To predict three-dimensional temperature distribution of molten aluminum and its influencing factors inside an industrial aluminum holding furnace,a fluid-solid coupled method was presented.The fluid-solid coupled mat...To predict three-dimensional temperature distribution of molten aluminum and its influencing factors inside an industrial aluminum holding furnace,a fluid-solid coupled method was presented.The fluid-solid coupled mathematics models of aluminum holding furnace in the premixed combustion processing were established based on mass conservation,moment conservation,momentum conservation,energy conservation and chemistry species conservation.Computational results agree well with the test data of the typical condition.The maximum combustion temperature is 1 850 K.The average temperature of the molten aluminum is 1 158 K,and the maximum temperature difference is about 240 K.The average temperature increases 0.3 ℃ while the temperature of combustion air increases 1 ℃.The optimal excess air ratio is 1.25-1.30.展开更多
For acquiring the details in aluminum holding furnace with bottom porous brick purging system,efforts were performed to try to find out the potential optimal operation schemes.By adopting transient analysis scheme and...For acquiring the details in aluminum holding furnace with bottom porous brick purging system,efforts were performed to try to find out the potential optimal operation schemes.By adopting transient analysis scheme and constant boundary temperature,combustion in the furnace was investigated numerically using computational fluid dynamics(CFD).The predicted gas temperature shows good agreement with the measured results,and the predicted energy distribution of the furnace is consistent with that obtained from energy balance experiment,which confirms the reliability of the numerical solution.The results show that as the fuel-air mixture temperature rises up from 300 K to 500 K,the energy utilization of the furnace could increase from 34.55% to 37.14%.However,as the excess air coefficient increases from 1.0 to 1.4,energy utilization drops from 34.55% to 29.56%.Increasing the combustion temperature is the most effective way to improve the energy efficiency of the furnace.High reactant temperature and medium excess air coefficient are recommended for high operation performance,and keeping the furnace jamb sealed well for avoiding leakage has to be emphasized.展开更多
The numerical model for predicting the flow and temperature fields of the melt in holding furnace with porous brick purging system were set up using Euler-Lagrange approach.In this model,bubbles coalescence and disint...The numerical model for predicting the flow and temperature fields of the melt in holding furnace with porous brick purging system were set up using Euler-Lagrange approach.In this model,bubbles coalescence and disintegration were ignored based on the dimensionless analysis,and the bubble size was assumed to be obedient to Rosin-Rammler distribution with a mean size of 0.6 mm.The results show that on reference operating condition,during the heating and agitation process,melt mixes well in the furnace,and the melt velocity increases with the increase of gas flux.Holding the melt for 30 min causes the max temperature in the bulk melt to increase to 60 K.After holding the heat,the agitation processing restarts,and it takes 10 min for the stratified melt to retrieve the homogeneous temperature field when the gas flux is 10 L/min,which shows deficient alloying and degassing in the melt.With the increase of gas flux from 10 to 20,30 and 40 L/min,the necessary recovery time decreases from 10 to 6,5 and 4 min gradually,which shows the improvement of the stirring efficiency.Depending on the processing purposes,for both good degassing performance and gas saving,proper operating strategy and parameters (gas flux,primarily) could be adjusted.展开更多
Hypereutectic Al-40 wt.%Si alloys were fabricated by the combination of gas atomization and spark plasma sintering(SPS) technology. The effects of holding time(15-60 min) on phase composition, microstructure, density,...Hypereutectic Al-40 wt.%Si alloys were fabricated by the combination of gas atomization and spark plasma sintering(SPS) technology. The effects of holding time(15-60 min) on phase composition, microstructure, density,mechanical properties of Al-Si alloys were investigated by XRD, SEM, a hydrostatic balance, an automatic micro hardness tester and a universal tensile testing machine. The results showed that homogenous distribution of ultrafine primary Si and high density of alloys can be obtained at holding time of 30 min. Compared with primary Si(3.7 μm)fabricated by gas atomization, the average size increased from 5.17 to 7.72 μm with the increase of holding time during SPS process. Overall, the relative density, maximum tensile strength and Vickers hardness of 94.9%, 205 MPa and HV;196.86 were achieved at holding time of 30 min, respectively. In addition, all the diffraction peaks were corresponded to α-Al or β-Si and no other phase can be detected. Finally, the densification process of SPS was also discussed.展开更多
OZOHE PROTECTION FOR THE 90’S INTERNATIONAL WORKSHOP AFCAM and AIRAH,assistance from DASETT,have been holding a South East Asian and South Pacific Workshop on Ozoen Protection for the’90s at the National Convention,...OZOHE PROTECTION FOR THE 90’S INTERNATIONAL WORKSHOP AFCAM and AIRAH,assistance from DASETT,have been holding a South East Asian and South Pacific Workshop on Ozoen Protection for the’90s at the National Convention,Centre,Canberra from 23 to 26 March 1992. The workshop focus technology transfer,under UNEP,to countries in south East Asia and the South Pacific.This should significantly assist ozone protection in the region and provide commercial opportunities for Australian firms and organlsations. The Ozone Protection for the’90s workshop provide a forum for papers and lssues fordiscussion include:展开更多
Yes, we perceive that the environment in which comp an ies operate, is changing at higher speeds then before. Globalisation, higher inn ovation rates, customisation, more intense competition, technological developmen ...Yes, we perceive that the environment in which comp an ies operate, is changing at higher speeds then before. Globalisation, higher inn ovation rates, customisation, more intense competition, technological developmen ts account for these changes effecting the way industrial companies operate and eventually their structures and processes. Companies have to adapt themselves to these changes. The question arose whether the approach of the Section Industria l Organisation and Management that it has practised for redesign of processes an d organisational structures also withholds in this era of continuous change. Sec ondly, firms are also looking for contingencies in processes and structures to i mprove their chances for survival. These two questions into the processes and st ructures within the firm that it needs to support adaptation to the ever-changi ng environment direct this research. Industrial companies will have to increase to their Complexity Handling Capabili ty, the ability to cope with changes in its environment and imposed complexity p ouring in from the environment. To do so, they might decrease their internal com plexity through redefining their organisations and product structure. The effect of these measurements seems limited; more might be won by learning to increase its base of capabilities. The increase of capabilities holds parallels to the de velopment of species in biology and paleontology for which two models exist: the punctuated equilibrium and the phyletic gradualism. The punctuated equilibr ium supposes that periods of turmoil are interchanged by periods of fermentation giving rise to new variants and products (for companies). The phyletic graduali sm relies on the development of characteristics in species that are initially ha rd to detect but will lead at the end to new species. Whatever might be true for biology and palaeontology, these two models appear as a possibility for cla ssifying the theories of organisational change. Also, these theories put forward insights in the development of organisations that stretch beyond the classical insights on the adaptation of organisations based on one-time interventions ass uming balance between demands from the environment and internal structure. Little research has been done so far in this field of adaptation of companies to the dynamics of the environment. Most literature does not address the internal processes and structures necessary for coping with change. This paper will prese nt initial findings of case studies of graduation theses that took place to generate data on the validity of the evolutionary models. This way the research should not only lead to a theoretical framework but also to practical implicatio ns for industrial companies.展开更多
Introduction Regenerative medicine holds great promise for the treatment of diseases that are unbeatable at present,such as various gene and neurological disorders,cardiovascular diseases,as well as hematological mali...Introduction Regenerative medicine holds great promise for the treatment of diseases that are unbeatable at present,such as various gene and neurological disorders,cardiovascular diseases,as well as hematological malignancies.Realization of this potential remains limited by current challenges associated with the control of cell phenotype and function in cell culture.In this respect,the fate of cells is dictated by the in vivo microenvironment where these cells interact with both the extracellular matrix(ECM)and with neighboring cells.The ECM serves as a structural support for cells and provides,in concert with spatio-temporally arranged biochemical cues such as soluble factors,topographical and mechanical cues that direct cell adhesion,spreading,migra-展开更多
In order to improve the teaching evaluation effect,it is very significant to study the teachers evaluation indicator system and offer the algorithm of the evaluation methods.The teachers evaluation indicator system in...In order to improve the teaching evaluation effect,it is very significant to study the teachers evaluation indicator system and offer the algorithm of the evaluation methods.The teachers evaluation indicator system includes two parts:one part is the solid indicator of the teaching activities,that is,the fixed indicator;the other part is the Soft indicator of the teaching activities,that is,the Fuzzy indicator.The solid indicator contains lessons,hours,achievements,etc;the Fuzzy indicator consists of teachers qualification,teaching methods,student understanding and satisfaction,etc.,which can not be easily measured by fixed values.Fuzzy indicator holds an important position during teaching evaluation.Since there are no better indicator systems and quantified algorithm in higher education institutes these days,we will focus on studying the fuzzy indicator system here.展开更多
The intense competition in the current marketplace ha s forced firms to reexamine their methods of doing business, using superior manu facturing practices in the form of just-in-time (JIT), production with JIT pra cti...The intense competition in the current marketplace ha s forced firms to reexamine their methods of doing business, using superior manu facturing practices in the form of just-in-time (JIT), production with JIT pra ctices pursue completion on time and zero inventory, which is often instruct ed according to the custom’s demand or the sale contract. Earliness and tardine ss are undesirable because both of them will bring the extra cost, cost will als o be increased by some factors such as operation condition, intermediate storage , clean method, etc, to minimize the total cost is often the main scheduling objective, but sometime it is most important for factories to eliminate the tar diness cost in order to maintain the commercial credit and to avoid penalty, the refore, minimum of tardiness cost becomes the first objective. It is more import ant to select a reasonable objective by the actual condition during scheduli ng. In this paper scheduling problem of chemical batch process with due date is studied, two different intermediate storage policies and two different productio n modes are also discussed, production scheduling with different intermediate st orage policy and different production mode is proposed and the result is compare d. In order to complete all products within the due date, not only earliness and tardiness but also holding problem is considered, the objective is to selec t a proper intermediate storage policy and production mode and to minimize the c ost resulted by the earliness and tardiness, even the cost result by the interme diate storage. Scheduling with multiple stage and multiple machine is known as a NP-hard problem, mathematical program (MP) method, such as branch-and-bound (BAB), mixed integer linear program (MILP), etc, is often used to solve the sche duling problem. But as is well known, MP method is not good for combination opti mization, especially for large scale and complex optimal problem, whereas geneti c algorithm (GA) can overcome the MP method’s shortcoming and is fit for solvin g such scheduling problem. In this paper a modified genetic algorithm with speci al crossover operator and mutation operator is presented to solve this schedulin g problem. The results show such problem can be solved effectively with the pres ented method.展开更多
We present a method of test generation for acyclic sequential circuits with hold registers. A complete (100% fault efficiency) test sequence for an acyclic sequential circuit can be obtained by applying a combinationa...We present a method of test generation for acyclic sequential circuits with hold registers. A complete (100% fault efficiency) test sequence for an acyclic sequential circuit can be obtained by applying a combinational test generator to all the maximal time-expansion models (TEMs) of the circuit. We propose a class of acyclic sequential circuits for which the number of maximal TEMs is one, i.e, the maximum TEM exists. For a circuit in the class, test generation can be performed by using only the maximum TEM. The proposed class of sequential circuits with the maximum TEM properly includes several known classes of acyclic sequential circuits such as balanced structures and acyclic sequential circuits without hold registers for which test generation can be also performed by using a combinational test generator. Therefore, in general, the hardware overhead for partial scan based on the proposed structure is smaller than that based on balanced or acyclic sequential structure without hold registers.展开更多
基金Project(2006AA03Z523) supported by the National High-Tech Research and Development Program of ChinaProject(08C26224302178) supported by the Innovation Foundation of Central South University,China
文摘To predict three-dimensional temperature distribution of molten aluminum and its influencing factors inside an industrial aluminum holding furnace,a fluid-solid coupled method was presented.The fluid-solid coupled mathematics models of aluminum holding furnace in the premixed combustion processing were established based on mass conservation,moment conservation,momentum conservation,energy conservation and chemistry species conservation.Computational results agree well with the test data of the typical condition.The maximum combustion temperature is 1 850 K.The average temperature of the molten aluminum is 1 158 K,and the maximum temperature difference is about 240 K.The average temperature increases 0.3 ℃ while the temperature of combustion air increases 1 ℃.The optimal excess air ratio is 1.25-1.30.
基金Project(2009GK2009) supported by the Science and Technology Program of Hunan Province,China
文摘For acquiring the details in aluminum holding furnace with bottom porous brick purging system,efforts were performed to try to find out the potential optimal operation schemes.By adopting transient analysis scheme and constant boundary temperature,combustion in the furnace was investigated numerically using computational fluid dynamics(CFD).The predicted gas temperature shows good agreement with the measured results,and the predicted energy distribution of the furnace is consistent with that obtained from energy balance experiment,which confirms the reliability of the numerical solution.The results show that as the fuel-air mixture temperature rises up from 300 K to 500 K,the energy utilization of the furnace could increase from 34.55% to 37.14%.However,as the excess air coefficient increases from 1.0 to 1.4,energy utilization drops from 34.55% to 29.56%.Increasing the combustion temperature is the most effective way to improve the energy efficiency of the furnace.High reactant temperature and medium excess air coefficient are recommended for high operation performance,and keeping the furnace jamb sealed well for avoiding leakage has to be emphasized.
基金Project(2008AA11A116) supported by the National High Technology Research and Development Program of China
文摘The numerical model for predicting the flow and temperature fields of the melt in holding furnace with porous brick purging system were set up using Euler-Lagrange approach.In this model,bubbles coalescence and disintegration were ignored based on the dimensionless analysis,and the bubble size was assumed to be obedient to Rosin-Rammler distribution with a mean size of 0.6 mm.The results show that on reference operating condition,during the heating and agitation process,melt mixes well in the furnace,and the melt velocity increases with the increase of gas flux.Holding the melt for 30 min causes the max temperature in the bulk melt to increase to 60 K.After holding the heat,the agitation processing restarts,and it takes 10 min for the stratified melt to retrieve the homogeneous temperature field when the gas flux is 10 L/min,which shows deficient alloying and degassing in the melt.With the increase of gas flux from 10 to 20,30 and 40 L/min,the necessary recovery time decreases from 10 to 6,5 and 4 min gradually,which shows the improvement of the stirring efficiency.Depending on the processing purposes,for both good degassing performance and gas saving,proper operating strategy and parameters (gas flux,primarily) could be adjusted.
基金Project(18JS060) supported by the Shaanxi Key Laboratory of Nano-materials and Technology,ChinaProject(2018JQ5087) supported by Natural Science Basic Research Plan of Shaanxi Province,China。
文摘Hypereutectic Al-40 wt.%Si alloys were fabricated by the combination of gas atomization and spark plasma sintering(SPS) technology. The effects of holding time(15-60 min) on phase composition, microstructure, density,mechanical properties of Al-Si alloys were investigated by XRD, SEM, a hydrostatic balance, an automatic micro hardness tester and a universal tensile testing machine. The results showed that homogenous distribution of ultrafine primary Si and high density of alloys can be obtained at holding time of 30 min. Compared with primary Si(3.7 μm)fabricated by gas atomization, the average size increased from 5.17 to 7.72 μm with the increase of holding time during SPS process. Overall, the relative density, maximum tensile strength and Vickers hardness of 94.9%, 205 MPa and HV;196.86 were achieved at holding time of 30 min, respectively. In addition, all the diffraction peaks were corresponded to α-Al or β-Si and no other phase can be detected. Finally, the densification process of SPS was also discussed.
文摘OZOHE PROTECTION FOR THE 90’S INTERNATIONAL WORKSHOP AFCAM and AIRAH,assistance from DASETT,have been holding a South East Asian and South Pacific Workshop on Ozoen Protection for the’90s at the National Convention,Centre,Canberra from 23 to 26 March 1992. The workshop focus technology transfer,under UNEP,to countries in south East Asia and the South Pacific.This should significantly assist ozone protection in the region and provide commercial opportunities for Australian firms and organlsations. The Ozone Protection for the’90s workshop provide a forum for papers and lssues fordiscussion include:
文摘Yes, we perceive that the environment in which comp an ies operate, is changing at higher speeds then before. Globalisation, higher inn ovation rates, customisation, more intense competition, technological developmen ts account for these changes effecting the way industrial companies operate and eventually their structures and processes. Companies have to adapt themselves to these changes. The question arose whether the approach of the Section Industria l Organisation and Management that it has practised for redesign of processes an d organisational structures also withholds in this era of continuous change. Sec ondly, firms are also looking for contingencies in processes and structures to i mprove their chances for survival. These two questions into the processes and st ructures within the firm that it needs to support adaptation to the ever-changi ng environment direct this research. Industrial companies will have to increase to their Complexity Handling Capabili ty, the ability to cope with changes in its environment and imposed complexity p ouring in from the environment. To do so, they might decrease their internal com plexity through redefining their organisations and product structure. The effect of these measurements seems limited; more might be won by learning to increase its base of capabilities. The increase of capabilities holds parallels to the de velopment of species in biology and paleontology for which two models exist: the punctuated equilibrium and the phyletic gradualism. The punctuated equilibr ium supposes that periods of turmoil are interchanged by periods of fermentation giving rise to new variants and products (for companies). The phyletic graduali sm relies on the development of characteristics in species that are initially ha rd to detect but will lead at the end to new species. Whatever might be true for biology and palaeontology, these two models appear as a possibility for cla ssifying the theories of organisational change. Also, these theories put forward insights in the development of organisations that stretch beyond the classical insights on the adaptation of organisations based on one-time interventions ass uming balance between demands from the environment and internal structure. Little research has been done so far in this field of adaptation of companies to the dynamics of the environment. Most literature does not address the internal processes and structures necessary for coping with change. This paper will prese nt initial findings of case studies of graduation theses that took place to generate data on the validity of the evolutionary models. This way the research should not only lead to a theoretical framework but also to practical implicatio ns for industrial companies.
基金supported by the National Institute of Health(NIH HL83008)
文摘Introduction Regenerative medicine holds great promise for the treatment of diseases that are unbeatable at present,such as various gene and neurological disorders,cardiovascular diseases,as well as hematological malignancies.Realization of this potential remains limited by current challenges associated with the control of cell phenotype and function in cell culture.In this respect,the fate of cells is dictated by the in vivo microenvironment where these cells interact with both the extracellular matrix(ECM)and with neighboring cells.The ECM serves as a structural support for cells and provides,in concert with spatio-temporally arranged biochemical cues such as soluble factors,topographical and mechanical cues that direct cell adhesion,spreading,migra-
文摘In order to improve the teaching evaluation effect,it is very significant to study the teachers evaluation indicator system and offer the algorithm of the evaluation methods.The teachers evaluation indicator system includes two parts:one part is the solid indicator of the teaching activities,that is,the fixed indicator;the other part is the Soft indicator of the teaching activities,that is,the Fuzzy indicator.The solid indicator contains lessons,hours,achievements,etc;the Fuzzy indicator consists of teachers qualification,teaching methods,student understanding and satisfaction,etc.,which can not be easily measured by fixed values.Fuzzy indicator holds an important position during teaching evaluation.Since there are no better indicator systems and quantified algorithm in higher education institutes these days,we will focus on studying the fuzzy indicator system here.
文摘The intense competition in the current marketplace ha s forced firms to reexamine their methods of doing business, using superior manu facturing practices in the form of just-in-time (JIT), production with JIT pra ctices pursue completion on time and zero inventory, which is often instruct ed according to the custom’s demand or the sale contract. Earliness and tardine ss are undesirable because both of them will bring the extra cost, cost will als o be increased by some factors such as operation condition, intermediate storage , clean method, etc, to minimize the total cost is often the main scheduling objective, but sometime it is most important for factories to eliminate the tar diness cost in order to maintain the commercial credit and to avoid penalty, the refore, minimum of tardiness cost becomes the first objective. It is more import ant to select a reasonable objective by the actual condition during scheduli ng. In this paper scheduling problem of chemical batch process with due date is studied, two different intermediate storage policies and two different productio n modes are also discussed, production scheduling with different intermediate st orage policy and different production mode is proposed and the result is compare d. In order to complete all products within the due date, not only earliness and tardiness but also holding problem is considered, the objective is to selec t a proper intermediate storage policy and production mode and to minimize the c ost resulted by the earliness and tardiness, even the cost result by the interme diate storage. Scheduling with multiple stage and multiple machine is known as a NP-hard problem, mathematical program (MP) method, such as branch-and-bound (BAB), mixed integer linear program (MILP), etc, is often used to solve the sche duling problem. But as is well known, MP method is not good for combination opti mization, especially for large scale and complex optimal problem, whereas geneti c algorithm (GA) can overcome the MP method’s shortcoming and is fit for solvin g such scheduling problem. In this paper a modified genetic algorithm with speci al crossover operator and mutation operator is presented to solve this schedulin g problem. The results show such problem can be solved effectively with the pres ented method.
文摘We present a method of test generation for acyclic sequential circuits with hold registers. A complete (100% fault efficiency) test sequence for an acyclic sequential circuit can be obtained by applying a combinational test generator to all the maximal time-expansion models (TEMs) of the circuit. We propose a class of acyclic sequential circuits for which the number of maximal TEMs is one, i.e, the maximum TEM exists. For a circuit in the class, test generation can be performed by using only the maximum TEM. The proposed class of sequential circuits with the maximum TEM properly includes several known classes of acyclic sequential circuits such as balanced structures and acyclic sequential circuits without hold registers for which test generation can be also performed by using a combinational test generator. Therefore, in general, the hardware overhead for partial scan based on the proposed structure is smaller than that based on balanced or acyclic sequential structure without hold registers.
