• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1134-1139
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• 2004

Recently, development of flame control scheme has been hot issues in the combustion engineering. It has been held that flame shape can be controllable by pressure inside combustor. The influence of combustor atmospheric pressure on flame shape was investigated in the present study. The flame shape, flammable limit, flame temperature and nitric oxide emission were measured as functions of combustor atmospheric pressure and equivalence ratio. The reaction region became longer and wider with decreasing combustor atmospheric pressure by direct photography, hence reduction of blow off limit. This tendency was also observed in the mean flame temperature distribution. Nitric oxide emission decreased with decreasing combustor atmospheric pressure. Low NOx combustion is ascribed to wide-spread reaction region in the low atmospheric pressure condition. These results demonstrate that flame shape and nitric oxide emission can be controllable with combustor atmospheric pressure.

• Journal of ILASS-Korea
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• v.7 no.4
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• pp.16-22
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• 2002

The characteristics of free spray with ultra injection pressure was analyzed to clear the limit pressure of diesel engine. To obtain final goal, ultra high pressure injection equipment was developed, spray patterns were visualized under various ultra injection pressures. Spray penetration and spray width, volume and entrained air mass were increased with the increase of injection pressure. Sauter mean diameter and injection durstion wert decreased. But over 3,000bar of ultra injection pressure region the rates of increase show almost similar and finally the reversed tendencies at 4,140bar.

• Journal of the Korean GEO-environmental Society
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• v.15 no.5
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• pp.67-74
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• 2014

In this study, a constant rate of strain test (CRS) and oedometer test was performed in order to study the consolidation characteristics to the liquid limit using a re-shaped clay which was preconsolidated at a constant pressure. Consolidation samples were made of kaolinite which was mixed with bentonite of 6 %, 9 %, 12 % and 15 % of it by weight and the test value of liquid limit of samples were appeared in 77 %, 84 %, 88 % and 91 % respectively. And then consolidation samples which were agitated sufficiently adding distilled water 2 times of liquid limit were preconsolidated in the condition of a constant pressure of 0.2 MPa. The oedometer test which is commonly used recently and the consolidation test of constant rate of strain which were applied in 0.001 %/min, 0.004 %/min, 0.01 %/min rate of strain according to ASTM, D4186-82 were performed and the preconsolidation pressures were compared and analyzed at 0.2 MPa preconsolidated pressure. As a result, in the case of low value of liquid limit, preconsolidation pressure was appeared same as 0.2 MPa preconsolidated pressure at the high speed strain rate, and in the case of high value of liquid limit, preconsolidation pressure was appeared same as 0.2 MPa preconsolidated pressure at the low speed strain rate.

• Geomechanics and Engineering
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• v.13 no.2
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• pp.301-318
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• 2017

Based on the existing research results, a three-dimensional failure mechanism of tunnel face was constructed. The dynamic seismic effect was taken into account on the basis of quasi-static method, and the nonlinear Mohr-Coulomb failure criterion was introduced into the limit analysis by using the tangent technique. The collapse pressure along with the failure scope of tunnel face was obtained through nonlinear limit analysis. Results show that nonlinear coefficient and initial cohesion have a significant impact on the collapse pressure and failure zone. However, horizontal seismic coefficient and vertical seismic proportional coefficient merely affect the collapse pressure and the location of failure surface. And their influences on the volume and height of failure mechanism are not obvious. By virtue of reliability theory, the influences of horizontal and vertical seismic forces on supporting pressure were discussed. Meanwhile, safety factors and supporting pressures with respect to 3 different safety levels are also obtained, which may provide references to seismic design of tunnels.

• Journal of Preventive Medicine and Public Health
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• v.7 no.2
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• pp.395-401
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• 1974

In order to figure out the normal range, lower limit of hypertension and upper limit of hypotension of the blood pressure of Korean, authors had measured blood pressure according to Korotkow's method for 31,897 healthy persons as samples who were occupied different levels of the social class except cases who would seem to be the essential hypertension and had the diseases affecting to secondary hypertension. A following conclusion was induced by actual measurement and statistical reasoning. 1. The normal range and limits of hypo- and hypertension by sex and age groups of Korean were demonstrated in Table 1 and Figure 1. 2. The more aging the higher value of blood pressure in both sexes, especially women rather than men and systolic as to diastolic. 3. Generally, blood pressure values of female were lower than male, after 55 years of age, however, the crossing phenomenon was recognizable. 4. To settle the normal and abnormal ranges of the blood pressure of Korean, it was attempted that $M{\pm}1.282{\sigma}$ as normal range, $M+2{\sigma}$ as lower limit of hypertension and $M-2{\sigma}$ as upper limit of hypotension were calculated, and regression lines were drawn to adjust the biological variables and derive continuity from each age class. (Fig. 2 and 3) 5. The blood pressure levels were becoming elevated as to getting increased of the body weight, particularly diastolic value at 40-49 age group in male and systolic value at 30-39 age group in female.

• Geomechanics and Engineering
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• v.8 no.4
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• pp.523-540
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• 2015

Based on limit equilibrium principles, this study presents a theoretical derivation of a new analytical formulation for estimating magnitude and lateral earth pressure distribution on a retaining wall subjected to seismic loads. The proposed solution accounts for failure wedge inclination, unit weight and friction angle of backfill soil, wall roughness, and horizontal and vertical seismic ground accelerations. The current analysis predicts a nonlinear lateral earth pressure variation along the wall with and without seismic loads. A parametric study is conducted to examine the influence of various parameters on lateral earth pressure distribution. Findings reveal that lateral earth pressure increases with the increase of horizontal ground acceleration while it decreases with the increase of vertical ground acceleration. Compared to classical theory, the position of resultant lateral earth force is located at a higher distance from wall base which in turn has a direct impact on wall stability and economy. A numerical example is presented to illustrate the computations of lateral earth pressure distribution based on the suggested analytical method.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.5
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• pp.50-59
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• 2003

It was known that high pressure injection is an effective method to enhance thermal efficiency and decrease exhaust emissions in diesel engines. If injection pressure becomes ultra high, it is predicted that there may be a suitable injection pressure which the enhancement rate of spray characteristics is moderate. Also, there may be a limit injection pressure which spray characteristics is reversed and get worse. But these are unknown. To investigate a suitable injection pressure and a limit injection pressure, ultra high pressure injection equipment(UHPIE), which can realize the injection pressure of 3,200bar, was developed. UHPIE is a basic apparatus of single shot injection, and ultra high pressure was achieved by second stage rapid compression in short time. From the evaluation of UHPIE, a injection curve like a conventional diesel engine(jerk type) was realized. Also, it was proved that repetition of experiment was excellent. Therefore it was found that there was no problem to perform the study on the ultra high pressure injection with UHPIE. Consequently, the foundation of the study on ultra high pressure injection could be established.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.7 s.250
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• pp.671-681
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• 2006

This study focuses on the development of numerical procedure to analyze the nonlinear combustion instabilities in liquid rocket engine. Nonlinear behaviors of acoustic instabilities are characterized by the existence of limit cycle in linearly unstable engines and nonlinear or triggering instability in linearly stable engines. To discretize convective fluxes with high accuracy and robustness, approximated Riemann solver based on characteristics and Euler-characteristic boundary conditions are employed. The present procedure predicts well the transition processes from initial harmonic pressure disturbance to N-like steep-fronted shock wave in a resonant pipe. Longitudinal pressure oscillations within the SSME(Space Shuttle Main Engine) engine have been analyzed using the pressure-sensitive time lag model to account for unsteady combustion response. It is observed that the pressure oscillations reach a limit cycle which is independent of the characteristics of the initial disturbances and depends only on combustion parameters and operating conditions.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.338-345
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• 2000

In this study, applicability of PMT in domestic area and test procedure were studied. At six test holes of three construction sites in Pusan, PMT using Elastometer-200 type was done. The problems during test were investigated and the test results were analysed. Limit pressure, p$\sub$ι/ could be determined by p- Δv/v method. Using PMT results, marine soil in Pusan could be classified approximately. Net limit pressure value was in the range of 6.4 ∼ 22.5 kg/$\textrm{cm}^2$ in clay, 2.2 ∼ 30.0 kg/$\textrm{cm}^2$ in sand, 13.0 ∼ 58.0 kg/$\textrm{cm}^2$ in weathered soil and 47.0 ∼ 190.0 kg/$\textrm{cm}^2$ in weathered rock. Also, E$\sub$m//p$\sub$ι/ value was in the range of 2.4 ∼ 7.0 in clay, 2.6 ∼ 12.1 in sand, 6.8 ∼ 17.1 in weathered soil and 7.2 ∼ 29.6 in weathered rock.

• Journal of the Korean Society of Safety
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• v.19 no.1
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• pp.6-11
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• 2004

CNG buses were introduced in 2002 to reduce air pollution to the big cities. The durability and safety evaluation were performed for the NGV-2 type cylinders taken from two buses after 30 months of running. No external damage and no internal corrosion was observed on the container surfaces. Defect exceeding the allowable limit was not found in the UT test. Permanent volume expansion was about 1.2% which is much smaller than the required design limit. Cycling test showed no failure after 11,250cycles and burst pressures were still above the maximum design pressure. Both the longitudinal and circumferential failure mode were observed, where both the fracture strengths were far above the design limit. This study showed the present CNG fuel cylinders were safe enough for further usage.