• Journal of the Korea Society of Computer and Information
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• v.28 no.10
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• pp.163-170
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• 2023

The user-based collaborative filtering technique, one of the implementation methods of the recommendation system, recommends the preferred items of neighboring users based on the calculations of neighboring users with similar rating histories. However, it fundamentally has a data scarcity problem in which the quality of recommendations is significantly reduced when there is little common rating history. To solve this problem, many existing studies have proposed various methods of combining Jaccard index with a similarity measure. In this study, we introduce a time-aware concept to Jaccard index and propose a method of weighting common items with different weights depending on the rating time. As a result of conducting experiments using various performance metrics and time intervals, it is confirmed that the proposed method showed the best performance compared to the original Jaccard index at most metrics, and that the optimal time interval differs depending on the type of performance metric.

• Atmosphere
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• v.33 no.5
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• pp.519-530
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• 2023

Deep convection can make adverse effects on safe and efficient aviation operations by causing various weather hazards such as convectively-induced turbulence, icing, lightning, and downburst. To prevent such damage, it is necessary to accurately predict spatiotemporal distribution of deep convective area near the airport and airspace. This study developed a new index, the Aviation Convective Index (ACI), for deep convection, using the operational global Unified Model of the Korea Meteorological Administration. The ACI was computed from combination of three different variables: 3-hour maximum of Convective Available Potential Energy, averaged Outgoing Longwave Radiation, and accumulative precipitation using the fuzzy logic algorithm. In this algorithm, the individual membership function was newly developed following the cumulative distribution function for each variable in Korean Peninsula. This index was validated and optimized by using the 1-yr period of radar mosaic data. According to the Receiver Operating Characteristics curve (AUC) and True Skill Score (TSS), the yearly optimized ACI (ACI_YrOpt) based on the optimal weighting coefficients for 1-yr period shows a better skill than the no optimized one (ACI_NoOpt) with the uniform weights. In all forecast time from 6-hour to 48-hour, the AUC and TSS value of ACI_YrOpt were higher than those of ACI_NoOpt, showing the improvement of averaged value of AUC and TSS by 1.67% and 4.20%, respectively.

• Journal of Environmental Science International
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• v.33 no.1
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• pp.17-25
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• 2024

This study aimed to determine the most suitable coir substrate mixing ratio for optimizing the growth and yield of the "lpduelkkae 1" cultivar. We comprehensively analyzed the physicochemical properties, growth, and yields of four different substrate combinations: perlite (coir with mixing ratios of 70:30 (PC30), 50:50 (PC50), and 30:70 (PC70)) and 100% coir (C100). The results revealed substantial differences in substrate properties. C100 exhibited the highest total porosity and the lowest solid phase, indicating excellent air permeability. The pH levels and electrical conductivity (EC) values ranged from 5.4-6.8 and 1.2-3.1 dS·m^-1, respectively. Leaf growth parameters, including length, width, and dry weight, showed positive correlations with high coir ratios, except for PC30. PC70 and C100 outperformed other substrates in stem growth, exhibiting superior stem diameter and fresh and dry weights. The quantity of marketable leaves was the highest in the C100 substrate. Furthermore, C100 comprised integrated levels of essential nutrients, such as Ca and Mg, owing to its high coir content. In conclusion, a coir ratio of approximately 70% (v/v) should be maintained in the substrate for creating an optimal cultivation environment. Furthermore, the selection of humidity-resistant varieties as well as precise nutrient and moisture management for different seasons and growth stages are crucial for a successful perilla leaf hydroponic cultivation.

• Korean Journal of Radiology
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• v.20 no.6
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• pp.880-893
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• 2019

Objective: To assess the technical performance of two-dimensional shear wave elastography (2D-SWE) for measuring liver stiffness. Materials and Methods: The Ovid-MEDLINE and EMBASE databases were searched for studies reporting the technical performance of 2D-SWE, including concerns with technical failures, unreliable measurements, interobserver reliability, and/or intraobserver reliability, published until June 30, 2018. The pooled proportion of technical failure and unreliable measurements was calculated using meta-analytic pooling via the random-effects model and inverse variance method for calculating weights. Subgroup analyses were performed to explore potential causes of heterogeneity. The pooled intraclass correlation coefficients (ICCs) for interobserver and intraobserver reliability were calculated using the Hedges-Olkin method with Fisher's Z transformation of the correlation coefficient. Results: The search yielded 34 articles. From 20 2D-SWE studies including 6196 patients, the pooled proportion of technical failure was 2.3% (95% confidence interval [CI], 1.3-3.9%). The pooled proportion of unreliable measurements from 20 studies including 6961 patients was 7.5% (95% CI, 4.7-11.7%). In the subgroup analyses, studies conducting more than three measurements showed fewer unreliable measurements than did those with three measurements or less, but no intergroup difference was found in technical failure. The pooled ICCs for interobserver reliability (from 10 studies including 517 patients) and intraobserver reliability (from 7 studies including 679 patients) were 0.87 (95% CI, 0.82-0.90) and 0.93 (95% CI, 0.89-0.95), respectively, suggesting good to excellent reliability. Conclusion: 2D-SWE shows good technical performance for assessing liver stiffness, with high technical success and reliability. Future studies should establish the quality criteria and optimal number of measurements.

• The Korean Journal of Applied Statistics
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• v.37 no.4
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• pp.499 -508
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• 2024

In this paper, we investigate hierarchical time series forecasting that adhere to a hierarchical structure when deriving predicted values by analyzing segmented data as well as aggregated datasets. The occurrences of food poisoning by a specific pathogen are analyzed using zero-inflated Poisson regression models and negative binomial regression models. The occurrences of major, miscellaneous, and overall food poisoning are analyzed using Poisson regression models and negative binomial regression models. For hierarchical time series forecasting, the MinT estimation proposed by Wickramasuriya et al. (2019) is employed. Negative predicted values resulting from hierarchical adjustments are adjusted to zero, and weights are multiplied to the remaining lowest-level variables to satisfy the hierarchical structure. Empirical analysis revealed that there is little difference between hierarchical and non-hierarchical adjustments in predictions based on pathogens. However, hierarchical adjustments generally yield superior results for predictions concerning major, miscellaneous, and overall occurrences. Without hierarchical adjustment, instances may occur where the predicted frequencies of the lowest-level variables exceed that of major or miscellaneous occurrences. However, the proposed method enables the acquisition of predictions that adhere to the hierarchical structure.

• Korean Journal of Construction Engineering and Management
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• v.17 no.2
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• pp.135-145
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• 2016

In Korea, a series of noise-reduced aluminum forms are being recently used in apartment housing construction. However, their complicated and time-consuming work processes, and the noise which is still generated due to the inherent property of aluminum when especially installing and dismantling them have been pointed out as a problem to be certainly solved for increasing their practical use in construction sites. The primary objectives of this study are proposing an optimal conceptual design of a newly designed noise-reduced aluminum form and verifying the technical feasibility by conducting a working mock-up drive experiment. Thus, conventional noise-reduced aluminum forms have been analyzed and three conceptual designs of a newly noise-reduced aluminum forms have been deducted. AHP has been applied to a survey data collected by interviewing field experts. A trade-off analysis results have shown that 'Noise-reduced System Aluminum Form with a Drop-down Floor Post and Adaptive Beam' the highest weights of safety(0.52), work convenience(0.54) and thus selected. The suggested conceptual design in this study improved problems of conventional system aluminum forms. It is also expected that the suggested design will be used as a reliable guideline for the actual development of an aluminum form that ensures noise-reduce, work convenience and labor safety.

• Horticultural Science & Technology
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• v.35 no.4
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• pp.431-438
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• 2017

This study investigated the effect of pre-planting nitrogen (N) fertilization levels added to a soilless root medium on the growth of 'Dotaerang Dia' tomato seedlings. The N levels were varied for a total of 7 treatments: 0, 100, 250, 500, 750, 1,000, or $1,500mg{\cdot}L^{-1}$. The pH of the root media gradually rose in all treatments as the seedlings grew; however, the differences in the pH were not significant among the treatments. The electrical conductivity (EC) of the root media was significantly different among the treatments from sowing to week three, then drastically decreased after week four, which diminished the differences in the EC among the treatments. At week six, plant height, leaf length, leaf width, number of leaves, and fresh and dry weights of the shoot were highest for the treatment with $500mg{\cdot}L^{-1}N$. In contrast, the treatment with $1,500mg{\cdot}L^{-1}N$ had the lowest results for all growth measurements. The fresh weight was 67% heavier in the $500mg{\cdot}L^{-1}N$ treatment compared to the $1,500mg{\cdot}L^{-1}N$ treatment. The total N content in the tissues was lowest in the treatment with $0mg{\cdot}L^{-1}N$ and highest in the treatment with $1,000mg{\cdot}L^{-1}N$. The contents of calcium (Ca), magnesium (Mg), and metal micronutrients in the tissues were highest in the $250mg{\cdot}L^{-1}N$ treatment. A previous study demonstrated that adjusting the fertilization level to promote growth to over 90% of the maximum growth is a good strategy for lowering production costs and preventing damage due to excessive fertilizer absorption by crops. Our results indicated that the optimal pre-planting N fertilization level for tomato plug seedlings should be lower than $500mg{\cdot}L^{-1}$ and the optimum tissue N contents should be around 3.21% to 4.60%.

• Asian-Australasian Journal of Animal Sciences
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• v.25 no.2
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• pp.151-162
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• 2012

Analysis for back fat thickness (BFAT) and daily body weight gains from birth to the end of a performance test were conducted to find an optimal method for estimation of weaning age effects and to ascertain impacts of weaning age on the growth performance of purebred Berkshire pigs from a closed population in Korea. Individual body weights were measured at birth (B), at weaning (W: mean, 22.9 d), at the beginning of the performance test (P: mean, 72.7 d), and at the end of the performance test (T: mean, 152.4 d). Further, the average daily gains in body weight (ADG) of 3,713 pigs were analyzed for the following periods: B to W (DGBW), W to P (DGWP), P to T (DGPT), B to P (DGBP), B to T (DGBT), and W to T (DGWT). Weaning ages ranged from 17 to 34 d, and were treated as fixed (WF), random with (WC) and random without (WU) consideration of an empirical relationship between weaning ages in the models. WF and WC produced the lowest AIC (Akaike Information Criterion) and least fractions of error variance components in multi-traits analysis, respectively. The fractions of variances due to diverse weaning age and the weaning age correlations among ADGs of different stages (when no overlapping allowed) by WC ranged from 0.09 to 0.35 and from -0.03 to 0.44, respectively. The maximum weaning age effects and optimal back fat thicknesses were attained at weaning ages of 27 to 32 d. With the exception of DGBW, the effects of weaning age on the ADGs increased (ranging from 1.50 g/d to 7.14 g/d) with increased weaning age. In addition, BFAT was reduced by 0.106 mm per increased day in weaning age. In conclusion, WC produced reasonable weaning age correlations, and improved the fitness of the model. Weaning age was one of crucial factors (comparable with heritability) influencing growth performance in Berkshire pigs. Further, these studies suggest that increasing weaning age up to 32 d can be an effective management strategy to improve growth performance. However, additional investigations of the costs and losses related to extension of the suckling period and on the extended range of weaning age are necessary to determine the productivity and safety of this practice in a commercial herd and production system.

• Asian-Australasian Journal of Animal Sciences
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• v.23 no.10
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• pp.1308-1318
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• 2010

The purpose of this study was to evaluate the effect of replacing soybean meal with treated castor meal with (CMT) or without lime (CMNT) on the nutrient intake, performance, carcass characteristics, and yield of commercial cuts of beef cattle from a feedlot. Thirty male, castrated, crossbreed zebu cattle were used in the study, with an average initial weight of $360{\pm}30.27\;kg$. Five animals were used as a control group and were slaughtered at the beginning of the experiment; the remaining animals (n = 25) were distributed in random blocks (repetitions), with body weight as the criterion for block assignment. The animals were fed a diet containing 65% corn silage and 35% of concentrate on dry matter (DM) basis. Five diets consisted of four levels of soybean meal (SM) substituted with CMT (0, 33, 67 and 100%) on a DM basis and a diet with 100% of SM replaced with CMNT. At the end of the experiment, all animals were slaughtered, and their gastrointestinal tracts were emptied to determine their empty body weights (EBW). No significant effects were observed (p>0.05) for the substitution of soybean meal with CMT on intake of dietary nutrients, the average daily body weight gain (ADG) or EBW gain (EBWG). In spite of greater (p<0.05) ricin intake for the diet containing CMNT (3.06 mg/kg BW) compared to the CMT diet (0.10 mg/kg BW/d), there were no effects (p>0.05) on intake of dietary nutrients, ADG or EBWG. The average intake of DM and the ADG were 10,664.63 and 1,353.04 g/d, respectively. Regarding carcass characteristics, only carcass yield in relation to body weight was linearly reduced (p<0.05) upon substitution of SM by CMT. There was no effect (p>0.05) of the substitution of SM by CMT or CMNT on the yield of carcass basic cuts. CMT prices that are higher than 85% of the SM price do not economically justify the use of CMT. For CMT prices between 20 and 80% of the SM price, the optimal level was 67% substitution, while for prices below 15% of the SM price, the optimal level was 100% substitution with CMT. It can be concluded that treated castor meal with 6% lime can totally replace soybean meal in beef cattle diets.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.6
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• pp.563-569
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• 2016

This paper presents the resizing method of columns and beams that considers column-to-beam strength ratios to simultaneously control the initial stiffness and ductility of steel moment frames. The proposed method minimizes the top-floor displacement of a structure while satisfying the constraint conditions with respect to the total structural weight and column-to-beam strength ratios. The design variable considered in this method is the sectional area of structural members, and the sequential quadratic programming(SQP) technique is used to obtain optimal results from the problem formulation. The unit load method is applied to determine the displacement participation factor of each member for the top floor lateral displacement; based on this, the sectional area of each member undergoes a resizing process to minimize the top-floor lateral displacement. Resizing members by using the displacement participation factor of each member leads to increasing the initial stiffness of the structure. Additionally, the proposed method enables the ductility control of a structure by adjusting the column-to-beam strength ratio. The applicability of the proposed optimal drift design method is validated by applying it to the steel moment frame example. As a result, it is confirmed that the initial stiffness and ductility could be controlled by the proposed method without the repetitive structural analysis and the increment of structural weights.