• Journal of Korean Society of Environmental Engineers
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• v.33 no.4
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• pp.258-266
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• 2011

Scale induced by hardness materials in water must be controled because of it can be result in remarkable damages of pipeline as well as water quality deterioration. Especially hot water system is one of scale management required facility as scale formation can be accelerated by temperature. The scale control performance of frequency driver (FD) was tested instead of existing methods such as chemical, physical and electromagnetic methods which needs chemicals and electric power. Three kinds of pipe coupons were submerged in test water with 500 mg/L of hardness for 33 days and XRD and SEM were analysed for comparing scale formation characteristics of these coupons. Calcite ($CaCO_3$) which came from hardness of water was formed on only cast iron pipe coupon and this coupon showed higher corrosion rate than copper and stainless steel pipe coupon. Hot water circulating system connected cast iron pipe with and without FD was operated with 300 mg/L of hardness water at $50^{\circ}C$ for monitoring of scale formation and water quality with and without FD. XRD showed that FD leaded to magnetite ($Fe_3O_4$) scale which is good scale for preventing corrosion than calcite and SEM image also indicated the scale control effect of FD. Scales of 16% on pipe joint, 14% on pipe length, and 42% on heat exchanger decreased with FD comparing scales of those parts without FD. From the results of water quality, FD reduced crystallization of hardness material without chemical reaction in water and it can indicate that FD is safe and proenvironmental technology for scale reduction.

• The Research Journal of the Costume Culture
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• v.20 no.2
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• pp.169-183
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• 2012

This study was aimed at finding out the preferences and satisfaction levels regarding the type of fashion retailer's sales promotion based on consumers' empirical characteristics. A total of 223 questionnaires were used for the survey of this study. The methods of this study were descriptive analysis, factor analysis, reliability tests, one-way ANOVA, $t$-tests and ${\chi}^2$-test. The consumer groups were divided by habitual experience and self-evaluated knowledge relate to apparel product. The results of this study showed that consumers have different preferences and post-utilization satisfaction regarding the type of sales promotion offered by fashion retailers. Consumers with more experiences in apparel product and with higher self-evaluated knowledge were more active in utilizing the benefits offered through the value-added type of sales promotions, such as the gift certificate or coupon. Consumers with more experience in apparel product also showed higher satisfaction with both the utilitarian and hedonic types of sales promotions, such as gift certificate offer, special price, price discount event, and coupon or courtesy card offer. Furthermore, consumers with higher self-evaluated knowledge showed higher satisfaction with the utilitarian types of sales promotion, such as gift certificate offer and regular sale. Therefore, by identifying the accurate understanding of consumers'empirical characteristics, an enterprise might be able to satisfy consumer by offering more appropriate and subdivided types of sales promotion.

• Journal of Mechanical Science and Technology
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• v.16 no.3
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• pp.292-301
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• 2002

Ultrasound waves interact strongly with the orientation and sequence of the plies in a layup when propagating in the thickness direction of composite laminates. Also the layup orientation greatly influences its properties in a composite laminate. If the layup orientation of a ply is misaligned, it could result in the part being rejected and discarded. Now, most researchers cut a small coupon from the waste edge and use a microscope to optically verify the ply sequences on important parts. This may add a substantial cost to the production since the test is both labor intensive and performed after the part is cured. A nondestructive technique would be very beneficial, which could be used to test the part after curing and requires less time than the optical test. Therefore we have developed, reduced, and implemented a novel ply-by-ply vector decomposition model for composite laminates fabricated from unidirectional plies. This model decomposes the transmission of a linearly polarized ultrasound wave into orthogonal components through each ply of a laminate. High probability is found, by comparisons between the model and tests, in characterizing cured layups of the laminates by using the proposed method.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.401-406
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• 2001

When propagating the thickness direction of composite laminates ultrasound waves interacts strongly with the orientation and sequence of the plies in a layup. Also the layup orientation greatly influences its properties in a composite laminate. If one ply of the layup orientation is misaligned, it could result in the part being rejected and discarded. Now, most researchers cut a small coupon from the waste edge and use a microscope to optically verify the ply sequences on important parts. Those may add a substantial cost to the product since the test is both labor hard and performed after the part is cured. A nondestructive technique would be very beneficial, which could be used to test the part after curing and require less time than the optical test. Therefore we have developed, reduced, and implemented a novel ply-by-ply vector decomposition model for composite lam mates fabricated from unidirectional plies. This model decomposes the transmission of a linearly polarized ultrasound wave into orthogonal components through each ply of a laminate. It is found that a high probability shows between the model and tests developed in characterizing cured layups of the laminates.

• Journal of Korean Society for Atmospheric Environment
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• v.17 no.1
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• pp.75-84
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• 2001

Hot gas filtration method via using ceramic filters is an evolving technology applicable to numerous industrial and air pollution control processes. Alumino silicate, organic and inorganic binders were the major raw materials in manufacturing ceramic filters. In this work, disc type ceramic filters(50$\phi$$\times$10t) were manufactured by vacuum forming processes using ceramic raw materials. The porosity and bulk density of disc type ceramic filers ranged from 86 to 89% and from 0.27 to 0.36 g/㎤, respectively. In this work disc type ceramic medium were tested utilizing coupon experimental apparatus. Disc type filters showed high collection efficiencies over 99.96% with Darchs law coefficients of 4.1$\times$10(sup)10~9.63$\times$10(sup)10/$m^2$ depending on mean pore sizes. In addition, filtration and detachment of ceramic filters turned out to be performed effectively using 10 cm/sec face velocity, 5 minutes filtration cycle, 100msec pulse jet valve opening time and 3 bar pulsing pressure.

• Computational Structural Engineering
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• v.9 no.4
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• pp.15-26
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• 1996

항공기용 복합재료는 여전히 많은 응용의 여지를 갖고 있으나 또한 시급히 해결하여야 할 많은 기술적인 문제점을 갖고 있다. 즉 복합재료 항공기용 구조물은 반드시 인증 절차를 밟아야 실제 항공기에 장착/판매될 수 있는데 수치해석 기법에 의한 구조해석을 거친 기본/상세 설계과정과 성형 제작된 실물 구조물에 대해 가혹환경 조건하(95% 상대습도, 70.deg. C 온도에서 30일간의 방치)에서 설계에서 제시한 최대 하중의 150%를 견디어야 하는 까다로운 full-scale testing 및 각종 복합재료관련 coupon test(표 7 참조)들을 수행하여야 한다. 이와 같은 기술적인 문제점들은 향후 연구결과에 따라 충분히 극복할 수 있으나 이와 더불어 현재 각각의 항공기 제작사가 보유하고 있는 material specification, design manual, process standard 등의 규격이 전세계적으로 통일될 수 있는 제도적인 보완이 뒷받침 된다면 복합재료의 응용도 훨씬 앞당겨질 수 있을 것으로 예상된다.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.38-42
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• 2002

An apparatus was developed to repetitively apply a $-196^{\circ}C$ thermal load to coupon-sized mechanical test specimens. Using this device, IM7/5250-4 (carbon / bismaleimide) cross-ply and quasi-isotropic laminates were submerged in liquid nitrogen ($LN_2$) 400 times. Ply-by-ply micro-crack density, laminate modulus, and laminate strength were measured as a function of thermal cycles. Quasi-isotropic samples of IM7/977-3 (carbon / epoxy) composite were also manually cycled between liquid nitrogen and an oven set at $120^{\circ}C$ for 130 cycles to determine whether including elevated temperature in the thermal cycle significantly altered the degree or location of micro-cracking. In response to thermal cycling, both materials micro-cracked extensively in the surface plies fellowed by sparse cracking of the inner plies. The tensile modulus of the IM7/5250-4 specimens was unaffected by thermal cycling, but the tensile strength of two of the lay-ups decreased by as much as 8.5%.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.151-155
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• 2003

An apparatus was developed to repetitively apply a -196 $^{\circ}C$ thermal load to coupon-sized mechanical test specimens. Using this device, IM7/5250-4 (carbon / bismaleimide) cross-ply and quasi-isotropic laminates were submerged in liquid nitrogen (L$N_2$) 400 times. Ply-by-Ply micro-crack density, laminate modulus, and laminate strength were measured as a function of thermal cycles. Quasi-isotropic samples of IM7/977-3 (carbon / epoxy) composite were also manually cycled between liquid nitrogen and an oven set at 120 $^{\circ}C$ for 130 cycles to determine whether including elevated temperature in the thermal cycle significantly altered the degree or location of micro-cracking. In response to thermal cycling, both materials micro-cracked extensively in the surface plies followed by sparse cracking of the inner plies. The tensile modulus of the IM7/5250-4 specimens was unaffected by thermal cycling, but the tensile strength of two of the lay-ups decreased by as much as 8.5 %.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.3
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• pp.15-21
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• 2009

The anisotropic mechanical properties were measured for the three orthogonal orientations of plain weave glass fabric reinforced epoxy resin laminate. In tensile and flexural tests, axial and edge type specimens failed by pull-out of warp and fill yarns, respectively. In contrast, the thickness type specimens failed by adhesive failure process. Longitudinal cracking occurred in several of the edge type specimens during tensile test. That cracking caused pop-in in the stress-strain curve. Defects induced by improper coupon machining caused that cracking.

• Structural Engineering and Mechanics
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• v.10 no.5
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• pp.505-516
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• 2000

This paper is a presentation of an experimental study about the elastic-partly plastic behavior of rectangular hollow steel pinned struts subjected to static cyclic axial loading and the evaluation of the compressive strength of retrofitted crooked struts. Retrofitting is achieved by welding stiffening plates along the webs of damaged struts. The material follows a quasi-kinematic hardening hysteresis path as observed from coupon tests. Test results are compared to those of an analytical model showing a good agreement for both standard and retrofitted struts. The comparison of different stiffener plate dimensions shows that more efficient strengthening is achieved by using long thin stiffeners rather than short thick ones.