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NDE Inspection of Terahertz Waves in Wind Turbine Composites
David Kuei Hsu,임광희,이길성,박제웅,우용득 한국정밀공학회 2012 International Journal of Precision Engineering and Vol. No.
An investigation of terahertz waves was made for the nondestructive evaluation of composite materials and structures in the wind turbine. The modalities of the terahertz radiation used were time domain spectroscopy (TDS) and continuous wave (CW). The composite materials and structures investigated include both non-conducting polymeric composites and conducting carbon fiber composites. Terahertz signals in the TDS mode resembles that of ultrasound; however, unlike ultrasound, a terahertz pulse was able to detect a smaller crack hidden behind a larger crack. This was demonstrated in thick GFRP (glass fiber reinforced plastics) laminates of the wind turbine using saw slots. In carbon composites the penetration of terahertz waves is quite limited and the detection of flaws is strongly affected by the angle between the electric field direction of the terahertz waves and the intervening fiber directions. The structures used in this study included both solid laminates and the parts in the wind turbine. The defects and anomalies investigated by terahertz radiation were foreign material inclusions, simulated disband, delamination and mechanical impact damage. The effectiveness and limitations of terahertz radiation are defined and noted for the NDE of composites.
Hsu-Hsin Chiang,Tzu-Shian Han,David McConville 글로벌지식마케팅경영학회 2014 Global Marketing Conference Vol.2014 No.7
In this paper we explore the relationships between brand-centered human resource management (HRM) and brand citizenship behavior. The roles of person-brand fit and brand commitment are discussed, and seven hypotheses presented. Using multilevel analysis, we test whether these concepts mediate the relationship between brand-centered HRM and brand citizenship behavior.
Hsu-Hsin Chiang,Tzu-Shian Han,David McConville 글로벌지식마케팅경영학회 2014 Global Marketing Conference Vol.2014 No.10
In this paper we explore the relationships between brand-centered human resource management (HRM) and brand citizenship behavior. The roles of person-brand fit and brand commitment are discussed, and seven hypotheses presented. Using multilevel analysis, we test whether these concepts mediate the relationship between brand-centered HRM and brand citizenship behavior.
박제웅,임광희,David K. Hsu,정종안,양인영 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.7
The importance of carbon fiber reinforced plastics (CFRP) has been generally recognized, and CFRP composite laminates have become widely used. Thus, a nondestructive technique would be very useful for evaluating CF/epoxy composite laminates. A pitch-catch UT signal is more sensitive than is a normal incidence backwall echo of a longitudinal wave in composites. The depth of the sampling volume where the pitch-catch UT signal came from is relatively shallow, but the depth can be increased by increasing the separation distance of the transmitting and receiving probes. Moreover, a method is utilized to determine the porosity content of a composite lay-up by processing micrograph images of the laminate. The porosity content of a composite structure is critical to the overall strength and performance of the structure. The image processing method developed utilizes software to process micrograph images of the test sample. The results from the image processing method are compared with existing data. Beam profile is characterized in unidirectional CFRP using pitch-catch Rayleigh probes. The one-sided and two-sided pitch-catch techniques are utilized to produce C-scan images with the aid of an automatic scanner. The pitch-catch ultrasonic signal corresponds with the simulated results of unidirectional CFRP composites.
Spinal Dural Arteriovenous Fistula: Imaging Features and Its Mimics
Ying Jeng,David Yen-Ting Chen,Hui-Ling Hsu,Yen-Lin Huang,Chi-Jen Chen,Ying-Chi Tseng 대한영상의학회 2015 Korean Journal of Radiology Vol.16 No.5
Spinal dural arteriovenous fistula (SDAVF) is the most common spinal vascular malformation, however it is still rare and underdiagnosed. Magnetic resonance imaging findings such as spinal cord edema and dilated and tortuous perimedullary veins play a pivotal role in the confirmation of the diagnosis. However, spinal angiography remains the gold standard in the diagnosis of SDAVF. Classic angiographic findings of SDAVF are early filling of radicular veins, delayed venous return, and an extensive network of dilated perimedullary venous plexus. A series of angiograms of SDAVF at different locations along the spinal column, and mimics of serpentine perimedullary venous plexus on MR images, are demonstrated. Thorough knowledge of SDAVF aids correct diagnosis and prevents irreversible complications.
Terahertz spectroscopy approach of the fiber orientation influence on CFRP composite solid laminates
박제웅,임광희,David K. Hsu,정종안,양인영 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.7
Terahertz ray (T-ray) imaging applications have provided one of the most promising new powerful nondestructive evaluation techniques,and new application systems are under process development for area applications. Detecting flaws and defects in fiber reinforced plastic (FRP) composite laminates due to flaws in FRP composite laminate that affect laminate properties, including stiffness, strength,and thermal behavior, is very important. In this study, a new time-domain spectroscopy system was utilized for detecting and evaluating the flaws in FRP solid composite laminates. Extensive experimental measurements in reflection mode were made to map out T-ray images. In particular, electromagnetic properties, such as refractive index, were estimated in this characterization procedure. The estimates of properties were in good agreement with known data. Using these characteristic material properties, we successfully demonstrated the characteristics of the T-ray behavior propagating through FRP composites. Furthermore, layup effect and flaws of FRP composite laminates were observed in reflection mode, and limitations were discussed in the T-ray processing.
Moayyeri, Alireza,Hsu, Yi-Hsiang,Karasik, David,Estrada, Karol,Xiao, Su-Mei,Nielson, Carrie,Srikanth, Priya,Giroux, Sylvie,Wilson, Scott G.,Zheng, Hou-Feng,Smith, Albert V.,Pye, Stephen R.,Leo, Paul J IRL Press 2014 Human molecular genetics Vol.23 No.11
<P>Quantitative ultrasound of the heel captures heel bone properties that independently predict fracture risk and, with bone mineral density (BMD) assessed by X-ray (DXA), may be convenient alternatives for evaluating osteoporosis and fracture risk. We performed a meta-analysis of genome-wide association (GWA) studies to assess the genetic determinants of heel broadband ultrasound attenuation (BUA; <I>n</I> = 14 260), velocity of sound (VOS; <I>n</I> = 15 514) and BMD (<I>n</I> = 4566) in 13 discovery cohorts. Independent replication involved seven cohorts with GWA data (<I>in silico n</I> = 11 452) and new genotyping in 15 cohorts (<I>de novo n</I> = 24 902). In combined random effects, meta-analysis of the discovery and replication cohorts, nine single nucleotide polymorphisms (SNPs) had genome-wide significant (<I>P</I> < 5 × 10<SUP>−8</SUP>) associations with heel bone properties. Alongside SNPs within or near previously identified osteoporosis susceptibility genes including <I>ESR1</I> (6q25.1: rs4869739, rs3020331, rs2982552), <I>SPTBN1</I> (2p16.2: rs11898505), <I>RSPO3</I> (6q22.33: rs7741021), <I>WNT16</I> (7q31.31: rs2908007), <I>DKK1</I> (10q21.1: rs7902708) and <I>GPATCH1</I> (19q13.11: rs10416265), we identified a new locus on chromosome 11q14.2 (rs597319 close to <I>TMEM135</I>, a gene recently linked to osteoblastogenesis and longevity) significantly associated with both BUA and VOS (<I>P</I> < 8.23 × 10<SUP>−14</SUP>). In meta-analyses involving 25 cohorts with up to 14 985 fracture cases, six of 10 SNPs associated with heel bone properties at <I>P</I> < 5 × 10<SUP>−6</SUP> also had the expected direction of association with any fracture (<I>P</I> < 0.05), including three SNPs with <I>P</I> < 0.005: 6q22.33 (rs7741021), 7q31.31 (rs2908007) and 10q21.1 (rs7902708). In conclusion, this GWA study reveals the effect of several genes common to central DXA-derived BMD and heel ultrasound/DXA measures and points to a new genetic locus with potential implications for better understanding of osteoporosis pathophysiology.</P>
On Fiber Orientation Characterization of CERP Laminate Layups Using Ultrasonic Azimuthal Scanners
Im Kwang-Hee,Hsu, David K.,Sim Jae-Gi,Yang, In-Young,Song, Sung-Jin The Korean Society for Nondestructive Testing 2003 한국비파괴검사학회지 Vol.23 No.6
Carbon-fiber reinforced plastics (CFRP) composite laminates often possess strong in-plane elastic anisotropy attributable to the fiber orientation and layup sequence. The layup orientation thus greatly influences its properties in a composite laminate. It could result in the part being rejected or discarded if the layup orientation of a ply is misaligned. A nondestructive technique would be very beneficial, which could be used to test the part after curing and to require less time than the optical test. In this paper, ultrasonic scanners were set out for different measurement modalities for acquiring ultrasonic signals as a function of in-plane azimuthal angle. The motorized scanner was built first for making transmission measurements using a pair of normal-incidence shear wave transducers. Another scanner was then built fer the acousto-ultrasonic configuration using contact transducers. A ply-by-ply vector decomposition model has been developed, simplified, and implemented for composite laminates fabricated from unidirectional plies. We have compared the test results with model data. It is found that strong agreement are shown between tests and the model developed in characterizing cured layups of the laminates.