• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.11-19
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• 2021

In this paper, we propose a non-orthogonal multiple access (NOMA) method based on channel alignment to simultaneously transmit multiple unicast and multicast streams in frequency-efficient manner. In this method, all receivers in a multicast cluster use the receive beamforming vectors that align their channels, and the base station uses the aligned channel information to design the transmit beamforming vectors that eliminate interference between multicast clusters. Using the effective receive channel information combined with the transmit beamforming vectors, unicast receivers design their own receive beamforming vectors that eliminate interference between unicast receivers. Since the proposed method effectively eliminates the interference, it achieves a higher sum rate than the existing orthogonal multiple access (OMA) method in high SNR regions. In addition, we present a hybrid method that exploits the benefits of the proposed NOMA method and the existing OMA method. Depending on the channel state, the hybrid method adaptively employs the existing OMA method, which improves the received signal power, in low SNR regions and the proposed NOMA method, which effectively eliminates the interference, in high SNR regions, thereby achieving a good sum rate over the entire SNR region.

• Journal of Society of Preventive Korean Medicine
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• v.17 no.3
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• pp.177-185
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• 2013

Objective : Eucommiae Cortex is bark of Eucommia ulmoides Oliver, a deciduous tree native to China. Today, teas or herbal drugs made from E. ulmoides leaves are widely consumed as a healthy food especially in Eastern Asia including Japan, China and Korea. This study was aimed to verify the extraction efficiency of bioactive compounds from Eucommiae Cortex depending on characteristics of decoction water. Method : Six types of decoction water with various origin were prepared and the contents of minerals in water were analyzed by ICP-AES and ICP-MS. The contents of extracted bioactive compounds were analyzed by HPLC and the relationship between mineral contents and extracted bioactive compounds in the decoction water were analysed by multiple factor analysis. The decoction waters could be classified in three groups by hierarchical cluster analysis. Result : Extracted amounts of compounds in Eucommiae Cortex showed a positive relationship with Na, Si, K concentration in decoction water, while a negative relationship with Ca, Mg concentration. Conclusion : The study proved that the minerals in water influenced the extraction efficiency of bioactive compounds from Eucommiae Cortex.

• Journal of Gastric Cancer
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• v.20 no.2
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• pp.115-126
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• 2020

Peritoneal metastasis (PM) frequently occurs in patients with gastric cancer (GC) and confers a dismal prognosis despite advances in systemic chemotherapy. While systemic chemotherapy has poor peritoneal penetration, intraperitoneal (IP) chemotherapy remains sequestered, resulting in high peritoneal drug concentrations with less systemic side-effects. The first application of IP treatment was hyperthermic intraperitoneal chemotherapy (HIPEC) with cytoreductive surgery (CRS) for gastric cancer peritoneal metastasis (GCPM); but was associated with an increased morbidity and mortality rate without significantly improving overall survival (OS). While CRS confers limited benefit, the potential role of prophylactic HIPEC and laparoscopic neoadjuvant HIPEC are currently being evaluated. Combination systemic and IP chemotherapy (SIPC) gained popularity in the 1990s, since it provided the benefits of IP treatment while reducing surgical morbidity, demonstrating promising early results in multiple Phase II trials. Unfortunately, these findings were not confirmed in the recent PHOENIX-GC randomized controlled trial; therefore, the appropriate treatment for GCPM remains controversial. Small observational studies from Japan and Singapore have reported successful downstaging of PM in GC patients receiving SIPC who subsequently underwent conversion gastrectomy with a median OS of 21.6-34.6 months. Recently, the most significant development in IP-directed therapy is pressurized IP aerosol chemotherapy (PIPAC). Given that aerosol chemotherapy achieves a wider distribution and deeper penetration, the outcomes of multiple ongoing trials assessing its efficacy are eagerly awaited. Indeed, IP-directed therapy has evolved rapidly in the last 3 decades, with an encouraging trend toward improved outcomes in GCPM, and may offer some hope for an otherwise fatal disease.

• Journal of Environmental Health Sciences
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• v.42 no.4
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• pp.280-292
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• 2016

Objectives: The objective of this study was to build COD regression models for the Han River and evaluate water quality. Methods: Water quality data sets for the dry season (as of January) during a four-year period (2012-2015) were collected from the database of the Han River automatic water quality monitoring stations. Statistical techniques, including combined genetic algorithm-multiple linear regression (GA-MLR) were used to build five-descriptor COD models. Multivariate statistical techniques such as principal component analysis (PCA) and cluster analysis (CA) are useful tools for extracting meaningful information. Results: The $r^2$ of the best COD models provided significant high values (> 0.8) between 2012 and 2015. Total organic carbon (TOC) was a surrogate indicator for COD (as COD/TOC) with high reliability ($r^2=0.63$ in 2012, $r^2=0.75$ for 2013, $r^2=0.79$ for 2014 and $r^2=0.85$ for 2015). The ratios of COD/TOC were calculated as 2.08 in 2012, 1.79 in 2013, 1.52 and 1.45 in 2015, indicating that biodegradability in the water body of the Han River was being sustained, thereby further improving water quality. The BOD/COD ratio supported these findings. The cluster analysis revealed higher annual levels of microorganisms and phosphorous at stations along the Hangang-Seoul and Hantangang areas. Nevertheless, the overall water quality over the last four years showed an observable trend toward continuous improvement. These findings also suggest that non-point pollution control strategies should consider the influence of upstreams and downstreams to protect water quality in the Han River. Conclusion: This data analysis procedure provided an efficient and comprehensive tool to interpret complex water quality data matrices. Results from a trend analysis provided much important information about sources and parameters for Han River water quality management.

• Journal of the Korean Home Economics Association
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• v.33 no.5
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• pp.75-88
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• 1995

The objectives of this study were to classify the contents of clothing shopping orientation, to group women into shopper types, and to examine the differences in clothing purchase criteria according to the shopper types. Samples were 335 women(20-49 years of age) in Seoul, Korea. The data were analyzed using factor analysis, cluster analysis, one-way ANOVA, Duncan's multiple range test, X2 test, paired t-test, multiple regression analysis. The results of the study were the followings. 1. Five factors of clothing shopping orientation derived by factor analysis : F.1 'impulsive shopping' ; F.2 'rational shopping' ; F.3 'independent shopping' ; F.4 'economic shopping' ; F.5 'convenient shopping'. Three shopper types were classified by cluster analysis of the 5 factors : T.1 'convenient shopper' ; T.2 'impulsive shopper' ; T.3 'rational shopper'. 2. Significant differences were found among the 3 shopper types in all clothing purchase criteria. Rational shopper perceived all purchase criteria as more important than did the other 2 types. Impulsive shopper perceived 'fashion', 'attractiveness', 'style', and 'bland' as more important than did convenient shopper. 3. Married women and unemployed women were more distributed in rational shopper, while the unmarried and the employed more in impulsive shopper. Impulsive shopper used more credit care, purchased suits and blouses at department store and brand specialty store more than did rational shopper. Rational shopper purchased at discount store and wholesale store more than did impulsive shopper. 4. Women assessed 'color and fabric design' as most important in suit and blouse purchase criteria. 'Care' was perceived more important in blouses than in suits, and the other 9 purchase criteria(fashion, attractiveness, style, color and fabric design, fabric, durability, costruction, comfort, and brand) were perceived more important in suits than in blouses. 5. Rational and economic shopping orientation scores were higher in suit purchase than in blouse, while impulsive, independent, and convenient shopping orientation scores were higher in blouse purchase. 6. Post-purchase suit satisfaction was influenced by rational shopping orientation, educational level, style, income, and comfort. The explanatory power of the 5 variables was 17.2%. Post-purchase blouse satisfaction was influenced by style, care, rational shopping orientation, and independent shopping orientation. The explanatory power of the 4 variables was 10.2%.

• Journal of Intelligence and Information Systems
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• v.11 no.1
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• pp.169-189
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• 2005

In order to derive a better classifier with a limited number of training examples, active teaming alternately repeats the querying stage fur category labeling and the subsequent learning stage fur rebuilding the calssifier with the newly expanded training set. To relieve the user from the burden of labeling, especially in an on-line environment, it is important to minimize the number of querying steps as well as the total number of query examples. We can derive a good classifier in a small number of querying steps by using only a small number of examples if we can select multiple of diverse, representative, and ambiguous examples to present to the user at each querying step. In this paper, we propose a cluster-based batch query selection method which can select diverse, representative, and highly ambiguous examples for efficient active learning. Experiments with various text data sets have shown that our method can derive a better classifier than other methods which only take into account the ambiguity as the criterion to select multiple query examples.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.14 no.2
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• pp.39-53
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• 2015

The paper analyzes factors to affect pedestrian volumes by land-use type using 2012 Seoul Pedestrian Survey. First of all, five groups were classified based on land-use types around survey points such as residential, commercial, industrial and green uses, using k-average cluster analysis. Then, differences in average pedestrian volumes by group were compared for a day and time of day. In addition, multiple regression analysis was employed to identify factors to affect pedestrian volumes, considering physical features, land use types, public transportation accessibility, and socio-economic indices as independent variables by spatial hierarchy. Model results show that the walkway width positively influenced on pedestrian volumes for all groups, whereas other variables differently affected by group. Our results can be used as basic data for establishing polices with respect to pedestrian road design and improvement as well as estimating pedestrian demand by land-use type.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.8
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• pp.1773-1779
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• 2015

Shore-to-sea visible light communication using color clustered multiple-input and multiple-output (MIMO) is presented. The proposed maritime visible light communication (MVLC) offers a low-cost, high-speed wireless link for shore-to-sea maritime communications. Each color cluster is comprised of 50 red, green and blue (RGB) light emitting diodes (LEDs) and is modulated using on-off-keying (OOK). Selection combining is performed at the receiver, producing diversity effect within that color cluster. In this paper, we employ sea states (wave height, wind speed, etc.) data from both Pierson-Moskowitz and JONSWAP spectrum models under atmospheric turbulence conditions. Based on the simulation model, the maritime link quality is analysed in terms of coverage distance and bit error rate performance. The results show that the proposed system provides an efficient MVLC, while satisfying International Association of Lighthouse Authorities (IALA) requirements for maritime buoyage system and also offering sufficient illumination from high power LEDs.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.129.1-129.1
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• 2011

We have applied an advanced multi-aperture indexing photometry and sophisticated de-trending method to existing Taiwanese-American Occultation Survey (TAOS) data sets. TAOS, a wide-field ($3^{\circ}{\times}3^{\circ}$) and rapid photometry (5Hz) survey, is designed to detect small objects in the Kuiper Belt. Since TAOS has fast and multiple exposures per zipper mode image, point spread function (PSF) varies in a given image. Selecting appropriate aperture among various size apertures allows us to reflect these variations in each light curve. The survey data turned out to contain various trends such as telescope vibration, CCD noise, and unstable local weather. We select multiple sets of stars using a hierarchical clustering algorithm in such a way that the light curves in each cluster show strong correlations between them. We then determine a primary trend (PT) per cluster using a weighted sum of the normalized light curves, and we use the constructed PTs to remove trends in individual light curves. After removing the trend, we can get each synthetic light curve of star that has much higher signal-to-noise ratio. We compare the efficiency of the synthetic light curves with the efficiency of light curves made by previous existing photometry pipelines. Our photometric method is able to restore subtle brightness variation that tends to be missed in conventional aperture photometric methods, and can be applied to other wide-field surveys suffering from PSF variations and trends. We are developing an analysis package for the next generation TAOS survey (TAOS II) based on the current experiments.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.30.2-30.2
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• 2009

There is a growing body of evidence for the presence of multiple stellar populations in some globular clusters, including NGC 1851. For most of these peculiar globular clusters, however, the evidence for the multiple red giant-branches (RGBs) having different heavy elemental abundances as observed in $\omega$ Centauri is hitherto lacking, although spreads in some lighter elements are reported. It is therefore not clear whether they also share the suggested dwarf galaxy origin of $\omega$ Cen or not. Here we show from the CTIO 4m UVI photometry of the globular cluster NGC 1851 that its RGB is clearly split into two in the U - I color. The two distinct RGB populations are also clearly separated in the abundance of heavy elements as traced by Calcium, suggesting that the type II supernovae enrichment is also responsible, in addition to the pollutions of lighter elements by intermediate mass asymptotic giant branch stars or fast-rotating massive stars. The RGB split, however, is not shown in the V - I color, as indicated by previous observations. Our stellar population models show that this and the presence of bimodal horizontal-branch distribution in NGC 1851 can be naturally reproduced if the metal-rich second generation stars are also enhanced in helium.