This paper introduces the principles, instrumentation, implementation, and industrial applications of an on- line thermal neutron prompt- gamma element analysis system (using a 252Cf neutron source, Am- Be neutron sou...This paper introduces the principles, instrumentation, implementation, and industrial applications of an on- line thermal neutron prompt- gamma element analysis system (using a 252Cf neutron source, Am- Be neutron source, or neutron generator). The energy resolution of the system at the H prompt- gamma full- energy photopeak (2.22325 MeV) is 3.6 keV. The concentration measurement error of A12O3, Fe2O3, CaO and SiO2 is ±0.3%,±0.1%.±0.4% and ±0.4%, respectively.The system has been tested on- site at both the Shandong and the Zhengzhou Aluminum Works. Our preliminary on- site measurements confirm that the stability, reliability, measurement range, and accuracy of the system can meet the requirements of the aluminum production process. Facilitation of this measurement at aluminum plants is expected to reduce plant costs by over 3 million dollars annually through reduced energy consumption, more rapid qualification of pulps being mixed during the production process, and in reduced labor costs.展开更多
In first-year and second-year seminars, students were assigned homework requiring them to upload entries in a LP （learning portfolio） to a designated website every week. Students selected what they considered to be ...In first-year and second-year seminars, students were assigned homework requiring them to upload entries in a LP （learning portfolio） to a designated website every week. Students selected what they considered to be the most impressive lesson in a given week and reflected on ways to put the material contained in the lesson to practical use. Additionally they reflected on their experience outside the classroom in order to relate this experience to material covered in the lessons. Students had positive feelings about the LPs and recognized that the LPs helped them grow as students. But students had difficulty comprehending connections between the material presented in lessons and out-of-class experiences. Students indicated that the instructor＇s comments increased their motivation to continue working on the LPs. Instructors should make time to meet with students to discuss LPs in class, and this ideally would increase reciprocal understanding between instructors and students.展开更多
南瑞 ON-2000系统是我国第一套基于 Windows 2000操作系统、具有一体化数据采集系统和支撑平台、集多种应用功能于一体的综合调度自动化系统。文章介绍了 ON-2000的系统结构,软、硬件平台以及该系统在杨家坪供电局调度自动化系统中的功...南瑞 ON-2000系统是我国第一套基于 Windows 2000操作系统、具有一体化数据采集系统和支撑平台、集多种应用功能于一体的综合调度自动化系统。文章介绍了 ON-2000的系统结构,软、硬件平台以及该系统在杨家坪供电局调度自动化系统中的功能应用。系统投运以来,运行稳定,维护简便。展开更多
This review chronicles the development of the research on CRISPR/Cas9 (Clustered Regularly Interspaced Short Palindromic Repeat/CRISPR associated protein 9) during the last 30 years from the discovery of CRISPR sequen...This review chronicles the development of the research on CRISPR/Cas9 (Clustered Regularly Interspaced Short Palindromic Repeat/CRISPR associated protein 9) during the last 30 years from the discovery of CRISPR sequence, of biological significance and of the molecular mechanism for adaptive bacterial immunity. It describes recent works on structural and functional diversity of CRISPR/Cas systems, and on three-dimensional structure-based improvements of on-target specificity of CRISPR/Cas9 and Cpf1 endonucleases. The review ends with the application of CRISPR/Cas9 to targeted editing of plant genomes. Importantly, plant commodities modified by CRISPR-Cas9 have not been considered as genetically modified organisms (GMO) as long as foreign DNAs from plant pests were not introduced, according to the recent determination by the USDA.展开更多
The boost type power supplies are widely used in portable consumer electronics to step up the input voltage to adapt for the high voltage applications like light-emitting diode(LED) driving and liquid crystal display(...The boost type power supplies are widely used in portable consumer electronics to step up the input voltage to adapt for the high voltage applications like light-emitting diode(LED) driving and liquid crystal display(LCD) biasing.In these applications,a regulator with small volume,fewer external components and high efficiency is highly desired.This paper proposes a projected off-and on-time boost control scheme,based on which a monolithic IC with an on-chip VDMOS with 0.2 Ω on-state resistance RDS-ON was implemented in 1.5 μm bipolar-CMOS-DMOS(BCD) process.A 12 V,0.3 A boost regulator prototype is presented as well.With projected off-time and modulated on-time in continuous conduction mode(CCM),a quasi fixed frequency,which is preferred for ripple control,is realized.With projected on-time and modulated off-time in discontinuous conduction mode(DCM),pulse frequency modulation(PFM) operation,which is beneficial to light load efficiency improvement,is achieved without extra control circuitry.Measurement results show that an efficiency of 3% higher than that of a conventional method under 0.5 W output is achieved while a step load transient response comparable to that of current mode control is maintained as well.展开更多
文摘This paper introduces the principles, instrumentation, implementation, and industrial applications of an on- line thermal neutron prompt- gamma element analysis system (using a 252Cf neutron source, Am- Be neutron source, or neutron generator). The energy resolution of the system at the H prompt- gamma full- energy photopeak (2.22325 MeV) is 3.6 keV. The concentration measurement error of A12O3, Fe2O3, CaO and SiO2 is ±0.3%,±0.1%.±0.4% and ±0.4%, respectively.The system has been tested on- site at both the Shandong and the Zhengzhou Aluminum Works. Our preliminary on- site measurements confirm that the stability, reliability, measurement range, and accuracy of the system can meet the requirements of the aluminum production process. Facilitation of this measurement at aluminum plants is expected to reduce plant costs by over 3 million dollars annually through reduced energy consumption, more rapid qualification of pulps being mixed during the production process, and in reduced labor costs.
文摘In first-year and second-year seminars, students were assigned homework requiring them to upload entries in a LP （learning portfolio） to a designated website every week. Students selected what they considered to be the most impressive lesson in a given week and reflected on ways to put the material contained in the lesson to practical use. Additionally they reflected on their experience outside the classroom in order to relate this experience to material covered in the lessons. Students had positive feelings about the LPs and recognized that the LPs helped them grow as students. But students had difficulty comprehending connections between the material presented in lessons and out-of-class experiences. Students indicated that the instructor＇s comments increased their motivation to continue working on the LPs. Instructors should make time to meet with students to discuss LPs in class, and this ideally would increase reciprocal understanding between instructors and students.
文摘This review chronicles the development of the research on CRISPR/Cas9 (Clustered Regularly Interspaced Short Palindromic Repeat/CRISPR associated protein 9) during the last 30 years from the discovery of CRISPR sequence, of biological significance and of the molecular mechanism for adaptive bacterial immunity. It describes recent works on structural and functional diversity of CRISPR/Cas systems, and on three-dimensional structure-based improvements of on-target specificity of CRISPR/Cas9 and Cpf1 endonucleases. The review ends with the application of CRISPR/Cas9 to targeted editing of plant genomes. Importantly, plant commodities modified by CRISPR-Cas9 have not been considered as genetically modified organisms (GMO) as long as foreign DNAs from plant pests were not introduced, according to the recent determination by the USDA.
基金Project (No.90707002) supported by the National Natural Science Foundation of China
文摘The boost type power supplies are widely used in portable consumer electronics to step up the input voltage to adapt for the high voltage applications like light-emitting diode(LED) driving and liquid crystal display(LCD) biasing.In these applications,a regulator with small volume,fewer external components and high efficiency is highly desired.This paper proposes a projected off-and on-time boost control scheme,based on which a monolithic IC with an on-chip VDMOS with 0.2 Ω on-state resistance RDS-ON was implemented in 1.5 μm bipolar-CMOS-DMOS(BCD) process.A 12 V,0.3 A boost regulator prototype is presented as well.With projected off-time and modulated on-time in continuous conduction mode(CCM),a quasi fixed frequency,which is preferred for ripple control,is realized.With projected on-time and modulated off-time in discontinuous conduction mode(DCM),pulse frequency modulation(PFM) operation,which is beneficial to light load efficiency improvement,is achieved without extra control circuitry.Measurement results show that an efficiency of 3% higher than that of a conventional method under 0.5 W output is achieved while a step load transient response comparable to that of current mode control is maintained as well.
基金supported by NSFC of China(Nos.11671324,11471266)the Natural Science Foundation Project of CQ CSTC(No.cstc 2015jcyjA00020)the Science and Technology Project of Chongqing Education Committee(No.KJ 1600325)
