Axial slit wall effect on the flow instability and heat transfer in rotating concentric cylinders

Dong Liu,Chang-qing Chao,Ying-ze Wang,Fang-neng Zhu,김형범 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.12

The slit wall effect on the flow instability and heat transfer characteristics in Taylor-Couette flow was numerically studied by changing the rotating Reynolds number and applying the negative temperature gradient. The concentric cylinders with slit wall are seen in many rotating machineries. Six different models with the slit number 0, 6, 9, 12, 15 and 18 were investigated in this study. The results show the axial slit wall enhances the Taylor vortex flow and suppresses the azimuthal variation of wavy Taylor vortex flow. When negative temperature gradient exists, the results show that the heat transfer augmentation appears from laminar Taylor vortex to turbulent Taylor flow regime. The heat transfer enhancement become stronger as increasing the Reynolds number and slit number. The larger slit number model also accelerates the flow transition regardless of the negative temperature gradient or isothermal condition.

Numerical simulation of slit wall effect on the Taylor vortex flow with radial temperature gradient

Dong Liu,Chang-qing Chao,Fang-neng Zhu,Xi-qiang Han,Chengtang Liu 한국유체기계학회 2015 International journal of fluid machinery and syste Vol.8 No.4

Numerical simulation was applied to investigate the Taylor vortex flow inside the concentric cylinders with a constant radial temperature gradient. The reliability of numerical simulation method was verified by the experimental results of PIV. The radial velocity and temperature distribution in plain and 12-slit model at different axial locations were compared, and the heat flux distributions along the inner cylinder wall at different work conditions were obtained. In the plain model, the average surface heat flux of inner cylinder increased with the inner cylinder rotation speed. In slit model, the slit wall significantly changed the distribution of flow field and temperature in the annulus gap, and the radial flow was strengthen obviously , which promoted the heat transfer process at the same working condition.

Numerical simulation of slit wall effect on the Taylor vortex flow with radial temperature gradient

Liu, Dong,Chao, Chang-qing,Zhu, Fang-neng,Han, Xi-qiang,Tang, Cheng Korean Society for Fluid machinery 2015 International journal of fluid machinery and syste Vol.8 No.4

Numerical simulation was applied to investigate the Taylor vortex flow inside the concentric cylinders with a constant radial temperature gradient. The reliability of numerical simulation method was verified by the experimental results of PIV. The radial velocity and temperature distribution in plain and 12-slit model at different axial locations were compared, and the heat flux distributions along the inner cylinder wall at different work conditions were obtained. In the plain model, the average surface heat flux of inner cylinder increased with the inner cylinder rotation speed. In slit model, the slit wall significantly changed the distribution of flow field and temperature in the annulus gap, and the radial flow was strengthen obviously, which promoted the heat transfer process at the same working condition.

Arabidopsis thaliana Metallothionein, AtMT2a, Mediates ROS Balance during Oxidative Stress

Wei Zhu,Dong-Xiao Zhao,Qing Miao,Tong-Tong Xue,Xin-Zheng Li,Cheng-Chao Zheng 한국식물학회 2009 Journal of Plant Biology Vol.52 No.6

Cold stress has been shown to induce the production of reactive oxygen species (ROS), which can elicit a potentially damaging oxidative burden on cellular metabolism. Here, the expression of a metallothionein gene (AtMT2a) was upregulated under low temperature and hydrogen peroxide (H2O2) stresses. The Arabidopsis T-DNA insertion mutant, mt2a, exhibited more sensitivity to cold stress compared to WT plants during the seed germination, and H2O2 levels in mt2a mutant were higher than that in WT plants during the cold stress. Synthetic GFP fused to AtMT2a was observed to be localized in cytosol. These results indicated that AtMT2a functions in tolerance against cold stress by mediating the ROS balance in the cytosol. Interestingly, mRNA level of AtMT2a was increased in seedlings of Arabidopsis cat2 mutant after cold treatment compared to WT seedlings, and overexpression of AtMT2a in cat2 could improve CAT activity under chilling stress. Moreover, the enzymatic activity of CAT in mt2a was higher than that in WT plants after cold treatment, suggesting that AtMT2a and CAT might complement each other in antioxidative process potentially in Arabidopsis. Taken together, our results provided a novel insight into the relationship between MTs and antioxidative enzymes in the ROS-scavenging system in plants.

Beneficial effects of natural Jeju groundwaters on lipid metabolism in high-fat diet-induced hyperlipidemic rats

Yan-chao Wang,Jin-miao Lu,Hui-zi Jin,Ai-niu Ma,Jin-yang Zhang,Nian Gong,Qi Xiao,Bin Zhu,Ying-fang Lv,Na Yu,Wei-dong Zhang,Yong-xiang Wang 한국영양학회 2014 Nutrition Research and Practice Vol.8 No.2

BACKGROUND: Groundwater is believed to possess many beneficial effects due to its natural source of various minerals. In this study, we examined the effects of natural Jeju groundwater S1 (SamdasooTM), S2 and S3 pumped up from different locations of Jeju Island, Korea, along with local tap water, on body weight gain, serum lipids and lipoproteins, and liver histopathology in high-fat diet-induced hyperlipidemic rats. MATERIALS/METHODS: Rats were randomly and equally divided into 6 groups. Different water samples were supplied to the hyperlipidemic rats as their daily drinking water and the widely-used anti-hyperlipidemic drug simvastatin was used as a positive control. Body weight, serum lipids and lipoproteins were measured weekly. Liver weight, liver index and liver histopathology were examined after the execution of the rats. RESULTS: After drinking Jeju groundwaters for two months, S2 but not S3 significantly reduced weight growth and serum triglycerides levels and increased high density lipoprotein-C (HDL-C) without affecting total cholesterol or LDL-C. S1 and particularly S2 significantly reduced the severity of liver hypertrophy and steatosis. All Groundwaters had much higher contents of vanadium (S3>S2>S1>>tap water) whereas S1 and S2 but not S3 markedly blocked autoxidation of ferrous ions. CONCLUSION: Jeju Groundwater S1 and particularly S2 exhibit protective effects against hyperlipidemia and fatty liver and hypothesize that the beneficial effect of Jeju Groundwaters may be contributed from blockade of autoxidation of ferrous ions rather than their high contents of vanadium.

Sizing Up Chinese Military Buildup: The Limitations to Defense Modernization

( Jing Dong Yuan ),( Yu Chao Zhu ) 한국국방연구원 1996 The Korean Journal of Defense Analysis Vol.8 No.1

This article documents and analyzes China`s recent defense modernization programs, in particular its arms acquisitions from the United States and Russia since the early 1980s. It examines how China`s changing security perspectives and the concomitant shifts in strategic doctrines have informed and conditioned the country`s defense modernization priorities and programs. On the one hand, the doctrinal shift from an emphasis on "people`s war" to one on "local war under hi-tech conditions" has highlighted the needs to modernize equipment in several key mission areas, which remains deficient. On the other hand, China`s domestic defense industry appears unable to provide the kind of sophisticated weaponry that modern warfare requires. To close this mission-capability gap requires imports of both advanced defense equipment and military technology. Significant weapons acquisitions are antithesis to the long-held principle of self-reliance and may create a politically unacceptable dependence relationship with foreign suppliers; nor is such a quick-fix tactic financially feasible or realistic. Consequently, while selective purchases of equipment in high-priority and "bottleneck" areas remain an important policy option, a long-term strategy has been to enhance the overall technological level of the domestic defense industrial base, with an emphasis on the importation of technology, licensed production, coproduction, and co development of weapons. China`s arms acquisitions from the United States and the Soviet Union or Russia during 1980-95 have shown that major purchases have been limited and selective, and mainly in the areas where the PLA needed immediate equipment improvement, or in the areas where imports could result in military technology transfers. China`s experience with buying US defense equipment, where actual purchases consistently fell far below what was allowed, is a clear indication of Chinese approaches. At the same time, the recent "buying spree" of Russian weaponry notwithstanding, such significant purchases were largely motivated by opportunities (e.g., attractive price and payment arrangements). Even here, Chinese defense planners have sought to obtain Soviet/Russian military technology, license-production rights, and/or coproduction arrangements. And the recent Sino-Russian agreement on completing the long-stalled sale of Su-27s may clear the way for the transfer of Su-27 production technology to Chinese aerospace industries, with significant long-term implications for China`s defense modernization and regional military balance. However, in overall terms, China`s current abilities to obtain advanced defense equipment from abroad will remain limited due both to domestic resource limitations and to Western (and even Russian) export control policies. Clearly, there are limitations to the pace and scope of Chinese military buildup, which recent analyses tend to overestimate. A more balanced analysis needs to take into consideration opportunities as well as constraints that may affect the progress of Chinese defense modernization.

Fibulin-5 is a Prognostic Marker that Contributes to Proliferation and Invasion of Human Glioma Cells

Sheng, Xu-Dong,Chen, Hu,Wang, Hui,Ding, Zhi-Bin,Xu, Gang-Zhu,Zhang, Jun-Feng,Lu, Wen-Chao,Wu, Tao,Zhao, Ling Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.2

Fibulin-5 has recently been considered as a potential tumor suppressor in human cancers. Several studies have shown that it is down-regulated in a variety of tumor types and inhibits tumor growth and metastasis. This study was aimed to investigate the clinical significance of fibulin-5 in glioma and its role in cell proliferation and invasion. We found that the expression of fibulin-5 in glioma tissues was significantly lower than those in normal brain (NB) tissues. Negative expression was significantly correlated with advanced clinical stage (grade III+IV). Furthermore, Fibulin-5 negative expression was correlated with a shorter overall survival of glioma patients. Multivariate Cox repression analysis indicated that fibulin-5 was an independent factor for predicting overall survival of glioma patients. Overexpression obviously inhibited cell proliferation in U251 and U87 cells. Furthermore, it significantly reduced the number of migrating and invading glioma cells. In conclusion, impaired expression of fibulin-5 is correlated with the advanced tumor stage in glioma. Otherwise, Fibulin-5 is an independent prognostic marker for predicting overall survival of glioma patients. Mechanistically, it may function as a tumor suppressor via inhibiting cell proliferation and invasion in gliomas.

Numerical analysis of unstable turbulent flows in a centrifugal pump impeller considering the curvature and rotation effect

Weixiang Ye,Zu-chao Zhu,Zhong-Dong Qian,Xianwu Luo 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.7

In this study, a modified partially averaged Navier–Stokes model (MSST PANS) is proposed by treating a modified shear stress transport (SST) k–ω model as the parent turbulence model. The unstable turbulent flow in a centrifugal pump that considers the curvature and rotation effect is investigated as the test case to evaluate the performance of the MSST PANS model and analyze the flow instability in a centrifugal pump. The SST k–ω and the standard k–ε PANS models are also evaluated for comparison. Results show that the MSST PANS model exhibits excellent performance and delivers the most satisfactory prediction results of the positive slope of the characteristic curve, time-averaged internal flows, and velocity profiles. The energy loss based on the energy balance equations is adopted to provide an explanation of the internal flow evolutions in pumps. The findings also indicate energy loss distribution is associated with the positive slope phenomenon. The high-velocity gradient flows at the entrance of the blade-toblade passage and the reverse flows at the impeller exit are the main reasons for the high turbulent kinetic energy in the impeller. The MSST PANS model demonstrates promising applications in the field of hydraulic machinery, where unstable turbulent flows are prevalent.

A DNA-Based Approach Assigns Species Identity to Extreme Sexual Dimorphism: A Case Study of Fig Wasps (Hymenoptera, Chalcidoidea, Agaonidae)

Da-Wei Huang,Zi-Feng Jiang,Chao-Dong Zhu 한국응용곤충학회 2005 한국응용곤충학회 학술대회논문집 Vol.2005 No.05

Associations Between Infiltrating Lymphocyte Subsets and Hepatocellular Carcinoma

Guo, Cun-Li,Yang, Hai-Chao,Yang, Xiu-Hua,Cheng, Wen,Dong, Tian-Xiu,Zhu, Wen-Jing,Xu, Zheng,Zhao, Liang Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.11

Aims: We aimed to analyze the phenotype of tumor-infiltrating lymphocytes (TILs) and non-tumor infiltrating lymphocytes (NILs) in HCC and non-tumor tissues, and evaluate relationships between changes in these cells and the prognosis of HCC. Methods: Lymphocytes were isolated from HCC and corresponding non-tumor tissues and tested by flow cytometry. For comparison, clinical parameters were analyzed. Results: Compared with the non-tumor tissue, tumor tissue had a lower intensity of NK, NKT andCD8+T cell infiltration. TILs had higher intensity of CD4+CD25+Foxp3+regulatory T cell (Treg cells) infiltration compared with that in NILs. The prevalence of Treg cells was associated with fewer CD8 + T lymphocytes in the HCC immune microenvironment. The frequencies of NK cells and CD8+T cells in TILs of HCC patients with metastasis less than 12 months were lower than those without metastasis. However, the frequency of Treg cells was higher than those without metastasis. Conclusion: These results suggest that the frequencies of CD8+T, NK and NKT cells as well as Treg cells in the tumor tissue of HCC are significantly associated with patient survival, and could be applied as predictive indicators for HCC prognosis.