• 대한기계학회논문집B
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• 제33권12호
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• pp.952-960
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• 2009

Selective Catalytic Reduction (SCR) system is a high-effective NOx reduction technology in diesel engines. As the emission standard of diesel engines is more stringent, vehicle manufactures makes efforts on emission technologies. This paper discusses the performance of Urea-SCR system according to the engine operating conditions in a passenger diesel engine. Engine test results in this paper show that it is important to consider the catalyst temperature and space velocity to obtain high NOx conversion efficiency. In condition of high catalyst temperature, over 90% NOx conversion efficiency is indicated. However, when catalyst temperature is low, NOx conversion efficiency was decreased. Also, it was shown that space velocity mainly effects on the DeNOx performance under 220 degree celsius of SCR catalyst temperature. As the urea injection pressure was decreased, NOx conversion efficiency was declined. It is concerned about urea droplet atomization. This work shown in this paper can lead to improved overall NOx conversion efficiency.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제2권1호
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• pp.88-93
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• 1998

It is frequently important to approximate a rational B$\acute{e}$zier curve by an integral, i.e., polynomial one. This need will arise when a rational B$\acute{e}$zier curve is produced in one CAD system and is to be imported into another system, which can only handle polynomial curves. The objective of this paper is to present an algorithm to approximate rational B$\acute{e}$zier curves with polynomial curves of higher degree.

• Bulletin of the Korean Chemical Society
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• 제17권8호
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• pp.696-699
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• 1996

Silicate and borosilicate gels were prepared by the sol-gel process and thermally treated in the 150-850 ℃ temperature range. Solid-state 1H MAS and 29Si CP/MAS NMR spectroscopy were used to investigate the effects of heat treatments on the silicate gel to glass conversion process. The 1H NMR isotropic chemical shifts and the relative intensities of hydrogen bonded and isolated silanol groups have been used to access the information concerning the dehydration process on the silicate gel surface. The 29Si NMR isotropic chemical shifts affected by the local silicon environment have been used to determine the degree of crosslinking, i.e. the number of siloxane bonds. These NMR results suggest that the silicate gel to glass conversion process is occurred by two stages which are dependent on the temperature; (1) the formation of particles up to 450 ℃ and (2) the formation of large particles by aggregation of each separated single particle above 450 ℃. In addition, the effects of B atom on the formation of borosiloxane bonds in borosilicates have been discussed.

• 한국농촌생활과학회지
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• 제5권2호
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• pp.185-197
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• 1994

This study is to investigate the factors which affect self- esteem of the aged parents. In this study questionaires were used to measure solidarity between aged parents and adults children, self- esteem of aged parents. Subjects were 234 male and 235 female parents who were aged over 60. The data were analyzed by using frequency, percentage, mean, standard deviation, ANOVA, and stepwise regression analysis. The results are as follows : 1) The solidarity between the aged parents and their adult children is average 65.5(Conversion value by 100 : 51.9) and shows the average level. The relations between solidarity and background variables are variables affected by education, pocket money, health, social activity and religion. 2) The degree of self- esteem in the aged parents is presented to average 26.1(Conversion value by 100 : 56.5) and shows the average level and it according to the background variables has a significant difference depending on education, pocket money, family living together, health, social activity, religion and the number of children. 3) To investigate the degree of self- esteem according to the degree of solidarity, the sub-areas of solidarity are subdivided into five groups. higher solodarity the group has, higher self- esteem it has. 4) The degree of effects of the variables which affect self- esteem in the aged parents is in such order as affectional solidarity($\beta$＝0.32), helping($\beta$＝0.14), education($\beta$＝0.10), solidarity by contact($\beta$＝0.09) and solidarity by argument($\beta$＝0.09) and $R^2$ of such variables are 30%.

• 대한치과보철학회지
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• 제47권4호
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• pp.416-423
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• 2009

연구목적: 이번 연구의 목적은 PLV 수복물의 접착 시 사용되는 광중합형 레진 시멘트의 중합도를 Fronrier transform infrared spectroscope로 측정하여 도재의 두께, 광원 및 광조사 시간에 따른 중합도의 차이를 비교하기 위함이다. 연구재료 및 방법: 대조군으로는 1.0 mm의 투명한 slide glass를 사용하였고, 도재 시편은 IPS Empress Esthetic shade ETC1을 선택하여 0.5, 1.0, 1.5 mm의 두께로 제작하였다. 레진 시멘트는 광중합형 레진 시멘트인 Rely $X^{TM}$ Veneer Shade A3를 사용하였다. 광원으로는 Quartz Tungsten Halogen (QTH), Light Emitting Diode (LED), Plasma arc curing (PAC) 광중합기를 사용하였다. 레진 시멘트의 중합도는 FT-IR과 OMNIC 프로그램을 이용하여 측정하였다. 통계분석은 one-way ANOVA와 Tukey HSD를 이용하였다 ($\alpha$=0.05). 결과: 대조군에서 QTH와 LED로 광중합을 시행하였을 때 PAC로 광조사를 시행한 경우보다 중합도가 높았다. QTH와 LED로 광조사를 시행한 경우, 대조군과 0.5 mm, 1.0 mm, 1.5 mm의 도재 두께에서 유의차를 보이지 않았다. 반면, PAC로 광조사를 시행한 결과, 도재의 두께가 1.5 mm인 실험군의 중합도가 대조군과 0.5 mm에서 보다 통계적으로 유의하게 낮은 결과를 보인다 (P<.05). 두께가 1.0 mm의 도재와 LED 광중합기로 광조사하여 중합도를 비교한 결과, 20초간 광조사를 시행하였을 때와 비교하여 80초와 160초간 광조사를 시행한 경우 통계적으로 유의하게 중합도의 평균값이 높았다 (P<.05). 결론: 이번 연구의 한계 내에서, 도재의 두께가 0.5-1.5 mm 이내의 PLV 접착 시, PAC 중합기의 사용은 고려되지 않으며, QTH나 LED로 40초 이상 중합한다면 광중합형 레진 시멘트를 사용할 수 있다. 또한, 광중합형 레진 시멘트를 LED로 중합시킬 경우, 광조사 시간의 증가가 중합도의 증가와 비례하지 않으며, 일정시간 이상의 광조사가 중합도에 큰 영향을 끼치지 않는다.

• 한국전기전자재료학회논문지
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• 제31권7호
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• pp.443-449
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• 2018

We investigated the temperature-dependent photoluminescence spectroscopy of colloidal InZnP/ZnSe/ZnS (core/shell/shell) quantum dots with varying ZnSe and ZnS shell thickness in the 278~363 K temperature range. Temperature-dependent photoluminescence of the InZnP-based quantum dot samples reveal red-shifting of the photoluminescence peaks, thermal quenching of photoluminescence, and broadening of bandwidth with increasing temperature. The degree of band-gap shifting and line broadening as a function of temperature is affected little by shell composition and thickness. However, the thermal quenching of the photoluminescence is strongly dependent on the shell components. The irreversible photoluminescence quenching behavior is dominant for thin-shell-deposited InZnP quantum dots, whereas thick-shelled InZnP quantum dots exhibit superior thermal stability of the photoluminescence intensity.

• The Korean Journal of Ceramics
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• 제4권3호
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• pp.245-248
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• 1998

Porous carbon fiber composites (CFCs) having variable specific surface area ranging 35~1150 $\m^2$/g were reacted to produce silicon carbide fiber composites with SiO vapor generated from a mixture of Si and $SiO_2$ at 1673 K for 2 h under vacuum. Part of SiO vapor generated during conversion process condensed on to the converted fiber surface as amorphous silica. Chemical analysis of the converted CFCs resulting from reaction showed that the products contained 27~90% silicon carbide, 7~18% amorphous silica and 3~63% unreacted carbon, and the composition depended on the specific carbide, 7~18% amorphous silica and 3~63% unreacted carbon, and the composition depended on the specific surface area of CFCs. CFC of higher specific surface area yielded higher degree of conversion of carbon to silicon and conversion products of lower mechanical strength due to occurrence of cracks in the converted caron fiber. As the conversion of carbon to silicon carbide proceeded, pore size of converted CFCs increased as a result of growth of silicon carbide crystallites, which is also linked to the crack formation in the converted fiber.

• 공업화학
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• 제4권2호
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• pp.335-341
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• 1993

메탄올 전환반응에서, 헤테로폴리산 화합물의 산특성이 촉매활성에 미치는 영향에 대하여 연구하였다. 구리로 치환된 12-텅스토인산 촉매를 수소로 전처리하면 메탄올의 전환율과 프로판에 대한 선택도가 증가하였으며, 알루미늄이온으로 치환된 12-텅스토인산 촉매에서는 물로 전처리하면 산의 세기가 증가하였다. 반응물에 첨가된 물은 메탄올의 전환율을 감소시켰고, 전처리온도는 메탄올의 전환율에는 영향을 미치지 않았으나, propylene/propane의 생성비에는 영향을 미쳤다. 알루미튬이온에 의해 부분적으로 이온교환된 여러 가지의 12-텅스토인산염들은 알루미늄이온의 치환정도에 따라 서로 다른 촉매활성을 보여주었다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2005년도 추계종합학술대회
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• pp.261-264
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• 2005

This paper presents the design of a down-conversion mixer with built-in active balun integrated in a $0.25\;{\mu}m$ pHEMT process. The active balun consists of series-connected common-gate FET and common-source FET. The designed balun achieved broadband characteristics by optimizing gate-width and bias condition for the reduction in parasitic effect. From DC to more than 6GHz, the active balun shows the phase error of less than 3 degree and the gain error of less than 0.4 dB. A single-balanced down-conversion mixer with built-in broadband active balun has been designed with optimum width, load resistor and bias for conversion gain and without any matching component for broadband operating. The designed mixer whose size of including on-chip bias circuit is $1\;mm{\times}1\;mm$ shows the conversion gain of better than 7 dB from 2 GHz to 6 GHz and $P_{1dB}$ of -10 dBm at 5.8 GHz

• 한국BIM학회 논문집
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• 제6권2호
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• pp.47-57
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• 2016

Recently, the introduction and spread of BIM technology has been actively promoted at the domestic level and abroad. However, the BIM adoption and diffusion rate in the whole construction industry has been slower than expected, this is because they applied to construction projects in a way that does not meet the basic objective of BIM adoption. The objective of this paper is to derive a BIM adoption strategy that can provide benefits and efficiency from the design phase, by analyzing issues related to design errors identified in two real world projects based on the 2D to BIM conversion process. Types of issues, type distribution, and degree of BIM contribution to find issues were analyzed in a quantitative way, and then a BIM adoption strategy was derived. As a result, this paper identified that there obviously exists a limit in the 2D to BIM conversion process by repeating the problems that occur in the traditional 2D design process. Therefore, the authors of this paper insist that the design firms should adopt BIM-based design processes, fully, to get financial benefits as well as to improve the design quality.