Journal articles on the topic 'Single Scan Track'
To see the other types of publications on this topic, follow the link: Single Scan Track.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Single Scan Track.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Aversa, Alberta, Mandanà Moshiri, Erica Librera, Mehdi Hadi, Giulio Marchese, Diego Manfredi, Massimo Lorusso, et al. "Single scan track analyses on aluminium based powders." Journal of Materials Processing Technology 255 (May 2018): 17–25. http://dx.doi.org/10.1016/j.jmatprotec.2017.11.055.
Full text
2
Musicki, Darko, Barbara La Scala, and Robin Evans. "Integrated track splitting filter-efficient multi-scan single target tracking in clutter." IEEE Transactions on Aerospace and Electronic Systems 43, no. 99 (2007): 1409–25. http://dx.doi.org/10.1109/taes.2007.4407467.
Full text
3
Musicki, D., B. F. La Scala, and R. J. Evans. "Integrated track splitting filter - efficient multi-scan single target tracking in clutter." IEEE Transactions on Aerospace and Electronic Systems 43, no. 4 (October 2007): 1409–25. http://dx.doi.org/10.1109/taes.2007.4441748.
Full text
4
Ning, Jinqiang, Daniel Sievers, Hamid Garmestani, and Steven Liang. "Analytical Modeling of In-Process Temperature in Powder Bed Additive Manufacturing Considering Laser Power Absorption, Latent Heat, Scanning Strategy, and Powder Packing." Materials 12, no. 5 (March 8, 2019): 808. http://dx.doi.org/10.3390/ma12050808.
Full textAbstract:
Temperature distribution gradient in metal powder bed additive manufacturing (MPBAM) directly controls the mechanical properties and dimensional accuracy of the build part. Experimental approach and numerical modeling approach for temperature in MPBAM are limited by the restricted accessibility and high computational cost, respectively. Analytical models were reported with high computational efficiency, but the developed models employed a moving coordinate and semi-infinite medium assumption, which neglected the part dimensions, and thus reduced their usefulness in real applications. This paper investigates the in-process temperature in MPBAM through analytical modeling using a stationary coordinate with an origin at the part boundary (absolute coordinate). Analytical solutions are developed for temperature prediction of single-track scan and multi-track scans considering scanning strategy. Inconel 625 is chosen to test the proposed model. Laser power absorption is inversely identified with the prediction of molten pool dimensions. Latent heat is considered using the heat integration method. The molten pool evolution is investigated with respect to scanning time. The stabilized temperatures in the single-track scan and bidirectional scans are predicted under various process conditions. Close agreements are observed upon validation to the experimental values in the literature. Furthermore, a positive relationship between molten pool dimensions and powder packing porosity was observed through sensitivity analysis. With benefits of the absolute coordinate, and high computational efficiency, the presented model can predict the temperature for a dimensional part during MPBAM, which can be used to further investigate residual stress and distortion in real applications.
5
Wang, Li, Qing Song Wei, Yu Sheng Shi, Jin Hui Liu, and Wen Ting He. "Experimental Investigation into the Single-Track of Selective Laser Melting of IN625." Advanced Materials Research 233-235 (May 2011): 2844–48. http://dx.doi.org/10.4028/www.scientific.net/amr.233-235.2844.
Full textAbstract:
Selective laser melting(SLM) is driven by the need to fabricate functional metallic parts and tools with near shape and density. The method of process to fabricate a metal part will save materials, time and energy compared to the traditional manufacturing methods. Unlike the selective laser sintering (SLS), the metal powder particles are molten by the laser beam during the process of selective laser melting. In this paper, IN625 powders were adopted to investigate the characters of single molten track. The factors that affect the surface quality and relative density are the process parameters such as the laser energy, scan speed and so on. They were studied to find out the correlation between the parameters and formation of single-track. It has been found that Optimal ratio between laser power and scanning speed (P/v) is 1-1.5 for IN625 SLM. P/v is the linear energy density. It also has been found that the width and height of single-track can be calculated when the linear energy density is given. In this study the laser power, scan spacing and the hatch spacing which affect the surface quality and the relative density of the metallic parts were optimized.
6
Childs, T. H. C., C. Hauser, and M. Badrossamay. "Mapping and Modelling Single Scan Track Formation in Direct Metal Selective Laser Melting." CIRP Annals 53, no. 1 (2004): 191–94. http://dx.doi.org/10.1016/s0007-8506(07)60676-3.
Full text
7
Park, Suyeul, Seok Kim, and Heechang Seo. "Study on Representative Parameters of Reverse Engineering for Maintenance of Ballasted Tracks." Applied Sciences 12, no. 12 (June 11, 2022): 5973. http://dx.doi.org/10.3390/app12125973.
Full textAbstract:
Reverse engineering (RE) is a technology used to create three-dimensional (3D) models by scanning structures and can be used to examine the current condition of structures. Applying RE to the maintenance of railroad facilities with a high proportion of safety accidents can be an alternative to increase the efficiency of railroad facilities. However, most tasks while constructing Building Information Modeling (BIM) after 3D scanning and extracting two-dimensional (2D) drawings are still performed manually. In particular, denoising, registration, and 3D modeling based on point clouds are labor-intensive and time-consuming tasks, and their efficiency needs to be enhanced by introducing automation technology. In this study, we selected point clouds-based representative parameters for ballasted tracks of a straight single-line section for automating railroad maintenance. Scan data and a BIM of a ballasted track were compared using the selected representative parameters. In addition, the types of damage to ballasted track requiring maintenance were examined. And a testbed was consisted of ballasted a track was selected, and 3D scanning was performed to obtain point cloud data of a testbed. Then, a BIM model was created by measuring the numerical values corresponding to the representative parameters on the scan data. The feasibility of constructing a railroad maintenance BIM based on representative 3D object detection parameters during RE work on the ballasted track was evaluated.
8
Martucci, Alessandra, Fabrizio Marinucci, Antonio Sivo, Alberta Aversa, Diego Manfredi, Federica Bondioli, Paolo Fino, and Mariangela Lombardi. "An Automatic on Top Analysis of Single Scan Tracks to Evaluate the Laser Powder Bed Fusion Building Parameters." Materials 14, no. 18 (September 9, 2021): 5171. http://dx.doi.org/10.3390/ma14185171.
Full textAbstract:
The production of dense samples produced by laser powder bed fusion (LPBF) is mainly determined by the choice of the best combination of construction parameters. Parameter optimization is the first step in the definition of an LPBF process for new alloys or systems. With this goal, much research uses the single scan track (SST) approach for a preliminary parameter screening. This study investigates the definition of a computer-aided method by using an automatic on top analysis for the characterization of SSTs, with the aim of finding ranges of laser power and scan speed values for massive production. An innovative algorithm was implemented to discard non-continuous scans and to measure the SSTs quality using three regularity indexes. Only open source software were used to fine tune this approach. The obtained results on Al4Cu and AlSi10Mg realized with two different commercial systems suggest that it is possible to use this method to easily narrow the process parameter window that allows the production of dense samples.
9
Degenhardt, Brian F., Zane Starks, and Shalini Bhatia. "Reliability of the DIERS Formetric 4D Spine Shape Parameters in Adults without Postural Deformities." BioMed Research International 2020 (February 13, 2020): 1–10. http://dx.doi.org/10.1155/2020/1796247.
Full textAbstract:
The DIERS formetric 4D provides a safe method to monitor and track the progression of postural deformities over time. However, further evaluation of reliability is necessary. Reference values are also needed to indicate postural change. The current study examined the reliability of spine shape parameters produced by the formetric 4D in adults without postural abnormalities and established reference values to determine when real change occurs. Thirty participants were scanned during 1 week. Intraclass correlation coefficients (ICCs) were calculated for 40 spine shape parameters for scans with participants stationary between scans, scans with repositioning between scans, and between days. Within-day and between-day standard error of measurement (SEM), absolute relative SEM, and smallest detectable change (SDC) were reported. ICC for stationary scans was excellent for 29 parameters, good for 10 parameters, and fair for 1 parameter. With repositioning, ICC was excellent for 27 parameters, good for 12 parameters, and fair for 1 parameter. Between days, ICC was excellent for 26 parameters, good for 10 parameters, and fair for 4 parameters. Within-day SEM% was greater than 10% for 6 parameters. Within-day SDC ranged from 1.80 to 25.03 units for a single scan and from 0.97 to 17.93 units for 6 scans. Between-day SEM% was greater than 10% for 9 parameters. Between-day SDC ranged from 1.44 to 28.24 units for a single scan and from 1.05 to 22.2 units for 6 scans. Thirty-six of the 40 spine shape parameters from the DIERS formetric 4D reliably distinguished between participants over time. Reference values were established that can be used to track patient postural change over time. Future research should investigate the clinical relevance of these 40 spine shape parameters and determine when a clinically important change in posture occurs.
10
Jhavar, S., C. P. Paul, and N. K. Jain. "Experimental investigation on geometrical aspects of micro-plasma deposited tool steel for repair applications." International Journal of Modern Physics: Conference Series 32 (January 2014): 1460347. http://dx.doi.org/10.1142/s2010194514603470.
Full textAbstract:
Recent advancement in direct material deposition processes found wide applications in rapid prototyping, manufacturing and tooling industry. Micro-plasma deposition is one of the recent developments in this domain. This paper reports the deployment of newly integrated micro-plasma deposition system for the deposition of AISI P-20 tool steel on the AISI P20 tool steel substrate. A number of test tracks for single track deposition were deposited at the various combination of processing parameters. The sets of parameters yielding good deposits were selected to deposit overlap tracks. The geometry of single and overlapped tracks was evaluated to understand the parametric dependence. The study indicates that the aspect ratio of track geometry (ratio of width to height of track) is dependent on the processing parameters and the discharge current is identified as the most dominating parameters (contribution = 44%), followed by scan speed (contribution = 26.68%) and wire feed rate (contribution = 26.98%) with almost same effect. The microscopic study of the deposits indicates that the material deposited at the optimum processing parameters is free from surface and bulk defects. The estimated material properties are found to be at par with conventional processed material. This feasibility study proved that the micro-plasma deposition can be used for the generation of surfaces and multi-featured material deposition. It paved a way for the application of the process in die/mold repairs.
11
Hu, Bin, Jianhai Han, and Junhua Wang. "Parameter Study and Economic Efficiency Optimization for Laser Cladding with Wide-Band Fiber Laser." International Journal of Optics 2022 (December 14, 2022): 1–12. http://dx.doi.org/10.1155/2022/6373772.
Full textAbstract:
With the aim of investigating the cladding geometry characteristics by a wide-band fiber laser with coaxial rectangular nozzle, and optimizing the powder efficiency and deposition speed for economy efficiency, Fe-based alloy powder was deposited on AISI 1045 substrate by a 3000 W fiber laser in this study. Laser power (P), scan speed (V), and powder feed rate (F) were selected for a factorial design. The effects of the three process parameters on the geometry characteristics and economic efficiency of single tracks were statistically analyzed, and a linear regression model was established between the combined parameters and the relevant characteristics (including track height, ratio of track width to height, powder efficiency, and deposition speed). A process map was developed with the track shape and key economic indexes as boundaries. A flat-top feature of the track profile was found and can be utilized to achieve good cladding evenness. The process map showed that the powder efficiency and deposition speed were higher than 50% and 20 mm3/s, respectively, when selecting process parameters in the as-built operation window.
12
Alkahari, Mohd Rizal, Tatsuaki Furumoto, Takashi Ueda, and Akira Hosokawa. "Melt Pool and Single Track Formation in Selective Laser Sintering/Selective Laser Melting." Advanced Materials Research 933 (May 2014): 196–201. http://dx.doi.org/10.4028/www.scientific.net/amr.933.196.
Full textAbstract:
Selective Laser Sintering/Selective Laser Melting (SLS/SLM) is one of Additive Manufacturing (AM) processes that utilize layer by layer powder deposition technique and successive laser beam irradiation based on Computer Aided Design (CAD) data. During laser irradiation on metal powders, melt pool was formed, which then solidified to consolidated structure. Therefore, melt pool is an important behavior that affects the final quality of track formation. The study investigates the melt pool behavior through visualization of the consolidation process during the single track formation on the first layer. In order to understand the transformation process of metal powder to consolidated structure and mechanism involved, high speed camera was used to monitor the process. Yb:fiber laser beam was irradiated on metal powder at maximum power of 150W. The laser processing parameters such as laser power, scan speed and layer thickness were varied in order to investigate their influence on the consolidation process. The result shows the size of melt pool increased with laser power and decreasing with increment in scan speed. Furthermore, with the increase of layer thickness, melt pool formation was unstable with chaotic movement. Significant amount of molten powder splattering was recorded from the melt pool. At high layer thickness also, the molten powder formed spherical shaped and the solidified molten powder failed to wet with the substrate.
13
Wright, C. Steven, M. Youseffi, S. P. Akhtar, T. H. C. Childs, C. Hauser, and P. Fox. "Selective Laser Melting of Prealloyed High Alloy Steel Powder Beds." Materials Science Forum 514-516 (May 2006): 516–23. http://dx.doi.org/10.4028/www.scientific.net/msf.514-516.516.
Full textAbstract:
This paper presents the results of a recent comprehensive investigation of selective laser melting (slm) of prealloyed gas and water atomised M2 and H13 tool steel powders. The objective of the study was to establish the parameters that control the densification of single and multiple layers with the aim of producing high density parts without the need for infiltration. Powders were processed using continuous wave (CW) CO2 and Nd:YAG lasers. Relationships between alloy composition, powder particle size and shape, flowability, microstructure (phases present, their size, morphology and distribution), track morphology, post scanned density, surface finish and scan conditions (Laser power, spot size and scan speed) are discussed for single track, single layer and multi-layer (up to 25 layers) constructions. Processing with a Nd:YAG laser with powders placed on substrates rather than on a loose powder bed gave more stable builds than with the CO2 laser. Using the Nd:YAG laser densities up to ~90% relative were possible with H13 powder compared with a maximum of ~70% for M2 in multi-layer builds. Maximum density achieved with CW CO2 processing was only ~60%, irrespective of powder composition. The paper compares the processibility of these materials with stainless steel powders processed to higher densities (up to 99% relative) under similar conditions. The results of the work show that a crucial factor for high density processing is melt pool wettability and this is controlled largely by carbon content; low carbon contents producing better wettability, flatter tracks and higher densities. The significance of this observation for the processing high alloy steels by slm will be discussed.
14
Katagiri, Jun, Masahiro Kusano, Satoshi Minamoto, Houichi Kitano, Koyo Daimaru, Masakazu Tsujii, and Makoto Watanabe. "Melt Pool Shape Evaluation by Single-Track Experiments and Finite-Element Thermal Analysis: Balling and Lack of Fusion Criteria for Generating Process Window of Inconel738LC." Materials 16, no. 4 (February 20, 2023): 1729. http://dx.doi.org/10.3390/ma16041729.
Full textAbstract:
Defects occur in laser powder bed fusion (L-PBF) such as the keyholing, lack of fusion, and the balling depending on the laser power (P) and the scan speed (V). The figure shows that the occupied regions of each defect are the process window and are essentially important to fabricate a high-quality part. This paper is a study of process window generation using single-track experiments and finite-element method simulation of thermal conduction for Inconel738LC alloy. A series of single-track experiments were conducted varying the range of P and V and the results were classified into keyholing, lack of fusion, balling, and good track. A series of simulations were conducted and validated by comparison with the experiments. To quantitively identify the balling, the isolines from the contour map generated by the results of simulations and the balling criteria of the ratio of melt pool length and the depth (L/D) of 7.69 were determined considering the past theoretical studies. The lack of fusion criteria: the ratio of the overlap depth in fabrication using multi-scan (Dov) and powder layer thickness (t) of 0.1 was obtained. Using the criteria obtained from the experiments and simulation, the process window was generated.
15
Grünewald, Jonas, Florian Gehringer, Maximilian Schmöller, and Katrin Wudy. "Influence of Ring-Shaped Beam Profiles on Process Stability and Productivity in Laser-Based Powder Bed Fusion of AISI 316L." Metals 11, no. 12 (December 9, 2021): 1989. http://dx.doi.org/10.3390/met11121989.
Full textAbstract:
A major factor slowing down the establishment of additive manufacturing processes as production processes is insufficient reproducibility and productivity. Therefore, this work investigates the influence of ring-shaped beam profiles on process stability and productivity in laser-based powder bed fusion of AISI 316L. For this purpose, the weld track geometries of single tracks and multi-track segments with varying laser power, scan speed, hatch distance, and beam profile (Gaussian profile and three different ring-shaped profiles) are analyzed. To evaluate the process robustness, process windows are identified by classifying the generated single tracks into different process categories. The influence of the beam profiles on productivity is studied by analyzing the molten cross-sectional areas and volumes per time. When using ring-shaped beam profiles, the process windows are significantly larger (up to a laser power of 1050 W and a scanning speed of 1700 mm/s) than those of Gaussian beams (laser power up to 450 W and scanning speed up to 1100 mm/s), which suggests a higher process robustness and stability. With ring-shaped beam profiles, larger volumes can be stably melted per track and time. The weld tracks created with ring-shaped profiles are significantly wider than those generated with Gaussian profiles (up to factor 2 within the process window), allowing enlargement of the hatch distances. Due to the higher scanning speeds and the enlarged hatch distances for ring-shaped beam profiles, the process can be accelerated by a factor of approximately 2 in the parameter range investigated.
16
Ghanima, Waleed, Vibeke Almaas, Saad Aballi, Dorje Christina, and Per Morten Sandset. "A Fast Track Strategy for Managing Suspected Pulmonary Embolism (PE) in Outpatients." Blood 104, no. 11 (November 16, 2004): 1766. http://dx.doi.org/10.1182/blood.v104.11.1766.1766.
Full textAbstract:
Abstract Background: Several strategies for managing patients with suspected PE have been validated. However, most of these strategies are complicated, involving multiple rounds of tests, and are thus, time consuming, costly and difficult to apply in clinical practice. Aiming to introduce a simple, fast and cost-effective strategy, we adopted a new diagnostic approach combining clinical probability assessment, D-Dimer and multi-slice spiral CT (MSSCT) scanning. Aims: The aim of this study was to assess the safety and efficacy of this management strategy by a prospective outcome study with 3-month follow-up. Methods: 495 consecutive patients referred to the Emergency Department at Østfold Hospital, Fredrikstad, Norway, for suspected PE, between Feb 2002 and Dec 2003, were considered for inclusion. 63 (12.7%) patients were excluded and the final cohort consisted of 432 patients. Patients were managed by serial non-invasive testing starting with D-Dimer test. Normal plasma D-Dimer (Liatest, latex agglutination assay, Stago-France, cut-off <0.4 mg/L) was deemed to rule out PE in patients with low-intermediate clinical probability (CP). CP for PE was assessed according to the categories proposed by Hyers. Patients with normal D-Dimer, but with high CP, and patients with elevated D-Dimer proceeded to MSSCT scan. A 4-row detector spiral CT scan was used in the study (scans were done with 2.5 mm collimation, pitch of 1.25). If MSSCT diagnosis was inconclusive, bilateral compression ultrasonography was recommended followed by a perfusion scan and eventually pulmonary angiography if further verification was necessary. Patients with verified PE received anticoagulation according to the hospitals guidelines. The entire cohort were followed-up for 3 months. Results: Normal D-Dimer and low-intermediate CP ruled out PE in 100 patients (23.1%). Twenty patients had normal D-Dimer but high CP and proceeded to MSSCT. All proved negative for PE. A total of 332 patients underwent MSSCT examination. PE was diagnosed in 95 patients (22%) and was ruled out by negative MSSCT in 221 patients. In 16 patients (4.8%), MSSCT was inconclusive due to suboptimal contrast filling (n=7), artefacts (n=2), or uncertain peripheral emboli (n=7). In ten, interpretation was inconclusive but decision to anticoagulate was made by the attending physician. Compression ultrasonography was performed in three of those; two had positive findings for DVT. In the remaining six, anticoagulation was withheld. Five had undergone further examination with ultrasound; none had DVT. Pulmonary angiography was carried out in one and perfusion lung scan in another patient; both examinations were negative. The diagnostic algorithm yielded a definite diagnosis in 96.3% of the patients. Follow-up was successfully completed in 321 (98.1%) of the patients in whom anticoagulation was withheld. Five of 321 patients (1.5%) in whom the diagnostic algorithm ruled out PE died during the follow-up period. The cause of death was adjudicated as not related to PE in three and possibly related to PE in two. No patient developed venous thromboembolism during the 3 month follow-up period, resulting in a 3-month thromboembolic rate of 0%, 95%CI (0–1.1%). Conclusions: Our results compare favorably to the results reported in previous outcome studies, and confirm the safety and efficacy of this management strategy combining D-Dimer as a first step test followed by MSSCT as a single imaging test in patients with elevated D-Dimer.
17
Sun, Shou Jin, and Milan Brandt. "Investigation of Hastelloy C Laser Clad Melt Pool Size and its Effect on Clad Formation." Key Engineering Materials 384 (June 2008): 213–27. http://dx.doi.org/10.4028/www.scientific.net/kem.384.213.
Full textAbstract:
The melt pool size of a single-track clad in the laser cladding of Hastelloy C, a Nickel based alloy, on mild steel substrate has been investigated. The effect of laser processing parameters, such as laser power density, scan rate and powder mass flow rate on the melt pool size has been examined. It was found that the melt pool size is strictly controlled by the melt pool temperature which increases with laser power but decreases with increasing scan rate and powder mass flow rate. The melt pool size is critical for the clad formation in terms of clad height and dilution with the substrate. The clad height increases linearly with the ratio of melt pool size to powder stream diameter while the dilution is an exponential function of the ratio of melt pool size to laser spot size.
18
Sreekanth, Suhas, Ehsan Ghassemali, Kjell Hurtig, Shrikant Joshi, and Joel Andersson. "Effect of Direct Energy Deposition Process Parameters on Single-Track Deposits of Alloy 718." Metals 10, no. 1 (January 7, 2020): 96. http://dx.doi.org/10.3390/met10010096.
Full textAbstract:
The effect of three important process parameters, namely laser power, scanning speed and laser stand-off distance on the deposit geometry, microstructure and segregation characteristics in direct energy deposited alloy 718 specimens has been studied. Laser power and laser stand-off distance were found to notably affect the width and depth of the deposit, while the scanning speed influenced the deposit height. An increase in specific energy conditions (between 0.5 J/mm2 and 1.0 J/mm2) increased the total area of deposit yielding varied grain morphologies and precipitation behaviors which were comprehensively analyzed. A deposit comprising three distinct zones, namely the top, middle and bottom regions, categorized based on the distinct microstructural features formed on account of variation in local solidification conditions. Nb-rich eutectics preferentially segregated in the top region of the deposit (5.4–9.6% area fraction, Af) which predominantly consisted of an equiaxed grain structure, as compared to the middle (1.5–5.7% Af) and the bottom regions (2.6–4.5% Af), where columnar dendritic morphology was observed. High scan speed was more effective in reducing the area fraction of Nb-rich phases in the top and middle regions of the deposit. The <100> crystallographic direction was observed to be the preferred growth direction of columnar grains while equiaxed grains had a random orientation.
19
Bell, Michael M., and Wen-Chau Lee. "Objective Tropical Cyclone Center Tracking Using Single-Doppler Radar." Journal of Applied Meteorology and Climatology 51, no. 5 (May 2012): 878–96. http://dx.doi.org/10.1175/jamc-d-11-0167.1.
Full textAbstract:
AbstractThis study presents an extension of the ground-based velocity track display (GBVTD)-simplex tropical cyclone (TC) circulation center–finding algorithm to further improve the accuracy and consistency of TC center estimates from single-Doppler radar data. The improved center-finding method determines a TC track that ensures spatial and temporal continuities of four primary characteristics: the radius of maximum wind, the maximum axisymmetric tangential wind, and the latitude and longitude of the TC circulation center. A statistical analysis improves the consistency of the TC centers over time and makes it possible to automate the GBVTD-simplex algorithm for tracking of landfalling TCs. The characteristics and performance of this objective statistical center-finding method are evaluated using datasets from Hurricane Danny (1997) and Bret (1999) over 5-h periods during which both storms were simultaneously observed by two coastal Weather Surveillance Radar-1988 Doppler (WSR-88D) units. Independent single-Doppler and dual-Doppler centers are determined and used to assess the absolute accuracy of the algorithm. Reductions of 50% and 10% in the average distance between independent center estimates are found for Danny and Bret, respectively, over the original GBVTD-simplex method. The average center uncertainties are estimated to be less than 2 km, yielding estimated errors of less than 5% in the retrieved radius of maximum wind and wavenumber-0 axisymmetric tangential wind, and ~30% error in the wavenumber-1 asymmetric tangential wind. The objective statistical center-finding method can be run on a time scale comparable to that of a WSR-88D volume scan, thus making it a viable tool for both research and operational use.
20
Liu, Jian, Erica Stevens, Qingchen Yang, Markus Chmielus, and Albert C. To. "An analytical model of the melt pool and single track in coaxial laser direct metal deposition (LDMD) additive manufacturing." Journal of Micromechanics and Molecular Physics 02, no. 04 (December 2017): 1750013. http://dx.doi.org/10.1142/s2424913017500138.
Full textAbstract:
An analytical model was developed for the melt pool and single scan track geometry as a function of process parameters. For computational efficiency, the developed model has simple mathematical forms with essential physics taken into account, without the need for complicated numerical simulation. In this research, a non-diverging Gaussian laser beam and coaxial diverging Gaussian powder stream combination is used to represent the coaxial laser direct metal deposition (LDMD) process. Analytical laser-powder interaction model is used to obtain the distribution of attenuated laser intensity and temperature of heated powders at the substrate. On the substrate, the melt pool is calculated by integrating Rosenthal's point heat source model. An iterative procedure is used to ensure the mass–energy balances and to calculate the melt pool and catchment efficiency. By assuming that the assimilated powder will reshape due to surface tension before solidification, a simple clad geometry model is established. The proposed model is used to simulate the geometry of single track depositions of Ti6Al4V, which shows a good agreement between model prediction and experimental results. This work demonstrates that the developed model has the potential to be used to narrow the parameter space for process optimization.
21
Chadwick, Alexander F., and Peter W. Voorhees. "The Effects of Melt Pool Geometry and Scan Strategy on Microstructure Development During Additive Manufacturing." IOP Conference Series: Materials Science and Engineering 1274, no. 1 (January 1, 2023): 012010. http://dx.doi.org/10.1088/1757-899x/1274/1/012010.
Full textAbstract:
Abstract During the powder bed fusion additive manufacturing (AM) process, hundreds of grains may solidify simultaneously within the melt pool, depending upon the processing conditions and the grain size of the base plate and powder. Thus, a small variation in the shape of the melt pool or scan strategy may result in very different as-printed microstructures, since new grains may become more favourably aligned with the overall direction of growth. The microstructure affects the performance of the additively built component, and it is therefore critical to understand the interplay between the initial microstructure, material properties, heat source, and scan strategy on determining the as-printed microstructure. We examine columnar grain growth during AM using a phase-field model to perform simulations with single melt pools predicted by the cylindrically symmetric Rosenthal solution. Quantitative measures of the competitive grain growth are extracted from the simulation data. To aid in their understanding, we map these quantities onto visualizations of the microstructure and compare them to the inverse pole figure map, from which we find that the crystallographic directions of the grains that grow closest to the centre of the laser track may not be preferentially aligned with the scan direction.
22
Martin, Thomas, Carla Janzen, Xinzhou Li, Irish Del Rosario, Teresa Chanlaw, Sarah Choi, Tess Armstrong, et al. "Characterization of Uterine Motion in Early Gestation Using MRI-Based Motion Tracking." Diagnostics 10, no. 10 (October 19, 2020): 840. http://dx.doi.org/10.3390/diagnostics10100840.
Full textAbstract:
Magnetic resonance imaging (MRI) is a promising non-invasive imaging technique that can be safely used to study placental development and function. However, studies of the human placenta performed by MRI are limited by uterine motion and motion in the uterus during MRI remains one of the major limiting factors. Here, we aimed to investigate the characterization of uterine activity during MRI in the second trimester of pregnancy using MRI-based motion tracking. In total, 46 pregnant women were scanned twice (first scan between 14 and 18 weeks and second scan between 19 and 24 weeks), and 20 pregnant subjects underwent a single MRI between 14 and 18 weeks GA, resulting in 112 MRI scans. An MRI-based algorithm was used to track uterine motion in the superior-inferior and left-right directions. Uterine contraction and maternal motion cases were separated by the experts, and unpaired Wilcoxon tests were performed within the groups of gestational age (GA), fetal sex, and placental location in terms of the overall intensity measures of the uterine activity. In total, 22.3% of cases had uterine contraction during MRI, which increased from 18.6% at 14–18 weeks to 26.4% at 19–24 weeks GA. The dominant direction of the uterine contraction and maternal motion was the superior to the inferior direction during early gestation.
23
Wen, Yongbing, Jianmin Song, Xinjian Fan, Danish Hussain, Hao Zhang, and Hui Xie. "Fast Specimen Boundary Tracking and Local Imaging with Scanning Probe Microscopy." Scanning 2018 (2018): 1–11. http://dx.doi.org/10.1155/2018/3979576.
Full textAbstract:
An efficient and adaptive boundary tracking method is developed to confine area of interest for high-efficiency local scanning. By using a boundary point determination criterion, the scanning tip is steered with a sinusoidal waveform while estimating azimuth angle and radius ratio of each boundary point to accurately track the boundary of targets. A local scan region and path are subsequently planned based on the prior knowledge of boundary tracking to reduce the scan time. Boundary tracking and local scanning methods have great potential not only for fast dimension measurement but also for sample surface topography and physical characterization, with only scanning region of interest. The performance of the proposed methods was verified by using the alternate current mode scanning ion-conductance microscopy, tapping, and PeakForce modulation atomic force microscopy. Experimental results of single/multitarget boundary tracking and local scanning of target structures with complex boundaries demonstrate the flexibility and validity of the proposed method.
24
Carbuhn, Aaron F., Daniel Yu, Lawrence M. Magee, Patrick C. McCulloch, and Bradley S. Lambert. "Anthropometric Factors Associated With Bone Stress Injuries in Collegiate Distance Runners: New Risk Metrics and Screening Tools?" Orthopaedic Journal of Sports Medicine 10, no. 2 (February 1, 2022): 232596712110703. http://dx.doi.org/10.1177/23259671211070308.
Full textAbstract:
Background: Lower limb bone stress injury (BSI) of the pelvis, femur, and tibia is prevalent in collegiate track and field distance runners. Bone mineral density (BMD), body composition (BComp), and anthropometric parameters before initial collegiate injury have not been compared between runners with BSI and their noninjured counterparts. Purpose: To characterize bone health in relation to BComp and anthropometric measurements from total-body dual x-ray absorptiometry (DXA) scans in collegiate male and female distance runners before BSI and develop BMD prediction models. Study Design: Case-control study; Level of evidence, 3. Methods: Distance runners (N = 79) from a single university track and field team were retrospectively enrolled into this study. The runners completed a DXA scan during the fall season (August-November) and participated in sport activities before the scan. Three months after scanning, electronic medical records were reviewed for the occurrence of BSI. An independent-sample t test was used to compare BMD (total and regional [spine, pelvis, and legs]), BComp (% body fat, fat mass, and lean mass), and anthropometric measurements (shoulder width and leg, arm, and trunk length) between runners with versus without BSI (included subgroup analysis by sex). Multiple linear regression with stepwise removal was used to determine variables most predictive of BMD. Results: Of the 79 enrolled participants (42 male, 37 female), 18 runners (22.8%; 11 female, 7 male) sustained a lower limb BSI. Compared with the noninjured group, injured runners had lower total and regional BMD ( P < .001 for all) and shorter leg and arm lengths ( P < .05 for both), whereas injured male runners had lower fat mass and injured female runners had lower lean mass in the legs ( P < .05 for both). Injured runners’ age-matched total BMD Z score (-0.1 ± 0.6) was considered clinically normal. BComp and anthropometric measures were predictive of total and regional BMD ( P < .05; R 2 = 0.64-0.80; percentage error = 3.8%-4.8%). Conclusion: The DXA scans of injured runners prior to incidence indicated lower BMD compared with noninjured runners. Shorter limb lengths, lower fat mass (male), and lower leg lean mass (female) may also be indicative of risk. Certain BComp and anthropometric measures were predictive of BMD.
25
Shi, Wentian, Yude Liu, Xuezhi Shi, Yanjun Hou, Peng Wang, and Guohua Song. "Beam Diameter Dependence of Performance in Thick-Layer and High-Power Selective Laser Melting of Ti-6Al-4V." Materials 11, no. 7 (July 18, 2018): 1237. http://dx.doi.org/10.3390/ma11071237.
Full textAbstract:
A 400 W high-power laser was used to fabricate 200-µm-thick Ti-6Al-4V samples to evaluate the effects of small (50 μm) and large (200 μm) beam diameter on density, microstructure and mechanical properties. A series of single-track experiments demonstrated that it was challenging for the small-beam laser to fabricate smooth and defect-free scan tracks. A larger beam diameter efficiently avoided process instability and provided a more stable and uniform melt pool. By increasing the beam diameter, the density of multilayer samples reached 99.95% of the theoretical value, which is much higher than that achieved with the small beam diameter. However, it was difficult to completely eliminate defects due to serious spatter and evaporation. Moreover, all of the generated samples had relatively coarse surfaces. For the large beam diameter of 200 µm, the optimal yield strength, ultimate tensile strength and elongation were 1150 MPa, 1200 MPa and 8.02%, respectively. In comparison, the small beam diameter of 50 µm resulted in values of 1035 MPa, 1100 MPa and 5.91%, respectively. Overall, the large-diameter laser is more suitable for high-power selective laser melting (SLM) technology, especially for thick layers.
26
Liles, Jordan, Dean Taylor, Brian Lau, and Sarah Lander. "Poster 133: Validation of 3D MRI in Glenohumeral Instability Evaluation of Glenoid and Humeral Bone Loss including Glenoid Track Compared to CT Scan." Orthopaedic Journal of Sports Medicine 10, no. 7_suppl5 (July 1, 2022): 2325967121S0069. http://dx.doi.org/10.1177/2325967121s00694.
Full textAbstract:
Objectives: The objective of our study is to determine whether the addition of 3-dimensional (3D) MRI to standard MRI sequences is comparable to 3D CT scan evaluation of glenoid and humeral bone loss in glenohumeral instability. There is increasing understanding of the importance of the glenoid, as well as humeral bone loss in outcomes and surgical decision making in patients with shoulder instability. Although magnetic resonance imaging (MRI) is performed as standard of care for soft tissue evaluation of shoulder instability, CT scan remains the gold standard in bony measurements. Standard MRI evaluation has been shown to inaccurately measure bone loss. However, additional CT scans result in increased financial, time, and ionizing radiation cost to the patient. Methods: Eighteen patients who presented with glenohumeral instability were prospectively enrolled and received both MRI and CT within 1 week of each other. The MRI included an additional sequence (VIBE) which underwent post-processing for reformations (Figure 1a). The addition of a VIBE protocol, on average is an addition 4 to 4.5minutes in the scanner. CT data also underwent 3D post-processing (Figure 1b) and therefore each patient had four imaging modalities (2D CT, 2D MRI, 3D CT reformats, and 3D MRI reformats). Each sequence underwent the following measurements from two separate reviewers: glenoid defect, glenoid defect percent, humeral defect, humeral defect percentage (Figure 2a and 2b), and evaluation of glenoid track and version. Paired t-tests were used to assess differences between imaging modalities and chi squared for glenoid track. Intra-observer and inter-observer reliability were evaluated. Bland-Altman tests were also performed to assess the agreement between CT and MRI. In addition, we determined cost of each imaging modality at our single institution. Results: 3D MRI measurements for glenoid and humeral bone loss measurements were comparable to 3D CT (Table 1). There were no significant differences for glenoid defect size and percentage, or humeral defect size and percentage (P>0.05) (Table 2). Bland-Altman analysis demonstrated strong agreement with small measurement errors for 3D CT and 3D MRI percentage glenoid bone loss. There was also no difference in evaluation for determining on vs off track between any of the imaging modalities. Inter- and intra-rater reliability was good to excellent for all CT and MRI measurements (r >= 0.7). Conclusions: 3D MRI measurements for bone loss in glenohumeral instability through utilization of VIBE sequence were equivalent to 3D CT. At our institution, the costs of MRI with 3D reconstruction was 1.67x cheaper than MRI and CT with 3D reconstructions. 3D MRI may be a useful adjuvant to standard MRI sequences to allow concurrent soft tissue and accurate assessment of glenoid and humeral bone loss in glenohumeral instability. [Figure: see text][Figure: see text][Table: see text][Table: see text]
27
Keller, Sarah, Zhiyue J. Wang, Amir Golsari, Anne Catherine Kim, Hendrik Kooijman, Gerhard Adam, and Jin Yamamura. "Feasibility of peripheral nerve MR neurography using diffusion tensor imaging adapted to skeletal muscle disease." Acta Radiologica 59, no. 5 (August 10, 2017): 560–68. http://dx.doi.org/10.1177/0284185117726100.
Full textAbstract:
Background Diffusion tensor imaging (DTI) of peripheral nerves may provide additional information about nerve involvement in muscular disorders, but is considered difficult due to different optimal scan parameters tailored to magnetic resonance (MR) signal properties of muscle and neural tissues. Purpose To assess the feasibility of sciatic nerve DTI using two different approaches of region of interest (ROI)-localization in DTI scans with b-values 500 s/mm2, in participants with muscular disorders and in controls. Material and Methods DTI of the thigh was conducted on a 3T system in ten patients (6 men, 4 women; mean age =54 ± 15 years) with neuromuscular disorders and ten controls. T1-weighted (T1W) images were co-registered to fractional anisotropy (FA) color-encoded images. The apparent diffusion coefficient (ADC), FA, and fiber track length (FTL) were analyzed by two operators using a freehand ROI and a single-point ROI covering the sciatic nerve. Interclass correlation coefficient (ICC) and Bland–Altman analysis were used for evaluation of inter-operator and inter-technical agreement, respectively. Results Three-dimensional visualization of sciatic nerve fiber was achievable using both techniques. The ICC of DTI metrics showed excellent inter-operator agreement both in patients and controls. Bland–Altman analysis revealed good agreement of both techniques. A maximum FTL was achieved using the single-point ROI technique, but with a lower inter-operator agreement (ICC = 0.99 vs. 0.83). The ADC and maximum FTL were significantly decreased in patients compared to controls. Conclusion Both ROI localization techniques are feasible to analyze the sciatic nerve in the setting of muscular disease. A maximum FTL is reached using the single-point ROI, however, at the cost of lower inter-operator agreement.
28
Wang, Di, Yang Liu, Yongqiang Yang, and Dongming Xiao. "Theoretical and experimental study on surface roughness of 316L stainless steel metal parts obtained through selective laser melting." Rapid Prototyping Journal 22, no. 4 (June 20, 2016): 706–16. http://dx.doi.org/10.1108/rpj-06-2015-0078.
Full textAbstract:
Purpose The purpose of this paper is to provide a theoretical foundation for improving the selective laser melting (SLM) surface roughness. To improve the part’s surface quality during SLM process, the upper surface roughness of SLM parts was theoretically studied and the influencing factors were analyzed through experiments. Design/methodology/approach The characteristics of single track were first investigated, and based on the analysis of single track, theoretical value of the upper surface roughness would be calculated. Two groups of cubic sample were fabricated to validate SLM parts’ surface roughness, the Ra and relative density of all the cubic parts was measured, and the difference between theoretical calculation and experiment results was studied. Then, the effect of laser energy density on surface roughness was studied. At last, the SLM part’s surface was improved by laser re-melting method. At the end of this paper, the curved surface roughness was discussed briefly. Findings The SLM upper surface roughness is affected by the width of track, scan space and the thickness of powder layer. Measured surface roughness Ra value was about 50 per cent greater than the theoretical value. The laser energy density has a great influence on the SLM fabrication quality. Different laser energy density corresponds to different fabricating characteristics. This study divided the SLM fabrication into not completely melting zone, balling zone in low energy density, successfully fabricating zone and excessive melting zone. The laser surface re-melting (LSR) process can improve the surface roughness of SLM parts greatly without considering the fabricating time and stress accumulation. Originality/value The upper surface roughness of SLM parts was theoretically studied, and the influencing factors were analyzed together; also, the LSR process was proven to be effective to improve the surface quality. This study provides a theoretical foundation to improve the surface quality of SLM parts to promote the popularization and application of metal additive manufacturing technology.
29
Zhu, Chengcheng, Xiaoming Chen, Honglin Wu, Jun Zhu, Tao Peng, Jingxiang Lv, and Yihang Wu. "Multi-Objective Optimization of Selective Laser Melting Processes for Minimizing Energy Consumption and Maximizing Product Tensile Strength." Metals 12, no. 11 (October 23, 2022): 1782. http://dx.doi.org/10.3390/met12111782.
Full textAbstract:
As a sustainable manufacturing technology, selective laser melting (SLM) is a typical additive manufacturing (AM) method with high flexibility and material efficiency. However, SLM is intrinsically energy-intensive than conventional machining processes. By contrast, part quality, especially the tensile strength, is critical for applying SLM technology. Therefore, this study aims to minimize the process energy consumption and maximize the part tensile strength by optimizing three essential process parameters, namely laser power, scan speed, and overlap rate. First, single track and single layer experiments are applied to determine the constraints of process parameters. Then, analytical and statistical models are used to calculate energy consumption and part tensile strength. Finally, the process parameters to achieve compromised optimal solutions are located using the nondominated sorting genetic algorithm II (NSGA-II). A case study of a waveguide part manufactured via the SLM process is employed to demonstrate the effectiveness of the proposed approach. Results showed that both energy consumption and part tensile strength could be improved moderately using the proposed method. This study can potentially guide the process parameter selection for new material AM processes and improve the AM product quality.
30
Mazzucato, Federico, Alberta Aversa, Roberto Doglione, Sara Biamino, Anna Valente, and Mariangela Lombardi. "Influence of Process Parameters and Deposition Strategy on Laser Metal Deposition of 316L Powder." Metals 9, no. 11 (October 28, 2019): 1160. http://dx.doi.org/10.3390/met9111160.
Full textAbstract:
In blown powder additive manufacturing technologies the geometrical stability of the built parts is more complex with respect to more conventional powder bed processes. Because of this reason, in order to select the most suitable building parameters, it is important to investigate the shape and the properties of the single metal bead formation and the effect that a scan track has on the nearby ones. In the present study, a methodology to identify an appropriate laser metal deposition process window was introduced, and the effect of the building parameters on the geometry of circular steel samples was investigated. The effect of the scanning strategy on the deposited part was also investigated. This work draws the attention to the importance of the obtainment of the most suitable melt pool shape, demonstrating that the laser power and the scanning strategy have a strong influence not only on the shape but also on the mechanical properties of the final component.
31
Harrison, M. J. K., J. L. Sullivan, and G. S. A. M. Theunissen. "Wear mechanisms of sandwich-type video heads." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 211, no. 4 (April 1, 1997): 263–77. http://dx.doi.org/10.1243/1350650971542471.
Full textAbstract:
Differential wear between the various material components of composite magnetic recording heads is observed upon running against the magnetic medium. A developing level difference between the magnetic material and the medium bearing surface leads to signal degradation, exponential with the difference and the signal frequency. Experimental evidence is presented for a three-body erosion mechanism in the case of sandwich heads employed in commercial helical scan, Hi-8 video tape recorders. Two sintered ceramic substrates, CaTiO3 and composite Zr-doped CaTiO3, in combination with three soft magnetic materials, amorphous CoNbZr and the nanocrystalline iron alloys FeNbSiN and FeTaN, have been studied. They have been studied in conjunction with commercial metal evaporated (ME) and metal particulate (MP) tapes. Level difference has been measured by interferometry and AFM (atomic force microscopy), the latter also observing level differences between the various components of the sandwich: soft magnetic metal, ceramic laminations and the metallic bonding layer. AFM shows a pull-out of particles from the ceramic substrate with similar sized particles observed on the track. Scanning Auger micrographs have shown the transfer of ceramic particles on to the track and of metal on to the substrate. Wear rates and wear mechanisms have been identified for the materials in isolation by studying single-material dummy heads. This has been identified as plastic deformation controlled microabrasion, transforming to grain pull-out in the crystalline materials in some instances. It is speculated that these pull-outs are responsible for the wear of the soft metallic track when this is out of contact with the tape. The evidence for chemical wear is inconclusive. The involvement of transfer material from the tape to the head is speculated upon.
32
Muster, Viktoria, Markus Wallner, Albrecht Schmidt, Martin Kapl, Friederike von Lewinski, Peter Rainer, Pia Reittner, et al. "Heart rate-reducing therapy with add-on ivabradine and bisoprolol before coronary computed tomographic angiography in a fast-track ambulatory setting." Journal of International Medical Research 46, no. 6 (April 3, 2018): 2249–57. http://dx.doi.org/10.1177/0300060518761302.
Full textAbstract:
Objective This study was performed to determine whether add-on oral ivabradine in patients treated with beta blockers 1 hour before coronary computed tomographic angiography (CCTA) is effective in lowering the heart rate and thus improving CCTA quality. Methods In this single-center cohort study, the data of 294 patients referred for ambulant CCTA were retrospectively screened. Patients with an initial heart rate of ≥75 bpm (n = 112) were pretreated with either a combination of bisoprolol and ivabradine or with bisoprolol alone. Results During the scan, there was no difference in heart rate between the two groups Likewise, there was no significant difference in additionally administered intravenous bradycardic agents, the number of motion artifacts, or the radiation dose. Both drug regimens were tolerated well. Conclusion Additive oral ivabradine 1 hour before CCTA does not result in a further reduction of the heart rate. Consequently, neither movement artifacts nor radiation dose can be reduced. Therefore, pretreatment with ivabradine does not seem reasonably appropriate in an outpatient clinical setting with short patient contact.
33
Perlitz, Julian F. A., Heiko Broß, and Stefan Will. "Measurement of Water Mole Fraction from Acoustically Levitated Pure Water and Protein Water Solution Droplets via Tunable Diode Laser Absorption Spectroscopy (TDLAS) at 1.37 µm." Applied Sciences 11, no. 11 (May 29, 2021): 5036. http://dx.doi.org/10.3390/app11115036.
Full textAbstract:
In order to understand the evaporation and particle formation processes of sprays in technical applications such as fuel injectors or drying processes in the food and pharmaceutical industries in detail, single droplet drying experiments, for example, acoustic levitation, are widely used as model experiments. We combined acoustic levitation and tunable diode laser absorption spectroscopy (TDLAS) to measure the absolute H2O concentration in the exhaust gas of a levitation chamber to investigate drying and particle formation processes from single droplets of pure water and protein–water solutions. To that end, we designed and developed a non-invasive, calibration-free TDLAS-based hygrometer to analyze the 1.4 µm overtone band. To increase the detection range of the developed hygrometer and to track the complete drying process of protein solution droplets even after the critical point of drying, the absorption length was extended to a path length of 18 m using an astigmatic multipass cell of the Herriott type. The setup was validated by drying pure water droplets, resulting in a determination of the water mole fraction in a range from 73 ppm to 1314 ppm, with a single scan resolution of 1.7 ppm. For protein solution droplets, the entire drying process, even beyond the critical point of drying, can be tracked and the different phases of the drying process can be characterized at different drying temperatures.
34
Dahl, Nathan A., and David S. Nolan. "Using High-Resolution Simulations to Quantify Errors in Radar Estimates of Tornado Intensity." Monthly Weather Review 146, no. 7 (July 1, 2018): 2271–96. http://dx.doi.org/10.1175/mwr-d-17-0333.1.
Full textAbstract:
Abstract Observation experiments are performed on a set of high-resolution large-eddy simulations of translating tornado-like vortices. Near-surface Doppler wind measurements are taken by emulating a mobile radar positioned from 1 to 10 km south of each vortex track and conducting single-level scans every 2 s. The departure of each observed gust (wind measurement averaged over two successive scans) from the corresponding true maximum 3-s gust at 10 m AGL (“S10–3s”) is partitioned into error sources associated with resolution volume size, wind direction relative to the radar beam, beam elevation, and temporal sampling. The distributions of each error type are diagrammed as functions of range, observed wind speed, and predicted deviation between the wind direction and the radar beam. The results indicate that the deviation between the wind direction and the radar beam is the predominant source of error in these rapid scan scenarios, although range is also a substantial factor. The median total error is ~10% for small deviation at close range, but it approximately doubles if the range is increased from 1 to 10 km; a more pronounced increase in both the median value and the variance of the total error is seen as the deviation becomes large. Because of this, the underestimate of the global maximum S10–3s approaches 30–40 m s−1 at a longer range, although the global maximum of the time-averaged observed wind speed gives a reasonable approximation of the time-mean maximum S10–3s in many cases. Because of simplifying assumptions and the limited number of cases examined, these results are intended as a baseline for further research.
35
Magee, Lawrence, Patrick McCulloch, and Bradley Lambert. "Poster 124: Intrinsic Anthropometric Factors are Associated with Bone Stress Injuries in Collegiate Distance Runners: New Risk Metrics & Screening Tools?" Orthopaedic Journal of Sports Medicine 10, no. 7_suppl5 (July 1, 2022): 2325967121S0068. http://dx.doi.org/10.1177/2325967121s00685.
Full textAbstract:
Objectives: Lower limb bone stress injuries (BSI) of the pelvis, femur, and tibia are prevalent in collegiate track & field distance runners. However, it is not known the population’s bone, body composition (BComp), and anthropometric parameters prior to first respective collegiate injury compared to non-injured counterpart. This respective injury has been reported to require an extended timeframe for recovery as well as increases the risk, prospectively, for sustaining another similar injury. Extrinsic factors such as greater running frequency, mileage, pace, and change in terrain is known to influence risk which, during a competitive season, commonly occurs in collegiate runners. Intrinsic risk factors related to bone health and body composition of the runner have also been identified as important factors that further influence risk indicating proper screening of these respective intrinsic factors are necessary and recommended in order to better identify risk and prompt further evaluation. In light of previous observations and a clinical need in this unique population, the purpose of this study was to characterize bone mineral density, body composition, and skeletal dimensions assessed vai dual energy x-ray absorpitometry (DXA) in collegiate male and female distance runners prior to lower limb BSI status (i.e. injured or non-injured) during a competitive season as well as provide indices of risk specific DXA assessment. We hypothesized that 1) collegiate distance runners with a lower limb BSI will exhibit lower BMD relative to runners without injury; 2) total and regional body composition (i.e. fat and lean) as well as skeletal dimension differences will be observed between respective BSI status groups thus, allowing for identification of potential threshold cutoffs for this population; 3) measures of body composition and skeletal dimensions could be used to develop prediction models for regional and total BMD that may be utilized in the abscence of DXA for those with out readily available access. Methods: This was a retrospective case-control study design that was conducted at a University athletic training facility during the fall (August-November) 2013-2019 cross country seasons. Study measurements included a total body (TB) DXA scan, weight (kg), height (cm), and body mass index (BMI; kg/m2). The inclusion scan for the study participants with a lower limb BSI was the scan before first respective injury of collegiate career while study participants with no injury during collegiate career had their last scan of eligible fall season included. This study included male and female distance running athletes who were members of a NCAA D1A collegiate track and field team at a single University. Inclusion criteria included participation in sport-related activity prior to and after DXA scan for three months as well as only scans prior to first collegiate lower limb BSI. Exclusion criteria included any bone-related injury or recovery from such injury at time of DXA scan that prohibited prospective sport-related activities as well as scans prior to reoccurring lower limb BSI. Enrolled runners completed a DXA scan (August-November) and participated in sport activities before scan. Three months following scan, electronic medical records were reviewed to determine whether or not a BSI occurred. Independent samples t-test was used to compare BMD, BComp, and anthropometric measures between BSI vs non-injured (included subgroup analysis by sex). Multiple linear regression with stepwise removal was used to determine measures most predictive of BMD. Significance was set at p<0.05. Results: Demographics are shown in Table 1. Figure 1 shows athlete BMD characteristics among athletes (i.e. all, males, and females) with or without lower limb BSI. Overall, those in the NoBSI group had significantly higher BMD values for total, spine, pelvis, and legs (p<0.001). In males, the NoBSI group had significantly higher total, pelvis, and leg BMD (p<0.05) while no difference was observed in spine BMD compared to BSI group. Within females, the NoBSI group had significantly higher BMD in all respective measures compared to BSI group (p<0.001). Regression analysis revealed BComp and anthropometric measures were predictive of total bone mass [BM = (0.046 x age, yrs) + (0.024 x weight, kg) + (0.014 x %Fat) + (-0.017 x ARML) + (0.017 x SHWIDTH) + (-0.009 x TRNKL) + (0.037 x LL)]; P<0.05, R2 = 0.61 g/cm2, percent error = 11.01). In addition to predicted BM, as shown in Figure 2, other BComp and anthropometric measures [age, height, weight, BMI, FM, %Fat, BM, LL, SHWIDTH, TRNKL, and ARML) were predictive of total and regional BMD (P<0.05, R2 = 0.64-0.80 g/cm2, %error = 3.8-4.8). A physiologic comparison of those with and without long bone BSIs is shown in Table 2. No differences were found between BSI and NoBSI group demographics (i.e. height, weight, age, and BMI) in all athletes including males and females. BComp values in males found FM to be significantly lower in BSI compared to NoBSI while women leg LM in BSI group was significantly lower than NoBSI. Among all athletes, the BSI group had significantly shorter arm and leg limb lengths as well as a lower leg/trunk ratio compared to NoBSI group. Conclusions: Lower limb bone stress injuries are common in collegiate distance runners wherby total and regional BMD measures tend to be lower compared to runners who were not injured. Shorter limb lengths, lower fat mass (male), and lower leg lean mass (female) may also be indicative of BSI risk in this population. Interestingly, BComp and anthropometric measures are highly predictive of BMD in this sport population. These metrics may serve as sport-specific benchmarks for lower limb BSI risk and the equations developed here may be suitable for BMD screening in collegiate distance runners without readily availalbe access to DXA. [Figure: see text][Figure: see text][Table: see text][Table: see text]
36
ABDULRAHMAN, Hayder J., and Suzan B. MOHAMMED. "DEVELOPMENT OF ULTRA-SHORT HIGH INTENSITY LASERS FOR THE VISIBLE SPECTRA RANGE." Periódico Tchê Química 17, no. 35 (July 20, 2020): 739–52. http://dx.doi.org/10.52571/ptq.v17.n35.2020.63_abdulrahman_pgs_739_752.pdf.
Full textAbstract:
Ultra-short laser pulses are particularly suitable for processing micro tools made of ultra-hard and dielectric materials. Ultra-short laser pulses provide a contact-free and precise fabrication of heat-sensitive materials such as visible spectra range. Visible spectra range has unique properties, which makes it an essential material in the tool, jewelry, and semiconductor industries. The processing of visible spectra range by ultra-short laser pulses is complex, as visible and near-infrared light is generally not absorbed. However, the intensity of ultra-short laser pulses is extremely high, so that the absorption scales nonlinearly with the intensity and, thus, visible or near-infrared light can be absorbed. The complexity also results from many partially interdependent process variables, such as the repetition rate, pulse overlap, track overlap, and scan speed. Excellent knowledge of the process is, therefore, essential for the production of micro tools. To make the laser processing accessible to a broader user field, the operator can be supported by a computer-aided design (CAD). The aim of this research was to the modeling of an ultra-short high-intensity laser for the visible spectra range in different environments of the angle of incidence, scanning speed, pulse, and track overlap. The experimental process included ultra-short pulsed laser processing of visible spectra range and surface analysis concerning modifications and ablation of the ultra-short laser. Ablation volumes were analyzed for single pulses, multi-pulses, and pockets. Pump-probe experiments reveal transient optical properties such as transmission or reflectivity. It was concluded that ultraviolet laser pulses are best suited to induce damage or modifications to visible spectra range surfaces. Additionally, shorter wavelengths have further advantages such as potentially longer Rayleigh lengths and smaller spot sizes.
37
Edwardson, S. P., J. Griffiths, K. R. Edwards, G. Dearden, and K. G. Watkins. "Laser forming: Overview of the controlling factors in the temperature gradient mechanism." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 224, no. 5 (March 19, 2010): 1031–40. http://dx.doi.org/10.1243/09544062jmes1776.
Full textAbstract:
Laser forming (LF) offers the industrial promise of controlled shaping of metallic and non-metallic components for prototyping, the correction of design shape or distortion, and precision adjustment applications. The potential process advantages include precise incremental adjustment, flexibility of application, and no mechanical ‘spring-back’ effect. To date, there has been a considerable amount of work carried out on two-dimensional LF, using multi-pass straight-line scan strategies to produce a reasonably controlled bend angle in a number of materials, including aerospace alloys. A key area, however, where there is a limited understanding, is the variation in the bend angle per pass during multi-pass temperature gradient mechanism-based LF along a single irradiation track, in particular, the decrease in the bend angle per pass after many irradiations for a given set of process parameters. Understanding this is essential if the process is to be fully controlled for a manufacturing environment. The research presented in this paper through empirical data and numerical simulation of the LF of sheet mild steel, Ti6Al4V and AA5251, by CO2 laser offers a novel coherent picture of the key influencing factors and at which point in the bend evolution each is dominant, which has not been presented before.
38
Wang, Mingjun, Ming Xue, Kun Zhao, and Jili Dong. "Assimilation of T-TREC-Retrieved Winds from Single-Doppler Radar with an Ensemble Kalman Filter for the Forecast of Typhoon Jangmi (2008)." Monthly Weather Review 142, no. 5 (April 30, 2014): 1892–907. http://dx.doi.org/10.1175/mwr-d-13-00387.1.
Full textAbstract:
Abstract A tropical cyclone (TC) circulation Tracking Radar Echo by Correlation technique (T-TREC) developed recently is applied to derive horizontal winds from single Doppler radar reflectivity Z data (combined with radial velocity Vr data when available). The typically much longer maximum range of Z observations compared to Vr data allows for much larger spatial coverage of the T-TREC-retrieved winds (VTREC) when a TC first enters the maximum range of a coastal radar. Retrieved using data from more than one scan volume, the T-TREC winds also contain valuable cross-beam wind information. The VTREC or Vr data at 30-min intervals are assimilated into the Advanced Regional Prediction System (ARPS) model at 3-km grid spacing using an ensemble Kalman filter, over a 2-h window shortly after Typhoon Jangmi (2008) entered the Vr coverage area of an operational weather radar of Taiwan. The assimilation of VTREC data produces analyses of the typhoon structure and intensity that more closely match observations than analyses produced using Vr data or the reference Global Forecast System (GFS) analysis. Subsequent 28-h forecasts of intensity, track, structure, and precipitation are also improved by assimilating VTREC data. Further sensitivity experiments show that assimilation of VTREC data can build up a reasonably strong vortex in 1 h, while a longer assimilation period is required to spin up the vortex when assimilating Vr. Although the difference between assimilating VTREC and Vr is smaller when the assimilation window is longer, the improvement from assimilating VTREC is still evident. Assimilating Z data in addition to Vr or VTREC results in little further improvement.
39
Oliver, R., T. Powles, P. Ell, U. Somasundram, and J. Shamash. "22 year phase 1/2 study of single agent carboplatin in metastatic seminoma: Potential for acceleration by a new surrogate end point, 72 hr PET scan response?" Journal of Clinical Oncology 24, no. 18_suppl (June 20, 2006): 14565. http://dx.doi.org/10.1200/jco.2006.24.18_suppl.14565.
Full textAbstract:
14565 Background: That metastatic seminoma may be more chemo-curable than non-seminoma was first suggested by Samuels (1980 Proc ASCO 21 abst 415) 4 of 5 patients durable CR to single agent cisplatin and by Oliver (1984 Proc ASCO 3. Abst 636) 9 of 10 durable responses. Carboplatin proved less effective and in randomised trials involving 361 patients relapse free survival was 72% with Carbo and 92% with cisplatin-based combination. Prompted by successful dose escalation of carboplatin in ovarian cancer, the initial phase 1 study that preceded the UK randomised trial was reopened and dosage escalated to AUC 8 and then 10. This abstract updates this study and provides more prolonged follow up of the previous reported cases. Methods: Initially patients received Carboplatin 450 mg/m2 (1983–7) and then AUC 7 (88–94), 8 (95–6) and 10 (97–06). The treatment was repeated q21 when possible and if delayed because of toxicity blood counts were repeated every 24 hours. Results: 60 metastatic seminoma patients have been treated between 1983 and 2006. 79%/95% of 19 receiving 450 mg/m2, 88%/94% of 17 receiving AUC 7 or 8 and 92%/100% of 24 receiving AUC 10 are progression free/alive. Overall 58 (97%) are alive and with 28 patients followed more than 10 years there have been no relapses after 26 months. Mild and rapidly recovering (med 14 d) transaminitis in 64% of AUC × 10 (med 93 range 51–541) suggests this may be the upper limit for safe use. As a pilot study 5 seminomas receiving AUC × 10 and 6 non-seminomas receiving BEP had PET scan before and at 72 hours after treatment. The only patient failing to respond substantially was a seminoma who showed increased PET activity on AUC × 10 but achieved complete remission of PET activity after one course of BEP. Conclusion: This data confirms the need for more studies of single agent platinum analogues in seminomas and reinforces the view that it may be preferable to radiotherapy for patients electing adjuvant treatment. With increasing attention being paid to late events, minimizing treatment toxicity and finding a fast track approach to proving safety is an increasing need. The data presented demonstrates the potential of early PET scan as a surrogate for response and could have accelerated the phase 1/2 study reported. No significant financial relationships to disclose.
40
Bériault, Silvain, Abbas F. Sadikot, Fahd Alsubaie, Simon Drouin, D. Louis Collins, and G. Bruce Pike. "Neuronavigation using susceptibility-weighted venography: application to deep brain stimulation and comparison with gadolinium contrast." Journal of Neurosurgery 121, no. 1 (July 2014): 131–41. http://dx.doi.org/10.3171/2014.3.jns131860.
Full textAbstract:
Careful trajectory planning on preoperative vascular imaging is an essential step in deep brain stimulation (DBS) to minimize risks of hemorrhagic complications and postoperative neurological deficits. This paper compares 2 MRI methods for visualizing cerebral vasculature and planning DBS probe trajectories: a single data set T1-weighted scan with double-dose gadolinium contrast (T1w-Gd) and a multi–data set protocol consisting of a T1-weighted structural, susceptibility-weighted venography, and time-of-flight angiography (T1w-SWI-TOF). Two neurosurgeons who specialize in neuromodulation surgery planned bilateral STN DBS in 18 patients with Parkinson's disease (36 hemispheres) using each protocol separately. Planned trajectories were then evaluated across all vascular data sets (T1w-Gd, SWI, and TOF) to detect possible intersection with blood vessels along the entire path via an objective vesselness measure. The authors' results show that trajectories planned on T1w-SWI-TOF successfully avoided the cerebral vasculature imaged by conventional T1w-Gd and did not suffer from missing vascular information or imprecise data set registration. Furthermore, with appropriate planning and visualization software, trajectory corridors planned on T1w-SWI-TOF intersected significantly less fine vasculature that was not detected on the T1w-Gd (p < 0.01 within 2 mm and p < 0.001 within 4 mm of the track centerline). The proposed T1w-SWI-TOF protocol comes with minimal effects on the imaging and surgical workflow, improves vessel avoidance, and provides a safe cost-effective alternative to injection of gadolinium contrast.
41
Pu, Zhaoxia, Xuanli Li, Christopher S. Velden, Sim D. Aberson, and W. Timothy Liu. "The Impact of Aircraft Dropsonde and Satellite Wind Data on Numerical Simulations of Two Landfalling Tropical Storms during the Tropical Cloud Systems and Processes Experiment." Weather and Forecasting 23, no. 1 (February 1, 2008): 62–79. http://dx.doi.org/10.1175/2007waf2007006.1.
Full textAbstract:
Abstract Dropwindsonde, Geostationary Operational Environmental Satellite-11 (GOES-11) rapid-scan atmospheric motion vectors, and NASA Quick Scatterometer (QuikSCAT) near-surface wind data collected during NASA’s Tropical Cloud Systems and Processes (TCSP) field experiment in July 2005 were assimilated into an advanced research version of the Weather Research and Forecasting (WRF) model using its three-dimensional variational data assimilation (3DVAR) system. The impacts of the mesoscale data assimilation on WRF numerical simulation of Tropical Storms Cindy and Gert (2005) near landfall are examined. Sensitivity of the forecasts to the assimilation of each single data type is investigated. Specifically, different 3DVAR strategies with different analysis update cycles and resolutions are compared in order to identify the better methodology for assimilating the data from research aircraft and satellite for tropical cyclone study. The results presented herein indicate the following. 1) Assimilation of dropwindsonde and satellite wind data into the WRF model improves the forecasts of the two tropical storms up to the landfall time. The QuikSCAT wind information is very important for improving the storm track forecast, whereas the dropwindsonde and GOES-11 wind data are also necessary for improved forecasts of intensity and precipitation. 2) Data assimilation also improves the quantitative precipitation forecasts (QPFs) near landfall of the tropical storms. 3) A 1-h rapid-update analysis cycle at high resolution (9 km) provides more accurate tropical cyclone forecasts than a regular 6-h analysis cycle at coarse (27 km) resolution. The high-resolution rapidly updated 3DVAR analysis cycle might be a practical way to assimilate the data collected from tropical cyclone field experiments.
42
Bond, Marcus. "The phase transition in bis(methyl(2-phenylethyl)ammonium) tetrabromidocuprate(II)." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C1688. http://dx.doi.org/10.1107/s2053273314083119.
Full textAbstract:
Bis(methyl(2-phenylethyl)ammonium) tetrachloridocuprate(II) is a well-known thermochromic compound that exhibits an abrupt color change (from green to yellow) at 353 K that is caused by a change in coordination geometry from square planar to flattened tetrahedral [1]. As part of a reinvestigation of established thermochromic chloridocuprate(II) and their related compounds, the bromide analog [bis(methyl(2-phenylethyl)ammonium) tetrabromidocuprate(II)] has been studied anew. The structure redetermination at ambient temperature agrees with the original [2] (CSD refcode: FUTTIX), i.e. alternating layers of flattened tetrahedral tetrabromidocuprate(II) complexes and of organic cations stacked along the a-axis of the monoclinic C2/c unit cell. A DSC scan from ambient temperature to 183 K reveals an exothermic peak (and corresponding endothermic peak upon heating) at 215 K. Single crystal structures, determined from ambient temperature to 120 K in steps of ~20 K, track a steady increase in b-axis length on cooling to the transition temperature. Across the transition temperature abrupt 1.1% and 0.74% increases in lengths of the b- and c-axes, respectively. and a 0.23% decrease in the a-axis length are observed with no change in space group. Slight changes of the organic cation phenyl group conformation are observed across the transition temperature that cause the organic layer to spread out and become thinner so that neighbouring layers are stacked more closely together along a. However, the flattened tetrahedral geometry of the tetrabromidocuprate(II) complex remains essentially unchanged across the transition.
43
Hsu, Jingmei, Eric von Hofe, Michael Hsu, Koen Van Besien, Thomas Fahey, Jana Ivanidze, Janusz Puc, Karrie Du, and Moonsoo Jin. "121 ICAM-1-specific affinity tuned CAR T cells expressing SSTR2 for real-time imaging." Journal for ImmunoTherapy of Cancer 9, Suppl 2 (November 2021): A130. http://dx.doi.org/10.1136/jitc-2021-sitc2021.121.
Full textAbstract:
BackgroundThe use of CAR T cells for solid tumors has a number of challenges, such as lack of tumor-specific targets, CAR T cell exhaustion, and the immunosuppressive tumor microenvironment. To address these challenges, AffyImmune has developed technologies to affinity tune and track CAR T cells in patients. The targeting moiety is affinity tuned to preferentially bind to tumor cells overexpressing the target while leaving normal cells with low basal levels untouched, thereby increasing the therapeutic window and allowing for more physiological T cell killing. The CAR T cells are designed to express SSTR2 (somatostatin receptor 2), which allows for the tracking of CAR T cells in vivo via PET/CT scan using FDA-approved DOTATATE.MethodsAIC100 was generated by affinity tuning the I-domain of LFA-1, the physiological ligand to ICAM-1. Various mutants with 106-fold difference in affinity were evaluated for affinity. This allowed structure activity relationships to be conducted using CAR T cells expressing the various affinity mutants against targets with varying antigen densities. The variant with micromolar affinity was clearly the most effective in non-clinical animal models. AIC100 is currently being evaluated to assess safety, CAR T expansion, tumor localization, and preliminary activity in patients with advanced thyroid cancer in a phase I study (NCT04420754). Our study uses a modified toxicity probability interval design with three dosage groups of 10 x 106, 100 x 106, and 500 x 106 cells.ResultsPreclinical studies demonstrated greater in vivo anti-tumor activity and safety with lower affinity CAR T cells. A single dose of AIC100 resulted in tumor elimination and significantly improved survival of animals. AIC100 activity was confirmed in other high ICAM-1 tumor models including breast, gastric, and multiple myeloma. In a Phase I patient given 10-million CAR T cells, near synchronous imaging of FDG and DOTATATE revealed preliminary evidence of transient CAR T expansion and tumor reduction at multiple tumor lesions, with the peak of CAR T density coinciding with the spike in CAR T numbers in blood.ConclusionsWe have developed affinity tuned CAR T cells designed to selectively target ICAM-1 overexpressing tumor cells and to spatiotemporally image CAR T cells. Near-synchronous FDG and DOTATATE scans will enhance patient safety by early detection of off-tumor CAR T activity and validation of tumor response. We anticipate that our ‘tune and track’ technology will be widely applicable to developing potent yet safe CAR T cells against hard-to-treat solid cancers.Trial RegistrationNCT04420754Ethics ApprovalIRB number19-12021154IACUC (animal welfare): All animal experiments were performed in accordance with the National Institute of Health’s Guide for the Care and Use of Laboratory Animals. Animal handling protocols were approved by the Institutional Laboratory Animal Use and Care Committee of Weill Cornell Medicine (Permit Number: 2012–0063).
44
Hsu, Jingmei, Yen-Michael Hsu, Koen van Besien, Thomas J. Fahey, Jana Ivanidze, Janusz Puc, Karrie Du, et al. "Abstract 5579: First-in-human study of ICAM-1-specific affinity tuned CAR T cells against advanced thyroid cancer." Cancer Research 82, no. 12_Supplement (June 15, 2022): 5579. http://dx.doi.org/10.1158/1538-7445.am2022-5579.
Full textAbstract:
Abstract Background: The use of chimeric antigen receptor (CAR) T cells for solid tumors has a number of challenges, such as lack of tumor-specific targets, CAR T cell exhaustion, and the immunosuppressive tumor microenvironment. To address these challenges, AffyImmune has developed technologies to affinity tune and track CAR T cells in patients. The targeting moiety is affinity tuned to preferentially bind to tumor cells overexpressing the target while leaving normal cells with low basal levels untouched, thereby increasing the therapeutic window and allowing for more physiological T cell killing. The CAR T cells are engineered to co-express somatostatin receptor 2 (SSTR2), which allows for the tracking of CAR T cells in vivo via PET/CT scan using FDA-approved DOTATATE. Methods: AIC100 was generated by affinity tuning the I-domain of LFA-1, the physiological ligand to ICAM-1. Various mutants with 106-fold difference in affinity were evaluated for structure activity relationships using targets with varying antigen densities. The AIC100 with micromolar affinity was clearly the most effective in non-clinical animal models. AIC100 is currently being evaluated to assess safety, CAR T expansion, tumor localization, and preliminary activity in patients with advanced thyroid cancer (ATC) in a phase I study (NCT04420754). Our study uses a modified toxicity probability interval design with three dosage groups of 10 × 106, 100 × 106, and 500 × 106 cells. Results: Preclinical studies demonstrated greater in vivo anti-tumor activity and safety with micromolar affinity CAR T cells. A single dose of AIC100 resulted in tumor elimination and significantly improved survival of animals bearing ATC xenografts. AIC100 activity was confirmed in other high ICAM-1 tumor models including breast cancer, gastric cancer, and multiple myeloma. In a Phase I patient given 10 × 106 CAR T cells, near synchronous imaging of FDG and DOTATATE revealed preliminary evidence of transient CAR T expansion and tumor reduction at multiple tumor lesions, with the peak of CAR T cell density coinciding with the spike in CAR T cell numbers in blood. Conclusion: We have developed affinity tuned CAR T cells designed to selectively target ICAM-1 overexpressing tumor cells and to spatiotemporally image CAR T cells. Near-synchronous FDG and DOTATATE scans will enhance patient safety by early detection of off-tumor CAR T activity and validation of tumor response. We anticipate that our “tune and track” technology will be widely applicable to developing potent yet safe CAR T cells against hard-to-treat solid cancers. Citation Format: Jingmei Hsu, Yen-Michael Hsu, Koen van Besien, Thomas J. Fahey, Jana Ivanidze, Janusz Puc, Karrie Du, Yanping Yang, Yogindra Vedvyas, Irene M. Min, Eric von Hofe, Moonsoo M. Jin. First-in-human study of ICAM-1-specific affinity tuned CAR T cells against advanced thyroid cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5579.
45
Angel, Yoseline, Darren Turner, Stephen Parkes, Yoann Malbeteau, Arko Lucieer, and Matthew F. McCabe. "Automated Georectification and Mosaicking of UAV-Based Hyperspectral Imagery from Push-Broom Sensors." Remote Sensing 12, no. 1 (December 20, 2019): 34. http://dx.doi.org/10.3390/rs12010034.
Full textAbstract:
Hyperspectral systems integrated on unmanned aerial vehicles (UAV) provide unique opportunities to conduct high-resolution multitemporal spectral analysis for diverse applications. However, additional time-consuming rectification efforts in postprocessing are routinely required, since geometric distortions can be introduced due to UAV movements during flight, even if navigation/motion sensors are used to track the position of each scan. Part of the challenge in obtaining high-quality imagery relates to the lack of a fast processing workflow that can retrieve geometrically accurate mosaics while optimizing the ground data collection efforts. To address this problem, we explored a computationally robust automated georectification and mosaicking methodology. It operates effectively in a parallel computing environment and evaluates results against a number of high-spatial-resolution datasets (mm to cm resolution) collected using a push-broom sensor and an associated RGB frame-based camera. The methodology estimates the luminance of the hyperspectral swaths and coregisters these against a luminance RGB-based orthophoto. The procedure includes an improved coregistration strategy by integrating the Speeded-Up Robust Features (SURF) algorithm, with the Maximum Likelihood Estimator Sample Consensus (MLESAC) approach. SURF identifies common features between each swath and the RGB-orthomosaic, while MLESAC fits the best geometric transformation model to the retrieved matches. Individual scanlines are then geometrically transformed and merged into a single spatially continuous mosaic reaching high positional accuracies only with a few number of ground control points (GCPs). The capacity of the workflow to achieve high spatial accuracy was demonstrated by examining statistical metrics such as RMSE, MAE, and the relative positional accuracy at 95% confidence level. Comparison against a user-generated georectification demonstrates that the automated approach speeds up the coregistration process by 85%.
46
Полупан, Антон Сергійович, and Валерій Терентійович Сікульський. "Теоретичне визначення режимів селективного лазерного плавлення для виготовлення деталей з мінімальним рівнем пористості." Aerospace technic and technology, no. 2 (April 25, 2022): 38–46. http://dx.doi.org/10.32620/aktt.2022.2.05.
Full textAbstract:
The subject of this article is the process of manufacturing parts of aerospace technology by selective laser melting (SLM) using metal powder of heat-resistant alloy Inconel 718. Objectives: to determine the reasonable size of the melt bath in relation to certain process parameters; to examine the level of porosity based on the obtained values of the melt bath; to determine the most acceptable mode of the SLM process. The methods used are mathematical models of optimization and methods for solving nonlinear problems. The simulation took into account such parameters as the power of the laser radiation, the scanning speed, the size of the laser spot, the temperature of the construction plate, the thickness of the powder layer and the hatch spacing. The following results were obtained. According to the obtained data, the optimal dimensions of the melt bath were determined, which ensure the stability and productivity of the SLM process, the minimum level of porosity, a high level of tightness and the reliability of aerospace parts. Conclusions. The scientific novelty of the obtained results is as follows: the values of the optimal parameters of the SLM process for the manufacture of parts with a minimum level of porosity for heat-resistant alloy material Inconel 718 were confirmed. LPBF methods, namely SLM. It was found that the optimal single track was formed at two combinations of scanning modes, namely: at a laser power of 100 W, and a scanning speed of 600 mm/s; at a laser power of 100 W, and a scanning speed of 700 mm/s. According to the simulation results, according to the criterion, the level of porosity (solids ratio) was less than 0.5%, the highest growth rate was detected at 100 W, scan speed 700 mm/s and hatch spacing 0.1 mm.
47
&NA;. "New Technology Gives Single-Scan View of Urinary Tract." Journal of Clinical Engineering 35, no. 4 (October 2010): 172. http://dx.doi.org/10.1097/jce.0b013e3181f591f5.
Full text
48
Callander, Natalie S., William T. Phillips, Darlene F. Metter, Leonel Ochoa-Bayona, Cesar O. Freytes, and Sharon A. Primeaux. "TECHNITIUM-99m-SESTAMIBI SCANNING (MIBI) CORRELATES WITH DISEASE ACTIVITY IN PATIENTS (PTS) WITH MULTIPLE MYELOMA UNDERGOING AUTOLOGOUS PERIPHERAL BLOOD STEM CELL TRANSPLANTATION (PBSCT)." Blood 104, no. 11 (November 16, 2004): 2469. http://dx.doi.org/10.1182/blood.v104.11.2469.2469.
Full textAbstract:
Abstract Traditional radiographs are often used to establish a diagnosis of MM, as over 80% of patients will have some form of bone disease, including osteolysis and osteopenia. However, radiographs offer incomplete and sometimes misleading information regarding an individual patient’s progress. Pace et al (Eur J Nuc Med, 1998) initially reported the use of MIBI scans to examine bone disease in pts with MM. We hypothesized that MIBI scans could provide a convenient, reproducible method to track pts with MM. We therefore investigated the ability of MIBI scans, in comparison with radiographs and dual energy x-ray absorptiometry (DEXA) to diagnose and follow MM disease progression, as assessed by clinical criteria. Methods: Patients were subjects enrolled in an autologous PBSCT protocol using escalating doses of busulfan and melphalan. Pts received a complete bone survey, DEXA scanning and MIBI scanning prior to PBSCT. Pts able to return for follow up received all 3 tests at various time intervals. MIBI scans consisted of the injection of 30 mCi of technietium-99m-sestamibi followed by immediate scanning with a dual headed gamma camera to produce whole body images. Spot films were made of areas of increased activity. Two radiologists blinded to clinical outcomes reviewed and scored the MIBI films based on scan intensity rated as 0–4 in each of five areas. Scores were averaged, then summed and reported as a total score for each pt. Interrater reliability was determined by using Cohen’s kappa statistic. Results: 31 pts were enrolled on the PBSCT protocol, with 29 pts receiving baseline MIBI scanning. The initial total MIBI scores ranged from 2.5 to 16.5 with a mean score of 11 out of a possible 20. Of note, pts categorized as having either a complete remission (CR) or near complete remission (nCR) (n=4, mean score 6.1) had significantly lower (p=.02) MIBI scores in comparison to pts graded as either stable or progressive disease (n=12, mean score 11.5) prior to PBSCT . Eleven pts had serial scans performed at intervals of 6 to 12 months. Of these, 6 pts with stable/progressive disease had pre PBSCT MIBI scores ranging from 9 to 16.5 with a median score of 12. The single pt with nCR had a MIBI score of 5.5. At the first follow up, pts in stable/PD group had MIBI scores that significantly improved, ranging from 1.5 to 5.5 (median=3.3) with concomitant laboratory and marrow improvement (near CR-3, PR-3) but no change in their xray or DEXA scans. The pt with a nCR also showed improvement in protein and marrow findings to a CR with follow up MIBI score of 1.5. Two of 11 pts classified before PBSCT as "non secretory" MM with negative bone marrow biopsies had prePBSCT MIBI scores of 10.5 and 12, which improved post PBSCT to 3 and 6, respectively and corresponded to subjective improvement in bone pain and anemia. With median follow up of 30 mos for these 11 patients, 2 pts have relapsed by standard criteria, with corresponding increase in MIBI score, but no new lytic lesions documented by radiographs or DEXA. Conclusions: Technitium-99m-sestamibi scans provide a simple, inexpensive method (average cost per MIBI $175) to follow the clinical course of MM patients, especially those with nonsecretory disease, and may prove more cost effective and accurate than other imaging methods for tracking total disease burden. We believe that further investigation of MIBI scanning for this indication is warranted.
49
Glatthor, N., M. Höpfner, K. Semeniuk, A. Lupu, P. I. Palmer, J. C. McConnell, J. W. Kaminski, et al. "The Australian bush fires of February 2009: MIPAS observations and GEM-AQ model results." Atmospheric Chemistry and Physics Discussions 12, no. 6 (June 12, 2012): 15009–48. http://dx.doi.org/10.5194/acpd-12-15009-2012.
Full textAbstract:
Abstract. On 7 February 2009, and the following days Southeast Australia was devastated by large bush fires, which burned an area of about 3000 km2. This event was extraordinary, because a large number of combustion products was transported into the uppermost troposphere and lower stratosphere within a few days. Various biomass burning products released by the fire were observed by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on the ENVISAT satellite. We track the plume using MIPAS C2H2, HCN and HCOOH single-scan measurements on a day-to-day basis. The measurements are compared with a high-resolution model run of the Global Environmental Multiscale-Air Quality (GEM-AQ) model. Generally there is very good agreement between the spatial distribution of measured and modelled pollutants during the first two weeks after the outbreak of the fire even over intercontinental distances. Both MIPAS and GEM-AQ show a fast south-eastward transport of the pollutants to New Zealand within one day. During the following 3–4 days the plume was located north and eastward of New Zealand and centered at altitudes of 15 to 18 km. Thereafter its eastern part was transported eastward at altitudes of 15–16 km, followed by westward transport of its western part at somewhat higher altitudes. On 17 February the eastern part had reached Southern South America and on 20 February the South African west coast. On the latter day a second relic of the plume was observed moving eastward above the Southern Pacific, whereas the westward transported pollutants were located above Australia at altitudes of 18–20 km. First evidence for entry of the pollutants into the stratosphere was found in MIPAS data of 11 February, followed by larger amounts on 17 February and the days thereafter. Between 20 February and the first week of March the stratospheric pollutants above Australia were transported further westward over the Indian Ocean towards Southern Africa.
50
Jakoby, Rolf, Alexander Gaebler, and Christian Weickhmann. "Microwave Liquid Crystal Enabling Technology for Electronically Steerable Antennas in SATCOM and 5G Millimeter-Wave Systems." Crystals 10, no. 6 (June 16, 2020): 514. http://dx.doi.org/10.3390/cryst10060514.
Full textAbstract:
Future satellite platforms and 5G millimeter wave systems require Electronically Steerable Antennas (ESAs), which can be enabled by Microwave Liquid Crystal (MLC) technology. This paper reviews some fundamentals and the progress of microwave LCs concerning its performance metric, and it also reviews the MLC technology to deploy phase shifters in different topologies, starting from well-known toward innovative concepts with the newest results. Two of these phase shifter topologies are dedicated for implementation in array antennas: (1) wideband, high-performance metallic waveguide phase shifters to plug into a waveguide horn array for a relay satellite in geostationary orbit to track low Earth orbit satellites with maximum phase change rates of 5.1°/s to 45.4°/s, depending on the applied voltages, and (2) low-profile planar delay-line phase shifter stacks with very thin integrated MLC varactors for fast tuning, which are assembled into a multi-stack, flat-panel, beam-steering phased array, being able to scan the beam from −60° to +60° in about 10 ms. The loaded-line phase shifters have an insertion loss of about 3 dB at 30 GHz for a 400° differential phase shift and a figure-of-merit (FoM) > 120°/dB over a bandwidth of about 2.5 GHz. The critical switch-off response time to change the orientation of the microwave LCs from parallel to perpendicular with respect to the RF field (worst case), which corresponds to the time for 90 to 10% decay in the differential phase shift, is in the range of 30 ms for a LC layer height of about 4 µm. These MLC phase shifter stacks are fabricated in a standard Liquid Crystal Display (LCD) process for manufacturing low-cost large-scale ESAs, featuring single- and multiple-beam steering with very low power consumption, high linearity, and high power-handling capability. With a modular concept and hybrid analog/digital architecture, these smart antennas are flexible in size to meet the specific requirements for operating in satellite ground and user terminals, but also in 5G mm-wave systems.