- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
EXPRESS: Two-Dimensional Temperature Measurement in a High Temperature and Pressure Combustor Using Computed Tomography Tunable Diode Laser Absorption Spectroscopy (CT-TDLAS) with a Wide-Scanning Laser at 1335–1375 nm
摘要： Tunable diode laser absorption spectroscopy (TDLAS) technology is a developing method for temperature and species concentration measurements with the features of non-contact, high precision, high sensitivity, etc. The difficulty of two-dimensional (2D) temperature measurement in actual combustors has not yet been solved because of pressure broadening of absorption spectra, optical accessibility, etc. In this study, the combination of computed tomography (CT) and TDLAS with a wide scanning laser at 1335–1375 nm has been applied to a combustor for 2D temperature measurement in high temperature of 300–2000 K and high pressure of 0.1–2.5 MPa condition. An external cavity type laser diode with wide wavelength range scanning at 1335–1375 nm was used to evaluate the broadened H2O absorption spectra due to the high temperature and high pressure effect. The spectroscopic database in high temperature of 300–2000 K and high pressure of 0.1–5.0 MPa condition has been revised to improve the accuracy for temperature quantitative analysis. CT reconstruction accuracy was also evaluated in different cases, which presented the consistent temperature distribution between CT reconstruction and assumed distributions. The spatial and temporal distributions of temperature in the high temperature and high pressure combustor were measured successfully by CT-TDLAS using the revised spectroscopic database.
关键词： high temperature and high pressure field,TDLAS,computed tomography,2D,Two-dimensional temperature measurement,combustion,CT,tunable diode laser absorption spectroscopy
更新于2025-09-12 10:27:22
-
An investigation into the effect of gradients on the manufacturing fidelity of triply periodic minimal surface structures with graded density fabricated by selective laser melting
摘要： Triply periodic minimal surfaces (TPMSs) have attracted increasing attention for their high manufacturability, biocompatibility, and mechanical properties. In this work, graded Gyroid cellular structures (GCSs) with varying gradient directions were mathematically designed and manufactured via selective laser melting (SLM). The effect of gradients on manufacturing fidelity, i.e. degree of conformity between the manufactured part and engineering design, of these structures was investigated using X-ray computed tomography (CT). The results indicate that relative density and volume fraction of as-built GCSs are higher than those specified in the engineering design due to strut diameters being larger than specification and the presence of bonded powder particles. Manufacturing fidelity is shown to depend on the geometry of the struts in these structures, including inclination angle of struts, relative density, and density gradient direction. Bonded powder particles were particularly present at the upper inner walls of sphere-like pores, where inclination angles are low and as a result there is a lack of support and non-ideal transfer of heat from the melt pool. Decreasing density along the building direction reduces the occurrence of bonded powder particles and increases manufacturing fidelity. The empirical findings in this study provide insight into the effects of part geometry on the quality of its manufacture by SLM. Results are used to establish guidelines for optimal design of cellular structures.
关键词： Graded cellular structure,Gyroid,Selective laser melting,Triply periodic minimal surface,X-ray computed tomography
更新于2025-09-12 10:27:22
-
[IEEE 2019 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - St. Petersburg, Russia (2019.10.17-2019.10.18)] 2019 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - Radiomics: Extracting more Features using Endoscopic Imaging
摘要： Cancer is the leading cause of death in the world and delayed detection being the cause of the most significant factor for its high mortality rate. Computers can help radiologists in analyzing medical images and detection of cancer. Radiomics refers to the computerized extraction of information from medical images and provides the potential for making cancer screening with high rapid and more accurate using machine learning algorithms. Endoscopic imaging and X-ray imaging (Computed tomography) are two common methods used in medical imaging. In this paper, the advantages and limitations of endoscopic and CT scan images discussed. Then the features that can be extracted from endoscopic and CT scans are discussed and finally these two imaging methods are considered and compared to use for computer-aided detection systems.
关键词： feature extraction,Computed tomography (CT) scan,Endoscopic image,Radiomics,texture features
更新于2025-09-12 10:27:22
-
On the occurrence of weld bead porosity during laser vacuum welding of high pressure aluminium die castings
摘要： Due to porosity and incomplete fusion, aluminium high pressure die castings are materials that are known to be difficult to weld. Hereby porosity is mainly caused by hydrogen which is trapped within the weld bead during solidification as a result of insufficient degassing. To enhance degassing and to reduce the influence of surrounding air, laser vacuum welding was applied within the current study. The main goal was to investigate the occurrence of porosity during laser beam welding of aluminium high pressure die castings. To reach this aim, die casting plates were laser welded at varied ambient pressure and investigated by x-ray computed tomography. The analysis of the welds focuses on the size, position, amount and shape of the detected defects depending on the ambient pressure during welding. The results showed a dependency of the occurrence of porosity and the ambient pressure whilst welding.
关键词： Aluminium die castings,Laser vacuum welding,Aluminium,X-ray computed tomography,Laser welding,Porosity
更新于2025-09-12 10:27:22
-
Mitigation of porosity defects in fiber laser welding under low vacuum
摘要： Laser welding trials were conducted under low vacuum to reduce porosity defects. The effect of vacuum on the characteristics of porosity was quantitatively evaluated using 3D micro-CT. To explore the mechanisms of porosity formation at atmospheric pressure and porosity defects mitigation under vacuum, the weld pool and fluid flow behaviors were directly observed by placing a transparent glass plate on one side of the weld pool. The results showed that the vacuum condition was favorable for reducing porosity, especially process porosity. It was also found that the weld pool size and fluid flow were totally different at atmospheric pressure and under vacuum. At atmospheric pressure, bubbles were trapped in the vortex induced by two opposing fluid flows, failed to escape from the weld pool and finally formed pores. Under vacuum, suppression of vapor plume and reduction in the boiling point led to a deeper keyhole and a thinner weld pool, resulting in an upward flow in the rear weld pool. In this case, the bubbles could escape easily from the weld pool with the help of the upward flow.
关键词： 3D micro-computed tomography,Fluid flow,Low vacuum,Laser welding,Porosity,Ambient pressure
更新于2025-09-12 10:27:22
-
Application of fused image in detecting abnormalities of temporomandibular joint
摘要： Objectives: To present a method for image fusion of cone-beam computed tomography (CBCT)/computed tomography (CT) and magnetic resonance imaging (MRI) and to explore whether the image data sets fused in such a way could aid the detection of temporomandibular joint (TMJ) anatomical structures and lesions. Methods: There were five cases included in this study. One case was space occupying lesion giant cell tumor of tendon sheaths (GCTTS), one case was chronic inflammation in the condyle, one case was articular disc calcification of the bilateral TMJs, and the other two cases were temporomandibular joint disorders (anterior disc displacement without reduction). The digital imaging and communications in medicine (DICOM) format data of CT/CBCT and MRI of the cases were collected, and then imported to the Amira visual software where the registration process was conducted. Based on the different scan model, the registration process could be separated into automatic registration of CT/CBCT with quadrature slice MR images and the semi-automatic registration of CT/CBCT with oblique slice MR images by altering the registration parameters. Rigid transform model and the similarity metric of normalization mutual information (NMI) was used for registration in the present study. Results: The relationship between the soft mass and hard tissue was shown clearly in the fused images when compared to sole observation of CBCT/CT or MR images. The fused images could define the tumor outline and the destructive bone clearly in the same image. The fused results helped the observers to ensure uncertain defects which could not be confirmed only by one image data set. Conclusions: The CT/CBCT and MR images could be fused to aid detection of TMJ anatomical structures and related lesions.
关键词： multi-detector computed tomography,magnetic resonance imaging,diagnosis,cone-beam computed tomography,temporomandibular joint
更新于2025-09-11 14:15:04
-
CH <sub/>4</sub> Concentration Distribution in a Semiconductor Process Chamber Measured by the CT-TDLAS
摘要： We measured methane (CH4) concentration distribution in a semiconductor process chamber by using the computed tomography-tunable diode laser spectroscopy (CT-TDLAS). We designed the CT-TDLAS measurement system with a 32-laser-path. The CH4 concentration distribution was measured by the CT-TDLAS based on the 32 absorption spectra which were collected by scanning the laser wavelength around the CH4 absorption peak of 1653.7 nm. We checked linearity of the measurement, validity of the algorithm, and resolution of the computed tomography (CT) reconstructed distribution. In the algorithm check, we measured a simple concentration distribution generated in a ?ve-fold concentric cylinder. Next, we designed a semiconductor process chamber in which the 32-laser-path was installed. After quantitative evaluations of the CT reconstructed distributions by comparing the simulated results of computational ?uid dynamics, we actually measured the CH4 concentration distribution in the chamber when we streamed 10% CH4 from one of four inlet ports and nitrogen from other three ports into the chamber. The measured distributions were obviously different in accordance with the CH4 inlet location, although all the inlet ports were located cyclic-symmetrically. Those results indicated that the ?ow impedances of the four exhaust holes on the susceptor were different depending their locations.
关键词： computed tomography,semiconductor process chamber,CT-TDLAS,methane concentration distribution,tunable diode laser spectroscopy
更新于2025-09-11 14:15:04
-
Utility of PET/CT in diagnosis, staging, assessment of resectability and metabolic response of pancreatic cancer
摘要： Pancreatic cancer is one of the most common gastrointestinal tumors, with its incidence staying at a high level in both the United States and China. However, the overall 5-year survival rate of pancreatic cancer is still extremely low. Surgery remains the only potential chance for long-term survival. Early diagnosis and precise staging are crucial to make proper clinical decision for surgery candidates. Despite advances in diagnostic technology such as computed tomography (CT) and endoscopic ultrasound, diagnosis, staging and monitoring of the metabolic response remain a challenge for this devastating disease. Positron emission tomography/CT (PET/CT), a relatively novel modality, combines metabolic detection with anatomic information. It has been widely used in oncology and achieves good results in breast cancer, lung cancer and lymphoma. Its utilization in pancreatic cancer has also been widely accepted. However, the value of PET/CT in pancreatic disease is still controversial. Will PET/CT change the treatment strategy for potential surgery candidates? What kind of patients benefits most from this exam? In this review, we focus on the utility of PET/CT in diagnosis, staging, and assessment of resectability of pancreatic cancer. In addition, its ability to monitor metabolic response and recurrence after treatment will be emphasis of discussion. We hope to provide answers to the questions above, which clinicians care most about.
关键词： Staging,Pancreatic cancer,Metabolic response,Position emission tomography/computed tomography,Diagnosis
更新于2025-09-10 09:29:36
-
[Ocular Trauma] Anatomy and Examination in Ocular Trauma || Imaging Examination
摘要： Technology advances at a great pace. Particularly in medicine and, one may venture to say, even more so in the field of ophthalmology. Yet, regarding ocular trauma, the physician stands between multiple crossroads when deciding which imaging examination method to choose from. He must find balance between cost-benefit, medicolegal purposes, immediate or intermediate availability, and prioritizing strategy-modifying information, more often than not relying on century-old techniques, mixed with state-of-the-art technologies, and always based on solid clinical evaluation to make the best decision in a reasonably short time. This chapter will attempt to introduce the imaging examination techniques of X-ray, computed tomography scan, magnetic resonance imaging, B-ultrasound, biomicroscopy, optical coherence tomography, and specular microscopy now available for the assessment in ocular trauma, their working mechanisms, scopes, as well as their strong and weak points.
关键词： Computed tomography scan,Ocular trauma,Magnetic resonance imaging,B-ultrasound,Optical coherence tomography,Specular microscopy,Examination,X-ray,Biomicroscopy,UBM
更新于2025-09-10 09:29:36
-
Pattern-Based Interpretation Criteria for 18F-Fludeoxyglucose Positron Emission Tomography/Computed Tomography in the Assessment of Pyogenic Spine Infection
摘要： 18F-?udeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) is the procedure of choice for investigation of pyogenic spine infection (PSI) when other imaging fails to provide a de?nitive diagnosis, and for assessment of treatment response when patients are not responding as expected to antibiotic therapy [1]. Interpretation criteria for 18F-FDG PET/CT in the initial diagnosis of spine infection have previously relied on the intensity of the 18F-FDG activity. Sites with activity greater than in normal marrow are generally considered actively infected. Results from different series are dif?cult to compare because of different imaging techniques and inclusion criteria. PET-only systems (without the bene?t of a localization CT) were used prior to the availability of hybrid PET/CT. Patient populations were heterogeneous and included spine and peripheral osteomyelitis cases, infection with pyogenic organisms and tuberculosis, and non-operated and postoperative patients with and without hardware. Despite these shortcomings, a review of the early literature [2] and more recent series [3e6] have all reported high sensitivity and speci?city in the diagnosis of spine infection. The localization of 18F-FDG is nonspeci?c and occurs with infection but also with non-septic in?ammation, fracture, or neoplasm. The references quoted above have consisted of random cases, or prospective series of cases, of suspected spine infection. The prevalence of 18F-FDG-avid non-septic conditions in these series is likely low, explaining the relatively high speci?cities reported. False-positive 18F-FDG PET/CT using intensity-based criteria may be more common in problem cases done for initial diagnosis because imaging other than 18F-FDG PET/CT failed to provide a de?nitive diagnosis. Non-septic activity is commonly seen if 18F-FDG PET/CT is done for assessment of antibiotic treatment response for PSI.
关键词： Antibiotic treatment response,18F-?udeoxyglucose positron emission tomography/computed tomography,Pyogenic spine infection,Discitis,Vertebral osteomyelitis
更新于2025-09-10 09:29:36