scholarly journals RECONSTRUCTION OF THE TWO VARIABLES DISCONTINUOUS FUNCTION BY DIFFERENT INFORMATION OPERATORS USING TRIANGULAR ELEMENTS

2021 ◽  
pp. 84-96
Author(s):  
Iuliia Pershyna
Keyword(s):  
Computed Tomography ◽  
Approximation Error ◽  
Digital Signal ◽  
Integral Form ◽  
The Body ◽  
Discontinuous Function ◽  
Discontinuous Approximation ◽  
Body Design ◽  
Triangular Elements ◽  
Function Of Two Variables

The paper examines methods for constructing mathematical models of two variables discontinuous functions using various information about them: one-sided values at points and one-sided traces along a given system of lines. The case is considered when the domain of the required function is triangulated by right-angled triangles. If interpolation or approximation methods are used, then for their construction the values of the function at given points must be given; if we use interlination methods, then traces of the desired function along a given system of lines. In this work, we construct a discontinuous interpolation and approximation splines for approximating a discontinuous function of two variables with given one-sided values in a given system of points (in our case, at the vertices of right-angled triangles), and prove theorems on the estimation of the approximation error by constructed discontinuous structures. In the paper a discontinuous interlination spline, which uses completely different information about the discontinuous function, namely one-sided traces along a given system of lines (in our case, along the sides of right-angled triangles) is also built. Interlination of functions can find wide application in the aircraft and automobile body design automation; when receiving and processing the results of sonar and radar, when solving problems of computed tomography, in digital signal processing and in many other areas. In the paper theorems on the integral form and an estimate of the approximation error by the constructed discontinuous interlination operator are also proved. Computational experiments that compare the results of the approximation of a discontinuous function of two variables by different information operators using triangular elements are presented. In the future, it is planned to apply the constructed operators of discontinuous approximation and interlination to solve a two-dimensional problem of computed tomography with a significant use of the inhomogeneity of the internal structure of the body, which must be reconstructed.

Direct coronal computed tomography of the body

1984 ◽  
Vol 20 (3) ◽  
pp. 697
Author(s):  
Y J Yoon ◽  
H S Suh ◽  
J S Lee ◽  
S M Hong ◽  
S Y Chung ◽  
...  
Keyword(s):  
Computed Tomography ◽  
The Body

scholarly journals Correlation of age, sex and season with the state of human decomposition as quantified by postmortem computed tomography

2021 ◽  
Author(s):  
Dominic L. C. Guebelin ◽  
Akos Dobay ◽  
Lars Ebert ◽  
Eva Betschart ◽  
Michael J. Thali ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Demographic Data ◽  
Sociodemographic Factors ◽  
The State ◽  
The Body ◽  
Seasonal Effects ◽  
Whole Body ◽  
Postmortem Computed Tomography ◽  
Whole Body Computed Tomography ◽  
Urban Study

AbstractDead bodies exhibit a variable range of changes with advancing decomposition. To quantify intracorporeal gas, the radiological alteration index (RAI) has been implemented in the assessment of postmortem whole-body computed tomography. We used this RAI as a proxy for the state of decomposition. This study aimed to (I) investigate the correlation between the state of decomposition and the season in which the body was discovered; and (II) evaluate the correlations between sociodemographic factors (age, sex) and the state of decomposition, by using the RAI as a proxy for the extent of decomposition. In a retrospective study, we analyzed demographic data from all autopsy reports from the Institute of Forensic Medicine of Zurich between January 2017 to July 2019 and evaluated the radiological alteration index from postmortem whole-body computed tomography for each case. The bodies of older males showed the highest RAI. Seasonal effects had no significant influence on the RAI in our urban study population with bodies mostly being discovered indoors. Autopsy reports contain valuable data that allow interpretation for reasons beyond forensic purposes, such as sociopolitical observations.

scholarly journals The double Fourier series of a discontinuous function

1924 ◽  
Vol 106 (737) ◽  
pp. 299-314 ◽  
Keyword(s):  
Fourier Series ◽  
Finite Number ◽  
Double Fourier Series ◽  
General Term ◽  
Discontinuous Function ◽  
Lebesgue Integral ◽  
Function Of Two Variables

A function of two variables may be expanded in a double Fourier series, as a function of one variable is expanded in an ordinary Fourier series. Purpose that the function f ( x, y ) possesses a double Lebesgue integral over the square (– π < π ; – π < y < π ). Then the general term of the double Fourier series of this function is given by cos = є mn { a mn cos mx cos ny + b mn sin mx sin ny + c mn cos mx sin ny + d mn sin mx cos ny } There є 00 = ¼, є m0 = ½ ( m > 0), є 0n = ½ ( n > 0), є ms = 1 ( m > 0, n >0). the coefficients are given by the formulæ a mn = 1/ π 2 ∫ π -π ∫ π -π f ( x, y ) cos mx cos ny dx dy , obtained by term-by-term integration, as in an ordinary Fourier series. Ti sum of a finite number of terms of the series may also be found as in the ordinary theory. Thus ∫ ms = Σ m μ = 0 Σ n v = 0 A μ v = 1/π 2 ∫ π -π ∫ π -π f (s, t) sin( m +½) ( s - x ) sin ( n + ½) ( t - y )/2 sin ½ ( s - x ) 2 sin ½ ( t - y ) if f ( s , t ) is defined outside the original square by double periodicity, we have sub S ms = 1/π 2 ∫ π 0 ∫ π 0 f ( x + s , y + t ) + f ( x + s , y - t ) + f ( x - s , y + t ) + f ( x - s , y - t ) sin ( m + ½) s / 2 sin ½ s sin ( n + ½) t / 2 sin ½ t ds dt .

Computed Tomography of the Body

1983 ◽  
Vol 309 (19) ◽  
pp. 1160-1165 ◽  
Author(s):  
Jack Wittenberg
Keyword(s):  
Computed Tomography ◽  
The Body

scholarly journals Computed tomography of the body: when should it be used?

BMJ ◽  
1982 ◽  
Vol 284 (6308) ◽  
pp. 4-8 ◽  
Author(s):  
J E Husband ◽  
S J Golding
Keyword(s):  
Computed Tomography ◽  
The Body

scholarly journals FOSSA NAVICULARIS MAGNA AT THE SKULL BASE: EMBRYOGENESIS AND ITS DETECTION BY COMPUTED TOMOGRAPHY

2018 ◽  
Vol 99 (3) ◽  
pp. 153-157
Author(s):  
S. L. Kabak ◽  
V. V. Zatochnaya ◽  
Yu. M. Mel’nichenko ◽  
N. A. Savrasova ◽  
E. A. Dorokh
Keyword(s):  
Computed Tomography ◽  
Congenital Anomaly ◽  
Skull Base ◽  
Paranasal Sinuses ◽  
Ventral Surface ◽  
The Body ◽  
Spiral Computed ◽  
Edge Defect ◽  
Medical Centers ◽  
Fossa Navicularis

Fossa navicularis magna was detected in multislice spiral computed  tomography in two patients who turned to the medical centers with  pathology of the paranasal sinuses. Its appearance is determined during  the development of the basilar part of the occipital bone and the body of the sphenoid bone in embryogenesis. This fossa has the  appearance of an edge defect on the ventral surface of the clivus in  CBCT scans. Practical radiologist should interpret such a finding as a  congenital anomaly of development, but not as an invasive lesion.

Many-legged maneuverability: dynamics of turning in hexapods

1999 ◽  
Vol 202 (12) ◽  
pp. 1603-1623 ◽  
Author(s):  
D.L. Jindrich ◽  
R.J. Full
Keyword(s):  
Horizontal Plane ◽  
Center Of Mass ◽  
Vertical Plane ◽  
Force Production ◽  
The Body ◽  
Mean Velocity ◽  
Blaberus Discoidalis ◽  
Body Design ◽  
Reaction Forces ◽  
Straight Ahead

Remarkable similarities in the vertical plane of forward motion exist among diverse legged runners. The effect of differences in posture may be reflected instead in maneuverability occurring in the horizontal plane. The maneuver we selected was turning during rapid running by the cockroach Blaberus discoidalis, a sprawled-postured arthropod. Executing a turn successfully involves at least two requirements. The animal's mean heading (the direction of the mean velocity vector of the center of mass) must be deflected, and the animal's body must rotate to keep the body axis aligned with the heading. We used two-dimensional kinematics to estimate net forces and rotational torques, and a photoelastic technique to estimate single-leg ground-reaction forces during turning. Stride frequencies and duty factors did not differ among legs during turning. The inside legs ended their steps closer to the body than during straight-ahead running, suggesting that they contributed to turning the body. However, the inside legs did not contribute forces or torques to turning the body, but actively pushed against the turn. Legs farther from the center of rotation on the outside of the turn contributed the majority of force and torque impulse which caused the body to turn. The dynamics of turning could not be predicted from kinematic measurements alone. To interpret the single-leg forces observed during turning, we have developed a general model that relates leg force production and leg position to turning performance. The model predicts that all legs could turn the body. Front legs can contribute most effectively to turning by producing forces nearly perpendicular to the heading, whereas middle and hind legs must produce additional force parallel to the heading. The force production necessary to turn required only minor alterations in the force hexapods generate during dynamically stable, straight-ahead locomotion. A consideration of maneuverability in the horizontal plane revealed that a sprawled-postured, hexapodal body design may provide exceptional performance with simplified control.

Evaluation of Radiation Doses from Computed Tomography Conducted in Al Jouf Region (Saudi Arabia)

2021 ◽  
Vol 11 (8) ◽  
pp. 2130-2136
Author(s):  
Ziyad Awadh Alrowaili ◽  
M. Ashari
Keyword(s):  
Computed Tomography ◽  
Saudi Arabia ◽  
Effective Dose ◽  
Computer Software ◽  
Northern Region ◽  
The Body ◽  
Adult Patients ◽  
Dose Length Product ◽  
Comparison Of The Results ◽  
Dose Index

A safe radiation dose from computed tomography (CT) is normally specified through the Computed Tomography Dose Index (CTDI) as an “effective dose.” Radiation exposure from CT is relatively high in comparison with other radiological tests. In this paper, we evaluate doses used on adult patients during typical CT scans, in Al Jouf, the northern region of Saudi Arabia. Scanning processes were taken place in different parts of the body; including the pelvis, head, abdomen, and chest. The dose indices were calculated using the CT-expo v2.5 computer software. A comparison of the results with similar investigations, regionally and globally, was made. Other comparisons between displayed and calculated dose indices were also performed. The main values of CT volume are the dose index (CTDIvol) and dose-length product (DLP). The effectiveness results for head CTs were 45.0 mGy, 488 mGy.cm, and 5.2 mSv; while for pelvic CTs they were 16.4 mGy, 391 mGy.cm, and 4.0 mSv; whereas for abdominal CTs they were 22.2 mGy, 613 mGy.cm, and 6.5 mSv; finally they were 17.5 mGy, 380 mGy.cm, and 3.9 mSv for chest CTs. It is confirmed that the values obtained are within the internationally accepted values, except for the values of the head examination, in which the effective dose value of 5.2 mSv was higher than the recommended value. This work gives an overview of the doses received by adult patients during regular CT examination. It is the first regional CT dose survey and provides a baseline for improvement and quality control in the region of Al Jouf.

P1828Aortic calcification detected by computed tomography and aortic vulnerable plaques: aortic angioscopy study

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
K Kojima ◽  
Y Ebuchi ◽  
S Migita ◽  
T Morikawa ◽  
T Mineki ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Cardiovascular Disease ◽  
Suspected Coronary Artery Disease ◽  
The Body ◽  
Aortic Calcification ◽  
Plaque Instability ◽  
Risk Of Death ◽  
Vulnerable Plaques ◽  
Increased Risk ◽  
Atheromatous Plaques

Abstract Background Aortic calcification is associated with atherosclerotic risk factors and an increased risk of death and cardiovascular disease. However, the relationships aortic calcification and aortic plaque instability are not yet elucidated. Recently, some reports showed non-obstructive aortic angioscopy seemed to visualize atherosclerotic changes of aortic wall more clearly compared with computed tomography (CT). The purpose of this study was to evaluate whether aortic calcification is associated with aortic vulnerable plaques in patients with cardiovascular disease. Methods We investigated 60 consecutive patients with confirmed or suspected coronary artery disease who underwent both aortic angioscopy and CT. The AC volume (ACV) was measured using the volume-rendering method by extracting the area >130 HU within the whole aorta. ACV index (ACVI) was defined as ACV divided by the body surface area. We evaluated the number of ruptured plaque (RP), ulceration and fissure by aortic angioscopy in the whole aorta. We excluded 4 hemodialysis patients. All patients were divided into the median value of ACVI. Results The mean age of patients was 68±10. The median of ACVI was 10.7 ml/m2 [3.9–22.7]. High ACVI patients had significantly greater number of RP, ulceration and atheromatous plaques detected by aortic angioscopy compared with those of low ACVI (2.2±2.7 vs 0.8±1.1, p=0.033, 1.6±1.2 vs 0.9±1.0, p=0.041, 4.0±3.1 vs 1.9±1.8, p=0.009, respectively). Furthermore, the patients without aortic calcification did not have RP at all. In a multivariate model, the number of the atheromatous plaques was independently associated with high ACVI (odds ratio 1.57, 95% confidence interval 1.07–2.69, p=0.018) Conclusions Aortic calcification detected by CT was related to aortic vulnerable plaques in patients with cardiovascular disease.

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