- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
[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) - Design of a Cell-Based Refractometer with Small End-Effects
摘要： In cell-based laser refractometers, interferometer pathlength uncertainty introduced by deformation and stress in the windows through which the beams pass can be the chief factor limiting measurement accuracy. The fractional contribution of pathlength uncertainty to our recent determination of the Boltzmann constant was 9.8 × 10?6, and more than two times larger than the next largest uncertainty component. We briefly describe the error, and propose a design in which cell window effects contribute less than 3 × 10?6 fractional error to the measurement of helium refractivity; performance that would be competitive with state-of-the-art primary thermometry and barometry.
关键词： Interferometry,length metrology,refractive-index gas thermometry
更新于2025-09-10 09:29:36
-
Self-activated emission and spectral temperature-dependence of Gd8V2O17 phosphor
摘要： Gd8V2O17 was prepared via the facile solid-state reaction. The optical absorption, temperature-dependent luminescence, and decay lifetimes were investigated. Gd8V2O17 has a direct allowed electronic transition with band gap energy of 3.18 eV. Under the excitation of UV light, the phosphor shows the typical self-activated luminescence from the charge transfer (CT) transitions in VO4 3? groups. The emission intensity has a nearly constant value from 10 to 150 K, while it increases above 150 K. And the emission has an abnormal blue-shift with the increase of temperature from 10 to 300 K, so the luminescence color varies from green to blue. Over the whole temperature ranges, the maximum emission wavelength showed a linear dependence on temperature; consequently, the temperature-dependent properties have a potential advantage in luminescence thermometry. The luminescence mechanism was discussed on the proposed two VO4 emission centers and the energy transfer between them.
关键词： Vanadate,Luminescence,Optical materials and properties,Optical thermometry,Phosphorescence
更新于2025-09-10 09:29:36
-
Optical investigation of Er3+ and Er3+/Yb3+ doped zinc-tellurite glass for solid-state lighting and optical thermometry
摘要： Er3+ and Er3+/Yb3+ doped zinc tellurite (ZnO/TeO2) glasses were prepared using melt quenching technique. Spectroscopic properties of the glasses were studied by absorption spectroscopy, luminescence spectroscopy, and color chromaticity coordinates (CIE-1931) measurements. Upconverted-emission intensities and the CIE-1931 coordinates were strongly affected by the presence of Yb3+ ion, as well as the excitation power density of 975 nm laser light. Effect of temperature on green upconverted-emissions from two thermally coupled 2H11/2 and 4S3/2 levels of Er3+ ions were measured and fluorescence intensity ratio technique was applied to investigate the temperature sensing properties. High sensitivity and short response time properties make ZnO/TeO2 glasses a very good candidate for non-contact optical temperature sensor applications. The maximum sensitivity of the glasses doped with Er3+ and Er3+/Yb3+ were found to be 72×10-4 K-1 and 120×10-4 K-1 at 429 K, respectively which are much higher than previously reported temperature sensors based on Er3+ ion doped materials. Hence, Er3+/Yb3+ doped zinc-tellurite glass can be more suitable than that of doped with Er3+ ions only for color tunable solid-state lighting and non-contact optical thermometry applications.
关键词： Solid-state lighting,non-contact optical thermometry,fluorescence intensity ratio (FIR),zinc-tellurite glass,upconversion
更新于2025-09-09 09:28:46
-
Application of Biophotonics with Near Infrared Excitation for Theranostics; 近赤外励起バイオフォトニクスのセラノスティクスへの展開;
摘要： Near infrared wavelength region is known to have the most transparency of live body for electromagnetic wave with wavelength around the visible wavelength. Namely, the near infrared with a wavelength longer than 1000 nm (OTN-NIR) shows more transparency than that with shorter wavelength. The observation depth can be several centimeters with the OTN-NIR fluorescence, while that is limited to be only several millimeters with visible fluorescence. As OTN-NIR fluorescent agents, dyes, quantum dots, carbon nanotubes and rare-earth doped ceramic nanoparticles (RED-CNP) are known. A special feature of the RED-CNP is to show infrared-to-visible upconversion to emit visible light with a near infrared excitation, simultaneously with the OTN-NIR fluorescence. As a theranostic approach, nanomaterials for achieving photodynamic therapy with the near infrared excitation are introduced. Another special feature of the RED-CNP is the potential use for fluorescence nanothermometry. A scheme for ratiometric fluorescence nanothermometry with the OTN-NIR fluorescence is described. By using a RED-CNP with holomium and erbium co-doping, ratiometric fluorescence nanothermometry was successfully demonstrated. As shown with the case of photodynamic therapy with near infrared excitation, by applying an upconversion excitation scheme, visible light emission for photochemical reaction is possible with a near infrared excitation with high transparency in a live body. By constructing these multiple functions on the RED-CNP, various theranostic approach can be achieved. The size and bio distribution controls are important issues for applications of the RED-CNP for medical applications.
关键词： thermometry,near infrared,nanoparticle,rare-earth,PDT
更新于2025-09-09 09:28:46
-
A feasibility study on monitoring the evolution of apparent diffusion coefficient decrease during thermal ablation
摘要： Purpose: Evaluate whether a decrease in apparent diffusion coefficient (ADC), associated with loss of tissue viability (LOTV), can be observed during the course of thermal ablation of the prostate. Methods: Thermal ablation was performed in a healthy in vivo canine prostate model (N = 2, ages: 5 yr healthy, mixed breed, weights: 13–14 kg) using a transurethral high-intensity ultrasound catheter and was monitored using a strategy that interleaves diffusion weighted images and gradient-echo images. The two sequences were used to measure ADC and changes in temperature during the treatment. Changes in temperature were used to compute expected changes in ADC. The difference between expected and measured ADC, ADCDIFF, was analyzed in regions ranging from moderate hyperthermia to heat fixation. A receiver operator characteristic (ROC) curve analysis was used to select a threshold of detection of LOTV. Time of threshold activation, tLOTV, was compared with time to reach CEM43 = 240, tDOSE. Results: The observed relationship between temperature and ADC in vivo (2.2%/ ?C, 1.94%–2.47%/ ?C 95% confidence interval) was not significantly different than the previously reported value of 2.4%/ ?C in phantom. ADCDIFF changes after correction for temperature showed a mean decrease of 25% in ADC 60 min post-treatment in regions where sufficient thermal dose (CEM43 > 240) was achieved. Following our ROC analysis, a threshold of 2.25% decrease in ADCDIFF for three consecutive time points was chosen as an indicator of LOTV. The ADCDIFF was found to decrease quickly (1–2 min) after reaching CEM43 = 240 in regions associated with heat fixation and more slowly (10–20 min) in regions that received slower heating. Conclusions: Simultaneous monitoring of ADC and temperature during treatment might allow for a more complete tissue viability assessment of ablative thermal treatments in the prostate. ADCDIFF decreases during the course of treatment may be interpreted as loss of tissue viability.
关键词： apparent diffusion coefficient,thermal therapies,tissue viability monitoring,MR thermometry
更新于2025-09-09 09:28:46
-
Thermal management and characterization of high-power wide-bandgap semiconductor electronic and photonic devices in automotive applications
摘要： GaN-based high-power wide-bandgap semiconductor electronics and photonics have been considered as promising candidates to replace conventional devices for automotive applications due to high energy conversion efficiency, ruggedness, and superior transient performance. However, performance and reliability are detrimentally impacted by significant heat generation in the device active area. Therefore, thermal management plays a critical role in the development of GaN-based high-power electronic and photonic devices. This paper presents a comprehensive review of the thermal management strategies for GaN-based lateral power/RF transistors and light-emitting diodes (LEDs) reported by researchers in both industry and academia. The review is divided into three parts: (1) a survey of thermal metrology techniques, including infrared thermography, Raman thermometry, and thermoreflectance thermal imaging, that have been applied to study GaN electronics and photonics, (2) practical thermal management solutions for GaN power electronics, and (3) packaging techniques and cooling systems for GaN LEDs used in automotive lighting applications.
关键词： semiconductor,Raman thermometry,infrared thermography,high-power,automotive applications,LEDs,thermoreflectance thermal imaging,GaN,thermal management,wide-bandgap
更新于2025-09-04 15:30:14
-
Applicability of Dy-doped yttrium aluminum garnet (YAG:Dy) in phosphor thermometry at different oxygen concentrations
摘要： Phosphor thermometry is a method used to measure temperature based on the temperature-dependent phosphorescence of phosphors and elucidate heat transfer phenomena, such as high-temperature gas flow. Although various rare earth-doped thermographic phosphors are in use, the effect of oxygen concentration on their phosphorescence has not been sufficiently explored. We explore herein the applicability of Dy-doped yttrium aluminum garnet (YAG:Dy), a well-known rare earth-doped phosphor with temperature sensitivity above 1000 K, in phosphor thermometry at different oxygen concentrations. A third-harmonic Nd:YAG laser excited the sample. Phosphorescence was measured using a photomultiplier tube for lifetime detection. A spectrometer was used to detect the intensity ratio between two emission lines. The chamber was filled with a nitrogen–oxygen mixture with a controlled concentration. The phosphorescence intensity ratio depended on temperature over a wide temperature range and varied with the oxygen concentration, especially above 1000 K. The YAG:Dy lifetimes could be detected over the entire temperature range and remained constant up to 1000 K. In addition, the lifetimes decreased with the increasing oxygen concentration, especially above 1000 K, confirming the oxygen quenching effect. Consequently, YAG:Dy is confirmed to be sensitive to oxygen concentration for determining the intensity ratio and lifetime, especially above 1000 K.
关键词： Lifetime method,Intensity ratio method,Oxygen quenching,Phosphor thermometry
更新于2025-09-04 15:30:14