• International Journal of Aeronautical and Space Sciences
• /
• v.12 no.1
• /
• pp.57-62
• /
• 2011

The effects of swirl chamber's diameter and length on injector's dynamic characteristics were investigated through an experimental study. A mechanical pulsator was installed in front of the manifold of a swirl injector which produces pressure oscillations in the feed line. Pressure in the manifold, liquid film thickness in the orifice and the pressure in the orifice were measured in order to understand the dynamic characteristic of the simplex swirl injector with varying geometry. A direct pressure measuring method (DPMM) was used to calculate the axial velocity of the propellant in the orifice and the mass flow rate through the orifice. These measured and calculated values were analyzed to observe the amplitude and phase differences between the input value in the manifold and the output values in the orifice. As a result, a phase-amplitude diagram was obtained which exhibits the injector's response to certain pressure fluctuation inputs. The mass flow rate was calculated by the DPMM and measured directly through the actual injection. The effect of mean manifold pressure change was insignificant with the frequency range of manifold pressure oscillation used in this experiment. Mass flow rate was measured with the variation of injector's geometries and amplitude of the mass flow rate was observed with geometry and pulsation frequency variation. It was confirmed that the swirl chamber diameter and length affect an injector's dynamic characteristics. Furthermore, the direction of geometry change for achieving dynamic stability in the injector was suggested.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.10 no.4
• /
• pp.275-279
• /
• 1977

During the experimental rearing period of common carp in a small simple recirculating aquarium combined with frequent exchanges of water and cleanings, some observations were made on the conditions of fish growing which was directly and instantly affected by the cleaning frequency of strainer, changing rate of water, division and frequency of feed supply, prohibition of excess feeding and the amount of dissolved oxygen. The fish don't seem to be stressed by the manipulation for the change of rearing water, cleaning of detritus in the strainer and filter. It appeared that the most hazzardous matters to fish growth were : 1) supplying feed when fish do not show active response to feed supplied, and 2) giving ample amount of feed at one time. When especially the amount of the feed is within the range fish instantly can swallow, the water clarity is maintained even after feeding operation, but if any excess amount is given the fish intake into mouth much more feed than able to instantly swallow and try to swallow it resulting in much dissolving and suspension of feed materials in water, making the water quite cloudy. Consequently all the water as well as filter bed becomes significantly polluted.

• Earthquakes and Structures
• /
• v.14 no.5
• /
• pp.467-476
• /
• 2018

The seismic vulnerability of skewed bridges had been observed in many past earthquakes. Researchers have found that the in-plane rotation of the girders was one of the main reasons for the vulnerability of these types of bridges. To date, not many experimental works have been done on this topic, especially those including pounding between adjacent structures. In this study, shake table tests were performed on a bridge-abutment system consisting of a straight, $30^{\circ}$, and $45^{\circ}$ bridge with and without considering pounding. Skewed bridges with the same fundamental frequency and those having the same girder mass as the straight bridge were studied. Under the loadings considered, skewed bridges with the same frequency as the straight tend to have smaller responses than those with the same mass. The average maximum bending moment developed in the piers of the $30^{\circ}$ bridge with the same mass as that of the straight when pounding was not considered was 1.6 times larger than when the frequencies were the same. It was also found that the NZTA recommendations for the seat lengths of skewed bridges could severely underestimate the relative displacements of these types of bridges in the transverse direction, especially when pounding occurs. In the worst case, the average transverse displacement of the $45^{\circ}$ bridge was about 2.6 times the longitudinal displacement of the straight, which was greatly over the limit suggested by the NZTA of 1.25 times.

• Structural Engineering and Mechanics
• /
• v.72 no.5
• /
• pp.541-555
• /
• 2019

Wind induced dynamic responses on hyperbolic cooling tower (HCT) shells are complicated functions of structure and wind properties, such as the fundamental frequency f_min, damping ratio ζ, wind velocity V, correlationship in meridian direction and so on, but comprehensions on the sensitivities of the dynamic responses to these four factors are still limited and disagree from each other. Following the dynamic calculation in time domain, features of dynamic effects were elaborated, focusing on the background and resonant components σ_B and σ_R, and their contributions to the total rms value σ_T. The σ_R is always less than σ_B when only the maximum σ_T along latitude is concerned and the contribution of σ_R to σ_T varies with responses and locations, but the σ_R couldn't be neglected for structural design. Then, parameters of the above four factors were artificially adjusted respectively and their influences on the gust responses were illustrated. The relationships of σ_R and the former three factors were expressed by fitted equations which shows certain differences from the existing equations. Moreover, a new strategy for wind tunnel tests aiming at surface pressures and the following dynamic calculations, which demands less experiment equipment, was proposed according to the influence from meridian correlationship.

• Asian Pacific Journal of Cancer Prevention
• /
• v.17 no.11
• /
• pp.4939-4944
• /
• 2016

Background: An upward trend has been noted for the incidence of prostate cancer (PCa) in Vietnam, but information is limited on modifiable factors associated with this form of cancer. This case-control study was conducted to ascertain any relationship between habitual tea consumption and PCa risk. Materials and Methods: Two hundred and fifty-three incident patients with histologically confirmed PCa and 419 (340 community-based and 79 hospital-based) controls, matched by age, were recruited in Ho Chi Minh City during 2013-2015. Information on frequency, quantity and duration of tea consumption, together with demographics, habitual diet and lifestyle characteristics, was obtained by direct interviews using a validated questionnaire. Logistic regression analyses were performed to assess associations between tea consumption variables and PCa risk. Results: The control subjects reported higher tea consumption levels in terms of cumulative exposure, frequency and quantity of tea drank than the PCa patients. After accounting for confounding factors, increasing tea consumption was found to be associated with reduced risk of PCa. The adjusted odds ratios (95% confidence intervals) were 0.52 (95% CI 0.35-0.79) and 0.30 (95% CI 0.18-0.48) for participants drinking 100-500 ml/day and > 500 ml/day, respectively, relative to those drinking < 100 ml/day. Significant inverse dose-response relationships were also observed for years of drinking and number of cups consumed daily (P <0.01). Conclusion: Habitual tea consumption is associated with a reduced risk of PCa in Vietnamese men.

• The Korean Journal of Pain
• /
• v.21 no.1
• /
• pp.18-26
• /
• 2008

Background: Because genetic manipulation is commonly accomplished in mice, mouse models for pain have advanced our understanding of the mechanisms of persistent pain. The purpose of this experimental study is to develop a mouse model for understanding incision induced postoperative pain. Methods: A longitudinal incision was made at the hindpaw of male DBA/2 mice. The withdrawal frequency(WF) from applications of von Frey filaments and the response frequency (RF) to blunt mechanical stimulation were examined in an incision group and a control grouP. The withdrawal latency (WL) to radiant heat and a pain score based on weight bearing were also measured. Tests were performed 1 day before incision, and 2 hours, 1-3 days, 5 days and 7 days after incision. Results: The WF for the strongest filament was $35.0{\pm}9.1%$ before incision and this increased to $100.0{\pm}0%$ at 2 hours and to $65.0{\pm}9.1%$ at 7 days after incision. The RF to the blunt stimulus was $4.1{\pm}4.1%$ before incision and $100.0{\pm}0.0%$ at 2 hours and $42.8{\pm}10.8%$ at 7 days after incision. The WL was $6.6{\pm}0.5sec$ before incision and $2.4{\pm}0.3sec$ at 2 hours and $5.9{\pm}0.6sec$ at 7 days after incision. The pain score increased from $1.1{\pm}0.8$ to $7.4{\pm}1.5$ at 2 days after incision. Conclusions: A mouse model of acute postoperative pain was developing by making a surgical incision in the mouse hindpaw. Mechanical hyperalgesia and allodynia lasting for several days demonstrate that this model has similarities to the human post-operative pain state. Future studies will allow us to further investigate the genetic and molecular mechanisms of incisional pain.

• Journal of Korean Ophthalmic Optics Society
• /
• v.5 no.1
• /
• pp.49-53
• /
• 2000

Sodium borate silicate glass of composition $10Na_2O-39B_2O_3-50SiO_2-CoO$ and $20Na_2O-14B_2O_3-65SiO_2-CoO$ were prepared by melting oxide mixtures in alumina crucible at $1210^{\circ}C$ in an electric furance in air for 2h, and then quenching in air. The dielectric behavior of the quenched glasses are the subject of the present work. Properties such as dielectric constant and resistivity as a function frequency and temperature are reported. From the dielectric spectra, the glass phase transition temperature has been found to decrease at a rate $Na_2O$ 20 mol% and the dielectric constants increase with increasing $Na_2O$ content. The frequency dependent resistivity response of glass exhibits a non-Debye type relaxation.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.8
• /
• pp.3925-3932
• /
• 2013

Emotion is closely related to the life of human, so has effect on many parts such as concentration, learning ability, etc. and makes to have different behavior patterns. The purpose of this paper is to extract important features based on physiological signals to recognize negative emotion. In this paper, after acquisition of electrocardiography(ECG), electroencephalography(EEG), skin temperature(SKT) and galvanic skin response(GSR) measurements based on physiological signals, we designed an accurate and fast algorithm using combination of linear discriminant analysis(LDA) and genetic algorithm(GA), then we selected important features. As a result, the accuracy of the algorithm is up to 96.4% and selected features are Mean, root mean square successive difference(RMSSD), NN intervals differing more than 50ms(NN50) of heart rate variability(HRV), ${\sigma}$ and ${\alpha}$ frequency power of EEG from frontal region, ${\alpha}$, ${\beta}$, and ${\gamma}$ frequency power of EEG from central region, and mean and standard deviation of SKT. Therefore, the features play an important role to recognize negative emotion.

• Journal of the Korean Society of Safety
• /
• v.22 no.2 s.80
• /
• pp.59-66
• /
• 2007

As the need of handling heavy materials increases, various cranes are used in industries. However, the effectiveness of crane also entails industrial accidents such as falling, constriction etc. In fact, the number of fatal accidents caused by crane is still high in Korea. To find out the causes of the accidents in terms of human error, we developed a man-machine system model that consists of two axes; human information processing and crane life cycle. In the human information processing dimension, we simplified it as five functions; sensing and perception, decision making and memory, response etc. In the crane life cycle dimension, we divided it into nine phases; design, production, operation etc. For the 152 fatal accident records during 1999-2006 years, we classified them into 45 cells made by two axes. Then we identified the preceding causes of the classified crane accident based on performance shaping factors. As the results of statistical analysis, the overall trend of crane fatal accidents was described. For the cause analysis, wrong decision making in work plan phase shows the highest frequency. Next, the poor information input in crane operation followed in accident frequency. In ergonomics view, the problems of interface design in displays and controls made 11.8% of fatal accidents. Following the analysis, several ergonomic design guidelines to prevent crane accidents were suggested.

• The Korean Journal of Physiology and Pharmacology
• /
• v.4 no.3
• /
• pp.227-234
• /
• 2000

Many reports suggest that neurotensin (NT) in the gastrointestinal tract may play a possible role as a neurotransmitter, a circulating hormone, or a modulator of motor activity. NT exerts various actions in the intestine; it produces contractile and relaxant responses in intestinal smooth muscle. This study was designed to investigate the effect of NT on motility of antral circular muscle strips in guinea-pig stomach. To assess the role of $Ca^{2+}$ influx in underlying mechanism, slow waves were simultaneously recorded with spontaneous contractions using conventional intracellular microelectrode technique. At the concentration of $10^{-7}$ M, where NT showed maximum response, NT enhanced the magnitude $(863{\pm}198%,\;mean\;SEM,\;n=13)$ and the frequency $(154{\pm}10.3%,\;n=11)$ of spontaneous contractions. NT evoked a slight hyperpolarization of membrane potential, tall and steep slow waves with abortive spikes $(278{\pm}50%,\;n=4).$ These effects were not affected by atropine $(2\;{\mu}M),$ guanethidine $(2\;{\mu}M)$ and tetrodotoxin (0.2μM). NT-induced contractile responses were abolished in $Ca^{2+}-free$ solution and reduced greatly to near abolition by $10\;{\mu}M$ of verapamil or 0.2 mM of $CdCl_2.$ Verapamil attenuated the effects of NT on frequency and amplitude of the slow waves. Taken together, these results indicate that NT enhances contractility in guinea-pig gastric antral circular muscle and $Ca^{2+}$ influx through the voltage-operated $Ca^{2+}$ channel appears to play an important role in the NT-induced contractile mechanism.