• 한국기계가공학회지
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• 제17권3호
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• pp.102-108
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• 2018

The objective of this study is to develop the mechanical properties of an AlSiCu aluminum alloy using the two-step solution heat treatment. The microstructure of the gravity casting specimen represents a typical dendrite structure with a secondary dendrite arm spacing (SDAS) of 40 um. In addition to the Al matrix, a large amount of coarsen eutectic Si phase, $Al_2Cu$ intermetallic phase, and Fe-rich phases is generated. The eutectic Si phases are fragmented and globularized with the solution heat treatment. The $Al_2Cu$ intermetallic phase is also resolutionized into the Al matrix. The $2^{nd}$ solution temperature at $525^{\circ}C$ may be an optimal condition to enhance the mechanical properties of the AlSiCu aluminum alloy.

• 한국주조공학회지
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• 제10권6호
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• pp.528-537
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• 1990

7XXX aluminum alloy powders produced by the self-manufactured rotating disc atomizer were investigated to determine the influence of the atomization parameters on the particle size distributions in air atmosphere. The particle size distributions are almost always bimodal with the dominant mode on the large particle size. Average powder size of 7XXX aluminum alloy is $74/{\mu}m~125/{\mu}m$ when melt is poured with the rate of 9g /sec at 730$^{\circ}C$ on a rotating disc of 30㎜ diameter at 6300rad/sec. The mass of finer particle increased when disc diameter, angular velocity, pouring temperature increased and pouring rate decreased. The powder shapes of bimodal change from acicular to tear-drop and from tear-drop to ligament with increasing powder size. Powder shape was determined by the atomization mechanism and oxidation in liquid state. Microstructure of powders appeared to be cell and cellular dendrite. The SDAS of Al-7.9wt%Zn-2.4wt%Mg-1.5wt%Cu-0.9wt%Ni Powders is $0.8{\mu}m~1.0{\mu}m$ for the powders of $size＋44{\mu}m~53{\mu}m$ and $1.6{\mu}m∼1.8{\mu}m$ for the powders of $size＋105{\mu}m~125{\mu}m$, repectively.

• Bulletin of the Korean Chemical Society
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• 제29권1호
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• pp.111-116
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• 2008

A piperazinylalkylisoxazole library containing 86 compounds was constructed and evaluated for the binding affinities to dopamine (D3) and serotonin (5-HT2A/2C) receptor to develop antipsychotics. Dopamine antagonists (DA) showing selectivity for D3 receptor over the D2 receptor, serotonin antagonists (SA), and serotonin-dopamine dual antagonists (SDA) were identified based on their binding affinity and selectivity. The analogues were divided into three groups of 7 DAs (D3), 33 SAs (5-HT2A/2C), and 46 SDAs (D3 and 5-HT2A/2C). A classification model was generated for identifying structural characteristics of those antagonists with different affinity profiles. On the basis of the results from our previous study, we conducted the generation of the decision trees by the recursive-partitioning (RP) method using Cerius2 2D descriptors, and identified and interpreted the descriptors that discriminate in-house antipsychotic compounds.

• 한국주조공학회지
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• 제32권5호
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• pp.231-240
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• 2012

In present study, the effect of heat treatment on the microstructure and mechanical properties of the gravity cast superchargers housing using A356 alloy were investigated. In order to identify the characteristics of superchagers housing casting with heat treatment, Vickers hardness test, electrical conductivity test, opical and scanning electron microscopy were performed. And also, to investigate their mechanical properties, the T6 treated superchagers housing casting in optimum heat treatment condition were carried out tensile test using UTM (Universal Testing Machine).

• 한국주조공학회지
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• 제38권2호
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• pp.41-47
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• 2018

In a numerical study, equations relating the mechanical properties and cooling rate in a casting process have been applied to an AC4CH cast aluminum alloy. Good agreement was found between the measured and predicted material properties. Step-shaped steel blocks were made to comprise a casting mold with a Y-shaped cavity. Thermometers were inserted into each step of the mold to investigate temperature changes. The microstructure and mechanical properties, such as hardness and tensile stress were measured for each cut of piece. The correlation between the cooling rate and SDAS was found by curved fitting. Moreover, both the solidification time and the temperature were simulated using a commercial package, ZCast. The simulation results for yield strength, tensile strength, elongation, and hardness were compared with experimental results. Using the estimated K and n values, the hardness values of a ship propeller were simulated, and the results were similar to those obtained for actual castings.

• Asian Pacific Journal of Cancer Prevention
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• 제13권6호
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• pp.2923-2930
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• 2012

Background: Little is known about interest in faith-based health promotion programs among Asian American populations. Among the Christian denominations, the Seventh-day Adventist (SDA) church is known to place a strong doctrinal emphasis on health. Objectives: To understand appropriate ways to develop and implement health promotion programs and to conduct research among Korean American SDAs. Methods: We collaborated with the North American Division of Korean SDA Churches which sponsors annual week-long religious retreats for their church members. We developed and administered a 10-page questionnaire at their 2009 retreat in order to assess socio-demographic and church characteristics, religiosity, perceived relationship between health and religion, and interest and preferences for church-based health promotion programs. Results: Overall, 223 participants completed our survey (123 in Korean and 100 in English). The sample consisted of regular churchgoers who were involved in a variety of helping activities, and many holding leadership positions in their home churches. The vast majority was interested in receiving health information at church (80%) in the form of seminars, cooking classes and workshops (50-60%). Fewer respondents were interested in support groups (27%). Some interests and preferences differed between English and Korean language groups. Conclusion: Korean American SDA church retreat participants from a large geographic area are very interested in receiving health information and promoting health at their churches and can potentially serve as "agents of influence" in their respective communities.

• 열처리공학회지
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• 제27권6호
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• pp.281-287
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• 2014

Microstructural and mechanical characteristics of Al-6Si-2Cu alloy for engine mount bracket prepared by gravity casting (as-cast) and die-casting (as-diecast) process have been investigated. For the microstructural characterization, the inductively coupled plasma mass spectrometry (ICP-MS), optical microscope (OM), scanning electron microscope (SEM) and electron probe microanalysis (EPMA) analyses are conducted. For the intermetallic phases, the X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) are also conducted with quantitative and qualitative analysis. Micro Vickers hardness and static tensile test are achieved in order to measure mechanical properties of alloys. Secondary dendrite arm spacing (SDAS) of as-cast and as-diecast show 37um and 18um, respectively. A large amount of coarsen eutectic Si, $Al_2Cu$ intermetallic phase and Fe-rich phases are identified in the Al-6Si-2Cu alloy. Mechanical properties of gravity casting alloy are much higher than those of die-casting alloy. Especially, yield strength and elongation of gravity casting alloy show 2 times higher than die-casting alloy. After shot peening, shot peening refined the surface grains and Si particles of the alloys by plastic deformation. The surface hardness value shows that shot peening alloy has higher value than unpeening alloy.

• 한국정보통신학회논문지
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• 제22권1호
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• pp.54-62
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• 2018

기술의 발전에 따라 다양한 응용을 위한 장치가 연구 및 개발되고 있으며 운전자 보조 시스템은 그 중 대표적인 기술이다. 운전자 보조 시스템 기술은 차량 주변의 정보를 인식하기 위해 영상인식 기법을 사용한다. 차량에 적용되는 운전자 보조 장치는 계산시간이 오래 걸리는 다수의 영상인식기법을 실시간으로 처리하는데 어려움이 존재한다. 이를 위해 제한된 하드웨어에서 영상인식 기법의 실시간 처리를 위한 동적 프레임 제외 기법을 제안한다. 기존의 연구에서 프레임 제외는 처리시간에 비례하여 정적으로 설정되었으며 처리 할 수 있는 영상인식기법의 수가 적음을 알 수 있다. 차량의 속도와 가속도를 통해 주행상태를 파악하여 동적으로 프레임 제외률을 설정하고 그에 맞게 영상인식 기법을 처리하여 그 수를 최대화시켰다. 실험을 통해 처리 수가 정적 기법에 비해 32.5% 상승함을 확인하였다.

• 소성∙가공
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• 제28권1호
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• pp.34-42
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• 2019

In this study, various alloying elements (Cr, Sr, Ca, Cd) were added to improve the mechanical properties of ADC12 fabricated by a die casting process. The effect of alloying elements on the microstructure and mechanical properties were investigated. The phase analysis results of the modified ADC12 alloy with conventional ADC12 alloy, showed the similar characteristics of Al matrix, Si phase, $CuAl_2$ phase and the Fe intermetallic phase. As a result of the microstructure observation, the secondary dendrite arm spacing (SDAS) was shown to have decreased after the addition of the alloying elements. The eutectic Si phase, which existed as flake form in the conventional ADC12 alloy, was modified finely as a fiber form in the modified ADC12 alloy. It was observed that the $CuAl_2$ phase as the strengthening phase was relatively finely distributed in the modified ADC12 alloy. The Fe intermetallic appeared as a Chinese script shaped $Al_6$ (Mn,Fe) which is detrimental to mechanical properties in conventional ADC12 alloy. On the other hand, in the modified ADC12 alloy, polyhedral ${\alpha}-Al_{15}Si_2$ $(Fe,Mn,Cr)_3$ was observed. The tensile properties were improved in the modified ADC12 alloy. The yield strength and tensile strength increased by 12.4% and 10.0%, respectively, in the modified ADC12 alloy, and the elongation was also seen to have been increased. As a result of the pin on disk wear test, the wear resistance properties were also improved by up to about 7% in the modified ADC12 alloy. It is noted that the wear deformation microstructures were also observed, and it was found that the fine eutectic Si and strengthening phases greatly improved abrasion resistance.