Analysis of algebraic reconstruction technique for accurate imaging of gas temperature and concentration based on tunable diode laser absorption spectroscopy

An improved algebraic reconstruction technique（ART） combined with tunable diode laser absorption spectroscopy（TDLAS） is presented in this paper for determining two-dimensional（2D） distribution of H2O concentration and temperature in a simulated combustion flame.This work aims to simulate the reconstruction of spectroscopic measurements by a multi-view parallel-beam scanning geometry and analyze the effects of projection rays on reconstruction accuracy.It finally proves that reconstruction quality dramatically increases with the number of projection rays increasing until more than 180 for 20 × 20 grid,and after that point,the number of projection rays has little influence on reconstruction accuracy.It is clear that the temperature reconstruction results are more accurate than the water vapor concentration obtained by the traditional concentration calculation method.In the present study an innovative way to reduce the error of concentration reconstruction and improve the reconstruction quality greatly is also proposed,and the capability of this new method is evaluated by using appropriate assessment parameters.By using this new approach,not only the concentration reconstruction accuracy is greatly improved,but also a suitable parallel-beam arrangement is put forward for high reconstruction accuracy and simplicity of experimental validation.Finally,a bimodal structure of the combustion region is assumed to demonstrate the robustness and universality of the proposed method.Numerical investigation indicates that the proposed TDLAS tomographic algorithm is capable of detecting accurate temperature and concentration profiles.This feasible formula for reconstruction research is expected to resolve several key issues in practical combustion devices.

A Sound Field Separation and Reconstruction Technique Based on Reciprocity Theorem and Fourier Transform

We show a method to separate the sound field radiated by a signal source from the sound field radiated by noise sources and to reconstruct the sound field radiated by the signal source. The proposed method is based on reciprocity theorem and the Fourier transform. Both the sound field and its gradient on a measurement surface are needed in the method. Evanescent waves are considered in the method, which ensures a high resolution reconstruction in the near field region of the signal source when evanescent waves can be measured. A simulation is given to verify the method and the influence of measurement noise on the method is discussed.

AENO:a Novel Reconstruction Method in Conjunction with ADER Schemes for Hyperbolic Equations

In this paper,we present a novel spatial reconstruction scheme,called AENO,that results from a special averaging of the ENO polynomial and its closest neighbour,while retaining the stencil direction decided by the ENO choice.A variant of the scheme,called m-AENO,results from averaging the modified ENO(m-ENO)polynomial and its closest neighbour.The concept is thoroughly assessed for the one-dimensional linear advection equation and for a one-dimensional non-linear hyperbolic system,in conjunction with the fully discrete,high-order ADER approach implemented up to fifth order of accuracy in both space and time.The results,as compared to the conventional ENO,m-ENO and WENO schemes,are very encouraging.Surprisingly,our results show that the L_(1)-errors of the novel AENO approach are the smallest for most cases considered.Crucially,for a chosen error size,AENO turns out to be the most efficient method of all five methods tested.

Multifactor analysis of the technique in total laparoscopic gastric cancer

BACKGROUND Esophageal gastric anastomosis is a common surgical technique used to treat patients with gastric cancer who undergo total gastrectomy.However,using simple anastomosis techniques alone may not meet the needs of patients in some cases and can lead to complications such as anastomotic stenosis and ulceration.In order to overcome these issues and improve patient prognosis,muscle flap reconstruction technique has emerged.Muscle flap reconstruction is a method of improving gastric-esophageal anastomosis by transplanting muscle tissue.By covering the anastomotic site with muscle tissue,it not only enhances the stability of the anastomosis site but also increases blood supply,promoting healing and recovery of the anastomosis.Therefore,the use of muscle flap reconstruction technique in esophageal gastric anastomosis during total gastrectomy for gastric cancer is increasingly widely applied.AIM To determine the effectiveness of esophagogastric anastomosis using the muscle flap reconstruction technology in total abdominal gastrectomy for gastric cancer and perform follow-up experiments to understand the factors affecting patients’prognosis.METHODS The study subjects were 60 patients with gastric cancer who were admitted to our hospital between October 2018 and January 2022.All patients underwent esopha-gogastric anastomosis using the double muscle flap reconstruction technology in total abdominal gastrectomy.Perioperative indicators were determined,and INTRODUCTION Gastric cancer is one of the most common tumors of the digestive system worldwide.Although gastric cancer may not have significant manifestations in the early stage,as the disease progresses,systemic symptoms such as emaciation,anemia,and gastric perforation are observed[1].Surgery is the main treatment strategy for gastric cancer.With recent advances in total laparoscopy,total laparoscopic radical resection has gradually become an important treatment strategy for gastric cancer.Conventional laparoscopic surgery may require at least 5-6 incisions,whereas total laparoscopic surgery requires only 3-4 small incisions,decreasing surgical trauma and postoperative pain[2].Furthermore,because total laparoscopic surgery is less invasive than conventional laparoscopic surgery,patients can generally return to normal living and working conditions more quickly[3].Moreover,total laparoscopic surgery does not leave obvious surgical scars;therefore,it is advantageous for patients who pay attention to appearance[4].Esophagogastrostomy is a method used to repair gastrointestinal anastomosis,called the“double muscle valve”.This technique requires folding the fundus of the stomach,followed by sealing it with two layers of tissue,forming a structure similar to a valve.The application of esophagogastrostomy to total laparoscopic radical resection for gastric cancer can effectively decrease the incidence of complications such as anastomotic incontinence and bile reflux and improve the surgical cure rate and postoperative quality of life,which is a recent topic of interest for surgeons.At present,systematic multivariate analyses of the application effects of esophagogastrostomy in total laparoscopic surgery for gastric cancer and their effects on prognosis remain scarce[5].In the present study,we conducted surgery and postoperative follow-up of patients with gastric cancer and collected relevant clinical data for esophagogastric anastomosis during postoperative resection for gastric cancer to ACKNOWLEDGEMENTS I would like to express my sincere thanks to all those who participated in the manuscript.

Billroth II anastomosis combined with brown anastomosis reduce reflux gastritis in gastric cancer patients

BACKGROUND The surgeon performing a distal gastrectomy,has an arsenal of reconstruction techniques at his disposal,Billroth II among them.Braun anastomosis performed during a Billroth II procedure has shown evidence of superiority over typical Billroth II,in terms of survival,with no impact on postoperative morbidity and mortality.AIM To compare Billroth II vs Billroth II and Braun following distal gastrectomy,regarding their postoperative course.METHODS Patients who underwent distal gastrectomy during 2002-2021,were separated into two groups,depending on the surgical technique used(Billroth II:74 patients and Billroth II and Braun:28 patients).The daily output of the nasogastric tube(NGT),the postoperative day that NGT was removed and the day the patient started per os feeding were recorded.Postoperative complications were at the same time noted.Data were then statistically analyzed.RESULTS There was difference in the mean NGT removal day and the mean start feeding day.Mean total postoperative NGT output was lower in Braun group(399.17 mL vs 1102.78 mL)and it was statistically significant(P<0.0001).Mean daily postoperative NGT output was also statistically significantly lower in Braun group.According to the postoperative follow up 40 patient experienced bile reflux and alkaline gastritis from the Billroth II group,while 9 patients who underwent Christodoulidis G et al.Billroth II and Braun compared with Billroth II WJM https://www.wjgnet.com 2 March 20,2024 Volume 14 Issue 1 Billroth II and Braun anastomosis were presented with the same conditions(P<0.05).CONCLUSION There was evidence of superiority of Billroth II and Braun vs typical Billroth II in terms of bile reflux,alkaline gastritis and NGT output.

Surgical treatment of left-sided renal carcinoma with grade II inferior vena cava tumour thrombus: a report and review of the literature

The surgical removal of renal cancer,along with the thrombectomy of the inferior vena cava tumour thrombus,represents a remarkable milestone in urological surgery.This procedure is not only technically demanding but also requires a high level of surgical expertise.Managing renal cancer combined with a vena cava tumour thrombus poses significant challenges,especially when dealing with combined grade Ⅱ-Ⅳ inferior vena cava tumour thrombus.The complexity of these cases is further exacerbated by the delicate anatomical structures involved and the need to preserve critical vessels while effectively removing the tumour.The Upper Urethral Tumour Treatment Centre of Weifang People's Hospital successfully treated a challenging case of left renal tumour combined with grade II inferior vena cava tumour thrombus.The surgical team,led by experienced urological surgeons,meticulously planned and executed the procedure,ensuring minimal trauma to the patient and complete removal of the tumour.This achievement not only demonstrates the hospital's commitment to providing state-of-the-art surgical care but also highlights the importance of continued research and training in urological oncology.The successful outcome of this case is a testament to the expertise and dedication of the medical team and offers hope to patients facing similar complex surgical challenges.

Passive seismic velocity tomography on longwall mining panel based on simultaneous iterative reconstructive technique (SIRT)

Mining operation, especially underground coal mining, always has the remarkable risks of ground control. Passive seismic velocity tomography based on simultaneous iterative reconstructive technique （SIRT） inversion is used to deduce the stress redistribution around the longwall mining panel. The mining-induced microseismic events were recorded by mounting an array of receivers on the surface, above the active panel. After processing and filtering the seismic data, the three-dimensional tomography images of the p-wave velocity variations by SIRT passive seismic velocity tomography were provided. To display the velocity changes on coal seam level and subsequently to infer the stress redistribution, these three-dimensional tomograms into the coal seam level were sliced. In addition, the boundary element method （BEM） was used to simulate the stress redistribution. The results show that the inferred stresses from the passive seismic tomograms are conformed to numerical models and theoretical concept of the stress redistribution around the longwall panel. In velocity tomograms, the main zones of the stress redistribution arotmd the panel, including front and side abutment pressures, and gob stress are obvious and also the movement of stress zones along the face advancement is evident. Moreover, the effect of the advance rate of the face on the stress redistribution is demonstrated in tomography images. The research result proves that the SIRT passive seismic velocity tomography has an ultimate potential for monitoring the changes of stress redistribution around the longwall mining panel continuously and subsequently to improve safety of mining operations.

Gray weighted algorithm for variable voltage CT reconstruction

In conventional computed tomography （CT） reconstruction based on fixed voltage, the projective data often ap- pear overexposed or underexposed, as a result, the reconstructive results are poor. To solve this problem, variable voltage CT reconstruction has been proposed. The effective projective sequences of a structural component are obtained through the variable voltage. The total variation is adjusted and minimized to optimize the reconstructive results on the basis of iterative image using algebraic reconstruction technique （ART）. In the process of reconstruction, the reconstructive image of low voltage is used as an initial value of the effective proiective reconstruction of the adjacent high voltage, and so on until to the highest voltage according to the gray weighted algorithm. Thereby the complete structural information is reconstructed. Simulation results show that the proposed algorithm can completely reflect the information of a complicated structural com- ponent, and the pixel values are more stable than those of the conventional.

A new inversion method for reconstruction of plasmaspheric He^(+)density from EUV images

The Computer Tomography(CT)method is used for remote sensing the Earth’s plasmasphere.One challenge for image reconstruction is insufficient projection data,mainly caused by limited projection angles.In this study,we apply the Algebraic Reconstruction Technique(ART)and the minimization of the image Total Variation(TV)method,with a combination of priori knowledge of north–south symmetry,to reconstruct plasmaspheric He+density from simulated EUV images.The results demonstrate that incorporating priori assumption can be particularly useful when the projection data is insufficient.This method has good performance even with a projection angle of less than 150 degrees.The method of our study is expected to have applications in the Soft X-ray Imager(SXI)reconstruction for the Solar wind–Magnetosphere–Ionosphere Link Explorer(SMILE)mission.

Novel Fourier-based iterative reconstruction for sparse fan projection using alternating direction total variation minimization

Sparse-view x-ray computed tomography （CT） imaging is an interesting topic in CT field and can efficiently decrease radiation dose. Compared with spatial reconstruction, a Fourier-based algorithm has advantages in reconstruction speed and memory usage. A novel Fourier-based iterative reconstruction technique that utilizes non-uniform fast Fourier transform （NUFFF） is presented in this work along with advanced total variation （TV） regularization for a fan sparse-view CT. The proposition of a selective matrix contributes to improve reconstruction quality. The new method employs the NUFFT and its adjoin to iterate back and forth between the Fourier and image space. The performance of the proposed algorithm is demonstrated through a series of digital simulations and experimental phantom studies. Results of the proposed algorithm are compared with those of existing TV-regularized techniques based on compressed sensing method, as well as basic algebraic reconstruction technique. Compared with the existing TV-regularized techniques, the proposed Fourier-based technique significantly improves convergence rate and reduces memory allocation, respectively.

Terrain reconstruction from Chang'e-3 PCAM images

The existing terrain models that describe the local lunar surface have limited resolution and accuracy, which can hardly meet the needs of rover navigation,positioning and geological analysis. China launched the lunar probe Chang＇e-3 in December, 2013. Chang＇e-3 encompassed a lander and a lunar rover called ＂Yutu＂（Jade Rabbit）. A set of panoramic cameras were installed on the rover mast. After acquiring panoramic images of four sites that were explored, the terrain models of the local lunar surface with resolution of 0.02 m were reconstructed. Compared with other data sources, the models derived from Chang＇e-3 data were clear and accurate enough that they could be used to plan the route of Yutu.

The Matrix Transform for Reconstruction on Finite-Element-Based Photoacoustic Tomography

Numerical Finite-element method (FEM) based algorithms have been widely applied for the reconstruction of the photoacoustic image. As compared with the traditional analytic methods, the FEM based methods can be easily used to deal with problems with irregularly shaped imaging domain. However, the FEM based algorithms are usually computationally intensive because repeated manipulations of matrices with larger size are needed during the reconstruction process. To tackle such a problem, a novel method is proposed for reducing the size of the matrix to be inversed during the reconstruction process and hence speed up the inverse reconstruction without any sacrifice of the reconstruction accuracy.

Principle of subtraction ghost imaging in scattering medium

Scattering medium in light path will cause distortion of the light field,resulting in poor signal-to-noise ratio(SNR)of ghost imaging.The disturbance is usually eliminated by the method of pre-compensation.We deduce the intensity fluctuation correlation function of the ghost imaging with the disturbance of the scattering medium,which proves that the ghost image consists of two correlated results:the image of scattering medium and the target object.The effect of the scattering medium can be eliminated by subtracting the correlated result between the light field after the scattering medium and the reference light from ghost image,which verifies the theoretical results.Our research may provide a new idea of ghost imaging in harsh environment.

Tropospheric Wet Refractivity Tomography Based on the BeiDou Satellite System

This paper presents a novel approach for assessing the precision of the wet refractivity field using BDS （BeiDou navigation satellite system） simulations only,GPS,and BDS＋GPS for the Shenzhen and Hongkong GNSS network.The simulations are carried out by adding artificial noise to a real observation dataset.Instead of using the δ and σ parameters computed from slant wet delay,as in previous studies,we employ the Bias and RMS parameters,computed from the tomography results of total voxels,in order to obtain a more direct and comprehensive evaluation of the precision of the refractivity field determination.The results show that：（1） the precision of tropospheric wet refractivity estimated using BDS alone （only 9 satellites used） is basically comparable to that of GPS; （2） BDS＋GPS （as of current operation） may not be able to significantly improve the data＇s spatial density for the application of refractivity tomography; and （3） any slight increase in the precision of refractivity tomography,particularly in the lower atmosphere,bears great significance for any applications dependent on the Chinese operational meteorological service.

Dual-basis reconstruction techniques for tomographic PIV

As an inverse problem, particle reconstruction in tomographic particle image velocimetry attempts to solve a large-scale underdetermined linear system using an optimization technique. The most popular approach, the multiplicative algebraic reconstruction technique(MART), uses entropy as an objective function in the optimization. All available MART-based methods are focused on improving the efficiency and accuracy of particle reconstruction. However, those methods do not perform very well on dealing with ghost particles in highly seeded measurements. In this report, a new technique called dual-basis pursuit(DBP), which is based on the basis pursuit technique, is proposed for tomographic particle reconstruction. A template basis is introduced as a priori knowledge of a particle intensity distribution combined with a correcting basis to enable a full span of the solution space of the underdetermined linear system. A numerical assessment test with 2D synthetic images indicated that the DBP technique is superior to MART method, can completely recover a particle field when the number of particles per pixel(ppp) is less than 0.15, and can maintain a quality factor Q of above 0.8 for ppp up to 0.30. Unfortunately, the DBP method is difficult to utilize in 3D applications due to the cost of its excessive memory usage. Therefore, a dual-basis MART was designed that performed better than the traditional MART and can potentially be utilized for 3D applications.

Effective and robust approach for fluorescence molecular tomography based on CoSaMP and SP_(3)model

Fluorescence molecular tomography(FMT)allows the detection and quantification of various biological processes in small animals in vrivo,which expands the horizons of pre clinical rescarch and drug development.Eficient three dimensional(3D)reconstruction algorithm is the key to accurate localization and quant ification of fAuorescent target in FMT.In this paper,3D recon-struction of FMT is regarded as a sparse signal recovery problem and the compressive sampling matching pursuit(CoSaMP)algorithm is adopted to obtain greedy recovery of fuorescent sig-nals.Moreover,to reduce the modeling error,the simplified spherical harmonics approximation to the radiative transfer equation(RTE),more specifically SP_(3),is utilized to describe light prop-agation in biological tissues.The performance of the proposed reconstruction method is thor-oughly evaluated by simulations on a 3D digital mouse model by comparing it with three representative greedy methods including orthogonal matching pursuit(OMP),stagewise OMP(StOMP),and regularized OMP(ROMP).The CoSaMP combined with SP_(3)shows an im-provement in reconstruction accuracy and exhibits distinct advantages over the comparative algorithms in multiple targets resolving.Stability analysis suggests that CoSaMP is robust to noise and performs stably with reduction of measurements.The feasibility and reoonstruction accuracy of the proposed method are further validated by phantom experimental data.

ANALYSIS AND APPLIED STUDY OF DYNAMICCHARA CTERISTICS OF CHAOTIC REPELLER IN COMPLICATED SYSTEM

Fractal characters and fractal dimension of time series created by repeller in complicated system were studied and the time series were reconstructed by applying the theory of phase space reconstruction for chaotic time series. The influence of zero_mean treatment, Fourier filter on prediction for time series were studied. The choice of prediction sample affects the relative error and the prediction length which were also under good concern. The results show that the model provided here are practical for the modeling and prediction of time series created by chaotic repellers. Zero_mean treatment has changed prediction result quantitatively for chaotic repeller sample data. But using Fourier filter may decrease the prediction precision. This is theoretical and practical for study on chaotic repeller in complicated system.

Terahertz two-pixel imaging based on complementary compressive sensing

A compact terahertz（THz） imaging system based on complementary compressive sensing has been proposed using two single-pixel detectors. By using a mechanical spatial light modulator, sampling in the transmission and reflection orientations was achieved simultaneously, which allows imaging with negative mask values. The improvement of THz image quality and anti-noise performance has been verified experimentally compared with the traditional reconstructed image, and is in good agreement with the numerical simulation. The demonstrated imaging system, with the advantages of high imaging quality and strong anti-noise property, opens up possibilities for new applications in the THz region.

Radar Imaging Based on Iterative Algorithms

It has long been realized that the problem of radar imaging is a special case of image reconstruction in which the data are incomplete and noisy. In other fields, iterative reconstruction algorithms have been used successfully to improve the image quality. This paper studies the application of iterative algorithms in radar imaging. A discrete model is first derived, and the iterative algorithms are then adapted to radar imaging. Although such algorithms are usually time consuming, this paper shows that, if the algorithms are appropriately simplified, it is possible to realize them even in real time. The efficiency of iterative algorithms is shown through computer simulations.