Microstructure‑Strengthening Interrelationship of an Ultrasonically Treated Hypereutectic Al–Si (A390) Alloy

Soo‑Bae Kim,Young‑Hee Cho,Jae‑Gil Jung,Woon‑Ha Yoon,Young‑Kook Lee,Jung‑Moo Lee 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.6

Ultrasonic melt treatment (UST) was applied to an A390 hypereutectic Al–Si alloy in a temperature range of 750–800 °Cand its influence on the solidification structure and the consequent increase in strength was investigated. UST at such a hightemperature, which is about 100 °C above the liquidus temperature, had little effect on the grain refinement but enhanced thehomogeneity of the microstructure with the uniform distribution of constituent phases (e.g. primary Si, α-Al and intermetallics)significantly refined. With the microstructural homogeneity, quantitative analysis confirmed that UST was found tosuppress the formation of Cu-bearing phases, i.e., Q-Al5Cu2Mg8Si6, Al2Cuphases that form in the final stage of solidificationwhile notably increasing the average Cu contents in the matrix from 1.29 to 2.06 wt%. A tensile test exhibits an increasein the yield strength of the as-cast alloy from 185 to 208 MPa, which is mainly associated with the solute increment withinthe matrix. The important role of UST in the microstructure evolution during solidification is discussed and the mechanismcovering the microstructure-strengthening interrelationship of the ultrasonically treated A390 alloy is proposed.

Effect of Ultrasonic Melt Treatment on Solidification Microstructure of Al–5Ti–1B Alloy Containing Numerous Inoculant Particles

Soo‑Bae Kim,Jae‑Gil Jung,Young‑Hee Cho,Su‑Hyeon Kim,Kwangjun Euh,Jung‑Moo Lee 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.7

The effect of ultrasonic melt treatment (UST) on the solidification microstructure of an Al–5Ti–1B alloy containing highvolumefractions of Al3Tiand TiB2particles is investigated for various UST times with different melt holding times. Theas-cast Al–5Ti–1B alloy is composed of TiB2and polygonal Al3Tiparticles (present prior to UST), plate-like Al3Tiparticles,and Al grains (formed during UST and/or solidification). The UST causes a size reduction and homogeneous distributionof the TiB2-agglomerated region containing many submicron-sized TiB2particles pushed to the grain boundaries. The USTslightly decreases the size and improves the distribution of polygonal Al3Tiparticles enriched in the TiB2-agglomeratedregion. Unlike the TiB2and polygonal Al3Tiparticles, which exhibit a minor refining effect, the plate-like Al3Tiparticlesshow a significant refinement with UST application. The UST has a significant effect on the size distribution of Al grains byinducing the formation of medium-sized grains at the expense of small and large grains; however, it only has a slight effecton grain refinement. The degree of microstructure modification increases with increasing UST time but decreases with meltholding time after UST. The mechanisms for the refinement and dispersion of the TiB2and Al3Tiparticles and Al grains arediscussed considering fragmentation, nucleation, and growth behaviors induced by the UST and subsequent solidification.

점토굴착 사면의 거동에 관한 원심모형실험 및 수치해석

최민수,정길수,박병수,유남재 강원대학교 산업기술연구소 2005 産業技術硏究 Vol.25 No.B

This paper is the results of experimental and numerical works on analyzing the geotechnical engineering behavior and characteristics of excavated clay slope formed by the method of excavated replacement which is one of treatments in soft soil ground. For the centrifuge model tests, models of excavated clay slope were prepared by remolding the marine clayey soil sampled from the field. Tests were performed with changing the slope to investigate the behavior of them. On the other hand, numerical analyses were carried out to analyze the change of safety factor against instability of slope with time. Changes of pore water pressure, shear strength and displacement were also investigated. As results of centrifuge model tests with slopes of 1:1.5 and 1:3 using the confining body of simulating the effect of excavation, for the case of 1:1.5, slope failure occurred right after remove the confining body whereas relatively small displacements within the range of 3.2mm, implying to maintain the stability of slope, were observed for the case of 1:3 slope. From the results of numerical analyses using the software of PLAXIS to investigate the stability of slope after excavation, the minimum safety factor against slope failure was 1.28 for the case of 1:3 slope. The further researches in the future are required with considerations of build up of static pore water pressures during acceleration of centrifuge, depth of excavation influencing the behavior of the slope and permeability of the slope since excavation of the slope was not simulated well resulted from the limitations of apparatus at the stage of excavation during the centrifuge tests.

모래다짐말뚝과 널말뚝으로 처리된 연약점토지반의 거동

유남재,정길수,박병수,김경수 강원대학교 산업기술연구소 2006 産業技術硏究 Vol.26 No.B

Centrifuge model experiments were performed to investigate the confining effects of the sheet piles, installed to the sides of soft clay ground treated with sand compaction piles, on the bearing capacity and concentration ratio of composite ground. For the given g-level in the centrifuge model tests, replacement ratio of SCP and the width of surcharge loads on the surface of ground with SCP, the confining effects of installing the sheet piles on the edges of SCP ground on the bearing capacity, change of stress concentration ratio and failure mechanism were investigated. Kaolin, one of typical clay mineral, and Jumunjin standard sand were used as a soft clay ground and sand compaction pile irrespectively. As results of experiments, lateral confining effect by inserting the model sheet piles fixed to the loading plate was observed. For the strip surcharge loading condition, the yielding stress intensity in the form of the strip surcharge loads tends to increase with increasing the embedded depth of sheet piles. The stress concentration ratio was found not to be influenced consistently with the embedded depth of sheet piles whereas the effect of stress intensity on stress concentration ratio shows the general trend that values of stress concentration ratio are relatively high at the initial stage of loading and tend to decrease and converge to the certain values. For the failure mechanism in the case of reinforced with sheet piles, displacement behavior related to the punching failure, settlement right beneath the loading plate occurred since the soil was confined with sheet piles, was observed.

계약에 대한 8세기 예언자들의 침묵 : 아모스 호세아를 중심으로

서길원 목원대학교 신학연구소 1997 신학과 현장 Vol.7 No.-

아모스나 호세아는 ‘계약’이나 ‘율법’에 관하여 침묵한다. 그들이 이스라엘의 파멸을 선포한 것은 계약의 파괴 때문이 아니고, 이스라엘이 야훼의 구원행위를 잊어버리고 진실하게 사랑하지 못했기 때문이다. 예언자들은 야훼와 이스라엘의 관계를 법적인 계약관계로 보지 않고 ‘역동적인 사랑의 관계’로 파악했다. 이와 같은 예언자 운동이 있은 후에 깨어진 야훼와의 관계를 회복하고 재정립하기 위해서 야훼와 이스라엘의 관계를 법적인 계약의 관계로 이해하고 이 계약을 유지하기 위해 이스라엘 백성들이 지켜야 할 기본적인 지시와 규정이 정리되어 율법서가 되었다. 이런 면에서 예언자들은 고대 계약이나 율법 전통에 서서 그것을 해석한 사람들이 아니고 도리어 깨어진 관계를 회복하고 새롭게 긍정적인 관계로 나아가도록 길을 열어준 자들 즉 6-7세기에 등장한 계약 및 율법사상이 있게 한 자들이다. 계약사상의 출현은 8세기 예언자들의 멸망선언 이후, 이들의 예언이 적중되어갈 무렵, 즉 이스라엘의 야훼신앙이 완전한 위기에 처하게 되었을 때 새로운 가능성과 희망을 위해 나타났다. 국가 멸망에 처한 이스라엘은 절망하거나 야훼를 원망하거나 포기하지 않고 새로운 가능성을 모색하였는데 그것이 바로 계약신학이다. 이로써 이스라엘은 예언자들에게 정당성을 부여하고 또 자신들은 새로운 가능성을 갖게 된 것이다. 이처럼 계약 신학의 발견은 위기극복을 위한 야훼 하나님의 또 한번의 은총의 사건이었고 8세기 예언자들은 이 은총이 나타나도록 길을 열어 준 사람들이다.

대학생들의 식이행동 양상 및 식습관에 관한 연구 : 경주대학교 재학생을 중심으로 Focused on Kyongju University Students

최수근,전병길 경주대학교 창의력개발연구소 2000 創意力開發硏究 Vol.- No.4

University students are likely to be price sensitive in terms of consuming foods. furthermore, they tend to experience irregular meal time, overeating, excessive drinking and smoking. These undesirable habits might be able to lead to nutrition imbalance. In this regard, the authors intend to identify the food consuming style and habits of Kyongju university students. 225 questionnaires were distributed to the students and 199 out of the total (88.4% response rate) wear returned. The main research findings can be summarized as follows, 53.3% out of the total take meals twice a day and 89.9% responded that their meal time is irregular, which implies they are not aware of the importance of nutrition balance and they are probably not in good health. In addition, students prefer cookies and sweets followed by fried stuffs as a snack while they are willing to drink fruit juices and cokes as a beverage. In terms of alcohol drinking and smoking, it is turned out that 47.9% drinks once or twice a month and 24.9% are smokers. Interestingly, the female students outnumbered the male students in terms of the quantity of consuming alcohol. Approximately, half of the total respondents replied that they are not confident of whether they are in good health. This study suggest that students must recognize the importance of nutrition balance and a proper education must be provided to help the students understand it.

도시환경에서의 Sound Amenity개념

장길수,한명호 동신대학교 환경연구소 1999 환경연구 Vol.4 No.1

캐나다의 R.M,Schafer에 의해 사운드스케이라는 개념이 도입됨으로써 그동안 의 환경소음제어 분야에 종사하는 많은 사람들에게 방법론상의 획기적 사고전환을 가져왔다. 사운드스케이프 디자인 분야에서 매우 번번하게 사용되고 있는 주요 용어는 "소음의 쾌적성(sound amenity)"이다. 따라서 사운드스케이프의 개념전개를 위해서는 sound scape의 정확한 개념파악이 선행되어야 하며, 아직 이 분야에서의 본격적인 연구가 부재한 국내의 실정에서는 이를 토대로 다양한 사례조사와 관련연구를 필요로 한다. 본 연구의 주요내용은 sound amenity의 개념을 다양한 문헌을 통해 소개하고, 이 분야의 연구방향을 파악해 보는 데 있으며, 이를 통해 쾌적한 도시환경을 조성하는 새로운 패러다임을 모색하는 계기가 되기를 기대한다. The word "sound amenity" is now very popular in the field of soundscape design. The concept of soundscape which was first proposed by Canadian composer R.M.Schafer gave an impact on the methodology of environmental acoustics on which conventional researchers in the field of noise control engineers relied on. But in Korea, the concept of sound amenity or soundscape has not yet been recognized and also relative studies has not yet been carried. This paper is aim to introduce the concept and new trend of sound amenity to the noise control engineer, and is aim to provide them with noise control philosophy and methdology for the design of urban environment.

歸鄕에 나타난 Thomas Hardy의 自然과 人間

金吉洙 진주교육대학교 1986 論文集 Vol.30 No.1

Thomas Hardy was born in Dorset in 1840. Nearly all his novels set in Dorset in the south of England. The Wessex he describes in The Return of the Native is the heath country which is guite useless for growing anything because the soil is a light sand. Generally The Return of the Native, which is about a young man who returns to his place of birth to pursue an impossible ideal, is regarded as a tragedy of environment and character. In the Return of the Native, "Chance" and "Coincidence" which is part of Hardy's narrative techniaue play a decisive role in bring about human tragedies. The effect of nature is more vividly and powerfully seen in The Return of the Native than Hardy's other novels. In this norel, however, the events take place in a single setting, Egdon Heath. Egdon Heath is a kind of character that plays the most important and prominent role in this novel, causing human tragedies. Egdon Heath is presented as a kind of principle or norm to which human beings must adapt themselves or surrender in order to survive. Thomasin and Diggory Venn don't resist to their lot, and also they are at beast not unhappy. Eustacia is forced to live in the Egdon Heath but hates it. Eustacia and Wildeve vigorously resist the force of the heath, and thisis the very source of the tragedy. In the end they die, downed in the flooded weir a night of wind and storm. Clym, born on Egdon Heath, went to Paris where he was successful as a manager to a diamond merchant ; hence the title of the this novel. The tragedy of The Return of the Native grows out of the nostalgia that drives Clym Yeobright. He pursues an important ideal. In his pursuit he happens to be the indirect cause of the deaths of his mother, wife, and cousin's husband. At the end he finds his vocation as a preacher.

제주공항 항공등화 제어시스템의 고효율 운전대책

이길수,김일환 濟州大學校 産業技術硏究所 2000 산업기술연구소논문집 Vol.11 No.2

This paper presents the new control method of aeronautical ground lighting conrol system at Jeju airport. In the computer simulation. it is shown how to make a design for high efficiency aeronautical ground lighting control system using PWM inverter and active power filter with PI control. To verify the theoretical analysis. the conventional aero lighting control system using SCR and the proposed control system are built. Results of computer simulation are presented to support discussion.

中止未遂에 관한 고찰 : 法的 性格과 自意性을 중심으로

金秀吉 濟州大學校 社會發展硏究所 2003 社會發展硏究 Vol.18 No.-