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Search Results: 1 - 10 of 28711 matches for " Jung-Ryul Lee "
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Laser Ultrasonic System for Surface Crack Visualization in Dissimilar Welds of Control Rod Drive Mechanism Assembly of Nuclear Power Plant
Yun-Shil Choi,Hyomi Jeong,Jung-Ryul Lee
Shock and Vibration , 2014, DOI: 10.1155/2014/296426
Abstract: In this paper, we propose a J-groove dissimilar weld crack visualization system based on ultrasonic propagation imaging (UPI) technology. A full-scale control rod drive mechanism (CRDM) assembly specimen was fabricated to verify the proposed system. An ultrasonic sensor was contacted at one point of the inner surface of the reactor vessel head part of the CRDM assembly. Q-switched laser beams were scanned to generate ultrasonic waves around the weld bead. The localization and sizing of the crack were possible by ultrasonic wave propagation imaging. Furthermore, ultrasonic spectral imaging unveiled frequency components of damage-induced waves, while wavelet-transformed ultrasonic propagation imaging enhanced damage visibility by generating a wave propagation video focused on the frequency component of the damage-induced waves. Dual-directional anomalous wave propagation imaging with adjacent wave subtraction was also developed to enhance the crack visibility regardless of crack orientation and wave propagation direction. In conclusion, the full-scale specimen test demonstrated that the multiple damage visualization tools are very effective in the visualization of J-groove dissimilar weld cracks. 1. Introduction Control rod drive mechanism (CRDM) assembly includes a reactor vessel head (RVH) and many penetration nozzles made of carbon steel and alloy 690, respectively, as shown in Figure 1(a). The two dissimilar metal parts, namely, the RVH and penetration nozzle, are coupled with welding as shown in the unit structure of the CRDM assembly in Figure 1(b). The inner surface of the RVH, which is in direct contact with the primary coolant, is covered with cladding to prevent any reaction between the carbon steel ingredient in the RVH and the boric ingredient in the coolant. During a nuclear power plant (NPP) operation period, thermal and pressure loadings are concentrated on the penetration nozzles and dissimilar metal welding, which are comparatively fragile spots. As the operation period of nuclear plants has increased, there has been an increase in the growth of primary water stress corrosion (PWSCC) on the welds of dissimilar metals or penetration nozzles by cyclic stress. As shown in Figure 2(a), these PWSCCs ultimately grow into surface cracks and become the path of primary water leakage. While the boric acid ingredient in the coolant not only accumulates on the outer surface of the reactor vessel as boric acid deposits, but it also creates a cavity by reacting with the carbon steel ingredient of the RVH, as shown in Figure 2(b) [1]. Practically,
Development of a Numerical Model for an Expanding Tube with Linear Explosive Using AUTODYN
Mijin Choi,Jung-Ryul Lee,Cheol-Won Kong
Shock and Vibration , 2014, DOI: 10.1155/2014/436156
Abstract: Pyrotechnic devices have been employed in satellite launch vehicle missions, generally for the separation of structural subsystems such as stage and satellite separation. Expanding tubes are linear explosives enclosed by an oval steel tube and have been widely used for pyrotechnic joint separation systems. A numerical model is proposed for the prediction of the proper load of an expanding tube using a nonlinear dynamic analysis code, AUTODYN 2D and 3D. To compute a proper core load, numerical models of the open-ended steel tube and mild detonating tube encasing a high explosive were developed and compared with experimental results. 2D and 3D computational results showed good correlation with ballistic test results. The model will provide more flexibility in expanding tube design, leading to economic benefits in the overall expanding tube development procedure. 1. Introduction Pyrotechnic devices are widely used in many space applications. They are used to perform releasing, cutting, pressurization, ignition, switching, and other mechanical work to initiate flight sequences during space missions, such as the separation of subsystems, boosters, fairings, stages, or payload satellites. Such explosive separation devices generate a shock environment that could have a destructive effect on the structure and hardware, especially on electromechanical and optical equipment. The environment is very complex, and studies have revealed that little information is available describing the basic mechanism of shock transmission and predicting shock response. Therefore, improved guidelines for pyrotechnic design, development, and qualification are clearly needed [1–3]. Pyrotechnic devices may generally be divided into point sources and line sources. Typical point sources include explosive bolts, separation nuts, pin pullers and pushers, and certain combinations of point sources for low explosive actuation. Typical linear sources include flexible linearly shaped charges, mild detonating fuses, and Super*Zip for high explosive actuation [4, 5]. An example of line sources is shown in Figure 1. The pyrotechnic device shown is a high-load-carrying separation system that must act without contamination of the payload and is called an expanding tube in this study. The device is one of the greatest shock producers in aerospace separation systems. The detailed components of the expanding tube are also represented in Figure 1, consisting of an MDF (mild detonating fuse), support, and a flattened steel tube. The MDF is a small diameter extruded tube containing a single strand of
Advances in Structural Health Management and Composite Structures 2012
Gyuhae Park,Jung-Ryul Lee,Chan-Yik Park
Shock and Vibration , 2014, DOI: 10.1155/2014/109678
Abstract:
Analysis of the near-resonant fluorescence spectra of a single rubidium atom localized in a three-dimensional optical lattice
Wookrae Kim,Changwon Park,Jung-Ryul Kim,Yea-Lee Lee,Jisoon Ihm,Kyungwon An
Physics , 2010,
Abstract: Supplementary information is presented on the recent work by W. Kim et al. on the matter-wave-tunneling-induced broadening in the near-resonant spectra of a single rubidium atom localized in a three-dimensional optical lattice in a strong Lamb-Dicke regime.
Fully Noncontact Wave Propagation Imaging in an Immersed Metallic Plate with a Crack
Jung-Ryul Lee,Jae-Kyeong Jang,Cheol-Won Kong
Shock and Vibration , 2014, DOI: 10.1155/2014/895693
Abstract: This study presents a noncontact sensing technique with ultrasonic wave propagation imaging algorithm, for damage visualization of liquid-immersed structures. An aluminum plate specimen (400?mm × 400?mm × 3?mm) with a 12?mm slit was immersed in water and in glycerin. A 532?nm Q-switched continuous wave laser is used at an energy level of 1.2?mJ to scan an area of 100?mm × 100?mm. A laser Doppler vibrometer is used as a noncontact ultrasonic sensor, which measures guided wave displacement at a fixed point. The tests are performed with two different cases of specimen: without water and filled with water and with glycerin. Lamb wave dispersion curves for the respective cases are calculated, to investigate the velocity-frequency relationship of each wave mode. Experimental propagation velocities of Lamb waves for different cases are compared with the theoretical dispersion curves. This study shows that the dispersion and attenuation of the Lamb wave is affected by the surrounding liquid, and the comparative experimental results are presented to verify it. In addition, it is demonstrated that the developed fully noncontact ultrasonic propagation imaging system is capable of damage sizing in submerged structures. 1. Introduction Lamb waves are useful for the detection of damages in thin sheet materials and tubular properties. Extensive developments in the application of the Lamb wave provide a foundation for the inspection of many products in the aerospace, pipe, pipeline, and transportation industries. Lamb waves are composed of a combination of two fundamental modes: symmetric and antisymmetric. For each of these modes, their velocity (phase or group) of Lamb waves varies with frequency; in other words, they are all dispersive. And, their energy is spread in time and space as it propagates. Hence, as the distance increases, the signal duration increases and the peak amplitude decreases. Also, attenuation is of concern in specimens immersed in liquid, because of leaky Lamb waves. For example, when guided Lamb waves are propagating in a plate that is placed in vacuum or in air, both plate surfaces are considered to be untrammeled. But, if one or both of the surfaces are in contact with liquid, the guided plate waves become leaky Lamb waves, because the energy of the wave leaks to the adjacent liquid. Ultrasonic waves are increasingly being investigated for nondestructive evaluation (NDE) and structural health management (SHM) of engineering systems, because they can propagate over long distances and cover relatively large areas of thin plates. They can travel
Novel Fiber Optic Sensor Probe with a Pair of Highly Reflected Connectors and a Vessel of Water Absorption Material for Water Leak Detection
Tae-Sik Cho,Ki-Sun Choi,Dae-Cheol Seo,Il-Bum Kwon,Jung-Ryul Lee
Sensors , 2012, DOI: 10.3390/s120810906
Abstract: The use of a fiber optic quasi-distributed sensing technique for detecting the location and severity of water leakage is suggested. A novel fiber optic sensor probe is devised with a vessel of water absorption material called as water combination soil (WCS) located between two highly reflected connectors: one is a reference connector and the other is a sensing connector. In this study, the sensing output is calculated from the reflected light signals of the two connectors. The first reflected light signal is a reference and the second is a sensing signal which is attenuated by the optical fiber bending loss due to the WCS expansion absorbing water. Also, the bending loss of each sensor probe is determined by referring to the total number of sensor probes and the total power budget of an entire system. We have investigated several probe characteristics to show the design feasibility of the novel fiber sensor probe. The effects of vessel sizes of the probes on the water detection sensitivity are studied. The largest vessel probe provides the highest sensitivity of 0.267 dB/mL, while the smallest shows relatively low sensitivity of 0.067 dB/mL, and unstable response. The sensor probe with a high output value provides a high sensitivity with various detection levels while the number of total installable sensor probes decreases.
Fluorescence spectra of atoms in a phase-stabilized magneto-optical trap as an optical lattice
Seokchan Yoon,Youngwoon Choi,Sungsam Kang,Wook-Rae Kim,Jung-Ryul Kim,Kyungwon An
Physics , 2015,
Abstract: We present a study on characteristics of a magneto-optical trap (MOT) as an optical lattice. Fluorescence spectra of atoms trapped in a MOT with a passively phase-stabilized beam configuration have been measured by means of the photon-counting heterodyne spectroscopy. We observe a narrow Rayleigh peak and well-resolved Raman sidebands in the fluorescence spectra which clearly show that the MOT itself behaves as a three-dimensional optical lattice. Optical-lattice-like properties of the phase-stabilized MOT such as vibrational frequencies and lineshapes of Rayleigh peak and Raman sidebands are investigated systematically for various trap conditions.
Three-Step Method for Proliferation and Differentiation of Human Embryonic Stem Cell (hESC)-Derived Male Germ Cells
Jung Jin Lim, Myung Sun Shim, Jeoung Eun Lee, Dong Ryul Lee
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0090454
Abstract: The low efficiency of differentiation into male germ cell (GC)-like cells and haploid germ cells from human embryonic stem cells (hESCs) reflects the culture method employed in the two-dimensional (2D)-microenvironment. In this study, we applied a three-step media and calcium alginate-based 3D-culture system for enhancing the differentiation of hESCs into male germ stem cell (GSC)-like cells and haploid germ cells. In the first step, embryoid bodies (EBs) were derived from hESCs cultured in EB medium for 3 days and re-cultured for 4 additional days in EB medium with BMP4 and RA to specify GSC-like cells. In the second step, the resultant cells were cultured in GC-proliferation medium for 7 days. The GSC-like cells were then propagated after selection using GFR-α1 and were further cultured in GC-proliferation medium for 3 weeks. In the final step, a 3D-co-culture system using calcium alginate encapsulation and testicular somatic cells was applied to induce differentiation into haploid germ cells, and a culture containing approximately 3% male haploid germ cells was obtained after 2 weeks of culture. These results demonstrated that this culture system could be used to efficiently induce GSC-like cells in an EB population and to promote the differentiation of ESCs into haploid male germ cells.
Electro-Acupuncture at Acupoint ST36 Reduces Inflammation and Regulates Immune Activity in Collagen-Induced Arthritic Mice
Yun-Kyoung Yim,Hyun Lee,Kwon-Eui Hong,Young-Il Kim,Byung-Ryul Lee,Chang-Gue Son,Jung-Eun Kim
Evidence-Based Complementary and Alternative Medicine , 2007, DOI: 10.1093/ecam/nel054
Abstract: This study aimed to investigate the anti-inflammatory, anti-arthritic and immuno-regulatory effects of electro-acupuncture (EA) at ST36 on Collagen-induced arthritis (CIA) in mice. Male DBA/1J mice were divided into five groups: Normal, Control, NR (needle retention), EAI and EAII. All mice except those in the normal group were immunized with Collagen II for arthritis induction. Acupuncture needles were inserted into mice ST36 and electrical currents at a frequency of 2 Hz in a continuous rectangular wave form were conducted through the needles for 15 min, 3 times a week. EA treatments were administered for 5 weeks in the EAI group and for 9 weeks in the EAII group. The mice in the NR group were acupunctured in the same manner as the EA groups and the needles were retained for 15 min without electrical stimulation. CIA incidence analysis, ELISA, histological analysis and FACS analysis were performed to evaluate the effect of EA on CIA. EA at ST36 significantly reduced CIA incidence, IL-6, TNF-a, INF-γ, collagen II antibody, IgG and IgM levels in CIA mice serum and prevented knee joint destruction. EA at ST36 also reduced CD69+/CD3e+ cells and CD11a+/CD19+ cells in CIA mice lymph nodes, and CD11b+/Gr1+ cells in CIA mice knee joints. The ratios of CD3e+ cells to CD19+ cells, and CD8+ cells to CD4+ cells were maintained closer to the normal range in the EA groups as compared with the control group or the NR group. EAII was more effective than EAI throughout all the measurements. The NR was effective as well, though less effective than EA. EA at ST36 may have an anti-inflammatory, anti-arthritic and immuno-regulatory effects on CIA in mice. The effectiveness is stronger when EA starts earlier and is applied longer. Needle retention without electrical stimulation may be effective on CIA as well, however less effective than EA. Electrical stimulation and acupoint ST36 may have synergistic effects on CIA.
Role of IGF-Binding Protein 3 in the Resistance of EGFR Mutant Lung Cancer Cells to EGFR-Tyrosine Kinase Inhibitors
Yun Jung Choi, Gun Min Park, Jin Kyung Rho, Sun Ye Kim, Gwang Sup So, Hyeong Ryul Kim, Chang-Min Choi, Jae Cheol Lee
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0081393
Abstract: Most patients treated with EGFR-tyrosine kinase inhibitors (EGFR-TKIs) eventually develop acquired resistance. Loss of expression of insulin-like growth factor (IGF)-binding protein-3 (IGFBP-3) has been suggested as a possible mechanism of resistance to EGFR-TKIs in the A431 and HN11 cell lines. Here, we investigated IGFBP-3 expression in two EGFR mutant lung cancer cell lines with resistance to EGFR-TKIs and examined the value of serum IGFBP-3 level as a marker of resistance. The effect of the induction or suppression of IGFBP-3 expression on resistance was also evaluated. HCC827 sublines with resistance to gefitinib (HCC827/GR) and erlotinib (HCC827/ER) were established. Loss of IGFBP-3 expression was detected by Western blotting in both cell lines without changes in transcriptional activity, and ELISA showed significantly lower amounts of secreted IGFBP-3 in the culture media of the mutant cell lines than in that of the parental line. Despite the loss of IGFBP-3 expression, IGFR signalling activity remained unchanged. Forced expression of IGFBP-3 by adenovirus-mediated transfection or recombinant IGFBP-3 slightly increased the growth-inhibitory and apoptotic effects of EGFR-TKIs, whereas suppression of IGFBP-3 did not affect sensitivity to EGFR-TKI. Serum IGFBP-3 levels measured by ELISA before and after the development of EGFR-TKI resistance in 20 patients showed no significant changes (1815.3±94.6 ng/mL before treatment vs. 1778.9±87.8 ng/mL after EGFR-TKI resistance). In summary, although IGFBP-3 downregulation is associated with the acquisition of resistance to EGFR-TKIs regardless of the mechanism, its effect on resistance was not significant, indicating that IGFBP-3 may not play an important role in resistance to EGFR-TKIs and serum IGFBP-3 level is not a reliable indicator of resistance.
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