The multiple cracking and deflection hardening performance of polyvinyl alcohol fiber reinforced engineered cementitious composites(PVA-ECC)under four-point flexural loading have been investigated.Matrices with differ...The multiple cracking and deflection hardening performance of polyvinyl alcohol fiber reinforced engineered cementitious composites(PVA-ECC)under four-point flexural loading have been investigated.Matrices with different binder combinations and W/B ratios(from 0.44 to 0.78)providing satisfactory PVA fiber dispersion were specially designed.Effect of pre-existing flaw size distribution modification on deflection hardening behavior was comparatively studied by adding 3 mm diameter polyethylene beads into the mixtures(6%by total volume).Natural flaw size distributions of composites without beads were determined by cross sectional analysis.The crack number and crack width distributions of specimens after flexural loading were characterized and the possible causes of changes in multiple cracking and deflection hardening behavior by flaw size distribution modification were discussed.Promising results from the view point of deflection hardening behavior were obtained from metakaolin incorporated and flaw size distribution modified PVA-ECCs prepared with W/B=0.53.The dual roles of W/B ratio and superplasticizer content on flaw size distribution,cracking potential and fiber-matrix bond behavior were evaluated.Flaw size distribution modification is found beneficial in terms of ductility improvement at an optimized W/B ratio.展开更多
Suppose that Z1 , Z2,’’’ Zn are independent normal random variables with common meanμ and variance σ2. Then S2 and have distribution andtn-1 distribution respectively. If the normal assumption fails, there will b...Suppose that Z1 , Z2,’’’ Zn are independent normal random variables with common meanμ and variance σ2. Then S2 and have distribution andtn-1 distribution respectively. If the normal assumption fails, there will be the remaindersof the distribution functions and density functions. This paper gives the direct expansions ofdistribution functions and density functions of S2 alld T up to o(n-1). They are more intuitiveand convenient than usual Edgeworth expansions.展开更多
The methodology for modeling no-frost refrigerator is described based on the component models developed in PartⅠ,and then,system simulation is applied to a BCD-235W refrigerator-freezer(RF).Experiments are carried ou...The methodology for modeling no-frost refrigerator is described based on the component models developed in PartⅠ,and then,system simulation is applied to a BCD-235W refrigerator-freezer(RF).Experiments are carried out to study'pull-down'and steady-state performance of the RF,and to determine how the experiment and simulation temperature stack up against each other.Good match is found between simulated and measured results for the'pull-down'period.For the steady-state period,the simulation results are also found to agree well with experiment ones except for the temperature profiles of the refrigerator compartment(RC) and freezer compartment(FC).The average temperature and the energy consumption errors between measurement and simulation are less than 10%.Although the model can not reflect the non-uniform air temperature fields in the RC and FC,the variation range and periodicities of the temperature correlate well between the simulation and experiment.We conclude that such a model is valid for investigating the performance of no-frost refrigerator.展开更多
基金Project(114M246)supported by the Scientific and Technological Research Council of Turkey
文摘The multiple cracking and deflection hardening performance of polyvinyl alcohol fiber reinforced engineered cementitious composites(PVA-ECC)under four-point flexural loading have been investigated.Matrices with different binder combinations and W/B ratios(from 0.44 to 0.78)providing satisfactory PVA fiber dispersion were specially designed.Effect of pre-existing flaw size distribution modification on deflection hardening behavior was comparatively studied by adding 3 mm diameter polyethylene beads into the mixtures(6%by total volume).Natural flaw size distributions of composites without beads were determined by cross sectional analysis.The crack number and crack width distributions of specimens after flexural loading were characterized and the possible causes of changes in multiple cracking and deflection hardening behavior by flaw size distribution modification were discussed.Promising results from the view point of deflection hardening behavior were obtained from metakaolin incorporated and flaw size distribution modified PVA-ECCs prepared with W/B=0.53.The dual roles of W/B ratio and superplasticizer content on flaw size distribution,cracking potential and fiber-matrix bond behavior were evaluated.Flaw size distribution modification is found beneficial in terms of ductility improvement at an optimized W/B ratio.
文摘Suppose that Z1 , Z2,’’’ Zn are independent normal random variables with common meanμ and variance σ2. Then S2 and have distribution andtn-1 distribution respectively. If the normal assumption fails, there will be the remaindersof the distribution functions and density functions. This paper gives the direct expansions ofdistribution functions and density functions of S2 alld T up to o(n-1). They are more intuitiveand convenient than usual Edgeworth expansions.
文摘The methodology for modeling no-frost refrigerator is described based on the component models developed in PartⅠ,and then,system simulation is applied to a BCD-235W refrigerator-freezer(RF).Experiments are carried out to study'pull-down'and steady-state performance of the RF,and to determine how the experiment and simulation temperature stack up against each other.Good match is found between simulated and measured results for the'pull-down'period.For the steady-state period,the simulation results are also found to agree well with experiment ones except for the temperature profiles of the refrigerator compartment(RC) and freezer compartment(FC).The average temperature and the energy consumption errors between measurement and simulation are less than 10%.Although the model can not reflect the non-uniform air temperature fields in the RC and FC,the variation range and periodicities of the temperature correlate well between the simulation and experiment.We conclude that such a model is valid for investigating the performance of no-frost refrigerator.
