• Advances in Computational Design
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• v.8 no.3
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• pp.219-236
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• 2023

In this paper, finite element modeling of the laser ultrasonics (LU) process in ablation regime is of interest. The momentum resulting from the removal of material from the specimen surface by the laser beam radiation in ablation regime is modeled as a pressure pulse. To model this pressure pulse, two equations are required: one for the spatial distribution and one for the temporal distribution of the pulse. Previous researchers have proposed various equations for the spatial and temporal distributions of the pressure pulse in different laser applications. All available equations are examined and the best combination of the temporal and spatial distributions of the pressure pulse that provides the most accurate results is identified. This combination of temporal and spatial distributions has never been used for modeling laser ultrasonics before. Then by using this new model, the effects of variations in pulse duration and laser spot radius on the shape, amplitude, and frequency spectrum of ultrasonic waves are studied. Furthermore, the LU in thermoelastic regime is simulated by this model and compared with LU in ablation regime. The interaction of ultrasonic waves with a defect is also investigated in the LU process in ablation regime. Good agreement of the results obtained from the new finite element model and available experimental data confirms the accuracy of the proposed model.

• Nuclear Engineering and Technology
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• v.55 no.12
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• pp.4607-4616
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• 2023

We implement machine learning regression models to predict peak pressures of primary and secondary systems, a major safety concern in Loss Of Condenser Vacuum (LOCV) accident. We selected the Multi-dimensional Analysis of Reactor Safety-KINS standard (MARS-KS) code to analyze the LOCV accident, and the reference plant is the Korean Optimized Power Reactor 1000MWe (OPR1000). eXtreme Gradient Boosting (XGBoost) is selected as a machine learning tool. The MARS-KS code is used to generate LOCV accident data and the data is applied to train the machine learning model. Hyperparameter optimization is performed using a simulated annealing. The randomly generated combination of initial conditions within the operating range is put into the input of the XGBoost model to predict the peak pressure. These initial conditions that cause peak pressure with MARS-KS generate the results. After such a process, the error between the predicted value and the code output is calculated. Uncertainty about the machine learning model is also calculated to verify the model accuracy. The machine learning model presented in this paper successfully identifies a combination of initial conditions that produce a more conservative peak pressure than the values calculated with existing methodologies.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.33 no.2
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• pp.103-111
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• 2011

Purpose: Choukroun's platelet-rich-fibrin (PRF) is composed of platelets, white blood cells and fibrin matrix. It does not induce enough bone formation by itself but it can improve bone formation with calcium. Silk fibroin does not cause inflammatory reactions because it is bio-compatible and degradable. The purpose of this study was to exam the bone formation when a combination of Choukroun's PRF and silk fibroin was used. Methods: In this study, cell reactions to silk powder with differing molecular weights was first tested to select the appropriate silk powder. Then we applied these bone graft materials on defects of skull and in a peri-implant bony defect model in New Zealand rabbits. The results between the experimental and control s (non-grafted) group were analyzed. Results: The small sized silk fibroin powder showed increased cellular proliferation for bone-regeneration. There was no statistically significant difference between the experimental group and the control group at 6 weeks, but more new bone formation was observed in the combination graft group at 12 weeks (P<0.05). And in the dental implant model, the combination bone graft group showed much improved torque test results, which was statistically significant. Histomorphometric analysis showed more regenerated cortical bone and a higher mean bone to implant in the experimental group. Both were statistically significant. Conclusion: The combination graft of Choukroun's platelet-rich-fibrin (PRF) and silk fibroin powder can successfully restore the bony defects in a skull defected model and a peri-implant bony defects model.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.9 no.2
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• pp.79-89
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• 1999

A quantitative fit test, condensation nuclei counting (Portacount 8025, TSI), was performed concurrently with a banana oil (isoamyl acetate: IAA) qualitative fit test (MSA) to evaluate reliability on IAA QLFT and correlation between two methods. One brands of quarter mask (3M model 7500 medium) was prepared for QLFT with HEPA filter and gas & vapor removing media, i.e., combination cartridge. 110 subjects (65 male, 45 female) were fit tested QNFT and QLFT each three times. For a wearer combination having a FF<10, as determined by CNC QNFT, the point es timate (${\beta}$-error) of the probability of that combination not being rejected by the banana oil QLFT was found to be 0.0 with 95% confidence that this statistic is not expected to exceed 0.15. For a wearer combination having a FF<100, as determined by CNC QNFT, the point estimate of the probability of that combination not being rejected by the banana oil QLFT was found to be 0.07 with 95% confidence that this statistic is not expected to exceed 0.13. The uncertainty associated with each estimate, however, is large due to the small number of study subjects with inadequately fitting respirators.

• Journal of KIISE:Software and Applications
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• v.31 no.2
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• pp.153-163
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• 2004

Many recommender systems are based on Content-based Filtering and Social Filtering Both methods have their own advantages and disadvantages, and they complement each other rather than compete. So incorporating of both methods can make the better system and combination technique controls the quality of the entire recommender system. In this paper, we presented each user has his own tendency to decide which is the better recommendation for himself among the various recommendation results, and suggested the Personalized combination technique. To represent user tendency, we defined and used loyalty, diversity and pioneerity and showed by experiments that our combination technique is useful. This combination technique improved the average coverage 23% and for the ceiling 40%.

• Journal of the Korean Society of Clothing and Textiles
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• v.46 no.1
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• pp.33-48
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• 2022

This study was performed to compare the color emotion and preference of Koreans and Chinese for a two-color combination by dyeing cotton fabric with persimmon and indigo and to establish prediction models of color preference. Nine specimens prepared by combining two different colored fabrics (persimmon and indigo) were evaluated for color emotion and preference by Korean and Chinese groups of female college students. Koreans described most specimens as natural and traditional, whereas the Chinese described them as more pleasant and elegant as well as warmer and lighter than Koreans did. The contrast tone was the most preferred combination by both groups, whereas it was perceived as more modern and less warm by Koreans. Relationships between physical color variables and color emotions were quantified; these relationships were applied to establish a prediction model of color preference with tone combination types for each group. These results could help in making the design of fashion textiles more preference- and emotion-oriented for Korean and Chinese consumers.

• Journal of Technology Innovation
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• v.5 no.2
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• pp.22-47
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• 1997

This paper suggests a model of Living & Learning Nation as a new ploicy framework. It is a combination of Living Nation and Learning Nation. Living Nation model takes the nation as a living entity composed of spirit, resource, and communication : it grows but healthy and balanced growth is needed, its organs are closely connected, it has a circulation system, the 'spirit' factor plays the central role, etc.. Learning Nation model is a national level version of learning organization concept. The model defines new perspectives on the objectives, span of means, and the role of government in S&T policy. Therefore, the model can be used to give new insights to policymakers of developing countries facing the knowledge-based economy.

• Journal of the Korean Society for information Management
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• v.27 no.3
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• pp.227-239
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• 2010

Opinion retrieval is to retrieve items which are relevant to the user information need topically and include opinion about the topic. This paper aims to find a method to represent user information need for effective opinion retrieval and to analyze the combination methods for opinion features through various experiments. The experiments are carried out in the inference network framework using the Blogs06 collection and 100 TREC test topics. The results show that our suggested representation method based on hidden 'opinion' concept is effective, and the compact model with very small opinion lexicon shows the comparable performance to the previous model on the same test data set.

• Journal of Ocean Engineering and Technology
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• v.18 no.1
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• pp.53-62
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• 2004

The Purpose of this study is to recycle the waste concrete, which is generated in huge quantities, from construction works. in order to achieve this goal, it is important to determine the compressive strength, workability, slump, and ultrasonic velocity of recycled aggregate concrete. Thus, several experiment parameters are considered, such as water-cement ratios, sand percentage, and fine aggregate composition ratios, in order to apply the recycled aggregate concrete to pre-cast artificial fishing reefs. From the results, it has been shown that the proper mix designs for reef concrete are W/C=45%, S/a=50%, SR50:SN50 in recycled sand and natural sand mix combination case, W/C=45%, S/a=50%, SC50:SN50 in crushed sand and natural sand mix combination case, W/C=45%, S/a=50%, SR50:SC50 in recycled sand and crushd sand mix combination case. Also, this study shows that the shape and surface roughness of fine aggregate particles have an effect on the strength, slump, ultrasonic velocity of tested concrete, and the compressive strength ratios of 7days' and 90days' curing ages of recycled aggregate concrete are about 70% and 110% of 28days' curing age.

• Food Science of Animal Resources
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• v.32 no.2
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• pp.149-154
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• 2012

It is known that lactic-acid bacteria (LAB) helps keeping the intestine healthy and to enhance its immunologic competence. In addition, it is known to control the composition of the enterobacteria and the intestinal inflammatory reaction by inducing immunological enhancement. This study was performed, in a mouse model, to test the treatment and preventive effects of LAB of inflammatory bowel disease (IBD), which was induced by a blend of LAB-administering trinitrobenzene sulfonic acid (TNBS). To obtain the animal model of IBD, 2% TNBS was rectally administered once to a five-week-old male Balbc/J mouse. A probiotic combination was administered to the prevention group five times a week for eight weeks before the inducement of enteritis, and the mixture was administered to the treatment group five times a week, after the administration of TNBS. The changes in the levels of the cytokines of the lymph nodes and the tissue of the large intestine were observed, both with the naked eye and with a microscope. The observation showed that the levels of inflammatory cells, infiltration, and necrosis were much lower in the LAB-administered groups than in that of the control group. In addition, the inflammatory cytokines (e.g., TNF-${\alpha}$, IL-17A) decreased in the lymph nodes and the tissues of the large intestine. The results indicated that the administration of the combination to the animal model suppressed the inflammatory cytokines in the large intestine and in the lymph nodes, which in turn suppressed the progression of colitis.