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RISS 인기검색어
- 검색키워드
- 저자 : Depeng Li (검색결과 4 건)
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Reentry Risk and Safety Assessment of Spacecraft Debris Based on Machine Learning
Hu Gao,Zhihui Li,Depeng Dang,Jingfan Yang,Ning Wang 한국항공우주학회 2024 International Journal of Aeronautical and Space Sc Vol.25 No.1
Uncontrolled spacecraft will disintegrate and generate a large amount of debris in the reentry process. Ablative debris may cause potential risks to the safety of human life and property on the ground. Therefore, predicting the landing points of spacecraft debris and forecasting the degree of risk of waste to human life and property is very important. In view that it is difficult to predict the reentry process and the reentry point in advance, the debris generated from reentry disintegration may cause ground damage for the uncontrolled space vehicle on the expiration of service. In this paper, we adopt the object-oriented approach to consider the spacecraft and its disintegrated components as consisting of simple basic geometric models and introduce three machine learning models: the support vector regression (SVR), decision tree regression (DTR), and multilayer perceptron (MLP) to predict the velocity, longitude, and latitude of spacecraft debris landing points for the first time. Then, we compare the prediction accuracy of the three models. Furthermore, we define the reentry risk and the degree of danger, and we calculate the risk level for each spacecraft debris and make warnings accordingly. The experimental results show that the proposed method can obtain high-accuracy prediction results in at least 10 s and make safety-level warning more real-time.
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Exploiting Multi-Hop Relaying to Overcome Blockage in Directional mmWave Small Cells
Yong Niu,Chuhan Gao,Yongliang Ma,Li Su,Depeng Jin 한국통신학회 2016 Journal of communications and networks Vol.18 No.3
With vast amounts of spectrum available in themillimeter wave (mmWave) band, small cells at mmWave frequenciesdensely deployed underlying the conventional homogeneousmacrocell network have gained considerable interest fromacademia, industry, and standards bodies. Due to high propagationloss at higher frequencies, mmWave communications are inherentlydirectional, and concurrent transmissions (spatial reuse)under low inter-link interference can be enabled to significantlyimprove network capacity. On the other hand, mmWave linksare easily blocked by obstacles such as human body and furniture. In this paper, we develop a multi-hop relaying transmission(MHRT) scheme to steer blocked flows around obstacles by establishingmulti-hop relay paths. In MHRT, a relay path selectionalgorithm is proposed to establish relay paths for blocked flowsfor better use of concurrent transmissions. After relay path selection,we use a multi-hop transmission scheduling algorithm to computenear-optimal schedules by fully exploiting the spatial reuse. Through extensive simulations under various traffic patterns andchannel conditions, we demonstrate MHRT achieves superior performancein terms of network throughput and connection robustnesscompared with other existing protocols, especially under seriousblockage conditions. The performance ofMHRT with differenthop limitations is also simulated and analyzed for a better choiceof the maximum hop number in practice.
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Yuanyuan Zhang,Qiuxiang Zhao,Hui Tang,Huiling Li,Depeng Li,Zhiyong Wang,Xin Gao,Fanye Wang 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.5
Enantiopure esomeprazole is an important drug in the treatment of gastric ulcer. The asymmetric sulfoxidation of omeprazole thioether was catalyzed by immobilized cells of a mutant of Rhodococcus rhodocrous ATCC 4276 to synthesize esomeprazole. The bioreaction was carried out in a biphasic system (chloroform-water), at a high substrate concentration (200mM), and optimized using response surface methodology (RSM). The optimal yield of esomeprazole obtained was 94.8% with e.e. (>99%) without the formation of the sulfone form as a byproduct, under the optimal conditions: the concentration of immobilized cells, 283.5 g/L, the incubation temperature, 37.05 oC, and pH of phosphate buffer, 7.35, respectively. A quadratic polynomial model was developed with R2 of 0.9998, which indicates that the model predicts the observed data with very high accuracy. The mutant exhibited a high enantioselective activity and substrate and product tolerance. The small size of immobilized cell beads (0.5-1 mm) creates a large reaction interface. The aerated flask provides enough oxygen for a high concentration of cells. The significant improvement of substrate tolerance may mainly be attributed to employing the chloroform-water biphasic system because organic substrates may be partitioned in the organic phase, eliminating potential damage and inhibition to cells. Based on the above, the asymmetric sulfoxidation catalyzed by immobilized bacterial cells is therefore more promising for efficient synthesis of chiral sulfoxides.
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Hao Han,Jingming Hou,Zongxue Xu,Haixiao Jing,Jiahui Gong,Depeng Zuo,Bingyao Li,Shaoxiong Yang,Yongde Kang,Run Wang 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.3
Frequent urban rainstorm inundations can cause serious damages to human life and social economy. Reliable simulation of urban rainstorm inundation is an effective approach for performing flood risk analysis to reduce losses. In this work, a full 2D high-performance hydrodynamic model for urban rainstorm inundation simulation based on Graphic Processing Unit (GPU) was developed. The idealized V-shape catchment and sponge city district of Fengxi New City were selected as the study areas to assess performance of the model. The model was validated against analytical benchmark results of the idealized V-catchment test which show good agreement between the modelled flow and analytical solutions. The model was then applied to simulate actual urban rainstorm inundation process under measured rainfall. The results indicated that the model can be applied to high-resolution urban region simulations. Specifically, the validation results indicated that the proposed model had a good performance, with an accepted error of less than 15%. When applied to compute the Fengxi New city under design rainstorms with different annual return periods of 1, 5, 10, 20, 50, and 100 years, it was found that the model effectively evaluated the temporal and spatial variation process of urban inundation, and quantitatively investigated flood risks according to the water depth change. The model has been substantially accelerated on GPU to quickly predict urbaninundation. The accuracy and rapid simulation speed of the model were verified based on the actual study area. Therefore, the proposed model can help to predict the dynamic processes of urban flood inundation and thus reduce flood inundation disasters. This is essential for future optimal sponge urban construction planning in China.
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