• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.6A
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• pp.506-514
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• 2009

To minimize energy consumption, most of MAC Protocols in WSNs exploit low duty cycling. Among those, RMAC [4] allows a node to transmit a data packet for multiple hops in a single duty cycle, which is made possible by exploiting a control frame named Pioneer (PION) in setting up the path. In this paper, we present a MAC Protocol called Hop Extended MAC (HE-MAC) that transmits the data packet for more multiple hops in a single duty cycle. It employs an EXP (Explorer) frame to set up the multiple hop transmission, which contains the information of the maximum hop that a packet can be transmitted. With the use of the information in EXP and an internal state of Ready to Receive (RTR), HEMAC extends the relay of the packet beyond the termination of the data period by two more hops compared to RMAC. Along with our proposed adaptive sleeping method, it also reduces power consumption and handles heavy traffic efficiently without experiencing packet inversion observed in RMAC. We analytically obtain the packet delivery latency in HE-MAC and evaluate the performance through ns-2 simulations. Compared to RMAC, HE-MAC achieves 14% less power consumption and 20% less packet delay on average for a random topology of 300 nodes.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2001.04a
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• pp.35-43
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• 2001

Flip chip assembly on organic substrates using ACAs have received much attentions due to many advantages such as easier processing, good electrical performance, lower cost, and low temperature processing compatible with organic substrates. ACAs are generally composed of epoxy polymer resin and small amount of conductive fillers (less than 10 wt.%). As a result, ACAs have almost the same CTE values as an epoxy material itself which are higher than conventional underfill materials which contains lots of fillers. Therefore, it is necessary to lower the CTE value of ACAs to obtain more reliable flip chip assembly on organic substrates using ACAs. To modify the ACA composite materials with some amount of conductive fillers, non-conductive fillers were incorporated into ACAs. In this paper, we investigated the effect of fillers on the thermo-mechanical properties of modified ACA composite materials and the reliability of flip chip assembly on organic substrates using modified ACA composite materials. Contact resistance changes were measured during reliability tests such as thermal cycling, high humidity and temperature, and high temperature at dry condition. It was observed that reliability results were significantly affected by CTEs of ACA materials especially at the thermal cycling test. Results showed that flip chip assembly using modified ACA composites with lower CTEs and higher modulus by loading non-conducting fillers exhibited better contact resistance behavior than conventional ACAs without non-conducting fillers. Microwave model and high-frequency measurement of the ACF flip-chip interconnection was investigated using a microwave network analysis. ACF flip chip interconnection has only below 0.1nH, and very stable up to 13 GHz. Over the 13 GHz, there was significant loss because of epoxy capacitance of ACF. However, the addition of $SiO_2filler$ to the ACF lowered the dielectric constant of the ACF materials resulting in an increase of resonance frequency up to 15 GHz. Our results indicate that the electrical performance of ACF combined with electroless Wi/Au bump interconnection is comparable to that of solder joint.

• Korean Institute of Interior Design Journal
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• v.26 no.6
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• pp.97-105
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• 2017

Korea is promoted STEAM education since 2011. Furthermore, in high school education, based on the in-depth elective course's teaching and learning contents of science. The STEAM program can improve students' competence because it encourages to self-directed learning through the vocational project performance. Therefore, in this study, we researched a design education program for the experience of fusion and complex design based on STEAM education concept. We developed an education program to design insulation wall systems using up-cycling concepts to increase energy efficiency. As a result, the characteristics of the fusion education and the theoretical study about the learner-centered education curriculum, the analysis of the high school curriculum, the STEAM elements, The program was revised and supplemented through consultation with STEAM experts. In addition, the developed program was applied to high school students, and each step were analyzed based on the educational method theory. The following results were obtained. First, this study presented a program to cope with the needs of high school intensive education. Second, it provided learning motivation by combining flipped-learning as a way to train STEAM education contents. Third, it is required to develop differentiated and continuous program development and data sharing Fourth, in order to operate and promote the future environment design STEAM school, it is necessary to expand educational programs for high school students in the region through linkage with various universities.

• Korean Chemical Engineering Research
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• v.51 no.5
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• pp.540-544
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• 2013

During start up and shut down of a proton exchange membrane fuel cells (PEMFC), the performance and lifetime of PEMFC were reduced. In this study, effect of startup and shutdown were investigated in dead-end type PEMFC using oxygen as a cathode gas with polarization curve, impedance spectroscopy (EIS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Dummy load which eliminates residual hydrogen and oxygen during startup and shutdown operation should be applied to mitigated the degradation of PEMFC performance. At 50% relative humidity (RH) under the repetitive on/off cycling, the cell performance decayed faster than at 100% RH because of corrosion of the cathode carbon support. Water suppling into cell reduced the degradation rate of dead-end type PEMFC during start up and shut down cycling at 50% RH.

• The Research Journal of the Costume Culture
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• v.26 no.6
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• pp.899-918
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• 2018

Upcycling is the process of repurposing abandoned resources or useless products into products of better quality or higher environmental value. Upcycling products are evaluated to be sustainable because they demonstrate environmental values. However, domestic upcycling companies are operating on a small scale with a slow growth rate. This study aims to examine the value and risk factors of upcycling products from previous literature and clarify the effect of these ambivalent characteristics on purchase intention. This provides direction regarding factors upcycling companies should focus on. The data were collected via an online experiment with women in their 20s and 30s residing in South Korea, nationwide. The data were statistically analyzed using SPSS 21.0 and AMOS 18.0. Analysis of this data suggests that environmental, design, and self-expression value positively affect purchase intention. This extends previous upcycling literature by identifying design and self-expression value as important antecedents of purchase intention. However, in contrast to previous literature, no significant effect of performance or diversity risk was found. These results indicate that ethical attitude has a moderating effect on the relationship between environmental value and purchase intention. This study confirms that consumers intend to purchase upcycling products when they possess not only environmental value but also design and self-expression value.

• Herbal Formula Science
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• v.30 no.4
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• pp.281-291
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• 2022

Objectives : In this study, acute oral toxicity test of pomace Schisandra chinensis extracts was conducted in order to up-cycling to a high value-added industry using by-products discarded in the production process of Schisandra chinensis products and active ingredients such as dibenzocyclooctadiene lignans in Schisandra chinensis. Methods : Pomace Schisandra chinensis extracts were orally administered to SD-rats(female, n=3) without a control group according to the 'OECD guidelines'. After, mortality and clinical signs were observed, and the deceased animals were subjected to an autopsy. In addition, acute oral toxicity test was sequentially performed in step I (300 mg/kg), step II(300 mg/kg), step III(2,000 mg/kg), and step IV(2,000 mg/kg) according to the mortality. Results : There were no abnormalities caused by pomace Schisandra chinensis extracts in step I and step II. However, one animal each died in step III and step IV. In addition, clinical signs(salivation, decrease in food intake, prone position, decrease of locomotor activity, loss of locomotor activity, convulsion, hypothermia, lacrimation, staining around mouth, soiled perineal region, reddish urine, chromaturia, decrease of fecal volume, lying on side, blackish stool, no stool, compound-colored stool, refusal to feed, excitement, hypersensitivity, rigidity, dorsal position, etc.) were observed. But, no clinical signs were observed from 5th day, and experiment animals recovered completely. Conclusions : As a result of this study, pomace Schisandra chinensis extracts may exhibit acute toxicity at concentrations of 2,000 to 5,000 mg/kg, and the GHS classification was designated as 'Category 5'.

• Journal of the Korea Fashion and Costume Design Association
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• v.25 no.2
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• pp.1-16
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• 2023

Due to the current seriousness of environmental pollution and the eco-friendly movement of the fashion industry, research on sustainable fashion design is being actively conducted. In this study, consumer perception of upcycling products, are divided into image, function, and meaning; and image is further divided into shape, color, and material. It was redefined as pattern, and image recognition was evaluated among men and women in their 20s and 30s, and men and women in their 40s and 50s used as subjects. First, factors that determine each image were extracted based on qualitative analysis of the precedent cases of upcycling bags, and quantitative analysis of the subjects was induced through a questionnaire. As a result of the analysis of evaluation items related to image association, the average frequency analysis of all subjects for each stimuli and the cognitive variance of the frequency analysis by generation by gender were found to be similar. However, awareness of some stimuli by generation showed a significant difference. Overall, in the three stimuli with high overall preference, common features, such as the basic box-shaped symmetrical structure, the monochromatic color of the Munsell system, solid and practical texture, and appropriate use of patterns were identified. In addition, it was confirmed that there was a difference with factors such as femininity, simplicity, touch, and splendor in the measurement factors. In conclusion, it is considered that the main significance of this study is that it excluded the recognition and meaning of upcycling products and explored the original design and image elements of products. Therefore, it is expected that this study will be used as a basic data for responding to the gender image of each generation as an alternative method of sustainable fashion design, and it will be an opportunity to expand the scope of the study to a detailed study beyond the biased topic.

• Herbal Formula Science
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• v.31 no.4
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• pp.327-339
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• 2023

Objectives : This study conducted a repeated dose 90-day oral toxicity test in order to up-cycling Schisandra fruit extract powder(SFEP) using discarded Schisandra chinensis by-products and evaluated the NOAEL of SFEP. Methods : SD-rats were orally administered SFEP at concentrations of 0, 62.5, 125, and 250 mg/kg once daily for 90 days. Body weights and clinical signs were observed during the administration period. After completion of the experiment, the experimental animals were autopsied to observe necropsy findings and organ weights changes, and hematological parameters and blood chemistry values were measured. Results : During the SFEP administration period, clinical signs such as salivation, wounds, and erosion were sporadically observed in 1 to 2 animals. In the SFEP 250 mg/kg administered group, weights of the liver and thyroid gland significantly increased compared to the control group, but no significant changes were observed in organ weights according to body weights. As a result of measuring hematological parameters and blood chemistry values, a decrease in RDW, T-BIL, and TBA, and an increase in TP, ALB, and Ca were observed due to SFEP administration. However, these changes following SFEP administration were accidental and not dose-dependent. Additionally, no correlation was found between gender and other parameters. Conclusions : Therefore, the NOAEL of SFEP was confirmed to be 250 mg/kg.

• Journal of Fashion Business
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• v.28 no.2
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• pp.125-138
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• 2024

The purpose of this study is to develop and implement a step-by-step upcycling fashion education program that can be utilized within the local community. This program aims to provide basic data by analyzing the current state of community-based upcycling projects and upcycling center programs. To achieve this, the study first examined the meaning and value of upcycling in fashion through literature research and explored upcycling projects and programs in connection with local communities. Subsequently, an upcycling fashion education program platform was developed and applied using the design thinking process. The program involved students from nine high schools in Gwangju Metropolitan City. Depending on the school's circumstances, the time and difficulty level of the upcycling education program were adjusted accordingly. A unique eco-bag making kit, using jeans developed in this study, was employed. Following the completion of the program, a satisfaction survey was conducted among 167 participating students from the high school community class. The findings indicated that the majority of students experienced an increased appreciation, attraction, and interest in upcycling products. They also demonstrated an understanding of the environmental impact of upcycling products and the distinction between upcycling and recycling. It is believed that the educational program developed in this study can promote ethical fashion and foster a sense of value-based consumption. This program can be customized and flexibly adapted to different educational levels and institutional characteristics, making it accessible to a wide range of learners.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.2
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• pp.37-45
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• 2008

In this study, reliabilities of Cu (60 um)/SnAg (20 um) double-bump flip chip assemblies were investigated for the flip chip interconnections on organic substrates with 100 um pitch. After multiple reflows at $250^{\circ}C\;and\;280^{\circ}C$, bump contact resistances were almost same regardless of number of reflows and reflow temperature. In the high temperature storage test, there was no bump contact resistance change at $125^{\circ}C$ up to 2000 hours. However, bump contact resistances slightly increased at $150^{\circ}C$ due to Kirkendall voids formation. In the electromigration test, Cu/SnAg double-bump flip chip assemblies showed no electromigration until about 600 hours due to reduced local current density. Finally, in the thermal cycling test, thermal cycling failure mainly occurred at Si chip/Cu column interface which was found out the highest stress concentration site in the finite element analysis. As a result, Al pad was displaced out under thermal cycling. This failure mode was caused by normal compressive strain acting Cu column bumps along perpendicular direction of a Si chip.