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Abstract: Background: Our hospital has been using Varian VitalBeam linear accelerator since December 2020. Daily quality control of accelerator beam stability in precision radiotherapy is very important. In this paper, we compare and analyze the beam stability of the accelerator with two monitoring methods. Objective: The long-term stability analyze and study of VitalBeam linear accelerator by using machine Machine Performance Check (MPC) and Morning Check. Methods: The energies of 6MV and 10MV x-ray most commonly used by Varian Linear accelerator (VitalBeam) for patient treatment were analyzed and compared，Firstly, the absolute dose of 6MV and 10MV X-ray energies of VitalBeam was calibrated. Collected and analyzed the morning checking data of VitalBeam from November 2021 to May 2022, including the CAX, SYM and FLAT offset data; the MPC daily data was collected and analyzed at the same time, which include beam output change, uniformity change and beam center shift data. The beam output changes were statistically analyzed, and the stability of other data was analyzed. Results: The Morning Check and MPC can accurately detect the change of accelerator beam performance, and the measured values are stable and within the tolerance range，The comparison of 6MV and 10MV beam outputs between the morning detector and MPC was statistically significant (P<0.05). Conclusion: Both MPC and Morning Check can detecte the requirements of accelerator quality assurement, the beam output monitoring morning detector has advantages, but MPC has faster execution efficiency than morning detector instrument, and is more suitable for units with a large number of patients treated daily.Abstract: Background: Our hospital has been using Varian VitalBeam linear accelerator since December 2020. Daily quality control of accelerator beam stability in precision radiotherapy is very important. In this paper, we compare and analyze the beam stability of the accelerator with two monitoring methods. Objective: The long-term stability analyze and stud...Learn More
Abstract: The temperature effect has a great impact on the reasonable completion state of the steel box girder. The relevant research has an important role in promoting the design, construction and operation and maintenance of the steel box girder. Firstly, the effects of uniform temperature difference and gradient temperature difference are analyzed, and three gradient temperature difference modes are compared; Based on the construction monitoring project of a continuous steel box girder, the longitudinal bridge displacement of the support under different uniform temperature difference conditions is calculated. The results show that the overall displacement and relative displacement are considered in the pre deflection of the support; The beam end angle under three different gradient temperature difference modes is compared, and the calculation formula of the top and bottom plate cutting caused by the beam end angle is proposed. This paper systematically studies the influence of uniform temperature difference and gradient temperature difference on the positioning of steel box girder support and the closure of weld seam, and puts forward countermeasures, which will provide some theory and engineering experience for similar projects in the future.Abstract: The temperature effect has a great impact on the reasonable completion state of the steel box girder. The relevant research has an important role in promoting the design, construction and operation and maintenance of the steel box girder. Firstly, the effects of uniform temperature difference and gradient temperature difference are analyzed, and th...Learn More
Abstract: The deep neural network has been applied well in many fields at present, but the security problem of the deep model has become increasingly prominent. Recent research shows that the neural network model will output the wrong classification by confronting samples. Therefore, confrontation samples are a major obstacle that must be overcome for the further development of deep neural networks. At present, the main task is to design an efficient and powerful defense model with strong robustness that can defend against multiple attack algorithms. This paper proposes a defense model based on multi-scale feature fusion circular confrontation generation network by combining the generation of generic adversarial networks (GAN) with existing attack algorithms. First, use the confrontation samples generated by the attack algorithm as the training samples of GAN, and use the unique network structure of CycleGan to make the reconstructed image closer to the clean image and remove potential disturbances. On the generator side, this paper uses multi feature fusion TernausNet structure to ensure that the feature information of the image can be restored as much as possible during the process of disturbance removal, and adds attention mechanism to the discriminator side to increase the receptive field, establish global dependency, and train a more robust discriminator to help GAN training through experiments on CIFAR-10 and ImageNet datasets. It is proved that after the training, the model can directly classify the original samples and confrontation samples correctly, and achieve good defense effect for all kinds of confrontation attack algorithms. Compared with the existing methods, the defense effect is good, and the robustness of the depth model is enhanced.Abstract: The deep neural network has been applied well in many fields at present, but the security problem of the deep model has become increasingly prominent. Recent research shows that the neural network model will output the wrong classification by confronting samples. Therefore, confrontation samples are a major obstacle that must be overcome for the fu...Learn More
Abstract: In order to further improve the comprehensive experimental skills of undergraduates and penetrate the concept of green chemistry education, a comprehensive experiment was designed to prepare polymer crosslinked gel plugging agent with polymer as the main agent and loofah pulp as the toughening material, and evaluate its effectiveness in simulating downhole leakage layer. This experiment applies organic/inorganic compound chemistry knowledge to the field of oilfield chemistry, and combines experimental skills with field work (TaHe Oilfield) to improve students' professional skills and oilfield field adaptability. TaHe Oilfield is the main position for the construction of tens of millions of tons of Northwest Oil Field. During the "Fourteenth Five-Year Plan" period, the large caves were basically under full control. How to develop small and medium-sized fractures and improve the use of reserves and realize the stable production of Tahe Oilfield is facing greater challenges. When adopting the "one well multiple control" method to develop small and medium-sized fractures and cavities, the key technical problem is the low success rate of plugging in carbonate fracture-cavity reservoirs, which requires plugging operations. Through this experiment, students can understand the mechanism of plugging agent in the leakage channel, and master the preparation and performance evaluation methods of gel plugging agent. Let students understand the site construction technology.Abstract: In order to further improve the comprehensive experimental skills of undergraduates and penetrate the concept of green chemistry education, a comprehensive experiment was designed to prepare polymer crosslinked gel plugging agent with polymer as the main agent and loofah pulp as the toughening material, and evaluate its effectiveness in simulating ...Learn More
