This study investigated the viscoelastic and rheometeric properties of PVC stabilized with tannin-Ca complex as totally bio-based thermal stabilizer. Dynamic mechanical thermal analysis (DMTA) used to characterize the...This study investigated the viscoelastic and rheometeric properties of PVC stabilized with tannin-Ca complex as totally bio-based thermal stabilizer. Dynamic mechanical thermal analysis (DMTA) used to characterize the viscoelastic properties of PVC samples obtained by thermal mixing of PVC with three composition percentages (1.0, 2.0, and 3.0) part per hundred ratios (phr) of tannin-Ca complex with this polymer. The torque rheometery test used to monitor the effect of tannins derivative on the thermal stability and mixing properties of PVC formulations during samples processing. For that purpose, PVC sample with 2 phr commercial thermal stabilizer (Reapak B-NT/ 7060) was used for comparison and considered as reference samples. Before the glass transition temperature of PVC at 30°C - 60°C, the DMTA curves show that the values of storage modulus and tan delta of PVC samples stabilized with tannin derivative were very similar with those of PVC sample stabilized with commercial thermal stabilizer. The glass transition temperature (Tg) of PVC stabilized with commercial thermal stabilizer and with tannin-Ca complex occurred at about 76°C. In a sequence, after the glass transition region of PVC samples, the DMTA scans confirmed that the PVC samples with 2 phr tannin-Ca complex have relatively longer flowing stage which occurs at lower temperatures by 18°C per that of PVC sample stabilized with commercial stabilizer. Global results of the torque rheometery which have suitable plateau stages and the DMTA show that the processing thermal stability and thermal flexibility of PVC are clearly increased with the incorporation of tannin-Ca complex. All the PVC formulations with tannins-Ca complex show excellent viscoelastic properties which were found to be slightly best or much closed to those obtained for PVC stabilized with commercial thermal stabilization.展开更多
CA (Computer aided) investment casting technique used in superalloy castings of aerospace engine parts was presented. CA investment casting integrated computer application, RP (Rapid Prototyping) process, solidificati...CA (Computer aided) investment casting technique used in superalloy castings of aerospace engine parts was presented. CA investment casting integrated computer application, RP (Rapid Prototyping) process, solidification simulation and investment casting process. It broke the bottle neck of making metal die. Solid model of complex parts were produced by UGII or other software, then translated into STL(Stereolithography) file, after RP process of SLS(Selective Laser Sintering), wax pattern used in investment casting can be acquired without metal die in short time. These can reduce period and cost greatly of complex superalloy parts development of engine. The key processes of CA investment casting were discussed. The accuracy of model translation should match that of RP system. Choice of RP material, surface polishing, sintering parameter plays important role in RP process. Other processes, like solidification simulating and optimization of gate system were introduced. The conclusion was that complex parts can be produced by CA investment casting with lots of advantages. The accuracy of castings can reach CT5～7,and the smoothness can get Ra3～13 mm. These parts of engines worked well.展开更多
The emergence of Accountable Care Organizations(ACOs)in the landscape of the U.S.healthcare system marks a paradigm shift in healthcare operations.The potential impact of ACOs has been a topic of intense debate.Tradit...The emergence of Accountable Care Organizations(ACOs)in the landscape of the U.S.healthcare system marks a paradigm shift in healthcare operations.The potential impact of ACOs has been a topic of intense debate.Traditional analytical approaches do not lend themselves to examining the complex phenomenon of the emergence and growth of ACOs in the healthcare network.We adopt a complex adaptive system lens to examine the growth of ACOs among physician groups and explore factors that influence this growth.We also discuss the impact of ACOs on the profit of physician groups.An agent-based model was built to simulate physician groups'ACO entrance and exit based on a set of simple rules and their complex interactions with other agents.Based on the simulation results,we derive patterns of ACO expansion and contraction,following four stages of wait-and-see,rollercoaster,fast growth,and stabilizing.Findings suggest that the growth of ACOs is sensitive to the initial state of ACO membership.When the initial size of ACO membership increases,it helps to eliminate the rollercoaster stage.In addition,the growth of the ACO varies depending on the cost–quality tradeoff.When both cost and quality objectives can be met simultaneously,the growth of ACO membership follows wait-and-see and fast growth stages followed by a different stage that we term sticky state.The impact of ACOs on physician groups’cumulative profit varies by the service quality level of the physician group.Physician groups affiliated with insurance companies charging the lowest or the highest level of health insurance premiums are worse off with the ACO option.However,the ACO benefits physician groups affiliated with an insurance company charging a moderate level of premiums.展开更多
文摘This study investigated the viscoelastic and rheometeric properties of PVC stabilized with tannin-Ca complex as totally bio-based thermal stabilizer. Dynamic mechanical thermal analysis (DMTA) used to characterize the viscoelastic properties of PVC samples obtained by thermal mixing of PVC with three composition percentages (1.0, 2.0, and 3.0) part per hundred ratios (phr) of tannin-Ca complex with this polymer. The torque rheometery test used to monitor the effect of tannins derivative on the thermal stability and mixing properties of PVC formulations during samples processing. For that purpose, PVC sample with 2 phr commercial thermal stabilizer (Reapak B-NT/ 7060) was used for comparison and considered as reference samples. Before the glass transition temperature of PVC at 30°C - 60°C, the DMTA curves show that the values of storage modulus and tan delta of PVC samples stabilized with tannin derivative were very similar with those of PVC sample stabilized with commercial thermal stabilizer. The glass transition temperature (Tg) of PVC stabilized with commercial thermal stabilizer and with tannin-Ca complex occurred at about 76°C. In a sequence, after the glass transition region of PVC samples, the DMTA scans confirmed that the PVC samples with 2 phr tannin-Ca complex have relatively longer flowing stage which occurs at lower temperatures by 18°C per that of PVC sample stabilized with commercial stabilizer. Global results of the torque rheometery which have suitable plateau stages and the DMTA show that the processing thermal stability and thermal flexibility of PVC are clearly increased with the incorporation of tannin-Ca complex. All the PVC formulations with tannins-Ca complex show excellent viscoelastic properties which were found to be slightly best or much closed to those obtained for PVC stabilized with commercial thermal stabilization.
文摘CA (Computer aided) investment casting technique used in superalloy castings of aerospace engine parts was presented. CA investment casting integrated computer application, RP (Rapid Prototyping) process, solidification simulation and investment casting process. It broke the bottle neck of making metal die. Solid model of complex parts were produced by UGII or other software, then translated into STL(Stereolithography) file, after RP process of SLS(Selective Laser Sintering), wax pattern used in investment casting can be acquired without metal die in short time. These can reduce period and cost greatly of complex superalloy parts development of engine. The key processes of CA investment casting were discussed. The accuracy of model translation should match that of RP system. Choice of RP material, surface polishing, sintering parameter plays important role in RP process. Other processes, like solidification simulating and optimization of gate system were introduced. The conclusion was that complex parts can be produced by CA investment casting with lots of advantages. The accuracy of castings can reach CT5～7,and the smoothness can get Ra3～13 mm. These parts of engines worked well.
文摘The emergence of Accountable Care Organizations(ACOs)in the landscape of the U.S.healthcare system marks a paradigm shift in healthcare operations.The potential impact of ACOs has been a topic of intense debate.Traditional analytical approaches do not lend themselves to examining the complex phenomenon of the emergence and growth of ACOs in the healthcare network.We adopt a complex adaptive system lens to examine the growth of ACOs among physician groups and explore factors that influence this growth.We also discuss the impact of ACOs on the profit of physician groups.An agent-based model was built to simulate physician groups'ACO entrance and exit based on a set of simple rules and their complex interactions with other agents.Based on the simulation results,we derive patterns of ACO expansion and contraction,following four stages of wait-and-see,rollercoaster,fast growth,and stabilizing.Findings suggest that the growth of ACOs is sensitive to the initial state of ACO membership.When the initial size of ACO membership increases,it helps to eliminate the rollercoaster stage.In addition,the growth of the ACO varies depending on the cost–quality tradeoff.When both cost and quality objectives can be met simultaneously,the growth of ACO membership follows wait-and-see and fast growth stages followed by a different stage that we term sticky state.The impact of ACOs on physician groups’cumulative profit varies by the service quality level of the physician group.Physician groups affiliated with insurance companies charging the lowest or the highest level of health insurance premiums are worse off with the ACO option.However,the ACO benefits physician groups affiliated with an insurance company charging a moderate level of premiums.
