ABSTRACT
The development of a cost-effective and accurate model for predicting the fatigue life of materials is essential for designing thermal power plants and assessing their structural reliability under operational conditions. This paper reports a novel energy-based approach for developing unified models that predict the fatigue life of boiler tube materials in ultra-supercritical (USC) power plants. The proposed method combines the Masing behavior with a cyclic stress-strain relationship and existing stress-based or strain-based fatigue life prediction models. Notably, the developed models conform to the structure of the modified Morrow model, which incorporates material toughness (a temperature compensation parameter) into the Morrow model to account for the effects of temperature. A significant advantage of this approach is that it eliminates the need for tensile tests, which are otherwise essential for assessing material toughness in the modified Morrow model. Instead, all material constants in our models are derived solely from fatigue test results. We validate our models using fatigue data from three promising USC boiler tube materials-Super304H, TP310HCbN, and TP347H-and their welded joints at operating temperatures of 500, 600, and 700 °C. The results demonstrate that approximately 91% of the fatigue data for all six materials fall within a 2.5× scatter band of the model's predictions, indicating a high level of accuracy and broad applicability across various USC boiler tube materials and their welded joints, which is equivalent to the performance of the modified Morrow model.
ABSTRACT
Highly selective etching of silicon nitride (Si3N4) and silicon dioxide (SiO2) has received considerable attention from the semiconductor community owing to its precise patterning and cost efficiency. We investigated the etching selectivity of Si3N4 and SiO2 in an NF3/O2 radio-frequency glow discharge. The etch rate linearly depended on the source and bias powers, whereas the etch selectivity was affected by the power and ratio of the gas mixture. We found that the selectivity can be controlled by lowering the power with a suitable gas ratio, which affects the surface reaction during the etching process. X-ray photoelectron spectroscopy of the Si3N4 and QMS measurements support the effect of surface reaction on the selectivity change by surface oxidation and nitrogen reduction with the increasing flow of O2. We suggest that the creation of SiOxNy bonds on the surface by NO oxidation is the key mechanism to change the etch selectivity of Si3N4 over SiO2.
ABSTRACT
The importance of monitoring the electron density uniformity of plasma has attracted significant attention in material processing, with the goal of improving production yield. This paper presents a non-invasive microwave probe for in-situ monitoring electron density uniformity, called the Tele-measurement of plasma Uniformity via Surface wave Information (TUSI) probe. The TUSI probe consists of eight non-invasive antennae and each antenna estimates electron density above the antenna by measuring the surface wave resonance frequency in a reflection microwave frequency spectrum (S11). The estimated densities provide electron density uniformity. For demonstration, we compared it with the precise microwave probe and results revealed that the TUSI probe can monitor plasma uniformity. Furthermore, we demonstrated the operation of the TUSI probe beneath a quartz or wafer. In conclusion, the demonstration results indicated that the TUSI probe can be used as an instrument for a non-invasive in-situ method for measuring electron density uniformity.
ABSTRACT
Additively manufactured austenitic stainless steel 316L is composed of a cellular structure, which has a directionality, and is observed with a different morphology depending on the observation direction. The cellular structure morphology that appears with a high probability in grains with a specific grain orientation is determined. Taylor factor, which is calculated by considering grain orientation, is related to cellular structure morphology due to the directional cellular structure in additively manufactured austenitic stainless steel 316L. The Taylor factor affects the mechanical properties. The yield strength of additively manufactured SUS316L can be explained by the correlation between cellular structure morphology, grain orientation, and Taylor factor.
ABSTRACT
Arcing is a ubiquitous phenomenon and a crucial issue in high-voltage applied systems, especially low-temperature plasma (LTP) engineering. Although arcing in LTPs has attracted interest due to the severe damage it can cause, its underlying mechanism has yet to be fully understood. To elucidate the arcing mechanism, this study investigated various signals conventionally used to analyze arcing such as light emission, arcing current and voltage, and background plasma potential. As a result, we found that light emission occurs as early as 0.56 µs before arcing current initiation, which is a significant indicator of the explosive development of arcing as well as other signals. We introduce an arcing inducing probe (AIP) designed to localize arcing on the tip edge along with multiple snapshot analysis since arcing occurs randomly in space and time. Analysis reveals that the prior light emission consists of sheath and tip glows from the whole AIP sheath and the AIP tip edge, respectively. Formation mechanisms of these emissions based on multiple snapshot image analysis are discussed. This light emission before arcing current initiation provides a significant clue to understanding the arcing formation mechanism and represents a new indicator for forecasting arcing in LTPs.
Subject(s)
Cold Temperature , Weapons , TemperatureABSTRACT
We demonstrated how the photoelectrochemical (PEC) performance was enhanced by conformal deposition of an amorphous molybdenum sulfide (a-MoSx) thin film on a nanostructured surface of black Si using atomic layer deposition (ALD). The a-MoSx is found to predominantly consist of an octahedral structure (S-deficient metallic phase) that exhibits high electrocatalytic activity for the hydrogen evolution reaction with a Tafel slope of 41 mV/dec in an acid electrolyte. The a-MoSx has a smaller work function (4.0 eV) than that of crystalline 2H-MoS2 (4.5 eV), which induces larger energy band bending at the p-Si surface, thereby facilitating interface charge transfer. These features enabled us to achieve an outstanding kinetic overpotential of â¼0.2 V at 10 mA/cm2 and an onset potential of 0.27 V at 1 mA/cm2. Furthermore, the a-MoSx layer provides superior protection against corrosion of the Si surface, enabling long-term PEC operation of more than 50 h while maintaining 87% or more performance. This work highlights the remarkable advantages of the ALD a-MoSx layer and leads to a breakthrough in the architectural design of PEC cells to ensure both high performance and stability.
ABSTRACT
Precipitation strengthening has been the basis of physical metallurgy since more than 100 years owing to its excellent strengthening effects. This approach generally employs coherent and nano-sized precipitates, as incoherent precipitates energetically become coarse due to their incompatibility with matrix and provide a negligible strengthening effect or even cause brittleness. Here we propose a shear band-driven dispersion of nano-sized and semicoherent precipitates, which show significant strengthening effects. We add aluminum to a model CoNiV medium-entropy alloy with a face-centered cubic structure to form the L21 Heusler phase with an ordered body-centered cubic structure, as predicted by ab initio calculations. Micro-shear bands act as heterogeneous nucleation sites and generate finely dispersed intragranular precipitates with a semicoherent interface, which leads to a remarkable strength-ductility balance. This work suggests that the structurally dissimilar precipitates, which are generally avoided in conventional alloys, can be a useful design concept in developing high-strength ductile structural materials.
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Mitochondrial targeted therapy is a next-generation therapeutic approach for cancer that is refractory to conventional treatments. Mitochondrial damage caused by the excessive accumulation of reactive oxygen species (ROS) is a principle of mitochondrial targeted therapy. ROS in nonthermal plasma-activated media (NTPAM) are known to mediate anticancer effects in various cancers including head and neck cancer (HNC). However, the signaling mechanism of HNC cell death via NTPAM-induced ROS has not been fully elucidated. This study evaluated the anticancer effects of NTPAM in HNC and investigated the mechanism using transcriptomic analysis. The viability of HNC cells decreased after NTPAM treatment due to enhanced apoptosis. A human fibroblast cell line and three HNC cell lines were profiled by RNA sequencing. In total, 1 610 differentially expressed genes were identified. Pathway analysis showed that activating transcription factor 4 (ATF4) and C/EBP homologous protein (CHOP) were upstream regulators. Mitochondrial damage was induced by NTPAM, which was associated with enhancements of mitochondrial ROS (mtROS) and ATF4/CHOP regulation. These results suggest that NTPAM induces HNC cell death through the upregulation of ATF4/CHOP activity by damaging mitochondria via excessive mtROS accumulation, similar to mitochondrial targeted therapy.
Subject(s)
Head and Neck Neoplasms/metabolism , Mitochondria/metabolism , Reactive Oxygen Species/metabolism , Apoptosis/drug effects , Cell Line, Tumor , Cell Survival/drug effects , Cisplatin/pharmacology , Drug Resistance, Neoplasm/drug effects , Head and Neck Neoplasms/drug therapy , Humans , Mitochondria/drug effects , Transcriptome/physiologyABSTRACT
(1) Background: Nonthermal plasma (NTP) induces cell death in various types of cancer cells, providing a promising alternative treatment strategy. Although recent studies have identified new mechanisms of NTP in several cancers, the molecular mechanisms underlying its therapeutic effect on thyroid cancer (THCA) have not been elucidated. (2) Methods: To investigate the mechanism of NTP-induced cell death, THCA cell lines were treated with NTP-activated medium -(NTPAM), and gene expression profiles were evaluated using RNA sequencing. (3) Results: NTPAM upregulated the gene expression of early growth response 1 (EGR1). NTPAM-induced THCA cell death was enhanced by EGR1 overexpression, whereas EGR1 small interfering RNA had the opposite effect. NTPAM-derived reactive oxygen species (ROS) affected EGR1 expression and apoptotic cell death in THCA. NTPAM also induced the gene expression of growth arrest and regulation of DNA damage-inducible 45α (GADD45A) gene, and EGR1 regulated GADD45A through direct binding to its promoter. In xenograft in vivo tumor models, NTPAM inhibited tumor progression of THCA by increasing EGR1 levels. (4) Conclusions: Our findings suggest that NTPAM induces apoptotic cell death in THCA through a novel mechanism by which NTPAM-induced ROS activates EGR1/GADD45α signaling. Furthermore, our data provide evidence that the regulation of the EGR1/GADD45α axis can be a novel strategy for the treatment of THCA.
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Flattened plates often show the lower or higher yield strength than initial leveled plates because tensile and compressive strains are repeatedly experienced at outer and inner walls during the pipe-forming and flattening, but reasons for the yield-strength variation after the pipe-forming are not sufficiently verified yet. In this study, ten line-pipe steels were fabricated by controlling alloying elements and finish rolling temperatures (FRTs), and the yield strength of pipe-flattened steel plates was predicted by using cyclic simulation tests, based on competing contributions of Bauschinger effect (BE) and strain hardening (SH) effect quantified from yield drop (YD) and yield rise (YR) parameters, respectively. High-FRT-treated steels (H steels) showed the lower BE and the higher SH than low-FRT-treated steels (L steels), thereby resulting in the smaller yield-strength reduction. This lower BE in the H steels was caused by the lower total boundary density, while the higher SH was caused by the higher fraction of granular bainite. According to the SH analyses between the YR parameters obtained from cyclic simulation tests and the yield ratios obtained from ordinary tensile tests, the decrease in yield-strength reduction with decreasing yield ratio was not attributed to the increase in ordinary tensile SH but to the increase in YR parameter.
ABSTRACT
Reversible solvent-triggered single-crystal-to-single-crystal (SCSC) transformations are observed between two copper(II) azamacrocyclic complexes: [Cu(C16H38N6)(H2O)2](C12H6O4) (1) and [Cu(C16H38N6)(C12H6O4)] (2). Complex (1) was prepared via self-assembly of a copper(II) azamacrocyclic complex containing butyl pendant groups, [Cu(C16H38N6)(ClO4)2], with 2,7-naphthalenedicarboxylic acid. When monomeric compound (1) was immersed in CH3OH, coordination polymer (2) was obtained, indicating a solvent-triggered SCSC transformation. Furthermore, when (2) was immersed in water, an reverse SCSC transformation from (2) to (1) occurred. Complex (1) presents a 3D supramolecular structure formed via intermolecular hydrogen-bonding interactions, whereas complex (2) features a 1D zigzag coordination polymer. The reversible SCSC transformation of (1) and (2) was characterized using single-crystal X-ray diffraction and in situ powder X-ray diffraction techniques. Despite its poor porosity, complex (2) displayed interesting CO2 adsorption behaviour under CO2 gas.
ABSTRACT
Photoelectrochemical (PEC) cells, which represent a promising technology for the production of hydrogen fuel through water splitting reactions, must meet two criteria to achieve high-performance operation: (i) a high thermodynamic open-circuit potential and (ii) a low kinetic overpotential. Herein, we achieved these criteria in both an oxygen-evolving n-Si photoanode and hydrogen-evolving p-Si photocathode by simple electrodeposition of a nanocrystalline thin film of Ru. The bifunctional electrocatalytic activity of the nanocrystalline Ru led to low overpotentials in both the acidic oxygen evolution reaction (0.27 V) and alkaline hydrogen evolution reaction (0.04 V). In addition, the nanocrystalline Ru/Si junctions influenced the interface energetics via the induction of an extrinsic electrochemical potential on the surface of the Ru nanocrystals through a redox reaction rather than the chemical potential of the electrons (work function) of bulk Ru. The nanocrystalline Ru film exhibited bipolar applicability, enabling both Ru/n-Si and Ru/p-Si junctions with high Voc values of 0.63 and 0.5 V, respectively. As a result, the n-Si photoanode in the acidic electrolyte and the p-Si photocathode in the alkaline electrolyte generated a photocurrent of 10 mA/cm2 at record values of 0.87 and 0.42 V versus the reversible hydrogen electrode, respectively. These results provide insight into the development of high-performance PEC cells based on a nanocrystalline electrocatalyst.
ABSTRACT
Since flattened steel sheets often show the unexpectedly lower or higher yield strength than leveled sheets, unceasing efforts have been made to accurately predict the yield strength in pipe-forming industries. In the present investigation, the yield strength of line-pipe or casing-pipe steels was predicted by competing Bauschinger effect and strain hardening occurred during the pipe-forming. Yield drop (YD) and yield rise (YR) parameters were newly defined from cyclic simulation analyses of outer and inner walls of pipes to express more reasonably the Bauschinger effect and strain hardening. The YD increased abruptly until the pre-strain of about 1%, and then saturated, while the YR increased linearly with increasing pre-strain. By combining the YD and YR, the variation in yield strength (Δσ) showed a down-and-up behavior as the Bauschinger effect and strain hardening were dominant at low and high pre-strains, respectively, and plausibly explained the relationship of Δσ and piping strain used in pipe-forming industries. According to the microstructural analyses related to the down-and-up Δσ behavior, the polygonal ferrite reduced the yield-strength reduction in the low pre-strain range, whereas the granular bainite or pearlite expanded it. This yield strength prediction coupled with microstructural analyses provide a good idea for designing and reliably predicting the yield strength of in various steel pipes.
ABSTRACT
We demonstrated surface passivation of a black Si-based solar cell using an (NH4)2S solution to mitigate surface recombination velocity. Incorporated S at the interface between atomic-layer-deposited Al2O3 and black Si by (NH4)2S solution treatment boosted the density of negative fixed charges, S-enhanced field-effect passivation. Furthermore, NH4OH generated during (NH4)2S solution treatment removed the defective Si phase at the black Si surface, the surface cleaning effect. The optimized (NH4)2S solution treatment significantly enhanced the internal quantum efficiency up to â¼17.2% in the short wavelength region, suggesting suppressed surface recombination. As a result, photoconversion efficiency of the cell increased from 11.6 to 13.5%, by 16% compared to the control cells without (NH4)2S solution treatment.
ABSTRACT
OBJECTIVE: The psoas muscle (PS), 1 of the paravertebral core muscles, is associated with sarcopenia. It also has clinical relevance in lateral-access spinal surgery (LASS) as a determinant structure affecting the operative window. We aimed to identify age-related patterns of PS degeneration, and we propose that our results be used to evaluate the operative window in LASS. METHODS: We included 164 participants with back pain, no leg symptoms or claudication, and normal lumbar lordosis and sagittal balance. We evaluated the cross-sectional morphology of the PS on magnetic resonance imaging, specifically assessing the anterior to posterior (AP)/medial to lateral (ML) ratio and the cross-sectional area (CSA). We assessed the locational relationship of the PS and the intervertebral disc using the anterior margin gap (AMG; the distance between the anterior margins of the PS and the intervertebral disc) and the center gap, and compared all measurements by surgical level, sex, and age group. RESULTS: At the L2-3 to L4-5 levels, the PS showed a decreased AP/ML ratio, increased CSA, ventral retraction of the anterior margin without center shift, and decreased operative window length. The degeneration patterns were decreased ML width and CSA and dorsal retraction of the anterior margin. Youth, male sex, and lower lumbar level were associated with higher AMGs, indicating an increased need for the transpsoas approach in LASS. CONCLUSIONS: In patients without sagittal imbalance, the PS showed significant imaging characteristics. Our detailed data may aid the identification of degeneration patterns and specific preoperative planning regarding the operative window for LASS.
Subject(s)
Aging/pathology , Back Pain/diagnostic imaging , Psoas Muscles/diagnostic imaging , Sarcopenia/diagnostic imaging , Adult , Age Factors , Aged , Female , Humans , Magnetic Resonance Imaging , Male , Middle Aged , Organ Size , Psoas Muscles/pathology , Sarcopenia/pathology , Sex Factors , Young AdultABSTRACT
Quasi-static and dynamic compressive properties of an FCC-based metastable HEA (composition; V10Cr10Fe45Co35 (at.%)) showing both Transformation Induced Plasticity (TRIP) and TWinning Induced Plasticity (TWIP) were investigated at room and cryogenic temperatures. During the quasi-static and dynamic compression at room temperature, the FCC to BCC TRIP occurred inside FCC grains, and resulted in very high strain-hardening rate and consequently maximum compressive strength over 1.6 GPa. The dynamic compressive strength was higher by 240 MPa than the quasi-static strength because of strain-rate-hardening effect, and kept increasing with a high strain-hardening rate as the twinning became activated. The cryogenic-temperature strength was higher than the room-temperature strength as the FCC to BCC TRIP amount increased by the decrease in stability of FCC phase with decreasing temperature. Under dynamic loading at cryogenic temperature, twins were not formed because the increase in SFE due to adiabatic heating might not be enough to reach the TWIP regime. However, the dynamically compressed specimen showed the higher strength than the quasi-statically compressed specimen as the strain-rate-hardening effect was added with the TRIP.
ABSTRACT
The title compound, [Cu(NO3)2(C10H16N2O)], has been synthesized and characterized by synchrotron single-crystal diffraction at 100â K. The CuII ion has a distorted square-pyramidal coordination geometry with two N and one O atoms of the C10H16N2O ligand and one nitrate anion in the equatorial plane and another nitrate anion at the axial position. The equatorial Cu-N and Cu-O bond lengths are in the range 1.9608â (14)-2.0861â (15)â Å, which are shorter than the axial Cu-Onitrate bond length [2.1259â (16)â Å]. In the crystal, mol-ecules are linked via inter-molecular N-Hâ¯O and O-Hâ¯O hydrogen bonds, forming a sheet structure parallel to the bc plane. The sheets are further linked through a face-to-face π-π inter-action [centroid-centroid distance = 3.994â (1)â Å]. Weak inter-molecular C-Hâ¯O inter-actions are also observed in the sheet and between adjacent sheets.
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Among a variety of comorbidities of ankylosing spondylitis (AS), the association between dementia and AS by using an extensive dataset from the Korean National Health Insurance System was evaluated in this study. We extracted 15,547 newly diagnosed AS subjects among the entire Korean population and excluded wash-out patients (n = 162) and patients that were inappropriate for cohort match (n = 1192). Finally, 14,193 subjects were chosen as the AS group, and through 1:5 age- and sex-stratified matching, 70,965 subjects were chosen as the control group. We evaluated patient demographics, household incomes, and comorbidities, including hypertension, diabetes, and dyslipidemia. The prevalence of overall dementia (1.37%) and Alzheimer's dementia (AD) (0.99%) in the AS group was significantly higher than in the control group (0.87% and 0.63%), respectively. The adjusted hazard ratio of the AS group for overall dementia (1.758) and AD (1.782) showed statistical significance also. On the other hand, the prevalence of vascular dementia did not differ significantly between the two groups. Subgroup analyses revealed the following risk factors for dementia in the AS group: male gender, greater than 65 years in age, fair income (household income greater than 20% of the median), urban residency, no diabetes, and no hypertension. From the nationwide, population-based, retrospective, longitudinal cohort study, AS patients showed a significantly higher prevalence of overall dementia and Alzheimer's dementia. Comprehensive patient assessment using our subgroup analysis could help to prevent dementia in patients suffering from AS.
Subject(s)
Dementia/epidemiology , Spondylitis, Ankylosing/epidemiology , Adult , Aged , Alzheimer Disease/epidemiology , Cohort Studies , Comorbidity , Databases, Factual , Dementia, Vascular/epidemiology , Diabetes Mellitus/epidemiology , Female , Humans , Hypertension/epidemiology , Longitudinal Studies , Male , Middle Aged , Prevalence , Proportional Hazards Models , Republic of Korea/epidemiology , Retrospective Studies , Risk Factors , Young AdultABSTRACT
A heterojunction of TiO2 grown on g-C3N4 particles is demonstrated using atomic layer deposition (ALD), equipped with a specifically designed rotary reactor for maintaining stable mechanical dispersion of g-C3N4 particles during ALD. The photocatalytic activity of the g-C3N4@ALD-TiO2 core-shell composites was examined using the degradation of rhodamine B dye under visible light irradiation. The optimal composite with 5 ALD cycles of TiO2 exhibited the highest photocatalytic reaction rate constant among the composites with a range of ALD cycles from 2 to 200 cycles, which was observed to be 3 times higher than that of pristine g-C3N4 and 2 times higher than that of g-C3N4@TiO2 composite prepared using a simple impregnation method. The ALD-TiO2 were well-dispersed on the g-C3N4 surface, while TiO2 nanoparticles were agglomerated onto the g-C3N4 in the g-C3N4@TiO2 composite prepared by the impregnation method. This created uniform and stable heterojunctions between the g-C3N4 and TiO2, thus, enhancing the photocatalytic activity.