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RISS 인기검색어
- 검색키워드
- 저자 : Kraemer (검색결과 18 건)
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Kraemer, Peter,Friedmanna, Herbert Techno-Press 2015 Wind and Structures, An International Journal (WAS Vol.21 No.6
The efficiency of wind turbines (WT) is primarily reflected in their ability to generate electricity at any time. Downtimes of WTs due to "conventional" inspections are cost-intensive and undesirable for investors. For this reason, there is a need for structural health monitoring (SHM) systems, to enable service and maintenance on demand and to increase the inspection intervals. In general, monitoring increases the cost effectiveness of WTs. This publication concentrates on the application of two vibration-based SHM algorithms for stability and structural change monitoring of offshore WTs. Only data driven, output-only algorithms based on stochastic subspace identification (SSI) in time domain are considered. The centerpiece of this paper deals with the rough mathematical description of the dynamic behavior of offshore WTs and with the basic presentation of stochastic subspace-based algorithms and their application to these structures. Due to the early stage of the industrial application of SHM on offshore WT on the one side and the required confidentiality to the plant manufacturer and operator on the other side, up to now it is not possible to analyze different isolated structural damages resp. changes in a systematic manner, directly by means of in-situ measurement and to make these "acknowledgements" publicly available. For this reason, the sensitivity of the methods for monitoring purposes are demonstrated through their application on long time measurements from a 1:10 large scale test rig of an offshore WT under different conditions: undamaged, different levels of loosened bolt connections between tower parts, different levels of fouling, scouring and structure inclination. The limitation and further requirements for the approaches and their applicability on real foundations are discussed along the paper.
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Peter Kraemer,Herbert Friedmann 한국풍공학회 2015 Wind and Structures, An International Journal (WAS Vol.21 No.6
The efficiency of wind turbines (WT) is primarily reflected in their ability to generate electricity at any time. Downtimes of WTs due to “conventional” inspections are cost-intensive and undesirable for investors. For this reason, there is a need for structural health monitoring (SHM) systems, to enable service and maintenance on demand and to increase the inspection intervals. In general, monitoring increases the cost effectiveness of WTs. This publication concentrates on the application of two vibration-based SHM algorithms for stability and structural change monitoring of offshore WTs. Only data driven, output-only algorithms based on stochastic subspace identification (SSI) in time domain are considered. The centerpiece of this paper deals with the rough mathematical description of the dynamic behavior of offshore WTs and with the basic presentation of stochastic subspace-based algorithms and their application to these structures. Due to the early stage of the industrial application of SHM on offshore WT on the one side and the required confidentiality to the plant manufacturer and operator on the other side, up to now it is not possible to analyze different isolated structural damages resp. changes in a systematic manner, directly by means of in-situ measurement and to make these “acknowledgements” publicly available. For this reason, the sensitivity of the methods for monitoring purposes are demonstrated through their application on long time measurements from a 1:10 large scale test rig of an offshore WT under different conditions: undamaged, different levels of loosened bolt connections between tower parts, different levels of fouling, scouring and structure inclination. The limitation and further requirements for the approaches and their applicability on real foundations are discussed along the paper.
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Gorman, Leah,Kraemer, George P.,Yarish, Charles,Boo, Sung Min,Kim, Jang K. The Korean Society of Phycology 2017 ALGAE Vol.32 No.1
The red alga Gracilaria vermiculophylla, a species native to the waters of Korea and Japan, has invaded marine coastal areas of Europe and the Americas, thriving in conditions that differ from those of its native habitat. In recent years, G. vermiculophylla has been discovered in the Long Island Sound (LIS) estuary growing alongside the native congener Gracilaria tikvahiae. The goal of this study was to determine whether the two strains of G. vermiculophylla from different regions of the world have evolved genetic differences (i.e., ecotypic differentiation) or if the physiological performance of the strains simply reflects phenotypic plasticity. Two strains of G. vermiculophylla (isolated in Korea and LIS) and a strain of the LIS native G. tikvahiae were grown for four weeks under temperatures ranging from 20 to $34^{\circ}C$ using a temperature gradient table (all other environmental conditions were kept constant). At the end of each week, wet weight of each sample was recorded, and thalli were reduced to the original stocking density of $1gL^{-1}$ (excess biomass was preserved for tissue carbon and nitrogen analysis). Generally, the growth rates of Korean G. vermiculophylla > LIS G. vermiculophylla > G. tikvahiae. After one week of growth G. tikvahiae grew 9.1, 12.0, 9.4, and 0.2% $d^{-1}$, at temperatures of 20, 24, 29, and $34^{\circ}C$, respectively, while G. vermiculophylla (LIS) grew 6.6, 6.2, 5.7, and 3.6% $d^{-1}$. G. vermiculophylla (Korea) grew 15.4, 22.9, 23.2, and 10.1% $d^{-1}$, much higher than the two strains currently inhabiting the LIS. On average, the LIS G. vermiculophylla strain contained 4-5% DW N, while the Korean strain and G. tikvahiae had more modest levels of 2-3% N DW. However, tissue N content declined as temperature increased in LIS and Korean G. vermiculophylla. The non-native haplotype may have evolved genetic differences resulting in lower growth capacity while concentrating significantly more nitrogen, giving the non-native a competitive advantage.
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Operational modal analysis for Canton Tower
Niu, Yan,Kraemer, Peter,Fritzen, Claus-Peter Techno-Press 2012 Smart Structures and Systems, An International Jou Vol.10 No.4
The 610 m high Canton Tower (formerly named Guangzhou New Television Tower) is currently considered as a benchmark problem for structural health monitoring (SHM) of high-rise slender structures. In the benchmark study task I, a set of 24-hour ambient vibration measurement data has been available for the output-only system identification study. In this paper, the vector autoregressive models (ARV) method is adopted in the operational modal analysis (OMA) for this TV tower. The identified natural frequencies, damping ratios and mode shapes are presented and compared with the available results from some other research groups which used different methods, e.g., the data-driven stochastic subspace identification (SSI-DATA) method, the enhanced frequency domain decomposition (EFDD) algorithm, and an improved modal identification method based on NExT-ERA technique. Furthermore, the environmental effects on the estimated modal parameters are also discussed.
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Leah Gorman,GeorgeP.Kraemer,Charles Yarish,부성민,김장균 한국조류학회I 2017 ALGAE Vol.32 No.1
The red alga Gracilaria vermiculophylla, a species native to the waters of Korea and Japan, has invaded marine coastal areas of Europe and the Americas, thriving in conditions that differ from those of its native habitat. In recent years, G. vermiculophylla has been discovered in the Long Island Sound (LIS) estuary growing alongside the native congener Gracilaria tikvahiae. The goal of this study was to determine whether the two strains of G. vermiculophylla from different regions of the world have evolved genetic differences (i.e., ecotypic differentiation) or if the physiological performance of the strains simply reflects phenotypic plasticity. Two strains of G. vermiculophylla (isolated in Korea and LIS) and a strain of the LIS native G. tikvahiae were grown for four weeks under temperatures ranging from 20 to 34°C using a temperature gradient table (all other environmental conditions were kept constant). At the end of each week, wet weight of each sample was recorded, and thalli were reduced to the original stocking density of 1 g L−1 (excess biomass was preserved for tissue carbon and nitrogen analysis). Generally, the growth rates of Korean G. vermiculophylla > LIS G. vermiculophylla > G. tikvahiae. After one week of growth G. tikvahiae grew 9.1, 12.0, 9.4, and 0.2% d−1, at temperatures of 20, 24, 29, and 34°C, respectively, while G. vermiculophylla (LIS) grew 6.6, 6.2, 5.7, and 3.6% d−1. G. vermiculophylla (Korea) grew 15.4, 22.9, 23.2, and 10.1% d−1, much higher than the two strains currently inhabiting the LIS. On average, the LIS G. vermiculophylla strain contained 4–5% DW N, while the Korean strain and G. tikvahiae had more modest levels of 2–3% N DW. However, tissue N content declined as temperature increased in LIS and Korean G. vermiculophylla. The non-native haplotype may have evolved genetic differences resulting in lower growth capacity while concentrating significantly more nitrogen, giving the non-native a competitive advantage.
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RT-PA(Recombinant Tissue Plasminogen Activator)가 굴근건 유착에 미치는 영향에 관한 연구
안상태,Bruce A, Kraemer,Margie Mohler,Margie Mohler,M.S. 대한성형외과학회 1992 Archives of Plastic Surgery Vol.19 No.3
Formation of peritendinous adhesions often impairs the outcome of flexor tendon repairs. Peritendinous blood collections which form around injured tendons may act as a scaffold for later adhesion formation. Modification of the peritendinous wound by recombinant tissue plasminogen activator(rt-PA) could possibily lyse the peritendinous blood clot and decrease tendon adhesions. After evaluating the activity of rt-PA in chickens, a new flexor tendon adhesion model was developed to study its effect on the tendon adhesions. Adult chicken long toe flexor profundus tendons were uniformly injured and then treated with either rt-PA in sodium hyaluronate vehicle, sodium hyaluronate vehicle alone or nothing(controls). After 2 weeks of immobilization, the tendons were pulled to full flexion using a tensometer to generate a stress-strain curve. Rt-PA showed an in vitro effect in chickens at doses 25 times the dose needed in rabbits and 100 times the dose needed in humans. However, in vivo plasminogen studies suggested a 5 fold increased dose was needed in chickens as compared to rabbits. The total energy required for full DIP joint flexion in the operated control toes was 6 times that of the unoperated controls. There was no significant difference between any of the treatment groups. Use of a model which induces less adhesions, a repetitive drug dosing regimen or study of another species with greater rt-PA response is needed to determine the effectiveness of rt-PA in reducing peritendinous adhesions.
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Operational modal analysis for Canton Tower
Yan Niu,Claus-Peter Fritzen,Peter Kraemer 국제구조공학회 2012 Smart Structures and Systems, An International Jou Vol.10 No.4
The 610 m high Canton Tower (formerly named Guangzhou New Television Tower) is currently considered as a benchmark problem for structural health monitoring (SHM) of high-rise slender structures. In the benchmark study task I, a set of 24-hour ambient vibration measurement data has been available for the output-only system identification study. In this paper, the vector autoregressive models (ARV) method is adopted in the operational modal analysis (OMA) for this TV tower. The identified natural frequencies, damping ratios and mode shapes are presented and compared with the available results from some other research groups which used different methods, e.g., the data-driven stochastic subspace identification (SSIDATA) method, the enhanced frequency domain decomposition (EFDD) algorithm, and an improved modal identification method based on NExT-ERA technique. Furthermore, the environmental effects on the estimated modal parameters are also discussed.
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