Carbon nanotube (CNT) yarns exhibit tensile strengths comparable to or even exceeding those of high-strength polyacrylonitrile-based carbon fibers. However, the mechanisms governing the tensile failure of CNT yarns embedded in polymer matrices remain poorly understood. Therefore, in this study, the tensile failure mechanisms of CNT yarns embedded in polymer matrices were investigated using synchrotron radiation X-ray computed tomography (XCT) combined with digital volume correlation (DVC) and Raman spectroscopy upon tensile loading. DVC revealed heterogeneous strain fields within the surrounding epoxy matrix, including localized strain concentrations associated with damage sites and strain perturbations in apparently intact regions where no damage was detectable via 0.50 mu m/pixel XCT. Subsequent 32 nm/pixel XCT confirmed the presence of previously undetected damage. Raman spectroscopy further revealed the heterogeneous axial-strain distributions and persistent load-bearing capacities of the damaged regions of the yarn. Therefore, load transfer between the CNT bundles progressively deteriorated in a spatially distributed manner rather than via damage localization into a single dominant fracture site. The combined observations indicated that the tensile failure of the polymerembedded CNT yarns was governed by the progressive accumulation of spatially distributed inter-bundle damage and associated deterioration of load transfer between the CNT bundles. This failure mode fundamentally differed from that of a conventional brittle fiber, in which failure is typically characterized by localized fracture, followed by recovery of axial stress and subsequent fragmentation. These findings provide mechanistic insights for developing failure and strength prediction frameworks for hierarchical CNT-yarn composite systems.
We revisit the physical origin of the achromatic peaks and breaks observed several thousand seconds after the burst in the multi-wavelength afterglows of XRF 080330 and GRB 080710. Using a numerical afterglow model that consistently incorporates finite ejecta thickness and a generalized external density profile, we perform Bayesian inference to estimate model parameters describing these events. Our analysis shows that the gradual rise and achromatic temporal features in both events are more naturally explained by jet dynamical evolution with finite shell thickness rather than by off-axis viewing effects. The inferred initial radial width of the ejecta is of order 1013 cm for both bursts, implying a central engine activity timescale significantly longer than that suggested by the prompt gamma-ray duration alone. Taken together, these results demonstrate that early afterglow light curves are strongly influenced by transition dynamics when finite ejecta thickness is properly taken into account, thereby providing a physical link between the prompt and afterglow phases and highlighting limitations of simply applying the thin-shell approximation when interpreting early-time afterglows. Furthermore, Bayesian model comparison strongly favors a generalized circumburst density profile over the canonical uniform or steady-wind models, suggesting that fixing the external density structure to idealized profiles a priori may obscure crucial information about the progenitor’s pre-burst activity.
This study aimed to develop a measurement scale for the ability to learn from experiences based on experiential learning theory. Following a scale development approach, we conducted interviews with high-performing employees (n = 25) to collect items of the scale and subsequently performed a two-wave questionnaire survey of employees (n = 999) in Japanese organisations to identify the dimensions of the ability to learn from experience. We conducted a series of exploratory and confirmatory factor analyses to develop and evaluate the measurement scale. The results generated a four-dimensional scale with 22 items consisting of proactive challenge, emotional control through dialogue, learning from others, and meta-reflection and adjustment. These dimensions were positively associated with the three types of psychological satisfaction (autonomy, relatedness, and competence) and work engagement. These findings were discussed both theoretically and practically.
This article presents a wide operating range switched-capacitor (SC) converter designed for miniaturized photovoltaic (PV) energy sources. In millimeter-scale devices, PV power transfer is limited by low generated voltage and available power, posing significant challenge for power conversion. To address this constraint, the proposed SC converter employs an input-powered $3 imes $ differential switching signal generation and boosting path, which enhances performance in the subthreshold operating region while maintaining sub-microwatt operation and cold-start capability across the operating range. The converter also incorporates an exponential reconfigurable charge pump topology that achieves high voltage multiplication gain with a reduced number of stages and capacitor footprint. To maintain compatibility with the most efficient monolithic PV implementation, the converter is designed to operate in the negative supply domain. The proposed circuit was implemented in 180 nm CMOS process and experimentally verified using both a controlled voltage source and a discrete 2.1-mm2 silicon photodiode. Measurement results demonstrate robust operation over an input range of 140-400mV with a peak power conversion efficiency of 56.6% and up to 9.89 & times; voltage gain, enabling energy harvesting from incident light intensities as low as 20 nW/mm2.
HiZ-GUNDAM is a candidate for a Japan Aerospace Exploration Agency satellite mission expected to launch in the 2030s, aiming to detect high-redshift gamma-ray bursts (GRBs) and explore the early universe. The wide-field X-ray monitor EAGLE, onboard the HiZ-GUNDAM satellite and responsible for GRB detection and localization, employs lobster-eye-type micro-pore optics (MPOs) and a pnCCD as the focal-plane detector to focus soft X-rays in the 0.4 to 4.0 keV range. We established an alignment strategy for a modular lobster-eye MPO system, and the required alignment accuracy was derived through Monte Carlo simulations that reproduce the point spread function and localization performance. The optical characteristics of individual MPO segments were then evaluated to select and arrange four segments for a breadboard-level alignment demonstration. Subsequently, alignment tuning was performed by adjusting the angular positions of the MPO segments with actuators under X-ray irradiation in a vacuum environment, followed by an evaluation of the resulting direction-determination accuracy. The resulting angular response measurements show that the estimated incident angles derived from the focal positions achieve systematic uncertainties of less than 3 arcmin over more than 95% of the field of view. This level of performance satisfies the localization requirement for the EAGLE instrument when considering systematic errors intrinsic to the MPO-based detection system. These results demonstrate the feasibility of precise MPO alignment in a segmented lobster-eye optics system and provide practical feedback for the design, alignment strategy, and mechanical tolerance definition of future engineering and flight models of the EAGLE X-ray optics.
