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Reporting of light irradiation conditions in 300 laboratory studies of resin-composites
摘要： Objective. To evaluate how the light delivered to resin-composites was described in recent articles. Method. PubMed was searched for 300 articles published between January 2017 and May 2018 with keywords relating to photocuring of dental materials. The articles examined a wide range of resin-composite properties and performance. For each article, the information provided about the light curing unit (LCU), the light curing conditions and the characteristics and quantity of the light used in the study were recorded. Specifically, the type of LCU used; the irradiance; how the irradiance was measured; the exposure times; whether the light energy (radiant exposure) received by the specimen was determined, or if only the light output at the LCU tip was measured; whether the distance between the tip of the LCU and the specimen was reported; and whether the emission spectrum from the LCU was reported. Where possible, the resin manufacturer’s minimum energy requirement (MER: the product of the recommended minimum exposure time and irradiance) was compared to the radiant exposure delivered to the specimen. Results. Of the 300 articles examined, 217 were published in 2017 and 83 in 2018. Of these articles, 130 (43%) were found in open access journals, and 170 (57%) were in subscription-based journals. The name of the LCU used was not provided in 31 articles, 14 articles did not provide the exposure time, and 227 articles did not report the distance to the specimen. An irradiance value was reported in 231 articles, but this was the irradiance received by the specimen in only 48 instances. The emission spectrum from the LCU was reported in 15 articles. There was a large range in the radiant exposures from below 10 J/cm2 to greater than 100 J/cm2. Significance. The majority of articles from 2017 and early 2018 did not include sufficient description of the characteristics and quantity of the light received by the resin-composite specimens to allow the study to be replicated. It is recommended that future articles should report: (1) the identity of the LCU used; (2) the radiant exposure received by the specimen (J/cm2); and (3) appropriate reference to the emission spectrum from the LCU.
关键词： Research reproducibility and replicability,Bond strength,Resins,Light curing,Bulk fill,Light measurement
更新于2025-09-23 15:23:52
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Open-path Halon 1301 NDIR sensor with temperature compensation
摘要： Halon 1301 (bromotrifluoromethane) is a kind of fire extinguishing agent in aviation industry. Volume concentration measurement of Halon 1301 is necessary in the design of aircraft fire protection systems. In this research, an open-path Halon 1301 non-dispersive infrared (NDIR) sensor has been developed for in-situ measurement, a novel cavity-type absorption module was designed to get fast response and more compact structure. Experiment results show that measurement was remarkably affected by temperature. Therefore, temperature compensation algorithm was also studied in this thesis, which was proven to be effective within the range of 25 oC-105 oC.
关键词： non-dispersive infrared (NDIR),mid-infrared absorption spectrum,Halon 1301,temperature compensation,concentration measurement
更新于2025-09-23 15:23:52
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Multi-step approach for automated scaling of photogrammetric micro-measurements
摘要： Photogrammetry can be used for the measurement of small objects with micro-features, with good results, low costs, and the possible addition of texture information to the 3D models. The performance of this technique is strongly affected by the scaling method, since it retrieves a model that must be scaled after its elaboration. In this paper, a fully automated multi-step scaling system is presented, which is based on machine vision algorithms for retrieving blurred areas. This method allows researchers to find the correct scale factor for a photogrammetric micro model and is experimentally compared to the existing manual method basing on the German guideline VDI/VDE 2634, Part 3. The experimental tests are performed on millimeter-sized certified workpieces, finding micrometric errors, when referred to reference measurements. As a consequence, the method is candidate to be used for measurements of micro-features. The proposed tool improves the performance of the manual method by eliminating operator-dependent procedures. The software tool is available online as supplementary material and represents a powerful tool to face scaling issues of micro-photogrammetric activities.
关键词： Depth from focus,Photogrammetry,Micro-features,Measurement,International standards,Image analysis,Scale
更新于2025-09-23 15:23:52
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Improved reflection technique for the permittivity measurement of ferrites using slotted coaxial samples
摘要： This paper presents the effect of magnetic permeability on the permittivity measurement using coaxial line reflection technique. It discusses in detail about the design aspects, analysis and simulation of the slotted co-axial sample and fixture for dielectric characterization of the ferrites and garnets possessing both dielectric and magnetic properties. This technique makes use of improved coaxial fixture and APC 07 compatible slotted coaxial sample geometry to measure the complex permittivity of the ferrite material. Permittivity is calculated from the impedance of sample loaded fixture, which is independent of magnetic permeability, because of air slot cut in the coaxial hollow cylindrical sample along the length. Characterization data of dielectrics and ferrites is used in design of ferrite circulators, and pulse magnets for particle accelerator applications. This is also used in many other RF applications including design of dielectric resonator for spin wave line width measurement of ferrites. Design work is aimed at accurate measurement of complex permittivity; using reflection measurement in coaxial fixture over a wide frequency range of 20 kHz to 1 GHz. Reflection measurement technique is further explored for accurate measurement of complex permittivity.
关键词： Complex permittivity,Network analyzer,Coaxial open ended fixture,Wide band measurement technique
更新于2025-09-23 15:23:52
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Optical measurements based on practical methods for detecting time-wise morphing structures
摘要： Nowadays non-contact measurement methods have become widely used systems in several fields especially robotics, aerospace, architecture, and cultural heritage. Practical devices, taken from mass markets, are increasingly being used in scientific and engineering research fields thanks to their ability to combine good accuracy with to the low-cost and ready-to-use experimental setup. In the present paper, digital image analysis (based on digital camera devices) and three-dimensional scanning technique (based on Kinect I and Kinect II sensors) are compared to evaluate their performance in detecting a time-wise shape modification. Digital camera and Kinect sensors are used to the non-contact detection of a morphing blade able to modify its geometry according to airflow temperature variation. The comparison showed the capability of the digital image technique to provide quantitative information when a proper alignment is adopted, while the three-dimensional scanning process allows the continuous blade detection useful to quantify the shape modification. Two-dimensional and three-dimensional blade shape reconstruction processes are also discussed.
关键词： Reverse Engineering,Non-contact measurement,Point cloud,Kinect sensor,Optical method,Digital image analysis
更新于2025-09-23 15:23:52
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An omnidirectional DIC system for dynamic strain measurements on soft biological parts to An omnidirectional DIC system for dynamic strain measurement on soft biological tissues and organs
摘要： A limitation to the potential use of inverse methods in identifying the spatially varying properties of biological tissues consists in obtaining the required set of experimental data. In fact, whereas on the numerical side there are almost no limits to complexity in terms of geometry and material behavior of the model, on the experimental side, the collection of full-field displacement and strain data over the full surface of complex 3D geometries still represents a challenge. To address this issue, this work proposes an omnidirectional-DIC method capable of obtaining full-field information over the entire surface of native intact biological parts undergoing large deformation. This is made possible by the use of a concave conical mirror that enlarges the field of view of a conventional binocular stereo-DIC system up to 360° × 320°. The pair of highly distorted panoramic scenes reflected by the conical mirror are then matched by using a novel iterative image deformation scheme. In particular, first, a robust feature-based algorithm is used to calculate the gross disparity between images, then, an iterative NURBS-based intensity interpolation scheme refines the correlation through a hybrid local-global DIC approach. The accuracy of the developed image matching scheme was evaluated on synthetically generated images simulating a large and heterogeneous deformation field. Then, the potential of the proposed omnidirectional-DIC method was tested with rubber analogs reproducing the most representative geometries and loading states involved in biological materials characterization. Finally, as an illustrative example of application, full-field DIC shape and deformation measurements was performed over a whole porcine eye tested in-vitro under reproduced physiological load.
关键词： Eye,Omnidirectional measurement,Finite deformation,Digital image correlation,Inflation test
更新于2025-09-23 15:23:52
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[Micro/Nano Technologies] Micro Electro Mechanical Systems Volume 2 || Micro Thermal Flow Sensor
摘要： Measurement of ?uid mechanics is very important in various ?elds, and ?ow sensors have been widely applied to execute accurate and ef?cient measurements. Compared with other sensing principle, thermal ?ow sensors are based on convective heat transfer and take merits of simple structure and easy use and thus offer a practical solution for various ?uidics applications. In this chapter, we describe mainly hot-?lm anemometer fabricated on polyimide substrate. Hot-?lm or hot-wire anemometer utilizes a thermal element that serves as both a joule heater and a temperature sensor. We introduce the principle of thermal ?ow sensing, design and fabrication of the micro hot-?lm ?ow sensor, the measurement methodology, and application cases by using the micro hot-?lm ?ow sensors.
关键词： Flow sensor,Temperature compensation,Micro anemometer,Hot ?lm,Measurement principle
更新于2025-09-23 15:23:52
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High-precision FBG demodulation using amplitude ratio curve with sharp peak
摘要： For the fiber Bragg grating (FBG) sensor based on the reflection peak position searching demodulation algorithms, a key problem is that the demodulation precision of measurement signal is seriously limited by the full width half maximum (FWHM) of the FBG reflection spectrum. In this paper, in order to overcome this problem and enhance the measurement precision, we proposed a high-precision demodulation method based on amplitude ratio curve to instead of the FBG reflection spectrum, which can increase the sensing precision significantly. In this method, the Bragg wavelength of FBG is modulated periodically with a sinusoidal function to obtain a series of reflection spectra. Then at each wavelength the amplitude ratio between second harmonic frequency component and fundamental frequency component is calculated to create the amplitude ratio curve. Here, we present a comprehensive theoretical analysis and experimental demonstration to verify the advantages of this method. Comparing with the demodulation method based on the FBG reflection spectrum, the average maximum measure error (MME) of Bragg wavelength is reduced from ± 1.54 pm to ± 0.15 pm, which improved by 10.3 times. In addition, the influence of the modulation amplitude and sampling frequency on demodulation accuracy are also studied in this paper.
关键词： Amplitude ratio curve,High precision temperature measurement,Fiber Bragg grating
更新于2025-09-23 15:23:52
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Study on sliding-window length based on Rayleigh backscattering spectrum correlation in distributed optical-fiber strain measurement
摘要： A theoretical model is established for estimating the strain measurement error based on the Rayleigh backscattering spectrum correlation in distributed optical fiber strain measurements. Assuming the signal is much larger than the noise, the theoretical model predicts the strain measurement error using noise variance and the defined quality factor Q of the Rayleigh backscattering spectrum. Furthermore, an algorithm based on the quality factor Q is proposed to select an optimized sliding-window. The sliding-window length can be obtained by calculating the threshold value of the quality factor using a theoretical model corresponding to the required strain measurement accuracy. Compared with the traditional method where the sliding-window length is defined by the user based on spatial resolution requirements or an empirical definition, the sliding-window length determined by the algorithm is more reasonable and can be automatically defined, alleviating the requirement for user inputs. To verify the correctness of the theoretical model, two experiments are set up: a self-correlation experiment, that analyzes the effect of the quality factor on the strain measurement accuracy, and a virtual experiment of the noise influence, which analyzes the effect of different noise variances. The experimental results are in good agreement with those of the model.
关键词： Distributed optical fiber strain measurement,Rayleigh backscattering spectrum correlation,Optical frequency domain reflectometer
更新于2025-09-23 15:23:52
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20?W 1952?nm tandem hybrid single and double clad TDFA
摘要： A simple engineering design is important for achieving high Thulium-doped ampli?er (TDFA) performance such as good power conversion, low noise ?gure (NF), scalable output power, high gain, and stable operation over a large dynamic range. In this paper we report the design, performance, and simulation of two stage high-power 1952 nm hybrid single and double clad TDFAs. The ?rst stage of our hybrid ampli?er is a single clad design, and the second stage is a double clad design. We demonstrate TDFAs with an output power greater than 20 W with single-frequency narrow linewidth (i.e. MHz) input signals at both 1952 and 2004 nm. An optical 10 dB bandwidth of 80 nm is derived from the ASE spectrum. The power stage is constructed with 10 μm core active ?bers showing a maximum optical slope e?ciency greater than 50%. The experimental results lead to a 1 dB agreement with our simulation tool developed for single clad and double clad TDFAs. Overall this hybrid ampli?er o?ers versatile features with the potential of much higher output power.
关键词： Simulation,Fiber ampli?er,Multistage,Single frequency,Fiber measurement,Thulium
更新于2025-09-23 15:23:52