• Restorative Dentistry and Endodontics
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• v.14 no.2
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• pp.49-64
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• 1989

The purpose of this study was to evaluate the effect of several materials on the healing process of apical wound. Sixteen mandibular premolars obtained from 4 healthy dogs were used for this study. Under general anesthesia, the pulpal chamber of each tooth was opened and the pulps were extirpated. The root canals were then instrumented with H-file and irrigated with physiologic saline solution ; the apices were purposely perforated and enlarged with the engine K-reamer. In the experimental groups, apical wounds were filled with one of calcium hydroxide, hydroxylapatite, and tricalcium phosphate materials, mixture of each materials and physiologic saline solution, with a lentulo spiral. In the control group, apical wounds were not filled with any material. All the root canals were filled by the lateral condensation technique with gutta-percha cone and ZOE sealer. The access opening of all the teeth were closed with amalgam. On the 10, 20, 40 and 60th day after experiment, experimental animals were sacrificed. Segments of jaws, each containing one tooth, were fixed in 10% formalin solution and decalcified in Plank-Rychlo solution. The specimens were embedded in paraffin and serially sectioned to an average thickness of $6{\mu}m$. The sections were stained by hematoxylin-eosin and Masson's trichrome stain method and examined under light microscope. The results were as follows : 1. In the experimental groups, the new bone formations were observed in apical wounds. 2. Fourty days later, apical wounds were healed by granulation tissue in the experimental groups, but were not healed by granulation tissue in the control group, and the healing process of experimental groups were more rapid than that of control group. 3. Sixty days later, chronic inflammation disappeared in the experimental groups, and the materials used showed biologic affinity to the periapical tissue. 4. In all the groups, the resorption of cementum appeared on the 10th and 20th day after experiment, and the deposition of cementum appeared on the 40th and 60th day after experiment, especially showing narrowness of apical foramen due to newly formed cementum in calcium hydroxide group. 5. Calcum hydroxide and tricalcium phosphate particles were gradually resolved, but hydroxylapatite particles were not resolved through the experimental period.

• Cross-Cultural Studies
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• v.40
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• pp.239-264
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• 2015

In the early 20th century, Japan built theaters to take possession of colonial culture while establishing the Imperial University, libraries, and museums to accumulate and spread the knowledge of "imperial" Japan. Many different genres made a hit in theaters including theatrical troupes, theatrical companies, and motion pictures. One of the various features of expositions was "spectacles" or unusual events. They were integrated with a national festival in celebration of "5th anniversary of political commencement." In 1915, the longest hit series in Keijo (Seoul) was the dance performance by professional Japanese beauties and entertainers, whose songs delivered the legitimacy of governance. This study focused on the performance in the space of "cultural" spread called theaters, thus examining the "imperial" cultural waves they were in charge of. The study also focused on the tensional relations of Hierarchie along those cultural borders. The performance at the theater Engeikan(演芸館) in 1915 was especially an epoch-making event in the Japanese theatrical community of Keijo (Seoul): first, it marked the emergence of large-scale performance hall called Engeikan(演芸館); secondly, the performance kept its ongoing, stable streak for about 50 days; and it led to the appearance of leading troupes including Geijutuza(芸術座), which put on a show in Keijo (Seoul) in November, 1915. The study examined the issues of theater Engeikan(演芸館) performance in 1915 involving the art company, performance genre, and audience composition, showed that there was the coexistence of entertainment and governance through cultural ruling while securing amusement and entertainment, and found it was accompanied by the organized operation of "Keijo Sponsorship Council（京城協贊會）" which brought together the cultural capabilities of Japanese people living in Joseon. The performance at theater Engeikan(演芸館) in Keijo (Seoul) in 1915 fully reflected the issues involving the tensional relations between different artistic genres, the competing relations between the subjects of performance, and the cultural power.

• Journal of IKEEE
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• v.22 no.4
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• pp.1025-1030
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• 2018

The proposed modulator is designed by utilizing a conventional structure employing time division technique to realize the 4th order delta-sigma modulator using one op-amp. In order to reduce the influence of KT/C noise, the capacitance in the first and second integrators reused was chosen to be 20pF and capacitance of third and fourth integrators was designed to be 1pF. The stage variable technique in the low power reconfigurable op-amp was used to solve the stability issue due to different capacitance loads for the reduction of KT/C noise. This technique enabled the proposed modulator to reduce the power consumption of 15% with respect to the conventional one. The proposed modulator was fabricated with 0.18um CMOS N-well 1 poly 6 metal process and consumes 305uW at supply voltage of 1.8V. The measurement results demonstrated that SNDR, ENOB, DR, FoM(Walden), and FoM(Schreier) were 66.3 dB, 10.6 bits, 83 dB, 98 pJ/step, and 142.8 dB at the sampling frequency of 256kHz, oversampling ratio of 128, clock frequency of 1.024 MHz, and input frequency of 250 Hz, respectively.

• The Journal of the Petrological Society of Korea
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• v.19 no.4
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• pp.255-267
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• 2010

The primary utilization of recently improved (U-Th)/He thermochronometry is to reveal the low-T thermal histories of shallow crustal sections or transient episodes (such as wildfires or meteorite impacts) because of the high sensitivity of He diffusion to temperature in host minerals. In this contribution, we present reviews and perspectives regarding how this method can be used to characterize the ejection-related shock metamorphism of Martian meteorites. The temperature conditions of shock metamorphism can be constrained through shock recovery experiments, paleomagnetism, and $^{40}Ar/^{39}Ar$ and (U-Th)/He dating. The most reliable constraints can be deduced when these independent approaches are combined. However, the thermal history of the ALH84001 Martian meteorite has been under serious debate because the different methods have yielded contrasting results. Recent work has shown how single-grain (U-Th)/He and $^{40}Ar/^{39}Ar$ dating, two noble-gas based thermochronometries with different T sensitivities, can be used to resolve this issue, providing a good example for future research on other meteorites.

• Journal of Educational Research in Mathematics
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• v.15 no.2
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• pp.177-196
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• 2005

In the Korean curriculum, students learn the concept of sample, sampling and other concepts related to sample and sampling, when they have reached the 10th grade of high school. But before the 10th grade, they have an activity about data collection, data analysis and the formulation of conclusion. We then investigated and analyzed the informal knowledge of students before they receive formal instructions. The results enabled the identification of the maximum response rate for each question that each student agreed or disagreed with. In particular, it didn't agree with how students consider the characteristic of population in the process of sampling, and the students agreed on a sampling process without considering the characteristic of the population or the components that consist the population. It showed that 5th grade students didn't investigate the data connected with sampling, and didn't understand the validity of sample survey process. While, 6th grade students equally understood sample size, sampling process, the reliance of data acquired through sample survey that applied to the source of judgment. But in details, it revealed that student had a misconception, or stayed at a subjective judgment level. The significant point is that many high school students didn't adequately understood a sample size with sampling. Though statistics instruction has traditionally been delayed until upper secondary education, this inquiry convinced us that this delay is unnecessary.

• Journal of The Korean Association of Information Education
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• v.9 no.4
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• pp.649-659
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• 2005

A window presentation style, either tiled window or single page design, determines the spatial arrangement of information in a modern computer-based instructional design. This study investigates the interaction between spatial ability and window presentation style in terms of student's achievement of cognitive knowledge through Web-based instruction. Seventy-one students from the Falk School in Pennsylvania were pre-tested to determine their level of spatial ability, then randomly divided into two treatment groups in order to study a Web-based instructional unit on flowering plants. The Web-based instructional package was organized with either tiled window presentation or single page presentation. A posttest measured participants'acquisition of the instructional content. Posttest and spatial ability test scores were analyzed using multi-variate linear regression for the full sample (n=71) and three sub-samples: (a) 4th and 5th grade students only, (b) female students only, and (c) 4th and 5th grade female students only. The goals of the data analysis included the examination of (i) the correlation between spatial ability and posttest scores; (ii) the correlation between window presentation style and posttest score; and (iii) the interaction between spatial ability (aptitude) and presentation style (treatment).The data from all four sample groups showed a significant relationship between spatial ability and achievement of cognitive knowledge at the 1% level of significance. The aptitude-treatment interaction between spatial ability and style of window presentation was not significant in the full sample, but was significant in the sub-samples either at the 10% or 5% level. In neither the full sample nor any sub-sample data did window presentation style have an impact on average posttest score. In all analyses, the higher the level of spatial ability, the higher the posttest score. The sub-samples revealed that students with low spatial ability performed better with the tiled window presentation, while those with high spatial ability did better with the single page presentation. Neither window presentation style was shown to better foster learning by children of all levels of spatial ability.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.14 no.1
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• pp.74-80
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• 2011

Purpose: Based on previous research findings, it is well-known that the timing of surgery is generally considered the most important prognostic factor for a Kasai portoenterostomy, the primary treatment for biliary atresia. This research aimed to identify the optimal timing of a Kasai portoenterostomy and to verify if the proposed optimal timing corresponds to previous studies. All patients were classified by the timing of surgery, and pre- and post-operative fibrotic changes of the liver were measured with the elasticity value from fibroscans. Methods: The stiffness scores of the pre- and post-operative fibroscans in 34 patients who were treated by Kasai portoenterostomy from October 2007 to September 2010 in Severance children's hospital were reviewed. Results: The earlier the patients were treated by Kasai portoenterostomy, the lower the fibroscan scores. When the patients were treated prior to the 8th week, the post-operative scores of the fibroscans were significantly better than those patients who were treated after the 8th week, and some even recovered partially. Moreover, when operated before the 8th week, the differences between each pre- and postoperative fibroscan score also showed statistical relevance (p=0.0002). Conclusion: The earlier the patient was treated by Kasai portoenterostomy, the less liver fibrosis that developed, the lower the level of post-operative fibrosis, and the less the degree of fibrotic progress before and after the operation. Thus, this research proposal reconfirms once more that the 8th week is the optimal timing for a Kasai portoenterostomy.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.4
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• pp.971-980
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• 2013

System performance improvement through the concentrated residual dispersion per span (RDPS) in special transmission fiber spans in optical transmission links with dispersion management (DM) for wavelength division multiplexed (WDM) transmission is investigated through the comparison with the performance in optical transmission links with uniform RDPS in every fiber spans. It is confirmed that, in optical links with RDPS of 0 ps/nm uniformly distributed in the rest fiber spans, if RDPS of 300 ps/nm and 1,320 ps/nm are concentrated in 5th-13th fiber spans and 6th-13th fiber spans, respectively, then the best performance is obtained. It is also confirmed that optimal net residual dispersion (NRD) controlled by precompensation and postcompensation are 10 ps/nm and -10 ps/nm, respectively, in all two cases, and the effective launching power range below 1 dB eye opening penalty (EOP) in the concentrated RDPS of 300 ps/nm and 1,320 ps/nm are improved by 2 dB and 6 dB than optical transmission links with the uniformly distributed RDPS, respectively.

• Journal of Korean Society of Transportation
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• v.20 no.7
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• pp.95-105
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• 2002

Under a specific roadway alignment condition by design-speed standards, safety of the roadway is determined by an actual operating speed of a driver. This research takes first lanes of four-lane(hi-direction) rural highways as target facility. It also takes the straight and curved lanes of the selected highways for in-depth study. This study used NC-97 to detect speeds of passenger cars whose speeds are not affected by front vehicles. This research analyzed properties of 85th percentile operating speed at upstream of horizontal and through curves under various alignment conditions. The results show that 53∼65 Percent of drivers drive faster than the posted speed-limit (80KPH) by 14∼20 KPH on average. It also shows that the 85th-percentile operating speeds are the lowest at the middle point of curve length when curve radius is smaller. However, they are lowest at 1/4 point of curve length when curve radius is greater. Along roadways where curve radius is small, difference between upstream speed and the speed along the curve is considerably large. On the other hand. the speed difference is setting smaller as the curve radius is increasing. According to the results, significant variables affecting the 85th percentile operating speeds are curve radius and the 85th-Percentile operating speeds of upstream curves.

• Journal of The Korean Association For Science Education
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• v.36 no.4
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• pp.519-526
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• 2016

The purpose of this study is to investigate the influences of small group learning using smart devices in science classes on students' achievement, learning motivation, attitude toward science lessons, and perception of small group learning using smart devices. Four 11th-grade classes (N=133) at a coed high school in Seoul were randomly assigned to a control group and a treatment group. The intervention of small group learning using smart devices emphasized collaborative writing on activity sheet. The students were taught about acid, base, and neutralization reaction for six class periods. After the instructions, an achievement test, the learning motivation test, the attitude toward science lessons test, and a questionnaire on the perception of small group learning using smart devices were administered. Two-way ANCOVA results revealed that there was a statistically significant interaction effect by their previous chemistry achievement in the achievement test scores. Only low-level students in small group learning using smart devices significantly improved their achievement probably by having the opportunities to get help from high-level students. The adjusted means of the treatment group were significantly higher than those of the control group in learning motivation and attitude toward science lessons. Students' perceptions of small group learning using smart devices tended to be positive. Educational implications of this study are discussed.