Path Changes Research Articles

Enhanced deep-water circulation facilitated rare earth elements enrichment in pelagic sediments from the northwestern Pacific Ocean

The lack of knowledge about the enrichment mechanism of rare earth elements and yttrium (REY) in deep-sea sediments is impeding the development of theories and exploration strategies for pelagic REY-rich sediments. Ocean circulation variability seems to be crucial in enriching REY in pelagic sediments, which, however, has not been extensively studied. Here, we examined the Pb-Nd isotopic signals of bottom water recorded by the authigenic ferromanganese oxyhydroxide fractions, as well as the Mn/Al and Mn/Ti ratios of bulk samples from a well-dated sediment core in the northwestern Pacific Ocean. These proxies consistently indicate that enhanced deep-water circulation occurred in the study area at ∼11.5–9.5 Ma, which was most likely to be caused by changes in the flow path of bottom currents. The age of this distinct event consists with the forming age of highly REY-rich sediments. We propose that enhanced deep-water circulation in seamount areas could increase the flux of micronodules and fish debris into the pelagic sediments, facilitating the scavenging of REY from seawater. Our findings establish a connection between enhanced deep-water circulation and the enrichment of REY in pelagic sediments.

Joint Microstructure and Performance of Brazing Si3N4‐MoSi2 Composites to Nb with AgCuTi and AgCuTi+MoSi2p Active Fillers

MoSi2 particle (MoSi2p), the component of Si3N4‐MoSi2 composites, is added into an AgCuTi filler to strengthen the interface bonding without bringing new elements into the Nb/Si3N4‐MoSi2 brazed joint. In this new brazing system, microstructure evolution and strength of Nb/Si3N4‐MoSi2 joints as a function of brazing temperature and holding time, as well as MoSi2p content, are investigated. With an AgCuTi filler, the reaction of active Ti and Si3N4‐MoSi2 forms a composite layer consisting of Mo5Si3, TiN, and Ti5Si3 at the interface. The extensive growth of the layer is observed from 1.9 μm at 860 °C to 5.0 μm at 920 °C, and from 1.3 μm for 5 min to 4.6 μm for 20 min as the chemical reactions between Ti and Si3N4‐MoSi2 are more sufficient. Adding 6 wt% MoSi2p to the filler, the joints exhibit a peak shear strength of 154 MPa, an increase of 20% over that of a commercial AgCuTi filler, with the fracture path changing from the Si3N4‐MoSi2 to the brazing seam. The enhancement of the joint is attributed to the reinforcement of the seam by in situ reaction of the dispersed MoSi2p with Ti, refining the microstructure and reducing the thickness of the Mo5Si3+TiN+Ti5Si3 reaction layer.

Personalized process–type learning path recommendation based on process mining and deep knowledge tracing

Personalized learning path recommendation considers learning goals, learning abilities, and other personalized characteristics of learners to generate a suitable learning path. Existing approaches include global optimal and local iterative path recommendation, which recommend a sequence of learning objects. Consequently, the learner can only learn in the order specified by the learning path, which provides limited flexibility for the learner. In addition, existing studies cannot both present the complete path and handle changes in the learner's knowledge state while learning along the path. This study proposes a process-type learning path model and its recommendation approach, which presents a learning path in the form of a flowchart and dynamically recommends path branches according to the knowledge states of the learner during the learning process. Specifically, deep knowledge tracing is used to annotate the knowledge states of learners in historical logs, and process mining is used to generate a personalized process–type learning path that contains sequences, parallel relationships, and selection relationships between learning objects. In addition, the correlation between the knowledge state and the selection of different branches of a learning path in historical logs can be obtained via decision mining. Thus, a branch recommendation model is trained and used to recommend a path branch in a process-type path with the highest probability of mastering the target learning object of the learner based on the learner's knowledge state. The experimental results demonstrate that the learning effectiveness and efficiency of the proposed approach are better than those of the existing approaches.

High-Frequency Electrochemical Impedance Spectroscopy for Detecting Li Deposition Toward Assessing Thermal Stability in LiBs

Li-deposition is a critical factor in one of the degradation modes of lithium-ion batteries (LiB). The Li-deposition increases the risk of internal short circuits and lowers thermal runaway onset temperature, compromising safety1. Detecting the Li-deposition is possible through disassembly or analysis using large-scale equipment such as muonic X-ray visualization 2. On the other hand, a non-destructive and convenient evaluation technique is required to assess batteries’ safety in commercial use.A novel inspection technique using high-frequency electrochemical impedance spectroscopy (HF-IS) has been developed to detect the presence of Li-deposition3. Electrochemical impedance spectroscopy (EIS), which nondestructively observes ionic diffusion, reaction, and charge transfer in 10 mHz to 10 kHz response, is commonly used for diagnosing the state of battery degradation4. Compared to the conventional EIS, the HF-EIS uses the real part of battery impedance Re(Zbat ) above 100 kHz, allowing observation of only the electronic behavior of the battery in high-frequency regions where ion behavior cannot be tracked. It utilizes the phenomenon of current concentration at interfaces of materials with different conductivities, known as the "skin effect," which is caused by a high-frequency electromagnetic field. Since the Li-deposition occurs at the interface between the negative electrode and the electrolyte, the interface within the high-frequency current path changes from the negative electrode to the Li-metal. This change induces alterations in the electromagnetic field and the high-frequency current path, subsequently resulting in a variation in Re(Zbat ).Figure 1 displays a representative result illustrating the relationship between the thermal runaway onset temperature and the change in Re(Zbat )| freq =1MHz. We conducted a degradation test to deposit Li-metal and a thermal runaway test using two types of 18650 cylindrical cells (NCA-3400 mAh, NCM-2650 mAh). Two batteries subjected to excessive charging C-rates demonstrated the proportional relationship between the decrease in thermal runaway onset temperature and the reduction in Re(Z bat)| freq =1MHz in individual cases. The results indicate that different battery types have different thermal stability of LiB against the Li-deposition.The HF-EIS is not only a safety diagnostic tool but can also contribute to developing battery materials by reducing destructive testing costs. This method of on-the-spot safety quantification diagnosis is expected to contribute to the safer proliferation of the LiBs.Reference1 Li, Y. L. et al. Thermal Runaway Triggered by Plated Lithium on the Anode after Fast Charging. Acs Applied Materials & Interfaces 11, 46839-46850 (2019). https://doi.org/10.1021/acsami.9b165892 Umegaki, I. et al. Nondestructive High-Sensitivity Detections of Metallic Lithium Deposited on a Battery Anode Using Muonic X-rays. Analytical Chemistry 92, 8194-8200 (2020). https://doi.org/10.1021/acs.analchem.0c003703 Ishigaki, M. et al. Operando Li metal plating diagnostics via MHz band electromagnetics. Nature Communications 14, 7275 (2023). https://doi.org/10.1038/s41467-023-43138-w4 Barsoukov, E. Impedance Spectroscopy Theory, Experiment, and Applications Second Edition Preface. Impedance Spectroscopy: Theory, Experiment, and Applications, 2nd Edition, XII-+ (2005). Figure 1

Business model innovations in high-velocity environments

High-velocity environments trigger Schumpeterian changes in industry structure, consumer preferences, and technological paths. The ensuing uncertainties lower entry barriers and diminish the efficacy of technological innovations in sustaining the competitive advantage. Further, lower entry barriers encourage forays by new entrants that may use existing technologies with business model innovations (BMI), posing a significant challenge for incumbents. Against this backdrop, our paper investigates the relatively unexplored role of BMI in high-velocity environments by studying three innovating firms from the global consumer devices industry. We propose that high-velocity environments not only necessitate but also facilitate BMI by enabling new and unexplored possibilities for value creation and appropriation. Our results underscore the role of BMI as a critical response strategy, particularly in high-velocity environments.

Analysis of Precipitable Water Vapor, Liquid Water Path and Their Variations before Rainfall Event over Northeastern Tibetan Plateau

A ground-based microwave radiometer (MWR) provides continuous atmospheric profiles under various weather conditions. The change in total precipitable water vapor (PWV) and liquid water path (LWP) before rainfall events is particularly important for the improvement in the rainfall forecast. However, the analysis of the PWV and LWP before rainfall event on the plateau is especially worth exploring. In this study, the MWR installed at Xining, a city located over the northeastern Tibetan Plateau, was employed during September 2021 to August 2022. The results reveal that the MWR-retrieved temperature and vapor density demonstrate reliable accuracy, when compared with radiosonde observations; PWV and LWP values during the summer account for over 70% of the annual totals in the Xining area; both PWV and LWP at the initiating time of rainfall events are higher during summer, especially after sunset (during 20-00 local solar time); and notably, PWV and LWP anomalies are enhanced abruptly 8 and 28 min prior to the initiating time, respectively. Furthermore, the mean of LWP anomaly rises after the turning time (the moment rises abruptly) to the initiating time; as the intensity of rainfall events increases, the occurrence of the turning time is delayed, especially for PWV anomalies; while the occurrence of the turning time is similar for both convective cloud and stratiform cloud rainfall events, the PWV and LWP anomalies jump more the initiating time; as the intensity of rainfall events increases, the occurrence of the turning time is delayed, especially for PWV anomalies; while the occurrence of the turning time is similar for both convective cloud and stratiform cloud rainfall events, the PWV and LWP anomalies jump more dramatically after the turning time in convective cloud events. This study aims are to analyze the temporal characteristics of PWV and LWP, and assess their potential in predicting rainfall event.

Navigating Delays: A Comprehensive Study of Public Building Retrofitting Projects in Kathmandu Valley

The objective of the study was to find out the present scenario of delays of retrofitting of public building with case of 11projects of Kathmandu valley. An observation and study of the project document is carried out along with questionnaire survey with 50 respondents. The maximum rate of delay in the retrofitting project is found to be 167% time overrun and minimum is found to be 42% of time overrun. Only one project among them is within the schedule with physical progress of 22%. A multiple linear regression analysis was performed to examine the influence of the variables Time overrun (Months) and Time extension with respect to initial contract (%) on the variable Physical Progress. A model summary model is obtained as follows: Physical Progress = 0.57 + 0.02 * Time overrun (Months) - 0.15 * Time extension with respect to initial contract (%) The top ranked specific delay contributing factors in a retrofitting project are as found as Impractical project schedule and duration (frequent changes in critical path), Unavailability of the numbers and skilled workforce for retrofitting projects, Delays occurred due to lack of coherence in architectural, structural, electrical, sanitary, and HVAC drawings, Approvals of shop drawings submitted by the contractor and Unavailability of the specific materials as per BOQ.

Low Temperature NO and CO Conversion with a Mechanistic Approach on Ru-Composed Cerium Oxide.

Catalytic reduction of NO with CO at a lower temperature is an extremely challenging task, thus requiring conceivable surfaces to overcome such issues. Ru-substituted CeO2 catalysts prepared via the solution combustion method were employed in CO oxidation and NO-CO conversion studies. The characterization for material formation and surface structure was carried out through XRD, SEM, TEM, and BET surface area. The catalytic study revealed the promising behavior of 5% Ru in CeO2 for the 100% conversion of NO-CO at 150 °C, proving it to be an excellent exhaust material. These observed results are also supported by temperature-programmed studies, i.e. TPD of NO and CO in addition to NH3-TPD and H2-TPR for their convincible surface interaction that is inclined toward a significant change in the conversion path. Additionally, the proposed mechanism, based on the experimental evidence, sheds light on the NO-CO redox reaction, directing the reaction pathway toward the Langmuir-Hinshelwood and Mars-Van Krevelen-type route. Moreover, the exceptional performance can be attributed to the strategic incorporation of Ru in CeO2, where the strong interaction of Ru-Ce is able to gain a high synergy for NO and CO conversion.

Mechanical properties of AlCoCrFeNi2.1 EHEA controlled via the coherent nano-precipitated phase during hot rolling

In the present work, the AlCoCrFeNi2.1 EHEA was hot rolled in multiple passes at different temperatures and reductions. The L12/B2 lamellar eutectic structure of the as-cast alloy disappeared after hot rolling and evolved into an irregular distribution of FCC and B2 phases resembling a heterogeneous structure. Combined with SEM and TEM microscopic characterization, it is evident that the nanoprecipitates in both the FCC and B2 phases simultaneously maintain a highly coherent relationship with their matrix structure, with the ordered L12 nanoprecipitates in FCC phase rich in Al and Ni, and the disordered BCC nanoprecipitates in B2 phase rich in Cr. The strength of the alloy can be greatly improved through microstructure evolution which can be directly derived from the back stress effect in the heterogeneous structure. The tensile fracture morphology and fracture mechanism were analyzed to further study this effect. More importantly, this work examined the effects of changes in the mean-free path of the dislocation induced by the morphology evolution and density of the nanoprecipitates on the mechanical properties. As a result, the microstructure and mechanical properties of hot rolled AlCoCrFeNi2.1 EHEA can be controlled to a certain extent.

Dynamic Interferometry With Retrace Error Correction Using Fringe Projection For High-Gradient Fields

This paper introduces an innovative approach aimed at advancing the characterization of high-gradient flow fields through the integration of dynamic interferometry and fringe projection techniques. Traditional interferometry offers a precise tool sensitive to optical path changes, typically used to measure refractive index variations induced by factors such as density changes in fluid flow. Rays are usually considered as straight lines, and refraction can be neglected. However, in scenarios involving high-gradient fields, such as supersonic flow with shock waves, optical path changes due to ray bending become significant. In these high-gradient fields, the trajectory of the ray is altered, leading to longer optical paths (resulting in incorrect values) and geometric distortions of the image (resulting in inaccuracies in position). Although retrace error corrections using numerical models of refractive index distribution can mitigate some effects, complete compensation is often challenging. To address this, our proposed technique integrates fringe projection, which is highly sensitive to ray deflections caused by variations in the index of refraction within a transparent medium. The method involves projecting a precisely defined multiplexed cosine fringe pattern across the measured area. Modifications in the pattern indicate ray bending, providing data for interferometric corrections. Real-time interferometry is seamlessly combined with the fringe projection technique to compensate for optical path length changes and mitigate mapping errors induced by ray deflections. The dynamic nature of this combined approach enables the instantaneous capture of both interferometric and fringe-projection data, making it a suitable tool for real-time measurements. Experimental verification of the technique demonstrates its efficacy, with a comparative study against traditional interferometry showcasing a significant reduction in mapping errors.

Effect of strain path and short-term post-annealing on the microstructure, texture, and mechanical anisotropy of low-carbon steel

In this research, the effect of strain path and short-term post-annealing on the microstructure, texture, and mechanical anisotropy of low-carbon steel was investigated. Asymmetric unidirectional rolling (AUR) and asymmetric cross rolling (ACR) were applied on Fe-0.072C steel. The ACR-processed sheet revealed a very limited number of new grains compared to the AUR-processed sheet, which was due to the dynamic recovery induced by strain path change. The average ferrite grain size of the post-annealed AUR- and ACR-processed samples was 11.5 and 14.1 μm, respectively. The dominant recrystallization in the annealed AUR-processed sheet was discontinuous static recrystallization, while that in the annealed ACR-processed sheet was continuous static recrystallization. The weak typical rolling textures (γ-fiber and α-fiber) at the midthickness of both rolled sheets demonstrated that the shear deformation effectively contributed to the formation of the shear textures during asymmetric cold rolling. The ACR decreased the intensity of the overall texture more than the AUR process due to the changes in the reference frame of deformation after each pass, which destabilized ideal texture components. The results showed that Goss and {111}〈112〉 components were continuous and discontinuous static recrystallization textures in the asymmetrically cold-rolled low-carbon steel sheet during the annealing treatment, respectively. The annealed AUR-processed sheet revealed a weaker texture as compared to the annealed ACR-processed sheet. The significant changes in the preferred orientations of the annealed AUR-processed sample led to weaker texture intensity compared to the annealed ACR-processed sheet. The hardness of the annealed AUR-processed sheet (183.8 HV) was higher than that of the annealed ACR-processed steel (156.9 HV), which was owing to the larger grain size and also the elimination of the γ-fiber texture in the annealed ACR-processed sheet. The strength along the rolling direction was lower than that along the transverse direction in the AUR-processed sheet. However, in the ACR-processed sheet, the values of strength were similar along three different tensile directions. As an important conclusion, if both high-strength and low-anisotropy are needed in the low-carbon steel sheets, it's better to apply ACR rather than AUR. In addition, if both high toughness and low anisotropy are essential, it's better to use AUR followed by post-annealing rather than ACR + post-annealing. The length of the intermediate stage of work hardening in the annealed ACR-processed sample was much less than the annealed AUR-processed sheet due to the presence of harder orientations (〈111〉 and 〈110〉) along rolling and transverse directions in the annealed ACR-processed sample. Finally, the fracture behavior of deformed and post-annealed steel sheets for both strain paths was ductile and shear ductile.

O-264 Profiling Tumor-Initiating Cells in Uterine Leiomyoma through Single-Cell Multi-omics

Abstract Study question What are the molecular and cellular features that contribute to the transformation of myometrial stem cells into tumor-initiating cells within uterine leiomyoma? Summary answer Transformative changes in differentiation and genetic processes, in a distinct subset of M/LM cells drives their progression into a tumorigenic state. What is known already Uterine leiomyomas (LM), which are benign smooth muscle-derived tumours of myometrium, impact approximately 75% of women, causing significant physical and psychological challenges and imposing substantial healthcare costs. The widespread consensus postulates a monoclonal origin for LM, implying their derivation from a dysregulated single multipotent stem cell that could give rise to tumor-initiating cells (TICs). While previous studies have shown cellular heterogeneity in both myometrium (M) and LM, the precise identity of the originating cells is unknown. Study design, size, duration Prospective, observational, and biomedical study conducted at Hospital La Fe (Valencia, Spain) for one year. Eight sample pairs of LM and M underwent single-nuclei RNAseq (snRNA-seq; n = 16) and single-cell proteomic (scP; n = 16) analyses, to generate a detailed transcriptomic and proteomic map decoupled from cell type, state, and spatial location. We further employed single-cell RNA velocity inference for differentiation trajectory [BR1] analysis of mesenchymal cells, followed by the identification of potential driver genes in LM tumorigenesis. Participants/materials, setting, methods Upon obtaining informed consent, we procured LM and M samples from eight patients aged 35-50 undergoing hysterectomies. Part of these samples were preserved in paraffin for spatial transcriptomics utilizing VISIUM (10x Genomics). The remaining tissues were dissociated into single-cell suspensions and underwent scRNA-seq and scP using Chromium Controller and Orbitrap Eclipse Tribid mass spectrometry, respectively. The analysis of the collected data was carried out using publicly accessible R/Python tools. Main results and the role of chance Analysis of snRNAseq (∼52,000 cells) revealed similar cellular compositions in M and LM, including endothelial, perivascular, smooth muscle cells (SMC), fibroblasts, and immune cells. Further trajectory analysis unveiled a subset of myometrial cells with potential as TICs, exhibiting reduced expression of hormone receptors like PGR. Analysis of these cells [BR1] suggested differentiation into two distinct cell types -fibroblasts and SMCs- with elevated hormone expression over pseudotime. Differential analysis between M and LM also showed a dysregulated transcriptomic profile in the TICs within the tumor, as evidenced by upregulation of RAD51B and HMGA2 and downregulation PGR among other genes. These genes are indicative markers, underscoring their significant roles in the tumorigenesis of LM by influencing hormone response and disrupting DNA repair mechanisms. Spatial transcriptomic analysis confirmed these findings and suggested that the distribution of TICs could be ubiquitous, since the expression of potential myometrial-stem markers, was markedly increased only on certain spots within the tissue across both LM and M. Lastly, scProt profiling (∼5,000 cells) also allowed the identification of putative TICs, which showed upregulation in LM of specific proteins involved in replication, transcription, and translation. Limitations, reasons for caution Our study sets the basis for TICs isolation in LM, yet functional validation studies need to be performed to address the clinical potential of our findings. Further studies including more patients, and addressing racial disparities will help to generalize these findings to a broader population. Wider implications of the findings Our findings indicate the presence of a particular subset of M/LM cells whose changes in differentiation path and genetic processes seem to drive the transformation of these cells into a tumorigenic state to develop LM. Targeting these markers might show promise for effectively treating these tumors. Trial registration number NCT04214457

A Practical Approach to Tracking Estimation Using Object Trajectory Linearization

In the field of image processing and machine vision, object tracking is a significant and rapidly developing subfield. The numerous potential applications of object tracking have garnered much attention in recent years. The effectiveness of tracking and detecting moving targets is directly related to the quality of motion detection algorithms. This paper presents a new method for estimating the tracking of objects by linearizing their trajectories. Estimating the movement paths of objects in dynamic and complex environments is one of the fundamental challenges in various fields, such as surveillance systems, autonomous navigation, and robotics. Existing methods, such as the Kalman filter and particle filter, each have their strengths and weaknesses. The Kalman filter is suitable for linear systems but less efficient in nonlinear systems, while the particle filter can better handle system nonlinearity but requires more computations. The main goal of this research is to improve the accuracy and efficiency of estimating the movement paths of objects by combining path linearization techniques with existing advanced methods. In this method, the nonlinear model of the object's path is first transformed into a simpler linear model using linearization techniques. The Kalman filter is then used to estimate the states of the linearized system. This approach simplifies the calculations while increasing the estimation accuracy. In the subsequent step, a particle filter-based method is employed to manage noise and sudden changes in the object's trajectory. This combination of two different methods allows leveraging the advantages of both, resulting in a more accurate and robust estimate. Experimental results show that the proposed method performs better than traditional methods, achieving higher accuracy in various conditions, including those with high noise and sudden changes in the movement path. Specifically, the proposed approach improves movement forecasting accuracy by about 12% compared to existing methods. In conclusion, this research demonstrates that object trajectory linearization can be an effective tool for improving object tracking estimation. Combining this technique with existing advanced methods can enhance the accuracy and efficiency of tracking systems. Consequently, the results of this research can be applied to the development of advanced surveillance systems, self-driving cars, and other applications.

Towards reliability assessment of ultra-wideband microwave leakage monitoring in detecting stringer debondings in composite airframes

Ultra-wideband guided electromagnetic waves have been proposed recently for non-destructive testing and structural health monitoring applications. Among the multitude of possible microwave waveguides, recent works explored the concept of microwave leakage monitoring to detect stringer debondings in hollow carbon composite structures. The principle is to monitor the wave propagation characteristics within the cavity formed by the stringer and the airframe skin using transmission measurements. Changes in the transmission path, e.g. occurring from microwave leakage in the debonded region, can be assessed through a damage indicator approach. To proof the reliability of this concept, an experimental campaign was carried out according to the building block approach typically used in aeronautics. First, a small-scale specimen with a debonded stringer was investigated in the laboratory to proof the methodology. Then, a large-scale fuselage segment was used for technology demonstration enabling stringer debonding with increasing severity through static and fatigue loading. The paper shows that the microwave characteristics in the waveguide (stringer tunnel) is affected by the debonding conditions according to its severity and depth. In addition, extending the same approach on a number of test cases, the probability of detection was carried out showing the minimum defect size which can be identify reliably. This allows designing a reliable structural health monitoring system based on guided electromagnetic waves trapped in the tunnel.

Dual-Function Wearable Hydrogel Optical Fiber for Monitoring Posture and Sweat pH.

In recent years, wearable devices have been widely used for human health monitoring. Such monitoring predominantly relies on the principles of optics and electronics. However, electronic detection is susceptible to electromagnetic interference, and traditional optical fiber detection is limited in functionality and unable to simultaneously detect both physical and chemical signals. Hence, a wearable, embedded asymmetric color-blocked optical fiber sensor based on a hydrogel has been developed. Its sensing principle is grounded in the total internal reflection within the optical fiber. The method for posture sensing involves changes in the light path due to fiber bending with color blocks providing wavelength-selective modulation by absorption changes. Sweat pH sensing is facilitated by variations in fluorescence intensity triggered by sweat-induced conformational changes in Rhodamine B. With just one fiber, it achieves both physical and chemical signal detection. Fabricated using a molding technique, this fiber boasts excellent biocompatibility and can accurately discern single and multiple bending points, with a recognition range of 0-90° for a single segment, a detection limit of 0.02 mm-1 and a sweat pH sensing linear regression R2 of 0.993, alongside great light propagation properties (-0.6 dB·cm-1). With its extensive capabilities, it holds promise for applications in medical monitoring.

Lifetime study of uniform and non-uniform multi-crack fusion and extension in an approximate plane

The threat of cracks is very fatal for engineering structures. Usually, the main crack is fused by several secondary microcracks, so the investigation of the fusion mechanism and life of microcracks is crucial to improve the reliability of engineering structures. In this paper, firstly, the applicability and accuracy of linear elastic fracture mechanics are verified by comparing the test results and FEA results of small-scale yielding. Secondly, the fusion mechanism and life-solution of uniform and non-uniform multi-cracks are thoroughly investigated. It is also pointed out that the homogeneity of cracks is caused by the abrupt change of crack extension path by affecting the level of stress intensity factor (SIF). Finally, the effects of maximum load and stress ratio on crack fusion are explored. The results demonstrate that the maximum load has a positive effect on the ratio of the crack fusion life to the overall crack extension process life, but the effect of the stress ratio is essentially unchanged.

Field, frequency, and temperature dependencies of the surface resistance of nitrogen diffused niobium superconducting radio frequency cavities

We investigate the rf performance of several single-cell superconducting radio-frequency cavities subjected to low temperature heat treatment in nitrogen environment. The cavities were treated at temperature 120–165 °C for an extended period of time (24–48 h) either in high vacuum or in a low partial pressure of ultrapure nitrogen. The improvement in Q0 with a Q rise was observed when nitrogen gas was injected at ∼300 °C during the cavity cooldown from 800 °C and held at 165 °C, without any degradation in accelerating gradient over the baseline performance. The treatment was applied to several elliptical cavities with frequency ranging from 0.75 to 3.0 GHz, showing an improved quality factor as a result of low temperature nitrogen treatments. The Q rise feature is similar to that achieved by nitrogen alloying Nb cavities at higher temperature, followed by material removal by electropolishing. The surface modification was confirmed by the change in electronic mean free path and tuned with the temperature and duration of heat treatment. The decrease of the temperature-dependent surface resistance with increasing rf field, resulting in a Q rise, becomes stronger with increasing frequency and decreasing temperature. The data suggest a crossover frequency of ∼0.95 GHz above that the Q rise phenomenon occurs at 2 K. Some of these results can be explained qualitatively with an existing model of intrinsic field-dependence of the surface resistance with both equilibrium and nonequilibrium quasiparticle distribution functions. The change in the Q slope below 0.95 GHz may result from masking contribution of trapped magnetic flux to the residual surface resistance. Published by the American Physical Society 2024

Effect of magnetic field on macroscopic hysteresis and microscopic magnetic domains for different ferromagnetic materials

The macroscopic hysteresis of ferromagnetic materials is influenced by their microscopic magnetic domains, establishing a correspondence between the two that enables a fundamental understanding of the magnetization process of ferromagnetic materials. Based on this, this study employs the phase field method to investigate the macroscopic hysteresis and microscopic magnetic domain evolution of soft, hard, and rectangular ferromagnetic materials. The hysteresis loops of the three materials present narrow, wide and rectangular characteristics respectively, which are quantitatively consistent with the experimental data. Subsequently, the influence of the magnetic field on the macroscopic hysteresis is analyzed. The results show that the hysteresis loop area increases when the magnetic field amplitude increases. Furthermore, the proportion of each type of energy under different magnetic fields is discussed, the dominant energy terms are generally consistent for the same category of ferromagnetic materials. Additionally, the corresponding magnetic domain evolution under different magnetic field is displayed, with soft magnetic materials exhibiting no vortex structures, hard ferromagnetic materials presenting a 45° vortex structure, and rectangular magnetic material showcasing a 90° vortex structure. Finally, the asymmetric characteristics of the major hysteresis loop and minor hysteresis loops are discussed. The change of the magnetic field path leads to the corresponding change of the major and minor hysteresis loops. At the same magnetic field, distinctions in magnetic domain configurations between the major and minor hysteresis loops are evident.

The impact of core curriculum revisions on Japanese medical schools: Navigating curriculum evolution

Purpose This study examines the impact of the 2010 and 2016 Model Core Curriculum (MCC) revisions on medical education across all 82 medical schools in Japan. Methods A cross-sectional survey was conducted in 2021, focusing on the response to the MCC revisions, curriculum changes, and factors influencing these changes. The survey included questions on approaches to implementing the MCC revisions, timing of curriculum updates, factors triggering these revisions, changes in student performance and career paths, and the introduction of new subjects. Results The response rate was 100%. Most universities rapidly implemented changes following the 2016 MCC revision, demonstrating agility in adapting to national standards. Key factors influencing curriculum revisions included external evaluations and the MCC revisions themselves. Despite no significant changes in student performance or career paths from faculties’ perspective, an increase in scholarly activities was noted. The introduction of new subjects post-2016 reflects a shift toward holistic perspectives such as behavioral science, general medicine/community medicine, and professionalism. Conclusions The findings highlight a commitment to maintaining educational quality in Japanese medical education. The responsiveness to MCC revisions suggests a growing interest in medical education among faculties and an alignment with global medical education trends to meet evolving healthcare needs.

Design of the primary mirror assembly for a space gravitational wave based on the optical path variation model

As an important component of the gravitational wave detection interferometric measurement system, the telescope’s main function is to receive and emit laser signals. Under the influence of in-orbit environmental disturbances, the telescope will experience structural deformation. This can result in changes in the propagation path of the laser within the telescope, which in turn affects the ranging accuracy. Therefore, it is necessary to suppress the optical path variation caused by the deformation of the telescope during the design phase of the telescope structure. In this paper, a calculation and analysis model of the non-geometric optical path length variation within the telescope was established using the first 36 orders of the fringe Zernike polynomials. The derivation of the geometric optical path variation within the telescope was completed, and the optical system error analysis was performed based on the internal optical path variation of the telescope as an evaluation index. The primary mirror components that meet the detection requirements were designed. The results showed that for the off-axis four-mirror optical system, under the same disturbance, the geometric optical path variation caused by the rigid displacement of the primary mirror dominates. When the environmental temperature stability is 2.8×10−6K⋅Hz−1/2 @0.1 Hz, the system’s optical path stability is reduced from the original 8.5pm⋅Hz−1/2 @0.1 Hz to 0.45pm⋅Hz−1/2 @0.1 Hz.