• Nuclear Engineering and Technology
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• v.34 no.6
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• pp.545-552
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• 2002

We developed an ultra low background gamma ray spectrometer particularly suitable for experiment which require lower detection limit. The background of a germanium spectrometer is suppressed by applying active and passive shielding technique at the same time. The active shielding devices consist of plastic scintillating plates of 50 mm thick and anti-coincidence electronic system. The shielding is made of 150 mm thick walls of very low activity lead,20 mm with activity of <10 Bq/kg and 130 mm with activity of <50 Bq/kg. The observed background count rates are 1.2 $s^{-1}$ and 0.36 $s^{-1}$ without and with the active shielding, respectively, overall the energy regions from 30 keV to 3 MeV The cosmic ray induced background is suppressed by a rate of 0.8 $s^{-1}$ at the present work. The detection efficiency curve necessary to obtain the radioactivity of environmental samples has been precisely determined on the energy regions from 80 to 2000 keV with a 10$^3$ ml marinelli beaker sample, consisting of the calibrated radionuclides $^{109}$ Cd, $^{57}$ CO, $^{139}$ Ce, $^{203}$ Hg, $^{113}$ Sn, $^{85}$Sr, $^{137}$ Cs, $^{60}$ Co and $^{88}$ Y. Virtues Of the method are demonstrated by measuring the activity of $^{137}$ Cs contained in the powdered milk.

• Journal of Korean Society of Steel Construction
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• v.11 no.4 s.41
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• pp.329-338
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• 1999

A systematic procedure to evaluate fatigue damages and to predict remaining fatigue lives is introduced for a steel railway bridge. Fatigue damages are evaluated by using the currently available fatigue damage theory. Fatigue lives with the condition of fatigue crack initiation are estimated by the probabilistic approach based on the reliability theory as well as the simplified procedure. A equivalent deterministic procedure is also suggested to assess the remaining fatigue life under various traffic conditions. Numerical simulations are used to assess dynamic stress histories with correction factors. Loading models are obtained from the passenger volume data. Train coincidences are also considered. Based on the results, the fatigue life is found to be underestimated by without considering the coincidence of trains on the bridge. The simplified method proposed in this study are found to yield approximately the same results as the systematic procedure.

• Archives of Plastic Surgery
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• v.36 no.4
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• pp.489-492
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• 2009

Purpose: Autologous fat injection is ideal for patients who wish to add contour, projection and gross volumization of the aging, atrophic face and is claimed to be a safe procedure. However, there are several case reports in the literature where patients have suffered from acute visual loss and cerebral infarction after facial fat injection. This paper will explore a rare case of vessel related complication, an arteriovenous fistula that occurs after fat injection on forehead. Method: A 28 - year - old female who showed a non - tender, soft $1.0{\times}2.5cm$ sized mass on forehead for 3 weeks. A thrill could be detected on the totuous dilatated vessel - like structure around the mass. She had a fat injection on forehead for soft tissue augmentation 3 months prior to developing the mass. 3 - dimensional brain CT angiography showed arteriovenous fistula. Results: The fistula is totally excised with ligation of feeding vessels. Pathology report showed an atypical vessel which had intimal thickening, myxoid degeneration and thrombus formation. There were no evidences of recurrence at least for 2 months of follow - up. Conclusion: An occurrence of arteriovenous fistula after autologous fat injection is very rare. After perforation of artery and vein by coincidence, blood extravasates with the formation of a hematoma capsule and a pseudocapsule around it. The hematoma capsule would expand and clot would reabsorb resulting in a cavity leading to fistula formation. Other vessel related complications like acute visual loss or cerebral infarction are very severe. Therefore, surgeons should be cautious during facial fat injection to avoid vessel injuries.

• Journal of Korea Trade
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• v.24 no.7
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• pp.73-92
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• 2020

Purpose - The letter of credit has been playing a major role to diminish overall risks which exist among concerned parties even though there are differences such as language, culture, law, and distance. This paper reviews essence of the letter of credit and its transaction principles, as well as overall practical questions based on the L/C transaction principle. It also investigates the risk of fraud occurrences in L/C transactions and the importance of fraud prevention and preventive measures in international L/C transactions, including the Fraud Rule, which is a major topic to consider in business transactions. Design/methodology - It is considered that an importing country's concerned parties and an exporting country's concerned parties face different situations. This study employs the existing framework to identify liability, responsibility, and obligation for all concerned parties across countries. Using a quite direct measurement of principles in the letter of credit, such as principle of independence, principle of abstraction, and principle of strictness and coincidence, we studied these differences. Findings - Our main findings can be summarized as follow. The paper enhances the efficiency of the L/C payment method to provide fraud generated from L/C transactions, presentation of a theoretical framework about fraud and fraud prevention, which international trading companies should acknowledge in a material way based on fraud risk resulting from taking advantage of L/C transaction principles. Originality/value - Existing studies focus on fraud accidents in L/C transactions by taking bad advantage of the characteristics of the letter of credit without suggesting risks of fraud. This paper attempts to evaluate and provide preventive measures as a solution for fraud and risky international business in a letter of credit transaction. This area of trade studies is underexplored, both empirically and theoretically, although the issue has long been important to Korean and world community foreign trade.

• Journal of Convergence for Information Technology
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• v.12 no.2
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• pp.47-53
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• 2022

Recently, with the change of the intelligent security paradigm, study to apply various information generated from various information security systems to AI-based anomaly detection is increasing. Therefore, in this study, in order to convert log-like time series data into a vector, which is a numerical feature, the CBOW and Skip-gram inference methods of deep learning-based Word2Vec model and statistical method based on the coincidence frequency were used to transform the published ADFA system call data. In relation to this, an experiment was carried out through conversion into various embedding vectors considering the dimension of vector, the length of sequence, and the window size. In addition, the performance of the embedding methods used as well as the detection performance were compared and evaluated through GRU-based anomaly detection model using vectors generated by the embedding model as an input. Compared to the statistical model, it was confirmed that the Skip-gram maintains more stable performance without biasing a specific window size or sequence length, and is more effective in making each event of sequence data into an embedding vector.

• The Journal of Economics, Marketing and Management
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• v.6 no.4
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• pp.17-27
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• 2018

Purpose - As Korea is reaching a post-aged society, the number of chronic illness is increasing, and the demand for rehabilitation medical device is growing. Although there is high potential for the growth in rehabilitation industry, because most of the related companies in Korea are relatively small, lacking capital or R&D resource, it is difficult for them to create an innovative product, and currently most of the high-tech equipments are imported. Therefore a medical device cluster, where business, research, medical institutes and universities may work cooperatively to enhance research development and solve issues is necessary for future development. Research design, data, methodology - In this method we have done a literature review of the rehabilitation industry and industrial cluster. Based on the studies, we have conducted an exploratory factor analysis by studying examples of foreign and domestic medical clusters and drawing success factors in forming a medical cluster. Next based on the studies we have conducted a survey to domestic medical device companies to find their difficulties and needs to form a successful medical device cluster. Results - This paper provides both theoretic review on success factors of forming a medical device cluster and practical analysis using case study and survey. Conclusion - The significance of this paper is that based on the literature review, we have compared actual examples of domestic/foreign medical clusters and drawn difference and coincidence between literature and actual cluster success factor. We were also able to conduct a survey on actual medical device companies and through the results we were able to search difficulties and necessities of medical device companies.

• Computational Structural Engineering
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• v.1 no.2
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• pp.101-109
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• 1988

The evaluation of the system reliability is generally quite difficult and costly as the structure becomes large and complex, especially when it is subjected to multiple time varying loads, and for redundant structures which have many possible modes of failur, e.g., system collapse through the formation of plastic hinge mechanisms. In reality most loadings acting on the structures are random in intensity as well as in occurrence time and duration. To include the load variability in time, the loads are described in terms of stochastic processes. Based on a tri-modal upper bound, a point estimate for the system reliability has been developed for more accuracy without extensive computational effort. This tri-modal point estimate also ensures the continuity of the system reliability function, which is a necessary condition in many nonlinear programming techniques. In addition, the Load Coincidence method, by which the combined effect of time varying loads are taken into account, has been modified to suitable for cases with an always-on load.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.21 no.2
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• pp.142-150
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• 1985

In this paper, stress distribution were given in consideration of bending effects in hemi-spherical shell and a modified equation of buckling load was represented with implicating the effects of plastic deformations and shape parameters. Especially, the distributions of shell near it's vertex were analyzed numerically, according to several cases of loading. For the sake of more good estimation of plastic dissipating energy, we used the yield-line method from plate theory. The modified criterion of bucking, P super(*) sub(cr), that was suggested in this study, was applied to SUS 302 stain-less steel hemi-spherical shell which had it's Poisson's ratio and Young's modulus with 0.33 and 19700 kg/mm$^2$. From some experiments and comparisons with other results, 재 suggested the critical buckling-load-equation with P super(*) sub(cr)=2E super(*).(t super(2)/a super(2)).{3(1-ν super(*2)} and computed the buckling initiation load with this equation. Because these result from modified criterion have more coincidence than previous one, we prospect this equation can be magnified it's utilities to the other materials.

• Nuclear Engineering and Technology
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• v.51 no.2
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• pp.526-532
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• 2019

In this study, an in-house $^{152}Eu$ calibration source was produced from a custom epoxy matrix with a density of ${\rho}=1.14g\;cm^{-3}$, which is chemically stable and durable form after its solidification. The homogeneity of $^{152}Eu$ in matrix was obtained better than 98%. For a Marinelli beaker geometry, an efficiency calibration procedure was applied to a n-type, coaxial, 78.5% relative efficient HPGe detector in the energy range of 121.7-1408.0 keV by using in-house $^{152}Eu$ calibration source. Then the measured efficiencies for Marinelli geometry were compared with the results calculated by MEFFTRAN and ANGLE softwares for the validation. Although MEFFTRAN and ANGLE have two different efficiency transfer algorithms to calculate the efficiencies, they usually need to use a reliable and accurate reference efficiency values as input data. Hence, reference efficiency values were obtained experimentally from a multinuclide standard source for the same detector-Marinelli geometry. In the present source characterization, the corrections required for self-absorption and true coincidence summing effects for $^{152}Eu$ gamma-rays were also obtained for a such close counting geometry condition. The experimental results confirmed the validity of efficiency calculations obtained by MEFFTRAN and ANGLE softwares that are calculation tools.

• Journal of Radiation Protection and Research
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• v.34 no.4
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• pp.170-175
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• 2009

For the emergency radiation monitoring using gamma spectrometry, we should sufficiently survey the background spectra as environmental samples with systematic nuclide identification method. In this study, we obtained the gamma ray energy spectrum using a HPGe gamma spectrometry system from an air sample. And we identified nuclide of the gamma ray energy peaks in the spectrum using two methods -1) Half life calculation and 2) survey for cascade coincidence summing peaks using nuclear data. As the results, we produced the nuclide identification results for the air sample.