• Journal of Powder Materials
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• v.31 no.3
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• pp.213-219
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• 2024

Additive Manufacturing (AM) is a process that fabricates products by manufacturing materials according to a three-dimensional model. It has recently gained attention due to its environmental advantages, including reduced energy consumption and high material utilization rates. However, controlling defects such as melting issues and residual stress, which can occur during metal additive manufacturing, poses a challenge. The trial-and-error verification of these defects is both time-consuming and costly. Consequently, efforts have been made to develop phenomenological models that understand the influence of process variables on defects, and mechanical/ electrical/thermal properties of geometrically complex products. This paper introduces modeling techniques that can simulate the powder additive manufacturing process. The focus is on representative metal additive manufacturing processes such as Powder Bed Fusion (PBF), Direct Energy Deposition (DED), and Binder Jetting (BJ) method. To calculate thermal-stress history and the resulting deformations, modeling techniques based on Finite Element Method (FEM) are generally utilized. For simulating the movements and packing behavior of powders during powder classification, modeling techniques based on Discrete Element Method (DEM) are employed. Additionally, to simulate sintering and microstructural changes, techniques such as Monte Carlo (MC), Molecular Dynamics (MD), and Phase Field Modeling (PFM) are predominantly used.

• Herbal Formula Science
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• v.21 no.2
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• pp.144-157
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• 2013

Objectives : The aim of this study was to evaluate the efficacy of Hwangnyeonhaedok-tang (HH) and Geongangbuja-tang (GB) on the plasma hormone level in mice exposed to cold stress. HH and GB are the representative prescriptions of cold and hot property, respectively. Methods : We established cold condition by confining ICR mice to a $4^{\circ}C$ cage for 24 hours, ICR mice were given a HH (100, 300, 1000 mg/kg) or GB (100, 300, 1000 mg/kg) extract orally twice a day for three consecutive days. From the second day, they were given cold stress ($4^{\circ}C$) for twenty four hours. To measure the plasma corticosterone, insulin, thyroxine, epinephrine and norepinephrine levels of mice, their blood samples were collected from cardiac puncture, immediately centrifuged at $4^{\circ}C$. The protein level of HSP70 and JNK was examined using western blot analysis in cortex and hypothalamus. Results : Oral administration of GB more significantly reduced plasma corticosterone level raised by cold stress than HH. Gardeniae Fructus (CJ), the constituent of HH, significantly increased the thyroxine level. Western blot analysis showed that cold stress-induced Heat shock protein 70 (HSP70) expression was increased by HH and GB, HH decreased JNK expression and GB increased JNK expression dose-depently in hypothalamus. Scutellariae Radix (HG), Zingiberis Rhizoma (GG) and Aconiti Tuber (BJ) decreased HSP70 in hypothalamus and GG, BJ decreased HSP70 in cortex as well. Conclusions : These results suggest Geongangbuja-tang (GB) is more effective for ameliorating the stress response caused by cold stress.

• Toxicological Research
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• v.14 no.4
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• pp.515-523
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• 1998

Oxidative stress by reactive oxygen species (ROS) damages cellular DNA, RNA, proteins, lipids and others causing various diseases such as cancer, arthritis, and heart diseases. 8-Hydroxyguanine (8-OHG) is one of the products formed from DNA or RNA damaged by ROS. Since high amounts of 8-OHG can be excreted in urine, it may serve as a potential biomarker indicating the level of oxidative damage to nucleic acids. Residents in industrial area with severe air pollution are expected to be affected by higher level of oxidative stress from pollutants like polyaromatic hydrocarbons (PAHs), etc. Smokers are also expected to be damaged by higher level of oxidative stress from cigarette smoke components like PAHs than non-smokers. To examine if the determination of the urinary concentration of 8-OHG could be used as exposure biomarker for the oxidative stress caused by air-pollutants, this study was performed to determine and compare the urinary concentrations of 8-OHG in smokers and non-smokers, or non-polluted area residents and polluted area residents. Urine samples were collected and purified by a strong cation exchange and cellulose partition column, then analyzed by HPLC with electrochemical detector at 600 ㎷ potential. Concentrations of urinary 8-OHG in non-smokers and smokers of Seoul area college male students were determined as 15.12$\pm$9.68 (ng/mg creatinine) and 34.72$\pm$11.72 (ng/mg creatinine), respectively, showing significantly higher level of 8-OHG in smokers than in non-smokers. Urine samples of elementary school students were collected from Sokcho area, which is known to be non-polluted, and 3 representative polluted areas; Yocheon industrial area, Ulsan urban and Ulsan industrial area. The concentrations of 8-OHG in these samples were 12.42$\pm$8.27 (ng/ mg creatinine, Sokcho), 22.55$\pm$9.12 (ng/mg creatinine, Yocheon), 17.41$\pm$2.30 (ng/mg creatinine, Ulsan urban), 55.04$\pm$39.73 (ng/mg creatinine, Ulsan industrial). Thus, samples from polluted area tend to have higher level of 8-OHG and the levels of Yocheon and Ulsan industrial area were significantly higher than that of Sokcho area. The results indicate that the residents of polluted industrial area or smokers are more severely exposed to oxidative stress probably caused by air pollutants like PAHs. Thus, the determination of urinary 8-OHG concentration could be used as biomarker for the extent of body exposure to oxidative stress caused by various pollutants.

• Journal of the Korean Society for Library and Information Science
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• v.47 no.3
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• pp.181-205
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• 2013

The purpose of this study is to develop a job-stress scale for librarians who work in university libraries. The study was first conducted by analyzing existing representative job-stress scales that are used domestically and internationally. To understand the characteristic of particular job stress that academic librarians have, the in-depth interview among qualitative research methods was selected, and 15 librarians who work at a 4-year system university libraries participated in this study. Based on the results of the questionnaire survey, the reliability and validity were verified. To analyze the validity, exploratory factor analysis was carried out. To extract factors, principal component analysis was used. To extract factors, principal component analysis was used. For the rotation method, a varimax rotation was applied. A tertiary measurement tool with a total of 46 questions for 11 factors was developed after removing measurement questions that were rejected as a result of the analysis. As a result of factor analysis on the tertiary measurement tool, 11 factors were extracted. Those 11 factors include 'peer relation conflict factor(factor 1)', 'superior-subordinate relation conflict factor (factor 2)', 'work compensation evaluation factor(factor 3)', 'emotional labor factor(factor 4)', 'physical environmental factor(factor 5)', 'employment stability(factor 6)', 'job demand factor(psychological) (factor 7)', 'decision-making and responsibility factor(factor 8)', 'work complexity factor(factor 9)', 'work boundary conflict factor(factor 10)', and 'job demand factor(physical)(factor 11)'.

• Journal of the Korean Society for Advanced Composite Structures
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• v.2 no.3
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• pp.1-11
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• 2011

The typical truss-lattice material successively packed by repeated cubic symmetric unit cells consists of sub-elements (SE) proposed in this study. The representative continuum model for this truss-lattice material such as the effective strain and stress relationship can be formulated by the homogenization procedure based on the notation of averaged mechanical properties. The volume fractions of micro-scale struts have a significant influence on the effective strength as well as the relative density in the lattice plate with replicable unit cell structures. Most of the strength contribution in the lattice material is induced by axial stiffness under uniform stretching or compression responses. Therefore, continuum based constitutive models composed of homogenized member stiffness include these mechanical characteristics with respect to strength, internal stress state, material density based on the volume fraction and even failure modes. It can be also recognized that the stress state of micro-scale struts is directly associated with the continuum constitutive model. The plastic flow at the micro-scale stress can extend the envelope of the analytical stress function on the surface of macro-scale stress derived from homogenized constitutive equations. The main focus of this study is to investigate the basic topology of unit cell structures with the cubic symmetric system and to formulate the plastic models to predict pressure dependent macro-scale stress surface functions.

• Cartoon and Animation Studies
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• s.40
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• pp.477-496
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• 2015

Emotional awareness is the image of a person is represented by different tendencies. Currently, the emotion computing to objectively evaluate the emotion recognition research is being actively studied. However, existing emotional computing research has many problems to run. First, the non-objective in emotion recognition if it is inaccurate. Second, the correlation between the emotion recognition is unclear points. So to test the regularity of image sensitivity to the need of the present study is to control emotions in the computing system. In addition, the screen number of the emotion recognized for the purpose of this study, applying the method of objective image emotional computing system and compared with a similar degree of emotion of the person. The key features of the image emotional computing system calculates the emotion recognized as numbered digital form. And to study the background of emotion computing is a key advantage of the effect of the James A. Russell for digitization of emotion (Core Affect). Pleasure emotions about the core axis (X axis) of pleasure and displeasure, tension (Y-axis) axis of tension and relaxation of emotion, emotion is applied to the computing research. Emotional axis with associated representative sensibility very happy, excited, elated, happy, contentment, calm, relaxing, quiet, tired, helpless, depressed, sad, angry, stress, anxiety, pieces 16 of tense emotional separated by a sensibility ComputingIt applies. Course of the present study is to use the color of the color key elements of the image computing formula sensitivity, brightness, and saturation applied to the sensitivity property elements. Property and calculating the rate sensitivity factors are applied to the importance weight, measured by free-level sensitivity score (X-axis) and the tension (Y-axis). Emotion won again expanded on the basis of emotion crossed point, and included a representative selection in Sensibility size of the top five ranking representative of the main emotion. In addition, measuring the emotional image of a person with 16 representative emotional score, and separated by a representative of the top five senses. Compare the main representative of the main representatives of Emotion and Sensibility people aware of the sensitivity of the results to verify the similarity degree computing emotion emotional emotions depending on the number of representative matches. The emotional similarity computing results represent the average concordance rate of major sensitivity was 51%, representing 2.5 sensibilities were consistent with the person's emotion recognition. Similar measures were the degree of emotion computing calculation and emotion recognition in this study who were given the objective criteria of the sensitivity calculation. Future research will need to be maintained weight room and the study of the emotional equation of a higher concordance rate improved.

• Journal of Physiology & Pathology in Korean Medicine
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• v.21 no.1
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• pp.190-198
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• 2007

Alzheimer's disease, a representative neurodegenerative disorder, is characterized by the presence of senile plaques and neurofibrillary tangles accompanied by neuronal damages. b-Amyloid peptide is considered to be responsible for the formation of senile plagues that accumulate in the brains of patients with Alzheimer's disease. There has been compelling evidence supporting that b-amyloid-induced cytotoxicity is mediated through generation of reactive oxygen species. In this study, we have investigated the possible protective effect of Rehmannia glutihosaagainst b-amyloid-induced oxidative ceil death in cultured human neuroblastoma SH-SY5Y cells. SH-SY5Y cells treated with b-amyloid underwent apoptotic death as determined by morphological features and positive in situterminal end-labeling (TUNEL staining). Rehmannia glutinosawater extract, wine, and vinegar pretreatments attenuated b-amyloid-induced cytotoxicity and apoptosis. Rehmannia glutinosa vinegar exhibited maximum protective effect by increasing the expression of anti-apoptotic protein, Bcl-2. in addition to oxidative stress, b-amyloid-treatment caused nitrosative stress via marked increase in the levels of nitric oxide, which was effectively blocked by Rehmannia glutinosa. To further explore the possible molecular mechanisms underlying the protective effect of Rehmannia glutinosa, we assessed the mRNA expression of cellular antioxidant enzymes. Treatment of Rehmannia glutinosa vinegar led to up-regulation of heme oxygemase-1 and catalase. These results suggest that Rehmannia glutinosa could modulate oxidative neuronal cell death caused by b-amyloid and may have preventive or therapeutic potential in the management of Alzheimer's disease. Particularly, Rehmannia glutinosa vinegar can augment cellular antioxidant capacity, there by exhibiting higher neuroprotective potential.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.4 no.2
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• pp.72-82
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• 1992

To accurately estimate nearshore current in shallow water regions. it is necessary to investigate the irregular wave transformation characteristics and radiation stress produced by random sea waves. This research is to investigate the application or the individual wave Analysis Method. the Component Wave Analysis Method and Representative Wave Analysis Method in the shallow water region. These methods were estimated by wave shallowing transformation when the waves propagate from deep water to shallow water region b)r generating regular waves, two component waves and irregular waves (Bretschneider-Mitsuyasu type). That is, the Indivisual Wave Analysis Method is to investigate from the viewpoint of shallow water transformation of wave statistical characteristics and their zero-down-crossing waves (wave height period and wave celerity). And the component Wave Analysis Method is to investigate from the view point of shallow water transformation of basic frequency component wave and their interference frequency component wave. In addition, this research is to compare the measured mean water level elevation with the calculated one from radiation stress of irreguar waves that is assumed in the three methods above.

• Cartoon and Animation Studies
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• s.33
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• pp.403-423
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• 2013

Video images of emotional happiness or unhappiness, stress or emotional division of tranquility in the form of a tree is evaluated by weighting. Representative evaluation of the video image brightness contrast sensitivity ratings 1 car happy, unhappy or nervous, calm and refined with two car dependency, sensitivity to visual images are separated. Emotion Recognition of four compared to the numerical data is measured by brightness. OpenCV implementation through evaluation graph the stress intensity contrast, tranquility, happiness, unhappiness with changes in the value of four, separated by sensitivity to computing. Contrast sensitivity of computing the brightness according to the input value 'unhappy' to 'happy' or 'stress' to 'calm' the emotional changes are implemented. Emotion computing the regularity of the image to calculate the sensitivity localized computing system can be controlled according to the emotion of the contrast value of the brightness changes are implemented. The future direction of industry on the application of emotion recognition will play a positive role.

• Journal of Welding and Joining
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• v.34 no.1
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• pp.26-34
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• 2016

Automotive today has been transforming to an electronic product by adopting a lot of convenience and safety features, suggesting that joining materials and their mechanical reliabilities are getting more important. In this study, a Sn-Cu-Cr-Ca solder composition having a high melting temperature ($>230^{\circ}C$) was fabricated and its joint properties and reliability was investigated with an aim to evaluate the suitability as a joining material for electronics of engine room. Furthermore, mechanical properties change under complex environment were compared with several existing solder compositions. As a result of contact angle measurement, favorable spreadability of 84% was shown and the average shear strength manufactured with corresponding composition solder paste was $1.9kg/mm^2$. Also, thermo-mechanical reliability by thermal shock and vibration test was compared with that of the representative high temperature solder materials such as Sn-3.5Ag, Sn-0.7Cu, and Sn-5.0Sb. In order to fabricate the test module, solder balls were made in joints with ENIG-finished BGA and then the BGA chip was reflowed on the OPS-finished PCB pattern. During the environmental tests, resistance change was continuously monitored and the joint strength was examined after tests. Sn-3.5Ag alloy exhibited the biggest degradation rate in resistance and shear stress and Sn-0.7Cu resulted in a relatively stable reliability against thermo-mechanical stress coming from thermal shock and vibration.