Effect of Heat Treatment on Microstructure and Fracture Behavior of STS304-Zr Alloys for Metal Waste Forms

Three kinds of STS304-Zr alloys were fabricated by varying the Zr content, and their microstructure and fracture properties were analyzed. Moreover, we performed heat treatment to improve their properties and studied their microstructure and fracture properties. The microstructure of the STS304-Zr alloys before and after the heat treatment process consisted of α-Fe and intermetallics: Zr(Cr, Ni, Fe)2 and Zr6Fe23. The volume fraction of the intermetallics increased with an increasing Zr content. The 11Zr specimen exhibited the lowest hardness and fine dimples and cleavage facets in a fractured surface. The 15Zr specimen had high hardness and fine cleavage facets. The 19Zr specimen had the highest hardness and large cleavage facets. After the heat treatment process, the intermetallics were spheroidized and their volume fraction increased. In addition, the specimens after the heat treatment process, the Laves phase (Zr(Cr, Ni, Fe) 2) decreased, the Zr6Fe23 phase increased and the Ni concentration in the intermetallics decreased. The hardness of all the specimens after the heat treatment process decreased because of the dislocations and residual stresses in α-Fe, and the fine lamellar shaped eutectic microstructures changed into large α-Fe and spheroidized intermetallics. The cleavage facet size increased because of the decomposition of the fine lamellarshaped eutectic microstructures and the increase in spheroidized intermetallics.11Yscopuskc

무형가치와 공시행태에 관한 연구

학위논문(박사)--서울대학교 대학원 :경영대학 경영학과,2019. 8. 백복현.This dissertation is comprised of two essays on intangible value and disclosing behaviors. The first essay, entitled Firm Innovation and Narrative R&D Disclosure, investigates the association between firms innovativeness and their narrative disclosures on research and development (R&D) activities. As innovation becomes increasingly more important for product market competition, firms R&D activities for new products/technologies are of interest to investors as well as competitors in the product markets. Using all available annual reports (Form 10-K) for U.S. firms, I examine whether firm innovation increases or decreases their narrative R&D disclosure in annual reports. My textual analysis of narrative R&D disclosures in annual reports shows that high-innovation firms tend to be less forthcoming in providing information about their R&D investment activities. This tendency is stronger when firms face severe competition in the product markets, while it is weaker when they anticipate external financing. These findings, together, suggest that firms narrative R&D disclosure is an outcome of the tradeoff between proprietary costs and valuation benefits, and that firm innovation tips the scales towards proprietary costs, thereby decreasing narrative R&D disclosure. The second essay, entitled Trust and Disclosure Transparency in Financial Reporting of Government Agencies, examines the impact of trust on disclosure transparency in financial reporting of government agencies. Using unique data from Korean central government agencies (hereafter agencies) for the period of 2011-2015, I provide evidence that trust enhances government financial disclosure transparency. Specifically, I document that high-trust agencies are more likely to classify their accounting errors as material and disclose these errors (as a separate line item) in financial statements. This contrasts with the practice of low-trust agencies that classify similar-magnitude accounting errors as immaterial and conceal them in undisclosed internal filings. I further find that high-trust (low-trust) agencies tend to provide more disaggregated (aggregated) service cost information. In cross-sectional analyses, I find that the impact of trust on both disclosure of accounting errors and disaggregation of service cost information is amplified when agencies have an outsider head, are more decentralized, and face higher parliamentary inspection pressure, the situations in which more information coordination is required. Taken together, my findings suggest that trust contributes to higher disclosure transparency of government financial reporting by facilitating internal information flow.본 논문은 무형가치와 공시행태에 관한 두 개의 독립된 논문으로 구성된다. 기업혁신과 서술적 연구개발 공시 제하의 첫 번째 논문은 기업의 혁신 수준이 연구개발활동에 대한 서술적 공시에 미치는 영향을 분석한다. 시장경쟁 환경에서 혁신 가치의 중요성이 증대됨에 따라 새로운 제품과 기술에 대한 기업의 연구개발활동은 투자자는 물론 동일 시장에서 활동하는 경쟁기업에게도 주요 관심사항으로 작용하고 있다. 1997년부터 2010년까지 미국 상장사 사업보고서(Form 10-K)를 토대로 분석한 결과 혁신 수준이 높은 기업일수록 연구개발활동에 대한 서술적 정보 공시에 미온적 경향을 보이는 것으로 관측된다. 이러한 기업혁신과 서술적 연구개발 공시 간의 음(-)의 관계는 해당 기업이 속한 시장의 경쟁 수준이 높을수록 강화되는 반면, 향후 외부자금조달 계획이 예정된 경우 완화되는 것으로 나타난다. 이상의 분석결과는 서술적 연구개발 공시가 경쟁기업에게 유리한 정보가 유출됨에 따라 발생가능한 재산적 비용(proprietary cost)과 외부정보이용자에게 유용한 정보를 제공함으로써 기대되는 가치평가 효익(valuation benefits) 간의 상충관계가 전략적으로 고려된 산출물이며, 기업혁신은 가치평가 효익에 대한 기대보다 재산적 비용에 대한 우려를 상대적으로 크게 증가시켜 결과적으로 서술적 연구개발 공시 감소에 기여하고 있음을 시사한다. 신뢰와 중앙부처 재무보고 투명성 제하의 두 번째 논문은 우리나라 중앙부처의 조직내 신뢰 수준이 해당 부처의 재무보고 투명성에 미치는 영향을 분석한다. 2011년부터 2015년까지 우리나라 중앙부처의 고유 데이터를 토대로 분석한 결과 신뢰 수준이 높은 중앙부처일수록 재무투명성이 높은 것으로 관측된다. 구체적으로 신뢰 수준이 높은 중앙부처일수록 회계오류 발생시 이를 중대한 오류로 간주하여 재무제표상 별도 계정과목으로 공시하는 경향이 강하게 나타나는 바, 이는 신뢰 수준이 낮은 중앙부처일수록 유사 규모의 오류를 중대하지 않은 것으로 간주하여 해당 오류를 외부공시 없이 내부보고로 종결하는 행태와 대비된다. 신뢰 수준이 높은(낮은) 중앙부처일수록 세분화(통합)된 예산집행정보를 제공함으로써 구체적 활동내역 공개에 적극적 (소극적)인 경향을 보이는 것도 동일한 맥락에서 해석가능하다. 추가 횡단면 분석에서는 부처 수장이 외부출신인 경우, 조직의 분산화 수준이 높은 경우, 국회로부터의 조사 압력이 높은 경우 등 정보통합(information coordination) 노력이 크게 요구되는 상황에서 신뢰 수준이 회계오류 공시나 예산집행정보 세분화 수준에 미치는 영향이 일관되게 증대되는 방향으로 나타난다. 상기 분석결과는 조직내 신뢰 수준이 정보통합 비용을 감소시켜 원활한 내부정보흐름을 유도함으로써 중앙부처의 재무보고 투명성 제고에 기여하고 있음을 시사한다.Essay 1. Firm Innovation and Narrative R&D Disclosure 1 1. Introduction 2 2. Literature Review and Hypothesis Development 10 3. Research Design 14 3.1. Data 14 3.2. Research Design 15 3.2.1. R&D Disclosure Opacity 15 3.2.2. Innovativeness 18 3.2.3. Regression Models 19 4. Results 20 4.1. Descriptive Statistics and Correlations 20 4.2. Univariate Analysis 22 4.3. Multivariate Analysis 23 5. Additional Analyses 25 5.1. Competition and R&D Disclosure Opacity 25 5.2. Capital Market Transactions and R&D Disclosure Opacity 29 5.3. Firm Innovation and Protection of Proprietary Value 31 5.4. Alternative Model Specifications for R&D Disclosure Opacity 32 5.5. Propensity Score Matching 34 5.6. R&D Disclosure Opacity and Financial Reporting Quality 36 5.7. Other Issues 37 5.7.1. Reverse Causality 37 5.7.2. Correlated Omitted Variables Problem 38 6. Conclusion 39 Appendix A. Examples of Qualitative R&D Disclosure 42 Appendix B. Sample Selection Process 47 Appendix C. Variable Definition 48 Appendix D. Conceptual Distinction between Missing R&D and Opaque R&D 51 References 52 Essay 2. Trust and Disclosure Transparency in Financial Reporting of Government Agencies 80 1. Introduction 81 2. Literature Review and Hypothesis Development 90 2.1. Trust 90 2.2. Materiality Decision 91 2.3. Disaggregation of Financial Information 93 2.4. Hypothesis Development 95 3. Research Design 98 3.1. Data 98 3.2. Main Variables 99 3.2.1. Disclosure Transparency in Financial Reporting of Central Government Agencies 99 3.2.1.1. Concealment of Accounting Errors 99 3.2.1.2. Aggregation of Service Cost Information 101 3.2.2. Trust of Central Government Agencies 103 3.3. Regression Models 105 4. Results 107 4.1. Descriptive Statistics and Correlations 107 4.2. Multivariate Analysis 109 4.2.1. Trust and Concealment of Accounting Errors 109 4.2.2. Trust and Aggregation of Service Cost Information 111 5. Additional Analyses 112 5.1. Insider- versus Outsider-Head 112 5.2. Centralization versus Decentralization 113 5.3. Parliamentary Inspection Pressure 115 5.4. Other Discussions and Analyses 116 5.4.1. Reverse Causality 116 5.4.2. Large Government Agencies 120 5.4.3. Inflation Adjustment 121 5.4.4. Detailed Expense Items 121 6. Conclusion 122 Appendix A. List of Government Agencies used in the Analyses 124 Appendix B. Sample Selection Process 125 Appendix C. Financial Reporting Example of Korean Central Government Agencies 126 Appendix D. Variable Definition 130 Appendix E. Anti-Corruption Survey Questions 132 References 135Docto

페라이트계 경량철강의 압연 균열 및 기계적 특성에 미치는 κ-carbide의 영향

DoctorMany efforts to reduce the weight of steel plates in automotive industries have been conducted in order to increase fuel efficiency and to decrease CO2 emissions. In addition to light weight needs, automotive steels require excellent strength to sustain automotive structures and to reduce the impact or shock in cases of accidents. Thus, highly deformable steel plates such as transformation induced plasticity (TRIP) steels and twinning induced plasticity (TWIP) steels have been actively developed. Recently, a large amount of Mn and Al has been added to automotive steels to achieve the lightweight effect as well as excellent strength and ductility, and their total amounts are generally larger than 15 wt.%. This addition leads to about 10% weight reduction in comparison with TRIP or TWIP steels, and often offers excellent properties such as strengths of over 780 MPa and elongation of over 30%. Lightweight steels containing a large amount of Mn have posed problems of the increased manufacturing cost or the deteriorated productivity due to the temperature decrease of the melt during the steel-making process. Thus, efforts to reduce the Mn content have been made. When the Mn and Al addition is lower than 10 wt.%, however, the productivity decreases because cracks often occur on hot-rolled and cold-rolled steel plates. Since the lightweight steels containing about 10 wt.% of Mn and Al are ones of new advanced steels under recent development, the detailed formation process of microstructures or the deformation and fracture mechanisms are hardly known. Furthermore, very few studies have been conducted in order to systematically explain the deformability and cracking phenomenon of rolled steel plates in terms of microstructural parameters, except some studies related with the textures and the segregation of precipitates.Alloying elements used for lightweight steels mainly include Mn, Al, and C because the decreased specific gravity due to substitutional or interstitial atoms works to reduce the weight. Mn raises the volume fraction of austenite at high temperatures as an austenite stabilizer, but the increased Mn content often leads to the formation of a large amount of ferrite during cooling. It also poses problems such as increased manufacturing costs and deteriorated productivity because the temperature of the steel melt can be lowered during the steel-making process. Thus, efforts to reduce the Mn content in the lightweight steels have been made. Al, a ferrite stabilizer, helps form a dual phase structure of ferrite and austenite at high temperatures, and promotes the precipitation during cooling. When the steels contain hardenability elements such as C, precipitates such as carbides or nitrides are well formed, and the amount of precipitates varies with contents of Mn and Al as well as C. According to these precipitates, the steels often expose to the cracking occurring during cold rolling.Several recent investigations revealed that the Al addition up to ~10 wt.% into the high Mn austenitic steels is beneficial for achieving not only remarkable weight savings but also mechanical properties comparable to or better than those of TWIP steels. These improvements mainly result from the SFE increase with increasing the Al content in the high Mn austenitic steels and the corresponding change of the deformation mode from TWIP to dislocation slip. It is also reported that the C addition into the high Mn–Al austenitic steels provides further strengthening by κ-carbides precipitation. As compared to austenite-base lightweight steels, however, the ferrite-base lightweight steels have not been received attention at all. Considering that the properties of steels are largely dependent on the types of constituent phases, it is of scientific and technological interests to study the deformation and fracture behavior, and mechanical properties of lightweight steels with various matrix and second phases.Lightweight steels can be divided into austenite- and ferrite-based ones according to their matrix microstructures. Typical austenitic lightweight steels are transformation-induced plasticity (TRIP) steels or twinning-induced plasticity (TWIP) steels, in which the austenite is stabilized at room temperature. There have been many researches which intend to increase the formability by adding Al, which raises the stacking fault energy and stabilizes the ferrite, and by controlling deformation mechanisms. Ferritic lightweight steels have advantages of lightweight effects because of the higher content of Al rather than Mn. They have only the ferrite as a matrix at room temperature, although both the austenite and ferrite exist at high temperatures. The development of ferritic lightweight steels started in late 1990’s as Baligidad et al., suggested Fe-Al-C alloying systems. Controlling Al and C contents in 8.5~11 wt.% and 0.5~1.0 wt.%, respectively, both the strength and ductility were improved by homogeneously distributing large amounts of κ-carbides, which have the composition of (Fe,Mn)3-Al-C and perovskite structure. In 1980’s when researches on κ-carbides just began, it was thought that κ-carbides had a harmful effect on ductility because of its hardness, and the formation of κ-carbides was inhibited by adding precipitation-hardening elements such as B, Ti, and Nb. Recently, κ-carbides have been used for increasing mechanical properties by controlling their size, fraction, and distribution. However, the formation processes of κ-carbides have not yet been fully understood, and it still has been reported that κ-carbides induced the cracking by forming band structures during hot- or cold-rolling of ferritic lightweight steels. Therefore, for the successful development of ferritic lightweight steels, the verification of formation mechanisms of κ-carbides, which can vary with rolling or heat-treatment conditions, is essentially needed. From these understandings, it is possible to fabricate lightweight steels without any defects and to improve their mechanical properties simultaneously

First Record of the Genus Dracognomus Allen & Noffsinger, 1978 (Desmodorida, Draconematidae) from a Geniculate Coralline Algal Bed in the Intertidal Zone of the Northwest Pacific Ocean

We report a novel occurrence of the free-living marine nematode genus Dracognomus Allen & Noffsinger, 1978 (Desmodorida, Draconematidae), identified from geniculate coralline algal assemblages in the intertidal zone along the eastern coast of Korea in the Northwest Pacific Ocean. This newly documented species of Dracognomus is distinguished from its congeners by the following features: a relatively long body length (522 ㎛); long and straight amphids positioned almost entirely behind the rostrum (7 ㎛), extending to the fifth body annule; presence of both normal and modified adhesion tubes; and body annules with minute spine-like ornamentation along their margins. Morphological details and illustrations of this Dracognomus species were acquired using differential interference contrast microscopy. Furthermore, we provide information on the geographic distribution and character comparisons for species within the genus Dracognomus.2