Space Reconstruction Research Articles

86: Iterative Reconstruction of Clinical Electron Beam Phase Space for Intra-Operative Radiation Therapy

To apply the yields in the reference materials to patient cases, a biunique conversion of the elemental composition of human tissues to a composition from the reference materials has been established. Since the measured yields do not contain any information on the lateral properties of the beam, a model for the spread caused by multiple Coulomb scattering in thick targets [3] has been implemented. The width of the beam as provided by the accelerator is taken from the accelerator beam parameters. Furthermore, an extended analytical model for the positron range distribution around the emitting isotopes has been included in the software [4]. For comparison in-beam PET measurements were used, which were acquired by means of a detector system installed at the irradiation site in the framework of the carbon therapy project at GSI Helmholtzzentrum fur Schwerionenforschung [5]. Results: Figure 1 shows the measured activity distribution (a), the conventional condensed history MC simulation (b) and the yield based simulation (c) of a patient suffering from a skull base tumor in coronary view. The iso-activity lines have a distance of 10%. The PTV is shown in pink. The yield based simulation produces a reasonable activity distribution. Compared to the conventional code, a superior accordance is observed.

Reconstruction of Compressively Sampled Ray Space by Statistically Weighted Model

Reconstruction of Compressively Sampled Ray Space by Statistically Weighted Model

Reconstruction of an additive space- and time-dependent heat source

In this paper, we consider the inverse problem of simultaneous determination of an additive space- and time-dependent heat source together with the temperature in the heat equation, with Dirichlet boundary conditions and two over-determination conditions. These latter ones consist of a specified temperature measurement at an internal point and a time-average temperature condition. The mathematical problem is linear but ill-posed since the continuous dependence on the input data is violated. In discretised form, the problem reduces to solving an ill-conditioned system of linear equations. We investigate the performances of several regularisation methods and examine their stability with respect to noise in the input data. The boundary element method combined with either the truncated singular value decomposition, or the Tikhonov regularisation, using various methods for choosing regularisation parameters, e.g. the L-curve method, the generalised cross-validation criterion, the discrepancy principle and the ...

A Blind Watermarking Method Based on Space Reconstruction

Watermarking embeds information into a digital signal like audio, image, or video. Reversible image watermarking can restore the original image without any distortion after the hidden data is extracted. In this paper, we propose a blind watermarking method based on space reconstruction. Through calculating the statistical property of the digital image, we are able to separately obtain the feature spaces. Passing spaces decomposing and reconstructing of the feature spaces, constructing the embedding matrix, we obtain that the robustness of the approach lies in hiding a watermark in the subspace that is the least susceptible to potential modification; and realize the optimization statistics of the embedding watermark. Through analysis and constraint the conditions of subspace, the algorithm we proposed can obtain a high detection probability and security, a low false alarm probability. The robustness of the watermarking method is demonstrated by a kind of attacks through computer simulation.

A Blind Watermarking Method Based on Space Reconstruction

Watermarking embeds information into a digital signal like audio, image, or video. Reversible image watermarking can restore the original image without any distortion after the hidden data is extracted. In this paper, we propose a blind watermarking method based on space reconstruction. Through calculating the statistical property of the digital image, we are able to separately obtain the feature spaces. Passing spaces decomposing and reconstructing of the feature spaces, constructing the embedding matrix, we obtain that the robustness of the approach lies in hiding a watermark in the subspace that is the least susceptible to potential modification; and realize the optimization statistics of the embedding watermark. Through analysis and constraint the conditions of subspace, the algorithm we proposed can obtain a high detection probability and security, a low false alarm probability. The robustness of the watermarking method is demonstrated by a kind of attacks through computer simulation.

Motivational Task: Methodology and Method of Work Motivation Diagnostics

The article features a new assesment technique of work motivation diagnostics based on the concept of motivational task. A motivational task is a tool for self-appraisal of the field of motivational objects allowing further reconstruction of motivational space. The conditions of the motivational task resolution have been implemented in the assesment procedure named Motivational Map. The diagnostics procedure consists in multiple visual appraisal of 16 motivational objects (J.Nuttin) within a dimensional graphic space determined by 6 evaluation scales. Approbation of new assesment technique was conducted on a sample of 206 financial specialists. Collected results were compared with the scores received with the help of standard questionnaires. The results of psychometric verification of validity and reliability are presented in the article.

Transformation Design and Research about Community of Large Enterprises in Baotou City in 1990s in Order to Appropriate the Aged

Industrialized cities - Baotou City specific existing settlement patterns and future settlements trends, the current status of China has entered the aging society, studies the old community of large and medium-sized enterprises in Baotou City, to the "appropriate the aged community "transformation design, in order to take full advantage of existing settlements form, to protect the original neighborhood relations and the relationship between colleagues, transformation of appropriate the old settlements lifelong available. Fully adapt to the current inhabitation form, to achieve reuse, and starting to think about building environment and space reconstruction and improvement from both the content and level to meet the needs of aged people living behavior.

Grid Lagrange Stability Analysis Based on Chaos Analysis

The power system is a typical non-linear system, of which the influencing factors are complex. The existing power system stability analysis methods can only determine whether the system into chaos, and deem chaos unstable. The development of the science of chaos has opened up a new way for the power system stability analysis. First, chaotic time series based on the power system calculate the largest Lyapunov exponent of the power system time series by the use of C-C method in the chaos theory and reconstruction of phase space. Then it identifies Chaos according to the largest Lyapunov exponent. Finally, it determines whether the power system is the Lagrange stability according to the size of the index combined with systemic phase diagram. The analysis of actual power system simulation proved that it is feasible to use chaos theory to analyze the stability of the grid Lagrange.

The brain's 'superformula': perceptual reconstruction of complex shape spaces

The brain's 'superformula': perceptual reconstruction of complex shape spaces

A study on the evaluation of usefulness depending on the image reconstruction method in bone SPECT scan

The recent advances in image-processing techniques have led to the development of many methods to reduce the scan time without degrading the image quality. In particular, tomography has improved image reconstruction methods with the concomitant improvement of high-quality images. In this study, PRECEDENCE 16 was used to reconstruct images using the filtered back projection method, which is generally used, and the Astonish method and three-dimensional ordered-subsets expectation maximization method, which are based on repetition techniques. In qualitative and quantitative analysis of the reconstructed images, a comparison was made between images with different acquisition times and between images with the same acquisition time, which aimed at determining the optimal method for reconstructing high-quality images. A blind test for qualitative analysis confirmed almost no difference in image quality depending on the image acquisition time. Furthermore, in quantitative analysis, there was no significant difference in image quality depending on the image acquisition time. On the other hand, the results of the analysis in the image reconstruction method with the same acquisition time demonstrated a significant difference. The images reconstructed by the Astonish method, which uses a repetition technique, are believed to be excellent because they have high resolution and provide clinical diagnostic information. This study confirmed that the reconstruction method with a repetition technique could be used to improve image quality and reduce the scan time, despite not being in general use until recently due to the lengthy time needed for image reconstruction and lack of storage space.

Multicomponent Chirp-like Jammer Excision in DSSS Communication Systems Using Hilbert-Huang Hough Transform

A novel and efficient approach for multicomponent chirp-like jammer excision in direct sequence spread spectrum (DSSS) communication systems using Hilbert-Huang Hough (HH-H) transform is proposed, which is the generalization of marginal Hilbert spectrum. The approach iteratively decomposes the received signal into intrinsic mode functions (IMFs) and applies Hilbert transform to each IMF to yield Hilbert spectrum (HS), by which the embedded jammers can be well concentrated in the time-frequency plane along their instantaneous frequency laws. By performing Hough transform over the HS and searching peaks in the parameter space, parameters estimation and components reconstruction of the multicomponent chirp-like jammer are implememted. Simulation results are presented showing performance comparison between the proposed method and the fractional Fourier transform (FrFT) based method in the case of two chirp-like jammer components. DOI: http://dx.doi.org/10.11591/telkomnika.v11i4.2372

A Study on Investigation and Reconstruction of Negative Spaces in an Old-Street Area in Nanning - Analysis of Thermal Environment in Negative Spaces

This paper focuses on the thermal environment in an old urban block called Water Street in Nanning. Based on the field investigation, measurement data of ten selected points and related research data, we analyzed the thermal environment especially in negative spaces. The purpose of this study is to provide a theory basis for understanding characteristics of negative spaces, regenerating their vitality and improving spatial comfort.

Adaptive multiscale scheme based on numerical density of entropy production for conservation laws

AbstractWe propose a 1D adaptive numerical scheme for hyperbolic conservation laws based on the numerical density of entropy production (the amount of violation of the theoretical entropy inequality). This density is used as an a posteriori error which provides information if the mesh should be refined in the regions where discontinuities occur or coarsened in the regions where the solution remains smooth. As due to the Courant-Friedrich-Levy stability condition the time step is restricted and leads to time consuming simulations, we propose a local time stepping algorithm. We also use high order time extensions applying the Adams-Bashforth time integration technique as well as the second order linear reconstruction in space. We numerically investigate the efficiency of the scheme through several test cases: Sod’s shock tube problem, Lax’s shock tube problem and the Shu-Osher test problem.

High-Order Wave Propagation Algorithms for Hyperbolic Systems

We present a finite volume method that is applicable to hyperbolic PDEs including spatially varying and semilinear nonconservative systems. The spatial discretization, like that of the well-known Clawpack software, is based on solving Riemann problems and calculating fluctuations (not fluxes). The implementation employs weighted essentially nonoscillatory reconstruction in space and strong stability preserving Runge--Kutta integration in time. The method can be extended to arbitrarily high order of accuracy and allows a well-balanced implementation for capturing solutions of balance laws near steady state. This well-balancing is achieved through the $f$-wave Riemann solver and a novel wave-slope WENO reconstruction procedure. The wide applicability and advantageous properties of the method are demonstrated through numerical examples, including problems in nonconservative form, problems with spatially varying fluxes, and problems involving near-equilibrium solutions of balance laws.

Three-dimensional oil and gas pool-forming dynamic simulation system: principle, method and applications

Based on the theories and methods of system engineering, the reconstruction of physical space for oil and gas generation, expulsion, migration, accumulation and diffusion is realised by combining the dynamics simulation with topological structure simulation and applying the topological structure simulation. The integral non-linear process of petroleum system is described successfully with the combination of general and system dynamic simulation. The integration of numerical simulation and artificial intelligence simulation solves the non-linear process description of petroleum generation, expulsion, migration, accumulation and diffusion. At the same time, the basin geological body and its oil and gas generation, expulsion, migration, accumulation process of the three-dimensional visualisation of dynamic modelling, spatial analysis and trap evaluation technologies were further developed in this system. The software has been applied successfully in modelling petroleum systems of Tarim River Oilfield, Zhu III Depression, Linqing Depression, Baise Basin and Dongying Depression, China.

U-Invariant Sampling and Reconstruction in Atomic Spaces With Multiple Generators

Given a U-invariant sampling scheme on a Hilbert space H. This paper characterizes atomic subspaces A of H such that every signal x ∈ A can be reconstructed from its generalized samples acquired with the U-invariant sampling scheme. If signal recovery is possible a linear filter is derived which reconstructs the signal from the samples. Moreover, the paper gives necessary and sufficient conditions on a sequence of sampling functions such that it forms a pseudoframe or pseudo-Riesz basis for a given atomic subspace A.

Solution of plane Dirichlet problem using compactly supported 2D wavelet scaling functions

The paper presents the solution of the homogeneous plane Dirichlet problem using the wavelet-Galerkin method with various 2D compactly supported wavelet scaling functions. An analysis of approximation accuracy was performed with respect to the orders of investigated wavelet scaling functions and the level of approximation. The most effective scaling functions for solving the Dirichlet problem were indicated and discussed. The wavelets theory is relatively new, but an effective mathematical tool for solving many theoretical and engineering problems. The wide range of its applica� tions covers developed numerical algorithms for approximation of ordinary differ� ential equations (ODE) and partial differential equations (PDE), image processing, signal analysis etc. The algorithms based on wavelet theory for solving ODE and PDE offer several advantages in comparison with the algorithms based on finite difference and finite element methods, e.g. low timeconsumption and good accu� racy (1). The two most popular waveletbased methods for solvi ng differential equations (DE) are (2): the collocation method and the waveletGalerkin method (WGM). According to some good properties, e.g. the possibility of multiresolution analysis and stability of decomposition and reconstruction in spaces of squareintegrable functions L 2 (R n ), solution stability, WGM gain great popularity. The crucial task in application of waveletbased num erical approximation algo� rithms is the choice of appropriate wavelet scaling functions. In the function ap� proximation problems, the wavelets with infinite support results in poor effects, therefore the orthogonal wavelets were primarily chosen for solving DE (3). One of the most popular wavelets is the Daubechies' ( db ) wavelet, which is often used for solving DE (4, 5). However, several authors used other wavelet scaling func� tions for solving DE, e.g. symlets ( sym ), coiflets ( coif ), Bspline wavelets ( bsp ), biorthogonal ( bior ) and reversed biorthogonal ( rbio ) wavelets (6�8). Due to the separability property of the abovementio ned compactly supported wavelets, they could be simply generalized to the higher dimensions by tensor

Iterative reconstruction of dual-source coronary CT angiography: assessment of image quality and radiation dose

To assess the image quality and radiation dose of low-dose dual-source CT (DSCT) coronary angiography reconstructed using iterative reconstruction in image space (IRIS), in comparison with routine-dose CT using filtered back projection (FBP). Eighty-one patients underwent low-dose coronary DSCT using IRIS with two protocols: (a)100 kVp and 200 mAs per rotation for body mass index (BMI) < 25 (group I), (b)100 kVp and 320 mAs for BMI ≥ 25 (II). For comparison, two sex-and BMI-matched groups using standard protocols with FBP were selected: (a)100 kVp and 320 mAs for BMI < 25 (III), (b)120 kVp and 320 mAs for BMI ≥ 25 (IV). Image noise, signal to noise ratio (SNR) and modulation transfer function (MTF) 50% were objectively calculated. Two blinded readers then subjectively graded the image quality. Radiation dose was also measured. Image noise tended to be lower in IRIS of low-dose protocols: 22.0 ± 4.5 for group I versus 24.8 ± 4.0 for III (P < 0.001); 20.9 ± 4.5 for II versus 21.6 ± 4.9 for IV (P = 0.6). SNR was better with IRIS: 25.8 ± 4.4 for I versus 22.7 ± 4.6 for III (P < 0.001); 24.6 ± 5.4 for II versus 18.7 ± 4.5 for IV (P < 0.001). No differences in MTF 50% or image quality scores were seen between each two groups (P > 0.05). Radiation reduction was 40% for I and 51% for II, compared to standard protocols. Compared with routine-dose CT using FBP, low-dose coronary angiography using IRIS provides significant radiation reduction without impairment to image quality.

Emasculated Bodies of Hijras

The article examines through a historical lens, how the emasculated body of hijras takes on different and often contrasting meanings embodied in social roles, statuses and identities. It follows the trajectory of the historical space occupied by hijras since the beginning of the Mughal Empire in the 16th century and traces the roles and identities of hijras that have continuously been in a state of dynamism through their construction, reconstruction and reinvention in time and space. It is argued in the article that the corporeal act of emasculation performed on the body of hijras is a medium through which identities have been imposed, resisted and negotiated. From eunuch-slaves to cultural performers, religious ascetics and followers of Bahuchara Mata, the differentiated bodies of hijras have served as the single most important vehicle of their identity formation and their social interaction with society. What is essentially brought out then is the interplay of traditional and rational action through the retention of the ritualised practice of emasculation centred on the worship of the goddess Bahuchara, and the redefinition of traditional roles in response to changing social structures.

The Prediction Model of Chaotic Series Based on Support Vector Machine and its Application to Runoff

Chaos and support vector machine theory has opened up a new route to study complicated and changeable non-linear hydrology time series. Applying the Chaos and non-linear time series based on the support vector machine regression principle, this paper proposes a method and its characteristic and the choosing of key parameters to forecast and set up models. According to Phase Space Reconstruction theory carry on reconstruction of Phase Space to monthly surface flow course, have discussed that probed into the non-linear prediction model of time series of Chaos of the support vector machine, application in the monthly surface flow, have introduce it through to the nuclear function of the base in the course of setting up the model of support vector machine, has simplified the course of solving the non-linear problems. The instance indicates that the model can deal with the complicated hydrology data array well, and there is the good prediction precision.