A useful mid course guidance law for long range multi purpose missiles is proposed. The law consists of two parts. One is used in the horizontal guidance plane, and the other in the vertical guidance plane. The mid ...A useful mid course guidance law for long range multi purpose missiles is proposed. The law consists of two parts. One is used in the horizontal guidance plane, and the other in the vertical guidance plane. The mid course is combined with variable structure proportional navigation in the homing phase. Simulation results show that the proposed guidance law can meet the demands for starting up the homing phase and so the handing over between mid course guidance and terminal guidance can be carried out successfully.展开更多
Urban expansion brought by the rapid progress of urbanization has caused many problems in China. It is a significant issue to evaluate the extent of urban expansion and to make appropriate controls over the sprawl of ...Urban expansion brought by the rapid progress of urbanization has caused many problems in China. It is a significant issue to evaluate the extent of urban expansion and to make appropriate controls over the sprawl of urban areas. With a comparative study of international experiences, this article analyzed the mechanism and consequences of urban expansion, reviewed the typical planning and financial policies adopted by other countries for controlling urban sprawl, and discussed the suitable densities of urban areas. The analysis results suggested that Chinese cities have no better choice but compact urban forms. To achieve the goal of compact development, intensive use of public transportation and high proportion of collective houses should be encouraged, and 60–100 m2 per capita is recommended as the reasonable range of urban density in large cities.展开更多
Engineered Corynebacterium glutamicum was constructed for L-ornithine production by disrupting genes of argF and proB to prevent the flux away from L-ornithine.Effect of the inactivation of 2-oxoglutarate de-hydrogena...Engineered Corynebacterium glutamicum was constructed for L-ornithine production by disrupting genes of argF and proB to prevent the flux away from L-ornithine.Effect of the inactivation of 2-oxoglutarate de-hydrogenase complex(ODHC) on L-ornithine production was also investigated.It was found that the inactivation of ODHC by knockout of the kgd gene enhanced L-ornithine production.The engineered C.glutamicum ATCC13032(ΔargFΔproBΔkgd) produced L-ornithine up to 4.78 g·L-1 from 0.24 g·L-1 of the wild-type strain.In order to understand the mechanism of L-ornithine production in C.glutamicum ATCC13032(ΔargFΔproBΔkgd) and find out new strategies for further enhancing L-ornithine production,the comparative proteome between the wild-type and the engineered strain was analyzed.L-Ornithine overproduction in the engineered strain was related to the up-regulation of the expression levels of enzymes involved in L-ornithine biosynthesis pathway and down-regulation of the expression levels of proteins involved in pentose phosphate pathway.The overexpression of genes in the upstream pathway of glutamate to increase the availability of endogenous glutamate may further in-crease ornithine production in the engineered C.glutamicum and the ornithine synthesis enzymes(ArgCJBD) may not be the limiting enzymes in the engineered C.glutamicum.展开更多
The degradation of p-nitrotoluene by O3/H2O2 process in a bubble contact column was investigated. Effects of the molar ratio of hydrogen peroxide to ozone,pH value and t-butanol on the oxidation process were discussed...The degradation of p-nitrotoluene by O3/H2O2 process in a bubble contact column was investigated. Effects of the molar ratio of hydrogen peroxide to ozone,pH value and t-butanol on the oxidation process were discussed. It was found that the proper H2O2/O3 molar ratio for the degradation of p-nitrotoluene was around 0.6, different pH values and the presence of t-butanol highly influenced the removal efficiency of p-nitrotoluene. 5-methyl-2-nitrophenol, 2-methyl-5-nitrophenol, (4-nitrophenyl) methanol, 5-(hydroxymethyl)-2-nitro phenol, acetic acid, 2-methylpropane diacid and 2-(hydroxylmethyl)propane diacid were identified as degradation intermediates and products through GC-MS. Radical reaction mechanism and degradation pathway were proposed based on the results of experiments. It is deduced that the benzene ring of p-nitrotoluene can be only destroyed by hydroxyl radicals through a polyhydroxy intermediate pathway. Then unstable polyhydroxy intermediates can be oxidized to different acids with low molecular weight rapidly.展开更多
This article presents the development of a robotic controller for technical training, academic teaching, and research. The controller was designed to interact from 1 to 6 DOF （degrees of freedom） serial robotic arms...This article presents the development of a robotic controller for technical training, academic teaching, and research. The controller was designed to interact from 1 to 6 DOF （degrees of freedom） serial robotic arms, actuated by brushed DC （direct current） servomotors equipped with incremental encoders. Controller architecture is based on four components： a processor, a reconfigurable FPGA （field-programmable gate array）, measurement I/O hardware and software. Functionality of the robotic controller has been proved by means of the interaction with an SCARA （selective compliance assembly robot arm）. The proposed controller presents the potential to teach technical courses （like robotics, control, electronics and programming） and to implement and validate advanced control algorithms.展开更多
The successful bid for the 2022 Winter Olympics has provided a new opportunity for the popularization of ice-snow sports and making improvements in the efficiency of ice-snow tourism in China.Taking Zhangjiakou City i...The successful bid for the 2022 Winter Olympics has provided a new opportunity for the popularization of ice-snow sports and making improvements in the efficiency of ice-snow tourism in China.Taking Zhangjiakou City in Hebei Province as the research object and using questionnaire analysis and the structural equation model(SEM),this paper examined several hypotheses of the relationship between tourist experiential value and tourist loyalty in the context of ice-snow tourism,and a mediation analysis was conducted to explore the moderating role of travel companions.The results show that:(1)The functional value,emotional value and social value have significant positive effects on tourist loyalty;(2)Tourist satisfaction is a partial mediator between functional value,emotional value,social value and tourist loyalty,and a full mediator between cognitive value and tourist loyalty;and(3)Travel companions play a significant moderating role in the influence of emotional value on tourist loyalty.Based on these findings,several suggestions are put forward for the high-quality development of ice-snow tourism in China,including developing ice-snow family tourism products,building an ice-snow brand with winter Olympics characteristics,constructing the ice-snow industrial system,and cultivating ice-snow culture.展开更多
Needs analysis as the central force of EAP has received insufficient practice, resulting in dissatisfactory pedagogy. This study proposes a framework of CEAPNA （comprehensive EAP needs analysis）, and illustrates how...Needs analysis as the central force of EAP has received insufficient practice, resulting in dissatisfactory pedagogy. This study proposes a framework of CEAPNA （comprehensive EAP needs analysis）, and illustrates how the framework helps to shape learning-centered EAP pedagogy. The CEAPNA survey covered 452 undergraduates and 83 faculty members from science and engineering departments, and was triangulated with the researchers＇ retrospection of seven years of pedagogical practice. Major findings in the study suggest multiple sources as a must in a comprehensive and accurate analysis of EAP learner needs. In the meantime, the specificity of learner needs addresses EAP practitioners＇ endeavors to specify these needs in various dimensions, so as to negotiate a satisfactory balance between language, cognition and affect in EAP pedagogy. Due to realistic constraints in specifying and balancing the needs, this paper wishes to oblige with a conceptual interpretation as well as a pedagogical retrospection.展开更多
文摘A useful mid course guidance law for long range multi purpose missiles is proposed. The law consists of two parts. One is used in the horizontal guidance plane, and the other in the vertical guidance plane. The mid course is combined with variable structure proportional navigation in the homing phase. Simulation results show that the proposed guidance law can meet the demands for starting up the homing phase and so the handing over between mid course guidance and terminal guidance can be carried out successfully.
基金supported by Natural Science Foundation of China (Grant no. 40671063)
文摘Urban expansion brought by the rapid progress of urbanization has caused many problems in China. It is a significant issue to evaluate the extent of urban expansion and to make appropriate controls over the sprawl of urban areas. With a comparative study of international experiences, this article analyzed the mechanism and consequences of urban expansion, reviewed the typical planning and financial policies adopted by other countries for controlling urban sprawl, and discussed the suitable densities of urban areas. The analysis results suggested that Chinese cities have no better choice but compact urban forms. To achieve the goal of compact development, intensive use of public transportation and high proportion of collective houses should be encouraged, and 60–100 m2 per capita is recommended as the reasonable range of urban density in large cities.
基金Supported by the National Natural Science Foundation of China (30970089,20876181,20831006)the Natural Science Foundation of Guangdong Province (9351027501000003)
文摘Engineered Corynebacterium glutamicum was constructed for L-ornithine production by disrupting genes of argF and proB to prevent the flux away from L-ornithine.Effect of the inactivation of 2-oxoglutarate de-hydrogenase complex(ODHC) on L-ornithine production was also investigated.It was found that the inactivation of ODHC by knockout of the kgd gene enhanced L-ornithine production.The engineered C.glutamicum ATCC13032(ΔargFΔproBΔkgd) produced L-ornithine up to 4.78 g·L-1 from 0.24 g·L-1 of the wild-type strain.In order to understand the mechanism of L-ornithine production in C.glutamicum ATCC13032(ΔargFΔproBΔkgd) and find out new strategies for further enhancing L-ornithine production,the comparative proteome between the wild-type and the engineered strain was analyzed.L-Ornithine overproduction in the engineered strain was related to the up-regulation of the expression levels of enzymes involved in L-ornithine biosynthesis pathway and down-regulation of the expression levels of proteins involved in pentose phosphate pathway.The overexpression of genes in the upstream pathway of glutamate to increase the availability of endogenous glutamate may further in-crease ornithine production in the engineered C.glutamicum and the ornithine synthesis enzymes(ArgCJBD) may not be the limiting enzymes in the engineered C.glutamicum.
基金Sponsored by the National Natural Science Foundation of China(Grant No.50378028)
文摘The degradation of p-nitrotoluene by O3/H2O2 process in a bubble contact column was investigated. Effects of the molar ratio of hydrogen peroxide to ozone,pH value and t-butanol on the oxidation process were discussed. It was found that the proper H2O2/O3 molar ratio for the degradation of p-nitrotoluene was around 0.6, different pH values and the presence of t-butanol highly influenced the removal efficiency of p-nitrotoluene. 5-methyl-2-nitrophenol, 2-methyl-5-nitrophenol, (4-nitrophenyl) methanol, 5-(hydroxymethyl)-2-nitro phenol, acetic acid, 2-methylpropane diacid and 2-(hydroxylmethyl)propane diacid were identified as degradation intermediates and products through GC-MS. Radical reaction mechanism and degradation pathway were proposed based on the results of experiments. It is deduced that the benzene ring of p-nitrotoluene can be only destroyed by hydroxyl radicals through a polyhydroxy intermediate pathway. Then unstable polyhydroxy intermediates can be oxidized to different acids with low molecular weight rapidly.
文摘This article presents the development of a robotic controller for technical training, academic teaching, and research. The controller was designed to interact from 1 to 6 DOF （degrees of freedom） serial robotic arms, actuated by brushed DC （direct current） servomotors equipped with incremental encoders. Controller architecture is based on four components： a processor, a reconfigurable FPGA （field-programmable gate array）, measurement I/O hardware and software. Functionality of the robotic controller has been proved by means of the interaction with an SCARA （selective compliance assembly robot arm）. The proposed controller presents the potential to teach technical courses （like robotics, control, electronics and programming） and to implement and validate advanced control algorithms.
基金The National Social Science Foundation of China(20BJY199).
文摘The successful bid for the 2022 Winter Olympics has provided a new opportunity for the popularization of ice-snow sports and making improvements in the efficiency of ice-snow tourism in China.Taking Zhangjiakou City in Hebei Province as the research object and using questionnaire analysis and the structural equation model(SEM),this paper examined several hypotheses of the relationship between tourist experiential value and tourist loyalty in the context of ice-snow tourism,and a mediation analysis was conducted to explore the moderating role of travel companions.The results show that:(1)The functional value,emotional value and social value have significant positive effects on tourist loyalty;(2)Tourist satisfaction is a partial mediator between functional value,emotional value,social value and tourist loyalty,and a full mediator between cognitive value and tourist loyalty;and(3)Travel companions play a significant moderating role in the influence of emotional value on tourist loyalty.Based on these findings,several suggestions are put forward for the high-quality development of ice-snow tourism in China,including developing ice-snow family tourism products,building an ice-snow brand with winter Olympics characteristics,constructing the ice-snow industrial system,and cultivating ice-snow culture.
基金supported by the National Social Science Funding Project (17BYY109)~~
文摘Needs analysis as the central force of EAP has received insufficient practice, resulting in dissatisfactory pedagogy. This study proposes a framework of CEAPNA （comprehensive EAP needs analysis）, and illustrates how the framework helps to shape learning-centered EAP pedagogy. The CEAPNA survey covered 452 undergraduates and 83 faculty members from science and engineering departments, and was triangulated with the researchers＇ retrospection of seven years of pedagogical practice. Major findings in the study suggest multiple sources as a must in a comprehensive and accurate analysis of EAP learner needs. In the meantime, the specificity of learner needs addresses EAP practitioners＇ endeavors to specify these needs in various dimensions, so as to negotiate a satisfactory balance between language, cognition and affect in EAP pedagogy. Due to realistic constraints in specifying and balancing the needs, this paper wishes to oblige with a conceptual interpretation as well as a pedagogical retrospection.
