Effect of Circuit Parameters on Stability of Voltage-fed Buck-Boost Converter in Discontinuous Conduction Mode

Zhao-He Feng,Ren-Xi Gong,Qing-Yu Wang 대한전기학회 2014 Journal of Electrical Engineering & Technology Vol.9 No.4

The state transition matrix are obtained by solving state equations in terms of Laplace inverse transformation and Cayley-Hamilton theorem, and an establishment of a precise discreteiterative mapping of the voltage-fed buck-boost converter operating in discontinuous conduction mode is made. On the basis of the mapping, the converter bifurcation diagrams and Lyapunov exponent diagrams with the input voltage, the resistance, the inductance and the capacitance as the bifurcation parameters are obtained, and the effect of the parameters on the system stability is deeply studied. The results obtained show that they have a great influence on the stability of the system, and the general trend is that the increase of either the voltage-fed coefficient, input voltage or the load resistance, or the decrease of the filtering inductance, capacitance will make the system stability become poorer, and that all the parameters have a critical value, and when they are greater or less than the values, the system will go through stable 1T orbits, stable 2T orbits, 4T orbits, 8T orbits and eventually approaches chaos.

Effect of Circuit Parameters on Stability of Voltage-fed Buck-Boost Converter in Discontinuous Conduction Mode

Feng, Zhao-He,Gong, Ren-Xi,Wang, Qing-Yu The Korean Institute of Electrical Engineers 2014 Journal of Electrical Engineering & Technology Vol.9 No.4

The state transition matrix are obtained by solving state equations in terms of Laplace inverse transformation and Cayley-Hamilton theorem, and an establishment of a precise discrete-iterative mapping of the voltage-fed buck-boost converter operating in discontinuous conduction mode is made. On the basis of the mapping, the converter bifurcation diagrams and Lyapunov exponent diagrams with the input voltage, the resistance, the inductance and the capacitance as the bifurcation parameters are obtained, and the effect of the parameters on the system stability is deeply studied. The results obtained show that they have a great influence on the stability of the system, and the general trend is that the increase of either the voltage-fed coefficient, input voltage or the load resistance, or the decrease of the filtering inductance, capacitance will make the system stability become poorer, and that all the parameters have a critical value, and when they are greater or less than the values, the system will go through stable 1T orbits, stable 2T orbits, 4T orbits, 8T orbits and eventually approaches chaos.

Influence of ultrasonic impact treatment on microstructure and mechanical properties of nickel-based alloy overlayer on austenitic stainless steel pipe butt girth joint

Zhao Xilong,Ren Kangming,Lu Xinhong,He Feng,Jiang Yuekai 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.11

Ultrasonic impact treatment (UIT) is carried out on the Ni-based alloy stainless steel pipe gas tungsten arc welding (GTAW) girth weld, the differences of microstructure, microhardness and shear strength distribution of the joint before and after ultrasonic shock are studied by microhardness test and shear punch test. The results show that after UIT, the plastic deformation layer is formed on the outside surface of the Ni-based alloy overlayer, single-phase austenite and g type precipitates are formed in the overlayer, and a large number of columnar crystals are formed on the bottom side of the overlayer. The average microhardness of the overlayer increased from 221 H V to 254 H V by 14.9%, the shear strength increased from 696 MPa to 882 MPa with an increase of 26.7% and the transverse average residual stress decreased from 102.71 MPa (tensile stress) to 18.33 MPa (compressive stress), the longitudinal average residual stress decreased from 114.87 MPa (tensile stress) to 84.64 MPa (compressive stress). The fracture surface has been appeared obvious shear lip marks and a few dimples. The element migrates at the fusion boundary between the Ni-based alloy overlayer and the austenitic stainless steel joint, which is leaded to form a local martensite zone and appear hot cracks. The welded joint is cooled by FA solidification mode, which is forming a large number of late and skeleton ferrite phase with an average microhardness of 190 H V and no obvious change in shear strength. The base metal is all austenitic phase with an average microhardness of 206 H V and shear strength of 696 MPa

Parameter design method for the heat transfer performance of a fan-driven gearbox under planetary gear opening and oil-return conditions

Feng-xia Lu,Lijuan Yuan,Zhiqiang Zhao,Chun-lei Wang,He-yun Bao 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.9

On the basis of the computational fluid dynamics (CFD) method, this study calculates the surface convective heat transfer coefficients of the sun gear, planetary gear, ring gear, and bearing before and after the opening of the planetary gear of a fan-driven gearbox. A numerical fitting method is used to establish the calculation model of the convective heat transfer coefficients of the sun gear, planetary gear, ring gear, and bearing under the open-hole oilreturn condition. The convective heat transfer coefficients of each element are compared before and after the hole is bored, and the design method for the gearbox parameters with the objective of heat transfer performance is proposed. Result shows that the convective heat transfer coefficients of each element are increased after oil is returned from the hole of the planetary gear, and the change rate of the convective heat transfer coefficient of the raceway in the planetary gear bearing is the highest. When the aperture of the planetary gear is 7 mm and the number of holes is four, the heat transfer performance of the gearbox is the best. The maximum error between the convection heat transfer coefficient fitting formula value and the CFD simulation calculation result is 1.0558 %.

Paleoenvironmental changes of source rocks from the Carboniferous to Permian sediments of the Mahu Sag, Junggar Basin, China

Feng Chong,Ma Mingze,He Wenjun,Li Teng,Wu Qiuyu,Zhang Zexin,Zhao Haiyang 한국자원공학회 2020 Geosystem engineering Vol.23 No.5

There are four sets of source rocks from Carboniferous (C) to Permian in Mahu Sag, and the paleoenvironment is the decisive factor for the differences of source rocks. In order to study the controlling effect of paleoenvironmental evolution on the change of source rock properties, the major, trace elements and the total organic carbon (TOC) of 47 core samples from four sets of source rocks were tested. The results indicate that the paleoenvironmental evolution of these four sets of source rocks from C to Permian in Mahu Sag can be divided into five stages. At the end of C and the early stage of deposition of Wuerhe formation (P2w), the paleo climate became warm and humid, and the salinity of water body became small. Meanwhile, the oxidizability of water body gradually became stronger. At the deposition stage of Jiamuhe Formation (P1j), Fengcheng Formation (P1f) and the late stage of deposition of P2w, the paleo climate gradually became hot and dry, and the salinity of water body gradually increased. Meanwhile, the reducibility of water body became stronger. The paleoenvironmental factors controlling the abundance of organic matter in source rocks are different in different stages.

The effect of cobalt ions doping in ZnCr2O4 spinel oxide for the catalytic activity of methane combustion

He Jia,Shao Xiaoqiang,Su Qin,Zhao Donglin,Feng Shaojie,오원춘 한국세라믹학회 2023 한국세라믹학회지 Vol.60 No.1

A series of novel cobalt ion-doped ZnCr2−xCoxO4 (x = 0, 0.1, 0.15, 0.2) spinel oxides were synthesized with the hydrothermal method. X-ray diffraction, scanning electron microscope, specific surface area, Raman spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed desorption of oxygen, and other analytical techniques were used to characterize the structure, morphology, and catalytic performance of each sample. Experiment results showed that the doping of cobalt ion significantly promoted the phase crystallization of spinel oxide. Cobalt ion-doped ZnCr2−xCoxO4 (x = 0.1, 0.15, 0.2) nanoparticles with high specific surface area were synthesized at 773 K, with ZnCr2O4 forming a spinel phase at 1173 K. Catalytic experiments revealed that the catalytic activity of ZnCr2−xCoxO4 was effectively improved. Cobalt ion-doped ZnCr1.85Co0.15O4 catalyst catalyzed methane combustion reaction temperature at T90% (the temperature where 90% of methane was converted) of about 573 K, while the undoped ZnCr2O4 sample had the highest catalytic performance at T90% of about 773 K. The order of catalytic activity was: ZnCr1.85Co0.15O4 > ZnCr1.9Co0.1O4 > ZnCr1.8Co0.2O4 > ZnCr2O4. Results of catalytic experiments showed that the surface area of the catalyst increased after partial replacement of chromium ions by cobalt ions and that the increase in surface area of the catalyst provided more active sites, thus improving the reaction activity.

Three dimensional reconstruction and measurement of underwater spent fuel assemblies

Zhao Jianping,He Shengbo,Yang Li,Feng Chang,Wu Guoqiang,Cai Gen 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.10

It is an important work to measure the dimensions of underwater spent fuel assemblies in the nuclear power industry during the overhaul, to judging whether the spent fuel assemblies can continue to be used. In this paper, a three dimensional reconstruction method for underwater spent fuel assemblies of nuclear reactor based on linear structured light is proposed, and the topography and size measurement was carried out based on the reconstructed 3D model. Multiple linear structured light sensors are used to obtain contour size data, and the shape data of the whole spent fuel assembly can be collected by onedimensional scanning motion. In this paper, we also presented a corrected model to correct the measurement error introduced by lead-glass and water is corrected. Then, we set up an underwater measurement system for spent fuel assembly based on this method. Finally, an underwater measurement experiment is carried out to verify the 3D reconstruction ability and measurement ability of the system, and the measurement error is less than ±0.05 mm.

In-Situ Dehydration Test of Shield Spoil in Mudstone and Pebble Soil Composite Stratum

Dongping Zhao,Sixun Wen,Qi He,Feng Wang,Baihao Zhang,Zhuyan Wang,Huachang Fang,Ye Qin 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.1

When earth pressure balance (EPB) shield machine is driving in mudstone sand pebble composite stratum, it will produce a large amount of spoil with high water content. The high moisture content of spoil not only increases the difficulty and cost of transportation, but also easily leads to environmental pollution problems. In this paper, based on the shield tunnel project of Chengdu Metro Line 30, the hydraulic characteristic of shield spoil was tested, and on this basis, laboratory tests of shield spoil dehydration were carried out according to the designed precipitation scheme. The results show that: 1) The moisture content of the EPB shield spoil in the mudstone sand pebble composite stratum is as high as 55.2%, and its permeability coefficient is basically the same as that of silt, and the shield residue has the condition of in-situ dehydration. 2) The dehydration amount and residue moisture content of spoil in slope-type spoil pit showed a linear relationship with time, and the dehydration rate is slow and the total precipitation is less. In other schemes, the dehydration amount and water content of spoil increase rapidly in the first 24 hours and slowly in the later period. 3) Considering the total amount and speed of dehydration within 24 hours, the dehydration effect of spoil pit is ranked from high to low: 3D gravel cage wall spoil pit > 3D spoil pit with vacuum pumping > 3D permeable stone spoil pit > 3D spoil pit > Slope-type spoil pit. 4) 3D gravel cage wall spoil pit has high dewatering efficiency, and vacuum pumping can assist the discharge of water. It is recommended to use 3D gravel cage wall spoil pit and vacuum pumping scheme for on-site EPB tunnel spoil dewatering.

Investigation on microstructure and mechanical properties of ni-based alloy overlayer by ultrasonic impact treatment

Xilong Zhao,Kangming Ren,Xinhong Lu,Feng He,Yuekai Jiang 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.8

Ultrasonic impact treatment (UIT) was performed on the Ni-based alloy overlayer of austenitic stainless steel pipe girth weld. The difference of microstructure, microhardness and maximum shear strength distribution of the joint before and after UIT was studied by autobiographic test and shear punch test. The electrode potential data were tested by a threeelectrode electrochemical workstation and tafel curve was drawn. The results show that a grain refinement layer of about 30 um and a transition layer of about 60 um are formed in the overlayer of nickel-based alloy after UIT. Meanwhile, the transition layer has high corrosion sensitivity to oxalic acid solution, and the main precipitates in the overlayer are austenite and M23C6. In 3.5 % NaCl solution, the self-corrosion potential is -432 mV. The average microhardness of the overlayer of nickel-based alloy is 270 HV, which is 18.9 % higher than that of the sample without UIT. In the meantime, the maximum shear strength of nickel-based alloy is 955 MPa, which is 9.6 % higher than the sample without UIT. It is found that the ferrite is mainly lath and skeleton with no obvious change under UIT or not. Meanwhile, an average microhardness is 191 HV, and shear strength is 678 MPa. The microstructure of the welded joint is mainly consisted of austenite phase and ferrite phase, and FA solidification mode has been a major influence in the welding process. At the boundary between overlayer and circumferential welded joint of 304 austenitic stainless steel, reheat cracks in this area are occurred easily. Due to the migration of carbon, local martensite bands will be formed which will lead to large heterogeneity of microhardness.

Research and utilization of medicinal insects in China

Ying FENG,Min ZHAO,Zhao HE,Zhiyong CHEN,Long SUN 한국곤충학회 2009 Entomological Research Vol.39 No.5

The research and utilization of medicinal insects in China is introduced briefly in this paper. Medicinal insects have been used to treat human diseases from ancient times. There are approximately 300 medicinal insects species distributed in 70 genera, 63 families and 14 orders at present. An estimated 1700 traditional Chinese medicine prescriptions include medicinal insects or insect-derived crude drugs. Many insect-derived compounds have been studied and show efficient therapeutic functions. Techniques for mass rearing and cultivation of medicinal insects have been developed in order to have sufficient quantities of medicinal insects. Suggestions are made towards the uses of medicinal insects and it is proposed that insects will be a main resource for the future discovery of new drugs.