This study aimed to identify and to analyze characteristics of top-cited articles published in the Web of Science chemical engineering subject category from 1899 to 2011.Articles that have been cited more than 100 tim...This study aimed to identify and to analyze characteristics of top-cited articles published in the Web of Science chemical engineering subject category from 1899 to 2011.Articles that have been cited more than 100 times were assessed regarding publication outputs,and distribution of outputs in journals.Five bibliometric indicators were used to evaluate source countries,institution and authors.A new indicator,Y-index,was created to assess quantity and quality of contribution to articles.Results showed that 3828 articles,published between 1931 and 2010,had been cited at least 100 times.Among them 54% published before 1991,and 49% top-cited articles originated from US.The top eight productive institutions were all located in US.The top journals were Journal of Catalysis,AIChE Journal,Chemical Engineering Science and Journal of Membrane Science.Y-index was successfully applied to evaluate publication character of authors,institutions,and countries/regions.展开更多
The optimal control design for singularly perturbed time-delay systems affected by external distur-bances is considered.Based on the decomposition theory of singular perturbation,the system is decom-posed into a fast ...The optimal control design for singularly perturbed time-delay systems affected by external distur-bances is considered.Based on the decomposition theory of singular perturbation,the system is decom-posed into a fast subsystem without time-delay and a slow time-delay subsystem with disturbances.Theoptimal disturbances rejection control law of the slow subsystem is obtained by using the successive ap-proximation approach(SAA)and feedforward compensation method.Further,the feedforward and feed-back composite control(FFCC)law for the original problem is developed.The FFCC law consists of lin-ear analytic terms and a time-delay compensation term which is the limit of the solution sequence of theadjoint vector equations.A disturbance observer is introduced to make the FFCC law physically realiz-able.Numerical examples show that the proposed algorithm is effective.展开更多
English majors＇ B.A. （Bachelor of Arts） thesis writing is an important part and test of the students＇ four-year undergraduate education. It lays solid foundation for their future study and work. Yet serious proble...English majors＇ B.A. （Bachelor of Arts） thesis writing is an important part and test of the students＇ four-year undergraduate education. It lays solid foundation for their future study and work. Yet serious problems exist during the process. The author of the paper collects and analyzes the 289 titles of English majors＇ B.A. writing in the recent two years in Changchun University, China. The results of the analysis reveal that almost 40% of the titles are on literature every year and among them there are some similar titles. In view of this situation, the author first explores the reasons that caused those problems. One of the important reasons is that the increasing of the supervisors and reference materials cannot keep the pace of the expanding of students＇ numbers. The author, after that, makes some reflections on those problems, then proposes five practical supervising strategies, and makes some relevant suggestions for English major＇s thesis writing. Meanwhile some other related problems in thesis writing in China are also discussed.展开更多
CFD （computational fluid dynamics） is following the trend of CAD and FEA （finite element analysis） to undergraduate education especially with recent advances in commercial codes. It will soon take its place as an ...CFD （computational fluid dynamics） is following the trend of CAD and FEA （finite element analysis） to undergraduate education especially with recent advances in commercial codes. It will soon take its place as an expected skill for new engineering graduates. CFD was added as a component to an experiment in a junior level fluid mechanics course. The objectives were to introduce CFD, as an analysis tool, to the students and to support the theoretical concepts of the course. The students were asked to complete an experimental two-dimensional study for a wing in a wind tunnel, to use CFD to simulate the flow, and to predict the aerodynamic lift using CFD as well as the experimentally obtained pressure distribution. In addition, they had to compare their results to published data for the studied wing. Details of the course, the wind tunnel test and the CFD simulations are presented. Samples from the students＇ work are used in the discussion. The lab activities were successfully completed by the students and the learning objectives were well addressed. One of the valuable outcomes from this lab was the opportunity for the students to integrate multiple fluid mechanics analysis tools and learn about the limits for each tool. CFD also enhanced the learning in the lab activities and increased students＇ interest in the subject.展开更多
By using the method of least square linear fitting to analyze data do not exist errors under certain conditions, in order to make the linear data fitting method that can more accurately solve the relationship expressi...By using the method of least square linear fitting to analyze data do not exist errors under certain conditions, in order to make the linear data fitting method that can more accurately solve the relationship expression between the volume and quantity in scientific experiments and engineering practice, this article analyzed data error by commonly linear data fitting method, and proposed improved process of the least distance squ^re method based on least squares method. Finally, the paper discussed the advantages and disadvantages through the example analysis of two kinds of linear data fitting method, and given reasonable control conditions for its application.展开更多
We report an experimental investigation on the impact of the freezing rate on the cryo-deformation and cryo-damage of cementitious materials.Saturated,dried and air-entrained mortar specimens are subjected to laborato...We report an experimental investigation on the impact of the freezing rate on the cryo-deformation and cryo-damage of cementitious materials.Saturated,dried and air-entrained mortar specimens are subjected to laboratory freeze-thaw cycles under three freezing rates without moisture exchange with the environment.In addition to basic mechanical properties and pore distribution,the measurement is also effectuated for freezing expansion,residual deformation of the specimens in each cycle.From the results it is observed that a high freezing rate does augment the freezing expansion of material while the cryo-damage is more important for a low freezing rate.Accordingly,both the freezing rate and freezing duration should be taken into account for the cyro-damage extent of cementitious materials.展开更多
文摘This study aimed to identify and to analyze characteristics of top-cited articles published in the Web of Science chemical engineering subject category from 1899 to 2011.Articles that have been cited more than 100 times were assessed regarding publication outputs,and distribution of outputs in journals.Five bibliometric indicators were used to evaluate source countries,institution and authors.A new indicator,Y-index,was created to assess quantity and quality of contribution to articles.Results showed that 3828 articles,published between 1931 and 2010,had been cited at least 100 times.Among them 54% published before 1991,and 49% top-cited articles originated from US.The top eight productive institutions were all located in US.The top journals were Journal of Catalysis,AIChE Journal,Chemical Engineering Science and Journal of Membrane Science.Y-index was successfully applied to evaluate publication character of authors,institutions,and countries/regions.
基金the National Natural Science Foundation of China(No.60574023,40776051)the Natural Science Foundation of Zhejiang Province(No.Y107232)+1 种基金the Scientific Research Found of Zhejiang Provincial Education Department(No.Y200702660)the 123 Talent Funding Project of China Jiliang University(No.2006RC17)
文摘The optimal control design for singularly perturbed time-delay systems affected by external distur-bances is considered.Based on the decomposition theory of singular perturbation,the system is decom-posed into a fast subsystem without time-delay and a slow time-delay subsystem with disturbances.Theoptimal disturbances rejection control law of the slow subsystem is obtained by using the successive ap-proximation approach(SAA)and feedforward compensation method.Further,the feedforward and feed-back composite control(FFCC)law for the original problem is developed.The FFCC law consists of lin-ear analytic terms and a time-delay compensation term which is the limit of the solution sequence of theadjoint vector equations.A disturbance observer is introduced to make the FFCC law physically realiz-able.Numerical examples show that the proposed algorithm is effective.
文摘English majors＇ B.A. （Bachelor of Arts） thesis writing is an important part and test of the students＇ four-year undergraduate education. It lays solid foundation for their future study and work. Yet serious problems exist during the process. The author of the paper collects and analyzes the 289 titles of English majors＇ B.A. writing in the recent two years in Changchun University, China. The results of the analysis reveal that almost 40% of the titles are on literature every year and among them there are some similar titles. In view of this situation, the author first explores the reasons that caused those problems. One of the important reasons is that the increasing of the supervisors and reference materials cannot keep the pace of the expanding of students＇ numbers. The author, after that, makes some reflections on those problems, then proposes five practical supervising strategies, and makes some relevant suggestions for English major＇s thesis writing. Meanwhile some other related problems in thesis writing in China are also discussed.
文摘CFD （computational fluid dynamics） is following the trend of CAD and FEA （finite element analysis） to undergraduate education especially with recent advances in commercial codes. It will soon take its place as an expected skill for new engineering graduates. CFD was added as a component to an experiment in a junior level fluid mechanics course. The objectives were to introduce CFD, as an analysis tool, to the students and to support the theoretical concepts of the course. The students were asked to complete an experimental two-dimensional study for a wing in a wind tunnel, to use CFD to simulate the flow, and to predict the aerodynamic lift using CFD as well as the experimentally obtained pressure distribution. In addition, they had to compare their results to published data for the studied wing. Details of the course, the wind tunnel test and the CFD simulations are presented. Samples from the students＇ work are used in the discussion. The lab activities were successfully completed by the students and the learning objectives were well addressed. One of the valuable outcomes from this lab was the opportunity for the students to integrate multiple fluid mechanics analysis tools and learn about the limits for each tool. CFD also enhanced the learning in the lab activities and increased students＇ interest in the subject.
文摘By using the method of least square linear fitting to analyze data do not exist errors under certain conditions, in order to make the linear data fitting method that can more accurately solve the relationship expression between the volume and quantity in scientific experiments and engineering practice, this article analyzed data error by commonly linear data fitting method, and proposed improved process of the least distance squ^re method based on least squares method. Finally, the paper discussed the advantages and disadvantages through the example analysis of two kinds of linear data fitting method, and given reasonable control conditions for its application.
基金supported by the National Natural Science Foundation of China(No. 50538060)the Fundamental Research Grant of Tsinghua University(No.JCqn2005004),China
文摘We report an experimental investigation on the impact of the freezing rate on the cryo-deformation and cryo-damage of cementitious materials.Saturated,dried and air-entrained mortar specimens are subjected to laboratory freeze-thaw cycles under three freezing rates without moisture exchange with the environment.In addition to basic mechanical properties and pore distribution,the measurement is also effectuated for freezing expansion,residual deformation of the specimens in each cycle.From the results it is observed that a high freezing rate does augment the freezing expansion of material while the cryo-damage is more important for a low freezing rate.Accordingly,both the freezing rate and freezing duration should be taken into account for the cyro-damage extent of cementitious materials.
