scholarly journals Radiosity Approach for the Shortwave Surface Radiation Balance in Complex Terrain

2009 ◽  
Vol 66 (9) ◽  
pp. 2900-2912 ◽  
Author(s):  
Nora Helbig ◽  
Henning Löwe ◽  
Michael Lehning
Keyword(s):  
Complex Terrain ◽  
Gaussian Approximation ◽  
Three Dimensional ◽  
Gaussian Random Fields ◽  
Surface Radiation ◽  
Radiation Balance ◽  
Length Scales ◽  
Mean Values ◽  
Terrain Effects ◽  
The Mean

Abstract The influence of topography on the radiation balance in complex terrain has so far been investigated either with very simple or very sophisticated approaches that are limited, respectively, by an uncontrolled spatial representation of radiative fluxes or heavy computational efforts. To bridge this gap in complexity, this paper proposes the radiosity approach, well known in computer graphics, to study anisotropic reflections of radiation in complex terrain. To this end the radiosity equation is rederived in the context of three-dimensional radiative transfer. The discretized equation is solved by means of an adapted version of progressive refinement iteration. To systematically study terrain effects, the geometrical disorder provided by the topography is considered in its simplest approximation by Gaussian random fields. These model topographies capture the most important length scales of complex terrain, namely a typical elevation and a typical valley width via the variance and the correlation length of the field, respectively. The mean reflected radiation is computed as a function of these length scales and sun elevation, thereby explicitly addressing finite system sizes and grid resolutions. A comparison with an isotropic parameterization of terrain reflections reveals that mean values are similar whereas spatial distributions vary remarkably. It is also shown that the mean reflected radiation in real topography is reasonably well characterized by the Gaussian approximation. As a final application of the method, the effective albedo of a topography is shown to vary with sun elevation and domain-averaged albedo, leading to albedo differences up to 0.025.

scholarly journals The correlation between the three-dimensional radiolucency area around the crown of impacted maxillary canines and dentigerous cysts

2020 ◽  
Vol 49 (4) ◽  
pp. 20190402
Author(s):  
Junliang Chen ◽  
Dongmei Lv ◽  
MingXia Li ◽  
Wei Zhao ◽  
Yun He
Keyword(s):  
Cone Beam Ct ◽  
Dentigerous Cyst ◽  
Three Dimensional ◽  
Cone Beam ◽  
Hard Tissue ◽  
Mean Values ◽  
Dentigerous Cysts ◽  
Impacted Canine ◽  
The Mean ◽  
Surgical Operations

This study aimed to reveal the correlation between the radiolucency area around the crown of impacted maxillary canines and dentigerous cysts using cone beam CT (CBCT). CBCT data were obtained from patients with impacted maxillary canines. Three points of five areas (tooth cusp area and buccal, lingual, mesial and distal areas of the crown) were randomly selected, and the distance between the point and the surrounding hard tissue was measured respectively. The mean values were recorded as the radiolucency area. These results were compared with the occurrence of dentigerous cysts during surgery. 58 patients with 76 impacted maxillary canines were included. 14 of the 76 impacted canines were accompanied by cysts (18.42%). With the increase in the thickness of the radiolucency area, the incidence of cysts was significantly increased (p < 0.05). No cysts were found in the compacted canines with 0–1 mm thickness of the radiolucency area. The highest incidence (71.43%) was observed in canines with 3–4 mm thickness of the radiolucency area. This study found that the thickness of the radiolucency area around the crown of the maxillary impacted canine was closely related to the occurrence of dentigerous cysts. CBCT can be used to estimate the occurrence possibility of dentigerous cyst and guide surgical operations.

scholarly journals Vectors of subsurface stormflow in a layered hillslope during runoff initiation

2006 ◽  
Vol 10 (3) ◽  
pp. 309-320 ◽  
Author(s):  
M. Retter ◽  
P. Kienzler ◽  
P. F. Germann
Keyword(s):  
Three Dimensional ◽  
Volume Flux ◽  
Wetting Front ◽  
Experimental Assessment ◽  
Mean Values ◽  
Top Soil ◽  
Wave Guides ◽  
The Mean ◽  
Vector Approach

Abstract. The focus is the experimental assessment of in-situ flow vectors in a hillslope soil. We selected a 100 m2 trenched hillslope study site. During prescribed sprinkling an obliquely installed TDR wave-guide provides for the velocity of the wetting front in its direction. A triplet of wave-guides mounted along the sides of an hypothetical tetrahedron, with its peak pointing down, produces a three-dimensional vector of the wetting front. The method is based on the passing of wetting fronts. We analysed 34 vectors along the hillslope at distributed locations and at soil depths from 11 cm (representing top soil) to 40 cm (close to bedrock interface). The mean values resulted as follows vx=16.1 mm min-1, vy=-0.2 mm min-1, and vz=11.9 mm min-1. The velocity vectors of the wetting fronts were generally gravity dominated and downslope orientated. Downslope direction (x-axis) dominated close to bedrock, whereas no preference between vertical and downslope direction was found in vectors close to the surface. The velocities along the contours (y-axis) varied widely. The Kruskal-Wallis tests indicated that the different upslope sprinkling areas had no influence on the orientation of the vectors. Vectors of volume flux density were also calculated for each triplet. The lateral velocities of the vector approach are compared with subsurface stromflow collected at the downhill end of the slope. Velocities were 25-140 times slower than lateral saturated tracer movements on top of the bedrock. Beside other points, we conclude that this method is restricted to non-complex substrate (skeleton or portion of big stones).

scholarly journals Evaluation of three-dimensional acromiohumeral distance in the standing position and comparison with its conventional measuring methods

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Yuki Yoshida ◽  
Noboru Matsumura ◽  
Yoshitake Yamada ◽  
Minoru Yamada ◽  
Yoichi Yokoyama ◽  
...  
Keyword(s):  
Supine Position ◽  
Humeral Head ◽  
Three Dimensional ◽  
Standing Position ◽  
Ct Scanner ◽  
Mean Values ◽  
Measuring Methods ◽  
The Mean ◽  
Acromiohumeral Distance ◽  
2D And 3D

Abstract Background Narrowing of the acromiohumeral distance (AHD) implies a rotator cuff tear. However, conventional AHD measurements using two-dimensional (2D) imaging or with the patient in the supine position might differ from that while standing during daily activity. This study aimed to evaluate the three-dimensional (3D) actual distance between the acromion and humeral head in the standing position and compare the AHD values with those obtained using conventional measuring methods. Methods Computed tomography (CT) images of 166 shoulders from 83 healthy volunteers (31 male and 52 female; mean age 40.1 ± 5.8 years; age range, 30–49 years) were prospectively acquired in the supine and standing positions using conventional and upright CT scanners, respectively. The minimum distance between the acromion and humeral head on the 3D surface models was considered as the 3D AHD. We measured the 2D AHD on anteroposterior digitally reconstructed radiographs. The AHD values were compared between the supine and standing positions and between the 2D and 3D measurements. Results The mean values of 2D AHD were 8.8 ± 1.3 mm (range, 5.9–15.4 mm) in the standing position and 8.1 ± 1.2 mm (range, 5.3–14.3 mm) in the supine position. The mean values of 3D AHD were 7.3 ± 1.4 mm (range, 4.7–14.0 mm) in the standing position and 6.6 ± 1.2 mm (range, 4.4–13.7 mm) in the supine position. The values of 3D AHD were significantly lower than those of 2D AHDs in both the standing and supine positions (P < 0.001). The values of 2D and 3D AHDs were significantly lower in the supine position than in the standing position (P < 0.001). Conclusions This study evaluated the 3D AHD of normal shoulders in the standing position using an upright CT scanner. The present results indicated that assessments in the supine position can underestimate the value of the AHD compared with those made in the standing position and that assessments using 2D analysis can overestimate the value.

Sand bars in tidal channels. Part 1. Free bars

2001 ◽  
Vol 440 ◽  
pp. 49-74 ◽  
Author(s):  
G. SEMINARA ◽  
M. TUBINO
Keyword(s):  
Three Dimensional ◽  
Basic Mechanism ◽  
Critical Value ◽  
Suspended Load ◽  
Tidal Channels ◽  
Three Dimensional Model ◽  
Mean Values ◽  
Depth Ratio ◽  
Mean Width ◽  
The Mean

We investigate the basic mechanism whereby bars form in tidal channels or estuaries. The channel is assumed to be long enough to allow neglect of the effects of end conditions on the process of bar formation. In this respect, the object of the present analysis differs from that of Schuttelaars & de Swart (1999) who considered bars of length scaling with the finite length of the tidal channel. The channel bottom is assumed to be cohesionless and consisting of uniform sediments. Bars are shown to arise from a mechanism of instability of the erodible bed subject to the propagation of a tidal wave. Sediment is assumed to be transported both as bedload and as suspended load. A fully three-dimensional model is employed both for the hydrodynamics and for sediment transport. At the leading order of approximation considered, the effects of channel convergence, local inertia and Coriolis forces on bar instability are shown to be negligible. Unlike fluvial free bars, in the absence of mean currents tidal free bars are found to be non-migrating features (in the mean). Instability arises for large enough values of the mean width to depth ratio of the channel, for given mean values of the Shields parameter and of the relative channel roughness. The role of suspended load is such as to stabilize bars in the large-wavenumber range and destabilize them for small wavenumbers. Hence, for large values of the mean Shields stress, it turns out that the first critical mode (the alternate bar mode) is characterized by a very small value of the critical width to depth ratio. Furthermore, the order-m mode being characterized by a critical value of the width to depth ratio equal to m times the critical value for the first mode, it follows that for large values of the mean Shields stress several unstable modes are simultaneously excited for relatively low values of the aspect ratio. This suggests that the actual bar pattern observed in nature may arise from an interesting nonlinear competition among different unstable modes.

scholarly journals Surface Layer Turbulent Characteristics over the Complex Terrain of the Loess Plateau Semiarid Region

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Zhida Zhang ◽  
Jiening Liang ◽  
Min Zhang ◽  
Qi Guo ◽  
Lei Zhang
Keyword(s):  
Surface Layer ◽  
Transfer Coefficient ◽  
Loess Plateau ◽  
Turbulence Intensity ◽  
Complex Terrain ◽  
Semiarid Region ◽  
The Loess Plateau ◽  
Mean Values ◽  
The Mean ◽  
Standard Deviations

Surface layer turbulence has an important influence on land-air interactions and pollutant dispersion, and studying the characteristics of surface layer turbulence in complex terrain can contribute to understanding land-air interactions, improving model surface layer parameterization, and enhancing pollution prediction capabilities. The surface layer turbulence observations from the Semi-Arid Climate and Environment Observatory (SACOL) of Lanzhou University in 2008 were processed in this study. High-quality turbulence parameters were calculated, the statistical and transfer characteristics of turbulence were analyzed, and the formation of turbulence was assessed in terms of dynamics and thermodynamics. The atmospheric stability in the semiarid region of the Loess Plateau is basically dominated by neutral/near-neutral and weakly unstable/weakly stable conditions; this pattern is significantly different from the preponderance of unstable and stable layers at other sites. The turbulence intensity differs significantly in both the horizontal and vertical directions and basically shows the relationship I u ≈ I v > I w . The mean values of I u and I v are 0.42 and 0.40, respectively, and the mean value of I w is 0.14, which is different from the general pattern of I u > I v > I w , indicating that the turbulence intensity at SACOL is characterized by a large lateral wind contribution. The dimensionless standard deviations of the nonneutral wind velocity components satisfy the “1/3rd law,” and the dimensionless standard deviations of u, v , and w components are 3.35, 2.98, and 1.26, respectively, in the semiarid Loess Plateau. These values are larger than those over flat terrain. The contribution of the shear term to the formation of turbulence is greater than that of the buoyancy term, and the mean annual values of the shear term and the buoyancy in the kinetic energy budget equation in SACOL are 47.94 × 10−4 m2·s−3 and 11.32 × 10−4 m2·s−3, respectively. The annual mean values of the momentum transfer coefficient C D and the heat transfer coefficient C H under near-neutral conditions are 8.54 × 10−3 and 2.52 × 10−3, respectively.

About approximation of 3-D random fields and statistical simulation

2003 ◽  
Vol 11 (3) ◽  
Author(s):  
Zoya O. Vyzhva
Keyword(s):  
Random Fields ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Statistical Simulation ◽  
Gaussian Random Fields ◽  
Statistical Characteristics ◽  
Mean Square ◽  
The Mean ◽  
Isotropic Random ◽  
Three Dimensional Space

The estimator of the mean-square approximation of 3-D homogeneous and isotropic random field is investigated. The problem of statistical simulation of realizations of random fields in threedimensional space is considered. The algorithm for the receiving of this realization has been formulated, which has been constructed on the base the mean-square approximation of random fields estimator. It has been constructed the statistical model for the Gaussian random fields in three-dimensional space, which has been given by its statistical characteristics.

scholarly journals Evaluation of three-dimensional acromiohumeral distance in the standing position and comparison with its conventional measuring methods

2020 ◽  
Author(s):  
Yuki Yoshida ◽  
Noboru Matsumura ◽  
Yoshitake Yamada ◽  
Minoru Yamada ◽  
Yoichi Yokoyama ◽  
...  
Keyword(s):  
Supine Position ◽  
Humeral Head ◽  
Three Dimensional ◽  
Standing Position ◽  
Ct Scanner ◽  
Mean Values ◽  
Measuring Methods ◽  
The Mean ◽  
Acromiohumeral Distance ◽  
2D And 3D

Abstract Background: Narrowing of the acromiohumeral distance (AHD) implies a rotator cuff tear. However, conventional AHD measurements using two-dimensional (2D) imaging or with the patient in the supine position might differ from that while standing during daily activity. This study aimed to evaluate the three-dimensional (3D) actual distance between the acromion and humeral head in the standing position and compare the AHD values with those obtained using conventional measuring methods.Methods: Computed tomography (CT) images of 166 shoulders from 83 healthy volunteers (31 male and 52 female; mean age 40.1 ± 5.8 years; age range, 30–49 years) were prospectively acquired in the supine and standing positions using conventional and upright CT scanners, respectively. The minimum distance between the acromion and humeral head on the 3D surface models was considered as the 3D AHD. We measured the 2D AHD on anteroposterior digitally reconstructed radiographs. The AHD values were compared between the supine and standing positions and between the 2D and 3D measurements.Results: The mean values of 2D AHD were 8.8 ± 1.3 mm (range, 5.9–15.4 mm) in the standing position and 8.1 ± 1.2 mm (range, 5.3–14.3 mm) in the supine position. The mean values of 3D AHD were 7.3 ± 1.4 mm (range, 4.7–14.0 mm) in the standing position and 6.6 ± 1.2 mm (range, 4.4–13.7 mm) in the supine position. The values of 3D AHD were significantly lower than those of 2D AHDs in both the standing and supine positions (P < 0.001). The values of 2D and 3D AHDs were significantly lower in the supine position than in the standing position (P < 0.001). Conclusions: This study evaluated the 3D AHD of normal shoulders in the standing position using an upright CT scanner. The present results indicated that assessments in the supine position can underestimate the value of the AHD compared with those made in the standing position and that assessments using 2D analysis can overestimate the value.

scholarly journals Geomorphological applications of multi-model photogrammetry

1992 ◽  
Vol 156 ◽  
pp. 63-67
Author(s):  
O Humlum
Keyword(s):  
Three Dimensional ◽  
Surface Radiation ◽  
Radiation Balance ◽  
Software Models ◽  
Terrain Models

The application of multi-model photogrammetry to steep cliff faces is described and examples given of the manipulation of the digitised data to produce three-dimensional terrain models, and by using other software models to estimate surface radiation balance.

scholarly journals TL 18092 - Hindfoot alignment of adult acquired flatfoot deformity

2019 ◽  
Vol 13 (Supl 1) ◽  
pp. 76S
Author(s):  
Alexandre Leme Godoy-Santos ◽  
Cesar Cesar Netto ◽  
Lauren Roberts ◽  
Francois Lintz ◽  
Lew C Schon ◽  
...  
Keyword(s):  
Clinical Assessment ◽  
Cone Beam Ct ◽  
Intraclass Correlation ◽  
Three Dimensional ◽  
Hindfoot Alignment ◽  
Mean Values ◽  
Alignment Angle ◽  
Adult Acquired Flatfoot Deformity ◽  
The Mean ◽  
Calcaneal Tuberosity

Introduction: Clinical assessment of hindfoot alignment (HA) in adult acquired flatfoot deformity (AAFD) can be challenging, and the weightbearing (WB) cone beam CT (CBCT) may potentially better demonstrate this three-dimensional (3D) deformity. Objective: To compare clinical and WB CBCT assessments of HA in patients with AAFD. Methods: In this prospective study, we included 12 men and 8 women (mean age: 52.2 years, range: 20-88) with flexible AAFD. All subjects also underwent WB CBCT and clinical assessment of hindfoot alignment. Three fellowship-trained foot and ankle surgeons performed six hindfoot alignment measurements on the CT images. Intra- and Inter-observer reliabilities were calculated using Intraclass correlation (ICC). Measurements were compared by paired T-tests, and p-values less than .05 were considered significant. Results: The mean of clinically measured hindfoot valgus was 15.2 (95% confidence interval [CI]: 11.5 - 18.8) degrees. It was significantly different from the mean values of all WB CBCT measurements: Clinical Hindfoot Alignment Angle, 9.9 (CI: 8.9 - 11.1) degrees; Achilles tendon/Calcaneal Tuberosity Angle, 3.2 (CI: 1.3 - 5.0) degrees); Tibial axis/Calcaneal Tuberosity Angle, 6.1 (CI: 4.3 - 7.8) degrees; Tibial axis/Subtalar Joint Angle, 7.0 (CI: 5.3 - 8.8) degrees, and Hindfoot Alignment Angle, 22.8 (CI: 20.4 - 25.3) degrees. We found overall substantial to almost perfect intra- (ICC range: 0.87-0.97) and interobserver agreement (ICC range: 0.51-0.88) for all WB CBCT measurements. Conclusion: Using 3D WB CBCT can help characterize the valgus hindfoot alignment in patients with AAFD. The different CT measurements were reliable and repeatable, significantly differing from the clinical evaluation of hindfoot valgus alignment.

Sign in / Sign up

Export Citation Format

Share Document