• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.10
• /
• pp.24-30
• /
• 2018

As the demand for underground space increases, many researchers have been studying the load reduction method using high compressible materials to solve for the stability problem of the overhead load and for the increase of the earth pressure which decreases the function of the underground structure. This paper determines the optimum soft zone and the effect of the using EPS Geofoam as a load reduction material to arch structures. A finite element analysis program, ABAQUS, is used to analyze the soil-structure interaction and the behavior of buried arch structures considering different four EPS Geofoam forms to confirm the most conservative shape. The optimum cross-sectional shape was determined by comparing the results of earth pressure reduction rate in accordance with the change of span-rise ratio and span length of the arch structure. It was confirmed that the earth pressure generated in the arch structure using the optimal soft zone selected by the numerical analysis was reduced by an average of 78%. In this study, the effect of EPS Geofoam on soil pressure reduction and its applicability to underground arch structures will provide an economical and conservative way to design underground structures and will help to increase the usability of deep underground space.

• The Korean Journal of Pharmacology
• /
• v.2 no.1 s.2
• /
• pp.49-69
• /
• 1966

For the purpose of stydying the pharmacodynamic action of methemoglobin, the author made the following experiments: 1. Preparation of hemoglobin and methemoglobin solutions: Red cell suspension from rabbit blood was hemolysed with distilled water and then divided into two portions. One portion was dialysed through cellophane paper and made isotonic with the proper amount of sodium chloride. The second portion was treated with sodium nitrite to convert hemoglobin to methemoglobin, dialysed through cellophane paper and made isotonic. 2. The concentration of methemoglobin in solution, plasma and urine was determined by Horecker and Brackette's method, and that of hemoglobin by the cyanmethemoglobin method. 3. The concentration of methemoglobin and hemoglobin in the plasma and urine of rabbits was measured at several intervals of time after infusion of the above samples. 4. The blood pressure and respiration of rabbits were recorded on a kymograph, and the effects of the samples on them were observed. 5. The effects of the samples on the movements of the in-situ heart and the isolated intestine of rabbits were studied. 6. The kidneys of rabbits were excised 4 to 5 hours after injection of the samples, and histopathological examinations were made. These experiments revealed the following results: 1. When methemoglobin solution was allowed to stand in room air, there was no decrease in the concentration of methemoglobin. 2. When methemoglobin solution was mixed with whole blood and incubated at $37^{\circ}C$, the concentration of methemoglobin decteased gradually. 3. After the infusion of methemoglobin and hemoglobin solutions, the rate of disappearance of methemoglobin in the plasma was more rapid than that of hemoglobin in the plasma. The higher the initial concentration in the plasma, the larger was the rate of disappearance of methemoglobin. 4. The rate of disappearance of methemoglobin was exceedingly rapid for 30 minutes after the infusion. 5. The urinary excretion of methemoglobin was more rapid than that of hemoglobin. 6. It would seem that the circulating blood contains substances which are promptly mobilized in the plasma to reduce methemoglobin to hemoglobin. 7. Moderate amounts of methemoglobin solution caused some rise in the blood pressure and a transient acceleration of the respiration of the rabbits. These effects of methemoglobin were milder than those of hemoglobin. 8. The movements of the in-situ heart and the isolated intestine of rabbits were accelerated by methemoglobin. These accelerating effects were milder than those of hemoglobin. 9. In the kidneys of rabbits treated with methemoglobin solution, hyperemia of the glomeruli, cloudy swelling and hemoglobin deposit in the tubular epithelium, hemoglobin casts in the tubular lumina of the proximal tubules, and interstitial congestion were constantly observed. There was no definite difference between the histological findings in the rabbit kidneys injected with methemoglobin, and those injected with hemoglobin solutions.

• International Journal of Aeronautical and Space Sciences
• /
• v.16 no.3
• /
• pp.418-424
• /
• 2015

The chemical response of energetic materials is analyzed in terms of 1) the thermal decomposition under the thermal stimulus and 2) the reactive flow upon the mechanical impact, both of which give rise to an exothermic thermal runaway or an explosion. The present study aims at building a set of chemical kinetics that can precisely model both thermal and impact initiation of a heavily aluminized cyclotrimethylene-trinitramine (RDX) which contains 35% of aluminum. For a thermal decomposition model, the differential scanning calorimetry (DSC) measurement is used together with the Friedman isoconversional method for defining the frequency factor and activation energy in the form of Arrhenius rate law that are extracted from the evolution of product mass fraction. As for modelling the impact response, a series of unconfined rate stick data are used to construct the size effect curve which represents the relationship between detonation velocity and inverse radius of the sample. For validation of the modeled results, a cook-off test and a pressure chamber test are used to compare the predicted chemical response of the aluminized RDX that is either thermally or mechanically loaded.

• Transactions of the Korean hydrogen and new energy society
• /
• v.23 no.3
• /
• pp.227-235
• /
• 2012

Finding an alternative fuel and reducing environmental pollution are the main goals for future internal combustion engines. The purpose of this study is to obtain low-emission and high-efficiency by hydrogen enriched LPG fuel in constant volume chamber. An experimental study was carried out to obtain fundamental data for the combustion and emission characteristics of pre-mixed hydrogen and LPG in a constant volume chamber (CVC) with various fractions of hydrogen-LPG blends. To maintain equal heating value of fuel blend, the amount of LPG was decreased as hydrogen was gradually added. Exhaust emissions were measured using a HORIBA exhaust gas analyzer for various fractions of hydrogen-LPG blends. The results showed that the rapid combustion duration was shortened, and the rate of heat release elevated as the hydrogen fraction in the fuel blend was increased. Moreover, the maximum rate of pressure rise also increased. These phenomena were attributed to the burning velocity which increased exponentially with the increased hydrogen fraction in the $H_2$-LPG fuel blend. Exhaust HC and $CO_2$ concentrations decreased, while NOX emission increased with an increase in the hydrogen fraction in the fuel blend. Our results could facilitate the application of hydrogen and LPG as a fuel in the current fossil hydrocarbon-based economy and the strict emission regulations in internal combustion engines.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.22 no.6
• /
• pp.75-82
• /
• 2021

Low-temperature combustion (LTC) strategies, such as HCCI (Homogeneous Charge Compression Ignition), PCCI (Premixed Charge Compression Ignition), and RCCI (Reactivity Controlled Compression Ignition), have been developed to effectively reduce NOx and PM while increasing the thermal efficiency of diesel engines. Through numerical analysis, this study examined the effects of the injection timing and two-stage injection ratio of diesel fuel, a highly reactive fuel, on the performance and exhaust gas of RCCI engines using gasoline as the low reactive fuel and diesel as the highly reactive fuel. In the case of two-stage injection, combustion slows down if the first injection timing is too advanced. The combustion temperature decreases, resulting in lower combustion performance and an increase in HC and CO. The injection timing of approximately -60°ATDC is considered the optimal injection timing considering the combustion performance, exhaust gas, and maximum pressure rise rate. When the second injection timing was changed during the two-stage injection, considering the combustion performance, exhaust gas, and the maximum pressure increase rate, it was judged to be optimal around -30°ATDC. In the case of two-stage injection, the optimal result was obtained when the first injection amount was set to approximately 60%. Finally, a two-stage injection rather than a single injection was considered more effective on the combustion performance and exhaust gas.

• Journal of Nutrition and Health
• /
• v.16 no.3
• /
• pp.209-215
• /
• 1983

In high sodium societies, the incidence in blood pressure with childhood growth is more abrupt than the rate of rise in low sodium populations. Thus, it appears that a lower level of dietary sodium intake is required to correct established hypertension and to prevent its appearance In present work, an investigation was made to estimate the correlation between urinary sodium, potassium and creatinine excretion, weight, height, upper arm circumference, blood pressures and the number of heart rate. Sixty- four children aged 12-16 years (41 boys and 23 girls) were measured. Twenty -four-hour urinary sodium and potassium excretion averaged 132.8 mEq and 42.1 mEq in boys, 126.4 mEq and 41.3 mEq in girls. Twenty- four -hour urinary creatinine excretion averaged 795.7 mg and 744.3mg in boys and girls, respectively. Systolic and diastolic blood pressure were 117.6mmHg and 49.7mmHg in boys, 95.5mmHg and 58.2mmHg in girls. Systolic blood pressure correlated positively weight, height and urinary creatinine but diastolic blood pressure correlated positively with upper arm circumference and negatively with urinary potassium. It was concluded that urinary sodium does not explain the blood pressure.

• Geomechanics and Engineering
• /
• v.21 no.5
• /
• pp.433-445
• /
• 2020

The weakening and softening behavior of soft clay subjected to cyclic loading due to the build-up of excess pore water pressure is well-known. During the design stage of the foundation of highways and coastal high-rise buildings, it is important to study the mechanical behavior of marine soils under cyclic loading as they undergo greater settlement during cyclic loading than under static loading. Therefore, this research evaluates the cyclic stress-strain and shear strength of untreated and treated marine clay under the effects of wind, earthquake, and traffic loadings. A series of laboratory stress-controlled cyclic triaxial tests have been conducted on both untreated and treated marine clay using different effective confining pressures and a frequency of 0.5 and 1.0 Hz. In addition, treated samples were cured for 28 and 90 days and tested under a frequency of 2.0 Hz. The results revealed significant differences in the performance of treated marine clay samples than that of untreated samples under cyclic loading. The treated marine clay samples were able to stand up to 2000 loading cycles before failure, while untreated marine clay samples could not stand few loading cycles. The untreated marine clay displayed a higher permanent axial strain rate under cyclic loading than the treated clay due to the existence of new cementing compounds after the treatment with recycled tiles and low amount (2%) of cement. The effect of the effective confining pressure was found to be significant on untreated marine clay while its effect was not crucial for the treated samples cured for 90 days. Treated samples cured for 90 days performed better under cyclic loading than the ones cured for 28 days and this is due to the higher amount of cementitious compounds formed with time. The highest deformation was found at 0.5 Hz, which cannot be considered as a critical frequency since smaller frequencies were not used. Therefore, it is recommended to consider testing the treated marine clay using smaller frequencies than 0.5 Hz.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.19 no.1
• /
• pp.61-67
• /
• 2015

The cooling of hot exhaust gas is an important issue for the construction of combustor test facility. Water spray is an effective method for exhaust gas cooling due to its large latent heat in process of evaporation. In this study, 1-D analysis has been performed based on continuity, energy conservation, and saturated vapor property to understand water spray cooling of combustion gas. In the exhaust duct of combustor test facility, the injected water decreases combustion gas temperature, and evaporates in the combustion gas. However, some of the injected water is collected in the sump due to condensation. The evaporation of water helps combustion gas cooling, but causes pressure increase inside the exhaust duct due to increase of vapor pressure. These phenomena has been analyzed by 1-D modeling in this study. From 1-D analysis, the adequate mass flow rate of water spray to cool combustion gas and to avoid excessive pressure rise inside the exhaust duct has been decided.

• Journal of the Korean Geotechnical Society
• /
• v.18 no.6
• /
• pp.5-16
• /
• 2002

A hydrogeomechanical numerical model is presented to evaluate rainfall impacts on groundwater flow in slopes and slope stability. This numerical model is developed based on the fully coupled poroelastic governing equations for groundwater flow in deforming variably saturated geologic media and the Galerkin finite element method. A series of numerical experiments using the model developed are then applied to an unsaturated slope under various rainfall rates. The numerical simulation results show that the overall hydromechanical slope stability deteriorates, and the potential failure nay initiate from the slope toe and propagate toward the slope crest as the rainfall rate increases. From the viewpoint of hydrogeology, the pressure head and hence the total hydraulic head increase as the rainfall rate increases. As a result, the groundwater table rises, the unsaturated zone reduces, the seepage face expands from the slope toe toward the slope crest, and the groundwater flow velocity increases along the seepage face. From the viewpoint of geomechanics, the horizontal displacement increases, and the vertical displacement decreases toward the slope toe as the rainfall rate increases. This may result from the buoyancy effect associated with the groundwater table rise as the rainfall rate increases. As a result, the overall deformation intensifies toward the slope toe, and the unstable zone, in which the factor of safety against shear failure is less than 1, becomes thicker near the slope toe and propagates from the slope toe toward the slope crest. The numerical simulation results also suggest that the potential tension failure is likely to occur within the slope between the potential shear failure surface and the ground surface.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.17 no.4
• /
• pp.419-427
• /
• 2011

The characteristics for hydrogen production and the thermochemical properties of high temperature steam electrolysis(HTSE) device have been numerically analyzed in a two-dimension, steady-state with using the COMSOL $Multiphysics^{(R)}$. The main parameters for the calculation are applied voltage, ASR(Area-specific Resistance), temperature and pressure of the inlet gas flow. The results showed that thermal-neutral voltage was 1.2454 V and rather than the cell temperature increases or decreases with increasing applied voltage by thermal-neutral voltage starting this voltage the temperature in high voltage tended to rise and temperature in the low voltage tended to fall. And with, increasing the values of ASR, temperature inside the cell and the hydrogen production rate were decreased.