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Laser ultrasonic imaging and damage detection for a rotating structure
Park, Byeongjin,Sohn, Hoon,Yeum, Chul-Min,Truong, Thanh C SAGE Publications 2013 Structural health monitoring Vol.12 No.5
<P>This study presents a laser ultrasonic imaging and damage detection technique that creates images of ultrasonic waves propagating on a rotating structure and identifies damage. Laser ultrasonics is attractive for nondestructive testing mainly because of two reasons: (1) ultrasonic waves can be generated and/or measured in a noncontact manner and (2) even a small defect can be detected when laser ultrasonic scanning produces ultrasonic images with high spatial resolution. However, when it comes to a moving target, it becomes challenging to create reliable ultrasonic images. In this study, ultrasonic wave propagation images are obtained from a rotating blade using a pulse laser beam for ultrasonic generation, a galvanometer for laser scanning, and an embedded piezoelectric sensor for ultrasonic measurement. To properly estimate the laser excitation points during the scanning process rather than to precisely control the excitation points, a simple but rather effective localization technique is developed so that ultrasonic images can be constructed even from a moving target. Once the ultrasonic wave propagation images are created, damage on the target structure is visualized using a specially designed standing wave filter.</P>
Park, Byeongjin,Sohn, Hoon,Malinowski, Pawel,Ostachowicz, Wieslaw Taylor Francis 2017 Nondestructive testing and evaluation Vol.32 No.1
<P>In this study, a two-level scanning strategy for a noncontact laser ultrasonic measurement system is proposed to expedite the inspection of a wind turbine blade. First, coarse scanning of the entire blade is performed with a low spatial resolution for initial delamination localisation. Then, dense scanning with a high spatial resolution is performed only within the identified delaminated region for delamination visualization. This study especially focuses on the initial delamination localisation using adaptive coarse scanning. Laser ultrasonic responses from two pitch-catch paths, names inspection pairs, are obtained within a specified coarse scanning grid. Then, potential delamination locations within the given grid are estimated through time-of-flight analysis of delamination reflected waves. Once potential delamination locations are estimated, new inspection pairs are placed near the potential locations for precise localisation. These steps are repeated for every coarse scanning grids on the target wind turbine blade. The feasibility of the proposed technique for rapid delamination detection is demonstrated with a 10 kW glass fibre reinforced plastic wind turbine blade.</P>
Park, Byeongjin,Sohn, Hoon Institute of Physics Publishing 2017 Smart materials & structures Vol.26 No.7
<P>Laser ultrasonic scanning, especially full-field wave propagation imaging, is attractive for damage visualization thanks to its noncontact nature, sensitivity to local damage, and high spatial resolution. However, its practicality is limited because scanning at a high spatial resolution demands a prohibitively long scanning time. Inspired by binary search, an accelerated damage visualization technique is developed to visualize damage with a reduced scanning time. The pitch-catch distance between the excitation point and the sensing point is also fixed during scanning to maintain a high signal-to-noise ratio (SNR) of measured ultrasonic responses. The approximate damage boundary is identified by examining the interactions between ultrasonic waves and damage observed at the scanning points that are sparsely selected by a binary search algorithm. Here, a time-domain laser ultrasonic response is transformed into a spatial ultrasonic domain response using a basis pursuit approach so that the interactions between ultrasonic waves and damage, such as reflections and transmissions, can be better identified in the spatial ultrasonic domain. Then, the area inside the identified damage boundary is visualized as damage. The performance of the proposed damage visualization technique is validated excusing a numerical simulation performed on an aluminum plate with a notch and experiments performed on an aluminum plate with a crack and a wind turbine blade with delamination. The proposed damage visualization technique accelerates the damage visualization process in three aspects: (1) the number of measurements that is necessary for damage visualization is dramatically reduced by a binary search algorithm; (2) the number of averaging that is necessary to achieve a high SNR is reduced by maintaining the wave propagation distance short; and (3) with the proposed technique, the same damage can be identified with a lower spatial resolution than the spatial resolution required by full-field wave propagation imaging.</P>
The Peroxisomal Localization of Hsd17b4 Is Regulated by Its Interaction with Phosphatidylserine
Lee, Sang-Ah,Lee, Juyeon,Kim, Kwanhyeong,Moon, Hyunji,Min, Chanhyuk,Moon, Byeongjin,Kim, Deokhwan,Yang, Susumin,Park, Hyunjin,Lee, Gwangrog,Park, Raekil,Park, Daeho Korean Society for Molecular and Cellular Biology 2021 Molecules and cells Vol.44 No.4
Phosphatidylserine (PS), a negatively charged phospholipid exclusively located in the inner leaflet of the plasma membrane, is involved in various cellular processes such as blood coagulation, myoblast fusion, mammalian fertilization, and clearance of apoptotic cells. Proteins that specifically interact with PS must be identified to comprehensively understand the cellular processes involving PS. However, only a limited number of proteins are known to associate with PS. To identify PS-associating proteins, we performed a pulldown assay using streptavidin-coated magnetic beads on which biotin-linked PS was immobilized. Using this approach, we identified Hsd17b4, a peroxisomal protein, as a PS-associating protein. Hsd17b4 strongly associated with PS, but not with phosphatidylcholine or sphingomyelin, and the Scp-2-like domain of Hsd17b4 was responsible for this association. The association was disrupted by PS in liposomes, but not by free PS or the components of PS. In addition, translocation of PS to the outer leaflet of the plasma membrane enriched Hsd17b4 in peroxisomes. Collectively, this study suggests an unexpected role of PS as a regulator of the subcellular localization of Hsd17b4.
Kang Byeongjin,Noh Maengseok,Park Hyun Jun 대한남성과학회 2022 The World Journal of Men's Health Vol.40 No.4
Purpose: To determine the compliance rate with testosterone replacement therapy (TRT) in patients with testosterone deficiency syndrome (TDS), we evaluated the treatment continuation rate and the reasons for discontinuation of initial treatment according to each formulations and patient characteristics. Materials and Methods: Among men over 40 years of age who were diagnosed with TDS and then underwent TRT, their medical records were retrospectively analyzed for those who were followed up for more than 10 years. Results: A total of 640 patients were included in the analysis. It was found that 75.9% of patients continued treatment for 1 year after starting. Patients treated with 1,000 mg of testosterone undecanoate injection had the highest treatment rate. Inconvenience of medication was the most common reason for discontinuing treatment, followed by cost, concern about side effects, lack of efficacy, and symptom recovery. The reasons for discontinuing treatment differed according to the type of formulations, and the longest continuous treatment period in all patients was 15.4±7.6 months on average. The treatment continuation rate tended to be high in patients with low serum total testosterone before starting treatment, in patients with severe erectile dysfunction, and in patients using phosphodiesterase-5 (PDE5) inhibitors. Conclusions: Among the various formulations of TDS, testosterone undecanoate injection (1,000 mg) had the highest compliance rate. In addition, it was found that the reasons for discontinuation of treatment varied according to the characteristics of each formulation.
After cell death: the molecular machinery of efferocytosis
Moon Byeongjin,Yang Susumin,Moon Hyunji,Lee Juyeon,Park Daeho 생화학분자생물학회 2023 Experimental and molecular medicine Vol.55 No.-
Cells constituting a multicellular organism die in a variety of ways throughout life, and most of them die via apoptosis under normal conditions. The occurrence of apoptosis is especially prevalent during development and in tissues with a high cellular turnover rate, such as the thymus and bone marrow. Interestingly, although the number of apoptotic cells produced daily is known to be innumerable in a healthy adult human body, apoptotic cells are rarely observed. This absence is due to the existence of a cellular process called efferocytosis that efficiently clears apoptotic cells. Studies over the past decades have focused on how phagocytes are able to remove apoptotic cells specifically, swiftly, and continuously, resulting in defined molecular and cellular events. In this review, we will discuss the current understanding of the clearance of apoptotic cells at the molecular level.
김병진(Byeongjin Kim),박재훈(Chaehoon Park),장인배(Inbae Chang) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.5
The artificial arm is developed for medical trainees to exercise pulsimeter and tonometer. The arm has a pressure gage to monitor the cuff pressure. If the cuff pressure changes to the blood pressure range which is set by external controller, a audio speaker which is driven by MP3 chip plays the Korotkoff sounds an artificial vane which is located at the wrist which is driven by a solenoid actuator beats. The touch screen type LCD monitor is adopted for external controller and the control system can set not only the blood pressure but also various types of disease. The artificial arm which is developed in this paper can be applied for training the student nurses.