• Journal of the Korean Orthopaedic Association
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• v.54 no.3
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• pp.211-218
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• 2019

Herniation of the intervertebral disc is a medical disease manifesting as a bulging out of the nucleus pulposus or annulus fibrosis beyond the normal position. Most lumbar disc herniation cases have a favorable natural course. On the other hand, surgical intervention is reserved for patients with severe neurological symptoms or signs, progressive neurological symptoms, cauda equina syndrome, and those who are non-responsive to conservative treatment. Numerous surgical methods have been introduced, ranging from conventional open, microscope assisted, tubular retractor assisted, and endoscopic surgery. Among them, microscopic discectomy is currently the standard method. Biportal endoscopic spinal surgery (BESS) has several merits over other surgical techniques, including separate and free handling of endoscopy and surgical instruments, wide view of the surgical field with small skin incisions, absence of the procedure of removing fog from the endoscope, and lower infection rate by continuous saline irrigation. In addition, existing arthroscopic instruments for the extremities and conventional spinal instruments can be used for this technique and surgery for recurred disc herniation is applicable because delicate surgical procedures are performed under a brightness of 2,700 to 6,700 lux and a magnification of 28 to 35 times. Therefore, due to such advantages, BESS is a novel technique for the surgical treatment of lumbar disc herniation.

• Journal of Intelligence and Information Systems
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• v.21 no.1
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• pp.119-142
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• 2015

With the explosive growth in the volume of information, Internet users are experiencing considerable difficulties in obtaining necessary information online. Against this backdrop, ever-greater importance is being placed on a recommender system that provides information catered to user preferences and tastes in an attempt to address issues associated with information overload. To this end, a number of techniques have been proposed, including content-based filtering (CBF), demographic filtering (DF) and collaborative filtering (CF). Among them, CBF and DF require external information and thus cannot be applied to a variety of domains. CF, on the other hand, is widely used since it is relatively free from the domain constraint. The CF technique is broadly classified into memory-based CF, model-based CF and hybrid CF. Model-based CF addresses the drawbacks of CF by considering the Bayesian model, clustering model or dependency network model. This filtering technique not only improves the sparsity and scalability issues but also boosts predictive performance. However, it involves expensive model-building and results in a tradeoff between performance and scalability. Such tradeoff is attributed to reduced coverage, which is a type of sparsity issues. In addition, expensive model-building may lead to performance instability since changes in the domain environment cannot be immediately incorporated into the model due to high costs involved. Cumulative changes in the domain environment that have failed to be reflected eventually undermine system performance. This study incorporates the Markov model of transition probabilities and the concept of fuzzy clustering with CBCF to propose predictive clustering-based CF (PCCF) that solves the issues of reduced coverage and of unstable performance. The method improves performance instability by tracking the changes in user preferences and bridging the gap between the static model and dynamic users. Furthermore, the issue of reduced coverage also improves by expanding the coverage based on transition probabilities and clustering probabilities. The proposed method consists of four processes. First, user preferences are normalized in preference clustering. Second, changes in user preferences are detected from review score entries during preference transition detection. Third, user propensities are normalized using patterns of changes (propensities) in user preferences in propensity clustering. Lastly, the preference prediction model is developed to predict user preferences for items during preference prediction. The proposed method has been validated by testing the robustness of performance instability and scalability-performance tradeoff. The initial test compared and analyzed the performance of individual recommender systems each enabled by IBCF, CBCF, ICFEC and PCCF under an environment where data sparsity had been minimized. The following test adjusted the optimal number of clusters in CBCF, ICFEC and PCCF for a comparative analysis of subsequent changes in the system performance. The test results revealed that the suggested method produced insignificant improvement in performance in comparison with the existing techniques. In addition, it failed to achieve significant improvement in the standard deviation that indicates the degree of data fluctuation. Notwithstanding, it resulted in marked improvement over the existing techniques in terms of range that indicates the level of performance fluctuation. The level of performance fluctuation before and after the model generation improved by 51.31% in the initial test. Then in the following test, there has been 36.05% improvement in the level of performance fluctuation driven by the changes in the number of clusters. This signifies that the proposed method, despite the slight performance improvement, clearly offers better performance stability compared to the existing techniques. Further research on this study will be directed toward enhancing the recommendation performance that failed to demonstrate significant improvement over the existing techniques. The future research will consider the introduction of a high-dimensional parameter-free clustering algorithm or deep learning-based model in order to improve performance in recommendations.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.12
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• pp.1-8
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• 2006

An experimental study was carried out in order to investigate the influence of Reynolds number on the near-wake of an oscillating airfoil. An NACA 0012 airfoil was sinusoidally pitched at the quarter chord point, and is oscillated over a range of instantaneous angles of attack of $\pm$6$^{\circ}$. An X-type hot-wire probe was employed to measure the near-wake of an oscillating airfoil, and the smoke-wire visualization technique was used to examine the flow properties of the boundary layer. The free-stream velocities were 1.98, 2.83 and 4.03 m/s and the corresponding chord Reynolds numbers were 2.3${\times}10^4$, 3.3$\times$104 and 4.8${\times}10^4$, respectively. The frequency of airfoil oscillation was adjusted to fix a reduced frequency of K=0.1. The results show that the properties of the boundary layer and the near-wake can dramatically be distinguished in the range of Reynolds numbers between 2.3${\times}10^4$ and 3.3${\times}10^4$, on the other hand, it is similar in the cases of Re=3.3$\times$104 and 4.8$\times$104. This is caused by that the unsteady separation point is dramatically delayed in case of Re= 2.3${\times}10^4$.

• The Korean Journal of Physiology and Pharmacology
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• v.22 no.2
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• pp.215-223
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• 2018

Intracellular $Ca^{2+}$ mobilization is closely linked with the initiation of salivary secretion in parotid acinar cells. Reactive oxygen species (ROS) are known to be related to a variety of oxidative stress-induced cellular disorders and believed to be involved in salivary impairments. In this study, we investigated the underlying mechanism of hydrogen peroxide ($H_2O_2$) on cytosolic $Ca^{2+}$ accumulation in mouse parotid acinar cells. Intracellular $Ca^{2+}$ levels were slowly elevated when $1mM\;H_2O_2$ was perfused in the presence of normal extracellular $Ca^{2+}$. In a $Ca^{2+}-free$ medium, $1mM\;H_2O_2$ still enhanced the intracellular $Ca^{2+}$ level. $Ca^{2+}$ entry tested using manganese quenching technique was not affected by perfusion of $1mM\;H_2O_2$. On the other hand, $10mM\;H_2O_2$ induced more rapid $Ca^{2+}$ accumulation and facilitated $Ca^{2+}$ entry from extracellular fluid. $Ca^{2+}$ refill into intracellular $Ca^{2+}$ store and inositol 1,4,5-trisphosphate ($1{\mu}M$)-induced $Ca^{2+}$ release from $Ca^{2+}$ store was not affected by $1mM\;H_2O_2$ in permeabilized cells. $Ca^{2+}$ efflux through plasma membrane $Ca^{2+}-ATPase$ (PMCA) was markedly blocked by $1mM\;H_2O_2$ in thapsigargin-treated intact acinar cells. Antioxidants, either catalase or dithiothreitol, completely protected $H_2O_2-induced$ $Ca^{2+}$ accumulation through PMCA inactivation. From the above results, we suggest that excessive production of $H_2O_2$ under pathological conditions may lead to cytosolic $Ca^{2+}$ accumulation and that the primary mechanism of $H_2O_2-induced$ $Ca^{2+}$ accumulation is likely to inhibit $Ca^{2+}$ efflux through PMCA rather than mobilize $Ca^{2+}$ ions from extracellular medium or intracellular stores in mouse parotid acinar cells.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.35 no.3
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• pp.94-104
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• 2017

This study carried out field evaluation by experts, monitoring by the public, and visitor satisfaction survey for 77 cases of utilization of cultural property projects that received support from "Living and Breathing Hyanggyo and Seowon" in 2016. The result was 'normal' for the comprehensive evaluation, and by section, 'good' for planning, operating, performance, outcome and annual special index. The field evaluation by experts was rated as 'good', monitoring by the public was 'good', and also 'good' for visitor satisfaction survey. The advantages of the project were as follows; increased chance for enjoyment of local cultural heritage, expansion of human network for utilization of local cultural heritage, utilization of cultural heritage as community place, diversification of educational contents by using cultural heritage. On the other hand, the disadvantages were as follows; decline of program's quality, shortage of putting plan in practice, insufficient interest and participation of local government, insufficient promoting, shortage of educational contents for free semester system. At last, we suggested measures to develop the project as follows; develop program by using local characteristics, develop programs for foreigner, training experts, increasing on-line promotion, develop new lecture technique, utilization of cultural heritage as a local community place, utilization planning by each space, improvement of evaluation system, tightening up reflection of visitor's opinions, consulting for each programs.

• The Journal of the Convergence on Culture Technology
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• v.5 no.3
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• pp.61-70
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• 2019

The painting group of Late Ming and Early Qing Dynasty is an era of confusion between the orthodox who faithfully cooperated with the Qing Dynasty and the individualist who had a hostile attitude. The country was ruined by these dynasties, and the family left the real world with the suffering of the breakdown and stayed in the mountains.Paldaesanin and Seokdo, the representative Yumin painters, did not form any a sect as a unique expression style for finding a true self.And, through his work, he expressed on madness and oddity through new ideas and composition that he feels misery and anger in his heart. The paintings of these paintings had semi-normative and impromptuous views of nature, which even the self burdened with grief was forgotten.And I expressed my own individuality and originality by forming a simple and free, on madness and oddity art aesthetic. The paintings of these paintings had semi-normative and impromptuous views of nature, which even the self burdened with grief was forgotten.And I expressed my own individuality and originality by forming a simple and free, on madness and oddity art aesthetic. Paldaesanin portrayed a strange figure with a spirit of resistance and a sad and angered emotion, through a unique technique of painting.The content is cynical, satirical, ironic, and on madness and oddity. On the other hand, Seokdo explained "ilhoeg" that the method of writing and the method of writing in "Hwaeolog" agree with each other.This has allowed us to achieve autonomy as a "rule without rules" that goes beyond the existing rules. And he delicately portrayed beauty, desire, and emotion with the use of sensuous brushes and the beauty of the colors.Their unique paintings were later conveyed to yangjupalgoe and led to the flow of paintings in the 18th century.