• International Journal of Fluid Machinery and Systems
• /
• v.2 no.4
• /
• pp.303-314
• /
• 2009

The present paper shows the results of numerical and experimental modal analyses of Francis runners, which were executed in air and in still water. In its first part this paper is focused on the numerical prediction of the model parameters by means of FEM and the validation of the FEM method. Influences of different geometries on modal parameters and frequency reduction ratio (FRR), which is the ratio of the natural frequencies in water and the corresponding natural frequencies in air, are investigated for two different runners, one prototype and one model runner. The results of the analyses indicate very good agreement between experiment and simulation. Particularly the frequency reduction ratios derived from simulation are found to agree very well with the values derived from experiment. In order to identify sensitivity of the structural properties several parameters such as material properties, different model scale and different hub geometries are numerically investigated. In its second part, a harmonic response analysis is shown for a Francis runner by applying the time dependent pressure distribution resulting from an unsteady CFD simulation to the mechanical structure. Thus, the data gained by modern CFD simulation are being fully utilized for the structural design based on life time analysis. With this new approach a more precise prediction of turbine loading and its effect on turbine life cycle is possible allowing better turbine designs to be developed.

• Proceedings of the KOSOMBE Conference
• /
• v.1989 no.05
• /
• pp.27-28
• /
• 1989

In conventional line scan angiography, flow signal has been enhanced by the time_of_flight effect while the signal from stationary tissues has been suppressed by the saturation rf pulse followed by spoiling gradients. Due to the inhomogeneous rf field and the tissue dependent T1 relaxation time, however, stationary tissues can not be suppressed completely or uniformly, and the remnant stationary signal deteriorates the resultant angiogram. Here, the complete cancellation of stationary tissues is made possible by the spectral analysis of a series of repetitive line images of the same slice. The Fourier transformation of a set of line images results in the spectrum images, where stationary tissues are collected into the dc component while arteries are included in harmonic components because of the variation of the flow velocity and the resultant flow signal in arteries according to the cardiac cycle. The summation of harmonic components excluding the dc component results in the angiogram of arteries with the complete cancellation of stationary tissues.

• Journal of Engineering Education Research
• /
• v.15 no.6
• /
• pp.80-85
• /
• 2012

This study investigates significant factors regarding college freshman engineering students and analyses each factors influence on student satisfaction in the College of Engineering core curriculum. We carried out a survey targeting 505 students who completed their fundamental education for major course learning in the 2011 academic year while attending one college in Gwangju and ruled out inadequate respondents. A total sample size 437 students were analyzed. The seven independent variables are academic fees, academic term period, academic environment of the classroom, learning material content, time of lecture, student sincerity and student need for the program. The dependent variable is fundamental education satisfaction level. As a result of multiple regression analysis, the following factors were found to be significant in the following order: learning material content, time of lecture, student sincerity, student need for the program, academic fees and academic environment of the classroom. On the other side academic term period was not significant. For improving fundamental education satisfaction, there is a need for prudent consideration regarding learning material development and lecture times. Also further investigation should take place for policies necessary for increasing learner motivation and sincerity, and expand appropriate conditions for learners to become self-aware of the education they need within their major.

• Biomolecules & Therapeutics
• /
• v.22 no.3
• /
• pp.254-259
• /
• 2014

The pentacyclic triterpenoid ursolic acid (UA) and its isomer oleanolic acid (OA) are ubiquitous in food and plant medicine, and thus are easily exposed to the population through natural contact or intentional use. Although they have diverse health benefits, reported cardiovascular protective activity is contentious. In this study, the effect of UA and OA on platelet aggregation was examined on the basis that alteration of platelet activity is a potential process contributing to cardiovascular events. Treatment of UA enhanced platelet aggregation induced by thrombin or ADP, which was concentration-dependent in a range of $5-50{\mu}M$. Quite comparable results were obtained with OA, in which OA-treated platelets also exhibited an exaggerated response to either thrombin or ADP. UA treatment potentiated aggregation of whole blood, while OA failed to increase aggregation by thrombin. UA and OA did not affect plasma coagulation assessed by measuring prothrombin time and activated partial thromboplastin time. These results indicate that both UA and OA are capable of making platelets susceptible to aggregatory stimuli, and platelets rather than clotting factors are the primary target of them in proaggregatory activity. These compounds need to be used with caution, especially in the population with a predisposition to cardiovascular events.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.17 no.1 s.118
• /
• pp.41-47
• /
• 2007

Scattering fields of two dimensional acoustic waves by a circular cylinder are investigated. The present numerical approach for the acoustic scattering problem has difficulties of numerical robustness, long-time stability and suitability of far-field boundary treatments. The time-dependent periodic acoustic source is used to analyze Interference patterns between incident waves and waves reflected by the cylinder. Characteristic boundary algorithms coupled with 4th order Modified-Flux-Approach ENO(essentially non-oscillatory) schemes are employed in generalized coordinates to examine the effect of the wane frequency on the interference patterns. Non-reflecting boundary conditions, which is crustal for accurate computations of aeroacoustic problems, are used not to contaminate scattering fields by reflected waves at the outer boundary. Computed scattering fields show the circumferential acoustic modes generated by interacting between acoustic sources and scattered waves. At a lower frequency, the wave passes almost straight through the cylinder without Interacting with circular cylinder. Simulation results are presented and compared with the analytic solution. Computed RMS-pressure distribution on the cylinder wall is good agreement with exact solution.

• Journal of fish pathology
• /
• v.1 no.2
• /
• pp.123-130
• /
• 1988

General anaesthetics have been usually used for a long time because handling and transportation of live fish constitutes an important aspect in fisheries science. Numerous investigations, however, have shown that the majority of fish anaesthetics cause strong toxic effect to marine fishes. Therefore, less toxic and more effective anaesthetics are essential for marine fishes. Lidocaine belongs to a group of anaesthetics which are used as a local anaesthetic in human medicine. This chemical was tested for 11 commercially important marine fishes. Anaesthetic effects were clearly dose dependent and acute or chronic toxicities were not observed within clinical doses. The recovery time in the tested fish after anaesthetization was 3 to 4 minutes.

• Archives of Pharmacal Research
• /
• v.25 no.5
• /
• pp.669-674
• /
• 2002

Glycosaminoglycans (GAGs) were isolated from the porcine testis, and their immuno-modulating and anticoagulant activity was investigated. From anion exchange chromatography (Dowex Macropolous Resin) used for further isolation of porcine testis GAGs (PT-GAGs), two fractions (PT-GAG-1.5 and PT-GAG-16) eluted by different salt concentration were obtained. In immunomodulating activity test, PT-GAG-1.5, but not PT-GAG-16, significantly enhanced the growth of murine peritoneal macrophages. In addition, treatment with PT-GAG-1.5 induced the production of cytokines, interleukin-1$\beta$ (IL-1$\beta$), interferon-${\gamma}$ (IFN-${\gamma}$) and tumor necrosis factor-$\alpha$ (TNF-$\alpha$), from murine microphages. Unexpectedly, both of PT-GAGs had no effect on the growth of murine splenocytes. The anticoagulant activity of PT-GAG-1.5 and PT-GAG-16 was examined by activated partial thromboplastin time (aPTT) assay and thrombin time (TT) assay. Both of PT-kGAGs significantly increased the clotting times of aPTT and TT in a dose-dependent manner. The anticoagulant activity of PT-GAG-16 was found to be higher than that of PT-GAG-1.5. These results suggest that PT-GAGs possess biological activities such as immunomodulating activity and anticoagulant activity.

• Archives of Pharmacal Research
• /
• v.27 no.5
• /
• pp.554-561
• /
• 2004

Trichostatin A, an antifungal antibiotics, and HC-toxin are potent and specific inhibitors of histone deacetylase activity. Histone deacetylase inhibitors are new class of chemotherapeutic drugs able to induce tumor cell apoptosis and/or cell cycle arrest. In this study, the antiproliferative activities of trichostatin A and HC-toxin were compared between estrogen receptor positive human breast cancer cell MCF-7 and estrogen receptor negative human breast cancer cell MDA-MB-468. Trichostatin A and HC-toxin showed potent antiproliferative activity in both MCF-7 and MDA-MB-468 cells. In MCF-7 cells that contain high level estrogen receptor, trichostatin A and HC-toxin brought about three-times more potent cell growth inhibitory effect than estrogen receptor negative MDA-MB-468 cells. Both trichostatin A and HC-toxin showed cell cycle arrest at G$_2$/M phases of MCF-7 and MDA-MB-468 cells in a dose- and time- depen- dent manner. Trichostatin A and HC-toxin also induced apoptosis from MCF-7 and MDA-MB-468 cells in a dose- and time-dependent manner. Results of this study suggested that antipro-liferative effects of trichostatin A and HC-toxin might be involved in estrogen receptor signaling pathway, but cell cycle arrest and apoptosis of trichostatin A and HC-toxin might not be involved in estrogen receptor system of human breast cancer cells.

• Archives of Pharmacal Research
• /
• v.28 no.11
• /
• pp.1257-1262
• /
• 2005

MMP-9 is a metalloproteinase capable of basement membrane degradation in vivo. Expression of MMP-9 can be found in normal conditions such as trophoblasts, osteoclasts, and leukocytes and their precursors. They also occur as well as in pathological conditions, such as the invasive growth of primary tumors, metastasis, angiogenesis, rheumatoid arthritis, and periodontal diseases. MMP-9 upregulation can be highly induced by a wide range of agents. These agents include growth factors, cytokines, cell-cell, and cell-ECM adhesion molecules, and agents altering cell shape. Here, we observed that TNF-$\alpha$ stimulated human monocytic cell line, HL-60 produced MMP-9 in a dose and time dependent manner. Real time PCR results indicated transcriptional upregulation of MMP-9 as early as 3 h post TNF-$\alpha$ stimulation. To investigate the signaling pathway underlined in TNF-$\alpha$ induced MMP-9 expression, three MAP kinase inhibitors were added to cells 1 h prior to TNF-$\alpha$ treatment. The ERK inhibitor completely abolished MMP-9 expression by TNF-$\alpha$. But neither p38 MAP kinase nor JNK inhibitor had an effect on TNF-$\alpha$ induced MMP-9 expression, suggesting that ERK activation is required for the MMP-9 induction by TNF-$\alpha$. Taken together, we found that TNF-$\alpha$ stimulation facilitates ERK activation, which results in the transcriptional upregulation of MMP-9 gene and subsequent MMP-9 production and secretion.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.5 no.4
• /
• pp.50-56
• /
• 2001

The present study is an experimental work of the soni $c^ersonic air ejector-diffuser system. The pressure-time dependence in the secondary chamber of this ejector system is measured to investigate the steady operation of the ejector system. Six different primary nozzles of two sonic nozzles, two supersonic nozzles, petal nozzle, and lobed nozzle are employed to drive the ejector system at the conditions of different operating pressure ratios. Static pressures on the ejector-diffuser walls are to analyze the complicated flows occurring inside the system. The volume of the secondary chamber is changed to investigate the effect on the steady operation. the results obtained show that the volume of the secondary chamber does not affect the steady operation of the ejector-diffuser system but the time-dependent pressure in the secondary chamber is a strong function of the volume of the secondary chamber.er.