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Reducing rotor secondary losses in a turbine stage through endwall airfoil profiling
Ren Dai,Liu Chen,Haojie Duan 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.12
The rotor blade of an experiment turbine for low Reynolds number flow conditions is recontoured on the hub endwall to reduce the hub’s secondary flow losses. The baseline rotor blade is radially stacked with airfoils of free vortex twisting. The hub section airfoil of the rotor blade is reprofiled for three considerations. The first is to reduce the inlet metal angle to fit with the vane’s exit flow angle near the hub endwall. The second is to reduce the airfoil’s stagger angle to reduce the pitchwise pressure gradient on the hub endwall. The third is to extend the airfoil’s axial chord to a limited distance before the baseline one to build a leading edge fillet. A steady RANS flow computation is carried out to compare the flow fields inside the baseline and the new contoured rotor passages. Flow comparison reveals that the passage vortex intensity is reduced and that the total pressure loss is reduced by 8.9 % in the hub region. The new contoured rotor shows potential application in reducing rotor secondary losses through the stacking of two-dimensional sectional airfoils.
Research On Optimization In NC Bending Process Of Thin-walled Tube Based on Orthogonal Experiment
Ren Sheng-le,Wang Peng,Dai Ye 보안공학연구지원센터 2015 International Journal of Hybrid Information Techno Vol.8 No.1
In the process of research and development of tube bending forming technology, the way of improving the forming quality and establishing the optimization of forming process parameters has become an important problem that should be solved quickly. This text simulated the process of bend forming with the way of finite element, combined with the effects of geometric and physical parameters on the forming quality of bending pipe, taking the important parameters which are measurements of the pipe wall thickness variation as test indexes, made the virtual orthogonal experiment and gained the laws of the bending angle, relative bending radius, relative wall thickness, thrust, pipe friction coefficient between mode have effects on the forming quality of wall thinning rate and wall thickening. Through the comprehensive analysis and additional test, obtained the optimal parameters values, improved the accuracy of simulation and the optimization results of orthogonal test, improved the quality of tube bending forming.
A Bi-Target Based Mobile Relay Selection Algorithm for MCNs
( Huijun Dai ),( Xiaolin Gui ),( Zhaosheng Dai ),( Dewang Ren ),( Yingjie Gu ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.11
Multi-hop cellular networks (MCNs) reduce the transmit power and improve the system performance. Recently, several research studies have been conducted on MCNs. The mobile relay selection scheme is a rising issue in the design of MCNs that achieves these advantages. The conventional opportunistic relaying (OR) is performed on the single factor for maximum signal-to-interference-plus-noise ratio (SINR). In this paper, a comprehensive OR scheme based on Bi-Target is proposed to improve the system throughput and reduce the relay handover by constraining the amount of required bandwidth and SINR. Moreover, the proposed algorithm captures the variability and the mobility that makes it more suitable for dynamic real scenarios. Numerical and simulation results show the superiority of the proposed algorithm in both enhancing the overall performance and reducing the handover.
The Modeling Methods of Heavy NC Machine Tool Bolt Joint Based on Virtual Media
Ren Sheng-Le,Gao Fei,Dai Ye,Wang Peng,Cheng Tian-Yu 보안공학연구지원센터 2015 International Journal of Smart Home Vol.9 No.9
The Department of Heavy NC machine tool has a great influence on the performance of machine tools. The 30%-50% static stiffness, more than 50% of the dynamic stiffness depends on the combining part, and the influence on damping reached 90%.Machine tool with the Department of static and dynamic performance directly determines the accuracy and reliability of Heavy NC machine tool. Therefore, in conjunction with the Department of research and design of Heavy NC machine tool is very important. In this paper, based on Hertz contact theory, the contact at the micro level, considering the combination form of machine tool, and the machine joints as a virtual media simulation, a combination of virtual media framework, and calculation of characteristic parameters of the virtual material, then use the ANSYS Workbench to solve the combination of the natural frequency of the whole, the first five order modal extraction. Using modal test technology, get the specimens of natural frequency and damping of the true value, natural frequency are compared with theory, prove the formula of virtual media is reliable, can be used in the modeling of heavy machine tool.
Dai-Zheng Huang,Ren-Xi Gong,Shu Gong 대한전기학회 2015 Journal of Electrical Engineering & Technology Vol.10 No.1
It is very important to make accurate forecast of wind power because of its indispensable requirement for power system stable operation. The research is to predict wind power by chaos and BP artificial neural networks (CBPANNs) method based on genetic algorithm, and to evaluate feasibility of the method of predicting wind power. A description of the method is performed. Firstly, a calculation of the largest Lyapunov exponent of the time series of wind power and a judgment of whether wind power has chaotic behavior are made. Secondly, phase space of the time series is reconstructed. Finally, the prediction model is constructed based on the best embedding dimension and best delay time to approximate the uncertain function by which the wind power is forecasted. And then an optimization of the weights and thresholds of the model is conducted by genetic algorithm (GA). And a simulation of the method and an evaluation of its effectiveness are performed. The results show that the proposed method has more accuracy than that of BP artificial neural networks (BP-ANNs).
Dai Zhong,Ren Peng-Gang,Zhang Hua,Gao Xin,Jin Yan-Ling 한국탄소학회 2021 Carbon Letters Vol.31 No.6
Here, a novel nitrogen-doped carbon nano-material (N-CGNM) with hierarchically porous structure was prepared from spent cofee ground for efcient adsorption of organic dyes by a simple one-step carbonization process (the uniform mixture consists of spent cofee ground, urea, and CaCl2 with the ratio of 1:1:1, which was heated to 1000 °C with a rate of 10 °C min−1 and held at 1000 °C for 90 min in N2 atmosphere to carry out carbonization, activation, and N-doping concurrently). The morphology and structure analysis show that the prepared N-CGNM exhibits hierarchical pore structure, high specifc surface area (544 m2 /g), and large numbers of positively charged nitrogen-containing groups. This unique structure and chemical composition endow N-CGNM with an excellent adsorption capacity toward anion Congo red (623.12±21.69 mg/g), which is obviously superior to that (216.47±18.43 mg/g) of untreated spent cofee ground-based carbon nano-materials (CGM). Oppositely, the adsorption capacity of N-CGNM towards cation methylene blue is inferior to that of CGM due to the existence of electrostatic repulsion. These fndings show a great guidance for the development of low-cost but efcient selective adsorbent.
Clinical Significance and Prognostic Value of Pentraxin-3 as Serologic Biomarker for Lung Cancer
Zhang, Dai,Ren, Wei-Hong,Gao, Yun,Wang, Nian-Yue,Wu, Wen-Jun Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.7
Purposes: Lung cancer is prevalent worldwide and improvements in timely and effective diagnosis are need. Pentraxin-3 as a novel serum marker for lung cancer (LC) has not been validated in large cohort studies. The aim of the study was to assess its clinical value in diagnosis and prognosis. Methods: We analyzed serum PTX-3 levels in a total of 1,605 patients with LC, benign lung diseases and healthy controls, as well as 493 non-lung cancer patients including 12 different types of cancers. Preoperative and postoperative data were further assessed in patients undergoing LC resection. The diagnostic performance of PTX-3 for LC and early-stage LC was assessed using receiver operating characteristics (ROC) by comparing with serum carcinoembryonic antigen (CEA), cytokeratin 19 fragments (CYFRA 21-1). Results: Levels of PTX-3 in serum were significantly higher in patients with LC than all controls. ROC curves showed the optimum diagnostic cutoff was 8.03ng/mL (AUC 0.823, [95%CI 0.789-0.856], sensitivity 72.8%, and specificity 77.3% in the test cohort; 0.802, [95%CI 0.762-0.843], sensitivity 69.7%, and specificity 76.4% in the validate cohort). Similar diagnostic performance of PTX-3 was observed for early-stage LC. PTX-3 decreased following surgical resection of LC and increased with tumor recurrence. Significantly elevated PTX-3 levels were also seen in patients with non-lung cancers. Conclusions: The present data revealed that PTX-3 was significantly increased in both tissue and serum samples in LC patients. PTX-3 is a valuable biomarker for LC and improved identification of patients with LC and early-stage LC from those with non-malignant lung diseases.