• Transactions of Materials Processing
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• v.23 no.8
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• pp.501-506
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• 2014

Progressive shearing with blanking dies is commonly employed to produce large quantities of tiny sheet metal electronic parts. Sheet metal pins, which are narrow and long, that are sheared with a progressive die set are often twisted. The twist in the sheet metal pins, which usually occurs in the final shearing operation, generally decreases with increasing blank holding force. The blank holding forces in all shearing operations are not the same because of different shearing positions and areas. In the current study, the optimal layout of the springs in a progressive die set to minimize the twist of the sheet metal pin is proposed. In order to find the holding force acting on the tiny narrow blanks produced with the proposed springs during the shearing process, the equivalent area method is used in the structural analysis. The shearing of the sheet-metal pin was simulated to compute the twist angle associated with the blank holding force. The constraint condition satisfying the pre-set blank holding force from the previous shearing operations was imposed. A design of experiments (DOE) was numerically implemented by analyzing the progressive die structure and by simulating the shearing process. From the meta-model created from the experimental results and by using a quadratic response surface method (PQRSM), the optimal layout of the springs was determined. The twist of sheet metal pin associated with the optimal layout of the springs found in the current study was compared with that of an existing progressive die to obtain a minimal amount of twist.

• Tuberculosis and Respiratory Diseases
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• v.47 no.2
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• pp.255-258
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• 1999

Pneumoconiosis, very popular to coal miners who are exposed to coal dusts dominantly, was introduced in the 19th century to describe lung diseases consequent to the inhalation of mineral dusts. Coal workers' pneumoconiosis(CWP) colloquially called "black lung" in the United States, is a distinct pathologic entity resulting from the tissue reaction to deposits of dust include the coal macule, which associated with focal emphysema constitutes the characteristic lesion of simple CWP and complicated CWP or progressive massive fibrosis(PMF). Coal mining are also associated with chronic bronchitis, chronic airflow limitation, and/or generalized emphysema. Progressive massive fibrosis lesions may imprint on and obliterate airways and vessels, and cavitation is not uncommon, being the consequence of ischemic necrosis or mycobacterial infections. We report a case which is unusual form of progressive massive fibrosis to be differentiated from lung carcinoma. It is a rapid growing PMF with ischemic necrosis. By the studies which are about risk of having progressive massive fibroois, it is predicted to be 1.4%. And the other study shows that simple pneumoconiosis clearly predisposed to PMF, with five year attack rates of 13.9%, 12.5%, 4.4% and 0.2% among men with categories 3, 2, 1, and 0 respectively at the start of the risk periods.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.4
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• pp.435-442
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• 2007

Since the Ronan Point apartment collapsed in 1968, researches on the progressive collapse have been intermittently conducted, and the collapse of the World Trade Center twin towers made the researches active again. In the United States guidelines such as GSA (2003) and DoD (2005) were provided for design and analysis of building structures against the progressive collapse. In this study the progressive collapse-resisting capacity of steel moment resisting frames designed by KBC-2005 was investigated using linear elastic static analysis and linear dynamic analysis procedures suggested in the guidelines. The results showed that in accordance with the GSA guideline the moment frame designed only for gravity load turned out to be vulnerable to the progressive collapse, whereas the lateral load resisting frame designed for earthquake load satisfied the criteria for progressive collapse. However both systems sailed to satisfy the criteria of the DoD-2005 guideline.

• Journal of the Korean Data Analysis Society
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• v.20 no.6
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• pp.2813-2827
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• 2018

Progressive censoring schemes have become quite popular in reliability study. Under progressive censored data, however, some units can be failed between two points of observation with exact times of failure of these units unobserved. For example, loss may arise in life-testing experiments when the failure times of some units were not observed due to mechanical or experimental difficulties. Therefore, multiply progressive censoring scheme was introduced. So, we derives a maximum likelihood estimator of the parameter of exponential distribution. And we introduced the goodness-of-fit test statistics using order statistic and Lorenz curve. We carried out Monte Carlo simulation to compare the proposed test statistics. In addition, real data set have been analysed. In Weibull and chi-squared distributions, the test statistics using Lorenz curve are more powerful than test statistics using order statistics.

• Composites Research
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• v.34 no.2
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• pp.101-107
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• 2021

Composite structures have components and joints. Theses connections or joints can be potentially weak points in the structure. The failure mode of the composite bolted joint is designed as a bearing failure mode for structural safety. The load-displacement relation exhibits bearing failure mode shows a nonlinear behavior after the initial failure and progressive failure behavior. In order to accurately predict the failure behavior of composite bolted joints, this study modified the shear damage variable calculation process in the existing progressive failure analysis model. The results of the bearing stress-bearing strain of the composite bolted joint were predicted using the modified progressive failure analysis model, and the modified model was verified through comparison with the previous progressive analysis model.

• Steel and Composite Structures
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• v.44 no.3
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• pp.437-450
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• 2022

When the vertical load-bearing members in high-rise structures fail locally, the beam-column joints play an important role in the redistribution of the internal forces. In this paper, a static laboratory test of three full-scale flush flange beam-reinforced connections with side and cover plates (CP-FBSP connection) with double half-span steel beams and single L-shaped columns composed of concrete-filled steel tubes (L-CFST columns) was conducted. The influence of the side plate width and cover plate thickness on the progressive collapse resistance of the substructure was thoroughly analyzed. The failure mode, vertical force-displacement curves, strain variation, reaction force of the pin support and development of internal force in the section with the assumed plastic hinge were discussed. Then, through the verified finite element model, the corresponding analyses of the thickness and length of the side plates, the connecting length between the steel beam flange and cover plate, and the vertical-force eccentricity were carried out. The results show that the failure of all the specimens occurred through the cracking of the beam flange or the cover plate, and the beam chord rotations measured by the test were all greater than 0.085 rad. Increasing the length, thickness and width of the side plates slightly reduced the progressive collapse resistance of the substructures. The vertical-force eccentricity along the beam length reduced the progressive collapse resistance of the substructure. An increase in the connecting length between the beam flange and cover plate can significantly improve the progressive collapse resistance of substructures.

• Journal of the Korea Computer Graphics Society
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• v.30 no.3
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• pp.141-147
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• 2024

Progressive photon mapping is a widely adopted rendering technique that conducts a kernel-density estimation on photons progressively generated from lights. Its hyperparameter, which controls the reduction rate of the density estimation, highly affects the quality of its rendering image due to the bias-variance tradeoff of pixel estimates in photon-mapped results. We can minimize the errors of rendered pixel estimates in progressive photon mapping by estimating the optimal parameters based on gradient-based optimization techniques. To this end, we derived the gradients of pixel estimates with respect to the parameters when performing progressive photon mapping and compared our estimated gradients with finite differences to verify estimated gradients. The gradient estimated in this paper can be applied in an online learning algorithm that simultaneously performs progressive photon mapping and parameter optimization in future work.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.1
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• pp.105-116
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• 2010

Purpose: To analyze and compare differences between single vision lenses and functional progressive addition lenses and improvement to binocular visual function wearing functional lenses for pre-presbyopes altered their single vision lenses to functional progressive addition lenses with low addition. Methods: Healthy 32 subjects aged 24.03${\pm}$1.87 (male 23, female 9) who were recruited from university students wore functional progressive addition lenses (EYE-T, Chemilens Co., Korea, ADD 0.750) for 2 months. Objective refraction, corrected visual acuity at distance and near, near point of convergence, near point of accommodation, accommodative facility, phoria at distance and near were measured. And subjective satisfaction was investigated by using a questionnaire designed to fatigue, comfort, discomfort, overall satisfaction and preference. Results: Functional progressive addition lenses were better than single vision lenses at near point of convergence and accommodation, accommodative facility. Exo phoria measured at distance with single vision and functional progressive addition lenses. Exo phoria measured at near with functional progressive addition lenses was higher than that with single vision lenses. As a survey, the satisfaction was increased in questions related near work. However, single vision lenses were preferred in distance test of overall satisfaction, easy 10 adapt, lime to adapt. A survey showed thai preference of functional progressive addition lenses were increased 75.00% to 81.26% for near work, 50.00% to 65.63% for visual fatigue, 47.75% to 50.00% for visual comfort and 31.25% to 46.88% for overall comfort. Conclusions: Comparing between single vision lenses and functional progressive addition lenses, binocular visual function related near work, subjective satisfaction and preference was improved after wearing functional progressive addition lenses. This study suggested that functional progressive addition lenses were useful for long time near work.

• Archives of Plastic Surgery
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• v.34 no.5
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• pp.611-616
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• 2007

Purpose: The latissimus dorsi muscle flap is a versatile flap used in a variety of reconstructive procedures. The most common complication of LD muscle flap is donor site seroma, reported to occur in 20 to 79 percent of cases. The formation of dead space under the flap is intimately associated with seroma formation. The authors think that the use of progressive tension suture at closing donor site can decrease the formation of dead space and ultimately reduce the incidence of donor site seroma. Methods: A retrospective review was performed with 38 patients who underwent latissimus dorsi muscle harvest for breast reconstruction from March 2003 to September 2004. Progressive tension sutures were used during donor site closure in 22 patients. This group was compared with controls group(16 patients) who underwent latissimus dorsi muscle harvest without using this technique. Operation time, length of hospital stay, period of drainage, complication, and satisfaction about postoperative scar of donor site were examined. Results: The average length of hospital stay was 10.2 days and 12.7 days, and the mean duration of drainage were 7.3 days and 11.7 days in each progressive suture group and control group. These results were statistically significant (p<0.05). In the 22 patients who underwent progressive tension suture, none had seroma, hematoma or skin necrosis. In control group(16 patients), there happened one seroma formation and one partial skin necrosis. These complications were healed by aspiration of seroma and wound revision. The patients' satisfaction was not statistically significant, but the higher points were given by the patients who underwent progressive tension suture. Conclusion: This technique, progressive tension suture, is an effective method to reduce or eliminate donor site seroma, which is the most common complication associated with latissimus dorsi muscle harvest.

• The Journal of the Korean dental association
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• v.37 no.5 s.360
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• pp.359-364
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• 1999