhaowei Chen,Xiangyang Xu 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.76 No.2

Due to the rugged terrain, metro lines in mountain city across numerous wide rivers and deep valleys, resulting in instability of high-pier bridge and insecurity of metro train subjected to fluctuating crosswind. To ensure the safe operation in metro lines in mountain cities, running safety of the metro train over the high-pier bridge under crosswind is analyzed in this paper. Firstly, the dynamic model of the wind-train-bridge (WTB) system is built, in which the speed-up effect of crosswind is fully considered. On the basis of time domain analysis, the basic characteristics of the WTB system with high-pier are analyzed. Afterwards, the dynamic responses varies with train speed and wind speed are calculated, and the safety zone of metro train over a high-pier bridge subjected to fluctuating crosswind in mountain city is determined. The results indicate that, fluctuating crosswind triggers drastic vibration to the metro train and high-pier bridges, which in turn causes running instability of the train. For this reason, the corresponding safety zone for metro train running on the high-pier is proposed, and the metro traffic on the high-pier bridge should be closed as the mean wind speed of standard height reaches 9 m/s (15.6 m/s for the train).

Dynamic analysis of metro vehicle traveling on a high-pier viaduct under crosswind in Chongqing

Yunfei Zhang,Jun Li,Zhaowei Chen,Xiangyang Xu 한국풍공학회 2019 Wind and Structures, An International Journal (WAS Vol.29 No.5

Due to the rugged terrain, metro lines in mountain city across numerous wide rivers and deep valleys, resulting in instability of high-pier bridge and insecurity of metro train under crosswind. Compared with the conditions of no-wind, crosswind triggers severer vibration of the dynamic system; compared with the short-pier viaduct, the high-pier viaduct has worse stability under crosswind. For these reasons, the running safety of the metro vehicle traveling on a high-pier viaduct under crosswind is analyzed to ensure the safe operation in metro lines in mountain cities. In this paper, a dynamic model of the metro vehicle-track-bridge system under crosswind is established, in which crosswind loads model considering the condition of wind zone are built. After that, the evaluation indices and the calculation parameters have been selected, moreover, the basic characteristics of the dynamic system with high-pier under crosswind are analyzed. On this basis, the response varies with vehicle speed and wind speed are calculated, then the corresponding safety zone is determined. The results indicate that, crosswind triggers drastic vibration to the metro vehicle and high-pier viaduct, which in turn causes running instability of the vehicle. The corresponding safety zone for metro vehicle traveling on the high-pier is proposed, and the metro traffic on the high-pier bridge under crosswind should not exceed the corresponding limited vehicle speed to ensure the running safety.

Electrical and Mechanical Properties of Epoxy Composites Reinforced with Kaolin-Coated Basalt Fibers

He-Chen Liu,Yu Sun,Mingjia Zhang,Yun-Peng Liu,Yunfei Yu,Hong Yu 한국섬유공학회 2023 Fibers and polymers Vol.24 No.1

Basalt fiber (BF) is appropriately used for manufacturing insulating rods because of its excellent aging resistance, hightemperature resistance, electrical insulation, and mechanical strength. However, due to the inert structure on the surface ofthe fiber, the close bonding between the fiber and the resin is hindered. The low bonding strength of the fiber/resin interfacewill significantly reduce the mechanical and insulation properties of the composite, which limits its application in electricalequipment such as insulating rods and insulators. Therefore, this paper attempts to improve the surface roughness of BF byusing Kaolin to strengthen the bonding strength between BF and matrix resin, and analyze and study the mechanical and insulationproperties of the composites before and after modification. The Kaolin content coated on BF ranged from 0.5 to 2 wt%,and the composites modified by 1.5wt%Kaolin (1.5-wt%-K-BFRP) exhibited excellent electrical insulation and mechanicalperformance. Compared with untreated BFRP, the electrical breakdown strength and flashover voltage of 1.5-wt%-K-BFRPincreased by 18.49% and 10.69%, elevated to the 20.57 kV/mm and 13.04 kV, respectively, and the dielectric loss decreasedby 49%, down to 0.83%. The above results indicate that modified BFRP has excellent insulation strength and is suitable forthe manufacture of insulating devices. Furthermore, the bending strength, bending modulus, tensile strength, and interlayershear strength of 1.5-wt%-K-BFRP increased by 67.59%, 21%, 14.56%, and 103.7%, respectively, compared with untreatedBFRP, reach to 465.17 MPa, 31.49 GPa, 562.3 MPa, 26.44 MPa.

Cdyl2-60aa encoded by CircCDYL2 accelerates cardiomyocyte death by blocking APAF1 ubiquitination in rats

Deng Yunfei,Zeng Xiaochen,Lv Yifei,Qian Zhiyuan,Guo Peijie,Liu Yi,Chen Shaoliang 생화학분자생물학회 2023 Experimental and molecular medicine Vol.55 No.-

The loss of cardiomyocytes (CMs) after myocardial infarction (MI) is widely acknowledged to initiate the development of heart failure (HF). Herein, we found that circCDYL2 (583 nt) derived from chromodomain Y-like 2 (Cdyl2) is significantly upregulated in vitro (oxygen-glucose deprivation (OGD)-treated CMs) and in vivo (failing heart post-MI) and can be translated into a polypeptide termed Cdyl2-60aa (~7 kDa) in the presence of internal ribosomal entry sites (IRES). Downregulation of circCDYL2 significantly decreased the loss of OGD-treated CMs or the infarcted area of the heart post-MI. Additionally, elevated circCDYL2 significantly accelerated CM apoptosis via Cdyl2-60aa. We then discovered that Cdyl2-60aa could stabilize protein apoptotic protease activating factor-1 (APAF1) and promote CM apoptosis; heat shock protein 70 (HSP70) mediated APAF1 degradation in CMs by ubiquitinating APAF1, which Cdyl2-60aa could competitively block. In conclusion, our work substantiated the claim that circCDYL2 could promote CM apoptosis via Cdyl2-60aa, which enhanced APAF1 stability by blocking its ubiquitination by HSP70, suggesting that it is a therapeutic target for HF post-MI in rats.

MICROWAVE-ASSISTED HYDROTHERMAL SYNTHESIS AND LUMINESCENCE PROPERTIES OF Eu3+-DOPED CdTe QUANTUM DOTS

HU CHEN,YUNFEI LIU,YINONG LU,HONGMING WU,HAO QIAN,BAOSHUAI HUANG 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2014 NANO Vol.9 No.4

The Eu3+-doped CdTe quantum dots (QDs) have been successfully synthesized in aqueous phase through microwave-assisted hydrothermal method. The as-prepared products were characterized by X-ray diffraction (XRD) technique, high-resolution transmission electron microscope (HRTEM), energy dispersive spectrum (EDS), X-ray photoclectron spectrum (XPS), UV-visble (UV-Vis) absorption spectrum and photoluminescence (PL). As the results show, the average sizes of the cubic phase CdTe and CdTe:1%Eu3+ are an average size of 3.7 nm and 3.5 nm, respectively. The average lattice parameter of CdTe:Eu3+ decreases with increasing Eu3+ ions concentration. Furthermore, compared to green emission of the host CdTe, the CdTe:1%Eu3+ presents additional orange fluorescence emission of Eu3+ ions. Recombination luminescence color is almost located in the yellow region of the CIE 1931, and the CIE 1931 coordinate is (0.448, 0.513). The effect of different Eu3+ doping concentration on the luminescence of CdTe:Eu3+ QDs was discussed in detail. It suggests that CdTe:Eu3+ QDs are potential phosphors for white light-emitting materials.

Wireless Energy-Harvesting Cognitive Radio with Feature Detectors

( Yan Gao ),( Yunfei Chen ),( Zhibin Xie ),( Guobing Hu ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.10

The performances of two commonly used feature detectors for wireless energy-harvesting cognitive radio systems are compared with the energy detector under energy causality and collision constraints. The optimal sensing duration is obtained by analyzing the effect of the detection threshold on the average throughput and collision probability. Numerical examples show that the covariance detector has the optimal sensing duration depending on an appropriate choice of the detection threshold, but no optimal sensing duration exists for the ratio of average energy to minimum eigenvalue detector.

Back-Calculation Method of Rock Mass Pressure in a Shallow-Buried Super Large-Span Tunnel Using Upper-Bench CD Method

Yanbin Luo,Yunfei Wu,Jianxun Chen,Fangfang Dong,Weiwei Liu,Lijun Chen,Yao Li,Zhou Shi 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.1

Rock mass pressure has always been a research hotspot in the field of tunnel engineering, especially in the super large-span tunnel, which is characterized by flat section, large excavation span, and complex stress field. Based on the Letuan Tunnel (a bi-directional tunnel with eight traffic lanes) of Binlai expressway expansion project in Shandong Province, China, this paper focused on the calculation method of rock mass pressure and the evolution law of load release in the construction process of the super large-span tunnel excavated by upper-bench central diaphragm (CD) method. Based on field measured data of Letuan Tunnel, the deformation behavior of primary lining and the distribution state of rock mass pressure during the tunnel construction were analyzed. According to the bearing mode of supporting structure, the mechanical models of different construction stages were established. Then, the rock mass pressures in different construction stages were back-calculated using mechanical models and compared with the measured values, and the evolution law of load release during the tunnel construction was discussed. The study results show that the tunnel deformation and rock mass pressure were significantly affected by the construction process and support form, and the excavation span was the key factor affecting the stability of rock mass. For the shallow-buried super large-span tunnel constructed by upper-bench CD method, the primary support of upper bench was under eccentric pressure. The comparison between the back-calculated value and the field measured value indicated that they were similar, and the average relative error was 17.23%. According to the concept of load release coefficient proposed in this paper, the load release coefficient after the pilot tunnel ahead (Part I) excavation reached 63%, and the load release coefficient after the pilot tunnel behind excavation (Part II) was 37%, which means that the rock mass pressure of Part I is increased about 59% due to the excavation of Part II.