• Journal of Mechanical Science and Technology
• /
• v.17 no.10
• /
• pp.1563-1571
• /
• 2003

A fast response NO analyzer was applied to investigate the relation between cycle-by-cycle NO emissions and combustion chamber pressure. NO emissions were sampled at an isolated exhaust manifold of 4-stroke spark ignition engine to avoid the interference of exhaust gas from other cylinders. The linear correlation analysis was performed with collected data of NO emissions and combustion chamber pressure with respect to the various air-fuel mixture ratios and engine loads. The sampled data sets were obtained during 200 cycles at each operating condition. The results showed that there was a typical pattern in NO emissions from an exhaust port through a cycle. It was possible to set a block of crank angle in which the linear correlation coefficient between NO emissions and combustion chamber pressure was high. As the engine load increased, NO emissions were more dependent on combustion chamber pressure after TDC. It was also analyzed that the correlation between two parameters with respect to air-fuel mixture ratio tended to increase as mixture went leaner. Furthermore, this correlation coefficient for the mixture near the lean limit seemed to be kept high even though combustion was unstable.

• The KSFM Journal of Fluid Machinery
• /
• v.17 no.6
• /
• pp.64-68
• /
• 2014

This paper is intended to provide experimental data for the design of the small VAWT(vertical axis wind turbine). Three types(lift, drag, and hybrid) of the blade of VAWT are tested with digital wind tunnel in this study. From the test, the relation of power coefficient and tip speed ratio for the blades are evaluated and compared each other depending on the blade type. Especially, the characteristics of hybrid blade which is shown to be expanded in the market without any logical data is proposed in the relation of power coefficient and tip speed ratio. It is shown that the hybrid blade can be used to make higher starting torque with trade off of degradation of power coefficient.

• Korean Journal of Health Education and Promotion
• /
• v.17 no.2
• /
• pp.99-110
• /
• 2000

The purpose of this research was to provide basic data to the welfare policy for the aged by studying the relation of health concern, health behavior, and subjective health condition between the aged and the preliminary aged group. Subjects were composed of a total of 259 (116 males, 143 females) living in seoul, aged 50-64(preliminary old people) and over 65(old people), and they were asked to answer the survey Questionnaires The data were analyzed by descriptive statistics, chi-square test, and spearman's correlation coefficient. As a result of the study, the preliminary aged group was significant than the aged group in all three variables. In the relation of health concern and health behavior, there was significance both for the preliminary aged(p〈0.01) and the aged group(p〈0.001). Also, there was significance in the relation of health behavior and subjective health condition of two groups(p〈0.001). However, in the relation of subjective health condition and health concern, there was significance only for the aged group(p〈0.001). For the correlation among three variables, there was significance in the relation between health concern and health behavior and between health behavior and subjective health condition of the preliminary aged group(p〈0.01), but there was significance in the relation between health concern and health behavior and between health behavior and subjective health condition of the aged group(p〈0.01).

• Journal of Korea Water Resources Association
• /
• v.50 no.6
• /
• pp.419-427
• /
• 2017

In mountainous rivers, the drag force acting on cobbles abundant in the riverbed surface is important in predicting behavior and response of the river. However there is little research for the drag coefficients of cobbles. This paper is to carry out the experiments for drag force of cobble and analyze the relation between the cobble shape and the drag coefficient. The effects of the shape factor on the drag coefficients $C_D$ when the long axis or the short axis of the cobbles are parallel to the direction of flow velocity were analyzed. The coefficient of drag force increased with the nominal diameter Reynolds number $R_{ep}$. The drag coefficients are greater in short axis than long axis. The coefficient of determination of the relation between $C_D$ and $R_{ep}$ is greater in long axis than short axis. This means that the drag forces acting on the irregularly-shaped cobbles depend on the axis. A change of the drag force distribution has brought about the alternative swing of cobbles. For $R_{ep}$ > 12,000, the amplitude of the swing has been increased sharply and especially was greater in short axis than long axis.

• Aerospace Engineering and Technology
• /
• v.6 no.2
• /
• pp.126-133
• /
• 2007

An experimental apparatus has been designed and prepared in order to measure a pressure loss coefficient of hydropneumatic components, which is an important parameter in a hydropneumatic system Blow-down system has been adopted for the experimental apparatu to meet the high flow energy requirement as well as the apparatus safety. Especially, pressure loss coefficient measurements of pyrostarter filters have been performed and the pressure loss coefficient, K of CQSF has been experimentally acquired. Then it is shown that the turbine inlet pressure $p_2$, which is predicted from the measured K, is in accord with the results of combustion tests. Moreover, the relation between K and combustion pressure $p_0$ has been presented and it is disclosed that the relation accords well with the results of combustion tests. It is anticipated that K of a filter could play a role in PS size reduction by rising up the combustion pressure resulting in increasing the burning rate of solid propellant.

• Journal of Korea Water Resources Association
• /
• v.51 no.5
• /
• pp.405-415
• /
• 2018

Hydraulic variables such as discharge coefficient, gate opening, and upstream water depth are required to calculate the discharge of vertical lift gate. It is very important for a precise gate design, because it may affect the rest, to predict the behavior of gate opening during operation. In this study, an equation by which gate opening could be predicted with any upstream water depths was derived from the relation between the calculated value from buoyancy theory and measured one from experiment for a floating gate model. Downpull force was the reason for the differences between the calculated and the measured and it was verified using pressure coefficient. Also, the relation of discharge coefficient with gate opening ratios was derived. The derived relations were used for flood routing and it was realized that downpull force effect should be fully taken into account during gate design.

• Journal of Korean society of Dental Hygiene
• /
• v.11 no.3
• /
• pp.313-323
• /
• 2011

Objectives : The purpose of this study was to examine effect of attribution disposition and self-efficacy on test anxiety in selected college students who major in dental hygiene. This study provides basic data to develop a program for dental hygiene students to reduce test anxiety. Methods : 328 students from A college in Kyungnam, B college in Chunnam and C university in Chungnam who majored in dental hygiene were asked to answer the self-efficacy scale, attribution disposition and test anxiety scale in November and December. 2008. Total of 311 copies were analyzed. Using SPSS 15.0, correlation analysis was conducted and structural model was verified using AMOS 7.0. Evaluation of mediated effect of attribution disposition in suggested structural model was assessed using Sobel verification. Results : 1. Looking at the correlation among self-efficacy, attribution disposition and test anxiety. Self-efficacy had negative relation with external attribution disposition and test anxiety. External attribution disposition had positive relation with test anxiety. 2. Path coefficient from self-efficacy to internal attribution disposition was significant positively and path coefficient from self-efficacy to external attribution disposition was significant negatively. However, the path coefficient from self-efficacy to test anxiety was insignificant. 3. Path coefficient from external attribution disposition to self-efficacy was positively significant. However, the path coefficient from internal attribution disposition to self-efficacy was not significant statistically. 4. In structural model among attribution disposition, test anxiety and self-efficacy, indirect effect of external attribution dispositions was significant statistically. The students with higher self-efficacy showed lower external attribution disposition, the students with lower external attribution disposition showed lower test anxiety. Conclusions : To reduce test anxiety, educators should find a strategy that can improve students' self-efficacy and change their attribution disposition.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2008.05a
• /
• pp.234-238
• /
• 2008

The energy conservation theory is introduced for investigating processes of runoff and soil erosion on the hillslope system changed vegetation condition by wildfire The rainfall energy, input energy consisted of kinetic and potential energy, is influenced by vegetation coverage and height. Output energy at the outlet of hillslope is decided as the kinetic energy of runoff and erosion soil, and mechanical work according to moving water and soil is influenced dominantly by the work rather than the kinetic energy. Relationship between output and input energy is possible to calculate the energy loss in the runoff and erosion process. The absolute value of the energy loss is controlled by the input energy size of rainfall because energy losses of runoff increase as many rainfall pass through the hillslope system. The energy coefficient which is dimensionless is defined as the ratio of input energy of rainfall to output energy of runoff water and erosion soil such as runoff coefficient. The energy coefficient and runoff coefficient showed the highest correlation coefficient with the vegetation coverage. Maximum energy coefficient is about 0.5 in the hillslope system. The energy theory for output energy of runoff and soil erosion is presented by the energy coefficient theory associated with vegetation factor. Also runoff and erosion soil resulting output energy have the relation of power function and the rates of these increase with rainfall.

• Journal of the Korean Society of Industry Convergence
• /
• v.6 no.3
• /
• pp.185-192
• /
• 2003

This study consolidation undrain Triaxial Compression Tests using constant confining pressure in clay that receive preconsolidation stress that is different and, void ratio, pore water pressure coefficient, shear strength compare with another thing theory and studied analyzing change relation of elastic modules. The summary of analysis is follows: If preconsolidation stress increases in same confining stress in relation of preconsolidation stress and deviator stress, deviator stress is proportional and increased. Can know that excess void pressure is proportional and decreases in size of preconsolidation stress in same confining stress state if preconsolidation stress increases preconsolidation stress and relation of excess void pressure. Also, over consolidated state can assume that this is thing by Dilatancy's effect though excess void pressure decreased remarkably. Preconsolidation stress and relation of stress path can know that shear strength degree increases preconsolidation stress increases, and specially, preconsolidation stress was appear in stress path form of overconsolidated state case of clay that receive at 300, 400, 500kPa in 100, 150kPa's deviator stress.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.42 no.3
• /
• pp.89-96
• /
• 2000

Most soft ground in the southern and western coasts in Korea consists of very compressible alluvial deposits. Four samples in these alluvial deposite were selected to manifest the constitutive relations of consolidation. A series of tests were performed to investigate void ratio -effective stress relationand void ratio-coefficient of permeability relation on soil samples obtained at Haenam. Jindo Mankyung and Janghung permeabilities by CRS thoery were similar to directly measured data but those of indirectly computed by $C\upsilon$ shows difference. Several models about compressibility and permeability were compared with test data.