At present, with the development and progress of science and technology, social productivity is constantly improving, and the role of frequency conversion technology in coal mine mechanical and electrical equipment co...At present, with the development and progress of science and technology, social productivity is constantly improving, and the role of frequency conversion technology in coal mine mechanical and electrical equipment control is becoming more and more obvious. Frequency conversion technology has the advantages of regulation and control, etc. The application of this technology in mines can promote the production efficiency of transportation and ventilation. Frequency conversion technology is widely used in modern life. Applying frequency conversion technology to mining equipment in modern coal mine mechanical and electrical engineering can ensure the smooth operation of mechanical and electrical equipment to a great extent. Therefore, this paper will focus on the application of frequency conversion technology in modern coal mine electromechanical engineering.展开更多
Power supply transformation technology is a required course for new energy major, which is a comprehensive course. Under the traditional teaching mode, students have no concept of waveform, which brings many difficult...Power supply transformation technology is a required course for new energy major, which is a comprehensive course. Under the traditional teaching mode, students have no concept of waveform, which brings many difficulties to teaching and experiment. A power transformation technology based on PSIM simulation is proposed. Before class, students solve the task of building the simulation model, and then introduce the knowledge points. This can not only make up for the lack of experimental facilities and also stimulate students interest in learning. Classroom teaching practice shows that this method can effectively improve the teaching and experiment efficiency.展开更多
In the past years, bistatic Radar Cross Section (RCS) characteristic has been caught increasing attention. The paper presents a bistatic RCS measurement system of full-size goals, which uses photoelectric conversion t...In the past years, bistatic Radar Cross Section (RCS) characteristic has been caught increasing attention. The paper presents a bistatic RCS measurement system of full-size goals, which uses photoelectric conversion technology to solve the problem that excessive electrical signal attenuation exits because of the large distance between sending and receiving antenna. The paper analyzes the basic principle of photoelectric conversion and RCS measurement system, applies photoelectric conversion technology to RCS measurement system, and tests whether RCS measurement system works well while using photoelectric conversion technology. The test results show that the system can efficiently obtain the bistatic RCS characteristic of full-size targets.展开更多
Fracturing equipment is the core device in shale gas reservoir stimulation.As domestic shale gas exploration and development steps into deep layers,the development of fracturing technology puts forward higher requirem...Fracturing equipment is the core device in shale gas reservoir stimulation.As domestic shale gas exploration and development steps into deep layers,the development of fracturing technology puts forward higher requirements for relevant equipment.Electric drive is an important devel-opment direction of fracturing equipment technology.In this paper,the technical progress of electric drive fracturing equipment in China and abroad was investigated.It is shown that a high-power frequency conversion system is the key technology to determine the performance of electric drive fracturing equipment.After the adaptability of the high-power frequency conversion technology to electric drive fracturing equipment was analyzed,based on the fracturing operation of Model 2500 electric drive fracturing trucks in the Weiyuan Block of the Sichuan Basin for shale gas reservoir stimulation,electric drive and diesel-driven fracturing equipment were comparatively analyzed from the aspects of economic and technical in-dicators.And the following research results were obtained.First,compared with a diesel-driven fracturing truck of the same power,an electric drive fracturing truck can realize a full power coverage and a continuous adjustment of output displacement,and can better meet the operation re-quirements of fracturing process for a precise control of the pumping displacement,while reducing the power cost by 68%and the equipment purchase cost by 10e20%.Second,compared with the skid mounted equipment,an electric drive fracturing truck has a better transport performance,being suitable for the fracturing well sites with poor road conditions,such as loess gullies,hills and mountains.It is suggested that the following development direction of the electric drive fracturing equipment should focus on the improvement of single machine power density.In addition,it is recommended to enhance the basic studies on high-pressure and high-power semiconductor devices and make a good plan for the power demand of shale gas platform construction in advance,so as to give a better play to the operating cost advantage of electric drive fracturing equipment.展开更多
Dear Editor,Allele conversion technology has broad application value in plant breeding.Here,we report a user-friendly allele conversion technology based on clustered regularly interspaced short palindromic repeats(CRI...Dear Editor,Allele conversion technology has broad application value in plant breeding.Here,we report a user-friendly allele conversion technology based on clustered regularly interspaced short palindromic repeats(CRISPR)-Cas9 and hyperrecombination lines(HRLs)(Figure 1A).Many agronomically important traits are controlled by single nucleotide polymorphisms(SNPs),insertions or deletions,and other types of small variations between alleles.Traditionally,breeders have relied on backcrossing and selection to introduce a useful allele into the genome of another variety.展开更多
Biomass supplies about 80% of the energy needs for cooking and heating in rura<span>l Ghana. It is predominantly used in traditional and inefficient for</span>ms (firewood and<span> charcoal), which ...Biomass supplies about 80% of the energy needs for cooking and heating in rura<span>l Ghana. It is predominantly used in traditional and inefficient for</span>ms (firewood and<span> charcoal), which presents environmental and health concerns. In order to better the living standard in rural Ghana, efforts must be made to provide modern energy services. Most rural communities in Ghana are so remote that an extension of the national grid is uneconomical, hence biomass electricity provides a viable alternative. Biomass is pivotal to the socio-economic</span> development of rural Ghana due to its easy accessibility and enormous potential in the production of varied energy forms. In this paper, a comprehensive review of biomass resources, biomass energy conversion technologies and bioenergy production potential for rural development in Ghana is provided. The most important feedstock from an energy perspective was found to be crop residues. Based on 2017 statistics, Ghana has a theoretical potential of 623.84 PJ of energy from agricultural crop residues and 64.27 PJ of energy from livestock production. Evidence from literature suggests that biomass gasification is the best conversion technology to expand electricity access rate for rural households in Ghana. The paper concludes that although ample biomass resources exist, cocoa pod husks (CPH) which is very common in rural Ghana can be pelletized and used as feedstock for rural power generation system</span><span style="font-family:"">s</span><span style="font-family:"">.展开更多
The conversion of CO_(2)into high-value fuels and chemicals has garnered research interest worldwide.The conversion and utilization of CO_(2)has become one of the most urgent tasks for society.In this context,using so...The conversion of CO_(2)into high-value fuels and chemicals has garnered research interest worldwide.The conversion and utilization of CO_(2)has become one of the most urgent tasks for society.In this context,using solar energy to convert CO_(2)into high-value fuels such as CH4 and CH_(3)OH has extremely high potential application value.Herein,the research progress and results of applying various photocatalysts in photocatalytic CO_(2)reduction with various novel catalysts were reviewed.Furthermore,strategies for improving photocatalytic performance were reviewed.Finally,improving the catalytic mechanism of catalysts and designing novel highactivity,high-stability catalysts through comprehensive exploration of the reaction mechanism were suggested to meet the future requirements of industrial production.展开更多
Carbon nanotube field effect transistor（CNFET） shows lower threshold voltage and smaller leakage current in comparison to its CMOS counterpart. In this paper, two kinds of CNFET-based rectifiers, full-wave rectifier...Carbon nanotube field effect transistor（CNFET） shows lower threshold voltage and smaller leakage current in comparison to its CMOS counterpart. In this paper, two kinds of CNFET-based rectifiers, full-wave rectifiers and voltage doubler rectifiers are presented for biomedical implantable applications. Based on the standard 32 nm CNFET model, the electrical performance of CNFET rectifiers is analyzed and compared. Simulation results show the voltage conversion efficiency（VCE） and power conversion efficiency（PCE） achieve 70.82% and 72.49% for CNFET full-wave rectifiers and 56.60% and 61.17% for CNFET voltage double rectifiers at typical 1.0 V input voltage excitation, which are higher than that of CMOS design. Moreover, considering the controllable property of CNFET threshold voltage, the effect of various design parameters on the electrical performance is investigated.It is observed that the VCE and PCE of CNFET rectifier increase with increasing CNT diameter and number of tubes. The proposed results would provide some guidelines for design and optimization of CNFET-based rectifier circuits.展开更多
文摘At present, with the development and progress of science and technology, social productivity is constantly improving, and the role of frequency conversion technology in coal mine mechanical and electrical equipment control is becoming more and more obvious. Frequency conversion technology has the advantages of regulation and control, etc. The application of this technology in mines can promote the production efficiency of transportation and ventilation. Frequency conversion technology is widely used in modern life. Applying frequency conversion technology to mining equipment in modern coal mine mechanical and electrical engineering can ensure the smooth operation of mechanical and electrical equipment to a great extent. Therefore, this paper will focus on the application of frequency conversion technology in modern coal mine electromechanical engineering.
文摘Power supply transformation technology is a required course for new energy major, which is a comprehensive course. Under the traditional teaching mode, students have no concept of waveform, which brings many difficulties to teaching and experiment. A power transformation technology based on PSIM simulation is proposed. Before class, students solve the task of building the simulation model, and then introduce the knowledge points. This can not only make up for the lack of experimental facilities and also stimulate students interest in learning. Classroom teaching practice shows that this method can effectively improve the teaching and experiment efficiency.
文摘In the past years, bistatic Radar Cross Section (RCS) characteristic has been caught increasing attention. The paper presents a bistatic RCS measurement system of full-size goals, which uses photoelectric conversion technology to solve the problem that excessive electrical signal attenuation exits because of the large distance between sending and receiving antenna. The paper analyzes the basic principle of photoelectric conversion and RCS measurement system, applies photoelectric conversion technology to RCS measurement system, and tests whether RCS measurement system works well while using photoelectric conversion technology. The test results show that the system can efficiently obtain the bistatic RCS characteristic of full-size targets.
基金Project supported by CNPC's Major Engineering Technology Field Test Project“Integration and field test of online monitoring system of Model 7000 electric fracturing skid and diesel-driven fracturing unit”(No.:2019F-30)Shaanxi Province Postdoctoral Science Foundation Project“Research on key technologies of intelligent control system of electric drive fracturing device”(No.:2018BSHQYXMZZ04).
文摘Fracturing equipment is the core device in shale gas reservoir stimulation.As domestic shale gas exploration and development steps into deep layers,the development of fracturing technology puts forward higher requirements for relevant equipment.Electric drive is an important devel-opment direction of fracturing equipment technology.In this paper,the technical progress of electric drive fracturing equipment in China and abroad was investigated.It is shown that a high-power frequency conversion system is the key technology to determine the performance of electric drive fracturing equipment.After the adaptability of the high-power frequency conversion technology to electric drive fracturing equipment was analyzed,based on the fracturing operation of Model 2500 electric drive fracturing trucks in the Weiyuan Block of the Sichuan Basin for shale gas reservoir stimulation,electric drive and diesel-driven fracturing equipment were comparatively analyzed from the aspects of economic and technical in-dicators.And the following research results were obtained.First,compared with a diesel-driven fracturing truck of the same power,an electric drive fracturing truck can realize a full power coverage and a continuous adjustment of output displacement,and can better meet the operation re-quirements of fracturing process for a precise control of the pumping displacement,while reducing the power cost by 68%and the equipment purchase cost by 10e20%.Second,compared with the skid mounted equipment,an electric drive fracturing truck has a better transport performance,being suitable for the fracturing well sites with poor road conditions,such as loess gullies,hills and mountains.It is suggested that the following development direction of the electric drive fracturing equipment should focus on the improvement of single machine power density.In addition,it is recommended to enhance the basic studies on high-pressure and high-power semiconductor devices and make a good plan for the power demand of shale gas platform construction in advance,so as to give a better play to the operating cost advantage of electric drive fracturing equipment.
基金supported by the National Natural Science Foundation of China(32272727)the Technology Innovation Program of the Chinese Academy of Agricultural Sciences(CAAS-ASTIP-IVFCAAS).
文摘Dear Editor,Allele conversion technology has broad application value in plant breeding.Here,we report a user-friendly allele conversion technology based on clustered regularly interspaced short palindromic repeats(CRISPR)-Cas9 and hyperrecombination lines(HRLs)(Figure 1A).Many agronomically important traits are controlled by single nucleotide polymorphisms(SNPs),insertions or deletions,and other types of small variations between alleles.Traditionally,breeders have relied on backcrossing and selection to introduce a useful allele into the genome of another variety.
文摘Biomass supplies about 80% of the energy needs for cooking and heating in rura<span>l Ghana. It is predominantly used in traditional and inefficient for</span>ms (firewood and<span> charcoal), which presents environmental and health concerns. In order to better the living standard in rural Ghana, efforts must be made to provide modern energy services. Most rural communities in Ghana are so remote that an extension of the national grid is uneconomical, hence biomass electricity provides a viable alternative. Biomass is pivotal to the socio-economic</span> development of rural Ghana due to its easy accessibility and enormous potential in the production of varied energy forms. In this paper, a comprehensive review of biomass resources, biomass energy conversion technologies and bioenergy production potential for rural development in Ghana is provided. The most important feedstock from an energy perspective was found to be crop residues. Based on 2017 statistics, Ghana has a theoretical potential of 623.84 PJ of energy from agricultural crop residues and 64.27 PJ of energy from livestock production. Evidence from literature suggests that biomass gasification is the best conversion technology to expand electricity access rate for rural households in Ghana. The paper concludes that although ample biomass resources exist, cocoa pod husks (CPH) which is very common in rural Ghana can be pelletized and used as feedstock for rural power generation system</span><span style="font-family:"">s</span><span style="font-family:"">.
基金Financial support for carrying out this work was provided by the Doctoral Research Foundation of Weifang University(2022BS13).
文摘The conversion of CO_(2)into high-value fuels and chemicals has garnered research interest worldwide.The conversion and utilization of CO_(2)has become one of the most urgent tasks for society.In this context,using solar energy to convert CO_(2)into high-value fuels such as CH4 and CH_(3)OH has extremely high potential application value.Herein,the research progress and results of applying various photocatalysts in photocatalytic CO_(2)reduction with various novel catalysts were reviewed.Furthermore,strategies for improving photocatalytic performance were reviewed.Finally,improving the catalytic mechanism of catalysts and designing novel highactivity,high-stability catalysts through comprehensive exploration of the reaction mechanism were suggested to meet the future requirements of industrial production.
基金Project supported by the National Natural Science Foundation of China(Nos.61131001,61404077,61571248)the Science and Technology Fund of Zhejiang Province(No.2015C31090)+2 种基金the Natural Science Foundation of Ningbo(No.2014A610147)State Key Laboratory of ASIC&System(No.2015KF006)the K.C.Wong Magna Fund in Ningbo University
文摘Carbon nanotube field effect transistor（CNFET） shows lower threshold voltage and smaller leakage current in comparison to its CMOS counterpart. In this paper, two kinds of CNFET-based rectifiers, full-wave rectifiers and voltage doubler rectifiers are presented for biomedical implantable applications. Based on the standard 32 nm CNFET model, the electrical performance of CNFET rectifiers is analyzed and compared. Simulation results show the voltage conversion efficiency（VCE） and power conversion efficiency（PCE） achieve 70.82% and 72.49% for CNFET full-wave rectifiers and 56.60% and 61.17% for CNFET voltage double rectifiers at typical 1.0 V input voltage excitation, which are higher than that of CMOS design. Moreover, considering the controllable property of CNFET threshold voltage, the effect of various design parameters on the electrical performance is investigated.It is observed that the VCE and PCE of CNFET rectifier increase with increasing CNT diameter and number of tubes. The proposed results would provide some guidelines for design and optimization of CNFET-based rectifier circuits.
