• Hwankyungkyoyuk
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• v.20 no.2
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• pp.108-122
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• 2007

Recently, a new revised national curriculum('2007 Revised') of the 'Environment' subject for middle and high schools was announced, which is namely the 7th revised national curriculum. In the new national curriculum, the name of the 'environment' subject for middle schools has been unchanged, but the name of the subject for high schools has been changed from the 'Ecosystem & Environment' to 'Environment'. And some of the contents have been revised to incorporate the changed status of environmental education areas since the last announcement of the 'Environment' curriculum, which was in the late of 1997. Especially, in this new curriculum, the concept of the 'Education for Sustainable Development (ESD)' was implemented. The purpose of this research is to investigate the process of developing the new 'Environment' curriculum for middle and high schools and to examine the resulted, new revised curriculum. In order to do these, this research examined the main directions of the revision, compared the new announced curriculum with the current and the proposed one, which was researched by the authors in this article. And this research discussed the process and the announced results of the revised national curriculum of the 'Environment' subject.

• Tribology and Lubricants
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• v.22 no.2
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• pp.59-65
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• 2006

In hard disk drives as the head to disk spacing continues to decrease to facilitate recording densities, slider disk interactions have become much more severe due to direct contact of head and disk surfaces in both start/stop and flying cases. The slider disk interaction in CSS (contact-start-stop) mode is an important source of particle generation and tribocharge build-up. The tribocharge build-up in the slider disk interface can cause ESD (electrostatic discharge) damage. In turn, ESD can cause severe melting damage to MR or GMR heads. The spindle speed of typical hard disk drives has increased in recent years from 5400 rpm to 15000 rpm and even higher speeds are anticipated in the near future. And the increasing disk velocity leads to increasing disk acceleration and this might affect the tribocharging phenomena of the slider/disk interface. We investigated the tribocurrent/voltage build-up generated in HDD, operating at increasing disk accelerations. In addition, we examined the effects with relative humidity conditions and rest time. We found that the tribocurrent/voltage was generated during pico-slider/disk interaction and its level was about $3\sim16pA$ and $0.1\sim0.3V$, respectively. Tribocurrent/voltage build-up was reduced with increasing disk acceleration. Higher humidity conditions $(75\sim80%)$ produced lower levels tribovoltage/current. Therefore, a higher tribocharge is expected at a lower disk acceleration and lower relative humidity condition. Rest time affected the charge build-up at the slider-disk interface. The degree of tribocharge build-up increased with increasing rest time.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.2
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• pp.369-376
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• 2021

The International Maritime Organization has developed the Energy Efficiency Design Index, an index related to carbon dioxide emissions, to enforce regulations on newly built ships. In this study, a new type of energy-saving device called the ring stator was used for 158k crude oil carriers, whose hull form was developed as a very thin after-body hull to reduce the resistance by delaying separation. The Energy-Saving Device (ESD) particularly involving the duct, is not adapted to the thin-after body hull form-like container ship. This new ring stator was developed considering these characteristics. A parametric study was conducted through Computational Fluid Dynamics (CFD) analysis using the Star-CCM+ program, and approximately 3.4 % improvement in propulsion efficiency was achieved. Further optimization investigations and experimental studies should be conducted in the future.

• Journal of Gastric Cancer
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• v.23 no.1
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• pp.146-158
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• 2023

Endoscopic resection (ER) is widely performed for early gastric cancer (EGC) with a negligible risk of lymph node metastasis (LNM) in Eastern Asian countries. In particular, endoscopic submucosal dissection (ESD) leads to a high en bloc resection rate, enabling accurate pathological evaluation. As undifferentiated EGC (UD-EGC) is known to result in a higher incidence of LNM and infiltrative growth than differentiated EGC (D-EGC), the indications for ER are limited compared with those for D-EGC. Previously, clinical staging as intramucosal UD-EGC ≤2 cm, without ulceration, was presented as 'weakly recommended' or 'expanded indications' for ER in the guidelines of the United States, Europe, Korea, and Japan. Based on promising long-term outcomes from a prospective multicenter study by the Japan Clinical Oncology Group (JCOG) 1009/1010, the status of this indication has expanded and is now considered 'absolute indications' in the latest Japanese guidelines published in 2021. In this study, which comprised 275 patients with UD-EGC (cT1a, ≤2 cm, without ulceration) treated with ESD, the 5-year overall survival (OS) was 99.3% (95% confidence interval, 97.1%-99.8%), which was higher than the threshold 5-year OS (89.9%). Currently, the levels of evidence grades and recommendations for ER of UD-EGC differ among Japan, Korea, and Western countries. Therefore, a further discussion is warranted to generalize the indications for ER of UD-EGC in countries besides Japan.

• Journal of Gastric Cancer
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• v.10 no.1
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• pp.1-4
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• 2010

Purpose: Gastric epithelial dysplasia (GED) was defined as "unequivocally neoplastic epithelium that may be associated with or give rise to invasive adenocarcinoma" and GED also represents a direct precursor of intestinal type adenocarcinoma of the stomach. The recommended treatment guidelines for GED in the medical literature are endoscopic mucosal resection (EMR) or surgery for high grade dysplasia (HGD) and annual endoscopic surveillance with biopsy for low grade dysplasia (LGD) The aim of this study was to determine the treatment plan for GED that is diagnosed by endoscopic biopsy. Materials and Methods: We enrolled 148 patients who were treated by endoscopic mucosal resection (EMR) or endoscopiccsubmucosal dissection (ESD) for GED: there were 63 patients with HGD and 85 patients with LGD and all of them were diagnosed by endoscopic biopsy from January 2006 to December 2008. The results of the final histopathologic reports after EMR or ESD were compared with the results of the endoscopic biopsies. Results: The final histopathologic results of the 148 patients with GED showed 49 (33.1%) patients with adenocarcinoma, 40 (27.0%) patients with HGD and 59 (39.9%) patients with LGD. Among the 63 patients with HGD, 34 (54.0%) patients had adenocarcinoma, 20 (31.7%) patients had HGD and 9 (14.3%) patients had LGD. For the 85 patients with LGD, 15 (17.6%) patients had adenocarcinoma, 20 (23.5%) patients had HGD and 50 (58.8%) patients had LGD Conclusion: Complete resection, including EMR or ESD, is needed for patients with GED diagnosed by endoscopic biopsy and they have HGD. For patients with LGD, EMR or ESD may be needed in addition to endoscopic surveillance with biopsy for making the correct diagnosis and proper treatment because of the possibility of adenocarcinoma.

• Journal of Chest Surgery
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• v.40 no.5 s.274
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• pp.329-340
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• 2007

Background: Matrix Metalloproteinase (MMP) inhibition has emerged as a potential therapeutic strategy for the left ventricular dilatation that occurs after myocardial infarction. This study is designed to evaluate which treatment is better for attenuating the left ventricular remodeling via MMP inhibition 1) during the early, short highly MMP producing period of the initial phase or 2) during most of the period of the initial phase after myocardial infarction. Material and Method: Myocardial infarction was induced by ligation of the left anterior descending coronary artery in rabbits. The experimental group was divided into 3 groups. The myocardial infarction only (MI only) group consisted of 7 cases. The MMP inhibitor administered for 5 days after MI (MMPI 50) group had 6 cases, and these rabbits were given MMP inhibitor for 5 days after myocardial infarction, beginning with the postoperative first day. MMP inhibitor administered for 9 days (MMPI 90) group consisted of 5 cases and these rabbits were given MMPI for 9 days the same manner as above. CG2300 was used as a selective MMPI; this is a potent MMP-2 and -9 inhibitor Two-D echocardiograms were performed on all the groups at the time of preoperative period, the post-operative 1st week, the postoperative 20 week and the postoperative 30 week, and we measured the end-diastolic dimension (EDD), the end-systolic dimension (ESD), and the ejection fraction (EF). Result: The echocardiograms generally showed postoperative left ventricular dilatation in the MI only group. The EDD was increased significantly higher in the postoperative 1 week compared to the preoperative value (p<0.05). The ESD was also increased significantly higher in the postoperative 1st week, the postoperative 20 week and the postoperative 30 week compared to the preoperative value (p<0.05). Left ventricular dilatation was noted to be less In the MMPI 9d group than in the MI only and MMPI 5d groups. In the MMPI 9d group, there was no significant change of EF postoperatively compared to the preoperative period. MMP-2 and MMP-9 were measured from the infarcted myocardial tissue at post-MI 4 weeks by performing western blotting and zymography. The changes the of protein expression and activity of MMP-2 and MMP-9 were not significant in the three MI groups and the normal heart group. Histopathologic examination revealed severe collagen deposition in the MI only group. Collagen accumulation was reduced in both the MMPI groups. The MMPI 9d group revealed an increased number of capillaries. Conclusion: Left ventricular dilatation developed rapidly after, MI from ligation of the coronary artery and MMPI attenuated the ventricular dilatation. The effect of MMPI seemed to have better a result from its usage during most of the period of the initial phase after myocardial infarction. This suggested that increased neovascularization by MMPI may also contribute to attenuation of the left ventricular remodeling.

• Journal of Radiation Protection and Research
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• v.40 no.2
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• pp.118-123
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• 2015

The frequency of diagnostic radiation examinations in medical institutions has recently increased to 220 million cases in 2011, and the annual exposure dose per capita was 1.4 mSv, 51% and 35% respectively, compared to those in 2007. The number of chest radiography was found to be 27.59% of them, the highest frequency of normal radiography. In this study, we developed a shielding device to minimize radiation exposure by shielding areas of the body which are unnecessary for image interpretation, during the chest radiography. And in order to verify its usefulness, we also measured the difference in entrance surface dose (ESD) and the absorbed dose, before and after using the device, by using an international standard pediatric (10 years) phantom and a glass dosimeter. In addition, we calculated the effective dose by using a Monte Carlo simulation-based program (PCXMC 2.0.1) and evaluated the reduction ratio indirectly by comparing lifetime attributable risk of cancer incidence (LAR). When using the protective device, the ESD decreased by 86.36% on average, nasal cavity $0.55{\mu}Sv$ (74.06%), thyroid $1.43{\mu}Sv$ (95.15%), oesophagus $6.35{\mu}Sv$ (78.42%) respectively, and the depth dose decreased by 72.30% on average, the cervical spine(upper spine) $1.23{\mu}Sv$ (89.73%), salivary gland $0.5{\mu}Sv$ (92.31%), oesophagus $3.85{\mu}Sv$ (59.39%), thyroid $2.02{\mu}Sv$ (73.53%), thoracic vertebrae(middle spine) $5.68{\mu}Sv$ (54.01%) respectively, so that we could verify the usefulness of the shielding mechanism. In addition, the effective dose decreased by 11.76% from $8.33{\mu}Sv$ to $7.35{\mu}Sv$ before and after wearing the device, and in LAR assessment, we found that thyroid cancer decreased to male 0.14 people (95.12%) and female 0.77 people (95.16%) per one million 10-year old children, and general cancers decreased to male 0.14 people (11.70%) and female 0.25 people (11.70%). Although diagnostic radiation examinations are necessary for healthcare such as the treatment of diseases, based on the ALARA concept, we should strive to optimize medical radiation by using this shielding device actively in the areas of the body unnecessary for the diagnosis.

• Progress in Medical Physics
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• v.26 no.3
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• pp.160-167
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• 2015

Radiation exposure from medical diagnostic imaging procedures to patients is one of the most significant interests in diagnostic x-ray system. A miniature x-ray intraoral tube was developed for the first time in the world which can be inserted into the mouth for imaging. Dose evaluation should be carried out in order to utilize such an imaging device for clinical use. In this study, dose evaluation of the new x-ray unit was performed by 1) using a custom made in vivo Pig phantom, 2) determining exposure condition for the clinical use, and 3) measuring patient dose of the new system. On the basis of DRLs (Diagnostic Reference Level) recommended by KDFA (Korea Food & Drug Administration), the ESD (Entrance Skin Dose) and DAP (Dose Area Product) measurements for the new x-ray imaging device were designed and measured. The maximum voltage and current of the x-ray tubes used in this study were 55 kVp, and 300 mA. The active area of the detector was $72{\times}72mm$ with pixel size of $48{\mu}m$. To obtain the operating condition of the new system, pig jaw phantom images showing major tooth-associated tissues, such as clown, pulp cavity were acquired at 1 frame/sec. Changing the beam currents 20 to $80{\mu}A$, x-ray images of 50 frames were obtained for one beam current with optimum x-ray exposure setting. Pig jaw phantom images were acquired from two commercial x-ray imaging units and compared to the new x-ray device: CS 2100, Carestream Dental LLC and EXARO, HIOSSEN, Inc. Their exposure conditions were 60 kV, 7 mA, and 60 kV, 2 mA, respectively. Comparing the new x-ray device and conventional x-ray imaging units, images of the new x-ray device around teeth and their neighboring tissues turn out to be better in spite of its small x-ray field size. ESD of the new x-ray device was measured 1.369 mGy on the beam condition for the best image quality, 0.051 mAs, which is much less than DRLs recommended by IAEA (International Atomic Energy Agency) and KDFA, both. Its dose distribution in the x-ray field size was observed to be uniform with standard deviation of 5~10 %. DAP of the new x-ray device was $82.4mGy*cm^2$ less than DRL established by KDFA even though its x-ray field size was small. This study shows that the new x-ray imaging device offers better in image quality and lower radiation dose compared to the conventional intraoral units. In additions, methods and know-how for studies in x-ray features could be accumulated from this work.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2165-2170
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• 2007

At nanoscales, the Boltzmann transport equation (BTE) can best describe the behavior of phonons which are energy carriers in crystalline materials. Through this study, the phonon transport in some micro/nanoscale problems was simulated with the Monte Carlo method which is a kind of the stochastic approach to the BTE. In the Monte Carlo method, the superparticles of which the number is the weighted value to the actual number of phonons are allowed to drift and be scattered by other ones based on the scattering probability. Accounting for the phonon dispersion relation and polarizations, we have confirmed the one-dimensional transient phonon transport in ballistic and diffusion limits, respectively. The thermal conductivity for GaAs was also calculated from the kinetic theory by using the proposed model. Besides, we simulated the electrostatic discharge event in the NMOS transistor as a two-dimensional problem by applying the Monte Carlo method.

• JSTS:Journal of Semiconductor Technology and Science
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• v.9 no.4
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• pp.198-204
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• 2009

Inductive peaking using T-coils has been widely used in broadband I/O interfaces. In this paper, we analyze technical effects and limitations of the T-coil, and discuss several methods that can overcome these restrictions and improve the practicality of the T-coil. In particular we also propose and verify a circuit topology which can further extend bandwidth beyond the limit that conventional T-coil can achieve, and transfer 20 Gb/s data without noticeable distortion.