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.

곰솔(Pinus thunbergii )에서 소나무재선충병 예방을 위한 나무주사용 약제선발

이상명(Sang Myeong Lee),김동수(Dong Soo Kim),이상길(Sang Gil Lee1),박남창(Nam Chang Park),이동운(Dong Woon Lee) 한국농약과학회 2009 농약과학회지 Vol.13 No.4

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.

자연파열된 신혈관근지방종 2례

이길호,선판일,성영훈,최영석,조철희,김철성,장대수 朝鮮大學校 附設 醫學硏究所 1993 The Medical Journal of Chosun University Vol.18 No.1

Renal angiomyolipoma is an uncommon benign tumor of the kidney that consists of smooth muscle, blood vessels and mature adipose tissues. The most common benign renal tumor associated with spontaneous non-traumatic perirenal hemorrhage is angiomyolipoma, because of high vascularity. The ultrasonographic and computed tomographic images are sufficiently characteristic to permit accurate preoperative diagnosis. We report 2 cases of renal angiomyolipoma with spontaneous perirenal hemorrhage which were managed with nephrectomy.

원심모형시험에 의한 복개터널 복공의 토압특성에 관한 연구

이명욱,박병수,정길수,유남재 江原大學校 産業技術硏究所 2004 産業技術硏究 Vol.24 No.B

This thesis is results of experimental works on the behavior of the cut-and-cover tunnel. Centrifuge model tests were performed to simulate the behavior of the cut-and-cover tunnels having cross sections of national road and subway tunnels. Model experiments were carried out with changing the cut slope and the slope of filling ground surface. Displacements of tunnel lining resulted from artificially accelerated gravitational force up to 40g of covered material used in model tests, were measured during centrifuge model tests. In model tests, Jumunjin Standard Sand with the relative density of 80 % and the zinc plates were used for the covered material and the flexible tunnel lining, respectively. Basic soil property tests were performed to obtain it's the property of Jumumjin Standard Sand. Shear strength parameters of Jumunjin Standard Sand were obtained by performing the triaxial compression tests. Direct shear tests were also carried out to find the mechanical properties of the interface between the lining and the covered material. Compared results model tests estimation with respect to displacements of the lining.

이온교환법에 의한 고분자전해질형 연료전지용 전극의 제조와 특성 고찰

이주성,박수길,오태영,이홍기,심중표 한양대학교 에너지.환경기술연구소 1995 에너지·環境技術論文集 Vol.2 No.-

고분자전해질형 연료전지용 전극의 백금 이용률을 높이기 위해 촉매제조시 이온교환법을 이용하여 백금을 carbon에 담지하고 이에 따른 전지성능변화를 고찰하였다. 전극제조시 Nafion이 첨가되지 않은 경우 이온교환양이 증가함에 따라 전기화학적인 활성이 증가하여 전지성능이 증가하였다. 전극제조시 Nafion이 첨가된 경우, Nafion첨가량이 증가함에 따라 전지성능은 증가하였는 데 Nafin첨가에 의해 이온교환되지 않은 백금이 전기화학적인 활성을 가지게 되어 전지성능은 증가하였다. To improve platinum utilization of PEMFC(Proton exchange membrane fuel cell) electrode, in preparing catalytic powder, platinum was impregnated on carbon by ion exchange method and its cell performance was investigated. When electrode was prepared without adding Nafion solution, as Nafion pre-impregnated amount was increased, electrochemically active area and cell performance was increased. When electrode was prepared with Nafion solution, increase of adding Nafion amount was improvement of cell performance. By adding Nafion at preparation of electrode, non ion-exchange platinum was shown electrochemical activity, cell performance was improved.

도심 공원의 음 풍경 디자인을 위한 실험적 연구

이태강,송민정,전지현,장길수 대한건축학회 2005 대한건축학회논문집 Vol.21 No.1

This study is an experimental study to introduce the soundscape design in urban parks Objective 4 urban parks were surveyed And four or three subdivision area in these parks were investigated the sound source frequently to be heard and the degree of satisfaction for visual and auditory atmosphere measuring the sound level in 5 minute subjective response to soundscape for each subdivision area were earned out using 7 scale S D method based on pair of adjectives In order to recognized the effect environment sound (bird Sing, sweet ecological music, and nature sounds)for enriching the present soundscape, this study analyzed the subjective response for soundscape before and after providing environmental sound Result of the evaluation of public perception and their sound were vaned at the each subdivision area, which represented the special characteristics of the urban parks The score for image of the places were always higher than those of the sounds, thus visual Image were affected more positively than auditory image The effect of the environmental sound usually resulted in improvement of the subjective cvaluation at cach subdivision area Factor analyzing of the 25 korean vocabulary for using S D method could be induced the appropriate three factors "impression", "calmness" and "delight" These factors can be used for soundscape design of sound sources and images to provide

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.

나선형 사각덕트 형상변화에 따른 온도분포 및 냉각특성에 관한 연구

이경우,김수태,김용길 國立 昌原大學校 産業技術硏究所 1999 産技硏論文集 Vol.13 No.-

Temperature distributions and cooling characteristics of cooling jacket for spindle system with built-in motor are studied. Numerical analysis is carried out on six helical quadrilateral duct to investigate the temperature distribution and the cooling characteristics in the helical quadrilateral duct. For the analysis, three dimensional model for the cooling jacket is built by using finite volume method. The three dimensional model includes the estimation on the amount of heat generation of bearing and built-in motor and the thermal characteristic values such as heat transfer coefficients on the boundary. The temperature distributions and the cooling characteristics are analyzed by using the commercial software FLUENT, and the results of numerical analysis are compared with the experimental data. Numerical results show that stream-wise cross section area and pitch are important factors for cooling characteristics of cooling jacket. Cooling performance of cooling jacket is good, when stream-wise cross section area and pitch are small. This results show that heat transfer is dominated by velocity profile and heat transfer area. It is concluded that cooling characteristic of jacket can be reasonably estimated by using the three dimensional numerical model.

강제치환 거동특성에 관한 원심모형실험

이종호,박병수,정길수,유남재 강원대학교 산업기술연구소 2003 産業技術硏究 Vol.23 No.A

This thesis is results of centrifuge model experiments to investigate the behavior of replacement method in dredged and reclaimed ground For experimental works. centrifuge model tests were carried out to investigate the behavior of replacement method in soft clay ground. Basic soil property). tests were performed to find mechanical properties of clay soil sampled from the southern coast of Korea which was used for ground material in the centrifuge model tests Reconstituted clay ground of model was prepared by applying preconsolidation pressure in 1g condition with specially built model container. Centrifuge model tests were carried out under the artificially accelerated gravitational level of 50g Replacing material of leads having a certain degree of angularity was used and placed until the settlement of embankment of replacing material was reached to the equilibrium state. Vertical displacement of replacing material was monitored during tests. Depth and shape of replacement. especially the slope of penetrated replacing material and water contents of clay ground were measured after finishing tests Model tests of investigating the stability of embankment after backfilling were also performed to simulate the behavior of the dike treated with replacement and backfilled with sandy material. As a result of centrifuge model test. the behavior of replacement, the mechanism of the replacing material being penetrated into clay ground and depth of replacement were evaluated