- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
CO2 laser interactions with wood tissues during single pulse laser-incision
摘要： Incising is a technique used to improve fluid flow in impermeable woods during wood treatment processes. Previous studies relating to the laser-incision of wood have neglected many aspects such as detailed analysis of the anatomy of the wood, including consideration of tangential/radial faces and earlywood/latewood interactions with the laser beam. By considering wood anatomy, a complete investigation of the CO2 laser-incision processes is presented that yields new knowledge of laser beam interaction with growth rings when incising into tangential/radial faces, and the low-density earlywood and higher density latewood within the growth ring. Southern Yellow Pine, Radiata Pine, European Redwood and Beech, each having different bulk densities, were laser-incised using a 2 kW ROFIN CO2 laser with radiation in the far-infrared regime (10.6 μm). Microstructural characterisations were carried out to better understand the effect of CO2 laser-incision and its parameters on the depth, diameter and quality of the incised holes. The laser-incised hole shapes were found to be uniform in depth, however, the hole circularity was significantly affected by the presence of earlywood and latewood tissues. Maximum and minimum diameters of incised holes were measured in the Radiata Pine (~1.3 mm) and in the Beech (~0.7 mm), respectively. Similarly, for equal laser powers used, the maximum and minimum depths of laser-incised holes were measured in the European Redwood (~33 mm) and in the Beech (~25 mm), respectively, with the laser incident on the radial face of the samples. CO2 laser pulse duration had a greater effect on diameter and depth of incised holes when compared to laser power and showed that the CO2 laser pulse duration is a dominant parameter when designing CO2 laser-incision processes.
关键词： Laser-incision,Wood,Circularity,Depth,Diameter,CO2 laser
更新于2025-11-21 11:24:58
-
Mapping Forest Structure Using UAS inside Flight Capabilities
摘要： We evaluated two unmanned aerial systems (UASs), namely the DJI Phantom 4 Pro and DJI Mavic Pro, for 3D forest structure mapping of the forest stand interior with the use of close-range photogrammetry techniques. Assisted flights were performed within two research plots established in mature pure Norway spruce (Picea abies (L.) H. Karst.) and European beech (Fagus sylvatica L.) forest stands. Geotagged images were used to produce georeferenced 3D point clouds representing tree stem surfaces. With a flight height of 8 m above the ground, the stems were precisely modeled up to a height of 10 m, which represents a considerably larger portion of the stem when compared with terrestrial close-range photogrammetry. Accuracy of the point clouds was evaluated by comparing field-measured tree diameters at breast height (DBH) with diameter estimates derived from the point cloud using four different fitting methods, including the bounding circle, convex hull, least squares circle, and least squares ellipse methods. The accuracy of DBH estimation varied with the UAS model and the diameter fitting method utilized. With the Phantom 4 Pro and the least squares ellipse method to estimate diameter, the mean error of diameter estimates was ?1.17 cm (?3.14%) and 0.27 cm (0.69%) for spruce and beech stands, respectively.
关键词： point cloud,diameter at breast height (DBH),photogrammetry,obstacle sensing,forestry,unmanned aerial system (UAS),vision positioning system
更新于2025-09-23 15:23:52
-
[IEEE 2018 IEEE International Conference on Imaging Systems and Techniques (IST) - Krakow, Poland (2018.10.16-2018.10.18)] 2018 IEEE International Conference on Imaging Systems and Techniques (IST) - A Novel MRA-Based Framework For Detecting Correlation Between Cerebrovascular Changes and Mean Arterial Pressure
摘要： Systemic hypertension is a signi?cant contributor for strokes and cognitive impairment and is a leading cause of mortality in the USA. Changes in cerebral vascular diameter and cerebral perfusion pressure have been reported to precede elevation of systemic blood pressures. A novel, non-invasive Time-of-Flight - Magnetic Resonance Angiography (TOF-MRA) based framework for detection of cerebrovascular changes is presented. The proposed framework analyzes brain TOF-MRA data to quantify changes in cerebral vascular diameter and cerebral perfusion pressure. The framework has three major steps: 1) Adaptive segmentation to extract large and small diameter cerebral vessels from TOF-MRA images using both appearance and 3-D spatial information of the vascular system; 2) Estimation of the Cumulative Distribution Function (CDF) of the 3-D distance map of the cerebral vascular system, which represents the changes in diameter of the 3-D vascular system ; and 3) Statistical and correlation analysis that measured the effect of Mean Arterial Pressure (MAP) on blood vessels’ diameter changes. The ef?cacy of the framework was evaluated using MRA images and blood pressure (BP) measurements obtained from 15 patients (M=8, F=7, Age=49.2±7.3 years) on Day 0 and Day 700. The framework had a dice similarity coef?cient of 92.23%, a sensitivity of 94.8% and a speci?city of ～ 99% in detecting elevated vascular pressures compared to ground truth. Statistical analysis demonstrated an inverse relationship between blood vessels diameters and MAP. This correlation was valid for both upper (above the circle of Willis) and lower (circle of Willis and below) sections of the brain. The proposed methodology may be used to quantify changes in cerebral vasculature and cerebral perfusion pressure non-invasively through MRA image analysis, which may be a useful tool for clinicians to optimize medical management of pre-hypertension and hypertension.
关键词： Vessel Diameter,Skull Stripping,CDF,Automatic Segmentation,Mean Arterial Pressure,Blood Vessels,MRA,Hypertension,Median Vascular Radius
更新于2025-09-23 15:22:29
-
Fabrication and performance of Lu2O3:Eu3+ nanowire arrays with different nanowire diameters
摘要： Lu2O3:Eu3+ nanowire arrays with different nanowire diameters were successfully fabricated by sol-gel process using submicron porous anodic aluminum oxide (AAO) templates. The nanowires in each array are homogeneous and highly ordered, and have uniform diameter defined by the template. They exhibit polycrystalline with Lu2O3 cubic structure. The crystallite sizes of the Lu2O3:Eu3+ nanowires increase with the increase of the pore diameters of AAO templates and are less than that of nanopowder prepared in the same conditions due to the confinement of AAO template on the coalescence of Lu2O3:Eu3+ nanocrystallites. The Lu2O3:Eu3+ nanowire arrays within AAO templates exhibit good performances of photoluminescence and X-ray excited optical luminescence. The emission peaks can be ascribed to 5D0→7FJ transitions of Eu3+ (J = 0, 1, 2, 3). The luminescent intensities of the Lu2O3:Eu3+ nanowire arrays also enhance with the increase of the pore diameters of AAO templates. This phenomenon is not only due to the increase of the filling ratio of Lu2O3:Eu3+, but also relates to the improvement of crystallinity. The latter mechanism is further confirmed by the fluorescent decay times of Eu3+ emission in the nanowires with different diameters. It is believed that the Lu2O3:Eu3+ nanowire array can become a promising high-spatial-resolution scintillation screen used in X-ray imaging.
关键词： Lu2O3:Eu3+ nanowire array,Diameter and crystallinity,Luminescence,AAO template and sol-gel method
更新于2025-09-23 15:21:21
-
[IEEE IGARSS 2019 - 2019 IEEE International Geoscience and Remote Sensing Symposium - Yokohama, Japan (2019.7.28-2019.8.2)] IGARSS 2019 - 2019 IEEE International Geoscience and Remote Sensing Symposium - Evaluation of Three Methods for Estimating Diameter at Breast Height from Terrestrial Laser Scanning Data
摘要： Terrestrial laser scanning (TLS) is widely used in forest inventory surveys. Diameter at breast height (DBH) is one of the most important parameters in the forest inventory survey. There are many methods to estimate DBH. In this study, cylinder fitting algorithm, circle fitting algorithm and Hough transform algorithm are used to estimate DBH of two larches of different ages to find a better DBH extraction algorithm. Compared with the circle fitting algorithm and Hough transform algorithm, the cylinder fitting algorithm achieves the highest accuracy. In addition, it is worth noting that different structure of the trees may affect the accuracy of these methods greatly.
关键词： Tree point cloud,Terrestrial laser scanning (TLS),Diameter at breast height (DBH)
更新于2025-09-23 15:21:01
-
Investigation of the track width-dependent melt pool characteristics during laser-sintering of polyamide 12 in correlation to various focus diameters
摘要： Factors such as not only costs, production time, reproducibility, but also the quality of the components are decisive factors in assessing the economic efficiency of a manufacturing process. With additive manufacturing processes, component production is made possible directly from a 3D CAD model. This means that small series and prototypes can already be produced economically today. In this area, the laser-sintering process, in particular, offers great potential for series production due to its high strength values and ductility. With laser-sintering systems that allow an optical widening of the laser focus, a faster exposure of the component and thus a shortening of the building time is possible. We developed a laser-sintering system whose laser focus diameter is adjustable in its cross-sectional area from 0.47 to 2 mm. The goal for the future is to produce large-area components significantly faster by widening the focus diameter, thus making laser-sintering more productive. In this paper, the focus-dependent melt pool formation is examined in correlation to different hatch distances during the laser-sintering of polyamide 12. For this purpose, a test specimen was developed which can display single tracks as well as a multitude of different track widths for all feasible focus level variations. This knowledge is required to determine and investigate the track width-dependent melt pool formation as a function of the focal diameter of the component cross sections.
关键词： Laser-sintering,Focus diameter,Single track,Polyamide 12
更新于2025-09-23 15:21:01
-
Nonresonant Polarized Raman Spectra Calculations of Nitrogen-Doped Single-Walled Carbon Nanotubes: Diameter, Chirality, and Doping Concentration Effects
摘要： Raman spectra of nitrogen-doped single-walled carbon nanotubes are calculated using the spectral moment’s method combined with the bond polarizability model. The influence of the nanotube diameter and chirality is investigated. We also address the important question of the effect of the N-doping concentration, and we propose an equation to estimate the doping concentration from the knowledge of the tube diameter and the frequency of the radial breathing mode.
关键词： spectral moment’s method,Raman spectra,N-doping concentration,nanotube diameter,nitrogen-doped single-walled carbon nanotubes,bond polarizability model,chirality
更新于2025-09-23 15:21:01
-
Effect of Pulse Energy, Pulse Frequency, and Tip Diameter on Intracanal Vaporized Bubble Kinetics and Apical Pressure During Laser-Activated Irrigation Using Er:YAG Laser
摘要： Objective: Er:YAG laser-activated irrigation (LAI) is an effective method of root canal cleaning, but irrigant extrusion from the apical foramen has been a concern. We aimed to analyze the effects of pulse energy, pulse frequency, and laser tip diameter on intracanal vapor bubble kinetics and periapical pressure generation during LAI with Er:YAG laser. Background: Irrigant vapor bubble kinetics are one of indices of root canal cleaning ef?cacy. However, few studies have compared laser pulse conditions to vapor bubble kinetics, in relation to periapical pressure. Methods: A plastic root canal model (apical diameter 0.50 mm, 6% taper, 20 mm long) was ?lled with distilled water, and LAI with Er:YAG laser (Erwin AdvErl Unit; 30, 50, or 70 mJ; 10, or 20 pulses per second; laser tip R200T or R600T) was performed with the end of the tip ?xed at 15 mm from the root apex. The number, maximum diameter, and velocity of vapor bubbles were analyzed by high-speed video imaging. Pressure generated outside the apical foramen was measured with a pressure sensor. Results: Vapor bubble count and maximum diameter increased signi?cantly with pulse energy, pulse frequency, and tip diameter. Vapor bubble velocity increased signi?cantly with pulse frequency, but not with pulse energy or tip diameter. Periapical pressure increased signi?cantly with pulse energy, pulse frequency, and tip diameter. Conclusions: The pulse frequency was the single factor that signi?cantly affected all the examined parameters (the number, diameter, and velocity) of vapor bubble kinetics together with the periapical pressure.
关键词： Er:YAG laser,vapor bubble maximum diameter,vapor bubble velocity,laser-activated irrigation,vapor bubble count
更新于2025-09-23 15:21:01
-
Application and Validation of a Model for Terrain Slope Estimation Using Space-Borne LiDAR Waveform Data
摘要： The terrain slope is one of the most important surface characteristics for quantifying the Earth surface processes. Space-borne LiDAR sensors have produced high-accuracy and large-area terrain measurement within the footprint. However, rigorous procedures are required to accurately estimate the terrain slope especially within the large footprint since the estimated slope is likely affected by footprint size, shape, orientation, and terrain aspect. Therefore, based on multiple available datasets, we explored the performance of a proposed terrain slope estimation model over several study sites and various footprint shapes. The terrain slopes were derived from the ICESAT/GLAS waveform data by the proposed method and five other methods in this study. Compared with five other methods, the proposed method considered the influence of footprint shape, orientation, and terrain aspect on the terrain slope estimation. Validation against the airborne LiDAR measurements showed that the proposed method performed better than five other methods (R2 = 0.829, increased by ~0.07, RMSE = 3.596?, reduced by ~0.6?, n = 858). In addition, more statistics indicated that the proposed method significantly improved the terrain slope estimation accuracy in high-relief region (RMSE = 5.180?, reduced by ~1.8?, n = 218) or in the footprint with a great eccentricity (RMSE = 3.421?, reduced by ~1.1?, n = 313). Therefore, from these experiments, we concluded that this terrain slope estimation approach was beneficial for different terrains and various footprint shapes in practice and the improvement of estimated accuracy was distinctly related with the terrain slope and footprint eccentricity.
关键词： terrain slope,Geoscience Laser Altimeter System (GLAS),estimation accuracy,footprint diameter,Light Detection and Ranging (LiDAR)
更新于2025-09-23 15:21:01
-
The effect evaluation of advanced penlight
摘要： Pupil diameter measurement is crucial for physical assessment and disease monitoring in a health and nursing care situation. A general penlights (GPLs) is frequently used and allow for an approximate and indirect measurement of the pupil diameter. Health caregivers or nurses generally have less confidence in the value of the pupil diameter measured using the GPL. The Advanced Penlight (APL) is a new device designed for accurate measurement of the pupil diameter. The purpose of the presented research was to compare the accuracies and operational times of the pupil diameter measurements by means of the GPL and APL. One-group post-test and single-blind study designed was used in this study. The innovation of the APL is the addition of a perspective measurement ruler (PMR) attached to one side of the penlight that allows precise measurement of the pupil diameter before and after pupillary contraction. The PMR can be rotated by any angle for adaptation to the measurement conditions. After standard pupil diameter measurements by a refractometer (RM) were performed on a subjects, ninety study participants measured the pupil diameters of the same subject separately by the GPL and APL. A self-administered questionnaire was used to assess the opinions of the participants after using the GPL compare to the APL. The mean age of the participants was 20.01 (SD = 0.47) years and 83% of them were female senior nursing students. There were no statistically significant differences between the average values of pupil diameters measured by the APL and the RM. Compared to the GPL, the pupil diameter measured by APL was much similar to the RM measurement. The average operational time was 8.72 seconds shorter (t = -3.81, p = 0.001) for the APL measurement compared to the GPL measurement. The average scores of convenience and confidence on pupil diameter measurements of questionnaire were higher for the APL compared to the GPL. The APL can increase the accuracy and save operating time of pupil diameter measurement and thereby promote the quality of health assessment and nursing care practice.
关键词： nursing care,general penlights,advanced penlight,pupil diameter measurement,health assessment
更新于2025-09-23 15:21:01