바이오 디젤유 생산을 위한 대두유 에스테르화 반응의 속도론적 연구

황우람,신용섭 慶星大學校 環境問題硏究所 2002 環境硏報 Vol.12 No.1

The esterification of vegetable oil with methanol is one of the best ways to improve it's combustion characteristics. Therefore, in this study, the process which produce the bio-diesel oil from vegetable oil by the esterification reaction was investigated. Especially, the kinetic study on the esterification reaction of soybean oil was performed. Catalysts used in this study were sodium hydroxide as a homogeneous catalyst and calcium hydroxide as a heterogeneous catalyst. Because sodium hydroxide reacted with free fatty acid in the soybean oil and 0.5wt% of the sodium hydroxide was greater than the free fatty acid content in the soybean oil, it is very important for the completion of esterification reaction that the free fatty acid in the soybean oil should be removed before the esterification reaction. Compared with reaction rate constant of the esterification reaction rate constant of saponification had constant value in case of using sodium hydroxide catalyst. Interestingly, rate constant of the esterification reaction was decresed with increase of sodium hydroxide dosage. Compared with reaction rate constant of the esterification reaction, reaction rate constant of saponification had constant value in case of using sodium hydroxide catalyst. Interestingly, rate constant of the esterification reaction was decresed with increase of sodium hydroxide dosage. Using calcium hydroxide catalyste, reaction rate constants in FAMEs production step were Measured from 0.9141 min-1 to 1.0377 min-1, and reaction rate constants in monoglyceride and diglyceride production steps were measured from 0.0093 min-1 to 0.0386 min-1 according to the calcium hydroxide dosage. So, monoglyceride and diglyceride production steps rate controlling steps in overall esterification reaction.

Calibration and verification of the reaction rate for an insensitive PBX

박정수,윤성기,이재민 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.12

To investigate the detonation characteristics of an insensitive Plastic bonded explosive (PBX), the reaction rate was obtained and used in the numerical simulation of diverse case problems in the one-dimensional and two dimensional space. To calibrate the reaction rate, Detonation shock dynamics (DSD) theory was adopted, and two-dimensional steady-state experimental data were used to determine the shock front curvature function ( ) n D k . The reaction rate was calibrated by numerically integrating the master equation of the DSD theory. For the calibrated reaction rate, the simulation of the Large scale gap test (LSGT) and EIDS CAP test with regard to the shock sensitivity problem were carried out. Two numerical example were investigated using the reaction rate. First, an underwater explosion, which is basically a one-dimensional problem, was solved. Second, to also validate the reaction rate detonation wave progress, a corner turning problem was solved. Considering the results of the simulations and the experimental test, it was concluded that the calibrated reaction rate well describes the detonation characteristics of insensitive PBX with a reasonable degree of accuracy. The present study is the first case to obtain the reaction rate of an insensitive castable PBX using the DSD theory. Moreover the reaction rate obtained was verified using different detonation tests such as the gap sensitivity test, the underwater explosion test and the detonation wave propagation test.

Estimating Diffusion-Controlled Reaction Parameters in Photoinitiated Polymerization of Dimethacrylate Macromonomers

최영선 한국고분자학회 2003 Macromolecular Research Vol.11 No.5

The kinetics of photoinitiated polymerization of dimethacrylate macromonomers have been studied to determine the diffusion-controlled reaction parameters using attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). A predicted kinetic rate expression with a diffusion control factor was employed to estimate an effective rate constant and to define the reaction-controlled and diffusion-controlled regimes in the photopolymerization. An effective rate constant, ke, can be obtained from the predicted kinetic rate expression. At the earlier stages of polymerization, the average values of kinetic rate constants do not vary during the reaction time. As the reaction conversion, α, reaches the critical conversion, αc, in the predicted kinetic expression, the reaction becomes to be controlled by diffusion due to the restricted mobility of dimethacrylate macromonomers. A drop in value of effective rate constant causes a drastic decrease of reaction rate at the later stages of polymerization. By determining the effective rate constants, the reaction-controlled and diffusion-controlled regimes were properly defined even in the photopolymerization reaction system.

탄화규소 휘스커의 합성(I) : 반응기구의 율속반응

최헌진,이준근 한국세라믹학회 1998 한국세라믹학회지 Vol.35 No.12

A twt -step carbothermal reduction scheme has been employed for the synthesis of SiC whiskers in an Ar or a H2 atmosphere via vapor-solid two-stage and vapor-liquid-solid growth mechanism respectively. It has been shown that the whisker growth proceed through the following reaction mechanism in an Ar at-mosphere : SiO2(S)+C(s)-SiO(v)+CO(v) SiO(v)3CO(v)=SiC(s)whisker+2CO2(v) 2C(s)+2CO2(v)=4CO(v) the third reaction appears to be the rate-controlling reaction since the overall reaction rates are dominated by the carbon which is participated in this reaction. The whisker growth proceeded through the following reaction mechaism in a H2 atmosphere : SiO2(s)+C(s)=SiO(v)+CO(v) 2C(s)+4H2(v)=2CH4(v) SiO(v)+2CH4(v)=SiC(s)whisker+CO(v)+4H2(v) The first reaction appears to be the rate-controlling reaction since the overall reaction rates are enhanced byincreasing the SiO vapor generation rate.

정량적 반응 속도 측정 탐구 도구 개발 -과산화 수소 반응을 이용하여-

권용석,이주호,손미현 한국현장과학교육학회 2022 현장과학교육 Vol.16 No.2

The purpose of this study is to improve the reaction rate measurement experiment with high applicability to school sites by analyzing the research activities related to the reaction rate measurement experiment presented in the 'Reaction Rate and Catalyst' section of the Chemistry II textbook and identifying the problems of the experiment in the textbook. As a result of analyzing 6 types of Chemistry II textbooks, out of 53 inquiry activities, 20 were student-led experimental inquiry activities. And there were two textbooks that included experiments that students could explore on their own to understand the concept of reaction rate. As a result of experimenting with the reaction of dilute hydrochloric acid and magnesium presented in the textbook, it was found that there are several problems. We tried to improve the limitations of solid phase reactants and the problems of the volumetric method. In order to overcome the limitations of solid phase reactants, the decomposition reaction of hydrogen peroxide was used, and the method for measuring gas volume was improved by using a safe, low-chemical, and inexpensive SSC experimental equipment. As a result of the experiment with the improved device and material, it was confirmed that the volume change was very consistent with the theory, the difficulty of installing the experimental device and conducting the experiment was reduced. In addition, it was confirmed that the reaction time was about 15 minutes, which could be sufficiently performed within the class time of 50 minutes. If the improved inquiry device is used in school, it will be helpful for students to learn about the concept of reaction rate, as they can obtain accurate results consistent with the theory in a safe experimental environment.

신용등급 차이와 주가표류현상1)

전경민,이재형,김현표 한국회계학회 2024 회계저널 Vol.33 No.4

본 연구는 2002년부터 2020년까지 국내 상장기업에 대한 신용등급의 자료를 이용하여 기업의 신용등급 차이와 주가표류현상 간의 관계를실증 분석하였다. 주요 결과는 다음과 같다. 첫째, 하나의 기업에 대해 복수의 신용평가기관이 각각 다른 신용등급으로 평가하는 경우 이익공시일이후 주가표류현상이 나타난다는 것을 발견하였다. 이는 신용등급이 일치하는 기업에 비해 불일치하는 기업은 신용평가기관들 사이에 정보비대칭이 존재하거나 평가기업 정보의 불확실성이 높다는 것을 나타내며, 이러한 기업들의 이익정보에 대한 투자자들의 반응 시기가 다르게 나타난 것으로 해석할 수 있다. 둘째, 기대신용등급과 실제신용등급이 불일치한 기업은 주가표류현상이 더 증가하는 것으로 나타났다. 이러한 결과는 기대신용등급과 실제신용등급의 불일치가 발생한 기업은 이러한 등급 차이를 일치시키기 위해, 재량적인 이익조정의 유인이 작용하여, 기업과 투자자 사이에 정보비대칭이 더욱 증가하여 주가표류현상이 증가한 것으로 추론된다. 신용등급 차이가 주가표류현상에 미치는 영향을 살펴본 본 연구는 다음과 같은 공헌점을 갖는다. 첫째, 신용등급 자체의 정보효과를 살펴본 기존의선행연구와는 달리 복수의 신용평가기간 간 평가등급의 차이가 미치는 영향을 분석한 연구라는 점에서 그 의의가 있으며, 둘째, 자본시장 참여자들이 의사결정을 함에 있어 기업의 신용등급에 대한 정보를 이용할 때 복수의 신용평가기관들이 제공하는 신용등급이 불일치하는 경우 투자자들에게추가적으로 유용한 정보로서 가치가 있을 것으로 기대된다. The purpose of this study is to examine the relationship between split credit ratings and post earnings announcement drift. Specifically, we examine whether firms with split credit ratings have higher post earnings announcement drift. The sample of this study is 2,175 Korea listed firm-year observations from 2002 to 2020. Empirical findings are summarized as follows. First, we find that firms with split credit ratings have significantly higher post earnings announcement drift. Second, firms have higher post earnings announcement drift when they are below(above) their expected ratings. Specifically, we find higher post earnings announcement drift when the credit rating lower than expected ratings. The impact on credit ratings evaluation vary depending on firm’s information environment. When firms have higher information asymmetry, they are more likely to have split credit ratings. The difference in credit ratings is due to information asymmetry, and firms with split credit ratings have greater information asymmetry, which can be interpreted as a higher probability of post earnings announcement drift. Nowadays, despite of a growing number of study on the effect of split credit ratings in various fields, it is largely unexplored in accounting literature. This study extends to the literature by relating credit rating to capital market reaction such as post earnings announcement drift..

회사채 신용등급에 대한 차별적 시장반응

박현섭 ( Hyeon Seop Park ),송인만 ( In Man Song ) 한국회계학회 2005 會計學硏究 Vol.30 No.2

본 연구는 외환위기 이후 신뢰성 있는 신용등급에 대한 수요가 확대되는 상황에서 회사채 신용등급 변경에 대한 주식시장의 반응을 상향 및 하향집단으로 구분해서 검토하고 있다. 구체적으로 첫째, 등급변경에 대한 주가반응이 등급변경정도에 따라 차이가 존재하는지 여부를 분석 하였다. 둘째, 동일한 등급변경정도에도 무형자산비중에 따라 시장반응에 차이가 존재하는지 여부와 외환위기 전후의 등급변경 공시에 질적 차이가 있는지를 분석하였다. 분석결과 등급하향의 경우에만 등급변경정도에 따른 정보효과가 존재하는 것으로 나타났다. 이처럼 등급하향의 경우에만 정보효과가 나타나는 이유로는 등급변경의 시기적절성, 발행자 우위의 시장구조, 경영자의 비대칭적 정보공시 유인 등이 제시될 수 있다. 특히 무형자산비중이 큰 기업일수록 등급변경에 따른 시장반응이 큰 것으로 나타났다. 또한 외환위기 전후의 등급변경공시도 시장반응에 차이가 있는 것으로 나타났다. 본 연구를 통해서 신용등급의 유용성이 확인되었다. 또한 지식정보화 사회의 도래와 함께 기업의 무형자산에 대한 효과적인 측정과 보고가 어려워 전통적인 재무제표의 역할이 감소되고 있는 상황에서 무형자산과 관련된 또 하나의 실증적 증거를 제공하고 있다는데 큰 의의를 찾을 수 있다. This study examines bond rating changes. The objectives of this study are a) whether stock price reactions for the rating changes differ depending on the degree of the rating change, and b) the market reactions differ according to the portion of intangible assets out of total assets, given the same degree of the rating change. The results show that the rating change is informative only for the downgrading. This seems to be attributable to the timeliness of rating changes, the market structure in which issuers are in dominant position, and asymmetric announcement of information by management. In cross-sectional analysis, the downgrading samples showed a statistically significant market reaction to the degree of the grade change. In addition, the percentage of intangible assets and the announcement of rating changes after foreign exchange crisis appear to significantly affect the market reaction. For the upgrading change, however, the explanatory power of model is not meaningful. Overall, this study confirms "information contents of credit rating change". In particular, this analysis provides another empirical evidence on the importance of intangible assets when the role of the traditional financial statement has become weak due to the difficulty of effectively assessing and reporting intangible assets.

신용평가등급 변화에 따른 차별적 시장반응

박미희(Park, Mi-Hee),노밝은(Roh, Bahl-Geun) 글로벌경영학회 2014 글로벌경영학회지 Vol.11 No.1

본 연구는 기업의 신용평가등급 변화에 따라 시장의 반응이 어떠한 차이를 보이는지를 검증하는 것을 주된 목적으로 하고, 신용평가 등급이 하락한 경우와 상승한 경우에 따라 시장이 차별적 으로 반응하는지에 대하여 검증하고자 한다. 만약 시장참가자들이 신용평가 등급의 변화를 감지 하고 이를 투자의사결정에 반영한다면, 신용평가등급이 하락하거나 또는 상승함에 따라 차별적인 반응을 보일 것으로 예상된다. 이를 검증하기 위하여, 2004년부터 2008년까지 1,656개의 기업-년 표본을 대상으로 분석을 수행한 결과, 신용평가등급이 하락한 기업의 경우 그렇지 않은 기업에 비하여 시장은 부정적으로 반응하고 있었다. 반면 신용평가등급이 상승한 기업의 경우에는 그렇지 않은 기업에 비하여 긍정적인 시장반응이 나타났다. 또한 신용평가등급이 하락한 기업에 대한 부정적인 평가가 신용평가등 급이 상승한 기업에 대한 긍정적인 평가보다 크게 나타나고 있어, 시장은 신용평가 등급 하락과 상승에 대하여 차별적으로 반응하고 있으며, 부정적인 정보에 대하여 더욱 민감하고 반응하고 있음을 발견하였다. 신용평가등급과 관련한 기존 연구들은 주로 신용평가등급의 개선을 위하여 이익조정을 수행하 는지와 신용평가등급 자체가 주가에 어떠한 영향을 미치는지 분석한 연구가 대부분이다. 본 연구는 이에 더하여 신용평가등급 변화에 초점을 맞추고, 신용평가등급이 상승하는 경우와 하락하는 경우에 따라 차별적인 시장반응이 나타나는지를 검증하였다는 데에 의의가 있다. 일부 선행연구 에서 신용평가등급에 대한 시장반응을 살펴본 바 있으나 신용평가 등급의 상승 또는 하락을 구분 하여 분석을 수행한 연구는 찾아보기 어렵다. 본 연구는 신용평가등급의 변화를 시장에서 감지하고 이를 투자의사결정에 반영하고 있으며, 신용평가 등급이 상승하거나 하락하는 경우에 따라 투자자들이 차별적으로 반응하고 있음을 검증한 최초의 연구로, 본 연구의 결과는 자본시장에서의 다양한 이해관계자들의 투자의사결정에 도움을 줄 것으로 기대되며, 정책당국과 채권자 및 신용 평가정보의 생산자인 신용평가회사의 합리적인 의사결정에도 기여할 수 있을 것으로 판단된다. This study investigates the association between credit rating changes and market reaction. Credit rating agencies provide opinions on the credit worthiness of entities and their obligations. Their role is to improve the efficiency of securities markets by increasing the transparency of securities and reducing information asymmetry between investors and issuers. Anecdotal evidence suggests that managers generally describe their capital structure policy in terms of target credit ratings and tend to make a variety of financing, hedging, and investment choices that allow them achieve their desired rating. Therefore, the credit rating is considered as a useful indicator to investors and bondholders. The sample consists of non-banking firms(1,656 Firm-years)with December fiscal year listed in Korean Stock Exchange over 2004-2008. The credit rating information and other firm-specific data are collected from Kis-Value Ⅲ database. The credit rating haves from 1 point to 10 points. 1 point represents firms with the worst credit rank and 10 points represents firms with the best credit rank. The empirical results are summarized as follows. First, the credit rating downgrades have a non-significantly positive influence on the price. Also, we find that managers have a motivation to obtain higher credit rating because credit ratings affect financing cost and the growth and the profitability of companies. Second, the credit rating upgrades are significantly positive influence on the price. The results in this paper imply that credit significantly changes affect price. This paper will contribute to accounting and tax research that examines price and to several lines of existing research on credit rating as well.

나이퀴스트 표본화 이론을 이용한낙하 충격 실험의최적 표본화 속도 제안

이진영,김단비,권기연,윤영수 한국방재학회 2015 한국방재학회논문집 Vol.15 No.3

Current concrete structures are quite often exposed to terroristic threats. Therefore, estimating concrete mechanical properties under dynamic loading conditions starts to become important. Due to the high rates of loading and highly dynamic behavior of the specimens, it is hard to be applied the same sampling rates used in common static loading tests to dynamic tests. The objective of this study is to estimate effects of concrete types and applying different impact loads on recommended sampling rates for measuring reaction force and acceleration. The recommended sampling rates in this study were determined according to the Nyquist’s sampling theorem. The Nyquist’s theorem states that the sampling rate should be at least twice the maximum response frequency(Nyquist frequency) for avoiding aliasing. The results of this study showed the following things: I) the recommended sampling rates for reaction force and acceleration were not influenced by types of concrete and levels of applied impact energy, but the sampling rates was affected by type of measuring data, ii) the recommended sampling rate for acceleration was faster than that for reaction force, so the sampling rate for entire impact test system should be determined based on the sampling rate for acceleration, iii) there was not any relationship between the frequency at the maximum value in power spectrum and the recommended sampling rate. 최근 테러의 위협이 증가하면서 콘크리트 재료의 충격 저항 특성을 파악하는 것이 중요해지기 시작하였다. 재료 충격 시험은 기존 정하중 조건에서의 재료 시험보다 시험 종료 시점이 빠르므로, 기존 정하중의 표본화 속도를 그대로 적용하기 어렵다. 따라서 충격 실험조건에서 적절한 표본화 속도를 제안하는 연구는 반드시 필요하다. 이에 본 연구에서는 콘크리트 재료의 충격 저항 성능 평가 시험 시요구되는 적절한 표본화 속도를 제안하고자 한다. 적절한 표본화 속도 제안을 위하여, 충격 실험을 통해 측정된 시간 영역의 데이터를주파수 영역의 데이터, 즉 파워 스펙트럼으로 전환하였다. 전환된 파워 스펙트럼에 나이퀴스트 이론을 적용하여, 추천 표본화 속도를결정하였다. 주요 실험 변수는 콘크리트 종류와 가해지는 충격 에너지의 크기였으며, 반력하중과 가속도 측정 데이터를 분석 대상으로하였다. 충격 에너지는 일정한 질량의 추를 시험체에 자유낙하 시켜 가하는 방법을 채택하였다. 연구 수행 결과, 추천 표본화 속도는콘크리트 종류와 가해지는 충격 에너지 크기에 영향을 받지 않고, 반력하중과 가속도 데이터의 종류에만 영향을 받는 것으로 파악되었다. 반력하중 측정을 위한 표본화 속도보다는 가속도 측정을 위한 추천 표본화 속도가 빠르므로, 충격 시험 수행 시 가속도 측정 장비의 표본화 속도를 기준으로 전체 표본화 속도를 결정하는 것이 바람직하다는 결론을 얻었다. 그리고 파워 스펙트럼 상에서 최댓값이발생하는 주파수를 이용한 추천 표본화 속도 추정은 불가능 한 것으로 판단되었다.

Reactive force-field simulation of the effect of heating rate on pyrolysis behavior of lignite

Fang Xu,Qing Wang,Chengchang Wu 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.3

With the help of ReaxFF-MD simulations, the non-isothermal pyrolysis behavior of lignite, especially the effect of heating rate on pyrolysis products, has been investigated in detail. The results demonstrate that increasing the heating rate is very helpful for the production of tar at lower heating rates. By contrast, at relatively high heating rates, further increasing the heating rate has less effect on the distribution of pyrolysis products. Moreover, the evolution tendencies of char and tar at lower heating rates are different from those at the relatively higher heating rates, which exist as remarkable turning points in the high temperature region. This is probably because the reaction time is longer at lower heating rates, and the possibilities of condensation and further decomposition of tar are much greater at high temperatures. Additionally, the relationship between system energy and reaction mechanism was revealed. The results indicate that with the same reaction mechanism, the system energies of non-isothermal pyrolysis are approximately equal and hardly affected by the heating rate. Finally, taking 2 K/ps as an example, the secondary reaction mechanism of tar was further analyzed, and some possible secondary reaction pathways were proposed.