• Journal of Korea Foundry Society
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• v.38 no.5
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• pp.87-94
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• 2018

The effects of Sr and (Ti-B) additives on the tensile properties of AC4A recycled (35% scrap content) aluminum alloys were investigated. An acicular morphology of the eutectic Si phase of as-cast specimens was converted to a fibrous morphology upon the addition of Sr. Moreover, morphology of the Sr modified eutectic Si phase became finer due to a T6 heat treatment. The grain size of the ${\alpha}$-solid solution was decreased by the addition of (Ti-B) additives. Depending on the treatment conditions of the as-cast specimens, i.e., no addition, a Sr addition and a (Ti-B)+Sr addition, the tensile strength levels of the as-cast specimens were 182, 192, and 204MPa, respectively. The corresponding strengths of T6 heat-treated specimens were 293, 308, and 318MPa. Elongations of the as-cast specimens were 2.2, 3.1, and 5.6%, and the corresponding elongations of the T6 heat-treated specimens were 4.6, 6.1, and 7.6%. The percentage of the reduced section area in the tensile specimens was also increased by the Sr and (Ti-B) additives. Sr and (Ti-B) additives changed the microstructure and the distribution of defects in the castings, resulting in an improvement of the tensile properties of AC4A aluminum alloys. According to our test results, recycled (35% scrap content) AC4A aluminum alloy met all of the KS requirements of the tensile strength and elongation values of AC4A aluminum alloy except for the elongation value of the one specimen condition, in this case the as-cast no-addition condition.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.3
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• pp.170-177
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• 2006

Hydrogen can extend the lean misfire limit to a large extent when it is mixed with conventional fuels for a spark ignition engine. In this study, hydrogen-enriched gaseous fuels by reforming process were simulated according to their proportions of $H_2$, CO, $CO_2$ and $N_2$ gases. Pure hydrogen and two different hydrogen-enriched gaseous mixtures(A-, B-composition) were tested for their basic effects on the engine performances and emissions in a single cylinder research engine. A- and B-composition showed different results from 100% $H_2$ addition because air/fuel mixtures were more diluted by their additions. Even though the energy fraction of reformed gases was increased, combustion stabilities and lean misfire limits were not sensitively improved. It means that combustion augmentation by $H_2$ addition was offset by the charge dilution of $N_2$ and $CO_2$. In addition, the low flammability of CO gas deteriorated thermal efficiencies. CO emission was drastically increased with B-composition which included higher CO component. However, $NO_x$ was reduced as energy fraction($X_e$) rised except for the case of 100% $H_2$ addition at $\lambda=1.2$ and was, for A-composition, lowered to a factor of ten when compared with that of $H_2$ addition. HC emissions were largely influenced by $COV_{imep}$ due to misfire and partial burns.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.336-337
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• 2005

ZnO varistor ceramics were fabricated as a function of the amount of $Y_2O_3$ addition and sintered at $1250^{\circ}C$ for 2 hour. The average grain size was decreased from 14.2 ${\mu}m$ to 8.3 ${\mu}m$ with the amount of $Y_2O_3$ addition, and varistor voltage was increased from 433 V to 563 V with $Y_2O_3$ addition. Nonlinear coefficient a of all specimens were increased with the amount of $Y_2O_3$ more than 67, in case of $Y_2O_3$ 0.01wt% addition showed the excellent results of 87. And leakage current was less than $1{\mu}A$ at 82% of varistor voltage. The clamping voltage ratio of the specimens added 0.01wt% $Y_2O_3$ was 1.41 at 25A [8/20${\mu}s$]. At the specimen 0.01wt% $Y_2O_3$ addition. endurance of surge current and deviation of varistor voltage were 5700A/$cm^2$ and $\Delta$-2.86%, respectively.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.4
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• pp.103-107
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• 2008

Purpose: This research measured the near addition powers of presbyopia in wearing the near spectacle for the first time. Methods: We evaluated age, sex, working group, spherical power and cylindrical power and measured the power of refractive error performed the both eyes (310 eyes) of 155 subjects subjectively noncycloplegic and power of addition using the cross cylinder method. Results: There were measured the near addition powers in the range of +0.75D ~ +1.75D. In case of the average addition, they were measured with +1.06D in subjects under 43 years of age, +1.08D in 44 to 46 years, +1.23D in 47 to 49 years and +1.46D in over 50 years of age. The average age in subjects was 47.6 years old and 74 male, 81 female, 71 near sighted working group and 83 far sighted working group. Conclusions: Near addition was correlated with age, working group and cylindrical power (P<0.05, P<0.05, P<0.05).

• Journal of Aquaculture
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• v.9 no.4
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• pp.419-427
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• 1996

In order to obtain the basic information for seedling production of surf clam, Spisula sachalinensis, spawning induction and egg development were investigated. $NH_4OH$ addition and serotonin injection could induce the spawning in surf clam. Water temperature rising, sperm suspension immersion, UV-ray irradiated seawater and $H_2O_2$ addition less affected on induction of spawning than $NH_4OH$ and serotonin did. On the other hand, males were more sensitive to the treatments than females. The response time to initial spawning in the case of $NH_4OH$ addition was $3\~4$ hours. However in the case of serotonin injection, it was within 5 minutes. The number of eggs released by $NH_4OH$ addition were significantly more than those released by serotonin injection. The serotonin injection induced higher rates of germinal vesicle breakdown than the $NH_4OH$ addition. Fertilizing and hatching rates of the eggs also were the similar results. Eggs of surf clam were demersal isolated eggs and averaging $65.2{\pm}±1.8\;{\mu}m$ in diameter after spawning. Optimum range of water temperature for the development of egg was $15\~20^{\circ}C$, The required time for development of D-shaped larvae was 42 hours at $15^{\circ}C$ and 27 hours at $20^{\circ}C$, respectively.

• Architectural research
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• v.9 no.1
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• pp.1-8
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• 2007

These days the copyright plays a significant role in various fields of creative works and it has expanded dramatically into unprecedented ways. In Korea, architectural works copyright cases are rare due to the lack of information and understanding of the architectural works copyright. Architectural works copyright can promote architects' creative activities and enhance the quality of architectural works as art. Nevertheless, there is little effort to advance the studies of architectural works copyright in the architectural design area. Under these circumstances, this research attempts to share the basic case laws and remedies for various architectural works copyright issues in the U.S. cases. This Article examines the Thomas Shine v. David M. Childs and Skidmore Owings & Merrill, LLP Case which is the most recent case as I could reach. This case is about a story between two architects, one is from a very prestigious architectural design firm and the other, once Yale Architectural student, now practices his design work as an up-and-coming architect. A close examination of this case will provide a legal and architectural spectrum of copyright. That is, it will make it more specific how to solve the copyright infringement. Artistic and technological contexts are overlapped in Architectural works copyright as its inherent characteristics. Therefore, different ways from other copyrighted works are needed to access the untangled equations of the architectural works copyright protection. In addition, more comprehensible and specific regulations that can impose a remedy more suited to the architectural works copyright violations are needed and they should enable architects to fulfill their architectural activities under wide range of copyright protection. Moreover, in prior to all efforts to handle those equations, fundamental knowledge of architectural works copyright is required to improve the copyright protection in the architectural design area as well as to provide for the globalizing design practice. Ultimately, all of these efforts will be rewarded when constant researches based on Korean and other countries' architectural copyright cases can support them and it would be great if this research can set the stage for resolving expected copyright conflicts within the architectural design area.

• Journal of the Korea Convergence Society
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• v.11 no.10
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• pp.225-229
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• 2020

In this study, the deformation and stress on each model was analyzed and the strength was compared with each other when the impacts on a total of four smart phone models was given. Models B and D with cases can be seen to have less deformation and stress than models A and C without cases. The models including the case have higher masses than the models without the case. So, the deformation and stress can be reduced by absorbing the impact force. In addition, the masses of models C and D are smaller than models A and B, but the stresses and deformations are seen to be smaller. If a case specialized for edge protection is chosen and designed when manufacturing a smart-phone in order to absorb the shock while weighing less, it is thought to improve the strength of the smart-phone and increase the durability. And it is seen that this study is adequate at the efficient design with durability of smart phone case practically and the aesthetic convergence of smart phone.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.5
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• pp.1861-1885
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• 2020

Test Case Prioritization (TCP) involves the rearrangement of test cases on a prioritized basis for various services. This research work focuses on TCP in web services, as it has been a growing challenge for researchers. Web services continuously evolve and hence require reforming and re-execution of test cases to ensure the accurate working of web services. This study aims to investigate gaps, issues, and existing solutions related to test case prioritization. This study examines research publications within popular selected databases. We perform a meticulous screening of research publications and selected 65 papers through which to answer the proposed research questions. The results show that criteria-based test case prioritization techniques are reported mainly in 41 primary studies. Test case prioritization models, frameworks, and related algorithms are also reported in primary studies. In addition, there are eight issues related to TCP techniques. Among these eight issues, optimization and high effectiveness are most discussed within primary studies. This systematic review has identified that a significant proportion of primary studies are not involved in the use of statistical methods in measuring or comparing the effectiveness of TCP techniques. However, a large number of primary studies use 'Average Percentage of Faults Detected' (APFD) or extended APFD metrics to compute the performance of techniques for web services.

• Journal of the Korean Institute of Landscape Architecture
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• v.35 no.6
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• pp.21-28
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• 2008

This study deals with the participatory design process of renovating a children's park. The process should proceed with two major elements. Firstly, the children's park should be designed from the perspective of children. Secondly, it should be designed in consideration of the context of the community. This study is divided into two parts. First is the review of theory concerning the meaning and roles of the children's park as a community space, the importance of children's participation in the design and the participatory method of the children. The second is the case study. The site for the case study is Ssial Park in Nowon-Gu, Seoul. The entire process of the case study is with community participation, from identifying the park's problems to the actual construction. At every step, through the participatory programs, the community participates in the decision making. In addition, mutual understanding among participants is pursued through diverse means of communication. The following results of the case study were found. Firstly, diverse participatory programs and the active trial to enable the community to communicate contribute to the sense of ownership and responsibility concerning the park Secondly, the community can negotiate the differences in opinions without needing the help of experts. Of course, there are limits in the case study, such as the fact that the community organization, which is the core of communication and maintenance concerning the park, is not organized through the process of a case study. Another is that more diverse methods, which inform all community members of the participatory process, should have been used.

• The Journal of Korean Association of Computer Education
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• v.14 no.5
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• pp.19-28
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• 2011

The purpose of the study is to investigate the effects of multimedia case-based learning on preservice teachers' critical thinking disposition and practices. Forty-nine students among the seventy-five preservice teachers who enrolled in the class, Introduction to Special Education, participated in this study. Pretest and a case were presented at the beginning of the semester and then 4 cases and multimedia learning resources were provided during 13 weeks. In addition, small and whole class discussion were used for learning activities to share their opinions. At the end of the semester, the posttest and practices regarding a new case data were collected. Results found that no significant difference in the critical thinking disposition survey, however, the multimedia group showed better practices in a new case than the control group. Suggestions and future research were discussed.