• 대한기계학회논문집A
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• 제30권4호
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• pp.402-408
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• 2006

Dissimilar friction welding were produced using 15(mm) diameter solid bar in chrome molybedenum steel(KS SCM440) to carbon steel(KS S45C) to investigate their mechanical properties. The main friction welding parameters were selected to endure good quality welds on the basis of visual examination, tensile tests, Vickers hardness surveys of the bond of area and H.A.Z and microstructure investigations. The specimens were tested as-welded and post-weld heat treated(PWHT). The tensile strength of the friction welded steel bars was increased up to 100% of the S45C base metal under the condition of all heating time. Optimal welding conditions were n=2,000(rpm), $P_1=60(MPa),\;P_2=100(MPa),\;t_1=4(s),\;t_2=5(s)$ when the total upset length is 5.4 and 5.7(mm), respectively. The peak of hardness distribution of the friction welded joints can be eliminated by PWHT. Two different kinds of materials are strongly mixed to show a well-combined structure of macro-particles without any molten material and particle growth or any defects.

• 아동학회지
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• 제30권6호
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• pp.1-14
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• 2009

Korean families have been undergone tremendous changes during the past three decades with societal changes. Korean families become smaller, diverse, and multi-cultural. These family changes challenge child development research. Family is not just an intimate relationship. Family is also a structural environment, a system linking micro and macro system, an institution, and an ideology. Consequently, researchers need to pay attention to various ways family influence child development and take into account family as a whole unit. Researchers are also challenged to make a stance regarding family changes and diversity. Temporality is another important issue in studying how family development and child development interact. In terms of public policy, social services should be developed to cope with the new social risks from family changes and to mitigate a growing developmental gap among the children of families with different economic classes.

• 말소리와 음성과학
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• 제2권3호
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• pp.81-89
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• 2010

Korean and three other languages (English, Arabic, and Japanese) were compared with regard to the compensatory movements in a VC (Vowel and Consonant) sequence and word. For this, Korean data were collected from an experiment and the other languages' data from literature. All the test words of the languages had the same syllabic contexture, i.e., /CVCV(r)/, where C was an oral stop and intervocalic consonants were either bilabial or alveolar stops. The present study found that (1) Korean is most striking in the durational variations of segments (vowel and the following hetero-syllabic consonant); (2) unlike the three languages that show a constant sum of VC, Korean yields a three-way distinction in the length of VC according the type (lax unaspirated vs. tense unaspirated vs. tense aspirated) of the following stop consonant; (3) a durational constancy is maintained up to the word level in the three languages, but Korean word duration varies as a function of the feature tenseness of the intervocalic consonants; (4) consonant duration is proven to differentiate Korean the most from the other languages. It is suggested that the durational difference between a lax consonant and its tense cognate(s) and the degree of compensation between V and C are determined by the phonology in each language.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2005년도 학술발표회 논문집
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• pp.215-219
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• 2005

A macro spreadsheet model, WEANES (Wet Pond Annual Efficiency Simulation Model), has been developed to predict the long-term or annual removal efficiencies of wet retention/detention basins. The model uses historical, site-specific, multi-year, rainfall data, usually available from a nearby National Oceanic and Atmospheric Administration (NOAA) climatological station to estimate basin efficiencies which are calculated based on annual mass loads. Other required input parameters are: 1) watershed parameters; drainage area, pervious curve number, directly connected impervious area, and ti me of concentration, 2) pond parameters; control and overflow elevations, pond side slopes, surface areas at control elevation and pond bottom; 3) outlet structure parameters; 4) pollutant event mean concentrations; and 5) pond loss rate which is defined as the net loss due to evaporation, infiltration and water reuse. The model offers default options for parameters such as pollutant event mean concentrations and pond loss rate. The model can serve as a design, planning, and permitting tool for consulting engineers, planners and government regulators.

• 한국재료학회지
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• 제2권1호
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• pp.52-57
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• 1992

용응인상법에 의해 융성시킨 $LiNbO_3$ 단결정의 거시적 결함은 단결정 육성인자인 성장속도, 온도구배 및 결정회전속도에 강하게 영향을 받았다. Cell 구조가 형성되지 않고 결정의 직경제어가 용이하며 결정성장 후 냉각시 에도 crack이 발생되지 않는 1" 직경의 $LiNbO_3$ 단결정의 성장조건은 온도기울기 $70~100^{circ}C/cm$, 성장속도 5~10 mm/hr, 결정회전속도 40 rpm 이었다. 이었다.

• 한국재료학회지
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• 제28권4호
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• pp.221-226
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• 2018

The property changes of 18, 14, and 8K green gold alloys for jewelry are observed by adding 0.0, 3.0, and 5.0 wt% of indium (In), respectively. To check the composition of the alloys, an energy dispersive spectroscopy (EDS) analysis is conducted. Color and microstructure analysis is executed through bare-eye, macro camera, UV-VIS-NIR-colormeter, and optical microscope. The melting point, wetting angle, and hardness are measured using TGA-DTA, a wetting angle tester, and a Vickers hardness tester. The EDS analysis result demonstrates that each of the green gold alloys was manufactured with purposed contents. The color analysis result shows that the color of the alloys is similar to the color of the conventional 4 wt%-Cd 18K green gold, and the green color improves as the In content increases. The micro structure analysis result demonstrates that grain refinement improves as the amount of In increases. Enhancements in the melting point, wettability, and Vickers hardness changes appear as the In content increases and Au content decreases. The hardness is up to 260, which implies good durability. Therefore, the results suggest that the proposed 18, 14, and 8K In-added green gold alloys enhance the properties of jewelry products with regard to the green color, castability, and durability.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.457-462
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• 2006

This paper is concerned with the active vibration control experiment on cylindrical shell equipped with Macro Fiber Composite(MFC) actuators. The MFC actuators were glued to the cylindrical shell in circumferential directions. To verify the theoretical result, vibration test using impact hammer and accelerometer was carried out. It was found from experiments that theoretical result predicts experimental result to some extent. The positive position feedback controllers were designed and applied to the test article. It was observed that the resonant amplitude of the fundamental mode was reduced by 20dB thus achieving active vibration control. The active vibration control of the response subject to non resonant excitation has been of interest. We developed the combination of the positive position feedback controller which can cope with the fundamental mode and the positive position feedback controller which can counteract the external disturbance with non resonant frequency. It was found from experiments that the hybrid controller can suppress the vibration amplitude successfully.

• 한국컴퓨터산업학회논문지
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• 제2권2호
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• pp.211-218
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• 2001

본 논문에서는 동영상 부호화기에서 프레임 메모리 인터페이스의 하드웨어 구현을 위해 기존의 DRAM이 아닌 SDRAM을 사용하여 효율적인 메모리 맵의 구조를 제안한다. 동일한 버스에서도 효과적인 메모리 맵과 내부 버퍼 크기를 줄여 하드웨어 복잡도을 개선하고 내부 로직을 간략화하여 면적을 최소화하였다. 기존의 시스템은 매크로 블록 단위로 메모리에 저장하고 다시 출력을 위해서 랜덤하게 저장되어 있는 데이터를 액세스하여 많은 시간을 소비한다. 따라서 데이터를 라인 단위로 저장 및 처리하므로 메모리의 엑세스 시간을 효과적으로 줄일 수 있는 방법을 제시하였다.

• The Journal of Asian Finance, Economics and Business
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• 제6권4호
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• pp.53-63
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• 2019

The paper examines the influence of profitability on distance to default (DD) in Vietnam securities market. The investigated sample consists of 211 companies listed on HOSE during 18 years from 2010 to 2017. We apply KMV model to calculate distance to default and use both macroeconomics factors and firm specific factors as independent variables. Using General Least Squared (GLS) method, we find evidence to confirm the positive relationship between profitability and distance to default. This result showed that, although profitability did not directly reflect the cash flow generated, a good profitable enterprise would be an important factor to help facilitate and generate cash flow and at the same time debt was guaranteed when it was due. Besides, the test results revealed that the financial structure and sales on assets have the inverse effect on the distance to default at the significance level of 5%. The results also revealed that a group of macro factors had an influence on the distance to default of businesses, including spread, GDP and trade balance (via exchange rates). Gross domestic income had certain impacts on the distance to default of businesses. This was also a basic indicator measuring the national economic cycle.

• 한국CDE학회논문집
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• 제19권2호
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• pp.182-190
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• 2014

Parametric modeling is one of BIM's characteristics and BIM have being utilized for constructability analysis, energy efficiency analysis, and so on in diverse construction field. However, parametric information's interoperation is not solved until now because different BIM tools have specific algorithm and methods to generate geometric information. To solve the problem, previous research suggested IFC-XML methodology. In this paper, authors studied connections between IFC-XML structure and script-based modeling commends to make libraries in commercial BIM tools such as ArchiCAD$^{TM}$ and Digital Project$^{TM}$. In addition, they made commends mapping tables to exchange geometry information of architectural components. Moreover, mapping system was developed to certify the mapping tables which is classified modeling commends. Finally, translated architectural component model was confirmed using exchanged geometry information in browser.