JW
J. Worp
info
Please Note
<p>This page displays the records of the person named above and is not linked to a unique person identifier. This record may need to be merged to a profile.</p>
2 records found
1
Do the elderly use thigh push off in sit-to-stand to compensate for a lack of stability?
Application of the Stability Basin method to assess the stability of compensatory sit-to-stand strategies in young and elderly participants
Due to neuromuscular capacity decline, sit-to-stand, an essential daily life activity, is increasingly difficult to perform for elderly. In practice, elderly frequently use compensatory arm-strategies in sit-to-stand. However, the specific advantages of these compensatory strategies are unclear. The focus of this research is to study the influence of thigh push-off, a common compensatory strategy, on the stability of sit-to-stand for both the young and elderly. Motion data was retrieved from 50 young and elderly participants who performed sit-to-stand with and without thigh push-off. To mimic realistic daily-life strategies, participants were not restricted in sit-to-stand style in any way but arm-use. The experimental sit-to-stand data was fitted to a pendulum model with feedforward and feedback control to simulate the stability limits of the observed sit-to-stand strategies. The model allows us to explore stability limits without the need of perturbation. For each arm-strategy and participant a stability basin, i.e. all potential trajectories of motion, was formed. We compared the stability basins between arm-strategies and between age-groups. The size of the computed stability basin for thigh push-off was larger than for no arm push-off implicating thigh push-off is a more stable sit-to-stand strategy. The difference between arm strategies was larger for the elderly than for the young participants. Overall, the stability basins of the elderly were larger compared to those of the young participants, for both arm strategies. The resulting stability basins suggest that thigh push-off increases the stability of sit-to-stand and thus could indeed be an effective compensatory strategy. Stability basin shape differences indicate that without thigh push-off elderly compensate for possible early sit-down and a step halfway sit-to-stand, and with the thigh push-off strategy only for early sit-down. The age-groups differences confirm stability basins quantify the stability of the observed movement strategy rather than the stability of the participants. We observed that elderly use more precautious sit-tot-stand movements.
...
Due to neuromuscular capacity decline, sit-to-stand, an essential daily life activity, is increasingly difficult to perform for elderly. In practice, elderly frequently use compensatory arm-strategies in sit-to-stand. However, the specific advantages of these compensatory strategies are unclear. The focus of this research is to study the influence of thigh push-off, a common compensatory strategy, on the stability of sit-to-stand for both the young and elderly. Motion data was retrieved from 50 young and elderly participants who performed sit-to-stand with and without thigh push-off. To mimic realistic daily-life strategies, participants were not restricted in sit-to-stand style in any way but arm-use. The experimental sit-to-stand data was fitted to a pendulum model with feedforward and feedback control to simulate the stability limits of the observed sit-to-stand strategies. The model allows us to explore stability limits without the need of perturbation. For each arm-strategy and participant a stability basin, i.e. all potential trajectories of motion, was formed. We compared the stability basins between arm-strategies and between age-groups. The size of the computed stability basin for thigh push-off was larger than for no arm push-off implicating thigh push-off is a more stable sit-to-stand strategy. The difference between arm strategies was larger for the elderly than for the young participants. Overall, the stability basins of the elderly were larger compared to those of the young participants, for both arm strategies. The resulting stability basins suggest that thigh push-off increases the stability of sit-to-stand and thus could indeed be an effective compensatory strategy. Stability basin shape differences indicate that without thigh push-off elderly compensate for possible early sit-down and a step halfway sit-to-stand, and with the thigh push-off strategy only for early sit-down. The age-groups differences confirm stability basins quantify the stability of the observed movement strategy rather than the stability of the participants. We observed that elderly use more precautious sit-tot-stand movements.
After the earthquake in 2015 that struck Nepal, students of the Delft University of Technology commenced the multidisciplinary project program “Shock Safe Nepal”. This report describes the effort of the sixth group of students who travelled to Nepal. Following conclusions and specific recommendations of Team 5, the present research has one main goal. This research focuses on improving the overall quality of CSEB and making sure that the final strength of the bricks is constant. This is done by predicting the final strength of CSEB during the early curing stage and using this knowledge to develop a testing method, so the Nepali can monitor the CSEB quality easily and accurately on site in an early production stage. The secondary goal was to perform a dynamic seismic analysis of the pilot house in Ratankot and to get a better understanding of earthquake engineering in Nepal.
To predict the final strength of CSEB, a research into the existence of a drying/hardening curve was performed. Different regions in Nepal ask for different CSEB mixtures because of differences in humidity, temperature, altitude and soil consistency. The biggest influence of the change in hardening process is presumably the cement percentage and therefore also the water/cement ratio. In the Nepali practice this percentage is between 5 and 15 percent, depending on local soil type. Therefore, in this research all soil parameters were kept constant except cement percentages, they range from 5 till 15 percent. To develop a hardening curve, bricks were tested after 5, 8, 14, 21 and 28 days. This was done using a (calibrated) compression machine. Results of these tests showed wide spread. The tested bricks were still moist and it was decided to test the CSEB after 38 days as well. This resulted in an even bigger gain in strength such that the bricks after 38 days were twice the strength of the bricks after 28 days.
General conclusion can be drawn that the time period between the curing and testing of the brick makes a significant difference in the results, so this has to be monitored accurately. Furthermore continued curing does not necessarily contribute to the strength of the bricks or might even have a negative effect.
Results from the compression test showed that the general quality, and thus compression strength, of the bricks was lacking. Only bricks with 15% cement surpass the minimum strength of 3.50 MPa after 38 days. This showed that production site was not working properly, therefor Build Up Nepal was informed. This lack of strength is probably caused by a change in variables. The weather in the winter is very different than in summer, but the curing process wasn’t modified. Also the soil composition differs every time new soil is brought to the site, which can change the strength drastically.
While researching the hardening curves for CSEB, an alternative testing method was developed. Multiple ideas have been tested, such as a torque wrench with vice, a drop test and finally a lever arm test. The first two methods were deemed unusable as they broke down or were not able to produce reliable results. The lever arm test was most promising as this method produced constant results. Against expectations, the strength of the bricks tested by the lever arm tested was much higher than the strength of the bricks tested with the compression tester. This indicated that not exactly the same properties were measured. The results cannot be directly compared to each other. Before the method can be implemented there is more research necessary about which property is tested with the lever arm and the converting factor.
...
To predict the final strength of CSEB, a research into the existence of a drying/hardening curve was performed. Different regions in Nepal ask for different CSEB mixtures because of differences in humidity, temperature, altitude and soil consistency. The biggest influence of the change in hardening process is presumably the cement percentage and therefore also the water/cement ratio. In the Nepali practice this percentage is between 5 and 15 percent, depending on local soil type. Therefore, in this research all soil parameters were kept constant except cement percentages, they range from 5 till 15 percent. To develop a hardening curve, bricks were tested after 5, 8, 14, 21 and 28 days. This was done using a (calibrated) compression machine. Results of these tests showed wide spread. The tested bricks were still moist and it was decided to test the CSEB after 38 days as well. This resulted in an even bigger gain in strength such that the bricks after 38 days were twice the strength of the bricks after 28 days.
General conclusion can be drawn that the time period between the curing and testing of the brick makes a significant difference in the results, so this has to be monitored accurately. Furthermore continued curing does not necessarily contribute to the strength of the bricks or might even have a negative effect.
Results from the compression test showed that the general quality, and thus compression strength, of the bricks was lacking. Only bricks with 15% cement surpass the minimum strength of 3.50 MPa after 38 days. This showed that production site was not working properly, therefor Build Up Nepal was informed. This lack of strength is probably caused by a change in variables. The weather in the winter is very different than in summer, but the curing process wasn’t modified. Also the soil composition differs every time new soil is brought to the site, which can change the strength drastically.
While researching the hardening curves for CSEB, an alternative testing method was developed. Multiple ideas have been tested, such as a torque wrench with vice, a drop test and finally a lever arm test. The first two methods were deemed unusable as they broke down or were not able to produce reliable results. The lever arm test was most promising as this method produced constant results. Against expectations, the strength of the bricks tested by the lever arm tested was much higher than the strength of the bricks tested with the compression tester. This indicated that not exactly the same properties were measured. The results cannot be directly compared to each other. Before the method can be implemented there is more research necessary about which property is tested with the lever arm and the converting factor.
...
After the earthquake in 2015 that struck Nepal, students of the Delft University of Technology commenced the multidisciplinary project program “Shock Safe Nepal”. This report describes the effort of the sixth group of students who travelled to Nepal. Following conclusions and specific recommendations of Team 5, the present research has one main goal. This research focuses on improving the overall quality of CSEB and making sure that the final strength of the bricks is constant. This is done by predicting the final strength of CSEB during the early curing stage and using this knowledge to develop a testing method, so the Nepali can monitor the CSEB quality easily and accurately on site in an early production stage. The secondary goal was to perform a dynamic seismic analysis of the pilot house in Ratankot and to get a better understanding of earthquake engineering in Nepal.
To predict the final strength of CSEB, a research into the existence of a drying/hardening curve was performed. Different regions in Nepal ask for different CSEB mixtures because of differences in humidity, temperature, altitude and soil consistency. The biggest influence of the change in hardening process is presumably the cement percentage and therefore also the water/cement ratio. In the Nepali practice this percentage is between 5 and 15 percent, depending on local soil type. Therefore, in this research all soil parameters were kept constant except cement percentages, they range from 5 till 15 percent. To develop a hardening curve, bricks were tested after 5, 8, 14, 21 and 28 days. This was done using a (calibrated) compression machine. Results of these tests showed wide spread. The tested bricks were still moist and it was decided to test the CSEB after 38 days as well. This resulted in an even bigger gain in strength such that the bricks after 38 days were twice the strength of the bricks after 28 days.
General conclusion can be drawn that the time period between the curing and testing of the brick makes a significant difference in the results, so this has to be monitored accurately. Furthermore continued curing does not necessarily contribute to the strength of the bricks or might even have a negative effect.
Results from the compression test showed that the general quality, and thus compression strength, of the bricks was lacking. Only bricks with 15% cement surpass the minimum strength of 3.50 MPa after 38 days. This showed that production site was not working properly, therefor Build Up Nepal was informed. This lack of strength is probably caused by a change in variables. The weather in the winter is very different than in summer, but the curing process wasn’t modified. Also the soil composition differs every time new soil is brought to the site, which can change the strength drastically.
While researching the hardening curves for CSEB, an alternative testing method was developed. Multiple ideas have been tested, such as a torque wrench with vice, a drop test and finally a lever arm test. The first two methods were deemed unusable as they broke down or were not able to produce reliable results. The lever arm test was most promising as this method produced constant results. Against expectations, the strength of the bricks tested by the lever arm tested was much higher than the strength of the bricks tested with the compression tester. This indicated that not exactly the same properties were measured. The results cannot be directly compared to each other. Before the method can be implemented there is more research necessary about which property is tested with the lever arm and the converting factor.
To predict the final strength of CSEB, a research into the existence of a drying/hardening curve was performed. Different regions in Nepal ask for different CSEB mixtures because of differences in humidity, temperature, altitude and soil consistency. The biggest influence of the change in hardening process is presumably the cement percentage and therefore also the water/cement ratio. In the Nepali practice this percentage is between 5 and 15 percent, depending on local soil type. Therefore, in this research all soil parameters were kept constant except cement percentages, they range from 5 till 15 percent. To develop a hardening curve, bricks were tested after 5, 8, 14, 21 and 28 days. This was done using a (calibrated) compression machine. Results of these tests showed wide spread. The tested bricks were still moist and it was decided to test the CSEB after 38 days as well. This resulted in an even bigger gain in strength such that the bricks after 38 days were twice the strength of the bricks after 28 days.
General conclusion can be drawn that the time period between the curing and testing of the brick makes a significant difference in the results, so this has to be monitored accurately. Furthermore continued curing does not necessarily contribute to the strength of the bricks or might even have a negative effect.
Results from the compression test showed that the general quality, and thus compression strength, of the bricks was lacking. Only bricks with 15% cement surpass the minimum strength of 3.50 MPa after 38 days. This showed that production site was not working properly, therefor Build Up Nepal was informed. This lack of strength is probably caused by a change in variables. The weather in the winter is very different than in summer, but the curing process wasn’t modified. Also the soil composition differs every time new soil is brought to the site, which can change the strength drastically.
While researching the hardening curves for CSEB, an alternative testing method was developed. Multiple ideas have been tested, such as a torque wrench with vice, a drop test and finally a lever arm test. The first two methods were deemed unusable as they broke down or were not able to produce reliable results. The lever arm test was most promising as this method produced constant results. Against expectations, the strength of the bricks tested by the lever arm tested was much higher than the strength of the bricks tested with the compression tester. This indicated that not exactly the same properties were measured. The results cannot be directly compared to each other. Before the method can be implemented there is more research necessary about which property is tested with the lever arm and the converting factor.