• Journal of Korean Society of Industrial and Systems Engineering
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• v.41 no.2
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• pp.159-166
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• 2018

The proliferation of information technologies made it possible to produce information products of different versions at much lower cost comparing to traditional physical products. Thus it is common for information product manufacturers to consider vertically differentiated product line for more profit through improved market coverage. Another salient characteristic of most information product is network externality. Existing researches dealing with vertical differentiation and network externality usually assumed oligopolistic market where vertically differentiated products are provided by competing companies, respectively. Moreover, they analyzed the essentially dynamic characteristic of network externality statically. In this study, different from the previous researches, the vertical differentiation strategy of a monopolistic company under network externality is dynamically analyzed. We used a two-period model to accommodate the dynamic feature of network externality. Based on the two-period model, the profit maximizing solutions are analyzed. The results showed that a monopolistic company has no incentive to differentiate products vertically when the network externality is absent. On the contrary, when the network externality exists, the monopolistic company can derive more profit by vertically differentiating the product line. It is also shown that, for more profit, the monopolistic company should keep the quality difference between the high quality product and the low quality product as greater as possible.

• ETRI Journal
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• v.45 no.5
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• pp.887-898
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• 2023

Aerial base stations (ABSs) seem promising to enhance the coverage and capacity of fifth-generation and upcoming networks. With the flexible mobility of ABSs, they can be positioned in air to maximize the number of users served with a guaranteed quality of service (QoS). However, ABSs may be overloaded or underutilized given inefficient placement, and user association has not been well addressed. Hence, we propose a three-dimensional ABS placement scheme with a delay-QoS-driven user association to balance loading among ABSs. First, a load balancing utility function is designed based on proportional fairness. Then, an optimization problem for joint ABS placement and user association is formulated to maximize the utility function subject to statistical delay QoS requirements and ABS collision avoidance constraints. To solve this problem, we introduce an efficient modified gray wolf optimizer for ABS placement with a greedy user association strategy. Simulation results demonstrate that the proposed scheme outperforms baselines in terms of load balancing and delay QoS provisioning.

• International Commerce and Information Review
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• v.7 no.2
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• pp.75-94
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• 2005

This study is focused on evaluating the computer-integrated just-in-time (CI-JIT) production system of a semi-conductor manufacturing firm in Korea. Approaching the mid-1980s, the emphasis was on low price, low-cost operations, and quality, especially in USA. American companies have shifted output to low-wage countries like the Philippines, Korea, Japan, Malaysia and allied countries that can make quality products at low prices. Korea and other Asian countries forego short-term profits to gain a solid foothold in a product market, recognizing that larger market share leads to lower cost and higher profit in the long run. They bring manufacturers and suppliers together to improve material management and operation management, using project teams that investigate topics, such as Just-In-Time(JIT)manufacturing, among others. The "Kanban" word means "card" in Japanese, and is used to indicate the desired final delivery schedule. The operation for a particular item produced is scheduled for a specific time. The same process is extended to the external suppliers. More recently, the cards are gradually being replaced by electronic procedures that follow the same concept. Its capacity must be capable of handling the various transactions required by the JIT coverage as well as some allowances for expanded applications.

• Journal of Environmental Impact Assessment
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• v.15 no.2
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• pp.121-127
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• 2006

The conventional water quality measurements by point sampling provide only site specific temporal water quality information but not the synoptic geographic coverage of water quality distribution. To circumvent these limitations in temporal and spatial measurements, the use of remote sensing is increasingly involved in the water quality monitoring research. In other to assess a trophic state of Yongdam reservoir using satellite imagery data, I obtained Landsat ETM data and water quality data on 16th September and 18th October 2001. The approach involved acquisition of water quality samples from boats at 33 sites on 16th September and 30 sites on 18th October 2001, simultaneous with Landsat-7 satellite overpass. The correlation coefficients between the DN values of the imagery and the concentrations of chlorophyll-a were analyzed. The visible bands(band 1,2,3) and near infrared band(band 4) data of September image showed the correlation coefficient values higher than 0.9. The October image showed the correlation coefficient values about 0.7 due to the atmospheric effect and low variation of chlorophyll-a concentration. Regression models between the chrophyll-a concentration and DN values of the Landsat imagery data have been developed for each image. The regression model was determined based on the spectral characteristics of chlorophyll, so the green band(band 2) and near infrared band(band 4) were selected to generate a trophic state map. The coefficient of determination(R2) of the regression model for 16th September was 0.95 and that of the regression model for 18th October was 0.55. According to the trophic state map made based on Aizaki's TSI and chlorophyll-a concentration, the trophic state of Yongdam reservoir was mostly eutrophic state during this study.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.556-559
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• 2007

The Urban Environmental Quality (UEQ) indicates a complex and various parameters resulting from both human and natural factors in an urban area. Vegetation, climate, air quality, and the urban infrastructure may interact to produce effects in an urban area. There are relationships among air pollution, vegetation, and degrading environmental the urban heat island (UHI) effect. This study investigates the application of multi-spectral remote sensing data from the Landsat ETM and TM sensors for the mapping of air quality and UHI intensity in Seoul from 2000 to 2006 in fine resolution (30m) using the emissivity-fusion method. The Haze Optimized Transform (HOT) correction approach has been adopted for atmospheric correction on all bands except thermal band. The general UHI values (${\Delta}(T_{urban}-T_{rural})$) are 8.45 (2000), 9.14 (2001), 8.61 (2002), and $8.41^{\circ}C$ (2006), respectively. Although the UHI values are similar during these years, the spatial coverage of "hot" surface temperature (>$24^{\circ}C$) significantly increased from 2000 to 2006 due to the rapid urban development. Furthermore, high correlations between vegetation index and land surface temperature were achieved with a correlation coefficients of 0.85 (2000), 0.81 (2001), 0.84(2002), and 0.89 (2006), respectively. Air quality is shown to be an important factor in the spatial variation of UEQ. Based on the quantifiable fine resolution satellite image parameters, UEQ can promote the understanding of the complex and dynamic factors controlling urban environment.

• Journal of the Korea Convergence Society
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• v.8 no.6
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• pp.311-323
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• 2017

The purpose of this study is to compare factors influencing the quality of life of osteoarthritis patients in urban and rural areas. The data were derived from the sixth Korea national health and nutrition examination survey in 2014 and analyzed using the IBM SPSS Statistics version 21.0 software package considering complex samples analysis. The subjects of study were 599 adults with osteoarthritis over 50 years. The results of the study show that the factors affecting the urban patients' quality of life are healthcare coverage types, knee joint pain, knee ankylosis, hip joint pain, low back pain, limited activities, and subjective health status. The rural patients' quality of life are influenced by knee joint pain, limited activities, and alcohol consumptions. Therefore, the government should create differentiating strategies and approaches, including community rehabilitation programs, to improve the quality of life of urban and rural patients with osteoarthritis.

• Food Science and Preservation
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• v.14 no.2
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• pp.142-147
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• 2007

We optimized braising time to improve the storage quality of braised kidney beans. The beans were prepared with different heating times between 25 and 50 min. and then stored at $10^{\circ}C$ for 20 day. Physical, chemical, microbiological, and organoleptic quality indices were monitored throughout storage. Longer braising times yielded products with lower concentrated brine coverage. Bis resulted in higher soluble contents and slightly lower water activities. Excessive heating time exposed the kidney beans to air and caused rapid microbial growth on the surfaces of the beans, which negatively affected product quality. The longest heating time of 50 min. also resulted in a large increase in product hardness. A braising time of 30 min. was best for preservation, as good sensory quality was mainatained.

• Journal of Distribution Science
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• v.21 no.6
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• pp.107-117
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• 2023

Purpose: To know the existence of tax services, it is seen as a redistribution of income to ensure the implementation of national development and social welfare carried out by the state to the community and determine the effect of the quality of tax services, tax audits and tax collection against either simultaneously or partially against the tax ratio in the area of the Primary Tax Service Office of West Makassar. Research Design Data and Methodology: The tax revenue rate is too low based on the Revenue Statistics in Asian and Pacific report, released by the OECD at the end of July 2017. Tax revenue growth is also difficult to increase because of typical inelastic tax revenues. Consequently, tax growth cannot exceed GDP growth. The government boosted the tax ratio by minimizing tax payment irregularities and optimizing tax data utilization as well as distribution income for national social welfare. Transforming all sectors in the real economy so that it is affordable to tax, diversification of taxation is directed towards new sources of economic growth. The data analysis method used is multiple linear regression. Results: The results showed that the quality of tax services and tax audits were dominant in determining tax ratios, whereas Tax collection offers a significant but lower value.Conclusion: The existence of tax services, it is seen as a redistribution of income to ensure the implementation of national development and social welfare carried out by the state to the community.Quality and service in taxation services to create and maintain trust and cooperation relationships between tax officials and taxpayers.

• Korean Journal of Remote Sensing
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• v.33 no.1
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• pp.1-13
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• 2017

This study investigates the geometric and spatial image quality analysis of KOMPSAT-3A stereo pair. KOMPSAT-3A is, the latest satellite of KOMPSAT family, a Korean earth observation satellite operating in optical bands. A KOMPSAT-3A stereo pair was taken on 23 November, 2015 with 0.55 m ground sampling distance over Terrassa area of Spain. The convergence angle of KOMPSAT-3A stereo pair was estimated as $58.68^{\circ}$. The investigation was assessed through the evaluation of the geopositioning analysis, image quality estimation and the accuracy of automatic Digital Surface Model (DSM) generation and compared with those of KOMPSAT-3 stereo pair with the convergence angle of $44.80^{\circ}$ over the same area. First, geopositioning accuracy was tested with initial rational polynomial coefficients (RPCs) and after compensating the biases of the initial RPCs by manually collected ground control points. Then, regarding image quality, relative edge response was estimated for manually selected points visible from two stereo pairs. Both of the initial and bias-compensated positioning accuracy and the quality assessment result expressed that KOMPSAT-3A images showed higher performance than those of KOMPSAT-3 images. Finally, the accuracy of DSMs generated from KOMPSAT-3A and KOMPSAT-3 stereo pairs were examined with respect to the reference LiDAR-derived DSM. The various DSMs were generated over the whole coverage of individual stereo pairs with different grid spacing and over three types of terrain; flat, mountainous and urban area. Root mean square errors of DSM from KOMPSAT-3A pair were larger than those for KOMPSAT-3. This seems due to larger convergence angle of the KOMPSAT-3A stereo pair.

• Horticultural Science & Technology
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• v.33 no.3
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• pp.340-348
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• 2015

Mowing turfgrasses, especially fast growing species like perennial ryegrass, is one of the most time and money consuming tasks of their management. Trinexapac-ethyl (TE) is a popular plant growth regulator used to reduce mowing requirements, improve stress tolerance, and enhance turf quality. This study was conducted to investigate the effect of TE rate and frequency of applications on growth response and traffic tolerance of perennial ryegrass. The experiment was a split-plot laid out in a randomized complete block (RCB) design with three replications. TE was applied to main plots at 0.00, 0.25, and $0.50kg\;a.i.\;ha^{-1}$. Application pattern included an initial application, followed by two sequential applications at 6-wk intervals. Traffic treatment was applied to subplots with a cleated roller. Results demonstrated that TE consistently reduced vertical shoot growth, clippings dry weight, with maximum growth reduction of 59% and 65%, for 0.25 and $0.50kg\;a.i.\;ha^{-1}$, respectively, occurring at 2 weeks after initial TE treatment (WAT). Traffic also dramatically reduced vertical shoot growth and clippings dry weight. Overall, quality of perennial ryegrass was enhanced by sequential TE applications, however, turf quality and surface coverage reduced greatly under traffic, regardless of TE treatment. Total chlorophyll, chlorophyll a and chlorophyll b and total carbohydrates (TC) contents were also positively influenced following sequential TE application. Our results indicated that TE reduces mowing frequency and enhances turf quality rather than influencing traffic resistance.