수익률곡선 정보를 활용한 기대수익률 추정 및 금리정책 효과 분석

서상원 ( Sang Won Suh ),최재훈 ( Jae Hun Choi ),박충원 ( Choong Won Park ) 한국금융연구원 2014 금융연구 Vol.28 No.1

We propose a method to extract information about market expectations of future yields using market yield curve. In addition, we empirically analyze the effects of market participants` expectations on the interest rate channel To this end we first set up a theoretical term-structure model and then estimate it with Korean market yield data. After verifying the validity of the model with empirical results, we then use it to assess the effects on market yields of the demand on domestic bonds from foreign investors which have showed wide fluctuations since 2007. Next, we propose a method to extract information about market expectations of future policy rate as well as market yields using market yield curve. We then investigate into the accuracy of those market expectation- based forecasts. In addition to this theoretical term-structure model approach, we also use regression-based approaches to estimate market expectations implied with market yield curve. Using these estimates of market expectations about monetary policy, we then decompose actual policy rate changes into the expected portions and the unexpected ones. This decomposition enables us to analyze the relative importance of the two components in the interest rate channel of This paper contributes to the literature by providing an analysis of monetary policy shock with respect to the interest rate channel of monetary policy which has not been extensively studied yet. In addition, growing effects of foreign investors on bond yields have been rarely studied, which is another contribution of this paper. This paper also provides empirical results for the forecasting ability of market expectations extracted from market yield curve. Our empirical results show that market expectations extracted from yield curve turn out to be useful for yield forecasting. Secondly, after decomposing changes in policy rates into unexpected changes and expected ones, we found that the unexpected changes in policy rate exert impacts no less than the expected changes in policy rate. Lastly, by conducting counter-factual exercises, we found that market yields have been significantly affected by foreign investors` demand on Korean bonds, which has been suspected from the fact that foreign investors` Korean bond holdings has greatly increased since 2007 and then fluctuated widely during the recent global financial crisis period.

정보비대칭과 신용평가사의 평판이 회사채스프레드에 미치는 영향

정윤영,박래수 한국재무학회 2018 한국재무학회 학술대회 Vol.2018 No.05

본 연구는 정보비대칭으로 발생하는 회사채 등급차이와 신용평가사의 평가경향이 회사채 수익률스프레드에 영향을 미치는지에 대하여 분석하였으며, 주요 실증분석결과는 다음과 같 다. 먼저 전체표본을 대상으로 신용평가사 간 평가차이가 회사채스프레드에 영향을 미치는지 에 대해 다중선형회귀모형을 이용하여 분석한 결과, 등급수익률과 상위등급을 통제변수로 설 정한 분석에서 정보비대칭을 나타내는 등급차이여부 변수가 회사채스프레드에 유의한 양의 관계를 보여 정보비대칭가설을 지지하고 있는 것으로 나타났다. 이를 통해 등급차이발생 채 권의 경우 긍정적인 등급정보 보다는 부정적인 등급정보에 치우쳐 수익률스프레드가 결정되 는 것으로 드러났다. 다음으로 신용등급차이 발생 시 신용평가사의 평판과 회사채스프레드와의 관련성을 살펴 본 결과, 평소 보수적인 평가경향을 보이는 B신평사가 신용등급을 보수적 혹은 우호적으로 부여하였을 때 수익률스프레드에 유의한 영향을 미치는 것으로 나타났다. 이는 추가적으로 등급차이 발생채권만을 대상으로 한 분석과도 유사한 결과를 보여, 신용평가사의 평판 가설 역시 타당한 것으로 해석된다. 따라서 신용평가사 간 평가차이에 따른 정보비대칭과 신용평 가사들의 평가경향으로 발생하는 평판이 국내 회사채 스프레드에 영향을 미치고 있는 것으 로 분석되었다. This paper investigate the effect on split bond rating and bond yield spread in Korea. We analyzed the effects of the information asymmetry and Credit Rating Agency's reputation on bond yield spread, which is caused by the split bond rating of CRAs. For analysis, We do multivariate analysis, using bond rating and bond yield spread data in Korea 2004 to 2015. The empirical results are as follows. First, we examined whether information asymmetry affected the bond yield spread using multiple linear regression. As a result, the information asymmetry measured by split rating variable were significant, which supports the information asymmetry hypothesis. Additionally we can find bond yield spread is decided by negative credit grade rather than positive credit grade under split rating condition. Next, we examined the relationship between the reputations of CRAs and the bond yield spreads in case of split rating. As a result, the bond yield spread is changed depending on the specific CRAs grade which having conservative rating tendency. This result similar with CRAs reputation analysis using only split rating sample, which supports CRAs reputation hypothesis. Thus, This result suggest information asymmetry caused by split rating and reputation measured by CRA’s rating tendency are affect bond yield spread.

정보비대칭과 신용평가사의 평판이 회사채 수익률 스프레드에 미치는 영향

정윤영 ( Yun Yeong Jung ),박래수 ( Rae Soo Park ) 한국파생상품학회(구 한국선물학회) 2018 선물연구 Vol.26 No.2

본 연구는 정보비대칭으로 인해 발생하는 회사채 등급차이와 신용평가사의 평가경향으로 나타나는 신용평가사의 평판이 회사채 수익률 스프레드에 미치는 영향을 분석하였다. 주요 실증분석결과는 다음과 같다. 먼저 신용평가사 간 평가차이가 회사채 수익률 스프레드에 영향을 미치는지에 대해 분석한 결과, 등급불일치 현상과 같이 불완전한 정보가 주어졌을 때 추가적인 회사채 수익률 스프레드가 발생하여 정보비대칭가설을 지지하는 것으로 나타났다. 주요 통제변수인 등급변수를 상위등급과 등급수익률 스프레드로 설정한 분석에서는 정보비대칭을 나타내는 등급차이여부변수가 회사채 수익률 스프레드에 유의한 영향을 미쳤으나 하위등급을 기준으로 한 분석에서는 영향을 주지 못하는 것으로 나타나, 등급차이 발생채권의 경우 긍정적인 등급정보 보다는 부정적인 등급정보에 편중되어 수익률 스프레드가 결정되는 것으로 드러났으며, 그 정도는 평균적인 등급수익률 스프레드보다 높은 것으로 나타났다. 다음은 등급차이 발생 시 신용평가사의 평판이 회사채 수익률 스프레드에 영향을 주는지를 살펴본 결과, 상대적으로 보수적인 평가경향을 보이는 신용평가사가 신용등급을 보수적 혹은 우호적으로 부여하였을 때 하위등급 기준에서 수익률 스프레드에 유의한 영향을 미치는 것으로 나타났다. 이는 해당 신용평가사의 상대적 지위나 신뢰성에 따른 수익률 스프레드의 변화가능성을 시사하고 있어 신용평가사의 평판가설을 지지하는 결과로 해석된다. 따라서 신용평가사 간 평가차이에 따른 정보비대칭과 신용평가사들의 평가경향으로 발생하는 평판이 국내 회사채 수익률 스프레드에 영향을 미치고 있는 것으로 분석되었다. This paper investigates the effects of information asymmetry and Credit Rating Agency's reputation on bond yield spread, which is caused by the split bond rating of CRAs. For analysis, We do multivariate analysis, using bond rating and bond yield spread data in Korea from 2004 to 2015. The empirical results are as follows. First, we examines whether information asymmetry affects the bond yield spread. using split rating data. As a result, the information asymmetry measured by split rating variable is significant, which supports the information asymmetry hypothesis. Additionally we can find bond yield spread is decided by negative credit grade rather than positive credit grade under split rating condition. Next, we examines the relationship between the CRA’s reputation and the bond yield spread in case of split rating. Here, samples were divided into full samples and split rating samples. Summarizing the result, both samples are suggest similar result, the bond yield spread is changed depending on the specific CRA’s grading which having conservative rating tendency. Thus, This result suggest information asymmetry caused by split rating and CRA’s reputation measured by CRA’s rating tendency affect bond yield spread in Korea.

Association of Duration and Rate of Grain Filling with Grain Yield in Temperate Japonica Rice (Oryza sativa L.)

Yang, Woon-Ho,Park, Tae-Shik,Kwak, Kang-Su,Choi, Kyung-Jin,Oh, Min-Hyuk The Korean Society of Crop Science 2007 Korean journal of crop science Vol.52 No.1

Grain filling is a crucial factor that determines grain yield in crops since it is the final process directly associated with crops' yield performance. Grain filling process can be characterized by the interaction of rate and duration of grain filling. This study was conducted, using 16 temperate japonica rice genotypes, with aims to (1) seek variations in grain filling duration and rate on area basis, (2) compare the contribution of grain filling duration and rate to grain yield, and (3) examine the influence of temperature and solar radiation for effective grain filling on grain yield in relation to grain filling duration and rate. Grain filling rate and duration exhibited highly significant variations in the ranges of $20.7{\sim}46.3\;g\;m^{-2}d^{-1}\;and\;11.2{\sim}35.5$ days, respectively, depending on rice genotypes. Grain yield on unit area basis was associated positively with grain filling duration but negatively with grain filling rate. Grain filling rate and duration were negatively correlated with each other. Final grain weight increased linearly with the rise in both cumulative mean temperature and cumulative solar radiation for effective grain filling. Higher cumulative mean temperature and cumulative solar radiation for effective grain filling were the results of longer grain filling duration, but not necessarily higher daily mean temperature and daily solar radiation for effective grain filling. Grain filling rate demonstrated an increasing tendency with the rise in daily mean temperature for effective grain filling but their relationship was not obviously clear. It was concluded that grain filling duration, which influenced cumulative mean temperature and cumulative solar radiation for effective grain filling, was the main factor that determined grain yield on unit area basis in temperate Japonica rice.

Photocatalytic CO₂ conversion on highly ordered mesoporous materials: Comparisons of metal oxides and compound semiconductors

Lee, Yoon Yun,Jung, Han Sol,Kim, Ji Man,Kang, Yong Tae Elsevier 2018 Applied Catalysis B Vol.224 No.-

<P><B>Abstract</B></P> <P>In this study, the ordered mesoporous metal oxides (TiO<SUB>2</SUB> and SnO<SUB>2</SUB>) and compound semiconductors (ZnS, ZnSe, CdS, and CdSe) are manufactured and they exhibit several micrometers (μm) of particle size, and high surface area of about 100m<SUP>2</SUP>g<SUP>−1</SUP>. Well-developed crystallinities are prepared <I>via</I> simple nano-replication method by using a 3-D bicontinuous cubic <I>Ia</I>3<I>d</I> meso-structured ordered mesoporous silica KIT-6 as a hard-template. The visible-light-driven photocatalytic CO<SUB>2</SUB> conversion into CH<SUB>4</SUB> is carried out in the presence of H<SUB>2</SUB>O over various mesoporous materials. Prepared mesoporous materials show different light absorption behaviors and photocatalytic activities for conversion of CO<SUB>2</SUB>. The mesoporous compound semiconductors show higher CO yield rates than the mesoporous metal oxides, while mesoporous metal oxides show higher CH<SUB>4</SUB> yield rates than the mesoporous compound semiconductors. Compared to the commercial TiO<SUB>2</SUB> material (P25, Degussa), the mesoporous metal oxides (TiO<SUB>2</SUB>, SnO<SUB>2</SUB>) show 9 to 10 times higher yields of CH<SUB>4</SUB> and 2 to 3 times higher yields of CO owing to their high surface area. Especially, the mesoporous ZnS shows the highest CH<SUB>4</SUB> yield rate (3.620μmolg<SUB>cat</SUB> <SUP>−1</SUP>h<SUP>−1</SUP>) and the mesoporous CdSe shows the highest CO yield rate (5.884μmolg<SUB>cat</SUB> <SUP>−1</SUP>h<SUP>−1</SUP>) out of all photocatalysts considered in the present study. Although mesoporous CdS and ZnSe have great visible light absorption properties, they show relatively low CH<SUB>4</SUB> yield rates.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Highly ordered mesoporous metal oxides and compound semiconductors are manufactured. </LI> <LI> The photocatalytic CO2 conversion experiments are carried out on various mesoporous materials. </LI> <LI> Mesoporous ZnS photocatalyst shows the highest CH4 yield rate. </LI> <LI> Mesoporous CdSe photocatalyst shows the highest CO yield rate. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Average yield rates of CH<SUB>4</SUB> and CO by using various photocatalysts.</P> <P>[DISPLAY OMISSION]</P>

신용등급이 타인자본비용에 미치는 추가적인 정보가치 -비상장기업을 중심으로-

박종일 한국세무학회 2011 세무와 회계저널 Vol.12 No.2

본 논문은 주식시장이 부재한 비상장기업을 대상으로 신용등급이 좋은 기업일수록 기업의 타인 자본비용이 하향조정되는가를 규명하는데 목적이 있다. 특히 타인자본비용에 영향을 미칠 수 있는 기본적인 재무정보 및 기업특성변수를 통제한 후에도 신용등급 정보가 타인자본비용에 추가적인 정보효과(incremental informational value)를 가지고 있는가를 분석하고자 한다. 비상장시장의 채권자들이 회계정보의 질을 반영하는 것 외에도 신용평가기관이 산출하는 신용등급을 고려한 대출 의사결정이 수행되고 있는지에 대해서는 국내외로 잘 알려진 바가 없다. 따라서 본 연구에서는 재무정보나 기업특성을 고려한 후에도 신용정보(credit information)가 추가적인 정보가치가 있는가를 비상장기업의 부채조달비용 관점에서 검증하고자 한다. 본 연구의 가설은 신용평가기관이 공시하는 신용등급 정보에는 기업관련 비공개된 정보까지 정보로서 반영되어 산출된다는 점에서 재무정보(financial information)와는 다른 정보를 내포하고 있을 것으로 기대되며, 그러한 점에서 타인자본비용에 영향을 미칠 수 있는 재무정보 및 기업특성 변수를 고려한 후에도 신용정보는 타인자본 비용에 추가적 정보력을 가질 것으로 기대하였다. 특히 신용등급과 비상장기업의 타인자본비용간에는 역의 관계가 성립할 것으로 예상하였다. 이러한 검증가능한 의문사항을 알아보기 위하여 본 연구는 타인자본비용의 대용치로 부채차입이 자율과 차입이자율 스프레드를 이용하였고, 신용등급은 NICE신용평가정보(주)에서 공시된 기업신용등급 자료를 이용하였다. 또한 타인자본비용의 측정방법도 연속변수와 소수의 순위등급변수인 경우로 나누어 비교분석을 수행하였다. 분석기간은 2004년부터 2009년까지 6년간이며, 표본은 충분한 자료인 46,616개 기업/연 자료가 이용되었다. 연구결과에 따르면, 타인자본비용에 영향을 미칠 수 있는 재무정보나 기업특성을 통제한 후에도 신용등급이 좋은 기업일수록 타인자본비용(부채차입이자율 및 차입이자율 스프레드)은 1% 이내의 수준에서 유의하게 감소된 결과로 나타났다. 이러한 결과는 종속변수를 연속변수로 측정하거나 소수의 순위등급변수로 측정한 경우와 상관없이, 그리고 OLS 결과뿐 아니라 이분산성 및 횡단면-시계열적 종속성 문제를 통제한 후 t 통계치를 제공하는 Newey and West(1987) 검증결과 모두에서 일관성 있게 강건한 것으로 나타났다. 이상의 결과로 볼 때, 비상장시장에서 기업신용정보는 채권자들의 대출의사결정시에 기업의 재무정보나 기업특성 외에도 중요한 정보원으로 활용되고 있음을 시사한다. 국내외로 비상장기업을 대상으로 한 연구가 미미한 실정에서 비상장기업들을 대상으로 타인자본비용의 결정모형에서 재무 정보나 기업특성 변수 외에 신용평가기관의 신용정보가 중요하게 채권자들의 정보원으로 이용되고 있음을 보여주고 있다는 점에서 본 연구는 의의가 있다. 본 연구의 결과는 비상장시장 특히 채권시장에서 채권자들의 대출의사결정과정을 파악하고 이해하는데 있어 도움이 되며, 그러한 맥락에서 학계 및 규제기관에게도 유익한 정보를 제공해 줄 것으로 기대된다. The purpose of this paper is to investigate the effect of credit rating on cost of debt in non-listed firms. A firm’s credit rating reflects a rating agency’s opinion of an entity’s overall creditworthiness and its capacity to satisfy its financial obligations. The principal research issue addressed in this study is the nature of the interrelations between cost of debt, credit ratings, and financial information with particular focus on the role of credit ratings. But the nature of the interrelationships between credit ratings, cost of debt, and financial information has not been fully resolved by previous research. Resolution of these interrelationships is important both as a contribution to the body of accounting research on the properties of accounting numbers and in a practical sense. The importance of credit ratings continues to rise with the globalization of capital markets and the increased use of credit ratings in financial regulation and contracting (Frost 2007). Despite the vital role that credit ratings play in capital markets, relatively little is known about the information used by credit analysts in making rating recommendations. Credit ratings supply a signal about the firms’ default risk. Credit ratings and cost of debt are negatively correlated ; In other words, higher yields are required by debtholders to compensate for the risk of investing in lower-rated (high default-risk). This correlation does not imply causation, however, since credit ratings and cost of debt could be determined by a third factor: concurrent publicly available information. Recent research discussed indicates that both credit ratings and financial information may have independent effects on cost of debt. The research design used in this study provides evidence on the issue of whether credit ratings directly determine the cost of debt, whether financial information directly determines the cost of debt, and whether financial information affects the cost of debt indirectly through determining credit ratings. To do this, this paper use credit ratings from KIS-Value Ⅲ. Initially, 1 point represents firms with the best credit rank and 10 point represents firms with the worst credit rank. However, for the purpose of interpretation, remark credit rank oppositely. That is, 1 point represents firms with the worst credit rank and 10 point represents firms with the best credit rank. For a dependent variable, cost of debt are borrowing’s interests rates and borrowing’s yield spread. The borrowing yield spread is calculated as deducting a 3-year treasury bond from loan interest rate. Observations of this paper are 46,616 firm-year in non-listed companies which are not listed in Korea security market from 2004 to 2009. Findings of this paper are following, firms received a good credit rating after controlling for other financial variables and firms characteristics that affect negatively the cost of debt (borrowing’s interests rates and borrowing’s yield spread). These results are still hold even after appling a fractional ranks variable rather than a continuous variable as a dependent variable. And also t-statistics from Newey and West (1987) are significant, suggesting that this results are robust. This study primary analysis documents that firms’ credit ratings affects the cost of debt. Therefore, these findings of this study are very useful and provide a lot of important implications to regulators, investors and creditors that are interested in cost of debt. Academics can also apply the discussion in this paper for related researches.

유로존 위기와 유럽 국채금리의 결정요인에 관한 연구

강유덕 한국유럽학회 2015 유럽연구 Vol.33 No.3

This study focuses on determinants of sovereign bond yield rate of Eurozone countries in the context of the Euro crisis. Sovereign bond yield rates had been considerably lowered during the preparation of introducing euro and remained converged to German bund level. However, sovereign bond yield rates started to diverge each other from the global financial crisis and fragile countries in Eurozone faced sovereign crisis. European Central Bank has intervened in financial market in increasingly active manner and the crisis was mitigated by its announcement of the Outright monetary transaction (OMT). This study analyzes determinants of sovereign bond yield rates focusing on different periods and examine them in comparative manner for euro and non-euro countries. The empirical study shows that fiscal and macroeconomic variables explained well yield rates of sovereign bond before the introduction of euro. However, fiscal variables increasingly lost their explanatory powers since the introduction of the single currency and this trend had continued till the global financial crisis in 2008. After the crisis, the yield rats started to respond increasingly to fiscal deficit and current account. Since ECB's OMT announcement, influence of current account to yield rate reduced, while fiscal deficit have relatively strong effect on yield rate. In addition, global risk perception seems to exert increasingly strong impact to government bond yield rate of Eurozone countries. This means that Eurozone sovereign markets have been increasingly sensitive to global risk factors. 본 연구는 재정위기의 확산현상을 연구함에 있어 유로존 회원국 국채금리의 결정요인을 분석하였다. 유로화 도입을 전후하여 각국의 국채금리는 하락하여 장기간 독일 국채금리를 중심으로 수렴현상이 유지되었다. 그러나 글로벌 금융위기 이후 취약국의 국채금리가 연쇄적으로 상승하면서 국채 간 금리격차는 확대되었으며, 이는 유로화 체제에대한 위기의식으로 이어졌다. 이 현상은 유럽중앙은행의 국채매입 선언 이후 완화되었다. 본 연구에서는 시기별 유로존 국채금리의 결정요인을 분석하고, 비유로존 국가와의비교를 통해 유로존만의 특수성을 도출하고자 하였다. 실증분석 결과 유로화 도입 이전 재정 및 거시경제상황과 관련된 일반적인 설명변수들은 유로존과 비유로존 회원국의 국채금리에 대해 높은 설명력을 보였다. 반면에 유로화 도입 이후에는 재정관련 변수는 유로존 국채금리 형성에 점차 영향을 미치지 못하였고, 이 현상은 글로벌 금융위기 직전까지 지속되었다. 반면에 2008년의 글로벌 금융위기 이후 국채금리는 각국의 재정상황에 대해 보다 민감하게 반응하기 시작하였으며, 특히 경상수지가 국채금리에 큰 영향을 미치는 것으로 나타났다. 유럽중앙은행의 국채매입 선언 이후 경상수지가 국채금리에 미치는 영향은 현저히 줄어들었으나, 재정수지는 과거에 비해 더 큰 영향을 미치는 것으로 나타났다. 한편 과거에 비해 글로벌 리스크 요인이 유로존 국채금리에 미치는 영향력도 크게 증가한 것으로 나타나는 바, 유로존 국채시장 또한 국제적 차원의 불확실성 증가에 큰 영향을 받는 것으로 나타났다.

금융자산시장에서의 외국인투자와 환율에 관한 연구: 한국의 채권이자율과 주가수익률을 중심으로

홍유정,하홍열 동국대학교 사회과학연구원 2019 사회과학연구 Vol.26 No.1

This study analyzes the correlation between base rate and exchange rate in the bond market and stock market after the global financial crisis of 2008. It empirically tests the transmission mechanism of the bond yields and stock returns to exchange rate from June 2009 to June 2018 by applying structural VAR model. The main findings are as follows. First, there are a positive correlation between base rate and bond yields, a positive correlation between bond yields and foreigners’ bond investment, and a negative correlation between foreigners' bond investment and exchange rate. Second, there are a negative correlation between base rate and stock returns, a positive correlation between stock returns and foreigners' stock investment and a negative correlation between foreigners' stock investment and exchange rate. Third, this study came to the conclusion that there are a negative correlation between base rate and exchange rate in the bond market and a positive correlation between base rate and exchange rate in the stock market. 본 연구는 한국의 금융자산시장에서 채권이자율과 주가수익률이 환율에 미치는 영향을실증분석하는 것을 그 목적으로 한다. 선행연구는 대부분 이자율평가조건을 기본전제로 하여 채권이자율과 환율의 상관관계를 분석하였다. 그런데 분석대상국가, 기간, 통계처리기법에 따라 그 결과가 서로 다르게 나타났다. 한국의 경우에는 자본자유화의 진전, 1997년의외환위기, 2008년의 글로벌금융위기를 겪으면서 채권시장과 주식시장의 상대적 크기가 변화해 온 만큼, 두 시장을 동시에 고려해야 한다. 이에 본 연구는 2009년 6월부터 2018년 6 월까지 한국의 월별통계를 이용하여 채권이자율과 주가수익률이 환율에 미치는 전달경로를분석하였다. 그 결과는 다음과 같다. 첫째, 금리와 채권이자율이 정(+)의 관계라는 가정 하에, 채권이자율과 외국인채권투자는 정(+), 외국인채권투자와 환율은 부(-)의 관계를 갖는것으로 나타났다. 둘째, 금리와 주가수익률이 부(-)의 관계라는 가정 하에 주가수익률과 외국인주식투자는 정(+), 외국인주식투자와 환율은 부(-)의 관계를 갖는 것으로 나타났다. 셋째, 금리는 채권시장과 주식시장 모두에서 환율에 영향을 미치는데 그 영향은 각각 부(-) 와 정(+)으로 나타났다. 결국 분석기간 중 외국인들의 채권투자와 주식투자 중 어느 것이더 규모가 큰가에 따라 금리와 환율의 상관관계는 정반대로 나타날 수 있다.

Strain rate-dependent behaviors of mechanical properties of structural steel investigated using indentation and finite element analysis

Nguyen, Ngoc-Vinh,Pham, Thai-Hoan,Kim, Seung-Eock Elsevier 2019 Mechanics of materials Vol.137 No.-

<P><B>Abstract</B></P> <P>In this study, a series of experiments, which consist of constant strain rate indentation, and optical microscope examination, and finite element analysis were performed to investigate the strain rate-dependent behaviors of the mechanical properties of SS400 structural steel. The microstructures of SS400 steel was characterized using optical microscope examination. The influences of strain rate indentation on the characteristics of the loading/unloading curves were presented and the results showed a higher applied load, a higher loading curvature, and a higher loading work for a higher strain rate level. The strain rate-dependent behaviors of indentation hardness (<I>H</I>), yield strength (<I>σ<SUB>y</SUB> </I>), and work hardening (<I>n</I>) were investigated. When the strain rate level increased, both <I>H</I> and <I>σ<SUB>y</SUB> </I> strongly increased, while work hardening showed an almost linear increase. The strain rate-dependent behaviors of material properties were validated through the experimental and the numerical verifications. The strain rate sensitivity (SRS) value of 0.056 ± 0.02 was reported for SS400 steel and was highly consistent with the general trend reported for several types of structural steel in the literature.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The pile-up phenomena occurred at all strain rate indentation levels, while the pop-in events can be observed to be more pronounced at low strain rate. </LI> <LI> The results showed higher applied load, higher loading curvature, higher total work, and higher contact stiffness for higher strain rate condition. </LI> <LI> The strain rate sensitivity of 0.056 ± 0.03 was well reported for SS400 steel. </LI> <LI> As the strain rate increased, indentation hardness yield stress strongly increased, while work hardening showed an almost linear increase. </LI> <LI> The strain rate-dependent behaviors of both yield stress and work hardening were validated through the experimental and numerical verifications. </LI> </UL> </P>

Association of Duration and Rate of Grain Filing with Grain Yield in Temperate Japonica Rice (Oryza sativa L.)

Woonho Yang,Taeshik Park,Kangsu Kwak,Kyungjin Choi,Minhyuk Oh 韓國作物學會 2007 Korean journal of crop science Vol.52 No.1

Grain filling is a crucial factor that determines grain yield in crops since it is the final process directly associated with crops' yield performance. Grain filling process can be characterized by the interaction of rate and duration of grain filling. This study was conducted, using 16 temperate japonica rice genotypes, with aims to (1) seek variations in grain filling duration and rate on area basis, (2) compare the contribution of grain filling duration and rate to grain yield, and (3) examine the influence of temperature and solar radiation for effective grain filling on grain yield in relation to grain filling duration and rate. Grain filling rate and duration exhibited highly significant variations in the ranges of 20.7~46.3~;g~;m-2d-1~;and~;11.2~35.5 days, respectively, depending on rice genotypes. Grain yield on unit area basis was associated positively with grain filling duration but negatively with grain filling rate. Grain filling rate and duration were negatively correlated with each other. Final grain weight increased linearly with the rise in both cumulative mean temperature and cumulative solar radiation for effective grain filling. Higher cumulative mean temperature and cumulative solar radiation for effective grain filling were the results of longer grain filling duration, but not necessarily higher daily mean temperature and daily solar radiation for effective grain filling. Grain filling rate demonstrated an increasing tendency with the rise in daily mean temperature for effective grain filling but their relationship was not obviously clear. It was concluded that grain filling duration, which influenced cumulative mean temperature and cumulative solar radiation for effective grain filling, was the main factor that determined grain yield on unit area basis in temperate Japonica rice.