• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.3
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• pp.48-57
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• 2003

A cylindrical constant volume combustion chamber was used to investigate the flow characteristics at spark plug and the combustion characteristics of homogeneous charge methane-air mixture under various initial pressure, excess air ratio and ignition times in quiescent mixture. The flow characteristics such as mean velocity and turbulence intensity was analyzed by hot wire anemometer. Combustion pressure development measured by piezoelectric pressure transducer and flame propagation acquired by ICCD camera were used to investigate the effect of initial pressure, excess air ratio and ignition times on pressure, combustion duration, flame speed and burning velocity. Mean velocity and turbulence intensity had the maximum value at 200 or 300ms and then decreased to near 0 value gradually after 3 seconds. Combustion duration, flame speed and burning velocity were observed to be promoted with excess air ratio of 1.1, lower initial pressure and ignition time of 300ms.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.3
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• pp.569-577
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• 1992

The effect of combustion promotion in a constant volume combustion chamber with sub- chamber located in the vicinity of spark plug, was analyzed for variables such as sub- chamber volume and diameter of orifice, and was also compared and evaluated with that of the chamber with sub-chamber which spark plug was located in the sub-chamber. Consequently, it was shown that decrease of duration of combustion in the latter case was larger than in the former case, but comparing by rate of overall combustion promotion that duration of combustion and pressure were both considered, the optimum configuration factor and the effect of combustion promotion were almost same in both cases.

• Journal of Nutrition and Health
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• v.28 no.4
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• pp.331-344
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• 1995

The process of breast feeding was investigated from the 36th week of pregnancy to 12 weeks postnatal, in order to analyze the factors affecting breast feeding duration and provide the basic data on an education program for successful breast feeding. The general characteristics of study group had no marked effects on the breastfeeding duration. The young and highly condition during pregnancy and the degree of morning sickness affected the practice of breastfeeding. In the study of prenatal sociobehavioral factors, intended duration affected the breastfeeding duration, and the maternal perception that breastfeeding is good for weight loss after delivery as well as infant formula milk is not as good as breast milk, led to successful breast feeding. Among the postnatal biological factors, the duration of gestation affected the breast feeding. Among the postnatal biological factors, the duration of gestation affected the breastiffeding outcome. In the case of early parturition, breastfeeding rate was low. Among the postnatal biocultural factors, time of first feed, milk volume and maternal perception of infant's sucking ability affected the bresatfeeding duration. From these result, it is suggested that an education program such as participation of nursing class to the pregnant women should be provided for successful breastfeeding.

• Imaging Science in Dentistry
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• v.53 no.4
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• pp.313-323
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• 2023

Purpose: This study aimed to investigate the potential factors that could affect the reduction rate of odontogenic cysts following decompression using cone-beam computed tomography (CBCT) for 3-dimensional volumetric analysis. Materials and Methods: The study sample consisted of CBCT images of 41 individuals who underwent decompression of odontogenic cysts at the Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, Chulalongkorn University, between 2010 and 2022. Preoperative and postoperative CBCT results were collected, and a volumetric analysis was conducted to evaluate the differences in the reduction rate and the percentage of volume reduction of cystic lesions based on different parameters. Correlations between these parameters were analyzed to determine associations. Results: In this study, the average time of decompression for odontogenic cysts was 316 days. Males demonstrated a higher reduction rate than females (P<0.05). The reduction rate was directly proportional to initial cyst volume, with higher reduction rates for cysts with large initial volume than those with small initial volume (P<0.05). Spearman's rank correlation coefficient indicated a weak positive correlation between the initial cyst volume and the duration of decompression. Additionally, a strong positive correlation was observed between the initial volume and the reduction rate. Conclusion: Knowledge of the reduction rate of odontogenic cysts is vital for surgeons to evaluate the duration of decompression before enucleation and to determine a definitive treatment plan. Sex and initial lesion volume had significant effects on the reduction rate.

• Journal of ILASS-Korea
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• v.1 no.3
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• pp.29-36
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• 1996

The present study systematically investigates the effect of evaporation rate on the combustion characteristics and the flame stabilization in a gasoline engine. A constant volume combustion chamber was used to elucidate a basic combustion characteristics and the premixer was installed to control temperature and equivalence ratio. And the maximum pressure, combustion duration and flame propagation according to the evaporation rate were measured to determine the optimal temperature range for evaparating a gasoline fuel. These experimental results indicate that the combustion characteristics such as combustion chamber pressure and combustion duration were deteriorated by decreasing surrounding temperature of fuel injected. It was also found that the overall gasification process for gasoline fuel was strongly influenced by a combustion chamber temperature rather than a premixer temperature.

• Journal of Pharmaceutical Investigation
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• v.9 no.1
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• pp.7-14
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• 1979

The relative efficacy on the renal function of rabbits by oral administration of furosemide and 1 : 2 furosemide-PVP coprecipitate was compared by measuring the urine volume in response to maximal response and the amounts of electrolytes excreted in urine. The furosemide produced a rapid onset, short duration of diuresis, in contrast, the 1: 2 furosemide-PVP coprecipitate, a rapid onset, significantly larger magnitude, and longer duration of diuresis and therefore the bioavailability of furosemide from the coprecipitate were increased significantly. The average urine volume and the amount of sodium and potassium excreted in urine were increased about 2.9-, 14.8-, and 1.8-fold from furosemide, and about 6.2-, 24.2-, and 3.6-fold from 1 : 2 furosemide- PVP 40,000 coprecipitate, rerpectively, comparing by their control values.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.9
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• pp.2308-2315
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• 1995

We studied the effects on the ignitability of mixture, the combustion duration, and the maximum combustion pressure, of various initial combustion factors such as temperature, pressure, and each equivalence ratio in order to identify the combustion characteristics of lean mixture and improve ignitability through the proper control of the ignition energy. It is concluded that there is an optimum turbulent intensity that enables the combustion to have the best ignitability and the shortest duration under each equivalent ratio, and the combustion duration is only dependent upon the distribution and magnitude of discharge energy within the limit of inflammability.

• Journal of Mechanical Science and Technology
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• v.16 no.7
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• pp.935-941
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• 2002

This work is to investigate the combustion characteristics and flame propagation of the LPG (liquified petroleum gas) and gasoline fuel. In order to characterize the combustion processes of the fuels, the flame propagation and combustion characteristics were investigated by using a constant volume combustion chamber The flame propagation of both LPG and gasoline fuels was investigated by the laser deflection method and the high-speed Schlieren photography. The result of laser deflection method show that the error of measured flame propagation speed by laser method is less than 5% compared with the result of high-speed camera. The flame propagation speed of the fuel is increased with the decrease of initial pressure and the increase of initial temperature in the constant volume chamber. The results also show that the equivalence ratio has a grate effect on the flame speed, combustion pressure and the combustion duration of the fuel-air mixture.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.2
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• pp.389-396
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• 1994

It is very important to clarify the ignition and flame propagation processes of methanol fuel in the Spark-ignition engine. High speed Schlieren photography and pressure trace analyses were used to study on combustion characteristics of methanol fuel in a constant volume chamber. Methanol-air mixtures equivalence rations from lean limit to 1.4 were ignited at initial pressure (0.1, 0.3, 0.5 MPa), temperature (313 343, 373 K) and ignition energy (40, 180 mJ). As the result of this study, we verified the characteristics such as ignition delay, effective thermal efficiency, flame propagation velocity, lean limit, ignitability and combustion duration. Obatained results are as follows. (1) The time to 10% reach of maximum pressure was 40-50% of the total combustion duration for this experimental condition hardly affected by equivalence ratio. (2) The Effective thermal efficiency, as calculated from maximum pressure was the highest when the mixture was slightly lean $({\phi} 0.8-0.9)$ and maximum pressure was the highest when the mixiture was slightly rich $({\phi} 1.2-1.2).$

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.2
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• pp.96-103
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• 2003

In this paper, the heat loss to the constant volume vessel wall was investigated using instantaneous heat flux sensor, schlieren visualization, pressure rise curve. And the heat loss characteristics of plasma jet ignition were compared with conventional spark ignition. In case of plasma jet ignition, the flame kernel moves toward the center of combustion vessel in the initial period of combustion, and the flame surface spread out to the vessel wall. However, in case of conventional spark ignition, the flame surface contact with combustion vessel wall in the initial period of combustion. As a result, heat loss in the combustion duration for conventional spark ignition increase faster than that of plasma jet ignition. And the combustion enhancement rate of plasma jet ignition is higher than that of conventional spark ignition, and it was found that the heat loss rate is inversely proportional to the combustion enhancement rate.