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.

사이클론 내부의 유동특성에 관한 연구

김대욱,윤완중,손현철,박길문 朝鮮大學校 機械技術硏究所 2000 機械技術硏究 Vol.3 No.2

For manufacturing the small-type incinerator with collecting performance of high efficiency, the experimental study was carried out with considering cyclone characteristics, tangential velocity, radial velocity and pressure of the internal cyclone. The model cyclone consisted of slick acryl was made for similarity and data of tangential inflow velocity were acquired by using a vinyl particle as a working fluid. The results obtained from the experimentation are summarized as follows : 1. Tangential velocity of internal cyclone increases as the size of particle become bigger 2. Pressure is maximum value at the wall of cyclone and decreases toward the center of cyclone. 3. The difference of pressure between maximum and minimum value is increased as the size of particle become bigger.

Delay Line을 이용한 1차 미분 임펄스 발생기 설계

김은정,임재현,김길겸,김학선 한밭대학교 정보통신전문대학원 2004 정보통신전문대학원 논문집 Vol.2 No.1

본 논문에서는 UWB (Ultra-WideBand)시스템에 사용되는 짧은 폭의 임펄스 발생기를 설계하였다. SRD와 두개의 단락된 전송 선로를 이용 하였다. 단락된 전송 선로는 시간 지연과 위상의 반전을 효과적으로 제공 한다. RC 미분기 대신에 단락된 전송 선로(Delay Line)을 이용하여 1차 미분 임펄스를 발생시켰다. 시뮬레이션을 통해 700psec의 펄스폭과 600mV(p.p)의 진폭, 펄스 모양의 좋은 대칭성을 확인하였고 또한, 펄스 주변의 떨림 현상이 거의 발생하지 않았다. In this paper, we have designed impulse generator of short pulse width for UWB(Ultra-Wide band) system using SRD and two short-circuited stubs. The short-circuited stub provides good time delay and reverse of phase. The first derivative impulse was generated by using short-circuited stub(Delay Line) instead of RC differentiator. A first derivative impulse of 700 psec pulse duration, 600mV(p.p) pulse amplitued, and good symmetry has been demonstrated though simulation. Also, there are extremely small amount of ringing around the first derivative impulse.

모바일 로봇의 견실제어를 위한 제네틱 알고리즘 개발

김홍래,배길호,정경규,한성현 한국공작기계학회 2004 한국공작기계학회 춘계학술대회논문집 Vol.2004 No.-

This paper proposed trajectory tracking control of mobile robot. Trajectory tracking control scheme are real coding genetic-algorithm and back-propergation algorithm. Control scheme ability experience proposed simulation. Stable tracking control problem of mobile robots have been studied in recent years. These studies have guaranteed stability of controller, but the performance of transient state has not been guaranteed. In some situations, constant gain controller shows overshoots and oscillations. So we introduce better control scheme using Real coding Genetic Algorithm(RCGA) and neural network. Using RCGA, we can find proper gains in several situations and these gains are generalized by neural network. The generalization power of neural network will give proper gain in untrained situation. Performance of proposed controller will verify numerical simulations and the results show better performance than constant gain controller.

방위특징 탐지 단순신경세포들의 배열순서에 관한 연구

김길중,김정국,서광명,서용수 동서대학교부설연구소 1998 연구소 논문집 Vol.3 No.-

Cells in avisual cortex line in columns which are perpendicular to the cortical surface and the cortical cells in a column prefer to respond to an orientation of each line segments of an sesory image. orientation preference of each cortical column is highly correlated to those of nearbycolumns and varies smoothly anlong the surface of the cortex. To elucidate the mechanism of this columnar organization, we propose a simple model consisting of orientation selective neruons(OSNs) with local facilitation and lateral inhibition. it is playsible that modifiable connections play an important role in forming and refining the organization togher with the sensory experience. Thus the feed-forward connections between OSNs and LGN cells are modifiable. The interactions between OSNs in the same layer take place by way of feedback pathways and are excitatory and inhibitory. The behavior of the model is described by a STM equations of Growwberg and critical parameter of negative one dimensional ??G function, σ would give variety to the differences in detected orientations.

모래다짐말뚝 개량폭에 따른 보강효과에 관한 연구

김시운,정길수,박병수,유남재 江原大學校 産業技術硏究所 2005 産業技術硏究 Vol.25 No.A

In this research, centrifuge model experiments and numerical approach of finite element method to analyze experimental results were performed to investigate the behavior of improved ground with sand compaction piles. One of typical clay minerals, kaolinite powder, were prepared for soft ground in model tests. Jumunjin standard sand was used to sand compaction pile installed in the soft soil. In order to investigate the characteristics of mechanical behavior of sand compaction piles with low replacement ratios, centrifuge model experiments with the replacement ratio of 40%, changing the width of improved area with respect to testing results the width of surcharge loads, were carried out to obtain of bearing capacity, characteristics of load-settlement, vertical stresses acting on the sand pile and the soft soil failure mechanism in improved ground.

거짓말탐지기(POLYGRAPH) 검사 사례

김정길,최효택 內務部 國立科學搜査硏究所 1996 國立 科學 搜査 硏究所 年報 Vol.28 No.-

지도자의 경쟁가치리더십과 선수만족 및 인지된 경기력의 관계

김종욱,양용길,이정수,장갑석,정종환 한국스포츠리서치 2004 한국 스포츠 리서치 Vol.15 No.3

The purpose of this study was to identify the relationships among competing value leadership, athlete satisfaction and performance in sport field, The instrument for data collection was a questionnaire in which competing value leadership consisted as identified by Ha(1996), athlete satisfaction consisted as identified by Che(1997), and performance consisted as identified by An(2002), 350 subjects were selected from universities in Seoul by the stratified cluster sampling method, Among these selected subjects, 322 responded, and data analyses consisted of employing descriptive statistics, one-way ANOVA, multiple-regression using SPSS/PC version 11.0. First, competing value leadership and athlete satisfaction differ statistically and partially according to socio-demographic variables of athletes, Second, athlete satisfaction and performance statistically and significantly is influenced by competing value leadership of leader, Third, athlete satisfaction statistically and significantly influence performance of athletes.

황국균과 백국균의 대두 코지제조중 키토산의 효과

정순택,문길만,조건식,강성국,김설희 木浦大學校 工業技術硏究所 1998 工業技術硏究誌 Vol.8 No.-

The effect of chitosan in soybean koji preparation and characteristics of chitosan-koji were investigated. Aspergillus oryzae KCTC 6096 and Aspergillus kawachii KCCM 11458 was used for koji preparation. a-Amylase activity of soybean koji prepared with 0.25% 10cp chitosan was excellent relative to 30 cp chitosan and 1.6 times higher than non-added soybean koji. Acid and neutral protease activities of soybean koji prepared with 0.25%, 10 cp chitosan were showed simillary higher value than non-chitosna added koji. The period of koji preperation was reduced 30% by adding chitosan.

에타놀 섭취 후 두부 상하위시 혈역학적 변화

김지영,김형진,홍정길 대한순환기학회 1998 Korean Circulation Journal Vol.28 No.1