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

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

제주공항 항공등화 제어시스템의 고효율 운전대책

이길수,김일환 제주대학교 산업기술연구소 2000 尖端技術硏究所論文集 Vol.11 No.2

This paper presents the new control method of aeronautical ground lighting control 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.

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.

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.

CMS에서 전력제어를 위한 AGC의 성능 개선에 관한 연구

이원구,이철희,천종훈,박수봉,박종안,신용길 조선대학교 동력자원연구소 1996 動力資源硏究所誌 Vol.18 No.1

CDMA 시스템에서는 이동국이 Open-loop 전력제어 및 Close-Loop 전력제어를 할 때 비 선형적인 AGC의 특성으로 인해 수신기의 감도가 현저히 낮아진다. 본 논문에서는 AGC의 비선형적인 특성 곡선값을 S/W로 선형화 시켜 RAS RAMDATA를 생성하고 이를 RAS RAM에 넣어 선형적으로 보상된 AGC특성을 얻는 알고리즘을 제안하였다. 그리고 실험을 통하여 그 유효성을 증명한다. In CDMA system, the sensitivity of receivers is lowered significantly due to characteristics of non-linear AGC when the mobile station implements open-loop power control and closed-loop power control. In this paper, We propose a algorithm that obtains linearly conpensated AGC characteristic by inserting the RAS RAM DATA in RAS RAM, which linearizes the value of non-linear characteristic graph in AGC by S/W, and the experimental results shows the validity.

계면활성제의 체인길이에 따른 구형 MCM-41의 합성

이두형,최병열,장원철,서길수,이태진 영남대학교 공업기술연구소 1999 工業技術硏究所論文集 Vol.27 No.1

Mesoporous MCM-41 exibits a hexagonal arrangement of uniform mesopores whose dimensions may be engineered in the range of ∼20Å to greater than 100Å. The MCM-41 typically have high surface areas above 1000m2/g, and then capacities of MCM-41 to accommodate the larger hydrocarbon is still higher than the general molecular sieve. At the present, many surfactants as organic templates have been proposed for various formations of these MCM-41. In this study, we synthesized mesoporous MCM-41 which has a spherically hexagonal structure. Also, the pore size of MCM-41 could be changed by the control of alkyl chain length of surfactants.

경사진 사석층의 지지력에 관한 원심모형실험 및 수치해석

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 paper is an experimental and numerical research works about the effects of the bearing capacity of sloped rubble mound on the density of rubble mound and the position of footing. Centrifuge model tests were performed to investigate the bearing capacity of rubble mound by changing the density of rubble mound and the location of loading in forms of strip loading to simulate the caisson. Materials of rubble mound used in the model tests were crushed rocks having similar value of uniformity coefficient to the value in field. Two different relative densities of 80% and 90% were prepared during tests. The dimens ions of centrifuge model were trapezoidal shape of model mound having the bottom width of mound, 30cm and height of mound, 10cm. Gravity level applied during the centrifuge test was 50G. Surcharge loading in the forms of strip loading was applied on the top of the sloped model mound. Tests were carried out by changing the position of loadi ng. The rigid model footing was located in the center of top of the model rubble mound and the edge of model footing was at the crest of mound. Test results were analyzed by using the limit equilibrium methods proposed by Meyer hof(1957) and Bowles(1982) and the numerical approach with FLAC being available commercially software. For the numerical estimations with FLAC, the rubble mound was simulated with the constitutive relationship of Mohr-Coulomb elasto-plastic model.

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.