• Journal of the Korean Society of Safety
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• v.31 no.5
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• pp.35-41
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• 2016

Particulate filtering facepiece respirators (PFFR) is one of the most widely used items of personal protective equipments, and a tight fit of the respirators on the wearers is critical for the protection effectiveness. In order to effectively protect the workers through the respirators, it is important to find and evaluate the ways that can be readily applicable at the workplace to improve the fit of the respirators. This study was designed to evaluate effects of mask style (cup or foldable type) and donning training on fit factors (FF) of the respirators, since these are available at various workplace, especially at small business workplace. A total of 40 study subjects, comprised of 30~50s aged male and female workers in metalworking industries, were enrolled in this study. The FF were quantitatively measured before and after training related to the proper donning and use of cup or foldable-type respirators. The pass/fail criterion of FF was set at 100. After the donning training for the cup-type mask, subjects who passed the fit test were increased from 10 to 33. Moreover, the geometric mean (GM) of FF was increased by 340% in subjects who failed the test. In addition, the training effects for the cup-type mask were significant in female and 50s aged subjects. On the other hand, although the GM of FF for the foldable-type mask was also increased after the donning training, the GM of FF for the foldable-type mask and it's increase rate were smaller as compared to the cup-type mask. Furthermore, the differences of the increase rates of the GM of FF in sex and aged of the subjects were not significantly for the foldable-type mask. The multi-distribution of leak points for the foldable-type mask may be one of causes for the less effect of training on the fit of the foldable-type mask. These results imply that the raining on the donning and use of PFFR can enhance the protection effectiveness of cup or foldable-type mask, and that the training effects for the foldable-type mask is less significant than that for the cup-type mask. Therefore, It is recommended that the donning training and fit tests should be conducted before the use of the PFFR, and that efficient tranining programs for the foldable-type mask are required.

• Journal of the Korean Society of Safety
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• v.33 no.6
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• pp.28-36
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• 2018

There was a difference in recognition of respirators according to the educational performance environment. they were showed higher recognition of respirators of group by internal and external mix trainer, less than 6 months, over 1hour, more than 5 times, variety of education. To identify the relationship between types of job classification(typical and atypical)and the levels of recognition of respirators, a total of 153 workers in a business workplace. mainly, typical workers showed higher recognition of respirators than atypical workers. Training of correct wearing showed high demands both typical and atypical workers. Descriptive statistics(SAS ver 9.2)was performed. the results of recognition of respirators were analyzed the mean and standard deviation by t-test, and anova, fit factor is used geometric means(geometric standard deviation), paired t-test, Wilcoxon analysis(P=0.05). Particulate filtering facepiece respirators (PFFR) is one of the most widely used items of personal protective equipments, and a tight fit of the respirators on the wearers is critical for the protection effectiveness. In order to effectively protect the workers through the respirators, it is important to find and evaluate the ways that can be readily applicable at the workplace to improve the fit of the respirators. This study was designed to evaluate effects of mask style (cup or foldable type) and donning training on fit factors (FF) of the respirators, since these are available at various workplace, especially at small business workplace. A total of 40 study subjects, comprised of employment type workers in metalworking industries, were enrolled in this study. The FF were quantitatively measured before and after training related to the proper donning and use of cup or foldable-type respirators. The pass/fail criterion of FF was set at 100. After the donning training for the cup-type mask, fit test were increased by 769%. but foldable-type mask was also increased after the donning training, the GM of FF for the foldable-type mask and it's increase rate were smaller as compared to the cup-type mask. Furthermore, the differences of the increase rates of the GM of FF in employment type of the subjects were not significantly for the foldable-type mask. These results imply that the raining on the donning and use of PFFR can enhance the protection effectiveness of cup or foldable-type mask, and that the training effects for the foldable-type mask is less significant than that for the cup-type mask. Therefore, it is recommended that the donning training and fit tests should be conducted before the use of the PFFR, and listening to workers opinion regularly.

• Journal of the Korean Geosynthetics Society
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• v.8 no.4
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• pp.19-25
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• 2009

In this study, field pull-out tests were performed for steel pipe nailing installed foldable wedge and non-wedge type steel pipe nailing under the same test conditions. This is to evaluate pull-out resistance improvement effect of steel pipe nailing installed foldable wedge. Evaluating for field pull-out characteristics of steel pipe nailing installed foldable wedge was performed through analysis of ultimate pull-out resistance ($T_L$), ultimate unit skin friction ($q_s$, $u_{max}$), tensile normal stiffness ($K_{\beta}$), tension of nail. As a result, the steel pipe nailing installed foldable wedge have an effect of pull-out resistance increased about 30% in comparison with non-wedge type steel pipe nailing.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.6C
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• pp.313-319
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• 2009

In this study, field pull-out test and 3-D FEM analysis have been performed for examining and reflecting the behavior of steel pipe nailing installed foldable wedge. Field pull-out test was performed under various conditions. As a result, the steel pipe nailing installed foldable wedge has an effect of pull-out resistance increased about 30% in comparison with non-wedge type steel pipe nailing. Through back analysis in 3-D FEM for behavior of non-wedge type steel pipe nailing, friction characteristics between nail to soil was analyzed and obtained first consistent with field pull-out behavior. Then, the frictional characteristic was used for analyzing the behavior of the steel pipe nailing installed foldable wedge. The result was compared with the test results. Consequently, friction coefficient (${\mu}$) of about 1.2 between grout to soil leads to good agreement with analysis results and test results. And a limited pull-out resistance, $$T_L{\sim_=}32$$ tonf is similar to field pull-out test result which is improved about 33% in comparison with non-wedge type steel pipe nailing's $$T_L{\sim_=}24$$ tonf.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.2 s.179
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• pp.172-180
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• 2006

Although there existed many types of manual/power hybrid wheelchairs, their use was not widespread because of their inconvenience in converting drive system and in folding frames. To carry a wheelchair in the car or to convert driving methods, some hard work of disassembling or exchanging wheels was required for most of currently available hybrid wheelchairs. In this study, the standard foldable manual wheelchair was reformed to a power wheelchair by installing the newly developed Axial Flux Permanent Magnet(AFPM) type of brush less direct current(BLDC) motor on each rear hub of wheelchair. This wheelchair could be driven by manual or electric power without exchanging. wheels, thus no additional work was needed for carriage or for power conversion. The developed wheelchair was evaluated for durability, stability, maneuverability, cost, and reliability in accordance with the Korean standards. The results indicated that the developed hybrid wheelchair was good enough for commercialization comparing to other imported wheelchairs.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.29-29
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• 2008

Realization of electronics with performance equal to established technologies that use rigid semiconductor wafers, but in lightweight, foldable and stretchable formats would enable many new application possibilities. Examples include wearable systems for personal health monitoring, 'smart' surgical gloves with integrated electronics and electronic eye type imagers that incorporate focal plane arrays on hemispherical substrates. Circuits that use organic or certain classes of inorganic electronic materials on plastic or steel foil substrates can provide some degree of mechanical flexibility, but they cannot be folded or stretched. Also, with few exceptions such systems offer only modest electrical performance. In this talk, I will present a new approach to high performance, flexible and stretchable integrated circuits. These systems combine single-crystal silicon nanoribbons with thin plastic or elastomeric substrates using both "top-down" and "transfer-printing" technologies. The strategies represent promising routes to high performance, flexible and stretchable optoelectronic devices that can incorporate established, high performance inorganic electronic materials.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.57.3-58
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• 2016

We analyze an optical system of a telescope based on Fresnel type objective lens as suggested by Hyde (1999). The Fresnel objective lens can be thin, light-weight and foldable, and therefore it is possible to develop a space telescope with an aperture larger than that of traditional telescopes. Moreover a lens, whatever it is either Fresnel type or conventional, allows much larger fabrication tolerances. We design a medium-sized telescope adopting Fresnel lens as an objective lens for use in space and possibly on the ground. The well-known chromatic aberration of the Fresnel primary lens is corrected by a field lens and another Fresnel lens using Schupmann method. An additional lens is used for forming images. We analyze the chromatic and off-axis aberrations of the proposed system analytically and suggest methods for the minimization of off-axis aberrations and for the operation in wider spectral range. We also conduct ray tracing and optimize the whole optical system with commercial software. Finally we present the design parameters of a telescope with an aperture of 0.5 to 1 meters, enabling diffraction limited operation for a moderate field of view about 10 arc-minutes.

• Journal of Semiconductor Engineering
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• v.1 no.1
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• pp.38-45
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• 2020

With the recent emergence of foldable electronic devices, interest in flexible organic memory is significantly growing. There are three types of flexible organic memory that have been researched so far: floating-gate (FG) memory, ferroelectric field-effect-transistor (FeFET) memory, and resistive memory. Herein, performance parameters and operation mechanisms of each type of memory device are introduced, along with a brief summarization of recent research progress in flexible organic memory.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.7 s.184
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• pp.114-121
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• 2006

In this paper, the concept of design for environment (DFE) was introduced to mechanical design and manufacturing of cellular phone case. A new evaluation method integrated in existing product manufacturing process was developed and applied to two different types of cellular phone cases: foldable type and slider type. The evaluation results suggested that scores for 'refurbishments & recycle' criterion were relatively low for their cases. This evaluation method may assist designers to draw a checklist of the product's weak points from the perspective of DFE. From the checklist, the designers can consider possible improvements in future design.

• Korea Science and Art Forum
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• v.37 no.2
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• pp.219-230
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• 2019

According to the National Statistical Office, the number of senior citizens aged 65 or over has exceeded 7 million as of 2017, and the number of senior citizens who live alone among them exceeded 1.3 million. Most of the senior citizens who live alone suffer from absolute poverty (68.5% of them has monthly income less than 500,000 won) and they have difficulties for basic living in the blind spot of our society. In particular, the heating is quite a serious issue for the senior citizens who live alone and belong to vulnerable social group in the winter, and to make it worse, they are exposed to frequent fire accidents due to the negligence in handling electric appliances such as electric heaters and electric pads. The main reason the indoor tent products are being used by senior citizens who live alone is that it saves energy, ensures warm sleep, and improves fire safety. Following the expansion of the indoor tent market, this study focused on the idea that there is a need for an in door tent suitable for senior citizens who live alone and belong to low income bracket and intended to improve its efficiency in relation to use, resting, and storage. For this, a basic survey was conducted on the products of existing brands to analyze advantages and disadvantages and it was possible to understand the demands that consumers have for existing products. Accordingly, a survey on consumer preference was conducted using a designed model and the Zabara typp, which demonstrated the best efficiency in terms of installation convenience, space usability, and appearance design was selected. Based on the results of selection, the product design and final prototype were completed. The results and details of the study are as follows; First, factors that were not recognized in product development phase could be identified through usability survey and interview with actual users. Second, for the effective aspect of the prototype, senior citizens could install and fold the tend more easily and quickly than expected. Based on these results of this study, it is expected that not only senior citizens who live alone but also various other users can use the tent to create another comfortable private space indoors.