• The Mathematical Education
• /
• v.57 no.3
• /
• pp.197-213
• /
• 2018

Descriptive problems can be used to grow student's ability of thinking logically and creatively, because it shows if the students had a reasonable way of thinking. Rate of descriptive problems is increasing in middle and high school exams. However, students in middle and high schools are generally used to answering multiple-choice or short-answer questions rather than describing the solving process. The purpose of this paper is to gain a theoretic ground to increase the rate of descriptive problems. In this study, students were to solve some multiple-choice problems, and after a few weeks, to solve the problems of same contents in the form of descriptive problems which requires the students to write the solving process. The difference of the scores were measured for each problems to each students, and students were asked what they think the reason for rise or fall of the score is. The result is as follows: First, average scores of 7 of 8 problems used in this study had fallen when it was in descriptive form, and for 5 of them in the rate of 11.2%~16.8%. Second, the main reason of falling is that the students have actual troubles of describing the solving process. Third, in the case of rising, the main reason was that partial scores were given in the descriptive problems. Last, there seems a possibility gender difference in the reason of falling. From these results, followings are suggested to advance the learning, teaching and evaluation in mathematics education: First, it has to be emphasized enough to describe the solving process when solving a problem. Second, increasing the rate of descriptive problems can be supported as a way to advance the evaluation. Third, descriptive problems have to be easier to solve than multiple-choice ones and it is convenient for the students to describe the solving process. Last, multiple-choice problems have to be carefully reviewed that the possibility of students' choosing incorrect answer with a small mistake is minimal.

• Journal of the Korean Society for Precision Engineering
• /
• v.21 no.8
• /
• pp.112-119
• /
• 2004

This paper develops a computer model of a cabover type large truck for estimating the effects of the mounted method of frame on handling performance. The computer model considers two mounted methods of frame; flange mounted and web mounted. Frame is modeled by finite elements using MSC/NASTRAN in order to consider the flexibility of frame. The reliability of the developed computer model is verified by comparing the actual vehicle test results with the simulation results. The actual vehicle test is performed in a double lane change course, and lateral acceleration, yaw rate, and roll angle are measured. To estimate the effects of the mounted method of frame on handling performance, simulations are performed with the flange mounted and web mounted frame. Simulation results show that the web mounted frame＇s variations of roll angle, lateral acceleration, and yaw rate are larger than the flange mounted frame＇s variations, especially in the high test velocity and the second part of the double lane course. Also, simulation results show that the web mounted frame＇s tendencies of roll angle, lateral acceleration, and yaw rate advance the flange mounted frame＇s tendencies, especially in the high test velocity and the second part of the double lane course.

• Fire Science and Engineering
• /
• v.22 no.1
• /
• pp.37-44
• /
• 2008

The reduced scale fire test provides basic data but it is not enough to analysis real fire problem directly because there is no exact analogy theory between a real fire and the reduced scale model. Therefore, we have developed the 10 MW large scale calorimeter in order to real scale fire test. This advanced large scale calorimeter used for physical properties such as a heat release rate, based upon consumption of $O_2$ method. Using the heptane pool fire, we carried out the calibration in order to evaluation for heat release rate. It is approve that this facility has the reliability and it is capable of applying to the advance fire research in the future.

• Journal of the Korean institute of surface engineering
• /
• v.36 no.3
• /
• pp.234-241
• /
• 2003

SiC nanorod was synthesized directly on Si substrate using hexamethyldisilabutane and Fe catalyst with (111) direction. Fe acted a liquid catalyst at growth condition. Grown SiC nanorod has about 30nm diameter and $5{\mu}m$ length. SiC nanorod growth was divided by trro regions with diameter distribution. This diameter distribution were occurred by surface deposition at as - grown nanorod's surface by limitation of growth rate. At higher temperature, these division not occurred. Growth temperature and flow rates affected diameter and morphology of nanorods. With increasing flow rate of source gas, nanorod's diameter increased because of deactivation effect. Case of the increasing temperature, growth rate increased so deactivation did not occurred.

• Journal of Industrial Technology
• /
• v.32 no.A
• /
• pp.95-102
• /
• 2012

To advance luminance efficiency of Titania at visible range, N-doped $TiO_2$ was prepared by using ammonium hydroxide as a source of nitrogen. The photoactivities of the synthesized $TiO_2$ were evaluated on the basis of degradation of humic acid in aqueous solutions with different light sources, UV-C, UV-A and fluorescent lamp. As a result, at UV-C is high efficiency $UV_{254}$ decrease and TOC removal. In this study, the best synthetic conditions of N-doped $TiO_2$ were 5.0 M of ammonium hydroxide concentration and calcination temperature of $550^{\circ}C$. The degradation rate of humic acid as an evaluation of photoactivities of the catalysts were conducted with pH variation, decrease rate of molecular absorption, removal rate of total organic carbon and fluorescece evolution for humic acid solution. XRD and SEM were applied for analysis of surface analysis of the catalysts.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2019.05a
• /
• pp.45-46
• /
• 2019

Accident rate in domestic construction industry has been increased rapidly in every year. In particular, the rate of death has been shown very high compared with other industries. It means that safety activities performed by government is not effective in reducing the rate of accident. To solve these problems, the risk factors should be predicted in advance, controlled, monitored and managed from start of project to end of project. However, most studies have been conducted by using frequency of occurrence of accident and only listed the importance of risk. Therefore, the objective of this study is to provide basic material to develop risk quantifying model for human accidents on construction site in South Korea. In the future, it is expected to be used as a reference of study on developing safety mangement checklist in construction industry and model for forecasting accident.

• Journal of Hydrogen and New Energy
• /
• v.27 no.1
• /
• pp.106-113
• /
• 2016

Lean burn engine, classified into port injection and direct injection, is recognized as a promising way to meet better fuel economy. Especially, LPG direct injection engine is becoming increasingly popular due to their potential for improved fuel economy and emissions. Also, LPDi engine has the advantages of higher power output, higher thermal efficiency, higher EGR tolerance due to the operation characteristics of increased volumetric efficiency, compression ratio and ultra-lean combustion scheme. However, LPDi engine has many difficulties to be solved, such as complexity of injection control mode (fuel injection timing, injection rate), fuel injection pressure, spark timing, unburned hydrocarbon and restricted power. This study is investigated to the influence of spark timing, fuel injection position and fuel injection rate on the combustion stability of LPDi engine. Piston shape is constituted the bowl type piston. The characteristics of combustion is analyzed with the variations of spark timing, fuel injection position and fuel injection rate (early injection, late injection) in a LPDi engine.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.22 no.6
• /
• pp.609-620
• /
• 2002

It is well known that during tensile testing, a part of the mechanical work done on the specimen is transformed into heat energy. However, the ultimate temperature rise and the rate of temperature rise is related to the nature of the material, conditions of the test and also to the deformation behaviour of the material during loading. The recent advances in infrared sensors and image/data processing techniques enable observation and quantitative analysis of the heat energy dissipated during such tensile tests. In this study, infrared imaging technique has been used to characterise the tensile deformation in AISI type 316 nuclear grade stainless steel. Apart from identifying the different stages during tensile deformation, the technique provided an accurate full-field temperature image by which the point and time of strain localization could be identified. The technique makes it possible to visualise the region of deformation and failure and also predict the exact region of fracture in advance. The effect of thermal gradients on plastic flow in the case of interrupted straining revealed that the interruption of strain and restraining at a lower strain rate not only delays the growth of the temperature gradient, but the temperature rise per unit strain decreases. The technique is a potential NDE tool that can be used for on-line detection of thermal gradients developed during extrusion and metal forming process which can be used for ensuring uniform distribution of plastic strain.

• Korea journal of population studies
• /
• v.9 no.2
• /
• pp.42-52
• /
• 1986

An attempt had been made to obtain current information on induced abortion among currently married women aged 15 to 44. The source of data was 1985 National Fertility and Family Planning Survey conducted by Korea Institute for Population and Health in may 1985. 1. At the time of the survey, 53 percent of currently married women aged 15 to 44 had experienced induced abortion: 25.5 percent of the respondents who had experienced induced abortion only one time and another 27.6 percent more than two times. 2. The proportion of women who had experienced induced abortion seemed to increase according to the advance in age. It seemed that there was no significant difference in the experience rate of induced abortion by academic career, and there was inverse relationship between the experience rate of induced abortion and the age at first marriage. The experience rate if induced abortion by the number of living children was highest among those who had three children as 65.6 percent. 3. To analyze the effect of induced abortion on fertility, this study employed multiple regression analysis as a statistical technique. Instead of index representing fertility level the number of living children served as dependent variable. Independent variables used in analysis included age, age at first marriage, education level, ideal number of children, religion, frequency of induced abortion, total number of pregnancies and participation in labor force. Standardized partial regression coefficient of induced abortion was no less than -0.61. So, it can be concluded that induced abortion offered the great contribution on the birth control. A consistant health education and efficient management of family planning program would be essential for effectiveness of contraceptive practice.

• Journal of Advanced Navigation Technology
• /
• v.28 no.2
• /
• pp.216-224
• /
• 2024

This paper presents a method for analyzing the reliability of hardware electronic equipment, taking into account failures caused by radiation. Traditional reliability analysis primarily focuses on the wear out failure rate and often neglects the impact of radiation failure rates. We calculate the wear out failure rate through physics of failure analysis, while the radiation failure rate is semi-empirically estimated using the Verilog Fault Injection tool. Our approach aims to ensure reliability early in the development process, potentially reducing development time and costs by identifying circuit vulnerabilities in advance. As an illustrative example, we conducted a reliability analysis on the ISCAS85 circuit. Our results demonstrate the effectiveness of our method compared to traditional reliability analysis tools. This thorough analysis is crucial for ensuring the reliability of FPGAs in environments with high radiation exposure, such as in aviation and space applications.