• Transactions of the Korean Society of Automotive Engineers
• /
• v.6 no.5
• /
• pp.153-161
• /
• 1998

The knock in a spark ignition engine has been investigated to avoid the damage to the engine and unpleasant feeling caused by the pressure waves propagating across the combustion chamber. Knock intensity and knock onset angle were used as physical parameters to quantify the knock characteristics. The knock intensity is defined as a peak to peak value of the bank pass filtered combustion pressure signal and the knock onset angle is determined as the crank angle at which this signal exceeded the threshold level on each cycle. The cyclic variation of knock in four valve single cylinder engine was investigated with these two parameters. The location of autoignition was also examined by ion probes in the cylinder head gasket and squish region in the combustion chamber. For this measurement, a single cylinder engine was modified to accept the pressure transducer, 18 ion probes in the squish region and 8 ion probes in the specially designed PCB (Printed \ulcornerCircuit Board) cylinder head gasket.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.6 no.3
• /
• pp.1-10
• /
• 1998

In this paper, we investigated the improvement of characteristics of knock, emission and fuel consumption rate by optimizing the location and size of water transfer holes in cylinder head gasket without change of engine water jacket design itself. The cooling system was modified in the direction of reducing the metal temperature in the head and increasing the metal temperature in the block. The optimization of water transfer holes in cylinder head gasket was obtained by "flow visualization test". The water transfer holes were concentrated in front side of the engine in order to reduce thermal boundary layer in the water jacket of No. 2 and No. 3 combustion changer in the cylinder head, which would have a large knock intensity, and increase thermal boundary layer in the water jacket of the cylinder block. When the modified coolant flow pattern was applied as proposed in this paper, the knock characteristic was improved. The spark timing was advanced up to 2$^{\circ}$ in low and middle speed range at a full load. In addition, HC emission at MBT was reduced by 5.2%, and the fuel consumption rate was decreased up to 1% in the driving condition of 2400 rpm and 250 KPa. However, since this coolant flow pattern mentioned in this paper might deteriorate the performance of vehicle cooling system due to the coolant flow rate reduction, a properly optimized point should be obtained. obtained.

• Journal of Korean Biological Nursing Science
• /
• v.22 no.1
• /
• pp.45-52
• /
• 2020

Purpose: The purpose of this study was to investigate the risk factors of intracranial hemorrhage in children with skull fractures from head trauma. Methods: The retrospective study included 205 patients diagnosed with a skull fracture in a pediatric emergency room. Data were analyzed using 𝓍²-test, Fisher's exact test, t-test, and logistic regression analysis with the SPSS/WIN24.0 program. Results: Intracranial hemorrhage was diagnosed in 71 patients. There were statistically significant differences between the hemorrhagic group and non-hemorrhagic group in age group, places of accident, type of accident, location of the fracture, and symptoms. Intracranial hemorrhage by age group was higher in school-age and adolescence than in infancy. The places of accidents of hemorrhage were higher in street and school than in the home. The types of an accident of bleeding were higher in the case of knock and traffic accident than in fall. Symptoms of nausea, headache, and loss of consciousness were associated with higher intracranial hemorrhage. Multivariable logistic regression analysis showed that knock (OR= 3.29, 95% CI= 1.50-7.22), traffic accident (OR= 4.78, 95% CI= 1.31-17.43), nausea (OR= 4.18, 95% CI= 1.42-12.31), and loss of consciousness (OR= 3.29, 95% CI= 1.41-9.50) were risk factors for intracranial hemorrhage. Conclusion: In this study, the risk factors of intracranial hemorrhage were identified in pediatric patients with skull fractures caused by head trauma. It is recommended that the results of this study be used to manage and educate patients, caregivers, and medical staff after head trauma hemorrhage.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.7 no.4
• /
• pp.17-23
• /
• 2008

Development of die technology for holder and barrel dies is necessary according to minimization of lens assembly, image sensor, and connectors. In these cases, there are two technical problems arising from die design. One is determination of knock-out pin location in die set. Minimization of lens assembly size make it difficult to obtain ejecting space. The other is whether or not high-precision die technology is possible to reduce torque variation when holer and barrel products is assembled. In this study, multi-cavity die set was developed taking advantage of gear-driven ejecting method. In the developed technology, die manufacturing technology was guaranteed with a high-precision level.

• Journal of Astronomy and Space Sciences
• /
• v.19 no.2
• /
• pp.151-162
• /
• 2002

Two approximate calculation models for a cosmic radiation shielding in satellite are compared with detailed 3-dimensional calculation results. One is a sectoring method and the other is a chord-length distribution method. Shielding caltulation is performed for KITSAT-1 under the assumed environment at SAA (South Atlantic Anomaly) location with AP-8 radiation spectrum model. When both approximate models are applied, calculation error is expected compared with 3-D detailed geometry calculation because of straight knock-on assumption neglecting the deflection of incident proton. However, both approximate models showed good agreements with 3-dimensional detailed Monte Carlo calculation in two dose detector locations.

• Journal of Mechanical Science and Technology
• /
• v.15 no.10
• /
• pp.1442-1450
• /
• 2001

The EGR system has been widely used to reduce nitrogen oxides (NO$\_$x/) emission, to improve fuel economy and suppress knock by using the characteristics of charge dilution. However, as the EGR rate at a given engine operating condition increases, the combustion instability increases. The combustion instability increases cyclic variations resulting in the deterioration of engine performance and emissions. Therefore, the optimum EGR rate should be carefully determined in order to obtain the better engine performance and emissions. An experimental study has been performed to investigate the effects of EGR on combustion stability, engine performance,70x and the other exhaust emissions from 1.5 liter gasoline engine. Operating conditions are selected from the test result of the high speed and high acceleration region of SFTP mode which generates more NO$\_$x/ and needs higher engine speed compared to FTP-75 (Federal Test Procedure) mode. Engine power, fuel consumption and exhaust emissions are measured with various EGR rate. Combustion stability is analyzed by examining the variation of indicated mean effective pressure (COV$\_$imep/) and the timings of maximum pressure (P$\_$max/) location using pressure sensor. Engine performance is analyzed by investigating engine power and maximum cylinder pressure and brake specific fuel consumption (BSFC)