• Journal of the Korean Society for Nondestructive Testing
• /
• v.29 no.4
• /
• pp.374-382
• /
• 2009

Steam generator(SG) tube, as a barrier isolating primary to the secondary coolant system of nuclear power plants(NPP), must maintain the structural integrity far the public safety and its efficient power generation capacity. And SG tubes bearing defects must be timely detected and taken repair measures if needed. For the accomplishment of these objectives, SG tubes have been periodically examined by eddy current testing(ECT) on the basis of administrative notices and intensified SG management program(SGMP). Stress corrosion cracking(SCC) on the SG tubes is not easily detected and even missed since it has lower signal amplitude and other disturbing factors against its detection. However once SCC is developed, that can cause detrimental affects to the SG tubes due to its rapid propagation rate. Accordingly SCC is categorized as prime damage mechanism challenging the soundness of the SG tubes. In this study, reproduced EDM notch specimens are examined for the detectability and quantitative characterization of the axial ODSCC by +PT MRPC probe, containing pancake, +PT and shielded pancake coils apart in a single plane around the circumference. The results of this study are assumed to be applicable fur providing key information of engineering evaluation of SCC and improvement of confidence level of ECT on SG tubes.

• Korean Journal of Agricultural Science
• /
• v.42 no.3
• /
• pp.191-199
• /
• 2015

We conducted this research to observe the changes of surface morphology and composition of clay minerals influenced by various concentrations of fluoric acid. Hydrofluoric acid (HA), a solution of hydrogen fluoride (HF) in water, is a colourless solution that is highly corrosive, capable of dissolving many materials, especially oxides. To do this, we treated several concentrations of HA on the ground soil samples collected from the agricultural experimental station located at Chungnam National University to observe the influence of fluoric acid on the changes of surface structures and elemental composition of clay particles. Generally, microscopic examination showed that the HA can not only attack an edge of clay particles but also start at any point where structural defects and weaknesses predisposed sites to acid. The orderly flake arrangement of clay minerals may reflect certain crystal symmetry elements. The ESEM-EDS results of element composition of clay particles influenced by HA indicated the changes of structures of clay minerals. It is also clear from the formation of etch figures and element composition of clay particles that the product layer at least partially dissolved or disintegrated in the presence of acid. Conclusively, the clay structures can be strongly influenced by concentrations of HA, resulting in changes of physical and chemical properties that can determine the behavior of solute transport as well as mobility of ions in soils.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.41 no.6
• /
• pp.25-31
• /
• 2004

In this paper, we introduce kinetic Monte Carlo (kMC) methods for simulating diffusion process in nano-scale device fabrication. At first, we review kMC theory and backgrounds and give a simple point defect diffusion process modeling in thermal annealing after ion (electron) implantation into Si crystalline substrate to help understand kinetic Monte Carlo methods. kMC is a kind of Monte Carlo but can simulate time evolution of diffusion process through Poisson probabilistic process. In kMC diffusion process, instead of. solving differential reaction-diffusion equations via conventional finite difference or element methods, it is based on a series of chemical reaction (between atoms and/or defects) or diffusion events according to event rates of all possible events. Every event has its own event rate and time evolution of semiconductor diffusion process is directly simulated. Those event rates can be derived either directly from molecular dynamics (MD) or first-principles (ab-initio) calculations, or from experimental data.

• Archives of Reconstructive Microsurgery
• /
• v.14 no.1
• /
• pp.1-13
• /
• 2005

Purpose: The purpose of this study is to present extended indications for the use of arterialized venous flaps in reconstructing soft tissue, tendon, nerve, blood vessel, and composite tissue defects of the hand of various sizes based on researches and clinical experiences of the authors. Moreover, procedures to achieve complete flap survival and postoperative results are presented. Materials & methods: This study is based on 154 cases of arterialized venous flaps performed to reconstruct the hand during the past 11 years. The most common cause of injury was industrial accidents with 125 cases. One hundred thirty patients or 84% of the cases had emergency operation within 2 weeks of the injury. The flaps were categorized depending on the size of the flap. Flaps smaller than $10\;cm^2$ were classified as small (n=48), those larger than $25\;cm^2$ classified large (n=42) and those in between medium (n=64). Classified according to composition, there were 88 cases (57.1 %) of venous skin flaps, 28 cases of innervated venous flaps, 15 cases of tendocutaneous venous flaps, which incorporated the palmaris longus tendon, for repair of extensor tendons of the fingers, and 17 cases of conduit venous flaps to repair arterial defect. There were 37 cases where multiple injuries to multiple digits were reconstructed. Moreover, there were 6 cases of composite tissue effects that involved soft tissue, blood vessels and tendons. The donor sites were ipsilateral forearm, wrist and thenar area, foot dorsum, and medial calf. The recipient sites were single digit, multiple digits, first web space, dorsum and palm of hand, and wrist. Results: There were seven cases (4.5%) of emergent re-exploration due to vascular crisis, and 3 cases of flap failure characterized by more than 50% necrosis of the flap. The survival rate was 98.1 % (151/154). In small flaps, an average of 1.01 afferent arteries and 1.05 efferent veins were microanastomosed, and in large flaps, an average of 1.88 afferent arteries and 2.19 efferent veins were anastomosed. In 8 cases where innervated flaps were used for reconstructing the palm of the hand, the average static two-point discrimination was $10\;(8{\sim}15)\;mm$. In 12 cases where tenocutaneous flaps were used, active range of motion at the proximal interphalangeal joint was 60 degrees, 20 degrees at the distal interphalangeal joint, and 75 degrees at the metacarpophalangeal joint. Conclusion: We conclude that the arterialized venous flap is a valuable and effective tool in the reconstruction of hand injuries, and could have a more comprehensive set of indications.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.32 no.4
• /
• pp.410-417
• /
• 2012

Currently domestic thermal and nuclear power plants are comprised of many type's condenser and steam generator tubes to produce the electricity of good quality. There are some methods to inspect these tubes in the event that several defects were discovered in these facilities. Among many non-destructive methods, we used guided wave to inspect the soundness of tubes, because this method is very fast to detect the defect and very simple to install the equipment and also, can inspect up to the long range at a fixed point. Also, this method has a drawback that does not detect a very small size defect. So, we made an effort to overcome this drawback through the experimentation and signal analysis according to the size and shape of the defect through the manufacture of various artificial cracks capable to generate within the small size tube in the study and we anticipate that these detect limits can be overcome along with the development of the signal processing and manufacturing technology of the sensor for the inspection.

• Journal of the Korean Vacuum Society
• /
• v.6 no.3
• /
• pp.235-241
• /
• 1997

The crystallinity and the structure of heteroepitaxially grown $Y_2O_3$ films on the silicon substrates deposited by Ultra High Vacuum Ionized Cluster Beam(UHV-ICB) were investigated by Back-scattering Spectroscopy(BS)/channeling. The channeling minimum values, $X_{min}$, of the $Y_2O_3$ films deposited by other methods were 0.8~0.95 up to the present, which indicates amorphous or highly polycrystalline nature of the $Y_2O_3$ films. On the contrary, the channeling minimum value of heteroepitaxially grown $Y_2O_3$ films on Si(100) and Si(111) deposited by UHV-ICB are 0.28 and 0.25 respectively. These results point out fairly good crystalline quality. It is also observed that the top region of $Y_2O_3$ films have less crystalline defects than the bottom region regardless of the crystal direction of the Si substrates. The axis of $Y_2O_3$<111> epitaxially grown on Si(111) is tilt by $0.1^{\circ}$ with respect to Si<111>. That of $Y_2O_3$<110> on Si(100) is parallel to the Si<001>. The $Y_2O_3$ film on Si(100) grew with single domain structure and that on Si(111) grew with double domain structure. From the result of oxygen resonance BS/channeling, the oxygen atoms in heteroepitaxially grown $Y_2O_3$ film on Si(111) substrate have the crystallinity, but that on Si(100) shows almost channeling amorphous state.

• Journal of the Korean Vacuum Society
• /
• v.6 no.2
• /
• pp.143-150
• /
• 1997

In this study, doffusion barrier properties of 1000 $\AA$ thick molybdenum compound(Mo, Mo-N, $MoSi_2$, Mo-Si-N) films were investigated using sheet resistance measurement, X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), Scanning electron mircoscopy(SEM), and Rutherford back-scattering spectrometry(RBS). Each barrier material was deposited by the dc magnetron sputtering and annealed at 300-$800^{\circ}C$ for 30 min in vacuum. Mo and MoSi2 barrier were faied at low temperatures due to Cu diffusion through grain boundaries and defects in Mo thin film and the reaction of Cu with Si within $MoSi_2$, respectively. A failure temperature could be raised to $650^{\circ}C$-30 min in the Mo barrier system and to $700^{\circ}C$-30 min in the Mo-silicide system by replacing Mo and $MoSi_2$ with Mo-N and Mo-Si-N, respectively. The crystallization temperature in the Mo-silicide film was raised by the addition of $N_2$. It is considered that not only the $N_2$, stuffing effect but also the variation of crystallization temperature affects the reaction of Cu with Si within Mo-silicide. It is found that Mo-Si-N is the more effective barrier than Mo, $MoSi_2$, or Mo-N to copper penetraion preventing Cu reaction with the substrate for $30^{\circ}C$min at a temperature higher than $650^{\circ}C$.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.9
• /
• pp.291-300
• /
• 2020

The cartridges used for illuminating a desired point or area are virtually limited in tests and evaluations because of limitations, such as noise during launch, the possibility of fires caused by illuminant charge, and the annual testable quantity. Therefore, to solve these problems, a ground fixed test, which replaces the firing test, or an evaluation method to perform limited tests, can be applied more efficiently. In this paper, the results of an 81mm illuminating cartridge, KM series performed in 2019 were analyzed comprehensively to identify the trends in reliability and quality characteristics and to estimate the shelf life. The shelf life was estimated to be at least 10 years based on the time when the lower confidence level reached 80% at a confidence level of 90%. Considering only major defects, the shelf life can be estimated to be approximately 23 years. On the other hand, the shelf life was estimated to be approximately 11 to 15 years and 25 to 28 years according to the effective illuminating time. Finally, an assessment plan of illuminating cartridges for the mortars was also presented as an improvement plan for an assessment method in the future.

• Korean Journal of Materials Research
• /
• v.13 no.6
• /
• pp.347-351
• /
• 2003

II-Ⅵ ZnO compound semiconductor thin films were grown on $\alpha$-Al$_2$O$_3$(0001) single crystal substrate by radical beam assisted molecular beam epitaxy and the optical properties were investigated. Zn(6N) was evaporated using Knudsen cell and O radical was assisted at the partial pressure of 1$\times$10$^{4}$ Torr and radical beam source of 250-450 W RF power. In $\theta$-2$\theta$ x-ray diffraction analysis, ZnO thin film with 500 nm thickness showed only ZnO(0002)and ZnO(0004) peaks is believed to be well grown along c-axis orientation. Photoluminescence (PL) measurement using He-Cd ($\lambda$=325 nm) laser is obtained in the temperature range of 9 K-300 K. At 9 K and 300 K, only near band edge (NBE) is observed and the FWHM's of PL peak of the ZnO deposited at 450 RF power are 45 meV and 145 meV respectively. From no observation of any weak deep level peak even at room temperature PL, the ZnO grains are regarded to contain very low defect density and impurity to cause the deep-level defects. The peak position of free exciton showed slightly red-shift as temperature was increased, and from this result the binding energy of free exciton can be experimentally determined as much as $58\pm$0.5 meV, which is very closed to that of ZnO bulk. By van der Pauw 4-point probe measurement, the grown ZnO is proved to be n-type with the electron concentration($n_{e}$ ) $1.69$\times$10^{18}$$cm^3$, mobility($\mu$) $-12.3\textrm{cm}^2$/Vㆍs, and resistivity($\rho$) 0.30 $\Omega$$\cdot$cm.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2018.06a
• /
• pp.102-102
• /
• 2018

Electronic industry had required the finer size and the higher performance of the device. Therefore, 3-D die stacking technology such as TSV (through silicon via) and micro-bump had been used. Moreover, by the development of the 3-D die stacking technology, 3-D structure such as chip to chip (c2c) and chip to wafer (c2w) had become practicable. These technologies led to the appearance of HBM (high bandwidth memory). HBM was type of the memory, which is composed of several stacked layers of the memory chips. Each memory chips were connected by TSV and micro-bump. Thus, HBM had lower RC delay and higher performance of data processing than the conventional memory. Moreover, due to the development of the IT industry such as, AI (artificial intelligence), IOT (internet of things), and VR (virtual reality), the lower pitch size and the higher density were required to micro-electronics. Particularly, to obtain the fine pitch, some of the method such as copper pillar, nickel diffusion barrier, and tin-silver or tin-silver-copper based bump had been utillized. TCB (thermal compression bonding) and reflow process (thermal aging) were conventional method to bond between tin-silver or tin-silver-copper caps in the temperature range of 200 to 300 degrees. However, because of tin overflow which caused by higher operating temperature than melting point of Tin ($232^{\circ}C$), there would be the danger of bump bridge failure in fine-pitch bonding. Furthermore, regulating the phase of IMC (intermetallic compound) which was located between nickel diffusion barrier and bump, had a lot of problems. For example, an excess of kirkendall void which provides site of brittle fracture occurs at IMC layer after reflow process. The essential solution to reduce the difficulty of bump bonding process is copper to copper direct bonding below $300^{\circ}C$. In this study, in order to improve the problem of bump bonding process, copper to copper direct bonding was performed below $300^{\circ}C$. The driving force of bonding was the self-annealing properties of electrodeposited Cu with high defect density. The self-annealing property originated in high defect density and non-equilibrium grain boundaries at the triple junction. The electrodeposited Cu at high current density and low bath temperature was fabricated by electroplating on copper deposited silicon wafer. The copper-copper bonding experiments was conducted using thermal pressing machine. The condition of investigation such as thermal parameter and pressure parameter were varied to acquire proper bonded specimens. The bonded interface was characterized by SEM (scanning electron microscope) and OM (optical microscope). The density of grain boundary and defects were examined by TEM (transmission electron microscopy).