Journal articles on the topic 'Local deviation angle'
To see the other types of publications on this topic, follow the link: Local deviation angle.
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 'Local deviation angle.'
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
Wu, Yuanhao, Chunyang Wang, Xuelian Liu, Chunhao Shi, and Xuemei Li. "A DASKL Descriptor via Encoding the Information of Keypoints and a 3D Local Surface for 3D Matching." Electronics 11, no. 15 (July 27, 2022): 2328. http://dx.doi.org/10.3390/electronics11152328.
Full textAbstract:
Three-dimensional matching is widely used in 3D vision tasks, such as 3D reconstruction, target recognition, and 3D model retrieval. The description of local features is the fundamental task of 3D matching; however, the descriptors only encode the surrounding surfaces of keypoints, and thus they cannot distinguish between similar local surfaces of objects. Therefore, we propose a novel local feature descriptor called deviation angle statistics of keypoints from local points and adjacent keypoints (DASKL). To encode a local surface fully, we first calculate a multiscale local reference axis (LRA); second, a local consistent strategy is used to redirect the normal direction, and the Poisson-disk sampling strategy is used to eliminate the redundancy in the data. Finally, the local surface is subdivided by two kinds of spatial features, and the histogram of the deviation angle between the LRA and the normal point in each subdivision space is generated. For the coding between keypoints, we calculate the LRA deviation angle between the nearest three keypoints and the adjacent keypoint. The performance of our DASKL descriptor is evaluated on several datasets (i.e., B3R, UWAOR, and LIDAR) with respect to Gaussian noise, varying mesh resolutions, clutter, and occlusion. The results show that our DASKL descriptor has achieved excellent performance in terms of description, robustness, and efficiency. Moreover, we further evaluate the generalization ability of the DASKL descriptor in a LIDAR real-scene dataset.
2
Schuler, Alexander, Albert Weckenmann, and Tino Hausotte. "Enhanced measurement of high aspect ratio surfaces by applied sensor tilting." ACTA IMEKO 3, no. 3 (September 23, 2014): 22. http://dx.doi.org/10.21014/acta_imeko.v3i3.124.
Full textAbstract:
During tactile surface measurements the contact point between probing tip and surface varies depending on the local surface angle. To reduce the resulting measurement deviation on high slopes a probing principle is investigated that applies a dynamic surface dependent sensor tilt. This probing process and the logics for the angle determination have been evaluated by simulation. A test stand based on a nanometer coordinate measuring machine is developed and fitted with a rotation kinematic based on stacked rotary axes. Systematic positioning deviations of the kinematic are reduced by a compensation field. The test stand has been completed and results are presented.
3
Tomków, Jacek, Anna Janeczek, Grzegorz Rogalski, and Adrian Wolski. "Underwater Local Cavity Welding of S460N Steel." Materials 13, no. 23 (December 4, 2020): 5535. http://dx.doi.org/10.3390/ma13235535.
Full textAbstract:
In this paper, a comparison of the mechanical properties of high-strength low-alloy S460N steel welded joints is presented. The welded joints were made by the gas metal arc welding (GMAW) process in the air environment and water, by the local cavity welding method. Welded joints were tested following the EN ISO 15614-1:2017 standard. After welding, the non-destructive—visual, penetrant, radiographic, and ultrasonic (phased array) tests were performed. In the next step, the destructive tests, as static tensile-, bending-, impact- metallographic (macroscopic and microscopic) tests, and Vickers HV10 measurements were made. The influence of weld porosity on the mechanical properties of the tested joints was also assessed. The performed tests showed that the tensile strength of the joints manufactured in water (567 MPa) could be similar to the air welded joint (570 MPa). The standard deviations from the measurements were—47 MPa in water and 33 MPa in the air. However, it was also stated that in the case of a complex state of stress, for example, bending, torsional and tensile stresses, the welding imperfections (e.g., pores) significantly decrease the properties of the welded joint. In areas characterized by porosity the tensile strength decreased to 503 MPa. Significant differences were observed for bending tests. During the bending of the underwater welded joint, a smaller bending angle broke the specimen than was the case during the air welded joint bending. Also, the toughness and hardness of joints obtained in both environments were different. The minimum toughness for specimens welded in water was 49 J (in the area characterized by high porosity) and in the air it was 125 J (with a standard deviation of 23 J). The hardness in the heat-affected zone (HAZ) for the underwater joint in the non-tempered area was above 400 HV10 (with a standard deviation of 37 HV10) and for the air joint below 300 HV10 (with a standard deviation of 17 HV10). The performed investigations showed the behavior of S460N steel, which is characterized by a high value of carbon equivalent (CeIIW) 0.464%, during local cavity welding.
4
Nenajdenko, A. S., V. I. Poddubnyj, and A. I. Valekzhanin. "Modeling the movement control of a wheeled agricultural machine in real time." Traktory i sel hozmashiny 85, no. 3 (June 15, 2018): 32–38. http://dx.doi.org/10.17816/0321-4443-66386.
Full textAbstract:
The research, which purpose is the development of a motion control system for wheeled agricultural machines, is conducted in Polzunov Altai State Technical University. One of the most important steps in this case is the testing of the developed control algorithms. It is advisable to replace the field trials by real-time motion modeling, which allows to significantly reduce financial and time costs. The developed control algorithm can be conditionally divided into global and local regulation. Global regulation must determine the angle of rotation of the steered wheels (or the angle of the frame break) by a deviation from the specified trajectory, which ensures the motion along the specified trajectory. Input parameters are the specified path of motion, the current coordinates of the machine and the projection of speed on fixed axes. Local control provides the implementation of the set value of the angle of rotation of the steered wheels. To the input of the local adjustment program is given the values of the set and current angles of rotation of the wheels and the direction of rotation of the electric motor of the maneuvering device. The algorithm for determining the required angle of rotation of the wheels is based on the method of predicting the position of the wheeled vehicle through the predetermined forecast time. In real-time tests, the wheeled vehicle is replaced by its mathematical model, obtained using the differential equations of plane motion. The complex of equipment provides registration and generation of the necessary parameters for the operation of the control system in real time. The tests were carried out on the experimental stand «steering - front suspension of the vehicle». The front steerable wheels were rotated by an electromechanical maneuvering device to an angle providing movement along a given trajectory. The motion along rectilinear and curvilinear trajectories was modeled taking into account perturbations from the side of the support surface and without them. When moving along a curvilinear trajectory, the deviation from the specified trajectory does not exceed 0,3 meters at a speed of 3,33 m/s. Based on the results of the experiments, it was established that the implemented control algorithm ensures motion along a given trajectory with a sufficient degree of accuracy.
5
SU, PING, WEN-CHEN ZHENG, and HONG-GANG LIU. "CALCULATION OF THE PHOTOLUMINESCENCE SPECTRA FOR Yb3+-DOPED CuInS2 CRYSTAL." Modern Physics Letters B 25, no. 30 (November 21, 2011): 2307–12. http://dx.doi.org/10.1142/s0217984911027455.
Full textAbstract:
Six crystal field energy levels obtained from the photoluminescence spectra of Yb 3+-doped CuInS 2 semiconductor crystal are calculated from the diagonalization (of energy matrix) method. The root-mean-square (r.m.s) deviation σ is 4.5 cm-1 and so the calculated results are in good agreement with the experimental values. The local tetragonal distortion angle θ for the Yb 3+ center in CuInS 2 (which is different from the corresponding angle θh in the host crystal) is obtained from the calculation.
6
Fukuda, Yusuke, Kentaro Kutsukake, Takuto Kojima, Yutaka Ohno, and Noritaka Usami. "Study on electrical activity of grain boundaries in silicon through systematic control of structural parameters and characterization using a pretrained machine learning model." Journal of Applied Physics 132, no. 2 (July 14, 2022): 025102. http://dx.doi.org/10.1063/5.0086193.
Full textAbstract:
We report on the effects of grain boundary (GB) structures on the carrier recombination velocity at GB ( vGB) in multicrystalline Si (mc-Si). The fabricated artificial GBs and an originally developed machine learning model allowed an investigation of the effect of three macroscopic parameters, misorientation angle α for Σ values, asymmetric angle β, and deviation angle θ from the ingot growth direction. Totally, 13 GBs were formed by directional solidification using multi-seeds with controlled crystal orientations. vGB was evaluated directly from photoluminescence intensity profiles across GBs using a pre-trained machine learning model, which allowed a quantitative and continuous evaluation along GBs. The evaluation results indicated that the impact of θ on vGB would be relatively large among the three macroscopic parameters. In addition, the results for the Σ5 and Σ13 GBs suggested that the minimum vGB would be related to the GB energy. These results were discussed in terms of the complexity of the local reconstruction of GB structures. The deviation would make a more complex reconstructed GB structure with local distortion, resulting in an increase in the electrical activity of GBs. The obtained knowledge will contribute to improving various polycrystalline materials through a comprehensive understanding of the relationship between GB structures and their properties.
7
Oldmixon, E. H., J. P. Butler, and F. G. Hoppin. "Dihedral angles between alveolar septa." Journal of Applied Physiology 64, no. 1 (January 1, 1988): 299–307. http://dx.doi.org/10.1152/jappl.1988.64.1.299.
Full textAbstract:
To determine the dihedral angle, alpha, at the characteristic three-way septal junctions of lung parenchyma, we examined photomicrographs of sections. The three angles, A, formed where three septal traces meet on section, were measured and found to range between approximately 50 and 170 degrees. Theoretical considerations predicted that the dispersion of alpha is much narrower than that of A. The mean of A and alpha is identically 120 degrees. The standard deviation of alpha was inferred from the cumulative distribution function of A. In lungs inflated to 30 cmH2O (VL30), the standard deviation of alpha was very small (approximately 2 degrees) and increased to approximately 6 degrees in lungs inflated to 0.4 VL30. These findings imply that at VL30 tensions exerted by septa are locally homogeneous (2% variation) and at lower lung volumes become less so (6% variation). At high distending pressures, tissue forces are thought to dominate interfacial forces, and therefore the local uniformity of tensions suggests a stress-responsive mechanism for forming or remodeling the connective tissues. The source of the local nonuniformity at lower volumes is unclear but could relate to differences in mechanical properties of alveolar duct and alveoli. Finally, local uniformity does not imply global uniformity.
8
AlRatrout, Ahmed, Martin J. Blunt, and Branko Bijeljic. "Wettability in complex porous materials, the mixed-wet state, and its relationship to surface roughness." Proceedings of the National Academy of Sciences 115, no. 36 (August 17, 2018): 8901–6. http://dx.doi.org/10.1073/pnas.1803734115.
Full textAbstract:
A quantitative in situ characterization of the impact of surface roughness on wettability in porous media is currently lacking. We use reservoir condition micrometer-resolution X-ray tomography combined with automated methods for the measurement of contact angle, interfacial curvature, and surface roughness to examine fluid/fluid and fluid/solid interfaces inside a porous material. We study oil and water in the pore space of limestone from a giant producing oilfield, acquiring millions of measurements of curvature and contact angle on three millimeter-sized samples. We identify a distinct wetting state with a broad distribution of contact angle at the submillimeter scale with a mix of water-wet and water-repellent regions. Importantly, this state allows both fluid phases to flow simultaneously over a wide range of saturation. We establish that, in media that are largely water wet, the interfacial curvature does not depend on solid surface roughness, quantified as the local deviation from a plane. However, where there has been a significant wettability alteration, rougher surfaces are associated with lower contact angles and higher interfacial curvature. The variation of both contact angle and interfacial curvature increases with the local degree of roughness. We hypothesize that this mixed wettability may also be seen in biological systems to facilitate the simultaneous flow of water and gases; furthermore, wettability-altering agents could be used in both geological systems and material science to design a mixed-wetting state with optimal process performance.
9
Frayssinhes, Rémy, Stéphane Girardon, Louis Denaud, and Robert Collet. "Modeling the Influence of Knots on Douglas-Fir Veneer Fiber Orientation." Fibers 8, no. 9 (August 21, 2020): 54. http://dx.doi.org/10.3390/fib8090054.
Full textAbstract:
This study presents a method for predicting the local fiber orientation of veneers made from peeled Douglas-fir logs based on the knowledge of the tree branch characteristics (location, radius, insertion angle, azimuth angle, and living branch ratio). This model is based on the Rankine oval theory approach and focuses on the local deviation of the fiber orientation in the vicinity of knots. The local fiber orientation was measured online during the peeling process with an in-house-developed scanner based on the tracheid effect. Two logs from the same tree were peeled, and their ribbons were scanned. The knot locations and fiber orientation were deduced from the scanner data. The first objective was to compare the fiber orientation model with measurements to enhance and validate the model for French Douglas-fir. The second objective was to link data measurable on logs to veneer quality.
10
Machado, R. R., S. Low, and A. Germak. "CCM pilot study overview: geometrical measurement of the Rockwell diamond indenter." ACTA IMEKO 9, no. 5 (December 31, 2020): 250. http://dx.doi.org/10.21014/acta_imeko.v9i5.979.
Full textAbstract:
This paper describes an overview of the capability of the NMIs that participated on the CCM Pilot Study measurement systems, conducted by the CIPM/CCM/Working Group on Hardness, to characterize the Rockwell hardness diamond indenter geometry, by measuring the included cone angle, the straightness of the generatrix, the spherical tip radius, the deviation of the local radius and the tilt angle. <br />Nine NMIs took part in this study: INMETRO (Brazil); INRiM (Italy); KRISS (South Korea); NIM/PR (China); NIMT (Thailand); NIST (USA); PTB (Germany); TUBITAK UME (Turkey); VNIIFTRI (Russia), where INMETRO (Brazil) served as pilot laboratory.
11
Montazerin, N., A. Damangir, and A. Kazemi Fard. "A study of slip factor and velocity components at the rotor exit of forward-curved squirrel cage fans, using laser Doppler anemometry." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 215, no. 4 (June 1, 2001): 453–63. http://dx.doi.org/10.1243/0957650011538712.
Full textAbstract:
Velocity profiles outside the rotor of four squirrel cage fans are measured in order to calculate their local slip factors. They show that the fluid exit angle from the rotor and the blade outlet angle of such fans are very different. Inlet configuration and volute spread angle both affected the direction of the flow out of the rotor and hence the slip factor. The general understanding in centrifugal turbomachines is that more energy transfer per unit mass is equivalent to a larger tangential component of velocity and therefore a larger slip factor. In squirrel cage fans a small slip factor results from a large radial velocity component out of the rotor. This gives a larger volumetric flowrate with no sensible head loss. The advantages of a large incidence angle and a large deviation mean that flow adherence to the blades is not always a prime design criterion in such fans.
12
Alhamer, Essa, Addison Grigsby, and Rydge Mulford. "The Influence of Seasonal Cloud Cover, Ambient Temperature and Seasonal Variations in Daylight Hours on the Optimal PV Panel Tilt Angle in the United States." Energies 15, no. 20 (October 12, 2022): 7516. http://dx.doi.org/10.3390/en15207516.
Full textAbstract:
A variety of variables influence the optimal tilt angle of a PV panel, including the characteristics of the panel, the local seasonal weather variations, the number of daylight hours the panel is exposed to and the ambient temperature of the surroundings. In this study, the optimal PV tilt angle and maximum energy output of PV arrays was calculated for every county in the United States and compared against the practice of setting the PV tilt angle to be equivalent to the latitude angle of the PV geographic location. A PVWatts API, implemented through Python, was used in conjunction with the SciPy optimization package to find the optimal tilt angle for each county using a direct line search algorithm. Most counties (95.8%) showed a difference between the location latitude and the optimal tilt of more than one degree. Many counties showed a deviation of 2–6° lower than the location latitude. The variation of daylight hours had the largest influence on tilt angle and seasonal cloud cover and ambient temperature had varying levels of influence. Generally, winter cloud cover decreased the optimal tilt angle whereas high summer temperatures increased the tilt angle.
13
Khanamiri, Hamid Hosseinzade, Per Arne Slotte, and Carl Fredrik Berg. "Contact Angles in Two-Phase Flow Images." Transport in Porous Media 135, no. 3 (October 27, 2020): 535–53. http://dx.doi.org/10.1007/s11242-020-01485-y.
Full textAbstract:
AbstractIn this work, we calculate contact angles in X-ray tomography images of two-phase flow in order to investigate the wettability. Triangulated surfaces, generated using the images, are smoothed to calculate the contact angles. As expected, the angles have a spread rather than being a constant value. We attempt to shed light on sources of the spread by addressing the overlooked mesh corrections prior to smoothing, poorly resolved image features, cluster-based analysis, and local variations of contact angles. We verify the smoothing algorithm by analytical examples with known contact angle and curvature. According to the analytical cases, point-wise and average contact angles, average mean curvature and surface area converge to the analytical values with increased voxel grid resolution. Analytical examples show that these parameters can reliably be calculated for fluid–fluid surfaces composed of roughly 3000 vertices or more equivalent to 1000 pixel2. In an experimental image, by looking into individual interfaces and clusters, we show that contact angles are underestimated for wetting fluid clusters where the fluid–fluid surface is resolved with less than roughly 500 vertices. However, for the fluid–fluid surfaces with at least a few thousand vertices, the mean and standard deviation of angles converge to similar values. Further investigation of local variations of angles along three-phase lines for large clusters revealed that a source of angle variations is anomalies in the solid surface. However, in the places least influenced by such noise, we observed that angles tend to be larger when the line is convex and smaller when the line is concave. We believe this pattern may indicate the significance of line energy in the free energy of the two-phase flow systems.
14
Hasiotis, Stephen T., Marjorie A. Chan, and Judith Totman Parrish. "Defining bounding surfaces within and between eolian and non-eolian deposits, Lower Jurassic Navajo Sandstone, Moab Area, Utah, U.S.A.: Implications for subdividing erg system strata." Journal of Sedimentary Research 91, no. 12 (December 20, 2021): 1275–304. http://dx.doi.org/10.2110/jsr.2021.027.
Full textAbstract:
ABSTRACT A model-independent, sequence stratigraphic approach is used to define bounding surfaces in the Navajo Sandstone in order to identify an architectural hierarchy of genetically related sedimentary packages and the surfaces that bound them across multiple scales of both eolian and non-eolian components of an erg system. Seven bounding surfaces and eight depositional units are defined, from small to large scale. A lamina-deviation surface bounds wedge- and tabular-shaped sets of laminae and/or laminasets, separating those that have different angle orientations on the dune slipface. A bed-deviation surface bounds a succession of beds (crossbeds) that lie at different angles or orientations to bedding above, below, or adjacent to it. A bedset-deviation surface is curved, inclined, and/or wavy and irregular that bounds bedsets and their internal stratification patterns; that is, bed-deviation surfaces, and lamina-deviation surfaces. A simple surface is gently inclined with or without small, concave or convex segments that bound beds and bedsets. A composite surface is horizontal with or without concave, curved, or irregular portions of that surface. A complex surface is laterally extensive (∼ 1–10+ km) that regionally bounds and truncates underlying conterminous and interfingered eolian and non-eolian strata. An amalgamated surface is a regionally extensive (∼ 10 to 100s km) mappable unconformity, merged unconformities, and their laterally equivalent conformable surface that can exhibit local to regional pedogenic modification, lags, and significant (meters to 10s m) paleotopographic relief. The genetically related sedimentary packages typically bounded by like or higher-rank surfaces are defined as laminae, laminasets, bed, bedsets, and simple, composite, complex, and amalgamated units. Field relationships of strata and surfaces are key to reconstructing the interactions between eolian and non-eolian deposits and the processes they represent at the local, regional, and basin scale. This classification scheme can be applied to erg-system strata to fully integrate changes in diverse facies within and between contiguous deposits.
15
TUDORACHI, Nicoleta-Bianca, Iuliana EVA, Mihaela MOSCALU, Rami AL- HIARY, Aurelian-Corneliu MORARU, Bogdan BARBIERU, Costin STANCIU, Calin CORCIOVA, and Valeriu ARDELEANU. "Evaluating risk factors involved in the alteration of biomechanics in relation to knee osteoarthritis." Balneo Research Journal 10, Vol 10 No. 4 (December 10, 2019): 574–79. http://dx.doi.org/10.12680/balneo.2019.305.
Full textAbstract:
The knee joint is very complex in terms of degrees of mobility and for normal biomechanics it is necessary for all the anatomical structures at this level to be within physiological limits. Problems can be caused by a number of risk factors such as age, sex, weight, or local risk factors such as patellar changes represented by patela alta or patella baja, which can lead to instability of the lower limb. Risk factors that may influence the development and progression of knee osteoarthritis have been evaluated. Changes in patellar position in relation to knee osteoarthritis were also studied. A group of 377 patients hospitalized for unilateral or bilateral knee pain with instability were included in the study. 239 of the 377 starting group presented knee osteoarthritis, constituting the study group. The risk factors analyzed were age, patient sex, BMI, weight status, anatomical changes in position of the patella (patella alta and patella baja), COBB angle and spine deviation. The results indicated that obesity, anatomical changes in the position of the patella, (patella alta), COBB angle and spine deviations represent significant risk factors in the onset of knee osteoarthritis. Key words: risk factors, joint instability, knee osteoarthritis,
16
Chen, Bo, and Yuzhe Qian. "Effects of Blade Suction Side Modification on Internal Flow Characteristics and Hydraulic Performance in a PIV Experimental Centrifugal Pump." Processes 10, no. 12 (November 22, 2022): 2479. http://dx.doi.org/10.3390/pr10122479.
Full textAbstract:
In this paper, the effects of blade trailing edge (TE) profile modification of the suction side on the internal flow and hydraulic performance in a low-specific speed centrifugal pump are investigated through particle image velocimetry (PIV) analysis. Three impellers with different blade trailing edge profiles named original trailing edge (OTE), arc trailing edge 1 (ATE1), and arc trailing edge 2 (ATE2) are designed for PIV experiments. Results show that blade trailing edge modification of the suction side can significantly change the flow pattern, affecting the hydraulic performance of the model pumps. There is a definite counterclockwise backflow vortex near the suction side of OTE at deep-low flow rate, resulting in a decrease in the uniformity of the flow field at the outlet and the hydraulic performance. ATE1 with a reasonable larger blade outlet angle has the best flow field, and the head and efficiency are increased by about 1.2% and 8%, respectively under the same working condition. The hydraulic performance of ATE2 with the blade outlet angle of 59° is better than that of OTE under low flow rate, but it is less than that of OTE under high flow rate due to the streamline deviation generated on the pressure side. Meanwhile, the energy conversion abilities of the modified model pumps are evaluated by slip factor and the deviation degree of the nominalized local Euler head distribution (NLEHD). Since there is no definite counterclockwise backflow vortex at the outlet after modification, the slip factor of ATEs increases and the energy conversion ability is enhanced. Moreover, the jet-wake phenomenon of ATEs is weakened, and the local Euler head (LEH) increases near the outlet, decreasing the deviation degree of the NLEHD to obtain better energy conversion ability.
17
Kobalava, H., and D. Konovalov. "Numerical simulation of the regime and geometric characteristics influence on the pressure loss of a low-flow aerothermopressor." Refrigeration Engineering and Technology 55, no. 2 (April 30, 2019): 66–76. http://dx.doi.org/10.15673/ret.v55i2.1355.
Full textAbstract:
In this paper, a study of gasdynamic processes that occur in a low-flow aerothermopressor has been done. The aerothermopressor is a two-phase jet apparatus for contact cooling, in which, due to the removal of heat from the air flow, the air pressure is increased (thermogasdynamic compression) and its cooling is taken place. Highly effective operation of the aerothermopressor is influenced by primarily the flow part design and the water injected method in the apparatus. Constructive factors that influence energy costs to overcome friction losses and local resistances on the convergent-divergent sections of the aerothermopressor are exerted a significant impact on the working processes in the apparatus. In this paper, a study of a number of typical low-flow aerothermopressor models has been conducted by using computer CFD modeling. Determination of the main parameters of the air flow (total pressure, dynamic pressure, velocity, temperature, etc.) has been carried out for a number of taper angles of a confuser a and a diffuser b, as well as for a number of values of the relative air velocity in the working chamber M = 0.4-0.8. Comparison of the obtained data with experimental data has been carried out. The deviation of the calculated values of local resistances coefficients in the confuser and in the diffuser from those obtained by computer CFD modeling does not exceed 7–10%. The recommended angles were determined: confuser convergent angle – 30° and diffuser divergent angle – 6°, corresponding to the minimum pressure loss is 1.0 – 9.5 %, and therefore also to the maximum pressure increase as a result of the thermogasdynamic compression that occurs during injection and evaporation of liquid in the working chamber. Thus, analytical dependences are obtained for determining the local resistance coefficients for the confuser (nozzle) and the diffuser, which can be recommended to use in the design methodology for low-flow aerothermopressors.
18
Daghighi, Abtin, and Hans Tropp. "Defining the effective deformation of the vertebral column." Biometrical Letters 57, no. 2 (December 1, 2020): 131–50. http://dx.doi.org/10.2478/bile-2020-0010.
Full textAbstract:
Summary The Cobb angle is calculated in the coronal plane, irrespective of vertebral rotation, lordokyphosis and local wedge properties of individual verte-brae other than the end plates used for the measurement. Rigorous three-dimensional generalizations of the Cobb angle are complicated for at least two reasons. Firstly, the vertebral column is segmented, not continuous, making the choice of rigorous model ambiguous. Secondly, there exists an inherent curvature (in terms of thoracic kyphosis and lumbar lordosis) that may be considered physiologically healthy or ’normal’. When attempting to find a three-dimensional deviation measure, such normal sagittal curvature must be compensated for. In this paper we introduce a three-dimensional local deformation parameter (which we call the local effective deformation) motivated by both biomechanics and the basic theory of spatial curves, and simultaneously introduce a technical procedure to estimate the parameter from CT scans using MPR (multi-phase reconstruction) in PACS (IDS-7). A detailed description of the proposed modelling of vertebral column deformation is given, together with a stepwise procedure to estimate the three-dimensional deformation (in terms of local effective deformation). As a deformation measure it requires knowledge about the natural healthy kypholordosis. A method is described by which such knowledge may be incorporated in future work.
19
Malishevskaya, Tatiana N. "Age-related desynchronosis in primary open-angle glaucoma patients: cause or consequence? Correction possibilities." Ophthalmology journal 9, no. 4 (December 15, 2016): 31–42. http://dx.doi.org/10.17816/ov9431-42.
Full textAbstract:
Purpose of this investigation was to study the circadian biologic rhythm dysregulation of intraocular pressure (IOP), blood pressure (BP), and heart rate (HR) in primary open-angle glaucoma (POAG) patients of different age groups. Objectives: to reveal the desynchronosis pattern of biologic rhythm parameters in POAG patients, to study the influence of peptide bioregulatory complex on the synchronization of chosen parameters, to investigate correction possibilities from the perspective of the optic nerve tolerance enhancement, ischemia decrease and ocular perfusion improvement.Materials and methods. At the first stage, we performed a representative selection of patients with BP, HR and IOP dysregulation among POAG patients and subjects without glaucoma of corresponding age (n = 330). For mathematic justification of the desynchronosis identification, we used cosinor-analysis of circadian changes of functional indices. At the second stage, we performed a randomized study with parallel comparison groups masked for the investigator estimating the results. Patients with revealed desynchronosis (n = 56) were randomly divided into two groups for comparison. The main group consisted of 27 patients who, in addition to systemic and local pressure-lowering therapy, received 1 tablet of epifamin (Longvi-Farm, Russia) 3 times a day for 30 days; сortexin (Geropharm, Russia) 10 mg daily for 10 days; retinalamin (Geropharm, Russia) 5 mg daily as peribulbar injections for 10 days. 29 control group patients received traditional treatment (vitamins, spasmolytics, antioxydants) together with local and systemic pressure-lowering therapy. In compared groups, we calculated the tolerant pressure level, investigated the dynamics of retinal sensitivity mean deviation (MD), registrated the oscillatory potentials (OP) with the OP index calculation.Results. In elderly patients with glaucoma, significant changes of the temporal order of physiological parameters were found (deviation of IOP daily rhythm curves, systolic blood pressure (SBP), diastolic blood pressure (DBP), and hemodynamic indices).Conclusion. Through hemodynamic, nootropic, neurotrophic effects of the investigated bioregulatory peptide complex, the optic nerve tolerance to the stress influence of IOP, SBP and DBP asynchronous fluctuations increased, and ocular perfusion enhanced.
20
Perdichizzi, A., and V. Dossena. "Incidence Angle and Pitch–Chord Effects on Secondary Flows Downstream of a Turbine Cascade." Journal of Turbomachinery 115, no. 3 (July 1, 1993): 383–91. http://dx.doi.org/10.1115/1.2929265.
Full textAbstract:
This paper describes the results of an experimental investigation of the three-dimensional flow downstream of a linear turbine cascade at off-design conditions. The tests have been carried out for five incidence angles from −60 to +35 deg, and for three pitch-chord ratios: s/c = 0.58, 0.73, 0.87. Data include blade pressure distributions, oil flow visualizations, and pressure probe measurements. The secondary flow field has been obtained by traversing a miniature five-hole probe in a plane located at 50 percent of an axial chord downstream of the trailing edge. The distributions of local energy loss coefficients, together with vorticity and secondary velocity plots, show in detail how much the secondary flow field is modified both by incidence and by cascade solidity variations. The level of secondary vorticity and the intensity of the crossflow at the endwall have been found to be strictly related to the blade loading occurring in the blade entrance region. Heavy changes occur in the spanwise distributions of the pitch-averaged loss and of the deviation angle, when incidence or pitch–chord ratio is varied.
21
Egerton, R. F., and S. C. Cheng. "Thickness Measurement by EELS." Proceedings, annual meeting, Electron Microscopy Society of America 43 (August 1985): 398–99. http://dx.doi.org/10.1017/s0424820100118862.
Full textAbstract:
Electron energy-loss spectroscopy offers a rapid method of estimating the local thickness of a TEM specimen. The best-known procedure requires only measurement of the integrated intensity IO under the zero-loss peak and of the integral It under the whole spectrum (up to some suitable energy loss Δ). The thickness t is obtained from the formula:where λ(β) is the mean free path for inelastic scattering up to some angle β which is determined by the collection aperture (e.g. objective aperture in CTEM). In agreement with previous work we find that Eq. (1) is applicable over a wide range of thickness, typically 10-500 nm for EO = 100keV incident energy; see Fig. 1. Some deviation at large thickness might be expected as a result of the angular broadening produced by plural scattering, and because of contributions from electrons elastically scattered through angles greater than β.
22
BERNUI, ARMANDO, MARCELO J. REBOUÇAS, and ANTONIO F. F. TEIXEIRA. "LARGE-ANGLE NON-GAUSSIANITY IN SIMULATED HIGH-RESOLUTION CMB MAPS." International Journal of Modern Physics: Conference Series 03 (January 2011): 286–93. http://dx.doi.org/10.1142/s2010194511001383.
Full textAbstract:
A detection or nondetection of primordial non-Gaussianity by using the cosmic microwave background radiation (CMB) offers a way of discriminating inflationary scenarios and testing alternative models of the early universe. This has motivated the considerable effort that has recently gone into the study of theoretical features of primordial non-Gaussianity and its detection in CMB data. Among such attempts to detect non-Gaussianity, there is a procedure that is based upon two indicators constructed from the skewness and kurtosis of large-angle patches of CMB maps, which have been proposed and used to study deviation from Gaussianity in the WMAP data (see Refs. 1 and 2). Simulated CMB maps equipped with realistic primordial non-Gaussianity are essential tools to test the viability of non-Gaussian indicators in practice, and also to understand the effect of systematics, foregrounds and other contaminants. In this work we extend and complement the results Refs. 1 and 2 by performing an analysis of non-Gaussianity of the high-angular resolution simulated CMB temperature maps endowed with non-Gaussianity of the local type, for which the level of non-Gaussianity is characterized by the dimensionless parameter [Formula: see text].
23
Lan, Zhi Chao, Lin Tao Hu, Yin Xue, and De Liang Zen. "The Modeling and Simulation of Wind Turbines and the Design of Pitch Control System." Advanced Materials Research 347-353 (October 2011): 2323–29. http://dx.doi.org/10.4028/www.scientific.net/amr.347-353.2323.
Full textAbstract:
An increasing number of large wind turbines with a variable-speed variable pitch control mechanism are developed to improve the response speed of wind turbines and get maximum active power .Designing a reasonable pitch control system requires both a good control scheme and a more accurate wind turbine model. Base on the analysis of wind turbines’ principle, a local linearization model of wind turbine is built by using linearization method of small deviation in this paper. The model’s inputs are the data of wind speed and pitch angle, and the output is the active power. The accuracy of the model is verified by studying the active power output of wind turbine under different circumstances in which the pitch angle changes with a constant wind speed and the wind speed changes with a constant pitch angle. At the same time, this paper provides pitch control program based on internal model control after analyzing the disadvantages of PID pitch controller. When the wind speed is beyond the rating, the active power can be limited reasonably around the power rating of wind turbines by adjusting the pitch angle.
24
Wang, H., H. Lühr, S. Y. Ma, and H. U. Frey. "Interhemispheric comparison of average substorm onset locations: evidence for deviation from conjugacy." Annales Geophysicae 25, no. 4 (May 8, 2007): 989–99. http://dx.doi.org/10.5194/angeo-25-989-2007.
Full textAbstract:
Abstract. Based on 2760 well-defined substorm onsets in the Northern Hemisphere and 1432 in the Southern Hemisphere observed by the FUV Imager on board the IMAGE spacecraft, a detailed statistical study is performed including both auroral regions. This study focuses on the hemispheric comparisons. Southward pointing interplanetary magnetic field (IMF) is favorable for substorm to occur, but still 30% of the events are preceded by northward IMF. The magnetic latitude (MLat) of substorm onset depends mainly on the merging electric field (Em) with a relationship of |dMLat|= −5.2 Em0.5, where dMLat is the deviation from onset MLat. In addition, seasonal effects on onset MLat are also detected, with about 2 degrees higher latitudes during solstices than equinoxes. Both IMF By and solar illumination have a significant influence on the magnetic local time (MLT) of onsets. An average relation, dMLT=0.25 By between IMF By and the deviation from onset MLT, was found. The By dependence varies slightly with the onset latitude. At lower latitudes (higher activity) it is reduced. After removal of the relationship with IMF By a linear relationships remains between the solar zenith angle and onset MLT with dMLT=1 min/deg. Therefore, both solar illumination and IMF By can contribute to hemispheric longitudinal displacements of substorm onset locations from conjugacy. No indications for systematic latitudinal displacements between the hemispheres have been found.
25
Guo, Haipeng, Guangnian Li, and Zaojian Zou. "Numerical Simulation of the Flow around NACA0018 Airfoil at High Incidences by Using RANS and DES Methods." Journal of Marine Science and Engineering 10, no. 7 (June 22, 2022): 847. http://dx.doi.org/10.3390/jmse10070847.
Full textAbstract:
In this work, the flow around the NACA0018 airfoil with a wide range of attack angles was investigated based on the open-source computational fluid dynamics (CFD) platform OpenFOAM. Two numerical methods, Reynolds-averaged Navier–Stokes (RANS) and the detached eddy simulation (DES), were employed. Under the premise of a grid convergence analysis, the computed lift and drag coefficients were validated by the available experimental data. The pressure distribution, the complex flow mechanisms of the airfoil under the attached flow regime, the mild separation flow regime, and the post-stall flow regime, combined with the shedding vortex structures, streamlines, and vorticity distributions, are discussed. From the numerical results, it can be seen that the DES computation presents a better accuracy in the prediction of the lift and drag coefficients, with a deviation less than 10% at the largest angle of attack. Meanwhile, it also presents remarkable improvements in capturing the local flow field details, such as the unsteady separated flow and the shedding vortex structures.
26
Hong, Beichuan, Varun Venkataraman, and Andreas Cronhjort. "Numerical Analysis of Engine Exhaust Flow Parameters for Resolving Pre-Turbine Pulsating Flow Enthalpy and Exergy." Energies 14, no. 19 (September 28, 2021): 6183. http://dx.doi.org/10.3390/en14196183.
Full textAbstract:
Energy carried by engine exhaust pulses is critical to the performance of a turbine or any other exhaust energy recovery system. Enthalpy and exergy are commonly used concepts to describe the energy transport by the flow based on the first and second laws of thermodynamics. However, in order to investigate the crank-angle-resolved exhaust flow enthalpy and exergy, the significance of the flow parameters (pressure, velocity, and temperature) and their demand for high resolution need to be ascertained. In this study, local and global sensitivity analyses were performed on a one-dimensional (1D) heavy-duty diesel engine model to quantify the significance of each flow parameter in the determination of exhaust enthalpy and exergy. The effects of parameter sweeps were analyzed by local sensitivity, and Sobol indices from the global sensitivity showed the correlations between each flow parameter and the computed enthalpy and exergy. The analysis indicated that when considering the specific enthalpy and exergy, flow temperature is the dominant parameter and requires high resolution of the temperature pulse. It was found that a 5% sweep over the temperature pulse leads to maximum deviations of 31% and 27% when resolving the crank angle-based specific enthalpy and specific exergy, respectively. However, when considering the total enthalpy and exergy rates, flow velocity is the most significant parameter, requiring high resolution with a maximum deviation of 23% for the enthalpy rate and 12% for the exergy rate over a 5% sweep of the flow velocity pulse. This study will help to quantify and prioritize fast measurements of pulsating flow parameters in the context of turbocharger turbine inlet flow enthalpy and exergy analysis.
27
Dong, Hui-Ning, Xu-Sheng Liu, and Hong-Fei Zhou. "The studies of the spin Hamiltonian parameters and local structures for various 3d3 hexacyanometallates of paramagnetic salts with diluents." International Journal of Modern Physics B 30, no. 27 (October 17, 2016): 1650204. http://dx.doi.org/10.1142/s0217979216502040.
Full textAbstract:
The spin Hamiltonian parameters (SHPs) ([Formula: see text] factors, hyperfine structure constants and zero-field splittings (ZFSs)) and local structures for various [Formula: see text] hexacyanometallates of paramagnetic salts K3Cr(CN)6 and K4V(CN)[Formula: see text]3H2O with the diluents K3Co(CN)6, K3Mn(CN)6 and K4Fe(CN)[Formula: see text]3H2O are theoretically investigated from the perturbation calculations of these parameters for a rhombically distorted octahedral [Formula: see text] cluster. The paramagnetic systems are found to undergo the local axial distortions [Formula: see text] [Formula: see text]0.19, −0.18 and 0.09 Å[Formula: see text] and the planar bond angle variations [Formula: see text] [Formula: see text] 3.5[Formula: see text], 5.3[Formula: see text] and 1.4[Formula: see text] for K3Cr(CN)6 with K3Co(CN)6, K3Cr(CN)6 with K3Mn(CN)6 and K4V(CN)[Formula: see text]3H2O with K4Fe(CN)[Formula: see text] 3H2O, respectively. The signs for ZFSs [Formula: see text] and [Formula: see text] are analyzed in the light of those for [Formula: see text] and the rhombic distortion angle [Formula: see text] [Formula: see text] related to an ideal octahedron. Microscopically, the magnitudes of [Formula: see text] and [Formula: see text] can be conveniently illustrated by the axial (ADD) and perpendicular distortion degrees (PDD), respectively, for the paramagnetic systems with the corresponding diluents. The local structural properties are analyzed from the relative ionic radius deviation [Formula: see text] of the equivalent diluent cation from the host paramagnetic cation, the axial and perpendicular ZFS variations [Formula: see text] and [Formula: see text] for ZFSs with the diluent related to the host, the relative deviation [Formula: see text]Dq of the cubic crystal-field parameter for the diluent related to the host. The above studies would be helpful to the investigations on synthesis, structures and properties of [Formula: see text] hexacyanometallates in paramagnetic salts.
28
Yatsui, K., A. Tokuchi, H. Tanaka, H. Ishizuka, A. Kawai, E. Sai, K. Masugata, M. Ito, and M. Matsui. "Geometric focusing of intense pulsed ion beams from racetrack type magnetically insulated diodes." Laser and Particle Beams 3, no. 2 (May 1985): 119–55. http://dx.doi.org/10.1017/s026303460000135x.
Full textAbstract:
Focusing properties and mechanisms are experimentally investigated of an intense pulsed light-ion beam or a medium-mass ion beam extracted from racetrack type magnetically insulated diodes. Quantitative determinations are made for three factors that affect the focusing ability of the beam, i.e., local divergence angle, deviation angle from ideal trajectory and space-charge effect. Behaviour of electrons in an anodecathode gap as well as neutralizing process of the ion beam by electrons are studied in connection with beam focusing. It is found that there is a close correlation between ion yield and electron irradiation on the anode. By adopting a perforated cathode instead of a vane cathode to ensure good uniformity of electric field in the accelerating gap, we have succeeded in significantly reducing the divergence angle. Several new diagnostic techniques and methods have been developed, yielding information such as the time-resolved trajectory and profile or incident angle of the beam. Electron temperature of the anode plasma is theoretically anticipated from the ions observed experimentally. From an estimate of beam divergence due to a space-charge effect, it is suggested that ‘breakeven’ can be achieved without using conventional z-discharged plasma channels if a bunch of boron beams is utilized.
29
Meng, Fan, Yanjun Li, Jia Chen, Lei Xu, and Yalin Li. "The Effect of Airfoil Camber on Pressure Fluctuation in Bidirectional Axial-Flow Pump." Processes 10, no. 3 (February 25, 2022): 468. http://dx.doi.org/10.3390/pr10030468.
Full textAbstract:
To obtain the influence of airfoil camber on the internal pressure fluctuation of a bidirectional axial-flow pump, the unsteady Reynolds time-averaged Navier–Stokes (URANS) equation was solved to predict the internal flow structure under three airfoil camber cases. The airfoil camber was quantitatively controlled by airfoil camber angle. The pressure standard deviation was used to define the local pressure fluctuation intensity (PFI) inside the impeller and guide vane. Fast Fourier transform was applied to analyze the frequency-domain characteristics of the pressure signal near the impeller–straight pipe interface and impeller–guide vanes interface. The results were validated by the external characteristic test. Under the forward condition, the area of high PFI near the outlet and leading edge of the impeller increased with a decrease in airfoil camber angle, and that near the leading edge of the guide vanes shifted to the middle section with a decrease in airfoil camber angle. The main frequency of the pressure signal near the impeller–guide vanes interface was the blade-passing frequency (BPF), and the main frequency amplitude increased with a decrease in airfoil camber angle. Under the reverse condition, the high PFI area near the inlet and the leading edge of the impeller declined with the decrease in airfoil camber angle. The main frequency of the pressure signal near the impeller–straight pipe interface and impeller–guide vanes interface was the BPF, and the main frequency amplitude decreased with a decrease in airfoil camber angle.
30
Yang, Yongming, Chunfeng Yu, Yuanchao Wang, Nan Hua, and Haipeng Kuang. "Imaging Attitude Control and Image Motion Compensation Residual Analysis Based on a Three-Axis Inertially Stabilized Platform." Applied Sciences 11, no. 13 (June 24, 2021): 5856. http://dx.doi.org/10.3390/app11135856.
Full textAbstract:
The airborne area camera has received broad application in aerial reconnaissance, land resource surveying, environmental monitoring, photogrammetry mapping, and natural disaster information acquisition. A three-axis, inertially stabilized platform with a large rotation range for the roll axis is designed, which is based on the cantilever structure, in order to realize a large-angle sweep imaging function for airborne area cameras. An image attitude control algorithm in the inertial space is proposed, which can regulate the line of sight (LOS) as well as the image orientation. The area camera image motion calculation model and image motion compensation residual computing method are proposed, utilizing space position and velocity vector transformation mathematics and derivations. The variation of linear velocity of the image motion in the sensor frame is analyzed, and the changing laws of the maximum deviation of image motion with the image attitude are studied. Flight tests imply that the vertical imaging technique correctly regulates the LOS along the local geodetic vertical. The along-flight overlap rate is greater than 65%, which meets the stereo mapping requirement. The sweep imaging technique considerably enlarges the cross-flight angle of view. The LOS and image orientation during sweep imaging are correctly controlled, and gap-free coverage of the survey area is maintained. The image’s azimuth or roll deviation is less than 0.1°, and the image pitch deviation is less than 0.35°. The quality of the test images is superior. Black and white line pairs for evaluation can be clearly distinguished. The image’s motion is well compensated, and the image motion compensation residual is well constrained. These verify the validity of the proposed imaging technique and the image motion analysis model.
31
Kahlen, Katrin, Dirk Wiechers, and Hartmut Stützel. "Modelling leaf phototropism in a cucumber canopy." Functional Plant Biology 35, no. 10 (2008): 876. http://dx.doi.org/10.1071/fp08034.
Full textAbstract:
Leaf phototropism might have significant effects on the light interception, dry matter production and yield of cucumber (Cucumis sativus L.). The objective of the present study was to model the phototropism of leaves in a greenhouse cucumber canopy. The dynamic structural model of cucumber using a parametric L-system was extended to mimic the leaf movement induced by gradients in the local light environment of each leaf. The red to far-red (R : FR) ratio is known to be a driving force in shade avoidance reactions of plants. In the model, R : FR ratios on the left and right leaf half of each individual leaf lamina were calculated and the change in tropism angle per phyllochron was based on the R : FR gradient across the leaf halves. The tropism angle of a leaf describes the deviation of the present leaf azimuth from the initial leaf orientation, which is predefined by the phyllotaxis of the plant. Even in its simple form, the model simulated photo-morphogenic canopy responses.
32
Zhang, Q. M. "A revised cone model and its application to non-radial prominence eruptions." Astronomy & Astrophysics 653 (September 2021): L2. http://dx.doi.org/10.1051/0004-6361/202141982.
Full textAbstract:
Context. The traditional cone models achieve great success in studying the geometrical and kinematic properties of halo coronal mass ejections (CMEs). Aims. In this Letter, a revised cone model is proposed to investigate the properties of CMEs as a result of non-radial prominence eruptions. Methods. The cone apex is located at the source region of an eruption instead of the Sun center. The cone axis deviates from the local vertical by an inclination angle of θ1 and an angle of ϕ1. The length and angular width of the cone are r and ω, respectively. Results. The model was successfully applied to two CMEs originating from the western limb on 2011 August 11 and 2012 December 7. By comparing the projections of the cones with the CME fronts simultaneously observed by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory and the Extreme-Ultraviolet Imager on board the ahead Solar TErrestrial RElations Observatory, the properties of the CMEs were derived, including the distance, angular width, inclination angle, deviation from the plane of the sky, and true speed in space. Conclusions. This revised cone model provides a new and complementary approach in exploring the whole evolutions of CMEs.
33
Tewes, M., J. Zweck, and H. Hoffmann. "Investigations using wide-angle electron diffraction on pair ordering mechanisms in FeTb alloys by thermal annealing." Proceedings, annual meeting, Electron Microscopy Society of America 52 (1994): 660–61. http://dx.doi.org/10.1017/s0424820100171031.
Full textAbstract:
In our recent work we have shown that electron diffraction is a suitable and precise method to observe short range ordering in various amorphous FeTb alloys by calculating pair distribution functions (PDFs) from these data by means of a fourier inversion. A PDF g(r) is an autocorrelation function of the specimen’s density fluctuations: g(r) = 4πr(ϱ(r) - ϱo) with ϱ(r): autocorrelation of the local density in a distance r, and ϱo macroscopic density of the specimen. The spatial resolution that can be achieved is better than 0.02 nm, and the fine structure of the first coordination shell of the short range order has been described quantitatively with an isotropic structure model. The deviation between calculated and measured PDFs has been about 2%.However, the origin of the uniaxial perpendicular anisotropy in rare earth / transition metal amorphous alloys like FeTb is in general attributed to small anisotropic concentration fluctuations on an atomic scale as introduced in pair ordering, band orientation or stress induced anisotropy models.
34
Bourguet, Rémi, and Michael S. Triantafyllou. "Vortex-induced vibrations of a flexible cylinder at large inclination angle." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 373, no. 2033 (January 28, 2015): 20140108. http://dx.doi.org/10.1098/rsta.2014.0108.
Full textAbstract:
The free vibrations of a flexible circular cylinder inclined at 80° within a uniform current are investigated by means of direct numerical simulation, at Reynolds number 500 based on the body diameter and inflow velocity. In spite of the large inclination angle, the cylinder exhibits regular in-line and cross-flow vibrations excited by the flow through the lock-in mechanism, i.e. synchronization of body motion and vortex formation. A profound reconfiguration of the wake is observed compared with the stationary body case. The vortex-induced vibrations are found to occur under parallel, but also oblique vortex shedding where the spanwise wavenumbers of the wake and structural response coincide. The shedding angle and frequency increase with the spanwise wavenumber. The cylinder vibrations and fluid forces present a persistent spanwise asymmetry which relates to the asymmetry of the local current relative to the body axis, owing to its in-line bending. In particular, the asymmetrical trend of flow–body energy transfer results in a monotonic orientation of the structural waves. Clockwise and counter-clockwise figure eight orbits of the body alternate along the span, but the latter are found to be more favourable to structure excitation. Additional simulations at normal incidence highlight a dramatic deviation from the independence principle, which states that the system behaviour is essentially driven by the normal component of the inflow velocity.
35
Shi, Yangyang, Qiongqiong Li, Shengqiang Bu, Jiafu Yang, and Linfeng Zhu. "Research on Intelligent Vehicle Path Planning Based on Rapidly-Exploring Random Tree." Mathematical Problems in Engineering 2020 (March 24, 2020): 1–14. http://dx.doi.org/10.1155/2020/5910503.
Full textAbstract:
Aiming at the problems of large randomness, slow convergence speed, and deviation of Rapidly-Exploring Random Tree algorithm, a new node is generated by a cyclic alternating iteration search method and a bidirectional random tree search simultaneously. A vehicle steering model is established to increase the vehicle turning angle constraint. The Rapidly-Exploring Random Tree algorithm is improved and optimized. The problems of large randomness, slow convergence speed, and deviation of the Rapidly-Exploring Random Tree algorithm are solved. Node optimization is performed on the generated path, redundant nodes are removed, the length of the path is shortened, and the feasibility of the path is improved. The B-spline curve is used to insert the local end point, and the path is smoothed to make the generated path more in line with the driving conditions of the vehicle. The feasibility of the improved algorithm is verified in different scenarios. MATLAB/CarSim is used for joint simulation. Based on the vehicle model, virtual simulation is carried out to track the planned path, which verifies the correctness of the algorithm.
36
Vafaei Sadr, A., and S. M. S. Movahed. "Clustering of local extrema in Planck CMB maps." Monthly Notices of the Royal Astronomical Society 503, no. 1 (March 16, 2021): 815–29. http://dx.doi.org/10.1093/mnras/stab368.
Full textAbstract:
ABSTRACT The clustering of local extrema will be exploited to examine Gaussianity, asymmetry, and the footprint of the cosmic-string network on the CMB observed by Planck. The number density of local extrema (npk for peak and ntr for trough) and sharp clipping (npix) statistics support the Gaussianity hypothesis for all component separations. However, the pixel at the threshold reveals a more consistent treatment with respect to end-to-end simulations. A very tiny deviation from associated simulations in the context of trough density, in the threshold range ϑ ∈ [−2–0] for NILC and CR component separations, are detected. The unweighted two-point correlation function, Ψ, of the local extrema illustrates good consistency between different component separations and corresponding Gaussian simulations for almost all available thresholds. However, for high thresholds, a small deficit in the clustering of peaks is observed with respect to the Planck fiducial ΛCDM model. To put a significant constraint on the amplitude of the mass function based on the value of Ψ around the Doppler peak (θ ≈ 70–75 arcmin), we should consider ϑ ≲ 0.0. The scale-independent bias factors for the peak above a threshold for large separation angle and high threshold level are in agreement with the value expected for a pure Gaussian CMB. Applying the npk, ntr, Ψpk − pk and Ψtr − tr measures on the tessellated CMB map with patches of 7.52 deg2 size prove statistical isotropy in the Planck maps. The peak clustering analysis puts the upper bound on the cosmic-string tension, Gμ(up) ≲ 5.59 × 10−7, in SMICA.
37
Li, Mingzhe, and Xinan Yue. "Statistically analyzing the effect of ionospheric irregularity on GNSS radio occultation atmospheric measurement." Atmospheric Measurement Techniques 14, no. 4 (April 22, 2021): 3003–13. http://dx.doi.org/10.5194/amt-14-3003-2021.
Full textAbstract:
Abstract. The Global Navigation Satellite System (GNSS) atmospheric radio occultation (RO) has been an effective method for exploring Earth's atmosphere. RO signals propagate through the ionosphere before reaching the neutral atmosphere. The GNSS signal is affected by the ionospheric irregularity including the sporadic E (Es) and F region irregularity mainly due to the multipath effect. The effect of ionospheric irregularity on atmospheric RO data has been demonstrated by several studies in terms of analyzing singe cases. However, its statistical effect has not been investigated comprehensively. In this study, based on the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) RO data during 2011–2013, the failed inverted RO events occurrence rate and the bending angle oscillation, which is defined as the standard deviation of the bias between the observed bending angle and the National Center for Atmospheric Research (NCAR) climatology model bending angle between 60 and 80 km, were used for statistical analysis. It is found that at middle and low latitudes during the daytime, the failed inverted RO occurrence and the bending angle oscillation show obvious latitude, longitude, and local time variations, which correspond well with the Es occurrence features. The F region irregularity (FI) contributes to the obvious increase of the failed inverted RO occurrence rate and the bending angle oscillation value during the nighttime over the geomagnetic equatorial regions. For high latitude regions, the Es can increase the failed inverted RO occurrence rate and the bending angle oscillation value during the nighttime. There also exists the seasonal dependency of the failed inverted RO event and the bending angle oscillation. Overall, the ionospheric irregularity effects on GNSS atmospheric RO measurement statistically exist in terms of failed RO event inversion and bending angle oscillation. Awareness of these effects could benefit both the data retrieval and applications of RO in the lower atmosphere.
38
Muck, Rachael, and Hans Van Dongen. "095 Steering Wheel Angle Excursions as a Measure of Fatigue-Related Driver Performance Impairment." Sleep 44, Supplement_2 (May 1, 2021): A39—A40. http://dx.doi.org/10.1093/sleep/zsab072.094.
Full textAbstract:
Abstract Introduction Fatigue from sleep loss and circadian misalignment causes automobile driving performance impairment. Metrics based on steering wheel angle, which is straightforward to measure, could be used to quantify this impairment. As the tail of the distribution of steering wheel angles (absolute magnitude of deviation from center) increases with fatigue, we investigated whether driving performance impairment could be quantified based on the prevalence of steering wheel excursions beyond a given angle threshold. We used data from two published laboratory studies of simulated shift work, in which fatigue remained low during day shifts but increased across time awake during night shifts. Methods N=37 healthy adults (ages 26.8±5.2y; 25 men) were assigned to a simulated night shift schedule (awake 20:00-10:00) or day shift schedule (awake 08:00-22:00; study 1 only). After an adaptation period, participants underwent two 5-day shift cycles with an intervening rest period. Driving performance was measured on a high-fidelity simulator during adaptation (data not used) and four times at 3h intervals during each shift day. Every drive involved 30min driving at 55mph, including ten 0.5mi uneventful straightaways being considered here. Steering wheel angle was measured at 72Hz (study 1) or 60Hz (study 2). A total of 1,471 drives (31,394,498 angle measurements) were available for analysis. Results We investigated angle thresholds across 0.01-0.25rad in 0.01rad intervals and counted the corresponding number of threshold excursions in each drive for each participant. For study 1, we applied mixed-effects ANOVA with fixed effects for condition and time awake, and their interaction, and determined the local effect size for interaction. A 0.03rad (1.7°) threshold yielded the greatest effect size, f²=0.031 (small). For this threshold, we repeated the analysis using the data from both studies, controlling for study. The interaction was significant (F[3,1428]=13.23, p<0.001), showing low driving impairment across time awake during day shifts but increasing impairment across time awake during night shifts. Conclusion The prevalence of steering wheel excursions beyond a 1.7° angle threshold yielded sensitivity to fatigue-related driving performance impairment during simulated night shifts. Further research will extend our results to driving through curves and with greater fatigue levels. Support (if any) FMCSA DTMC75-07-D-00006
39
Magnussen, S., and C. W. Yeatman. "Early testing of jack pine.: II. Variance and repeatability of stem and branch characters." Canadian Journal of Forest Research 17, no. 6 (June 1, 1987): 460–65. http://dx.doi.org/10.1139/x87-079.
Full textAbstract:
Results on within-tree repeatability and among-tree variances of branch angle, stem and branch traits at age 6 years are presented from an intensively managed jack pine trial in the Petawawa National Forestry Institute's nursery (Ontario, Canada). Four local seed lots were tested at spacings of 2, 1, and 0.5 m. The expected response to changing growing space was observed in the mean values of all quantitative traits. Seedlot effects were unimportant. A method to estimate a tree's "genetic" value from multiple measurements is presented. The method is based on phenotypic residuals from analysis of covariance and the within-tree repeatability of a trait. Heteroscedacity of environmental and within-tree variances in the original data was removed in most traits by the procedure applied. Improvement of jack pine timber quality by breeding for wider branch angle is feasible within the four seed lots judged upon a standard deviation of 7° among trees and a within-tree repeatabilities between 0.22 and 0.36. Branch length and branch diameter were less promising traits for improvement.
40
CHEN, CHING-TAI, HSIN-NAN LIN, TING-YI SUNG, and WEN-LIAN HSU. "HYPLOSP: A KNOWLEDGE-BASED APPROACH TO PROTEIN LOCAL STRUCTURE PREDICTION." Journal of Bioinformatics and Computational Biology 04, no. 06 (December 2006): 1287–307. http://dx.doi.org/10.1142/s0219720006002466.
Full textAbstract:
Local structure prediction can facilitate ab initio structure prediction, protein threading, and remote homology detection. However, the accuracy of existing methods is limited. In this paper, we propose a knowledge-based prediction method that assigns a measure called the local match rate to each position of an amino acid sequence to estimate the confidence of our method. Empirically, the accuracy of the method correlates positively with the local match rate; therefore, we employ it to predict the local structures of positions with a high local match rate. For positions with a low local match rate, we propose a neural network prediction method. To better utilize the knowledge-based and neural network methods, we design a hybrid prediction method, HYPLOSP (HYbrid method to Protein LOcal Structure Prediction) that combines both methods. To evaluate the performance of the proposed methods, we first perform cross-validation experiments by applying our knowledge-based method, a neural network method, and HYPLOSP to a large dataset of 3,925 protein chains. We test our methods extensively on three different structural alphabets and evaluate their performance by two widely used criteria, Maximum Deviation of backbone torsion Angle (MDA) and Q N , which is similar to Q3 in secondary structure prediction. We then compare HYPLOSP with three previous studies using a dataset of 56 new protein chains. HYPLOSP shows promising results in terms of MDA and Q N accuracy and demonstrates its alphabet-independent capability.
41
Chen, Boqing. "Optimal Needle Entry Angle for Cervical Transforaminal Epidural Injections." Pain Physician 2;17, no. 2;3 (March 14, 2014): 139–44. http://dx.doi.org/10.36076/ppj.2014/17/139.
Full textAbstract:
Background: Cervical epidural steroid injections can be performed through either interlaminar or transforaminal approaches, although the interlaminar approach is more frequently used, for cervical radicular pain as a result of cervical disc herniation or spinal stenosis. Cervical selective nerve root block (CSNRB) is an injection that uses a similar approach to that of cervical transforaminal epidural steroid injection (CTFESI) but CSNRB is mainly used for diagnostic injection, often with local anesthetic only. Objective: The aim of this study was to investigate an optimal needle entry angle for cervical transforaminal epidural steroid injection (CTFESI) or cervical selective nerve root block (CSNRB) using the fluoroscopically guided anterior oblique approach. The angle for optimal entry into the neuroforamen was measured at various vertebral levels using cross-sectional cervical spine computed tomography (CT) scans. Study Design: Retrospective case series analysis. Methods: From March 2009 to July 2012, consecutive patients with presumed discogenic neck pain underwent cervical post discography CT scans. The axial images of these CT scans were used to measure the optimal angle for needle entry into the neuroforamen. The angles were taken bilaterally at levels of C3-4, C4-5, C5-6, C6-7, and C7-T1. The average angle between the patient’s left and right side was calculated. A total of 190 patients were analyzed, including 73 men and 117 women, with ages ranging from 21 to 78 years old. Results: In both men and women, the mean optimal angle (in degrees) with standard deviation measured in the 190 patients at C3-4, C4-5, C5-6, C6-7, and C7-T1 were 48 ± 4, 49 ± 4, 49 ± 4, 49 ± 5, 48 ± 6, respectively. The 95% confidence interval for the true value of the parameter is within 39.84 to 57.56 degrees. Limitations: The data for the optimal needle entry angle for CTFESI has yet to be tested or confirmed in clinical studies. Conclusion: This is the first study investigating the optimal needle entry angle for performing CTFESIs or CSNRB. Based on a patient population of 190, the optimal entry angle using the anterior oblique approach appears to be between the range of 33 to 68 degrees with an average of slightly less than 50 degrees. Further research with angle of needle entry and/or initial fluoroscopic alignment of approximately 50 degrees in CTFESI or CSNRB is warranted to confirm the usefulness of these findings. Key words: Pain medicine, transforaminal, cervical, epidural, cervical selective nerve root block, cervical disc herniation, interlaminar, neck pain, vertebral artery, radiculomedullary artery
42
Shalish, Miri, Leslie A. Will, and Stephen Shustermann. "Malposition of Unerupted Mandibular Second Premolar in Children with Cleft Lip and Palate." Angle Orthodontist 77, no. 6 (November 1, 2007): 1062–66. http://dx.doi.org/10.2319/052106-207.
Full textAbstract:
Abstract Objective: To determine whether distoangular malposition of the unerupted mandibular second premolar (MnP2) is more frequent in children with unilateral clefts of the lip and palate. Materials and Methods: This retrospective study examined panoramic radiographs from 45 patients with unilateral clefts of the lip and/or palate who had no previous orthodontics. A control sample consisted of age- and sex-matched patients. The distal angle formed between the long axis of MnP2 and the tangent to the inferior border was measured. The mean, standard deviation, and range were calculated for the angles measured in the cleft and the control groups. The significance of the differences between the means was evaluated by the paired t-test. The angles of the cleft and noncleft sides were also measured and compared. Results: The mean inclination of the MnP2 on the cleft side was 73.6°, compared with 84.6° in the control group. This difference was highly significant statistically (P < .0001). The difference in angles from the cleft and noncleft sides was 0.7°, not statistically significant. A significant association was found between clefting and distoangular malposition of the developing MnP2, suggesting a shared genetic etiology. This association is independent of the clefting side, ruling out possible local mechanical effects. Conclusion: Clinicians should be aware of the potential for anomalous development of MnP2 in children with clefts.
43
Li, Chengxiang, Shuhu Li, and GuiJie Yu. "Microscopic Interface and Multiscale Failure Analysis of Proposed Molecular Chain Polymers Based on Aifantis Strain Gradient Theory." Computational Intelligence and Neuroscience 2022 (May 18, 2022): 1–9. http://dx.doi.org/10.1155/2022/1153080.
Full textAbstract:
A study on the microscopic morphology of real-world polymer blends and its mechanism of change showed that the microscopic morphology of equiproportional mixtures gradually changed from a dense body structure to a network structure with the addition of the total polymer concentration up to 20%; the microscopic morphology of mixtures with different proportions was characterized by the most uniform network structure of equiproportional mixtures when the total polymer concentration was 20%. The polymer acts as a defoamer in the mixed system. In this paper, the relationship between the microscopic morphology of each mixture and the physicochemical behavior of the two polymer chains in the mixed system was investigated on the basis of the Aifantis strain gradient theory. Molecular polymer microscopic interface and multiscale failure analysis are proposed. It is shown that for the dihedral angle distribution of four consecutive coarse-grained particles, the peaks obtained from all atomic-scale simulation data are reproduced in the coarse-grained model simulations. The deviation is within 2.5% in most places, except for the local area where the deviation exceeds 5%. Therefore, we have achieved good results for large-scale failures.
44
Guo, Shanchuan, Xuyu Bai, Yu Chen, Shaoliang Zhang, Huping Hou, Qianlin Zhu, and Peijun Du. "An Improved Approach for Soil Moisture Estimation in Gully Fields of the Loess Plateau Using Sentinel-1A Radar Images." Remote Sensing 11, no. 3 (February 10, 2019): 349. http://dx.doi.org/10.3390/rs11030349.
Full textAbstract:
As an essential ecological parameter, soil moisture is important for understanding the water exchange between the land surface and the atmosphere, especially in the Loess Plateau (China). Although Synthetic Aperture Radar (SAR) images can be used for soil moisture retrieval, it is still a challenge to mitigate the impacts of complex terrain over hilly areas. Therefore, the objective of this paper is to propose an improved approach for soil moisture estimation in gully fields based on the joint use of the Advanced Integral Equation Model (AIEM) and the Incidence Angle Correction Model (IACM) from Sentinel-1A observations. AIEM is utilized to build a simulation database of microwave backscattering coefficients from various radar parameters and surface parameters, which is the data basis for the retrieval modeling. IACM is proposed to correct the deviation between the local incidence angle at the scatterer and the radar viewing angle. The study area is located in the Loess Plateau of China, where the main land cover is mostly bare land and the terrain is complex. The Sentinel-1A SAR data in C-band with dual polarization acquired on October 19th, 2017 was adopted to extract the VV&VH polarimetric backscattering coefficients. The in situ measurements of soil moisture were collected on the same day of the SAR acquisition, for evaluating the accuracy of the SAR-derived soil moisture. The results showed that, firstly, the estimated soil moisture with volumetric content between 0% and 20% was in the majority. Subsequently, both the RMSE of estimation values (0.963%) and the standard deviation of absolute errors (0.957%) demonstrated a good accuracy of the improved approach. Moreover, the evaluation of IACM confirmed that the improved approach coupling IACM and AIEM was more efficient than employing AIEM solely. In conclusion, the proposed approach has a strong ability to estimate the soil moisture in the gully fields of the Loess Plateau from Sentinel-1A data.
45
Murray, Timothy E., Damien C. O'Neill, and Michael J. Lee. "Accessing Implantable Ports: An Opportunistic Computed Tomography-Based Audit." Journal of the Association for Vascular Access 22, no. 4 (December 1, 2017): 193–98. http://dx.doi.org/10.1016/j.java.2017.09.002.
Full textAbstract:
Abstract Aim: Implantable ports are typically inserted by interventional radiologists or surgeons; however, daily maintenance, access, and de-access are often performed by members of nursing staff in accordance with manufacturers' guidelines and local policy. An audit of port access using retrospective computed tomography (CT) scanning was proposed. Methodology: Across a 4-year period, all CT scans performed for any reason while a port was accessed were reviewed. Results: Fifty-four CT scans of accessed ports were included. Mean depth of tissue between skin and port was 3.74 mm, and between port and pectoralis major was 5.91 mm. Port tilt in side-to-side and up-down axes measured 6.9° and 10.6°, respectively. Mean distance from needle to center of the septum was 1.96 mm. Mean distance from center of the chamber to the needle tip was 2.73 mm. In 2 cases (3.7%), the needle bevel was malpositioned, with the bevel still within the silicone-rubber septum. Mean angulation of the access needle from perpendicular was 11.5°. Angulation of the needle correlated with port tilt (r = 0.37; P = .006). Angle of the needle bevel relative to the port exit channel was 140.8°. No significant correlation between needle bevel directionality and needle angle, depth of port, or tilt of port was detected (all P values > .21). Conclusions: Variability in accessing of implantable ports is described relative to research- and manufacturer-recommended needle bevel angle, needle puncture angle, and central puncture position. The extent to which such deviation influences port function deserves focused clinical research.
46
Dong, Yan, Xuejin Sun, and Qinghui Li. "A Method for Retrieving Cloud-Top Height Based on a Machine Learning Model Using the Himawari-8 Combined with Near Infrared Data." Remote Sensing 14, no. 24 (December 16, 2022): 6367. http://dx.doi.org/10.3390/rs14246367.
Full textAbstract:
Different cloud-top heights (CTHs) have different degrees of atmospheric heating, which is an important factor for weather forecasting and aviation safety. AHIs (Advanced Himawari Imagers) on the Himawari-8 satellite are a new generation of visible and infrared imaging spectrometers characterized by a wide observation range and a high temporal resolution. In this paper, a cloud-top height retrieval algorithm based on XGBoost is proposed. The algorithm comprehensively utilizes AHI L1 multi-channel radiance data and calculates the input parameters of the generated model according to the characteristics of the cloud phase, texture, and the local brightness temperature change of the cloud. In addition, the latitude, longitude, solar zenith angle and satellite zenith angle are input into the model to further constrain the influence of the geographical and spatial factors such as the sea and land location, on CTH. Compared with the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) cloud-top height data (CTHCAL), the results show that: the algorithm retrieved the cloud-top height (CTHXGB) with a mean error (ME) of 0.3 km, a standard deviation (Std) of 1.72 km, and a root mean square error (RMSE) of 1.74 km. Additionally, it improves the problem of the large systematic deviation in the cloud-top height products released by the Japan Meteorological Agency (CTHJMA), especially for ice clouds and multi-layer clouds with ice clouds on the top layer. For water clouds below 2 km and multi-layer clouds with water clouds at the top, the algorithm solves the systematically serious CTHJMA problem. XGBoost can effectively distinguish between different cloud scenarios within the model, which is robust and suitable for CTH retrieval.
47
Cai, Guo Yong, Rui Lv, Li Yuan Wang, and Hao Wu. "A Novel Map Matching Algorithm." Applied Mechanics and Materials 556-562 (May 2014): 4139–45. http://dx.doi.org/10.4028/www.scientific.net/amm.556-562.4139.
Full textAbstract:
Presently, most of the researches on Map Matching focus on high sampling rate and accurate GPS points. This paper discusses a challenging problem with low GPS sampling rate and some continuous points with large deviation. To solve the problem efficiently, a novel matching method named F&PT is proposed. Firstly we employ a new method to generate sets of candidate roads. The GPS error analysis based on points is translated into based on roads. Secondly, a local strategy based on potential real trajectories is applied to solve the core problem of selecting an optimal road from the sets which contain only two candidate roads. In this approach, we consider not only the spatial location information and orientation angle information but also the influence of local points on the matching point from a new sight. We evaluate our method based on a real trajectory dataset. The experiments show that the proposed method has a higher accuracy compared with the related methods, e.g. ST-matching algorithm and IVMM algorithm, when the sampling interval is less than 210s.
48
Namgung, Ho. "Local Route Planning for Collision Avoidance of Maritime Autonomous Surface Ships in Compliance with COLREGs Rules." Sustainability 14, no. 1 (December 25, 2021): 198. http://dx.doi.org/10.3390/su14010198.
Full textAbstract:
A maritime autonomous surface ship (MASS) ensures safety and effectiveness during navigation using its ability to prevent collisions with a nearby target ship (TS). This avoids the loss of human life and property. Therefore, collision avoidance of MASSs has been actively researched recently. However, previous studies did not consider all factors crucial to collision avoidance in compliance with the International Regulations for Preventing Collisions at Sea (COLREGs) Rules 5, 7, 8, and 13–17. In this study, a local route-planning algorithm that takes collision-avoidance actions in compliance with COLREGs Rules using a fuzzy inference system based on near-collision (FIS-NC), ship domain (SD), and velocity obstacle (VO) is proposed. FIS-NC is used to infer the collision risk index (CRI) and determine the time point for collision avoidance. Following this, I extended the VO using the SD to secure the minimum safe distance between the MASS and the TS when they pass each other. Unlike previous methods, the proposed algorithm can be used to perform safe and efficient navigation in terms of near-collision accidents, inferred CRI, and deviation from the course angle route by taking collision-avoidance actions in compliance with COLREGs Rules 5, 7, 8, and 13–17.
49
Fair, Phillip S., Jitendra Kikani, and Christopher D. White. "Modeling High-Angle Wells in Laminated Pay Reservoirs." SPE Reservoir Evaluation & Engineering 2, no. 01 (February 1, 1999): 46–52. http://dx.doi.org/10.2118/54656-pa.
Full textAbstract:
Introduction Productivity improvement and acceleration projects have gained substantially from the success of horizontal well drilling technology. Successful placement of near-horizontal wells in difficult reservoir configurations has become routine. However, not all reservoir situations are amenable to horizontal drilling. Specifically, laminated reservoirs such as thinly bedded turbidites in the Gulf of Mexico (GOM) have been perceived as poor targets. Potentially large reserves are locked in these reservoirs. These laminated turbidite systems have near-zero vertical permeability at the Bouma sequence1 scale and extremely small kv/kh ratios kv/kh?0 at the full field, reservoir simulation grid-block scale. In general, a low well count helps minimize development costs. Highly deviated wells (80∘≤θw<90∘) cutting the entire sand package may make it possible to obtain both high field production rates and low well counts. Slanted wells have been known to improve productivity of wells with kv /kh?0. However, the slanted well model given by Cinco 2,3 does not predict any improvement in well productivity for such wells. This apparent paradox is reconciled in this paper. Bed thickness, well diameter, and well angle determine the geometric pseudoskin of these thin-bedded sequences. For wells that are nearly horizontal, a simple technique is introduced to calculate the geometric skin without complex modeling. The range of validity of this approximation was determined by comparison with fine-grid simulations. This paper provides a method to simulate a highly deviated well in a thin-bedded reservoir at field scale without the use of fine grids or local grid coarsening. These inflow relationships have been used to construct the well models for simulations of GOM reservoirs. A field example is presented with guidelines to determine the correct well kh as validated by a grid sensitivity study. Implications of Existing Slanted Well Solutions Thin-bedded turbidite reservoirs in the deep water Gulf of Mexico are currently being developed.4 These reservoirs are comprised of beds that are on the order of 0.25 in. thick and are separated by very low permeability shales. There are two ways to apply Cinco's2,3 slanted well solution to account for this heterogeneity to determine the potential productivity improvement for slanted wells. The first method treats the entire reservoir as an anisotropic system with zero vertical permeability, whereas the second method considers the thin beds explicitly. However, neither of these methods predict any productivity improvement. For the first method (in which the reservoir is modeled as having no vertical permeability, kv=0), the explanation for no improvement in productivity predicted from Cinco's slanted well solution is trivial. It follows from the definition of the anisotropic angle of slant, which becomes zero (as for a vertical well), for a zero vertical permeability reservoir. In the second method, Cinco's2,3 model is applied separately to each bed and the bed productivities are summed to determine the total well productivity. The productivity improvement due to well angle can be determined by examining Cinco's solution for vanishing bed thickness. Fig. 1 shows the geometric pseudoskin as a function of bed thickness normalized by the wellbore radius for various angles between zero and 88°. These results were generated using Cinco's slanted well solution. As the bed thickness approaches zero, the geometric pseudoskin also tends to zero indicating that the well performance will be unchanged compared with a vertical well. This is true for all deviation angles. The slanted well model generally considers a line source well with flux distributed evenly. To mimic the more realistic infinite-conductivity boundary condition, the uniform-flux solution is evaluated at a particular point on an equivalent wellbore. The particular point is located on the semiminor axis of the ellipse that is defined by the intersection of a horizontal plane with the cylindrical wellbore (Fig. 2). This point is located one wellbore radius away from the line source at a distance of either two-tenths or eight-tenths of the bed thickness from the lower bed boundary. When bed thickness tends to zero and there is no vertical component of flow, the particular point is the same point used to evaluate a line source solution for a vertical well in a porous medium of constant horizontal permeability. Thus, this solution indicates no productivity improvement when compared to vertical wells completed in thinly bedded reservoirs. We offer an alternative limiting solution. Highly Deviated Well Model for Thin Beds The limiting solution we offer considers the wellbore to be represented by a fracture at the bed-thickness level. The "fracture" length is governed by the well deviation angle. The intersection of a slanted wellbore with a bedding plane is an ellipse as depicted in Fig. 2(a). For high deviation angles (80∘≤θ<90∘), the size of this ellipse may be significant. The semiminor axis is rw and the semimajor axis is rw/cos(?). Fig. 2(b) is a plot of ellipses for various well angles. The axes of each ellipse have been normalized using the length of the semimajor axis to illustrate the aspect ratio of the ellipses. For well angles greater than 80°, an infinite-conductivity vertical fracture model that approximates an ellipse seems more applicable than the line source approximation.
50
Akhsakhalyan A. A. and Akhsakhalyan A. D. "A new technology of thermoplastic glass bending for the manufacture of cylindrical surfaces of hard X-ray range mirrors." Technical Physics 92, no. 8 (2022): 943. http://dx.doi.org/10.21883/tp.2022.08.54554.125-22.
Full textAbstract:
The paper presents a new technique for thermoplastic bending of glass. The technique makes it possible to produce cylindrical surfaces with a guide in the form of a parabola, ellipse, etc. for mirrors in the hard X-ray wavelength range (λ~0.1 nm). Three samples of the surface of an elliptical cylinder were prepared using this technique. The production time for each sample was two days. The deviation of the guide and its local angle from the calculated values for all samples does not exceed Delta y=0.5 μm and Deltaα=7·10-5 rad, respectively. It is shown that when such surfaces are etched for two hours, their accuracy can be improved by more than two orders of magnitude (Delta y=2 nm, Deltaα=5·10-7 rad). Keywords: focusing X-ray mirrors, cylindrical mirrors, multilayer structures