The Experts below are selected from a list of 63204 Experts worldwide ranked by ideXlab platform
Hu Zongmin - One of the best experts on this subject based on the ideXlab platform.
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ADVANCES IN SHOCK Wave Reflection PHENOMENA
Advances in Mechanics, 2012Co-Authors: Hu ZongminAbstract:Advances in the study on shock Wave Reflection phenomena are reviewed.Some aspects of the advances are particularly elaborated in accordance with the research focuses of shock Wave Reflection phenomena in the past decade: weak shock Reflection,Wave configurations and transition criteria of nonstationary shock Wave Reflection,Wave configurations of steady shock Wave Reflection,and the hysteresis of shock Wave Reflection.In view of their significances in practical applications,the advances in three-dimensional shock Wave Reflection phenomena are also presented and the problems confronted are discussed.In the mean time,directions of further studies on shock Wave Reflection are suggested.
Leslie J. Struble - One of the best experts on this subject based on the ideXlab platform.
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Using ultrasonic Wave Reflection to monitor false set of cement paste
Cement and Concrete Composites, 2017Co-Authors: Chul-woo Chung, John S. Popovics, Prannoy Suraneni, Leslie J. StrubleAbstract:Abstract The standard mechanical penetration approach for monitoring cement paste stiffening (Vicat needle method, ASTM C191 ) does not distinguish responses associated with false set of cement paste caused by secondary gypsum formation. The objective of this research is to determine whether ultrasonic Wave Reflection, using a testing set up with high measurement sensitivity, could be used to monitor false set of cement paste. Penetration resistance, P-Wave, and S-Wave Reflection coefficients were measured on cement pastes with water-to-cement ratio 0.5. The S-Wave Reflection coefficient showed a sharp and abrupt linear drop associated with secondary gypsum formation, thereby indicating that S-Wave ultrasonic Wave Reflection can be used to monitor false set of cement pastes. False set could not be distinguished in penetration resistance or P-Wave UWR test data.
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Application of ultrasonic P-Wave Reflection to measure development of early-age cement-paste properties
Materials and Structures, 2013Co-Authors: Chul-woo Chung, John S. Popovics, Leslie J. Struble, Prannoy Suraneni, W. Jason WeissAbstract:Ultrasonic Wave Reflection (UWR), well established for the study of stiffening and strength development of cement-based materials, normally uses shear Waves (S-Waves) because they are sensitive to microstructural development. This study demonstrates possible application of UWR with longitudinal Waves (P-Waves) using a low impedance buffer for investigating stiffening in hydrating cement paste. The P-Wave Reflection coefficient was seen to increase modestly as hydration progressed. Also, the P-Wave Reflection coefficient showed higher values for pastes with lower water to cement ratios, which are primarily attributed to the higher density of low w/c pastes, and similar effects with addition of fly ash and entrained air. Partial debonding between paste and buffer was observed in most pastes at a time that coincided with final set as measured using S-Waves; and the debonding appears to be associated with the development of pore water under-pressure that occurs after solidification (due to chemical shrinkage).
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Setting time measurement using ultrasonic Wave Reflection
ACI Materials Journal, 2012Co-Authors: Chul-woo Chung, John S. Popovics, Prannoy Suraneni, Leslie J. StrubleAbstract:Ultrasonic shear Wave Reflection was used to investigate setting times of cement pastes by measuring the Reflection coefficient at the interface between hydrating cement pastes of varying water-to-cement ratio and an ultrasonic buffer material. Several different buffer materials were employed, and the choice of buffer was seen to strongly affect measurement sensitivity; high impact polystyrene showed the highest sensitivity to setting processes because it had the lowest acoustic impedance value. The results show that ultrasonic shear-Wave Reflection can be used successfully to monitor early setting processes of cement paste with good sensitivity when such a very low impedance buffer is employed. Criteria are proposed to define set times, and the resulting initial and final set times agreed broadly with those determined using the standard penetration resistance test.
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Flocculation and sedimentation in suspensions using ultrasonic Wave Reflection
The Journal of the Acoustical Society of America, 2011Co-Authors: Chul-woo Chung, John S. Popovics, Leslie J. StrubleAbstract:This work was undertaken to help understand and interpret the ultrasonic Wave Reflection response of Portland cement paste as it transforms from a fluid-like suspension to a solid in the first hours after mixing. A high impact polystyrene buffer (delay line) was used to measure small changes in the P- and S-Wave Reflection coefficients. Two materials were studied: a non-hydrating colloidal alumina suspension whose microstructure was manipulated between dispersed and flocculated states by adjusting the pH and a coarse silica suspension that readily sedimented. The S-Wave Reflection coefficient clearly distinguished between dispersed and flocculated states. Sedimentation of particles in dispersed suspensions was distinguished using the P-Wave Reflection coefficient. Based on these findings, the observed P- and S-Wave responses from hydrating Portland cement paste are interpreted in terms of flocculation and sedimentation processes.
Chul-woo Chung - One of the best experts on this subject based on the ideXlab platform.
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Using ultrasonic Wave Reflection to monitor false set of cement paste
Cement and Concrete Composites, 2017Co-Authors: Chul-woo Chung, John S. Popovics, Prannoy Suraneni, Leslie J. StrubleAbstract:Abstract The standard mechanical penetration approach for monitoring cement paste stiffening (Vicat needle method, ASTM C191 ) does not distinguish responses associated with false set of cement paste caused by secondary gypsum formation. The objective of this research is to determine whether ultrasonic Wave Reflection, using a testing set up with high measurement sensitivity, could be used to monitor false set of cement paste. Penetration resistance, P-Wave, and S-Wave Reflection coefficients were measured on cement pastes with water-to-cement ratio 0.5. The S-Wave Reflection coefficient showed a sharp and abrupt linear drop associated with secondary gypsum formation, thereby indicating that S-Wave ultrasonic Wave Reflection can be used to monitor false set of cement pastes. False set could not be distinguished in penetration resistance or P-Wave UWR test data.
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Application of ultrasonic P-Wave Reflection to measure development of early-age cement-paste properties
Materials and Structures, 2013Co-Authors: Chul-woo Chung, John S. Popovics, Leslie J. Struble, Prannoy Suraneni, W. Jason WeissAbstract:Ultrasonic Wave Reflection (UWR), well established for the study of stiffening and strength development of cement-based materials, normally uses shear Waves (S-Waves) because they are sensitive to microstructural development. This study demonstrates possible application of UWR with longitudinal Waves (P-Waves) using a low impedance buffer for investigating stiffening in hydrating cement paste. The P-Wave Reflection coefficient was seen to increase modestly as hydration progressed. Also, the P-Wave Reflection coefficient showed higher values for pastes with lower water to cement ratios, which are primarily attributed to the higher density of low w/c pastes, and similar effects with addition of fly ash and entrained air. Partial debonding between paste and buffer was observed in most pastes at a time that coincided with final set as measured using S-Waves; and the debonding appears to be associated with the development of pore water under-pressure that occurs after solidification (due to chemical shrinkage).
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Setting time measurement using ultrasonic Wave Reflection
ACI Materials Journal, 2012Co-Authors: Chul-woo Chung, John S. Popovics, Prannoy Suraneni, Leslie J. StrubleAbstract:Ultrasonic shear Wave Reflection was used to investigate setting times of cement pastes by measuring the Reflection coefficient at the interface between hydrating cement pastes of varying water-to-cement ratio and an ultrasonic buffer material. Several different buffer materials were employed, and the choice of buffer was seen to strongly affect measurement sensitivity; high impact polystyrene showed the highest sensitivity to setting processes because it had the lowest acoustic impedance value. The results show that ultrasonic shear-Wave Reflection can be used successfully to monitor early setting processes of cement paste with good sensitivity when such a very low impedance buffer is employed. Criteria are proposed to define set times, and the resulting initial and final set times agreed broadly with those determined using the standard penetration resistance test.
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Flocculation and sedimentation in suspensions using ultrasonic Wave Reflection
The Journal of the Acoustical Society of America, 2011Co-Authors: Chul-woo Chung, John S. Popovics, Leslie J. StrubleAbstract:This work was undertaken to help understand and interpret the ultrasonic Wave Reflection response of Portland cement paste as it transforms from a fluid-like suspension to a solid in the first hours after mixing. A high impact polystyrene buffer (delay line) was used to measure small changes in the P- and S-Wave Reflection coefficients. Two materials were studied: a non-hydrating colloidal alumina suspension whose microstructure was manipulated between dispersed and flocculated states by adjusting the pH and a coarse silica suspension that readily sedimented. The S-Wave Reflection coefficient clearly distinguished between dispersed and flocculated states. Sedimentation of particles in dispersed suspensions was distinguished using the P-Wave Reflection coefficient. Based on these findings, the observed P- and S-Wave responses from hydrating Portland cement paste are interpreted in terms of flocculation and sedimentation processes.
Marco R. Di Tullio - One of the best experts on this subject based on the ideXlab platform.
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arterial stiffness and Wave Reflection sex differences and relationship with left ventricular diastolic function
Hypertension, 2012Co-Authors: Cesare Russo, Zhezhen Jin, Vittorio Palmieri, Mitchell S.v. Elkind, Shunichi Homma, Ralph L. Sacco, Tatjana Rundek, Marco R. Di TullioAbstract:Increased arterial stiffness and Wave Reflection have been reported in heart failure with normal ejection fraction (HFNEF) and in asymptomatic left ventricular (LV) diastolic dysfunction, a precursor of HFNEF. It is unclear whether women, who have higher frequency of HFNEF, are more vulnerable than men to the deleterious effects of arterial stiffness on LV diastolic function. We investigated, in a large community-based cohort, whether sex differences exist in the relationship among arterial stiffness, Wave Reflection, and LV diastolic function. Arterial stiffness and Wave Reflection were assessed in 983 participants from the Cardiovascular Abnormalities and Brain Lesions study using applanation tonometry. The central pulse pressure/stroke volume index, total arterial compliance, pulse pressure amplification, and augmentation index were used as parameters of arterial stiffness and Wave Reflection. LV diastolic function was evaluated by 2-dimensional echocardiography and tissue-Doppler imaging. Arterial stiffness and Wave Reflection were greater in women compared with men, independent of body size and heart rate (all P<0.01), and showed inverse relationships with parameters of diastolic function in both sexes. Further adjustment for cardiovascular risk factors attenuated these relationships; however, a higher central pulse pressure/stroke volume index predicted LV diastolic dysfunction in women (odds ratio, 1.54; 95% confidence intervals, 1.03 to 2.30) and men (odds ratio, 2.09; 95% confidence interval, 1.30 to 3.39), independent of other risk factors. In conclusion, in our community-based cohort study, higher arterial stiffness was associated with worse LV diastolic function in men and women. Women's higher arterial stiffness, independent of body size, may contribute to their greater susceptibility to develop HFNEF.
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Arterial Wave Reflection and subclinical left ventricular systolic dysfunction.
Journal of hypertension, 2011Co-Authors: Cesare Russo, Zhezhen Jin, Yasuyoshi Takei, Takuya Hasegawa, Shun Koshaka, Vittorio Palmieri, Mitchell S.v. Elkind, Shunichi Homma, Ralph L. Sacco, Marco R. Di TullioAbstract:ObjectivesIncreased arterial Wave Reflection is a predictor of cardiovascular events and has been hypothesized to be a cofactor in the pathophysiology of heart failure. Whether increased Wave Reflection is inversely associated with left-ventricular (LV) systolic function in individuals without heart
John S. Popovics - One of the best experts on this subject based on the ideXlab platform.
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Using ultrasonic Wave Reflection to monitor false set of cement paste
Cement and Concrete Composites, 2017Co-Authors: Chul-woo Chung, John S. Popovics, Prannoy Suraneni, Leslie J. StrubleAbstract:Abstract The standard mechanical penetration approach for monitoring cement paste stiffening (Vicat needle method, ASTM C191 ) does not distinguish responses associated with false set of cement paste caused by secondary gypsum formation. The objective of this research is to determine whether ultrasonic Wave Reflection, using a testing set up with high measurement sensitivity, could be used to monitor false set of cement paste. Penetration resistance, P-Wave, and S-Wave Reflection coefficients were measured on cement pastes with water-to-cement ratio 0.5. The S-Wave Reflection coefficient showed a sharp and abrupt linear drop associated with secondary gypsum formation, thereby indicating that S-Wave ultrasonic Wave Reflection can be used to monitor false set of cement pastes. False set could not be distinguished in penetration resistance or P-Wave UWR test data.
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Application of ultrasonic P-Wave Reflection to measure development of early-age cement-paste properties
Materials and Structures, 2013Co-Authors: Chul-woo Chung, John S. Popovics, Leslie J. Struble, Prannoy Suraneni, W. Jason WeissAbstract:Ultrasonic Wave Reflection (UWR), well established for the study of stiffening and strength development of cement-based materials, normally uses shear Waves (S-Waves) because they are sensitive to microstructural development. This study demonstrates possible application of UWR with longitudinal Waves (P-Waves) using a low impedance buffer for investigating stiffening in hydrating cement paste. The P-Wave Reflection coefficient was seen to increase modestly as hydration progressed. Also, the P-Wave Reflection coefficient showed higher values for pastes with lower water to cement ratios, which are primarily attributed to the higher density of low w/c pastes, and similar effects with addition of fly ash and entrained air. Partial debonding between paste and buffer was observed in most pastes at a time that coincided with final set as measured using S-Waves; and the debonding appears to be associated with the development of pore water under-pressure that occurs after solidification (due to chemical shrinkage).
-
Setting time measurement using ultrasonic Wave Reflection
ACI Materials Journal, 2012Co-Authors: Chul-woo Chung, John S. Popovics, Prannoy Suraneni, Leslie J. StrubleAbstract:Ultrasonic shear Wave Reflection was used to investigate setting times of cement pastes by measuring the Reflection coefficient at the interface between hydrating cement pastes of varying water-to-cement ratio and an ultrasonic buffer material. Several different buffer materials were employed, and the choice of buffer was seen to strongly affect measurement sensitivity; high impact polystyrene showed the highest sensitivity to setting processes because it had the lowest acoustic impedance value. The results show that ultrasonic shear-Wave Reflection can be used successfully to monitor early setting processes of cement paste with good sensitivity when such a very low impedance buffer is employed. Criteria are proposed to define set times, and the resulting initial and final set times agreed broadly with those determined using the standard penetration resistance test.
-
Flocculation and sedimentation in suspensions using ultrasonic Wave Reflection
The Journal of the Acoustical Society of America, 2011Co-Authors: Chul-woo Chung, John S. Popovics, Leslie J. StrubleAbstract:This work was undertaken to help understand and interpret the ultrasonic Wave Reflection response of Portland cement paste as it transforms from a fluid-like suspension to a solid in the first hours after mixing. A high impact polystyrene buffer (delay line) was used to measure small changes in the P- and S-Wave Reflection coefficients. Two materials were studied: a non-hydrating colloidal alumina suspension whose microstructure was manipulated between dispersed and flocculated states by adjusting the pH and a coarse silica suspension that readily sedimented. The S-Wave Reflection coefficient clearly distinguished between dispersed and flocculated states. Sedimentation of particles in dispersed suspensions was distinguished using the P-Wave Reflection coefficient. Based on these findings, the observed P- and S-Wave responses from hydrating Portland cement paste are interpreted in terms of flocculation and sedimentation processes.
