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Development of an Experimental Platform for Combinative Use of an XFEL and a High-Power Nanosecond Laser
摘要： We developed an experimental platform for combinative use of an X-ray free electron laser (XFEL) and a high-power nanosecond laser. The main target of the platform is an investigation of matter under high-pressure states produced by a laser-shock compression. In this paper, we show details of the experimental platform, including XFEL parameters and the focusing optics, the laser irradiation system and X-ray diagnostics. As a demonstration of the high-power laser-pump XFEL-probe experiment, we performed an X-ray di?raction measurement. An in-situ single-shot X-ray di?raction pattern expands to a large angle side, which shows a corundum was compressed by laser irradiation.
关键词： X-ray di?raction,high-pressure science,laser shock,XFEL
更新于2025-09-23 15:21:01
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An Optical Fiber Fabrya??Perot Pressure Sensor with Optimized Thin Microbubble Film Shaping for Sensitivity Enhancement
摘要： A pressure-assisted arc discharge method of preparing silicon microbubbles with a glass tube was utilized for decreasing the bubble film’s thickness and improving the bubble’s uniformity. By controlling the arc discharge intensity, discharge time and the position of the fiber carefully, the thickness of the microbubble film was reduced to the micrometer scale. Later, the thin film of the microbubble was transferred to the end the single-mode-fiber/glass-tube structure, for forming the FP (Fabry–Perot) interference cavity. As the thin film is sensitive to the outer pressure, such a configuration could be used for a high-sensitive-pressure measurement. Experimental results show that the sensitivity of this FP (Fabry–Perot) cavity was 6790 pm/MPa when the outer pressure ranges from 100 to 1600 kPa, and the relationship between the structural parameters of the thin film and the outer pressure was theoretically analyzed. Moreover, this special structure made of the end silicon film microbubble is more suitable for high-sensitivity applications.
关键词： interference cavity,pressure sensing,FP (Fabry–Perot),microbubble
更新于2025-09-23 15:21:01
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Electrical features of radio-frequency atmospheric pressure helium discharge with and without dielectric electrodes
摘要： In this paper, a comparative study of radio-frequency atmospheric pressure glow discharge (rf APGD) generated in helium with and without dielectric electrodes to investigate the effect of electrodes insulation on electrical features of APGD, is presented. In α mode both the rf APGDs remain volumetric, stable and uniform. In γ mode the APGD without dielectric electrodes shrinks into a constricted plasma column whereas APGD with dielectric electrodes remains stable and retains the same volume without plasma constriction even at higher densities of discharge current. A comparison of electrical features of both rf APGDs in normal and abnormal glow discharge regimes is presented. In both APGDs with and without dielectric electrodes, impedance measurements have been performed and compared with equivalent circuit models. The measured impedance data is found to be in good agreement with simulated data.
关键词： dielectric electrodes,radio-frequency atmospheric pressure glow discharge,plasma stability control
更新于2025-09-23 15:21:01
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Unexpected robustness of the band gaps of TiO <sub/>2</sub> under high pressures
摘要： Titanium dioxide (TiO2) is a wide band gap semiconducting material which is promising for photocatalysis. Here we present first-principles calculations to study the pressure dependence of structural and electronic properties of two TiO2 phases: the cotunnite-type and the Fe2P-type structure. The band gaps are calculated using density functional theory with the generalized gradient approximation, as well as the many-body perturbation theory with the GW approximation. The band gaps of both phases are found to be unexpectedly robust across a broad range pressures. The corresponding pressure coefficients are significantly smaller than that of diamond and silicon carbide, whose pressure coefficient is the smallest value ever measured by experiment. The robustness originates from the synchronous change of valence band maximum and conduction band minimum with nearly identical rates of changes. A step-like jump of band gaps around the phase transition pressure point is expected and understood in light of the difference in crystal structures.
关键词： band gap,robustness,TiO2,first-principles calculations,high pressure
更新于2025-09-23 15:21:01
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Kontinuierliche nicht-invasive Blutdruckmessung mittels Pulswellen-Transit-Zeit bei Kindern und Jugendlichen
摘要： Background As an alternative to ambulatory 24-h blood pressure monitors, the continuous, non-invasive blood pressure recording using pulse transit time (PTT) was compared with both oscillometric and intra-arterial measurement. Methods In 144 pediatric patients (9.4 ± 5.2 years) acute blood pressure was determined using three different methods of measurement. In 57 patients (11.4 ± 4.9 years) of the pediatric normal ward, the blood pressure was simultaneously determined continuously by means of PTT compared to the intermittent oscillometric long-term measurement. In 9 patients (9.8 ± 6.8 years) of the pediatric intensive care unit with continuous intra-arterial blood pressure measurement, the blood pressure was measured in parallel by means of PTT. Results Compared to the gold standard sphygmomanometry, mean systolic blood pressure values were comparable to 2 different oscillometric devices, but in the case of diastolic pressure measurement the pressure values were significantly lower or higher than with sphygmomanometry and auscultation. The results of the non-invasive comparative long-term measurements showed better correlations for systolic rather than diastolic pressure. Similar results were obtained comparing the direct intra-arterial blood pressure measurement with the SOMNOtouch? NIBP device which measures blood pressure using the PTT. Conclusion Continuous, indirect blood pressure recording using pulse transit time provides good correlations to the reference measurements for long-term measurement of blood pressure in children and adolescents and appears to be a usable method to measure the blood pressure of children especially at rest.
关键词： auscultation,blood pressure,sphygmomanometry,pulse transit time,oscillometry
更新于2025-09-23 15:21:01
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Flexible Capacitive Pressure Sensor Based on PDMS Substrate and Ga-In Liquid Metal
摘要： A novel flexible pressure sensor, based on polydimethylsiloxane (PDMS) and eutectic gallium indium (EGaIn) liquid metal, was developed for detecting various applied pressures. The sensor was fabricated with PDMS polymer based electrode channels that are filled with EGaIn liquid metal. The liquid metal based electrodes were designed to form four capacitors (C1, C2, C3 and C4). Conventional PCB technology was used to manufacture the master mold to form the PDMS based electrode channels. Corona discharge treatment was employed to bond the PDMS layers at room temperature, under atmospheric pressure. The capability of the fabricated pressure sensor was demonstrated by investigating the capacitive based response of the device for varying applied pressures. Average capacitance changes ranging from 2.3% to 12.0%, 2.6% to 11.8%, 2.5% to 12.2% and 2.7% to 13.1% when compared to the based capacitance of 14.1 pF, 15.1 pF, 13.8 pF and 13.3 pF was obtained for C1, C2, C3 and C4, respectively, for applied pressures ranging from 0.25 MPa to 1.10 MPa. A linear relationship was obtained for the average capacitance change with a sensitivity of 0.11%/MPa, and a correlation coefficient of 0.9975. The results obtained thus demonstrate the feasibility of employing liquid metal based electrodes for the fabrication of flexible pressure sensing devices.
关键词： Corona treatment,Polydimethylsiloxane (PDMS),Eutectic Gallium - Indium (EGaIn),Printed circuit board (PCB),Pressure Sensor
更新于2025-09-23 15:21:01
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Coexistence of pressure-induced structural phases in bulk black phosphorus: a combined x-ray diffraction and Raman study up to 18 GPa
摘要： We report a study of the structural phase transitions induced by pressure in bulk black phosphorus by using both synchrotron x-ray diffraction for pressures up to 12.2 GPa and Raman spectroscopy up to 18.2 GPa. Very recently black phosphorus attracted large attention because of the unique properties of few-layers samples (phosphorene), but some basic questions are still open in the case of the bulk system. As concerning the presence of a Raman spectrum above 10 GPa, which should not be observed in an elemental simple cubic system, we propose a new explanation by attributing a key role to the non-hydrostatic conditions occurring in Raman experiments. Finally, a combined analysis of Raman and XRD data allowed us to obtain quantitative information on presence and extent of coexistences between different structural phases from ~5 up to ~15 GPa. This information can have an important role in theoretical studies on pressure-induced structural and electronic phase transitions in black phosphorus.
关键词： high pressure,black phosphorus,x-ray diffraction,Raman spectroscopy,phase transitions
更新于2025-09-23 15:21:01
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Advance on Single Pressure Refractive Index Gas Thermometry
摘要： A novel single pressure refractive index gas thermometry(SPRIGT) of thermodynamic temperature of helium gas filled in quasi-spherical microwave cavity resonator(QMCR) by combination of microwave measurements, temperature and pressure control. A long-term temperature stability better than 0.2mK is demanded for the QMCR from 5K to 24.5561 K. The uncertainty below 4ppm for pressure needs to precisely control the oscillation of temperature along the gas line. Microwave resonance frequency measurement in QMCR should be better than 2ppb. To meet these requirements, SPRIGT has been built in China and the first run experimental data was analysis in this paper.
关键词： Pressure control,Temperature control,SPRIGT,Thermodynamic temperature,Microwave measurement,QMCR,Primary thermometry
更新于2025-09-23 15:21:01
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[IEEE 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - Honolulu, HI, USA (2018.7.18-2018.7.21)] 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - InstaBP: Cuff-less Blood Pressure Monitoring on Smartphone using Single PPG Sensor
摘要： Cuff-less Blood Pressure (BP) monitoring has gained interest of the research community in recent years, due to its importance in continuous and non-invasive monitoring of BP for early detection of hypertension, thereby reducing mortality. Several approaches that involve photoplethysmography (PPG) and Pulse Transit Time (PTT) have been explored with promising results; however the requirement of two sensors makes them obtrusive for continuous use. Single PPG sensor approaches using machine learning have also been attempted, but there are certain deficiencies in these methods as they go for a one-size-fits-all approach. In this work, we develop an ensemble of BP prediction models based on demographic and physiological partitioning. Also, we incorporate a set of unique PPG features into our models, which results in test accuracies of 5 mmHg Mean Absolute Error (MAE) for Diastolic BP, and 6.9 mmHg MAE for Systolic BP. Given our marked improvement over ubiquitous models (18% for Diastolic BP and 11.5% for Systolic BP), this approach opens up avenues where single PPG sensor based methods can predict BP with a high degree of accuracy. This is a big step towards developing continuous BP monitoring systems, and can help in better management of cardiac health.
关键词： machine learning,Cuff-less Blood Pressure monitoring,Pulse Transit Time,photoplethysmography,demographic and physiological partitioning
更新于2025-09-23 15:21:01
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Persistence of the R3m Phase in Powder GeTe at High Pressure and High Temperature
摘要： As a phase-change material, rhombohedral GeTe (space group R3m) was believed to transform to the cubic rock-salt phase (B1) at 3–4 GPa, associated with the disappearance of a Peierls distortion. However, using a combination of synchrotron X-ray diffraction and theoretical calculations, we found that the R3m phase persists from ambient pressure up to pressures of about 15.8 GPa, in contrast to previous reports. Neither was the B1 phase observed in a heating X-ray powder diffraction experiment. The spurious transformation from R3m to B1 is caused by changes to the compression ratio of lattice parameters in the R3m phase under high pressure/temperature. These findings provide insight into transitions of phase-change materials, relevant to other materials undergoing displacive transitions under high pressure/temperature.
关键词： structural phase transitions,density-functional theory,high pressure,phase-change materials,high temperature,GeTe,synchrotron X-ray diffraction
更新于2025-09-23 15:21:01