• Journal of the Korean School Mathematics Society
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• v.15 no.3
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• pp.565-584
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• 2012

This study investigates how the GSP helps gifted and talented students understand geometric principles and concepts during the inquiry process in the generalization of the internal triangle, and how the students logically proceeded to visualize the content during the process of generalization. Four mathematically gifted students were chosen for the study. They investigated the pattern between the area of the original triangle and the area of the internal triangle with the ratio of each sides on m:n respectively. Digital audio, video and written data were collected and analyzed. From the analysis the researcher found four results. First, the visualization used the GSP helps the students to understand the geometric principles and concepts intuitively. Second, the GSP helps the students to develop their inductive reasoning skills by proving the various cases. Third, the lessons used GSP increases interest in apathetic students and improves their mathematical communication and self-efficiency.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.44 no.6
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• pp.43-50
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• 2007

In this paper we propose a method that identifies users at H.264 streaming using watermarking with fingerprints. The watermark can efficiently reduce the potential danger of forgery or alteration. Especially a biometric watermark has various advantages. Among entire biometric characteristics, the fingerprint is the most convenient and economical. In this paper we propose a novel fingerprint-based watermarking technique that can survive under very low bit-rate compression. The proposed algorithm consists of enhancement of a fingerprint image, the watermark generation using the extracted feature coordinates, watermark insertion using discrete wavelet transform, and authentication. The proposed algorithm can achieve robust watermark extraction against 0.264 compressed videos.

• The Journal of Korean Association of Computer Education
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• v.10 no.1
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• pp.77-88
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• 2007

More flexible learning models are needed, and learning environments that operate through mobile technologies such as portable multimedia players(PMP) provide useful tools in implementing these learning models. The main attractant of PMP is often their versatility: being able to load and play different formats of video, audio, digital images, and interactive media. In this paper, we investigate the factors influencing the usage and acceptance of the PMP for study, based on the extended version of the Technology Acceptance Model (TAM). Based on data collected from online survey, we show that perceived usefulness, perceived ease of use, flow and perceived enjoyment are the major determinants for users to play PMP for study purpose. Factors, including ease of use, contents-credibility are shown to determine the level of perceived usefulness; additionally, perceived usefulness, ease of use and perceived enjoyment are shown to directly affect the level of flow. Based upon the statistical results, some useful guidelines for developing learning contents are also provided.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.7
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• pp.380-388
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• 2014

Transmission methods for terrestrial UHDTV broadcasting have been actively studied in order to provide enhanced broadcasting service in many countries. Most of the countries are considering multi-carrier transmission methods based on OFDM and some of them have performed UHDTV experimental broadcasting by using the DVB-T2 standard with the adoption of an improved data compression technique. However, since single carrier transmission methods, which are known to be susceptible to multi-path fading, could remedy this defect by using the SC-FDE method where a frequency domain equalizer is utilized in the receiver, they may achieve a similar transmission performance with multi-carrier transmission methods. In consideration of these circumstances, we compare the transmission performances of two-type methods to provide a decision criterion on a suitable transmission method for UHDTV broadcasting.

• The Journal of Advanced Prosthodontics
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• v.9 no.4
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• pp.271-277
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• 2017

PURPOSE. This in vitro study aimed to evaluate the effect of implant connection design (external vs. internal) on the fit discrepancy and torque loss of zirconia and titanium abutments. MATERIALS AND METHODS. Two regular platform dental implants, one with external connection ($Br{\aa}nemark$, Nobel Biocare AB) and the other with internal connection (Noble Replace, Nobel Biocare AB), were selected. Seven titanium and seven customized zirconia abutments were used for each connection design. Measurements of geometry, marginal discrepancy, and rotational freedom were done using video measuring machine. To measure the torque loss, each abutment was torqued to 35 Ncm and then opened by means of a digital torque wrench. Data were analyzed with two-way ANOVA and t-test at ${\alpha}=0.05$ of significance. RESULTS. There were significant differences in the geometrical measurements and rotational freedom between abutments of two connection groups (P<.001). Also, the results showed significant differences between titanium abutments of internal and external connection implants in terms of rotational freedom (P<.001). Not only customized internal abutments but also customized external abutments did not have the exact geometry of prefabricated abutments (P<.001). However, neither connection type (P=.15) nor abutment material (P=.38) affected torque loss. CONCLUSION. Abutments with internal connection showed less rotational freedom. However, better marginal fit was observed in externally connected abutments. Also, customized abutments with either connection could not duplicate the exact geometry of their corresponding prefabricated abutment. However, neither abutment connection nor material affected torque loss values.

• Ocean and Polar Research
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• v.31 no.1
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• pp.111-119
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• 2009

Biogenic surface films, which are often present in coastal areas, may enhance the signatures of hydrodynamic processes in microwave, optical, and infrared imagery. We analyzed ERS-1/2 Synthetic Aperture Radar (SAR) and Envisat Advanced Synthetic Aperture Radar (ASAR) images taken over the Japan/East Sea (JES). We focused on the appearance of the contrast SAR signatures, particularly the dark features of different scales caused by various oceanic and atmospheric phenomena. Spiral eddies of different scales were detected through surface film patterns both near the coast and in the open regions of the JES in warm and cold seasons. During field experiments carried out at the Pacific Oceanological Institute (POI) Marine Station 'Cape Shults' in Peter the Great Bay, the sea surface roughness characteristics were measured during the day and night using a developed polarization spectrophotometer and various digital cameras and systems of floats. The velocity of natural and artificial slicks was estimated using video and ADCP time series of tracers deployed on the sea surface. The slopes of gravity-capillary wave power spectra varied between .4 and .5. Surface currents in the natural and artificial slicks increased with the distance from the coast, varying between 4 and 40 cm/s. The contrast of biogenic and anthropogenic slicks detected on vertical and horizontal polarization images against the background varied over a wide range. SAR images and ancillary satellite and field data were processed and analyzed using specialized GIS for marine coastal areas.

• Journal of Broadcast Engineering
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• v.21 no.5
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• pp.749-759
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• 2016

As image contents in broadcasting have been created in HDTVs and monitors have been commercialized, facial expression of objects in broadcasting lighting has become a very significant task. Figure modeling of objects in HDTVs requires smoother and cleaner video images owing to the expansion of precision of image expression by light. Lighting methods that enlighten characters in the digital generation have come to require a new change. Character modeling methods used on expression features of underlight are receiving attention for aesthetic expression of figures in HD images. Accordingly, the influence of underlight light source intensity, distance, and size on character modeling characteristics was experimentally measured and comparatively analyzed. The experiment results show that good results can be obtained only when the intensity is 17%∼25.5% in contrast to total brightness, distance is beyond 40cm, and the size is at least 20cm, to exhibit the optimum effect of underlight. This data will become material with high usage to gain smoother and cleaner images of characters in future high-quality images.

• The Journal of the Korea Contents Association
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• v.19 no.11
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• pp.270-277
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• 2019

These days, with the advent of digital broadcasting, media environment offers users an opportunity to enjoy differentiated contents in a more aggressive fashion through user-media interactions based on computer technology. In fact, the development of contents which can induce spontaneous acts from users such as outdoor ads which use certain sensors and devices and exhibition halls has been active. With the development of low-price motion recognition devices, people have been able to enjoy diverse interaction-applied media by recognizing users' motion data without body contact. In this paper, we developed an interactive media player that can recognize the user's motion and control the video in the web service environment without installing a specific program. In addition, we set user motion recognition range and developed a user motion recognition algorithm suitable for the Leap Motion equipment installed in the kiosk. The results of this study can be experienced by various interactive media such as interactive tourism, education, and movie contents in kiosks that can be installed in public places.

• Korean Journal of Applied Biomechanics
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• v.17 no.4
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• pp.149-156
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• 2007

The purpose of this study was to compare the world class women's hurdlers with kinematic variables Lee Yeon-Kyoung's in the 100m hurdle. Among korea elite female hurdler, Lee Yeon-Kyoung was participated as a subject. Eight JVC video cameras(GR-HD1KR) were used to film the performance of Lee Yeon-Kyoung at a frame rate of 60fields/s. The real-life three-dimensional coordinate data of digitized body landmarks were smoothed using a fourth order Butterworth low pass recursive digital filter with an estimated optimum cutoff frequency of 7.4Hz. After analyzing and comparing Lee Yeon Kyung's kinematic variables with the world top class hurdlers in the woman's 100m hurdle run, the following conclusions were obtained. 1. Lee should be able to increase the speed with over 5.4m/s from start to first hurdle and then maintain the speed range from 8.33m/s to 8.67m/s until 10th hurdle. Lee should have to maintain the speed with 8.51m/s from 10th hurdle to finish line. 2. Lee has to reach her maximum running speed at 5th hurdle and then has to shorten running time with 0.5sec between hurdles. 3. Lee should be able to run around 2.5sec from start to frist hurdle and then maintain under 1.00sec following phases. Lee should be able to maintain under 1.10sec from 10th hurdle to finish line. 4. Lee needs to control a consistent takeoff and landing distance pattern, Lee needs to lower the height of the center of gravity of the body with 0.33m when she clears the hurdles.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.7C
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• pp.443-450
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• 2011

Recently, various transmission techniques for communication and broadcasting systems have been developed to meet the dramatically increasing requirement of consumers. Because UWB (Ultra-Wideband) is a wireless communication technique that supports high data rate with low power, it can satisfy the requirement and can be applied to various wireless communication services. The multi-band orthogonal frequency division multiplexing (MB-OFDM) system, one of UWB system, is the wireless communication system that satisfies the transmission characteristic for UWB and so it can be used for various wireless communication services. In this paper, we propose a scheme that uses hierarchical modulation which is applied in digital video broadcasting system at the source and adaptive modulation based on the channel quality at the relays. The simulation results have shown that the proposed scheme has both the advantages of the increased throughput by 33% and similar BER performance to conventional scheme.