Combining separated SHPB test device of Ф50 mm with ZDKT-type 1 transient magnetic resonance test system, long drop bar of 400 mm was used to impact coal specimens at four different speeds: 1.275, 3.287, 6.251, and ...Combining separated SHPB test device of Ф50 mm with ZDKT-type 1 transient magnetic resonance test system, long drop bar of 400 mm was used to impact coal specimens at four different speeds: 1.275, 3.287, 6.251, and 7.404 m/s. The change in waveform, the dynamic mechanical properties, and the generated effect of transient field during the coal deformation and fracture under the loads were discussed and analyzed. While magnetic signals during the coal fracture firstly needed EEMD, decomposition then had a FFT with Data Demon. The main results of the experiment are the following: the main frequency of magnetic signals was between 220 and 450 kHz and the instantaneous frequency during the damage of coal would have the instantaneous jump.展开更多
The distillation column with side reactors (SRC) can overcome the temperature/pressure mismatch in the traditional reactive distillation, the column operates at temperature/pressure favorable for vapor-liquid separati...The distillation column with side reactors (SRC) can overcome the temperature/pressure mismatch in the traditional reactive distillation, the column operates at temperature/pressure favorable for vapor-liquid separation, while the reactors operate at temperatures/pressures favorable for reaction kinetics. According to the smooth operation and automatic control problem of the distillation column with side reactors (SRC), the design, simulation calculation and dynamic control of the SCR process for chlorobenzene production are discussed in the paper. Firstly, the mechanism models, the integrated structure optimal design and process simulation systems are established, respectively. And then multivariable control schemes are designed, the controllability of SRC process based on the optimal steady-state integrated structure is explored. The dynamic response performances of closed-loop system against several disturbances are discussed to verify the effectiveness of control schemes for the SRC process. The simulating results show that the control structure using conventional control strategies can effectively overcome feeding disturbances in a specific range.展开更多
Regarding construction projects, no project is implemented exactly as planned. Changes in construction projects are common due to the dynamic nature of the construction process. It is necessary to use effective and ap...Regarding construction projects, no project is implemented exactly as planned. Changes in construction projects are common due to the dynamic nature of the construction process. It is necessary to use effective and appropriate tools by project management to support decision-making and control changes during all stages of project implementation. This study examined the effects of change orders through technical programs on construction projects in Jordan and focused on how to overcome these effects by making usual orders that can be handled by each of the contracting parties. Also, this study added an advantage by not addressing the negative effects of change orders, but it provided many positive effects of change orders by using technical programs method, which has not been yet researched in Jordanian studies in particular, and in global studies in general. The researcher used descriptive analytical method by interviews to collect data through nine questions to a random sample of 30 engineers selected form constructions projects in Jordan. The results related to the study questions on the effect of change orders through technical programs on construction projects in Jordan showed that, most of the study samples confirm that change orders through technical programs decrease the cost of the projects, cause no need for more materials, cause no delay in the completion schedule, enhances the quality of work, and increase the productivity of the work force. The study recommended applying integrated change management system with technical supports form different technologies, developing effective innovative and practical solution to manage change orders and increase training programs to qualify and increase engineering skills in dealing with ICT (information and communication technologies) program.展开更多
Excitation system is one of the significant elements affecting the dynamic performance of electric power systems. The power engineering as area of science and industry is subjected to rapid modernization, which is cau...Excitation system is one of the significant elements affecting the dynamic performance of electric power systems. The power engineering as area of science and industry is subjected to rapid modernization, which is caused by technological progress. However, not all elements of the power system are developing simultaneously. The old type of elements sometimes is sufficient to adapt old system to the new operational conditions. The work developed and proposed in this paper deals with analysis of possible optimization of synchronous generator's excitation system. Authors examined influence of excitation system's parameters to the dynamics of transient processes in the power system. Authors investigated optimal parameters of excitation system of the Kegums hydro power plant. For optimization of parameters objective functions were used. The problem of the mutual influence of excitation systems of neighbor power plants was investigated. Investigation of transient processes using developed model proved that optimization of excitation parameters improves efficiency of regulation of excitation system, damping of active power oscillation and in some cases can prevent out-of-step condition.展开更多
文摘Combining separated SHPB test device of Ф50 mm with ZDKT-type 1 transient magnetic resonance test system, long drop bar of 400 mm was used to impact coal specimens at four different speeds: 1.275, 3.287, 6.251, and 7.404 m/s. The change in waveform, the dynamic mechanical properties, and the generated effect of transient field during the coal deformation and fracture under the loads were discussed and analyzed. While magnetic signals during the coal fracture firstly needed EEMD, decomposition then had a FFT with Data Demon. The main results of the experiment are the following: the main frequency of magnetic signals was between 220 and 450 kHz and the instantaneous frequency during the damage of coal would have the instantaneous jump.
基金Supported by the National Natural Science Foundation of China (61203020, 21276126)the Natural Science Foundation of Jiangsu Province (BK2011795)+1 种基金Jiangsu Province Higher Education Natural Science Foundation (09KJA530004)China Postdoctoral Science Foundation (20100471325)
文摘The distillation column with side reactors (SRC) can overcome the temperature/pressure mismatch in the traditional reactive distillation, the column operates at temperature/pressure favorable for vapor-liquid separation, while the reactors operate at temperatures/pressures favorable for reaction kinetics. According to the smooth operation and automatic control problem of the distillation column with side reactors (SRC), the design, simulation calculation and dynamic control of the SCR process for chlorobenzene production are discussed in the paper. Firstly, the mechanism models, the integrated structure optimal design and process simulation systems are established, respectively. And then multivariable control schemes are designed, the controllability of SRC process based on the optimal steady-state integrated structure is explored. The dynamic response performances of closed-loop system against several disturbances are discussed to verify the effectiveness of control schemes for the SRC process. The simulating results show that the control structure using conventional control strategies can effectively overcome feeding disturbances in a specific range.
文摘Regarding construction projects, no project is implemented exactly as planned. Changes in construction projects are common due to the dynamic nature of the construction process. It is necessary to use effective and appropriate tools by project management to support decision-making and control changes during all stages of project implementation. This study examined the effects of change orders through technical programs on construction projects in Jordan and focused on how to overcome these effects by making usual orders that can be handled by each of the contracting parties. Also, this study added an advantage by not addressing the negative effects of change orders, but it provided many positive effects of change orders by using technical programs method, which has not been yet researched in Jordanian studies in particular, and in global studies in general. The researcher used descriptive analytical method by interviews to collect data through nine questions to a random sample of 30 engineers selected form constructions projects in Jordan. The results related to the study questions on the effect of change orders through technical programs on construction projects in Jordan showed that, most of the study samples confirm that change orders through technical programs decrease the cost of the projects, cause no need for more materials, cause no delay in the completion schedule, enhances the quality of work, and increase the productivity of the work force. The study recommended applying integrated change management system with technical supports form different technologies, developing effective innovative and practical solution to manage change orders and increase training programs to qualify and increase engineering skills in dealing with ICT (information and communication technologies) program.
文摘Excitation system is one of the significant elements affecting the dynamic performance of electric power systems. The power engineering as area of science and industry is subjected to rapid modernization, which is caused by technological progress. However, not all elements of the power system are developing simultaneously. The old type of elements sometimes is sufficient to adapt old system to the new operational conditions. The work developed and proposed in this paper deals with analysis of possible optimization of synchronous generator's excitation system. Authors examined influence of excitation system's parameters to the dynamics of transient processes in the power system. Authors investigated optimal parameters of excitation system of the Kegums hydro power plant. For optimization of parameters objective functions were used. The problem of the mutual influence of excitation systems of neighbor power plants was investigated. Investigation of transient processes using developed model proved that optimization of excitation parameters improves efficiency of regulation of excitation system, damping of active power oscillation and in some cases can prevent out-of-step condition.