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Huang, Xue Wei, Sun Ing Bao i Jing Wang. "An Optimization Design for Coefficient of Weld Reinforcement in Rapid Prototyping Based on Robotic Pulse MAG Forming". Applied Mechanics and Materials 217-219 (listopad 2012): 2148–53. http://dx.doi.org/10.4028/www.scientific.net/amm.217-219.2148.
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During the process of rapid prototyping based on robotic pulse MAG forming, the coefficient of weld reinforcement is crucial to the geometric accuracy and mechanical property of metallic parts. The orthogonal design method, as well as the range analysis and variance analysis, were applied in this article to study the effects of wire feed rate, welding speed, pulse correction and arc length correction on coefficient of weld reinforcement, finding out the factors which were significant to the coefficient of weld reinforcement and optimizing the process parameters. The experimental results show that the order of the significance of parameters is as following: the welding speed, the arc length correction, the wire feed rate, and the pulse correction. Among them, the welding speed and arc length correction have the greatest influence on the coefficient of weld reinforcement, as is 0.025. The optimal process parameters are: arc length correction 8%, welding speed 14mm/s, wire feed rate 7.2m/min and pulse correction 0. At the same time, the coefficient of weld reinforcement is between 2.94 and 3.00, as the degree of confidence is 97.5%.
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Brown, R. James. "Elimination of near-source ellipticity corrections to body-wave travel times by use of equidistant latitudes". Bulletin of the Seismological Society of America 75, nr 6 (1.12.1985): 1713–18. http://dx.doi.org/10.1785/bssa0750061713.
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Abstract The use of equidistant latitudes has been proposed by the author to eliminate discrepancies between angular and kilometric epicentral distances. This is done in combination with a path-length correction which depends on the inclination of the great ellipse containing the epicenter-receiver path. If there were a one-to-one correspondence between source-receiver surface arc length (in kilometers) and, say, P-wave travel time (for constant focal depth) for a standard spheroidal Earth, the ellipticity (time) correction could then be replaced by the distance correction described. However, one would only expect this to be approximately valid for small epicentral distances Δ. In this paper, the travel-time corrections made by using equidistant latitudes (and the great-ellipse correction) are compared with the “true” ellipticity corrections due to Dziewonski and Gilbert. It is seen that the present equidistant-latitude method gives P-wave correction values that, for example, are always within 0.05 sec of the “true” values for Δ ≦ 14° and normal focal depth (h ≦ 40 km). For large Δ(⪞ 45°) and/or great focal depth (h⪞ 475 km), these values may differ by more than 0.2 sec. This equidistant-latitude method of correcting body-wave travel times is thus not recommended for routine use, but it could be used to advantage in special studies involving smaller Δ and h.
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Zhang, Rui Ying, Yun Yan Hu i Jun Wang. "Research on the Technology for DC CMT Welding of AZ31B Magnesium Alloy". Applied Mechanics and Materials 483 (grudzień 2013): 18–22. http://dx.doi.org/10.4028/www.scientific.net/amm.483.18.
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Orthogonal experiment method was used on DC CMT welding of AZ31B magnesium alloy sheet. The tensile test was carried out on the CMT5305 microcomputer control universal testing machine .The effect regular of welding current, arc length correction and welding speed on tensile strength and elongation was analyzed and acquired the optimal combination of process parameters. That is, welding current is 62A, arc length correction is +30% and welding speed is 50cm/min. The microhardness test on joints was carried out. Its found that the curve of microhardness is "W" shaped and the micro-hardness of HAZ is minimum and that of weld zone is maximum.
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Cai, Menglei, Chenhui Wu i Xin Gao. "The Influence of Arc Length Correction on Welding in CMT Welding". IOP Conference Series: Earth and Environmental Science 170 (lipiec 2018): 042106. http://dx.doi.org/10.1088/1755-1315/170/4/042106.
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Ruckhofer, Josef, Josef Stoiber, Michael D. Twa i G. ünther Grabner. "Correction of astigmatism with short arc- length intrastromal corneal ring segments". Ophthalmology 110, nr 3 (marzec 2003): 516–24. http://dx.doi.org/10.1016/s0161-6420(02)01773-6.
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He, Kuan Fang, Ji Gang Wu i Si Wen Xiao. "Synchronic Fuzzy Control of Master and Slave Arc in Twin-Wire Pulsed Metal Active Gas Welding". Advanced Engineering Forum 2-3 (grudzień 2011): 69–73. http://dx.doi.org/10.4028/www.scientific.net/aef.2-3.69.
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This research aims at the retention of the stability of arcs in twin-arc pulsed metal active gas welding process. That is, a correction-factor fuzzy logic controller (FLC) is designed to keep the stability of arcs of twin-arcs pulsed metal active gas welding (MAG) process. In the controller, the peak arc voltage of the master welding power is controlled by the pulse base time with means of feed back of arc voltage. The peak arc voltage of slave welding power is controlled by the wire feeding speed with means of feed back of peak arc voltage. The adjusting fuzzy control rule with correction factor is introduced to design for controlling rule and table, and the FLC is realized in a Look-Up-Table (LUT) method. With the controller, the arc length can be kept stable in welding process. Experimental results are provided to confirm the effectiveness of this approach.
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Dan, Li. "A Three-Dimensional Display Technology of Reflected Acoustic Logging and Its Application Example". Geofluids 2023 (15.04.2023): 1–12. http://dx.doi.org/10.1155/2023/7979348.
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Reflection acoustic logging is a new technology for identifying geological structures around the well. It can be used to describe the geological structure, such as formation interface, fracture, and limestone cave. Based on the acoustic logging tool composed of the source and array receiver, the method can be used to image the geological structure around the well. Through migration imaging, the section crossing the well can be obtained in any azimuth. In the current three-dimensional (3D) display technology of reflection acoustic logging, the reflection plane around the well is always displayed as a reflection arc. The arc surface correction method can correct the arc surface in 3D imaging into a plane. According to the similarity criterion in a physical experiment and the need for practical research, we designed a scale model well experiment of dipole reflection acoustic logging. We obtained the 3D display of the reflection structure around the well by the experiment and realized the arc surface correction of the 3D display in reflection acoustic logging. The application shows the method can qualitatively describe the lateral extension length of the geological structure around the well. After the arc surface correction, the geological structure can be more accurately described.
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Erkorkmaz, Kaan, i Yusuf Altintas. "Quintic Spline Interpolation With Minimal Feed Fluctuation". Journal of Manufacturing Science and Engineering 127, nr 2 (25.04.2005): 339–49. http://dx.doi.org/10.1115/1.1830493.
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This paper presents a parameterization and an interpolation method for quintic splines, which result in a smooth and consistent feed rate profile. The discrepancy between the spline parameter and the actual arc length leads to undesirable feed fluctuations and discontinuity, which elicit themselves as high frequency acceleration and jerk harmonics, causing unwanted structural vibrations and excessive tracking error. Two different approaches are presented that alleviate this problem. The first approach is based on modifying the spline tool path so that it is optimally parameterized with respect to its arc length, which allows it to be accurately interpolated in real-time with minimal complexity. The second approach is based on scheduling the spline parameter to accurately yield the desired arc displacement (hence feed rate), either by approximation of the relationship between the arc length and the spline parameter with a feed correction polynomial, or by solving the spline parameter iteratively in real-time at each interpolation step. This approach is particularly suited for predetermined spline tool paths, which are not arc-length parameterized and cannot be modified. The proposed methods have been compared to approximately arc-length C3 quintic spline parameterization (Wang, F.-C., Wright, P. K., Barsky, B. A., and Yang, D. C. H., 1999, “Approximately Arc-Length Parameterized C3 Quintic Interpolatory Splines,” ASME J. Mech. Des, 121, No. 3., pp. 430–439) and first- and second-order Taylor series interpolation techniques (Huang, J.-T., and Yang, D. C. H., 1992, “Precision Command Generation for Computer Controlled Machines,” Precision Machining: Technology and Machine Development and Improvement, ASME-PED 58, pp. 89–104; Lin, R.-S. 2000, “Real-Time Surface Interpolator for 3-D Parametric Surface Machining on 3-Axis Machine Tools,” Intl. J. Mach. Tools Manuf., 40, No.10, pp. 1513–1526) in terms of feed rate consistency, computational efficiency, and experimental contouring accuracy.
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Kruchinin, A. M., M. Ya Pogrebisskiy, E. S. Ryazanova i A. Y. Chursin. "The arc voltage gradient as a multifactorial basic electrical characteristic of an arc steelmaking furnace". Physics and Chemistry of Materials Treatment 4 (2022): 23–31. http://dx.doi.org/10.30791/0015-3214-2022-4-23-31.
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The structure of the complex process of heating with an electric arc in an arc steelmaking furnace (ASF) due to radiation and convection depends primarily on the length of the arc. Identification of arc length required in process of melting control in ASF is impossible without knowledge of arc voltage gradient values. The arc voltage gradient is highly dependent on the temperature of the furnace and thereby on the heat exchange conditions of the arc in the melting space of the furnace during melting. Using the example of ASF, an engineering technique for determining the arc voltage gradient as a multifactorial basic electrical characteristic is proposed. Using the methods of the electric arc heat exchange model allows performing a basic two-factor version of the analytical calculation of the average voltage gradient of the arc column as a function of two parameters - the reactance of the furnace and the secondary voltage of the furnace transformer. Correction of the basic function is shown taking into account the value of the resistance of the equivalent ASF circuit and the electrode thermal mode index. The proposed method allows, already at the stage of development of the detailed design specification, to calculate analytically the most important energy physical characteristics of the ASF and, as a result, to choose a rational electrical mode of the ASF in order to improve energy and dynamic smelting indicators.
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Short, Mark, James J. Quirk, Chad D. Meyer i Carlos Chiquete. "Steady detonation propagation in a circular arc: a Detonation Shock Dynamics model". Journal of Fluid Mechanics 807 (18.10.2016): 87–134. http://dx.doi.org/10.1017/jfm.2016.597.
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We study the physics of steady detonation wave propagation in a two-dimensional circular arc via a Detonation Shock Dynamics (DSD) surface evolution model. The dependence of the surface angular speed and surface spatial structure on the inner arc radius ($R_{i}$), the arc thickness ($R_{e}-R_{i}$, where $R_{e}$ is the outer arc radius) and the degree of confinement on the inner and outer arc is examined. We first analyse the results for a linear $D_{n}$–$\unicode[STIX]{x1D705}$ model, in which the normal surface velocity $D_{n}=D_{CJ}(1-B\unicode[STIX]{x1D705})$, where $D_{CJ}$ is the planar Chapman–Jouguet velocity, $\unicode[STIX]{x1D705}$ is the total surface curvature and $B$ is a length scale representative of a reaction zone thickness. An asymptotic analysis assuming the ratio $B/R_{i}\ll 1$ is conducted for this model and reveals a complex surface structure as a function of the radial variation from the inner to the outer arc. For sufficiently thin arcs, where $(R_{e}-R_{i})/R_{i}=O(B/R_{i})$, the angular speed of the surface depends on the inner arc radius, the arc thickness and the inner and outer arc confinement. For thicker arcs, where $(R_{e}-R_{i})/R_{i}=O(1)$, the angular speed does not depend on the outer arc radius or the outer arc confinement to the order calculated. It is found that the leading-order angular speed depends only on $D_{CJ}$ and $R_{i}$, and corresponds to a Huygens limit (zero curvature) propagation model where $D_{n}=D_{CJ}$, assuming a constant angular speed and perfect confinement on the inner arc surface. Having the normal surface speed depend on curvature requires the insertion of a boundary layer structure near the inner arc surface. This is driven by an increase in the magnitude of the surface wave curvature as the inner arc surface is approached that is needed to meet the confinement condition on the inner arc surface. For weak inner arc confinement, the surface wave spatial variation with the radial coordinate is described by a triple-deck structure. The first-order correction to the angular speed brings in a dependence on the surface curvature through the parameter $B$, while the influence of the inner arc confinement on the angular velocity only appears in the second-order correction. For stronger inner arc confinement, the surface wave structure is described by a two-layer solution, where the effect of the confinement on the angular speed is promoted to the first-order correction. We also compare the steady-state arc solution for a PBX 9502 DSD model to an experimental two-dimensional arc geometry validation test.
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Ji, Shuai, Tianliang Hu, Zuguang Huang i Chengrui Zhang. "A NURBS curve interpolator with small feedrate fluctuation based on arc length prediction and correction". International Journal of Advanced Manufacturing Technology 111, nr 7-8 (22.10.2020): 2095–104. http://dx.doi.org/10.1007/s00170-020-06258-x.
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Lotfalian, M., E. H. Zadeh i S. A. Hosseini. "Calculating the correction factor of skidding distance based on forest road network". Journal of Forest Science 57, No. 11 (2.12.2011): 467–71. http://dx.doi.org/10.17221/1/2011-jfs.
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Average skidding distance for forest stands is an important parameter for the determination of the optimum road density and spacing. In this research the real mean skidding distance and theoretical mean skidding distance were measured to calculate the correction factor of skidding distance for Chafrood forest in Hyrcanian zone. The length and azimuth of skid trails from road and depot junction to forest interior were measured. Moreover, the position of skid trail was recorded by GPS. These skid trails with a buffer of 140 m were designed on a topographical map using Arc GIS software. Results indicated that the road spacing of 500 m in the study area resulted in a theoretical mean skidding distance of 125 m. For a real mean skidding distance of 525.9 m and for the mean slope of 40%, the correction factor was estimated to be 4.2.
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Wang, Jun, Yong An Zheng i Zhong Ke Shi. "Realization of High Angle of Attack Simulation Based on Cylindrical Projection System". Advanced Materials Research 538-541 (czerwiec 2012): 915–20. http://dx.doi.org/10.4028/www.scientific.net/amr.538-541.915.
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Geometrical calibration is one of the key technologies for multi-channel projection system. In consideration of the complexity and cost of existing correction methods which need camera to collect the feedback images, another algorithm was proposed to correct geometrical distortion. Firstly, the pixels of the uncorrected image were mapped to the cylindrical screen with equal-arc length method. Then the correction of the geometrical distortion was realized by transforming the pixels on the cylindrical screen to the 2D coordinate of pre-corrected image according to perspective projection. Combined with simplified edge blending method, this system completed the high-angle-of-attack flight simulation based on two-channel projection and could be a platform for high-angle-of-attack flight test and flight accident reconstruction.
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Tan, Ding Zhong, Ying Qiu i Qi Ming Wang. "Magnetic Circuit Design and Analysis Used in Magnetic Sealing Drive Device". Advanced Materials Research 875-877 (luty 2014): 2047–50. http://dx.doi.org/10.4028/www.scientific.net/amr.875-877.2047.
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according to the requirement of designing the magnetic sealing drive, the magnetic sealing drive torque design and calculation is completed. It is also analyzed the magnetic circuit and the whole structure of the drive. The matching problem of magnet thickness and arc length of magnetic pole surface is analyzed. The research also includes the method to calculate torque of combination of push pull magnetic circuit and method of its power matching calculation and correction. The magnetic sealing drive is tested and the results show that the design of the magnetic sealing drive complies with the design requirements.
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Zhang, Pengfei, i Chao Yang. "Correction to: A theoretical proof of the invalidity of dynamic relaxation arc-length method for snap-back problems". Computational Mechanics 69, nr 1 (29.10.2021): 345. http://dx.doi.org/10.1007/s00466-021-02108-z.
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Zhao, Huan, LiMin Zhu i Han Ding. "A parametric interpolator with minimal feed fluctuation for CNC machine tools using arc-length compensation and feedback correction". International Journal of Machine Tools and Manufacture 75 (grudzień 2013): 1–8. http://dx.doi.org/10.1016/j.ijmachtools.2013.08.002.
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Zhong, Jun, i Shane D. Ross. "Differential correction and arc-length continuation applied to boundary value problems: Examples based on snap-through of circular arches". Applied Mathematical Modelling 97 (wrzesień 2021): 81–95. http://dx.doi.org/10.1016/j.apm.2021.03.027.
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Raj, Desh, Ranganath M. Singari i M. Vipin. "Study and analyses of arc length correction and mechanical properties on weld bead geometry for AA6061T6 by CMT process". Materials Today: Proceedings 56 (2022): 3475–83. http://dx.doi.org/10.1016/j.matpr.2021.11.122.
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Long, R. C., i B. J. Mitchell. "A New Approach to Directional Survey Interpretation and Course Correction by the Sectional Method". Journal of Energy Resources Technology 114, nr 2 (1.06.1992): 163–74. http://dx.doi.org/10.1115/1.2905937.
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An oblique circular arc representation for wellbore trajecories, a geometric analysis termed the sectional method, is presented. This approach permits projected line segments to be functions of the dogleg angle and to be related to usually measured displacements between survey stations. The advantages of this analysis are: a solution for the dogleg angle and a method of survey interpretation, the sectional method; a procedure for exact interpolation of true vertical depth, azimuth, and inclination between survey stations; a basis of solution for a computer program which provides course correction information during a turn to a target. The program provides a solution summary for a course correction from various survey stations in a well to any planned target. As a result, an optimum course correction or “minimum plugback depth” can be quickly determined. Once the desired kickoff point is selected, the program provides an exact solution of true vertical depth, azimuth, inclination, and toolface angle for every 100 of correction course length. The latter result provides a dramatic improvement in existing technology because all measurements used to control the correction run are now based on a center of turn rather than the arbitrary reference used in the typical ouija board solution; and because the solution is exact, such variables as effective toolface angle can better be evaluated and precisely corrected resulting in the smoothest possible turn with minimum doglegs.
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Feng, Chaolu, Jinzhu Yang, Chunhui Lou, Wei Li, Kun Yu i Dazhe Zhao. "A Global Inhomogeneous Intensity Clustering- (GINC-) Based Active Contour Model for Image Segmentation and Bias Correction". Computational and Mathematical Methods in Medicine 2020 (1.06.2020): 1–18. http://dx.doi.org/10.1155/2020/7595174.
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Image segmentation is still an open problem especially when intensities of the objects of interest are overlapped due to the presence of intensity inhomogeneities. A bias correction embedded level set model is proposed in this paper where inhomogeneities are estimated by orthogonal primary functions. First, an inhomogeneous intensity clustering energy is defined based on global distribution characteristics of the image intensities, and membership functions of the clusters described by the level set function are then introduced to define the data term energy of the proposed model. Second, a regularization term and an arc length term are also included to regularize the level set function and smooth its zero-level set contour, respectively. Third, the proposed model is extended to multichannel and multiphase patterns to segment colorful images and images with multiple objects, respectively. Experimental results and comparison with relevant models demonstrate the advantages of the proposed model in terms of bias correction and segmentation accuracy on widely used synthetic and real images and the BrainWeb and the IBSR image repositories.
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Rajesh Kannan, A., N. Siva Shanmugam i S. Naveenkumar. "Effect of Arc Length Correction on Weld Bead Geometry and Mechanical Properties of AISI 316L Weldments by Cold Metal Transfer (CMT) Process". Materials Today: Proceedings 18 (2019): 3916–21. http://dx.doi.org/10.1016/j.matpr.2019.07.331.
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Voulgari, Nafsika, Michael A. Grentzelos, George A. Kontadakis, Erwin Samutelela i George D. Kymionis. "Femtosecond-Assisted Elliptical LASIK Flap for the Correction of Post-Arcuate Keratotomy Residual Astigmatism". Case Reports in Ophthalmology 10, nr 3 (13.11.2019): 379–83. http://dx.doi.org/10.1159/000504288.
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We report the application of an elliptical femtosecond laser-assisted in situ keratomileusis (LASIK) flap for the management of post-arcuate keratotomy (AK) residual astigmatism. An 82-year-old male was referred to our institute for evaluation of his right eye due to residual regular astigmatism 1 year after AK. On examination, uncorrected distance visual acuity (UDVA) was 20/50 and corrected distance visual acuity was 20/25 (+3.25 –5.50 × 125). Slit-lamp examination revealed two 70-arc length peripheral corneal incisions at the 7.50-mm zone. The patient underwent femtosecond-assisted LASIK for the correction of residual astigmatism. An elliptical LASIK flap was adjusted intraoperatively with a 2-dimension diameter of 7.98 × 6.69 mm in order to avoid intersection of the flap with the AK incisions. The short flap diameter was placed along the meridian of the incisions and the long diameter in the perpendicular meridian, corresponding to the excimer laser astigmatic ablation pattern. No intraoperative or postoperative complications were encountered. Six months postoperatively, UDVA improved to 20/25 with a manifest refraction of pl –0.75 × 5. No AK incision flap-related complications were observed.
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Zhuo, Shufang, i Yanwei Huang. "CHMM Object Detection Based on Polygon Contour Features by PSM". Sensors 22, nr 17 (30.08.2022): 6556. http://dx.doi.org/10.3390/s22176556.
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Since the conventional split–merge algorithm is sensitive to the object scale variance and splitting starting point, a piecewise split–merge polygon-approximation method is proposed to extract the object contour features. Specifically, the contour corner is used as the starting point for the contour piecewise approximation to reduce the sensitivity of the contour segment for the starting point; then, the split–merge algorithm is used to implement the polygon approximation for each contour segment. Both the distance ratio and the arc length ratio instead of the distance error are used as the iterative stop condition to improve the robustness to the object scale variance. Both the angle and length as two features describe the shape of the contour polygon; they have a strong coupling relationship since they affect each other along the contour order relationship. To improve the description correction of the contour, these two features are combined to construct a Coupled Hidden Markov Model to detect the object by calculating the probability of the contour feature. The proposed algorithm is validated on ETHZ Shape Classes and INRIA Horses standard datasets. Compared with other contour-based object-detection algorithms, the proposed algorithm reduces the feature number and improves the object-detection rate.
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Nikityuk, I. E., i S. V. Vissarionov. "Features of postural control in children with severe forms of idiopathic scoliosis". Perm Medical Journal 38, nr 3 (16.07.2021): 76–87. http://dx.doi.org/10.17816/pmj38376-87.
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Objective. The study of postural stability in children with severe degrees of idiopathic scoliosis and assessment of body balance disorders after surgical correction of spinal deformity.
Material and methods. The study of 18 patients aged 1417 years with idiopathic scoliosis of the IIIIV degree with localization of the main arc according to Lenke I, III, V and VI was conducted. The vertical balance of the body was evaluated using a stabilometric platform MBN "Biomechanica" (LLC "MBN", Moscow) before and 910 days after the surgical correction of spinal deformity using transpedicular spinal systems. The results were compared with a stabilometric survey of 18 healthy children.
Results. In patients with idiopathic scoliosis before surgery, a decrease in the stability of the vertical balance of the body, manifested by pronounced deviations from the nominal values of the stabilometric parameters, was revealed. The correlation analysis showed a pathologically strong relationship between the length L, the area S and the amplitude of fluctuations of the pressure center A in patients statokinesiograms compared to the group of healthy children.
In the immediate postoperative period, the postural control system disorders are aggravated in patients.
Conclusions. In children with severe idiopathic scoliosis, violations of the postural control system were revealed, which led to the formation of a suboptimal motor stereotype due to dysfunction of sensorimotor integration.
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Abad, Juan-Carlos, Jaime Arango i Camilo Tobon. "Comparison of Astigmatism Correction Using Shorter Arc Length 90°/120° Asymmetric Intacs Severe Keratoconus Versus 150° Single-Segment Intacs Severe Keratoconus in Asymmetric Keratoconus". Cornea 30, nr 11 (listopad 2011): 1201–6. http://dx.doi.org/10.1097/ico.0b013e3182182bc6.
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Guven, Jemal, Martin Michael Müller i Pablo Vázquez-Montejo. "Isometric bending requires local constraints on free edges". Mathematics and Mechanics of Solids 24, nr 12 (26.07.2019): 4051–77. http://dx.doi.org/10.1177/1081286519865003.
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While the shape equations describing the equilibrium of an unstretchable thin sheet that is free to bend are known, the boundary conditions that supplement these equations on free edges have remained elusive. Intuitively, unstretchability is captured by a constraint on the metric within the bulk. Naïvely one would then guess that this constraint is enough to ensure that the deformations determining the boundary conditions on these edges respect the isometry constraint. If matters were this simple, unfortunately, it would imply unbalanced torques (as well as forces) along the edge unless manifestly unphysical constraints are met by the boundary geometry. In this article, we identify the source of the problem: not only the local arc-length but also the geodesic curvature need to be constrained explicitly on all free edges. We derive the boundary conditions which follow. In contrast to conventional wisdom, there is no need to introduce boundary layers. This framework is applied to isolated conical defects, both with deficit as well, but more briefly, as surplus angles. Using these boundary conditions, we show that the lateral tension within a circular cone of fixed radius is equal but opposite to the radial compression, and independent of the deficit angle itself. We proceed to examine the effect of an oblique outer edge on this cone perturbatively demonstrating that both the correction to the geometry as well as the stress distribution in the cone kicks in at second order in the eccentricity of the edge.
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Tracey, Joseph, Danny Arora, Christopher E. Gross i Selene G. Parekh. "Custom 3D-Printed Total Talar Prostheses Restore Normal Joint Anatomy Throughout the Hindfoot". Foot & Ankle Specialist 12, nr 1 (14.03.2018): 39–48. http://dx.doi.org/10.1177/1938640018762567.
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Background: Third generation total talar prostheses (TTPs) are viable options for talar avascular necrosis (AVN) in the absence of neighboring joint pathology. The use of modern three-dimensional (3D) printing allows the production of custom implants that exactly mimic the patient’s anatomy. The aim of this study is to determine the accuracy of 3D printing in reproducing a synthetic talus and, in doing so, restoring more normal anatomical relationships. We hypothesize that this mode of replication will restore and maintain normal radiographic alignment of the ankle, subtalar, and forefoot joints in the setting of talar AVN. Methods: A retrospective analysis was performed on all patients undergoing TTP implantation for the treatment of talar AVN between 2016 and 2017. Radiographic measurements were taken preoperatively and postoperatively to determine native talar dimensions, TTP implant dimensions, and the corresponding radiographic alignment about the forefoot, hindfoot, and ankle. Results: A total of 14 patients were identified in our cohort. Talar arc length and width were not found to be significantly changed; however, talar height was significantly increased with use of TTP. Five alignment dimensions were measured, of which, only talar tilt angle was significantly changed. Instances of Meary’s angle correction were observed in cavus and planus foot deformity. Conclusion: As a proof of concept, 3D-printed TTP was successful in restoring talar height and talar tilt in the setting of AVN. Additionally, the procedure maintained normal alignment in nonpathological joints. TTPs, based on our cohort, are a viable option to restore more normal anatomical alignment. Levels of Evidence: Level IV: Case series
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Schönfeld, Dennis, Samantha Koss, Nils Vohl, Fabian Friess, Dieter Drescher i Thorsten Pretsch. "Dual Stimuli-Responsive Orthodontic Aligners: An In Vitro Study". Materials 16, nr 8 (14.04.2023): 3094. http://dx.doi.org/10.3390/ma16083094.
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Aligner therapy for orthodontic tooth movement is gaining importance in orthodontics. The aim of this contribution is to introduce a thermo- and water-responsive shape memory polymer (SMP), which could lay the foundation for a new type of aligner therapy. The thermal, thermo-mechanical, and shape memory properties of thermoplastic polyurethane were studied by means of differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and various practical experiments. The glass transition temperature of the SMP relevant for later switching was determined to be 50 °C in the DSC, while the tan δ peak was detected at 60 °C in the DMA. A biological evaluation was carried out using mouse fibroblast cells, which showed that the SMP is not cytotoxic in vitro. On a digitally designed and additively manufactured dental model, four aligners were fabricated from an injection-molded foil using a thermoforming process. The aligners were then heated and placed on a second denture model which had a malocclusion. After cooling, the aligners were in a programmed shape. The movement of a loose, artificial tooth and thus the correction of the malocclusion could be realized by thermal triggering the shape memory effect, at which the aligner corrected a displacement with an arc length of approximately 3.5 mm. The developed maximum force was separately determined to be about 1 N. Moreover, shape recovery of another aligner was realized within 20 h in 37 °C water. In perspective, the present approach can help to reduce the number of orthodontic aligners in therapy and thus avoid excessive material waste.
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Tracey, Joseph, Danny Arora i Selene Parekh. "Custom 3D-printed Total Talar Prostheses Restore Normal Joint Anatomy Throughout the Hindfoot". Foot & Ankle Orthopaedics 3, nr 3 (1.07.2018): 2473011418S0012. http://dx.doi.org/10.1177/2473011418s00125.
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Category: Hindfoot Introduction/Purpose: Third generation total talar prostheses (TTP) are viable options for talar avascular necrosis (AVN) in the absence of neighboring joint pathology. The use of modern three-dimensional (3D) printing allows for the production of custom implants that exactly mimic the patient’s anatomy. The aim of this study is to determine the accuracy of 3D printing in reproducing a synthetic talus, and in doing so, restoring more normal anatomic relationships. We hypothesize that this mode of replication will restore and maintain normal radiographic alignment of the ankle, subtalar, and forefoot joints in the setting of talar AVN. Methods: A retrospective analysis was performed on all patients undergoing TTP implantation for the treatment of talar AVN between 2016 and 2017. Pertinent demographic and operative factors were recorded. Radiographic measurements were taken pre- and post-operatively to determine native talar dimensions, TTP implant dimensions, and the corresponding radiographic alignment about the forefoot, hindfoot, and ankle. Results: Fourteen patients, treated for AVN between 2016-2017, were identified in our cohort. Talar arc length and width were not found to be significantly changed, however talar height was significantly increased with use of TTP. Five alignment dimensions were measured (tibiotalar alignment, talar tilt angle, Boehler’s angle, talar declination angle, and Meary’s Angle), of which, only talar tilt angle was significantly changed. Instances of Meary’s angle correction were observed in cavus and planus foot deformity. Conclusion: This study represents the largest case series of TTP performed in the United States, and is the first to investigate the 3D printed TTP. As a proof-of-concept, 3D printed TTP was successful in restoring talar height and talar tilt in the setting of AVN. Additionally, the procedure maintained normal alignment in non-pathologic joints. Total talar prosthesis, based on our cohort, is a viable option to restore more normal anatomic alignment.
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Nitsche, Ludwig C., i Prashanth Parthasarathi. "Stokes flow singularity at the junction between impermeable and porous walls". Journal of Fluid Mechanics 713 (24.10.2012): 183–215. http://dx.doi.org/10.1017/jfm.2012.454.
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AbstractFor two-dimensional, creeping flow in a half-plane, we consider the singularity that arises at an abrupt transition in permeability from zero to a finite value along the wall, where the pressure is coupled to the seepage flux by Darcy’s law. This problem represents the junction between the impermeable wall of the inflow section and the porous membrane further downstream in a spiral-wound desalination module. On a macroscopic, outer length scale the singularity appears like a jump discontinuity in normal velocity, characterized by a non-integrable $1/ r$ divergence of the pressure. This far-field solution is imposed as the boundary condition along a semicircular arc of dimensionless radius 30 (referred to the microscopic, inner length scale). A preliminary numerical solution (using a least-squares variant of the method of fundamental solutions) indicates a continuous normal velocity along the wall coupled with a weaker $1/ \sqrt{r} $ singularity in the pressure. However, inconsistencies in the numerically imposed outer boundary condition indicate a very slow radial decay. We undertake asymptotic analysis to: (i) understand the radial decay behaviour; and (ii) find a more accurate far-field solution to impose as the outer boundary condition. Similarity solutions (involving a stream function that varies like some power of $r$) are insufficient to satisfy all boundary conditions along the wall, so we generalize these by introducing linear and quadratic terms in $\log r$. By iterating on the wall boundary conditions (analogous to the method of reflections), the outer asymptotic series is developed through second order. We then use a hybrid computational scheme in which the numerics are iteratively patched to the outer asymptotics, thereby determining two free coefficients in the latter. We also derive an inner asymptotic series and fit its free coefficient to the numerics at $r= 0. 01$. This enables evaluation of the singular flow field in the limit as $r\ensuremath{\rightarrow} 0$. Finally, a uniformly valid fit is obtained with analytical formulas. The singular flow field for a solid–porous abutment and the general Stokes flow solutions obtained in the asymptotic analysis are programmed in Fortran for future use as local basis functions in computational schemes. Numerics are required for the intermediate-$r$ regime because the inner and outer asymptotic expansions do not extend far enough toward each other to enable rigorous asymptotic matching. The logarithmic correction terms explain why the leading far-field solution (used in the preliminary numerics) was insufficient even at very large distances.
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LYKHOTA, Kostiantyn, Oleksandra PETRYCHENKO, Vasylyna ARDYKUTSE, Larysa MYKHAILOVSKA i Anatoii KUTSIUK. "Treatment of malocclusions in the temporal period of bite, children with speech disorders by means of myogymnastics and face tapping." Balneo Research Journal 10, Vol.10, No.3 (3.09.2019): 218–24. http://dx.doi.org/10.12680/balneo.2019.260.
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Introduction: The article deals with the current problems of modern orthodontics, aimed at increasing the effectiveness of treatment of sagittal anomalies of bite, which are complicated by speech disorders, patients in the period of bite. The effectiveness of the proposed methods of treatment is investigated, and their complex approach to the correction of this pathology is evaluated. Materials and methods: We were taken on the treatment of 47 children with temporary bite, aged 3 to 5 years old, who experienced dental anomalies in combination with organic dyslallia. Depending on the pathology of bite, patients were divided into subgroups A and B. Subgroup A included children with distal bite, to subgroup B - with mesial. According to the chosen method of orthodontic treatment, patients of experimental groups were additionally divided into 2 subgroups. In 1 subgroup included children, the treatment of which was carried out according to the proposed method, to 2 subgroups - according to the standard. The control group included 11 children with physiological bites of similar age without speech disorders. Results: The effectiveness of proposed schemes of orthodontic and logopedic rehabilitation was proved by clinical, anthropometric and functional indicators, which were determined prior to and at different times after starting treatment. Clinical efficacy of performed orthodontic treatment is established on the term of treatment, normalization of articulation motility, normalization of anthropometric indices, normalization of palatogram characteristics, indexes of functional activity of the tooth-jaw system, normalization of occlusal ratios of dentitions. Conclusion: Using the proposed method of orthodontic treatment (with the use of orthodontic equipment in combination with modified myogymnastics and facial tapping), the dynamics of all the studied parameters correlated with the timing of the pathology elimination and indicated an increased effectiveness of treatment in applying the proposed method, namely: all patients had normalization forms of dental arches, normalized indexes of width and length of the dental arc. Immediately after the end of the treatment, electromyographic indices were normalized and occlusive relationships restored. Similar indicators for those who were treated according to the standard method, although they showed positive dynamics, but differed both from the indicators of persons who were treated according to the proposed method, and from the indicators of the control group. Key words: maxillofacial area, malocclusions, sagittal anomalies, speech disorders, tapping,
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Susko, Edward, i Andrew J. Roger. "On the Use of Information Criteria for Model Selection in Phylogenetics". Molecular Biology and Evolution 37, nr 2 (5.11.2019): 549–62. http://dx.doi.org/10.1093/molbev/msz228.
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Abstract The information criteria Akaike information criterion (AIC), AICc, and Bayesian information criterion (BIC) are widely used for model selection in phylogenetics, however, their theoretical justification and performance have not been carefully examined in this setting. Here, we investigate these methods under simple and complex phylogenetic models. We show that AIC can give a biased estimate of its intended target, the expected predictive log likelihood (EPLnL) or, equivalently, expected Kullback–Leibler divergence between the estimated model and the true distribution for the data. Reasons for bias include commonly occurring issues such as small edge-lengths or, in mixture models, small weights. The use of partitioned models is another issue that can cause problems with information criteria. We show that for partitioned models, a different BIC correction is required for it to be a valid approximation to a Bayes factor. The commonly used AICc correction is not clearly defined in partitioned models and can actually create a substantial bias when the number of parameters gets large as is the case with larger trees and partitioned models. Bias-corrected cross-validation corrections are shown to provide better approximations to EPLnL than AIC. We also illustrate how EPLnL, the estimation target of AIC, can sometimes favor an incorrect model and give reasons for why selection of incorrectly under-partitioned models might be desirable in partitioned model settings.
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Bobojć, Andrzej, i Sławomir Cellmer. "Piecewise acceleration orbital modeling: a GOCE satellite case study". Acta Geophysica 70, nr 1 (21.01.2022): 399–413. http://dx.doi.org/10.1007/s11600-021-00713-3.
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AbstractIn this work, the Precise Science Orbit (PSO) of the Gravity Field and Steady-State Ocean Circulation Explorer Mission (GOCE) satellite, acquired via the European Space Agency, served as the reference orbit for the testing various variants of the GOCE satellite orbit modeling. The GOCE satellite positions along the reduced-dynamic PSO orbit were treated as pseudo-observations in the satellite orbit improvement process in the least squares sense. This process was realized using dedicated extended Toruń Orbit Processor software which enabled determining corrections to the orbital initial conditions and the set of parameters, necessary to determine additional empirical accelerations of the satellite in the radial-track, along-track and cross-track directions. These piecewise accelerations were determined in successive equal intervals (pieces) into which the processed orbital arcs were divided. For modeling the accelerations, polynomials of different degrees were used. The obtained RMS differences between the improved orbits and the reference PSO orbit were determined for various orbital arc lengths up to 1-day. The best RMS of the fits for the 1-day arcs was in the range from 2.0 to 3.2 mm with significantly worst results for along-track direction. Based on the set of solutions determined, the number of orbital parameters for adopted accuracy thresholds and the upper limit of their number, that can be estimated depending on the length of the orbital arc, under given numerical conditions were obtained. The optimal form of the polynomial modeling of the estimated accelerations also depends partly on the length of the processed orbital arc. For shorter arcs (45 min and less), the second- third- and fourth-order polynomial gives the best results, while for longer arcs (90, 180, 360, 720 and 1440 min), zero- and first-degree polynomials are the most effective. A very promising solution with the RMS of the fit of 0.1 mm for a 1-min arc using the fourth-order polynomial was obtained in a perspective of the future use of the short arc approach to the fit of 1-day arcs. Additionally, solution variants with non-equal numbers of orbital pieces for the radial-along-and cross-track directions were obtained. In the case of the solution for an arc length of 1-day, the distribution of residuals and their statistics in the aforementioned radial-, along-and cross-track directions are presented.
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Wang, Lei, Liang Zeng i Jian Li. "AEC-GAN: Adversarial Error Correction GANs for Auto-Regressive Long Time-Series Generation". Proceedings of the AAAI Conference on Artificial Intelligence 37, nr 8 (26.06.2023): 10140–48. http://dx.doi.org/10.1609/aaai.v37i8.26208.
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Large-scale high-quality data is critical for training modern deep neural networks. However, data acquisition can be costly or time-consuming for many time-series applications, thus researchers turn to generative models for generating synthetic time-series data. In particular, recent generative adversarial networks (GANs) have achieved remarkable success in time-series generation. Despite their success, existing GAN models typically generate the sequences in an auto-regressive manner, and we empirically observe that they suffer from severe distribution shifts and bias amplification, especially when generating long sequences. To resolve this problem, we propose Adversarial Error Correction GAN (AEC-GAN), which is capable of dynamically correcting the bias in the past generated data to alleviate the risk of distribution shifts and thus can generate high-quality long sequences. AEC-GAN contains two main innovations: (1) We develop an error correction module to mitigate the bias. In the training phase, we adversarially perturb the realistic time-series data and then optimize this module to reconstruct the original data. In the generation phase, this module can act as an efficient regulator to detect and mitigate the bias. (2) We propose an augmentation method to facilitate GAN's training by introducing adversarial examples. Thus, AEC-GAN can generate high-quality sequences of arbitrary lengths, and the synthetic data can be readily applied to downstream tasks to boost their performance. We conduct extensive experiments on six widely used datasets and three state-of-the-art time-series forecasting models to evaluate the quality of our synthetic time-series data in different lengths and downstream tasks. Both the qualitative and quantitative experimental results demonstrate the superior performance of AEC-GAN over other deep generative models for time-series generation.
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Xu, Liang, Zhonghui Chen, Yong Qiu, Xi Chen, Song Li, Changzhi Du, Qingshuang Zhou i Xu Sun. "Case-matched comparative analysis of spinal deformity correction in arthrogryposis multiplex congenita versus adolescent idiopathic scoliosis". Journal of Neurosurgery: Pediatrics 23, nr 1 (styczeń 2019): 22–29. http://dx.doi.org/10.3171/2018.7.peds18347.
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OBJECTIVEAs scoliosis in arthrogryposis multiplex congenita (AMC) is unusual and the number of cases reviewed in previous studies is also relatively small, no previous study exists that has directly compared the results of spinal deformity correction between AMC and adolescent idiopathic scoliosis (AIS) patients. The aim of this study was to compare the radiographic and clinical outcomes of surgical correction of spinal deformity associated with AMC versus AIS.METHODSTwenty-four adolescents with AMC were matched with 48 AIS patients in terms of Cobb angle of main curve, curve pattern, sex, age at surgery, Risser grade, and length of follow-up. Patients in both groups underwent posterior-only spinal correction and fusion procedures. The surgical outcomes and complications were analyzed and compared between the 2 groups.RESULTSIn comparison to the AIS group, the AMC group had a significantly longer mean operation time (5.6 vs 4.4 hours, p = 0.002), more blood loss (1620 ± 250 ml vs 840 ± 260 ml, p < 0.001), and more fusion levels (14.1 ± 2.3 levels vs 12.4 ± 2.5 levels, p = 0.007) as well as a lower correction rate (44.3% ± 11.1% vs 70.8% ± 12.4%, p < 0.001) and a higher rate of loss of correction (5.0% ± 3.1% vs 2.1% ± 1.9%, p < 0.001). Nine patients in the AMC group had preoperative pelvic obliquity, which was corrected from a mean of 14.2° ± 8.4° to a mean of 4.3° ± 3.2° (p < 0.001) after the surgery. The thoracic lordosis and sagittal vertical axis were significantly improved in the AMC group. Notably, however, the AMC group was found to have higher rates of screw malpositioning (15.9% vs 9.5%, p = 0.002) and complications (8/24 [33.3%] vs 4/48 [8.3%], p = 0.016) as compared to the AIS group.CONCLUSIONSCorrection of AMC-associated scoliosis tends to require a longer operating time and involve more fusion levels but results in less correction, more blood loss, and more complications, in comparison with AIS. In addition, more attention should be paid to pelvic obliquity and sagittal hyperlordosis in AMC patients.
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Al-Seraji, Najm A., i Riyam A. Al-Ogali. "Classification of Arcs in Finite Projective Plane of Order Sixteen". Al-Mustansiriyah Journal of Science 29, nr 1 (31.10.2018): 138. http://dx.doi.org/10.23851/mjs.v29i1.184.
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The aim of the paper is to classify certain geometric structures, called arcs. The main computing tool is the mathematical programming language GAP. In the plane PG(2,16),the important arcs are called complete and are those that cannot be increased to a larger arc. So far, all arcs up to size eighteen have been classified. Each of these arcs gives rise to an error-correcting code that corrects the maximum possible number of errors for its length.
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Liu, Bo-Shi, Rui Niu, Qiong Chen, Ze-Tong Nie, Jiao-Ting Wei i Bo-Jie Hu. "Refractive outcomes after vitrectomy combined with phacoemulsification of idiopathic macular holes". International Journal of Ophthalmology 14, nr 2 (18.02.2021): 250–54. http://dx.doi.org/10.18240/ijo.2021.02.11.
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AIM: To report the refractive outcomes after vitrectomy combined with phacoemulsification and intraocular lens (IOL) implantation (phaco-vitrectomy) in idiopathic macular holes (IMH). METHODS: A total of 56 eyes with IMH (IMH group) that underwent phaco-vitrectomy and 44 eyes with age-related cataract (ARC group) that underwent cataract surgery were retrospectively reviewed. The best corrective visual acuity (BCVA), predicted refractive error (PRE), actual refractive error (ARE), axial length (AL), were measured in both groups before and 6mo after operation. The power calculation of IOL and the predicted refractive error (PRE) were calculated according to the SRK/T formula. The difference of PRE and ARE between the two groups were compared and analyzed. RESULTS: In the IMH group, the diameters of macular holes were 271.73±75.85 μm, the closure rate was 100%. The pre- and post-operative BCVA were 0.80±0.35 and 0.40±0.35 logMAR. The PRE of A-ultrasound and IOL Master in the IMH group was -0.27±0.25 and 0.10±0.66 D. The postoperative mean absolute prediction error (MAE) was observed to be 0.58±0.65 and 0.53±0.37 D in the IOL Master and A-ultrasound (P=0.758). The PRE and ARE of the IMH group were 0.10±0.66 D and -0.19±0.64 D (P=0.102). The PRE and ARE of the ARC group was -0.43±0.95 and -0.31±0.93 D (P=0.383). The difference between PRE and ARE was -0.33±0.81 and 0.09±0.64 D in the IMH and ARC groups (P=0.021). The proportion of myopic shift was 67.9% in the IMH group and 27.3% in the ARC group (P=0.004). CONCLUSION: The myopic shift can be observed in patients with IMH after phaco-vitrectomy.
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Robertson, Andrew W., Jian-Hua Qian, Michael K. Tippett, Vincent Moron i Anthony Lucero. "Downscaling of Seasonal Rainfall over the Philippines: Dynamical versus Statistical Approaches". Monthly Weather Review 140, nr 4 (kwiecień 2012): 1204–18. http://dx.doi.org/10.1175/mwr-d-11-00177.1.
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The additional value derived from a regional climate model (RCM) nested within general circulation model (GCM) seasonal simulations, over and above statistical methods of downscaling, is compared over the Philippines for the April–June monsoon transition season. Spatial interpolation of RCM and GCM gridbox values to station locations is compared with model output statistics (MOS) correction. The anomaly correlation coefficient (ACC) skill at the station scale of seasonal total rainfall is somewhat higher in the RCM compared to the GCM when using spatial interpolation. However, the ACC skills obtained using MOS of the GCM or RCM wind fields are shown to be generally—and rather equally—superior. The ranked probability skill scores (RPSS) are also generally much higher when using MOS, with slightly higher scores in the GCM case. Very high skills were found for MOS correction of daily rainfall frequency as a function of GCM and RCM seasonal-average low-level wind fields, but with no apparent advantage from the RCM. MOS-corrected monsoon onset dates often showed skill values similar to those of seasonal rainfall total, with good skill over the central Philippines. Finally, it is shown that the MOS skills decrease markedly and become inferior to those of spatial interpolation when the length of the 28-yr training set is halved. The results may be region dependent, and the excellent station data coverage and strong impact of ENSO on the Philippines may be factors contributing to the good MOS performance when using the full-length dataset over the Philippines.
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Silva, Leonardo Leiria de Moura da, Bibiana de Borba Telles, Jamile Dutra Correia, Daniélle Bernardi Silveira, Ernani Bohrer da Rosa, Maurício Rouvel Nunes, Diego da Costa Cardoso, Daniel Hoyer de Carvalho Barcellos, Paulo Ricardo Gazzola Zen i Rafael Fabiano Machado Rosa. "Influence of Congenital Heart Defect Types over Cardiopulmonary Bypass, Aortic Cross-Clamping, and Intensive Care Unit Length of Stay and Their Association with Genetic Factors". Cardiology and Angiology: An International Journal 12, nr 4 (9.06.2023): 85–93. http://dx.doi.org/10.9734/ca/2023/v12i4346.
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Aim: Surgical correction of congenital heart defects (CHD) often requires interruption of blood flow through cardiopulmonary bypass (CPB) and aortic cross-clamping (ACC), for which duration(s) are considered to be prognostic factors, along with intensive care unit (ICU) length of stay (ICULOS). The aim of this study was to evaluate these surgical prognostic factors in pediatric patients with different types of CHD regarding their type of lesion and associated genetic factors.
Study Design: Cross-sectional cohort study with 307 pediatric patients.
Place and Duration of Study: Pediatric Intensive Care Unit (ICU) of Hospital da Criança Santo Antônio, in Porto Alegre/RS, Brazil, from 2006-2009 (3 years)
Methodology: After inclusion criteria, we studied 266 pediatric patients admitted for the first time in a reference cardiac pediatric ICU from Southern Brazil following cardiac surgery. Intraoperative prognostic factors such as duration of CPB, ACC and ICULOS, in addition to dysmorphological and cytogenetic examinations were compiled and analyzed. P-values of <0.05 were considered significant.
Results: CPB time was associated to four outflow tract defects (Tetralogy of Fallot [ToF], transposition of the great arteries [TGA], double outlet right ventricle, and truncus arteriosus [TA]), atrioventricular septal defect, and hypoplastic left heart syndrome (HLHS) (P < 0.001). ACC duration was associated with three outflow tract defects (ToF, TGA, and TA) and HLHS (P < 0.001). Moreover, CPB and ACC times showed an association with cyanotic and complex heart defects, as well as prolonged ICULOS (P < 0.001). There was no relationship between these prognostic factors and syndromic aspects or cytogenetic findings.
Conclusions: CHD type has an impact over CPB and ACC duration and ICULOS, whereas genetic factors are not associated with those prognostic factors.
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Kawamorita, Takushi, Hiroshi Uozato, Tetsuro Oshika, Kazuno Negishi, Takashi Fujikado, Akira Murakami, Kazutaka Kamiya i in. "Evaluation of ocular biometry in the Japanese population using a multicenter approach: Prospective observational study". PLOS ONE 17, nr 7 (27.07.2022): e0271814. http://dx.doi.org/10.1371/journal.pone.0271814.
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This prospective observational study aimed to evaluate the ocular biometry of Japanese people through a multicenter approach. The uncorrected and corrected distance visual acuity (UDVA and CDVA, respectively) in the log minimum angle of resolution (logMAR), subjective and objective spherical equivalent values (SE) of ocular refraction, anterior and posterior corneal curvature (ACC and PCC, respectively), anterior and posterior corneal asphericity (ACA and PCA, respectively), central corneal thickness (CCT), anterior chamber depth (ACD), and ocular axial length (AL) were measured in the eyes of 250 participants (mean age = 46.5 ± 18.0 years, range: 20–90 years) across five institutions in Japan. The mean UDVA, CDVA, subjective SE, objective SE, ACC, PCC, ACA, PCA, CCT, ACD, and AL were 0.68, −0.08, −2.42 D, −2.66 D, 7.77 mm, 6.33 mm, −0.31, −0.39, 0.55 mm, 2.92 mm, and 24.78 mm, respectively. Age-related changes and sex-based differences were noted in the visual acuity, refraction, corneal shape, ACD, and AL. Our results serve as basis for future studies aiming to develop refractive correction methods and various vision-related fields.
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Brunsting, Louis A., J. Scott Rankin, Kimberly C. Braly i Robert S. Binford. "Robotic Artificial Chordal Replacement for Repair of Mitral Valve Prolapse". Innovations: Technology and Techniques in Cardiothoracic and Vascular Surgery 4, nr 4 (lipiec 2009): 229–32. http://dx.doi.org/10.1097/imi.0b013e3181b0aa5d.
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Artificial chordal replacement (ACR) has emerged as a superior method of mitral valve repair with excellent early and late efficacy. It is also ideal to combine with robotic techniques for correction of mitral prolapse, and this article presents a current method of robotic Gore-Tex ACR. Patients with isolated posterior leaflet prolapse are approached with the fourth-generation DaVinci robotic system and endoaortic balloon occlusion. A pledgetted anchor stitch is placed in a papillary muscle, and a 2-o Gore-Tex suture is passed through the anchor pledget. After full annuloplasty ring placement, the Gore-Tex suture is woven into the prolapsing segment and positioned temporarily with robotic forceps. Chordal length is then “adjusted” by lengthening or shortening the temporary knot over 1-cm increments as the valve is tested by injection of cold saline into the ventricle. After achieving good leaflet position and valve competence, the chord is tied permanently. The “adjustable” ACR procedure preserves leaflet surface area and produces a competent valve in the majority of patients. Postoperative transesophageal echo shows a large surface area of coaptation. Patient recovery is facilitated by the minimally invasive approach, while long-term stability of similar open ACR techniques have been excellent with a 2% to 3% failure rate over 10 years of follow-up. Robotic Gore-Tex ACR without leaflet resection is a reproducible procedure that simplifies mitral repair for prolapse. The outcomes observed in early robotic applications have been excellent. It is suggested that most patients with simple prolapse might validly be approached in this manner.
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Zehe, A., A. Ramírez, O. Starostenko i Adolfo Sánchez. "Bioimpedance Spectra of Small Particles in Liquid Solutions: Mathematical Modeling of Erythrocyte Rouleaux in Human Blood". Materials Science Forum 480-481 (marzec 2005): 251–56. http://dx.doi.org/10.4028/www.scientific.net/msf.480-481.251.
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For the modeling of erythrocyte rouleaux we develop an approximation procedure for the dipole moment in short cylinders, which contains the case of ellipsoidal bodies only as a first approximation, but allows to include corrections for short cylinders, more representative for such particles. In dependence on the number of erythrocytes forming an aggregation, i.e. on different but discrete measures of rouleaux lengths, the dielectrophoretic force is calculated and represented against the frequency of the applied a.c. field. Predictions of frequency regions in the range of 107 to 108 Hz are made, where the amount and the direction of dielectrophoresis forces is different for different rouleaux sizes.
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Mathkour, Mansour, Stephen Z. Shapiro, Tyler Scullen, Cassidy Werner, Mitchell Kilgore, Velina S. Chavarro i Daniel R. Denis. "Single Level Spondylolisthesis Associated Sagittal Plane Imbalance Corrected by Pre-Psoas Interbody Fusion Using Anterior Column Release with 30° Expandable Hyperlordotic Cage". Medicina 58, nr 9 (29.08.2022): 1172. http://dx.doi.org/10.3390/medicina58091172.
Pełny tekst źródłaStreszczenie:
Background: Loss of lumbar lordosis caused by single level degenerative spondylolisthesis can trigger significant sagittal plane imbalance and failure to correct lumbopelvic parameters during lumbar fusion can lead to poor outcome or worsening deformity. Anterior column release (ACR) through a pre-psoas approach allows the placement of a hyperlordotic cage (HLC) to improve lumbar lordosis, but it is unclear if the amount of cage lordosis affects radiological outcomes in real-life patient conditions. Methods: Three patients were treated with ACR and 30° expandable HLC for positive sagittal imbalance secondary to single-level spondylolisthesis. Patients reported baseline and post-operative Oswestry Disability Index (ODI) and Numeric Pain Score (NRS). Radiographic parameters of sagittal balance included lumbar lordosis (LL), sagittal vertical axis (SVA) and pelvic incidence-lumbar lordosis mismatch (PI-LL). Results: Surgical indications were sagittal plane imbalance caused by L4–L5 degenerative spondylolisthesis (n = 2) and L3–L4 spondylolisthesis secondary to adjacent segmental degeneration (n = 1). Average post-operative length of stay was 3 days (range 2–4) and estimated blood loss was 266 mL (range 200–300). NRS and ODI improved in all patients. All experienced improvements in LL (x¯preop = 33°, x¯postop = 56°), SVA (x¯preop = 180 mm, x¯postop = 61 mm) and PI-LL (x¯preop = 26°, x¯postop = 5°). Conclusion: ACR with expandable HLC can restore sagittal plane balance associated with single-level spondylolisthesis. Failure to perform ACR with HLC placement during pre-psoas interbody fusion may result in under correction of lordosis and poorer outcome for these patients.
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Ma, Chuang, Hong Li i Zhenyu Gong. "Research on MPPT Based on Fuzzy Auto-disturbance Rejection". E3S Web of Conferences 118 (2019): 02077. http://dx.doi.org/10.1051/e3sconf/201911802077.
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For the classical maximum power point tracking algorithm, the setting of small step increases the speed of maximum power tracking of photovoltaic power generation system and the stability of operation in stable state. To solve this problem, this paper designs a maximum power point tracking system based on booster circuit, and adopts fuzzy auto-disturbance rejection control to improve the conductance increment method with variable step length. Based on the relationship between the rate of conductance change and the maximum power point conductance, the step size of the adrc is adjusted by using the fuzzy logic control. The MPPT system of photovoltaic power generation is designed by combining the incremental conductance method and the improved fuzzy control method with the correction factor. The control method does not depend on the mathematical model of the system, the design is flexible, the control effect is robust, stable and accurate. It can be used for reference for other types of solar photovoltaic power generation control system.
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Roussel, N., F. Frappart, G. Ramillien, J. Darrozes, C. Desjardins, P. Gegout, F. Pérosanz i R. Biancale. "Simulations of direct and reflected wave trajectories for ground-based GNSS-R experiments". Geoscientific Model Development 7, nr 5 (2.10.2014): 2261–79. http://dx.doi.org/10.5194/gmd-7-2261-2014.
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Abstract. The detection of Global Navigation Satellite System (GNSS) signals that are reflected off the surface, along with the reception of direct GNSS signals, offers a unique opportunity to monitor water level variations over land and ocean. The time delay between the reception of the direct and reflected signals gives access to the altitude of the receiver over the reflecting surface. The field of view of the receiver is highly dependent on both the orbits of the GNSS satellites and the configuration of the study site geometries. A simulator has been developed to determine the location of the reflection points on the surface accurately by modeling the trajectories of GNSS electromagnetic waves that are reflected by the surface of the Earth. Only the geometric problem was considered using a specular reflection assumption. The orbit of the GNSS constellation satellites (mainly GPS, GLONASS and Galileo), and the position of a fixed receiver, are used as inputs. Four different simulation modes are proposed, depending on the choice of the Earth surface model (local plane, osculating sphere or ellipsoid) and the consideration of topography likely to cause masking effects. Angular refraction effects derived from adaptive mapping functions are also taken into account. This simulator was developed to determine where the GNSS-R receivers should be located to monitor a given study area efficiently. In this study, two test sites were considered: the first one at the top of the 65 m Cordouan lighthouse in the Gironde estuary, France, and the second one on the shore of Lake Geneva (50 m above the reflecting surface), at the border between France and Switzerland. This site is hidden by mountains in the south (orthometric altitude up to 2000 m), and overlooking the lake in the north (orthometric altitude of 370 m). For this second test site configuration, reflections occur until 560 m from the receiver. The planimetric (arc length) differences (or altimetric difference as WGS84 ellipsoid height) between the positions of the specular reflection points obtained considering the Earth's surface as an osculating sphere or as an ellipsoid were found to be on average 9 cm (or less than 1 mm) for satellite elevation angles greater than 10°, and 13.9 cm (or less than 1 mm) for satellite elevation angles between 5 and 10°. The altimetric and planimetric differences between the plane and sphere approximations are on average below 1.4 cm (or less than 1 mm) for satellite elevation angles greater than 10° and below 6.2 cm (or 2.4 mm) for satellite elevation angles between 5 and 10°. These results are the means of the differences obtained during a 24 h simulation with a complete GPS and GLONASS constellation, and thus depend on how the satellite elevation angle is sampled over the day of simulation. The simulations highlight the importance of the digital elevation model (DEM) integration: average planimetric differences (or altimetric) with and without integrating the DEM (with respect to the ellipsoid approximation) were found to be about 6.3 m (or 1.74 m), with the minimum elevation angle equal to 5°. The correction of the angular refraction due to troposphere on the signal leads to planimetric (or altimetric) differences of an approximately 18 m (or 6 cm) maximum for a 50 m receiver height above the reflecting surface, whereas the maximum is 2.9 m (or 7 mm) for a 5 m receiver height above the reflecting surface. These errors increase deeply with the receiver height above the reflecting surface. By setting it to 300 m, the planimetric errors reach 116 m, and the altimetric errors reach 32 cm for satellite elevation angles lower than 10°. The tests performed with the simulator presented in this paper highlight the importance of the choice of the Earth's representation and also the non-negligible effect of angular refraction due to the troposphere on the specular reflection point positions. Various outputs (time-varying reflection point coordinates, satellite positions and ground paths, wave trajectories, first Fresnel zones, etc.) are provided either as text or KML files for visualization with Google Earth.
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Xu, Yu, Qi Li i Zhenzhou Tang. "Accurate and Contactless Vital Sign Detection in Short Time Window with 24 GHz Doppler Radar". Journal of Sensors 2021 (5.10.2021): 1–14. http://dx.doi.org/10.1155/2021/1565567.
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Breathing and heartbeat are critical vital signs which reflect the health status of human beings. Aiming to accurately measure the vital sign in short time window, a novel signal processing method for Doppler radar vital sign detection is proposed. Firstly, a two-step I/Q mismatch correction method which, respectively, estimates the time invariant phase imbalance and gain ratio of I/Q channels in the calibration step and the direct-current offsets during normal operation has been proposed. By decreasing the number of estimation parameters from 5 to 2, the parameters can be effectively estimated with data distributed over shorter arc lengths. Then, to solve the discontinuity occurred in arctangent demodulation, the displacement information of chest movement is extracted from the calibrated I/Q signals by extended differentiate and cross multiply algorithm. Finally, instead of Fourier transform-based methods which require long time windows to guarantee sufficient frequency resolution, the optimal parameters of respiration and heartbeat are found by the intelligent search of the differential evolution algorithm. The experimental results show that the proposed method can accurately measure respiratory rate and heartbeat rate with a short time window. For the 8 s time window, the mean absolute errors of respiration and heartbeat were 0.52 bpm and 0.79 bpm, respectively, demonstrating its promise in real-time applications.
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Probo, Monica, Marcello Guadagnini, Giulia Sala, Paola Amodeo i Agostino Bolli. "Calving Ease Risk Factors and Subsequent Survival, Fertility and Milk Production in Italian Holstein Cows". Animals 12, nr 6 (8.03.2022): 671. http://dx.doi.org/10.3390/ani12060671.
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The objectives of this study were to investigate the main risk factors associated with calving ease (CE) in Italian Holstein cow herds, and to estimate the association between CE and subsequent survival, fertility and milk production. Data obtained from Holstein cows in 40 Italian herds were retrospectively investigated. Calvings were surveilled and classified into two categories of CE, unassisted calving or assisted calving, based on the need for intervention. The following factors were analyzed as possible risk factor affecting CE: herd, number of calvings/herd/year, age at first calving (AFC), cow parity, gestation length, twinning, calf sex, previous calving-to-conception interval, previous milk yield, dry period and close-up length, and season of calving. The association between CE and culling risk within the first 30 days-in-milk (DIM), cumulative 60-d milk yield and predicted 305-d milk yield, and pregnancy risk within 150 DIM were also investigated. Of the 47,672 calvings, 37,892 (79.5%) were unassisted, while 9780 (20.5%) required some type of assistance. Among the risk factors, only the AFC was not correlated with CE, while for all the other risk factors an association with CE was detected. Assisted calvings were associated with an increased culling risk at 30 DIM, decreased 60-d milk yield, decreased 305-d milk yield and reduced pregnancy risk at 150 DIM. In conclusion, dairy herd management should aim at correcting/reducing the risk factors in order to limit the incidence of assisted calving, and possibly improve the quality of calving assistance; controlling CE within the herd is crucial to reducing culling risk, and achieving higher lactation and reproductive performance.
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Kravchenko, Maria I., Joshua M. Tate, Philip G. Clerc, Whitney L. Forbes, Morgan C. Gettle, Jana L. Wardian i Jeffrey A. Colburn. "IMPACT OF STRUCTURED INSULIN ORDER SETS ON INPATIENT HYPOGLYCEMIA AND GLYCEMIC CONTROL". Endocrine Practice 26, nr 5 (maj 2020): 523–28. http://dx.doi.org/10.4158/ep-2019-0341.
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Objective: In hospitalized patients, glycemic excursions outside recommended glycemic targets have been associated with increased morbidity and mortality. Despite recommendations to avoid use of correctional insulin alone for managing hyperglycemia, this approach remains common. We performed a quality improvement project aimed at both reducing hypoglycemic events and promoting increased use of basal insulin by updating our insulin order sets to reflect clinical practice guideline recommendations. Methods: Brooke Army Medical Center correctional insulin order sets were modified to reflect higher treatment thresholds and targets, and a basal insulin order was added with a recommended weight-based starting dose. Pre- and postintervention analyses were performed. Patients were included if they were prescribed subcutaneous insulin during their hospital stay. The following outcomes were measured: ( 1) glucose levels, and ( 2) prescriptions for basal insulin. Results: A significant reduction in hypoglycemia events was noted following the intervention (glucose <70 mg/dL: 9.2% pre-intervention vs. 8.8% postintervention; glucose <55 mg/dL: 4.2% pre-intervention vs. 2.2% postintervention). When excluding patients that were ordered correctional insulin alone but did not receive a dose, an increase in basal insulin use was seen (50% pre-intervention vs. 61% postintervention). Rates and severity of hyperglycemia (glucose >180 mg/dL) remained unchanged. Conclusion: The alteration in insulin order set parameters resulted in a significant reduction in hypoglycemia without significant increases in hyperglycemia. Although basal insulin use increased, optimal dosing recommendations were not often utilized. Further interventions are necessary to reduce hyperglycemia. Abbreviations: CPOE = computerized provider order entry; EMR = electronic medical record; HbA1c = hemoglobin A1c; LOS = length of stay; QI = quality improvement; SSI = sliding scale insulin
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Pennycuick, C. J., T. Alerstam i A. Hedenström. "A new low-turbulence wind tunnel for bird flight experiments at Lund University, Sweden". Journal of Experimental Biology 200, nr 10 (1.05.1997): 1441–49. http://dx.doi.org/10.1242/jeb.200.10.1441.
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A new wind tunnel for experiments on bird flight was completed at Lund University, Sweden, in September 1994. It is a closed-circuit design, with a settling section containing five screens and a contraction ratio of 12.25. The test section is octagonal, 1.20 m wide by 1.08 m high. The first 1.2 m of its length is enclosed by acrylic walls, and the last 0.5 m is open, giving unrestricted access. Experiments can be carried out in both the open and closed parts, and comparison between them can potentially be used to measure the lift effect correction. The fan is driven by an a.c. motor with a variable-frequency power supply, allowing the wind speed to be varied continuously from 0 to 38 m s-1. The whole machine can be tilted to give up to 8 ° descent and 6 ° climb. A pitot-static survey in the test section showed that the air speed was within ±1.3 % of the mean at 116 out of 119 sample points, exceeding this deviation at only three points at the edges. A hot-wire anemometer survey showed that the turbulence level in the closed part of the test section was below 0.04 % of the wind speed throughout most of the closed part of the test section, rising to approximately 0.06 % in the middle of the open part. No residual rotation from the fan could be detected in the test section. No decrease in wind speed was detectable beyond 3 cm from the side walls of the closed part, and turbulence was minimal beyond 10 cm from the walls. The installation of a safety net at the entrance to the test section increased the turbulence level by a factor of at least 30, to 1.2 % longitudinally and 1.0 % transversely.
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Law, Ian, Hidehiro Iida, Søren Holm, Sam Nour, Egill Rostrup, Claus Svarer i Olaf B. Paulson. "Quantitation of Regional Cerebral Blood Flow Corrected for Partial Volume Effect Using O-15 Water and PET: II. Normal Values and Gray Matter Blood Flow Response to Visual Activation". Journal of Cerebral Blood Flow & Metabolism 20, nr 8 (sierpień 2000): 1252–63. http://dx.doi.org/10.1097/00004647-200008000-00010.
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One of the most limiting factors for the accurate quantification of physiologic parameters with positron emission tomography (PET) is the partial volume effect (PVE). To assess the magnitude of this contribution to the measurement of regional cerebral blood flow (rCBF), the authors have formulated four kinetic models each including a parameter defining the perfusable tissue fraction (PTF). The four kinetic models used were 2 one-tissue compartment models with (Model A) and without (Model B) a vascular term and 2 two-tissue compartment models with fixed (Model C) or variable (Model D) white matter flow. Furthermore, rCBF based on the autoradiographic method was measured. The goals of the study were to determine the following in normal humans: (1) the optimal model, (2) the optimal length of fit, (3) the model parameters and their reproducibility, and (4) the effects of data acquisition (2D or 3D). Furthermore, the authors wanted to measure the activation response in the occipital gray matter compartment, and in doing so test the stability of the PTF, during perturbations of rCBF induced by visual stimulation. Eight dynamic PET scans were acquired per subject (n = 8), each for a duration of 6 minutes after IV bolus injection of H215O. Four of these scans were performed using 2D and four using 3D acquisition. Visual stimulation was presented in four scans, and four scans were during rest. Model C was found optimal based on Akaike's Information Criteria (AIC) and had the smallest coefficient of variance after a 6-minute length of fit. Using this model the average PVE corrected rCBF during rest in gray matter was 1.07 mL·min−1·g−1 (0.11 SD), with an average coefficient of variance of 6%. Acquisition mode did not affect the estimated parameters, with the exception of a significant increase in the white matter rCBF using the autoradiographic method (2D: 0.17 mL·min−1·g−1 (0.02 SD); 3D: 0.21 mL·min−1·g−1 (0.02 SD)). At a 6-minute fit the average gray matter CBF using Models C and D were increased by 100% to 150% compared with Models A and B and the autoradiographic method. There were no significant changes in the perfusable tissue fraction by the activation induced rCBF increases. The largest activation response was found using Model C (median = 39.1%). The current study clearly demonstrates the importance of PVE correction in the quantitation of rCBF in normal humans. The potential use of this method is to cost-effectively deliver PVE corrected measures of rCBF and tissue volumes without reference to imaging modalities other than PET.