Development of thermal barrier coatings with excellent delamination resistant property by extreme internal oxidation

In Japan, the proportion of thermal power generation has increased since after the Great East Japan Earthquake in 2011, accounting for approximately 85% in 2015. Compared to other power generations, thermal power plants have a large amount of carbon dioxide emissions relative to the amount of power generation. Therefore, it is an urgent task to reduce carbon dioxide emissions by improving the efficiency of thermal power plants. Increasing the turbine inlet gas temperature improves the efficiency of the gas turbine thermal power plants. However, high-temperature components, such as rotating blades, are close to their maximum service temperature. Therefore, application of the thermal barrier coating (TBC) on the turbine blade substrate is needed to protect a structure. The TBC system usually consists of ceramic top-coating (TC) and intermediate metallic bond-coating (BC) on a Ni-based superalloy substrate. To reduce the effect of the heat flux on the structure, heat resistant material, such as Yttria-Stabilized Zirconia (YSZ), is commonly used for TC layer. While, for BC, MCrAlY (M: Co and/or Ni) alloy is commonly used to protect the substrate from oxidation and corrosion, as well as to improve the bonding strength between the TC and the BC layers. However, delamination of the TBC can occur, because of significant thermal stresses generated when the coating cools down from high to room temperature. Therefore, improvement of TBC delamination resistance is indispensable. Delamination of the TBC is caused by the Thermally Grown Oxide (TGO) formed at the interface between TC and BC, because of the discrepancy in the thermal expansion coefficient between TGO and TC or BC. Therefore, the TBC formation control is important to improve the delamination resistance of TBC. Previously, authors have succeeded in improving the delamination resistance of TBC by adding cerium (Ce) to the CoNiCrAlY alloy as a BC which assist the formation of the inward TGO. The inward TGO reduces the thermal stress experienced by TBC through the formation of vertical cracks initiated by the inward TGO. However, the inward TGO only forms when the temperature is over 1100°C, which is higher than the substrate temperature during the gas turbine thermal power plants operation temperature. As a result of further research, authors have succeeded in reducing the inward TGO formation temperature to 1000ºC close to the actual use environment by adding ceria (CeO2) instead of Ce to the BC materials. In our studies, it was improved that the TBC delamination resistance thanks to the introduction of internal oxidation during BC formation using High Velocity Oxy-Fuel (HVOF) technique. It was showed that internal oxidation introduced during the film formation proceeded sufficient inward oxide at high-temperature exposure (900°C) and exhibited high delamination resistance. Thus, adding CeO2 to the CoNiCrAlY alloy and introducing internal oxidation during BC formation is efficient to reduce the inward oxide formation temperature. However, when the inward oxide is introduced to BC, the internal oxidation might reduce the oxidation resistance of TBC system. In addition, oxidation and corrosion of the substrate can occur due to direct exposure to the combustion environment through vertical cracks. Therefore, it is needed to develop a new BC combining oxidation resistance and delamination resistance. Two-layer BC is considered. The first layer of the BC, located on the substrate side, has less internal oxidation and helps in the protection of the substrate. The second layer of the BC, located on the TC side, has a lot of internal oxides and improves the coating delamination resistance. Thus, it possible to develop TBC compatible with delamination resistance properties and substrate protection properties. The aim of our study is to improve the delamination resistance of TBC and develop TBC with reduced inward TGO formation temperature. For this purpose, TBC with CeO2 and ZrO2 added to the BC material were prepared. To perform TBC specimens with internal oxide in the BC, BC materials with several particle sizes and several BC spraying methods were used. The internal oxide amount and delamination resistant property of these TBC specimens were evaluated with SEM observation and four-point bending test. And also, the high-temperature oxidation behavior and the delamination resistance of TBC with two layers of BC, aiming to achieve both delamination resistance and substrate protection, were evaluated

Identification of Strain Hardening Phenomena in Sheet Metal at Large Plastic Strains

AbstractA new experimental/numerical method to identify post-necking strain hardening phenomena in ductile sheet metal is presented. The identification of the post-necking strain hardening behaviour is based on the minimization of the external and the internal work in the necking zone during a tensile test. The proposed method takes the material state and the shape of the whole deforming tensile specimen into account. The post-necking hardening behaviour of a cold rolled interstitial-free steel sheet is identified. A hardening law which enables disentangling pre –and post-necking strain hardening behaviour is presented. The method is experimentally validated using an independent material test. For that purpose, the uniaxial tube expansion test is conducted to obtain uniaxial strain hardening behaviour beyond the point of maximum uniform strain in a tensile test. Finally, the presented method is compared with a hydraulic bulge test

The Subaru/XMM-Newton Deep Survey (SXDS) -VII. Clustering Segregation with Ultraviolet and Optical Luminosities of Lyman-Break Galaxies at z~3

We investigate clustering properties of Lyman-break galaxies (LBGs) at z~3 based on deep multi-waveband imaging data from optical to near-infrared wavelengths in the Subaru/XMM-Newton Deep Field. The LBGs are selected by U-V and V-z' colors in one contiguous area of 561 arcmin^2 down to z'=25.5. We study the dependence of the clustering strength on rest-frame UV and optical magnitudes, which can be indicators of star formation rate and stellar mass, respectively. The correlation length is found to be a strong function of both UV and optical magnitudes with brighter galaxies being more clustered than faint ones in both cases. Furthermore, the correlation length is dependent on a combination of UV and optical magnitudes in the sense that galaxies bright in optical magnitude have large correlation lengths irrespective of UV magnitude, while galaxies faint in optical magnitude have correlation lengths decreasing with decreasing UV brightness. These results suggest that galaxies with large stellar masses always belong to massive halos in which they can have various star formation rates, while galaxies with small stellar masses reside in less massive halos only if they have low star formation rates. There appears to be an upper limit to the stellar mass and the star formation rate which is determined by the mass of hosting dark halos.Comment: 16 pages, 15 figures, accepted for publication in Ap

Unilateral Abducens Nerve Palsy as an Early Feature of Multiple Mononeuropathy Associated with Anti-GQ1b Antibody

Patients with anti-GQ1b antibody syndrome show various combinations of ophthalmoplegia, ataxia, areflexia, or altered sensorium as clinical features. We describe herein a unique case with unilateral abducens nerve palsy as an early feature of multiple mononeuropathy involving dysfunctions of the inferior dental plexus and the ulnar nerve, which was thought to be associated with anti-GQ1b antibody. A 27-year-old man presented with acute-onset diplopia. He subsequently experienced numbness not only in the right lower teeth and gums but also on the ulnar side of the left hand. Neurological examinations revealed dysfunctions of the right abducens nerve, the right inferior dental plexus, and the left ulnar nerve, suggesting multiple mononeuropathy. Serum anti-GQ1b antibody was positive. This is a rare case report of a patient with unilateral abducens nerve palsy as an early feature of multiple mononeuropathy associated with anti-GQ1b antibody. We suggest that anti-GQ1b antibody syndrome should be taken into consideration as a differential diagnosis of acute multiple mononeuropathy if ophthalmoplegia is present unilaterally

Increased Circulating Malondialdehyde-Modified Low-Density Lipoprotein Level Is Associated with High-Risk Plaque in Coronary Computed Tomography Angiography in Patients Receiving Statin Therapy

Objective: To evaluate the association of serum malondialdehyde low-density lipoprotein (MDA-LDL), an oxidatively modified LDL, with the prevalence of high-risk plaques (HRP) determined with coronary computed tomography angiography (CTA) in statin-treated patients. Methods: This study was a single-center retrospective cohort comprising 268 patients (mean age 67 years, 58% men) with statin therapy and who underwent coronary CTA for suspected stable coronary artery disease. Patients were classified into two groups according to median MDA-LDL level or median LDL-C level. Coronary CTA-verified HRP was defined when two or more characteristics, including positive remodeling, low-density plaques, and spotty calcification, were present. Results: Patients with HRP had higher MDA-LDL (p = 0.011), but not LDL-C (p = 0.867) than those without HRP. High MDA-LDL was independently associated with HRP (odds ratio 1.883, 95% confidential interval 1.082-3.279) after adjustment for traditional risk factors. Regarding incremental value of MDA-LDL for predicting CTA-verified HRP, addition of serum MDA-LDL levels to the baseline model significantly increased global chi-square score from 26.1 to 32.8 (p = 0.010). Conclusions: A high serum MDA-LDL level is an independent predictor of CTA-verified HRP, which can lead to cardiovascular events in statin-treated patients

合成可能かつ静的検査可能なドメイン専用言語のためのプラットフォーム

学位の種別: 課程博士審査委員会委員 : （主査）東京大学教授 稲葉 雅幸, 東京大学教授 本位田 真一, 東京大学教授 千葉 滋, 東京大学講師 中山 英樹, 東京大学講師 蜂須賀 恵也, 国立情報学研究所准教授 蓮尾 一郎University of Tokyo(東京大学

Numerical analysis of microstrip antenna by using electromagnetic simulators

The probe-fed truncated square patch microstrip antenna is calculated by using WIPL-D based on the method of moment, Micro-Stripes based on TLM method and Fidelty based on FDTD method. Its input impedance and radiation characteristics are compared and discussed.ACES-2004, April 19-23, 2004, Syracuse, N

Association of Oxidized Low-Density Lipoprotein in Nonalcoholic Fatty Liver Disease with High-Risk Plaque on Coronary Computed Tomography Angiography: A Matched Case-Control Study

Nonalcoholic fatty liver disease (NAFLD) is a risk factor for the development of atherosclerotic cardiovascular diseases (CVDs), and oxidative stress has been proposed as a shared pathophysiological condition. This study examined whether oxidized low-density lipoprotein (LDL) is involved in the underlying mechanism that links coronary atherosclerosis and NAFLD. This study included 631 patients who underwent coronary computed tomography angiography (CTA) for suspected coronary artery disease. NAFLD was defined on CT images as a liver-to-spleen attenuation ratio of <1.0. Serum-malondialdehyde-modified LDL (MDA-LDL) and coronary CTA findings were analyzed in a propensity-score-matched cohort of patients with NAFLD (n = 150) and those without NAFLD (n = 150). This study analyzed 300 patients (median age, 65 years; 64% men). Patients with NAFLD had higher MDA-LDL levels and a greater presence of CTA-verified high-risk plaques than those without NAFLD. In the multivariate linear regression analysis, MDA-LDL was independently associated with NAFLD (beta = 11.337, p = 0.005) and high-risk plaques (beta = 12.487, p = 0.007). Increased MDA-LDL may be a mediator between NAFLD and high-risk coronary plaque on coronary CTA. Increased oxidative stress in NAFLD, as assessed using MDA-LDL, may be involved in the development of CVDs

The Association of Triglyceride to High-Density Lipoprotein Cholesterol Ratio with High-Risk Coronary Plaque Characteristics Determined by CT Angiography and Its Risk of Coronary Heart Disease

The triglyceride to high-density lipoprotein cholesterol (TG/HDL-C) ratio is an independent risk index for cardiovascular events. This study aimed to evaluate the association between TG/HDL-C ratio and coronary plaque characteristics as seen on coronary computed tomography angiography (CCTA) and the corresponding increase in the likelihood of cardiovascular events. A total of 935 patients who underwent CCTA for suspected coronary artery disease (CAD) were included. High-risk plaques (HRP) were defined based on three characteristics: positive remodeling, low-density plaques, and spotty calcification. Significant stenosis was defined as luminal narrowing of >70%. Patients with a higher TG/HDL-C ratio showed significantly greater prevalence of HRP and significant stenosis than patients with low TG/HDL-C ratios (p < 0.01). Multivariate logistic analysis demonstrated that the TG/HDL-C ratio was significantly associated with the presence of HRP (p < 0.01) but not with significant coronary stenosis (p = 0.24). During the median follow-up period of 4.1 years, 26 cardiovascular events including cardiovascular death and acute coronary syndrome occurred. The highest TG/HDL-C tertile was associated with cardiovascular events, with the lowest TG/HDL-C tertile as the reference (hazard ratio, 3.75; 95% confidence interval, 1.04-13.50). A high TG/HDL-C ratio is associated with the presence of CCTA-verified HRP, which can lead to cardiovascular events in patients with suspected CAD