• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.12
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• pp.1771-1776
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• 2013

Most cases of power transformer failure are caused by physical factors linked to the transient vibrations of multiple 120Hz combinations. In addition, the noise generated in the transformer from this vibration not only directly contributes to the worsening of the work environment but also causes psychological stress, resulting in the worsening of the workers efficiency and of the living environment of the inhabitants around the power plant. Thus, to remedy these problems, the mechanical-excitation forces working on a power transformer were categorized in this study, and the mechanical-damage mechanism was identified through the vibration transfer paths acting on machines or structures. In addition, a study on active noise cancellation in a transformer using the FXLMS algorithm was conducted to develop a system that is capable of multiple-sound/channel control, which resulted in the active noise reduction effect when applied on the field.

• Journal of Korea Foundry Society
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• v.20 no.3
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• pp.167-172
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• 2000

Squeeze casting was performed to fabricate the SiC whisker reinforced magnesium matrix composites, and the suitability of the squeeze casting for the production of the sound composites was determined by micro/macro-structures observations and tensile test. The two-directional infiltration of the melt and the removal of air during infiltration using the devised mold were necessary to produce the composites. The pressure of 100 MPa was effective for the production of composites with the SiC whisker volume fraction of 30%, but the pressure should be lower than 50 MPa in case of below 20% in the volume fraction. The SiC whiskers in the squeeze cast composites were randomly and densely aligned, and the SiC whiskers/magnesium interfaces were continuously well-bonded. The elastic modulus, 0.2% proof stress and tensile strength in the composite were about 2.5times, l0times and 4times as large as those of magnesium, respectively, indicating that the squeeze casting sufficiently provides the high strength magnesium composites reinforced with SiC whiskers.

• Proceedings of the KSPS conference
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• 2000.07a
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• pp.47-58
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• 2000

For the learners of English as a foreign language, oral repetition of model sentences is an e essential practice to improve their listening and speaking abilities of English. Skill training of both speech perception and production is involved in this practice. This paper reports on an observation of production e$\pi$ors in such practice made by Japanese college students in my class. The teaching material used is intended for acquainting the learners with basic English rhythm and intonation p patterns. The students were required to repeat each sentence in a series of conversations after a model reading. Although the vocabulary and expressions were rather limited, I monitored different kinds of errors in their repetition. Putting aside intonation, their difficulties are classified into five types; 1. Omission of words or morphemes, 2. Addition of unnecessary words or morphemes, 3. Replacement of words, 4. Japanization of English sounds, 5. Wrong rhythm caused by improper stress assignment. Accurate listening, especially to weakly stressed syllables and to assimilated sounds, as has often been pointed out, is the most difficult part in perception for them. Japanese sound system interferes in production of English sounds. More often than not their knowledge of grammar or the context does not work at all to guess the words they are hearing

• Journal of the Korean Society for Precision Engineering
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• v.24 no.4 s.193
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• pp.102-108
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• 2007

The characteristic properties of aluminum, high strength stiffness to weight ratio, good formability, good corrosion resistence, and recycling potential make it the ideal candidate to replace heavier materials in the car to respond to the weight reduction demand within the automotive industry. In this paper, FE simulation was carried out to design an appropriate extrusion die for the automobile control arm. Based on the FE simulation result, a new die design has been proposed for uniform material flow in the cross section of extruded product. And then the welding pressure, extrusion load, and the tendency of mandrel deflection were estimated to verify high quality. In the extrusion experiment, it was possible to produce sound product without defects.

• Journal of Soil and Groundwater Environment
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• v.20 no.3
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• pp.51-64
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• 2015

In the present study, we develop two history matching techniques based on Markov chain Monte Carlo method where radial basis function and Gaussian distribution generated by unconditional geostatistical simulation are employed as the random walk transition kernels. The Bayesian inverse methods for aquifer characterization as the developed models can be effectively applied to the condition even when the targeted information such as hydraulic conductivity is absent and there are transient hydraulic head records due to imposed stress at observation wells. The model which uses unconditional simulation as random walk transition kernel has advantage in that spatial statistics can be directly associated with the predictions. The model using radial basis function network shares the same advantages as the model with unconditional simulation, yet the radial basis function network based the model does not require external geostatistical techniques. Also, by employing radial basis function as transition kernel, multi-scale nested structures can be rigorously addressed. In the validations of the developed models, the overall predictabilities of both models are sound by showing high correlation coefficient between the reference and the predicted. In terms of the model performance, the model with radial basis function network has higher error reduction rate and computational efficiency than with unconditional geostatistical simulation.

• Korean Journal of Health Education and Promotion
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• v.2 no.1
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• pp.79-95
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• 2000

The objective of this study is to stress the importance of sexuality education at school, to define its goals and to discuss ways on how to reinvigorate sexuality education. The negative conditions for adolescent sexual issues are now being expanded into all areas of Korean society. In particular, they should be regarded as one of serious social issues because of their adverse influences on adolescent groups. Various reports on juvenile sexual delinquencies have expressed serious concern over reckless and impulsive juvenile sexual deviations because they are closely related to the confusion of the youth in their sexual values and their common sexual deviations. Thus, for the youth who have attracted serious public concern, it is most important to have sound sexual awareness and attitude for the development of their healthy personality. In general, sexuality education should be conducted under individual responsibility of various levels of schools, families and communities. However, the role of schools where sexuality education should be conducted with concrete goals, that is, to interpret physical and psychological developments of youth in terms of education and teach them on the systematic goals of sexuality education, this role of schools is the most important than anything else in conducting sexuality education for youth.

• Korean Journal of Materials Research
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• v.13 no.4
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• pp.213-218
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• 2003

Fibrous monolithic control of$ Al_2$$O_3$ -$ZrO_2$composite was investigated by multi-pass extrusion process. To obtain sound $Al_2$$O_3$-X $O_2$sintered bodies, burning out and sintering process were carefully carried out. The sintered bodies showed continuous, fibrous monolithic microstructure without any swelling. Many microcracks were observed at the $Al_2$$O_3$-$ZrO_2$interfaces due to the mismatching of thermal expansion coefficient between $Al_2$$O_3$ and $ZrO_2$phase. Most of m- $ZrO_2$grains included twin defects such as (001), (010) and (011) type to accommodate the phase transformation induced stress.

• Proceedings of the Korea Information Processing Society Conference
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• 2016.04a
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• pp.620-623
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• 2016

열차의 진로를 제어하는 선로전환기는 열차의 안정적인 주행에 있어서 매우 중요한 시설이다. 본 논문에서는 선로전환기의 작동 시 발생하는 소리 정보를 이용하여 선로전환기의 스트레스를 탐지하는 시스템을 제안한다. 먼저 제안하는 시스템은 선로전환기에 스트레스가 쌓인 상태의 소리 정보와 스트레스가 제거된 소리 정보를 수집한 후, 다양한 소리특징들을 추출한다. 추출된 특징들로 부터 t-test를 이용하여 유의성이 확보된 소리 특징 파마미터만을 최종 특징벡터로 선택한다. 마지막으로, 소리 특징 벡터를 입력으로 하는 이진 분류기인 SVM(Support Vector Machine)을 이용하여, 선로전환기의 스트레스 상태 여부를 실시간으로 탐지한다. 실제 테스트용 선로전환기에서 취득한 소리 정보 데이터 셋을 이용하여 본 논문에서 제안하는 시스템의 성능을 실험적으로 검증한다.

• Journal of Digital Convergence
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• v.10 no.7
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• pp.245-251
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• 2012

The significance of this study lies in the fact that it looks into the function of games as one of the important leisure activities at the moment when negative perception on overall game industry is becoming an obstacle in settlement of sound game culture. Game is one of the activities enjoyed in leisure time. The main positive effects of game were analyzed classifying them into 10 types including the stress relief and alleviation of tension, diverse identity experience and positive socialization experience, strengthening of self-respect and ideal self-realization, strengthening of independent thinking and problem-solving capacity, motivation for learning, enhancement in physical capacity, decrease in aggressive tendencies, cultivation of awareness on equality, increase in familiarity with the civilization of technology, and strengthening of individuality based on diversity.

• Nuclear Engineering and Technology
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• v.40 no.3
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• pp.233-238
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• 2008

This study investigates the surface modification of a Hastelloy X plate and diffusion bonding in the assembly of surface modified plates. These types of plates are involved in the key processes in the fabrication of a process heat exchanger (PHE) for a $SO_3$ decomposer. Strong adhesion of a SiC film deposited onto Hastelloy X can be achieved by a thin SiC film deposition and a subsequent N ion beam bombardment followed by an additional deposition of a thicker film that prevents the Hastelloy X surface from becoming exposed to a corrosive environment through the pores. This process not only produces higher corrosion resistance as proved by electrolytic etching but also exhibits higher endurance against thermal stress above 9$900^{\circ}C$. A process for a good bonding between Hastelloy X sheets, which is essential for a good heat exchanger, was developed by diffusion bonding. The diffusion bonding was done by mechanically clamping the sheets under a heat treatment at $900^{\circ}C$. When the clamping jig consisted of materials with a thermal expansion coefficient that was equal to or less than that of the Hastelloy X, sound bonding was achieved.