Parameter design method for the heat transfer performance of a fan-driven gearbox under planetary gear opening and oil-return conditions

Feng-xia Lu,Lijuan Yuan,Zhiqiang Zhao,Chun-lei Wang,He-yun Bao 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.9

On the basis of the computational fluid dynamics (CFD) method, this study calculates the surface convective heat transfer coefficients of the sun gear, planetary gear, ring gear, and bearing before and after the opening of the planetary gear of a fan-driven gearbox. A numerical fitting method is used to establish the calculation model of the convective heat transfer coefficients of the sun gear, planetary gear, ring gear, and bearing under the open-hole oilreturn condition. The convective heat transfer coefficients of each element are compared before and after the hole is bored, and the design method for the gearbox parameters with the objective of heat transfer performance is proposed. Result shows that the convective heat transfer coefficients of each element are increased after oil is returned from the hole of the planetary gear, and the change rate of the convective heat transfer coefficient of the raceway in the planetary gear bearing is the highest. When the aperture of the planetary gear is 7 mm and the number of holes is four, the heat transfer performance of the gearbox is the best. The maximum error between the convection heat transfer coefficient fitting formula value and the CFD simulation calculation result is 1.0558 %.

Oil film deposition characteristics and judgment of lubrication effect of splash lubricated gears

Feng-xia Lu,Kun Wei,Meng Wang,Mou Li,He-yun Bao 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.5

To study the oil film deposition characteristics of splash lubricated gears and determine whether their meshing area is completely lubricated, this study proposes the concept of judging the splash lubrication-deposition characteristics-inlet oil film thickness-lubrication effect. The critical oil film thickness that characterizes the full lubrication of the gear meshing area was obtained as 14.5428 μm by using elastohydrodynamic lubrication (EHL) theory. Based on computational fluid dynamics (CFD) method, based on the renormalization group (RNG) k-ɛ two-equation turbulence model, dynamic mesh model and volume of fluid (VOF) model, the numerical calculation of the intermediate gearbox in splash lubrication is carried out. The oil film deposition thickness of the gear tooth that was about to enter the meshing area was calculated to be 95.6207 μm. It was found that the meshing area is fully lubricated under the rated operating conditions.

Nonlinear tribo-dynamic model of helicopter mid-reducer system under light loss of lubrication

Feng-xia Lu,Xuechen Cao,He-yun Bao,Rupeng Zhu 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.11

When the helicopter tail transmission system loses oil due to damage, the system needs to persist for 30 minutes. Therefore, the nonlinear tribo-dynamics model of the helicopter intermediate reducer (HIR) is established, which is coupled with the loss of oil lubrication. To simulate condition of the HIR system under the loss of lubrication (LOL), this study begins by establishing a complete HIR system CFD model, and analyse the lubrication of the gear tooth surface and the oil churning/windage under different lubrication conditions. Then, a coupled model based on the result of the CFD is proposed to calculate the coefficient of friction (COF) under the condition of light loss of lubrication (LLOL). The results show that COF gradually decreases first and then increases rapidly.

Development of the 3.7 GHz LHCD System on HL-2A

B. Lu,M. Huang,H. Zeng,X. Y. Bai,X. H. Mao,Z. H. Lu,J. Liang,Z. H. Kang,M. W. Wang,K. Feng,H. Wang,C. Wang,J. Q. Wang,S. Wei,T. Yao,Y. N. Bu,J. Feng,G. Y. Cheng,S. D. Song,D. H. Xia,J. Rao 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.8

A 2 MW-3.7 GHz lower hybrid current drive (LHCD) system is under development for physicsexperiments on the HL-2A device. The RF Power is generated by four TH2103A klystron amplifiersand propagates in the TE10 mode through WR284 waveguides. The transmission lines with a lengthof 20 m to 30 m are pressurized with 2 bars of nitrogen to decrease the possibility of arcing. Thelauncher, based on the passive-active multi-junction (PAM) concept, has been developed and iscurrently being realized. It was designed for a power spectrum peaked at Nk = 2.75 with goodcoupling properties over a wide range of plasma parameters. The four klystrons are fed by ahigh-voltage power supply (HVPS) based on the pulse step modulation (PSM) concept with a fastswitch-off time of less than ten μs. This system is expected to be in operation within 1 years and willexplore many international thermonuclear experimental reactor (ITER) related LH experiments inthe following years.

Noise Reduction-Oriented Flight Aircraft Type

Xia Feng,Fangli Sun,Min Lu 보안공학연구지원센터 2015 International Journal of Database Theory and Appli Vol.8 No.5

With the rapid development of civil aviation and raising public awareness of environmental issues, it is extremely crucial to reduce airport noise impact in the vicinity of airports. Reduction of noise at source and operation restrictions are two prominent noise abatement approaches, both of which reduce aircraft noise impact by selecting appropriate aircraft types for flights. However, reduction of noise at source requires high cost while operation restrictions would restrict the ability of full operation of the airport. To tackle with the above issue, the paper studies the problem of aircraft type selection for noise reduction, the target of which is to select aircraft type with the lowest noise from a variety of candidate types. To this end, the paper employs weighted equivalent continuous perceived noise level to measure the noise level, and then utilizes Integrated Noise Model (INM) to calculate noise impact area at the interval of noise level. Experimental results on Beijing International Airport noise monitoring dataset show that the proposed algorithm can indeed obtain the aircraft type with minimal aircraft noise impact.

Anti-tumor Effects of Penfluridol through Dysregulation of Cholesterol Homeostasis

Wu, Lu,Liu, Yan-Yang,Li, Zhi-Xi,Zhao, Qian,Wang, Xia,Yu, Yang,Wang, Yu-Yi,Wang, Yi-Qin,Luo, Feng Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.1

Background: Psychiatric patients appear to be at lower risk of cancer. Some antipsychotic drugs might have inhibitory effects on tumor growth, including penfluridol, a strong agent. To test this, we conducted a study to determine whether penfluridol exerts cytotoxic effects on tumor cells and, if so, to explore its anti-tumor mechanisms. Methods: Growth inhibition of mouse cancer cell lines by penfluridol was determined using the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. Cytotoxic activity was determined by clonogenic cell survival and trypan blue assays. Animal tumor models of these cancer cells were established and to evaluate penfluridol for its anti-tumor efficacy in vivo. Unesterified cholesterol in cancer cells was examined by filipin staining. Serum total cholesterol and tumor total cholesterol were detected using the cholesterol oxidase/p-aminophenazone (CHOD-PAP) method. Results: Penfluridol inhibited the proliferation of B16 melanoma (B16/F10), LL/2 lung carcinoma (LL/2), CT26 colon carcinoma (CT26) and 4T1 breast cancer (4T1) cells in vitro. In vivo penfluridol was particularly effective at inhibiting LL/2 lung tumor growth, and obviously prolonged the survival time of mice bearing LL/2 lung tumors implanted subcutaneously. Accumulated unesterified cholesterol was found in all of the cancer cells treated with penfluridol, and this effect was most evident in LL/2, 4T1 and CT26 cells. No significant difference in serum cholesterol levels was found between the normal saline-treated mice and the penfluridol-treated mice. However, a dose-dependent decrease of total cholesterol in tumor tissues was observed in penfluridol-treated mice, which was most evident in B16/F10-, LL/2-, and 4T1-tumor-bearing mice. Conclusion: Our results suggested that penfluridol is not only cytotoxic to cancer cells in vitro but can also inhibit tumor growth in vivo. Dysregulation of cholesterol homeostasis by penfluridol may be involved in its anti-tumor mechanisms.

Intersubband Transitions in Nonpolar GaN-based Resonant Phonon Depopulation Multiple-Quantum Wells for Terahertz Emissions

Ya-Feng Song,Xiong-Xiong Kong,Wei-Bin Tang,Zhong-Qiang Suo,Huan Zhang,Chen-Yang Li,Qian Jia,Cai-Xia Xue,Yan-Wu Lu,Chao-Pu Yang 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.74 No.11

We investigate the polarization effect in intersubband transitions in polar and nonpolar GaN-based multiple-quantum well (MQW) structures for terahertz (THz) emissions by using systematic comparisons and design a nonpolar GaN/Al$_{0.2}$Ga$_{0.8}$N two-well-based MQW structure with an emitting photon of 7.27 THz (30.07 meV). Its lower energy separation (92.7 meV) matches the resonant phonon depopulation condition for better population inversion. It shows a lower threshold current density $J\rm_{th}$ at all temperatures (1.548 kA/cm$^2$ at 90 K) and a higher output power of up to 86.1 mW at 5.8 K and 33.6 mW at 100 K. Our results for the polar GaN MQW are very close to the experimental data in the literature. We find that the $J\rm_{th}$ of the nonpolar GaN MQW increases more slowly than that of the polar GaN MQW as temperature increases, indicating the nonpolar GaN MQW may be a worth-trying direction for improving the operation temperature. These results can provide meaningful references for the design and fabrication of nonpolar GaN-based THz MQW or quantum cascade structures.

Towards Attacks and Defenses of Anonymous Communication Systems

Tianbo Lu,Puxin Yao1,Lingling Zhao,Yang Li,Feng Xie,Yamei Xia 보안공학연구지원센터 2015 International Journal of Security and Its Applicat Vol.9 No.1

Anonymous communication system has been hot topic in the field of information security, and attack techniques against anonymous systems are endless. This paper first classifies and summarizes the study of attacks against anonymous communication system in recent years, then analyzes the trend of the research on different attack technologies; secondly, it provides a comparative analysis of defense capability the mainstream anonymous communication system to the various attacks; Finally, combining the advantages and disadvantages of different systems, the authors propose an improved node selection and router forwarding algorithms for anonymous communication systems, and design an architecture of anonymous communications software based on the algorithm.

Effects of Allogeneic Blood Transfusion in Patients with Stage II Colon Cancer

Meng, Jin,Lu, Xiao-Bo,Tang, Yuan-Xin,Sun, Gong-Ping,Li, Xin,Yan, Yi-Fei,Liang, Gao-Feng,Ma, Si-Ping,Li, Xiao-Xia Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.1

The aim of the present study was to determine whether allogeneic red blood cell transfusions showed a deleterious effect and what might be preoperative risk factors for blood transfusion in patients with TNM stage II colon cancer. Total 470 patients who fulfilled inclusion criteria were selected for a further 10-year follow-up study. We found that there were statistical significance between non-transfused and transfused group in mortality (P=0.018), local recurrence (P=0.000) and distant metastasis (P=0.040). Local recurrence and distant metastasis between 1 to 3 units and more than 3 units group did not show any significant differences. There was no difference in survival rate between non-transfused and 1 to 3 units group (log rank=0.031, P=0.860). The difference between different blood transfusion volume in transfused patients was found (78.77% vs 63.83%, P=0.006). Meanwhile, the significant difference of survival rate was existed between non-transfused group and more than 3 units group (84.83% vs 63.83%, P=0.002 ). Univariate analysis showed the following 3 variables to be associated with an increased risk of allogeneic blood transfusions: preoperative CEA level (P<0.05), location of tumor (P<0.01) and diameter of tumor (P<0.01). Multivariate analysis revealed that location of tumor and diameter of tumor are two independent factors for requirement of perioperative transfusions. Therefore, allogeneic transfusion increase the postoperative tumor mortality, local recurrence and distant metastasis in patients with stage II colon cancer. The postoperative tumor mortality, local recurrence and distant metastasis were not associated with the blood transfusion volume. The blood transfusion volume was associated with the survival rate. Location of tumor and diameter of tumor were the independent preoperative risk factors for blood transfusion.

Characteristics of Refractive Index Profiles at Different Temperatures in LiNbO₃ and KTiOPO₄ Waveguide Formed by 350 keV Light Ions

Ke-Ming Wang,Feng Chen,Hui Hu,Hui-Hao Xia,Xue-Lin Wang,Bo-Rong Shi,Qing-Ming Lu 한국진공학회(ASCT) 2003 Applied Science and Convergence Technology Vol.12 No.S1

Both LiNbO₃ and KTiOPO₄ samples were implanted with 350 keV H^+ and He^+ ions at different doses ranging from 1×10^(16) to of 5×10^(16) ions/㎠. Single and multi-energy implantations were performed at room temperature. Mono-mode or a few modes in both LiNbO₃ and KTiOPO₄ waveguides were observed. The effect of temperature on the refractive index profiles of LiNbO₃ and KTiOPO₄ waveguids was studied. The temperature covered from room temperature, 200℃, 194.5 K (dry ice) and 77K (liquid nitrogen). Different mechanisms are needed to interpret the observed behavior. A n_e increased mono-mode LiNbO₃ waveguide was formed by multi-energy keV He^+ ions.