• ETRI Journal
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• v.44 no.5
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• pp.715-732
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• 2022

Despite the successful launch of Advanced Television Systems Committee (ATSC) 3.0 broadcasting worldwide, broadcasters are facing obstacles in constructing void-less large-scale single-frequency networks (SFNs). The bottleneck is the absence of decent on-channel repeater (OCR) solutions necessary for SFNs. In the real world, OCRs suffer from the maleficent feedback interference (FI) problem, which overwhelms the desired input signal. Moreover, the undesired multipaths between studio-linked transmitters and the OCR deteriorate the forward signals' quality as well. These problems crucially restrict the feasibility of conventional OCR systems, arousing the strong need for cost-worthy advanced OCR solutions. This paper presents an ATSC 3.0-specific solution of advanced OCR that solves the FI problem and refines the input signal. To this end, the FI canceler and channel equalizer functionalities are carefully implemented into the OCR system. The presented OCR system is designed to be fully compliant with the ATSC 3.0 specifications and performs a fast and efficient signal processing by exploiting the specific frame structure. The real product of ATSC 3.0 OCR is fabricated as well, and its feasibility is verified via field and laboratory experiments. The implemented solution is installed at a commercial on-air site and shown to provide substantial coverage gain in practice.

• Journal of The Korean Association For Science Education
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• v.27 no.4
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• pp.328-336
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• 2007

In this research we conducted a survey on the actual status of the 7th National Earth Science I & II curriculum to explore ways of revising the next Earth Science curriculum for better education. Of the 180 Earth Science teachers, 60% responded to the survey. The domains of the survey consist of (1) the necessity of Earth Science I & II curriculum revision, (2) educational goals, (3) content coverage, (4) level of difficulty and students' interest for Earth Science content, and (5) ways to overcome the crisis of Earth Science education. Majority of the respondents demanded the revision of Earth Science I, II curriculum because of overlapping and repetition of contents among 10th grade science and Earth Science I and overcrowded Earth Science II contents. Based on the survey results, recommendations on how to improve Earth Science I, II curriculum and how to adjust Earth Science contents are suggested. In addition to curriculum improvement, systematic supports are required for Earth science not to be excluded and turned down by the student and the scholastic aptitude test for university admission.

• Journal of Advanced Navigation Technology
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• v.27 no.6
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• pp.828-834
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• 2023

In this paper, we studied an antenna that forms a wide beam width by applying a horn-shaped reflector to a patch array antenna. To implement a wide beam width, three patches were arranged in each of the four directions on a square microstrip substrate, and a horn-shaped reflector was applied to the rear of the array antenna. Through this structure, the vertical beam pattern formed from the patch was converted to a diagonal direction, and as a result, the beam widths formed in each of the four sectors were added to create a wide beam width close to a hemisphere. The proposed antenna was studied for application to UAV(unmanned aerial vehicle), and the simulation test results confirmed that the 4.5 dBi beam width was 146.8°.

• The Journal of Advanced Prosthodontics
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• v.2 no.3
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• pp.111-115
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• 2010

PURPOSE. This study was conducted to evaluate clinical validity of a zirconia full-coverage crown by comparing zirconia's wear capacity over antagonistic teeth with that of feldspathic dental porcelain. MATERIALS AND METHODS. The subject groups were divided into three groups: the polished feldspathic dental porcelain group (Group 1), the polished zirconia group (Group 2), and the polished zirconia with glazing group (Group 3). Twenty specimens were prepared from each group. Each procedure such as plasticity, condensation, and glazing was conducted according to the manufacturer's manual. A wear test was conducted with 240,000 chewing cycles using a dual-axis chewing simulator. The degree of wear of the antagonistic teeth was calculated by measuring the volume loss using a three-dimensional profiling system and ANSUR 3D software. The statistical significance of the measured degree of wear was tested with a significant level of 5% using one-way ANOVA and the Tukey test. RESULTS. The degrees of wear of the antagonistic teeth were $0.119{\pm}0.059\;mm^3$ in Group 1, $0.078{\pm}0.063\;mm^3$ in Group 3, and $0.031{\pm}0.033\;mm^3$ in Group 2. Statistical significance was found between Group 1 and Groups 2 and between Group 2 and 3, whereas no statistical significance was found between Group 1 and Group 3. CONCLUSION. Despite the limitations of this study on the evaluation of antagonistic teeth wear, the degree of antagonistic tooth wear was less in zirconia than feldspathic dental porcelain, representing that the zirconia may be more beneficial in terms of antagonistic tooth wear.

• The Journal of Engineering Geology
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• v.23 no.4
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• pp.503-510
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• 2013

Shear wave velocity is widely used as an parameter for investigating subsurface characteristics and for obtaining the design parameters based on theoretical equations. This study seeks to estimate the coefficient of shear wave velocity in Busan clay via laboratory tests. Eight specimens were extracted at depths of 10, 12, 15, 20, 22, 25, 30, and 31 m. The specimens were subjected to the consolidation test to determine the relationship between effective stress and shear wave velocity. The relationship shows a non-linear trend and is similar to the results of a previous study. The coefficient shows constant coverage and a relationship between ${\alpha}$ and ${\beta}$ is suggested. The results demonstrate that this coefficient could be used as a reference value to determine engineering parameters based on the shear wave velocity.

• Bulletin of the Korean Space Science Society
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• 2011.04a
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• pp.23.1-23.1
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• 2011

The SMT is a subsystem of the UFFO (Ultra-Fast Flash Observatory) pathfinder onboard the Lomonosov spacecraft planed to be launched in November 2011. The UFFO is designed for extremely fast observation of optical afterglow of Gamma Ray Burst (GRB). This study is primarily concerned with performance measurement of the SMT optical system under the integration and test phase. SMT is a 100mm Ritchey-Chretien type telescope with a motorized slewing mirror and a $256{\times}256$ pixels Intensified Charge-Coupled Device (ICCD) of 22.2${\mu}m$ in pixel size. SMT is designed to operate over the wavelength coverage between 200 nm and 650 nm. It has 17 arcmin FOV (Field of View), providing 4arcsec in detector pixel resolution. In this study, we describe the integration and test process of the SMT optical system and interim performance measurement results with motorized slewing mirror and ICCD.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.8 no.2
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• pp.90-97
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• 2005

This study aimed to address problems and suggest solutions in applying seed mixture design criterior of slope revegetation works according to the "Slope revegetation design and guidelines(proposed)" proposed by the Ministry of Construction and Transportation. To do this, a proper thickness of attaching soil media was identified in April experiment where the thickness and slopes varied. The results were as follows. In the test, the coverage rate of plot where exotic grass was not sowed increased with time and was 79.3% after three months of seeding, which indicated less risk of soil erosion. When applying the provisional standards of the plant mix proposed by the Ministry of Construction and Transportation, tree seeds and native plants were found ill in the early stage in all test lands due to exotic grass. This was because exotic grass which grew well in the early stage, could grow densely, so it might hamper the growth of other plants. When slope revegetation were planted and goals were set for herb, shrub and tree dominant mixture types, it was required to shift focus toward nursing up native plants first rather than early plantation of exotic grass.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.3
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• pp.215-220
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• 2018

This paper limited the participation of large corporations in the mass information market by revising the Software Industry Promotion Act in order to increase business opportunity, equality of opportunity, and capacity building for small and medium sized IT companies. However, it is a fact that the medium and small SW companies have insufficient business capacity and expose various problems such as quality degradation of public information business, inadequate risk management, and deterioration of schedule management. In order to solve this problem, this paper derived the factors of quality deterioration in the system integration project and proposed to carry out the project by using some activities of VISUALIZATION, rigorous test management and Agile Methodology as a solution. Applying these measures to healthcare IT projects developed by midsize / small-sized IT companies has improved communications, improved quantitative progress management and improved project visibility. In addition, it contributed to minimizing defect resolution time, improving the requirement coverage ratio, and shortening unnecessary meeting time.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.6
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• pp.2473-2476
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• 2014

Background: Little is known about the cancer screening prevalence and correlates in older adults from different racial backgrounds. In the context of heightened efforts for prevention and early diagnosis, we collected information on screening for two major types of cancers: cervical and breast cancer in order to establish their prevalence estimates and correlates among older South African women who participated in the Study of Global Ageing and Adults Health (SAGE) in 2008. Materials and Methods: We conducted a national population-based cross-sectional study with a multi-stage stratified cluster sample of 3,840 individuals aged 50 years or older in South Africa in 2008. In this analysis, we only considered the female subsample of (n=2202). The measures used included socio-demographic characteristics, health variables, anthropometric and blood pressure measurements. Multivariable regression analysis was performed to assess the association of socio-demographic factors, health variables and cancer screening. Results: Overall, regarding cervical cancer screening, 24.3% ever had a Papanicolaou (PAP) smear test, and regarding breast cancer screening, 15.5% ever had a mammography. In multivariate logistic regression analysis, younger age, higher education, being from the White or Coloured population group, urban residence, greater wealth, and suffering from two or more chronic conditions were associated with cervical cancer screening, and higher education, being from the White or Indian/Asian population group, greater wealth, having a health insurance, and suffering from two or more chronic condtions were associated with breast cancer screening. Conclusions: Cancer screening coverage remains low among elderly women in South Africa in spite of the national guideline recommendations for regular screening in order to reduce the risk of dying from these cancers if not detected early. There is a need to improve accessibility and affordability of early cervical and breast cancer screening for all women to ensure effective prevention and management of cervical and breast cancer.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.12
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• pp.4903-4907
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• 2014

Background: This study aimed to identify factors associated with women's decisions to attend cervical cancer screening and to explore those linked with intention to attend in the coming year and to continue regular screening. Materials and Methods: A community based case-control study was conducted among woman 30-60 years of age in catchment area of Chatapadung Contracting Medical Unit (CCMU), networking of Khon Kaen Center Hospital, Thailand. Self-administered questionnaires were used to collect data, and in-depth interviews were then performed to explore in greater detail. Results: There were 195 participants. Only one third (32.3 %) had been screened for cervical cancer within the past 5 years. Some 67.7% reported that they had not been screened because they had no abnormal symptoms, single marital status, and no children. Only 10.6% of those never had screening intent to be screened within the next 12 months. High family income (adjusted OR=2.16, 95%CI=1.13-4.14), good attitude towards a Pap test (OR=1.87, 95%CI=1.09-4.23), and having received a recommendation from health care providers were important factors associated with decisions to attend cervical cancer screening (OR=1.73, 95%CI=1.01-4.63). From in-depth interviews, there were five reasons of their decisions to attend cervical cancer screening including yearly check-up, postpartum check-up, having abnormal symptom, encouragement by health care providers, and request from workplace. Conclusions: High family income, good attitude towards a Pap test, and receiving proper recommendation by health care providers, were important factors associated with decision to have cervical cancer screening among women 30-60 years old. Trying to enhance these factors and reduce barriers regarding screening, may increase the coverage rate for cervical cancer screening in Thailand.