• 설비공학논문집
• /
• 제15권7호
• /
• pp.563-571
• /
• 2003

The forty vapor-liquid equilibrium data of the binary system, HFC125＋Propane, were measured between 273.15 and 313.15 K at 10 K interval and the composition range 0.2∼0.75, respectively. Experiments were performed in a circulation type apparatus in which the vapor phase was forced through the liquid phase. The composition at equilibrium were mea-sured by gas chromatography, and its response was calibrated using gravimetrically prepared mixtures. Vapor-liquid equilibrium data were calculated by using CSD equation of state and compared with the experimental data.

• 한국세라믹학회지
• /
• 제28권8호
• /
• pp.577-584
• /
• 1991

Among various forming techniques for ceramics, we have studied the slip casting method for the binary system of SiC and carbon. The stability of the slip of silicon carbide and carbon were investigated by measurements of zeta potential, viscosity, sedimentation height, and also studied as functions of PH and amounts of dispersants. A preform of SiC and C was prepared by slip casting and heat treatment at 400∼600$^{\circ}C$ under N2 gas. The preform was reacted with Si metal at 1550$^{\circ}C$, 10-1 mmHg to give rise a reaction bonded SiC with a density of 3.0g/㎤ and a bending strength of 580 MPa.

• 한국주조공학회지
• /
• 제13권2호
• /
• pp.168-174
• /
• 1993

It has been known that the grain refinement of Cu base alloys greatly improved mechanical properties, castability, workability and hot shortness resistance etc. In this study CuZr50, CuP7, CuFe7, CuMg10 binary alloys were added as grain refiners in CuZn36 alloy. The alloys melted in vacuum and controlled in mixed gas conditions and casted at $1050^{\circ}C$. Zr-P-X compound has significantly grain refined but oxygen has been found detrimental to grain refinement. In the case of Zr /B ratio below 4, B acted as grain growth element in this alloy.

• Journal of Welding and Joining
• /
• 제10권3호
• /
• pp.1-12
• /
• 1992

A literature review was conducted to survey informations available on the welding metallurgy of aluminum alloys and its effect on fusion weldability, especially on solidification cracking and pore formation. Solidification cracking behavior of Al weld is a complicate matter as compared to other high alloys, where a relatively simple Fe-X(most detrimental elements S, P, B, Si, etc) binary diagram can be successfully applicable. Both additive and synergistic effects of elements should be considered together. A same element play a different role from system to system. Porosity, caused by hydrogen contamination of the weld is one of the most troublesome welding problems. The primary sources of hydrogen are believed to be an absorbed moisture on the filler metal or base metal and in the shielding gas. It is extremely important that reliable quality-control procedures be employed to eliminate all possible sources of hydrogen contamination. Selection of proper process and parameters is sometimes more important than controlling of alloying elements in order to make a defect-free weld.

• 청정기술
• /
• 제9권4호
• /
• pp.153-161
• /
• 2003

벤젠과 톨루엔을 활성탄에 흡착하는 공정을 개발하기 위한 기초 실험을 수행하였다. 정적흡착실험은 온도와 압력의 변화에 따른 벤젠과 톨루엔의 흡착특성을 연구하였다. 흡착제로는 활성탄 12~20mesh와 20~40mesh를 사용하였으며 흡착질로는 벤젠, 톨루엔, 질소를 사용하였다. 실험결과는 Langmuir isotherm으로 fittimg하였고, 온도의존성을 계산하였고, 흡착열과 흡착상수를 얻었다. 이성분 정적흡착실험에서는 Langmuir isotherm parameter들이 Extended Langmuir isotherm에 일반적으로 적용할 수 있는 지를 확인하였다. 이때 사용한 실험기법은 기존의 방법에서처럼 흡착 전후의 기상의 몰분율을 측정하여 실험하는 방법이 아닌 압력변화반을 측정하는 정용적법에 기초한 방법을 사용하였다. 동적흡착실험올 수행하여 실험결과를 전사모사로부터 얻어진 결과와 비교하였다. 본 연구에서는 공정에서 흡착조건을 결정할 수 있는 기본 데이터를 획득할 수 있었다.

• 천문학회지
• /
• 제49권3호
• /
• pp.93-107
• /
• 2016

Augmenting the Wide Field Infrared Survey Telescope (WFIRST) microlensing campaigns with intensive observations from a ground-based network of wide-field survey telescopes would have several major advantages. First, it would enable full two-dimensional (2-D) vector microlens parallax measurements for a substantial fraction of low-mass lenses as well as planetary and binary events that show caustic crossing features. For a significant fraction of the free-floating planet (FFP) events and all caustic-crossing planetary/binary events, these 2-D parallax measurements directly lead to complete solutions (mass, distance, transverse velocity) of the lens object (or lens system). For even more events, the complementary ground-based observations will yield 1-D parallax measurements. Together with the 1-D parallaxes from WFIRST alone, they can probe the entire mass range M ≳ M_⊕. For luminous lenses, such 1-D parallax measurements can be promoted to complete solutions (mass, distance, transverse velocity) by high-resolution imaging. This would provide crucial information not only about the hosts of planets and other lenses, but also enable a much more precise Galactic model. Other benefits of such a survey include improved understanding of binaries (particularly with low mass primaries), and sensitivity to distant ice-giant and gas-giant companions of WFIRST lenses that cannot be detected by WFIRST itself due to its restricted observing windows. Existing ground-based microlensing surveys can be employed if WFIRST is pointed at lower-extinction fields than is currently envisaged. This would come at some cost to the event rate. Therefore the benefits of improved characterization of lenses must be weighed against these costs.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2011년도 제40회 동계학술대회 초록집
• /
• pp.285-285
• /
• 2011

EUVL (Extreme Ultra Violet Lithography) is one of competitive lithographic technologies for sub-30nm fabrication of nano-scale Si devices that can possibly replace the conventional photolithography used to make today's microcircuits. Among the core EUVL technologies, mask fabrication is of considerable importance since the use of new reflective optics having a completely different configuration compared to those of conventional photolithography. Therefore new materials and new mask fabrication process are required for high performance EUVL mask fabrication. This study investigated the etching properties of SnO2 (Tin Oxide) as a new absorber material for EUVL binary mask. The EUVL mask structure used for etching is SnO2 (absorber layer) / Ru (capping / etch stop layer) / Mo-Si multilayer (reflective layer) / Si (substrate). Since the Ru etch stop layer should not be etched, infinitely high selectivity of SnO2 layer to Ru ESL is required. To obtain infinitely high etch selectivity and very low LER (line edge roughness) values, etch parameters of gas flow ratio, top electrode power, dc self - bias voltage (Vdc), and etch time were varied in inductively coupled Cl2/Ar plasmas. For certain process window, infinitely high etch selectivity of SnO2 to Ru ESL could be obtained by optimizing the process parameters. Etch characteristics were measured by on scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analyses. Detailed mechanisms for ultra-high etch selectivity will be discussed.

• 한국정보시스템학회지:정보시스템연구
• /
• 제29권1호
• /
• pp.75-91
• /
• 2020

Purpose Retrofit, defined to be addition of new technologies or features to the old system to increase efficiency or to abate GHG emissions, is considered as an important alternative for the old coal-fired power plant. The purpose of this study is to propose mathematical method to model multiple alternative retrofit in Generation Capacity Expansion Planning(GCEP) problem, and to get insight to the retrofit patterns from realistic case studies. Design/methodology/approach This study made a multi-alternative retrofit GECP model by adopting some new variables and equations to the existing GECP model. Added variables and equations are to ensure the retrofit feature that the life time of retrofitted plant is the remaining life time of the old power plant. We formulated such that multiple retrofit alternatives are simultaneously compared and the best retrofit alternative can be selected. And we found that old approach to model retrofit has a problem that old plant with long remaining life time is retrofitted earlier than the one with short remaining life time, fixed the problem by some constraints with some binary variables. Therefore, the proposed model is formulated into a mixed binary programming problem, and coded and run using the GAMS/cplex. Findings According to the empirical analysis result, we found that approach to model the multiple alternative retrofit proposed in this study is comparing simultaneously multiple retrofit alternatives and select the best retrofit satisfying the retrofit features related to the life time. And we found that retrofit order problem is cleared. In addition, the model is expected to be very useful in evaluating and developing the national policies concerning coal-fired power plant retrofit.

• 한국연소학회지
• /
• 제18권2호
• /
• pp.32-41
• /
• 2013

This study presents both experimental and numerical investigation of ignition delay time of n-heptane and n-butanol binary fuel. The $O_2$ concentration in the mixture was set to 9-10% to make high exhaust gas recirculation( EGR) rate condition which leads low NOx and soot emission. Experiments were performed using a rapid compression machine(RCM) at compressed pressure 20bar, several compressed temperature and three equivalence ratios(0.4, 1.0, 1.5). In addition, a numerical study on the ignition delay time was performed using CHEMKIN codes to validate experimental results and predict chemical species in the combustion process. The results showed that the ignition delay time increased with increasing the n-butanol fraction due to a decrease of oxidation of n-heptane at the low temperature. Moreover, all of the binary fuel mixtures showed the combustion characteristics of n-heptane such as cool flame mode at low temperature and negative-temperature-coefficient(NTC) behavior. Due to the effect of high EGR rate condition, the operating region is reduced at lean condition and the ignition delay time sharply increased compared with no EGR condition.

• 한국가스학회지
• /
• 제17권6호
• /
• pp.67-72
• /
• 2013

인화점은 공기와 섞인 가연성 증기의 농도가 발화하기에 충분할 때의 최저 온도로, 가연성 액체 용액의 화재 및 폭발 위험성을 분석하는데 사용되는 주된 물리적 특성치이다. 단일 성분의 인화점 정보는 여러 문헌에서 얻을 수 있으나, 가연성 이성분계 혼합물의 인화점은 충분히 제공되어 있지 않다. 본 연구의 목적은 이성분계 가연성 액체 혼합물인 아세트산-포름산계의 인화점을 측정하고, 산출하는 것이다. 인화점 측정은 Cleveland 개방식 장치를 사용하였고, 실험값은 van Laar 식과 Wilson 식을 활용한 최적화 기법에 의해 산출된 값과 비교하였다. 그리고 라울의 법칙에 의해 산출된 값과 비교되었다. 그 결과, 최적화 기법에 의한 산출값이 Rauolt의 법칙에 의한 산출값보다 실험값에 보다 근접하였다.